Isothermal vapour-liquid equilibria data of methanol + propan-2-OL, methanol + 2-methyl propan-2-OL + 2-methylpropan-2-0L binary mixtures at 333.15k

Abstract

The vapour-liquid equilibria (VLE) data of methanol + propan-2-ol + 2-methylpropan-2-ol binary mixtures are investigated at 333.15k, using gas chromatographic technique. For binary mixtures, the total pressure, the compositions of the components in the vapour phase are obtained from the instrument and these data are then used to calculate the second virial coefficients of pure components to account for the deviations of these mixtures from ideal solution behaviour. The excess Gibbs free energies of mixing for these binary systems are then determined. The y-x plots reveals that the mixtures methanol + propan-2-ol and methanol +2-methylpropan-2-ol deviate strongly from ideal solution behaviour. The excess Gibbs free energies (GE) of mixing for these binary systems are negative quantities, confirming negative deviations from ideality. Minimum GE value of 450 J.mol-1 is obtained for methanol + 2-methylpropan-2-ol mixtures at 0.45 mole fraction of methanol. Methanol + propan-2-ol mixtures exhibit a minimum GE value of 100 J mol-1 at 0.5 mole fraction of methanol. The least minimum GE value of 15 J. mol-1 is obtained for propan-2-ol +2-methyl propan-2-ol mixtures at 0.5 mole fraction of propan-2-ol. The consistency of these data is verified using Wilson's model for calculating GE values. The calculated change in Gibbs free energies (GEcalc) obtained were in good agreement with the experimentally determined GE values. KeyWords: VLE, Spectrometric, Deviation, Excess, Ideality. (Global Journal of Pure and Applied Sciences: 2002 8(4): 483-490)