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.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (228 K)Download as PowerPoint slideHighlights► 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.