LIQUID-PHASE OXIDATION AT METAL-IONS AND COMPLEXES IN CONSTRAINED ENVIRONMENTS

Various approaches towards the rational design of novel catalysts base d on the concept of confinement (site-isolation) of redox active metal centres in molecular sieves are reviewed. These comprise (a) substitu tion of T elements (Si, Al and P) in the framework of silicates, zeoli tes, AIPOs and SAPOs, (b) encapsulation of metal complexes in intrazeo lite space (ship-in-a-bottle catalysts) and (c) grafting or tethering of metal complexes to the internal surface of the molecular sieves. Re lated materials - redox pillared clays, clay intercalated metal comple xes, redox aerogels and metal complexes incorporated in aerogels - are also reviewed. The advantages and limitations of the various material s with regard to activity and selectivity as catalysts for liquid phas e oxidations with O-2, H2O2 and RO2H and stability towards leaching, a re discussed. (C) 1998 Elsevier Science B.V. All rights reserved.