Preparation of solutions of imido-alkancarboxylic acids suitable for peroxidation processes

Purification process of imido-alkancarboxylic acids from contaminants represented by carboxylic acid, lactam or aminoacids and water comprising:

• A) preparation of the imido-alkancarboxylic acid by reaction of:
• a1) an anhydride of formula ##STR5## or the corresponding acids, with b1) an aminoacid of formula ##STR6## with c1) water;
• or
• a1) with
• b2) a lactam of general formula ##STR7## with c1) water;
• at temperatures comprised betweeen 100.degree. C. and 250.degree. C., under pressure of an inert gas from 1 to 30 bar, for reaction times from 2 to 20 hours;
• wherein A indicates a group of formula ##STR8## n is an integer 0, 1 or 2, R.sup.1 is hydrogen, chlorine, bromine, alkyl C.sub.1 -C.sub.20, alkenyl
• C.sub.2 -C.sub.20, aryl or alkylaryl,
• R.sup.2 is hydrogen, chlorine, bromine or a group of formula--SO.sub.3 M, --CO.sub.2 M, --CO.sub.3 M, --OSO.sub.3 M,
• M indicates hydrogen, an alkaline metal or ammonium ion or the equivalent of an alkaline-earth metal ion and X indicates alkylene C.sub.1 -C.sub.19 or arylene;
• Y=X wherein the ratio by moles between a1/(b1 or b2)/c1 is comprised between 1/1.0-1.2/0.5-3;
• B) discharge of precursor obtained in phase A) in a solvent immiscible with water;
• C) separation of aqueous phases from an organic phase;
• D) recovery of the organic phase for the successive peroxidation reaction.