Kinetic study of the desulfonation of DOWFAX surfactants

Kinetic study on the desulfonation of DOWFAX is performed in the temperature range of 177 to 272 C, and a pH range of 2.0 to 7.0. The rate data support that the desulfonation is a stepwise reaction catalyzed by hydrogen ion. The desulfonation rate is first order with respect to both surfactant and hydrogen ion concentrations. As a result, pH of the reaction system has a very significant effect on the stability of the surfactants and may outweight the effect of temperature. The half-life of DOWFAX at 235 C and pH 5.5 buffer solution is 1035 days; at 272 C and pH 7.0, buffer solution half-life is 295 days. These results indicate that DOWFAX surfactants can be used in most oil reservoir steamflood applications, especially when the rock formation may buffer the pH to ca 7.0.