无机盐调控Raney Ni催化硝基苯类化合物硝基加氢的研究

	无机盐调控Raney Ni催化硝基苯类化合物硝基加氢的研究
	刘霞
学位类型	硕士
导师	夏传海
	2015-05-22
学位授予单位	中国科学院研究生院
学位授予地点	北京
学位专业	海洋化学
关键词	硝基苯类化合物苯胺类化合物催化加氢 Raney Ni 金属盐助剂
摘要	苯胺类化合物(ANs)作为一类重要的有机合成中间体，在精细化工领域占有非常重要的地位。苯胺类化合物主要是由相应的硝基苯类化合物(NBs)还原制得，其中液相催化加氢还原法因其环境友好而成为合成苯胺类化合物的主要方法。金属催化剂是影响液相催化加氢效率的关键因素，其中Raney Ni催化剂，因其价格较贵金属催化剂便宜，而更适合实际工业化生产。但是Raney Ni的催化活性有待进一步提高，而且硝基苯类化合物加氢过程中中间产物的积累影响加氢反应的进程，有待改善。针对以上问题，本文选用Raney Ni为催化剂，研究了一些金属盐添加剂对其催化一些NBs加氢反应的影响，探讨了这些金属盐添加剂对Raney Ni催化硝NBs加氢反应速度的影响以及对其反应历程的调控，并对其有效作用机理进行了探讨，具体研究结果如下：当向Raney Ni催化对氯硝基苯(4-CNB)加氢的反应体系中添加一定量的金属盐，尤其是金属氟化盐NaF，KF，MgF₂和CaF₂，Raney Ni的催化活性得到大幅度提高。这些金属氟化盐对其他的NBs的催化加氢，如硝基苯，对硝基苯甲腈和间二硝基苯，同样表现出一定的促进作用。这些金属氟化盐的促进作用可能的作用原理可以用一种电子效应的假说来解释。添加的金属氟化盐会有一部分沉积在催化剂表面，而且沉积的金属氟化盐和催化剂之间可能存在一种电子相互作用，这种电子作用可能会改变催化剂表面的电子结构，从而改变其催化性能。改变后的催化剂可以促进反应物向目标产物的转化，提高反应速度。通过过渡金属盐对Raney Ni催化硝基苯类化合物加氢反应过程的影响研究发现，一些过渡金属氯化盐如FeCl₂，对中间产物有显著的抑制作用。并且通过将FeCl₂的加入量控制在0.5~1%之间时，可以在不影响反应速度的条件下，使中间产物大幅度减少甚至完全消失。FeCl₂可以用于有中间产物苯基羟胺类化合物生成的硝基苯类化合物加氢反应历程的调控，它可以有效减少苯基羟胺类化合物的积累。FeCl₂对中间产物苯基羟胺类化合物的有效抑制作用，可能是因为FeCl₂的加入改变了Raney Ni催化剂活性中心的结构，形成的新的Ni-Fe双活性中心可以加快中间产物的转化，从而大幅度的减少其积累或使其消失。综上所述，在Raney Ni催化硝基苯类化合物加氢反应中，加入金属氟化盐作为助剂并控制其加入量，可以大幅度提高反应的速度，提高生产效率；而加入FeCl₂作为辅助催化剂，可以调控反应历程，有效的抑制了中间产物的积累。
其他摘要	Aromatic amines (ANs) are commercially important for the large scale production of many fine chemicals. Liquid-phase hydrogenation of nitro aromatic compounds (NBs) over metal catalyst is recognized as an efficient and environmentally friendly procedure to produce ANs because no other harmful effluents are produced except water. In catalytic reaction, the catalyst plays a very important part. Catalysts base on noble and non-noble metals have been widely studied. Raney Ni is applied more widely than noble metal catalysts in industry production of ANs because of its abundant resources and low price. However, the catalytic activity of Raney Ni is lower than noble metal catalysts, and the accumulation of phenylhydroxylamines produced in hydrogenation of NBs is harmful, both of which need to be improved. To solve the problem mentioned above, we investigated the hydrogenation of NBs over Raney Ni under the influence of some metal salt additives, and the possible reason for the effect of these metal salts was discussed. The main results are listed as following. Raney Ni catalyst with addition of a moderate amount of metal salts, especially metal fluorides (NaF, KF, MgF₂ and CaF₂) exhibited much higher catalytic performance for the hydrogenation of 4-chloronitrobenzene (4-CNB). The metal flourides also showed the promoting effect on the hydrogenation of some other NBs, such as nitrobenzene, p-nitrophenylnitrile and m-dinitrobenzene. The possible reason of the promoting effect of these metal fluorides might be interpreted by a speculation of electronic effect. The added metal fluoride could absorb on Raney Ni surface, and there might exist some electronic interaction between the deposited fluoride and Raney Ni. The electronic interaction might change the electronic property of Raney Ni. And as a result, the changed Raney Ni could accelerate the conversion of the substrate to the target product. Raney Ni catalyst with addition of some transition metal salts, especially FeCl₂, exhibited a remarkable inhibiting effect on the accumulation of phenylhydroxylamines produced in hydrogenation of NBs. The accumulation of phenylhydroxylamines could be reduced to zero by controlling the FeCl₂ amount within 0.5~1.0%. The inhibiting effect of FeCl₂ was also found in the hydrogenation of some other NBs only if there was phenylhydroxylamine produced.The possible reason of the inhibiting effect of these metal fluorides might be interpreted by the formation of a new kind of Ni-Fe active site. The deposited FeCl₂ could possibly cover part of the original Ni active site and a new kind of Ni-Fe active site might form, which benifited the conversion of phenylhydroxylamine leading to its disappearance. In conclusion, Raney Ni catalyst with a moderate amount of metal fluorides exhibited much higher catalytic performance for the NBs hydrogenation, which could enhance productivity. And FeCl₂ exhibited a remarkable inhibiting effect on the accumulation of phenylhydroxylamines produced in NBs hydrogenation over Raney Ni.
语种	中文
文献类型	学位论文
条目标识符	http://ir.yic.ac.cn/handle/133337/8965
专题	中国科学院烟台海岸带研究所知识产出_学位论文
作者单位	中国科学院烟台海岸带研究所
第一作者单位	中国科学院烟台海岸带研究所
推荐引用方式 GB/T 7714	刘霞. 无机盐调控Raney Ni催化硝基苯类化合物硝基加氢的研究[D]. 北京. 中国科学院研究生院,2015.

条目包含的文件
文件名称/大小	文献类型	版本类型	开放类型	使用许可
?????Raney Ni???????（2123KB）	学位论文		开放获取	CC BY-ND	浏览请求全文