Department of Chemical Engineering, Tsinghua University, Beijing , People s Republic of China

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1 570 J. Chem. Eng. Dt 2000, 45, Isobric Vpor-Liquid Equilibri nd Excess Volumes for the Binry Mixtures Wter + Sulfolne, Wter + Tetrethylene Glycol, nd Benzene + Tetrethylene Glycol Yng-Xin Yu, Jin-Gng Liu, nd Gung-Hu Go* Deprtment of Chemicl Engineering, Tsinghu University, Beijing , People s Republic of Chin Isobric vpor-liquid equilibrium dt were determined t kp for the binry mixtures of wter + sulfolne nd wter + tetrethylene glycol. Clcultions of the nonidelity of the vpor phse were mde with the second viril coefficients obtined from the Hyden-O Connell method. The boiling points nd vpor-phse compositions reported were well correlted by the Wilson, NRTL, nd UNIQUAC models. In ddition, the densities of binry mixtures of wter + sulfolne, wter + tetrethylene glycol, nd benzene + tetrethylene glycol were determined over the entire concentrtion rnge t K nd tmospheric pressure by using n oscillting tube densimeter. Excess volumes were clculted for ech dt point. All mixtures exhibit negtive excess volumes with minimum which occurs t x = 0.5 for the benzene + tetrethylene glycol system; it is shifted towrd the wter-rich region for the wter + sulfolne nd wter + tetrethylene glycol systems. The experimentl excess volumes were correlted using the Redlich-Kister eqution. Introduction Solvent extrction is one of the most importnt methods to produce high-purity romtic extrcts from ctlytic reformtes. In recent yers, sulfolne or tetrethylene glycol hs been employed more nd more in new or improved extrction processes. Therefore, it is necessry to hve complete thermodynmic dt for these systems. Severl reserchers 1-4 hve studied the vpor-liquid nd liquid-liquid equilibri for mixtures contining n romtic nd sulfolne or tetrethylene glycol. Herskowitz nd Gottlieb 5 reported the ctivity coefficients of the solvent in the wter + tetrethylene glycol system by n isopiestic method t K. For the volumetric properties, excess volumes for nitrile + sulfolne 6,7 nd n romtic hydrocrbon + sulfolne 2,8 hve been well documented for resonble rnge of temperture. To our knowledge, for the systems involving tetrethylene glycol, only queous solutions nd solutions with HFC-134 hve been studied. 9 Lepori nd Mollic 10 hve reported the volumetric properties of dilute queous solutions of tetrethylene glycol, nd some density dt for this system hve been given by Müller nd Rsmussen. 11 In this work, the isobric vpor-liquid equilibrium dt for the mixtures of wter + sulfolne nd wter + tetrethylene glycol were mesured t kp, nd the excess volumes of wter + sulfolne, wter + tetrethylene glycol, nd benzene + tetrethylene glycol systems were reported t K, covering the whole concentrtion rnge. Experimentl Section Chemicls. Pure benzene nd sulfolne were obtined from Beijing Chemicl Engineering Plnt. Tetrethylene glycol ws procured from Beijing Ynshn Petrochemicl Compny. All the chemicls were purified by distilltion (sulfolne nd tetrethylene glycol distilled under vcuum), Tble 1. Densities (G) nd Refrctive Indices (n D) of Pure Components nd Comprison with Literture Vlues t K F/g cm -3 n D component exptl lit. exptl lit. benzene sulfolne b ,b d ,d c tetrethylene e g glycol f Riddick et l. 12 b Extrpolted vlue. c Interpolted dt from Jnnelli et l. 6 d Dt t K. e Dt from Müller nd Rsmussen. 