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 degrees C, using tert-butyl hydroperoxide as oxygen source. Si/Al-pr-NH-et-N=methyl-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. (C) 2011 Elsevier B.V. All rights reserved.