Measurement and Correlation of the Solubility of Disodium 4, 4

Jun 25, 2013 - The solubility data of disodium 4,4′-dinitrostilbene-2,2′-disulfonate (DNSNa) in aqueous organic solutions (ethanol + water) and (e...
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Measurement and Correlation of the Solubility of Disodium 4,4′Dinitrostilbene-2,2′-disulfonate in Aqueous Organic Solutions Ming-Xing Du, Wei Zou, Qing Xia,* Ling-Xin Wang, Jia Kang, Feng-Bao Zhang, and Guo-Liang Zhang School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, P. R. China

ABSTRACT: 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.

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the electrolyte nonrandom two-liquid (E-NRTL)16 model; meanwhile the E-NRTL model parameters are obtained.

INTRODUCTION

Data on the solubility play an important role in the design and optimization of crystallization, extraction, and other industrial unit operations.1 Disodium 4,4′-dinitrostilbene-2,2′-disulfonate C14H8N2O10S2·2Na (DNSNa) (CAS No. 3709-43-1) is a light yellow powdered crystal, which is produced from 4,4′dinitrostilbene-2, 2′-disulfonate (DNS). DNS is an intermediate product in the process of 4,4′-diaminostilbene-2,2′disulfonic acid (DSD acid) synthesis. DSD acid is used broadly in producing green dyes, insecticides, and fluorescent brighteners due to its noncarcinogenic character and relative low material cost. The process for DSD acid synthesis has been discussed in our previous paper.2 The DSD acid is prepared from p-nitrotoluene by a sulfonation reaction,3,4 an oxidation reaction,5,6 and a reduction reaction7,8 in which the yield of oxidation p-nitrotoluene-o-sulfonic acid to DNS is much lower than other two steps. The researchers9−11 have been working on increasing the oxidation reaction yield, and using aqueous organic solutions to replace traditional aqueous solution as reaction solvent12−14 is a feasible method. We have worked on the determination of relative solubility data, which is helpful in searching suitable organic solvents.2,15 In this work, we continue to determine the solubility of DNSNa in solvent mixtures (ethanol + water) and (ethylene diglycol + water) in the temperature range from (280 to 323) K at atmospheric pressure. The experimental equilibrium data are correlated by © XXXX American Chemical Society

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EXPERIMENTAL SECTION

Materials Preparation. Purchased DNSNa was recrystallized three times from deionized water, and its purity was detected by high-performance liquid chromatography (HPLC) analysis (Hitachi L-7100, Japan). Deionized water (electrolytic conductivity 18 MΩ·cm) was obtained from Nankai Chemical Reagents Co., Tianjin, China. The detailed information of the materials used in the experiment is listed in Table 1, and all of the solvents were used without further purification. Apparatus and Procedure. The solubility of DNSNa in different solvent systems was measured by the dynamic method17 combined with the laser monitoring technique. Predetermined solute and solvent were weighed by an analytical balance (Gibertini, Crystal 200, Italy, accuracy of 0.1 mg) and transferred into the jacket vessel. The mixtures in the vessel were heated slowly with continuous stirring. To prevent the evaporation of the solvent, a cold-water condenser tube was connected with the vessel, and the open end of the tube was sealed by a rubber plug. When the last crystal disappeared, the equilibrium was reached, and the temperature was recorded. Received: December 20, 2012 Accepted: June 12, 2013

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Table 1. Information on Source and Purity (Mass Fraction) of the Materials Used in the Experiments material DNSNa ethanol ethylene diglycol

source Hebei Huayu Chemical Co. Ltd., Hebei, China. Guangfu Chemical Reagents Co., Tianjin, China. Guangfu Chemical Reagents Co., Tianjin, China.

water contamination in mass fraction

Table 2. Mole Fraction Solubility of DNSNa (x1) at Temperature (Texp) in Aqueous Ethanol Solution for Different Solute-Free Ethanol Mole Fraction (x03) (Experimental Pressure Is 0.1 MPa)a

mass fraction purity

x1·103

99.6 % 0.03 %

99.7 %

0.05 %

99.0 %

Texp/K

x1·103 x03

Duplicate experiments were carried out, and the uncertainty of the determined temperature was ± 0.3 K. The temperature in the jacket vessel was controlled by a refrigerated/heating circulator (Julabo FP45-HE, Germany, temperature stability ± 0.01 K), and detected by a platinum resistance thermometer Pt100 (calibrated with an accuracy of 0.01 K).