11 f Interpolted dt from Kumgi et l. 9 g Dt from Dubert nd Dnner. 13 nd their middle frctions were collected. Then they were dried using type 0.5 nm moleculr sieves nd the wter content ws found to be <0.01 mss%, s determined with Mitsubishi moisture meter (Model CA-05). To minimize the contct of these deliquescent regents with moist ir, ll the purified chemicls were kept in seled bottles in desicctors. Doubly distilled wter ws used in ll solutions. The purity ws tested by GLC, which indicted minimum purity of 99.8 mol %, nd no pprecible peks of impurities were detected. The densities nd refrctive indices of the purified chemicls re reported in Tble 1 in comprison with the literture dt t K nd tmospheric pressure. Vpor-Liquid Equilibrium Mesurements. An inclined ebulliometer with pumplike stirrer developed by Zhou et l. 14 nd described by Yu et l. 3 ws used. It is recircultion type, in which both liquid nd vpor phse recirculte continuously, nd the equilibrium compositions of both phses cn be determined. The ebulliometer ws operted t tmospheric pressure ( kp). The stedy stte ws usully reched fter 1.5 h of opertion. The temperture in the equilibrium chmber ws mesured /je990276q CCC: $ Americn Chemicl Society Published on Web 05/31/2000

2 Journl of Chemicl nd Engineering Dt, Vol. 45, No. 4, using mercury thermometer. The uncertinty in the temperture mesurement is (0.05 K. The compositions of the smpled liquid phse nd vpor phse were nlyzed by mesuring their densities t K with vibrting tube densimeter, fter clibrtion with grvimetriclly prepred stndrd solutions. The ccurcy of the equilibrium composition mesurements ws ( mole frction. Since there is lrge difference between the boiling points of wter nd of tetrethylene glycol, the mount of tetrethylene glycol present in the vpor phse ws so smll tht is ws not detected by the densimeter. Therefore, the vpor-phse composition ws not mesured for the wter + tetrethylene glycol system. Density Mesurements. An Anton Pr (Grz, Austri) DMA60 oscillting tube densimeter equipped with density mesuring cell (DMA602) ws used to mesure densities of pure components nd binry mixtures t K. The temperture of the U-shped tube ws checked continuously using clibrted digitl thermometer (Anton Pr DT100-20) with n ccurcy of (0.01 K. The system ws mintined t constnt temperture to within (0.005 K by mens of Hetotherm ultrthermostted wter bth (Heto, Type CB7). All the mesurements were crried out t tmospheric pressure. The density determintion is bsed on mesuring the period of oscilltion of vibrting U-shped hollow tube tht is filled with the smple. The reltion between the period τ nd density F is F)A(τ 2 - B) (1) where A nd B re temperture-dependent constnts determined by clibrtion with doubly distilled wter nd dry ir. The precision for the mesured period τ is s, which leds to precision in densities nd excess molr volumes of ( g cm -3 nd ( cm 3 mol -1, respectively. The pprtus, the mixture stndrd smple preprtion, nd the procedure of density mesurements hve been described elsewhere. 