3.1. Experimental LLE data
LLE data for the ternary system of mesityl oxide + diethoxymethane + water in the organic and aqueous phases at 303.15, 313.15, and 323.15 K are shown in Table 2. The reported values are mass fractions measured by gas chromatography. The experimental LLE phase diagrams of the ternary system are shown in Figs. 1. The distribution coefficient (D) and selectivity coefficients (S) are the essential parameters available for conducting liquid-liquid equilibrium operations, in particular, to check the suitability of a solvent for liquid extraction[4]. The distribution coefficient and selectivity were calculated with the following formula:
$$D={w}_{2}^{\text{I}}/{w}_{2}^{\text{I}\text{I}}$$
1
$$S=\left({w}_{2}^{\text{I}}/{w}_{2}^{\text{I}\text{I}}\right)/\left({w}_{3}^{\text{I}}/{w}_{3}^{\text{I}\text{I}}\right)$$
2
where w2 and w3 are mass fractions of diethoxymethane and water in organic(Ⅰ), and aqueous(Ⅱ) phases, respectively. The distribution coefficient and selectivity values are reported in Table 2. The distribution coefficient changes with the increase of diethoxymethane content in water at different temperatures, as shown in Fig. 2 and also, and the selectivity is shown in Fig. 3.
Table 2
Experimental LLE data in mass fraction for mesityl oxide (1) + diethoxymethane (2) + water (3) ternary system at 303.15, 313.15, 323.15 K at 101.3 kPa, together with the distribution coefficient (D) and selectivity coefficients (S). a
T / K
|
FEED
|
Organic phase (I)
|
Aqueous phase (II)
|
D
|
S
|
\({w}_{1}^{\text{I}}\)
|
\({w}_{2}^{\text{I}}\)
|
\({w}_{1}^{\text{I}}\)
|
\({w}_{2}^{\text{I}}\)
|
\({w}_{1}^{\text{I}\text{I}}\)
|
\({w}_{2}^{\text{I}\text{I}}\)
|
303.15
|
0.4936
|
0
|
0.9645
|
0
|
0.0226
|
0
|
-
|
-
|
0.4767
|
0.0176
|
0.9318
|
0.0333
|
0.0215
|
0.0019
|
17.49
|
489.52
|
0.4457
|
0.0486
|
0.8725
|
0.0930
|
0.0189
|
0.0042
|
21.98
|
622.22
|
0.4315
|
0.0629
|
0.8455
|
0.1206
|
0.0175
|
0.0052
|
23.39
|
673.99
|
0.4146
|
0.0793
|
0.8138
|
0.1526
|
0.0153
|
0.0060
|
25.50
|
744.09
|
0.3976
|
0.0972
|
0.7805
|
0.1872
|
0.0147
|
0.0072
|
26.00
|
786.06
|
0.3761
|
0.1194
|
0.7386
|
0.2305
|
0.0137
|
0.0082
|
27.95
|
883.11
|
0.3475
|
0.1482
|
0.6847
|
0.2865
|
0.0104
|
0.0099
|
28.94
|
982.23
|
0.3302
|
0.1662
|
0.6502
|
0.3217
|
0.0102
|
0.0107
|
30.02
|
1048.59
|
0.3125
|
0.1838
|
0.6155
|
0.3565
|
0.0095
|
0.0111
|
32.03
|
1120.85
|
313.15
|
0.4916
|
0
|
0.9612
|
0
|
0.0219
|
0
|
-
|
-
|
0.4769
|
0.0156
|
0.9327
|
0.0299
|
0.0212
|
0.0014
|
21.88
|
572.46
|
0.4614
|
0.0318
|
0.9022
|
0.0611
|
0.0207
|
0.0026
|
23.50
|
624.47
|
0.4467
|
0.0457
|
0.8744
|
0.0882
|
0.0190
|
0.0033
|
26.93
|
704.05
|
0.4317
|
0.0615
|
0.8460
|
0.1187
|
0.0175
|
0.0043
|
27.35
|
757.98
|
0.3570
|
0.1381
|
0.7012
|
0.2673
|
0.0128
|
0.0089
|
29.94
|
928.98
|
0.3560
|
0.1395
|
0.6997
|
0.2700
|
0.0123
|
0.0090
|
29.96
|
968.00
|
0.3300
|
0.1658
|
0.6482
|
0.3217
|
0.0117
|
0.0099
|
32.48
|
1057.56
|
0.3134
|
0.1823
|
0.6161
|
0.3541
|
0.0107
|
0.0104
|
33.93
|
1114.13
|
0.3003
|
0.1957
|
0.5902
|
0.3807
|
0.0103
|
0.0106
|
35.74
|
1202.62
|
323.15
|
0.4902
|
0
|
0.9617
|
0
|
0.0186
|
0
|
-
|
