MXPA97008890A - Process for the catalytic hydrogenation of nitro aromati compounds - Google Patents

Abstract

An object of the invention is a process for the catalytic hydrogenation of nitro aromatic compounds in solution or in melt, in the presence of hydrogen and, at least one noble metal catalyst, a nickel catalyst, or a cobalt catalyst, in said The process comprises a catalytic amount of at least one vanadium compound, in which the vanadium has the oxidation state 0, II, IVóV. It has been discovered that the catalytic hydrogenation of aromatic nitro compounds can almost completely prevent the accumulation of hydroxyl amines by the addition of catalytic amounts of vanadium compounds, which normally results in concentrations of < 1 percent amine hydroxylic. The resulting hydrogenated products are whiter (purest) than those obtained without the addition of the vanadium compound, because almost no azo or azoxy compounds are obtained. The hydrogenation, in particular the final phase, proceeds faster than without this addition. According to the above, there are substantial advantages with respect to the consistency of quality and economy.

Description

PROCESS FOR THE CATALYTIC HYDROGENATION OF NITRO AROMATIC COMPOUNDS The present invention relates to a process for the hydrogenation of unsubstituted or substituted nitro aromatic compounds, with hydrogen, in the presence of known hydrogenation catalysts, usually Rh, Ru, Pt, Pd, Ir, Ni or Co, where they must be present catalytic amounts of hydrogenation of at least one vanadium compound. The invention also relates to the use of vanadium compounds in the catalytic hydrogenation of aromatic nitro compounds with hydrogen, in the presence of known hydrogenation catalysts. The catalytic hydrogenation of aromatic nitro compounds is a reaction that is industrially important, for example, for the preparation of intermediates for agrochemicals, dyes and fluorescent whitening agents. For the preparation of styling fluorescent whitening agents, for example, 4,4'-dinitrostilbene-2,2'-disulfonic acid has to be reduced to obtain 4,4'-diaminostylene-2,2'-disulfonic acid, which can be achieved by conventional reduction processes, or by catalytic hydrogenation. The preparation of azo dyes requires large amounts of diazonium salts, which in turn are prepared from the corresponding amines. The catalytic hydrogenations of the aromatic nitro compounds to obtain the corresponding aromatic amines proceed through several intermediate steps. Among these are relevant nitrogenous compounds, and in particular, the hydroxyl amine intermediate, as described, inter alia, by M. Freifelder in Handboo of Practical Catalytic Hydrogenation, Wiley-Intersciepce erlag, New York 1971. This intermediary of Hydroxylic amine presents a special problem in practice, because, under specific conditions, it can accumulate in large quantities in the reaction solutions. This applies in particular to aromatic nitro compounds, whose hydrogenation results in relatively stable arylhydroxylic amines. This is particularly critical when the hydrogenation is carried out in a batch reactor of pastes. In the extreme case, several tons of arylhydroxylamine can be formed in this manner. Arylhydroxylic amines are in many aspects problematic. On the one hand, it is known that these compounds are often thermally unstable, and may be disproportionate during heating with or without Ha with a strong heat emission. The released heat can trigger other decomposition reactions, which can then result in incidents with heavy explosions. W.R. Tong et al., AICHE Loss Prev. 1977, (11), 71-75 describe this incident, during the reduction of 3,4-dichloronitrobepcene in 3,4-dichloroaniline. This instability makes a complete and elaborate thermal examination of the hydrogenation mixtures imperative. In particular, the thermal behavior of the possible hydroxyl amine intermediates should be fully examined. F. Stoessel, J. Loss Prev. Process Ind., 1993, volume 6, No. 2, 79-85 describes this process, using the hydrogenation of nitrobenzene to obtain aniline as an example. Arylhydroxylic amines are also known as strong carcinogens, and therefore, constitute a high risk potential in the case of interrupted or incomplete hydrogenation (J.A. Miller, Cancer Res. 3 (1970), 559). The preparation of a pure amine constitutes a third complex of problems. If, during the hydrogenation or at the end of the reaction, there are significant amounts of arylhydroxyl amine present, then this can lead to condensations with the formation of undesired and stained azo or azo products. Since the amount of arylhydroxylamine can change from batch to batch, the quality of the resulting product differs in purity and appearance. The problems indicated above are further aggravated by the fact that the resulting concentrations can not be predicted, or even the maximum possible concentrations of this hydroxyl amine intermediate, even in processes that are known and well studied. The presence of impurities in the trace range can trigger the spontaneous accumulation of hydroxyl amine intermediates in an unpredictable manner. For example, in Catalysis of Organic Reactions, volume 18, (1988), 135, J.R. Kosak reports that the simple addition of 1 percent NaNÜ3 increases the accumulation during the hydrogenation of 3,4-dichloronitrobenzene from <; 5 percent initial, up to about 30 percent. To solve these problems, different processes have been proposed in the prior art. German Patent DE-OS-25 19 838, for example, discloses a continuous process for the catalytic hydrogenation of nitro compounds, to obtain the corresponding amino compounds, wherein the catalyst particles of 0.5 to 3 millimeters are configured in a fixed bed, and nitro compounds are carried in the drip phase. The catalyst is preferably applied to a carrier, usually aluminum oxide or silicic acid. A similar continuous process is disclosed in the German Patent No. DE-OS-22 14 056. In this process, the nitro compound is also conducted on the fixed catalyst. This catalyst consists of aluminum spinel as a carrier, on which palladium and vanadium or vanadium compounds are fixed.

