A solvent-free preparation method of L molecular sieve

Abstract

The application belongs to the technical field of molecular sieve preparation method, and particularly relates to a solvent-free preparation method of L molecular sieve. The method comprises the following steps: (1) mixing a solid silicon source and a solid potassium source and placing them in a mortar for grinding; (2) adding a solid aluminum source to the sample ground in step (1) and continuing to grind; (3) placing the sample ground in step (2) in a reaction kettle for crystallization reaction; and (4) performing calcination treatment on the sample crystallized in step (3) to obtain the L molecular sieve. According to the application, the L molecular sieve with good crystallinity and controllable silicon-aluminum ratio can be prepared, the synthesis route only involves the mixing of primary raw materials, and does not use any solvent, the synthesis steps are greatly simplified compared with the traditional method, and the yield and single-kettle utilization rate are greatly improved. The production cost is greatly reduced, energy is saved and emission is reduced, and the application has great industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the technical field of molecular sieve preparation methods, and particularly relates to a solvent-free preparation method for L molecular sieves. Technical Background

[0002] L-type molecular sieves are potassium-containing synthetic zeolites whose basic structural units are nepheline cages and hexagonal columnar cages. Alternating hexagonal columnar cages and nepheline cages overlap along the c-axis and then rotate about a sixfold axis to create a one-dimensional channel structure with twelve-membered rings, a pore size of 0.71 nm, and a kinetic diameter of 0.81 nm. L-type molecular sieves have a wide range of applications, especially Pt-supported L-type molecular sieves, which exhibit much higher activity and selectivity than traditional bifunctional catalysts for the aromatization of C6-C8 alkanes. Furthermore, L-type molecular sieve catalysts also show high activity and selectivity for the directed chlorination of toluene to the synthesis of p-chlorotoluene.

[0003] Currently, the synthesis of L-zeolite is primarily achieved through hydrothermal crystallization, which requires the gradual hydrolysis of silicon and aluminum sources. The amount of water used in the synthesis process is difficult to control, making the operation complex, time-consuming, and costly, with significant post-processing challenges. Furthermore, this method suffers from numerous drawbacks, such as low raw material utilization, excessively long crystallization time, the tendency for impurities to contaminate the synthesized product, demanding reaction conditions, and low economic efficiency, hindering industrial production. Therefore, there is an urgent need to develop a novel synthesis method for L-zeolite molecular sieves. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a solvent-free preparation method for L molecular sieves that reduces costs, improves efficiency, and is safer.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A solvent-free method for preparing L-type molecular sieves, the method comprising the following steps:

[0007] (1) Mix the solid silicon source and the solid potassium source and grind them in a mortar;

[0008] (2) Add the solid aluminum source to the sample ground in step (1) and continue grinding;

[0009] (3) Place the ground sample from step (2) into a reaction vessel and carry out a crystallization reaction;

[0010] (4) The crystallized sample from step (3) is calcined in air to obtain L molecular sieve.

[0011] In the above technical solution, further, in step (1), the aluminum source is one or a mixture of two or more of aluminum hydroxide, sodium aluminate, and aluminum sulfate; the potassium source is one or a mixture of two or more of potassium hydroxide, potassium bromide, and potassium silicate.

[0012] In the above technical solution, further, in step (1), the molar ratio of silicon source to potassium source is 1:1 to 1:10, preferably 1:1 to 1:3; the grinding time is 10 to 120 minutes.

[0013] In the above technical solution, further, in step (2), the silicon source is one or a mixture of two of solid silica gel and fumed silica.

[0014] In the above technical solution, further, in step (2), the molar ratio of aluminum source to silicon source is 1:3 to 1:50, preferably 1:3 to 1:20; the grinding time is 10 to 60 minutes.

[0015] In the above technical solution, further, in step (3), the temperature of the crystallization reaction is 170-200℃ and the time of the crystallization reaction is 4-24h.

[0016] In the above technical solution, further, in step (4), the calcination temperature is 400-600℃ and the calcination time is 1-5h.

