GB2122607A - Preparation of o-phenylenediamine - Google Patents

Abstract

The preparation of o- phenylenediamine by hydrogenation of compounds of the general formula (I> <IMAGE> in which X stands for hydrogen or chlorine, in the presence of a hydrogenation catalyst, is characterized in that hydrogenation is performed in the presence of 30 to 70% of ammonia and 10 to 50% of water. In this manner the use of inflammable solvents can be avoided, the ammonium chloride by- product can easily be eliminated and made use of, and as a starting material the reaction mixture obtained by the amination of the compounds of the general formula (II> <IMAGE> wherein X has the same meaning as defined above, which contains the compounds of the general formula (I) can be directly used, without the isolation of the compounds of formula (I).

Description

SPECIFICATION Process for the preparation of o-phenylenediamine The invention relates to a new process for the preparation of o-phenylenediamine, a useful intermediate for the production of pharmaceutically active compounds and plant protecting agents. More particularly, the invention concerns a new process for the preparation of o-phenylenediamine starting from compounds of the formula (I)

in which X stands for hydrogen or chlorine, which are reduced with hydrogen or a hydrogen-containing gas in an aqueous, ammoniacal medium, in the presence of an active hydrogenating catalyst to give the desired end product.

According to the known methods o-phenylenediamine is generally prepared by reducing o-nitroaniline.

The reduction is conventionally carried out in an aqueous medium with iron, zinc or tin [Winnacker-Küchler: KBmaia technol6gia 1.742-748, Muszaki Könyvkiadó, Budapest, 1962] or a sodium sulfide solution [FIAT Final Report No. 1313] as a reducing agent.

According to the more recent publications o-nitroaniline is reduced by catalytic hydrogenation, which may be performed in a vapour phase, in the presence of copper (Brown, Carrick: J. Am. Chem. Soc. 41,439) or palladium-on-Fuller earth catalyst [British Patent No. 1,077,920], or in liquid phase, in a solvent, using Raney nickel [Chem. Zvesti 2, (1948)] or palladium or platinum catalysts on a carrier [Published German Patent Application No. 2,461,615; United States Patent Specification No.3,230,259] as a catalyst.

o-Phenylenediamine can be prepared also by reducing o-dinitrobenzene, this starting material is, however, practically not available on industrial scale.

The preparation of o-phenylenediamine by the ammonolysis of o-dichlorobenzene is the object of more Japanese patents [Japanese Patent Specifications Nos. 77,95,615-77,95,617]. At 200 OC, in the presence of a copper oxide catalyst ammonolysis takes about 16 hours.

The amination of aniline to o-phenylenediamine at 350 "C, 300-400 bar, in the presence of a nickel catalyst containing Mg-, Sr- and Zn-oxides can be accomplished only with moderate yields [Published German Patent Specification No. 2,114,170].

The non-catalytic reductions of o-nitroaniline are disadvantageous due to the formation of a large amount of by-products and waste water, which are difficult to tackle. Of the catalytic methods the vapour phase reductions are carried out at temperatures exceeding 250 "C, which should be further increased if an increased pressure is employed to accelerate the hydrogenation reaction.

The liquid phase methods, using suspension catalysts have been almost exclusively performed discontinuously. According to these methods o-nitroaniline is dissolved in suitable organic solvents (aromatic hydrocarbons, esters or alcohols), the catalysts are suspended in the solution and hydrogenation is performed under vigorous stirring. The realization of these methods on industrial scla involves the regeneration of a substantial amount of organic solvents.

o-Nitroaniline is an intermediate which has been prepared in more reaction steps, therefore the most valuable methods for the preparation of o-phenylenediamine are those which start from benzene as a starting material or an earlier intermediate (chlorobenzene, nitrobenzene) and lead to the desired end product in more steps. A common disadvantage of these methods which afford o-phenylediamine through o-nitroaniline is that when preparing the o-bifunctional intermediate (o-chloro-nitro-benzene, o-nitroacetanilide), a double amount of p-intermediate may also be formed, and this by-product decreases the yield.

The process disclosed in the Hungarian Patent Specification No. 175,397 by which o-phenylenediamine is prepared by the nitration of p-dichlorobenzene, a subsequent amination and catalytic hydrogenation, is devoid of this drawback and does not produce by-products.

