Polymer membranes are attractive for molecular-scale separations such as hydrogen purification because of inherently low energy requirements. However, membrane materials with outstanding hydrogen separation performance in feed streams containing high-pressure carbon dioxide and impurities such as hydrogen sulfide and water are not available. We report highly permeable, reverse-selective membrane materials for hydrogen purification, as exemplified by molecularly engineered, highly branched, cross-linked poly(ethylene oxide). In contrast to the performance of conventional materials, we demonstrate that plasticization can be harnessed to improve separation performance.

Electrobalance and fixed-bed reactors have been used to study the capture of CO 2 from simulated flue gas using a regenerable Na 2 CO 3 sorbent. CO 2 capture was effective in the temperature range of 60-70 °C, while regeneration occurred in the range of 120-200 °C, depending on the partial pressure of CO 2 in the regeneration gas. Equal molar quantities of CO 2 and H 2 O are produced during sorbent regeneration, and pure CO 2 suitable for use or sequestration is available after condensation of the H 2 O. Capture of as much as 90% of the CO 2 was possible at appropriate reaction conditions, and little or no reduction in either carbonation rate or sorbent capacity was observed in limited multicycle tests. The concept is potentially applicable to the capture of CO 2 from existing fossil fuel-fired power plants, where amine scrubbing is the only CO 2 capture process currently available.

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