JPS5936974B2 - Method for producing p-phenylenediamine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention provides p-phenylenediamine (P
PD).

p-Phenylenediamine is an intermediate for the production of polymers such as fully aromatic polyamides. One method for producing this diamine is to diazotize-couple alinine to form 1,3-diphenyltriazene, rearrange this triazene to p-aminoazobenzene, and then
This process consists of reducing the p-aminoazobenzene to p-phenylenediamine and aniline. U.S. Pat. No. 4,020,052 (issued April 26, 1977) discloses the catalytic oxidation of ammonia to form a gas mixture containing diluted nitrogen dioxide, preferably mixed with nitrogen monoxide; An improved process for the production of 1,3-diphenyltriazene is presented which consists of contacting a gas mixture with excess aniline. U.S. Patent No. 4,02
No. 0,051 describes a method for preventing the accumulation of potentially hazardous benzenediazonium nitrate in lines leading to residual gases from aniline diazotization-coupling reactions. In the process of US Pat. No. 4,020,052, the reaction product obtained from aniline is 1,3-diphenyltriazene dissolved in the aniline.

A method for rearranging the triazene in this solution to p-aminoazobenzene with a high para/ortho isomer ratio and with minimal formation of multiple by-products is disclosed in U.S. Pat. No. 4,279.
It is described in No. 815. In this rearrangement method,
An aniline solution containing up to about 30% by weight of triazene is contacted with about 0.4 to 2.0% by weight of a strong acid, preferably nitric acid, at a temperature of about 50°C (120°C) until the solution is essentially homogeneous.p- Aminoazobenzene can also be recovered from the rearrangement reaction product, but if the rearrangement forms part of a step in p-phenylenediamine synthesis, it may be recovered from the remaining steps of the synthesis, i.e., the p-aminoazobenzene. It would of course be preferable if the reduction of diamines could be carried out without isolating the aminoazo compound.Like catalytic hydrogenation, chemical reduction methods can also be used for the reduction of diamines of p-aminoazobenzene. This method has been shown so far.

A reduction method using iron and mineral acid was published in U.S. Patent No. 2,708,6.
No. 80, and according to this method, aniline is converted to 1,3 diphenyl triazene by reacting with an aqueous sodium nitrite solution and hydrochloric acid, and the triazene in the reaction mixture is rearranged to become aminoazobenzene. , the aminoazobenzene is reduced by adding iron and water to the rearrangement reaction mixture. The contact methods described so far are applicable to the hydrogenation of aminoazobenzenes in solution, but not to hydrogenations in rearrangement reaction mixtures without separation of the aminoazobenzenes. For example, Andrews
et al.'s Journal Of the American Che
micalSOciety9vOl. 56, page 14
11-1412 (1934), LU was obtained by treating an alcoholic solution of PAAB with hydrogen in the presence of platinum oxide.
It has been shown to reduce B to PPD. The hydrogenation method using cobalt, nickel or copper chromite as a catalyst is disclosed in Japanese Publication J54OO3-018.
This is done with AAB aniline solution. US Patent No. 4
, 191,708, PAAB is purified and recovered before catalytic hydrogenation. The use of nickel and palladium catalysts for the hydrogenation of p-azo N,N-disubstituted anilines is described in U.S. Pat. No. 891,234.
No. Nickel is also known as a catalyst for the hydrogenation of azo compounds to hydrazo compounds (US Pat. No. 1,589,936). US Patent No. 4
, 279,815, the typical reaction product obtained from the rearrangement process of triazenes is a liquid that separates into two phases at temperatures ranging from about 25 to 40°C, one phase of which The organic phase consists mostly of aniline in which PAAB and water are dissolved, and the other phase is an aqueous phase separated from the above-mentioned phase, and the weight ratio of the organic phase and the aqueous phase is Approximately 25
/1.