German Patent Number DE-OS 2849002 discloses a process for the hydrogenation of nitrobenzene in the vapor phase, in a continuous process, in the presence of a multi-component carrier catalyst comprising 1 to 20 grams of a noble metal , and from 1 to 20 grams of, for example, vanadium or a vanadium compound per liter of carrier material. For the reduction of the aromatic nitro compounds in a batch reaction, US Pat. No. US-A-4,212,824 proposes the use of an iron-modified platinum catalyst for hydrogenation. In practice, however, this iron-modified platinum catalyst can not entirely satisfy. In many cases the formation of hydroxyl amine is not completely prevented, on the one hand, but on the other hand, the hydrogenation rate can be remarkably slower. These proposals of the prior art all have in common that the actual catalyst is modified, and in this way its activity is adjusted, so that a large amount of hydroxyl amine accumulation can not occur, particularly in the continuous process. In continuous processes, this is in any case substantially less critical than in batch processes, because the continuous processes have a lower physical quantity of product and product in the actual reaction volume. On the other hand, continuous processes are only economical in the case of products with large tonnages, so that there is still a desire for an easily controllable reaction, essentially without accumulation of hydroxyl amine. This is particularly important with respect to batch reactions. In addition, the preparation of the fixed bed catalysts described above involves a large amount of expense and is complicated, which also reduces the economics of these operating processes. Surprisingly, it has now been discovered that, in the catalytic hydrogenation of aromatic nitro compounds, the accumulation of hydroxyl amines can be almost completely prevented by the addition of catalytic amounts of vanadium compounds, which usually results in concentrations of < 1 percent hydroxyl amine. This result can be achieved with any commercially available hydrogenation catalyst. No special pretreatment or modification of the catalyst is necessary, as is known from the prior art. The resulting hydrogenated products are whiter (purest) than those obtained without the addition of the vanadium compound, because almost no azo or azoxy compounds are obtained. The hydrogenation, in particular the final phase, proceeds faster than without this addition. In accordance with the above, there are substantial advantages with respect to the constancy of quality and economy.

