Effect of Cu and Zn ion-exchange locations on mordenite performance in dimethyl ether carbonylation

Cu2+ and Zn2+ ion-exchange locations in mordenite (MOR) were evaluated using infrared spectroscopy, pore size distribution, and temperature-programmed reduction. Isolated copper ions were the most abundant ion exchanged species, as detected by UV-vis spectroscopy, in addition to oxide nanoparticles, with no presence of binuclear species, which was assigned to a low copper loading of 0.3 Cu/Al. The characterization revealed that only zinc could exchange in 8-membered rings. Hartree-Fock modeling confirmed copper exchange into 12-membered rings involving at least one T1 atom, and zinc exchange in T4 sites and in 8-membered structures, including T3 sites. Copper ion exchange did not offer improvement in the dimethyl ether carbonylation rate or selectivity over acidic mordenite. Zinc ion exchange led to the selectivity and stability improvement with some loss of activity. This work contributes to the understanding of acid and metal site contribution to DME carbonylation and contributes to the understanding for Cu2+ and Zn2+ ion-exchange locations in MOR with a low metal/Al loading (< 0.2).