助剂引入方式对镍/二氧化硅催化剂结构和加氢性能的影响

采用等体积浸渍法制备了K_2O和La_2O_3改性的Ni/SiO_2催化剂.考察了K_2O和La_2O_3助刑引入方式对Ni/SiO_2催化剂催化间二硝基苯加氢制间苯二胺的影响.并用比表面积法(BET)、程序升温还原实验(TPR)和X射线衍射法(XRD)等对催化剂的结构进行了表征.结果表明,K_2O和La_2O_3的引入方式对Ni/SiO_2催化剂的物化性质和加氢性能影响明显.当K_2O、La_2O_3和Ni以共浸渍方式引入时,大大削弱载体与镍物种之间的相互作用,镍晶粒度变小,分散度增加,催化剂活性显著提高.加入催化剂1.2g、间二硝基苯40g和溶剂乙醇100mL,在3.0MPa、373K条件下反应4.5h后,间二硝基苯的转化率和间苯二胺的选择性分别达到99.8%和99.5%.

Effect of Introducing Method of La2O3 and K2O Promoters on Structure and Hydrogenation Performance of Ni/SiO2 Catalyst

A series of silica supported nickel catalysts promoted by lanthana and potassium oxide were prepared by using the incipient wetness co-impregnation and sequential impregnation methods.The effect of La_2O_3 and K_2O introducing methods on the catalytic performance of Ni/SiO_2 catalyst for m-dinitrobenzene hydrogenation to m-phenylenediamine were investigated,and the physical and chemical properties of the catalysts were analyzed by the techniques of BET,X-ray diffraction(XRD) and temperature-programmed reduction(TPR).The results showed that the addition sequence of K_2O and La_2O_3 promoters played a substantial role in determining the catalytic hydrogenation properties of the nickel-based catalysts.When incipient wetness co-impregnation method was used, the interaction between nickel and support was obviously weakened,the nickel crystallites was almost reduced entirely,and the nickel species were well dispersed,thus the particle size of nickel crystallites was significantly reduced,and the activity of catalyst was apparently improved in hydrogenation of m-dinitrobenzene.Under the reaction conditions of 373K,3.0MPa,catalyst 1.2g,m-dinitrobenzene 40g,solvent 100 mL,the supported nickel-based catalyst,Ni-K_2O-La_2O_3/SiO_2,exhibited very good catalytic performance.After reaction for 4.5h or so,the conversion of m-dinitrobenzene and selectivity of m-Phenylenediamine were 99.8%and 99.5%respectively.