钾盐沉积对VMoTi催化剂脱硝性能的影响

Effect of Potassium Salt Deposition on Denitration Perfor-mance of VMoTi Catalyst

摘要:

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、NH₃-程序升温脱附（TPD）、H₂-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V⁴⁺、Mo⁴⁺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TiO₂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V⁴⁺、Mo⁴⁺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。

Abstract:

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, NH₃-temperature programmed desorption (TPD), H₂-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 vanadium-titanium-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 V⁴⁺, Mo⁴⁺, and surface active oxygen. Therefore, VMoTi (Sol-gel) catalyst shows a good denitration efficiency stabilized at ~100% in the temperature range of 180~320 °C. 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 TiO₂, 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 V⁴⁺ and Mo⁴⁺, decreases. These factors are the main reasons of the catalyst inactivity.