Two-stage continuous process of methyl ester from high free fatty acid mixed crude palm oil using static mixer coupled with high-intensity of ultrasound

Abstract

The two-stage continuous process of methyl ester from high free fatty acid (FFA) mixed crude palm oil (MCPO) was performed by using static mixer coupled with high-intensity of ultrasound. The 2×1000W ultrasonic homogenizers were operated at 18kHz frequency in the 2×100mL continuous reactors. For the first-step, acid-catalyzed esterification was employed with 18vol.% of methanol, 2.7vol.% of sulfuric acid, 60°C of temperature, and 20Lh−1 of MCPO flow rate, for reducing the acid value from 28mgKOHg−1 to less than 2mgKOHg−1. For the second-step, base-catalyzed transesterification was carried out under 18vol.% of methanol, 8gKOHL−1 of oil, and 20Lh−1 of esterified oil flow rate at 30°C. The high yields of esterified oil and crude biodiesel were attained within the residence time of less than 20s in the ultrasonic reactors. The yields of each stage process were: 103.3vol.% of esterified oil, 105.4vol.% of crude biodiesel, and 92.5vol.% of biodiesel when compared with 100vol.% MCPO. The quality of the biodiesel meets the specification of biodiesel standard in Thailand.