Solubilities of Phthalic Acid and o-Toluic Acid in Binary Acetic Acid+

Jul 28, 2016 - The solubilities of phthalic acid and o-toluic acid in binary acetic acid (HAc) + water and HAc + o-xylene solvent mixtures were measur...
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Solubilities of Phthalic Acid and o‑Toluic Acid in Binary Acetic Acid + Water and Acetic Acid + o‑Xylene Solvent Mixtures Zhipeng Shen,† Qinbo Wang,*,† Linhui Chen,‡ Xiaoxiao Sheng,† and Yinchuan Pei† †

Department of Chemical Engineering, Hunan University, Changsha, 410082 Hunan, P. R. China Hangzhou Xingyong Multiplex Material Co. Ltd., Hangzhou, 312402 Zhejiang, P. R. China

‡

ABSTRACT: The solubilities of phthalic acid and o-toluic acid in binary acetic acid (HAc) + water and HAc + o-xylene solvent mixtures were measured by a dissolution temperature method at atmospheric pressure. The mole fractions of HAc in the corresponding solvent mixtures range from 0.00 to 1.00. The measured data show that, within the temperature range studied, the solubilities of phthalic acid and o-toluic acid increase with the increasing temperature at constant solvent composition and initially decrease with the decreasing mole fraction of HAc in HAc + o-xylene and HAc + water solvent mixtures at constant temperature, respectively. It also shows that, within the solvent composition range studied, the HAc + water solvent mixtures with the mole fraction of HAc at 0.5467 has the highest dissolving capacity for phthalic acid at constant temperature, and the highest solubility of o-toluic acid is obtained in HAc + o-xylene solvent mixtures with the mole fraction of HAc of 0.5408 at constant temperature. The experimental solubilities were correlated by both the nonrandom two-liquid (NRTL) and Apelblat equations, and the calculated solubilities within ±11.9% relative deviation agree satisfactorily with the measured results.

1. INTRODUCTION Phthalic acid and o-toluic acid are important chemicals widely used as intermediates in the preparation of plasticizers, polyester resins, agrichemicals, and medicines. Commercially, they can be produced by liquid-phase catalytic oxidation of o-xylene with air in a conventional oxidation reactor. During the oxidation process, acetic acid (HAc) is used as the solvent and cobalt/ manganese/bromide as catalyst, which is a more environmentally friendly way than using nitric acid as an oxidant.1,2 In this technique, o-xylene is oxidized by air and converted into phthalic acid or o-toluic acid at different operating conditions, and water is one of the main byproducts. Sequentially, the reaction mixtures comprising crude phthalic acid, o-toluic acid products, and mother liquor must be separated to produce pure phthalic acid or o-toluic acid. Usually, crystallization is used in the relevant purification process for obtaining products with high purity.3 Solubility data are essential for designing the separation equipment, as well as for setting the relevant operating conditions. To the best of our knowledge, the solubilities of phthalic acid have been measured in water4−10 and HAc.11,12 Wang et al.11 and Li12 have studied the solubility of phthalic acid in HAc + water solvent mixtures with the mass fraction of HAc ranged from 0.75 to 1.00. However, no reports on the solubility of phthalic acid in HAc + o-xylene solvent mixtures are available. Meanwhile, only a few reports on the solubility of o-toluic acid in water13,14 could be found, let alone that in HAc + water and HAc + o-xylene solvent mixtures. Thus, it is necessary to measure the solubilities of phthalic acid and o-toluic acid in the aforementioned solvent mixtures. © XXXX American Chemical Society

In this work, the solubilities of phthalic acid and o-toluic acid in the HAc + water mixtures and HAc + o-xylene mixtures at different temperature were measured by using the dissolution temperature method. The reliabilities of the experimental solubility data were verified by comparison with the literature data. Moreover, the experimental solubility data were correlated with the nonrandom two-liquid (NRTL)15 and modified Apelblat16,17 equations. The equation parameters were obtained, and the calculated solubilities within ±11.9% relative deviation agree satisfactorily with the measured results.

2. EXPERIMENTAL SECTION 2.1. Materials. Phthalic acid (mass fraction >0.990) and o-toluic acid (mass fraction >0.980) were purchased from Aladdin Chemistry Co., Shanghai, and Shanghai Titanchem Co., Ltd., Shanghai, respectively. Acetic acid (mass fraction >0.990) and o-xylene (mass fraction >0.980) were purchased from Sinopharm Chemical Reagent Co., Shanghai. Purified water produced by Hangzhou Wahaha Group Co., Hangzhou, was bought from supermarket (596 mL each bottle) and had the measured resistivity of 18.2 MΩ·cm. The mass fraction of phthalic acid and o-toluic acid were checked by high-performance liquid chromatography (HPLC). The purities of HAc and o-xylene were checked by gas chromatograph (GC), and no impurity peaks were detected. All of the chemicals were used in the experiments without further purifications. The detailed Received: April 20, 2016 Accepted: July 7, 2016

A

DOI: 10.1021/acs.jced.6b00324 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

equilibrium cell that was heated in a thermostatic water bath. A mercury thermometer with an uncertainty of ±0.1 K was used for determining the equilibrium temperature. Continuous stirring was achieved by the magnetic stirrer system, and the temperature at which a (solid + liquid) mixture of known composition dissolves was determined by the laser-detecting system. In the experiment, the equilibrium cell can let the laser beam to pass through it, and the intensity of laser beam was recorded in real time by a computer in terms of the photovoltage. To determine the mass of solvent or solute, a double weighing must have been done. In each experiment, predetermined amounts of solvent and solute were accurately weighed by an electronic balance (type AL204, Mettler Toledo instrument Co. Ltd., uncertainty of 0.0001 g) and added into the equilibrium cell. Then, the cell was put into a thermostatic water bath, and the mixture was heated very slowly (at less than 0.2 K·h−1 near the equilibrium temperature) with continuous stirring. At the early stages of the experiment, the laser beam passing through the solvent−solute mixture was partly obscured due to the undissolved particles of solute. Thus, the intensity of the laser beam passing through the mixture was lower. The intensity increased gradually with the decrease of the amount of solute undissolved. At last when the crystals disappeared, the intensity of the laser beam reached a maximum value and kept steady,

