Sn-beta molecular sieve as well as preparation method and application thereof
By concentrating the distribution of tin atoms on the outer surface of the Sn-beta molecular sieve, the problem of uneven distribution of tin atoms is solved, the activity and selectivity of the catalytic reaction are improved, and the preparation cost is reduced.
Patent Information
- Application Number
- CN202410187142.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-02-20
- Publication Date
- 2025-08-22
AI Technical Summary
The uneven distribution of tin atoms in existing Sn-beta molecular sieves leads to low utilization efficiency of reactive sites and limits the reaction effect.
The tin atoms are concentrated on the outer surface of the molecular sieve through ion exchange, desiliconization and solid phase reaction, and combined with dealumination treatment, forming an efficient Sn-beta molecular sieve.
The proximity and utilization of reactants of Sn-beta molecular sieve to reactants and the utilization rate of active sites are improved, the activity and selectivity of catalytic reactions are enhanced, and the preparation cost is reduced.
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Abstract
Description
Technical Field
[0001] The present invention belongs to the field of molecular sieve synthesis, and relates to a heteroatom beta molecular sieve and a preparation method and application thereof, and in particular to a Sn-beta molecular sieve and a preparation method and application thereof. Background Art
[0002] Heteroatom molecular sieves are molecular sieves containing other elements formed by isomorphously replacing some silicon, aluminum, or phosphorus atoms in the molecular sieve framework with other heteroatoms. Since the introduction of heteroatoms into the molecular sieve framework often causes a certain degree of change in the original structure and properties of the molecular sieve (such as acidity, particle size, pore properties, etc.), in recent years, it has gradually overcome the limitations on the use of traditional silicon-aluminum molecular sieves and broadened the application field of molecular sieves. The synthesis of heteroatom molecular sieves is also regarded as an important branch of the molecular sieve synthesis field with potential commercial value, and is currently receiving increasing attention.
[0003] Since the successful synthesis of TS-1 molecular sieve, people have prepared a variety of heteroatom (such as tin, iron, gallium, zirconium, vanadium, etc.) molecular sieves, among which the synthesis of tin-based molecular sieves has attracted much attention. In 1997, Sn-beta molecular sieve was synthesized. Since Sn is embedded in the molecular sieve framework, it provides the molecular sieve with a unique Lewis acid center, which can be used to catalyze a variety of chemical reactions, such as Baeyer-Viiliger catalytic oxidation, Meerwein–Ponndorf–Verley (MPV) reduction reaction, glucose isomerization to produce fructose, sugar conversion to produce lactic acid derivatives, etc. It is a very promising new molecular sieve material. However, since the radius size of Sn atoms does not match the radius of Si and Al atoms in molecular sieves, it is quite difficult to embed Sn atoms into the framework of silicon-aluminum molecular sieves.
[0004] Avelino Corma et al. reported a Sn-beta molecular sieve and its synthesis method in "Sn-zeolite beta as a heterogeneous chemoselective catalyst for Baeyer-Villiger oxidations," Volume 412 of Nutrients. Using tetraethyl orthosilicate (TEOS) as a silicon source, SnCl₄·5H₂O as a tin source, and HF as a mineralizer, the Sn-beta molecular sieve was crystallized at high temperature for 20 days with the aid of dealuminated nano-beta seeds. However, the resulting molecular sieve had a low framework tin content, and the framework Sn atoms were largely distributed within the beta molecular sieve. During the reaction, the Sn-containing active sites were affected by diffusion rates when contacting the reactants, resulting in inefficient utilization of the Sn atoms.
[0005] Ceri Hammond et al. reported a Sn-beta molecular sieve and a method for synthesizing it in "Simple and Scalable Preparation of Highly Active Lewis Acidic Sn-beta", Volume 51 of "ANGEWANDTE CHEMIE-INTERNATIONAL EDITION". This document deals with acid dealumination of an H-beta molecular sieve, then grinds the dealuminated beta molecular sieve with tin acetate. After uniform grinding, the mixture is calcined in an air atmosphere at high temperature for a period of time to obtain a Sn-beta molecular sieve with a high Sn content. However, the molecular sieve synthesized by this method has framework Sn present in both the interior and outer layers of the molecular sieve, which is easily affected by the diffusion rate. In addition, the molecular sieve contains a large amount of non-framework tin, resulting in low activity during the reaction. Summary of the Invention
[0006] In response to the deficiencies in the prior art, the present invention provides a Sn-beta molecular sieve, a preparation method thereof, and an application thereof. In the Sn-beta molecular sieve, the Sn species are mainly concentrated on the outer surface of the beta molecular sieve, and the internal Sn species are relatively small. This makes the Lewis acidic sites of the Sn-beta molecular sieve of the present invention mainly concentrated on the surface of the molecular sieve, which has better accessibility to the reactant molecules and is almost not limited by the diffusion rate during the reaction process. The Sn species that provide Lewis acidic sites are efficiently utilized.
