Selective Transformation of Methanol to Ethanol in the Presence of Syngas over Composite Catalysts

Abstract

The direct synthesis of ethanol from methanol via precise C–C coupling is a highly attractive but challenging target. Herein, we report the selective production of ethanol from methanol in the presence of syngas (CO/H2) by tandem catalysis over composite catalysts composed of mordenite (H–MOR) zeolite coated by carbon layer (H–MOR–DA@C) and Pt–Sn/CNT. This tandem route starts from methanol carbonylation with CO to acetic acid over H–MOR–DA@C, followed by acetic acid hydrogenation to ethanol over Pt–Sn/CNT. The selectivity of ethanol reached up to 60% with a CH3OH conversion of 98%. As compared to the H–MOR–DA matrix, the side reaction of ethanol dehydration to ethylene is effectively hindered over composite catalysts with H–MOR–DA coated by carbon layer. The special “carbon nest” with oxygenated functional groups such as ester or carboxylic acid, existing on the surface of H–MOR–DA@C, is crucial to preventing ethanol from dehydration, and thus improves the ethanol selectivity and catalytic stability. This work offers an effective strategy for direct synthesis of ethanol from methanol and design of efficient composite catalysts for tandem catalysis by controlling the reaction pathway.