Solvent Extraction Research and Development, Japan, Vol. 22, No 1, 1 – 15 (2015)

Liquid-Liquid Equilibria of Three Ternary Systems: Glycerol + Acetone + Water, Glycerol +

1, 4-Dioxane + Water, and Glycerol + Acetonitrile + Water

Hirotake KATAYAMA* and Tomoya SATOH

Department of Applied Chemistry, Hosei University, 3-7-2 Kajinocho, Koganei, Tokyo 184-8584, Japan

(Received August 31, 2014, Accepted October 13, 2014)

Liquid–liquid equilibria of three ternary systems {glycerol + acetone + water}, {glycerol + 1, 4-dioxane +

water}, and {glycerol + acetonitrile + water} were measured at temperatures of 288.15, 298.15, and 308.15

K. The results of the first two systems were satisfactorily correlated with the UNIQUAC equation with

average deviations of 0.74 and 0.81%, respectively. Those of the last system were well correlated with a

deviation of 2.49%. Glycerol was verified as a suitable solvent to remove water from acetone + water and

acetonitrile + water solutions, through investigation of the distribution coefficients and selectivity for water,

combining vapor-liquid equilibria of the systems {acetone + water} and {acetonitrile + water} at

atmospheric pressure.

1. Introduction

Solvent extraction is an important separation technique for organic compounds. The operation requires

reliable knowledge of the liquid-liquid equilibrium (LLE) between the mixture to be separated and the

solvents selected. Because of strong polarity differences between the molecular species of the mixture and

those of the solvents, LLE predictions are much more difficult than those for vapor-liquid equilibrium

(VLE).

Since the VLE of two binary mixtures of {1, 4-dioxane and water} and {acetonitrile and water} give

azeotropic mixtures at atmospheric pressure, the mixtures cannot be separated by conventional distillation.

The mixture of {acetone and water} has no azeotrope; however the relative volatility of the mixture shows

a near unity value in the high purity region for acetone. To obtain high-purity acetone from an aqueous

mixture, a distillation column with a large number of theoretical plates is required.

Glycerol is partially miscible with acetone, 1, 4-dioxane, and acetonitrile, but arbitrarily miscible with

water. In addition, it has a high normal boiling point (563.7 K) and a high density (1261.3 kg/m3 at 293 K)

[1]. After extraction of acetone, 1, 4-dioxane, and acetonitrile with glycerol, the separation of the mixtures

and glycerol by distillation is easy.

In this work, in order to determine the feasibility of glycerol as a solvent to eliminate water from

aqueous solutions containing acetone, 1, 4-dioxane, and acetonitrile, the LLE of these three systems were

measured at temperatures of 288.15, 298.15, and 308.15 K, and their phase diagrams were determined. As

far as we know, the LLE of the glycerol + acetone + water system has been measured at 293.15 and 298.15

K by Hampe and Schermuly [2], and Krishna et al. [3], respectively, but the LLE of the last two systems

have not been studied.

- 1 -

The experimental results were correlated with the UNIQUAC equation. The correlations are discussed.

Distribution coefficients for water and degree of selectivity were also investigated, combining the VLEs of

the related binary mixtures at atmospheric pressure.

2. Experimental

2.1 Reagents

The organic reagents used (glycerol, acetone, 1, 4-dioxane, acetonitrile, ethylene glycol, and

1-propanol) were purchased from Wako Pure Chemical Industries, Ltd., all of which were stated to be

minimum assays of 99.5 mass %. After dehydrated with molecular sieves 4A, the reagents were used

without further purification. Tap water was distilled before use.

2.2 Apparatus and Procedure

The experimental method and apparatus are similar to those already described [4,5]. Temperature

was measured using an F25 platinum resistance thermometer (Automatic System Laboratories, Ltd.) with a

stated accuracy of 0.03 K and a stated resolution of 0.001 K. The temperature fluctuation of the water bath

was within 0.08 K. Each 50-mL mixture of glycerol, acetone (or 1, 4-dioxane or acetonitrile), and water

was poured into six 50-cm3 flasks sealed with glass stopcocks, and the flasks were immersed in the bath.

