Bayer Aktiengesellschaft

Andreas Groschl

Ingo Janisch

Nikolaus Muller

Josef Bremen

Adolf Winkler

Wolfgang Scheinert

Wolf Mehl

A process as been found for the removal of water from reaction mixtures of acids or acid anhydrides or of aqueous alkali metal hydroxide solutions with alcohols using vapor permeation/pervaporation at the boiling point of the reaction mixture, which includes initially introducing the lowest-boiling educt in less than the stoichiometric amount, based on the other particular educt, together with this other educt, heating the reaction mixture to the boiling point and freeing the vapor mixture, which is formed from the boiling reaction mixture and includes chiefly water and the lowest-boiling component, from water on a membrane, recycling the vapor mixture which has been freed from water into the reaction mixture and topping up the reaction mixture with the lowest-boiling educt in the course of the reaction.

Removal of water from reaction mixtures

A process has been found for the preparation of dialkyl maleates from maleic acid, maleic anhydride or monoalkyl maleates with C.sub.1 -C.sub.8 -alcohols, in particular ethanol, in the presence or absence of an acidic catalyst and at boiling heat, which is characterized in that the escaping water/alcohol/vapour mixture, together with its condensed phase if appropriate, is conducted as feed along a hydrophilic membrane at which it is purged of water and the dehydrated alcohol is returned to the reaction mixture.

Process for the preparation of dialkyl maleates

A first alkanol having from 1 to 3 carbon atoms can be separated off from other organic compounds of higher carbon number from the group comprising other alcohols, polyalcohols, ethers, oxo compounds, esters of carboxylic acids and of carbonic acid, haloaliphatics, amines, amides, hydrocarbons, carboxylic acids and nitriles, which in each case have at least 1 carbon atom more than the first alkanol, where in the case of halogenoaliphatics, halogen substituents are counted as further carbon atoms, by permeation on membranes, if a water content from 1 to 30% by weight, preferably from 5 to 15% by weight, based on the amount of mixture and water, is maintained.

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Leverkusen, Germany

Andreas Groschl