氧化锆负载镍基甲烷化催化剂的制备及性能调变

发布时间：2018-02-12 09:13

本文关键词： 镍基催化剂晶相影响二氧化碳甲烷化单层分散　出处：《太原理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：化石燃料的燃烧排放出的大量二氧化碳(CO_2)是导致地球气候变暖的根本原因,由此诱发了一系列的生态环境问题。因此,CO_2捕集及其资源化利用成为一个当今全球性的重要研究课题。CO_2可以作为一种重要的化工原料,用于加氢反应、碳酸酯及尿素等化学品的合成。甲烷(CH_4)作为代用天然气的主要组成成分,在国民生产中占据着十分关键的地位,将CO_2加氢转化为CH_4等能源产品具有重要的意义。因此,CO_2加氢甲烷化反应有很大的发展前景。电制气技术(PtG)通过太阳能或者风能等新能源发电制氢,进而利用CO_2加氢反应合成CH_4,是一个重要的CO_2利用途径。近年来,德国、日本、美国等国已经建成多个PtG示范项目。我国应当大力发展新能源发电技术和CO_2捕获技术,大幅降低PtG技术的工艺成本,有效实现CO_2减排,同时缓解天然气供应不足的问题。本论文首先合成出三种不同晶相的氧化锆(单斜、四方、立方),采用常规浸渍法制备出Ni/ZrO_2催化剂,添加Re和W助剂,考察了各种催化剂样品在CO_2甲烷化反应中的性能,结合表征结果,分析了氧化锆载体晶相结构、添加助剂对催化剂甲烷化反应性能的影响,主要研究内容总结如下:(1)ZrO_2晶相对负载Ni的尺寸有显著的影响,通过谢乐公式计算得到Ni/t-ZrO_2催化剂的Ni的晶粒尺寸最小(16.79 nm);(2)Ni/t-ZrO_2催化剂表面相对较多的碱性位点和氧空缺对CO_2有较强的吸附,进而生成的单齿或双齿碳酸盐更容易分解脱附CO_2;(3)制备出不同负载量(1-9 wt%)的Ni/t-ZrO_2催化剂,发现负载量为7 wt%时催化剂活性最高,此时达到金属镍在t-ZrO_2表面的单层分散阈值(0.388 g/g);(4)添加4 wt%的Re或W后,Ni/t-ZrO_2催化剂的CO_2转化率略有提高,在500°C的反应条件下,CO_2转化率大于80%,CH_4选择性达到85%,添加助剂增加了催化剂表面的氧空缺数量,进而改善了甲烷化反应性能。
[Abstract]:A lot of CO2 emissions from fossil fuel combustion are the root cause of global warming. As a result, a series of ecological and environmental problems have been induced. Therefore, the collection of CO2 and its utilization of resources have become an important research topic in the world today. COS2 can be used as an important chemical raw material for hydrogenation reactions. Synthesis of Carbonate and Urea. Methane CH4) as the main component of alternative natural gas, it plays a key role in national production. It is of great significance to convert CO_2 hydrogenation to CH_4 and other energy products. Therefore, the hydromethanation reaction of CO_2 2 has great development prospects. Electricity gas production technology, PtG, generates hydrogen through new energy sources, such as solar or wind energy. In recent years, many PtG demonstration projects have been built in Germany, Japan, the United States and other countries. China should vigorously develop new energy generation technology and CO_2 capture technology. In this thesis, three kinds of zirconia (monoclinic, tetragonal, monoclinic, tetragonal) have been synthesized. Ni/ZrO_2 catalyst was prepared by conventional impregnation method. Re and W auxiliaries were added to the catalyst. The properties of various catalyst samples in CO_2 methanation reaction were investigated. The crystal phase structure of zirconia carrier was analyzed with the results of characterization. The effect of additives on the methanation reaction performance of the catalyst was studied. The main contents of the study were summarized as follows: the size of Ni loaded on ZrO2 crystal was significantly affected by the addition of additives. By using the Xie Lecong formula, the grain size of Ni in Ni/t-ZrO_2 catalyst is the smallest (16.79 nm). The surface of Ni / t-ZrO _ 2 catalyst has relatively more basic sites and oxygen vacancies on the surface of the catalyst, and there is a strong adsorption of CO_2 on the surface. The monodentate or bicententate carbonate can be easily separated into two groups of Ni/t-ZrO_2 catalysts with different loading amount (1 ~ 9 wt). It is found that the catalyst activity is the highest when the loading amount is 7 wt%. At this time, the monolayer dispersion threshold of nickel on t-ZrO _ 2 surface is 0.388 g / g / g ~ (4)) the CO_2 conversion of Ni / t-ZrO _ 2 catalyst increases slightly after adding 4 wt% re or W, Under the reaction conditions of 500 掳C, the selectivity of COS _ 2 conversion greater than 80% CHS _ 4 reached 85%. The addition of additives increased the number of oxygen vacancies on the surface of the catalyst and improved the methanation reaction performance.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X701;O643.36

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