U.S. patent application number 14/765045 was filed with the patent office on 2015-12-24 for process for producing polyols.
This patent application is currently assigned to Eastman Chemical Company. The applicant listed for this patent is EASTMAN CHEMICAL COMPANY. Invention is credited to Eugenen H. Brown, Thomas K. Brown, Kenneth Wayne Hampton, JR., Kevin S. Howe, Amy K. Paris, Thomas Allen Puckette.
Application Number | 20150368171 14/765045 |
Document ID | / |
Family ID | 50514200 |
Filed Date | 2015-12-24 |
United States Patent
Application |
20150368171 |
Kind Code |
A1 |
Hampton, JR.; Kenneth Wayne ;
et al. |
December 24, 2015 |
PROCESS FOR PRODUCING POLYOLS
Abstract
A process for producing polyols (such as neopentyl glycol) is
disclosed which comprises reacting formaldehyde and another
aldehyde in the presence of a trialkylamine catalyst and a base
promoter to form an Aldol condensation reaction product. The base
promoter improves removal of nitrogen containing salts prior to
hydrogenation of the hydroxy aldehyde to produce the polyol. The
improved process also reduces trialkylamine catalyst usage,
improves trialkylamine catalyst recovery, and reduces
nitrogen-containing salts prior to hydrogenation.
Inventors: |
Hampton, JR.; Kenneth Wayne;
(Glimer, TX) ; Brown; Eugenen H.; (Gilmer, TX)
; Brown; Thomas K.; (Hallsville, TX) ; Paris; Amy
K.; (Glenpool, OK) ; Howe; Kevin S.;
(Longview, TX) ; Puckette; Thomas Allen;
(Longview, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
EASTMAN CHEMICAL COMPANY |
Kingsport, |
TN |
US |
|
|
Assignee: |
Eastman Chemical Company
Kingsport
TN
|
Family ID: |
50514200 |
Appl. No.: |
14/765045 |
Filed: |
January 17, 2014 |
PCT Filed: |
January 17, 2014 |
PCT NO: |
PCT/US2014/012032 |
371 Date: |
July 31, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13755910 |
Jan 31, 2013 |
8710278 |
|
|
14765045 |
|
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Current U.S.
Class: |
568/464 ;
568/862 |
Current CPC
Class: |
C07C 29/141 20130101;
C07C 45/45 20130101; C07C 29/141 20130101; C07C 47/19 20130101;
C07C 31/20 20130101; C07C 45/75 20130101; C07C 45/75 20130101 |
International
Class: |
C07C 29/141 20060101
C07C029/141; C07C 45/45 20060101 C07C045/45 |
Claims
1. A process for producing a polyol comprising: contacting
formaldehyde and another aldehyde in the presence of an amine
catalyst and a base promoter under Aldol condensation conditions to
produce hydroxy aldehyde; and hydrogenating the hydroxy aldehyde to
form a polyol.
2. The process according to claim 1, further comprising purifying
said hydroxy aldehyde prior to hydrogenation and recovering said
amine catalyst.
3. The process according to claim 1, wherein the polyol comprises
propylene glycol, ethylene glycol, dipropylene glycol, diethylene
glycol, 1,4-butanediol, neopentyl glycol, triethanolamine, or
glycerol.
4. The process according to claim 1, wherein the hydroxy aldehyde
comprises 3-hydroxypropanal, dimethylolethanal, trimethylolethanal
(pentaerythrital), 3-hydroxybutanal (acetaldol),
3-hydroxy-2-ethylhexanal (butyl aldol), 3-hydroxy-2-methylpentanal
(propyl aldol), 2-methylolpropanal, 2,2-dimethylolpropanal,
3-hydroxy-2-methylbutanal, 3-hydroxypentanal, 2-methylolbutanal,
2,2-dimethylolbutanal, or hydroxypivaldehyde.
5. The process according to claim 1, wherein said another aldehyde
comprises formaldehyde, propionaldehyde, n-butyraldehyde,
isobutyraldehyde, valeraldehyde, 2-methylbutyraldehyde,
3-methylbutyraldehyde (isovaleraldehyde),
2,2-dimethylpropionaldehyde (pivalinaldehyde), caproaldehyde,
2-methylvaleraldehyde, 3-methylvaleraldehyde,
4-methylvaleraldehyde, 2-ethylbutyraldehyde,
2,2-dimethylbutyraldehyde, 3,3-dimethylbutyraldehyde, caprylic
aldehyde, capric aldehyde, or glutaraldehyde.
6. The process according to claim 1, wherein the amine catalyst is
triethylamine, tri-n-propylamine, tri-n-butylamine, trimethlyamine,
or mixtures thereof.
7. The process according to claim 1, wherein the base promoter
comprises a carbonate, a hydrogen carbonate, or a hydroxide, or
mixtures thereof of an alkali metal or alkaline earth metal.