Table 1. Suppliers and Mass Fraction Purity of the Chemicals components

suppliers

phthalic acid Aladdin Chemistry Co., Shanghai o-toluic acid Shanghai Titanchem Co., Ltd., Shanghai acetic acid Sinopharm Chemical Reagent Co., Shanghai o-xylene Sinopharm Chemical Reagent Co., Shanghai water Hangzhou Wahaha Group Co., Hangzhou a

mass fraction purity

analysis method

>0.990 >0.980

HPLCa HPLCa

>0.990

GCb

>0.980

GCb

>0.999

High-performance liquid chromatograph. bGas chromatograph.

suppliers and mass fraction of the used chemicals are listed in Table 1. 2.2. Apparatus and Procedures. The solid−liquid equilibrium (SLE) experiment was carried out by a dissolution temperature method. The details of apparatus and procedures used in this work have been described in detail by Wang et al.18,19 and Chen et al.20 Briefly, the apparatus consists of a solid−liquid equilibrium cell, a magnetic stirring system, a temperature-controlling and measurement system, and a laserdetecting system. The experiment was carried out in a 125 mL

Table 2. Experimental Solubility (x1) of Phthalic Acid (1) in HAc (2) + Water (3) Solvent Mixtures at Different Temperatures and Pressure p = 101.3 kPaa T/K

102 x1

102 xc1b

RD1/%

102 xc2b

T/K

RD2/%

102 x1

102 xc1b

RD1/%

102 xc2b

RD2/%

0.2252 0.2487 0.2726 0.3002 0.3323 0.3765

0.2195 0.2455 0.2736 0.3012 0.3265 0.3747

−2.52 −1.26 0.356 0.323 −1.76 −0.472

0.2265 0.2531 0.2818 0.3103 0.3365 0.3867

0.580 1.78 3.39 3.36 1.25 2.71

0.5884 0.6898 0.7894 0.8945 1.032

0.5996 0.7067 0.8024 0.8918 1.040

1.90 2.46 1.65 −0.297 0.769

0.5541 0.6558 0.7493 0.8395 0.9895

1.062 1.215 1.366 1.551 1.734

1.059 1.222 1.354 1.529 1.686

−0.314 0.587 −0.849 −1.44 −2.76

1.080 1.258 1.412 1.619 1.815

1.71 3.61 3.38 4.37 4.67

1.430 1.619 1.803 1.986 2.172

1.434 1.591 1.786 1.961 2.191

0.260 −1.70 −0.932 −1.28 0.858

1.426 1.586 1.780 1.960 2.191

−0.258 −1.98 −1.25 −1.29 0.872

1.743 1.934 2.112 2.299 2.510

1.733 1.946 2.085 2.318 2.511

−0.568 0.601 −1.25 0.800 0.024

1.748 1.952 2.095 2.318 2.515

0.316 0.937 −0.802 0.826 0.188

c

306.95 311.05 314.15 316.65 319.35 322.15

0.1089 0.1311 0.1455 0.1601 0.1781 0.2019

0.1075 0.1256 0.1414 0.1557 0.1728 0.1925

−1.28 −4.22 −2.80 −2.75 −3.01 −4.69

0.1121 0.1307 0.1469 0.1614 0.1788 0.1989

307.75 313.65 317.35 320.95 323.55

0.2709 0.3377 0.3897 0.4404 0.4994

0.2794 0.3545 0.4110 0.4743 0.5245

3.14 4.99 5.47 7.71 5.03

0.2603 0.3278 0.3789 0.4363 0.4831

306.65 311.05 315.75 320.35 323.85

0.4847 0.5754 0.6640 0.7536 0.9072

0.4887 0.5788 0.6937 0.8000 0.9319

0.834 0.593 4.47 6.15 2.73

0.4928 0.5818 0.6944 0.8009 0.9408

306.55 311.35 315.95 319.95 323.45

0.7048 0.8609 1.004 1.134 1.271

0.6858 0.8249 0.9665 1.103 1.239

−2.69 −4.18 −3.69 −2.70 −2.55

0.7169 0.8492 0.9830 1.112 1.242

310.35 318.25 322.45 325.55 329.65

0.9280 1.125 1.269 1.411 1.567

0.8836 1.103 1.258 1.382 1.568

−4.78 −1.98 −0.861 −2.10 0.025

0.9170 1.149 1.294 1.414 1.588

x2,solv = 0.0000 2.99 325.55 −0.319 328.45 0.957 331.25 0.840 333.75 0.390 335.85 −1.50 339.45 x2,solv = 0.0701 −3.90 327.05 −2.92 331.35 −2.76 334.75 −0.929 337.65 −3.26 341.85 x2,solv = 0.1665 1.67 327.55 1.11 331.65 4.58 334.75 6.26 338.45 3.70 341.55 x2,solv = 0.3109 1.72 328.25 −1.36 331.65 −2.06 335.35 −1.91 338.45 −2.26 342.05 x2,solv = 0.5467 −1.18 333.05 2.08 336.95 1.98 339.45 0.170 343.05 1.31 345.95

