Highly efficient solvent free oxidation of ethylbenzene using some recyclable catalysts: The role of linker in competency of manganese nanocatalysts

SiO2–Al2O3 mixed-oxide was functionalized with 3-aminopropyl-triethoxysilane (3-APTES) and 2-aminoethyl-3-aminopropyl-trimethoxysilane (2-AE-3-APTMS) groups. The resulting modified nanosized SiO2–Al2O3 mixed-oxides were further functionalized with three different Schiff base groups followed by complexation with Mn(OAc)2 to afford the corresponding immobilized Mn catalysts. The synthesized materials were characterized by FT-IR spectroscopy, UV–vis, CHN elemental analysis, ICP-MS, EPR, SEM, and TEM. The catalytic activities of the heterogenized Mn catalysts were studied in the oxidation of ethylbenzene without the need of any solvent, at 80 °C, using tert-butyl hydroperoxide as oxygen source. Si/Al-pr-NH-et-Nmethyl-2-pyridylketone-Mn had high catalytic activity and selectivity to acetophenone (93%), and could be reused at least 4 times without significant loss in activity.

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► The Mn catalysts immobilized on functionalized nanosized SiO2–Al2O3 used as catalysts.
► These catalysts were studied in the oxidation of ethylbenzene to acetophenone.
► Without the need of any solvent.
► The selectivity of acetophenone reached to 93% at TBHP/ethylbenzene molar ratio (1:1).