Bayer Aktiengesellschaft

Gunter Schummer

Walter Merz

Karlheinz Feltgen

Christian Pieper

Christoph Jupe

Surinder S Sandhu

Jurgen Baumert

A process is described for the isolation of pyrocatechol and hydroquinone from mixtures containing the same, and phenol and higher boiling accompanying substances. The mixture can be one obtained by reacting phenol with a peroxidic hydroxylating agent and removing some of the phenol and the substances which have a lower boiling point than phenol. The mixture is subjected to a first rectification in which phenol and substances which have a boiling point between phenol and pyrocatechol are obtained overhead to leave behind a bottom product containing pyrocatechol and hydroquinone. The bottom product is subjected to a second rectification in which the pyrocatechol is obtained overhead to leave behind a bottom product containing hydroquinone and higher boiling accompanying substances. This bottom product is fed to a concentrating unit in which hydroquinone is evaporated overhead to leave behind high boiling accompanying substances as residue.

Process for the isolation of pyrocatechol and hydroquinone

The recovery of dimethylacylamides from solutions which are formed during the production of fibres is particularly economical if the solution is concentrated in a separating column to produce a sump product having a DMA content of 30 to 90% at pressures of more than 300 Torr, using the evaporation heat of the head product for heating the column, with the aid of a compressor and then separating the sump product which is concentrated in DMA by distillation.

Process for the recovery of dimethylacylamides

A process for the treatment of waste water obtained in the condensation of thiocarbohydrazide and an aqueous solution of an .alpha.-keto carboxylic acid such as, e.g., 3,3-dimethyl-2-oxo-butyric acid, which comprises mixing said waste water with a water-immiscible ketone, preferably selected from the group consisting of methyl isobutyl ketone, cyclohexanone and pinacolone, said ketone being employed in an amount sufficient to form two phases, separating said two phases, and discharging as waste the aqueous phase. Advantageously the pH of the waste water is no higher than about 6 and its temperature is 20.degree. to 50.degree. C. The organic phase comprises the ketone containing dissolved therein an adduct of the ketone with thiocarbohydrazide and/or similar amino materials originally present in waste water. The excess of the ketone may be recovered from the organic phase by distillation, or the organic phase may be treated with alkali to effect hydrolysis of such adducts, the ketone separated and recycled and the amino materials recovered.

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Cologne, Germany

Gunter Schummer