−5.83 −4.92 −5.08 −6.15 −4.10

a

Standard uncertainties u are u(T) = 0.05 K, ur(p) = 0.02, ur(x1) = 0.05, and ur(x2,solv) = 0.02. bxc1 and xc2 represent the NRTL model and Apelblat model correlated solubility, respectively. cx2,solv is the mole fraction of HAc in HAc + water mixture solvent. B

DOI: 10.1021/acs.jced.6b00324 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

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Table 3. Experimental Solubility (x1) of Phthalic Acid (1) in HAc (2) + o-Xylene (3) Solvent Mixtures at Different Temperatures and Pressure p = 101.3 kPaa T/K

102 x1

102 xc1b

RD1/%

102 xc2b

T/K

RD2/%

102 x1

102 xc1b

RD1/%

102 xc2b

RD2/%

0.3808 0.4303 0.4847 0.5405 0.5966

0.3898 0.4292 0.4822 0.5382 0.5894

2.37 −0.252 −0.529 −0.413 −1.20

0.3890 0.4291 0.4837 0.5421 0.5961

2.16 −0.268 −0.220 0.309 −0.073

0.8347 0.9193 1.005 1.126 1.245

0.8340 0.9268 0.9979 1.128 1.233

−0.078 0.817 −0.671 0.200 −0.935

0.8281 0.9217 0.9943 1.128 1.237

−0.782 0.259 −1.03 0.165 −0.654

1.014 1.123 1.241 1.374 1.584

1.036 1.142 1.246 1.366 1.615

2.17 1.62 0.401 −0.583 1.94

1.035 1.140 1.244 1.366 1.615

2.12 1.51 0.312 −0.612 1.93

1.076 1.183 1.291 1.457 1.658

1.057 1.180 1.303 1.418 1.629

−1.80 −0.299 0.948 −2.71 −1.71

1.056 1.175 1.295 1.410 1.618

−1.88 −0.688 0.320 −3.22 −2.39

0.9977 1.156 1.313 1.470 1.627 1.803

1.002 1.170 1.345 1.500 1.641 1.794

0.402 1.26 2.45 1.99 0.849 −0.487

0.9927 1.159 1.332 1.486 1.628 1.783

−0.496 0.311 1.45 1.08 0.069 −1.10

c

308.75 318.05 321.45 326.95 330.55

0.1885 0.2441 0.2717 0.3070 0.3417

0.1868 0.2436 0.2679 0.3120 0.3442

−0.876 −0.218 −1.39 1.64 0.746

0.1894 0.2440 0.2677 0.3111 0.3432

315.15 323.45 330.35 333.45 337.25

0.4091 0.5159 0.6105 0.6826 0.7583

0.4008 0.5121 0.6256 0.6831 0.7605

−2.03 −0.728 2.47 0.062 0.288

0.4017 0.5096 0.6203 0.6774 0.7544

312.15 317.25 321.95 326.55 330.65

0.5355 0.6240 0.7185 0.8123 0.9182

0.5305 0.6220 0.7189 0.8274 0.9361

−0.929 −0.333 0.047 1.87 1.94

0.5408 0.6300 0.7246 0.8303 0.9370

311.75 315.35 318.85 322.45 325.45

0.6524 0.7317 0.8153 0.8974 0.9815

0.6382 0.7144 0.7967 0.8911 0.9772

−2.17 −2.36 −2.29 −0.702 −0.437

0.6470 0.7217 0.8021 0.8937 0.9775

294.45 300.55 305.95 310.45 315.85 320.45

0.4013 0.4867 0.5722 0.6580 0.7712 0.8845

0.4068 0.4895 0.5767 0.6604 0.7766 0.8904

1.37 0.584 0.772 0.364 0.698 0.663

0.4019 0.4849 0.5716 0.6548 0.7697 0.8824

x2,solv = 0.3133 0.482 335.15 −0.029 338.75 −1.45 343.15 1.35 347.35 0.442 350.85 x2,solv = 0.5398 −1.80 340.55 −1.23 344.35 1.61 347.05 −0.766 351.55 −0.517 354.85 x2,solv = 0.7263 1.00 334.05 0.952 337.35 0.840 340.35 2.23 343.55 2.04 349.35 x2,solv = 0.8763 −0.822 328.05 −1.37 331.65 −1.62 334.95 −0.419 337.85 −0.405 342.55 x2,solv = 1.000 0.168 324.45 −0.370 329.75 −0.118 334.55 −0.490 338.35 −0.189 341.55 −0.242 344.75

a

Standard uncertainties u are u(T) = 0.05 K, ur(p) = 0.02, ur(x1) = 0.05, and ur(x2,solv) = 0.02. bxc1 and xc2 represent the NRTL model and Apelblat model correlated solubility, respectively. cx2,solv is the mole fraction of HAc in HAc + o-xylene mixture solvent.

Table 4. Experimental Solubility (x1) of o-Toluic Acid (1) in HAc (2) + Water (3) Solvent Mixtures at Different Temperatures and Pressure p = 101.3 kPaa T/K

