Chemical looping ammonia synthesis process mediated by metal imides as nitrogen carriers Feng, Sheng 1,2 , Gao, Wenbo 2 Cao, Hujun 1 Guo, Jianping 1 Chen, Ping 1,2 1 Chinese Academy of Sciences, China, 2 Dalian University of Technology, China Ammonia is not only the main raw material of nitrogen fertilizer, but also a promising energy carrier for the storage and utilization of renewable energy. The fossil fuel-based Haber-Bosch ammonia synthesis industry is an energy- consuming and high CO 2 -emission process. For the sustainable growth of human society, it is critical important to develop “green” ammonia synthesis processes driven by renewable energy. Chemical looping process ammonia synthesis (CLAS) process involves a series of individual reactions which produce ammonia in a different manner to the catalytic process. This process has advantages in avoiding competitive adsorptions and intervening in the scaling relationships. The nitrogen carriers with favorable thermodynamic and kinetic properties are critical for such a process typically under mild conditions. Recently, we developed a chemical looping ammonia synthesis process mediated by alkali or alkaline earth metal imides as nitrogen carriers. And the kinetic performances of the imides nitrogen carriers have been improved by introducing transition metals (Fe, Co, Ni, etc.) or forming multi- functional complex nitrogen carriers (MnN-imides). In addition, we are also exploring the feasibility of changing the thermodynamic properties of CLAS by introducing external fields (electric energy, etc.). These findings have opened up new possibilities for designing and developing efficient nitrogen carriers for the CLAS process, which may be helpful to improve the chemical looping ammonia synthesis processes driven by renewable energy. References 1. Gálvez, M. E.; Halmann, M.; Steinfeld, A. Ammonia Production via a Two-Step Al 2 O 3 /AlN Thermochemical Cycle. 1. Thermodynamic, Environmental, and Economic Analyses. Ind. Eng. Chem. Res. 2007, 46 (7), 2042-2046. 2. Michalsky, R.; Avram, A. M.; Peterson, B. A.; Pfromm, P. H.; Peterson, A. A. Chemical Looping of Metal Nitride Catalysts: Low-Pressure Ammonia Synthesis for Energy Storage. Chem. Sci. 2015, 6 (7), 3965-3974. 3. McEnaney, J. M.; Singh, A. R.; Schwalbe, J. A.; Kibsgaard, J.; Lin, J. C.; Cargnello, M.; Jaramillo, T. F.; Nørskov, J. K. Ammonia Synthesis from N 2 and H 2 O Using a Lithium Cycling Electrification Strategy at Atmospheric Pressure. Energy Environ. Sci. 2017, 10 (7), 1621-1630. 4. Gao, W.; Guo, J.; Wang, P.; Wang, Q.; Chang, F.; Pei, Q.; Zhang, W.; Liu, L.; Chen, P. Production of Ammonia via a Chemical Looping Process Based on Metal Imides as Nitrogen Carriers. Nat. Energy 2018, 3 (12), 1067-1075. 5. Feng, S.; Gao, W. B.; Wang, Q. R.; Guan, Y. Q.; Yan, H. X.; Wu, H.; Cao, H. J.; Guo, J. P.; Chen, P. A Multi-Functional Composite Nitrogen Carrier for Ammonia Production via a Chemical Looping Route. J. Mater. Chem. A 2021, 9 (2), 1039- 1047.
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