1844
Ind. Eng. Chem. Res. 2010, 49, 1844–1847
Experimental Determination of Vapor-Liquid Equilibria and Excess Enthalpy Data for the Binary System 2-Methyl-1-butanol + 3-Methyl-1-butanol as a Test Mixture for Distillation Columns Sarah Thiede,† Sven Horstmann,*,† Thomas Meisel,‡ Jacobus Sinnema,‡ and Ju¨rgen Gmehling†,§ LTP (Laboratory for Thermophysical Properties) GmbH, Associated Institute at the UniVersity of Oldenburg, Marie-Curie-Strasse 10, D-26129 Oldenburg, Germany, Dow Haltermann Custom Processing, Dow Chemical Company, B-9130 Kallo (Kieldrecht), Belgium, and Department of Industrial Chemistry, UniVersity of Oldenburg, D-26111 Oldenburg, Germany
Isothermal vapor-liquid equilibrium data for 2-methyl-1-butanol + 3-methyl-1-butanol were measured using a static synthetic method at temperatures of 343.15, 353.69, 368.15, and 404.45 K. Additionally, excess enthalpy (HE) data for the system were measured with an isothermal flow calorimeter at 363.13 K. The experimental data were correlated using temperature dependent interaction parameters for the NRTL model which were fitted to all measured data. The system was chosen as a test system for distillation columns. 1. Introduction For the accurate design and optimization of separation processes like distillation columns, reliable knowledge of the phase equilibrium behavior is required. Active amyl alcohol (2-methyl-1-butanol) and isoamyl alcohol (3-methyl-1butanol) are main components of fusel oil. The similar volatilities and chemical structures of the pure components lead to separation factors close to unity, which complicates the separation by distillation. For that reason 2-methyl-1butanol and 3-methyl-1-butanol can be used as a test system for distillation columns. Different test mixtures are available in the literature,1 but most of them show larger separation factors. In this work, isothermal P-x data measured with the static method are presented for the system 2-methyl-1-butanol + 3-methyl-1-butanol at 343.15, 353.69, 368.15, and 404.45 K. Excess enthalpy (HE) data were measured at 363.13 K, which are important for a correct description of the temperature dependence of activity coefficients following the GibbsHelmholtz equation:
(
∂ ln γi ∂1/T
)
P,x
)
HEi R
(1)
The experimental vapor-liquid equilibrium (VLE) and HE data of this work are presented together with an NRTL correlation which can be used in simulation software packages. 2. Experimental Section 2.1. Materials. 2-Methyl-1-butanol and 3-methyl-1-butanol were purchased from a commercial source. Both components were dried over molecular sieves and afterward distilled and degassed as described by Fischer and Gmehling.2 The final purity and water content were determined by gas chromatography and Karl Fischer titration and are given in Table 1. * To whom correspondence should be addresssed. Tel.: +49 441 36 11 19 0. E-mail:
[email protected]. † LTP, University of Oldenburg. ‡ DOW Chemical Company. § Department of Industrial Chemistry, University of Oldenburg.
2.2. Apparatus and Procedure. The VLE measurements (isothermal P-x data) were carried out in two different static devices following the principle proposed by Gibbs and Van Ness.3 For the measurement of the system 2-methyl-1-butanol (1) + 3-methyl-1-butanol (2) at 343.15 and 363.15 K, a computer operated static apparatus was used.4,5 For the measurements at 353.69 and 404.45 K a static apparatus operated manually2,6 was employed. The principle of the measurements is the same for both devices. The thermostated, purified, and degassed compounds were filled into the thermoregulated equilibrium cell by means of precise piston injectors. In the case of the computer-controlled equipment, the injectors were driven by stepping motors. In the other case, manual piston pumps (Model 2200-801, RUSKA) were used for the injection of the compounds. The pressure inside the equilibrium cell was measured with a calibrated pressure sensor (Model 245A, Paroscientific) or a dead weight pressure balance (Model 80005, Desgranges and Huot), respectively. For the temperature measurement a Pt100 resistance thermometer (Model 1506, Hart Scientific) was used in both cases. The feed compositions were determined from the known quantities of liquids injected into the equilibrium cell by piston injector. The liquid phase compositions in equilibrium were obtained by solving mass and volume balance equations which also took the vapor-liquid equilibrium into account. The experimental uncertainties for both setups are σ(T) ) 0.03 K, σ(P) ) 20 Pa + 0.0001(P/Pa), and σ(xi) ) 0.0002. For the determination of the excess enthalpy data a commercial isothermal flow calorimeter (Model 7501, Hart Scientific) described by Gmehling7 was used. In this apparatus, two syringe pumps (Model LC-2600, ISCO) provide a flow of constant composition through a calorimeter cell (placed in a thermostat) equipped with a pulsed heater and a Peltier cooler. The Peltier cooler is working at constant power, causing a constant heat loss from the calorimeter cell. To keep the temperature constant, this heat flow is compenTable 1. Properties of the Pure Components component
supplier
purity/%
water content/mass ppm
2-methy-1-butanol 3-methyl-1-butanol
Acros Acros
99.8 99.8
