Finely Iron-Dispersed Particles on β Zeolite from Solvated Iron Atoms: Promising Catalysts for NH₃-SCO

Abstract

Beta zeolite has been functionalized with ca. 2 wt.% Fe to obtain catalysts for the NH3-SCO reaction.Iron deposition was performed on the zeolite surface by solvated metal atom dispersion (SMAD) and ionic-exchange (IE) procedures. ZSM-5 was selected as reference structure known to assure high dispersion of isolated centers when functionalized with iron by IE. Transmission electron microscopy techniques combined with element maps enlightened on the iron-species distribution and dimension on the two zeolites. As expected, highly homogeneous dispersed iron species were present on the ZSM-5 sample prepared by IE, while with Beta zeolite the same deposition method led to the formation of FeOx aggregates (2.5-10 nm) together with isolated iron species. On the other hands, by SMAD approach, well-formed FeOx-nanoparticles ranging 1.0 -4.5 nm were revealed on Beta zeolite.Ammonia oxidation activity (NH3-SCO) on iron-containing zeolites started at ca. 300°C, without no clear effect of the size of Fe on the reaction activity/selectivity. Ammonia conversion regularly increased with temperature with always very high selectivity to dinitrogen (98-100%), without any NOx or N2O formation, on iron containing Beta zeolites, in particular. Only very limited increase of iron particle dimensions were observed on the used Fe-catalysts, in any case.The collected experimental results indicated that not only isolated well-dispersed iron species are associated with high activity and selectivity in the NH3-SCO reaction. SMAD-derived iron nanoparticles worked with excellent performances in the ammonia oxidation reaction with high activity in terms of conversion, selectivity to dinitrogen, and stability.

Ferrierite and Its Delaminated Forms Modified with Copper as Effective Catalysts for NH3-SCO Process

“…(2) transition metal oxides, typically active at higher temperatures but more selective to dinitrogen than noble metals [12][13][14]; and (3) zeolites modified with transition metals, which are catalytically active at temperatures higher than noble metals but are significantly more selective to dinitrogen [15][16][17].…”

Environmental Reactions of Air-Quality Protection on Eco-Friendly Iron-Based Catalysts

“…At the outlet of SCR reactor, unreacted ammonia must not be vented in the atmosphere, therefore, a catalytic process is required to abate the unreacted slipped ammonia. The addition of a selective oxidation (SCO) catalyst in cascade could help in solving the problem of ammonia slipping [34,35]. However, in some cases, and specifically at high temperatures, N 2 O is formed as main undesired by-product in the NH 3 -SCR and SCO processes.…”

Size-dependent catalytic effect of magnetite nanoparticles in the synthesis of tunable magnetic polyaniline nanocomposites

“…The synthesis of Fe-SMA was carried out in a static metal vapor synthesis reactor described elsewhere (Evangelisti et al, 2015) and equipped with an alumina-coated tungsten crucible heated by Joule effect with a generator with a maximum power of 2 kW. Fe-solvated metal atoms (SMA) were prepared according to a previously described procedure (Barbaro et al, 2015;Campisi et al, 2019). Briefly, Fe vapors generated in high vacuum (1•10 -5 mbar) by resistive heating of an alumina-coated tungsten crucible, filled with approximately 300 mg of iron, were co-condensed at −196 °C with acetone vapor (100 mL) in the glass reactor chamber for 1 h. The reactor chamber was then warmed to the melting point of the solid matrix (ca.…”

“…To study how the NP size affects the catalytic polymerization of AD and the properties of the resulting nanocomposite, we prepared magnetite NPs of different size by different procedures, each yielding NPs with good size dispersity and uniform shape. We used thermal decomposition to prepare medium and large NPs (Hyeon et al, 2001;Park et al, 2004), whereas very small NPs were synthesized by metal vapor synthesis technique (Barbaro et al, 2015;Campisi et al, 2019). TEM images of the NP samples are reported in Figure 1.…”