JPS593987B2 - P- Phenylenediamine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for producing p-phenylenediamine by nitrating azobenzene with nitric acid and then hydrogenolyzing it with molecular hydrogen in the presence of a catalyst.

p-Phenylenediamine is used in a wide variety of industrial applications. For example, it is an important compound used as a raw material for the production of heat-resistant polymers, a raw material for color formers, dyes, and pigments in photography, and as an antioxidant in the rubber industry. Conventionally, p
-Methods for synthesizing phenylenediamine include reducing p-nitroaniline with iron monohydrochloric acid, ammonorinsing p-dichlorobenzene, hydrogenating reduction of p-dinitrobenzene, and Hofmann decomposition of terephthalic acid amide. Methods are known.

Furthermore, a method of hydrogenating 4-aminoazobenzene as a raw material has been reported. That is, U.S. Patent No. 270,868
The specification of No. 0 proposes a method of hydrogenating 4-aminoazobenzene with iron monohydrochloric acid. Nu, JACS56
1411 (1934) proposed a hydrogenation method using platinum or nickel as a catalyst. However, since these methods simultaneously produce a large amount of aniline with the same number of moles as the target p-phenylenediamine from the raw material 4-aminoazobenzene, they cannot be said to be effective methods in terms of product separation and economics. No. Helv
, Chim, Acta 30735 (1947), p-phenylenediamine is obtained by hydrogenating 4-nitroazobenzene using a Raney-nickel catalyst.

However, this method cannot be said to be an effective synthesis method because p-phenylenediamine and a large amount of aniline having the same number of moles are simultaneously produced as by-products. Furthermore, Berichted,
D, Chem, Gesellschaff5235 (1
872), p-
There is a statement that phenylenediamine was obtained.

However, in this reaction using ammonium sulfide, it takes time and effort to separate and purify the p-phenylenediamine produced. H5: Moreover, sulfur compounds are produced as by-products, which are problematic to dispose of, and this method cannot be said to be a good synthesis method. The present inventors have made extensive efforts to synthesize p-phenylenediamine by using azobenzene as a starting material, reacting it with nitric acid to obtain a nitrated product at the p-1 position relative to the azo group, and further hydrogenating this product30. As a result of research, they discovered a method for obtaining p-phenylenediamine in high yield and arrived at the present invention. That is, in the present invention, in the first step, azobenzene is treated with nitric acid, and the obtained 4.4'-
Dinitroa 35 zobenzene and/or p- are characterized by hydrogenolyzing 4,4'-dinitroazoxybenzene with molecular hydrogen in the presence of a catalyst in the second step.
This is a method for producing C4-phenylenediamine.

The reaction method of the present invention consists in synthesizing 4,4'-dinitroazobenzene and 4,4'-dinitroazoxybenzene by reacting azobenzene with nitric acid in the first step.

The desired desired products in this reaction are 4,4'-dinitroazobenzene and 4,4'-dinitroazoxybenzene, and it is particularly desirable to obtain a high proportion of 4,4'-dinitroazobenzene. The nitration reaction of azobenzene of the present invention is as follows: (1) Azobenzene is reacted with fuming nitric acid to obtain 4,4'-dinitroazobenzene, as described by Berichted. D.
Chem. Gesellschaft323256(1
899) and J. Chem. SOc. l9532l5
How to report to O.

(Ii) A method for obtaining 4,4'-dinitroazobenzene by reacting a mixed acid with azobenzene.

(Iii) A method in which 4-nitroazobenzene is obtained by reacting azobenzene with nitric acid, and then 4,4'-dinitroazobenzene is obtained by reacting a mixed acid with 4-nitroazobenzene.

0'V) A method is used in which 4-nitroazobenzene is obtained by reacting azobenzene with nitric acid containing a small proportion of sulfuric acid, and then 4-nitroazobenzene is reacted with a mixed acid to obtain 4,4'-dinitroazobenzene.

In these nitration reactions (1) HV), the methods (1i1) and 0V robustness are preferred from the viewpoint of yield and selectivity, and the method (g) is particularly desirable.