102 x1

102 xc1b

RD1/%

102 xc2b

T/K

RD2/%

102 x1

102 xc1b

RD1/%

102 xc2b

RD2/%

0.0620 0.0724 0.0840 0.0960 0.1186 0.1427

0.0592 0.0692 0.0835 0.0968 0.1173 0.1423

−4.60 −4.37 −0.696 0.828 −1.10 −0.258

0.0587 0.0683 0.0770 0.0895 0.1123 0.1413

−5.38 −5.63 −8.37 −6.82 −5.32 −0.986

0.2399 0.2866 0.3493 0.4181 0.4919

0.2415 0.2965 0.3579 0.4251 0.5031

0.685 3.48 2.46 1.69 2.28

0.2659 0.3080 0.3771 0.4638 0.5504

10.9 7.50 7.96 10.9 11.9

1.016 1.451 1.883 2.420 3.116

0.9794 1.438 1.834 2.333 2.988

−3.55 −0.863 −2.56 −3.60 −4.14

0.9943 1.323 1.762 2.244 2.875

−2.08 −8.83 −6.43 −7.27 −7.74

3.858 5.057 6.772

3.801 4.948 6.721

−1.47 −2.17 −0.754

4.177 5.210 6.822

c

−6.57 1.59 3.50 6.27 1.64 −2.08

306.55 312.35 316.45 319.45 321.85 324.45

0.0217 0.0273 0.0323 0.0378 0.0448 0.0531

0.0203 0.0277 0.0334 0.0402 0.0455 0.0520

306.75 313.35 318.45 322.65 325.95

0.0831 0.1152 0.1444 0.1736 0.2027

0.0843 0.1159 0.1530 0.1810 0.2068

303.55 309.85 314.25 318.95 322.15

0.3116 0.4221 0.5325 0.6643 0.7960

0.2956 0.4051 0.5175 0.6427 0.7622

−5.15 −4.03 −2.80 −3.25 −4.25

0.2976 0.4123 0.5184 0.6630 0.7844

303.55 310.15 314.35

1.172 1.536 1.878

1.105 1.493 1.837

−5.74 −2.81 −2.17

1.089 1.565 1.978

1.43 0.579 5.95 4.26 2.02

0.0201 0.0275 0.0342 0.0402 0.0456 0.0523 0.0835 0.1171 0.1519 0.1882 0.2226

x2,solv = 0.0000 −7.29 326.65 0.753 329.55 6.14 331.85 6.23 334.75 1.86 339.15 −1.51 343.65 x2,solv = 0.0698 0.481 329.45 1.58 332.35 5.18 336.35 8.40 340.45 9.83 343.85 x2,solv = 0.1668 −4.50 326.65 −2.33 332.05 −2.63 336.35 −0.194 340.25 −1.46 343.85 x2,solv = 0.3104 −7.08 327.45 1.84 331.25 5.32 335.85 C

8.27 3.02 0.737

DOI: 10.1021/acs.jced.6b00324 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

Table 4. continued T/K

102 x1

102 xc1b

RD1/%

102 xc2b

318.95 323.35

2.457 3.122

2.374 3.031

−3.38 −2.93

2.564 3.297

302.05 308.75 312.45 316.55 320.75

3.583 4.764 5.761 6.776 7.851

3.723 4.945 5.928 7.049 8.327

3.92 3.81 2.91 4.03 6.06

3.778 4.818 5.562 6.567 7.843

T/K

RD2/%

x2,solv = 0.3104 4.37 340.95 5.61 346.75 x2,solv = 0.5454 5.45 324.15 1.15 328.45 −3.46 333.55 −3.08 338.45 −0.101 344.55

102 x1

102 xc1b

RD1/%

102 xc2b

RD2/%

8.977 12.66

9.214 13.07

2.64 3.20

9.222 13.03

2.73 2.88

9.131 10.97 13.90 17.46 24.02

9.236 11.21 14.04 17.93 24.66

1.15 2.19 0.944 2.66 2.65

9.102 11.06 14.05 17.82 24.21

−0.315 0.786 1.01 2.03 0.754

a

Standard uncertainties u are u(T) = 0.05 K, ur(p) = 0.02, ur(x1) = 0.05, and ur(x2,solv) = 0.02. bxc1 and xc2 represent the NRTL model and Apelblat model correlated solubility, respectively. cx2,solv is the mole fraction of HAc in HAc + water mixture solvent.

Table 5. Experimental Solubility (x1) of o-Toluic Acid (1) in HAc (2) + o-Xylene (3) Solvent Mixtures at Different Temperatures and Pressure p = 101.3 kPaa T/K

