硼烷氨和氨类储氢材料释氢反应的理论研究

发布时间：2018-01-08 02:00

本文关键词：硼烷氨和氨类储氢材料释氢反应的理论研究　出处：《河南大学》2015年硕士论文　论文类型：学位论文

【摘要】：氢能作为一种高能量密度、清洁、可再生的绿色新能源,引起了世界各国的高度关注。目前,储氢问题是氢能应用的主要瓶颈。确定材料的释氢机理是改进储氢材料性能和开发新型储氢材料的关键因素。本文研究了当前比较热门的硼烷氨和氨类潜在储氢材料的释氢反应机理,旨在从理论上确定单分子储氢材料难于释氢的原因,并为其寻找有效的催化剂,从而为开发高效、清洁和可行的储氢材料提供理论依据。共开展了以下三个方面的研究：1.采用分子轨道理论探究了铝烷膦和硼烷膦在有无硼烷或铝烷催化下的释氢反应机理。首先在MP2/aug-cc-pVDZ水平下优化了所有驻点的构型,然后在CCSD(T)/aug-cc-pVTZ水平下对MP2优化的几何构型进行了能量校正。理论结果表明,单分子的铝烷膦和硼烷膦,释氢能垒高于Al-P/B-P键的离解能,释氢反应无法进行。催化剂铝烷和硼烷都可以促进铝烷膦的释氢反应,但是当对应的前期络合物稳定存在时,硼烷膦的释氢能垒仍然高于A1-P离解能,释氢过程难以进行。同样,对于硼烷膦的释氢过程,铝烷和硼烷也可以大幅降低释氢能垒,有一定的催化作用,并且通过比较得知,硼烷的催化效果优于铝烷。除此之外,在铝烷和烷催化下,硼烷膦比铝烷膦更有可能成为潜在的储氢材料。因此,对于膦系列的储氢材料,由于它们的释氢能垒高于Al-P/B-P键的离解能,需要为其寻找有效的催化剂以降低释氢能垒。硼烷将是较合适的催化剂,在它的催化下,硼烷膦释氢反应的能垒低于B-P键的断裂能,释氢过程容易进行。2.采用量子化学方法研究了甲胺在有无硼烷、铝烷、乙硼烷、乙铝烷和硼烷-铝烷催化下的释氢反应机理。首先在MP2/aug-cc-pVDZ水平下优化了所有驻点的构型,然后基于此优化的几何构型,在CCSD(T)/aug-cc-pVTZ水平下进行了能量校正。结果表明,单分子甲胺释氢能垒较高,释氢反应难以进行,因此释氢过程需要合适的催化剂。所研究的催化剂都可以加快甲胺的释氢反应,然而,对于单分子催化剂硼烷和铝烷来说,由于它们催化下的甲胺释氢能垒仍然高于其对应前期络合物中的B-N/Al-N键的离解能,因此并无真正的催化作用。而双分子催化剂乙硼烷、乙铝烷和混合催化剂硼烷-铝烷可以大幅降低甲胺的释氢能垒,有较好的催化作用,且混合催化剂硼烷-铝烷由于催化释氢反应能垒最低和反应历程最短,因此它的催化效果最好。此外,通过比较各个催化剂的相同点和不同点,得知氢键的形成和六元环结构是降低释氢能垒的两个重要因素。3.在CCSD(T)/aVTZ//MP2/aVDZ水平下研究了硼氢化合物和铝氢化合物催化甲基肼释氢反应的反应机理。结果表明,单分子的甲基肼释氢能垒太高,释氢反应难以进行。而所研究的五种催化剂既可以进攻甲基肼氨基中的N原子,也可以进攻亚氨基中的N原子,并且都可以加快甲基肼的释氢反应。对于单分子的硼烷和铝烷,当对应的前期络合物稳定存在时,其催化甲基肼释氢反应的能垒仍然较高,并无真正的催化作用；而双分子催化剂可以使甲基肼有效的释氢,且混合催化剂硼烷-铝烷的催化效果最好。此外,经过比较得知,虽然催化剂更容易进攻甲基肼亚氨基的N原子,但其释氢能垒高于催化剂进攻氨基N原子的能垒,因此,当催化剂进攻甲基肼的氨基N原子时,释氢反应更容易进行。
[Abstract]:Hydrogen is a kind of high energy density, clean, new green renewable energy, has aroused great attention in the world. At present, hydrogen storage is the main bottleneck of the application of hydrogen energy. Determining the material release mechanism of hydrogen is the key factor to improve the performance of hydrogen storage materials and development of new hydrogen storage materials. Hydrogen reaction mechanism was studied in this paper. Release the current hot ammonia borane ammonia and potential hydrogen storage materials, to ascertain the cause of single molecular hydrogen storage material is difficult to release hydrogen from the theory, and to find effective catalyst for the development of efficient, so as to provide a theoretical basis for the hydrogen storage materials, clean and feasible. A total of three studies were carried out 1.: using molecular orbital theory to explore the aluminum alkyl phosphine and phosphine borane in a borane or alanes catalyzed hydrogen release reaction mechanism. First optimized at the MP2/aug-cc-pVDZ level all of the stationary points of the configuration, and then in the CCSD (T) /aug-cc-pVTZ levels on the geometry optimization of MP2 of energy correction. The theoretical results show that the single molecule aluminum alkyl phosphine and phosphine borane, release hydrogen dissociation barrier is higher than that of the Al-P/B-P bond can release hydrogen reaction. The catalyst cannot alanes and borane can promote hydrogen release of aluminum alkyl phosphine, but when there is a stable complex corresponding to the early release of phosphine borane, hydrogen barrier is still higher than the A1-P dissociation energy, hydrogen release process is very difficult. Similarly, the process of hydrogen release phosphine borane, aluminum alkyl borane and also can significantly reduce the release of hydrogen barrier has a catalytic effect, and the result shows