JPH06107627A - Production of epsilon-caprolactam and method for improving catalyst life - Google Patents

Abstract

PURPOSE:To obtain a method for producing epsilon-caprolactam in extremely high selectivity in a state capable of reacting with cyclohexanone oxime also in high conversion and remarkably improved in the life of a catalyst. CONSTITUTION:The objective method for producing epsilon-caprolactam and the objective method for improving the life of a catalyst comprises bringing cyclohexanone oxime into contact with a solid catalyst in the presence of methylamines in vapor phase.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a process for producing ε-caprolactam from cyclohexanone oxime under a gas phase reaction condition using a solid catalyst.

[0002]

PRIOR ART AND PROBLEMS TO BE SOLVED BY THE INVENTION 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 method for producing ε-caprolactam by rearrangement (Beckmann rearrangement) of cyclohexanone oxime in the presence of a lower alcohol, an ether compound and the like in the reaction system under gas phase reaction conditions using a solid catalyst. (Japanese Patent Laid-Open Nos. 2-275850 and 2-250866).

As a result of further diligent studies on the rearrangement reaction of cyclohexanone oxime, the present inventors have found that methylamines are allowed to coexist in the reaction system.
Even under the condition that cyclohexanone oxime reacts at a high conversion rate, it was found that ε-caprolactam can be obtained with an extremely high selectivity and the life of the catalyst is remarkably improved, and the present invention has been completed.

[0005]

The present invention is a process for producing ε-caprolactam, which is industrially excellent, and is characterized by contacting cyclohexanone oxime with a solid catalyst in the gas phase in the presence of methylamines. It provides an improvement method.

The present invention will be described in detail below. Examples of the solid catalyst used in the present invention include silica-alumina,
Zeolite and the like can be mentioned, and among these, zeolite is preferable, and among them, crystalline silica and crystalline metallosilicate are more preferable.

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 for example, one 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. To be Here, as the metal, 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 can be mentioned. Si / Me
The atomic ratio can be determined by a usual analysis means such as an atomic absorption method and a fluorescent X-ray method.

Further, these catalysts can be produced by a known method. Various crystalline forms of these crystalline silicas and crystalline metallosilicates are known, but those belonging to the 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, which are used in combination of two or more kinds. You can also The amount of methylamines used is appropriately 10 times or less, preferably 1 time or less, and more preferably 0.001 to 0.8 times the molar ratio of the supplied cyclohexanone oxime. Also ammonia, ε
-Caprolactam can also be used in combination with these methylamines.

In the present invention, an alcohol or ether compound may be allowed to coexist with methylamines in the reaction system. This case is preferable because the selectivity of the target substance is further improved. Examples of the alcohol or ether compound include compounds represented by the following general formula (1). R ₁ —O—R ₂ (1) (In the formula, R ₁ represents a lower alkyl group optionally substituted by a fluorine atom, R ₂ is a hydrogen atom, a lower alkyl group optionally substituted by 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, 2,
Examples thereof include lower alcohols having 6 or less carbon atoms such as 2,2-trifluoroethanol, and among them, methanol and ethanol are preferable. Further, 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. To be These alcohols and ether compounds can be used in combination of two or more, and it is also possible to use the alcohol and ether compound in combination.

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

Next, a reaction method for carrying out the present invention will be described. Although cyclohexanone oxime as a raw material is catalytically reacted in a gas state, the reaction may be carried out by either a fixed bed system or a fluidized bed system. The 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 may be dividedly supplied. In the case of the fixed bed system, it is preferable that the cyclohexanone oxime is sufficiently mixed with methylamines to pass through the catalyst layer, and thus the former method is usually adopted.

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

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

The present invention can be carried out under any of increased pressure, normal pressure and reduced pressure, for example, usually 0.05 to 10 kg.
/ Cm ² of reaction conditions.

Separation and purification of ε-caprolactam from the reaction mixture can be carried out, for example, by cooling the reaction product gas to condense it and then conducting extraction, distillation or crystallization. Further, 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 the reaction product gas to condense it and then distilling it.

The catalyst whose activity has been lowered by long-term use can be easily prepared by calcining in a molecular oxygen-containing gas, for example, in an air stream or in a molecular oxygen-containing gas to which alcohol such as methanol is added. It can be used repeatedly by activating its original performance.

