Patent ID: 8629293

Claim:
A process for the preparation of iron(III) chelates of N,N′-di(2-hydroxybenzyl)ethylenediamine-N,N′-diacetic acid and its derivatives of the formula (I) wherein both R substituents have the same meaning and represent H, C 1 -C 4 alkyl, CH 2 OH, SO 3 M or COOM, and M is a sodium, potassium or ammonium cation, characterised in that a starting aqueous solution of the chelating agent of the formula (II) wherein R and M are as defined above is prepared, the aqueous solution is contacted with metallic iron by the circulation of said aqueous solution through the bed of pieces of metallic iron in a flow reactor while simultaneously blowing air or oxygen through the aqueous solution of the chelating agent in the flow reactor, and a hydrogen peroxide solution is optionally added to the aqueous solution of the chelating agent received from the flow reactor and before returning it to the flow reactor, whereby said circulating aqueous solution is continuously enriched with the iron chelate of the formula (I).