Process for the production of metal salts of trifluoromethane sulphonic acid and their use as esterification catalysts

1. Process for the production of metal salts of trifluoromethane sulphonic acid comprising at least one trifluoromethane sulphonic acid group comprising reacting trifluoromethane sulphonic acid (CF 3 SO 3 H) with a metal alcoholate, at a temperature of −40° C. to +100° C., the metal being selected from the group consisting of Li, Na, K, Ba, Mg, Ca, Al, In, Sn, Sc, Y, La, Ti, Zr, Fe, Cu, Ag, Zn and mixtures thereof and the alcoholate group(s) of the metal alcoholate comprising independent of each other 1 to 28 carbon atoms as well as optionally hydroxy groups (—OH), ether bonds (C—O—C) and/or more than one alcoholate bond (M—O—).

2. Process according to claim 1 characterised in that the metal salt of the trifluoromethane sulphonic acid is

(CF 3 SO 3 ) m M (OR) n

wherein

the sum of (m+n) corresponds to the valency of the metal cation and m is at least 1,

R is a hydrocarbon moiety with 1 to 6 carbon atoms and, optionally ether bonds (C—O—C) or is hydrogen and R can be different for each n and

M is Al.

3. A method for producing hydroxycarboxylic acid esters comprising reacting one or more hydroxycarboxylic acids with one or more alcohols in the presence of a metal salt of a trifluoromethane sulphonic acid exhibiting at least one trifluoromethane sulphonic acid group wherein the metal salts of the trifluoromethane sulphonic acid comprise Mg, Ca, Al, Sn,Ti, Zr, Fe, Cu or Zn as metal.

4. The method of claim 3 characterised in that the metal of the metal salts of the trifluoromethane sulphonic acid comprises MgrZn Al, Ti or Zr as metal.

5. The method of any one of claims 3 or 4 characterised in that the alcohols exhibit 1 to 28 carbon atoms and, optionally furthermore 1 to 8 ether groups and/or further 1 to 5 hydroxy groups.

6. The method of any one of claims 3 or 4 characterised in that the esterification is carried out at temperatures of 60 to 250° C. and, independently thereof, at pressures of 0.2 to 10 bar.

7. The method of any one of claims 3 or 4 characterised in that the esterification is carried out in the presence of an entrainer and water is removed by azeotropic distillation, the entrainer being preferably an aliphatic hydrocarbon, an aromatic hydrocarbon, a dialkyl ether or an alcohol, preferably the alcohol used for the esterification itself and/or its/their mixture.

8. The method of any one of claims 3 or 4 characterised in that the molar ratio of the alcohol used to the carbonyl groups of the hydroxycarboxylic acid used is from 1:0.5 to 4.0, preferably 1.0 to 2.0.

9. The method of any one of claims 3 or 4 characterised in that the catalyst is used in a quantity of 0.05 to 1.0 % by weight, based on the hydroxycarboxylic acid used.

10. The method of any one of claims 3 or 4 characterised in that the esterification is terminated by treating the crude product with metal alcoholates, alkali hydroxides or alkaline earth hydroxides and subsequently worked up by distillation.

11. A method of producing a hydroxycarboxylic acid ester comprising transesterification of a hydroxycarboxylic acid ester with at least one hydroxy group and at least one carboxylic acid ester group (—COO—), optionally having free carboxylic acid groups,

with an alcohol and/or another ester, in the presence of a catalyst comprising a metal salt of trifluoromethane sulphonic acid having at least one trifluoromethane sulphonic acid group

whereby at least one alcohol is removed from the reaction mixture and; wherein the metal of the salts of the trifluoromethane sulphonic acid comprise Mg, Ca, Al, Sn, Ti, Zr, Fe, Cu or Zn-as-metal.

12. The method of claim 11 characterised in that the metal salts of trifluoromethane sulphonic acid comprises Al.

13. The method of any one of claims 11 or 12 characterised in that the alcohols used comprise 1 to 28 carbon atoms and, optionally 1 to 8 ether groups and/or further 1 to 5 hydroxy groups.

14. The method of any one of claims 11 or 12 characterised in that the transesterification is carried out at temperatures of 60 to 250° C. and, independently thereof, at pressures of 0.05 to 10 bar.

15. The method of any one of claims 11 or 12 characterised in that the molar ratio of the alcohol employed relative to the ester groups of the hydroxycarboxylic acid ester to be converted is from 0.5 to 2.0.

16. The method of any one of claims 11 or 12 characterised in that the catalyst is used in a quantity of 0.02 to 1.0 % by weight, based on the hydroxycarboxylic acid ester to be converted.

17. The method of any one of claims 3 or 11 characterised in that the work-up of the hydroxycarboxylic acid ester takes place by distillation at temperatures in the range of 60° C. to 250° C. and pressures of 1 hPa to 1013 hPa or by stripping with a water vapour steam at temperatures of 120° C. to 200° C. and pressures of 1 hPa to 1013 hPa, in particular directly from the crude product or after removal of the catalyst and filtration of the crude product.

18. The method of claim 17 characterised in that the distillative work-up takes place after prior removal of the catalyst with activated carbon, aluminium hydroxide or aluminosilicate.

19. The method of any one of claims 3 or 11 wherein the metal salts of trifluoromethane sulphonic acid are used in the presence of water.

20. The method of claim 19 wherein the metal salts of trifluoromethane sulphonic acid are used in an aqueous environment comprising water, in particular as solvent or diluent, in addition to any water being formed in the course of the reaction.

21. The method of claim 1 wherein said metal is Al.

22. The process of claim 1 wherein said metal is Zr.

23. The process of claim 1 wherein said metal is Ti.

24. Process according to any one of claims 1 , 2 , 21 , 22 or 23 characterised in that the reaction is conducted in the presence of a solvent selected from the group consisting of alcohols, aliphatic hydrocarbon, aromatic hydrocarbon, ethers having 2 to 32 carbon atoms, ketones having 2 to 32 carbon atoms, water and mixtures thereof.

25. Process according to any one of claims 1 , 2 , 21 , 22 or 23 characterised in that the trifluoromethane sulphonic acid, optionally distributed with a solvent, is added to the metal alcoholate, optionally diluted with a solvent.

26. Process according to any one of claims 1 , 2 , 21 , 22 or 23 characterised in that the metal alcoholate, optionally diluted with a solvent, is added to the trifluoromethane sulphonic acid, optionally diluted with a solvent.