15,16 The density F of the binry solutions ws used to clculte the excess molr volume V E, ccording to V E /cm 3 mol -1 ) x 1 M 1 + x 2 M 2 F - x 1 M 1 F 1 - x 2 M 2 F 2 (2) where x i is the mole frction, M i is the molr mss, nd F i is the density of component i. Results nd Discussion Isobric vpor-liquid equilibri were mesured t kp for wter + sulfolne nd wter + tetrethylene glycol systems. The results re shown in Tbles 2 nd 3, respectively. The liquid-phse ctivity coefficients γ i were clculted with φ i y i P ) γ i x i P st i φ st i exp[ V L i (P - P st i ) RT ] (3) where φ i nd φ i st re the fugcity coefficients of component i in the mixture nd pure vpor, respectively. T is the equilibrium temperture, P is the pressure, P i st is the sturted vpor pressure, V i L is the sturted liquid molr volume, x i is the liquid-phse molr frction, nd y i is the vpor-phse molr frction of component i. The vpor pressures of the pure components were obtined using fitted prmeters from Reid et l., 17 Riddick Tble 2. Vpor-Liquid Equilibrium Dt for Wter (1) + Sulfolne (2) Mixtures t kp T/K x 1 y 1 γ b 1 γ b Experimentl vlues. b Clculted from the experimentl dt. Tble 3. Vpor-Liquid Equilibrium Dt for Wter (1) + Tetrethylene Glycol (2) Mixtures t kp T/K x 1 y 1 γ b 1 γ Clculted vlues from NRTL eqution. b Clculted from the experimentl dt when tetrethylene glycol in the vpor phse ws neglected. Tble 4. Coefficients Used in the Determintion of the Pure Vpor Pressure of the Component component A B C D wter sulfolne b tetrethylene glycol c Coefficients 17 of the eqution ln(p st /P c) ) (1 - x) -1 (Ax + Bx Cx 3 + Dx 6 ), where x ) 1 - T/T c, P st is the sturted pressure, P c is the criticl pressure, nd T c is the criticl temperture. b Coefficients 12 of the eqution log(p st /kp) ) A - B/(T/K) - C log(t/k). c Coefficients 18 of the eqution log(p st /kp) ) A - B/ (T/K + C). et l., 12 nd Stephenson nd Mlnowski. 18 These re reproduced in Tble 4. The fugcity coefficient ws clculted by using the viril eqution of stte truncted fter the second viril term. The second viril coefficient ws determined by the Hyden-O Connell method. 19 The criticl properties nd other prmeters required for estimting the second viril coefficients, obtined from Domnsk et l., 20 Nikitin et l., 21 Prusnitz et l., 22 Steele et l., 23 nd Yu et l., 3 re listed in Tble 5. The vlue of the solvtion prmeter is tken s zero for the wter + sulfolne system nd 1.55 for the wter + tetrethylene glycol system. The liquid molr volumes were clculted from the Hnkinson- Brobst-Thomson eqution. 17 The clculted ctivity coefficients for the wter + sulfolne mixture re lso listed in Tble 2. The experimentl vpor-liquid equilibrium dt for the wter + sulfolne system were shown to be thermodynmiclly

3 572 Journl of Chemicl nd Engineering Dt, Vol. 45, No. 4, 2000 Tble 5. Criticl Properties nd Prmeters Used in the Determintion of the Second Viril Coefficients in the Vpor Phse, Where T c Is the Criticl Temperture, P c Is the Criticl Pressure, RD Is the Men Rdius of Gyrtion, DM Is the Dipole Moment, nd η Is the Assocition Prmeter component T c/k P c/mp RD/nm DM/D η wter sulfolne b b c 4.10 c 0.00 tetrethylene glycol d d e 5.84 e 1.55 e Dt from Prusnitz et l. 22 b Dt from Steele et l. 23 c Dt from Domnsk et l. 20 d Dt from Nikitin et l. 21 e Dt from Yu et l. 3 Tble 6. UNIQUAC Pure Component Prmeters for Volume (r) nd Surfce Are (q) of Ech Compound 29 component r q wter sulfolne tetrethylene glycol Tble 7. Correltion Prmeters nd Absolute Averge Devitions in Boiling Temperture ( T) nd Vpor-Phse Mole Frction ( y) for the Binry Mixtures model A 12/K b A 21/K b R 12 y c T (%) d Wter (1) + Sulfolne (2) Wilson NRTL UNIQUAC Wter (1) + Tetrethylene Glycol (2) Wilson NRTL UNIQUAC