Surfactants chemical structure

When both oil (o) and water (w) are present, o/w microemulsions will be formed when v/a0lc < 1 w/o microemulsions when v/ac c>U and lamellar phases when v/a0lc 1 (Israelachvili etal., 1980 Mitchell and Ninham, 1981). The v/a ratio depends on the surfactant chemical structure (lc and v) and on surface repulsions between headgroups (aD), (Mitchell and Ninham, 1981). When repulsions increase, the surfactant parameter (v/aGlc) increases and micelles get smaller. As a consequence, size and CMC are related surfactants with low CMC aggregate into large molecules, while the higher the CMC, the smaller the micelles. 

Effects of Surfactant Chemical Structure on One-Atmosphere Foaming Properties... 

Surfactant foaming properties are related to surfactant chemical structure parameters such as hydrophobe size, ethylene oxide chain length, and hydrophile functional group. 

Increasing the test pressure from one atmosphere to 2500 psig COj did not alter the effect of surfactant chemical structure on relative foaming performance. 

Correlation equations relating surfactant chemical structure to performance characteristics and physical properties have been established. One atmosphere foaming properties of alcohol ethoxyl-ates and alcohol ethoxylate derivatives have been related to surfactant hydrophobe carbon chain length, ethylene oxide content, aqueous phase salinity, and temperature. Similar correlations have been established for critical micelle concentration, surfactant cloud point, and surfactant adsorption. 

Foam exhibits higher apparent viscosity and lower mobility within permeable media than do its separate constituents.(1-3) This lower mobility can be attained by the presence of less than 0.1% surfactant in the aqueous fluid being injected.(4) The foaming properties of surfactants and other properties relevant to surfactant performance in enhanced oil recovery (EOR) processes are dependent upon surfactant chemical structure. Alcohol ethoxylates and alcohol ethoxylate derivatives were chosen to study techniques of relating surfactant performance parameters to chemical structure. These classes of surfactants have been evaluated as mobility control agents in laboratory studies (see references 5 and 6 and references therein). One member of this class of surfactants has been used in three field trials.(7-9) These particular surfactants have well defined structures and chemical structure variables can be assigned numerical values. Commercial products can be manufactured in relatively high purity. 

Foaming properties can be quantitatively related to surfactant chemical structure, surfactant physical properties, and test conditions using the technique of multiple correlation analysis.(11) The current studies were restricted to linear correlation equations to permit the analyses to be performed on a small microcomputer. While non-linear equations having higher correlation coefficients than obtained herein can be developed, theoretical insights are often limited due to the complexity of the various terms of such equations. The quality of the correlations were assessed using the correlation coefficient (r ) criteria of Jaffe (12)... 

Interfacial tension (IFT) between injected fluids and formation crude oil is a critical parameter in EOR processes. The results reported herein suggest that the relationship between IFT and surfactant chemical structure can be quantified. Equation 8 was used to relate the IFT to alcohol ethoxylate chemical structure ... 

Both the use of one atmosphere foaming experiments and the technique of multiple correlation analysis have a common purpose minimizing the effort required to develop new surfactants for mobility control and other EOR applications. Proper use of these techniques with due consideration of their limitations can substantially reduce the number of experiments required to develop new surfactants or to understand the effect of surfactant chemical structure on physical properties and performance parameters. ... 

Other surfactant physical properties and performance parameters such as critical micelle concentration, cloud point, and interfacial tension may be related to surfactant chemical structure using multiple correlation analysis. 

Such systems can form the thread-like micelles necessary for surfactant solutions to be DR under the shearing conditions in turbulent flows. The thread-like micelles align themselves along the flow direction causing DR of the solution. Details of microstructures DR of aqueous cationic surfactant solutions vary with surfactant chemical structure and concentration, counterion chemical structure and... 

III. THE RELATION OF SURFACTANT CHEMICAL STRUCTURE TO FOAMING IN AQUEOUS SOLUTION... 

FIG. 10 The effect on emulsion type of changing the hydrophobic tail length of n-alkyl carboxylate surfactants. The question mark domain corresponds to the emulsion breaking region where emulsion type was found to be uncertain. C9, Cll, C13, and C15 stand for m = 9, 11, 13, and 15 in the above surfactant chemical structure (From Ref. 152.)... 

In spite of the various potential applications little is known on the important issue of how to optimize surfactant chemical structure for CO2 dispersions. This is partly due to a lack of suitable, well-characterized compounds, and that one of... 

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