Phase equilibria of binary systems of 3-methylthiophene with four different hydrocarbons

Fluid Phase Equilibria 288 (2010) 155–160

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Phase equilibria of binary systems of 3-methylthiophene with four different hydrocarbons Erlin Sapei a,∗ , Petri Uusi-Kyyny a , Kari I. Keskinen a,b , Ville Alopaeus a a b

Department of Biotechnology and Chemical Technology, Helsinki University of Technology, P.O. Box 6100, FI-02015 Espoo, HUT, Finland Neste Jacobs Oy, P.O. Box 310, FI-06101 Porvoo, Finland

a r t i c l e

i n f o

Article history: Received 25 March 2009 Received in revised form 30 October 2009 Accepted 4 November 2009 Available online 10 November 2009 Keywords: Vapor–liquid equilibrium 3-Methylthiophene 2-Methylpentane n-Hexane Methylcyclopentane Methylcyclohexane UNIFAC

a b s t r a c t Isothermal vapor–liquid equilibrium (VLE) for systems 3-methylthiophene + 2-methylpentane at 333.15 K, 3-methylthiophene + n-hexane at 333.15 K, 3-methylthiophene + methylcyclopentane at 343.15 K, and 3-methylthiophene + methylcyclohexane at 373.15 K were measured with a recirculation still. All systems exhibit positive deviation from Raoult’s law. No azeotropic behavior was found in any of the systems at the measured temperatures. The experimental results were correlated with the Wilson model and also compared with the original UNIFAC and UNIFAC-Dortmund predictive models. Liquid and vapor-phase composition were determined with gas chromatography. All VLE measurements passed the used thermodynamic consistency tests (integral, infinite dilution and point test). The activity coefficients at infinite dilution are also presented. © 2009 Elsevier B.V. All rights reserved.

1. Introduction To meet the standards of new environmental legislation and to avoid SOx pollution during fuel combustion, ultra-low-sulfur fuel is required by 2010 in many countries [1]. New developments on sulfur separation process designs to further decrease the sulfur level have become one of the major challenges to the refining industry [2]. Design of separation processes to accomplish the removal of sulfur compounds requires the knowledge of the behaviour of sulfur compounds in hydrocarbons. Information of such systems is scarce and experimental work is required. The major components of gasoline or its blending components originate from Fluid Catalytic Cracking (FCC) unit and contain cycloalkanes in addition to alkanes. Also organic sulfur compounds are present in these refinery streams. 3-Methylthiophene is one of the organic sulfur compounds present in the products [3]. In this work, we measured vapor–liquid equilibrium (VLE) for systems 3-methylthiophene + 2-methylpentane at 333.15 K, 3-methylthiophene + n-hexane at 333.15 K, 3-methylthiophene + methylcyclopentane at 343.15 K, and 3-methylthiophene + methylcyclohexane at 373.15 K with a recirculation still. No other VLE data for binaries studied in this work have been found in the literature search. In the previous work, Sapei et al. [4] measured

∗ Corresponding author. Tel.: +358 9 4512638; fax: +358 9 451 2694. E-mail address: [email protected].fi (E. Sapei). 0378-3812/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.fluid.2009.11.004

VLE data for systems 3-methylthiophene + 2,2,4-trimethylpentane at 368.15 K, 3-methylthiophene + 2,4,4-trimethyl-1-pentene at 368.15 K, 3-methylthiophene + cyclohexane at 348.15 K, and 3-methylthiophene + 1-hexene at 333.15 K. 2. Experimental 2.1. Materials 3-Methylthiophene, 2-methylpentane, methylcyclopentane, and methylcyclohexane were provided by Sigma–Aldrich, Finland. o-Xylene, which was used as a diluent in gas chromatographic analysis, was purchased from Fluka, Finland. The purity of all substances was checked by gas chromatography (GC) equipped with a flame ionization detector (FID). All chemicals were dried over molecular sieves (Merck 3 Å) for 24 h. The refractive indexes, nD , of the pure liquids were measured at 298.15 K with ABBEMAT-HP automatic refractometer (Dr. Kernchen, Germany) with accuracy ±0.00002. The purity and measured refractive indexes of the chemical used are presented in Table 1. The measured refractive indexes corresponded well with literature values [5]. 2.2. Apparatus The VLE runs were conducted with a circulation still of the Yerazunis-type [6] built at the glass workshop of Helsinki University of Technology with minor modifications to the original design