8. The process according to claim 7, wherein the base promoter is
Na.sub.2CO.sub.3, K.sub.2CO.sub.3, CaCO.sub.3, NaHCO.sub.3,
KHCO.sub.3, NaOH, KOH, Ca(OH).sub.2, or combinations thereof.
9. A process for producing neopentyl glycol comprising: contacting
formaldehyde and isobutyraldehyde in the presence of an amine
catalyst and a base promoter under Aldol condensation conditions to
produce hydroxypivaldehyde; and hydrogenating the
hydroxypivaldehyde to form neopentyl glycol.
10. The process according to claim 9, further comprising purifying
said hydroxypivaldehyde prior to hydrogenation and recovering said
catalyst.
11. The process according to claim 9, wherein the amine catalyst is
triethylamine, tri-n-propylamine, tri-n-butylamine, trimethlyamine,
or mixtures thereof.
12. The process according to claim 9, wherein the base promoter
comprises a carbonate, a hydrogen carbonate, or a hydroxide, or
mixtures thereof of an alkali metal or alkaline earth metal.
13. The process according to claim 12, wherein the base promoter is
Na.sub.2CO.sub.3, K.sub.2CO.sub.3, CaCO.sub.3, NaHCO.sub.3,
KHCO.sub.3, NaOH, KOH, Ca(OH).sub.2, or combinations thereof.
14. A process for producing a hydroxy aldehyde comprising:
contacting formaldehyde and another aldehyde in the presence of an
amine catalyst and a base promoter under Aldol condensation
conditions to produce hydroxy aldehyde.
15. The process according to claim 14, further comprising purifying
said hydroxy aldehyde and recovering said catalyst.
16. The process according to claim 14, wherein the hydroxy aldehyde
comprises 3-hydroxypropanal, dimethylolethanal, trimethylolethanal
(pentaerythrital), 3-hydroxybutanal (acetaldol),
3-hydroxy-2-ethylhexanal (butyl aldol), 3-hydroxy-2-methylpentanal
(propyl aldol), 2-methylolpropanal, 2,2-dimethylolpropanal,
3-hydroxy-2-methylbutanal, 3-hydroxypentanal, 2-methylolbutanal,
2,2-dimethylolbutanal, or hydroxypivaldehyde.
17. The process according to claim 14, wherein said another
aldehyde comprises formaldehyde, propionaldehyde, n-butyraldehyde,
isobutyraldehyde, valeraldehyde, 2-methylbutyraldehyde,
3-methylbutyraldehyde (isovaleraldehyde),
2,2-dimethylpropionaldehyde (pivalinaldehyde), caproaldehyde,
2-methylvaleraldehyde, 3-methylvaleraldehyde,
4-methylvaleraldehyde, 2-ethylbutyraldehyde,
2,2-dimethylbutyraldehyde, 3,3-dimethylbutyraldehyde, caprylic
aldehyde, capric aldehyde, or glutaraldehyde.
18. The process according to claim 14, wherein the amine catalyst
is triethylamine, tri-n-propylamine, tri-n-butylamine,
trimethlyamine, or mixtures thereof.
19. The process according to claim 14, wherein the base promoter
comprises a carbonate, a hydrogen carbonate, or a hydroxide, or
mixtures thereof of an alkali metal or alkaline earth metal.
20. The process according to claim 19, wherein the base promoter is
Na.sub.2CO.sub.3, K.sub.2CO.sub.3, CaCO.sub.3, NaHCO.sub.3,
KHCO.sub.3, NaOH, KOH, Ca(OH).sub.2, or combinations thereof.
21. The process according to claim 1, wherein the contacting of
formaldehyde and another aldehyde is carried out in an Aldol
reactor, wherein the base promoter is added to the Aldol
reactor.
22. The process according to claim 1, wherein the contacting of
formaldehyde and another aldehyde is carried out in an Aldol
reactor, wherein the base promoter is added to the formaldehyde
upstream of the Aldol reactor.
23. The process according to claim 1, wherein the contacting of
formaldehyde and another aldehyde causes the formation one or more
amine salts.
24. The process according to claim 23, wherein the base promoter is
present in an amount sufficient to achieve dissociation of the
amine salts.
25. The process according to claim 23, wherein the base promoter is
present in an amount that is less than 10 weight percent excess
compared to the weight percent of the amine salts.
26. The process according to claim 1, wherein the contacting of
formaldehyde and another aldehyde is carried out in an Aldol
reactor, wherein the base promoter is present in the Aldol reactor
in an amount of about 500 ppm to about 3000 ppm by weight.
27. The process according to claim 1, wherein the contacting of
formaldehyde and another aldehyde is carried out in a homogeneous
reaction mixture.
28. The process according to claim 1, wherein the another aldehyde
is isobutyralaldehyde, the amine catalyst is trimethylamine, and
the alkaline additive is NaOH.
