Bayer Aktiengesellschaft

Paul Losacker

Norbert Schenk

Wulf Schwerdtel

Wolfgang Swodenk

Manfred Martin

Rutger Neeff

Rudolf Braden

Karl-Werner Thiem

Wolfgang Auge

Kurt Halcour

Jorg Krekel

Kurt Halcourt

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.

Preparation of anthraquinone from tetrahydroanthraquinone

A process has been found for the preparation of anthraquinone by catalytic oxidation of naphthalene in the gas phase to provide a reaction product, obtained by quenching, cooling or quenching and cooling, containing naphthaquinone and phthalic anhydride, treating said reaction product directly with butadiene to provide tetrahydroanthraquinone, oxidation by means of molecular oxygen to the tetrahydroanthraquinone contained in this reaction product, to give anthraquinone, and separation of naphthalene, phthalic anhydride, anthraquinone and by-products by distillation, the gases produced in the quenching and/or cooling of the gases from the naphthalene oxidation and the gases from the oxidation of the tetrahydroanthraquinone to give anthraquinone being completely or partially recycled to the oxidation of naphthalene, in which a compound with an alkaline reaction is introduced between the reactor in which naphthalene is oxidized and the reactor in which the reaction with butadiene takes place, and/or into the gas streams which are recycled to the oxidation of naphthalene. The process of the invention reduces considerably the formation of higher-boiling products formed in the continuous preparation of anthraquinone from naphthalene and increases the selectivity of the conversion of naphthalene to anthraquinone. In addition, the process of the invention provides greater freedom in separation of the reaction products since the production of troublesome high-boilers is minimized; and the process results in a reduced formation of carbon dioxide in the oxidation of naphthalene.

Process for the preparation of anthraquinone

A process for removing 1,4-naphthoquinone from phthalic anhydride has now been found, which is characterized in that phthalic anhydride containing 1,4-naphthoquinone, or mixtures containing phthalic anhydride and also containing 1,4-naphthoquinone, are subjected to a heat treatment at temperatures from 200 .degree. to 300.degree. C. in the presence of 1,4,4a,9a-tetrahydroanthraquinone.

Process for removing 1,4-naphthoquinone from phthalic anhydride

1-Amino anthraquinone is prepared by reacting 1-nitro-anthraquinone with ammonia in water and/or an organic solvent and thereafter treating the 1-amino-anthraquinone imine formed with water thereby converting said imine into 1-amino anthraquinone.

Process for preparing 1-amino anthraquinone

In the preparation of isoprene by reacting isobutene with formaldehyde to produce 4,4-dimethyl-m-dioxane in a first stage, and decomposing the dioxane to isoprene and formaldehyde in a second stage, formaldehyde in the effluent streams of either or both of said stages is recovered. The formaldehyde-containing liquids are distilled to separate high boilers; the overhead, which is formaldehyde-rich, is extracted with isobutene feed to the process, whereby the isobutene extracts low boilers from the formaldehyde-containing liquid; and the formaldehyde-containing liquid, having at some point after said distillation been treated with an alkaline material, is subjected to rectification to produce as head product, the recovered formaldehyde.

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Leichlingen, Germany

Paul Losacker