Preparation method of Sn-MWW molecular sieve, molecular sieve prepared by same and application of Sn-MWW molecular sieve

Abstract

The invention discloses a preparation method of a Sn-MWW molecular sieve, the molecular sieve prepared by the preparation method and application of the Sn-MWW molecular sieve. Comprising the following steps: mixing raw materials containing a silicon source, a tin source, a template agent, an additive and water, crystallizing in a stainless steel reaction kettle, and pickling a solid product to obtain the Sn-MWW molecular sieve. According to the method, the Sn-MWW molecular sieve can be prepared by reasonably matching the addition amounts of the tin source, the additive and the template agent, and the method has the characteristics of short crystallization time and adjustable framework tin content of the Sn-MWW molecular sieve product. The method is low in synthesis cost, environment-friendly, easy for large-scale production and wide in product application range.

Description

Technical Field

[0001] The present application relates to a method for preparing a Sn-MWW molecular sieve, the prepared molecular sieve and its application, and belongs to the field of chemical synthesis of inorganic materials. Background Art

[0002] Sn-MWW molecular sieves have shown superior catalytic performance in the fields of biomass conversion, especially in the fields of sugar conversion and sugar-based biomass platform compounds. Compared with tin-silicon molecular sieves with other topological structures, Sn-MWW can better adsorb substrate molecules and provide a place for the reaction due to its unique layered twelve-membered ring supercage and ten-membered ring sinusoidal pore structure. It is generally believed that tin species entering the framework will form Lewis acidic sites, which are active sites for sugar conversion. Therefore, controlling the framework tin content has an important influence on regulating the number of Lewis acidic sites of the catalyst, which is of great significance for improving the activity of sugar conversion.

[0003] The synthesis strategy of Sn-MWW molecular sieves reported in the literature is mainly the post-treatment tin insertion method, that is, the boron-containing MWW molecular sieve is treated with acid to remove the boron to obtain an MWW precursor containing rich holes, and then tin is introduced. There are fewer reports on direct synthesis. Professor Wu Peng's team reported a method for directly synthesizing Sn-MWW, using hexamethyleneimine (HMI) and N,N,N-trimethyladamantylammonium hydroxide (TMAdaOH) as templates for hydrothermal crystallization combined with acid treatment to remove tin species outside the framework, but this method requires a highly toxic template, and the tin content in the product is uncontrollable. In addition, there are solid-phase conversion methods, secondary crystallization methods, etc., but these methods all require complex processing processes, and the amount of framework tin introduced is uncontrollable.

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

[0005] The purpose of the present invention is to develop a method for synthesizing a Sn-MWW molecular sieve with controllable framework tin content. The method can prepare the Sn-MWW molecular sieve by reasonably matching the addition amounts of the tin source, the additive and the template agent, and has the characteristics of short crystallization time and adjustable framework tin content of the Sn-MWW molecular sieve product. The present invention has low synthesis cost, is environmentally friendly, is easy to mass produce, and has a wide range of product applications.

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

[0007] The raw materials containing silicon source, tin source, template, additive and water are mixed, crystallized, dried and acid-washed in a closed container to obtain the Sn-MWW molecular sieve.

[0008] The silicon source is selected from at least one of solid silica gel, white carbon black 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 mixed template agent of piperidine and N,N,N-trimethyladamantyl ammonium hydroxide;

[0011] The additive is selected from at least one of the hydrochlorides, phosphates, nitrates, sulfates, carbonates and hydroxides of at least one of potassium, cobalt, copper, titanium, cesium, magnesium, calcium, iron, nickel, lanthanum and cerium.

[0012] The molar ratio of the water to the 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 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 calculated based on the molar amount of silicon dioxide therein.

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

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

[0019] The crystallization is dynamic crystallization.

[0020] The drying temperature is 120°C;

[0021] The drying time is 6 to 24 hours;

[0022] The pickling comprises the following steps:

[0023] impregnating the dried product in an 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 to 2M;

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

[0027] The immersion temperature is 40 to 90° C.

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

[0029] After pickling, it is necessary to wash and dry.

