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

Małgorzata Rutkowska,Urbano Díaz,Andrzej Kowalczyk,Ewelina Różycka-Dudek,Wiktoria Dubiel,Aleksandra Jankowska,Lucjan Chmielarz,Zofia Piwowarska,Sebastián Llopis

doi:10.3390/catal10101139

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).

Highlights

MCM-22 zeolite, synthesized in the 1990s, by the Mobile researches [1], due to its unusual pore structure, combining large 12 MR (Membered Ring) cavities and medium (10 MR channels) pores, as well as specific 2D alignment of the zeolitic layers, is under a great scientist’s interest for possible application in catalysis
The XRD pattern obtained for the parent MCM-22(P) sample is characteristic of MWW zeolites family and the presence of the (002) reflection at 2θ about 6.5◦ (d-spacing ~2.7 nm) confirms the layers’ separation and 2D structure of the as-synthesized material [43,44]
In the presented studies, layered MCM-22-type zeolite was modified in order to achieve the highest activity in N2 O decomposition

Summary

Introduction

MCM-22 zeolite, synthesized in the 1990s, by the Mobile researches [1], due to its unusual pore structure, combining large 12 MR (Membered Ring) cavities and medium (10 MR channels) pores, as well as specific 2D alignment of the zeolitic layers, is under a great scientist’s interest for possible application in catalysis. Swollen parent MCM-22(P) material subjected to pillarization or exfoliation processes results in MCM-36 [20] (layers separated by pillars, face-to-face orientation) and in ITQ-2 [21]. The relatively simple procedure used for the ITQ-2 synthesis results in material composed of sheets (2.5 nm thick), with the easy accessible 12 MR cups, whose entrances were not available for the catalyzed molecules in calcined 3D MCM-22 zeolite [22,23]. Such modification of the MCM-22 layers’ alignment to form ITQ-2 was found to be very attractive for various catalytic processes. Carriço et al [10] found ITQ-2 to be more catalytically active than

Methods

Results

Conclusion