Aqueous Rhodium Colloidal Suspension in Reduction of Arene Derivatives in Biphasic System: a Significant Physico-chemical Role of Surfactant Concentration on Catalytic Activity

Abstract

The hydrogenation of benzene derivatives represents an important industrial catalytic transformation. An original approach is to use transition metal nanoparticles that are finely dispersed in liquid media. During the last decade, these nanoparticles have been largely characterized by sophisticated techniques. Recently, we have described the hydrogenation of arene derivatives in liquid-liquid systems catalyzed by an aqueous suspension of rhodium nanoparticles stabilized by a cationic surfactant. Here, we demonstrate that the modulation of surfactant concentration fundamentally influences the turnover frequencies (TOF's) in hydrogenation of classical benzene derivatives such as anisole, toluene and p-xylene. A maximum TOF is obtained when the surfactant concentration is about the critical micellar concentration. In this condition, the Rh(0) stabilized nanoparticles are up to 5-fold more active.