CN111790433A

CN111790433A - Catalyst containing silicon molecular sieve with MFI topological structure, preparation method and application thereof, and gas phase Beckmann rearrangement reaction method

Info

Publication number: CN111790433A
Application number: CN202010635831.1A
Authority: CN
Inventors: 程时标; 何怡璇; 蒋肇斌; 张忠光
Original assignee: Zhejiang Henglan Technology Co Ltd
Current assignee: Zhejiang Henglan Technology Co Ltd
Priority date: 2020-07-03
Filing date: 2020-07-03
Publication date: 2020-10-20

Abstract

The invention relates to the field of catalyst preparation, and discloses a catalyst containing an MFI topological structure silicon molecular sieve, a preparation method and application thereof, and a cyclohexanone oxime gas phase Beckmann rearrangement reaction method, wherein the catalyst contains the MFI topological structure silicon molecular sieve and a binder; the content of the molecular sieve in the catalyst is 70-100 wt% based on the dry weight of the catalyst, and the content of the binder in terms of oxide is 0-30 wt%; the crush strength of the catalyst is 15-60N/particle; the molecular sieve contains metal elements, and ions of the metal elements have Lewis acid characteristics; based on the total amount of the molecular sieve, the content of the metal elements in the molecular sieve is 5-100 mu g/g. The catalyst has the characteristics of higher crushing strength, higher cyclohexanone oxime conversion rate and higher caprolactam selectivity.

Description

Catalyst containing silicon molecular sieve with MFI topological structure, preparation method and application thereof, and gas phase Beckmann rearrangement reaction method

Technical Field

The invention relates to the field of preparation of catalysts, and particularly relates to a catalyst containing a silicon molecular sieve with an MFI topological structure, a preparation method and application thereof, and a cyclohexanone oxime gas-phase Beckmann rearrangement reaction method.

Background

The silicon molecular sieve is an aluminum-free molecular sieve with MFI topological structure, can be used as a material for membrane separation, and can also be used as a catalyst for producing caprolactam through cyclohexanone-oxime gas-phase Beckmann rearrangement reaction. However, the silicon molecular sieve synthesized by the prior art has more amorphous silicon oxide content, poorer relative crystallinity and larger crystal particles.

US4061724A discloses a silicon molecular sieve, which does not contain an aluminum source in its preparation raw materials, only contains a silicon source, an alkali source, a template agent and water, and is different from a silicon molecular sieve formed by extracting framework aluminum, and is a directly synthesized silicon molecular sieve having an MFI topological crystal structure. The silicon source used by the silicon molecular sieve is one of silica sol, silica gel or white carbon black, and the silica source is 700H with the molar composition of 150-₂O：13-50SiO₂：0-6.5 M₂O：Q₂The reaction mixture of O is synthesized by hydrothermal crystallization for 50-150 hours at the temperature of 100-250 ℃ and the autogenous pressure, wherein M is alkali metal, Q is the molecular formula R₄X⁺R represents hydrogen or an alkyl group having 2 to 6 carbon atoms, and X is phosphorus or nitrogen.

JP59164617A discloses a silicon molecular sieve with MFI structure, which is prepared by taking tetraethoxysilane as a silicon source, tetrapropylammonium hydroxide as a template agent and an alkali source.

CN102050464A discloses a synthesis method of a silicon molecular sieve, comprising the following steps: (1) mixing ethyl orthosilicate and tetrapropylammonium hydroxide at room temperature, stirring, fully hydrolyzing, and adding water to form a molar composition TPAOH/SiO₂＝0.05-0.5，EtOH/SiO₂＝4，H₂O/SiO₂A mixture of 5 to 100; (2) and (3) crystallizing the mixture in a closed reaction kettle under autogenous pressure, filtering, washing, drying, and roasting at the temperature of 400 ℃ and 600 ℃ for 1-10 hours to obtain the silicon molecular sieve.

Caprolactam is a main raw material for producing three series products of nylon, industrial cord and nylon engineering plastics, has always strong demand, and is generally prepared by the Beckmann rearrangement reaction of cyclohexanone oxime. At present, the liquid phase rearrangement process using concentrated sulfuric acid or fuming sulfuric acid as a catalyst is generally adopted in industry. The caprolactam produced by the process accounts for about 90 percent of the total caprolactam production in the world, but the process needs to consume a large amount of sulfuric acid and ammonia water, a byproduct of 1.3 to 1.8 tons of ammonium sulfate is produced every 1 ton of caprolactam, the production cost is high, and the use of sulfuric acid can also cause the problems of equipment corrosion, environmental pollution and the like.

The gas phase Beckmann rearrangement reaction of cyclohexanone oxime on a solid acid catalyst is a new process for realizing the sulfur-free ammonification of caprolactam, has the problems of no equipment corrosion, no environmental pollution and the like, and greatly simplifies the separation and purification of products, so the gas phase Beckmann rearrangement reaction process of the sulfur-free ammonification is greatly concerned by the persons in the industry.

In order to develop a solid acid catalyst suitable for the gas phase beckmann rearrangement reaction, researchers at home and abroad have conducted a great deal of research on catalysts such as oxides (composite oxides), zeolite molecular sieves, etc., as disclosed in EP576295, a molecular sieve is made into microspheres by spray drying without adding any binder, and then heat-treated in water, so that the microsphere catalyst can be used in the reaction of converting cyclohexanone oxime into caprolactam. Although the catalyst has certain activity, the strength of the catalyst cannot meet the requirement of industrial application, and the catalyst is easy to deactivate and short in service life and cannot meet the requirement of industrialization.

In summary, the catalyst prepared by the prior art has insufficient strength and short service life, and cannot meet the requirement of industrialization, when the catalyst is applied to cyclohexanone oxime gas phase beckmann rearrangement reaction, the improvement effects of cyclohexanone oxime conversion rate and caprolactam selectivity are not obvious, and the catalyst in the prior art is lack of matching with the cyclohexanone oxime gas phase beckmann rearrangement integral process, and the economic efficiency of industrial production needs to be further improved, so that a new catalyst for gas phase beckmann rearrangement reaction needs to be developed.

Disclosure of Invention

The invention aims to solve the problems of lower catalyst strength, lower cyclohexanone oxime conversion rate and lower caprolactam selectivity in the prior art, and provides a catalyst containing a silicon molecular sieve with an MFI topological structure, a preparation method and application thereof, and a cyclohexanone oxime gas-phase Beckmann rearrangement reaction method.

In order to achieve the above object, a first aspect of the present invention provides a catalyst containing a silicon molecular sieve of MFI topology, the catalyst comprising a silicon molecular sieve of MFI topology and a binder; the content of the molecular sieve in the catalyst is 70-100 wt% based on the dry weight of the catalyst, and the content of the binder in terms of oxide is 0-30 wt%; the crush strength of the catalyst is 15-60N/particle;

the molecular sieve contains metal elements, and ions of the metal elements have Lewis acid characteristics; based on the total amount of the molecular sieve, the content of the metal elements in the molecular sieve is 5-100 mu g/g.

In a second aspect, the present invention provides a process for the preparation of a catalyst comprising a silicalite molecular sieve of MFI topology, the process comprising the steps of:

(1) mixing ethyl orthosilicate, ethanol, a metal source, tetrapropyl ammonium hydroxide and water to obtain a colloid mixture; wherein, SiO is used₂The calculated molar ratio of the ethyl orthosilicate, the ethanol, the tetrapropylammonium hydroxide and the water is 1: (4-25): (0.05-0.45): (6-100); with SiO₂The weight ratio of the tetraethoxysilane to the metal source calculated by the metal elements is (10000- & 200000): 1;

(2) crystallizing the colloid mixture by using a two-section temperature-variable ethanol-hydrothermal system, wherein the crystallization conditions of the two-section temperature-variable ethanol-hydrothermal system comprise: crystallizing at 40-80 deg.C for 0.5-5 days, and crystallizing at 80-130 deg.C for 0.5-5 days;

(3) sequentially filtering and drying the crystallized mother liquor obtained in the step (2) to obtain molecular sieve raw powder;

(4) crushing the molecular sieve raw powder, optionally mixing the crushed molecular sieve raw powder with a binder, and then carrying out rotational molding to obtain spherical particles;

(5) roasting the spherical particles, contacting the spherical particles with an alkaline buffer solution containing a nitrogen compound, and then drying the spherical particles;

the ions of the metal element in the metal source have Lewis acid characteristics.

Preferably in SiO₂The weight ratio of the tetraethoxysilane to the metal source calculated by the metal elements is (10000) -100000): 1.

in a third aspect, the invention provides a catalyst containing the silicon molecular sieve with MFI topological structure prepared by the method. The catalyst has higher strength and is particularly suitable for cyclohexanone oxime gas-phase Beckmann rearrangement reaction.

Therefore, the fourth aspect of the present invention provides the application of the catalyst containing the silicon molecular sieve with MFI topological structure in the cyclohexanone oxime gas-phase beckmann rearrangement reaction.

The fifth aspect of the present invention provides a method for gas-phase beckmann rearrangement of cyclohexanone oxime, which comprises: under the condition of cyclohexanone oxime gas-phase Beckmann rearrangement reaction, in the presence of a solvent (preferably ethanol), the cyclohexanone oxime is contacted with a catalyst for reaction, wherein the catalyst is the catalyst containing the silicon molecular sieve with the MFI topological structure provided by the first aspect or the third aspect.

