多级孔Ti-MCM-41的制备及其催化氧化性能的研究

发布时间：2017-12-28 05:00

本文关键词：多级孔Ti-MCM-41的制备及其催化氧化性能的研究　出处：《哈尔滨工业大学》2016年硕士论文　论文类型：学位论文

【摘要】：环氧化反应在工业上具有极其重要的地位,介孔Ti-MCM-41材料由于在催化环氧化合物方面有良好的催化性能,引起研究者们的普遍关注。虽然介孔Ti-MCM-41具有很高的比表面积,但由于其介孔内部存在扩散阻力,在催化大分子类有机化合物时,由于扩散限制,无法接近催化剂内部的活性位点,大大降低了材料的催化活性。在介孔材料内部引入更大介孔或大孔孔道能有效解决这一问题,在保证材料具有较高比表面积的同时提升反应物与催化剂内部活性位点的接触几率,增强催化剂的催化性能。因此,本文以粒径在300 nm左右的聚苯乙烯微球为模板,制备具有介孔-大孔分级结构的多级孔Ti-MCM-41,研究不同实验条件对多级孔材料形貌及其性能的影响,同时探究了材料在催化环氧化反应中的特性。利用乳液聚合法制备了单分散的聚苯乙烯微球(PS),并以其为牺牲硬模板,十六烷基三甲基溴化铵(CTAB)为表面活性剂,硅源为正硅酸四乙酯(TEOS),钛源为钛酸四丁酯,先后使用水热法和溶剂挥发诱导自组装法探索制备的条件,最终运用溶剂挥发诱导自组装法成功制备出多级孔Ti-MCM-41材料。确定了最佳的硅钛比为40:1,表面活性剂的加入量是n(CTAB):n(TEOS)=2:10。XRD、UV-Vis和氮气吸附脱附等表征结果表明,材料内部具有十分有序的介孔结构,介孔孔道大小为2.23 nm,比表面积为1281.6 m2/g,孔容大小为0.59 cm3/g,钛物种已进入材料内部并且为四配位结构。运用扫描电镜和透射电镜等测试手段进一步证明材料内部存在规则排列的大孔结构,大孔的孔壁间分布高有序性的介孔孔道。分别以环己烯、环十二烷基三烯、顺-环辛烯以及环十二烯等大环烯烃为反应底物,研究多级孔Ti-MCM-41相对于介孔Ti-MCM-41在催化大分子环氧化反应的性能,多级孔Ti-MCM-41作为催化剂的上述反应均表现出较高的转化率和TOF值。说明引入大孔二级孔道,能够有效地减小大环烯烃的传输阻力,提高活性位点的可接近性,提升催化活性和利用率。同时研究了催化剂循环使用4次的重复利用性和Ti物种流失的leaching实验等催化剂重要性能。实验证明多级孔Ti-MCM-41具有极好的催化稳定性和重复利用性,Ti物种在材料内部十分稳定,极少流失。
[Abstract]:Epoxidation is of great importance in industry. Mesoporous Ti-MCM-41 materials have attracted widespread attention due to their good catalytic performance in the catalytic epoxides. Although mesoporous Ti-MCM-41 has a high specific surface area, due to the existence of diffusion resistance in mesopores, when it catalyzes macromolecular organic compounds, it can not get close to the active sites within the catalyst due to the diffusion limitation, which greatly reduces the catalytic activity of the materials. The introduction of larger mesoporous or macroporous channels in mesoporous materials can effectively solve this problem, while ensuring the high specific surface area of materials, while enhancing the contact probability between reactants and internal active sites of catalysts, and enhancing the catalytic performance of catalysts. Therefore, based on the particle size of polystyrene microspheres was about 300 nm as template, the preparation of hierarchical porous Ti-MCM-41 mesopore macropore structure, study the different effect of experimental conditions on the morphology and properties of hierarchical porous materials, and explores the characteristics of ring material in oxidation reaction in catalysis. Polymerization preparation of monodisperse polystyrene microspheres by emulsion (PS), and the expense of the hard template, sixteen alkyl three methyl bromide (CTAB) as surfactant, four ethyl orthosilicate as silicon source (TEOS), titanium source is four butyl titanate, successively using hydrothermal method and solvent evaporation induced self-assembly method to explore the preparation conditions, the ultimate use of solvent prepared hierarchical porous Ti-MCM-41 material induced self-assembly method successfully. The optimum silicon and titanium ratio is 40:1, and the amount of surfactant is n (CTAB): n (TEOS) =2:10. The characterization results of XRD, UV-Vis and nitrogen adsorption desorption showed that the material had a very ordered mesoporous structure, the mesoporous pore size was 2.23 nm, the specific surface area was 1281.6 m2/g, the pore volume was 0.59 cm3/g, and the titanium species had entered the four internal coordination structure. Scanning electron microscopy and transmission electron microscopy are used to further prove that there are regularly ordered macroporous structures in the materials, and the ordered mesopores are distributed between the macropores. With cyclohexene ring, twelve alkyl three limonene, CIS cyclooctene and ring twelve vinyl macrocyclic olefin as the substrate of multi hole Ti-MCM-41 relative to the performance of the mesoporous Ti-MCM-41 in catalytic epoxidation of macromolecules, Ti-MCM-41 as the hierarchical porous catalyst showed a higher conversion rate and TOF value. It is indicated that the introduction of large hole two channel can effectively reduce the transmission resistance of macrocyclic olefins, improve the accessibility of the active site, and improve the catalytic activity and utilization. At the same time, the important properties of the catalyst, such as 4 repeated utilization of the catalyst and the leaching experiment of Ti species loss, were also studied. The experimental results show that the multilevel hole Ti-MCM-41 has excellent catalytic stability and reutilization, and the Ti species are very stable within the material and are rarely lost.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O643.36

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