29. The process according to claim 1, wherein the contacting of
formaldehyde and another aldehyde is carried out at a temperature
in the range of from about 20.degree. C., to about 150.degree. C.,
a pressure in the range from about 5 psig to about 100 psig, and a
total reaction time in the range of from about 30 minutes to about
2 hours.
30. The process according to claim 1, wherein the process is a
continuous process.
31. The process according to claim 14, wherein the contacting of
formaldehyde and another aldehyde is carried out in an Aldol
reactor, wherein the base promoter is added to the Aldol reactor or
to the formaldehyde upstream of the Aldol reactor.
32. The process according to claim 14, wherein the contacting of
formaldehyde and another aldehyde causes the formation one or more
amine salts.
33. The process according to claim 32, wherein the base promoter is
present in an amount sufficient to achieve dissociation of the
amine salts.
34. The process according to claim 32, wherein the base promoter is
present in an amount that is less than 10 weight percent excess
compared to the weight percent of the amine salts.
35. The process according to claim 14, wherein the contacting of
formaldehyde and another aldehyde is carried out in an Aldol
reactor, wherein the base promoter is present in the Aldol reactor
in an amount of about 500 ppm to about 3000 ppm by weight.
36. The process according to claim 14, wherein the another aldehyde
is isobutyralaldehyde, the amine catalyst is trimethylamine, and
the alkaline additive is NaOH.
37. The process according to claim 14, wherein the contacting of
formaldehyde and another aldehyde is carried out at a temperature
in the range of from about 20.degree. C. to about 150.degree. C., a
pressure in the range from about 5 psig to about 100 psig, and a
total reaction time in the range of from about 30 minutes to about
2 hours.
38. The process according to claim 15, wherein the purifying is by
distillation and produces an overhead stream, wherein the
contacting of formaldehyde and another aldehyde is carried out in
an Aldol reactor, wherein at least a portion of said overhead
stream is recycled back to the Aldol reactor, wherein the overhead
stream comprises at least a portion of the amine catalyst.
39. A process comprising: conducting an Aldol condensation reaction
in an Aldol reactor containing an amine catalyst to thereby produce
a reaction mixture comprising a hydroxy aldehyde, wherein one or
more amine salts are produced during the Aldol condensation
reaction; and contacting the amine salts with a base to thereby
cause dissociation of at least a portion of the amine salts.
40. The process according to claim 39, wherein the base is added to
the Aldol reactor.
41. The process according to claim 39, wherein the base is added
upstream of the Aldol reactor.
42. The process according to claim 39, wherein the base is added in
an amount that is less than 10 weight percent excess compared to
the weight percent of the amine salts.
43. The process according to claim 39, wherein the base is added in
an amount of about 500 ppm to about 3000 ppm based on the weight of
the reaction mixture.
44. The process according to claim 39, wherein the amine catalyst
is triethylamine, tri-n-propylamine, tri-n-butylamine,
trimethlyamine, or mixtures thereof.
45. The process according to claim 39, wherein the base comprises a
carbonate, a hydrogen carbonate, or a hydroxide of an alkali metal
or alkaline earth metal.
46. The process according to claim 39, wherein the base is
Na.sub.2CO.sub.3, K.sub.2CO.sub.3, CaCO.sub.3, NaHCO.sub.3,
KHCO.sub.3, NaOH, KOH, Ca(OH).sub.2, or combinations thereof.
47. The process according to claim 39, wherein the hydroxy aldehyde
comprises 3-hydroxypropanal, dimethylolethanal, trimethylolethanal
(pentaerythrital), 3-hydroxybutanal (acetaldol),
3-hydroxy-2-ethylhexanal (butyl aldol), 3-hydroxy-2-methylpentanal
(propyl aldol), 2-methylolpropanal, 2,2-dimethylolpropanal,
3-hydroxy-2-methylbutanal, 3-hydroxypentanal, 2-methylolbutanal,
2,2-dimethylolbutanal, or hydroxypivaldehyde.
48. The process according to claim 39, wherein the amine catalyst
is trimethylamine, the base is NaOH, and the hydroxy aldehyde is
hydroxypivaldehyde.
49. The process according to claim 39, wherein the Aldol
condensation reaction includes contacting formaldehyde and another
aldehyde with the amine catalyst.
50. The process according to claim 49, wherein the another aldehyde
comprises formaldehyde, propionaldehyde, n-butyraldehyde,
isobutyraldehyde, valeraldehyde, 2-methylbutyraldehyde,
3-methylbutyraldehyde (isovaleraldehyde),
2,2-dimethylpropionaldehyde (pivalinaldehyde), caproaldehyde,
2-methylvaleraldehyde, 3-methylvaleraldehyde,
4-methylvaleraldehyde, 2-ethylbutyraldehyde,
2,2-dimethylbutyraldehyde, 3,3-dimethylbutyraldehyde, caprylic
aldehyde, capric aldehyde, or glutaraldehyde.
