Method for synthesizing aluminum-rich beta molecular sieve with high silicon-aluminum ratio by A molecular sieve crystal transformation
By employing the A-type molecular sieve crystallization method, utilizing calcination, alkaline treatment, and seed induction, combined with pore expansion using long-chain alkyl quaternary ammonium salts, a high-crystallinity aluminum-rich Beta molecular sieve with low template agent was successfully synthesized. This solved the problems of high synthesis cost and significant pollution associated with high-alumina Beta molecular sieves, enabling efficient and environmentally friendly industrial production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- DALIAN UNIV OF TECH
- Filing Date
- 2026-04-20
- Publication Date
- 2026-06-26
AI Technical Summary
Existing technologies are insufficient for the efficient synthesis of high-aluminum-content Beta molecular sieves. Furthermore, traditional methods are costly and polluting, making it difficult to achieve high crystallinity and pure phase alumina-rich Beta molecular sieves with low template agent content.
The A molecular sieve crystallization method is adopted. Through calcination pretreatment, alkaline treatment, addition of seed crystals and template agent, the silicon-aluminum ratio is controlled to be 5~10. Combined with in-situ pore expansion of long-chain alkyl quaternary ammonium salt, multi-level channels are formed, reducing the amount of template agent used.
The synthesis of low-cost, high-crystallinity, pure-phase aluminum-rich Beta molecular sieves has been achieved, which is suitable for industrial production and has excellent catalytic performance and environmental benefits.
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Figure CN122276775A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of molecular sieve synthesis technology, specifically relating to a method for synthesizing alumina-rich Beta molecular sieves by transforming A molecular sieves into crystals. Background Technology
[0002] Molecular sieves are crystalline silicate compounds with specific pore structures. Due to their unique pore structure, excellent acidity, numerous active sites, and good hydrothermal stability, they are widely used in many fields, such as petrochemicals, environmental protection, chemical synthesis, gas adsorption and separation, and have broad application prospects in the chemical industry and environmental fields. Among them, Beta molecular sieves, with their high defect rate and highly reactive framework structure, are currently the only artificially synthesizable molecular sieves with a twelve-membered ring and a three-dimensional cross-pore system, and are widely used in reactions such as alkylation, alkyl transfer, isomerization, and cracking. Their hierarchical porous structure enhances mass transfer and improves stability.
[0003] Aluminum-rich beta molecular sieves (Si / Al=5-10) are *BEA-type molecular sieves with high aluminum content. Due to their high aluminum content, they exhibit high acidity, making them excellent in acid-catalyzed reactions and suitable for a range of such reactions. They also possess high thermal stability, maintaining structural and performance stability at high temperatures. The superior properties of aluminum-rich beta molecular sieves have led to their widespread application in adsorption, separation, and catalysis. However, conventional synthesis methods require high amounts of template agents (TEA⁺ / Si > 0.3), resulting in high costs, significant pollution, and difficulty in stably preparing pure-phase aluminum-rich beta with Si / Al=5-10. Currently, aluminum-rich beta molecular sieves are mainly synthesized via template-free methods, which typically require the addition of large amounts of seed crystals (greater than 10%) and long crystallization times (5 days or more), or result in low yields, hindering large-scale industrial production. Therefore, there is an urgent need in this field for an efficient method for synthesizing aluminum-rich beta molecular sieves to expand their application range.
[0004] Transcrystalline synthesis is a method for transforming one type of molecular sieve into another. In this method, under specific reaction conditions, the crystal structure of the original molecular sieve is utilized, and the transformation of the molecular sieve structure is achieved by changing parameters such as reactant composition, temperature, and reaction time. Because the amorphous aluminosilicate species formed from the starting zeolite retain the locally ordered structure and morphology of the starting zeolite, it promotes unique synthetic behavior. Transcrystalline synthesis often uses X and Y molecular sieves with FAU topology as raw materials, and it is difficult to simultaneously achieve alumina-rich hierarchical pores in a one-step system. Summary of the Invention
[0005] To solve the above-mentioned technical problems, the present invention provides a method for synthesizing alumina-rich Beta molecular sieves by transcrystallization of A molecular sieves, achieving controllable preparation with low template agent, high crystallinity, and pure phase.
