Silicotungstic acid catalyst supported onto functionalized halloysite nanotubes (HNTs) utilized for the production of 5-hydroxymethylfurfural (5-HMF) from fructose

Abstract

5-Hydroxymethylfurfural (5-HMF) is a valuable organic compound commonly derived from sugars such as fructose and glucose. Silicotungstic acid (HSiW), a unique Keggin-type heteropolyacid, is a typical catalyst for organic compound production. To synthesize 5-HMF from fructose, we developed a novel catalyst, HSiW@F-HNTs, by combining HSiW and functionalized halloysite nanotubes (F-HNTs) modified with (3-amino-propyl) triethoxysilane (APTES), 2,4,6-trichloro-1,3,5-triazine (TCT), and l-arginine. We analyzed the physicochemical properties of HSiW@F-HNTs using the FT-IR, XRD, BET, FESEM, EDS, and XPS characterization techniques, confirming their suitability for fructose-to-5-HMF conversion. Through response surface methodology (RSM), we investigated and optimized the effects of reaction conditions on 5-HMF production yield. Optimal conditions were found to be a 102 °C reaction temperature, a 65 min reaction time, and an 8.5 wt.% catalyst loading, resulting in a 95 % yield of fructose-to-5-HMF conversion. We also conducted the kinetic and thermodynamic analyses to determine the reaction rate and activation energy (Ea) and estimate the changes in Gibbs free energy (ΔG), enthalpy (ΔH), and entropy (ΔS) of the catalytic conversion reaction. Additionally, the prepared HSiW@F-HNTs catalyst could be recycled up to 9 times without a significant loss in activity, demonstrating its high stability for real-world applications.