Abstract

The synthesis of bio-based molecules from biomass offers a sustainable alternative to petrochemical-derived products. This study explores the continuous production of 5-hydroxymethylfurfural (HMF) from glucose using a biphasic microreactor system catalyzed by Lewis (AlCl3) and Br & oslash;nsted (HCl) acids. Natural solvents with high affinity for HMF were identified using the COSMO-RS method. Carvacrol and the natural deep eutectic solvent (NADES, mix of carvacrol:thymol) outperform conventional solvents like MIBK and ethyl acetate in extraction efficiency. Under optimized conditions 160 degrees C, an organic to aqueous (O/A) volume ratio of 2:1, equimolar catalyst concentrations (AlCl3/HCl) of 40 mM, and a residence time of 12 min a maximum HMF yield of 55 mol% was achieved with carvacrol and 52 mol% with carvacrol:thymol, compared to 43 mol% obtained with MIBK, all at similar glucose conversions (similar to 85 mol%). MALDI-TOF MS analysis demonstrated that terpenoid-based solvents inhibit the formation of humin precursors, enabling selective HMF production. The proposed first-order kinetic model further revealed that the use of carvacrol minimizes the formation of by-products such as formic acid and levulinic acid, enhancing the HMF yield to as high as 65 mol% under optimized conditions but increasing the residence time in 12 min compared to the experimental conditions. Additionally, calculated overall liquid-liquid mass transfer coefficient indicates the absence of significant mass transfer limitations within the studied parameters. These findings highlight the effectiveness of combining terpenoid-based solvents with AlCl3/HCl catalysts for sustainable and efficient HMF production.