Preparation and characterization of carbon and carbon/zeolite membranes from ODPA–ODA type polyetherimide

Abstract

A novel precursor, 3,3′,4,4′-oxydiphthalic dianhydride-4,4′-oxydianiline (ODPA–ODA) type polyetherimide (PEI), was synthesized and used to prepare carbon membranes by preoxidation and heat treatment. The thermal stability of the ODPA–ODA type PEI was evaluated by thermogravimetric analysis. The surface properties, elemental composition, microstructure, morphology and gas separation performance of the as-made carbon membranes were examined by the Fourier transform infrared spectroscopy, elemental analysis, X-ray diffraction, scanning electron microscopy and gas permeation techniques. The effects of the preoxidation temperature and zeolite incorporation on the microstructure and gas separation performance of carbon membranes were investigated. The results have shown that ODPA–ODA type PEI is a good precursor for producing carbon membranes. The preoxidation of the ODPA–ODA type PEI is essential to make defect-free carbon membranes, which also helps to improve the thermal stability and porosity during pyrolysis by forming crosslinking structure in precursor. The carbon membranes made after preoxidation at 480°C and heat treatment at 650°C have an oxygen permeability of 131.5 Barrer and an ideal O2/N2 selectivity of 9.7. The incorporation of ZSM-5 into the carbon membranes further helps to improve the separation performance of the carbon/zeolite membranes for H2/N2 gas mixture.