JP5067413B2 - Method for crushing zeolite compact - Google Patents

Description

  The present invention relates to a method for crushing a zeolite compact, for example, a zeolite compact that has been used as a catalyst for a Beckmann rearrangement reaction.

  Conventionally, as one method for producing ε-caprolactam, there is known a method in which cyclohexanone oxime is subjected to a Beckmann rearrangement reaction in the gas phase in the presence of a solid catalyst (see, for example, Patent Documents 1 and 2). As this catalyst, zeolite such as crystalline silica or crystalline metallosilicate is advantageous, and it is usually used after being formed into pellets or fine particles (see, for example, Patent Document 3). In addition, since the activity of this catalyst usually decreases due to precipitation of carbonaceous material, thermal deterioration, or the like as the usage time elapses, various regeneration methods such as calcination and chemical treatment have been proposed (for example, Patent Documents 4 to 4). 7).

JP-A-2-250866 JP-A-2-275850 JP-A-6-72706 JP-A-3-207454 JP 2003-236394 A JP-A-5-170732 JP 2003-320260 A

  If the zeolite molded body as described above is used as a catalyst and its regeneration and reuse are repeated, the properties of the molded body, such as pore volume, bulk density, strength, etc., change, making it difficult to perform stable operation. It may be difficult to obtain stable reaction results. For this reason, it is desirable to crush and remold a zeolite compact that has been regenerated and reused to some extent in order to restore its properties. As a method for crushing the molded body, a physical method such as a dry method using a hammer mill or a jet mill or a wet method using a ball mill or an attritor is generally employed. However, if the zeolite compact is pulverized by these physical methods, the crystallinity may be lowered or the pulverization may not be sufficiently performed, and a zeolite suitable for remolding may not be obtained. Accordingly, an object of the present invention is to provide a method capable of efficiently crushing a zeolite compact while suppressing a decrease in crystallinity.

  As a result of intensive studies, the present inventors have found that the above object can be achieved by mixing a zeolite compact with a specific aqueous solution, and have completed the present invention. That is, the present invention relates to a zeolite molding characterized in that a zeolite molding used as a catalyst for the Beckmann rearrangement reaction of cyclohexanone oxime is mixed with a basic aqueous solution containing at least 2% by weight of quaternary ammonium and not containing ammonia. It relates to the body crushing method.

  According to the present invention, the zeolite compact can be efficiently crushed while suppressing a decrease in crystallinity.

  Hereinafter, the present invention will be described in detail. The object of application of the pulverization method of the present invention is a zeolite compact, and among them, a pentasil-type zeolite compact, particularly an MFI-type zeolite compact is preferred. Zeolite is a porous crystalline body containing silicon and oxygen as elements constituting the skeleton, and may be crystalline silica substantially composed of silicon and oxygen alone, or constitutes the skeleton. It may be a crystalline metallosilicate containing another element as an 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. Zeolite can be preferably produced by subjecting a silicon compound to a hydrothermal synthesis reaction together with a templating agent, a metal compound, and the like as necessary.

  The shape of the zeolite compact can be selected according to the application, and the molding method can be selected according to the shape. For example, when used as a catalyst for a fixed bed reaction, a pellet-shaped molded body such as a columnar or cylindrical shape is advantageously produced by extrusion molding or compression molding. Further, when used as a catalyst for a fluidized bed reaction or moving bed reaction, a fine particle shaped body such as a sphere is advantageously produced by spray drying of the slurry.

  As the zeolite to be molded, those having a primary particle diameter of 5 μm or less, preferably 1 μm or less are usually used. In molding, a binder may be used as necessary. Moreover, when processing, such as baking and activation, may be performed before shaping | molding, you may carry out after shaping | molding, and you may carry out both before shaping | molding and after shaping | molding.

