(191ai) PRESSURE – TEMPERATURE PHASE DIAGRAMS of CLATHRATE HYDRATES of HFC-134a, HFC-152a and HFC-32

Clathrate hydrates are crystalline water-based solids physically resembling ice, in which small non polar molecules (typically gases) are trapped inside cages of hydrogen bonded water molecules. But unlike ice, they can form at temperatures well above the ice point. Clathrate hydrates of hydrofluorocarbons (HFCs) are generally formed at low-pressures at ambient temperatures. The low-pressure hydrate formation conditions of HFCs can have different applications in chemical engineering. Examples are: water desalination, air conditioning and cold storage, food and pharmaceutical industry etc. A preliminary study shows that the there are some inconsistencies among the phase equilibrium data for clathrate hydrates of some HFCs, which warrants new phase equilibrium measurements. In this work, we report dissociation pressures for clathrate hydrates of C2H2F4 (1,1,1,2-tetrafluoroethane or HFC-134a or R-134a), C2H4F2 (1,1-difluoroethane or HFC-152a or R-152a) and CH2F2 (difluoromethane or HFC-32 or R-32) in the temperature ranges of (279.4 to 282.9) K, (279.7 to 287.7) K and (278.1 to 291.3) K, respectively. The experimental data were generated using an isochoric pressure-search method. The hydrate dissociation data are compared with the experimental data reported in the literature and a discussion is made on their reliabilities.