JP2011153047A - Method for producing zeolite and method for producing ε-caprolactam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing zeolite excellent in catalytic activity and catalytic life, and to provide a method for producing ε-caprolactam with high yield for a long period of time by using the zeolite thus obtained. <P>SOLUTION: The zeolite is produced by firing a crystal obtained by a hydrothermal synthesis of a silicon compound, subjecting the crystal to a contact treatment with an aqueous solution containing ammonia and/or an ammonium salt, and heat treating the crystal at 500 to 700°C. The obtained zeolite is used as a catalyst to produce ε-caprolactam by Beckmann rearrangement reaction of cyclohexane in a gas phase in the presence of the catalyst. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing zeolite. The present invention also relates to a method for producing ε-caprolactam from cyclohexanone oxime using zeolite as a catalyst.

  Conventionally, as one method for producing ε-caprolactam, a method has been proposed in which zeolite is used as a solid catalyst and cyclohexanone oxime is subjected to Beckmann rearrangement reaction in the gas phase in the presence of the zeolite (for example, Patent Document 1). 2). As a method for producing such a zeolite, for example, in JP-A-5-170732 (Patent Document 3), after calcination of a crystal obtained by a hydrothermal synthesis reaction of a silicon compound, ammonia, lower alkylamine, allylamine and A method of contact treatment with an aqueous solution of a basic substance selected from alkylammonium hydroxide and an ammonium salt, or aqueous ammonia has been proposed. Japanese Patent Application Laid-Open No. 2004-75518 (Patent Document 4) proposes a method in which a crystal obtained by a hydrothermal synthesis reaction of a silicon compound is calcined and then contact-treated with an aqueous solution of a quaternary ammonium salt and ammonia. Has been.

JP-A-2-250866 JP-A-2-275850 JP-A-5-170732 JP 2004-75518 A

  However, the conventional methods are not always satisfactory in terms of catalyst activity and catalyst life. Accordingly, an object of the present invention is to provide a method for producing zeolite that is excellent in terms of catalyst activity and catalyst life. Another object of the present invention is to provide a method capable of producing ε-caprolactam over a long period of time with high productivity by reacting cyclohexanone oxime at a high conversion rate using the zeolite thus obtained as a catalyst. It is in.

  As a result of intensive studies to achieve the above object, the present inventors have completed the present invention.

  That is, the present invention is characterized in that after a crystal obtained by a hydrothermal synthesis reaction of a silicon compound is calcined, it is contact-treated with an aqueous solution containing ammonia and / or an ammonium salt, and then heat-treated at 500 to 700 ° C. A method for producing zeolite is provided.

  The present invention also provides a method for producing ε-caprolactam by subjecting cyclohexanone oxime to a Beckmann rearrangement reaction in the gas phase in the presence of the zeolite produced by the above method.

  According to the present invention, a zeolite having excellent catalytic activity and catalyst life can be produced, and cyclohexanone oxime is increased by causing Beckmann rearrangement reaction of cyclohexanone oxime in the gas phase using the zeolite thus obtained as a catalyst. The reaction can be carried out at a conversion rate, and ε-caprolactam can be produced with good productivity over a long period of time.

  Hereinafter, the present invention will be described in detail. The zeolite to be produced by the present invention contains silicon and oxygen as elements constituting the skeleton, and may be crystalline silica substantially composed of silicon and oxygen. It may be a crystalline metallosilicate that further contains other elements as an element constituting the element. In the case of metallosilicates and the like, elements that may exist other than silicon and oxygen include, for example, Be, B, Al, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Sb, La, Hf, Bi, etc. are mentioned, and two or more of them may be included as necessary.

  As the zeolite, those having various structures are known. Among them, those having a pentasil type structure are preferable, and those having an MFI structure are particularly preferable.

  For the hydrothermal synthesis reaction of the silicon compound, a known method can be adopted as appropriate, and among them, a formulation in which the silicon compound is mixed with water and tetraalkylammonium hydroxide and the mixed solution is heat-treated is suitably employed. The As the silicon compound, tetraalkyl orthosilicate such as tetramethyl orthosilicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate is preferably used. Tetraalkylammonium hydroxide can act as a templating agent or base, and tetramethylammonium hydroxide or tetrapropylammonium hydroxide is preferably used.

