DE2149855B2 - METHOD FOR PREPARING SECONDARY ALKYL PRIMARY AMINES - Google Patents

Description

The invention relates to a process for the preparation of secondary alkyl primary amines by hydrogenation of mononitroparaffins with 6 to 25 carbon atoms and a non-terminal nitro group in a hydrogen atmosphere at elevated pressure and elevated temperature in the presence of a palladium-carbon catalyst.

From US-PS 28 23 235 is known nitro compounds to reduce to amines in the presence of catalysts made of palladium and / or platinum on carbon. These catalysts quickly become less effective.

A process for the production of secondary alkyl primary amines by hydrogenating nitroparaffins is described in US Pat. No. 3,470,250. A variety of catalysts are suggested for this, however are problems such as achieving a high conversion and using a catalyst with a long life not addressed.

Hauben-Weyl, "Methods of Organic Chemistry", Volume XI, 1, pages 363-365, can be found that the reduction of nitro compounds is one of the simplest reactions and that one can mainly used platinum, palladium and nickel catalysts In "Catalytic Hydrogenation in the Organic Chemistry Laboratory", 1956, p. 24, writes Zymalkowski, that palladium and platinum catalysts show significant differences in selectivity and that partial and selective hydrogenations with palladium catalysts are more likely than with platinum catalysts. This reference suggests that a palladium catalyst with regard to the formation of Secondary-alkyl-primary-amines is less selective than with regard to the formation of secondary-alkyl-secondary-amines.

The invention is based on the object of a process for the hydrogenation of mononitroparaffins with 6 to 25 carbon atoms and non-terminal nitro group in a hydrogen atmosphere increased pressure and temperature in the presence of a palladium-carbon catalyst create, in which secondary-alkyl-primary-amines in high yields and the catalyst maintains its activity over a long period of operation In addition, the catalyst should have high compressive strength and that which is produced during the hydrogenation Water does not soften.

The object is achieved by carrying out the hydrogenation at 373 to 232 ^° C. and under one pressure

from 10 to 300 kg / cm ² in the presence of a palladium-carbon catalyst which has been heated to 260 to 649 ° C. in the presence of a non-oxidizing gas for at least one hour
From DT-PS 8 38 785 it is known to stabilize platinum-carbon catalysts with heat treatment. The publication teaches that it is expedient to decompose the platinum salt on the carbon support at higher temperatures, preferably between 300 and 400 ^° C., since heating in a hydrogen atmosphere at elevated temperatures increases the activity of the catalyst. It has now surprisingly been found that catalysts produced in this way, but containing palladium as the catalytically active metal, remain active for much longer and have a higher compressive strength. In addition, it has been shown that palladium catalysts produced in this way selectively convert mono-nitroparaffins with non-terminal nitro groups into amines with regard to formation

jo primary amines affect, while the corresponding Platinum catalysts selectively influence the conversion with respect to the formation of secondary amines. The catalyst used in the process according to the invention contains 0.1 to 10% by weight of palladium, which is deposited on activated carbon.

Activated charcoal, a component of the heterogeneous catalyst used in the process according to the invention, is usually made from charcoal, petroleum coke, and animal and vegetable material. The raw material is first carbonized by heating at 316-649 ⁰ C in a non-oxidizing atmosphere and then comprises, in a vapor stream, the small amounts of air or superheated steam, activated at 649-927 ° C In addition to increase of pore volume and surface area in the activation of oxygen passed onto the carbon surface, which holds the oxygen in various ways, generally referred to as oxidized surface. The partially oxidized surfaces are hydrophilic and promote wetting of the activated carbon with aqueous palladium salt impregnation solutions.

An activated carbon is used to produce the catalyst used in the process according to the invention with an ash content of less than 5% by weight, in particular 2% by weight, is preferred. Activated carbon with a Ash content below 5% by weight is commercially available. The activated carbon, which acts as a carrier for the heterogeneous Catalyst is used has a large surface area, e.g. B. from about 800 to 1400 mVg.

To produce the stabilized heterogeneous catalyst used according to the invention, the activated carbon is treated with an aqueous solution of palladium chloride or palladium nitrate. After thorough mixing of the impregnation solution and activated carbon, ^{drying is carried out at 93 to 121 °} C. and a catalytically active palladium-carbon catalyst is obtained.

