U.S. patent application number 09/776801 was filed with the patent office on 2001-08-30 for process for the preparation of n- (phosphonomethyl) glycine by oxidizing n-substituted n-(phosphonomethyl) glycine.
Invention is credited to Dzenitis, John M., Ludwig, Cindy, McKenzie, David E., Morgenstern, David A., Oburn, David, Orth, Robert, Wan, Kam-To.
Application Number | 20010018536 09/776801 |
Document ID | / |
Family ID | 26791438 |
Filed Date | 2001-08-30 |
United States Patent
Application |
20010018536 |
Kind Code |
A1 |
Morgenstern, David A. ; et
al. |
August 30, 2001 |
Process for the preparation of n- (phosphonomethyl) glycine by
oxidizing n-substituted n-(phosphonomethyl) glycine
Abstract
This invention is directed to an improved process for the
preparation of N-(phosphonomethyl)glycine (i.e., "glyphosate"), a
salt of N-(phosphonomethyl)glycine, or an ester of
N-(phosphonomethyl)glycine. The process comprises combining an
N-substituted N-(phosphonomethyl)glyci- ne reactant with oxygen in
the presence of a noble metal catalyst. The N-substituted
N-(phosphonomethyl)glycine reactant has formula (V): 1 wherein
R.sup.1 and R.sup.2 are independently selected from the group
consisting of hydrogen, halogen, --PO.sub.3R.sup.12R.sup.13,
--SO.sub.3R.sup.14, --NO.sub.2, hydrocarbyl, and substituted
hydrocarbyl other than --CO.sub.2R.sup.15; and R.sup.7, R.sup.8,
R.sup.9, R.sup.12, R.sup.13, R.sup.14, and R.sup.15 are
independently selected from the group consisting of hydrogen,
hydrocarbyl, substituted hydrocarbyl, and an agronomically
acceptable cation.
Inventors: |
Morgenstern, David A.; (St.
Louis, MO) ; McKenzie, David E.; (House Springs,
MO) ; Orth, Robert; (Cedar Hill, MO) ; Oburn,
David; (St. Louis, MO) ; Ludwig, Cindy; (St.
Louis, MO) ; Wan, Kam-To; (Manchester, MO) ;
Dzenitis, John M.; (St. Louis, MO) |
Correspondence
Address: |
SENNIGER POWERS LEAVITT AND ROEDEL
ONE METROPOLITAN SQUARE
16TH FLOOR
ST LOUIS
MO
63102
US
|
Family ID: |
26791438 |
Appl. No.: |
09/776801 |
Filed: |
February 5, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09776801 |
Feb 5, 2001 |
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09263171 |
Mar 5, 1999 |
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6232494 |
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09263171 |
Mar 5, 1999 |
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09023404 |
Feb 12, 1998 |
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6005140 |
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60096207 |
Aug 12, 1998 |
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Current U.S.
Class: |
558/87 |
Current CPC
Class: |
C07F 9/3813 20130101;
Y02P 20/582 20151101 |
Class at
Publication: |
558/87 |
International
Class: |
C07F 009/38 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 12, 1998 |
WO |
PCT/US98/02883 |
Claims
We claim:
1. A process for the preparation of N-(phosphonomethyl)glycine, a
salt of N-(phosphonomethyl)glycine, or an ester of
N-(phosphonomethyl)glycine, the process comprising combining an
N-substituted N-(phosphonomethyl)glyc- ine reactant with oxygen in
the presence of a catalyst comprising a noble metal on a polymer
support, wherein the N-substituted N-(phosphonomethyl)glycine
reactant has formula (V): 32R.sup.1 and R.sup.2 are independently
selected from the group consisting of hydrogen, halogen,
--PO.sub.3R.sup.12R.sup.13, --SO.sub.3R.sup.14, --NO.sub.2,
hydrocarbyl, and substituted hydrocarbyl other than
--CO.sub.2R.sup.15; and R.sup.7, R.sup.8, R.sup.9, R.sup.12,
R.sup.13, R.sup.14, and R.sup.15 are independently selected from
the group consisting of hydrogen, hydrocarbyl, substituted
hydrocarbyl, and an agronomically acceptable cation.
2. The process of claim 1 wherein the polymer support comprises a
basic polymer.
3. The process of claim 1 wherein the polymer support comprises a
polymer selected from the group consisting of polyamide, polyimide,
polycarbonate, polyurea, and polyester.
4. The process of claim 1 wherein the polymer support comprises a
polymer selected from the group consisting of polyethylene imine,
polyaminostyrene, sulfonated polystyrene, polyvinyl pyridine, and a
salt of polyacrylic acid.
5. The process of claim 1 wherein the polymer support comprises
polystyrene.
6. The process of claim 1 wherein the polymer support comprises
sulfonated polystyrene.
7. The process of claim 1 wherein the polymer support comprises
polyvinyl pyridine.
8. The process of claim 1 wherein the polymer support comprises
polystyrene substituted with dimethyl amine groups.
9. The process of claim 1 wherein the catalyst further comprises a
hydrophobic electroactive molecular species.
10. The process of claim 1 wherein the N-substituted
N-(phosphonomethyl)glycine reactant is combined with oxygen in the
presence of the catalyst and 2,2,6,6-tetramethyl piperidine
N-oxide.
11. The process of claim 1 wherein the catalyst further comprises a
compound selected from the group consisting of triphenylmethane;
N-hydroxyphthalimide; 5,10,15,20-tetrakis(pentafluorophenyl)-21H,
23H-porphine iron (III) chloride; 2,4,7-trichlorofluorene;
triarylamine; 2,2,6,6-tetramethyl piperidine N-oxide;
5,10,15,20-tetraphenyl-21H,23H-po- rphine iron(III) chloride;
4,4'-difluorobenzophenone; 5,10,15,20-tetraphenyl-21H,23H porphine
nickel(II); and phenothiazine.
12. The process of claim 1 wherein the catalyst further comprises a
triarylamine.
13. The process of claim 1 wherein the catalyst further comprises
tris(4-bromophenyl)amine.
14. The process of claim 1 wherein the catalyst further comprises
N,N'-bis-(3-methylphenyl)-N,N'-diphenyl benzidine.
15. A process for the preparation of N-(phosphonomethyl)glycine, a
salt of N-(phosphonomethyl)glycine, or an ester of
N-(phosphonomethyl)glycine, the process comprising combining an
N-substituted N-(phosphonomethyl)glyc- ine reactant with oxygen in
the presence of a catalyst comprising a noble metal and a promoter,
wherein the N-substituted N-(phosphonomethyl)glycin- e reactant has
formula (V): 33R.sup.1 and R.sup.2 are independently selected from
the group consisting of hydrogen, halogen,
--PO.sub.3R.sup.12R.sup.13, --SO.sub.3R.sup.14, --NO.sub.2,
hydrocarbyl, and substituted hydrocarbyl other than
--CO.sub.2R.sup.15; R.sup.7, R.sup.8, R.sup.9, R.sup.12, R.sup.13,
R.sup.14, and R.sup.15 are independently selected from the group
consisting of hydrogen, hydrocarbyl, substituted hydrocarbyl, and
an agronomically acceptable cation; the promoter comprises a metal
selected from the group consisting of aluminum, ruthenium, osmium,
indium, gallium, tantalum, tin, and antimony; and at least about
0.05% by weight of the catalyst consists of the promoter.
16. The process of claim 15 wherein the promoter comprises
indium.
17. The process of claim 15 wherein the promoter comprises
gallium.
18. The process of claim 15 wherein the promoter comprises
ruthenium.
19. The process of claim 15 wherein the promoter comprises
osmium.
20. The process of claim 15 wherein R.sup.1 and R.sup.2 are
independently selected from the group consisting of hydrogen,
hydrocarbyl, and substituted hydrocarbyl other than
--CO.sub.2R.sup.15; and R.sup.7, R.sup.8, and R.sup.9 are
independently selected from the group consisting of hydrogen and an
agronomically acceptable cation.
21. The process of claim 15 wherein the noble metal and promoter
are on a support.
22. The process of claim 21 wherein the support comprises graphitic
carbon.
23. The process of claim 21 wherein the support comprises a
polymer.
24. A process for the preparation of N-(phosphonomethyl)glycine, a
salt of N-(phosphonomethyl)glycine, or an ester of
N-(phosphonomethyl)glycine, the process comprising: contacting a
surface of a carbon support with an oxidizing agent; depositing a
noble metal onto the oxidized surface to form a carbon-supported
oxidation catalyst; and combining an N-substituted
N-(phosphonomethyl)glycine reactant with oxygen in the presence of
the carbon-supported oxidation catalyst, wherein the N-substituted
N-(phosphonomethyl)glycine reactant has formula (V): 34R.sup.1 and
R.sup.2 are independently selected from the group consisting of
hydrogen, halogen, --PO.sub.3R.sup.12R.sup.13, --SO.sub.3R.sup.14,
--NO.sub.2, hydrocarbyl, and substituted hydrocarbyl other than
--CO.sub.2R.sup.15; and R.sup.7, R.sup.9, R.sup.9, R.sup.12,
R.sup.13, R.sup.14, and R.sup.15 are independently selected from
the group consisting of hydrogen, hydrocarbyl, substituted
hydrocarbyl, and an agronomically acceptable cation.
25. The process of claim 24 wherein the oxidizing agent comprises
H.sub.2O.sub.2.
26. The process of claim 24 wherein (a) the carbon-supported
oxidation catalyst further comprises a promoter, and (b) at least
about 0.05% by weight of the catalyst consists of the promoter.
27. The process of claim 26 wherein the promoter comprises
indium.
28. The process of claim 26 wherein the promoter comprises
gallium.
29. The process of claim 26 wherein the promoter comprises
ruthenium.
30. The process of claim 26 wherein the promoter comprises
osmium.
31. A process for the preparation of N-(phosphonomethyl)glycine, a
salt of N-(phosphonomethyl)glycine, or an ester of
N-(phosphonomethyl)glycine, the process comprising: combining an
N-substituted N-(phosphonomethyl)glycine mixture comprising an
N-substituted N-(phosphonomethyl)glycine reactant with oxygen in
the presence of a noble metal catalyst in an oxidation reaction
zone to form an N-(phosphonomethyl)glycine mixture comprising
N-(phosphonomethyl)glycine, the salt of N-(phosphonomethyl)glycine,
or the ester of N-(phosphonomethyl)glycine; separating
N-(phosphonomethyl)glycine, the salt of N-(phosphonomethyl)glycine,
or the ester of N-(phosphonomethyl)glycine from the
N-(phosphonomethyl)glycine mixture to recover the separated
N-(phosphonomethyl)glycine, salt of N-(phosphonomethyl)glycine, or
ester of N-(phosphonomethyl)glycine and form a residual mixture;
feeding at least a portion of the residual mixture back into the
oxidation reaction zone, wherein the N-substituted
N-(phosphonomethyl)glycine reactant has formula (V): 35R.sup.1 and
R.sup.2 are independently selected from the group consisting of
hydrogen, halogen, --PO.sub.3R.sup.12R.sup.13, --SO.sub.3R.sup.14,
--NO.sub.2, hydrocarbyl, and substituted hydrocarbyl other than
--CO.sub.2R.sup.15; and R.sup.7, R.sup.8, R.sup.9, R.sup.12,
R.sup.13, R.sup.14, and R.sup.15 are independently selected from
the group consisting of hydrogen, hydrocarbyl, substituted
hydrocarbyl, and an agronomically acceptable cation.
32. The process of claim 31 wherein when from about 20 to about 95%
of the N-substituted N-(phosphonomethyl)glycine reactant initially
in the N-substituted N-(phosphonomethyl)glycine mixture has been
consumed, N-(phosphonomethyl)glycine, the salt of
N-(phosphonomethyl)glycine, or the ester of
N-(phosphonomethyl)glycine is separated from the
N-(phosphonomethyl)glycine mixture to recover the separated
N-(phosphonomethyl)glycine, salt of N-(phosphonomethyl)glycine, or
ester of N-(phosphonomethyl)glycine and form the residual
mixture.
33. The process of claim 32 wherein N-(phosphonomethyl)glycine, the
salt of N-(phosphonomethyl)glycine, or the ester of
N-(phosphonomethyl)glycine is separated from the
N-(phosphonomethyl)glycine mixture when from about 50 to about 90%
of the N-substituted N-(phosphonomethyl)glycine reactant initially
in the N-substituted N-(phosphonomethyl)glycine mixture has been
consumed.
34. The process of claim 32 wherein N-(phosphonomethyl)glycine, the
salt of N-(phosphonomethyl)glycine, or the ester of
N-(phosphonomethyl)glycine is separated from the
N-(phosphonomethyl)glycine mixture when from about 50 to about 80%
of the N-substituted N-(phosphonomethyl)glycine reactant initially
in the N-substituted N-(phosphonomethyl)glycine mixture has been
consumed.
35. The process of claim 32 wherein N-(phosphonomethyl)glycine, the
salt of N-(phosphonomethyl)glycine, or the ester of
N-(phosphonomethyl)glycine is separated from the
N-(phosphonomethyl)glycine mixture when from about 50 to about 70%
of the N-substituted N-(phosphonomethyl)glycine reactant initially
in the N-substituted N-(phosphonomethyl)glycine mixture has been
consumed.
36. The process of claim 31 wherein the residual mixture is divided
into a recycle mixture and a waste mixture by being pressurized and
contacted with a membrane which selectively passes a contaminant
from the residual mixture while retaining (a) the N-substituted
N-(phosphonomethyl)glycine reactant, and (b)
N-(phosphonomethyl)glycine, the salt of N-(phosphonomethyl)glycine,
or the ester of N-(phosphonomethyl)glycine, wherein the waste
mixture comprises any portion of the residual mixture which passes
through the membrane; and the recycle mixture (a) comprises any
portion of the residual mixture which does not pass through the
membrane, and (b) comprises the portion of the residual mixture
which is fed back into the oxidation reaction zone.
37. The process of claim 36 wherein the contaminant is a salt.
38. The process of claim 31 wherein the residual mixture is divided
into a recycle mixture and a waste mixture by being pressurized and
contacted with a membrane having a molecular weight cutoff of less
than about 1,000 daltons, wherein the waste mixture comprises any
portion of the residual mixture which passes through the membrane;
and the recycle mixture (a) comprises any portion of the residual
mixture which does not pass through the membrane, and (b) comprises
the portion of the residual mixture which is fed back into the
oxidation reaction zone.
39. A process for the preparation of N-(phosphonomethyl)glycine, a
salt of N-(phosphonomethyl)glycine, or an ester of
N-(phosphonomethyl)glycine, the process comprising introducing
oxygen into a mixture comprising an N-substituted
N-(phosphonomethyl)glycine reactant and a noble metal catalyst,
wherein the oxygen is introduced into the mixture through a
membrane; the N-substituted N-(phosphonomethyl)glycine reactant has
formula (V): 36R.sup.1 and R.sup.2 are independently selected from
the group consisting of hydrogen, halogen,
--PO.sub.3R.sup.12R.sup.13, --SO.sub.3R.sup.14, --NO.sub.2,
hydrocarbyl, and substituted hydrocarbyl other than
--CO.sub.2R.sup.15; and R.sup.7, R.sup.8, R.sup.9, R.sup.12,
R.sup.13, R.sup.14, and R.sup.15 are independently selected from
the group consisting of hydrogen, hydrocarbyl, substituted
hydrocarbyl, and an agronomically acceptable cation.
40. A process for the preparation of N-(phosphonomethyl)glycine, a
salt of N-(phosphonomethyl)glycine, or an ester of
N-(phosphonomethyl)glycine, the process comprising forming a
reaction mixture by combining an N-substituted
N-(phosphonomethyl)glycine reactant with oxygen in the presence of
a noble metal catalyst, wherein no greater than about 10% by volume
of the reaction mixture consists of undissolved oxygen; the
N-substituted N-(phosphonomethyl)glycine reactant has formula (V):
37R.sup.1 and R.sup.2 are independently selected from the group
consisting of hydrogen, halogen, --PO.sub.3R.sup.12R.sup.13,
--SO.sub.3R.sup.14, --NR.sub.2, hydrocarbyl, and substituted
hydrocarbyl other than --CO.sub.2R.sup.15; and R.sup.7, R.sup.8,
R.sup.9, R.sup.12, R.sup.13, R.sup.14, and R.sup.15 are
independently selected from the group consisting of hydrogen,
hydrocarbyl, substituted hydrocarbyl, and an agronomically
acceptable cation.
41. The process of claim 40 wherein no greater than about 4% by
volume of the reaction mixture consists of undissolved oxygen.
42. The process of claim 40 wherein no greater than about 1% by
volume of the reaction mixture consists of undissolved oxygen.
43. A process for the preparation of N-(phosphonomethyl)glycine, a
salt of N-(phosphonomethyl)glycine, or an ester of
N-(phosphonomethyl)glycine, the process comprising introducing
oxygen into a mixture comprising an N-substituted
N-(phosphonomethyl)glycine reactant and a noble metal catalyst in a
stirred tank reactor, wherein the oxygen is introduced into the
mixture as gas bubbles in a manner such that essentially no gas
bubbles enter a region of the reactor through which an impeller
passes; the N-substituted N-(phosphonomethyl)glycine reactant has
formula (V): 38R.sup.1 and R.sup.2 are independently selected from
the group consisting of hydrogen, halogen,
--PO.sub.3R.sup.12R.sup.13, --SO.sub.3R.sup.14, --NO.sub.2,
hydrocarbyl, and substituted hydrocarbyl other than
--CO.sub.2R.sup.15; and R.sup.7, R.sup.8, R.sup.9, R.sup.12,
R.sup.13, R.sup.14, and R.sup.15 are independently selected from
the group consisting of hydrogen, hydrocarbyl, substituted
hydrocarbyl, and an agronomically acceptable cation.
44. A process for the preparation of N-(phosphonomethyl)glycine, a
salt of N-(phosphonomethyl)glycine, or an ester of
N-(phosphonomethyl)glycine, the process comprising: combining an
N-substituted N-(phosphonomethyl)glycine reactant with oxygen in
the presence of a noble metal catalyst in an oxidation reaction
zone to form an oxidation product comprising (a) a ketone, and (b)
N-(phosphonomethyl)glycine, the salt of N-(phosphonomethyl)glycine,
or the ester of N-(phosphonomethyl)glycine; separating the ketone
from the oxidation product to recover the ketone; using the
recovered ketone as a starting material to form the N-substituted
N-(phosphonomethyl)glycine reactant; and combining the
N-substituted N-(phosphonomethyl)glycine reactant derived from the
ketone with oxygen in the presence of the noble metal catalyst in
the oxidation reaction zone, wherein the N-substituted
N-(phosphonomethyl)glycine reactant has formula (V): 39the ketone
has formula (VIII): 40R.sup.1 and R.sup.2 are independently
selected from the group consisting of hydrocarbyl and substituted
hydrocarbyl other than --CO.sub.2R.sup.15; and R.sup.7, R.sup.8,
R.sup.9, and R.sup.15 are independently selected from the group
consisting of hydrogen, hydrocarbyl, substituted hydrocarbyl, and
an agronomically acceptable cation.
45. The process of claim 44 wherein R.sup.7, R.sup.8, and R.sup.9
are independently selected from the group consisting of hydrogen
and an agronomically acceptable cation.
46. The process of claim 44 wherein R.sup.1 is methyl, and R.sup.2
is selected from the group consisting of methyl and ethyl.
47. The process of claim 44 wherein: the ketone is combined with
H.sub.2 and a glycine reactant in the presence of a
metal-containing catalyst to form an N-substituted glycine
reactant, and the N-substituted glycine reactant is
phosphonomethylated to form the N-substituted
N-(phosphonomethyl)glycine reactant, wherein the glycine reactant
has formula (IX): 41the N-substituted glycine reactant has formula
(II): 42R.sup.3 and R.sup.11 are independently selected from the
group consisting of hydrogen and an agronomically acceptable
cation.
48. The process of claim 47 wherein the metal-containing catalyst
comprises a metal selected from the group consisting of platinum
and palladium.
49. The process of claim 44 wherein: the ketone is combined with
H.sub.2 and ammonia in the presence of a metal-containing catalyst
to form a primary amine, the primary amine is combined with HCN and
a source of CH.sub.2O to form a nitrile, the nitrile is hydrolyzed
to form an N-substituted glycine reactant, and the N-substituted
glycine reactant is phosphonomethylated to form the N-substituted
N-(phosphonomethyl)glycine reactant, wherein the N-substituted
glycine reactant has formula (II): 43R.sup.3 is selected from the
group consisting of hydrogen and an agronomically acceptable
cation.
50. The process of claim 44 wherein: the ketone is combined with
H.sub.2 and ammonia in the presence of a first catalyst comprising
a metal to form a primary amine, the primary amine is converted
into an amide, the amide is combined with CO and a source of
CH.sub.2O in the presence of a second catalyst comprising a metal
selected from the group consisting of cobalt and palladium to form
an N-substituted glycine amide, the N-substituted glycine amide is
hydrolyzed to form an N-substituted glycine reactant, and the
N-substituted glycine reactant is phosphonomethylated to form the
N-substituted N-(phosphonomethyl)glycine reactant, wherein the
N-substituted glycine reactant has formula (II): 44R.sup.3 is
selected from the group consisting of hydrogen and an agronomically
acceptable cation.
51. The process of claim 44 wherein: the ketone is combined with
H.sub.2 and monoethanolamine in the presence of a metal-containing
catalyst to form an N-substituted monoethanolamine, the
N-substituted monoethanolamine is combined with a strong base in
the presence of a catalyst comprising copper to form an
N-substituted glycine reactant, and the N-substituted glycine
reactant is phosphonomethylated to form the N-substituted
N-(phosphonomethyl)glycine reactant, wherein the N-substituted
monoethanolamine has formula (XI): 45the N-substituted glycine
reactant has formula (II): 46R.sup.3 is selected from the group
consisting of hydrogen and an agronomically acceptable cation.
52. The process of claim 51 wherein the base comprises NaOH.
53. The process of claim 51 wherein the ketone, monoethanolamine,
and H.sub.2 are combined essentially in the absence of any
non-reactive solvent.
54. The process of claim 53 wherein the ketone is acetone.
55. A process for the preparation of N-(phosphonomethyl)glycine or
a salt thereof, the process comprising: converting an N-substituted
glycine salt into an N-substituted glycine free acid,
phosphonomethylating the N-substituted glycine free acid to form an
N-substituted N-(phosphonomethyl)glycine, and combining the
N-substituted N-(phosphonomethyl)glycine or a salt thereof with
oxygen in the presence of a noble metal catalyst in an oxidation
reaction zone, wherein the N-substituted glycine free acid has
formula (XII): 47the N-substituted glycine salt has formula (XIII):
48the N-substituted N-(phosphonomethyl)glycine has formula (I):
49R.sup.1 and R.sup.2 are independently selected from the group
consisting of hydrogen, halogen, --PO.sub.3R.sup.12R.sup.13,
--SO.sub.3R.sup.14, --NO.sub.2, hydrocarbyl, and substituted
hydrocarbyl other than --CO.sub.2R.sup.15; R.sup.6 is an
agronomically acceptable cation; R.sub.12, R.sup.13, and R.sup.14
are independently selected from the group consisting of hydrogen,
hydrocarbyl, and substituted hydrocarbyl; and R.sup.15 is selected
from the group consisting of hydrogen, hydrocarbyl, substituted
hydrocarbyl, and an agronomically acceptable cation.
