Prediction of excess free energies by a group solution model with application to alkane/ketone mixtures

The group solution model of Ratcliff and Chao for the excess free energies of liquid mixtures has been tested and found satisfactory for eight mixtures of alkanes and ketones. The model was tested by comparing experimental and predicted vapor-liquid equilibrium data. Group contribution functions were generated from experimental data on acetone/n-heptane mixtures at 65°C, and are presented. These functions allow the prediction of excess free energies of binary or multicomponent mixtures containing alkanes and ketones at 65°C. No experimental data is required. Predictions at temperatures close to 65°C, using the same functions, should be satisfactory.     

Prediction of heats of mixing by a group solution model with application to alkane/alcohol mixtures

Group solution models of liquid mixtures have been used previously to predict excess free energies of non-ideal systems. With increasing experimental data available on heats of mixing, the application of a similar model to excess enthalpies has been investigated. The model allows for both structural and group contributions to excess enthalpies. The former contribution is determined from experimental data on mixtures of alkanes. The group contribution has been determined at 25°C and 45°C for systems containing alkanes and alcohols. Predictions require no experimental data on the system in question, and are in good agreement with experiment. Limited extrapolation to other temperatures and group compositions should be satisfactory.     

Prediction of heats of mixing of liquid mixtures by an analytical group solution model

An analytical group solution model has been developed for the prediction of heats of mixing of liquid mixtures using the Wilson equation. This procedure obviates some of the limitations and inaccuracies of the previous model, and is well suited to computer calculation. It was tested for a wide range of alcohol/alkane mixtures and gives good results. The group Wilson parameters were generated from experimental data for methylene/hydroxyl mixtures at 15°C to 55°C. At temperatures within or close to this range, these group parameters allow prediction of heats of mixing of binary or multicomponent mixtures containing these two groups. No experimental data are required.     

Prediction of heats of mixing of liquid mixtures containing alkane,chloroalkane and alcohol by an analytical group solution model

An analytical group solution model (AGSM) previously developed for the prediction of heats of mixing has been applied to ternary group, ternary component mixtures. A simple temperature dependence is proposed for the group interaction parameters. Temperature independent coefficients were obtained in the temperature range 15 to 35°C for mixtures containing CH₂, OH and Cl groups. These coefficients allow the prediction of heat of mixing for binary or ternary mixtures containing alcohols, chloroalkanes and alkanes. Heats of mixing for the following systems are reported: 1-chlorobutane and 2-chlorobutane with both n-hexane and n-octanol at 35°C; n-octanol — n-hexane at 25 and 35°C; and three chords of the ternary system 1-chlorobutane — n-octanol — n-hexane at 25 and 35°C.     

Prediction of excess free energies of liquid mixtures containing aromatic hydrocarbons using a group solution model

The group solution model of Ratcliff and Chao for the excess free energies of liquid mixtures has been tested and found satisfactory for six mixtures of alcohols and aromatic hydrocarbons. The model was tested by comparing experimental and predicted vapor-liquid equilibrium data. The assumption that aliphatic and aromatic carbon atoms are equivalent appears satisfactory for the mixtures considered. Group contribution functions were generated from experimental data on ethanol/benzene mixtures at 45°C, and are presented. These functions allow the prediction of excess free energies of mixtures containing alcohols and aromatic hydrocarbons at 45°C. No experimental data is required. Predictions at temperatures close to 45°C, using the same functions, should be satisfactory. The group contribution functions were close to those generated previously from alcohol/alkane data. The latter may be used for predicting excess free energies of alcohol/aromatic hydrocarbon mixtures with little loss of accuracy.     

Heats of mixing of amine-alcohol systems. An analytical group solution model approach

Measured heats of mixing for amylamine with n-propanol, n-butanol and n-pentanol at 15°C and 35°C are reported. This experimental information has been used together with other literature heats-of-mixing data on amine-alcohol systems to test the ability of the extended Analytical Croup Solution Model (AGSM) to correlate and predict exothermic heats of mixing. Predictions for amine-alcohol systems, not included in the set of reference systems, are good with the exception of the predictions for systems containing methanol.     

Heats of mixing for ternary systems: n-Alkanes + Two n-Alcohols

Heats of mixing for 21 ternary systems of one n-alkane + two n-alcohols are reported at 25°C. Evaluation of four equations permitting the prediction of heats of mixing of ternary systems from binary data is made. Scatchard's modified equation for systems containing a polar component was found to be the most accurate.     

Prediction of excess free energies of liquid mixtures by an analytical group solution model

The group solution model of Ratcliff and Chao for the excess free energies of liquid mixtures has been put in analytical form using the Wilson equation. This procedure obviates some of the limitations and inaccuracies of the previous model, and is well suited to computer calculation. It was tested and found satisfactory for a wide range of mixtures containing the groups methylene and hydroxyl Group Wilson parameters were generated from experimental data for methylene/hydroxyl mixtures at 25°C to 95°C, and are given by At temperatures within or close to this range, these parameters allow the prediction of excess free energies of binary or multicomponent mixtures containing these two groups. No experimental data are required. Good results are obtained for aqueous systems.     

