A sheet-like silicalite-1 molecular sieve catalyst, a preparation method and application thereof

Abstract

The application discloses a kind of sheet Silicalite-1 molecular sieve catalyst and its preparation method and application, its b axis length is 50-250nm, BET specific surface area is 300-500m 2 / g, the preparation method is as follows: silicon source, amide compound, organic template agent and water are mixed to obtain colloidal mixture;The colloidal mixture is hydrothermally crystallized to obtain crystallization product;The crystallization product is washed, separated and treated, and then calcined to obtain the sheet Silicalite-1 molecular sieve catalyst.Compared with the silicalite-1 molecular sieve in the prior art, the sheet silicalite-1 molecular sieve in the application has larger external specific surface area and smaller b axis length, and can improve the conversion rate of cyclohexanone oxime and the selectivity of caprolactam when applied to the reaction of preparing caprolactam by gas-phase Beckmann rearrangement of cyclohexanone oxime.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of Silicalite-1 molecular sieve catalyst, in particular to a kind of sheet Silicalite-1 molecular sieve catalyst and its preparation method and application. BACKGROUND

[0002] Silicalite-1 molecular sieve, also known as full-silica molecular sieve, is a kind of aluminum-free molecular sieve with MFI topological structure, which only contains silicon atoms and oxygen atoms in the framework, and the basic structural unit is SiO4 tetrahedron, with a determined crystal structure of ZSM-5 type molecular sieve, due to its special pore structure, good hydrothermal stability, high specific surface area and suitable acidity, it is paid more and more attention and widely used in adsorption separation, purification, catalysis and other fields.

[0003] The synthesis method of full-silica molecular sieve generally adopts traditional hydrothermal method, and the silicon source can be selected from solid silicon oxide, silica sol, white carbon black, tetraethyl orthosilicate (abbreviated as TEOS) and the like, the template agent is mainly tetrapropylammonium hydroxide (abbreviated as TPAOH), low-carbon hydrocarbon quaternary ammonium salt or mixture thereof, amine compound and the like, and the crystallization is usually carried out at a temperature of about 170 ℃ for three days. However, the silica molecular sieve synthesized by the existing technology has a high content of amorphous silicon oxide, a relatively poor relative crystallinity and large crystal particles.

[0004] Caprolactam is an important organic raw material, mainly used for preparing nylon-6, polyamide plastic, polycaprolactam fiber resin, cyclohexylamine and the like, and widely used in the fields of textile, automobile, electronics, machinery and the like. It is generally obtained by Beckmann rearrangement reaction of cyclohexanone oxime. At present, the liquid phase rearrangement process using concentrated sulfuric acid or fuming sulfuric acid as catalyst is usually adopted in industry. This process needs to consume a large amount of sulfuric acid and ammonia water, and generally 1.3-1.8 tons of low-value ammonium sulfate is by-produced for producing 1 ton of caprolactam, and the production cost is high. In addition, the use of sulfuric acid will cause problems such as equipment corrosion and environmental pollution. Therefore, developing a new environmentally friendly catalyst has become the key to overcoming the shortcomings in the production process of caprolactam.

[0005] CN102050464A discloses a synthesis method of silica molecular sieve, which is prepared by using tetraethyl orthosilicate as silicon source, tetrapropylammonium hydroxide as alkali source and template agent, and the molar composition of the gel mixture before crystallization of the molecular sieve is TPAOH / SiO2=0.05-0.5, EtOH / SiO2=4 and H2O / SiO2=5-100. The above mixture is crystallized in a closed reaction kettle at a temperature of 80-120 ℃ and autogenous pressure for 1-3 days to obtain silica molecular sieve.

[0006] US4061724A discloses a silicon molecular sieve, which is prepared from a raw material containing no aluminum source, only silicon source, alkali source, template agent and water, different from the silicon molecular sieve formed by extracting framework aluminum, and is directly synthesized silicon molecular sieve with MFI topological crystal structure. The silicon source used in the silicon molecular sieve is one of silica sol, silica gel or white carbon black, and the molar composition of the gel mixture before crystallization of the molecular sieve is 13-50 SiO2: 150-700 H2O: 0-6.5 M2O: Q2O, wherein M is an alkali metal, and Q is a quaternary cation with a molecular formula of R4X + , R represents hydrogen or an alkyl group with 2-6 carbon atoms, and X is phosphorus or nitrogen. The mixture is hydrothermally crystallized at a temperature of 100-250℃ and autogenous pressure in a sealed reaction kettle for 50-150 hours.

