RU2207335C2 - Method for preparing aromatic amines by reduction of corresponding nitro-compounds - Google Patents

Abstract

FIELD: organic chemistry, chemical technology. SUBSTANCE: invention relates to method for preparing aromatic amines, namely to preparing unsubstituted or N-methyl- substituted aromatic amines that are used in production of dyes, drugs, antioxidants and antidetonating additives to fuel and so on. Method for preparing aromatic amines involves the reduction reaction of corresponding nitro-compounds with methanol in vapor phase at elevated temperature in the presence of industrial copper-containing catalyst, for example, type "Virgon", or "S-40", or "NTK-10-7F" modified with nickel or palladium, or platinum and taken in the amount 0.3-10 wt.-%. Usually process is carried out at temperature 200-260 C, under atmosphere pressure and feeding rate of the parent liquid mixture of methanol with aromatic nitro-compound from 0.5 to 2.5 t^-1 and maintaining the ratio methanol/aromatic nitro- - compound in the parent mixture from 1:1 to 5:1. Proposed method ensures to enhance the total yield of aromatic amines up to 99.5%, output by product up to 0.4-1.3 g/g x h and safety of process due to exclusion of hydrogen and carrying out the process under atmosphere pressure. Method allows depending on ratio of used reagents to alternate ratios of synthesized N-methyl-substituted and unsubstituted aromatic amines. EFFECT: improved preparing method. 4 cl, 1 tbl

Description

 The invention relates to a method for producing aromatic amines by reduction of the corresponding nitro compounds and, more particularly, to a method for producing N-methyl-substituted aromatic amines by reductive alkylation of the corresponding nitro compounds with methanol. Such aromatic amines are valuable products of organic synthesis and are used in the manufacture of dyes, drugs, antioxidant and antiknock additives for fuel, etc.

A known method of producing N-alkyl substituted aromatic amines by reductive alkylation of the corresponding nitro compounds with carbonyl compounds in the presence of a supported platinum catalyst. The method is carried out at a temperature of 120-175 ^o With and a hydrogen pressure of 1.4-10.5 MPa [US Patent 3384664, class. 260-577, 1968]. The disadvantage of this method is the relatively small yield of the target amines, from 50 to 89%, and the harsh process conditions. A significant disadvantage of using carbonyl compounds as reducing agents is the need to use a large excess of reducing agent (at least 3 mol / mol of nitro compound) in combination with hydrogen.

There is also known a method for producing aromatic amines by reacting the corresponding nitro compounds with hydrogen and alcohol in the presence of a copper chromite catalyst promoted with elements Fe, Ba, Mg and Mn [US Patent 4082802, cl. C 07 C 91/16, 1978]. The interaction is carried out at a temperature of 150-400 ^o C, a hydrogen pressure of 2.0-10 MPa and a molar ratio of alcohol / nitro compound from 1 to 20. The disadvantage of this method is the low productivity of the process for the product (less than 0.1 g per 1 g of catalyst per hour ) and insufficiently high yield of N-alkyl-substituted aromatic amines, 85-90%. Another disadvantage is the need to use a large excess of hydrogen under pressure.

Closest to the proposed method in technical essence is a method for producing N-alkyl-substituted aromatic amines by reacting the corresponding nitro compounds with hydrogen and alcohol in the presence of an oxide copper-containing catalyst on an alumina support comprising a metal oxide promoter such as manganese, iron, zinc, cobalt, magnesium other. The reaction is carried out in the vapor phase at elevated temperature (above 200 ^o C) under a hydrogen pressure of up to 1 MPa [US Patent 5097071, cl. C 07 C 209/00, 1990]. The disadvantages of this method include the low productivity and yield of the target product: for example, N-methylaniline from nitrobenzene and methanol is obtained with a yield of 72.5% with a catalyst productivity of 0.08 g / ml • h. In addition, the need to use high hydrogen pressure at elevated temperatures complicates the process design and affects the fire safety of the process.