[0017] In the above technical solution, the method further includes: before the crystallization reaction, adding L molecular sieve seed crystals with a mass ratio of 1:10 to 1:100 with the silicon source to the solid raw material and grinding them together for 10 to 120 minutes;

[0018] The method for synthesizing the L-type molecular sieve seed crystals includes the following steps:

[0019] (1) Mix the solid silicon source and the solid potassium source in a mortar and grind for 10 minutes;

[0020] (2) Add the solid aluminum source to the sample ground in step (1) and continue grinding for 10 minutes;

[0021] (3) Place the ground sample from step (2) into a reaction vessel and crystallize it at 175°C for 24 hours;

[0022] (4) The crystallized sample from step (3) was calcined at 550°C for 4 hours to obtain L molecular sieve seed crystals.

[0023] The molar ratio of each reactant is: 3.5K2O:0.5Al2O3:10SiO2.

[0024] The present invention has the following beneficial effects:

[0025] 1. The present invention can produce L molecular sieves with good crystallinity and controllable silicon-aluminum ratio, and the prepared products can be used directly for performance research without filtration or centrifugation and can be calcined.

[0026] 2. In the preparation of L molecular sieves, no organic template agents or solvents need to be added. The synthesis route is green and simple, which reduces the cost of raw materials and eliminates safety hazards in the experiment. It greatly simplifies the traditional hydrothermal synthesis method, improves the yield, saves energy, and reduces environmental pollution, and has great potential for industrial application. Attached Figure Description

[0027] Figure 1 Flowchart for the hydrothermal preparation of L-molecular sieves;

[0028] Figure 2 The image shows the XRD pattern of the L-type molecular sieve prepared in Example 1 using Al(OH)3 as the aluminum source.

[0029] Figure 3 The image shows the XRD pattern of the L-type molecular sieve prepared in Example 4 using NaAlO2 as the aluminum source.

[0030] Figure 4 The image shows the XRD pattern of the L molecular sieve prepared by adding L molecular sieve seeds in Example 8.

[0031] Figure 5 The image shows the XRD pattern of the L molecular sieve prepared by the conventional hydrothermal method in Comparative Example 1. Detailed Implementation

[0032] The following detailed description is provided in conjunction with the embodiments and accompanying drawings:

[0033] Example 1

[0034] First, weigh 1.8g of solid raw materials, including silica and potassium hydroxide, and grind them in a mortar for 15 minutes. Then, add 0.936g of aluminum hydroxide and grind for another 20 minutes. Add the reaction raw materials to a polytetrafluoroethylene stainless steel reactor and crystallize at 170°C for 24 hours. The resulting product does not require filtration or washing and is directly calcined at 550°C for 4 hours in air to obtain the final L molecular sieve.

[0035] X-ray diffraction analysis revealed that its structure is L-zeolite molecular sieve.

[0036] Figure 2 The XRD pattern synthesized using this method.

[0037] Example 2

[0038] First, weigh 1.8g of solid raw materials, including silica and potassium hydroxide, and grind them in a mortar for 15 minutes. Then, add 0.468g of aluminum hydroxide and grind for another 15 minutes. Add the reaction raw materials to a polytetrafluoroethylene stainless steel reactor and crystallize at 170℃ for 24 hours. The resulting product does not require filtration or washing and is directly calcined at 550℃ for 4 hours in air to obtain the final L molecular sieve.

[0039] Example 3

[0040] First, weigh 1.8g of solid raw materials, including silica and potassium hydroxide, and grind them in a mortar for 15 minutes. Then, add 0.234g of aluminum hydroxide and grind for another 10 minutes. Add the reaction raw materials to a polytetrafluoroethylene stainless steel reactor and crystallize at 170℃ for 24 hours. The resulting product does not require filtration or washing and is directly calcined at 550℃ for 4 hours in air to obtain the final L molecular sieve.

[0041] Example 4

[0042] First, weigh 1.8g of solid silica gel and 1.19g of potassium bromide, and grind them in a mortar for 15 minutes. Then add 0.246g of sodium aluminate and grind for another 10 minutes. Add the reaction materials to a polytetrafluoroethylene stainless steel reactor and crystallize at 170℃ for 24 hours. The product obtained does not need to be filtered or washed. It is directly calcined at 550℃ for 4 hours in air to obtain the final L molecular sieve.

[0043] X-ray diffraction analysis revealed that its structure is L-zeolite molecular sieve.

[0044] Figure 3 The XRD pattern synthesized using this method.

