La_(1-x)K_xCoO_3钙钛矿型催化剂在柴油车尾气净化中的性能

Purifying Diesel Exhaust Over La_(1-x)K_xCoO_3 Perovskite-Type Catalyst

采用低温燃烧合成法制备了纳米级不同K取代量的La1-xKxCoO3催化剂,通过H2-TPR,XRD,BET和化学分析等多种方法对催化剂的组成和结构进行了表征,利用程序升温氧化反应(TPO)评价了催化剂同时净化碳颗粒物和NOx的催化活性,考察了K+掺杂后晶体结构和表面氧化性能的变化对催化剂性能的影响。结果表明,K+部分取代La3+会影响La1-xKxCoO3的晶体结构和组成。当x≤0.3时,La1-xKxCoO3仍为单一的斜方晶型钙钛矿结构,晶格参数和晶粒度增大;当x≥0.4后,出现不能进入晶格析出的Co3O4晶体。La1-xKxCoO3钙钛矿型催化剂对碳烟和NOx同时净化具有良好的催化活性,La0.7K0.3CoO3催化剂氧的非化学计量值λ最大为0.0176,表面氧空位量最多,催化活性最好,碳烟在催化剂上的起燃温度下降到290℃,NOx的转化率为53%。

A series of pervoskite--type oxides, La1-xKxCoO3 complex catalysts, with nanometric size were synthesized with low temperature through a combustion process. The catalysts were characterized for crystal structure and chemical composition using H2 --TPR, XRD, BET and chemical analysis. The catalytic activities in simultaneous removal of NO x and soot from diesel exhaust were evaluated via temperature programmed oxidation （TPO） equipment, and the effluents of crystal structure and chemical composition on the catalytic activities were also discussed. The results show that after partial substitution of La^3＋ with K^＋, the structure and component of La1-xKxCoO3 will be changed. When x≤0. 3, La1-xKxCoO3 is single rhombic perovskite-type phase, the crystal parameters and crystal distances are also increased. And when x≥0.4, Co3O4 is detected in the samples. La1-xKxCoO3 catalysts have better catalytic activities for simultaneous purification soot and NOx. La0.7 K0.3 CoO3, with the biggest amounts of non--stoichiometric oxygen and oxygen vacancy, shows the highest catalytic activities. The ignition temperature for soot combustion on La0.7K0.3CoO3 is dropped to 290℃, the conversion ratio of NOx can reach to 53 %.