STUDIES OF NONEQUILIBRIUM BEHAVIOR IN SURFACTANT SYSTEMS USING VIDEOMICROSCOPY AND DIFFUSION PATH ANALYSIS (EMULSIFICATION, MICROEMULSION, INSTABILITY)

[摘要] Videomicroscopy was used to study nonequilibrium phenomena in various systems containing oil, water, and surfactant. This novel technique included the use of a vertical configuration microscope to allow easy observation of intermediate phase formation, interfacial instabilities, and spontaneous emulsification. In most systems, diffusion path analysis was utilized to explain the observed events.A petroleum sulfonate system typical of those used in surfactant flooding of oil reservoirs was examined to determine salinity effects on nonequilibrium phenomena. Microemulsions and/or brine phases formed as intermediate layers at all salinities. Diffusion paths calculated for a model system match the experimental results with regard to the number and rate of formation of the intermediate phases.Contacting experiments were also performed between an oil phase containing oleic acid and caustic brine solutions of varying salinity and pH. In these experiments, which are pertinent to enhanced oil recovery by alkaline flooding, interfacial turbulence and liquid crystal formation were commonplace. Spontaneous emulsification of water in the oil was observed at conditions where the surfactant was oil-soluble. Oil-in-water emulsions formed spontaneously at conditions where the surfactant was hydrophilic.For application to low-temperature detergency, hydrocarbons were contacted with aqueous solutions of pure ethoxylated alcohol surfactants. Enhanced solubilization of oil was seen at temperatures above the cloud point of the nonionic surfactant solutions due to the presence of surfactant-rich phases. In addition, intermediate liquid crystal and microemulsion layers typically formed near the phase inversion temperature, while conversion of oil into a water-in-oil microemulsion occurred at higher temperatures. Comparison of a pure ethoxylated alcohol system was also made to formulations having the same cloud point but containing a different ethoxylated alcohol and a lipophilic additive. Differences in nonequilibrium behavior were observed upon contacting with hydrocarbons due to partitioning of additive into the oleic phase.Finally, contacting experiments were compared to calculated diffusion paths for a well-characterized oil-water-alcohol system. One of the more interesting observations was the formation of an interface across a three-phase region. This phenomenon, which has not previously been reported for liquid systems, also occurred at certain conditions in the experiments using surfactants.

[发布机构] Rice University

[效力级别] engineering