Bayer Aktiengesellschaft

Josef Heinen

Karl-Werner Thiem

Adolf Hamers

The present invention relates to an improved continuous process for the preparation of mononitro-aromatic compounds which comprises (1) nitrating a reactive aromatic compound in the absence of sulphuric acid until mono-nitration is essentially complete, said nitration being carried out in 40 to 68% strength by weight nitric acid, (2) separating mechanically the nitration reaction mixture into an inorganic phase and an organic phase, (3) washing of the organic phase with water and dilute alkali solution and subsequent separation of the unconverted starting material end of the adhering water by means of rectification (4) feeding the inorganic phase and, if necessary, the wash water of the first water wash of the organic phase, to a rectification column in which (a) water is withdrawn over the top (b) optionally a fraction which has a lower nitric acid content than the feed is withdrawn from a sidestream takeoff in the rectifying section of the column and (c) a fraction which has a higher nitric acid content than the feed is taken off from the sump, (5) recycling said material withdrawn from the sump of the column to the nitration reaction vessel with the addition of fresh concentrated nitric acid and (6) withdrawing from the system an amount of the top product from the column which corresponds to the water of reaction and that which enters with the nitric acid that is added.

Growing community of inventors

Leverkusen, Germany

Josef Heinen