x1

xc1b

RD1/%

xc2b

T/K

RD2/%

x1

xc1b

xc2b

RD2/%

0.2726 0.3238 0.3633 0.4105 0.4513

0.2740 0.3244 0.3678 0.4178 0.4601

0.513 0.164 1.23 1.76 1.95

0.2753 0.3179 0.3609 0.4107 0.4545

1.01 −1.83 −0.672 0.030 0.713

0.3582 0.3893 0.4375 0.4787 0.5142

0.3567 0.3894 0.4360 0.4810 0.5216

−0.430 0.018 −0.339 0.499 1.43

0.3545 0.3866 0.4314 0.4762 0.5169

−1.03 −0.701 −1.40 −0.520 0.527

0.3606 0.3952 0.4263 0.4602 0.4904

0.3602 0.3925 0.4257 0.4583 0.4886

−0.116 −0.683 −0.136 −0.432 −0.362

0.3653 0.3976 0.4316 0.4644 0.4952

1.30 0.602 1.24 0.891 0.984

0.3482 0.3816 0.4117 0.4445 0.4739

0.3441 0.3773 0.4024 0.4392 0.4656

−1.20 −1.14 −2.26 −1.20 −1.74

0.3465 0.3819 0.4077 0.4479 0.4756

−0.497 0.090 −0.972 0.748 0.354

0.3151 0.3532 0.3874 0.4239 0.4543

0.3078 0.3430 0.3747 0.4141 0.4433

−2.32 −2.90 −3.27 −2.32 −2.42

0.3094 0.3462 0.3794 0.4227 0.4536

−1.82 −1.99 −2.04 −0.282 −0.141

0.3227 0.3504 0.3782 0.4295 0.4819 0.5512

0.3101 0.3414 0.3665 0.4150 0.4640 0.5384

−3.89 −2.56 −3.09 −3.38 −3.71 −2.33

0.3274 0.3617 0.3845 0.4308 0.4732 0.5549

1.45 3.22 1.68 0.298 −1.81 0.673

RD1/%

c

300.75 305.45 309.75 313.35 317.65 321.45

0.1103 0.1344 0.1572 0.1788 0.2094 0.2379

0.1129 0.1332 0.1546 0.1759 0.2069 0.2374

2.40 −0.868 −1.66 −1.63 −1.23 −0.197

0.1104 0.1333 0.1575 0.1804 0.2111 0.2415

303.85 308.75 312.85 316.75 321.95

0.2079 0.2356 0.2614 0.2855 0.3238

0.2066 0.2330 0.2578 0.2829 0.3209

−0.621 −1.11 −1.38 −0.916 −0.898

0.2057 0.2325 0.2571 0.2824 0.3194

302.65 308.15 312.25 315.75 320.35

0.2213 0.2448 0.2670 0.2879 0.3217

0.2217 0.2478 0.2703 0.2915 0.3226

0.178 1.19 1.25 1.24 0.281

0.2224 0.2512 0.2748 0.2966 0.3275

300.65 306.15 310.05 314.95 320.45

0.2004 0.2258 0.2497 0.2790 0.3154

0.2061 0.2307 0.2516 0.2796 0.3149

2.88 2.19 0.774 0.211 −0.163

0.1998 0.2273 0.2489 0.2788 0.3163

300.35 305.55 309.55 313.65 317.75

0.1755 0.2000 0.2230 0.2484 0.2722

0.1807 0.2030 0.2235 0.2465 0.2707

2.95 1.52 0.210 −0.747 −0.556

0.1732 0.1986 0.2204 0.2449 0.2720

300.25 307.35 311.35 314.95 320.05 324.15

0.1453 0.1794 0.2026 0.2199 0.2628 0.2936

0.1430 0.1726 0.1982 0.2110 0.2480 0.2778

−1.62 −3.80 −2.18 −4.05 −5.66 −5.38

0.1471 0.1812 0.2033 0.2253 0.2599 0.2911

x2,solv = 0.0000 0.053 325.25 −0.794 329.55 0.215 333.45 0.877 337.55 0.785 340.85 1.54 x2,solv = 0.3071 −1.08 326.45 −1.31 330.25 −1.64 335.15 −1.07 339.65 −1.36 343.45 x2,solv = 0.5408 0.499 325.45 2.59 329.45 2.92 333.35 3.01 336.85 1.80 339.95 x2,solv = 0.7263 −0.297 324.45 0.664 328.75 −0.299 331.65 −0.065 335.85 0.307 338.55 x2,solv = 0.8761 −1.32 322.85 −0.685 327.35 −1.17 331.05 −1.39 335.45 −0.082 338.35 x2,solv = 1.000 1.18 328.45 0.971 332.15 0.381 334.45 2.42 338.75 −1.10 342.35 −0.832 348.55

a

Standard uncertainties u are u(T) = 0.05 K, ur(p) = 0.02, ur(x1) = 0.05, and ur(x2,solv) = 0.02. bxc1 and xc2 represent the NRTL model and Apelblat model correlated solubility, respectively. cx2,solv is the mole fraction of HAc in HAc + o-xylene mixture solvent.

uncertainty of temperature was ±0.05 K. The uncertainty of mass measurement was ±0.0001 g. The reliability of the experimental technique and apparatus has been verified in our recent work.18,19 The solubility (x1) is defined as the mole fraction of solute in solvent mixture.

the SLE was considered to be reached. The temperature corresponding to the maximum intensity was taken as SLE temperature of the mixture. To ensure the accuracy of the measured solubility data, each experimental data point was duplicated, and the standard D

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3. RESULTS AND DISCUSSION 3.1. Experimental Results. In this work, the measured solubilities of phthalic acid and o-toluic acid in HAc + water and HAc + o-xylene mixtures are summarized in Tables 2−5 and plotted in Figures 1−4, respectively. However, the solubility data of phthalic acid in o-xylene cannot be obtained because phthalic acid is not detectably soluble in o-xylene. From Figures 1−4, it can be seen that the solubilities of phthalic acid and o-toluic acid in HAc + water and HAc + o-xylene mixtures increase with the increase of temperature at constant solvent composition. Furthermore, Figure 1 shows the influence of solvent composition on the solubility of phthalic acid in HAc + water mixtures. Within the temperature and solvent composition range studied, the binary HAc + water solvent mixtures with a mole fraction of HAc at 0.5467 have the best dissolving capacity for phthalic acid. Figures 2 and 3 give the results that the solubilities of phthalic Figure 3. Mole fraction solubilities (x1) of o-toluic acid (1) in HAc (2) + water (3) solvent mixtures: ■, x2,solv = 0.0000; ●, x2,solv = 0.0698; ▲, x2,solv = 0.1668; ▼, x2,solv = 0.3104; ◀, x2,solv = 0.5454. Scatter, experimental data;  (solid line), NRTL equation correlated; --- (dotted line), Apelblat equation correlated.

