Measurement and Correlation of Liquid-Liquid Equilibrium Data for Ethanol-Water-KF and Ethanol-Water

第2卷第3期过程工程学报VoL 2 No. 32002年6月The Chinese Journal of process engineerinJune 2002Measurement and Correlation of Liquid-Liquid Equilibrium Datafor Ethanol-Water-KF and ethanol-Water-K, CO3 SystemsXU Wen-you(许文友), YUAN Xi-gang(袁希纲)(. Macromolecule Sci. Eng Key lab, Yantai University, Yantai, Shandong 264005, Chir2. Chemical Engineering Research Center; Tianjin University, Tianjin 300072, ChinaAbstract: The liquid-liquid equilibrium data for two ternary systems, ethanoh-water-KF and ethanol-ater-K,CO,, were determined at 25'C. Experiments show that by adding KF or K, CO, into thethanoh-water system two phases are formed: an ethanol-rich phase with negligibl salt and a water-richphase with negligibl ethanol, thus water can be separated out easily. A mathematical calculation of theliquid-liquid equilibrium data was carried out with the Pitzer theory on water activity in the aqueousphase, and with the Wilson or NRTl or UNIQUAC equations for that in the ethanol phase, which is ingood agreement with experimental data.Key words: ethanoh-water-KF; ethanoh-water-K,CO; liquid-liquid equilibrium; Pitzer theory; wilsonequation; NRTL equation; UNIQUAC equation; correlationCLC No. TQ013 1 Document Code: A Article ID: 1009-606X(2002)03-0209-01 INTRODUCTIONEthanol and water fordistillation.In ethanol-2-propanol-1-butanol-water2, ethanol-acetone-1-butanol-water3I and acetonitrile-water4I systems, water was successfully separated out by adding salts. The measurement andcorrelation of liquid-liquid equilibrium data for ethanol-water-KF and ethanol-water-KCO3 systemswith relatively high concentration of KF and K,CO3 at 25C have not been reported yet. Due to thesalting outeffect, adding KF or K,CO3 into the ethanol-water system leads to an ethanol-rich phasewith negligible salt and a water-rich phase with negligible ethanol, so large amount of water can beseparated from ethanol by simple and efficient phase separation2 EXPERIMENTAL2.1 ProcedureAnalytically pure ethanol, KF and K, CO3 were used in the experiments. Salt, distilled water andethanol were added into ground stoppered test tubes. Then the tubes were shaken(150 r/min) at 25C for3 h in a constant temperature shaker, followed by standing still for 3 h. After that, liquid-liquidequilibrium was reached, ethanol was analyzed by gas chromatography, and salt concentration wascalculated by mass balance. In order to examine the reliability of experimental results, the liquid-liquiduilibrium data of the ethanol-water-potassium carbonwere determined at 25C. andcompared with a few measurement 5), which are only data中国煤化工ar. The maximumCNMHGReceived date: 2002-03-18, Accepted date: 2002-05-15Biography: XU Wen-you(1963-), male, native of Penglai city, Shandong Province, Ph. D, associate professor, majoring in separation210过程工程学报2卷deviation of ethanol content in the ethanol phase was 0.8% when the concentration of potassiumcarbonate in the water phase was the same, which shows that the experimental data are reliable by thepresent experimental method412.2 Liquid-Liquid Equilibrium DataThe liquid-liquid equilibrium data for the two ternary systems, ethanol-water-KF and ethanolwater-K,CO,, were determined at relatively high concentrations of KF and K,CO3. No ethanol in thewater phase was detected by gas chromatography and the salt in ethanol phase was 10(mass fraction)The liquid-liquid equilibrium data with negligible ethanol in water phase and negligible salt in ethanolphase are listed in Tables I and 2, which demonstrate that water can be separated out from ethanol byadding KF or K,coTable 1 Liquid-liquid equilibrium data and correlation for the ethanol (1)-water(2)-KF (3)system at 25CEthanol laverWater layerEthanol laverWater layerEthanol layerWater laverEthanol layerPitzerNRTLPitzerUNIQUAC60.153914.3885625931406915.08849259.1840.8215.1884.82594740.53149685.04590041.0013.568644582941.7114.1385875813418714.248576584841.52139986579242.08128187.1957.3042.7013.2886.7257,1242.88134086605751424913.1286.8868543.1512.108790563243.6812488752561143.89126287,385655434512.3187695.7244.2811.388862552844.7211.68883255058388175553444711.518849546545.3510.72892854.2745.731097890354.00460011.13888754.53454710.7989.21536046.4010.l898953.2846.7210.3089.7053.0047.00104789535357464310.1389.87957904351.8048.209.7590.255240476094190.591.2948.718.8491.16510748938.9691.0450.7249289.1590513648648.8091.208050.208.109190496250.388.19918149.2450.768.3891499350.070.450.450.320.320740.740.480.250,250.19Nole: Average absolute deviation= 2IWd-Wes I/NTable 2 Liquid-liquid equilibrium data and correlation for the ethanol (1)-water(2)-KCO,(3)system at 25'CEthanol laverWater layerEthanol