Журнал мембранных наук и технологий

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Turning Commercial Ceramic Membranes into a First Stage of Membranes for Post-Combustion CO2 Separation

Sophie Cerneaux, Vincent Germain, Gil Francisco, David Cornu, Cédric Loubat, Eric Louradour, André Larbot and Eric Prouzet

This report describes how commercial tubular ceramic membranes, initially designed for liquid filtration, can be modified to provide the core separation components of a first stage of flue gas treatment and enrichment in post-combustion CO2 separation. Commercially available tubular NanoFiltration (NF) ceramic membranes were turned into a membrane for CO2 separation by a two-step process including additional ceramic coating and chemical grafting. The combination of ceramic coating and chemical grafting drastically modify the membrane properties and turn the membrane initially designed for liquid filtration into a membrane that displays CO2 vs N2 selectivity at the opposite of Knudsen-based selectivity, with a CO2:N2 ideal selectivity of 2.3. A second step of this study addressed the reduction of membrane cost, by starting with a low ultrafiltration (UF) 200 nm ceramic support specifically manufactured for this application in place of a NF membrane. After successful coating of a 5 nm and a 1 nm ceramic membranes, this membrane, grafted with a commercial fluorosilane molecule was tested in pure gas permeation of CO2 and N2, with an ideal selectivity CO2:N2=3. Finally, the same membrane, grafted with glymo, was tested against separation of a CO2 (20%):N2 (80%) mixture, and as a function of the permeation stage-cut. A CO2:N2 selectivity of 4 was obtained for a stage-cut of 0.5, and even higher (CO2:N2 selectivity=14) for low stage-cuts usually used for testing dense polymer membranes. These results demonstrate that commercial ceramic porous membranes can be used as starting elements for a first stage of CO2 post-combustion gas cleaning and CO2 enrichment.