-
|
0.4751
|
0.0158
|
0.9318
|
0.0305
|
0.0184
|
0.0010
|
30.33
|
789.75
|
0.4654
|
0.0258
|
0.9129
|
0.0500
|
0.0180
|
0.0016
|
31.04
|
818.46
|
0.4461
|
0.0458
|
0.8750
|
0.0887
|
0.0172
|
0.0028
|
31.54
|
853.26
|
0.4324
|
0.0601
|
0.8486
|
0.1166
|
0.0162
|
0.0036
|
32.45
|
914.21
|
0.4162
|
0.0764
|
0.8177
|
0.1486
|
0.0148
|
0.0043
|
34.64
|
1007.11
|
0.4000
|
0.0928
|
0.7867
|
0.1806
|
0.0133
|
0.0050
|
36.21
|
1087.27
|
0.3800
|
0.1137
|
0.7476
|
0.2215
|
0.0124
|
0.0060
|
37.20
|
1179.58
|
0.3598
|
0.1337
|
0.7091
|
0.2606
|
0.0104
|
0.0068
|
38.30
|
1244.69
|
0.3113
|
0.1839
|
0.6134
|
0.3592
|
0.0092
|
0.0087
|
41.26
|
1479.15
|
a Standard uncertainties u are u(T) = 0.1 K, u(p) = 0.1 kPa, u(w) = 0.0015.
Table 3 lists the experimental and literature values of the solubility of water and solvents, which shows that the experimental values are in good agreement with the literature values. It is related to the method of use or measurement accuracy [19].
Table 3
The solubility data (mole fraction) of the experimental and literature values.
T/K
|
Water in solvent
|
Solvent in water
|
wexp.
|
wlit.
|
δ
|
wexp.
|
wlit.
|
δ
|
303.2
|
0.0355
|
0.0367[20]
|
-3.39
|
0.0226
|
0.0266[20]
|
-17.83
|
0.0409[21]
|
-15.19
|
0.0230[21]
|
-1.65
|
0.0392 b [22]
|
-10.38
|
0.0240 b [22]
|
-6.28
|
313.2
|
0.0388
|
0.0382[20]
|
1.48
|
0.0219
|
0.0256[20]
|
-16.84
|
0.0420[22]
|
-8.25
|
0.0214[22]
|
2.30
|
0.0417[21]
|
-7.45
|
0.0219[21]
|
-0.10
|
323.2
|
0.0383
|
0.0451[21]
|
-17.75
|
0.0186
|
0.0203[21]
|
-9.14
|
0.0455[22]
|
-18.80
|
0.0196[22]
|
-5.38
|
a The binary data were taken from the interpolated data in the literature. [22] |
b Relative deviation: δ = \(100\times ({x}_{exp}-{x}_{lit})/{x}_{exp}\).
The LLE phase diagrams of the ternary system are shown in Fig. 1. It can be seen from the figure that the feed is on the tie-line and follows the principle of leverage, indicating that the LLE data complies with the law of conservation of mass [23, 24]. Meanwhile, since diethoxymethane + mesityi oxide is a miscible binary mixture, and water + mesityl oxide and water + diethoxymethane are partially miscible binary mixtures, the system conforms to Treybal's type II ternary phase behavior [25].
As shown in Table 2 and Fig. 3, the selectivity coefficients are all greater than 1, indicating that the mesityl oxide has a good selective extraction effect on diethoxymethane. As can be seen from Figs. 2 and 3, with the increase of diethoxymethane in the organic phase, D and S of the mesityl oxide system increase simultaneously. At the same time, it can be seen from the figure that the D and S of the mesityl oxide system increase with the increase in temperature, indicating that the increase in temperature is conducive to improving the selective extraction ability of the mesityl oxide system. It can be seen from Fig. 2 and Fig. 3 that the extraction capacity of mesityl oxide to extract diethoxymethane from water is found to be ethyl acetate, mesityl oxide, MTBE, MIBK, isoamyl alcohol by comparison with the literature values. The selective order is MTBE, ethyl acetate, mesityl oxide, MIBK, and isoamyl alcohol.
