Study On Simultaneous Catalytic Reduction Of Sulfur Dioxide And Nitric Oxide On Rare Earth Oxide

Sulfur dioxide(SO2) and nitric oxide(NO) resulting from the combustion process of coal, are two major air pollutants which have caused serious damage to the eco-environment. In recent years, as the protection of the ecological system was further enhanced, coal-fired power plants were requried supporting facilities to control the total emissions of SO2 and NOx. Simultaneous application the traditional facilities of desulfurization and denitrification cannot be endure even in developed country because of the high costs of investment and operation. So increasing importance has been attached to the technology of simultaneous catalytic reduction of SO2 and NO. This techonlgy is desirable for its compact construction and low price. In the flue gas, CO which is the production of incomplete combustion is easy to be obtained and it can simultaneously reduce SO2 to elemental sulfur as well as NO to nitrogen. Compared with other ordinary FGD process, the catalytic reduction of SO2 and NO avoid the secondary pollution. What's more, the end product of sulfur is a kind of important industry stuff.Preparation of catalysts is an important factor which affects the performance for desulfurization or denitrification. In the paper, activated alumina (γ-Al2O3),silica gel(SiO2) and zeolite were used as the carriers of the catalysts, and rare earth oxides and nickel oxide were chosen as active components. A series of simplex and complex catalysts were prepared by impregnating in certain ratio. Separate removal of SO2 over the prepared catalysts has been reserched. The effects the carries, the order of dipping component to the carrier and temperature on the activies of the catalysts were investigated. The phase characteristics of catalysts were also analyzed by X-ray diffraction. Furthermore, simultaneous reduction of SO2 and NO by CO over selected catalysts in desulfurization process have been researched in the thesis.The results of experiments indicate that, in the desulphurization process, the activity of catalyst La2O3-NiO/γ-Al2O3 is much higher than other catalysts, and the reaction can be soon actived at centigrade 500, while the SO2 conversion rate is over 99%. The activated catalysts will keep high activity between centigrade 400~300. It is favor in the process that La component was impregnated after nickel component. The effect of the kinds of carries on the activites of the catalysts is distinct. SO2 conversion is below 90% over the compound catalyst CeO2-NiO/γ-Al2O3 and above 99% over CeO2-NiO/SiO2 as well as that above 97% over CeO2-NiO/zeolite. In NO+ SO2+CO system, NiO/γ-Al2O3, La2O3-NiO/γ-Al2O3 and CeO2-NiO/γ-Al2O3 catalysts both have high activity for simultaneous reduction of SO2 and NO, and the activities are higher over the same catalysts after sulfuration in the CO+SO2 system. It means that the sulfuration of the catalyst can increase the activity resulting in rapid startup of the reaction. The SO2 and NO conversions are all above 99% over CeO2-NiO/γ-Al2O3 catalyst after sulfuration. At the same time, reaction mechanism is also initial inferred based on the experimental results and catalyst XRD analysis. Good desulfurization and denitrification effect over CeO2-NiO/γ-Al2O3 maybe the result of cooperation of COS intermediate phase and redox of CeO2.