Propene Surface Species and Their Role in NO Reduction
over Cu-ZSM-5 in the Excess of Oxygen

V. A. Matyshak*, A. A. Ukharskii*, A. N. Il’ichev*, V. A. Sadykov**, and V. N. Korchak*

* Semenov Institute of Chemical Physics, Russian Academy of Sciences, Moscow, 117977 Russia
** Boreskov Institute of Catalysis, Siberian Division, Russian Academy of Sciences, Novosibirsk, 630090 Russia

Received July 16, 1997

Abstract—The nature and reactivity of surface complexes under the conditions of NO reduction by propene
over Cu-ZSM-5 in the excess of oxygen are studied in situ by IR spectroscopy. The - and -allyl complexes
are formed during the interaction of C₃H₆ or C₃H₆ + O₂ with the zeolite surface at low temperatures, whereas
coke is formed at higher temperatures. Complexes with organic nitro compounds are observed in the presence
of NO at relatively low temperatures, and nitrito complexes are found under the reaction conditions (300°C).
NO reduction by propene over Cu-ZSM-5 in the excess of O₂ occurs via two routes. One involves the formation
of coke on the surface followed by the interaction of coke with NO to yield the reaction products. In this pro-
cess, coke by itself serves is a reducing agent. In this reaction, copper ions increase the rate of the coke forma-
tion and change the ratio between the amounts of “soft” and “hard” coke. The other route involves the reaction
between propene and the Cu²⁺–O–N=O complex formed on copper ions followed by the formation of reaction
products. This process is analogous to that observed earlier for NO_x reduction by propane in these systems.

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