(414r) Membranes Containing Cation-Exchanged Zeolites for CO2 Separation

As concerns over the impact of rising concentrations of atmospheric CO₂ on climate change continue to mount, there is an urgent need for the development and implementation of technologies that capture CO₂ in anthropogenic sources. The CO₂ separation technology can also be implemented in many energy-production processes such as natural gas treatment, hydrogen purification in steam reforming process, and the recovery of CH₄ from biogas produced by anaerobic digestion of wastes. Meanwhile, membrane-based molecular separations, energy-efficient and environment-friendly processes that can replace conventional energy-intensive separation methodologies, have attracted a great amount of interests. However, current polymeric membranes which can be produced in a large scale due to their excellent processibility often showed the limited performance. To design high-performance membranes while utilizing the advantages of polymeric materials, various nanoporous materials have been incorporated into polymer membranes.

 Most recently, we have found that cation-exchanged zeolites exhibit outstanding CO₂ separation properties. For example, the Ca-A zeolite outperforms Mg₂(dobdc) metal-organic framework, one of the best performing CO₂-capture materials reported so far, in terms of the CO₂ adsorption capacity and CO₂/N₂ selectivity at the conditions relevant to dry flue gas. Furthermore, compared to metal-organic frameworks, zeolites are inexpensive nanoporous materials, which are currently produced in large scales for many industrial applications. Motivated by these facts, membranes containing cation-exchanged zeolites were fabricated for applications in CO₂/N₂ and CO₂/CH₄ separations.  Not only gas permeation properties of the membranes but also the methodology to control the zeolite-polymer interfacial contact in mixed-matrix membranes, which has been a key prerequisite in designing high-quality zeolite/glassy polymer composite membranes, will also be discussed.