[0006] The present invention adopts the following technical solution: A method for synthesizing alumina-rich Beta molecular sieves by crystallization of A molecular sieves, comprising the following steps: (1) Pre-treatment of molecular sieve A by calcination; (2) Add the pretreated A molecular sieve to the alkaline solution with a solid-liquid mass ratio of 1.0 to 7.5; crystallize at 100 to 150°C for 2 to 6 hours to controllably decompose the A molecular sieve framework and release silicon-aluminum active species to obtain a silicon-aluminum active species slurry. (3) Add Beta seed crystals to the slurry obtained in step (2), with a mass ratio of seed crystals to A molecular sieve of 3% to 10%; stir at 50 to 90°C for 1 to 4 hours to allow the decomposition products of A molecular sieve to be oriented and grow in an orderly manner on the seed crystal surface (growing towards Beta molecular sieve). (4) Add the template agent OSDA to the product obtained in step (3); add a supplementary silicon source to obtain a mixed gel; crystallize the mixed gel; the mixed gel contains Si:Al:OSDA:H2O:OH - The molar ratio is 1:0.1~0.2:0.1~0.2:6~10:0.1~0.6; (5) Centrifuge and wash the crystallized product obtained in step (4) until neutral, dry and calcine to obtain aluminum-rich Beta molecular sieve.
[0007] The preferred step (2) has an alkaline solution concentration of 8% to 13%.
[0008] The preferred step (2) is to use a NaOH solution or a NaOH-KOH mixed alkaline solution.
[0009] The preferred step (1) has a Si / Al ratio of 1 for the molecular sieve A.
[0010] The preferred step (4) involves supplementing the silicon source with at least one of solid silica gel, water glass, sodium silicate, silica sol, tetraethyl orthosilicate, and fumed silica. Further, the supplementing silicon source comprises solid silica gel powder with a SiO2 content of 20%–90%.
[0011] In preferred step (4), the template agent OSDA is selected from at least one of tetraethylammonium hydroxide, tetraethylammonium bromide, and tetraethylammonium chloride. Further, the template agent may include tetraethylammonium hydroxide (TEAOH).
[0012] The preferred step (4) involves a mixed gel crystallization temperature of 110~150℃ and a crystallization time of 48~72h.
[0013] Preferably, step (4) further includes adding a long-chain alkyl quaternary ammonium salt ethanol solution to the crystallized product, crystallizing it again, constructing mesopores in situ, and forming multi-level channels.
[0014] Preferably, the molar ratio of the long-chain alkyl quaternary ammonium salt to ethanol is 0.05~0.15:2.5~7.5; the molar ratio of the long-chain alkyl quaternary ammonium salt to Si in the mixed gel is 0.05~0.15.
[0015] The preferred crystallization temperature after adding a long-chain alkyl quaternary ammonium salt ethanol solution is 110~150℃, and the crystallization time is 12~36h.
[0016] Preferably, the long-chain alkyl quaternary ammonium salt is selected from at least one of dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, and octadecyltrimethylammonium bromide.
[0017] The preferred drying temperature in step (5) is 100~120℃ and the drying time is 10~24h.
[0018] The preferred roasting temperature in step (5) is 550~650℃ and the roasting time is 4~8h.
[0019] The silica-to-alumina ratio of alumina-rich Beta molecular sieves is 5-10.
[0020] The present invention also provides the application of the aluminum-rich Beta molecular sieve obtained by the method in the catalytic synthesis of anthraquinone compounds from benzoylbenzoic acid compounds.
[0021] Preferably, the benzoylbenzoic acid compounds include at least one of BB acid (2-benzoylbenzoic acid), BE acid (2-(4'-ethylbenzoyl)benzoic acid), and ABB acid (2-(4-pentylbenzoyl)benzoic acid).
[0022] Preferably, the anthraquinone compound includes at least one of anthraquinone, 2-ethylanthraquinone, and 2-pentylanthraquinone.
