The reduction of nitric oxide by ammonia over polycrystalline platinum model catalysts in the presence of oxygen
1992; Elsevier BV; Volume: 135; Issue: 2 Linguagem: Inglês
10.1016/0021-9517(92)90045-j
ISSN1090-2694
Autores Tópico(s)Electrocatalysts for Energy Conversion
ResumoThe reaction system of nitric oxide, ammonia, and oxygen was studied using batch-mode measurements in partial pressure ranges of 65–1000 Pa (0.5–7.6 Torr) on polycrystalline Pt foils over the temperature range 423–598 K. Under these conditions the oxidation of nitric oxide was not detectable. The ammonia oxidation reaction, using dioxygen, occurred in the temperature range 423–493 K, producing nitrogen and water as the only products. The activation energy of the nitrogen formation was found to be 86 kJ/mol. Above this temperature range, flow-mode measurements showed the formation of both nitrous oxide and nitric oxide. The reaction rate betwen ammonia and oxygen was greatly decreased (about a factor of 10) by nitric oxide, while the reaction rate between nitric oxide and ammonia was accelerated (about 10-fold) due to the presence of oxygen. Nitric oxide reduction by ammonia in the presence of oxygen occurred in the temperature range 423–598 K. The products of the reaction were nitrogen, oxygen, nitrous oxide, and water. The Arrhenius plot of the reaction showed a break near 523 K. Below this temperature the activation energy of the reaction ws 13 kJ/mol, and in the higher-temperature range it was 62 kJ/mol. At 473 K, the N2/N2O ratio was about 0.6 and O2 formation was also monitored. At 573 K, the N2/N2O ratio was approximately 2 and oxygen was consumed in the course of the reaction as well.
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