A method for preparing aluminum-rich Beta molecular sieve without fluoride assistance

Abstract

The present application discloses a method for preparing aluminum-rich Beta molecular sieves without fluoride assistance, comprising the following steps: mixing a silicon source and a template under certain conditions to prepare a silicon source solution containing the template; mixing an aluminum source and water to prepare an aluminum source solution; mixing the aluminum source solution with the silicon source solution, adjusting the pH of the mixture to 7.5-8.5 with acid, and then reacting at a certain temperature for a certain time; spray drying the silicon-aluminum source mixed slurry to prepare silica-alumina gel; mixing the silica-alumina gel with urea and Beta molecular sieve seed crystals in a kneader, and adjusting the moisture content of the material to within the range of 15-20% with an appropriate amount of deionized water; transferring the above-mentioned materials to a pressure-resistant palladium dryer and performing a crystallization reaction under certain reaction conditions; drying and calcining the crystallized product to obtain a hydrogen-type aluminum-rich Beta molecular sieve. The dry material of the present invention maintains a nearly dry powder state during the reaction process, and the crystallized product can be directly dried and calcined to prepare a hydrogen-type molecular sieve, simplifying the preparation process flow, while the utilization rate of the silicon source and aluminum source is also close to 100%.

Description

Technical Field

[0001] The present invention relates to a method for preparing aluminum-rich Beta molecular sieve, and in particular to a method for preparing aluminum-rich Beta molecular sieve without the assistance of fluoride. Background Art

[0002] Beta molecular sieves with a silicon-aluminum ratio below 19.3 are called aluminum-rich beta molecular sieves. Due to their high catalytic activity and selectivity, aluminum-rich beta molecular sieves are widely used in many important industrial reactions. For example, in the petrochemical industry, aluminum-rich beta molecular sieves are used in reactions such as catalytic cracking and hydrorefining to improve the quality and yield of petroleum products. Furthermore, aluminum-rich beta molecular sieves are widely used in environmental protection applications, such as denitrification and desulfurization, to reduce pollutant emissions.

[0003] A Chinese invention patent with publication number CN101274764B and invention name "Method for preparing nano-aluminum-rich beta zeolite" discloses a method for preparing aluminum-rich beta zeolite. The method comprises mixing an alcohol-soluble silicon source and a hydrolyzing agent into a gel, aging and drying the gel to obtain silica gel, and then uniformly mixing the gel with hydrated alumina and an acid to obtain a silica-aluminum mixed gel. After aging, the gel is uniformly mixed with a tetraethylammonium cationic compound, a F-ion-containing compound, and water, and then crystallized and the crystallized product is recovered.

[0004] A Chinese invention patent with publication number CN101353168B and invention name "A method for synthesizing nano-aluminum-rich beta zeolite" discloses a method for synthesizing nano-aluminum-rich beta zeolite, which comprises: (1) mixing an aluminum source with an acid to form an aluminum sol, uniformly mixing the aluminum sol with silicon source particles, drying and crushing the aluminum sol into silica-aluminum sol particles, wherein the molar ratio of the aluminum source to the silicon source is 0.05-0.2; (2) adding a template to the silica-aluminum sol particles obtained in step (1), uniformly mixing the mixture to form a reaction mixture, crystallizing the mixture at a temperature of 80-190°C for 1-6 days, and recovering the product; the molar ratio of the reaction mixture is: template / silicon source = 0.1-1.0, water / silicon source = 2-12, and the template is a mixture of a tetraethylammonium compound and a fluoride, or tetraethylammonium fluoride.

[0005] Both of the above methods use silica-alumina gel as the silica and aluminum source and prepare nano-aluminum-rich Beta molecular sieves in the presence of fluoride. The resulting product has a silica-aluminum ratio of less than 20. However, the preparation process of the above patents requires the introduction of fluoride, which places high demands on equipment and makes fluoride-containing wastewater difficult to treat. Summary of the Invention

[0006] In view of the defects of the preparation of aluminum-rich Beta molecular sieve in the prior art, the purpose of the present invention is to provide a method for preparing aluminum-rich Beta molecular sieve without the assistance of fluoride, which does not require the use of fluorine-containing raw materials and has a silicon source and aluminum source utilization rate close to 100%.

