Solubilities of Adamantane and Diamantane in Pressurized Hot Water

Abstract

Aqueous solubilities of lower diamondoid hydrocarbons, adamantane (C10H16) and diamantane (C14H20), were measured along the 5 MPa isobar at temperatures between 313 K and the solid–liquid–vapor triple-point temperature of the solute. The activity coefficients of the individual diamondoids in saturated aqueous solutions were estimated from the solubility data employing two different approximations of the pure-solute heat capacity difference ΔCP2. The aqueous solubilities and activity coefficients of diamondoids were compared with those of polycyclic aromatic hydrocarbons with the same carbon numbers. Depending on temperature and on the approximation of ΔCP2, the activity coefficient of adamantane in saturated aqueous solution exceeds that of naphthalene by a factor ranging within 70 to 150, whereas the activity coefficient of diamantane in saturated aqueous solution exceeds that of anthracene by a factor ranging within 10 to 50.