Ir/C and Brφnsted acid functionalized ionic liquids: an efficient catalytic system for hydrogenation of nitrobenzene to p-aminophenol

Abstract

In this study, we found that the phenylhydroxylamine intermediate could desorb more easily from an Ir surface than from a Pt surface, which is beneficial for inhibiting the over-hydrogenation of phenylhydroxylamine to aniline. On the other hand, the Brφnsted acid functionalized ionic liquids with sulfonic acid and bisulfate anions were acidic enough to catalyze the Bamberger rearrangement to form p-aminophenol from phenylhydroxylamine. On this basis, a new catalytic system constructed by Ir/C and Brφnsted acid functionalized ionic liquid was applied, for the first time, to the one-pot hydrogenation of nitrobenzene to p-aminophenol. Our results indicate that the PAP selectivity of Ir/C and [SO₃H-bmim][HSO₄] Brφnsted functionalized ionic liquid was far more than that of the traditional Pt/C and sulfuric acid catalyst system. Furthermore, the dually functionalized ionic liquid ([HSO₃-b-N-Bu₃][HSO₄]) can be used simultaneously as an acid catalyst and also as a surfactant, due to its higher lipophilicity. Therefore, our new catalytic system has unique advantages in the hydrogenation of nitrobenzene to p-aminophenol.