In the prior art, for the MFI topological structure molecular sieve, the molecular sieve with high Si/Al ratio is beneficial to the gas phase Beckmann rearrangement reaction, the nearly neutral silicon hydroxyl is the active center of the gas phase Beckmann rearrangement reaction, and the acid site formed by the metal-O-Si is the active center of the side reaction, so that the gas phase Beckmann rearrangement reaction is not favorably carried out. Therefore, it is considered in the prior art that metal ions having Lewis acid characteristics affect the beckmann rearrangement reaction, resulting in an increase in side reactions, and thus a metal element whose ion has Lewis acid characteristics is not generally introduced in the preparation of a catalyst. The inventor of the invention finds that in the process of preparing the catalyst containing the molecular sieve, when the molecular sieve contains extremely trace metal elements of which ions have Lewis acid characteristics, the stability of the catalyst is favorably improved, and the molecular sieve is applied to cyclohexanone oxime gas phase Beckmann rearrangement reaction to ensure that the conversion rate of cyclohexanone oxime and the selectivity of caprolactam are higher.

According to the preparation method of the catalyst provided by the invention, ethanol is used, simultaneously, a trace amount of metal with Lewis acid characteristics, particularly metal with + 3-valent and/or + 4-valent ionic valence states is added (the preferable mode enables the metal to enter a molecular sieve framework easily, and charges are balanced easily), a two-section temperature-variable ethanol-hydrothermal system is adopted for crystallization, and the molecular sieve catalyst containing Lewis acid-characteristic metal ions is obtained through rotation forming, roasting and post-treatment.

In addition, the invention adopts ethanol in the preparation process of the catalyst containing the molecular sieve, can recover the ethanol in the preparation process, and can improve the selectivity of caprolactam, reduce the production cost and reduce the environmental protection pressure when being applied to the gas phase Beckmann rearrangement reaction which adopts the ethanol as a reaction solvent.

Drawings

FIG. 1 is an X-ray diffraction pattern of a catalyst containing a molecular sieve with MFI topology according to example 1 of the present invention;

FIG. 2 is a photograph of a catalyst containing a molecular sieve having an MFI topology according to example 1 of the present invention.

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

In a first aspect, the present invention provides a catalyst comprising an MFI topology silicalite, the catalyst comprising the MFI topology silicalite and optionally a binder; the content of the molecular sieve in the catalyst is 70-100 wt% based on the dry weight of the catalyst, and the content of the binder in terms of oxide is 0-30 wt%; the crush strength of the catalyst is 15-60N/particle;

The ions of the metal element have a Lewis acid property, which means that the ions of the metal element can accept an electron pair.

It should be noted that, the content of the metal elements in the MFI topological structure silicon molecular sieve of the present invention is very trace, and it can be concluded that trace metal elements exist in the molecular sieve framework in the form of metal ions.

In the catalyst provided by the invention, the metal elements in the silicon molecular sieve with the MFI topological structure exist in the molecular sieve framework in the form of metal cations.

In the present invention, the content of the metal element is measured using an ICP inductively coupled plasma atomic emission spectrometer 7000DV, manufactured by PE (perkin elmer) in the united states under the following test conditions: dissolving the molecular sieve by HF acid or aqua regia to completely dissolve silicon oxide and metal oxide in the sample, and measuring the content of metal ions in the aqueous solution.

According to the invention, the molecular sieve also contains silicon element and oxygen element, the content of the silicon element and the oxygen element in the molecular sieve is selected in a wide range, and in a specific embodiment, the sum of the content of the silicon element, the content of the oxygen element and the content of the metal element in the molecular sieve is 100% based on the total amount of the molecular sieve.

In the present invention, a metal element whose ion has Lewis acid property may be used, and preferably, the metal element is at least one selected from the group consisting of transition metal elements, group IIIA elements and group IVA elements.

According to the present invention, preferably, the transition metal element is at least one selected from the group consisting of group IB, group IIB, group IVB, group VB, group VIB, group VIIB, and group VIII metal elements.

According to a preferred embodiment of the present invention, the metal element is at least one element selected from the group consisting of Al, Ga, Ge, Ce, Ag, Co, Ni, Cu, Zn, Mn, Pd, Pt, Cr, Fe, Au, Ru, Rh, Pt, Rh, Ti, Zr, V, Mo and W elements.

Still more preferably, the metal element has an ionic valence of +3 and/or an ionic valence of + 4. In the research process, the inventor of the present invention finds that the metal element with the ionic valence state of +3 and/or +4 is more favorable for the metal element to enter the molecular sieve framework and more favorable for charge balance.

According to the present invention, the metal element is further preferably at least one of Fe, Al, Ga, Cr, Ti, Zr, and Ce elements. In this preferred embodiment, it is more advantageous to improve the performance of the catalyst, thereby improving the conversion of cyclohexanone oxime and the selectivity of caprolactam.

According to a preferred embodiment of the present invention, the content of the metal element in the molecular sieve is 6 to 90. mu.g/g, preferably 30 to 80. mu.g/g, based on the total amount of the molecular sieve. Specifically, for example, the concentration may be any value in a range of 30. mu.g/g, 35. mu.g/g, 40. mu.g/g, 45. mu.g/g, 50. mu.g/g, 55. mu.g/g, 60. mu.g/g, 70. mu.g/g, 75. mu.g/g, 80. mu.g/g, or any two of these values. In this preferred embodiment, the catalyst has better performance, and is more favorable for improving the conversion rate of cyclohexanone oxime and the selectivity of caprolactam. In the invention, the content of the metal element is too much, so that the Lewis acid property of the molecular sieve is possibly enhanced, unnecessary side reactions are induced, and the selectivity of caprolactam is not favorably improved; and the low content of the metal element is not beneficial to prolonging the service life of the catalyst containing the molecular sieve and improving the stability.

According to the invention, the molecular sieve preferably has a BET specific surface area of 420-450m²(ii) in terms of/g. In this preferred case, it is more advantageous to improve the performance of the catalyst.

The invention has wide selection range of the external specific surface area of the molecular sieve, and preferably, the external specific surface area of the molecular sieve is 35-60m²A/g, preferably from 30 to 50m²(ii) in terms of/g. In the invention, the BET specific surface area and the external specific surface area of the molecular sieve adopt N₂The adsorption-desorption method is used for measuring, in particular, the method is measured by an automatic adsorption instrument of American Micromeritics ASAP-2460, and the measuring conditions are as follows: n is a radical of₂As adsorbate, the adsorption temperature is-196.15 deg.C (liquid nitrogen temperature), and degassing is carried out at constant temperature of 1.3Pa and 300 deg.C for 6 h.

The grain size of the molecular sieve is selected in a wide range, and preferably, the grain size of the molecular sieve is 0.1-0.3 μm, preferably 0.1-0.25 μm, and more preferably 0.1-0.2 μm. In this preferred case, it is more advantageous to improve the catalytic performance of the catalyst. In the present invention, the grain size of the molecular sieve is measured by a scanning electron microscope of the S-4800 field emission type, Hitachi, Japan.

In the present invention, the particle size of the catalyst is selected from a wide range, and preferably, the particle size of the catalyst is 0.5 to 3mm, preferably 0.8 to 2.5 mm. In this preferable case, it is more advantageous to improve the stability of the catalyst and further improve the catalytic performance of the catalyst.

In the present invention, the particle size refers to the maximum linear distance between any two different points on the particle. For example, when the particles are spherical, the particle size refers to the diameter thereof.

According to a preferred embodiment of the present invention, preferably, the crush strength of the catalyst is 20 to 60N per particle. In this preferred embodiment, the catalyst is stronger and thus more conducive to increasing the useful life of the catalyst. In the present invention, the higher the crush strength, the higher the strength of the catalyst. In the present invention, the crushing strength was measured on a particle strength measuring instrument model QCY-602 (manufactured by alkali industry research institute of the department of Processary engineering) according to the RIPP25-90 method of petrochemical analysis (Yankeeding et al, scientific Press, 1990).

According to a preferred embodiment of the present invention, the molecular sieve is present in the catalyst in an amount of 70 to 95 wt.%, preferably 80 to 95 wt.%, and the binder is present in an amount of 5 to 30 wt.%, preferably 5 to 20 wt.%, calculated as oxide, based on the dry weight of the catalyst. In this preferred embodiment, it is more advantageous to increase the conversion of cyclohexanone oxime and the selectivity of caprolactam.

According to a preferred embodiment of the invention, the binder is silica.

In the present invention, the molar ratio and the weight ratio of the materials in the catalyst preparation process refer to the molar ratio and the weight ratio of the amounts of the materials when the materials are fed (charged), unless otherwise specified.

According to a preferred embodiment of the present invention, the method for preparing the catalyst does not include adding an organic amine. In this preferred embodiment, the catalyst performs better. In the present invention, the organic amine refers to at least one of aliphatic amine compounds, and may be, for example, at least one of mono-n-propylamine, di-n-propylamine, tri-n-propylamine, ethylamine, n-butylamine, ethylenediamine, and hexamethylenediamine.

According to the invention, a catalyst with a specific structure is obtained by adopting a specific silicon source, a specific metal source and a specific organic template agent and matching ethanol under the condition of specific dosage, and the catalyst has better catalytic performance. The catalyst is particularly suitable for cyclohexanone oxime gas phase Beckmann rearrangement reaction, and is more favorable for improving the economy of the whole process.

According to a preferred embodiment of the invention, SiO is used₂The calculated molar ratio of the ethyl orthosilicate, the ethanol, the tetrapropylammonium hydroxide and the water is 1: (4-15): (0.06-0.3): (15-49), more preferably 1: (6-14): (0.1-0.25): (20-40). In this preferred embodiment, the catalyst obtained has better catalytic performance.

According to a preferred embodiment of the invention, SiO is used₂The weight ratio of the tetraethoxysilane to the metal source calculated by the metal elements is (10000) -100000): 1, more preferably (15000-50000): 1. In this preferred embodiment, a more suitable amount of metal entering the framework of the molecular sieve is more beneficial to improving the catalytic performance of the catalyst.

According to the method provided by the present invention, the selection of the metal element in the metal source is as described above, and is not described herein again.

