Mesoporous Sn-beta molecular sieve as well as synthesis method and application thereof

Abstract

The invention discloses a mesoporous Sn-beta molecular sieve as well as a synthesis method and application thereof. The method comprises the following steps: (1) uniformly mixing an H-beta molecular sieve, alkali, quaternary ammonium salt and anhydrous sodium stannate, and then carrying out hydrothermal treatment; (2) roasting the material subjected to hydrothermal treatment in the step (1); and (3) washing, filtering and drying the roasted material to obtain the final mesoporous Sn-beta molecular sieve product. In the Sn-beta molecular sieve, the content of Sn in a framework is relatively high, the content of lewis acid is relatively high, and a large number of mesopores are contained in a molecular sieve crystal, so that the molecular diffusion performance of reactants is relatively good.

Description

Technical Field

[0001] The invention belongs to the field of molecular sieve synthesis and relates to a mesoporous Sn-beta molecular sieve and a synthesis method and application thereof. Background Art

[0002] Mobil Corporation first synthesized beta zeolite in 1967, and it has been widely used since its synthesis. Due to its unique topological structure, high silicon-aluminum ratio, and strong acidity, beta zeolite exhibits excellent thermal stability, acid resistance, coking resistance, and catalytic activity in a range of catalytic reactions. As the application value of beta zeolite in the petrochemical industry continues to be understood, research on its synthesis has deepened. Introducing heteroatoms into the beta zeolite framework is one of the key approaches to improving the catalytic performance of molecular sieves. Heteroatom molecular sieves are molecular sieves containing other elements, formed by replacing part of the silicon, aluminum, or phosphorus in the molecular sieve framework with other elements. The introduced heteroatoms can be metal atoms or non-metal atoms, and after the introduction of heteroatoms, the molecular sieve can retain its original framework structure.

[0003] In recent years, Sn-beta molecular sieves have attracted the attention of numerous researchers. These molecular sieves can be used to catalyze a variety of chemical reactions, such as the Baeyer-Viiliger oxidation of cyclohexanone. The framework Sn atoms in the Sn-beta molecular sieve possess Lewis acidity, activating the carbonyl group of cyclohexanone. H2O2 then inserts an oxygen atom into the position of the Sn-activated carbonyl group, and the intermediate undergoes structural rearrangement to form ε-caprolactone. Sn-beta is a very promising new molecular sieve material, but traditional Sn-beta molecular sieves have a microporous structure. In recent years, reports on the synthesis of Sn-beta with a hierarchical pore structure to improve its diffusion properties have gradually increased.

[0004] Dapsens et al. reported a method for synthesizing mesoporous Sn-beta zeolite in "Alkaline-assisted stannation of beta zeolite as a scalable route to Lewis-acid catalysts for the valorization of renewables" in Volume 40 of "New Journal of Chemistry". They placed the beta molecular sieve in a mixed solution containing SnCl4·5H2O or SnSO4, TPABr and NaOH, and implanted Sn atoms while desiliconizing in the liquid phase to obtain a hierarchical Sn-beta molecular sieve. However, the molecular sieve prepared by this method has a low Sn content and is prone to produce non-framework SnO2 species. In addition, a large amount of waste liquid is generated during the preparation process, the reactor utilization rate is low, and the preparation is relatively complicated.

[0005] Jo et al. reported a method for synthesizing mesoporous Sn-beta zeolite in “Synthesis of mesoporous zeolites in fluoride media with structure-directing multiammonium surfactants” in Microporous and Mesoporous Materials, Vol. 239. They used (C 22-6 )TMP(OH - )6 is a template agent, and a multi-level porous Sn-beta molecular sieve is synthesized by hydrothermal crystallization at 140 ° C for 7 days in a F ion system. However, this method requires the synthesis of a template agent with a complex structure first, which takes a long time to synthesize, has a high preparation cost, and requires the use of fluoride ions. Solvents are required during the synthesis process, and the synthesized molecular sieve has a low Sn content. Summary of the Invention

