Process for preparing 5-hydroxymethylfurfural via 5-acyloxymethylfurfural as an intermediate

1. A process for preparing a 5-acyloxymethylfurfural, comprising:

(a) reacting at ambient pressure a saccharide comprising a monosaccharide unit having 6 carbon atoms with

(i) an acid which is not an acidic ion exchanger in the presence of a metal cation selected from the group consisting of alkali metal ions, alkaline earth metal ions, aluminum ions and mixtures thereof,

thereby obtaining a mixture;

(b) adding an anhydride and/or chloride of a carboxylic acid R—(—COOH) x wherein R and x are each as defined in formula (II) to the mixture from (a) and allowing them to react to form a 5-acyloxymethylfurfural of formula (II); and

(c) recovering the 5-acyloxymethylfurfural of the formula (II)

wherein

x =1 or 2,

R is an alkyl, alkenyl, aryl or heteroaryl radical when x =1,

R is an alkylene, alkenylene, arylene or heteroarylene radical when x =2.

2. The process according to claim 1 , wherein R is methyl.

3. The process according to claim 1 , wherein acetic anhydride is added in (b).

4. The process according to claim 1 , wherein the acid in (a)(i) is at least one selected from the group consisting of oxalic acid, acetic acid, and hydrochloric acid.

5. The process according to claim 1 , wherein the metal cation in (a)(i) is Mg 2+ .

6. The process according to claim 1 , wherein the saccharide reacted in (a) is a sugar or a saccharide mixture which comprises sugars.

7. The process according to claim 1 , wherein the saccharide used in (a) is selected from the group consisting of D-fructose in free form, a saccharide which contains D-fructose in bound form, and a saccharide mixture which contains D-fructose in free form, a saccharide which contains D-fructose in bound form and mixtures thereof.

8. The process according to claim 1 , wherein reaction (b) is conducted in the presence of a basic catalyst.

9. The process according to claim 8 , wherein the basic catalyst is 4-(N,N-dimethylamino)pyridine.

10. A process for preparing 5-hydroxymethylfurfural of formula (I)

preparing a 5-acyloxymethylfurfural according to claim 1 ; and

(d) dissolving the 5-acyloxymethylfurfural in an alcohol, thereby obtaining a solution;

(e) adding a base selected from the group consisting of (i) alkali metal carbonates and hydrogencarbonates, alkaline earth metal carbonates and hydroxides, basic salts of alkaline earth metals, aluminum carbonate, aluminum hydroxide, aluminum oxide hydroxide, and basic salts of aluminum, mixtures of the above and (ii) basic ion exchangers in the OH form, to the solution from step (d) and allowing them to react in order to form 5-hydroxymethylfurfural, and (f) recovering the 5-hydroxymethylfurfural.

11. The process according to claim 10 , wherein the alcohol for dissolving the 5-hydroxymethylfurfural in step (d) is methanol.

12. The process according to claim 10 , wherein the base in step (e) is potassium carbonate.

13. The process according to claim 10 , wherein the recovery of the 5-hydroxymethylfurfural in step (f) comprises a short-path distillation of the 5-hydroxymethylfurfural.

14. The process according to claim 10 , wherein the recovery of the 5-hydroxymethylfwfural in step (f) comprises crystallization of the 5-hydroxymethylfurfural from a suitable solvent.