Solubility of itaconic acid in different organic solvents: Experimental measurement and thermodynamic modeling

Solubility of itaconic acid in different organic solvents: Experimental measurement and thermodynamic modeling

Fluid Phase Equilibria 314 (2012) 180–184 Contents lists available at SciVerse ScienceDirect Fluid Phase Equilibria journal homepage: www.elsevier.c...

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Fluid Phase Equilibria 314 (2012) 180–184

Contents lists available at SciVerse ScienceDirect

Fluid Phase Equilibria journal homepage: www.elsevier.com/locate/fluid

Solubility of itaconic acid in different organic solvents: Experimental measurement and thermodynamic modeling Wenge Yang, Yonghong Hu ∗ , Zhaoguo Chen, Xinmin Jiang, Jikui Wang, Ruirong Wang College of Biotechnology and Pharmaceutical Engineering, Nanjing University of Technology, No.200, North Zhongshan Road, Nanjing, 210009, PR China

a r t i c l e

i n f o

Article history: Received 10 July 2011 Received in revised form 23 September 2011 Accepted 25 September 2011 Available online 4 October 2011 Keywords: Solubility Itaconic acid Solid–liquid equilibrium Correlation

a b s t r a c t Data on corresponding solid–liquid equilibrium of itaconic acid in different organic solvents are essential for industrial design and further theoretical studies. In this study, the solubility of itaconic acid was measured in methanol, ethanol, 1-propanol, acetonitrile, 2-propanol, ethyl acetate, and acetone with the temperature range of 283.15–328.15 K by the analytical stirred-flask method under atmospheric pressure. The experiment results showed that the solubility of itaconic acid was highest in methanol and followed by 2-propanol, ethanol and 1-propanol. For the temperature range investigated, the solubilities of itaconic acid in the solvents increased with increasing temperature. Results of these measurements were well-correlated with the modified Apelblat equation and the Buchowski–Ksiazaczak h equation. The calculated solubilities showed good agreement with the experimental data. The modified Apelblat equation was found to regress the solubility data much better than the Buchowski–Ksiazaczak h equation. © 2011 Elsevier B.V. All rights reserved.

1. Introduction Itaconic acid (C5 H6 O4 , FW 130.10, CAS Registry No. 97-654, shown in Fig. 1) is a white crystalline solid, which is widely used as an important intermediate for many other organic substances applied in the field of pharmaceuticals, resins, plasticizers, adhesives, coatings, surfactants, herbicides, and deodorants [1–3]. Itaconic acid is an organic acid produced by fermentation of stains of Aspergillus terreus or A. itaconicus. Crude itaconic acid was gained after concentrating and filtrating and can be purified by crystallization. Crystallization processes are the critical steps that determine the quality of final product of itaconic acid. Therefore, knowing the solubility of the product is a necessary condition in order to design the crystallization process properly and improve the purity and yield of itaconic acid. Unfortunately, limited data is available on the solubility and temperature dependence of the solubility of itaconic acid. The aim of this paper is to explore the solubility of itaconic acid in seven solvents, that is, methanol, ethanol, 1-propanol, acetonitrile, 2-propanol, ethyl acetate, and acetone in the temperature range 283.15–328.15 K and to provide important experimental data correlation model. Modeling of experimental solubility data enables researchers to represent mathematical aspects of solubility. A number of methods

∗ Corresponding author. Tel.: +86 25 83587108; fax: +86 25 83587108. E-mail address: [email protected] (Y. Hu). 0378-3812/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.fluid.2011.09.027

have been presented in order to estimate the solubility of solute in solvent mixtures. According to these methods, the solubility of a solute could be predicted in different systems [4]. In the present study, the solubility of itaconic acid in seven solvents was measured and the modified Apelblat equation and the Buchowski–Ksiazaczak h equation was used to correlate and predict the solubility of itaconic acid in pure solvents. 2. Experimental 2.1. Materials A white crystalline powder of itaconic acid with a mass fraction of higher 0.9965 was purchased from TianJin Chemical Industry Co., Ltd., China. Its purity was measured by high performance liquid chromatography (HPLC type DIONEX P680 DIONEX Technologies), and its melting temperature was found to be 440.15 K determined by different scanning calorimeter (Netzsch DSC 204). The ethanol, methanol, 1-propanol, acetonitrile, 2-propanol, ethyl acetate, and acetone for dissolving the itaconic acid were analytical purity grade with mass fraction purity higher than 0.995, which are obtained from Tianjin Kemel Chemical Reagents Co. The purities of the solvents were determined in our laboratory by gas chromatography, for ethanol, 99.93 mass%; for methanol, 99.90 mass%; for 1-propanol, 99.95 mass%; for 2-propanol, 99.94 mass%; for acetonitrile, 99.91 mass%; for ethyl acetate, 99.98 mass%; for acetone, 99.96 mass%; All chemicals were used received without further purification (Table 1).

