JP3470357B2 - Method for producing anilines - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing anilines in high yield by reacting phenols with an aminating agent in the presence of a specific catalyst.

[0002]

BACKGROUND OF THE INVENTION Anilines 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 of 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 waste water containing the salt is generated. In addition, equipment corrosion due to the acid handled becomes a problem,
There is an unfavorable problem that expensive materials are required and air pollution due to scattering of nitrogen oxides occurs.

The method using an aromatic halide uses a highly corrosive halogen, such as chlorine, for halogenating an aromatic, so that it is necessary to use an expensive corrosion resistant material. Further, the yield is low even when the aromatic halide is reacted with an aminating agent such as ammonia at high temperature and high pressure,
It has hardly been put to practical use industrially.

In order to solve these problems, a method of reacting phenols with an aminating agent has attracted attention as a process for obtaining anilines. That is, since the aniline can be produced by simply passing the phenols and the aminating agent through the fixed bed catalyst, the production process can be extremely simplified, and there is no large amount of waste acid or waste water accompanying the neutralization step, and
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, the disclosed catalyst system is a strongly acidic solid acid, and although the initial activity of the amination reaction is high, it causes a decomposition reaction of the formed aniline and a by-product of the resinous substance, resulting in a sharp decrease in activity. Therefore, it is necessary to frequently perform a catalyst regeneration operation using oxygen, air, or the like.

Attempts have been made to modify alumina, which is a weakly acidic metal oxide, as a catalyst for improving such activity deterioration. For example, JP-B-49-14738 discloses a method of treating γ-alumina with boric acid.
9-29176 discloses a method of treating γ-alumina with aluminum chloride, and JP-A-63-126549 discloses acid treatment of γ-alumina to reduce the content of alkali metal to 0.5% by weight or less. A method for doing so is disclosed. However, since the activity of these catalyst systems modified with alumina is still low, the conversion rate of phenols is increased by lowering the feed rate of phenols as a raw material. For example, in the above-mentioned Japanese Patent Laid-Open No. 63-126549, the supply rate of phenol, that is, the liquid hourly space velocity (LHSV) is
Although an example in which the conversion rate is increased by lowering HSV to 0.045 / hr is disclosed, the reactor is too large, which is economically extremely disadvantageous.

Further, in JP-A-48-67229 and JP-A-48-96475, titania-zirconia, titania-silica, titanium-tungsten, titanium-niobium, zirconium-niobium, and weak acid strength are disclosed. A complex oxide solid acid catalyst selected from zirconium-tungsten is disclosed. However, these catalyst systems require a high reaction temperature of 400 to 500 ° C., and under such severe temperature conditions, a decomposition reaction of the produced aniline compound and a by-product of a resinous substance are caused, resulting in a rapid activity. A decline occurs. Also, under such conditions, decomposition of the aminating agent, eg ammonia, is unavoidable. As a result, the reactor often suffers from nitrogen embrittlement, which shortens the useful life of the reactor.

On the other hand, Japanese Unexamined Patent Publication (Kokai) No. 57-179138 discloses an aniline synthesis method using a zeolite such as ZSM-5 or ZSM-11 as a catalyst. JP-A-57-17
The characteristics of the zeolite disclosed in Japanese Patent No. 9138 are as follows.
Decomposition rate ratio of n-hexane and 3-methylpentane C.I.
I. (Constraint index) is classified into zeolites from 1 to 12 (reference: J. Catalog)
l. , 67, 218 (1981)). A feature of the crystal structure of the disclosed zeolite is that it has a medium pore size pore opening portion formed by a 10-membered ring of oxygen atoms. It is said that by using such a zeolite as a catalyst, a high aniline selectivity of about 97% can be obtained, and since the by-product of the resinous substance is suppressed, the catalyst regeneration interval can be extended. ing.

However, although these zeolites have a high aniline selectivity, their catalytic activity is not industrially satisfactory. In the examples described in the above publications, the yield can be increased by reacting at a reaction temperature as high as 510.degree. I am raising.
However, under such a high temperature condition, the above-mentioned by-product of the resinous substance and the problem of nitrogen embrittlement occur, which is not preferable.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above prior art, and an object thereof is to provide a method for efficiently producing anilines at a low reaction temperature.

[0012]

Means for Solving the Problems The inventors of the present invention have made extensive studies to solve the above-mentioned problems. As a result, when zeolite β is used as a catalyst in the reaction for producing anilines by reacting phenols with an aminating agent,
Compared with conventional oxide catalysts and medium pore size zeolite catalysts such as ZSM-5, anilines can be produced with high activity and high yield and can be reacted at low temperature. It has been found that the decomposition of the resin hardly occurs, and the by-product of the resinous substance can be suppressed, and the present invention has been completed. That is, the present invention is a method for producing anilines by reacting phenols with an aminating agent,
A method for producing anilines, which comprises using zeolite β as a catalyst. Hereinafter, the present invention will be described in detail.

