Mechanistic Study of Hydrogen-Driven Deoxydehydration over Ceria-Supported Rhenium Catalyst Promoted by Au Nanoparticles

Abstract

The structure and activity of ReOx-Au/CeO2 catalysts for deoxydehydration (DODH) of polyols to alkenes with H2 were investigated in detail. Based on X-ray diffraction (XRD) and transmission electron microscopy (TEM), the sizes of Au particles are in a similar scale to CeO2 support particles and the number of Au particles is much smaller than that of CeO2 support particles. Nevertheless, the catalytic activity and temperature-programmed reduction (TPR) data of the physical mixture of Re/CeO2 and Au/CeO2 indicate that Re species on all the CeO2 particles can be reduced with H2 and can work as a catalytic center. The H2 activation ability of the catalyst with larger (∼12 nm) Au particles (impAu; “imp” means impregnation for loading) is lower than that with smaller (∼3 nm) Au particles (dpAu; “dp” means deposition–precipitation for loading), and the DODH reaction rate over ReOx-impAu/CeO2 is limited by the H2 activation rate. The CeO2-supported dpAu particles have also higher activity in C═C hydrogenation, C═...