JPS6147446A - Preparation of aniline - Google Patents

Abstract

PURPOSE:To obtain aniline in high yield, by separating a reaction product solution obtained by hydrogenating nitrobenzene, extracting the aniline dissolved in the separated aqueous phase with nitrobenzene, and mixing the extracted aniline with the raw material nitrobenzene. CONSTITUTION:Nitrobenzene is hydrogenated in the presence of a catalyst, e.g. Pd or Pt, in a reactor 1, and the resultant reaction product solution is separated into an aniline phase and aqueous phase in a separation tank 7 to feed the aniline to a crude aqueous aniline storage tank 15. The aqueous phase is passed through a crude aqueous aniline storage tank 9 and line 10 to an extractor 11, and the aniline dissolved in the above-mentioned aqueous phase is extracted with nitrobenzene and mixed with the raw material nitrobenzene in a nitrobenzene storage tank 13 for use. Since the nitrobenzene is used as an extractant, and directly usable as a reaction raw material, separation operation for separating the aniline from the nitrobenzene is not required, and energy can be saved. The aniline present in the nitrobenzene will not inhibit the activity of the catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing aniline, and particularly to an industrially constructed process for producing aniline.

Technical Background of the Invention Aniline is an extremely useful intermediate for precision chemicals such as rubber chemicals, pharmaceuticals, and dyes, and is industrially produced in large quantities.

The manufacturing method for this product has almost been completed on an industrial scale, but there is still room for improvement in the industrial manufacturing method. In other words, there is improvement in the yield of the product and energy saving.
As a problem in factory production, the present inventors have found a method and operation for recovering aniline, a reaction product obtained by hydrogenating nitrobenzene, which is carried away to the separated aqueous phase. In order to solve the above-mentioned problems in the industrial production method of aniline, we conducted intensive studies.

As a result, the reaction product obtained by hydrogenating nitrobenzene was separated to separate aniline, and the aqueous phase containing dissolved aniline was extracted with nitrobenzene to extract the aniline in the aqueous phase. nitrobenzene as it is,
When the raw material was mixed with 2 liters of benzene and hydrogenated, surprisingly, the activity of the catalyst used in the reaction was not inhibited, and the quality of the aniline obtained was no different from that obtained from purified nitrobenzene as a raw material. They found that there is no problem and completed the method of the present invention.

The production of aniline in the process of the present invention is by already known methods, generally by hydrogenation of nitrobenbin, which is a continuous process for the production of aniline.

using aniline as a solvent, at least 1
Palladium deposited on lipophilic carbon with an oil absorption rate of 0.00 or palladium-platinum suspended as a catalyst? %1
Soil stain, alkali metal hydroxide, alkali metal carbonate,
In the presence of a compound selected from alkali metal bicarbonate, zinc acetate, and zinc nitrate, while keeping the concentration of nitrobenzene in the aniline reaction solution at 0.5% by weight or less,
The reaction is carried out in a hot draft at 0°C, and aniline and water produced by the reaction are continuously distilled off as steam from the reaction product, and the reaction is carried out in the substantial absence of water to produce aniline. It is something to do.

In this method, the catalyst used is a non-porous oil absorption rate of 1
Para 0 deposited on lipophilic carbon of L.
It is a metal catalyst, or a palladium-platinum catalyst.

It is necessary that the carrier is a lipophilic carbon having an oil absorption rate of 100 or more, preferably 150 to 300.

The appropriate concentration of palladium and palladium and platinum deposited on monolipophilic carbon is 0.1 to 5 weight tS, particularly preferably 0.5 to 1.0% by weight.

Palladium may be used alone, but when used in combination with platinum, it is particularly effective in terms of activity and selectivity, and in that case it is desirable to use platinum in an amount of about 5 to 20% by weight relative to palladium. It is also possible to mix a small amount of oxide or hydroxide of metals such as iron and nickel. The concentration of the catalyst in the reaction mixture system is usually 0.2 to 2.0% by weight.

It is necessary to constantly remove water generated during the reaction from the system and carry out the reaction substantially in the presence of water.

Almost all of the reaction products are evaporated using a portion of the generated reaction heat, the vapor is condensed, water and aniline are separated, and water is removed from the system. At this time, it is desirable to return a portion of the aniline condensate to the reactor as necessary to maintain a substantially constant amount of liquid in the reactor to carry out the reaction.

In this method, hydrogenation can be carried out under atmospheric pressure, but it is preferably carried out at a pressure of 1.5 to 10 atm, particularly preferably 3 to 7 atm.

In the method of the present invention, the reaction product thus obtained is separated into an aniline phase and an aqueous phase, and the aqueous phase is post-treated to obtain a specific aniline.

After completely separating the aniline phase and aqueous phase, the aqueous phase from which the aniline phase was separated is shown below. Process as follows.

That is, add nitrobembin to the aqueous phase and mix well;
Thereafter, the aniline dissolved in the aqueous phase is extracted into nitrobenzene.

The amount of nitrobenzene used in the aqueous phase is 0.2 to 2 times the amount of aniline in the aqueous phase, usually 0. 〒 double amount is enough.

Extraction can usually be carried out at room temperature.

The nitrobenzene phase separated by this process is separated from the aqueous phase.

