Study of the diffusion coefficient of solute-type extracts in supercritical carbon dioxide: Volatile oils, fatty acids and fixed oils

Supercritical carbon dioxide (SCCO) extraction is an innovative and efficient method to recover valued substances from vegetal materials. The diffusion behavior of the extract in the supercritical solvent is an important parameter to understand the mass transfer behavior of the process. In this work, experimental data from the literature were utilized to analyze the diffusivity of lipophilic chemically similar solutes in SCCO. Substances with similar chemical structure, molecular weight and volatility, have also very similar diffusion coefficients, which are mainly determined by temperature, pressure and, in turn, by the corresponding physicochemical properties of the supercritical solvent (density and viscosity). Based on this premise, general correlations were derived to represent the diffusion coefficient of volatile oils, fatty acids and its esters, and fixed oils (triglycerides) in SCCO as a function solely of pressure and temperature. The diffusion coefficients obtained were satisfactory compared with those calculated with theoretical and semi-empirical models from the literature, which require pure component parameters.López-Padilla A thanks to COLCIENCIAS (568–2012) and Medellin Mayor's Office (Sapiencia/Enlaza Mundos Program, 2013) for the Ph.D. fellowship. This work was financed thanks ALIBIRD, S2013/ABI-2728 (Comunidad de Madrid) project.Peer Reviewe