  When preparing the mixed solution, components other than the silicon compound, water, and tetraalkylammonium hydroxide may be used as a mixed raw material as necessary. For example, in order to adjust the hydroxide ion concentration in the mixed solution, a basic compound such as sodium hydroxide or potassium hydroxide may be mixed. Further, in order to adjust the tetraalkylammonium ion concentration in the mixed solution, a tetraalkylammonium salt such as tetraalkylammonium bromide may be mixed.

  In the mixed solution, the molar ratio of water to silicon is usually adjusted to 5 to 100, preferably 10 to 60, and the molar ratio of tetraalkylammonium ions to silicon is usually 0.1 to 0.6, preferably 0. The molar ratio of hydroxide ion to silicon is usually adjusted to 0.1 to 0.6, preferably 0.2 to 0.5. Moreover, when mixing the compound containing elements other than silicon and oxygen exemplified above, the molar ratio of silicon to these elements in the mixed solution is preferably adjusted to 5 or more, more preferably 500 or more. .

  The heat treatment temperature for subjecting the mixed solution to a hydrothermal synthesis reaction is usually 80 to 160 ° C., and the heat treatment time is usually 1 to 200 hours.

  Crystals are separated from the reaction mixture obtained by the hydrothermal synthesis reaction by concentration, filtration or the like, and the crystals are subjected to a treatment such as drying as necessary, and then baked. This firing is usually suitably performed at a temperature of 400 to 600 ° C. in an oxygen-containing gas atmosphere, for example, in an air atmosphere or a mixed gas atmosphere of air and nitrogen. Further, before or after firing in an oxygen-containing gas atmosphere, firing in an inert gas atmosphere such as nitrogen may be performed.

  The fired crystals are subjected to contact treatment with an aqueous solution containing ammonia and / or an ammonium salt. The ammonium salt used here is a salt of ammonia, and examples thereof include ammonium chloride, ammonium sulfate, and ammonium nitrate. In addition, before the contact treatment with this aqueous solution, the fired crystals may be subjected to other treatments as necessary, for example, by performing contact treatment with water or water vapor at 200 ° C. or lower. The crystal strength can be improved.

  The concentration of ammonia and / or ammonium salt contained in the aqueous solution is preferably adjusted so that the pH of the aqueous solution is usually 9 or more, preferably 9 to 13. Moreover, components other than ammonia and ammonium salt may be contained in the aqueous solution as necessary. For example, an amine or a quaternary ammonium compound may be added.

  Examples of the amine include alkylamines such as monomethylamine, monoethylamine, monopropylamine, monobutylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, trimethylamine, triethylamine, tripropylamine, tributylamine, Examples include allylamines such as monoallylamine, diallylamine, and triallylamine, and two or more of them may be used as necessary.

  Examples of the quaternary ammonium compound include tetramethylammonium, tetraethylammonium, n-propyltrimethylammonium, tetra-n-propylammonium, tetra-n-butylammonium, 4,4′-trimethylenebis (dimethylpiperididium). , Quaternary ammonium halides such as benzyltrimethylammonium, dibenzyldimethylammonium, 1,1′-butylenebis (4-aza-1-azoniabicyclo [2,2,2] octane), trimethyladamantylammonium, sulfate Nitrates and the like, and two or more of them can be used as necessary. Among them, a quaternary ammonium halide such as tetra-n-propylammonium bromide is preferable.

  The contact treatment with the aqueous solution may be performed batchwise or continuously, for example, the crystal may be immersed in the aqueous solution in a stirring tank and stirred, or the tube filled with the crystal You may distribute | circulate the said aqueous solution to a container.

  The temperature of the contact treatment with the aqueous solution is usually 50 to 250 ° C., preferably 50 to 200 ° C., more preferably 60 to 150 ° C., and the contact treatment time is usually 0.1 to 10 hours. Moreover, the usage-amount of the said aqueous solution is 100-5000 weight part normally with respect to 100 weight part of crystals.

  The crystals after the contact treatment with the aqueous solution are subjected to treatments such as washing with water and drying as necessary. In addition, you may perform the contact process by the said aqueous solution in multiple times as needed.

  The crystals after the contact treatment with the aqueous solution are heat-treated at 500 to 700 ° C. The temperature of the heat treatment is usually 500 to 700 ° C, preferably 525 to 675 ° C, more preferably 550 to 650 ° C, and the heat treatment time is usually 0.1 to 100 hours.

  The heat treatment may be performed in an oxygen-containing gas atmosphere or an inert gas atmosphere such as nitrogen. Further, the heat treatment may be performed in multiple stages in an atmosphere of an oxygen-containing gas or an inert gas.

