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Solid−Liquid Equilibrium and Phase Diagram for the Ternary Succinic Acid + Glutaric Acid + Water System Yijie Deng, Xiaobo Sun, Li Xu,* Zhixin Ma, and Guoji Liu* †

School of Chemical Engineering and Energy, Zhengzhou University, Zhengzhou, Henan 450001, P. R. China ABSTRACT: The solid−liquid equilibria (SLE) data of the ternary system succinic acid + glutaric acid + water were measured at the three given temperatures (298.15, 303.15, and 308.15) K using the isothermal solution dissolution equilibrium method, and the densities of equilibrium liquid phase were determined experimentally at the corresponding temperatures. The corresponding isothermal phase diagrams and the diagrams of densities versus mass fraction of component were constructed on the basis of the experimental results. There existed two pure solid phases at (298.15, 303.15 and 308.15) K, including pure succinic acid and pure glutaric acid, which were confirmed and determined by the method of Schreinemaker’s wet residue and X-ray diffraction. The results indicate obviously that there was no solid solution formed in the studied system. The phase diagram at 298.15 K is similar to those at (303.15 and 308.15) K and the crystallization region of glutaric acid is far smaller than that of succinic acid at each temperature. The crystalline fields of succinic acid increase with rising temperature, while crystalline fields of glutaric acid decrease with an increase in temperature.

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INTRODUCTION Glutaric acid is an important chemical raw material which is widely used in the production of plastics, dyes, surfactants, polyamides, and polyurethanes, particularly for the manufacture of pharmaceuticals, agricultural chemicals, synthetic rubbers, and so forth.1−3 In the chemical industry, much waste liquid is generated in the production process of adipic acid, which is produced by the method of oxidation of cyclohexane.4 The mixed dibasic acids (DBA), which are also called nylon acids, are byproducts of the production processes of adipic acid, and these byproducts contain about 45%−55% (mass fraction) of glutaric acid, 15%−20% (mass fraction) of succinic acid, and 15%−25% (mass fraction) of adipic acid.4−8 To protect the environment and reduce production costs, it is important to to separate and recover glutaric acid from the mixed DBA byproduct. In industrial manufacturing processes, glutaric acid can be obtained via crystallization from mixed dibasic acids. However, it is difficult to obtain high purity glutaric acid. Compared with solubilities of glutaric acid and succinic acid in water, the solubilities of adipic acid in water are extremely small. Therefore, the key to separate and recover glutaric acid from the byproducts (mixed dibasic acid) is to eliminate succinic acid.9 It is well-known that solid−liquid phase equilibrium data play an important role in the development and operation of crystallization processes. Pure glutaric acid can be obtained by the method of repeated recrystallization from some common solvents, such as cyclohexanol, cyclohexanone, water, acetone, and so on.10 Obviously, solubility data alone of binary systems are not enough for producing high purity glutaric acid, and separating and recovering glutaric acid from byproducts (DBA) by the method of crystallization in water is dependent on the solid−liquid equilibrium phase diagrams for the ternary succinic acid + glutaric acid + water system at © 2014 American Chemical Society

different temperatures. Consequently, it is of great importance and necessary to improve the separation process to study and construct the solid liquid equilibrium phase diagrams for the ternary succinic acid + glutaric acid + water system. Recently, the solubility data of glutaric acid and succinic acid in several common organic solvents were reported in the literature.11−14 However, up to now, there has been no further study on the density data and solid−liquid equilibrium phase diagrams for the ternary glutaric acid + succinic acid + water system at different temperatures in the open literature. The main aim of the investigation in this paper is to study and generate the ternary phase diagrams for the ternary of succinic acid + glutaric acid + water system at (298.15, 303.15 and 308.15) K by using the method of Schreinemaker’s wet residue and indicate the relation between temperature and the ternary phase diagrams.15 Additionally, to provide guidance and basic data for design of the crystallizer, which is employed to separate glutaric acid from byproducts (DBA), the densities of saturated solutions for these ternary systems are also determined on the basis of experimental data. When solid−liquid equilibrium in the ternary system is reached, coexisting phases in the solid−liquid equilibrium system would at least include one liquid phase and one solid phase. During the experimental measurement the equilibrium liquid phase and wet solid phase are usually employed to indirectly determine the composition of the equilibrium solid phase, which is based on the method of Schreinemaker’s wet residue, because eliminating a small amount of adhering saturated liquid from the solid phase and obtaining the pure Received: April 28, 2014 Accepted: July 22, 2014 Published: July 29, 2014 2589

