Biodiesel Production from Waste Cooking Oil Using Sequential Process Intensification Technique (Ultrasound and Microwave)

Abstract

The use of biodiesel as a renewable fuel has increasingly become more attractive due to its environmental advantages such as non-toxicity and biodegradability. While biodiesel has the capability to mitigate the energy crisis, its production is hindered by the availability of feedstock. The general drawbacks of the transesterification-based synthesis include high energy consumption, high operating cost, high separation times, and low production efficiency. The present study demonstrates an innovative and industrially viable biodiesel production process from waste cooking oil (WCO) as feedstock and KOH as a catalyst using sequential ultrasound (22kHz + 35kHz) and microwave (0 – 1000W) reactor. The sequential approach of ultrasound and microwave removes the barrier of mass transfer (high-velocity liquid jets and turbulence induced by ultrasound) and enhances the heat transfer (rapid dipolar moment induced by microwave) by their synergism while significantly improving the reaction efficiency and overall economics of the process. The reaction conditions that can attain a maximum yield of 96.9% were methanol/oil molar ratio, 7:1, catalyst concentration, 0.9 wt%, and reaction temperature, 62°C in 5 minutes of reaction time for a sample size of 4500 mL.