Design And Preparation Of Micro / Mesoporous Nanocomposites And Study On Catalytic Purification Of Diesel Car

Energy saving and environmental protection have become two major topics in today’s social development, which is also an urgent problem to achieve social economic sustainable development. Diesel engine has attracted more and more public attentions owing to its high thermal efficiency, good fuel economy and durability in various power plants, since it was invented by the German of Searle in 1905. However, the serious exhaust emission of diesel vehicle has caused a series of environmental problems. With the emission regulations become more and more stringent, a lot of researches have been carried out at home and abroad. How to effective purify the exhaust emissions and reduce their harmful to the people health has becoming an urgent issue. Recently, some micro/mesoporous structured materials with specific functions have shown extremely broad prospects in the field of diesel exhaust purification.In this thesis, various micro/mesoporous nanocomposite materials have been designed and synthesized for the selective catalytic reduction of NOx, also for the catalytic oxidation of CO and CH. The main research contents and conclusions include the following three parts:(1) A series of Cu Bi co-doped mesoporous zeolite Beta(CuxBiy-mBeta) were synthesized via a facile one-pot hydrothermal treatment approach, by which the copper and bismuth species could be well incorporated into the framework of mesoporous zeolite Beta. The prepared catalysts were applied to the selective catalytic reduction of NOx with NH3. The optimized Cu1Bi1-mBeta not only shows an excellent NH3-SCR activity and high N2 selectivity(closely to 100%) toward NOx in a broad operation temperature window(170-430 °C), but also exhibits an extremely high resistance to H2O/SO2 and excellent catalytic stability.(2) A green environment-friendly preparation method with template-free facile redox precipitation strategy was proposed to synthesize a series of mesoporous MnOx/CeO2 nano-composite oxides and employed as the DOC for the catalytic oxidation of CO and CH. The optimized catalyst MnOx/Ce O2-64 with high surface area, exhibits the best redox capability and excellent catalytic activity to the oxidation of CO, C3H6 and C3H8, with very low light-off temperature(105 oC, 140 oC and 180 oC) and completely transformation temperature(150 oC, 190 oC and 230 oC), respectively. The superior catalytic activity of the catalyst could be ascribed to the generation of a large number of active oxygen species due to a synergetic catalytic effect between valence-varied Cen+ and Mnn+ active species.(3) The effects of different coating processes, assistant La, precious metals Pt and different reducing agent on the performances of monolithic catalysts have been investigated. Afterwards, the catalytic activities of synthesized DOC monolithic catalysts for the catalytic oxidation of CO and HC were evaluated. It is found that two-step coating processes is the best coating method, also adding a small amount of assistant La and precious metals Pt can be beneficial to improve the catalytic activity. Thereinto, the DOC monolithic catalysts(optimized preparation conditions) shows the highest oxidation activityof CO, C3H6 and C3H8 with the lowest light-off temperatures(125 oC, 145 oC and 210 oC) and the complete conversion temperatures(175 oC, 175 oC and 260 oC), respectively.