56. The process of claim 55 wherein the N-substituted glycine salt
is converted into the N-substituted glycine free acid by contacting
a mixture comprising the N-substituted glycine salt with a first
side of a cation exchange membrane while simultaneously contacting
a second side of the cation exchange membrane with an N-substituted
N-(phosphonomethyl)glycine mixture comprising (a) the N-substituted
N-(phosphonomethyl)glycine or the salt thereof, and (b) a strong
acid having a pK.sub.a of no greater than about 1.0.
57. The process of claim 56 wherein the strong acid comprises
H.sub.2SO.sub.4.
58. The process of claim 56 wherein, after being contacted with the
second side of the cation exchange membrane, the N-substituted
N-(phosphonomethyl)glycine mixture is combined with oxygen in the
presence of the noble metal in the oxidation reaction zone.
59. The process of claim 58 wherein R.sup.1 is methyl, and R.sup.2
is selected from the group consisting of methyl and ethyl.
60. The method of claim 58 wherein the N-substituted
N-(phosphonomethyl)glycine mixture does not contain a halogen.
61. The process of claim 55 wherein the N-substituted glycine salt
is converted into the N-substituted glycine free acid by contacting
a mixture comprising the N-substituted glycine salt with a first
side of a cation exchange membrane while simultaneously contacting
a second side of the cation exchange membrane with a mixture
comprising a strong acid having a pK.sub.a of no greater than about
1.0.
62. The process of claim 55 wherein the N-substituted glycine salt
is converted into the N-substituted glycine free acid by a process
comprising: combining PCl.sub.3 and water to form a PCl.sub.3
hydrolysis mixture comprising H.sub.3PO.sub.3 and HCl; separating
HCl from the PCl.sub.3 hydrolysis mixture to form an
H.sub.3PO.sub.3-containing mixture and an HCl-containing mixture;
and contacting the HCl-containing mixture with a first side of a
cation exchange membrane while simultaneously contacting a second
side of the cation exchange membrane with a mixture comprising the
N-substituted glycine salt.
63. The method of claim 62 wherein R.sup.1 and R.sup.2 are
hydrogen.
64. A process for the preparation of an N-substituted
N-(phosphonomethyl)glycine or a salt thereof, the process
comprising: combining a source of H.sub.3PO.sub.3, a source of
CH.sub.2O, and an N-substituted glycine salt in a reaction zone to
form a first mixture which comprises (a) the N-substituted
N-(phosphonomethyl)glycine or the salt thereof, and (b) a salt
precipitate; separating salt precipitate from the first mixture to
form a second mixture which comprises the N-substituted
N-(phosphonomethyl)glycine or the salt thereof; adding a base to
the second mixture to precipitate N-substituted
N-(phosphonomethyl)glycine or the salt thereof; and separating the
precipitated N-substituted N-(phosphonomethyl)glycine or salt
thereof from the second mixture to recover the precipitated
N-substituted N-(phosphonomethyl)glycine or salt thereof and form a
residual mixture, wherein the N-substituted
N-(phosphonomethyl)glycine has formula (I): 50the N-substituted
glycine salt has formula (XIII): 51R.sup.1 and R.sup.2 are
independently selected from the group consisting of hydrogen,
halogen, --PO.sub.3R.sup.12R.sup.13, --SO.sub.3R.sup.14,
--NO.sub.2, hydrocarbyl, and substituted hydrocarbyl other than
--CO.sub.2R.sup.15; R.sup.6 is an agronomically acceptable cation;
R.sup.12, R.sup.13, and R.sup.14 are independently selected from
the group consisting of hydrogen, hydrocarbyl, and substituted
hydrocarbyl; and R.sup.15 is selected from the group consisting of
hydrogen, hydrocarbyl, substituted hydrocarbyl, and an
agronomically acceptable cation.
65. The process of claim 64 wherein the source of H.sub.3PO.sub.3
comprises PCl.sub.3.
66. The process of claim 64 wherein the salt precipitate comprises
chlorine.
67. The process of claim 64 wherein R.sup.1 and R.sup.2 are
hydrogen.
68. The process of claim 64 wherein R.sup.1 is methyl and R.sup.2
is hydrogen.
69. The process of claim 64 wherein R.sup.1 is methyl and R.sup.2
is selected from the group consisting of methyl and ethyl.
70. The process of claim 64 wherein at least a portion of the
residual mixture is recycled to the reaction zone.
71. The process of claim 64 further comprising the preparation of
N-(phosphonomethyl)glycine or a salt thereof by a process
comprising combining the recovered N-substituted
N-(phosphonomethyl)glycine or the salt thereof with oxygen in the
presence of a noble metal catalyst.
72. A process for the preparation of an N-substituted
N-(phosphonomethyl)glycine or a salt thereof, the process
comprising: combining a source of H.sub.3PO.sub.3 and an
N-substituted glycine salt in a reaction zone to form a first
mixture which comprises (a) an N-substituted glycine free acid, and
(b) a salt precipitate; separating salt precipitate from the first
mixture to form a second mixture comprising the N-substituted
glycine free acid; adding a source of CH.sub.2O to the second
mixture to form a third mixture which comprises the N-substituted
N-(phosphonomethyl)glycine or the salt thereof; adding a base to
the third mixture to precipitate N-substituted
N-(phosphonomethyl)glycine or the salt thereof; and separating
precipitated N-substituted N-(phosphonomethyl)glycine or the salt
thereof from the third mixture to recover the precipitated
N-substituted N-(phosphonomethyl)glycine or salt thereof and form a
residual mixture; wherein the N-substituted
N-(phosphonomethyl)glycine has formula (I): 52the N-substituted
glycine salt has formula (XIII): 53the N-substituted glycine free
acid has formula (XII): 54R.sup.1 and R.sup.2 are independently
selected from the group consisting of hydrogen, halogen,
--PO.sub.3R.sup.12R.sup.13, --SO.sub.3R.sup.14, --NO.sub.2,
hydrocarbyl, and substituted hydrocarbyl other than
--CO.sub.2R.sup.15; R.sup.6 is an agronomically acceptable cation;
R.sup.12, R.sup.13, and R.sup.14 are independently selected from
the group consisting of hydrogen, hydrocarbyl, and substituted
hydrocarbyl; and R.sup.15 is selected from the group consisting of
hydrogen, hydrocarbyl, substituted hydrocarbyl, and an
agronomically acceptable cation.
73. The process of claim 72 wherein the source of H.sub.3PO.sub.3
comprises PCl.sub.3.
74. The process of claim 72 wherein the salt precipitate comprises
chlorine.
75. The process of claim 72 wherein R.sup.1 and R.sup.2 are
hydrogen.
76. The process of claim 72 wherein R.sup.1 is methyl and R.sup.2
is hydrogen.
77. The process of claim 72 wherein at least a portion of the
residual mixture is recycled to the reaction zone.
78. The process of claim 72 further comprising the preparation of
N-(phosphonomethyl)glycine or a salt thereof by a process
comprising combining the recovered N-substituted
N-(phosphonomethyl)glycine or the salt thereof with oxygen in the
presence of a noble metal catalyst.
79. A process for the preparation of an N-substituted
monoethanolamine, the process comprising combining a ketone,
monoethanolamine, and H.sub.2 in the presence of a metal-containing
catalyst and essentially in the absence of any non-reactive
solvent, wherein the N-substituted monoethanolamine has formula
(XI): 55the ketone has formula (VIII): 56R.sup.1 and R.sup.2 are
independently selected from the group consisting of hydrocarbyl and
substituted hydrocarbyl.
80. The process of claim 79 wherein the metal-containing catalyst
comprises a metal selected from the group consisting of palladium
and platinum.
81. The process of claim 79 wherein the ketone is acetone.
82. An oxidation catalyst comprising a noble metal and an
electroactive molecular species.
83. The oxidation catalyst of claim 82 wherein the electroactive
molecular species is hydrophobic.
84. The oxidation catalyst of claim 82 wherein the electroactive
molecular species has an oxidation potential of at least about 0.3
volts vs. SCE.
85. The oxidation catalyst of claim 82 wherein the electroactive
molecular species comprises a compound selected from the group
consisting of triphenylmethane; N-hydroxyphthalimide;
2,4,7-trichlorofluorene; tris(4-5 bromophenyl)amine;
2,2,6,6-tetramethyl piperidine N-oxide;
5,10,15,20-tetraphenyl-21H,23H-porphine iron(III) chloride;
5,10,15,20-tetraphenyl-21H,23H porphine nickel(II);
4,4'-difluorobenzophenone;
5,10,15,20-tetrakis(pentafluorophenyl)-21H,23H- -porphine iron
(III) chloride; and phenothiazine.
86. The oxidation catalyst of claim 82 wherein the electroactive
molecular species comprises 2,2,6,6-tetramethyl piperidine
N-oxide.
87. The oxidation catalyst of claim 82 wherein the electroactive
molecular species comprises a triarylamine.
88. The oxidation catalyst of claim 82 wherein the electroactive
molecular species comprises N,N'-bis(3-methylphenyl)-N,N'-diphenyl
benzidine.
89. The oxidation catalyst of claim 82 wherein (a) the catalyst
further comprises a promoter, and (b) at least about 0.05% by
weight of the catalyst consists of the promoter.
90. The oxidation catalyst of claim 89 wherein the promoter
comprises a metal selected from the group consisting of aluminum,
ruthenium, osmium, indium, gallium, tantalum, tin, and
antimony.
91. The oxidation catalyst of claim 82 further comprising a support
comprising a material selected from the group consisting of carbon,
alumina, silica, titania, zirconia, siloxane, and barium
sulfate.
92. The oxidation catalyst of claim 91 wherein the support
comprises a material selected from the group consisting of alumina,
silica, titania, zirconia, siloxane, and barium sulfate.
93. The oxidation catalyst of claim 91 wherein the support
comprises a material selected from the group consisting of silica,
titania, and barium sulfate.
94. The oxidation catalyst of claim 91 wherein the support
comprises graphitic carbon.
95. The oxidation catalyst of claim 82 wherein the noble metal is
on a support which comprises a polymer.
96. The oxidation catalyst of claim 95 wherein the support
comprises a polymer selected from the group consisting of
polyamide, polyimide, polycarbonate, polyurea, and polyester.
97. The oxidation catalyst of claim 95 wherein the support
comprises a polymer selected from the group consisting of
polyethylene imine, polyaminostyrene, sulfonated polystyrene,
polyvinyl pyridine, and a salt of polyacrylic acid.
98. The oxidation catalyst of claim 95 wherein the support
comprises polystyrene.
99. The oxidation catalyst of claim 95 wherein the support
comprises polystyrene substituted with dimethylamine groups.
Description
BACKGROUND OF THE INVENTION
[0001] This invention generally relates to an improved process for
reacting N-substituted N-(phosphonomethyl)glycines (sometimes
referred to as "N-substituted glyphosates"), salts of N-substituted
N-(phosphonomethyl)glycines, and esters of N-substituted
N-(phosphonomethyl)glycines to form N-(phosphonomethyl)glycine
(sometimes referred to as "glyphosate"), salts of
N-(phosphonomethyl)glycine, and esters of
N-(phosphonomethyl)glycine via a noble-metal catalyzed oxidation
reaction. This invention is particularly directed to such reactions
using N-substituted N-(phosphonomethyl)glycines, salts of
N-substituted N-(phosphonomethyl)glycines, and esters of
N-substituted N-(phosphonomethyl)glycines which have a single
N-carboxymethyl functionality.
[0002] N-(phosphonomethyl)glycine is described by Franz in U.S.
Pat. No. 3,799,758, and has the following formula: 2
[0003] N-(phosphonomethyl)glycine and its salts conveniently are
applied as a post-emergent herbicide in an aqueous formulation. It
is a highly effective and commercially important broad-spectrum
herbicide useful in killing or controlling the growth of a wide
variety of plants, including germinating seeds, emerging seedlings,
maturing and established woody and herbaceous vegetation, and
aquatic plants.
[0004] Various methods for the preparation of
N-(phosphonomethyl)glycine from N-substituted
N-(phosphonomethyl)glycines are known in the art. For example, in
U.S. Pat. No. 3,956,370, Parry et al. teach that N-benzylglycine
may be phosphonomethylated to N-benzyl N-(phosphonomethyl)glycine,
and then reacted with hydrobromic or hydroiodic acid to cleave the
benzyl group and thereby produce N-(phosphonomethyl)glycine. In
U.S. Pat. No. 3,927,080, Gaertner teaches that N-t-butylglycine may
be phosphonomethylated to form N-t-butyl
N-(phosphonomethyl)glycine, and then converted into
N-(phosphonomethyl)glycine via acid hydrolysis.
N-(phosphonomethyl)glycin- e also may be produced from N-benzyl
N-(phosphonomethyl)glycine via hydrogenolysis, as described, for
example, in European Patent Application No. 55,695. A separate
discussion directed to producing N-(phosphonomethyl)glycine from
N-benzyl N-(phosphonomethyl)glycine via hydrogenolysis may be found
in Maier, L., Phosphorus, Sulfur and Silicon, 61, 65-7 (1991).
These processes are problematic in that they produce undesirable
byproducts such as isobutylene and toluene which create
difficulties due to their potential toxicities. Moreover, acid
hydrolysis and hydrogenation of N-substituted
N-(phosphonomethyl)glycines have been reported only for hydrocarbyl
groups such as tertiary butyl and benzyl groups which are generally
known to be susceptible to such reactions; there has not been
reported a general method for dealkylation of N-substituted
N-(phosphonomethyl)glycines.
[0005] Other methods for the preparation of
N-(phosphonomethyl)glycine include those directed to oxidatively
cleaving N-(phosphonomethyl)iminodi- acetic acid (sometimes
referred to as "PMIDA"): 3
[0006] PMIDA may be synthesized, for example, from phosphorus
trichloride, formaldehyde, and an aqueous solution of the disodium
salt of iminodiacetic acid, as described by Gentilcore in U.S. Pat.
No. 4,775,498: 4
[0007] This reaction is complicated by the necessity of removing
sodium chloride from the PMIDA product. Sodium chloride has low
solubility in the presence of HCl due to the common ion effect, and
both iminodiacetic acid and PMIDA are insoluble in HCl and in water
under neutral conditions. Thus, salt separation requires that the
NaCl be dissolved after the reaction forming PMIDA is complete.
This is done by neutralizing the HCl with a base, and then adding
water to ensure that all the NaCl dissolves. This large volume of
water leads to significant losses of PMIDA during recovery, and
increases the volume of waste.
[0008] Various methods for converting PMIDA into
N-(phosphonomethyl)glycin- e are well known in the art. These
include:
[0009] 1. Heterogeneous catalytic oxidation. This method is
discussed, for example by Franz in U.S. Pat. No. 3,950,402. A
separate discussion may be found in Balthazor et al., U.S. Pat. No.
4,654,429.
[0010] 2. Homogeneous catalytic oxidation. This method is
described, for example, in Riley et al., J. Amer. Chem. Soc. 113,
3371-78 (1991). A separate discussion may be found in Riley et al.,
Inorg. Chem., 30, 4191-97 (1991).
[0011] 3. Electrochemical oxidation using carbon electrodes. This
method is described, for example, by Frazier et al. in U.S. Pat.
No. 3,835,000.
[0012] Such methods oxidatively remove one of the two
N-carboxymethyl groups from PMIDA. Generally, such oxidative
decarboxylations rely on a one-electron oxidation of PMIDA
accompanied by loss of carbon dioxide to form a carbon based
radical. The radical is then oxidized to N-(phosphonomethyl)glycine
in a subsequent one-electron step. These reactions are summarized
as follows: 5
[0013] Oxidative decarboxylations, in general, are well known in
the art, particularly for electrochemical oxidations (also known as
the Kolbe reaction) . The Kolbe reaction is particularly facile
with carbon electrodes. See, e.g., S. Tonii and H. Tanaka, Organic
Electrochemistry, 535-80 (H. Lund and M. M. Baizer eds., Marcel
Dekker, 3rd ed. 1991).
[0014] The methods used to oxidize PMJDA to
N-(phosphonomethyl)glycine have not been reported to be useful for
preparing N-(phosphonomethyl)glyc- ine from N-substituted
N-(phosphonomethyl)glycines having only one N-carboxymethyl group,
i.e., where R' in the following formula is a functionality other
than a carboxymethyl: 6
[0015] If R' is other than a carboxymethyl, removal of R' typically
requires a single, two-electron oxidation of the N-substituted
N-(phosphonomethyl)glycine, rather than two successive one-electron
oxidations.
SUMMARY OF THE INVENTION
[0016] As the foregoing suggests, there is a need for a more
general process for oxidizing N-substituted
N-(phosphonomethyl)glycines and their salts and esters (sometimes
collectively referred to as "N-substituted
N-(phosphonomethyl)glycine reactants") to prepare
N-(phosphonomethyl)glyc- ine and its salts and esters. Such a
process would allow a wider range of N-substituted glycines and
salts thereof (sometimes collectively referred to as "N-substituted
glycine reactants") to be used as raw materials to make
N-(phosphonomethyl)glycine and its salts and esters. Such a process
also would allow for N-(phosphonomethyl)glycine to be made from
N-methyl N-(phosphonomethyl)glycine (sometimes referred to as
"NMG"), an undesirable byproduct from the carbon-catalyzed
oxidation of PMIDA. Such a process would further allow for the use
of the various N-substituted glycine reactants and N-substituted
N-(phosphonomethyl)glycine reactants that--unlike iminodiacetic
acid and PMIDA--are soluble in HCl, and therefore more easily
separated from the chloride salt byproduct which forms when
PCl.sub.3 and CH.sub.2O are used to phosphonomethylate
N-substituted glycine salts.
[0017] This invention addresses the above-described need. More
specifically, this invention provides processes for preparing
N-(phosphonomethyl)glycine and its salts and esters by the
oxidation of N-substituted N-(phosphonomethyl)glycine reactants
having a single N-carboxymethyl functionality. This invention also
provides processes for preparing various starting materials used to
prepare N-(phosphonomethyl)glycine and its salts and esters. This
invention further provides a novel catalyst which may be used to
catalyze the oxidation reaction.
[0018] Briefly, therefore, in one embodiment directed to a process
for preparing N-(phosphonomethyl)glycine, a salt of
N-(phosphonomethyl)glycin- e, or an ester of
N-(phosphonomethyl)glycine, the process comprises combining an
N-substituted N-(phosphonomethyl)glycine reactant with oxygen in
the presence of a catalyst comprising a noble metal on a polymer
support. The N-substituted N-(phosphonomethyl)glycine reactant has
the formula (V): 7
[0019] with R.sup.1 and R.sup.2 being independently selected from
the group consisting of hydrogen, halogen,
--PO.sub.3R.sup.12R.sup.13, --SO.sub.3R.sup.14, --NO.sub.2,
hydrocarbyl, and substituted hydrocarbyl other than
--CO.sub.2R.sup.15; and R.sup.7, R.sup.8, R.sup.9, R.sup.12,
R.sup.13, R.sup.14, and R.sup.15 being independently selected from
the group consisting of hydrogen, hydrocarbyl, substituted
hydrocarbyl, and an agronomically acceptable cation.
[0020] In another embodiment directed to a process for preparing
N-(phosphonomethyl)glycine, a salt of N-(phosphonomethyl)glycine,
or an ester of N-(phosphonomethyl)glycine, the process comprises
combining an N-substituted N-(phosphonomethyl)glycine reactant with
oxygen in the presence of a catalyst comprising a noble metal and a
promoter. The N-substituted N-(phosphonomethyl)glycine reactant has
the formula (V), as defined in the preceding paragraph. The
promoter comprises a metal selected from the group consisting of
aluminum, ruthenium, osmium, indium, gallium, tantalum, tin, and
antimony. At least about 0.05% by weight of the catalyst consists
of the promoter.
[0021] In another embodiment directed to a process for preparing
N-(phosphonomethyl)glycine, a salt of N-(phosphonomethyl)glycine,
or an ester of N-(phosphonomethyl)glycine, the process comprises
first contacting a surface of a carbon support with an oxidizing
agent, and then depositing a noble metal onto the oxidized surface
to form a carbon-supported oxidation catalyst. An N-substituted
N-(phosphonomethyl)glycine reactant is then combined with oxygen in
the presence of the carbon-supported oxidation catalyst. The
N-substituted N-(phosphonomethyl)glycine reactant has the formula
(V) (as defined in the preceding paragraphs).
[0022] In another embodiment directed to a process for preparing
N-(phosphonomethyl)glycine, a salt of N-(phosphonomethyl)glycine,
or an ester of N-(phosphonomethyl)glycine, the process comprises
combining an N-substituted N-(phosphonomethyl)glycine mixture
comprising an N-substituted N-(phosphonomethyl)glycine reactant
with oxygen in the presence of a noble metal catalyst in an
oxidation reaction zone to form an N-(phosphonomethyl)glycine
mixture comprising N-(phosphonomethyl)glyci- ne, the salt of
N-(phosphonomethyl)glycine, or the ester of
N-(phosphonomethyl)glycine. N-(phosphonomethyl)glycine, the salt of
N-(phosphonomethyl)glycine, or the ester of
N-(phosphonomethyl)glycine is then separated from the
N-(phosphonomethyl)glycine mixture to recover the separated
N-(phosphonomethyl)glycine, salt of N-(phosphonomethyl)glycine, or
ester of N-(phosphonomethyl)glycine and form a residual mixture.
Subsequently, the residual mixture is divided into a recycle
mixture and a waste mixture, and the recycle mixture is fed back
into the oxidation reaction zone. In this embodiment, the
N-substituted N-(phosphonomethyl)glycine reactant has the formula
(V) (as defined in the preceding paragraphs).
[0023] In another embodiment directed to a process for preparing
N-(phosphonomethyl)glycine, a salt of N-(phosphonomethyl)glycine,
or an ester of N-(phosphonomethyl)glycine, the process comprises
introducing oxygen into a mixture comprising an N-substituted
N-(phosphonomethyl)glyc- ine reactant and a noble metal catalyst.
Here, the oxygen is introduced into the mixture through a membrane.
The N-substituted N-(phosphonomethyl)glycine reactant has the
formula (V) (as defined in the preceding paragraphs).
[0024] In another embodiment directed to a process for preparing
N-(phosphonomethyl)glycine, a salt of N-(phosphonomethyl)glycine,
or an ester of N-(phosphonomethyl)glycine, the process comprises
forming a reaction mixture by combining an N-substituted
N-(phosphonomethyl)glycine reactant with oxygen in the presence of
a noble metal catalyst. In this embodiment, no greater than about
10% by volume of the reaction mixture consists of undissolved
oxygen. The N-substituted N-(phosphonomethyl)glyc- ine reactant has
the formula (V) (as defined in the preceding paragraphs).
