Hoechst Aktiengesellschaft

Iwo Schaffelhofer

Siegfried Rebsdat

Sigmund Mayer

Josef Riedl

Josef Alfranseder

Walter Frohlich

Reinhard Krumbock

Peter Schwarzmaier

Wenzel Kuhn

Gerhard Link

Erich Mittermaier

Georg Prantl

The hot, vinyl chloride-containing gases leaving the cracking furnace heat liquid 1,2-dichloroethane in a first container to the boiling point or to its immediate vicinity, and the 1,2-dichloroethane is transferred into a second container in which it is partly evaporated under a lower pressure than in the first container. The evaporated 1,2-dichloroethane is fed into the cracking furnace, and the nonevaporated 1,2-dichloroethane is fed back into the first container. By supplying fresh, optionally prewarmed 1,2-dichloroethane into the second container, the amount of product evaporated therein is replaced, the prewarming advantageously being regulated through the level of the liquid 1,2-dichloroethane in the second container. The prewarming of the 1,2-dichloroethane can take place in the convection zone of the cracking furnace or by means of a temperature-control medium, for example steam, which has been heated in the convection zone of the cracking furnace. Compared to processes according to the prior art, higher cracking conversions and a more favorable energy utilization are achieved.

Process for the production of vinyl chloride through thermal cracking of

A process for the purification of 1,2-dichloroethane is described, in which the crude product, containing not more than 3% by weight of high-boilers, is distilled in a first column at 125.degree. to 180.degree. C. in such a way that the bottom product contains not more than 7% by weight of high-boilers. The purified, vaporous 1,2-dichloroethane discharged at the head of this column is used to heat product streams containing 1,2-dichloroethane. The bottom product from the first column is distilled in a second column, advantageously at a pressure of 5 to 40 kPa, together with a feed composed of vaporous 1,2-dichloroethane obtained from the reaction of ethylene with chlorine. The process makes it possible to purify 1,2-dichloroethane with a saving in energy.

Process for the purification of 1,2-dichloroethane

Ethylene oxide and water are reacted in a reactor and the reaction product is subjected to distillation in a plurality of distillation columns, in the first columns water and components having a boiling point below that of monoethylene glycol and higher ethylene glycols, if any, being distilled off. To obtain extremely pure monoethylene glycol alkali metal compounds are added at a point between the reactor and the monoethylene glycol distillation column in an amount to adjust the pH of the product entering the latter column to a value of from 7 to 10. The monoethylene glycol obtained in this manner is especially pure and has very low UV absorption values. It is, therefore, especially suitable for the manufacture of polyester fibers.

Process for the manufacture of extremely pure monoethylene glycol

Supported silver catalysts, which should have as high an activity as possible, are employed for the manufacture of ethylene oxide by oxidizing ethylene by means of oxygen or air. A process is described for improving the activity of supported silver catalysts which have already been used, in which the used catalyst is first washed with an inert liquid containing ammonia and/or aliphatic amines and 1 to 1,000 parts, per 1 million parts of catalyst, of cesium, rubidium or a mixture thereof is then deposited on the washed catalyst. The deposition is generally effected with the aid of an impregnating solution containing the cesium and/or rubidium compounds in a suitable quantity. This process makes it possible to improve considerably the activity of supported silver catalysts which have already been in use for the oxidation of ethylene by means of oxygen or air.

Process for improving the activity of supported silver catalysts

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Burghausen, Germany

Iwo Schaffelhofer