AlOOH结构及其催化性能的研究

发布时间：2018-02-11 06:05

本文关键词： AlOOH 乙醛分层装填低碳醇水热法　出处：《太原理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：在前期研究中发现本课题组自主创新提出的完全液相法制备的CuZn Al催化剂中Al组分是以一种介稳相Al OOH的形式存在,而不是以常规的γ-Al2O3存在。AlOOH是一类结晶不完整的氧化铝水合物,具有特殊的双层结构。AlOOH具有界面自由能高、孔隙率和比表面积大、分散性好的特点。目前,AlOOH主要用于γ-Al2O3前驱体的制备,作为吸附剂和负载型催化剂载体,以其为催化剂鲜有报道。前期课题组单独制备了AlOOH,将其与工业甲醇合成催化剂C302机械混合用于CO加氢反应,产物中出现选择性较高的C2+OH,但其作用机理尚不明确。为了探究AlOOH的催化作用,本文采用水热法制备了几种不同结构的AlOOH,将其用于甲醇与CO或合成气反应,考察了AlOOH结构对反应性能的影响,推测AlOOH可能的作用机理。以此为基础进一步选用不同方法制备了AlOOH,并将其与C302复合分层装填用于CO加氢反应,考察了不同制备方法对CO加氢反应性能的影响,主要得出以下结论:1.常压下AlOOH用于催化甲醇与CO或合成气反应,AlOOH对CO活化能力极弱而对甲醇脱水能力较强。同时通入甲醇与合成气会影响AlOOH对甲醇的吸附,进而影响其转化率。2.压力对AlOOH催化甲醇与CO或合成气反应产物分布存在显著影响。常压下产物以二甲醚和烃类为主,高压(4 MPa)下以乙醛和二甲醚为主。表征结果表明催化剂结晶度高、具有较大孔径、对CO发生解离吸附且表面具有适宜酸碱性有利于乙醛的生成。3.根据表征和活性评价结果推测乙醛的生成是通过CH3与HCO中间体的偶联完成的,证实AlOOH具有碳链增长作用。4.不同制备方法会显著影响AlOOH的结构及复合催化剂的产物分布。经过水热处理的AlOOH结晶度提高,层状结构完整,表面酸性发生明显改变。活性最好和C2+OH选择性最优的催化剂与其晶形完整、择优取向晶面明显,具有适宜比例的强弱酸位和强弱碱位的协同作用密切相关。5.催化剂的不同装填方式对催化剂性能影响显著,机械混合较分层复合更有利于C2+OH的生成,说明AlOOH与CuZn组分的协同作用对C2+OH的生成存在一定的影响。
[Abstract]:In previous studies, it was found that Al component in the CuZn Al catalyst prepared by the complete liquid phase method proposed by our group was in the form of a metastable Al OOH. Instead of using conventional 纬 -Al2O3, AlOOH is a kind of alumina hydrate with incomplete crystallization. It has special double layer structure. AlOOH has high interface free energy, high porosity and large specific surface area. At present, AlOOH is mainly used in the preparation of 纬 -Al _ 2O _ 3 precursor, which is used as adsorbent and supported catalyst carrier. AlOOH was prepared separately and mechanically mixed with commercial methanol synthesis catalyst C302 for CO hydrogenation. In order to investigate the catalytic action of AlOOH, several AlOHs with different structures were prepared by hydrothermal method, which were used in the reaction of methanol with CO or syngas. The effect of AlOOH structure on the reaction performance was investigated, and the possible mechanism of AlOOH action was speculated. Based on this, AlOOHs were prepared by different methods, and were mixed with C302 for CO hydrogenation. The effects of different preparation methods on the performance of CO hydrogenation were investigated. The main conclusions are as follows: 1. Under atmospheric pressure, AlOOH is used to catalyze the reaction between methanol and CO or syngas. AlOOH has very weak activation ability to CO and strong dehydration ability to methanol. At the same time, adding methanol and syngas will affect the adsorption of AlOOH to methanol. The pressure has a significant effect on the distribution of the products of the reaction between methanol and CO or syngas catalyzed by AlOOH. The main products under atmospheric pressure are dimethyl ether and hydrocarbons. Acetaldehyde and dimethyl ether are the main catalysts at high pressure (4MPa). The characterization results show that the catalyst has high crystallinity and large pore size. The dissociation and adsorption of CO and suitable acidity and alkalinity on the surface are beneficial to the formation of acetaldehyde. According to the results of characterization and activity evaluation, it is inferred that the formation of acetaldehyde is accomplished by the coupling of CH3 and HCO intermediates. It is proved that AlOOH has the function of carbon chain growth. 4. The structure of AlOOH and the product distribution of the composite catalyst can be significantly affected by different preparation methods. The crystallinity of AlOOH after hydrothermal treatment is increased and the layered structure is intact. The surface acidity changed obviously. The catalyst with the best activity and the best selectivity of C 2OH was integrated with its crystal shape, and the preferred orientation crystal plane was obvious. The synergistic effects of strong and weak acid sites and strong weak base sites are closely related to each other. 5. The different loading modes of catalysts have a significant effect on the performance of the catalysts, and mechanical mixing is more favorable to the formation of C 2OH than stratified compounding. The results show that the synergistic effect of AlOOH and CuZn on the formation of C 2OH has a certain effect on the formation of C 2OH.
【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】：O643.36

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