U.S. patent application number 09/774628 was filed with the patent office on 2001-08-30 for preparation of n-methy1-2-pyrrolidone (nmp).
Invention is credited to Liebe, Jorg, Melder, Johann-Peter, Ohlbach, Frank, Ross, Karl-Heinz, Rudloff, Martin.
Application Number | 20010018528 09/774628 |
Document ID | / |
Family ID | 7629805 |
Filed Date | 2001-08-30 |
United States Patent
Application |
20010018528 |
Kind Code |
A1 |
Ohlbach, Frank ; et
al. |
August 30, 2001 |
Preparation of N-methy1-2-pyrrolidone (NMP)
Abstract
N-Methyl-2-pyrrolidone (NMP) is prepared by preparing a mixture
comprising monomethylamine, dimethylamine and trimethylamine and
ammonia in a first process step by reacting ammonia with methanol
at elevated temperature in the presence of a catalyst, separating
off the ammonia, reacting the mixture comprising the methylamines
with gamma-butyrolactone (.gamma.-BL), in a molar ratio of
monomethylamine to .gamma.-BL of at least 1 in a second process
step at elevated temperature and superatmospheric pressure,
separating NMP and unreacted methylamines from the reaction product
and returning unreacted methylamines to the first process step for
reaction with methanol and ammonia.
Inventors: |
Ohlbach, Frank; (Dossenhcim,
DE) ; Melder, Johann-Peter; (Bohl-Iggelheim, DE)
; Ross, Karl-Heinz; (Grunstadt, DE) ; Rudloff,
Martin; (Weisenheim, DE) ; Liebe, Jorg;
(Tokyo, JP) |
Correspondence
Address: |
Herbert B. Keil
KEIL & WEINKAUF
1101 Connecticut Ave. N.W.
Washington
DC
20036
US
|
Family ID: |
7629805 |
Appl. No.: |
09/774628 |
Filed: |
February 1, 2001 |
Current U.S.
Class: |
548/552 |
Current CPC
Class: |
C07D 207/267
20130101 |
Class at
Publication: |
548/552 |
International
Class: |
C07D 207/267 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 4, 2000 |
DE |
10004909.5 |
Claims
We claim:
1. A process for preparing N-methyl-2-pyrrolidone (NMP), which
comprises preparing a mixture comprising monomethylamine,
dimethylamine and trimethylamine and ammonia in a first process
step by reacting ammonia with methanol at elevated temperature in
the presence of a catalyst, separating off the ammonia, reacting
the mixture comprising the methylamines with gamma-butyrolactone
(.gamma.-BL), in a molar ratio of monomethylamine to .gamma.-BL of
at least 1 in a second process step at elevated temperature and
superatmospheric pressure, separating NMP and unreacted
methylamines from the reaction product and returning unreacted
methylamines to the first process step for reaction with methanol
and ammonia.
2. A process as claimed in claim 1, wherein the reaction of the
first process step is carried out continuously at from 300 to
500.degree. C. and in the presence of a solid acid catalyst.
3. A process as claimed in claim 1 or 2, wherein the mixture
obtained in the first process step after separating off ammonia has
a content of the three methylamines, water and methanol of at least
96% by weight.
4. A process as claimed in any of claims 1 to 3, wherein the
reaction of the second process step is carried out at from 200 to
300.degree. C.
5. A process as claimed in any of claims 1 to 4, wherein the
reaction of the second process step is carried out at a pressure of
from 50 to 150 bar.
6. A process as claimed in any of claims 1 to 5, wherein the molar
ratio of monomethylamine to .gamma.-BL in the second process step
is from 1.05 to 1.5.
7. A process as claimed in any of claims 1 to 6, wherein the
reaction of the second process step is carried out continuously in
a tube reactor at a residence time in the reactor of from 1.5 to 5
hours.
8. A process as claimed in any of claims 1 to 7, wherein the
unreacted methylamines for return to the first process step are
dimethylamine and trimethylamine.
Description
[0001] The present invention relates to a process for preparing
N-methyl-2-pyrrolidone (=1-methyl-2-pyrrolidinone, NMP).
[0002] Owing to its ready volatility, thermal stability, high
polarity and aprotic properties, NMP is suitable as a solvent for
polymers and as a solvent for numerous organic syntheses, e.g.
alkylations or preparation of carboxylic acids and their
derivatives.
