(704b) Polymeric Moisture Swing Membranes for Carbon Dioxide Capture from Gas Mixtures

Processes permitting efficient carbon dioxide capture from gas mixtures could find application in large-scale industrial gas separations, production of synthetic carbon-containing fuels, and greenhouse gas removal from the atmosphere.  Membrane-based processes provide several advantages over traditional carbon dioxide removal technologies, including mechanical simplicity, a relatively small footprint, and energy efficiency.  Here, we describe the synthesis, characterization, and analysis of polymeric anion exchange materials for carbon dioxide concentration from gas mixtures.  Transport of carbon dioxide through the membrane is promoted by an opposing flux of water, which reacts with carbon dioxide through several equilibrium reactions to form charged species (bicarbonate, carbonate, and hydroxide) within the membrane matrix.  Transport of carbon dioxide through the membrane will be discussed as a function of material characteristics, including charge density, and process characteristics, such as feed stream relative humidity, crossflow velocity over the membrane surface, and carbon dioxide concentration on both sides of the membrane. The development of several membrane materials, including those based on poly(phenylene oxide) and imidazolium chemistries, will be discussed.  Results of experimental gas transport studies in a crossflow test cell will be presented.  Optimal operating conditions for maximum carbon capture will be proposed.  Of particular interest is the integration of a carbon dioxide capture membrane into an artificial photosynthesis system, which would permit the combination of hydrogen and oxygen from solar water splitting with captured carbon dioxide from the atmosphere to create synthetic, carbon-rich fuels.