layerPitzerNRTIUNIQUAC587741232456754459.3340.6723.7176.295917408323.92760858994101241975.81576242382279772158.1641.842201779958.04419622.1677.84579242082232776864543.55208979.11568243.1820.38796256.7443.26204979.51566943.3120.5479465530447019.14808655524448188681.145545445518958105554744.53189081.1054.1245881745825554.1945.811737826354.124588174582.5554214579173382675300470015.96840452954705160283985286471416.1283.8853.0246981593840751.8248.1814.51854951674833146785.3351.5748414.55854550.35496512.8587.1550.12498813.0986.91499950.0113.2286.7850.274973129387.0749.1050.9011598841488751.1311.8288.1848.715129119788.03490450.9611.65883.2989.746.9953.0Average absolute deviation0.270.270.350350.290.290.31031Note: Average absolute deviatio =2IWe-WerI/N,3 CORRELATION OF LIQUID-LIQUID EQUILIBRIUM DATA3.1 Basic HypothesisV中国煤化工Experimental results show that the ethanol-water-saCNMHethanol-water and water-salt. The water phase can be calculated by une rllzer theory and the ethanolphase by either the Wilson equation, NRTL equation or the UNIQUAC equation3 #H XU Wen-you et al.: Measurement and Correlation of Liquid-Liquid Equilibrium Data for Ethanol-Water-KF and EthanoH-Water-KCO, Systems3.2 Data Correlation3. 2. 1 Water PhaseThe water phase consisting of salt and water can be calculated by the Pitzer theoryZ=-1zx14,1vMX)C+11+1.2/05vmMIn ae1000The simplified equations for 1-l type KF are as followsI1+1.2/+mB+Be1+m2c+1,In a20.036nOwhereβo,β P and c for kf areβ=0082,β=1.085,c=0.0020244, respectively.Atis0.3910atThe simplified equations for 1-2 type K,CO3 are as followsI=3nO=-2A+-m+1l+1.2I×32lna2=-0.054mOthe values ofβo,β I and c for KcO3areβo=0.128,1=1.433,c=-0.0005向, respectively. Aa is the3.2.2 Ethanol PhaseFor calculation of the ethanol-water-KF and ethanol-water-KCO3 systems in phase equilibrium,pure water was used as the standard state in the water phase and in the ethanol phase, thus wateractivities both in water and ethanol phases are equal. If the salt mass molar concentration in water phais known, water activity can be calculated by using the Pitzer equation, therefore the composition in theethanol phase can be obtained by using either the Wilson equation, NRTL 4 equation or UNIQUACIIequation.The wilson equation is as followsIny,=-In(x,+A,x)+xH中国煤化工CNMHG212过程工程学报ith4g2V=5869.vL=18071RTThe nrtl equation is as follows:x2τ1=△g1/RT,τ2=△g2/RT,G12=exp(-0x1212),G21=exp(-x12t2The UNIQUAC equation is as followsTaxInq2In(St12+S2)+S, 9withτ12=exp(-△g1/RT,τ2=eXp(-△g2/RT),l1=5(r1-q1)(r1-1),l2=5(r2q2)(r21),S=q1x/(q1x1+q2x2),S2=1-s,v1=rx/(r1x+r2x2),v2=1-v,r2=0.92,q2=14,r1=2.1055,q1=1.9720(3)gmehling et al. gave energy parameters of the Wilson and NRTL and UNIQUAC models for theethanol-water system which are listed in Table 3. A,2, A2l, T 12, t 2 were calculated from Eqs. (1)-(3)andare listed in Table 4Table 3 Energy parameters of wilson and NRTL and UNIQUAC modelsNRTLUNIQUACSystemEthanol( 1)-water(2)158573314866-1701185912600.1803547003811Table 4 Parameters of Wilson and nrtl and UNIQUAC modelsWilsonNTTUNIQUACSystemEthanol(1)water(2)0.16240.9119-0.68632.38520.18030.80200.85753.3 CorrelaticIn order to compare the experimental data with correlation for ethanol-water-KF and ethanol-waterK_, systems, the composition of water phase corresponding to the same composition of the ethanolphase and that of ethanol phase with the same composicorrelations and the results are listed in tables 1 andTH中国煤化工 predicted from theCN Ghe correlated andexperimental results are in good agreement3 #H XU Wen-you et al. Measurement and Correlation of Liquid-Liquid Equilibrium Data for Ethanol-Water-KF and Ethanol-Water-KCO, SystemsNOTATIONDebve-Huickel coeA312, A2 Interaction energy between ethanol and water (/mol)Ionic strength(molkg)M.Salt mass molar concentration(molkGas constant J/(mok K)Volume parameter of ethanolArea fraction of ethanolArea fraction of waterStoichiometrical numbers of positive and negative ionsf pure water(ml/molMolar fraction of ethanol and water in ethanol phaCharge numbers of ions∠MzxCharge numbers of positive and negative ionsNRTL equation sequence parameterβ3°,A2, Ae Wilson equation parameterst2,1NRTL and UNIQUAC equations parametersREFERENCES[1] Gmehling J, Onken U, Art W. Vapor-Liquid Equilibrium Data Collection: Aqueous-Organic Systems [M]. Frankfurt: DeutscheGesellschaft fur Chemisches Apparatewesen, 1981. 136, 157, 691[2] Card J C, Farrell L M. Separation of Alcohoh-Water Mixtures Using Salts, ORNL/MIT-338 [R]. Oak Ridge: Oak Ridge3]XU WY. Separation of Ethanoh-Acetone-Butanol-Water System Using Potassium Carbonate []. The Chinese Journal ofProcess Engineering, 2001, 1(3): 318-320(in Chinese(41 XU WY. Measurement and Correlation of Liquid-Liquid Equilibrium Data for Acetonitrile-Water-Potassium Fluoride andAcetonitrile-Water-Potassium Carbonate Systems [J] Journal of Chemical Industry and Engineering, 2001, 52(8): 742-745 (in5] Stephen H, Stephen T. Solubilities of Inorganic Compounds, TerrJV凵中国煤化工 Ltd,x4CNMHG[6] Silvester L E, Pitzer KS. Thermodynamics of Electrolytes [J]. J. Phys. Chem., 1977, 81(19): 1822-1828[7 Roy rN, Pitzer ks Thermodynamics of Aqueous Carbonate Solutions []. J. Chem. Thermodynamics, 1984, 16: 303-305