JP2676895B2 - Process for producing ε-caprolactam - Google Patents

Description

The present invention relates to a method for producing ε-caprolactam from cyclohexanone oxime under gas phase reaction conditions using a solid acid catalyst.

<Problems to be Solved by Conventional Techniques and Inventions> ε-caprolactam is an important basic chemical raw material used as a raw material for nylon and the like, and its manufacturing method has conventionally used fuming sulfuric acid or concentrated sulfuric acid as a catalyst.
A method of rearranging cyclohexanone oxime in the liquid phase has been adopted.

However, this method not only requires a large amount of fuming sulfuric acid, but also has a problem of correcting a large amount of ammonium sulfate.

On the other hand, as a method of solving such a problem, various methods of using a solid acid catalyst and performing rearrangement in a gas phase have been proposed. For example, a boric acid-based catalyst (JP-A-53-37686,
No. 6-12125), a silica-alumina catalyst (British Patent No. 831,927), a solid phosphoric acid catalyst (British Patent No. 881,926)
No.), composite metal oxide catalysts (Journal of the Chemical Society of Japan, 1977 ,
(1) 77), zeolite catalyst (Journal of Catalysis)
6, 247 (1966), a method using a JP 57-139062 publication) or the like. However, all of these methods have problems in terms of the reaction selectivity of the target ε-caprolactam, the life of the catalyst, the productivity per catalyst, the quality of the product ε-caprolactam, and the like.

For example, JP-A-57-139062 discloses that 40-60
A specific example using a crystalline zeolite such as ZSM-5 having an Si / Al atomic ratio of is shown, and the reaction rate of cyclohexanone oxime is described as quantitative, but the selectivity of ε-caprolactam is not described. . The results also show that the catalyst life is as short as 15 to 20 hours.

The present inventors have also actually studied using a ZSM-5 zeolite having a Si / Al atomic ratio as described in the publication as a catalyst, but not only the life of the catalyst but also the selectivity to ε-caprolactam is insufficient. Value.

On the other hand, JP-A-62-123167 and JP-A-63-54358 disclose crystalline aluminosilicate in which the Si / Al atomic ratio is 500 or more and the amount of acid outside the pores is a specific value or less, or Si / Al. An example using a crystalline metallosilicate having a metal atom ratio of 500 or more as a catalyst is shown. The selectivity of this is considerably improved compared to the conventional silica-based catalyst technology,
JP-A-62-281856 discloses that the selectivity can be improved by treating the surface of crystalline zeolite with an organometallic compound.

<Means for Solving the Problems> In view of the above situation, the present inventors have conducted a study on a gas phase Beckmann rearrangement reaction which is superior to the conventional method using a solid acid catalyst, and as a result, cyclohexanone oxime was added to the reaction system. The reaction rate of cyclohexanone oxime is substantially 100 by coexisting with an ether compound.
The inventors have found that ε-caprolactam can be obtained with an extremely high selectivity even under the condition of about%, and that the life of the catalyst is remarkably improved, and the present invention has been completed.

That is, the present invention provides a method for producing ε-caprolactam from cyclohexanone oxime using a solid acid catalyst, characterized by allowing an ether compound to coexist in the reaction system.

 Hereinafter, the present invention will be described in detail.

In the present invention, the solid acid conventionally used as a catalyst may be mentioned. Among the solid acids, silicon oxide containing catalyst,
Particularly, crystalline aluminosilicate or crystalline metallosilicate is preferable. In particular, crystalline aluminosilicates with a Si / Me atomic ratio of 5 or more or Si / Al atomic ratios (here Me
Is Ga, Fe, B, Zn, Cr, Be, Co, La, Ti, Zr, Hf, V, Ni, Sb, Bi, Cu, Nb
A crystalline metallosilicate having 5 or more of 1 or 2 or more kinds of metal elements selected from the above) is more preferable. Si
The / Al atomic ratio and the Si / Me atomic ratio can be determined by ordinary analytical means such as atomic absorption method and fluorescent X-ray method.

These catalysts are produced by a known method. Various crystalline forms are known for such crystalline aluminosilicate or crystalline metallosilicate, but those belonging to the so-called pentasil type structure are particularly preferable.

