Solvent-aqueous-surfactant process

The Relation of Surfactant Properties to the Extraction of Bitumen from Athabasca Tar Sand by a Solvent-Aqueous-Surfactant Process... 

The paddle mill was used to study the effect of surfactant type on a solvent-aqueous-surfactant extraction scheme for the recovery of bitumen from Athabasca tar sand. n the experiments of Figures 4,5 and 6, bitumen recovered from the surface phases was measured as a function of the mole fraction of ethylene oxide in the surfactant and as a function of the extraction step in which the surfactant was added. The results are reported as the % of the total bitumen present in the surface fraction. The amount of surfactant used was that required to give a final aqueous concentration of 0.02% (w/v), but in different sets of experiments the surfactant was added at various stages in the process. 

A linear correlation is obtained between bitumen extraction with the paddle mill and the adhesion tension against water saturated pyrophyllite. That the degree of water saturation of the pyrophyllite is important in explaining the difference between the 2 extraction processes indicates that it will be necessary to study each process in terms of the relevant adhesion tensions. These results demonstrate that adhesion tension is the most important parameter found to date in determining the degree of separation in the presence of surfactants. Measurements of adhesion tension between surfactant solutions and minerals similar to those found in tar sand may be of considerable value in studies of surfactant utility in both aqueous-surfactant, solvent-aqueous-surfactant and in situ extraction processes. In addition, if appropriate model situations can be developed, measurements of adhesion tension may be useful in upgrading bitumen-water-clay emulsions obtained by a variety of in situ and heavy oil recovery processes. 

Lewis acids as water-stable catalysts have been developed. Metal salts, such as rare earth metal triflates, can be used in aldol reactions of aldehydes with silyl enolates in aqueous media. These salts can be recovered after the reactions and reused. Furthermore, surfactant-aided Lewis acid catalysis, which can be used for aldol reactions in water without using any organic solvents, has been also developed. These reaction systems have been applied successfully to catalytic asymmetric aldol reactions in aqueous media. In addition, the surfactant-aided Lewis acid catalysis for Mannich-type reactions in water has been disclosed. These investigations are expected to contribute to the decrease of the use of harmful organic solvents in chemical processes, leading to environmentally friendly green chemistry. 

Colloidal liquid aphrons (CLAs), obtained by diluting a polyaphron phase, are postulated to consist of a solvent droplet encapsulated in a thin aqueous film ( soapy-shell ), a structure that is stabilized by the presence of a mixture of nonionic and ionic surfactants [57]. Since Sebba s original reports on biliquid foams [58] and subsequently minute oil droplets encapsulated in a water film [59], these structures have been investigated for use in predispersed solvent extraction (PDSE) processes. Because of a favorable partition coefficient for nonpolar solutes between the oil core of the CLA and a dilute aqueous solution, aphrons have been successfully applied to the extraction of antibiotics [60] and organic pollutants such as dichlorobenzene [61] and 3,4-dichloroaniline [62]. 

According to various experimental information the hydrocarbon core of the "aqueous micelle has a liquid-like structure (3,4). This has been confirmed, in particular, by spectroscopic probing techniques (5,6). Hence the micelle in aqueous surfactant solutions presents itself to the surfactant monomer as an equivalent with respect to the (macroscopical) oil/water interface. It might be not unreasonable, therefore, to consider this type of micelle formation an "auto-solubilization" to stress the close resemblance between adsorption and homoassociation processes. The hydrocarbon core of a micelle in aqueous surfactant solutions is characterized by its excellent solvent power for crystalline non-polar compounds (7). This latter feature appears remarkable and could serve as a more fundamental distinction between "normal" and inverted micelles than the generally cited apparently more obvious differences. The free energy of micellization is customarily (8) referred to the standard free energy of a monomer in a micelle, i.e. AG° represents the free energy of transfer of a monomer from the aqueous solution to a micelle of size n. 

Semi-aqueous cleaning processes apply hydrocarbon solvent-surfactant emulsions in concentrated form followed by a water rinse, or emulsions in water are used in processes similar to aqueous cleaning. Semi-aqueous cleaning processes are very effective in removing heavy grease, tar, waxes, and other hydrocarbon-based soils. Cleaning solutions can be made compatible with most metals and polymers and metals are not likely to be etched as the solutions are neutral. 

Figure 4c illustrates interfacial polymerisation encapsulation processes in which the reactant(s) that polymerise to form the capsule shell is transported exclusively from the continuous phase of the system to the dispersed phase—continuous phase interface where polymerisation occurs and a capsule shell is produced. This type of encapsulation process has been carried out at Hquid—Hquid and soHd—Hquid interfaces. An example of the Hquid—Hquid case is the spontaneous polymerisation reaction of cyanoacrylate monomers at the water—solvent interface formed by dispersing water in a continuous solvent phase (14). The poly(alkyl cyanoacrylate) produced by this spontaneous reaction encapsulates the dispersed water droplets. An example of the soHd—Hquid process is where a core material is dispersed in aqueous media that contains a water-immiscible surfactant along with a controUed amount of surfactant. A water-immiscible monomer that polymerises by free-radical polymerisation is added to the system and free-radical polymerisation localised at the core material—aqueous phase interface is initiated thereby generating a capsule sheU (15). 

A process is described for the production of finely divided gelatin-free dispersions of photographic additives in an aqueous medium in the presence of a high-boiling solvent and a phosphorus-containing surfactant. Thus, a yellow... 

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