Methods for the production of L-carnitine

1. A method for the production of L-carnitine, comprising the steps of

(a) providing a solution comprising at least 5% (w/w) carnitine in a first solvent, wherein the carnitine is a mixture of a mole fraction of D-carnitine and a mole fraction of L-carnitine, wherein the L-carnitine has an enantiomeric excess with respect to the D-carnitine, and wherein the enantiomeric excess is defined as the absolute difference between the mole fraction of L-carnitine and the mole fraction of D-carnitine in percent,

(b) optionally seeding the solution with L-carnitine crystals,

(c) adding a second solvent, in which the L-carnitine is not soluble or has a low solubility, and

(d) isolating crystals comprising L-carnitine,

wherein the first solvent is selected from the group consisting of ethanol, methanol, water, acetonitrile and mixtures thereof, and wherein the second solvent is selected from acetone, 2-butanone, methylacetate, ethylacetate, butylacetate, tetrahydrofuran, toluene and mixtures thereof,

wherein in steps (a) to (d) the enantiomeric excess of the L-carnitine is enhanced by more than 2%.

2. The method of claim 1 , wherein in step (a) the concentration of total carnitine in the first solvent is 5 to 75% (w/w).

3. The method of claim 1 , wherein in step (a) the carnitine comprises more than 80% (e.e.) L-carnitine and in step (d) the crystals comprise more than 95% (e.e.) L-carnitine.

4. The method of claim 1 , wherein step (a) comprises heating the solution to a temperature of above 40° C.

5. The method of claim 1 , wherein the solubility of L-carnitine in the second solvent is below 2% (w/w) at 25° C.

6. The method of claim 1 , wherein in the seeding step (b) the solution has a temperature of 25 to 50° C.

7. The method of claim 1 , wherein in step (c) the ratio of the first solvent to the second solvent is between 1:1 and 1:10 (w/w).

8. The method of claim 1 , wherein after the seeding step (b), before or during step (c), or after adding the second solvent in step (c), the temperature of the solution is adjusted to between 10° C. and 30° C.

9. The method of claim 1 , wherein in step (c) the second solvent is added to the solution during a time span of 20 min to 24 h.

10. The method of claim 1 , wherein after the addition of the second solvent in step (c) the composition is incubated for 10 min to 2 days at a temperature below 20° C.

11. The method of claim 1 , wherein in step (d) the crystals comprise more than 99% (e.e.) L-carnitine.

12. The method of claim 1 , wherein in step (d) the crystals are isolated by filtration or sedimentation.

13. The method of claim 1 , wherein the first solvent is ethanol and the second solvent is acetone.