Experimental and Theoretical Studies of Ethanol Synthesis from Syngas over CuZnAl Catalysts without Other Promoters

Ethanol synthesis from syngas over CuZnAl catalyst without other promoters is studied using theoretical and experimental methods. The possible reaction paths of the ethanol synthesis in thermodynamic and dynamic over Cu cluster and Cu–O species adsorbed on ZnO surface are systematically identified at the molecular level. Three possible paths involving the formation of CH₃ as the key intermediate are proposed, which are COH, CHOH, CH₂OH, and CH₃; CHO, CH, CH₂, and CH₃; and CH₃OH and CH₃. CO insertion into the CH₃ intermediate produces CH₃CO, which is further hydrogenated to yield CH₃CHO and CH₃CHOH and finally obtain ethanol. The CuZnAl catalyst, which is prepared by complete liquid-phase technology, has high ethanol selectivity and stability because of the strong interaction between Cu species and ZnO. In summary, the coexistence of both Cu⁰ and Cu⁺ is necessary for ethanol synthesis from syngas over CuZnAl catalyst without other promoters