A method for preparing Sn-MWW molecular sieves, the prepared molecular sieves, and their applications.

Abstract

This application discloses a method for preparing Sn-MWW molecular sieves, the prepared molecular sieves, and their applications. The method includes the following steps: mixing raw materials containing a silicon source, a tin source, a template agent, additives, and water; crystallizing the mixture in a stainless steel reactor; and acid washing the solid product to obtain the Sn-MWW molecular sieve. This method can prepare Sn-MWW molecular sieves by rationally matching the amounts of tin source, additives, and template agents, and features short crystallization time and adjustable skeletal tin content in the Sn-MWW molecular sieve product. The synthesis cost of this invention is low, environmentally friendly, easy to scale up, and the product has a wide range of applications.

Description

Technical Field

[0001] This application relates to a method for preparing Sn-MWW molecular sieves, the prepared molecular sieves, and their applications, belonging to the field of inorganic material chemical synthesis. Background Technology

[0002] Sn-MWW molecular sieves exhibit superior catalytic performance in biomass conversion and other fields, particularly showing broad application prospects in carbohydrate conversion and the production of platform compounds from carbohydrates. Compared to other tin-silicon molecular sieve topologies, Sn-MWW, due to its unique layered twelve-membered ring supercage and ten-membered ring sinusoidal channel structure, can better adsorb substrate molecules, and the supercage provides a reaction site. It is generally believed that tin species entering the framework form Lewis acid sites, which are active sites for carbohydrate conversion. Therefore, controlling the tin content in the framework has a significant impact on regulating the number of Lewis acid sites in the catalyst, and is of great importance for improving carbohydrate conversion activity.

[0003] Currently reported synthetic strategies for Sn-MWW molecular sieves mainly involve post-treatment tin insertion, where boron-containing MWW molecular sieves are acid-treated to remove boron, yielding a hole-rich MWW precursor, which is then introduced with tin. Direct synthesis is less common. Professor Wu Peng's team reported a direct synthesis method for Sn-MWW using hexamethyleneimine (HMI) and N,N,N-trimethyladamantyl ammonium hydroxide (TMAdaOH) as templates. This method involves hydrothermal crystallization combined with acid treatment to remove tin species outside the framework. However, this method requires highly toxic templates, and the tin content in the product is uncontrollable. Other methods include solid-phase transformation and secondary crystallization, but these all require complex processing steps, and the amount of tin introduced into the framework is uncontrollable.

[0004] In summary, there is a lack of effective direct synthesis methods for Sn-MWW molecular sieves, and the tin content in the framework is uncontrollable, so it is necessary to explore suitable controllable synthesis strategies. Summary of the Invention

[0005] The purpose of this invention is to develop a method for synthesizing Sn-MWW molecular sieves with controllable framework tin content. This method can prepare Sn-MWW molecular sieves by rationally matching the amounts of tin source, additives, and template agents, and features short crystallization time and adjustable framework tin content in the Sn-MWW molecular sieve product. The synthesis cost of this invention is low, environmentally friendly, easy to scale up, and the product has a wide range of applications.

[0006] According to one aspect of this application, a method for preparing Sn-MWW molecular sieves is provided, comprising the following steps:

[0007] Raw materials containing silicon source, tin source, template agent, additives and water are mixed in a sealed container, crystallized, dried and acid-washed to obtain the Sn-MWW molecular sieve.

[0008] The silicon source is selected from at least one of solid silica gel, fumed silica, and silica sol.

[0009] The tin source is selected from at least one of tin oxide and tin tetrachloride;

[0010] The template agent is selected from piperidine or a mixture of piperidine and N,N,N-trimethyladamantyl ammonium hydroxide;

[0011] The additive is selected from at least one of the following elements: potassium, cobalt, copper, titanium, cesium, magnesium, calcium, iron, nickel, lanthanum, and cerium, as well as its hydrochloride, phosphate, nitrate, sulfate, carbonate, or hydroxide.

[0012] The molar ratio of water to silicon source is 10 to 50;

[0013] The molar ratio of the tin source to the silicon source is 0.001 to 0.05;

[0014] The molar ratio of the template agent to the silicon source is 0.05 to 1;

[0015] The molar ratio of the additive to the silicon source is 0.01 to 1;

[0016] The molar amount of the silicon source is measured by the molar amount of silicon dioxide therein.

[0017] The crystallization temperature is 120–160°C;

[0018] The crystallization time is 48–168 hours;

[0019] The crystallization is dynamic crystallization.

[0020] The drying temperature is 120°C;

[0021] The drying time is 6–24 hours;

[0022] The pickling process includes the following steps:

[0023] The dried product is then immersed in acid.

[0024] The acid is selected from at least one of nitric acid, hydrochloric acid, sulfuric acid, oxalic acid, and citric acid;

[0025] The concentration of the acid is 0.2–2 M;

[0026] The solid-liquid ratio is 1g molecular sieve: 5-50mL acid solution;

[0027] The impregnation temperature is 40–90°C;

[0028] The soaking time is 6 to 24 hours.

