| Abstrakt: |
The solubilities of N2, CO2, CH4, C2H6, C3H8, and C3F8and permeabilities of N2, O2, CO2, CH4, C2H6, and C3H8were determined in a glassy, amorphous fluoropolymer prepared from 80 mol % 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole (TTD) and 20 mol % tetrafluoroethylene (TFE), commercially known as Hyflon AD 80. This polymer exhibits lower increases in hydrocarbon gas and vapor solubility with increasing penetrant critical temperature than conventional hydrocarbon polymers. On the basis of a best fit of the natural logarithm of solubility vs critical temperature, Hyflon AD 80 should have much lower solubility for high molar mass hydrocarbon compounds (e.g., n-decane) than conventional hydrocarbon polymers. Pure gas CO2/CH4separation properties of this polymer are comparable with those of some hydrocarbon polymers considered for natural gas purification. When exposed to a feed stream containing a mixture of CO2and CH4, the polymer exhibits a CO2permeability of approximately 250 barrers and a CO2/CH4mixed-gas selectivity of 10.6 at 1.6 atm CO2partial pressure. The mixed gas selectivity decreases minimally as CO2partial pressure increases to 10.6 atm. The mixed gas selectivity is also maintained when moderate amounts of toluene and n-hexane are present in the CO2−CH4feed stream. Diffusion coefficients, calculated from pure gas permeability and solubility coefficients, suggest membrane plasticization at higher pressures of CO2and C2H6. The polymer also exhibits reversible hysteresis in C3H8permeability with pressure. |