dx.doi.org/10.1021/je5003785 | J. Chem. Eng. Data 2014, 59, 2589−2594

Journal of Chemical & Engineering Data

Article

sold phase is very difficult.15 The basic principle of this method is as described. The extension of connecting lines that join the composition points of the saturated liquid phase and corresponding wet solid phase in the solid−liquid equilibrium phase must intersect at one point, representing the composition of the corresponding equilibrium solid phase.15−17 Therefore, in this paper, the method of Schreinemaker’s wet residue was employed to determine the composition of the equilibrium solid phase and establish solid−liquid equilibrium phase diagrams for the ternary succinic acid + glutaric acid + water system at (298.15, 303.15 and 308.15) K.

jacketed dissolution vessel. The actual temperature of the equilibrium system was measured using a precision mercury thermometer inserted into a saturated solution in the vessel, and the uncertainty of the precision mercury thermometer was ± 0.01 K. System equilibration was reached and verified by means of measuring repeatedly the composition (glutaric acid and succinic acid) of the saturated solution and by preequilibrium of the solution at a higher temperature.18 During experimental measurement, the thermodynamic equilibration was considered as being reached when the composition of solution did not change any more. It was shown that the solution would reach equilibrium after 24 h. When the ternary system was in phase equilibrium, the wet solid phase and saturated liquid phase were respectively moved into beakers, completely dissolved, and added to 100 mL volumetric flasks to fix quantity. The solutions were quantitatively analyzed by HPLC (Agilent; Agilent-1100). The wet solid phases were dried in a drying oven at 25 °C and qualitatively analyzed by Xray diffraction (XRD; Bruker AXS D8 Advance). When this experimental procedure was conducted repeatedly by varying the ratio of glutaric acid and succinic acid, different compositions of the equilibrium liquid phase and wet solid phase in solubility curves were obtained. Analytical Methods. The same amount of wet solid phase samples and saturated liquid phase of glutaric acid and of succinic acid were respectively removed from the apparatus and dissolved in water. Each was then added to a 100 mL volumetric flask respectively to fix their quantity (mass concentration). The mass fractions of glutaric acid and succinic acid in aqueous solution were quantitatively analyzed with a high performance liquid phase chromatograph (Agilent-1100, HPLC), and its analysis chromatographic column was Diamonsil C18 (150 mm × 4.6 mm). The densities of the equilibrium liquid phase were measured by the pycnometer method.21 All of the measurements were repeated at least three times, and the average data of corresponding experimental measurements were considered to be the solubility data. The related standard uncertainty of measured solubilities is estimated as ur(x) = 0.02, and the experimental uncertainty is mainly due to temperature measurements and sampling procedure during experimental measurements. To verify the reliability of our experimental apparatus, the solubility of adipic acid in water was measured using our experimental apparatus. The compared results between the experiment values and literature values are shown in Table 2, and it is indicated that the experimental data are in good agreement with the data in the literature.11