  When an oxygen-containing gas is used for the heat treatment, air or pure oxygen is usually used as the oxygen source, and diluted with an inert gas as necessary. Of these, air is preferred as the oxygen-containing gas. Firing performed in an oxygen-containing gas atmosphere is usually performed in an oxygen-containing gas stream.

  Examples of the inert gas used for the heat treatment include inert gases such as nitrogen, carbon dioxide, helium, and argon. Among these, nitrogen is preferable as the inert gas. Baking performed under an inert gas atmosphere is usually performed under an inert gas stream.

  The heat treatment is preferably performed in a gas atmosphere containing water vapor. The water vapor concentration in the gas containing water vapor is usually 0.05 to 100% by volume, preferably 0.5 to 30% by volume, more preferably 2.0 to 20% by volume, and most preferably 3.0 to 10% by volume. %. Examples of components other than water vapor that can be contained in the gas containing water vapor include the oxygen-containing gas and the inert gas. Moreover, the usage-amount of water vapor | steam is 0.1-10000 weight part normally with respect to 100 weight part of crystals, Preferably it is 1.0-1000 weight part, More preferably, it is 10-100 weight part.

  The heat treatment may be performed in a fluidized bed type or a fixed bed type. For example, at least one of the oxygen-containing gas, the inert gas and the gas containing water vapor in a tubular container filled with crystals. Can be distributed.

  The zeolite of the present invention can be used for various applications including a catalyst for organic synthesis reaction. Among them, as a catalyst for producing ε-caprolactam by carrying out a Beckmann rearrangement reaction of cyclohexanone oxime in a gas phase. Can be used.

  Zeolite as the catalyst can be molded and used in accordance with the reactor to be used. Examples of the molding method include a method of compressing and molding a solid, and a method of spraying and drying a slurry. In addition, the strength of the molded catalyst can be improved by performing contact treatment with water or water vapor at 200 ° C. or lower, for example. Further, this catalyst may be substantially composed only of zeolite, or may be one in which zeolite is supported on a carrier.

The reaction conditions for the Beckmann rearrangement are a reaction temperature of usually 250 to 500 ° C., preferably 300 to 450 ° C., and a reaction pressure of usually 0.005 to 0.5 MPa, preferably 0.005 to 0.2 MPa. This reaction may be carried out in a fixed bed format or a fluidized bed format, and the feed rate of the raw material cyclohexanone oxime is determined according to the feed rate (kg / h) per kg of the catalyst, that is, the space velocity WHSV (h ⁻¹ ) is usually 0.1 to 20 h ⁻¹ , preferably 0.2 to 10 h ⁻¹ .

  Cyclohexanone oxime, for example, may be introduced alone into the reaction system, or may be introduced together with an inert gas such as nitrogen, argon or carbon dioxide. Further, a method of coexisting an ether as described in JP-A-2-250866, a method of coexisting a lower alcohol as described in JP-A-2-275850, an alcohol as described in JP-A-5-201965, and A method of coexisting ether and water, a method of coexisting ammonia as described in JP-A No. 5-201966, a method of coexisting methylamine as described in JP-A No. 6-107627 are also effective.

  In addition, the reaction may be performed in combination with an operation of calcining the catalyst in an oxygen-containing gas atmosphere such as air, and by this catalyst calcining treatment, the carbonaceous material deposited on the catalyst can be removed by combustion. The sustainability of the conversion ratio of cyclohexanone oxime and the selectivity of ε-caprolactam can be increased. For example, when the reaction is carried out in a fixed bed type, cyclohexanone oxime is supplied together with other components to the fixed bed type reactor filled with the solid catalyst as necessary, and then the reaction is carried out. Stopping, then supplying an oxygen-containing gas, firing, and further repeating these reactions and firing are suitably employed. Further, when the reaction is performed in a fluidized bed type, the cyclohexanone oxime is supplied to the fluidized bed reactor in which the solid catalyst has flowed together with other components as necessary, and the reaction is carried out from the reactor. Is preferably employed in such a manner that is extracted continuously or intermittently, calcined in a calciner, and returned to the reactor again.

  In addition, as a post-treatment operation of the reaction mixture obtained by the reaction, a known method can be appropriately employed. For example, after cooling and condensing the reaction product gas, extraction, distillation, crystallization, etc. By performing the operation, ε-caprolactam can be separated.