[0025] In another embodiment directed to a process for preparing
N-(phosphonomethyl)glycine, a salt of N-(phosphonomethyl)glycine,
or an ester of N-(phosphonomethyl)glycine, the process comprises
introducing oxygen into a mixture comprising an N-substituted
N-(phosphonomethyl)glyc- ine reactant and a noble metal catalyst in
a stirred tank reactor. In this embodiment, the oxygen is
introduced into the reactor as gas bubbles in a manner such that
essentially no gas bubbles enter a region of the reactor through
which an impeller passes. The N-substituted
N-(phosphonomethyl)glycine reactant has the formula (V) (as defined
in the preceding paragraphs).
[0026] In another embodiment directed to a process for preparing
N-(phosphonomethyl)glycine, a salt of N-(phosphonomethyl)glycine,
or an ester of N-(phosphonomethyl)glycine, the process comprises
first combining an N-substituted N-(phosphonomethyl)glycine
reactant with oxygen in the presence of a noble metal catalyst in
an oxidation reaction zone to form an oxidation product comprising
(a) a ketone, and (b) N-(phosphonomethyl)glycine, the salt of
N-(phosphonomethyl)glycine, or the ester of
N-(phosphonomethyl)glycine. The ketone is then separated from the
oxidation product, and used as a starting material to form the
N-substituted N-(phosphonomethyl)glycine reactant. This reactant,
in turn, is combined with oxygen in the presence of the noble metal
catalyst in the oxidation reaction zone. The N-substituted
N-(phosphonomethyl)glyc- ine reactant has the formula (V) (as
defined in the preceding paragraphs, except that R.sup.1 and
R.sup.2 are independently selected from the group consisting of
hydrocarbyl and substituted hydrocarbyl other than
--CO.sub.2R.sup.15).
[0027] This invention is also directed to a process for preparing
N-(phosphonomethyl)glycine or a salt thereof. In one embodiment,
the process comprises first converting an N-substituted glycine
salt into an N-substituted glycine free acid. The N-substituted
glycine free acid is then phosphonomethylated to form an
N-substituted N-(phosphonomethyl)glyc- ine or a salt thereof.
Afterwards, the N-substituted N-(phosphonomethyl)glycine or the
salt thereof is combined with oxygen in the presence of a noble
metal catalyst in an oxidation reaction zone. The N-substituted
glycine free acid has the formula (XII): 8
[0028] the N-substituted glycine salt has the formula (XIII): 9
[0029] the N-substituted N-(phosphonomethyl)glycine has the formula
(I): 10
[0030] In this embodiment, R.sup.1 and R.sup.2 are independently
selected from the group consisting of hydrogen, halogen,
--PO.sub.3R.sup.12R.sup.1- 3, --SO.sub.3R.sup.14, --NO.sub.2,
hydrocarbyl, and substituted hydrocarbyl other than
--CO.sub.2R.sup.15; R.sup.6 is an agronomically acceptable cation;
R.sup.12, R.sup.13, and R.sup.14 are independently selected from
the group consisting of hydrogen, hydrocarbyl, and substituted
hydrocarbyl; and R.sup.15 is selected from the group consisting of
hydrogen, hydrocarbyl, substituted hydrocarbyl, and an
agronomically acceptable cation.
[0031] This invention is also directed to a process for preparing
an N-substituted N-(phosphonomethyl)glycine or a salt thereof. In
one embodiment, the process comprises first combining a source of
H.sub.3PO.sub.3, a source of CH.sub.2O, and an N-substituted
glycine salt in a reaction zone to form a first mixture which
comprises (a) the N-substituted N-(phosphonomethyl)glycine or the
salt thereof, and (b) a salt precipitate. The salt precipitate is
separated from the first mixture to form a second mixture which
comprises the N-substituted (phosphonomethyl)glycine or the salt
thereof. Base is added to this second mixture to precipitate
N-substituted N-(phosphonomethyl)glycine or the salt thereof. The
precipitated N-substituted N-(phosphonomethyl)glyci- ne or salt
thereof is then separated from the second mixture to recover the
precipitated N-substituted N-(phosphonomethyl)glycine or salt
thereof and form a residual mixture. Here, the N-substituted
N-(phosphonomethyl)glycine has the formula (I) and the
N-substituted glycine salt has the formula (XIII) (both formulas
being as defined in the preceding paragraph).
[0032] In another embodiment directed to process for preparing an
N-substituted N-(phosphonomethyl)glycine or a salt thereof, the
process comprises first combining a source of H.sub.3PO.sub.3 and
an N-substituted glycine salt in a reaction zone to form a first
mixture which comprises (a) an N-substituted glycine free acid, and
(b) a salt precipitate. The salt precipitate is separated from the
first mixture to form a second mixture comprising the -substituted
glycine free acid. A source of formaldehyde is then added to the
second mixture to form a third mixture which comprises the
-substituted -(phosphonomethyl)glycine or the salt thereof. A base
is added to the third mixture to precipitate N-substituted
N-(phosphonomethyl)glycine or the salt thereof. Afterward, the
precipitated N-substituted N-(phosphonomethyl)glycine or the salt
thereof is separated from the third mixture to recover the
precipitated N-substituted N-(phosphonomethyl)glycine or salt
thereof and form a residual mixture. The N-substituted
N-(phosphonomethyl)glycine has the formula (I), the N-substituted
glycine salt has the formula (XIII), and the N-substituted glycine
free acid has the formula (XII) (all the formulas being as defined
in the preceding two paragraphs).
[0033] This invention also is directed to a process for preparing
an N-substituted monoethanolamine. In one embodiment, this process
comprises combining a ketone, monoethanolamine, and H.sub.2 in the
presence of a metal-containing catalyst and in a reaction medium
consisting essentially of no non-reactive solvent. The
N-substituted monoethanolamine has the formula (XI): 11
[0034] the ketone has the formula (VIII): 12
[0035] Here, R.sup.1 and R.sup.2 are independently selected from
the group consisting of hydrocarbyl and substituted
hydrocarbyl.
[0036] This invention is further directed to an oxidation catalyst
comprising a noble metal and a hydrophobic electroactive molecular
species.
[0037] Other features of this invention will be in part apparent
and in part pointed out hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] FIG. 1 is a schematic diagram of a preferred embodiment for
phosphonomethylating salts of N-substituted glycines.
[0039] FIG. 2 is a schematic diagram of a preferred embodiment for
oxidizing N-substituted N-(phosphonomethyl)glycines wherein (1) the
reaction mixture is withdrawn from the oxidation reaction zone
before the oxidation is complete, (2) the
N-(phosphonomethyl)glycine product in the mixture is precipitated
and recovered, and (3) a portion of the mixture is returned to the
reaction zone.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0040] The present invention provides novel and useful methods for
preparing N-(phosphonomethyl)glycine and its salts and esters.
These compounds generally have the following formula (IV): 13
[0041] wherein R.sup.3, R.sup.4, and R.sup.5 are independently
selected from the group consisting of hydrogen, hydrocarbyl,
substituted hydrocarbyl, and an agronomically acceptable cation
(more typically, R.sup.3, R.sup.4, and R.sup.5 are independently
selected from the group consisting of hydrogen and an agronomically
acceptable cation; and even more typically, R.sup.3 is selected
from the group consisting of hydrogen and an agronomically
acceptable cation, and R.sup.4 and R.sup.5 are hydrogen). The
methods of this invention are directed to making these compounds by
oxidatively cleaving an N-substituted N-(phosphonomethyl)glycine
reactant with oxygen over a noble metal catalyst. Advantages of
preparing N-(phosphonomethyl)glycine and its salts and esters from
N-substituted N-(phosphonomethyl)glycine reactants using these
methods include the simplicity of the procedure, the low cost of
the oxidant (e.g., air or molecular oxygen), and the durability of
the catalyst (i.e., little or no deactivation of the catalyst over
several cycles).
[0042] The methods of this invention are not limited to the
oxidation of PMIDA (which has two N-carboxymethyl functionalities).
Instead, they may be used to make N-(phosphonomethyl)glycine, salts
of N-(phosphonomethyl)glycine, or esters of
N-(phosphonomethyl)glycine by oxidatively cleaving N-substituted
N-(phosphonomethyl)glycine reactants having only one
N-carboxymethyl functionality. Thus, a wide range of N-substituted
glycine reactants and N-substituted N-(phosphonomethyl)glyc- ine
reactants may be used as starting materials in accordance with this
invention. This invention also is advantageous because it provides
a method to prepare N-(phosphonomethyl)glycine from NMG, an
undesirable byproduct from the carbon-catalyzed oxidation of PMIDA.
This invention is further advantageous because it may be used with
N-substituted glycine reactants and N-substituted
N-(phosphonomethyl)glycine reactants that are soluble in HCl, and
therefore more easily separated from chloride salts than
iminodiacetic acid and PMIDA.
[0043] A. Preparation of Various N-Substituted Glycine
Reactants
[0044] Several methods may be used to prepare N-substituted glycine
reactants. The following discussion provides several examples of
such methods.
[0045] In one embodiment of this invention, the N-substituted
glycine reactant is prepared by the condensation of hydrogen
cyanide, formaldehyde, and an N-substituted amine, followed by
hydrolysis: 14
[0046] This reaction is known as the Strecker synthesis. The
Strecker synthesis is well-known in the art and described in Dyker,
G., Angewandte Chimie Int'l Ed. in English, Vol. 36, No. 16, 1700-2
(1997) (incorporated herein by reference).
[0047] In another embodiment of this invention, an N-substituted
glycine is prepared by dehydrogenation of N-substituted
ethanolamine in the presence of a base (preferably NaOH): 15
[0048] This reaction is described by Franczyk in U.S. Pat. Nos.
5,292,936 (incorporated herein by reference). An additional
separate discussion directed to this reaction may be found in
Franczyk, U.S. Pat. No. 5,367,112 (incorporated herein by
reference). A further separate discussion may be found in Ebner et
al., U.S. Pat. No. 5,627,125 (incorporated herein by reference).
The N-substituted ethanolamine precursor may be prepared in at
least two ways. First, a ketone may be condensed with
monoethanolamine in the presence of hydrogen, a solvent, and a
noble metal catalyst. This reaction is described in Cope, A. C. and
Hancock, E. M. J. Am. Chem. Soc., 64, 1503-6 (1942) (incorporated
herein by reference). N-substituted ethanolamines also may be
prepared by combining a mono-substituted amine (such as
methylamine) and ethylene oxide to form the mono-substituted
ethanolamine. This reaction is described by Y. Yoshida in Japanese
Patent Application No. 95-141575 (incorporated herein by
reference).
[0049] In an alternative embodiment of this invention, an
N-substituted amide, formaldehyde, and carbon monoxide are combined
in the presence of a catalyst (e.g., a catalyst comprising Co).
This amide is then hydrolyzed to form the N-substituted glycine.
This reaction is summarized as follows: 16
[0050] The condensation reaction forming the amide (i.e.,
"carboxymethylation") is described by Beller et al. in European
Patent Application No. 0680948. This reaction also is described in
a separate discussion by Knifton, J. F., Applied Homogeneous
Catalysis, 159-68 (B. Cornils et al. eds., VCH, Weinheim, Germany
1996) (incorporated herein by reference).
[0051] In a further embodiment of this invention, the N-substituted
glycine reactant is prepared by the reductive alkylation of glycine
achieved by combining a carbonyl compound, glycine, and H.sub.2 in
the presence of a catalyst: 17
[0052] This reaction is described by Sartori et al. in U.S. Pat.
No. 4,525,294 (incorporated herein by reference).
[0053] B. Preparation of Various N-Substituted
N-(phosphonomethyl)glycine Reactants From N-Substituted Glycine
Reactants
[0054] The N-substituted N-(phosphonomethyl)glycine reactants which
may be oxidized to form N-(phosphonomethyl)glycine and its salts
and esters in accordance with the methods of the present invention
generally have the following formula (V): 18
[0055] wherein preferably R.sup.1 and R.sup.2 are independently
selected from the group consisting of hydrogen, halogen,
--PO.sub.3R.sup.12R.sup.1- 3, --SO.sub.3R.sup.14, --NO.sub.2,
hydrocarbyl, and substituted hydrocarbyl other than
--CO.sub.2R.sup.15; and R.sup.7, R.sup.8, R.sup.9, R.sup.12,
R.sub.13, R.sup.14, and R.sup.15 are independently selected from
the group consisting of hydrogen, hydrocarbyl, substituted
hydrocarbyl, and an agronomically acceptable cation. It should be
recognized that R.sup.1 and R.sup.2 may also together form a ring.
This ring may be either a hydrocarbon ring or a heterocycle, and at
least one hydrogen on the ring may be substituted as defined below
for substituted hydrocarbyl functionalities.
[0056] In a preferred embodiment, R.sup.1 is hydrogen; R.sup.7,
R.sup.8, and R.sup.9 are hydrogen or an agronomically acceptable
cation; and R.sup.2 is a linear, branched, or cyclic hydrocarbyl
containing up to about 19 carbon atoms. In a more preferred
embodiment, R.sup.7, R.sup.8, and R.sup.9 are hydrogen or an
agronomically acceptable cation; and --CHR.sup.1R.sup.2 is selected
from the group consisting of methyl (i.e., R.sup.1 and R.sup.2 are
hydrogen), ethyl (i.e., R.sup.1 is hydrogen and R.sup.2 is
--CH.sub.3), isopropyl (i.e., R.sup.1 and R.sup.2 are each
--CH.sub.3), benzyl (i.e., R.sup.1 is hydrogen and R.sup.2 is
phenyl), and n-pentyl (i.e., R.sup.1 is hydrogen and R.sup.2 is a
4-carbon, straight-chain hydrocarbyl).
[0057] Many N-substituted N-(phosphonomethyl)glycines suitable for
use with this invention may be prepared by phosphonomethylating the
corresponding N-substituted glycines by, for example, the following
reaction: 19
[0058] Phosphonomethylation of secondary amines in general is
well-known in the art, and discussed at length in Redmore, D.,
Topics in Phosphorous Chemistry, Vol. 8, 515-85 (E. G. Griffith
& M. Grayson eds., John Wiley & Sons 1976) (incorporated
herein by reference). It is also separately discussed at length in
a chapter entitled ".alpha.-substituted Phosphonates" in Mastalerz,
P., Handbook of Organophosphorus Chemistry, 277-375 (Robert Engel
ed., Marcel Dekker 1992) (incorporated herein by reference). One
example of a secondary amine phosphonomethylation is the
phosphonomethylation of iminodiacetic acid to form PMIDA, as taught
in Baysdon et al. in U.S. Pat. No. 5,688,994 (incorporated herein
by reference).
[0059] The phosphonomethylation reaction preferably is conducted at
an elevated temperature. The preferred temperature range is from
about 100 to about 150.degree. C. The preferred time of reaction is
from about 10 to about 120 minutes, with the more preferred
reaction time being from about 20 to about 60 minutes. Preferably,
the amount of water used for the reaction is minimized to optimize
recovery of the N-substituted N-(phosphonomethyl)glycine.
[0060] The formaldehyde used in the phosphonomethylation reaction
may typically be derived from any source of formaldehyde. Suitable
sources of formaldehyde include, for example, formaldehyde itself,
formalin, and paraformaldehyde.
[0061] The phosphorous acid (H.sub.3PO.sub.3) used in the
phosphonomethylation reaction also may typically be derived from
any source of phosphorous acid. Suitable sources of phosphorous
acid include, for example, neat phosphorous acid, phosphorous
trichloride, phosphorous tribromide, phosphorous acid esters,
chlorophosphonic acid, phosphorous acid esters, chlorophosphonic
acid and esters of chlorophosphonic acid. One preferred source is
phosphorous trichloride (PCl.sub.3), which is particularly
preferred where the N-substituted glycine starting material is a
salt. When PCl.sub.3 is combined with water, the PCl.sub.3 is
hydrolyzed to form H.sub.3PO.sub.3 and 3 equivalents of HCl (the
rate of PCl.sub.3 addition preferably is determined by the rate at
which the HCl gas evolved in the reaction can be safely removed).
This hydrolysis reaction is well known in the art and is described
in, for example, G. Bettermann, W. Krause, G. Riess, and T.
Hofmann, Ullmann's Encyclopedia of Industrial Chemistry, vol. A19,
p. 527-43 (B. Elvers, S. Hawkins, & G. Schulz, eds., VCH,
Weinheim, 5th ed. 1991) (incorporated herein by reference). The
following reaction of an N-substituted glycine sodium salt
exemplifies the phosphonomethylation of an N-substituted glycine
salt reactant using PCl.sub.3: 20
[0062] wherein preferably R.sup.1 and R.sup.2 are independently
selected from the group consisting of hydrogen, halogen,
--PO.sub.3R.sup.12R.sup.1- 3, --SO.sub.3R.sup.14, --NO.sub.2,
hydrocarbyl, and substituted hydrocarbyl other than
--CO.sub.2R.sup.15; and R.sup.2, R.sup.13, R.sup.14, and R.sup.15
are selected from the group consisting of hydrogen, hydrocarbyl,
substituted hydrocarbyl, and an agronomically acceptable cation.
Other salts besides sodium salts may be used, with salts comprising
agronomically acceptable cations being preferred. Alkali metal
salts of an N-substituted glycine are especially preferred because
of the favorable cost of such salts, and because ammonium salts (a
well-known alternative salt) can potentially lead to undesirable
side reactions during phosphonomethylation.
[0063] The order of adding CH.sub.2O and PCl.sub.3 to the
N-substituted glycine salt solution is not critical (especially
where both the N-substituted glycine reactant and N-substituted
N-(phosphonomethyl)glyci- ne product are soluble in the presence of
HCl), and they may be added in the same or separate reactors (i.e.,
the "reaction zone" may comprise one or more reactors). In
addition, the CH.sub.2O may be added to the mixture before or after
the chloride salt precipitate is removed (again, especially where
both the N-substituted glycine reactant and N-substituted
N-(phosphonomethyl)glycine product are soluble in the presence of
HCl). It is often most preferred to add the CH.sub.2O after the
PCl.sub.3 has been added and the chloride salt has been
removed.
[0064] Preferably, approximately equimolar quantities of
H.sub.3PO.sub.3 and the N-substituted glycine reactant are combined
with at least an equimolar quantity of CH.sub.2O in the presence of
a strong acid having a pK.sub.a of no greater than about 1.0. The
concentration of the strong acid in the solution preferably is
greater than that of the H.sub.3PO.sub.3, and the number of moles
of CH.sub.2O added to the reaction mixture preferably is at least
10% greater than the number of moles of either the H.sub.3PO.sub.3
and the N-substituted glycine reactant, and more preferably is from
about 15 to about 25% greater. The CH.sub.2O preferably is added to
the solution over a period of from about 3 to about 20 minutes as
an aqueous solution comprising from about 37% to about 50%
CH.sub.2O, although both lesser and greater concentrations also may
be used.
[0065] In one particularly preferred embodiment of this invention,
the N-substituted glycine reactant and the resulting N-substituted
N-(phosphonomethyl)glycine phosphonomethylation product are soluble
in the presence of HCl. Such N-substituted glycines and
N-substituted N-(phosphonomethyl)glycines may be easily separated
(using, for example, any convenient filtration method) from the
NaCl or other chloride salt which precipitates after the PCl.sub.3
is added to the solution. This makes phosphonomethylation of such
compounds less difficult than phosphonomethylation of iminodiacetic
acid to PMIDA using PCl.sub.3 (as discussed above in the Background
of the Invention section, both iminodiacetic acid and PMIDA are
substantially insoluble in the presence of HCl, making salt
separation more costly). In an especially preferred embodiment, the
N-substituted glycine reactant is selected from the group
consisting of sarcosine (i.e., N-methyl glycine) and N-ethyl
glycine, with sarcosine being most preferred.
[0066] FIG. 1 schematically shows one embodiment that may be used
to prepare an N-substituted N-(phosphonomethyl)glycine by combining
an N-substituted glycine salt, CH.sub.2O, PCl.sub.3, and water. For
illustration purposes, the N-substituted glycine salt is sodium
sarcosinate (i.e., sodium N-methyl glycine). In this embodiment,
the PCl.sub.3 preferably is introduced into a hydrolyzer reactor 1
comprising a stirred aqueous mixture of CH.sub.2O and the sodium
N-methyl glycine. The resulting reaction forms HCl and an NaCl
precipitate as by-products, in addition to the desired N-methyl
N-(phosphonomethyl)glycine ("NMG"). The NaCl precipitate preferably
is removed from the mixture using, for example, a filter 2. After
the salt precipitate is removed from the solution, the NMG
preferably is precipitated by both adding a base (preferably NaOH)
to the solution and removing water from the solution (preferably
using an evaporator/crystallizer 3). It is preferred not to remove
so much water that further salt (e.g., NaCl) produced from the base
addition precipitates. The base may be added before, at the same
time, or after the water is removed. The amount of base added
preferably is the amount required to substantially neutralize the
HCl present in the solution. After the NMG precipitates, it
preferably is recovered from the solution using, for example, a
centrifuge 4. Example 18 further illustrates this
phosphonomethylation process.
[0067] It should be noted that the process may be varied widely.
For example, as noted above, the process may be conducted in a
single reaction vessel, or in two or more reaction vessels in
series so that, for example, the CH.sub.2O and PCl.sub.3 are added
to the N-substituted glycine salt solution in separate reaction
vessels. The N-substituted N-(phosphonomethyl)glycine also may, at
least in part, be precipitated by cooling the reaction mixture.
Furthermore, the process may be conducted in a batch-wise,
semi-batch-wise, or a continuous manner. In a particularly
preferred embodiment of this invention, at least a portion of the
solution (remaining after removal of the NMG) is recycled back to
the hydrolyzer reactor 1 to take advantage of any un-reacted
N-methyl glycine reactant which is still present in the solution
and to reduce the loss of un-precipitated NMG. The embodiment shown
in FIG. 1 includes such a recycle stream.
[0068] One particular embodiment of this invention is directed to
phosphonomethylating N-substituted glycine salts having the formula
(XIII): 21
[0069] wherein R.sup.1 and R.sup.2 are independently selected from
the group consisting of hydrogen, halogen,
--PO.sub.3R.sup.12R.sup.13, --SO.sub.3R.sup.14, --NO.sub.2,
hydrocarbyl, and substituted hydrocarbyl other than
--CO.sub.2R.sup.15; R.sup.6 is an agronomically acceptable cation;
R.sup.12, R.sup.13, and R.sup.14 are independently selected from
the group consisting of hydrogen, hydrocarbyl, and substituted
hydrocarbyl; and R.sup.15 is selected from the group consisting of
hydrogen, hydrocarbyl, substituted hydrocarbyl, and an
agronomically acceptable cation. In this embodiment, the salt is
converted into an N-substituted glycine free acid before being
phosphonomethylated. The free acid has the formula (XII): 22
[0070] wherein R.sup.1 and R.sup.2 are as previously defined for
the N-substituted glycine salt. This embodiment provides a means to
avoid the difficulties associated with salts of R.sup.6 that form
when N-substituted glycine salts are phosphonomethylated
directly.
