Methyl Acetate Synthesis from Dimethyl Ether Carbonylation over Mordenite Modified by Cation Exchange

Abstract

Various metal-modified HMOR catalysts for the carbonylation of dimethyl ether (DME) were prepared by ion exchange with Cu, Ni, Co, Zn, or Ag. The catalysts were characterized by the Brunauer−Emmett−Teller method, X-ray diffraction measurements, transmission electron microscopy, X-ray photoelectron spectroscopy, nuclear magnetic resonance spectroscopy, temperature-programmed desorption of ammonia, and temperature-programmed oxidation. We found that the pore structure of mordenite (HMOR) was well maintained and that the metal species were highly dispersed on the zeolite. On HMOR subjected to ion exchange with Cu, Ni, Co, or Zn, the metal ions were mainly at the zeolite exchange sites with some corresponding metal oxides. Some Brønsted acid sites were converted to Lewis acid sites, and some strong acid sites were formed together. HMOR modified with Cu, Ni, or Co showed good catalytic performance, with Cu/HMOR exhibiting the highest performance. DME conversion and methyl acetate selectivity were close to 100% under the optimum reaction conditions, which is attributed to the joint participation of Brønsted acid sites contributing to DME conversion and metal Lewis acid sites contributing to CO binding, along with the appropriate coordination structure. Modification with Cu not only improved the catalytic activity, but also suppressed carbon deposition and extended the catalyst lifetime.

Zinc Hinders Deactivation of Copper-Mordenite: Dimethyl Ether Carbonylation

“…More importantly, the presence of zinc prevented the copper from sintering during the catalytic reaction and ensured its high dispersion as seen from the transmission electron microscopy (TEM) of the fresh calcined and spent catalysts ( Figure 3). Similar copper/copper oxide nanoparticles were reported for ion-exchanged mordenites, 8,27,29 and their presence was suggested to be concomitant with the activity loss in DME carbonylation because of the active species migration from ion-exchanged positions to the external surface and agglomeration. 29 No detectable nanoparticles were observed with the most efficient 1Cu-4Zn/H-MOR catalyst after completion of the catalytic reaction in the reductive CO atmosphere, suggesting their negligible catalytic function.…”

“…It was suggested that a similar decrease of the high-temperature peak for the Cu/H-MOR, compared to that of the H-MOR, occurred due to the formation of new Lewis acid sites, which bind CO and suppress hydrocarbon formation. 27 When Zn is added, the overall coke formation is significantly depressed, which is concomitant with the increased lifetime. Fresh catalysts chemisorbed similar DME quantities (0.78, 0.72, 0.68, and 0.74 mol CH 3 /mol Al for H-MOR, Cu/H-MOR, 1Cu-4Zn/H-MOR, and Zn/H-MOR, respectively), but the adsorption strength and mode changed for bimetallic catalysts, as evidenced by the temperature-programmed desorption (TPD) tracing the mass-spectrum signal of intact DME ( Figure 2b).…”

Dimethyl ether carbonylation over zeolites

“…The chemical principle is that transition metals have strong ability for CO adsorption and activation, which facilitates CO insertion into the methyl group adsorbed on a vicinal acid site of HMOR. Cu, Ni, Co, Zn modified HMOR catalysts, prepared either by impregnation or ion-exchange, showed higher activity or stability than the parent HMOR in DME carbonylation, with Cu as the most efficient promoter [38,44,[51][52][53][54][55][56][57][58] . Interestingly, co-addition of Cu and Zn to HMOR resulted in more dramatic improvement in both activity and stability as compared to the addition of either Cu or Zn individually.…”

Recent advances in the synthesis and applications of mordenite zeolite – review

“…96 A newer and effective ethanol synthesis approach is immediately needed. [97][98][99] In recent times, the synthesis of ethanol through a greener approach has received signicant consideration particularly through carbonylation of dimethyl ether (DME). 100,101 Still, the catalytic performance and consistency of the catalysts towards carbonylation of dimethyl ether must be signicantly enhanced.…”