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EXPERIMENTAL SECTIONS Materials. The glutaric acid, adipic acid, and succinic acid were all supplied by Sinopharm Chemical Reagent Co., Ltd., China, and their mass fraction purities are 0.99. After crude materials were repeatedly purified by the method of cooling crystallization in water, the mass fraction purities of glutaric acid, adipic acid, and succinic acid were all higher than 0.99 as determined by HPLC (Agilent; Agilent-1100) in our laboratory (values listed in Table 1). The water used in the experimental Table 1. Sources and Mass Fraction Purity of Materials mass fraction purities

purification method

succinic acid

0.997

recrystallization

glutaric acid

0.998

recrystallization

adipic acid

0.997

recrystallization

materials

a

sources Sinopharm Chemical Reagent Co.Ltd.(China) Sinopharm Chemical Reagent Co.Ltd.(China) Sinopharm Chemical Reagent Co.Ltd.(China)

analytical method HPLCa HPLC HPLC

High performance liquid chromatography.

measurement was distilled twice (conductivity < 4 μS·cm−1). A standard analytical balance (Shimadzu AX200) in the experiment was employed to measure mass and its uncertainty was ± 0.0001 g. Apparatus and Procedure. The solid−liquid phase equilibrium in this research work was studied by employing the method of isothermal solution saturation which was described in the literature.18−20 The pure equilibrium solid phase was identified via the method of Schreinemaker’s wet residue15 and redetected by X-ray diffraction (XRD). A jacketed dissolution vessel was used to dissolve the solute in the experiment. The working volume was about 50 mL. The dissolution process of the solutes was facilitated by continuous stirring of the solutes with an electromagnetic agitator at a desired temperature for at least 3 days to ensure equilibrium. An isothermal water bath circulator was employed to keep the experimental temperature constant. A certain amount of water used as solvent was added to the vessel. The system points of the ternary system were prepared by putting a certain amount of glutaric acid and/or succinic acid on the basis of the ternary cosaturation points and binary invariant points at studied temperatures in the jacketed dissolution vessel. To make composition points of the saturated solution fall in the desired positions of the solubility curves, the components of initial systems should be taken in proper proportion. To prevent the solvents from evaporating, the reflux condenser in the experimental measurement was directly connected to the

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RESULTS AND DISCUSSION The solid−liquid equilibrium solubility data and densities (ρ) of saturated solution for the ternary of glutaric acid + succinic acid + water system at (298.15, 303.15 and 308.15) K are listed in Tables 3, 4, and 5 respectively, and corresponding ternary phase diagrams are shown in Figures 1, 2, and 3. The compositions of the equilibrium liquid phase and wet solid phase are expressed in mass fraction in the phase diagrams. In these ternary phase diagrams, points G, S, and W represent the pure compound of glutaric acid, succinic acid, and water, respectively. Moreover, the points K1, K2, and K3 stand for the equilibrium solubilities of glutaric acid in water at (298.15, 303.15, and 308.15) K, respectively, and L1, L2, and L3 stand for the solubilities of succinic acid at the corresponding temperatures. Points E1, E2, and E3 are invariant points at 2590



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divided by two solubility curves, and the corresponding regions are designated as follows: the crystallization regions of glutaric acid (GK1E1 in Figure 1, GK2E2 in Figure 2, GK3E3 in Figure 3), including the coexisting phases of pure solid glutaric acid and the saturated solution correspondingly; the unsaturated regions (WL1E1K1 in Figure 1, WL2E2K2 in Figure 2, WL3E3K3 in Figure 3); the crystallization regions of succinic acid (SL1E1 in Figure 1, SL2E2 in Figure 2, SL3E3 in Figure 3), including the coexisting phases of pure solid succinic acid and saturated solution correspondingly; the solid phases mixture crystallization regions of glutaric acid and succinic acid (SE1G in Figure 1, SE2G in Figure 2, SE3G in Figure 3), including the coexisting phases of pure solid compound succinic acid, glutaric acid, and a saturated solution saturated with them correspondingly. The dependences of the ternary system phase diagrams for glutaric acid + succinic acid + water on temperature are clearly demonstrated in Figures 1, 2, and 3. The experimental solubilities of glutaric acid and succinic acid increase with an increase in temperature from (298.15 to 308.15) K, and the ternary invariant point moves downward and the unsaturated region of phase diagram become apparently larger. In each phase diagram, the crystalline field of succinic acid increases as the temperatures increase, while the crystalline field of glutaric acid decreases with increasing temperature. Furthermore, the phase diagram at 298.15 K is similar to those at (303.15 and 308.15) K. At each temperature, the crystallization field of succinic acid is far larger than that of glutaric acid, and the solubility of glutaric acid decreases as the mass fraction of succinic acid increases. Therefore, compared with glutaric acid, succinic acid is more easily separated out from mixed dibasic acid (DBA). On the basis of the experimental densities given in Tables 3, 4, and 5, the relationships between the mass fraction data of glutaric acid (w1) and the densities of saturated solutions in the ternary system succinic acid + glutaric acid + water at (298.15, 303.15 and 308.15) K are established and plotted in Figure 4. It