[0071] One particularly preferred method for converting an
N-substituted glycine salt into the corresponding free acid
comprises neutralization of a solution comprising the salt using a
cation exchange membrane. More specifically, the solution
comprising the N-substituted glycine salt is contacted with one
side of a cation exchange membrane while the other side of the
membrane is simultaneously contacted with a solution comprising a
strong acid which is capable of neutralizing the salt. The two
solutions neutralize each other across the membrane, as shown
schematically below for a solution comprising an N-substituted
glycine sodium salt and a solution comprising an arbitrary acid
("HA"): 23
[0072] A stream comprising the N-substituted glycine free acid and
a stream comprising a sodium salt of HA are produced. To avoid
membrane fouling, the concentration of the N-substituted glycine
salt preferably is less than the solubility of the corresponding
N-substituted glycine free acid at the neutralization temperature.
In addition, the amount of acid used preferably is sufficient to
completely neutralize the N-substituted glycine salt, but does not
substantially exceed this amount. The strong acid preferably has a
pK.sub.a of no greater than about 1.0. It is particularly preferred
to use non-halogen-containing acids (e.g, methane sulfonic acid,
toluene sulfonic acid, nitric acid, sulfuric acid) to avoid
contaminating the N-substituted glycine free acid stream with
halogens in the event of a torn membrane. Reducing the risk of such
contamination is desirable due to the deleterious effect that
halogens have on the oxidization catalysts that are used following
phosphonomethylation to convert the N-substituted
N-(phosphonomethyl)glyc- ine into N-(phosphonomethyl)glycine.
[0073] Preferably, the cation exchange membrane is mechanically
stable under the reaction conditions (e.g., the membrane preferably
does not decompose temperatures of at least about 50.degree. C.),
and does not allow the N-substituted glycine salt and free acid to
leak across the membrane. Examples of suitable cation exchange
membranes are ESC7000 and Sybron MC3470 membranes available from
the Electrosynthesis Company of Lancaster, Pa.; ICE-450 membranes
from Gelman Sciences and Neosepta cation exchange membranes from
Tokoyama Soda Co. Ltd, Tokyo, Japan; Ionclad and Raipore membranes
from Pall Specialty Materials of Port Washington, N.Y.; and Nafion
117, 350, and 450 membranes produced by DuPont Corporation and
available from the Electrosynthesis Company and from Aldrich
Chemical Co., Milwaukee, Wis.. Neutralization via ion exchange
(known as "Donnan dialysis") in general is well known in the art,
and is described in, for example, K. Scott, Handbook of Industrial
Membranes at 705 (Elsevier, New York, 1995) (incorporated herein by
reference).
[0074] Electrohydrolysis is an alternative means to convert an
N-substituted glycine salt into the corresponding free acid.
Conversion of acid salts to the free acid by electrohydrolysis
(also known as "electrodialysis") is well known in the art. The
general process is described in, for example, H. P. Gregor,
Encyclopedia of Chemical Processing and Design, 17, 349-63 (J. J.
McKetta & W. A. Cunninghams, eds., Marcel Dekker, New York,
N.Y. 1983) (incorporated herein by reference). Examples of
conversion of amino acid salts to the corresponding free acids by
electrohydrolysis may be found in Kuwata et al., U.S. Pat. No.
3,330,749 (incorporated herein by reference). Electrohydrolysis is
less preferred than ion-exchange neutralization because
electrolysis tends to offer less control over the degree of
conversion of the salt to free acid.
[0075] Once the N-substituted glycine free acid has been formed by
ion exchange neutralization, electrohydrolysis, or another suitable
method, it preferably is phosphonomethylated to form an
N-substituted N-(phosphonomethyl)glycine having formula (I) or a
salt thereof: 24
[0076] wherein R.sup.1 and R.sup.2 are independently selected from
the group consisting of hydrogen, halogen,
--PO.sub.3R.sup.12R.sup.13, --SO.sub.3R.sup.14, --NO.sub.2,
hydrocarbyl, and substituted hydrocarbyl other than
--CO.sub.2R.sup.15; R.sup.12, R.sup.13, and R.sup.14 are
independently selected from the group consisting of hydrogen,
hydrocarbyl, and substituted hydrocarbyl; and R.sup.15 is selected
from the group consisting of hydrogen, hydrocarbyl, substituted
hydrocarbyl, and an agronomically acceptable cation. The
phosphonomethylation preferably is conducted by a process
comprising combining the N-substituted glycine free acid, water, a
source of CH.sub.2O, a strong acid having a pK.sub.a of no greater
than about 1.0, and a source of H.sub.3PO.sub.3. The source of
H.sub.3PO.sub.3 may be PCl.sub.31 which, for example, may be added
directly into a solution comprising the N-substituted glycine free
acid. Alternatively, the source of H.sub.3PO.sub.3 may be, for
example, free of halogens, with neat H.sub.3PO.sub.3 or an aqueous
solution comprising H.sub.3PO.sub.3 being especially preferred. A
solution comprising H.sub.3PO.sub.3 may be obtained by, for
example, hydrolysis of alkyl phosphites, followed by distillation
of the alcohols. In a particularly preferred embodiment, the
solution is formed by hydrolyzing PCl.sub.3 in water in a vessel
separate from the solution comprising the N-substituted glycine
free acid. Although, about 3 equivalents of HCl are formed when
PCl.sub.3 hydrolyzes, substantially all the HCl goes into the gas
phase and therefore may be readily separated from the hydrolysis
reaction mixture. The HCl gas may then be combined with water to
form an aqueous HCl solution. Thus, two solutions may be formed
with little difficulty: (1) an HCl-containing solution, and (2) an
H.sub.3PO.sub.3-containing solution having a low halogen (i.e.,
chloride) concentration. The HCl solution may, in turn, be used as
the source of acid for the ion-exchange neutralization of
N-substituted glycine salt solutions.
[0077] If the source of H.sub.3PO.sub.3 is free of halogens, it is
particularly preferable for the source of acid for the
phosphonomethylation reaction to also be free of halogens. In this
instance, H.sub.2SO.sub.4 is especially preferred. As noted above,
use of such halogen-free acid sources is desirable due to the
deleterious effect that halogens have on the oxidization catalysts
that are used following phosphonomethylation to convert the
N-substituted N-(phosphonomethyl)glyc- ine reactant into
N-(phosphonom
[0078] In general, at the conclusion of a phosphonomethylation
reaction, it is preferable to neutralize the strong acid.
Neutralization typically aids in the recovery of the N-substituted
N-(phosphonomethyl)glycine. Neutralization also tends to reduce the
problems associated with the presence of strong acids when the
N-substituted N-(phosphonomethyl)glycin- es are used to synthesize
N-(phosphonomethyl)glycine, a salt of N-(phosphonomethyl)glycine,
or an ester of N-(phosphonomethyl)glycine; strong acids tend to
inhibit the oxidation of N-substituted N-(phosphonomethyl)glycines
to N-(phosphonomethyl)glycine.
[0079] In a preferred embodiment, the phosphonomethylation reaction
mixture is neutralized by using the strong acid present in the
mixture as the source of acid to convert (via the cation exchange
membrane process discussed above) an N-substituted glycine salt
into an N-substituted glycine free acid for subsequent use as a
starting material in the phosphonomethylation reaction. In this
case, the phosphonomethylation reaction mixture is contacted with
one side of the cation exchange membrane while the other side of
the membrane is simultaneously contacted with a solution comprising
the N-substituted glycine salt: 25
[0080] Example 29 further illustrates this embodiment.
[0081] Alternatively, the phosphonomethylation reaction mixture may
be neutralized by simply adding a base to the reaction mixture
after the phosphonomethylation reaction is substantially complete.
In this embodiment, if an N-substituted glycine free acid is used
as the starting material for the phosphonomethylation, NaOH is
typically the preferred base for the neutralization. On the other
hand, if an N-substituted glycine salt is used as the staring
material, the generally preferred base is the hydroxide of the same
cation as in the N-substituted glycine salt. For example, if sodium
N-substituted glycinate is used, NaOH would be the preferred
base.
[0082] The above processes for neutralizing the
phosphonomethylation reaction mixture also may be combined. Use of
such a combination is preferred when the degree of neutralization
achieved by the cation exchange membrane process is less than that
required to substantially neutralize all the strong acid in the
mixture. In this instance, sufficient base preferably is added to
substantially neutralize the strong acid following completion of
the cation exchange membrane neutralization process.
[0083] Under many circumstances, it is preferred to recover the
N-substituted N-(phosphonomethyl)glycine as a solid following the
phosphonomethylation. This may be achieved, for example, by forming
a reaction mixture containing a supersaturated concentration of the
N-substituted N-(phosphonomethyl)glycine (either during
phosphonomethylation or after phosphonomethylation) so that the
N-substituted N-(phosphonomethyl)glycine will precipitate. Use of
such an embodiment is especially preferred when the N-substituted
N-(phosphonomethyl)glycine precipitates readily at supersaturated
conditions, such as N-methyl N-(phosphonomethyl)glycine. This
supersaturation may be achieved by, for example, (1) using a high
concentration of the N-substituted glycine reactant (and adding the
source of CH.sub.2O after any halogen-containing salt precipitate
has been removed); or (2) removing water from the reaction mixture,
adding base to the reaction mixture, and/or lowering the
temperature of the reaction mixture following the
phosphonomethylation and removal of any halogen-containing salt
precipitate. Precipitating the N-substituted
N-(phosphonomethyl)glycine is often particularly preferable when
conducting the phosphonomethylation in a continuous reaction
system, which reduces the need for a neutralization step to recover
the N-substituted N-(phosphonomethyl)glycine. In this instance, the
N-substituted N-(phosphonomethyl)glycine preferably is filtered
from the reaction mixture as it precipitates, and the filtrate is
returned to the phosphonomethylation reactor. In such a system,
preferably a portion of the water in the reaction mixture is
removed; this allows a constant volume to be maintained in the
phosphonomethylation reaction zone. This removal may be conducted
via, for example, evaporation following filtration of the
N-substituted N-(phosphonomethyl)glycine. In an especially
preferred embodiment, however, at least a portion of the water is
removed (e.g., by evaporation) from the reaction mixture before
filtration to cause a greater amount of N-substituted
N-(phosphonomethyl)glycine to precipitate.
[0084] In some circumstances, it is less preferred to recover the
N-substituted N-(phosphonomethyl)glycine as a solid following
phosphonomethylation. Unlike NMG, some N-substituted
N-(phosphonomethyl)glycine reactants (e.g., N-isopropyl
N-(phosphonomethyl)glycine) do not precipitate readily, even at
supersaturated conditions. In these cases, it is often preferable
to neutralize the phosphonomethylation reaction mixture and perform
the subsequent catalytic oxidation directly on the neutralized
mixture without isolation of the N-substituted
N-(phosphonomethyl)glycine reactant as a solid. Under such an
approach, it is desirable for the reaction mixture to be free of
halogens because, as noted above, halogens tend to have a
deleterious effect on the noble metal catalysts used to oxidize the
N-substituted N-(phosphonomethyl)glycine reactants. Thus, in such
situations, the phosphonomethylation reaction preferably uses a
source of H.sub.3PO.sub.3 which, in contrast to PCl.sub.3, does not
contain halogens. Likewise, it is preferred to use an acid during
the phosphonomethylation reaction which does not contain halogens
(H.sub.2SO.sub.4 being especially preferred).
[0085] It should be noted that the above phosphonomethylation
methods are not the only processes by which N-substituted
N-(phosphonomethyl)glycine reactants may be obtained. For example,
NMG is produced as an undesirable byproduct from the
carbon-catalyzed oxidation of PMIDA.
[0086] C. Preparation of N-(phosphonomethyl)glycine and its salts
and esters by oxidizing N-Substituted N-(phosphonomethyl)glycine
reactants
[0087] N-(phosphonomethyl)glycine and its salts and esters are
prepared in accordance with this invention by oxidizing
N-substituted N-(phosphonomethyl)glycine reactants. This oxidation
is normally a heterogenous catalysis reaction. Preferably, a
solution containing an N-substituted N-(phosphonomethyl)glycine
reactant is introduced into a reactor along with an
oxygen-containing gas or a liquid comprising dissolved oxygen. In
the presence of a noble metal catalyst (i.e., a catalyst comprising
a noble metal), the N-substituted N-(phosphonomethyl)glycine
reactant is oxidatively converted into N-(phosphonomethyl)glycine
and various byproducts: 26
[0088] wherein preferably R.sup.1 and R.sup.2 are independently
selected from the group consisting of hydrogen, halogen,
--PO.sub.3R.sup.12R.sup.1- 3, --SO.sub.3R.sup.14, --NO.sub.2,
hydrocarbyl, and substituted hydrocarbyl other than
--CO.sub.2R.sup.15; and R.sup.3, R.sup.4, R.sup.5, R.sup.7,
R.sup.8, R.sup.9, R.sup.12, R.sup.13, R.sup.14, and R.sup.15 are
independently selected from the group consisting of hydrogen,
hydrocarbyl, substituted hydrocarbyl, and an agronomically
acceptable cation. Preferably, the catalyst subsequently is
separated by filtration and the N-(phosphonomethyl)glycine then is
isolated by precipitation, for example, evaporation of a portion of
the water and cooling.
[0089] The noble metal catalyst preferably comprises a noble metal
selected from the group consisting of platinum (Pt), palladium
(Pd), rhodium (Rh), iridium (Ir), osmium (Os), and gold (Au). In
general, platinum and palladium are more preferred, with platinum
being most preferred. Because platinum is most preferred, much of
the following discussion will be directed to the use of platinum.
It should be understood, however, that the same discussion is
generally applicable to the other noble metals and combinations
thereof.
[0090] The noble metal catalyst may be unsupported, e.g., platinum
black, commercially available from various sources such as Aldrich
Chemical Co. (Milwaukee, Wis.), Engelhard Corp. (Iselin, N.J.), and
Degussa Corp. (Ridgefield Park, N.J.).
[0091] Alternatively, the catalyst may comprise a noble metal on
the surface of a support, such as carbon, alumina
(Al.sub.2O.sub.3), silica (SiO.sub.2), titania (TiO.sub.2),
zirconia (ZrO.sub.2), siloxane, or barium sulfate (BaSO.sub.4).
Supported metals are common in the art and may be commercially
obtained from various sources, e.g., 5% platinum on activated
carbon, Aldrich Catalogue No. 20,593-1; platinum on alumina powder,
Aldrich Catalogue No. 31,132-4; palladium on barium sulfate
(reduced), Aldrich Catalogue No. 27,799-1; and 5% palladium on
activated carbon, Aldrich Catalogue No. 20,568-0. A catalyst
comprising a noble metal on a support also may be prepared by
depositing the noble metal onto the surface of the support using
any of the various methods well-known in the art. Such methods
include liquid phase methods such as reaction deposition techniques
(e.g., deposition via reduction of noble metal compounds, and
deposition via hydrolysis of noble metal compounds), ion exchange
techniques, excess solution impregnation, and incipient wetness
impregnation; vapor phase methods such as physical deposition and
chemical deposition; precipitation; electrochemical deposition; and
electroless deposition. Metal deposition methods are described, for
example, in Cameron, D. S., Cooper, S. J., Dodgson, I. L.,
Harrison, B., and Jenkins, J. W. "Carbons as Supports for Precious
Metal Catalysts," Catalysis Today, 7, 113-137 (1990) (incorporated
herein by reference). Metal deposition methods also are described
in a separate discussion in Stiles, A. B., Catalyst Supports and
Supported Catalysts, Theoretical and Applied Concepts
(Butterworths, Boston, Mass. 1987) (incorporated herein by
reference). A further separate discussion of various methods for
depositing metals onto support surfaces may be found in a chapter
by R. L. Moss in Experimental Methods in Catalytic Research, Vol.
2, Ch. 2, pp. 43-94 (R. B. Anderson & P. T. Dawson, eds.,
Academic Press, New York, N.Y. 1976) (incorporated herein by
reference).
[0092] If a carbon support is used, the support preferably is
graphitic (such supports tend to have greater
N-(phosphonomethyl)glycine selectivity) or has a surface which was
oxidized with a strong oxidizing agent before the noble metal was
deposited onto the surface. As to the latter type, oxidation of the
support may be carried out, for example, by immersing the support
in a boiling solution comprising H.sub.2O.sub.2. Preferably, at
least about 10 wt % (i.e., 10% by weight) of the solution is
H.sub.2O.sub.2. More preferably, at least about 20 wt % of the
solution is H.sub.2O.sub.2, and even more preferably, at least
about 30 wt % of the solution is H.sub.2O.sub.2. The support
preferably is immersed in the boiling solution for at least about
15 min., more preferably at least about 30 min., and even more
preferably at least about 60 min.
[0093] In another particularly preferred embodiment of this
invention, the noble metal is supported on a polymeric support
(i.e., a support comprising a polymer). The polymeric support
preferably is mechanically stable (e.g., the polymer preferably
remains hard and is resistant to attrition, thermal degradation,
hydrolysis, and acid attack) under the reaction conditions. In
addition, the polymer preferably is in the form of cross-linked
beads which allow the catalyst to be easily handled, dispersed in
the reaction mixture, and filtered following the reaction.
Preferably, the beads are porous and have a surface area of at
least about 10 m.sup.2/g, with the noble metal being well-dispersed
on the surface. In one particularly preferred embodiment, the
polymer also is basic (i.e., the polymer preferably is capable of
being protonated by an acidic noble metal compound), so that it may
be readily impregnated with a noble metal (e.g., platinum) using an
acidic noble metal compound (e.g., H.sub.2PtCl.sub.6). Various
polyamides, polyimides, polycarbonates, polyureas, and polyesters
may be used as the polymer. Preferably, the polymer is selected
from the group consisting of polyethylene imine, salts of
polyacrilic acid, polystyrene, polyaminostyrene, polystyrene
substituted with dimethylamine groups, sulfonated polystyrene, and
polyvinyl pyridine ("PVP"). More preferably, the polymer is
selected from the group consisting of PVP and sulfonated
polystyrene. In some embodiments, PVP is most preferred.
[0094] The noble metal may be deposited onto the polymer support
using any of the various well-known methods for depositing a noble
metal onto the surface of a support (see above). In a particularly
preferred embodiment, the noble metal is platinum and is deposited
onto the surface of the support using a solution comprising
H.sub.2PtCl.sub.6. After the noble metal is deposited onto the
support, the support and noble metal preferably are treated with a
reducing environment, preferably an aqueous solution comprising
sodium borohydride. Examples 20 and 22 further illustrate this
method.
[0095] The concentration of the noble metal on the surface of a
support may vary within wide limits. Preferably it is in the range
of from about 0.5 to about 20 wt % ([mass of noble metal.div.total
mass of catalyst].times. 100%), more preferably from about 3 to
about 15 wt., and even more preferably from about 5 to about 10 wt
%. At concentrations greater than about 20 wt %, layers and clumps
of noble metal tend to form. Thus, there are fewer surface noble
metal atoms per total amount of noble metal used. This tends to
reduce the activity of the catalyst and is an uneconomical use of
the costly noble metal.
[0096] The weight ratio of the noble metal to the N-substituted
N-(phosphonomethyl)glycine reactant in the reaction mixture
preferably is from about 1:500 to about 1:5. More preferably, the
ratio is from about 1:200 to about 1:10, and even more preferably
from about 1:50 to about 1:10.
[0097] In a preferred embodiment of this invention, the catalyst
may comprise a noble metal and a promoter. The promoter may be on
the surface of an unsupported noble metal, or on the surface of the
noble metal and/or its support in the case of a supported noble
metal catalyst. Noble metal catalysts comprising a promoter often
tend to exhibit increased selectivity over noble metal catalysts
consisting of a noble metal without a promoter. Preferably, the
promoter comprises a metal selected from the group consisting of
aluminum (Al), .ruthenium (Ru), osmium (Os), indium (In), gallium
(Ga), tantalum (Ta), tin (Sn), and antimony (Sb). More preferably,
the promoter comprises a metal selected from the group consisting
of gallium, indium, ruthenium, and osmium.
[0098] Although a promoter may come from various sources (e.g., the
catalyst may comprise a support which naturally contains a
promoter), it typically is added to the surface of the noble metal
(it should be recognized that if the catalyst comprises a support,
the promoter typically is added to the surface of the noble metal,
the surface of the support, or both). Methods used to deposit the
promoter are generally known in the art, and include the same
methods which may be used to deposit a noble metal onto a support
discussed above. In a particularly preferred embodiment, a solution
of a halogen compound of the promoter is used to deposit the
promoter by stirring the catalyst in the solution. Examples of
suitable halogen compounds that may be used to deposit promoters
include: for indium, InBr.sub.3; for gallium, GaBr.sub.3; for iron,
FeCl.sub.3.multidot.6H.sub.2O; and for tin,
SnCl.sub.2.multidot.2H.- sub.2O. Example 25 demonstrates the
deposition of a promoter using a solution comprising a halogen
compound of the promoter.
[0099] The amount of promoter used (whether associated with the
noble metal, a support on which the noble metal is deposited, or
both) may vary within wide limits, depending in part on the
promoter used. Preferably, the weight percentage of the promoter is
at least about 0.05% ([mass of promoter.div.total mass of the
catalyst].times.100%). In one preferred embodiment, the promoter is
added to the catalyst by exposing the catalyst precursor to an
excess of the promoter so that the maximum amount of promoter is
deposited onto the surface of the catalyst.
[0100] In another preferred embodiment of this invention, the noble
metal catalyst comprises an electroactive molecular species (i.e.,
a molecular species that may be reversibly oxidized or reduced by
electron transfer). Preferably, this electroactive molecular
species is on the surface of the noble metal (if the catalyst
comprises a support, the electroactive molecular species preferably
is on the surface of the noble metal, the surface of the support,
or both). It has been discovered in accordance with this invention
that selectivity and/or conversion of the noble metal catalyst may
be improved by the presence of the electroactive molecular species,
particularly where the catalyst is being used to effect the
oxidation of NMG to form N-(phosphonomethyl)glycine. In this
instance, the electroactive molecular species preferably is
hydrophobic and has an oxidation potential (E.sub.1/2) of at least
about 0.3 volts vs. SCE (saturated calomel electrode).
[0101] Electroactive molecular species also are useful in the
context of the oxidation of N-isopropyl N-(phosphonomethyl)glycine
to form N-(phosphonomethyl)glycine. In that context, it is
especially preferable for the catalyst to comprise a noble metal
and an electroactive molecular species on a graphitic carbon
support. In the presence of the graphitic or oxidized activated
carbon support, the electroactive molecular species has been found
in accordance with this invention to increase the
N-(phosphonomethyl)glycine selectivity of the noble metal
catalyst.
