Study On The Preparation And Catalytic Hydrogenation Performance Of Amorphous Ni-P Alloy

Amorphous alloy is a green,efficient catalytic material.Due to its unique structure with short-range order,long-range disorder and a highly unsaturated surface and high surface energy,Amorphous alloy catalyst exhibits better hydrogenation performance than Raney Ni catalyst.At present,many papers about Ni-P amorphous alloy catalyst had been published,but Ni-P catalyst has the disadvantages of small specific surface area,easy aggregation and poor thermal stability,which seriously affects its practical application.In this thesis,in order to solve the problems of the Ni-P amorphous alloy and improve its stability.the Ni-P amorphous alloy catalyst was studied from the facts of preparation method,adding additives and dispersing load,and then it was applied to the nitrobenzene hydrogenation reaction to test the catalytic performance.Firstly,the effect of preparation method on the performance of Ni-P amorphous alloy catalyst was investigated.The structure of Ni-P amorphous alloy was characterized by XRD,TEM,DSC and other methods.In the liquid-phase hydrogenation of nitrobenzene,the selectivity for corresponding aniline and the catalytic activity of the Ni-P amorphous alloy catalyst were investigated.The results showed that the short-range ordered range of Ni-P?30??amorphous alloy catalyst which induce-sythesized by KBH₄ is better than that of Ni-P?90??amorphous state alloy catalyst;the thermal stability of Ni-P?30??amorphous alloy catalyst was greatly improved.After the introduction of W,Ni-W-P amorphous alloy catalyst reduces the cost of response.In the nitrobenzene hydrogenation reaction,when the condition of Ni-P?30??0.17g,reaction time 2h,H₂ pressure 1.25MPa was employed,the reaction conversion and selectivity were 100%and 99.66%respectively.Secondly,Ni-P amorphous alloy was modified by adding additive W?Co?Mo and analyzed by a series of characterization methods.Then,the modified Ni-P amorphous alloy catalyst was used in the nitrobenzene hydrogenation reaction.The results showed that the catalytic activity of Ni-W-P amorphous alloy was much better than Ni-Co-P and Ni-Mo-P.The reason is that the atomic radius of W is bigger than the atomic radius of Co?Mo.At the same time,the specific surface area and the thermal stability of Ni-P amorphous alloy were improved by the introduction of w.Under the optimized reaction conditions,the amount of catalyst was 0.15g,the pressure of H₂ was 1.0MPa,the reaction temperature was 100?,the reaction time was 90min,the conversion of nitrobenzene and the selectivity of aniline reached100%which was better than that of Ni-P.The introduction of W greatly improved the stability of Ni-P amorphous alloy.The reaction conversion and selectivity were 99%and 97%after the catalyst was reused for 5 times,respectively.Finally,the supported Ni-P/ZrO₂ amorphous alloy catalyst was prepared by silver-catalyzed electroless plating.The catalyst was characterized by X-ray diffraction,transmission electron microscopy,differential thermal analysis,specific surface area-pore size distribution.The catalytic properties and structure of supported Ni-P/ZrO₂ amorphous alloy catalyst was discussed.In the liquid-phase hydrogenation of nitrobenzene,the selectivity for corresponding aniline and the catalytic activity of the as-prepared Ni-P/ZrO₂ amorphous alloy catalyst were investigated.The results showed that the particle size of Ni-P amorphous alloy after loading is obviously reduced,and the thermal stability of Ni-P amorphous alloy catalyst is obviously improved a lot.Ni-P particles were evenly dispersed on Ni-P/ZrO₂ due to Ag-induced directing deposition of the active component Ni-P.When the Ni loading was 30%,the amout of catalyst was 0.17g,with the reaction temperature of 383K,hydrogen pressure of 2.0 MPa and reaction time of 120 min,the conversion of nitrobenzene and selectivity of aniline all reached 100%.