Hierarchical zeolite FeZSM-5 as a heterogeneous Fenton-type catalyst

Series of hierarchical zeolites ZSM-5 and FeZSM-5 were prepared by hydrothermal treatment using polystyrene spheres template and characterized by X-ray diffraction, UV–vis diffuse reflectance spectroscopy, scanning and high-resolution transmission electron microscopies, and N2 sorption techniques. Walls of the macroporous structure consisted of ZSM-5 nanocrystals with a size of 20–300 nm and amorphous globules of SiO2. Hierarchical FeZSM-5 contained iron in the form of iron oxide particles with a size of 2–3 nm. Hierarchical zeolites had high values of surface area (437–613 m2/g), external surface area (131–462 m2/g), and pore volume (0.36–0.76 cm3/g). Iron-containing zeolites were tested in the H2O2 decomposition reactions in the absence and presence of iron-complexing agent, as well as in oxidation of low and high molecular weight organic compounds by H2O2 at 25 °C and compared with homogeneous Fe(NO3)3 solution. Hierarchy of the zeolite porosity resulted in a significant improvement of the catalyst properties.

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► PS size depends nonlinearly on the polymerization temperature.
► A humidity of the PS template plays a crucial role during zeolite crystallization.
► Hierarchical zeolites ZSM-5 and FeZSM-5 consist of nanozeolites and amorphous silica.
► Conventional FeZSM-5 allows increasing the efficiency of H2O2 utilization in low molecular weight organics oxidation.
► The hierarchical FeZSM-5 is preferential catalyst for high molecular weight organics oxidation by H2O2.