The degradation of clopyralid with the homogeneous and heterogeneous Fenton process was carried out under mild reaction conditions in aqueous solution. A complete degradation of clopyralid was obtained with the homogeneous Fenton reaction. Therefore, the influence of several parameters such as the initial concentrations of the catalyst, clopyralid, and H2O2 as well as the initial pH value on the homogeneous reaction was investigated. Several reaction intermediates and end products could be identified and allowed one to propose a degradation pathway of clopyralid. The heterogeneous degradation of clopyralid could only be achieved in the presence of HCl. Under these conditions, iron ions were detected in the reaction suspension, which indicates that the reaction is not heterogeneously but rather homogeneously catalyzed.

A mixture of hexafluoroisopropanol (HFIP) and water was used as a new and unknown monophasic reaction solvent for fructose dehydration in order to produce HMF. HFIP is a low-boiling fluorous alcohol (b.p. 58 °C). Hence, HFIP can be recovered cost efficiently by distillation. Different ion-exchange resins were screened for the HFIP/water system in batch experiments. The best results were obtained for acidic macroporous ion-exchange resins, and high HMF yields up to 70% were achieved. The effects of various reaction conditions like initial fructose concentration, catalyst concentration, water content in HFIP, temperature and influence of the catalyst particle size were evaluated. Up to 76% HMF yield was attained at optimized reaction conditions for high initial fructose concentration of 0.5 M (90 g/L). The ion-exchange resin can simply be recovered by filtration and reused several times. This reaction system with HFIP/water as solvent and the ion-exchange resin Lewatit K2420 as catalyst shows excellent performance for HMF synthesis.

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In this study, we show that the fluorous alcohol hexafluoroisopropanol (HFIP) can act as a superior solvent for the in situ extraction of 5‐hydroxymethylfurfural (HMF) from an aqueous reaction system. HFIP has a far higher partition coefficient for HMF than common extraction solvents such as methyl isobutyl ketone (MIBK) and n‐butanol and has a significantly lower boiling point of 58–59 °C. In a system containing fructose, HCl as the catalyst, and HFIP as the extraction solvent, a high HMF yield of 89 % is achieved, which is far better than the HMF yields in common MIBK/butanol extraction systems. HFIP extracts HMF from the reaction phase without extraction of the fructose educt. In addition, the aqueous catalyst phase can be reused.

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.