The syntheses which provide o-phenylenediamine not through o-nitroaniline but a different route have not gained much use in the practice, due to the unaccessability of the starting materials or because of the extreme reaction conditions required and the small yields obtained.

As an industrial process amination of o-chloro-nitrobenzene and reduction of the o-nitroaniline obtained is most widely used. In this process o-chloro-nitro-benzene forms as an isomeric product together with p-chloro-nitro-benzene, hence its utilization depends of the possibility of the utilization of p-chloro-nitrobenzene. If this probleme is solved, o-phenylenediamine can advantageously be prepared by this process.

After a detailed review of the state of art we can conclude that of the known processes those based on the catalytic hydrogenation of o-nitroaniline prepared from o-chloro-nitro-benzene, and 2-nitro-4-chloro-aniline prepared from p-dichlorobenzene appear the most advantageous.

In our experiments we have suprisingly found that the hydrogenation can be performed more advantageously in an aqueous medium containing 40 to 90 %, preferably 50 to 60 % of ammonia than in an organic medium. The aqueous solutions containing more than 40 % of ammonia, particularly over 100 %, form a homogenous reaction mixture with the organic reactants; e.g. compounds of the general formula (I), in which X stands for hydrogen or chlorine and a mixture containing 30 % of ammonia, 30% of water and about 20 % of 2-nitro-4-chloro-aniline form a single, homogeneous liquid phase, over 100 C. In addition, the presence of ammonia, since it ensures a constant pH-value in the medium, has a positive influence on the activity of the palladium-on-activated carbon catalyst. If the hydrogenation is accompanied by the hydrogenolysis of the halogen, the high excess of ammonia absorbs the hydrochloric acid split off and at the same time keeps the ammonium chloride by-product formed in solution. If organic solvents are employed, a precipitation of salts is expected, which may cause considerable difficulties, especially in equipments operated continuously, under pressure.The excess of ammonia can easily be blowed off from hydrogenation mixtures the temperature of which exceeds 100 "C, and from the remaining aqueous solution o-phenylenediamine precipitates during cooling in a crystalline form, while ammonium chloride remains in the solution. The efficiency of the separation of o-phenyienediamine and the ammonium chloride by-product can further be increased by extraction methods.

The separation by extraction can be performed also by omission of the previous crystallization step, in this case the separated o-phenylenediamine and ammonium chloride solutions are subjected to further manufacturing.

The use of an aqueous ammoniacal medium has also an additional important advantage. Compounds of the general formula (I) are almost exclusively prepared by the ammonlysis of the compounds of the general formula (II)

wherein in the formulae X stands for hydrogen or chlorine. The ammonlysis should be carried out in the presence of an excess amount of ammonia. The compounds of the general formula (i) are conventionally isolated by boiling off ammonia and separating the ammonium chloride by-product formed. If the preparation of o-phenylenediamine by hydrogenation is coupled with the ammonolytic preparation of the compounds of the general formula (I), the latter compounds need not be isolated.The mixture of ammonia, water, compound of the general formula (I) and the ammonium chloride by-product, produced by the reaction, in which the amination has taken place can directly be lead into the hydrogenation reactor, where the compounds of the general formula (I) can be converted into o-phenylenediamine by hydrogenation, after the addition of an aqueous suspension of the hydrogenating catalyst and the introduction of hydrogen gas, and the reaction mixture remains homogeneous. In view of the fact that o-phenylenediamine can be prepared the most advantageously by these amination and hydrogenation steps, the combination of the two steps has essential technical advantages.

According to the invention o-phenylenediamine is prepared by admixing a compound of the general formula (I) with an aqueous solution containing 50 to 60 % of ammonia, in an apparatus equipped with a stirrer, under pressure, at a temperature of 100 "C, to form a homogeneous mixture, adding 0.05 to 2 % of a 5-10 % palladium-on-activated carbon catalyst, as a 1 to 10 % aqueous suspension, and carrying out hydrogenation by introducing hydrogen or a hydrogen-containing gas at 100 to 160 'C, under a pressure of 60 to 200 bar. Under these conditions in 20 to 60 minutes a more than 98 % conversion can be achieved.The excess of ammonia is blown off from the hydrogenated reaction mixture while hot, the catalyst is eliminated by filtration and at least 80 % of the o-phenylenediamine formed is isolated from the solution by cooling, crystallization and filtration. o-Phenylenediamine is separated from the mother liquor by solvent extraction.