[0003] NMP is industrially important for, in particular, the
separation of acetylene from cracker gas or of butadiene from
C.sub.4 fractions, for the extraction of aromatics or for the
absorption of acidic constituents in gas scrubbers.
[0004] The industrial preparation of NMP is predominantly carried
out by reaction of gamma-butyrolactone (.gamma.-BL) with
monomethylamine (MMA) in a tube reactor, e.g. a shaft reactor, at
from 200 to 350.degree. C. and superatmospheric pressure, e.g.
about 10 MPa (Ullmann's Encyclopedia of Industrial Chemistry,
5.sup.th ed., Vol. A22, pages 458 to 459 (1993)).
[0005] For example, JP-A-10 158 238 (Derwent Abstr. 98-393443/34)
describes the reaction of .gamma.-BL with excess MMA at from 250 to
300.degree. C. in the presence of water to form NMP.
[0006] JP-A-1 190 667 (Derwent Abstr. 89-260914/36) describes the
preparation of NMP by reaction of .gamma.-BL with excess MMA, with
the MMA remaining unreacted after the reaction and also the
dimethylamine (DMA) and trimethylamine (TMA) obtained as
by-products together with added water are returned to the reaction
of .gamma.-BL with excess MMA.
[0007] JP-A-7 218 751 (Derwent Abstr. 35795T-E) reports the
synthesis of NMP by heating .gamma.-BL or open-chain derivatives
thereof with DMA and/or TMA at above 200.degree. C. In an example,
the reaction of .gamma.-BL with aqueous DMA at 270.degree. C./3 h
gives NMP in a yield of 80%.
[0008] JP-A-1 186 864 (Derwent Abstr. 89-259000/36) discloses the
preparation of N-alkylated lactams by reaction of the corresponding
lactones with secondary amines in the presence of water via the
corresponding N,N-dialkyl-omega-hydroxycarboxamides as
intermediates. According to Example 1 of this patent application,
the reaction of .gamma.-BL with aqueous DMA gives an NMP yield of
60% and additionally forms methylamides of .gamma.-hydroxybutyric
acid. In the single further example according to the application,
too, an NMP yield of 60% is reported for the corresponding reaction
of .gamma.-BL with DMA.
[0009] JP-A-1 186 863 (Derwent Abstr. 89-258999/36) describes the
preparation of N-alkylated lactams by reaction of corresponding
lactones with tertiary amines or with tertiary or quaternary
ammonium compounds in the presence of water with elimination of a
corresponding alcohol. According to Example 1 of this patent
application, the reaction of .gamma.-BL with aqueous TMA gives an
NMP yield of 8% and forms large amounts of by-products such as
methylamides of .gamma.-hydroxybutyric acid, 2-pyrrolidone and
.gamma.-hydroxybutyric acid.
[0010] The methylamines monomethylamine (MMA), dimethylamine (DMA)
and trimethylamine (TMA) are prepared industrially in a continuous
process by (exothermic) reaction of ammonia with methanol in the
presence of a catalyst at elevated temperature (e.g.: Kirk-Othmer,
Encyclopedia of Chemical Technology, 4.sup.th ed., Vol. 2, pages
373 to 375 (1992) and Ullmann's Encyclopedia of Industrial
Chemistry, 5th Ed., Vol. A16, pages 535 to 541 (1990)).
[0011] Catalyst used are acid catalysts, in particular solid acid
catalysts such as silicon oxides (silica, SiO.sub.2), aluminum
oxides (alumina, Al.sub.2O.sub.3), silica-alumina
(SiO.sub.2.Al.sub.2O.sub.3), titanium oxides (titania, TiO.sub.2),
tungsten oxides, phosphates (AlPO.sub.4), zeolites and clays
(method 1) or metal catalysts such as cobalt-, nickel- or
copper-containing catalysts (e.g. copper chromite) (method 2). The
catalyst is usually installed as a fixed bed.
[0012] The reaction temperatures in method 1 are generally from 300
to 500.degree. C., in particular from 390 to 430.degree. C., and
the reaction temperatures in method 2 are generally from 130 to
250.degree. C.
[0013] In method 1, the pressure is generally from 790 to 3550 kPa,
in particular from 1500 to 3000 kPa; method 2 is usually carried
out in the presence of hydrogen.