Figure 1. Mole fraction solubilities (x1) of phthalic acid (1) in HAc (2) + water (3) solvent mixtures: ■, x2,solv = 0.0000; ●, x2,solv = 0.0701; ▲, x2,solv = 0.1665; ▼, x2,solv = 0.3109; ◀, x2,solv = 0.5467. Scatter, experimental data;  (solid line), NRTL equation correlated; --- (dotted line), Apelblat equation correlated. Figure 4. Mole fraction solubilities (x1) of o-toluic acid (1) in HAc (2) + o-xylene (3) solvent mixtures: ■, x2,solv = 0.0000; ●, x2,solv = 0.3071; ▲, x2,solv = 0.5408; ▼, x2,solv = 0.7263; ◀, x2,solv = 0.8761; ▶, x2,solv = 1.000. Scatter, experimental data;  (solid line), NRTL equation correlated; --- (dotted line), Apelblat equation correlated.

acid in HAc + o-xylene and o-toluic acid in HAc + water mixtures decrease with the decreasing mole fraction of HAc at a constant temperature. Figure 4 shows that, within solvent composition range studied, the highest solubility of o-toluic acid is obtained in HAc + o-xylene solvent mixtures with the mole fraction of HAc of 0.5408 at constant temperature, and a similar conclusion can also be deduced from Table 5. To check the reliability of the obtained solubility data, the measured solubilities of phthalic acid and o-toluic acid in pure water and HAc were compared with the literature reported data in Figures 5−7. From Figure 5, it can be seen that the solubility data of phthalic acid in water measured in this work have good agreement with the literature data, which indicates the reliability of our experimental technique and the accuracy of the measured solubility data. Figure 6 shows that the solubility data of phthalic acid in HAc agree well with the literature data from Li.12 However,

Figure 2. Mole fraction solubilities (x1) of phthalic acid (1) in HAc (2) + o-xylene (3) solvent mixtures: ●, x2,solv = 0.3133; ▲, x2,solv = 0.5398; ▼, x2,solv = 0.7263; ◀, x2,solv = 0.8763; ▶, x2,solv = 1.000. Scatter, experimental data;  (solid line), NRTL equation correlated; --- (dotted line), Apelblat equation correlated. E

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over the whole temperature range, the solubility data of phthalic acid in HAc deviate significantly from the data reported by Wang et al.11 Considering that there is a large discrepancy between this work and Wang et al., the solubility of phthalic acid in HAc was measured at least two times. The repetitive experiments testified that the solubility data of phthalic acid in HAc measured in this work are reliable and that reported by Li also demonstrate the same conclusion. The discrepancy may be attributed to different measurement methods. Wang et al. used the static analytical method to determine the solubility of phthalic acid in HAc. In their experimental procedure, the vial of sampled solution was placed in vacuo at 323.15 K for more than 3 h for drying. After the solvent in the vial had completely evaporated, the vial was weighed to determine the solubility of phthalic acid. However, it is difficult to know the details of vacuo and whether the vacuo equipment worked normally or not. The solubility of phthalic acid determined by Wang et al. is larger than that of our work and Li, so we suppose one possible reason might be the residual solvent has an effect on the solubility of determination. Moreover, the undissolved particles of solute might be withdrawn together with the clear upper portion of the solution. It could also cause the determined solubility is larger than the real solubility. As shown in Figure 7, the measured solubilities of o-toluic acid in water are consistent with the literature data from Strong13 but deviate from the results reported by Jia.14 Because the reliability of our experimental technique has been verified and the measured solubilities of o-toluic acid have no important deviations with the literature data from Strong, we hold the view that the measured solubilities of o-toluic acid in this work are reliable. 3.2. Correlation of Experimental Data. NRTL Correlation. The SLE can be approximated in a general manner by the eq 1 that involves the enthalpy of fusion of the solute and phase transition and the melting point of the solute.20,21

Figure 5. Experimental solubilities and literature data of phthalic acid in water: ●, measured in this work; □, ref 4; ○, ref 5; △, ref 6; ▽, ref 7; ◊, ref 8; ◁, ref 9; ▷, ref 10. x1 is the solubility of phthalic acid.

ln(γ1x1) = −

ΔfusH ⎛ 1 1 ⎞ ΔtrsH ⎛ 1 1 ⎞ ⎜ − ⎟− ⎜ − ⎟ R ⎝T Tfus ⎠ R ⎝T Ttrs ⎠ (1)

Figure 6. Experimental solubilities and literature data of phthalic acid in HAc: ●, measured in this work; □, ref 11; ○, ref 12. x1 is the solubility of phthalic acid.

For the four studied systems, the solid−solid phase does not occur, and thus the eq 1 can be simplified to the form shown as eq 2. ln(γ1x1) = −

ΔfusH ⎛ 1 1 ⎞ ⎟ ⎜ − R ⎝T Tfus ⎠

(2)

In eqs 1 and 2, γ1 is the activity coefficient of solute, and x1 is the mole fraction of solute in solution. ΔfusH and ΔtrsH are the molar fusion enthalpy of solute and molar enthalpy of solid− solid phase transition. Tfus and Ttrs are the fusion temperature and transition temperature. R is the universal gas constant, and T is the absolute temperature. Because activity coefficient (γ1) depends on the mole fraction and temperature, eq 2 must be solved iteratively. For the calculation of activity coefficient, the NRTL activity coefficient model was employed in this work as15 3

ln γi =

∑ j = 1 τjiGjixj 3 ∑k = 1 Gkixk

τij = aij +

Figure 7. Experimental solubilities and literature data of o-toluic acid in water: ●, measured in this work; □, ref 13; ○, ref 14. x1 is the solubility of o-toluic acid.