[0007] JP59164617A discloses an MFI structure silicon molecular sieve prepared from tetraethyl orthosilicate as silicon source and tetrapropylammonium hydroxide as template agent and alkali source.

[0008] However, the silicon molecular sieve synthesized by the above-mentioned technology has no obvious effect on improving the conversion rate of cyclohexanone oxime and the selectivity of caprolactam when used as a catalyst for the gas phase Beckmann rearrangement reaction of cyclohexanone oxime, and therefore it is necessary to develop a new silicon molecular sieve. SUMMARY

[0009] The present application is to overcome the problem that the Silicalite-1 molecular sieve as a catalyst for the gas phase Beckmann rearrangement reaction of cyclohexanone oxime has no obvious effect on improving the conversion rate of cyclohexanone oxime and the selectivity of caprolactam in the prior art, and provides a lamellar Silicalite-1 molecular sieve catalyst and a preparation method and application thereof. The molecular sieve catalyst has a shorter b-axis length, and can effectively improve the conversion rate of cyclohexanone oxime and the selectivity of caprolactam when used as a catalyst for the gas phase Beckmann rearrangement reaction of cyclohexanone oxime.

[0010] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0011] In a first aspect, the present application provides a lamellar Silicalite-1 molecular sieve catalyst, which has a b-axis length of 50-250 nm and a BET specific surface area of 300-500 m 2 / g.

[0012] In a second aspect, the present application provides a preparation method of the above-mentioned lamellar Silicalite-1 molecular sieve catalyst, which comprises the following steps:

[0013] a. mixing a silicon source, an amide compound, an organic template agent and water to obtain a colloidal mixture;

[0014] b. subjecting the colloidal mixture obtained in step a to hydrothermal crystallization to obtain a crystallized product;

[0015] c. subjecting the crystallized product obtained in step b to washing and separation treatment to obtain a laminar Silicalite-1 molecular sieve;

[0016] d. subjecting the laminar Silicalite-1 molecular sieve obtained in step c to calcination treatment to obtain a laminar Silicalite-1 molecular sieve catalyst.

[0017] In a third aspect, the present application provides a use of the laminar Silicalite-1 molecular sieve catalyst in a gas-phase Beckmann rearrangement reaction of cyclohexanone oxime.

[0018] The present application can obtain a high-crystallinity, laminar, nearly neutral Silicalite-1 molecular sieve by adding a certain amount of amide compound during the synthesis of the Silicalite-1 molecular sieve, and can effectively change the performance of the Silicalite-1 molecular sieve. Compared with the Silicalite-1 molecular sieve synthesized by the prior art, the laminar Silicalite-1 molecular sieve synthesized by the present application has a larger external specific surface area and a smaller b-axis length, and can improve the conversion rate of cyclohexanone oxime and the selectivity of caprolactam in the reaction of preparing caprolactam from cyclohexanone oxime by gas-phase Beckmann rearrangement. In a mobile bed or fixed bed reaction system, the method for preparing caprolactam by the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime with the laminar Silicalite-1 molecular sieve as the catalyst can realize long-period and continuous production of caprolactam, and has higher selectivity of caprolactam than the existing spherical Silicalite-1 molecular sieve catalyst. Since the total amount of by-products is reduced, the energy consumption for product separation is also reduced, and the technical and economic efficiency is effectively improved.

[0019] Preferably, in the colloidal mixture of step a, the molar ratio of SiO2, the amide compound, the organic template agent and water is 1:(0.40-1.80):(0.30-0.85):(20-60).

[0020] Preferably, in step a, the silicon source is selected from at least one of silica gel, silica sol and organosilicate; the amide compound is selected from at least one of formamide, acetamide, propionamide and carbamide; and the organic template agent is selected from at least one of aliphatic amine compound, alcohol amine compound and quaternary amine base compound.