The present invention has a wide range of choices for the metal source, which is a compound containing various metal elements capable of providing the above metal elements, and the compound containing the metal elements is preferably soluble. In the present invention, the solubility means that the solvent is capable of being dissolved in a solvent directly or in the presence of a co-solvent, and the solvent is preferably water.

According to the present invention, preferably, the metal source is selected from at least one of a nitrate of a metal, a chloride of a metal, a sulfate of a metal, an acetate of a metal, and an ester-type metal compound. In one embodiment, the metal ester compound is tetraethyl titanate and/or tetrabutyl titanate.

According to the present invention, preferably, when the metal is an Al element, the metal aluminum source may also be a compound in the form of alumina, such as SB powder, V250, pseudoboehmite, or the like.

According to a preferred embodiment of the invention, the metal source is preferably Fe (NO)₃)₃、Ni(NO₃)₂Tetrabutyl titanate, Pd (NO)₃)₂、Ce(NO₃)₄、Al(NO₃)₃、Cu(NO₃)₂、ZrOCl₂、Ga(NO₃)₃、 H₂PtCl₆And Cr (NO)₃)₃More preferably Fe (NO)₃)₃Tetrabutyl titanate, Al (NO)₃)₃、Ga(NO₃)₃And Cr (NO)₃)₃At least one of (1). The metal source may or may not contain crystal water, and the present invention is not particularly limited thereto.

The mixing order in the step (1) is not particularly limited, as long as the colloidal mixture can be obtained, and any two of the above substances may be mixed first and then mixed with the rest of the substances, or any three of the above substances may be mixed first and then mixed with the rest of the substances. Preferably, it is desirable to avoid gel formation during the addition and also to prevent excessive temperature rise of the liquid phase during the addition. Specifically, for example, ethanol and tetrapropylammonium hydroxide may be mixed, then water and a metal source may be added, and then tetraethoxysilane may be added; or, ethanol and tetrapropylammonium hydroxide can be mixed, then water and ethyl orthosilicate are sequentially added, and then a metal source is added; or, ethyl orthosilicate, ethanol and tetrapropyl ammonium hydroxide can be mixed, and then the water and the metal source are sequentially added; alternatively, ethyl orthosilicate, ethanol, tetrapropylammonium hydroxide may be mixed, then water added, and then a metal source added. In the present invention, the metal source may be introduced alone or may be introduced in the form of a solution.

According to the present invention, preferably, the mixing of step (1) comprises: ethanol and tetrapropylammonium hydroxide are mixed, then ethyl orthosilicate is added, and then water and a metal source are added.

The specific operational options of the present invention for the mixing are wide, and according to a preferred embodiment of the present invention, the mixing is performed under stirring conditions. In the present invention, the stirring time is not particularly limited, so long as the colloidal mixture can be obtained. For example, the stirring may be carried out at ordinary temperature (25 ℃ C.) for 2 to 6 hours.

According to a preferred embodiment of the present invention, the crystallization conditions of the two-stage temperature-variable ethanol-hydrothermal system include: crystallizing at 50-80 deg.C for 1-1.5 days, and crystallizing at 100-120 deg.C for 1-3 days. Under the optimal mode, the utilization rate of crystallization raw materials is further improved under the specific crystallization condition, and the prepared catalyst has better catalytic performance. In the present invention, the two-stage temperature-variable ethanol-hydrothermal crystallization is preferably performed in a closed system under autogenous pressure, for example, in a closed reaction vessel.

According to the invention, the crystallization mother liquor preferably has a pH greater than 11, preferably not less than 13, for example between 13 and 14.

In the present invention, the crystallization of the ethanol-water system means that the crystallization is performed under a saturated vapor pressure of a specific temperature in the co-presence of alcohol and water.

In the present invention, the filtration in the step (3) is not particularly limited, and various filtration methods currently used in the art may be used as long as the purpose of solid-liquid separation can be achieved.

According to the present invention, preferably, before the filtering, the step (3) further comprises: washing the crystallized mother liquor. The washing method of the present invention is not particularly limited, and may be any of various washing methods conventionally used in the art, and the detergent used in the washing process of the present invention is not particularly limited, and may be, for example, water. The water may be pure water, deionized water, ion exchange water, chemical water, etc. without anions and cations.

According to a preferred embodiment of the present invention, the crystallization mother liquor is washed with water at 20-80 ℃, preferably until the pH of the washing solution is 7.5-10.

According to a preferred embodiment of the present invention, the washing and filtration of the molecular sieve is carried out by means of membrane filtration, for example using a six-tube membrane.

According to the method provided by the present invention, preferably, the method further comprises: the crystallization mother liquor is subjected to ethanol removal prior to the filtration (if washing is also included, preferably prior to washing) in step (3). In the present invention, since ethanol contains organic oxygen industrially, its discharge into wastewater causes environmental problems, and thus ethanol removal operation is required.

In the present invention, the ethanol removing conditions are selected from a wide range for the purpose of removing ethanol, and preferably, the ethanol removing conditions include: the temperature is 50-90 ℃, preferably 60-90 ℃; the time is 1-24h, preferably 1-12 h.

Specifically, the temperature of the reaction kettle can be lowered to an operable temperature, the reaction kettle is opened, and the reaction kettle is raised to 50-90 ℃ so that the ethanol is evaporated. In the invention, in the ethanol removing operation, water can be added into the reaction kettle to maintain the liquid level of the reaction kettle, which is beneficial to improving the ethanol removing efficiency.

According to the method provided by the invention, in the step (3), the drying conditions are selected from a wide range, and preferably, the drying conditions can comprise: the drying temperature is 80-150 ℃, and the drying time is 2-36 h. Further preferably, the drying temperature is 100-120 ℃ and the drying time is 10-30 hours.

According to the invention, in step (4), the molecular sieve raw powder is preferably pulverized to 100-1000 mesh. In this preferred case, the rotational molding is more advantageously performed. In the present invention, the above-mentioned pulverization method is not particularly limited, and the pulverization can be carried out by selecting any conventional technique, specifically, for example, a pulverizer.

The rotational molding of the present invention has conventional definitions in the art. The conditions for the rotational molding are preferably such that the particles obtained by the rotational molding have a particle diameter of 0.5 to 3mm, preferably 0.8 to 2.5 mm.

According to the present invention, the rotational molding in the step (4) may be performed in the presence or absence of a binder, and preferably, the rotational molding is performed by pulverizing the molecular sieve raw powder and mixing the pulverized molecular sieve raw powder with a binder. The binder is added to bond the powder particles to each other during rotation, thereby further improving the strength of the molded product.

According to the invention, the molecular sieve is preferably mixed with SiO on a dry basis₂The weight ratio of the calculated binder is 1: (0.05-1), preferably 1: (0.1-0.8), more preferably 1: (0.1-0.42). According to the method provided by the invention, the purpose of adding the binder is to enable the molecular sieve raw powder to be mutually bonded when rotating so as to further improve the strength of the catalyst formed product. If the amount of the binder is not sufficient, the spherical product tends to be softened and sticky, and the improvement of the strength is not facilitated.

According to the invention, preferably, the rotational moulding is carried out in a carousel moulding machine. Specifically, an embodiment of the present invention is illustrated, in part, BY a model BY-1200 sugarcoating machine purchased from Tiantai pharmaceutical machinery, Inc., of Thai, Jiangsu.

The inventor of the invention carries out extensive research and understanding on the operation conditions of the turntable rolling ball forming through a large number of experiments, and the experiments show that various factors including residence time, turntable inclination angle, turntable diameter D, turntable depth H and turntable rotating speed can influence the rotary forming. In the present invention, the residence time is the average time from the time when the molecular sieve raw powder is fed into the rotary disc forming machine to the time when the molecular sieve raw powder is formed into spherical particles and is separated from the rotary disc forming machine, and the residence time can be usually 10 to 600 minutes, and preferably 30 to 180 minutes. The inclination angle of the rotating disc is an angle between the rotating disc and the horizontal line, preferably 40-55 degrees, more preferably 45-50 degrees, and may be, for example, 40 degrees, 45 degrees, 50 degrees, 55 degrees, or an angle between any two of the above values. At less than 40 degrees, it is not preferable to ensure the molding state, and the diameter of the spherical particles becomes smaller as the inclination angle becomes larger. Preferably, the relationship between the diameter D of the turntable and the depth H of the turntable is 0.1 to 0.3D, preferably 0.1 to 0.25D. According to the method provided by the invention, the rotating speed of the rotary table is properly controlled, the rotating speed of the rotary table is too high, the forming state is not ideal, and a dumbbell shape can appear. Preferably, the rotational speed of the turntable is 10 to 50rpm, preferably 20 to 40 rpm.

In the invention, in order to obtain better mechanical strength and shape preservation property of the catalyst molded product, proper operation process conditions need to be selected to avoid the layering and peeling of product particles. The throughput of the rotary disk former, preferably based on the amount of catalyst produced per hour, can be from 20 to 100kg/h, preferably from 40 to 80 kg/h. During the molding process of the turntable rolling ball, the material storage amount can also influence the rotation molding, the material storage amount in the turntable refers to the amount of micro and small ball catalysts which do not reach the qualified diameter in the turntable, and the material storage amount is preferably controlled to be 1/10-1/4 treatment amount.

According to the invention, the rotary forming also results in particular in a material having a particle size which is not in the range from 0.1 to 3mm, referred to herein as reject material. The invention is not particularly limited to the treatment of the rejected material, for example, the rejected material may be sent to a crusher for further crushing as a raw material for the next batch preparation.

According to the method provided by the invention, preferably, the binder is a precursor of silicon oxide and/or water (preferably deionized water), preferably a precursor of silicon oxide. The invention has wider selection range of the precursor of the silicon oxide, and takes the precursor which can be converted into the silicon oxide through subsequent roasting as a reference. Preferably, the precursor of the silicon oxide is silica sol and/or white carbon black, and more preferably, silica sol.

