Evaluation of manganese OMS-like cryptomelane supported on SBA-15 in the oxidation of ethyl acetate

We report the synthesis of four manganese catalysts supported on SBA-15 via a multistep impregnation method. The successive impregnations allowed as much as 13.8% manganese to be deposited without loss of the mesoporous structure of the SBA-15, although the surface area of the catalysts and their pore size distributions were lower than those of the pure SBA-15. The data obtained using different analysis techniques indicate that the manganese was incorporated into the pure SBA-15 in different positions: grafted onto the internal surface of the walls, incorporated into the framework of the SBA-15 and on the external surface and at the pores mouth of the SBA-15, which partially blocked the porosity. The XRD results showed that cryptomelane phase was formed in all of the catalysts; the remaining P123 in the SBA-15 structure and the presence of K+ during the impregnation most likely favored the formation of the cryptomelane phase. Total oxidation of ethyl acetate in air was obtained at temperatures less than 350 °C for all of the catalysts.

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► Mn deposited on SBA-15 without structural damage losing surface area and pore volume.
► Mn located in different positions of the catalysts.
► Remaining P123 in SBA-15 and K+ from KMnO4 favored cryptomelane phases.
► Activity in the oxidation of ethyl acetate is inversely proportional to Mn content.
► Increasing K+ content favors oxidation of ethyl acetate.