[0021] Preferably, in step a, the silicon source is tetramethyl orthosilicate and / or tetraethyl orthosilicate; the amide compound is carbamide; and the organic template agent is tetraethylammonium hydroxide and / or tetrapropylammonium hydroxide.

[0022] As preferred, the hydrothermal crystallization in step b is carried out at a temperature of 160-200℃ for 2-5 days.

[0023] As preferred, the calcination in step d is carried out at a temperature of 500-600℃ for 3-5 hours.

[0024] As preferred, the reaction conditions of the gas phase Beckmann rearrangement of cyclohexanone oxime are as follows: cyclohexanone oxime is mixed with a reaction solvent, and after vaporization, the mixture is introduced into a fixed bed reactor filled with a layered Silicalite-1 molecular sieve catalyst, and the Beckmann rearrangement is carried out at normal pressure and at a reaction temperature of 300-400℃.

[0025] As preferred, the reaction solvent comprises ethanol and water, the weight of ethanol is 60-70% of the weight of cyclohexanone oxime, and the weight of water is 0.5-1% of the weight of cyclohexanone oxime; the weight space velocity of cyclohexanone oxime is 10-20h -1 .

[0026] Therefore, the present application has the following beneficial effects: by adding a certain amount of amide compounds during the synthesis of Silicalite-1 molecular sieve, a high-crystallinity, near-neutral, layered Silicalite-1 molecular sieve with a larger external specific surface area and a smaller b-axis length can be obtained, and when applied to the reaction of preparing caprolactam from cyclohexanone oxime through gas phase Beckmann rearrangement, the conversion rate of cyclohexanone oxime and the selectivity of caprolactam can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 X-ray diffraction spectrum of the layered Silicalite-1 molecular sieve catalyst prepared in Example 1 of the present application;

[0028] Figure 2 Scanning electron microscope image of the layered Silicalite-1 molecular sieve catalyst prepared in Example 1 of the present application;

[0029] Figure 3 Infrared transmission spectrum of the layered Silicalite-1 molecular sieve catalyst prepared in Example 1 of the present application;

[0030] Figure 4 1H MAS NMR spectrum of the layered Silicalite-1 molecular sieve catalyst prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0031] The present application will be further described below in combination with the accompanying drawings and specific embodiments.

[0032] In the present application, all the equipment and raw materials can be purchased from the market or commonly used in the industry, and the methods in the following examples are conventional methods in the art unless otherwise specified.

[0033] The BET specific surface of the sample of the sheet Silicalite-1 molecular sieve in the embodiment of the present application is made by an automatic adsorption instrument of the type of Micromeritics ASAP-2400 in the United States, and the test conditions are as follows: N2 as the adsorbate, adsorption temperature of -196.15 ℃ (liquid nitrogen temperature), constant temperature degassing at 1.3 Pa and 300 ℃ for 6 h. The X-ray diffraction spectrum data are made by a Rigaku Ultimate VI diffractometer in Japan, and the test conditions are as follows: Cu target K α Radiation, tube voltage 40 kV, tube current 40 mA. Scanning electron microscope (SEM) images are taken on a Hitachi SU-1510 electron microscope. 1 H magic angle spinning (MAS) nuclear magnetic resonance spectroscopy is performed on a Bruker AVANCE III HD spectrometer. Fourier transform infrared (FT-IR) spectra are recorded using the KBr method on a Nicolet iS10 spectrometer.

[0034] General examples:

[0035] A sheet Silicalite-1 molecular sieve catalyst, the length of the b axis is 50-250 nm, the BET specific surface area is 300-500 m 2 / g; the preparation method comprises the following steps:

[0036] a. mixing a silicon source, an amide compound, an organic template agent and water to obtain a colloidal mixture;

[0037] b. performing hydrothermal crystallization on the colloidal mixture obtained in step a to obtain a crystallization product;

[0038] c. performing washing and separation treatment on the crystallization product obtained in step b to obtain a sheet Silicalite-1 molecular sieve;