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RESULTS AND DISCUSSION Solubility Data of DNSNa. The experimental solubility data of DNSNa in various solvent mixtures are given in Tables 2 and 3, in which Texp is the experimentally measured temperature, x1 is the mole fraction solubility of DNSNa in aqueous organic solutions, and x03 and x04 are the solute-free mole fraction of ethanol and ethylene diglycol in solvent mixtures, respectively. The water contamination values which have been given in Table 1 have been taken into account in the calculation of mole fractions. Figures 1 and 2 represent the curves of x1 versus temperature at different x30 and x40, respectively. By comparing the solubility of DNSNa in the two different binary solvents, we found that (ethylene diglycol + water) has much higher dissolving power than that of (ethanol + water). As represented in Figure 1, the solubility of DNSNa increases as the temperature increases. The influence of ethanol mole fraction in the binary solvent mixtures is gradually enhanced. The solubility change from x03 = 0.0416 to x03 = 0.1434 is nearly negligible. But with the increase mole fraction of ethanol in the binary solvent mixtures, a more apparent decrease on the solubility appears. In pure ethanol solvent, DNSNa is almost insoluble. Besides, the solubilitytemperature dependence becomes weak with the increase of ethanol concentration, the solubility is nearly independent with temperature at x03 = 0.7779. Another result which needs attention is that the solubility difference at low temperature is less obvious in comparison with its behaviors at high temperature range. In Figure 2, the solubility data increase with temperature and the addition of ethylene diglycol. Further, the solubility difference is tiny at the temperature range of 315−325 K for x04 larger than 0.1016. The opposite effect on the solubility of DNSNa is exhibited by adding ethanol and ethylene diglycol into water. DNSNa solubility decreases when ethanol is added into water, while DNSNa solubility increases when ethylene diglycol is added into water. DNSNa is the reaction product of oxidation sodium 4nitrotoluene-2-sulfonate (NTSNa) in aqueous solution. The solubility of DNSNa decreases with the addition of ethanol, which means if water is replaced by ethanol aqueous solution as the reaction solvent, reaction product DNSNa would be easy to precipitate out, and it would help to improve the reaction yield. However, according to the solubility data2 of NTSNa in

1.299 1.696 1.973 2.278

284.85 290.35 293.05 296.45

0.9654 1.123 1.271 1.462 1.645

283.45 286.05 288.35 290.75 293.35

0.7205 0.9719 1.217 1.573

283.75 285.45 288.15 292.55

1.148 1.428 1.628 2.069

286.65 290.55 293.35 297.65

0.5517 0.7256 0.9050 1.068 1.289

283.15 286.85 290.45 293.95 297.55

0.04393 0.08059 0.1232 0.1349 a

283.45 286.05 292.65 295.95

3.023 3.530 3.937 4.336 x03 1.868 2.219 2.488 2.828 3.188 x03 1.945 2.346 2.833 3.513 x03 2.340 2.607 2.892 3.187 x03 1.483 1.774 1.882 1.981

Texp/K

= 0.0000 301.45 304.55 307.75 309.85 = 0.0416 295.85 298.65 300.75 302.75 304.95 = 0.1434 296.35 299.75 303.15 307.95 = 0.2809 300.35 302.65 305.45 307.75 = 0.4767 300.75 304.85 306.95 308.55

x03 = 0.7779 0.1558 300.35 0.1903 306.35 0.2115 310.15 0.2194 313.85

x1·103

Texp/K

4.984 5.951 6.744 7.560

312.05 316.25 319.25 321.95

3.379 3.776 4.529 5.306

306.65 308.85 311.55 314.75

3.923 4.484 5.099

309.95 312.35 314.75

3.634 4.547 5.067 5.609

311.25 315.15 318.15 321.35

2.322 2.481 2.711 2.824

313.75 316.45 319.45 322.05

0.2374 0.2625

316.05 318.95

Standard uncertainties u are u(T) = 0.3 K and u(x) = 2·10−5.

