Research Of Catalyst On Nitrobenzene Hydrogenation To P-Aminophenol

Green chemistry has attracted more and more attention in recent years. CO2 and H2O are very attractive because they have some unique features such as being non-toxic, non-flammable, abundant, cheap and easy to obtain. p-Aminophenol is an important intermediate for the production of analgesic and antipyretic drugs, such as acetaminophen. It is through a single-step catalytic hydrogenation of nitrobenzene in acidic medium. The process involves the catalyzed hydrogenation of nitrobenzene and the acid-catalyzed Bamberger Rearrangement of the hydrogenation intermediate product, PHA It is well known that CO2 can react with water, leading to the formation and dissociation of carbonic acid. The CO2-H2O system can replace conventional hazardous acids such as H2SO4 and solid acid for the catalysis rearrangement of phenylhydroxylamine, and the solution can be easily neutralized by depressurization without requiring salt disposal.This thesis discussed the effect of CO2 and H2 and substrate concentration and reaction temperature or solvent by selecting different catalyst such as Pt/C or Pt/Al2O3.Further-more, we discussed the role of CO2-H2O and hydrogenation catalyst in the hydrogenation of nitrobenzene to PAP.The research result show that the nitrobenzene nearly all consummation by the hydroph-obic catalyst Pt/C within 5h. The catalyst main disperses the phase of nitrobenzene because of the immiscible of nitrobenzene and water and this leaded to the intermediate hard to desorb from the surface of catalyst. We can only gain the 21% yields of PAP in the discussed experiment parameters. However, the phase behaviour changed if we selected the hydrophilic catalyst Pt/Al2O3. The intermediate can easy desorb from the surface of catalyst with the effect of scCO2.There is a possibility of the formation and adsorption of CO through reverse water gas shift reaction when hydrogenation reaction are conducted with supported metal catalysts in the presence of pressurized H2 and CO2. We can gain the 71% yields of PAP in the discussed experiment parameters.