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Ternary Liquid−Liquid Equilibrium for Mixtures of Water + (±)αPhenylethylamine + n‑Hexane at T = 298.2, 318.2, and 333.2 K Longfei Wen,† Ning Zhang,‡ Huichang Li,† Qiang Huang,*,† Xiaoru Wu,† Xinying Hao,† Mingjian Wu,† Chunlan Ban,† and Jianhong Zhao*,† †

School of Chemical Engineering and Energy, Zhengzhou University, Zhengzhou 450001, China School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001, China

‡

ABSTRACT: Liquid−liquid equilibrium (LLE) data for the ternary (water + (±)α-phenylethylamine + n-hexane) system were obtained experimentally at T = 298.2, 318.2, and 333.2 K, respectively, and atmospheric pressure by gas chromatography for the first time. The binodal curve data at 333.2 K was determined using the cloud point method. The system exhibits two-liquid-phase-coexisting at 333.2 K while it presented the state of three two-liquid-phase-coexisting regions and one three-liquid-phase-coexisting region in the triangle phase diagram at 298.2 and 318.2 K. Separation factor was calculated to evaluate the extraction efficiency of this system. Correlation of the experimental tie lines was conducted through the use of the NTRL and UNIQUAC equation, which provides good correlation of the experimental data.

1. INTRODUCTION Recently, (±)α-phenylethylamine and its derivatives, as drug intermediates for industrial asymmetric synthesis, have been widely used in pharmaceutical, emulsifier, and dyestuff industry.1−4 Because of the powerful chiral adjuvant, they can be applied as chiral solvating agents and ligands in asymmetric catalysts synthesis.5−9 (±)α-Phenylethylamine is obtained mainly from the reaction of acetophenone and ammonium formate, namely Leuckart reaction, which is the most common method in industry.10 In general, the alkali aqueous solution would reduce the yield of (±)α-phenylethylamine because parts of the target product are dissolved in water.10−12 It is urgent to design a suitable method to separate water and (±)α-phenylethylamine and hence improve its yield. Considering the similar separation effect, extraction is a more simple method when compared with distillation. Recently, a number of works have been devoted to the development of liquid−liquid extraction for the separation of complex mixtures.13−17 In addition, the phase equilibrium data of the system ((±)α-phenylethylamine + n-hexane + water) can be measured by gas chromatography to test the reliability of the existing activity coefficient models. To the best of our knowledge, the liquid−liquid equilibrium data of the ternary (water + (±)α-phenylethylamine + nhexane) systems have not been reported in literatures. In this work, three different temperatures (298.2, 318.2, and 333.2 K) were chosen to observe the change of equilibrium phase compositions. The liquid−liquid equilibrium data at corresponding temperature were determined by the method of static balance, then the data were correlated using the nonrandom two-liquid (NRTL) and universal quasi-chemical (UNIQUAC) model. In order to evaluate the extracting capability of the © XXXX American Chemical Society

selected solvent, distribution coefficients and separation factors were experimentally determined from the tie line data. Transformation temperature from three-liquid-phase-coexisting to two-liquid-phase-coexisting was also determined. According to the liquid−liquid equilibrium data under the experimental temperature, the triangular phase diagrams of ((±)α-phenylethylamine + n-hexane + water) system were drawn and analyzed.

2. EXPERIMENTAL SECTION 2.1. Material. In this work, n-hexane was purchased from Sinopharm Chemical Reagent Co. (±)α-Phenylethylamine was purchased from Alfa Aesar. Deionized water was prepared in our laboratory, and the measured resistivity was 10.6 MΩ·cm (UPE-1000L,YOUPU). The mass purities were both greater than 0.99 after purification. Purities of all the materials were determined by a gas chromatography (GC) equipped with a thermal conductivity detector and no impurity peaks were detected. The water and n-hexane were used without further purification. The detailed information about the materials is listed in Table 1. 2.2. Apparatus and Procedure. LLE data for the studied ternary system were measured at 298.2, 318.2, and 333.2 K, respectively, under atmospheric pressure. The experiment was performed in a glass cell with a magnetic stirrer. A jacket around inner cell has an inlet and an outlet to pass though the water (heating and cooling the mixture) from a super thermostat. A known proportion of the mixture was presented Received: December 26, 2016 Accepted: May 11, 2017

A

DOI: 10.1021/acs.jced.6b01064 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

Table 1. Details of Chemicals Used in This Work CAS

initial mass fraction purity

Alfa Aesar Co.