[0014] In these reactions of ammonia with methanol, a mixture of
the methylamines MMA, DMA and TMA together with water is always
obtained. The total selectivity to the methylamines is about 94%;
secondary reactions are dissociations to form CO, CO.sub.2,
CH.sub.4, H.sub.2 and N.sub.2 (cf., for example, K. Weissermel et
al., Industrielle Organische Chemie, 3.sup.rd edition, pages 53 to
54 (1990)).
[0015] The crude reaction product comprising essentially ammonia,
water, possibly unreacted methanol and the methylamines is
fractionated by means of a continuous multistage, technically
complicated distillation (combination of various pressure
distillations and extractive distillations). A typical process
diagram for the synthesis of methylamines and their isolation is
shown in FIG. 2 in Kirk-Othmer, Encyclopedia of Chemical
Technology, 4.sup.th ed., Vol. 2, pages 375 (1992), which is hereby
incorporated by reference.
[0016] For example, in a distillation sequence which is technically
complicated overall, ammonia and part of the TMA is firstly
separated from the reaction mixture and the remaining TMA is
subsequently separated off in an extraction column using water.
Ammonia is returned to the reaction. In a subsequent dewatering
column, MMA and DMA are separated off by the top and separated from
one another in a separate column. Methanol is taken off at a side
outlet of the dewatering column and separated from water in a
separate column and returned to the synthesis. DMA and TMA can
likewise be returned in principle to the reaction of NH.sub.3 with
methanol, with mixtures of MMA, DMA and TMA again being formed from
DMA and TMA under the reaction conditions (thermodynamic
equilibrium; cf., for example, Ullmann's Encyclopedia of Industrial
Chemistry, 5.sup.th ed., Vol. A16, page 537 (1990)).
[0017] Further configurations of the methylamine production process
may be found in J. Ramioulle et al., Hydrocarbon Processing, July
1981, pages 113 to 117 (cf., for example, FIG. 6 on page 117 of
this document), which is hereby likewise incorporated by
reference.
[0018] A disadvantage of the processes of the prior art for
preparing NMP from ammonia, methanol and .gamma.-BL is that the MMA
required for the reaction with .gamma.-BL firstly has to be
isolated from the crude reaction product from the synthesis of
methylamines by means of a technically very complicated
distillation cascade (plurality of distillation columns connected
in series) (as described above).
[0019] It is an object of the present invention to overcome the
disadvantages of the prior art by finding an efficient, selective,
economical and technically less complicated process for preparing
NMP in high yields (based on .gamma.-BL) and high space-time yields
from ammonia, methanol and .gamma.-BL.
[0020] We have found that this object is achieved by a process for
preparing N-methyl-2-pyrrolidone (NMP), which comprises preparing a
mixture comprising monomethylamine, dimethylamine and
trimethylamine and ammonia in a first process step by reacting
ammonia with methanol at elevated temperature in the presence of a
catalyst, separating off the ammonia, reacting the mixture
comprising the methylamines with gamma-butyrolactone (.gamma.-BL),
in a molar ratio of monomethylamine to .gamma.-BL of at least 1 in
a second process step at elevated temperature and superatmospheric
pressure, separating NMP and unreacted methylamines from the
reaction product and returning unreacted methylamines to the first
process step for reaction with methanol and ammonia.
[0021] According to the present invention, the technically very
complicated fractionation of the crude reaction product from the
reaction of methanol with ammonia to give the individual
methylamines MMA, DMA and TMA or the corresponding binary mixtures
(e.g. MMA+DMA) can be dispensed with.
[0022] The process of the present invention can be carried out as
follows:
[0023] Ammonia is reacted with methanol in the presence of an acid
catalyst, particularly preferably a solid acid catalyst (e.g.
AlO.sub.x), or a metal catalyst, with the catalyst particularly
preferably being installed in the reactor as a fixed bed, at
elevated temperature according to the known methods of the prior
art as have been described above to give a mixture consisting
essentially of the three methylamines MMA, DMA and TMA, ammonia,
water and possibly unreacted methanol. (First process step).
[0024] In this context, "essentially" means that the total content
of the three methylamines, ammonia, water and, if present, methanol
in the mixture is at least 95% by weight, preferably at least 97%
by weight, in particular at least 98% by weight, particularly
preferably at least 99% by weight.
