Regulating the Cu0-Cu+ ratio to enhance metal-support interaction for selective hydrogenation of furfural under mild conditions

Controllable carbonyl group (CO) hydrogenation is the key to the transformation of furfural molecules into high-value furfuryl alcohol chemicals. Herein, a non-noble copper metal catalyst (Cu/MgO) was prepared for the efficient hydrogenation of furfural to furfuryl alcohol under mild conditions. At 383 K and 2 MPa H2, 99.9% conversion of furfural with 99.9% selectivity to furfuryl alcohol was achieved within 80 min while the turnover frequency (TOF) was 56.87 h−1. The temperature of a reductive pretreatment can be used to tune the nature of the interfaces between reduced copper and the metal oxides present in copper-magnesium oxide catalysts. The valence copper species exhibited unique catalytic properties in the hydrogenation of furfural to furfuryl alcohol. Besides, the Cu/MgO-350 exhibited excellent stability and reusability without significant activity loss. These results were accounted for by the MgO alkaline interface contributing to the effective formation and high dispersion of different valence Cu species. The active site had strong adaptability to the adsorption of reactants and desorption of products, thus avoiding excessive hydrogenation of furfural. According to the analysis of the characterization data, furfural adsorption mainly existed in η1(O)-aldehyde binding mode which was consistent with the density functional theory (DFT) calculation. DFT calculations of the reaction process showed that the theoretical results favored the hydrogenation of furfural through a hydroxyalkyl intermediate rather than of an alkoxide intermediate.