When the reaction of the present invention was carried out in one step, it was carried out by reacting azobenzene with fuming nitric acid or a mixed acid.

The reaction is preferably carried out by reacting 4 to 40 molar equivalents of nitric acid and 0 to 40 molar equivalents of concentrated sulfuric acid to azobenzene. However, it is not particularly limited to this range. If the amount of acid used is small, the reaction rate will be slow, and if it is too large, it will take time and effort to dispose of the excess acid after the reaction. The concentration of nitric acid used has a specific gravity of 1.12~
1.52, and sulfuric acid with a specific gravity of 1.8 is used,
It is not particularly limited to this range. The amount of sulfuric acid to be used relative to nitric acid is preferably 0 to 1.0 molar equivalent; if the ratio of sulfuric acid is small, the reaction rate will be slow. When this ratio is large, by-products other than the target product increase. The reaction is carried out by adding nitric acid and sulfuric acid to azobenzene at a predetermined temperature with stirring, but it is also possible to carry out the reaction by adding other solvents to further improve the stirring effect. As such a solvent, a solvent that does not react with nitric acid and sulfuric acid in this reaction system, such as acetic acid, is used. Separation of the product is carried out by filtering and separating the target product precipitated in the reaction mixture. The main component of the compound obtained by this separation is 4.
4'-dinitroazobenzene, and 4,4/
-dinitroazoxybenzene, 4-nitroazobenzene and 4-nitroazoxybenzene. All of these compounds are hydrogenated and converted into p-phenylenediamine in the second step. When carrying out the nitration reaction of azobenzene in two steps, 4-nitroazobenzene is obtained by reacting azobenzene with nitric acid or nitric acid containing a small proportion of sulfuric acid, and then a mixed acid is reacted with the obtained 4-nitroazobenzene. 4,4'-dinitroazobenzene is synthesized. To explain this method in more detail, 4-nitroazobenzene is produced by reacting azobenzene with nitric acid.
It is convenient for the concentration of nitric acid to have a specific gravity of 1.12 to 1.47. The concentration of nitric acid is influenced by the reaction temperature and the presence or absence of sulfuric acid in the reaction system. The ratio of nitric acid to azobenzene is 1 to 40 molar equivalents to azobenzene. If the proportion of nitric acid is too small, the reaction will not proceed at a sufficient reaction rate, and the proportion of unreacted raw materials will increase. On the other hand, if the amount is too high, it will be troublesome to dispose of the excess nitric acid. The amount of sulfuric acid used is O to 1.0 molar equivalent to nitric acid. Generally, adding sulfuric acid increases the rate of nitrification. However, when used in excess, an azoxy compound tends to be produced, and at the same time, a large amount of unintended by-products may be produced. The reaction temperature of the present invention is -5 to 100°C.

The preferable range of the reaction temperature is determined by other reaction conditions, such as the concentrations of nitric acid and sulfuric acid and their ratios to the raw materials. As a general tendency, when the reaction temperature is low, the reaction rate becomes slow, and when the reaction temperature is too high, the formation of side reactants tends to occur. Separation of the product is obtained by filtering and separating the target product precipitated in the reaction mixture. Separation may also be made easier by injecting water into the reaction mixture. The main component of the compound thus obtained is 4-nitroazobenzene. This compound is supplied as is or after further purification to the second stage of nitration. In the second step of nitration, 4-nitroazobenzene is nitrated to produce 4,4'-dinitroazobenzene and/or 4-nitroazobenzene.
4'-dinitroazoxybenzene is obtained.

This reaction is carried out by adding sulfuric acid and, if necessary, nitric acid to the reaction mixture containing 4-nitroazobenzene in the reactor at the end of the first stage reaction, or by changing reaction conditions such as reaction temperature. In the first step of the nitration reaction, the separated 4-nitroazobenzene is reacted with nitric acid and sulfuric acid.

