Optimization of CO2-CH4 separation performance of integrally skinned asymmetric membranes prepared from poly(2,6-dimethyl-1,4-phenylene oxide) by factorial design

Integrally skinned asymmetric flat sheet membranes were prepared from poly( 2,6-dimethyl 1,4-phenylene oxide)(PPO) for CO2-CH4 separation. Various expe riments were carried out to identify PPO membranes, which have good mechani cal strength and gas separation abilities. Membrane strength and selectivit y depend on the interplay of the rate of precipitation and the rate of crys tallization of the PPO. The effects of major variables involved in the memb rane formation and performance, including the concentration of the polymer, solvent, and additive, the casting thickness, the evaporation time before gelation, and the temperature of the polymer solution, were investigated. F actorial design experiments were carried out to identify the factor effects . The membrane performance was modelled and optimized to approach preset va lues for high CO2 permeance and a high CO2: CH4 permeance ratio. Membranes were prepared based on the optimum conditions identified by the model. Esse ntially, defect-free membranes were prepared at these conditions, which res ulted in a pure gas permeance of 9.2 x 10(-9) mol/m(2) s Pa for CO2 and a p ermeance ratio of 19.2 for CO2: CH4. (C) 1999 John Wiley & Sons, Inc.