Process for the production of dialkyl succinate from maleic anyhdride

Abstract

In a process for the production of dialkyl succinate from a feedstock comprising maleic anhydride, feed in the liquid phase is provided to a reactor operated at a temperature of at least about 150° C. The feed is contacted with hydrogen at a pressure of at least about 300 psig in the presence of an acid tolerant catalyst and an alkanol wherein at least some of the carbon carbon double bonds of the maleic anhydride are hydrogenated to form succinic acid and that the heat generated promotes esterification to dialkyl succinate in situ. A stream of dialkyl succinate is recovered from the reactor.

Claims

1. A process for the production of dialkyl succinate from a feedstock comprising maleic anhydride, said process comprising the steps of: (a) providing the feed in the liquid phase to a reactor operated at a temperature of at least about 150° C.; (b) contacting said feed with hydrogen at a pressure of about 300 psig to about 900 psig in the presence of an acid tolerant catalyst and methanol wherein at least some of the carbon carbon double bonds of the maleic anhydride are hydrogenated to form succinic acid and that the heat generated promotes esterification to dialkyl succinate in situ; and (c) recovering a stream comprising dialkyl succinate from the reactor.

2. The process according to claim 1 wherein the feed to the reactor comprises at least 90% maleic anhydride.

3. The process according to claim 1 wherein the reaction is carried out at a temperature of from about 150° C. to about 240° C.

4. The process according to claim 1 wherein the esterification reaction is carried out in the absence of a catalyst.

5. The process according to claim 1 wherein an esterification catalyst is used.

6. The process according to claim 5 wherein a combined catalyst is used.

7. The process according to claim 1 wherein the saturation reaction is carried out at a temperature in the range of from about 150° C. to about 240° C.

8. The process according to claim 1 wherein the succinate produced is recycled to the reactor.

Description

(1) The present invention will now be described by way of example with reference to the accompanying drawings in which:

(2) FIG. 1 is a schematic illustration of a flow sheet according to the present invention

(3) FIG. 2 is Scheme 1 illustrating a reaction path according to the present invention

(4) It will be understood by those skilled in the art that the drawings are diagrammatic and that further items of equipment such as reflux drums, pumps, vacuum pumps, temperature sensors, pressure sensors, pressure relief valves, control valves, flow controllers, level controllers, holding tanks, storage tanks, and the like may be required in a commercial plant. The provision of such ancillary items of equipment forms no part of the present invention and is in accordance with conventional chemical engineering practice.

(5) The invention will be discussed with reference to the methylation of maleic anhydride. However, it is equally applicable to the use of other alkanols.

(6) Maleic anhydride is fed in line 1 to the reactor 2 containing a hydrogenation catalyst and operating under hydrogenation conditions. Hydrogen is fed to the reactor 2 in line 3. An alkanol, such as methanol, is added in line 4. This may be fresh methanol or may be methanol recovered from downstream in the reaction. A product stream comprising dimethyl succinate will be removed in line 5. The stream may also include monomethyl succinate. The product stream may be passed in line 5 is passed to an ester separator 10. The dimethyl succinate is removed in line 11 as a liquid or a vapour product. It may then be passed to a hydrogenolysis reactor (not shown) where tetrahydrofuran, and/or 1,4-butanediol and/or γ-butyrolactone may be produced. Hydrogen may be supplied in line 12 to the separator 10 to assist in the separation. The monomethyl succinate may be returned in line 13 to the reactor 2.

(7) Methanol and water are removed from the reactor 2 in line 6. It is passed to a methanol/water separator 7. The water is removed in line 8 and the methanol is recycled in line 9 where it is returned to line 4. Methanol from the subsequent hydrogenolysis reaction may be returned in line 14 to the reactor 2.

(8) Any suitable reactor may be used for the reactor in which the hydrogenation/esterification reaction occurs. Suitable reactors include continuous stirred tank type reactors, or a fixed bed reactor with a liquid recycle. The reactor may optionally have internal or external cooling. A separate additional reaction column may be installed downstream to complete the esterification reaction which does not occur in the main reactor.

EXAMPLE 1

(9) Maleic anhydride and 3 mol equivalents of methanol and a palladium on carbon catalyst were placed in an autoclave at 500 psig hydrogen and 190° C. The product analysis gave:

(10) TABLE-US-00001 Methanol 17.12 wt %  Maleic anhydride 0.51 wt % Dimethyl maleate 2.93 wt % Dimethyl succinate 55.06 wt %  Methoxy dimethyl succinate 0.03 wt % Monomethyl maleate 0.13 wt % Monomethyl succinate 16.31 wt %  Maleic acid 1.24 wt % Fumaric acid 0.10 wt % Water 6.52 wt %

EXAMPLES 2 AND 3

(11) Unless otherwise stated, all testwork was performed using a 300 ml autoclave. Hydrogen was used as the gas to generate pressure. Water was analysed using a Karl Fischer Aquapal. GC analysis was by FID using Regisil to allow for acids analysis.

EXAMPLE 2—AUTOCATALYTIC ESTERIFICATION STAGE 1

(12) To the autoclave was charged succinic acid (40 g, 0.34 mol) and methanol (21.7 g, 0.68 mol, 2 eqv). The vessel was pressurised to 500 psig and heated to 190° C. 1 hour then cooled and discharged. The product was analysed by dissolving 50 mg of the sample in Regisil (500 mg) and acetonitrile (250 mg) then analysed using FID GC.

(13) Using the previously described Regisil method the light components (methanol and water) were removed by crude flash distillation at 150° C. under ambient pressure.

EXAMPLE 3

(14) 50 g, 0.5 mol maleic anhydride, 49 g, 1.53 mol, 3 eqv methanol, 1 g, equivalent to 0.32 g, 0.6 wt % palladium-carbon paste were charged to the autoclave. The vessel was sealed and then pressurised to 300 psig with hydrogen and heated to 190° C. The internal temperature of the vessel was recorded with time and, to ensure that any exotherm above the desired maximum temperature was monitored, the cooling system was turned off.

(15) The results indicated that, although the rate of temperature increase did go up, the temperature did not exceed the maximum operating parameter. Analysis of the product showed significant conversion of the maleate species to succinate with (methanol free) selectivity to mono methyl maleate and mono maleate succinate of 7.28 mol % and 11.08 mol % respectively. Selectivity to di-methyl maleate and dimethyl succinate were 3.59 mol % and 26.41 mol % respectively.

(16) The results are set out in the following table.

(17) TABLE-US-00002 Run Number 1208-04 Temperature, ° C. 190 RT at 190° C., min 10 GC Analysis, wt % MeOH 24.87 MAH 0.38 DMM 4.41 DMF 3.70 DMS 32.90 DMC 0.04 MeODMS 0.06 MMM 8.07 MMS 12.48 MMF 4.48 MMC 0.20 HO-DMS 0.02 MAC 0.47 SAC 0.88 FAC 0.44 Water 6.47