关键词: 柴油机尾气, 炭烟颗粒, 催化燃烧, 钙钛矿, 溶胶-凝胶

Abstract: Diesel engines are currently facing serious challenges to reduce exhaust pollution, especially the particulate soot, which is harmful to human beings. Simultaneous removal of NOx and soot has been studied for the past two decades and perovskite-type LaMO3 (M= Co, Mn) proved to be an effective catalyst. In this work, a series of nanostructured K+-doped perovskite-type La1-xKxCoO3 catalysts were prepared by sol-gel method using sucrose as complex agent. The influences of K+ doping and high temperature calcining on the structure and soot oxidation activity of the catalyst were studied by XRD and TPR techniques. The results indicated that nanostructured perovskite catalyst with single phase formed at the temperature higher than 600℃, and it showed much higher activity for soot oxidation in the mixed gas of NO and O2. K+ could be inserted into perovskite lattices, enhancing the phase transformation from cubic to rhombohedral structure. The resulting phase was more stable at high temperatures. The catalyst of La0.90K0.10CoO3 (about 30 nm) calcined at 700℃ with rhombohedral structure exhibited the highest activity for soot oxidation in 0.5% NO and 5% O2, which led to the low Tig and Tend as 240 and 387℃ respectively, almost 200℃ lower than the temperature of soot combustion without the catalyst. In the reaction system of soot-NO-O2, both the crystal structure and particle size of the perovskite catalysts were most influential, and the rhombohedral structure together with small size perhaps was beneficial to soot oxidation.

Key words: diesel exhaust, soot, catalytic oxidation, perovskite-type oxide, sol-gel