Study On Methyl Acetate Synthesis Through Dimethyl Ether Carbonylation Over Mordenite Zeolites

Ethanol is regarded as one of the promising alternative fuels and has a broadapplication prospects. In recent years, the production of ethanol attracts thewidespread attention. Based on a novel ethanol synthesis routes (dimethyl ether(DME) carbonylation–methyl acetate (MA) hydrogenation), we mainly investigatedthe carbonylation of DME over Mordenite (MOR) in this work.Upon increasing the temperature to220C, the conversion of DME overcommercial H-MOR (H-MOR-C) increased, and the maximal DME conversion of74.0%was obtained at220C. However, serious coking at higher temperatureresulted in the deactivation of the catalyst. The optimal reaction temperature, wasobtained at180C that the H-MOR possessed better stability and DME conversionremained at20.0%. Thereafter, we investigated the carbonylation of DME over theH-MOR supported copper prepared by ion exchange method (IE-Cu) and solid statereaction method (SSR-Cu). The results showed that the sample IE-Cu exhibited thehigher catalytic activity because most of copper cations existed in the zeolite channels,and the DME conversion reached36.9%. While the sample SSR-Cu exhibited loweractivity (only6.7%) because most of copper was in the form of CuO on the zeolitesurface.In order to further improve the catalytic performance of H-MOR, we synthesizedthe H-MOR catalyst by the hydrothermal method. The as-prepared H-MOR(H-MOR-S) was more uniform in morphology as well as the size. The catalyticactivity was investigated over the synthetic H-MOR with a range of different Si/Alratios. The results showed that the sample with a Si/Al ratio of7.4exhibited thehighest DME conversion (53.0%) which is more than twice of the commercialH-MOR.Finally, the catalytic activities of the H-MOR-S and H-MOR-C upon DMEcarbonylation to MA were compared through XRD, BET, SEM and NH3-TPDcharacterizations. The reasons of the H-MOR-S sample with the better catalyticactivity were described as follows: Firstly, the sample H-MOR-S had the larger BETsurface areas, which made the activity sites on the catalyst has a higher contactprobability with reactants. Secondly, the average pore size of the H-MOR-S samplewas0.43nm, which was close to the size of the eight-membered ring (8-MR) channels in zeolites. It indicated the increased amount of effective DME adsorptionactivity sites in the H-MOR-S sample, which further improved the DMEcarbonylation activity. Thirdly, the sample H-MOR-S was in the form of theellipsoidal particles assembled of smoothly and orderly two-dimensional sheets. Thismorphology accelerated the diffusion rate of reactants, as well as products, in thec-axis direction, which thus enhanced the DME carbonylation activities.