Preparation method and application of mixed acid modified hollow hierarchical pore TS-1 molecular sieve

Abstract

The application discloses a preparation method of a mixed acid modified hollow multi-level hole TS-1 molecular sieve catalyst. The method comprises the following steps: placing the TS-1 molecular sieve raw powder in an alkali solution, and performing hydrothermal reaction at 80-200 DEG C to prepare the hollow multi-level hole TS-1 molecular sieve; then immersing the hollow multi-level hole TS-1 molecular sieve into a mixed acid solution, stirring, and then performing reflux reaction at 40-100 DEG C for 2-12 hours; and finally washing, drying and calcining to prepare the mixed acid modified hollow multi-level hole TS-1 molecular sieve catalyst; the mixed acid is tartaric acid and phosphoric acid. The catalyst prepared by the method keeps the hollow porous structure of the molecular sieve, has the nano porous structure, and in the cyclohexanone oxime rearrangement reaction, the space velocity is 10h ‑1 , the reaction time is 8 hours, the conversion rate is 70%, and the conversion rate is increased by nearly 40%.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalyst, in particular to a mixed acid modified hollow TS-1 zeolite molecular sieve catalyst and a preparation method thereof. BACKGROUND

[0002] Caprolactam is an important organic chemical raw material, mainly used for the production of nylon-6 fiber and resin, widely used in the fields of automobile, ship, electronic and electrical appliances, textile and so on. The caprolactam is generally prepared by Beckmann rearrangement reaction of cyclohexanone oxime, and the reaction process is shown in formula (I). At present, the caprolactam is mainly prepared by using concentrated sulfuric acid as catalyst and adopting liquid phase Beckmann rearrangement process. The process technology is mature, the product purity is high, and the reaction conditions are mild. However, the process consumes a large amount of sulfuric acid and ammonia water, generates a large amount of low-value-added ammonium sulfate, and has high production cost. At the same time, using concentrated sulfuric acid as catalyst will cause corrosion of equipment and pollution of environment.

[0003]

[0004] The application of solid acid catalyst in the preparation of caprolactam by gas phase Beckmann rearrangement of cyclohexanone oxime is a new process for realizing no generation of ammonium sulfate. The process does not corrode the equipment and pollute the environment, greatly simplifies the separation and purification of the product, and has the advantages of high efficiency and reusability. The preparation of caprolactam by solid acid catalytic gas phase Beckmann rearrangement of cyclohexanone oxime has attracted widespread attention from researchers. In recent years, the use of molecular sieve as catalyst to catalyze Beckmann rearrangement reaction has attracted attention. Among them, TS-1 molecular sieve is the most excellent. TS-1 molecular sieve has MFI structure and belongs to Pentasil type heteroatomic molecular sieve, which has three-dimensional pore structure. TS-1 molecular sieve has microporous structure, and the pore size is about 0.55 nm. The multi-level pore molecular sieve has micropore, mesopore and macropore, which is beneficial to the catalytic conversion of large-size reactants, has suitable acid center, excellent activity and stability. At the same time, the diffusion path of reactant and product molecules is effectively shortened, the diffusion efficiency is greatly improved, the carbon deposition resistance of the catalyst is improved, and the service life of the catalyst is prolonged

[0005] Jin Xin et al. synthesized TS-1 molecular sieve with intracrystalline mesopore by aggregating nanoparticles, and treated it with tetrapropylammonium hydroxide. The treated molecular sieve was used to catalyze Beckmann rearrangement reaction, which effectively reduced the deactivation rate of the molecular sieve. However, when used for Beckmann rearrangement reaction, the reaction deactivation rate was fast at a large space velocity of 10h -1 -1. The conversion rate was only 30% after 8h of reaction. Although the molecular sieve has intracrystalline mesopore, the molecular sieve particles are large due to the aggregation of nanoparticles, and the microspheres are 10 microns.

[0006] CN 114873604A discloses a method for preparing zirconium-modified hierarchical pore TS-1 molecular sieve, which utilizes acid-base modification to prepare hierarchical pore TS-1 molecular sieve, and uses multiple zirconium salts to modify the hierarchical pore TS-1 molecular sieve, thereby improving the acidity of the modified hierarchical pore TS-1 molecular sieve. The authors load metal on the molecular sieve to change its acidity, which has certain economic cost.

