Abstract
As an alternative to toxic organic solvents, supercritical carbon dioxide (scCO2) has attracted much attention over the last decade since it is nontoxic, inflammable, environmentally friendly, low cost and readily available in large quantities. With these advantages, together with its unique properties as a supercritical fluid such as adjustable solvent power, enhanced mass transfer characteristics and low surface tension, scCO2 has prompted extensive research to develop scCO2-based processes. Unfortunately, because CO2 is nonpolar and has weak van der Waals forces, it is not suitable for dissolving polar substances; this fact has limited its application to processes such as separation, reaction, and material formation. One approach to overcoming this limitation is to employ specialized scCO2 soluble surfactants that induce formation of reversed micelles with polar-solvent-cores (for example, water or ionic liquids) in the continuous scCO2 phase. Since such systems would combine the attractive characteristics of scCO2 with the solvating properties of polar solvents, those are expected to be a 'universal solvent'. This paper introduces studies for self-organization of surfactants in scCO2, specially a W/CO2 microemulsion.
