Patent ID: 8350089

Claim:
A process for the production of 2-methyl-1,4-naphthoquinone and its bisulfite adducts, comprising the following steps: a) oxidizing 2-methyl-naphthalene (2-MNA) to achieve an organic phase containing 2-methyl-naphthoquinone (2-MNQ) and 6-methyl-naphthoquinone (6-MNQ); b) subjecting said organic phase to treatment with an aqueous solution of a bisulfite salt to extract preferentially the 6-MNQ isomer from the organic phase; c) separating said organic phase from the aqueous phase; d) subjecting the organic phase of process step c) to a second bisulfidation step with an aqueous solution of a bisulfite salt, resulting in an organic phase containing 2-MNA and trace amounts of 2-MNQ and an aqueous phase containing 2-MSB and trace amounts of 6-MSB; e) optionally removing interfering bisulfite ions from the aqueous phase of process step c); f) raising the pH of the aqueous phase from step c) or e) to higher than 8.5 in the presence of a solvent resulting in an organic phase containing 2-MNQ; g) combining the organic phase from step f) with the organic phase being treated in the process step d); h) recycling the organic phase from step d) back to step a) to be used as solvent for the oxidation reaction of 2-MNA.