Abstract
To discover particular features of pure supercritical fluids, important for the supercritical fluid extraction and cleaning technologies, the preprocessed and generalized experimental data from the US National Institute of Standards and Technology (NIST) online database have been analyzed. The soft transition between gas-like and liquid-like structures in pure supercritical fluids has been considered in comparison with the abrupt vapor-liquid phase transition. A rough, diffused and boiling boundary between these structures in conditions of extra high gravity is opposed to a flat vapor-liquid boundary at a moderate gravity. The model for molecular diffusivity in carbon dioxide at temperatures near the critical temperature discovers its proportionality to the monomer fraction density. The cluster fraction based model for small molecular weight solids’ solubility in supercritical fluids has been suggested and successfully compared with the well-known experimental results for the solubility of silica in water.The model shows that at growing pressure the dissolution process has already startedin a real gas and discovers the cluster fractions’ role in the solubility process.
Highlights
Supercritical Fluids (SFs) present a growing interest for modern chemical technologies, such as the Supercritical Fluid Extraction (SFE) [1,2] and Supercritical Fluid Cleaning (SFC) [3]
A high resolution of the Supercritical Fluid Chromatography and Supercritical Fluid Chromatography—Mass Spectrometry in pharmacological analysis was demonstrated by Ilia Brondz and Anton Brondz in [4]
The data improvement process is developed by the Thermodynamics Research Center (TRC) of the US National Institute of Standards and Technology [9] and is named as the critical evaluation of experimental data
Summary
Supercritical Fluids (SFs) present a growing interest for modern chemical technologies, such as the Supercritical Fluid Extraction (SFE) [1,2] and Supercritical Fluid Cleaning (SFC) [3]. High diffusivity and low viscosity of SFs permit higher flows of substances in chromatography columns, which provide a quicker separation, better resolution and effectiveness of the chromatography process and higher purity of selected products. The data improvement process is developed by the Thermodynamics Research Center (TRC) of the US National Institute of Standards and Technology [9] and is named as the critical evaluation of experimental data. Its main idea sounds as: “critical evaluation is a process of analyzing all available experimental data for a given property to arrive at recommended values together with estimates of uncertainty, providing a highly useful form of thermodynamic data for our customers. More practical goals are to correlate the pressure driven steep solubility growth in SFs [1,10] with the structural transition from the gas-like to the liquid-like supercritical fluid and to correlate the high diffusivity [1] of molecules in supercritical fluids with the monomer fraction density [11]
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