TECHNICAL DESCRIPTION

5-HMF(5-hydroxymethylfurfural) is a value-added molecule obtained from renewable feedstock since its main derivative, FDCA (Furandicarboxylic acid), presents structural similitude with terephtalic acids, which makes this molecule of high interest to produce bio-polymers.
Indeed, FDCA could replace terephtalic acids, the actual monomers used in the synthesis of polyamides and  polyesters. The present invention describes a carbon efficient and environmentally friendly process to produce 5-HMF  by dehydration of  fructose in concentrated solutions of carboxylic acids such as acetic acid or formic acid and in the presence of a solid acid. The process of the invention solves the problems of the poor
selectivity of the reaction due to the formation furanic polymers (humins) especially when strong mineral acids such as HCl are employed. The present invention solves also the drawbacks of the alternative recent methods which describe the use of toxic organic solvents to extract 5-HMF and/or complexe reaction mixtures ( ionic liquid or concentrated solutions of transition metallic salts) to get high selectivities in 5-HMF. The process of the
invention can provide a total conversion of fructose, and selectivity in 5-HMF higher than 75%. The invention describes also the production of aqueous solutions of carboxylic acid containing more than 10 wt% of  5-HMF, depending only of the hexose solubility in the aqueous solution of carboxylic acid. Aqueous solution of

5-HMF free of carboxylic acid can be easily obtained when a volatile organic acid is used such as acetic acid.

This invention reports a durable and an efficient process to produce 5-HMF since 1) it avoids the use of a fossil and toxic solvent to extract 5-HMF  2) it circumvent the use of complexes media (ionic liquid or concentrated solutions of salts of transition metals 3) the process is selective in 5-HMF and leads to limited carbon losses in humins formation due to the stabilisation of 5-HMF in concentrated aqueous solutions of carboxylic acids by contrast to solutions of mineral acids of equivalent pH 4) the presence of solid acids such as modified carbons improve the HMF selectivity.

INDUSTRIAL APPLICATIONS

Applications include: the conversion of biomass containing C6 sugars and of concentrated aqueous solutions of C6 sugars to produce aqueous solutions of HMF. The aqueous solutions of HMF, eventually free of carboxylic acid, can be used as in further transformations in FDCA as example.