(377c) Membrane NH3 Separation from N2 and H2 at High Temperature Close to the Haber-Bosch Process

NH₃ is one of the largest-volume chemicals synthesized in the world, consuming ~2% of the world's energy and generating 1% of the global CO₂ emission. Currently, over 90% of NH₃ is synthesized by the Haber-Bosch (HB) process at 150-350 bar and 400-500 ^oC. The NH₃ synthesis reaction is thermodynamically unfavorable and in equilibrium limitation, leading to a single-pass NH₃ yield of only ~15%. Low yield of NH₃ in the product stream necessitates the recovery of NH₃ and the recycling of the unreacted mixture gases (N₂+H₂). Typically, NH₃ is recovered via a combination of cryogenic condensation (at -18 to -33 ^oC) and compression process, and the large quantity of unreacted gas mixture is subsequently reheated back to the reaction temperature for recycling to the feed. Therefore, the process is highly energy-intensive and costive. In this study, we explored the employment of our novel Na⁺-gated nanochannel membrane for NH₃ separation from abundant H₂ and N₂ at high temperature up to 400 ^oC and pressure up to 35 bar. Results indicated that the Na⁺-gated nanochannel membrane was robust and remained highly NH₃-selective at temperatures in the range of 250 to 400 ^oC. The selectivity of NH₃/H₂ and NH₃/N₂ was higher than 100 and 400, respectively. The Na⁺-gated nanochannel membrane, therefore, showed the potential to be used in membrane reactor for NH₃ synthesis.