Heterogeneous Catalytic Oxidation of Ammonia by Various Transition Metals

A well-known demonstration is adapted to simplify the illustration of heterogeneous catalytic oxidation of ammonia. Various metal catalyst wires are placed above the liquid level in a flask containing concentrated ammonia. After brief preheating, some metal wires continue to glow, providing visual e...

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Bibliographic Details
Published in:Journal of chemical education 2019-10, Vol.96 (10), p.2266-2270
Main Authors: Laan, Petrus C. M, Franke, Mareena C, van Lent, Richard, Juurlink, Ludo B. F
Format: Article
Language:English
Subjects:
Ammonia
Catalysis
Catalysts
Demonstration
Exothermic reactions
Heating
Iridium
Liquid levels
Metals
Oxidation
Palladium
Platinum
Power supplies
Selectivity
Smoke
Transition metals
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Summary:A well-known demonstration is adapted to simplify the illustration of heterogeneous catalytic oxidation of ammonia. Various metal catalyst wires are placed above the liquid level in a flask containing concentrated ammonia. After brief preheating, some metal wires continue to glow, providing visual evidence of an overall exothermic reaction taking place at the catalyst surface. Thermal heating by a butane flame prior to insertion and in situ resistive heating using a power supply yield identical results. Active catalysts are the group 9 and 10 elements Rh, Ir, Pd, and Pt. Besides the illustration of the Sabatier principle, the effect of the ammonia-to-oxygen ratio can also be visualized, and active metals vary in the production of a grayish smoke. These observations provide a starting point to discuss catalytic selectivity, a topic of great relevance to industrial catalytic oxidation of ammonia.
ISSN:0021-9584
1938-1328
DOI:10.1021/acs.jchemed.9b00351