Synthesis method of silicon-aluminum ITQ-13 zeolite molecular sieve

Abstract

The invention discloses a synthesis method of a silicon-aluminum ITQ-13 zeolite molecular sieve, which belongs to the technical field of molecular sieve synthesis, and comprises the following steps: uniformly mixing a silicon source, an aluminum source, an organic template agent R, water and a seed crystal, placing in a reaction kettle, and carrying out crystallization reaction at 170-180 DEG C for 7-12 days; and carrying out suction filtration and drying on the product to obtain the silicon-aluminum ITQ-13 zeolite molecular sieve. The invention provides a novel synthesis method, the silicon-aluminum ITQ-13 zeolite molecular sieve can be synthesized under the condition of no addition of HF and Ge, the risk of experiments is greatly reduced, and meanwhile, under the condition of no addition of germanium, aluminum is introduced into the framework of the ITQ-13 zeolite molecular sieve, so that the synthesis cost and the complicated operation of post-treatment are greatly reduced.

Description

Technical Field

[0001] The present invention relates to a method for synthesizing a silicon-alumina ITQ-13 zeolite molecular sieve, and in particular to a method for synthesizing the silicon-alumina ITQ-13 zeolite molecular sieve by using a template without adding HF, belonging to the technical field of molecular sieve synthesis. Background Art

[0002] Zeolite molecular sieve materials, including silica-alumina molecular sieves and phosphate-alumina molecular sieves, are widely used in petrochemicals, fine chemicals, and environmental protection. Among them, ITQ-13 zeolite molecular sieve is a silica-alumina molecular sieve with a typical ITH topology. Its three-dimensional 9x10x10 pore system makes it one of the few molecular sieves with an odd number of ring members. It exhibits excellent activity and selectivity in the methanol-to-olefins (MTO) reaction.

[0003] However, traditional ITQ-13 zeolite molecular sieves typically require synthesis under neutral or acidic conditions in the presence of HF. For example, Chinese Patent Publication No. CN106698456A discloses a one-step method for synthesizing aluminum-containing ITQ-13 molecular sieves using a linear polyquaternary ammonium base organic template. This method involves mixing a silicon source, an aluminum source, a linear polyquaternary ammonium base organic template (T), and hydrofluoric acid or ammonium fluoride. The mixture is stirred evenly and then placed in a reactor for crystallization. The product is then filtered and dried to obtain the ITQ-13 zeolite molecular sieve. However, HF is highly hazardous and environmentally unfriendly during use.

[0004] Corma et al. published a study in J. Catal (2006, 238, 79–87) on the introduction of germanium (Ge) species to reduce the energy of the D4Rs unit. They successfully synthesized Ge-ITH zeolite by adding Ge in the absence of HF. However, post-treatment is required to obtain the silicon-alumina ITQ-13 molecular sieve. Moreover, the use of Ge not only increases the cost but also reduces the stability of the zeolite.

[0005] Therefore, it is crucial to synthesize this zeolite without adding HF and Ge and develop a new method for synthesizing silica-alumina ITQ-3 zeolite molecular sieve.

[0006] Currently, N,N-bis(3-fluorobenzyl)-N,N,N,N-tetramethyl-1,6-hexanediammonium cation is used as a template to synthesize ITQ-13 molecular sieves. However, this method can only produce all-silicon ITQ-13 molecular sieves for the Beckmann rearrangement reaction of cyclohexanone oxime. Summary of the Invention

[0007] The purpose of the present invention is to overcome the deficiencies in the prior art and synthesize a silicon-alumina ITQ-13 zeolite molecular sieve without adding HF and Ge.

[0008] To solve the technical problem, the solution of the present invention is: A method for synthesizing a silicon-aluminum ITQ-13 zeolite molecular sieve comprises the following steps: uniformly mixing a silicon source, an aluminum source, an organic template agent R, water, and seed crystals, and then placing the mixture in a reactor for crystallization at 170-180° C. for 7-12 days; and filtering and drying the product to obtain the silicon-aluminum ITQ-13 zeolite molecular sieve.

[0009] Further settings are: The addition amounts of silicon source, aluminum source, organic template R, and water are controlled so that the molar ratio is SiO2: Al2O3: organic template R: H2O = 1: 0.00-0.0025: 0.5: 2-5.

[0010] The aluminum source is aluminum isopropoxide.

[0011] The silicon source is tetraethyl silicate.

[0012] The water is deionized water.

[0013] The seed crystals are ITQ-13 molecular sieve seed crystals.

