Jørgen Mollerup

A note on excess Gibbs energy models, equations of state and the local composition concept

Abstract A density-dependent local composition expression for the residual energy is derived from a generalized NRTL expression for the excess energy and the van der Waals fluid theory. Integration of this expression yields a volume-dependent expression for the Helmholtz energy from which equations of state utilizing the local composition concept are derived and which in the high-density limit contain the well-known activity coefficient models. The local composition versions of the Carnahan—Starling—van der Waals, the Redlich—Kwong—Soave and the Peng—Robinson equations of state are derived. It is further shown that the group contribution versions of the NRTL, the Wilson and the UNIQUAC excess models may be derived from the generalized NRTL expression for the residual energy when applied to groups instead of molecules. It is thus demonstrated that all current local composition activity-coefficient models can be derived from a local composition version of the van der Waals equation of state using different sets of assumptions. In the same way the van Laar, the Scatchard—Hildebrand and the Flory—Huggins activity coefficient models are obtained from the van der Waals equation of state using the original mixing rules.

Mass transfer properties of monoliths

The mass transfer properties of polyglycidylmethacrylate–ethylenedimethacrylate monolithic ion-exchangers (convective interaction media disks) were evaluated. As a reference material, the particulate ion-exchanger Source 30 was selected. The model proteins lysozyme, bovine serum albumin, and IgG were loaded at different concentrations and velocities. The mass transfer zones obtained with the monoliths were affected by neither the linear flow velocity nor the protein concentration in the mobile phase. The reduced height equivalent to one theoretical plate (HETP) of monoliths were independent of the reduced velocity. This was not the case for the particulate material.

Whey proteins as a model system for chromatographic separation of proteins

Although chromatographic separation of whey proteins has been considered too expensive, whey may serve as an excellent model mixture to investigate and validate the use of simulation tools in the development and optimization of chromatographic separations and the outcome could easily be utilized since the model system has an intrinsic value. Besides, milk from transgenic animals could be an attractive source of pharmaceuticals which must be separated from the other proteins in the milk. Several whey proteins are of interest especially, alpha-lactalbumin, beta-lactoglobulins, immunoglobulins, lactoperoxidase, and lactoferrin. The scope of the project is to develop a consistent set of chromatographic data for whey proteins including isotherms, transport properties and scale-up studies and to develop the appropriate models for the anion exchangers Q-Sepharose XL, Source 30Q, Ceramic Q-HyperD F, and Merck Fractogel EMD TMAE 650 (S). In this work we have determined and correlated gradient and isocratic retention volumes in the linear range of the isotherm for alpha-lactalbumin, beta-lactoglobulin A and B, and bovine serum albumin at a pH from 6 to 9 at various NaCl concentrations.

Vapour-liquid equilibrium data for the systems C2H6 + N2, C2H4 + N2, C3H8 + N2, and C3H6 + N2

Abstract High pressure vapour-liquid equilibrium data for the C 2 H 6 + N 2 , C 2 H 4 + N 2 , C 3 H 8 + N 2 , and C 3 H 6 + N 2 systems are presented. The data are obtained isothermally in the range from 200 K to 290 K. For each point of data, temperature, pressure and liquid and vapour phase mole fractions are measured. Values for the vapour phase mole fractions are calculated from the obtained pressure, temperature and liquid phase mole fractions. The calculated values are compared with the experimental results, and it is found that the average mean deviation between calculated and experimental mole fractions is less than 0.009 for the systems considered in this work.

Separation of constituents of fish oil using supercritical fluids: a review of experimental solubility, extraction, and chromatographic data

Abstract The use of supercritical fluids, especially carbon dioxide, in separation of fish oil and derived compounds has increased the last decade due to the expected advantages of supercritical separation processes. In pursuit of the design of supercritical fluid separation processes, phase equilibria and pilot plant data are essential. In this paper we present a survey of literature references of experimental phase equilibria and solubility data on binary and multicomponent systems of supercritical fluids and fish oil or derived compounds, as well as experimental data on supercritical fluid extraction (SFE) and supercritical fluid chromatography (SFC). The fish oil related compounds include triglycerides, free fatty acids, fatty acid methyl and ethyl esters, cholesterol, α-tocopherol, phospholipids, squalene etc. The list of references include the experimental pressure and temperature ranges, the number of data points/experiments, and some remarks to the kind of measurements performed and components involved. The literature retrieval includes references to the end of 1992 and a few from 1993.