The mixtures were agitated for 4 h, and then allowed to settle for more than 12 h. Samples (1-mL) were

withdrawn from both phases with long needle syringes, and then 1-mL of ethylene glycol for the systems

{glycerol (1) + acetone (2) + water (3)} and {glycerol (1) + acetonitrile (2) + water(3)}, or 1-mL

1-propanol for the system {glycerol (1) + 1, 4-dioxane (2) + water (3)},was added to the sample as an

internal standard.

The samples were analyzed by gas chromatography on a Shimadzu GC-8A Model unit with a thermal

conductivity detector, in which a 2-m column of Porapak-Q was installed. Helium gas was used as the

carrier gas.

The analytical limit for each component was 0.0002 mole fraction. However, because of the

reproducibility of the numerical values, the concentrations were reported to three decimal places.

3. Results and Discussion

3.1 Experimental data

The results for the LLE of the ternary systems {glycerol (1) + acetone (2) + water (3)}, {glycerol (1)

+ 1, 4-dioxane (2) + water (3)}, and {glycerol (1) + acetonitrile (2) + water (3)} are given in Tables 1-3 and

in Figures 2-4 (shown as filled circles), respectively. The compositions are given in terms of mole fractions.

Figure 1 shows the experimental results at 298.15 K for the system {glycerol (1) + acetone (2) + water (3)},

which are in good agreement with those of Krishna et al.

Figures 2-4 show that the magnitudes of the two-phase areas for the three ternary systems are in the

order of {glycerol + acetonitrile + water} > {glycerol + acetone + water} > {glycerol + 1, 4-dioxane +

water}, and those of their tie-line slopes are also in the same order. From these data, the polarity of the

substances used is considered to be in the order of glycerol > water >1, 4-dioxane > acetone > acetonitrile.

- 2 -

Figure 1. Comparison of the experimental results with those of the literature for the LLE of the system

{glycerol (1) + acetone (2) + water (3)} at 298.15 K. Solid and dotted lines show the tie lines from this

work, and those of Krishna et al., respectively.

3.2 Correlation with the UNIQUAC equation

The experimental results were correlated by the UNIQUAC equation [6]. The parameters A12 and A21

for the binary systems｛glycerol (1) + acetone (2)}, {glycerol (1) + 1, 4-dioxane (2)}, and {glycerol (1) +

acetonitrile (2)} were obtained by means of the least-squares method, using the respective binary data of

Tables 1-3. The A12 and A21 values obtained are shown in the first and second columns of Table 4. The four

remaining Aij parameters (i.e., A23, A32, A31, and A13) for the systems {glycerol (1) + acetone (2) +water (3)},

{glycerol (1) + 1, 4-dioxane (2) + water (3)}, and {glycerol (1) + acetonitrile (2) + water (3)} were

determined by minimizing the following objective function, Fobj, using the modified Marquardt method [7]:

2 32

, , , , , ,

1 1 1

( , )( )N

obj k j n exptl. k j n cal.

n k j

F w k j x x

(1)

where k is the number of phases (1 and 2), j is the number of components (1, 2, and 3), n is the number of

data (1 to N = 8-16), w (k, j) is a weighting factor of phase k and component j, and x is the mole fraction.

Subscripts (exptl. and cal.) represent experimental and calculated values, respectively. Parameter Aij is in

Kelvin.

