Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2000-02-04
2001-06-19
McKane, Joseph K. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C548S552000
Reexamination Certificate
active
06248902
ABSTRACT:
The present invention relates to the production of N-methyl pyrrolidone. In particular, it relates to the use of gamma-butyrolactone and monomethylamine as starting materials for that purpose, by a continuous process, in such a way that the product is obtained in optimal purity and yields.
It is known from the prior art that there exist several processes for the synthesis of N-methyl pyrrolidone (NMP) with gamma butyrolactone (GBL) and monomethylamine (MMA) as starting materials.
In J.Am.Chem.Soc., March 1949, pag. 897, Elvain and Vozza described a synthetic strategy aimed at the production of NMP with GBL and MMA as starting materials that exploited a discontinuous process, and with a double amount of the latter two in comparison with their stoichiometric values.
After 4 hours of reaction at 280° C., NMP was recovered by distillation with a 90-93% yield.
In 1936 Spath and Lunder (Berichte 69, pag 2727) described a similar process wherein a large excess of methylamine (4 mols per mol of GBL) was fed to a discontinuous reactor, with an approximately 90% conversion after 3 hours.
NMP product purification involved complex dissolution processes, to be carried out in the ether from the effluent of the reaction and the ensuing distillations.
In several patents (JP 7 221 420; JP 7400259; JP 7 420 585; JP 7 642 107) Mitsubishi Chemical industries Co. Ltd. of Japan described continuous processes for the synthesis of NMP using GBL and MMA as starting materials. These are characterised by reactions with high molar ratios between water and shot GBL (typically ranging between 3 and 4 mols of water for each mol of GBL) and by the presence of great amounts of MMA (typically with molar ratios ranging between 1.4 and 3 mols of MMA per mol of GBL).
The processes designed by Mitsubishi result to be disadvantaged in terms of the high costs involved with the separation of unreacted MMA and its recovery and with the separation of the water forwarded to the reaction to which synthesis water adds up (one mol of water for each mol of reacted GBL).
To avoid the drawbacks associated with the discontinuous reaction in the presence of excess MMA and water, alternative methodologies have been proposed and these are based on the employment of catalysts.
In German Patent n
o
2,159,858 owned by Mobil Oil a synthesis with GBL, MMA in the presence of 13X type zeolites is described.
In German Patent 4,203,527 owned by AKZO, a synthesis involving GEL, MMA and steam in the gas phase and at a temperature of 275° C., on an NaX type zeolite is described.
The above processes did not succeed in being applied industrially, as the employment of a catalyst subject to regenerations is disadvantageous in terms of the economic balance of the process as compared with non catalytic processes.
A first aim of the present invention is that of proposing a process wherein no catalysts are employed and thanks to which a high percentage of MMA and GBL is converted with high selectivities. The above features give way to the production of NMP at low investment costs and raw material and utility consumption.
Another aim of the present invention is to get the reaction to take place in a continuous fashion, without feeding any water, and with low molar ratios between shot MMA and GBL.
The above aims were accomplished by the employment of a process for the production of N-methyl-pyrrolidone obtained by reaction of gamma butyrolactone and monomethylamine, characterised in that the synthesis is carried out by a continuous non catalytic process in the liquid phase, via three distinct reaction stages connected in series.
These and other features will be more readily apparent from the following description of a preferred not limiting embodiment of the invention with reference to the accompanying drawings in which the process scheme is shown.
According to the present invention the three stages of the reaction are characterised by what follows:
I stage of reaction
MMA:GBL molar ratio
=between 1.05 and 1.4
Temperature
=between 150
(reactor outlet)
and 220° C.
Residence time
=between 5 and 30
minutes
II stage of reaction
Temperature
=between 220 and
270° C.
Residence time
=between 1 and 3
hours
III stage of reaction
Temperature
=between 250 and
310° C.
Residence time
=between 0.5 and
2.0 hrs
In the three reactors pressure ranges between 30 and 90 ATE, so as to keep the reactants in their liquid phase. An ATE is a Technical Atmosphere. One Technical Atmosphere equals 1.103 bar, thus 30 ATE equals 30.39 barg and 90 ATE equals 91.17 barg.
In the three reaction stages, all reactors are of the adiabatic type and preferably tubular in shape.
Adequate reactors are also vessels subdivided into compartments by means of separation septs that avoid the reaction products to mix again as the reaction progresses.
In the first reactor GBL exothermally reacts with MMA to afford N-methyl-hydroxylbutyramide (NMH).
In the following reactor an NMH cyclisation reaction is triggered with formation of water and NMP.
In the final stage, the NMP formation reaction goes to completion at high temperature.
The succession of the three subsequent reaction stages as they are described in the present process leads to a reduction in GBL and NMP contents in the reaction effluents, which is a necessary condition for producing high purity NMH (99.5% minimum weight).
GBL, whose boiling point at STM is very close to that of NMP (202° C.) could not be separated from NMP by distillation.
REFERENCES:
patent: 3775431 (1973-11-01), Rodewald
patent: 6008375 (1999-12-01), Bergfeld et al.
patent: 2159859 (1972-07-01), None
patent: 4203527 (1993-08-01), None
Chemical Abstracts, vol. 124, No. 11, Mar. 11, 1996, Yang, Yuanyi et al, “Improved process for producing N-methylpyrrolidone and 2-pyrrolidone”.
Chemical Abstracts, vol. 43, No. 11, Jun. 10, 1949, McElvain et al, “Piperidine Derivatives. XX. The preparation and Reactions of 1-methyl-3-piperidone”.
Chemical Abstracts, vol. 31, No. 7, Apr. 10, 1937, Spath et al, “Formation of lactams from lactones”.
Abstract of JP 7221420, Aug. 18, 1995.
Albrecht Ludwig Harreus, Ullman's Encyclopedia of Industrial Chemisty, 5threvised edition, vol. A22, pp. 457-459, 1993.
McKane Joseph K.
Pantochim S. A.
Stevens Davis Miller & Mosher LLP
Wright Sonya
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