Evaluation of [bmim][PF6] as an ionic solvent for the extraction of propylbenzene from aliphatic compounds

J. Chem. Thermodynamics 54 (2012) 322–329

Contents lists available at SciVerse ScienceDirect

J. Chem. Thermodynamics journal homepage: www.elsevier.com/locate/jct

Evaluation of [bmim][PF6] as an ionic solvent for the extraction of propylbenzene from aliphatic compounds Mohamed S. Fandary ⇑, Khaled H.A.E. Alkhaldi, Adel S. Al-Jimaz, Mohsen H. Al-Rashed, Mohammad S. AlTuwaim Chemical Engineering Department, College of Technological Studies, PAAET, P.O. Box 42325, Shuwaikh 70654, Kuwait

a r t i c l e

i n f o

Article history: Received 16 April 2012 Received in revised form 8 May 2012 Accepted 11 May 2012 Available online 17 May 2012 Keywords: LLE Ionic solvent Alkane Propylbenzene UNIQUAC NRTL

a b s t r a c t The evaluation of using 1-butyl-3-methylimidazolium hexaflurophosphate ionic liquid, [bmim][PF6], as a solvent for the extraction of propylbenzene from aliphatic compounds was studied. The (liquid + liquid) equilibrium (LLE) for two ternary systems comprising {dodecane or tetradecane + propylbenzene + [bmim][PF6]} were analysed at atmospheric pressure and two temperatures, (313 and 333) K. The consistency of the experimental tie line data was ascertained by applying the Othmer–Tobias correlation. The effect of temperature, n-alkane chain length and solvent to feed ratio upon solubility, distribution ratio, selectivity, and per cent removal of the aromatic were investigated. The experimental LLE data were correlated using the UNIQAC and NRTL models for the activity coefficient with estimation of new interaction parameters, using the simplex minimization method and a composition based objective function. The calculated results from both methods are considered satisfactory. Ó 2012 Elsevier Ltd. All rights reserved.

1. Introduction Solvent extraction is the most used conventional process for separation of aromatic compounds from naphtha. Moreover removal of aromatics from lube oil is essential to produce a lube base oil of better smoke point, high cetane number, high viscosity index and low pour point. Typical polar solvents, used for aromatic extraction are sulfolane [1,2], N-methyl-2-pyrrolidone (NMP) [3,4], and N-formylmorpholine (NFM) [5,6]. These solvents need additional distillation steps to separate the solvent from the raffinate phase with consequently more investment and energy consumption. In the past decade, ionic liquids (ILs) have been widely used as alternative solvents for aromatic extraction. Ionic liquids belong to a class of neoteric solvents that are constituted of bulky asymmetric organic cations and anions to create a highly polar medium. Ionic liquid properties, such as low vapour pressure, thermal stability up to about 200 °C and a large liquid existence range are highly desirable for adequate solvent [7]. It is noticeable that most ionic liquids used for extraction of the aromatic compounds are PF6-containing imidazolium-based ionic liquids. The reason is that these ionic liquids are very versatile and easy to prepare [8]. The 1-butyl-3-methylimidazolium hexafluorophosphate [bmim][PF6] is one of the few ILs that has shown both ⇑ Corresponding author. E-mail address: [email protected] (M.S. Fandary). 0021-9614/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jct.2012.05.010

high selectivity and extractive capacity to extract aromatics from alkanes [9]. Phase equilibrium data are essential to understand the solvent extraction process. Currently, there are few data published for {[bmim][PF6] + aromatic + n-alkane (C5–C9)} and hardly any for systems containing carbon number greater than 9 for the aliphatic and/or aromatic compounds [10,11]. This paper is a continuation of our study on liquid–liquid phase equlibria for de-aromatization of Kuwait middle distilled fraction [12–14]. Our interest in IL is to provide experimental new LLE data, and to examine the effect of n-alkane chain length, temperature and solvent to feed ratio upon solubility, the per cent removal of aromatic, the distribution ratio (K), and the selectivity (S) for two systems, viz. system I {dodecane (1) + propylbenzene (2) + [bmim][PF6] (3)} and system II {tetradecane (1) + propylbenzene (2) + [bmim][PF6] (3)}. The reliability of the experimentally measured tie line data was ascertained by the Othmer–Tobias correlation [15]. Finally, the UNIQUAC and the NRTL models were used to correlate the experimental data [16,17]. 2. Experimental 2.1. Chemicals The [bmim][PF6] and propylbenzene were stored under 4 nm molecular sieves. The water content was regularly determined using the Karl Fischer titration method. Water mass fractions were

323

M.S. Fandary et al. / J. Chem. Thermodynamics 54 (2012) 322–329

less than 6  104 and no increase of water content was observed. The purity of the n-alkane s and propylbenzene was determined by gas chromatography. All chemicals were used without further purification. The purities and refractive indices of all chemicals used in this study are presented in table 1.

