Bayer Aktiengesellschaft

Heinz Landscheidt

Alexander Klausener

Erich Wolters

Paul Wagner

Eberhard Zirngiebl

Heinz U Blank

Heinz-Ulrich Blank

Lothar Puppe

Udo Birkenstock

Zoltan Kricsfalussy

Joerg-Dietrich Jentsch

Reinhard Langer

Helmut Kraus

Kaspar Hallenberger

Wolfgang Kiel

Jorg-Dietrich Jentsch

Werner Struver

Edwin Ritzer

Ingo Janisch

Matthias Stenger

Witold Broda

Konrad Hable

Bernd Pennemann

Walter Kipshagen

Eberhard Zirngbiebl

Bernd Lenders

Substituted cyclohexanones of the formula ##STR1## where R.sup.1 to R.sup.5 are as defined in the description, can be obtained by catalytic hydrogenation of phenols of the formula ##STR2## where R.sup.1 to R.sup.5 are as defined in the description. The reaction is carried out at from 20.degree. to 250.degree. C., from 1 to 200 bar and in an ether as solvent. If desired, an alkaline alkali metal, alkaline earth metal or ammonium compound is used as additive.

Process for preparing substituted cyclohexanones

Alkyl carbazates of the formula R.sup.1 --O--CO--NH--NH.sub.2 (I) are prepared in an advantageous manner by reacting an alkyl carbazate of the formula R.sup.2 --O--CO--NH--NH.sub.2 (II) with alcohols of the formula R.sup.1 --OH (III) in the presence of a catalyst, where the symbols used in the formulae are as defined in the description.

Process for the preparation of carbazates

It has been found that cyclopentene and hydrogen bromide can be continuously reacted in a simple manner to give cyclopentyl bromide in good yields and good selectivities if the reaction is carried out in the presence of a heterogeneous catalyst. The reaction can be carried out continuously and unreacted cyclopentene and possibly other constituents can be recirculated to the reaction.

Process for preparing cyclopentyl bromide

Substituted chloroaromatics are obtained in a simple manner in virtually isomer-free form when substituted phenols of the formula (II) ##STR1## where R.sup.1 to R.sup.5 are each, independently of one another, hydrogen, C.sub.1 -C.sub.10 -alkyl, unsubstituted or substituted C.sub.6 -C.sub.10 -aryl or halogen, with at least one of these radicals being different from hydrogen, are reacted with dichlorotriphenylphosphorus.

Process for preparing substituted chloroaromatics

C.sub.1 -C.sub.4 -Alkyl nitrites can be prepared by reaction of C.sub.1 -C.sub.4 -alkanols with nitrogen oxides with the participation of oxygen in a reactor designed as a scrubber column, nitrogen oxides having a proportion of more than 50% of NO of the total amount of gram atoms of N of the nitrogen oxides, oxygen and optionally inert gas being fed into the lower part of the reactor. 5 to 60% of the total amount of C.sub.1 -C.sub.4 -alkanol used is likewise fed into the lower part of the reactor in vaporous or atomized form, while the remaining C.sub.1 -C.sub.4 -alkanol is delivered to the column head.

Process for the preparation of C.sub.1 -C.sub.4 -alkyl nitrites

Substituted 1,2,3,4-tetrahydrocarbazoles of the formula ##STR1## having the meaning for R.sup.1 to R.sup.8 indicated in the description, can be prepared by catalytically hydrogenating a substituted phenol of the formula ##STR2## reacting the hydrogenation solution with a phenylhydrazine of the formula ##STR3## to give the hydrazone and cyclizing the hydrazone under acidic conditions.

Process for the preparation of substituted 1,2,3,4-tetrahydrocarbazoles

Alkyl nitrite-containing exhaust gases are purified in continuous form by treating them with equimolar to excess amidosulphuric acid in the form of an aqueous solution in the manner of a counter-current scrubbing at a temperature of 0.degree.-100.degree. C.

Purification of alkyl nitrite-containing exhaust gases

The reaction of nitrogen dioxide with hydrogen chloride to give nitrosyl chloride and nitric acid can be advantageously carried out in cocurrent in a reactor in such a way that the reactants are introduced at the bottom and the nitrosyl chloride is taken off at the top and the nitric acid is taken off at the bottom of the reactor.

Process for the continuous preparation of nitrosyl chloride

p-Amino-phenols are advantageously prepared by catalytic hydrogenation of the aromatic nitro compounds on which they are based in a reaction medium of aqueous sulphuric acid in the sense of a Bamberger rearrangement at elevated temperature by a procedure in which the reaction medium additionally contains a water-miscible organic solvent.

Process for the preparation of p-amino-phenols

Dimethyl carbonate (DMC) is prepared by continuous gas reaction of carbon monoxide and methyl nitrite a heterogeneous catalyst comprising a platinum at 50.degree. to 170.degree. C. under 1 to 5 bar.

Process for the preparation of dimethyl carbonate

Dimethyl carbonate is obtained with a high selectivity and great constancy over time by reacting carbon monoxide with methyl nitrite in a continuous gas phase reaction in the presence of a heterogeneous catalyst prepared by the application to a suitable support of one or more palladium compounds of the formula

Heterosubstituted acetals of the formula ##STR1## can be obtained by reacting vinyl compounds of the formula

Process for the preparation of heterosubstituted acetals

Dialkyl carbonates can be prepared by reacting carbon monoxide with alkyl nitrites in a continuous gas phase reaction in the presence of a heterogeneous platinum metal catalyst, the activity of this catalyst being maintained by the addition of small amounts of halogen. The dialkyl carbonates are thus formed with almost quantitative selectivity and no deactivation of the catalyst occurs.

Process for the preparation of dialkyl carbonates

Methanol can be substantially removed from dimethyl carbonate (DMC)/methanol mixtures by absorption on ion exchange resins. The enriched DMC is obtained as filtrate. The absorption is carried out at from -50.degree. C. to +100.degree. C. and 0.1-10 bar.

Process for separating off methanol from a mixture of dimethyl carbonate

Dialkyl carbonates can be prepared by reacting carbon monoxide with alkyl nitrites in a continuous gas phase reaction in the presence of a catalyst using a fixed bed reactor with a short catalyst bed in the direction of flow. The dialkyl carbonates are formed with almost quantitative selectivity; thermal decomposition of the alkyl nitrite, with the resulting formation of decomposition products, is not observed.

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Duisburg, Germany

Heinz Landscheidt