Table 2. Comparisons of the Literature and Experimental Mole Fraction Solubility of Adipic Acid as Function of Temperature in Water (p = 0.1 MPa)a T/K

103xlit

103xexp

102RDb

273.15 283.15 293.15 303.15 313.15 333.15

0.86 1.40 2.27 3.77 6.27 20.80

0.86 1.41 2.25 3.76 6.26 20.77

0.00 −0.71 0.88 0.27 0.16 0.14

a

x, mole fraction; xlit, literature mole fraction solubilities of adipic acid; xexp, experimental mole fraction solubilities of adipic acid. Standard uncertainties u are u(T) = 0.01 K, and relative standard uncertainties are ur(p)= 0.05, and ur(x) = 0.02. bRD, relative deviation = (xlit − xexp)/xlit.

corresponding temperatures, which include the two pure solid phases (glutaric acid and succinic acid) and a saturated liquid phase saturated with them. The mass fractions of glutaric acid and succinic acid in the invariant points at each studied temperature are shown in Tables 3, 4, and 5, respectively. Along the solubility curves L1E1, L2E2, and L3E3, when the composition points of equilibrium liquid phase and corresponding wet residue are linked and extended, the intersection of the extension line of these connecting lines is approximately the point S representing the pure solid phase (succinic acid). Similarly, along the solubility curves E1K1, E2K2, and E3K3, when the composition points of the equilibrium liquid phase and corresponding wet residue are linked and extended, the intersection of the extension line of these connecting lines is approximately the point G representing the pure solid phase (glutaric acid). It can be clearly seen that a new solid phase (solid solution) does not appear for the ternary succinic acid + glutaric acid + water system at the three given temperatures (298.15, 303.15 and 308.15) K, which is well consistent with the experimental results analyzed by XRD. As shown in Figures 1, 2, and 3, the equilibrium phase diagrams include four regions

Table 3. Experimental Mass Fraction Solubility and Density Values for the Ternary Glutaric Acid (1) + Succinic Acid (2) + Water (3) System at T = 298.15 K and Pressure p = 0.1 MPaa composition of liquid phase

densities of liquid phase (ρ/g·cm−3)

composition of wet solid phase

100·w1

100·w2

100·w3

100·w1

100·w2

100·w3

equilibrium solid phase

exp. value

calc. value

100RDb

59.37 58.59 57.33 56.07 54.26 52.39 49.21 43.65 40.92 37.55 33.31 27.63 22.39 15.37 8.46 0.00

0.00 0.60 1.55 2.92 4.19 5.63 5.72 6.03 6.19 6.24 6.33 6.52 6.86 7.40 7.82 7.83

40.63 40.81 41.12 41.01 41.55 41.98 45.07 50.32 52.89 56.21 60.36 65.85 70.75 77.23 83.72 92.17

81.51 81.28 79.11 77.29 74.62 55.42 8.39 8.89 8.08 6.56 6.04 4.79 3.57 3.42 1.36 0.00

0.00 0.27 0.76 1.51 2.32 24.95 83.93 80.86 81.48 83.62 83.00 83.78 85.16 79.39 85.18 82.17

18.49 18.45 20.13 21.20 23.06 19.63 7.68 10.25 10.44 9.82 10.96 11.43 11.27 17.19 13.46 17.83

