Method for the preparation of (S)-2-acetyloxypropionic acid and derivatives thereof

A method for preparing an (S)-2-acetyloxypropionic acid in a preparation assembly comprising a distillation section (A) and a reaction section (B), the distillation section (A) comprising a top portion and a bottom portion connected to said reaction section (B), the method comprising the steps of:

• a. continuously feeding an aqueous solution of a lactic acid to the top portion of the distillation section (A);
• b. feeding an acetic anhydride into the reaction section (B);
• c. reacting the lactic acid with the acetic anhydride in the reaction section (B), thus forming the (S)-2-acetyloxypropionic acid and an acetic acid;
• d. evaporating a vapor mixture of the acetic acid and of the unreacted acetic anhydride from the reaction section (B);
• e. feeding the vapor mixture of step d to the distillation section (A) for stripping water from the aqueous solution of lactic acid to form a substantially anhydrous lactic acid which counterflows through said distillation section (A) towards the reaction section (B), so that a mixture of the substantially anhydrous lactic acid and the acetic acid enters the reaction section (B) from the bottom portion of the distillation section (A);
• f. recovering the (S)-2-acetyloxypropionic acid from the reaction section (B);
• and
• g. collecting a diluted aqueous solution of the acetic acid at the top portion of the distillation section (A).