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Table 1 Purity and refractive indexes (nD ) of pure components. Component

GC purity (mass %)

3-Methylthiophene 2-Methylpentane n-Hexane Methylcyclopentane Methylcyclohexane o-Xylene (used as diluent)

99.78 99.98 99.99 99.75 99.97 99.99

nD (298.15 K) Experimental

Literature [5]

1.5172 1.3685 1.3724 1.4067 1.4025 1.5028

1.5176 1.3687 1.3723 1.4070 1.4026 1.5029

perature. The temperature was held constant for approximately 30–45 min before sampling. After equilibration, the temperature in the equilibrium cell was measured and then vapor and liquid samples were withdrawn with a 1 ml Hamilton Sample Lock syringe and after that injected into the cooled 2 ml auto sampler vial containing approximately 1 ml o-xylene (as diluent). The compositions of both samples were immediately measured by gas chromatography (GC). To prevent spreading of the unpleasant odor of the sulfur compounds, the GC was placed in a closed and ventilated cupboard. 2.4. Analysis and GC calibration

[7]. Experimental setup is described in detail in the previous works [7,8]. Approximately 80 ml of reagents were needed to run each measurement. Temperatures were measured with a Pt-100 resistance temperature probe, which was located at the bottom of the packed section of the equilibrium chamber and connected to Thermometer (F200, Tempcontrol) which has a manufacturer’s stated accuracy of ±0.02 K and the calibration uncertainty was ±0.01 K. The uncertainty of the whole temperature measurement system is estimated to be ±0.05 K. Pressure was measured with a Druck pressure transducer PMP 4070 (0–100 kPa) connected to a Red Lion panel meter. The inaccuracy of the instruments was reported to be ±0.07 kPa by the manufacturer. The pressure measurement system was calibrated against BEAMEX PC 105-1166 pressure calibrator. The uncertainty of the whole pressure measurement system including the calibration uncertainty is expected to be less than ±0.17 kPa. In order to improve mixing in the sampling chambers and mixing chamber of the condensed vapor phase and the liquid phase, DC electric motors (Graupner speed 400) were equipped with magnetic stirrer bars, which deliver stirring action in the chambers.

The liquid and vapor samples were analyzed with a Agilent 6850A gas chromatograph equipped with an auto sampler and a FID. The GC-column used was a HP-1 Dimethylpolysiloxane (60.0 m × 250 ␮m × 1.0 ␮m). The injector and FID were set at 250 ◦ C. Helium was used as the carrier gas at a constant flow rate of 1 ml min−1 and inlet split ratio 100:1. The initial oven temperature was held at 70 ◦ C for 2 min and then increased subsequently to 150 ◦ C at rate of 8 ◦ C min−1 and was held at 150 ◦ C for 3 min. The total run time was 15 min. The pure components were used to determine the retention times, after that the GC was calibrated with 15 mixtures of known composition that were prepared gravimetrically. To reduce the volume of the sample, o-xylene was used as solvent. The response factor of component 2 (F2 ) was calculated from Eq. (1): m2 A1 = F2 m1 A2

Therefore, the vapor or liquid composition of component 1 can be calculated from: x1 =

2.3. Experimental procedures Pure component 1 was introduced in the recirculation still and its vapor pressure was measured at several temperatures. Then component 2 was introduced into the recirculation still. It took approximately from 30 min to 45 min to achieve constant tem-

(1)

A1 /M1





(2)

A1 /M1 + F2 (A2 /M2 )

where A1 and A2 are the GC peak areas, M1 and M2 are the molar masses, and m1 and m2 were masses in the gravimetrically prepared sample of components 1 and 2, respectively. The maximum error of liquid and vapor composition measurements is estimated to be 0.003 mole fraction.

