J. Chem. Thermodynamics 1998, 30, 799]804Article No. ct980346

Liquid extraction equilibria of type 2:( )tert-amyl methyl ether H1-octonal H water

( )at T s 298.15 and 308.15 K

Alberto Arcea and Manuel BlancoDepartment of Chemical Engineering, Uni ersity of Santiago de Compostela,E-15706 Santiago, Spain

Ž . ŽExperimental liquid q liquid equilibrium data for tert-amyl methyl ether q 1-octanol q. Ž .water at T s 298.15 and 308.15 K were satisfactorily fitted with UNIQUAC, TK-Wilson,

and NRTL equations, and predicted by the UNIFAC group contribution method. Q 1998Academic Press

KEYWORDS: LLE; TAME; 1-octanol; correlation; prediction; ternary mixture

1. Introduction

ŽSeveral ethers are considered to be anti-knocking agents, including MTBE 2-.methoxy-2-methylpropane, or methyl tert-butyl ether which has a higher octane

boosting value in gasoline than an oxygenate. Hence, many MTBE plants havebeen constructed worldwide. Another component with similar properties is 2-

Ž .methoxy-2-methylbutane tert-amyl methyl ether, or TAME . The thermodynamicbehaviour of this component in liquid mixtures is also of interest not only in itsapplication for reformulated gasoline but also in extraction or separation operationswith other components. Following a previous publicationŽ1. we consider in this

Ž . Ž . Žpaper the liquid q liquid equilibrium LLE of tert-amyl methyl ether q 1-. Žoctanol q water , a system of type 2 two pairs partially miscibles, TAME q water,

.and 1-octanol q water , at T s 298.15 and T s 308.15 K. The LLE data obtainedwere correlated using the NRTL, UNIQUAC, and TK-Wilson models.

2. Experimental

TAME and 1-octanol were supplied by Aldrich and had nominal mass fractionpurities ) 0.998 and ) 0.995, respectively. These purities were verifiedchromatographically, and both compounds were used without further purification.Water contents in mass fraction of TAME and 1-octanol were determined with a

a To whom correspondence should be addressed.

0021]9614r98r070799 q 06 $30.00r0 Q 1998 Academic Press

A. Arce and M. Blanco800

� Ž . Ž . ŽTABLE 1. Experimental tie-lines for x C H C CH OCH q x CH CH OH q 1 y x y1 2 5 3 2 3 2 3 2 7 1. 4x H O where x and x represent compositions in mole fraction2 2 1 2

Organic phase Aqueous phaseŽ . Ž .x x 1 y x y x x x 1 y x y x1 2 1 2 1 2 1 2

T s 298.15 K

0.9713 0.0000 0.0287 0.0014 0.0000 0.99860.7777 0.1356 0.0867 0.0001 0.0000 0.99990.7110 0.1835 0.1055 0.0003 0.0000 0.99970.6122 0.2533 0.1345 0.0003 0.0000 0.99970.5566 0.2931 0.1503 0.0006 0.0000 0.99940.4843 0.3454 0.1703 0.0001 0.0000 0.99990.4117 0.4010 0.1873 0.0003 0.0000 0.99970.3356 0.4567 0.2077 0.0004 0.0000 0.99960.2228 0.5452 0.2320 0.0002 0.0000 0.99980.1046 0.6421 0.2533 0.0001 0.0000 0.99990.0000 0.7320 0.2680 0.0000 0.0000 1.0000

T s 308.15 K

0.9671 0.0000 0.0329 0.0000 0.0000 1.00000.8301 0.0919 0.0780 0.0000 0.0000 1.00000.6877 0.1977 0.1146 0.0000 0.0000 1.00000.5045 0.3293 0.1662 0.0000 0.0000 1.00000.4092 0.4000 0.1908 0.0000 0.0000 1.00000.3001 0.4857 0.2142 0.0000 0.0000 1.00000.1822 0.5779 0.2399 0.0000 0.0000 1.00000.0900 0.6514 0.2586 0.0000 0.0000 1.00000.0000 0.7316 0.2684 0.0000 0.0000 1.0000

. y4Coulometer Metrohm 737 KF as 2 10 for both components. Water was obtainedfrom a Milli-Q Plus system.

