非晶态Ni-B/SiO_2催化硝基苯加氢及其晶化失活

Nitrobenzene Hydrogenation Catalyzed by Ni-B/SiO_2 Amorphous Catalyst and its Crystallization Deactivation

采用化学还原法制备了负载型Ni－B/SiO2非晶态合金催化剂，采用高压液相硝基苯的加氢反应，测定了上述催化剂的加氢活性和选择性，并与其他Ni系催化剂（Ni／SiO2和RaneyNi催化剂）进行了比较，发现所有催化剂均具有很高的催化活性和选择性，而Ni－B／SiO2非晶态合金的催化活性和选择性最高．通过高温处理获得对应的晶态Ni－B／SiO2催化剂,Ni－B／SiO2非晶态合金的加氢活性明显高于对应的晶态催化剂，表明催化剂存在晶化失活现象，结合催化剂的表征，讨论了非晶态合金催化剂的晶化失活机理，主要归因于高温团聚导致催化剂活性比表面积下降．

The hydrogenation of nitrobenzene over supported Ni-B amorphous catalysts prepared by chemical reduction was investigated in a liquid phase batch reactor. The results showed that the all those Ni-based catalysts exhibited high catalytic acitivity and selectivity. The superiority of the amorphous structure in the hydrogenation was determined by comparing amorphous Ni-B catalyst w1th its corresponding Ni/SioO2 as well as Raney Ni catalysts. Effects of the reaction conditions including the temperature, the concentration of nitrobenzene, and the pressure of hydrogen on the hydrogenation activity and selectivity were investigated and the reaction kinetics was discussed. The result showed that the reaction is zeroth order with respect to nitrobenzene and first order to hydrogen. The deactivation of the as-prepared amorphous catalyst during the crystallization process caused by heating treatment was also observed, which was explained according to the decrease of the surface active area due to the gathering the Ni-B alloy particles ad determined by SEM.