The nitrobendane thus obtained can be mixed with the new nitrobenzene and used as a raw material 210benzene to carry out the reaction as described above.

Actions and Effects Previously, in the method for producing aniline, the reaction product liquid obtained after hydrogenation was separated into two liquids, and after separating the aniline, the aqueous phase was treated with an oil to extract the aniline, and the aniline was extracted from the extracted liquid. Therefore, a considerable amount of energy was required for recovering aniline, refining oil, etc.

However, according to the method of the present invention, nitrobenzene is used as an oil agent, and nitrobenzene is not necessary for extracting aniline.
It also saves energy. Also, the aniline present in nitrobenzene does not inhibit the activity of the catalyst.

Moreover, aniline can be recovered with high efficiency and can be obtained with zero phosphorus quality. There is no problem either.

As described above, the method of the present invention is an extremely industrially superior method.

Hereinafter, the present invention will be explained in detail with reference to Examples.

EXAMPLES Reactions were carried out using a series of reactors shown in the production flow sheet of FIG. 1.

Aniline 14i was charged into reactor 1, and platinum, palladium, and iron were added to each lipophilic carbon and 0.0.
1%, 0.8%, and 0.8% by weight of catalyst were suspended in water to a slurry concentration of about 4.5%, and this was stored in catalyst storage tank 2, and 1401 was added to the reactor.

The internal temperature of the reactor was maintained at 200°C, and 9 parts of purified nitrobenzene was continuously fed at 3,200 g/hr.

1.77 while stirring under pressure of 55 kg/crIG
Hydrogen was introduced at a rate of 6 g/h to carry out a hydrogenation reaction.

Nitrobenzene is hydrogenated, and 24 in kg of aniline is produced per hour together with water from the reactor, and the produced aniline passes through line 3 as an azeotrope with water to cooler
The aniline water is condensed and stored in the aniline water receiver 5. Furthermore, it passes through a cooler 6 and is sent to a separation tank 7. During this time, about 301 liters of aniline liquid containing the catalyst is extracted every day. The reaction is continued while replenishing the removed catalyst, new catalyst suitable for aniline, and aniline.

In the separation tank 7, the liquid is separated into an aniline phase and an aqueous phase, and each phase is recovered.

Aniline passes through line 8 and is sent to crude aniline storage tank 15. The amount produced was approximately 2,400 kg. The aqueous phase passes through a crude aniline water storage tank 9 and a line 10 to an extraction tank 1.
Send to 1.

Nitrobenzene is continuously flowed down from the upper part of the extraction tank 11,
Continuously inject the aqueous phase from the bottom.

Draw 1゜In-flight 3. , yo ~ 4 months. , with a horizontal board; 14□. , a stirrer is installed, and the nitrobenzene and aqueous phases are gently stirred. Aniline dissolved in the aqueous phase is extracted into nitrobenzene.

In normal operation, approximately 54 parts of nitrobenzene are added to 100 parts of this aqueous phase.

Nitrobenzene from which aniline has been extracted has a high specific gravity and is continuously discharged from the bottom of the extractor and stored in the aniline-extracted nitrobenzene storage tank 12.

The aqueous phase washed with nitrobenzene has a low specific gravity, so it floats to the surface and flows out from the top of the extractor.

Extraction can usually be carried out at room temperature.

The diameter and height of the extractor may be determined based on the conditions for optimal extraction.

The above-described production of aniline was repeated by mixing 350 kg/h of this extracted nitrobenzene with 850 kg/h of nitrobenzene used as a raw material.

When aniline is produced using refined nitrobenzene, the resulting aniline is colorless to pale yellow and has a water content of 5.
As a result of chromatography analysis, cyclohexanol trace 1 cyclohexanone 9.5 pp
m, 3.9 ppm of cyclohexylideneaniline, and trace of unreacted nitrobenzene.

On the other hand, when aniline is produced using a mixture of nitrobenzene from which aniline has been extracted and raw material nitrobenzene, the obtained aniline is also colorless or pale yellow, and has a water content of 4.
．． Contains 9 chlorides, and as a result of chromatography analysis, cyclohexanol trace.

Cyclohexanone 9.3 ppm, cyclohexylidene aniline 4. lppm, unreacted nitrobenzene trace
There is almost no difference in quality.

[Brief explanation of the drawing]

FIG. 1 shows a manufacturing flow sheet implementing the method of the invention. Each symbol in the figure has the following meaning. 1: Reactor 2: Catalyst preparation tank 3 Nianiline, water vapor line 4: Cooler 5 Nianiline water receiver 6: Cooler 7: Separator
8: Separated aniline outflow line 9: Crude aniline water storage tank 10: Crude aniline line to extractor 11: Extractor 12 Nianiline extraction nitrobenzene storage tank 13: Raw material nitrobenzene storage tank 14: Extraction and purification nitrobenzene storage tank 15: Crude aniline storage tank 16: Hydrogen gas 17: Nitrogen gas 18: Catalyst 19: Residual gas line

Claims (1)

[Claims] 1) In a method for producing aniline by hydrogenating nitrobenzene in the presence of a catalyst, the aniline dissolved in the aqueous phase is extracted with nitrobenzene from the aqueous phase from which aniline has been separated from the reaction product liquid, and this is combined with the raw material nitrobenzene. A method for producing aniline, characterized in that it is used in combination.