[0014] The organic template R is prepared by the following method: N, N, N, N-tetramethyl-1,6-hexanediamine and halogenated hydrocarbon are weighed in a molar ratio of 1:2.2, dissolved in acetonitrile, reacted at room temperature for 24 hours to obtain a white solid, the white solid is filtered and dried to obtain a quaternary ammonium salt of the organic template R, the quaternary ammonium salt of the organic template R is dissolved in water, and the halogen in the quaternary ammonium salt of the organic template R is completely exchanged with hydroxide using a strongly basic anion exchange resin, and the resin is filtered to obtain an organic template R solution.

[0015] The crystallization reaction is carried out at 175° C. for 7 days.

[0016] After the silicon source, aluminum source, organic template R, water and seed crystals are evenly mixed, they are placed in an 80°C oven for dehydration and dealcoholization. To ensure that the alcohol can be completely removed and does not affect the crystallization of the molecular sieve, drying for more than 12 hours is required.

[0017] A method for synthesizing a silicon-aluminum ITQ-13 zeolite molecular sieve comprises adding aluminum isopropoxide, an aluminum source, to a solution of an organic template agent R for dissolution, then adding tetraethyl silicate, a silicon source, and mixing. After the tetraethyl silicate is fully hydrolyzed, the mixture is weighed and placed in an 80°C oven for dehydration and dealcoholization. To ensure that the alcohol is completely removed and does not affect the crystallization of the molecular sieve, the mixture is dried for more than 12 hours. The mixture is weighed again and water is added to adjust the H2O / SiO2 molar ratio to 2-5. After seed crystals are added and mixed uniformly, the gel is transferred to a polytetrafluoroethylene stainless steel reactor and crystallized at 175°C for 7 days. The product is filtered and dried to obtain the product.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention provides a new synthesis method that can synthesize silicon-alumina ITQ-13 zeolite molecular sieve without adding HF and Ge, greatly reducing the risk of the experiment.

[0019] 2. The present invention provides an organic template that can introduce aluminum into the framework of ITQ-13 zeolite molecular sieve without adding germanium, greatly reducing the cost of synthesis and the complexity of post-processing operations.

[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the XRD spectrum of the silicon-alumina ITQ-13 zeolite molecular sieve product (completely crystallized) prepared in Example 1 of the present invention.

[0022] Figure 2 This is a scanning electron microscope photograph of the silicon-alumina ITQ-13 zeolite molecular sieve product (completely crystallized) prepared in Example 1 of the present invention.

[0023] Figure 3 This is the XRD spectrum of the silicon-alumina ITQ-13 zeolite molecular sieve product (uncrystallized and amorphous) prepared in Example 2 of the present invention.

[0024] Figure 4 This is the XRD spectrum of the silicon-alumina ITQ-13 zeolite molecular sieve product prepared in Example 5 of the present invention (not completely crystallized, molecular sieve and amorphous form coexist). DETAILED DESCRIPTION

[0025] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments: the raw materials described in the examples are commercially available or known products unless otherwise specified.

[0026] The organic template R used in the present invention is prepared by the following method: Preparation of organic template R1: N, N, N, N-tetramethyl-1,6-hexanediamine and 3-fluorobenzyl bromide were weighed in a molar ratio of 1:2.2, dissolved in acetonitrile, and reacted at room temperature for 24 hours to obtain a white solid. The white solid was filtered and dried to obtain a quaternary ammonium salt of the organic template R1. The quaternary ammonium salt of the organic template R1 was dissolved in water, and the bromine in the quaternary ammonium salt of the organic template R1 was completely exchanged with hydroxide using a strong basic anion exchange resin (IRN-78, Sigma-Aldrich Co., Ltd.). After filtering the resin, an organic template R1 solution was obtained.

[0027] Preparation of organic template R2: N, N, N, N-tetramethyl-1,6-hexanediamine and 4-fluorobenzyl bromide were weighed in a molar ratio of 1:2.2, dissolved in acetonitrile, and reacted at room temperature for 24 hours to obtain a white solid. The white solid was filtered and dried to obtain a quaternary ammonium salt of the organic template R2. The quaternary ammonium salt of the organic template R2 was dissolved in water, and the bromine in the quaternary ammonium salt of the organic template R2 was completely exchanged with hydroxide using a strong basic anion exchange resin (IRN-78, Sigma-Aldrich Co., Ltd.). After filtering the resin, an organic template R2 solution was obtained.

