ACTIVITY AND INFRARED STUDIES DURING CARBON-MONOXIDE OXIDATION OVER BIMETALLIC PALLADIUM-RHODIUM SILICA CATALYSTS

A study of the activity of bimetallic Pd-Rh catalysts supported on silica in the oxidation of carbon monoxide by oxygen is presented. The catalysts were prepared by three different methods (1) palladium and rhodium were coimpregnated on the support, (2) rhodium was impregnated first and, after calcining, the sample was impregnated with palladium, (3) the monometallic palladium and rhodium catalysts were physically mixed. The results showed that the activity of the catalysts prepared by coimpregnation was much lower than that of the other two catalysts. The low activity of the coimpregnated catalyst can be explained by the formation of alloys which affect the surface concentration of each metal and the dispersion of rhodium. The most active catalyst was the one prepared by physical mixture, which also shows the highest concentration of linearly adsorbed carbon monoxide detected by FT-IR.