JP3254753B2 - Method for producing ε-caprolactam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art ε-Caprolactam is an important basic chemical raw material used as a raw material for nylon and the like.

The present inventors have proposed a process for producing ε-caprolactam by rearranging cyclohexanone oxime (Beckmann rearrangement) in the presence of a lower alcohol, an ether compound and the like in a reaction system under gas phase reaction conditions using a solid catalyst. (JP-A-2-275850 and JP-A-2-250866).

The present inventors have further studied the rearrangement reaction of cyclohexanone oxime, and as a result, by coexisting methylamines in the reaction system,
Under conditions in which cyclohexanone oxime reacts at a high conversion, it has been found that ε-caprolactam can be obtained with an extremely high selectivity and that the life of the catalyst is significantly improved, and the present invention has been completed.

[0005]

DISCLOSURE OF THE INVENTION The present invention relates to a monomethyl alcohol
Choose from min, dimethylamine and trimethylamine
The present invention provides an industrially excellent method for producing ε-caprolactam, comprising contacting cyclohexanone oxime with a solid catalyst in the gas phase in the presence of at least one of the following.

Hereinafter, the present invention will be described in detail. As the solid catalyst used in the present invention, for example, silica-alumina,
Zeolite and the like are mentioned, and among them, zeolite is preferable, and among them, crystalline silica, crystalline metallosilicate and the like are more preferable.

[0007] The crystalline silica in the present invention is substantially composed of silicon and oxygen. The crystalline metallosilicate includes a metal in addition to silicon and oxygen, and includes, for example, those having a ratio of the number of silicon atoms to the number of metal atoms (Si / Me atomic ratio) of 5 or more, preferably 500 or more. Can be Here, metals such as Al, Ga,
Fe, B, Zn, Cr, Be, Co, La, Ge, T
One or more metals selected from i, Zr, Hf, V, Ni, Sb, Bi, Cu, Nb, and the like. Si / Me
The atomic ratio can be determined by ordinary analysis means, for example, an atomic absorption method, a fluorescent X-ray method, or the like.

[0008] These catalysts can be produced by a known method. Various crystalline types are known for these crystalline silicas and crystalline metallosilicates, but those belonging to a so-called pentasil type structure are preferred.

The present invention is characterized in that methylamines are allowed to coexist in the reaction system. Examples of such methylamines include monomethylamine, dimethylamine and trimethylamine. Can also. The amount of the methylamines to be used is usually suitably 10 times or less, preferably 1 time or less, more preferably 0.001 to 0.8 times, in terms of molar ratio with respect to the supplied cyclohexanone oxime. Ammonia, ε
-Caprolactam can also be used in combination with these methylamines.

In the present invention, an alcohol or an ether compound may coexist with methylamines in the reaction system. This case is preferable because the selectivity of the target substance is further improved. Examples of such an alcohol or ether compound include a compound represented by the following general formula (1). R ₁ —O—R ₂ (1) (wherein, R ₁ represents a lower alkyl group optionally substituted with a fluorine atom, and R ₂ represents a lower alkyl group optionally substituted with a hydrogen atom or a fluorine atom. Or a phenyl group.) Specific examples of the alcohol include, for example, methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, isobutanol, n-amyl alcohol, n-hexanol,
Examples thereof include lower alcohols having 6 or less carbon atoms such as 2,2-trifluoroethanol, and among them, methanol and ethanol are preferable. As the ether compound, R ₁
Is preferably a methyl group or an ethyl group, and examples thereof include ether compounds having 8 or less carbon atoms such as dimethyl ether, methyl ethyl ether, diethyl ether, methyl-n-propyl ether, methyl isopropyl ether, methyl tert-butyl ether, and anisole. Can be Two or more of these alcohol and ether compounds can be used in combination, and an alcohol and an ether compound can be used in combination.

Further, in the present invention, 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 coexisted in the reaction system as a diluent gas.

Next, a reaction method for carrying out the present invention will be described. The starting material cyclohexanone oxime is brought into contact in a gaseous state, and the reaction may be carried out in any of a fixed bed system and a fluidized bed system. Methylamines may be mixed with cyclohexanone oxime in advance and supplied to the reactor, or may be supplied separately from cyclohexanone oxime. In the latter case, methylamines can be supplied in a divided manner. In the case of the fixed bed system, it is preferable that cyclohexanone oxime is allowed to pass through the catalyst layer in a state of being sufficiently mixed with methylamines. Therefore, the former method is usually employed.

The space velocity of the raw material cyclohexanone oxime is usually WHSV = 0.1 to 40 hr ^-1 (that is, 1 kg of catalyst).
Cyclohexanone oxime supply rate per unit is 0.1 to 40
kg / hr), preferably from 0.2 to 20 hr ^-1 , more preferably from 0.5 to 10 hr ^-1 .

The reaction temperature of the present invention is usually from 250 to 500 ° C.
However, it is preferably from 300 to 450 ° C, more preferably from 300 to 400 ° C. At a temperature lower than 250 ° C., the reaction rate is not sufficient, and the selectivity for ε-caprolactam tends to decrease. On the other hand, when the temperature exceeds 500 ° C., the selectivity for ε-caprolactam tends to decrease.

The present invention can be carried out under any of pressurized, normal, and reduced pressures.
/ Cm ² reaction conditions.

The separation and purification of ε-caprolactam from the reaction mixture can be carried out, for example, by cooling and condensing the reaction product gas, followed by extraction, distillation or crystallization. The methylamines added to the reaction system can be separated and recovered from the reaction product and reused. Separation and recovery of methylamines can be performed, for example, by cooling and condensing the reaction product gas and then distilling it.