[0007] CN 111186842A discloses a method for preparing hierarchical pore TS-1 molecular sieve, which connects a silicon source and a titanium source on the same polymer to form a silicon-titanium ester polymer, thereby preparing hierarchical pore TS-1 molecular sieve, but containing a small amount of non-framework titanium. SUMMARY

[0008] The technical problem to be solved by the present application is to provide a method for preparing and application of mixed acid-modified hollow hierarchical pore TS-1 molecular sieve, aiming at the above technical deficiencies. The method does not need to load metal, but only needs to modify TS-1 with a mixed acid composed of tartaric acid and phosphoric acid, thereby removing the non-framework titanium on the surface while loading phosphorus elements and changing the acidity of the molecular sieve. The present application maintains the hollow porous structure of the molecular sieve, and has a nano-porous structure. In the cyclohexanone oxime rearrangement reaction, the conversion rate is 70% when the space velocity is 10h-1 and the reaction time is 8h, which is increased by nearly 40%. -1

[0009] The present application adopts the following technical solutions:

[0010] A method for preparing a mixed acid-modified hollow hierarchical pore TS-1 molecular sieve catalyst, comprising the following steps:

[0011] (1) uniformly mix tetraethyl silicate, tetrabutyl titanate, a template agent and water, then place the mixed solution in a hydrothermal kettle, seal, and hydrothermally synthesize at 80-200℃ for 12-72h, then wash, dry and calcine to obtain white TS-1 molecular sieve raw powder;

[0012] The molar ratio of the tetraethyl silicate, tetrabutyl titanate, template agent and water is 1:(0.003-0.05):(0.2-0.3):(10-30);

[0013] (2) place the above-mentioned TS-1 molecular sieve raw powder in an alkali solution, hydrothermally react at 80-200℃ for 2-72h, then wash, dry and calcine to obtain hollow hierarchical pore TS-1 molecular sieve;

[0014] The alkali solution is one of tetrapropylammonium hydroxide, tetraethylammonium hydroxide and tetrapropylammonium bromide; the concentration is 0.01-3mol / L; and the solid-liquid ratio of the molecular sieve to the alkali solution is 1:(5-50)g / mL; ​

[0015] (3) immersing the hollow multi-level pore TS-1 molecular sieve obtained above into a mixed acid solution, stirring, and refluxing at 40-100 ℃ for 2-12 h, washing, drying, and calcining to obtain a mixed acid modified hollow multi-level pore TS-1 molecular sieve catalyst;

[0016] The mixed acid is a mixed solution containing tartaric acid and phosphoric acid, and the molar concentration of the tartaric acid and the phosphoric acid in the mixed acid is 0.01-3 mol / L; the molar ratio of the tartaric acid to the phosphoric acid is 0.01-3:0.01-3.

[0017] The solid-liquid ratio of the hollow multi-level pore TS-1 molecular sieve to the mixed acid solution is 1:(5-50) g / mL.

[0018] The template agent is tetrapropylammonium hydroxide, tetraethylammonium hydroxide, or tetrapropylammonium bromide.

[0019] The particle size of the TS-1 molecular sieve raw powder is 100-400 nm.

[0020] The washing mode in steps (1), (2), and (3) is centrifugal washing; the drying temperature is 50-150 ℃, and the drying time is 2-24 h; the calcining temperature is 300-650 ℃, and the calcining time is 2-10 h.

[0021] The reaction in step (3) is carried out in a water bath.

[0022] Preferably,

[0023] The molar concentration of the alkali solution in step (2) is 0.05-2 mol / L; and the solid-liquid ratio of the TS-1 molecular sieve synthesized by the hydrothermal method to the alkali solution is 1:(5-30) g / mL.

[0024] The reaction in step (2) is carried out at 100-180 ℃ for 8-48 h.

[0025] The concentrations of the tartaric acid and the phosphoric acid in the mixed acid in step (3) are 0.05-2.5 mol / L and 0.05-2.5 mol / L, respectively.

[0026] The solid-liquid ratio of the hollow multi-level pore TS-1 molecular sieve to the mixed acid is 1:(5-30) g / mL.

[0027] The water bath stirring in step (3) is refluxed at 50-90 ℃ for 2-10 h.

