261110 Asymmetric Hollow Fiber Membranes for Aggressive Sour Gas Purification
Carbon dioxide (CO2) and hydrogen sulfide (H2S) are present in high concentration in a large fraction of natural gas reserves. These species must be removed prior to transport through natural gas pipelines in order to prevent corrosion, increase the heating value of natural gas and because of the dangers associated with H2S. A series of novel crosslinkable materials based on the glassy polyimide 6FDA-DAM:DABA, which has been used in the past for CO2/CH4 separations, has been developed for use in the simultaneous removal of H2S and CO2 from aggressive natural gas feeds. These materials exhibit significantly improved H2S/CH4 selectivity and plasticization resistance over the base polymer without sacrificing the outstanding CO2/CH4 permselectivity of 6FDA-DAM:DABA. Following dense film permeation and sorption studies, one of these crosslinkable 6FDA-DAM:DABA derivatives was identified as a promising candidate for asymmetric hollow fiber formation and testing. In dense film form, this material has an H2S/CH4 selectivity as high as 23.5 and a CO2/CH4 selectivity just below the intrinsic value when using a 20% H2S/20% CO2/60% CH4 mixture at feed pressures up to 900 psi. The dense film characterization results as well as those for asymmetric hollow fiber spinning and preliminary permeation testing will be discussed.