Catalytic soot oxidation by Ag/BaCeO₃ having tolerance to SO₂ poisoning

Abstract

The effect of SO₂ and NO on the catalytic oxidation of diesel particulate (soot) was studied over two Ce oxides, CeO₂ and BaCeO₃. Silver catalysts loaded on both Ce oxides exhibited the high activity, which was accelerated by the pretreatment in a flow of NO/O₂ mixtures. The adsorption species in the form of NO₂/NO₃ should play a role of oxidizing agents for soot. However, the pretreatment of Ag/CeO₂ in a flow of SO₂/O₂ mixtures caused significant deactivation. Strong adsorption of SO₂ onto active site at the three-phase boundary between soot, Ag/CeO₂ and the gas phase would be a reason for the deactivation. Ag/BaCeO₃ was found to be a catalyst having much improved tolerance to SO₂. The tolerance may be explained by the SO₂ adsorption site residing apart from the catalytically active oxygen site.