Low-temperature NOx reduction with ethanol over Ag/Y: A comparison with Ag/[gamma]-Al2O3 and BaNa/Y

A multistep mechanism has been elucidated for the reduction of NOx in the presence of ethanol over silver-exchanged zeolite Y (Ag/Y). Ethanol reacts with O2 and/or NO2 to form acetaldehyde at temperatures as low as 200 degrees C. Surface acetate ions, formed from the oxidation of acetaldehyde, react...

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Bibliographic Details
Published inJournal of catalysis Vol. 246; no. 2; p. 413
Main Authors Yeom, Young Hoon, Li, Meijun, Wolfgang M.H. Sachtler, Weitz, Eric
Format Journal Article
LanguageEnglish
Published San Diego Elsevier BV 10.03.2007
Subjects
Catalysis
Chemical reactions
Chemistry
Comparative studies
Ions
Oxidation
Silver
Temperature
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Summary:A multistep mechanism has been elucidated for the reduction of NOx in the presence of ethanol over silver-exchanged zeolite Y (Ag/Y). Ethanol reacts with O2 and/or NO2 to form acetaldehyde at temperatures as low as 200 degrees C. Surface acetate ions, formed from the oxidation of acetaldehyde, react with NO2 to yield nitromethane, a critical intermediate in subsequent deNOx chemistry. CN-, NC-, and NCO- are intermediates likely bound to silver ions. Both CN- and NC- are stable toward reaction under experimental conditions. A significant difference exists between the catalytic activities of Ag/Y and Ag/gamma-Al2O3; oxidation of ethanol to acetate at low temperature is significantly faster over Ag/Y than over Ag/gamma-Al2O3, and both NO2 and O2 are effective oxidants over Ag/Y. With Ag/Y, pretreatment with either O2 or H2 does not affect the yield of N2, which approaches 60% and remains constant for at least 5 h, making this catalyst promising for NOx reduction. [PUBLICATION ABSTRACT]
ISSN:0021-9517
1090-2694
DOI:10.1016/j.jcat.2006.12.013