[0102] Examples of generally suitable electroactive molecular
species include triphenylmethane; N-hydroxyphthalimide;
5,10,15,20-tetrakis(penta- fluorophenyl)-21H,23H-porphine iron
(III) chloride (abbreviated "Fe(III)TPFPP chloride");
2,4,7-trichlorofluorene; triarylamines, such as
N,N'-bis(3-methylphenyl)-N,N'-diphenyl benzidine (sometimes
referred to as "TPD") and tris(4-bromophenyl)amine;
2,2,6,6-tetramethyl piperidine N-oxide (sometimes referred to as
"TEMPO"); 5,10,15,20-tetraphenyl-21H,23- H-porphine iron(III)
chloride (sometimes referred to as "Fe(III)TPP chloride");
4,4'-difluorobenzophenone; 5,10,15,20-tetraphenyl-21H,23H porphine
nickel(II) (sometimes referred to as "Ni(II) TPP"); and
phenothiazine. When the noble metal catalyst is being used to
catalyze the oxidation of NMG to N-(phosphonomethyl)glycine, the
particularly preferred electroactive molecular species are
triarylamines; N-hydroxyphthalimide; TEMPO; Fe(III)TPP chloride;
and Ni(II) TPP. In many embodiments, triarylamines (especially TPD)
are the most preferred electroactive molecular species. For
example, at reaction temperatures greater than about 130.degree.
C., the most preferred electroactive molecular species is TPD.
[0103] The oxidation potentials for electroactive molecular species
may be found in the literature. A compilation showing the oxidation
potential and reversibility for a large number of electroactive
molecular species may be found in Encyclopedia of Electrochemistry
of the Elements (A. Bard and H. Lund eds., Marcel Dekker, New York,
publication dates vary between volumes) (incorporated herein by
reference). For example, the oxidation potential for
triphenylmethane may be found in Perichon, J., Herlem, M.,
Bobilliart, F., and Thiebault, A., Encyclopedia of Electrochemistry
of the Elements, vol. 11, p. 163 (A. Bard and H. Lund eds., Marcel
Dekker, New York, N.Y. 1978)). Other sources for oxidation
potentials include, for example, the following:
[0104] 1. The oxidation potential for N-hydroxyphthalimide may be
found in Masui, M., Ueshima, T. Ozaki, S., J. Chem. Soc. Chem.
Commun., 479-80 (1983) (incorporated herein by reference).
[0105] 2. The oxidation potential for triarylamines may be found in
Dapperheld, S., Steckhan, E., Brinkhaus, K., Chem. Ber., 124,
2557-67 (1991) (incorporated herein by reference). A separate
source for the oxidation potential for triarylamines is Koene, B.
E., Loy, D. E., and Thompson, M. E., Chem Mater., 10, 2235-50
(1998) (incorporated herein by reference).
[0106] 3. The oxidation potential for 2,2,6,6-tetramethyl
piperidine N-oxide may be found in Semmelhack, M., Chou, C., and
Cortes, D., J. Am. Chem. Soc., 105, 4492-4 (1983);
[0107] 4. The oxidation potential for
5,10,15,20-tetrakis(pentafluoropheny- l)-21H,23H-porphine iron
(III) chloride may be found in Dolphin, D., Traylor, T., and Xie,
L., Acc. Chem. Res., 30, 251-9 (1997) (incorporated herein by
reference).
[0108] 5. The oxidation potentials for various porphyrins may be
found in Fuhrhop, J. H., Porphyrins and Metalloporphyrins 593 (K.
Smith, ed., Elsevier, New York, 1975) (incorporated herein by
reference).
[0109] 6. The oxidation potential for phenothiazine may be found in
D. Alagli, G. Bazan, M. Wrighton, and R. Schrock, J. Am. Chem.
Soc., 114, 4150-58 (1992) (incorporated herein by reference).
[0110] An electroactive molecular species may be deposited onto the
noble metal catalyst before the catalyst is added to the oxidation
reaction mixture. Various methods generally known in the art may be
used for this deposition. For example, the electroactive molecular
species may be adsorbed onto the catalyst using liquid phase
deposition or gas phase deposition. Example 8 illustrates using
liquid phase deposition to deposit the electroactive molecular
species.
[0111] Alternatively, the electroactive molecular species may be
added directly to the oxidation reaction mixture separately from
the noble metal catalyst. For example, 2,2,6,6-tetramethyl
piperidine N-oxide ("TEMPO") may be added to the reaction mixture
without first being deposited onto the noble metal catalyst, as
illustrated in Example 13. Without being bound by any particular
theory, it is believed that in such an embodiment, the
electroactive molecular species deposits onto the noble metal
catalyst while in the reaction mixture.
[0112] The concentration of N-substituted
N-(phosphonomethyl)glycine reactant initially in the reaction
medium may vary widely. Typically, the concentration is from about
1 to about 80 wt % ([mass of N-substituted
N-(phosphonomethyl)glycine reactant.div.total reaction
mass].times.100%). More preferably, the concentration is from about
5 to about 50 wt %, and still more preferably from about 20 to
about 40 wt %.
[0113] The oxygen source for the oxidation reaction may be, for
example, any oxygen-containing gas or a liquid comprising dissolved
oxygen. Preferably, the oxygen source is an oxygen-containing gas.
As used herein, an "oxygen-containing gas" is any gaseous mixture
comprising molecular oxygen which optionally may comprise one or
more diluents which are non-reactive with the oxygen, the reactant,
and the product under the reaction conditions. Examples of such
gases include air, pure molecular oxygen, or molecular oxygen
diluted with helium, argon, neon, nitrogen, or other non-molecular
oxygen-containing gases. Preferably, at least about 20% by volume
of the oxygen-containing gas is molecular oxygen, and more
preferably, at least about 50% of the oxygen-containing gas is
molecular oxygen.
[0114] The oxygen preferably is fed into the reaction mixture at a
rate which is sufficient to maintain the dissolved oxygen
concentration at a finite level. At reaction temperatures of about
125.degree. C. or below, the oxygen is fed at a rate sufficient to
maintain the dissolved oxygen concentration at no greater than
about 2.0 ppm, but at a high enough concentration to sustain the
desired reaction rate.
[0115] The oxygen may be introduced by any convenient means into
the reaction medium in a manner which maintains the dissolved
oxygen concentration in the reaction mixture at the desired level.
If an oxygen-containing gas is used, it preferably is introduced
into the reaction medium in a manner which maximizes the contact of
the gas with the reaction solution. Such contact may be obtained,
for example, by dispersing the gas through a diffuser such as a
porous glass or metal frit (preferably having pores which are no
greater than about 20 .mu.m in their largest dimension, and more
preferably no greater than about 1 .mu.m in their largest
dimension), while shaking or stirring the reactor contents to
improve liquid-gas contact and dissolution of the oxygen. Less
preferred, although suitable, alternative methods for introducing
the oxygen include, for example (1) introducing oxygen into the
headspace of the reactor and then drawing it into the reaction
mixture using a vortex created by an impeller (this method is
sometimes described as a back-mixed operation); or (2) passing the
oxygen through a tubular reactor packed with catalyst through which
the reaction medium also passes.
[0116] It has been discovered in accordance with this invention
that an excessive amount of oxygen-containing gas bubbles (i.e.,
undissolved oxygen) can reduce the selectivity of the reaction.
Thus, it is preferable to minimize the amount of undissolved oxygen
in the solution, and particularly preferable to minimize the amount
of undissolved oxygen which comes into contact with the noble metal
catalyst. One way to achieve this is to introduced the oxygen
through a membrane which is in contact with the solution. The use
of membranes for bubble-free gas transfer is discussed generally
in, for example, Semmens, M. J. and Gantzer, C. J., in FED Vol.
187, Aeration Technology, Book No. G00865, pp. 51-8 (R.E.A. Arndt
and A. Prosperetti, eds., 1994) (incorporated herein by reference).
The membrane preferably is stable (i.e., does not decompose) under
the reaction conditions.
[0117] In a particularly preferred embodiment, the reaction is
conducted in a stirred-tank reactor employing a rotating impeller
and having oxygen-containing gas bubbles introduced into the
reaction solution below the upper surface of the solution. To avoid
(or at least diminish) the reduction in selectivity due to the
oxygen-containing bubbles, the impeller speed preferably is no
greater than the speed necessary to prevent the oxygen-containing
bubbles from rising directly to the surface of the solution upon
their introduction into the solution. Alternatively,
oxygen-containing bubbles may be introduced into the solution at a
distance from the impeller such that the essentially no bubbles
enter the region of the reactor through which the impeller passes,
and more preferably such that no bubbles enter the region through
which the impeller passes. For example, the oxygen may be
introduced just below the upper surface of the liquid and well
above the impeller, thereby allowing the bubbles to escape into the
headspace rather than forming a gas/liquid turbulent zone around
the impeller. Example 27 further illustrates introducing oxygen
into a stirred-tank reactor just below the surface of the reaction
solution.
[0118] The adverse effects of undissolved oxygen also may often be
avoided or diminished by introducing oxygen into the reaction
mixture in a manner such that no greater than about 10% by volume
of the reaction mixture consists of undissolved oxygen. In a more
preferred embodiment, no greater than about 4% by volume of the
reaction mixture consists of undissolved oxygen, and most
preferably, no greater than about 1% by volume of the reaction
mixture consists of undissolved oxygen.
[0119] The adverse effects of undissolved oxygen in the reaction
solution also may often be avoided or diminished by using a noble
metal catalyst comprising an electroactive molecular species, as
described above. The presence of an electroactive molecular species
(particularly N,N'-bis-(3-methylphenyl)-N-N'-diphenyl benzidine)
has been found to be especially beneficial for the oxidation of NMG
to N-(phosphonomethyl)glyc- ine. Example 27 further illustrates the
use of N,N'-bis-(3-methylphenyl)-N- -N'-diphenyl benzidine to
reduce the adverse effects of undissolved oxygen.
[0120] Preferably, the oxidation reaction is conducted at a
temperature of from about 50 to about 200.degree. C. More
preferably, the reaction is conducted at a temperature of from
about 100 to about 190.degree. C., and still more preferably from
about 125 to about 160.degree. C.
[0121] The pressure in the reactor during the oxidation depends, in
part, on the temperature used. Preferably, the pressure is
sufficient to prevent the reaction mixture from boiling. If an
oxygen-containing gas is used as the oxygen source, the pressure
also preferably is adequate to cause the oxygen to dissolve into
the reaction mixture at a rate sufficient to sustain the desired
rate of reaction. The pressure preferably is at least equal to
atmospheric pressure. Preferably, the oxygen partial pressure is
from about 5 to about 500 psig. More preferably, when the
temperature is in the range of from about 125 to about 160.degree.
C., the oxygen partial pressure is from about 50 to about 200
psig.
[0122] The oxidation reaction may be carried out using a wide
variety of batch, semi-batch, or continuous reactor systems. Such
systems may also include recycling a residual solution remaining
after at least a portion of the N-(phosphonomethyl)glycine product
has been removed from the reaction product mixture. Recycling the
residual solution allows any unreacted N-substituted
N-(phosphonomethyl)glycine reactant to be utilized and enhances
recovery of any un-precipitated N-(phosphonomethyl)glycine product
in the reaction product mixture.
[0123] In one embodiment of this invention for continuous systems,
only a portion of the residual solution is recycled; the rest is
purged. This embodiment is particularly useful for reaction systems
in which a contaminant is present in the residual solution. Such a
contaminant may, for example, be a salt byproduct which is formed
when a strong acid is neutralized following the
phosphonomethylation of an N-substituted glycine reactant. If the
entire residual solution is recycled back to the oxidation reaction
zone, the salt contaminant concentration in the reaction mixture
will build up over time. Ultimately, the build up will result in
the formation of a salt precipitate which will contaminate the
N-(phosphonomethyl)glycine product. To reduce the rate of
contaminant build up, a portion of the residual solution may be
purged (this purged portion is sometimes referred to as the "waste
solution"). The remaining portion (sometimes referred to as the
"recycle solution") is recycled back to the oxidation reaction
zone. The purging may be achieved by, for example, pressurizing the
residual solution and contacting it with a membrane which
selectively passes the contaminant to form the waste solution while
retaining the N-substituted N-(phosphonomethyl)glycine reactant and
the unprecipitated N-(phosphonomethyl)glycine product to form the
recycle solution. Because the membrane selectively passes the
contaminant and retains the N-substituted
N-(phosphonomethyl)glycine reactant and unprecipitated
N-(phosphonomethyl)glycine product, the waste solution (also called
"the permeate") contains a greater concentration of the contaminant
and a lower concentration of the N-substituted
N-(phosphonomethyl)glycine reactant and unprecipitated
N-(phosphonomethyl)glycine reactant than the recycle solution.
Preferably, the membrane has a molecular weight cutoff of less than
about 1,000 daltons and is mechanically stable under the reaction
conditions. Examples of suitable commercially available membranes
include the SelRO membranes, MPF-34 and MPF-36, available from LCI
Corporation (Charlotte, N.C.). This embodiment is further described
in Example 30.
[0124] In another embodiment of this invention, the oxidation
reaction is discontinued before complete conversion of the
N-substituted N-(phosphonomethyl)glycine reactant is obtained. It
has been discovered in accordance with this invention that the
activity and selectivity of the catalyst tends to decline as the
oxidation reaction nears completion. It has further been
discovered, however, that because many N-substituted
N-(phosphonomethyl)glycine reactants (including NMG and N-isopropyl
N-(phosphonomethyl)glycine) are more soluble than
N-(phosphonomethyl)glyc- ine itself (or salts thereof or esters
thereof), the decline in activity and selectivity can be overcome
by removing the N-(phosphonomethyl)glycin- e, the salt of
N-(phosphonomethyl)glycine, or the ester of
N-(phosphonomethyl)glycine before the oxidation is complete. This
may be achieved by, for example, removing the catalyst (by, for
example, filtration), evaporating a portion of the water in the
reaction mixture, and cooling the reaction mixture before there has
been less-than-complete conversion. The evaporation and cooling
steps precipitate much of the N-(phosphonomethyl)glycine product in
the solution, thereby allowing the N-(phosphonomethyl)glycine
product to be removed from the reaction solution. The residual
solution comprising the un-reacted N-substituted
N-(phosphonomethyl)glycine is then recycled back to the oxidation
reactor.
[0125] Preferably, the N-(phosphonomethyl)glycine is precipitated
and removed when from about 20 to about 95% of the N-substituted
N-(phosphonomethyl)glycine has been consumed. More preferably, the
N-(phosphonomethyl)glycine is precipitated and removed when from
about 50 to about 90% of the N-substituted
N-(phosphonomethyl)glycine has been consumed, even more preferably
when from about 50 to about 80% of the N-substituted
N-(phosphonomethyl)glycine has been consumed, and most preferably
when from about 50 to about 70% of the N-substituted
N-(phosphonomethyl)glycine has been consumed. Lower conversions
lead to undesirably high recycle rates, whereas greater conversions
(as discussed above) are associated with poor catalyst activity and
reduced selectivity.
[0126] A suitable reaction system employing this embodiment is
shown schematically in FIG. 2, where, for illustration purposes,
the N-substituted N-(phosphonomethyl)glycine reactant is NMG. An
aqueous solution of NMG is combined with a heterogeneous noble
metal catalyst and heated in the presence of oxygen in an oxidation
reactor 1 until the desired conversion (described above) to
N-(phosphonomethyl)glycine is achieved. When the desired conversion
is achieved, the catalyst is removed by, for example, filtration or
centrifugation, and the filtrate is partially evaporated in an
evaporator 2 to precipitate at least a portion of the
N-(phosphonomethyl)glycine product. The N-(phosphonomethyl)glycine
precipitate is then separated from the filtrate by, for example,
centrifugation in a centrifuge 3 to recover the
N-(phosphonomethyl)glycine and form a second filtrate, which then
may be again combined with the noble metal catalyst in the presence
of oxygen in the oxidation reactor 1 to continue the oxidation
reaction of the NMG still remaining in the second filtrate. In a
continuous process, preferably only a portion of the filtrate is
fed back into the oxidation reactor; the remaining portion is
purged from the system to maintain purity in the reaction
system.
[0127] A particularly useful method for the production of
N-(phosphonomethyl)glycine or a salt thereof involves recycling the
ketone which is produced as a by-product when an N-substituted
N-(phosphonomethyl)glycine reactant, having a secondary alkyl group
as its substituent, is oxidized: 27
[0128] wherein preferably R.sup.1 and R.sup.2 are independently
selected from the group consisting of hydrocarbyl and substituted
hydrocarbyl other than --CO.sub.2R.sup.15; R.sup.3, R.sup.4,
R.sup.5, R.sup.7, R.sup.8, R.sup.9 and R.sup.15 are independently
selected from the group consisting of hydrogen, hydrocarbyl,
substituted hydrocarbyl, and an agronomically acceptable cation. In
this embodiment, the ketone by-product is used as a starting
material to further synthesize an N-substituted glycine reactant,
which in turn may be phosphonomethylated and then oxidized to form
N-(phosphonomethyl)glycine or a salt thereof. Numerous well-known
N-substituted glycine synthesis pathways that use ketones as
starting materials may be used for this purpose. Typically, the
ketone is coupled to an amine by reductive alkylation or reductive
amination, a reaction which is well-known in the art. See,
generally, A. Streitwieser, Jr. and C. H. Heathcock, Introduction
to Organic Chemistry, 748 (Macmillan, New York, N.Y., 2nd ed. 1981)
(incorporated herein by reference).
[0129] In a preferred embodiment of this invention, the ketone is
used as a starting material to form the corresponding N-substituted
glycine reactant by a reductive alkylation of glycine over a noble
metal catalyst, preferably platinum or palladium: 28
[0130] wherein preferably R.sup.1 and R.sup.2 are independently
selected from the group consisting of hydrocarbyl and substituted
hydrocarbyl other than --CO.sub.2R.sup.5; and R.sup.15 is selected
from the group consisting of hydrogen, hydrocarbyl, substituted
hydrocarbyl, and an agronomically acceptable cation. This reaction
is described, for example, in Sartori et al., U.S. Pat. No.
4,525,294 (incorporated herein by reference).
[0131] In a particularly preferred embodiment of this invention,
the ketone is reacted with H.sub.2 and ammonia in the presence of a
metal-containing catalyst to form a primary amine. This primary
amine may be converted into an N-substituted glycine by any of the
several methods known in the art. Many of these methods are
described in Dyker, G. Angewandte Chimie Int'l Ed. in English, Vol.
36, No. 16, 1700-2 (1997) (incorporated herein by reference). Two
particularly useful methods are: (1) the Strecker reaction
(described above), in which the primary amine is reacted with an
aqueous solution of CH.sub.2O and HCN, followed by hydrolysis; and
(2) the Wakamatsu reaction, in which the amine is first converted
into the corresponding amide, and then reacted with CH.sub.2O and
CO over a cobalt or palladium catalyst, followed by hydrolysis.
[0132] In a further particularly preferred embodiment of this
invention, the ketone is reacted with monoethanolamine and H.sub.2
over a solid metal-containing catalyst to form the N-substituted
monoethanolamine, which may be converted into a salt of the
corresponding N-substituted glycine by combining it with a strong
base (preferably NaOH) over a solid copper-containing catalyst:
29
[0133] wherein preferably R.sup.1 and R.sup.2 are independently
selected from the group consisting of hydrocarbyl and substituted
hydrocarbyl other than --CO.sub.2R.sup.15; and R.sup.15 is selected
from the group consisting of hydrogen, hydrocarbyl, substituted
hydrocarbyl, and an agronomically acceptable cation. As to the
first step, Example 28 (below) illustrates such a reductive
alkylation of monoethanolamine with ketones and H.sub.2 over
metal-containing catalysts. This reaction has been shown to be
highly selective using ethanol as a solvent. See Cope, A.C. and
Hancock, E. M., J. Am. Chem. Soc., 64, 1503-6 (1942) (incorporated
herein by reference). Example 28 demonstrates that this reaction
also may be conducted over catalysts comprising Pt or Pd
essentially in the absence of ethanol or any other non-reactive
solvent (i.e., the reaction mixture consists essentially of no
non-reactive solvent, and more preferably consists of no
non-reactive solvent). As to the second step in the above reaction,
the copper-catalyzed dehydrogenation of alcohols to salts of the
corresponding carboxylic acids is known in the art and described by
Franczyk in U.S. Pat. Nos. 5,292,936 (incorporated herein by
reference). It is separately described in Franczyk, U.S. Pat. No.
5,367,112 (incorporated herein by reference). It is further
separately described by Ebner et al. in U.S. Pat. No. 5,627,125
(incorporated herein by reference).
[0134] Regardless of the pathway used to synthesize the
N-substituted glycine reactant from the ketone by-product, the
N-substituted glycine reactant may be phosphonomethylated to form
the corresponding N-substituted N-(phosphonomethyl)glycine reactant
in accordance with the earlier discussion directed to
phosphonomethylating N-substituted glycine reactants.
[0135] It should be noted that the methods of this invention have
the ability to oxidize N-substituted N-(phosphonomethyl)glycine
reactants in the presence of other chemical species which may arise
in the course of previously known methods for preparing
N-(phosphonomethyl)glycine. For example, these methods have the
ability to oxidize NMG in the presence of phosphoric acid and/or
phosphonomethylated species that are products of the
carbon-catalyzed oxidation of PMIDA, such as aminomethylphosphonic
acid ("AMPA"), methyl-aminomethylphosphonic acid ("MAMPA"), and
N-(phosphonomethyl)glycine.
DEFINITIONS
[0136] Unless otherwise stated, the following definitions should be
used:
[0137] The term "hydrocarbyl" is defined as a radical consisting
exclusively of carbon and hydrogen. The hydrocarbyl may be branched
or unbranched, may be saturated or unsaturated, and may comprise
one or more rings. Suitable hydrocarbyl moieties include alkyl,
alkenyl, alkynyl, and aryl moieties. They also include alkyl,
alkenyl, alkynyl, and aryl moieties substituted with other
aliphatic or cyclic hydrocarbyl groups, such as alkaryl, alkenaryl
and alkynaryl.
[0138] The term "substituted hydrocarbyl" is defined as a
hydrocarbyl wherein at least one hydrogen atom has been substituted
with an atom or group of atoms other than hydrogen. For example,
the hydrogen atom may be replaced by a halogen atom, such as a
chlorine or fluorine atom. The hydrogen atom alternatively may be
substituted by an oxygen atom to form, for example, a hydroxy
group, an ether, an ester, an anhydride, an aldehyde, a ketone, or
a carboxylic acid. The hydrogen atom also may be replaced by a
nitrogen atom to form, for example, an amide or a nitro
functionality, although substitution by nitrogen to form an amine
or a nitrile functionality preferably is avoided. In addition, the
hydrogen atom may be replaced with a sulfur atom to form, for
example, --SO.sub.3H, although substitution by sulfur to form a
thiol preferably is avoided.
[0139] The term "agronomically acceptable cation" is defined as a
cation which allows agriculturally and economically useful
herbicidal activity of an N-(phosphonomethyl)glycine anion. An
agronomically acceptable cation may be, for example, an alkali
metal cations (e.g., a Na ion), an ammonium ion, an isopropyl
ammonium ion, a tetra-alkylammonium ion, a trialkyl sulfonium ion,
a protonated primary amine, a protonated secondary amine, or a
protonated tertiary amine.
EXAMPLES
[0140] To further illustrate and explain the invention, several
examples are presented below.
General
[0141] High pressure liquid chromatography ("HPLC") using an ion
exchange separation was used to analyze the products formed during
the reactions discussed in the following examples. The analytes
were detected using UV/visible detection following post-column
reaction to form phosphomolybdate complexes. This method can
distinguish between NMG, glyphosate, and phosphoric acid, but
cannot distinguish between AMPA and MAMPA because they co-elute.