The white carbon black can be obtained by commercial purchase. The silica sol may be an acidic silica sol or an alkaline silica sol, and may be commercially available or prepared according to any one of the prior art.

According to the invention, preferably, in the silica sol, SiO₂The content is 20 to 45% by weight, preferably 30 to 40% by weight.

According to the invention, the silica sol may also contain sodium ions, the content of which is selected within a wide range, and preferably the content of sodium ions is not higher than 1000 ppm. In this preferred case, it is more advantageous to improve the performance of the catalyst.

According to the invention, in the step (4), the powder sample obtained after crushing and the binder can be respectively added into the rotary forming machine, or the powder sample and the binder can be added into the rotary forming machine after being uniformly mixed in advance.

In the present invention, the binder may be added at one time or may be added in multiple times, and in order to further improve the mixing uniformity, the binder is preferably added in multiple times (for example, 2 to 10 times). In the present invention, the adhesive can be referred to as a first adhesive, a second adhesive, and so on, depending on the number of times of addition. For example, when the binder is added in two portions, the binder is referred to as a first binder and a second binder in this order. Likewise, in the present invention, when divided into two additions, the molecular sieves are referred to as a first powder sample and a second powder sample in this order. In the present invention, the first and second are not limitative, but to distinguish between operations performed at different stages and materials added.

According to a preferred embodiment of the present invention, the binder is added in two portions, the binder is divided into a first binder and a second binder in this order, the powder samples are referred to as a first powder sample and a second powder sample in this order, and the step (4) includes steps (4-1) and (4-2):

the step (4-1) comprises the following steps: selecting a first powder sample with the particle size of 100-1000 meshes from the solid substances obtained by crushing, mixing the first powder sample with a first binder, and carrying out first rotation forming to obtain first particles with the particle size of 0.1-0.8mm, wherein the mass ratio of the first powder sample to the first binder is 1: (0.2-1);

the step (4-2) comprises the following steps: selecting a second powder sample with the particle size of 100-1000 meshes from the solid matter obtained by crushing, mixing the second powder sample, a second binder and the first particles, and carrying out second rotational molding to obtain second particles with the particle size of 1.3-2.5mm, wherein the mass ratio of the second powder sample to the second binder is 1: (0.001-0.5). In this preferred embodiment, the catalyst has a higher crush strength and better catalytic performance.

According to the invention, the first powder sample and the second powder sample in the step (4-1) and the step (4-2) can adopt the same sieved powder sample or different sieved powder samples. Preferably, different sieved powder samples are used. In this preferred case, the resulting spherical particles have a higher molecular sieve content and a higher crush strength. Specifically, for example, the first powder-like particle size is 100-.

According to the present invention, the second powder sample and the second binder in step (4-2) may be separately fed into a rotary disc forming machine, or may be fed after being mixed in advance. Preferably, the second powder sample is mixed with a second binder, and then is crushed again to 30 meshes or less, and then is fed into a rotary disc forming machine having the first granules described in step (4-1). In the present invention, the speed of feeding the molecular sieve and the binder to the rotary disk molding machine is not particularly limited, and specifically, for example, 20 to 60kg of a mixture of the powder and the binder may be fed per hour.

The invention has wider selection range of the weight ratio of the first powder sample to the second powder sample, can be in any proportion according to actual needs, and can be adjusted at any time according to the condition of balling of the powder samples. Preferably, the weight ratio of the first powder sample to the second powder sample is 1: 20-100. According to the present invention, preferably, the first spherical particles have a particle size of 0.05 to 1.5 mm. According to the present invention, preferably, the spherical particles have a particle size of 0.8 to 3 mm.

According to the present invention, preferably, after the rotational molding in step (4), the method further comprises drying the molded product to obtain the spherical particles. The drying in the step (4) is not particularly limited in the present invention, and any conventional technique in the art may be used as long as moisture is removed, and the drying method includes, but is not limited to, natural drying, heat drying, and forced air drying. The drying temperature can be 80-200 ℃, and the drying time can be 2-24 hours.

According to a preferred embodiment of the present invention, after the rotational forming (preferably before the drying) in the step (4), the method further comprises: and polishing the product obtained by rotational molding. With this preferred embodiment, on the one hand, the roundness of the outer surface of the spherical catalyst can be increased and, on the other hand, the crush strength of the catalyst can be further increased. The polishing treatment may be performed according to the means known in the art. Specifically, for example, the product obtained by rotational molding is blown at 20 to 50 ℃ (water can be removed), trace water is supplemented for many times (for example, 3 to 10 times) in the blowing process (the catalyst surface can be wetted, slight small-range deformation is easy, the roundness of the ball is improved), and then tightening is carried out (blowing is carried out without water, and generally 1 to 4 hours can be carried out).

According to the present invention, preferably, in the step (5), the roasting conditions include: the temperature is 200-600 ℃, preferably 400-580 ℃, and the time is 1-20h, preferably 2-18 h.

According to a preferred embodiment of the present invention, the basic buffer solution of a nitrogen-containing compound contains an ammonium salt and a base. The solvent of the basic buffer solution of the nitrogen-containing compound is selected from a wide range, and is preferably water. In the present invention, the ammonium salt may be a water-soluble ammonium salt, preferably at least one selected from ammonium carbonate, ammonium fluoride, ammonium chloride, ammonium acetate and ammonium nitrate, and the ammonium salt is preferably ammonium nitrate and/or ammonium acetate.

According to the present invention, preferably, the base is selected from at least one of aqueous ammonia, tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrapropylammonium hydroxide, preferably aqueous ammonia.

According to a preferred embodiment of the invention, the ammonium salt is present in an amount of 0.1 to 20% by weight, preferably 0.5 to 15% by weight; the alkali content is 5 to 30% by weight, preferably 10 to 28% by weight.

According to the present invention, the pH of the basic buffer solution of the nitrogen-containing compound is preferably 8.5 to 13.5, preferably 10 to 12, and more preferably 11 to 11.5.

The invention has wide selection range of the using amount of the nitrogen-containing compound alkaline buffer solution, and preferably, the using amount of the nitrogen-containing compound alkaline buffer solution is 500-1500 parts by weight, preferably 700-1200 parts by weight, relative to 100 parts by weight of the product obtained by roasting on a dry basis.

According to the present invention, preferably, the conditions of the contacting include: the temperature is 50-120 ℃, and the optimal temperature is 70-100 ℃; the pressure is 0.5-10kg/cm²Preferably 1.5 to 4kg/cm²(ii) a The time is 0.1 to 5 hours, preferably 1 to 3 hours. In the present invention, the contacting is preferably performed under stirring conditions. The stirring speed is not particularly limited in the present invention, and can be appropriately selected by those skilled in the art according to the actual situation.

According to the method provided by the invention, the contact process can be repeated. The number of repetitions is not particularly limited, and may be determined according to the effect of the contact in order to improve the performance of the catalyst, and may be repeated, for example, 1 to 3 times.

In the present invention, the drying conditions in step (5) are not particularly limited, and may be performed according to any means known in the art as long as the solvent is removed, and the drying method includes, but is not limited to, natural drying, heat drying, and forced air drying, and specifically, for example, the drying temperature may be 100 ℃ to 120 ℃, and the drying time may be 2 to 36 hours.

According to the present invention, preferably, after the contacting in the step (5) and before the drying, the method further comprises: and (4) sequentially filtering and washing substances obtained after the roasted product obtained in the step (4) is contacted with an alkaline buffer solution containing a nitrogen compound. In the present invention, the filtration in step (5) may be any means known in the art, and preferably, the filtration is performed by membrane filtration. In the present invention, the detergent used in the washing step (5) is not particularly limited, and may be, for example, water. Specifically, the washing process may include: washing until the pH of the filtrate is 8-10.5.

In a third aspect, the present invention provides a catalyst comprising a silicalite molecular sieve of MFI topology prepared by the above process. The catalyst prepared by the preparation method provided by the invention has the advantages that metal ions with Lewis acid characteristics enter a molecular sieve framework, the catalyst has higher strength and better performance, and is particularly suitable for cyclohexanone oxime gas phase Beckmann rearrangement reaction.

Therefore, the fourth aspect of the present invention provides the application of the catalyst containing the silicon molecular sieve with MFI topological structure in the cyclohexanone oxime gas-phase beckmann rearrangement reaction. The catalyst containing the molecular sieve is used for the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime, the conversion rate of the cyclohexanone oxime and the selectivity of caprolactam are higher, the strength of the catalyst is higher, the service life of the catalyst is longer, and the economy of a new gas-phase Beckmann rearrangement process technology is improved.

The fifth aspect of the present invention provides a method for gas-phase beckmann rearrangement of cyclohexanone oxime, which comprises: under the condition of cyclohexanone oxime gas-phase Beckmann rearrangement reaction and in the presence of a solvent, the cyclohexanone oxime is contacted with a catalyst for reaction, wherein the catalyst is the catalyst containing the silicon molecular sieve with the MFI topological structure provided by the first aspect or the third aspect of the invention.

According to the present invention, preferably, the solvent is ethanol. More preferably, at least part of the ethanol is obtained in the step (3) in the preparation method of the catalyst containing the MFI topological structure silicalite molecular sieve provided by the invention, and the ethanol is preferably recovered by evaporating the crystallized solution. By adopting the preferred embodiment, the economic efficiency of the novel gas-phase Beckmann rearrangement process technology is improved. The recovery process is not particularly limited, and specifically, for example, the solution obtained by the crystallization may be subjected to evaporation (preferably at a temperature of 60 to 90 ℃) to obtain hydrous ethanol by adding an appropriate amount of water during the evaporation, and the hydrous ethanol may be subjected to distillation dehydration, membrane filtration dehydration and/or molecular sieve adsorption dehydration. In the present invention, the distillation dehydration may be carried out by any of the prior art techniques in the field. In the present invention, the membrane filtration and dehydration are not particularly limited, and may be carried out using, for example, a six-tube membrane. The specific operation is well known to those skilled in the art and will not be described herein. In the present invention, the molecular sieve adsorption dehydration is not particularly limited, and may be performed by the existing operation in the field, and the present invention is not described herein again.

