复合氧化物催化剂(Cu)CeO_2上硝基苯加氢反应的研究

Studies on Hydrogenation of Nitrobenzene over (Cu)CeO_2 Composite Oxide Catalyst

基于用FT IR表征H2 与硝基苯在催化剂 (Cu)CeO2 上的吸附和反应行为 ,对硝基苯加氢反应进行了研究 .结果表明 ,氢在催化剂表面的吸附主要为解离吸附 ,硝基苯的吸附也主要为化学吸附 ;两种吸附物种在催化剂上进行表面反应生成易脱附的苯胺 ,避免了产物与反应物间的竞争吸附 ,有利于反应物完全转化 .在 (Cu)CeO2 催化剂上 ,硝基苯加氢反应机理为朗格缪尔 欣谢伍德型 。

Nitrobenzene hydrogenation is the main method for producing aniline. In the fixed-bud process, Pd or Pt noble metal catalyst supported on active carbon and Cu-Mn multicomponent catalyst were used widely. But the noble metal catalyst costs high and the non-noble metal catalyst has been generally used at higher temperature and high H-2 pressure. At the mean time, the selectivity for aniline over these catalysts is usually less than 99%. So it is very significative to develop new catalytic materials for nitrobenzene hydrogenation. The adsorption states and reaction behavior of H-2 and nitrobenzene over reduced (Cu)CeO2 composite oxide were studied by FT-IR. The nitrobenzene hydrogenation was investigated after the influence of inside diffusion outside diffusion and difference in temperature were removed, when the H-2 flow was larger than 200 ml/min, the particle size of catalyst was larger than 20 mesh and the catalyst was diluted with quartz sand (QS; V(QS)/V((Cu)CeO2) =5). The results indicated that the adsorption of some hydrogen was dissociative chemisorption. Since a large amount of nitrobenzene was also chemisorbed on the surface of the catalyst, aniline, which can be desorbed easily, was generated on the catalyst surface through surface reaction. The reaction mechanism of nitrobenzone hydrogenation over (Cu)CeO2 was Langmiur-Hinshelwood (L-H) one, and the surface reaction was the rate-determining step.