Promoting the production of 5-hydroxymethylfurfural from high-concentration fructose by creating micro-reactors in a mixed solvent

• Published in: Green chemistry : an international journal and green chemistry resource : GC Vol. 25; no. 2; pp. 661 - 67
• Main Authors: Hu, Yexin, Li, Hui, Hu, Ping, Li, Linzhen, Wu, Di, Xue, Zhidan, Hu, Changwei, Zhu, Liangfang
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 23.01.2023
• Subjects: Anions; Biorefineries; Bromine; Catalytic converters; Cetyltrimethylammonium bromide; Condensates; Conversion; Dehydration; Fructose; Green chemistry; Hydrophobicity; Hydroxymethylfurfural; Intermediates; Ions; Mass transfer; Micelles; Microreactors; Reactors; Rehydration; Solvents; System effectiveness
• ISSN: 1463-9262; 1463-9270
• DOI: 10.1039/d2gc04295a

The severe formation of humins during the conversion of high-concentration fructose is a crucial bottleneck restricting the large-scale production of 5-hydroxymethylfurfural (HMF) from fructose. Herein, we report an efficient catalytic system for the conversion of high-concentration (10.0-60.0 wt%) fructose into HMF by creating micro-reactors with cetyltrimethylammonium bromide (CTAB) in a mixed solvent of 1,4-dioxane and water (DIO-H 2 O), wherein the formation of humins is remarkably restrained. The micro-reactors were composed of reversed micelles constructed by the assembly of amphiphilic CTAB in the mixed solvent ( V DIO / V H 2 O = 95/5). The confinement of fructose and bromine anions within the hydrophilic moiety of the micro-reactors enabled facile interactions between fructose and Br − ions, thereby enlarging the promotional effect of Br − ions on fructose-to-HMF dehydration via accelerating the deprotonation of oxocarbenium ion intermediates. Afterwards, the hydrophobic moiety assisted in the transfer of HMF into the organic solvent outside the micro-reactor protected HMF from further rehydration or condensation to humins. The competitive degradation and condensation of oxocarbenium ion intermediates to humins were significantly mitigated, resulting in high HMF yield (70.3%) and TOF (186.0 h −1 ) after reacting high-concentration (50.0 wt%) fructose at 140 °C within 15 min. This work highlights the utilization of a multifunctional micro-reactor to fix the reaction zone and facilitate mass transfer, thereby providing a valuable guidance for designing effective catalytic systems for future HMF biorefineries. An efficient catalytic system for producing 5-hydroxymethylfurfural from high-concentration fructose has been built by creating micro-reactors with cetyltrimethylammonium bromide in a mixed solvent of 1,4-dioxane and water.