Promotion Effect of Mo in Amorphous Ni-P Catalysts for the Liquid-Phase Catalytic Hydrogenation of Nitrobenzene to Aniline

摘要

Amorphous Ni-P catalysts were prepared by a chemical reduction method, and the promotional effects of Mo on the hydrogenation of nitrobenzene to aniline on Ni-P catalyst were investigated. However, the two crystallization temperatures of the 1% Ni-Mo-P catalyst were 644 K and 723 K, which were 15 K and 43 K higher, respectively, than those of the Ni-P catalyst itself; these results indicate that the presence of Mo increased the thermal stability of the Ni-P catalysts. SEM results showed that the particle size of the active component of Ni-P in the 1.0% Ni-Mo-P catalyst was smaller than that in the amorphous Ni-P catalyst. The N2 adsorption isotherms for the amorphous Ni-Mo-P catalysts were the III-type, and the N2 isothermal adsorption-desorption curves exhibited Hj-type hysteresis loops. H2-TPR results showed that the addition of Mo had no effect on the reduction of NiO in the catalyst but negatively affected the reduction of Ni-P-O. H2-TPD results showed that the hydrogen adsorption capacity of the amorphous Ni-P catalysts can be enhanced through the addition of Mo, and the optimal amount of Mo was determined to be 7.0%. The XPS results indicated the presence of a small amount of free metallic Mo in the amorphous Ni-Mo-P catalysts in addition to the Mo in MoO3. The use of 7% amorphous Ni-Mo-P catalyst at 383 K and under 1.0 M Pa of hydrogen for 3.0h resulted in a nitrobenzene conversion rale and aniline selectivity of 64.5% and 98.8%, respectively.