Process for the production of trioxane

1. A process for producing a cyclic acetal comprising:

contacting a formaldehyde source with a liquid medium comprising a sulfur-containing organic compound and a catalyst, the catalyst comprising trifluoromethanesulfonic acid, perchloric acid, methanesulfonic acid, toluenesulfonic acid, sulfuric acid, or a solid acid ion-exchange materiel; and

at least partially converting the formaldehyde source into a cyclic acetal, wherein the cyclic acetal comprises trioxane.

2. A process according to claim 1 , wherein the sulfur-containing organic compound has a boiling point of 140° C. or higher, determined at 1 bar.

3. A process according to claim 1 wherein higher than 10% of the formaldehyde source is converted into one or more cyclic acetals during the reaction.

4. A process according to claim 1 wherein the liquid medium comprises at least 20 wt.-%, of the sulfur-containing organic compound.

5. A process according to claim 1 , wherein the sulfur-containing organic compound is selected from the group consisting of organic sulfoxides, organic sulfones, organic sulfonate esters, and mixtures thereof.

6. A process according to claim 1 wherein the sulfur-containing organic compound is selected from the group consisting of cyclic or alicyclic organic sulfoxides, alicyclic or cyclic sulfones, and mixtures thereof.

7. A process according to claim 1 wherein the sulfur-containing organic compound is represented by formula (I):

wherein

n is an integer ranging from 1 to 6, and

wherein the ring carbon atoms may optionally be substituted by one or more substituents, selected from C 1 -C 8 -alkyl which may be branched or unbranched or by the formula (II):

wherein R 1 and R 2 are independently selected from C 1 -C 8 -alkyl which may be branched or unbranched or by the formula (III):

wherein

n is an integer ranging from 1 to 6, and

wherein the ring carbon atoms may optionally be substituted by one or more substituents, selected from C 1 -C 8 -alkyl which may be branched or unbranched; or by the formula (IV):

wherein R 3 and R 4 are independently selected from C 1 -C 8 -alkyl which may be branched or unbranched.

8. A process according to claim 1 wherein the sulfur-containing organic compound is sulfolane.

9. A process according to claim 1 wherein the reaction produces trioxane and tetroxane.

10. A process according to claim 1 wherein during the process a reaction mixture includes the formaldehyde source, the sulfur-containing organic compound, and the catalyst, and wherein the reaction mixture comprises the sulfur-containing organic compound in an amount ranging from about 25 wt.-% to about 90 wt.-%.

11. A process according to claim 1 , wherein the catalyst comprises trifluoromethanesulfonic acid, perchloric acid, methanesulfonic acid, toluenesulfonic acid, or sulfuric acid.

12. A process according to claim 1 , wherein the formaldehyde source has a water content of less than about 20 wt.-%.

13. A process according to claim 1 , wherein the formaldehyde source comprises an aqueous formaldehyde solution.

14. A process according to claim 13 , wherein the aqueous formaldehyde solution contains formaldehyde in an amount from about 60 wt. % to about 90 wt. %.

15. A process according to claim 1 , further comprising the step of separating the cyclic acetal from the liquid medium by distillation.

16. A process according to claim 1 , further comprising the step of manufacturing polyoxymethylene from the cyclic acetal.

17. A process according to claim 1 , wherein the formaldehyde source comprises gaseous formaldehyde.

18. A process for producing cyclic acetal comprising

i) preparing a liquid reaction mixture comprising

a) a formaldehyde source,

b) an aprotic compound comprising a sulfur-containing organic compound and

c) a catalyst, the catalyst comprising trifluoromethanesulfonic acid, perchloric acid, methanesulfonic acid, toluenesulfonic acid, sulfuric acid, or a solid acid ion-exchangepaterial; and

ii) converting the formaldehyde source into cyclic acetals;

wherein the cyclic acetals comprise trioxane.

19. A process according to claim 1 , wherein the catalyst comprises a solid acid ion-exchange material.

20. A process according to claim 10 , wherein the reaction mixture includes the formaldehyde source in an amount from about 20 wt. % to about 70 wt. %, contains the aprotic compound in an amount from about 25 wt. % to about 75 wt. %, and contains water in an amount less than about 20 wt. %.

21. A process according to claim 13 , wherein during the process a reaction mixture comprises the formaldehyde source, the sulfur containing organic compound, and the catalyst and wherein the reaction mixture contains water in an amount less than about 20 wt. %.

22. A process for producing a cyclic acetal comprising:

contacting a formaldehyde source with a liquid medium comprising a sulfur-containing organic compound in the presence of a catalyst, the sulfur-containing organic compound comprising an organic sulfoxide, a sulfone, or mixtures thereof; and

at least partially converting the formaldehyde source into a cyclic acetal, wherein the cyclic acetal comprises trioxane.

23. A process as defined in claim 22 , wherein the sulfur-containing organic compound comprises sulfolane.