GB1576608A

GB1576608A - Catalytic reduction of nitronaphthalene sulphonic acids

Info

Publication number: GB1576608A
Application number: GB50645/75A
Authority: GB
Original assignee: Imperial Chemical Industries Ltd
Current assignee: Imperial Chemical Industries Ltd
Priority date: 1975-12-10
Filing date: 1975-12-10
Publication date: 1980-10-08

Description

(54) CATALYTIC REDUCTION OF NITRONAPHTHALENE SULPHONIC ACIDS (71) We, IMPERIAL CHEMICAL INDUSTRIES LIMITED, Imperial Chemical House, Millbank, London SWIP 3JF, a British Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a chemical reduction process and more particularly to a catalytic reduction process for the manufacture of aminonaphthalene sulphonic acids.

It is well known to reduce nitronaphthalene sulphonic acids to the corresponding naphthylamine sulphonic acids by contacting with iron and mineral acid. This process sometimes produces difficulties in filtration and disposal of the iron oxide formed, and it is desirable to find an alternative method which does not pose these problems.

Catalytic hydrogenation using small amounts of such well-known catalysts as Raney nickel or palladised carbon provides one potential alternative. Unfortunately, unpurified nitronaphthalene sulphonic acids contain compounds which can poison the catalyst and affect their activity. This is particularly evident in systems where all the nitro and catalyst are charged prior to reduction. Rates of reduction can be much slower than normal allowing build up of reduction intermediates such as azoxy compounds, these being very difficult to reduce further to amine. It has now been found that these difficulties can be overcome and the nitronaphthalene sulphonic acids reduced by hydrogenation catalysts by introducing the nitro compound into a reduction chamber containing the catalyst and hydrogen under pressure at a rate substantially equal to that at which hydrogenation takes place.

As examples of nitronaphthalene sulphonic acids which can be reduced by the new process there may be mentioned more especially those of the general formula:

where X represents H, halogen, NO2 or SO3H, and Y represents H, halogen or SOCH.

As specific examples of these, there may be mentioned: 8 - nitronaphthalene - 1,3,6 - trisulphonic acid 8 - nitronaphthalene - 1 - sulphonic acid 8 - nitronaphthalene - 1,6 - disulphonic acid.

The nitronaphthalene sulphonic acids may be in an unpurified form, in which case the process of the invention minimises the difficulties previously experienced.

Metals which may be used as hydrogenation catalysts are the metals of Group VIII in Meldeleef's Period System of the Elements especially cobalt, nickel, platinum and palladium. Nickel and palladium are the preferred metals. The art of preparing such metals in a catalytically active form is well known. In the process of the invention the metal catalysts may be used in supported or unsupported form.

More particularly the following catalysts are usable: Raney nickel, Raney cobalt,.pjatinum black, nickel-on-kieselguhr, cobalt-onkieselguhr, platinised charcoal, palladised charcoal. The preferred catalyst is Raney nickel.

The amount of catalyst used and the conditions used for reduction are factors defending mainly on the catalyst used. It is well known, for example, that Raney nickel is less effective as a hydrogenation catalyst than palladium or platinum and must be present in a larger amount and/or the hydrogenation must be carried out under higher pressure and/or higher temperature than if the latter two are used.

The process can conveniently be carried out in hydrogenation autoclaves fitted for pump feeding and preferably one fitted with agitation and means for gas recirculation.

Prior to introducing the nitronaphthalene sulphonic acid, the catalyst preferably in a small amount of water, is charged to the autoclave and the latter is closed, swept free from oxygen, pressurised with hydrogen and heated to the desired temperature.

Using Raney nickel as catalyst, e.g. a suitable amount is from 0.1-10%, preferably 0.53 /n by weight of the total amount of nitronaphthalene sulphonic acid to be reduced. Suitable reduction conditions are, e.g. from 70--1500C, preferably 95--1300C, and a pressure up to 600 p.s.i.g., preferably 150300 p.s.i.g.

The nitronaphthalene sulphonic acid is preferably reduced in the form of an alkali metal salt, preferably the sodium salt and can conveniently be introduced into the autoclave by pumping in an aqueous slurry of the salt, preferably a slurry containing from 20 to 33 /n by weight of the salt, circulation of hydrogen being continued at such a rate that the hydrogen pressure is maintained fairly constant. The reduction process is exothermic and this factor should be taken into consideration as the reduction proceeds. Samples of the liquor may be taken from the autoclave at intervals to ensure that there is no build-up of nitro compound.

Provided that a proper balance of feed rate and reduction conditions is maintained, the process is completed shortly after that last of the nitronaphthalene sulphonic acid has been fed to the autoclave and the latter can be discharged and the contents be worked up by filtration of the catalyst and isolation of the amine sulphonic acid by acidification of the filtrate.

The invention may be illustrated but is not limited by the following Example in which parts and percentages are by weight.

Example Into a hydrogenation autoclave fitted for pump feeding and equipped with agitation and gas circulation, there is charged 41 parts of a Raney nickel catalyst in 2000 parts of water. The autoclave is sealed, purged with nitrogen then hydrogen and pressurised to 200 psig with hydrogen. Agitation and gas circulation are commenced and the autoclave contents are heated to 1300C.

11000 parts of a 25.0% aqueous slurry of 8 nitronaphthalene - 1,3,6 - trisulphonic acid trisodium salt, pH 7.5-9.5, are then pumped into the autoclave over 2 hours maintaining temperature at l30+50C and pressure 200+50 psig. Evolution of heat is observed to cease directly after termination of pumping and reduction is complete. The autoclave contents are discharged, filtered free of catalyst to yield 8 - aminonaphthalene - 1,3,6 - trisulphonic acid trisodium salt, (12900 parts at 19.5% w/w) equivalent to a yield of 99.0 /n. The product can be isolated in paste form by the addition of sulphuric acid (1420 parts) to yield Koch Acid (7226 parts at 30.0% w/w) equivalent to an isolated yield of 85.0%.

