Highly Efficient Catalytic Hydrodeoxygenation for Aliphatic Acid to Liquid Alkane: The Role of Molybdenum

A series of NiM/SiO2 (M = Ce, Co, Cu, Fe, Sn, Zr, Mo) catalysts are prepared and used in the selective hydrodeoxygenation (HDO) of aliphatic acid to produce alkanes with the same number of carbon atoms as the reactant (alkane-Cx). The results indicate the introduction of Mo promotes the hydrodehydration of aliphatic alcohol and suppresses the decarbonylation of aliphatic aldehyde. The selective to alkane-Cx is more than 70% in the case of a complete conversion of aliphatic acid. A mechanism study proves that, due to the higher electronegativity of Mo, electrons transfer from Ni to Mo easily and facilitate the reduction of Mo, and the partially reduced Mo species is favorable for the hydrodehydration of aliphatic alcohol. Meanwhile, the adsorption of alcohol on Mo is more favorable than on the Ni site, and the hydrogen bond between hydroxyl hydrogen and O atoms on the catalyst improves the adsorption stability of aliphatic alcohol. Further COHP analysis indicates that the C-OH bond was activated when alcohol was adsorbed on the Ni5/MoO2 surface, which promoted the hydrodehydration of aliphatic alcohols and improved carbon atom utilization.