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.