Examples of the present invention will be described below, but the present invention is not limited thereto. The space velocity WHSV (h ⁻¹ ) of cyclohexanone oxime was calculated by dividing the supply rate (g / h) of cyclohexanone oxime by the catalyst weight (g). The analysis of cyclohexanone oxime and ε-caprolactam was carried out by gas chromatography. The conversion rate of cyclohexanone oxime and the selectivity of ε-caprolactam were X for the number of moles of cyclohexanone oxime supplied and the number of moles of unreacted cyclohexanone oxime. Y and the number of moles of the produced ε-caprolactam were set as Z and were calculated by the following formulas.

Conversion of cyclohexanone oxime (%) = [(X−Y) / X] × 100
Ε-caprolactam selectivity (%) = [Z / (XY)] × 100

Example 1
(A) Production of zeolite [hydrothermal synthesis (1)]
In a stainless steel autoclave, 100 parts by weight of tetraethyl orthosilicate [Si (OC ₂ H ₅ ) ₄ ], 57.4 parts by weight of a 40% by weight aqueous tetra-n-propylammonium hydroxide solution, and 0.36% by weight of a 48% by weight aqueous potassium hydroxide solution 0.36. Part by weight and 279 parts by weight of water were added and stirred vigorously at room temperature for 120 minutes, and then stirred at 105 ° C. for 36 hours to conduct a hydrothermal synthesis reaction. The obtained reaction mixture was filtered, and the residue was continuously washed with ion-exchanged water until the pH of the washing solution was around 9, and then dried at 110 ° C. to obtain crystals.

[Firing (1)]
The crystals obtained in [Hydrothermal Synthesis (1)] were baked under nitrogen flow at 530 ° C. for 1 hour, and then baked under air flow at 530 ° C. for 1 hour to obtain powdered white crystals. . The powdery white crystals were identified as MFI zeolite as a result of powder X-ray diffraction analysis.

[Contact treatment with aqueous solution (1)]
7.0 parts by weight of the crystals obtained in the above [calcination (1)] were put in an autoclave, and a mixture of 77 parts by weight of 7.5% by weight aqueous ammonium nitrate solution and 118 parts by weight of 25% by weight aqueous ammonia solution ( pH = 11.5) was added and the mixture was stirred at 90 ° C. for 1 hour, and then the crystals were separated by filtration. The same treatment with a mixed solution of an ammonium nitrate aqueous solution and an ammonia aqueous solution as described above was further repeated twice, and then the crystals were washed with water and dried.

[Heat treatment (1)]
1.0 g of the crystal obtained in the above [contact treatment with aqueous solution (1)] is filled in a quartz glass reaction tube having an inner diameter of 1.2 cm to form a catalyst layer, and contains 3.7% by volume of water vapor. The temperature was raised from room temperature to 600 ° C. over 3 hours while flowing air at a rate of 70 ml / min, and then held at 600 ° C. for 5 hours. The zeolite thus obtained was used as a catalyst in the following (b).

(B) Production of ε-caprolactam 0.375 g of the zeolite obtained in (a) above was filled in a quartz glass reaction tube having an inner diameter of 1 cm to form a catalyst layer, and under a flow of 4.2 L / h of nitrogen. And pre-heat treatment at 350 ° C. for 1 hour. Next, the temperature of the catalyst layer was lowered to 327 ° C. under a flow of 4.2 L / h of nitrogen, and then a vaporized mixture of cyclohexanone oxime / methanol = 1 / 1.8 (weight ratio) was 8.4 g / h ( The reaction was carried out by supplying the reaction tube at a feed rate of cyclohexanone oxime (WHSV = 8 h ⁻¹ ). The reaction gas from 5.5 hours to 5.75 hours after the start of the reaction was collected and analyzed by gas chromatography. The conversion of cyclohexanone oxime was 99.93% and the selectivity for ε-caprolactam was 95.73%.

Example 2
In [Heat Treatment (1)], the same operation as in Example 1 (a) was performed except that the temperature was raised from room temperature to 650 ° C. over 3.5 hours and then maintained at 650 ° C. for 5 hours. Using the obtained zeolite as a catalyst, a reaction was carried out in the same manner as in Example 1 (b). The conversion of cyclohexanone oxime was 99.90% and the selectivity for ε-caprolactam was 96.18%.