[0045] Example 5

[0046] First, weigh 1.8g of solid raw materials, including silica and potassium silicate, and grind them in a mortar for 15 minutes. Then, add 0.99g of aluminum sulfate and grind for another 10 minutes. Add the reaction raw materials to a polytetrafluoroethylene stainless steel reactor and crystallize at 170℃ for 24 hours. The resulting product does not require filtration or washing and is directly calcined at 550℃ for 4 hours in air to obtain the final L molecular sieve.

[0047] Example 6

[0048] First, weigh 1.8g of solid raw materials, including silica and potassium hydroxide, and grind them in a mortar for 15 minutes. Then, add 0.117g of aluminum hydroxide and grind for another 10 minutes. Add the reaction raw materials to a polytetrafluoroethylene stainless steel reactor and crystallize at 170°C for 24 hours. The resulting product does not require filtration or washing and is directly calcined at 550°C for 4 hours in air to obtain the final L molecular sieve.

[0049] Example 7

[0050] First, weigh 1.8g of solid raw materials, including silica and potassium hydroxide, and grind them in a mortar for 15 minutes. Then, add 0.234g of aluminum hydroxide and grind for another 15 minutes. Add the reaction raw materials to a polytetrafluoroethylene stainless steel reactor and crystallize at 200°C for 4 hours. The resulting product does not require filtration or washing and is directly calcined at 550°C for 4 hours in air to obtain the final L molecular sieve.

[0051] Example 8

[0052] First, weigh 1.8g of solid raw materials, including silica and potassium hydroxide, and grind them in a mortar for 15 minutes. Then, add 0.234g of aluminum hydroxide and grind for another 20 minutes. Finally, add 0.18g of L-molecular sieve seed crystals synthesized in Example 5 and grind for 15 minutes. Add the reaction raw materials to a polytetrafluoroethylene stainless steel reactor and crystallize at 170°C for 4 hours. The resulting product does not require filtration or washing and is directly calcined at 550°C for 4 hours in air to obtain the final L-molecular sieve.

[0053] The obtained sample was analyzed by X-ray diffraction and its structure was identified as L-zeolite molecular sieve.

[0054] Figure 4 The XRD pattern synthesized using this method.

[0055] Example 9

[0056] First, weigh 1.8g of solid raw materials, including silica and potassium hydroxide, and grind them in a mortar for 15 minutes. Then, add 0.234g of aluminum hydroxide and grind for another 20 minutes. Finally, add 0.09g of L-molecular sieve seed crystals synthesized in Example 5 and grind for 15 minutes. Add the reaction raw materials to a polytetrafluoroethylene stainless steel reactor and crystallize at 170°C for 8 hours. The resulting product does not require filtration or washing and is directly calcined at 550°C for 4 hours in an air atmosphere to obtain the final L-molecular sieve.

[0057] Example 10

[0058] First, weigh 1.8g of solid raw materials, including silica and potassium hydroxide, and grind them in a mortar for 15 minutes. Then, add 0.234g of aluminum hydroxide and grind for another 20 minutes. Finally, add 0.018g of L-molecular sieve seed crystals synthesized in Example 5 and grind for 15 minutes. Add the reaction raw materials to a polytetrafluoroethylene stainless steel reactor and crystallize at 170°C for 12 hours. The resulting product does not require filtration or washing and is directly calcined at 550°C for 4 hours in air to obtain the final L-molecular sieve.

[0059] Comparative Example 1

[0060] The traditional hydrothermal method for preparing L-molecule sieves is shown in the flowchart below. Figure 1 As shown.

[0061] First, weigh 1.178 g of potassium hydroxide and 0.234 g of aluminum hydroxide, pour them into a 50 ml beaker, then add 6.33 g of H2O, stir at room temperature for 1 h, then add 6 g of SiO2 (30%) sol, continue stirring for 4 h, then add the mixture to a polytetrafluoroethylene stainless steel reactor, crystallize at 170 °C for 24 h, the obtained product is washed several times with deionized water until neutral, the washed product is dried in an 80 °C oven for 12 h, and then calcined at 550 °C for 4 h in air atmosphere to obtain the final L molecular sieve.

[0062] The obtained sample was analyzed by X-ray diffraction and its structure was identified as L-zeolite molecular sieve.

[0063] Figure 5 The XRD pattern synthesized using this method.

