Ultrasound Induced Intensified Synthesis of Tricaprin Using the Homogeneous Acid Catalyst para-Toluene Sulfonic Acid

Abstract

The intensified process for synthesis of tricaprin from capric acid and glycerol is demonstrated using ultrasound in the presence of para-toluene sulfonic acid (PTSA) as the catalyst. The reaction was performed under solvent-free conditions with a fixed stoichiometric ratio of 3:1 (capric acid:glycerol), focusing on understanding the effect of the ultrasonic power and duty cycle as well as process parameters such as temperature and catalyst loading on the conversion of capric acid to tricaprin. Maximum conversion of 95.5% was obtained under optimum conditions of 100 W power dissipation, 70% duty cycle, 0.5% PTSA loading, and 80 °C. Use of a conventional approach under the same optimum conditions resulted in only 68.92% conversion. The reaction was studied at different temperatures, with and without ultrasound, to estimate the kinetic rate constants. It was found that the reaction followed first-order kinetics with a rapid increase in rate constants with an increase in temperature along with ultrasound. The activation energies were 12.16 and 18.8 kJ/mol for the ultrasound-assisted process and the conventional process, respectively, suggesting the intensification brought about by the use of ultrasound. Overall, it was clearly determined that the ultrasound-based technique intensified the reaction rate and lowered the activation energy compared to the conventional approach.