【作者】 刘海燕；

【导师】 孙继红；

【作者基本信息】 北京工业大学 ， 应用化学， 2008， 硕士

【摘要】 离子液体作为新兴的绿色溶剂成为有机合成、分离分析及功能材料等领域的研究热点之一,但成本较高、用量大、催化剂不易分离等缺点限制了其广泛应用。目前人们提出的解决方法之一就是将离子液体负载在无机多孔材料或者有机高分子材料上,然后把催化剂再溶解在固载化后的离子液体中,制得多相催化剂,从而把离子液体的特性转移到多相固体催化剂上。目前固载型离子液体用于催化反应主要集中在两方面,一是将酸性离子液体固定,用作反应的酸性催化剂;另一方面是将离子液体作为过渡金属催化剂载体再固定于有机或无机介质中进行催化研究。双模型孔道介孔分子筛(BMMs)是孔道尺寸可以在2nm~20nm范围内得到有效调控的新型材料,其孔道内表面均带有丰富的羟基,与单一孔道的介孔分子筛相比,双孔结构有助于大分子在孔道内的扩散,减少反应物和产物的堆积,从而提高反应效率,为负载型离子液体催化剂根据具体要求进行分子设计和结构“剪裁”提供了可能。本论文以双模型介孔分子筛(BMMs)作为载体,将锇金属催化剂与离子液体结合,利用离子液体的高沸点、低蒸汽压等特点,力图实现一种金属催化剂与离子液体所构成的均相催化体系“高分散”装载于介孔材料中的制备过程,并选用较全面的结构表征方法(如XRD、TEM、FT-IR、TG-DTA等)研究离子液体在介孔分子筛孔道内的微环境以及两者间的相互影响规律,同时将固载型离子液体用于不对称双羟基化反应以考察其催化活性。在保持金属络合物-离子液体体系的活性和选择性的同时又具有担载催化剂的活性组分高度分散、用量少、易与产物分离的优点,这就在实现均相催化剂多相化而保持均相催化特点的同时,又降低了离子液体的用量,形成一种与以往“均相催化多相化”催化剂不同的催化剂体系。本论文的主要工作有:1.功能化介孔分子筛固载离子液体制备了双模型介孔分子筛(BMMs)并通过3-氨丙基三乙氧基硅烷改性后引入-NH2基团,利用氨基与离子液体阳离子的配位作用将离子液体[2AlCl3/Et3NHCl]和一系列咪唑类离子液体固载到BMMs上,同时研究了不同负载时间和负载浓度对分子筛结构的影响。通过XRD、BET及TEM等分析表征证明BMMs具有双模型介孔特征分布,两种孔分布分别是最大孔23.6nm、小孔2.9nm,比表面积为959m2/g,孔体积为2.0cm3/g。改性并负载离子液体后没有改变BMMs的典型孔道结构,且随着离子液体浓度的增加使得分子筛的结构有序性下降。FT-IR分析测试中1560 cm-1处的振动峰表明-NH2成功锚固在BMMs表面,C-N键特征吸收在944cm-1和1083cm-1的出现也说明离子液体[2AlCl3/Et3NHCl]在与氨丙基修饰的分子筛组装时与氨基发生配位作用从而成功地固载到分子筛表面。TG分析测试中330℃~650℃之间一系列弱的失重速率峰,对应于分子筛表面-NH2基团和离子液体在空气中的氧化分解,对应失重10%左右。离子液体固载于改性后BMMs在不对称双羟基化(AD)反应中由于分子筛改性引入的氨基与锇催化剂的配位作用使其失去活性。2.嫁接法固载离子液体制备了阳离子上含有-Si(OMe)3基团的离子液体,并通过分子筛表面羟基与-Si(OMe)3硅氧基团的缩聚反应将离子液体阳离子基团键连到介孔分子筛BMMs表面。XRD分析测试表明,在105℃下负载12h后BMMs孔道结构的有序性大大降低。FT-IR表征结果中在1576cm-1、1460cm-1处出现的峰为咪唑环骨架振动的特征峰,证明了离子液体在分子筛上的存在。在AD反应中当锇催化剂投入量降到0.1%mmol时仍能达到57%的产率和99%的e.e值。3.溶胶-凝胶法固载离子液体通过溶胶-凝胶法在模板剂作用下,以含有-Si(OMe)3基团的离子液体与正硅酸乙酯(TEOS)的混合物作为硅源前驱体一步共聚合成介孔材料,使离子液体有机官能团存在于介孔材料骨架中。XRD结果表明,当离子液体引入量从10%逐渐降低到2%时,所得样品的(100)衍射峰逐渐明显并增强,说明所得介孔材料的结构有序度渐强。TEM分析可看到固载型离子液体材料焙烧(550℃)所得样品孔径约为2.3nm,萃取所得样品孔径约为1.7nm且与焙烧样品相比孔道更为发达。TG分析测试中420℃~440℃范围内的样品失重(~8%)对应于咪唑盐离子液体的热分解。FT-IR分析测试中3000cm-1~2700cm-1及1600cm-1~1400cm-1波数范围内的谱带被认为是饱和的C-H伸缩振动和芳环骨架振动,说明离子液体的存在,这些峰只在萃取样品中出现,可见键连的离子液体的结构在焙烧过程中被破坏。该类材料在AD反应中可达到87%的产率和96%的e.e值,用于循环使用时可重复利用4次以上。更多还原