(ethanol + water) binary solvent mixtures, the solubility of NTSNa also decreases with the addition of ethanol. The solubilities of NTSNa are similar with the solubilities of DNSNa at low concentration ethanol aqueous solutions. Although the solubilities of NTSNa are much higher than that of DNSNa at high concentration ethanol aqueous solutions, the dissolving capacity of high concentration ethanol aqueous solution is too low to be a suitable reaction solvent. Therefore, ethanol aqueous solution cannot be considered as a suitable reaction solvent. Continuous work is necessary in searching for suitable solvent to improve yield of oxidation process of DSD acid production. Correlation of Experimental Data. The solubility product constant can be used to describe solid−liquid equilibrium as follows, in which the solubility product equation is defined by activity coefficient and mole fraction of constituent ions. Ks = a+v +a−v − = (γ+x+)v + (γ−x−)v −

(1)

where a, γ, x, and v denote the activity, the activity coefficient, the salt solubility in units of mole fraction, and the electrolyte stoichiometric coefficient, respectively. The subscripts (−) and (+) refer to the anion and cation. Equation 1 is fit for aqueous solutions, organic, and mixed solvent electrolyte solutions.18 B

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Table 3. Mole Fraction Solubility of DNSNa (x1) at Temperature (Texp) in Aqueous Ethylene Diglycol Solution for Different Solute-Free Ethylene Diglycol Mole Fraction (x04) (Experimental Pressure Is 0.1 MPa)a x1·103

Texp

x1·103 x04

a

1.558 1.815 2.213 2.589

283.07 285.8 290.3 293.85

2.2567 2.496 2.759 3.270 4.017

281.85 284.05 286.25 290.1 296.05

4.673 5.082 5.697 6.290

286.35 290.55 293.65 296.65

5.413 5.742 6.125 6.529

283.85 286.75 289.65 292.45

6.594 7.111 7.540 8.090 8.536

283.05 286.65 289.95 294.75 298.05

= 2.975 3.411 3.893 5.037 x04 = 4.516 5.087 6.414 7.482 8.439 x04 = 6.937 8.048 8.587 9.330 x04 = 7.408 8.207 8.695 9.485 x04 = 8.825 9.174 9.790 10.35 10.61

Texp 0.0407 297.85 299.55 302.45 308.5 0.1016 298 300.5 304.85 308.75 311.9 0.2028 299.75 305.15 308.95 311.65 0.2835 297.35 302.05 304.75 308.35 0.4041 299.95 303.05 306.65 309.15 311.65

x1·103

Texp

5.723 6.447 7.507 8.420

311.85 314.25 317.15 320.05

9.624 10.93 12.22

315.05 318.45 321.45

10.12 10.93 12.11

314.55 317.55 320.6

10.06 10.84 11.56 12.22

311.55 314.95 317.95 320.75

11.00 11.56 11.83 12.21

313.85 317.05 318.45 320.55

Figure 2. Mole fraction solubility of DNSNa against temperature in aqueous ethylene diglycol solution. Points, experimental data for different solute-free ethylene diglycol mole fraction system. △, 0.0000; □, 0.0407; ◇, 0.1016; ○, 0.2028; ☆, 0.2835; ▽, 0.4041; lines, calculated results by the E-NRTL model.

Table 4. Correlated Solubility Product Equation Parameters Defined by Equation 2 solvent system

Am

Bm/K

water (m = 2) ethanol (m = 3) ethylene diglycol (m = 4)

−435.03 −405.66 −672.07

−72773 −79523 −7315.2

where T is absolute temperature in Kelvin; Am and Bm are constants obtained by regressing solubility data, which are given in Table 4; m = 2, 3, 4 represents for water, ethanol, and ethylene diglycol, respectively. In the solvent mixtures, eq 2 needs to be modified. The following linear function which has been successfully used in solubility data regression for mixed-solvent electrolyte system is introduced.2,15

Standard uncertainties u are u(T) = 0.3 K and u(x) = 2·10−5.

ln Ksm1, m2 = (xm0 1A m1 + (1 − xm0 1)A m2 + (xm0 1Bm1 + (1 − xm0 1)Bm2 )/T )

