The synergistic action between imidazolium based ionic liquid (IL) [bmim][OcOSO3] and Co(II)/N‐hydroxyphthalimide (NHPI) systems in the catalytic aerobic oxidation of ethylbenzene under solvent‐free conditions have been here demonstrated by reaching a 35 % conversion with 83 % of selectivity in acetophenone at 80 °C. This highly performing catalytic system have been selected after screening several different IL and Co(II) salt combinations, and making sure that the complete solubilization of the polar NHPI in the lipophilic medium, without thus requiring any chemical modification of the organic catalyst, could be attained. This solubilizing effect can be ascribed to a direct interaction between [bmim][OcOSO3] IL and NHPI as revealed by a detailed NMR investigation which also allowed to exclude the formation of higher IL aggregates in the form of micelles or vesicles.

N-Hydroxyphthalimide was immobilized via ester bond on commercially available silica gel (SiOCONHPI) and then coated with various ionic liquids containing dissolved CoCl2 (SiOCONHPI@CoCl2@IL). New catalysts were characterized by means of FT IR spectroscopy, elemental analysis, SEM and TGA analysis and used in ethylbenzene oxidation with oxygen under mild solvent-free conditions (80 °C, 0.1 MPa). High catalytic activity of SiOCONHPI was proved. In comparison to a non-catalytic reaction, a two-fold increase in conversion of ethylbenzene was observed (from 4.7% to 8.6%). Coating of SiOCONHPI with [bmim][OcOSO3], [bmim][Cl] and [bmim][CF3SO3] containing CoCl2 enabled to increase the catalytic activity in relation to systems in which IL and CoCl2 were added directly to reaction mixture. The highest conversion of ethylbenzene was obtained while SiOCONHPI@CoCl2@[bmim][OcOSO3] were used (12.1%). Catalysts recovery and reuse was also studied.

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Studies on the possibility of application of ionic liquids or scCO 2 as solvents in hydrocarbons oxidation with oxygen in the presence of N-hydrophthalimide have been reported. Various alkylaromatics (cumene, ethylbenzene, mono-and diisopropylnaphthalene, mono-and diisopropylbiphenyl) and α-methylstyrene were used as starting materials.