τij ≠ τji , F

bij T

,

3

+

⎛

Gijxj ⎜τ 3 ⎜ ij j = 1 ∑k = 1 Gkjxk ⎝

∑

Gij = exp( −αijτij), τii = 0

∑k = 1 τkjGkjxk ⎞ ⎟ 3 ∑k = 1 Gkjxk ⎟⎠ 3

−

(3)

αij = αji , (4)

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where xi and γi denote the mole fraction and the activity coefficient of component i, respectively. aij and bij are the parameters needed to be regressed. The term αij in the NRTL model was fixed at 0.3, as recommended by Prausnitz22 according to the molecular polarity. In order to calculate the solubility, the molar fusion enthalpy of solute (ΔfusH) and the fusion temperature (Tfus) are required. ΔfusH and Tfus used in this work for phthalic acid are 55497 J·mol−1 and 481.2 K, and those for o-toluic acid are 20149 J·mol−1 and 377.1 K, which can be obtained from the literature.11,23 By using model eqs 1 and 3, the measured solubility data, as shown in Tables 2−5, for the four studied systems were correlated. The optimized model parameters are listed in Table 6. The regression of model parameters was performed using the Matlab program, and the Matlab (Mathwork, MA) function fminsearch with the procedure is based on the Simplex approach proposed by Nelder and Mead.24 Function fminsearch in the optimization toolbox of Matlab (Mathwork, MA) uses the Nelder−Mead Simplex approach and can be used for the minimization of the objective function, which is the averaged relative deviation (ARD) between experimental and calculated solubility defined in this work as RDi =

xci − xi × 100, xi

ARD =

1 n

2 3 A = A 0 + A1x 2,solv + A 2 x 2,solv + A3x 2,solv 2 3 B = B0 + B1x 2,solv + B2 x 2,solv + B3x 2,solv 2 3 C = C0 + C1x 2,solv + C2x 2,solv + C3x 2,solv

where x2,solv is the mole fraction of HAc in HAc + water or HAc + o-xylene mixtures and Ai, Bi, and Ci are model parameters. Once again, the measured solubilities data for the four studied systems were correlated by using model eqs 6 and 7, and the model parameters were optimized. The optimum algorithm used in the parameter estimation program was same as to that applied in the NRTL correlation, and the objective function is chosen as that defined in eq 5. The calculated results with Apelblat model along with the corresponding RD are listed in Tables 2−5, and the obtained model parameters and the ARD are given in Table 7. For comparison, the calculated results are also plotted in Figures 1−4, respectively. It clearly shows that a good agreement between the experimental solubilities with that calculated. Therefore, the modified Apelblat equation is suitable to correlate the solubilities of phthalic acid and o-toluic acid in binary HAc + water and HAc + o-xylene solvent mixtures.

n

∑ abs(RDi) i=1

Table 7. Apelblat Equation Parameters (A, B, and C) for Phthalic Acid + HAc + Water, Phthalic Acid + HAc + oXylene, o-Toluic Acid + HAc + Water, and o-Toluic Acid + HAc + o-Xylene

(5)

where xci and xi are the ith calculated and experimental solubility and n is the total number of experimental points. The corresponding RD are presented in Tables 2−5, respectively. The averaged relative deviation (ARD) defined in eq 5 is listed in Table 6. For comparison, the calculated data along with the experimental data are illustrated in Figures 1−4. As can be seen from these figures, the calculated data have good agreement with the experimental data. It indicates that the NRTL model can be used to correlate the solubilities of phthalic acid and o-toluic acid in binary HAc + water and HAc + o-xylene solvent mixtures. Modified Apelblat Correlation. The modified Apelblat equation16,17 was also applied to correlate the experimental solubility data in this work. The form of equation proposed by Apelblat is shown as ln x1 = A +

B + C ln T T

(7)

Ai

(6)

In eq 6, x1 is the mole fraction of phthalic acid or o-toluic acid, T is the absolute temperature, A, B, and C are the empirical model parameters. In order to use eq 6 to correlate the solubility of phthalic acid and o-toluic acid at various solvent compositions, the following empirical correlations were adopted.25−27

i i i i

= = = =

0 1 2 3

i i i i

= = = =

0 1 2 3

i i i i

= = = =

0 1 2 3

i i i i

= = = =

0 1 2 3

Bi

Ci

Phthalic Acid + HAc + Water −191.70 5448.5 29.189 374.93 −20115 −51.619 −271.43 36209 20.927 −267.87 −16454 60.960 Phthalic Acid + HAc + o-Xylene −144.35 4072.2 21.653 136.89 −5498.5 −20.409 −185.61 6052.3 29.258 105.01 −3269.7 −16.793 o-Toluic Acid + HAc + Water −157.15 2434.7 24.574 −514.48 30141 76.680 −231.24 −27050 48.912 333.25 41330 −76.739 o-Toluic Acid + HAc + o-Xylene 39.425 −5017.4 −4.3717 −251.31 17059 34.554 92.789 −10809 −10.457 69.047 −1359.2 −11.214

ARD/% 1.87

0.890

4.51

1.05

Table 6. Parameters of the NRTL Model for Phthalic Acid (1) in HAc (2) + Water (3) + o-Xylene (4) and o-Toluic Acid (1) in HAc (2) + Water (3) + o-Xylene (4) solute