(3)

x0m1

where m1 and m2 denote two different solvents and is the solute-free mole fraction of the m1 component in the binary solvent mixtures. A thermodynamic model is required in obtaining the activity coefficients of all species generated in the solutions. The ENRTL model which is based on the complete dissociation assumption and local electroneutrality is used to regress the experimental solubility data. The asymmetric activity coefficient of ion species i is written as follows

Figure 1. Mole fraction solubility of DNSNa against temperature in aqueous ethanol solution. Points, experimental data for different solute-free ethanol mole fraction system. +, 0.0000; △, 0.0416; ○, 0.1434; □, 0.2809; ◇, 0.4767; *, 0.7779; lines, calculated results by the E-NRTL model.

ln γi* = ln γi*PDH + ln γi*lc

where γ*i is the asymmetrical activity coefficient of ionic species i. The asymmetrical activity coefficient γ*i is the combination of the long-range interaction contribution γi*PDH and the shortrange interaction contribution γi*lc, which are described by the PDH equation and the NRTL equation, respectively. The detailed expressions for ln γ*i PDH and ln γ*i can refer to the ref 16. The binary interaction parameter τij is expressed as the following general temperature-dependent equation.

Furthermore, the solubility product in pure m solvent, Ksm which is a function of temperature can be expressed by the following van’t Hoff equation ln Ksm = A m + Bm /T

(4)

(2) C

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Table 5. Correlated E-NRTL Binary Interaction Parameters for the Two Systems: (DNSNa + Ethanol + Water) and (DNSNa + Ethylene Diglycol + Water) i

j

DNSNa ethanol DNSNa DNSNa ethylene diglycol a

ethanol water water ethylene diglycol water

aij

aij

bij/K

711.26 14.063b 85.173 33.191 −1.6134·105

−46.104 41.888b −77.924 −88.896 −9665.5

−2.0843·10 −2060.1b −50799 −23450 5.0181·109

5

bij/K

aij = aji

424.33 −24442b −9652.7 −6965.4 3.1099·106

0.39586 0.3a 0.2a 0.20696 0.3a

Obtained from ref 19. bObtained from ref 2.

τij = aij + bij /T

operational temperature ranging from (280 to 323) K. Raising the temperature leads to increasing DNSNa solubility in all solvent systems. However, the addition of ethanol and ethylene diglycol leads to contrary influence on the DNSNa solubility. The solubility of DNSNa in water decreases with the adding of ethanol and increases with the adding of ethylene diglycol. The E-NRTL thermodynamic model was used to describe the phase equilibrium of crystal DNSNa in the abovementioned solutions. The predicted solubilities with model parameters were satisfactory, and the root-mean-square deviations range from (0.40 to 1.22) K. Continuous work is necessary in searching for suitable solvents to improve the yield of oxidation steps of DSD acid production.

(5)

where i and j are used for all ions and molecules, aij and bij are model parameters describing the temperature dependence of τij, which are obtained from solubility data and listed in Table 5. The nonrandomness factor for solvent−solvent and water− salt are fixed as 0.3 and 0.2 in the regression process, respectively. For single-solvent electrolyte system, a satisfactory result can be obtained by fixing the value of solvent-salt nonrandomness factor as 0.2; however, this value needs to be revised in the description of phase equilibrium of mixed-solvent electrolyte systems.19 Therefore, we regressed this value through all of the available data in the present work. The Nelder−Mead Simplex Method has been applied for model parameter determination.2,15,20 The object function is the root-mean-square deviation σ between the experimental equilibrium temperature Texp and calculated equilibrium temperature T.

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Corresponding Author

*Tel.: +86-22-27400292. Fax: +86-22-27408778. E-mail address: [email protected].

N

Funding

σ = [∑ (T exp − T )2 /(N − 1)]0.5

The authors thank the support by the Program of Introducing Talents of Discipline to Universities, China, No. B06006.

