Gas transport in bisphenol A poly(ether ether ketone ketone) membrane

A homogeneous dense membrane of bisphenol A poly(ether ether ketone ketone) (PEEKK) has been prepared by a solution casting technique with chloroform as solvent and characterized by wide-angle X-ray diffraction and tensile te ster. Permeating characteristics of five pure gases through the membrane ha s been described systematically. The permeability, diffusivity, solubility, and their selectivities of oxygen, nitrogen, carbon dioxide, methane, and hydrogen through the membrane have been measured by a change in operating t emperature and upstream pressure in a time-lag apparatus. A continuously en hanced permselectivity for gas pairs of carbon dioxide/methane, and hydroge n/nitrogen. an enhanced diffusivity selectivity for gas pairs of oxygen/nit rogen, carbon dioxide/methane, as well as a decreased permeability and diff usivity for five pure gases, have been observed with decreasing operating t emperature. The solubility of five gases in the PEEKK membrane increases wi th decreasing temperature. The solubility selectivity hardly ever varies wi th operating temperature. Especially, the permeability, diffusivity, solubi lity, and their selectivities in the PEEKK membrane almost maintain constan t with changing the upstream pressure. The highest oxygen/nitrogen, carbon dioxide/methane, and hydrogen/nitrogen selectivity coefficients were, respe ctively, equal to 7.06, 23.1, and 106.1. A relationship between the permeab ility or diffusivity and molecule diameter of the gases across the PEEKK me mbrane was discussed. The gas solubility in the membrane is believed to be a linear function of the critical temperature of the gases. (C) 2001 Elsevi er Science Ltd. All rights reserved.