In the present invention, zeolite β is used as a catalyst. Zeolite is generally _{M 2 / n · T 2 O} 3 · x
It is a crystalline silicate designated as SiO ₂ . Here, T is an element in the zeolite skeleton, aluminum,
Trivalent metals such as iron and boron are common, and x is usually an integer of 2 or more. Zeolite is a crystalline compound in which TO ₄ tetrahedra and SiO ₄ tetrahedra are regularly and three-dimensionally arranged through oxygen atoms so that the O / (Si + T) ratio is 2. Since T is a trivalent cation, TO ₄ has a negative charge, and therefore, M having a positive charge is required to neutralize this negative charge. Therefore M
In order to maintain the skeletal structure of zeolite, only a cation is necessary, and hydrogen, alkali metal and alkaline earth metal are common. n is 1 when M is a monovalent cation, and is 2 or 3 when M is a divalent or trivalent cation. Thus, the basic structure of zeolite is TO
₄ and SiO ₄ tetrahedra, and M can be ion-exchanged.

The zeolite β used in the method of the present invention is a zeolite defined by the following characteristic pattern by X-ray diffraction.

[0015]

[Table 1]

Such zeolite β has pores consisting of a 12-membered oxygen ring, and has a C.I. I. It has the characteristic that the value (constraint index) is 0.6 and smaller than 1.
For the structure of zeolite β, see, for example, “Atlas
of Zeolite Structure Type
In addition, there is no particular limitation on the method for synthesizing zeolite, and for example, US Pat. No. 3,308,069.
No. 4,642,226 and European Patent Application 15984.
It can be synthesized by the method described in No. 6, 165208, 186447 or the like.

The atomic ratio of silicon to T element of zeolite β is 2 to 1000, preferably 2.5 to 300. If necessary, the zeolite β may be treated with dealumination before use. The dealumination treatment can be performed by a known method. For example, dealumination can be easily carried out by immersing in a hydrochloric acid aqueous solution kept at a predetermined temperature.

The zeolite β may be used in the alkali metal form, but it is preferably converted into the proton form before being used in the reaction. A method of converting into a proton type may be a known method, for example, an alkali metal ion may be exchanged with an ammonium ion, followed by firing to convert into a proton type. Further, the proton type zeolite may be ion-exchanged with another suitable metal ion of Group IB to VIII of the periodic table. At this time, the proton exchange rate is usually 10 to 100%, more preferably 50 to 100%.
Is.

The zeolite β used in the present invention may be powder,
It may be molded and used, but it is preferably molded and used. As a molding method, a known method such as kneading extrusion or tablet molding can be used. A binder may be used together with the zeolite β in order to facilitate the molding. As the binder, an inorganic compound such as silica, alumina or clay or an organic compound such as cellulose can be used.

The phenols used as raw materials in the present invention are compounds having a hydroxyl group in the aromatic ring, and examples thereof include monohydric phenols such as phenol and cresol, polyhydric phenols such as catechol, hydroquinone and resorcin, or methylphenol, Examples thereof include alkylphenols such as ethylphenol. Of these, phenol is particularly preferably used.

On the other hand, the aminating agent used in the present invention is ammonia, a compound that generates ammonia, or an organic amine. The compound that generates ammonia is an inorganic compound that generates 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.

In the present invention, in the reaction for producing anilines by reacting phenols with an aminating agent using a catalyst, the reaction may be carried out in a gas phase or a liquid phase. The gas phase reaction is more preferable for obtaining the anilines with high yield and high selectivity. The reaction temperature is about 20.
0 to 600 ° C, more preferably 300 to 500 ° C
Is. The reaction pressure may be normal pressure or increased pressure, preferably about 1 to 50 atm. Further, the molar ratio of the aminating agent to the phenols is about 1 to 50.
Is preferable, and more preferably 5 to 30. If necessary in carrying out this reaction, it can be diluted with an inert gas such as nitrogen, argon or steam.

As one of the reaction conditions in the present invention, the liquid hourly space velocity (LHSV) range is 0.01 to 10 /.
It can be carried out in hr, preferably 0.05 to 2 / hr
Is. 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 may be carried out by either a continuous method or a batch method, but from the industrial viewpoint, it is preferable to carry out the continuous method.

Below, phenol is used as the phenol.
A case where aniline is synthesized by a continuous gas phase reaction using ammonia as an aminating agent will be described. For example, the raw materials are mixed by vaporizing and mixing a mixture of phenol or phenol and a solvent and liquid ammonia together or separately, or by passing heated ammonia through heated ammonia to be vaporized. . This mixed gas is then fed into the reactor filled with catalyst. After the reaction, the pressure of the reaction product taken out of the reactor is returned to normal pressure and cooled. Since a large amount of ammonia is dissolved in this reaction product, the ammonia is separated by distillation separation and is recycled to the reactor 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.

