Direct Conversion of Syngas into Methyl Acetate, Ethanol, and Ethylene by Relay Catalysis via the Intermediate Dimethyl Ether

Selective conversion of syngas (CO/H-2) into C2+ oxygenates is a highly attractive but challenging target. Herein, we report the direct conversion of syngas into methyl acetate (MA) by relay catalysis. MA can be formed at a lower temperature (ca. 473K) using Cu-Zn-Al oxide/H-ZSM-5 and zeolite mordenite (H-MOR) catalysts separated by quartz wool (denoted as Cu-Zn-Al/H-ZSM-5 vertical bar H-MOR) and also at higher temperatures (603-643K) without significant deactivation using spinel-structured ZnAl2O4 vertical bar H-MOR. The selectivity of MA and acetic acid (AA) reaches 87% at a CO conversion of 11% at 643K. Dimethyl ether (DME) is the key intermediate and the carbonylation of DME results in MA with high selectivity. We found that the relay catalysis using ZnAl2O4 vertical bar H-MOR vertical bar ZnAl2O4 gives ethanol as the major product, while ethylene is formed with a layer-by-layer ZnAl2O4 vertical bar H-MOR vertical bar ZnAl2O4 vertical bar H-MOR combination. Close proximity between ZnAl2O4 and H-MOR increases ethylene selectivity to 65%.