Preparation of anthraquinone from tetrahydroanthraquinone

US4284576A · kind A · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

• Norbert Schenk
• Jorg Krekel
• Paul Losacker · Leichlingen, DE
• Wolfgang Swodenk

Key dates

• Filing date: Sep 22, 1978
• Grant date: Aug 18, 1981
• Expiry date: Sep 22, 1998

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C07C46/02
• WIPO field: Chemical engineering
• WIPO sector: Chemistry

Abstract

In the preparation of anthraquinone by reacting a mixture containing naphthalene, phthalic anhydride and tetrahydroanthraquinone with oxygen at elevated temperature while simultaneously separating off at least part of the naphthalene, the improvement which comprises supplying the naphthalene, phthalic anhydride and tetrahydroanthraquinone to a distillation system which consists of a column having a rectifying section, a stripping section and a boiler, at least one of the stripping section and the boiler being designed so that rapid through-passage of the feed mixture is prevented. Downcomers in the stripping section maintain liquid levels on the trays of about 5 to 500 mm and the boiler may have several successive chambers to provide the desired residence time in the system. A liquid mixture of naphthalene, phthalic anhydride and anthraquinone is removed from the boiler while a gas mixture including naphthalene is taken off from the rectifying section, being cooled to condense naphthalene for use in oxidation to naphthoquinone and phthalic anhydride.