Pt-Co/SiO2 Bimetallic planar model catalysts for selective hydrogenation of crotonaldehyde

Surface science models of silica-supported Pt-Co bimetallic catalysts with various Pt/Co ratios were successfully prepd. using the spin-coating technique. Platinum and cobalt loadings on a series of silica-supported model catalysts were quantified by Rutherford backscattering spectrometry. At. force microscopy images indicate that flattish layer-like structures were obtained in all cases. The electronic state of Co and Pt was studied using XPS and near-edge x-ray absorption fine structure (NEXAFS). NEXAFS shows that cobalt mainly forms octahedrally coordinated Co2+ species in the unreduced catalysts. The formation of the active phase was studied by XPS and in situ soft x-ray absorption spectroscopy (XAS). The NEXAFS measurements performed under 1-2 mbar of H2 reveal that cobalt is fully reduced to Co0 at relatively low temp. in bimetallic catalysts and reveal a decrease of the electron d. of Co as the Pt/(Pt + Co) ratio increases, indicating the formation of alloyed bimetallic particles. This is also supported by XPS measurements. The crotonaldehyde hydrogenation was studied on planar surface science model catalyst under diffusion-limitation-free conditions in gas phase at atm. pressure and temps. between 100 and 150 Deg. The addn. of Co significantly improved the selectivity toward crotyl alc. This improvement is correlated with the electronic properties of the active phase. [on SciFinder (R)