Innovative microwave and continuous flow synthesis of 5-Hydroxymethylfurfural from Biomass-Derived Resources using Deep eutectic solvents

• Microwave-assisted synthesis with DES solvents achieved a high yield of 5-HMF (73.4%) in a short time. • Continuous flow synthesis of 5-HMF provided a promising yield of 40.5% from glucose. • Molecular dynamic simulations were used to explain the underlying mechanisms of glucose conversion. The conversion of glucose into 5-hydroxymethylfurfural (5-HMF), a crucial precursor for bio-based polymers, is an important area of research considering its potential for renewable materials. Current approaches frequently pose efficiency and cost difficulties. Herein we devise an optimal, efficient, and cost-effective technique for converting D-(+)-glucose monohydrate to 5-HMF using tetrabutylammonium bromide (TBAB) and two innovative synthesis methods: microwave-assisted and continuous flow reactors. We used a TBAB-based deep eutectic solvent (DES) system that incorporated microwave irradiation and an isopropanol/water solvent matrix. Crucial variables such as reaction time, temperature, solvent ratio, reactant and catalyst concentration were optimized. Surpassing the existing literature, we obtained 5-HMF yield of 73.4 %, at 110 °C in 1 min. In addition, synthesis was also carried in an innovative continuous flow reactor system to compare with microwave synthesis, which gave a yield of 40.55 % at 170 °C with a residence time of 20 min under optimized conditions, demonstrating scalability. The extraction of 5-HMF from the reaction matrix was carried with ethyl acetate with an efficiency of 92 %. Molecular dynamics simulations were implemented to analyze the initial mechanism of conversion of D-glucose monohydrate. Simulations revealed that the solvent composition, specifically the presence of Br - and Cl – ions, significantly influences hydrogen bond formation and catalytic performance, enhancing the conversion efficiency. Our novel approaches, which use microwave-assisted and continuous flow reactors, greatly enhance 5-HMF yield and efficiency while minimizing reaction time and energy consumption. The continuous flow system is essential for scaling up production since it provides a sustainable and energy-efficient solution for industrial applications.