Production of Biodiesel from Crude Tall Oil via Microwave-Assisted Transesterification - Kinetic Studies

Abstract

Crude tall oil (CTO), a renewable by-product of the kraft pulping industry, is a promising non-food feedstock for biodiesel production. However, its high free fatty acid content and complex composition present significant challenges for efficient conversion using conventional heating methods. This study investigates the production of biodiesel from CTO through microwave-assisted transesterification and compares its reaction kinetics, and conversion efficiency with those of conventional heating. Transesterification reactions were carried out using methanol and sodium hydroxide (NaOH) as the catalyst under various temperatures and reaction times. Microwave-assisted reactions were performed in an Anton Paar Monowave reactor, while conventional heating experiments were conducted under comparable conditions. Reaction progress and biodiesel formation were monitored using high-performance liquid chromatography (HPLC), gas chromatography (GC), Raman spectroscopy, and Fourier-transform infrared spectroscopy (FTIR). Reaction kinetics were evaluated using a pseudo-first-order model, and activation energy was determined through Arrhenius analysis. The results showed that microwave-assisted transesterification significantly accelerated biodiesel production compared with conventional heating, achieving higher conversion in substantially shorter reaction times. The enhanced performance was attributed to rapid volumetric heating, improved heat and mass transfer, and more efficient energy utilization. Kinetic analysis further confirmed faster reaction rates under microwave irradiation. Overall, this study demonstrates that microwave-assisted transesterification is an effective process intensification strategy for converting crude tall oil into biodiesel. The findings provide valuable insight into the reaction kinetics of CTO transesterification and highlight the potential of microwave technology to improve the sustainability, efficiency, and economic viability of biodiesel production from industrial biomass-derived feedstocks.