[0039] d. performing calcination treatment on the sheet Silicalite-1 molecular sieve obtained in step c to obtain a sheet Silicalite-1 molecular sieve catalyst; preferably, in the colloidal mixture in step a, the molar ratio of SiO2, the amide compound, the organic template agent and water is 1:(0.40-1.80):(0.30-0.85):(20-60);

[0040] Preferably, the silicon source in step a is selected from at least one of silica gel, silica sol and organosilicate; more preferably, the silicon source is methyl orthosilicate and / or ethyl orthosilicate;

[0041] Preferably, the amide compound in step a is at least one selected from formamide, acetamide, propionamide, and carbamide; more preferably, the amide compound is carbamide;

[0042] Preferably, the organic template in step a is at least one selected from aliphatic amine, alcohol amine, and quaternary amine base; more preferably, the organic template is tetraethylammonium hydroxide and / or tetrapropylammonium hydroxide;

[0043] Preferably, the hydrothermal crystallization in step b is performed at a temperature of 160-200°C for 2-5 days.

[0044] Preferably, the calcination in step d is performed at a temperature of 500-600°C for 3-5 hours.

[0045] Example 1

[0046] A method for preparing a sheet-like Silicalite-1 molecular sieve catalyst, comprising the steps of:

[0047] Mixing 2.8 g of tetraethyl orthosilicate, 3.83 g of 25 wt% tetrapropylammonium hydroxide (TPAOH), 0.65 g of carbamide (urea), and 5.61 g of water, stirring at room temperature for 12 hours to form a colloidal mixture, the molar ratio of SiO2:TPAOH:H2O:urea in the colloidal mixture being 1:0.35:35:0.81, transferring the mixture into a 25 mL stainless steel autoclave lined with polytetrafluoroethylene, crystallizing at 180°C for 3 days, washing, filtering, drying at 100°C for 24 hours, and calcining at 550°C for 4 hours to obtain the sheet-like Silicalite-1 molecular sieve catalyst prepared in this example.

[0048] The sheet-like Silicalite-1 molecular sieve catalyst prepared in this example has a BET specific surface area of 367 m2 / g, the X-ray diffraction spectrum of the product is shown in 2 Figure 1 , the scanning electron microscope image is shown in Figure 2 , the infrared transmission of the product is shown in Figure 3 , the product has a 1 H MAS NMR as shown in Figure 4 ​The X-ray diffraction (XRD) spectrum thereof is consistent with the standard XRD spectrum characteristics of MFI structure recorded in Microporous Materials, Vol 22, p637, 1998, which shows that the molecular sieve has MFI crystal structure; from the scanning electron microscope, it can be seen that the b axis of the sheet Silicalite-1 molecular sieve is 80 nm; from the infrared transmission diagram, it can be seen that the sheet Silicalite-1 molecular sieve has more silanol pits and less terminal silanol; from the 1 H MAS NMR, it can be seen that the sheet Silicalite-1 molecular sieve has more strong hydrogen bonds.

[0049] Example 2:

[0050] A preparation method of a sheet Silicalite-1 molecular sieve catalyst, the steps are:

[0051] 2.80 grams of tetraethyl orthosilicate, 3.28 grams of 25% by weight of tetrapropylammonium hydroxide (abbreviated as TPAOH), 0.32 grams of carbamide and 2.39 grams of water are mixed, stirred at room temperature for 12 hours to form a colloidal mixture, the molar ratio in the colloidal mixture is SiO2:TPAOH:H2O:urea=1:0.30:20:0.40, the above mixture is moved into a 25 mL stainless steel reaction kettle lined with polytetrafluoroethylene, crystallized at 200°C for 2 days, washed, filtered, dried at 100°C for 24 hours, and calcined at 550°C for 4 hours to obtain the sheet Silicalite-1 molecular sieve catalyst prepared in this example;

[0052] The sheet Silicalite-1 molecular sieve catalyst prepared in this example has a BET specific surface area of 389 m 2 / g and a b axis of 80 nm.

