The Research Of Hydrogenation Catalyst And Acid Catalyst Of Nitrobenzene Single Step To Synthesize P-Aminophenol

P-aminophenol (PAP) is an important organic intermediate and widely used for the production of medicine, dyestuff, rubber, etc. Single step synthesis of p-aminophenol by catalytic hydrogenation of nitrobenzene has the advantages of high yield, less waste emissions, low production costs, which is now recognized as the best route to the synthesis of PAP.Activated carbon supported noble metal (Pd、Pt) catalysts were used as the hydrogenation catalysts of synthesis of p-aminophenol by catalytic hydrogenation of nitrobenzene, the effect of physical-chemical properties of activated carbon supports and Pd/C\Pt/C catalysts metal particle size by HNO3pretreatment of activated carbon supports was researched. By N2-physical adsorption、Boehm、TEM、CO-chemiadsorption characterization, the average metal particle sizes of Pd、Pt catalyst of HNO3pretreatment of activated carbon supports and p-aminophenol selectivity all showed a regular change, which meaned synthesis of p-aminophenol by catalytic hydrogenation of nitrobenzene used activated carbon supported Pd、Pt catalysts was structure sensitive reaction. The average metal particle sizes of Pd、Pt catalyst first decreased and then increased with increasing HNO3pretreatment concentration, and p-aminophenol selectivity first increased and then decreased with increasing HNO3pretreatment concentration. The average metal particle sizes of Pd/C catalyst of5%HNO3pretreatment and Pt/C catalyst of1%HNO3pretreatment were the smallest, and p-aminophenol selectivity was the highest. P-aminophenol selectivity was relevant to adsorption capacity of active metal on intermediate hydroxy aniline, active metal with small size on intermediate hydroxy aniline had weak adsorption capacity, intermediate hydroxy aniline desorbed easily then p-aminophenol was generated by Bamberger rearrangement reaction. Meanwhile, adsorption capacity of Pt on intermediate hydroxy aniline was weaker than Pd greatly.A novel ionic liquid of Bronsted acidic quaternary phosphonium salt [HSO3-(CH2)4-P(Ph)3]HSO4was synthesized to instead of sulfuric acid was used for the single step synthesis of p-aminophenol. Under the reaction conditions of85℃、0.2MPa、4h、Pt/C0.2g、NB3.5g、CTAB0.03g、ILs40mL(mILs/mNB=7/1)、1000r-min-1, p-aminophenol selectivity was56.60%. Which achieved recycling of hydrogenation catalyst and acid catalyst.