Dissolved water is about 3-4% by weight of the organic phase. Both phases also contain dissolved anions of the strong acid used in the rearrangement reaction, usually nitric acid. The amount of anions derived from strong acids, such as nitrate ions, contained in the product is usually up to about 1-2% by weight. Naturally, any method used to reduce PAAB in a product to PPD as described above will result in a reduction in the amount of PAD that occurs when the material used for reduction is mixed with a product containing PAA. must be specifically planned to take into account possible interactions.

For example, in catalytic hydrogenation, for the catalyst used,
Interactions with deleterious effects may occur that would not occur if PAAB were hydrogenated essentially solvent-free. The present invention is a process for the preparation of p-phenylenediamine comprising contacting an aniline solution of p-aminoazobenzene (PAAB) with hydrogen in the presence of a nickel catalyst at a temperature in the range of about 100 to 13°C. wherein the solution contains up to about 6% by weight, preferably up to about 4% by weight, of dissolved water and less than about 500 ppm (by weight) of anions derived from a strong acid, substantially free of mixed free water. We provide a manufacturing method that we do not have.

The BiM solution that is brought into contact with hydrogen according to the method of the invention is obtained by the following steps.

(a) The product obtained by contacting a solution of 1,3-dipnyeltriazene in aniline with about 0.4 to 20% by weight of a strong acid, preferably nitric acid, is separated into an organic phase and an aqueous phase.

The product is heated (1
) A two-phase liquid having an organic phase consisting of aniline having p-aminoazobenzene and water dissolved therein, and (2) an aqueous phase, both of which are prepared using a strong acid, preferably nitric acid. Contains dissolved. The product is optionally pre-neutralized, and the separation takes about 2
5 at a temperature in the range of -4'C to leave an organic phase in which the concentration of anions, such as nitrate ions, derived from strong acids is lower than the two-phase liquid, e.g., less than about 5,000 ppm, weight C). (b) The organic phase separated in step (a) is
Contacting ammonium hydroxide with an aqueous solution of a base selected from the group consisting of ammonium carbonate and alkyl amines at a temperature in the range of 5 to 40°C, thereby forming a salt formed by the reaction of the base with a strong acid. A product is obtained consisting of a dissolved aqueous phase and an organic phase having a lower concentration of anions than the organic phase separated in step (a), ie less than about 500 ppm (by weight).

(c) separating the product of step (b) into an organic phase and an aqueous phase; The organic phase of the product of step (b) separated in step (c) is essentially free of free water, but contains a few percent
For example, up to about 6% and usually about 407? Contains dissolved water up to. The p-aminoazobenzene in the organic phase of the product of step (b) separated in step (c) is in a state where it can be directly converted into p-phenylenediamine by the catalytic hydrogenation method of the present invention.

Therefore, following step (c), the organic phase is heated at about 1000C to 130C, preferably at 115C, in the presence of a nickel catalyst, preferably nickel supported on an aluminosilicate support.
Contact with hydrogen at a temperature range of 125°C to 125°C. Catalyst activity (i.e. % PAABO converted to product)
and the productivity (PrOductivity) (i.e. the weight of PPD obtained per unit amount of catalyst) in step (b).
) is higher when the organic phase obtained in step (a) is used for hydrogenation than when the two-phase rearrangement liquid or the organic phase separated in step (a) is used. This invention provides that a nickel catalyst used when hydrogenating PAAB in a liquid product containing aniline, water and a strong acid obtained by rearrangement of 1,3-diphenyltriazene has a strong acid anion concentration in the liquid. It is based on the discovery that when a small amount of water is present in solution in Anili-7, its activity and productivity are increased, as free water is reduced and free water is removed.

The PAAB solution used in the method of the present invention is the product of a rearrangement reaction as described in US Pat. No. 4,279,815.

