DE1131206B - Process for the continuous production of cyclohexanone - Google Patents

Description

Various methods for producing crude cyclohexanol are known, e.g. B. the oxidation of cyclohexane with air to a mixture consisting of cyclohexanol and cyclohexanone or the Hydrogenation of phenol to cyclohexanol or the hydrogenation and hydrolysis of aniline or nitrobenzene to a mixture containing cyclohexanol and cyclic amines (cf. Ulimanns Enzyklopadie der Technische Chemie, 3rd Edition, Vol. 5, 1954, pp. 685 to 687). Let all of these reaction products are converted into cyclohexanone over suitable catalysts, if appropriate with the addition of steam (cf. Ulimann's Encyclopedia of Industrial Chemistry, 3rd Edition, Vol. 5, 1954, pp. 691 and 692).

For example, phenol is hydrogenated in accordance with the process of German patent specification 752 239, and this in vapor form Accruing crude cyclohexanol is dehydrated immediately. From the German patent specification 1052 983 is a Process known to produce cyclohexanone from aniline, after which the crude cyclohexanol in the presence is passed over the catalyst by steam. According to the German interpretation procedure 1,078,569 is the heat content of the hot reaction products for heating the starting materials used.

For the production of a pure cyclohexanone, as it is for example for the production of caprolactam is required as a starting material, the known dehydrogenation processes are not suitable because the Cyclohexanone produced in this way has too low permanganate numbers. You can also use these procedures do not carry out continuously, as the life of the catalytic converter is very limited with them.

It has now been found that crude cyclohexanol obtained by conventional processes can be used by evaporation, expediently in a preheated state, optionally in the presence of steam, Dehydrogenation over conventional dehydrogenation catalysts at elevated temperature, such as 250 to 300 ° C, condensation of the reaction products and, optionally after separation of the aqueous phase, Distillation a pure cyclohexanone is obtained in a continuous manner even with long periods of operation, if after the first evaporation of the cyclohexanol, advantageously in a falling film or circulation evaporator, separates the liquid components and a second evaporator, expediently a thin-film evaporator, supplied, broken down into vaporizable parts and a non-vaporizable residue, the vaporizable components, advantageously after condensation, fed back to the first vaporizer, the Vapors escaping from the first evaporator Process for continuous production of cyclohexanone

Applicant:

Aniline & Soda Factory in Baden
Aktiengesellschaft, Ludwigshafen / Rhein

Dr. Günter Pöhler, Ludwigshafen / Rhine,

Dr. Anton Wegerich, Limburgerhof (Palatinate),

Dipl.-Ing. Hellmut Giehne, Ludwigshafen / Rhine, and Dr. Otto Göhre, Heidelberg,

have been named as inventors

in the usual way, expediently by heat exchange, heated to the dehydrogenation temperature and then at a speed of at least 50 cm / second through a heated, with a Dehydrating catalyst is fed through a tubular furnace.

It is known from the German patent specification 964 237 that in the air oxidation of cyclohexane Accruing cyclohexane-cyclohexanone-cyclohexanol-carboxylic acid mixture over several thin-film evaporators to distill quickly. But one could not conclude from this that an evaporation of a mixture consisting essentially of cyclohexanol associated with advantages in dehydrogenation would be.

The technical progress of the new process consists in the fact that even with long periods of operation a uniformly pure cyclohexanone is obtained, which is well suited for the production of caprolactam. In the known processes, one obtains at new catalyst charge a usable cyclohexanone, but after a short time the catalyst activity drops after, and the quality of the cyclohexanone becomes poor or the process has to be interrupted and replace the catalytic converter.

The evaporator can be a heated pipe coil with a connected separation vessel or Advantageously use a circulation evaporator, which is operated so that at the bottom of the subsequent Column a liquid level is maintained. The evaporated fractions escape at the top of the column, while the non-evaporated portions in the

209 609/420

Get into the sump, where the hard-to-evaporate fractions accumulate. One can also benefit from one Use falling film evaporators in which the reaction product flows through the tubes of a heated tube bundle flows from top to bottom. At least about 80% evaporate in the process; the non-evaporated liquid is separated in a separation vessel. Part of the separated liquid becomes a second Times fed to the falling film evaporator. To this

Separation of the aqueous phase by distillation into pure cyclohexanone and unchanged cyclohexanol separated.

example 1

An advantageous embodiment of the process is that the reaction product is already mixed with approximately the same amount of steam by weight before the first evaporator.