- 3 -

Table 1. Liquid-liquid equilibria for the system {glycerol (1) + acetone (2) + water (3)}

Temp. acetone-rich phase (I) glycerol-rich phase (II) β 3 S

[K] x 1 x 3 x 2 x 3

288.15 0.0274 0.0000 0.144 0.0000

0.0238 0.0024 0.142 0.0151 6.40 43.9

0.0262 0.0119 0.146 0.0515 4.31 28.4

0.0275 0.0296 0.139 0.149 5.05 34.2

0.0290 0.0410 0.147 0.177 4.32 27.2

0.0302 0.0645 0.153 0.289 4.47 26.4

0.0303 0.0874 0.163 0.351 4.01 21.7

0.0356 0.110 0.175 0.391 3.56 17.4

0.0356 0.120 0.179 0.414 3.44 16.2

0.0371 0.139 0.190 0.434 3.13 13.6

0.0420 0.171 0.204 0.465 2.73 10.5

0.0440 0.196 0.221 0.489 2.49 8.56

0.0501 0.217 0.237 0.493 2.27 7.01

298.15 0.0301 0.0000 0.157 0.0000

0.0267 0.0011 0.152 0.0065 6.06 38.8

0.0259 0.0021 0.151 0.0126 6.04 38.8

0.0325 0.0110 0.151 0.0404 3.67 23.3

0.0266 0.0255 0.153 0.118 4.63 28.7

0.0323 0.0355 0.150 0.159 4.49 28.0

0.0318 0.0442 0.158 0.210 4.76 27.8

0.0357 0.0544 0.162 0.236 4.34 24.4

0.0414 0.0816 0.163 0.289 3.54 19.1

0.0378 0.0973 0.180 0.343 3.52 16.9

0.0489 0.131 0.183 0.386 2.95 13.2

0.0511 0.155 0.193 0.419 2.69 11.1

0.0549 0.181 0.213 0.448 2.47 8.85

0.0517 0.189 0.219 0.458 2.43 8.40

0.0595 0.220 0.242 0.475 2.15 6.41

0.0643 0.217 0.235 0.470 2.16 6.62

308.15 0.0395 0.0000 0.169 0.0000

0.0378 0.0023 0.178 0.0068 2.88 15.6

0.0401 0.0116 0.166 0.0403 3.48 19.9

0.0410 0.0359 0.166 0.144 4.00 22.3

0.0446 0.0592 0.168 0.222 3.75 20.0

0.0481 0.0768 0.178 0.280 3.64 18.0

0.0508 0.107 0.188 0.336 3.13 14.1

0.0547 0.132 0.198 0.378 2.87 11.8

0.0565 0.146 0.211 0.401 2.75 10.4

0.0609 0.171 0.218 0.419 2.45 8.62

0.0683 0.205 0.236 0.443 2.16 6.64

0.0788 0.252 0.266 0.459 1.82 4.60

- 4 -

Table 2. Liquid-liquid equilibria for the system {glycerol (1) + 1, 4-dioxane (2) + water (3)}

Temp. 1, 4-dioxane-rich phase (I) glycerol-rich phase (II) β 3 S

[K] x 1 x 3 x 2 x 3

288.15 0.0467 0.0000 0.171 0.0000

0.0440 0.0228 0.172 0.120 5.26 28.5

0.0476 0.0414 0.182 0.216 5.22 26.1

0.0455 0.0600 0.196 0.280 4.67 21.3

0.0479 0.0771 0.204 0.332 4.30 18.4

0.0507 0.0914 0.211 0.362 3.97 16.1

0.0520 0.114 0.230 0.398 3.50 12.7

0.0567 0.154 0.261 0.441 2.86 8.65

298.15 0.0547 0.0000 0.192 0.0000

0.0565 0.0282 0.195 0.119 4.22 19.8

0.0593 0.0495 0.208 0.214 4.33 18.6

0.0606 0.0675 0.216 0.274 4.05 16.3

0.0631 0.0906 0.227 0.321 3.55 13.2

0.0665 0.112 0.240 0.358 3.20 10.9

0.0701 0.138 0.259 0.388 2.81 8.58

0.0813 0.196 0.305 0.421 2.14 5.08

308.15 0.0714 0.0000 0.210 0.0000

0.0727 0.0307 0.226 0.124 4.22 19.8

0.0745 0.0585 0.234 0.212 4.33 18.6

0.0744 0.0846 0.248 0.265 4.05 16.3

0.0789 0.113 0.258 0.310 3.55 13.2

0.0844 0.137 0.282 0.347 3.20 10.9

0.0936 0.171 0.307 0.364 2.81 8.58

0.109 0.234 0.393 0.370 2.14 5.08

- 5 -

Table 3. Liquid-liquid equilibria for the system {glycerol (1) + acetonitrile (2) + water (3)}

