Mn-SBA15 catalysts prepared by impregnation: Influence of the manganese precursor

The purpose of this study was to evaluate the effect of the precursors on the synthesis of MnOx-SBA15 catalysts. The influence of the manganese phase on the activity of catalysts in the complete oxidation of ethyl acetate was also tested. SBA15 was synthesized according to a standard method reported in the literature and manganese was introduced onto the support following an incipient wetness method using three different precursors. The catalysts were characterized by N2 adsorption, XRD, FTIR, TPR and HAADF and HRTEM microscopy. Then, they were tested in the oxidation of ethyl acetate. The results showed on one hand that the crystalline phase of deposited MnOx depended on the precursor used for the impregnation and on the other, that the manganese oxide was deposited both on the external surface and inside the mesoporosity of the SBA15 that preserved it structure, although it lost textural properties by pore blockage. The activity of the catalysts depended on the crystalline phase, being the most active those with Mn4+/Mn3+ pairs.

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► Textural data and STEM-HAADF technique indicates that MnOx was deposited on the external surface and inside the porosity of SBA15.
► Crystalline phase of MnOx supported on SBA15 depends on the precursor.
► TPR and EELS data indicate that Mn oxidation state in SBA15-NO3 and SBA15-KMnO4 is about +4 and +2.7–3 for SBA15-Ac.
► MnOx crystalline phase containing Mn4+/Mn3+ pairs were the most active in the oxidation of ethyl acetate.