Nevertheless, because AMPA and MAMPA have the same response factor
(on a molar basis), the sum of the AMPA and MAMPA concentrations
can be reliably determined. This value is reported as (M)AMPA in
the examples below.
EXAMPLE 1
[0142] This example illustrates a typical synthesis of NMG.
[0143] Approximately 89.09 g of sarcosine (1.00 mole), 82.0 g of
phosphorous acid (1.0 mole), and 110 g of concentrated hydrochloric
acid were mixed and refluxed in a 130.degree. C. oil bath. Next,
89.3 g of 37% formalin (1.1 mole) was added dropwise over 20 min,
and the reaction was continued for an additional 85 min. At this
point, NMR revealed the following product distribution (on a molar
basis): 89.9% NMG, 2.1% phosphorous acid, 1.9% phosphoric acid,
0.4% hydroxymethyl phosphorous acid, and 5.7% of an unknown product
(NMR: triplet, 8.59 ppm). After cooling to room temperature, 40 g
of NaOH was added, followed by 250 g of water. This led to the
formation of a white precipitate which subsequently was recovered
by filtration and assayed by HPLC. The total recovered yield of NMG
was 70.5% based on the amount of sarcosine and phosphorous acid
used.
[0144] Other N-alkyl glyphosates also may be made in a similar
manner.
EXAMPLE 2
[0145] This example illustrates the conversion of NMG to glyphosate
using a Pt catalyst and oxygen.
[0146] Approximately 10.0 g of NMG, 140 g of water, and 1 g of
platinum black (Aldrich Chemical Co., Inc., Milwaukee, Wis.) were
combined in a round bottom flask equipped with a water-cooled
reflux condenser immersed in a 150.degree. C. oil bath. Oxygen was
bubbled through for 4 hr as the solution was stirred. At the end of
this period, HPLC analysis revealed the following product
distributions (on a molar basis): 86.4% glyphosate, 8.7% NMG, 2.2%
(M)AMPA, and 2.7% phosphoric acid. Glyphosate precipitated from the
solution after cooling to room temperature.
[0147] In a second experiment, a mixture of 10.0 g of NMG, 2.0 g of
platinum black, and sufficient water to bring the total volume of
the mixture to 200 ml, was stirred for 2.7 hr at 80.degree. C.
while oxygen was bubbled through the mixture at 1 atm. Analysis of
the reaction mixture indicated the following product distribution
in molar terms: 85.4% glyphosate, 8.1% phosphoric acid, and 6.5%
unknown components. No NMG was detected.
EXAMPLE 3
[0148] This example illustrates the conversion of N-isopropyl
glyphosate to glyphosate using a Pt catalyst and oxygen.
Approximately 1.0 g of N-isopropyl glyphosate, 10 g of water, and
0.3 g of platinum black (Aldrich Chemical Co., Inc., Milwaukee,
Wis.) were combined in a round bottom flask (equipped with a
water-cooled reflux condenser) and immersed in a 80.degree. C. oil
bath. A stream of oxygen was introduced at the solution surface for
18 hr as the solution was stirred. At the end of this period,
.sup.31P NMR revealed the following product distributions (on a
molar basis): 91% glyphosate, 1% amino phosphonic acid, 6%
phosphoric acid, and 2% unknown product (15.0 ppm). Glyphosate
precipitated from solution after cooling to room temperature.
EXAMPLE 4
[0149] Various N-alkyl glyphosates were used under the same
conditions as described in Example 3 to produce glyphosate. In
other words, the only parameter which was varied was R.sup.1 in the
following formula: 30
[0150] Table 1 shows the alkyl group (i.e., R.sup.1) used, as well
as the conversion and glyphosate selectivity.
1TABLE 1 Use of Various N-Alkyl Glyphosates to Prepare Glyphosate
Glyphosate Alkyl Conversion Selectivity Group (%) (%) methyl 91 95
isopropyl 79 98 isopropyl 100 91 n-pentyl 62 82 benzyl 81 89
cyclohexyl 66 11
EXAMPLE 5
[0151] This example illustrates the conversion of NMG to glyphosate
using unsupported platinum and a variety of catalysts in which
platinum is dispersed on a non-carbonaceous support.
[0152] Approximately 1.0 g of NMG, 10 g of water, and 2.0 g of 5%
platinum on barium sulfate were combined in a round bottom flask
(equipped with a water-cooled reflux condenser) and immersed in a
95.degree. C. oil bath. Oxygen was bubbled through the reaction for
23 hr as the solution was stirred. At the end of this period, HPLC
analysis revealed the following product distributions (on a molar
basis): 78.2% glyphosate, 2.4% NMG, 9.4% (M)AMPA, and 10.0%
phosphoric acid. Glyphosate precipitated from solution after
cooling to room temperature.
[0153] In a separate experiment, the data in Table 2 was obtained
by heating to reflux a mixture comprising 1 g of NMG, 20 ml of
water, and sufficient catalyst to contain 5 mg of platinum metal in
a magnetically-stirred, round-bottom flask equipped with a reflux
condenser. Oxygen was bubbled through for 5 hr using a needle. The
catalyst was then removed by filtration and the filtrate analyzed
by HPLC.
[0154] As Table 2 indicates, two of the catalysts tested were
platinum black catalysts. The Engelhard V2001 (Engelhard Corp.,
Iselin, N.J.) catalyst has a much smaller surface area than the
Aldrich platinum black catalyst (Aldrich Chemical Co., Inc.,
Milwaukee, Wis.). As the results in Table 2 show, the Engelhard
V2001 catalyst had a lower selectivity and conversion, even though
30 times more of the Engelhard catalyst (i.e., 150 mg) was used
compared to the Aldrich catalyst (i.e., 5 mg).
2TABLE 2 Use of Unsupported and Supported Pt During NMG Oxidation
Glyphosate (M)AMPA H.sub.3PO.sub.4 Conversion Select. Select.
Select. Catalyst (%) (%) (%) (%) Pt black 14.7 85.3 3.0 11.7
(Aldrich) Pt black 2.7 70.0 17.9 12.1 (Engelhard V2001) (150 mg) 5%
Pt/SnO.sub.2 18.0 88.7 2.6 8.7 5% Pt/ZrO.sub.2 13.9 89.5 7.3 3.2 5%
Pt/BaSO.sub.4 31.2 92.2 2.8 5.1 5% Pt/BaSO.sub.4 34.0 88.6 2.8 8.7
(different catalyst) 5% Pt/TiO.sub.2 47.4 91.9 1.7 6.4 5%
Pt/SiO.sub.2 23.7 88.9 2.3 8.8
[0155] A third experiment was conducted which illustrates that
aluminum oxide and siloxanes (Deloxan, Degussa Corp., Ridgefield
Park, N.J.) may be used as supports for the metal catalyst. The
following experiments were conducted overnight at 95.degree. C. and
1 atm using 1 g of NMG, 10 ml of water, and sufficient catalyst to
be equivalent to 0.1 g of platinum metal. Oxygen was introduced
through a needle at 50 sccm (i.e., standard cm.sup.3 per min.). The
resulting solution was filtered and analyzed by HPLC. The dissolved
platinum concentration was analyzed by inductively-coupled
plasma/mass spectrometry. The results are shown in Table 3.
3TABLE 3 Use of Unsupported and Supported Pt During NMG Oxidation
Glyphosate (M)AMPA H.sub.3PO.sub.4 Conversion Select. Select.
Select. Catalyst (%) (%) (%) (%) Pt black 98.5 85.7 6.1 8.2
(Aldrich) Pt black 76 82.3 11.5 6.1 (Engelhard S3005) 5%
Pt/SiO.sub.2 82.7 79.1 11.1 9.8 5% Pt/SiO.sub.2 96.7 83.6 10.6 5.9
(different catalyst) 5% Pt/BaSO.sub.4 97.6 80.1 9.6 10.2 5%
Pt/TiO.sub.2 61.3 83.5 12.2 4.2 3% Pt/siloxane 52.4 52.8 39.2 8.0
5% Pt/siloxane 57.7 70.9 26.5 2.6 5% Pt/alumina 33.8 46.7 44.4 8.9
5% Pt/alumina 48.5 37.9 50.1 5.8 (different catalyst) 5% Pt/alumina
55.2 44.4 51.6 4.0 (different catalyst)
EXAMPLE 6
[0156] This example illustrates the use of palladium instead of
platinum as a catalyst for the oxidation of NMG to glyphosate.
[0157] A solution containing of 3.0 g of NMG, 0.3 g of palladium
black, and 57 g of water was refluxed in air over a weekend under a
water-cooled reflux condenser. NMR analysis indicated the following
product distribution (on a molar basis): 97.2% NMG, 2.8%
glyphosate, and 0.05% phosphoric acid.
EXAMPLE 7
[0158] This example compares the conversions and selectivities
using a catalyst comprising non-graphitic carbon, a catalyst
comprising moderately graphitic carbon, and a catalyst comprising
graphitic carbon. This example suggests that catalysts comprising
graphitic carbon tend to have a better selectivity for glyphosate
during the oxidation of NMG.
[0159] Three different catalysts comprising platinum dispersed on
commercially available carbon supports were used in separate runs
to oxidize NMG:
[0160] 1. 5%Pt/F106 carbon (ethanol washed). F106 carbon and
Pt/F106 carbon are available from Degussa Corp. (Ridgefield Park,
N.J.). F106 carbon is not graphitic.
[0161] 2. 3%Pt/Sibunit carbon. Sibunit carbon is manufactured as
described by Surovikin et al. in U.S. Pat. No. 4,978,649
(incorporated herein by reference), and may be purchased from the
Boreskov Institute of Catalysis in Novosibirsk, Russia (as can
platinum catalysts supported on Sibunit carbon). The carbon is
moderately graphitic (i.e., more graphitic than F106 carbon, and
less graphitic than Vulcan SC-72R carbon). The particular catalyst
used here was prepared by impregnating the carbon with platinum
salt, followed by reduction with sodium borohydride. The general
preparation of platinum on a carbon support is well-known in the
art and is described, for example, in Stiles, A. B., Catalyst
Supports and Supported Catalysts, Theoretical and Applied Concepts
(Butterworths, Boston, Mass. 1987). A separate discussion regarding
the general preparation of Pt on a carbon support may be found in a
chapter by R. L. Moss in Experimental Methods in Catalytic
Research, Vol. 2, Ch. 2, pp. 43-94 (R. B. Anderson & P. T.
Dawson, eds., Academic Press, New York, N.Y. 1976) (incorporated
herein by reference).
[0162] 3. 20%Pt/Vulcan LX-72R carbon. This catalyst comprises
graphitic carbon. It is manufactured by Johnson-Matthey and may be
purchased through Alfa/Aesar (Ward Hill, Mass.).
[0163] During the NMG oxidations, approximately 100 mg of the
catalyst (except as noted), 10 ml of water, and 1 g of NMG were
refluxed for 5 hr while oxygen was bubbled through via a needle.
The reaction mixture was then filtered and analyzed by HPLC. Table
4 shows the results.
4TABLE 4 Use of a Support Comprising Graphitic Carbon During NMG
Oxidation Glyphosate (M)AMPA H.sub.3PO.sub.4 Conver. Select.
Select. Select. Catalyst (%) (%) (%) (%) 5% Pt/F106 98.9 62.2 29.0
8.7 carbon; ethanol- washed (50 mg) 3% Pt/Sibunit 53.7 73.7 18.1
8.2 carbon 20% Pt/Vulcan 53.6 83.5 10.4 6.1 XC-72R carbon
EXAMPLE 8
[0164] This example shows selectivities obtained using a catalyst
comprising a noble metal and an electroactive species. All the
electroactive molecular species deposited onto platinum black in
this example undergo oxidation and reduction by electron transfer.
Thus, the treatment of the platinum black by both electroactive
molecular species and their oxidative precursors is exemplified
herein.
[0165] To prepare each organic-treated catalyst (i.e., those
containing N-hydroxyphthalimide, tris(4-bromophenyl)amine, TEMPO,
triphenylmethane, or 4,4'-difluorobenzophenone), 0.5 g of platinum
black (Aldrich Chemical Co., Inc., Milwaukee, Wis.) was added to a
solution of 25 mg of the electroactive molecular species in 50 ml
of anhydrous acetonitrile. The mixture sat capped in an Erlenmeyer
flask for four days (except that the 4,4'-difluorobenzophenone
catalyst only was exposed to solution for only one day). The
catalyst subsequently was recovered by filtration, rinsed with
acetonitrile and diethyl ether, and air-dried overnight.
[0166] The 2,4,7-trichlorofluorene catalyst was prepared using 0.3
g of Pt black and 30 ml of a solution containing 834.5 ppm of
2,4,7-trichlorofluorene in acetonitrile/1% CH.sub.2Cl.sub.2
solution (used to facilitate dissolution of the electroactive
molecular species) which was allowed to evaporate at room
temperature. The catalyst subsequently was washed with ethanol and
air-dried.
[0167] Each inorganic-treated catalyst was prepared by combining
0.50 g of Pt black, 50 ml of tetrahydrofuran, and either 25 or 100
mg of the inorganic electroactive molecular species, and stirring
overnight at room temperature in a sealed 125 ml Erlenmeyer flask.
The catalyst was recovered by filtration, washed with diethyl
ether, and air-dried overnight. The inorganic species used, all of
which are available from Aldrich Chemical (Milwaukee, Wis.),
were:
[0168] 1. 5,10,15,20-tetrakis(pentafluorophenyl)-21H,23H-porphine
iron (III) chloride (abbreviated "Fe(III)TPFPP chloride" in Table
5).
[0169] Approximately 25 mg was used to prepare the catalyst.
[0170] 2. 5,10,15,20-tetraphenyl-21H,23H-porphine iron (III)
chloride (abbreviated "Fe(III) TPP chloride" in Table 5).
Approximately 25 mg was used to prepare the catalyst.
[0171] 3. 5,10,15,20-tetraphenyl-21H,23H-porphine nickel (II)
(abbreviated as "Ni(II) TPP" in Table 5).
[0172] Approximately 25 mg was used to prepare the catalyst.
[0173] 4. Ruthenium-tris(2,2'-bipyridine) dichloride (abbreviated
as "[Ru(bpy).sub.3]Cl.sub.2" in Table 5). Approximately 100 mg was
used to prepare the catalyst.
[0174] 5. Ferrocene. Approximately 100 mg was used to prepare the
catalyst.
[0175] Each oxidation was conducted by heating to reflux a mixture
containing 1 g of NMG, 20 ml of water, and a catalyst containing 50
mg of platinum metal in a magnetically-stirred, round-bottom flask
equipped with a reflux condenser. Oxygen was bubbled through the
mixture for 5 hr using a needle. The catalyst was then removed by
filtration and the filtrate analyzed by HPLC.
[0176] Table 5 shows the results. Where available, literature data
on the oxidation potential (E.sub.12) of the electroactive
molecular species is reported in Table 5. This example shows that
electroactive molecular species which are relatively soluble in
water (e.g., ferrocene and Ru(bpy).sub.3]Cl.sub.2] tended to be
less effective at enhancing glyphosate selectivity. The hydrophobic
electroactive molecular species tended to increase the selectivity
of the catalyst. Electroactive molecular species having oxidation
potentials more negative than about +0.3 V vs SCE tended to
decrease conversion. Thus, the preferred electroactive molecular
species for enhancing the selectivity and conversion of NMG
oxidation may be either organic or inorganic, but preferably are
hydrophobic and have oxidation potentials more positive than about
0.3 volts vs. SCE.
5TABLE 5 Use of Electroactive Molecular Species on NMG Oxidation
Glypho- E.sub.1/2 sate H.sub.3PO.sub.4 V vs Conv. Select (M)AMPA
Select Poison SCE (%) (%) Select (%) (%) None -- 45.7 83.1 9.0 7.95
2,4,7-trichloro- -- 52.9 93.5 2.5 4.0 fluorene N-hydroxy- +1.44
56.3 93.2 2.4 4.4 phthalimide tris(4-bromophenyl) +1.05 35.3 93.5
2.5 4.0 amine TEMPO +0.6 71.2 92.9 2.4 4.6 triphenylmethane +0.27
22.1 93.4 .about.0 6.6 4,4'-difluorobenzo- -- 8.6 91.4 .about.0
10.9 phenone Fe(III)TPFPP +0.07 22.9 89.7 4.0 6.3 chloride
Fe(III)TPP chloride +1.11 69.3 91.1 2.6 6.3 Ni(II)TPP +1.15 53.8
90.3 2.9 6.8 [Ru(bpy).sub.3]Cl.sub.2 +1.32 37.9 68.9 12.1 19.1
Ferrocene +0.307 70.8 82.6 6.0 11.4
EXAMPLE 9
[0177] This example illustrates the effect of electroactive
molecular species on the platinum-catalyzed oxidation of
N-isopropyl glyphosate using the commercially available catalyst
20% Pt on Vulcan XC-72R carbon (manufactured by Johnson-Matthey and
available from Alfa/Aesar (Ward Hill, Mass.)). The commercial
catalyst was compared with a catalyst comprising
N-hydroxyphthalimide and a catalyst comprising
triphenylmethane.
[0178] These catalysts were used to oxidize N-isopropyl glyphosate
by the method described in the previous example (approximately 1 g
of N-isopropyl glyphosate was substituted for the NMG). The
electroactive molecular species improved the selectivity of
platinum on carbon catalysts for this reaction. The modifier with
less positive oxidation potential (triphenylmethane) was more
effective than the modifier with the more positive oxidation
potential ( N-hydroxyphthalimide). The graphitic support having
platinum on its surface was less effective in suppressing undesired
side reactions during the oxidation of N-isopropyl glyphosate than
it was during the oxidation of NMG (see Example 7).
6TABLE 6 Use of Electroactive Molecular Species During Oxidation of
N-Isopropyl Glyphosate E.sub.1/2 H.sub.3PO.sub.4 V vs Conv.
Glyphosate (M)AMPA Select Catalyst SCE (%) Select (%) Select (%)
(%) Platinum black -- 77.0 79.8 8.9 11.3 20% Pt/Vulcan +0.07 81.9
20.5 72.1 7.4 XC-72R carbon (25 mg used) 20% Pt/Vulcan +1.44 41.2
31.6 62.1 6.2 treated with N-hydroxyphthal- imide loading 35.3 mg/g
(26 mg used) 20% Pt/Vulcan +0.27 60.2 50.1 25.4 24.5 treated with
triphenylmethane loading 305 mg/g (32.6 mg used)
EXAMPLE 10
[0179] This example suggests that both selectivity and conversion
may be improved by minimizing the dissolved oxygen
concentration.
[0180] In a 300 mg 316 stainless steel autoclave reactor, 4.4 g of
NMG were combined with 1 g of platinum black in 145 g of deionized
water. The reaction mixture was heated to 70.degree. C. at 60 psig,
and a nitrogen/oxygen mixture was bubbled through the mixture while
vigorously mixing the mixture for 4 hr. The dissolved oxygen
concentration was measured using an Orbisphere dissolved oxygen
probe, calibrated to read 26.4 ppm O.sub.2 at 70.degree. C./60 psig
air saturation, and controlled by varying the N.sub.2/O.sub.2
blend. Two runs were conducted with the dissolved O.sub.2
concentration being maintained at 2-3 ppm and 10 ppm. Data from
HPLC analysis of the reaction mixture at 2 hrs and 4 hrs is shown
in Table 7.
7TABLE 7 Minimizing Dissolved Oxygen Concentration During NMG
Oxidation Dissolved Oxygen (M)AMPA H.sub.3PO.sub.4 Concentration
Time Conv. Glyphosate Select Select (ppm) (hr) (%) Select (%) (%)
(%) 2.75 2 66% 75.96 5.48 18.56 2.75 4 82% 76.16 5.95 17.89 10.4 2
60% 70.70 14.97 14.33 10.2 4 76% 69.83 16.21 13.97
EXAMPLE 11
[0181] This example illustrates the platinum-catalyzed oxidation of
N-substituted glyphosates in which the N-substituted group contains
atoms other than carbon or hydrogen. In particular, this example
describes the oxidation of glyphosine
(--HO.sub.2CCH.sub.2N(CH.sub.2PO.sub.3H.sub.2).su- b.2) and
N-hydroxyethyl glyphosate, which are prepared by reacting glycine
and N-hydroxyethyl glycine, respectively, with CH.sub.2O and
H.sub.3PO.sub.3 phosphorous acid in the presence of heat and a
strong acid. Phosphonomethylation reactions in general are
described in, for example, Redmore, D., Topics in Phosphorous
Chemistry, Vol. 8, 515-85 (E. G. Griffith & M. Grayson eds.,
John Wiley & Sons 1976) (incorporated herein by reference).
Phosphonomethylation reactions in general also are described, for
example, in a separate discussion in a chapter entitled
".alpha.-substituted Phosphonates" in Mastalerz, P., Handbook of
Organophosphorus Chemistry, 277-375 (Robert Engel ed., Marcel
Dekker 1992) (incorporated herein by reference).
[0182] Approximately 1 g of the substrate, 20 ml of water, and 50
mg of platinum black were combined in a round-bottom flask. The
oxidation was conducted by the same procedure used for the
oxidation of NMG in Example 8. The product distribution was
analyzed via .sup.31P NMR.
[0183] Approximately 74.9% of the glyphosine was oxidized with a
glyphosate selectivity of 50.2%. The other major product was
bis(phosphonomethyl)amine (-- HN(CH.sub.2PO.sub.3H.sub.2).sub.2),
which accounted for 39.1% of the oxidized glyphosine. Small
quantities of AMPA and of unidentified products also were detected.
The use of the platinum black catalyst treated with
tris(4-bromophenyl)amine described in Example 8 led to an increase
in conversion to 86.8%, but no change in selectivity.
[0184] Approximately 46.7% of the N-hydroxyethyl glyphosate was
oxidized. The product distribution (on a molar basis) was 61.2%
glyphosate, 22.4% N-hydroxyethyl-aminomethylphosphonic acid, and
16.3% phosphoric acid.
EXAMPLE 12
[0185] This example illustrates the rates and selectivities
obtained by conducting the oxidation of NMG over platinum black at
125.degree. C. Here, no deactivation of the catalyst was detectable
over seven cycles.
[0186] A 300 ml glass pressure bottle was equipped with a
thermocouple and two fritted filters. One of the filters was
located about half an inch above the center of the bottom of the
bottle and was used for gas dispersion. The second filter, located
about an inch from the bottom and not centered, was used for the
withdrawal of liquids. A gas exit line leading to a back pressure
regulator set to maintain the pressure at 50 psig also was
provided. Approximately 60 g of NMG was loaded into the vessel
along with 3 g of platinum black from Aldrich Chemical (Milwaukee,
Wis.) and 180 ml of water. The bottle was immersed in an oil bath,
magnetically stirred (with a stir bar) and heated under a slow
nitrogen flow until the internal temperature reached 125.degree.
