Mechanism by which Tungsten Oxide Promotes the Activity of Supported V2 O5 /TiO2 Catalysts for NOX Abatement: Structural Effects Revealed by 51 V MAS NMR Spectroscopy.
The selective catalytic reduction (SCR) of NOx with NH3 to N2 with supported V2 O5 (-WO3 )/TiO2 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 TiO2 forms oligomeric vanadia structures and reveals a proportional relationship of SCR reaction rate to [surface VOx concentration]2 , implying a 2-site mechanism. Unreactive surface tungsta (WO3 ) also promote the formation of oligomeric vanadia (V2 O5 ) 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 V2 O5 /TiO2 catalysts.
['Jaegers|Nicholas R|NR|http://orcid.org/0000-0002-9930-7672', 'Lai|Jun-Kun|JK|', 'He|Yang|Y|', 'Walter|Eric|E|', 'Dixon|David A|DA|', 'Vasiliu|Monica|M|', 'Chen|Ying|Y|', 'Wang|Chongmin|C|', 'Hu|Mary Y|MY|', 'Mueller|Karl T|KT|', 'Wachs|Israel E|IE|', 'Wang|Yong|Y|', 'Hu|Jian Zhi|JZ|http://orcid.org/0000-0001-8879-747X']
NOx NMR spectroscopy selective catalytic reduction (SCR) heterogeneous catalysis vanadium