Compared to the prior art, this invention has the substantial advantage that catalytic amounts of a vanadium compound can easily be dissolved or dispersed in the reaction medium, providing excellent hydrogenation results. An object of the invention is a process for catalytic hydrogenation of aromatic nitro compounds in solution or in a melt, in the presence of hydrogen and at least one noble meta1 catalyst, a nickel catalyst, or a ccaattaalliizzazioneer of carbon dioxide, in said process a catalytic amount of a least vanadium compound is present, wherein the vanadium has the oxidation state 0, II, III, IV or V. A preferred process is that in which the vanadium compound is dissolved or dispersed in amounts catalytic in the reaction medium; preferably it dissolves. Another equally preferred process is obtained when the vanadium compound is mixed with or applied to the catalyst. It is also preferred to apply the vanadium compound first to a suitable carrier, and then to disperse it in this form in the reaction medium. Suitable carrier materials are, for example, all those used for the preparation of commercial hydrogenation catalysts in powder form, such as those indicated below.

The application to the catalyst or carrier material is carried out in a simple manner, usually by dissolving the vanadium compounds, suspending the catalyst or carrier material in the solution, and subsequently filtering. If the vanadium compounds are not soluble in the reaction medium, then they can also be mixed in a dispersed paste form with the paste catalyst, and filtered together. Suitable vanadium compounds from oxidation state 0, II; III, IV or V, are elemental vanadium, as well as purely inorganic compounds, but organic complexes are also possible with, for example, oxalate or acetylacetonate. The preferred vanadium compounds are Uf) s or those which constitute a purely inorganic salt, an oxo salt, or the hydrate of a purely inorganic salt or of an oxo salt. Typical examples are vOCl3, VC1?, [VO (SCN)] 42? 'VOSO, NHtívO 3 VC13 VCl the corresponding halides with F or Br. The compounds are obtained in aqueous solution in different hydrate forms, depending on the pH (FA Cotton, G. Wilkinson, Anorganische Chemie, Verlag Chemie Weinheim 1968, 2nd edition, pages 757 -766). Particularly preferred vanadate or hydrate vanadates are those of the oxidation state V. Vapadates of ammonium, lithium, sodium, or potassium, or a hydrate of these vanadates are very particularly preferred.

