Basf Aktiengesellschaft

Dietrich Luetzow

Klaus Volkamer

Ulrich Wagner

Werner Hefner

Luise Spiske

Christof Herion

Norbert Neth

Klaus Kuessner

Water is removed from a mixture containing water, CO.sub.2 and one or more amines by pervaporation by bringing the mixture into contact with one side of a membrane and removing the water-containing permeate as a vapor from the other side of the membrane.

Removal of water from a mixture of water, CO.sub.2 and amines

A process for the manufacture of symmetrical dialkylureas by reacting monoalkylamines with CO.sub.2 at an elevated temperature and under superatmospheric pressure, in which the unconverted starting materials, water and the by-products formed in the reaction zone, as well as alkylamine alkylcarbamate, after thermal decomposition into monoalkylamine, CO.sub.2 and water, are separated from the dialkylurea formed, and thereafter a part of the unconverted starting materials plus by-products, with or without water, may or may not be recycled to the reaction zone, before isolating an aqueous solution, containing monoalkylamines, CO.sub.2 and other by-products, which solution is treated with alkali metal hydroxide solution in a column, the monoalkylamine, after separation from carbon dioxide and water, being recycled to the reaction zone. The dialkylureas obtained contain not more than 1% of monoalkylurea and 1% of trialkylurea, and may be used as starting materials for various syntheses.

Manufacture of symmetrical dialkylureas

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Limburgerhof, Germany

Dietrich Luetzow