Sulfonated graphene oxide/MnFe2O4 magnetic nanocomposite for effective 5-hydroxymethylfurfural etherification in biofuel production.

Herein, a solid acid catalyst, SO3H-GO/MnFe2O4, was synthesized through a three-step process, including the preparation of graphene oxide (GO), deposition of MnFe2O4 nanoparticles onto GO, and subsequent sulfonation with chlorosulfonic acid. The synthesized catalyst was completely analyzed by numerous techniques, including FT-IR, TEM, XRD, EDX, VSM, and acid-base titration, approving the successful incorporation of MnFe2O4 nanoparticles and -SO3H groups onto GO. The activity of prepared SO3H-GO/MnFe2O4 was determined in the etherification of 5-hydroxymethylfurfural (HMF) to 5-ethoxymethylfurfural (EMF). The reaction factors were optimized and the optimum condition was obtained at 120 °C, 30 mg of catalyst dosage, and time of 6 h, providing high EMF yield (93.2%), and selectivity (96%). The prepared particles were easily isolated from the mixture by a magnet and showed excellent recyclability, retaining most of its activity over four consecutive cycles. Moreover, the catalyst was also efficient in the direct conversion of biomass-derived sugars (fructose, glucose, and sucrose) to EMF.