Specifically, ethanol obtained in the catalyst synthesis can be used as a solvent for gas phase Beckmann rearrangement reaction after distillation dehydration, membrane filtration dehydration and/or molecular sieve adsorption dehydration. Taking a 10-ten-thousand-ton/year caprolactam production device as an example, the device consumes 300 tons of ethanol as a reaction solvent every year and about 35 tons of catalyst for gas-phase Beckmann rearrangement reaction. About 35 tons of molecular sieve is needed in the preparation process of the catalyst for the gas phase Beckmann rearrangement reaction, and about 120 tons of ethanol can be recovered in the process of synthesizing about 30 tons of molecular sieve. Therefore, the recovered ethanol is used in the gas phase Beckmann rearrangement reaction solvent, so that the production cost is greatly reduced (about 40% of the solvent cost is saved), and the pollutant discharge is reduced (in the existing molecular sieve synthesis process, when the crystallized slurry is washed and filtered, the filtered filtrate is directly discharged into water).

According to the present invention, preferably, the cyclohexanone oxime vapor phase beckmann rearrangement reaction is carried out under an inert atmosphere. In the present invention, the inert atmosphere is provided by an inert gas, preferably the inert gas is selected from at least one of nitrogen, helium, argon, and neon, more preferably nitrogen.

According to a preferred embodiment of the invention, the method further comprises passing a quantity of NH in the nitrogen₃、(CH₃)₃N, and the like. The use of this preferred embodiment is more advantageous in improving the rearrangement performance of the catalyst. The amount of the nitrogen-containing basic gas to be added may be selected as necessary by those skilled in the art in view of the actual circumstances.

According to the present invention, preferably, the molar ratio of the inert gas to cyclohexanone oxime is 10 to 80: 1, preferably 40 to 60: 1.

according to a preferred embodiment of the present invention, the cyclohexanone oxime vapor phase beckmann rearrangement reaction conditions include: the reaction temperature is 300-500 ℃, preferably 350-400 ℃, and more preferably 360-390 ℃; the reaction pressure is 0.05-0.8MPa, preferably 0.1-0.5MPa in terms of gauge pressure; the weight space velocity of the cyclohexanone-oxime is 0.1-15h^-1Preferably 0.5 to 2h^-1。

According to the present invention, preferably, cyclohexanone oxime constitutes 20 to 50 wt.% of the sum of cyclohexanone oxime and solvent (preferably ethanol).

According to the present invention, preferably, the method further comprises mixing cyclohexanone oxime with water (preferably in a molar ratio of 1: 0.01-2.5), and then contacting the mixture with the catalyst in the presence of the solvent to perform a gas phase beckmann rearrangement reaction. The use of this preferred embodiment is more advantageous in extending the life of the catalyst.

The cyclohexanone oxime gas phase Beckmann rearrangement reaction process of the catalyst prepared by the invention under the specific process condition is beneficial to further improving the economy of the whole process. Compared with the prior art that the filtrate obtained by filtering is directly discharged in the catalyst preparation process, the method can apply the ethanol recovered in the catalyst preparation process to the gas phase Beckmann rearrangement reaction using the ethanol as a reaction solvent, thereby not only improving the caprolactam selectivity, but also reducing the production cost and reducing the environmental protection pressure.

The present invention is described in detail below by way of examples.

In the following examples, unless otherwise specified, the pressure is gauge pressure; atmospheric pressure means one atmosphere; the normal temperature is 25 ℃;

the content of the metal elements is measured by using an ICP atomic emission spectrometer 7000DV model manufactured by PE (Perkin Elmer) of America, and the test conditions are as follows: dissolving the molecular sieve by using HF acid or aqua regia to completely dissolve silicon oxide and metal oxide in the sample, and measuring the content of metal ions in an aqueous solution;

the external and BET specific surface areas of the molecular sieves are determined by the United statesThe method is characterized in that the method comprises the following steps of (1) measuring by a Micromeritics ASAP-2460 type automatic adsorption instrument: n is a radical of₂As adsorbate, with adsorption temperature of-196.15 deg.C (liquid nitrogen temperature), degassing at 1.3Pa and 300 deg.C for 6 hr;

the X-ray diffraction spectrum is recorded by a Miniflex type 600 diffractometer in Japan, and the test conditions are as follows: cu target Kalpha radiation, a Ni optical filter, tube voltage of 40kV and tube current of 40 mA;

the crush strength of the catalyst was measured on a particle strength measuring apparatus model QCY-602 (manufactured by alkali industry research institute of the department of Processary engineering) according to the RIPP25-90 method of petrochemical analysis (Yankee et al, scientific Press, 1990).

The rotary table forming machine in the following embodiment is a sugarcoating machine of BY-1200 type, produced BY Tiantai pharmaceutical machinery factory, Taizhou, Jiangsu;

in the following examples, washing was carried out with water until the pH of the filtered wash water was 9-10.5.

Example 1

The method for preparing the catalyst provided by the invention comprises the following specific steps:

(1) 482kg of 95% by weight ethanol and 302kg of 22.5% by weight aqueous tetrapropylammonium hydroxide solution were added to 2M, respectively³347kg of ethyl orthosilicate was added to a stainless steel reaction vessel with stirring, and after stirring for 30 minutes, 332kg of water and 38.65 g of Fe (NO) were added₃)₃·9H₂Continuously stirring for 4 hours at normal temperature to form a colloid mixture; wherein, SiO is used₂Calculated ethyl orthosilicate: ethanol: tetrapropylammonium hydroxide: the molar ratio of water is 1: 10: 0.2: 20; with SiO₂The weight ratio of the tetraethoxysilane to the metal source calculated by the metal elements is 18666: 1;

(2) crystallizing the colloid mixture by an ethanol-hydrothermal system, wherein the crystallization conditions comprise: crystallizing at 70 deg.C for 1 day, and crystallizing at 100 deg.C for 2 days to obtain crystallized mother liquor;

(3) evaporating ethanol from the crystallized mother liquor at 85 deg.C for 10 hr (adding water continuously, maintaining the material at a certain liquid level, and recovering ethanol solution containing water for use); then washing and filtering are carried out in sequence, and drying is carried out for 24 hours at 120 ℃ to obtain 135.5kg of molecular sieve raw powder;

roasting a proper amount of the molecular sieve raw powder at 550 ℃ for 6 hours to obtain a molecular sieve sample, wherein the content of metal elements is 49.4ppm, and the BET specific surface area is 426m²Per g, external specific surface 44m²(iv)/g, the product has an X-ray diffraction pattern as shown in FIG. 1, and the X-ray diffraction (XRD) pattern is characterized in accordance with the MFI structure standard XRD pattern described in microporus Materials, Vol 22, p637, 1998, indicating that the molecular sieve has an MFI crystal structure;

as can be seen from the scanning electron microscope photos, the MFI topological structure molecular sieve has uniform grain size, and the grain diameter is 0.1-0.2 μm;

(4) the molecular sieve raw powder is crushed, 2kg of 1000-mesh powder sample which is sieved into 100 meshes is placed in a turntable forming machine, the diameter of a turntable of the turntable forming machine (a sugar coating machine, a model BY-1200 of Tiantai pharmaceutical machinery factory in Thai, Jiangsu province) is 1.2m, the depth of the turntable is 450mm, the inclination angle of the turntable is determined to be 50 degrees, and the rotation speed of the turntable is set to be 30 rpm. Spraying 1.5kg of deionized water thereto to obtain first spherical particles having a particle size of about 0.2-0.8 mm;

in addition, 110kg of 800 mesh powder sample sieved by 200 meshes and 50kg of alkaline silica sol (sodium ion content 543ppm, SiO)₂ Content 30 wt%) 2.2: 1, and crushing again, taking particles with the size less than 30 meshes, adding 160kg of the particles into the turntable forming machine with the first spherical particles at a constant speed, and finishing the adding within 240 min; then sieving with 12 mesh and 9 mesh sieves to obtain about 100kg of spherical particles with the particle size of 1.5-2 mm;

(5) blowing 100kg of the obtained spherical particles at 45 ℃, replenishing trace water for many times in the process, tightening for 2 hours, drying at 120 ℃ for 24 hours, and roasting at 550 ℃ for 10 hours to obtain 72kg of roasted product with the molecular sieve content of 86%;

45kg of the above-mentioned roasted product and 450kg of an alkaline buffer solution (the alkaline buffer solution is a mixed solution of aqueous ammonia and aqueous ammonium nitrate solution, wherein the content of the aqueous ammonia is 26 wt%, the content of the ammonium nitrate in the aqueous ammonium nitrate solution is 7.5 wt%, and the weight ratio of the aqueous ammonia to the aqueous ammonium nitrate solution isIs 3: pH of the alkaline buffer solution 11.35) to 1M³In a pressure reactor at 82 deg.C and 2.3kg/cm²Stirring for 1.5 hours under pressure, and then washing, filtering and drying to obtain a catalyst S1;

the catalyst has a particle size of 1.4-1.8mm and a crush strength sigma of 28N per particle.

