摘要
采用等体积浸渍法制备了La_2O_3改性的Ni/Si O_2催化剂,考察了La_2O_3的引入方法对Ni/Si O_2催化剂催化间二硝基苯加氢制间苯二胺反应性能的影响,并采用XRD、TPR和XPS等表征技术对催化剂的物化性质进行了研究.结果表明,La_2O_3的添加顺序对Ni/Si O_2催化剂的物化性质和加氢性能影响非常明显.当镧以先于镍浸渍方式引入时,将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,催化剂的活性显著提高,间二硝基苯转化率和间苯二胺收率分别达到97·1%和93·5%.在以镍和镧共浸方式制备的催化剂中,La_2O_3的存在也使Ni/Si O_2催化剂的反应性能有所改善,但效果没有镧先于镍浸渍方式突出.当以先浸镍后浸镧的方式加入助剂时,催化剂中的镍晶粒增大,分散性变差,催化剂的活性大幅度下降.
A series of silica supported nickel catalysts promoted by lanthanumozide were prepared by using the incipient wetness co-impregnation and sequential impregnation methods. The effect of La2O3 introducing method on the activity and selectivity of Ni/SiO2 catalyst for m-dinitrobenzene hydrogenation to m-phenylenediamine was studied, and the physical and chemical properties of the catalysts were investigated by the techniques of X-ray diffraction （XRD）, temperature-programmed reduction （TPR）, and X-ray photoelectron spectroscopy （XPS）. The results showed that the addition sequence of La promoter played a substantial role in determining the catalytic hydrogenation properties of the nickel-based catalysts. When stepwise incipient impregnation method was used and La component was firstly impregnated on support before nickel component, the interaction between nickel and support was obviously weakened, the particle size of nickel crystallites was significantly reduced, and the nickel species were well dispersed, thus the activity of catalyst was apparently improved. In hydrogenation of m-dinitrobenzene under the conditions of hydrogen pressure 2.6 MPa, temperature 373 K and reaction time for 1 h, the conversion of m-dinitrobenzene and the yield of m-phenylenediamine on the above catalyst were up to 97.1%and 93.5 %, respectively. The sample prepared by the La-Ni co-impregnation method also positively affected the catalytic performance of catalyst, but not as good as the component, however, the particle size of nickel decrease of catalyst activity. former. When La component was impregnated after nickel crystallites increased apparently, thus resulting in dramatic
出处
《化工学报》
EI
CAS
CSCD
北大核心
2005年第11期2114-2118,共5页
CIESC Journal
关键词
氧化镧助剂
镍/二氧化硅催化剂
间二硝基苯
加氢
间苯二胺
lanthanium oxide promoter
Ni/Si02 catalyst
m-dinitrobenzene
hydrogenation
m-phenylenediamine
