Chemical looping ammonia synthesis at atmospheric pressure benefiting from synergistic effect of Mn- and Fe-based nitrogen carriers

Chemical looping ammonia synthesis (CLAS) based on the synergistic effect of Mn- and Febased nitrogen carriers, is proposed as an environmental-friendly NH3 production alternative. This approach has superiority of intermittent and simplified operation, especially in locations where implementing sophisticated Haber-Bosch process is challenging. This work revealed that nitrogen carriers could yield up to 166.3 mmol NH3 per gram of Mn after conversion with H2 at 600 degrees C. NH3 production capacity was deteriorated by sintering and ammonia decomposition at high temperature. Pores resulting from the elimination of molecular nitrogen by bursting out of the surface were found at 700 degrees C, which could be explained by the parasitic conversion of N to N2 rather than NH3. N-carrier with 50% Al2O3 was the most interesting candidate with outstanding conversion ratio of lattice nitrogen. Generally, simple design, operational security and low cost make CLAS possible to scale up for industrial usage in the future.(c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.