JP3254751B2 - Method for producing ε-caprolactam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for producing .epsilon.-caprolactam from cictohexanone 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 and an ether compound in a reaction system under gas phase reaction conditions using a solid catalyst. Japanese Patent Application Laid-Open Nos. 2-275850 and 2-250866.

[0004] The present inventors have further studied the rearrangement reaction of cyclohexanone oxime, and as a result, the coexistence of ammonia in the reaction system allows the selection of cyclohexanone oxime to be performed at a very high conversion rate even under conditions in which the reaction proceeds at a high conversion. Ε-caprolactam can be obtained at a rate, and the life of the catalyst is remarkably improved.
The present invention has been completed.

[0005]

That is, the present invention provides a method for synthesizing cyclohexanone oxime in the gas phase in the presence of ammonia.
The present invention provides an industrially excellent method for producing an ε-caplactam, which is characterized by being brought into contact with olilite.

Hereinafter, the present invention will be described in detail. In the present invention
Is zero zeolite is used as a solid catalyst, among others crystalline silica, crystalline metallosilicate or the like is 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, as the metal, Al, Ga,
Fe, B, Zn, Cr, Be, Co, La, Ge, T
At least one metal selected from i, Zr, Hf, V, Ni, Sb, Bi, Cu, Nb, and the like is included. Si
The / Me atomic ratio can be determined by ordinary analytical means such as an atomic absorption method and a fluorescent X-ray method.

[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 ammonia is allowed to coexist in the reaction system. The amount of ammonia to be used is suitably usually 10 times or less in molar ratio with respect to cyclohexanone oxime to be supplied. Is 1 time or less, more preferably 0.001 to 0.8 times.
Further, methylamines and ε-caprolactam can be used in combination with ammonia.

In the present invention, an alcohol or an ether compound can coexist with ammonia 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, those in which R ₁ is a methyl group or an ethyl group are preferable, and for example, the carbon number of dimethyl ether, methyl ethyl ether, diethyl ether, methyl-n-propyl ether, methyl isopropyl ether, methyl-tert-butyl ether, anisole, etc. And 8 or less ether compounds. 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.

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 may coexist as a diluent gas in the reaction system.

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. The ammonia to be added 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, ammonia can be added in portions. In the case of a fixed bed reaction, it is preferable that cyclohexanone oxime is sufficiently mixed with ammonia to pass through the catalyst layer, and thus 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 4
0 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 300 to 450 ° C, more preferably 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.

Further, the present invention can be carried out under any of pressurized, normal, and reduced pressures.
Carried out under a pressure of / cm ² .

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 ammonia added to the reaction system can be separated and recovered from the reaction product and reused. For example, when the reaction product gas is cooled and condensed, ammonia can be recovered in a gaseous state.

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

[0019]

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

[0020]

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 (0C 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.

REFERENCE EXAMPLE 2 (Treatment of Catalyst) 1 g of the catalyst prepared in Reference Example 1 was filled in a quartz glass reaction tube and preheat-treated at 500 ° C. for 3 hours under a nitrogen stream (4.2 l / hr). Then, the temperature was lowered to 100 ° C., and the nitrogen was switched to a mixed gas (4.2 l / hr) of nitrogen (95% by volume) -ammonia (5% by volume) and maintained for 10 hours. Thereafter, the atmosphere was switched to nitrogen (4.2 l / hr) again, the temperature was raised to 350 ° C. at a rate of 1 ° C. per minute, and held for 1 hour. Then, it was cooled to room temperature while supplying nitrogen.

Example 1 0.375 g (0.6 ml) of the catalyst prepared in Reference Example 1 was filled in a quartz glass reaction tube having an inner diameter of 1 cm, and the reaction mixture was placed in a nitrogen stream (4.2).
1 / hr) at 350 ° C. for 1 hour. Then, nitrogen was switched to a mixed gas (4.2 l / hr) of nitrogen (95% by volume) -ammonia (5% by volume). Next, while supplying the above mixed gas, a mixed liquid having a cyclohexanone oxime / methanol weight ratio of 1 / 1.8 was supplied to the reaction tube at a rate of 8.4 g / hr to cause a reaction. 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 was continued for 6.25 hours, after which all feeds were stopped and terminated. The reaction product was collected under water cooling and analyzed by gas chromatography.

Here, the space velocity WHSV is calculated by the following equation, and the conversion of cyclohexanone oxime and ε-
The selectivity of caprolactam was also calculated by the following formula. WHSV (hr ^-1 ) = O / C Conversion of cyclohexanone oxime (%) = [(XY) / X] × 100 Selectivity (%) of ε-caprolactam = [Z / (XY)] × 100 In addition, O, C, X, Y and Z are as follows. O = feed rate of cyclohexanone oxime (kg / hr) C = weight of catalyst (kg) X = number of moles of raw material cyclohexanone oxime supplied Y = number of moles of unreacted cyclohexanone oxime Z = mole of ε-caprolactam in the product number

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 maintained 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 heated to 430 ° C.
And then treated at that temperature for 23 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).

Subsequently, the reaction and the operation of removing the carbonaceous substance were repeated 30 times in total under the same conditions as described above. The results of each reaction are shown in Table 1.

[0028]

[Table 1]

Comparative Example 1 The reaction and the removal of the carbonaceous substance were carried out a total of 30 times under the same conditions as in Example 1 except that nitrogen was supplied without switching to the nitrogen-ammonia mixed gas in Example 1. Table 2 shows the results of each reaction.

[0030]

[Table 2]

Comparative Example 2 0.375 g of the catalyst treated in Reference Example 2 instead of the catalyst prepared in Reference Example 1 was placed in a quartz glass reaction tube having an inner diameter of 1 cm.
(0.6 ml) under the same conditions as in Comparative Example 1,
The reaction and the operation of removing the carbonaceous substance were repeated 30 times in total. Table 3 shows the results of each reaction.

[0032]

[Table 3]

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-B-48-16516 (JP, B1) JP-B-51-3914 (JP, B1) JP-B-46-23745 (JP, B1) (58) Field (Int.Cl. ⁷ , DB name) C07D 201/04

Claims (1)

(57) [Claims] 1. A process for producing ε-caprolactam, comprising contacting cyclohexanone oxime with zeolite in the gas phase in the presence of ammonia.