 Thus, in all known technical solutions for producing aromatic amines by reduction of the corresponding nitro compounds, low productivity catalysts are used, and the process is carried out under hydrogen pressure.

 The present invention is to develop a method for producing aromatic amines by reduction of the corresponding nitro compounds, which provides improved yield and productivity, as well as increased production safety.

 The problem is solved by the proposed method for producing N-alkyl-substituted aromatic amines by reduction of the corresponding nitro compounds with methanol in the vapor phase at an elevated temperature in the presence of a copper-containing catalyst, in which according to the invention a copper-containing catalyst modified with nickel or palladium or platinum is used.

In preferred instances of the method:
- Nickel, or palladium, or platinum is introduced in an amount of 0.3-10 wt.%;
- industrial catalysts of the Virgon or S-40 or NTK-10-7F brand are used as a copper-containing catalyst;
- the process is carried out at a temperature of 200-260 ^o C, atmospheric pressure and the feed rate of the liquid source mixture of methanol with an aromatic nitro compound from 0.5 to 2.5 h ^-1 ;
- the ratio of methanol / aromatic nitro compound in the initial mixture is from 1: 1 to 5: 1.

 The essence of the method is as follows.

Used in the proposed method, the copper-containing catalyst may contain various promoters metal oxides - aluminum, zinc, manganese, iron and others. Examples of such catalysts are industrial catalysts of the Virgon brand, having the composition (wt.%.): CuO 9.8-11.9, Mn ₃ O ₄ 1.7-2.4 and Al ₂ O ₃ 85.7-88, 5; C-40 composition (wt.%): CuO 10-12, Mn ₃ O ₄ 1.8-2.6, Fe ₂ O ₃ 3.5-4.1 and AlO ₃ 81.3-84.7; NTK-10-7F composition (wt.%): ZnO 27.2, CaO 7.5, CuO 42.9, AlO ₃ 21.3, Mn ₃ O ₄ 1.1, etc. [cm. Industrial catalysts of the USSR. Short reference book / UMNTK "Catalyst". Novosibirsk, 1988, 232 p. ], which are modified with nickel, or palladium or platinum, preferably in an amount of 0.3-10 wt.%.

The choice of a copper-containing catalyst, as well as a modifier and its amount, is determined by the fact that it is necessary to disperse the active phase of copper and stabilize such an active phase with respect to sintering, erosion, etc. At the beginning of the process, the catalyst is activated by feeding methanol for 30 minutes at a temperature of 190-260 ^o C.

 The ionic compounds of Cu (II) and a Group VIII metal are reduced to form bimetallic alloys based on Cu (O), for example Cu-Ni, or Cu-Pd, or Cu-Pt.

The process is carried out in the vapor phase at a temperature of 200-260 ^o C, atmospheric pressure and a feed rate of a liquid mixture of methanol (MeOH) with an aromatic nitro compound (AN) from 0.5 to 2.5 h ^-1 . The MeOH / AN ratio is usually from 1: 1 to 5: 1. The use of methanol and a copper-containing catalyst modified with nickel or palladium or platinum makes it possible to obtain a mixture of hydrogen and carbon monoxide, which effectively reduces the nitro group in statu nascendi, by decomposition of methanol under the process conditions on the specified catalyst. Thus, the use of gaseous hydrogen as a starting reagent is completely excluded.

In accordance with the stoichiometric equation of reaction (1) with an equimolar ratio of reactants (1: 1), the main reduction product is the corresponding aromatic amine ArNH ₂
ArNH ₂ + CH ₃ OH -> ArNH ₂ + CO ₂ + H ₂ O, (1)
which is subsequently alkylated with nitrogen in the presence of an excess of methanol:
ArNH ₂ + CH ₃ OH -> ArNH ₃ + H ₂ O. (2)
Therefore, if the target product is the N-methylated aromatic amine ArNHCH ₃ , the ratio of methanol / AN should be from 2.5: 1 to 5: 1. According to the invention, aromatic amines of the general formula ArNHR can be prepared, where R = H, CH ₃ , Ar = phenyl, tolyl, chlorophenyl, p-methoxy, p-methoxy, phenylacetyl, hydroxyphenyl.