2.2. Apparatus and procedure The experimental apparatus used for extraction consists of six 60 cm3 water jacketed glass cells in order to maintain a fixed temperature. The temperature was controlled with an uncertainty of ±0.2 K. The cells were connected to a Haake K15 water bath fitted with a Haake DC1 thermostat. Mixtures, comprising of 20 g of [bmim][PF6], 20 g of n-alkanes, and different amounts of propylbenzene were placed in the extraction vessels. The mixtures were vigorously stirred for 1 h, and then left to settle for 4 h. A series of LLE measurements at two temperatures (313 and 333) K were performed.

2.3. Measurements of phase compositions Samples of 0.5 cm3 were carefully taken by a syringe from the lower and upper layers. Each sample was dissolved in 0.5 cm3 1-butanol in order to avoid splitting, and to maintain a homogeneous mixture. The analysis was via a Varian 450 gas chromatograph equipped with an auto sampler (Varian CP-8400), an on-column injector, flame ionization detector (FID), and a data processing system. The column used was Varian VF-5 ms CP8944 (30 m length and 0.25 mm I.D., 0.25 lm film thickness). The ionic solvent, [bmim][PF6], has negligible vapour pressure and so it cannot be analysed using the GC. In the ternary mixture, only two components need to be analysed; the third one, the ionic liquid, was determined by mass balance of the measured mass fractions of dodecane, tetradecane and propylbenzene. In order to avoid inaccuracy of the analysis caused by fouling of the GC column by the ionic liquid, a pre-column was used to protect the column and collect the ionic solvent in order not to disrupt the analysis. The GC column temperature was programmed for an initial temperature of 363 K maintained for 2 min, and a final temperature of 673 K maintained for 5 min. The heating rate was 35 K  min1, and the carrier gas (Helium, grade 5.6) flow rate was maintained at 3  106 m3  min1. The injection temperature was 523 K and the detector temperature was 573 K. The temperature was controlled with a precision of ±0.03 K. Each mole fraction was measured repeatedly for three times to reduce experimental uncertainty associated with random errors and the average value was recorded. The compositions in mole fractions were measured with an experimental uncertainty of ±5  104.

3. Results and discussion 3.1. Experimental data The equilibrium mole fractions of the tie lines were measured at two temperatures, (313 and 333) K, for the ternary systems; I and II and are listed in tables 2 and 3 respectively. The upper layer (alkane rich phase) is free of IL for the two systems. This was demonstrated by visual observation of the immiscibility of the IL in both pure alkanes. Also, this was confirmed 1H NMR analysis of some hydrocarbons-rich phase samples by other studies [20]. However, the lower layer (IL rich phase) has low concentrations of alkane as given by the same tables. These two tables show that the temperature and/or the concentration of propylbenzene in the feed have no effect on the solubility of [bmim][PF6] in the n-alkane rich phase, while these two factors have little effect upon the solubility of n-alkane in the ionic solvent rich phase. The complete absence of [bmim][PF6] in the n-alkane rich phase is desirable, since it allows one to avoid the need of a unit for recovering the solvent from the raffinate phase in a continuous extraction process. Tables 2 and 3 include the corresponding per cent removal of the aromatic which is expressed as 100  (amount of aromatic extracted divided by the initial amount of aromatic in the feed). The per cent removal of the aromatic increases slightly with increasing temperature and/or concentration of aromatic in the feed. Comparing the miscibility of ternary systems containing linear alkane, dodecane is more soluble in IL than tetradecane, i.e., the solubility increases as the chain length of alkane decreases. This behaviour agrees with that published using other ILs [21]. The experimental and predicted tie lines for the two ternary systems at T = (313 and 333) K are shown in figures 1 and 2. It is observed from these figures that increase in temperature leads to a slight decrease in the size of the immiscibility region. This behaviour conforms to the results obtained by others [22,23]. The Othmer–Tobias correlation given in equation 1, ascertained the reliability of the experimentally measured tie line data:

