The effect of NO2 on the activity of fresh and aged zeolite catalysts in the NH3-SCR reaction

Fe‐Beta@CeO2 core‐shell catalyst with tunable shell thickness for selective catalytic reduction of NOx with NH3

“…By contrast, Beta zeolite possesses a stronger acidity and better hydrothermal stability. 26,27 Moreover, compared with the CHA-zeolite, Beta possesses a larger pore size, which is not easily blocked by the outer oxide shell. Therefore, it can enhance the access of reactant molecules to the catalytically active centers.…”

Effect of Oxygen Concentration in NH₃-SCR Reaction over Fe- and Cu-loaded Beta Zeolites

“…Of the reported transition metal ion-exchanged zeolite catalysts, Fe-and Cu-loaded beta zeolite catalysts have received significant attention due to their high catalytic activity, with differences in the catalytic behaviour of the two catalysts being discussed. Rahkamaa-Tolonen et al have investigated the NH3-SCR of NO over a number of transition metal ion-exchanged beta zeolite catalysts and found that the catalytic activity at temperatures lower than 400 decreased as follows: Fe Cu Ag H. The loaded metal species served as the active component for catalysing the oxidation of NO to NO2 1) . Colombo et al have reported notable differences in the NH3 effect on the NH3-SCR activity between Fe-and Cu-loaded beta zeolite catalysts, namely a negligible effect of NH3 on the Cu-loaded zeolite and a severe inhibitory effect of NH3 on the Fe-loaded zeolite 2) .…”

Enhancing the Low-T NH3-SCR Activity of a Commercial Fe-Zeolite Catalyst by NH4NO3 Dosing: an Experimental and Modeling Study

“…8, it is evident that the black line, which identifies the run carried out feeding 400 ppm of NO + 100 ppm of NO 2 , and the green line, which is referred to the run with 500 ppm of NO + 100 ppm of AN in the feed, are completely overlapped, indicating the same DeNOx activity. This result definitely establishes a direct equivalence between NO 2 fraction in the NOx feed and the NH 4 NO 3 dose that generates an identical amount of NO 2 in the reactor, according to Reaction (4). Based on other similar runs with AN feed concentrations up to 250 ppm (not shown for brevity), it is possible to extend the AN-NO 2 equivalence to higher AN feed contents, provided that the AN reacts quantitatively.…”

“…It is a matter of fact that the NH 3 /urea-SCR plays a major role among the DeNOx technologies [1][2][3][4]; nevertheless, it is also well known in literature that the Standard-SCR Reaction (S-SCR) (1) is associated with a lower DeNOx activity in the 200-300°C temperature range than the Fast-SCR Reaction (F-SCR) (2) [5,6]:…”