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Mechanism by which Tungsten Oxide Promotes the Activity of Supported V 2 O 5 /TiO 2 Catalysts for NO X Abatement: Structural Effects Revealed by 51 V MAS NMR Spectroscopy
Author(s) -
Jaegers Nicholas R.,
Lai JunKun,
He Yang,
Walter Eric,
Dixon David A.,
Vasiliu Monica,
Chen Ying,
Wang Chongmin,
Hu Mary Y.,
Mueller Karl T.,
Wachs Israel E.,
Wang Yong,
Hu Jian Zhi
Publication year - 2019
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201904503
Subject(s) - catalysis , tungsten , oxide , chemistry , reaction mechanism , redox , selective catalytic reduction , heterogeneous catalysis , inorganic chemistry , chemical engineering , materials science , organic chemistry , engineering
The selective catalytic reduction (SCR) of NO x with NH 3 to N 2 with supported V 2 O 5 (‐WO 3 )/TiO 2 catalysts is an industrial technology used to mitigate toxic emissions. Long‐standing uncertainties in the molecular structures of surface vanadia are clarified, whereby progressive addition of vanadia to TiO 2 forms oligomeric vanadia structures and reveals a proportional relationship of SCR reaction rate to [surface VO x concentration] 2 , implying a 2‐site mechanism. Unreactive surface tungsta (WO 3 ) also promote the formation of oligomeric vanadia (V 2 O 5 ) sites, showing that promoter incorporation enhances the SCR reaction by a structural effect generating adjacent surface sites and not from electronic effects as previously proposed. The findings outline a method to assess structural effects of promoter incorporation on catalysts and reveal both the dual‐site requirement for the SCR reaction and the important structural promotional effect that tungsten oxide offers for the SCR reaction by V 2 O 5 /TiO 2 catalysts.