Ammonium chloride remains in the aqueous solution and can be isolated by evaporation in a crystalline form. In this way ammonium chloride is isolated in an industrially utilizable form, on the other hand, the water is released from its inorganic salt content, which would otherwise have a harmful effect on the environment.

For solvent extraction, a chlorinated hydrocarbon, e.g. chloroform, 1 2-dichloroethane, trichloroethylene, perchloroethylene, 1 ,1,2-trichloroethane or benzene, toluene, ethers of esters can be used. If the extraction separation is performed after blowing off the ammonia, without crystallization of o-phenylenediamine, the total amount of o-phenylenediamine is isolated from the solvent phase, by crystallization or evaporation.

Hydrogenation can be accomplished discontinuously, in a reactor equipped with a stirrer, or in a cascade reactor obtained by connecting such reactors with each other, or continuously, in a column or pipe reactor.

In the reactor the catalyst is kept in a suspension phase by mechanical or gas stirring. From the gas passed through the reactor ammonia is regenerated by washing off by aqueous absorption under pressure, and hydrogen is blown off or recycled. Instead of hydrogen hydrogen-containing ammonia synthesis gas can also be employed.

According to a preferred embodiment of the process according to the invention the hydrogenation is directly connected with the amination reaction. In this case a compound of the general formula (II) is admixed with an aqueous solution containing 70 to 90 % of ammonia to form a homogeneous mixture, and amination is performed at a temperature of 180 to 220 "C. The amination can be carried out discontinuously or continuously. After a reaction time of 20 to 40 minutes, the reaction mixture is cooled to 100 to 160 "C and is introduced into the hydrogenation reactor, in which the suspension of catalyst and the introduction of hydrogen are carried out as described above.

The operation of a continuous experimental apparatus for a combined performance of amination and hydrogenation is illustrated on the attached flow sheet.

o-Chloro-nitro-benzene or 2,5-dichloro-nitro-benzene is fed from the container 2 by the pump 6 and the concentrated aqueous ammonia solution is fed from the container 3 by the pump 7. After admixture the homogenous, liquid phase reaction mixture is fed into the aminating pipe reactor 9, where amination takes place at 200 to 220 "C. The reaction mixture containing ammonia, water, ammonium chloride and o-nitroaniline or 2-nitro-4-chloro-aniline is cooled to 100 to 160 C in a heat exchanger and is led to the bottom of the hydrogenating reactor 11. To the same part of the reactor an aqueous suspension of the palladium-on-activated carbon catalyst is fed from the feeding container 4 by the pump 8. The hydrogen gas is also fed at the bottom of the hydrogenating reactor, under a pressure of 60 to 200 bar.The reaction mixture leaving the hydrogenating reactor 11 enters the separator 12, where the hydrogen gas saturated with ammonia is separated from the liquid phase, which contains the catalyst. The gas is led into the absorber 13, which is under pressure, where ammonia is washed off with water. The regenerated aqueous ammonia solution can be repeatedly utilized after concentration with fresh ammonia. From the separator 12 the liquid phase is continuously led into the ammonia boiler 14. The ammonia gas leaving the ammonia boiler 14 is led into the absorber 13, where it is absorbed.From the liquid phase discharged from the ammonia boiler 14 the catalyst is filtered off through the filter 17, whereupon the hot, saturated solution containing o-phenylenediamine and ammonium Chioride is fed into the counter-stream reactor 15, in which o-phenylenediamine is extracted by the solvent fed by means of the feeding pump 5. The liquid solution containing only ammonium chloride is led into the container 19. From the extractor 15 a hot solvent solution, saturated with o-phenylenediamine is passed into the crystallizer 16, where it is cooled down. The o-phenylenediamine end product is separated by the filter 18. The product is collected in the container 21.

The mother liquor passed through the filter 18, which contains about 2 to 5 % of o-phenylenediamine is collected in the container 20 and if desired, is subjected again to extraction.

