Feasibility of Using High-Intensity Ultrasound Assisted Biodiesel Production from Mixed Crude Palm Oil in Two-Step Process

Abstract

Biodiesel from a high free fatty acid (FFA) mixed crude palm oil (MCPO) can be produced to high fatty acid methyl ester (FAME) conversion by a two-step process. The first process is an acid-catalyzed esterification to reduce FFA in oil followed by a base-catalyzed transesterification process to produce biodiesel from esterified oil. In this study, the transesterification of esterified oil with methanol in the presence of potassium hydroxide (KOH) was performed in a 1,000 W ultrasonic homogenizer at a low frequency of 18 kHz. The use of high-intensity ultrasound to accelerate the reaction, the high surface power density of 1.62 W.mm-2 and the volumetric acoustic energy of 20 W.mL-1 were fixed. The objective of this study was to determine the various parameters (methanol concentration, KOH concentration, and initial temperature of oil) to produce the FAME conversion. The results showed that over 98 wt.% of FAME could be achieved with 5 g KOH/liter of oil, 15 vol.% of methanol, the total residence time of 20 seconds, and temperature of 30 oC. Moreover, the glycerides were rapidly converted to the FAME within reaction time of 10 seconds when the base-catalyst of 10 g KOH/liter of oil, and 20 vol.% of methanol were used. Consequently, the use of high-intensity ultrasonic irradiation can minimize the chemical cost, electricity cost, and reaction time.