Experimental Sdudy On The Simultaneous Catalytic Removal Of Diesel Engine PM And NO_X

Particulate Matter (PM) and Nitrogen Oxides (NO_x) are the primary harmful emissions of diesel engine, as their contradictory relationship of generation mechanisms, only depending on the in-engine purification measures has already hardly to meet the more and more stringent emission regulations, while a variety of traditional after treatment technology should be used to simultaneously reduce PM and NO_x. Development and application of after treatment technology with low cost, high efficiency and high adaptability will be more promising.The feasibility of catalytic removal of PM and NO_x was researched based on the experimental analysis in this paper. A series of A₂BO₄-type composite oxide catalysts were prepared by sol-gel and their catalitic activity were evaluated through the temperature-programmed reaction. The experiment results show that La₂Cu_0.7Fe_0.3O₄ catalyst has good simultaneous removal efficiency on PM-NO_x, the soot ignition temperature is 342℃and the maximum conversion of NO is 44.4%. The absorption and desorption properties of catalysts were characterized by H₂-TPR,XPS and TPD. Experiment dates show that the surface of catalyst exsits two kinds of oxygen which are aborbed oxygen and lattice oxygen. The adsorbed oxygen has strong activity and can dissociate from the surface of catalyst to the surface of particulats, while the lattice oxygen can provide oxygen vacancies for the adsorption and desorption of NO.Use the La₂Cu_0.7Fe_0.3O₄ catalyst which has the best catalytic activity as research object, it was coated on the support which was then packaged to a catalytic diesel particulate filter (CDPF) for the engine bench test. The operating condition were chosen based on European standard steady state test cycle, purifying effect of working condition with load of 50%, 75% and 100% at 1300r/min, 1600r/min and 1900r/min was compared. The experimental results indicate that catalyst prepared can simultaneously remove PM-NO_x with a better effect in high-speed and high-load. The conversion effect with different support,different exhaust temperature and different oxygen concentration were investigated in the following test, results show that material of support with SiC,500℃and oxygen concentration of 10% is more favorable for the catalytic removal of PM-NO_x. Fuel spray strategy of post injection induces to a high concentration of unburned HC and CO which will provide a favorable reduction atmosphere for NO_x, at condition of 1600r/min and 75% load, the NO_x conversion can be increased by about 10% when using the the crank angle between main injection and post injection was 50°CA.