W. Yang et al. / Fluid Phase Equilibria 314 (2012) 180–184

181

Table 1 Example sample table. Chemical name

Source

Mole fraction purity

Purification method

Analysis method

Itaconic acid Ethanol Methanol 1-Propanol 2-Propanol Acetonitrile Ethyl acetate Acetone

TianJin Chemical Industry Tianjin Kemel Chemical Tianjin Kemel Chemical Tianjin Kemel Chemical Tianjin Kemel Chemical Tianjin Kemel Chemical Tianjin Kemel Chemical Tianjin Kemel Chemical

0.9965 0.9993 0.9990 0.9995 0.9994 0.9991 0.9998 0.9996

None None None None None None None None

HPLCa HPLC HPLC HPLC HPLC HPLC HPLC HPLC

High performance liquid chromatography, type DIONEX P680 DIONEX Technologies, USA.

2.2. Differential scanning calorimetric (DSC) measurements Approximately 5 mg of itaconic acid powder was put in a hermetic DSC pan. For each DCS experiment, an empty DSC was used as a blank reference. The samples were scanned from 373 to 503 K at a 2 K/min heating rate. The uncertainties of the measurements are estimated to be ±0.3 K for the temperature. 2.3. Solubility determination The solubility of itaconic acid in different solvents was determined by the analytical stirred-flask method and the compositions of the saturated solutions were measured using the gravimetric method. The apparatus and detailed procedure for solubility measurement have already been described in our previous work [5–7] and here only some apparatus changes are described. For solubility measurements, an excessive amount of solutes were put into a double layer jacket glass equilibrium cell, which had a working volume of 100 mL. The temperature of the equilibrium cell was controlled by circulating water from a super thermostatic water-circulator bath (type HWC-52, ShangHai Cany Precision Instrument Co., Ltd.) through the jacket of the cell. A mercury-in-glass thermometer with an uncertainty of ±0.05 K (calibrated by using a standard thermometer) was inserted into the inner chamber of equilibrium cell for measuring the solution equilibrium temperature. Continuous stirring was achieved for fully mixing the suspension using a magnetic stirrer at the required temperature. The stirring was kept for about 12 h to ensure the solid–liquid equilibrium and the solution was kept still for 3 h in order to allow the undissolved solid to settle down in the lower portion of the equilibrium cell. After enough time of solid–liquid mixing and gravitational setting, around 2 mL upper solution was extracted by injector (membrane filtration, and 0.22 ␮m) and quickly taken out to another previously weighed measuring vial. The vial was then quickly and tightly closed and weighed again to determine the mass of the sample. Then the vial was put into a dryer at room temperature with the cap half-closed to allow the complete evaporation of the solvent. After that, the vial together with the solutes remaining was weighed again. Periodical measurements were conducted until the constant weight of the vial was obtained. An analytical balance (type Sartorius, BS210S) with an uncertainty 0.0001 g was used for all the mass measurements. All the experiments were conducted three times, and the mean values were used to calculate the mole fraction solubility.

The saturated mole fraction solubility of the solute (x) in solvent is obtained as follow: x=

m1 /M1 m1 /M1 + m2 /M2

(1)

where m1 represents the mass of solute and m2 represents the mass of solvents, respectively. M1 is the molecular mass of solute; M2 is the molecular mass of solvents, correspondingly. The uncertainty in the experimental solubility values is about 3.0%. The uncertainty in the solubility values can be due to uncertainties in the weighing procedure, temperature measurements, excess addition of solute, and instabilities of the water bath. 3. Results and discussion 3.1. Solubility data Experimentally measured temperature-dependent equilibrium mole fraction of itaconic acid in ethanol, methanol, 1-propanol, acetonitrile, 2-propanol, ethyl acetate, and acetone are showed in Table 2. For each solvent studied herein, the equilibrium solubility mole fraction of itaconic acid increased with temperature. Throughout the entire range of temperature studied, the order of increasing mole fraction solubility of itaconic acid was: methanol > 2-propanol > ethanol > 1propanol > acetone > ethyl acetate > acetonitrile (Fig. 2). The result suggested that the polarity of the solvent is not the only factor to determine the solubility, as the solvent’s polarity is in the following order: methanol > ethanol > 1-propanol > 2propanol > acetonitrile > acetone > ethyl acetate [8]. This solubility

0.14 0.12 0.10 0.08

X

a

0.06 0.04 0.02

O O

HO

CH2

OH

Fig. 1. Chemical structure of itaconic acid.