G G G G G G+S S S S S S S S S S S

1.1670 1.1767 1.1847 1.1984 1.2074 1.2145 1.1997 1.1777 1.1673 1.1539 1.1377 1.1169 1.0992 1.0766 1.0548 1.0274

1.1880 1.1890 1.1906 1.1949 1.1966 1.1992 1.1885 1.1711 1.1627 1.1515 1.1377 1.1200 1.1048 1.0852 1.0657 1.0395

−1.80 −1.05 −0.50 0.29 0.90 1.26 0.93 0.56 0.39 0.21 −0.01 −0.27 −0.51 −0.80 −1.03 −1.18

a

w, mass fraction; S, succinic acid; G, glutaric acid. Standard uncertainty of experimental temperature u is u(T) = 0.01 K, and relative standard uncertainties are ur(w) = 0.02 and ur(p) = 0.05. The combined expanded uncertainty Uc is Uc(ρ) = 0.0001g·cm−3 (0.95 level of confidence). bRD, relative deviation = ( exp. value − calc. value)/exp. value. 2591



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100·w1

100·w2

100·w3

100·w1

100·w2

100·w3


exp. value

calc. value

100RDb

64.44 62.91 61.35 59.52 58.28 56.55 52.87 48.79 43.99 38.51 35.01 31.21 26.50 22.59 15.88 8.57 0.00

0.00 1.10 2.40 3.64 4.62 5.75 5.80 6.16 6.49 6.69 7.05 7.20 7.38 7.63 8.07 8.35 9.14

35.56 35.99 36.25 36.84 37.10 37.70 41.33 45.05 49.52 54.80 57.94 61.59 66.12 69.78 76.05 83.08 90.86

81.89 81.33 83.68 80.86 78.64 56.35 13.67 12.88 11.31 9.66 9.61 7.39 6.35 5.52 3.30 1.86 0.00

0.00 0.55 1.01 1.72 2.37 26.63 75.64 75.23 75.97 76.60 74.48 78.02 77.81 77.43 80.92 80.07 82.58

18.11 18.12 15.31 17.42 18.99 17.02 10.69 11.89 12.72 13.74 15.91 14.59 15.84 17.05 15.78 18.07 17.42

G G G G G G+S S S S S S S S S S S S

1.2105 1.2153 1.2212 1.2278 1.2291 1.2333 1.2161 1.2002 1.1815 1.1600 1.1478 1.1336 1.1166 1.1033 1.0812 1.0573 1.0325

1.2230 1.2230 1.2240 1.2235 1.2240 1.2234 1.2094 1.1956 1.1792 1.1598 1.1487 1.1356 1.1196 1.1069 1.0856 1.0619 1.0369

−1.03 −0.63 −0.23 0.35 0.41 0.80 0.55 0.38 0.19 0.02 −0.08 −0.17 −0.27 −0.33 −0.40 −0.43 −0.43

a

w, mass fraction; S, succinic acid; G, glutaric acid. Standard uncertainty of experimental temperature u is u(T) = 0.01 K, and relative standard uncertainties are ur(w) = 0.02 and ur(p) = 0.05. The combined expanded uncertainty Uc is Uc(ρ) = 0.0001 g·cm−3 (0.95 level of confidence). bRD, relative deviation = (exp. value − calc. value)/exp. value.




100·w1

100·w2

100·w3

100·w1

100·w2

100·w3


exp. value

calc. value

100RDb

69.17 67.09 65.13 63.35 62.09 59.32 56.53 52.27 49.64 44.41 39.92 36.77 34.56 30.30 23.10 16.24 9.39 0.00

0.00 1.38 2.74 3.87 4.84 6.65 6.92 7.41 7.60 7.93 8.19 8.70 8.76 9.16 9.68 10.33 10.77 11.70

30.83 31.53 32.13 32.78 33.07 34.03 36.55 40.32 42.76 47.66 51.89 54.53 56.68 60.54 67.22 73.43 79.84 88.30

