Catalytic Activity and Stability of K/CeO2 Catalysts for Diesel Soot Oxidation

Abstract A series of CeO 2 supported potassium nitrate and carbonate catalysts were prepared by an impregnation method. The catalytic activity and stability for soot oxidation were investigated by thermal gravimetric/differential thermal analysis and temperature-programmed oxidation cycle techniques. K/CeO 2 substantially promotes the catalytic activity, which can be gauged by the lowering of the soot total removal temperature by more than 200 °C compared with the uncatalyzed reaction. The influence of K precursor on the catalytic activity and stability was addressed. The effect is discussed in terms of the combined functions of K and CeO 2 , potassium mobility and basicity. For potassium-promoted ceria catalysts the potassium nitrate can preserve the high catalytic activity and good stability through several cycles. When K was present as K 2 CO 3 , the activity and stability of catalyst were lower than those of KNO 3 /CeO 2 . This behavior is attributed to the higher melting point and stronger basicity of K 2 CO 3 which lead to irreversible adsorption of CO 2 generated during soot combustion on the catalyst.