  As described above, when the zeolite compact is used, for example, as a catalyst for the Beckmann rearrangement reaction of cyclohexanone oxime, the activity decreases with time. Therefore, the regeneration treatment is performed at an appropriate timing. If regeneration and reuse are repeated in this way, it will be difficult to continue operation and maintain reaction results due to changes in the properties of the zeolite compact, so the zeolite compact that has been regenerated and reused to some extent is based on its properties. In order to return, it is desirable to crush and remold. Therefore, in the present invention, in order to crush the zeolite compact such as the spent catalyst, it is mixed with a basic aqueous solution containing quaternary ammonium. By adopting such a prescription, it is possible to suppress the decrease in crystallinity of the zeolite, perform efficient crushing, and advantageously obtain a zeolite suitable for remolding.

  The basic aqueous solution can be typically prepared by dissolving quaternary ammonium hydroxide, which is a basic substance containing quaternary ammonium, in water. Alternatively, a quaternary ammonium salt such as a quaternary ammonium chloride, bromide, sulfate or nitrate, and a basic substance other than quaternary ammonium hydroxide may be dissolved in water. Furthermore, as a dissolved component, quaternary ammonium hydroxide and other basic substances can be used in combination, or quaternary ammonium hydroxide and a quaternary ammonium salt can be used in combination.

  A typical example of quaternary ammonium contained in the basic aqueous solution can be represented by the following formula (1).

R ¹ R ² R ³ R ⁴ N ⁺ (1)
(In the formula, R ¹ , R ² , R ³ and R ⁴ each represent an alkyl group, an aralkyl group, an aryl group or an allyl group.)

In the formula (1), when at least one of R ¹ , R ² , R ³ and R ⁴ is an alkyl group, examples of the alkyl group include a methyl group, an ethyl group, a propyl group, and a butyl group. The carbon number is usually about 1-4. When at least one of R ¹ , R ² , R ³ and R ^{4 is} an aralkyl group, examples of the aralkyl group include a benzyl group and a tolylmethyl group, and the number of carbons is usually about 7 to 10. When at least one of R ¹ , R ² , R ³ and R ^{4 is} an aryl group, examples of the aryl group include a phenyl group and a tolyl group, and the carbon number is usually about 6 to 10 is there.

  Examples of the quaternary ammonium represented by the formula (1) include tetramethylammonium, tetraethylammonium, n-propyltrimethylammonium, tetra-n-propylammonium, tetra-n-butylammonium, benzyltrimethylammonium, dibenzyldimethylammonium. Etc. Examples of quaternary ammonium other than those represented by the formula (1) include 4,4′-trimethylenebis (dimethylpiperidinium), 1,1′-butylenebis (4-aza-1-azoniabicyclo [2, 2,2] octane), trimethyladamantyl ammonium and the like. Of these, tetraalkylammonium is preferred.

  Examples of basic substances other than quaternary ammonium hydroxide that can be used in the preparation of the basic aqueous solution include ammonia, primary, secondary, and tertiary amines, sodium hydroxide, and potassium hydroxide. Examples thereof include metal hydroxides.

  The concentration of quaternary ammonium in the basic aqueous solution is at least 2% by weight, preferably 4% by weight or more. When the concentration of the quaternary ammonium is too low, it becomes difficult to crush the zeolite compact. The upper limit of the concentration of quaternary ammonium is appropriately adjusted, but is usually up to 40% by weight.

  Moreover, pH of the said basic aqueous solution is 10 or more normally, Preferably it is 11-14. If the pH is too low, it will be difficult to crush the zeolite compact.

  Mixing of the zeolite molded body and the basic aqueous solution can be suitably performed by immersing the zeolite molded body in the basic aqueous solution and stirring in a stirring tank. In addition, this mixing may be performed batchwise or continuously. The mixing temperature is usually 50 to 250 ° C, preferably 50 to 170 ° C, more preferably 60 to 120 ° C, and the mixing time is usually 0.1 to 100 hours. Moreover, the usage-amount of the said basic aqueous solution is 80-5000 weight part normally with respect to 100 weight part of zeolite molded bodies.

  The zeolite slurry obtained by pulverizing the zeolite compact thus obtained in the basic aqueous solution can be subjected to re-molding as it is or after being subjected to treatments such as concentration, dilution, filtration, washing, and drying. . This reshaping may be performed by mixing with new zeolite or a slurry thereof.