 The method according to the invention is illustrated by the following examples.

Example 1. In a rotary evaporator, 100 g of freshly calcined C-40 catalyst is charged, pumped out to a pressure of approximately 4 kPa and poured with an ammonia solution of palladium dichloride containing 0.3 g of Pd. Stand for 12 hours. Excess ammonia water is pumped out with stirring and heating in a rotary evaporator. Obtain 103 g of a wet catalyst containing 0.3 wt.% Palladium (CT1). 25 ml of catalyst 0.3 wt.% Are loaded into a flow tube reactor. Pd / C-40 and heat it to 190 ^o C in a stream of nitrogen. Then methanol is fed into the reactor at a space velocity of 1 h ⁻¹ to activate the catalyst for 0.5-1 h.

Example 2. Under the conditions of example 1, starting from 100 g of a sample of NTK-10-7F and a hydrochloric acid solution of H ₂ PtCl ₆ , in a rotary evaporator, 104 g of catalyst containing 1 wt.% Are obtained. Pt (Kt2).

Example 3. Under the conditions of example 1, starting from 100 g of a sample of NTK-10-7F and a hydrochloric acid solution of H ₂ PtCl ₆ , 103.5 g of a catalyst containing 0.5 wt.% Pt (Kt3) are obtained in a rotary evaporator.

Example 4. Under the conditions of example 1, starting from 100 g of a Virgon sample and a hydrochloric acid solution of NiCl ₂ , 114 g of a catalyst containing 10 wt.% Ni (Kt4) are obtained in a rotary evaporator.

Example 5. Under the conditions of example 1, starting from 100 g of sample C-40 and a hydrochloric acid solution of NiCl ₂ , 106 g of a catalyst containing 4 wt.% Ni (Kt5) are obtained in a rotary evaporator.

Example 6. In a flow tube reactor, 25 ml of a catalyst of 0.3 wt.% Pd / C-40 (sample Kt1) is charged and heated to 190 ^{° C.} in a stream of nitrogen (2-3 l / h). Then methanol is fed into the reactor at a space velocity of 1 h ⁻¹ to activate the catalyst for 0.5–1 h. During activation, the temperature of the reactor is gradually increased to the synthesis temperature, i.e. 230 ^o C, and at atmospheric pressure in a stream of nitrogen for 10 h serves a mixture of methanol and nitrobenzene (3: 1) with a space velocity V ₀ = 1.6 h ^-1 The vapors leaving the reactor are condensed in a water cooler and separated in a separator by organic and aqueous phases. The stationary state of the catalyst is established after 1-2 hours, after which an organic product of constant composition is obtained, characterized by gas chromatography.

 The conversion of nitrobenzene is about 99.5%, 5-6% methanol, 7-8% aniline, 86-88% monomethylaniline (MMA) and less than 0.1% dimethylaniline are found in the reaction products. Thus, the total yield of the target products, aniline and MMA, is more than 99%, the catalyst productivity for these products is 0.4 g / g • h.

Example 7. In the conditions of example 6 load and activate 25 ml of catalyst 10 wt.% Ni / Virgon (Kt4). Then at a temperature of 200 ^o With atmospheric pressure in a stream of nitrogen for 10 h serves a mixture of methanol and 2-methoxynitrobenzene (1: 1) with a space velocity V ₀ = 2.5 h ^-1 .

 According to chromatographic analysis, the organic product has the following composition: 3.7% 3-methoxynitrobenzene, 93-94% 3-methoxyaniline and 2.3-3% N-methyl-3-methoxyaniline. Thus, the total yield of the target products, 3-methoxyaniline and N-methyl-3-methoxyaniline, is about 96%, the catalyst productivity for these products is 1.2 g / g • h.