All models in ln γ form. b Energy prmeters A ji ) (λ ji - λ ii)/r for the Wilson model, A ji ) (g ji - g ii)/r for the NRTL model, nd A ji ) (U ji - U ii)/r for the UNIQUAC model. c y ) 1 N y i exp - y i clc /N. d T ) (100/N) 1 N T i exp - T i clc /T i exp, where N is the number of experimentl points. consistent by using Herington nlysis 24 with (D - J) < 10 nd the test described by Fredenslund et l. 25 The ctivity coefficients of wter in tetrethylene glycol were clculted by neglecting the mount of tetrethylene glycol present in the vpor phse. The vlues of γ i for the wter + tetrethylene glycol system re <1. This is in greement with the result of Herskowitz nd Gottlieb 5 with n isopiestic method t K. The experimentl vpor-liquid equilibrium dt were then used to obtin the binry prmeters in vrious ctivity coefficient models. The Wilson, 26 NRTL, 27 nd UNIQUAC 28 models were used in the regressions. The UNIQUAC pure component prmeters for the surfce re (q) nd volume (r) of the molecules were clculted from Wls 29 nd re listed in Tble 6. The following objective function ws minimized in the regressions: N OF ) j)1 j 100[ T exp - T clc j T j exp (1 - w) + w y j exp - y j clc ] (4) where N is the number of experimentl points, w ) 0.5 for the wter + sulfolne system, nd w ) 0 for the wter + tetrethylene glycol system becuse the vpor-phse composition for the ltter system ws not mesured in this work. The regression results re shown in Tble 7. The devitions in vpor-phse compositions nd equilibrium tempertures re resonbly smll, nd this indictes tht ll three ctivity coefficient models re suitble to represent Figure 1. Activity coefficient curves for the system wter (1) + sulfolne (2): comprison of experimentl dt (O) with the prediction of the NRTL model (s). Figure 2. Activity coefficient curves for the system wter (1) + tetrethylene glycol (2): comprison of experimentl dt (O) with the prediction of the NRTL model (s). Tble 8. Densities (G) nd Excess Molr Volumes (V E ) for Binry Mixtures t K x 1 g cm -3 cm 3 mol -1 x 1 g cm -3 cm 3 mol -1 F/ V E / F/ V E / Wter (1) + Sulfolne (2) Wter (1) + Tetrethylene Glycol (2) Benzene (1) + Tetrethylene Glycol (2) the binry experimentl dt. The comprison between the experimentl ctivity coefficients nd the prediction by the NRTL model for the systems of wter + sulfolne nd wter + tetrethylene glycol is shown in Figures 1 nd 2.

4 Journl of Chemicl nd Engineering Dt, Vol. 45, No. 4, Tble 9. Vlues of the Coefficients of the Correltion Eqution nd Stndrd Devitions for Excess Molr Volumes t K system σ/cm 3 mol -1 wter + sulfolne wter + tetrethylene glycol benzene + tetrethylene glycol nlysis 24 nd the method of Frendenslund et l. 25 Anlysis of the experimentl vpor-liquid equilibrium dt for the two binry systems (by using the Wilson, NRTL, nd UNIQUAC models) shows tht ll three models generlly give stisfctory results. Densities nd excess volumes for three mixtures of wter + sulfolne, wter + tetrethylene glycol, nd benzene + tetrethylene glycol were determined t K. The excess volumes for the three binry systems were successfully correlted using the Redlich- Kister eqution. Figure 3. Excess molr volumes s function of composition t K for binry systems. Experimentl points: (2) wter (1) + sulfolne (2) (this work); (b) benzene (1) + tetrethylene glycol (2) (this work); ([) wter (1) + tetrethylene glycol (2) (this work); (]) wter (1) + tetrethylene glycol (2) (Müller nd Rsmussen 11 ). The curves were clculted with eq 3. The experimentl densities nd excess molr volumes for the binry mixtures of wter + sulfolne, wter + tetrethylene glycol, nd benzene + tetrethylene glycol t K re given in Tble 8. The excess molr volume s function of composition is grphiclly represented in Figure 3. The mesured excess molr volumes V E were fitted to the following expression by lest-squres method: V E ) x 1 (1 - x 1 ) j (1-2x 1 ) j-1 (5) j)1 Coefficients j re given in Tble 9 long with the stndrd devition σ for ech system, defined s N where m is the number of djustble prmeters j in eq 5. The superscripts clc nd exp refer to the vlues clculted by using eqs 5 nd 2, respectively. The literture excess volumes for the wter + tetrethylene glycol system reported by Müller nd Rsmussen 11 re lso included in Figure 3. Good greement ws seen between the literture vlues nd the present dt. It cn be seen from Tble 8 tht, for ll cses, the excess volumes re negtive. For the benzene + tetrethylene glycol system, the minimum excess molr volume occurs t x = 0.5, nd it shifted towrd the wter-rich region for the wter + sulfolne nd wter + tetrethylene glycol systems, s shown in Figure 3. Excess molr volumes for queous tetrethylene glycol solutions re smller thn those for the other two systems studied; this cn be interpreted s n increse in the order of the system due to the formtion of hydrogen bonds between wter nd tetrethylene glycol molecules. Conclusion Vpor-liquid equilibri of two binry mixtures of wter + sulfolne nd wter + tetrethylene glycol were mesured t kp nd tested by using the Herington m σ 2 ) 1 (V E,clc j - V E,exp j ) 2 (6) N - m j)1 Literture Cited (1) Hssn, M. S.; Fhim, M. A.; Mumford, C. J. Correltion of Phse Equilibri of Nphth Reformte with Sulfolne. J. Chem. Eng. Dt 1988, 33, (2) Huschild, T.; Knpp, H. Liquid-Liquid-Equilibri nd Densities of Multicomponent Mixtures Contining Heptne-Ethylbenzene in Sulfolne. J. Solution Chem. 1991, 20, (3) Yu, Y.-X.; Liu, J.-G.; Go, G.-H. Isobric Vpor-Liquid Equilibri of Three Aromtic Hydrocrbon-Tetrethylene Glycol Binry Systems. Fluid Phse Equilib. 1999, 157, (4) Sørensen, J. M.; Arlt, M. Liquid-Liquid Equilibri Dt Collection, Vol. V, Prt 3; Frnkfurt/Min: DECHEMA, (5) Herskowitz, M.; Gottlieb, M. Vpor-Liquid Equilibrium in Aqueous Solutions of Vrious Glycols nd Poly(ethylene glycols). 2. Tetrethylene Glycols nd Estimtion of UNIFAC Prmeters. J. Chem. Eng. Dt 1984, 29, (6) Jnnelli, L.; Lopez, A.; Siello, S. Thermodynmic nd Physicl Properties of Binry Mixtures Involving Sulfolne. Excess Volumes nd Dielectric Constnts of Benzonitrile-Sulfolne nd Acetonitrile-Sulfolne Systems. J. Chem. Eng. Dt 1980, 25, (7) Lopez, A.; Jnnelli, L.; Silvestri, L. Thermodynmic Properties of Binry Mixtures Involving Sulfolne. 1. Excess Volumes on Mixing Sulfolne nd Propionitrile, Butyronitrile, nd Vleronitrile. J. Chem. Eng. Dt 1982, 27, (8) Yu, Y.-X.; Li, Y.-G. Excess Molr Volumes of Sulfolne in Binry Mixtures with Six Aromtic Hydrocrbons t K. Fluid Phse Equilib. 1998, 147, (9) Kumgi, A.; Mochid, H.; Tkhshi, S. Liquid Viscosities nd Densities of HFC Glycol Mixtures. Int. J. Thermophys. 