In the second step of nitration, 4-nitroazobenzene is reacted with 4 to 40 molar equivalents of nitric acid. The concentration of nitric acid is conveniently within the range of specific gravity 1.12 to 1.52.
Sulfuric acid is used in an amount of O to 1.0 molar equivalent to nitric acid. Conveniently, the concentration of sulfuric acid used has a specific gravity of 1.8. The reaction temperature is carried out at -5 to 100[deg.] C., but it varies depending on the concentration of nitric acid and sulfuric acid and the ratio to the raw material 4-nitroazobenzene, and is not particularly limited to the above range.
However, when the reaction temperature is low, the reaction is slow, and when the reaction temperature is high, by-products other than the target product increase. Separation of the product is obtained by filtering and separating the target product precipitated in the reaction mixture. The main component of the compound obtained here is 4,4'-dinitroazobenzene, and may also contain 4,4'-dinitroazoxybenzene, 4-nitroazobenzene, and 4-nitroazoxybenzene. All of these compounds are hydrogenated and converted into p-phenylenediamine in the second step. The hydrogenation reaction in the second step involves hydrogenolyzing the 4,4'-dinitroazobenzene and 4,4'-dinitroazoxybenzene obtained in the first step with molecular hydrogen in the presence of a hydrogenation catalyst. - It produces phenylenediamine.

In the second step of this reaction, 4,4'-dinitroazobenzene and 4,4'-dinitroazoxybenzene are dissolved or suspended in a suitable solvent. A hydrogenation catalyst is added to this to prepare a reaction solution. This is brought into contact with hydrogen at a predetermined temperature with stirring to cause a reaction. In addition, if necessary, the reaction is carried out with hydrogen under high pressure in a pressure-resistant reactor. The hydrogenation catalyst used in the present invention reduces the nitro group contained in 4,4'-dinitroazobenzene to an amino group, and hydrogenates the azo group and/or azoxy group to convert it into an amino group. It is necessary to have activity.

Many common hydrogenation catalysts are employed in the present invention to serve this purpose. For example, platinum group metals,
Catalysts include nickel, cobalt, copper, rhenium, and iridium. More specifically, platinum black, colloidal platinum, platinum oxide, palladium black, palladium carbon, palladium oxide, colloidal palladium, reduced nickel, Raney nickel, rhenium black, colloidal iridium, copper chromium oxide, molybdenum oxide, cobalt chromium oxide. etc. are listed. Among these, platinum group metals and nickel are particularly effective catalysts. In some cases, it is effective to increase the surface area of the catalyst and increase the reaction rate by attaching the catalyst to the carrier. From this point of view, the use of carriers is desirable in many cases. Examples of the carrier used include alumina, silica gel, diatomaceous earth, activated earth, asbestos, magnesium oxide, zinc oxide, chromium oxide, barium carbonate, and the like. These catalysts may be used alone or in combination. As for the amount of catalyst used in the present invention, a larger amount is advantageous in terms of increasing the reaction rate, but the amount used is determined by the type of catalyst, reaction conditions, and reaction operation.

The amount of catalyst generally used in the present invention is 4.4'
-Dinitroazobenzene and 4.4/-dinitroazoxybenzene are suitably used in an amount of 0.1 to 30% by weight, but are not limited to this range in any way. The solvent used in the present invention needs to be stable without causing reactions such as hydrogenation in the reaction system, and such a solvent can be used in many cases, but the raw material 4
- It is more preferable if it can dissolve 4'-dinitroazobenzene and/or 4.l-dinitroazoxybenzene well.

When water is used as a solvent or a mixed solvent, unintended side reactions may sometimes occur in strong acidity. Examples of the solvent used include water, methanol, ethanol, dioxane, tetrahydrofuran, benzene, ether, acetic acid, enal acetate, dimethylformamide, and the like. Molecular hydrogen, which is industrially produced in large quantities, is sufficient as the hydrogen used in the present invention.

