Gas separation performance of poly(4-vinylpyridine)/polyetherimide composite hollow fibers

The preparation and gas permeation performance (H-2, CO2, O-2, N-2, CH4) of silicone rubber/poly(4-vinylpyridine)/polyetherimide (SR/P4VP/PEI) multi-l ayer composite hollow fiber membranes are described. Dilute P4VP solutions form a defective coating layer on the top of PEI hollow fiber surface but r educe the surface porosity significantly, which makes the SR plugging feasi ble to regain the gas permselectivity of P4VP/PEI composite hollow fiber. P olyethylene glycol (PEG) additive in the PEI spinning dopes suppresses the growth of macro-voids and produces a membrane morphology having a more poro us skin surface and more compact substructure, which provides a lower skin resistance and a higher substructure resistance for gas permeation. Substan tial substructure resistance can deteriorate the membrane performance. Sinc e the unfavorable influence of substructure resistance on the gas permeance is more pronounced for the fast permeating gas and in the order of H-2 > C O2 > O-2 > N-2 > CH4, the gas selectivities of H-2/N-2, CO2/CH4, and O-2/N- 2 decrease accordingly. The PEI hollow fibers prepared from a PET/PEG/NMP ( 23/0/77) spinning dope, after coated with 0.2 wt.% P4VP and 3 wt.% SR coati ng solutions. have gas permeances of H-2 = 41, CO2 = 7.4, and O-2 = 2.0 GPU (1 GPU = 1 x 10(-6) cm(3) (STP)/cm(2)-s-cmHg) with selectivities of H-2/N- 2 = 117. CO2/CH4 = 62, and O-2/N-2 = 5.8. (C) 2001 Elsevier Science B.V. Al l rights reserved.