Kinetics of the used cooking oil transesterification in the presence of slaked lime and the triethanolamine:menthol deep eutectic solvent

Abstract

AbstractThe biodiesel production from the used cooking oils from the frying of different food items (French fries, chicken breasts, or pork steaks) and methanol in the presence of slaked lime as a catalyst and the triethanolamine:menthol (1:2 mol/mol) deep eutectic solvent as a cosolvent was studied. This deep eutectic solvent accelerated the transesterification reaction. The transesterification reaction involves only the chemical reaction controlled region from its beginning and follows the pseudo‐first‐order reaction rate law. A good agreement between the model and the experimental data was confirmed by a low mean relative percent deviation between the predicted and observed values of triacylglycerol conversion degree (<3.5%). The highest apparent reaction rate constant of 0.421 min−1 was achieved with the used cooking oil from frying pork steaks at 60°C. The activation energy increases in the following order of the used cooking oils from frying the food items:French fries (23.1 kJ/mol) chicken breasts (30.7 kJ/mol) pork steaks (41.6 kJ/mol). A methyl esters content higher than 97.5% was achieved within 40 min of the transesterification of the used cooking oils over slaked lime combined with the triethanolamine:menthol deep eutectic solvent.