As previously mentioned, this material forms, in a temperature range of about 25°C to 40°C, (1) an organic phase consisting of aniline with p-aminoazobenzene and water dissolved therein, and (2) an aqueous phase. (However, both phases contain in solution the strong acid used in the rearrangement reaction, preferably nitric acid, and the concentration of anions derived from this acid is typically up to about 1-2% by weight. It is a two-phase liquid consisting of This two-phase liquid is separated into an organic phase and an aqueous phase, preferably by decanting or other methods. The liquid product obtained by the rearrangement reaction, optionally after neutralization, can be placed in a settling tank to separate the organic and aqueous phases, with the aqueous phase being removed from the bottom of the tank. The purpose of this separation is to obtain an organic product essentially free of free water and with a reduced content of anions derived from strong acids. For this purpose, the separation is conveniently carried out at low temperatures, for example from about 25°C to 40°C. High temperatures such as 60°C must be avoided.

If carried out at high temperatures, the acid-containing water will dissolve in the aniline, and the aqueous phase will only separate again when the organic phase is brought to room temperature after separation. Prior to the separation just described, the two-phase liquid rearrangement reaction product is neutralized, for example by adding an aqueous solution of alkali metal hydroxide or ammonium hydroxide, to provide a large density for rapid separation of the two phases. It can make a difference.

The separated, essentially free, water-free strong acid anion concentration (regardless of whether the two-phase liquid has been previously neutralized) is less than about 5000 ppm (by weight) (usually about 2000 to 40
00 ppm) is contacted with an aqueous solution of a base selected from the group consisting of ammonium hydroxide, ammonium carbonate and alkyl amines, which reacts with a strong acid to form a salt which is extracted into the separated aqueous phase. to obtain an organic phase with a low strong acid anion concentration of 1, i.e., less than 500 ppm (by weight) and containing about 1 to 6% by weight of dissolved water depending on the difference in extraction temperature.

In most cases, the strong acid anion concentration in a single extraction is approximately 2
00-300 ppm. And two extractions would reduce it to about 50 ppm or less.
Base extractants are effective at low concentrations, such as less than about 10% by weight. For example, if the extractant has a base concentration of about 1 to 5%, more than about 90% of the strong acid can be easily removed.
It is believed that the small amount of base not only reacts with the acid but also contributes to the sharp and rapid separation of the organic and aqueous phases. Ammonium hydroxide is a particularly preferred base because of its good compatibility with process residues, including waste products. Approximately 40 minutes during extraction
Keeping the liquid below °C creates sufficient phase density differences for rapid separation. Despite the deleterious effects of free water, the small amount of dissolved water left in the organic phase after the extraction step, e.g. about 1-6% by weight, usually about 3-4% by weight, can absorb hydrogen. The addition has a beneficial effect on the catalytic activity.

The organic phase obtained in the extraction step described above is separated from the aqueous phase and is ready to be used in the process of the present invention to convert the PAA contained therein into PPD by extended catalytic hydrogenation.

The organic phase is contacted with hydrogen in the presence of a nickel catalyst, preferably nickel supported on an aluminosilicate support. The concentration of strong acid anions in the liquid to be brought into contact with the catalyst is less than about 200 ppm, preferably less than about 50 ppm; as the liquid with this concentration, the organic phase obtained by separation after extraction can be used as is, or The concentrated organic phase can also be diluted with the recycle stream resulting from the hydrogenation with aniline or a sufficiently low strong acid anion concentration to form a sufficiently low concentration mixed liquid before use. Hydrogenation can be carried out under a wide range of temperatures and pressures.

However, since too low a pressure or temperature will reduce the reaction rate, it is generally preferred to use a temperature of at least about 100° C. and a pressure of at least about 2070 KPa. A preferred temperature range is about 115-125°C. Approximately 1
Temperatures above 30° C. are not used because they hydrogenate the rings and reduce the yield. Pressures of about 5000 KPa or higher can be used but provide little or no improvement in hydrogenation rate. During hydrogenation, the reactor feed exposed to the catalyst is essentially free of free water, has a low strong acid anion concentration, i.e., less than about 500 ppm (by weight), and has a concentration of several percent, e.g., up to 6% by weight. Contains 1 ml of dissolved water.

