Preparation of ultrafine palladium particles in reverse micelles and application for hydrogenation catalysts

The preparation of ultrafine Pd and Pd-Au particles, in AOT (sodium bis(2-ethylhexyl) sulfosuccinate), CTAC (cetyltrimethylammonium chloride) and C(18)E(7) (polyoxyethylene (7) oleyl ether) reverse micelles, using KBH(4) as a reducing agent, has been studied. Excess KBH4 is required, because part of this is lost by hydrolysis and also by reduction of the surfactants. The particles in reverse micellar solution exhibit an activity for the hydrogenation of both water-soluble allyl alcohol and water-insoluble styrene, but the activity is inhibited by the surfactant molecules. Immobilization of the particles on solid supports, derivatized with a thiol-terminated silane, was carried out, aiming at possible applications as supported catalysts. The supported catalysts also exhibit hydrogenation activity, when the surfactant molecules are removed from the surface of the catalysts by calcination.