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.

The nitration process as one step in 2-amino-5-chloro-4-methylbenzenesulfonic acid synthesis was improved by optimizing nitration reaction conditions, improving product separation method to eliminate salty scrap acid and cycle use of the concentrated sulfuric acid. The effect of various parameters such as temperature, quality of fuming sulfuric acid, quality of fuming nitric acid, and reaction time was studied for optimization of the nitration reaction condition. In the optimum conditions, the mass ratio of fuming sulfuric acid to sodium 2-chlorotoluene-4-sulfonate and molar ratio of fuming nitric acid to sodium 2-chlorotoluene-4-sulfonate were 4 and 1.05, respectively. The reaction temperature was −5 °C, and the time of reaction was 3 h. By applying the optimum reaction conditions, the yield of nitration reaction was increased to 91%, larger than that of the current industrial process whose yield is only 65.7%. The solubilities of sodium 2-chloro-5-nitrotoluene-4-sulfonate in aqueous sulfuric acid solutions were determined by a dynamic method, and the results showed that the lowest sodium 2-chloro-5-nitrotoluene-4-sulfonate solubility was exhibited in 0.7 mass fraction aqueous sulfuric acid solutions. So the product sodium 2-chloro-5-nitrotoluene-4-sulfonate of nitration reaction was separated by filtration from 0.7 mass fraction aqueous sulfuric acid solutions, and the obtained concentrated aqueous sulfuric acid solution was reused.

The solubility of disodium 4,4′-dinitrobibenzyl-2,2′-disulfonate (DNDNa) in aqueous ethylene glycol monoethyl ether solution and aqueous ethylene glycol monobutyl ether solution was measured over the temperature range from 278 to 334 K at atmospheric pressure by a dynamic method. The solubility of DNDNa in aqueous ethylene glycol monoethyl ether solution and aqueous ethylene glycol monobutyl ether solution increased with temperature over all solvent mixture compositions investigated. A synergistic effect on DNDNa solubility was observed with the maximum solubility at solute-free mass fraction of ethylene glycol monoethyl ether w30=0.6003 and solute-free mass fraction of ethylene glycol monobutyl ether w40=0.4054 , respectively. The solubility data were correlated using the electrolyte non-random two-liquid model and model parameters were determined simultaneously. It was found that around 0.4 (solute-free mass ratio) ethylene glycol monobutyl ether solution is suitable as the reaction medium in oxidation 4-nitrotoluene-2-sulfonic acid to 4,4′-dinitrostilbene-2,2′-disulfonic acid. The effect of different aqueous organic solutions on the oxidation reaction was discussed.

The aim of this work is to analyze the possibility of separating isopropyl acetate and 2-propanol, an azeotropic system, by using glycerol. Thus, liquid–liquid equilibrium (LLE) data for the ternary system of isopropyl acetate + 2-propanol + glycerin have been determined at various temperatures T = (298.15, 308.15, 318.15) K under atmospheric pressure. The consistency of the experimental data was verified by the mass balance. The extraction capacity was evaluated throughout the distribution coefficient and selectivity parameters. Phase diagrams have been obtained at each temperature. To facilitate the manipulation of the obtained data for industrial applications, the NRTL and the UNIQUAC models have been applied to correlate the experimental data and low deviations were obtained.

The solubilities of the sodium 2-chlorotoluene-4-sulfonate (CTSNa) in water, methanol, formic acid, dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), binary (methanol + water) mixed solvents, and binary (ethanol + water) mixed solvents were determined experimentally over the temperature range from (280 to 335) K at atmospheric pressure using a dynamic method. The mole fraction of water in the two solvent mixtures ranged from 0.0000 to 1.0000 and 0.2006 to 1.0000, respectively. A synergistic effect on CTSNa solubility was observed with the maximum solubility at solute-free mole fraction of ethanol x20 = 0.2082 and solute-free mole fraction of methanol x30 = 0.3985, respectively. The solubility data were correlated with the thermodynamic electrolyte nonrandom two-liquid (E-NRTL) model and the root-mean-square deviations of solubility temperature varied from (0.24 to 1.10) K.

The solubilities of 2-naphthalenesulfonic acid monohydrate and sodium 2-naphthalenesulfonate in sulfuric acid solutions were measured at temperatures ranging from 278.15 to 338.15 K by using a dynamic method. The concentration of sulfuric acid solution ranged from 0 to 80wt%,. The solubilities of 2-naphthalenesulfonic acid monohydrate and sodium 2-naphthalenesulfonate increased with temperature, and both of them were the lowest at 70wt%, of sulfuric acid solution(w30 =0.70)while the highest in pure water. The solubility data were correlated by the modified Apelblat equation. Based on the solubility difference between 2-naphthalenesulfonic acid monohydrate and sodium 2-naphthalenesulfonate, a new technique in which sodium sulfate was used to replace sodium sulfite in the neutralization reaction was developed. The suitable mole ratio of H2O to Na2SO4 in the neutralization reaction was 80:1, and that of 2-naphthalenesulfonic acid monohydrate to Na2SO4 was 3.2:1. The material balance under the suitable mole ratios was given and discussed.