The catalyst produced in this way, which initially has high catalytic activity and compressive strength

when it is used as a hydrogenation catalyst, loses its activity continuously within a short time, since it is exposed to the reaction by-product water. It has now been found that by heating the catalyst for at least one to 24 hours, preferably 2 to 8 hours 260 to 649 ° C, preferably 371 to 593 ° C, a catalyst with stabilized activity and increased compressive strength is obtained in a non-oxidizing atmosphere. It is believed that this treatment reduces and removes the level of surface oxides and renders the catalyst hydrophobic. A variety of non-oxidizing gases can be used, e.g. B. nitrogen, methane, argon, helium, neon, ethane and propane. Particularly preferred is hydrogen or a mixture of hydrogen and light hydrocarbons. The mixture can be, for example, the exhaust gas from a catalytic reformer. The preferred atmosphere, namely, the reducing atmosphere of hydrogen results in superior catalytic properties, resulting in a long lasting and improved catalyst activity, particularly after treatment at 371-593 ⁰ C, in the inventive process, in which considerable quantities of water as a byproduct , demonstrate. In general, the heating is carried out in a non-oxidizing atmosphere at pressures of 0 to 70.3 kg / cm ² , preferably 21.1 to 49.2 kg / cm ² . Conversely, oxidizing conditions during heating, for example the presence of air or oxygen, lead to rapid catalyst softening prior to its use and to deactivation when the catalyst is used in the water-forming reaction.

The catalyst used according to the invention is stabilized by allowing a non-oxidizing gas to flow over or through the catalyst bed at the temperatures and pressures indicated above, the gas at a rate of at least 0.127 Nm ³ per 0.09 m ² reactor cross-section and hour at least one hour, preferably 2 to 8 hours, is passed over.

It has been found that a palladium-carbon catalyst stabilized in this way can be used for the hydrogenation of mononitroparaffins with 6 to 25 carbon atoms and non-terminal nitro groups at low temperatures of 37.5 to 232 ^° C. under a pressure of 10 to 300 kg / cm ² to secondary alkyl primary amines are particularly suitable. Favorable space-time velocities are 0.2 to 20.

The starting material for the process according to the invention are secondary mononitroparaffins in which a nitro group is bonded to any carbon atom but not to a terminal carbon atom. These mononitroparaffins include
2- or 3-nitrohexane, 2-, 3- or 4-nitroheptane, 2-, 3- or 4-nitrooctane, 2-, 3-, 4- or 5-nitrodecane,
2-, 3-, 4-, 5- or 6-nitroundecane,
2-, 3-, 4-, 5- or 6-nitrododecane,
2-, 3-, 4-, 5-, 6- or 7-nitrotridecane,
2-, 3-, 4-, 5-, 6- or 7-nitrotetradecane,
2-, 3-, 4-, 5,6,7-, 8- or 9-nikrooctadecane
and mixtures thereof, e.g. B. Mixtures of Ciobis Cn-Nitroparaffins. The mononitroparaffins which can be used are produced by reactions of a Q ₁ to C 2 5 paraffin hydrocarbon, preferably a straight hydrocarbon, in the liquid phase with a vaporous nitrating agent, such as. B. nitrogen dioxide or nitric acid, at about 121 to 260 ° C and 1 to 20 atmospheres

The nitration reaction can be discontinuous or be allowed to run continuously until about 5 to 50% of the paraffin in nitrated crude product, which is about 5 to 45% mononitroparaffin and 95 to 50% unreacted paraffin together with small amounts of Ce to Czs ketone, alcohol, carboxylic acid and polyfunctional compounds,

; o are walking. The mononitroparaffins produced in this way can, if desired, be obtained from the crude product by distillation and, according to the invention, converted into the corresponding amines. Usually the nitration in the presence of C ₆ - bis

! _S Cis-Paraffinkoblenwasserstoffien as diluents performed, the raw material can be nitrated but also directly with unreacted paraffin forms the reaction medium The nitrated crude product can also be washed to remove formed in the nitration acid byproducts alkaline.

