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-layer composite hollow fiber membranes are described. Dilute P4VP solutions form a defective coating layer on the top of PEI hollow fiber surface but reduce the surface porosity significantly, which makes the SR plugging feasible to regain the gas permselectivity of P4VP/PEI composite hollow fiber. Polyethylene glycol (PEG) additive in the PEI spinning dopes suppresses the growth of macro-voids and produces a membrane morphology having a more porous skin surface and more compact substructure, which provides a lower skin resistance and a higher substructure resistance for gas permeation. Substantial substructure resistance can deteriorate the membrane performance. Since 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 > CO2 > 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 coating 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. All rights reserved.