Oxidation selectivity between n-hexane and sulfur dioxide in diesel simulated exhaust gas over platinum-supported zirconia catalyst

We examined the oxidation reaction of n-C6H14 and SO2 over two types of Pt/ZrO2 catalysts with low (8 m(2)/g) and high (75 m(2)/g) surface areas of the ZrO2 supports (referred to as ZrO2-8 and ZrO2-75, respectively). The catalytic activity was evaluated under simulated diesel exhaust gas which simultaneously contained n-C6H14 and SO2. The Pt/ZrO2-75 exhibited a desirably higher selectivity for the complete oxidation of n-C6H14 than that of SO2, as compared with the Pt/ZrO2-8. In order to clarify the cause of this selective oxidation, we investigated the Arrhenius parameter for these oxidation reactions and characterized these catalysts using X-ray photoelectron spectra (XPS), X-ray diffraction (XRD), Transmission electron micrograph (TEM), IR and CO2 temperature-programmed desorption (CO2-TPD) methods. The amount of Pt-0 (metal) in the Pt/ZrO2-75 was significantly lower than that in Pt/ZrO2-8, because the high basicity of the ZrO2-75 support stabilized the high oxidation state of Pt such as Pt2+ and Pt4+. It was concluded that the difference in the number of Pt-0 sites as catalytic active sites causes the apparent selectivity to change due to the much slower reaction rate for the SO2 oxidation than that for the n-C6H14 oxidation. (C) 2002 Elsevier Science B.V. All rights reserved.