The solubilities of adipic acid in acetic acid + ε-caprolactone mixtures and in cyclohexanone + ε-caprolactone mixtures were measured by using the method of dynamic laser under atmospheric pressure. The experimental temperature ranged from 305.55 to 343.15 K, and the mass fraction of ε-caprolactone in the solvent mixtures ranged from 0.100 to 1.000, respectively. It was found that with the increasing of mass fraction of ε-caprolactone in solvent mixtures (0.100 to 1.000), the measured solubilities of adipic acid in acetic acid + ε-caprolactone mixtures decreased at the same temperature. However, in cyclohexanone + ε-caprolactone mixtures, the solubility showed an opposite trend with the increasing of mass fraction of ε-caprolactone in solvent mixtures. The experimental data were correlated by the modified NRTL activity coefficient model, and the values of the solubility calculated showed good agreement with the experimental observations.

Under atmospheric pressure, the solubilities of adipic acid, glutaric acid, and succinic acid in acetic acid + cyclohexanone mixtures were measured respectively by using the laser dynamic method in which the temperature ranged from 298.55 to 340.85 K and the mass fraction of cyclohexanone in the binary solvent mixtures ranged from 0.0 to 1.0. The results showed that the solubilities of adipic acid, glutaric acid, and succinic acid in acetic acid + cyclohexanone solvent mixtures all increased with decreasing of the mass fraction of cyclohexanone in the solvent mixtures at the constant temperature, and with the gradually increasing of temperature the measured solubilities of adipic acid, glutaric acid and succinic acid in acetic acid + cyclohexanone solvent mixtures would increase at the constant proportion solvent mixtures. The λh equation and the nonrandom two liquid (NRTL) activity coefficient model were used to correlate the experimental solubilities, and the average relative deviation was lesser than 2% respectively. It was found that the solubilities calculated by these models showed a good agreement with the experimental observations. In addition, the λh equation with a small number of adjustable parameters is very suitable for engineers so that they could use directly. Compared with the λh equation, the NRTL equation has a wider range of applications due to the stronger theory.

By using the method of dynamic laser, the solubilities of succinic acid and glutaric acid in ε-caprolactone + acetic acid mixtures and ε-caprolactone + cyclohexanone mixtures were determined under atmospheric pressure. The experimental temperature ranged from 293.35 to 340.65 K, and the mass fraction of ε-caprolactone in the solvent mixtures ranged from 0.0 to 1.0, respectively. It was found that with the increase of the temperature at constant concentration, the measured solubilities of succinic acid and glutaric acid in ε-caprolactone + acetic acid mixtures and ε-caprolactone + cyclohexanone mixtures would increase. Moreover, when the mass fraction of ε-caprolactone in ε-caprolactone + acetic acid mixtures increases at the same temperature, the measured solubilities of succinic acid and glutaric acid would decrease. However, it would increase as the mass fraction of ε-caprolactone increases for the system of ε-caprolactone + cyclohexanone at the same temperature. The experimental data were correlated by using the modified nonrandom two liquid activity coefficient model. The maximum value of average relative deviation was 1.50%.

The solubilities of adipic acid, glutaric acid, and succinic acid in dimethyl adipate + methanol solvent mixtures were measured by the method of dynamic laser under 101.3 kPa. The mass fraction of dimethyl adipate in the solvent mixtures ranged from 0.0 to 1.0, and the temperature ranged from 283.95 to 328.15 K. It was found that with the increase of mass fraction for dimethyl adipate in mixed solvents, the measured solubilities of adipic acid, glutaric acid, and succinic acid would decrease at the same temperature, and with the gradually increase of temperature the measured solubilities of adipic acid, glutaric acid, and succinic acid would increase at the constant proportion solvent mixtures. The experimental data were correlated by the Apelblat model, λh model, and the modified nonrandom two liquid activity coefficient model. Results showed that the largest values of relative average deviation and root-mean-square deviations obtained by the three models were 4.49% and 0.35%, respectively. The three models were proven to give a good representation of the experimental solubilities results. The result of Akaike Information Criterion (AIC) analysis shows that the Apelblat model is the best model to correlate the solubilities of adipic acid and succinic acid and the λh model is the best model to correlate the solubilities of glutaric acid in dimethyl adipate + methanol mixed solvent.