Study On The Equilibrium Of Solid And Solid Mixture In Supercritical Fluid With Cosolvents

Supercritical fluid science and technology is very promising, and the equilibrium of solid and solid mixture in supercritical fluid is always indispensable to the development of supercritical fluid science and technology. Therefore, some works have been carried out as follows:On the basis of researching in the equilibrium of single solute in supercritical fluid, after the establishment of new analytical methods, the study on the equilibrium of solid mixture in supercritical multi-system had been carried out in this thesis.When turn to the experimental research, the influence of operational condition on the solubility of single solute or solid mixture in supercritical fluid has been fully investigated in this thesis. The investigated single solute included p-nitrobenzoic acid, p-hydroxybenzoate and4-methylbenzenesulfonic acid. The investigated solid mixture included 5-sulfosalicylic acid + p-aminobenzoic acid (1: 1 equal-molar mixed), o-phthalic acid + p-aminobenzoic acid (1: 1 equal-molar mixed) and ethyl p-hydroxybenzoate + ethyl p-aminobenzoate (1: 1 equal-molar mixed). The pure cosolvent included methanol, ethanol, normal propanol, normal butyl alcohol, acetone, normal hexane, ethyl acid and ethyl acetate. The mixed cosolvents are acetone + normal hexane (1:1 equal-molar mixed) and ethyl acid + ethyl acetate (1:1 equal-molar mixed). The experimental temperatures are 308.15, 318.15 and 328.15K, and the pressure ranging from 8.0 to 21.0 MPa. 325 data points had been measured in this thesis.The effect of temperature, pressure, molecular structure on the solubility of single solute in pure supercritical CO₂ was investigated, and the influence of temperature, concentration and category on the effect of single or the mixed cosolvent was also studied.The solubility of a given solid in a ternary system increased relative to the value of the corresponding binary system, and was in proportion to the solubilities of the other solid in the ternary system. The selectivity of supercritical carbon dioxide to the solid mixture increased with the increasing temperature. The cosolvent effect and selectivity for the same entrainer on the single solute and the given solute of solid mixture was compared for analysis.Based on the cross-sectional study on the structural chemistry and topology theory, the novel valence had been defined and then some revised molecular connectivity indices (RMCIs) have been established. After inserting RMCIs into density-based models, some new model had been consequently exploited: Enlightened by the law of large numbers, a model is established by virtue of molecular topology through the one-off correlation of large training sets. After the self-consistent tests on the solubility data of one solute and a series of aromatic solutes, this model can eliminate both the operational and systematic errors that exist in solubility data. Whether solubility data of measured compounds are underestimated or overestimated can also be diagnosed by this model.Enlightened by inductive-deductive thought, through the introduction of molecular topology into the supercritical field, the relation of aromatic solutes' solubility to their molecular structures is developed by a one-off correlation of large training sets, and then this inductive relation has been used to predict the solubility data for other aromatic compounds. The application of RMCIs in other supercritical fluid had also been considered in this thesis.Because the multi-system investigated belongs to the system of high-dissymmetry, in order to match the EOS and mixing rules, the model of EOS-G^E-UNIFAC was selected to study the experimental data. However, there were not interactive parameters among the specific group and CO₂, so the Simplex Method was used to correlate these parameters by virtue of computer procedure. Referring to some points of Perturbed Hard Chain Theory (PHCT), and the EOS-GE-UNIFAC was extended to the 3-parameter EOS to form a new MTC-PT-MDUNIFAC model.To mach the EOS and mixing rules, the items associated with volume (i.e. the b_m, c_m of PT EOS and combination item of MDUNIFAC) were systematic restructured in this thesis, and then the effect of "1+1+1>3" has been obtained. Lastly, the MTC-PT-MDUNIFAC was applied to predict solubility of some single solutes and solid mixture in supercritical fluid. Through the calculated results of different models, the quality of simulation is as follows: MTC-PT-MDUNIFAC > PT+WS > PR + VDW > PT + VDW. That is to say, it is not always true to select the more complex EOS and mixing rules, the coordination and cooperation of EOS and mixing rules may be more important.This work has been supported by the National Natural Science Foundation of China (No.20676008), the University Doctor of Science Foundation of China (No. 20020010004), and the Important Sci-Tech Research Program of the Ministry of Education of China (Important: 00017).