DE2519838A1 - Catalyst for hydrogenation of nitro cpds. to amines - contg. palladium or platinum and opt. vanadium on a carrier - Google Patents

Abstract

Catalytic hydrogenation of nitro cpds. to amines in the spray phase over a stationary catalyst is improved by using a catalyst having particles with a dia. of 0.5-3 mm (pref. 1.5-2.5 mm) in the form of spheres (pref.) cylinders, extruded bodies, granules or flakes. The catalyst pref. contains Pd and/or Pt opt. with V (pref. Pt and V) on a carrier such as alumina (pref.), silica, or aluminosilicate, a spinel, magnesia, baryte or active carbon. The catalyst has long service life (>10,000 k), and there is no encrustation on the catalyst particles.

Description

Process for the preparation of amino compounds.

The present invention relates to a method for producing Amino compounds through catalytic reduction of nitro compounds in the trickle phase over a fixed catalyst.

It is already known that nitro compounds can be catalytically converted into amino compounds to hydrate. Such hydrogenations are carried out both in the gas phase and in the liquid phase Phase carried out (Houben-Weyl, Methods of Organic Chemistry, Volume XI / I, 4. Edition 1952, page 364, lines 1 to 4 from below) When working in the gas phase the following disadvantages occur: The nitro compound to be hydrogenated must be carried out before the hydrogenation evaporated and the resulting amino compound condensed after the hydrogenation; relatively high temperatures are required for working in the gas phase the selectivity-reducing side reactions are favored; the gas phase process is limited to the hydrogenation of mononitro compounds because of the temperatures the gas phase hydrogenation for the hydrogenation of compounds with a higher degree nitration, e.g. of di- and trinitro compounds, for safety reasons are too high; A large excess of hydrogenation gas is necessary for better dissipation of the very high heat of reaction necessary. These disadvantages in gas phase hydrogenation are rented out, if the hydrogenation of nitro compounds is carried out in the liquid phase. The hydrogenation in the liquid phase therefore also reaches a considerable amount for the implementation of the process Scope of application. In the liquid phase process, the catalyst is used technically usually used in suspended form. The disadvantage of this procedure is in that the catalyst is introduced into the process in suspended form and has to discharge it from the process in mostly pyrophoric form.

In the liquid phase hydrogenation in the form of the trickle phase over firmly arranged Catalyst eliminates these disadvantages. For example, in DOS 2 106 644 a Process for the hydrogenation of dinitrotoluenes in the trickle phase described in the gas and liquid in the form of the so-called transition flow over the catalyst are to be directed; the so-called transition flow has to be measured in each case determine the pressure difference in the reactor as a function of the liquid loading, which, however, is a major disadvantage, since the so-called transition flow depends on the shape and size of the catalyst and the pipe diameter and pipe length and must therefore first be determined for these state variables. Since then the liquid load during normal operation of a technical trickle phase hydrant system is varied and the pressure difference is not constant, is a constant Verify the conditions required to be in the area of the so-called transition flow to hydrate. In addition, it is disadvantageous that there is no exposure to the liquid can vary within wide ranges, as for the range of the so-called transition flow, only a certain, relatively narrowly limited fluid load is an issue comes.

Another disadvantage is that often with previously known Process, e.g. according to DT-AS 2 106 644, the trickle phase hydrogenation of nitro compounds must be carried out in relatively long reaction tubes in order to be as complete as possible Hydrogenation to knit the nitro compounds.

Another disadvantage can be explained on the basis of DT-OS 2 044 6575 in which describes a process for the preparation of toluenediamine in the trickle phase is, the essential feature of which is that from the circulating reaction mixture the water contained therein and the solvent are separated off before the tolylenediamine how it is fed back into the hydrogenation zone to dilute the fresh feed. There the fresh use is diluted again with the (distilled off) solvent represents the previous distilling off of solvent and water before recycling a major disadvantage in terms of cost.

It has now been found that all of the disadvantages listed above can be avoided can, if one considers the catalytic hydrogenation of nitro compounds to the corresponding Amino compounds in the trickle phase over a fixed catalyst in the manner carried out that one catalysts with a particle size of 0.5 to 3 mm diameter used. Preference is given to using catalysts with particle sizes from 1.5 to 2.5 mm.