To separate a salt mixture (mainly consisting of Na2CO3 and Na2SO4) which is formed from the 4,4′-diaminostilbene-2,2′-disulfonic acid wastewater treatment, the solubility data of Na2CO3 and NaHCO3 in Na2SO4–water solvent mixtures were measured using a dynamic method over the 275–335 K temperature range. The solute-free mass fraction of Na2SO4 in the solvent mixtures extended from 0 to 0.25. The solubility of Na2CO3 and NaHCO3 in Na2SO4–water solvent mixtures decreased with addition of Na2SO4. With rising temperature, the solubility of NaHCO3 increased while the solubility of Na2CO3 increased at first and then decreased after transition points. The experimental data were correlated with the electrolyte nonrandom two-liquid model. The root-mean-square deviations of solubility temperature varied from 0.35 to 1.50 K. Based on the solubility data of this work, a new strategy for separating the Na2CO3 and Na2SO4 mixture was proposed theoretically.

•The solubility of dimethyl succinylsuccinate in (methanol + water) solvent mixtures was measured from (283.75 to 327.25) K.•The solubility of dimethyl succinylsuccinate in (methanol + dimethyl succinate) solvent mixtures was measured.•The melting point and the fusion enthalpy of dimethyl succinylsuccinate were measured by DSC.•The Wilson and the NRTL models provide good accuracies in correlating the SLE of the systems, respectively.•A suggestion is provided to improve the dimethyl succinylsuccinate process.In order to improve the process of dimethyl succinylsuccinate production, the solubility data of dimethyl succinylsuccinate in the binary solvent mixtures consisting of (methanol + water) and (methanol + dimethyl succinate) were measured within the temperature range of (283.75 to 327.45) K by a dynamic method. The solubility of dimethyl succinylsuccinate in both of the selected solvent mixtures increase with temperature, and the solvent mixtures (methanol + dimethyl succinate) have much more dissolving capacity for DMSS solute. The experimental data were well-correlated with the Wilson model and the NRTL model, and the root-mean-square deviations for the Wilson and the NRTL models ranged from (0.20 to 0.94) K and (0.18 to 0.93) K, respectively. The melting point and the fusion enthalpy of dimethyl succinylsuccinate were detected by differential scanning calorimetry (DSC). The improvement of dimethyl succinate process was suggested according to the determined data.

The solubilities of dimethyl terephthalate (DMT) and monomethyl terephthalate (MMT) in methanol aqueous solutions were determined in the temperature range of 280–336 K. The solute-free mass fractions of methanol extended from 0.3 to 1.0. Both the solubilities of DMT and MMT in aqueous methanol solution increase with the temperature and the addition of methanol. The experimental data were correlated with the Wilson and the NRTL models. The root-mean-square deviations for the system of (DMT + methanol + water) were 1.30 and 1.33 K calculated by the Wilson and the NRTL models, respectively, while for the system of (MMT + methanol + water), the root-mean-square deviations were 0.55 and 0.82 K. The melting points and the enthalpy of fusion of DMT and MMT were detected by the differential scanning calorimetry (DSC). A simple purification and recycling process was designed to separate MMT from the esterification reaction product according to the solubility difference between DMT and MMT.

The solubilities of p-toluenesulfonic acid monohydrate (PTSA·H2O) and sodium p-toluenesulfonate (NaPTS) in aqueous sulfuric acid solutions were investigated at a temperature range from 278.45 to 342.95 K. The experimental results showed that the solubilities of PTSA·H2O and NaPTS in aqueous sulfuric acid solutions increased with temperature from 278.45 to 342.95 K and decreased with sulfuric acid concentrations from 0 to 0.7. The experimental data were correlated with the modified Apelblat equation. The calculated results showed good agreement with the experimental data. A new strategy which sodium sulfate was used as a starting material in the preparation of NaPTS was profiled according to the solubility difference between PTSA·H2O and NaPTS. In the continuous preparation of NaPTS, the favorable mole ratio (PTSA·H2O to sodium sulfate) is chosen as 4.0, and the optimum operation conditions of the recycle process were determined, which improved the present process of 4-methylphenol production.