51. The process according to claim 49, wherein the another aldehyde
is isobutyralaldehyde.
52. The process according to claim 39, further comprising purifying
at least a portion of the reaction mixture in a purification zone
to thereby produce a purified product comprising at least a portion
of the hydroxy aldehyde.
53. The process according to claim 52, further comprising
hydrogenating the purified product to form a polyol.
54. The process according to claim 53, wherein the polyol is
neopentyl glycol.
55. The process according to claim 53, wherein the amine catalyst
is trimethylamine, the base is NaOH, and the hydroxy aldehyde is
hydroxypivaldehyde, and the polyol is neopentyl glycol.
56. The process according to claim 52, wherein the purifying is by
distillation and produces an overhead stream, wherein at least a
portion of said overhead stream is recycled back to the Aldol
reactor, wherein the overhead stream comprises at least a portion
of the amine catalyst.
57. The process according to claim 52, further comprising measuring
the sodium and nitrogen content of the purified product, further
comprising controlling the amount of the base contacted with the
amine salt based on the measured sodium and nitrogen content of the
purified product.
58. The process according to claim 39, wherein the Aldol
condensation reaction is carried out at a temperature in the range
of from about 20.degree. C. to about 150.degree. C., a pressure in
the range from about 5 psig to about 100 psig, and a total reaction
time in the range of from about 30 minutes to about 2 hours.
59. The process according to claim 39, wherein the reaction mixture
is homogeneous.
60. The process according to claim 39, wherein the process is
continuous.
61. The process according to claim 39, wherein the Aldol
condensation reaction includes contacting formaldehyde and another
aldehyde with the amine catalyst, wherein the Aldol condensation
reaction is carried out at a temperature in the range of from about
20.degree. C. to about 150.degree. C., a pressure in the range from
about 5 psig to about 100 psig, and a total reaction time in the
range of from about 30 minutes to about 2 hours, further comprising
purifying at least a portion of the reaction mixture in a
purification zone to thereby produce a purified product comprising
at least a portion of the hydroxy aldehyde, further comprising
hydrogenating the purified product to form a polyol, wherein the
hydroxy aldehyde is hydroxypivaldehyde and the polyol is neopentyl
glycol.
62. The process according to claim 61, wherein the amine catalyst
is triethylamine, tri-n-propylamine, tri-n-butylamine,
trimethlyamine, or mixtures thereof, wherein the base comprises a
carbonate, a hydrogen carbonate, or a hydroxide of an alkali metal
or alkaline earth metal.
63. The process according to claim 61, wherein the amine catalyst
is trimethylamine and the base is NaOH.
Description
BACKGROUND
[0001] Polyols and especially neopentyl glycol (NPG;
2,2-dimethyl-1,3-propanediol) are widely used as starting materials
for preparation of various useful products such as lubricants,
plastics, surface coatings, surfactants, and synthetic resins.
Polyalcohols like NPG are typically produced by a two-step process.
The first step is an Aldol condensation of an enolizable aldehyde,
such as isobutyraldehyde, with formaldehyde to form a hydroxy
aldehyde intermediate such as hydroxypivaldehyde (HPA). The second
step is the hydrogenation of the hydroxy aldehyde over a metal
containing catalyst to form the polyalcohol such as NPG as shown in
Scheme 1.
[0002] Scheme 1 Preparation of Polyalcohols by Aldol Condensation
and Hydrogenation
##STR00001##
[0003] A parameter to watch in the first step of the preparation of
polyols is how efficiently the reactants are converted to the
hydroxy aldehyde intermediate. The formaldehyde concentration in
the Aldol product is frequently considered as an indicator of the
efficiency of the reaction because the levels of formaldehyde in
the Aldol product can be readily measured by a number of analytical
techniques.
[0004] Although a large number of catalysts have been previously
published, the commercially viable Aldol condensation catalysts can
be divided into two groups: (1) a strong alkaline catalyst such as
sodium hydroxide or sodium carbonate and (2) a tertiary amine such
as TMA or triethylamine.
Alkaline Catalyst Systems
[0005] The alkaline catalyst systems have been publically known for
many years. In general, these systems are biphasic and consist of a
mixture of aldehyde and an aqueous formalin solution. The alkaline
catalyst is usually consumed during the process by side reactions
such as the Cannizzaro reaction which forms salts of the carboxylic
acids that correspond to the aldehydes. Examples of these acids are
formic acid, isobutyric acid and hydroxypivalic acid. The salts of
the acids need to be removed from the stream prior to distillation
and hydrogenation to prevent breakdown to retro Aldol products in
the distillation column and hydrogenation reactor. When an
excessive amount of formaldehyde is reacted with aldehyde in the
presence of a strong alkaline catalyst, large amounts of formate
salts are formed as byproducts, making this process commercially
unsuitable. On the other hand, when an excessive amount of aldehyde
is employed, the excessive amount of aldehyde reacts i) with the
product to form esters or ii) with itself to form Aldols and
acetals. These byproducts require several additional steps for the
purification process and ultimately result in yield loss.
