A comparative study of N2O formation during the selective catalytic reduction of NOx with NH3 on zeolite supported Cu catalysts

Abstract

a b s t r a c tA comparative study was carried out on a small-pore Cu-CHA and a large-pore Cu-BEA zeolite catalyst to understand the lower N 2 O formation on small-pore zeolite supported Cu catalysts in the selective catalytic reduction (SCR) of NOx with NH 3 . On both catalysts, the N 2 O yield increases with an increase in the NO 2 /NOx ratios of the feed gas, suggesting N 2 O formation via the decomposition of NH 4 NO 3 . Temperature-programmed desorption experiments reveal that NH 4 NO 3 is more stable on Cu-CHA than on Cu-BEA. In situ FTIR spectra following stepwise (NO 2 + O 2 ) and ( 15 NO + NH 3 + O 2 ) adsorption and reaction, and product distribution analysis using isotope-labeled reactants, unambiguously prove that surface nitrate groups are essential for the formation of NH 4 NO 3 . Furthermore, Cu-CHA is shown to be considerably less active than Cu-BEA in catalyzing NO oxidation and the subsequent formation of surface nitrate groups. Both factors, i.e., (1) the higher thermal stability of NH 4 NO 3 on Cu-CHA, and (2) the lower activity for this catalyst to catalyze NO oxidation and the subsequent formation of surface nitrates, likely contribute to the higher SCR selectivity with less N 2 O formation on this catalyst as compared to Cu-BEA. The latter is determined as the primary reason since surface nitrates are the source that leads to the formation of NH 4 NO 3 on the catalysts.

Recent Progress in Atomic-Level Understanding of Cu/SSZ-13 Selective Catalytic Reduction Catalysts

“…However, this will not alter the final product formed, NH 4 NO 3 . In fact, NH 4 NO 3 has been found to be particularly stable on Cu/SSZ-13, thus displaying a considerable low-temperature inhibition of SCR by blocking pores and channels of the small-pore support [51].…”

Thermal Decomposition CharacteristicS of Ammonium Nitrate(v) in the Presence of Mn2O3/Graphene Oxides

“…In Ref. [34] it was thought that N 2 O is formed when NH 3 reacts with NOx at less than 200 °C. According to the results in Ref.…”

Synergistic catalytic removal NOX and the mechanism of plasma and hydrocarbon gas

“…17,18 The rate of denitrification was in the downward trend because of the free radicals in the accumulation phase at the beginning of a few minutes. 19,20 The reaction (3) begins to occur with the accumulation of free radical and the removal rate of NO was increased. The energy of the N 2 is transferred to NO with the increase of NO.…”