Study On Solubility Of Solute In Pure And Modified Supercritical Carbon Dioxide

Supercritical carbon dioxide has been paid more and more attention indifferent fields by virtue of the low critical temperature （T_c=304.2K）,solvent-free residue, inexpensive，non-polluting and other characteristics.Solubility data of compounds in supercritical carbon dioxide （SCCO₂） areamong the most important fundamental data, which are essential to thesupercritical fluid process design. Researches on the experimental andtheoretical aspects in this field are relatively scarce currently. In this article,the solubility of organic solids were measured in supercritical carbon dioxidewith or without cosolvents at temperature range （308-328） K and pressurerange （10.0-21.0） MPa, the experimental data have been correlated bydifferent models with satisfactory results. Sovova model has been modifiedwith better precision about5%on average. The major reasearches arepresented as follows:As for the experimental research aspect, the solubility of o-tolidine,o-nitrobenzoic acid （o-NBA） and the solid mixture of o-nitrobenzoic acid and3,5-dinitrobenzoic acid （3,5-DNBA） in supercritical carbon dioxide with orwithout cosolvents have been measured; ethanol, ethyl acetate, ethylene glycolwere chosen as the cosolvents. The effects of temperature, pressure, functionalgroup, different concentrations and types of cosolvents on the solubility wereinvestigated, and the interaction between multiple components of the solidmixture has also been analyzed.135sets of solubility data have beenmeasured in this article, which could enrich the database of the supercriticalfluid phase equilibrium and make useful exploration for the development ofsupercritical fluid technology.As for the theoretical research aspect, the experimental data have beencorrelated by Chrastil, Bartle, Méndez-Santiago and Teja （MST） and K-Jmodels in the system without cosolvents and by modified Chrastil, modifiedMST and Sovova models in the system with cosolvents, the results aresatisfactory. Based on the theory that complex relationship may exsit betweensolubility and temperature，pressure, density of the SCF, Sovova model hasbeen modified. Using1465sets of data of23compounds in this paper and theliterature, the correlation result shows that the calculation error of modifiedSovova model was reduced from11.58%for Sovova model to6.30%formodified Sovova model on average, which proves that the modified modelcould receive a good correlation result with better precision.