Conversion of Fructose to HMF in a Continuous Fixed Bed Reactor with Outstanding Selectivity

Abstract

5-Hydroxymethylfurfural (HMF) is a very promising component for bio-based plastics. Efficient synthesis of HMF from biomass is still challenging because of fast degradation of HMF to by-products under formation conditions. Therefore, different studies, conducted mainly in monophasic and biphasic batch systems with and without water addition have been published and are still under investigation. However, to produce HMF at a large scale, a continuous process is preferable. Until now, only a few studies have been published in this context. In this work, it is shown that fluorous alcohol hexafluoroisopropanol (HFIP) can act as superior reaction solvent for HMF synthesis from fructose in a fixed bed reactor. Very high yields of 76% HMF can be achieved in this system under optimized conditions, whilst the catalyst is very stable over several days. Such high yields are only described elsewhere with high boiling reaction solvents like dimethylsulfoxide (DMSO), whereas HFIP with a boiling point of 58 °C is very easy to separate from HMF.

Catalytic Transformation of Biomass Derivatives to Value‐Added Chemicals and Fuels in Continuous Flow Microreactors

“…In an alternative single phase system of water in hexafluoroisopropanol (HFIP), the dehydration of fructose to HMF was executed using a stainless steel packed bed reactor (d C = 9.5 mm) with Lewatit K2420 (an acidic ion exchanger consisting of sulfonic acid on cross-linked polystyrene) as catalyst (Table 4, entry 14). [229] In 20 min residence time, a full fructose conversion with 76 % HMF yield was obtained at 100°C and 20 bar. HFIP is a low boiling point solvent and hence facilitates the distillative retrieval of HMF after its production.…”

“…Several researches focused on the heterogeneously catalyzed dehydration of fructose to HMF (derivatives) in single phase operation (Table 4, entries [12][13][14], [227][228][229] or xylose to furfural in biphasic flow (Table 4, entries [15][16] [230,231] using milli-scale packed bed reactors (d C = 4-10 mm). These millireactors could be easily transferred into microreactor configurations and thus give valuable insights in the potential of the latter for the heterogeneous synthesis of furans from sugars.…”

Catalytic Dehydration of Fructose to 5-Hydroxymethylfurfural (HMF) in Low-Boiling Solvent Hexafluoroisopropanol (HFIP)

“…The good reusability, the high fructose concentration and the short reaction time enable high space-time yields, which are necessary for an efficient continuous HMF production. Consequently, further investigations will focus on the continuous HMF production [ 25 ].…”

Continuous Flow Upgrading of Selected C2–C6Platform Chemicals Derived from Biomass

“…Therefore, researchers alternatively studied continuous flow processes involving packed-bed reactors loaded with solid heterogeneous acid catalysts (Figure ). Catalysts described included resins, ,− metal oxides, ,,− or metal oxides functionalized with organic sulfonic acid moieties. , Although processes catalyzed by homogeneous mineral acids almost exclusively relied on biphasic solvent conditions (Table ), the literature describing the use of heterogeneous catalysts mostly relies on homogeneous reaction media. The sugar substrate typically requires polar solvents in the feedstock solution for solubility reasons, but water tends to promote a side-reaction toward levulinic acid (Scheme ).…”

“…Almost pure HMF (97% purity) was recovered in high yield (90%) after evaporation of the solvents, which could be reused for further operations (Table , entry 2). The most advanced example was most likely reported by Prüße et al upon utilization of hexafluoro­isopropanol (HFIP)/water as reaction medium and Lewatit K2420 acidic resin as catalyst . High selectivity toward HMF (80-74%) and almost quantitative conversion (99–95%) were maintained for an outstanding time (almost 9 days) of continuous operation (entry 8).…”