Properties of Rh-exchanged SiO2–Al2O3 sol–gel catalysts

Abstract

The addition of Al³⁺ to silica sol–gels reduces their N₂ adsorption capacity, total surface area and microporosity, but increases their ion-exchange capacity towards Rh⁺ to the extent that over half of the Al sites have exchange capacity towards Rh⁺. The metal so introduced is readily reduced in H₂ and is active in alkene hydrogenation, especially when present in less microporous gels produced by the presence of Al³⁺. The potential of this type of catalyst and how it might be optimised in future are considered.