C., giving a homogeneous solution. Oxygen and nitrogen were then
bubbled through the reaction mixture at rates of 1.5 and 0.5 slpm
(i.e., standard liters per min.), respectively, for 30 min. The
reaction was continued for another 30 min using a flow rate of 1
slpm for both the oxygen and nitrogen. The reaction then was
continued for a further 30 min using a nitrogen flow rate of 1.5
slpm and an oxygen flow rate of 0.5 slpm. Stirring was continued
and the mixture remained homogeneous throughout the entire 90 min
period. A slow nitrogen flow was then established to maintain the
pressure. The contents of the bottle were withdrawn through the
liquid withdrawal frit, leaving the catalyst in the bottle. About
100 ml of water was injected through the frit and then withdrawn to
remove residues from the reaction. The bottle was then allowed to
cool. The cycle was repeated 6 more times, each time using 60 g of
NMG and 180 ml of water. The results are shown in Table 8.
[0187] Platinum concentrations in solution at the end of the runs
varied from 0.3 to 1.1 ppm after the first cycle, as determined by
inductively-coupled plasma mass spectrometry. Although a greater
amount of platinum leached into solution during the first cycle
(i.e., the concentration of dissolved platinum was 4.2 ppm), it is
believed that most of the lost platinum was primarily unreduced
platinum on the surface of the platinum black.
8TABLE 8 Repeated Oxidation of NMG over Pt Black at 125.degree. C.
Glyphosate (M)AMPA H.sub.3PO.sub.4 Run Conversion Selectivity
Selectivity Selectivity no. (%) (%) (%) (%) 1 89.8 82.4 5.6 12.0 2
80.9 87.1 3.6 9.2 3 84.7 79.0 8.5 12.5 4 66.7 83.4 5.6 11.0 5 79.1
81.8 7.6 10.6 6 75.6 79.5 7.3 13.2 7 78.1 79.4 9.0 11.6
EXAMPLE 13.
[0188] This example shows the selectivities, conversions, and noble
metal loss obtained for the oxidation of N-substituted glyphosates
using low rates of oxygen delivery, moderate conversion, and an
electroactive molecular species (i.e., 2,2,6,6-tetramethyl
piperidine N-oxide). The electroactive species was added directly
to the reaction mixture; thus, there was no pretreatment of the
catalyst with an electroactive molecular species.
[0189] Approximately 60 g of NMG, 180 ml of water, 3 g of platinum
black (Aldrich Chemical, Milwaukee, Wis.), and 40 mg of TEMPO
(dissolved in 1 ml of acetonitrile) were combined in the pressure
reactor described in Example 12. The mixture was heated to
125.degree. C. while stirring under a 50 psig nitrogen atmosphere,
forming a homogeneous mixture. A nitrogen/oxygen mixture (75%
nitrogen, 25% oxygen by volume) was bubbled through the mixture for
90 min at a flow rate of 1 slpm while the pressure was maintained
at 50 psig. The reaction mixture then was withdrawn through a
fritted filter, leaving the catalyst behind. Another 60 g of NMG,
180 ml of water, and 40 mg of TEMPO (in 1 ml of acetonitrile)
subsequently was added to the flask and the cycle was repeated.
Four cycles in all were performed. In all cases, (M)AMPA
concentrations were below quantifiable limits, although traces were
detected. The only quantifiable byproduct detected was phosphoric
acid. The conversions and selectivities at the end of each of the
four cycles are shown in Table 9.
[0190] As in Example 12, the concentration of dissolved platinum
was determined at the end of each run by inductively-coupled plasma
mass spectrometry. This dissolved platinum concentration was less
than 0.1 ppm in cycles 2, 3, and 4. This is less than the leaching
observed in Example 12. As with Example 12, a greater amount of
platinum leached into solution during the first cycle (i.e., the
concentration of dissolved platinum was 8.3 ppm), although it is
again believed that most of the lost platinum was primarily
unreduced platinum on the surface of the platinum black.
9TABLE 9 Oxidation of NMG in the Presence of TEMPO at 125.degree.
C. for 90 Min. Cycle Conversion Glyphosate H.sub.3PO.sub.4 Number
(%) Selectivity (%) Selectivity (%) 1 32.6 98.3 1.7 2 38.0 98.1 1.9
3 43.3 98.1 1.9 4 46.2 97.3 2.7
EXAMPLE 14
[0191] This example shows the selectivities obtained when NMG was
prepared via the direct phosphonomethylation of sarcosine amides
(e.g., N-acetyl and N-propionyl sarcosine or sarcosine anhydride),
rather than sarcosine itself.
[0192] Approximately 20.0 g of N-acetyl sarcosine (152.5 mmole),
12.5 g of phosphorous acid (152.4 mmole), and 37.6 g of
concentrated hydrochloric acid were mixed and refluxed in a
120.degree. C. oil bath. Approximately 13.6 g of 37% formalin
(167.6 mmol) was added dropwise over 20 mln. The reaction was
continued for an additional 19 hr. HPLC analysis revealed a 99%
yield of NMG based on moles charged.
[0193] Under the same conditions, 20.0 g N-propionylsarcosine
(137.8 mmole) was converted into NMG using 11.3 g of phosphorous
acid (137.8 mmole), 10.0 g of concentrated hydrochloric acid, and
12.3 g of 37% formalin (152.1 mmole). HPLC analysis revealed a
96.6% yield of NMG based on moles of N-propionylsarcosine
charged.
[0194] Also under the same conditions, 2.06 g of sarcosine
anhydride (14.50 mmole) was converted into NMG using 2.38 g of
phosphorous acid (29.02 mmole), 5.7 g of concentrated hydrochloric
acid, and 2.6 g of 37% formalin (32.02 mmole). HPLC analysis
revealed a 97.2% yield of NMG based on moles of sarcosine anhydride
charged.
[0195] In an additional experiment, 2.0 g of N-acetyl sarcosine
(15.3 mmole) and 1.25 g of phosphorous acid (15.3 mmole) were mixed
with 3.1 g of concentrated sulfuric acid and 1.7 g of water, and
then refluxed in a 120.degree. C. oil bath. Approximately 1.4 g of
37% formalin (16.7 mmol) was added dropwise over 20 min. The
reaction was continued for an additional 18 hr. 31P NMR analysis
revealed a 98% yield of NMG based on moles of N-acetyl sarcosine
charged.
EXAMPLE 15
[0196] This example demonstrates the oxidization of NMG under
conditions very similar to those of Example 12, except that a
sub-stoichiometric amount of base is present in the reaction
mixture.
[0197] Approximately 60 g of NMG, 9.6 g of 28-30% ammonium
hydroxide (0.25 equivalents), and 170 ml of water were combined in
the apparatus described in Example 12 and stirred for 1 hr at an
internal temperature of 125.degree. C. while 0.75 slpm of pure
oxygen was bubbled through the mixture at a pressure of 50 psig.
HPLC analysis of the reaction mixture indicated that 23.5% of the
NMG had been oxidized with a selectivity to glyphosate of 65.7%.
The selectivities of (M)AMPA and H.sub.3PO.sub.4 were 21.1% and
13.2%, respectively.
[0198] As the results indicate, the NMG oxidation proceeds,
although conversion and selectivity were less than those that may
be obtained in the absence of base.
EXAMPLE 16
[0199] This example demonstrates that NMG may be oxidized
selectively to glyphosate in the presence of glyphosate and similar
compounds. One gram of platinum black was combined with 300 g of a
solution containing about 6% NMG and lower quantities of
glyphosate, AMPA, MAMPA, formaldehyde, formic acid, and sodium
chloride. The mixture was heated to 150.degree. C. for 4 hr while
oxygen was passed through the reactor at a pressure of 70 psig. At
the conclusion of the reaction, NMR and HPLC analysis indicated
that most the NMG had been converted into glyphosate.
EXAMPLE 17
[0200] This example shows the effect of Pt loading on the oxidation
of NMG in a 300 ml stirred autoclave reactor equipped with fritted
tubes for gas introduction and liquid withdrawal. The liquid
withdrawal frit was located below the stirrer and the gas
introduction frit was located above and to the side of the
stirrer.
[0201] Approximately 160 g of an aqueous NMG suspension (25 wt %
NMG) was combined with a variable amount of platinum black (Aldrich
Chemical, Milwaukee, Wis.). The reactor was closed and pressurized
to 85 psig with N.sub.2, and heated to 150.degree. C. while
stirring at 1000 rpm. When the temperature had stabilized, the gas
was switched to 400 sccm of a 25/75 mixture of oxygen and nitrogen
(on a molar basis). The reaction was continued for about 80
min.
[0202] Table 10 shows the results. The selectivity was only weakly
dependent on catalyst loading except at the very lowest loadings,
where selectivity deteriorated. Conversion increased with
increasing catalyst loading, but less steeply.
10TABLE 10 Effect of loading on the oxidation of 25% NMG over
platinum black at 150.degree. C. Pt Rxn loading time Conv.
Selectivity (%) (g) (min.) (%) Glyphosate (M)AMPA H.sub.3PO.sub.4
1.875 81 61.9 88.3 3.6 8.1 0.939 80 50.4 91.8 1.8 6.4 0.703 80 47.9
91.1 2.4 6.4 0.469 80 36.7 90.7 2.0 7.2 0.236 80 24.8 83.8 2.7 13.5
0.117 160 28.8 79.9 5.0 15.1
EXAMPLE 18
[0203] This example describes the reaction between PCl.sub.3 and
aqueous sodium sarcosinate to form H.sub.3PO.sub.3, HCl, sarcosine,
and precipitated NaCl. It also demonstrates the near-quantitative
removal of NaCl by filtration.
[0204] Approximately 200.5 9 of sarcosine and 90.03 9 of NaOH
(i.e., 2.25 moles each) were combined with 209.4 g of water to make
500 ml of a 50 wt % solution of sodium sarcosinate. The solution
was mechanically stirred in a glass vessel while 324.7 g of
PCl.sub.3 was pumped continuously into the solution below the
surface of the solution over 61 min. Upon completion of the
PCl.sub.3 addition, the temperature of the mixture was 109.degree.
C. Sodium chloride crystallized during the addition. The mixture
was filtered immediately after the conclusion of the PCl.sub.3
addition using two glass fritted Buchner funnels, and the salt cake
was sucked dry on the filters without rinsing.
[0205] The cake contained 6.8 wt % H.sub.3PO.sub.3, and an equal
number of moles of sarcosine. The chloride content of the filter
cake was determined by dissolving a sample in water and titrating
with silver nitrate. This analysis indicated that the cake was 85
wt % NaCl, corresponding to a dry weight of NaCl of 133.2 g (2.28
moles). Thus, approximately all the NaCl formed in the reaction was
removed by filtration.
EXAMPLE 19
[0206] This example shows the use of a Pt on carbon catalyst
prepared by depositing Pt on activated carbon which has been
subjected to a vigorous oxidation. This example also shows the
results obtained by treating this catalyst with various metal
halides.
[0207] Approximately 15-20 g of KB-FF carbon (Norit Americas Inc.,
Atlanta, Ga.) was placed into a 500 ml Erlenmeyer flask. The carbon
was slowly wetted with 30% H.sub.2O.sub.2. A minimal amount heat
was generated. More 30% H.sub.2O.sub.2 was added until the volume
of the suspension was approximately 150 ml. The H.sub.2O.sub.2
solution then was brought to a boil on a hot plate for
approximately 2 hr. Afterward, the hot plate was turned off, and
the carbon was allowed to stand overnight in the H.sub.2O.sub.2
solution. The following day the carbon was filtered on a glass
frit, rinsed with deionized water, and dried in a vacuum oven at
100.degree. C.
[0208] Approximately 4.6 g of the carbon was placed into an
Erlenmeyer flask. Deionized water was added to produce a dilution
of the carbon of at least 30:1 (water to carbon). The pH was
adjusted to 6.5 with aqueous KOH. Approximately 2.335 g of
H.sub.2PtCl.sub.6 was dissolved in 160 ml of water in a separate
beaker, and the pH adjusted to 11 with 45% aqueous KOH. The Pt
solution was slowly added to the stirring carbon in 10-20 ml
aliquots over a 5 hr period. The pH was periodically adjusted to
8-8.5 with 45 wt % KOH. The mixture was stirred overnight. The pH
was adjusted to 10.3 in the morning, and stirring was continued for
2 more hours while the pH was maintained at 10.2 using 45% KOH. The
mixture was then heated rapidly to 85.degree. C., and a 5 ml
aliquot of 37% CH.sub.2O solution was added. The solution was
brought to a boil as rapidly as possible. After 10 min. of boiling,
another 5 ml of 37% CH.sub.2O was added. The pH was checked several
times and adjusted to between 8.5 and 10 while boiling. After
boiling for 1 hr, the mixture was cooled and filtered on a glass
frit. The catalyst was washed with deionized water and dried in a
vacuum oven. This process yielded an 18.9% Pt/C catalyst.
[0209] A sample of the catalyst was further modified with metal
halides by the procedure in Example 25, except that 0.3-0.5 g of
catalyst was used. Approximately 100 mg of each of these catalysts
was used to oxidize 1.0 g of NMG in 20 ml of water to form
glyphosate. Each run was conducted for 5 hr in a 50 ml round-bottom
flask equipped a water-cooled reflux condenser. Oxygen was bubbled
through the reaction mixture for the entire 5 hr at reflux. At the
completion of each run, the reaction mixture was filtered to remove
the catalyst.
[0210] Table 11 shows the results. The GaBr.sub.3 enhanced both
selectivity and conversion. The AlBr.sub.3 decreased conversion and
had no significant effect on selectivity. The NbCl.sub.5 was
detrimental to selectivity.
11TABLE 11 Screening of NMG Oxidation Activity of Pt Catalysts on
Norit KB-FF Carbon Oxidized with 30% H.sub.2O.sub.2 Glyphosate
(M)AMPA H.sub.3PO.sub.4 Conv. Selectivity Selectivity Selectivity
Treatment (%) (%) (%) (%) None 41.6 90.2 3.4 6.4 AlBr.sub.3 28.9
88.9 4.0 7.1 GaBr.sub.3 57.0 93.6 2.9 3.5 NbCl.sub.5 49.7 70.0 23.9
6.1
EXAMPLE 20
[0211] This example describes the preparation and use of Pt on PVP
catalysts. In this example, the PVP support was ground in a blender
to increase its surface area, and the Pt was deposited primarily
onto the surface of the PVP.
[0212] Twenty-five grams of wet Reillex HP polymer (as received
from Reilly Industries, Indianapolis, Ind.) was suspended in 100 ml
of water and ground in a blender for 20 min. Approximately 1.56 g
of H.sub.2PtCl.sub.6 (Aldrich Chemical, Milwaukee, Wis.), with a
nominal platinum metal content of a least 37.5 wt %, was added to
the polymer suspension in a 250 ml round-bottom flask. The light
yellow color of H.sub.2PtCl.sub.6 transferred entirely to the resin
within 1 min, indicating complete take-up of H.sub.2PtCl.sub.6 by
the PVP resin. Three grams of 12 wt % NaBH.sub.4 in 14 molar NaOH
(Aldrich Chemical) was then added. The resin turned black instantly
as the NaBH.sub.4 reduced the Pt. After stirring for 1 hr, the
mixture was filtered, and the solid was washed with water. The
catalyst then was dried under vacuum at 105.degree. C.
Approximately 7.25 g of catalyst was recovered. Analysis by ICP-MS
indicated that the catalyst was 3.5 wt % Pt.
[0213] Various loadings of the catalyst were used to oxidize 1.0 g
of NMG in 20 ml of water to form glyphosate. Each run was conducted
for 5 hr in a 50 ml round-bottom flask equipped a water-cooled
reflux condenser. Oxygen was bubbled through the reaction mixture
for the entire 5 hr at reflux. At the completion of each run, the
reaction mixture was filtered to remove the catalyst. For
comparison purposes, separate runs using platinum black (Aldrich
Chemical) as a catalyst also were conducted under the same reaction
conditions.
[0214] The results are shown in Table 12. The PVP-supported
catalyst was more active per gram Pt than the platinum black, while
exhibiting selectivity very close to that of platinum black.
12TABLE 12 PVP Supported Platinum Catalyst vs. Platinum Black
Catalyst Gly- (M) Catalyst Pt phosate AMPA H.sub.3PO.sub.4 Loading
loading Conv. Selectivity Selectivity Select Catalyst (mg) (mg) (%)
(%) (%) (%) 3.5% 100 3.5 19.9 70.9 12.0 17.1 Pt/Reillex HP same 200
7.0 43.7 79.3 7.3 13.4 same 300 10.5 70.8 82.1 6.3 11.6 same 400
14.0 71.1 79.9 6.9 13.2 same 500 17.5 85.5 83.2 5.7 11.2 Platinum 5
5 <1 -- -- -- black same 10 10 <1 -- -- -- same 20 20 57.5
86.1 3.7 10.1 same 30 30 74.8 95.2 3.6 1.2 same 50 50 80.6 84.2 4.0
11.8 same 100 100 84.0 90.7 2.3 7.0 Note: The selectivity of NMG
could not be reliably determined for conversions less than 1%.
EXAMPLE 21
[0215] This example demonstrates that the catalyst of Example 20 is
an active and selective catalyst for the oxidation of NMG to
glyphosate at 125 and 150.degree. C. This example also compares
conversions and selectivities for different oxygen
concentrations.
[0216] Approximately 4.501 g of the catalyst from Example 20 was
combined with 116.6 g of water, 40.06 g of NMG, and 0.65 ml of a
0.041 g/ml solution of TEMPO in acetonitrile in a 300 ml stirred
autoclave equipped with fritted tubes for gas introduction and
liquid withdrawal. The liquid withdrawal frit was located below the
stirrer, and the gas introduction frit was above and to the side of
the stirrer. The reactor was closed and pressurized to 85 psig with
nitrogen and heated to 125.degree. C. while stirring at 1000 rpm.
When the temperature had stabilized, the gas was switched to 400
sccm of a 25/75 mixture of oxygen and nitrogen (on a molar basis).
After 37 min, the temperature set point was raised to 150.degree.
C. The reactor reached 150.degree. C. 8 min later. One hour into
the run, the composition of the gas mixture was changed to 37.5%
oxygen in nitrogen at the same total flow rate.
[0217] The results are shown in Table 13. The conversion and
selectivity for each 15 min segment of the run are shown. The
highest selectivity was achieved during the 45-60 min segment when
the temperature was 150.degree. C. and a flow rate of 400 sccm of
25% oxygen was employed. Lower selectivities were achieved at the
lower temperature (125.degree. C.) and higher oxygen
concentration.
13TABLE 13 Oxidation of 25% NMG over Pt/Attrited PVP O.sub.2 mole
Incremental Incremental Interval Temp. fraction Conversion
Selectivity (min.) (.degree. C.) (%) (%) (%) 0-15 125 25 10.2 --
15-30 125 25 8.9 86.7 30-45 heating 25 9.0 81.8 45-60 150 25 6.1
96.5 60-75 150 37.5 8.8 80.8 75-90 150 37.5 7.9 71.9
EXAMPLE 22
[0218] This example describes the preparation of Pt on PVP
catalysts using a method involving pre-treatment of the PVP resin
with an acid or mixture of acids followed by neutralization and
reduction in non-aqueous solvents, typically alcohols. The purpose
of the acid pre-treatment is to improve the dispersion of Pt by
causing the Pt to deposit primarily in the interior of the polymer
bead rather than the outer surface. The acid preferably is
neutralized before reduction so that it does not destroy the
NaBH.sub.4 reducing agent. The use of non-aqueous solvents is
preferred for this step because treatment of PVP impregnated with
H.sub.2PtCl.sub.6 with aqueous base leads to leaching of most the
Pt from the resin. This does not occur when ethanol, methanol, or
similar solvents are used instead.
[0219] In this example, Reillex HP PVP, having a moisture content
of 69.3 wt %, was used as received from Reilly Industries
(Indianapolis, Ind.). Six 32.6 g samples of the wet resin (10.0 g
dry weight) were combined with 100 ml of water in separate
round-bottom flasks equipped with stir bars. Approximately 0.105
moles of acid were added to each of the suspensions. The acids used
are shown in Table 14.
14TABLE 14 Acids Used to Pre-Treat the PVP Resin Proportion of Mass
of Sample Acids Acid (mole Acid Number Used %) (g) 1 Acetic Acid
100 6.31 2 Trifluoroacetic 100 11.97 Acid 3 Nitric acid 100 6.62
(70% in H.sub.2O) 4 Acetic acid 25 1.58 Trifluoroacetic 75 8.58
Acid 5 Acetic Acid 50 3.15 Trifluoroacetic 50 5.99 Acid 6 Acetic
Acid 75 4.73 Trifluoroacetic 25 2.99 Acid
[0220] Approximately 1.35 g of H.sub.2PtCl.sub.6 (Aldrich Chemical,
Milwaukee, Wis.) was added after the acid resin mixture had been
stirred for 80 min. After 1 hr of stirring, the platinized resin
was recovered by filtration, washed three times with 150 ml of
water, and 20 dried under vacuum at 120.degree. C. for 68 hr. Each
sample then was suspended in 100 ml of a mixture formed by mixing
136 g of 25 wt % sodium methoxide in methanol with 450 ml of
methanol. After stirring the suspension for 1 min, 6.5 g of 12 wt %
NaBH.sub.4 in 14 molar NaOH was added. The suspensions were stirred
for 90 min., and then allowed to sit for 16 hr. The solid was
recovered by filtration, washed 3 times with 150 ml of water, and
dried overnight under vacuum at 120.degree. C.
[0221] The relative amounts of Pt on the surface and interior of
the beads were qualitatively determined by optical microscopy. It
was apparent using this method that catalysts 2 and 3 (treated with
trifluoroacetic and nitric acid, respectively) had Pt deposited
deep in the interior. Deeper penetration was observed where nitric
acid (a stronger acid) (catalyst 3) was used. Catalysts 1 and 4-6,
which used acetic acid and mixtures of acetic acid with stronger
acid, had Pt deposition mostly near, but not on, the surface of the
bead.
[0222] The activity and selectivity of the catalysts for NMG
oxidation was determined under the reaction conditions of Example
8. Table 15 shows the results. In general, the conversions of the
catalysts pre-treated with acid are poor compared to catalysts not
pre-treated with acid, see, e.g., Examples 20 and 21. This suggests
that catalysts having the Pt primarily in the interior of the PVP
bead are less active for N-substituted glyphosate oxidation than
catalysts in which the Pt is mostly on the bead surface. A more
detailed examination of the data further reveals that the use of
stronger acid, which leads to deposition of the platinum deeper in
the particle, tends to lead to progressively less active and less
selective catalysts. Thus, the preferred Pt on PVP catalysts for
the oxidation of N-substituted glyphosates are those in which the
Pt is primarily deposited onto the surface of the support.
15TABLE 15 Conversion and selectivity of catalysts prepared using
acid pretreatment Sample Acids Conv. Selectivity (%) No. Used* (%)
Glyphosate (M)AMPA H.sub.3PO.sub.4 1 Acetic 19.3 86.8 11.2 2.0 2
TFA 8.8 69.7 22.4 7.9 3 Nitric 3.7 45.8 44.0 10.2 acid 4 3:1 12.3
60.2 34.8 5.0 TFA:Acetic 5 1:1 10.5 72.4 22.6 5.0 TFA:Acetic 6 1:3
11.2 63.4 31.2 5.4 TFA:Acetic *TFA = trifluoroacetic acid
EXAMPLE 23.
