DE1185623B - Process for the preparation of alkyl hydroxylamines - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Class: C 07 c

German class: 12 q -13

Number: 1185 623

File number: P 29453IV b / 12 q

Filing date: May 21, 1962

Opening day: January 21, 1965

Attempts have already been made several times by catalytic hydrogenation of corresponding nitroalkanes Manufacture alkyl hydroxylamines. The Swiss patent specification 325 080 describes a process in which the reduction of the nitroalkanes in an organic diluent such as a saturated one Hydrocarbon, alcohol, ether or in water. In this procedure However, the yield does not meet the expectations, especially because it does not it is possible to stop the reduction at the N-alkylhydroxylamine stage. Rather, it runs usually further, so that the reaction product is contaminated by considerable amounts of amine.

The same disadvantage of the excessive reduction also applies to the German method Auslegeschrift 1028 088 according to which aliphatic or cycloaliphatic nitro compounds to the corresponding hydroxylamines on catalysts made from silver oxide and hydrogenating agents Heavy metal oxides are hydrogenated.

Finally, the Austrian patent specification 188 326 describes an electrolytic reduction process, in the case of the nitroalkane in purely aqueous sulfuric acid solution to the corresponding alkylhydroxylamines be reduced.

Apart from the fact that basically a comparison between the electrolytic reduction process and the catalytic reduction process as used in the present invention finds, is not possible and therefore a transfer of the reaction conditions is not obvious, are also the results of this procedure are by no means satisfactory.

The disadvantages inherent in the processes outlined above are now avoided according to the invention that, for the preparation of alkylhydroxylamines with 1 to 3 carbon atoms in the alkyl part by catalytic hydrogenation of corresponding nitroalkanes over palladium catalysts at <? 5O ⁰ C, in particular ^ 3O ⁰ C, in acidic aqueous solution carries out the catalytic hydrogenation in the presence of at least one equivalent of H ₂ SO ₄ per mole of nitroalkane.

This procedure leads to very high yields of the N-alkylhydroxylamines without the reaction going any further to the alkylamine. It is believed that this selectivity is at least partially attributable to a poisoning effect of the sulfuric acid on the catalyst, which prevents the catalyst from reacting beyond the hydroxylamine stage
of alkyl hydroxylamines

Applicant:

E. I. du Pont de Nemours and Company, Wilmington, Del. (V. St. A.)

Representative:

Dr.-Ing. W. Abitz, patent attorney, Munich 27, Pienzenauer Str. 28

Named as inventor:
Donald Lee Smathers,
Landenburg, Pa. (V. St. A.)

Claimed priority:

V. St. v. America May 22, 1961 (111452)

to catalyze. It is further assumed that the sulfuric acid chemically during the reaction is bound and thus accelerates the formation of hydroxylamine.

The method according to the invention will likely proceed as follows:

2R-NOo

4H ₂

H ₂ SO ₄
(Pd: C)

(R-NHOH) ₂ -H ₂ SO ₄

The method according to the invention can be used using any nitroalkane having an alkyl group of not more than 3 carbon atoms be performed. One can therefore use:

Nitromethane,
Nitroethane,

1-nitropropane,
2-nitropropane.

The use of nitromethane is preferred. The nitroalkane is dissolved or suspended in aqueous sulfuric acid solution. There must be at least one equivalent weight of H ₂ SO ₄ per mole of nitroalkane

409 769/427

3 4

be present, d. i.e., on 61 g of nitromethane, solution or slurry of the nitroalkane meet

at least 49 g of H ₂ SO ₄ . But you can more use a mixing or stirring device

Use sulfuric acid, for example 5 to be brought into intimate contact.

6 equivalents. However, this is an acid damage. Since the reaction is exothermic, it should be

waste. 5 moderately chilled to bring the temperature to one

The ratio of water to H ₂ SO ₄ can be kept in a wide range that is not significantly higher than approximately

Area fluctuate. The solution can is proportionate 5O ⁰ C. The temperature is preferably maintained

be moderately diluted or thoroughly concentrated. below 30 ⁰ C. With the help of a cooling device

This is mainly a question of expediency, one can work at temperatures up to ⁰ ° C. Exercise

and the existing device. You can definitely keep room temperature.