[0007] In a Sn-beta molecular sieve, the surface silicon-tin molar ratio (SiO2 / SnO2) is 30-50, preferably 35-45, and the bulk silicon-tin molar ratio (SiO2 / SnO2) is 170-250, preferably 190-230.
[0008] In the above Sn-beta molecular sieve, the pyridine infrared phosphine content of the molecular sieve at a desorption temperature of 200° C. is 100-200 μmol / g, preferably 130-170 μmol / g.
[0009] In the above Sn-beta molecular sieve, the pyridine infrared L acid / B acid content ratio of the molecular sieve at a desorption temperature of 200° C. is 110-150, preferably 125-135.
[0010] In the above Sn-beta molecular sieve, the bulk silicon-to-aluminum ratio (SiO2 / Al2O3) of the molecular sieve is 3000-4000.
[0011] In the above Sn-beta molecular sieve, the molecular sieve has a specific surface area of 500-600m 2 / g, preferably 530-570m 2 / g.
[0012] In the above Sn-beta molecular sieve, the molecular sieve pore volume is 0.30-0.40 mL / g, preferably 0.33-0.37 mL / g.
[0013] The preparation method of the above-mentioned Sn-beta molecular sieve comprises the following steps:
[0014] 1) performing ion exchange on the beta molecular sieve in an aqueous solution containing quaternary ammonium salt cations, and washing, filtering, and drying the exchanged molecular sieve;
[0015] 2) weighing the quaternary ammonium salt cation-exchanged beta molecular sieve obtained in step 1) and the dried sodium bromide powder, grinding and mixing them uniformly in a glove box, and then transferring them to a tubular furnace reactor, introducing an inert gas into one end of the tubular furnace and venting the other end, then maintaining the inert gas circulation state in the furnace, heating to a certain temperature for reaction, cooling after the reaction, taking out the solid, washing, filtering, and drying to obtain the Na ion-exchanged beta molecular sieve;
[0016] 3) placing the Na ion-exchanged beta molecular sieve obtained in step 2) in ammonia water of a certain concentration for desiliconization, filtering and washing after the treatment to obtain the desiliconized beta molecular sieve;
[0017] 4) Grinding and mixing the desiliconized beta molecular sieve and anhydrous stannous chloride powder in a glove box until uniformly mixed, and then transferring the mixture to a tubular furnace reactor. Inert gas is introduced into the tubular furnace, and the temperature is increased to react for a period of time. The temperature is then lowered, the product is removed, and the mixture is washed, filtered, and dried.
[0018] 5) calcining the material obtained in step 4) in an air atmosphere for a period of time.
[0019] 6) The material obtained in step 5) is treated in an aqueous solution containing an acid, filtered, and washed to obtain a dealuminated Sn-beta molecular sieve product.
[0020] In step 1) of the method of the present invention, the silicon-aluminum ratio (SiO2 / Al2O3) of the beta molecular sieve is 50-80, preferably 60-70.
[0021] In step 1) of the method of the present invention, the quaternary ammonium salt is one or a combination of tetramethylammonium bromide, tetraethylammonium bromide and tetrapropylammonium bromide.
[0022] In step 1) of the method of the present invention, the concentration of the quaternary ammonium salt aqueous solution is 1.5-3.5 mol / L, preferably 2.0-3.0 mol / L; the ion exchange temperature is 75-95° C., preferably 80-90° C.; and the number of exchanges is 1-3 times.
[0023] In step 2) of the method of the present invention, the mass ratio of the sodium bromide to the beta molecular sieve after quaternary ammonium salt cation exchange is 0.02 to 0.09, preferably 0.04 to 0.07. The inert gas introduced into the tubular furnace is one of nitrogen, helium, and argon, or a mixture thereof in any proportion.
[0024] In step 2) of the method of the present invention, the reaction temperature is 350-450° C., preferably 370-430° C., and the reaction time is 60-150 min, preferably 80-130 min.