[0223] This example describes the preparation of a Pt catalyst
supported on a different polymer support, sulfonated polystyrene.
The resin is sulfonated to convert it to a cation exchange resin,
and a base metal (preferably iron) is deposited and reduced to
serve as an in situ reducing agent for Pt. A specific preparation
procedure follows.
[0224] A. Sulfonation
[0225] The following steps were conducted in a fume hood, due to
the fact that SO.sub.3 is evolved during this process.
[0226] Approximately 20 g of a polystyrene resin (Amberlite XAD-16,
Sigma Chemical, St. Louis, Mo.) was placed into a beaker. The resin
was sulfonated by slowly adding chlorosulfonic acid to the resin by
pipet. Small amounts were added in a step-wise fashion because the
reaction is vigorous. Enough chlorosulfonic acid was added to
barely cover the resin, so that a paste-like consistency resulted.
The resin was allowed to stand in the chlorosulfonic acid for
approximately 2 hr, with occasional stirring with a spatula. The
resin turned black during this procedure. In a separate beaker,
approximately 300 ml of a cold saturated solution of sodium sulfate
was prepared, and a few ml of concentrated sulfuric acid were added
to it. The resin was then poured into the sodium sulfate solution.
Afterward, the resin was filtered and rinsed on a glass frit with
saturated sodium sulfate solution. Finally the resin was rinsed
with deionized water and dried in a vacuum oven at 100.degree.
C.
[0227] B. Base Metal Treatment
[0228] This procedure preferably is performed as rapidly as
possible or under an inert atmosphere, because the iron on the
resin is relatively unstable in air.
[0229] Approximately 1.01 g of dry sulfonated XAD-16 resin and 60
ml of water were combined in a beaker on a stir plate. Ferric
chloride in excess (3-4 g) was added to the solution while
stirring. The resin then was filtered and washed on a glass frit
with deionized water. The resin was returned to a beaker, more
deionized water was added, and NaBH.sub.4 was added to reduce the
iron. The resin was filtered on a glass frit and returned to the
beaker so that more water could be added.
[0230] C. Depositing Pt on the Resin
[0231] The XAD-16 was re-suspended in 60 ml of water, and 0.32 g of
H.sub.2PtCl.sub.6 dissolved in 30 ml of water was added. The amount
of H.sub.2PtCl.sub.6 was based on the weight of the resin and the
desired Pt content of the final catalyst. This solution was added
in several portions to the base metal resin while stirring. After
stirring for approximately 20 min, the resin was filtered and
rinsed on a glass frit with deionized water. The resin was then
reduced with NaBH.sub.4. After the Pt was reduced, the catalyst was
washed several times with 10-30% sulfuric acid to remove residual
iron. The catalyst was filtered and rinsed with deionized water and
then dried in a vacuum oven at 100.degree. C. This made a catalyst
containing about 10% Pt.
[0232] D. Catalyst Performance
[0233] Approximately 100 mg of catalyst was used to effect the
oxidation of 1.0 g of NMG in 20 ml of water to form glyphosate.
Each run was conducted for approximately 5 hr in a 50 ml
round-bottom flask equipped a water-cooled reflux condenser. oxygen
was bubbled through the reaction mixture for the entire 5 hr at
reflux. At the completion of each run, the reaction mixture was
filtered to remove the catalyst. For comparison purposes,
approximately 100 mg of the sulfonated and un-sulfonated resin were
also tested under the same reaction conditions.
[0234] The results are shown in Table 16. The resins without Pt
were inactive, and the selectivity of the Pt on sulfonated resin
was similar to that of platinum black and Pt on PVP.
16TABLE 16 Use of a Polystyrene Resin Supported Catalysts to
Oxidize NMG to Glyphosate Glyphosate (M)AMPA H.sub.3PO.sub.4 Conv.
Select. Select. Select. Catalyst (%) (%) (%) (%) XAD-16 untreated
<2 -- -- -- Sulfonated XAD-16 <2 -- -- -- 10% Pt/sulfonated
9.2 82.7 3.4 13.9 XAD-16
EXAMPLE 24
[0235] This example demonstrates the preparation and use of a
platinum catalyst on an acidic hydrophilic polymer bead support
(i.e., H.sup.+ form sulfonated cross-linked polystyrene).
[0236] Approximately 20 g of H.sup.+ form sulfonated polystyrene
beads (Amberlyst 15, Rohm & Haas, Philadelphia, Pa.) was
combined with a solution containing 2.7 g of H.sub.2PtCl.sub.6
(37.5% Pt, equivalent to 1.0 g of Pt, Aldrich Chemical, Milwaukee,
Wis.) in 120 ml of absolute ethanol and 80 ml of water. The
solution was refluxed while stirring in a 95.degree. C. oil bath
for 40 hr. Afterwards, the resin was black and the solution was
clear. The catalyst was recovered by filtration; rinsed with water;
and soaked, unstirred for 1 hr in 200 g of 20% Na.sub.2SO.sub.4 to
de-protonate the --SO.sub.3H groups. The catalyst was again
recovered by filtration and washed with water, but not dried.
[0237] Subsequently, the catalyst was used to oxidize NMG to form
N-(phosphonomethyl)glycine. To conduct the oxidation, the catalyst
was placed into the 300 ml autoclave reactor described in Example
17, along with 105.4 ml of water and 47.1 g of NMG. The reaction
was conducted at a temperature of 135.degree. C., a pressure of 66
psig, and an oxygen flow rate of 100 sccm for 2 hr. Table 17 shows
the selectivities and conversions achieved.
17TABLE 17 Oxidation of NMG Using Platinum on H.sup.+ Form
Sulfonated Polystyrene Beads Time Conversion Selectivity (%)*
(min.) (%) glyphosate (M)AMPA H.sub.3PO.sub.4 30 14.8 93.5 2.1 4.4
60 29.3 92.0 2.4 5.6 90 40.8 87.2 4.4 8.4 120 50.6 81.2 8.4 9.5
*Incremental selectivities
EXAMPLE 25
[0238] This example describes the preparation and use of Pt
catalysts in conjunction with inorganic modifiers (also referred to
as "promoters"). In this example, a variety of metal compounds
(mostly metal halides) were used to modify platinum black. The
platinum black and all of the metal compounds were obtained from
Aldrich Chemical Co., Milwaukee, Wis. The metal compounds tested
are listed in table 18 below.
[0239] Because all the metal compounds are moisture sensitive, all
manipulations other than hydrolysis were performed in a dry glove
box under a N.sub.2 atmosphere. Separate portions of platinum black
(0.15-0.25 g) were placed into 40 ml vials with Teflon faced septa
outside of the glove box. Each portion was designated as to which
metal compound would be used for treatment. All materials were
transferred into the dry glove box, taking care to remove air
before actual glove box procedures. A small amount of the metal
compound (approximately 1 g) was placed into its designated 40 ml
vial in the glove box. Chlorobenzene (approximately 40 ml) was
added to each metal compound. Each vial was capped and mixed to
effect dissolution. All these solutions were saturated, as
evidenced by solid metal compound remaining on the bottom of the
vials. The metal compound solutions (3-5 ml) were poured into the
designated vials containing platinum black, taking care not to add
the metal compound which had not dissolved. Each vial containing
platinum black was capped and mixed by shaking in the glove box.
The vials were then uncapped and allowed to stand for 1 hr inside
the glove box. The vials containing platinum black were then capped
and removed from the glove box and placed into a hood. Deionized
water (approximately 20 ml) was carefully added to each vial to
hydrolyze the metal compound salts. Each catalyst then was filtered
on a glass frit filter, washed with copious amounts of water, and
dried under vacuum overnight.
[0240] Approximately 30 mg of each of the catalysts so prepared
were used to effect the oxidation of 1.0 g of NMG in 20 ml of water
to form glyphosate. Each run was conducted for approximately 5 hr
in a 50 ml round-bottom flask equipped a water-cooled reflux
condenser. oxygen was bubbled through the reaction mixture for the
entire 5 hr at reflux. At the completion of each run, the reaction
mixture was filtered to remove the catalyst. For comparison
purposes, a control sample of unmodified platinum black also was
used to effect the NMG oxidation under the same conditions.
[0241] Table 18 lists the metal compounds tested and their effects
on selectivity. Compounds of gallium, indium, ruthenium, and osmium
were effective in raising selectivity.
18TABLE 18 Screening of Platinum Black Catalysts Treated with Metal
Compounds Metal Conv. Selectivity to (%) Compound (%) Glyphosate
(M)AMPA H.sub.3PO.sub.4 None 34.2 85.5 4.5 10.0 InBr.sub.3 33.0
94.3 2.1 3.6 RuBr.sub.3 45.8 91.9 1.3 6.7 OsO.sub.4 47.5 90.4 2.1
7.6 GaBr.sub.3 10.4 90.0 2.6 7.4 SbBr.sub.3 38.5 84.7 1.5 13.8
TaBr.sub.5 44.5 84.4 2.2 13.4 SnBr.sub.4 32.0 70.5 4.6 24.8
MnCl.sub.2 27.5 70.0 9.0 21.0 RhBr.sub.3 20.3 68.6 6.0 25.4
FeCl.sub.3 23.7 56.0 15.4 28.6 BiBr.sub.3 5.2 40.2 13.5 46.3
(NH.sub.4).sub.2WO.sub.4 28.0 38.1 9.6 52.3 Ce(OH).sub.4 57.6 20.4
5.9 73.7
EXAMPLE 26
[0242] This example illustrates the influence of stirring rate on
selectivity in the oxidation of N-substituted glyphosates at
greater temperatures and oxidation rates.
[0243] In each of 3 runs, approximately 4.501 g of catalyst was
combined with 116.6 9 of water, 40.06 g of NMG, and 0.65 ml of a
0.041 g/ml solution of TEMPO in acetonitrile in a 300 ml stirred
autoclave equipped with fritted tubes for gas introduction and
liquid withdrawal. The liquid withdrawal frit was located below the
stirrer, and the gas introduction frit was above and to the side of
the stirrer. The reactor was closed and pressurized to 85 psig with
nitrogen and heated to 125.degree. C.
[0244] Tables 19, 20, and 21 below give the stirrer rate at each
interval in the three runs, as well as the selectivity and average
oxidation rate achieved during the interval. Both rate and
selectivity are seen to improve with stir rate up to a clear
optimum of 1000 rpm. The reported rate is expressed in terms of
moles of NMG oxidized per liter per hour. When the stirring was
increased to 1200 rpm during the second run, the selectivity
decreased. The 1200 rpm selectivity was even worse at the beginning
of the third run.
[0245] In the reactor described, the degree to which gas is pulled
down into the vortex created by the impeller and prevented from
bubbling, un-reacted, to the surface increases with the stirring
rate up to about 950 rpm, at which point virtually all the gas is
pulled into the turbulent zone around the impeller. As the stir
rate increases further, however, the turbulent zone of gas-liquid
mixing around the impeller widens until, at about 1500 rpm, it
fills most of the liquid volume. The data below demonstrates that
the optimal stirrer speed for the aerobic oxidation of NMG is that
which is just sufficient to substantially prevent the gas bubbles
from rising directly to the upper surface of the solution upon
their introduction into the solution. Stirrer speeds significantly
less than this preferred value tend to cause lower reaction rates
and selectivities, while stirrer speeds significantly greater than
the preferred value tend to create a wider zone of turbulence which
also tends to cause a lower selectivity.
19TABLE 19 Effect of Stirring Rate on NMG Oxidation, Run 1 Stir
Glyphosate Interval rate Rate Selectivity (min.) (rpm) (mol/L-hr)
(%) 0-60 200 0.10 81.8 60-120 400 0.30 81.4 120-210 600 0.48
88.0
[0246]
20TABLE 20 Effect of Stirring Rate on NMG Oxidation, Run 2 Stir
Glyphosate Interval rate Rate Selectivity (min.) (rpm) (mol/L-hr)
(%) 0-30 600 0.31 90.0 30-60 800 0.47 94.0 60-90 1000 0.75 95.4
90-105 1200 0.47 93.8
[0247]
21TABLE 21 Effect of stirring rate on NMG oxidation, Run 3 Stir
Glyphosate Interval rate Rate Selectivity (min.) (rpm) (mol/L-hr)
(%) 0-15 1200 0.67 78.7 15-30 1400 0.63 81.8 30-45 1600 0.74 82.9
45-60 1800 0.75 83.4
EXAMPLE 27
[0248] This example illustrates various methods that have been used
in accordance with this invention to reduce the adverse effect of
undissolved oxygen in the reaction solution.
[0249] Three runs were conducted. In each, NMG was oxidized to
N-(phosphonomethyl)glycine using a platinum black (Aldrich Chemical
Co., Milwaukee, Wis.) catalyst. This reaction was conducted in the
stirred reactor used in Example 17 with a stir rate of 1000
rpm.
[0250] In the first run, the platinum black catalyst was modified
by depositing N,N'-bis-(3-methylphenyl)-N,N'-diphenyl benzidine
("TPD") onto the surface of the catalyst. This catalyst was
prepared by suspending 0.70 g of platinum black in 20 ml of
methylene chloride containing 7 mg of dissolved TPD. The catalyst
was introduced into the reactor along with 40.1 g of NMG and 113 g
of water. The pressure was maintained at 90 psig. Approximately 200
sccm of oxygen were bubbled through the mixture once the solution
reached the reaction temperature (150.degree. C.). After 32 min.,
the conversion was 60.4% and the selectivity was 90.8%. After 56
min., the conversion was 77.2% and the selectivity was 83.1%.
[0251] In the second run, the reactor was loaded with 0.70 g. of
platinum black , 40.0 g of NMG, and 113.3 g of water. The pressure
was maintained at 90 psig. The reactor used in Example 17 was
modified so that oxygen was introduced through a frit which was
placed near the surface of the reaction solution (i.e., about 1.3
cm from the surface in a reaction mixture having a total depth of
about 15.2 cm) so that essentially all the oxygen bubbles could
escape into the headspace without first coming into contact with
the impeller (before this modification, the location of the frit
was lower in the reaction mixture, thereby allowing a significant
amount of oxygen bubbles to come into contact with the impeller).
Approximately 200 sccm of oxygen were bubbled through the mixture
once the solution reached the reaction temperature (150.degree.
C.). After 30 min, the conversion was 59.6% and the selectivity was
92.0%. After 60 min, the conversion was 80.5% and the selectivity
was 81.8%.
[0252] In the third run, 47.2 g of NMG, 103.7 ml of water, and 2.00
g of platinum black were loaded into the reactor using the same
frit position as in the third run. The pressure was maintained at
66 psig. When the solution reached the reaction temperature
(135.degree. C.), oxygen was bubbled into the solution at a flow
rate of 100 sccm. Table 22 shows the conversion and incremental
selectivity during the reaction.
22TABLE 22 Oxidation of NMG Using a Frit Positioned Away From
Impeller Time Conversion Selectivity (%)* (min.) (%) glyphosate (M)
AMPA H.sub.3PO.sub.4 18 15.7 94.9 1.2 3.9 36 31.7 97.3 0.3 2.3 55
49.6 93.6 1.0 5.4 72 66.0 96.1 1.1 2.8 90 83.3 92.3 2.2 5.5
*Incremental selectivities
EXAMPLE 28
[0253] This example describes the reductive coupling of
monoethanolamine with acetone to form N-isopropyl monoethanolamine
(abbreviated "IMEA").
[0254] A series of runs were conducted utilizing various
Pt-containing and Pd-containing catalysts. In each run, the
catalyst was suspended in 25 ml of acetone in a glass pressure
bottle equipped with a stir bar. Approximately 6.1 g (0.1 mole) of
monoethanolamine was then added to the pressure bottle, and the
mixture was stirred and allowed to stand for 5-10 min. A small
amount of heat was evolved. The bottle was then pressurized to 90
psig with H.sub.2, and stirred overnight at room temperature at the
same pressure. Subsequently, the bottle was de-pressurized, and the
relative proportions of monoethanolamine, N-isopropyl
monoethanolamine, and N,N-diisopropyl ethanolamine were determined
by gas chromatography.
[0255] The catalysts shown in Table 23 were found to be the
preferred catalysts for the reaction. Although rhodium on carbon
(not shown in Table 23) was found to promote the reductive
alkylation of acetone and monoethanolamine, it gave primarily the
di-alkylated product. Raney nickel (also not shown in Table 23)
exhibited low activity for the desired reaction (< 40%
conversion using 0.205 g. of 5% Rh/C).
[0256] Without being bound by any particular theory, it is believed
that the acetone derivatives quantified in Table 23 are a result of
the aldol condensation, as shown by the following equation: 31
[0257] In addition to showing the preferred catalysts for the
reaction, this example also demonstrates that acetone may be used
as both solvent and reagent, eliminating the need to use ethanol or
any other non-reactive solvent (i.e., any solvent which is
non-reactive with the reactants and the desired product under the
reaction conditions) under traditional protocols.
23TABLE 23 Room temperature reductive alkylations of
Monoethanolamine with acetone at 90 psi H.sub.2 Catalyst
Diisopropyl Loading IMEA MEA % Acetone Catalyst (g) (%) (%)
Derivatives 5% Pt/SiO.sub.2 .262 96 0.1 0.9 53% Pd on carbon .438
78.8 0.2 20 (1% H.sub.2SO.sub.4 in the acetone) 10% Pt on NCP-14
.301 90.1 2.1 7.3 carbon 5% Pd on carbon .310 81.7 0.1 13.4
Palladium 91.7 73.3 ND 14.3 hydroxide Palladium oxide .0373 27 ND
13.6 No catalyst -- 1 ND 42.2
EXAMPLE 29
[0258] This example demonstrates the neutralization of sodium
sarcosinate mediated by ion exchange membranes. The neutralization
was conducted in an apparatus composed of two glass pieces. The
lower piece was bowl-shaped except for a flange at the top with a
groove inscribed for a 44 mm O-ring. The upper piece was
cylindrical with a flange on the bottom identical to that on the
lower piece. During operation, a Viton O-ring was placed in the
upper flange and a piece of the membrane was sandwiched between the
flange on the lower piece and the O-ring. The two pieces were held
tightly together with a clamp.
[0259] To prepare the apparatus for use, the lower piece of the
apparatus was filled with a phosphonomethylation mixture (27 ml)
prepared by combining 37.5 g (0.205 moles) of NMG, 20.9 g of
concentrated sulfuric acid (1.0 equiv.), 16.6 g of 37% formalin
(0.20 equiv.), and 212.3 g of water. This yielded a 15% NMG
solution containing amounts of sulfuric acid and formalin which are
typical of phosphonomethylation mixtures.
[0260] After the lower piece was completely filled with the
phosphonomethylation mixture, the membrane was placed on top before
assembling the apparatus. Care was taken to avoid bubbles between
the phosphonomethylation mixture and the membrane. Once the
apparatus was assembled, 50 ml of a 5% aqueous solution of sodium
sarcosinate was added to the upper (cylindrical) piece. A pH probe
was inserted into the sodium sarcosinate solution, and magnetic
stirring of the two solutions was initiated. The pH of the upper
solution decreased as the neutralization proceeded.
[0261] The following membranes were tested using the above
equipment and protocol: Nafion 117 (manufactured by DuPont Co. of
Wilmington, De. and available from Aldrich Chemical of Milwaukee,
Wis.); Ionclad EDS R4010 membrane (Pall Specialty Materials of Port
Washington, N.Y.); and Raipore R1010, Ionac, and ESC 7000 membranes
(available from The Electrosynthesis Company of East Amherst,
N.Y.). All the membranes were effective in mediating the
neutralization. The R4010 membrane was the fastest and exhibited
proton fluxes of 0.03 amperes per square centimeter.
EXAMPLE 30
[0262] This example demonstrates the use of nanofiltration
membranes to remove bisulfate ions from a simulant also containing
NMG, glyphosate, and dihydrogen phosphate. The proportions of these
components in the simulant are representative of those in processes
in which an N-substituted glyphosate is prepared by
phosphonomethylation catalyzed by H.sub.2SO.sub.4, and then
oxidized to glyphosate after neutralization of the H.sub.2SO.sub.4
without first isolating the N-substituted glyphosate as a solid.
The example suggests that molecular weight cutoffs below 1000
daltons are preferred for this application.
[0263] The composition of the simulant was 1.0% NMG, 0.2%
glyphosate, 2.7% NaHSO.sub.4.circle-solid.H.sub.2O, and 0.3%
NaH.sub.2PO.sub.4.circle-soli- d.H.sub.2O in water (pH= 1.4). The
mixture was homogeneous at room temperature. Approximately 100 ml
of the simulant was charged to a SepaST stirred membrane test cell
(Osmonics Laboratory and Specialty Products Group, Livermore,
Calif.). The cell held a 45 mm disk of the membrane being tested.
Helium pressure was applied to the chamber holding the simulant and
the permeate was collected and analyzed for NMG, glyphosate, and
phosphate concentration by HPLC and for sulfate content by ion
chromatography.
[0264] Table 24 shows the results for two types of low molecular
weight cutoff nanofiltration membranes. The first set are Nova 1k,
3k, and 5k membranes (Pall Gelman, Ann Arbor, Mich.). These
membranes are characterized by their manufacturer as possessing
molecular weight cutoffs of 1000, 3000 and 5000 daltons,
respectively. The other set are two SelRO membranes, MPF-34 and
MPF-36 (LCI Corporation, Charlotte, N.C.). The manufacturer does
not specify a molecular weight cutoff, but the membranes exhibit
95% and 50% rejection of sucrose (molecular weight= 342),
respectively. Thus, the order of molecular weight cutoff is Nova 5k
> Nova 3k > Nova 1k > SelRO MPF-36 > SelRO MPF-34.
[0265] Table 24 shows the rejection efficiencies for NMG and
glyphosate and the relative selectivity of the membrane for sulfate
and phosphate with respect to NMG. A selectivity value of 1.0 means
that the membrane is not selective. The SelRO membranes exhibit
selectivities significantly greater than 1.0, and are therefore
effective for this application.
24TABLE 24 Membrane Selectivity for Separation of Sulfate and
Phosphate from NMG and Glyphosate Pressure Rejection Efficiency
Relative Selectivity Membrane (psi) NMG Glyphosate SO.sub.4/NMG
PO.sub.4/NMG Nova 5k 70 0.05 0.05 1.02 1.01 Nova 3k 100 0.05 0.05
0.99 1.00 Nova 1k 100 0.10 0.10 1.05 1.04 SelRO MPF-36 440 0.93
0.80 4.87 1.03 SelRO MPF-34 440 0.93 0.99 4.63 1.49
[0266] The above description of the preferred embodiment is
intended only to acquaint others skilled in the art with the
invention, its principles, and its practical application, so that
others skilled in the art may adapt and apply the invention in its
numerous forms, as may be best suited to the requirements of a
particular use. The present invention, therefore, is not limited to
the above embodiments and may be variously modified.
* * * * *