Evaluation and kinetic study of alkaline ionic liquid for biodiesel production through transesterification of sunflower oil

Biodiesel production is performed in the industry by alkaline transesterification of oils with a low amount of free fatty acids. In order to reduce the disposal of conventional catalysts used industrially, ionic liquids (ILs) have been studied to be applied as catalysts in transesterification since they can be recovered and reused in subsequent reaction cycles. In this work, the ionic liquid choline hydroxide (ChOH) was successfully applied as a catalyst for the transesterification reaction of triacylglycerols present in sunflower oil with methanol. A kinetic modeling study under the specific conditions of 2 wt% catalyst dosage, 1:10 oil/methanol molar ratio, for 0–120 min at 35–65 ℃ was conducted, and liquid–liquid extraction with water/butanol was evaluated as a process to recover the IL. A 95.0% ester yield content was achieved in this work for a short reaction time (30 min). Furthermore, the results of the kinetic study demonstrated that a first-order model was the best fit for the reaction with a rate constant (k) estimated as 0.1182 min 1 and activation energy (Ea) of 13.64 kJ/mol. For the tested conditions, the complete recovery of the IL using liquid–liquid extraction did not occur since it is noted the presence of ChOH in both phases.The authors acknowledge Paula Plasencia and Maria João Afonso for their assistance in the laboratory. Furthermore, the authors are grateful to the Foundation for Science and Technology (FCT, Portugal) and FEDER under Programme PT2020 for financial support to CIMO (UIDB/0690/2020).