乙腈液相选择性加氢中Ni-B非晶态合金和Raney Ni催化性能的比较

Comparative study on the catalytic performance of the Ni-B amorphous alloy and raney Ni during the liquid phase acetonitrile selective hydrogenation

以乙腈液相选择性加氢为目标反应,分别考察了超细Ni B非晶态合金和RaneyNi的催化性能,发现两者的质量比活性相似,但单位活性比表面积上前者的活性及对乙胺的选择性显著高于后者,乙胺的最高得率前者为67 6%后者为40%。通过催化剂的系统表征,结合考察乙腈加氢反应的动力学,从几何效应和电子效应两方面阐述了Ni B非晶态合金催化性能与催化剂结构和表面电子态的关系。

The ultrafine NiB amorphous alloy catalyst was employed in the liquid phase selective hydrogenation of acetonitrile,which exhibited much higher activity per m2 of the active surface area and better selectivity to ethlyamine than Raney Ni.The optimum yield of ethylamine over the NiB catalyst could reach 676%,much higher than 40% obtained over Raney Ni.According to various characterizations and the kinetic studies,the correlation of the catalytic performance to the structure and surface electronic state was discussed briefly.The higher activity of the NiB amorphous alloy than that of Raney Ni could be attributed to both the structural effect and electronic effect,such as the unique amorphous structure,the highly unsaturated Ni active sites,and the electronic interaction between the metallic Ni and the alloying B which made Ni electronenriched.While,the better selectivity to ethylamine on the NiB amorphous alloy than that on Raney Ni was mainly attributed to the electronic effect.According to the reaction mechanism of the acetonitrile hydrogenation,the reaction of the aldimine(CH3CH=NH)played a key role in determining the selectivity.The electronenriched Ni active sites were favorable for the aldimine hydrogenation leading to the ethylamine while unfavorable for the aldimine condensation with ethylamine leading to the diethylamine.