(441g) Comprehensive Thermodynamic Modeling of Complex Mixed-Solvent Electrolyte Systems: An Investigation on Water-Hydrogen Chloride-Methanol Ternary System

Sina Hassanjani Saravi and Chau-Chyun Chen

Department of Chemical Engineering, Texas Tech University

The binary system of HCl + Water which was comprehensively presented in our previous thermodynamic modeling work [1] is extended to cover the ternary system of HCl + water + methanol. Prior studies on the HCl + water + methanol ternary system, a complex mixed-solvent electrolyte system, are rare. Lu et al. [2] reported experimental VLLE data (TPxy) for this system in atmospheric pressure and temperature range from 70 to 95 °C. Furthermore they calculated mean ionic activity coefficient based on Pitzer model up to 8 molal. Deyhimi et al. [3] determined mean molal activity coefficients for HCl in the mixture based on potentiometric data of a galvanic cell and modeled the system by use of Pitzer and Pitzer â?? Simonson â?? Clegg ion-interaction equations with HCl concentration limited to 5.75 molality at 298.15 K.

In this study, a comprehensive thermodynamic model is presented based on symmetric electrolyte Non-Random Two-Liquid (eNRTL) activity coefficient model. The model includes phase equilibrium properties such as vapor-liquid equilibrium and liquid-liquid equilibrium, calorimetric properties such as liquid enthalpy and heat capacity, and speciation properties such as molecular and ionic species concentrations. With use of binary interaction parameters accounting for molecule-molecule binary interactions and molecule-electrolyte interactions, the model accurately correlates and calculates all thermodynamic properties including mean ionic activity coefficient, osmotic coefficient, vapor pressure, boiling point, dew point, excess enthalpy and heat capacity. Hence, a reliable extrapolation can be performed to predict various properties over the entire range of concentrations. The VLE and LLE predictions along with calorimetric predictions for heat capacity and excess enthalpy of the solution are calculated and reported in this work. Speciation results which show the ionization of the solution species are depicted. Finally the ternary phase diagram which shows the two-phase region for this ternary system is illustrated.

References:

1. S.H, Saravi, C.-C., Chen â??Thermodynamic modeling of hydrochloric acid-water binary system with electrolyte Non-Random Two-Liquid (eNRTL) model,â? Manuscript in preparation
2. X. Lu, Y. Wang, J. Shi, â??The thermodynamics of concentrated nonaqueous strong electrolyte solutions -vapor - liquid equilibrium of hydrochloride - methanol mixture,â? Journal of Huagong Xuebao, 41 (1991) 695-701
3. F. Deyhimi, Z. Karimzadeh, M. Abedi, â??Pitzer and Pitzerâ??Simonsonâ??Clegg ion-interaction modeling approaches: ternary HCl + methanol + water electrolyte system,â? Journal of Molecular Liquids, 150 (2009) 62â??67