Activity and sulfur resistance of Pt-Pd/CeO₂ catalysts for the oxidation of diesel exhaust

A series of Pt-Pd/CeO₂ catalysts with different Pt/Pd ratios were synthesized by impregnation method; their catalytic activity and sulfur resistance in the oxidation of diesel exhaust were investigated. The results showed that Pt-Pd synergy is able to reduce the ignition temperature and broaden the active window of Pt-Pd/CeO₂ catalysts for the oxidation of diesel exhaust. The ratio of Pt/Pd has a great effect on catalytic performance; The Pt_0.2Pd_0.8/CeO₂ catalyst shows the highest activity in the oxidation of simulated diesel exhaust containing C₃H₆, CO and NO. H₂-TPR results suggest that the amount of surface active oxygen increases with the Pt/Pd ratio, which is also well related to the sulfur resistance of the Pt-Pd/CeO₂ catalysts; higher Pt/Pd ratio is of benefit to the oxidation of diesel exhaust in the presence of SO₂, as the active sites of PtO₂ and PdO are easily covered by sulfate.