Optimization of Glucose Dehydration to 5-Hydroxymethylfurfural over Fe<sub>3</sub>O<sub>4</sub>–SiO<sub>2</sub>/Al<sub>2</sub>O<sub>3</sub> Catalyst Using Response Surface Methodology in a Biphasic System

<jats:p>Converting glucose into 5-hydroxymethylfurfural (HMF) via catalytic methods is essential for creating renewable chemicals and biofuels. Nonetheless, the process faces challenges due to by-products. This research introduces a cost-effective iron monometallic catalyst supported on silica-alumina (Fe3O4-SiO2/Al2O3), prepared by a straightforward co-precipitation technique. Its structure and active sites were extensively characterized using FTIR, TGA, XRD, SEM-EDX, XPS, and N₂ adsorption–desorption (BET). Glucose dehydration was performed in a biphasic water/methyl isobutyl ketone (H₂O: MIBK, 1:4, v/v) system, which facilitated in situ HMF extraction and reduced humin formation. Parameters such as temperature (170-190°C), reaction time (10-14 hours), and catalyst loading (25-75 wt.%) were optimized through response surface methodology using a Box-Behnken Design (RSM–BBD). The synergistic effect among Si, Al, and Fe increased the number of Lewis and Brønsted acid sites, thereby enhancing glucose isomerization to fructose and boosting HMF selectivity. Under optimal conditions (180°C, 14 hours, 50 wt.% catalyst), a maximum HMF yield of 63.91% with 99.22% glucose conversion was obtained, along with a notable reduction in by-products. This yield is among the highest reported for monometallic catalysts under similar conditions. The catalyst was reused up to four times and could be regenerated, showing fair stability. Overall, this work offers a scalable, eco-friendly method for efficient glucose conversion, underscoring the potential of bifunctional monometallic catalysts combined with biphasic systems for sustainable HMF production.</jats:p>