The support effect in oxidizing atmosphere on propane combustion over platinum supported on TiO2, TiO2-SiO2 and TiO2-SiO2-WO3

The platinum catalyst supported on TiO2-SiO2-WO3, TiO2-SiO2 and TiO2 was studied with respect to the support effect in the oxidizing atmosphere on propane combustion. The catalysts and supports were characterized by using BET, XPS, IR, acidity measurement by the titration method and pulsed CO chemisorption. Although for the reduction-pretreated catalyst, the propane combustion activity is slightly changed with the support materials, for the oxidation-pretreated catalyst it significantly varies with the support materials and increases in the order of Pt/TiO2 < Pt/TiO2-SiO2 < Pt/TiO2-SiO2-WO3, indicating that the Pt/TiO2-SiO2-WO3 catalyst exhibits the most superior catalytic performance. In agreement with this order, the acidity at fairly strong acid strengths, particularly Bronsted acidity of the corresponding support is enhanced, thereby preventing platinum from the oxidation, as evidenced by the XPS result that the platinum on TiO2-SiO2-WO3, TiO2-SiO2 and TiO2 exists in metallic state, partially oxidized state and platinum oxide, respectively. These results suggest that the excellent propane combustion activity and good durability of the Pt/TiO2-SiO2-WO3 catalyst are attributed to the superior oxidation-resistance of platinum which is due to that the support has higher acidities at fairly strong acid strengths of -5.6 <= H-0 <= 3.0 containing Bronsted acidities rather than very strong acid strengths of H-0 <= -5.6. (c) 2006 Elsevier B.V. All rights reserved.