[0023] Preferred solvents include at least one of benzene, toluene, and trimethylbenzene.
[0024] The beneficial effects of this invention are as follows: It utilizes inexpensive and readily available A-type molecular sieves for directional crystallization into alumina-rich hierarchical Beta crystals with a silicon-to-aluminum ratio of 5-10; the template agent dosage is only 0.1-0.2 times the molar ratio of Si, significantly reducing cost and pollution; seed induction results in high crystallinity, fewer impurities, and high crystallization efficiency; in-situ pore expansion with long-chain quaternary ammonium salts forms hierarchical channels, leading to excellent mass transfer; the process is stable, yields high, and easily scaled up, making it suitable for industrial production. It exhibits excellent catalytic performance in the catalytic reaction of benzoylbenzoic acid compounds to anthraquinone compounds. The crystallization process of this invention is simple to operate, the formulation is stable, the yield is high, the silicon-to-aluminum ratio is low, the synthesis process is easy to repeat and scale up, resulting in good economic and environmental benefits. Attached Figure Description
[0025] Figure 1The X-ray diffraction (XRD) patterns are for Examples 1-11.
[0026] Figure 2 The X-ray diffraction (XRD) patterns are shown in Comparative Examples 1-4. Detailed Implementation
[0027] The X-ray diffraction (XRD) instrument used was a DX-2700B X-ray diffractometer from Dandong Haoyuan Instrument Co., Ltd. The analysis conditions were CuKα radiation power supply, tube voltage 45kV, tube current 200mA, scanning step size 0.02°, and scanning range 2θ = 5-40°.
[0028] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.
[0029] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased commercially. In this application, the dehydration pretreatment of molecular sieves adopts conventional drying or calcination methods. In the examples, the dehydration pretreatment of molecular sieves is carried out according to the following method: the catalyst is placed in a muffle furnace and heated to 540°C for calcination for 3 hours at room temperature for 2 hours. Example 1
[0030] This embodiment provides a method for synthesizing alumina-rich hierarchical porous Beta molecular sieves using A molecular sieve crystallization. The specific steps are as follows: (1) Pre-treatment of molecular sieve A (Si / Al = 1) by calcination to remove water; (2) Mix 0.48g of molecular sieve A obtained from step (1) pretreatment, 0.48g of sodium hydroxide and 3.44g of water evenly, transfer to the reaction vessel, and then place the reaction vessel in an oven for crystallization at 150℃ for 12h to obtain a silicon-aluminum active species slurry. (3) Add the slurry obtained in step (2) to 0.03g of Beta molecular sieve seed crystals (Si / Al is 14) and stir at 50℃ for 1h; (4) Add 2.83g of tetraethylammonium hydroxide solution (mass concentration of 35%) and 2.74g of solid silica gel (SiO2 content of 90%) to the mixed product in step (4), stir and mix well to obtain mixed gel I; (5) Transfer the mixed gel I from step (4) to the reaction vessel, and place the reaction vessel in an oven for crystallization at 150°C for 60 hours; (6) Take out the reaction vessel obtained in step (5), cool it down, and then add 1.68g of cetyltrimethylammonium bromide (CTAB) and 10.46g of anhydrous ethanol to obtain mixed gel II; (7) Transfer the mixed gel II from step (6) to the reaction vessel, and place the reaction vessel in an oven for crystallization at 150°C for 24 hours; (8) The crystallized product obtained in step (7) is centrifuged and washed, dried in an oven at 110°C, and then placed in a muffle furnace and calcined in an air stream at 560°C for 6 hours to obtain the aluminous hierarchical porous Beta molecular sieve.