Hydrogen is the raw material 4,4'-dinitroazobenzene and (nuha)! A container containing 4,4'-dinitroazoxybenzene, a hydrogenation catalyst and a solvent is charged and used for the reaction. The charging hydrogen pressure varies depending on the hydrogenation catalyst used, the reaction temperature, and the weight of the raw materials to be charged, but it is convenient to charge the hydrogen at 1 to 150 atm, but the hydrogen pressure is not limited to this range in any way. A higher value is desirable in terms of accelerating the reaction rate. Hydrogen can be charged in the amount necessary for reduction from the beginning, or as the amount of hydrogen consumed as the reaction progresses, it can be replenished with an amount equivalent to this consumption, or a larger or smaller amount than the consumed amount. The reaction temperature in the present invention varies depending on the type of hydrogenation catalyst used, hydrogen pressure, etc., and is generally 10
~300°C, but is not limited to this range in any way.

Although it depends on the type of catalyst, if the reaction temperature is too low, the reaction may be slow, stop at a reaction intermediate, or not proceed at all. On the other hand, if the reaction temperature is too high, unintended reactants, such as by-products such as hydrides of aromatic nuclei and diarylamine, may be produced. The end point of the reaction is generally determined by the decrease in the amount of hydrogen charged.

That is, the absorption of the calculated amount of hydrogen is measured by the absorption capacity in reactions at normal pressure, and by the decreasing pressure of the manometer in pressurized reactions. The advantage of this reaction is that azobenzene is used as a raw material, and a nitro group is introduced at the p-1 position with respect to an azo group with high selectivity through nitration. Furthermore, the obtained nitroazobenzene is subjected to catalytic hydrogenation without any particular purification. p-phenylenediamine is produced and the product is easily separated from the reaction mixture.

That is, the separation of p-phenylenediamine produced with high selectivity from the reaction mixture after the completion of the reaction is easily carried out by evaporating the solvent of the solution obtained by filtering off the catalyst. Nu,
Separation and purification can be easily carried out by distilling a solution in which the catalyst has been over-separated. Furthermore, even if azobenzene is nitrated and 4-nitroazobenzene and 4-nitroazoxybenzene exist as intermediates in addition to the target 4,4'-dinitroazobenzene and 4,4-dinitroazoxybenzene, especially By hydrogenating the mixture without purification or removal, aniline is produced as a by-product from 4-nitroazobenzene and 4-nitroazoxybenzene, but p-phenylenediamine is produced. That is, the azobenzene nitration reaction mixture effectively converts the mixture of 4,4'-dinitroazoben, 4,1-dinitroazoxybenzene, 4-nitroazobenzene, and 4-nitroazoxybenzene after removing the nitrating agent. Since it can be used as a raw material for the desired synthesis of p-phenylenediamine, it has the advantage that separation and purification of the product from the nitration reaction of azobenzene does not require much effort. Examples will be described below.

Example 1 (~ First step) Azobenzene 4,57 and nitric acid (specific gravity 1.42) 25 ml were charged into a 100 ml glass reactor equipped with a stirrer, and the reaction was carried out at 50° C. for 5 hours with stirring.

The reaction mixture was filtered at room temperature to yield 5.07 g of dry solid. As a result of gas chromatographic analysis of this product, the yield based on azobenzene was 93% for 4-nitroazobenzene and 25% for 4,4'-dinitroazobenzene.
It was %. Next, in a 200 ml glass reactor equipped with a stirrer, the previously obtained reaction product 5.07 and nitric acid (specific gravity 1
．． 42) 30 ml and 30 ml of sulfuric acid (specific gravity 1.8) were charged, and the reaction was carried out at 15 to 20°C for 3 hours with stirring.

The reaction mixture was filtered at room temperature to obtain 6.6y of dry solid after washing with water. As a result of gas chromatographic analysis of this product, the yield of 4,41-dinitroazobenzene based on the initial raw material azobenzene was 83.5%.
The contents were 5% of 4-nitroazobenzene, 7% of 4-nitroazoxybenzene, and 1% of 4,4'-dinitroazoxybenzene. (B) Second step Next, 6.6 ml of the solid obtained in the first step was placed in a 500 m1 pressure-resistant reactor equipped with a stirrer, a pressure gauge, a thermometer, and a gas inlet tube.
V, 0.17 Pd-carbon (containing 5% Pd) as a catalyst, and 200 ml of ethanol were charged.