According to the invention, the mononitroparaffins are reduced to secondary-alkyl-primary-amines, the The reaction is exothermic and temperatures exceeding 232 ° C affect the formation of primary amines adversely affect. At temperatures above 232 ° C the formation of secondary amines increases sharply. The proportion of nitroparaffin based on the amount of catalyst is not limited, and optimal proportions

■ to can be quickly determined through experiments.

In general, the following applies: the greater the ratio of catalyst to nitro compound, the faster the reaction away.

It has been found that, unlike other metals, the formation of palladium is primary Amines favored in comparison to the formation of secondary amines.

The process according to the invention can be carried out batchwise or continuously. Suitable reactors are charged and pressurized, preferably moved, and the progress of the reaction is monitored by the hydrogen pressure. It is optionally possible to work continuously, the nitro paraffin being allowed to run through and over the catalyst in the presence of hydrogen under the temperature and pressure conditions specified above at a flow rate of 0.2 to 20 vol / vol / h.
Usual methods can be used to isolate the amine, such as. B. fractional distillation of the crude product. The amine can also first be isolated as the amine salt by reaction with an organic acid, set free again by subsequent treatment with alcohol and then obtained by distillation. The amines obtained according to the invention are used as mold release agents, freeze-thaw stabilizers for emulsions, pigment dispersants, polyurethane catalysts, caking agents and anti-dust agents. They are also suitable as corrosion inhibitors, bacteriostatics, sludge dispersants and as detergents and de-icing agents for gasoline

After prolonged use, the catalyst can be partially deactivated. The Rcgene-

However, hs rierumg can easily be achieved by the catalyst again in a non-oxidizing gas. preferably hydrogen, among those for stabilization specified temperature and time conditions

The initial heat treatment and regeneration can be done in situ in the reactor be made, in which the nitroparaffin in Amine is converted.

The following examples are intended to further illustrate the process according to the invention to serve.

Example I.

A mixture of palladium on charcoal ι ο by dissolving 10 grams of palladium chloride in 100 cc of water, 100 cc of concentrated ammonium hydroxide and 400 cc methyl alcohol, adding this solution at 0 ^c C to 594 grams (mm 4) commercially available extruded activated carbon in tablet form and The mixture was stirred vigorously for 1 hour. The solid particles were separated off by filtration, dried at 57.2 ° C. for 16 hours and then heated to 104.4 ° C. in nitrogen gas for 6 hours. 574 grams of catalyst at 0.97% by weight were % Palladium obtained on activated carbon.

A 54 gram sample of this catalyst was at 232 ° C in a reactor with a diameter of 2.54 cm for 4 hours in a hydrogen stream at a flow rate of 0.0283 to 0.0566 mVh. treated at 42.2 kg / cm ² - Catalyst A.

Two further 54 gram samples of the catalyst were heated for 4 hours at 566 ° C in a stream of hydrogen at a flow rate of 0.0283 to 0.0566 mV hr at 42.2 kg / cm ² - Catalysts B and C

A C10 to Cu starting material composed of 14.6% by weight of nitrated n-paraffin, 82.1% by weight of n-paraffin, 0.4% by weight of ketone and 2.9% by weight of bifunctional paraffin was used with at a rate of 100 grams / hour in a hydrogenation reactor containing 54 g of catalyst A, and in a further hydrogenation reactor containing 54 g / catalyst C, fed in each reactor 135 ° C and a pressure of 42.2 kg / cm ² H ₂ prevailed. The product analyzes after a flow time of 60 hours showed that the catalyst A had lost 11% of its activity between the 12th and 48th hour. Catalyst C used under the same conditions showed stabilized activity in that the activity would only have decreased by 4% within 12 to 48 hours during the conversion of nitroparaffin to primary amine.

The above-written Ci ₀ - to Cu-n-nitro-paraffin starting material was placed in a reactor containing 54 g of Catalyst C at 135 ⁰ Q, a hydrogen pressure of 42.2 kg / cm ² and a hydrogen flow rate of 0.04 to 0.0566 mVh, entered at a rate of 130 grams / hour. Catalyst C showed no deactivation after 80 hours.

