Bayer Aktiengesellschaft

Norbert Schenk

Wulf Schwerdtel

Paul Losacker

Jorg Krekel

Manfred Martin

Wolfgang Swodenk

Axel Vogel

Kurt Halcour

Wolfgang Biedermann

Joachim Priemer

Hubert Lauer

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

Producton of cyclopentene by splitting of dicyclopentadiene to produce cyclopentadiene and hydrogenating the cyclopentadiene to produce the cyclopentene in crude form, and distilling the crude cyclopentene to separate low boilers and high boilers therefrom and provide the cyclopentene product. The high boilers are recycled to the dicyclopentadiene splitting stage and serve to reduce resin formation in that stage. The process is particularly effective where the dicyclopentadiene has a low content of the so-called 'codimers' which, if present in sufficient amount, would reduce resin formation.

Process for the production of cyclopentene from dicyclopentadiene

2-Methylpropane-1,3-diol is prepared by reacting 2-methylenepropane-1,3-diol diacetate with a monohydric, lower aliphatic alcohol in the presence of a base. Thereafter the resulting 2-methylenepropane-1,3 diol is catalytically hydrogenated to form 2-methylpropane-1,3-diol.

Process for preparing 2-methylpropane-1,3-diol

To isolate naphthoquinone and phthalic anhydride from the gas obtained in the gas phase oxidation of naphthalene, the gas product at 250.degree. to 500.degree. C is first quenched with a counter-current liquid stream of naphthalene, naphthoquinone and phthalic anhydride. The liquid is raised to at most 200.degree. C, cooled and partly recycled, the coolant temperature being within 70.degree. C of the temperature of the liquid being cooled. The portion of the quench liquid which is not recycled is the product, viz. a solution of naphthoquinone and phthalic anhydride in naphthalene. The quenched gas is scrubbed with liquid naphthalene and most of the liquid product is cooled and re-cycled, the balance of the liquid product being passed to the quencher. The gas which leaves the scrubber is substantially free from naphthoquinone and phthalic anhydride. The initial gas may have been pre-cooled by evaporative cooling. The surfaces of the quencher, cooler and pipes of the quenching system are preferably of stainless steel or are smoothed either mechanically or by coating with plastic, enamel, ceramic or metal.

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Leverkusen, Germany

Norbert Schenk