Tertiary Amine Catalyst Systems
[0006] The tertiary amine catalyst systems are usually run at a
molar ratio with an excessive amount of aldehyde which enables the
reaction to be carried out in a homogeneous reaction mixture. In
these processes, the selectivity of Aldol is increased compared to
the alkaline catalyst systems. The use of tertiary amine catalysts
in the Aldol condensation is not perfect.
[0007] The tertiary amine catalysts react with organic acids such
as formic acid to form salts. Formic acid exists in commercial
formaldehyde raw material.
[0008] Formaldehyde also reacts with isobutyraldehyde and HPA to
form isobutyric acid and hydroxypivalic acid. These acids form
salts with the tertiary amine catalyst.
[0009] The amine salts cannot be separated from the hydroxy
aldehyde by distillation. These amine salts are carried on into the
hydrogenation reactor, contacting the metal catalyst therein. The
amine salts can deactivate the metal catalyst in the hydrogenation
reaction. Further, the amine salts can promote the decomposition of
the Aldol condensation product during the distillation of product
at high temperatures. Thus, overall yields are dramatically
decreased. The amine salts can also cause undesired color and/or
odors in the downstream products.
SUMMARY
[0010] This invention provides simplified processes of preparing
polyols via the Aldol condensation reaction of formaldehyde with
another aldehyde to form a hydroxy aldehyde intermediate and
hydrogenating the hydroxy aldehyde to form the polyol. Additional
details of example methods are further described below in the
Detailed Description. This summary is not intended to identify
essential features of the claimed subject matter, nor is it
intended for use alone in determining the scope of the claimed
subject matter.
[0011] According to an embodiment, the present invention describes
a process for producing a polyol comprising:
[0012] contacting formaldehyde and another aldehyde in the presence
of an amine catalyst and a promoter under Aldol condensation
conditions to produce hydroxy aldehyde; and
[0013] hydrogenating the hydroxy aldehyde to form a polyol.
[0014] Another embodiment describes a process for producing a
neopentyl glycol comprising:
[0015] contacting formaldehyde and isobutyraldehyde in the presence
of an amine catalyst and a promoter under Aldol condensation
conditions to produce hydroxypivaldehyde; and
[0016] hydrogenating the hydroxypivaldehyde to form neopentyl
glycol.
[0017] Yet another embodiment describes a process for producing a
hydroxy aldehyde comprising:
[0018] contacting formaldehyde and another aldehyde in the presence
of an amine catalyst and a promoter under Aldol condensation
conditions to produce hydroxy aldehyde.
DETAILED DESCRIPTION
[0019] According to an embodiment, the invention describes a
process for reducing the presence of nitrogen containing salts
(e.g. amine salts) in a stream of Aldol product prior to the
hydrogenation of the stream to polyols. For example, an embodiment
concerns reducing nitrogen containing salts from a hydroxy
aldehyde, such as HPA, containing stream that is used for the
production of a polyol, such as NPG. This invention also describes
a method for reusing the amine catalyst in the Aldol condensation
reaction in the Aldol reactor.
[0020] According to an embodiment, the invention describes a
process for the preparation of a polyol. For example, the process
comprises i) contacting formaldehyde and another aldehyde in the
presence of an amine catalyst and a promoter under Aldol
condensation conditions to produce a stream comprising hydroxy
aldehyde and nitrogen containing salts and ii) hydrogenating the
hydroxy aldehyde to form a polyol.
[0021] The hydroxy aldehyde may also optionally be purified before
hydrogenation by any means or process that removes low boilers
(e.g. unreacted started materials, amine catalyst which has been
disassociated from the nitrogen containing salts, and other
volatile contaminants that boil-off with water) such as
distillation or evaporation. Moreover, the recovered catalyst can
be recycled for reuse in the Aldol reactor. For example, the
hydroxy aldehyde may be purified by distillation (e.g. on a low
boiler removal column), wherein distillation is carried out on the
obtained hydroxy aldehyde and nitrogen containing salt stream. The
hydroxy aldehyde is freed from water, unreacted starting materials
and disassociated catalyst by purification, such as distillation at
appropriate combinations of temperature and pressure. Typical
conditions may be, for example, a temperature of from about
80.degree. C. to about 135.degree. C.; or from about 85.degree. C.
to about 120.degree. C.; or from about 90.degree. C. to about
115.degree. C. Moreover, the distillation pressure can be from
about 0 mm to about 1000 mm; or from about 100 mm to about 500 mm;
or from about 220 mm to about 300 mm; or even at about 250 mm.
