纳米碱金属氢化物的性能应用及纳米镧系金属粉末的制备

【作者】 吴强；

【导师】 范荫恒；

【作者基本信息】 辽宁师范大学 ， 物理化学， 2003， 硕士

【摘要】 本文应用络合催化法，在常温常压下，在萘/TiCl4催化体系作用下合成纳米尺寸碱金属氢化物（以NaH为代表）、纳米尺寸镧系金属氢化物（以SmH3为代表）和镧系金属有机化合物（以蒽镧为代表），并通过真空热解镧系金属有机化合物得到高分散度的纳米尺寸镧系金属粉末（以La为代表），主要考察如下三个方面的内容。1. 纳米NaH 高化学反应活性的研究本文通过选择加氢还原、氯苯脱氯、二甲基亚砜金属化及催化加氢四个典型反应，在初始反应阶段定量考察了纳米NaH与商品NaH两者之间的反应速率与反应活性的关系。实验发现纳米NaH的化学反应活性比商品NaH呈数量级提高。结果表明极大的比表面积和极高的表面能是决定纳米NaH高活性的两个关键因素。实验进一步说明，纳米NaH能使某些原来热力学上允许进行但动力学上难以进行或"不能进行"的有关反应得以进行；使一些过去认为低收率无价值的反应，大幅度提高反应速率和产率，使其成为有实际意义的反应。2．纳米碱金属氢化物高选择性还原肉桂醛为肉桂醇的研究 应用纳米MH作还原剂对肉桂醛进行还原反应，实验结果表明，采用纳米LiH和NaH作还原剂时，反应的选择性都可以达到99 % 以上，并具有很高的转化率。实验还同时考察了温度、MH的比例、加样顺序等因素对选择还原反应的影响：其中，温度的升高能加快反应的速度并提高反应的转化率和选择性；MH比例的增大也能加快反应速度并提高反应的选择性和转化率；另一方面，改变加样的先后顺序会明显改变反应的选择性和转化率。3. 纳米尺寸镧系金属粉末制备的研究 温和条件下，采用络合催化法合成镧系金属有机化合物，利用它的热不稳定性，在真空条件下进行热分解来制备纳米尺寸镧系金属粉末。TEM测试结果表明真空条件下（13-40Pa），热分解制得的活性金属粉末的颗粒大小为20-40 nm，分散度好且纯度高。更多还原

【Abstract】 Nano-alkali metal hydrides and lanthanide hydrides can be prepared easily by the direct hydrogenation catalyzed by TiCl4 in tetrahydrofunan (THF) under normal pressure. Lanthanide powder of nanometric size in a finely dispersed active form was generated by the thermal decomposition of organolanthanide in vacuum.1. Four kinds of model reactions were employed to draw comparisons of initial reaction rates between nano―NaH and the commercial one. The experimental results indicate that the initial reaction rates of nano-NaH are several orders of magnitude higher than those of the commercial one. The large specific surface area and the high surface energy of nano-NaH should be the main factors for their extremely high chemical reactivity. With nano―NaH, many reactions can be carried out efficiently.2. Using nano―LiH and nano―NaH as reducers, in refluxing THF and under normal pressure, cinnamaldehyde were selectively reduced to cinnamyl alcohol with selectivities of 99 % at higher conversions. Changing reaction temperature or the molar ratio between reactants and cinnamaldehyde can improve the selectivities and conversions. In addition, the sequence of the reactants is another factor to affect the selectivity and conversion in this reaction. 3. The reaction of lanthanide powder with anthracene in the presence of TiCl4 catalyst in tetrahydrofuran at 0-60℃under normal pressure generated organolanthanide compounds, which are less thermal. It was found that the decomposition of the organolanthanide compounds in vacuum could give rise to lanthanide powder of nanometric size with high purity accordingly. Transmission electron micrographs showed that the resulted lanthanide were in the form of nanoparticles with an average primary particle size around 20-40 nm.更多还原