Synergistic effect of surface Cu0 and Cu+ species on improved selective hydrogenation of furfural to furfuryl alcohol over hydrotalcite-derived CuxMg3Al oxides

In the selective hydrogenation of furfural (FAL) to furfuryl alcohol (FOL), it is important to develop a simple and cheap non-precious metal catalyst to replace the precious metal catalyst. Therefore, CuxMg3AlOy (x = 0.3, 0.5, 0.7, 0.9, 1.1) composite metal oxide catalysts were prepared by CuMgAl-LDHs as precursor for the selective hydrogenation of FAL to FOL. In this series of catalysts, Cu0.9Mg3AlOy has the best catalytic activity, with 99% FAL conversion and 98.4% selectivity under the mild reaction conditions of 1.6 MPa H2 pressure, 1.5 h and 120 ℃, and good reusability. XRD, TEM, H2-TPR, CO2-TPD, XPS and in-situ DRIFTS characterization were used to investigate the activate species for hydrogenation reaction. It can be proved that Cu2+ and Cu+ on the surface of CuxMg3AlOy can be partially reduced to the Cu0 species in-situ during the reaction, promoting the hydrogenation of FAL. Various studies confirm that Cu0 is mainly responsible for the activation and dissociation of H2, and both Cu0 and Cu+ are used to adsorb the carbonyl group in FAL to improve the selectivity of FOL. Moreover, the appropriate amount of the Cu0 and Cu+ species plays an important role in selective hydrogenation of FAL to FOL through their synergy.