Esterification of guaiacol with octanoic acid over functionalized mesoporous silica

Ester products, obtaining from guaiacol and octanoic acid which were the degeneration products of lignin, were tested over sulfonic acid-functionalized SiO2 materials. The results showed that the functionalized mesoporous SiO2 had a high activity and stability, resulting in ester yield of 62%. The ratio of S/phenyl played an important role in the activity and stability of SiO2-Phenyl-SO3H. Moreover, the optimal guaiacol to octanoic acid molar ratio is 8:1. The physicochemical, structural, textural and thermal stability characteristics of the synthesized mesoporous catalysts were investigated by X-ray diffraction (XRD), surface area analysis (Brunauer–Emmett–Teller equation), FT-IR and thermogravimetric analysis (TGA). The result of catalyst characterization and experiment of filtering catalysts from mixture showed that the SO3H- group incorporated with functionalized silica precursors. Moreover, the catalytic results indicated that SO3H-phenyl- group was the active part and the phenyl group increased the hydrophobicity of the catalyst surface, which accelerated the mobility of water, shifted the equilibrium, protected the acid sites and enhanced the activity of catalysts.