【作者】 郑明远；

【导师】 张涛；

【作者基本信息】 中国科学院研究生院（大连化学物理研究所） ， 物理化学， 2005， 博士

【摘要】 程序升温反应法（Temperature-Programmed Reaction, TPR）制备的过渡金属氮化物或碳化物,如氮化钼、碳化钨具有良好的肼分解活性,表现出类贵金属的催化性质。然而TPR法制备氮化铁并用于催化肼分解反应的研究和报道并不多见。本论文从TPR法制备氮化铁出发,研究了不同制备条件的影响以及由氧化铁制氮化铁的反应机制;考察了氮化铁催化剂上肼分解活性和反应路径;向氮化铁中引入镍以进一步提高肼分解活性;论文还研究了VIII族金属催化剂上肼分解反应。研究发现:以纳米氧化铁为前体,由TPR方法可以得到相对较高比表面积的纳米尺度氮化铁,并有可能降低氮化温度。氮化过程中Fe₂O₃首先在350℃附近被还原为Fe₃O₄,继而随制备温度升高而被部分氮化为Fe₂N与Fe₃O₄混合物,最终在450℃附近被完全氮化为Fe₂N。制备过程中低的升温速率和高的氨空速有利于获得较大比表面积的氮化铁。氮化铁具有良好的肼分解反应催化活性。与已经报道的氮化物肼分解催化剂相比,活性顺序为Mo₂N～FeN_x>>NbN。氮化铁催化剂上肼分解途径与氮化钼上相同,存在两个阶段:在300℃以下时生成N₂和NH₃;温度高于300℃时,中间产物NH₃发生分解并在500℃附近完全分解为N₂和H₂。铁镍双金属氮化物催化剂具有明显优于任一单独组分的肼分解活性。镍的引入调变了催化剂对氢和氮的活化能力,从而显著改善了肼分解活性。Ni/SiO₂、Pd/SiO₂、Pt/SiO₂催化剂在室温附近能够高选择性地催化肼分解制氢,尤其以Ni/SiO₂为最佳。Ru/SiO₂、Co/SiO₂、Rh/SiO₂和Ir/SiO₂催化剂在高温下表现出很高的肼分解制氢活性,有可能用于自热催化肼分解制氢。密度泛函计算结果表明Ni/SiO₂上室温肼分解遵循分子内氮氢断键机理。更多还原

【Abstract】 Transition metal nitrides or carbides, such as Mo₂N and WC_x, prepared by temperature-programmed reaction （TPR） have high specific surface areas. They exhibit platinum-like catalytic characters and have been reported to be efficient for the catalytic decomposition of hydrazine. However, there are few studies on preparing iron nitrides by TPR and no study on applying them into the hydrazine decomposition. This thesis firstly focused on the synthesis of iron nitrides and their catalytic behaviors for the hydrazine decomposition. Then, nickel as a promoter was introduced in order to further improve the catalytic activity. In addition, the hydrazine decomposition over group VIII metal catalysts was also investigated. The main results are presented as follows. Nano-iron nitrides having high surface areas were formed at relatively lower nitridation temperatures from some nano-iron oxide precursors and they inherited morphologies of the oxide precursors. The iron nitride from mesoporous precursor lost the porous structure. During the TPR process, iron oxide was firstly reduced into magnetite intermediate at ca. 350℃, and then was partially nitrided into a mixture of Fe₂N and Fe3O4 as a continuing increase in temperature. When the temperature reached ca. 450℃or higher, the iron oxide was converted into Fe₂N completely. It was also found that a high space velocity of ammonia and a low heating rate were beneficial for the formation of high surface iron nitride. The structures of iron nitrides were dependent on the preparation temperature and the更多还原