ADSORPTION SITES ON PD/AL2O3

On a Pd/Al2O3 catalyst, CO and H2 interact to form CH3O on the Al2O3 support. This CH3O hydrogenates to CH4 at a faster rate than the CO adsorbed on Pd. At high CH3O coverages, CH3O decomposition competes with hydrogenation. The effects of H2 pressure and adsorption temperature on the rate of CH3O formation were measured. Isotope studies show that CO adsorbs on Pd and then spills over onto Al2O3 where CH3O is more readily hydrogenated to CH4. The higher methanation activity of CH3O than of CO on Pd may be responsible for the much higher, steady-state methanation activity observed for Pd/Al2O3 than for Pd/SiO2 catalysts. © 1991.