Abstract
5-Hydroxymethylfurfural (5-HMF) is an important bio-sourced intermediate, formed from carbohydrates such as glucose or fructose. The treatment at 150–250 °C of glucose or fructose in pure water and batch conditions, with catalytic amounts of most of the usual acid-basic solid catalysts, gave limited yields in 5-HMF, due mainly to the fast formation of soluble oligomers. Niobic acid, which possesses both Lewis and Brønsted acid sites, gave the highest 5-HMF yield, 28%, when high catalyst/glucose ratio is used. By contrast, we disclose in this work that the reaction of fructose in concentrated aqueous solutions of carboxylic acids, formic, acetic or lactic acids, used as reactive solvent media, leads to the selective dehydration of fructose in 5-HMF with yields up to 64% after 2 hours at 150 °C. This shows the potential of such solvent systems for the clean and easy production of 5-HMF from carbohydrates. The influence of adding solid catalysts to the carboxylic acid media was also reported, starting from glucose.
Highlights
Among the organic compounds that can be obtained from biomass, 5-hydroxymethylfurfural (5-HMF) is probably one of the most important platform molecules
We choose in a first set of experiments to study the reactivity of glucose in water in the absence, in the presence, of various solid catalysts chosen as regards their acid-basic features
We first reported in this paper our results on the hydrothermal conversion of glucose and fructose, in batch conditions, varying the reaction conditions, temperature and acidity, in the presence of a large panel of usual solid catalysts
Summary
Among the organic compounds that can be obtained from biomass, 5-hydroxymethylfurfural (5-HMF) is probably one of the most important platform molecules. The authors concluded that the glucose conversion into 5-HMF required a preliminary glucose-fructose isomerization promoted by basic sites In line with this approach, in 2010, Ohara et al [34] reported the use of a combination of a basic catalyst, HDT, and an acid one, Amberlyst 15, to perform the direct conversion of glucose in 5HMF, but using DMF (dimethyl formamide) as solvent. Niobium or vanadium phosphates have been applied to dehydrate fructose and inulin, giving high yields up to 50% at 80–100 °C [36,37,38] This is certainly the highest 5-HMF yield reported to date in pure water without the assistance of an extractive solvent. On the other side we introduce our first results in the use of aqueous concentrated liquid carboxylic acids as an alternative reactive solvent system
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