83.54 80.75 81.36 85.12 85.06 59.28 10.67 9.25 10.34 11.35 8.49 11.23 7.58 5.54 3.55 3.11 1.68 0.00

0.00 0.81 1.46 1.57 1.91 29.51 82.43 83.61 80.75 76.47 80.47 72.12 79.97 83.39 86.12 82.83 84.03 88.05

16.46 18.44 17.18 13.31 13.03 11.21 6.90 7.14 8.91 12.18 11.04 16.65 12.45 11.07 10.33 14.06 14.29 11.95

G G G G G G+S S S S S S S S S S S S S

1.2212 1.2283 1.2308 1.2382 1.2407 1.2502 1.2388 1.2222 1.2115 1.1907 1.1732 1.1629 1.1538 1.1394 1.1144 1.0923 1.0701 1.0425

1.2372 1.2371 1.2373 1.2369 1.2376 1.2373 1.2280 1.2144 1.2054 1.1875 1.1721 1.1633 1.1555 1.1422 1.1192 1.0985 1.0772 1.0503

−1.31 −0.71 −0.53 0.10 0.25 1.03 0.87 0.64 0.51 0.27 0.09 −0.04 −0.15 −0.25 −0.43 −0.57 −0.66 −0.74

a

w, mass fraction; S, succinic acid; G, glutaric acid. Standard uncertainty of experimental temperature u is u(T) = 0.01 K, and relative standard uncertainties are ur(w) = 0.02 and ur(p) = 0.05. The combined expanded uncertainty Uc is Uc(ρ) = 0.0001 g·cm−3 (0.95 level of confidence). bRD, relative deviation = (exp. value − calc. value)/exp. value.

303.15 and 308.15) K observed in Figure 4 correspond to the invariant points E1 in Figure 1, E2 in Figure 2, and E3 in Figure 3, respectively. The following empirical eq 1 could be used to describe the relationship between composition and density of electrolyte solution, which is based on the limited partial molar volume of the electrolyte solution.22 Moreover, according to previous works,23 this equation has a good fitting result for weak electrolyte, strong electrolyte, and nonelectrolyte solutions.

is shown that at a certain temperature the density data of a saturated liquid phase first increase with increasing mass fraction of glutaric acid, and then decrease with rising mass fraction of glutaric acid. The densities of the equilibrium solution in the ternary system increase with increasing temperature, which is mainly due to the solid solubility increasing with rising temperature. Furthermore, the size of densities of the saturated liquid phase is mainly dependent on total composition of succinic acid and glutaric acid in the saturated solution. The maximum density values at (298.15, 2592



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Figure 1. Solid−liquid equilibrium phase diagram of the ternary glutaric acid (1) + succinic acid (2) + water (3) system at 298.15 K: S, succinic acid; G, glutaric acid; W, water; K1, L1, solubility of glutaric acid and succinic acid in water, respectively; E1, cosaturated point; WL1E1K1, unsaturated region; L1SE1, region including one solid phase (succinic acid) and a saturated liquid phase; K1E1G, region including one solid phase (glutaric acid) and a saturated liquid phase; E1SG, region including two pure solid phases (succinic acid and glutaric acid) and a saturated liquid phase (E1) saturated with them; w1, mass fraction of glutaric acid; w2, mass fraction of succinic acid; w3, mass fraction of water.



⎛d ⎞ ln⎜ s ⎟ = ⎝ do ⎠

∑ Aiwi

Figure 4. Experimental densities (ρ) of the saturated solution for the ternary succinic acid + glutaric acid + water system at (298.15, 303.15 and 308.15) K: w1, mass fraction of glutaric acid.

and 308.15) K, and wi is mass fraction of the corresponding component i in aqueous solution. The values of constants Ai of glutaric acid (1) and succinic acid (2) for the calculation of solution density at different temperatures are given in Table 6. The comparison between fitting results and experimental values are shown in Tables 3 to 5. As can be seen from Tables 3 to 6, all the calculated RDs absolute values do not exceed 1.80 %, and the corresponding RMSD values are not more than 0.99 %. This indicates that eq 1 is suitable to fit the measured density data of ternary system succinic acid + glutaric acid + water at (298.15, 303.15 and 308.15) K.

