Abstract
The present paper examines the performance of cubic equations of state (CEoSs) and semi-empirical density-based models in correlating the solubility in supercritical carbon dioxide (scCO2) of several solid compounds of interest to the food industry, namely 2-propenamide, bixin, β-carotene and C-tetramethylcalix[4]resorcinarene. The four target solutes are with increasing structural complexity and, are typically pure solids, at ambient or slightly elevated temperatures.The Soave-Kwong-Redlich (SRK) CEoS with the one-fluid van der Waals mixing rule was chosen as representative of the class of CEoSs, while the group of the density-based models includes Chrastil model, Kumar and Johnston model, Bartleet al. model, Méndez–Santiago and Teja model, Garlapati and Madras model, Nejadet al. model and Khansaryet al. model.The results obtained reveal that the more recently advocated density-based models (Garlapati and Madras, Nejadet al. and Khansaryet al. models) perform better than the other models with overall average absolute deviations, AARD %, of 6.3, 7.8 and 7.2 %, respectively. The 9.1% overall AARD for the SRK CEoS was considered satisfactory since it can be used as a reliable thermodynamic model to predict the solubility of any compound for which there are no sufficient experimental data available.
Highlights
In recent years, supercritical fluid (SCF) technology has considerably outgrown its first modest applications and nowadays a substantial number of high added value substances of interest to the food, nutraceutical, pharmaceutical, cosmetic, body care and hygiene industries are produced using SCFs [1]
The solutes of interest to the food industry are in their majority relatively non-volatile complex solids, and to correlate their solubility in scCO2 usually two groups of models are used: equations of state (EoSs) and semi-empirical equations
The results obtained for the two groups of models will be given and a comparison of their performance will be made on the basis of percentage average absolute deviations, AARD %, calculated between the experimentally measured and correlated results
Summary
Supercritical fluid (SCF) technology has considerably outgrown its first modest applications and nowadays a substantial number of high added value substances of interest to the food, nutraceutical, pharmaceutical, cosmetic, body care and hygiene industries are produced using SCFs [1]. The solutes of interest to the food industry are in their majority relatively non-volatile complex solids, and to correlate their solubility in scCO2 usually two groups of models are used: equations of state (EoSs) and semi-empirical equations. Other researchers examined semi-empirical models and their performance in correlating the solubility of important compounds in scCO2 [6 - 9]. The results obtained for the two groups of models will be given and a comparison of their performance will be made on the basis of percentage average absolute deviations, AARD %, calculated between the experimentally measured and correlated results These numbers, don’t reveal in an explicit manner the difficulties, both informational and numerical, accompanying the application of EoSs. We will just mention the necessity to know the solid solute properties like critical and fusion properties, solid molar volume, etc. On the other end are the density–based models which do not require any such data and their application is straight forward
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