Studies On Acid Catalysts For One-pot Synthesis Of P-aminophenol By Nitrobenzene

P-aminophenol(PAP)is an important commercial chemical raw material and widely used in the field of pharmaceuticals,dyestuffs,polyurethanes and photographic chemicals.The one-pot synthesis of PAP from nitrobenzene(NB)is regarded as the most promising route among the many synthetic methods.But this method need to use a large amount of low concentration of sulfuric acid as an acid catalyst for the Bamberger rearrangement reaction which brings about some serious problems such as considerable effluents and equipment corrosion.So,it has been one of the key points to replace sulfuric acid with another reusable acid catalysts in this reaction.On the basic study of hydrogenation of catalysts,we found that the phenylhydroxylamine intermediate could desorb more easily from Ir surface than from Pt surface,which was beneficial to inhibit the over hydrogenation of phenylhydroxylamine to aniline.In this paper,ionic liquids and commercial sulfonic acid resins used as acid catalysts with Ir/C hydrogenation catalyst were used to catalyze the one-pot hydrogenation of nitrobenzene to p-aminophenol.The use of ionic liquid and sulfonic acid resins is intended to replace sulfuric acid and achieve recycling.On the other hand,the synthetic ionic liquids are further modified to replace the surfactant simultaneously which is aimed to simplify the reaction system.Our results indicated that the selectivity of PAP had a significant relationship with the acidity of ionic liquids.The ionic liquids with sulfonic acid groups worked better than the simple protonic ionic liquids.Among these ionic liquids,([SO3H-bmim][HSO4])possessed the best catalytic performance and was better than that of traditional sulfuric acid system.Under the optimal reaction conditions,NB could be converted completely and the selectivity of PAP reached 64.8%.On the other hand,we found that the quaternary ammonium ionic liquid[HSO3-b-N-Bu3][HSO4]could serve as acid catalyst and surfactant simultaneously and showed good catalytic performance.The NB could be converted completely and the selectivity of PAP reached 50.8%without surfactant and better than that of sulfuric acid.At the same time,the catalytic performance of the bifunctional ionic liquid[HSO3-b-N-Bu3][HSO4]did not significantly decreased after used three times.For sulfonic acid resin,acidity is also a key factor affecting the selectivity of PAP.The PAP selectivity was higher than others when used CD650 sulfonic acid resin which has the stronger acidity.Under the reaction conditions of 100mL H2O,NB/resin = 0.3,0.05g CTAB,0.6MPa H2,110?,0.2g Ir/C and 600r.min-1,the conversion of NB was 100%and the selectivity of PAP was 36.1%.But the sulfonic acid resin need to be acidified to achieve the ability of reuse.