ZrO 2-Promoted Rh/SiO 2 Catalysts in CO Hydrogenation and Temperature-Programmed Reduction

Abstract

The hydrogen chemisorption, high-pressure CO hydrogenation, and temperature-programmed reduction of ZrO 2-promoted Rh/SiO 2 catalysts were studied. The promoter decreased the adsorption capacity of the catalysts by covering the metal surface. The covering of Rh by ZrO 2 seemed to occur during reduction. At low ZrO 2 loadings this covering created new active sites for CO hydrogenation, while at higher ZrO 2 loadings both activity and turnover frequency were decreased. The impregnation sequence in the pore volume impregnation had no influence on the catalytic behavior. By applying different calcination procedures, however, the interactions between ZrO 2 and the SiO 2 support, as well as between ZrO 2 and Rh 2O 3, could be intensified and the catalytic behavior altered. When ZrO 2 is in contact with Rh, it can be partly reduced and forms Zr 3+ ions. Thus, the interaction between Rh and ZrO 2 is similar to the strong metal-support interaction.