Dissolution of surfactants in supercritical CO2 with co-solvents

Abstract The dissolution of surfactant-like compounds in supercritical CO 2 in presence of co-solvents was investigated. The solubility measurement was conducted using a visualized PVT cell combined with UV spectrophotometer method at different pressures and 313 K. The viscosity of mixtures of CO 2 and co-solvents with or without dissolved surfactants was also measured at similar conditions using a capillary tube rheometer. Nonionic surfactants (N-NP-10c, branched alkylphenol ethoxylates and APG-1214, alkyl polyglucoside) and anionic surfactants (N-NP-15c-H, sulfonated alkylphenol ethoxylates) were studied, which are good CO 2 foaming agents. Experimental results showed that increasing pressure and addition of co-solvents could effectively improve solubility of surfactants in supercritical CO 2 . The addition of ethanol as a co-solvent could increase N-NP-10c's solubility in CO 2 from 0.15 g (100 g) −1 to 1.76 g (100 g) −1 (over 11 times). APG-1214 with a mixture of ethanol and ethylene glycol as co-solvents exhibited an immediate dissolution capability in CO 2 , and its solubility could reach up to 1.99 g (100 g) −1 . The solubility of N-NP-15c-H in comparison with APG-1214 was relatively low, only 0.57 g (100 g) −1 was obtained with the same co-solvents and at similar conditions. The addition of ethanol into CO 2 could slightly increase its viscosity, while the effect of ethylene glycol and surfactants was much higher than that of ethanol, which indicates that the dissolution of surfactants in CO 2 with co-solvents involves complicated interactions between molecules.

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