FP of PAAB by catalytic hydrogenation according to the present invention
A method for treating the 1,3-diphenyltriazene rearrangement product for use in converting it to D is now described by way of example and the process diagram shown in FIG.

Example 1 A 1,3-diphenyltriazene rearrangement product was prepared by the method described in Example 1 of US Pat. No. 4,279,815.

The disclosures of said patents are incorporated herein by reference.
This method is as follows. Production of 11,3-difnyeltriazene (according to U.S. Pat. No. 4,020,052) a Synthesis of a gas mixture containing nitrogen oxide Nitrogen monoxide and air were each introduced into a pipeline reactor at 648 kPa at 0 It is introduced at a rate of .57 x 10-4, 0.61 x 10-4 i/sec, and 95-97% of the introduced oxygen reacts to contain equal volumes of nitrogen dioxide and nitrogen monoxide. Hold up enough to form a gas mixture.
p) Time was maintained.

The heated nitrogen is added to the generated gas at a rate of 0.39×10
Add at a rate of -3 i/sec and at a temperature of 74°C for 10.
A final stream containing 8 mole percent nitrogen oxide and less than 0.14 mole percent residual oxygen was created. This gas mixture is
12.3 in air at 80% relative humidity at 30°C, excluding water. It is similar to the mixture made by burning ammonia. b Reaction of Ni Oxide with Aniline Aniline and water (in the amount of water that would be present in the gas obtained by the step of oxidizing ammonia described in paragraph (a)) were each reacted at 108 f1/min, 4 A vapor-liquid separator (VapOr-11qu) designed to allow continuous extraction through a water-cooled condenser at a rate of .3 m1/min.
idsseparat0r).

The reaction product solution (1,3-diphenyltriazene dissolved in aniline) and gas produced in the tubular reactor are also passed through a separator, from which the liquid is continuously withdrawn and kept at a constant level. Ta. Collect some of the liquid taken out.7
, and a portion was then recycled to the tubular reactor at a rate of about 2300 ml/min via a condenser to maintain a temperature of 40-50°C. A stream of gas containing nitrogen oxide produced as described in paragraph (a) is passed through the reactor co-currently with a stream of recycled aniline solution to produce the product (
liquid and gas) were passed through the separator.

The liquid recovered from the separator had the following composition:

(by weight) Rearrangement of 1,3 Diphenyl Triazene Part I (supra) of the essentially homogeneous triazene-containing reaction product solution obtained by the diazotization coupling of alinine as described in Part I (above) 1.09
C7rL, the first 0.34m of which was filled with fine wire mesh constituting the mixing zone, was heated to 1.
It flowed at a rate of 12 ml/min.

The temperature of the preheating tube was 40°C. At the same time, 20% of nitric acid
weight χ} solution was introduced into the mixing zone of the preheat tube at a rate of 3.6 d/min. The amount of nitric acid contacting the aniline solution was 0.9% by weight. The mixture exiting the preheating tube is then heated to a tube with an outer diameter of 1.3 (7n) and a length of 12 m (inner diameter 1.09 (1)
The hold-up time was 10 minutes (reactor capacity: 1145 mm).
CC). Hot water was circulated in a jacket around the tubular reactor and the reaction temperature was maintained at 85°C at the reactor outlet. The effluent from the reactor (rearrangement products) contained 75.5% by weight aniline, 16.1% by weight PAAB and 0.8% by weight nitrate ions. Removal of nitrate ions 3 Removal of free water A batch of 190 kg of the rearrangement product (a) was decanted into a vessel 1 (Fig. 1)
That is, the batch was separated into an organic phase 4 and an aqueous phase 5 by charging the batch into a 2081 stainless steel tank equipped with take-off lines 2 and 3 on the bottom and sides, respectively, and maintaining the batch at about 25° C. for 4 hours.

