2-Methyl Pyrazine를 포함하는 삼성분 혼합계의

등온 기액평형과 과잉 몰부피

Theories and Applications of Chem. Eng., 2002, Vol. 8, No.1

화학공학의 이론과 응용 제 8권 제 1 호 2002년

한규진 , 오종혁 , 원동복 , 박소진

충남대학교 공과대학 화학공학과

Isothermal Vapor-Liquid Equilibria and Excess Molar Volumes

for the Ternary Mixtures Containing 2-Methyl Pyrazine

Kyu-Jin Han, Jong-Hyeog Oh, Dong-Bok Won, So-Jin Park

Department of Chemical Engineering, Chungnam National University

INTRODUCTION

2-Methyl pyrazine(2MP) has several commercial applications, especially as a pharmaceutical intermediate compound for anti tuberculosis. However the synthesis of 2MP include separation problem of this nitric compound(2MP) from the aqueous reaction products because they have azeotropic point. For finding appropriate entrainers and for designing of these separation processes properly, phase behavior and thermodynamic properties of relate mixtures containing 2MP have to be known. In our previous works[1,2], weve therefore reported isothermal VLE and LLE data and excess molar volumes for some binary mixtures of 2MP with water or solvents; n-hexane, cyclohexane, n-heptane, MCP, MCH and ethyl acetate.

The present work on the isothermal VLE data at 353.15K and VE at 298.15K for the binary systems of EA(1)+cyclohexane(2) and EA(1)+n-hexane(2) and for the ternary systems of EA(1)+cyclohexane(2)+2MP(3) and EA(1)+ n-hexane(2)+2MP(3) at the same conditions are in a systematic study on thermo-physical data of the 2MP mixtures. The experimental binary VLE data were correlated using common gE model equations; Margules, van Laar, Wilson, NRTL. While the ternary measured VLE data were compared with calculated data by correlated binary Wilson parameters. The experimental excess molar volumes were correlated using Redlich-Kister polynomial and Cibulkas equation for the binary and ternary systems, respectively.

EXPERIMENTAL

All the chemicals used in this investigation were of analytical commercial grade of purity and doubly distilled water was used. The purity of chemicals was checked by gas chromato-graphy and by measuring densities and comparing with those reported in the literature.

Isothermal VLE measurement has been carried out using headspace gas chromatography (HSGC) for all the binary and ternary systems. The HSGC consists of a gas chromatograph (HP 5890 series II) and a headspace sampler (HP19395A), which has an electro-pneumatic sampling system and a precision thermostat, having an accuracy of 0.1 K. HP-FFAP (Hewlett-Packard, polyethylene glycol-TPA modified, 50m0.2mm 0.3m) capillary column and a thermal conductivity detector were used for the analysis. By HSGC method, only equilibrated vapor phase is automatically analyzed with a help of electro-pneumatic sampling system, while the liquid phase compositions are calculated with thermodynamic relations and mass balance starting from the feed compositions. The accuracy of the calculated mole fraction is 1×10-4.

Excess molar volumes VE are calculated from directly measured densities of the pure and mixture samples. Densities are measured using a digital vibrating glass tube densimeter (Anton Paar, model DMA 48, Graz, Austria). The uncertainty of this densimeter is less than 1×10-4 gcm-3. Before each set of measurements, the apparatus was calibrated with doubly distilled water and dried air. Mixture samples were prepared in ca. 5ml vial by mass using a microbalance with a precision of 1×10-5g, charging the heavier component first to minimize vaporization effects The detail operating procedures have been described elsewhere [1,3,4].

RESULTS AND DISCUSSIONS

The experimental VLE compositions and pressures for EA(1)+cyclohexane(2) and EA(1)+n-hexane(2) binary systems at 353.15 K are determined by using HSGC method. Both binary systems have minimum boiling azeotropes at the experimental condition at the composition of x1=0.544 for the former and x1=0.370 for the latter systems. All the calculated and experimental vapor phase equilibrium data were agreed very well and their deviations were less than 0.1 mole %.

