Effect of operating variables on the enhanced SCR reaction over a commercial V2O5–WO3/TiO2 catalyst for stationary applications

The Selective Catalytic Reduction by NH3/urea is a world-wide established after treatment technology for the removal of NOx in the stack gases of power plants and of other stationary sources. Typical SCR catalysts operate between 300 and 400 °C, however for some applications SCR systems with reasonable DeNOx activity at temperatures as low as 180 °C are required nowadays.It was recently shown that over both V2O5–WO3/TiO2 and Fe-ZSM-5 commercial SCR catalysts the addition of aqueous solutions of NH4NO3 to a NO–NH3 containing feed stream results in the occurrence of the “Enhanced SCR” (E-SCR) reaction (2NH3 + 2NO + NH4NO3 → 3N2 + 5H2O), characterized by superior NO reduction efficiencies in the 200–350 °C range. In this paper we present a systematic experimental study of the E-SCR reaction over a commercial V-based Haldor Topsøe catalyst. The effects of three operating variables, namely space velocity (18–75 k h−1), temperature (180–250 °C) and ammonium nitrate feed content (0–100% of stoichiometric feed), are addressed in order to identify the best process conditions in view of the specific application of this new technology to stationary SCR installations.

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► NH4NO3 promoted the low-T NH3-SCR activity of a V-based Haldor Topsøe catalyst.
► At 180 °C and 18 k h−1 the NO conversion was enhanced from 40% to ∼90%.
► Substoichiometric NH4NO3 feeds were totally converted.
► NH4NO3 addition did not result in N2O formation.