Fabrication and gas permeation of CMS/C composite membranes based on polyimide and phenolic resin

Abstract

Carbon molecular sieving (CMS) membranes were fabricated on a support of phenolic resin-based carbon sheets, using a 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene-1,2,3,4-cyclobutanetetracarboxylic dianhydride type polyimide as a precursor, through coating, drying and pyrolysis. The thermal stability of the precursor, the morphology, functional groups, porous structure and microstructure of the CMS/C membranes were characterized by thermogravimetric analysis, electron microscopy, infrared spectroscopy, nitrogen adsorption and X-ray diffraction, respectively. The effects of coating times, pyrolysis temperature, and permeation temperature and pressure on the gas permeation of the CMS/C membranes were investigated. In addition, zeolite ZSM-5 was also utilized as an additive to adjust the microstructure and gas permeation of the CMS/C membranes. The results show that the best gas permeability and selectivity could be attained for the CMS/C membranes under the fabrication condition of coating six times and a pyrolysis temperature of 650 °C. The permeability of the CMS/C membranes improves with an increase in the permeation temperature or a decrease in the pyrolysis temperature. Also, the incorporation of ZSM-5 reduces the thermal stability of the precursor and the gas permeability of the resultant CMS/C membranes.