Ionic liquids for low-tension oil recovery processes: Phase behavior tests.

Chemical flooding with surfactants for reducing oil-brine interfacial tensions (IFTs) to mobilize residual oil trapped by capillary forces has a great potential for Enhanced Oil Recovery (EOR). Surface-active ionic liquids (SAILs) constitute a class of surfactants that has recently been proposed for this application. For the first time, SAILs or their blends with an anionic surfactant are studied by determining equilibrium phase behavior for systems of about unit water-oil ratio at various temperatures.

Modeling micelle formation and interfacial properties with iSAFT classical density functional theory.

Surfactants reduce the interfacial tension between phases, making them an important additive in a number of industrial and commercial applications from enhanced oil recovery to personal care products (e.g., shampoo and detergents).

Characteristics of spontaneously formed nanoemulsions in octane/AOT/brine systems.

Nanoemulsions were formed spontaneously by diluting water-in-oil (W/O) or brine-in-oil (B/O) microemulsions of a hydrocarbon (octane), anionic surfactant (Aerosol-OT or AOT) and water or NaCl brine in varying levels of excess brine. The water-continuous nanoemulsions were characterized by interfacial tension, dynamic light scattering, electrophoresis, optical microscopy and phase-behavior studies. The mechanism of emulsification was local supersaturation and resulting nucleation of oil during inversion.

Solubilisation of triolein by microemulsions containing C12E4/hexadecane/water: equilibrium and dynamics.

Increasing triolein content of oil-in-water microemulsions in the pure C(12)E(4)/water/n-hexadecane/triolein system while maintaining a fixed surfactant concentration and volume fraction of drops raises the temperature of the solubilisation boundary, where excess oil separates, but has only a slight effect on the (higher) cloud point temperature, where excess water appears. Thus, the temperature range of the single-phase microemulsion shrinks and ultimately disappears. When such microemulsions are in equilibrium with excess oil, the hexadecane/triolein ratio is greater in the microemulsion, probably because the larger triolein molecules are unable to penetrate the hydrocarbon chain region of the surfactant films of the microemulsion droplets.

Solubilization rates of oils in surfactant solutions and their relationship to mass transport in emulsions.

Information on solubilization rates of oils in aqueous micellar solutions is reviewed. For ionic surfactants electrostatic repulsion prevents close approach of micelles to the oil-water interface, so that solubilization results from oil molecules dissolving individually in the solution and being taken up by micelles during and/or after transport across a diffusion boundary layer to the bulk solution. Experiments with SDS solutions and single oil drops having low (but not negligible) solubility indicate that mass transfer is often not rate-controlling.

Defoaming effect of calcium soap.

The effect of calcium oleate on foam stability was studied for aqueous solutions of two commonly used surfactants (anionic and nonionic) under alkaline conditions in the absence of oil. For the anionic surfactant, defoaming by calcium oleate appears to involve two mechanisms. One is that oleate and calcium ions are presumably incorporated into the surfactant monolayers with a resulting decrease in the maximum of the disjoining pressure curve and therefore produces less stable thin films.

Mechanism for defoaming by oils and calcium soap in aqueous systems.

The effect of oils, hardness, and calcium soap on foam stability of aqueous solutions of commercial surfactants was investigated. For conditions where negligible calcium soap was formed, stability of foams made with 0.1 wt% solutions of a seven-EO alcohol ethoxylate containing dispersed drops of n-hexadecane, triolein, or mixtures of these oils with small amounts of oleic acid could be understood in terms of entry, spreading, and bridging coefficients, i.

Spontaneous Emulsification Produced by Chemical Reactions.

Spontaneous emulsification of small oil droplets was produced in three different systems by chemical reactions which converted lipophilic surfactants initially dissolved in the oil phase to hydrophilic surfactants. The resulting reversal of spontaneous curvature from a water-in-oil to an oil-in-water configuration reduced the solubilization capacity for oil to such an extent that supersaturation occurred, leading to nucleation of oil droplets. In one case a dilute solution of phenylboronic acid in water diffused into an oil phase containing a monoglyceride.