New approach for sulfonation of carbonaceous materials: Highly efficient solid acid catalysts for benzaldehyde acetalization with ethylene glycol

Abstract

Three kinds of carbonaceous solid materials, namely activated carbon (AC), graphene oxide (GO), and graphene oxide–magnetite nanocomposite (GO/SCMNPs), have been utilized as catalyst supports to immobilize active acid sites on their surfaces. In this regard, three solid acid catalysts were prepared by a two-step synthetic approach: (a) surface chemical modification with a suitable nitrogen-containing spacer group and (b) chemical appending of sulfonic acid groups on the immobilized functional groups derived from step (a). Various methods have been exploited for characterization of the synthesized solid acid catalysts, such as FTIR and energy-dispersive X-ray (EDX) spectroscopies, elemental analysis, X-ray diffraction (XRD) analysis, N2 adsorption–desorption, thermogravimetric analysis (TGA), and vibrating sample magnetometry (VSM). The catalytic activities of these carbonaceous acid catalysts have been examined in an acetalization reaction using benzaldehyde and ethylene glycol as starting substrates. An outstanding result was achieved for the acid catalyst based on AC due to a higher concentration of incorporated sulfonic acid groups. Nevertheless, even the good efficiencies of the other two catalysts matched those of previously reported catalyst systems.