[0029] After pickling, it needs to be washed and dried again.

[0030] According to another aspect of this application, a Sn-MWW molecular sieve prepared by the above-described preparation method is provided, wherein the Sn content in the Sn-MWW molecular sieve is 0.1 to 2 wt%.

[0031] According to another aspect of this application, an application of the above-described Sn-MWW molecular sieve is provided for biomass conversion.

[0032] The beneficial effects that this application can produce include:

[0033] 1) The purpose of this invention is to develop a method for synthesizing Sn-MWW molecular sieves with controllable framework tin content. This method can prepare Sn-MWW molecular sieves by reasonably matching the amount of tin source, additives and template agent, and has the characteristics of short crystallization time and adjustable framework tin content of Sn-MWW molecular sieve products.

[0034] 2) The synthesis cost of this invention is low, environmentally friendly, easy to scale up, and the product has a wide range of applications. Attached Figure Description

[0035] Figure 1 The image shows the X-ray diffraction (XRD) pattern of product A from Example 1. Detailed Implementation

[0036] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0037] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0038] Example 1

[0039] According to the molar ratio of 1.0 SiO2:50 H2O:0.2 P1:0.3 TMAdaOH:0.1 KNO3:0.1 SnO2, 69.3 g of silica, 691.4 g of deionized water, 17 g of piperidine, 253.6 g of TMAdaOH solution, 10.1 g of potassium nitrate, and 30.6 g of tin tetrachloride pentahydrate were mixed in sequence and stirred until homogeneous. Then, the mixture was dynamically crystallized at 150 °C for 120 h. After washing with deionized water until neutral, the mixture was centrifuged and dried overnight at 120 °C to obtain the solid product.

[0040] To confirm the skeletal tin content, the product was treated with 2M nitric acid at a solid-liquid ratio of 1g:10ml at 60℃ for 10h to ensure that all non-skeleton tin was removed. The elemental composition of the product was then detected by X-ray fluorescence spectroscopy (XRF), and the results are shown in Table 1.

[0041] Figure 1 The image shows the X-ray diffraction (XRD) pattern of product A from Example 1.

[0042] like Figure 1 As shown, the X-ray diffraction (XRD) pattern of product A in this embodiment shows that it has an MWW topology.

[0043] Comparative Example 1

[0044] According to the molar ratio of 1.0SiO2:50H2O:0.2PI:0.3TMAdaOH:0.1SnO2, 69.3g of silica, 691.4g of deionized water, 17g of piperidine, 253.6g of TMAdaOH solution, and 30.6g of tin tetrachloride pentahydrate were mixed in sequence and stirred until homogeneous. Then, the mixture was dynamically crystallized at 150℃ for 120h. After washing with deionized water until neutral, the mixture was centrifuged and dried overnight at 120℃ to obtain the solid product.

[0045] The product was found to be amorphous upon testing.

[0046] Comparative Example 2

[0047] According to the molar ratio of 1.0 SiO2:50 H2O:0.3 TMAdaOH:0.1 KNO3:0.1 SnO2, 69.3 g of silica, 691.4 g of deionized water, 253.6 g of TMAdaOH solution, 10.1 g of potassium nitrate, and 30.6 g of tin tetrachloride pentahydrate were mixed in sequence and stirred until homogeneous. Then, the mixture was dynamically crystallized at 150℃ for 120 h. After washing with deionized water until neutral, the mixture was centrifuged and dried overnight at 120℃ to obtain the solid product.

[0048] The product was found to be amorphous upon testing.

[0049] Example 2

[0050] According to the molar ratio of 1.0SiO2:30H2O:0.3PI:0.2K2CO3:0.3SnO2, 198.7g of silica sol, 382.9g of deionized water, 25.5g of piperidine, 27.6g of potassium carbonate, and 91.8g of tin tetrachloride pentahydrate were mixed in sequence until homogeneous. Then, the mixture was dynamically crystallized at 160℃ for 48h. After washing with deionized water until neutral, the mixture was centrifuged and dried overnight at 120℃ to obtain the solid product.

[0051] To confirm the skeletal tin content, the product was treated with 2M nitric acid at a solid-liquid ratio of 1g:10ml at 60℃ for 10h to ensure that all non-skeleton tin was removed. The elemental composition of the product was then detected by X-ray fluorescence spectroscopy (XRF), and the results are shown in Table 1.

[0052] The X-ray diffraction (XRD) pattern of the product in this embodiment is similar to... Figure 1 similar.

[0053] Example 3

[0054] According to the molar ratio of 1.0SiO2:10H2O:0.7PI:0.05TMAdaOH:1Na2SO4:0.2SnO2, 69.3g of silica, 126.4g of deionized water, 59.5g of piperidine, 55.3g of TMAdaOH, 142g of sodium sulfate, and 61.2g of tin tetrachloride pentahydrate were mixed in sequence and stirred until homogeneous. Then, the mixture was dynamically crystallized at 170℃ for 168h. After washing with deionized water until neutral, the mixture was centrifuged and dried overnight at 120℃ to obtain the solid product.