Solution which contains 10 percent by weight H ₂ SO ₄ . From the water and from the device came

or a solution containing up to 50 percent by weight of metal impurities can be beneficial

contains, or, less commonly, 99% by weight with a small amount of a chelating agent

use percent H ₁₁ SO ₄ . Make smaller amounts of harmless. Used as a chelating agent

H ₁ SO ₄ can also be used; but 15 ethylenediaminetetraacetic acid, nitrolotriacetic acid

offers the use of a more dilute solution or gelatin suitable.

usually only minor advantage. In practice The following examples illustrate the invention,

reaction is carried out at about 10 to 5O ^fl / cent H ₂ SO _4, · 1 1 τι

The amount of nitroalkane, based on the weight of the egg

of acid plus water should be measured so that a mixture of 2,640 parts by weight is added, the heat of reaction can be easily dissipated. Water, 232 parts by weight of concentrated sulfur - In general, it is preferred to use acid (218 parts by weight H ₂ SO ₄ ), 259 parts by weight of an amount of nitroalkane close to saturation in the nitromethane and 10 parts by weight of a 5% aqueous system; However, even larger palladium-carbon catalysts can be used in a stirrer to autoclave suspensions with concentration. The vessel is closed and trations are flushed out with nitrogen to the limit of what is possible by hand. Then you give hydrogen to make it ready. to a hydrogen pressure of 14.1 atm. The domestic

The sulfuric acid and also the nitroalkane hold the autoclave is stirred while the

can be used during the process, which also maintains a continuous temperature between 20 and 30 ° C until the

is practically feasible. 30 hydrogen uptake ceases, which is

The hydrogenation is preferably started with it shows that no further pressure drop takes place,

a certain amount of nitromethane in sulfur- this process takes about 2 hours,

acid and adds after the hydrogenation has proceeded- Thereafter, the catalyst is removed by filtration

is stepped to add more nitromethane. separated from the solution. The aqueous solution contains

Such a reaction can also be carried out in the manner of about 200 parts by weight of N-methylhydroxylamine sulfate

perform that one with a sizeable and sulfuric acid. The yield is essentially

Acid excess begins, or you can borrow the acid quantitatively,

add when adding nitroalkane. Instead of nitromethane, one can use nitroethane, 1-nitro-

The hydrogenation is catalyzed by palladium. propane or 2-nitropropane with recovery in

The palladium catalyst can be used as metal 40 in substantial quantitative yields of the corresponding

or use as oxide in the usual way in fine-grained N-alkylhydroxylamines,

split form to apply or to. T 9

Carbon or other inert carriers. ü e 1 s ρ 1 e

Palladium on carbon has proven to be particularly advantageous

proved to be a strong catalyst. 45 one 189 1 water, 3.6 kg 5% palladium-carbon

The amount of catalyst can vary widely in granules, which are thinned through a sieve with a

pass through a mesh size of 0.84 mm in accordance with normal working practices, and

vary. _{In general, commercially available 96% H 2} SO ₄ should be used per 10 000 weight 152.4 kg. To

parts nitroalkane about 1 part by weight of palladium before flushing the vessel with nitrogen

be available, either as metal or as oxide and 5 ° hydrogen and nitrogen (20:80) up to one

optionally on suitable carriers. A pressure of 70.3 atmospheres (hydrogen partial pressure

Use larger amounts, of course, but it is 14.1 atm.

relatively uneconomical if more (the vessel is equipped with a device, than about 100 parts by weight of metal per 10,000 Ge around the nitrogen-hydrogen mixture from the major parts of the nitroalkane used. The catalyst 55 vapor space through a sprayer to the bottom of the should of course be pumped in accordance with usual measuring vessel and so mixing through methods are recovered and used in the process- bubbling the gases through the liquid be returned. Recovery will be made possible.) Now nitromethane is pumped into one lightened when the catalyst is on a dense, amount of 90.7 kg / h. into the autoclave. Additional coarse, particulate carriers are added when so hand is. is necessary to maintain the pressure.

The hydrogenation is carried out in the customary manner. The temperature is kept at about 25.degree. To the nitromethane feed is stopped using gaseous hydrogen for 2 hours, through under pressure. The pressure can largely release hydrogen and trap the catalyst vary; in general, the use is 65 separate.

generation of a hydrogen pressure of about 7 to 35 atmospheres. 527.1 kg of a 27% methylhydrogen

necessary. Inert gases can also be added, a xylamine sulphate solution. The yield is essentially

for example nitrogen. The hydrogen is said to be quantitatively borrowed with the.

Claims (1)

Claim: Process for the preparation of alkylhydroxylamines with 1 to 3 carbon atoms in the alkyl part by catalytic hydrogenation of corresponding nitroalkanes under pressure over palladium catalysts at 0 to 50 ⁰ C, in particular <Ξ 30 ^c C. in acidic aqueous solution, characterized in that the hydrogenation in The presence of at least one equivalent of H ₂ SO ₄ per mole of nitroalkane. Documents considered: German Auslegeschrift No. 1024 088; Swiss Patent No. 325 080; Austrian patent specification No. 188 326. When the application was announced, a declaration of priority transfer was laid out. 409 769/427 1.65 ι Bundesdruckerei Berlin