Temp. acetonitrile-rich phase (I) glycerol-rich phase (II) β 3 S

[K] x 1 x 3 x 2 x 3

288.15 0.0069 0.0000 0.145 0.0000

0.0083 0.0074 0.144 0.0154 2.08 14.2

0.0067 0.0076 0.138 0.0304 3.99 28.6

0.0076 0.0210 0.135 0.175 8.33 59.8

0.0081 0.0409 0.123 0.348 8.52 65.7

0.0091 0.0527 0.125 0.421 7.98 60.0

0.0097 0.0700 0.120 0.492 7.03 53.9

0.0097 0.0792 0.123 0.532 6.71 49.9

0.0093 0.103 0.123 0.594 5.77 41.8

0.0098 0.111 0.125 0.618 5.56 39.1

0.0093 0.128 0.127 0.646 5.06 34.5

0.0093 0.146 0.129 0.677 4.62 30.2

0.0099 0.155 0.130 0.685 4.41 28.3

0.0100 0.171 0.136 0.707 4.14 25.0

0.0111 0.226 0.145 0.738 3.26 17.2

298.15 0.0102 0.0000 0.161 0.0000

0.0114 0.0078 0.156 0.0198 2.54 16.0

0.0098 0.0237 0.148 0.168 7.08 46.2

0.0133 0.0481 0.139 0.344 7.15 48.3

0.0127 0.0642 0.141 0.409 6.37 41.8

0.0113 0.0819 0.138 0.479 5.85 38.5

0.0109 0.0936 0.139 0.517 5.52 35.5

0.0128 0.123 0.142 0.584 4.76 29.0

0.0104 0.135 0.144 0.612 4.52 26.7

0.0124 0.153 0.145 0.632 4.14 23.9

0.0123 0.178 0.153 0.664 3.73 19.8

0.0118 0.184 0.154 0.678 3.69 19.3

0.0126 0.263 0.179 0.716 2.73 11.0

308.15 0.0166 0.0000 0.179 0.0000

0.0186 0.0060 0.175 0.0196 3.28 18.2

0.0169 0.0281 0.166 0.162 5.79 33.2

0.0170 0.0545 0.157 0.326 5.98 35.3

0.0175 0.0727 0.148 0.405 5.57 34.3

0.0172 0.0990 0.159 0.468 4.72 26.2

0.0144 0.119 0.161 0.508 4.26 22.9

0.0184 0.145 0.164 0.563 3.88 19.8

0.0185 0.159 0.167 0.591 3.71 18.2

0.0177 0.183 0.173 0.614 3.37 15.5

0.0184 0.218 0.181 0.637 2.92 12.3

0.0167 0.238 0.185 0.646 2.72 11.0

0.0192 0.331 0.227 0.671 2.03 5.80

- 6 -

Figure 2. LLE for the system {glycerol (1) + acetone (2) + water (3)}. Solid lines: experimental tie lines.

Dotted lines: predicted tie lines.

- 7 -

Figure 3. LLE for the system {glycerol (1) + 1, 4-dioxane (2) + water (3)}. The solid and dotted lines are

defined as in Figure 2. The symbol (□) represents the azeotropic point of the system {1, 4-dioxane + water}

at atmospheric pressure [9]. The broken line passes through the azeotropic point and the point for pure

glycerol.

