Effect of Formaldehyde in Selective Catalytic Reduction of NOx by Ammonia (NH3-SCR) on a Commercial V2O5-WO3/TiO2 Catalyst under Model Conditions

The impact of formaldehyde (HCHO, formed in vehicle exhaust gases by incomplete combustion of fuel) on the performance of a commercial V2O5-WO3/TiO2 catalyst in NH3-SCR of NOx under dry conditions has been analyzed in detail by catalytic tests, in situ FTIR and transient studies using temporal analy...

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Bibliographic Details
Published in:Environmental science & technology 2020-10, Vol.54 (19), p.11753
Main Authors: Ngo, Anh Binh, Vuong, Thanh Huyen, Atia, Hanan, Bentrup, Ursula, Kondratenko, Vita A, Kondratenko, Evgenii V, Rabeah, Jabor, Ambruster, Udo, Brückner, Angelika
Format: Article
Language:English
Subjects:
Ammonia
Carbon dioxide
Catalysts
Chemical reduction
Dehydration
Exhaust gases
Formaldehyde
Gases
Nitrogen oxides
Reducing agents
Selective catalytic reduction
Selectivity
Titanium dioxide
Tungsten oxides
Vanadium pentoxide
Vehicle emissions
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Summary:The impact of formaldehyde (HCHO, formed in vehicle exhaust gases by incomplete combustion of fuel) on the performance of a commercial V2O5-WO3/TiO2 catalyst in NH3-SCR of NOx under dry conditions has been analyzed in detail by catalytic tests, in situ FTIR and transient studies using temporal analysis of products (TAP). HCHO reacts preferentially with NH3 to a formamide (HCONH2) surface intermediate. This deprives NH3 partly from its desired role as a reducing agent in the SCR and diminishes NO conversion and N2 selectivity. Between 250 and 400 °C, HCONH2 decomposes by dehydration (major pathway) and decarbonylation (minor pathway) to liberate toxic HCN and CO, respectively. HCN was proven to be oxidized by lattice oxygen of the catalyst to CO2 and NO, which enters the NH3-SCR reaction.
ISSN:0013-936X
DOI:10.1021/acs.est.0c00884