[0006] To address the shortcomings of the existing technology, the present invention provides a mesoporous Sn-beta molecular sieve, its synthesis method, and applications. The Sn-beta molecular sieve has a high framework Sn content, a high Lewis acid content, and a large number of mesopores within the molecular sieve crystals, resulting in excellent diffusion properties for reactant molecules. The mesoporous Sn-beta molecular sieve exhibits excellent catalytic performance in the Baeyer-Viiliger reaction of cyclohexanone, with high selectivity and yield for the reaction product, ε-caprolactone. The Sn-beta molecular sieve prepared using this method is simple to prepare, has a short preparation time, is low in cost, generates minimal wastewater, and poses minimal environmental pollution, making it suitable for large-scale industrial production.

[0007] A method for synthesizing a mesoporous Sn-beta molecular sieve, comprising the following steps:

[0008] (1) mixing H-beta molecular sieve, alkali, quaternary ammonium salt and anhydrous sodium stannate uniformly and then performing hydrothermal treatment;

[0009] (2) calcining the material after the hydrothermal treatment in step (1);

[0010] (3) The calcined material is washed, filtered, and dried to obtain the final mesoporous Sn-beta molecular sieve product.

[0011] In step (1) of the method of the present invention, the silicon-aluminum molar ratio (SiO2 / Al2O3) of the H-beta molecular sieve raw material is 50 to 80. The specific surface area of ​​the beta molecular sieve raw material is 520-610m 2 / g, the total pore volume is 0.30-0.36mL / g, and the mesopore volume is 0.11-0.17mL / g.

[0012] In step (1) of the method of the present invention, the base is a solid base, preferably an inorganic base, and the inorganic base used is one or more of sodium hydroxide, potassium hydroxide, and lithium hydroxide.

[0013] In step (1) of the method of the present invention, the quaternary ammonium salt is one or more of tetramethylammonium bromide, tetraethylammonium bromide and tetrapropylammonium bromide.

[0014] In step (1) of the method of the present invention, the molar ratio of the materials formed after the H-beta molecular sieve, alkali, quaternary ammonium salt and anhydrous sodium stannate are ground and mixed uniformly is (50-80)SiO2:Al2O3:(5-15)MOH:(10-20)QAC:(1.5-4.5)Na2SnO3, preferably (56-74)SiO2:Al2O3:(7-13)MOH:(12-18)QAC:(2.0-4.0)Na2SnO3, wherein MOH represents the alkali and QAC represents the quaternary ammonium salt.

[0015] In step (1) of the method of the present invention, H-beta molecular sieve, solid base, quaternary ammonium salt and anhydrous sodium stannate are ground and mixed uniformly in a glove box, and then transferred to a tubular furnace reactor, into which a mixture of inert gas and water vapor is introduced.

[0016] In step (1) of the method of the present invention, the inert gas introduced into the tubular furnace is one of nitrogen, helium, and argon, or a mixture thereof in any proportion.

[0017] In step (1) of the method of the present invention, the molar ratio of water vapor to inert gas introduced into the tube furnace is 3.0 to 6.0, preferably 3.5 to 5.5.

[0018] In step (1) of the method of the present invention, the hydrothermal treatment temperature is 160-210° C., preferably 170-200° C.; and the reaction time is 70-180 min, preferably 90-160 min.

[0019] In step (1) of the method of the present invention, after the mixed gas is introduced into the tubular furnace, the total pressure in the tubular furnace is controlled to be 0.01 to 0.03 MPa, preferably 0.014 to 0.026 MPa.

[0020] In step (2) of the method of the present invention, calcination is carried out in an atmosphere of a mixed gas containing oxygen, wherein the other gas is one of nitrogen, helium, and argon, or a mixture thereof in any proportion. In the mixed gas containing oxygen, the molar ratio of oxygen to the other gas is 0.33 to 1, preferably 0.46 to 0.87.

[0021] In step (2) of the method of the present invention, the calcination temperature is 450-550° C., preferably 470-530° C.; the calcination time is 100-200 min, preferably 120-180 min.

[0022] In step (2) of the method of the present invention, the calcination pressure is 0.03 to 0.08 MPa, preferably 0.04 to 0.07 MPa.

