Na2SO4中毒SCR催化剂对SO3生成特性的影响

Effect of Na2SO4 Poisoned SCR Catalyst on SO3 Generation Characteristics

为研究Na2SO4中毒SCR催化剂(V2O5-WO3/TiO2催化剂)对SO3生成特性的影响,采用湿式浸渍法制备w(Na)为3%的Na2SO4中毒SCR催化剂,并通过N2物理吸附/脱附、XRD(X射线衍射)技术、SEM(扫描电镜)、XPS(X射线光电子能谱)分析技术对催化剂的物理化学特性进行表征.结果表明:①随着反应温度的升高,所有催化剂上的SO3生成率逐渐增加.当温度升至490℃时,SCR催化剂上的SO3生成率为0. 85%,而3%Na2SO4中毒SCR催化剂上的SO3生成率高达1. 36%. SO^2-4的存在导致V—O—S增多,从而促进SO3的生成.②随入口ρ(SO2)的增加,SO3生成率呈下降的趋势.当入口ρ(SO2)为1 000 mg/m^3时,3%Na2SO4中毒SCR催化剂上的SO3生成率为1. 02%,而SCR催化剂上仅为0. 60%.ρ(SO2)对SO3生成率的影响主要依赖于温度和催化剂活性位点数等.③N2物理吸附/脱附、XRD和SEM表征结果表明,与SCR催化剂相比,Na2SO4中毒SCR催化剂表面有Na2SO4的积聚,出现了裂纹和大孔隙,催化剂的比表面积和孔容下降,这些变化均不利于催化剂的催化性能;XPS结果表明,Na2SO4的加入提高了表面化学吸附氧含量,降低了活性组分中w(V^4+)/w(V^5+)的值.研究显示,相比于SCR催化剂,Na2SO4中毒SCR催化剂上的SO3生成率大幅增加.

In order to study the effect of Na2SO4 poisoned SCR catalyst(V2O5-WO3/TiO2 catalyst)on SO3 generation characteristics,the Na2SO4 poisoned SCR catalysts with w(Na)of 3%Na2SO4 was prepared by the wet impregnation method,and the physicochemical properties of the catalyst were characterized by N2 physical adsorption/desorption,XRD(X-ray diffraction),SEM(scanning electron microscope)and XPS(X-ray photoelectron spectroscopy).The results showed that:(1)As the reaction temperature increased,the SO3 generation rate of all catalysts gradually increased.When the temperature increased to 490℃,the SO3 generation rate was 0.85%for the SCR catalyst.However,the SO3 generation rateincreased to 1.36%for the 3%Na2SO4 poisoned SCR catalyst.The presence of SO^2-4caused an increase in the number of V-O-S bonds,thereby promoting SO3 generation.(2)Increasing the inletρ(SO2),the SO3 generation rate tended to decrease.When the inletρ(SO2)was 1000 mg/m^3,the SO3 generation rate of the 3%Na2SO4 poisoned SCR catalyst was 1.02%,while the SCR catalyst was only 0.60%.The effect ofρ(SO2)on the SO3 generation rate mainly depended on the temperature and the number of active sites of the catalyst.(3)The results of N2 physical adsorption/desorption,XRD and SEM showed that compared with the SCR catalyst,Na2SO4 accumulated on the surface of the Na2SO4 poisoned SCR catalyst.Cracks and macropores appeared,while the specific surface area and pore volume of the catalyst decreased.These changes were unfavorable to the catalytic performance of the catalyst.XPS results showed that the addition of Na2SO4 increased the surface chemisorption of oxygen and reduced the w(V^4+)/w(V^5+)ratio in the active component.The above results suggested that the SO3 generation rate of the Na2SO4 poisoned SCR catalyst greatly increased as compared with the SCR catalyst.