Experimental identification of the active sites over a plate-like mordenite for the carbonylation of dimethyl ether

Mordenite effectively catalyzes the carbonylation of dimethyl ether to methyl acetate, and the activity is ascribed to the amount of the Brønsted acid sites in its 8-member-ring pore. Quantitatively describing the catalytic chemistry over the respective acid sites, however, is experimentally challenging. Here, we report that the specific activity of the T3 site is 4 times greater than that of the T4 site at 473 K, based on selectively populating Al atoms at the T3 and T4 sites over mordenites and precisely discriminating their coordination environments by a combined approach of solid-state NMR experiments and DFT calculations. The exclusive location of Al atom at the T3 site on a plate-like mordenite yields unprecedentedly high activity and elucidates the reaction chemistry for this unique site. Varying the population of Al atoms at the T3 and T4 positions on reference mordenites reveals that the T4 site catalyzes the reaction as well, but to a much lesser extent.