Abstract
We investigate ultrasound-assisted transesterification for biodiesel production. We use inline Raman spectroscopy to quantify its impact on reaction kinetics, catalyst reduction, and temperature sensitivity. We perform a systematic experimental study at different temperatures (50, 55, and 60 °C), different catalyst loadings, with and without ultrasound. The results show that ultrasound significantly accelerates early reaction kinetics at all temperatures, with the strongest effect observed at 55 °C, where both Fatty Acid Methyl Ester (FAME) formation rate and final conversion increase by up to 7 wt%. Under reduced catalyst conditions, ultrasound restores high conversion levels, leading to up to 20 wt% higher final FAME compared to operation without ultrasound and achieving performances comparable to, or exceeding, those obtained with (normal) catalyst without ultrasound. This is mainly because ultrasound primarily enhances mass transfer and phase contact, thereby reducing the system's sensitivity to catalyst loading. These findings demonstrate that ultrasound enables catalyst reduction while maintaining high biodiesel yields, enabling more sustainable and intensified transesterification processes.