[0025] In step 3) of the method of the present invention, the mass concentration of the ammonia water is 15 to 25 wt%, preferably 18 to 22 wt%.
[0026] In step 3) of the method of the present invention, in the desiliconization treatment of the molecular sieve, the solid-liquid mass ratio of the beta molecular sieve after Na ion exchange and the ammonia solution is 1:5 to 1:17, preferably 1:8 to 1:14.
[0027] In step 3) of the method of the present invention, the desiliconization treatment of the molecular sieve is performed at a temperature of 40 to 70° C., preferably 50 to 60° C., for a time of 40 to 90 minutes, preferably 50 to 80 minutes, and is repeated 1 to 2 times.
[0028] In step 4) of the method of the present invention, the mass ratio of the anhydrous stannous chloride to the desiliconized beta molecular sieve is between 0.10 and 0.30, preferably between 0.15 and 0.25. The inert gas introduced into the tube furnace is one of nitrogen, helium, and argon, or a mixture thereof in any proportion.
[0029] In step 4) of the method of the present invention, the reaction temperature is 400-500° C., preferably 430-470° C.; the reaction time is 80-150 min, preferably 100-130 min.
[0030] In step 5) of the method of the present invention, the calcination temperature in air is 500-550° C., and the calcination time is 3-6 hours.
[0031] In step 6) of the method of the present invention, the acid is one or more of hydrochloric acid, nitric acid, and sulfuric acid.
[0032] In step 6) of the method of the present invention, the acid concentration is 2.0 mol / L to 3.0 mol / L, preferably 2.3 to 2.8 mol / L; the treatment temperature is 50 to 90° C., preferably 70 to 80° C.; the treatment time is 1 to 4 hours, preferably 2 to 3 hours; the solid-liquid mass ratio during treatment is 1:10 to 1:30, preferably 1:15 to 1:20; and the number of treatments is 1-3 times.
[0033] Application of the above Sn-beta molecular sieve in the Baeyer-Viiliger reaction of cyclohexanone.
[0034] This synthesis method exchanges the cations on the beta molecular sieve for quaternary ammonium salt cations through ion exchange in aqueous solution, and then exchanges the quaternary ammonium salt cations on the outer layer of the beta molecular sieve for sodium ions by means of solid phase ion exchange through precise control of the reaction conditions, thus obtaining a quaternary ammonium salt with Na on the outer layer. + , beta molecular sieve with quaternary ammonium salt cations inside. The beta molecular sieve is desiliconized using the weak alkalinity of ammonia. Because the internal framework silicon is protected by the quaternary ammonium salt cations, ammonia selectively removes the framework silicon atoms on the outer surface of the beta molecular sieve, forming silanol vacancies in the outer layer of the molecular sieve. Sn atoms are then implanted into the outer framework of the molecular sieve through a high-temperature solid-solid phase reaction. Finally, the quaternary ammonium salt cations are burned off, and the molecular sieve is dealuminated to obtain the final Sn-beta molecular sieve product.
[0035] The Sn-beta molecular sieve provided by the present invention has improved activity in the Baeyer-Viiliger reaction of cyclohexanone, and has high selectivity and yield for the reaction product, ε-caprolactone. The Sn-beta molecular sieve prepared using this method is simple to operate, has a short preparation time, and is low in cost, making it suitable for industrial production needs. DETAILED DESCRIPTION
[0036] The characterization method of Sn-beta molecular sieve described in the present invention is as follows:
[0037] 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, and the external specific surface area was obtained by t-Plot method.
[0038] 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).
[0039] X-ray photoelectron spectroscopy (XPS) was used to characterize the elemental content on the molecular sieve surface. XPS characterization was performed on a Kratos Axis ultra X-ray photoelectron spectrometer using an Al Kα (1486.6 eV) excitation source. The XPS spectrum was calibrated with C1s (284.8 eV) binding energy, and the silicon-to-aluminum ratio and silicon-to-tin ratio on the molecular sieve surface were then converted.
[0040] The L-acid and B-acid contents of the molecular sieve were measured by pyridine-infrared spectroscopy. The sample was prepared into a self-supporting sheet, heated to 500°C and maintained for 2 hours, then vacuumed. The sample was allowed to cool naturally and then adsorbed with pyridine for 30 minutes at room temperature. The sample was then heated to 200°C and vacuumed to remove the adsorbed pyridine molecules. The infrared spectrum of pyridine at this temperature was recorded, and the infrared L-acid and B-acid contents were obtained after integrating the peak area of the spectrum.