Further details of the invention are illustrated by the following Examples, which are given for illustration and not limitation of our invention.

Example 1 13.8 g of o-nitroaniline are weighed into a high-pressure vessel equipped with a stirrer and heating, 18 g.

of water are added followed by the addition of 28 g. of liquid ammonia from a feeding vessel under pressure, after the vessel containing o-nitroaniline has been sealed. The content of the vessel is heated up to 100 "C under stirring. 40 mg. of a 10% palladium-on-activated carbon catalyst are suspended in 10 g. of water and the suspension is poured into a hydrogenating reactor of 0.2 dm3. equipped with a heating jacket and a perforated gas distributor. The catalyst is kept in a suspension phase by gas stirring. The temperature of the reactor is adjusted to 130 "C, the pressure is kept at 100 bar and the mixture of o-nitroaniline, ammonia and water is pumped into the hydrogenating reactor by nitrogen overpressure.After 40 minutes hydrogen stream is stopped and the ammonia is blown off through a valve by boiling. The content of the reactor is then discharged and the catalyst is eliminated by filtration. From the hot, saturated aqueous solution 8 g. of crystalline o-phenylenediamine are filtered off, melting at 101 "C after drying. By evaporating the mother liquor a further 2.6 g. portion of the product is obtained melting at 98 "C.

Example 2 To 17.2 g. of 2-nitro-4-chloroaniline 18 g. of water and 28 g. of liquid ammonia are given under stirring, at 100 "C, as described in Example 1. To a hydrogenating reactor described in Example 1 a suspension of 100 mg. of a 10% palladium-on-activated carbon catalyst in 10 g. of water is added. After hydrogenation for 60 minutes following the procedure described in Example 1, termination of the overpressure, boiling off ammonia and filtering off the catalyst 8.5 g. of o-phenylenediamine are separated from the solution by filtration. The mother liquor is extracted with three 20-mI. portions of chloroform. Evaporation of the chloroform solution affords a further 2 g. portion of o-phenylenediamine. By evaporation of the aqueous phase 5 g. of crystalline ammonium chloride are separated.

Example 3 15.8 g. of o-chloro-nitro-benzene are fed intio a 120-ml. autoclave made of stainless steel. 30 g. of liquid ammonia and 8 g. of water are added. The autoclave is cooled to 220 "C with shaking. Into a hydrogenation reactor according to Example 1 a suspension of 80 mg. of a 5 % palladium-on-activated carbon catalyst in 20 g. of water is added. Hydrogen flow is started, the temperature is adjusted to 140 "C and the pressure to 100 bar, and the reaction mixture is pumped into the hydrogenating reactor. After 40 minutes the gas stream is terminated, the ammonia is boiled off, catalyst is separated from the hot reaction mixture by filtration and the filtrate is extracted with five 20-ml. portions of benzene.By evaporating the benzene solution 10.2 g. of o-phenylenediamine melting at 99 "C are isolated.

Example 4 The amination and hydrogenation described in Example 1 are performed with 19.3 g. of 2,5-dichloro-nitrobenzene. For the amination 30 g. of liquid ammonia and 8 g. of water are employed. Amination is carried out at a temperature of 200 "C for 20 minutes. In the hydrogenation process a suspension of 200 mg. of a 10 % palladium-on-activated carbon catalyst in 20 g. of water is employed. Hydrogenation is carried out at 120 "C, under a pressure of 80 bar for 60 minutes. The reaction mixture released from ammonia is extracted with 1,2-dichloroethane, after filtering off the catalyst. For the extraction three 20-ml. portions of the solvent are used.By evaporating the solvent 10.3 g. of o-phenylenediamine are isolated, having a melting point of 100 "C. By evaporating the aqueous phase 10.1 g. of ammonium chloride are isolated.

Example 5 In an equipment according to the attached flow sheet o-phenylenediamine is manufactured continuously.