Example 8. In the conditions of example 6 load and activate 25 ml of catalyst 4 wt.% Ni / C-40 (Kt5). Then at a temperature of 260 ^o With at atmospheric pressure in a stream of nitrogen for 10 hours serves a mixture of methanol and nitrotoluene (5: 1) with a space velocity V ₀ = 2.0 h ^-1 . According to chromatographic analysis, the conversion of nitrotoluene is 99.7%, while the organic product has the following composition: 0.3% 4-nitrotoluene, 2.2% 4-toluidine and 97.5% M-methyl-4-toluidine. The productivity of the catalyst for these products is 0.4 g / g • h.

Example 9. In the conditions of example 6 load and activate 25 ml of catalyst 1 wt.% P1 / NTK-10-7F (KT2). Then at a temperature of 240 ^o With atmospheric pressure in a stream of nitrogen for 10 h serves a mixture of methanol and 2-chloronitrobenzene (3: 1) with a bulk velocity V ₀ = 1.2 h ^-1 .

 The conversion of 2-chloronitrobenzene is 98.5%, the reaction products found: 1.5% 2-chloronitrobenzene, 6.5% 2-chloroaniline and 92.0% N-methyl-2-chloraniline, the productivity of the catalyst for organic products is 0 39 g / g • h.

Example 10. In the conditions of example 6 load and activate 25 ml of catalyst 0.5 wt.%. P1 / NTK-10-7F (Kt3). Then at a temperature of 220 ^o With atmospheric pressure in a stream of nitrogen for 10 h serves a mixture of methanol and 3-acetonitrobenzene (1: 1) with a bulk velocity V ₀ = 0.5 h ^-1 .

 According to chromatographic analysis, the synthesis product has the following composition: 4.3% 3-acetonitrobenzene, 93.5% 3-acetoaniline and 2.2% N-methyl-3-acetoaniline. Thus, the total yield of the target products, 3-acetoaniline and N-methyl-3-acetoaniline, is about 95.7%, the catalyst productivity for these products is 0.25 g / g • h.

Example 11. In the conditions of example 6 load and activate 25 ml of catalyst 1% wt. P1 / NTK-10-7F (Kt2). Then, at a temperature of 210 ^o With atmospheric pressure in a stream of nitrogen for 10 h serves a mixture of methanol and 4-hydroxy nitrobenzene, in a molar ratio of 2: 1 with a space velocity of V ₀ = 1.5 h ^-1 .

 The synthesis products have the following composition: 1.5% 4-hydroxy nitrobenzene, 6.5% 4-hydroxyaniline and 92.0% M-methyl-4-hydroxyaniline. Thus, the total yield of the target products, 4-hydroxyaniline and N-methyl-4-hydroxyaniline, is 98.5%, the catalyst productivity for these products is 0.5 g / g • h.

 Test data for all catalysts and nitro compounds (NS) are shown in the following table. The desired products can be isolated from the organic layer in pure form using methods known from the prior art, for example, rectification or extractive distillation.

Claims (4)

 1. The method of producing aromatic amines by reacting the corresponding nitro compounds with methanol in the vapor phase at elevated temperature in the presence of an industrial copper-containing catalyst, characterized in that they use a copper-containing catalyst modified with nickel or palladium or platinum, taken in an amount of 0.3-10 wt. %  2. The method according to claim 1, characterized in that industrial catalysts of the Virgon brand, or S-40, or NTK-10-7F are used as a copper-containing catalyst. 3. The method according to claim 1, characterized in that the process is carried out at a temperature of 200-260 ^o With atmospheric pressure and the feed rate of the liquid source mixture of methanol with an aromatic compound from 0.5 to 2.5 h ^-1 .  4. The method according to claim 4, characterized in that the ratio of methanol / aromatic nitro compound in the initial mixture is from 1: 1 to 5: 1.

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