Unlocking the significance of high H₂O resistance for nickel vanadate phases to improve the kinetic parameters or consequences of catalytic NO_X reduction and poison pyrolysis

Abstract

Anthropogenic flue gases consist of NOX/SO2/H2O, among which H2O resistance is often underrated in activating acidic/redox cycles of NH3-assisted catalytic NOX reduction (SCR), SO2/H2O-induced evolution of ammonium (bi)sulfate (AS/ABS) poisons,...

Unveiling the Catalytic Merits of LaV3O9 over Conventional LaVO4 Polymorphs to Boost Desired Kinetics of Humid NOX Reduction and Poison Disintegration

“…[10][11][12]34 In this regard, the hierarchy for the amount of O V (or O M ) on a per-V 5+ basis (N OV/OM ) should be comparable to that for N OL . [10][11][12]34 , but they were also not comprehensively investigated in decoupled manner in terms of the N BA /E BA and N OL /E OL /N OV/OM (∼N OM )/binding energy between O M and O V (E OM )/O M mobility for acidic and redox sites, respectively (Table S1). 38−42 Moreover, the importance of the BA − -H + sites for these catalysts in activating the SCR or catalytic pyrolysis of ammonium (bi)sulfate (AS/ ABS) poisons has been unclarified, to the best of our knowledge.…”

“…These temperatures were chosen to confirm the trend of SO Z 2− /HSO Z − concentrations found in the XP spectra of the catalysts and to precisely evaluate their SO Z 2− /HSO Z − compositions used for activating the low-temperature SCR, respectively. 9,11 The Raman spectra were curve-fitted to ten sub-bands, three of which with Raman shifts centered at ≤860 cm −1 could originate from symmetric (SYM; v 1 )/asymmetric (ASYM; − /HSO 4 − upon the surface being heated to 250 °C, as suggested elsewhere. 9,11 Nevertheless, the trend of SO 4 2− /HSO 4 − concentrations found in the Raman spectra were mostly invariant and independent of the analytic temperature (t-LaV-S (58.1%) < m-LaV-S (64.5%) < LaV 3 -S (73.5%) < LaV 3 -Sb-S (76.0%)).…”

“…9,11 The Raman spectra were curve-fitted to ten sub-bands, three of which with Raman shifts centered at ≤860 cm −1 could originate from symmetric (SYM; v 1 )/asymmetric (ASYM; − /HSO 4 − upon the surface being heated to 250 °C, as suggested elsewhere. 9,11 Nevertheless, the trend of SO 4 2− /HSO 4 − concentrations found in the Raman spectra were mostly invariant and independent of the analytic temperature (t-LaV-S (58.1%) < m-LaV-S (64.5%) < LaV 3 -S (73.5%) < LaV 3 -Sb-S (76.0%)). The in situ SO 2 /O 2 -DRIFT and XP/Raman spectral results allowed the following hierarchy to be constructed for the N NH3 values of the catalysts: t-LaV-S < m-LaV-S < LaV 3 -S < LaV 3 -Sb-S.…”

“…3,4,[9][10][11]53 The areas under the resulting NO-TPD profiles (NO signals evolved versus temperature; Figure S11) were used to evaluate the numbers of NO adsorbed in a per-gram of the catalysts (N NO ) at 250 °C (Figure 5B). 3,4,[9][10][11]53 The N NO values of LaV 3 -S/LaV 3 -Sb-S (25−27 μmol NO g CAT −1…”

“…To test this hypothesis, the NO-TPD profiles were deconvoluted to two sub-bands (Figure S11), whose T MAX values were again related to the corresponding β values by plotting ln (β/T MAX 2 ) versus 1/ T MAX (Figure 5B and Table S6). 3,4,[9][10][11]53 This enabled the E NO values of the catalysts to be assessed using the methodology analogous to that utilized for their E NH3 values. 3,4,[9][10][11]53 Indeed, the E NO values of LaV 3 -S/LaV 3 -Sb-S were 24 kJ mol NO −1 , which indicated that their O L species could bind with NO via enhanced physisorption.…”