# N‑Hydroxyphthalimide Dissolved in Ionic Liquids Supported on Carbon Nanotubes as a Hybrid Catalytic System for Solvent-Free Aerobic Oxidation of Ethylbenzene

## TL;DR

Researchers developed a new hybrid catalytic system using carbon nanotubes and ionic liquids to efficiently oxidize ethylbenzene without solvents.

## Contribution

A novel SILP and SCILL-SILP hybrid catalytic system using carbon nanotubes and ionic liquids for solvent-free ethylbenzene oxidation is introduced.

## Key findings

- The [bmim][Cl]-based SILP system achieved 12.2% ethylbenzene conversion with 84.1% selectivity toward acetophenone.
- The [bmim][NTf2]-based SCILL-SILP system reached 22.6% ethylbenzene conversion.
- The [bmim][OcOSO3]-based systems showed relative stability across multiple cycles.

## Abstract

Carbon nanotubes
have gained significant interest in
catalysis
(as catalysts and catalyst supports) for 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 (EB) (80 °C, 0.1 MPa, 6 h) using molecular
oxygen as a green oxidant. Among the SILP systems, the 1-butyl-3-methylimidazolium
chloride ([bmim]­[Cl])-based SILP system exhibited the highest conversion
of EB (12.2 ± 3.1%) with enhanced selectivity (84.1 ± 11.4%)
toward 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 EB (22.6 ± 1.2%) was achieved using 1-butyl-3-methylimidazolium
bis­(trifluoromethylsulfonyl)­imide ([bmim]­[NTf2]) as the
IL phase. Recyclability and reusability studies showed that the catalytic
activities of the SILP and SCILL-SILP hybrid systems generally decreased
in the subsequent cycles, except for 1-butyl-3-methylimidazolium octyl
sulfate ([bmim]­[OcOSO3])-based catalytic systems, which
were relatively stable.