The solubilities of p-nitrobenzoic acid in supercritical carbon dioxide and carbon dioxide + cosolvents were determined at (308, 318, and 328) K and over the pressure range from (8.0 to 21.0) MPa. The effect of cosolvents, cyclohexane, ethanol, cyclohexane + acetone (equal-molar mixture), and acetone on the solubility of p-nitrobenzoic acid was studied at a mole fraction of 3.0 % (cosolvents in supercritical mixtures). The solubility data in supercritical carbon dioxide in the absence and presence of cosolvents were correlated by the equations proposed by Mendez-Santiago and Teja with satisfactory agreement, respectively.

The solubilities of pure and equal-molar mixed o-phthalic acid and p-aminobenzoic acid in supercritical carbon dioxide, were determined at 308.15, 318.15, and 328.15 K, and over the pressure range from 8.0 to 21.0MPa. 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 solubility of the other solid in the ternary system. The selectivity of supercritical carbon dioxide to the solid mixture increased with the increasing temperature. The model proposed by Mendez-Santiago and Teja was applied using statistical software to correlate the solubility data of both binary and ternary systems with good results.

The solubilities of benzoic acid in supercritical CO2 with pure and mixed cosolvent were measured at pressures from 8.0 to 23.0MPa and 328. 15Kfor pure cosolvent, and 308. 15, 318. 15 and 328. 15Kfor mixed cosolvent. The experiments were carried out by using a flow-type phase equilibrium apparatus. The effect of cosolvents, ethyl acetate, ethanol and ethyl acetate + ethanol (molar ratio 1:1) was studied at the concentration of 2.0 mol%. The results showthat the solubility enhancement follows the order: ethanol > ethyl acetate + ethanol > ethyl acetate. The measured solubilities were correlated using a modified Chrastil equation, and the calculated results are in good agreement with the experimental data.

Based on the membrane-based absorption experiment of CO2 into water, shell-side flow distribution and mass transfer in a randomly packed hollow fiber module have been analyzed using subchannel model and unsteady penetration mass transfer theory. The cross section of module is subdivided into many small ceils which contains only one hollow-fiber. The cross sectional area distribution of these cells is presented by the normal probability density distribution function. It has been obtained that there was a most serious non-ideal flow in shell side at moderate mean packing density, and the large amount of fluid flowed and transferred mass through a small number of large voids. Thus mass transfer process is dominated by the fluid through the larger void area.. The mass transfer process in each cell is described by the unsteady penetration theory. The overall mass transfer coefficient equals to the probability addition of the mean mass transfer coefficient in each cell. The comparisons of the values calculated by the model established with the empirical correlations and the experimental data of this work have been done. The predicted overall mass transfer coefficients are in good agreement with experimental data.

Five kinds of expanded polytetrafluoroethylene (ePTFE) flat membranes with different porosity and micro-pore size were chosen to carry out the unsteady state gas absorption experiments. The influence of the membrane porosity and micro-pore size on the membrane absorption process was investigated. Experimental results showed that the membrane porosity had an impact on the membrane absorption process, and the degree of this impact depended on the absorption system and the membrane pore size. For a rapid mass transfer process, the porosity affected the mass transfer more significantly, while for the slow mass transfer process the porosity almost did not affect the mass transfer. The modeling analysis showed that the porosity affected the concentration profile of the solute near the membrane surface on the liquid side, which led to the reduction of the mass transfer area of the membrane. Hence, the apparent effect on the mass transfer of the membrane absorption process.