Fluid Phase Equilibria 290 (2010) 1520

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Fluid Phase Equilibria

journa l homepage: www.e lsev ier .co

Excess hyternary E),2,2,4-tr

FernandoMiguel Aa Departament -0900b Grupo de Term Vallad

a r t i c l

Article history:Received 22 JuReceived in reAccepted 9 NoAvailable onlin

Keywords:Excess enthalpOxygenated coGasoline

alpieter arP) anharacrime

1. Introduction

Presentlline to enhaproper desimulated gabehaviourneed to bedynamic prexperimentDBE+1-butbinary systused as bleis a basic cfore is alwais an essenhave been mexperimentand groupation indicaand thosedescribe themolecules i

CorresponE-mail add

2. Experimental

0378-3812/$ doi:10.1016/j.y several oxygenated compounds are added to gaso-nce the octane number and to reduce air pollution. Forgn of synthesis and separation processes of these refor-solines, which contain ethers and alcohols, the phaseand thermodynamic properties of the uid mixturesknown. As a part of our research work on thermo-operties of octane boosters [1,2], this paper presentsal excess molar enthalpies of the ternary systemanol +2,2,4-trimethylpentane and the correspondingems at T=298.15K and atmospheric pressure. DBE isnding agent in reformulated gasoline and 1-butanolomponent in the synthesis of the ether, and there-ys contained as an impurity. 2,2,4-Trimethylpentanetial component in gasoline. Excess molar enthalpieseasured with a quasi-isothermal ow calorimeter. The

al data have been tted using polynomial equationscontribution models. The values of the standard devi-te good agreement between the experimental resultscalculated from the equations. Data are also used tostructural effects and interactions that occur between

n the solutions.

ding author. Tel.: +34 947 258 916; fax: +34 947 259 088.ress: emontero@ubu.es (E.A. Montero).

All the chemicals used here were purchased from Fluka ChemieAG and were of the highest purity available, chromatography qual-ity reagents (of the series puriss p.a.) with a stated purity >99.5%.The purity of all reagents was checked by gas chromatography,and the values of purity obtained were >99.6% for DBE, >99.8% forTMP and >99.8% for 1-butanol. The water content of 1-butanol waschecked to be less than 0.009%.

Excess molar enthalpies have been measured with a quasi-isothermal ow calorimeter previously described [1]. Twoprecision positive displacement pumps deliver the liquids at pro-grammable constant ow rates into the mixing coil sitting in theowcell,which is included in themeasureunit immersed inawaterbath. In case of binary systems, the two liquids are the pure com-ponents and, in case of ternary systems, one of them is a purecomponent and the other the corresponding binary mixture inwhich the excess molar enthalpy value is known. The calorime-ter is thermostated at T=298.150.01K. To achieve this condition,a Peltier cooler and a controlled heater actuate simultaneously tomaintain the ow cell temperature constant. The calibration of themeasurement system is made by simulating an exothermic mix-ing process by a calibration resistor. The change of heating powerof the control-heater before, during and after measurements is anindirect measure for the excess enthalpy HE. The HE is calculatedfrom differences in the heating power control, once the calibrationprocedure has been performed.

see front matter 2009 Elsevier B.V. All rights reserved.uid.2009.11.010enthalpies of oxygenated compounds+mixtures containing dibutyl ether (DBimethylpentane at 298.15K

Aguilara, Fatima E.M. Alaouia, Jos J. Segoviab,. Villamannb, Eduardo A. Monteroa,

o de Ingeniera Electromecnica, Escuela Politcnica Superior, Universidad de Burgos, Eodinmica y Calibracin TERMOCAL, E.T.S. de Ingenieros Industriales, Universidad de

e i n f o

ne 2009vised form 4 November 2009vember 2009e 17 November 2009

ympound

a b s t r a c t

Measurements of excess molar enthin a quasi-isothermal ow calorimebutanol + 2,2,4-trimethylpentane (TMternary systems show endothermic cmodels have been used to t the expem/locate / f lu id

drocarbon mixtures: Binary and1-butanol and

6 Burgos, Spainolid, E-47071 Valladolid, Spain

s at the temperature of 298.15K and atmospheric pressuree reported for the ternary system dibutyl ether (DBE) +1-d the corresponding binary systems. All the binary and theter. The RedlichKister equation and the NRTL and UNIQUACntal data for the binary and ternary systems.