[0025] Subsequently, in a distillation column, the ammonia is
separated off via the top from the mixture consisting essentially
of the three methylamines, ammonia, water and possibly unreacted
methanol in accordance with known methods (cf., for example, FIG.
2. in Kirk-Othmer, Encyclopedia of Chemical Technology, 4.sup.th
ed., Vol. 2, page 375: first column after the reactor).
[0026] This gives a mixture consisting essentially of the three
methylamines, water and possibly methanol. In this context,
"essentially" means that the total content of the three
methylamines, water and, if present, methanol in the mixture is at
least 96% by weight, preferably at least 97% by weight, in
particular at least 98% by weight, particularly preferably at least
99% by weight.
[0027] The water content of this mixture is generally from 30 to
50% by weight, preferably from 35 to 45% by weight.
[0028] The methanol content of this mixture is generally from 0 to
10% by weight, preferably from 3 to 7% by weight.
[0029] The residual ammonia content of this mixture is generally
from 0 to 1% by weight, preferably from 0.1 to 0.8% by weight.
[0030] The weight ratio of the methylamines in this mixture is
generally MMA:DMA:TMA=(1-14):(6-12):(0.2-12), preferably
MMA:DMA:TMA=(1-2.7):(2-3):- (0.07-2).
[0031] In a subsequent extraction column and one or more
distillation columns, any methanol and water present in this
mixture can, if desired, be reduced in concentration or separated
off at the top and bottom respectively according to known methods
(cf., for example, FIG. 2. in Kirk-Othmer, Encyclopedia of Chemical
Technology, 4.sup.th ed., Vol. 2, page 375: second and third
columns after the reactor).
[0032] The mixture which is obtained after the above steps and
consists essentially of the three methylamines MMA, DMA and TMA,
possibly water and possibly methanol is reacted with
gamma-butyrolactone (.gamma.-BL) at elevated temperature,
preferably at from 180 to 350.degree. C., in particular from 200 to
300.degree. C., particularly preferably from 230 to 270.degree. C.,
and at superatmospheric pressure, preferably at from 5 to 300 bar,
in particular from 50 to 150 bar. (Second process step)
[0033] The molar ratio of MMA to .gamma.-BL here is at least 1,
preferably at least 1.05, particularly preferably at least 1.1.
Preferred ranges for the molar ratio of MMA to .gamma.-BL are from
1 to 2, preferably from 1.05 to 1.5, particularly preferably from
1.1 to 1.25.
[0034] The reaction can be carried out batchwise in a pressure
reactor (autoclave) or preferably continuously in a tube reactor
which may be fitted with internals for influencing the flow
behavior in the reactor, e.g. in a shaft reactor.
[0035] The residence time of the reaction mixture in the reactor
under the conditions indicated is generally from 1 to 6 hours,
preferably from 1.5 to 5 hours, particularly preferably from 2 to 4
hours.
[0036] For this reaction, preference is given to using a
gamma-butyrolactone (.gamma.-BL) having a purity of at least 98% by
weight, preferably at least 99% by weight.
[0037] The .gamma.-BL required can be obtained by known methods by
means of the endothermic cyclizing dehydrogenation of
1,4-butanediol in the gas phase over a metal catalyst (e.g. a
copper catalyst) at elevated temperature or by means of selective
hydrogenation of maleic anhydride at superatmospheric pressure and
elevated temperature over a metal catalyst and, in each case,
subsequent purification by distillation (Ullmann's Encyclopedia of
Industrial Chemistry, 5.sup.th ed., Vol. A4, page 496 (1985)).
[0038] The reaction product obtained comprises NMP, unreacted
methylamines (in particular unreacted DMA and TMA), water, small
amounts of by-products, possibly methanol and possibly unreacted
.gamma.-BL.
[0039] In general, the .gamma.-BL conversion in this process step
under the reaction conditions indicated is greater than 95%, in
particular greater than 97%, very particularly preferably greater
than 99%.
[0040] The by-product content of the reaction product is typically
less than 5% by weight, in particular less than 3.5% by weight,
very particularly preferably less than 2% by weight.
[0041] The desired process product NMP is isolated from the
reaction product by single-stage or multistage fractional
distillation.
