DE4100514A1 - Di:phenylamine and derivs. prodn. from corresp. N=cyclohexylidene aniline - Google Patents

Abstract

Prodn. of diphenylamines (I) is carried out by dehydrating N-cyclohexylidene-anilines (II) at 250-500degC, using a catalyst (III) contg. 0.05-5, pref. 0.05-4, esp. 0.1-3 (wt.)% Rh, up to 90% of which may be replaced by Pd, Pt and/or Ir, with addn. of 1-6% alkali metal hydroxide (IV) and 1-6% alkali metal sulphate (V), both w.r.t. (III). R1 = H, 1-6 C alkyl, 1-2 C alkoxy, 3-6 C cycloalkyl, benzyl or aryl; R2 = H, 1-6 C alkyl or 1-2 C alkoxy; R5 = H, 1-6 C alkyl, 1-6 C alkoxy, 3-6 C cycloalkyl, benzyl, aryl, OH, NH2, 1-6 C alkylamino, di-1-6-C-alkylamino, aryloxy or arylamino; R6 = H, 1-6 C alkyl, 1-6 C alkoxy, OH, NH2 or 1-6 C alkylamino; R3, R4, R7 and R8 independently = H or 1-2 C alkyl; aryl = phenyl or 5-6-membered heteroaryl attached in the 2-, 3- or 4-position and with 1 or 2 N, O and/or S heteroatom(s). The prepn. of (II) (not claimed) is described in the text (see below). Pref. (III) has a support of Al2O3 or Al spinel, opt. treated with Cr and Mn, which has a surface area of over 100 M2/g.

Description

The invention relates to a process for the preparation of Diphenylamine represented by lower alkyl and / or lower Alkoxy may be substituted by dehydrogenation of the corresponding N-cyclohexylidene-aniline in Gegen wart of a rhodium-containing supported catalyst.

For the preparation of diphenylamine and its derivatives is known from DE-OS 23 31 878 a method in which one of imines, such as N-cyclohexylidene-aniline and its Derivatives go out and they are in the gas phase in the presence supported catalysts based on nickel, Pla tin, palladium or copper-chromium dehydrated.

Furthermore, it is known from DE-OS 25 20 893, diphenyl amine by catalytic dehydrogenation of compounds and / or compound mixtures consisting of all or part hydrogenated diphenylamine, in the presence a nickel-chromium, aluminum, copper, manganese and alkali to produce containing dehydrogenation catalyst. When such compounds become dinuclear aromatic imines shown in the embodiments.  

The mentioned methods give insufficient sales and yields and are in every way for an indu process to be carried out must be improved tig. The desire to be technically easy to perform Process which ensures high yields and a allows easy workup of the reaction product, is satisfied by the invention.

The invention relates to a process for the preparation of Diphenylamine of the formula (I)

in which R ¹ and R ^2, independently of one another, denote hydrogen, C ₁ -C ₄ -alkyl or C ₁ -C ₄ -alkoxy,
which is characterized in that a N-Cyclohexy liden-aniline of FormeI (II)

in which R ¹ and R ^{2 have} the above meaning,
on a support containing 0.05-5 wt .-% rhodium on a support at 250-450 ° C, preferably 300-400 ° C, and 1-20 bar, preferably 1-6 bar treated.

The catalyst to be used according to the invention contains Rhodium or a combination of rhodium with one their platinum metal from the group palladium, platinum and Iridium. The precious metals are in a total amount of 0.05-5 wt.%, Preferably 0.05-4 wt.%, Especially before at 0.1-3 wt .-% before, based on the total weight of Catalyst.

Preferably, the invention includes einzu putting catalyst a combination of rhodium with at least one of said other platinum metals. In a preferred manner, rhodium with palladium or Platinum or a mixture of palladium and platinum kom bined. In a particularly preferred manner, the combi nation with the rhodium palladium or platinum alone used. In such a combination is the Proportion of rhodium 10-90%, preferably 15-80%, in particular It prefers 20-70% of the total weight of all precious metals metals.

The catalyst to be used also contains 1-6 wt .-%, preferably 2-5 wt .-%, based on the Ge total weight of the catalyst of an alkali metal hydroxide, such as Lithium hydroxide, sodium hydroxide, potassium hydroxide, Rubi diumhydroxid, cesium hydroxide, preferably Lithiumhy hydroxide, sodium hydroxide, potassium hydroxide, especially be preferably sodium hydroxide or potassium hydroxide. The einzu setting catalyst further contains in combination with one or more of said alkali metal hydroxides additionally 1-6 wt .-%, preferably 2-5 wt .-%, based on the total weight of the catalyst, an alkali metal  sulphates, such as lithium sulphate, sodium sulphate, potassium sulphate, Rubidium sulfate, cesium sulfate, preferably lithium sulfate, Sodium sulfate, potassium sulfate, more preferably Na triumsulfate or potassium sulfate.

