Coordination and activation of nitrous oxide by iron zeolites

Bols, Max L.; Snyder, B.; Rhoda, Hannah M.; Cnudde, Pieter; Fayad, Ghinwa; Schoonheydt, Robert A.; Speybroeck, Véronique Van; Solomon, Edward I.; Sels, Bert F.

doi:10.1038/s41929-021-00602-4

Cited by 65 publications

(83 citation statements)

References 51 publications

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“…For every Al(III) T atom, the lattice carries a negative charge that must be balanced by exchangeable cations. Zeolites exchanged with cationic iron are useful redox catalysts and attract attention for their stabilization of the α-Fe(II)/α-O sites. − These are well-known as the active sites for room temperature partial oxidation of methane to methanol and benzene to phenol and are likely also involved in selective catalytic reduction (SCR) of NO X and catalytic N 2 O decomposition. − On the Fe-*BEA zeolite, the α-Fe(II)/α-O active sites are formed in six membered ring (6MR) motifs of the zeolite framework with two Al(III) T atoms (Al FW ) at opposite sides of the 6MR . How these α-Fe(II) sites are formed from their precursors remains unclear.…”

Section: Introductionmentioning

confidence: 99%

Selective Formation of α-Fe(II) Sites on Fe-Zeolites through One-Pot Synthesis

et al. 2021

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α-Fe(II) active sites in iron zeolites catalyze N2O decomposition and form highly reactive α-O that selectively oxidizes unreactive hydrocarbons, such as methane. How these α-Fe(II) sites are formed remains unclear. Here different methods of iron introduction into zeolites are compared to derive the limiting factors of Fe speciation to α-Fe(II). Postsynthetic iron introduction procedures on small pore zeolites suffer from limited iron diffusion and dispersion leading to iron oxides. In contrast, by introducing Fe(III) in the hydrothermal synthesis mixture of the zeolite (one-pot synthesis) and the right treatment, crystalline CHA can be prepared with >1.6 wt % Fe, of which >70% is α-Fe(II). The effect of iron on the crystallization is investigated, and the intermediate Fe species are tracked using UV–vis-NIR, FT-IR, and Mössbauer spectroscopy. These data are supplemented with online mass spectrometry in each step, with reactivity tests in α-O formation and with methanol yields in stoichiometric methane activation at room temperature and pressure. We recover up to 134 μmol methanol per gram in a single cycle through H2O/CH3CN extraction and 183 μmol/g through steam desorption, a record yield for iron zeolites. A general scheme is proposed for iron speciation in zeolites through the steps of drying, calcination, and activation. The formation of two cohorts of α-Fe(II) is discovered, one before and one after high temperature activation. We propose the latter cohort depends on the reshuffling of aluminum in the zeolite lattice to accommodate thermodynamically favored α-Fe(II).

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Section: Introductionmentioning

confidence: 99%

Selective Formation of α-Fe(II) Sites on Fe-Zeolites through One-Pot Synthesis

et al. 2021

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“…The reported catalysts provide a complete conversion of nitrous oxide to nitrogen and oxygen at 620 K. Ru(0) nanoclusters prepared by the reduction of Ru(III) ions, as well as osmium(III) species were found to be less active compared with ruthenium ions. The systems containing Fe, Cu, Co, and Ru metal ions exhibited a much better catalytic performance in N 2 O decomposition as compared with other modified and non-modified zeolites [21], as well as other amorphous oxide systems [22,23]. The main disadvantages revealed, for example, by the Cu-catalysts for N 2 O decomposition are their low thermal stability (they irreversibly lose the activity after overheating to T > 870 K) and poor tolerance to admixtures of H 2 O, CO, CO 2 , and hydrocarbons, which are present in real gas mixtures and act as poisons.…”

Section: Introductionmentioning

confidence: 94%

Nitrous Oxide Adsorption and Decomposition on Zeolites and Zeolite-like Materials

2022

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Decomposition of N2O on modified zeolites, crystalline titanosilicalites, and related amorphous systems is studied by the catalytic and spectroscopic methods. Zinc-containing HZSM-5 zeolites and titanosilicalites with moderate Ti/Si ratios are shown to exhibit a better catalytic performance in N2O decomposition as compared with conventionally used Cu/HZSM-5 zeolites and amorphous Cu-containing catalysts. Dehydroxylation of the HZSM-5 zeolite by calcination at 1120 K results in an enhancement of the N2O conversion. The mechanism of the reaction and the role of coordinatively unsaturated cations and Lewis acid sites in N2O decomposition are discussed on the basis of the spectroscopic data.

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“…Upon exposure to N 2 O at room temperature, the 15900 cm −1 ligand field band of α-Fe(II) in Fe-*BEA decays and a new band appears at 11500 cm −1 (Figure 24A). 77 With subsequent heating, this band disappears, and the characteristic DR-UV−vis features of α-O are observed (Figure 24B). Combined data from Mossbauer spectroscopy, infrared spectroscopy, and density functional theory calculations indicate the 11500 cm −1 band derives from an S = 2 Fe(II)-NNO species (η 1 -N in Figure 24C).…”

Section: [Cu 2 O] 2+mentioning

confidence: 99%

“…Subsequent kinetics studies quantified the activation barrier for O atom transfer to be ΔH ⧧ = 17.7 kcal/mol. 77 Many zeolite lattices stabilize α-Fe(II) sites that can interact with N 2 O to form α-O. The α-Fe sites in the FeFER lattice, however, exhibit remarkable activity for the decomposition of N 2 O compared to α-Fe(II) sites in other lattices.…”

Section: [Cu 2 O] 2+mentioning

confidence: 99%

Second-Sphere Lattice Effects in Copper and Iron Zeolite Catalysis

et al. 2022

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Transition-metal-exchanged zeolites perform remarkable chemical reactions from low-temperature methane to methanol oxidation to selective reduction of NOx pollutants. As with metalloenzymes, metallozeolites have impressive reactivities that are controlled in part by interactions outside the immediate coordination sphere. These second-sphere effects include activating a metal site through enforcing an "entatic" state, controlling binding and access to the metal site with pockets and channels, and directing radical rebound vs cage escape. This review explores these effects with emphasis placed on but not limited to the selective oxidation of methane to methanol with a focus on copper and iron active sites, although other transitionmetal-ion zeolite reactions are also explored. While the actual active-site geometric and electronic structures are different in the copper and iron metallozeolites compared to the metalloenzymes, their second-sphere interactions with the lattice or the protein environments are found to have strong parallels that contribute to their high activity and selectivity.

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Coordination and activation of nitrous oxide by iron zeolites

Cited by 65 publications

References 51 publications

Selective Formation of α-Fe(II) Sites on Fe-Zeolites through One-Pot Synthesis

Selective Formation of α-Fe(II) Sites on Fe-Zeolites through One-Pot Synthesis

Nitrous Oxide Adsorption and Decomposition on Zeolites and Zeolite-like Materials

Second-Sphere Lattice Effects in Copper and Iron Zeolite Catalysis

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