Cyclic Oxygenate-Based Deactivation Mechanism in Dimethyl Ether Carbonylation Reaction over a Pyridine-Modified H-MOR Catalyst

The carbonylation of dimethyl ether (DME) over zeolite catalysts breaks through the traditional concept of metal-catalyzed carbonylation and has attracted extensive attention as a critical route for ethanol synthesis. However, the deactivation mechanism during DME carbonylation is complicated and controversial, resulting in great challenges for developing efficient catalysts. Herein, we discovered a catalyst deactivation pathway induced by cyclic oxygenates over the pyridine-modified H-MOR (H-MOR-py) catalyst, which is completely distinct from the classical aromatic-based deactivation route. As the key deactivated species, cyclic oxygenates are generated by the conversion of excessive acetyl groups to ketenes in the eight-membered ring (8-MR) side pockets and further transformation in the 12-MR channel of the H-MOR-py catalyst. A strategy to improve catalyst stability is proposed by rapidly consuming acetyl groups to inhibit the formation of cyclic oxygenates. This study would provide inspiration for DME carbonylation over zeolite catalysts.