[0023] In step (3) of the method of the present invention, the material calcined in step (2) is sequentially washed with water, filtered, acid-washed, filtered and dried to obtain the final mesoporous Sn-beta molecular sieve product.

[0024] In step (3) of the method of the present invention, the acid used in the pickling step is one or a combination of sulfuric acid, nitric acid and hydrochloric acid.

[0025] In step (3) of the method of the present invention, the acid concentration in the pickling step is 4.0 mol / L to 6.0 mol / L, preferably 4.5 to 5.5 mol / L; the treatment temperature is 75 to 95° C., preferably 80 to 90° C.; the treatment time is 1 to 3 h, preferably 1.5 to 2.5 h; the solid-liquid mass ratio during treatment is 1:15 to 1:30, preferably 1:18 to 1:27; and the number of treatments is 1 to 2 times.

[0026] In step (3) of the method of the present invention, the drying temperature is 110-150° C., and the drying time is 3-6 hours.

[0027] A mesoporous Sn-beta molecular sieve prepared by the above method, wherein the total pore volume of the molecular sieve is 0.41-0.55 mL / g, preferably 0.44-0.51 mL / g; and the mesopore volume of the molecular sieve is 0.25-0.40 mL / g, preferably 0.28-0.37 mL / g.

[0028] In the above-mentioned mesoporous Sn-beta molecular sieve, the silicon-tin molar ratio (SiO2 / SnO2) is 30-60, preferably 40-50.

[0029] In the above-mentioned mesoporous Sn-beta molecular sieve, the silicon-aluminum molar ratio (SiO2 / Al2O3) is 3300-4300, preferably 3500-4100.

[0030] In the above-mentioned mesoporous Sn-beta molecular sieve, the Sn-beta molecular sieve has a pyridine infrared phosphine content of 400-600 μmol / g, preferably 450-550 μmol / g, at a desorption temperature of 200°C.

[0031] In the above Sn-beta mesoporous molecular sieve, the molecular sieve has a specific surface area of ​​510-600m 2 / g, preferably 540-570m 2 / g.

[0032] Application of the above-mentioned mesoporous Sn-beta molecular sieve in the Baeyer-Viiliger reaction of cyclohexanone.

[0033] The present invention first performs desiliconization treatment on a beta molecular sieve at low temperature in a water vapor atmosphere, and the combined treatment of a quaternary ammonium salt and an inorganic base can better construct mesoporous channels and silanol nest vacancies inside the beta molecular sieve; then, the quaternary ammonium salt is burned off at high temperature in an oxygen-containing atmosphere, and Sn is inserted into the vacancies of the silanol nests to obtain a Sn-beta molecular sieve with a mesoporous structure; finally, the mesoporous Sn-beta is subjected to acid dealumination treatment to obtain a mesoporous Sn-beta molecular sieve with a high silicon-to-aluminum ratio.

[0034] The method of the present invention has simple operation steps, short synthesis time, does not require the use of solvents, and limits the generation of wastewater to the greatest extent. Therefore, the method is green, economical and convenient. DETAILED DESCRIPTION

[0035] The characterization method of the mesoporous Sn-beta molecular sieve described in the present invention is as follows:

[0036] The specific surface area and pore volume of the molecular sieve were measured by N2-adsorption desorption method. Before the measurement, the sample was first pretreated at 300℃ for 3h, and then tested by nitrogen adsorption at 77K. The specific surface area of ​​the molecular sieve was calculated by BET method, and the total pore volume was calculated by p / p 0 =0.98, the micropore volume was obtained by t-Plot method, and the mesopore volume of the molecular sieve was obtained by subtracting the micropore volume from the total pore volume.

[0037] The mass percentages of Si, Al, and Sn in the molecular sieves were measured using inductively coupled plasma atomic emission spectroscopy (ICP-AES). Before testing, the molecular sieve solid powder was pretreated by adding the powder to a mixture of water, nitric acid, and hydrofluoric acid. The solution was heated at 150°C until the sample was completely dissolved and transformed into a transparent solution. After cooling, the solution was transferred to a volumetric flask, made up to volume with deionized water, and shaken. Quantitative analysis was then performed using a standard curve method. The measured elemental contents were then converted into silicon-aluminum molar ratios (SiO2 / Al2O3) and silicon-tin molar ratios (SiO2 / SnO2).