[0053] Example 3:

[0054] A preparation method of a sheet Silicalite-1 molecular sieve catalyst, the steps are:

[0055] 2.8 grams of tetraethyl orthosilicate, 9.29 grams of 25% by weight of tetrapropylammonium hydroxide (abbreviated as TPAOH), 1.45 grams of urea and 7.57 grams of water are mixed, stirred at room temperature for 12 hours to form a colloidal mixture, the molar ratio in the colloidal mixture is SiO2:TPAOH:H2O:urea=1:0.85:60:1.80, the above mixture is moved into a 25 mL stainless steel reaction kettle lined with polytetrafluoroethylene, crystallized at 160°C for 5 days, washed, filtered, dried at 100°C for 24 hours, and calcined at 550°C for 4 hours to obtain the sheet Silicalite-1 molecular sieve catalyst prepared in this example;

[0056] The BET specific surface area of the sheet Silicalite-1 molecular sieve catalyst prepared in this embodiment is 410 m 2 / g, and the b axis is 210 nm.

[0057] Embodiment 4:

[0058] A method for preparing a sheet Silicalite-1 molecular sieve catalyst, comprising the following steps:

[0059] 2.8 grams of tetraethyl orthosilicate, 8.20 grams of 25 wt% tetrapropylammonium hydroxide (abbreviated as TPAOH), 0.65 grams of urea, and 2.33 grams of water were mixed, stirred at room temperature for 12 hours to form a colloidal mixture, the molar ratio in the colloidal mixture was SiO2:TPAOH:H2O:urea=1:0.75:35:0.81, the mixture was moved into a 25 mL stainless steel reaction kettle lined with polytetrafluoroethylene, crystallized at 180°C for 2 days, washed, filtered, dried at 100°C for 24 hours, and calcined at 550°C for 4 hours to obtain the sheet Silicalite-1 molecular sieve catalyst prepared in this embodiment;

[0060] The BET specific surface area of the sheet Silicalite-1 molecular sieve catalyst prepared in this embodiment is 400 m 2 / g, and the b axis is 230 nm.

[0061] Embodiment 5:

[0062] A method for preparing a sheet Silicalite-1 molecular sieve catalyst, comprising the following steps:

[0063] 2.8 grams of tetraethyl orthosilicate, 7.11 grams of 25 wt% tetrapropylammonium hydroxide (abbreviated as TPAOH), 0.65 grams of urea, and 3.15 grams of water were mixed, stirred at room temperature for 12 hours to form a colloidal mixture, the molar ratio in the colloidal mixture was SiO2:TPAOH:H2O:urea=1:0.65:35:0.81, the mixture was moved into a 25 mL stainless steel reaction kettle lined with polytetrafluoroethylene, crystallized at 180°C for 2 days, washed, filtered, dried at 100°C for 24 hours, and calcined at 550°C for 4 hours to obtain the sheet Silicalite-1 molecular sieve catalyst prepared in this embodiment;

[0064] The BET specific surface area of the sheet Silicalite-1 molecular sieve catalyst prepared in this embodiment is 391 m 2 / g, and the b axis is 200 nm.

[0065] Embodiment 6:

[0066] A preparation method of a sheet Silicalite-1 molecular sieve catalyst, steps are as follows:

[0067] 2.8 grams of tetraethyl orthosilicate, 6.01 grams of 25 wt% tetrapropylammonium hydroxide (TPAOH), 0.65 grams of urea and 3.97 grams of water are mixed, stirred at room temperature for 12 hours to form a colloidal mixture, the molar ratio of SiO2:TPAOH:H2O:urea in the colloidal mixture is 1:0.55:35:0.81, the mixture is moved into a 25 mL stainless steel reactor lined with polytetrafluoroethylene, crystallized at 180℃ for 2 days, washed, filtered, dried at 100℃ for 24 hours, calcined at 550℃ for 4 hours, and a sheet Silicalite-1 molecular sieve catalyst prepared in the embodiment is obtained;

[0068] The sheet Silicalite-1 molecular sieve catalyst prepared in the embodiment has a BET specific surface area of 383 m 2 / g, and the b axis is 180 nm.