The said components of the catalysts to be used are arranged on a carrier. Examples of such carriers are alumina, aluminum spinel, activated carbon, kieselguhr, bentonite, pumice, silica gel, ZrO ₂ , TiO ₂ , ZnO, MgO and rare earth oxides.

The said constituents of the catalysts to be used are preferably supported on a support of aluminum oxide or an aluminum spinel, more preferably on an Al ₂ O ₃ or Al spinel which has been treated with chromium and man gan. As alumina, in particular the α- and the γ-modification in question. Aluminum spinels are compounds of the formula Me (II) Al ₂ O ₄ or Me (I) AlO ₂ , in which Me (II) is a bivalent metal cation of iron, zinc, nickel, copper, cobalt, cadmium, magnesium or others , preferably of magnesium, and Me (I) is a monovalent cation, for example lithium (lithium aluminum spinel). The aluminum in the spinels may be partially replaced by trivalent iron, chromium or manganese. Al ₂ O ₃ , more preferably the γ-Al ₂ O ₃ , is preferably used. Such a carrier has in a particularly preferred manner, a content of chromium and manganese together of about 0.05-8 wt .-%, preferably 0.2-5 wt .-%, based on the total weight of the cata- sector on. The weight ratio of chromium and manganese is about 5: 1-1: 5, preferably 10: 9-1: 2. Such carriers treated with chromium and manganese are known from EP 2 08 933.

For the preparation of Ka catalysts described can be proceed in the most preferred manner so that on an Al ₂ O ₃ or aluminum spinel in the form of extrudates, pills or spheres with dimensions of about 2-10 mm compounds of chromium and manganese are applied, the so beauf beat carrier is heated to a higher temperature, then closing separated the noble metals and one or more mah and more alkali metal alkali and be applied; After each application, a drying is carried out, generally at 100-140 ° C at reduced to normal pressure, such as 1-1000 mbar, before given to 10-500 mbar, for example in a water-jet vacuum.

The application of chromium and manganese on the catalyst Torträger in the most preferred manner can at For example, by joint failure of a manganese Chromium hydroxide mixture consisting of a chromium and manganese salt Solution with alkali or ammonia and subsequent Wash out the soluble components with water. As chromium and manganese salts are in particular the Sul fate, chlorides, acetates and / or nitrates of said Elements into consideration. The deposition of the chromium and Manganese on the catalyst support can also be called Am monium-manganese chromate or ammonium-alkali-manganese Chromate from a solution of manganese (II) salts and Ammonium bichromate by means of ammonia and / or basic Alkaline compounds take place. Especially uniform and  adherent deposits are obtained when the bases Add slowly and evenly, avoiding larger ones Concentration differences occurs. This can be done at For example, the precipitation by means of urea under hydro lysing conditions are made, causing the Conditions of slow base addition particularly good are guaranteed.

After application of the chromium and manganese compounds and the precipitate described is the so beauf beat catalyst support free of soluble Verbindun before being heated to higher temperatures (approx 200-450 ° C, preferably 250-350 ° C) is heated. After the This tempering is applied to the chromium and manganese Carrier ready for impregnation with the other mentioned Ka talysatorbestandteilen.

The impregnation of the carrier with the precious metals or with Alkali hydroxide and alkali sulfate (one or more meh of these) is carried out separately. This can be so before to be gone first that the precious metals, at For example, in the form of aqueous solutions of their chlorides, Nitrates, acetates or other suitable salts on the Carriers are soaked, after drying another impregnation with an alkali metal hydroxide solution and an alkali metal sulfate solution takes place. In this Be The precious metals are treated in the form of their oxides or Hydroxides precipitated. The drinking of the or the Alka lihydroxide and the or the alkali metal sulfates separate or shared. After a final Continuing drying, the catalyst is available. He is preferably in the reactor before his  Use by treatment with hydrogen at elevated Temperature as at 120-400 ° C, preferably at 150-380 ° C, activated.

However, you can also first the carrier with an Alka Soak the lihydroxide solution, then dry and open the pretreated basic adjusted catalyst carriers apply the said salts of the precious metals, at the moment of impregnation also the precipitation of Precious metals in the form of their oxides or hydroxides takes place. In this variant, the additional drinking one or more alkali metal sulfates together with the alkali hydroxide, before or after the application of Al kalihydroxids or as a final soak after the Apply the precious metals. Here too a separate drying after each impregnation. After final drying is also after this variant the catalyst is ready for use and can be described in the description Prepare in advance with hydrogen at elevated tempera be activated.

