Intensified reactive extraction for the acid-catalyzed conversion of fructose to 5-hydroxymethyl furfural

We conduct an experimental study of fructose dehydration to 5-hydroxymethyl furfural (HMF) in a biphasic microreactor as a function of residence time, temperature, and sugar loading using methyl butyl iso-ketone (MIBK) and 2-pentanol as extracting solvents. We demonstrate stable operation with maximum HMF yields of 93% and 87% in the two solvents, respectively, at 200 degrees C and a residence time of 2 s for a 5 wt% fructose aqueous feed. We report the highest optimal HMF space-time yield of 60 kg/L-hr at 200 degrees C (10 - 2,500-fold higher than published reports). Unexpectedly, an optimum organic-to-water ratio exists that depends on the solvent. Notably, we observe experimentally an increased fructose rate and HMF yield well above the extraction thermodynamic limit and hypothesize that the solvent plays a dual role, that of an extractant to protect HMF from degradation and a modifier of the fundamental chemistry. We expose mass transfer limitations of microreactors at longer residence times and higher temperatures and provide reactivity maps for their design. We show that batch reactors are unfit for high throughput and distributed manufacturing where small, farm-based systems are necessary.

Automated summary

This study investigates fructose dehydration to HMF in a biphasic microreactor with high yields and optimal organic-to-water ratios identified at high temperatures. The research also uncovers the dual role of the solvent in both protecting HMF from degradation and modifying fundamental chemistry. Additionally, mass transfer limitations in microreactors at longer residence times and higher temperatures are revealed, highlighting the importance of reactor design and operation.