【作者】 雷浩；

【导师】 包信和；

【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， 2003， 博士

【摘要】 催化剂在化学反应中起着非常重要的作用。催化剂的性质不仅取决于催化剂的成分，而且与催化剂的制备方法、工艺条件密切相关。己内酰胺是石油化工生产中的一种重要化工原料，98％以上的己内酰胺用于生产尼龙-6。加氢精制是生产己内酰胺的重要步骤，通常使用Raney-Ni催化剂。Raney-Ni催化剂的制备步骤一般是：先将Ni和Al炼成Ni-Al合金碇，然后球磨成原始Ni-Al合金粉末，再用碱液浸取活化。这种方法制得的催化剂具有骨架结构，显示出很高的催化活性。目前，国产商品雷尼镍催化剂用于己内酰胺加氢精制的效果还不甚理想。传统工艺使用的常规冶炼和铸碇，也不可避免地带来合金催化剂成分和助剂的偏析，并且合金碇必须经过“破碎”才能“球磨”，导致原始Ni-Al合金成分只能在脆性合金的狭窄范围内（Ni含量约40～60wt％之间，Ni含量50wt％时为最佳）。因此石油化工科学研究院从材料的角度进行革新，通过快速凝固技术并辅以添加助剂和对合金进行高温预处理等手段制备原始Ni-Al合金以提高骨架镍催化剂的活性，并用于己内酰胺的加氢精制，取得了非常好的效果，但是对于快速凝固工艺和助剂的影响以及所生产的原始合金结构与催化剂结构和活性的构效关系，特别是对预处理的作用和机理等众多科学问题未得到澄清。此外，纳米材料由于具有大的比表面积，高密度表面晶格缺陷和高表面能等特性适合作高活性催化材料，纳米Ni-Al合金的制备和应用涉及到大量的纳米理论和技术问题。本论文针对以上问题，与石科院合作对用快速凝固技术制备的Ni-Al原始合金及催化剂进行了系统的研究，并对超细和纳米级Ni-Al原始合金的制备进行了初步探索，得到了如下有意义的结果： 1．采用单辊快速凝固法，通过改变铜辊的转速和添加不同种类和含量的过渡金属制备了原始Ni-Al合金，运用XRD、金相显微和XPS等手段分别考察了冷却速度和助剂对快速凝固原始合金结构及催化剂活性的影响，发现原始合金中Ni₂Al₃相的含量和相畴大小对活化有重要影响，而催化剂中Ni晶粒的大小以及快凝N卜Al合金结构及衍生骨架N!催化剂加氢特性的研究表面的Ni/A1和Ni创10是影响催化剂活性的重要因素，其中转速为500转/分的催化剂对己二睛加氢的选择性最高，在快凝原始合金中添加过渡金属Fe、Cr和Mo则有利于提高催化剂的环己酮加氢活性，过渡金属Fe的最适宜添加量为Zwt%。2.金相显微和XPS深度分析研究表明对快速凝固Ni一Al原始合金进行预处理，改变了原始合金相组成和相分布，导致不同的活化机理，活化后生成了具有大的比表面积的Ni微晶或非晶，残留的NiZA13相有助于催化剂的稳定，使活性Ni高度分散在催化剂表面的A1203上，有利于催化剂活性的提高。3.在LHS一12多功能表面能谱仪上分别建立了原位反应装置和低温吸附装置，经过对快速凝固原始合金的原位预处理，发现原位预处理使Al在合金表面大量偏析，并可能因此改变合金的相组成。低温吸附装置可使实用催化剂表面吸附反应物来研究催化剂表面吸附和脱附行为。4.采用高能球磨法制备了超细Ni一Al原始合金并活化成催化剂，发现随着球磨时间的增加，合金中NIA13相的相对含量逐渐减少，同时NiZA13相的晶粒也逐渐减小，导致生成的催化剂分散度增大，活性增加;采用电弧一等离子体法在不同气氛下制备了不同组成的纳米级Ni一AI原始合金，与甲烷气氛相比，惰性气氛下制备的合金组成更接近于传统方法所制备的，有利于活性组分的生成。另外，还可以通过控制合金组成和改变反应气氛，以减少Al在合金表面的偏析和改变合金的形貌与尺寸大小。更多还原

【Abstract】 Catalysts have a great influence on the product yields in many industrial processes. The catalytic performance is not only determined by the composition of catalysts but also closely related to the preparation method and the technological conditions. Hexanolactam is one of the most important raw materials for the petrochemical industry. Hydrofining is used to obtain high-quality hexanolactam with Raney-Ni as the preferred catalyst. Raney-Ni catalysts show high activity for hydrogenation reactions because of their skeletal structure, and are usually obtained by leaching the Ni-Al alloy powder. Raney-Ni catalysts from domestic chemical plants demonstrate lower activity than imported ones. Meanwhile, traditional technologies for preparing Ni-Al alloys (e.g. smelting, casting, etc.) inevitably lead to the segregation of components and additives. The process of ball milling after the breaking of alloy ingots demands a narrow Ni-Al alloys composition (Ni wt% as 40~60wt%). Therefore, the Research Institute of Petroleum Processing in Beijing (RIPP) designed a novel procedure for the preparation of highly active Raney-Ni catalysts. Ni-Al ribbons containing transition metal additives were obtained by melt-quenching and then ball-milled to powder. After high temperature pretreatment, the powder was activated through the leaching of Al with NaOH. However, the engineering fundamentals of the melt-quenching technology, the effects of the transition metal additives, the relationship between the Ni-Al alloys and the corresponding catalysts, especially the effect of pretreatment, have never been systematically studied. In addition, when the catalysts dimensions are reduced to nano scales, they will show unique catalytic characteristics due to the high density of crystal lattice defects, the large surface area and the high surface energy accordingly.In the present work, we have carried a systematical study of the relationshipbetween melt-quenched Ni-Al alloys and the corresponding catalysts, as well as the influence of technological conditions. Using high-energy ball milling and arc-discharge methods, we have also attempted to prepare Ni-Al alloys in ultrafine or nano scales. The results are as follows:1. By altering the rate of the copper roller or by varying the species or the amount of the transition metal additives, Ni-Al alloy ribbons as the precursors of the Raney-Ni catalysts are optimized through melt-quenching. Both the alloys and the final catalysts are characterized by XRD, XPS and metallographic microscopy. It is indicated that Raney-Ni catalysts derived from Ni-Al alloys with a rolling rate of 500 rpm and Fe, Cr or Mo additives, have high selectivity and catalytic activity for the hydrogenation of adiponitrile and cyclohexanone. The relative content and domain of the Ni2Al3 phase play a crucial role in the subsequent leaching process, and the catalytic performance relates directly to the size of Ni crystalline as well as the Ni/Al and Ni/NiO ratios on the surface.2. From the results of metallographic microscopy and XPS depth analysis, the obvious differences are observed in the phase composition and the distribution between the commercial and melt-quenched Ni-Al alloys, especially after pretreatment, causing a different leaching mechanism. In the catalysts from pretreated Ni-Al alloys, there exists microcrystalline or amorphous Ni, the residual Ni2Ah phase is a crucial factor for the enhancement of the stability, and the active Ni is distributed evenly on the catalyst framework with a large amount of Al oxide on the surface.3. Two additional parts are connected to the LHS-12 multifuctional surface analysis system: one is a high-pressure reactor, which can carry out in situ pretreatment for the catalysts . Followed by XPS experiments of the melt-quenched Ni-Al alloys, it is suggested that high-temperature pretreatment causes the segregation of Al component of Ni-Al alloys. The other is a device for the adsorption at low temperatures, with which the performanc更多还原