A solvent-free preparation method of a heteroatom-doped 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 a heteroatom-doped L molecular sieve. The method comprises the following steps: grinding and mixing weighed solid raw materials, i.e., a silicon source, an aluminum source, a potassium source and a heteroatom compound, putting the mixture into a reaction kettle after grinding is completed, and performing a crystallization reaction; and directly calcining the obtained product under an air atmosphere without filtration and washing to obtain a final product. Through the application, a molecular sieve catalyst with good crystallinity and controllable heteroatom doping amount can be prepared. The synthesis route only involves the mixing of primary raw materials, and does not use any solvent, so that the synthesis steps are greatly simplified compared with a traditional method, the yield is high, the production cost is reduced, energy saving and emission reduction are achieved, 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 solventless preparation method of heteroatom-doped L molecular sieves. Technical Background

[0002] L-zeolite is a potassium-containing synthetic zeolite with a one-dimensional channel structure of twelve-membered rings, a pore size of 0.71 nm, and a kinetic diameter of 0.81 nm. It is a catalytic material with excellent thermal stability and can be used to prepare catalysts for hydrocarbon conversion processes such as cracking, reforming, isomerization, aromatization, alkylation, and lubricating oil hydrogenation.

[0003] The most stable structure of L-zeolite zeolite is the silicon-aluminum structure, in which special heteroatoms can be introduced into the zeolite through certain methods. The introduction of heteroatoms with specific functions into the zeolite framework alters some of its properties, such as thermal stability, adsorption performance, and catalytic performance. The introduction of new atoms also endows the zeolite with new physical and chemical properties, giving the modified catalyst more unique catalytic characteristics and providing broader application prospects for L-zeolite catalysts. Current research shows that methods for introducing heteroatoms into L-zeolite zeolites, such as impregnation or ion exchange, result in heteroatoms being almost entirely loaded onto the zeolite surface, with limited loading capacity. Furthermore, the heteroatoms loaded on the zeolite are prone to detachment, affecting catalytic efficiency. A solid-phase synthesis method introduces heteroatom compounds in situ during the synthesis of the zeolite. These heteroatoms isomorphously replace silicon or aluminum in the zeolite framework, thus introducing them into the framework. Ultimately, this results in a more uniform distribution and a more homogeneous state within the zeolite, leading to higher loading capacity and superior catalytic performance. 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 heteroatom-doped L molecular sieves that reduces costs, improves efficiency, and is simpler and safer.

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

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

[0007] (1) Mix the solid silicon source, solid potassium source and solid heteroatom compound 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 in step (3) is calcined in air to obtain heteroatom-doped 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; and the heteroatom compound is any one of ferric chloride, chromium chloride, magnesium chloride, zirconium chloride, tin chloride, copper chloride, zinc chloride, nickel chloride, cerium chloride, boric acid, and boron oxide.

[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 molar ratio of heteroatom compound to silicon source is 1:10 to 1:100; and 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 min.

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

[0016] In the above technical solution, further, in step (4), the calcination temperature is 400-550℃ and the calcination time is 1-6h.

[0017] The beneficial effects of this invention are as follows:

[0018] 1. The present invention can produce heteroatom-doped L molecular sieves with good crystallinity, and the prepared products can be used directly for performance research without filtration or centrifugation and can be calcined.

[0019] 2. In the process of preparing heteroatom-doped L molecular sieves, heteroatoms can isomorphically replace aluminum or silicon in the molecular sieve and enter the L molecular sieve framework without the need to add any organic template agents and solvents. The synthesis route is green and simple, and has great potential for industrial application. Attached Figure Description

[0020] Figure 1 The XRD pattern of boron-doped L-type molecular sieve in Comparative Example 1 is shown.

[0021] Figure 2 The image shows the XRD pattern of the boron-doped L-type molecular sieve from Example 11. Detailed Implementation

[0022] The following detailed description is provided in conjunction with the embodiments and accompanying drawings:

[0023] Example 1

[0024] Solvent-free preparation of 0.7% Cr-L catalyst:

[0025] First, weigh 1.8g of solid raw materials, 1.178g of potassium hydroxide, and 0.475g of chromium chloride, and grind them in a mortar for 15 minutes. Then add 0.234g of aluminum hydroxide and grind for another 20 minutes. Add the reaction raw 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 and is directly calcined at 550℃ for 4 hours in an air atmosphere to obtain the final Cr-doped L molecular sieve.

[0026] Fourier transform infrared spectrum at 900 cm⁻¹ -1 The absorption peak at this point is attributed to the vibration of Si-O-Cr, and the X-ray electron spectroscopy peaks at binding energies of 579.8 eV and 588 eV correspond to Cr 2p, respectively. 3 / 2 and Cr 2p 1 / 2 This further indicates the presence of Cr(VI). All of the above results demonstrate that Cr atoms have entered the L molecular sieve framework.