[0038] The L-acid content of the molecular sieve is measured by pyridine-infrared spectroscopy. The sample is prepared into a self-supporting sheet, heated to 500°C and maintained for 2 hours, then vacuumed. The sample is allowed to cool naturally and then adsorbed with pyridine for 30 minutes at room temperature. The sample is then heated to 200°C and vacuumed to remove the adsorbed pyridine molecules. The infrared spectrum of pyridine at this temperature is recorded, and the infrared L-acid content is obtained after integrating the peak area of ​​the spectrum.

[0039] The effects and benefits of the method of the present invention are further illustrated below with reference to examples and comparative examples, but the following examples do not constitute a limitation to the method of the present invention.

[0040] Example 1

[0041] (1) H-beta molecular sieve (silicon-aluminum molar ratio of 50, specific surface area of ​​605m 2 / g, total pore volume 0.32mL / g, mesopore volume 0.12mL / g), sodium hydroxide, tetraethylammonium bromide and anhydrous sodium stannate were ground and mixed in a glove box. The molar ratio of the material formed after grinding was 50SiO2:Al2O3:14.5NaOH:10TEA + :1.6Na2SnO3, and then transferred to a tubular furnace reactor, a mixed gas of water vapor and nitrogen with a molar ratio of 6.0 was introduced into the tubular furnace, and the reaction was carried out at 210°C for 180 minutes, and the total pressure in the tubular furnace was controlled to be 0.03MPa.

[0042] (2) Maintaining a reaction temperature of 210°C, a mixture of oxygen and helium at a molar ratio of 0.33 was introduced into the reactor. After the original mixed gas in the reactor was fully replaced, the temperature was raised to 450°C and the reaction was carried out for 100 minutes. During the reaction, the total pressure in the tubular furnace was 0.03 MPa. After the reaction was completed, the mixture was cooled to 30°C under the mixture of oxygen and helium, and the Al-containing Sn-beta molecular sieve was obtained.

[0043] (3) The Al-containing Sn-beta molecular sieve obtained was sequentially washed with water, filtered, and acid-washed (the acid-washing step used 6.0 mol / L nitric acid, the treatment temperature was 95°C, the treatment time was 3 h, the solid-liquid mass ratio was 1:30, and the treatment was repeated twice), filtered, and dried at 120°C for 4 h to obtain a dealuminated Sn-beta molecular sieve product.

[0044] Example 2

[0045] (1) H-beta molecular sieve (silicon-aluminum molar ratio of 80, specific surface area of ​​580m 2 / g, total pore volume 0.35mL / g, mesopore volume 0.16mL / g), potassium hydroxide, tetrapropylammonium bromide and anhydrous sodium stannate were ground and mixed in a glove box. The molar ratio of the material formed after grinding was 80SiO2:Al2O3:6.0KOH:20TPA + :4.3Na2SnO3, and then transferred to a tubular furnace reactor, into which a mixture of water vapor and nitrogen with a molar ratio of 6.0 was introduced, and the reaction was carried out at 165°C for 80 minutes, and the total pressure in the tubular furnace was controlled to be 0.01 MPa.

[0046] (2) Maintaining a reaction temperature of 165°C, a mixture of oxygen and helium at a molar ratio of 0.98 was introduced into the reactor. After the original mixed gas in the reactor was fully replaced, the temperature was raised to 550°C and the reaction was carried out for 200 minutes. The total pressure in the tubular furnace during the reaction was 0.08 MPa. After the reaction was completed, the mixture was cooled to 30°C under the mixture of oxygen and helium, and the Al-containing Sn-beta molecular sieve was obtained.