ln



1  wII3 wII3



¼ a þ b ln

  1  wII1 ; II w1

ð1Þ

where w3II is the mass fraction of [bmim][PF6] in the IL-rich phase, w1I is the mass fraction of dodecane or tetradecane in the alkanerich phase and a and b are the fitting parameters of the Othmer– Tobias equation. The linearity of the plot indicates the degree of consistency of the data. The parameters of the Othmer–Tobias equation are given in table 4. The values of regression coefficient (R2) are very close to unity. This together with the low values of the standard deviation (r), presented in the same table, confirm the consistency of the experimental LLE data. 3.2. Distribution ratio and selectivity

TABLE 1 Details of the chemicals; purities, UNIQUAC structural parameters, and refractive indices (nD). Compound

[bmim][PF6] Dodecane Tetradecane Proylbenzene a b c

nD at 25 °C. Reference [18]. Reference [19].

Supplier

Merk Sigma Aldrich Fluka

Purity

UNIQUAC structural parameter

nD20

Mole fraction

r

q

exp

Lit

>0.98 >0.99 >0.99 >0.99

8.4606 8.5462 9.8950 5.4983

6.808 7.0960 8.1759 4.3560

1.3803 1.4220 1.4289 1.4915

1.3800a,b 1.4216c 1.4290 c 1.4920c

324

M.S. Fandary et al. / J. Chem. Thermodynamics 54 (2012) 322–329

TABLE 2 Experimental data for the ternary system-I {dodecane (1) + propylbenzene (2) + [bmim][PF6] (3)} at T = (313 and 333) K and P = 101.3 kPa. Feed (global composition)

Dodecane rich phase

x1

x1

x2

Solventrich phase

x2

0.5264 0.4847 0.4492 0.4186 0.3918 0.3683 0.3474 0.3288 0.3120 0.2969 0.2832

0.0859 0.1581 0.2198 0.2731 0.3195 0.3604 0.3966 0.4290 0.4581 0.4843 0.5081

0.8863 0.7951 0.7220 0.6611 0.6110 0.5671 0.5289 0.4962 0.4663 0.4410 0.4185

0.1137 0.2049 0.2780 0.3389 0.3890 0.4329 0.4711 0.5038 0.5337 0.5590 0.5815

0.5264 0.4847 0.4492 0.4186 0.3918 0.3683 0.3474 0.3288 0.3120 0.2969 0.2832

0.0859 0.1581 0.2198 0.2731 0.3195 0.3604 0.3966 0.4290 0.4581 0.4843 0.5081

0.8872 0.7971 0.7238 0.6648 0.6135 0.5701 0.5316 0.4994 0.4708 0.4453 0.4226

0.1128 0.2029 0.2762 0.3352 0.3865 0.4299 0.4684 0.5006 0.5292 0.5547 0.5774

x1 T = 313 K 0.0150 0.0153 0.0156 0.0159 0.0162 0.0165 0.0168 0.0171 0.0174 0.0177 0.0180 T = 333 K 0.0171 0.0175 0.0181 0.0185 0.0186 0.0188 0.0190 0.0193 0.0196 0.0196 0.0199

