(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.