Phase analysis was carried out by gas capillary chromatography in a Hewlett-Packard 6890 Series chromatograph equipped with a thermal conductivity detectorlinked to an HP6890 workstation. Calibration was carried out by internal standardsusing the solubility curves which were determined by the cloud point method. Theexperimental apparatus and procedure have been described in detail elsewhere.Ž2.

Conjugate phases were obtained by vigorously stirring mixtures having compositionslying in the immiscible region for 1 h and leaving them to stand for 4 h before asample of each phase was withdrawn and injected into the g.c. column. Theestimated precision of the measured mole fractions was "0.001.

3. Results

The compositions of the ends of tie-lines are listed in table 1. The UNIQUAC,Ž3.Ž4. Ž5. ŽTK-Wilson, and NRTL with the non-randomness parameter a set to 0.1, 0.2,

.and 0.3 equations were fitted to the experimental LLE data. The computerprogram used minimizes the objective function F:

32

F s x y x , 1Ž .ˆŽ .Ý i jk i jkis1

Ž .LLE of TAME q 1-octanol q water 801

Ž .TABLE 2. UNIQUAC, TK-Wilson, and NRTL a s 0.1, 0.2, and 0.3 correlation parameters and� Ž . Ž . Žabsolute mean deviation in mole fractions D for x C H C CH OCH q x CH CH OH q 1 y1 2 5 3 2 3 2 3 2 7

. 4x y x H O1 2 2

y1.Ž .Model Parameterr J mol D

T s 298.15 K

UNIQUAC Du s 5483.1 Du s y1647.812 21Du s 5873.1 Du s 1031.8 0.001013 31Du s 1586.8 Du s 1624.923 32

TK-Wilson Dl s y3277.9 Dl s y2663.812 21Dl s y3346.1 Dl s 10280 0.002313 31Dl s 1683.7 Dl s 3592.923 32

Ž .NRTL a s 0.1 D g s y4152.0 D g s y4156.712 21D g s y1415.9 D g s 12471 0.014313 31D g s y3610.3 D g s 1247023 32

Ž .NRTL a s 0.2 D g s y2326.2 D g s y7056.712 21D g s 2335.9 D g s 12446 0.005413 31D g s y734.33 D g s 1243923 32

Ž .NRTL a s 0.3 D g s y3030.5 D g s y7391.412 21D g s 5604.5 D g s 12170 0.001813 31D g s 1932.9 D g s 1188323 32

T s 308.15 K

UNIQUAC Du s y2135.4 Du s y2096.912 21Du s 4265.2 Du s 1986.0 0.002113 31Du s 130.53 Du s 6240.023 32

TK-Wilson Dl s y3821.6 Dl s y3931.412 21Dl s y2961.1 Dl s 10101 0.001813 31Dl s 10188 Dl s 3512.123 32

Ž .NRTL a s 0.1 D g s y4202.8 D g s y6302.412 21D g s y6309.5 D g s 8585.6 0.016013 31D g s y2047.6 D g s y6620.323 32

Ž .NRTL a s 0.2 D g s y7638.7 D g s y4911.612 21D g s 2722.8 D g s 11285 0.006713 31D g s y932.15 D g s 1246723 32

Ž .NRTL a s 0.3 D g s y7847.9 D g s y7733.712 21D g s 5841.7 D g s 10414 0.002813 31D g s 1822.2 D g s 1217223 32

UNIQUAC structural parametersComponent r q

TAME 4.7422 4.1721-Octanol 6.6219 5.828Water 0.9200 1.400

where x is the measured composition of component i in phase j on the k-thi jktie-line, and x indicates calculated values. In fitting UNIQUAC equations, thei jkstructural parameters r and q recommended by Prausnitz et al.Ž6. and Magnussenet al.Ž7. were used for the pure components. The goodness of fit was measured bythe absolute mean deviation in mole fractions. Table 2 lists the binary interaction

A. Arce and M. Blanco802

� Ž . Ž . Ž . 4FIGURE 1. Ends of tie-lines for x C H C CH OCH q x CH CH OH q 1 y x y x H O1 2 5 3 2 3 2 3 2 7 1 2 2at T s 298.15 K: `- - - - - -, experimental; B}}}, TK-Wilson; '}}}, UNIQUAC; %}}}, NRTLŽ .a s 0.30 .