[0007] The technical solution of the present invention to solve the above technical problems is:

[0008] A method for preparing aluminum-rich Beta molecular sieve without fluoride assistance comprises the following steps:

[0009] (1) mixing a silicon source and a template under stirring conditions, controlling the temperature of the mixed solution to 70 to 90° C., and mixing for 3 to 6 hours to obtain a silicon source solution containing the template;

[0010] (2) mixing an aluminum source and deionized water under stirring to prepare an aluminum source solution;

[0011] (3) adding the aluminum source solution obtained in step (2) to the solution obtained in step (1), adjusting the pH of the mixed solution to 7.5-8.5 with an acid, maintaining the temperature of the mixed solution at 70-90° C., and reacting for 3-6 hours;

[0012] (4) spray-drying the alumina-silica gel slurry obtained in step (3) to obtain alumina-silica gel;

[0013] (5) adding the silica-alumina gel obtained in step (4) to a kneader, urea, and Beta molecular sieve seed crystals to mix the materials, and adding an appropriate amount of deionized water to adjust the moisture content of the dry gel material to within the range of 15-20%, thereby obtaining a crystallized dry material;

[0014] (6) transferring the crystallized dry material obtained in step (5) to a pressure-resistant palladium dryer, and performing a crystallization reaction at a reaction temperature of 140 to 160° C., a reaction time of 60 to 96 h, and a stirring speed of 3 to 8 rpm;

[0015] (7) The crystallized product obtained in step (6) is dried and calcined to obtain a hydrogen-type aluminum-rich Beta molecular sieve.

[0016] Furthermore, the silicon source, aluminum source and template are calculated as SiO2, Al2O3 and ROH respectively, and the molar ratio of SiO2, Al2O3 and ROH is SiO2:Al2O3:ROH=8~20:1:2.4~7.0.

[0017] Preferably, the silicon source is ammonium silica sol, which is essentially spherical silicon dioxide nanoparticles. After reacting with alkali, the particle size is reduced and it is easier to form a gel with the aluminum source.

[0018] Preferably, the template is a 25-35% mass fraction of tetraethylammonium hydroxide aqueous solution.

[0019] Preferably, the aluminum source is aluminum sol, and the mass fraction of Al2O3 contained in the prepared aluminum source solution is 5-10%.

[0020] Furthermore, in step (3), the acid used for pH adjustment is a 5-10% by mass aqueous solution of hydrochloric acid.

[0021] Preferably, the molar amount of urea added is 0.7 to 1.5 times the molar amount of the template. Since urea is used as a raw material in this application, urea decomposes at high temperature to produce ammonia gas, which reacts with water to form ammonia water, providing an alkaline source for the reaction. Since the molar amount of urea added is 0.7 to 1.5 times the molar amount of the template, the system can maintain a certain alkalinity.

[0022] Furthermore, the amount of the Beta molecular sieve seed crystals added is 3-7% of the mass of SiO2 contained in the silicon source, and the molar ratio of SiO2 to Al2O3 contained in the Beta molecular sieve seed crystals is 20-30.

[0023] Furthermore, in the step (5), the water content of the dry glue material is tested using a halogen moisture meter, and the test conditions are: test temperature 120° C., and test time 10 minutes.

[0024] Furthermore, in step (7), the drying temperature is 90-120°C, and the drying time is 12-24 hours; the roasting temperature is 540-580°C, and the holding time is 6-10 hours. The roasting is carried out in a flowing air atmosphere with an air flow rate of 1-5 L / min.

[0025] The advantages and beneficial effects of the present invention are:

[0026] The present invention discloses a method for preparing aluminum-rich Beta molecular sieves without the assistance of fluoride. The method comprises preparing silica-alumina colloid using silica sol, a template and an aluminum source as raw materials, and mixing the silica-alumina colloid with urea and Beta molecular sieve seed crystals in a solid phase. The mixture is then placed in a pressure-resistant palladium dryer for stirring and crystallization to prepare aluminum-rich Beta molecular sieves. The crystallization raw materials used in the present invention are all conventional raw materials, which are cheap and easy to obtain. No fluorine-containing raw materials are required, and industrial production is easy. The silicon-aluminum ratio of the product tested by XRF is close to the silicon-aluminum ratio of the feed. The material crystallizes under conditions of 15-20% water content, and the material maintains a near-dry powder state during the crystallization process. Therefore, the crystallized product can be directly dried and calcined to prepare a hydrogen-type molecular sieve, reducing a series of traditional process steps such as water washing, ammonium exchange, filtration, secondary drying, and secondary calcination, simplifying the preparation process flow, and improving economic benefits. At the same time, the utilization rate of silicon source and aluminum source is also close to 100%. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is the X-ray powder diffraction pattern of the Beta molecular sieve powder prepared in Example 1;