[0028] The application of the mixed acid modified hollow multi-level pore TS-1 molecular sieve prepared by the method is used for preparing caprolactam by gas phase Beckmann rearrangement of cyclohexanone oxime.

[0029] Specifically comprising the following steps:

[0030] The mixed acid modified hollow multi-level pore TS-1 molecular sieve catalyst is loaded in a fixed bed reactor, activated at 400-500 DEG C for 0.5-2h, then cooled to 330-380 DEG C, and then a mixed liquid of cyclohexanone oxime and methanol is introduced, with nitrogen as the carrier gas, the space velocity being 1-10h -1 , to obtain caprolactam.

[0031] The mixed liquid is cyclohexanone oxime and methanol, with a mass ratio of 1:6-12.

[0032] The volume of the mixed liquid carried by 30-70ml of carrier gas flow is 0.1-0.47ml.

[0033] The application of the present application will be described in detail below through examples, but the scope of the present application should not be limited by these examples.

[0034] The present application has the following advantages:

[0035] 1) The present application uses a dissolution-crystallization secondary crystallization method to post-treat the molecular sieve matrix to prepare a hollow multi-level pore TS-1 molecular sieve, which is mixed and modified with a mixed acid of tartaric acid and phosphoric acid, thereby reducing the use of metal and lowering the preparation cost. The present application has the advantages of short preparation period, mixed acid modification, water bath condensation reflux stirring for 2-6h, and no need for reduction, simple and efficient preparation method, and low economic cost.

[0036] 2) In the present application, the alkaline solution secondary crystallization forms a hollow multi-level pore nano TS-1 molecular sieve. The mixed acid treatment of tartaric acid and phosphoric acid removes the non-framework titanium on the surface of the molecular sieve. At the same time, it is beneficial to the formation of mesopores on the surface of the molecular sieve and the improvement of the carbon deposition resistance of the catalyst. The modification of tartaric acid and phosphoric acid increases the weak B acid center of the catalyst and reduces the medium-strong acid center, thereby improving the catalytic activity. Under the optimal reaction conditions, the conversion rate of cyclohexanone oxime is greater than 99%, and the selectivity of caprolactam is greater than 99%. Under the condition of a space velocity of 10h -1 , the conversion rate is 70% after 8h of reaction, which is 40% higher than that of Jin Xin et al. under the same conditions. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a particle size distribution histogram of TS-1 raw powder;

[0038] Figure 2 is a transmission electron microscope image of TS-1 molecular sieve before and after treatment in Example 1, wherein, Figure 2 a is a transmission electron microscope image of TS-1 raw powder in Example 1, Figure 2 b is a transmission electron microscope image of hollow TS-1 formed after secondary crystallization synthesis; DETAILED DESCRIPTION

[0039] The reactor has a diameter of 8 mm and a length of 45 cm and is made of stainless steel. The middle of the reactor is filled with 0.1-0.5 g of catalyst (0.5 g in the following examples), and the upper and lower parts of the reactor are filled with 20-40 mesh quartz sand as a support.

[0040] The application provides a preparation method of a mixed acid modified hollow multi-level pore TS-1 molecular sieve catalyst, which comprises the following steps: uniformly stirring and mixing tetraethyl silicate, tetrabutyl titanate, a template agent and water in sequence, hydrothermally synthesizing, washing, drying and calcining to obtain TS-1 molecular sieve raw powder. The TS-1 molecular sieve raw powder is mixed with an alkali solution, and then hydrolysis, hydrothermal synthesis, washing, drying and calcining are sequentially performed to obtain the hollow multi-level pore TS-1 molecular sieve. The hollow multi-level pore TS-1 molecular sieve is mixed with a mixed acid solution, and then reaction, washing, drying and calcining are sequentially performed to obtain the mixed acid modified hollow multi-level pore TS-1 molecular sieve catalyst.

[0041] The technical solutions provided by the application are described in detail below in combination with examples, but they should not be understood as limitations to the protection scope of the application.