Example 2

(1) 810kg of 95% by weight ethanol and 305kg of 22.5% by weight aqueous tetrapropylammonium hydroxide solution were added to 2M, respectively³347kg of ethyl orthosilicate was added to a stainless steel reaction vessel with stirring, and after stirring for 30 minutes, 325kg of water and 58.39 g of Al (NO) were added₃)₃·9H₂Continuously stirring for 4 hours at normal temperature to form a colloid mixture; wherein, SiO is used₂Calculated ethyl orthosilicate: ethanol: tetrapropylammonium hydroxide: the molar ratio of water is 1: 14: 0.2: 20; with SiO₂The weight ratio of the tetraethoxysilane to the metal source calculated by the metal elements is 23700: 1;

(2) crystallizing the colloid mixture by an ethanol-hydrothermal system, wherein the crystallization conditions comprise: crystallizing at 80 deg.C for 1 day, and crystallizing at 100 deg.C for 2 days to obtain crystallized mother liquor;

(3) evaporating the crystallized mother liquor at 88 deg.C for 7 hr (adding water continuously, maintaining the material at a certain liquid level, and recovering aqueous ethanol solution for use); then washing and filtering are carried out in sequence, and drying is carried out for 24 hours at 120 ℃ to obtain about 131.6kg of molecular sieve raw powder;

roasting a proper amount of the molecular sieve raw powder at 550 ℃ for 6 hours to obtain a molecular sieve sample, wherein the content of metal elements is 41.8ppm, and the BET specific surface area is 425m²Per g, external specific surface 44m²(ii)/g, the product has an X-ray diffraction (XRD) pattern that is consistent with the MFI structure standard XRD pattern characteristics described in microporus Materials, Vol 22, p637, 1998, indicating that the molecular sieve has an MFI crystal structure;

(4) the molecular sieve raw powder is crushed, 2kg of 1000-mesh powder sample which is sieved into 100 meshes is placed in a turntable forming machine, the diameter of a turntable of the turntable forming machine (a sugar coating machine, a model BY-1200 of Tiantai pharmaceutical machinery factory in Thai, Jiangsu province) is 1.2m, the depth of the turntable is 450mm, the inclination angle of the turntable is determined to be 50 degrees, and the rotation speed of the turntable is set to be 30 rpm. Spraying 1.4kg of deionized water thereto to obtain first spherical particles having a particle size of about 0.2-0.8 mm;

100kg of 800 mesh powder sample sieved with 200 meshes and 20kg of alkaline silica sol (sodium ion content 543ppm, SiO)₂ Content 30 wt%) as 5: 1, adding 30kg of water, uniformly mixing and crushing again, taking particles with the particle size less than 30 meshes, adding 150kg of the particles into the rotary table forming machine with the first spherical particles at a constant speed, and finishing the adding within 300 min; then sieving with 12 mesh and 9 mesh sieves to obtain about 100kg of spherical particles with the particle size of 1.5-2 mm;

(5) blowing 100kg of the obtained spherical particles at 45 ℃, replenishing trace water for many times in the process, tightening for 2 hours, drying at 120 ℃ for 24 hours, and roasting at 550 ℃ for 10 hours to obtain 73.3kg of roasted product with the molecular sieve content of 93 percent;

45kg of the above-mentioned roasted product and 450kg of an alkaline buffer solution (which is a mixed solution of aqueous ammonia and aqueous ammonium nitrate solution, wherein the content of aqueous ammonia is 26% by weight, the content of ammonium nitrate in the aqueous ammonium nitrate solution is 7.5% by weight, the weight ratio of aqueous ammonia to aqueous ammonium nitrate solution is 3: 2, and the pH value of the alkaline buffer solution is 11.35) were added to 1M³In a pressure reactor at 100 ℃ and 3.3kg/cm²Stirring for 1.5 hours under pressure, and then washing, filtering and drying to obtain a catalyst S2;

the catalyst has a particle size of 1.4-1.8mm and a crush strength sigma of 33N per particle.

Example 3

(1) 725kg of 95% by weight ethanol and 305kg of 22.5% by weight aqueous tetrapropylammonium hydroxide solution were addedAre added to 2M respectively³347kg of ethyl orthosilicate was added to a stainless steel reaction vessel with stirring, and after stirring for 30 minutes, 330kg of water and 37.37 g of Cr (NO) were added₃)₃·9H₂Continuously stirring for 4 hours at normal temperature to form a colloid mixture; wherein, SiO is used₂Calculated ethyl orthosilicate: ethanol: tetrapropylammonium hydroxide: the molar ratio of water is 1: 13: 0.2: 20; with SiO₂The weight ratio of the tetraethoxysilane to the metal source calculated by the metal elements is 20600: 1;

(2) crystallizing the colloid mixture by an ethanol-hydrothermal system, wherein the crystallization conditions comprise: crystallizing at 65 deg.C for 1 day, and crystallizing at 120 deg.C for 2 days to obtain crystallized mother liquor;

(3) evaporating ethanol from the crystallized mother liquor at 85 deg.C for 10 hr (adding water continuously, maintaining the material at a certain liquid level, and recovering ethanol solution containing water for use); then washing and filtering are carried out in sequence, and drying is carried out for 24 hours at 120 ℃ to obtain 133.8kg of molecular sieve raw powder;

roasting a small amount of the molecular sieve raw powder at 550 ℃ for 6 hours to obtain a molecular sieve sample, wherein the content of metal elements is 48.4ppm, and the BET specific surface area is 434m²A specific external surface area of 45 m/g²(ii)/g, the product has an X-ray diffraction (XRD) pattern that is consistent with the MFI structure standard XRD pattern characteristics described in microporus Materials, Vol 22, p637, 1998, indicating that the molecular sieve has an MFI crystal structure;

(4) pulverizing molecular sieve raw powder, and sieving 110kg of 800 mesh powder sample with 200 meshes and 50kg of alkaline silica sol (sodium ion content 543ppm, SiO)₂ Content 30 wt%) 2.2: 1, uniformly mixing and re-crushing, taking particles smaller than 30 meshes, uniformly adding 160kg of the particles into a turntable forming machine within 240min, wherein the diameter of a turntable of the turntable forming machine (a sugarcoating machine, a Tiantai pharmaceutical machinery factory in Thai, Jiangsu, Thai, and the model is BY-1200) is 1.2m, the depth of the turntable is 450mm, the inclination angle of the turntable is determined to be 50 degrees, and the rotating speed of the turntable is set to be 30 rpm; then use 12 meshSieving with 9 mesh sieve to obtain about 100kg spherical granule with particle diameter of 1.5-2 mm;

(5) blowing 100kg of the obtained spherical particles at 45 ℃, replenishing trace water for many times in the process, tightening for 2 hours, drying at 120 ℃ for 24 hours, and roasting at 550 ℃ for 10 hours to obtain 72.8kg of roasted product with 86% of molecular sieve content;

45kg of the above-mentioned roasted product and 450kg of an alkaline buffer solution (which is a mixed solution of aqueous ammonia and aqueous ammonium nitrate solution, wherein the content of aqueous ammonia is 26% by weight, the content of ammonium nitrate in the aqueous ammonium nitrate solution is 7.5% by weight, the weight ratio of aqueous ammonia to aqueous ammonium nitrate solution is 3: 2, and the pH value of the alkaline buffer solution is 11.35) were added to 1M³In a pressure reactor at 82 deg.C and 2.3kg/cm²Stirring for 1.5 hours under pressure, and then washing, filtering and drying to obtain a catalyst S3;

the catalyst has a particle size of 1.4-1.8mm and a crush strength sigma of 26N per particle.

Example 4

(1) 725kg of 95% by weight ethanol and 305kg of 22.5% by weight aqueous tetrapropylammonium hydroxide solution were added to 2M, respectively³In a stainless steel reaction vessel, 347kg of ethyl orthosilicate was added under stirring, and after 30 minutes under stirring, 330kg of water and 12.1 g of Ce (NO) were added₃)₃·7H₂Continuously stirring for 4 hours at normal temperature to form a colloid mixture; wherein, SiO is used₂Calculated ethyl orthosilicate: ethanol: tetrapropylammonium hydroxide: the molar ratio of water is 1: 13: 0.2: 20; with SiO₂The weight ratio of the tetraethoxysilane to the metal source calculated by the metal elements is 26700: 1;

(3) evaporating ethanol from the crystallized mother liquor at 85 deg.C for 10 hr (adding water continuously, maintaining the material at a certain liquid level, and recovering ethanol solution containing water for use); then washing and filtering are carried out in sequence, and then the molecular sieve is dried for 24 hours at 120 ℃ to obtain about 134.2kg of molecular sieve raw powder;

roasting a proper amount of the molecular sieve raw powder at 550 ℃ for 6 hours to obtain a molecular sieve sample, wherein the content of metal elements is 36.4ppm, and the BET specific surface area is 437m²A specific external surface area of 45 m/g²(ii)/g, the product has an X-ray diffraction (XRD) pattern that is consistent with the MFI structure standard XRD pattern characteristics described in microporus Materials, Vol 22, p637, 1998, indicating that the molecular sieve has an MFI crystal structure;

(4) pulverizing molecular sieve raw powder, and sieving 110kg of 800 mesh powder sample with 200 meshes and 50kg of alkaline silica sol (sodium ion content 543ppm, SiO)₂ Content 30 wt%) 2.2: 1, uniformly mixing and re-crushing, taking particles smaller than 30 meshes, uniformly adding 160kg of the particles into a turntable forming machine within 240min, wherein the diameter of a turntable of the turntable forming machine (a sugarcoating machine, a Tiantai pharmaceutical machinery factory in Thai, Jiangsu, Thai, and the model is BY-1200) is 1.2m, the depth of the turntable is 450mm, the inclination angle of the turntable is determined to be 50 degrees, and the rotating speed of the turntable is set to be 30 rpm; then sieving with 12 mesh and 9 mesh sieves to obtain about 95kg of spherical particles with diameter of 1.5-2 mm;

(5) blowing the obtained 95kg of spherical particles at 45 ℃, replenishing trace water for many times in the process, tightening for 2 hours, drying at 120 ℃ for 24 hours, and roasting at 550 ℃ for 10 hours to obtain 74kg of roasted product with the molecular sieve content of 86%;

45kg of the above-mentioned roasted product and 450kg of an alkaline buffer solution (which is a mixed solution of aqueous ammonia and aqueous ammonium nitrate solution, wherein the content of aqueous ammonia is 26% by weight, the content of ammonium nitrate in the aqueous ammonium nitrate solution is 7.5% by weight, the weight ratio of aqueous ammonia to aqueous ammonium nitrate solution is 3: 2, and the pH value of the alkaline buffer solution is 11.35) were added to 1M³In a pressure reactor at 86 deg.C and 2.8kg/cm²Stirring for 1.5 hours under pressure, and then washing, filtering and drying to obtain a catalyst S4;

the catalyst has a particle size of 1.3-1.7mm and a crush strength sigma of 25N per particle.