[0022] According to an embodiment, examples of another aldehyde
include but are not limited to formaldehyde, propionaldehyde,
n-butyraldehyde, isobutyraldehyde, valeraldehyde,
2-methylbutyraldehyde, 3-methylbutyraldehyde (isovaleraldehyde),
2,2-dimethylpropionaldehyde (pivalinaldehyde), caproaldehyde,
2-methylvaleraldehyde, 3-methylvaleraldehyde,
4-methylvaleraldehyde, 2-ethylbutyraldehyde,
2,2-dimethylbutyraldehyde, 3,3-dimethylbutyraldehyde, caprylic
aldehyde, capric aldehyde, and glutaraldehyde.
[0023] According to an embodiment, examples of the hydroxy aldehyde
include but are not limited to 3-hydroxypropanal,
dimethylolethanal, trimethylolethanal (pentaerythrital),
3-hydroxybutanal (acetaldol), 3-hydroxy-2-ethylhexanal (butyl
aldol), 3-hydroxy-2-methylpentanal (propyl aldol),
2-methylolpropanal, 2,2-dimethylolpropanal,
3-hydroxy-2-methylbutanal, 3-hydroxypentanal, 2-methylolbutanal,
2,2-dimethylolbutanal, and HPA.
[0024] According to an embodiment, examples of the polyol include
but are not limited to propylene glycol, ethylene glycol,
dipropylene glycol, diethylene glycol, 1,4-butanediol, NPG,
triethanolamine, and glycerol.
[0025] According to an embodiment, the hydroxy aldehyde stream can
be prepared by reaction of formaldehyde and another aldehyde in the
presence of a tertiary amine catalyst and a promoter. Almost any
tertiary amine catalyst may be used. Moreover, examples of such
tertiary amines include but are not limited to triethylamine,
tri-n-butylamine, and TMA. According to an embodiment, TMA is used
due to the low boiling point of TMA compared to reactants and
products. The lower boiling point facilitates the distillative or
evaporative removal of the nitrogen containing salts in the low
boiler removal column once the stronger base promoter has
dissociated the amine counter ion.
[0026] According to an embodiment, a promoter is supplied to the
Aldol reactor which can, among other things, enhance formaldehyde
conversion and establish a hydrogenation feed with little to no
nitrogen containing salts. The promoter used can be any substance
that can achieve dissociation of the nitrogen containing salts due
to the strength of the base, measured on a pKa scale, such as
inorganic bases. The promoter can include but is not limited to
carbonates, hydrogen carbonates, and hydroxides of the alkali
metals and the alkaline earth metals. Suitable promoters include
but are not limited to Li.sub.2CO.sub.3, Na.sub.2CO.sub.3,
K.sub.2CO.sub.3, CaCO.sub.3, LiHCO.sub.3, NaHCO.sub.3, KHCO.sub.3,
NaOH, LiOH, KOH, and Ca(OH).sub.2. The amount of promoter should be
sufficient to remove nitrogen containing salts from the feed to the
hydrogenation while not catalyzing the retro Aldol reaction of
hydroxy aldehyde to formaldehyde and another aldehyde. The promoter
can be used as a solution, such as an aqueous solution, for
example, in a concentration of about 5% to about 50% by weight.
[0027] The amount of promoter supplied to the Aldol reactor may be
determined by the analysis of the hydrogenation feed for nitrogen
containing salts which is typically measured as total nitrogen
content. The amount of promoter that is added should correspond to
the promoter quantity which is sufficient to decompose the amine
salts and result in a total nitrogen content in the hydrogenation
feed of 25 ppm or less. The amount of promoter will vary because
the concentration of the nitrogen containing salts can vary
depending on the Aldol reactor variables and raw materials
used.
[0028] The salts are typically formed from acids in the reaction
mixture. These acids are typically formic acid, isobutyric acid,
and hydroxypivalic acid. The acids are present in the feedstocks or
are formed under reaction conditions. Moreover, the amine catalyst
reacts with the acids to form the formate, isobutyrate, and
hydroxypivalate salts. Under typical conditions, the concentration
of the nitrogen containing salts is from 3000 ppm to 5000 ppm, but
as explained above, the concentration can vary based on Aldol
reactor variables and raw materials used. It is believed that the
promoter breaks up these nitrogen containing salts during the
purification (e.g. in the distillation column) to liberate the
amine catalyst to be recovered in the low boiler stream. According
to an embodiment, about 50 ppm to about 5000 ppm; about 500 ppm to
about 3000 ppm; or even about 1000 ppm to about 2000 ppm of
promoter is added to the Aldol reactor with the other reactants.
Alternatively, the promoter is added to the Aldol reactor at a
weight percent excess when compared to the weight percent of the
nitrogen containing salts. For example, after the weight percent of
the nitrogen containing salts is determined, the promoter can be
added to the Aldol reactor at less than a 10 weight percent excess,
or less than a 5.0 weight percent excess; or less than a 1.0 weight
percent excess when compared to the previously determined weight
percent of the nitrogen containing salts.