0.00 280

290

300

310

320

330

T/K Fig. 2. Mole fraction solubility of itaconic acid in different solvents between (283.15 and 328.15 K).

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W. Yang et al. / Fluid Phase Equilibria 314 (2012) 180–184

Table 2 Mole fraction solubility of itaconic acid in selected solvents with the Temperature Ranging from (283.15 to 328.15 K). 102 RD

T (K)

x

283.15 288.15 293.15 298.15 303.15

0.1019 0.1044 0.1063 0.1093 0.1129

± ± ± ± ±

0.0009 0.0011 0.0023 0.0019 0.0051

283.15 288.15 293.15 298.15 303.15

0.0031 0.0038 0.0046 0.0055 0.0068

± ± ± ± ±

0.0007 0.0019 0.0039 0.0023 0.0017

283.15 288.15 293.15 298.15 303.15

0.0646 ± 0.0010 0.0676 ± 0.0021 0.0710 ± 0.0024 0.0746 ± 0.0019 0.0787 ± 0.0046

283.15 288.15 293.15 298.15 303.15

0.0073 0.0084 0.0096 0.0110 0.0126

± ± ± ± ±

0.0037 0.0029 0.0012 0.0022 0.0013

283.15 288.15 293.15 298.15 303.15

0.0692 0.0725 0.0754 0.0782 0.0823

± ± ± ± ±

0.0026 0.0019 0.0023 0.0016 0.0018

283.15 288.15 293.15 298.15 303.15

0.0787 0.0820 0.0843 0.0873 0.0906

± ± ± ± ±

0.0017 0.0023 0.0034 0.0025 0.0053

283.15 288.15 293.15 298.15 303.15

0.0413 0.0446 0.0477 0.0514 0.0552

± ± ± ± ±

0.0028 0.0015 0.0017 0.0029 0.0035

Methanol 0.07 0.20 −0.35 −0.19 0.22 Acetonitrile −0.004 −0.001 −0.006 0.003 0.03 1-Propanol 0.16 −0.15 -0.04 −0.11 0.02 Ethyl acetate −1.06 −0.31 0.25 0.67 1.59 Ethanol −0.17 0.42 0.17 −0.65 −0.06 2-Propanol −0.48 0.59 0.05 0.02 −0.14 Acetone −0.33 0.44 0.07 0.05 −0.32

order can reasonably be related to the possibility to form hydrogen bond between the itaconic acid molecules and the solvent molecules. We can see from Fig. 1 that there are two carboxyl groups in the itaconic acid molecule. The carboxyl group is polar with a hydrogen-bond donating as well as accepting functionality. Out of the solvents, of course the alcohols have both hydrogenbond donating and accepting functionalities, while acetonitrile, acetone, and ethyl acetate are only hydrogen-bond accepting. In case of ethanol, methanol, 1-propanol and 2-propanol, hydrogen bonds are easily set up hydrogen bond between its slightly positive hydrogen atoms and the long pairs on oxygen atoms in itaconic acid molecules. Acetone has a similar carbon chain structure to 2-propanol and oxygen atom with negative charge makes it a nice hydrogen bonds acceptor for the hydroxyl group in itaconic acid.

To describe solid–liquid equilibrium, the temperature dependence of the solubilities of itaconic acid in different organic solvents at different temperatures can be described as [9] ln

