Dehydration of fructose to 5-hydroxymethylfurfural in sub- and supercritical acetone

The dehydration of D-fructose (1) to 5-hydroxymethylfurfural (HMF, 2) is a well known reaction (acid-induced elimination of three moles of water), performed by many investigators during the last three decades. 1,2 HMF and its oxidation product 2,5-furandicarboxylic acid are so called 'sleeping giants' in the field of intermediate chemicals from regrowing resources. HMF is a key substance between carbohydrate chemistry and mineral oil-based industrial chemistry and it has the potential of a commodity like terephthalic acid. 3 Surprisingly, no technical process has been constructed until now. The reason is that high selectivities (in this context selectivity means yield divided by conversion in mol%) can only be obtained in high boiling polar solvents like dimethyl sulfoxide, dimethylformamide, acetonitrile, poly(glycol ether) etc. so that separation procedures are very expensive. 4 Unfortunately, in aqueous systems (supercritical water), only low selectivities can be achieved. 1 Considering the specifications for a modern sustainable and economical process, the use of green solvents like acetone, methanol or acetic acid in their sub- or supercritical states should be accounted for. The results for this reaction performed in sub- and supercritical acetone are presented here.