It must be described as extremely surprising that with the Use of the catalyst according to the invention in a very small particle size also in the case of a high liquid load and a very high gas load, nevertheless Differential pressure (JP P reactor inlet-reactor outlet) does not rise in such a way that the Hydrogenation can no longer be operated industrially; So there is no differential pressure increasing Deposits on the catalyst, as is the case for the hydrogenation of nitro compounds is known to be typical. This surprising advantage lasts even for very long periods Running times of the catalytic converter.

The catalysts come in the form of supported catalysts or full contacts to use. The supported catalysts or full contacts can be in the form of spheres, Cylinders, extrudates, Granules or flakes in the size of 095 to 3 mm, preferably 1.5 to 2.5 mm in diameter can be used. The preferred one Shape is the spherical shape.

Supported catalysts are preferably used for the process.

All customary support materials, such as e.g. Aluminum oxides, silica, aluminum silicate, spinels, magnesium oxide, barium sulfate or activated carbon, which can be used in lump form. Excellent aluminum oxides with a specific surface area) 200 m2 / g or the are suitable Spinels made from them, in particular lithium-aluminum spinel.

As catalytically active metals or compounds all come for that Hydrogenation of nitro compounds to amino compounds in suitable catalysts in Consideration. For example, all in Houben-Weyl, Volume XI / 1, pages 365 and 366 connecting paragraph, listed catalysts and catalyst combinations applied will. Noble metal catalysts are mainly used alone or as mixed catalysts with other noble metal catalysts and / or non-noble metal catalysts in the customary catalytic application forms used. When supported catalysts for Apply, the catalysts are generally only on the supports applied to the surface. Suitable are e.g.

Catalysts containing palladium and / or platinum and optionally vanadium. Platinum and platinum-vanadium catalysts are preferably used. The precious metal e.g. palladium or platinum, is applied to the carrier in a known manner.

For example, the precious metal is e.g. platinum, in amounts of 0.1 up to 5 percent by weight, preferably 0.5 to 2 percent by weight, based on the finished product Catalyst applied to the support. For this purpose you soak or spray the carrier, for example, with an aqueous precious metal salt, e.g. platinum salt solution. All commercially available precious metal compounds are suitable for soaking or spraying suitable. Before the reduction of the Precious metal compounds in the metallic Can form the noble metal compounds into noble metal hydroxide or noble metal oxide being transformed. The normally subsequent reduction of the noble metal compounds to the metal can for example with formaldehyde and hydrazine in neutral or alkaline Solution or carried out with formic acid, hydrogen, carbon oxide or ethylene will. However, other reduction methods can also be used. If Vanadium should also be included as an active component in the catalyst, so the vanadium can be used before or after the application of the main component, e.g. the precious metal, in the form of soluble vanadium compounds, e.g. vanadyl oxalate, applied to the carrier will. In general, the vanadium salt applied to the support is then used converted into the oxide form by annealing at temperatures of about 2000C to about 5000C. The vanadium content in the finished catalyst can be 0.1 to 2 percent by weight, preferably 0.2 to 0.8 percent by weight.

It is advantageous to use the catalysts prepared in this way to wash out the anions contained in the production process with distilled water. Platinum and platinum / vanadium catalysts, e.g. applied to spherical carriers, are particularly preferred. They stand out in the process according to the invention through excellent selectivities and also lead to a water of reaction, that after the separation by distillation only contains small amounts of pollutants laden wastewater results. The wastewater then falls into a first distillation column undertaken distillation of the solvent used as the top product of Distillation in a second fractionation column and contains part of the as By-products of pollutants; a high level of pollutants naturally makes them more expensive the wastewater treatment and thus the production costs of the amine produced, what is avoided in the procedure according to the invention.

The hydrogenation of the nitro compound can according to the invention Process continuously or discontinuously in the Trickle phase over the fixed bed fixed catalyst in a tube or shaft furnace from 1 to 8 m in length, at temperatures from 50 to 200 ° C and at pressures from 1 to 150 be carried out in cash.

The main advantage of the method according to the invention over the trickle phase process known hitherto consists in the trickle phase hydrogenation without prior, previously necessary determination of the so-called transition flow in a much broader range of the liquid load, e.g. with 2 to 40 kg of reaction medium per liter of catalyst per hour and also using of shorter reactors, e.g. with a pipe length of 1.50 m. Other advantages are the significantly longer service life (> 10,000 hours) of these catalysts and complete conversion of the nitro compounds over catalysts with larger carrier particle diameters.

