Effects of Polymer Precursors and Pyrolysis Conditions on Carbon Molecular Sieve Membranes for Gas Separation

摘要

Purification of natural gas and olefin-paraffin gases are important energy-intensive separations in the petrochemical industry. Although polymer membranes have been used for the applications, an upper limit in their ability to be improved, while maintaining economical manufacturing costs has been encountered. Molecular sieving materials have shown the potential to significantly exceed the current permeability and selectivity tradeoff line while potentially maintaining economically attractive manufacturing. These molecular sieving materials comprise carbon molecular sieves (CMS), zeolites, and metal-organic frameworks (MOF). CMS membranes can be formed by thermal decomposition of polymer precursors, resulting in almost pure carbon materials. Pores are formed from packing imperfections between ordered regions in the materials during pyrolysis, and the pore structure can be described with an idealized bimodal pore distribution, consisting "micropores" of 6-20 A° connected by smaller so-called "ultramicropores". The combination of ultramicropores and micropores provides the molecular sieving function and high permeability characteristics of these unusal CMS membranes.