Sustainable ammonia synthesis

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Efficient Ammonia Production Using Stable Absorbents Low Pressure Ammonia Production with Higher Yield Stable ammonia absorbents are used to efficiently separate the hydrogen/nitrogen mixture from ammonia, thereby improving the manufacturing efficiency of ammonia. These simple absorbents are comprised of chloride salts supported on inert organics. By adsorbing ammonia at reactor temperatures, these absorbents allow the reactor to achieve up to 100% nitrogen/hydrogen conversion to ammonia without major heat exchange. Such stable ammonia absorbents, especially those that operate at high temperatures, are valuable for either large or small-scale ammonia synthesis. They can quickly make ammonia at as little as 20 bar, vs. up 200 bar in the standard Haber-Bosch process. The higher yield and lower process pressure decreases energy use, resulting in overall reduction of manufacturing and capital equipment costs. In addition, this ammonia synthesis method enables storage of stranded energy via distributed manufacture of ammonia. It can efficiently make use of peak wind or solar-generated electricity to make hydrogen (from electrolysis of water) and nitrogen (by pressure swing absorption of air), and then storing this energy as ammonia. Thus, this process enables both improved large scale ammonia manufacturing plant efficiency and more widely distributed small scale ammonia manufacture. Solid Absorbents are More Efficient Current ammonia production, both large and small scale, is inefficient. Ammonia must be removed from the product stream and unreacted hydrogen and nitrogen must be recycled back to the reactor. Current methods to separate ammonia from the product stream are complex, expensive and ill-suited for small scale production. This new method makes ammonia at lower pressures than conventional Haber-Bosch processes. Absorption enables lower process pressure (versus condensation of liquid ammonia, as done conventionally). Using stable absorbents of high capacity, such as those created in this technology, overcomes current obstacles resulting from using unsupported chloride salts by creating new robust ammonia solid absorbents that can separate ammonia at lower temperatures and therefore use less energy. Researchers Ed Cussler, PhD, D.Sc Professor Emeritus, Chemical Engineering and Materials Science https://www.cems.umn.edu/people/faculty/edward-cussler Alon McCormick, PhD Professor, Chemical Engineering and Materials Science https://www.cems.umn.edu/people/faculty/alon-mccormick Technology Managed By Larry Micek Technology Licensing Officer 612-624-9568 Pilot Plant Michael Reese Publications Better Absorbents for Ammonia Separation ACS Sustainable Chemistry & Engineering, March 30, 2018; 6, 5, 6536-6546 https://pubs.acs.org/doi/abs/10.1021/acssuschemeng.7b04684