Example 5

The same procedure as in example 1 was followed, except that the metal source was replaced with tetrabutyltitanate and SiO₂The weight ratio of the tetraethoxysilane to the metal source calculated by the metal elements is 50000: 1;

the molecular sieve obtained has a metal content of 19.3. mu.g/g and a BET specific surface area of 431m²A specific external surface area of 49 m/g²/g；

Catalyst S5 was obtained, the particle size of the catalyst was 1.4-1.8mm, and the crush strength σ was 26N per particle.

Example 6

The process of example 1 was followed except that 95% by weight of ethanol in step (1) was used in an amount of 194kg and water in an amount of 366 kg;

with SiO₂Calculated ethyl orthosilicate: ethanol: tetrapropylammonium hydroxide: the molar ratio of water is 1: 6.4: 0.2: 20;

catalyst S6 was obtained, the particle size of the catalyst was 1.4-1.8mm, and the crush strength σ was 28N per particle.

Comparative example 1

The MFI topological structure all-silicon molecular sieve is synthesized according to the method disclosed in CN1338427A, and the method comprises the following steps:

139kg of ethyl orthosilicate is added into a reactor at room temperature, the mixture is stirred for 30 minutes, 120kg of 22.5 percent tetrapropylammonium hydroxide (abbreviated as TPAOH) aqueous solution is added into the ethyl orthosilicate, the mixture is stirred and hydrolyzed for 5 hours at room temperature, 147kg of water and 267kg of ethanol are added, the mixture is uniformly stirred to form sol, and the chemical composition of the mixed sol is H₂O/SiO₂＝20，EtOH/SiO₂＝12.7，TPAOH/SiO₂Crystallizing at 110 deg.C for 2 days, washing, filtering, drying at 120 deg.C for 24 hr, and calcining at 550 deg.C for 5 hr.

The BET specific surface area of the prepared MFI topological structure all-silicon molecular sieve sample is 441 m²Per gram, external specific surface 51 m²Per gram. The X-ray diffraction pattern of the sample was similar to that of fig. 1.

The MFI topology prepared above220kg and 100kg of SiO of chemical structure all-silicon molecular sieve₂The alkaline silica sol with the content of 30 weight percent is placed in a rotating disc type forming machine for rolling forming, the diameter of a rotating disc of the rotating disc type forming machine is 1.2m, the depth of the rotating disc is 450mm, the inclination angle of the rotating disc is determined to be 50 degrees, and the rotating speed of the rotating disc is set to be 30 rpm. Spherical particles having a diameter of about 1.7 to 2.2mm were obtained, dried at 120 ℃ for 24 hours, and calcined at 550 ℃ for 10 hours. Finally obtaining the spherical MFI topological structure all-silicon molecular sieve with the molecular sieve content of 86 percent;

adding 90kg of the spherical MFI topological structure all-silicon molecular sieve and 900kg of alkaline buffer solution (the alkaline buffer solution is a mixed solution of ammonia water and ammonium nitrate aqueous solution, wherein the content of the ammonia water is 26 wt%, the content of the ammonium nitrate in the ammonium nitrate aqueous solution is 7.5 wt%, the weight ratio of the ammonia water to the ammonium nitrate aqueous solution is 3: 2, and the pH value of the alkaline buffer solution is 11.35) into a pressure reaction kettle, and adding the mixture into the pressure reaction kettle at 85 ℃ and 2.8kg/cm²The mixture was stirred under pressure for 1.5 hours, followed by washing, filtration and drying, to obtain a catalyst D1 having a crush strength σ of 23N/pellet.

Comparative example 2

The MFI topology all-silica molecular sieve was synthesized according to the method of US4061724A example 1, as follows:

mixing NaOH solution and SiO₂Mixing 30 wt% hydrosol and tetrapropylammonium bromide (TPABr) solution to obtain a molar ratio of 4.1Na₂O：50SiO₂：691H₂O: 1TPABr, crystallizing the mixture at 200 deg.C for 3 days, washing, filtering, drying at 110 deg.C for 24 hr, and calcining at 600 deg.C for 4 hr.

The BET specific surface area of the prepared MFI topological structure all-silicon molecular sieve sample is 417 m²Per gram, external specific surface 36 m²In grams, the X-ray diffraction pattern of the sample was similar to that of figure 1.

220kg of MFI topological structure all-silicon molecular sieve prepared above and 100kg of SiO₂Placing 30 wt% alkaline silica sol in a turntable type forming machine for rolling formation, wherein the turntable of the turntable type rotary forming machine has a diameter of 1.2m, a depth of 450mm, a tilt angle of 50 ° and a rotation angleThe disc speed was set at 30 rpm. Spherical particles having a diameter of about 1.7 to 2.2mm were obtained and then dried at 120 ℃ for 24 hours and calcined at 530 ℃ for 10 hours. Finally obtaining the spherical MFI topological structure all-silicon molecular sieve with the molecular sieve content of 86 percent;

adding 90kg of the spherical MFI topological structure all-silicon molecular sieve and 900kg of alkaline buffer solution (the alkaline buffer solution is a mixed solution of ammonia water and ammonium nitrate aqueous solution, wherein the content of the ammonia water is 26 wt%, the content of the ammonium nitrate in the ammonium nitrate aqueous solution is 7.5 wt%, the weight ratio of the ammonia water to the ammonium nitrate aqueous solution is 3: 2, and the pH value of the alkaline buffer solution is 11.35) into a pressure reaction kettle, and adding the mixture into the pressure reaction kettle at 82 ℃ and 2.3kg/cm²The mixture was stirred under pressure for 1.5 hours, followed by washing, filtration and drying, to obtain a catalyst D2 having a crush strength σ of 18N/particle.

Comparative example 3

The process of example 1 was followed except that, in the step (2), the conditions for crystallization of the ethanol-hydrothermal system were: crystallizing the mixture in an ethanol-hydrothermal system at 100 ℃ for 3 days;

catalyst D3 was obtained with a crushing strength a of 18N/particle.

Comparative example 4

The procedure is as in example 1, except that in step (1) NO Fe (NO) is added₃)₃·9H₂O；

Catalyst D4 was obtained with a crushing strength σ of 20N/particle.

Comparative example 5

The same procedure as in example 4 was followed, except that in step (4), rotational molding was replaced with extrusion molding, specifically:

pulverizing molecular sieve raw powder, and sieving 110kg of 800-mesh powder sample with 200 meshes and 50kg of SiO₂An alkaline silica sol with a content of 30 wt.% was prepared as follows: 1, mixing uniformly and crushing again, taking particles with the particle size less than 30 meshes, extruding and molding on a kneading-extruding continuous production line at normal temperature, and adopting an orifice plate made of engineering plastics;

to obtain a strip-shaped catalyst D5 with the length of 5mm and the diameter of 1.8 mm; the crush strength σ of the catalyst was 7.5N/mm.

Test example 1

The test example is used for evaluating the catalysts containing the MFI topological structure molecular sieve prepared in the examples and the comparative examples, and gas phase Beckmann rearrangement reaction is carried out under the test condition 1 and the test condition 2 respectively:

test condition 1: the cyclohexanone oxime gas phase Beckmann rearrangement reaction is carried out in a normal pressure continuous flow fixed bed reactor, the inner diameter of the reactor is 5mm, 0.375 g of 40-60 mesh catalyst calculated by molecular sieve is filled in the reactor, coarse quartz sand with the height of about 30mm and the size of 30 meshes is filled on the catalyst bed layer, and fine quartz sand with the size of 50 meshes is filled under the catalyst bed layer. The catalyst was pretreated for 1 hour at normal pressure in a nitrogen atmosphere at 350 ℃ after being charged into the reactor. The rearrangement reaction conditions include: normal pressure; the reaction temperature is 380 ℃; the concentration of the raw material cyclohexanone oxime was 35% by weight; the weight space velocity (WHSV, cyclohexanone oxime flow in the feed/catalyst weight in the bed) of the cyclohexanone oxime was 16h^-1(ii) a The reaction solvent is ethanol; carrier gas (N)₂) The flow rate is 45mL/min, the reaction product enters a collecting bottle after being cooled by an ice-water mixture for gas-liquid separation, and the composition analysis of the product is carried out after the reaction is carried out for 6 hours.

Condition 2: the reaction device is a continuous flow fixed bed, the inner diameter of the reactor is 28 mm, and the loading amount of the catalyst calculated by a molecular sieve is 30 g; height of bed layer: 15 cm; reaction pressure: 0.1 MPa; the reaction temperature is 360-400 ℃; n is a radical of₂The molar ratio of the cyclohexanone oxime to the cyclohexanone oxime is 25: 1; the weight percentage of water to cyclohexanone oxime is 1.2 wt%; the temperature of the vaporizer is controlled to be 175 ℃; keeping the temperature of the pipeline at 185 ℃; the concentration of the raw material cyclohexanone oxime is 35 wt%, the solvent is ethanol, the weight space velocity (WHSV, cyclohexanone oxime flow in the feeding/catalyst weight calculated by molecular sieve in the bed) of the cyclohexanone oxime is 0.5h^-1And the reaction time is 600 hours for product composition analysis.

