Bayer Aktiengesellschaft

Deutsche Gold- Und Silber-scheideanstalt Vormals Roessler

Gunter Wolf

Willi Hofen

Wulf Schwerdtel

Gunter Prescher

Gerd Siekmann

Hubert Lauer

An improved process for working-up crude liquid vinyl acetate which contains vinyl acetate, acetic acid, water, and ethyl acetate, possibly together with small amounts of other impurities, by distillation is disclosed, wherein a mixture essentially containing vinyl acetate and water is obtained as the top product and essentially acetic acid is obtained as the bottom product, and a sidestream, in which ethyl acetate is concentrated is removed. According to the process the top product is condensed and, after phase separation, a portion of the vinyl acetate phase is recycled as reflux into the distillation. The improved process involves the introduction of water above the point of introduction of the crude vinyl acetate. Preferably, the water is introduced in an amount which is not greater than the amount required to achieve a maximum water content in the vapors leaving the distillation at the top.

Process for working up crude liquid vinyl acetate

A process for the continuous preparation of organic solutions of percarboxylic acids by reaction of an aqueous solution of hydrogen peroxide with the corresponding carboxylic acid in the presence of an acid, water-soluble catalyst which boils above 160.degree. C., extraction of the percarboxylic acid from the resulting reaction mixture using an organic solvent which is immiscible with water, reconcentration of the raffinate, which essentially contains hydrogen peroxide and the acid catalyst, by distilling off water in a distillation column and recycle of the raffinate, concentrated in this way, into the reaction with the carboxylic acid. The raffinate is divided into two partial streams in a ratio of 1 to 25:1. The raffinate is fed to a distillation column which is operated under reduced pressure and which has at least two take-off weirs as tray inserts, the first take-off weir being at least two theoretical plates above the sump phase, the second take-off weir being arranged at least two theoretical plates above the first take-off weir and the section of column between the second take-off weir and the top of the column having at least two theoretical plates. The larger partial stream of the raffinate is passed into the column below the first take-off weir and the smaller partial stream is passed into the column below the second take-off weir. Water is removed at the top of the distillation column. A first side stream, which essentially contains the hydrogen peroxide from the small partial stream of the raffinate from the extraction, is withdrawn from the second take-off weir and is a 2 to 40% strength by weight aqueous solution of hydrogen peroxide, which is optionally fed, together with the larger partial stream of the raffinate from the extraction, into the column below the first take-off weir. A second side stream is withdrawn from the first take-off weir and is an aqueous solution of the acid catalyst which optionally can be further worked up and re-used. The re-concentrated aqueous solution of hydrogen peroxide and acid catalyst, withdrawn as a sump product from the distillation, is recycled into the reaction with carboxylic acid. A third side stream can be taken from a third take-off weir which is arranged not more than 2 theoretical plates below the first take-off weir.

Process for the preparation of organic solutions of percarboxylic acids

Growing community of inventors

Leverkusen, Germany

Gunter Wolf