[0069] Example 7:

[0070] A preparation method of a sheet Silicalite-1 molecular sieve catalyst, steps are as follows:

[0071] 2.8 grams of tetraethyl orthosilicate, 4.92 grams of 25 wt% tetrapropylammonium hydroxide (TPAOH), 0.65 grams of urea and 4.79 grams of water are mixed, stirred at room temperature for 12 hours to form a colloidal mixture, the molar ratio of SiO2:TPAOH:H2O:urea in the colloidal mixture is 1:0.45:35:0.81, the mixture is moved into a 25 mL stainless steel reactor lined with polytetrafluoroethylene, crystallized at 180℃ for 2 days, washed, filtered, dried at 100℃ for 24 hours, calcined at 550℃ for 4 hours, and a sheet Silicalite-1 molecular sieve catalyst prepared in the embodiment is obtained;

[0072] The sheet Silicalite-1 molecular sieve catalyst prepared in the embodiment has a BET specific surface area of 368 m 2 / g, and the b axis is 120 nm.

[0073] Comparative Example 1 (Method Two of CN1338427A):

[0074] A preparation method of a Silicalite-1 molecular sieve catalyst, steps are as follows:

[0075] Into a 1000ml beaker, 139g of tetraethyl orthosilicate was poured and stirred for 30 minutes at room temperature. 120g of 22.5% aqueous solution of tetrapropylammonium hydroxide (abbreviated as TPAOH) was added to the tetraethyl orthosilicate, and the mixture was stirred at room temperature for 5 hours to hydrolyze. 147g of water and 267g of ethanol were added to the mixture to homogenize the mixture to form a sol. At this time, the chemical composition of the sol was H2O / SiO2=20, EtOH / SiO2=12.7, and TPAOH / SiO2=0.20. The sol was crystallized at 110°C for 2 days, washed, filtered, dried at 120°C for 24 hours, and calcined at 550°C for 5 hours to obtain a Silicalite-1 molecular sieve catalyst.

[0076] The Silicalite-1 molecular sieve catalyst sample prepared in the present comparative example had a BET specific surface area of 441m 2 / g, and the X-ray diffraction pattern of the sample was similar to Figure 1 that of the Silicalite-1 molecular sieve catalyst prepared in the above example.

[0077] Application Example:

[0078] The Silicalite-1 molecular sieve catalysts prepared in the above example and comparative example were used in a gas phase Beckmann rearrangement reaction of cyclohexanone oxime to test the catalytic reaction results.

[0079] The gas phase Beckmann rearrangement reaction of cyclohexanone oxime was carried out in a stainless steel fixed bed reactor. The reactor had an inner diameter of 8mm, and 0.5g of the Silicalite-1 molecular sieve catalyst prepared in the above example and comparative example was loaded in the reactor. A 60mm high 20-40 mesh coarse quartz sand was loaded above the catalyst bed, and a 20-40 mesh coarse quartz sand was loaded below the catalyst bed. During the reaction, cyclohexanone oxime was mixed with a reaction solvent, vaporized, and then introduced into the above stainless steel fixed bed reactor together with a carrier gas (N2) to carry out the Beckmann rearrangement reaction. The rearrangement reaction conditions were as follows: normal pressure; reaction temperature 370°C; weight hourly space velocity (WHSV) of cyclohexanone oxime 16h -1 ; the reaction solvent was ethanol and a small amount of water, the weight of ethanol was 64.3% of the weight of cyclohexanone oxime, and the weight of water was 0.7% of the weight of cyclohexanone oxime; the flow rate of the carrier gas (N2) was 80mL / min; and the reaction product was introduced into a collection bottle after being cooled by an ice water mixture to carry out gas-liquid separation. The product composition was analyzed after the reaction was carried out for 6 hours.

[0080] The reaction product was quantitatively analyzed by using a Shimadzu GC-2018PFsc chromatograph (hydrogen flame ionization detector, SE-54 capillary column, column length 50m). The vaporization chamber temperature was 533°K, the detection chamber temperature was 533°K, and the column temperature was programmed to increase at a rate of 20°K / min. The column temperature was held at 333°K for 3 minutes, increased to 453°K for 1 minute, and then increased to 513°K for 1 minute.

[0081] The molar percentage content of cyclohexanone oxime in the reaction product and the molar percentage content of caprolactam in the reaction product are obtained by the above analysis, and the conversion rate of cyclohexanone oxime and the selectivity of caprolactam are calculated, and the results are shown in Table 1.