Correlation of thermodynamic properties of mixtures using a random-mixture reference state

Abstract Mollerup, J., 1983. Correlation of thermodynamic properties of mixtures using a random-mixture reference state. Fluid Phase Equilibria, 15: 189–207. A new random-nonrandom-mixture equation for the Helmholtz energy of a fluid mixture is suggested. It combines the van der Waals random-mixture theory with the nonrandom-liquid theory of the local-composition concept. It can thus correlate the properties of most nonelectrolyte solutions, including alcohol-hydrocarbon mixtures, with high accuracy, using the same number of binary-interaction parameters as an equation of stae wit the classical mixing rules. In the random-mixture limit the mixing rules reduce to the classical mixing rules suggested by van der Waals. Vapour-liquid equilibria are correlated using the random-nonrandom approach, classical mixing rules and the density-dependent NRTL mixing rule. The improvements obtained using the new model are most pronounced for mixtures where nonrandomness is large, owing to disparity between the polar and nonpolar interactions.

Calculation of phase diagrams of gas-hydrates

Abstract The phase diagrams of gas-hydrates are calculated using van der Waals and Platteeuws model with a Kihara spherical-core potential for the interaction between water and the guest molecule. The Kihara parameters are obtained independent of the mutual solubility of gas and water by constraining the model to the experimental dissociation pressures along the hydrate-ice-gas equilibrium line. Further, the fugacity coefficients in that region are close to unity wherefor the Kihara parameters are rather insensitive to the choice of equation of state. We use the Redlich-Kwong-Soave equation of state to calculate the fugacity the guest molecule. The gas solubility in the water rich phase is likewise calculated from the Redlich-Kwong-Soave equation of state combined with the DDLC (Density Dependent Local Composition) mixture model. The calculated phase diagrams comprise the hydrate-ice-gas, the hydrate-water-gas/condensate, the hydrate-gas-condensate, and the hydrate structure I - structure II - gas/condensate lines. Further we have investigated the influence of the uncertainty of the lattice cavity size on the location of the hydrate structure I - structure II - gas/condensate equilibrium curve which turns out to be very sensitive to even minor changes in the cavity size. The thermodynamically stable phase is determined by a total Gibbs energy minimization of the system.

Mutual solubilities of mono-alcohols and carbon dioxide: A review of experimental data

Abstract A list of references from a literature retrieval presenting experimental mutual solubilities and phase equilibria of binary systems of carbon dioxide and monoalcohols is given. The list includes the pressure and temperature ranges, the number of data points, and the references. The literature retrieval includes references to the middle of 1992.

Phase equilibria of fish oil fatty acid ethyl esters and sub- and supercritical CO2

Abstract Measurements of phase equilibria of fish oil fatty acid ethyl esters in sub- and supercritical carbon dioxide were performed at pressures from 2 to 22 MPa at the temperatures 283.2, 313.2, and 343.2 K. Experimental temperatures, pressures, mass fractions, mole fractions, equilibrium ratios, and densities are reported. The K-values of the esters depend strongly on the system pressure and the number of carbon atoms and have a weaker dependence on the degree of unsaturation and position of the double bonds. The data show that the selectivity is high and the solubility is low at low operating pressure, while at high operating pressure the selectivity is low but the solubility is high. More than 95% of the natural mixture was identified.

Solubility of fish oil fatty acid ethyl esters in suband supercritical carbon dioxide

Mutual solubilities and K-values of fish oil fatty acid ethyl esters, prepared from sand launce oil, and sub- and supercritical carbon dioxide have been measured in an apparatus originally designed for phase equilibrium, density and gasoil ratio measurements of reservoir fluids. The measurements were performed at pressures from 2 to 22 MPa at temperatures of 283.2, 313.2 and 343.2°K. Experimental temperatures, pressures, solubilities, K-values and densities are reported. The K-values of ethyl myristate, palmitate, oleate, eicosapentaenoate and docosahexaenoate are compared with published experimental binary and/or multicomponent data. Because both vapor and liquid solubilities are reported, such data are applicable in the design of supercritical extraction plants.