Abstract
Divalent metallic ions (M2+ = Fe2+, Mn2+, Cu2+) have been successfully introduced into silicalite-2 via a crystallization process control method. When applied in Non-methane Hydrocarbon (NMHC) removal from cooking oil fumes, these synthesized M-S2 (M = Fe, Mn, Cu) samples present both higher adsorption capacity and good catalytic oxidation performance compared with Al-S2 composed of silicon and aluminum. XRD, FTIR, UV–Vis, SEM, STEM, N2 sorption, TG-DTA, 29Si MAS NMR and XPS were used to characterize the incorporation and dispersion of different divalent metallic ions in silicalite framework. It was found Fe2+ can be well incorporated into the zeolite framework as similarly as Al3+, then followed by Mn2+ and Cu2+, respectively. Mn2+ can exist in the form of extra-framework oxidized metallic species despite of the framework Mn species, while Cu species are mainly in the form of CuOx nanoparticles or clusters. Due to lacking SiOHAl, these divalent metal-MEL zeolites possess superior hydrophobicity compared with Al-MEL and this endows the former’s superior NMHC adsorption performance from cooking oil fumes. Moreover, owing to possess active metallic species with variable valence states, these divalent metal-MEL zeolites display good oxidation ability to VOCs. Particularly, Mn-S2 displays the best catalytic activity for NMHC, which can be attributed to both the good dispersion and the various valence states of Mn species in silicalite.
Published Version
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