2009 Elsevier B.V. All rights reserved.

16 F. Aguilar et al. / Fluid Phase Equilibria 290 (2010) 1520

Table 1Experimental excess molar enthalpies of binary systems DBE+2,2,4-trimethylpentane, DBE+1-butanol and 2,2,4-trimethylpentane+1-butanol at T=298.15K.

x HE/Jmol1 x HE/Jmol1 x HE/Jmol1 x HE/Jmol1

xDBE+ (1 x)2,2,4-trimethylpentane0.0497 54940.0997 59960.1497 64990.1998 69930.2501 7499

xDBE+ (1 x0.0501 55060.1002 59980.1497 65050.2003 70000.2503 7509

x2,2,4-trime0.0502 55000.1001 59970.1504 64970.2002 69980.2504 7498

a Data taken

Knowingand the dethe mixturemaximumcompositioby interpolthe measurpumps. Estand 805.75These resul[47]. Mixtthe ratio offraction canthe determ

3. Results

The expwork for thT=298.15Kmixture DB

For binaequations ping Redlichthe results,unweighted

HE = x(1

Binary syste[9], which eequation:

HE =n

i=1qi

where i =obtained aspresent in t

The NRTsystems. In

py is

RTi=

xi is

pk=1

xp(TL thnenthe nthreultsn Tay

[ni

zexplcular of pmic26.88 0.2995 109.48 0.51.00 0.3500 117.17 0.71.17 0.3997 121.05 0.86.08 0.4494 123.47 0.99.90 0.4994 122.95 0.

)1-butanola

119.4 0.3004 624.6 0.236.0 0.3498 698.4 0.344.5 0.4006 762.1 0.447.6 0.4507 814.0 0.540.2 0.4997 853.2 0.

thylpentane+ (1 x)1-butanol67.15 0.3000 395.64 0.

140.02 0.3502 449.14 0.210.84 0.4000 497.67 0.276.46 0.4498 540.40 0.338.99 0.5006 578.91 0.

from Ref. [1].

the volumetric ow rates delivered, the molar massesnsities of the pure compounds, the mole fractions ofs obtained in the mixing coil can be calculated. Theabsolute uncertainty of mole fraction at equimolarn is 0.0008. Densities of pure liquids are determinedating density data obtained from Riddick et al. [3] ated temperature of ow delivery of the displacementimated densities at T=298.15K, were 764.10, 687.80kgm3 for the DBE, TMP and 1-butanol, respectively.ts agree within 0) in the whole

mposition. The best t of the experimental data at thee of 298.15K is obtained with the RedlichKister equa-root mean square deviation, rms HE, of 0.5 Jmol1

imum value of the absolute deviation, max|HE|, ofDeviations obtained with the NRTL and UNIQUAC mod-ost the same. The maximum value of the excess molar124 Jmol1, obtained at a mole fraction of DBE aboutarison with data for the same system and temperaturePenget al. [7], shows that ourdata agree towithin10.2%e of composition 0.3 x0.7, being the experimentalwork higher than those of the reference [7].ary system DBE+1-butanol measured at a tempera-.15K is also endothermic. The maximum value of HE1, at a mole fraction of DBE about 0.60. RedlichKisterves the best t with a root mean square deviation, rms

F. Aguilar et al. / Fluid Phase Equilibria 290 (2010) 1520 17

Table 2Summary of parameters for the representation of HE by RedlichKister,NRTL (3 parameters) and UNIQUAC models, for binary systems DBE+2,2,4-trimethylpentane, DBE+1-butanol and 2,2,4-trimethylpentane+1-butanol atT=298.15K.

Binary syste

DBE (1) +2,2A0A1A2A312rms HE/Jmax|HE|max(|HE

DBE (1) +1-bA0A1A2A3A413rms HE/Jmax|HE|max(|HE

2,2,4-TrimetA0A1A2A3A4A523rms HE/Jmax|HE|max(|HE

a EquivalencA0 =u12; A1 =

HE, of 2.9lute deviatislightly worange of comand temper

The thirtem TMP+behaviour. Tmixture atfraction of Tbeen ttedQUAC moderootmean smumvalueNRTL and Uparameters

The terT=298.15Kof xed coming binaries0.6665, 1.5molar enthathe calculatof the binar