[0031] The mixed gel II contains Si:Al:OSDA:H2O:OH - The molar ratio of CTAB to anhydrous ethanol is 1:0.1:0.15:6.5:0.41:0.10:5.0. The sample obtained in this example is designated as sample 1#. Example 2
[0032] The operation is the same as in Example 1, except that the crystallization time is changed in step (5), and the crystallization time is 48h. The sample obtained in this example is recorded as sample 2#. Example 3
[0033] The operation is the same as in Example 1, except that the amount of hexadecyltrimethylammonium bromide in step (6) is changed to 0.84g. The sample obtained in this example is recorded as sample 3#. Example 4
[0034] The operation is the same as in Example 1, except that the amount of hexadecyltrimethylammonium bromide is changed in step (6) to 2.52g. The sample obtained in this example is recorded as sample 4#. Example 5
[0035] The operation is the same as in Example 1, except that in step (6), 1.42g of dodecyltrimethylammonium bromide is added. The sample obtained in this example is recorded as sample 5#. Example 6
[0036] The operation is the same as in Example 1, except that in step (6), 1.83g of octadecyltrimethylammonium bromide is added. The sample obtained in this example is recorded as sample 6#. Example 7
[0037] The operation is the same as in Example 1, except that the amount of anhydrous ethanol added in step (6) is changed to 5.23g. The sample obtained in this example is recorded as sample 7#. Example 8
[0038] The operation is the same as in Example 1, except that the amount of anhydrous ethanol added in step (6) is changed to 15.69g. The sample obtained in this example is recorded as sample 8#. Example 9
[0039] The operation is the same as in Example 1, except that steps (6) and (7) are omitted. The crystallized product obtained in step (5) is centrifuged and washed. The sample in this example is recorded as sample 9#. Example 10
[0040] This embodiment provides a method for synthesizing alumina-rich hierarchical porous Beta molecular sieves using A molecular sieve crystallization. The specific steps are as follows: (1) Pre-treatment of molecular sieve A (Si / Al = 1) by calcination to remove water; (2) Mix 0.48g of molecular sieve A obtained from step (1) pretreatment, 0.18g of sodium hydroxide and 1.89g of water evenly, transfer to the reaction vessel, and then place the reaction vessel in an oven for crystallization at 150℃ for 12h to obtain a silicon-aluminum active species slurry. (3) Add the slurry obtained in step (2) to 0.03g of Beta molecular sieve seed crystals (Si / Al is 14) and stir at 50℃ for 1h; (4) Add 2.53g of tetraethylammonium hydroxide solution (mass concentration of 35%) and 1.74g of solid silica gel (SiO2 content of 90%) to the mixed product in step (3), stir and mix well to obtain mixed gel I; (5) Transfer the mixed gel I from step (4) to the reaction vessel, and place the reaction vessel in an oven for crystallization at 150°C for 60 hours; (6) Take out the reaction vessel obtained in step (5), cool it down, and then add 0.56g of cetyltrimethylammonium bromide and 7.01g of anhydrous ethanol to obtain mixed gel II; (7) Transfer the mixed gel II from step (6) to the reaction vessel, and place the reaction vessel in an oven for crystallization at 150°C for 24 hours; (8) The crystallized product obtained in step (7) is centrifuged and washed, dried in an oven at 110°C, and then placed in a muffle furnace and calcined in an air stream at 560°C for 6 hours to obtain the aluminous hierarchical porous Beta molecular sieve.
[0041] The mixed gel II contains Si:Al:OSDA:H2O:OH - The molar ratio of CTAB to anhydrous ethanol is 1:0.14:0.2:6.5:0.34:0.10:5.0. The sample obtained in this example is designated as sample 10#. Example 11
[0042] The operation is the same as in Example 10, except that the amount of hexadecyltrimethylammonium bromide in step (7) is changed to 0.28g. The sample obtained in this example is recorded as sample 11#.
[0043] Comparative Example 1 The operation is the same as in Example 1, except that sodium hydroxide is not used to hydrolyze the A molecular sieve in step (2). Under these conditions, the Beta molecular sieve cannot be synthesized. The sample obtained in this comparative example is denoted as D1#.
[0044] Comparative Example 2 The operation is the same as in Example 1, except that no seed Beta molecular sieve is added in step (3). Under this condition, the relative crystallinity of the synthesized Beta molecular sieve is only 54% and there are impurities. The sample obtained in this comparative example is denoted as D2#.
