Simultaneous catalytic removal of nitrogen oxides and diesel soot particulate over perovskite-related oxides

Catalytic performance of perovskite-type (ABO3) and K2NiF4-type (A2BO4) oxides for the reduction of NOx by diesel soot particulate in the presence of excess oxygen, that is, the simultaneous removal of NOx and soot, has been investigated. Their catalytic activity, evaluated from the ignition temperature of soot and selectivity to NOx reduction into nitrogen largely depended on both A-site and B-site cations and the partial substitution of potassium at A-sites prominently promoted both the activity and selectivity. These mixed metal oxide catalysts were superior to transition metal simple oxides and Pt/A12O3 in the selectivity for NOx reduction. The ignition temperature of soot in NO + O2 gas stream was lower than that in NO or O2 gas stream, implying that nitrogen dioxide accelerates the oxidation or activation of soot.