In the present invention, an ether compound is allowed to coexist in the reaction system together with cyclohexanone oxime, and the ether compound used here is preferably an ether represented by the following general formula.

R ₁ —O—R ₂ Here, R ₁ is a methyl group or an ethyl group, and R ₂ is an alkyl group having 1 to 6 carbon atoms or a phenyl group.

Specifically, it is recommended to use one or more of dimethyl ether, methyl ethyl ether, diethyl ether, methyl-n-propyl ether, methyl isopropyl ether, methyl tert-butyl ether, anisole and the like. In particular, if one or more ether compounds in which R ₁ is a methyl group are used, a remarkable effect is exhibited in improving the selectivity of ε-caprolactam and the catalyst life,
More preferable.

 Next, a reaction method for carrying out the present invention will be described.

The reaction is carried out by an ordinary solid-phase or fluid-bed system gas-phase catalytic reaction. The starting material, cyclohexanone oxime, reacts with the catalyst layer in a gaseous state, but the ether compound may be mixed with cyclohexanone oxime in a gaseous state in advance, or may be supplied to the reactor separately from cyclohexanone oxime. In the case of the solid bed reaction, it is preferable that the cyclohexanone oxime and the ether compound are sufficiently mixed and passed through the catalyst layer. Further, in the case of the fluidized bed reaction, the cyclohexanone oxime and the ether compound do not necessarily have to be mixed in advance, and they can be separately supplied, and the ether compound can be divided and added. Further, in the case of a fluidized bed reaction, an ether compound may be added upstream of cyclohexanone oxime.

The amount of the ether compound to be coexisted in the reaction system is usually 0.1 to 20 times by weight ratio to cyclohexanone oxime, and if the amount is less than 0.1 times, the effect of addition of the ether compound is very small, and exceeds 20 times. Addition of a large amount of ether compound is generally not preferable because it is uneconomical and reduces the reaction rate of cyclohexanone oxime. For the purpose of increasing the selectivity of ε-caprolactam and improving the life of the catalyst, the coexisting amount of the ether compound is usually 0.3 to 15 by weight with respect to cyclohexanone oxime.
A double range is preferred.

As a diluent gas, a vapor of a compound inert to the reaction such as benzene, cyclohexane, toluene or the like or an inert gas such as nitrogen or carbon dioxide can be coexistent in the reaction system.

The reaction temperature is usually in the range of 250 ° C to 500 ° C. If the temperature is less than 250 ° C, the reaction rate is insufficient and the selectivity for ε-caprolactam tends to be low. On the other hand, when the temperature exceeds 500 ° C, the thermal decomposition of cyclohexanone oxime cannot be ignored, and the selectivity of ε-caprolactam decreases. A particularly preferred temperature range is 300 ° C to 450 ° C, and a most preferred temperature range is 300 ° C to 400 ° C.

The feed rate of the raw material cyclohexanone oxime is usually LH
SV = 0.1 to 40 hr ⁻¹ (that is, cyclohexanone oxime feed rate per catalyst 1 of 0.1 to 40 / hour). It is preferably 0.2 to 20 hr ^-1 , more preferably 0.5.
It is selected from the range of up to 10 hr ^-1 .

Separation of ε-caprolactam from the reaction mixture can be carried out by a conventional method. For example, the reaction product gas is cooled and condensed, and then ε-caprolactam purified by extraction, distillation or crystallization can be obtained.

The ether compound added to the rearrangement reaction system can be separated and recovered from the reaction product and reused.

Further, the catalyst whose activity has been reduced by long-term use can be easily activated to its original performance by calcining in an air stream, and can be used repeatedly.

<Effects of the Invention> As described above in detail, according to the present invention, ε-caprolactam is produced with an extremely high selectivity even under the condition that the reaction rate of cyclohexanone oxime is substantially around 100%. Also, in the method of the present invention, the life of the catalyst is significantly improved as compared with the conventional method. Further, the ether compound added to the reaction system can be recovered and reused. Since the method of the present invention has many advantages as compared with the conventionally known methods, its industrial value is enormous.

<Examples> Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto.

