【作者】 张凯；

【导师】 赵炜；

【作者基本信息】 江苏大学 ， 动力工程及工程热物理， 2020， 硕士

【摘要】 现代工业中氮氧化物（NO_x）的大量排放对生态环境和人类健康都有着极大的危害,氨选择性催化还原法（NH₃-SCR）脱硝技术是目前公认的高效率脱硝方法之一。现有的商用SCR催化剂活性窗口处于中高温度段且较窄,如何提升催化剂的低温活性,拓宽反应温度窗口,取得更好的经济性和实用性是现如今SCR催化剂领域研究的热点。本文利用Ti³⁺自掺杂来改性TiO₂载体,选用活性成分V₂O₅和CeO₂负载于TiO₂上,拓宽了传统V₂O₅/TiO₂催化剂的活性温度窗口,且具备优异的抗硫抗水性能。为研究改性前后催化剂的物化性质变化,分别利用了X射线衍射技术（XRD）、X射线光电子能谱技术（XPS）、拉曼光谱技术（Raman）、比表面积及孔结构分析、程序升温测试技术（TPD/TPR）、电子顺磁共振能谱分析技术（EPR）和扫描电子显微镜技术（SEM）等化学表征手段做出了机理分析。研究内容如下:首先,采用溶胶凝胶法制备了Ti³⁺自掺杂TiO₂载体,再选用浸渍法负载1 wt.%的活性成分V,制得富含氧空位的V₂O₅/TiO₂脱硝催化剂。结果表明,相较于无掺杂钒钛催化剂,Ti³⁺自掺杂V₂O₅/TiO₂催化剂在反应温度窗口内的活性效率整体明显提高,且有效的拓宽了低温度段的活性窗口。表征结果发现,Ti³⁺的自掺杂,能够抑制TiO₂金红石相的产生,稳定TiO₂锐钛矿晶型。Ti³⁺的引入产生了大量的氧空位,与吸附在TiO₂表面的氧气反应生成了对“快速”SCR反应具有促进作用的超氧自由基。同时,催化剂的表面酸性强度和氧化还原能力都得到提升,有助于提高NH₃-SCR反应的脱硝效率。其次,采用浸渍法在Ti³⁺自掺杂V₂O₅/TiO₂催化剂基础上引入稀土元素Ce,制得Ce-V双活性组分的钛基脱硝催化剂。结果表明,Ce的引入可有效地进一步降低钒含量且保持高效催化性能。当负载6 wt.%的Ce和0.5 wt.%的V时,该催化剂的整体活性最佳,在180℃时活性效率可达90.4%,进一步拓宽了催化剂的活性温度窗口。表征结果发现,掺杂Ce能够增加催化剂表面吸附氧含量,调控活性组分的多价态共存及进一步加强活性组分与载体的相互作用,从而有效改善催化剂的性能。另外,一方面考察了制备条件和反应条件对催化剂性能的影响,通过优化煅烧温度,使催化剂达到最优性能;另一方面,抗硫抗水性实验表明Ti³⁺自掺杂和Ce的引入均能改善V₂O₅/TiO₂催化剂的抗中毒性能。更多还原

【Abstract】 The massive emission of nitrogen oxides（NO_x）in modern industry has great harm to the ecological environment and human health.The ammonia selective catalytic reduction（NH₃-SCR）denitration technology is currently one of the recognized high-efficiency denitration methods.The active window of the existing commercial SCR catalyst is in the middle and high temperature range and is narrow.How to improve the low temperature activity of the catalyst,widen the reaction temperature window,and obtain better economy and practicality are the hotspots in the field of SCR catalyst research.In this paper,Ti³⁺ion modified TiO₂ support is used,and the active ingredients V₂O₅ and CeO₂ are selected to be loaded on TiO₂.The reaction temperature window of the traditional V₂O₅/TiO₂ catalyst is widened,and it has excellent sulfur and water resistance.In order to study the changes of the physicochemical properties of the catalyst before and after modification,X-ray diffraction（XRD）,X-ray photoelectron spectroscopy（XPS）,Raman spectroscopy（Raman）,specific surface area and pore structure analysis,and temperature-programmed tests were used respectively The technology（TPD/TPR）,electron paramagnetic resonance spectroscopy（EPR）and scanning electron microscope（SEM）and other chemical characterization methods made theoretical analysis.The research content is as follows:First,the Ti³⁺self-doped TiO₂ support was prepared by sol-gel method.The active component V of 1 wt.%was loaded with impregnation method,and the V₂O₅/TiO₂ denitration catalyst rich in oxygen vacancies was prepared.The results show that the activity efficiency of Ti³⁺self-doped V₂O₅/TiO₂ catalyst in the reaction temperature window is significantly higher than that of undoped vanadium titanium catalyst,and the active window in the low temperature range is effectively widened.The results show that the self doping of Ti³⁺can inhibit the formation of TiO₂ rutile phase and stabilize TiO₂ anatase crystal.The introduction of Ti³⁺resulted in a large number of oxygen vacancies,and the reaction with the oxygen adsorbed on the surface of TiO₂ resulted in the formation of superoxide radicals which promoted the rapid SCR reaction.At the same time,the surface acidity and redox ability of the catalyst are improved,which is helpful to improve the denitrification efficiency of NH₃-SCR reaction.Secondly,the Ti based denitration catalyst with two active components of Ce-V was prepared by impregnation and adding rare earth element Ce on the basis of Ti³⁺self-doped V₂O₅/TiO₂ catalyst.The results show that the introduction of Ce can effectively reduce the vanadium content and maintain high catalytic performance.When 6 wt.%Ce and 0.5 wt.%V are loaded,the overall activity of the catalyst is the best,and the activity efficiency can reach 90.4%at 180℃,which further widens the activity temperature window of the catalyst.The results show that Ce doping can increase the adsorbed oxygen content on the surface of catalyst,regulate the coexistence of multivalent active components and further strengthen the interaction between active components and support,so as to effectively improve the performance of catalyst.In addition,on one hand,the influence of preparation conditions and reaction conditions on the performance of the catalyst was investigated,and the calcination temperature was optimized to achieve the optimal performance of the catalyst;on the other hand,the sulfur resistance and water resistance experiments showed that Ti³⁺self-doping and the introduction of Ce could improve the poisoning resistance of V₂O₅/TiO₂ catalyst.更多还原