[0042] For example, the work-up of the reaction product by
distillation can be carried out in two stages, with DMA and TMA and
any MMA still present being taken off at the top as distillate in
the first distillation stage and water being separated off at the
top and the pure NMP being taken off at a side offtake in the
second distillation stage.
[0043] The methylamines obtained in the work-up of the reaction
product by distillation, in particular DMA and TMA, are, according
to the present invention, returned to the first process step of
reaction of ammonia with methanol.
[0044] Correspondingly, the methanol obtained can also be returned
to the first process step.
[0045] In the process of the present invention, the selectivity for
the formation of NMP (based on .gamma.-BL) is greater than 90%, in
particular greater than 93%, very particularly preferably at least
95%, at .gamma.-BL conversions of greater than 95%.
[0046] Since it was known from the prior art that DMA and TMA also
react with .gamma.-BL, but in each case NMP is obtained only in
very poor selectivities and yields because of the formation of
by-products, it is surprising that the process of the present
invention, in which MMA, DMA and TMA are reacted with .gamma.-BL
and unreacted methylamines are subsequently returned to the
reaction of NH.sub.3 with methanol, achieves very high
selectivities and yields for the formation of NMP (based on
.gamma.-BL).
[0047] This fact is illustrated by Examples 1 to 4 below.
[0048] Examples 1 and 2 below show that in each case .gamma.-BL
reacts virtually quantitatively even at 5.degree. C. to room
temperature with aqueous solutions of the excess methylamine MMA
and/or TMA to give the corresponding methylamides of
.gamma.-hydroxybutyric acid.
[0049] Example 2 shows that the amides obtained from .gamma.-BL and
MMA or DMA, namely .gamma.-hydroxybutyric acid monomethylamide or
.gamma.-hydroxybutyric acid dimethylamide and the internal salt
obtained from .gamma.-BL and TMA even at room temperature ("TMA-BL
adduct") of the formula 1
[0050] can be converted into NMP at elevated temperature,
preferably at above 200.degree. C., by cyclization and elimination
of water or methanol.
[0051] According to the present invention, it was recognized that
under comparable conditions the cyclization of the monomethylamide
to NMP proceeds significantly more quickly than that of the
dimethylamide or the TMA-BL adduct. It was also found that the
cyclization to NMP can be carried out either in aqueous solution or
in the absence of water. Under anhydrous conditions, the NMP yields
starting from DMA or TMA are significantly lower than when the
reactions are carried out in the presence of water (Examples 2a and
2b).
[0052] The yields of NMP obtained by reacting DMA or TMA with
.gamma.-BL at 255.degree. C./3 h are, however, at most only 63% in
Example 2. In these reactions with DMA or TMA, the .gamma.-BL
conversion is in each case significantly higher than the
corresponding NMP yield, since considerable amounts of by-products
such as .gamma.-hydroxybutyric acid dimethylamide or TMA-BL adduct
are present in the reaction product.
[0053] Furthermore, it was recognized according to the present
invention (see Example 3) that .gamma.-hydroxybutyric acid
monomethylamide and .gamma.-hydroxybutyric acid dimethylamide are
very readily converted into one another in the presence of excess
MMA or DMA at temperatures above about 80.degree. C., i.e. a
thermodynamic equilibrium between the two amides is established at
elevated temperature.
[0054] In addition, it was recognized according to the present
invention (Example 4) that the reaction of an equimolar mixture of
MMA and DMA with a molar excess of .gamma.-BL (based on MMA+DMA),
where MMA is present in an at least equimolar amount based on
.gamma.-BL, initially forms a mixture of the two corresponding
amides (hydroxybutyric acid monomethylamine and
.gamma.-hydroxybutyric acid dimethylamide) in a ratio of about 3:1
(with the monomethylamide being the major component) at room
temperature in a kinetically controlled reaction. Increasing the
temperature to above 80.degree. C. results in establishment of the
thermocynamic equilibrium between the two corresponding amides,
which is even more distinctly on the side of the monomethylamide.
At 270.degree. C., the ratio shifts to about 4:1 (again with the
monoamide as major component)
EXAMPLES
Example 1
[0055] Preparation of the Open-Chain Amides from .gamma.-BL and MMA
or DMA
[0056] The reactions were carried out in a round-bottomed flask
with ice cooling, and the corresponding aqueous amine solutions
were placed in the flask and the .gamma.-BL was added dropwise at
an internal temperature of 5.degree. C. The yields were in each
case determined as % by area by GC.
