Article pubs.acs.org/jced
Ternary Phase Diagram for Systems of Succinic Acid + Urea + Water, Glutaric Acid + Urea + Water, and Adipic Acid + Urea + Water at (288.15 and 303.15) K Gan-Bing Yao,* Ling Wang, Ya-Ping Sun, Jian-Kang Yi, Long Meng, and Hong-Kun Zhao College of Chemistry & Chemical Engineering, Yang Zhou University, Yang Zhou, Jiangsu 225002, People’s Republic of China ABSTRACT: The solid−liquid phase equilibrium for three systems of succinic acid + urea + water, glutaric acid + urea + water, and adipic acid + urea + water was determined at (288.15 and 303.15) K under atmospheric pressure (0.1 MPa). Six isothermal phase diagrams for these systems were constructed based the measured solubility. The solid-phases were confirmed by Schreinemaker’s method of wet residue, which corresponded to urea, succinic acid, and 2:1 urea-succinic acid cocrystal (mole ratio) for the succinic acid + urea + water system; urea, glutaric acid, 1:1 urea-glutaric acid cocrystal (mole ratio), and 2:1 ureaglutaric acid cocrystal (mole ratio) for the glutaric acid + urea + water system; and urea, adipic acid, and 2:1 urea-adipic acid cocrystal (mole ratio) for the adipic acid + urea + water system. The ternary systems of succinic acid + urea + water and adipic acid + urea + water included five crystallization fields, three invariant curves, and two invariant points, respectively. The phase diagram of glutaric acid + urea + water included seven crystallization fields, four invariant curves, and three invariant points at a certain temperature. The crystalline region of 2:1 urea-adipic acid cocrystal, 2:1 urea-glutaric acid cocrystal, or 2:1 urea-succinic acid cocrystal is larger than that of other solids for the three corresponding ternary systems. Furthermore, the densities of equilibrium liquid phase were acquired.
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INTRODUCTION The byproduct obtained in the production of an adipic acid is a dicarboxylic acid mixture which comprises glutaric acid, succinic acid, and adipic acid. Adipic acid is industrially produced by oxidizing cyclohexane with air and nitric acid.1−4 During the process of oxidation reaction, glutaric acid and succinic acid are produced as byproducts. The dicarboxylic acids are discharged in the form of an acid mixture composed mainly of glutaric acid, succinic acid, and adipic acid and generally having the following composition: (50 to 75) % by weight of glutaric acid; (15 to 35) % by weight of succinic acid; and (0 to 30) % by weight of adipic acid.5−8 It is well-known that glutaric acid and succinic acid are all important organic compounds with high additional value and widely used as an important intermediate in the production of agricultural chemicals, plastics, dyes, polyamides, polyurethanes, particularly for the synthesis of pharmaceuticals, surfactants, synthetic rubbers, and so forth.9−11 Up to now, many methods have been proposed for separation of the dibasic acid.5−8,12−18 It is very difficult and troublesome to separate and recover even one dicarboxylic acid component from the acid mixture with high quality by conventional techniques. For example, the conventional extraction-separation method by organic solvent or fractional distillation method cannot successfully separate or recover any one component by one step operation and requires multistage operations to isolate one component. Thus, the separation and recovery processes in the conventional methods are very complicated, and they cannot be practiced on an industrial scale. © XXXX American Chemical Society
Adductive crystallization is a special separation method that generates a crystalline solid phase which is adduct of the raw material with an extraneous agent added to system. The crystal crystalline adduct is isolated from the mother liquid by filtering, and then decomposes in an appreciate solvent. So the solute with high purity is obtained, and the solvent can be recovered and recycled. As a relative new separation method, adductive crystallization is an effective method to separate the dicarboxylic acid mixture.16−18 It is very easy for the dicarboxylic acid to form stable crystalline adducts with urea, which are separated easily by filtration from the solution. In the discharged dicarboxylic acid mixture, the urea adduct is only formed with dicarboxylic acid. The dicarboxylic acid adduct contains almost no other impurities, the colored materials and ions in the discharged dicarboxylic acid mixture can be removed, and as a result a high quality dicarboxylic acid can be obtained. Solid−liquid phase equilibrium data play an important role in adductive crystallization processes. During the separation process of dicarboxylic acid by adductive crystallization, the solubility of dicarboxylic acid in solvent must be determined beforehand. In the previous publications, the solubility of adipic acid, glutaric acid, and succinic acid in water and some pure organic solvents have been reported,19−25 Recently Chadwick and co-workers determined experimentally the phase equiliReceived: August 3, 2014 Accepted: October 31, 2014
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dx.doi.org/10.1021/je500725e | J. Chem. Eng. Data XXXX, XXX, XXX−XXX
Journal of Chemical & Engineering Data
Article
Table 1. Sources and Mass Fraction Purity of Materials Used in This Work materials
mass fraction purity
purification method
sources
analytical method
succinic acid glutaric acid adipic acid urea
0.998 0.997 0.999 0.992
recrystallization recrystallization recrystallization
Sinopharm Chemical Reagent Co.Ltd.(China) Sinopharm Chemical Reagent Co.Ltd.(China) Sinopharm Chemical Reagent Co.Ltd.(China) Shanghai Lin Di Chemical Industry Co, Ltd.(China).