Comparative Example 1
In [Heat Treatment (1)], the same operation as in Example 1 (a) was performed except that the temperature was raised from room temperature to 450 ° C. over 2.25 hours and then maintained at 450 ° C. for 5 hours. Using the obtained zeolite as a catalyst, a reaction was carried out in the same manner as in Example 1 (b). The conversion of cyclohexanone oxime was 99.77% and the selectivity for ε-caprolactam was 96.38%.

Comparative Example 2
In [Heat Treatment (1)], the same operation as in Example 1 (a) was performed except that the temperature was raised from room temperature to 750 ° C. over 4.25 hours and then maintained at 750 ° C. for 5 hours. Using the obtained zeolite as a catalyst, a reaction was carried out in the same manner as in Example 1 (b). The conversion of cyclohexanone oxime was 99.16% and the selectivity for ε-caprolactam was 95.09%.

Comparative Example 3
In Example 1 (a), the same operation was performed except that [Heat treatment (1)] was omitted. Using the obtained zeolite as a catalyst, a reaction was carried out in the same manner as in Example 1 (b). The conversion of cyclohexanone oxime was 99.86% and the selectivity for ε-caprolactam was 95.89%.

Comparative Example 4
In Example 1 (a), the same operation was performed except that [Contact treatment with aqueous solution (1)] was omitted. Using the obtained zeolite as a catalyst, a reaction was carried out in the same manner as in Example 1 (b). The conversion of cyclohexanone oxime was 8.16% and the selectivity for ε-caprolactam was 9.34%.

  The reaction results of Examples 1-2 and Comparative Examples 1-4 are summarized in Table 1.

Example 3
(C) Production of zeolite [hydrothermal synthesis (2)]
The same operation as in [Hydrothermal synthesis (1)] of Example 1 (a) was performed to obtain crystals.

[Firing (2)]
The crystals obtained in [Hydrothermal synthesis (2)] were fired under nitrogen flow at 530 ° C. for 1 hour, and then fired under air flow at 530 ° C. for 1 hour to obtain powdery white crystals. . The powdery white crystals were identified as MFI zeolite as a result of powder X-ray diffraction analysis. Next, this powdery white crystal was subjected to contact treatment with water vapor at 80 ° C. for 3 hours.

[Contact treatment with aqueous solution (2)]
8.8 parts by weight of the crystals obtained in the above [calcination (2)] were put in an autoclave, and 96 parts by weight of a 7.5% by weight aqueous ammonium nitrate solution, 147 parts by weight of a 25% by weight aqueous ammonia solution and tetrabromide- A mixed solution (pH = 11.5) with 0.003 part by weight of n-propylammonium was added and stirred at 90 ° C. for 1 hour, and then crystals were separated by filtration. The crystal was further treated twice with the same ammonium nitrate aqueous solution, ammonia aqueous solution and tetra-n-propylammonium bromide mixed solution as described above, and then washed with water and dried.

[Heat treatment (2)]
A catalyst layer is formed by filling 2.0 g of the crystal obtained in the above [contact treatment with aqueous solution (2)] into a reaction tube made of quartz glass having an inner diameter of 1.2 cm, and contains 3.7% by volume of water vapor. The temperature was raised from room temperature to 600 ° C. over 3 hours while flowing air at a rate of 70 ml / min, and then held at 600 ° C. for 5 hours. The zeolite thus obtained was used as a catalyst in the following (d).

(D) Production of ε-caprolactam 0.375 g of the zeolite obtained in (c) above was filled in a quartz glass reaction tube having an inner diameter of 1 cm to form a catalyst layer, and under a flow of nitrogen of 4.2 L / h And pre-heat treatment at 350 ° C. for 1 hour. Next, under a flow of 4.2 L / h of nitrogen, the temperature of the catalyst layer was lowered to 343 ° C., and then the vaporized mixture of cyclohexanone oxime / methanol = 1 / 1.8 (weight ratio) was 8.4 g / h ( The reaction was carried out by supplying the reaction tube at a feed rate of cyclohexanone oxime (WHSV = 8 h ⁻¹ ). The reaction gas 20 hours to 20.25 hours after the start of the reaction was collected and analyzed by gas chromatography. The conversion of cyclohexanone oxime was 99.98% and the selectivity for ε-caprolactam was 96.73%.

Example 4
In [Heat Treatment (2)], the same operation as in Example 3 (c) was performed except that dry air (water vapor concentration <500 ppm by volume) was used instead of air containing 3.7% by volume of water vapor. went. The obtained zeolite was used as a catalyst and reacted in the same manner as in Example 3 (d). The conversion of cyclohexanone oxime was 99.97% and the selectivity for ε-caprolactam was 96.41%.

