KSEF R&D Excellence: Novel Polymeric Membrane Materials for the Purification of Synthesis Gas

The gasification of coal is a key process in the nation's long-term energy strategy. Integrated gasification combined cycle (IGCC) processes provide a pathway to utilize coal at high efficiencies with low emissions. In the IGCC process, coal is gasified using air and the resulting syngas is converted to a mixture of predominantly hydrogen and carbon dioxide via shift reaction. Gas separation technology is then required to economically transform the H2/C02 mixture into high purity H2 and CO2 streams. Polymer membranes provide an attractive technology for the separation of CO2 from H2. Ideally, such membranes would be highly permeable to CO2 over H2, such that the (major) H2 component would be retained at high pressure. The retention of the H2 stream near its feed pressure eliminates the expense of repressurizing H2 for use in electric power generation, while the CO2 permeate is captured for sequestration. The objective of this proposal is the development and characterization of a new generation of "reverse-selective" membranes designed for the preferential transport of CO2 over H2. The membranes are comprised of rubbery, cross-linked copolymer networks based on polyethylene glycol acrylates. Preliminary studies have demonstrated that preferential transport of CO2 over H2 can be accomplished with these materials. However, the transport properties are found to be highly-sensitive to the details of the network (e.g. crosslink density; backbone pendant groups). To fully realize the potential of this new class of materials, a comprehensive experimental study is proposed to determine the relationships between polymer structure, chain dynamics and free volume, and gas separation properties. The project will lead to fundamental understanding as to the correlation of chain dynamics and morphology with gas separation performance for rubbery networks, and the establishment of design rules for the optimization of these materials for H2/C02 separation, and for reverse-selective membrane separations in general. KEYWORDS: polymers; membranes; hydrogen; coal; carbon sequestration