[0041] 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.
[0042] Example 1
[0043] (1) Beta molecular sieve with a silicon-aluminum ratio (SiO2 / Al2O3) of 50 was ion exchanged in a 3.5 mol / L tetraethylammonium bromide aqueous solution at a temperature of 95°C for three exchanges. The exchanged molecular sieve was washed, filtered, and then dried at 120°C for 8 h.
[0044] (2) Weigh the ion-exchanged beta molecular sieve and sodium bromide powder dried at 120°C and grind and mix them evenly in a glove box. The mass ratio of sodium bromide to beta molecular sieve is controlled at 0.09. The mixture is then transferred to a tubular furnace reactor. Nitrogen is introduced into one end of the tubular furnace and vented from the other end. The furnace is then heated to 450°C and reacted for 150 minutes while maintaining nitrogen flow. After the reaction is completed, the temperature is lowered, the solid is removed, washed, filtered, and dried at 120°C to obtain the Na ion-exchanged beta molecular sieve.
[0045] (3) The Na-exchanged beta molecular sieve was placed in ammonia water with a mass concentration of 25 wt% for desiliconization treatment. The solid-liquid mass ratio of the molecular sieve to the ammonia water was 1:17. The treatment temperature was 70 ° C. The treatment time was 90 min, and the treatment was repeated twice.
[0046] (4) The desiliconized beta molecular sieve and anhydrous stannous chloride powder were ground and mixed uniformly in a glove box, with the mass ratio of anhydrous stannous chloride to desiliconized beta molecular sieve being 0.30. The mixture was then transferred to a tubular furnace reactor, nitrogen was introduced into the tubular furnace, and the reaction was carried out at 500°C for 150 minutes. The product was then cooled and taken out. After washing, filtering, and drying at 120°C, Sn-beta molecular sieve was obtained.
[0047] (5) The Sn-beta molecular sieve was calcined in air at a high temperature of 530°C for 4 hours. (6) The Sn-beta molecular sieve was treated in 3.0 mol / L nitric acid at a temperature of 90°C for 4 hours with a solid-liquid mass ratio of 1:30, and the product was filtered and washed to obtain a dealuminated Sn-beta molecular sieve product.
[0048] Example 2
[0049] (1) Beta molecular sieve with a silicon-aluminum ratio (SiO2 / Al2O3) of 80 was ion exchanged in a 1.5 mol / L tetraethylammonium bromide aqueous solution at a temperature of 75°C and once. The exchanged molecular sieve was washed, filtered, and then dried at 120°C for 8 h.
[0050] (2) Weigh the ion-exchanged beta molecular sieve and sodium bromide powder dried at 120°C and grind and mix them evenly in a glove box. The mass ratio of sodium bromide to beta molecular sieve is controlled at 0.02. The mixture is then transferred to a tubular furnace reactor. Nitrogen is introduced into one end of the tubular furnace and vented from the other end. The furnace is then heated to 350°C and reacted for 60 minutes while maintaining nitrogen flow. After the reaction is completed, the temperature is lowered, the solid is removed, washed, filtered, and dried at 120°C to obtain the Na ion-exchanged beta molecular sieve.
[0051] (3) The Na-exchanged beta molecular sieve was placed in ammonia water with a mass concentration of 15 wt% for desiliconization treatment. The solid-liquid mass ratio of the molecular sieve and the ammonia water was 1:5. The treatment temperature was 40 ° C. The treatment time was 40 min, and the treatment was performed once.
[0052] (4) The desiliconized beta molecular sieve and anhydrous stannous chloride powder were ground and mixed uniformly in a glove box, with the mass ratio of anhydrous stannous chloride to desiliconized beta molecular sieve being 0.10. The mixture was then transferred to a tubular furnace reactor, nitrogen was introduced into the tubular furnace, and the reaction was carried out at 410°C for 90 minutes. The product was then cooled and taken out. After washing, filtering, and drying at 120°C, Sn-beta molecular sieve was obtained.
[0053] (5) The Sn-beta molecular sieve was calcined in air at a high temperature of 530°C for 4 hours. (6) The Sn-beta molecular sieve was treated in 2.0 mol / L nitric acid at a temperature of 50°C for 1 hour with a solid-liquid mass ratio of 1:10 for 3 times, and then filtered and washed to obtain a dealuminated Sn-beta molecular sieve product.
