载体对V_2O_5-MoO_3/TiO_2催化剂表面性质及其选择性催化还原脱硝性能的影响

Influence of texture structures of TiO_2 supports on surface properties and SCR performance of V_2O_5-MoO_3/TiO_2 catalyst

采用比表面积分别为101．86m^2·g^-1（A）、86．37m^2·g^-1（B）和7．78（C）m^2·g^-1（C）的TiO2载体，通过分步浸渍法制备V2O5-MoO3／TiO2（A，B，C）选择性催化还原脱硝催化剂。在空速为10000h^-1和氨氮体积比1．0条件下，以TiO2（A）与TiO2（B）为载体制备的催化剂脱硝活性在反应温度窗口（350—450）℃超过90％，且具有良好的高温抗硫中毒性能和相对较小的氨气氧化率。而以Ti02（C）为载体制备的脱硝催化剂活性温度窗口窄，在350℃时获得的最高脱硝活性仅为73％，且对NH3的氧化作用较强。利用X射线衍射、低温N2吸附-脱附、紫外-可见漫反射光谱、H2程序升温还原和NH3程序升温脱附等对载体和催化剂进行表征。结果表明，活性组分V2O5在载体TiO2（A）上分散性良好，主要以孤立态钒氧物种形式存在，因此，以TiO2（A）为载体制备的催化剂比表面积、氧化还原性和表面酸性等性能更优。

V2O5-MoO3/TiO2 （ A, B, C） catalysts for selective catalytic reduction （SCR） denitrification were prepared by using the stepwise impregnation method and TiO2 support with surface area of 101.86 m^2·g^-1,86.37m^2·g^-1 ,7. 78m^2·g^-1 respectively [ denoted as TiO2 （A,B, C）].The influ- ence of TiO2 texture parameters on the catalytic properties of the catalysts for De-NOx were studied. Under the condition of GHSV 10 000 h^-1 and NH3/NO volume ratio 1.0, NO conversion over catalysts supported on TiO2 （ A, B） reached more than 90% at （350 - 450） ℃, while the maximum NO conversion over the catalyst supported on TiO2 （C） was only 73 % at 350 ℃. Besides, the catalysts supported on TiO2 （A, B ） possessed better resistance performance to sulfur dioxide poisoning and lower oxidation rate of ammonia. The supports and catalysts were characterized by X-ray diffraction, N2 adsorption-desorption, UV-Vis diffuse reflection spectroscopy, H2 temperature-programmed reduction and NH3 temperature-programmed desorption. The results showed that compared with the catalysts supported on TiO2 （B, C ）, V2O5 was amorphous and highly dispersed on TiO2 （A） support,which would be mainly responsible for better redox property and surface acidity, subsequently the higher SCR activity.