 1  x x

=

fus H RTt

T

t

T



−1 −

x

308.15 313.15 318.15 323.15 328.15

0.1160 0.1194 0.1239 0.1279 0.1322

± ± ± ± ±

0.0021 0.0032 0.0017 0.0045 0.0012

0.02 −0.17 0.27 0.05 −0.14

308.15 313.15 318.15 323.15 328.15

0.0076 0.0093 0.0107 0.0130 0.0149

± ± ± ± ±

0.0013 0.0028 0.0036 0.0014 0.0022

−0.03 0.004 −0.02 0.02 −0.005

308.15 313.15 318.15 323.15 328.15

0.0829 0.0878 0.0924 0.0968 0.1033

± ± ± ± ±

0.0051 0.0034 0.0029 0.0023 0.0064

−0.04 0.43 0.10 −0.65 0.28

308.15 313.15 318.15 323.15 328.15

0.0140 0.0158 0.0182 0.0204 0.0232

± ± ± ± ±

0.0008 0.0027 0.0031 0.0019 0.0041

−0.56 −1.16 0.42 −0.40 0.29

308.15 313.15 318.15 323.15 328.15

0.0865 0.0910 0.0954 0.1007 0.1060

± ± ± ± ±

0.0034 0.0019 0.0026 0.0015 0.0036

0.11 0.25 −0.10 0.11 −0.10

308.15 313.15 318.15 323.15 328.15

0.0946 0.0986 0.1032 0.1083 0.1137

± ± ± ± ±

0.0031 0.0019 0.0012 0.0027 0.0045

0.08 −0.16 −0.08 0.05 0.06

308.15 313.15 318.15 323.15 328.15

0.0595 0.0650 0.0698 0.0755 0.0821

± ± ± ± ±

0.0019 0.0023 0.0017 0.0027 0.0018

−0.37 0.62 −0.01 −0.28 0.10

where  x is the activity coefficient of itaconic acid on a mole fraction basis, x is the mole fraction solubility of itaconic acid, fus H is the enthalpy of fusion of itaconic acid, Cp is the change of the heat capacity, T is the absolute temperature (K), Tt is the triple-point temperature of itaconic acid, R is the gas constant. For regular solutions, the activity coefficient is given by [10] ln x = a +

b T/K

(3)

where a and b are constants. Introducing  x from Eq. (3) into Eq. (2) and subsequent rearrangement results in Eq. (4) can be written as [11]



ln x =

 

Cp fus H (1 + ln Tt ) − a − b + + RTt R

Cp 1 − ln T T R

3.2. Thermodynamic modeling

Cp R

T

t

T



−1 +

Cp Tt ln R T

(2)

102 RD

T (K)

ln x =

A+B + C ln (T/K)



Cp fus H + RTt R

  Tt

(4)

T  K

(5)

where T is the absolute temperature, and the A, B, and C were parameters obtained by fitting the experimental solubility data and are showed in Table 3 together with the corresponding rootmean-square deviations (rmsds). The C value represents the effect

W. Yang et al. / Fluid Phase Equilibria 314 (2012) 180–184

183

Table 3 Parameters of Eq. (5) for mole fraction solubility of itaconic acid in pure solvents. Solvent

A

B

C

104 rmsd

102 RAD

Methanol Acetonitrile 1-Propanol Ethyl acetate Ethanol 2-Propanol Acetone

2561.2081 −5267.1034 2078.8301 875.1797 2771.1938 3385.6215 2962.5751

−68.8830 50.3105 −66.6103 −68.2352 −80.1150 −91.1617 −94.7540

10.1938 −6.6415 10.0121 10.6678 11.9837 13.5791 14.3654

0.17 0.01 0.25 0.67 0.33 0.17 0.26

2.21 1.31 2.66 1.05 3.29 2.10 1.88

of temperature on the fusion enthalpy, as a deviation of heat capacity. The values of B and C reflect the variation in the solution activity coefficient and provide an indication of the effect of solution nonidealities on the solute. The rmsds are calculated according to: rmsd =

1/2

1 (xci − xi ) N N

(6) 2

i=1

10 RD



where N is the number of experimental points and xci and xi represent the calculated and the experimental solubility values, respectively. The RDs between the calculated and the experimental values are also listed in the Table 2. The RDs are calculated according to: x − xci (7) RD = i xi

0.00

The relative average deviations (RAD) and the rmsd by Eq. (5) are also listed in the Table 3. The RAD is defined as follow:





1 xi − xci RAD = x N i N

(8)

1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 -0.2 -0.4 -0.6 -0.8 -1.0 -1.2 -1.4 0.02

0.04

0.06

0.08

0.10

0.12

0.14

X Fig. 3. Residual deviations (RD) of the solubility of itaconic acid in pure solvents for Eq. (4) as a function of experimental solubility x.

i=1

(1 − x) x

= h

1

(T/K)



1 (Tm /K)

