钾盐沉积对VMoTi催化剂脱硝性能的影响

Effect of Potassium Salt Deposition on Denitration Performance of VMoTi Catalyst

采用浸渍法(IM)与溶胶凝胶法(Sol-gel)制备VMoTi催化剂,并在实验室模拟选择性催化还原(SCR)催化剂的碱金属K中毒,通过X射线衍射、BET比表面积测试法、NH_(3)-程序升温脱附(TPD)、H_(2)-程序升温还原(TPR)和光电子能谱等方法对催化剂表面的理化性能进行分析,并探讨钒钛系催化剂的反应及失活机理。结果表明:与浸渍法制备的VMoTi催化剂相比,溶胶凝胶法制备的VMoTi催化剂具有较小的晶粒粒径,较大的比表面积和孔容,较多的表面酸量,较强的氧化还原能力以及较高的V^(4+)、Mo^(4+)和表面活性氧含量,因此,VMoTi(Sol-gel)催化剂表现出了较好的脱硝效率,在180~320℃的温度区间内,脱硝效率稳定在约100%。钾的加入会导致催化剂中毒,且不同方法制备的催化剂的中毒效应不同,K盐沉积对浸渍法制备的VMoTi催化剂的脱硝效率影响较大,溶胶凝胶法制备的VMoTi催化剂具有较好的抗K金属中毒的性能。通过对催化剂的表征发现,K盐削弱了活性成分与载体间的相互结合作用,增强了锐钛矿型TiO_(2)衍射峰的强度,降低了催化剂表面酸性及氧化还原性,同时催化剂表面的化学吸附氧及V^(4+)、Mo^(4+)等活性金属含量降低,这些因素是造成催化剂活性下降的主要原因。

VMoTi catalyst was prepared separately by impregnation method(IM)and sol-gel method,and the alkali metal K poisoning of the catalyst was simulated.The X-ray diffraction,BET specific surface area test,NH_(3)-temperature programmed desorption(TPD),H_(2)-temperature programmed reduction(TPR),and X-ray photoelectron spectroscopy(XPS)methods were used to analyze the physical and chemical properties of the VMoTi catalyst,and the reaction and deactivation mechanisms of the vanadiumtitanium-based catalyst were discussed.The results show that compared with the catalyst prepared by IM,i.e.,VMoTi(IM)catalyst,the catalyst prepared by the sol-gel method,i.e.,VMoTi(Sol-gel)catalyst,has a smaller grain size,a larger specific surface area and pore volume,a larger amount of surface acid,a stronger redox capacity,and a higher content of V^(4+),Mo^(4+),and surface active oxygen.Therefore,VMoTi(Sol-gel)catalyst shows a good denitration efficiency stabilized at~100%in the temperature range of 180~320℃.The addition of potassium(alkali metal)leads to catalyst poisoning,and the poisoning effect of the catalysts prepared by different methods is different.The K salt deposition has a great influence on the denitration efficiency of the VMoTi(IM)catalyst.The VMoTi(Sol-gel)catalyst has good resistance to K poisoning.Through the characterization of the catalyst,it is found that K salt weakens the interaction between the active ingredient and the carrier,enhances the intensity of the diffraction peak of anatase TiO_(2),and reduces the acidity and redox of the catalyst surface.At the same time,the content of chemical adsorption of oxygen and active metals,such as V^(4+)and Mo^(4+),decreases.These factors are the main reasons of the catalyst inactivity.