Efficient Production of 5‑Hydroxymethylfurfural Enhanced by Liquid–Liquid Extraction in a Membrane Dispersion Microreactor

Aimed at efficient production of 5-hydroxymethylfurfural (HMF) in a green and sustainable way, dehydrogenation of fructose was enhanced by liquid–liquid extraction in a membrane dispersion microreactor. On account of the high mass-transfer rate resulted from dripping flow, the obtained HMF was readily extracted from the aqueous phase to the organic phase, effectively preventing the sequence side reaction and leading to high HMF selectivity. Enhanced by efficient extraction, the reaction duration decreased from 60 min in a traditional stirred reactor to 4 min in the microreactor, leading to an increase in the space-time yield by 3 orders of magnitude. The effects of total volume flow rate, droplet size, and phase ratio relating to extraction efficiency and HMF yield were systematically investigated. The highest extraction efficiency of nearly 100% coupled with the HMF yield of 93.0% was achieved at the phase ratio of 2 with volume flow rate of 600 mL/h. Overall, this work not only delineates an efficient strategy for synthesizing HMF but also opens a new avenue for reaction systems with subsequent side reaction, which suffer from low selectivity of the intermediates due to the in-line separation bottleneck under conditions of limited mass transfer.