i−j

aij

aji

bij/K

bji/K

ARD

phthalic acid

1−2 1−3 2−3 1−4 2−4 1−2 1−3 2−3 1−4 2−4

2.363 8.459 −3.607 3.763 8.191 5.100 0.4671 −3.607 2.564 8.191

3.263 2.192 7.153 8.320 −1.341 −9.759 −2.154 7.153 3.216 −1.341

−1171 −2494 35.61 −1170 −2145 −1940 −106.5 35.61 −1135 −2145

−1171 −1085 −987.0 −2725 428.3 4010 2786 −987.0 −30.23 428.3

1.64%

o-toluic acid

G

2.19%

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(10) Ward, H. L.; Cooper, S. S. The System, Benzoic Acid, orthoPhthalic Acid, Water. J. Phys. Chem. 1929, 34, 1484−1493. (11) Wang, Q. B.; Hou, L. X.; Cheng, Y. W.; Li, X. Solubilities of Benzoic Acid and Phthalic Acid in Acetic Acid + Water Solvent Mixtures. J. Chem. Eng. Data 2007, 52, 936−940. (12) Li, Y. Determination and Correlation of Solubilities of Components Involving in TA Manufacture Residues with Aqueous HAC and Ethanol as Solvent. Master Thesis, Tianjin Univeristy, Tianjin, P. R. China, 2006. (13) Strong, L. E.; Neff, R. M.; Whitesel, I. Thermodynamics of Dissolving and Solvation Process for Benzoic Acid and the Toluic Acids in Aqueous Solution. J. Solution Chem. 1989, 18, 101−114. (14) Jia, Q. Z. Study on the Solubility and Octanol/Water Partition Coefficients of the Benzoic Acid Derivatives. Ph.D. Dissertation, Tianjin Univeristy, Tianjin, P. R. China, 2007. (15) Renon, H.; Prausnitz, J. M. Local Compositions in Thermodynamic Excess Functions for Liquid Mixtures. AIChE J. 1968, 14, 135−144. (16) Apelblat, A.; Manzurola, E. Solubilities of o-Acetylsalicylic, 4Aminosalicylic, 3,5-Dinitrosalicylic, and p-Toluic Acid, and Magnesium-DL-Aspartate in Water from T = (278 to 348) K. J. Chem. Thermodyn. 1999, 31, 85−91. (17) Manzurola, E.; Apelblat, A. Solubilities of L-Glutamic acid, 3Nitrobenzoic Acid, p-Toluic Acid, Calcium-L-Lactate, Calcium Gluconate, Magnesium-DL-Aspartate, and Magnesium-L-Lactate in Water. J. Chem. Thermodyn. 2002, 34, 1127−1136. (18) Wang, H.; Wang, Q. B.; Xiong, Z. H.; Chen, C. X.; Shen, B. W. Solubilities of Benzoic Acid in Binary (Benzyl Alcohol + Benzaldehyde) Solvent Mixtures. J. Chem. Thermodyn. 2015, 83, 61− 66. (19) Wang, H.; Wang, Q. B.; Xiong, Z. H.; Chen, C. X.; Shen, B. W. Solubilities of Benzoic Acid in Binary Methylbenzene + Benzyl Alcohol and Methylbenzene + Benzaldehyde Solvent Mixtures. J. Chem. Eng. Data 2015, 60, 643−652. (20) Chen, M. M.; Ma, P. S. Solid-Liquid Equilibria of Several Systems Containing Acetic Acid. J. Chem. Eng. Data 2004, 49, 756− 759. (21) Ma, P. S.; Xia, Q. Determination and Correlation for Solubility of Aromatic Acids in Solvents. Chin. J. Chem. Eng. 2001, 9, 39−44. (22) Prausnitz, J. M.; Lichtenthaler, R. N.; De Azevedo, E. G. Molecular Thermodynamics of Fluid-Phase Equilibria, 3rd ed.; Prentice Hall: Beijing, 1999. (23) Andrews, D. H.; Lynn, G.; Johnston, J. The Heat Capacities and Heat of Crystallization of Some Isomeric Aromatic Compounds. J. Am. Chem. Soc. 1926, 48, 1274−1287. (24) Nelder, J. A.; Mead, R. A. Simplex Method for Function Minimization. Comput. J. 1965, 7, 308−313. (25) Li, C. L.; Wang, Q. B.; Shen, B. W.; Xiong, Z. H.; Chen, C. X. Solubilities of 5,10,15,20-Tetrakis(p-chlorophenyl)porphyrin in Binary Propionic Acid + Water Solvent Mixtures at (293.2 to 353.2) K. J. Chem. Eng. Data 2014, 59, 3953−3959. (26) Li, C. L.; Wang, Q. B.; Shen, B. W.; Xiong, Z. H.; Chen, C. X. Solubilities of 5,10,15,20-Tetraphenylporphyrin and 5,10,15,20Tetraphenylporphyrin Manganese(III) Chloride in Binary Ethanol + Water Solvent Mixtures. J. Chem. Eng. Data 2015, 60, 925−931. (27) Li, C. L.; Wang, Q. B.; Shen, B. W.; Xiong, Z. H.; Chen, C. X. Solubilities of 5,10,15,20-Tetraphenylporphyrin and 5,10,15,20-Tetra(pchlorophenyl) porphyrin in Binary N,N-Dimethylformamide + Water Solvent Mixtures. J. Chem. Eng. Data 2015, 60, 2834−2842.

4. CONCLUSIONS In this work, the solubilities of phthalic acid and o-toluic acid in HAc + water and HAc + o-xylene solvent mixtures at atmospheric pressure have been measured by a dissolution temperature method. The solubilities of phthalic acid and o-toluic acid in the investigated solvent mixtures increase with the increase of temperature at constant solvent composition. The effects of mole fraction of HAc in the solvent mixtures at 0.00−1.00 on the solubility were studied. The solubility of phthalic acid in HAc + o-xylene and o-toluic acid in HAc + water mixtures decreases with the decreasing mole fraction of HAc at constant temperature. Meanwhile, it can be found that, within the solvent composition range studied, the HAc + water solvent mixtures with the mole fraction of HAc at 0.5467 has the highest dissolving capacity for phthalic acid at constant temperature, and the highest solubility of o-toluic acid is obtained in HAc + o-xylene solvent mixtures with the mole fraction of HAc of 0.5408 at constant temperature. Moreover, both the NRTL equation and the modified Apelblat equation were adopted to correlate the measured solubility data, and they fit satisfactorily to the experimental data. The measured solubility data in this work can be useful for the separation and purification of phthalic acid and o-toluic acid in the production process.

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AUTHOR INFORMATION

Corresponding Author

*E-mail address: [email protected]. Funding

The project was granted financial support from the Fundamental Research Funds for the Central Universities and the National Nature Science Fund (21302049). Notes

The authors declare no competing financial interest.

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REFERENCES

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