Study On Hydrogenation Catalysts Of Modified Ni-B Amorphous Alloy

Nowadays, Ni-B amorphous alloy which have the feture of short-range ordering,long-range disordering and metastable state of thermodynamic in strueture have beenwidely used in hydrogenation and became a focus in current research. The most commonmethod to prepare Ni-B amorphous alloy is chemical reduction. This method is anenvironmental friendly process because of its mild condition, water by-product and theboron oxide or boric acid which could be used for other processes. But the catalystsactivity were effected by the traditional preparation condition,the activity clusters ofnon-load amorphous alloy gathered easily and had the lower atom utilization, it is easy tooxidative inactivation, in addition it is easy to crystallize and the activity of catalystsuffered extent influence under high-temperature. Therefore, enhancing the catalytichydrogenation activity from the preparation of the catalyst is very important, such asmanipulation the surface properties, reducing the particle size of active component;increasing the dispersion of the activity atom clusters and improving the thermal stability.In this paper chemical reduction method was used to prepare the cheap, high activity,environmentally friendly nickel-based catalyst. Then the carrier and the nickel-basedcomplexes were inducted in this preparation. The surface properties of the catalysts werestudied by Transmission Electron Microscope（TEM）, Differential ScanningCalorimetry（DSC）, X-ray Diffraction（XRD）, X-ray Photoelectron Spectroscopy（XPS） andTemperature Programmed Desorption（TPD）, and the catalytic activity was studied by theliquid phase glucose hydrogenation.Investigate Ni-B respectively load on SiO₂and γ-Al₂O₃, via the nickel loading andthe carrier particle size changes to obtained that in the hydrogenation reaction, when theloading capacity is7.8%, the carrier particles mesh between40and60, the highconversion rate, and the catalyst was reused five times the impact of the conversion rate isvery small and can be reused.Industry use avermectin via selective hydrogenation to obtain ivermectin. Firstinvestigated the reaction conditions, that obtained optimal reaction conditions. PreparedNi-B/SiO₂, Ni-B/γ-Al₂O₃which the catalyst loading is7.8%, particle mesh between80and120when the reaction conversion and selectivity much better. The catalyst can bereused, and the catalyst is easy to product separation, greatly reduce the build cost to reduce environmental pollution, is green and environmentally friendly catalyst materials.The Ni-B amorphous alloy catalysts were prepared by reduction of nickel-hydrazinecomplexes with BH₄-under the ultrasonic power of100W, which exhibited the bestcatalytic activity, the higher dispersion and thermal stability, the uniform particle size （15nm）. But the particle size of Ni-B amorphous alloy catalysts which prepared by reductionof nickel-ethylenediamine complex with BH₄-under the ultrasonic power of100W wasabout10nm, the temperature of crystalline was enhanced and the thermal stability wasbetter.When reduction of Ni-based complexes with BH₄-, the first step was to broke thesteric hindrance formed by Ni2+and ligand, and then opened the bond energy of thecomplex, so the reduction could happen. Therefore the reduction rate of Ni-basedcomplexes was slow and avoided the unreacted metal ions to mix in the catalysts. Thekind and the number of the ligand are the both important factors to affect the catalystsforming. Moreover, the cavitation of ultrasonic have important effect to the surfaceproperties control of catalysts, and the catalysts of Ni-B amorphous alloy have the higherdispersion degree with surface activity center and the smaller particle size. But the effectsof the complexes with the surface properties can not to be neglected; only the combinedaction of the ultrasonic and the complexes can obtained the perfect Ni-B amorphous alloy.