Example II

A mixture of palladium on activated carbon was prepared by dissolving 6.7 g of palladium chloride in 70 ecm of water to which 100 ecm of ammonium hydroxide and 240 ecm of methyl alcohol had been added. This solution was added to 490 grams of a commercially available activated charcoal in tablet form (3.27 mm) with an ash content of 3.51% by weight. The mixture was stirred one hour at 0 ⁰ C vigorously, the solids then removed by filtration and 104.4 ⁰ C for 4 hours in a stream of nitrogen dried. The catalyst contained 0.92% by weight of palladium (chemically analyzed) on the activated carbon; - catalyst

D. The compressive strength was 6.485 kg and was determined by measuring the force that is necessary to grind the catalyst tablet between two parallel plates.

A 57-grain sample of catalyst D was heated in a reactor, diameter 25.4 mm, at 260 ° C. for two hours in a stream of hydrogen at a rate of 0.04 to 0.0566 mVh and 42.2 kg / cm ² .

Another 58-gram sample of the catalyst D was 2 hours at 510 ⁰ C in a hydrogen stream at a rate from 0.0283 to 0.0566 m ³ hours and 42 £ kg / cm ² heated - Catalyst F.

A Cio to Cu starting material (see Example I) was fed at a rate of 125 cc / hour. into one hydrogenation reactor containing 60 grams of Catalyst D and another hydrogenation reactor containing 57 grams of Catalyst E, each reactor maintaining 135 ° C and a hydrogen pressure of 42.2 kg / cm ² . The product analysis of the starting material treated with catalyst D showed that the catalyst had been deactivated rapidly during the flow time and had lost 11% of its activity between the 8th and 28th hour of flow time. The product analysis of the starting material treated with catalyst E showed that the catalyst had lost no activity during the 40 hour flow time.

58 grams of Catalyst F were treated in the same way. The starting material was treated with a Speed of 125 cc / hour at 135 ° C initiated. The catalyst F showed no deactivation within the flow time and in the product analysis Its high selectivity resulted from the fact that 9.7 milliequivalents of primary amine per gram of product along with a negligible amount of secondary amine were formed. The process conditions for Catalyst F were 107.2 ° C and 60 ccm / hour If the liquid flow was changed, there was again no deactivation at a high conversion within the flow time The compressive strength of the catalysts E and F was determined after their use measured and values of 9.07 and 7.26 kg were obtained.

Example III

1800 grams of commercially available activated charcoal in tablet form, 3.27 mm in diameter, with an ash content of 3.51 wt .-% were with 5 l of a solution of 3 volumes of concentrated HCl and 7 volumes of water mixed After digesting the material at 60 ° C for two hours, the solution became detached from the activated carbon filtered off and the solid particles washed with water until they were free of chlorine. Of the The ash content of the dried acid-treated coal was 1.37% by weight and the ash passed mainly from S1O2 in addition to small amounts of iron, magnesium, calcium and titanium.

25.7 grams of palladium chloride in 200 ecm of concentrated ammonium hydroxide, 140 ecm of water and 1000 ecm of methyl alcohol were added to the dried activated carbon. After intimate mixing Obergurig By the drying of the separated solids was conducted at 6O ⁰ C in a nitrogen stream. A catalyst sample was then heated at 371 ° C. for 4 hours in a stream of nitrogen at atmospheric pressure. The catalytic material had a palladium content of 1.08% by weight and a compressive strength of 9.07 ke

A Cio to C _M starting material (as in Example I) flowed at a rate of 88 cc / hr. into a reactor containing 41 grams of catalyst and having a temperature of 98.9 to 104.4 ° C and a hydrogen pressure of 42.2 kg / cm ² . Product analysis showed 4.4 garbage equivalents per gram of product of primary amine and no secondary amine. The reactor temperature was increased to 138 to 143 ° C and the rate of the starting material to 140 ccm / hour. increased, product analysis indicated 5.3 garbage equivalents primary amine and 0.2 garbage equivalents secondary amine.

Another catalyst sample was heated to 37 ° C. under nitrogen and then heated to 510 ° C. for 2 hours in a stream of hydrogen at a rate of 0.0283 to 0.0566 nWh. and 42 ^ 2 kg / cm ^{2 of} pressure treated. The Ci ₀ to Cn material was again entered at a rate of 85 ccm / hour. in a reactor containing 40 g of catalyst, a temperature of 98.9 to 104.4 ° C. and an H ₂ pressure of 42.2 kg / cm ² . Product analysis gave 5.0 milliequivalents of primary amine per gram of product and 0.1 milliequivalents of secondary amine. By increasing the reaction temperature to 138 to 143 ° C and the inflow rate of the starting material to 140 ccm / hour. 6.7 garbage equivalents of primary amine and 0.2 garbage equivalents of secondary amine resulted.