The hydrogenation of the nitro compound is expediently carried out with dilution Taken with suitable solvents. Such solvents come in particular into consideration, in which both the nitro compound to be hydrogenated and the resulting, reaction product consisting of amino compound and water are soluble.

Lower aliphatic alcohols such as Methanol, methanol, n-propanol, isopropanol and butanols.

Isopropanol is particularly suitable here, as it is known N-alkylation of the resulting N-alkylation, which occurs as a side reaction in the hydrogenation Amino compounds suppressed when using isopropanol as a solvent will. To dilute the nitro compound to be hydrogenated, initially only the solvent e.g. in a ratio of nitro compound to solvent such as 1: 100. After the occurrence of the hydrogenation point, this is essentially made up of an amino compound, Water and solvent existing reaction mixture in addition to diluting the recycled to hydrogenated nitro compound. The total is then the ratio of nitro compound to be hydrogenated to Thinner (solvent and water and amino compound) in general 1: 5 to 1: 200, preferably 1: 25 to 1: 100.

The liquid loading can be in the range from 2 to 40 kg of reaction medium can be varied per liter of catalyst and hour.

The gas loading can be 10Q to 1000% of the theoretical for the hydrogenation the nitro compound required hydrogen.

Any excess gas can be released after the reaction or it is returned to the process as cycle gas.

Both saturated aliphatic and cycloaliphatic compounds can be used as nitro compounds or aromatic as well as heterocyclic, optionally substituted nitr compounds can be used. Aliphatic nitro compounds are those with 1 to 12, preferably with 1 to 4 carbon atoms suitable as cycloaliphatic nitro compounds come those with 5 to 7 carbon atoms, preferably those with 6 carbon atoms in the ring system, into consideration. Aromatic nitro compounds used in the process of the invention can be used, generally contain 6 to 14 in the aromatic nucleus C atoms, preferably 6 C atoms. Preferred heterocyclic nitro compounds are 5- and 6-membered heterocycles, the heteroatoms of oxygen, nitrogen and / or May contain sulfur, suitable. The heterocyclic compounds can also once or twice with an optionally partially hydrogenated aromatic ring be fused. Corresponding compounds are, for example, 2-nitrothiophene, 3-nitrobenzothiophene-.

The nitro compounds to be hydrogenated can contain 1 to 3 nitro groups contained in the molecule. Halogen atoms, hydroxyl, Mercapto, amino, sulfonic acid, carboxyl and alkoxy groups and alkyl radicals are suitable.

Particularly preferred starting compounds are nitrobenzene, dinitrobenzenes, Nitraniline, Nitrotoluenes, Dinitrotoluenes, Nitrophenols, Nitrochlorbenzenes, Nitronaphthalene, Nitrodiphenylamine, nitropropane.

The technical implementation of the process is possible in illustrated in the following examples.

Examples a) Preparation of the catalysts.

Catalyst 1 4 liters of a spherical active alumina of 1.6 to 2.8 mm in diameter and a specific surface area of 380 m² / g soaked with 1600 ml of a solution containing 200 g of Na2PdCl4 and with an aqueous one Solution of 20 percent by weight sodium hydroxide and 20 percent by weight hydrazine during 5 hours treated. The remaining catalyst mass becomes neutral with water and Washed free of chloride and dried at 150ob. Then with a solution of 43 g of vanadium (V) oxide, in 150 ml of an approx. 70 to 90 C hot, aqueous 20 percent by weight Oxalic acid solution soaked, then dried and finally tempered for 6 hours at 3000C. The finished supported catalyst contains 1.8% palladium and 0.6% vanadium.

Catalyst 2 4 liters of a spherical active alumina 1.5 to 2.5 mm in diameter and a specific surface area of 380 m2 / g soaked with 1600 ml of a 155 g H2PtCl6-containing solution and with an aqueous Solution of 20 percent by weight sodium hydroxide and 20 percent by weight hydrazine during 5 hours treated. The remaining catalyst mass becomes neutral with water and Washed free of chloride and dried at 150 ° C. Then with a solution of 43 g of vanadium (V) oxide in 1500 ml of an approx. 70 to 9G- ° C, watery 20 weight percent oxalic acid solution soaked, then dried and finally 6 hours annealed at 3000C. The finished supported catalyst contains 1.8% platinum and 0.6 % Vanadium.