(1)

where Ai is the adjusting parameter of component i in the solid−liquid equilibrium system at (298.15, 303.15 and 308.15) K, do represents the density of pure water at (298.15, 303.15 2593



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Table 6. Values of Constants Ai of Glutaric Acid (1) and Succinic Acid (2) for the Calculation of Solution Density at (298.15, 303.15 and 308.15) K T/K

A1(·104)a

A2(·104)b

RMSD(·102)c

298.15 303.15 308.15

29.51 31.91 31.63

53.24 44.36 47.04

0.99 0.55 0.73

(3) Navarro, E.; Subirana, A.; Puiggali, J. The Structure of Nylon 12,5 Is Characterized by Two Hydrogen Bond Directions as Are Other Polyamides Derived from Glutaric Acid. J. Polymer. 1997, 38, 3429− 3432. (4) Campbell, C. R.; Hicks, J.; John, J.; Johnson, R. Separation of Adipic Acid, Glutaric Acid and Succinic Acid from Mother Liquors Obtained in the Manufacture of Adipic Acid. U.S. Patent 3,180,878, April 27, 1965. (5) Castellan, A.; Bart, J. Industrial Production and Use of Adipic Acid. J. Catal. Today 1991, 9, 237−254. (6) Kazuhiko, S.; Masao, A. A Green Route to Adipic Acid: Direct Oxidation of Cyclohexenes with 30% Hydrogen Peroxide. J. Sci. 1998, 281, 1646−1647. (7) Wang, J. Y.; Song, Q. S. Preparing Method for Mixed Dibasic Acid Ester from Adipic Acid Production Waste Liquid and Treatment Method for the Waste Liquid. CN Patent 101,016,245, August 15, 2007. (8) Sutradhar, B. C. Crystallization of Adipic Acid from Its Solution in Aqueous Nitric Acid. U.S. Patent 6,946,572, September 20, 2005. (9) Walter, D. R.; Gerd, D. H. Process for the Separation of Adipic Acid from Mixtures Containing Glutaric Acids and/or Succinic Acids. E.P. Patent 0,033,851, August 19, 1981. (10) Singrey, S. L.; Thomas, S. C. Process for Separation and Recovery of Glutaric, Succinic, and Adipic Acids. U.S. Patent 3,338,959, August 29, 1967. (11) Gaivoronskii, A. N.; Granzhan, V. A. Solubility of Adipic Acid in Organic Solvents and Water. J. Russ. J. Appl. Chem. 2005, 78, 404−408. (12) Song, W.; Ma, P. S.; Xiang, Z. L. Solubility of Glutaric Acid in Cyclohexanone, Cyclohexanol, Their Five Mixtures and Acetic Acid. J. Chin. Chem. Eng. 2007, 15, 228−232. (13) Stephen, H.; Stephen, T. Solubility of Inorganic and Organic Compounds; Pergamon: Oxford, UJ, 1979. (14) Dean, J. A. Lange’s Handbook of Chemistry, 15th ed.; McGrawHill: New York, 1999. (15) Schott, H. A Mathematical Extrapolation for the Method of Wet Residues. J. Chem. Eng. Data 1961, 6, 324−324. (16) Zhao, H. K.; Zhang, Q. H.; Li, R. R. Solid−Liquid Phase Equilibrium and Phase Diagram for Ternary o-Nitrobenzoic Acid + mNitrobenzoic Acid + Ethanol System. J. Chem. Eng. Data 2008, 53, 1367−1370. (17) Ji, H. Z.; Meng, X. C.; Zhao, H. K. Solid−Liquid Phase Equilibrium for the Ternary System 3-Chlorophthalic acid + 4Chlorophthalic acid + Water at (283.15 and 313.15) K. J. Chem. Eng. Data 2010, 55, 4013−4015. (18) Li, R. R.; Yao, G. B.; Xu, H.; Zhao, H. K. Solid−Liquid Equilibrium and Phase Diagram for the Ternary 4-Chlorophthalic Anhydride + 3-Chlorophthalic Anhydride + Ethyl Acetate System. J. Chem. Eng. Data 2014, 59, 163−167. (19) Nývlt, J. Solid-Liquid Phase Equilibria; Publishing House of the Czechoslovak: Prague, 1977. (20) Deng, T. L.; Yin, H. J.; Li, D. CH. Metastable Phase Equilibrium in the Aqueous Ternary System (Li2SO4 + MgSO4 + H2O) at 348.15 K. J. Chem. Eng. Data 2009, 54, 498−501. (21) Wang, L. C.; Xu, H. S.; Zhao, J. H.; Song, C. Y.; Wang, F. A. Densities and Viscosities of Niacin + 3-Picoline + Water Mixtures from (293.15 to 343.15) K. J. Chem. Eng. Data 2005, 50, 254−257. (22) Lin, L. J.; Fang, C. H.; Fang, Y.; Qin, X. F. A New Model for Prediction Density of Electrolyte Solutions. J. Salt. Lake. Res. 2006, 14 (2), 56−61. (23) Liu, M.; Tang, J. H.; Cui, C.; Li, C.; Chen, X. Z. Phase Equilibrium in the Aqueous Ternary System NaH2PO4 +CO(NH2)2 + H2O at 298.15 K. J. Chem. Eng. Data 2013, 58, 132−135.