[0028] Preparation of organic template R3: N, N, N, N-tetramethyl-1,6-hexanediamine and 3,5-difluorobenzyl bromide were weighed in a molar ratio of 1:2.2, dissolved in acetonitrile, and reacted at room temperature for 24 hours to obtain a white solid. The white solid was filtered and dried to obtain a quaternary ammonium salt of the organic template R3. The quaternary ammonium salt of the organic template R3 was dissolved in water, and the bromine in the quaternary ammonium salt of the organic template R3 was completely exchanged with hydroxide using a strong basic anion exchange resin (IRN-78, Sigma-Aldrich Co., Ltd.). After filtering the resin, an organic template R3 solution was obtained.

[0029] Example 1

[0030] In this embodiment, silicon-alumina ITQ-13 zeolite molecular sieve is synthesized using organic template R1, and the molar ratio of the reaction raw materials is: 1.0 SiO2 / 0.0025 Al2O3 / 0.5 organic template R1 / 2 H2O.

[0031] First, 0.0085 g of aluminum isopropoxide was added to 8.33 g of organic template R1 solution (0.5 mmol / g) to dissolve it. Then, 1.73 g of tetraethyl silicate was added and stirred for 30 minutes. After the tetraethyl silicate was fully hydrolyzed, the mixture was weighed and placed in an 80°C oven for dehydration and dealcoholization. To ensure complete alcohol removal without affecting the crystallization of the molecular sieve, the mixture was dried for at least 12 hours. Water was reweighed and added to achieve a molar ratio of H₂O / SiO₂ of 2. 0.05 g of seed crystals was added and mixed thoroughly. The gel was then transferred to a Teflon-lined stainless steel reactor and crystallized at 175°C for 7 days. The product was then filtered and dried to obtain the final product.

[0032] Product Characterization: The product prepared in Example 1 was subjected to XRD and SEM analysis. Figure 1 、 Figure 2 As shown: Figure 1 X-ray diffraction analysis showed that its structure was ITQ-13 zeolite molecular sieve. Figure 2 This is a scanning electron microscope (SEM) photograph of the ITQ-13 zeolite molecular sieve product. The SEM photograph shows that the synthesized product is completely crystallized and presents a uniform nanosheet structure.

[0033] In order to explore the effects of different aluminum sources on the performance of molecular sieves, experiments as shown in Examples 2 and 3 were carried out.

[0034] Example 2

[0035] In this embodiment, aluminum sulfate 18hydrate is used as the aluminum source to synthesize silicon-aluminum ITQ-13 zeolite molecular sieve. The molar ratio of the reaction raw materials is: 1.0 SiO2 / 0.0025 Al2O3 / 0.5 organic template R1 / 2 H2O.

[0036] First, 0.0139 g of aluminum sulfate 18hydrate was added to 8.33 g of organic template R1 solution (0.5 mmol / g) to dissolve it. Then, 1.73 g of tetraethyl silicate was added and stirred for 30 minutes. After the tetraethyl silicate was fully hydrolyzed, the mixture was weighed and placed in an 80°C oven for dehydration and dealcoholization. To ensure complete alcohol removal without affecting the crystallization of the molecular sieve, the mixture was dried for at least 12 hours. Water was reweighed to a molar ratio of H2O / SiO2 = 2, and 0.05 g of seed crystals were added and mixed thoroughly. The gel was then transferred to a Teflon-lined stainless steel reactor and crystallized at 175°C for 7 days. The product was then filtered and dried to obtain the final product.

[0037] Product Characterization: The product prepared in Example 2 was subjected to XRD analysis. Figure 3 As shown: Compared with the XRD pattern of the product prepared in Example 1, it can be found that the XRD spectrum of the sample after crystallization in Example 2 shows: uncrystallized amorphous state, uneven baseline, and only a small amount of seed peaks.

[0038] Example 3

[0039] In this embodiment, aluminum hydroxide is used as the aluminum source to synthesize the silicon-aluminum ITQ-13 zeolite molecular sieve. The molar ratio of the reaction raw materials is: 1.0 SiO2 / 0.0025 Al2O3 / 0.5 organic template R1 / 2 H2O.

[0040] First, 0.003218 g of aluminum hydroxide was added to 8.33 g of organic template R1 solution (0.5 mmol / g) to dissolve it. Then, 1.73 g of tetraethyl silicate was added and stirred for 30 minutes. After the tetraethyl silicate was fully hydrolyzed, the mixture was weighed and placed in an 80°C oven for dehydration and dealcoholization. To ensure complete alcohol removal without affecting the crystallization of the molecular sieve, the mixture was dried for at least 12 hours. The mixture was weighed again to replenish water to a molar ratio of H2O / SiO2 = 2. 0.05 g of seed crystals was added and mixed thoroughly. The gel was then transferred to a Teflon-lined stainless steel reactor and crystallized at 175°C for 7 days. The product was then filtered and dried to obtain the final product.

