Effect of catalyzed diesel particulate filter on gaseous emissions from automobile diesel engine

In order to research catalytic performance of CDPFs (catalyzed diesel particulate filters) loaded different catalysts, CDPF samples were evaluated through gas flow reactor and full-scale CDPFs tests were conducted in diesel engine bench based on AVL-SESAM(System for emission sampling and measurement) FT-IR. The results show that: the light-off temperature of CO and C₃H₈ decrease in turn as content of the precious metals increase. The light-off temperatures of CDPFs loaded same proportion of noble metals approximately shows linear dependence, while the difference of light-off temperature may result from different content of same proportion of noble metals. At high temperature condition, synergistic effects of content, proportion, valence state of noble metals and gaseous emission concentrations play obvious role on light-off performance of C₃H₈. In diesel engine bench test, full-scale CDPFs present lower light-off temperature of CO and THC. Within moderate inlet temperatures, increased Pt aids in oxidization of NO, which is speculated that PdO would help to oxidize NO. The existence of Pd may intensify thermal stability of the catalyst. The oxidized process of NO is inhibited by NO₂. Meanwhile O₂ concentration in the diesel exhaust also affects oxidization of NO. Higher Pd content in Al₂O₃ coating increase production of nitrate. With combination of Pt/Pd/Rh, the CDPF loaded lower Pd adsorbs much more SO₂ on the catalysts. However, as the temperature increases, CeO₂ promotes desorption of SO₂ on the catalysts, which leads to the sulfur tolerance of the CDPF.