| In the recent years, how to effectively remove the nitrogen oxides being contained in the exhaust of lean burn engines has been a challenge for environmental protection field all over the world due to the serious pollution caused by the pollutant gases. Selective catalytic reduction of NOx by hydrocarbons (HC-SCR) was generally believed to be one of the most promising ways to remove NOx from the lean-burn exhausts. To diminish engines'power loss due to the backup caused by the exhaust treatment, a monolithic catalyst must be practically used for the engine exhaust treatment. Thus, it is important to investigate an agglomerant that not only can fix active ingredients to monolithic carrier firmly, but also can supply large surface area and some activity sites for the monolithic catalyst.Due to a large surface area, alumina was generally used as binder material for the monolithic catalyst in the past years. This thesis thus aimed to obtain a Al2O3-based composite agglomerant with high activity to the selective catalytic reduction of NO by acetylene (C2H2-SCR), hence the property of alumina itself and modified by Ce being associated with the reaction were studied by varying preparation condition and doping the resulting material with Ce. NOx adsorption capacity and the activity of alumina for C2H2-SCR influenced by Lewis acid sites on the material and the rate-determining step of C2H2-SCR over alumina were focused in this thesis.Alumina was prepared by precipitation method and part of them was hydrothermally treateated before calcination. Lewis acid sites in population and NOx adsorption capacity of the samples were investigated by the FTIR. It was found that the latter (Al2O3-HT) obtained by additional hydrothermal treateatment has more Lewis acid sites with strong acidity in population and stronger capacity of NOx adsorption in comparison with the former (Al2O3). In C2H2-SCR reaction, the Al2O3-HT was more active for NOx removal than Al2O3. Based on the results, it was proposed that Lewis acid sites with strong acidity over Al2O3-HT are in favors of NOx adsorption and hence increase the C2H2-SCR.The NOx elimination influenced by NO2/(NO+NO2) ratio was investigated. It was found that with NO2/(NO+NO2) ratio increasing in the range of 13～56%, NOx conversion increased in a well proportional relations. Therefore, it was concluded that NO oxidation to NO2 is the rate-determining step of C2H2-SCR over Al2O3-HT.To accelerate the NO oxidation step and hence improve the reaction of C2H2-SCR, the alumina was doped with Ce and it was found that adding of 1.2wt.%Ce into Al2O3-HT significantly enhanced the activity of the catalyst for C2H2-SCR reaction. However, no corresponding higher activity of 1.2wt.%Ce-Al2O3-HT than Al2O3-HT could be found for NO oxidation, especially in lower temperature range (250～350℃). To investigate the mechanism of Ce enhancing the reaction of C2H2-SCR and give a explanation to the phenomenon, the surface species of 1.2wt.%Ce-Al2O3-HT under NO oxidation and C2H2-SCR reaction conditions were investigate by in situ FTIR, respectively. Based on the characterization results, it was proposed that under reaction conditions of NO oxidation to NO2, CeO2 supported on alumina has no special activity for the reaction, as its active sites can not work due to nitrate species formation on them; Whereas, under C2H2-SCR reaction conditions, as the nitrate species produced by the co-adsorption of NO+O2 are just reactive intermediate for C2H2-SCR, cerium effectively enhanced the reaction of C2H2-SCR by accelerating the rate-determining step.
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