The Preparation Of The Rare-earth Perovskite-type La_0.7Sr_0.3CoO₃Catalyst And Its NSR Performance

The La0.7Sr0.3CoO3perovskite catalyst with different appearances and surfaceareas was synthesized to remove NOxexhausted from lean-burn diesels in this work.We synthesized the well crystallized La0.7Sr0.3CoO3perovskite nanoparticles with themesoporous SiO2support by a facile impregnation method. Compared with theLa0.7Sr0.3CoO3perovskite catalyst synthesized by the conventional method, thisperovskite exhibited an extraordinarily high NOxadsorbability reaching5269.2mol/g in lean-burn atmospheres at300C, and its NO oxidbillity was85.6%.The H2-TPR results also suggested that the supported La0.7Sr0.3CoO3perovskitecatalyst presented an improved stability in reducing atmospheres. Our findings showthat the surface area of the La0.7Sr0.3CoO3phase plays a crucial role for NOxadsorption.The three dimensional order macroporous (3DOM) La0.7Sr0.3CoO3perovskitecatalyst was prepared by the PMMA colloidal crystal template method. The NOoxidbillity of3DOM La0.7Sr0.3CoO3perovskite catalyst was similar to theconventional La0.7Sr0.3CoO3perovskite catalyst prepared by sol-gel method, but theNOxstorage capacity and De-NOxperformance were even lower. The performance ofthe3DOM pore canal may be more proper for gas-solid reaction such as NOx-Sootremoval simultaneously.Our research suggests that SrCO3is an important storage phase on theLa0.7Sr0.3CoO3catalyst. The distribution of SrCO3on the La0.7Sr0.3CoO3catalyst alsoaffects its NSR performance. When SrCO3was highly dispersed on the La0.7Sr0.3CoO3catalyst and closely contacted with each other, the NOxstorage was enhanced underlean-burn conditions and the desorbed NOxwas easily reduced by active site onperovskite under fuel-rich conditions. When SrCO3was uneven distributed on theLa0.7Sr0.3CoO3catalyst and loosely contacted with each other, NOxstored slowly asnitrate species in lean-burn condition and the desorbed NOxwas hardly reduced byperovskite under fuel-rich conditions.