METHOD FOR THE PREPARATION OF ISOMERS OF HIGH PURITY BENZOYLDICARBONIC ACIDS

摘要

The method can be used in the chemical industry for themanufacture of high purity benzoyldicarbonic acids isomers withoutcarrying out any stage of catalytic reduction purification. Itincludes: (a) stage of oxidation when an isomer of xylene isoxidized with molecular oxygen or gas containing molecular oxygen,in the presence of catalytic system consisting of cobalt,magnesium, bromine and at least one element selected among nickel,chromium, zirconium and cerium, in a lower aliphatic carbonicacid; and (b) stage of extraction/postoxidation. In the secondstage the oxidation product crystallizes in order thatsedimentation of raw isomer of benzoyldicarbonic acid should beseparated, the sediment is again suspended by the addition ofaliphatic carbonic acid as solvent, followed by heating for theextraction of the impurities contained in the solvent, and thesuspension produced is oxidized by means of the catalytic systemat temperature by 2 to 80°C lower than that of the heating. Eachof the two stages is performed once or twice.19 claims