DE937590C - Process for the production of carbazole - Google Patents

Description

Process for the preparation of carhazole It is known that one. small Amounts of carbazole received when one. Diphenylamine or aniline at very high temperatures: heated. It is also known that: ß mann diphenylamine or dicyclorhexylamine can convert to carbazole by catalytic dehydrogenation, if, as a catalyst Active carbon containing 30% platinum is used. Both procedures, however, have none can acquire technical importance, partly because of the low yields, partly because because of the cost of the catalyst used.

It has now been found that: ß one gets in good yield, carbazole, if one, diphenylamine or its hydrogenation products, such as Dicyolor hexylaminoder N-phenylcyclahexylamine, in the presence of catalysts, which, if necessary, next to Carriers, essentially oxides of the metals of the second, third and / or or sixth Group and or or sulphides of the metals of the sixth group of the periodic table. included, heated to around, 25o, to 700 °.

The catalytic dehydrogenation can both in the gas phase as well be made in the liquid phase. One can. in the presence of: gaseous or vaporous, Diluents, such as nitrogen, hydrogen or water vapor, air flow. The most suitable reaction temperature depends on the particular catalyst used now and then, can easily determined by preliminary tests. As, catalysts are suitable e.g. B. zinc oxide, tungsten and Modyb @dänsulfide- alone or in a mixture with each other or with carriers, such as aluminum oxide or silica gel.

The process can be either discontinuous or continuous can be carried out at ordinary, elevated or reduced pressure.

The portion of the starting material not converted in the reaction is in the usual way, for. B. by distillation, separated from the resulting carbazole and, can be subjected to dehydration again.

That. Carbezol is a multifaceted: Intermediate product, especially for dyes and plastics. Example z -By a heated to 55o °. iron pipe from: 30 man. Inside diameter and length that with i 1 of a catalyst compressed into pills. filled with tungsten disulfide powder, the voir-heated vapors of 10 g diphenylamine and 15 g water, heated to 35o °, are sent every hour. In addition to un, converted diphenylamine, which is fed back into the reaction, and the water produced during the reaction, the reaction product is worked up by distillation every hour to obtain carb, azole, corresponding to an almost quantitative yield, based on the converted diphenylamine.

A mixture of compressed into pills is used as a catalyst: Tungsten disulfide powder with aluminum oxide powder gives a similar result.

EXAMPLE 2 Through the tube described in Example 1, 10 g of evaporated dicyclohexylamine per hour are passed over a catalyst consisting of pure tungsten disulfide at 55o °. In addition to hydrogen, unreacted dicyelohexylamine and ammonia, cyclohexane and benzotl formed by side reactions, 2 g of Carb, azo, l are obtained per hour. The Ca @ rb, az.o @ l partially crystallizes out. the crude reaction product from; the remainder is obtained by working up the liquid portion by distillation. EXAMPLE 3 338 parts by weight of diphenylamine, 60 parts by weight of powdered Wodfram disulphide and 30 parts by weight of anhydrous aluminum chloride are heated to 400 ° for 5 hours in an autoclave with a capacity of 1 liter. The dark-colored reaction product is extracted with boiling benzene. When the extract is processed by distillation. 32 parts by weight of carbiazoil are obtained.

Example 4 Through the pipe described in example i, i 1 one. Lump catalyst consisting of 940 / a zinc oxide and 6% aluminum oxide at 55o ° the hourly preheated to 35o ° vapors of 10 g diphenylamine and io g of water sent. In addition to unreacted diphenylamine, which is fed back into the implementation and the resulting: hydrogen is obtained per hour 1.5 g cairb, azole, accordingly about 100% yield based on the converted diphenylamine.

Example 5 Through the pipe described in Example i, about 1 1 of a catalyst consisting of 85% aluminum oxide and 15% molybdenum sulfide at 500 ° per hour the vapors of about 20 g of N-phenylcyclohexylamine and 20 g of water directed. In addition to diphenylamine, unreacted phenyl cyclohexylamine is obtained and hydrogen per hour based on 1 g of carbazole, corresponding to an 85% yield on the converted phenylcyclohexylamine.

Claims (1)

PATENT CLAIM: Process for the production of carbazole by catalytic Dehydrating diphenylamine or his. Hydrogenation products, characterized in that that the starting materials, if desired in dilution with inert gases or vapors, in the presence of catalysts, which, optionally in addition to supports, essentially oxides of the metals of the second, third and / or sixth group and / or contain sulfides of the metals of the sixth group of the periodic table, heated to about 25o to 700 °.