二硝基甲苯低压加氢Ni-La-B非晶态合金催化剂的制备及结构表征

用化学还原法制备了Ni-La-B非晶态合金催化剂,并采用X射线衍射、透射电镜、差热分析、X射线光电子能谱、电感耦合等离子光谱和H2程序升温脱附技术对催化剂进行了表征,研究了La含量对催化剂微观结构及其催化二硝基甲苯(DNT)加氢制二氨基甲苯(DAT)性能的影响.结果表明,随着助剂La含量的增加,Ni-La-B催化剂中非晶态结构的长程无序程度增大,催化剂平均粒径逐渐由70nm左右减小至10nm左右,分布更加均匀;同时降低了Ni吸附H2的强度,使H2吸附物种更易于在催化剂表面流动并参与反应.另外,La助剂还显著提高了催化剂的热稳定性和抗氧化性.在二硝基甲苯加氢反应中,催化剂性能随着La加入量提高至6%(摩尔分数)时,1MPa低压条件下DNT转化率和DAT选择性均达100%.当La加入量为8%时,催化剂的Ni活性中心数明显减少,其活性下降.

Preparation and Characterization of Ni-La-B Amorphous Alloy Catalyst for Low-Pressure Dinitrotoluene Hydrogenation

Ni-La-B amorphous alloy catalyst was prepared by KBH4 reduction for liquid phase hydrogenation of dinitrotoluene(DNT) to diaminotoluene(DAT).The effect of La content on microstructure and catalytic performance of Ni-La-B amorphous alloy catalyst for DNT hydrogenation was investigated.The catalyst was characterized by X-ray diffraction,transmission electron microscopy,differential scanning calorimetry,X-ray photoelectron spectroscopy,inductively coupled plasma emission spectroscopy,and H2 temperature-programmed desorption.The results showed that the addition of La could enhance the degree of long-range disorder,reduce the particle diameter from 70 to 10 nm,weaken the strength of Ni-H bond,and improve the thermal stability and antioxidation.The increasing of La addition from 0 to 6%(molar fraction) led to the enhancement of catalytic performance.When the addition of La was 0.6%,Ni-La-B catalyst exhibited the highest performance for low-pressure(1 MPa) DNT hydrogenation,the conversion of DNT and selectivity for DAT reached 100%.Further increasing of La addition from 6% to 8% led to decrease of the surface Ni content and the catalytic activity obviously.