Dimethyl Ether Carbonylation to Methyl Acetate over HZSM-35

Abstract

Dimethyl ether (DME) carbonylation to methyl acetate (MA) was comparatively investigated over HZSM-35 and mordenite (HMOR) zeolites. The HZSM-35 catalyst showed rather high selectivity and stability without obvious deactivation for 32 h on-stream at 473 K with a MA yield of *11%. On the other hand, the HMOR catalyst showed similar initial activity, but the yield of MA rapidly decreased to only 5% after 20 h on-stream. It was further revealed that the deposition rate of coke over the HZSM-35 catalyst was much lower than that on the HMOR zeolite, indicating that the formation rate of coke was strongly dependent on the pore sizes of the zeolites. The pore structure of HZSM-35 having a one-dimensional channel 10 member-ring (10-MR) and a perpendicularly intersected one-dimensional 8 member-ring (8-MR) channel effectively limited the formation of aromatic compounds which act as the precursors of coke.

Dimethyl Ether Carbonylation to Methyl Acetate over Nanosized Mordenites

“…The HMOR sample had a cubic morphology with sizes ranging from 50 to 100 nm, differing significantly from the traditional blocklike morphology with typical sizes of 2−6 μm. 9,10 The copper loading did not alter the morphology or size of the catalyst. TEM analysis did not reveal the presence of copper particles on the surface, implying that the copper species might exchange with the protons and locate inside the channels.…”

Potential routes for thermochemical biorefineries

“…Methyl acetate synthesis rates are proportional to CO pressure and independent of DME . DME carbonylation is primarily conducted in 8‐MR channels, in the case of mordenites, or in 10‐MR channels, in the case of ZSM‐35 . There is a possible deactivation due to coke formation on the catalyst .…”

“…Th e carbonylation of DME occurs in the presence of some kinds of zeolites, for example, mordenites, ferrierites and ZSM-35, at reaction conditions of up to 100 bar and 150-200ºC. 131,156,157 Th e carbonylation reaction is said to be conducted with a stable rate and without signifi cant catalyst deactivation. 131,156 Presence of water in the reaction mixture decreases methyl acetate formation and slightly increases that of methanol.…”

Coking on micrometer- and nanometer-sized mordenite during dimethyl ether carbonylation to methyl acetate

“…Clearly, the nanometer-sized HMOR-N catalyst had a much lower deactivation rate constant than the micrometer-sized HMOR-C catalyst. Figure 5(c) compares the TPO profiles of the coked catalysts after running the DME carbonylation reaction for 12 h at 473 K. Over the coked HMOR-C catalyst, two distinct evolution of carbon oxides appeared at 640-690 and 760-840 K. The low temperature peak is generally attributed to the combustion of soft coke, i.e., surface-bound methyl and acetyls associated with the formation of MA, while the high temperature desorption peak is ascribed to the combustion of hard coke [12,13,37,38]. The total amount of coke was 5.4 mmol C/gcat, with 20% soft coke and 80% hard coke.…”

“…In this reaction, DME initially reacts with CO to form MA on a solid zeolite, which is followed by the hydrogenation of MA to ethanol over supported copper catalysts [1][2][3]. H-mordenite (HMOR) is the most active catalyst for DME carbonylation to MA [4][5][6][7][8][9][10][11][12][13][14], but the HMOR catalysts suffered severe deactivation due to the heavy deposition of carbonaceous species during reaction. Mordenite has a two dimensional framework structure consisting of straight 12-membered ring (12-MR) pores (0.67 nm × 0.70 nm) that are connected by twisted (0.28 nm × 0.57 nm, side pockets along (001) crystal facet) and crossed (0.34 nm × 0.48 nm, along (010) crystal facet) 8-membered ring (8-MR) pores [14,15].…”