JPH06184062A - Production of aromatic amine - Google Patents

Abstract

PURPOSE:To provide a method for producing an aromatic amine in high yield and selectivity even at a low reactional temperature. CONSTITUTION:Phenol is made to react with ammonia by continuous type vapor-phase fixed-bed reaction using a catalyst supporting niobium oxide to produce aniline.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing an aromatic amine in high yield by reacting an aromatic hydroxyl group with an aminating agent in the presence of a specific catalyst.

[0002]

2. Description of the Related Art Aromatic amines are produced by catalytic reduction of aromatic nitro compounds, reaction of aromatic halides with an aminating agent at high temperature and high pressure, or reaction of phenols with an aminating agent. Has been done.

However, the method for catalytically reducing an aromatic nitro compound requires a large amount of nitric acid as a nitrating agent and a large amount of sulfuric acid as a catalyst in the step of synthesizing an aromatic nitro compound. Therefore, a large amount of alkaline substance is required in the neutralization step, and a large amount of high-concentration wastewater containing salts thereof is generated. In addition, there are problems such as corrosion due to the acid to be handled, an expensive material and the like are required, and further, air pollution due to scattering of nitrogen oxides is not preferable.

In the method using an aromatic halide, a highly corrosive halogen such as chlorine is used for halogenating an aromatic, so that it is necessary to use an expensive corrosion resistant material. Further, even if an aromatic halide is reacted with an aminating agent such as ammonia at high temperature and high pressure, the yield is low, and it has not been industrially practically used.

In order to solve these problems, a method of reacting phenols with an aminating agent has received attention as a process for obtaining anilines. That is, since the aniline can be produced simply by passing the phenols and the aminating agent through the fixed bed catalyst, the production process is extremely simple, and there is no large amount of waste acid or waste water accompanying the neutralization step. Excellent advantages such as no air pollution due to nitrogen oxides are recognized.

A method for producing anilines by reacting phenols with an aminating agent is disclosed in, for example, Japanese Patent Publication No. 42-2357.
The anilines are produced by reacting at a temperature of 300 to 600 ° C. in the presence of a catalyst selected from silica-alumina, zirconia-alumina, titania-alumina, etc.

However, although the disclosed catalyst system is a strongly acidic solid acid and the initial activity of the amination reaction is high,
The decomposition reaction of the produced aniline and the by-product of the resinous substance are caused, and the activity is rapidly reduced. Therefore, it is necessary to frequently perform a catalyst regeneration operation using oxygen, air, or the like.

In order to solve such a problem, JP-A-48-67229 or JP-A-48-9647 is used.
In JP-A No. 5-205, a selection is made from titania-zirconia, titania-silica, titanium-tungsten, titanium-niobium, zirconium-niobium and zirconium-tungsten, which have weaker acid strength than silica-alumina which is a strongly acidic solid acid. It is disclosed to use a complex oxide solid acid catalyst as described above. However, these catalyst systems require high reaction temperatures of 400-500 ° C,
Under such severe temperature conditions, decomposition of an aminating agent such as ammonia is inevitable. For this reason, there are problems that the reactor is often embrittled by nitrogen and the life of the reactor is shortened, or the activity is rapidly reduced in a short time.

[0009] There are also known some attempts to improve the catalytic activity by modifying alumina as a catalyst for producing anilines by reacting phenols with an aminating agent. For example, JP-B-49-14738 discloses a method of treating commercially available γ-alumina with boric acid, and JP-B-49-2.
No. 9176 discloses a method of treating with aluminum chloride,
Japanese Unexamined Patent Publication No. 63-126549 discloses a method in which γ-alumina is treated with an acid to reduce the content of alkali metal to 0.5% by weight or less.

However, since the activity of the catalyst system obtained by modifying these aluminas to increase the activity is low, the conversion rate is increased by suppressing the feed rate of the phenols low. For example, in the above-mentioned Japanese Patent Laid-Open No. 63-126549, the supply rate of phenol is 0.045 in terms of liquid hourly space velocity (LHSV).
Although there has been disclosed an example in which the conversion rate is increased by lowering hr ⁻¹ ), the reaction apparatus becomes excessively large, which is economically extremely disadvantageous.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing an aromatic amine with a high yield and a high selectivity even at a low reaction temperature.

[0012]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that in the reaction for producing an aromatic amine by reacting an aromatic hydroxyl group with an aminating agent, When a niobium catalyst is used as a catalyst, it is possible to produce an aromatic amine with a high activity and a high yield even at a low temperature, almost no decomposition of ammonia occurs, and it is possible to suppress a by-product of a resinous substance, and to complete the present invention. I arrived.

That is, the present invention provides a method for producing an aromatic amine characterized by using a niobium catalyst in a method for producing an aromatic amine by reacting an aromatic hydroxyl group with an aminating agent. Is. Hereinafter, the present invention will be described in detail.

The catalyst which can be used in the present invention is a niobium catalyst. Examples of the niobium catalyst include niobium and / or niobium halides and oxides. The niobium catalyst can be used as a catalyst by itself, but it is usually used by supporting it on a carrier.