The solubility data of disodium 4,4′-dinitrostilbene-2,2′-disulfonate (DNSNa) in aqueous organic solutions (ethanol + water) and (ethylene diglycol + water) were investigated over the temperature range from (280 to 323) K using a dynamic method. The mole fraction of water in the two different solvent mixtures ranged from 0.2221 to 1.0000 and 0.5959 to 1.0000, respectively. The electrolyte nonrandom two-liquid (E-NRTL) model proposed by Chen was applied to model the solubility data of DNSNa in the above systems. The binary interaction parameters of the E-NRTL model were obtained via regression of the experimental solubility data. The root-mean-square deviations of determined equilibrium temperature and the calculated equilibrium temperature varied from (0.40 to 1.22) K.

To investigate the effects of NaOH and ethanol on the solubility of disodium decanedioate in water, the solubilities of disodium decanedioate in two aqueous solutions (aqueous NaOH solutions and aqueous ethanol solutions) were determined in a temperature range of (284 to 345) K. The solute-free mole fraction of NaOH and ethanol in the solvent mixtures extended from 0 to 0.084 and 0 to 0.472, respectively. With the increase of the mole fractions of ethanol (or NaOH) in solvent mixtures, the solubilities decreased obviously. Alcohol-out and alkali-out phenomena could be evidently observed, between which the alkali-out effect was more prominent. The determined data were correlated with the new electrolyte nonrandom two-liquid (E-NRTL) model, and the root-mean-square deviations of solubility temperature varied from (0.26 to 0.91) K.

The solubilties of potassium chloride and potassium sulfate in aqueous glycerol solutions have been measured at temperatures ranging from (289 to 349) K using a dynamic method. The solute-free mass fractions of glycerol range from 0.0000 to 0.8001. The solubilities of KCl and K2SO4 in aqueous glycerol solutions increased with temperature and decreased with addition of glycerol. The experimental data were correlated with the electrolyte nonrandom two liquid (E-NRTL) model. The binary interaction parameters in the E-NRTL model were obtained simultaneously using the solubility data of the ternary systems. The calculated solid–liquid equilibrium (SLE) temperatures with the E-NRTL model were in good agreement with the experimental results. The root-mean-square deviations of solubility temperature varied from (0.36 to 1.05) K.

The solubility data have been measured experimentally for decanedioic acid in n-butanol, 2-butanol, n-pentanol, n-hexanol, and binary solvents 2-propanol + water from (294 to 351) K. The system containing decanedioic acid + 2-propanol + water exhibited a synergistic effect on solubility. The Wilson model, the nonrandom two-liquid (NRTL) model, and the universal quasi-chemical functional group activity coefficient (UNIFAC) model were applied to describe the solid−liquid equilibrium (SLE). It is shown that the Wilson model and the NRTL model can give better results. The primary reason for relatively larger deviations in the case of using the UNIFAC model was discussed.

The solubilities of sebacic acid in mixed solvents n-propanol + water have been measured by a dynamic method using a laser monitoring observation technique over a temperature range (288 to 351) K. A synergistic effect on solubility was found to occur in sebacic acid + n-propanol + water mixed systems. To detect the synergistic effect, solubilities of sebacic acid in 14.35 %, 36.97 %, 79.81 %, and 90.00 % mole fraction ethanol aqueous solution were determined to supplement our previous report. A weak synergistic effect was found for sebacic acid + ethanol + water mixed systems. The solid−liquid equilibrium (SLE) data have been fitted using the λh equation, the Wilson equation, and the NRTL equation. The comparison between the experimental and the calculated solubilities for the three models is reasonable, and the root-mean-square deviations for each system range from (0.30 to 1.95) K.

Solubilities of nonanedioic acid in binary ethanol + water solvent mixtures have been determined by the dynamic method using a laser monitoring observation technique over a temperature range from (292.35 to 345.52) K and a solvent composition, mole fraction of ethanol of solute-free x20, range from 0.0 to 1.0. The experimental results showed that in pure water the solubility of nonanedioic acid increased slowly with temperature below 342.77 K but increased significantly above 342.77 K. The nonanedioic acid + ethanol + water system was found to exhibit a synergistic effect on solubility. The fusion enthalpy and melting temperature of nonanedioic acid were measured by differential scanning calorimetry. The modified λh equation, the Wilson equation, and the NRTL equation have been applied to correlate a subset of the experimental data. These models can successfully describe the solubility of nonanedioic acid in the binary mixtures with an ethanol mole fraction higher or equal to 0.2811.

Solubilities of sebacic acid in binary ethanol + water solvent mixtures were measured by the dynamic method using a laser monitoring observation technique at a temperature range from (288 to 352) K. The mole fraction of ethanol in the solvent mixtures ranges from 0 to 1. The melting temperature and enthalpy of fusion of sebacic acid were determined by differential scanning calorimetry. The experimental results show that the slope of the solubility−temperature curve increases significantly with an increase in the mole fraction of ethanol in the solvent. The Wilson equation is applied to describe measured systems. The model parameters of the Wilson equation were expressed as a function of temperature.