Bayer Aktiengesellschaft

Wolfgang Auge

Karl-Werner Thiem

Rutger Neeff

Bernd Thelen

Bernd Schroeder

Rudolf Braden

Hans-Walter Brandt

Paul Losacker

Heinz Scheiter

Process for working up aqueous nitric acid which is of a concentration above the azeotropic concentration and contains organic compounds in solution for suspension wherein said nitric acid of a concentration about the azeotropic concentration is distilled off in one or more rectification steps until the azeotropic nitric acid is obtained. In the process, certain specified ratios of nitric acid and water to organic constituents must be maintained.

Process for working up nitric acid

A process has been developed for isolating aromatic dinitro compounds by using nitric acid in specified concentrations in different portions of a rectifying column and separating off the mixture of aromatic dinitro compounds from the sump of the rectifying column.

Process for isolating aromatic dinitro compounds

Process for the preparation of 1-alkylamino-anthraquinones which comprises reacting 1-nitroanthraquinone with a monoalkylamine in the presence of an ether, a hydrocarbon or a mixture of an ether and a hydrocarbon. The 1-alkylamino-anthraquinones which are obtained can be employed directly as dyestuffs or used, without further purification, for the production of dyestuffs. Process of the invention results in the procurement of 1-alkylamine-anthraquinones of high purity and in high yield and avoids the formation of undesired by-products.

Process for the preparation of 1-alkylamino-anthraquinones

The purification of high-melting organic products, such an anthraquinone and substituted anthraquinones, which is substantially free from lower-boiling impurities, by melting the product to be purified by heating, while mechanically conveying the same along a path with a screw conveyer, as for example, in a melting screw; degassing the melt at a reduced pressure in a column, as for example, at a pressure of 50 to 400 mm Hg; passing the degassed melt through a thin film evaporator at a reduced pressure of, for example, 5 to 250 mm Hg to evaporate the high-melting organic product and discharging the remaining high-boiling impurities and such impurities which are not capable of being distilled from the evaporator through a conically tapering sump, while mechanically scraping residue from the sump wall, preferably with the use of a rotating helical screw in the sump; the discharge from the sump being effected into and through an enclosed path at a rate sufficient to prevent liquid accumulating in the sump, while maintaining the central portion of the enclosed discharge path at a lower temperature than its end portion to form a crystal sludge in the central portion, which acts as a pressure seal; and solidifying and recovering the product discharging from the enclosed path. The enclosed path is preferably established through a screw-type pump which feeds into a crystallizing screw where the solidification takes place, the crystallizing screw being preferably maintained above the screw-type pump and is maintained filled with an amount of sump product which approximately corresponds to the amount of product in the sump take-off screw. The vapors produced in the thin film evaporator are passed via a heated rectifying column into a condenser, and a portion of the condensate is passed to the column as a reflux and another portion taken off and solidified in a crystallizing screw.

Process for the purification of high-melting organic products

.alpha.-Amino-.beta.'-nitroanthraquinone is prepared by reacting .alpha.,.beta.'-dinitroanthraquinone with ammonia in an ether, an aliphatic, a cycloaliphatic or an optionally alkyl-substituted aromatic hydrocarbon, water or a mixture of the foregoing.

Process for preparing .alpha.-amino-.beta.'-nitroanthraquinones

Aromatic mononitro compounds are prepared by nitrating aromatic compounds with nitric acid having a concentration between 70 and 100% by weight, working up of the nitration mixture in a rectification column and separation of the aromatic mononitro compound. In the nitration mixture and in the rectification column, depending upon the concentration of the nitric acid present, the ratio by weight of nitric acid plus water is controlled and not lowered below defined figures. Optionally water or nitric acid is introduced into the rectification column.

Process for the production of aromatic mononitro compounds

Pure 1-nitroanthraquinone substantially free of dinitroanthraquinone is prepared by:

Process for preparing pure 1-nitroanthraquinone

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

A mixture of dinitroanthraquinones of which at least 35% is 1,5-dinitroanthraquinone is dissolved at elevated temperature in a halogenated aromatic hydrocarbon, a carboxylic acid nitrile or a cyclic sulphone and is thereafter cooled selectively to precipitate substantially pure 1,5-dinitroanthraquinone. Preferred solvents are 1-chloronaphthalene, sulpholane and adipic acid dinitrile. The temperature of dissolution ranges from about 120.degree. C up to the boiling point and cooling is by about 10.degree. to 200.degree. C to a temperature not below about 0.degree. C.

Preparation of pure 1,5-dinitroanthraquinone

A mixture of dinitroanthraquinones of which at least 70% is 1,8-dinitroanthraquinone is dissolved at elevated temperature in a halogenated aromatic hydrocarbon, a carboxylic acid nitrile or a cyclic sulphone and is thereafter cooled selectively to precipitate substantially pure 1,8-dinitroanthraquinone. Preferred solvents are 1-chloronaphthalene, sulpholane and adipic acid dinitrile. The particular temperature of dissolution and cooling will depend upon the particular solvent.

Preparation of pure 1,8-dinitroanthraquinone

1-AMINO- AND/OR 1,5- AND/OR 1,8-DIAMINO AND/OR 1-AMINO-6-NITRO AND/OR 1-AMINO-7-NITRO-ANTHRAQUINONE ARE PREPARED BY REACTING 1-NITRO- AND/OR 1,5- AND/OR 1,8- AND/OR 1,6- AND/OR 1,7-DINITRO-ANTHRAQUINONE WITH AMMONIA IN THE PRESENCE OF A NITRILE.

Process for preparing amino-anthraquinones

Process for the preparation of 1-nitroanthraquinone by nitration of anthraquinone in the presence of highly concentrated nitric acid, characterised in that nitration is carried out at temperatures of 20.degree. to 80.degree.C, the reaction is terminated by lowering the nitric acid molar fraction in the reaction mixture to .ltoreq.0.85 by distilling off concentrated nitric acid and 1-nitroanthraquinone is precipitated by subsequently adjusting the nitric acid molar fraction to .ltoreq.0.7 to 0.4 and is separated off in a manner which is in itself known.

Process for the preparation of 1-nitroanthraquinone

Process for the preparation of 1,5- and/or 1,8-diaminoanthraquinone by reaction of 1,5- and/or 1,8-dinitroanthraquinone with ammonia in organic solvents, characterised in that the reaction is carried out in ethers, aliphatic or cycloaliphatic hydrocarbons or optionally alkyl-substituted aromatic hydrocarbons or in mixtures of these compounds.

Process for the preparation of 1,5- and 1,8-diamino-anthraquinone

Process for the preparation of 1-aminoanthraquinone by reaction of 1-nitroanthraquinone with ammonia in organic solvents, characterised in that the reaction is carried out in ethers, aliphatic or cycloaliphatic hydrocarbons or optionally alkyl-substituted aromatic hydrocarbons.

Process for the preparation of 1-aminoanthraquinone

Process for the manufacture of pure 1-nitroanthraquinone, characterised in that a nitroanthraquinone mixture obtained by nitration of anthraquinone in the presence of inorganic acids and, optionally, lowering the molar fraction of the acids in the reaction mixture after isolation of the reaction products which have precipitated and, optionally, further measures, is subjected to a rectification.

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Odenthal, Germany

Wolfgang Auge