Study On Application Of Catalytic Technique & Plasma Technique On Diesel Engine Exhaust

The application of non-thermal plasma technique (dielectric barrier discharge) and catalytic technique (with La_1-xSr_xMnO₃ catalysts of perovskite type structure) on diesel engine exhaust was discussed in this paper. The principle and reaction mechanism of nitrogen oxides (NO_x), total hydrocarbon compound (THC), and particulate matter (PM) from the diesel exhaust through plasma/catalysis were focused, which makes foundation for practical plasma/catalysis application on diesel emission in the future.A series of La_1-xSr_xMnO₃(A′:Ce,K) catalysts were synthesized by using a modified version of the citrates method, 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 8 to 13 m²/g. The crystal structure, phase character, surface texture and valence were characterized by XRD,SEM & Iodometry. Study of catalytic property for removal of NO_x, THC and PM from diesel exhaust was carried out by using temperature-programmed reaction (TPR). The results show that the Co³⁺-Co²⁺ system in La_1-xCe_xCoO₃ was found after La was partially substituted with Ce, and the Co³⁺-Co⁴⁺system in La_1-xK_xCoO₃ was found while La was substituted with K. Both La_1-xCe_xCoO₃ and La_1-xK_xCoO₃ can behave high catalytic activity in NO_x abatement. However, the catalytic efficiency of La_1-xK_xCoO₃ for PM is higher than La_1-xCe_xCoO₃ , and for THC vice versa.The effect of non-thermal plasma (NTP) on removal of PM, THC and NO_x in diesel exhaust was investigated. The result shows that when voltage is high enough NTP will be produced directly in gas, and NTP is capable of removing PM and THC effectively. Removal efficiency is about 100% for soot, 84% for SOF, over 90% for alkanes, 62% for aromatic hydrocarbon , all of which are from PM, and 87% for THC. However, the effect of NTP on NO_x is fairly complicated. Only when the energy input is kept at a relative low level, NO_x can be reduced effectvely. With the high energy input, only for a heavy load running the partial NO_x could be removed.On the bases of the former two techniques, purifying removal of diesel emission was researched when NTP is combined with La_0.8K_0.2CoO₃. The result shows that this system could effectively remove NO_x and PM.