Controlled synthesis of high performance carbon/zeolite T composite membrane materials for gas separation

A simple approach has been developed to synthesize the carbon/zeolite T composite membrane materials with the high gas separation performance. The precursors of the composite membrane are composed of polyimide matrix and dispersed zeolite T particles. The composite membranes prepared by pyrolysis at 973 K show excellent gas (H(2), CO(2), O(2), N(2), and CH(4)) permeability and selectivity (O(2)/N(2), CO(2)/CH(4)) for both single gas and mixed-gas. The gas separation performance of the composite membranes can be controlled in a wide range by only changing the zeolite T particle size. The maximum selectivity of O(2) over N(2) (21/79 mol%) for the composite membranes with the least zeolite T particle (0.5 mu m) is 15 with an O(2) permeability of 347 Barters (1 Barrer = 7.5 x 10(-18) m(2) s(-1) Pa(-1)) and the selectivity of CO(2) over CH(4) (50/50 mol%) reaches a value of 179 with a CO(2) permeability of 1532 Barters. It is believed that the increase of gas permeability is attributed to the ordered microchannels in the zeolite and the interfacial gaps formed between zeolite and carbon matrix in the composite membranes. And the gas selectivity is tuned by the size of interfacial gaps which are varied with the zeolite particle size. This technique will provide a simple and convenient route to efficiently improve the trade-off relationship between the permeability and the selectivity and enable the construction of carbon-based composite materials with novel functionalities in membrane science. (C) 2009 Elsevier Inc. All rights reserved