【作者】 赵海红；

【导师】 银董红；

【作者基本信息】 湖南师范大学 ， 有机化学， 2010， 博士

【摘要】 功能化离子液体以其优异的热力学稳定性、良好的溶解性以及阴、阳离子结构可设计性,作为溶剂和催化剂在精细化工和催化反应中显示出诱人的应用前景。针对均相催化反应中离子液体用量大且催化剂不易分离的缺点,本文利用介孔硅基材料具有可调节的纳米孔道和高比表面积等优点,将新型功能化离子液体结构引入介孔硅基材料孔道或骨架内,构建具有特殊结构和功能的催化活性中心,制备了一系列功能化离子液体杂化的新型介孔硅基材料。该类功能化离子液体杂化介孔硅基材料既保留了均相离子液体催化活性高的优点,又具有多相催化剂便于分离和可重复使用的特点。采用后嫁接法,将氯铁酸离子液体通过咪唑阳离子嫁接到MCM-41型介孔材料孔道表面,制备了Lewis酸离子液体杂化介孔硅基材料。采用XRD、N2吸附-脱附、FT-IR和TG-DTG等表征手段对其结构进行了确证。结果表明,Lewis酸性离子液体已成功嫁接于材料孔道表面,且未影响载体的孔道特征。在Friedel-Crafts(傅-克)烷基化反应中,该负载型氯铁酸离子液体表现出较均相氯铁酸离子液体更高的催化效率,催化剂用量仅为氯铁酸离子液体用量的1／50,且可简单分离并有效重复使用10次以上。此外,与MCM-41孔道内直接负载的FeCl3催化剂相比,重复使用性更好。设计并合成了含桥键型结构的咪唑离子液体硅氧烷前驱体,将其与正硅酸乙酯(TEOS)共水解-缩聚,制备了骨架中含离子液体结构的桥键嵌入型杂化SBA-15型介孔材料,加入氯化铟进行阴离子交换,制备了含氯铟酸离子液体结构单元的杂化介孔硅基材料。采用XRD、TEM、FT-IR、NMR、N2吸附-脱附等表征手段对其结构进行了确证。在Friedel-Crafts烷基化反应中,所得催化剂表现出优异的催化活性,且可简单分离并有效重复使用6次以上。与直接负载于纯硅介孔材料孔道内的InCl3催化剂相比,此固载型氯铟酸离子液体在重复使用过程中表现出更高的选择性,且In流失程度更低。此外,该催化剂对水不敏感,反应无需严格控制在无水条件下进行,具有较强的工业化应用价值。设计并合成了含胺基功能化碱性离子液体的有机硅氧烷前驱体,通过溶胶-凝胶法或后嫁接法,制备了三种碱性离子液体杂化介孔硅基材料。在以水为介质的Knoevenagel(克脑文盖尔)反应中,三种材料均表现出较相应均相离子液体催化剂更高的催化活性。其中,后嫁接法制备的材料催化性能更好,特别是采用后嫁接法以SBA-15型介孔材料为载体制备的催化剂具有高效催化和有效重复的特点。此外,与胺基功能化的杂化介孔硅基材料相比,该碱性离子液体杂化介孔硅基材料具有更高的重复使用性能。将咪唑离子液体嫁接到硅基SBA-15型介孔材料的孔道表面,用六甲基二硅氮烷气相屏蔽剩余硅羟基,再与磷钨酸进行阴离子交换,制备了磷钨酸离子液体杂化硅基SBA-15型介孔材料。离子液体的咪唑阳离子对金属中心的弱配位性及离子液体的极性均有利于稳定催化反应中间体,提高了催化剂的催化活性及稳定性。在以水为溶剂,双氧水(30%)为氧化剂的苯甲醇氧化反应中,该催化剂表现出较SBA-15直接负载磷钨酸催化剂更好的催化性能。在最佳反应条件下,苯甲醇转化率和苯甲醛选择性分别达97%和96%。由于硅羟基被屏蔽,磷钨酸仅以阴离子交换模式与离子液体单元作用,因此,催化剂表现出了较好的重复使用性能,在重复使用7次后,催化活性没有明显下降。更多还原

