CO ADSORPTION ON SUPPORTED PD CATALYSTS STUDIED BY ADSORPTION MICROCALORIMETRY AND TEMPERATURE-PROGRAMMED DESORPTION

The adsorption of CO on silica-, alumina- and titania-supported Pd cat alysts (2, 5, and 10 wt% Pd) has been studied by adsorption microcalor imetry and temperature programmed desorption (TPD) experiments in a fl ow system at atmospheric pressure. On supported Pd catalysts, bridge-b onded CO was found to be the dominant CO(ads) spec:es. The observed in fluence of Pd loading on CO adsorption energetics was explained in ter ms of particle size and/or surface structure of the Pd crystallites. S upport materials can be divided into active (TiO2, Al2O3) and inert (S iO2) supports, where Pd catalysts with active supports are characteriz ed by (1) an increased sensitivity of CO adsorption to reduction tempe rature, (2) promotion of CO dissociation, and (3) an increased activit y of surface carbon towards hydrogenation, as compared to Pd catalysts supported on inert silica.