Furthermore, after purging the inside of the airtight reactor with nitrogen, hydrogen was introduced from the gas introduction pipe at a pressure of 30 kg/Cd. The reaction was carried out in this reactor at 50° C. for 5 hours with stirring. After the reaction, excess hydrogen is released from the reactor.

Next, the reaction mixture is thoroughly filtered, and the solid catalyst is thoroughly washed with ethanol. The sap liquid and washed ethanol were combined and distilled. B. 4.77 fractions of pl57-160/13 muHg were obtained, M. pl is 45-147°C.

This fraction was determined by the 1R spectrum and gas chromatograph.
- Confirmed as phenylenediamine. The measurement conditions of the gas chromatograph are as follows. Filler Sil
lcOnSE-30 (manufactured by Nippon Chromato Industries) Impregnation rate 10
% Support "Dia Solid L" (manufactured by Nippon Chromato Kogyo) Column length Column inner diameter He flow rate Column temperature holding time 1 m 3 mm 50 m 1/min 4-Nitroazoben 1 minute Zen 4-nitroazoxy 1 minute 50 seconds Benzene 4,4'-dinitroa 3 minutes Zobenzene 4,4'-Dinitroa 3 minutes 45 seconds Zoxybenzene Example 2 (A) First step In a 200 ml glass reactor equipped with a stirrer, azobenzene 4657, 25 ml of nitric acid (specific gravity 1.42) and concentrated sulfuric acid (specific gravity 1.42) were added. 8) 25 ml was charged and the reaction was carried out at 5 to 10°C for 2 hours with stirring.

After the reaction, the reaction mixture was filtered and washed with water to obtain 6.47 g of a dried solid. As a result of gas chromatographic analysis of this product, the yield was 40% for 4,4'-dinitroazobenzene and 31% for 4-nitroazoxybenzene based on the starting material azobenzene. (B) Second step This was carried out using the same equipment and operation as in Example 1 (B).

That is, the solid obtained in the first step 6.4V, stabilized nickel 0
．． 37 and 200 ml of tetrahydrofuran were charged, and the reaction was further carried out for 5 hours at a hydrogen pressure of 80k9/c and a reaction temperature of 120°C. The solution obtained by filtering off the catalyst from the reaction mixture is distilled and B. 3.47 fractions with a pl of 56-160/13 mmHg were obtained. The pl was 45 to 147 g.

This fraction is 1. It was confirmed to be p-phenylenediamine from the R spectrum and gas chromatography results. Example
3 (A) First step Into a 100 ml glass reactor equipped with a stirrer, 4.57 ml of azobenzene, 10 ml of nitric acid (specific gravity 1.42) and 2 ml of concentrated sulfuric acid (specific gravity 1.8) were charged, and the mixture was heated at 40°C for 6 hours. The reaction was carried out under stirring.

Next, while maintaining the reaction mixture in the reactor at 15-16°C, 5 ml of nitric acid (specific gravity 1.42) and sulfuric acid (specific gravity 1,8
) Add 10 ml of the mixture under stirring. The reaction was further carried out at this temperature for 6 hours. The reaction mixture is filtered,
After washing with water and recrystallizing with acetic acid, orange crystals 5.3
'y' was obtained, M. It is p222.

This one is 1. 4.4 from R vector! - Confirmed as dinitroazobenzene. (B) Second step The second step was carried out using the same equipment and operation as in Example 1 (B).

Claims (1)

[Claims] 1 In the first step, azobenzene is treated with nitric acid, and the obtained 4,4'-dinitroazobenzene and/or 4.
A method for producing p-phenylenediamine, which comprises hydrogenolyzing 4'-dinitroazoxybenzene with molecular hydrogen in the presence of a catalyst in the second step.