The aqueous phase (7 kg) was removed from the tank via line 2 until the organic phase was visible in the sample. The aqueous phase removed contained 3.64% by weight aniline, 16.9% by weight nitrate ions, and less than 0.1% by weight PAAB. The organic phase (183 kg) in the obtained tilted container 1 was 7
It contained 5.5% by weight aniline, 3620 ppm nitrate ions, 16.1% by weight PAAB, about 4% by weight dissolved water and essentially no free water. b. The neutralized and extracted organic phase 4 is taken out from the tilter and vessel 1 through line 3, and passed through a pump 208 to remove residual nitrate ions.
1 into a stainless steel extractor 6 (if necessary, it can also be done in a tilted or vessel 1).

In addition, 39 kg of water and 30% water are added to the extractor 6 through line 7.
Ammonium hydroxide solution 2k9 was added. This is 1.
Equivalent to adding 41 kg of 7% ammonium hydroxide solution. The liquid in the extractor is mixed with an agitator and a recirculation pump 9.
After stirring for 1 hour at 5°C, it was left to stand for 4 hours, and the organic phase [
An aqueous phase was separated from 1. The upper aqueous phase (43 kg) was suctioned off from the organic phase (183 kg) via line 19. The aqueous phase was 3.2% by weight of aniline, 1.

It contained 5% by weight nitrate ions, less than 0.1% by weight PAAB.

On the other hand, the organic phase contains 75.4% by weight of aniline and 16.1% by weight of aniline.
wt% PAABl containing about 4wt% dissolved water and 2
Only 20 ppm of nitrate ions remained.
When the extraction process is repeated, the nitrate ion content is approximately 50 ppm.
decreased.

The following example illustrates the PAAB hydrogenation process of this invention.

Example 2 PAAB in an organic phase containing 220 ppm nitrate ions obtained as shown in Example 1 was hydrogenated by contacting the organic phase with hydrogen and a nickel catalyst.

Diameter 5cTrL length 189C! RL vertical reactor 12 (
Figure 2) was made of 50% nickel/aluminosilicate and had a diameter of 3.18 m1.
d) 1.4k9 of catalyst was loaded. PAAB-containing organic phase 11
and hydrogen were introduced cocurrently into the top of the reactor through lines 22 and 23, respectively, permeated through the catalyst bed, and were removed from the bottom of the reactor and introduced into a gas/liquid separator. A portion of the liquid leaving the separator was recycled to the reactor to limit the temperature rise from top to bottom of the reactor to 5-10°C. The reactor was pressurized to 3310 pKa with hydrogen, and the liquid leaving feed tank 6 (extractor of Example 1, part 1b) was sent through line L to reactor Vl to maintain the liquid level in the separator. 5 of total capacity
It was set to 0-70%.

The recirculation pump was started, the flow of liquid was stopped, and the temperature of the system was stabilized by the heater [5] in the recirculation line. When the temperature at the reactor inlet reaches 115°C, liquid raw material 1
1 was started and the product was continuously removed to maintain a constant separator level. The temperature at the reactor outlet was 120°C.
The hydrogen leaving the gas-liquid separator was recycled to the reactor via pressure regulator 24 and hydrogen compressor λ5 together with cylinder hydrogen introduced into line 13 to replenish the consumed hydrogen. The liquid stream is forced into the recirculation line VL by pump ▲ at a rate of 7.7 kg/hour to join the recirculation stream, which is heated to 118° C. in heater V5, and 92.5 kg
/ hour into the reactor.

This combined stream contains 2.3% by weight PAARsO. 3
It contained 8.26 wt.% aniline, 4 wt.% water and 50 ppm nitrate ions. The liquid product from the separator is 7.7
It was withdrawn into product tank 17 at a rate of k9/h. It contained 8% by weight PPD, 4% by weight H2O, 1% by weight PAAB and 50 ppm nitrate ions. PPD was separated by distillation to remove aniline and water from the product. Figure 3 shows the degree of catalytic activity and shelf life in the hydrogenation system A described above, in which a liquid containing 50 ppm (220 ppm at the feed stage to the reactor) of nitrate ions is brought into contact with the catalyst; A comparison is shown with that in system B in which the containing liquid is brought into contact with the catalyst.