It is advisable to leave the separation vessel after the first evaporator or from the sump of the Circulation evaporator continuously withdraw a part and a second evaporator, preferably one

A suitable procedure is described on the basis of Fig. 1:

From the oxidation mixture obtained in the oxidation of cyclohexane is first made by the Destil manner 90 to 98% and above of the cyclohexanol reaction can be separated off. 1000 kg of this portion product evaporate. ducts are from the storage tank 1 by means of

Pump 2 is fed through line 3 to the heat exchanger 4, in which it is heated with the aid of the hot reaction products is heated to -15 from the tube furnace 21 to 160 ° C. It passes through line 5 in the with Raschig rings 18 provided column 6. About 80% are evaporated, while the remaining part is in the Collects sump 7 of the column. The liquid level of the sump is controlled by an automatic

Thin film evaporator, feed. This second 20 level indicator 12 is monitored and controlled by the regulating evaporator is held constant at a preferred valve 13 by a few degrees. Part of the swamp wise kept at 20 ° C, higher temperature than passed through line 8 via the preheater 9, in the first or less pressurized, which it is heated to 165 ° C, through line 10 thus a complete separation in vaporizable again in the column 6. Another part of the Fractions and a small, non-evaporable sump flows through line 11 into a thin residue entry. The evaporated portion is stratified evaporator 14, in which the high-boiling neither in vapor form, but more advantageously separated from the vaporous cyclohexanol in condensate substances ized state, expedient together with the become. The vapors enter through line 15 Starting product, fed to the first evaporator. the condenser 16, from which the condensate in the The vapors 30 leaving the first evaporator container 1 flows. At the bottom of the thin film, optionally together with steam, evaporator 14 are 3 kg hochin through line 17 withdrawn from one or more heat exchangers with boiling fractions.

The vapors from column 6 pass through Leiden, vapors heated to 250 to 300 ° C and tion 19 in the heat exchanger 20, which is fed to a tube furnace. In the tubes there are 35 hot gases emanating from the tube furnace 21 as well as shaped catalyst pieces. Is heated as dehydration. The heated to 250 ° C cyclohexanol catalyst is used heavy metals of the 1st, 2nd, passes through line 22 into the tube furnace 21 and 6th or 8th group, z. B. copper, nickel, platinum, or flows through its tubes, which are formed with a, whose oxides, z. B. chromium oxide, manganese oxide, iron from copper and pumice stone existing catalyst oxide, cobalt oxide, nickel oxide or mixtures of these, 4 ° are filled with a speed of 60 cm / or halides or phosphates, z. B. alkaline earth second. These pipes are heated with nickel phosphate. The catalytically active substance 400 ° C hot combustion gases. The circuit is advantageously applied to carriers such as alumina, titanium oxide, fan 24 sucks the combustion gases from the zinc oxide, magnesia, cerium oxide, silica, silicate tube furnace 21 through line 26, the heat from or mixtures of these. The carrier can 45 exchanger 20 and conveys it through line 27 over the incinerator 28 and line 25 again pretreated in hydrogen with chlorine, bromine, iodine or fluorine or halogen. the tube furnace 21. The fresh heating gases and the

The pipes filled with catalyst are heated by combustion air through lines 23, preferably at a temperature of 400 and 23 α, into the incineration furnace. Some of the combustion gases flowing past Verbis at 500 ° C goes over the roof at 44. gases heated. However, the catalyst can also be used in this way.

be ordered so that it surrounds the tubes: in this device 29 the tube furnace and is in the case of heat failure the hot combustion gases are transferred through the exchanger 4 to the cyclo-tubes to be heated directed. With this catalyst arrangement from hexanol. The rest of the heat is turned into a must the tubes in the tube furnace are discharged very close to the cooler 30. The condensate collects are located to each other, so that the catalyst chamber one in the separation vessel 31, from which the split off has a small free cross-section. Hydrogen escapes through line 32. On the ground

The vapors of the vessel heated by the heat exchanger become liquid through line 33,968 kg of the reaction product are withdrawn in one or more reaction products, from which by distillation Stages dehydrated. You will, appropriately with 60 lation 755 kg of pure cyclohexanone and 180 kg about twice the weight of steam and modified cyclohexanol are obtained, at a speed of at least 50 cm / In a system in which 1000 kg of cyclo-