[0028] Figure 2 This is a scanning electron microscope image of Beta molecular sieve prepared in Example 1;

[0029] Figure 3 is the X-ray powder diffraction pattern of the Beta molecular sieve powder prepared in Example 2;

[0030] Figure 4 is the X-ray powder diffraction pattern of the powder Beta molecular sieve prepared in Example 3;

[0031] Figure 5 This is a scanning electron microscope image of Beta molecular sieve prepared in Example 3;

[0032] Figure 6 This is the X-ray powder diffraction pattern of the Beta molecular sieve powder prepared in Example 4. DETAILED DESCRIPTION

[0033] The following will be combined with the accompanying drawings in the embodiments of the present application to clearly describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of this application.

[0034] Unless otherwise specified, the experimental methods in the following examples are conventional methods and were performed according to the techniques or conditions described in the literature in the field or according to the product instructions. The materials and reagents used in the following examples, unless otherwise specified, were all commercially available.

[0035] Example 1

[0036] This embodiment provides a method for preparing aluminum-rich Beta molecular sieve without fluoride assistance, comprising the following steps:

[0037] (1) 1302.06 kg of ammonium silicate sol with a SiO2 content of 30.13 wt% and 1297.92 kg of a 25 wt% tetraethylammonium hydroxide aqueous solution were weighed and stirred at 70° C. for 6 hours to prepare a silicon source solution containing a template.

[0038] (2) Weigh 392.49 kg of aluminum sol with an Al2O3 content of 21.20 wt%, add an appropriate amount of deionized water to prepare an aluminum source solution with an Al2O3 content of 5 wt%, and set aside.

[0039] (3) Add the aluminum source solution to the silicon source solution containing the template, maintain the reaction temperature of the mixed solution at about 70°C, and adjust the pH value of the mixed solution to a range of 7.5 to 8.5 with a 5% by mass aqueous hydrochloric acid solution. After the pH adjustment is completed, continue the reaction at this temperature for 6 hours.

[0040] (4) The alumina-silica gel slurry obtained above is spray-dried to obtain alumina-silica gel containing a template.

[0041] (5) Weigh 92.64 kg of urea, 11.77 kg of Beta molecular sieve seed crystals, and the template-containing silica-alumina gel prepared in step (4) and transfer them to a kneader. Add an appropriate amount of deionized water to adjust the water content of the dry gel material to about 15% to obtain a crystallized dry material. The molar ratio of urea to template is 0.7, the amount of Beta molecular sieve seed crystals added is 3% of the mass of SiO2 contained in the silicon source, and the molar ratio of SiO2 to Al2O3 contained in the Beta molecular sieve seed crystals is 20.69. In this step, the water content of the dry gel material is tested using a halogen moisture meter under the following test conditions: test temperature 120°C, test time 10 minutes. The Beta molecular sieve seed crystals are produced by Tianjin Nanhua Catalyst Co., Ltd.

[0042] (6) The crystallized dry material was transferred to a pressure-resistant rake dryer and crystallized at a reaction temperature of 140°C and a stirring speed of 3 rpm for 96 hours.

[0043] The molar ratio of SiO2:Al2O3:ROH in the crystallized dry material is 8.00:1.00:2.70.

[0044] (7) After the crystallization reaction is completed, the resulting crystallized product is dried at 90°C for 24 hours. Figure 1 The powder X-ray diffraction pattern of the crystallized product shows that the product has typical Beta molecular sieve structural characteristics. Figure 2 This is a scanning electron microscope image of the crystallized product.

[0045] 1.0 kg of the dried crystallized product was placed in a muffle furnace and calcined at 540°C for 10 hours under a flowing air atmosphere at a flow rate of 1 L / min and a heating rate of 2°C / min. After calcination, the product was cooled to 40-60°C in an air atmosphere and the calcined product was collected to obtain the hydrogen-type aluminum-rich Beta molecular sieve.