618−36−0

0.985

Sinopharm Chemical Reagent Co. Ltd. homemade

110−54−3 7732−18−5

compound

source

(±)αphenylethylamine n-hexane water a

purification method

final mass fraction purity

analysis method

0.995

GCa

0.997

vacuum distillation none

0.997

GCa

0.998

none

0.998

GCa

Gas chromatography.

by weighing using an electronic balance (AX124ZH produced by Ohaus, a corporation of American). Solubility data of the ternary systems were determined by cloud point method:18−20 the homogeneous mixture solution of (±)α-phenylethylamine and n-hexane with known composition was placed in glass cell, and then the water was added drop by drop under stirring until a transition of the mixture solution from homogeneous to heterogeneous was observed. The titration end point was determined ultimately by repeating the above process three times. The mass of the added reagent was weighed by the electronic balance using decrement method, and accuracy of the electronic balance was 0.0001 g. Solubility values of the ternary ((±)α-phenylethylamine + n-hexane + water) system are listed in Tables 2, 3, and 4 and the corresponding solubility curve is showed as red solid line in Figures 1 and 2.

Table 4. Experimental Two-Liquid-Phase-Coexisting Solubility Curve in Mass Fraction with Standard Uncertainty for Ternary ((±)α-Phenylethylamine (1) + n-Hexane (2) + Water (3)) Systems at T = 298.2 K and P = 0.1 MPaa w1

w2

w1

w2

w1

w2

0.6706 0.6603 0.5676 0.7529 0.7314 0.6621

0.0523 0.0078 0.0000 0.1226 0.1829 0.2838

0.5759 0.4864 0.3931 0.2978 0.1996 0.1299

0.3839 0.4864 0.5896 0.6949 0.7983 0.8687

0.0000 0.0000 0.0001 0.0002

0.9999 0.0007 0.0007 0.0000

a Standard uncertainties are u(w) = 0.01 and u(T) = 0.1 K, u(p) = 1 kPa.

Table 2. Experimental Solubility Curve in Mass Fraction with Standard Uncertainty for Ternary ((±)αPhenylethylamine (1) + n-hexane (2) + water (3)) Systems at T = 333.2 K and P = 0.1 MPaa w1

w2

w1

w2

w1

w2

0.0908 0.2238 0.2427 0.2711 0.3168 0.3673 0.4204 0.4678

0.9092 0.7668 0.7483 0.7182 0.6693 0.6116 0.5482 0.4943

0.5365 0.5885 0.6419 0.6987 0.7378 0.7787 0.7917 0.7816

0.4071 0.3453 0.2719 0.1988 0.1413 0.0784 0.0406 0.0343

0.7662 1.04 × 10−3 0.0009 0.0008 0.0010 0.0002 0.0003 0.0000

0.0174 0.0000 0.0005 0.0004 0.0009 0.0006 0.0009 0.0001


Figure 1. Ternary phase diagram for (water + (±)α-phenylethylamine + n-hexane) system at T = 333.2 K and p = 0.1 MPa. Experimental tie line value (■, black solid lines), solubility curve value (●, red solid line).

Table 3. Experimental Two-Liquid-Phase-Coexisting Solubility Curve in Mass Fraction with Standard Uncertainty for Ternary ((±)α-Phenylethylamine (1) + n-Hexane (2) + Water (3)) Systems at T = 318.2 K and P = 0.1 MPaa w1