% Aromatic

K

S

0.0462 0.0873 0.1273 0.1639 0.2006 0.2321 0.2610 0.2897 0.3137 0.3395 0.3644

22.24 21.98 22.36 22.57 23.13 23.25 23.32 23.60 23.54 23.86 24.22

0.41 0.43 0.46 0.48 0.52 0.54 0.55 0.58 0.59 0.61 0.63

24.01 22.15 21.18 20.11 19.45 18.42 17.44 16.69 15.75 15.13 14.57

0.0478 0.0912 0.1312 0.1722 0.2068 0.2402 0.2687 0.2991 0.3270 0.3528 0.3774

23.09 23.11 23.22 24.03 24.11 24.40 24.34 24.78 25.11 25.39 25.71

0.42 0.45 0.47 0.51 0.53 0.56 0.57 0.60 0.62 0.64 0.65

21.99 20.48 18.99 18.46 17.64 16.94 16.05 15.46 14.84 14.45 13.88

% Aromatic

K

S

0.0587 0.1104 0.1544 0.1946 0.2281 0.2624 0.2947 0.3260 0.3587 0.3891 0.4208

22.24 21.98 22.36 22.57 23.13 23.25 23.32 23.60 23.54 23.86 24.22

0.49 0.52 0.53 0.55 0.56 0.58 0.60 0.62 0.65 0.68 0.71

50.69 45.98 41.15 37.53 33.83 31.48 29.50 27.87 26.77 25.69 24.97

0.0607 0.1123 0.1587 0.2001 0.2373 0.2724 0.3031 0.3338 0.3639 0.3941 0.4234

23.09 23.11 23.22 24.03 24.11 24.40 24.34 24.78 25.11 25.39 25.71

0.52 0.53 0.55 0.57 0.59 0.61 0.62 0.64 0.66 0.69 0.72

46.52 37.75 33.63 30.66 28.78 27.10 25.39 23.96 22.81 22.44 21.66

x2

TABLE 3 Experimental data for the ternary system-II {tetradecane (1) + propylbenzene (2) + [bmim][PF6] (3)} at T = (313 and 333) K and P = 101.3 kPa. Feed (global composition)

Tetradecane rich phase

Solvent rich phase

x1

x2

x1

x2

x1

0.4927 0.4512 0.4162 0.3862 0.3602 0.3375 0.3175 0.2998 0.2839 0.2696 0.2567

0.0919 0.1684 0.2330 0.2883 0.3361 0.3779 0.4148 0.4475 0.4768 0.5031 0.5269

0.8814 0.7875 0.7102 0.6469 0.5924 0.5479 0.5100 0.4777 0.4509 0.4273 0.4077

0.1186 0.2125 0.2898 0.3531 0.4076 0.4521 0.4900 0.5223 0.5491 0.5727 0.5923

0.4927 0.4512 0.4162 0.3862 0.3602 0.3375 0.3175 0.2998 0.2839 0.2696 0.2567

0.0919 0.1684 0.2330 0.2883 0.3361 0.3779 0.4148 0.4475 0.4768 0.5031 0.5269

0.8828 0.7886 0.7126 0.6496 0.5967 0.5523 0.5135 0.4807 0.4528 0.4291 0.4085

0.1172 0.2114 0.2874 0.3504 0.4033 0.4477 0.4865 0.5193 0.5472 0.5709 0.5915

T = 313 K 0.0086 0.0089 0.0092 0.0095 0.0098 0.0101 0.0104 0.0107 0.0110 0.0113 0.0116 T = 333 K 0.0098 0.0111 0.0117 0.0121 0.0122 0.0124 0.0126 0.0129 0.0132 0.0132 0.0135

The ability of using [bmim][PF6] as a solvent to separate (propylbenzene + dodecane or tetradecane) mixtures can be measured using the distribution ratio (K), which is the measure of the solvent power or capacity of IL.

K ¼ xII2 =xI2 :

ð2Þ

The effectiveness of the IL solvent can be expressed by the selectivity (S), which is a measure of the ability of IL to separate propylbenzene from dodecane or tetradecane, and is given by

S ¼ xI1 xII2 =xII1 xI2 ;

ð3Þ

x2

where x1I and x2I are the mole fractions of dodecane or tetradecane and propylbenzene, respectively in the upper phase (alkane-rich phase) and x1II and x2II are the mole fractions of dodecane or tetradecane and propylbenzene, respectively in the lower phase (IL-phase). The K and S values obtained for the two systems are presented in tables 2 and 3. The resulting tie lines and selectivity values indicate that a satisfactory separation of propylbenzene from dodecane or tetradecane can be obtained using the ionic liquid [bmim][PF6]. The results are compared with system III {dodecane (1) + propylbenzene (2) + [mebupy][BF4] (3)} of a pervious study [12]. Figure 3 represents the relationship of the solvent to feed ratio

M.S. Fandary et al. / J. Chem. Thermodynamics 54 (2012) 322–329

325

FIGURE 1a. Experimental and predicted LLE data for the ternary system I {Dodecane (1) + Propylbenzene (2) + [bmim][PF6] (3)} at T = 313 K: d, experimental; solid line, UNIQUAC; dashed line, NRTL.