[0026]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited thereto. In the examples, the analysis was carried out by gas chromatography for both the reaction solution and the gas phase. Columns are FFAP and CP
-WAX was used.

The selectivity and yield of the reaction product were calculated by the following formula.

Selectivity (%) = ((number of moles of aniline formed per unit time) / (number of moles of phenol reacted per unit time)) × 100 Yield (%) = ((aniline formed per unit time (Moles of phenol) / (moles of phenol fed per unit time)) x
100 Example 1 Zeolite β (CP811BL-25 manufactured by PQ) was used as a catalyst. The silica / alumina ratio of this zeolite β was 25. First, 0.65 g of zeolite β was charged in a reaction tube, and nitrogen and ammonia gas were mixed in a volume ratio of 5
It was circulated at a ratio of 0: 16.6, heated in an electric furnace and heated 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 450 ° C., a reaction pressure of normal pressure, a phenol feed rate of 1.29 / hr in terms of LHSV, and a feed molar ratio of ammonia to phenol of 9. A steady state was reached 4 hours after the start of the reaction. After that, a gas-liquid separator was placed at the outlet of the reaction tube to collect the reaction solution. When the product was analyzed, the yield of aniline was 2
1.2% was obtained. No diphenylamine by-product was detected.

Example 2 Zeolite β (Tβ-1 manufactured by Toso Corporation) was used as a catalyst.
03) was used. The silica / alumina ratio of this zeolite β determined by an atomic absorption method was 24.8. 10 g of zeolite β was filled in a reaction tube, and 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 at that time was a reaction temperature of 332 ° C., a reaction pressure of 15 kg / cm ² G, a phenol supply rate of 0.09 / hr in terms of LHSV,
It was carried out under the condition of a feed molar ratio of ammonia to phenol of 20. After reaching a steady state, a gas-liquid separator was placed at the outlet of the reaction tube to collect the reaction solution.

As a result of analysis of the product, the yield was 80.9%, the selectivity of aniline was 97.1%, and the by-product was only diphenylamine. A steady state was reached 2 hours after the start of the reaction, and no change with time was observed until 8 hours after the start of the reaction.

Example 3 A product was obtained by carrying out the reaction under the same conditions as in Example 2 except that the reaction temperature was changed to 357 ° C. Analysis of the product gave a yield of 95%. Aniline selectivity is 95.9%
The only by-product was diphenylamine. A steady state was reached 2 hours after the start of the reaction, and no change with time was observed until 8 hours after the start of the reaction.

Example 4 Zeolite β (Tβ-100 manufactured by Tosoh Corporation) was used as a catalyst. The silica / alumina ratio of this zeolite β was 35.9. The reaction was performed under the same conditions as in Example 2 to obtain a product. When the product was analyzed,
A yield of 82.3% was obtained. Aniline selectivity is 96.9%
The only by-product was diphenylamine. A steady state was reached 2 hours after the start of the reaction, and no change with time was observed until 8 hours after the start of the reaction.

Example 5 Zeolite β (Tβ-84 manufactured by Tosoh Corporation) was used as a catalyst. The silica / alumina ratio of this zeolite β was 46.3. The reaction was performed under the same conditions as in Example 2 to obtain a product. When the product was analyzed, the yield was 60.8%, the aniline selectivity was 97.2%, and the by-product was only diphenylamine. A steady state was reached 2 hours after the start of the reaction, and no change with time was observed until 8 hours after the start of the reaction.

Comparative Example 1 A reaction product was obtained under the same conditions as in Example 1 except that HZSM-5 (manufactured by JGC Corporation) was used. A steady state was reached 4 hours after the reaction started. Analysis of the product gave an aniline yield of 14.4%. No diphenylamine by-product was detected.

Comparative Example 2 HM-20 (JRC-Z-HM), which is a reference catalyst of the Japan Catalysis Society
A reaction was performed under the same conditions as in Example 1 except that -20) was used to obtain a product. The product was analyzed 3 hours after the reaction was started, and an aniline yield of 2.7% was obtained. No diphenylamine by-product was detected.

[0036]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, it is possible to produce economically advantageous anilines while maintaining a high yield and a high selectivity even when they are reacted at a low reaction temperature. Becomes

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Claims (2)

(57) [Claims] 1. A process for producing anilines by reacting phenols with an aminating agent, wherein zeolite β is used as a catalyst. 2. The production method according to claim 1, wherein the phenol is phenol and the aminating agent is ammonia.