铁基和锰基尖晶石催化剂的制备及其催化臭氧化脱硝性能的研究

发布时间：2018-01-01 05:42

本文关键词：铁基和锰基尖晶石催化剂的制备及其催化臭氧化脱硝性能的研究　出处：《南京理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：近年来,我国大气污染形势进一步恶化,氮氧化物(NOx)的排放是其形成的原因之一。工业炉窑、烧结机、催化裂化装置等排烟温度偏低,无适合安装选择性催化还原(SCR)脱硝装置的温度区。催化臭氧化作为高级氧化技术的一种用于低温脱硝不断的受到研究人员的重视。研究表明,多数的催化臭氧化过程遵循自由基机理,.OH主导催化脱硝活性。本实验以探讨表面羟基和氧空位对·OH的促进作用,及进一步提高尖晶石催化剂的低温脱硝活性为目的,提出制备尖晶石型催化剂以及采用CO预处理催化剂的思路,并对其进行脱硝活性评价和反应过程分析。首先使用催化剂的活性评价装置对CuO、Fe_2O_3金属氧化物以及CuFe_2O_4尖晶石催化剂的活性进行测试,结果表明,CuFe_2O_4催化剂脱硝活性较之前两者有了明显提高。结合一系列现代分析测试手段对催化剂进行系统研究,分析XPS得出尖晶石催化剂易变价使得氧空位容易被引进晶格中,结合热重(TG)等数据发现尖晶石拥有更多的表面羟基,证明氧空位和表面羟基两者的协同作用使得臭氧更高效快速降解为·OH,进而增强了脱硝活性。对催化剂进行长时间稳定性测试,发现CuFe_2O_4活性有了一定的降低,这对催化剂的实际应用是不利的,需要针对催化剂进行进一步的开发和研究。基于CuFe_2O_4催化剂的研究结果,又以进一步提高尖晶石催化剂的低温脱硝活性为目的,采用水热法制备了 CoMn_2O_4催化剂以及CO气氛下煅烧的CoMn_2O_4,并对催化剂进行脱硝活性评价。研究结果表明,CoMn_2O_4催化剂具有较好的低温脱硝活性,而CO预处理后的CoMn_2O_4催化脱硝活性有了进一步提升,高达85%的脱硝效率。利用一系列分析测试手段对催化剂进行分析测试。PL和XPS结果表明,CO预处理使得CoMn_2O_4催化剂的氧空位增多,由于还原气氛的影响,Co、Mn的价态发生改变促进了化学吸附氧的产生,并且诱导了氧空位的产生,进而增强了催化剂的催化能力。同时又对CoMn_2O_4催化剂反应前后进行表征,得出CoMn_2O_4催化剂反应前后物化性质保持稳定,这得益于催化剂放置于旁路烟道,表现出巨大的工业应用潜力。
[Abstract]:In recent years, the situation of air pollution in China has deteriorated further, and the emission of no _ x is one of the reasons for its formation. The exhaust gas temperature of industrial furnace, sintering machine, catalytic cracking unit and so on is low. There is no suitable temperature range for selective catalytic reduction (SCR) denitrification unit. As an advanced oxidation technology, catalytic ozonation has been paid more and more attention to at low temperature denitrification. Most of the catalytic ozonation processes follow the free radical mechanism. OH dominates the catalytic denitrification activity. This experiment was designed to investigate the effect of surface hydroxyl and oxygen vacancy on 路OH. In order to improve the denitrification activity of spinel catalyst at low temperature, the idea of preparing spinel catalyst and using CO pretreatment catalyst was put forward. The denitrification activity was evaluated and the reaction process was analyzed. Firstly, the CuO was evaluated by using the catalyst activity evaluation device. The activity of Fe_2O_3 metal oxide and CuFe_2O_4 spinel catalyst was tested. The denitrification activity of CuFe_2O_4 catalyst is obviously higher than that of the former two catalysts. A series of modern analytical and testing methods are used to study the catalyst systematically. The analysis of XPS shows that the spinel catalyst is easy to be introduced into the lattice because of the variable value of the catalyst, and it is found that the spinel has more surface hydroxyl groups in combination with the thermogravimetric data. It was proved that the synergistic action of oxygen vacancy and surface hydroxyl group resulted in the more efficient and rapid degradation of ozone to 路OH, which enhanced the denitrification activity and tested the stability of the catalyst for a long time. It was found that the activity of CuFe_2O_4 decreased to a certain extent, which was unfavorable to the practical application of the catalyst. Based on the research results of CuFe_2O_4 catalyst, the purpose of this study is to further improve the low-temperature denitrification activity of spinel catalyst. CoMn_2O_4 catalyst and CoMnman _ 2O _ 4 calcined in CO atmosphere were prepared by hydrothermal method. The denitrification activity of the catalyst was evaluated. CoMn_2O_4 catalyst has better denitrification activity at low temperature, while the CoMn_2O_4 catalyst after CO pretreatment has further enhanced its denitrification activity. A series of analytical methods were used to analyze and test the catalyst. PL and XPS showed that CO pretreatment increased the oxygen vacancy of CoMn_2O_4 catalyst. Because of the influence of reducing atmosphere, the change of valence state of CoCon mn promotes the generation of chemisorbed oxygen and induces the generation of oxygen vacancy. At the same time, the catalytic properties of CoMn_2O_4 catalyst were characterized before and after the reaction. It was concluded that the physicochemical properties of CoMn_2O_4 catalyst remained stable before and after the reaction. This is due to the fact that the catalyst is placed in the bypass flue, showing great potential for industrial application.
【学位授予单位】：南京理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;X701

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