A thermodynamic study of the (fluoromethane + water) system

A study of the (fluoromethane + water) system was conducted at temperatures between 255 K and 298 K, and pressures from 0.09 to 2.6 MPa. The solubility of fluoromethane in liquid water was measured from 280 K to 298 K, at pressures up to the hydrate formation pressure. The p–T behavior of the liquid + hydrate + vapor (LHV) three-phase equilibrium was measured from 273 K to 295 K. The p–T behavior of the ice + hydrate + vapor (IHV) three-phase equilibrium was measured from 251 K to 273 K. The intersection of the LHV and IHV curves was used to find the lower quadruple point, Q1, at T = 272.55 K and p = 0.2442 MPa. Solubility-corrected enthalpies of dissociation were determined at the lower quadruple point using the Clapeyron equation. The de Forcrand method was used to determine the hydration number of the hydrate at Q1. The results show that not all of the cages in the SI hydrate structure are filled.

► Solubility of fluoromethane in water as a function of (T, p) was observed.
► Liquid + hydrate + vapor phase equilibrium of the system was observed.
► Ice + hydrate + vapor equilibrium of the system was observed.
► Dissociation enthalpies were found for both equilibria.
► Stoichiometry of fluoromethane hydrate was determined.