Modification of MCM-22 Zeolite and Its Derivatives with Iron for the Application in N2O Decomposition

Abstract

Layered 2D zeolite MCM-22 and its delaminated derivative, ITQ-2, were modified with iron, by different methods (ion-exchange and direct synthesis), and with the use of different precursors (FeSO4∙7H2O, Fe(NO3)3∙9H2O, and [Fe3(OCOCH3)7∙OH∙2H2O]NO3 oligocations. The applied modifications were aimed at optimization of iron form in the samples (aggregation, amount, location, and reducibility), in order to achieve the highest catalytic activity in the N2O decomposition. The synthesis of the samples was verified with the use of XRD (X-Ray Diffraction), N2-sorption and ICP-OES (Inductively Coupled Plasma Optical Emission Spectroscopy) techniques, while the form of iron in the samples was investigated by UV–vis-DRS (UV–vis diffuse reflectance spectroscopy), H2-TPR (Hydrogen Temperature-Programmed Reduction) and HRTEM (High-Resolution Transmission Electron Microscopy). The highest activity in the N2O decomposition presented the sample Fe(O,IE)MCM-22, prepared by ion-exchange of MCM-22 with Fe3(III) oligocations. This activity was related to the oligomeric FexOy species (the main form of iron in the sample) and the higher loading of active species (in comparison to the modification with FeSO4∙7H2O).

Evaluation of Synthesis Method of Fe Loaded Amorphous Silica on the Adsorption of Glyphosate

“…Unlike the RF method, the adsorbent with a lower loading of FexOy oligomer and Fe2O3 was prepared. Such finding was consistent with the study by Rutkowska et al [33]. The Fe loaded MCM-22 using FeSO4.7H2O as a precursor under the reflux condition was studied by several techniques.…”

Catalytic Performance and Sulfur Dioxide Resistance of One-Pot Synthesized Fe-MCM-22 in Selective Catalytic Reduction of Nitrogen Oxides with Ammonia (NH3-SCR)—The Effect of Iron Content

“…Calcination of MCM-22 (P) yielded 3D zeolitic structure of MCM-22, confirmed by the overlap of (002) diffraction maximum with the intra-layer reflection (100). This result is assigned to the contraction of the zeolitic layers, caused by the condensation between the opposite external silanol groups, as the result of the removal of the organic template [46]. Additionally, the positions of the intra-layer (100) and inter-layer mixed (101) and (220) reflections did not noticeably change after calcination.…”

“…An alternative explanation of the decreasing amount of N 2 O can be found in the content and speciation of iron. Rutkowska and co-workers [46] investigated the catalytic activity of Fe-modified MCM-22 in N 2 O decomposition. In their research, the authors recognized oligomeric iron species as the key active centers, which catalyzed the reaction.…”

“…N2O production decreased with the increasing temperature for Fe-10 as well, however, it was observed between 250-400 °C. This effect can be explained by the possible decomposition of nitrous oxide over the FexOy clusters, present in the material (see XPS and UV-vis results) [46]. On the contrary, the N2O yield for Fe-5 was maintained at a similar level throughout the examined temperature range and was the highest among the one-pot synthesized catalysts.…”

“…All of the catalysts showed characteristic absorption bands in range of 200-600 nm and the spectra can be divided into four regions, ascribed to different iron species. The oxygen-to-metal charge-transfer bands below 300 nm, present for all of the materials, are assigned to the isolated, monomeric Fe 3+ cations in various coordination [37,42,46]. The particular position of the specific bands depends on the number of ligands.…”