| PATENT NUMBER | This data is not available for free |
| PATENT GRANT DATE | November 13, 2001 |
| PATENT TITLE |
Process for producing aminodiphenylamines |
| PATENT ABSTRACT | The present invention relates to the production of aminodiphenyl-amines resulting in good yields and high purity levels when aromatic amines are reacted with nitrohalobenzenes in the presence of a palladium catalyst and a base and the product thus obtained is subsequently hydrogenated with hydrogen |
| PATENT INVENTORS | This data is not available for free |
| PATENT ASSIGNEE | This data is not available for free |
| PATENT FILE DATE | February 2, 2001 |
| PATENT FOREIGN APPLICATION PRIORITY DATA | This data is not available for free |
| PATENT REFERENCES CITED |
Kirk-Othmer, Encyclopedia of Chemical Technology, 4.sup.th edition, vol. 3, (month unavailable) 1992, pp. 424-456, Antioxidants. Ullmann's Encyclopedia of Industrial Chemistry, 5.sup.th edition, vol. A3, (month unavailable) 1985, pp. 91-111, Antioxidants. Christian S. Rondestvedt Jr.: "Synthesis of 4-Aminodiphenylamine and Its Relatives", Journal of Organic Chemistry, Bd. 42, Nr. 10, 1977, Seiten 1786-1790, XP002166757, American Chemical Society, Easton., US ISSN: 0022-3263, Seite 1787, Splate 2, Zeile 33-Seite 1790, Spalte 2, Zeile 48. |
| PATENT CLAIMS |
What is claimed is: 1. A process for producing aminodiphenylamines comprising the steps of reacting aromatic amines with nitrohalobenzenes in the presence of a palladium catalyst and a base to produce a product and hydrogenating said product with hydrogen. 2. A process according to claim 1, wherein the nitro group of said nitrohalobenzene is in para-position relative to the halogen residue. 3. A process according to claim 1, wherein the aromatic amines are selected from the group consisting of aniline, o-toluidine, m-toluidine, p-toluidine, 4-ethylaniline, 4-butylaniline, 4-isopropylaniline, 3,5-dimethylaniline and 2,4-dimethylaniline. 4. A process according to claim 1, wherein 1 to 10 mol of aromatic amine is used per mol of nitrohalobenzene. 5. A process according to claim 1, wherein the palladium catalyst is a palladium/phosphine complex. 6. A process according to claim 5, wherein the molar ratio of phosphine to palladium is 40:1 to 1:1 in the palladium/phosphine complex. 7. A process according to claim 1, wherein the palladium catalysts are used in amounts of from 0.0001 mol % to 10 mol % relative to the nitrohalobenzenes used. 8. A process according to claim 1, wherein the bases used are pretreated by grinding and/or drying. 9. A process according to claim 1, wherein the specific surface areas of the bases after grinding ranges from 0.1 to 10 m.sup.2 /g (BET). -------------------------------------------------------------------------------- |
| PATENT DESCRIPTION |
FIELD OF THE INVENTION The invention relates to a process for producing aminodiphenyl-amines, particularly 4-aminodiphenylamine (4-ADPA), by reacting nitrohalobenzenes with aromatic amines in the presence of a palladium catalyst and a base and subsequently hydrogenating the intermediate product thus obtained. BACKGROUND OF THE INVENTION 4-aminodiphenylamine (4-ADPA) is an important starting product for the synthesis of antioxidants and stabilizers in the rubber and polymer industry (Kirk-Othmer, Encyclopedia of Chemical Technology, 4.sup.th Edition, 1992, Vol. 3, page 424-456; Ullmann's Encyclopedia of Industrial Chemistry, 5.sup.th Edition, Vol. A3, 1985, pages 91-111). 