Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

A series of AOT (aerosol-OT) analogue surfactants (sodium salt of dibutyl-2-sulfosuccinate, sodium salt of dipentyl- 2-sulfosuccinate, sodium salt of dihexyl-2-sulfosuccinate, and sodium salt of dioctyl-2-sulfosuccinate) were synthesized and characterized by 1H NMR and elemental analysis. A static method coupled with gravimetric analysis is developed to measure the solubility of the surfactants in 1,1,1,2-tetrafluoroethane (HFC-134a) and supercritical CO2 (scCO2). The solubilities of the surfactants in HFC-134a and scCO2 are affected by the temperature, pressure, and carbon atom number of the surfactant. The solubility of the same surfactant in HFC- 134a solvent is approximately two times that in the most commonly used supercritical solvent CO2. The pressuretemperature phase diagrams for water/HFC-134a microemulsions stabilized by the surfactants were determined using cloud-point measurements for a concentration range of the surfactant from (1.85 _ 10-3 to 5.60 _ 10-3) M, temperature up to 338 K, and pressure up to 40 MPa in a high-pressure vessel. At a fixed temperature, the cloud-point pressure increased with increasing water-to-surfactant molar ratio (Wo). At a fixed Wo, the cloudpoint pressure decreased with increasing temperature. The surfactant with the longest hydrocarbon chain has the highest cloud-point pressure even at lower surfactant concentrations.