Dimethyl ether vapor-phase carbonylation with

Vapor-Phase Carbonylation of Dimethyl Ether and Methyl Acetate with Supported Transition Metal Catalysts... 

It was found that a nickel-activated carbon catalyst was effective for vapor phase carbonylation of dimethyl ether and methyl acetate under pressurized conditions in the presence of an iodide promoter. Methyl acetate was formed from dimethyl ether with a yield of 34% and a selectivity of 80% at 250 C and 40 atm, while acetic anhydride was synthesized from methyl acetate with a yield of 12% and a selectivity of 64% at 250 C and 51 atm. In both reactions, high pressure and high CO partial pressure favored the formation of the desired product. In spite of the reaction occurring under water-free conditions, a fairly large amount of acetic acid was formed in the carbonylation of methyl acetate. The route of acetic acid formation is discussed. A molybdenum-activated carbon catalyst was found to catalyze the carbonylation of dimethyl ether and methyl acetate. 

Rh- or Ir-exchanged heteropolyacids supported on Si02 catalyze vapor-phase carbonylation of methanol or dimethyl ether to give methyl acetate at 498 K and 1 atm (370). As shown in Table XXXIII, with RhPWi2O40/SiO2, the yield of methyl acetate is 44%. At this temperature, the yield of methyl acetate dropped rapidly to < 1 % during 6 h of reaction time accompanied by increases in the yields of dimethyl ether, methanol, and hydrocarbons. 

Copper-containing mordenite catalysts have also been reported to be active for carbonylation of vapor-phase methanol [170]. Initially, the predominant reaction products were hydrocarbons resulting from methanol-to-gasoline chemistry, but after about 6 h on stream at 350 °C the selectivity of the catalyst changed to give acetic acid as the main product. A recent investigation was carried out with in situ IR and solid-state NMR spectroscopies to probe the mechanism by detecting surface-bound species. The rate of carbonylation was found to be enhanced by the presence of copper sites (compared to the metal-free system), and formation of methyl acetate was favored by preferential adsorption of CO and dimethyl ether on copper sites [171],... 

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