[0018]

According to the present invention, ε-caprolactam can be obtained with an extremely high selectivity even under the condition that cyclohexanone oxime is reacted at a high conversion rate, and the life of the catalyst is remarkably improved as compared with the conventional method. .

[0019]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited thereto.

Reference Example 1 (Preparation of catalyst) Tetraethyl orthosilicate (Si (OC ₂ H ₅ ) ₄ , Al content of 10 ppm or less) was placed in a 1.5-liter stainless steel autoclave.
00 g, 104.0% tetra-n-propylammonium hydroxide aqueous solution 224.0 g, and ethanol 214 g were charged, and 3
Stir vigorously for 0 minutes. The pH of the mixed solution was 13. After closing the lid of the autoclave, it was immersed in an oil bath to keep 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 inside the autoclave reached 2-3 kg / cm ² . The pH at the end of hydrothermal synthesis was 11.8. The white solid product was filtered off and then washed successively with distilled water until the pH of the wash liquor was around 7. After drying the white solid, 500 under air circulation.
Calcination at ˜530 ° C. for 4 hours gave 27 g of powdery white crystals. As a result of powder X-ray diffraction analysis of the crystal, it was identified as a pentasil-type zeolite. As a result of elemental analysis by an atomic absorption method, the content of Al was 3 ppm. To 10 g of this crystal, 100 g of 5% ammonium chloride aqueous solution was added, and an ion exchange treatment was performed at 50 to 60 ° C. for 1 hour.
The crystals were filtered off. After performing the ion exchange treatment four times, the crystals were washed with distilled water until Cl ⁻ ions were not detected in the washing liquid. Subsequently, the crystals were dried at 120 ° C. for 16 hours, and the obtained ammonium salt type crystals were pressure-molded and then sieved to 24-48 mesh. Further, the crystals were calcined under a nitrogen gas flow at 500 ° C. for 1 hour to obtain a catalyst.

Example 1 In a quartz glass reaction tube having an inner diameter of 1 cm, 0.375 g (0.6 ml) of the catalyst prepared in Reference Example 1 was filled, and a nitrogen stream (4.2) was charged.
1 / hr) was preheated at 360 ° C. for 1 hour. Then nitrogen to nitrogen (95% by volume) -trimethylamine (5% by volume)
The mixed gas (4.2 l / hr) was switched to. Then, while supplying the above-mentioned mixed gas, a mixed solution having a cyclohexanone oxime / methanol weight ratio of 1 / 1.2 at a rate of 6.6 g / hr and methanol at a rate of 1.8 g / hr were separately and simultaneously reacted in reaction tubes. And reacted for feeding. At this time, the space velocity WHSV of cyclohexanone oxime was 8 hr ⁻¹ , and the temperature of the catalyst layer (reaction temperature) was 350 ° C. The reaction is 45.2
After continuing for 5 hours, all feeds were stopped and terminated.
The reaction product was collected under water cooling and analyzed by gas chromatography. The results of the first reaction are shown in Table 1.

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 equations. WHSV (hr ^-1 ) = O / C Cyclohexanone oxime conversion (%) = [(X-
Y) / X] × 100 ε-caprolactam selectivity (%) = [Z / (X−
Y)] × 100 Further, O, C, X, Y and Z are as follows. O = Cyclohexanone oxime feed rate (kg / hr) C = Catalyst weight (kg) X = Number of moles of fed cyclohexanone oxime Y = Number of moles of unreacted cyclohexanone oxime Z = Number of moles 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% by volume: saturation concentration at 0 ° C.) to the reaction tube, the catalyst layer was 430
The temperature was raised to ℃ and treated for 96 hours. By this operation, the carbonaceous material deposited on the catalyst was removed.

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

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

[0026]

[Table 1]

Comparative Example 1 Under the same conditions as in Example 1 except that nitrogen was supplied to the mixed gas of nitrogen-trimethylamine in Example 1, the reaction and the carbonaceous substance removing operation were repeated three times in total. did. The results of each reaction are shown in Table 2.

[0028]

[Table 2]

Claims (2)

[Claims] 1. A process for producing ε-caprolactam, which comprises contacting cyclohexanone oxime with a solid catalyst in the gas phase in the presence of methylamines. 2. A method for improving the life of a catalyst for producing ε-caprolactam, which comprises contacting cyclohexanone oxime with a solid catalyst in the gas phase in the presence of methylamines.