Promotion effect and mechanism of Ga modification on dimethyl ether carbonylation catalyzed by mordenite

Dimethyl ether (DME) carbonylation is an important reaction for methyl acetate (MA) and ethanol production from syngas. Mordenite (MOR) has been used as an industrial catalyst due to the competitive catalytic properties, especially with extremely high selectivity of MA (>99%). Given the Brønsted acid sites (BAS) in 8-MR are proved the active centers, the properties of BAS are crucial factors that influence the reaction. Until now, most of the researches focus on increasing the number of BAS rather than tuning the acid strength. Here we modified H-MOR by Ga introduction using incipient wetness impregnation. Catalyst evaluation results suggest that Ga species can enhance DME conversion with a maintained MA selectivity. Combining with characterizations and DFT calculation, the textural and acidic properties along with the existing form of Ga species are determined. Further in-situ IR, theoretical and kinetics investigations demonstrated that the enhanced acid strength accelerates the reaction on Ga-modified MOR catalysts. This work inspires us that improving the acid strength is an efficient strategy for Brønsted acid-catalyzed reaction, such as DME carbonylation .