[0055] To confirm the skeletal tin content, the product was treated with 2M nitric acid at a solid-liquid ratio of 1g:10ml at 60℃ for 10h to ensure that all non-skeleton tin was removed. The elemental composition of the product was then detected by X-ray fluorescence spectroscopy (XRF), and the results are shown in Table 1.

[0056] The X-ray diffraction (XRD) pattern of the product in this embodiment is similar to... Figure 1 similar.

[0057] Example 4

[0058] According to the molar ratio of 1.0SiO2:20H2O:1PI:0.1MgCl2:0.05SnO2, 61.7g silica gel, 355.5g deionized water, 85g piperidine, 9.2g magnesium chloride, and 17.35g tin tetrachloride pentahydrate were mixed in sequence and stirred until homogeneous. Then, the mixture was dynamically crystallized at 120℃ for 72h. After washing with deionized water until neutral, the mixture was centrifuged and dried overnight at 120℃ to obtain the solid product.

[0059] To confirm the skeletal tin content, the product was treated with 2M nitric acid at a solid-liquid ratio of 1g:10ml at 60℃ for 10h to ensure that all non-skeleton tin was removed. The elemental composition of the product was then detected by X-ray fluorescence spectroscopy (XRF), and the results are shown in Table 1.

[0060] The X-ray diffraction (XRD) pattern of the product in this embodiment is similar to... Figure 1 similar.

[0061] Example 5

[0062] According to the molar ratio of 1.0 SiO2:50 H2O:0.2 PI:0.2 TMAdaOH:0.01 NaOH:0.1 SnO2, 64.7 g silica gel, 743 g deionized water, 17 g piperidine, 211.4 g TMAdaOH, 0.42 g sodium hydroxide, and 30.6 g tin tetrachloride pentahydrate were mixed in sequence and stirred until homogeneous. Then, the mixture was dynamically crystallized at 150 °C for 120 h. After washing with deionized water until neutral, the mixture was centrifuged and dried overnight at 120 °C to obtain the solid product.

[0063] To confirm the skeletal tin content, the product was treated with 2M nitric acid at a solid-liquid ratio of 1g:10ml at 60℃ for 10h to ensure that all non-skeleton tin was removed. The elemental composition of the product was then detected by X-ray fluorescence spectroscopy (XRF), and the results are shown in Table 1.

[0064] The X-ray diffraction (XRD) pattern of the product in this embodiment is similar to... Figure 1 similar.

[0065] Table 1. Tin content of the products in each example.

[0066]

[0067] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing Sn-MWW molecular sieves, characterized in that, Includes the following steps: Raw materials containing silicon source, tin source, template agent, additive and water are mixed in a sealed container, crystallized, dried and acid-washed to obtain the Sn-MWW molecular sieve. The tin source is selected from at least one of tin oxide and tin tetrachloride; The template agent is selected from piperidine or a mixture of piperidine and N,N,N-trimethyladamantyl ammonium hydroxide; The additive is selected from at least one of the following elements: potassium, cobalt, copper, titanium, cesium, magnesium, calcium, iron, nickel, lanthanum, and cerium, as well as its hydrochloride, phosphate, nitrate, sulfate, carbonate, and hydroxide. The molar ratio of water to silicon source is 10 to 50; The molar ratio of the tin source to the silicon source is 0.001 to 0.05; The molar ratio of the template agent to the silicon source is 0.05~1; The molar ratio of the additive to the silicon source is 0.01 to 1; The molar amount of the silicon source is measured by the molar amount of silicon dioxide therein.

2. The preparation method according to claim 1, characterized in that, The silicon source is selected from at least one of solid silica gel, fumed silica, and silica sol.

3. The preparation method according to claim 1, characterized in that, The crystallization temperature is 120~160℃; The crystallization time is 48~168h.

4. The preparation method according to claim 1, characterized in that, The drying temperature is 120°C; The drying time is 6 to 24 hours.

5. The preparation method according to claim 1, characterized in that, The pickling process includes the following steps: The dried product is then immersed in acid. The acid is selected from at least one of nitric acid, hydrochloric acid, sulfuric acid, oxalic acid, and citric acid; The concentration of the acid is 0.2~2 M.

6. The preparation method according to claim 5, characterized in that, The impregnation temperature is 40~90℃; The soaking time is 6 to 24 hours.

7. A Sn-MWW molecular sieve prepared by the preparation method according to any one of claims 1 to 6, characterized in that, The Sn content in the Sn-MWW molecular sieve is 0.1~2wt%.

8. An application of the Sn-MWW molecular sieve according to claim 7, characterized in that, Used for biomass conversion.

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