Support Modification With Binary Metal Oxides On MoO_x-CeO_y For Improving The Performance Of The Catalyst In Selective Catalytic Reduction Of NO By NH₃

The extensive developing type of the economy in our country，which is decidedby our country conditions，economic level and energy situation，has brought lots ofvisible problems to the environment of China. Emissions of NOx(NO and NO2) areaffecting the air quality and the health of the people badly. Controlling the emissionsof NOxhas been a serious challenge of our country and the government has decided totighten the emission standards the of NOxemission sourse.Selective catalysis reduction，which is known as SCR，is the most efficient andmost economical NOxcontrolling method all over the world. The catalysts in the SCRdevice was the core and key in the process，a stable and active catalyst promote theNO removal in a large scale. In this study，the author intended to optimize thecatalysts by the modification of the supports in the catalysts，during which the surfacematerial properties of the supports could be changed in the way of promoting the SCRactivity of the catalyst. This study also evaluated the SCR performance in thesimulated flue gas with a componential of NO (1000ppm)，1000ppm NH3，5%O2，500ppm SO2(when used)，5%H2O vapor (when used) and N2as the balance gas.Besides，the physical and chemical properties of the materials were also experimentedand analysed in detail.In this study，binary metal oxides supports Al2O3SiO2，Al2O3TiO2，andAl2O3ZrO2with different composition proportions were prepared by hydrolyzationand coprecipitation methods，after that a series of different amount of MnOx CeOywere loaded using isovolumetric impregnation method. MnOx CeOy/Al2O3，MnOx CeOy/SiO2，MnOx CeOy/TiO2and MnOx CeOy/ZrO2were also synthesized ascomparison. In the SCR perfermance evaluation，MnOx CeOy/Al2O3ZrO2(MCAZ)with8wt%MnOxand4wt%CeOyand Al2O3/ZrO2=3:1showed outstanding NOremoval efficiency and could abate the deactivation brought by SO2and H2O.Moreover，the fluctuation of gas hourly space velocity (GHSV) appeared only a bit ofinfluence on the activity at middle temperature. The author also investiged the effcetsof O2concentration and the ratio of NH3/NO as well. Characterizations for thesamples involved N2adsorption desorption， X ray diffraction (XRD)， X rayphotoelectron spectroscopy (XPS)，H2temperature programmed reduction (H2TPR)and Fourier transform infrared spectroscopy (FTIR). The characterization resultsexhibited that MnOx CeOy/Al2O3ZrO2owned bigger specific surface area and appropriate pore diameter，highly dispersed amorphous Mn2O3as well as rationalratio of Ce4+/Ce3+. The H2TPR results presented the promotion of the activity waspartially due to the stronger oxidation ability at low temperature. Through the FTIRanalysis，and combining with the mechanism proposed by earlier research，it wassupposed that the highly reactive nitrates on the surface favored the high NOconversion. Besides，FTIR revealed that the bidentate sulfates formed by adsorbedSO2produced new Lewis acid sites which promoted NH3adsorption and reduced thepoisoning effect of SO2and H2O. The conclusions in this study may be helpful to thelater investigation on the modification of middle high temperature SCR catalyst，andat the last of this paper the author proposed his outlook and suggestion for the futureresearch on the SCR catalyst.