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

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 °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 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. 采用不同的钾盐前体制备了一系列 K/CeO2 催化剂, 利用热重和程序升温氧化 (TPO) 等技术考察了其催化性能及稳定性. 结果表明, K/CeO2 催化剂可使碳黑完全燃烧温度降低近 200 ºC. 钾盐前体对催化活性和稳定性具有较大影响, 由于硝酸钾熔点低, 金属在载体上的流动性强, 有利于催化剂与碳黑的有效接触, 因而表现了较高的活性, 三次 TPO 循环试验中催化活性稳定. 碳酸钾的熔点高且碱性较强, 使碳黑燃烧生成的 CO2 不可逆吸附在其表面, 导致反应活性低, TPO 循环实验表明其反应速率降低, 失活明显.