Positron Emission Profiling Study on the Catalytic Ammonia Oxidation

Positron Emission Profiling Study on the Catalytic Ammonia Oxidation 

The PEP technique enables one to measure concentration profiles of labelled molecules (reactants and/or products) within reactors as a function of axial position and time. Once these profiles have been obtained, they provide substantial information on the reaction kinetics and involved intermediates. We will illustrate this with our research on the understanding of the mechanism of the ammonia oxidation on platinum based catalysts. 

The study of the oxidation of ammonia to nitrogen and water at low temperature has become more and more important in recent years due to agricultural and industrial waste streams. Noble metals (Pt, Ir) are suitable for the selective, low temperature oxidation of ammonia to nitrogen and water. Alumina supported platinum catalysts are promising in the conversion of gaseous ammonia to N2 and H2O. They possess a high activity and selectivity in N2 formation.I l However, these catalysts are susceptible to rapid deactivation due to irreversible adsorption of reaction intermediates such as NHx species. 

Gas phase ammonia oxidation on noble metal cataljrets has been extensively studied with surface science techniques, like SIMS, AES, LEED, EELS, TPD and The formation of NO, N2 and water was 

PEP experiments are performed using either NHs or [ 0]-02 to obtain further insight in the reaction mechanism and deactivation behaviour. Transient ammonia pulse experiments are performed to study the adsorption and dissociation of ammonia on pure platinum catalysts, followed by the focus on the deactivation of platinum. Finally, we will briefly discuss the influence of the alumina support. 

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