The influence of the support on the activity and selectivity of Pd in CO hydrogenation

Catalytic hydrogenation of carbon monoxide was studied over Pd supported on Al 2O 3, SiO 2, TiO 2, and ZrO 2. Both the activity and the selectivity of the catalysts were strongly affected by the nature of the support. As a major product, Pd/Al 2O 3 produces dimethyl ether, Pd/SiO 2 favors methanol formation, Pd/TiO 2 produces CH 4, and Pd/ZrO 2 yields methanol. Higher CO conversions over Pd/ZrO 2 and Pd/TiO 2 were ascribed to the presence of cationic palladium species formed through the metal–support interaction. Significant dimethyl ether formation over Pd/Al 2O 3 was attributed to the acidity of the support metal oxide. The catalytic natures of Pd catalysts were discussed based on the results of catalyst characterization by XPS, TEM, and temperature-programmed reduction and desorption.