[0047] (3) The Al-containing Sn-beta molecular sieve obtained was sequentially washed with water, filtered, and acid-washed (the acid-washing step used 4.2 mol / L nitric acid, the treatment temperature was 75°C, the treatment time was 1 hour, the solid-liquid mass ratio was 1:16, and the treatment was performed once), filtered, and dried at 120°C for 4 hours to obtain a dealuminated Sn-beta molecular sieve product.

[0048] Example 3

[0049] (1) H-beta molecular sieve (silicon-aluminum molar ratio of 60, specific surface area of ​​576m 2 / g, total pore volume 0.34mL / g, mesopore volume 0.14mL / g), sodium hydroxide, tetrapropylammonium bromide and anhydrous sodium stannate were ground and mixed in a glove box. The molar ratio of the material formed after grinding was 60SiO2:Al2O3:12.0NaOH:14.0TPA + :2.5Na2SnO3, and then transferred to a tubular furnace reactor, into which a mixture of water vapor and nitrogen with a molar ratio of 5.3 was introduced, and the reaction was carried out at 200°C for 90 minutes, and the total pressure in the tubular furnace was controlled to be 0.026MPa.

[0050] (2) Maintaining a reaction temperature of 200°C, a mixture of oxygen and helium with a molar ratio of 0.50 was introduced into the reactor. After the original mixed gas in the reactor was fully replaced, the temperature was raised to 470°C and the reaction was carried out for 120 minutes. The total pressure in the tubular furnace during the reaction was 0.045 MPa. After the reaction was completed, the mixture was cooled to 30°C under the mixture of oxygen and helium, and the Al-containing Sn-beta molecular sieve was obtained.

[0051] (3) The Al-containing Sn-beta molecular sieve obtained was sequentially washed with water, filtered, and acid-washed (the acid-washing step used 5.2 mol / L nitric acid, the treatment temperature was 90°C, the treatment time was 2.0 h, the solid-liquid mass ratio was 1:25, and the treatment was repeated twice), filtered, and dried at 120°C for 4 h to obtain a dealuminated Sn-beta molecular sieve product.

[0052] Example 4

[0053] (1) H-beta molecular sieve (silicon-aluminum molar ratio of 70, specific surface area of ​​606m 2 / g, total pore volume 0.35mL / g, mesopore volume 0.15mL / g), sodium hydroxide, tetraethylammonium bromide and anhydrous sodium stannate were ground and mixed in a glove box. The molar ratio of the material formed after grinding was 70SiO2:Al2O3:7.0NaOH:17.4TEA + :4.0Na2SnO3, and then transferred to a tubular furnace reactor, into which a mixture of water vapor and nitrogen with a molar ratio of 3.5 was introduced, and the reaction was carried out at 175°C for 155 minutes, and the total pressure in the tubular furnace was controlled to be 0.015MPa.

[0054] (2) Maintaining a reaction temperature of 175°C, a mixture of oxygen and helium with a molar ratio of 0.84 was introduced into the reactor. After the original mixed gas in the reactor was fully replaced, the temperature was raised to 530°C and the reaction was carried out for 180 minutes. During the reaction, the total pressure in the tubular furnace was 0.065 MPa. After the reaction was completed, the mixture was cooled to 30°C under the mixture of oxygen and helium, and the Al-containing Sn-beta molecular sieve was obtained.

[0055] (3) The Al-containing Sn-beta molecular sieve obtained was sequentially washed with water, filtered, and acid-washed (the acid-washing step used 4.6 mol / L nitric acid, the treatment temperature was 80°C, the treatment time was 2.0 h, the solid-liquid mass ratio was 1:20, and the treatment was repeated twice), filtered, and dried at 120°C for 4 h to obtain a dealuminated Sn-beta molecular sieve product.

[0056] Comparative Example 1 (Comparative Example 1, only high temperature treatment)

[0057] (1) H-beta molecular sieve (silicon-aluminum molar ratio of 50, specific surface area of ​​605m 2 / g, total pore volume 0.32mL / g, mesopore volume 0.12mL / g), sodium hydroxide, tetraethylammonium bromide and anhydrous sodium stannate were ground and mixed in a glove box. The molar ratio of the material formed after grinding was 50SiO2:Al2O3:14.5NaOH:10TEA + :1.6Na2SnO3.