HE123 = HE2+1The followi

HE123 = HE12msa Correlation

RedlichKister NRTL (3p) UNIQUAC

,4-trimethylpentane (2)492.8 0.0772 174.758.0 0.1745 270.518.2

35.71.47

mol1 0.5 0.7 0.8/Jmol1 1.0 1.7 1.5|/HE) 5.0% 8.6% 6.9%utanol (3)

3414.8 2.4081 2160.11259.1 0.8333 629.7741.4

1310.71021.7

0.31mol1 2.9 11.9 43.2/Jmol1 4.9 21.8 84.5|/HE) 3.5% 9.7% 23.1%hylpentane (2) +1-butanol (3)

2337.5 2.4838 2159.11457.5 0.7237 765.0134.1

1489.63080.24761.2

0.40mol1 13.3 31.0 59.7/Jmol1 30.4 93.0 171.7|/HE) 13.7% 28.2% 45.9%

e between parameters: NRTL A0 = 12 and A1 = 21; UNIQUACu21.

Jmol1 at T=298.15K. Themaximumvalue of the abso-on,max|HE|, is 4.9 Jmol1. The remainingmodels giverse ts. Our HE data agree to within 1.5% in the central

position with the measurements for the same systemature obtained from Kammerer and Lichtenthaler [12].d binary system which has been studied is the sys-1-butanol at T=298.15K, showing also endothermiche maximum value of the excess molar enthalpy of the

the temperature of 298.15K is 631 Jmol1 at the moleMP of 0.65 approximately. The experimental data haveby the RedlichKister equation, the NRTL and the UNI-ls. The RedlichKister equation gives the best t with aquare deviation, rmsHE, of 13.3 Jmol1 and themaxi-of the absolute deviation,max|HE| of 30.4 Jmol1. TheNIQUAC models show slightly higher values of tting.nary mixtures DBE (1) + TMP (2) +1-butanol (3) atwere formed by adding the TMP (2) to binary mixturesposition of DBE (1) +1-butanol (3). Four different start-were used, with values of the ratio x1/x3 of 0.2500,

002 and 4.008, respectively. The experimental excesslpies listed in Table 3 are determined by Eq. (7), usinged values of HE13 from the RedlichKister t of the datay system DBE (1) +1-butanol (3):

3 + (1 x2)HE13 (7)

ng equation was used to t the HE measurements

+ HE13 + HE23 + x1x2x3 HE123 (8)

Fig. 1. ExcessDBE+2,2,4-tri(); DBE+bentrimethylpentExperimentalues at T=298.1for 2,2,4-trimdata from Related values foparameters of

with

HE123=B0+

where thepsquares memolar enthalpy HE at T=298.15K. (a) Experimental results formethylpentane; this work (); DBE+ cyclohexane, data from Ref. [1]zene, data from Ref. [2] (); () calculated values for DBE+2,2,4-ane at T=298.15K with Eq. (1) using parameters of Table 2. (b)results for DBE+1-butanol, data from Ref. [1] (); () calculated val-5K with Eq. (1) using parameters of Table 2. (c) Experimental resultsethylpentane+1-butanol; this work (); cyclohexane+1-butanol,f. [1] (); benzene+1-butanol, data from Ref. [2] (); () calcu-r 2,2,4-trimethylpentane+1-butanol at T=298.15Kwith Eq. (1) usingTable 2.

B1x1+B2x2+B3x21+B4x22+B5x1x2 + B6x31 + B7x32 (9)

arametersBi weredeterminedby theunweighted least-thod. An alternative for the calculation of HE123 is Eq.

18 F. Aguilar et al. / Fluid Phase Equilibria 290 (2010) 1520

Table 3Experimental excess molar enthalpies HE2+13 at 298.15K for the additionof 2,2,4-trimethylpentane to DBE (1) +1-butanol (3) to form x1DBE+ x22,2,4-trimethylpentane+ (1 x1 x2)1-butanol, and values ofHE123 calculated fromEq. (7),using the smooth representation of HE13 by RedlichKister equationwith parametersgiven in Table 2.

