Emulsification with surfactant

Paraffin hydrocarbons of molecular mass 300 to 700 (i.e. 20-50 carbon atoms) require emulsification with surfactants. They show good resistance to oxidation and yellowing. 

Emulsification with caustic is possible with oils that have a fairly high total acid number (TAN). Below about 1.5 mg KOH/gm oil, the oils either will not emulsify or will form water-in-oil emulsions. The rate of emulsification with caustic is much faster than emulsification with surfactant mixtures, which is a characteristic property for emulsions generated via the agent-in-oil procedure (1 ). 

Emulsification The development of an emulsion by mixing two or more immiscible liquids together, such as oil and water. The liquids do not dissolve into each other, but the emulsion consists of distinct microscopic droplets of one or more liquids dispersed into the most abundant liquid (compare with surfactant). 

Emulsions are two-phase systems formed from oil and water by the dispersion of one liquid (the internal phase) into the other (the external phase) and stabilized by at least one surfactant. Microemulsion, contrary to submicron emulsion (SME) or nanoemulsion, is a term used for a thermodynamically stable system characterized by a droplet size in the low nanorange (generally less than 30 nm). Microemulsions are also two-phase systems prepared from water, oil, and surfactant, but a cosurfactant is usually needed. These systems are prepared by a spontaneous process of self-emulsification with no input of external energy. Microemulsions are better described by the bicontinuous model consisting of a system in which water and oil are separated by an interfacial layer with significantly increased interface area. Consequently, more surfactant is needed for the preparation of microemulsion (around 10% compared with 0.1% for emulsions). Therefore, the nonionic-surfactants are preferred over the more toxic ionic surfactants. Cosurfactants in microemulsions are required to achieve very low interfacial tensions that allow self-emulsification and thermodynamic stability. Moreover, cosurfactants are essential for lowering the rigidity and the viscosity of the interfacial film and are responsible for the optical transparency of microemulsions [136]. 

For removal of insoluble and/or water-immiscible inorganics by emulsification with detergent solutions For removal of ester and amide-based organics and inorganic salts by chemical hydrolysis with alkaline solutions For removal of metal ions from solutions and surfaces by chelation or complexation reactions For wetting and dispersion of soils with surfactants, suspension of soil residues in order to prevent resedimentation and recontamination on metal surface For removal of surface contaminations, rust scale, mill scale, and other bound moieties (including surface layers of metal itself) by chemical dissolution with acids or alkaline deoxidation with or without the application of an electric current... 

TABLE IV. Static Emulsification Tes ts Performed with Surfactants and Oelaware-Childers Oil... 

The emulsification properties of the crude oil must be determined. Some crude oils can be emulsified with surfactant mixtures, others with caustic. Some crudes, such as Hasley Canyon (Table III), are difficult to emulsify. Experiments can be performed to determine if in situ emulsification is feasible, or if an emulsion must be injected. If in situ emulsification is feasible, loss of chemicals to reservoir rock is a problem to be addressed. If in situ emulsification is employed in conjunction with steam, it must be determined if chemicals are most effective when injected with the flowing steam or when chemical/steam injections are alternated. Relative permeabilities of the injected fluids should be determined. All of this information is needed to calculate the economics of scale-up to a specific field situation. 

Crosslinking of the surfactant molecules may be induced by simultaneous activation of two neighbouring molecules with the net result that the molecular weight of the polymer increases until a three dimensional gel network is formed. As the hydrophilic poloxamers are surface-active, promoting o/w emulsification, oil-in-water emulsions may be prepared which contain the poloxamer in the continuous aqueous phase. After emulsification, the surfactant molecules can be crosslinked at the oil-in-water interface and in the continuous phase by Y i.rradiation, forming a network of surfactant molecules which link the dispersed oil globules. 

The microchannel emulsion technique has been extended to the formation of multiple emulsions [158-163], encapsulation [123, 158, 164—166], polymer bead formation [123, 125, 167-169], demulsification [116, 158, 170], and even microbubble formation [171]. New methods of stabilizing emulsions have also been investigated in this realm, including particle-stabilized [172] and protein-stabilized emulsions [173], with some work in emulsification without surfactants [135,146]. In the case of multiple emulsions, microchannel architecture can enable the formation of W/O/W emulsions in which two water droplets of different compositions can be encased in the same oil droplet [163]. 