The reaction products obtained under the two conditions are respectively subjected to quantitative analysis by adopting a 6890 gas chromatograph (a hydrogen flame ion detector, a PEG20M capillary chromatographic column, the column length is 50m) of Agilent company, the vaporization chamber temperature is 250 ℃, the detection chamber temperature is 240 ℃, the column temperature is programmed temperature rise, the temperature is kept constant at 110 ℃ for 8 minutes, the temperature is increased to 230 ℃ at the speed of 15 ℃/min, and then the temperature is kept constant for 14 minutes.

The content of rearrangement products of caprolactam and cyclohexanone-oxime after reaction is calculated by adopting an area normalization method, and the solvent does not participate in the integral.

The cyclohexanone oxime mole percentage content in the reaction product and the caprolactam mole percentage content in the reaction product are obtained through the analysis, and the cyclohexanone oxime conversion rate and the caprolactam selectivity are calculated according to the following formulas:

cyclohexanone oxime conversion (mol%) - (cyclohexanone oxime mole content in feed-cyclohexanone oxime mole content in product)/cyclohexanone oxime mole content in feed x 100%

Total caprolactam selectivity (mol%): caprolactam mole% in product/(cyclohexanone oxime mole% in product) × 100%

The ethyl-caprolactam imide (AEH) accounts for about 40% of the total amount of all the byproducts in the byproduct of the gas phase Beckmann rearrangement reaction of cyclohexanone oxime, and the byproduct is generated by the alcoholysis reaction of ethanol and enol-structure tautomer of caprolactam. Under the action of water, ethyl-caprolactam is continuously produced through hydrolysis reaction of caprolactam. Thus, the total caprolactam selectivity is calculated to include the amount of ethyl-caprolactam hydrolysis to caprolactam; the results are shown in Table 1.

TABLE 1

The crushing strength of A1-A5 of the catalyst containing the MFI topological structure silicon molecular sieve prepared by the method is higher and can reach 33N/particle at most.

The data in table 1 show that when the catalyst prepared by the method is applied to the cyclohexanone oxime gas phase Beckmann rearrangement reaction to prepare caprolactam, the conversion rate of the cyclohexanone oxime is higher, the conversion rate of the cyclohexanone oxime can reach 99.75% at most after the reaction is carried out for 6 hours at a higher space velocity, and the total selectivity of the caprolactam reaches 96.07%. Compared with the MFI topological structure all-silicon molecular sieve catalyst synthesized by the methods in the prior art CN1338427A and US4061724A, the method has higher conversion rate of cyclohexanone oxime.

Meanwhile, under a lower airspeed, after the catalyst provided by the invention is used for the cyclohexanone oxime gas-phase Beckmann rearrangement reaction for 600 hours, the conversion rate of the cyclohexanone oxime is still higher and can still reach 99.64 percent at most, which shows that the catalyst provided by the invention has higher activity, longer service life and obvious effect.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims

1. A catalyst comprising an MFI topology silicon molecular sieve, the catalyst comprising the MFI topology silicon molecular sieve and optionally a binder; the content of the molecular sieve in the catalyst is 70-100 wt% based on the dry weight of the catalyst, and the content of the binder in terms of oxide is 0-30 wt%; the crush strength of the catalyst is 15-60N/particle;

2. The catalyst according to claim 1, wherein the metal element is selected from at least one of transition metal elements, group IIIA and group IVA elements;

preferably, the transition metal element is selected from at least one of group IB, group IIB, group IVB, group VB, group VIB, group VIIB and group VIII metal elements;

preferably, the metal element is selected from at least one of Al, Ga, Ge, Ce, Ag, Co, Ni, Cu, Zn, Mn, Pd, Pt, Cr, Fe, Au, Ru, Rh, Pt, Rh, Ti, Zr, V, Mo and W elements;

further preferably, the metal element has an ionic valence of +3 and/or an ionic valence of + 4;

further preferably, the metal element is at least one of Fe, Al, Ga, Cr, Ti, Zr, and Ce elements.

3. The catalyst according to claim 1 or 2, wherein the content of the metal element in the molecular sieve is 6-90 μ g/g, preferably 30-80 μ g/g, based on the total amount of the molecular sieve;

preferably, the BET specific surface area of the molecular sieve is 400-500m²G, preferably 420-450m²/g；

Preferably, the grain size of the molecular sieve is 0.1-0.3 μm, preferably 0.1-0.25 μm;

preferably, the molecular sieve has an external specific surface area of 35 to 60m²A/g, preferably from 30 to 50m²/g。

4. A catalyst according to any one of claims 1 to 3, wherein the catalyst has a particle size of 0.5 to 3mm, preferably 0.8 to 2.5 mm;

preferably, the crush strength of the catalyst is from 20 to 60N per particle;

preferably, the molecular sieve is present in the catalyst in an amount of 70 to 95 wt% on a dry basis and the binder is present in an amount of 5 to 30 wt% on an oxide basis, based on the dry weight of the catalyst;

preferably, the binder is silica.

5. A method for preparing a catalyst containing an MFI topological structure silicon molecular sieve comprises the following steps:

6. The method of claim 5, wherein the SiO is used₂The calculated molar ratio of the ethyl orthosilicate, the ethanol, the tetrapropylammonium hydroxide and the water is 1: (4-15): (0.06-0.3): (15-49);

7. the method according to claim 5 or 6, wherein the metal element is selected from at least one of transition metal elements, group IIIA and group IVA elements;

further preferably, the metal element is at least one of Fe, Al, Ga, Cr, Ti, Zr, and Ce elements;

preferably, the metal source is selected from at least one of a nitrate of a metal, a chloride of a metal, a sulfate of a metal, an acetate of a metal, and an ester metal compound.

8. The method of any one of claims 5-7, wherein the two-stage temperature-varying ethanol-hydrothermal system crystallization conditions comprise: crystallizing at 50-80 deg.C for 1-1.5 days, and crystallizing at 100-120 deg.C for 1-3 days.

9. The method of any of claims 5-8, wherein the method further comprises: before the filtration in the step (3), ethanol is removed from the crystallized mother liquor;

preferably, the ethanol-driving conditions include: the temperature is 50-90 ℃, preferably 60-90 ℃; the time is 1-24h, preferably 1-12 h.

10. The method as claimed in any one of claims 5 to 9, wherein, in the step (4), the molecular sieve raw powder is pulverized to 100-1000 mesh;

preferably, the binder is a precursor of silicon oxide and/or water, preferably a precursor of silicon oxide;

preferably, the precursor of the silicon oxide is silica sol and/or white carbon black, and preferably the silica sol;

in the silica sol, SiO₂The content is 20-45 wt%;

preferably, the rotational forming is performed in a rotary disc forming machine;

preferably, the conditions of the rotational molding include: the inclination angle of the rotary table is 40-55 degrees, preferably 45-50 degrees; the relation between the diameter D of the rotary disc and the depth H of the rotary disc is 0.1-0.3D, preferably 0.1-0.25D; the rotating speed of the rotating disc is 10-50rpm, preferably 20-40 rpm;

preferably, the particle size of the particles obtained by rotational molding is 0.1-3mm, preferably 0.2-2.5 mm;

preferably, the molecular sieve raw powder is crushed and then mixed with a binder to carry out the rotational molding;

preferably, the molecular sieve is mixed with SiO on a dry basis₂The weight ratio of the calculated binder is 1: (0.05-1), preferably 1: (0.1-0.8);

preferably, the rotational molding of step (4) includes:

(4-1) selecting a first powder sample with the particle size of 100-1000 meshes from the solid substances obtained by crushing, mixing the first powder sample with a first binder, and carrying out first rotation forming to obtain first particles with the particle size of 0.1-0.8mm, wherein the mass ratio of the first powder sample to the first binder is 1: (0.2-1);

(4-2) selecting a second powder sample with the particle size of 100-1000 meshes from the solid matter obtained by crushing, mixing the second powder sample, a second binder and the first particles, and carrying out second rotation forming to obtain second particles with the particle size of 1.3-2.5mm, wherein the mass ratio of the second powder sample to the second binder is 1: (0.001-0.5).

11. The method of any one of claims 5 to 10, wherein in step (5), the firing conditions comprise: the temperature is 200-600 ℃, preferably 400-580 ℃, and the time is 1-20h, preferably 2-18 h;

preferably, the alkaline buffer solution containing the nitrogen-containing compound contains ammonium salt and alkali, the content of the ammonium salt is 0.1-20 wt%, the content of the alkali is 5-30 wt%, and the pH value of the alkaline buffer solution containing the nitrogen-containing compound is 8.5-13.5;

preferably, the nitrogen-containing compound alkaline buffer solution is used in an amount of 500-1500 parts by weight, preferably 700-1200 parts by weight, relative to 100 parts by weight of the product obtained by calcination on a dry basis;

preferably, the conditions of the contacting include: the temperature is 50-120 ℃, and the optimal temperature is 70-100 ℃; the pressure is 0.5-10kg/cm²Preferably 1.5 to 4kg/cm²(ii) a The time is 0.1 to 5 hours, preferably 1 to 3 hours.

12. A catalyst comprising a silicalite molecular sieve of MFI topology produced by the process of any of claims 5 to 11.

13. Use of the catalyst containing a silicalite with MFI topology according to any of claims 1-4 and 12 in the gas phase beckmann rearrangement reaction of cyclohexanone oxime.

14. A process for a cyclohexanone oxime vapor phase beckmann rearrangement reaction, which comprises: under the condition of cyclohexanone oxime gas-phase Beckmann rearrangement reaction, in the presence of a solvent, contacting cyclohexanone oxime with a catalyst to react, wherein the catalyst is the catalyst containing the MFI topological structure silicon molecular sieve of any one of claims 1 to 4 and 12; the solvent is preferably ethanol.