Acid-Catalyzed Esterification Pretreatment of High Free Fatty Acid Crude Rice Bran Oil for Biodiesel Production

This study investigated the acid-catalyzed esterification of two brands of crude rice bran oil (CRBO) with free fatty acids (FFAs) content of about 8 and 10%, respectively. Experimental variables included reaction time, methanol-to-FFA molar ratio and sulfuric acid content with temperature and stirring speed fixed at 60 °C and 600 RPM, respectively. A central composite design was used initially for sequential experimentation and followed by a Box-Behnken design to refine the optimum process conditions. Results showed that final FFA in CRBO could be reduced to less than 1% FFA in a single-step. The methanol-to-FFA molar ratio had the maximum influence on the esterification process and was followed by the reaction time and amount of catalyst. The optimum conditions for FFA conversion in CRBO were: reaction time 90 and 48 min, 62:1 and 70:1 methanol-to-FFA molar ratio, 22.5 and 20% (w/w) sulfuric acid based on FFA for Brand I and II, respectively. Under these pretreatment conditions, initial FFA was reduced to 0.61 and 0.70%, respectively making the CRBO suitable for biodiesel production

Optimization of Biodiesel Production Using Nanomagnetic CaO-Based Catalysts with Subcritical Methanol Transesterification of Rubber Seed Oil

The molar ratio of methanol to rubber seed oil (RSO), catalyst loading, and the reaction time of RSO biodiesel production were optimized in this work. The response surface methodology, using the Box–Behnken design, was analyzed to determine the optimum fatty acid methyl ester (FAME) yield. The performance of various nanomagnetic CaO-based catalysts—KF/CaO-Fe3O4, KF/CaO-Fe3O4-Li (Li additives), and KF/CaO-Fe3O4-Al (Al additives)—were compared. Rubber seed biodiesel was produced via the transesterification process under subcritical methanol conditions with nanomagnetic catalysts. The experimental results indicated that the KF/CaO-Fe3O4-Al nanomagnetic catalyst produced the highest FAME yield of 86.79%. The optimum conditions were a 28:1 molar ratio of methanol to RSO, 1.5 wt % catalyst, and 49 min reaction time. Al additives of KF/CaO-Fe3O4 nanomagnetic catalyst enhanced FAME yield without Al up to 18.17% and shortened the reaction time by up to 11 min