[0041] The product was analyzed to be in an uncrystallized amorphous state.

[0042] Example 4

[0043] This example mainly explores the effect of the choice of silicon source on the performance of the molecular sieve. Fine silica gel (SiO2) is used as the silicon source to synthesize the silicon-alumina ITQ-13 zeolite molecular sieve. The molar ratio of the reaction raw materials is: 1.0 SiO2 / 0.0025 Al2O3 / 0.5 organic template R1 / 2 H2O.

[0044] First, 0.0085 g of aluminum isopropoxide was added to 8.33 g of organic template R1 solution (0.5 mmol / g) to dissolve. Subsequently, 0.5 g of fine silica gel (SiO2) was added and stirred for 30 minutes. After sufficient hydrolysis, the mixture was weighed and placed in an 80°C oven for dehydration and dealcoholization, requiring drying for at least 12 hours. Water was reweighed to a molar ratio of H2O / SiO2 = 2. 0.05 g of seed crystals was added and mixed thoroughly. The gel was then transferred to a Teflon-lined stainless steel reactor and crystallized at 175°C for 7 days. The product was then filtered and dried to obtain the final product.

[0045] The product was analyzed to be in an uncrystallized amorphous state.

[0046] Example 5

[0047] This example mainly discusses the effect of the dealcoholization process on the performance of the molecular sieve. The molar ratio of the reaction raw materials is: 1.0 SiO2 / 0.0025 Al2O3 / 0.5 organic template R1 / 2 H2O.

[0048] First, 0.0085 g of aluminum isopropoxide was dissolved in 8.33 g of organic template R1 solution (0.5 mmol / g). Then, 1.73 g of tetraethyl silicate was added and stirred for 30 minutes. After the tetraethyl silicate was fully hydrolyzed, the mixture was weighed and placed in an 80°C oven for dehydration (drying was only performed to the specified moisture content; the alcohol was not completely removed). After adding 0.05 g of seed crystals and mixing thoroughly, the gel was transferred to a Teflon-lined stainless steel reactor and crystallized at 175°C for 7 days. The product was then filtered and dried to obtain the final product.

[0049] The product prepared in Example 5 was subjected to XRD analysis. Figure 4 As shown: Compared with the XRD pattern of the product prepared in Example 1, it can be found that the XRD spectrum of the sample after crystallization in Example 5 shows that ITQ-13 is crystallized, but not completely crystallized, and ITQ-13 molecular sieve and amorphous form coexist.

[0050] Example 6

[0051] This example mainly explores the effect of adding seed crystals on the performance of molecular sieves. The molar ratio of the reaction raw materials is: 1.0SiO2 / 0.0025Al2O3 / 0.5organic template R1 / 2H2O.

[0052] First, 0.0085 g of aluminum isopropoxide was added to 8.33 g of organic template R1 solution (0.5 mmol / g) to dissolve it. Then, 1.73 g of tetraethyl silicate was added and stirred for 30 minutes. After the tetraethyl silicate was fully hydrolyzed, the mixture was weighed and placed in an 80°C oven for dehydration and dealcoholization. To ensure complete alcohol removal without affecting the crystallization of the molecular sieve, the mixture was dried for at least 12 hours. The mixture was weighed again to replenish water to a molar ratio of H2O / SiO2 = 2. The mixture was then transferred to a Teflon-lined stainless steel reactor and crystallized at 175°C for 7 days. The product was then filtered and dried to obtain the product.

[0053] The product was analyzed to be in an uncrystallized amorphous state.

[0054] Example 7

[0055] This example mainly explores the effect of the timing of seed addition on the performance of the molecular sieve. The molar ratio of the reaction raw materials is: 1.0 SiO2 / 0.0025 Al2O3 / 0.5 organic template R1 / 2 H2O.

[0056] First, 0.0085 g of aluminum isopropoxide was added to 8.33 g of organic template R1 solution (0.5 mmol / g) to dissolve it. Then, 1.73 g of tetraethyl silicate was added and stirred for 30 minutes. After the tetraethyl silicate was fully hydrolyzed, 0.05 g of seed crystals were added and stirred evenly. After weighing, the mixture was placed in an 80°C oven for dehydration and dealcoholization. To ensure complete alcohol removal without affecting the crystallization of the molecular sieve, the mixture was dried for at least 12 hours. The mixture was weighed again to replenish water to a molar ratio of H2O / SiO2 = 2. The gel was then transferred to a Teflon-lined stainless steel reactor and crystallized at 175°C for 7 days. The product was then filtered and dried to obtain the final product.