【Abstract】 Ionic liquids with task-specific functionality have showed fascinating prospects in fine chemical and catalysis fields due to their unprecedented properties, such as high chemical and thermal stability, favorable solubility, tunable physical and chemical properties by the choice of organic cation and/or inorganic anion etc. However, such homogeneous species possess a number of inherent shortcomings, including high price, large consumption, and difficulties in separation and/or recovery. In order to overcome the above-mentioned problems, attempts have been, in this dissertation, made to combine mesoporous silicas having tunable nano-channel and rather high surface area with ionic liquids of task-specific functionality, aiming to fabricate the task-specific active sites on pore surface and/or in framework of mesostructure. As such, a series of novel mesoporous silica-supported functionalized ionic liquids were designed and prepared. The resultant immobilized functionalized ionic liquids not only remain high catalytic activity often observed for homogeneous functionalized ionic liquids, but also possess facility of separation. In relative reactions, such catalysts showed superior catalytic activities and reusabilities.Chloroferrate ionic liquid was grafted onto pore surface of MCM-41 via imidazolium cation by using a post-synthesis procedure. The obtained materials were well characterized by means of XRD, N2 adsorption-desorption, FT-IR, and TG-DTG. It was found that chloroferrate ionic liquid has been incorporated onto the support intactly and that the support remains its structural integrity during the grafting process. In comparison with pure chloroferrate ionic liquid, the immobilized ionic liquid showed much higher catalytic efficiency and more excellent reusability in Friedel-Crafts benzylation reactions. The consumption of ionic liquid in the immobilized chloroferrate ionic liquid was much lower than the pure ionic liquid (ca.1/50) and the solid catalyst could be reused for 10 times without significant loss of catalytic activity. Also, the immobilized chloroferrate ionic liquid possessed better reusability than siliceous MCM-41-supported FeCl3.An organic bridged silsesquioxane precursor containing ionic liquid unit was synthesized and successively co-condensed with tetraethyl orthosilicate, leading to a periodic mesoporous organosilica (PMO) material of SBA-15 incorporating ionic liquid moieties. The combination of the resultant PMO material with InCl3 gave rise to a immobilized Lewis acidic chloroindate(III) ionic liquid catalyst. The obtained materials were well characterized by means of XRD, N2 adsorption-desorption, TEM, FT-IR, and NMR. The immobilized chloroindate(III) ionic liquid showed rather good catalytic performance in the Friedel-Crafts reaction between benzene and benzyl chloride and could be reused at least for 6 times. In comparison with siliceous SBA-15-supported InCl3, the immobilized ionic liquid revealed higher selectivity and lower leaching of active species during the reuse process. It should be noted that such immobilized chloroindate(Ⅲ) ionic liquids had low moisture sensitivity, showing the great potential for practical applications.Three organic-inorganic hybrid mesoporous silicas incorporated with NH2-functionalized ionic liquid moieties were prepared via either post-synthesis or sol-gel procedure by using a synthesized organotrialkoxysilane as organosilane source. The obtained immobilized ionic liquids showed higher catalytic efficiency than their homogeneous counterpart in Knoevenagel condensations with water as solvent. Among them, the catalysts prepared by post-synthesis procedure, particularly that using siliceous SBA-15 as support, revealed better catalytic performance than that prepared by sol-gel procedure. Moreover, in comparison with NH2-functionalized mesoporous silicas, the immobilized ionic liquids possessed much better reusability, for example, the catalyst using siliceous SBA-15 as support could be reused for 10 times without significant loss of catalytic activity.Imidazolium-based ionic liquid was grafted onto pore surface of siliceous SBA-15. Then, the silanols presented in the organic-inorganic hybrid mesoporous silica were eliminated by reacting with 1,1,1,3,3,3-hexamethyldisilazane. The combination of the material so-obtained with phosphotungstic acid led to a series of immobilized phosphotungstic acid ionic liquids. It was found that weak complexation between the imidazolium cations and meter centre of phosphotungstic acid and polarity of the ionic liquid moieties are conducive to stabilizing reaction inter-mediate. As such, the immobilized phosphotungstic acid ionic liquids showed higher catalytic performance than siliceous SBA-15-supported phosphotungstic acid did in the oxidation of benzyl alcohol with water as media in the presence of 30% H2O2. Under optimum conditions, the conversion of benzyl alcohol and the selectivity to benzaldehyde were as high as 97% and 96%, respectively. The elimination of silanols forced phosphotungstic acid to interact with the ionic liquid moieties incorporated in the mesostructure exclusively, therefore, the immobilized phosphotungstic acid ionic liquid showed good reusability. Indeed, the optimum catalyst could be reused for 7 times without significant loss of catalytic activity.更多还原