(9)

where x is the mole fraction of the solubility of itaconic acid at the system temperature T, Tm is the normal melting temperature of itaconic acid,  and h are the model parameters determined by the experimental data in the system together with the corresponding rmsds which are listed in Table 4, respectively. The comparison between model prediction according to Eq. (5) and experimental data is showed in Fig. 2. The scatter plot of residual deviations of the solubility of itaconic acid for Eqs. (5) and (9) were plotted in Figs. 3 and 4, respectively. From Tables 3 and 4 and Figs. 3 and 4, it can be seen that the solubility data calculated by the Eqs. (5) and (9) show good agreement with the experiment data. Comparing the calculated results of 70 data points according to Eqs. Table 4 Parameters of Eq. (9) for mole fraction solubility of itaconic acid in pure solvents. Solvent



h

104 rmsd

102 RAD

Methanol Acetonitrile 1-Propanol Ethyl acetate Ethanol 2-Propanol Acetone

−0.0770 0.1543 0.0101 0.1001 −0.0060 −0.0302 0.0895

11775.3443 20144.0946 10767.4179 21317.1567 11183.2689 11542.4656 10048.3750

0.22 0.01 0.25 0.59 0.33 0.43 0.57

2.79 1.31 2.66 1.11 3.29 4.52 3.89

2



ln 1 +

(5) and (9) with the experimental ones, the overall rmsd by Eqs. (5) and (9) are 1.86 × 10−4 and 2.40 × 10−4 , respectively. It can be observed that the regression result of the modified Apelblat equation is more remarkable than that of the Buchowski–Ksiazaczak h equation. Compared with the Buchowski–Ksiazaczak h equation, the modified Apelblat equation is proposed for solid–liquid equilibria, and it is widely accepted to be capable of dealing with pure solvent systems.

10 RD

The Buchowski–Ksiazaczak h equation, Eq. (9), is another way to describe the solution behavior, which was suggested firstly by Buchowski et al. [12]. The Buchowski–Ksiazaczak h equation could fit the experimental data well for many systems with only two parameters  and h [13–16]. In this paper, the solubility data were also correlated with the Buchowski–Ksiazaczak h equation:

1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 -0.2 -0.4 -0.6 -0.8 -1.0 -1.2 -1.4 -1.6 0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

X Fig. 4. Residual deviations (RD) of the solubility of itaconic acid in pure solvents for Eq. (8) as a function of experimental solubility x.

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W. Yang et al. / Fluid Phase Equilibria 314 (2012) 180–184

Table 5 Mole fraction solubility of NaCl in water. NaCl T (K) x x(lit)17 RD

303.15 0.1004 ± 0.0004 0.1001 0.0029

313.15 0.1013 ± 0.0001 0.1009 0.0040

4. Conclusions Using the analytical stirred-flask method, the equilibrium solubility data of itaconic acid in selected organic solvents of methanol, 2-propanol, ethanol, 1-propanol, acetone, ethyl acetate, and acetonitrile over the temperature range of (278.15–333.15 K) were measured in this study. The molar solubility decreases in the order methanol > 2-propanol > ethanol > 1-propanol > acetone > ethyl acetate > acetonitrile. For the temperature range investigated, the solubility of itaconic acid in the solvents increased with increasing temperature. The solubility data were correlated with the modified Apelblat equation and the Buchowski–Ksiazaczak h equation. The deviation calculated of the modified Apelblat equation was less than that of the Buchowski–Ksiazaczak h equation. The modified Apelblat equation can provide more reasonable prediction for the solute considered. The solubility measured in this study can be used for the itaconic acid purification or optical resolution by the preferential crystallization procedure.

C N  h m1 m2 M1 M2 x xci xi

323.15 0.1022 ± 0.0003 0.1019 0.0029

333.15 0.1030 ± 0.0002 0.1026 0.0039

parameter of the Apelblat equation the number of data points parameter of the Buchowski–Ksiazaczak h equation parameter of the Buchowski–Ksiazaczak h equation mass of the solute mass of the solvent molecular mass of solute molecular mass of solvent molar fraction the calculated solubility values the experimental solubility values

Acknowledgements This research work was financially supported by The Six Talents Summit Project of Jiangsu Province (no. 2009118). This research work was also supported by the Fundamental University Science Project of Jiangsu Province in China. (no. 08KJA530002). We thank the editors and the anonymous reviewers.

Supporting information

References

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List of symbols x activity coefficient of solute fus H enthalpy of fusion Cp change of the heat capacity absolute temperature T R gas constant a parameter b parameter parameter of the Apelblat equation A B parameter of the Apelblat equation