The dramatic expansion of global energy consumption has prompted both significant concern for environmental degradation and an affiliated rise of pollution abatement technologies. Nitrogen oxides (NOX) are of particular concern due to their propensity to induce smog, acid rain, ozone depletion, and their role in climate change. A prominent mitigation technology, selective catalytic reduction (SCR), employs NH3 to reduce NOx to inert N2. Of the ~107 Mt of NOX released annually, stationary industrial facilities account for a significant (~40%) portion of emissions. The combined experimental approach reveals unambiguous molecular-level insights into the structure and reactivity of the supported V2O5(-WO3)/TiO2 catalysts that are employed for NOX removal at such facilities. The results provide unique, molecular-level insights on the structure of vanadia catalysts and shows that SCR performance is enhanced by the formation of larger vanadium oxide domains due to a dual-site requirement for catalytic turnover for supported V2O5/TiO2 catalysts. Promotion by unreactive surface tungsten oxide on the TiO2 support is found to proceed through a structural effect as its presence alters the vanadia species on the catalyst towards the formation of larger surface vanadium oxide domains which are beneficial for the two-site SCR reaction. The identification of this structural effect resolves a long-standing uncertainty on the impact of promoters on vanadium oxide-based SCR and outlines a method whereby promoter structural effects can be evaluated. The current findings reveal both the dual-site requirement for the SCR reaction and provides important clarity on the molecular structure of promoted and unpromoted V2O5/TiO2 catalysts.

Resolving the promotional mechanism in supported vanadium oxide SCR catalysts

2019 Fall National Meeting

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