LEWIS ACID SITES OF Mg2+-MODIFIED POLYSTYRENE SULFONIC ACID RESIN CATALYSYS FOR SYNTHESIS OF DIBUTYL SUCCINATE
The polystyrene sulfonic acid resin catalysts were fabricated, containing elements of Cl and Mg through oxidization and impregnation, and they were characterized by EDS, FT-IR spectra, Py-IR spectra, UV spectra, XPS and TGA to investigate their physiochemical properties. The catalytic performances of these catalysts were examined in the esterification reaction of succinic acid with n-butanol, and the catalytic results showed that modified resins exhibited the highest catalytic activity and achieved a high yield of dibutyl succinate (91.6%) in addition, the modified resin generated new Lewis acid sites and showed significantly higher thermal stability. The experimental results demonstrated that the Mg2+ coordinated with a sulfonic acid group to form stable active sites, which effectively decreased the deactivation caused by the thermal degradation of sulfonic acid. Moreover, the monomer structures of polystyrene sulfonic acid resin and modified polystyrene sulfonic acid resin have been modelled using B3LYP/6-311G(d,p) approximation.