Bayer Aktiengesellschaft

Lanxess Deutschland Gmbh

Michael Pies

Helmut Fiege

Josef Kasbauer

Lothar Puppe

Hermann Uhr

Wolfgang Zarges

Georg Martin

Kai Rohlk

Helmut Lahr

Uwe Boeger

Volker Hassmann

Guido Issling

Markus Koschorreck

Klaus Schönauer

Gebhard Merz

Uwe Böger

The invention relates to a process to produce phthalimides by heating diammonium phthalate in the presence of aromatic solvents and to a process to produce phthalimides by heating diammonium phthalate in the presence of aromatic solvents for their recycled use during the ion exchanger production process. The diammonium phthalate is prepared by making use of the phthalic add salts solution resulted from the on exchanger production process.

Process for the production of phthalimides

The present process serves for the hydrodehalogenation of halogenated meta-cresols of the formula (I) in which the Rto Rradicals are each as defined in the description, and is characterized in that halogenated meta-cresols of the formula (I) are contacted with a catalyst which has been prepared by applying one or more salts of palladium and/or platinum and optionally copper salts to an aluminum oxide or titanium oxide support material, together with hydrogen, at temperatures between 100 and 250&#xb0; C.

Method for the hydrodehalogenation of halogenated meta-cresols

Halogenated benzenes are hydrodehalogenated in a particularly advantageous manner and at low temperatures by contacting them at temperatures of between 100.degree. and 250.degree. C. together with hydrogen with a catalyst prepared by application of one or more salts of palladium and/or platinum and, if desired, of copper to an alumina or titanium dioxide support.

Process for the hydrodehalogenation of halogenated benzenes

Dialkyl dicarbonates are obtained particularly advantageously from halogenoformic esters by reaction with alkalis in the presence of water-immiscible organic solvents and in the presence of a catalyst, if the catalyst used is benzylalkyldimethylammonium halides. The catalyst is then particularly easy to separate off and to recycle from the reaction mixture.

Process for the preparation of dialkyl dicarbonates

In the preparation of m-chloroaromatics by isomerizing corresponding o- and/or p-chloroaromatics in the liquid phase over zeolites, the activity of the zeolites remains at a high level for a particularly long time if the process is carried out in the presence of from 1 to 30 mol % of hydrogen, based on the chloroaromatics used.

Process for preparing m-chloroaromatics

In a particularly advantageous process for isolating m-dichlorobenzene from mixtures of dichlorobenzene isomers by crystallization as eutectic crystals using a processing aid, the processing aid used is a compound of the formula (I) ##STR1## in which R.sup.1 to R.sup.6 are, independently of one another, hydrogen, halogen, C.sub.1 -C.sub.4 -alkyl, hydroxyl, NH.sub.2 or R--CO-- having R=C.sub.1 -C.sub.4 -alkyl, with 1-bromo-4-chlorobenzene and 1,4-dibromobenzene being excepted.

Process for isolating M-dichlorobenzene from mixtures of dichlorobenzene

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Duisburg, Germany

Michael Pies