【Abstract】 Ionic liquids (ILs) have received much attention in many areas of organic synthesis, segregation analysis and functional materials due to their potential as a“green solvents”. However, they are limited to be widely used in different fields because of high price, large dosage, inconvenient separation and purification of catalyst. One of the effective approaches to solve these problems is to immobilize the ionic liquid on a solid support, in order to transfer the desired catalytic properties of the liquids to a solid catalyst. Currently supported-ionic liquid used in catalytic reaction mainly are concentrated on two areas. Firstly, the acidic ionic liquids are immobilized and used as acid catalytic reaction. Secondly, ionic liquids as supports for transition metal catalyst and further fixed in the medium of organic or inorganic are researched in the study of catalysis.The bimodal mesoporous materials (BMMs) is a new kind of mesoporous materials with a controlled pore structure in the range of 2nm~20nm. There are abundant -OH groups on the surface of BMMs channels. Compared with the single channel of mesoporous sieve, bimodal structure of BMMs is beneficial for large molecular to diffuse inside, and helps to reduce the accumulation of reactant and production in order to improve the reaction efficiency. In this dissertation, preparation and characteristization of BMMs as support and therefore the supported metal catalysis-ionic liquid catalysts were studied by use of XRD, FT-IR, SEM, TEM, and TG-DTA techniques. As a result, it is shown that catalytic behavoiuor of catalysts above for asymmetric dihydroxylation is of high activity and good recycle properties.The main contents of this dissertation are as following:1. Immobilization of IL on functionalized BMMsThe BMMs was synthesized and modified by (3-aminopropyl)triethoxysilane (APTES) solution to improve its loading capability. Then, the [2AlCl3/Et3NHCl] and a series of N, N’- dialkylimidazolium-based ionic liquids were grafted onto the inner surface of BMMs through an aminosilane linker, and the effects of concentration and time of reaction on the structure of BMMs were investigated. The characterizations of XRD、BET and TEM analysis methods indicated that BMMs have bimodal mesoporous with the larger pore of 23.6nm, the smaller pore of 2.9nm, the specific surface area of 959m2/g and pore volume of 2.0cm3/g. The typical channel structure was maintained after modified by APTES and loaded by ionic liquid. However, the order degree of (100) peak for BMMs would be decreased with the increased concentration of ionic liquid. On the basis of FT-IR spectra, a new band at 1560 cm-1 indicated that the functional groups -NH2 was grafted onto inner surface of BMMs. And after loading IL, the bands appearing at 944cm-1 and 1083cm-1 suggested that the IL has been assembled into the modified BMMs via the coordination between -NH2 and [2AlCl3/Et3NHCl]. The results of TG-DTA curves revealed that the weight loss (~10%) during the temperature from 330℃to 650℃can be attributed to the oxidative decomposition of -NH2 and ionic liquid. Meanwhile, when the supported ionic liquid is used in asymmetric dihydroxylation reaction, there was no catalystic activity of osmium catalyst.2. Immobilization of IL by grafting methodThe 1-methyl-3-[3-(trimethoxysiyl)propyl]imidazolium chloride, which contains the cation of the ionic liquid, was prepared and grafted on the surface of the BMMs. The XRD patterns indicated that the mesoporous order degree of ionic liquid hybrid supported by BMMs would be decreased greatly when grafted with above ionic liquid at 105℃for 12h. FT-IR spectrum showed that the peaks located at 1576cm-1 and 1460cm-1 were assigned to the framework vibration feature of imidazole ring. In asymmetric dihydroxylation reaction, the activity of catalysis revealed yield of 57% and e.e of 99% even when the amount of Os catalyst decreased to 0.1%mmol.3. Immobilization of IL by sol-gel methodBy using mixture containing 1-methyl-3-[3-(trimethoxysiyl)propyl]imidazolium chloride and TEOS as silicon source, the mesoporous hybrids were prepared via template mechanism and sol-gel route. According to XRD patterns, the intensity of (100) peak of above the mesoporous hybrids increased with the amount of ionic liquid decreased. TEM images showed the mesoporous structure with the mean pore size of around 2.3nm after calcinations and 1.7nm after extraction. Meanwhile, TG-DTA results suggested that the weight loss (~8%) during the period temperature from 420℃to 440℃was corresponding to the oxidative decomposition of imidazolium ionic liquid. FT-IR spectrum showed that the new bands at 3000cm-1~2700cm-1 and 1600cm-1~1400cm-1 were assigned to the C-H telescopic vibration and the framework vibration feature of imidazole ring, besides the characteristic bands of BMMs appeared in all samples, however, all of characteristic bands for imidazolium ionic liquid disappeared in the samples when calcined at 550oC, which implied that the structure of imidazolium ionic liquid has been destroyed during calcinations. In asymmetric dihydroxylation, the activity of above hybrids revealed higher yield of 87% and e.e of 96%, whereas the catalyst can be reused over four times.更多还原