The solubilities of sodium p-toluenesulfonate (NaPTS), sodium sulfite (Na 2 SO 3 ), and sodium p-methylphenoxide (NaCRS) in aqueous NaOH solutions and Na 2 SO 3 in aqueous ethanol solutions were investigated using a dynamic method over the temperature range from 277 to 341 K at atmospheric pressure. The experimental results showed that the solubilities of NaPTS, Na 2 SO 3 , and NaCRS in aqueous NaOH solutions and Na 2 SO 3 in aqueous ethanol solutions decreased distinctly with the solutefree mass fraction of NaOH (w 4 0 ) and ethanol (w 5 0 ). Further, there were obvious transition points in the solubility−temperature curves of NaPTS and Na 2 SO 3 in aqueous NaOH solutions, and the transition points shifted to lower temperature as w 4 0 rose. The forming of transition point was due to the different equilibrium solid phase, which was revealed by characterization of the equilibrium solid phase. But the transition points in the solubility−temperature curves of Na 2 SO 3 in aqueous ethanol solutions remained constant at different w 5 0 values. As the temperature rose, the solubilities of NaPTS and NaCRS in aqueous NaOH solutions increased, while the solubilities of Na 2 SO 3 increased at first and then decreased after the transition points in both aqueous NaOH and ethanol solutions. The experimental data were correlated with the electrolyte nonrandom two-liquid (E-NRTL) model, and model parameters were determined simultaneously. On the basis of the solubility difference between Na 2 SO 3 and NaCRS, a new process for reusing the NaOH in the alkali fusion reaction residue was proposed theoretically.

The solubilities of naphthalene in decalin, octane, dodecane, dichloromethane, trichloromethane, carbon tetrachloride, 1,2-dichloroethane, o-dichlorobenzene, 1-octanol, 2-octanone, 4-methyl-2-pentanone, and benzene were measured by a dynamic method over the temperature range of 279 to 330 K at atmospheric pressure. By comparison, the experimental results indicated that the molality solubility in dichloromethane reached maximum at certain temperature. Then, the Apelblat equation, the λh equation, the Wilson equation, and the nonrandom two liquid (NRTL) equation were used to correlate the experimental data. The NRTL equation was regarded as the effective model for all the solvents. Finally, the mixing properties were also calculated based on the NRTL equation. All these data were particularly instructive for the process of recycling naphthalene.

The solubilities of sodium 1-and 2-naphthalenesulfonate (1-and 2-SNS) in aqueous sodium hydroxide solutions were measured over the temperature range from 276 to 337 K at atmospheric pressure by a dynamic method. The experimental results showed that the solubilities of 1-and 2-SNS both increased with temperature and decreased with concentrations of aqueous sodium hydroxide solutions. The experimental data were correlated with the new electrolyte nonrandom two-liquid (E-NRTL) model. The calculated results showed good agreement with the experimental data. A new strategy, based on the solubility difference between 1-and 2-SNS in aqueous sodium hydroxide solutions, was carried out in laboratory scale. This new strategy, in which the current process of blowing naphthalene was replaced by removing the byproduct according to the solubility difference, overcame the drawbacks of blowing naphthalene and made a good separation effect. The best separation effect was attained when the concentration of aqueous sodium hydroxide solution was 0.07 and the operating temperature was 298.15 K. The purities of obtained 1-and 2-SNS were 0.8369 and 0.9854 in this operating condition, respectively. The new strategy has potential in industrial application for optimizing the production of 2-naphthol.

An optimal design of the neutralization process in 1,5-dihydroxynaphthalene production was proposed and discussed. In the new strategy, instead of sodium chloride, sodium sulfate was used in the salting-out process to overcome the drawbacks of the traditional strategy. Then the precipitated mixtures, mainly naphthalene-1,5-disulfonic acid (1,5-H 2 NDS) and sodium sulfate, were neutralized to obtain naphthalene-1,5-disulfonic acid disodium (1,5-Na 2 NDS) and sulfuric acid. By adjusting the concentrations of sulfuric acid solutions to 0.3 and 0.5 mass fractions, 1,5-Na 2 NDS and 1,5-H 2 NDS were precipitated out, respectively. The yields of both 1,5-H 2 NDS and 1,5-Na 2 NDS reached 0.98. 1,5-Na 2 NDS was sent to the alkali fusion process, while 1,5-H 2 NDS was reused in the neutralization. In neutralization, the mole ratio (1,5-H 2 NDS to sodium sulfate) was chosen as 2.5 and the reaction temperature was 353 K. In order to determine the separation conditions, the solubilities of 1,5-H 2 NDS•2H 2 O and 1,5-Na 2 NDS•H 2 O in aqueous sulfuric acid solutions were measured over the temperature range from 277 to 337 K at atmospheric pressure by a dynamic method. The new strategy is particularly instructive for the industrial production of 1,5dihydroxynaphthalene.