- 8 -

Figure 4. LLE for the system {glycerol (1) + acetonitrile (2) + water (3)} in the absence of the weighting

factor. The solid and dotted lines are defined as in Figure 2. The symbol (□) represents the azeotropic point

of the system {acetonitrile + water } at atmospheric pressure.

- 9 -

Figure 5. LLE for the system {glycerol (1) + acetonitrile (2) + water (3)} in the presence of the weighting

factor, w(1,1) = 10,000.0. The solid and dotted lines are defined as in Figure 2.

3.2.1 Correlation with the weighting factor w (k, j) = 1.0 (no weighting factor)

As the w (k , j) (k = 1, 2; j = 1, 2, 3) values were set at unity, through minimizing Fobj, the four

- 10 -

parameters of Aij obtained for the three ternary systems are listed along with the root-mean-square

deviations (rmsd) in Table 4. Figures 2-4 show the comparison between the experimental values () and

the correlated ones ().

Table 4. UNIQUAC parameters of A ij for the three ternary systems correlated

without the weighting factor{w (k, j ) = 1.0, k = 1-2 and j = 1-3}

T [K] A 12 [K] A 21 [K] A 23 [K] A 32 [K] A 31 [K] A 13 [K] rmsd* remarks

glycerol (1) + acetone (2) + water (3) system

288.15 125.54 263.59 89.19 55.94 -195.37 -67.70 0.68 pl

298.15 122.44 271.14 26.17 137.15 -225.43 -4.43 0.77 pl

308.15 132.47 253.54 -44.64 182.13 -265.44 -27.79 0.77 pl

avdev ** 0.74

glycerol (1) + 1,4-dioxane (2) + water (3) system

288.15 82.61 250.31 236.74 -61.96 -147.36 -101.34 0.64 pl

298.15 79.28 252.25 170.64 -62.72 -185.60 -99.36 0.88 pl

308.15 87.72 236.71 86.58 -78.50 -273.84 -103.11 0.91 pl

avdev ** 0.81

glycerol (1) + acetonitrile (2) + water (3) system

288.15 209.44 344.92 56.69 232.09 -107.34 -257.28 0.62 no pl

298.15 215.53 323.27 42.72 228.79 -97.98 -256.07 0.71 no pl

308.15 229.14 288.83 -13.48 234.51 -168.61 -252.90 0.78 pl

avdev ** 0.70

*The root-mean-square deviation (rmsd) was defined as:

where N is the number of data points.

pl: the plait point is obtained. no pl: the plait point is not obtained.

**The average deviation (avdev) was defined as the arithmetic average values at the temperatures

of 288.15, 298.15, and 308.15 K.

Each plait point from the UNIQUAC equation is also calculated, and shown as an (×) in Figures 2, 3,

and 4(c1) for the systems {glycerol (1) + acetone (2) + water (3)}, {glycerol (1) + 1, 4-dioxane (2) + water

(3)}, and {glycerol (1) + acetonitrile (2) + water (3)}, respectively. The correlations of the two systems

{glycerol (1) + acetone (2) + water (3)} and {glycerol (1) + 1, 4-dioxane (2) + water (3)} are judged to be

satisfactory from Figures 2 and 3, and the small deviations (rmsd) of Table 4.

The Aij parameters of 288.15 and 298.15 K for the system {glycerol (1) + acetonitrile (2) + water (3)}

do not give a plait point. In other words, the binary system {acetonitrile + water} was calculated to be

partially miscible at these temperatures, as described in Figures 4(a1) and 4(b1). In practice, as acetonitrile

and water are completely miscible, the system {glycerol (1) + acetonitrile (2) + water (3)} also belongs to

2 3

2

, , , , , , .

1 1 1100.0

6

N

k j n exptl. k j n cal

n k j

x x

rmsdN

- 11 -

Type I as well as the other systems mentioned here. The calculated value of 308.15 K only gives the point

as marked in Figure 4(c1).

