Oxygen Selective Metal Organic Framework Adsorbent for High Efficiency Air Separation

While cryogenic ASU is the technology of choice to supply oxygen to large plants, it requires very expensive and complex hardware that prevents cost-effective scale down for small installations. At small scale, pressure swing adsorption (PSA) is widely used. PSA is based on the selective reversible adsorption of nitrogen (but not oxygen) onto molecular sieve sorbents. The conventional PSA process delivers a somewhat more expensive product, mainly due to the inefficiencies involved in the adsorption of the major component (nitrogen) from high pressure air and its subsequent discharge at ambient pressure (i.e., work input during compression is lost). Sandia National Laboratory researchers have recently identified novel open-pore metal-organic-frameworks (MOFs), which exhibits high uptake and selectivity for oxygen. This selectivity towards oxygen could potentially reduce the energy requirement of the PSA-based air separation process. TDA Research Inc. (TDA) will develop these materials into highly effective, manufacturable adsorbents and design an efficient air separation process utilizing the new sorbent supported with detailed engineering design and process simulations. In Phase I, we synthesized various sorbents pelletized then using low energy densification techniques. We also used modifiers that further increase the oxygen selectivity against nitrogen. In bench-scale tests, we demonstrated the stable operation of the new material through many cycles under representative conditions. We designed a process and a cycle sequence that achieves high product yield and purity. In a techno-economic analysis, we showed that the new technology could reduce the energy needs for the air separation compared to the conventional PSA process. In Phase II, we will continue to optimize the sorbent to enhance its O2 capacity and selectivity. We will assess the impact of critical process parameters at bench-scale and carry out at 20,000 (minimum) adsorption/desorption cycles. We will design and fabricate a prototype system capable of producing 10 kg/day oxygen to carry out proof-of-concept evaluations for the full unit. We will conduct process simulations and evaluate the techno-economic viability of the new air separation technology. Oxygen is a strategic chemical, with a $3.8 billion market value in the U.S. It supports many industrial processes and enters into oxidative combination with many materials. The new technology has the potential to provide a lower cost oxygen product.