Carbonylation process using a pretreated zeolite catalyst
A carbonylation process in the presence of a pretreated zeolite catalyst which comprises the sequential steps (i) pretreating the catalyst and (ii) carbonylating dimethyl ether with a carbon monoxide-containing gas to produce methyl acetate in which the catalyst pretreatment step (i) comprises a step (a) contacting the catalyst with a first treatment mixture comprising water vapour; and a step (b) contacting the treated catalyst of step (a) with a second treatment mixture comprising an inert gas and at least one of dimethyl ether and methanol.
1. A process for the carbonylation of dimethyl ether with a carbon monoxide-containing gas in the presence of a zeolite carbonylation catalyst which process comprises the sequential steps of:
(i) pretreating the catalyst; and
(ii) carbonylating the dimethyl ether with the carbon monoxide-containing gas to produce a reaction product comprising methyl acetate;
wherein the pretreatment of the catalyst in step (i) comprises the steps:
(a) contacting the catalyst with a first treatment mixture comprising water vapour;
(b) contacting the catalyst treated in step (a) with a second treatment mixture comprising an inert gas and at least one of dimethyl ether and methanol; and
(c) ceasing the inert gas component of the second treatment mixture.
2. A process according to claim 1 wherein the first treatment mixture is a mixture of water vapour and one or more inert gases.
3. A process according to claim 1 wherein the second treatment mixture further comprises water vapour.
4. A process according to claim 2 wherein the second treatment mixture comprises water vapour at a partial pressure in the range 0.8 to 8 bar (80 to 800 kPa).
5. A process according to claim 3 wherein the process further comprises during step (b), a step (b i ) ceasing the water vapour and continuing treatment with the inert gas and the at least one of dimethyl ether and methanol.
6. A process according to claim 5 wherein step (b) is carried out for a period of 1 minute to 1 hour prior to step (b i ).
7. A process according to claim 5 wherein prior to step (c) the at least one of dimethyl ether and methanol is discontinued.
8. A process according to claim 1 wherein the second treatment mixture comprises dimethyl ether in an amount of 1 to 20 mol %.
9. A process according to claim 1 wherein each of steps (a) and (b) is carried out at a temperature in the range 250° C. to 350° C.
10. A process according to claim 1 wherein the zeolite has 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 MOR, FER, OFF and GME.
12. A process according to claim 10 wherein the zeolite is mordenite.
13. A process according to claim 1 wherein the zeolite is composited with a binder material.
14. A process according to claim 12 wherein the binder material is an inorganic oxide selected from aluminas, silica-aluminas and silicas.
15. A process according to claim 1 wherein the carbon monoxide-containing gas is a mixture of hydrogen and carbon monoxide.
16. A process according to claim 15 wherein hydrogen and carbon monoxide are present in the mixture in a hydrogen to carbon monoxide molar ratio in the range 1 to 12:1.
17. A process according to claim 1 wherein the carbonylation step (ii) is carried out at a temperature in the range 250° C. to 350° C.
18. A process according to claim 1 wherein methyl acetate is recovered from the reaction product of step (ii) and some or all of the recovered methyl acetate is converted to acetic acid.