[0042] Example 1

[0043] According to the molar ratio of tetraethyl silicate:tetrabutyl titanate:template agent:water = 1:0.025:0.2:13.2, tetraethyl silicate, tetrabutyl titanate, tetrapropyl ammonium hydroxide and water are weighed. The template agent is added to water and stirred uniformly, and the mixture is recorded as solution A; the tetrabutyl titanate is added to the tetraethyl silicate and stirred uniformly, and the mixture is recorded as solution B. Under stirring, solution A is added to solution B, and the generated ethanol is removed by stirring in a water bath at 80℃. The mixed solution is added to a stainless steel reactor with a polytetrafluoroethylene lining, and crystallization is carried out at 170℃ for 48 h to obtain a milky white suspension. The suspension is washed by centrifugation until neutral, the centrifugation speed is 10000 rpm, and the centrifugation is carried out 10 times, 4 min each time. The obtained white solid is dried at 120℃ overnight and calcined at 550℃ for 6 h to obtain TS-1 molecular sieve raw powder.

[0044] The hollow hierarchical pore TS-1 molecular sieve was obtained by the following steps: 25% (mass percentage) tetrapropylammonium hydroxide was mixed with deionized water in a beaker at room temperature, stirred at room temperature for 0.5 hours, and uniformly stirred to obtain a tetrapropylammonium hydroxide aqueous solution with a molar concentration of 0.1 mol / L. The TS-1 molecular sieve raw powder was added to the aqueous solution at a solid-liquid ratio of 1:10 (g / mL), and stirred at room temperature for 1 hour until uniform. The mixture was moved into a stainless steel reaction kettle lined with polytetrafluoroethylene, and twice-crystallized at 170°C for 24 hours. The mixture was filtered, washed and centrifuged to neutral, the centrifugal speed was 10000 rpm, and the centrifugation was performed 15 times, each time for 3 min. The mixture was dried at 120°C overnight, and calcined at 550°C for 6 hours to obtain the hollow hierarchical pore TS-1 molecular sieve, which was recorded as catalyst 1. # .

[0045] The hollow hierarchical pore molecular sieve was mixed with mixed acid (the molar concentration of tartaric acid and phosphoric acid in the mixed acid was 0.5 mol / L) at a solid-liquid ratio of 1:10 (g / mL), and the mixture was refluxed at 80°C in a water bath for 4 hours. The mixture was filtered, washed and centrifuged to neutral, the centrifugal speed was 10000 rpm, and the centrifugation was performed 10 times, each time for 3 min. The mixture was dried at 100°C overnight, and calcined at 550°C for 6 hours to obtain the mixed acid modified hollow hierarchical pore TS-1 molecular sieve, which was recorded as catalyst 2. # .

[0046] Example 2

[0047] The hollow hierarchical pore molecular sieve 1 # was mixed with mixed acid (the molar concentration of tartaric acid and phosphoric acid in the mixed acid was 0.7 mol / L) at a solid-liquid ratio of 1:10 (g / mL), and the mixture was refluxed at 80°C in a water bath for 4 hours. The mixture was filtered, washed and centrifuged to neutral, and dried at 100°C overnight. The mixture was calcined at 550°C for 6 hours to obtain the mixed acid modified hollow hierarchical pore TS-1 molecular sieve, which was recorded as catalyst 3. # .

[0048] Example 3

[0049] The hollow hierarchical pore molecular sieve 1 # was mixed with mixed acid (the molar concentration of tartaric acid and phosphoric acid in the mixed acid was 1 mol / L) at a solid-liquid ratio of 1:10 (g / mL), and the mixture was refluxed at 80°C in a water bath for 4 hours. The mixture was filtered, washed and centrifuged to neutral, and dried at 100°C overnight. The mixture was calcined at 550°C for 6 hours to obtain the mixed acid modified hollow hierarchical pore TS-1 molecular sieve, which was recorded as catalyst 4. # .

[0050] Example 4

[0051] The hollow hierarchical pore molecular sieve 1 #The mixture was combined with a mixed acid (in which the molar concentrations of tartaric acid and phosphoric acid were both 1.3 mol / L) at a solid-liquid ratio of 1:10 (g / mL), refluxed in a water bath at 80°C for 4 hours, filtered, washed, and centrifuged until neutral, dried overnight at 100°C, and calcined at 550°C for 6 hours to obtain the mixed acid-modified hollow hierarchical porous TS-1 molecular sieve, denoted as catalyst 5. # .

