| The advantages of high efficiency, economy and durability of diesel engines have resulted in widely use in various power systems in recent years. However, the main pollutants, particulate matter (PM) and Nitrogen oxides (NOx), emitted by diesel engines have caused severe environmental and human health problems. There is a trade-off effect for PM and NOx control inside cylinder, so the simple way of the pollutants control techniques in engine is not enough to reduce PM and NOx at the same time. As the traditional removal approach cannot meet more and more stringent regulations nowadays, a new way to reduce PM and NOx by simultaneous catalytic removal technology has a promising propect.In this paper, a study of simultaneously catalytic removal of PM and NOx was carried out with perovskite oxides. Firstly, the reaction between PM and NOx in a surrounding rich in oxygen was studied using real diesel particulates on the surface of DPF coated with perovskite oxides by the Temperature Programmed Reaction (TPR) technique. Then a new research of simultaneous catalytic removal performance of real PM and NOx, which are emitted by diesel engine, with perovskite oxides was studied by the TPR technique. The research work and results are summarized as following:1. The catalytic performance of perovskite oxides of La-Mn-O was investigated. The influences of different replacing amounts with K and Cu were also discussed. Then the catalytic performances were studied by TPR technique, while the PM was simulated by carbon black and the NOx was simulated by NO. It was found that the replacement of K and Cu improved the catalytic performance of La-Mn-O. The results showed that calcination temperature at 850℃on the catalyst of La0.8K0.2Cu0.05Mn0.95O3 (LKCM) had the highest catalyst performance, while the ignition temperature of carbon black, at 270℃or so, was about 220℃lower than that without catalyst. Meanwhile, LKCM showed the strongest catalysis on NOx with the maximum conversion rate up to 34.4%.2. Mixed metal oxide catalysts LKCM were synthesized by solid-phase reaction at high temperature with transition metal elements and rare earth elements. By the means of XRD and BET surface area, material characters of the catalysts, catalyst carriers and transition layers as well as the coated methods of catalysts were investigated.γ-Al2O3 was tried to serve as transition layer, which causes the surface of the DPF more compact becauseγ-Al2O3 grains were permeated into the structure of DPF, making the catalyst coated on DPF uneven. The results showed that the outlet CO2 profiles of trapped PM combustion had two peaks corresponding to the combustion of SOF and soot respectively. And the formation of CO2 and the reduction of NOx were observed at the same temperature range. NOx is reduced by SOF at lower temperatures and by soot at higher temperatures.3. The results showed that the change ofγ-Al2O3 amount had little influence on catalytic performance while the LKCM amount stay unchanged by comparing with different loaded method of catalyst and transition layer. But the LKCM catalyst coated better on DPF as the catalyst increased and theγ-Al2O3 amount stayed unchanged, which resulting in a better simultaneous catalytic removal performance of PM and NOx. The performance of catalyst prepared by dipping method was better than that of slurry method, because the with dipping method, the catalyst covered well on the surface of DPF and a uniform layer of LKCM catalyst andγ-Al2O3 was formed and the contact condition between catalyst and PM is better for the scraggy carrier surface with catalyst powder on DPF, so the catalysts coated on the carrier in this way are better in performance.4. An after-treatment bench test was set up to remove the PM and NOx emitted by the diesel engine, and the simultaneous catalytic removal performance was studied. The results showed that the removal rated increased with the temperature increased for in high temperature and PM trapped on DPF is regenerated. Meanwhile, as the PM trapped in DPF, the NOx conversion rate increased slightly. But the catalytic reactivity decreased as the temperature got too low. It is worth noting that the DPF loaded with LKCM catalyst andγ-Al2O3 transition layer has a very good PM-NOx simultaneous removal efficiency, even in the temperature of exhaust pipes of diesel engine range.The method of simultaneously catalytic removal of PM and NOx can be regarded as a combined process of PM trapping and catalytic reactions of PM oxidation as well as NOx reduction by SOF and soot, and maintains a relatively high PM - NOx simultaneous removal rate at the exhaust temperature range. Therefore, it promises to be the most desirable mean of after-treatment of diesel exhausts.
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