Catalytic hydrogenation of furfural to furfuryl alcohol on hydrotalcite-derived CuxNi3−xAlOy mixed-metal oxides

It is highly desirable but quite challenging to replace precious metals with cheaper elements in the catalytic selective hydrogenation of unsaturated aldehydes. Herein, we report the preparation of a series of CuxNi3−xAlOy mixed-metal oxides (x = 0.5, 1, 2) derived from CuxNi3−xAl hydrotalcite to be used as catalysts for the promotion of the selective hydrogenation of furfural (FAL) to furfuryl alcohol (FOL). It was found that the catalyst with the Cu2Ni1AlOy stoichiometry exhibited the best performance, with 98% FAL conversion and 99% selectivity toward FOL after 1.5 h at 120 °C and under a H2 pressure of 1.6 MPa, and also good reusability. On the basis of the combined results from catalyst characterization studies using XRD, H2-TPR, TEM, XPS, and in-situ FT-IR, it was concluded that the CuOx species on the surface of the CuxNi3−xAlOy catalysts can be reduced in situ to metallic copper during reaction, and that this Cu0 species is likely the responsible for the adsorption and conversion of FAL. The addition of Ni to these mixed-metal oxides helps disperse the Cu phase and hence make it easier to reduce and activate. It may also be that NiO can promote H2 dissociation to aid with the hydrogenation catalysis. Our work advances a new strategy for the design of simple, cheap, and efficient catalysts for the hydrogenation of FAL to FOL.