[0054] Example 3
[0055] (1) Beta molecular sieve with a silicon-aluminum ratio (SiO2 / Al2O3) of 60 was ion exchanged in a 2.2 mol / L tetraethylammonium bromide aqueous solution at a temperature of 80°C for two exchanges. The exchanged molecular sieve was washed, filtered, and then dried at 120°C for 8 h.
[0056] (2) Weigh the ion-exchanged beta molecular sieve and sodium bromide powder dried at 120°C and grind and mix them evenly in a glove box. The mass ratio of sodium bromide to beta molecular sieve is controlled at 0.065. The mixture is then transferred to a tubular furnace reactor. Nitrogen is introduced into one end of the tubular furnace and vented from the other end. The furnace is then heated to 390°C and reacted for 130 minutes while maintaining nitrogen flow. After the reaction is completed, the temperature is lowered, the solid is removed, washed, filtered, and dried at 120°C to obtain the Na ion-exchanged beta molecular sieve.
[0057] (3) The Na-exchanged beta molecular sieve was placed in ammonia water with a mass concentration of 18 wt% for desiliconization treatment. The solid-liquid mass ratio of the molecular sieve to the ammonia water was 1:10, the treatment temperature was 60 ° C, the treatment time was 50 min, and the treatment was performed once.
[0058] (4) The desiliconized beta molecular sieve and anhydrous stannous chloride powder were ground and mixed uniformly in a glove box, with the mass ratio of anhydrous stannous chloride to desiliconized beta molecular sieve being 0.15. The mixture was then transferred to a tubular furnace reactor, nitrogen was introduced into the tubular furnace, and the reaction was carried out at 430°C for 130 minutes. The product was then cooled and taken out. After washing, filtering, and drying at 120°C, Sn-beta molecular sieve was obtained.
[0059] (5) The Sn-beta molecular sieve was calcined in air at a high temperature of 530°C for 4 hours. (6) The Sn-beta molecular sieve was treated in 2.8 mol / L nitric acid at a temperature of 80°C for 3 hours with a solid-liquid mass ratio of 1:20 for 3 times, and then filtered and washed to obtain a dealuminated Sn-beta molecular sieve product.
[0060] Example 4
[0061] (1) Beta molecular sieve with a silicon-aluminum ratio (SiO2 / Al2O3) of 70 was ion exchanged in a 2.8 mol / L tetraethylammonium bromide aqueous solution at a temperature of 90°C for three exchanges. The exchanged molecular sieve was washed, filtered, and then dried at 120°C for 8 h.
[0062] (2) Weigh the ion-exchanged beta molecular sieve and sodium bromide powder dried at 120°C and grind and mix them evenly in a glove box. The mass ratio of sodium bromide to beta molecular sieve is controlled at 0.045. The mixture is then transferred to a tubular furnace reactor. Nitrogen is introduced into one end of the tubular furnace and vented from the other end. The furnace is then heated to 430°C and reacted for 100 minutes while maintaining nitrogen flow. After the reaction is completed, the temperature is lowered, the solid is removed, washed, filtered, and dried at 120°C to obtain the Na ion-exchanged beta molecular sieve.
[0063] (3) The Na-exchanged beta molecular sieve was placed in ammonia water with a mass concentration of 22 wt% for desiliconization treatment. The solid-liquid mass ratio of the molecular sieve and the ammonia water was 1:14, the treatment temperature was 55 ° C, the treatment time was 80 min, and the treatment was performed once.
[0064] (4) The desiliconized beta molecular sieve and anhydrous stannous chloride powder were ground and mixed uniformly in a glove box. The mass ratio of anhydrous stannous chloride to desiliconized beta molecular sieve was 0.22. The mixture was then transferred to a tubular furnace reactor. Nitrogen was introduced into the tubular furnace. The reaction was carried out at 470°C for 130 minutes. The product was then cooled and taken out. After washing, filtering, and drying at 120°C, Sn-beta molecular sieve was obtained.
[0065] (5) The Sn-beta molecular sieve was calcined in air at a high temperature of 530°C for 4 hours. (6) The Sn-beta molecular sieve was treated in 2.3 mol / L nitric acid at a temperature of 80°C for 3 hours with a solid-liquid mass ratio of 1:17 for 3 times, and then filtered and washed to obtain a dealuminated Sn-beta molecular sieve product.
