Equilibrium Data For Systems Research Articles

Long range corrections for inhomogeneous fluids containing a droplet or a bubble

ABSTRACT Long range corrections for molecular simulations of inhomogeneous fluids with a spherical interface are presented. Correction terms for potential energy, force and virial are derived for the monatomic Lennard–Jones fluid. The method is generalised to the Mie potential and arbitrary molecular structures, employing a numerically efficient centre of mass cut-off scheme. The results are validated by a series of droplet simulations for one-centre and two-centre Lennard–Jones fluids with different cut-off radii r c . Systems with provide a check of self-consistence. Further, a system containing a bubble is investigated for the one-centre Lennard–Jones fluid. The equilibrium properties are almost completely independent on the cut-off radius. In comparison with vapour–liquid equilibrium data for systems without a curved interface, all properties show the expected behaviour. Simulation data are used to approximate the surface tension, which is in good agreement with the findings for planar interfaces, thus verifying the present corrections.

Liquid−Liquid Equilibrium for Ternary Systems Containing Ethyl Esters, Anhydrous Ethanol and Water at 298.15, 313.15, and 333.15 K

The most common method used for purifying biodiesel is washing with water. During the biodiesel washing process, two phases are formed, a water-rich phase and an ester-rich one. For this reason, knowledge of the corresponding phase equilibrium is an important step in optimizing the final purification of biodiesel. The objective of this work was to investigate the liquid−liquid equilibrium related to some esters of interest in the production of ethylic biodiesel, in particular the equilibrium data for systems containing ethyl laurate/ethyl myristate + ethanol + water at 298.15, 313.15, and 333.15 K. The data obtained were correlated with the cubic-plus-association equation of state (CPA EoS). It was shown that this model was able to provide a very good description of the phase diagrams of the systems studied.

Liquid-liquid Equilibria of ([C2mim][EtSO4] + Thiophene + 2,2,4-Trimethylpentane) and ([C2mim][EtSO4] + Thiophene + Toluene): Experimental Data and Correlation

Liquid + liquid equilibrium data for (1-ethyl-3-methyl imidazolium ethyl sulfate + thiophene + 2,2,4-trimethylpentane) and (1-ethyl-3-methyl imidazolium ethyl sulfate + thiophene + toluene) have been determined at 298.15 K and atmospheric pressure. The ionic liquid has a great capacity to dissolve not only thiophene but also the toluene, being practically immiscible with 2,2,4-trimethylpentane. Equilibrium data of systems with toluene have been fairly well correlated with the NRTL and UNIQUAC equations but for the system with 2,2,4-trimethylpentane high deviations have been found with both equations.

(Liquid + liquid) equilibria of ternary and quaternary systems containing n-hexane, toluene, m-xylene, propanol, sulfolane, and water at T = 303.15 K

(Liquid + liquid) equilibrium data for ternary and quaternary systems containing n-hexane (C 6H 14), toluene (C 7H 8), m-xylene (C 8H 10), propanol (C 3H 8O), sulfolane (C 4H 8SO 2), and water (H 2O) were measured at T = 303.15 K. Phase diagrams of { w 1C 4H 8SO 2 + w 2C 7H 8 + (1 − w 1 − w 2)C 6H 14}, { w 1C 4H 8SO 2 + w 2C 8H 10 + (1 − w 1 − w 2)C 6H 14}, { w 1C 4H 8SO 2 + w 2C 3H 8O + w 3C 7H 8 + (1 − w 1 − w 2 − w 3)C 6H 14} and also systems containing water: { w 1C 4H 8SO 2 + w 2H 2O + w 3C 7H 8 + (1 − w 1 − w 2 − w 3)C 6H 14} and { w 1C 4H 8SO 2 + w 2H 2O + w 3C 8H 10 + (1 − w 1 − w 2 − w 3)C 6H 14} ( w = mass fraction) were obtained at T = 303.15 K. The (liquid + liquid) equilibrium data of the systems were used to obtain interaction parameters in non-random two-liquid (NRTL) and universal quasi-chemical theory (UNIQUAC) activity coefficient models. These parameters can be used to predict equilibrium data of ternary and quaternary systems. The root mean square deviations (RMSDs) using these models were calculated and reported. The partition coefficients and the selectivity factors of solvents for extraction of toluene or m-xylene from n-hexane at T = 303.15 K are calculated and presented. The experimental selectivity factors of sulfolane for the system { w 1C 4H 8SO 2 + w 2C 7H 8 + (1 − w 1 − w 2)C 6H 14} at T = 298.15 K and T = 323.15 K were taken from the literature and the influence of temperature on the extraction of toluene was also investigated. The phase diagrams for the ternary and quaternary systems including both the experimental and correlated tie lines are presented. The tie-line data of the studied systems were also correlated using the Hand equation and the correlation parameters are calculated and reported.