Into a pipe reactor of 2 dm3 heated up to 200 "C on an oil bath 1000 g. of a melt of 2,5-dichloro-nitro-benzene and 2300 g. of a 80 % aqueous ammonia solution are fed pro hour, by the feeding pumps 6 and 7, respectively. The mixture leaving the reactor is cooled to 130 "C and is pumped into the hydrogenating reactor 11, in which the temperature is adjusted to 130 'C by hot water kept under pressure in the heating jacket. Into the reactor a suspension of 8 g. of a 10 % palladium-on-activated carbon catalyst in 1100 ml. of water is added by the pump 8. The reactor pressure is 150 bar. The liquid phase discharged from the separator 12 is released from ammonia in the boiler 14, whereupon the catalyst is separated on the filter 17 and is recycled for repeated use.From the hot, saturated solution of the product o-phenylenedamine is extracted by 1500 ml. of 1,2-trichloroethane pro hour, in the counter-flow, continuous extractor 15. By means of the crystallizer 16 and the filter 18, after aid drying 530 g./hour o-phenylenediamine are separated, melting at 100 "C. The aqueous ammonium chloride solution is collected in the tank 19. By evaporation 280 g of ammonium chloride/1000 ml. of solution are isolated in a crystallineform.

Example 6 In an equipment according to Example 5 using 820 g. of o-chloro-nitro-benzene, 2300 g. of a 80 % aqueous ammonia solution, 6 g. of a 5 % palladium-on-activated carbon catalyst suspended in 1100 ml. of water and 1500 ml. of recycled 1 ,2-dichloro-ethane extracting agent pro hour, keeping the temperature at 220 "C in the aminating reactor and at 150 "C, under a pressure of 150 bar in the hydrogenating reactor, the process described in Example 5 affords 543 g. of o-phenylenediamine pro hour, melting at 101 "C.

The main advantages of the process according to the invention 1. Due to the use of aqueous ammonia the process can be performed in the absence of inflammable solvents.

2. Ammonia, which is required for the hydrogenolysis of chlorine in addition to the adjustment of the pH of the reaction mixture provides a homogenous reaction mixture.

3. In the presence of ammonia as a result of the hydrogenolysis of chlorine ammonium chloride is formed, which is a useful by-product and its disposing does not cause environmental problems.

4. Following the process according to the invention the compound of the general formula (I) prepared by amination (X=H or Cl) need not be separated and dissolved again in a solvent for hydrogenation.

5. The process can advantageously be used for a continuous performance of the hydrogenation step, which used to be carried out discontinuously.

Claims (12)

1. Process for the preparation of o-phenylenediamine from the compounds of the general formula (I)

in which X stands for hydrogen or chlorine by reduction with hydrogen or a hydrogen-containing gas, in the presence of an activated hydrogenating catalyst, which comprises carrying out hydrogenation in the presence of 30 to 70 % of ammonia and 10 to 50 % of water, releasing the solution obtained from ammonia, filtering off the catalyst and isolating the product by solvent extraction and/or crystallization.

2. A process as claimed in claim 1, in which hydrogenation is carried out in the presence of 40 to 50 % of ammonia and 30 to 40 % of water.

3. A process as claimed in claim 1, in which hydrogenation is carried out continuously.

4. A process as claimed in any one of claims 1 to 3, in which compounds of the general formula (I), wherein X has the same meaning as defined in claim 1, are used in a reaction mixture obtained by the amination of compounds of the general formula (II)

wherein X has the same meaning as defined above, without isolation.

5. A process for the preparation of o-phenylenediamine, which process comprises hydrogenating a compound of the general formula (I)

wherein X represents hydrogen or chlorine, in the presence of an aqueous ammonia solution, the ammonia content of the solution being such that the solution forms a homogeneous mixture with the said compound of the formula (I).

6. A process as claimed in claim 5, wherein the ammonia content of the solution is at least 40%.

7. A process as claimed in claim 6, wherein the ammonia content of the solution is from 40 to 90%.

8. A process as claimed in claim 7, wherein the ammonia content of the solution is from 50 to 60%.

9. A process as claimed in claim 5, wherein the reaction mixture contains, by weight, 30 to 70% ammonia and 10to50%water.

10. A process substantially as hereinbefore described in connection with the accompanying drawing.

11. A process substantially as herein before described in any one of Examples 1 to 6.

12. o-phenylene diamine when made by a process as claimed in any one of claims 1 to 11.