PROCESS TO CONTINUOUSLY PREPARE A CYCLIC CARBONATE

Abstract

The invention is directed to a process to continuously prepare a cyclic carbonate product by reacting an epoxide with carbon dioxide in the presence of a heterogeneous catalyst activated by an activating compound. The process is performed in a first, second, third reactor, each reactor comprising a slurry of the heterogeneous catalyst and the cyclic carbonate product as present as a liquid. To the first reactor carbon dioxide and the epoxide compound is continuously supplied, liquid cyclic carbonate is discharged and unreacted carbon dioxide and epoxide is discharged as a first gaseous effluent stream to the second reactor while substantially all of the heterogeneous catalyst remains in the first reactor. To the third reactor the activating compound is added. In a next step of the process the third reactor becomes the second reactor, the second reactor becomes the first reactor and the first reactor becomes the third reactor.

Claims

1. A process to continuously prepare a cyclic carbonate product by reacting an epoxide compound with carbon dioxide in the presence of a heterogeneous catalyst which catalyst is activated by an activating compound, wherein the process is performed in at least a first, second, third reactor, each reactor comprising a slurry of the heterogeneous catalyst and the cyclic carbonate product as present as a liquid, wherein to the first reactor carbon dioxide and the epoxide compound is continuously supplied, liquid cyclic carbonate is discharged as a first product stream and unreacted carbon dioxide and epoxide are discharged as a first gaseous effluent stream while substantially all of the heterogeneous catalyst remains in the first reactor and wherein the heterogeneous catalyst deactivates in time, wherein to the second reactor the first gaseous effluent is continuously supplied, liquid cyclic carbonate is discharged as a second product stream and unreacted carbon dioxide and epoxide is discharged as a second gaseous effluent stream while substantially all of the heterogeneous catalyst remains in the second reactor, wherein to the third reactor the activating compound is added to activate the heterogeneous catalyst thereby obtaining a reactor comprising activated heterogeneous catalyst and wherein in a next step of the process the third reactor becomes the second reactor, the second reactor becomes the first reactor and the first reactor becomes the third reactor such to activate the deactivated catalyst present in said reactor.

2. The process according to claim 1, wherein the temperature in the first and second reactor is between 20 and 150° C. and the absolute pressure is between 0.1 and 0.5 MPa and wherein temperature is below the boiling temperature of the cyclic carbonate product at the chosen pressure.

3. The process according to claim 1, wherein the heterogeneous catalyst comprises an organic compound containing one or more nucleophilic groups.

4. The process according to claim 3, wherein the nucleophilic group is a quaternary nitrogen halide.

5. The process according to claim 4, wherein the heterogeneous catalyst is a supported dimeric aluminium salen complex and the activating compound is a halide compound.

6. The process according to claim 5, wherein the supported dimeric aluminium salen complex is represented by the following formula: ##STR00004## wherein S represents a solid support connected to the nitrogen atom via an alkylene group, wherein the supported dimeric aluminium salen complex is activated by a halide compound and wherein X.sup.1 is tertiary butyl and X.sup.2 is hydrogen and wherein Et is an alkyl group having 1 to 10 carbon atoms.

7. The process according to claim 6, wherein the support S is composed of particles having an average diameter of between 10 and 2000 μm.

8. The process according to claim 7, wherein the support S is a particle chosen from the group consisting of silica, alumina, titania, siliceous MCM-41 or siliceous MCM-48.

9. The process according to claim 5, wherein the halide compound is benzyl halide.

10. The process according to claim 9, wherein the benzyl halide is benzyl bromide.

11. The process according to claim 1, wherein the time period of one step is between 1-30 days.

12. The process according to claim 1, wherein the first product stream and the second product stream are combined in a combined stream and wherein epoxide present in the combined product stream is stripped out by contacting the combined product stream with carbon dioxide resulting in a cleaned product stream and a loaded carbon dioxide stream containing epoxide compound and wherein the loaded carbon dioxide stream is supplied to the first reactor.

13. The process according to claim 12, wherein the cyclic carbonate product as present in cleaned product stream is separated from the activating compound as present in the combined product stream in a distillation step wherein a purified cyclic carbonate product is obtained as a bottom product of the distillation step.

14. The process according to claim 13, wherein the activating compound obtained in the distillation step is used to activate the deactivated catalyst in the third reactor.

15. The process according to claim 13, wherein the first product stream and the second product stream and/or the combined stream pass a buffer vessel upstream of the distillation step.

16. The process according to claim 15, wherein the heterogeneous catalyst is a supported dimeric aluminium salen complex and the activating compound is a halide compound. and wherein the volume of the buffer vessel or vessels expressed in m.sup.3 relative to the amount of dimeric aluminium salen complex as present in the first and second reactor and expressed in kmol is between 5 and 50 m.sup.3/kmol.

17. The process according to claim 1, wherein part of the second gaseous effluent is recycled to the first reactor and part of the second gaseous effluent is purged from the process.

18. The process according to claim 1, wherein the epoxide compound has 2 to 8 carbon atoms.

19. The process according to claim 18, wherein the epoxide compound is ethylene oxide, propylene oxide, butylene oxide, pentene oxide, glycidol or styrene oxide.

Description

Comparative Example A

[0071] The operation as illustrated in FIGS. 1-2 is compared to an operation having a sequence of steps as shown in Table 2, wherein the reactor in bulk operation is used as the reactor in polishing operation in a next step and wherein the reactor in polishing operation is regenerated in this next step and wherein the cyclic carbonate production is equal to the operation as illustrated in FIGS. 1-2.

TABLE-US-00002 TABLE 2 Bulk Polishing Regeneration step operation (101) operation (102) operation (103) 1 Reactor A Reactor B Reactor C 2 Reactor C Reactor A Reactor B 3 Reactor B Reactor C Reactor A

[0072] In this comparison use is made of the catalyst deactivation properties and catalyst life time properties as experimentally obtained. Catalyst deactivation is determined by the loss of activating compound and takes place on a time scale of one process step which may be between 2 and 20 days. Catalyst life time is when the moment when the catalyst after regeneration is not capable to achieve a certain desired conversion in the illustrated process line up. Catalyst life time is on a time scale of several months. The comparison with the process according to the invention is shown in Table 3.

Comparative Example B

[0073] The operation as illustrated in FIGS. 1-2 is compared to an operation using two reactors, each having twice the volume of reactor A and containing twice the amount of catalyst. In one reactor cyclic carbonate is prepared and the other reactor is in regeneration operation. The calculation is based on a situation wherein the same cyclic carbonate production as in the process of FIGS. 1 and 2 is achieved.

TABLE-US-00003 TABLE 3 According to Comparative Comparative FIGS. 1 and 2 example A example B Catalyst life time 100 83.3 50 loss of epoxide via 100 118 95 purge

[0074] From Table 3 it is shown that in the sequence of Example A the catalyst life time is lower and the loss of epoxide via the purge is higher than when the process is performed according to the invention. Comparative example B shows that the moment when the catalyst after regeneration is not capable to achieve a certain desired conversion (ie the catalyst life time) is significantly shorter as compared to the process according to the invention. The loss of epoxide is smaller. However this does not compensate for the fact that the catalyst will have to be changed for new catalyst at a much higher frequency when only one vessel is used as compared to the process according to the invention.