A multi-walled carbon nanotube-supported acidic ionic liquid catalyst for the conversion of biomass-derived saccharides to 5-hydroxymethylfurfural

Abstract

Herein, the surface of multi-walled carbon nanotubes (MWCNTs) was functionalized with 3-mercaptopropyltrimethoxysilane followed by anchoring of 1-vinylimidazole on the surface through the thiol–ene click reaction. Then, sulfonic acid groups were immobilized on the surface of the ionic liquid-functionalized MWCNTs to afford a solid acid catalyst. Structural characterization of the synthesized catalyst was carried out by various methods including Fourier transform infrared spectroscopy (FT-IR), thermogravimetry analysis (TGA), energy dispersive X-ray spectroscopy (EDX), N₂ adsorption–desorption, X-ray diffraction (XRD), acid–base titration, and transmission electron microscopy (TEM). The catalyst exhibited a high activity for fructose transformation to a value added product, i.e. 5-hydroxymethylfurfural (HMF). The catalyst was also applicable to the other carbohydrates (glucose, maltose, and sucrose), providing HMF with satisfactory yields. Moreover, a high durability and recyclability of the catalyst were observed after five cycles of recovery.