聚合物负载过渡金属纳米体系的制备及其在催化中的应用研究

发布时间：2018-06-08 06:43

本文选题：高分子材料 + 镍　；参考：《宁波大学》2015年硕士论文

【摘要】：近年来,氢气已经成为了一种理想的能源,与传统的石化燃料相比,氢能源零碳排放、高热值的特性越来越受到人们的关注。固体储氢材料硼氢化钠与二甲氨基甲硼烷具有较高的质量储氢密度,常温下性质稳定、无毒,成本比氨硼烷低,并且水解产生的副产物偏硼酸盐又能回收利用,是未来固体储氢材料发展的方向。高分子凝胶材料在催化领域正高速发展。水凝胶是含有亲水性基团(-SO3H、-OH、-COOH、-NH2)的交联网络的亲水性高分子材料,具有很大的负载空间,其官能团能螯合或固定金属颗粒,使其免于凝聚、失活,具有良好的化学稳定性。水凝胶同时兼有固体和流体的性质,其交联的结构内部富含水或有机溶剂,既适合金属离子在内部均匀分散,也适合成为水溶液和非水溶液中的化学反应的场所。本工作分别以疏水性聚叔丁基丙烯酰胺纳米球和亲水的三元共聚物纳米凝胶为载体,先通过浸渍法在载体上引入少许的镍金属种子,然后通过化学镀镍法,在种子载体上镀上大量镍,制备出各种聚合物纳米球负载镍催化剂。纳米凝胶-Ni在水中能吸水膨胀,粒径从真空中的225 nm膨胀到水中的411.9 nm。相反,疏水性的聚叔丁基丙烯酰胺在水中不会吸水膨胀。由HRTEM与XPS表征可知,聚合物纳米球载镍上的镍主要以Ni O的形式存在。本工作还制备了聚丙烯酰胺水凝胶负载钯镍合金,并且发现钯镍比例会影响纳米合金的粒径。水凝胶的网格尺寸比金属颗粒尺寸略小,所合成的水凝胶在一定程度上可以束缚金属,保证金属纳米颗粒能牢牢固定在水凝胶中。本工作研究了聚合物负载镍或者钯镍合金催化硼氢化钠和二甲氨基甲硼烷水解的活性及可重复回收性能,发现它们都有较高的反应转换频率(TOF)和较低的活化能,水凝胶载Pd-Ni合金(Pd/Ni=1/20)催化二甲氨基甲硼烷水解时的活化能更是低至34.95 k J/mol,这些性能要比大多数非贵金属催化剂好,甚至比单一贵金属催化剂更好。聚合物载Ni通过简单的离心或者过滤能多次重复使用,可回收次数达7-10次,而水凝胶载Pd-Ni催化剂更是达到21次。目前,芳香胺化合物是极为重要的有机合成中间体,广泛应用于染料、农药、医药、精细化学品、摄影行业。使用水合肼还原芳硝基化合物具有选择性高、成本比硼氢化钠低廉等特点,并且水合肼的氧化产物为氮气和水,环境友好,因此水合肼倍受人们的亲睐。本工作使用纳米凝胶载Ni催化剂来催化芳香族硝基化合物的氢转移反应呈现出较高的活性。以硝基苯为底物考察了水合肼的用量对反应的影响,结果表明,底物与水合肼的摩尔比为1:15最适宜。将优化后的条件用于硝基苯衍生物的还原,都能得到高产率的芳香胺。动力学研究结果表明,硝基苯氢转移反应的活化能为133.7 k J/mol,焓变为130.9 k J/mol,熵变为102.8 J/(mol K)。
[Abstract]:In recent years, hydrogen has become an ideal energy source. Compared with traditional fossil fuels, the characteristics of zero carbon emission and high calorific value of hydrogen energy have attracted more and more attention. The solid hydrogen storage material, sodium borohydride and dimethylaminomethylborane, has high mass hydrogen storage density, stable properties at room temperature, non-toxic, lower cost than aminoborane, and the by-product of hydrolysis can be recycled. It is the development direction of solid hydrogen storage materials in the future. Polymer gel materials are developing rapidly in the field of catalysis. Hydrogel is a kind of hydrophilic polymer material containing hydrophilic group-so _ 3H _ 3H _ (+) -OH _ (+) -COOH _ (+) -NH _ (2). It has a large loading space, and its functional group can chelate or immobilize metal particles to avoid agglomeration, inactivation and good chemical stability. Hydrogels have the properties of both solid and fluid. The cross-linked structure is rich in water or organic solvents, which is suitable for the uniform dispersion of metal ions and the chemical reaction in aqueous and non-aqueous solutions. In this work, hydrophobic Ding Ji acrylamide nanospheres and hydrophilic terpolymer nanogels were used as carriers. A small amount of nickel seeds were first introduced into the carrier by impregnation, and then by electroless nickel plating. A variety of polymer nanospheres supported nickel catalysts were prepared by plating a large amount of nickel on the seed carrier. Nanogels-Ni can absorb water and expand from 225nm in vacuum to 411.9 nm in water. In contrast, hydrophobic polytertiary Ding Ji acrylamide does not swell in water. The results of HRTEM and XPS show that nickel on the polymer nanospheres mainly exists in the form of Ni O. The Pd-Ni alloy supported on polyacrylamide hydrogel was also prepared, and it was found that the ratio of Pd-Ni to Pd-Ni affected the particle size of the nano-alloy. The mesh size of hydrogels is slightly smaller than that of metal particles. The synthesized hydrogels can bind metals to a certain extent and ensure that metal nanoparticles can be firmly immobilized in hydrogels. The activity and repeatability of hydrolysis of sodium borohydride and dimethylaminoborane catalyzed by polymer-supported nickel or palladium nickel alloys were studied. It was found that both of them had higher reaction conversion frequency and lower activation energy. The activation energy of the hydrogel-supported Pd-Ni alloy Pd-Ni alloy for hydrolysis of dimethylaminomethylborane is even lower than that of most non-noble metal catalysts, or even higher than that of a single noble metal catalyst, the activation energy of which is even lower than that of the hydrogel-supported Pd-Ni alloy. Polymer-supported Ni can be reused repeatedly through simple centrifugation or filtration, and the recovery times can reach 7-10 times, while the hydrogel-supported Pd-Ni catalyst can reach 21 times. At present, aromatic amine compounds are very important organic synthesis intermediates, widely used in dyes, pesticides, medicine, fine chemicals, photography industry. The reduction of aromatic nitro compounds by hydrazine hydrate has the advantages of high selectivity, lower cost than sodium borohydride, and the oxidation products of hydrazine hydrate are nitrogen and water, which are environmentally friendly, so hydrazine hydrate is popular among people. In this work, nanogel supported Ni catalyst was used to catalyze the hydrogen transfer reaction of aromatic nitro compounds with high activity. The effect of the amount of hydrazine hydrate on the reaction was investigated with nitrobenzene as the substrate. The results showed that the molar ratio of the substrate to hydrazine hydrate was 1:15. The aromatic amines with high yield can be obtained when the optimized conditions are applied to the reduction of nitrobenzene derivatives. The kinetic results show that the activation energy, enthalpy and entropy of the transfer reaction of nitrobenzene are 133.7 kJ / mol, 130.9 kJ / mol and 102.8 J / mol / mol, respectively.
【学位授予单位】：宁波大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O643.36;TQ116.2

【共引文献】