w2

w1

w2

w1

w2

0.6320 0.7089 0.7379 0.7100 0.2981

0.0000 0.0216 0.0806 0.1775 0.6938

0.6421 0.5640 0.4805 0.3917 0.0006

0.2752 0.3760 0.4805 0.5875 0.0007

0.0005 0.0000 0.0000

0.0000 0.9999 0.0001

15 h. The uncertainty of temperature measurement is less than 0.1 K. A 1 μL lower phase (water-rich phase) sample was taken every time by a micro injector without containing the other two phases so that there was no need to supplement materials. The sample was analyzed by gas chromatography (GC-7890B), with a SE-30 (2 m × 3 mm) packed column, and a thermal conductivity detector (TCD), manufactured by Agilent Technologies Inc. Analysis conditions were shown as following: the temperature of injector was 483.2 K, the oven was 383.2 K, and the detector was 483.2 K, flow rate of carrier gas (hydrogen) was 40 mL/min, the chromatographic column pressure was 0.06 MPa, and the injection volume was 1 μL. (±)α-Phenylethylamine-rich phase was the middle phase, and the n-hexane-rich phase was the upper phase. In order to ensure enough data points, each consistent composition of (±)αphenylethylamine-n-hexane solution was mixed with different


Static balance method was used to obtain the tie-line data in experimental. A known composition mixture of (n-hexane + (±)α-phenylethylamine + water) system was added into glass cell at 298.2 K, stirring 2 h to ensure a good contact between materials. Without being disturbed it was separated into three phases and reached liquid−liquid equilibrium in the following B



Article

Table 5. Experimental Tie Line Data in Mass Fraction with Standard Uncertainty for Ternary ((±)α-Phenylethylamine (1) + n-Hexane (2) + Water (3)) Systems and Separation Factors (S) and Distribution Coefficients (D) of (±)αPhenylethylamine at T = 333.2 K and P = 0.1 MPaa organic-rich phase

water-rich phase

w1

w2

w1

w2

D

S

0.1812 0.2702 0.3815 0.4837 0.6222 0.6805 0.6863 0.7190 0.7567 0.7697 0.7814 0.7872 0.7903

0.8120 0.7194 0.5991 0.4849 0.3002 0.2362 0.2270 0.1718 0.1140 0.0265 0.0597 0.0445 0.0593

0.0007 0.0021 0.0011 0.0008 0.0006 0.0005 0.0005 0.0004 0.0003 0.0003 0.0003 0.0003 0.0003

0.0010 0.0022 0.0016 0.0012 0.0009 0.0008 0.0008 0.0007 0.0007 0.0005 0.0006 0.0005 0.0005

259 129 347 605 1037 1361 1373 1797 2522 2566 2605 2624 2634

37856 12383 17766 19186 13344 16317 15805 16448 19495 12581 16372 15575 17499

a

Standard uncertainties are u(w) = 0.01 and u(T) = 0.1 K, u(p) = 1 kPa.

Table 6. Experimental Tie Line Data in Mass Fraction with Standard Uncertainty for Ternary ((±)α-Phenylethylamine (1) + n-Hexane (2) + Water (3)) Systems at T = 318.2 K and P = 0.1 MPaa (±)αphenylethylamine-rich phase w1

w2

n-hexane-rich phase w1

w2

water-rich phase w1

w2

three-liquid-phase-coexisting 0.0806 0.2981 0.6938 0.0006 0.0007 two-liquid-phase-coexisting on water/n-hexane side 0.2068 0.7925 0.0003 0.0006 0.1656 0.8342 0.0002 0.0005 two-liquid-phase-coexisting on (±)α-phenylethylamine/n-hexane side 0.7301 0.1139 0.5412 0.4027 two-liquid-phase-coexisting on (±)α-phenylethylamine/water side 0.7248 0.0407 0.0005 0.0002 0.7379

Figure 2. Ternary liquid−liquid equilibria for the ((±)α-phenylethylamine + n-hexane + water) system (mass fraction) at (a) T = 318.2 K and (b) T = 298.2 K and p = 0.1 MPa. Experimental three-liquidphase-coexisting tie triangle (●, blue solid lines), experimental twoliquid-phase-coexisting solubility curve (●, red solid lines), experimental tie line (■, black solid lines).


amounts water to achieve three balances. The same method was used to obtain the tie-line data at 318.2 and 333.2 K.

