Ammonia synthesis by Haber-Bosch is responsible for 1% of global energy use per year, 2.5% of global CO2 emissions per year, and for supporting approximately 4 billion additional persons’ nutritional requirements 1–3. The importance of Ammonia to the world economy is not in doubt, but ammonia may also prove to be a future energy carrier due to its high hydrogen content. The chemical looping ammonia synthesis (CLAS) reaction seeks to decouple the high energy dinitrogen cleavage reaction from the ammonia synthesis reaction.The ammonia synthesis reaction may proceed as a hydrogenation or hydrolysis reaction, depending on how the loop is constructed. Due to the passive nature of this process, nitrogen may be stored and retrieved later at the site where it will be used. Coupled with renewable energy generation this process may reduce the long distances that centralized Haber-Bosch ammonia must be transported for use in agriculture. The productivity and kinetics of common CLAS candidates was experimentally evaluated using a number of different conditions. Common materials include Mn, Fe, and CoMo, as well as promoters and oxides. Many studies have speculated on the use of Li, Mn or Co as potential CLAS candidates, but they are strategic materials. Using a microwave fixed bed reactor, it was found that ammonia productivity with Fe as a CLAS material exceeded the performance of a conventional thermal fixed bed reactor at identical conditions. Additionally, future work is proposed which will consider using microwave plasma to pre-activate nitrogen and to texturize the surface of the CLAS catalysts. In addition, deactivation modes shall be examined using bulk and surface characterization techniques.

Chemical looping ammonia synthesis: Thermal, microwave, and plasma approaches

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.