P-Aminophenol synthesis in an organic/aqueous system using Pt supported on mesoporous carbons

Abstract

The biphasic conversion of nitrobenzene to p -aminophenol (PAP) via Pt/C-catalyzed hydrogenation of nitrobenzene and an acid-catalyzed rearrangement of the N -phenylhydroxylamine intermediate was studied. The effects of Pt/C catalyst loading, type of carbon support, reaction temperature, acid catalyst concentration, and additives were investigated. Pt catalysts supported on novel mesoporous carbons which have uniform pore diameters of 3 and 4.5 nm significantly outperform their counterpart supported on activated carbon. The biphasic conversion of nitrobenzene to p -aminophenol (PAP) via Pt/C-catalyzed hydrogenation of nitrobenzene and an acid-catalyzed rearrangement of the N -phenylhydroxylamine intermediate was studied. The effects of Pt/C catalyst loading, type of carbon support, reaction temperature, acid catalyst concentration, and additives on the reaction rate and PAP selectivity were investigated. At a given catalyst loading, nitrobenzene conversion and PAP selectivity were favored under a high reaction temperature and a high aqueous acid concentration. An increase in Pt/C catalyst loading leads to an increased hydrogenation rate but a lower PAP selectivity. Nitrobenzene conversion and PAP selectivity are both promoted by a small addition of N , N -dimethyl- n -dodecylamine, which may act as a phase transfer agent or emulsifier. Pt catalysts supported on novel mesoporous carbons – CMK-1 and CMK-3, which have uniform pore diameters of 3 and 4.5 nm – significantly outperform their counterpart supported on activated carbon with micropores. Two percent Pt/CMK-1 shows a catalytic activity equivalent to that of 5% Pt/C, but with significantly better PAP selectivity, i.e., 84% compared to 72%.