[0066] Comparative Example 1 (Comparative Example 1, beta molecular sieve was not treated before desiliconization)
[0067] (1) Beta molecular sieve with a silicon-aluminum ratio (SiO2 / Al2O3) of 50 was placed in ammonia water with a mass concentration of 25wt% for desiliconization treatment. The solid-liquid mass ratio of the molecular sieve to the ammonia water was 1:17. The treatment temperature was 70℃, the treatment time was 90min, and the treatment was repeated twice.
[0068] (2) The desiliconized beta molecular sieve and anhydrous stannous chloride powder were ground and mixed uniformly in a glove box, with the mass ratio of anhydrous stannous chloride to desiliconized beta molecular sieve being 0.30. The mixture was then transferred to a tubular furnace reactor, nitrogen was introduced into the tubular furnace, and the reaction was carried out at 500°C for 150 minutes. The product was then cooled and taken out. After washing, filtering, and drying at 120°C, Sn-beta molecular sieve was obtained.
[0069] (3) The Sn-beta molecular sieve was calcined in air at a high temperature of 530°C for 4 hours. (4) The Sn-beta molecular sieve was treated in 2.0 mol / L nitric acid at a temperature of 50°C for 1 hour with a solid-liquid mass ratio of 1:10, and the product was filtered and washed to obtain a dealuminated Sn-beta molecular sieve product.
[0070] The performance of the Sn-beta molecular sieves in the examples and comparative examples was evaluated using the Baeyer-Villiger reaction of cyclohexanone and hydrogen peroxide (35 wt%). The reaction was conducted in a 50 ml round-bottom flask with a condenser water cooler. 400 mg of the catalyst was weighed and added to the flask. Then, 5 mL of 1,4-dioxane (solvent), 2 mmol of cyclohexanone, 2 mmol of H2O2 (30 wt%), and 0.23 g of chlorobenzene (internal standard) were added. The reaction solution was placed in a 90°C oil bath for 2 h. After completion of the reaction, the solution was cooled to room temperature and centrifuged. The supernatant was analyzed by gas chromatography for cyclohexanone conversion, selectivity for the target product ε-caprolactone, and yield. The evaluation results are shown in Table 2.
[0071] Table 1 Structural properties of products in Examples and Comparative Examples
[0072]
[0073] Table 2 Performance evaluation results of molecular sieves in Examples and Comparative Examples
[0074] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Cyclohexanone conversion, % 44.1 42.3 46.6 45.7 39.8 ε-caprolactone selectivity, % 90.3 93.6 95.4 94.1 85.7 ε-caprolactone yield, % 39.8 39.6 44.5 43.0 34.1
Claims
1. A Sn-beta molecular sieve, characterized in that: The surface silicon-tin molar ratio (SiO2 / SnO2) is 30-50, preferably 35-45, and the bulk silicon-tin molar ratio (SiO2 / SnO2) is 170-250, preferably 190-230.
2. The Sn-beta molecular sieve according to claim 1, characterized in that: The molecular sieve has a pyridine infrared phosphodiester acid content of 100-200 μmol / g, preferably 130-170 μmol / g, at a desorption temperature of 200°C.
3. The Sn-beta molecular sieve according to claim 1, characterized in that: The molecular sieve has a pyridine infrared L acid / B acid content ratio of 110-150, preferably 125-135, at a desorption temperature of 200°C.
4. The Sn-beta molecular sieve according to claim 1, characterized in that: The bulk silicon-aluminum ratio (SiO2 / Al2O3) of the molecular sieve is 3000-4000.
5. The Sn-beta molecular sieve according to claim 1, characterized in that: The specific surface area of the molecular sieve is 500-600m 2 / g, preferably 530-570m 2 / g.
6. The Sn-beta molecular sieve according to claim 1, characterized in that: The molecular sieve pore volume is 0.30-0.40 mL / g, preferably 0.33-0.37 mL / g.