Instead of the said carrier for exposure to the He can also soak with suitable substances ten solutions are sprayed. The required for this Tools and the setting of the desired Beauf Suppression by choice of the quantity and concentration of the Lö Solutions of the elements mentioned are those skilled in the Prin zip known.

In addition to aqueous solutions are basically alko Holistic solutions or solutions in lower carboxylic acids or lower amines in question, if provided  Salts of the precious metals or the basic alkali metal compounds are soluble in it.

N-cyclohexylidene-anilines for the inventive Ver Driving through condensation are the underlying ones Anilines and cyclohexanones available.

The radicals R ¹ and R ² independently of one another have the meaning of hydrogen, C ₁ -C ₄ -alkyl or C ₁ -C ₄ -alkoxy. Examples of the abovementioned alkyl or alkoxy substituents are: methyl, ethyl, propyl, isopropyl, butyl, isobutyl, methoxy, ethoxy, propoxy, isopropoxy, butoxy or isobutoxy. Preferably, said substituents have 1-2 carbon atoms, more preferably methyl or methoxy. In a further preferred manner, one of the substituents R ¹ and R ^{2 has} the meaning of hydrogen, while the other substituent alkyl or alkoxy means in said extent. Most preferably, the process is directed to the preparation of unsubstituted diphenylamine.

The inventive method is at a temperature from 250-450 ° C, preferably 300-400 ° C, and a pressure of 1-20 bar, preferably 1-6 bar, in the gas phase Runaway leads. In a manner known to the expert in the generally lower temperatures in said range lower pressures of the area also disclosed assigned and vice versa, so that the reaction mixture remains in the gas phase.

The to be reacted, optionally substituted N-cyclo Of course, hexylidene-aniline can be used as such  used according to the invention. It is, however, of particular advantage that the N-cyclohexylidene-aniline also be used in a mixture with other substances can. Such other substances are for example additional Lich present, optionally substituted cyclo hexylamine, resulting from the cleavage of N-cyclohexy liden-aniline, or a mixture of additionally present, optionally substituted Cyclohexylamine and appropriately substituted N-cyclohexylaniline. Furthermore, if necessary substituted aniline present.

The N-cyclohexylidene-aniline or its mixture with a or more of the substances mentioned is advantageous with Help an inert carrier gas flow to the rhodium kata brought lysator. Such inert carrier gases are included For example, nitrogen, hydrogen, argon, low Hydrocarbons, such as methane or ethane and others or mixtures of these carrier gases. In preferred Way are nitrogen or hydrogen or a Ge mixed of them used as an inert carrier gas. The Carrier gas is output in an amount of 1-100 l / g material, preferably 1-50 l / g starting material, incorporated puts. The catalyst loading is 0.01-1 kg Starting material per liter of catalyst and hour set.

Examples example 1

200 g of spherical γ-Al ₂ O ₃ with a diameter of 2-5 mm and a specific surface area of 350 m ² / g were placed in a round bottom flask and with a solution of 16.6 g MnSO ₄ .4H ₂ O, 12 , 4 g (NH ₄ ) ₂ Cr ₂ O ₇ and 90 g of urea in 144 ml of water. Under rotation of the movement, the flask was maintained for 1 hour at 85 ° C, the unabsorbed liquid filtered off, washed the catalyst support sulfate-free and then dried within 25 hours at 110 ° C under water jet vacuum. Subsequently, the so-treated catalyst support was 30 minutes at 300 ° C getter pert.

The catalyst support thus prepared was impregnated with a solution prepared from 5.58 g of RhCl ₃ and 66 g of water. After intermediate drying, the catalyst was again soaked with a solution of 5.84 g of NaOH in 60 g of water and net again getrock.

50 g of the catalyst thus obtained were impregnated with a solution of 1.5 g K ₂ SO ₄ in 15 g of water and finally dried at 100 ° C for 18 hours.

30 ml (29 g) of the rhodium-containing kata thus prepared lysators were arranged in a vertical, elek heated glass tube of 17 mm inside diameter and  70 cm length, 66 hours in the hydrogen stream (10 l / h) at 400 ° C activated. For the dehydrogenation of N-cyclohexylidene aniline, the oven temperature was set to 360 ° C. and nitrogen (10 l / h) used as a carrier gas. N-Cyc Lohexyliden-aniline was calibrated using a Dosing device from above in co-current with the Carrier gas introduced (~6.5 g / h). In the upper part of the Reaction tube in which there were only packing, Evaporated the N-cyclohexylidene-aniline and flowed along with the carrier gas through the catalyst layer, located in the middle section of the reaction tube was. The resulting reaction product was auskon condensed and analyzed by gas chromatography.

