On the nature of different iron sites and their catalytic role in Fe-ZSM-5 DeNOx catalysts: new insights by a combined EPR and UV/VIS spectroscopic approach

Synthesis and characterization of Fe(III)-piperazine-derived complexes encapsulated in zeolite Y

“…40 At approximately 470 nm there is a shoulder, indicating the presence of octahedral Fe(III), with larger clusters of Fe 2 O 3 . 38,40 The spectra of the FeY zeolite and ligand-zeolite mixtures (Figure 3S, supplementary material and Figure 5b) are similar, showing the presence of octahedral Fe(III) ions, at 360 nm. These results show that the mechanical mixtures did not change the environment around the Fe(III) ion in the FeY zeolite.…”

“…39 For the encapsulated complexes, as observed previously by Kumar and co-workers, the band between 300 and 400 nm as well as that near 500 nm can be attributed to oxo-Fe(III) ligand-metal charge transfer (LMCT), indicating the presence of small and larger Fe x O y clusters, respectively. 38 Finally, there are no significant differences between the spectra of the encapsulated complexes, suggesting that their electronic structures are very similar. Encapsulated 5 and 6 presented bands of lower intensity when compared with the other complexes (in supplementary material).…”

“…For FeY, there are no bands under 300 nm, indicating the lack of Fe(III) atoms with tetrahedral coordination. 38,39 However, a band of high intensity close to 360 nm was observed for all encapsulated complexes, including FeY. This band is characteristic of Fe(III) atoms with octahedral coordination in the presence of small oligomeric clusters of Fe x O y .…”

The effect of Fe species distribution and acidity of Fe-ZSM-5 on the hydrothermal stability and SO2 and hydrocarbons durability in NH3-SCR reaction

“…2. Generally, the bands below 300 nm are assignable to isolated Fe 3+ species located on ion exchange sites, while bands above 300 nm are assignable to oligomeric clusters (between 300-400 nm) and Fe2O3 particles (above 400 nm) [17,18]. As shown in Fig.…”

CATALISADORES DE Fe PARA A CONVERSÃO DE METANO A FORMALDEÍDO

“…O pico em 300 nm observado para os catalisadores 1P2FeHZCS e 1P2FeHZCA, o pico em 345 nm para o catalisador 1P2FeHZB e o ombro em 390 nm para o catalisador 2FeHZA, podem estar relacionados a partículas de Fe 2 O 3 (Fierro et al, 2011). Bandas em 300-400 nm estão relacionadas a pequenos agregados de Fe x O y onde íons Fe 3+ são coordenados octaedricamente (Kumar et al, 2004); esses agregados se formam para teores relativamente elevados de Fe na zeólita.…”