Phase behavior, of system

In an earlier paper Q ), the authors presented an efficient procedure for predicting the phase behavior of systems exhibiting a water - rich liquid phase, a hydrocarbon - rich liquid phase, and a vapor phase. The Peng-Robinson equation of state (2) was used to reDresent the behavior of all three phases. It has the following form ... 

The phase behavior of systems containing pH-sensitive surfactants is another example of non-linearity of the mixing rule. If an oil phase containing an amphiphilic molecule, such as an organic acid, as in the case of naphtenic acids in crude oils, is put into contact with an alkaline water phase, the neutralization takes place at interface and results in a mixture of unneutralized acid (the lipophilic component) and its dissociated alkaline salt (the hydrophilic component). Hence, the interface contains a mixture of two surfactants whose relative proportion depends on the ionization (in the water and at interface), and thus of the pH [75]. 

Anton RE (1992) Contribution to the study of the phase behavior of systems containing a surfactant mixture, oil and water (in French). Doctoral dissertation. University of Pau, France... 

Shariati, A. and Peters, C. J., High-pressure phase behavior of systems with ionic liquids Measurements and modeling of the binary system fluoroform + l-ethyl-3-methylimidazolium hexafluorophosphate, /. Supercrit. Fluids, 25, 109, 2003. 

The phase behavior of nonaqueous colloidal suspensions containing nonadsorbing polymer was investigated by Gast et al. [3] on the basis of statistical mechanics. In their theory, a second-order perturbation approach was used to calculate the free energy. Rao and Ruckenstein [4,5] examined the phase behavior of systems involving steric, depletion, and van der Waals interactions. 

Shinoda and Kuineda [8] highlighted the effect of temperature on the phase behavior of systems formulated with two surfactants and introduced the concept of the phase inversion temperature (PIT) or the so-called HLB temperature. They described the recommended formulation conditions to produce MEs with surfactant concentration of about 5-10% w/w being (a) the optimum HLB or PIT of a surfactant (b) the optimum mixing ratio of surfactants, that is, the HLB or PIT of the mixture and (c) the optimum temperature for a given nonionic surfactant. They concluded that (a) the closer the HLBs of the two surfactants, the larger the cosolubilization of the two immiscible phases (b) the larger the size of the solubilizer, the more efficient the solubilisation process and (c) mixtures of ionic and nonionic surfactants are more resistant to temperature changes than nonionic surfactants alone. 

Phase Behavior and Surfactant Design. As described above, dispersion-based mobility control requires capillary snap-off to form the "correct" type of dispersion dispersion type depends on which fluid wets the porous medium and surfactant adsorption can change wettability. This section outlines some of the reasons why this chain of dependencies leads, in turn, to the need for detailed phase studies. The importance of phase diagrams for the development of surfactant-based mobility control is suggested by the complex phase behavior of systems that have been studied for high-capillary number EOR (78-82), and this importance is confirmed by high-pressure studies reported elsewhere in this book (Chapters 4 and 5). 

The phase rule is a useful tool which can be used to correlate and summarize the phase behavior of systems composed of one or more phases in eqiulibrimn with one another. In this respect it is particularly useful in predicting the qualitative behavior of multicomponent, multiphase systems whose phase behavior can be extremely complex. 

In this section, we consider the phase behavior of systems with three components. The Gibbs phase rule for a ternary mixture is... 

Knudsen, K., Stenby, E. H., and Andersen, J. G., 1994. Modelling the influence of pressure on the phase behavior of systems containing water, oil, and nonionic surfactants. Fluid Phase Eq., 93 55-74. 

Kahlweit M, Lessner E, Strey R. Influence of the properties of the oil and the surfactant on the phase behavior of systems of the type H20-oil-nonionic surfactant. J Phys Chem 1983 87 5032-5040. 

The equilibrium phase behavior of systems of oil and water containing appreciable amounts of surfactant is characterized by the presence of microemulsions. The microemulsions are stable oil-water dispersions caused by the incorporation of amphipathic molecules (surfactants and co-surfactants) in the oil and water phases. 

Figure 18 Phase behavior of systems containing a mixture of anionic and cationic surfactants with oil, water, and alcohol. (From Ref 99.)...

Figures 4.12 through 4.14 and the above discussion make clear that, even in the absence of oil, the phase behavior of systems containing water and one or more surface-active compounds can be quite complex. Many phase diagrams similar to Figure 4.14 may be found in Ekwall (1975).

Costantini, M Toussaint, V. A. Shariati, A. Peters, C. J. Kikic, 1. (2005). High-pressure phase Behavior of systems with ionic liquids Part IV. Binary system carbon dioxide+l-hexyl-3-methylimidazolium tetrafluoroborate. /. Chem. Eng. Data, 50, 52-... 

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