DE1643389A1 - Process for the preparation of aromatic amines substituted with chlorine - Google Patents

Description

The invention relates to a method for catalytic Reduction of aromatic chloronitro compounds to the corresponding chlorine-substituted amines, in which. Process the formation of non-chlorinated products is kept to a minimum. - '., "■ .-

; vlan has long been reducing aromatic nitro compounds, as well as' aromatic Chlornitroveibindungen to the corresponding aromatic amines in various ways and Way, for example using bite chips and dilute acid; zinc is also used for reduction,

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Tin, and tin (II) chloride with or without acid, ^ lialisulfide and a wide variety of other reducing agents.

In _s recent years, new procedures ^ has nowickelt, in which molecular hydrogen mix various catalysts for direct reduction cer liitroverbindungen used to amines. These catalytic .. "hydrogenations have numerous advantages over esa

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previously used chemical processes, in particular with a view to profitability, their ^ ov / andeloarlceit, with regard to the complexity of the process management, the separation the resulting products and the ease of adaptation to continuous process engineering. These catalytic hydrogenations are used in aromatic Nitro compounds carried out both in the liquid and in the vapor phase. One already has numerous catalyst systems for the various Techniques should be suitable, proposed or tried out, since there are numerous drawbacks oei aer application of the catalytic hydrogenation technology.

The main problem with the catalytic. Reduction of aromatic Ghlornitroverbinaun ^ en ko..frottiert, is the strong, during the process eri'olroiiic dechlorination » Kan already has numerous. Tried ways-

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To suppress this dechlorination, otherwise . the use of a complex copper-Ohroffi-K.atalysa-.ors, the use of rhodium as a catalyst in the presence 'of an organic solvent, the .nnwenuunj: more controlled Quantities of Itiagnesium Oxide or i «agnesiu: r.ayöro>: yö zuzar-kun. with a platinum catalyst arranged on carbon, εον / ie the use of piperazine or horpholine and theirs N-alky! Substituted derivatives as suppressors Dechlorination. The use of a platinum catalyst in connection with small amounts of horpliolin press ^ i dechlorination to a degree from 0.40 to £, rO Mole percent. . '

sets the device Q Vörfahroi eir.o leaps and bounds of catalytic leüuiirior; from aromatic chloronitro compounds because cie Biloun of the dechlorinated products to a degree of 0.20 Percent or even noctivveniger depressed ', virc.

i3s was surprisingly found that the formation of dechlorinated products during the period indicated by Ρΐ & τΐη catalyzed reduction of aromatic chloronitro compounds to a degree of 0.20 l.Iol percent ocer wenics i.e. is suppressed if the reduction is carried out in the presence of the catalyst described below and in Presence of triphenyl phosphite or iritolyl phosphite

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(m- and p-cresyl phosphite) at a temperature of '50 t 125 ⁰ C and a hydrogen gas pressure: -van "carries out about γ-105.atü.

In the practical implementation of the present jirfincur.g everyone can. A stainless steel autoclave equipped with a propeller stirrer with a speed of about yCu revolutions per minute, an electric heating device, a cooling jacket and a gas inlet connected to a hydrogen source and which can withstand a pressure of about 105 atmospheres. Depending on the α err. Gewicht.der aromatic chloronitro compound are inputted 0.01 to 0.08 is io of a catalyst consisting of 1 ois 5 P erteiltem platinum on carbon and 0.05 to above, 5 triphenyl phosphite or tritolyl phosphite in aen autoclave. After the autoclave had been flushed out with nitrogen and then charged with hydrogen, it was heated to 30 to 125 ° C. and the hydrogen pressure in the autoclave was increased to 7 to 105 atmospheres. Depending lower the temperature of the autoclave was, the slower reduction proceeded cie "At about 3O ⁰ C and a hydrogen pressure of 7 atm ven betrüg the reduction of time required ois Iy 17 St u ;; c ιr. By increasing the. With a temperature of 200 to 125 ° and the pressure to about 21 °, the reduction time was reduced to less than 1 hour. After the reduction has taken place, the resulting crude aromatic chloramino compound is removed from the autoclave by filtration from the Xataiys ^ ter