[0027] Example 2

[0028] Solvent-free preparation of 0.35% Zr-L catalyst:

[0029] First, weigh 1.8g of solid silica gel, 1.178g of potassium hydroxide, and 0.370g of zirconium chloride into a mortar and grind for 15 minutes. Then add 0.234g of aluminum hydroxide and grind for another 20 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 Zr-doped L molecular sieve.

[0030] Fourier transform infrared spectrum at 950 cm⁻¹ -1 The absorption peaks at these locations are attributed to vibrations in Si-O-Zr. The X-ray electron spectroscopy peaks at binding energies of 182.5 eV and 184.9 eV correspond to Zr 3d... 5 / 2 and Zr 3d 3 / 2 The above results all indicate that Zr atoms have entered the L molecular sieve framework.

[0031] Example 3

[0032] Solvent-free preparation of 0.07% Sn-L catalyst:

[0033] First, weigh 1.8g of solid raw materials, 1.19g of potassium bromide, and 0.078g of tin chloride, and grind them in a mortar for 15 minutes. Then, add 0.246g of sodium aluminate and grind for another 20 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 Sn-doped L molecular sieve.

[0034] Fourier transform infrared spectrum at 960 cm⁻¹ -1 The absorption peaks at these locations are attributed to the asymmetric stretching vibrations of Si-O-Sn, while the X-ray electron spectroscopy peaks at binding energies of 487.9 eV and 496.4 eV are attributed to the framework tetrahedral Sn species. These results all indicate that Sn atoms have entered the L molecular sieve framework.

[0035] Example 4

[0036] Solvent-free preparation of 0.7% Mg-L catalyst:

[0037] First, weigh 1.8g of silica, 2.6g of potassium silicate, and 0.286g of magnesium chloride into a mortar and grind for 15 minutes. Then add 0.99g of aluminum sulfate and grind for another 20 minutes. Add the reaction 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 Mg-doped L molecular sieve.

[0038] Fourier transform infrared spectrum at 640 cm⁻¹ -1 The absorption peak at this location is attributed to the vibrational peak of Si-O-Mg, and the X-ray electron spectroscopy peak at a binding energy of 52.2 eV is attributed to the Mg species in the framework. These results all indicate that Mg atoms have entered the L-zeolite framework.

[0039] Example 5

[0040] Solvent-free preparation of 0.7% Ce-L catalyst:

[0041] First, weigh 1.8g of solid raw materials, 1.178g of potassium hydroxide, and 0.739g of cerium chloride, and grind them in a mortar for 15 minutes. Then add 0.234g of aluminum hydroxide and grind for another 20 minutes. Add the reaction raw 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 an air atmosphere to obtain the final Ce-doped L molecular sieve.

[0042] Fourier transform infrared spectrum at 960 cm⁻¹ -1The absorption peak at [location] is attributed to the vibrational peak of Si-O-Ce, and the X-ray electron spectroscopy peak at a binding energy of 916 eV is attributed to the Ce species in the framework. These results all indicate that Ce atoms have entered the L molecular sieve framework.

[0043] Example 6

[0044] Solvent-free preparation of 0.7% Zn-L catalyst:

[0045] First, weigh 1.8g of solid raw materials, 1.178g of potassium hydroxide, and 0.408g of zinc chloride, and grind them in a mortar for 15 minutes. Then add 0.234g of aluminum hydroxide and grind for another 20 minutes. Add the reaction raw 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 an air atmosphere to obtain the final Zn-doped L molecular sieve.

[0046] Fourier transform infrared spectrum at 968 cm⁻¹ -1 The absorption peak at [location] is attributed to the vibrational peak of Si-O-Zn, and the X-ray electron spectroscopy peak at a binding energy of 1022.5 eV is attributed to the Zn species in the framework. These results all indicate that Zn atoms have entered the L-zeolite framework.

[0047] Example 7

[0048] Solvent-free preparation of 0.7% Ni-L catalyst:

[0049] First, weigh 1.8g of solid raw materials, 1.178g of potassium hydroxide, and 0.389g of nickel chloride, and grind them in a mortar for 15 minutes. Then add 0.234g of aluminum hydroxide and grind for another 20 minutes. Add the reaction raw 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 and is directly calcined at 550℃ for 4 hours in an air atmosphere to obtain the final Ni-doped L molecular sieve.

[0050] Fourier transform infrared spectrum at 970 cm⁻¹ -1 The absorption peaks at this point are attributed to the vibrations of Si-O-Ni. The X-ray electron spectroscopy peaks at binding energies of 858.7 eV and 876.5 eV correspond to Ni 2P, respectively. 3 / 2 and Ni 2P 1 / 2 This indicates the presence of a four-coordinated nickel framework. All of the above results demonstrate that Ni atoms have entered the L-zeolite framework.

