Influence of catalyst treatments on the adsorption properties of γ-Al2O3 supported Pt, Rh and Ru catalysts

The influence of different treatments (reduction with hydrogen, oxidation with air and treatment with inert gas) of alumina supported Pt, Rh and Ru catalysts on the adsorption of different n-alkanes, cycloalkanes, aromatics and chlorinated compounds was studied. The effect of these treatments is twofold: change in the oxidation state of the active metal, and the presence of adsorbed hydrogen or oxygen, which affects the adsorption of the organic compounds. The first effect was characterized by temperature-programmed reduction (TPR) and oxidation (TPO) of catalyst samples, whereas the strength of the O2 and H2 adsorption was determined by temperature-programmed desorption (TPD). Inverse gas chromatography (IGC) was used to characterize the adsorption of five n-alkanes (C6-C10) in the 200-230 °C temperature range. Moreover, heats of adsorption, entropies of adsorption and free energy of adsorption, are also reported. Interaction parameters of polar molecules (benzene, chloroform, trichloroethylene, etc.) with the stationary phase have also been determined and compared with those for the n-alkanes. It was observed that catalyst treatment affects the adsorption capacity, strength and nature of the studied catalysts.