Enhanced biodiesel production from diseased swine fat by ultrasound-assisted two-step catalyzed process.

• Biodiesel was from diseased swine by ultrasound-assisted two-step catalyzed process. • Optimal condition was methanol/oil molar ratio of 7.42, 1.11 wt% KOH, 62.3 °C, 116.14 min. • The highest biodiesel purity (98%) was obtained in 176.14 min, reducing time by 63.3%. In order to enhance the yield of high quality biodiesel form diseased swine fat, the ultrasound-assisted two-step catalyzed process was employed. First, three-dimensional ultrasound-assisted concentrated sulfuric acid pre-esterification experiment was carried out. Then, the transesterification reaction catalyzed by KOH was performed, and four parameters (catalyst concentration, reaction time, methanol/oil molar ratio and reaction temperature) were optimized using response surface methodology. The results showed that the optimal transesterification reaction conditions were catalyst concentration of 1.11 wt%, reaction temperature of 62.3 °C, methanol/oil molar ratio of 7.42:1, and reaction time of 116.14 min. The most significant factor affecting biodiesel purity was identified as catalyst concentration. Under the optimal conditions, the maximum biodiesel purity reached to 98% with the reaction time of 176.14 min, shortened by 63.3% compared with previous works. Furthermore, most of the biodiesel properties agreed the quality requirements established by Official Regulations of GB/25199-2017 of China. [ABSTRACT FROM AUTHOR]