Abstract:

As an important type of surfactants for oil flooding, the emulsification properties of heavy alkylbenzene sulfonates and their microscopic action mechanism at oil-water interface significantly affect the efficiency of oil flooding and the oil-water separation in the produced liquid. In this work, the emulsification properties of an isomer of sodium cetyl-o-xylene sulfonate（C16S）and its microscopic action mechanism at oil-water interface were investigated, and the influences of surfactant concentration, temperature, and NaCl concentration on the oil-water interfacial properties were also examined. The results showed that C16S significantly improved the stability of O/W and W/O simulated emulsions. When the mass concentration of C16S was increased from 10 mg/L to 60 mg/L, the Turbiscan stability index（TSI）and water separation percent（X）of the simulated emulsion both decreased, while the average backscattering light intensity（BS_avg）of the W/O emulsion increased from 24.02% to 36.12%, and the average transmitted light intensity（T_avg）of the O/W emulsion decreased from 7.72% to 1.52%. The results of molecular dynamics（MD）simulation showed that, when the number of C16S molecules increased, the peak strength of radial distribution function increased, the interface thickness increased, and the interface energy decreased, thus leading to the increase in the stability of interfacial film. Raising temperature resulted in a slight decrease in the peak strength of radial distribution function of C16S, and the increases in both interface thickness and interface energy. The effects of the number of NaCl molecules on interface thickness and interface energy were both relatively small.

Key words: emulsification property, interfacial property, aggregation behavior, molecular dynamics