[0051] Example 8

[0052] Solvent-free preparation of 0.7% Cu-L catalyst:

[0053] First, weigh 1.8g of solid raw materials, 1.178g of potassium hydroxide, and 0.403g of copper chloride, and grind them in a mortar for 15 minutes. Then add 0.234g of aluminum hydroxide and grind for another 20 minutes. Add the reaction raw 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 an air atmosphere to obtain the final Cu-doped L molecular sieve.

[0054] Fourier transform infrared spectrum at 960 cm⁻¹ -1 The absorption peak at this point is attributed to the asymmetric stretching vibration peak of Si-O-Cu, and the X-ray electron spectroscopy peaks at binding energies of 934 eV and 953.4 eV correspond to Cu 2P, respectively. 3 / 2 and Cu2P 1 / 2 The above results all indicate that Cu atoms have entered the L molecular sieve framework.

[0055] Example 9

[0056] Solvent-free preparation of 0.7% Fe-L catalyst:

[0057] First, weigh 1.8g of solid raw materials, 1.178g of potassium hydroxide, and 0.487g of ferric chloride, and grind them in a mortar for 15 minutes. Then add 0.234g of aluminum hydroxide and grind for another 20 minutes. Add the reaction raw 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 an air atmosphere to obtain the final Fe-doped L molecular sieve.

[0058] Fourier transform infrared spectrum at 652 cm⁻¹ -1 The absorption peak at this point is attributed to the asymmetric stretching vibration peak of Si-O-Fe, and the X-ray electron spectroscopy peaks at binding energies of 711.1 eV and 724 eV correspond to Fe 2P, respectively. 3 / 2 and Fe2P 1 / 2 The above results all indicate that Fe atoms have entered the L molecular sieve framework.

[0059] Example 10

[0060] Solvent-free preparation of 0.7% BL catalyst:

[0061] First, weigh 1.8g of solid raw materials, 1.178g of precipitated silica, 0.185g of potassium hydroxide, and 0.185g of boric acid. Pour them into a mortar and grind for 15 minutes. Then add 0.234g of aluminum hydroxide and grind for another 20 minutes. Add the reaction raw 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 an air atmosphere to obtain the final B-doped L molecular sieve.

[0062] Fourier transform infrared spectrum at 900 cm⁻¹ -1 The absorption peak at this point is attributed to the vibrational peak of Si-OB, and the X-ray electron spectroscopy peak at a binding energy of 1310 eV is attributed to the B species in the framework. These results all indicate that B atoms have entered the L molecular sieve framework.

[0063] Example 11

[0064] Solvent-free preparation of 0.7% BL catalyst:

[0065] First, weigh 1.8g of solid raw materials, 1.178g of potassium hydroxide, and 0.209g of boron oxide, and grind them in a mortar for 15 minutes. Then add 0.234g of aluminum hydroxide and grind for another 20 minutes. Add the reaction raw 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 and is directly calcined at 550℃ for 4 hours in an air atmosphere to obtain the final B-doped L molecular sieve.

[0066] Example 12

[0067] Solvent-free preparation of 0.35% BL catalyst:

[0068] First, weigh 1.8g of solid raw materials, 1.178g of potassium hydroxide, and 0.105g of boron oxide, and grind them in a mortar for 15 minutes. Then add 0.234g of aluminum hydroxide and grind for another 20 minutes. Add the reaction raw 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 and is directly calcined at 550℃ for 4 hours in an air atmosphere to obtain the final B-doped L molecular sieve.

[0069] Example 13

[0070] Solvent-free preparation of 0.07% BL catalyst:

[0071] First, weigh 1.8g of solid raw materials, 1.178g of potassium hydroxide, and 0.021g of boron oxide, and grind them in a mortar for 15 minutes. Then add 0.234g of aluminum hydroxide and grind for another 20 minutes. Add the reaction raw 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 and is directly calcined at 550℃ for 4 hours in an air atmosphere to obtain the final B-doped L molecular sieve.

[0072] Comparative Example 1

[0073] Synthesis of 0.7% B / L catalyst by conventional impregnation method:

[0074] 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 mixture 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 undoped L-molecular sieves. Weigh 0.185g of boric acid into a 50ml round-bottom flask and add 30ml of H2O to the flask, stirring until the boric acid is completely dissolved. Add all of the L-molecular sieves prepared above to the flask containing the boric acid solution and stir at 80℃ for 4 hours. Wash the resulting product multiple times with deionized water until neutral. Dry the washed product in an oven at 80℃ for 12 hours, and then calcine at 550℃ for 4 hours in air to obtain the final B-supported L-molecular sieve.

[0075] Fourier transform infrared spectrum at 1440 cm⁻¹ -1 The absorption peak at that point is attributed to the asymmetric stretching vibration peak of the BOB bond, indicating that the B atom did not enter the L molecular sieve framework, but instead formed a B2O3 species on the outside.