[0052] Example 5

[0053] Hollow multi-level porous molecular sieve 1 # The mixture was combined with a mixed acid (in which the molar concentrations of tartaric acid and phosphoric acid were both 1.5 mol / L) at a solid-liquid ratio of 1:10 (g / mL), refluxed in a water bath at 80°C for 4 hours, filtered, washed, and centrifuged until neutral, dried overnight at 100°C, and calcined at 550°C for 6 hours to obtain the mixed acid-modified hollow hierarchical porous TS-1 molecular sieve, denoted as catalyst 6. # .

[0054] Example 6

[0055] Hollow hierarchical molecular sieve 1# was mixed with a mixed acid (tartaric acid molar concentration of 0.5 mol / L and phosphoric acid molar concentration of 0.7 mol / L) at a solid-liquid ratio of 1:10 (g / mL). The mixture was then refluxed in a water bath at 80℃ for 4 hours, filtered, washed, and centrifuged until neutral. It was then dried overnight at 100℃ and calcined at 550℃ for 6 hours to obtain the mixed acid-modified hollow hierarchical molecular sieve TS-1, designated as catalyst 7. # .

[0056] Example 7

[0057] Hollow multi-level porous molecular sieve 1 # The mixture was combined with a mixed acid (in which the molar concentration of tartaric acid was 0.7 mol / L and the molar concentration of phosphoric acid was 0.5 mol / L) at a solid-liquid ratio of 1:10 (g / mL), refluxed in a water bath at 80℃ for 4 h, filtered, washed, and centrifuged until neutral, dried at 100℃ overnight, and calcined at 550℃ for 6 h to obtain the mixed acid-modified hollow hierarchical porous TS-1 molecular sieve, denoted as catalyst 8. # .

[0058] Example 8

[0059] Hollow multi-level porous molecular sieve 1 #The mixture was combined with a mixed acid (in which the molar concentration of tartaric acid was 0.7 mol / L and the molar concentration of phosphoric acid was 1 mol / L) at a solid-liquid ratio of 1:10 (g / mL), refluxed in a water bath at 80℃ for 4 h, filtered, washed, and centrifuged until neutral, dried at 100℃ overnight, and calcined at 550℃ for 6 h to obtain the mixed acid-modified hollow hierarchical porous TS-1 molecular sieve, denoted as catalyst 9. # .

[0060] Example 9

[0061] Hollow multi-level porous molecular sieve 1 # The mixture was prepared with a mixed acid (in which the molar concentration of tartaric acid was 1 mol / L and the molar concentration of phosphoric acid was 0.7 mol / L) at a solid-liquid ratio of 1:10 (g / mL), refluxed in a water bath at 80℃ for 4 h, filtered, washed, and centrifuged until neutral, dried at 100℃ overnight, and calcined at 550℃ for 6 h to obtain the mixed acid-modified hollow hierarchical porous TS-1 molecular sieve, denoted as catalyst 10. # .

[0062] Example 10

[0063] Hollow multi-level porous molecular sieve 1 # The mixture was combined with a mixed acid (in which the molar concentration of tartaric acid was 0.7 mol / L and the molar concentration of phosphoric acid was 1.3 mol / L) at a solid-liquid ratio of 1:10 (g / mL), refluxed in a water bath at 80℃ for 4 h, filtered, washed, and centrifuged until neutral, dried at 100℃ overnight, and calcined at 550℃ for 6 h to obtain the mixed acid-modified hollow hierarchical porous TS-1 molecular sieve, denoted as catalyst 11. # .

[0064] Example 11

[0065] Hollow hierarchical molecular sieve 1# was mixed with a mixed acid (tartaric acid molar concentration of 0.7 mol / L and phosphoric acid molar concentration of 1.5 mol / L) at a molar ratio of 0.7:1.5. The mixture was then refluxed in a water bath at 80℃ for 4 hours, filtered, washed, and centrifuged until neutral. The mixture was dried overnight at 100℃ and calcined at 550℃ for 6 hours to obtain the mixed acid-modified hollow hierarchical molecular sieve TS-1, denoted as catalyst 12. # .

