Direct conversion of syngas into methyl acetate by relay catalysis: From fabrication of active sites to process control

Abstract

The direct and selective conversion of syngas into C2+ oxygenates is challenging due to the complex reaction network. Here, we report a robust relay system for the direct synthesis of methyl acetate (MA) from syngas, which combines CuZnAlOx/H-ZSM-5 for syngas to dimethyl ether (DME) with modified H-MOR for DME carbonylation. The dehydration of methanol to DME on H-ZSM-5 significantly enhanced the hydrogenation of CO on CuZnAlOx, because of high DME equilibrium yields. Blocking of Brönsted acid sites with basic molecules or selective dealumination of 12-membered rings in H-MOR suppressed the zeolite coking. Besides, reaction temperatures above 240°C avoided H2O poisoning of carbonylation sites inside 8-MR side pockets of H-MOR, further benefiting the catalytic stability. Eventually, this relay system provided a high MA selectivity of 75% and an acetic acid selectivity of 13% at a CO conversion of 65%, outperforming reported catalysts.