The excess enthalpy of gaseous mixtures of carbon dioxide with methane

Excess enthalpies (heats of mixing) of mixtures of methane and carbon dioxide have been measured in a flow calorimeter at temperatures between 10°C and 80°C and pressures up to 100 atmospheres. All measurements were for the mixing of two gas phases. The results were compared with various predictions based on equations of state and the principle of corresponding states.     

Heats of mixing for binary systems: n-Alkanes + n-Alcohols and n-Alcohols

The heats of mixingof 23 binary systems are reported at 20, 25 and 30°C. Of these systems, 14 binaries are mixtures of n-alcohols + n-alkanes and the remaining 9 systems are mixtures of n-alcohols. The applicability of an extension of the principle of congruence to the data was investigated.     

Prediction of the viscosities of liquid mixtures by a group solution model

Group solution models of liquid mixtures have been used previously to predict thermodynamic properties of non-ideal systems. A model of this type has been developed which enables the viscosities of liquid mixtures to be predicted. The concept of an “ideal viscosity” is introduced, and allowance made for the interaction between the groups present and for the structural contributions of differing molecules. Predictions require a knowledge of only the viscosities of the pure components of a mixture. It has been tested for mixtures of alkanes, alcohols and water at 25°C, and gives good agreement with experiment. Experimental viscosities for ethanol/n-hexane, for n-propanol/water, and for four multi-component mixtures at 25°C are presented.     

A solution thermodynamic study of soybean oil/solvent systems by inverse gas chromatography

Inverse gas chromatography (IGC) has seen wide application in the characterization of molten polymers, fibrous materials, and natural products, such as proteins and carbohydrates, over the past fifteen years. This study describes a relatively simple IGC technique for evaluating solute-solvent interactions using a refined soybean oil as a solvent. Utilizing soybean columns that are 5–20% by weight of the inert support has allowed the determination of a number of thermodynamic solution parameters for 22 solute-solvent pairs in the temperature range of 55–125°C. Weight and mole fraction activity coefficients, along with Henry's Law constants at infinite dilution, are presented for six solute classes. In general, activity coefficients increase with carbon number for n-alkanes, alkyl-substituted benzenes, and n-alkanoic acids at all temperatures investigated, while the reverse is found for the n-alkanols. The activity coefficient data indicate that aromatic solutes, chlorinated hydrocarbons, ketones, and cyclohexane can readily dissolve soybean oil. Calculated heats of mixing for n-alkanols were found to be positive (to 2.84 kcal/mole) while recorded enthalpic interactions were weak for aromatic solutes, lower alkanes, and chlorinated hydrocarbons. The relevance of the above data to such problems as oil dissolution and solvent devolatilization are discussed. Presented at the American Oil Chemists' Society Annual Meeting in Phoenix, Arizona, in May 1988.     

Experimental heat capacities of nitrogen-carbon dioxide mixtures at elevated pressures

The heat exchanger method of determining the ratio of heat capacity at a pressure to the heat capacity at a low pressure was used to obtain data on two binary mixtures of nitrogen and carbon dioxide containing 6.77 and 31.70 mole percent nitrogen. The data were obtained at pressures up to 2150 psia in the temperature range from ambient to 90°C. The results are believed to be accurate within ± 0.5% in the regions removed from the pressure maxima and within ± 1% in regions close to the maxima. Heat capacities of the two binary mixtures calculated using the BWR equation of state and new mixing rules compared favourably with the experimental data.     

A method for correlating and extending vapour pressure data to lower temperatures using thermal data: Vapour pressure equations for some n-alkanes at temperatures below the normal boiling point

Vapour pressures for many liquids are available in the range 50–760 torr but accurate determinations at lower pressures are frequently absent. Extrapolation based on purely empirical equations is hazardous and a convenient method is proposed for extrapolating such data to lower temperatures by utilizing readily available thermal data. The method is based on thermodynamically exact relationships. It has the advantage over previous such approaches that it makes greatest use of data, such as ideal gas and liquid heat capacities at around the temperature at which the vapour pressure is required, which are likely to be available. When applied to the n-alkanes C₆–C₁₆ from the normal boiling temperature down to a reduced temperature of 0·41 the method leads to a convenient vapour equation of the form ln p⁰ = alnT + bT ? (d/T) + E.The constants in this equation have been obtained in a systematic way from the available thermal, volumetric and vapour pressure data for these alkanes. These constants, together with vapour pressures and latent heats at 25°C calculated from them, are listed. Agreement between the calculated quantities at 25°C and experimental values (where available) is good.     

