(377t) Electrochemical Synthesis of Ammonia, and Development of Nanoporous Carbon-Composite Adsorbent Exhibiting High Ammonia Uptake

Recently, we synthesized nanoporous composite of an activated carbon and organic acids, which exhibited high amount of ammonia adsorption under very low pressure range (lower than 9.3 mmHg). The present nanoporous material was prepared by simple impregnation of organic acids (e.g., succinic acid, itaconic acid, and adipic acid) into the commercial activated carbon. A systematic investigation was performed to find the best choice of the organic acid, the optimized amount of the organic acid impregnation and the best impregnation condition. The activated carbon impregnating succinic acid showed 108 cm³ g^-1 (STP) under 9.3 mmHg of NH₃ at 298 K. The dramatic increase of the ammonia uptake could be explained by the strong interaction in the pair of the organic acid and basic ammonia molecule, and by the high dispersion of the organic acid owing to its strong affinity to the hydrophobic activated carbon support. We investigated also the ammonia-breakthrough property of the new adsorbent under very low concentration of ammonia flow (100 ppm in argon balance). At the beginning of the measurement, the concentration of the ammonia in product gas decreased to almost zero, and the breakthrough occurred at ten hours of the adsorption. The breakthrough amount was 1.89 mmol g^-1. This adsorbent could recover 90% of initial breakthrough amount after regeneration process at 473 K under nitrogen flow. The present adsorbent shows high potential in the application fields of purification of land-fill gas and bio-gas.