[0046] X-ray fluorescence spectroscopy (XRF) test shows that the SiO2 / Al2O3 ratio of the hydrogen-type aluminum-rich Beta molecular sieve is 7.8. Calculated based on the silicon-aluminum ratio of the feed, the utilization rate of the silicon source is about 98%.

[0047] Example 2

[0048] This embodiment provides a method for preparing aluminum-rich Beta molecular sieve without fluoride assistance, comprising the following steps:

[0049] (1) 1341.87 kg of ammonium silicate sol with a SiO2 content of 30.13 wt% and 967.22 kg of a 35 wt% tetraethylammonium hydroxide aqueous solution were weighed and stirred at 90° C. for 3 hours to prepare a silicon source solution containing a template.

[0050] (2) Weigh 269.66 kg of aluminum sol with an Al2O3 content of 21.20 wt%, add an appropriate amount of deionized water to prepare an aluminum source solution with an Al2O3 content of 10 wt%, and set aside.

[0051] (3) Add the aluminum source solution to the silicon source solution containing the template, maintain the reaction temperature of the mixed solution at about 90°C, and adjust the pH value of the mixed solution to a range of 7.5 to 8.5 with a 10% by mass aqueous hydrochloric acid solution. After the pH adjustment is completed, continue the reaction at this temperature for 3 hours.

[0052] (4) The alumina-silica gel slurry obtained above is spray-dried to obtain alumina-silica gel containing a template.

[0053] (5) Weigh 207.10 kg of urea, 28.30 kg of Beta molecular sieve seed crystals, and the template-containing silica-alumina gel prepared in step (4) and transfer them to a kneader. Add an appropriate amount of deionized water to adjust the moisture content of the dry gel material to about 20% to obtain a crystallized dry material. The molar ratio of urea to template is 1.5, the amount of seed crystals added is 7% of the mass of SiO2 contained in the silicon source, and the silicon-alumina ratio is 30.45. In this step, the moisture content of the dry gel material is tested using a halogen moisture meter under the following test conditions: test temperature 120°C, test time 10 minutes. The Beta seed crystals are produced by Tianjin Nanhua Catalyst Co., Ltd.

[0054] (6) The crystallized dry material was transferred to a pressure-resistant rake dryer and crystallized at a reaction temperature of 160°C and a stirring speed of 8 rpm for 60 hours.

[0055] The molar ratio of SiO2:Al2O3:ROH in the crystallized dry material is 12.00:1.00:4.10.

[0056] (7) After the crystallization reaction is completed, the resulting crystallized product is dried at 120°C for 12 hours. Figure 3 The powder X-ray diffraction pattern of the crystallized product shows that the product has typical Beta molecular sieve structural characteristics.

[0057] 1.0 kg of the dried crystallized product was placed in a muffle furnace and calcined at 580°C for 6 hours under a flowing air atmosphere at a flow rate of 5 L / min and a heating rate of 2°C / min. After calcination, the product was cooled to 40-60°C in an air atmosphere and the calcined product was collected to obtain the hydrogen-type aluminum-rich Beta molecular sieve.

[0058] X-ray fluorescence spectroscopy (XRF) test shows that the SiO2 / Al2O3 ratio of the hydrogen-type aluminum-rich Beta molecular sieve is 11.6. Calculated based on the silicon-aluminum ratio of the feed, the utilization rate of the silicon source is about 97%.

[0059] Example 3

[0060] This embodiment provides a method for preparing aluminum-rich Beta molecular sieve without fluoride assistance, comprising the following steps:

[0061] (1) 1395.61 kg of ammonium silicate sol with a SiO2 content of 30.13 wt% and 1116.37 kg of a 30 wt% tetraethylammonium hydroxide aqueous solution were weighed and stirred at 80° C. for 4 hours to prepare a silicon source solution containing a template.

[0062] (2) Weigh 210.35 kg of aluminum sol with an Al2O3 content of 21.20 wt%, add an appropriate amount of deionized water, and prepare an aluminum source solution with an Al2O3 content of 7 wt%, and set aside.

[0063] (3) Add the aluminum source solution to the silicon source solution containing the template, maintain the reaction temperature of the mixed solution at about 80°C, and adjust the pH value of the mixed solution to a range of 7.5 to 8.5 with a 7% by mass aqueous hydrochloric acid solution. After the pH adjustment is completed, continue the reaction at this temperature for 4 hours.

