Redox features in the catalytic mechanism of the “standard” and “fast” NH3-SCR of NOx over a V-based catalyst investigated by dynamic methods

Kinetic Modeling of Dynamic Aspects of the Standard NH3-SCR Reaction Over V2O5-WO3/TiO2and Fe-Zeolite Commercial Catalysts for the Aftertreatment of Diesel Engines Exhausts

“…In parallel, a fast decrease in the NO outlet concentration together with a mirror-like increment of the N 2 concentration, associated with the startup of the SCR reaction were observed. The levels of NH 3 , NO and N 2 at steady-state were in all cases consistent with the stoichiometry of the standard SCR reaction (2) [2,3,5,10,12,13,20,21]. Results obtained in the presence of different oxygen contents were qualitatively very similar.…”

“…The presented models implement kinetic schemes derived from an extensive investigation of reactivity, chemistry and catalytic mechanism of all the main SCR reactions over commercial V 2 O 5 -WO 3 /TiO 2 and Fe-zeolite catalysts performed in our laboratories during the last few years [2][3][4][5][6][7][8][9][10][11][12][13][14].The related rate expressions were fitted to transient data collected over powdered catalysts in the chemical regime, and in their global form allow the kinetic analysis of the full NH 3 -NO/NO 2 SCR reacting system.…”

Effect of the Mn oxidation state and lattice oxygen in Mn-based TiO2 catalysts on the low-temperature selective catalytic reduction of NO by NH3

“…A similar trend of desorption was observed for all of the catalysts, except the catalyst calcined at 700 C, where a higher calcination temperature resulted in a reduced production of the oxidizing material. When both NO and NO 2 were included into the feed, a fast SCR may have occurred when compared with the standard SCR of NO Koebel et al, 2002aKoebel et al, , 2002bTronconi et al, 2007). The oxidation activity tests for the conversion of NO to NO 2 by O 2 on the Mn/ TiO 2 catalysts prepared at different calcination temperatures were performed (Figure 7).…”

VOx Surface Coverage Optimization of V2O5/WO3-TiO2 SCR Catalysts by Variation of the V Loading and by Aging

“…Extensive research has been undertaken to understand the different aspects of standard V-based SCR catalysts. These efforts were aimed at revealing mechanistic details such as the nature of the active centers and the rate determining steps [10][11][12][13][14][15][16][17], the origin of catalyst aging [18] and the electronic interactions between the various catalyst components and the poisoning phenomena [19][20][21]. For this purpose, parameters such as the synthesis of the TiO2 support material [22,23], the synthesis method, the loading and the nature of WO3 and V2O5 and the structural change upon thermal/hydrothermal treatment have been addressed.…”