Preparation of hollow fiber poly(ether block amide)/polysulfone composite membranes for separation of carbon dioxide from nitrogen

The separation of carbon dioxide from nitrogen is relevant to flue gas treatment for greenhouse gas emission control. This study deals with the preparation of hollow fiber poly(ether block amide) (PEBA)/polysulfone (PSf) composite membranes for CO2/N-2 separation. PEBA 2533 copolymer was shown to be a good permselective membrane material for CO2/N-2 separation. At 25 degreesC and 100 psig, a CO2 permeability of about 260 Barrer and a CO2/N-2 selectivity of 32 were obtained. The thin-film hollow fiber PEBA/PSf composite membrane comprising of a thin PEBA skin layer (<5 mum) and a porous polysulfone hollow fiber substrate was prepared by the dip-coating technique. The polysulfone hollow fiber substrate was formed by the solution extrusion/phase inversion process. The effects of parameters involved in the procedure of polysulfone hollow fiber spinning and PEBA layer deposition on the permselectivity of the resulting composite membranes were investigated. Defect-free PEBA/PSf composite membranes with an inside and an outside diameters of 350 and 600 mum, respectively, have been obtained which showed a CO2 permeance of 61 GPU and a CO2/N-2 selectivity close to the intrinsic selectivity of the PEBA dense membrane. It was shown that the N-2 permeability is essentially independent of the pressure, whereas CO2 permeability tends to increase with an increase in gas pressure, presumably due to plasticization of the membrane caused by the relatively high solubility Of CO2 in the membrane. (C) 2004 Elsevier B.V. All rights reserved.