6 research outputs found
Structural, Thermal, and Gas-Transport Properties of Fe3+ Ion-Exchanged Nafion Membranes
No full textGas Sorption, Diffusion, and Permeation in Nafion
No full textThe
gas permeability of dry Nafion films was determined at 2 atm and 35
°C for He, H<sub>2</sub>, N<sub>2</sub>, O<sub>2</sub>, CO<sub>2</sub>, CH<sub>4</sub>, C<sub>2</sub>H<sub>6</sub>, and C<sub>3</sub>H<sub>8</sub>. In addition, gas sorption isotherms were determined
by gravimetric and barometric techniques as a function of pressure
up to 20 atm. Nafion exhibited linear sorption uptake for low-solubility
gases, following Henry’s law, and convex behavior for highly
sorbing condensable gases, indicating rubber-like behavior at 35 °C.
XRD results demonstrated that Nafion contains bimodal amorphous chain
domains with average <i>d</i>-spacing values of 2.3 and
5.3 Ă…. Only helium and hydrogen showed relatively high gas permeability
of 37 and 7 barrers, respectively; all other gases exhibited low permeability
that decreased significantly as penetrant size increased. Dry Nafion
was characterized by extraordinarily high selectivities: He/H<sub>2</sub> = 5.2, He/CH<sub>4</sub> = 445, He/C<sub>2</sub>H<sub>6</sub> = 1275, He/C<sub>3</sub>H<sub>8</sub> = 7400, CO<sub>2</sub>/CH<sub>4</sub> = 28, CO<sub>2</sub>/C<sub>2</sub>H<sub>6</sub> = 79, CO<sub>2</sub>/C<sub>3</sub>H<sub>8</sub> = 460, H<sub>2</sub>/CH<sub>4</sub> = 84, H<sub>2</sub>/C<sub>2</sub>H<sub>6</sub> = 241, and H<sub>2</sub>/C<sub>3</sub>H<sub>8</sub> = 1400. These high selectivities
could make Nafion a potential candidate membrane material for dry
feeds for helium recovery and carbon dioxide separation from natural
gas and removal of higher hydrocarbons from hydrogen-containing refinery
gases