Ž .LLE of TAME q 1-octanol q water 803

� Ž .FIGURE 2. Experimental tie-lines and UNIFAC predictions for the system x C H C CH OCH1 2 5 3 2 3Ž . Ž . 4q x CH CH OH q 1 y x y x H O at T s 298.15 K: `, - - - - - -, experimental; v, }}},2 3 2 7 1 2 2

UNIFAC prediction.

parameters and the absolute mean deviation. The experimental data obtained atT s 298.15 K and the corresponding fitted tie-lines are compared in figure 1. Asimilar figure is obtained at T s 308.15 K.

Predictions of LLE of the system studied were obtained by the UNIFACmethodŽ8. using previously publishedŽ7. group interaction parameters to calculatethe activity coefficients of the components in each phase. The values of theresidual R defined by:Ž9.

1r23 3 32

R s 100 x y x r6M , 2Ž .ˆŽ .Ý Ý Ý i jk i jk½ 5k j i

where M is the number of tie-lines, are 1.37 at T s 298.15 K and 1.28 atT s 308.15 K. The experimental composition data at T s 298.15 K and thecorresponding predicted tie-lines are shown in figure 2. Prediction of similarquality were obtained at T s 308.15 K.

4. Conclusions

The effect of temperature did not practically affect the region of immiscibility

A. Arce and M. Blanco804

from T s 298.15 K to T s 308.15 K. Because of the almost total insolubilityof 1-octanol in water at the working temperatures the solubility curve for� Ž . Ž . Ž . 4x C H C CH OCH q x CH CH OH q 1 y x y x H O is almost1 2 5 3 2 3 2 3 2 7 1 2 2vestigial for the aqueous phase. The behaviour is similar to that of� Ž . Ž . Ž . 4x C H C CH OCH q x CH CH OH q 1 y x y x H O . UNIQUAC,1 2 5 3 2 3 2 3 2 7 1 2 2

Ž .TK-Wilson, and NRTL equations the latter for a randomness parameter a s 0.3fit the experimental data adequately, with similar deviations in all the cases. TheUNIFAC method predicts well the slope of tie-lines but the immiscibility areapredicted is smaller than the experimental one.

Ž .This work was partly supported by Xunta de Galicia Spain , project 20904B97, andŽ .DGICYT Spain , project PB94-0658.

REFERENCES

1. Arce, A.; Blanco, M.; Soto, A.; Vidal, I. J. Chem. Thermodynamics 1996, 28, 3]6.2. Correa, J. M.; Blanco, A.; Arce, A. J. Chem. Eng. Data 1989, 34, 95]97.3. Abrams, D. S.; Prausnitz, J. M. AIChE J. 1975, 21, 116]128.4. Tsuboka, T. and Katayama, T. J. Chem. Eng. Japan 1975, 8, 181]187.5. Renon, H.; Prausnitz, J. M. AIChE J. 1968, 14, 135]144.6. Prausnitz, J. M.; Lichtenthaler, R. N.; Azevedo, E. G. Molecular Thermodynamics of Fluid Phase

Equilibria: 2nd edition. Prentice-Hall Inc.: Englewood Cliffs, NJ. 1986.7. Magnussen, T. P.; Rasmussen, P.; Fredenslund, A. Ind. Eng. Chem. Process Des. De¨ . 1981, 20,

331]339.8. Fredenslund, A.; Gmehling, J.; Rasmussen, P. Vapor]Liquid Equilibria using UNIFAC. Elsevier,

Amsterdam. 1977.9. Sørensen, J.M .; Arlt, W. Liquid]Liquid Equilibrium Data Collection, Dechema Chemistry Data Series,

Vol.V, Part 2. Frankfurt. 1980.

( )Recei ed 21 October 1997; in final form 16 January 1998

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