[0064] (4) The alumina-silica gel slurry obtained above is spray-dried to obtain alumina-silica gel containing a template.

[0065] (5) Weigh 136.59 kg of urea, 21.03 kg of Beta molecular sieve seed crystals, and the template-containing silica-alumina gel prepared in step (4) and transfer them to a kneader. Add an appropriate amount of deionized water to adjust the moisture content of the dry gel material to about 17% to obtain a crystallized dry material. The molar ratio of urea to template is 1.0, the amount of seed crystals added is 5% of the mass of SiO2 contained in the silicon source, and the silicon-alumina ratio is 24.63. In this step, the moisture content of the dry gel material is tested using a halogen moisture meter under the following test conditions: test temperature 120°C, test time 10 minutes. The Beta seed crystals are produced by Tianjin Nanhua Catalyst Co., Ltd.

[0066] (6) The crystallized dry material was transferred to a pressure-resistant rake dryer and crystallized at a reaction temperature of 145°C and a stirring speed of 5 rpm for 72 hours.

[0067] The molar ratio of SiO2:Al2O3:ROH in the crystallization material is 16.00:1.00:5.20.

[0068] (7) After the crystallization reaction is completed, the resulting crystallized product is dried at 100°C for 12 hours. Figure 4 The powder X-ray diffraction pattern of the crystallized product shows that the product has typical Beta molecular sieve structural characteristics. Figure 5 This is a scanning electron microscope image of the crystallized product.

[0069] 1.0 kg of the dried crystallized product was placed in a muffle furnace and calcined at 550°C for 7 hours under a flowing air atmosphere at a flow rate of 2 L / min and a heating rate of 2°C / min. After calcination, the product was cooled to 40-60°C in an air atmosphere and the calcined product was collected to obtain the hydrogen-type aluminum-rich Beta molecular sieve.

[0070] X-ray fluorescence spectroscopy (XRF) test shows that the SiO2 / Al2O3 ratio of the hydrogen-type aluminum-rich Beta molecular sieve is 15.5. Calculated based on the silicon-aluminum ratio of the feed, the utilization rate of the silicon source is about 97%.

[0071] Example 4

[0072] This embodiment provides a method for preparing aluminum-rich Beta molecular sieve without fluoride assistance, comprising the following steps:

[0073] (1) Weigh 1366.83 kg of ammonium silica sol with a SiO2 content of 30.13 wt% and 1177.45 kg of a 30 wt% tetraethylammonium hydroxide aqueous solution, stir and react at 80° C. for 4 hours to obtain a silicon source solution containing a template.

[0074] (2) Weigh 164.81 kg of aluminum sol with an Al2O3 content of 21.20 wt%, add an appropriate amount of deionized water, and prepare an aluminum source solution with an Al2O3 content of 7 wt%, and set aside.

[0075] (3) Add the aluminum source solution to the silicon source solution containing the template, maintain the reaction temperature of the mixed solution at about 80°C, and adjust the pH value of the mixed solution to a range of 7.5 to 8.5 with a 7% by mass aqueous hydrochloric acid solution. After the pH adjustment is completed, continue the reaction at this temperature for 4 hours.

[0076] (4) The alumina-silica gel slurry obtained above is spray-dried to obtain alumina-silica gel containing a template.

[0077] (5) Weigh 172.88 kg of urea, 20.59 kg of Beta molecular sieve seed crystals, and the above-mentioned silica-alumina gel containing the template into a kneader, add an appropriate amount of deionized water, and adjust the moisture content of the dry gel material to about 17% to obtain a crystallized dry material. The molar ratio of urea to template is 1.2, the amount of seed crystals added is 5% of the mass of SiO2 contained in the silicon source, and the silicon-alumina ratio is 24.63. In this step, the moisture content of the dry gel material is tested using a halogen moisture meter under the following test conditions: test temperature 120°C, test time 10 minutes. The Beta seed crystals are produced by Tianjin Nanhua Catalyst Co., Ltd.

[0078] (6) The crystallized dry material was transferred to a pressure-resistant rake dryer and crystallized at a reaction temperature of 145°C and a stirring speed of 5 rpm for 72 hours.

[0079] The molar ratio of SiO2:Al2O3:ROH in the crystallization material is 20.00:1.00:7.00.