x2 HE2+13/Jmol1 HE123/Jmol

1 x2 HE2+13/Jmol1 HE123/Jmol

1

x1/x3 = 0.2500; HE13/Jmol1 = 444.1

0.1004 134.0 533.5 0.6005 524.3 701.70.2004 255.0 610.1 0.7002 527.4 660.60.2997 356.1 667.0 0.8004 495.3 583.90.3997 434.7 701.3 0.9002 414.8 459.10.4999 492.2 714.2

x1/x3 = 0.6665; HE13/Jmol1 = 764.1

0.0998 114.7 802.5 0.5998 429.5 735.30.2000 215.8 827.0 0.7002 434.4 663.40.2999 297.0 832.0 0.8005 414.6 567.00.3996 358.8 817.6 0.9002 354.4 430.70.4998 403.8 786.0

x1/x3 = 1.5002; HE13/Jmol1 = 890.0

0.0998 91.8 893.0 0.5999 348.1 704.20.2000 173.8 885.9 0.6998 354.0 621.20.3002 239.7 862.5 0.8000 340.2 518.20.4004 291.1 824.8 0.9001 291.7 380.60.5004 326.9 771.5

x1/x3 = 4.0008; HE13/Jmol1 = 776.4

0.1005 73.1 771.5 0.6001 273.4 583.90.2004 137.8 758.6 0.7003 275.0 507.70.2999 190.0 733.5 0.7999 259.3 414.70.3998 229.1 695.1 0.8998 209.9 287.70.5002 257.4 645.4

(10):

HE123 = B1

Table 4 prethe ternarymodels. Tabternary sys

Table 4Summary of the data reduction and prediction results obtained for the ternarysystem DBE (1) +2,2,4-trimethylpentane (2) +1-butanol (3) at 298.15K.

Correlationa HE123, Eq. (9) HE123, Eq. (10) NRTL UNIQUAC

B0 3289.8 8729.2 0.1020 705.5B1 26,267.8 15,771.4 0.5728 1371.5B2 43,717.1 7852.5 2.0861 2169.4B3 2538.2 0.7733 620.5B4 229,673.3 2.8942 2155.2B5 91,359.5 0.0832 776.7B6 32,537.6B7 25,7847.7 0.32rms HE/Jmol1 39.3 65.5 32.6 41.7max|HE|/Jmol1 91.7 158.2 78.0 115.0max(|HE|/HE) 31.9% 49.1% 26.4% 25.1%

Predictiona NRTL UNIQUAC

B0 0.0772 174.7B1 0.1745 270.5B2 2.4081 2160.1B3 0.8333 629.7B4 2.4838 2159.1B5 0.7237 765.012 1.4713 0.3123 0.40rms HE/Jmol1 42.9 90.7max|HE|/Jmol1 115.0 181.0max(|HE|/HE) 40.0% 55.1%a Equivalence between parameters: NRTL B0 = 12; B1 = 21; B2 = 13; B3 = 31;

B4 = 23; B5 = 32; UNIQUAC B0 =u12; B1 =u21; B2 =u13; B3 =u31; B4 =u23;B5 =u32.

the mtem

edws 32.6max|for tAC mx1 + B2x2 + B3x3 (10)

sents the summary of correlation results obtained forsystems with Eqs. (8)(10) and the NRTL and UNIQUACle 4 also shows the prediction results obtained for the

tems using the parameters of the binary systems.

For(3) at aobtainHE, iation,modelUNIQUFig. 2. Contours for constant values of HE123 for DBE (1) +2,2,4trimethylpeeasured ternary system, DBE (1) + TMP (2) +1-butanolperature of 298.15K, the best t of experimental data isith theNRTLmodel. The rootmeansquaredeviation, rmsJmol1, and the maximum value of the absolute devi-

HE|, is 78.0 Jmol1. Correlated results with the NRTLhe excess molar enthalpy HE123 are shown in Fig. 2. Theodel gives also a good t, as well as the one with Eqs.ntane (2) +1-butanol (3) at T=298.15K.

F. Aguilar et al. / Fluid Phase Equilibria 290 (2010) 1520 19

Fig. 3. Ex

(8) and (9).worse. Thisrange of com

Concern298.15K, Ftal ternaryof the NRTLbest qualitaimum relatthe ternaryQUAC mod55.1%.

