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The role of heterogeneous catalysts in the plasma-catalytic ammonia synthesis

Patil, Bhaskar S; Cherkasov, Nikolay; Srinath, Nadadur Veeraraghavan; Lang, Juergen; Ibhadon, Alex O.; Wang, Qi; Hessel, Volker

Authors

Bhaskar S Patil patilbhaskars@gmail.com

Nikolay Cherkasov

Nadadur Veeraraghavan Srinath

Juergen Lang

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Dr Alex Ibhadon A.O.Ibhadon@hull.ac.uk
Reader in Catalysis and Reactor Engineering

Qi Wang

Volker Hessel



Abstract

Ammonia, being the second largest produced industrial chemical, is used as a raw material for many chemicals. Besides, there is a growing interest in the applications of ammonia as electrical energy storage chemical, as fuel, and in selective catalytic reduction of NOx. These applications demand on-site distributed ammonia production under mild process conditions. In this paper, we investigated 16 different transition metal and oxide catalysts supported on γ-Al2O3 for plasma-catalytic ammonia production in a dielectric barrier discharge (DBD) reactor. This paper discusses the influence of the feed ratio (N2/H2), specific energy input, reaction temperature, metal loading, and gas flow rates on the yield and energy efficiency of ammonia production. The optimum N2/H2 feed flow ratio was either 1 or 2 depending on the catalyst-substantially above ammonia stoichiometry of 0.33. The concentration of ammonia formed was proportional to the specific energy input. Increasing the reaction temperature or decreasing gas flow rates resulted in a lower specific production due to ammonia decomposition. The most efficient catalysts were found to be 2 wt% Rh/Al2O3 among platinum-group metals and 5 wt% Ni/Al2O3 among transitional metals. With the 2 wt% Rh catalyst, 1.43 vol% ammonia was produced with an energy efficiency of 0.94 g kWh-1. The observed behaviour was explained by a combination of gas phase and catalytic ammonia formation reactions with plasma-activated nitrogen species. Plasma catalysts provide a synergetic effect by activation of hydrogen on the surface requiring lower-energy nitrogen species.

Citation

Patil, B. S., Patil, B. S., Cherkasov, N., Srinath, N. V., Lang, J., Ibhadon, A. O., …Hessel, V. (in press). The role of heterogeneous catalysts in the plasma-catalytic ammonia synthesis. Catalysis Today, https://doi.org/10.1016/j.cattod.2020.06.074

Journal Article Type Article
Acceptance Date Jun 28, 2020
Online Publication Date Jul 25, 2020
Deposit Date Sep 6, 2020
Publicly Available Date Jul 26, 2021
Journal Catalysis Today
Print ISSN 0920-5861
Publisher Elsevier
Peer Reviewed Peer Reviewed
DOI https://doi.org/10.1016/j.cattod.2020.06.074
Keywords Plasma catalysis; Ammonia production; Catalytic DBD reactor; Supported transition metal oxides; Energy efficiency; Haber-Bosch
Public URL https://hull-repository.worktribe.com/output/3428022
Publisher URL https://www.sciencedirect.com/science/article/abs/pii/S0920586120304661?via%3Dihub

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