The niobium catalyst can be prepared from known niobium compounds. Examples of niobium compounds that can be used here include niobium oxides, lithium niobate, niobate salts such as magnesium niobate, niobium pentachloride, niobium halides such as niobium pentafluoride, niobium methoxide, niobium such as niobium phenoxide. Examples thereof include organic acid salts of niobium such as alkoxide and niobium oxalate.

In the present invention, when a niobium catalyst is supported and used, a known carrier can be used, and examples thereof include metal oxides such as silica, alumina, titania, zirconia and magnesia, activated carbon and porous Vycor glass. . The shape of these carriers is not particularly limited, and may be powdery or molded. The surface area of the carrier is 10
˜500 m ² / g, preferably 50 to 300 m ² / g.

The niobium catalyst used as a catalyst in the present invention can be prepared from the above-mentioned niobium compound by a known method. For example, taking a method for preparing niobium oxide as an example, sulfuric acid, a method of hydrolyzing a niobium compound dissolved in hydrofluoric acid with ammonia, a method of thermally decomposing or hydrolyzing a niobium alkoxide, a niobium halide such as niobium chloride It can be prepared by a method such as hydrolysis.

There is no particular limitation on the method for preparing the catalyst when the niobium catalyst is supported on the carrier. For example, a niobium oxide or niobium oxide synthesized as described above is dissolved in an organic acid or an inorganic acid, and the above-mentioned carrier is added and immersed,
A method of evaporating and drying, which is carried by a so-called impregnation method and then hydrolyzed, may be mentioned. At this time, tartaric acid, oxalic acid and the like are used as the organic acid, and hydrochloric acid, sulfuric acid and the like are used as the inorganic acid. Further, a method in which a niobium halide such as niobium chloride is dissolved in an aromatic compound, for example, benzene, toluene and the like and carried by an impregnation method, and is hydrolyzed by a base such as ammonia or an alkali metal hydroxide, an alcohol solution of niobium alkoxide. Examples of the method include a method in which is carried out by an impregnation method and pyrolysis or hydrolysis with water, a method in which a niobium oxalate solution is hydrolyzed with ammonia, an alkali metal hydroxide or the like.

The niobium catalyst supported by these preparation methods is usually used after being calcined. The calcination temperature of the catalyst varies depending on the carrier, but is usually 200 to 700 ° C, preferably 300 to 500 ° C. At higher temperatures than this, the niobium oxide may crystallize and its surface area may be significantly reduced.

In the present invention, the amount of the niobium catalyst supported on the carrier is 0.1 to 70% by weight based on the whole catalyst,
It is preferably 1 to 50% by weight.

The compound having an aromatic hydroxyl group which can be used as a raw material in the present invention is a compound having a hydroxyl group in an aromatic ring, and examples thereof include monohydric phenols such as phenol, polyhydric phenols such as catechol, hydroquinone and resorcin, Alternatively, alkylphenols such as cresol and ethylphenol can be exemplified. Furthermore, compounds which are aromatic polycyclic compounds and have a hydroxyl group in the aromatic ring, such as naphthol and anthranol, can be exemplified. Of these, phenol is particularly preferably used.

On the other hand, the aminating agent used in the present invention is ammonia, inorganic amines and / or organic amines that generate ammonia. The inorganic amines that generate ammonia are inorganic compounds that generate ammonia gas by thermal decomposition or the like, and examples thereof include ammonium carbonate and ammonium sulfate. Examples of the organic amines include primary amines such as methylamine, ethylamine, propylamine, butylamine, aniline and cyclohexylamine, and secondary amines such as dimethylamine and diethylamine. Of these, ammonia is particularly preferably used.

The raw materials for these phenols and aminating agent may be supplied as they are, or may be supplied by using a solvent if necessary. As the solvent that can be used here, any solvent inert to this reaction may be used, and examples thereof include water, aromatic hydrocarbons such as benzene, toluene, xylene, ethers such as diisopropyl ether, tetrahydrofuran, dioxane, hexane, cyclohexane and the like. You may use hydrocarbon etc.

The reaction of the present invention for producing an aromatic amine by reacting an aromatic hydroxyl group with an aminating agent may be carried out in a gas phase or a liquid phase, but a gas phase reaction is more preferable.
The reaction temperature is about 200 to 600 ° C., preferably 30.
It is 0-400 degreeC. The reaction pressure may be normal pressure or increased pressure, and is preferably about 5 to 50 atm. Further, the molar ratio of the aminating agent to the phenols is about 1-50, preferably 5-30. If necessary in carrying out this reaction, it can be diluted with an inert gas such as nitrogen, argon or steam.

The liquid hourly space velocity (LHSV) range is 0.01
To 0.2, preferably 0.05 to 0.15. Here, the liquid hourly space velocity is a value obtained by dividing the supply volume (l / hr) of phenols per unit time by the catalyst volume (l) packed in the reaction column or tube. The reaction system may be either a continuous method or a batch method, but the continuous method is preferred from the industrial viewpoint.

