Mesoporous silica encapsulating Rh(0) colloids: structure and catalytic properties

Colloidal metallic precursors have been used successfully to prepare new rhodium(0) supported mesoporous catalysts. The aqueous dispersion of Rh(0) previously synthesized was added either (i) to preformed mesoporous silica (MCM-41 or SBA-15) or (ii) to the gel mixture used for the solid synthesis. The different materials have been characterized by TEM, N 2 adsorption-desorption, PXRD and elemental analysis. All the solids, especially those obtained by the direct route, reveal well-organized mesoporous structures. Their catalytic activity was investigated in the hydrogenation of aromatic ring (conversion of styrene into ethylcyclohexane) and was shown to be better in hexane than in ethanol. The solids prepared by impregnation of MCM-41 and SBA-15 with Rh(0) colloids (pathway (i), afforded the best yields of ethylcyclohexane (up to 100% in hexane and 72% in ethanol, respectively).