Hybrid catalytic systems employing carbon nanotubes as a support for the solvent-free aerobic oxidation of ethylbenzene

Carbon nanotubes have gained significant interest as catalysts and catalytic supports in hydrocarbon oxidation processes. In this study, pristine multiwalled carbon nanotubes and copper(II) functionalized multiwalled carbon nanotubes were coated with [bmim] cationic ionic liquids (ILs) containing dissolved N -hydroxyphthalimide (NHPI) to produce novel SILP and SCILL-SILP hybrid catalytic systems, respectively (SILP: supported ionic liquid phase and SCILL: solid catalyst with an ionic liquid layer). The catalytic activities of the produced systems were investigated for the solvent-free oxidation of ethylbenzene (80 ^o C, 0.1 MPa, 6 h) using molecular oxygen as a green oxidant. Among the SILP systems, the [bmim][Cl]-based SILP system exhibited the highest conversion of ethylbenzene (14.4%) with the highest selectivity (92.1%) towards acetophenone (AcPO). The catalytic activity of the SILP system increased with increasing lipophilicity of the alkyl group in the IL cation. Conversely, among the SCILL-SILP systems, the highest conversion of ethylbenzene (23.4%) was achieved using [bmim][NTf ₂ ] as the IL phase. Recyclability and reusability studies showed that the catalytic activities of the SILP and SCILL-SILP hybrid systems generally decreased in subsequent cycles, except for [bmim][OcOSO ₃ ]-based catalytic systems.