[0045] Comparative Example 3 The procedure was the same as in Example 1, except that A molecular sieve was not used as a precursor, and amorphous aluminum source sodium aluminate was used. Under these conditions, Beta molecular sieve could not be synthesized. The sample of this comparative example was designated as D3#.
[0046] Comparative Example 4 The operation is the same as in Example 1, except that sodium hydroxide is not used to hydrolyze the A molecular sieve in step (2) and no seed Beta molecular sieve is added in step (3). Under these conditions, it is impossible to synthesize aluminum-rich Beta molecular sieve. The sample in this comparative example is recorded as D4#, and the measured silicon-to-aluminum ratio of this sample is 13.
[0047] Table 1. Physical adsorption, relative crystallinity (reference sample is commercial Beta molecular sieve, crystallinity 100%), and elemental analysis of each sample. Sample number <![CDATA[Total pore volume (cm 3 g -1 )]]> <![CDATA[Micropore volume (cm 3 g -1 )]]> <![CDATA[Mesopore volume (cm 3 g -1 )]]> <![CDATA[Total ratio table (m 2 g -1 )]]> <![CDATA[Micropore specific surface area (m 2 g -1 )]]> <![CDATA[Mesoporous specific surface area (m 2 g -1 )]]> Relative crystallinity XRF elemental analysis (Si / Al) 1# 0.37 0.18 0.19 593 528 165 128 10 2# 0.38 0.21 0.17 667 511 156 109 9 3# 0.35 0.22 0.13 631 538 93 121 9 4# 0.36 0.21 0.15 642 524 118 114 10 5# 0.33 0.20 0.13 577 496 81 129 7 6# 0.37 0.18 0.19 585 447 138 104 8 7# 0.38 0.21 0.17 619 516 103 125 8 8# 0.37 0.20 0.17 597 486 111 123 7 9# 0.32 0.22 0.10 617 571 46 101 8 10# 0.33 0.21 0.12 615 538 77 107 6 11# 0.35 0.22 0.13 631 538 93 103 5 Application Example 1 This example demonstrates the performance evaluation of the catalysts obtained in Examples 1 to 11 in the synthesis reactions of anthraquinone, 2-ethylanthraquinone, and / or 2-pentylanthraquinone. The evaluation apparatus consisted of a reactor, a feed container, and a feed pump. The mass ratio of product precursor (BB acid, BE acid, or ABB acid) to catalyst was maintained at 2:1, and the mass ratio of solvent to toluene to catalyst was 5:1. The catalyst was placed in the reactor, and the dissolved precursor solution was introduced under constant temperature and pressure. After 6 hours of reaction, the reaction mixture was analyzed by high-performance liquid chromatography (HPLC) to determine the conversion rate of the reaction precursor and the selectivity of the product.
[0048] The test results are shown in Table 2-4 below: Table 2 Performance of the catalysts obtained in Examples 1-11 in catalyzing the conversion of BB acids to anthraquinones Sample number BB acid conversion rate / % Anthraquinone selectivity / % 1# 100.00% 99.90% 2# 99.44% 99.97% 3# 100.00% 99.91% 4# 99.87% 99.88% 5# 100.00% 99.92% 6# 99.37% 99.89% 7# 100.00% 100.00% 8# 100.00% 99.87% 9# 99.28% 99.97% 10# 99.40% 99.00% 11# 99.32% 100.00% Table 3 Performance of the catalysts obtained in Examples 1-11 in catalyzing the conversion of BE acid to 2-ethylanthraquinone Sample number BE acid conversion rate / % 2-Ethylanthraquinone selectivity / % 1# 97.64% 96.02% 2# 96.53% 96.11% 3# 97.50% 96.10% 4# 97.01% 95.94% 5# 98.85% 95.52% 6# 96.55% 95.48% 7# 99.53% 95.44% 8# 99.40% 95.31% 9# 95.42% 95.38% 10# 96.18% 94.81% 11# 95.89% 94.79% Table 4. Performance of the catalysts obtained in Examples 1-11 in catalyzing the conversion of ABB acids to 2-pentylanthraquinone Sample number ABB acid conversion rate / % 2-Pentylanthraquinone selectivity / % 1# 95.51% 81.52% 2# 92.17% 81.77% 3# 95.43% 81.89% 4# 95.31% 82.00% 5# 96.00% 83.30% 6# 92.20% 83.41% 7# 97.85% 83.89% 8# 96.50% 84.10% 9# 90.02% 83.22% 10# 93.24% 85.67% 11# 90.11% 88.81%
