CO adsorption on supported Pd catalysts studied by adsorption microcalorimetry and temperature programmed desorption Original Research Article

The adsorption of CO on silica-, alumina- and titania-supported Pd catalysts (2, 5, and 10 wt% Pd) has been studied by adsorption microcalorimetry and temperature programmed desorption (TPD) experiments in a flow system at atmospheric pressure. On supported Pd catalysts, bridge-bonded CO was found to be the dominant CO(ads) species. The observed influence of Pd loading on CO adsorption energetics was explained in terms of particle size and/or surface structure of the Pd crystallites. Support materials can be divided into active (TiO2, Al2O3) and inert (SiO2) supports, where Pd catalysts with active supports are characterized by (1) an increased sensitivity of CO adsorption to reduction temperature, (2) promotion of CO dissociation, and (3) an increased activity of surface carbon towards hydrogenation, as compared to Pd catalysts supported on inert silica.