Selective NO reduction by propane and propene over a Pt/ZSM-5 catalyst: a transient study of the reaction mechanism

• Published in: Applied catalysis. B, Environmental Environmental, 1996-12, Vol.11 (1), p.49-63
• Main Authors: Rottländer, Christian, Andorf, Renato, Plog, Carsten, Krutzsch, Bernd, Baerns, Manfred
• Format: Article
• Language: English
• Subjects: Mechanism; Nitric oxide; Propane; Propene; Pt/ZSM-5; Reduction; Temporal-analysis-of-products
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/S0926-3373(96)00038-0

The selective reduction of nitric oxide by propane and propene in an excess of oxygen has been studied over a Pt/ZSM-5 catalyst to elucidate the role of the reducing hydrocarbons in the reaction mechanism. Temperature-programmed reaction (TPR) and transient studies using the temporal-analysis-of-products (TAP) reactor have been performed. Propene is found to be the more efficient reductant compared to propane at T ⩽ 600K. Mechanistic studies demonstrate that even in an excess of oxygen carbon-containing species, formed from propene, are adsorbed on the catalyst, which further react with nitric oxide to N2, N2O and CO2; no such intermediates are formed from propane, giving rise to its far lower reduction efficiency. It is concluded that the main reaction pathway over Pt/ZSM-5 involves a surface reaction between propene-derived adsorbates and NO or, possibly, NO2. Catalytic surface reduction by hydrocarbons, followed by NO decomposition on reduced platinum sites, is proposed as a second, minor, mechanistic pathway at low reaction temperatures (T ⩽ 600K).