Ni/SiO_2催化剂的制备条件对催化间二硝基苯加氢反应性能的影响

EFFECTS OF PREPARATION CONDITIONS ON Ni/SiO_2 CATALYST ACTIVITY IN m-DINITROBENZENE HYDROGENATION

将Ni/SiO2 催化剂应用于间二硝基苯加氢反应中 ,考察了该催化剂制备过程中焙烧温度和还原温度对其催化性能的影响 ,并通过BET、XRD、TEM、TPR等方法对催化剂进行了表征 .结果表明 ,在实验研究范围内 ,随着焙烧温度的提高 ,Ni/SiO2 催化剂比表面积降低 ,NiO与载体SiO2 之间的相互作用逐渐增强 ,催化剂的还原温度明显提高 ,活性组分Ni的晶粒度增大 ,焙烧温度为 773K时催化剂具有最佳的催化反应性能 ,此时活性组分Ni以高分散状态存在 .催化剂的还原温度对Ni/SiO2 催化剂的结构和催化性能影响显著 ,当还原温度较低时 ,活性组分还原不完全 ,催化剂活性较低 ;而还原温度太高会使活性组分烧结 ,导致催化剂活性明显降低 ;还原温度为 72 3K时催化剂表现出最佳的活性和选择性 .

The effects of calcination temperature and reduction temperature on the silica supported nickel catalyst, which were prepared by impregnation of silica with nickel nitrate solution, were investigated in the liquid-phase hydrogenation of m-dinitrobenzene to m-phenylenediamine. The nature of the catalysts was discussed based on the characterization results of nitrogen adsorption-desorption (BET), X-ray diffraction (XRD), transmission electron microscopy (TEM) and temperature-programmed reduction (TPR). With increasing calcination temperature, the surface area of the catalyst decreased progressively, but the interaction between NiO and SiO 2 became stronger. At the same time, the crystallite of nickel increased with the increase of calcination temperature. The optimal calcination temperature was 773K, at which highly dispersed nickel species could be present. The reduction temperature also affected the properties of the catalyst. At a lower temperature, the catalyst could not be reduced completely, while an improperly high temperature would cause sintering of the catalyst. The catalyst reduced at 723K showed higher catalytic activity and selectivity.