[0082] Table 1: Test results of catalytic performance of cyclohexanone oxime gas phase Beckmann rearrangement reaction.

[0083] Catalyst number 6h conversion / % 6h selectivity / % Example 1 100 96.37 Example 2 100 96.02 Example 3 100 96.38 Example 4 100 96.75 Example 5 100 96.14 Example 6 100 96.25 Example 7 100 96.95 Comparative Example 1 98.07 94.57

[0084] From the above results, it can be seen that the sheet Silicalite-1 molecular sieve catalyst prepared by the method of the present application is used in the fixed bed process of preparing caprolactam by gas phase Beckmann rearrangement of cyclohexanone oxime, and when the weight hourly space velocity (WHSV) of cyclohexanone oxime is 16h -1 -1, the conversion rate can reach 100% after 6 hours of reaction, and the selectivity of caprolactam is also very high, which can reach 96.95% at the highest, which is significantly improved compared with the Silicalite-1 molecular sieve catalyst prepared by the method in Comparative Example 1.

[0085] The preferred embodiments of the present application are described in detail above in combination with the drawings. However, the present application is not limited to the specific details in the above-described embodiments, and various simple modifications can be made to the technical solutions of the present application within the technical concept of the present application, and these simple modifications all belong to the protection scope of the present application.

[0086] In addition, it should be noted that each specific technical feature described in the above-described specific embodiments can be combined in any appropriate manner without contradiction, and in order to avoid unnecessary repetition, the present application will not further describe various possible combinations.

[0087] In addition, various different embodiments of the present application can also be combined in any manner, as long as it does not deviate from the technical concept of the present application, and it should also be considered as disclosed content of the present application.

Claims

1. The use of a sheet of Silicalite-1 molecular sieve catalyst in the gas phase Beckmann rearrangement of cyclohexanone oxime, characterized in that The Silicalite-1 molecular sieve catalyst has a b-axis length of 50-250 nm, a BET specific surface area of 300-500 m 2 / g, and a preparation method comprising the following steps: a. mixing a silicon source, an amide compound, an organic template and water to obtain a colloidal mixture; the silicon source is selected from at least one of silica gel, silica sol and organosilicate; the amide compound is selected from at least one of formamide, acetamide, propionamide and carbonamide; b. hydrothermally crystallizing the obtained colloidal mixture to obtain a crystallized product; c. washing and separating the obtained crystallized product to obtain a Silicalite-1 molecular sieve with lamellar structure; d. calcining the obtained Silicalite-1 molecular sieve with lamellar structure to obtain a Silicalite-1 molecular sieve catalyst with lamellar structure.

2. Use according to claim 1, characterized in that, In the colloidal mixture of step a, the molar ratio of SiO2, the amide compound, the organic template and water is 1:(0.40-1.80):(0.30-0.85):(20-60).

3. Use according to claim 1 or 2, characterised in that The organic template in step a is selected from at least one of aliphatic amine compounds, alcohol amine compounds and quaternary amine base compounds.

4. The use according to claim 1, characterized in that The silicon source in step a is tetramethyl orthosilicate and / or tetraethyl orthosilicate; the amide compound is carbonamide; and the organic template is tetraethylammonium hydroxide and / or tetrapropylammonium hydroxide.

5. The use according to claim 1, characterized in that, The hydrothermal crystallization in step b is carried out at a temperature of 160-200℃ for 2-5 days.

6. The use according to claim 1, characterized in that, The calcination in step d is carried out at a temperature of 500-600℃ for 3-5 hours.

7. The use according to claim 1, characterized in that, The reaction conditions of the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime are as follows: mixing cyclohexanone oxime with a reaction solvent, vaporizing and then entering a fixed-bed reactor filled with the Silicalite-1 molecular sieve catalyst with lamellar structure, and carrying out the Beckmann rearrangement reaction at normal pressure and at a reaction temperature of 300-400℃.

8. Use according to claim 7, characterized in that, The reaction solvent includes ethanol and water, the weight of ethanol is 60-70% of the weight of cyclohexanone oxime, the weight of water is 0.5-1% of the weight of cyclohexanone oxime; the weight space velocity of cyclohexanone oxime is 10-20h -1 .

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