Description: Currently, NASA controls CO2 levels in a cabin’s atmosphere with CO2-removal assemblies comprised of packed beds of granules of zeolite. Problems and inefficiency associated with packed beds are related to random packing of granules, poor thermal management, and poor mechanical stability. An improved system is envisioned based on sorbent beds of 3D-printed monolithic lattices. For this project the extrusion–based additive manufacturing (AM) technique known as robocasting will be used to create lattices of zeolite (13X and 5A) that are more robust and efficient for reversibly adsorbing and desorbing CO2. Success requires development of zeolite paste feedstocks suitable for the robocasting process and able to partially sinter into robust structures while simultaneously retaining high surface area and microporosity. Great progress was made on this front in Phase I and 50mm monoliths were demonstrated to be feasible. Studies for continued development of effective sintering aids (inorganic binders) and optimal lattice design will be completed in order to scale-up fabrication. Another critical objective is to build and demonstrate the incorporation of heating elements into a zeolite assembly that dissipates heat uniformly and activates desorption of CO2. The target is to heat the zeolite monolith assembly in-situ up to 300C. A collaboration with Michigan Technological University will also be used to simulate, characterize, and optimize the lattice geometry for CO2 adsorption and pressure drop. Synergistically, this collaboration will advance the state-of-the-art for desiccant monoliths to ensure only dry air interacts with the zeolite assembly. The final deliverable for Phase II will be the demonstration of a 10L canister of lattice monoliths 125–200 mm in size made with zeolite 13X and/or zeolite 5A that meets the material targets for strength, CO2 adsorption capacity, and pressure drop and incorporates heating elements for uniform heating to 300C.

Benefits: Air Revitalization System (ARS) : NASA aims to use the 3D-printed sorbent beds as drop-in replacements for packed sorbent beds such as those found in the Carbon Dioxide Removal Assembly (CDRA) on the International Space Station (ISS) and for future NASA missions. Success will also have implications for water removal and humidity control of confined atmospheres.

Besides industrial-scale CO2 capture and specialty catalyst supports the most likely Non-NASA applications will be for gas separation to create concentrated oxygen. For example: zeolite-based oxygen concentrator systems are widely used to produce at-home and portable medical-grade oxygen and on-board oxygen generating systems (OBOGS) for aircrews at high altitudes.