[0064] Examples 1-10 detail the preparation of L-type molecular sieves under different conditions using a solvent-free method, while Comparative Example 1 shows the L-type molecular sieve prepared using a traditional hydrothermal method. By changing the experimental conditions, a higher yield of L-type molecular sieves was desired. The L-type molecular sieve yield was calculated as: mass of the obtained L-type molecular sieve product / total mass of reactants (excluding seed crystals). The main experimental parameters and important experimental results for each example are as follows:

[0065] Table 1

[0066]

[0067] As shown in the table above, all the above implementation cases can synthesize L molecular sieves. By increasing the reaction temperature and adding seed crystals, L molecular sieves can be synthesized in a short time, which greatly simplifies the traditional hydrothermal synthesis method, improves the yield and the yield is relatively high (>93%), and the synthesis route is more energy-saving and environmentally friendly.

[0068] Example 11

[0069] 0.1 g of N-acetylglucosamine was dissolved in 10 mL of N,N-dimethylacetamide, and 0.05 g of the L-molecular sieve prepared in Example 3 was added. The mixture was reacted at 170 °C for 1 h. High-performance liquid chromatography (HPLC) analysis showed that the yield of 3-acetamido-5-acetylfuran was 95%.

[0070] Comparative Example 2

[0071] 0.1 g of N-acetylglucosamine was dissolved in 10 mL of N,N-dimethylacetamide, and 0.05 g of the L-molecular sieve prepared in Comparative Example 1 was added. The mixture was reacted at 170 °C for 8 h. High-performance liquid chromatography (HPLC) analysis showed that the yield of 3-acetamido-5-acetylfuran was 64%.

[0072] The L-zeolite prepared by the solvent-free method provided in this invention exhibits superior catalytic performance for the conversion of N-acetylglucosamine to 3-acetamido-5-acetylfuran, achieving a higher 3A5AF yield in a shorter reaction time.

[0073] The above descriptions are merely several embodiments of the present invention and are not intended to limit the present invention in any way. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the disclosed structure and technical content to create equivalent embodiments without departing from the scope of the present invention. However, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A process for the solvent-free preparation of L molecular sieves, characterized by: The method comprises the following steps: (1) mixing a solid silicon source and a solid potassium source in a mortar and grinding; (2) adding a solid aluminum source to the sample ground in step (1) and continuing to grind; (3) placing the sample ground in step (2) in a reaction kettle and performing a crystallization reaction; (4) performing a calcination treatment on the sample crystallized in step (3) in an air atmosphere to obtain L molecular sieve; In step (4), the calcination temperature is 400-600 DEG C, and the calcination time is 1-5 h. 2.The method for preparing L molecular sieve without solvent according to claim 1, characterized in that: In step (1), the silicon source is one of solid silica gel and white carbon black or a mixture of the two; The potassium source is one of potassium hydroxide, potassium bromide and potassium silicate or a mixture of two or more thereof. 3.The method of claim 1, wherein the L-zeolite is prepared without a solvent. In step (1), the molar ratio of the silicon source to the potassium source is 1:1-1:10, and the grinding time is 10-120 minutes. 4.The method of claim 1, wherein the L-zeolite is prepared without a solvent. In step (2), the aluminum source is one of aluminum hydroxide, sodium metaaluminate and aluminum sulfate or a mixture of two or more thereof. 5.The method of claim 1, wherein the L-zeolite is prepared without a solvent. In step (2), the molar ratio of the aluminum source to the silicon source is 1:3-1:50, and the grinding time is 10-60 minutes. 6.The method of claim 1, wherein the L-zeolite is prepared without a solvent. In step (3), the temperature of the crystallization reaction is 170-200 DEG C, and the time of the crystallization reaction is 4-24 h. 7.The method of claim 1, wherein the L-zeolite is prepared without a solvent. The method further comprises: before the crystallization reaction, adding L molecular sieve seeds with a mass ratio of 1:10-1:100 to the solid raw material and co-grinding for 10-120 minutes; The synthesis method of the L molecular sieve seeds comprises the following steps: 1) mixing a solid silicon source and a solid potassium source in a mortar and grinding for 10 minutes; 2) adding a solid aluminum source to the sample ground in step (1) and continuing to grind for 10 minutes; 3) placing the sample ground in step 2) in a reaction kettle, performing a crystallization reaction at 175 DEG C for 24 h; 4) calcining the sample crystallized in step 3) at 550 DEG C for 4 h to obtain L molecular sieve seeds; The molar ratio of each reaction raw material is 3.5K2O:0.5Al2O3:10SiO2.

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