Table 2 Critical temperature (Tc ), critical pressure (Pc ), acentric factor (ω), liquid molar volume (Vi ) at 298.15 K, pure component vapor pressure equation parameters (A, B, and C) for the Antoine equation, recommended temperature range of the vapor pressure correlation (Tmin and Tmax ). Component

3-Methylthiophene

a

Tc (K) Pc a (MPa) ωa Vi a (cm3 mol−1 )

2-Methylpentane

n-Hexane

Methyl cyclopentane

Methyl cyclohexane

615.00 4.950 0.242 96.585

497.5 3.010 0.278 132.931

507.43 3.012 0.305 131.306

532.79 3.785 0.230 113.042

572.19 3.471 0.235 128.192

6.7218c 2886.0131c −68.3674c

7.532e 2998.063e −28.016e

6.980d 2724.960d −47.736d

6.881e 2731.000e −47.099e

6.909e 2998.940e −47.914e

333.15 387.89

290.34 333.37

307.31 342.00

300.40 345.10

325.39 373.90

|Paver |f (kPa)

0.19

0.03

0.01

0.09

0.09

|Paver |g (kPa)

0.16

0.22

0.41

0.11

0.12

Ab Bb Cb Tmin (K) Tmax (K)

a b c d e f

g

Ref. [5]. PS (MPa) = exp(A − [B/(T/K + C)]). Ref. [4]. Ref. [9]. This work.  

 NVLE P   −Pi,calculated  Paver  = i=1 i,measured .  NVLE  NVLE   Pi,measured −Pi,literature  Paver  = i=1 N VLE

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Table 4 Isothermal VLE measurements, liquid-phase (x1 ) and vapor-phase (y1 ) mole fractions, pressure (P), and activity coefficient ( i ), for the 3-methylthiophene (1) + 2-methylpentane (2) system at 333.15 K.

Fig. 1. Measured vapor pressures of pure substances in this work: , 2methylpentane; , methylcyclopentane; , methylcyclohexane. Measured vapor pressure from literature: , 2-methylpentane [10]; ♦, methylcyclopentane [10]; , methylcyclohexane; —, calculated from literature correlation [5].

3. Results and discussion 3.1. Vapor pressure measurements Vapor pressure of 3-methylthiophene and n-hexane were measured in the previous works [4,9]. The Antoine constants for 2-methylpentane, methylcyclopentane, and methylcyclohexane were regressed from the vapor pressures measured in this work. These parameters with the recommended temperature range of the vapor pressure equations are presented in Table 2. The absolute average deviation of pressure between measured and values calculated with regressed parameters of the Antoine equation (Paver ) for 3-methylthiophene, 2-methylpentane, nhexane, methylcyclopentane, and methylcyclohexane are 0.19 kPa, 0.03 kPa, 0.01 kPa, 0.09 kPa, and 0.09 kPa, respectively. The vapor pressures of 2-methylpentane, methylcyclopentane, and methylcyclohexane measured in this work are shown in Fig. 1 and presented in Table 3. The measured vapor pressure was compared with literature correlation [5]. The absolute average deviation of pressure between experimental and literature correlation [5] for 2-methylpentane, methylcyclopentane, and methylcyclohexane was: 0.22 kPa, 0.11 kPa, and 0.12 kPa, respectively. Measured vapor pressures of 2-methylpentane, methylcyclopentane, and methylcyclohexane are in line with ones measured by Willingham et al. [10]. 3.2. Vapor–liquid equilibrium measurements The isothermal VLE measurements (P, x1 , and y1 ) and calculated activity coefficients are reported in Tables 4–7 and P–x1 –y1 diagrams are presented in Figs. 2–5. The activity coefficient–composition diagrams are shown in Figs. 6–9. All sysTable 3 Experimental vapor pressure of 2-methylpentane, methylcyclopentane, and methylcyclohexane. 2-Methylpentane

Methylcyclopentane

Methylcyclohexane

T (K)

P (kPa)

T (K)

P (kPa)

T (K)

P (kPa)

333.37 329.74 326.15 322.26 317.93 312.92 307.12 299.70 290.34

101.76 90.32 80.11 70.13 60.24 50.23 40.39 30.13 20.30

345.10 341.25 337.50 333.37 328.97 323.75 317.69 310.16 300.40

102.31 90.53 80.18 69.94 60.22 50.16 40.24 30.18 20.25

373.90 369.98 365.75 361.45 356.44 350.71 344.10 336.27 325.39

101.60 90.64 79.96 70.17 60.05 49.96 40.07 30.47 20.25

x1

y1

P (kPa)

