Preparation of hollow fiber composite membrane for carbon dioxide/methane separation via orthogonal experimental design

Abstract

Coating active layer on a porous support membrane was an effective method to prepare composite membranes with both high permeability and selectivity for gas separation. However, most of the investigations are focused on the choice and optimization of novel active materials. In this paper, an orthogonal experimental method was used to optimize the structure of the polysulfone (PSF) support membrane. Polyvinylamine (PVAm) and polyvinyl alcohol (PVA) were blended and used as the active materials of hollow fiber composite membranes for the separation of CO2/CH4. The preparation parameters including additives content (A), polymer content (B), weight-average molecular weight of additives (C) and solvent concentration in bore fluid (D) were investigated. The results of statistical analysis indicated that the effects of these preparation parameters on the permeance and selectivity of CO2/CH4 both gradually weakened in the order of B, A, C and D. FESEM observation showed that PSF support membrane with the typical double finger-like pore structure could get a high separation factor and high CO2 permeance, rather than a single finger-like pore structure on the outer skin. The optimization of preparation parameters was as follows: PSF:PEG-400:DMAC (wt%)=19:5:76 and 10 wt% DMAC in bore fluid. Under the optimal preparation conditions, the resultant composite membrane exhibited a more excellent permselectivity of CO2/CH4 than commercial Prism membrane under low pressure (≤0.4 MPa).