[0080] (7) After the crystallization reaction is completed, the resulting crystallized product is dried at 100°C for 12 hours. Figure 6 The powder X-ray diffraction pattern of the crystallized product shows that the product has typical Beta molecular sieve structural characteristics.

[0081] 1.0 kg of the dried crystallized product was placed in a muffle furnace and calcined at 550°C for 7 hours under a flowing air atmosphere at a flow rate of 2 L / min and a heating rate of 2°C / min. After calcination, the product was cooled to 40-60°C in an air atmosphere and the calcined product was collected to obtain the hydrogen-type aluminum-rich Beta molecular sieve.

[0082] X-ray fluorescence spectroscopy (XRF) test shows that the SiO2 / Al2O3 ratio of the hydrogen-type aluminum-rich Beta molecular sieve is 19.5. Calculated based on the silicon-aluminum ratio of the feed, the utilization rate of the silicon source is about 98%.

[0083] Comparative Example 1

[0084] This comparative example provides a method for preparing aluminum-rich Beta molecular sieve without the aid of fluoride. The only difference between this comparative example and Example 1 is that urea is not added during the synthesis process:

[0085] 11.77 kg of Beta seed crystals (the amount of seed crystals added is 3% of the mass of SiO2 contained in the silicon source, and the silicon-aluminum ratio is 20.69) and the above-mentioned silica-aluminum gel containing the template are transferred to a kneader. An appropriate amount of deionized water is added to adjust the moisture content of the mixture to approximately 15% to obtain a crystallized dry material. The remaining steps are the same as in Example 1.

[0086] The powder X-ray diffraction pattern of the crystallized product prepared in this comparative example shows that the product has an amorphous structure and has no characteristic peaks of the Beta molecular sieve structure.

[0087] Comparative Example 2

[0088] This comparative example provides a method for preparing aluminum-rich Beta molecular sieve using silica-alumina gel as a raw material. The only difference between this comparative example and Example 1 is the amount of urea added. In this comparative example, 66.17 kg of urea was weighed (the molar ratio of urea to template was 0.5), and the remaining contents were the same as in Example 1.

[0089] The powder X-ray diffraction pattern of the crystallized product prepared in this comparative example shows that the product has a weak Beta molecular sieve characteristic diffraction peak, and the relative crystallinity tested by XRD peak intensity is 64.5% (Example 1 is a standard sample).

[0090] Comparative Example 3

[0091] This comparative example provides a method for preparing aluminum-rich Beta molecular sieve using silica-alumina gel as a raw material. The only difference between this comparative example and Example 1 is the amount of urea added. In this comparative example, 224.98 kg of urea was weighed (the molar ratio of urea to template was 1.7), and the remaining ingredients were the same as in Example 1.

[0092] The powder X-ray diffraction pattern of the crystallized product prepared in this comparative example shows that the product has characteristic diffraction peaks of Beta molecular sieve, and the relative crystallinity tested by XRD peak intensity is 105% (Example 1 is a standard sample). When the amount of urea is increased to the upper limit of the present invention, the relative crystallinity of the Beta molecular sieve does not change much.

[0093] Comparative Example 4

[0094] This comparative example provides a method for preparing aluminum-rich Beta molecular sieve using silica-alumina gel as raw material. The difference between this comparative example and Example 1 is only that:

[0095] Weigh 392.49 kg of aluminum sol with an Al2O3 content of 21.20 wt%, add appropriate amount of deionized water to prepare an aluminum source solution with an Al2O3 content of 5 wt%, and set aside.

[0096] 1302.06 kg of ammonium silica sol with a SiO2 content of 30.13 wt% and 1297.92 kg of a 25 wt% tetraethylammonium hydroxide aqueous solution were weighed to prepare a silicon source solution containing a template.

[0097] After all of the aluminum source solution was added to the template-containing silicon source solution, the reaction temperature of the mixed solution was raised to 70°C, and the pH of the mixed solution was adjusted to a range of 7.5 to 8.5 using a 5% by mass aqueous hydrochloric acid solution. After the pH adjustment, the reaction was continued at this temperature for 6 hours. The remaining steps were the same as in Example 1.

[0098] The powder X-ray diffraction pattern of the crystallized product prepared in this comparative example shows that the product has a weak Beta molecular sieve characteristic diffraction peak, and the relative crystallinity tested by XRD peak intensity is 71.5% (Example 1 is a standard sample).

