助剂对Ni/SiO2催化剂结构和间二硝基苯加氢性能的影响

采用等体积分步浸渍法，制备了添加Mg、Cu、Co、Ce、La助剂的Ni／SiO2催化剂，用于间二硝基苯加氢制间苯二胺反应，并采用XRD和TPR等手段表征了催化剂的物理化学性质。结果表明，助剂Mg、Cu、Co、Ce的加入均不同程度地抑制了催化剂的加氢活性；La的加入显著提高了催化剂的活性和选择性，在反应压力2．6MPa、反应温度373K时，反应1h，间二硝基苯转化率和间苯二胺产率分别为97．1％和93．5％。XRD和TPR的结果表明，稀土氧化物La2O3可使催化剂中Ni晶粒度变小，分散度增加，且能大大削弱载体与Ni物种之间的相互作用，从而增加催化剂中活性Ni物种的数目，增大催化剂的活性和选择性。

EFFECT OF PROMOTERS ON PHYSICO-CHEMICAL PROPERTIS AND CATALYTIC PERFORMANCE OF Ni/SiO2 IN m-DINITROBENZENE HYDROGENATION

Ni/SiO 2 catalysts promoted with the oxides of alkaline earth (Mg), transition metals (Cu and Co), or lanthanide (Ce and La) were prepared by consecutive impregnation of promoter and then nickel on silica support. The liquid phase hydrogenation of m dinitrobenzene to m phenylenediamine was studied over these catalysts in a stainless steel autoclave. The techniques of XRD and TPR were utilized to relate the performance of the catalyst to the physical and chemical properties of the catalyst. It was found that Mg, Cu, Co and Ce showed the negative effects and La 2O 3 showed a prominent positive effect on m dinitrobenzene conversion and m phenylenediamine yield over Ni/SiO 2 catalyst. The conversion of m dinitrobenzene and the yield of m phenylenediamine could reach up to 97.0% and 93.1%, respectively, under the reaction conditions of 2.6 MPa hydrogen pressure and 373 K and reaction time of 1 h over La 2O 3 promoted Ni/SiO 2 catalyst. The results of XRD and TPR showed that the interaction between Ni and the support of Ni/SiO 2 catalyst was obviously weakened, the amount of nickel species, which could be easily reduced, was increased, the particle size of nickel crystallites was significantly reduced, and the nickel species were well dispersed when the catalyst was promoted by La 2O 3, resulting in the apparent improvement of its catalytic activity.