Development of highly efficient solid acid catalysts supported on mesoporous KIT-6 for esterification of oleic acid

Abstract

This study aimed at the synthesis of heterogeneous acid catalysts by incorporating 12 tungstophosphoric acid (HPW) over mesoporous silica support KIT-6 via impregnation and sol-gel methods to improve the catalytic efficiency of the esterification reaction. The catalytic activity of the KIT-6 supported catalysts was investigated for esterification of oleic acid in the presence of MeOH. Synthesized catalysts were analyzed using scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) and Fourier transform infrared (FTIR) spectroscopy techniques. Characterization results showed the variation in porosity, roughness, presence of SiO2 and kegging structure after successful deposition of HPW over KIT-6 surface. Additionally, the textural property of synthesized catalysts was compared with highly active HPW and sulfated KIT-6. The ordered structure of mesoporous silica KIT-6 facilitated the dispersion of HPW resulting in better catalytic stability and activity. To evaluate the impact of synthesizing technique on catalytic activity and effectiveness of heterogeneous acid catalysts, loading of HPW over KIT-6 mesoporous silica was controlled between 10 to 30 wt%. Catalysts synthesized by impregnation and sol-gel methods showed the highest catalytic activity with 30-IM and 25-SG, respectively. The enhanced performance was ascribed to the improved textural property and amount of HPW, which led to higher activity, stability and reusability.