| Para-aminophenol(PAP)is an important organic chemical raw material and pharmaceutical intermediate.It is widely used in medicine,dyes,rubber and photographic industries.In medicine,it is mainly used for the production of antipyretics,VB1,etc.The dyes are mainly used for the synthesis of various functional dyes.At present,p-aminophenol is mainly prepared by one-step hydrogenation rearrangement of nitrobenzene in the world,and precious metals Pt and Pd are commonly used as active components,and there are problems such as high catalyst cost and unfriendly environment.With the development of catalytic technologies,more and more people are paying attention to new catalysts and inexpensive and readily available catalysts.At the same time,liquid-phase hydrogenation has the advantages of convenient operation,mild conditions,etc.Therefore,this paper mainly focuses on nitrobenzene(NB)plus The development of the hydrogen process,the optimization of the process to achieve low-cost,high-yield production of p-aminophenol,and focused on the cheap and easy to obtain activated carbon loaded non-noble nickel-catalyzed nitrobenzene liquid phase hydrogenation of p-aminophenol performance.The product of liquid phase hydrogenation was characterized by GC-MS.The main products were p-aminophenol,aniline and azo compound.HPLC was used for quantitative analysis.The standard curve was determined by external standard method.The mobile phase was methanol:Water = 70:30 establishes the optimum chromatographic conditions.A series of nickel-based catalysts were used for the liquid-phase hydrogenation of nitrobenzene.The catalysts were characterized by BET,XRD,H2-TPR,TEM and other methods.The nickel loading,sulfuric acid concentration,and surfactant were investigated.The effect of a series of factors such as the addition amount,temperature,pressure,and reaction time on the hydrogenation performance revealed that the catalyst was loaded with 20%Ni/AC catalyst at 140?,1.0 MPa,15%dilute sulfuric acid,and 4 hours reaction time.The performance is relatively optimal,the conversion of nitrobenzene reaches 75.56%,and the selectivity to p-aminophenol is close to 30%.Taking into account the performance issues of the previous single-active nickel-carbon catalyst,five metals,such as Pt,Zn,and Co,were selected to modify the nickel-carbon catalyst.The types of additives,the amount of additives added,and the reduction temperature were compared.Influence of Optimum process conditions on the hydrogenation performance of nitrobenzene in Liquid Phase.It is found that the modification of Ni/AC by additives is mainly reflected in lowering the reduction temperature of nickel oxide,promoting the reduction of nickel oxide in Ni/AC,and the dispersion of active metal nickel,thereby affecting the effect of hydrogenation.Through experimental comparison,it can be found that the effect of catalytic hydrogenation of 1.0%Pt-20%Ni/AC to prepare p-aminophenol is best.The reaction is carried out under the conditions of temperature 140?,hydrogen pressure 1.0MPa,reaction 4h,NB The conversion rate can reach 99.72%,and the selectivity of PAP can reach about 62.35%.At the end of this paper,a preliminary investigation of solid acid was conducted.By examining the effect of different silica-alumina ratio on the reaction results,the results showed that the selectivity of the target product was not significantly related to the acid position of solid acid. |
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