4-ADPA may be produced by various methods. One possible method of producing 4-ADPA is the two-stage reaction of aniline or aniline derivatives with p-nitrochloro-benzene in the presence of an acid acceptor or a neutralizing agent, optionally in the presence of a catalyst. Production by this method is described, for example, in DE-A 3,246,151, DE-A 3,501,698, DE-A 185663, U.S. Pat. Nos. 4,670,595, 4,187,249 and 4,187,248. The first stage is generally performed using copper catalysts, and the second stage is performed with different metal components, e.g. nickel (see for example U.S. Pat. No. 5,840,982). Reactions also of, for example, halogenated nitrobenzenes with amines in the presence of palladium catalysts are described in U.S. Pat. No. 5,576,460 and EP-A 846,676. The disadvantage of the processes described in the above literature is frequently inadequate selectivity, in particular, during formation of the intermediate product, whereby yield losses occur as a result of more or less complex purification steps, before the 4-aminodiphenylamines may be formed by hydrogenation. SUMMARY OF THE INVENTION It was, therefore, desirable to provide a process for producing aminodiphenylamines, which starts from aromatic amines and, through reaction with appropriate nitrohalobenzenes and subsequent hydrogenation of the intermediate product formed, results in the desired aminodiphenylamines having good yield and elevated purity. Therefore, the present invention provides a process for producing aminodiphenylamines by reacting nitrohalobenzenes with aromatic amines in the presence of a base and palladium catalyst and subsequently hydrogenating the product obtained with hydrogen. DETAILED DESCRIPTION OF THE INVENTION The nitrohalobenzenes used are preferably those in which the nitro group is in para-position relative to the halogen residue. Possible halogen residues are: fluorine, chlorine, bromine and iodine, preferably chlorine and bromine. The nitrohalobenzenes may also be substituted by one or more other residues, such as for example C.sub.1 -C.sub.4 alkyl residues. Naturally, the position of the nitro group relative to the halogen residues may also be other than the para-position, e.g. it may be in position 2 or 3. Nitrohalobenzenes used in the present invention are: 4-nitro-2-methylchlorobenzene, 4-nitro-3-methylchlorobenzene, 4-nitrochloro-benzene, 3-nitrochlorobenzene and 2 nitrochlorobenzene. 4-nitrochloro-benzene is preferred. Aromatic amines which may be used in the process according to the present invention are those aromatic amines which are known in relation to such a reaction, for example aniline, o-toluidine, m-toluidine, p-toluidine, 4-ethylaniline, 4-butylaniline, 4-isopropylaniline, 3,5-dimethyl-aniline or 2,4-dimethylaniline. Aniline is preferred. Naturally, the aromatic amines may also be used in the form of mixtures, in particular isomer mixtures. In the process according to the invention, 1 to 10 mol, preferably 1.5 to 6 mol, and most preferably 2 to 4 mol of the aromatic amine, are generally used per mol of nitrohalobenzene. According to the present invention, palladium catalysts, e.g. palladium/phosphine complexes, or other known palladium compounds or complexes may be used. Suitable palladium/phosphine complex compounds are those in which the palladium has the valency 0 or II and suitable phosphine ligands are compounds such as triphenylphosphine, tri-o-toluylphosphine, tricyclohexylphosphine, tri-t-butylphosphine, bisdiphenylphosphine ethane, bisdiphenylphosphine propane, bis(diphenylphosphino)butane, bis(dicyclohexylphosphino)ethane, bis(diphenylphosphino)ferrocene, 5,5'-dichloro-6,6'-dimethoxybiphenyl-2,2'-diyl-bisdiphenylphosphine, bis-4,4'-dibenzofuran-3,3'-yl-bisdiphenylphosphine, 1,1'-bis(diphenylphosphino)diphenyl ether or bis(diphenylphosphino)binaphthyl, wherein the stated phenyl residues may be substituted by sulfonic acid residues and/or by one or more C.sub.1 -C.sub.12 alkyl groups or C.sub.3 -C.sub.10 cycloalkyl groups. In addition, polymer-bound phosphines may serve as ligands, e.g. tPP polymer (commercially available). Triphenylphosphine is preferably used as a ligand. However, other palladium/phosphine complex compounds may also be used for the process according to the present invention, such as for example, nitrogen- or oxygen-containing ligands, such as 1,10-phenanthroline, diphenylethane diamine, [1,1']-binaphthenyl-2,2'-diol (BINOL) and 1,1'-binaphthenyl-2,2'-dithiol (BINAS), or indeed those with two or more different heteroatoms, such as O, N, S. Palladium compounds which may serve as