1

0.000 0.106 0.214 0.349 0.490 0.617 0.710 0.816 0.950 0.987 1.000

0.000 0.032 0.062 0.100 0.140 0.180 0.225 0.310 0.607 0.858 1.000

100.92 93.45 86.32 77.64 68.40 59.86 52.39 41.75 24.08 17.65 15.32

1.76 1.58 1.41 1.25 1.12 1.06 1.02 1.00 1.00 1.00

2 1.00 1.01 1.03 1.08 1.16 1.29 1.42 1.59 1.93 2.05

Table 5 Isothermal VLE measurements, liquid-phase (x1 ) and vapor-phase (y1 ) mole fractions, pressure (P), and activity coefficient ( i ), for the 3-methylthiophene (1) + n-hexane (2) system at 333.15 K. x1

y1

P (kPa)

1

0.000 0.130 0.222 0.325 0.430 0.524 0.630 0.730 0.805 0.915 0.984 1.000

0.000 0.048 0.080 0.115 0.151 0.185 0.234 0.292 0.362 0.564 0.876 1.000

76.69 70.41 66.09 61.44 56.66 52.30 46.77 40.98 35.60 25.34 17.71 15.62

1.61 1.48 1.35 1.25 1.15 1.09 1.03 1.01 1.00 1.00 1.00

2 1.00 1.01 1.02 1.06 1.11 1.18 1.28 1.42 1.54 1.74 1.89

Table 6 Isothermal VLE measurements, liquid-phase (x1 ) and vapor-phase (y1 ) mole fractions, pressure (P), and activity coefficient ( i ), for the 3-methylthiophene (1) + methylcyclopentane (2) system at 343.15 K. x1

y1

P (kPa)

1

0.000 0.056 0.140 0.249 0.380 0.525 0.637 0.791 0.877 0.939 0.979 1.000

0.000 0.023 0.054 0.095 0.146 0.209 0.273 0.411 0.549 0.706 0.873 1.000

95.93 92.73 87.70 81.29 73.75 65.14 57.65 45.39 37.25 30.41 25.59 22.79

1.61 1.44 1.33 1.22 1.12 1.07 1.03 1.02 1.00 1.00 1.00

2 1.00 1.00 1.01 1.03 1.07 1.14 1.22 1.36 1.45 1.57 1.62

Table 7 Isothermal VLE measurements, liquid-phase (x1 ) and vapor-phase (y1 ) mole fractions, pressure (P), and activity coefficient ( i ), for the 3-methylthiophene (1) + methylcyclohexane (2) system at 373.15 K. x1

y1

P (kPa)

1

0.000 0.093 0.211 0.337 0.467 0.589 0.705 0.787 0.867 0.931 0.974 1.000

0.000 0.083 0.180 0.277 0.375 0.473 0.575 0.661 0.762 0.860 0.943 1.000

99.11 98.25 96.62 94.15 90.84 86.95 82.37 78.54 74.01 69.62 66.22 64.11

1.36 1.27 1.19 1.13 1.08 1.04 1.03 1.01 1.00 1.00 1.00

2 1.00 1.00 1.01 1.04 1.08 1.13 1.21 1.27 1.35 1.43 1.51

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Fig. 2. Pressure–composition diagram for the 3-methylthiophene (1) + 2methylpentane (2) system at 333.15 K: , x1 measured; , y1 measured; , , UNIFAC [15]; , UNIFAC-Dortmund [17]. Wilson;

Fig. 5. Pressure–composition diagram for the 3-methylthiophene (1) + methylcyclohexane (2) system at 373.15 K: , x1 measured; , y1 measured; , Wilson; , UNIFAC [15]; , UNIFAC-Dortmund [17].

Fig. 6. Activity coefficient-composition diagram for the 3-methylthiophene (1) + 2methylpentane (2) system at 333.15 K: ,  1 from the data; ,  2 from the data; ,  1 ,  2 from the Wilson model; ,  1 ,  2 from UNIFAC [15]; , 1, 2 from UNIFAC-Dortmund [17]. Fig. 3. Pressure–composition diagram for the 3-methylthiophene (1) + n-hexane (2) , Wilson; , UNIFAC [15]; system at 333.15 K: , x1 measured; , y1 measured; , UNIFAC-Dortmund [17].

tems show positive deviation from Raoult’s law. No azeotropes were found in any of the systems studied. The activity coefficients  i were calculated from: i =

yi Pi exp xi Pis is

 P

PS i

ViL

RT

dP

(3)

where yi is the mole fraction of component i in the vapor phase, P is the total pressure of the system, i is the fugacity coefficient of

