NASA’s current systems controlling CO2 levels in a cabin’s atmosphere are problematic. Currently, packed beds of granules of zeolite are used as sorbents for CO2 in NASA CO2-removal assemblies. Problems and inefficiency associated with packed beds are related to random packing of granules and resulting poor thermal management and poor mechanical stability. A much improved system is envisioned if the basis for the sorbent bed is a 3D-printed monolithic lattice.
For this project the extrusion–based additive manufacturing (AM) technique known as robocasting will be used to create prototype lattices of zeolite 13X and zeolite 5A that are much more robust and efficient for reversibly adsorbing and desorbing CO2. Success requires the development of zeolite paste feestocks that are suitable for the robocasting process and also have the ability to partially sinter into robust structures while simultaneously retaining high surface area and microporosity. Studies for the development of effective sintering aids (inorganic binders) will be completed in order to suitably partially sinter zeolite particles together at temperatures of preferably <700C. Optimization of fugitive binder systems for creation of zeolite pastes with rheological properties appropriate for robocasting will also be completed and the successful fabrication and sintering of zeolite lattices demonstrated.
Furthermore, an objective is to build and demonstrate the incorporation of heating elements into a zeolite assembly that will induce rapid and complete desorption of CO2. The specific target goal is to be able to heat a zeolite monolith in-situ up to 300C
The final deliverable for Phase I will be the demonstration of a stack of lattice monoliths 25-50mm in diameter made with zeolite 13X and/or zeolite 5A that meets the material targets for strength, CO2 adsorption capacity, and pressure drop and incorporates a heating element capable of 300C.
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.
The most likely Non-NASA applications will be for catalyst supports and gas separators for industries involved with air separation, petroleum refining, petrochemicals, refrigerants, and natural gas. Other potential applications are feasible for the disinfection and purification of water for the creation of potable water in developing countries.