Bayer Aktiengesellschaft

Deutsche Gold- Und Silber-scheideanstalt Vormals Roessler

Jorg Krekel

Rolf Wirthwein

Norbert Schenk

Karl-Hermann Reissinger

Willi Hofen

Gerd Schreyer

Wulf Schwerdtel

Wolfgang Swodenk

Horst Brunn

Eckhard Bayer

Joachim Priemer

Paul Losacker

Bernd-Michael Holle

Berndt-Ullrich Kohler

The present invention relates to a process for the production of iron oxide brown, red and black pigments and to the use thereof.

Process for the thermal treatment of iron oxides in a circulating

The present invention relates to a process for the production of titanium dioxide pigments and the use thereof.

Process for the thermal treatment of titanium dioxide in a circulating

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

Process for isolating propylene glycol diacarboxylates in the preparation of propylene oxide by reaction of propylene with a solution of percarboxylic acid in an organic solvent, the boiling point of which is lower than that of the carboxylic acid which corresponds to the percarboxylic acid used as the epoxidizing agent, and higher than that of propylene oxide, separation, by distillation, of the reaction mixture which essentially contains propylene oxide, the carboxylic acid corresponding to the percarboxylic acid used as the epoxidizing agent and one or more of the by-products propyleneglycol, propylene glycol monocarboxylate and propylene glycol dicarboxylate as well as propylene and the organic solvent, into a fraction containing propylene oxide and propylene and a fraction containing the carboxylic acid, the by-products mentioned and the organic solvent and further separation of the fractions into the individual components by distillation. The fraction containing the carboxylic acid, one or more of the by-products propylene glycol, propylene glycol monocarboxylate and propylene glycol dicarboxylate, and the organic solvent is distilled in a column at pressures of 1.5 to 6 bars and with an average residence time of 10 to 90 minutes in the sump. The organic solvent is removed as the top product and the carboxylic acid and the corresponding propylene glycol dicarboxylate is obtained as the sump product. From the sump product the propylene glycol dicarboxylate is isolated in a manner which is in itself known.

Process for isolating propylene glycol diesters in the preparation of

Process for separating a solution, which essentially contains propylene oxide, propylene, a carboxylic acid containing 1 to 4 carbon atoms and benzene, by distillation. The solution is fed to a first distillation stage in which propylene, propylene oxide and an amount of the benzene contained in the solution such that the top product from this first distillation contains 20 to 70% by weight of benzene are distilled off over the top at a pressure of 1.0 to 2.5 bars, and in which the carboxylic acid and the remaining benzene are obtained as the sump product. The top product from the first distillation is fed to a second distillation column in which propylene and possibly present small fractions of components which boil lower than propylene oxide are distilled off over the top and a sump product which essentially consists of propylene oxide and benzene is obtained and part of this is returned as reflux to the first distillation column.

Process for separating solutions containing propylene oxide

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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Essen, Germany

Jorg Krekel