Catalyst 3 3 liters of spherical active alumina at 1.5 with a diameter of up to 2.8 mm 2 and a specific surface area of 360 m 1 liter of aqueous solution soaked at 300C, in successive 296 g of formic acid and 233 g of 54% lithium hydroxide aqueous solution was added. The soaked Aluminum oxide was dried in vacuo at 150 ° C., again with the same solution soaked and dried to 150 ° C in a vacuum. The carrier was then 6 hours Annealed at 10500 C to form lithium-aluminum spinel. 4 liters of the so produced The carrier is soaked in 1500 ml of a solution containing 155 g of H2PtCl6 and with an aqueous solution of 20 percent by weight sodium hydroxide and 20 percent by weight Treated hydrazine hydrate for 5 hours. The remaining catalyst mass was washed neutral and chloride-free with water and dried at 150.degree. The finished one Catalyst contains 1.8% platinum.

Catalyst 4 (comparative catalyst) This catalyst is like the catalyst 1 was prepared instead of the spherical active alumina from 1.6 to 2.8 mm, an aluminum oxide of 3 to 6 mm in spherical shape is used.

b) Hydrogenation Examples The experiments were carried out in: the trickle phase in: 1.50 m to 8 m long reactor tubes of 24 mm diameter carried out. The reaction tube, which was filled with the respective catalyst was surrounded by a jacket tube, through which heating or cooling medium flowed. The nitro compound to be hydrogenated was usually pumped in alcoholic solution from above onto the catalyst and trickled over the catalyst down into a separator, from which some of the dissolved Hydrogenation product again was pumped to use the reactor. A certain proportion was released from the gas phase of the separator. The hydrogenation was carried out at 30 to 80 bar hydrogen pressure, the hydrogen consumed was automatically pressed in each case.

The conditions of the individual, continuously carried out long-term tests and the results obtained are summarized in the following table. Experiment No. 11 is the comparative example.

Annex to the letter to the German Patent Office on June 18, 1975 0 C co 0 rH nitro-amino solutions; i C pressure Co cd zw connection connection (bar) w cd 1 1 dinitro diamino methanol 80 30 toluene toluene (80% 2.4) (80% 2.4) (20% 2.6) (20% 2.6) 2 1 .. .. methanol 80 30 3 1 n fl methanol 80 30 4 1 1I methanol 80 30 5 2 n .l methanol 120 30 6 2 1! Isopropanol 120 30 7 3 lv 7 isopropanol 130 80 8 2 m-dinitro- m-diamino-isopropanol 140 30 benzene benzene 9 2 o-nitroaniline o-diamino-isopropanol 140 30 benzene 10 1 o-nitro- o-toluidine methanol 70 30 toluene 11 4 dinitro diamino methanol 80-130 30-70 toluene toluene (80% 2.4) (80% 2.4) (20% 2.6) (20% 2.6) 'llitro- residual mBatZ t o | e ~> .trjr- | sesame, t- conn. gas 0 the the :: itro time ¢ ~ en ~ e velastz. . w Verd- eo Xerblfl Stdn. * /, -g / lwS rle aur 1 4 r2 1:75 1 4 22 1: 75 10 in a> 10,000 attempt I will ohr.e 'cn- tclkt-lDesa-tiXJiertzG ab- broken (.bwasser: CSz 30,000 irq ° 2/1) 2 1.5 40 1: 200 100 100 4,000 attempted cbne con- takt-DsaXtivierü? n off- broke 3 o 22 1: 100 imo 100 1,000 iv 1 4 1.5 5 1: 200 200 im 400 iv ~ (Sewage: C <only 5 1? 2: 100 i 1) 0 2,000 3,000 mg oo / 1) 1 Trial 2; 0 3,000 ohe 0 20 1: 120 50 100 3,000 broken. vomit 7 4 22 1: 100 10 l 100 4,000 vi 8 L 22 1: 100 10 in 4,000 ii 9 L 22 1: 100 10 100 4,000 iv ~ ~ 10 1.5 22 1: in 10 100 2,000 lv 1 1 4 - 8 22 1: 100 10 only for 36 Beginning in the then soon 250 | Insufficient CkUeavz up to C98 ~ such was from ebr.

c) Working up the reaction mixture The hydrogenation product became first the solvent (alcohol) used is distilled off and diluted the nitro compound to be hydrogenated is returned to the process. From the solvent The freed hydrogenation product is then distilled off. The accruing Water represents the wastewater of the process. The loading of this wastewater with the organic by-products formed during the hydrogenation come from the chemical Oxygen demand (COD) expresses and represents a cost factor in wastewater treatment represents: wastewater with a low COD value is less costly when it comes to wastewater treatment than wastewater with a high COD value. Hydrogenation products over Pd catalysts had a higher COD value in the wastewater (e.g. 30,000 mg 02 / l in Example 1) as the hydrogenation products in which Pt catalysts are used (e.g. 3000 mg 02/1 in Example 5).

