Modulation of Aluminum Species in Mordenite Zeolite for Enhanced Dimethyl Ether Carbonylation

Dimethyl ether (DME) carbonylation is an important intermediate step in the synthesis of methyl acetate (MA) and ethanol. H-form mordenite (MOR) can efficiently catalyze the reaction, in which Brønsted acid sites (BASs) associated with framework Al function as active sites. But the role of other Al species such as exteraframework Al (EFAl) and framework-associated Al still remains unknown. In this study, we have proposed two convenient approaches for controlling the two Al species and investigating their influence on the DME carbonylation reaction. NH3-TPD and Py-IR analyses revealed that the number of BASs increased after the removal of EFAl and the inhibition the formation of framework-associated Al. The reactivity results showed that the elimination of EFAl promoted the DME conversion from 28% to 46%. Additionally, through the implementation of in-situ calcination to impede the presence of framework-associated Al, the DME conversion increased from 28% to 50%. With the understanding that both EFAl and framework-associated Al have a detrimental effect on the reaction, the highest conversion is achieved with these two treatments, leading to 73% DME conversion with 99% selectivity to MA. Our findings provide a systematical strategy to effectively regulate the presence of Al species in zeolite, offering insights of rational design to optimize zeolite catalysts for important industrialized process.