  Examples of the present invention will be described below, but the present invention is not limited thereto. In the examples, the average particle diameter and X-ray diffraction intensity of the catalyst or crystal were measured by the following method.

[Average particle size]
Using a particle size distribution measuring apparatus ["MICROTRAC HRA Model 9320-X100" manufactured by Nikkiso Co., Ltd.], 50 volume% diameter (volume median diameter) was measured, and this was defined as the average particle diameter.

[X-ray diffraction intensity]
Using an X-ray diffractometer (“RINT-2100V” manufactured by Rigaku Corporation), copper Kα ray was measured as a light source.

Reference example 1 (gas phase Beckmann rearrangement reaction)
Zeolite compacts (secondary particles) having an average particle size of 60 μm formed by spherically molding zeolite (primary particles) having an average particle size of 0.2 μm made of crystalline silica having an MFI structure were used as catalysts. The reaction was carried out at 380 ° C. for 3 months by extracting the reaction product gas while supplying vaporized cyclohexanone oxime, methanol and nitrogen gas to the fluidized bed reactor in which the catalyst was flowed. During this time, the space velocity WHSV of cyclohexanone oxime [feed rate (g / h) with respect to catalyst weight (g)] was 2 h ^−1, and the feed ratio of cyclohexanone oxime / methanol / nitrogen gas was 1 kg / 1.8 kg / 0. It was 3 m ³ .
During this time, a part of the catalyst is taken out from the reactor, introduced into a calciner, calcined at 500 ° C. for 20 hours in an air stream, and then introduced into the reactor again. And circulated between the calciners. It was 56.3 micrometers as a result of adding water to the obtained used catalyst and making it a 5 weight% slurry, and measuring the average particle diameter. Further, as a result of measuring the X-ray diffraction intensity of this used catalyst, an MFI type structure was confirmed, and the peak intensity at 2θ = 23 ° was defined as a reference value (100%).

Example 1
300 g of the spent catalyst obtained in Reference Example 1 was placed in a beaker, and 700 g of a 6 wt% tetra-n-propylammonium hydroxide aqueous solution (tetra-n-propylammonium concentration 5.5 wt%; pH 13) was added thereto. And stirred at 110 ° C. for 6 hours. Water was added to the resulting slurry to make a 5 wt% slurry, and the average particle size was measured and found to be 0.2 μm.

  The slurry was filtered and the residual crystals were dried, then calcined at 530 ° C. for 1 hour under nitrogen flow, and then calcined at 530 ° C. for 1 hour under air flow to form a powdery white Crystals were obtained. As a result of measuring the X-ray diffraction intensity of this powdery white crystal, an MFI structure was confirmed, and the peak intensity at 2θ = 23 ° was 126% with respect to the same peak intensity of the used catalyst obtained in Reference Example 1. Met.

Comparative Example 1
1000 g of the used catalyst obtained in Reference Example 1 was placed in a plastic tank, and 1500 g of pure water was added thereto to prepare a 30 wt% slurry. This slurry was supplied to a ball mill at a rate of 300 ml / min to pulverize the catalyst. Water was added to the resulting slurry to make a 5 wt% slurry, and the average particle size was measured and found to be 2.0 μm.

  The slurry was filtered and the residual crystals were dried, then calcined at 530 ° C. for 1 hour under nitrogen flow, and then calcined at 530 ° C. for 1 hour under air flow to form a powdery white Crystals were obtained. As a result of measuring the X-ray diffraction intensity of this powdery white crystal, an MFI structure was confirmed, and the peak intensity at 2θ = 23 ° was 87% with respect to the same peak intensity of the used catalyst obtained in Reference Example 1. Met.

Claims (3)

  A method for pulverizing a zeolite compact, comprising mixing a zeolite compact used as a catalyst in a Beckmann rearrangement reaction of cyclohexanone oxime with a basic aqueous solution containing at least 2% by weight of quaternary ammonium and not containing ammonia.   The method according to claim 1, wherein the zeolite compact is a pentasil-type zeolite compact.   The method according to claim 1 or 2, wherein the quaternary ammonium is a tetraalkylammonium.