In thenon-polar +inuence tether +hydrthe dispersular forces.disruptionwith the nebetween unthe mixturecess molar enthalpy HE for DBE (1) +2,2,4-trimethylpentane (2) +1-butanol (3) at T=298

The results obtained with Eqs. (8) and (10) are slightlysystem shows endothermic behaviour in the wholeposition. The maximum value of HE is 893 Jmol1.

ing the prediction of data at the temperature ofig. 3 shows the graphical comparison of experimen-data and prediction data using the binary parametersand UNIQUAC models. The NRTL model presents the

tive description of ternary HE curves. Value of the max-ive deviation, max(|HE|/HE), is 40.0%. Prediction ofdata from binary parameters obtained with the UNI-

el is slightly worse, with values of max(|HE|/HE) of

mixtures presented in this work, containing somepolar and polar +polar compounds, interaction effectshe excess molar enthalpy data. In mixtures ofocarbon substances, which are non-polar substances,ion forces are the most signicant attractive molec-The positive contribution to HE associated with the

of interaction between like molecules in connectiongative contribution due to the creation of interactionlike molecules explains the endothermic character ofs DBE+TMP. The HE curve is slightly skewed towards

small moleof ether mother mixtuendothermmatic hydroas TMP.

The binaassociatingcomponentalkanol thrcontributiobehaviour otribution oupon mixintion of alkalow mole frcharacter o

With recurve is sking again itof the hydrpersion forc.15K: () experiment; () NRTL model; (- - -) UNIQUAC model.

fractions of ether, reecting the more active behaviourolecules. Comparison shown in Fig. 1a with data ofres DBE+hydrocarbon taken from [1,2], shows that theic character of the mixture increases for cyclic or aro-carbons with respect to a branched hydrocarbon such

ry mixture DBE+1-butanol contains one strong self-component (1-butanol) and a non-self-associating(DBE) which, however, can form associates with theough hydrogen bonding. In this case, the chemicaln dominates the excess properties. The endothermicf the mixture is explained by the greater positive con-f the destruction of alkanolalkanol hydrogen bondsg with reference to the negative term due to the forma-nolether complexes. The HE curve is skewed towardsactions of alcohol, reecting the strong self-associationf the alcohol.spect to the binary mixture TMP+1-butanol, the HE

ewed towards low mole fractions of alcohol, reect-s strong self-association character. The chemical forcesogen bonds in the alkanol are stronger than the dis-es of the hydrocarbon, which explain the endothermic

20 F. Aguilar et al. / Fluid Phase Equilibria 290 (2010) 1520

character of the mixture. When compared with the mixture cyclo-hexane+1-butanol [1], Fig. 1c shows that both mixtures presenta very similar endothermic character, but when compared withthe mixture benzene+1-butanol [2], the mixture aromatic hydro-carbon+1-alkanol reveals a greater endothermic character withrespect to the mixtures of the 1-alkanol with cyclic or branchedhydrocarbons.

4. Conclusions

Isothermal excess molar enthalpies at T=298.15K for theternary system DBE (1) +2,2,4-trimethylpentane (2) +1-butanol(3) and two of its constituent binary systems DBE (1) +2,2,4-trimethylpentane (2) and 2,2,4-trimethylpentane (2) +1-butanol(3) were determined by using an isothermal ow calorimeter.All the binary systems show endothermic and asymmetric HE

behaviour at the measured temperature. The asymmetric HE

behaviour is more pronounced in the binary mixtures contain-ing the alkanol, due to the hydrogen bonding association effectof the alkanol. Intermolecular and association effects involved inthese systems have been discussed. The measured excess molarenthalpies data were correlated well with the NRTL and UNIQUACmodels and polynomial equations.

List of symbolsAi, Bi adjustable parameters of the correlation equations and

modelsHE molar excess enthalpyi,j constituent identication: 1, 2 or 3max maximum value of the indicated quantityq molecular surface areaR universal gas constantrms root mean square

T absolute temperaturex mole fraction

Greek letters difference non-randomness parameter in the NRTL model energy interaction parameter in the NRTL and the UNI-

QUAC models

Acknowledgements

This paper is part of the Doctoral Thesis of F. Aguilar.Support for thiswork came from theDireccinGeneral de Inves-

tigacin (DGI), Ministerio de Educacin y Ciencia, Spain, ProjectsENE2006-12620, and from the Consejera de Educacin, Junta deCastilla y Len, Spain, Project BU021A08.

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Excess enthalpies of oxygenated compounds+hydrocarbon mixtures: Binary and ternary mixtures containing dibutyl ether (DBE), 1-butanol and 2,2,4-trimethylpentane at 298.15KIntroductionExperimentalResults and discussionConclusionsAcknowledgementsReferences