Claims (24)

Patent claims: (1) Process for the catalytic hydrogenation of nitro compounds too the corresponding amino compounds in the trickle phase over a fixed Catalyst, characterized in that there are catalysts with a particle size 0.5 to 3 mm in diameter are used. 2) Process according to claim 1, characterized in that there are catalysts with a particle size of 1.5 to 2.5 mm in diameter is used. 3) Process according to claim 1 and 2, characterized in that one the catalyst as a supported catalyst or full contact in the form of spheres, cylinders, Extrudate, granules or flakes used. 4) Process according to claim 1 to 3, characterized in that one the catalyst used in the form of balls. 5) Process according to claim 1 to 4, characterized in that one a catalyst containing palladium and / or platinum and optionally vanadium used. 6) Method according to claim 1 to 5, characterized. marked that one to achieve wastewater contaminated with only small amounts of pollutants a platinum and optionally vanadium-containing catalyst is used. 7) Method according to claim 1 to 6, characterized in that one a 0 ,! containing up to 2% by weight of platelets and optionally 0.2 to 0.8% by weight of vanadium Catalyst used. 8) Process according to claim 1 to 7, characterized in that one as a catalyst carrier aluminum oxide, silica, Aluminum silicate, Spinels5 uses magnesium oxide, barium sulfate or activated charcoal. 9) Process according to claim 1 to 8, characterized in that one aluminum oxide is used as a catalyst carrier. 10) Method according to claim 1 to 9, characterized in that one active aluminum oxide as a catalyst carrier with a specific surface area > 200 m / g used. 11) Method according to claim 1 to 10, characterized in that one the catalyst support before applying the active catalyst material a subjected to chemical pretreatment. 12) Method according to claim 1 to 11, characterized in that the chemical pretreatment is carried out on aluminum oxides as a catalyst carrier, conversion into spinels takes place. 13) Method according to claim 12, characterized in that at the conversion of aluminum oxides into spinels forms lithium aluminum spinel. 14) Method according to claim 1 to 13, characterized in that the hydrogenation is carried out at temperatures from 50 to 2000C. 15) Method according to claim 1 to 14, characterized in that the hydrogenation is carried out at pressures of 1 to 150 bar. 16) Method according to claim 1 to 15, characterized in that the hydrogenation is carried out in the presence of a solvent. 17) Method according to claim 1 to 16, characterized in that the hydrogenation in the presence of lower aliphatic Alcohols performs as a solvent. 18) Method according to claim 1 to 17, characterized in that the hydrogenation is carried out in the presence of isopropanol as solvent. 19) Method according to claim 1 to 18, characterized in that the solvent to the nitro compound to be hydrogenated in a ratio of 1: 100 admits. 20) Method according to claim 1 to 19, characterized in that the total liquid loading during the hydrogenation is 2 to 40 kg per reaction medium Liters of catalyst per hour. 21) Method according to claim 1 to 20, characterized in that one consisting essentially of amino compound, water and solvent Reaction mixture for additional dilution of the nitro compound to be hydrogenated recycled, the ratio of nitro compound to be hydrogenated to that as Reaction mixture used as diluent (solvent + water + amino compound) 1: 5 to 1: 200. 22) Method according to claim 1 to 21, characterized in that one with 100 to 1000% of the theoretically required for the hydrogenation of the nitro compound Amount of hydrogen hydrogenated. 23) Method according to claim 1 to 22, characterized in that the hydrogenation is carried out in tubular or shaft reactors from 1 to 8 m in length. 24) Process for the hydrogenation of aromatic nitro compounds too the corresponding amino compounds in the trickle phase over a fixed, a noble metal-containing catalyst, characterized in that a platinum containing alumina supported catalyst in spherical shape with a diameter from 0.5 to 3 mm used, the hydrogenation at temperatures of 50 to 200 ° C and at Cover from 1 to 150 bar in the presence of lower aliphatic alcohols with a Total liquid loading from 2 to 40 kg of reaction medium per liter of catalyst and hour and at a ratio of nitro compound to be hydrogenated to diluent (Solvent + water + amino compound) as 1: 5 to 1: 200.