Implementation of Advanced Sorbents in a Pressure-Swing Carbon Dioxide Removal System
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As the future ambitions of NASA have turned towards deep space missions, a search for an alternative to current carbon dioxide (CO2) removal systems, namely the Carbon Dioxide Removal Assembly (CDRA) on ISS, is underway. One promising area of research is the use of Metal Organic Frameworks (MOFs) to selectively capture CO2 due to the occurrence of open Lewis acidic coordination sites where CO2 can bind. Under contract with NASA/MSFC, an undergraduate-led team at Iowa State University synthesized and characterized samples of the magnesium-based MOF, Mg-MOF-74, and functionalized two different amine groups onto the base structure to study the adsorption potential of the MOF with the aforementioned modifications. Because of the low binding energy of the coordination sites, the MOFs could be quickly and easily saturated then purged of CO2. By incorporating MOF-packed beds into a vacuum pressure-swing system, the group studied the results of long-term CO2 exposure and pressure cycling. Cabin-feed air at 2650 ppm CO2 was flowed through the system and monitored until saturation occurred, at which point the packed beds were exposed to vacuum and desorbed, then purged using N2. Results showed an approximate 10% increase in weight when saturated, with the potential to mitigate several issues experienced by CDRA and for significant energy savings.