1993, 14, (10) Lepori, L.; Mollic, V. Volumetric Properties of Dilute Aqueous Solutions of Poly(ethylene glycols). J. Polym. Sci., Polym. Phys. Ed. 1978, 16, (11) Müller, E. A.; Rsmussen, P. Densities nd Excess Volumes in Aqueous Poly(ethylene glycol) Solutions. J. Chem. Eng. Dt 1991, 36, (12) Riddick, J. A.; Bunger, W. B.; Skno, T. K. Orgnic Solvents. Physicl Properties nd Methods of Purifiction, 4th ed.; John Wiley & Sons: New York, (13) Dubert, T. E.; Dnner, R. P. Physicl nd Thermodynmic Properties of pure Chemicls: Dt Compiltion; Hemisphere Publishing Corportion: New York, (14) Zhou, X.; Ni, L.; Hn, S. A Study on Pseudo-Sttic Method for VLE Determintion. J. Chem. Ind. Eng. (Chin) 1990, 41, (15) Fermegli, M.; Lpsin, R. Excess Volumes nd Viscosities of Binry Mixtures of Orgnics. J. Chem. Eng. Dt 1988, 33, (16) Yu, Y.-X.; Bo, T.-Z.; Go, G.-H.; Li, Y.-G. Densities nd Apprent Molr Volumes for Aqueous Solutions of HNO 3-UO 2(NO 3) 2 t K. J. Rdionl. Nucl. Chem. 1999, 241, (17) Reid, R. C.; Prusnitz J. M.; Poling, B. E. The Properties of Gses nd Liquids, 4th ed.; McGrw-Hill: New York, (18) Stephenson, R. M.; Mlnowski, S. Hndbook of the Thermodynmics of Orgnic Compounds; Elsevier: Amsterdm, (19) Hyden, J. G.; O Connell, J. P. A Generlized Method for Predicting Second Viril Coefficients. Ind. Eng. Chem. Process Des. Dev. 1975, 14, (20) Domnsk, U.; Sporzynski, A.; Moolln, W. C.; Letcher, T. M. Vpor-Liquid Equilibri of Binry Mixtures Contining Sulfolne. 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5 574 Journl of Chemicl nd Engineering Dt, Vol. 45, No. 4, 2000 (21) Nikitin, E. D.; Pvlov, P. A.; Popov, A. P. (Gs + Liquid) Criticl Tempertures nd Pressures of Polyethylene Glycols from HOCH 2- CH 2OH to H(OCH 2CH 2) v)13.2oh. J. Chem. Thermodyn. 1995, 27, (22) Prusnitz, J. M.; Anderson, T. F.; Grens, E. A.; Eckert, C. A.; Hsieh, R.; O Connell, J. P. Computer Clcultions for Multicomponent Vpor-Liquid nd Liquid-Liquid Equilibri; Prentice Hll: Upper Sddle River, New Jersey, (23) Steele, W. V.; Chirico, R. D.; Knipmeyer, S. E.; Nguyen, A. Vpor Pressure, Het Cpcity, nd Density long the Sturted Line, Mesurements for Cyclohexnol, 2-Cyclohexen-1-one, 1,2-Dichloropropne, 1,4-di-tert-Butylbenzene, (()-2-Ethylhexnoic Acid, 2- (Methylmino)ethnol, Perfluoro-n-Heptne, nd Sulfolne. J. Chem. Eng. Dt 1997, 42, (24) Herington, E. F. G. Tests for the Consistency of Experimentl Isobric Vpor-Liquid Equilibrium Dt. J. Inst. Pet. 1951, 37, (25) Fredenslund, A.; Gmehling, J.; Rsmussen, P. Vpor-Liquid Equilibri Using UNIFAC; Elsevier: Amsterdm, (26) Wilson, G. H. Vpor-Liquid Equilibrium. XI. A New Expression for Excess Free Energy of Mixing. J. Am. Chem. Soc. 1964, 86, (27) Renon, H.; Prusnitz, J. M. Locl Composition in Thermodynmics Excess Functions for Liquid Mixtures. AIChE J. 1968, 14, (28) Abrms, D. S.; Prusnitz, J. M. Sttisticl Thermodynmics of Liquid Mixtures; A New Expression for the Excess Gibbs Energy of Prtly or Completely Miscible Systems. AIChE J. 1975, 21, (29) Wls, S. M. Phse Equilibri in Chemicl Engineering; Butterworth Pulishers: Boston, Received for review October 11, Accepted Mrch 21, This work ws supported by the Stte Key Lbortory of Chemicl Engineering in Chin. JE990276Q

Isobaric vapor liquid equilibria of three aromatic hydrocarbon-tetraethylene glycol binary systems

Isobaric vapor liquid equilibria of three aromatic hydrocarbon-tetraethylene glycol binary systems Ž. Fluid Phse Equilibri 157 1999 299 307 Isobric vpor liquid equilibri of three romtic hydrocrbon-tetrethylene glycol binry systems Yng-Xin Yu ), Jin-Gng Liu, Gung-Hu Go Deprtment of Chemicl Engineering,