Thermodynamics of tautomeric solutions: vapour-liquid equilibrium for acetylacetone-alcohol mixtures

Isothermal vapour-liquid equilibrium data for systems containing the keto and enol tautomers of acetylacetone and an alcohol are reproduced using a chemical model. The model uses the thermodynamic equilibrium constant for tautomerisation, the four association constants for the alcohol, the solvation constants between the tautomers and the alcohol and the NRTL model to describe the activity coefficients of the pseudo-three components. Calculated vapour-liquid equilibrium values compare well with literature ones for six binary systems.

Applicability of the unifac method for prediction of binary and ternary vapour-liquid equilibrium data in systems formed by hydrocarbons and alcohols

The problem of the prediction and correlation of vapour-liquid equilibria in binary and ternary systems has been discussed and the limitation in the applicability of the UNIFAC method for this purpose has been pointed out. The total pressure data for six ternary systems (cyclohexane-2-propanol-benzene, cyclohexane-ethanol-benzene, n-heptane-1-propanol-benzene, n-hexane-ethanol- benzene, cyclohexane-methanol-benzene, cyclohexane-ethanol-toluene) and eighteen corresponding binary mixtures (benzene-2-propanol, benzene-cyclohexane, cyclohexane-2-propanol, cyclohexane-ethanol, cyclohexane-benzene, ethanol-benzene, ethanol-benzene, n-hexane-benzene, n-hexane-ethanol, benzene-1-propanol, benzene- n-hexane, n-heptane-1-propanol, cyclohexane-methanol, benzene-cyclohexane, benzene-methanol, cyclohexane-ethanol, benzene-cyclohexane, benzene-ethanol) have been selected and correlated by means of the Redlich-Kister equation and compared with the results predicted by the UNIFAC method. The correlation and the prediction results have been fully discussed from the point of view of intermolecular interactions and some recommendations have been made on the use of the methods investigated for such calculations.

Computer-aided graphics in distillation columns design

A portable computer simulator has been developed to aid in the design of distillation columns with either an internal reboiler or an open steam. The program (PANCHN) uses the traditional Ponchon-Savarit method and a modified form which incorporates a more exact analysis of the feed region in the case of a partially vaporized feed. Examples of this simulation program and its computer graphics output are presented to illustrate the program's capability and usefulness in studying the effect of operating parameters in the design of distillation columns. While equilibrium data for some systems are stored in its data bank, the present simulator has the flexibility of reading equilibrium data for other systems, as well as overriding stored data.

COMPUTER-AIDED GRAPHICS OF LIQUID-LIQUID EXTRACTION

An algorithm has been developed and tested for steady-state liquid-liquid extraction, using rectangular coordinates. It is capable of handling common types of stagewise contact, i.e., single stage extraction, multistage cross-current, and continuous countercurrent multistage extraction. The results depend on the nature of the extraction scheme and the extent of separation desired. While equilibrium data for some systems are stored in its data bank, the present portable computer simulator ( LIQEXT) has the flexibility of reading equilibrium data for other systems, as well as overriding stored data Both design and rating cases can be performed. In the design mode, i.e., given the feed and solvent rates and the outlet concentration, it calculates the number of stages, the exit stream flow rates, and the concentration profile. In the rating ( or simulation) mode, i.e., given the feed and solvent rates, and the number of stages, it computes the exit streams flow rates and compositions, and the concentration pr...

Liquid-vapour equilibria. XXIX. Measurement of equilibrium data in systems with high equilibrium ratio of the components

Liquid-vapour equilibria. XXIX. Measurement of equilibrium data in systems with high equilibrium ratio of the components