The solubilities of glutaric acid in binary cyclohexane + cyclohexanol solvent mixtures at 298.05− 343.65 K, in binary cyclohexane + cyclohexanone solvent mixtures at 299.10−340.65 K, in binary cyclohexanone + cyclohexanol solvent mixtures at 299.75−343.65 K, and in ternary cyclohexanol + cyclohexanone + cyclohexane solvent mixtures at 298.15−330.95 K were studied by the dynamic method. The results show that the solubility of glutaric acid increases as temperature increases at constant solvent composition in three determined binary solvent systems. For binary cyclohexane + cyclohexanol and cyclohexane + cyclohexanone solvent mixtures, solubilities of glutaric acid decrease monotonically with the increasing mass fraction of cyclohexane in solvent mixtures at constant temperature. However, for binary cyclohexanone + cyclohexanol solvent mixtures, cyclohexanone with a mass fraction at 0.6 in solvent mixtures has the best dissolving capacity for glutaric acid at constant temperature. The experimental solubility data of three determined binary solvent systems were correlated by the Apelblat equation and nonrandom two-liquid (NRTL) activity coefficient model, and the correlated solubilities data were in good accord with the experimental data. The obtained binary interaction parameters for the NRTL model were used to calculate the solubilities of glutaric acid in the ternary cyclohexanol + cyclohexanone + cyclohexane solvent mixtures, which were compared with the experimental solubilities data.

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The solubilities of succinic acid in binary cyclohexanone + cyclohexanol solvent mixtures at 304.25–354.65 K, in binary cyclohexane + cyclohexanol solvent mixtures at 300.15–346.15 K, in binary cyclohexane + cyclohexanone solvent mixtures at 297.65–351.25 K, and in ternary cyclohexanol + cyclohexanone + cyclohexane solvent mixtures at 306.95–343.15 K were determined by the synthetic method at atmospheric pressure. The experimental solubility data in binary solvent mixtures were correlated by the Apelblat equation and nonrandom two-liquid (NRTL) activity coefficient model, and the calculated solubility data by the models have a good agreement with the experimental data. Then, the solubilities of succinic acid in ternary cyclohexanol + cyclohexanone + cyclohexane solvent mixtures were predicted by the NRTL model and compared with the experimental solubility data. Finally, the solubilities of succinic acid in the three studied binary solvent mixtures were compared with the solubilities of glutaric acid and adipic acid in the same solvent systems at 303.15–343.15 K. The result shows that in the three studied solvent mixtures, glutaric acid with an odd number of carbon atoms is much more soluble than succinic acid and adipic acid with an even number of carbon atoms. The reasons for this “odd–even effect” phenomenon are the interlayer packing of molecule chains and the twist of the carbon chains.

The solubilities of phthalic acid and o-toluic acid in binary acetic acid (HAc) + water and HAc + o-xylene solvent mixtures were measured by a dissolution temperature method at atmospheric pressure. The mole fractions of HAc in the corresponding solvent mixtures range from 0.00 to 1.00. The measured data show that, within the temperature range studied, the solubilities of phthalic acid and o-toluic acid increase with the increasing temperature at constant solvent composition and initially decrease with the decreasing mole fraction of HAc in HAc + o-xylene and HAc + water solvent mixtures at constant temperature, respectively. It also shows that, within the solvent composition range studied, the HAc + water solvent mixtures with the mole fraction of HAc at 0.5467 has the highest dissolving capacity for phthalic acid at constant temperature, and the highest solubility of o-toluic acid is obtained in HAc + o-xylene solvent mixtures with the mole fraction of HAc of 0.5408 at constant temperature. The experimental solubilities were correlated by both the nonrandom two-liquid (NRTL) and Apelblat equations, and the calculated solubilities within ±11.9% relative deviation agree satisfactorily with the measured results.

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The solubility of adipic acid (AA), glutaric acid (GA), and succinic acid (SA) in acetic acid (HAc) + cyclohexanol solvent mixtures was measured by the laser dynamic method. The experimental temperature ranged from 300.75 to 347.05 K, and the mole fraction of HAc in the solvent mixtures ranged from 0.0000 to 1.0000. Together with the available solid–liquid equilibrium (SLE) and liquid–liquid equilibrium (LLE) data of the oxidation for cyclohexane in the published literatures, the interaction parameters of the NRTL (non-random two-liquid) model are determined by correlating a large number of experimental data. By using the new interaction parameters, the NRTL model predicted vapor–liquid equilibrium (VLE), SLE, and LLE data well in extrapolating temperature and solvent composition for the cyclohexane oxidation systems, which was in agreement with the experimentally determined results and was satisfactorily in agreement with previously published literatures. The results showed that the NRTL model would be a suitable one for the unified thermodynamics model which can be used for the correlation and prediction of the SLE, LLE, and VLE data for the cyclohexane oxidation process.

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The figure exhibited the material structure and formulated the corrosion path and the corrosion prevention mechanism.