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Prediction of vapor-liquid equilibria of binary mixtures using quantum calculations and activity coefficient models

In this work, the conductor-like screening model COSMO-SAC (segment activity coefficient) obatained from the density functional theory calculations DFT-VWN-BP with basis set DNP (double numerical basis set augmented with polarization function). The molecular-single sigma profiles were generated by using COSMO calculations. | Journal of Chemistry, Vol. 47 (5), P. 547 - 551, 2009 PREDICTION OF VAPOR-LIQUID EQUILIBRIA OF BINARY MIXTURES USING QUANTUM CALCULATIONS AND ACTIVITY COEFFICIENT MODELS Received 2 May 2008 PHAM VAN TAT Department of Chemistry, University of Dalat ABSTRACT In this work, the conductor-like screening model COSMO-SAC (segment activity coefficient) obatained from the density functional theory calculations DFT-VWN-BP with basis set DNP (double numerical basis set augmented with polarization function). The molecular-single sigma profiles were generated by using COSMO calculations. The vapor-liquid equilibria (VLE) for three binary mixtures water(1) - ethanol(2), methanol(1) - benzene(2) and toluene(1) chlorobenzene(2) were calculated from these sigma profiles. The VLE data of these mixtures turn out to be in good agreement with experimental data as far as such data resulting from the activity coefficient models Wilson [1] and NRTL (non-random two-liquid) [2]. RMS error, mean relative deviation of pressure (MRDp) and mean deviation of vapor composition (MDy) are less than 0.087, 9.052 and 0.065, respectively. Keywords: Vapor-liquid equilibria, conductor-like screening model COSMO-SAC. I - INTRODUCTION Prediction of vapor-liquid equilibria is a important goal in physical chemistry and chemical engineering. Reliable information of vapor-liquid equilibria is most decisive for developing the usual liquid fuels. The experimental measurement of VLE can be expensive and sometimes highly challenging in several industrial applications. Recent years, trustworthy theoretical methods based on ab initio quantum calculations [3, 4] and Gibbs ensemble Monte Carlo simulation technique [5, 6] are thus very desirable. The theoretical methods conductor-like screening model for real solvents COSMO-RS proposed by Klamt et al. [3] and the conductor-like screening model COSMO-SAC (segment activity coefficient) developed by Lin et al. [4] were used for prediction of vapor-liquid and .