Parts (a2), (b2), and (c2) of Figure 4, which correspond to enlargement of the abscissa of parts (a1),

(b1), and (c1) of Figure 4, respectively, show the different tendencies of the calculated and experimental

values in the acetonitrile-rich phase. As the water content increases, the calculated values for glycerol of

288.15 and 298.15 K approach the ordinate axis, and finally arrive at the axis. Thus, they do not belong to

the Type I category. There are large differences between the calculated and experimental values of 288.15,

298.15, and 308.15 K. Thus, the correlated results for the system {glycerol (1) + acetonitrile (2) + water

(3)} are considered unsatisfactory.

3.2.2 Correlation with the weighting factor w (1, 1) = 10000.0

The Aij (i.e., A23, A32, A31, and A13) parameters of the system {glycerol (1) + acetonitrile (2) + water

(3)} were again calculated using w (1, 1) factors of 100.0, 1000.0, and 10000.0 at 288.15, 298.15, and

308.15 K. The same A12 and A21 parameters obtained from the binary system {glycerol (1) + acetonitrile

(2)} were used. All other w (k , j) values except for w (1, 1), {w (k , j) = 1.0; k = j ≠ 1} , were taken as

unity. Here k = 1and k = 2 represent the acetonitrile-rich phase and the glycerol-rich phase, respectively. j =

1, j = 2, and j = 3 represent the components of glycerol (1), acetonitrile (2), and water (3), respectively.

As larger values of w (1, 1) are used, the difference between experimental and calculated values in

terms of mole fraction of glycerol in the acetonitrile-rich phase gradually decreases.

Table 5. UNIQUAC parameters of A ij for the glycerol (1) + acetonitile (2) + water (3) system

correlated with the weighting factors {w (1, 1) = 10000.0, and w (k, j ) = 1.0, k= j≠ 1}

T [K] A 12 [K] A 21 [K] A 23 [K] A 32 [K] A 31 [K] A 13 [K] rmsd remarks

288.15 209.44 344.92 -11.19 268.48 -132.31 -177.27 3.21 pl

298.15 215.53 323.27 -14.19 245.60 -83.63 -236.00 2.49 pl

308.15 229.14 288.83 -15.29 239.18 -79.44 -235.31 1.77 pl

avdev 2.49

The Aij parameters obtained from w (1, 1) = 10000.0 are listed in Table 5 along with the deviations

(rmsd).The values for the LLE calculated with Aij are indicated by the symbol () in Figure 5. The plait

points are also shown as the symbol (×).

The plots in parts (a2), (b2), and (c2) in Figure 5 demonstrate better agreement with the experimental and

calculated values for glycerol in the acetone-rich phase than those [in parts (a2), (b2), and (c2)] in Figure 4.

Inversely, those parts (a1), (b1), and (c1) in Figure 5 are in worse agreement with experimental and

calculated values of glycerol in the glycerol-rich phase, than those of [parts (a1), (b1), (c1)] in Figure 4.

The calculated values of the water component are overestimated in the acetonitrile-rich phase, and

underestimated in the glycerol-rich phase. The deviations (rmsd) of the LLE calculated from the Aij

parameters in Table 5 are larger than those of the LLE from the parameters in Table 4 by 2.3–5.2 times.

However, all the results from the parameters in Table 5 belong to Type I.

The structural parameters, ri and qi, for the pure components were obtained from Sorensen and Arlt

[8] and listed in Table 6.

- 12 -

Table 6. Structural parameters of the UNIQUAC equation

Components r-value q-value

glycerol 3.5857 3.0600

acetone 2.5735 2.3360

1,4-dioxane 3.1854 2.6400

acetonitrile 1.8701 1.7240

water 0.9200 1.4000

3.3 Capability of glycerol as a solvent for liquid-liquid extraction

The distribution coefficient (β3) and selectivity (S) are important indicators for liquid-liquid

extraction unit operation capability. The distribution coefficient for water (β3) is defined as follows

3 3 3/II Ix x

where x3II and x3

I represent the mole fractions of water(3) in the glycerol-rich phase (II) and in the acetone-,

or 1,4-dioxane-, or acetonitrile- rich phases (I), respectively.