[0029] Scheme 2 below shows an example of a proposed reaction of
NaOH (caustic), Na.sub.2CO.sub.3 (carbonate), or NaHCO.sub.3
(bicarbonate) to deprotonate the ammonium salt. Due to the low
boiling nature of TMA, the reaction is driven to completion and the
TMA catalyst recovered.
##STR00002##
[0030] According to an embodiment, the tertiary amine catalyzed
reaction is a single phase Aldol reaction. The single phase nature
of the reaction occurs because the promoter is in low enough
concentration that the process remains a single phase. According to
the present process, the combination of the promoter and the amine
catalyst results in a highly selective new catalyst that is
superior to either the amine or carbonate by themselves for the
conversion of formaldehyde.
[0031] According to an embodiment, the amount of promoter supplied
can be controlled via measurement of the sodium and nitrogen in the
hydrogenation feed. In general, the amount of promoter is regulated
such that the nitrogen measurement is minimized to a level that is
determined by cost benefit analysis. The promoter can be metered in
using flow control valves and metering pump. Formaldehyde can be
measured at the outlet of the Aldol reactor by any known method. It
is typically done with a colorimetric test based on the Hantzsch
reaction. The sodium and nitrogen are also measured after
purification (e.g. at the outlet of the distillation column)
generally by known techniques. Typical sodium analysis can be
accomplished with inductively coupled (ICP) optical emissions
spectrometer and nitrogen analysis with total nitrogen analyzers
(TN-10). All of these measurements can be online or by regular
sampling.
[0032] According to an embodiment, the hydroxy aldehyde is HPA
which can be prepared by reacting isobutyraldehyde and formaldehyde
in the presence of a tertiary amine catalyst and promoter. The
resulting HPA stream may optionally be purified and then
hydrogenated over a metal containing catalyst to form the polyol
such as NPG. Suitable metal catalysts include, but are not limited
to, metals and compounds of cobalt, nickel, palladium, platinum,
rhodium, molybdenum, mixtures thereof, and the like. Other metal
catalysts may comprise NiMo, NiCo, CuCr, CoMo, or CoNiMo
combinations, in various proportions and mixtures thereof.
[0033] The combining or contacting of the formaldehyde and another
aldehyde in the presence of the catalyst is carried out under Aldol
condensation reaction conditions and the resulting hydroxy aldehyde
stream is then hydrogenated over the metal containing catalyst to
form the polyol under hydrogenation reaction conditions. The
terminology "reaction conditions" is meant to mean those conditions
of temperature, pressure, length of contact time, etc., which
enable or allow the reaction to proceed. Included in such
conditions are those required to supply or to maintain the
reactant(s) in the liquid phase, i.e., temperature, pressure, so
that intimate contact with the catalyst is realized. Suitable
temperatures, for example, may range from about 0.degree. C. to
about 200.degree. C.; or from about 20.degree. C. to about
150.degree. C.; or from about 70.degree. C. to about 110.degree. C.
Pressures may be varied considerably, and may range from about 1
psig to about 300 psig; from about 5 psig to about 100 psig; or
from about 10 psig to about 40 psig. For a batch reaction, total
reaction times, i.e., the time to completion or substantial
completion of the condensation reaction, will vary considerably,
but in general will range from about 30 minutes to about 24 hours
or from about 30 minutes to about 2 hours. In the case of a
continuous process, with continuous feed to a reaction zone and
continuous withdrawal of product containing mixture, average
contact time may range from about 30 minutes to about 48 hours or
from about 30 minutes to about 2 hours, contact time herein being
understood as the liquid volume in the reactor divided by the
volumetric flow rate of the liquid.
EXAMPLES
[0034] The process according to the embodiments described above is
further illustrated by, but not limited to, the following examples
wherein all percentages given are by weight unless specified
otherwise.
Example 1
Continuous Synthesis of Neopentyl Glycol (NPG)
[0035] The process described herein is for the preparation of NPG.
A one gallon reactor equipped with a stirrer was continuously fed
with isobutyraldehyde, about 50% aqueous formaldehyde solution, and
6% TMA solution in isobutyraldehyde. The ratio of isobutyraldehyde
to formaldehyde was maintained in the range of 1.1:1 to 1.6:1 by
adjusting the feed rates to the Aldol reactor. Additionally, the
TMA concentration in the reactor was adjusted to 2% by adjusting
the feed rate of the 6% TMA in isobutyraldehyde solution. The
reactor was maintained at 70 to 110.degree. C. under a nitrogen
pressure of 10 to 40 psig. The residence time was adjusted to 1
hour by removing the condensation product mixture containing crude
HPA at a set rate. This condensation product mixture having the
composition shown in Table 1 was introduced continuously to the
middle of a multi stage distillation column. The multi staged
column was maintained at a sufficient temperature to remove TMA,
isobutyraldehyde, and water as overhead products and crude HPA as a
base overflow product. Table 1 illustrates the components of the
streams when the column bottom temperature was maintained between
80.degree. C. to 100.degree. C. at 5 psig. The overhead product was
returned to the Aldol reactor as the TMA catalyst feed.
