Study on multi-layer composite hollow fiber membranes for gas separation

Novel multi-layer composite hollow fiber membranes were prepared using sili cone rubber, poly(4-vinylpyridine) and polysulfone as sealing layer, select ive layer and support layer, respectively. The resultant composite membrane s possess a different structural configuration from the conventional multil ayer composite membranes, i.e. (sealing layer)/(selective layer)/(support l ayer) versus (selective layer)/(gutter layer) /(support layer). The new mem brane structure lead to high performance membranes for gas separation appli cations. For example, the polysulfone hollow fiber membrane coated from a 3 wt% silicone rubber solution and a 0.2 wt% poly(4-vinylpyridine) solution had an O-2 permeance of 6.69 x 10(-6) cm(3)(STP)/cm(2) s cmHg with O-2/N-2 selectivity of 7.26. From the permeation results of polysulfone hollow fibe rs coated with poly(4-vinylpyridine) and SEM photo micrographs, it was conc luded that the surface of poly(4-vinylpyridine) layer was defective and the high membrane performance was rendered only after coating with a silicone rubber layer. The analysis by a resistance model suggested that the poly(4- vinylpyridine) layer comprised most of the resistance (99%) and provided th e separation performance. The surface porosity of the polysulfone support l ayer and the permeability of poly(4-vinylpyridine) can also be roughly calc ulated by applying the resistance model. (C) 1999 Elsevier Science Ltd. All rights reserved.