The selectivity (S) is defined by the following equation

3 2/S

Where β2 (= x2II/x2

I) is the distribution coefficient for the second component (2) (acetone, or 1,4-dioxane, or

acetonitrile).

The distribution coefficient (β3) and selectivity(S) have been added to the last two columns in Tables

1-3.The β3 and S values for the system {glycerol (1) + acetone (2) + water (3)} are plotted against the

x3I-values in Figures 6 and 7, respectively, for comparison with the results from the UNIQUAC equation

with the parameters in Table 4.The values of β3 and S in the range of {x2= 0.94-1.0}, that is, in the

water-range of {x3= 0.06-0.00}, are found to be 3.7-6.4 and 20-44, respectively. The area of {x3=

0.06-0.00} is the most suitable for separation by liquid-liquid extraction. Dependences of β3 and S on the

temperature for the three systems studied are found to be small from Figures 6 and 7, and Tables 1-3.

In the range {x2= 0.94-1.0} in terms of acetone mole fraction, the VLE for the binary system

{acetone (2) + water (3)} at atmospheric pressure exhibits only small differences between vapor and liquid

compositions. For example, the relative volatility at {x2= 0.94, x3= 0.06} is 1.22. This shows that large

numbers of theoretical plates are required to remove small amounts of water from aqueous acetone

solutions by distillation.

- 13 -

Figure 6. Water-distribution coefficients, β3, for the system {glycerol (1) + acetone (2) + water (3)}.

Broken, solid, and dotted lines were drawn from values at 288.15, 298.15, and 308.15 K, respectively,

calculated by the UNIQUAC equation with the parameters in Table 4.

Figure 7. Selectivity, S, for the system {glycerol (1) + acetone (2) + water (3)}.

The broken, solid, and dotted lines are defined as in Figure 6.

The azeotropic point (x1= 0.000, x3= 0.509) for the system {1, 4-dioxane (2) + water (3)} at

atmospheric pressure is shown by the symbol (□) on the ordinate axis of Figure 3. A broken straight line

passing through the azeotropic point and the point for pure glycerol has been drawn in Figure 3 (a). The

line divides the two-liquid-phase area into upper and lower parts. Since the upper part is much smaller than

the lower, glycerol cannot be utilized as a solvent in separating mixtures of 1, 4-dioxane (2) and water (3)

in the vicinity of the azeotropic point.

The azeotropic point (x1= 0.000, x3= 0.318) for the system {acetonitrile (2) + water (3)} at

atmospheric pressure is shown by the symbol (□) on the ordinate axis of Figure 4. If a similar straight line

is drawn through the point and the point for pure glycerol in Figure 4, the area of the two-liquid phase will

be divided into upper and lower parts of the line as well as that in Figure 3. In this case, both parts have

sufficient magnitudes to separate mixtures of the azeotropic point by liquid extraction.

Combining two operations of liquid extraction using glycerol as the solvent and conventional

- 14 -

distillation, one can consider a process for obtaining pure acetone or acetonitrile from an aqueous solution

of acetone or acetonitrile.

4. Conclusion

LLE for the systems {glycerol + acetone + water}, {glycerol + 1,4-dioxane + water}, and {glycerol

+ acetonitrile + water} were measured at temperatures of 288.15, 298.145, and 308.15 K. The experimental

results of the former two systems were successfully correlated using the UNIQUAC equation. Those of the

latter system {glycerol + acetonitrile + water} were well correlated using the equation. Through the

investigation of the distribution coefficients for water and selectivity, combines with VLE for the systems

{acetone+ water} and {acetonitrile + water} at atmospheric pressure, glycerol was verified as a suitable

solvent to remove the water-component from acetone + water and acetonitrile + water solutions.

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