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freed and the water separated. Then it is distilled to recover the chloramine. According to the present invention, from the corresponding caloramines, reducible aromatic chloronato compounds include: 2-chloronitrobenzene, 3-chloronitrobenzene, 4-chloronitrobenzene, S-chloro - ^ - nitrotoluene, 4-chloro-2-nitrotoluene, 2-chlorine -4-nitrotoluene, 6-chloro-4-hitro-l, 2-diraetayl-deazol, 4-chloro-2 ~ nitro-l, 3-dimethylbenzene, 6-chloro-4-nitro-l _> 3 ~ dimethylbenzene, 2, 5-dichloronitrobenzene and a G-emic from crude Hitrochlorbenzolj the approximately 92 'fo meta isomer 4 contains, 3,4-dichloronitrobenzene, to 5 ° Y para-Isoraer and 2 to 3 jö ortho isomer. Crude starting products which have a low content of 3-chloroaltrobenzene with 2-chloro-ύηά 4-.loraitrobenzenes can easily be reduced by the process according to the invention without the original isomer ratio being changed. When reacting a chloronitrobenzene of 99.9 ^ purity, especially 3-ChlornitrobehzoI, used as the A-usgangsverbindung '{, is the readily available. Total yield of 3-chloroaniline 96 for theory.

The V / es of the present invention will now be further explained with reference to the following examples, in which ^; the weighted percentage of the; a platinum catalyst and the iriphenyl or iritolyl phosphite are added to the weight of the reduced to eataprföh ^ nd ^ n Qhlosjamip; ornamental aromatic GhlornitrovQxblndung refers.

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16Λ3389

Example 1:

Meta-chloronitrobenzene a 99.0 molprozentigen purity was consisted together with 0.05 1 ° of a catalyst consisting of 5% platinum on carbon distributed and input to einen.Autoklaven 0.10 / ° 2riphenylphosphit, then this. flushed with nitrogen and charged with hydrogen:!;, which had a pressure of 38.5 atü. The reactanxes vmräen. heated to 60 ⁰ G and this temperature was maintained for 4 to 5 hours, the reaction proceeding to completion. The reaction product was cooled and removed from the vaxoclave. The meta-chloronitrobenzene was completely reduced to the corresponding chloroaniline; only 0.13 mol percent of aniline could be found in the resulting product. After purification, it was obtained. a yield from m-chloroaniline of 93 »0 $> of theory; the purity: was $ 90.5.

Example 2;

Example 1 was repeated with the modification that the reactants were heated to a temperature of 100 G, as a result of which the reaction was already complete in less than 2 hours. Dechlorination was done only to a very limited extent, as could advertise determined 0.11 i ° Aniiingatialt, the yield and purity was the giisijDfee as in Example. 1.

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Example 3: '- -

• IEUs was Example 1 "repeated" ■ -with except 'that instead of. 0.1 i »Iriphenylphosphit 0.05 Triimenjlp.iosiJ.ii- and instead of 0.05 fi on carbon distributed" eta Pia j in 'this time 0.015 ⁰ A platinum were used.' The reaction κοηπce can be completely carried out in 6 hours. The dechlorination could "be reduced" to such an extent that only 0.08 mol percent of aniline was formed. The yield and d ⁴ .e purity of the reaction product were comparable to the α sr described in Example 1.

Example 4:

jSs Example 1 was repeated again, with the modification that the hydrogen pressure in the autoclave is 38.5 to 105 ^ tu. was and only 0.03 weight percent of a 5% on Aohie distributed platinum catalyst along with 0.05 weight percent Triphenylphosphite were used. Deehlorierung was reduced to such an extent that only 0.19 ool per cent Aniline was formed. The yield and purity was that same as in example 1.