It is preferred to use the vanadium compound in an amount of 1 to 2000 ppm, particularly preferably in an amount of 5 to 500 ppm, based on the aromatic nitro compound to be hydrogenated. The weight ratio of the vanadium compound to the catalyst is preferably from 1: 1 to 1: 10,000, particularly preferably from 1:10 to 1: 1,000 and very particularly preferably from 1:50 to 1: 750 . The aromatic nitro compounds can be substituted by any groups that are inert during hydrogenation, or also by additional groups that can be hydrogenated, for example, olefypic groups. Sometimes a concomitant hydrogenation of all groups may be desired. The aromatic nitro compounds may comprise one or more of a nitro group. Some examples of aromatic nitro compounds are aromatic hydrocarbons, typically benzenes, polycyclic hydrocarbons (also partially hydrogenated ones, such as tetralin), biphenyls, cyclopentadienyl anion and cycloheptatrienyl anion, heteroaromatics, typically pyridines, pyrroles, azoles, diazines, triazines, triazoles , furans, thiophenes, and oxazoles, condensed aromatics, typically naphthalene, aphecene, indoles, quinolines, isoquipolines, carbazoles, purines, phthalazipases, benzotriazoles, benzofurans, cinolins, quinazoles, acridines, and benzothiophenes. It will be understood that these compounds also include conjugated aromatic systems, such as stilbenes or cyanines, under the condition that the nitro group is linked to the aromatic part of the conjugated aromatic system. A preferred subgroup is formed by aromatic nitro compounds, wherein the aromatic radical is substituted by electrophilic groups. The electrophilic groups are usually halogen, sulphonic acid radicals and their derivatives, carboxylic acid radicals or their derivatives, such as ester, acid chloride, or nitriles. Halogen is fluorine, chlorine, bromine, or iodine. Fluorine, chlorine, or bromine are preferred. Preferred electrophilic groups are halogen, -SO3, -COX, wherein M is hydrogen or an alkali metal, and X is halogen or 0-alkyl of 1 to 12 carbon atoms. Alkyl of 1 to 12 carbon atoms can be methyl, ethyl, isopropyl, normal propyl, normal butyl, isobutyl, secondary butyl, tertiary butyl, as well as the different isomeric radicals of pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl , and dodecyl. Very particularly preferred is the aromatic nitro compound of 4,4'-dinitrostilbene-2,2'-disulphobic acid, or a compound of the formula II, III, or IV: In principle, the process is suitable for all reductions of aromatic nitro groups in aromatic amines made on a large industrial scale. Typical examples are intermediates for agrochemicals, fluorescent whitening agents, and dyes. The process of the invention is particularly suitable for the preparation of aromatic amino compounds, such as those disclosed, inter alia, in European Patent Number EP-A-42357, which are used for the preparation of diazopium salts in the synthesis of azo dyes. The reaction can be carried out in solution in a suitable solvent which is inert during the reaction, but can also be carried out in the melt of the educt. Suitable solvents are usually water. alcohols, such as methanol, etapol, normal propapol, isopropanol, normal butanol, isomeric butanols and cyclohexanol. ethers, esters, and ketones, typically diethyl ether, methyl tertiary butyl ether, tetrahydrofuran, dioxane, di ethoxyethane, ethyl acetate, butyl acetate, butyrolactone, acetone, methyl ethyl ketone, methyl isobutyl ketone, or cyclohexanone; carboxylic acids, typically acetic acid and propionic acid, dipolar / aprotic solvents, such as dimethyl formamide, N-methyl pyrrolidone, dimethyl acetamide, sulfolane, dimethyl sulfoxide or acetonitrile; apolar solvents, typically toluene or xylene, chlorinated aromatic hydrocarbons, typically methylene chloride, alkane of 3 to 7 carbon atoms, or cyclohexane. These solvents can be used in pure form or in the form of mixtures. The noble metal catalyst may contain rhodium, ruthenium, iridium, palladium or platinum as noble metals. Also suitable are nickel catalysts or cobalt catalysts. The nickel catalyst can be, for example, Raney nickel. In a preferred embodiment of this invention, the noble metal catalyst is platinum, palladium, iridium, rhodium, or ruthenium in a metallic or oxidized form that is applied to a carrier. The metal form is particularly preferred. Platinum or palladium are very particularly preferred. Particularly suitable carriers are activated carbon, silicic acid, silica gel, aluminum oxide, calcium carbonate, calcium phosphate, calcium sulfate, barium sulfate, titanium oxide, magnesium oxide, iron oxide, lead oxide. , lead sulfate, or lead carbonate. Activated carbon, silica gel, aluminum oxide, or calcium carbonate are very particularly suitable. It is preferred to use the noble metal catalyst in an amount of 0.1 to 5 weight percent, based on the aromatic nitro compound. The process of preference is carried out at a temperature of 1 »10-2 * 107pascals. The preference process is carried out in the temperature range from 0 ° C to 300 ° C, particularly preferably from 20 ° C to 200 ° C. The process can be carried out as a batch or continuous process. Batch process is preferred. The invention also relates to the use of vanadium compounds according to claim 1, for the catalytic hydrogenation of aromatic nitro compounds in solution or in melt in the presence of hydrogen and at least one noble metal catalyst, a nickel catalyst, or a cobalt catalyst. The following examples illustrate the invention in greater detail. The reaction rates were determined by nuclear magnetic resonance spectroscopy, and the percentages are by weight. 1 A 300 milliliter autoclave equipped with a disperser is charged, under pressure, with 77 grams of the compound of formula II: then add 110.5 milliliters of absolute tetrahydrofuran (Me'-ck pa), 530 milligrams of 5% Pd / C (Johnson Matthey 87L) and 19.4 milligrams of The air in the autoclave is replaced with N2, and the reaction mixture it is heated to 120 C. At 120 ° C, the N2 is replaced with H 2 (20 bar) and the disperser is started. After a reaction time of 120 minutes, 100 percent of the amino compound is obtained, and 0 percent of hydroxylic amine. During the entire reaction, hydroxyl amine formation can not be detected.