[0058] (2) The material from step (1) was placed in a tubular furnace, and a mixture of oxygen and helium with a molar ratio of 0.33 was introduced into the reactor. The reaction was carried out at 450° C. for 100 min. The total pressure in the tubular furnace during the reaction was 0.03 MPa. After the reaction was completed, the mixture was cooled to 30° C. under the mixture of oxygen and helium, and the Al-containing Sn-beta molecular sieve was obtained.

[0059] (3) The Al-containing Sn-beta molecular sieve obtained was sequentially washed with water, filtered, and acid-washed (the acid-washing step used 6.0 mol / L nitric acid, the treatment temperature was 95°C, the treatment time was 3 h, the solid-liquid mass ratio was 1:30, and the treatment was repeated twice), filtered, and dried at 120°C for 4 h to obtain a dealuminated Sn-beta molecular sieve product.

[0060] Comparative Example 2 (Comparative Example 1, only low temperature treatment)

[0061] (1) H-beta molecular sieve (silicon-aluminum molar ratio of 50, specific surface area of ​​605m 2 / g, total pore volume 0.32mL / g, mesopore volume 0.12mL / g), sodium hydroxide, tetraethylammonium bromide and anhydrous sodium stannate were ground and mixed in a glove box. The molar ratio of the material formed after grinding was 50SiO2:Al2O3:14.5NaOH:10TEA + :1.6Na2SnO3, and then transferred to a tubular furnace reactor, a mixed gas of water vapor and nitrogen with a molar ratio of 6.0 was introduced into the tubular furnace, and the reaction was carried out at 210°C for 180 minutes, and the total pressure in the tubular furnace was controlled to be 0.03MPa.

[0062] (2) The material of step (1) was sequentially washed with water, filtered, pickled (the pickling step used 6.0 mol / L nitric acid, the treatment temperature was 95 ° C, the treatment time was 3 h, the solid-liquid mass ratio was 1:30, and the treatment was repeated twice), filtered and dried at 120 ° C for 4 h to obtain a dealuminated Sn-beta molecular sieve product.

[0063] Table 1 Structural properties of products in Examples and Comparative Examples

[0064]

Claims

1. A method for synthesizing a mesoporous Sn-beta molecular sieve, characterized by: The method comprises the following steps: (1) H-beta molecular sieve, alkali, quaternary ammonium salt and anhydrous sodium stannate are uniformly mixed and then subjected to hydrothermal treatment; (2) calcining the material after the hydrothermal treatment in step (1); (3) The calcined material is washed, filtered, and dried to obtain the final mesoporous Sn-beta molecular sieve product.

2. The method according to claim 1, wherein: The silicon-aluminum molar ratio (SiO2 / Al2O3) of the H-beta molecular sieve raw material in step (1) is 50-80. The specific surface area of ​​the beta molecular sieve raw material is 520-610m 2 / g, the total pore volume is 0.30-0.36mL / g, and the mesopore volume is 0.11-0.17mL / g.

3. The method according to claim 1, wherein: The base in step (1) is a solid base, preferably an inorganic base, and the inorganic base used is one or more of sodium hydroxide, potassium hydroxide, and lithium hydroxide.

4. The method according to claim 1, wherein: The quaternary ammonium salt in step (1) is one or more of tetramethylammonium bromide, tetraethylammonium bromide and tetrapropylammonium bromide.

5. The method according to claim 1, wherein: The molar ratio of the materials formed after the H-beta molecular sieve, alkali, quaternary ammonium salt and anhydrous sodium stannate are ground and mixed uniformly in step (1) is (50~80)SiO2: Al2O3: (5~15)MOH: (10~20)QAC: (1.5~4.5)Na2SnO3, preferably (56~74)SiO2: Al2O3: (7~13)MOH: (12~18)QAC: (2.0~4.0)Na2SnO3, wherein MOH represents alkali and QAC represents quaternary ammonium salt.

