Reduction behavior of PdO-NiO/SiO2: how Pd location affects cinnamaldehyde hydrogenation

In this work, we study the reducibility of a PdO precursor placed by strong electrostatic adsorption on either NiO or SiO2 of NiO/SiO2 obtained by incipient wetness impregnation. The catalysts were characterized by HAADF-STEM, quasi-in situ XPS, CO IR spectroscopy and H2 chemisorption as a function of the reduction temperature and evaluated for their performance in cinnamaldehyde hydrogenation. PdO on SiO2 requires reduction at higher temperatures to achieve appreciable rates of cinnamaldehyde hydrogenation. Pd placed on NiO particles dispersed on the SiO2 support can already be reduced at room temperature and show a higher activity in cinnamaldehyde hydrogenation, which is argued to be due to the higher Pd dispersion obtained at low reduction temperatures.