catalysts include the following classes of compound, for example: palladium halides, acetates, carbonates, ketonates, nitrates, acetonates or palladacyclene, for example Pd.sub.2 dba.sub.3, Pd(acac).sub.2, Pd(OAc).sub.2, PdCl.sub.2, (CH.sub.3 CN).sub.2 Pd(NO.sub.2)Cl. Pd.sub.2 dba.sub.3, Pd(acac).sub.2, Pd(OAc).sub.2, PdCl.sub.2 are preferred. In addition, heterogeneous or immobilized palladium catalysts may also be used in the process according to the present invention, i.e. those which are applied to suitable inert supports, for example. In the case of the palladium/phosphine complexes to be used according to the present invention, the molar ratio of the corresponding ligands to palladium is approximately 40:1 to 1:1, preferably 10:1 to 2:1, most preferably 8:1 to 4:1. According to the present invention, the palladium catalysts, such as palladium/phosphine complexes and/or the other complexes or compounds which may be used, are generally used in amounts of from 0.0001 mol % to 10 mol %, preferably 0.001 mol % to 5 mol %, relative to the nitrohalobenzenes used. Bases which may be used in the process according to the present invention are alkali and/or alkaline earth metal carbonates, alkoxides and/or hydroxides, in particular, potassium and/or sodium carbonate, cesium carbonate, sodium methanolate and barium hydroxide. Potassium and/or sodium carbonate are preferably used. The bases may be used in a substoichiometric amount or in an excess of up to ten times the equivalent amount relative to the nitrohalobenzene. The bases are preferably used in a 0.3 to 2 times equivalent amount, relative to nitrohalobenzene. It is advantageous for the process according to the present invention for the bases used to be pretreated by grinding and/or drying. In the process according to the invention, grinding may be performed in commercially available mills. Grinding affects a drastic increase in specific surface area, which results in a clear increase in conversion. In many cases, grinding may increase the specific surface area by a factor of 10 to 20. After grinding, the specific areas of the bases are approx. 0.1 to 10 m.sup.2 /g, preferably 0.2 to 1 m.sup.2 /g (BET). As a result of the pronounced hygroscopic properties of the bases used in the process according to the present invention, the latter have a tendency towards the more or less marked absorption of atmospheric constituents, such as water or carbon dioxide. From a level of absorption of atmospheric constituents of approx. 30 weight percent, a marked influence on achievable conversion levels may be noted. Therefore, in addition to grinding, drying of the bases is also frequently indicated. Drying of the bases proceeds, for example, in that they are heated under a reduced pressure of approx. 0.01 to 100 mbar for several hours to temperatures of approx. 50 to 200.degree. C., preferably 100 to 160.degree. C. The first stage of the process according to the present invention may be performed at temperatures in the range of from 20 to 250.degree. C., preferably at temperatures of from 120 to 180.degree. C. The reaction temperatures depend, in particular, on the type of starting products, the catalyst and the bases used. The process according to the present invention may be performed both in the presence and in the absence of a suitable solvent. Examples of possible solvents are inert organic hydrocarbons, such as xylene and toluene. In addition, the aromatic amines used may themselves function as solvents. In the process according to the present invention, the reaction water arising may, if desired (as in DE-A 26 33 811 and DE-A 32 46 151), be removed, for example, by distillation with the aid of a suitable entraining agent. The amount of solvent used may be readily determined by appropriate preliminary tests. The process according to the present invention may be performed continuously or discontinuously by conventional methods. In the process according to the present invention, the reaction product obtained after reaction of the aromatic