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AssigneeBayer Aktiengesellschaft
InventorsNorbert Schenk, Jorg Krekel, Paul Losacker, Wolfgang Swodenk
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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.
In a process for the preparation of anthraquinone by reacting a liquid feed containing naphthalene, phthalic anhydride and tetrahydroanthraquinone with oxygen at elevated temperature while simultaneously separating off at least part of the naphthalene, in a distillation system which consists of a column having a rectifying section and a boiler, the improvement wherein the boiler of the distillation system has several chambers and is operated as a cascade and the liquid feed containing naphthalene, phthalic anhydride and tetrahydroanthraquinone is fed only into the lowest chamber of the boiler.
Dependencies are inferred from the claim text.