FIGURE 1b. Experimental and predicted LLE data for the ternary system I {Dodecane (1) + Propylbenzene (2) + [bmim][PF6] (3)} at T = 333 K: d, experimental; solid line, UNIQUAC; dashed line, NRTL.

(astf) with the measured distribution ratio (K) for systems I, II, and III at the two temperatures (313 and 333) K. The distribution ratio slightly increases as the temperature increases or/and the solvent to feed ratio (astf) decreases. Also, the distribution ratio values are higher than those obtained with [mebupy][BF4]. Figure 4 represents the relationship of the solvent to feed ratio (astf) with the measured selectivity values (S) for systems I, II, and III at the same

temperatures. The selectivity increases as the temperature decreases and/or the solvent to feed ratio (astf) increases. The selectivity values are lower than values obtained with [mebupy][BF4]. Temperature and selectivity are inversely related while temperature and distribution coefficient are directly related as shown in the same figures, this result is shown in similar studies [24–26]. Figures 3 and 4 show that the distribution ratio (K) and selectivity

326

M.S. Fandary et al. / J. Chem. Thermodynamics 54 (2012) 322–329

FIGURE 2a. Experimental and predicted LLE data for the ternary system II {Tetradecane (1) + Propylbenzene (2) + [bmim][PF6] (3)} at T = 313 K: d, experimental; solid line, UNIQUAC; dashed line, NRTL.

FIGURE 2b. Experimental and predicted LLE data for the ternary system II {Tetradecane (1) + Propylbenzene (2) + [bmim][PF6] (3)} at T = 333 K: d, experimental; solid line, UNIQUAC; dashed line, NRTL.

(S) for tetradecane are higher than in dodecane for the ternary systems under study. 3.3. Correlation of LLE data The required volume and surface area parameters, ri and qi of the UNIQUAC model are presented in table 1. Minimizing the differences between the experimental and calculated mole fractions

for each component determined the constituent binary parameters of both models over all the measured LLE data of the ternary systems. The objective function (OF) used was

OF ¼ min

2 XXX exp xijk  xcal ijk k

j

ð4Þ

i

where xexp and xcal are the experimental and calculated mole fractions, respectively. The subscripts i, j and k denote component,

327

M.S. Fandary et al. / J. Chem. Thermodynamics 54 (2012) 322–329 TABLE 4 Constants of the Othmer–Tobias correlation, correlation factor (R2) and standard deviation (r) at T = (313 and 333) K and P = 101.3 kPa. T/K 313 333 313 333

Ternary systems System-I System-I System-II System-II

a 0.9019 0.8653 0.5538 0.4601

b 0.8529 0.846 0.9221 0.9268

R2 0.9982 0.9978 0.9973 0.9967

r 0.0286 0.0318 0.0374 0.0415

phase, and tie line, respectively. The quality of the parameters can be evaluated according to the mean deviation in the compositions of coexisting phases. The interaction binary parameters optimized of UNIQUAC and NRTL models for the two ternary systems with

rmsd values are listed in tables 5 and 6. The rmsd values between experimental and calculated data, defined as:

( XXX

rmsd ¼ 100

k

j

cal xexp ijk  xijk

2

)1=2 =6n

ð5Þ

i

where n is the number of tie lines, the digit number 6 means the three component pairs in the two phases. Although NRTL has three parameters, we have chosen not to fit all three but to default the third parameter, alpha, to 0.2 or 0.3. It is suggested that values for alpha should never be negative and should rarely be larger than 0.6. Determining a suitable value for alpha is known in the literature [27]. Alpha was fixed at 0.2 or 0.3 because it is the customary value for systems that exhibit liquid–liquid separation [28]. The

FIGURE 3. Measured distribution coefficient (K) against solvent to feed ratio astf) for system I at: d, T = 313 K and s, 333 K; system II at: ., 313 K and D, 333 K; and system III at: j, 313 K and h, 333 K.

FIGURE 4. Measured selectivity (S) against solvent to feed ratio (astf) for system I at: d, 313 K and s, 333 K; system II at: ., 313 K and D, 333 K; and system III at: j, 313 K and h, 333 K.

328

M.S. Fandary et al. / J. Chem. Thermodynamics 54 (2012) 322–329

data of the two systems on the basis of analysis of the rmsd for the two systems (the average rmsd was 0.1791 for UNIQUAC and 0.2583 at a = 0.2 and 0.2222 at a = 0.3 for NRTL). Figures 5 and 6 show good agreement between the experimental and correlated distribution coefficient and selectivity, with coefficient of determination (R2) equal to 0.997 and 0.880 for (K) and (S), respectively.