S=

3. RESULTS AND DISCUSSION 3.1. Experimental Data and Separation Factors. Experimental LLE tie-line data for the ((±)α-phenylethylamine + n-hexane + water) ternary system were measured at 333.2, 318.2, and 298.2 K, respectively, and the results were listed in Tables 5, 6, and 7. At 333.2 K, the system exhibits only one two-liquid-phase-coexisting in the triangle phase diagram, as shown in Figure 1. This result indicates that the (±)αphenylethylamine mainly dissolves in n-hexane-rich phase. Different separation factors were obtained as the different mass fraction of (±)α-phenylethylamine. Separation factor (S) and distribution coefficients (D) (as shown in Table 5) were the important elements to evaluate extraction agent,21 defined as follows: w1, e D= w1, r (1)

w1,e/w1,r w3,e/w3,r

(2)

The w1,e and w1,r were the mass fractions of (±)α-phenylethylamine in extract phase and raffinate phase, respectively. The w3,e and w3,r represent water in extract phase and raffinate phase, respectively. Two-liquid-phase-coexisting is changed into three-liquidphase-coexisting when the temperature decreases from 333.2 to 331.2 K. While the system exhibits one three-liquid-phasecoexisting region and three two-liquid-phase-coexisting regions in triangle phase diagram at both 318.2 and 298.2 K. The corresponding triangular phase diagrams for the ternary system are plotted in Figure 2, which shows that the mass fraction of (±)α-phenylethylamine in middle layer ((±)α-phenylethylamine-rich phase) is higher than the other two phases. The mass fraction of (±)α-phenylethylamine in n-hexane-rich phase increases when the temperature increases from 298.2 to 318.2 C



Article

Table 7. Experimental Tie Line Data in Mass Fraction with Standard Uncertainty for Ternary ((±)α-Phenylethylamine (1) + n-Hexane (2) + Water (3)) Systems at T = 298.2 K and P = 0.1 MPaa (±)αphenylethylamine-rich phase w1

n-hexane-rich phase

w2

w1

li =

θi =

water-rich phase

w2

w1

Φi =

w2

three-liquid-phase-coexisting 0.0523 0.1299 0.8687 0.0001 0.0007 two-liquid-phase-coexisting on water/n-hexane side 0.0938 0.9059 0.0001 0.0002 two-liquid-phase-coexisting on (±)α-phenylethylamine/n-hexane side 0.7017 0.0809 0.4743 0.5008 0.7147 0.0924 0.6318 0.3195 0.7017 0.0809 0.5004 0.4703 two-liquid-phase-coexisting on (±)α-phenylethylamine/water side 0.6579 0.0203 0.0002 0.0002

Standard uncertainties are u(w) = 0.01 and u(T) = 0.1 K, u(p) = 1 kPa.

K. Judging from the three phase diagrams (Figures 1 and 2), the region of the two-liquid-phase-coexisting becomes larger with the increase of temperature, while the region of the threeliquid-phase-coexisting section becomes smaller, the composition difference between n-hexane-rich phase and (±)αphenylethylamine-rich phase would be decreased. In this experiment, two boundaries between three different phases could be observed while the temperature is lower than 333.2 K. The boundary existing between n-hexane-rich phase and (±)αphenylethylamine-rich phase would disappear and the two phases would merge into one phase ultimately when the temperature reached 331.2 K. 3.2. Data Correlation. The experimental LLE data for system ((±)α-phenylethylamine + n-hexane + water) is correlated by using NRTL and UNIQUAC models.22−25 The activity coefficient for NRTL model is calculated by the following equations:

∑k Gkixk

+

∑ j

⎛ ∑ τkjGkjxk ⎞ ⎜⎜τij − k ⎟⎟ ∑k Gkixk ⎠ ∑k Gkixk ⎝

(8)

rx i i c ∑i = 1 rx i i

(9)

Table 8. NRTL and UNIQUAC Parameters for Liquid + Liquid Equilibria of ((±)α-Phenylethylamine + n-Hexane + Water) System at T = 333.2 K under Atmospheric Pressure NRTL parameters Δg12

Δg21

Δg13

4369

5017

5417 20488 9510 UNIQUAC parameters

Δu12

u21

u13

u31

−2601.9

−547.3

−2271.5

−4081.4

n

RMSD =

(3) (4)

Gij = exp(−αijτij)(αij = αji)

