| Due to the unique characteristics of super- and subcritical fluid, such as high dissolving capacity, high diffusion coefficient, and low viscosity, super-and subcritical fluid technology has been widely used in many fields. The phase equilibrium data and phase equilibrium theory are important foundations for industrialization of super- and subcritical fluid technology. However, research on super- and subcritical phase is deficient. In this work, the phase equilibrium research for aromatic hydrocarbon derivatives and polymer was systematically studied with experimental and theoretical methods. The main contents of the thesis are as follows:The experimental equipment based on static method was modified, and the reliability of the instruments and the operational conditions applied for static method and dynamic method were verified. Solubilities of solid solute including aromatic hydrocarbon derivatives and polymer with different molecular weight in supercritical carbon dioxide (CO2) and subcritical 1,1,1, 2-tetrafluoroethane (R134a) were investigated in this work. At temperatures 308 K,318 K, and 328 K, solubilities of o-aminobenzamide (o-AB), o-nitrobenzoic acid (o-NBA), and their mixture were measured at pressure ranging from 10.0 to 21.0 MPa in supercritical CO2 and pressure ranging from 5.0 to 15.0 MPa in subcritical R134a. At temperatures 313 K,323 K, and 333 K, solubilities of polyvinyl alcohol (with molecular weight 16000,47000, and 74800 g-mol-1) were measured at pressure ranging from 9.0 to 18.0 MPa in supercritical CO2 and pressure ranging from 7.0 to 15.0 MPa in subcritical R134a. All solubility data obtained in this work are determined first and have not been reported in literature before. These solubilities make a great contribution to the super- and subcritical phase equilibrium data bases, which provides supporting for the industrial application of super- and subcritical fluid technology.The trends of solutes solubilities with experimental temperature, pressure, solvent species, and polymer molecular weight were investigated; the effects of saturated vapor pressure of solute, solvent density, functional group, dipolemoment, and solubility paremeter on solute solubility were analyzed; in addition, the effects of co-solute on solubilities of solute mixture were discussed.About 10 empirical models, including Chrastil, A-L, K-J, S-S, Bartle, M-T, Gonzalez, Sovova, M-M-T, and Z-J models, were used for correlating the experimental data of solutes in supercritical CO2 and subcritical R134a in this paper. The correlation accuracy of these models was all satisfied. The self-consistency of the experimental data was satisfactorily determined by M-T model. And the dissolving thermodynamic properties of solid solutes were calculated with Chrastil, K-J and Bartle models.Due to the the low correlation accuracy of expanded fluid models for solute solubility of super- and subcritical system, a modified expanded liquid model, named M-δ1/v1 model, was proposed in this paper in which the effect of heat capacity term on solute solubility was considered. To verify the correlation accuracy of the M-δ1/x1 model,2365 solubility data of 90 kinds of solid solutes from literature, coupled with solubility of o-AB and o-NBA in this work (2425 data points in total), were used to compare the correlation accuracy of the five expanded liquid models including δ2～ρ, δ2～ρd, δ2～δ1/v1, β12～ρ2, and M-δ1/v1 models; in addition, t test was done to investigate the effect of adjustable parameter number on correlation accuracy. The correlation results showed that the maximum correlation accuracy of M-δ1/v1 model among the five expanded liquid models can be attributed to the consideration of heat capacity and its accurate model expression, rather than the more adjustable paramers compared with other expanded liquid models. Based on phase equilibrium theory of supercritical system, this work built a model with density functional theory (DFT) to predict polymer solubility in supercritical CO2. The equilibrium expressions for polymer and CO2 in solid phase and supercritical CO2 phase were established respectively. And the solubility of poly[oxy(methyl-1,2-ethanediyl)], polydimethylsiloxane, and polyethylene oxide in supercritical CO2 were predicted by DFT model and compared with literature data. The result of DFT model showed good predictive accuracy for polymers that the average AARD% value was 6.80%. DFT model provides a new method for theoretical prediction of polymer solublity in supercritical CO2. |
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