CO2 hydrogenation reactivity and structure of Rh/SiO2 catalysts prepared from acetate, chloride and nitrate precursors

Silica-supported Rh catalysts (Rh/SiO2) were prepared from acetate, chloride and nitrate precursors by an impregnation method and were applied to CO2 hydrogenation reaction. CO2 conversion over the catalyst prepared from chloride precursor was lower than that over acetate or nitrate one, because of fewer active sites on catalysts, as estimated by Hz chemisorption. The main product was CO over the catalysts prepared from acetate and nitrate, but it was CH4 over the catalyst prepared from chloride precursor. Characterization of catalysts by TEM, FT-IR and XPS was carried out in order to elucidate the effect of metal precursor on the CO2 hydrogenation reactivity. The results of XPS showed that the O atomic ratio to Rh on surface hydroxyl groups increased in the order: chloride < nitrate < acetate precursor, The ratio of hydroxyl groups to Rh particles on SiO2 surface was expected to have a significant influence on the reactivity. (C) 2001 Elsevier Science B.V. All rights reserved.