Triethanolamine-based deep eutectic solvents as cosolvents in biodiesel production from black mustard (Brassica nigra L.) seed oil

Abstract

The application of triethanolamine (TEOA)-based deep eutectic solvents (DESs) with glycerol (G), propylene glycol (PEG), 1,3-dimethylurea (DMU), ethylene glycol (EG), menthol (M), oleic acid (OLA), decanoic acid (DEA), and choline chloride (ChCl) (1:1, 1:2 or 2:1 mol/mol) in the CaO-catalyzed black mustard seed oil (BMSO) ethanolysis was studied. The ethanolysis was performed at 70 ºC, 12:1 ethanol-to-oil molar ratio, 20% DES, and 10% CaO (to BMSO). It was accelerated by the DESs with G, PEG, ChCl, DMU, M, and DEA and resulted in a higher fatty acid ethyl ester (FAEE) content (≥95.2 ± 0.6%) in 15 min than the control reaction. The TEOA:ChCl DES was most effective, providing within only 1.5 min an FAEE content of about 98.5%. With the TEOA:M and TEOA:PEG DESs, the FAEE content of over 91% was achieved for this time. Furthermore, the final product separation was achieved faster with all the applied DES than in the control reaction. With the TEOA:M and TEOA:ChCl DESs, separation was achieved immediately after the stopping of mixing and for 1 min, respectively. Two kinetic models were used for modeling the BMSO ethanolysis over CaO assisted by the TEOA:ChCl DES. The CaO reusability in three runs exceeded the FAEE content of 90%.