The case where aniline is synthesized by a continuous gas phase fixed bed reaction using phenol as the substance having an aromatic hydroxyl group and ammonia as the aminating agent will be described below. As a raw material, phenol or a mixture of phenol and a solvent is mixed with liquid ammonia by vaporizing them separately or separately, or heated ammonia is passed through vaporized ammonia to be vaporized and mixed. This mixed gas is fed into a reactor filled with a catalyst. The pressure of the reaction mixture taken out of the reactor is returned to normal pressure and cooled. Since a large amount of ammonia is dissolved in this reaction mixture, it is separated by distillation separation and recycled for use. On the other hand, the reaction product liquid from which ammonia has been removed is sent to the next dehydration distillation step, and then aniline is separated and purified, aniline is recovered, and unreacted phenol is recycled to the reactor for reuse.

[0027]

INDUSTRIAL APPLICABILITY According to the present invention, a niobium-containing substance having a higher activity than conventionally known catalysts can be used as a catalyst while maintaining a high yield and a high selectivity even when the reaction is carried out at a low reaction temperature. The present invention proposes a method for producing an aromatic amine that is economically advantageous.

[0028]

EXAMPLES The preparation method of the catalyst according to the present invention and the reaction examples using the catalyst will be specifically described below, but the present invention is not limited thereto.

Example 1 Niobium oxide (CB was added to an aqueous solution of oxalic acid dissolved in distilled water.
(Manufactured by MM Co., Ltd.) was melted by heating, and an alumina carrier (manufactured by Sumitomo Chemical Co., Ltd.) baked at 600 ° C. was immersed therein.
At this time, oxalic acid precipitated from the solution was removed in advance. After drying, it was calcined at 600 ° C. under a flow of dry air. The niobium supported amount of the obtained niobium oxide supported catalyst was 19.9% by weight.

A reaction tube was filled with 10 g of the niobium oxide-supported catalyst thus prepared, and the reaction was carried out. The reaction was heated in an electric furnace under a flow of ammonia gas to raise the temperature to a predetermined temperature. Next, a predetermined amount of phenol was supplied by a pump. The reaction conditions at that time were a reaction temperature of 380 ° C., a reaction pressure of 15 kg / cm ² G, and a phenol supply rate of LHSV.
The conversion was 0.08 hr ^-1 , and the feed molar ratio of ammonia to phenol was 20.

A gas-liquid separator was placed at the outlet of the reaction tube to collect the reaction solution. The analysis was carried out by gas chromatography for both the reaction solution and the gas phase. Columns are FFAP and CP-WA
X was used.

The conversion rate, selectivity and yield of the reaction product were calculated by the following formulas.

Conversion rate (%) = (mol number of phenol reacted per unit time / mol number of phenol fed per unit time) × 100 Selectivity (%) = (mol number of aniline generated per unit time / unit Number of moles of phenol reacted in time) × 100 Yield (%) = (number of moles of aniline formed per unit time /
As a result of analysis, the conversion was 99.4%, the selectivity was 96.7%, the yield was 96.1%, and the only by-product was diphenylamine.

Example 2 The reaction was carried out under the same conditions as in Example 1 except that the reaction temperature was changed to 370 ° C. As a result of analysis of reaction products, conversion rate 9
The yield was 7.9%, the selectivity was 99.0%, and the yield was 96.9%. The only by-product was diphenylamine.

Example 3 The reaction was carried out under the same conditions as in Example 1 except that the reaction temperature was changed to 365 ° C. and the LHSV was changed to 0.093. As a result of analysis of reaction products, conversion rate was 90.5%, selectivity rate was 96.8%,
The yield was 87.6%. The only by-product was diphenylamine.

Example 4 A niobium oxide-supported catalyst was prepared in the same manner as in Example 1 except that an alumina carrier (manufactured by Sumitomo Chemical Co., Ltd.) calcined at 900 ° C. was used as the carrier. The amount of niobium oxide supported on the obtained supported niobium oxide catalyst was 19.6% by weight.

The reaction was carried out under the same reaction conditions as in Example 3. As a result of analysis of the reaction product, the conversion rate was 74.8%, the selectivity was 97.7%, and the yield was 73.2%. The only by-product was diphenylamine.

Comparative Example Using the alumina of Example 1 as a catalyst, the reaction was carried out under the same reaction conditions as in Example 1. As a result of analysis of the reaction product, the conversion rate was 8.7%, the selectivity was 99.5%, and the yield was 8.7%.
Met.

Claims (4)

[Claims] 1. A method for producing an aromatic amine, which comprises using a niobium catalyst in the method for producing an aromatic amine by reacting an aromatic hydroxyl group with an aminating agent. 2. The method according to claim 1, wherein the niobium catalyst is niobium and / or niobium oxide. 3. The method according to claim 1, wherein the niobium catalyst is supported on a carrier. 4. The method according to claim 1, wherein the aromatic hydroxyl group is phenol and the aminating agent is ammonia.