N-Hydroxyphthalimide Supported on Silica Coated with Ionic Liquids Containing CoCl2 (SCILLs) as New Catalytic System for Solvent-Free Ethylbenzene Oxidation

Gabriela Dobras,Beata Orlińska,Sebastian Jurczyk,Kornela Kasperczyk

doi:10.3390/catal10020252

Abstract

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.

Highlights

Hydrocarbon oxidation processes play an important role in organic synthesis and industrial processes
Its catalytic activity is attributed to a PINO radical generated in the system, which abstracts a hydrogen atom from oxidized hydrocarbon, from 2 to 20 times faster than peroxyl radicals in an autocatalytic process [3] (Figure 1)
The catalytic activity of NHPI immobilized on silica via ester bond SiOCONHPI

Summary

Introduction

Hydrocarbon oxidation processes play an important role in organic synthesis and industrial processes. Processes which use oxygen or air as an oxidizing factor often require the use of suitable catalytic systems. The most commonly used ones include compounds of transition metals, such as Co and Mn [1,2]. High activity of N-hydroxyphthalimide (NHPI) has been proved in reactions of this kind [3,4,5]. Its catalytic activity is attributed to a PINO radical generated in the system, which abstracts a hydrogen atom from oxidized hydrocarbon, from 2 to 20 times faster than peroxyl radicals in an autocatalytic process [3] (Figure 1). PINO is generated by various additives, e.g., azo compounds, peroxides, transition metals salts, aldehydes, and quinones and its derivatives [6]

Methods

Results

Conclusion