Example of Comparison Example 1 is repeated, but without the addition of NH 3 O 3 After a reaction time of 150 minutes, 84 percent of the amino compound, and 16 percent of hydroxylic amine are obtained. The maximum concentration of hydroxyl amine during the reaction is 41 percent.

Example 2. Preparation of amide (N-hexahexyl-N-methyl) of anilin-2-sulphonic acid A 500 milliliter shaker flask is charged with 13.0 grams of amide (N-cyclohexyl-N-methyl) of nitrobenzene-2-sulfonic acid, 130 grams of methanol, 0.895 grams of 5% Pd / C, and a modifier of vanadium (Table 1). The stirring flask is evacuated 3 times, and flooded with hydrogen. The temperature rises to 40-50 ° C, and the reaction starts (1.1 bar of hydrogen). During the reaction, 4 to 5 samples are taken to verify the reaction. These samples, as well as the reaction product, are analyzed with 1 H-NMR. The results mentioned in Table 1 are obtained.

Table 1 * tR - reaction time ** H4VO3 deposited on activated carbon, Example 3 Preparation of 3-amino-4-chloroacetic anuide Example 3a. A hydrogenation reactor is charged with 15 parts of sodium acetate, 60 parts of NaHCO 3, 1,320 parts of MeOH, and 1,015 parts of l-chloro-2,4-dinitrochlorobenzene under one hundred, 0.15 parts of 3 and 66 parts of water. The hydrogenation is carried out at 60 ° C and 18 bar. The product is isolated as annealed 3-amino-4-chloroacetic (785 parts, 85 percent theory). Example 3b. A 0.3 liter Hastalloy B autoclave is charged with 40.8 grams of l-chloro-2,4-dinitrochlorobenzene, 120 milliliters of methanol, and 0.21 grams of 5 percent Pt / C catalyst. The mixture is flooded with nitrogen, and then hydrogenated with hydrogen at 60 ° C and 10 bar. The selectivity with respect to dehalogenation is 66 percent.

Example 4. Preparation of 2,4,4'-trichloro-2'-aminodiphenyl ether (TAPE) TADE A 2-liter steel autoclave is charged with 330 grams of 2,4, '-trichloro-2'-nitrodiphenyl ether, 330 grams of MeOH, 2.8 grams of 1 percent Pt + 0.1 percent Cu / C. The autoclave closes and is flooded with nitrogen. The hydrogenation is carried out at a hydrogen pressure of 12 bar and at 60 ° C. After consumption of the specific percentages of the calculated amount of hydrogen, the hydrogenation is interrupted, and a sample of the reaction mixture is taken. The sample is heated in the programmed temperature differential scanning calorimeter to 4QC / minute, and the energy released from the decomposition is measured. The disproportionation of the arylhydroxy amine is given a thermal signal which is already visible at < 100 ° C. The decomposition of the nitro compound still present in the reaction mixture (mr) starts at > 200 ° C. The results are shown in Table 2.

Table 2 The risk that a spontaneous decomposition of the accumulated aryl hydroxyl amine triggers the decomposition of the nitro compound can be markedly reduced.

Example 5, Preparation of sodium 4,4'-diaminostilben-2,2 '' disulfonate (DAS) ABAS A 300-milliliter steel autoclave is charged with 48 grams of sodium 4,4'-dinitrostilbene-2,2'-disulfonate, 174 grams of water, 0.15 milliliters of H2SO ??.5M, 1.4 grams of activated carbon, 64 milligrams of Pt / C at 5 percent, and 12 milligrams of NH ^ O 3 The autoclave closes and is flooded with nitrogen. The hydrogenation is carried out at 70 ° C with the controlled addition of hydrogen of 2.5 Nl / h (maximum of 4 to 5 bar of hydrogen). After the hydrogenation is completed, the autoclave is made inert, the catalyst is filtered, and the reaction mixture is analyzed by high performance liquid chromatography. The results are shown in Table 3.