[0036] The base overflow stream was fed continuously to a trickle
bed hydrogenation reactor containing a nickel catalyst. The
hydrogenation reactor was maintained at 140.degree. C. to
180.degree. C. and 400 to 600 psig of hydrogen pressure. The ratio
of total liquid feed volume to fresh feed was maintained at 10:1.
The gas and liquid leaving the hydrogenation reactor pass through a
vapor liquid separator and the excess hydrogen is vented.
[0037] The liquid hydrogenation product stream having the
composition shown in Table 1 was treated with sodium hydroxide at
90.degree. C. and then distilled to remove isobutanol, methanol,
and water at 100.degree. C. and 760 mm Hg. The NPG/water mixture
was flash distilled from sodium containing salts at 150.degree. C.
and 130 mm Hg. A final distillation to remove water produces NPG
final product in a 95% yield from isobutyraldehyde and with the
composition shown in Table 1.
TABLE-US-00001 TABLE 1 Final Aldol Hydrogenation Hydrogenation
Product (wt %) Feed (wt %) Product (wt %) (wt %) Water 25 20 20 0
iBOH 7.5 -- -- 0 TMA and salts 1.95 0 -- 0 HPA 61.5 75 0.0 0 NPG
0.75 0.87 75 99.8 HCHO (ppm) 3000 250 0 0 Nitrogen NM 1050 NM 0
(ppm) Sodium (ppm) NM 0 NM 0 Others 3 4 5 0.2 24 hr averages; NM =
Not Measured
Example 2
Addition of Sodium Carbonate to the Aldol Reactor
[0038] The procedure of Example 1 was repeated except that an
additional feed line was added to the existing Aldol reactor feed
header. A 6% solution of sodium carbonate was continuously metered
into the reactor to maintain 1000 to 1500 ppm sodium in the
hydrogenation feed analysis. The resulting total nitrogen
measurement in the hydrogenation feed stream was controlled to less
than 25 ppm. Additionally, the formaldehyde concentration in the
Aldol product (exiting the reactor) was decreased from about 3000
ppm to 1250 ppm. This data demonstrate that the addition of sodium
carbonate to the Aldol reactor with TMA results in both TMA
recovery prior to hydrogenation reactor and enhanced catalytic
properties for the production of HPA.
Example 3
Addition of Sodium Bicarbonate to the Aldol Reactor
[0039] The procedure of Example 1 was repeated except that an
additional feed line was added to the existing Aldol reactor feed
header. A 6% solution of sodium bicarbonate was continuously
metered into the reactor to maintain 1000 to 1500 ppm sodium in the
hydrogenation feed analysis. The resulting total nitrogen content
in the hydrogenation feed stream was controlled to less than about
25 ppm. However, the formaldehyde concentration in the Aldol
product (exiting the reactor) did not change from about 3000 ppm.
This shows that the basicity of the bicarbonate is sufficient to
break up the TMA salts but it is not strong enough to impact the
formaldehyde conversion in the Aldol reactor.
Example 4
Addition of Sodium Carbonate to the HCHO Feed
[0040] The procedure of Example 1 was repeated except a 6% solution
of sodium carbonate was metered into the formaldehyde feed line
prior to the Aldol reactor as such a rate as to maintain 1000 to
1500 ppm sodium in the hydrogenation feed analysis. The resulting
total nitrogen in the hydrogenation feed was controlled to less
than 25 ppm and the formaldehyde concentration in the Aldol product
exiting the reactor was decreased from about 3000 ppm to 1250 ppm.
This data demonstrates that the addition of sodium carbonate to the
formaldehyde feed has the same effect as adding it directly to the
Aldol reactor.
Example 5
Decrease Trimethylamine Concentration in the Aldol Reactor
[0041] The procedure of example 2 was repeated. A solution of 6%
aqueous sodium carbonate was metered into the Aldol reactor to
maintain 1000 to 1500 ppm sodium in the hydrogenation feed
analysis. The TMA level in the reactor was reduced from 2% to 1%.
The resulting total nitrogen in the hydrogenation feed was
controlled to less than 25 ppm and the formaldehyde concentration
in the Aldol product exiting the reactor was 1250 ppm. This data
shows that the addition of sodium carbonate to the Aldol reactor
promotes the Aldol reaction sufficiently that the TMA content in
the reactor can be substantially reduced and achieve the same
conversion of formaldehyde.
[0042] Although embodiments have been described in language
specific to methodological acts, the embodiments are not
necessarily limited to the specific acts described. Rather, the
specific acts are disclosed as illustrative forms of implementing
the embodiments.
* * * * *