Ion Exchange Resins: Catalyst Recovery and Recycle

Recent achievements in the field of the heterogenization of homogeneous chemical catalysts onto ion-exchange resins are presented with the demonstration of recycling of the catalyst. The ion-exchange resins are based on cross-linked polystyrene-divinylbenzene copolymers bearing ion-exchanging functional groups and are classified as cation, strong acid, weak acid, and anion exchangers. The ruthenium derivative is found to be less selective compared to ruthenium in diphenylacetylene reduction, providing 1,2-diphenylethane in 62% yield, at 87.5% total conversion. Dicationic Mn-salen complexes immobilized on the macroporous strong cation exchange resins show that the catalysts are efficient and selective in the epoxidation of cyclic and linear alkenes. A strong cation exchanger Dowex 50WX8 used to immobilize the cationic porphyrins show that the supported iron porphyrins are characterized by activity and stability as compared to the corresponding homogeneous catalysts.