that the catalytic effect of borane better than the alanes. In addition, the aluminum alkyl and alkyl phosphine borane catalyzed alkyl phosphine than aluminum is more likely to be a potential hydrogen storage materials. Therefore, the hydrogen storage materials for phosphine series, due to their higher hydrogen dissociation barrier release Al-P/ B-P key can be. For which you want to find effective catalyst to reduce the release of hydrogen barrier. Borane will be a catalyst for more suitable, in its catalyzed borane hydrogen release reaction of phosphine fracture energy barrier than the B-P bond energy, hydrogen release process easy to.2. studied there in the methylamine borane, using quantum chemical method of aluminum alkoxide. B borane hydrogen release reaction mechanism of ethylene alanes and borane catalyzed alanes. First optimized at the MP2/aug-cc-pVDZ level of all point configuration, then the geometry optimization based on CCSD (T) /aug-cc-pVTZ level of energy correction. The results show that the single molecule hydrogen barrier of methylamine release higher hydrogen release the reaction is difficult, so the hydrogen release process requires a suitable catalyst. The catalyst can accelerate the reaction of hydrogen release, methylamine however, for single molecule catalyst borane and aluminium alkyl, because they are under the catalysis of methylamine release hydrogen barrier is still high In the early B-N/Al-N bond dissociation in the complex, so there is no real catalysis. And bimolecular catalyst diborane, ethylene alanes and mixed catalyst borane alanes can greatly reduce the hydrogen barrier release of methylamine, have good catalytic effect, and the mixed catalyst borane alanes due to catalytic hydrogen release reaction the lowest energy barrier and the reaction mechanism is the shortest, so it's the best catalytic effect. In addition, through the comparison of different catalysts and different points, that the formation of hydrogen bonds and six membered ring structure is the two important factors to reduce.3. release hydrogen barrier in CCSD (T) level on the reaction mechanism of /aVTZ//MP2/aVDZ boron hydrogen compounds hydrogen and aluminum compounds catalyzed by methyl hydrazine hydrogen release reaction. The results show that the single molecule of methyl hydrazine release hydrogen barrier is too high, difficult to release hydrogen. Five kinds of catalysts and the study can attack amino methyl hydrazine The N atoms, can also attack the imino atoms in the N, and can accelerate the reaction of methyl hydrazine hydrogen. For single molecule borane and aluminium alkyl, when there are early stable complex corresponding, the catalytic reaction of methyl hydrazine hydrogen energy barrier is still high, there is no real catalytic effect; while the two catalysts can make methyl hydrazine hydrogen effectively, and the catalytic effect of mixed catalyst borane alanes best. In addition, it was found that although the catalyst is easier to attack the imino methyl hydrazine N atoms, but the release of hydrogen barrier was higher than offensive amino N atomic energy barrier, therefore, when the catalyst the attack of methyl hydrazine amino N atoms, hydrogen release reaction more easily.

【学位授予单位】：河南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB34;TQ116.2

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