6. The method according to claim 1, wherein: In step (1), H-beta molecular sieve, solid base, quaternary ammonium salt and anhydrous sodium stannate are ground and mixed uniformly in a glove box, and then transferred to a tubular furnace reactor, into which a mixture of inert gas and water vapor is introduced.

7. The method according to claim 1, wherein: The inert gas introduced into the tubular furnace in step (1) is one of nitrogen, helium, and argon, or a mixture thereof in any proportion.

8. The method according to claim 1, wherein: The molar ratio of water vapor to inert gas introduced into the tube furnace in step (1) is 3.0-6.0, preferably 3.5-5.

5.

9. The method according to claim 1, wherein: In step (1), the hydrothermal treatment temperature is 160-210° C., preferably 170-200° C.; the reaction time is 70-180 min, preferably 90-160 min.

10. The method according to claim 1, wherein: After the mixed gas is introduced into the tubular furnace in step (1), the total pressure in the tubular furnace is controlled to be 0.01~0.03MPa, preferably 0.014~0.026MPa.

11. The method according to claim 1, wherein: In step (2), the calcination is carried out in an atmosphere of a mixed gas containing oxygen, and the other gas is one of nitrogen, helium, and argon, or a mixture thereof in any proportion. In the mixed gas containing oxygen, the molar ratio of oxygen to the other gas is 0.33 to 1, preferably 0.46 to 0.

87.

12. The method according to claim 1, wherein: In step (2), the calcination temperature is 450-550°C, preferably 470-530°C; the calcination time is 100-200 min, preferably 120-180 min.

13. The method according to claim 1, wherein: The calcination pressure in step (2) is 0.03~0.08MPa, preferably 0.04~0.07MPa.

14. The method according to claim 1, wherein: The material after calcination in step (3) is sequentially washed with water, filtered, acid-washed, filtered and dried to obtain the final mesoporous Sn-beta molecular sieve product.

15. The method according to claim 1, wherein: The acid used in the pickling step in step (3) is one or a combination of sulfuric acid, nitric acid and hydrochloric acid.

16. The method according to claim 1, wherein: The acid concentration in the pickling step in step (3) is 4.0 mol / L~6.0 mol / L, preferably 4.5~5.5 mol / L; the treatment temperature is 75~95°C, preferably 80~90°C; the treatment time is 1~3 h, preferably 1.5~2.5 h; the solid-liquid mass ratio during the treatment is 1:15~1:30, preferably 1:18~1:27; and the number of treatments is 1~2 times.

17. The method according to claim 1, wherein: The drying temperature in step (3) is 110-150° C., and the drying time is 3-6 hours.

18. A mesoporous Sn-beta molecular sieve prepared by the method according to any one of claims 1 to 17, characterized in that: The total pore volume of the molecular sieve is 0.41-0.55 mL / g, preferably 0.44-0.51 mL / g; the mesopore volume of the molecular sieve is 0.25-0.40 mL / g, preferably 0.28-0.37 mL / g.

19. The mesoporous Sn-beta molecular sieve according to claim 18, characterized in that: In the mesoporous Sn-beta molecular sieve, the silicon-tin molar ratio (SiO2 / SnO2) is 30-60, preferably 40-50.

20. The mesoporous Sn-beta molecular sieve according to claim 18, characterized in that: In the mesoporous Sn-beta molecular sieve, the silicon-aluminum molar ratio (SiO2 / Al2O3) is 3300-4300, preferably 3500-4100.

21. The mesoporous Sn-beta molecular sieve according to claim 18, characterized in that: In the mesoporous Sn-beta molecular sieve, the Sn-beta molecular sieve has a pyridine infrared phosphine content of 400-600 μmol / g, preferably 450-550 μmol / g, at a desorption temperature of 200°C.

22. The mesoporous Sn-beta molecular sieve according to claim 18, characterized in that: Sn-beta mesoporous molecular sieve, the molecular sieve has a specific surface area of ​​510-600m 2 / g, preferably 540-570m 2 / g.

23. Use of the mesoporous Sn-beta molecular sieve according to any one of claims 18 to 22 in the Baeyer-Viiliger reaction of cyclohexanone.

Images