Jiding Li

A gE model for single and mixed solvent electrolyte systems: 1. Model and results for strong electrolytes

Abstract Li, J., Polka, H.-M. and Gmehling, J., 1994. A gE model for single and mixed solvent electrolyte systems. 1. Model and results for strong electrolytes. Fluid Phase Equilibria, 94: 89-114. A gE model for electrolyte systems has been developed which is based on results from statistical thermodynamics and takes into account the interactions between all species present in the electrolyte solution. In this model the electrolyte solution is treated as a nonelectrolyte solution plus charge interactions, and it is assumed that the charge interactions show two effects, direct and indirect. The indirect effect differs not only from the long-range electrostatic interaction but also from the short-range interaction for nonelectrolyte solutions. With the help of a large data base the required parameters (164 in number) have been fitted for 10 solvents, 18 cations and 10 anions. The model parameters have been used to calculate the VLE behavior, osmotic coefficients and mean ion activity coefficients for a large number of systems with high accuracy.

Further development of the PSRK model for the prediction of gas solubilities and vapor-liquid -equilibria at low and high pressures II

Abstract To expand the range of applicability of the group contribution equation of state PSRK, 10 new main groups for the gases SO 2 , NO, N 2 O, He, Ne, Kr, Xe, HCl, HBr and SF 6 have been added to the already existing 59 main groups (50 main groups from original UNIFAC plus 9 groups for the gases NH 3 , CO 2 , CH 4 , O 2 , Ar, N 2 , H 2 S, H 2 and CO). The group interaction parameters for the new and already existing main groups have been determined for 128 group pairs with the help of experimental VLE data for low boiling substances. Typical results for gas solubilities and VLE using the PSRK model are presented. Using the idea of effective van der Waals volumes and surface areas for the subgroups CH 3 , CH 2 , CH and C, reliable results are also obtained for highly asymmetric systems over a large temperature and pressure range.

Prediction of vapor-liquid equilibria for asymmetric systems at low and high pressures with the PSRK model

Abstract The idea of effective Rk*, Qk* for the subgroups CH3, CH2, CH and C of UNIFAC in PSRK is proposed. Based on this idea, an empirical expression has been developed, allowing the reliable prediction of vapor–liquid equilibria for asymmetric systems at low and high pressures with the help of the PSRK model.

Prediction of the solubility and gas-liquid equilibria for gas-water and light hydrocarbonwater systems at high temperatures and pressures with a group contribution equation of state

Abstract A group contribution equation of state has been proposed. The model is based on the Weidlich-Gmehling modified UNIFAC and Soave-Redlich-Kwong equation of state, in which the modified Huron-Vidal excess Gibbs free energy mixing rule is used, the residual term of the modified UNIFAC is changed a little and the combinatorial term is improved. Nine interaction parameters between gas groups CO 2 , CO, N 2 , H 2 , H 2 S, CH 4 , C 2 H 6 , C 3 H 8 , C 4 H 10 and water are fitted. The model parameters have been used to predict solubility and gas-liquid equilibria for seven gas-water, and thirty-nine light hydrocarbonwater data sets in large temperature and pressure ranges (278–637 K, 1–1972 bar). The predicted results are in good agreement with the experiments, which makes it possible that the real phase behavior at high temperatures and pressures for gas-water and light hydrocarbonwater systems which are of interest to petroleum and natural gas exploitation industries, can be predicted reliably.

A gE model for single and mixed solvent electrolyte systems: 2. Results and comparison with other models

Abstract Polka, H.-M., Li, J. and Gmehling, J., 1994. A g E model for single and mixed solvent electrolyte systems. 2. Results and comparison with other models. Fluid Phase Equilibria , 94: 115-127. A new g E model describing the behaviour of single and mixed solvent electrolyte systems is used to calculate vapour-liquid equilibria of 185 ternary systems (two solvents one salt), and vapour pressure, osmotic coefficients and activity coefficients of 362 binary systems (one solvent one salt). The results are compared with the models of Sander, Macedo, Pitzer, Bromley and Chen. For the large data base used, the new model improves the results not only for the description of single solvent data but also for the calculation of VLE for mixed solvent systems. Despite the relative improvement compared to other models, in certain cases serious deviations are obtained.

