Separating off 5-hydroxymethylfurfural (HMF) from reaction solutions by steam distillation
Method for producing solutions which comprise 5-hydroxymethylfurfural (HMF) and have a reduced content of starting materials of the HMF synthesis or a reduced content of by-products of the HMF synthesis (hereinbelow called product solution), which comprises treating solutions which comprise HMF starting materials or by-products of the HMF synthesis and an organic solvent having at least two ether groups (for short polyether) (hereinbelow called starting solution) in an evaporator with steam.
1. A method for producing solutions which comprise 5-hydroxymethylfurfural (HMF) and have a reduced content of starting materials of the HMF synthesis or a reduced content of by-products of the HMF synthesis (hereinafter called product solution), which comprises treating solutions which comprise
HMF
starting materials or by-products of the HMF synthesis and
an organic solvent having at least two ether groups (for short polyether)
(hereinafter called starting solution) in an evaporator with steam.
2. The method of claim 1 , wherein the starting materials of the HMF synthesis are hexoses or oligomers or polymers composed of hexoses (hereinafter called saccharides).
3. The method of claim 1 , wherein the by-products of the HMF synthesis are HMF oligomers.
4. The method of claim 1 , wherein the polyether has a boiling point greater than 250° C., at standard pressure.
5. The method of claim 1 , wherein the polyether is a poly-C2- to C4-alkylene glycol, the terminal hydroxyl groups of which are optionally etherified with C1-C4 alkyl groups.
6. The method of claim 1 , wherein the starting solution comprises the polyether in amounts of from 5% to 90% by weight.
7. The method of claim 1 , wherein the starting solution is an aqueous solution.
8. The method of claim 1 , wherein the treatment with steam takes place at 100° C. to 200° C.
9. The method of claim 1 , wherein the treatment with steam takes place at a pressure of from 1 mbar to 300 mbar.
10. The method of claim 1 , wherein the method is carried out continuously, such that the starting solution and steam are fed to the evaporator continuously and the product solution is drawn off continuously.
11. The method of claim 1 , wherein the evaporator is a thin-film evaporator.
12. The method of claim 1 , wherein the steam is fed countercurrent to the starting solution.
13. The method of claim 1 , wherein the percentage content of all saccharides in the product solution is in total less than 20% of the content of all saccharides in the starting solution.
14. A process for producing 2,5-furandicarboxylic acid or 2,5-bis(hydroxymethyl)furan which comprises producing a product solution by the process of claim 1 and synthesizing 2,5-furandicarboxylic acid or 2,5-bis(hydroxymethyl)furan from the product solution.
15. The process according to claim 1 , wherein the product solution comprises at least 70% of the HMF of the starting solution.
16. The process according to claim 1 , wherein the ratio of volume of steam to volume of starting solution is from 0.5:1 to 2:1.
17. The process according to claim 1 , further comprising discharging the steam and the volatile constituents of the starting solution via a separator at the top of the evaporator and condensing the volatile constituents to form the product solution.