Reference Example stainless steel autoclave of tetraethyl orthosilicate (Preparation of _{Catalyst) 1.5 (Si (OC 2 H} 5) 4) 100g, 10% tetra -n- propyl aqueous ammonium 224 g, was sufficiently agitated of ethanol were charged 60 g. 48 g of a previously prepared aqueous solution of aluminum sulfate (Al ₂ (S
O ₄ ) ₃ · 16H ₂ O 20 mg / water 48 g) was added, and the mixture was vigorously stirred for 30 minutes. The pH of the mixed solution was 13. After closing the autoclave lid, immerse it in an oil bath and keep the internal temperature at 105 ° C to 400r.
Hydrothermal synthesis was performed for 120 hours while stirring at a rotation speed of pm or higher. During this time, the pressure inside the autoclave is 2 kg /
It reached 3 kg / cm ² from cm ² . The pH at the end of the hydrothermal synthesis was 11.8. The white solid product was filtered off and then washed continuously with distilled water until the pH of the filtrate was around 7. The white solid was dried and then calcined at 500 to 530 ° C. for 4 hours under air flow to obtain powdery white crystals. As a result of powder X-ray diffraction analysis of the crystal, it was fixed as a pentasil-type zeolite. As a result of elemental analysis by atomic absorption spectroscopy, the Si / Al atomic ratio was 7000
Met.

100 g of a 5% aqueous solution of ammonium chloride was added to 10 g of the crystals, subjected to an ion exchange treatment at 50 to 60 ° C for 1 hour, and then filtered. After performing this ion exchange treatment operation four times,
The crystals were washed with distilled water until no Cl ^- ions could be detected. Subsequently, the crystals were dried at 120 ° C. for 16 hours. The obtained ammonium salt type crystal was subjected to pressure molding and then sieved to 24-48 mesh. Further, the crystals were calcined at 500 ° C. for 1 hour under flowing nitrogen gas to obtain a catalyst.

Example 1 0.3 g of catalyst (0.5 g) was placed in a quartz glass reaction tube having an inner diameter of 1 cm.
ml) and preheated at 350 ° C. for 1 hour in a nitrogen stream. Then cyclohexanone oxime / methyl-tert-
A mixed solution of butyl ether / benzene weight ratio = 1 / 3.1 / 10.6 was fed to the reaction tube at a feed rate of 11.5 g / hr to cause a reaction.
The space velocity W / F at this time was 42.5 g · hr / mole, and the temperature of the catalyst layer (reaction temperature) was 350 ° C. 1 reaction product
It was collected under water cooling every hour and analyzed by gas chromatography.

 Table 1 shows the analysis results.

Here, the space velocity W / F is a value calculated by the following formula, and the reaction rate of cyclohexanone oxime and the selectivity of ε-caprolactam are calculated by the following formulas, respectively.

W / F (g · hr / mole) = catalyst weight (g) / cyclohexanone oxime supply rate (mole / hr) Cyclohexanone oxime reaction rate (%) = {(X-Y) / X} × 100 ε-caprolactam Selectivity (%) = {Z / (X−Y)} × 100 Yield (%) of ε-caprolactam = Z / X × 100 where X, Y, and Z are as follows.

X = the number of moles of the starting material cyclohexanone oxime supplied Y = the number of moles of unreacted cyclohexanone oxime Z = the number of moles of ε-caprolactam in the product Comparative Example Cyclohexanone oxime / benzene weight ratio without coexisting an ether compound in the reaction system = 1 / 11.5 mixed solution 1
The same procedure as in Example 1 was carried out except that the reaction tube was fed at a feed rate of 1.5 g / hr (W / F = 36.8).

 Table 2 shows the reaction results.

Examples 2 to 4 Using the same catalyst used in Example 1, methyl-
The reaction was carried out at a reaction temperature of 350 ° C. in the same manner as in Example 1 except that the ether compound, the raw material composition ratio, and the raw material supply rate shown in Table 3 were changed in place of tert-butyl ether.

 Table 3 shows the reaction results.

Claims (1)

(57) [Claims] 1. A method for producing ε-caprolactam from cyclohexanone oxime under a gas phase reaction condition using a solid acid catalyst, wherein an ether compound is allowed to coexist in the reaction system.