[0066] The catalyst 1 obtained above # -12 # Application in the gas-phase Beckmann rearrangement of cyclohexanone oxime

[0067] Catalyst 1 # -12 #After activation at 450℃ for 1h, the reaction was carried out at 350℃, with a raw material liquid of cyclohexanone oxime:methanol mass ratio of 1:9, nitrogen flow rate of 30ml / min, liquid flow rate of 0.1ml / min, and weight hourly space velocity of 1.06h -1 , for 8h; catalyst 9 # The reaction was carried out at 350℃, with a raw material liquid of cyclohexanone oxime:methanol mass ratio of 1:9, nitrogen flow rate of 30, 50, 70ml / min respectively, liquid flow rate of 0.1ml / min, and weight hourly space velocity of 1.06h -1 , for 8h; catalyst 9 # The reaction was carried out at 350℃, with a raw material liquid of cyclohexanone oxime:methanol mass ratio of 1:9, nitrogen flow rate of 30ml / min, liquid flow rate of 0.19ml / min, and weight hourly space velocity of 2.1h -1 , for 8h; catalyst 9 # The reaction was carried out at 350℃, with a raw material liquid of cyclohexanone oxime:methanol mass ratio of 1:9, nitrogen flow rate of 20ml / min, liquid flow rate of 0.25ml / min, and weight hourly space velocity of 5.3h -1 , for 8h; catalyst 9 # The reaction was carried out at 350℃, with a raw material liquid of cyclohexanone oxime:methanol mass ratio of 1:9, nitrogen flow rate of 20ml / min, liquid flow rate of 0.47ml / min, and weight hourly space velocity of 10h -1 , for 8h; catalyst 9 # The reaction was carried out at 340, 360℃ respectively, with a raw material liquid of cyclohexanone oxime:methanol mass ratio of 1:9, nitrogen flow rate of 30ml / min, liquid flow rate of 0.1ml / min, and weight hourly space velocity of 1.06h -1 , for 8h.

[0068] The reaction conditions are shown in Table 1; the composition of the product was analyzed using Agilent gas chromatography (FID detector, DB-WAX capillary column), and the results are shown in Table 1.

[0069] Table 1 Catalyst 1 # -12 # Catalytic performance data of catalyst 9 applied to the gas phase Beckmann rearrangement reaction of cyclohexanone oxime for 8h

[0070]

[0071] As shown in Table 1, under suitable reaction conditions: the modified hollow hierarchical pore TS-1 molecular sieve (catalyst 9 # ) has the best catalytic performance when the molar concentration ratio of tartaric acid and phosphoric acid is 0.7:1. The reaction temperature is 350℃, the nitrogen flow rate is 50ml / min, the space velocity is 1.06h -1The conversion rate of cyclohexanone oxime is greater than 99%, and the selectivity is greater than 99% when the space velocity is 10h -1 The conversion rate of cyclohexanone oxime is greater than 70% when the space velocity is 10h

[0072] It can be seen from the above examples that the catalyst prepared by using the mixed acid of tartaric acid and phosphoric acid to modify the TS-1 molecular sieve treated by secondary crystallization has high activity and selectivity, and has certain anti-carbon deposition performance, effectively prolonging the service life of the catalyst. The superiority of the catalyst may be related to the hollow multi-level pore TS-1 molecular sieve prepared by secondary crystallization of an alkali solution and the mixed acid modification. The TS-1 molecular sieve prepared by this method has a hollow multi-level pore structure and a surface mesoporous structure, and is loaded with phosphorus, thereby greatly improving the stability and selectivity of the catalyst. The selectivity of the target product caprolactam is as high as 98% or more, and good results are achieved. The anti-carbon deposition performance is effectively improved. Compared with Jin Xin et al., the conversion rate is increased by 40% when the space velocity is 10h -1 and 8h

[0073] The details of the present application are known technologies.