3.2. Reliability of LLE data
The reliability of the experimental data was verified by the Bachman[15] and Hand[16] equation. The expressions of Bachman and Hand are as follows:
$${w}_{1}^{I}=A+B\left(\frac{{w}_{1}^{I}}{{w}_{3}^{II}}\right)$$
3
$$\text{l}\text{n}\left(\frac{{w}_{2}^{\text{I}}}{{w}_{1}^{\text{I}}}\right)=C+D\text{l}\text{n}\left(\frac{{w}_{2}^{\text{I}\text{I}}}{{w}_{3}^{\text{I}\text{I}}}\right)$$
4
where A and B are Bachman parameters, and C and D are the Hand parameters. \({w}_{1}^{\text{I}}\) and \({w}_{2}^{\text{I}}\)denote the mass fractions of mesityl oxide and diethoxymethane in the organic phase; while \({w}_{2}^{\text{I}\text{I}}\) and \({w}_{3}^{\text{I}\text{I}}\) denote the mass fractions of diethoxymethane and water in the aqueous phase. The parameters and linear coefficient (R2) of equations A, B, C, and D were obtained through fitting, and their values were shown in Table 4, R2 greater than 0.99, indicating that the experimental data had good reliability.
Table 4
Bachman and Hand parameters at various temperatures.
T / K
|
Bachman
|
Hand
|
A
|
B
|
R2
|
C
|
D
|
R2
|
303.15
|
0.0049
|
0.9719
|
1.0000
|
6.2977
|
1.5582
|
0.9931
|
313.15
|
0.0022
|
0.9752
|
1.0000
|
5.8547
|
1.4294
|
0.9915
|
323.15
|
-0.0286
|
1.0197
|
0.9907
|
5.5005
|
1.3134
|
0.9889
|
3.3. Thermodynamic modeling
In this study, the NRTL[17] and UNIQUAC[18] thermodynamic models have been used to correlate with the experimental LLE data.
In this work, the optimum binary interaction parameters and NRTL non-randomness parameters were obtained by fitting experimental LLE data to the NRTL and UNIQUAC thermodynamic models. The UNIQUAC structural parameters r (molecular-geometric volume) and q (molecular-geometric surface) were taken from the Aspen Plus V11 physical properties data bank. The values r and q used in the UNIQUAC equation were provided in Table 5.
Table 5
The UNIQUAC structural parameters (r and q) for pure components.
Component
|
r
|
q
|
Mesityl oxide
|
3.8600
|
4.3632
|
Diethoxymethane
|
3.7960
|
4.3131
|
Water
|
0.9200
|
1.4000
|
The corresponding binary interaction parameters in the NRTL and UNIQUAC models were calculated by minimizing the objective function(OF)[27]:
$$\text{O}\text{F}=\sum _{k=1}^{M}\sum _{j=1}^{2}\sum _{i=1}^{3}\left[{\left({w}_{ijk}^{exp}-{w}_{ijk}^{cal}\right)}^{2}\right]$$
5
where wexp and wcal are the experimental and calculated mass fractions. Subscripts i, j, and k refer to the components i in phase j on tie-line k. and M is the number of tie-lines.
The accuracy of the two models was evaluated by the root mean square deviation (RMSD), and the equation is as follows [28]:
$$RMSD\left(\text{\%}\right)=100\times {\left\{\sum _{k=1}^{M}\sum _{j=1}^{2}\sum _{i=1}^{3}{\left({w}_{ijk}^{exp}-{w}_{ijk}^{cal}\right)}^{2}/6M\right\}}^{1/2}$$
6
where, k, j, i, M, wexp, wcal are the same as those of Eq. (5). The RMSD of both models at different temperatures is given in Table 6. which is less than 0.47%. It shows that both models can be applied to this system. Meanwhile, In Figs. 1–3, the calculated values of the two models are compared with the experimental data, which further proves that the two models can be applied to the system.
Table 6
The NRTL and UNIQUAC binary interaction parameters for the studied ternary systems.
model
|
i-j
|
aij
|
bij/K
|
aji
|
bji/K
|
α
|
RMSD/%
|
NRTL
|
1–2
|
-25.16
|
8642.43
|
9.29
|
-3313.33
|
0.3
|
0.4730
|
1–3
|
-0.33
|
491.90
|
5.40
|
-151.68
|
0.3
|
2–3
|
6.25
|
-1381.74
|
10.74
|
-2036.59
|
0.3
|
UNIQUAC
|
1–2
|
2.43
|
-592.07
|
-13.63
|
-6848.46
|
|
0.3129
|
1–3
|
-0.49
|
-155.36
|
-0.77
|
77.04
|
2–3
|
-3.63
|
18.40
|
-0.34
|
-44.07
|