Example 5: - _ - ~

2,5-dichloronitrobenzene "was introduced together with 0> 05 i» of a platinum catalyst mc 0, u5 > triphenylphosphite distributed on charcoal, the autoclave was flushed out with nitrogen and then charged with hydrogen at a pressure of 3S, 5 atti * The reactants 'were 8 to 9 hours on

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75 ⁰ C heated, within which time the reaction was brought to an end. The resulting product was cooled and removed from the autoclave. The 2,5-dichloronitrobenzene used was completely reduced to the corresponding 2,5-dichloroaniline with a trace of m-chloroaniline of less than 0.2 mol percent. The yield of 2,5-dichloroaniline after purification was 98 #.

Example 6; - ·

It was repeated Example 5, with the modification that, instead of 2,5-dichloronitrobenzene 3,4-Dichiörnitrobenzol used and was ernöht the temperature of 75 to 80 ⁰ G j, the heating was added 9 to 10 hours fortgeführ-s, within at which time a complete reduction of the 3,4-dichloronitrobenzene to the corresponding dichloroaniline takes place, which had only a trace of ohloraniline, namely less than 0.25 mol percent. The yield of 3,4-bichloroaniline after purification was 97 to 98 fi.

Example 7:

4-chloronitrobenzene was added together with 0.05? ° a catalyst which consisted of 5 ^ of dispersed platinum on carbon and 0.05 entered i »triphenyl phosphite in an autoclave, this purged with nitrogen and then with 'hydrogen under a pressure of 21 atü loaded. The reactants were ^{heated to 60 °} C. and this temperature was maintained for 8 hours, during which time the reaction took place

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went completely. The reaction product was cooled and removed from the autoclave. That of the starting compound the corresponding 4-chloroaniline formed had only one Content of 0.1 mol percent aniline as a dechlorination product. After purification, 99.5% strength 4-chloroaniline was obtained Purity.

Example 8:

Example 1 was repeated again, with the modification that instead of m-chloronitrobenzene this time 4-chloro-2-nitrotoluene was used. 'The latter compound became 4-chloro-2-aminotoluene by the process according to the invention reduced, which contained only a trace, namely less than 0.15 mole percent, 2-aminotoluene. To the purification gave a 99% p-chlorotoluene.

It should be emphasized that you can also use it at lower temperatures and printing satisfactory to those described above Results. In such cases, however, longer reaction times of up to 24 hours will be required.

While platinum distributed on carbon is the preferred catalyst was used, other catalysts can also be used with satisfactory results, for example spongy nickel, platinum black, palladium on activated carbon, Platinum, or palladium on aluminum and the like,

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Claims (6)

Claims 1.) Process for the preparation of aromatic amines substituted with chlorine by catalytic ^ hydrogenation of aromatic monocarbocyclic nitrohydrocarbons containing 1 or 2 chlorine atoms, characterized in that the hydrogenation is carried out in the presence of 0.01 to 0.08 pounds of a catalyst to 1 Ms 5 y ° consists of platinum sponge nickel, platinum black, palladium on activated carbon or platinum or palladium on aluminum distributed on carbon and from 0.05 to 0.5 $ triphenyl phosphite or tritolyl phosphite, based on the weight of the hydrocarbon to be hydrogenated a temperature of 30 ^ to 125 ° C and a hydrogen gas pressure of 7 to 105 atu carries out ♦ 2.) The method according to claim 1, characterized in that W dass.der aromatic monocarbocyclic nitrohydrocarbon consists of m-chloronitrobenzene. 3.) The method according to claim 1, characterized in that the aromatic monocarbocyclic nitrohydrocarbon consists of 2,5-dichloronitrobenzene. » 4.) Method according to claim 1, characterized in that that the aromatic monooarbocyelic kitro-carbon BAÖ ORlOfWAt. - patent claims - hydrogen consists of 5,4-dichloronitrobenzene. 5.) The method according to claim 1, characterized in that the aromatic monocarboeyclic nitrohydrogen consists of 4-chloronitrobenzene. .-. 6.) The method according to claim 1, characterized in that the aromatic monocarboey clische Nitrokoh.lenwasserstoff consists of 4-chloro * 2-litrotoluene. 109836/15 55