Study On Application Of Catalytic Technique On Diesel Engine Exhaust

The particulate matter (PM) and nitrogen oxides (NO_x) emissions from diesel exhaust are two of main pollutants damaging environment and human health. With stringenter and stringenter emission regulations, the diesel automotive industry is currently facing serious challenges to meet the specific regulations concerning both PM and NO_x. However, the future emissions targets cannot be reached by the combu- stion adjustment and the current after-treatment technologies. Therefore, new methods for simultaneous removal of PM and NO_x from rich oxygen diesel exhaust are needed. The investigation on the purification of diesel emission by the catalytic technology was carried out in this paper.Firstly, a series of La_1-xK_xCo_1-yFeyO₃ catalysts of perovskite type structure had been synthesized at low temperature through a combustion process, during which the catalysts with particle diameters that scatters in the domain of 90 and 200 nm was prepared , and the BET values of the catalysts range from 9 to 15 m2/g. The crystal structure, phase character, surface texture and valence were characterized by XRD, SEM, and TEM. These catalysts were investigated in removal of NO_x, and PM from diesel exhaust gases using temperature-programmed reaction. The results show that La_0.7K_0.3CoO₃ behaved high catalytic activity in NO_x abatement. However initiated temperature of PM dropped to 400℃under the catalytic effect of La_0.6K_0.4CoO₃.Secondly, perovskite catalysts available for catalytic diesel particulate filter was selected by thermal gravimetric—infrared ray with model gas in place of real diesel exhausts. This experiment was carried out with a 10:1 by weight mixture of soot and powder catalysts including La_1-xK_xCoO₃(x=0.1,0.2,0.3,0.4,0.5),. LaFe_yCo_1-yO₃(y=0.1,0.2,0.3,0.4,0.5,0.6,0.7)and La_1-xK_xFe_yCo_1-yO₃ (x=0.2,0.3,0.4,y=0.5,0.6). The results indicate that La0.8 K0.2 Fe 0.5Co0.5O3 have the highest activity for initiated temperature of PM, and the temperature decreased with increasing y value in La_1-xK_xFe_yCo_1-yO₃. In addition, NO_x extremely contribute to soot combustion compared with air, which implies that NO₂ plays an important role in PM removal in the process of diesel exhausts cleaning. NO also accelerates PM combustion. Because non-thermal plasma produce lots of NO_x, it is reasonable for using NTP in removal of PM in diesel exhausts.