Research On Perovskite-type Filter For Purification Of Diesel Exhaust Particulate

Automobile exhaust pollution problem has become to be one of the most serious problems of environmental pollution, directly affecting the survival of human health and hindering economic and social sustainable development.Driven by technological progress, diesel vehicles which were not taken seriously are becoming the strategic objectives of national car makers. The global automotive industry is stepping into a era of automotive diesel fuel. However, the pollution of diesel engine emissions is becoming more acute. A large number of harmful particulate matters in emissions, that's to say, whether the so-called "black smoke" issue can be effectively curbed turns to be the bottleneck for extensive use of both energy-saving and economical diesel vehicles of China.Reprocessing technology is the most direct and promising approach to solve the diesel engine emissions currently. At present, particulate trap is the most notably reprocessing technology. Too much accumulation of particulates will lead to deterioration of engine performance and they must be removed regularly, namely, filter regeneration. In view of this situation, in order to increase the removal efficiency of exhaust particulate, all nations apart from improving diesel engine working process are trying to develop the exhaust particulate filters and the catalysts are also being studied for purification of harmful diesel exhaust particulate and gaseous emissions. Up to now, precious metals of platinum, rhodium, palladium and so on are the mainly studied for catalysts, but because of the expensive price, practical application is tremendous difficult.According to the research of this area, this paper combined the particulate filter technology and oxidation catalytic converter technology to improve the removal efficiency of exhaust particulates and explore regeneration technology.In accordance with China's national conditions, the experiment made a perovskite-type metal-oxide catalyst (La_1-xK_xCoO₃) with China's rich reserves of rare earth and transition metal elements as the main raw materials. Had determined prepare the perovskite-type metal-oxide catalyst (La_1-xK_xCoO₃) with the sol-gel method, and had determined, when doping ratio is X=0.15, the catalyst La_0.85K_0.15CoO₃ has the strongest catalytic activity, and had further carried on the optimized choice of the catalyst preparation's calcination temperature, obtained when the calcination temperature of 700℃, the prepared catalyst La_0.85K_0.15CoO₃ has the strongest catalytic activity. Then dip the catalyst to the honeycomb ceramic vector, which was coated with activated alumina. The experiment also carried screening and evaluation of high- activity catalysts. Results showed that: using the coating technology to prepare Al₂O₃/honeycomb ceramic(at this point the quality of Al₂O₃ is ceramic's 10.05%) with dilution ratio of 1:3 for the impregnation of aluminum sol liquid and 25% La_0.85K_0.15CoO₃:Al₂O₃ as parameter, the overall ceramics had the best catalytic effect. And carried on the diesel engine bench test(under experimental operating condition, discharge temperature was about 185℃), the gantry experiment had obtained:The perovskite-type filter had the removal rate for PM, HC, CO and NOx were 98.83%, 27.62%, 40.56% and 5.22%, respectively.The experiment also carried out the regeneration research of filter, and the results showed that: regeneration time was determined by pressure loss; catalytic conversion activity for the PM was greatly enhanced of this perovskite-type filter. Its T50% is 365℃,and its t50% is 10min under the condition of 400℃.They are far superior to the blank ceramic filter.What's more important, exhaust gas temperature of diesel engine could reach 365℃⁴00℃easily under the high-speed and high load operating conditions. Exhaust gas temperature of some turbocharged engine were even higher and could meet the temperature range to achieve the regeneration of filter, without additional devices and renewable energy sources, greatly reducing the cost of regeneration.It can be seen that perovskite-type filter for diesel exhaust particulate removal has a good treatment effect and application prospect.