The effects of supercritical CO 2 (scCO 2 ) conditioning are examined through changes in gas permeability and solubility for 6FDA-based polyimide membranes. At pressures above the supercritical point, both CO 2 permeability and sorption unexpectedly decline, suggesting a structural rearrangement of the polymer facilitated by the presence of a highly soluble species. High-pressure permeability isotherms for He and N 2 do not exhibit a similar decline. Upon depressurization, a typical hysteresis is not observed; rather, CO 2 permeability remains at reduced levels compared to the original pressurization. Permeability isotherms of the conditioned polymer show a reduction in transport compared to unconditioned samples; however, sorption isotherms show an increase in penetrant solubility following scCO 2 conditioning. Pre- and post-CO 2 /CH 4 mixed gas permeation testing at 35 °C shows a reduction in membrane permeability with a corresponding increase in the separation factor after scCO 2 conditioning.
No takes yet. Share an insight, caveat, or question.
Kratochvil et al. (2009) studied this question.