(618f) Demonstration of Engineered Structured Sorbents in Various Adsorption Applications

Precision Combustion, Inc. (PCI) has designed, developed, and demonstrated an adsorption technology using beds consisting of structured metal meshes coated with sorbent materials. The engineered structured sorbents, consisting of metal mesh elements which are trademarked and patented as Microlith® by PCI, can be tailored to effectively adsorb a number of species of interest and have been demonstrated to provide beneficial performance for aerospace, building, and fuel cell applications, among others. The resulting sorbents have the potential for direct resistive heating by applying electric current directly to the Microlith® substrate, which offers the potential for rapid, periodic sorbent regeneration as opposed to the longer thermal cycles typical of packed bed adsorbers. As a result, a regenerable adsorber using adsorbent coated on Microlith® structures can reduce the system weight and volume compared to conventional packed bed configurations. Historically, sorbent systems have used some form of packed bed consisting of uniformly shaped pellets or beads, as well as irregularly-shaped granular particles of sorbent media. The downfall of this type of sorbent implementation is the propensity of the material to fluidize, erode, and generate fines. Sorbent media fines have proven problematic in some aerospace applications.

For aerospace (e.g., NASA) and building applications, these structured sorbents were implemented to remove CO₂ and trace contaminants from breathing air. For NASA, these systems must efficiently and reliably control CO₂ and trace contaminant concentrations to levels necessary for long-term crewed space exploration missions beyond low earth orbit. For building applications (e.g., Indoor Air Quality - IAQ or sick-building syndromes), these systems must be capable of providing a long operational window for removing the targeted components. Sorbents such as Zeolites and molecular sieves are excellent candidates for these applications because of their high affinity for capturing molecules of interest along with their chemically inert nature and non-flammable properties. Such properties make them attractive from both performance and safety perspectives. Finally, for fuel cell applications, this Microlith®-based adsorption technology has been implemented for efficient hydrogen sulfide (H₂S) removal from the fuel processor exhaust stream in a fuel reforming-fuel cell system. Our results indicated a significant improvement in performance compared to typical commercial ZnO pellets.

In this paper, the design, development, and optimization of engineered structured sorbent beds based on PCI’s Microlith® adsorption technology will be presented. Test results that demonstrate its benefits of increased structural stability gained by eliminating clay bound zeolite pellets that tend to fluidize and erode, and better thermal control during sorption leading to increased process efficiency will be highlighted. We will also discuss the results obtained from various sorption tests, such as removing CO₂ and trace organic contaminants for NASA cabin air cleaning applications and for IAQ applications. Additionally, the development of this technology for sulfur (e.g., H2S) removal in fuel cell applications will be presented.