[0057] The product was analyzed to be in an incompletely crystallized state, and was in an ITQ-13 molecular sieve + amorphous state.

[0058] Example 8

[0059] This example mainly explores the effect of the addition amount of aluminum isopropoxide on the performance of the molecular sieve. The molar ratio of the reaction raw materials is: 1.0 SiO2 / 0.00125 Al2O3 / 0.5 organic template R1 / 2 H2O.

[0060] First, 0.00425 g of aluminum isopropoxide was added to 8.33 g of organic template R1 solution (0.5 mmol / g) to dissolve it. Then, 1.73 g of tetraethyl silicate was added and stirred for 30 minutes. After the tetraethyl silicate was fully hydrolyzed, the mixture was weighed and placed in an 80°C oven for dehydration and dealcoholization. To ensure complete alcohol removal without affecting the crystallization of the molecular sieve, the mixture was dried for at least 12 hours. Water was reweighed to a molar ratio of H2O / SiO2 = 2, and 0.05 g of seed crystals were added and mixed thoroughly. The gel was then transferred to a Teflon-lined stainless steel reactor and crystallized at 175°C for 7 days. The product was filtered and dried to obtain the final product.

[0061] The product was analyzed to be completely crystallized with good crystallinity.

[0062] Example 9

[0063] This example mainly explores the effect of the H2O / SiO2 ratio on the performance of molecular sieves. The molar ratio of the reaction raw materials is: 1.0SiO2 / 0.0025Al2O3 / 0.5organic template R1 / 5H2O.

[0064] First, 0.0085 g of aluminum isopropoxide was added to 8.33 g of organic template R1 solution (0.5 mmol / g) to dissolve it. Then, 1.73 g of tetraethyl silicate was added and stirred for 30 minutes. After the tetraethyl silicate was fully hydrolyzed, the mixture was weighed and placed in an 80°C oven for dehydration and dealcoholization. To ensure complete alcohol removal without affecting the crystallization of the molecular sieve, the mixture was dried for at least 12 hours. The mixture was weighed again to replenish water to a molar ratio of H2O / SiO2 = 5. 0.05 g of seed crystals was added and mixed thoroughly. The gel was then transferred to a Teflon-lined stainless steel reactor and crystallized at 175°C for 7 days. The product was then filtered and dried to obtain the final product.

[0065] The product was analyzed to be completely crystallized with good crystallinity.

[0066] Example 10

[0067] This example mainly explores the effect of the H2O / SiO2 ratio on the performance of molecular sieves. The molar ratio of the reaction raw materials is: 1.0SiO2 / 0.0025Al2O3 / 0.5organic template R1 / 8H2O.

[0068] First, 0.0085 g of aluminum isopropoxide was added to 8.33 g of organic template R1 solution (0.5 mmol / g) to dissolve it. Then, 1.73 g of tetraethyl silicate was added and stirred for 30 minutes. After the tetraethyl silicate was fully hydrolyzed, the mixture was weighed and placed in an 80°C oven for dehydration and dealcoholization. To ensure complete alcohol removal without affecting the crystallization of the molecular sieve, the mixture was dried for at least 12 hours. Water was reweighed to a molar ratio of H2O / SiO2 = 8. 0.05 g of seed crystals was added and mixed thoroughly. The gel was then transferred to a Teflon-lined stainless steel reactor and crystallized at 175°C for 7 days. The product was filtered and dried to obtain the final product.

[0069] The product was analyzed to be in an uncrystallized amorphous state.

[0070] Example 11

[0071] This example mainly explores the effect of crystallization time on the performance of molecular sieves. The molar ratio of the reaction raw materials is: 1.0SiO2 / 0.0025Al2O3 / 0.5organic template R1 / 2H2O.

[0072] First, 0.0085 g of aluminum isopropoxide was added to 8.33 g of organic template R1 solution (0.5 mmol / g) to dissolve it. Then, 1.73 g of tetraethyl silicate was added and stirred for 30 minutes. After the tetraethyl silicate was fully hydrolyzed, the mixture was weighed and placed in an 80°C oven for dehydration and dealcoholization. To ensure complete alcohol removal without affecting the crystallization of the molecular sieve, the mixture was dried for at least 12 hours. The mixture was reweighed to replenish water to a molar ratio of H2O / SiO2 = 2. 0.05 g of seed crystals was added and mixed thoroughly. The gel was then transferred to a Teflon-lined stainless steel reactor and crystallized at 175°C for 4 days. The product was filtered and dried to obtain the final product.

