There is an active search for accurate and effective techniques to analyze sediments in extraterrestrial environments. A current method utilized on the Martian rover Curiosity involves pyrolysis – heating sediment samples to high temperatures – followed by subsequent GC-MS analysis. This method is problematic as larger organic molecules are fragmented into smaller compounds prior to analysis, leaving the identity of the original compound unknown.  An alternative approach is the utilization of supercritical carbon dioxide as a solvent for extraction of organic molecules in extraterrestrial environments. The relatively mild conditions temperature and pressure conditions would not degrade larger organic molecules. Solubility of some compounds in supercritical carbon dioxide can also be enhanced with addition of cosolvents such as water.  In this study, sulfur containing compounds such as those previously identified as present on Mars are analyzed for solubility in supercritical carbon dioxide and water. Through the use of Monte Carlo molecular simulation, the transferable potentials for phase equilibria-united atom and TIP4P-2005 water forcefields were employed to describe interactions between the solute and solvents. The five molecules studied were thiophene, benzothiophene, dibenzothiophene, methanethiol, and dimethyl sulfide. Vapor-liquid equilibria at 373 and 453 K were determined for compounds that were substantially soluble while pure component solubilities were calculated for sparingly soluble compounds.  Results are discussed in terms of structural analysis, solubility, and the impact of water cosolvent as well as pressure and temperature on these properties.

Solubility and vapor-liquid equilibrium of sulfur-containing compounds with supercritical carbon dioxide via Monte Carlo molecular simulation

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.