[0099] Comparative Example 5

[0100] This comparative example provides a method for preparing aluminum-rich Beta molecular sieve using silica-alumina gel as raw material. The only difference between this comparative example and Example 1 is that the molar ratio of SiO2, Al2O3, and ROH is different.

[0101] The molar ratio of SiO2:Al2O3:ROH in the crystallization material of this comparative example is 6.60:1.00:2.70. The rest is the same as in Example 1.

[0102] The powder X-ray diffraction pattern of the crystallized product prepared in this comparative example shows that the product has an amorphous structure and has no characteristic peaks of the Beta molecular sieve structure.

[0103] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of this application, ordinary technicians in this field can also make many forms without departing from the purpose of this application and the scope of protection of the claims, all of which are within the protection of this application.

Claims

1. A method for preparing aluminum-rich Beta molecular sieve without fluoride assistance, characterized in that: The steps include: (1) Mixing the silicon source and the template under stirring conditions, controlling the temperature of the mixed solution to 70-90°C, and mixing for 3-6 hours to obtain a silicon source solution containing the template; (2) mixing an aluminum source and deionized water under stirring conditions to prepare an aluminum source solution; (3) adding the aluminum source solution obtained in step (2) to the solution obtained in step (1), adjusting the pH of the mixture to 7.5-8.5 with acid, maintaining the temperature of the mixture at 70-90°C, and reacting for 3-6 hours; (4) spray-drying the alumina-silica gel slurry obtained in step (3) to obtain alumina-silica gel; (5) adding the silica-alumina gel obtained in step (4) to a kneader, urea, and Beta molecular sieve seed crystals to mix the materials, adding deionized water, and adjusting the moisture content of the dry gel material to be within the range of 15-20%, thereby obtaining a crystallized dry material; (6) The crystallized dry material obtained in step (5) is transferred to a pressure-resistant palladium dryer, and a crystallization reaction is carried out under the conditions of a reaction temperature of 140-160°C, a reaction time of 60-96 hours, and a stirring speed of 3-8 rpm; (7) The crystallized product obtained in step (6) is dried and calcined to obtain a hydrogen-type aluminum-rich Beta molecular sieve; The silicon source, aluminum source and template are calculated as SiO2, Al2O3 and ROH respectively, and the molar ratio of SiO2, Al2O3 and ROH in the crystallization dry material is SiO2:Al2O3:ROH =8~20:1:2.4~7.0; The molar amount of the urea added is 0.7 to 1.5 times the molar amount of the template.

2. The method for preparing aluminum-rich Beta molecular sieve without fluoride assistance according to claim 1, characterized in that: The silicon source is ammonium silica sol.

3. The method for preparing aluminum-rich Beta molecular sieve without fluoride assistance according to claim 1, characterized in that: The template is a 25-35% by mass tetraethylammonium hydroxide aqueous solution.

4. The method for preparing aluminum-rich Beta molecular sieve without fluoride assistance according to claim 1, characterized in that: The aluminum source is aluminum sol, and the mass fraction of Al2O3 contained in the prepared aluminum source solution is 5-10%.

5. The method for preparing aluminum-rich Beta molecular sieve without fluoride assistance according to claim 1, characterized in that: In step (3), the acid used for pH adjustment is a 5-10% by mass hydrochloric acid aqueous solution.

6. The method for preparing aluminum-rich Beta molecular sieve without fluoride assistance according to claim 1, characterized in that: The amount of the Beta molecular sieve seed crystal added is 3-7% of the mass of SiO2 contained in the silicon source, and the molar ratio of SiO2 to Al2O3 contained in the Beta molecular sieve seed crystal is 20-30.

7. The method for preparing aluminum-rich Beta molecular sieve without fluoride assistance according to claim 1, characterized in that: In step (5), the water content of the dry glue material is tested using a halogen moisture meter, and the test conditions are: test temperature 120°C, and test time 10 minutes.

8. The method for preparing aluminum-rich Beta molecular sieve without fluoride assistance according to claim 1, characterized in that: In step (7), the drying temperature is 90-120°C, and the drying time is 12-24 hours; the roasting temperature is 540-580°C, and the holding time is 6-10 hours. The roasting is carried out in a flowing air atmosphere with an air flow rate of 1-5 L / min.

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