In System B, Liquid 0 was not treated with the extraction process of the present invention and contained 2400 ppm nitrate ions. This liquid was combined with the recycle stream to reduce the nitrate ion content to 600 ppm. In system B, 3.11<g of catalyst was used.
As shown in Figure 3, PAAB in system A
The conversion level to products was at a high level (i.e. between 90 and
100% range) and, moreover, shows no signs of rapid decline with further production.

In System B, on the other hand, the catalyst is broken when it has produced approximately 40k9 PPD per 1k9 catalyst. That is, the conversion level drops rapidly. Example 3 Two tests (3A, 3B) on the lifetime and activity of the hydrogenation catalyst were carried out in a stirred autoclave using the same catalyst as described in Example 2, except in a slurry state. Ivy.

And the productivity was measured at 320k9 PP/kg of catalyst.
The period was extended until D was produced (indicated by A in Figure 4). Each test was conducted in a repeated cyclical manner in which the initially charged catalyst was reused in subsequent cycles of slurry hydrogenation batches and the charges were (a) 60% by weight of fresh rearrangement products and (b) ) Peel from previous cycle (
Heel) 40% by weight. The two experiments were conducted under exactly the same conditions except for the composition of rearrangement products in the feedstock.

That is, one test was carried out using a rearrangement product treated by the nitrate ion reduction process of the present invention, and the other was carried out using a rearrangement product that was not treated. Experiment 3A used Example 1 as the raw material.
A rearrangement product made as shown in Part 1 and processed as shown in Example 1 Parts 1a and b was used.

In this case, the organic phase U is diluted in a ratio of 1:1 with dried and fresh aniline after removal of the aqueous phase [p, 9.7% of PA
ABll. 4fl) 0AAB10% PPDl88%
of aniline, 0.2% water and less than 25 ppm nitrate ions was obtained. Experiment 3B (control)
As raw materials, about 11% aminoazobenzene, 2(!) parts water and 100% water, prepared as shown in Example 1 part and diluted with fresh aniline in a 1:1 ratio.
A rearrangement product containing 0 ppm of nitrate ions was used. Each hydrogenation cycle was performed as follows.

150m of triazene rearrangement product treated as above
1 and the catalyst shown in Example 2, all the particles were U. S
．． Grinded to a size that can pass through a 325 mm sieve (0.044 mm gap), it is operated semi-continuously without opening a gas recirculation turbine agitator, a thermostatically controlled cooling coil, and an autoclave. Electrically heated and stirred
Placed in a 0ml stainless steel autoclave.

Purge the system with nitrogen and then with hydrogen.
)did. The autoclave was heated under a hydrogen pressure of 3550 kPa for 120 min with stirring to keep the catalyst well suspended but to minimize hydrogen uptake.
heated to ℃.

A hydrogen reservoir of known capacity was adjusted to 3550 kPa, disconnected from the feed gas reservoir, and the stirring speed was increased to 1250 rpm, which signaled the start of the reaction. As soon as full agitation began, a sharp pressure drop, indicating hydrogen uptake, began and continued throughout as the aminoazobenzene continued to convert to phenylenediamine.

By flowing cooling water through the reaction coil during the cycle,
The temperature was maintained at 120±0.5°C. When hydrogen uptake ceases, the reaction mixture is cooled to below 5'C and approximately 40% by weight is added to the heel for the next hydrogenation cycle.
The remaining hydrogenate (Hydr
Ogenate) was removed from the reactor. Retention of the peel is achieved by installing a catalyst filter in the take-off line above the stirring blade. After removing the system, a new rearrangement reaction product with a weight equal to the removed Hydrogenate was introduced into the reactor and the next hydrogenation was repeated.

