Liquid-liquid equilibria and density data for pseudoternary systems of refined soybean oil + (hexanal, or heptanal, or butyric acid, or valeric acid, or caproic acid, or caprylic acid) + dimethyl sulfoxide at 298.15 K

Abstract

Odoriferous compounds and free fatty acids can be mildly removed from vegetable oils using organic liquid solvents. Liquid-liquid equilibrium data are presented for extraction of odoriferous compounds (hexanal, heptanal, butyric acid, valeric acid, caproic acid, and caprylic acid) from refined soybean oil using dimethyl sulfoxide. Six tie lines were measured for each system at 298.15 K and under atmospheric pressure. Quantification of mass fractions was carried out by gas chromatography-mass spectrometry (GC–MS) for hexanal and heptanal, by gravimetry in a vacuum oven for refined soybean oil, and by titration for carboxylic acids. Measured data showed a high extraction of short-chain carboxylic acids and very low amounts of oil in solvent-rich phases. Coefficients of partition lower than 1 were found for aldehydes. Satisfactory agreements were found for thermodynamic correlation by using the NonRandom Two-Liquids (NRTL) and the UNIversal QUAsiChemical (UNIQUAC) models, which presented global deviations lower than 0.55 and 0.71%, respectively. Moreover, four versions of the UNIFAC method were tested (UNIFAC-LL, UNIFAC-HIR, UNIFAC-DMD, and NIST-UNIFAC), wherein reasonable agreements were found for few cases.