Basf Aktiengesellschaft

Bernhard Holzknecht

Hugo Fuchs

Klaus Wintermantel

Herwig Hoffmann

Gerald Neubauer

Josef Ritz

Friedrich Wirth

Johannes E Schmidt

Eckhard Hetzel

Peter Thoma

Dieter Stockburger

Emile De Decker

Wilhelm Schultz

Caprolactam is recovered from caprolactam distillation low boilers or high boilers or mixtures thereof by the following steps:

Recovery of caprolactam from caprolactam distillation low boilers or

Frozen crystal layers are purified by a process in which these crystal layers, after they have been frozen out from a melt or solution on a cooling surface, are brought into contact with a purifying liquid and thus purified over their entire thickness, after which the said layers are separated from the purifying liquid and then melted, wherein the temperature of the crystal layers and of the purifying liquid is close to the melting point or solubility temperature, mass transfer at the phase boundary is intensified by forced convection, and this purification is carried out in the course of from 1 to 60 minutes on layers having a thickness of from 0.2 to 10 mm.

Purification of frozen crystal layers

A process for the preparation of phthalic anhydride (PA) of catalytic oxidation of naphthalene or o-xylene with air, a preheated mixture of air and naphthalene or o-xylene being passed into a reactor charged with the catalyst, and the reaction gas leaving the reactor being passed through a separator in which the PA is separated out as a solid, in which process the air fed to the reactor is preheated, before or after the admixture of naphthalene or of o-xylene, by using it to cool the reaction gas in the PA separator.

Preparation of phthalic anhydride

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Ellerstadt, Germany

Bernhard Holzknecht