Plasma-enhanced low temperature NH3-SCR of NOx over a Cu-Mn/SAPO-34 catalyst under oxygen-rich conditions

Abstract

In this work, a dielectric barrier discharge (DBD) plasma-enhanced NH3-selective catalytic reduction (NH3-SCR) of NOx over a Cu-Mn/SAPO-34 catalyst at low temperatures (<200 °C) and oxygen-rich conditions (14 vol.%) has been investigated using a two-stage post-plasma-catalytic (PPC) configuration. The results show a maximum NOx removal of 80 % and a 100 % N2 selectivity without NH3 slip or the formation of by-products at a low specific energy input (SEI) of 32 J/L. Adding water vapor (5.7 vol.%) into the plasma NH3-SCR process does not negatively affect the removal of NOx, while the presence of C3H6 enhances the removal of NOx. In situ diffuse reflectance infrared spectroscopy (DRIFTS) combined with optical emission spectroscopic diagnostics has been employed to elucidate the reaction mechanism in the plasma-catalytic removal of NOx. We find that the formation of NO2 via NO oxidation in the first stage plasma gas-phase reaction enhances the Eley-Rideal (E–R) reaction on the surface of the Cu-Mn/SAPO-34 catalyst in the second stage catalytic NH3-SCR of NOx. The Cu-Mn/SAPO-34 catalyst shows stable performance in the plasma-enhanced NH3-SCR of NOx after 5 cycles of catalyst regeneration. This work has successfully demonstrated a promising low-temperature plasma-catalytic solution for the effective NH3-SCR of NOx.