WHAT WE CLAIM IS: 1. A process for reduction of nitronaphthalene sulphonic acids to the corresponding aminonaphthalene sulphonic acids by catalytic reduction, wherein the nitronaphthalene sulphonic acid is introduced into a reduction chamber containing the hydrogenation catalyst and hydrogen under pressure at a rate substantially equal to that at which hydrogenation takes place.

2. A process as claimed in claim 1 wherein there is used a nitronaphthalene sulphonic acid of the formula:

where X is H, halogen, NO2 or SO3H and Y is H, halogen or SO3H.

3. A process as claimed in claim 1 or claim 2 wherein there is used a platinum or nickel catalyst.

4. A process as claimed in claim 3 wherein there is used a Raney nickel catalyst.

5. A process as claimed in claim 4 wherein the amount of Raney nickel used is from 0.5-3% by weight of the total amount of nitronaphthalene sulphonic acid to be reduced.

6. A process as claimed in claim 4 or claim 5 wherein the reduction is carried out at a temperature of from 95 to 1300C and at a pressure of from 150 to 300 p.s.i.g.

7. A process as claimed in any preceding claim substantially as herein described with reference to and as illustrated by the Example.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

present in a larger amount and/or the hydrogenation must be carried out under higher pressure and/or higher temperature than if the latter two are used.

The process can conveniently be carried out in hydrogenation autoclaves fitted for pump feeding and preferably one fitted with agitation and means for gas recirculation.

Prior to introducing the nitronaphthalene sulphonic acid, the catalyst preferably in a small amount of water, is charged to the autoclave and the latter is closed, swept free from oxygen, pressurised with hydrogen and heated to the desired temperature.

Using Raney nickel as catalyst, e.g. a suitable amount is from 0.1-10%, preferably 0.53 /n by weight of the total amount of nitronaphthalene sulphonic acid to be reduced. Suitable reduction conditions are, e.g. from 70--1500C, preferably 95--1300C, and a pressure up to 600 p.s.i.g., preferably 150300 p.s.i.g.

The nitronaphthalene sulphonic acid is preferably reduced in the form of an alkali metal salt, preferably the sodium salt and can conveniently be introduced into the autoclave by pumping in an aqueous slurry of the salt, preferably a slurry containing from 20 to 33 /n by weight of the salt, circulation of hydrogen being continued at such a rate that the hydrogen pressure is maintained fairly constant. The reduction process is exothermic and this factor should be taken into consideration as the reduction proceeds. Samples of the liquor may be taken from the autoclave at intervals to ensure that there is no build-up of nitro compound.

Provided that a proper balance of feed rate and reduction conditions is maintained, the process is completed shortly after that last of the nitronaphthalene sulphonic acid has been fed to the autoclave and the latter can be discharged and the contents be worked up by filtration of the catalyst and isolation of the amine sulphonic acid by acidification of the filtrate.

The invention may be illustrated but is not limited by the following Example in which parts and percentages are by weight.

Example Into a hydrogenation autoclave fitted for pump feeding and equipped with agitation and gas circulation, there is charged 41 parts of a Raney nickel catalyst in 2000 parts of water. The autoclave is sealed, purged with nitrogen then hydrogen and pressurised to

200 psig with hydrogen. Agitation and gas circulation are commenced and the autoclave contents are heated to 1300C.

11000 parts of a 25.0% aqueous slurry of 8 nitronaphthalene - 1,3,6 - trisulphonic acid trisodium salt, pH 7.5-9.5, are then pumped into the autoclave over 2 hours maintaining temperature at l30+50C and pressure 200+50 psig. Evolution of heat is observed to cease directly after termination of pumping and reduction is complete. The autoclave contents are discharged, filtered free of catalyst to yield 8 - aminonaphthalene - 1,3,6 - trisulphonic acid trisodium salt, (12900 parts at 19.5% w/w) equivalent to a yield of 99.0 /n. The product can be isolated in paste form by the addition of sulphuric acid (1420 parts) to yield Koch Acid (7226 parts at 30.0% w/w) equivalent to an isolated yield of 85.0%.

WHAT WE CLAIM IS: 1. A process for reduction of nitronaphthalene sulphonic acids to the corresponding aminonaphthalene sulphonic acids by catalytic reduction, wherein the nitronaphthalene sulphonic acid is introduced into a reduction chamber containing the hydrogenation catalyst and hydrogen under pressure at a rate substantially equal to that at which hydrogenation takes place.
2. A process as claimed in claim 1 wherein there is used a nitronaphthalene sulphonic acid of the formula:

where X is H, halogen, NO2 or SO3H and Y is H, halogen or SO3H.
3. A process as claimed in claim 1 or claim 2 wherein there is used a platinum or nickel catalyst.
4. A process as claimed in claim 3 wherein there is used a Raney nickel catalyst.
5. A process as claimed in claim 4 wherein the amount of Raney nickel used is from 0.5-3% by weight of the total amount of nitronaphthalene sulphonic acid to be reduced.
6. A process as claimed in claim 4 or claim 5 wherein the reduction is carried out at a temperature of from 95 to 1300C and at a pressure of from 150 to 300 p.s.i.g.
7. A process as claimed in any preceding claim substantially as herein described with reference to and as illustrated by the Example.
8. Aminonaphthalene sulphonic acids

whenever obtained by a process claimed in any of claims 1 to 7.