(6)

i=1

where N is the number of experimental data points; T is calculated from eqs 1 to 5. Figure 1 shows that the experimental data fit appropriately with the E-NRTL model for the studied (DNSNa + ethanol + water) system. For the (DNSNa + ethylene diglycol + water) ternary system, the deviation for x04 = 0.1016 is slightly larger (shown in Figure 2), but it is acceptable overall. The rootmean-square deviations for each investigated systems are summarized in Table 6, which range from (0.40 to 1.22) K.

Notes

The authors declare no competing financial interest.

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solvent system + + + + +

0.0416 0.1434 0.2809 0.4767 0.7779

ethanol ethanol ethanol ethanol ethanol

σ/K 0.61 0.46 0.80 0.76 0.73 0.81

σ/K

solvent system water water water water water

+ + + + +

0.0407 0.1016 0.2028 0.2835 0.4041

ethylene ethylene ethylene ethylene ethylene

diglycol diglycol diglycol diglycol diglycol

REFERENCES

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Table 6. Root-Mean-Square Deviations Defined by Equation 6 for Each System water water water water water water

AUTHOR INFORMATION

0.99 1.22 0.93 0.40 0.46

The average root-mean-square deviations for (DNSNa + ethanol + water) systems and (DNSNa + ethylene diglycol + water) systems are 0.79 K and 0.63 K, respectively. The results show that one can use E-NRTL model to estimate the solubility of DNSNa in binary aqueous organic solvents.

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CONCLUSIONS The dynamic method has been used for the solubility data determination for the two ternary systems: (DNSNa + ethanol + water) and (DNSNa + ethylene diglycol + water) with the D

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(9) Gao, W. T.; Zhang, S. F.; Yang, J. Z.; Huang, L. Metal phthalocyanine catalyzed oxidation of 4-nitrotoluene-2-sulfonic acid to 4,4′-dinitrostilbene-2,2′-disulfonic acid. Dyes Pigm. 2000, 44, 155−159. (10) Guglielmetti, L. Process for the preparation of 4,4′dinitrostilbene-2,2′-disulfonic acid and its salts. U.S. Patent 4719051, 1998. (11) Lund, R. B.; McConnell, W. W.; Ladd, S. G. Process for the preparation of 4,4′-dinitrostilbene-2,2′-disulfonic acid and its salts. U.S. Patent 4952725, 1990. (12) Schomäcker, R.; Waldmann, H.; Traenckner, H. J. Process for preparing 4,4′-dinitrostilbene-2,2′-disulphonic acid and its salts. U.S. Patent 5583252, 1996. (13) Schnatterer, A.; Fiege, H. Process for preparing 4,4′dinitrostilbene-2,2′-disulphonic acid. U.S. Patent 5808141, 1998. (14) Zhou, H. B. Preparing DNS acid by oxidation of NTS acid in a mixture of water and organic solvents. Dyestuff Ind. 2002, 39 (5), 41− 42. (15) Wang, L. X.; Yu, X. M.; Xia, Q.; Zhang, F. B.; Zhang, G. L. Solubility of sodium 4-nitrotoluene-2-sulfonate in (propanol+water) and (ethylene glycol+water) systems. J. Chem. Thermodyn. 2012, 44, 128−32. (16) Aspen Physical Property System 11.1: Aspen Technology: Cambridge, 2001. (17) Xia, Q.; Zhang, F. B.; Zhang, G. L.; Ma, J. C.; Zhao, L. Solubility of sebacic acid in binary water + ethanol + solvent mixtures. J. Chem. Eng. Data 2008, 53, 838−840. (18) Li, M.; Constantinescu, D.; Wang, L. Solubilities of NaCl, KCl, LiCl, and LiBr in methanol, ethanol, acetone, and mixed solvents and correlation using the LIQUAC model. Ind. Eng. Chem. Res. 2010, 4981−4988. (19) Chen, C. C.; Britt, H. I.; Boston, J. F.; Evans, L. B. Local composition model for excess gibbs energy of electrolyte systems. AIChE J. 1982, 28 (4), 588−596. (20) Wang, L. X.; Xia, Q.; Kang, J.; Du, M. X.; Zhang, G. L.; Zhang, F. B. Measurement and correlation of solubilities of potassium chloride and potassium sulfate in aqueous glycerol solutions. J. Chem. Eng. Data 2011, 56, 3813−3817.

E

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