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

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

[0032] The beneficial effects of this application include:

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

[0034] 2) The synthesis cost of the present invention is low, environmentally friendly, easy to produce on a large scale, and the product has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is the X-ray diffraction (XRD) spectrum of product A in Example 1. DETAILED DESCRIPTION

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

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

[0038] Example 1

[0039] According to the molar ratio of 1.0SiO2: 50H2O: 0.2PI: 0.3TMAdaOH: 0.1KNO3: 0.1SnO2, 69.3g of white carbon black, 691.4g of deionized water, 17g of piperidine, 253.6g of TMAdaOH solution, 10.1g of potassium nitrate and 30.6g of tin tetrachloride pentahydrate were stirred and mixed in sequence. Then, dynamic crystallization was carried out at 150°C for 120h. The solid product was washed with deionized water until neutral, centrifuged and dried at 120°C overnight to obtain a solid product.

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

[0041] Figure 1 This is the X-ray diffraction (XRD) spectrum of product A in Example 1.

[0042] like Figure 1 As shown, the X-ray diffraction (XRD) spectrum of product A of this example shows that it has a MWW topological structure.

[0043] Comparative Example 1

[0044] According to the molar ratio of 1.0SiO2: 50H2O: 0.2PI: 0.3TMAdaOH: 0.1SnO2, 69.3g of white carbon black, 691.4g of deionized water, 17g of piperidine, 253.6g of TMAdaOH solution and 30.6g of tin tetrachloride pentahydrate were stirred and mixed in sequence. Then, dynamic crystallization was performed at 150°C for 120h. The product was washed with deionized water until neutral, centrifuged and dried at 120°C overnight to obtain a solid product.

[0045] The product was found to be amorphous.

[0046] Comparative Example 2

[0047] According to the molar ratio of 1.0SiO2: 50H2O: 0.3TMAdaOH: 0.1KNO3: 0.1SnO2, 69.3g of white carbon black, 691.4g of deionized water, 253.6g of TMAdaOH solution, 10.1g of potassium nitrate and 30.6g of tin tetrachloride pentahydrate were stirred and mixed in sequence. Then, dynamic crystallization was performed at 150°C for 120h. The product was washed with deionized water until neutral, centrifuged and dried at 120°C overnight to obtain a solid product.

[0048] The product was found to be amorphous.

[0049] Example 2

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

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

[0052] The X-ray diffraction (XRD) spectrum of the product of this example is 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 white carbon black, 126.4g deionized water, 59.5g piperidine, 55.3g TMAdaOH, 142g sodium sulfate and 61.2g tin tetrachloride pentahydrate were stirred and mixed in sequence. Then, dynamic crystallization was carried out at 170℃ for 168h. The solid product was washed with deionized water until neutral, centrifuged and dried at 120℃ overnight.

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

[0056] The X-ray diffraction (XRD) spectrum of the product of this example is 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 stirred and mixed in sequence. Then, dynamic crystallization was performed at 120℃ for 72h. The product was washed with deionized water until neutral, centrifuged and dried at 120℃ overnight to obtain a solid product.

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

[0060] The X-ray diffraction (XRD) spectrum of the product of this example is Figure 1 similar.

[0061] Example 5

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

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

[0064] The X-ray diffraction (XRD) spectrum of the product of this example is Figure 1 similar.

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

[0066]

[0067] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing Sn-MWW molecular sieve, characterized in that: The following steps are involved: The raw materials containing silicon source, tin source, template, additive and water are mixed, crystallized, dried and acid-washed in a closed container to obtain the Sn-MWW molecular sieve.

2. The preparation method according to claim 1, characterized in that: The silicon source is selected from at least one of solid silica gel, white carbon black and silica sol; The tin source is selected from at least one of tin oxide and tin tetrachloride; The template agent is selected from piperidine or a mixed template agent of piperidine and N,N,N-trimethyladamantyl ammonium hydroxide; The additive is selected from at least one of the hydrochlorides, phosphates, nitrates, sulfates, carbonates and hydroxides of at least one of potassium, cobalt, copper, titanium, cesium, magnesium, calcium, iron, nickel, lanthanum and cerium.

3. The preparation method according to claim 1, characterized in that: The molar ratio of the water to the 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 to the silicon source is 0.05 to 1; The molar ratio of the additive to the silicon source is 0.01 to 1; The molar amount of the silicon source is calculated based on the molar amount of silicon dioxide therein.

4. The preparation method according to claim 1, characterized in that: The crystallization temperature is 120-160°C; The crystallization time is 48 to 168 hours.

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

6. The preparation method according to claim 1, characterized in that: The pickling comprises the following steps: impregnating the dried product in an 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 0.2-2M.

7. The preparation method according to claim 6, characterized in that: The immersion temperature is 40 to 90° C. The immersion time is 6 to 24 hours.

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

9. An application of the Sn-MWW molecular sieve according to claim 8, characterized in that: For biomass conversion.

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