Abstract: A series of CeO₂ 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/CeO₂ substantially promotes the catalytic activity, which can be gauged by the lowering of the soot total removal temperature by more than 200 ºC 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 CeO₂, 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 K₂CO₃, the activity and stability of catalyst were lower than those of KNO₃/CeO₂. This behavior is attributed to the higher melting point and stronger basicity of K₂CO₃ which lead to irreversible adsorption of CO₂ generated during soot combustion on the catalyst.

Key words: soot oxidation, potassium, ceria, temperature-programmed oxidation, stability