(5)

c ⎡ ⎢1 − ln(∑ θτ ) − j ji ⎢⎣ j=1

c

∑ j=1

Δg32

RMSD

18309

0.0121

u23

u32

RMSD

−1872.6

−5180.8

0.0276

2

3

exp cal 2 ∑k = 1 ∑ j = 1 ∑i = 1 (wijk − wijk )

6n

(11)

4. CONCLUSIONS The binodal curve data and precise tie-line data for the ternary mixtures ((±)α-phenylethylamine + n-hexane + water) were obtained at T = 298.2, 318.2, and 333.2 K and atmospheric pressure. The system presents three two-liquid-phase-coexisting sections and one three-liquid-phase-coexisting section in the triangle phase diagram while the temperature is lower than 331.2 K. The mutual solubility would be enlarged with

c

∑ xjlj + qi j=1

⎤ ⎥ c ∑k = 1 θkτkj ⎥⎦

Δg23

where n is the number of tie lines, i indicates components, j indicates phases, k = 1, 2, 3, ...n (tie lines), wexp ijk indexes the experimental mass fraction, and wcal ijk indexes the calculated mass fraction. The values of RMSD are no more than 0.03, which indicates that the NRTL and UNIQUAC model are consistent with the experimental LLE data for system ((±)α-phenylethylamine + n-hexane + water) at 333.2 K. Calculated values by the NRTL model are presented in Figure 3.

where γ is the activity coefficient, x is the mole fraction, Δgij is an interaction parameter between species i and j, and αij is a nonrandomness parameter. The optimum value for the nonrandomness parameter was taken to be α = 0.3, which produced better goodness-of-fits. While the activity coefficient for UNIQUAC model is calculated by the eq 6: Φi Φ θ z + qi ln i + li − i Φi 2 xi xi

Δg31

mass fraction) of RMSD (root-mean-square-deviation) are listed in Table 8, and is defined by

xjGij

τij = (gij − gjj)/RT = Δgij /RT

ln γi = ln

c

∑i = 1 qixi

where xi is the mole fraction, qi and ri are molecular structure parameters of the pure component and calculated from the van der Waals molecular area and volume, θi and ϕi are the fraction of molecular area and volume, z is the coordination number (z = 10), Δuji is binary interaction parameters between species i and j, which is determined by experimental tie line data. Equilibrium between n-hexane-rich phase and water-rich phase will be reached at 333.2 K. The values of interequilibrium phases are correlated with NRTL and UNIQUAC models, and the corresponding interaction parameters for system ((±)αphenylethylamine + n-hexane + water) are obtained using the nonlinear least-squares method in MATLAB and presented in Table 8. As the judgment of optimization results, the values (in

a

∑j τjiGjixj

(7)

qixi

⎛ Δuji ⎞ ⎛ uii − uji ⎞ ⎟ = exp⎜ τji = exp⎜ ⎟ ⎝ RT ⎠ ⎝ RT ⎠

0.6706

lnγi =

⎛z⎞ ⎜ ⎟(r − q ) − (r − 1) i i ⎝2⎠ i

θτ j ij

(6)

where D



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Figure 3. Ternary phase diagram for (water + (±)α-phenylethylamine + n-hexane) system at T = 333.2 K and P = 0.1 MPa. Experimental tie line value (■, black solid lines), calculated tie line value by NRTL model; (○, blue solid line).

increasing temperature. Consequently, low temperature is favorable for separation (±)α-phenylethylamine from water. All experimental data were well correlated with the NRTL (α = 0.3) and UNIQUAC model, as can be seen by comparing the experimental and the fitted data in the ternary diagrams under investigation. The separation factors and distribution coefficients of the system were calculated to determine the best condition of separating (±)α-phenylethylamine from water. The experimental data obtained in this work is advantageous to studying the separating (±)α-phenylethylamine from water. The mass fraction of (±)α-phenylethylamine in water-rich phase was less than 0.01, which confirms that n-hexane has potential as an extracting agent.

■

AUTHOR INFORMATION

Corresponding Authors

*[email protected]. *[email protected]. ORCID

Qiang Huang: 0000-0003-3496-9947 Notes

The authors declare no competing financial interest.

■

REFERENCES

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