SCILL-SILP hybrid catalytic system by employing carbon nanotubes as a support for the selective oxidation of ethylbenzene to acetophenone

Abstract

Hydrocarbon oxidation to more valuable products is one of the most crucial industrial petrochemical processes. To improve efficiency, economic effectiveness, and reduction of waste production by conventional processes, the development of active and selective catalysts is still an important area of research. To cope with these challenges, we developed a catalytic system that utilized molecular oxygen to oxidize ethylbenzene (EB) to acetophenone (AcPO). The catalyst was prepared by coating a thin layer of a mixture of selected ionic liquid 1-ethyl-3-methylimidazolium octylsulfate and N-hydroxyphthalimide over industrial-grade multiwalled carbon nanotubes functionalized with copper(II) ions. This unique catalyst represented a hybrid catalytic system via the combination of solid catalyst with an ionic liquid layer (SCILL) and a supported ionic liquid phase (SILP) system. The oxidation reactions were performed at 80 °C and 0.1 MPa for 6 h. SCILL-SILP hybrid catalytic system exhibited exceptional performance with ∼27 % EB conversion and ∼77 % AcPO selectivity. The recyclability and reusability of the prepared catalysts were also investigated. The copper content was determined using inductively coupled plasma mass spectrometry (ICP-MS). Scanning electron microscopy (SEM) and transmission electron microscopy(TEM)were used to study the morphologies of the catalysts. Energy dispersive spectroscopy (EDS) was used to detect the immobilized copper on the functionalized CNTs while N2 physisorption analysis was employed to study the textural properties of the catalysts. Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) were used to study the freshly synthesized and recycled catalysts.