Sulfonic acid functionalized poly (ethylene glycol dimethacrylate-1-vinyl- 1,2,4-triazole) as an efficient catalyst for the synthesis of methyl propionate

Abstract

Sulfonic acid functionalized poly (ethylene glycol dimethacrylate-1-vinyl-1,2,4-triazole), poly (EGDMA-VTAZ-SO3H) (average diameter 1.0-1.5 mm), was found to be efficient solid acid catalyst for the esterification of methanol and propionic acid under heterogeneous reaction conditions. The pristine polymer, poly (EGDMA-VTAZ), was produced by suspension polymerization and then proton-conducting polymer was obtained by blending of poly (EGDMA-VTAZ) with different percentage of H2SO4 solutions. The protonation of aromatic heterocyclic rings was proved with Fourier-transform infrared spectroscopy (FT-IR). Thermo gravimetric (TG) analysis showed that the catalyst is thermally stable up to 573 K. The surface morphology of the catalyst was characterized by scanning electron microscopy (SEM). Poly (EGDMA-VTAZ-SO3H) beads can be regenerated and reused, so this provides a potential application. It has a rate constant which exceeds that of Amberlyst-15 by a factor of about four at 333 K. As for the reaction equilibrium constant (K-e), which is independent of temperature ranging from 318 to 343 K, was determined to be 3.16. The apparent activation energy was found to be 41.6 kJ mol(-1) for poly (EGDMA-VTAZ-SO3H).