Recycable complex catalysts immobilized on mercaptan-functionalized glass-polymer supports

Abstract

The use of the mercaptan-functionalized bisphenol A diglycidyl ether epoxy (base material) encapsulated on glass core as matrices for metal catalysts was investigated. Here, the acquiring knowledge of recyclable palladium catalysts for organic reaction which can be mechanically separated from the reaction media and next use as a heterogeneous catalyst in large-scale industries was the most important goal. Homogeneous Pd precursor [PdCl2(PhCN)2] has been heterogenized by attaching to prepared glass-polymeric supports via ligand exchange process. Collected research results indicate that mercaptans used to cure epoxy resin can greatly affect the catalytic properties of the epoxy resin with supported palladium catalyst. The epoxy system modified with mercaptans has a few possible catalytic coordination centers especially oxygen and sulfur to which the palladium ion can be bound. It should be noted that although various concentrations of palladium complex were used, the amount of metal attached to epoxide supports remained the same, that is below the sorption capacity of the polymers. Presented new type of glass-polymer supports comparing to other used corresponding organic carriers offers several practical advantages such as morphological and chemical structure of the matrix, which affect the properties of the heterogenized catalyst in the selected organic reactions: Heck reaction and hydrogenation reaction were investigated. The catalytic activity of all formulated systems was similar to homogeneous palladium precursor PdCl2(PhCN)2. The resulting glass-polymeric matrices and heterogenized palladium catalysts were characterized by varied research techniques such as surface analysis technique (ToF–SIMS) and scanning electron microscopy with energy-dispersive X-ray analyzer (SEM-EDX). We used likewise the atomic absorption spectroscopy (AAS) method to quantify the amount of palladium loaded in the recyclable support and also the BET method to determine specific pore size distribution parameters. Furthermore, XPS spectroscopy showed information about surface structure and chemical states in the palladium-supported catalysts.