过渡金属铬、钴氧化物的制备及其催化燃烧性能研究

发布时间：2017-12-27 14:12

本文关键词：过渡金属铬、钴氧化物的制备及其催化燃烧性能研究　出处：《华北电力大学(北京)》2016年硕士论文　论文类型：学位论文

【摘要】：挥发性有机化合物(VOCs)是大气污染的主要源头之一,电厂锅炉燃烧、汽车尾气排放和垃圾焚烧发电等都会产生VOCs,其会对人体健康造成巨大危害,且会促进光化学烟雾的产生,同时也是PM2.5以及雾霾的主要影响因素。通过催化燃烧可以在低温下简单高效的去除VOCs,而且该方法在去除过程中可有效避免NOx和CO等二次污染物的产生。催化剂在催化氧化过程中起着举足轻重的作用,是催化燃烧效率的关键。研究和开发价格低廉、方便易得、催化活性高及热稳定性好的催化剂具有很重要的现实意义。过渡态金属氧化物是对VOCs有很好催化效果的新型催化剂,而传统制备这类催化剂的方法或者需要昂贵的生产成本,或者需要复杂的后处理过程,而得到样品的物相纯度与表面结构难以控制,为此设计搭建脉冲雾化热蒸发化学气相沉积(PSE-CVD)实验台,在成本相对低廉与操作简便易行的前提下,制备厚度和表面形态可控的氧化物薄膜。本文利用PSE-CVD法制备单相纳米氧化铬(Cr203)和氧化亚钴(CoO)薄膜,并利用丙烯(C3H6)的催化燃烧研究其催化性能。通过X射线衍射(XRD)、扫描电镜(SEM)和X射线光电子能谱(XPS)对所得薄膜的物相、表面形态和元素组成等物理化学性质进行了系统的表征。同时,利用原位漫反射红外光谱研究了催化剂薄膜的表面催化过程。结果表明,对于铬氧化物,沉积温度在425℃时,Cr203是形成的唯一物相,所得薄膜为纯净的单相结构,薄膜表面呈现光滑的圆形颗粒且分散均匀。而对于钻氧化物,在350℃的沉积温度下就可得到纯净的CoO薄膜,薄膜表面呈现均匀的块状晶体；在前驱体溶液中加入2.5%去离子水后,SEM结果显示所得薄膜表面晶体出现团聚现象。原位漫反射红外光谱测试的结果表明,这两种催化剂的表面催化反应过程均遵循L-H机理。催化性能测试在镀有催化剂薄膜的不锈钢网上进行。在同样的实验条件下,将C3H6在没有催化剂的空网上的氧化过程作为对比。结果表明Cr203和CoO均对C3H6有很好的催化活性；由加入2.5%去离子水的前驱体溶液制备得到的CoO,催化性能略有下降。另外,以C3H6转化率为50%时对应的反应温度T50作为参考,发现Cr203的催化性能与贵金属和钙钛矿等相似；而CoO可以使C3H6在更低的温度就开始反应并很快转化完全,表现出比Cr203更优越的催化性能。
[Abstract]:Volatile organic compounds (VOCs) is one of the main sources of air pollution, boiler combustion, automobile exhaust emissions and waste incineration power generation will have VOCs, it will cause great harm to human health, and will promote the photochemical smog produced at the same time, the main influence factors and the haze is PM2.5. By catalytic combustion, VOCs can be removed easily and efficiently at low temperature, and this method can effectively avoid the production of two pollutants such as NOx and CO during the process of removal. Catalyst plays an important role in the process of catalytic oxidation, and it is the key to catalyze the combustion efficiency. It is of great practical significance to study and develop a catalyst with low price, easy availability, high catalytic activity and good thermal stability. Transition metal oxide is a new type of catalyst has good catalytic effect on VOCs, while the traditional preparation method of the catalyst or the need for expensive production costs, or require complex postprocessing process, and get the sample material is difficult to control the phase purity and surface structure, building design for the pulse atomization thermal evaporation and chemical vapor deposition (PSE-CVD) experiment, in the premise of relatively low cost and easy operation under the oxide film thickness and surface morphology controllable. In this paper, using PSE-CVD preparation of single phase nanocrystalline chromium oxide (Cr203) and cobaltous oxide (CoO) thin films, and the use of propylene (C3H6) on the catalytic performance of the catalytic combustion. The physical and chemical properties of the films were characterized by X ray diffraction (XRD), scanning electron microscopy (SEM) and X ray photoelectron spectroscopy (XPS). At the same time, the surface catalysis of the catalyst film was studied by in situ diffuse reflectance infrared spectroscopy. The results show that Cr203 is the only phase formed when chromium oxide is deposited at 425 C. The obtained film is pure single-phase structure, and the surface of the film is smooth and round. For drilling oxide, pure CoO thin films can be obtained at the deposition temperature of 350 degrees. The surface of the films shows homogeneous bulk crystals. After adding 2.5% deionized water into the precursor solution, the SEM results show that the surface crystals of the films are agglomerated. The results of in-situ diffuse reflectance infrared spectroscopy (FTIR) showed that the surface catalytic reaction of the two catalysts followed the L-H mechanism. The catalytic performance test was carried out on the stainless steel network coated with the catalyst film. Under the same experimental conditions, the oxidation process of C3H6 on the empty net without catalyst was compared. The results show that both Cr203 and CoO have good catalytic activity to C3H6, and the catalytic performance of CoO obtained by the precursor solution added to 2.5% deionized water decreases slightly. In addition, when the conversion temperature of C3H6 is 50%, the corresponding reaction temperature T50 is used as reference. It is found that the catalytic performance of Cr203 is similar to that of noble metal and perovskite. CoO can make C3H6 start reaction at lower temperature and transform quickly, showing better catalytic performance than Cr203.
【学位授予单位】：华北电力大学(北京)
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O643.36

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