V-W/TiO_2/γ-Al_2O_3催化剂催化还原NO的研究

Comparative Study on V-W/TiO_2/γ-Al_2O_3 for Selective Catalytic Reduction of NO

掺杂15%TiO2对γ-Al2O3改性制备了TiO2/γ-Al2O3复合氧化物载体,以此复合氧化物及TiO2、γ-Al2O3为载体用浸渍法负载钒钨制备了一系列催化剂,采用比表面积和孔结构分析、X射线衍射(XRD)、高分辨电镜(HRTEM)、原位红外(in situ FT-IR)等技术对载体和催化剂进行宏观-微观表征,同时在模拟氨气选择性催化还原NO(NH3-SCR)的反应条件下对催化剂的脱硝反应活性进行考察,比较研究TiO2掺杂对V2O5-WO3/TiO2和V2O5-WO3/γ-Al2O3催化剂的改性作用。结果发现,少量TiO2掺杂制得的TiO2/γ-Al2O3复合载体中,TiO2和γ-Al2O3之间的协同作用使得V2O5-WO3/TiO2/γ-Al2O3催化剂的选择性催化还原脱硝效率及活性窗口明显优于单一载体制备的催化剂,并表现出了良好的热稳定性;各种表征结果表明,TiO2/γ-Al2O3复合载体中TiO2高度分散在γ-Al2O3上,复合载体具有较大的比表面积,载体表面存在大量的Br?nsted酸位和较多的活性中间产物,这些可能是TiO2/γ-Al2O3复合载体催化剂具有较好SCR活性的原因。

TiO2/γ-Al2O3 composite oxide carrier was prepared by 15%（weight ration） TiO2 doped toγ-Al2O3.A series of catalysts containing V2O5 and WO3 on the composite oxide,TiO2 and γ-Al2O3 carriers respectively were prepared by a wet-impregnation method,which were investigated by using various characterization techniques of BET surface area and aperture analysis,X-ray diffraction（XRD）,transmission electron microscope（HRTEM） and in situ Fourier transform infrared spectroscopy（in situ FT-IR）.Meanwhile their catalytic performance in NOx reduction reaction with NH3 was assessed to study the effect of TiO2 modification on V2O5-WO3/TiO2 and V2O5-WO3/γ-Al2O3 catalysts.Results showed that as a result of interaction of TiO2 andγ-Al2O3,the NO conversion of V2O5-WO3/TiO2/γ-Al2O3 catalyst was improved in a wider temperature range compared to the catalysts supported on the single oxide carriers.TiO2-doped catalyst exhibited better thermal stability.The combination of characterization results confirmed that TiO2 was highly dispersed on the surface of TiO2/γ-Al2O3 binary oxide and the catalyst possessed the larger BET surface area.Additionally,TiO2/γ-Al2O3 carrier was revealed that there were significant amounts of Bronsted acidity and active intermediate products on the surface,which might be main reason that V2O5 and WO3 contained TiO2/γ-Al2O3 composite oxide catalyst showed good catalytic activity.