Pumping with PCPs can be improved by downhole emulsification (25, 115, 116). Downhole emulsification uses surfactants to create oil-in-water emulsions of low viscosity. The benefits of downhole emulsi-... 

Hydrotropes have many features in common with micelles. The most important is the presence of a minimum hydrotrope concentration (CHC) analogous to the minimum micellar concentration (CMC) described earlier (Balasubramanian et al., 1989). The most important difference is that in hydrotropes, the dissolved solute is precipitated on dilution, whereas with surfactants dilution leads to emulsification with consequent problems of separation. Another difference is that surfactants show solubility enhancements at low concentrations, usually in the millimolar range, whereas hydrotropic solubilization occurs in the molar concentration range. Yet another difference is that, unlike micellar solubilization which is general and nonselective, hydrotropes do not solubilize all hydrotropic substances and are hence selective. This is obviously an advantage where reactant selectivity is important. 

Enhanced oil recovery by alkaline flooding was proposed some years ago as an inexpensive way to take advantage of the acid components that occur naturally in some crude oils [80,81]. The stabilization of oil-in-water emulsions can also be attained this way. In these cases the carboxylic acid contained in the crude oil adsorbs at the O/W interface, where it is neutralized into a carboxylic salt with surfactant properties such as interfacial tension lowering or emulsification. Fatty amines and their cationic counterparts at low pH are routinely used to stabilize asphalt emulsions for roads and pavement. 

One recent attempt to decrease the costs associated with surfactant flooding has been to inject surfactant-producing bacteria into oil reservoirs. This technique involves the injection of selected microorganisms into the reservoir and the subsequent stimulation and transportation of their growth products in order to recover more of the oil-in-place [34]. Some of the mechanisms proposed by which these microbes can stimulate oil production include reservoir repressurization, modification of reservoir rock, degradation and alteration of oil, decrease of viscosity, and increase in emulsification [35]. 

The reactions between the alkaline solution and reservoir oil generate the complex oil recovery mechanisms of AF postulated to date (1) in-situ surfactant generation by neutralization (saponification), (2) reduction of the interfacial tension (IFT) at the oil-water interface, (3) temporary wettability alteration, (4) emulsification with entrainment, (5) emulsification with entrapment, (6) emulsification with coalescence, (7) oil phase swelling, and (8) breaking out the rigid films. Thus, the consumption of alkalinity through the reactions of alkaline solution with reservoir waters and rock constituents has been accepted as the most important disadvantage of the AF process. ... 

Metallic sulfonates, such as sodium sulfonate, are often used as emulsifiers in both water-in-oil and oil-in-water emulsions. Other emulsifiers used include ethylene oxide condensation products and derivatives of polyhydroxy alcohols such as sorbitol and sulfosuccinates for water-in-oil emulsions. For oil-in-water emulsions, soaps of fatty acids, rosins, or naphthenic acids are often used as emulsifiers. In either application, the role of emulsifiers is to change the interfacial tension at the water and oil interface. In cases where emulsification with water is undesirable, demulsifiers are used. Frequently, the demulsifiers are heavy metal soaps, such as alkaline earth sulfonates. These surfactants function by lowering emulsion stability. 

The properties of a perfluorochemical emulsion depend critically on the surfactant used for emulsification. A surfactant used as an emulsifier in fluorochemical blood substitutes has to meet several criteria (1) provide a fine stable emulsion (2) be nontoxic, nonmutagenic, and nonhemolytic (3) be compatible with blood and endothelial cells (4) be pharmacologically, physiologically, or biochemically inactive and (5) either be excreted unchanged or in the form of harmless metabolites [41]. 

Early efforts to produce synthetic mbber coupled bulk polymerization with subsequent emulsification (9). Problems controlling the heat generated during bulk polymerization led to the first attempts at emulsion polymerization. In emulsion polymerization hydrophobic monomers are added to water, emulsified by a surfactant into small particles, and polymerized using a water-soluble initiator. The result is a coUoidal suspension of fine particles,... 

---