Thursday, 3 November 2005 - 2:30 PM
508g

Oxygenated Hydrocarbon Ionic Surfactants Exhibit CO2 Solubility

Xin Fan1, Juncheng Liu2, Robert M. Enick1, and Christopher B. Roberts2. (1) University of Pittsburgh, 1249 Benedum Hall, Pittsburgh, PA 15261, (2) Department of Chemical Engineering, Auburn University, 230 Ross Hall, Department of Chemical Engineering, Auburn, AL 36849

Several oxygenated hydrocarbons, including acetylated sugars, poly(propylene glycol) and oligo(vinyl acetate), have been used to generate CO2-soluble ionic surfactants. Surfactants with vinyl acetate tails yielded the most promising results, exhibiting levels of CO2 solubility comparable to those associated with fluorinated ionic surfactants. For example, a sodium sulfate with single, oligomeric vinyl acetate (VAc) tails consisting of 10 VAc repeat units was 7 wt% soluble in CO2 at 25 oC and 48 MPa. Upon introduction of water to these systems, only surfactants with the oligomeric vinyl acetate tails exhibited spectroscopic evidence of a polar environment that was capable of solubilizing the methyl orange into CO2-rich phase. For example, a single phase solution of CO2, 0.15 wt% sodium bis(vinyl acetate)8 sulfosuccinate and water, at loading of W values ranging from 10 to 40 at 25°C and 34.5 MPa, exhibited a methyl orange peak at 423 nm. This result indicated that the core of a reverse micelle provided a microenvironment with a polarity similar to that of methanol. Quantum chemical calculations indicate that the acetylated sugars may be too hydrophilic to readily form reverse micelles, whereas the VAc-based surfactants appear to have the correct balance of hydrophilic and hydrophobic forces necessary to form reverse micelles.

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