HPLC HPLC HPLC spectrophotometer
Table 2. Mass Fraction Solubility and Densities Value for the Ternary System of Succinic Acid (1) + Urea (2) + Water (3) under Pressure p = 0.1 MPaa liquid phase
moist solid phase
100·w1
100·w2
100·w1
100 ·w2
density of liquid phase (g·mL−1)
303.15 K 11.52 11.37 11.23
0 5.431 8.323
56.89 32.76
2.620 19.08
1.0042 1.0324 1.0366
4.291 1.824 1.123 0.9041 0.8413 0.7642 0.6815 0.5634
13.64 19.82 25.51 32.85 39.75 44.31 52.33 58.92
21.49 19.01 18.05 17.17 16.28 20.09 18.00 14.24
27.28 30.81 33.93 38.75 42.65 46.55 51.61 63.00
1.0375 1.0486 1.0729 1.0851 1.0881 1.1046 1.1168 1.1256
0.3513 0 288.15 K 4.952 4.234 3.832
59.18 59.99
0.2642
70.22
1.1183 1.1023
0 2.211 4.844
67.69 43.75
0.7621 23.07
1.0041 1.0152 1.0218
2.381 1.643 0.7914 0.6722 0.5631 0.3317 0.2126
10.98 15.34 24.08 34.87 38.41 45.54 48.07
23.66 23.67 24.79 34.71 26.36 37.15 20.43
28.52 31.37 37.02 46.01 44.87 49.30 60.95
1.0252 1.0331 1.0519 1.0631 1.0717 1.0985 1.1115
0
51.01
1.0802
equilibrium solid-phase C4H6O4 C4H6O4 C4H6O4+C4H6O4·2CO(NH2)2 invariant point C4H6O4·2CO(NH2)2 C4H6O4·2CO(NH2)2 C4H6O4·2CO(NH2)2 C4H6O4·2CO(NH2)2 C4H6O4·2CO(NH2)2 C4H6O4·2CO(NH2)2 C4H6O4·2CO(NH2)2 C4H6O4·2CO(NH2)2+CO(NH2)2 invariant point CO(NH2)2 CO(NH2)2 C4H6O4 C4H6O4 C4H6O4+C4H6O4·2CO(NH2)2 invariant point C4H6O4·2CO(NH2)2 C4H6O4·2CO(NH2)2 C4H6O4·2CO(NH2)2 C4H6O4 2CO(NH2)2 C4H6O4·2CO(NH2)2 C4H6O4·2CO(NH2)2 C4H6O4·2CO(NH2)2 + CO(NH2)2 invariant point CO(NH2)2
a
w, mass fraction. Standard uncertainties u are u(T) = 0.01K, ur(p) = 0.05, and ur(w) = 0.02 and the combined expanded uncertainty Uc is Uc(ρ) = 0.0001g·cm−3 (0.95 level of confidence).
recrystallized from CHC13 and again from water. The final purity used in following experiment was determined by an Agilent-1260 high-performance liquid-phase chromatograph (HPLC) in our laboratory. Urea, which is analytical grade and used without any further purification, was purchased from Shanghai Lin Di Chemical Industry Co, Ltd. Deionized water (conductivity