[0073] The product was analyzed to be in an incompletely crystallized state, and was in an ITQ-13 molecular sieve + amorphous state.

[0074] Example 12

[0075] This example mainly explores the effect of crystallization time on the performance of molecular sieves. The molar ratio of the reaction raw materials is: 1.0SiO2 / 0.0025Al2O3 / 0.5organic template R1 / 2H2O.

[0076] First, 0.0085 g of aluminum isopropoxide was added to 8.33 g of organic template R1 solution (0.5 mmol / g) to dissolve it. Then, 1.73 g of tetraethyl silicate was added and stirred for 30 minutes. After the tetraethyl silicate was fully hydrolyzed, the mixture was weighed and placed in an 80°C oven for dehydration and dealcoholization. To ensure complete alcohol removal without affecting the crystallization of the molecular sieve, the mixture was dried for at least 12 hours. The mixture was weighed again to replenish water to a molar ratio of H2O / SiO2 = 2. 0.05 g of seed crystals was added and mixed thoroughly. The gel was then transferred to a Teflon-lined stainless steel reactor and crystallized at 175°C for 12 days. The product was filtered and dried to obtain the final product.

[0077] The addition amount of each reaction raw material was controlled to make the molar ratio range: 1.0 SiO2 / 0.0025 Al2O3 / 0.5R / 2H2O. The product had good crystallinity.

[0078] The product was analyzed to be completely crystallized with good crystallinity.

[0079] Example 13

[0080] This example mainly explores the effect of different templates on the performance of molecular sieves. The organic template R2 was used to guide the synthesis of silicon-aluminum ITQ-13 zeolite molecular sieve. The molar ratio of the reaction raw materials was: 1.0 SiO2 / 0.0025 Al2O3 / 0.5 organic template R2 / 2 H2O.

[0081] First, 0.0085 g of aluminum isopropoxide was added to 8.33 g of organic template R2 solution (0.5 mmol / g) to dissolve it. Then, 1.73 g of tetraethyl silicate was added and stirred for 30 minutes. After the tetraethyl silicate was fully hydrolyzed, the mixture was weighed and placed in an 80°C oven for dehydration and dealcoholization. To ensure complete alcohol removal without affecting the crystallization of the molecular sieve, the mixture was dried for at least 12 hours. Water was reweighed to a molar ratio of H2O / SiO2 = 2, and 0.05 g of seed crystals were added and mixed thoroughly. The gel was then transferred to a Teflon-lined stainless steel reactor and crystallized at 175°C for 7 days. The product was filtered and dried to obtain the final product.

[0082] The product was analyzed to be completely crystallized with good crystallinity.

[0083] Example 14

[0084] This example mainly explores the effect of different templates on the performance of molecular sieves. The organic template R3 was used to guide the synthesis of silicon-aluminum ITQ-13 zeolite molecular sieve. The molar ratio of the reaction raw materials was: 1.0 SiO2 / 0.0025 Al2O3 / 0.5 organic template R3 / 2 H2O.

[0085] First, 0.0085 g of aluminum isopropoxide was added to 8.33 g of organic template R3 solution (0.5 mmol / g) to dissolve it. Then, 1.73 g of tetraethyl silicate was added and stirred for 30 minutes. After the tetraethyl silicate was fully hydrolyzed, the mixture was weighed and placed in an 80°C oven for dehydration and dealcoholization. To ensure complete alcohol removal without affecting the crystallization of the molecular sieve, the mixture was dried for at least 12 hours. The mixture was weighed again to replenish water to a molar ratio of H2O / SiO2 = 2. 0.05 g of seed crystals was added and mixed thoroughly. The gel was then transferred to a Teflon-lined stainless steel reactor and crystallized at 175°C for 7 days. The product was filtered and dried to obtain the final product.

[0086] XRD analysis showed that the product was completely crystallized and had good crystallinity.

[0087] Comparative Example 1 In this embodiment, the organic template R1 is used to guide the synthesis of all-silicon ITQ-13 zeolite molecular sieve, and the addition amount of each reaction raw material is controlled to make the molar ratio range: 1.0 SiO2 / 0.0 Al2O3 / 0.5 organic template R1 / 2 H2O, First, 8.33 g of organic template R1 solution (0.5 mmol / g) and 1.73 g of tetraethyl silicate were mixed and stirred for 10 minutes. After the excess water was dried off, the gel was transferred to a polytetrafluoroethylene stainless steel reactor and crystallized at 175°C for 7 days. The product was filtered and dried to obtain the product.

