Rhodium dispersion in a Rh/Ce0.68Zr0.32O2 catalyst investigated by HRTEM and H-2 chemisorption

The effect of reduction temperature on the hydrogen adsorption and Rh dispe rsion in a Rh/Ce0.68Zr0.32O2 catalyst with texturally stable Ce0.68Zr0.32O2 support was investigated. Rh dispersion data were also obtained from Rh pa rticle size analyses made using high-resolution transmission electron micro scopy (HRTEM) images. Comparison of the dispersion values obtained by using the two techniques showed that Hz adsorption at -80 degrees C is a suitabl e tool for the estimation of Rh dispersion at reduction temperature, T-red, less than or equal to 500 degrees C. For T-red > 500 degrees C, a partial suppression of H-2 chemisorption was observed. However, after a mild reoxid ation and low temperature reduction, the H-2 adsorption capacity of these s amples was regenerated and good agreement with the HRTEM data was again obt ained.