ZRO2-PROMOTED RH/SIO2 CATALYSTS IN CO HYDROGENATION AND TEMPERATURE-PROGRAMMED REDUCTION

The hydrogen chemisorption, high-pressure CO hydrogenation, and temperature-programmed reduction of ZrO2-promoted Rh/SiO2 catalysts were studied. The promoter decreased the adsorption capacity of the catalysts by covering the metal surface. The covering of Rh by ZrO2 seemed to occur during reduction. At low ZrO2 loadings this covering created new active sites for CO hydrogenation, while at higher ZrO2 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 ZrO2 and the SiO2 support, as well as between ZrO2 and Rh2O3, could be intensified and the catalytic behavior altered. When ZrO2 is in contact with Rh, it can be partly reduced and forms Zr3+ ions. Thus, the interaction between Rh and ZrO2 is similar to the strong metal-support interaction. © 1994 Academic Press, Inc.