铈钛催化剂的制备及催化臭氧化脱硝性能研究

发布时间：2018-02-27 15:15

本文关键词： 脱硝催化臭氧化 Mn-Ce/TiO_2催化剂 CeTi催化剂羟基自由基　出处：《南京理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：氮氧化物(NO_x)是主要的大气污染物之一,工业炉窑、烧结机、催化裂化装置等中小型锅炉排烟温度偏低,无适合安装选择性催化还原(SCR)脱硝装置的温度区(320～400 ℃)。基于臭氧治理工艺基础上提出的催化臭氧化脱硝技术是一种比较适合的脱硝工艺。为推进这一工艺的工业化进程,本文针对催化臭氧化脱硝技术,对其催化剂进行了制备、改性以及脱硝性能的研究,探究了反应过程机制,并制备了工业级催化剂进行了实际烟气脱硝性能测试以及工艺调试。首先,以Ce作为催化剂的活性成分,通过掺杂一定比例的Mn形成Mn-Ce固溶体然后负载在二氧化钛载体上制备得到了 Mn-Ce/TiO2催化剂作为研究对象,考察了不同合成方法和不同晶相的载体对催化剂催化活性的影响。通过对比发现,锐钛矿和单斜相混合晶相的二氧化钛载体所对应的催化剂具有最高的活性,在40 ℃时脱硝活性可达90%。此外还探究了催化臭氧化脱硝的反应机制,发现在催化臭氧化脱硝反应中,羟基自由基是主要的活性物质,催化剂表面的氧空位有利于表面羟基的生成,臭氧会与表面羟基作用生成羟基自由基而进行脱硝反应。但从催化臭氧化脱硝工业应用来讲,催化剂制备复杂,成功率不高,不利于进行实际工业应用,需要进一步改进。为此,用共沉淀法制备了无定形的CeTi复合氧化物催化剂,并采用非金属氟掺杂对其进行改性。氟掺杂促进了 Ce、Ti之间的相互作用,氟原子取代了晶格中的氧原子,增加了催化剂表面表面氧空位和表面羟基的数量,且使催化剂表面亲水性更强,更容易形成表面羟基,从而提升催化剂脱硝效率。相比较Mn-Ce/TiO2催化剂,CeTi催化剂同样表现出较好的催化活性,而制备过程更简单,适合大批量成型生产,是一种适合催化臭氧化脱硝工业应用的催化剂。按照Ce:Ti = 3:7的摩尔比制备了颗粒状CeTi催化剂,并在烟气管道上加入了臭氧发生器、高压喷头等催化臭氧化脱硝工艺设备。在燃煤锅炉实际烟气条件下对制备的催化剂进行了测试,并对工艺条件进行了一些优化,发现催化臭氧化工艺有一定的脱硝效果,但离实验室效果还是有一定差距,需要在催化剂成型以及工艺条件上进一步优化。在催化剂的制备成型和工艺条件上积累了一定经验,也为开发出更适合催化臭氧化脱硝的工业催化剂打下了基础。
[Abstract]:No _ x (no _ x) is one of the main air pollutants, and the flue gas temperature of small and medium-sized boilers, such as industrial furnaces, sintering machines, catalytic cracking units, etc., is on the low side. The catalytic ozonation denitrification technology based on ozone treatment technology is a more suitable denitrification process. In order to advance the industrialization process of this process, the catalytic ozonation denitrification technology is not suitable for the installation of selective catalytic reduction (SCR) denitrification unit. In this paper, the preparation, modification and denitrification performance of catalytic ozonation denitrification catalyst were studied, and the mechanism of reaction process was explored. The industrial grade catalyst was prepared to test the performance of flue gas denitrification and to adjust the process. Firstly, ce was used as the active component of the catalyst. The Mn-Ce catalyst was prepared by doping a certain proportion of mn to form a Mn-Ce solid solution and then supported on the TIO _ 2 carrier. The effects of different synthesis methods and supports of different crystal phases on the catalytic activity of the catalysts were investigated. It was found that the corresponding TIO _ 2 carriers with anatase and monoclinic mixed crystal phases had the highest catalytic activity. In addition, the mechanism of catalytic ozonation denitrification is investigated. It is found that hydroxyl radical is the main active substance in catalytic ozonation denitrification. The oxygen vacancy on the surface of the catalyst is favorable to the formation of the surface hydroxyl group, and ozone will react with the surface hydroxyl group to form hydroxyl radical for denitrification, but from the industrial application of catalytic ozonation denitration, the preparation of the catalyst is complicated and the success rate is not high. Therefore, amorphous CeTi composite oxide catalysts were prepared by coprecipitation method and modified by nonmetallic fluorine doping. Fluorine atoms replace the oxygen atoms in the lattice, increase the number of oxygen vacancies and surface hydroxyl groups on the surface of the catalyst, and make the surface hydrophilic of the catalyst more hydrophilic, making it easier to form surface hydroxyl groups. Compared with Mn-Ce/TiO2 catalyst, CeTi catalyst also showed better catalytic activity, and the preparation process was simpler and suitable for mass production. Granular CeTi catalyst was prepared according to the molar ratio of Ce:Ti = 3: 7, and the ozone generator was added to the flue gas pipeline. The catalytic ozonation process equipment, such as high pressure nozzle, has been tested and optimized under the actual flue gas condition of coal-fired boiler. It is found that the catalytic ozonation process has certain denitrification effect. However, there is still a certain gap from the laboratory, which requires further optimization in catalyst forming and process conditions. Some experience has been accumulated in the preparation, molding and process conditions of catalysts. It also lays a foundation for the development of a more suitable industrial catalyst for catalytic ozonation denitrification.
【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】：X701;O643.36

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