PROCESS FOR CARBONYLATING DIMETHYL ETHER

Abstract

A process for the production of methyl acetate by carbonylating dimethyl ether with carbon monoxide at a temperature of 250 to 350 C. in the presence of a zeolite catalyst and hydrogen such that the molar ratio of hydrogen to carbon monoxide is at least 1, and one or more compounds containing a hydroxyl functional group and in the absence of any added methyl acetate.

Claims

1. A process for the production of methyl acetate by carbonylation of dimethyl ether which process comprises contacting in a reactor dimethyl ether with carbon monoxide in the presence of a zeolite catalyst and hydrogen at a temperature of from 250 to 350 C. and at a molar ratio of hydrogen to carbon monoxide of at least 1, and wherein the process further comprises introducing into the reactor at least one compound containing a hydroxyl functional group and the process is carried out in the absence of added methyl acetate.

2. A process according to claim 1 wherein the zeolite is a templated zeolite.

3. A process according to claim 1 wherein the hydroxyl compound(s) is introduced into the reactor in a total amount of up to 1 mol % based on the total gaseous feed to the process.

4. A process according to claim 3 wherein the total amount of hydroxyl compound(s) is from 0.01 to 0.5 mol % based on the total gaseous feed to the process.

5. A process according to claim 1, wherein the one or more hydroxyl compound(s) is selected from aliphatic alcohols, aliphatic carboxylic acids, water and mixtures thereof.

6. A process according to claim 5 wherein the hydroxyl compound is a C.sub.1-C.sub.4 aliphatic alcohol.

7. A process according to claim 5 wherein the hydroxyl compound is a C.sub.1-C.sub.4 aliphatic carboxylic acid.

8. A process according to claim 5 wherein the hydroxyl compound is selected from one or more of acetic acid, methanol and water.

9. A process according to claim 1, wherein the molar ratio of hydrogen to carbon monoxide is in the range 1.5 to 4:1.

10. A process according to claim 1, wherein the catalyst is a zeolite having at least one channel which is defined by an 8-membered ring.

11. A process according to claim 10 wherein the zeolite has a framework type selected from the group consisting of MOR, FER, OFF, CHA, GME, MFS, EON and ETR.

12. A process according to claim 11 wherein the zeolite has the framework type MOR and is mordenite.

13. A process according to claim 1, wherein the process is carried out at a temperature of from 275 to 325 C.

14. A process according to claim 1, wherein methyl acetate product is hydrolysed to acetic acid.

15. A method of maintaining or reducing the deactivation rate of a catalyst in a process for the production of methyl acetate by carbonylation of dimethyl ether which process comprises contacting in a reactor dimethyl ether with carbon monoxide in the presence of a zeolite catalyst and hydrogen at a temperature of from 250 to 350 C. and at a molar ratio of hydrogen to carbon monoxide of at least 1, and wherein the process further comprises introducing into the reactor at least one compound containing a hydroxyl functional group and the process is carried out in the absence of added methyl acetate.

16. Use of one or more compounds containing a hydroxyl functional group to maintain or reduce the deactivation rate of a catalyst in a process for the production of methyl acetate by carbonylation of dimethyl ether which process comprises contacting in a reactor dimethyl ether with carbon monoxide in the presence of a zeolite catalyst and hydrogen at a temperature of from 250 to 350 C. and at a molar ratio of hydrogen to carbon monoxide of at least 1, and wherein the process further comprises introducing into the reactor at least one compound containing a hydroxyl functional group and the process is carried out in the absence of added methyl acetate.

Description

EXAMPLE 1

[0083] This Example demonstrates carbonylation of dimethyl ether with carbon monoxide in the presence of a templated zeolite catalyst under hydrogen-rich conditions and the addition of acetic acid, methanol or water.

[0084] Carbonylation was carried out in a stainless steel pipe reactor (1215 mm in length and 20.4 mm internal diameter) housing a catalyst bed of a uniform mixture of 110.0 mL 3.2 mm diameter templated mordenite catalyst extrudates and 203.2 mL of 3 mm diameter inert alumina spheres. Located within the catalyst bed were 9 points of a multipoint thermocouple. The effluent stream from the reactor was depressurized to atmospheric pressure and periodically analysed on two Varian gas chromatographs; one chromatograph being equipped with two FID detectors and the other with two TCD detectors to determine the concentration of carbonylation reactants and products.

[0085] Using the apparatus as described above, a gaseous stream comprising carbon monoxide and hydrogen in a molar ratio of 1:1.8, 9 mol % dimethyl ether, 3.8 mol % nitrogen and 0.2 mol % acetic acid at a gas hourly space velocity of 5000 h.sup.1 was introduced into the reactor which was operated at a pressure of 70 barg (7000 kPa), a temperature of 299.5 C. for 212 hours. After 212 hours, the acetic acid supply to the reactor was ceased and replaced by a supply of methanol in an amount of 0.2 mol % (based on the total gaseous feed) and the temperature was increased to 301.5 C. and the reaction was allowed to continue for a period of 146 hours. After 146 hours, the methanol supply to the reactor was ceased and replaced by a supply of water in an amount of 0.1 mol % (based on the total gaseous feed), the amount of nitrogen was increased to 3.9 mol %, the temperature was increased to 312 C. and the reaction was allowed to continue under these conditions for a period of 147 hours. After 147 hours, the methanol supply to the reactor was ceased and replaced by a supply of 0.15 mol % methanol, 0.02 mol % water and 0.01 mol % acetic acid (based on the total gaseous feed), and the amount of nitrogen was decreased to 3.8 mol %, the temperature was increased to 316 C. and the reaction was allowed to continue under these conditions for a further period of 96 hours.

[0086] The deactivation rate of the catalyst was determined by the change ( C. loss per day) in the average internal catalyst bed temperature. The average internal catalyst bed temperature was calculated from the sum of the 9 internal thermocouple points divided by 9. The results of this Example are shown in Table 1 below.

TABLE-US-00001 TABLE 1 Amount of hydroxyl Catalyst Hydroxyl compound(s) Temperature deactivation rate compound(s) (mol %) ( C.) ( C. loss per day) none 0 283.0 0.83 acetic acid 0.2 299.5 0.01 methanol 0.2 301.5 0.00 water 0.1 312.0 0.03 acetic acid, methanol 0.18 316.0 0.04 and water

Experiment A

[0087] This Experiment demonstrates carbonylation of dimethyl ether with carbon monoxide carried out in the presence of a templated zeolite catalyst and under hydrogen-rich conditions. In this Experiment, neither a hydroxyl compound nor methyl acetate was used as a feed to the carbonylation reaction.

[0088] Using the apparatus and 109.9 mL of catalyst as described in Example 1 above, a gaseous carbonylation feed of carbon monoxide and hydrogen in a molar ratio of 1:1.75, and 9 mol % dimethyl ether was supplied to the reactor under reaction conditions of a pressure of 70 barg (7000 kPa), a temperature of 283 C. and a gas hourly space velocity of 5000 h.sup.1 and the reaction allowed to continue for a period of 114 hours. The deactivation rate of the catalyst was determined by the change ( C. loss per day) in the average internal catalyst bed temperature and was determined to be 0.83 C. loss per day. The results of this Experiment are shown in Table 1 above.