Using the initially charged catalyst, hydrogenation was repeated until either a valid measurement result was obtained or the catalyst lost activity. The results are shown in FIG. A direct indication of catalyst activity is given by the hydrogen uptake rate, PAAB
The conversion rate measurements are shown in Figure 4 in moles of PAAB per minute. The conversion (consumption) of aminoazobenzene was 100% in all cases. Figure 4 shows that in run 3A there was a 32% reduction in catalyst activity by cycle 31, while in control run 3B the loss of catalyst activity at cycle 31 was 85% (note: Control run 3B ended at cycle 19 because the rate reading showed a reasonable slope and the catalyst life could be determined thereby.

The loss of catalyst activity in cycle 31 of this experiment was therefore determined by extrapolation). Catalyst productivity at the end of cycle 31 was approximately 320 kg p-phenylenediamine/k9 catalyst for run 3A and only 196 k9 for the control run.

[Brief explanation of the drawing]

FIG. 1 is a process diagram for removing free water and nitrate ions from the 1,3-diphenyltriazene rearrangement product, and FIG. −
Figures 3 and 4, which are process diagrams for catalytic hydrogenation of diphenyltriazene rearrangement products, illustrate the advantages of the treatment method of the present invention in terms of the activity and life of the hydrogenation catalyst. 1... Tilt and vessel, 4... Organic phase of rearrangement product, 5... Water phase of rearrangement product, 6...
...Extractor, 8...Stirrer, 10...
Aqueous phase after extraction, 11...Organic phase after extraction, 12
... Hydrogenation reactor, 13 ... Gas-liquid separator, 15 ... Soil tank, 17 ... Product tank, 24 ... ...Pressure regulator, 25...
...Hydrogen compressor, 9, 14, 18, 21...pump.

Claims (1)

[Claims] 1. An aniline solution of p-aminoazobenzene with hydrogen,
A process for the preparation of p-phenylenediamine comprising contacting in the presence of a nickel catalyst at a temperature in the range of about 100° to 130°C, said solution being derived from up to about 6% by weight of dissolved water and a strong acid. less than about 500 ppm (by weight) of anions and having substantially no admixed free water. 2. The method according to claim 1, wherein the anion is a nitrate ion. 3. The method of claim 1, wherein the catalyst is nickel supported on an aluminosilicate support. 4. The method according to claim 1, wherein said p
- A method in which the aminoazobenzene solution is obtained by a series of steps consisting of: (a) about 0.4 to 2.0% by weight of an aniline solution of 1,3-diphenyltriazene;
The product obtained by contacting with a strong acid of An organic phase consisting of aniline in which azobenzene and water are dissolved and (2
) a two-phase liquid consisting of an aqueous phase, said organic phase and said aqueous phase both containing a dissolved strong acid, said separation being carried out at a temperature in the range of about 25° to 40°C; (b) The organic phase separated in step (a) is heated at a temperature of about 25° to 40° C. with ammonium hydroxide and ammonium carbonate. and an aqueous phase containing a dissolved salt formed by the reaction of the base with a strong acid, and an anion concentration lower than that of the organic phase separated in step (a). and (c) separating the product of step (b) into an organic phase and an aqueous phase, said organic phase separated in step (c) being contacted with water. Construct a p-aminoazobenzene solution. 5. A method according to claim 4, comprising the step (
The two-phase liquid separated in a) contains nitric acid in its aqueous and organic phases. 6. A method according to claim 5, comprising the step (
The organic phase separated in a) is brought into contact with an aqueous ammonium hydroxide solution. 7. The method of claim 6, wherein the ammonium hydroxide solution has a concentration in the range of about 1-5% by weight. 8. A method according to claim 5, comprising the step (
The two-phase liquid to be separated in a) is neutralized before said separation.