镍负载量对邻氯硝基苯加氢制邻氯苯胺Ni/TiO_2催化剂性能的影响

Influence of Ni Loading on Properties of Ni/TiO_2 Catalyst for Hydrogenation of o-Chloronitrobenzene to o-Chloroaniline

用等体积浸渍法制备了一系列不同镍负载量的负载型Ni/TiO2催化剂,并将其应用于邻氯硝基苯加氢制邻氯苯胺的反应.采用N2吸附、X射线衍射、程序升温还原、透射电镜、H2化学吸附及间歇加压釜式反应器活性评价等方法,考察了镍负载量对Ni/TiO2催化剂的物化性质及邻氯硝基苯加氢反应性能的影响.结果表明,随着镍负载量的增加,Ni/TiO2催化剂上邻氯硝基苯的转化率逐渐提高;当镍负载量超过30%时,催化剂的活性和选择性不再明显变化.当催化剂中镍负载量高于20%时,在温度343K、氢压1·0MPa和催化剂/邻氯硝基苯质量比1/10的条件下反应210min后,邻氯硝基苯的转化率和邻氯苯胺的选择性均高于99%,催化剂具有良好的应用前景.分析表明,影响Ni/TiO2催化剂性能的主要因素为催化剂表面镍晶粒的活性表面积以及载体TiO2与金属镍之间的强相互作用.

A series of titania-supported nickel catalysts with different Ni loadings （10 % - 40 % ） were prepared by the incipient impregnation method and applied in the hydrogenation of o-chloronitrobenzene to o-chloroaniline. The effects of nickel loading on the physico-chemical properties of the Ni/TiO2 catalysts were studied by nitrogen adsorption-desorption, X-ray diffraction, temperature-programmed reduction, transmission electron microscopy, and He chemisorption. The catalyst performance for the hydrogenation was evaluated in an autoclave reactor. The results showed that the o-chloronitrobenzene conversion increased with increasing Ni loading of the Ni/TiO2 catalysts. When the Ni loading was higher than 30 %, no remarkable difference in catalyst performance was observed. For the catalysts with Ni loadings higher than 20 % under the reaction conditions of temperature 343 K, hydrogen pressure 1.0 MPa, and catalyst to o-chloronitrobenzene mass ratio of 1/10, both the o- chloronitrobenzene conversion and the selectivity for o-chloroaniline exceeded 99 % within 210 min. Hence, Ni/ TiO2 is a promising catalyst for the synthesis of o-chloroaniline. The characterization results suggested that Ni surface area and the strong metal-support interaction were important factors affecting the catalyst performance, whereas there was no distinct relation between the specific surface area and catalytic performance of the catalyst.