Claims

1. A method for preparing a mixed acid modified hollow hierarchical pore TS-1 molecular sieve catalyst for preparing caprolactam by gas phase Beckmann rearrangement of cyclohexanone oxime, characterized in that, The method comprises the following steps: (1) uniformly mixing tetraethyl silicate, tetrabutyl titanate, a template agent and water, placing the mixed solution in a hydrothermal kettle, hydrothermally synthesizing at 80-200 DEG C for 12-72 hours, then washing, drying and calcining to obtain white TS-1 molecular sieve raw powder; The molar ratio of the tetraethyl silicate, tetrabutyl titanate, template agent and water is 1:(0.003-0.05):(0.2-0.3):(10-30); (2) placing the TS-1 molecular sieve raw powder in an alkali solution, hydrothermally reacting at 80-200 DEG C for 2-72 hours, then washing, drying and calcining to obtain the hollow multi-level pore TS-1 molecular sieve; The alkali solution is one of tetrapropyl ammonium hydroxide, tetraethyl ammonium hydroxide and tetrapropyl ammonium bromide; the alkali solution concentration is 0.01-3 mol / L; the solid-liquid ratio of the molecular sieve and the alkali solution is 1:(5-50) g / mL; (3) immersing the hollow multi-level pore TS-1 molecular sieve obtained in the above step in a mixed acid solution, stirring, refluxing at 40-100 DEG C for 2-12 hours, then washing, drying and calcining to obtain the mixed acid modified hollow multi-level pore TS-1 molecular sieve catalyst; The mixed acid is a mixed solution containing tartaric acid and phosphoric acid, and the molar concentration of the tartaric acid and the phosphoric acid in the mixed acid is 0.01-3 mol / L; the molar ratio of the tartaric acid and the phosphoric acid is 0.01-3:0.01-3; The solid-liquid ratio of the hollow multi-level pore TS-1 molecular sieve and the mixed acid solution is 1:(5-50) g / mL; The template agent is tetrapropyl ammonium hydroxide, tetraethyl ammonium hydroxide or tetrapropyl ammonium bromide.

2. The preparation method of mixed acid modified hollow hierarchical pore TS-1 molecular sieve catalyst for preparing caprolactam by cyclohexanone oxime gas phase Beckmann rearrangement according to claim 1, characterized in that The particle size of the TS-1 molecular sieve raw powder ranges from 100 nm to 400 nm.

3. The preparation method of mixed acid modified hollow hierarchical pore TS-1 molecular sieve catalyst for preparing caprolactam by cyclohexanone oxime gas phase Beckmann rearrangement according to claim 1, characterized in that, In steps (1), (2) and (3), the washing mode is centrifugal washing; the drying temperature is 50-150 DEG C, and the drying time is 2-24 hours; the calcining temperature is 300-650 DEG C, and the calcining time is 2-10 hours.

4. The preparation method of mixed acid modified hollow hierarchical pore TS-1 molecular sieve catalyst for preparing caprolactam by cyclohexanone oxime gas phase Beckmann rearrangement according to claim 1, characterized in that, The reaction in step (3) is carried out in a water bath.

5. The preparation method of mixed acid modified hollow hierarchical pore TS-1 molecular sieve catalyst for preparing caprolactam by cyclohexanone oxime gas phase Beckmann rearrangement according to claim 1, characterized in that, In step (2), the molar concentration of the alkali solution is 0.05-2 mol / L; the solid-liquid ratio of the TS-1 molecular sieve synthesized by the hydrothermal method and the alkali solution is 1:(5-30) g / mL; In step (2), the reaction is carried out at 100-180 DEG C for 8-48 hours; In step (3), the concentration of the tartaric acid and the phosphoric acid in the mixed acid is 0.05-2.5 mol / L and 0.05-2.5 mol / L, respectively; The solid-liquid ratio of the hollow multi-level pore TS-1 molecular sieve and the mixed acid is 1:(5-30) g / mL; In step (3), the refluxing reaction is carried out at 50-90 DEG C under water bath stirring for 2-10 hours.

6. The use of the mixed acid modified hollow hierarchical pore TS-1 molecular sieve prepared by the method of claim 1, characterized in that, The application is used for preparing caprolactam from cyclohexanone oxime by gas phase Beckmann rearrangement.

7. The application according to claim 6, characterized by comprising the following steps: The mixed acid modified hollow hierarchical pore TS-1 molecular sieve catalyst is loaded in a fixed bed reactor, activated at 400-500 DEG C for 0.5-2h, then cooled to 330-380 DEG C, and then a mixed liquid of cyclohexanone oxime and methanol is introduced, with nitrogen as a carrier gas, and the space velocity is 1-10h -1 , to obtain caprolactam; The mixed liquid is cyclohexanone oxime and methanol, and the mass ratio of the two is 1:6-12; The volume of the mixed liquid carried by every 30-70 ml of carrier gas flow is 0.1-0.47 ml.

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