Fig. 4. Pressure–composition diagram for the 3-methylthiophene (1) + methylcyclopentane (2) system at 343.15 K: , x1 measured; , y1 measured; , Wilson; , UNIFAC [15]; , UNIFAC-Dortmund [17].

component i in the vapor phase, xi is mole fraction of the component i in the liquid phase, Pi S is the vapor pressure of pure component i at the system temperature, i S is the pure component-saturated liquid fugacity coefficient at the system temperature T, Vi L is the molar volume of pure component i in liquid phase at the system temperature, T is temperature in Kelvin, and R is the universal gas constant (8.31441 J K−1 mol−1 ). The VLEFIT program [11] was used for processing the measurements. The Soave–Redlich–Kwong equation of state with quadratic mixing rules in the attractive parameter and linear in co-volume was used for vapor-phase fugacity coefficient calculation [12]. The binary interaction parameter in the quadratic mixing rules was set to zero. The Rackett equation [13] was used to calculate the liquid

Fig. 7. Activity coefficient-composition diagram for the 3-methylthiophene (1) + n, hexane (2) system at 333.15 K: ,  1 from the data; ,  2 from the data; ,  1 ,  2 from UNIFAC [15]; ,  1 ,  2 from  1 ,  2 from the Wilson model; UNIFAC-Dortmund [17].

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159

Table 8 Correlation of Wilson parameters, absolute average deviation of activity coefficient ( aver ) for the measured system: 3-methylthiophene (1) + 2-methylpentane (2) at 333.15 K (System 1), 3-methylthiophene (1) + n-hexane (2) at 333.15 K (System 2), 3-methylthiophene (1) + methylcyclopentane (2) at 343.15 K (System 3), 3-methylthiophene (1) + methylcyclohexane (2) at 373.15 K (System 4). System

12 (J mol−1 )

21 (J mol−1 )

| 1,aver |a

| 2,aver |b

1 2 3 4

1716.904 1597.033 1194.658 863.327

444.173 358.602 326.473 495.553

0.02 0.01 0.01 0.00

0.01 0.01 0.01 0.00

a

Fig. 8. Activity coefficient-composition diagram for the 3-methylthiophene (1) + methylcyclopentane (2) system at 343.15 K: ,  1 from the data; ,  2 from ,  1 ,  2 from the Wilson model; ,  1 ,  2 from UNIFAC [15]; , the data;  1 ,  2 from UNIFAC-Dortmund [17].

b

   NVLE  −1,calculated 1,aver  = i=1 1,measured . NVLE   NVLE 2,measured −2,calculated  2,aver  = i=1 . N VLE

Table 9 Activity coefficients at infinite dilution, i∞ , calculated from Wilson model, original UNIFAC, and UNIFAC-Dortmund for the measured system: 3-methylthiophene (1) + 2-methylpentane (2) at 333.15 K (System 1), 3-methylthiophene (1) + n-hexane (2) at 333.15 K (System 2), 3-methylthiophene (1) + methylcyclopentane (2) at 343.15 K (System 3), 3-methylthiophene (1) + methylcyclohexane (2) at 373.15 K (System 4). System

1 2 3 4

Fig. 9. Activity coefficient-composition diagram for the 3-methylthiophene (1) + methylcyclohexane (2) system at 373.15 K: ,  1 from the data; ,  2 from ,  1 ,  2 from the Wilson model; ,  1 ,  2 from UNIFAC [15]; , the data;  1 ,  2 from UNIFAC-Dortmund [17].

molar volume in the Poynting factor. The Antoine parameters for vapor pressure, critical temperature, critical pressure, acentric factor and the liquid molar volume for each component used in the calculations are presented in Table 2. The liquid phase activity coefficients of all systems studied were correlated with the Wilson [14] model. The objective function [11] (O.F.) used for fitting of the activity coefficient parameters is given by Eq. (4), where NVLE is the number of points used in the fit. O.F. =

1 NVLE

   k NVLE 2  k     i,calc − i,exp

(4)

k i,exp

k=1 i=1

Wilson interaction parameters with small lambda (12 ) and (21 ) and the absolute average deviation of activity coefficients (| aver |) for the measured systems are presented in Table 8. The absolute

Wilson

UNIFAC [15]

UNIFAC-Do [17]