amines with the halonitroaromatics is hydrogenated with hydrogen, wherein hydrogenation may be performed in the presence of the palladium catalyst already present, optionally with the addition of a suitable inert catalyst support. It is also possible to perform hydrogenation in the presence of additional hydrogenation catalysts, such as those on a nickel, palladium or platinum basis, optionally using a suitable catalyst support. Suitable materials for use as catalyst support are all industrially conventional catalyst supports based on carbon, elemental oxides, elemental carbides or elemental salts in various forms. Examples of carbon-containing supports are coke, graphite, carbon black or activated carbons. Examples of elemental oxide catalyst supports are SiO.sub.2 (natural or synthetic silicic acid, quartz), Al.sub.2 O.sub.3 (.alpha., .gamma.-Al.sub.2 O.sub.3), aluminas, natural or synthetic aluminosilicates (zeolites), phyllosilicates such as bentonite and montmorillonite, TiO.sub.2 (rutile, anatase), ZrO.sub.2, MgO or ZnO. Examples of elemental carbides and salts are SiC, AlPO.sub.4, BaSo.sub.4, CaCO.sub.3. In principle, both synthetic materials and supports from natural sources, such as pumice stone, kaolin, bleaching earths, bauxites, bentonites, diatomaceous earth, asbestos or zeolites, may be used. Further supports which may be used for the catalysts usable according to the present invention are elemental mixed oxides and hydrogenated oxides of elements of the groups 2 to 16 of the periodic table together with rare-earth metals (atomic numbers 58 to 71), preferably from the elements Al, Si, Ti, Zr, Zn, Mg, Ca, Sn, Nb and Ce, which may inter alia be produced by means of mechanical mixing, joint precipitation of salts or via cogels of salts and/or alkoxides, as known to the person skilled in the art. The supports may be used both as chemically uniform pure substances and as mixtures. Materials in both lump and powder form are suited for use according to the present invention as catalyst supports. Where the supported catalyst is arranged as a fixed bed, the support is preferably used in the form of molded articles, e.g. balls, cylinders, rods, hollow cylinders or rings. Catalyst supports may optionally be further modified by extrusion, tabletting, optionally with the admixture of further catalyst supports or binders, such as SiO.sub.2 or Al.sub.2 O.sub.3, and calcining. The inner surface area of the support (BET surface area) is 1 to 2000 m.sup.2 /g, preferably 10 to 1600 m.sup.2 /g, most preferably 20 to 1500 m.sup.2 /g. Preparation and further processing are well known to the person skilled in the art and are known in the prior art. Activated carbons and Si-, Al-, Mg-, Zr- and Ti-containing materials are preferably used as support materials. Activated carbon is most preferred. The above-mentioned supports may also be loaded with palladium with a metal content of from 0.01 to 50 wt. %, preferably 0.1 to 10 wt. %, relative to the total weight of the catalyst. The above-mentioned support materials or the support materials loaded with palladium may be used in amounts of from 0.01 to 20 wt. %, relative to the halonitrobenzene used, preferably in amounts of from 0.01 to 10 wt. %. The use of activated carbon loaded with palladium is preferred. Hydrogenation may also be performed using other reduction methods, as are known to the person skilled in the art and listed, for example, in "Reductions in Organic Chemistry, Second Edition, ACS Monograph 188". The hydrogenation temperatures range from to approx. 0 to 200.degree. C., particularly 40 to 150.degree. C.; the pressures (hydrogen pressure) are around 0.1 to 150 bar, particularly 0.5 to 70 bar, most preferably 1 to 50 bar. Using the process according to the present invention, corresponding 4-aminodiphenylamines are obtained with high selectivities (>98%) and in yields of up to 99%. |
| PATENT EXAMPLES | available on request |
| PATENT PHOTOCOPY | available on request |
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