a

A1, the values of constants of glutaric acid (1) for the calculation of solution density, bA2, the values of constants of succinic acid (2) for the calculation of solution density. cRMSD is the root mean square deviations between experimental values and calculated values, RMSD = [(1/N)Σi N= 1(calc. value − exp. value)2]1/2, and N is the number of experimental points.

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CONCLUSIONS The solid−liquid phase equilibrium (SLE) solubility data of the ternary system of succinic acid + glutaric acid + water at (298.15, 303.15, 308.15) K were measured, the ternary phase diagrams were correspondingly constructed on the basis of the experimental data, and the density data of the equilibrium liquid phase were determined experimentally. The composition of the equilibrium solid phase was verified and identified by the method of Schreinemaker’s wet residue, and two pure solid phases (pure succinic acid and glutaric acid) existed in the ternary system succinic acid + glutaric acid + water at each temperature. There is one ternary invariant point, two equilibrium solubility curves, and three crystallization fields which include a mixture of succinic acid and glutaric acid, pure solid compound succinic acid, and pure solid compound glutaric acid in each ternary phase diagram. Meanwhile, at the same temperature, the crystallization field of glutaric acid is far smaller than that of succinic acid, and the solubilities of succinic acid and glutaric acid rise with rising temperature. The experimental density of a saturated solution is fitted by an empirical equation, and the computed results show that calculated density values are in good agreement with experimental density values. The solid−liquid equilibrium phase diagrams of the ternary system for succinic acid + glutaric acid + water at (298.15, 303.15 and 308.15) K could provide the basic and essential data for the processes of separating glutaric acid from mixed dibasic acids and purifying the separated acid.

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AUTHOR INFORMATION

Corresponding Authors

*Tel.: +86 0371 67781713. Fax: +86 0371 67781713. E-mail: [email protected] (L.X.). *Tel.: +86 0371 67781713. Fax: +86 0371 67781713. E-mail: [email protected] (G.L.). Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We appreciate the editors and the anonymous reviewers for their valuable suggestions. REFERENCES

(1) Stephen, C. Preparation of Glutaric Acid Derivatives. U.S. Patent 5,166,406, November 24, 1992. (2) McNamara, D.; Childs, S. L. Use of a Glutaric Acid Co-crystal To Improve Oral Bioavailability of a Low Solubility API. J. Pharm. Res. 2006, 23, 1888−1897. 2594


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