Table 3 The selectivity of the hydrogenation of DNS depends very much on the availability of hydrogen on the surface of the catalyst. Accordingly, the hydrogenation is preferably carried out under high pressure in reactors with good gasification. According to the process described, it is possible to carry out the hydrogenation at a low partial pressure of H2, and still obtain a good quality of the product. The hydrogenated product is an intermediate for the preparation of fluorescent whitening agents. The speed of the reaction, and consequently, also the heat flux resulting from the hydrogenation, can be controlled in this way by means of H2 dosing.

Claims (25)

1. A process for the catalytic hydrogenation of aromatic nitro compounds in solution or in melt, in the presence of hydrogen and at least one noble metal catalyst, a nickel catalyst, or a cobalt catalyst, in said process a catalytic amount of , at least one vanadium compound, wherein the vanadium has the oxidation state 0, II, III, IV, or V.

2. A process according to claim 1, wherein the vanadium compound is dissolved or dispersed. in catalytic amounts, in the reaction medium.

3. A process according to claim 1, wherein the vanadium compound is mixed with or applied to the catalyst.

4. A process according to claim 1, wherein the vanadium compound is mixed with or applied to a carrier material.

5. A process according to claim 1, wherein the vanadium compound is V £) or a purely inorganic salt, an oxo salt, or the hydrate of a purely inorganic salt or of an oxo salt.

6. A process according to claim 1, wherein the vanadium compound is a vanadate or the hydrate of a vanadate at oxidation state V.

7. A process according to claim 6, wherein the vanadium compound is a vanadate of ammonium, lithium, sodium, or potassium, or a hydrate of these salts.

8. A process according to claim 1, which comprises using the vanadium compound in an amount of 1 to 2,000 ppm, based on the aromatic nitro compound to be hydrogenated.

9. A process according to claim 1, which comprises using the vanadium compound in an amount of 5 to 500 ppm, based on the aromatic nitro compound to be hydrogenated.

10. A process according to claim 1, wherein the weight ratio of the vanadium compound to the catalyst is from 1: 1 to 1: 10,000.

11. A process according to claim 10, wherein the weight ratio of the vanadium compound to the catalyst is from 1:10 to 1: 1,000.

12. A process according to claim 11, wherein the weight ratio of the vanadium compound to the catalyst is from 1:50 to 1: 750.

13. A process according to claim 1, wherein the catalyst contains as a noble metal, rhodium, ruthenium, iridium, palladium, platinum, or as a base metal, nickel or cobalt.

A process according to claim 13 which comprises using a noble metal catalyst, wherein rhodium, ruthenium, iridium, platinum, or palladium is applied in a metallic or oxidized form on a carrier.

15. A process according to claim 14, wherein the carrier is activated carbon, silicic acid, silica gel, aluminum oxide, calcium carbonate, calcium phosphate, calcium sulfate, barium sulfate, titanium oxide, magnesium oxide, iron oxide, lead oxide, lead sulfate, or lead carbonate.

16. A process according to claim 15, wherein the carrier is activated carbon, silica gel, aluminum oxide, or calcium carbonate.

17. A process according to claim 16, wherein the catalyst comprises platinum or palladium.

18. A process according to claim 1, which comprises using the noble metal catalyst in an amount of 0.1 to 5 weight percent, based on the aromatic nitro compound.

19. A process according to claim 1, which is carried out at a pressure of 1 105-2 107 steps.

20. A process according to claim 1, which is carried out on the temperature scale of 0 ° C to 300 ° C.

21. A process according to claim 1, which is carried out on the temperature scale of 20. ° C to 200 ° C.

22. A process according to claim 1, which is carried out as a batch process.

23. A process according to claim 1, wherein the aromatic nitro compound comprises electrophilic substituents.

24. A process according to claim 1, wherein the aromatic nitro compound is 4,4'-dinitrostilbenedisulfonic acid, or a compound of formula II, III, or IV:

25. The use of a vanadium compound according to claim 1, for the catalytic hydrogenation of aromatic nitro compounds in solution or in melt, in the presence of hydrogen and, at least one noble metal catalyst, a nickel catalyst, or a cobalt catalyst.