A catalyst whose activity has been reduced over a long period of use can be easily prepared by calcining in a molecular oxygen-containing gas, for example, in an air stream, or calcining in a molecular oxygen-containing gas to which alcohol such as methanol is added. Activated to the original performance and can be used repeatedly.

[0018]

According to the present invention, .epsilon.-caprolactam can be obtained with an extremely high selectivity even under conditions in which cyclohexanone oxime reacts at a high conversion, and the life of the catalyst is significantly improved as compared with the conventional method. .

[0019]

EXAMPLES The present invention will now be described specifically with reference to examples, but the present invention is not limited to these examples.

REFERENCE EXAMPLE 1 (Preparation of catalyst) Tetraethyl orthosilicate (Si (OC ₂ H ₅ ) ₄ , Al content 10 ppm or less) was placed in a 1.5-liter stainless steel autoclave.
100 g, 224.0 g of a 10% aqueous solution of tetra-n-propylammonium hydroxide, and 214 g of ethanol.
Stir vigorously for 0 minutes. The pH of the mixed solution was 13. After closing the autoclave lid, it was immersed in an oil bath to maintain the internal temperature at 105 ° C., and hydrothermal synthesis was performed for 120 hours while stirring at a rotation speed of 400 rpm or more. During this time, the pressure in the autoclave reached 2-3 kg / cm ² . The pH at the end of the hydrothermal synthesis was 11.8. The white solid product was filtered off and washed successively with distilled water until the pH of the washings was around 7. After drying the white solid, 500
The mixture was calcined at ５530 ° C. for 4 hours to obtain 27 g of powdery white crystals. The crystal was analyzed by powder X-ray diffraction, and as a result, it was identified as a pentasil-type zeolite. As a result of elemental analysis by the atomic absorption method, the Al content was 3 ppm. 100 g of a 5% aqueous ammonium chloride solution was added to 10 g of the crystals, and an ion exchange treatment was performed at 50 to 60 ° C. for 1 hour.
The crystals were filtered off. After performing this ion exchange treatment operation four times, the crystals were washed with distilled water until no Cl ^- ions were detected in the washing solution. Subsequently, the crystals were dried at 120 ° C. for 16 hours, and the obtained ammonium salt type crystals were 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 0.375 g (0.6 ml) of the catalyst prepared in Reference Example 1 was charged into a quartz glass reaction tube having an inner diameter of 1 cm, and the reaction mixture was placed under a nitrogen stream (4.2).
1 / hr) at 360 ° C. for 1 hour. The nitrogen is then replaced with nitrogen (95% by volume) -trimethylamine (5% by volume).
(4.2 l / hr). Then, while supplying the above-mentioned mixed gas, the reaction mixture was separately and simultaneously mixed with a mixture of cyclohexanone oxime / methanol at a weight ratio of 1 / 1.2 at a rate of 6.6 g / hr and methanol at a rate of 1.8 g / hr. And reacted. At this time, the space velocity WHSV of cyclohexanone oxime was 8 hr ^-1 , and the temperature (reaction temperature) of the catalyst layer was 350 ° C. The reaction is 45.2
After 5 hours, all feeds were stopped and terminated.
The reaction product was collected under water cooling and analyzed by gas chromatography. Table 1 shows the results of the first reaction.

Here, the space velocity WHSV of cyclohexanone oxime was calculated by the following equation, and the conversion of cyclohexanone oxime and the selectivity of ε-caprolactam were also calculated by the following equation. WHSV (hr ^-1 ) = O / C Conversion of cyclohexanone oxime (%) = [(X−
Y) / X] × 100 ε-caprolactam selectivity (%) = [Z / (X−
Y)] × 100 Further, O, C, X, Y and Z are as follows, respectively. O = cyclohexanone oxime supply rate (kg / hr) C = catalyst weight (kg) X = mol number of supplied cyclohexanone oxime Y = mol number of unreacted cyclohexanone oxime Z = mol number of ε-caprolactam in the product

After completion of the reaction, a mixed gas of nitrogen gas (2.5 l / hr) and air (2.5 l / hr) was bubbled into methanol kept at 0 ° C. to obtain nitrogen, air and methanol. While supplying the mixed gas (methanol concentration 3.8 vol%: saturated concentration at 0 ° C.) to the reaction tube, the catalyst layer was 430
The temperature was raised to ° C. and the treatment was carried out for 96 hours. By this operation, the carbonaceous substance deposited on the catalyst was removed.

Next, the temperature was lowered to 350 ° C. while supplying nitrogen gas (4.2 l / hr).

The reaction and the operation of removing the carbonaceous substance were repeated three times in total under the same conditions as described above. The results of each reaction are shown in Table 1.

[0026]

[Table 1]

Comparative Example 1 A reaction and a carbonaceous substance removing operation were repeated three times in total under the same conditions as in Example 1 except that nitrogen was supplied without switching to a mixed gas of nitrogen and trimethylamine. did. Table 2 shows the results of each reaction.

[0028]

[Table 2]

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-5-170732 (JP, A) JP-B-48-39951 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C07D 201/04

Claims (1)

(57) [Claims] 1. Monomethylamine, dimethylamine and
A process for producing ε-caprolactam, comprising contacting cyclohexanone oxime with a solid catalyst in the gas phase in the presence of at least one selected from trimethylamine .