Claims
1. A method for synthesizing alumina-rich Beta molecular sieves by transcrystalline transformation of A molecular sieves, characterized in that: Includes the following steps: (1) Pre-treatment of molecular sieve A by calcination; (2) Add the pretreated A molecular sieve to the alkaline solution with a solid-liquid mass ratio of 1.0 to 7.5; crystallize at 100 to 150°C for 2 to 6 hours to obtain a slurry of silicon-aluminum active species. (3) Add Beta seed crystals to the slurry obtained in step (2), with the mass ratio of seed crystals to A molecular sieve being 3%~10%; stir at 50~90℃ for 1~4h; (4) Add the template agent OSDA to the product obtained in step (3); add a supplementary silicon source to obtain a mixed gel; crystallize the mixed gel; the mixture of Si:Al:OSDA:H2O:OH in the mixed gel is... - The molar ratio is 1:0.1~0.2:0.1~0.2:6~10:0.1~0.6; (5) Centrifuge and wash the crystallized product obtained in step (4) until neutral, dry and calcine to obtain aluminum-rich Beta molecular sieve.
2. The method for synthesizing alumina-rich Beta molecular sieves by crystallization of A molecular sieves as described in claim 1, characterized in that: Step (2) The concentration of the alkali solution is 8%~13%; and / or, The Si / Al ratio of the molecular sieve A mentioned in step (1) is 1.
3. The method for synthesizing alumina-rich Beta molecular sieves by transformation of A molecular sieves as described in claim 1, characterized in that: The supplementary silicon source in step (4) includes at least one of solid silica gel, water glass, sodium silicate, silica sol, tetraethyl orthosilicate, and silica fume.
4. The method for synthesizing alumina-rich Beta molecular sieves by transformation of A molecular sieves as described in claim 1, characterized in that: The template agent OSDA in step (4) is selected from at least one of tetraethylammonium hydroxide, tetraethylammonium bromide and tetraethylammonium chloride.
5. The method for synthesizing alumina-rich Beta molecular sieves by transformation of A molecular sieves as described in claim 1, characterized in that: Step (4) further includes adding a long-chain alkyl quaternary ammonium salt ethanol solution to the crystallized product and crystallizing it again.
6. The method for synthesizing alumina-rich Beta molecular sieves by transformation of A molecular sieves as described in claim 5, characterized in that: The molar ratio of the long-chain alkyl quaternary ammonium salt to ethanol is 0.05~0.15:2.5~7.5; the molar ratio of the long-chain alkyl quaternary ammonium salt to Si in the mixed gel is 0.05~0.
15.
7. The method for synthesizing alumina-rich Beta molecular sieves by transformation of A molecular sieves as described in claim 5, characterized in that: The crystallization temperature after adding long-chain alkyl quaternary ammonium salt ethanol solution is 110~150℃, and the crystallization time is 12~36h.
8. The method for synthesizing alumina-rich Beta molecular sieves by transformation of A molecular sieves as described in claim 5, characterized in that: The long-chain alkyl quaternary ammonium salt is selected from at least one of dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, and octadecyltrimethylammonium bromide.
9. The method for synthesizing alumina-rich Beta molecular sieves by transformation of A molecular sieves as described in claim 1, characterized in that: In step (5), the roasting temperature is 550~650℃ and the roasting time is 4~8h.
10. The application of the aluminum-rich Beta molecular sieve obtained by the method of claim 1 in the catalytic synthesis of anthraquinone compounds from benzoylbenzoic acid compounds.