Hydrogenation Reactions in Supercritical CO_2 Catalyzed by Metal Nanoparticles in a Water- in-Carbon Dioxide Microemulsion

摘要

Water-in-CO_2 microemulsions with diameters in the order of several nanometers are prepared by a mixture of AOT and a PFPE-PO_4 co-surfactant. The CO_2 microemulsions allow metal species to be dispersed in the nonpolar supercritical CO_2 phase. By chemical reduction, metal ions dissolved in the water core of the microemulsion can be reduced to the elemental state forming nanoparticles with narrow size distribution. The palladium and rhodium nanoparticles produced by hydrogen reduction of Pd~(2+)and Rh~(3+) ions dissolved in the water core are very effective catalysts for hydrogenation of olefins and arenes in supercritical CO_2.