Effects of solvent and polymer concentration on the performance of PEI composite membranes

摘要

Polyetherimide (PEI) gas separation membranes were prepared by the dry-wet phase inversion method. The effects of polymer concentration and the type of solvent on the membrane structure and gas permeation properties were investigated. The results indicated that the increase of polymer concentration in the casting solution resulted in a denser skin layer that intended to promote H2/N2 and O2/N2 selectivity but less permeability of PEI composite membranes for gas separation process. The membrane prepared from DMAc as a solvent exhibited a higher permeability but lower gas selectivity comparing with the membrane prepared with NMP. Scanning electron microscopy (SEM) cross-sectional images showed that the membrane prepared with NMP as a solvent exhibited a tear-like structure and the membrane prepared with DMAc as a solvent exhibited a channel-like structure, respectively. The dipping coating method was used to seal defects on the surface of membrane by dilute silicone. The PEI composite membrane exhibited H2 permeability of 8.5 GPU (1 GPU= 1 × 10 -6 cm 3 (STP)/(cm 2 ·s·cmHg)), with a H2/N2 and O2/N2 selectivity of 94.68 and 4.83, respectively, presenting high performance of the membrane.