Effect of permeate pressure on the mixed gas permeation of carbon dioxide and methane in a glassy polyimide

摘要

The permeabilities of glassy polymers to vairous gases depend on the feed pressure. The dependence of permeability on feed pressure for glassy polymers has been widely characterized on the basis of the dual-mode sorption and tansport model for the case of a vacuum permeate pressure. Non-zero permeate pressures are more typical in practical separateion systems. In this study we analyze and characterize the dependence of permeability on the permeate pressure for a glassy polyimide. Nonzero permeate pressures are shown to depress the selectivity of the carbon dioxide-methane system, because the permeability of the carbon dioxide is depressed more than the permeability of methane.