Second, hexanol is advantageously dehydrated in this way at 60 to 100 cm / second, is the or at even greater speed, on the Kata activity of the catalyst when using one bypassed the analyzer. They are then through 65 freshly prepared catalyst even after 4 months Heat exchangers run where their heat tiger operating time is still unchanged, release to the starting material and condense. If, on the other hand, the method is carried out in such a way that

The condensed product is, if necessary after the cyclohexanol only in an evaporator

evaporates, and one passes the vapors at a speed of 45 cm / second under otherwise the same Conditions over the catalyst, the activity of the catalyst already drops after IV2 weeks after, since the content of cyclohexanone in the end product is reduced. You can slack off this compensate by increasing the temperature on the catalyst. But even in this case you have to use the catalyst Regenerate after just 6 weeks. In general, regeneration is only 5 to 4 times of the catalytic converter, the operating periods becoming shorter after each regeneration.

Example 2

Another embodiment is described with reference to Fig. 2:

1000 kg of a reaction product formed during the hydrogenation and hydrolysis of aniline or nitrobenzene, Consisting of 71% cyclohexanol, 20% mono- and 9% dicyclohexylamine, are removed from the storage tank 1 by means of pump 2 through line 3 fed to the heat exchanger 4, in which they are preheated to 150 ° C. From here is the reaction product passed through line 5 to the mixer 34, in which it is through line 35 with 1000 kg Water vapor is mixed. The mixture passes into the falling film evaporator 36. The reaction product and the water vapor flow through the Tubes from top to bottom, with 98% of the reaction product evaporating. At the bottom of the Evaporator separates the mixture in a separator 37 in vapor and liquid components. The latter are with a pump 38 through line 39 on the upper tube sheet 40 of the falling film evaporator returned. In the separator 37, a liquid level is maintained by 15 kg of the liquid portions branches off through line 11 and introduced into a thin film evaporator 14, from the at 17 2 kg of pitch-like substances are withdrawn, while the vaporizable components via a condenser 16 flow, condense there and are collected in the template 41. From this become they are removed and returned via a barometric discharge line 42 upstream of the pump 2. at 43 is a vacuum connection. The vacuum is 40 torr.

The vapors removed from the separator 37 are passed through the line 19 via the heat exchanger 20 and preheated to 250 ° C. They reach the tube furnace 21 via the line 22. The tubes of this furnace are covered with a shaped catalyst made of iron oxide and copper filled and are heated with combustion gases of 400 ° C. The circulating gas fan 24 sucks the Combustion gases from the tube furnace through line 26 and convey them through an incinerator 28 back through line 25 into the tube furnace.

The cyclohexanol / steam mixture flows through at a speed of 60 cm / second the pipes fitted with the catalyst and arranged in parallel. The reaction mixture leaves at 300.degree the tube furnace and passes through the line 29 via the heat exchangers 20 and 4 into the water cooler 30. The condensate then passes into the separator 31, while the hydrogen formed in the reaction is removed via line 32.

The liquid components are separated into an aqueous and an oily phase. From the aqueous phase cyclohexanol / cyclohexanone is separated off by azeotropic distillation. The resulting oil is broken down together with the oily phase by distillation. 772 kg of cyclohexanone are obtained. kg of cyclohexanol and 70 kg of residue.

Claims (1)

PATENT CLAIM:
Process for the continuous production of cyclohexanone from crude cyclohexanol obtained by customary processes by evaporation, expediently in a preheated state, optionally in the presence of steam, dehydrogenation over conventional dehydrogenation catalysts at elevated temperature, such as 250 to 300 ° C, condensation of the reaction products and, optionally after separation of the aqueous phase, distillation, characterized in that after the first evaporation of the cyclohexanol, advantageously in a falling film or circulation evaporator, the liquid components are separated off and fed to a second evaporator, expediently a thin-film evaporator, and broken down into evaporable components and a non-evaporable residue, the vaporizable fractions, advantageously after condensation, are fed back to the first evaporator, the vapors escaping from the first evaporator are heated to the dehydrogenation temperature in the usual way, expediently by heat exchange, and then at a speed ity of at least 50 cm / second through a heated tubular furnace filled with a dehydrogenating catalyst. Considered publications:
German Patent Nos. 752239, 964 237;
German publication no. 1 078 569,
983,1008,730. For this purpose, 1 sheet of drawings © 209 609/420 6.