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.