Hoechst Aktiengesellschaft

Heinrich Lenzmann

Franz Landauer

Rudolf Lademann

Klaus Schmiedel

Dieter Arnold

Gunter Jacobsen

Heinz Wendt

Jorg Bartels

Manfred Stoltenberg

Wolfram Schwiersch

In this process for the preparation of ketene by the thermal, catalytic cracking of acetic acid under reduced pressure, the hot cracked gases are cooled to approx. 0.degree. to -10.degree. C. and, in the course thereof, water, unreacted acetic acid and acetic anhydride are condensed. The quantity of acetic acid employed for the thermal cracking reaction should be 0.5 to 2.5 t.times.hours.sup.-1 .times.m.sup.-3, relative to the volume V of a shell-and-tube heat exchanger through which the cracked gas is passed. The pressure drop in the tubular heat exchanger should be 50 to 150 mbars and the surface/volume ratio should be 60 to 120 m.sup.-1.

Process for the preparation of ketene

Continuous preparation of mono- or di-(trichloromethyl)-benzenes or of mono- or di-(trichloromethyl)-benzenes substituted in the benzene ring by halogen atoms from the corresponding mono- or dimethylbenzenes and chlorine in several steps with radiation by means of rays of high energy, is effected by reacting mono- or dimethylbenzene with chlorine in 4 to 14 steps, at a temperature in the range of from 20.degree. to 130.degree. C, whereby chlorine is introduced into the second step and the following steps, the resulting waste gas is introduced into step 1 and chlorine contained in the waste gas is reacted in reactor 1 with fresh mono- and dimethylbenzene. A preferred embodiment for carrying out the process is reaction in a reactor arrangement in cascade form, wherein the number of steps corresponds to the number of reactors and wherein as reactors circulation reactors are used.

Process for the continuous preparation of mono- or

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Heinrich Lenzmann