1∞

2∞

1∞

2∞

1∞

2∞

1.98 1.86 1.65 1.42

2.09 1.96 1.65 1.55

1.54 1.54 1.41 1.34

1.74 1.75 1.45 1.45

1.96 1.96 1.32 1.29

1.99 1.99 1.22 1.21

average deviations of the activity coefficients for all systems are very small. Good agreement between measurements and model were achieved for all systems. During the measurement 3-methylthiophene + 2-methylpentane system in the range of 0.85–0.95 mole fraction of 3methylthiophene, the equilibrium was not reached because of the large temperature fluctuation due to the large boiling point difference of the pure components. Thus measurements within this range were not possible with the equipment used. 3-Methylthiophene + 2-methylpentane at 333.15 K, 3-methylthiophene + n-hexane at 333.15 K, 3-methylthiophene + methylcyclopentane at 343.15 K, and 3-methylthiophene + methylcyclohexane at 373.15 K were predicted with the original UNIFAC [15] model with the parameters on the level of Wittig et al. [16] and UNIFAC-Dortmund [17]. The UNIFAC-Dortmund predictions were calculated using Aspen Plus version 2006.5. The results are presented in Figs. 6–9. No azeotropic behavior was found with either predictive model. The absolute pressure residual (|Paver |) and the absolute vapor fraction residual (|yaver |) calculated with original UNIFAC are presented in Table 10. The activity coefficients at infinite dilution, i∞ , calculated from Wilson model, original UNIFAC, and UNIFAC-Dortmund are given

Table 10 Results of integral test, infinite dilution test, averages of absolute vapor fraction residuals (yaver ) and averages of absolute pressure residuals (Paver ) for the Wilson model, UNIFAC, and UNIFAC-Dortmund for the measured system: 3-methylthiophene (1) + 2-methylpentane (2) at 333.15 K (System 1), 3-methylthiophene (1) + n-hexane (2) at 333.15 K (System 2), 3-methylthiophene (1) + methylcyclopentane (2) at 343.15 K (System 3), 3-methylthiophene (1) + methylcyclohexane (2) at 373.15 K (System 4). System

Integral test

Infinite dilution test (%)

1 2 3 4

Point test (Wilson)

Residuals (UNIFAC)

D (%)

I1 x1 = 0

I2 x1 = 1

|yaver |

|Paver | (kPa)

|yaver |

|Paver | (kPa)

5.8 1.2 2.9 2.0

−1.6 −9.0 2.2 −2.2

−12.9 −8.2 2.2 −2.4

0.001 0.002 0.001 0.001

0.14 0.22 0.10 0.04

0.013 0.009 0.009 0.004

2.11 1.49 1.19 0.81

b

a

The criterion for passing the test: a D < 10% [18].  

 

b

I1 = 100 I1∗  < 30 and I2 = 100 I2∗  < 30 [19].

c

|yaver | < 0.01 [18].

b

c

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in Table 9. The following thermodynamic consistency tests were applied to the measured VLE data: integral test [18], point test [18], and infinite dilution test [19]. The results are summarized in Table 10 including the residuals for original UNIFAC. The measurements passed all consistency tests applied. 4. Conclusions Vapor pressure of 2-methylpentane, methylcyclopentane, and methylcyclohexane were measured and compared with the literature data. Isothermal VLE data for systems 3-methylthiophene + 2methylpentane at 333.15 K, 3-methylthiophene + n-hexane at 333.15 K, 3-methylthiophene + methylcyclopentane at 343.15 K, and 3-methylthiophene + methylcyclohexane at 373.15 K were measured with a recirculation still. All the systems show positive deviation from Raoult’s law. Azeotropic behaviour was not found in the systems studied at the measured temperatures. All systems measured passed the thermodynamic consistency tests. The Wilson model gave good correlation for all systems. Original UNIFAC and UNIFAC-Dortmund models were used to predict the behavior of all systems studied. Azeotropic behavior in all systems studied was not observed with either model. The behaviour of the activity coefficients predicted with the original UNIFAC and UNIFAC-Dortmund are not yet inline with the activity coefficients calculated from the experimental data in this work for the systems containing cycloalkanes. Acknowledgements The authors acknowledge Neste Jacobs Oy and Neste Oil Oyj for the financial support. References [1] C.H. Twu, V. Tassone, W.D. Sim, Accurately predict the VLE of thiol-hydrocarbon mixture, Chem. Eng. Prog. 100 (2004) 39–45.

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