INFLUENCE OF PRETREATMENT ON THE STRUCTURAL AND CATALYTIC PROPERTIES OF SUPPORTED Pd CATALYSTS FOR CO OXIDATION

The effects of pretreating atmospheres ( H2 , O2 and Ar ) on the activity for CO oxidation and Pd dispersion of Pd/Pr6O11 catalyst were investigated. The result shows after the Pd/Pr6O11 catalyst was pretreated by hydrogen or oxygen at 550°C, its catalytic activity for CO oxidation can obviously increase, and the activity of H2 -pretreated catalyst is superior to that of O2 -pretreated catalyst, which is attributed to an increase of Pd dispersion. The catalyst pretreated by Ar behaves the worst catalytic activity for CO oxidation. The results of CO pulse, CO chemisorption and in situ DRIFT testing indicate that the surface species (hydroxyl species or active oxygen species) generated during pretreating processes can prevent Pd particles from immigrating and sintering, resulting in an increase of the Pd dispersion on the surface of support.