[0076] Analysis of the characterization results of heteroatom state in L-zeolite: FTIR and XPS characterization were performed on the heteroatom-doped L-zeolite samples, and the results are shown in Table 1.

[0077] Table 1. FTIR and XPS characterization results of heteroatom states in L-zeolite.

[0078]

[0079]

[0080] Examples 1-13 detail the preparation of heteroatom-doped L-type molecular sieves under different conditions using a solvent-free method. Comparative Example 1 illustrates the synthesis of heteroatom-supported L-type molecular sieves using a conventional impregnation method. By changing the experimental conditions, higher sample yields were desired. The molecular sieve sample yield was calculated as: mass of the obtained molecular sieve product / total mass of reactants. The main preparation parameters and sample yield results for each example are as follows:

[0081] Table 2 Preparation parameters and sample yield of Examples 1-13 and Comparative Example 1

[0082]

[0083] As shown in the table above, the molecular sieves synthesized in the above implementation cases have a high yield (>93%), and the heteroatoms in the samples prepared by the solvent-free method are all incorporated into the L molecular sieve framework, with no impurity crystals appearing in the samples, maintaining good crystallinity and purity.

[0084] Example 14

[0085] B-doped L molecular sieves catalyze the preparation of 3-acetamido-5-acetamidofuran from N-acetylglucosamine.

[0086] 0.1 g of N-acetylglucosamine was dissolved in 10 mL of N,N-dimethylacetamide, and 0.025 g of the B-doped L molecular sieve prepared in Example 10 was added. The mixture was reacted at 160 °C for 30 minutes. High-performance liquid chromatography (HPLC) analysis showed that the yield of 3-acetamido-5-acetylfuran was 91%.

[0087] Comparative Example 2

[0088] The traditional impregnation method was used to synthesize B-supported L molecular sieves (B / L) to catalyze the preparation of 3-acetamido-5-acetamidofuran from N-acetylglucosamine.

[0089] 0.1 g of N-acetylglucosamine was dissolved in 10 mL of N,N-dimethylacetamide, and 0.025 g of B-supported L molecular sieve prepared in Comparative Example 1 was added. The mixture was reacted at 160 °C for 4 h. The yield of 3-acetamido-5-acetylfuran was 71% by high performance liquid chromatography.

[0090] The heteroatom-doped L-type molecular sieve prepared in this invention was used to catalyze the conversion of N-acetylglucosamine to 3-acetamido-5-acetylfuran, and the catalytic performance was tested. The yield of 3A5AF was significantly improved after heteroatom doping modification, indicating that the method of this invention can effectively improve the catalytic performance of L-type molecular sieves.

[0091] 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 solvent-free preparation method for heteroatom-doped L-type molecular sieves, characterized in that: The method includes the following steps: (1) Mix the solid silicon source, solid potassium source and solid heteroatom compound and grind them in a mortar; (2) Add the solid aluminum source to the sample ground in step (1) and continue grinding; (3) Place the ground sample from step (2) into a reaction vessel and carry out a crystallization reaction; (4) The crystallized sample in step (3) is calcined in air to obtain heteroatom-doped L molecular sieve; In step (4), the calcination temperature is 400-550℃ and the calcination time is 1-6h.

2. The solvent-free preparation method of heteroatom-doped L-zeolite according to claim 1, characterized in that: In step (1), the silicon source is one or a mixture of two of solid silica gel and fumed silica; The potassium source is one or a mixture of two or more of potassium hydroxide, potassium bromide, and potassium silicate; The heteroatom compound is any one of ferric chloride, chromium chloride, magnesium chloride, zirconium chloride, tin chloride, copper chloride, zinc chloride, nickel chloride, cerium chloride, boric acid, and boron oxide.

3. The solvent-free preparation method of heteroatom-doped L-zeolite according to claim 1, characterized in that: In step (1), the molar ratio of silicon source to potassium source is 1:1 to 1:10; The molar ratio of heteroatom compound to silicon source is 1:10 to 1:100; The grinding time is 10 to 120 minutes.

4. The solventless preparation method of heteroatom-doped L-zeolite according to claim 1, characterized in that: In step (2), the aluminum source is one or a mixture of two or more of aluminum hydroxide, sodium aluminate, and aluminum sulfate.

5. The solventless preparation method of heteroatom-doped L-zeolite according to claim 1, characterized in that: In step (2), the molar ratio of aluminum source to silicon source is 1:3 to 1:50; The grinding time is 10 to 60 minutes.

6. The solventless preparation method of heteroatom-doped L-zeolite according to claim 1, characterized in that: In step (3), the crystallization reaction temperature is 170-200℃ and the crystallization reaction time is 4-24h.

Images