[0057] 1a) Reaction of .gamma.-BL with MMA
[0058] Starting materials: 65 ml (0.75 mol) of 40% strength MMA
solution 22 g (0.25 mol) of .gamma.-BL
[0059] Yield: >99.5% of N-methyl-.gamma.-hydroxybutyramide
[0060] 1b) Reaction of .gamma.-BL with DMA
[0061] Starting materials: 95 ml (0.75 mol) of 40% strength DMA
solution 22 g (0.25 mol) of .gamma.-BL
[0062] Yield: >99.5% of
N,N-dimethyl-.gamma.-hydroxybutyramide
[0063] 1c) Reaction of .gamma.-BL with an MMA/DMA mixture
[0064] Starting materials:
[0065] 65 ml (0.75 mol) of 40% strength MMA solution
[0066] 95 ml (0.75 mol) of 40% strength DMA solution
[0067] 44 g (0.5 mol) of .gamma.-BL
[0068] Yields:
[0069] 76.3% of N-methyl-.gamma.-hydroxybutyramide
[0070] 23.6% of N,N-dimethyl-.gamma.-hydroxybutyramide
Example 2
[0071] Reaction of .gamma.-BL with MMA, DMA or TMA to give NMP
[0072] 2a) Use of the Corresponding Aqueous Amine Solutions
[0073] The reactions were carried out in a 300 ml autoclave. The
appropriate amine was firstly placed in the autoclave as an aqueous
solution and .gamma.-BL was slowly added; in each case, the
corresponding amide (as described above) or in the case of TMA a
corresponding internal salt (TMA-BL adduct) was formed in an
exothermic reaction. After closing the autoclave, it was
pressurized with 20 bar of N.sub.2, heated to 255.degree. C.,
maintained at this temperature for 3 hours and then allowed to cool
again. The .gamma.-BL conversions and the corresponding NMP yields
were in each case determined as % by area by GC. Results:
1 unreacted .gamma.-BL Experiment Amine (%) NMP yield (%) 1 MMA
0.05 98.2 2 DMA 13.2 63.1 3 TMA 48.3 22.1
[0074] 2b) Use of the Corresponding Anhydrous Amines
[0075] The reactions were carried out as described under 2a) in a
300 ml autoclave, with the amines in each case being condensed
under pressure into the closed autoclave. After addition of
.gamma.-BL, the further procedure was as under 2a). Results:
2 unreacted .gamma.-BL Experiment Amine (%) NMP yield (%) 1 MMA 0
95 2 DMA 31.8 21.4 3 TMA 95.0 0.1
Example 3
[0076] Transalkylation of N,N-dimethyl-.gamma.-hydroxybutyramide
with MMA
[0077] 65 g (0.5 mol) of the dimethylamide and 86 ml of 40%
strength aqueous MMA solution (1 mol) were placed in a 500 ml
round-bottomed flask and heated at 80.degree. C. for 1 hour. 7.6%
of the corresponding monomethylamide were detected in the
product.
Example 4
[0078] Reaction of .gamma.-BL with an MMA/DMA Mixture
[0079] 0.75 mol of MMA solution and 0.75 mol of DMA solution (each
40% strength in water) were placed in a round-bottomed flask and
admixed with .gamma.-BL at 5.degree. C. with ice cooling. The
solution was subsequently passed with a residence time of 10
minutes through a tube which was at 270.degree. C. The products
were in each case analyzed by GC (reported in % by area).
Results:
3 corresponding corresponding monomethylamide dimethylamide NMP
Temperature (yield in %) (yield in %) (yield in %) 5.degree. C.
76.3 22.6 0 270.degree. C. (10 min.) 40.8 10.2 45
Example 5
[0080] Reaction of .gamma.-BL with a Methylamine Mixture
[0081] Using a method analogous to Example 2, a mixture of 0.1 mol
of MMA, 0.173 mol of DMA and 0.29 mol of TMA, in each case as 40%
strength aqueous solution, was heated with 0.09 mol of .gamma.-BL
at 255.degree. C. for 3 hours. The yield of NMP was 94.8% (0.0853
mol).
* * * * *