Pt/Fe-TiO2-Catalyzed Selective Carbonyl Hydrogenation: Fe-Promoted Hydrogen Spillover

PtFe catalysts have demonstrated their unique properties in the hydrogenation of carbonyl compounds, but the promotion effect of Fe is still under debate. Herein, a series of Pt/Fe-TiO2 catalysts with controllable Fe dispersion and similar Pt particle size were prepared as model catalysts to elucidate the role of Fe in the selective hydrogenation of furfural to furfuryl alcohol. The catalytic data suggest that the states of Fe significantly affect the catalytic performance of Pt/Fe-TiO2 and Pt/Fe-TiO2 with dispersed Fe oligomers is ca. 20-fold more active than Pt/TiO2. The combined results of reaction kinetic analysis and characterizations suggest that the high activity of Pt/Fe-TiO2 in furfural hydrogenation is mainly attributed to the promotion effect of Fe in hydrogen spillover, a phenomenon seldom reported for PtFe catalysts. The remote hydrogen spillover test by a physical mixture of Pt/TiO2 and Fe-TiO2 implies that the dispersed Fe oligomers on TiO2 are more favorable to enhance the hydrogen spillover than large Fe aggregates, which is possibly related with the high electron/charge conductivity of the former one. This explains the higher activity of Pt/Fe-TiO2 with dispersed Fe oligomers than with large Fe aggregates. The use of model catalysts is beneficial to elucidate the key factors affecting the catalytic performance of multicomponent catalysts and sheds light on the catalyst design.