Deacidification of Acidic Oil Catalyzed by Sulfonated Mesoporous Silica for Biodiesel Production: Optimization, Kinetic, and Enhancement by Using Calcined Kaolin

Acidified oil is characterized as high acid value. Hence, deacidification is indispensable in biodiesel production from acidic oil. Heterogeneous catalysts have many advantages over homogeneous counterparts in deacidification of acidic oil. Therefore, in the present work, sulfonated mesoporous silica (SMS) was prepared and characterized, followed by the systematical investigation on the effect of reaction variables on the deacidification rate (DR). Furthermore, response surface methodology (RSM) was employed to optimize the reaction parameters. Results showed that the optimal studied reaction variables for the deacidification process were as follows: reaction temperature 65 °C, methanol to oleic acid ratio 35:1, catalyst loading of 2%, in which, deacidification rate of 97.78% could be achieved. DR of 62.52% could still be obtained after catalyst had been used for four consecutive cycles. Finally, significant enhancement of DR could be achieved by using calcined kaolin to assist the deacidification of acidified oil with high water content, indicating that there is great potential in deacidification of acidic oil catalyzed by SMS with the assistance of calcined kaolin for biodiesel production.