[0088] The product was analyzed to be completely crystallized with good crystallinity.

[0089] analyze:

[0090] The corresponding product status statistics of ITQ-13 zeolite molecular sieves prepared under different process conditions of Examples 1-14 and Comparative Example 1 are shown in Table 1.

[0091] Table 1

[0092] Serial number Silicon source Aluminum source <![CDATA[Al2O3 / Si]]> <![CDATA[H2O / Si]]> Crystallization time Other conditions Product Status Comparative Example 1 Tetraethyl silicate / 0 2 7d ITQ-13 (completely crystallized) Example 1 Tetraethyl silicate Aluminum isopropylate 0.0025 2 7d ITQ-13 (completely crystallized) Example 2 Tetraethyl silicate Aluminum sulfate 18hydrate 0.0025 2 7d Amorphous (uncrystallized) Example 3 Tetraethyl silicate aluminum hydroxide 0.0025 2 7d Amorphous (uncrystallized) Example 4 <![CDATA[Fine silica gel (SiO2)]]> Aluminum isopropylate 0.0025 2 7d Amorphous (uncrystallized) Example 5 Tetraethyl silicate Aluminum isopropylate 0.0025 2 7d Incomplete dealcoholization ITQ-13+ amorphous (not completely crystallized) Example 6 Tetraethyl silicate Aluminum isopropylate 0.0025 2 7d Without seed crystal Amorphous (uncrystallized) Example 7 Tetraethyl silicate Aluminum isopropylate 0.0025 2 7d Add seed crystals before removing water ITQ-13+ amorphous (not completely crystallized) Example 8 Tetraethyl silicate Aluminum isopropylate 0.0125 2 7d ITQ-13 (completely crystallized) Example 9 Tetraethyl silicate Aluminum isopropylate 0.0025 5 7d ITQ-13 (completely crystallized) Example 10 Tetraethyl silicate Aluminum isopropylate 0.0025 8 7d Amorphous (uncrystallized) Example 11 Tetraethyl silicate Aluminum isopropylate 0.0025 2 4d ITQ-13+ amorphous (not completely crystallized) Example 12 Tetraethyl silicate Aluminum isopropylate 0.0025 2 12d ITQ-13 (completely crystallized) Example 13 Tetraethyl silicate Aluminum isopropylate 0.0025 2 7d Organic template R2 ITQ-13 (completely crystallized) Example 14 Tetraethyl silicate Aluminum isopropylate 0.0025 2 7d Organic template R3 ITQ-13 (completely crystallized)

[0093] As shown in Table 1: (1) Effects of silicon source and aluminum source on molecular sieve synthesis Comparison of Examples 1-4 demonstrates the crucial importance of the selection of silicon and aluminum sources in the synthesis scheme. When tetraethyl silicate was used as the silicon source and aluminum hydroxide and aluminum sulfate 18-hydrate were used as the aluminum sources, fully crystallized ITQ-13 molecular sieve could not be obtained. Furthermore, when aluminum isopropoxide and fine silica gel were used as the aluminum source, fully crystallized ITQ-13 molecular sieve could not be obtained. This demonstrates the crucial importance of the selection of silicon and aluminum sources. When aluminum isopropoxide and tetraethyl silicate were used as the raw materials, the initial stirring involved a hydrolysis process. This hydrolysis process fully mixed the silicon and aluminum sources, forming an amorphous silica-alumina gel that facilitated subsequent crystallization of the molecular sieve, resulting in a fully crystallized silica-alumina ITQ-13 molecular sieve.

[0094] (2) Effect of dealcoholization treatment on molecular sieve synthesis By comparing Example 1 with Example 5, it is shown that whether the dealcoholation is complete during the synthesis process will have an important impact on the crystallization result. If the ethanol produced during the hydrolysis of tetraethyl silicate and aluminum isopropoxide is not completely removed, it may affect the molecular sieve crystallization process. This step is very critical.

[0095] (3) Effect of seed addition and timing on molecular sieve synthesis By comparing Example 6 with Example 7, it is shown that the addition of seed crystals and the time of addition also have an impact on the crystallization results; if seed crystals are not added, a completely crystallized silicon-alumina ITQ-13 molecular sieve cannot be obtained; if seed crystals are added before high-temperature dehydration treatment, the seed crystals may partially dissolve in the high-temperature alkaline solution environment, which may also result in the failure to obtain a completely crystallized silicon-alumina ITQ-13 molecular sieve.

