Hoechst Aktiengesellschaft

Knut Riedel

Werner H Muller

Siegbert Rittner

Bernhard Wojtech

Dieter Freudenberger

Udo Dettmeier

Hans Krekeler

Guenter Roscher

Walter Steppich

Herbert Gortz

The invention relates to a process for preparing dimethyl vinylphosphonate by thermal dissociation of dimethyl 2-acetoxyethanephosphonate in the gas phase, which comprises vaporizing dimethyl 2-acetoxyethanephosphonate and dissociating it without catalysis at a temperature of from 400.degree. to 700.degree. C. into dimethyl vinylphosphonate and acetic acid.

Process for preparing dimethyl vinylphosphonate from dimethyl

The invention relates to a process for the preparation of pure cis- or trans-crotonic acid from a mixture of the two isomers by melt crystallization. To prepare trans-crotonic acid, an isomer mixture I containing at least 40% by weight of trans-crotonic acid is used as the starting material. On the other hand, if cis-crotonic acid is to be prepared, an isomer mixture II containing at least 80% by weight of cis-crotonic acid is used as the starting material. The particular isomer mixture is melted and then left to cool, trans-crotonic acid being allowed to crystrallize out of mixture I to a residual content of at least 35% by weight, and cis-crotonic acid being allowed to crystallize out of mixture II to a residual content of at least 75% by weight.

Process for the preparation of pure crotonic acids

The invention relates to a process for the extraction of carboxylic acids from aqueous solutions with a carboxylic acid content below 8% by weight. A mixture of an aliphatic amine with a total carbon number of at least 10 and a phenol or naphthol is used as extracting agent. The molar ratio of phenol:amine or alkylated phenol:amine or naphthol:amine is in the range from 0.1:1 to around 1.1:1.

Process for the extraction of carboxylic acids from dilute aqueous

The present invention is related to a process for the manufacture of resorcinols by catalytic dehydrogenation of cyclohexane diones-(1,3) in the liquid phase by means of a dehydrogenating mixture consisting of a solvent and of a catalyst containing a noble metal from Group VIII of the Periodic Table.

Growing community of inventors

Hofheim am Taunus, Germany

Knut Riedel