Comparative Example 5
In [Heat Treatment (2)], the same operation as in Example 3 (c) was performed except that the temperature was raised from room temperature to 750 ° C. over 4.25 hours and then maintained at 750 ° C. for 5 hours. The obtained zeolite was used as a catalyst and reacted in the same manner as in Example 3 (d). The conversion of cyclohexanone oxime was 98.21% and the selectivity for ε-caprolactam was 96.19%.

Comparative Example 6
In Example 3 (c), the same operation was performed except that [Heat treatment (2)] was omitted. The obtained zeolite was used as a catalyst and reacted in the same manner as in Example 3 (d). The conversion of cyclohexanone oxime was 99.95% and the selectivity for ε-caprolactam was 96.24%.

Example 5
0.375 g of the zeolite obtained in Example 3 (c) was charged into a quartz glass reaction tube having an inner diameter of 1 cm to form a catalyst layer, and 1 at 350 ° C. under a flow of 4.2 L / h of nitrogen. Preheated for hours. Next, under a flow of 4.2 L / h of nitrogen, the temperature of the catalyst layer was lowered to 343 ° C., and then the vaporized mixture of cyclohexanone oxime / methanol = 1 / 1.8 (weight ratio) was 8.4 g / h ( Cyclohexanone oxime WHSV = 8 h ⁻¹ ) was supplied to the reaction tube and reacted for 10.25 hours.

The supply of the cyclohexanone oxime / methanol mixture was stopped, nitrogen was switched to air, and the temperature of the catalyst layer was increased from 340 ° C. to 430 ° C. under a flow of 5 L / h, followed by calcination at 430 ° C. for 20 hours. . Thereafter, the air was switched to nitrogen, and the temperature of the catalyst layer was adjusted to 343 ° C. under a flow of 4.2 L / h of nitrogen.

  From the above reaction, a series of firing operations was further repeated 7 times, and a total of 8 reactions were performed. In each of the first, second, fifth, and eighth reactions, the reaction gas was collected for 10 to 10.25 hours after the start of the reaction, and the conversion rate of cyclohexanone oxime determined by gas chromatography analysis and Table 2 shows the selectivity of ε-caprolactam.

Comparative Example 7
In Example 3 (c), the same operation was performed except that [Heat treatment (2)] was omitted. Using the obtained zeolite as a catalyst, a series of operations from reaction to calcination was repeated in the same manner as in Example 5 for a total of 8 reactions. In each of the first, second, fifth, and eighth reactions, the reaction gas was collected for 10 to 10.25 hours after the start of the reaction, and the conversion rate of cyclohexanone oxime determined by gas chromatography analysis and Table 2 shows the selectivity of ε-caprolactam.
Comparative Example 8
In Example 1 (a), the same operation was performed except that [Heat treatment (1)] was omitted. Using the obtained zeolite as a catalyst, a series of operations from reaction to calcination was repeated in the same manner as in Example 5 for a total of 8 reactions. In each of the first, second, fifth, and eighth reactions, the reaction gas was collected for 10 to 10.25 hours after the start of the reaction, and the conversion rate of cyclohexanone oxime determined by gas chromatography analysis and Table 2 shows the selectivity of ε-caprolactam.

  As shown in Table 2, it can be seen that in Example 5, by using a catalyst that had been heat-treated at 600 ° C., the conversion rate of cyclohexanone oxime could be maintained high even when a series of operations from reaction to calcination was repeated. On the other hand, in Comparative Examples 7 and 8, when a catalyst not subjected to heat treatment was used and a series of operations from reaction to calcination was repeated, the reduction rate of the conversion rate of cyclohexanone oxime was larger than that in Example 5. I understand.

Claims (4)

  A method for producing a zeolite, comprising calcining a crystal obtained by a hydrothermal synthesis reaction of a silicon compound, followed by contact treatment with an aqueous solution containing ammonia and / or an ammonium salt, and then heat treatment at 500 to 700 ° C.   The manufacturing method according to claim 1, wherein the heat treatment is performed in a gas atmosphere containing water vapor.   The production method according to claim 1 or 2, wherein the zeolite is a pentasil-type zeolite.   A method for producing ε-caprolactam, comprising producing a zeolite by the method according to claim 1, and subjecting cyclohexanone oxime to a Beckmann rearrangement reaction in the gas phase in the presence of the zeolite.