Another 400 gram sample of catalyst was heated at 37 ° C. under nitrogen and placed in a reactor such that the catalyst formed a bed 254 mm deep in the reactor. Starting material flowed at 030 m ³ / hour and hydrogen at 0.283 mVh. under an H ₂ pressure of 40.8 kg / cm ² and a temperature of 149 to 177 ° C in the bed. The reaction was carried out for six weeks and gave the following result:

At the end of week 1, 9.4 garbage equivalents were primary amine and 0.9 garbage equivalents were secondary Amin, in the 2nd week 93 or 0.5 garbage equivalents of the both amines, in the 3rd week 9.4 or 0.4 garbage equivalents of the two amines and in the 6th week 8.9 and 0.4 garbage equivalents of the two amines were formed.

From this it can be seen that the heat treatment of the catalyst has a long activity and selectivity to convert nitroparaffin to primary amine below minimal Secondary amine formation is increased. After 6 weeks, the catalyst surprisingly had one improved compressive strength of 103 kg and a high selectivity of 92% with regard to the formation of primary amine from nitroparaffin.

Example IV

Another catalyst was prepared according to Example III and contained 037% by weight of palladium on activated carbon, which had an ash content of 1.84 % by weight and a surface area of 1.288 m ² / g. 337 grams

this catalyst, which had been heated to 371 ° C. under nitrogen, was placed in a hydrogenation reactor and starting material (see Example I) at a rate of 1.1 volumes of liquid per 0.45 kg of catalyst per hour under an H2 pressure of 42 , 2 kg / cm ² and a hearing speed of 0.283 mVh. introduced. The initial compressive strength of the catalyst was 8.16 kg and was determined to be 9385 kg after a contact time of 804 hours. It can be seen from the data below that the catalyst remained active for 804 hours and a constant amount of primary amine was obtained over this period. Secondary amine formation decreased, resulting in a higher selectivity for primary amine. The results are given in the table below in milliequivalents of amine per gram of product:

20 hours Primary amine Secondary amine 6th 8.9 1.1 12th 9.1 03 24 9.2 0.7 25 36 93 0.7 72 9.2 0.7 114 83 0.6 246 9.0 0.6 390 92 O ^ 30 525 92 0.6 804 8.9 0.5

After a test duration of 804 hours, the supply of nitroparaffin was interrupted and the catalyst was heated in situ in a stream of Hr, 0.283 mVh, at 42.2 kg H ₂ / cm ² , 482 ° C. for 4 hours. This was used to regenerate the catalyst by removing the deposits on the same. The catalyst was then brought into contact again with the starting material under the conditions already described. The following results show that the catalyst had not only become more active after the regeneration treatment, but also had an improved selectivity, since the formation of primary amine increased and the of the secondary amine had been reduced after comparable flow times. The results are given in the table below, milliequivalents of amine per gram of product.

hours

Pnnures Annn

Secondary amine

6th 9.2 03 12th 9Y 05 24 9.8 0, + 36 9 » 0.4

709525/515

Claims (3)

Patent claims: 1. A process for the preparation of ve π secondary alkyl primary amines by hydrogenation of mononitroparaffins having 6 to 25 carbon atoms and non-terminal nitro group in a hydrogen atmosphere at elevated pressure and temperature in the presence of a palladium-carbon catalyst, characterized in that one the hydrogenation is carried out at 37 J5 to 232 ° C. and under a pressure of 10 to 300 kg / cm ² in the presence of a palladium-carbon catalyst which has been heated to 260 to 649 ° C. in the presence of a non-oxidizing gas for at least one hour 2. The method according to claim 1, characterized in that the process is carried out in the presence of a palladium-carbon catalyst which has been heated ^{under a pressure of 21 to 29 kg / cm 2} 3. The method according to claim 1 or 2, characterized in that the hydrogenation is carried out under a pressure of 20 to 42 kg / cm ²