Experimental Study Of No_X Storage/reduction (NSR) Using DME As Reducer

Dimethy ether engine is the typical lean burn engine. As for the technology of lean burn engine NO_x reduction, NO_x selective catalytic reduction (SCR) and NO_x storage-reduction (NSR) are the two most practical application prospects. NSR possesses not only the advantage of low emission of SCR, but also the advantage of high efficiency of lean burn engine, which has become one of the most urgent and challenged project in the automotive field. With the support of National Natural Science Foundation, this project has done some research on NO_x storage-reduction, by using DME or DME reformed gas as the reductant. Its main researches include:It studies the effects of different addition agents by using Pt/M-BaO/γ-Al₂O₃(M=Fe,Cu,Co)as catalyst. The result shows that, with addition of Co, the Pt/Co-BaO/γ-Al₂O₃ owns best storage power, and it holds the longest absorption time if given the same 2 minutes reduction time, which can even reach 16 minutes. In view of the above, Pt/Co-BaO/γ-Al₂O₃ will be used as the catalyst in the follow-up reaches.It studies the general rule and effect of the experiment conditions on the catalyst of DME-NSR by using Pt/Co-BaO/γ-Al₂O₃ as the catalyst. The results indicate that the catalyst Pt/Co-BaO/γ-Al₂O₃ owns excellent NO_x absorption and reduction ability. When reduction time increases from 0.5 min to 1 min, the NO_x absorption efficiency would increase 25%, and the NO_x conversion efficiency would increase 10%. The higher DME concentration could deduct NO_x more effectively during the same reduction time. And the NO_x absorption and conversion efficiency would reach its max, which is 92.5% and 70.9% respectively when the temperature is about 375℃. Higher or lower temperature would result in negative effects on the efficiency. It studies the effects of O? and CO? on the catalyst by changing the mixture composition in the absorption and reduction periods. The results shows that O? makes no difference on the NO_x absorption efficiency; and NO_x conversion efficiency decreased 0.5% as O₂ concentration increased from 0% to 1.25% in the reduction period, and then it would stay the same. CO? shows up some poison effect on the catalyst and it could suppress the NO_x absorption and reduction.(4) It studies the thermol stability of the adsorption saturated catalyst Pt/Co-BaO/γ-Al₂O₃ and the effect of the reductant DME by applying temperature program desorption (TPD ) and DME temperature program surface reaction (TPSR). Compared the map of the N2-TPD and DME-TPSR, it can be observed that the NO_x desorption peak value decrease from 150ppm to 25ppm, and the temperature is 50℃forward lead when the peak value appears, which indicates that DME has some positive effect on the NO_x desorption and return most of the desorptioned NO_x effectively.(5) It simulates the DME reformed gas-NSR experiments by using the DME/H2 mixtures as the reductant. The results show that, the NO_x desorption peak value decreases as the H2 concentration increases; and the NO_x absorption time increases in the condition of the same reduction time.This paper studies in detail the general rule and effect of the experiment conditions on the catalyst of DME-NSR and it has preliminary research on the DME reformed gas-NSR, which lays the foundation for the follow-up studies based on the fuel restructuring and the NSR premixed fuel / direct injection combustion engine performance, and has vital theoretical and practical significance for the development of new efficient ultra-low-pollution engine technology.