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7735159 
Journal Article 
Effect of Hydrocarbons on the Separation of Carbon Dioxide From Methane through a Polyimide Gas Separation Membrane 
Gofferje, G; Hasan, R; Scholes, C; Stevens, GW; Kentish, SE 
2009 
Yes 
Industrial and Engineering Chemistry Research
ISSN: 0888-5885
EISSN: 1520-5045 
AMER CHEMICAL SOC 
WASHINGTON 
48 
11 
5415-5419 
English 
WOS:000266480500029 
The removal of carbon dioxide from natural gas by membrane gas separation is an important process in upgrading the gas for consumers. Hydrocarbons associated with natural gas have the potential to influence the CO2 separation performance of membranes. Here, a glassy polymeric membrane of poly (4,4′- hexafluoroisopropylidene diphthalic anhydride-2,3,5,6-tetramethyl- 1,4-phenylenediamine) (6FDA-TMPDA) was exposed to hexane and toluene at different partial pressures in a 90% CH4-10% CO2 gas mixture. The permeability of CO2 and CH4, as well as the selectivity, declined over time as both hexane and toluene competitively sorbed into the membrane. The resulting behavior fit the dual-sorption model for polymeric membrane separation and indicated Langmuir affinity constants of 0.13 ± 0.03 atm-1 for methane, 240 ± 100 atm-1 for hexane, and 980 ± 500 atm-1 for toluene (fugacity basis). The kinetics of the permeability decline were faster than that of the permeability recovery after the hydrocarbon contaminant was removed which may indicate that desorption from the Langmuir voids is the rate controlling step.