A theoretical and experimental heat of mixing study for polymer‐polymer mixtures

Heat of mixing is introduced as a guide for phase stability predictions of polymer mixtures, and an appropriate equation is presented for it. The form of this equation is a combined function of temperature and mixture composition. The capability of the presented equation has been treated qualitatively and it has been shown that all types of exothermic, endothermic, and s‐shaped or sigmoidal heat of mixing curves can be produced. Utilizing the low molecular weight analogue calorimetry method, heat of mixing was measured at two temperatures, 27°C and 37°C for three polymer mixtures—poly(styrene)/poly(vinylchloride) (PS/PVC), poly(styrene)/ poly(methylmethacrylate) (PS/PMMA), and poly(styrene)/poly(vinylacetate) (PS/ PVAc) at an entire composition range. It has been shown that excellent agreement between the results of the calculations and the experimental heat of mixing data was achieved. Using the results of analogue calorimetric measurements for phase stability studies of polymer mixtures, it was found that often, acceptable predictions can be made by this method, but they are not always completely true.     

Generalized Flory–Huggins model for heat‐of‐mixing and phase‐behavior calculations of polymer–polymer mixtures

An extended and generalized Flory–Huggins model for calculating the heats of mixing and predicting the phase stability and spinodal diagrams of binary polymer–polymer mixtures is presented. In this model, the interaction parameter is considered to be a function of both temperature and composition. It is qualitatively shown that the proposed model can calculate the heats‐of‐mixing curves containing exothermic, endothermic, and S‐shaped or sigmoidal types and predict the spinodals, including the upper and lower critical solution temperatures, and closed‐loop miscibility regions. Using experimental results of analog calorimetry for four polymer mixtures of polystyrene/poly(vinyl chloride) (PS/PVC), polycarbonate (PC)/poly(ethylene adipate) (PEA), polystyrene/poly(vinyl acetate) (PS/PVAc), and ethylene vinyl acetate copolymer (EVA Co)/chlorinated polyethylene (CPE), the capabilities of the proposed functionality for the interaction parameter was studied. It is shown that this function can be used satisfactorily for the heat‐of‐mixing calculations and phase‐behavior predictions. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1328–1340, 2000     

Specific heat capacities of some polyepoxides

Specific heat capacity measurements were made in a differential scanning calorimeter on a series of eight crosslinked epoxy/diamine polymers over a range of temperatures chosen, for each polymer, to include the glass transition. The tabular data at 5°C intervals was then fitted to a five-parameter empirical equation that represents the data with a deviation less than the experimental uncertainty of the measurements. The measured change in specific heat at the glass transition was an average of 1.9 cal/mol°C for each bead in the polymer repeat unit compared with 2.6 cal/mol°C bead found by Wunderlich for linear polymers. The measurements were then analyzed in terms of the molecular components of the polymers, assuming that the specific heat contribution of each component is independent of its neighbors, i.e., that specific heat is an additive property. In calculating empirical component values as a function of temperature, the polymer specific heats should be plotted as a function of T–T_g rather than T alone. In this manner, component specific heats as functions of T–T_g were determined over a range from the glassy to the rubbery state.     

A new method for predicting thermal conductivity of pure organic liquids and their mixtures

A new method based on Enskog's hard sphere theory for dense fluids and the principle of corresponding states is presented for predicting thermal conductivity of pure organic liquids and their mixtures. The thermal conductivities of alkanes, isoalkanes, aromatics, aldehydes, esters and ketones were calculated using this method which requires only critical properties and normal boiling point as input data. The predictions were compared with experimental data and other prediction methods over a wide range of temperatures (0.3 < T_r < 0.8) and highly satisfactory results were obtained. The method was also extended to mixtures employing simple mixing rules for calculating mixture properties.     

Reversible gelation of acrylonitrile–vinyl acetate copolymer solutions. II. Mechanical properties

Concentrated solutions of acrylonitrile polymers exhibit reversible gelation. The rate of gelation at 25°C. was determined for various solutions of an acrylonitrile copolymer containing 7.7% vinyl acetate in mixtures of dimethylacetamide (solvent) and water (nonsolvent) by measuring the shear modulus of the forming gel as a function of time. The mechanical properties were also measured on a series of gels formed by cooling solutions to ?78°C. It was found that both the rate of gelation at 25°C. and the modulus of gels formed at ?78°C. increase very rapidly as either the solids level of the solution of the water content of the solvent is increased. The gelation rate data wree correlated with the gel melting points of the gels. The results are discussed and compared with the analogous but limited data available for other systems.     

Measurement of vapor-liquid equilibria using a semi-continuous total pressure static equilibrium still

The total pressure static equilibrium still designed by Gibbs and Van Ness has been modified to increase its accuracy. It was tested by comparing calculated vapor compositions and excess Gibbs free energies with literature data for mixtures of ethanol and n-heptane at 30°C. Experimental data are presented for 1-pentanol/n-hexane mixtures at 30° and 50°C, for 1-pentanol/n-pentane mixtures at 30°C, and for 1-butanol/n-pentane mixtures at 30°C.