7. The method for preparing the Sn-beta molecular sieve according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: 1) performing ion exchange on the beta molecular sieve in an aqueous solution containing quaternary ammonium salt cations, and washing, filtering, and drying the exchanged molecular sieve; 2) weighing the quaternary ammonium salt cation-exchanged beta molecular sieve obtained in step 1) and the dried sodium bromide powder, grinding and mixing them uniformly in a glove box, and then transferring them to a tubular furnace reactor, introducing an inert gas into one end of the tubular furnace and venting the other end, then maintaining the inert gas circulation state in the furnace, heating to a certain temperature for reaction, cooling after the reaction, taking out the solid, washing, filtering, and drying to obtain the Na ion-exchanged beta molecular sieve; 3) placing the Na ion-exchanged beta molecular sieve obtained in step 2) in ammonia water of a certain concentration for desiliconization, filtering and washing after the treatment to obtain the desiliconized beta molecular sieve; 4) Grinding and mixing the desiliconized beta molecular sieve and anhydrous stannous chloride powder in a glove box until uniformly mixed, and then transferring the mixture to a tubular furnace reactor. Inert gas is introduced into the tubular furnace, and the temperature is increased to react for a period of time. The temperature is then lowered, the product is removed, and the mixture is washed, filtered, and dried. 5) calcining the material obtained in step 4) in an air atmosphere for a period of time. 6) The material obtained in step 5) is treated in an aqueous solution containing an acid, filtered, and washed to obtain a dealuminated Sn-beta molecular sieve product.
8. The method according to claim 7, wherein: In step 1), the silicon-aluminum ratio (SiO2 / Al2O3) of the beta molecular sieve is 50-80, preferably 60-70.
9. The method according to claim 7, wherein: In step 1), the quaternary ammonium salt is one or a combination of tetramethylammonium bromide, tetraethylammonium bromide, and tetrapropylammonium bromide.
10. The method according to claim 7, wherein: In step 1), the concentration of the quaternary ammonium salt aqueous solution is 1.5 to 3.5 mol / L, preferably 2.0 to 3.0 mol / L; the ion exchange temperature is 75 to 95° C., preferably 80 to 90° C.; and the number of exchanges is 1 to 3 times.
11. The method according to claim 7, wherein: In step 2), the mass ratio of the sodium bromide and the beta molecular sieve after quaternary ammonium salt cation exchange is 0.02 to 0.09, preferably 0.04 to 0.07; the inert gas introduced into the tubular furnace is one of nitrogen, helium, and argon, or a mixture thereof in any proportion.
12. The method according to claim 7, wherein: In step 2), the reaction temperature is 350-450° C., preferably 370-430° C., and the reaction time is 60-150 min, preferably 80-130 min.
13. The method according to claim 7, wherein: In step 3), the mass concentration of the ammonia water is 15-25 wt%, preferably 18-22 wt%.
14. The method according to claim 7, wherein: In step 3), in the desiliconization treatment of the molecular sieve, the solid-liquid mass ratio of the beta molecular sieve after Na ion exchange and the ammonia solution is 1:5 to 1:17, preferably 1:8 to 1:
14.
15. The method according to claim 7, wherein: In step 3), the desiliconization treatment of the molecular sieve is performed at a temperature of 40 to 70° C., preferably 50 to 60° C., for a time of 40 to 90 minutes, preferably 50 to 80 minutes, and the treatment is repeated 1 to 2 times.
16. The method according to claim 7, wherein: In step 4), the mass ratio of the anhydrous stannous chloride to the desiliconized beta molecular sieve is between 0.10 and 0.30, preferably 0.15 and 0.25; the inert gas introduced into the tube furnace is one of nitrogen, helium, and argon, or a mixture thereof in any proportion.
17. The method according to claim 7, wherein: In step 4), the reaction temperature is 400-500° C., preferably 430-470° C.; the reaction time is 80-150 min, preferably 100-130 min.
18. The method according to claim 7, wherein: In step 5), the calcination temperature in air is 500-550° C., and the calcination time is 3-6 hours.
19. The method according to claim 7, wherein: In step 6), the acid is one or more of hydrochloric acid, nitric acid, and sulfuric acid.
20. The method according to claim 7, wherein: In step 6), the acid concentration is 2.0 mol / L to 3.0 mol / L, preferably 2.3 to 2.8 mol / L; the treatment temperature is 50 to 90° C., preferably 70 to 80° C.; the treatment time is 1 to 4 h, preferably 2 to 3 h; the solid-liquid mass ratio during the treatment is 1:10 to 1:30, preferably 1:15 to 1:20; and the number of treatments is 1-3 times.
21. Use of the Sn-beta molecular sieve according to any one of claims 1 to 6 in the Baeyer-Viiliger reaction of cyclohexanone.