Study On The Perovskite-type Oxide Catalysts For Diesel Exhaust Gases Purification

The purification of the diesel exhaust gases becomes more important because the pollution caused by diesel exhaust gases gets worse day by day. The synthesis of perovskite-type oxide catalysts with larger specific surface area and higher activity was the main task in this paper. At the same time, the catalytic activity for the simultaneous removal of diesel soot particulate and NOx was studied using the the laboratory equipments in order to service for the development of new catalysts for automobile exhaust purification.LaCoO3 perovskite-type oxide catalysts were synthesized through co-precipitation method and sol-gel method respectively. The influence of various factors on the perovskite-type oxide structure and performance were studied. The results indicated that the LaCoO3 perovskite-type oxides prepared by co-precipitation method had smaller specific surface area and other phases appeared during the co-precipitation synthesizing process. And the precipitating agent concentration and the water amount used were the most important influencing factors for the specific surface area. However, during the sol-gel synthesizing process, the perovskite-type oxides with perfect crystalline phase and large specific surface area were obtained and the water amount used was the most important influencing factor. Then, the LaCoO3 perovskite-type oxides were modified by doping alkaline metal and the alkali earth metal. The FT-IR analysis showed that the B-O bond strength and BO6 symmertry of the modified samples increased, and the phenomena was more obvious for the modified perovskite-type oxides synthesized by sol-gel method.The catalytic activities of the synthesized perovskite-type oxides were studied on the established equipments in the laboratory and the results showed that the LaCoO3 perovskite-type oxide catalysts could obviously reduce the T10, T50 and T90 of soot and improve the selectivity of generating CO2. At the same time, the conversion from NOx to N2 has been improved. The La0.9K0.1CoO3 prepared by sol-gel method was of the best activity for the simultaneous removal of soot and NOx. T10 for soot was reduced by 104℃and T90 was reduced by 210℃. It could also remarkably promote the conversion from NOx to N2 of which the maximum could reach as high as 69 %.