The kinetics of H2 adsorption on supported ruthenium catalysts

Ruthenium catalysts supported on SiO2, Al2O3 and TiO2 were prepared by the impregnation method. Temperature-programmed desorption (TPD) method was applied to investigate the kinetics of hydrogen adsorption/desorption on these catalysts. All the TPD results show two-peak profile, except Ru/SiO2. The low-temperature peak was assigned to the hydrogen adsorbed on the Ru metal. The high-temperature peak was attributed to the spillover of hydrogen atoms from metal to the support. Both are activated process. The amount of adsorbed hydrogen increased with increasing adsorption temperature, and the maximum adsorption occurs at above 200 °C. The activation energy of adsorption is a function of catalyst support and the reduction temperature. It decreases in the order of Ru/TiO2 (500 °C reduction)>Ru/Al2O3>Ru/TiO2 (300 °C reduction)>Ru/SiO2. The results demonstrated that the strong metal–support interaction exerted on Ru/TiO2 would suppress hydrogen chemisorption at room temperature due to its high activation energy. However, hydrogen chemisorption on Ru/TiO2 was not suppressed at high temperature. One is able to measure the Ru dispersion by adsorption of hydrogen at high temperature.