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Aminosilane-Grafted SiO₂–ZrO₂ Polymer Hollow Fibers as Bifunctional Microfluidic Reactor for Tandem Reaction of Glucose and Fructose to 5-Hydroxymethylfurfural

He, Yingxin, Itta, Arun K., Alwakwak, Abdo-alslam, Huang, Ming, Rezaei, Fateme, Rownaghi, Ali A.
ACS sustainable chemistry & engineering 2018 v.6 no.12 pp. 17211-17219
Bronsted acids, catalysts, feedstocks, fructose, glucose, hydroxymethylfurfural, isomerization, moieties, nanoparticles, polymers, silica, spinning, temperature, zirconium oxide
In this study, we demonstrate the concept of tandem reaction for glucose and fructose to 5-hydroxymethylfurfural (HMF) in an aminosilane-grafted SiO₂–ZrO₂ polyamide–imide hollow fiber that acts as a bifunctional heterogeneous catalyst and microfluidic reactor. The bifunctional catalysts were formed by embedding SiO₂ and ZrO₂ nanoparticles into polyamide–imide polymer dope that underwent subsequent phase inversion through “dry-jet, wet-quench spinning” process to form hollow fibers, followed by postgrafting with aminosilane to incorporate amine moieties into the hollow fibers. The tandem strategy integrated the first step of glucose isomerization with the subsequent step of dehydration of fructose to HMF over bifunctional Lewis and Brønsted acid sites of hollow fiber microfluidic reactor at different temperatures (100–150 °C) and reaction times (1–8 h). Our results indicated, through optimizing the Lewis to Brønsted acid sites ratio in hollow fiber catalysts, the HMF selectivity was enhanced from 21% to 82% and 21% to 34% by using fructose and glucose as feedstocks, respectively. The effect of water on glucose isomerization and fructose dehydration to HMF was also studied. Investigation of the stability and efficiency of bifunctional catalysts through recycling experiments revealed that this tandem microfluidic system enables precise control of the reaction flow rate, temperature, and time while eliminating the need for an additional catalyst separation step and opening up new opportunities for the conversion of sugar molecules in a continuous-flow system.