Enhanced catalytic stability of in-modified ferrierite (FER) zeolite for gas-phase carbonylation of dimethyl ether

For a gas-phase carbonylation reaction of dimethyl ether (DME) to methyl acetate (MA), ferrierite (FER) zeolite revealed much higher stability and selectivity to MA with insignificant coke depositions, which was mainly attributed to its planner structures and suitable pore sizes for easy mass transfer of reactants resulted in less depositions of heavier coke precursors. The effects of indium species in the FER structures were investigated by using the FER-based zeolites prepared by one-pot synthesis or simple wet impregnation method with organic structure directing agent (OSDA) of pyrrolidine and indium nitrate (III) (In(NO₃)₃ precursor, which showed different distributions of active Brønsted acid sites (BAS) in 8-membered ring (8-MR) channels due to the adjusted FER surface properties. The catalyst deactivation rate of one-pot synthesized In(x)-FER zeolite with a small In content (In/Al molar ratio less than 0.005, denoted as In(1)-FER) was found to be slower than that of pristine FER with no indium species as well as same In/Al ratio of 0.005 prepared by wet-impregnation method (In(1)/FER) with a higher catalytic activity and MA selectivity at reaction temperature of 250 °C. Those observations demonstrated that a trace indium modification by one-pot synthesis revealed an significant positive effects on enhancing catalyst durability even under a harsh reaction condition with insignificant disintegrations of zeolite frameworks and degradation of acidic sites, which also suggested the effective strategy to other large-pore zeolites with cost-effective pretreatments with trace amount of metal oxides.