Reaction study for the esterification of oleic acid over M-SBA-15-SO3H (M=Al, Ti) catalysts.

Mesoporous M-SBA-15-SO3H materials with molar ratios of Si/M=10 (M=Al, Ti) and Si/S=10 were synthesized by sol-gel. The materials were characterised by SAXRD, nitrogen physisorption, UV-Vis-DRS, FT-IR, using pyridine as a probe molecule, and the H+ content was determined by sodium hydroxide titration. The incorporation of -SO3H groups resulted in Ti or Al mesoporous materials with the typical hexagonal arrangement of SBA-15. In addition, the materials possess Lewis and Brönsted acid sites, large surface areas and wide pores, being capable of catalyzing the esterification of oleic acid with high conversions (~97%) at 140°C. It was also demonstrated that the SBA-15-SO3H is more resistant to deactivation than Al-SBA-15-SO3H or Ti-SBA-15-SO3H catalysts. A simplified lumped first order reaction model reproduces well the experimental data for the acid esterification of oleic acid over SBA-15-SO3H at 60°C, 80°C, and 100°C. The calculated activation energy was 31.5 kJ mol-1, similar to other values reported for analogous systems.