KIT-6负载铜钴氧化物纳米材料及其苯乙烯环氧化催化活性研究

发布时间：2018-07-01 21:34

本文选题：KIT-6 + 介孔材料　；参考：《华南理工大学》2015年硕士论文

【摘要】：环氧苯乙烷是重要的精细化工中间体,工业上通常以苯乙烯为原料制备,该工艺存在能耗高,污染严重等弊端。目前科研界通过苯乙烯催化环氧化制备环氧苯乙烷探索中,负载型金属催化剂长期属于研究热点,而介孔分子筛通常被用作该反应的催化剂载体。作为一种以二氧化硅为骨架的新型立方介孔有序分子筛材料,KIT-6除了比表面积大,孔容孔径均匀规整等常规分子筛优点外,还具备独特的孔道内部连通性,并且孔道系统可根据水热温度适当调控。在上述基础上,本论文选用低温水热合成的KIT-6作为催化剂载体,铜钴氧化物为活性组分,通过浸渍法建立催化剂体系,考察其在叔丁基过氧化氢(TBHP)为氧化剂、反应温度为70 oC时苯乙烯环氧化中的催化性能并借助相关表征手段阐明影响催化剂活性的要素。本文探讨了焙烧温度(550 oC和250 oC)对催化剂活性的影响并分析了其原因。结果表明,铜物种是催化剂活性主要来源,而单独的钴物种活性较差。同时,550 oC焙烧的催化剂较250 oC具有更优越的性能。综合XRD、N2吸脱附、TEM、Raman光谱、XPS、AAS表征手段结果,揭示了在比表面积、孔道结构、金属含量等物理结构基本类似的情况下,较高温度焙烧的催化剂因Cu(II)进入Co3O4晶格从而提高了催化剂的性能,这也表明电子结构(electron structure)是影响该催化剂在反应中活性的主导因素。本文还考察了去除KIT-6的催化剂以及以MCM-41和SBA-15为载体的铜钴氧化物催化剂在苯乙烯环氧化中的催化性能。结果表明,催化剂在失去载体KIT-6支撑或者更换另两种载体后,活性急剧下降。借助上述表征方法则进一步确定了KIT-6有利于催化剂维持有序结构和金属氧化物均匀分散,因而保障其较高的催化活性。该结果证明了催化剂质构特性(textural properties)是影响其催化活性的重要因素。本文也优化了氧化剂TBHP用量、反应时间等反应条件。研究表明,在其他条件不变情况下,氧化剂用量或者反应时间的延长均可以提高苯乙烯转化率,但是目标产物环氧苯乙烷的选择性则呈下降趋势。反应最佳条件为反应物苯乙烯:TBHP物质的量比例为1:1,反应时间为8 h,可达53.8%的苯乙烯转化率和82.6%的环氧苯乙烷选择性。此外,本文还初步推测了反应机理。
[Abstract]:Epoxy-phenylene ethane is an important fine chemical intermediate, which is usually prepared from styrene in industry. This process has many disadvantages such as high energy consumption, serious pollution and so on. At present, supported metal catalysts have long been a hot topic in the research of epoxidation of epoxy-phenylethane from styrene, and mesoporous molecular sieve is usually used as catalyst carrier for this reaction. As a new ordered cubic mesoporous molecular sieve material with silica framework, KIT-6 has many advantages, such as large specific surface area, uniform pore volume and uniform pore size. And the pore system can be adjusted according to the hydrothermal temperature. On the basis of the above, KIT-6, synthesized by hydrothermal synthesis at low temperature, was used as the catalyst carrier and CuCo oxide as the active component. The catalyst system was established by impregnation method, and the catalyst system was investigated in the presence of tertiary Ding Ji hydrogen peroxide (TBHP) as oxidant. The catalytic properties of styrene epoxidation at 70 OC and the factors affecting the activity of the catalyst were elucidated by means of related characterization. The effect of calcination temperature (550 OC and 250 OC) on the activity of the catalyst was studied and the reasons were analyzed. The results showed that copper species were the main source of catalyst activity, while cobalt species had poor activity. At the same time, the catalyst calcined at 550oC has better performance than that of 250oC. By synthesizing the results of the Raman spectra of XRD- N _ 2 desorption and desorption, and the results of XPS-AAS characterization, it is found that the physical structures of XRDX N _ 2 adsorption and desorption have similar physical structures, such as specific surface area, pore structure, metal content, and so on. Due to Cu (II) entering the lattice of Co _ 3O _ 4, the catalyst calcined at a higher temperature improves the catalyst performance, which indicates that the electronic structure of (electron structure) is the dominant factor affecting the activity of the catalyst in the reaction. The catalytic properties of KIT-6 removal catalyst and copper-cobalt oxide catalysts supported on MCM-41 and SBA-15 in styrene epoxidation were also investigated. The results showed that the activity of the catalyst decreased sharply after losing the support of KIT-6 or replacing the other two kinds of support. With the help of the above characterization methods, it was further confirmed that KIT-6 was conducive to the maintenance of the ordered structure of the catalyst and the uniform dispersion of the metal oxides, thus ensuring its higher catalytic activity. The results show that (textural properties) is an important factor affecting the catalytic activity. The reaction conditions such as the amount of oxidant TBHP and the reaction time were also optimized. The results show that the conversion of styrene can be increased by the addition of oxidant or the prolongation of reaction time under the same conditions, but the selectivity of the target product epoxy-phenylethane is decreasing. The optimum reaction conditions are as follows: the molar ratio of styrene to TBHP is 1: 1, the reaction time is 8 h, the conversion of styrene is 53.8% and the selectivity of epoxy-phenylethane is 82.6%. In addition, the reaction mechanism was preliminarily speculated.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1;O621.251

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