TABLE 5 UNIQUAC interaction parameters and root mean square deviation (rmsd) at T = (313 and 333) K and P = 101.3 kPa. T/K

i

j

313

Dodecane Dodecane Propylbenzene Dodecane Dodecane Propylbenzene Tetradecane Tetraecane Propylbenzene Tetradecane Tetraecane Propylbenzene

Propylbenzene [bmim][PF6] [bmim][PF6] Propylbenzene [bmim][PF6] [bmim][PF6] Propylbenzene [bmim][PF6] [bmim][PF6] Propylbenzene [bmim][PF6] [bmim][PF6]

333

313

333

UNIQUAC aij

aji

88.76 685.44 187.23 204.31 716.70 234.18 161.50 685.47 211.16 162.47 700.93 242.55

44.11 96.33 110.78 166.13 105.61 162.41 119.61 97.66 153.22 128.84 108.98 167.19

rmsd

0.0979

4. Conclusions 0.0910

An investigation of equilibrium behaviour of two ternary systems, viz. {dodecane or tetradecane + propylbenzene + [bmim][PF6]} was carried out at two temperatures, (313 and 333) K, and atmospheric pressure. While the temperature and the concentration of propylbenzene in the feed have no effect on the solubility of [bmim][PF6] in the n-alkane rich phase, they have little effect upon the solubility of n-alkane in the ionic solvent rich phase. The distribution ratio (K) increases as concentration of propylbenzene in the feed and/or temperature increases and the solvent to feed ratio (astf) and/or chain length of n-alkane decreases. The selectivity (S) increased as concentration of propylbenzene in the feed and/or temperature decreased, and the solvent to feed ratio (astf) and/or chain length of n-alkane increased.

0.3156

0.2134

interaction parameters for the UNIQUAC and NRTL models as a function of temperature were used to calculate LLE tie lines for the present systems. The calculations based on both models adequately represented the tie line data for these systems. Both UNIQUAC and NRTL models accurately correlate the LLE experimental

TABLE 6 NRTL interaction parameters and root mean square deviation (rmsd) at T = (313 and 333) K and P = 101.3 kPa. T/K

i

j

313

Dodecane Dodecane Propylbenzene Dodecane Dodecane Propylbenzene Tetradecane Tetraecane Propylbenzene Tetradecane Tetraecane Propylbenzene

Propylbenzene [bmim][PF6] [bmim][PF6] Propylbenzene [bmim][PF6] [bmim][PF6] Propylbenzene [bmim][PF6] [bmim][PF6] Propylbenzene [bmim][PF6] [bmim][PF6]

333

313

333

NRTL (a = 0.2)

NRTL (a = 0.3)

aij

aji

729.86 1812 1504.3 814.12 1937.6 1570.4 1006.9 1803.5 1407.2 980.43 1906.5 1518

273.41 783.46 714.87 297.36 788.4 807.55 643.35 921.27 852.67 608.32 931.14 876.85

rmsd

0.1706

0.1883

0.3837

0.2907

aij

aji

1041.30 1640.90 1443.50 1175 1743.8 1500.5 119.29 1738.1 1130.1 111.36 1839 1186.1

539.79 1118.50 761.86 548.68 1151.8 907.22 1791.5 1056.5 299.6 1771.2 1075.5 309.33

FIGURE 5. Experimental and calculated distribution coefficient (K) for system I at: d, T = 313 K and s, 333 K; and system II at: ., 313 K and D, 333 K.

rmsd

0.1570

0.1747

0.2733

0.2840

M.S. Fandary et al. / J. Chem. Thermodynamics 54 (2012) 322–329

329

FIGURE 6. Experimental and calculated selectivity (S) for system I at: d, T = 313 K and s, 333 K; and system II at: ., 313 K and D, 333 K.