At a catalyst loading of 0.13-0.3 g of N-cyclo hexylidene-aniline / ml · h showed the reaction product following composition depending on the Be operating time of the catalyst (balance to 100% are Neben Products):

Example 2

100 g of a charged with manganese and chromium γ-Al ₂ O ₃ in spherical form (2-6 mm) were impregnated with a solution of 1.58 g of RhCl ₃ , 5.0 PdCl ₂ , 1.6 g of conc. Hydrochloric acid and 68 ml of water had been prepared. The moist catalyst pellets were dried at 120 ° C in Wasserstrahlva vacuum.

The catalyst pellets were first impregnated with a solution of 11 g of KOH in 60 ml of water and, after intermediate drying, again impregnated with a solution of 6 g of K ₂ SO ₄ in 60 ml of water and dried again at 120 ° C.

30 ml (25.3 g) of the catalyst thus prepared were using the reac described in Example 1 tion tube in hydrogen flow (10 l / h) to 380 ° C he warms and keeps at this temperature for 3 hours. Then the oven temperature was lowered and the dehydration reaction carried out at 320 ° C. There were 12.4 g of N-Cyc lohexyliden-aniline and 10 l nitrogen per hour together passed over the catalyst. The reaction product showed the following composition (remainder are 100% By-products):

Diphenylamine: | 85.2% Cyclohexylidene-aniline: 1.2% N-cyclohexyl-aniline: 3.4% Aniline: 6.7%

Example 3

200 g of a charged with chromium and manganese γ-Al ₂ O ₃ in the form of pellets were uniformly soaked in a round bottom flask with a solution of 2.64 g RhCl ₃ and 3.33 g H ₂ PtCl ₆ in 60 ml of water. The moist catalyst pellets were dried at 120 ° C in a water-jet vacuum net and then 8 hours at 400 ° C in a stream of hydrogen (30 l H ₂ / h) and then washed at room tempera ture chlorine-free. The re-dried cata- capacitor was impregnated with a solution prepared from 6 g of NaOH, 6 g K ₂ SO ₄ and 76 g of water. After this impregnation, the catalyst was dried again ge.

A reaction tube with a diameter of 17 mm and a length of about 600 mm, the upper part of which served as Ver evaporation zone and was filled in the lower part with 30 ml (26.7 g) of the prepared catalyst, was by an electric heating to 400 At this temperature, the catalyst was activated for the next 72 h in H ₂ stream (10 l / h). Using a calibrated metering device, 76 g of N-cyclohexylidene-aniline and 10 l of H ₂ / h were passed into the reaction tube within 15 h. The reaction product was condensed and analyzed by gas chromatography. It gave the following composition as an average of the 15-hour reaction run (rest to 100% are by-products):

Diphenylamine: | 92.1% N-cyclohexyl-aniline: 0.3% Aniline: 4.2%

Claims (7)

1. A process for the preparation of diphenylamine of the formula in which R ¹ and R ² independently of one another are hydrogen, C ₁ -C ₄ -alkyl or C ₁ -C ₄ -alkoxy,
characterized in that an N-cyclohexyl-aniline of the formula in which R ¹ and R ^{2 have} the above meaning,
at a 0.05-5 wt .-% rhodium-containing cata- capacitor on a support at 250-450 ° C, preferably 300-400 ° C, and 1-20 bar, preferably 1-6 bar, behan delt. 2. The method according to claim 1, characterized that one uses a catalyst, the rhodium  or a combination of Rh with at least one another platinum metal from the group Palladium, Pla tin and iridium on supports, the Precious metals in a total amount of 0.05-5% by weight, preferably 0.05-4 wt.%, particularly preferably 0.1-3 wt.%, and in the case of precious metals tallkombinationen the proportion by weight of rhodium on all precious metals 10-90%, preferably 15-80%, particularly preferably 20-70%, and wherein the Catalyst further additives 1-6 wt .-% of a Alkali hydroxide and 1-6 wt .-% of an alkali metal containing all percentages of the Total weight of the catalyst are related. 3. The method according to claim 2, characterized that the catalyst is a combination of rhodium Contains with another platinum metal. 4. The method according to claim 1, characterized in that the catalyst support is Al ₂ O ₃ or an Al spinel. 5. The method according to claim 4, characterized in that the catalyst support is treated with chromium and manganese Al ₂ O ₃ or a so-treated Alumi niumspinell. 6. The method according to claim 1, characterized that the N-cyclohexylidene-aniline in a mixture with Cyclohexylamine or in a mixture with cyclohexylamine and N-cyclohexyl-aniline.   7. The method according to claim 1, characterized that the N-cyclohexylidene-aniline using a Inert carrier gas stream brings to the catalyst.