Hydrocarbons, liquid thermodynamic parameters

TABLE 10.5 Thermodynamic Parameters of Electron in Hydrocarbon Liquids According to the Quasi-ballistic Model... 

Table 3.4 Thermodynamic parameters for transfer of hydrocarbons from water to liquid hydrocarbon at 25 °C.

MICHEAU - My comments deals with azeotropic binary mixtures. We have recently made some experimental measurements of the thermodynamic parameters of a thermochronic equilibrium in azeotropic liquid mixtures. Our thermochronic equilibrium (Nickel complexes NiR + 2S N1R2S2) is sensitive to the donor number of the solvent S which is an empirical measure of the availability of the electronic doublet of S. What we have found in azeotropic mixtures (alcohol + halogenated hydrocarbons) is that near the room temperature there is a kind of natural compensation of the alcohol doublet availability by the presence of halogenated hydrocarbons molecules this compensation shifts the equilibrium position near 50/50 (solvated vs non solvated complex). This property is spontaneous with the azeotropes we have studied, but must to be adjusted accurately by varying the molar ratio with similar binary mixtures not giving azeotropes. So, it appears that azeotropes exhibit from this point of view some singular propertie. My question is Do you have or do you know some results about reactivity studies in azeotropic mixtures Could an azeotrope be considered as a model of a particular supermolecule or cluster ... 

SCF carbon dioxide is a lipophilic solvent since the solubility parameter and the dielectric constant are small compared with a number of polar hydrocarbon solvents. Co-solvents(also called entrainers, moditiers, moderators) such as ethanol have been added to fluids such as carbon dioxide to raise the solvent strength while maintaining it s adjustability. Most liquid cosolvents have solubility parameters which are larger than that of carbon dioxide, so that they may be used to increase yields, or to decrease pressure and solvent requirements. A summary of the large increases in solubility that may be obtained with a simple cosolvent is given at the top of Table I. Cosolvents, unlike carbon dioxide, can form electron donor-acceptor complexes (for example hydrogen bonds) with certain polar solutes to influence solubilities and selectivities beyond what would be expected based on volatilities alone. Several thermodynamic models have been developed to correlate and in some cases predict effects of cosolvent on solubilities( ,2). They are used extensively in SCF research and development... 

With emulsions, nanoemulsions and microemulsions, the surfactant adsorbs at the oil/water (O/W) interface, with the hydrophilic head group immersed in the aqueous phase and leaving the hydrocarbon chain in the oil phase. Again, the mechanism of stabilisation of emulsions, nanoemulsions and microemulsions depends on the adsorption and orientation of the surfactant molecules at the Uquid/liquid (L/L) interface. Surfactants consist of a small number of units and are mostly reversibly adsorbed, which in turn allows some thermodynamic treatments to be applied. In this case, it is possible to describe adsorption in terms of various interaction parameters such as chain/surface, chain solvent and surface solvent. Moreover, the configuration of the surfactant molecule can be simply described in terms of these possible interactions. 

This work results in correlations which can be used to predict parameters for the RK equation of state for hydrocarbon and other nonpolar components for which the critical pressure, critical temperature, and acentric factor are known or can be estimated. However, the applicability of the correlations to large molecules is unproven because the generalized correlations of physical and thermodynamic properties used to develop Oa and Ob are based on components no heavier than n-decane (acentric factor = 0.4885). Although the predicted parameters are based on properties for the saturated liquid phase, the parameters are applied to both vapor and liquid phases. For components above their critical temperature (a reduced temperature greater than 1.00), the values of fia and Ob determined at a reduced temperature of unity are used. 

Thermodynamic properties of nonideal hydrocarbon mixtures can be predicted by a single equation of state if it is valid for both the vapor and liquid phases. Although the Benedict-Webb-Rubin (B-W-R) equation of state has received the most attention, numerous attempts have been made to improve the much simpler R-K equation of state so that it will predict liquid-phase properties with an accuracy comparable to that for the vapor phase. The major difficulty with the original R-K equation is its failure to predict vapor pressure accurately, as was exhibited in Fig. 4.3. Following the success of earlier work by Wilson, Soave added a third parameter, the Pitzer acentric factor, to the R-K equation and obtained almost exact agreement with pure hydrocarbon vapor pressure... 

For the prediction of viscosity of well-defined mixtures of liquids, the method of Cao et al. is very good in general [27,32]. However, since hydrocarbon mixtures form almost thermodynamically ideal solutions and their viscosities are simple functions of composition, simpler methods such as those of Allan and Teja [12] or of Orbey and Sandler [13] result in almost equal accuracy without the need for binary interaction parameters. These last two, simpler models can only be used for hydrocarbons, while the model of Cao et al. is of more general applicability. 

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