The experimental data for the ternary systems of EA(1)+cyclohexane(2) +2MP(3) and EA(1)+n-hexane(2)+2MP(3) at 353.15K are plotted in Figure 1, respectively. The ternary VLE data were predicted by using following Wilson equation (1) with parameters obtained from the experimental constituent binary data.

[eqn: ln gamma_i = - ln left( SUM_j=1^3 x_j `A_ij right) +1 - SUM_k=1^3 {x_j`A_ij} over {SUM_j=1^3 x_j `A_kj} `]	(1)

The experimental VLE data were compared with calculated values and showed good agreements. The Wilson parameters for cyclohexane(1)+2MP(2), n-hexane(1)+2MP(2) and EA(1)+2MP(2) binary mixtures were taken from our previous work[1].

The excess molar volumes for the multi-component mixtures are calculated from the measured densities of pure substances and mixtures from eq. (2). The experimental excess molar volumes for the binary systems correlated with five-parameter Redlich-Kister polynomial equation.

[eqn: V^E `=` {SUM_i `x_i `M_i} over {rho_m} - SUM_i `left( {x_i `M_i} over rho_i right) `]	(2)

[eqn: V_12 `=` x_1 `x_2 ` SUM_i=1^5 `A_i `(x_1 -x_2 )^i-1 `]	(3)

Both binary systems show positive deviations from the ideal solution .For the ternary system, excess molar property data are correlated with following Cibulkas equation[5] as a modification of Radojkovi□s equation[6]

[eqn: V_123^E `=` V_12*^E + V_23*^E + V_13*^E + x_1`x_2`x_3` (A_1 +A_2`x_1 +A_3`x_2 )`]	(4)

Where [eqn: V_12*^E`], [eqn: V_23*^E`] and[eqn: V_13*^E`] represent the excess molar volumes and x1, x2 and x3 are mole fractions of each components of ternary system.

The correlated values agreed well with experimental data with the standard deviations of 0.0339 for EA(1)+cyclohexane(2)+2MP(3) and 0.1201 for EA(1)+ n-hexane(2)+2MP(3) system.

CONCLUSION

The new isothermal VLE data at 353.15K and VE at 298.15K were experimentally determined for the binary systems of EA(1)+cyclohexane(2) and EA(1)+n-hexane(2) and also for the ternary systems of EA(1)+cyclohexane(2) +2MP(3) and EA(1)+n-hexane(2) +2MP(3). The binary VLE data have minimum boiling azeotropes and they were correlated very well with common gE model equations. Besides, the calculations using binary Wilson parameters gave satisfactory predictions of ternary VLE data. The measured binary VE show positive deviations from the ideality and they were correlated well with the Redlich-Kister polynomial, while the Cibulkas equation was applied well for the ternary systems.

ACKNOWLEDGEMENTS

This work was supported by grant No. 2000-1-30700-011-2 from the Basic Research Program of the Korea Science & Engineering Foundation.

REFERENCES

[1] Park, S.J. et al., Fluid Phase Equilibria, 180 (2001) 361-373

[2] Park, S.J. et al., HWAHAK KONGHAK, 39 (2001) 692-697

[3] Oh, J.H. and Park, S. J., J. Chem. Eng. Data, 43 (1998) 1009-1013.

[4] Oh, J.H. and Park, S. J., J. Chem. Eng. Data, 42 (1997) 517-522.

[5] Cibulka, I., Collect. Czech. Chem. Commun., 47 (1982) 1414

[6] Radojkovi□, N., Tasi□, A., Grozdani□, B. and Mali□, M., J. Chem. Thermodyn., 9 (1977) 349

Figure 1. Isothermal VLE for the ternary systems of EA(1)+cyclohexane(2) +2MP(3) and EA(1)+n-hexane(2)+2MP(3) at 353.15K.

( ● : liquid phase, ○ : vapor phase)

Figure 2. Line of constant excess molar volumes(cm3mol-1) for the ternary systems of EA(1)+cyclohexane(2)+2MP(3) and EA(1)+n-hexane(2)+2MP(3) at 298.15K.