Vapor–liquid equilibrium data and their correlation for binary systems consisting of ethanol, 2-propanol, 1,2-ethanediol and methyl benzoate

Abstract Isobaric vapor–liquid equilibrium data for the systems ethanol+1,2-ethanediol, ethanol+methyl benzoate, 2-propanol+1,2-ethanediol, 2-propanol+methyl benzoate and ethanol+2-propanol were measured at atmospheric pressure (0.1013 MPa) with a CP-I dual circulation vapor–liquid equilibrium still. The results of the correlation of the experimental data with three thermodynamic models, DORDF, UNIQUAC and NRTL, were compared.

Status and results of group contribution methods

Group contribution methods, such as UNIFAC or ASOG can be successfully applied to the prediction of the real behavior of non - electrolyte mixtures. Therefore these methods are used worldwide in the different process simulators for the synthesis and design of separation processes. Since the well known group contribution methods still show some weaknesses a modified version of the UNIFAC method has been de- veloped. Furthermore the solution of groups concept has been applied to equations of state. This allows the simultaneous description of sub and supercritical compounds and at the same time the prediction of other important properties, such as densities, enthalpies, etc. .

Vapor-liquid equilibrium properties for confined binary mixtures involving CO 2 , CH 4 , and N 2 from Gibbs ensemble Monte Carlo simulations

The effects of solid-fluid interactions on the vapor-liquid phase diagram, coexistence density, relative volatility and vaporization enthalpy have been investigated for confined binary systems of CO2-CH4, CO2-N2 and CH4-N2. The Gibbs ensemble Monte Carlo (GEMC) simulation results indicate that the confinement and the solid-fluid interaction have significant influences on the vapor-liquid equilibrium properties. The confinement and the strength of the solid-fluid interaction make the p-xi phase diagram move to higher pressure regions. They also make the two-phase region become narrower for each binary mixture. The strength of the solid-fluid interactions can cause increases in the coexistence liquid and vapor densities, and cause the decrease of the relative volatility and the vaporization enthalpy for the systems studied. As the pore width is decreased, the two-phase region of the binary mixture becomes narrower.

Activity coefficient data and their correlation for tributyl phosphate—hydrocarbon and uranyl nitrate tributyl phosphate complex—hydrocarbon solutions

Abstract Activity coefficient data for 20 binary and seven ternary systems composed of nC 6 H 14 , nC 7 H 16 , nC 8 H 18 , C 6 H 6 , cy-C 6 H 12 , CCl 4 , CHCl 3 , (C 4 H 9 ) 3 PO 4 and UO 2 (NO 3 ) 2 · 2((C 4 H 9 ) 3 PO 4 ) have been measured at 25 °C by head-space gas chromatography. The results of correlation of the experimental data with three thermodynamic models, the Scatchard-Hildebrand, NRTL and UNIQUAC models, are compared. All three models can be used to predict activity coefficient data for ternary systems by means of binary parameters.

A study of scatchard-hildebrand solution theory for metal solvent extraction systems

In this paper the thermodynamic properties of two important extractants in hydrometallurgy (D2EHPA and EHEHPA) are studied. The activity coefficients of various diluents in D2EHPA-hydrocarbon binary systems are measured by gas chromatographic headspace analysis. The experimental data are regressed by using the Scatchard-Hildebrand solution theory. After revision of the mixing entropy, departures from the geometric mean of the cohesive energy are determined. Some regularities have been found. A new parameter δ12 indicating the interaction energy between unlike molecules has been defined and discussed. The extension of Scatchard-Hildebrand equation from binary systems to multicomponent systems with metal complexes in organic phase (EHEHPA-nC7H16-CoSO4-CuSO4 extraction system) is also studied. The real “thermodynamic equilibrium constants” for metal extraction reactions have been determined.