Details

Autor(en) / Beteiligte

• Castoldi, Lidia
• Matarrese, Roberto
• Liu, Chuncheng
• Morandi, Sara
• Lietti, Luca

Titel

Dynamics and Selectivity of N2O Formation/Reduction During Regeneration Phase of Pt-Based Catalysts

Ist Teil von

• Topics in catalysis, 2018-10, Vol.61 (15-17), p.1672-1683

Ort / Verlag

New York: Springer US

Erscheinungsjahr

2018

Quelle

springer (창간호~2014)

Beschreibungen/Notizen

• The formation of N 2 O has been studied by means of isothermal lean-rich experiments at 150, 180 and 250 °C over Pt–Ba/Al 2 O 3 and Pt/Al 2 O 3 catalysts with H 2 and/or C 3 H 6 as reductants. This allows to provide further insights on the mechanistic aspects of N 2 O formation and on the influence of the storage component. Both gas phase analysis and surface species studies by operando FT-IR spectroscopy were performed. N 2 O evolution is observed at both lean-to-rich (primary N 2 O) and rich-to-lean (secondary N 2 O) transitions. The production of both primary and secondary N 2 O decreases by increasing the temperature. The presence of Ba markedly decreases secondary N 2 O formation. FT-IR analysis shows the presence of adsorbed ammonia at the end of the rich phase only for Pt/Al 2 O 3 catalyst. These results suggest that: (i) primary N 2 O is formed when undissociated NO in the gas phase and partially reduced metal sites are present; (ii) secondary N 2 O originates from reaction between adsorbed NH 3 and residual NO x at the beginning of the lean phase. Moreover, N 2 O reduction was studied performing temperature programming temperature experiments with H 2 , NH 3 and C 3 H 6 as reducing agents. The reduction is completely selective to nitrogen and occurs at temperature higher than 250 °C in the case of Pt–Ba/Al 2 O 3 catalyst, while lower temperatures are detected for Pt/Al 2 O 3 catalyst. The reactivity order of the reductants is the same for the two catalysts, being hydrogen the more efficient and propylene the less one. Having H 2 a high reactivity in the reduction of N 2 O, it could react with N 2 O when the regeneration front is developing. Moreover, also ammonia present downstream to the H 2 front could react with N 2 O, even if the reaction with stored NO x seems more efficient.