The Othmer–Tobias equation affirmed the consistency of the experimental LLE data. Both UNIQUAC and the NRTL models satisfactorily correlate the LLE experimental data, however the former model was more suitable for the two systems I and II. Since the selectivity in all cases is greater than unity, it can be concluded that the ionic liquid [bmim][PF6] can be used efficiently to separate propylbenzene from dodecane or tetradecane mixtures. Acknowledgements The authors thank the Public Authority for Applied Education and Training (PAAET-TS-06-03) for the financial support of this work. References [1] M.S. Hassan, M.A. Fahim, C.V. Mumford, J. Chem. Eng. 33 (1988) 162–168. [2] M.S. Hassan, M.A. Fahim, C.V. Mumford, J. Solvent Extraction Ion Exchange 7 (4) (1989) 677–687. [3] M.S. Fandary, A.S. Aljimaz, J.A. Al-Kandary, M.A. Fahim, J. Chem. Thermoyn. 38 (2006) 455–460. [4] V.R. Nigmatullin, R.R. Mukhametova, I.R. Nigmatullin, Chem. Technol. Fuels. Oils 44 (2008) 10–12. [5] T.A. Al-Sahhaf, E. Kapetanovic, Fluid Phase Equilib. 118 (2) (1996) 271–285. [6] W. Wang, Z.M. Gou, S.I. Zhu, J. Chem. Eng. Data 43 (1) (1998) 81–83. [7] M. Freemanle, Chem. Eng. News 76 (1998) 32–37. [8] R.P. Swatloski, J.D. Holbrey, R.D. Rogers, Green Chem. 5 (4) (2003) 361–363. [9] G.W. Meindersama, A.J.G. Podt, A.B. de Hann, Fuel Process. Technol. 87 (2005) 59–70. [10] G.W. Meindersama, A.J.G. Podt, A.B. de Hann, Fluid Phase Equilib. 247 (2006) 158–168.

[11] U. Doman´ska, A. Pobudkowska, M. Królikowski, Fluid Phase Equilib. 259 (2007) 173–179. [12] M.S. Al-Twaim, K.H.A.E. Alkhaldi, M.S. Fandary, A.S. Al-Jimaz, J. Chem. Thermodyn. 43 (2011) 1804–1809. [13] K.H.A.E. Alkhaldi, M.S. Al-Twaim, M.S. Fandary, A.S. Al-Jimaz, Fluid Phase Equilib. 309 (2011) 102–107. [14] M.S. Al-Twaim, K.H.A.E. Alkhaldi, M.S. Fandary, A.S. Al-Jimaz, Fluid Phase Equilib. 315 (2012) 21–28. [15] D.F. Othmer, P.E. Tobias, Ind. Eng. Chem. 34 (1942) 693–696. [16] D.S. Abrams, J.M. Prausnitz, AIChE J. 14 (1968) 135–144. [17] D.S. Abrams, J.M. Prausnetz, AIChE J. 21 (1975) 116–128. [18] J. Ortega, R. Vreekamp, E. Penco, E. Marrero, J. Chem. Thermodyn. 40 (2008) 1087–1094. [19] David R. Lide (Ed.), CRC Handbook of Chemistry and Physics, 86th ed., CRC Press, (2005–2006). [20] J. García, A. Fernández, J.S. Torrecilla, M. Oliet, F. Rodríguez, Fluid Phase Equilib. 282 (2009) 117–120. [21] N. Calvar, I. Dominguez, E. Gómez, Á. Domínguez, Chem. Eng. J. 175 (2011) 213–221. [22] E.J. González, N. Calver, B. González, A. Domínguez, J. Chem. Thermodyn. 41 (11) (2009) 1215–1221. [23] E.J. González, N. Calver, E. Gómez, A. Domínguez, J. Chem. Thermodyn. 42 (2010) 104–109. [24] S.I. Abu- Eishah, A.M. Dowaider, J. Chem. Eng. Data 53 (2008) 1708–1712. [25] E.J. González, I. Domínguez, B. González, J. Canosa, Fluid Phase Equilib. 269 (2010) 213–218. [26] E.J. González, N. Calver, E. Gómez, A. Domínguez, J. Chem. Eng. Data 55 (2010) 633–638. [27] J.M. Prausnitz, R.N. Lichtenthaler, E.G. de Azevedo, Molecular Thermodynamics of Fluid-Phase Equilibria, third ed., Prentice Hall, Upper Saddle River, NJ, 1999. 261. [28] J.M. Sørensen, W. Arlt, Liquid–Liquid Equilibrium Data Collection, DECHEMA, Frankfurt/Main, Germany, (1979–1980).

JCT 12-225