[0096] (4) Effect of crystallization time on molecular sieve synthesis By comparing with Examples 11-12, it can be seen that the crystallization time has a great influence on the synthesis of molecular sieves. Insufficient crystallization time will result in the incomplete crystallization of the silicon-alumina ITQ-13 molecular sieve. Generally speaking, a crystallization time of more than 7 days is better.

[0097] (5) Preparation of all-silicon ITQ-13 molecular sieve and silicon-aluminum ITQ-13 molecular sieve Combined with Comparative Example 1, it can be seen that the process conditions for preparing all-silicon ITQ-13 molecular sieve and silicon-aluminum ITQ-13 molecular sieve are not the same. All-silicon ITQ-13 molecular sieve does not require the addition of seed crystals. However, in the absence of HF, the synthesis of silicon-aluminum ITQ-13 molecular sieve has several key factors to consider, including not only the addition of seed crystals and their timing, but also the selection of silicon and aluminum sources, dealcoholization treatment, etc., which are key factors in determining whether the silicon-aluminum ITQ-13 molecular sieve is completely crystallized.

[0098] The above descriptions are merely examples of 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 reference to preferred embodiments, they are not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the present invention, make slight changes or modifications to the above-disclosed structures and technical contents to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the present invention are still within the scope of the present invention.

Claims

1. A method for synthesizing a silicon-aluminum ITQ-13 zeolite molecular sieve, characterized in that: The method comprises the following steps: uniformly mixing a silicon source, an aluminum source, an organic template agent R, water and a seed crystal, placing the mixture in a reactor and performing a crystallization reaction at 170-180° C. for 7-12 days; and filtering and drying the product to obtain a silicon-aluminum ITQ-13 zeolite molecular sieve.

2. The method for synthesizing a silicon-alumina ITQ-13 zeolite molecular sieve according to claim 1, characterized in that: The addition amounts of silicon source, aluminum source, organic template R, and water are controlled so that the molar ratio is SiO2: Al2O3: organic template R: H2O = 1: 0.00-0.0025: 0.5: 2-5.

3. The method for synthesizing a silicon-alumina ITQ-13 zeolite molecular sieve according to claim 1, characterized in that: The aluminum source is aluminum isopropoxide.

4. The method for synthesizing a silicon-alumina ITQ-13 zeolite molecular sieve according to claim 1, characterized in that: The silicon source is tetraethyl silicate.

5. The method for synthesizing a silicon-alumina ITQ-13 zeolite molecular sieve according to claim 1, characterized in that: The water is deionized water.

6. The method for synthesizing a silicon-alumina ITQ-13 zeolite molecular sieve according to claim 1, characterized in that: The seed crystals are ITQ-13 molecular sieve seed crystals.

7. The method for synthesizing a silicon-alumina ITQ-13 zeolite molecular sieve according to claim 1, characterized in that: The organic template R is prepared by the following method: N, N, N, N-tetramethyl-1,6-hexanediamine and halogenated hydrocarbon are weighed in a molar ratio of 1:2.2, dissolved in acetonitrile, reacted at room temperature for 24 hours to obtain a white solid, the white solid is filtered and dried to obtain a quaternary ammonium salt of the organic template R, the quaternary ammonium salt of the organic template R is dissolved in water, and the halogen in the quaternary ammonium salt of the organic template R is completely exchanged with hydroxide using a strongly basic anion exchange resin, and the resin is filtered to obtain an organic template R solution.

8. The method for synthesizing a silicon-alumina ITQ-13 zeolite molecular sieve according to claim 1, characterized in that: The crystallization reaction is carried out at 175° C. for 7 days.

9. The method for synthesizing a silicon-alumina ITQ-13 zeolite molecular sieve according to claim 1, characterized in that: After the silicon source, aluminum source, organic template R, water and seed crystals are mixed evenly, they are placed in an oven at 80° C. for dehydration and dealcoholization, and dried for more than 12 hours.

10. The method for synthesizing a silicon-alumina ITQ-13 zeolite molecular sieve according to claim 1, characterized in that: Aluminum isopropoxide, an aluminum source, is added to the organic template R solution for dissolution, and then tetraethyl silicate, a silicon source, is added and stirred. After the tetraethyl silicate is fully hydrolyzed, it is weighed and placed in an 80°C oven for dehydration and dealcoholization, and dried for more than 12 hours. It is weighed again and hydrated to make the H2O / SiO2 molar ratio 2-5. Then, seed crystals are added and mixed evenly. The gel is transferred to a polytetrafluoroethylene stainless steel reactor and crystallized at 175°C for 7 days. The product is filtered and dried to obtain the product.

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