Process for the synthesis of beta molecular sieves

Abstract

The present disclosure relates to a method for synthesizing a beta molecular sieve, comprising: mixing an inorganic alkali source, a first aluminum source, a silicon source and water to obtain a first gel; mixing a first beta molecular sieve seed with the first gel to perform a first crystallization to obtain a first crystallization product with obvious stratification; adding a second aluminum source and a second beta molecular sieve seed to the supernatant of the upper layer of the first crystallization product to obtain a second gel; and performing a second crystallization on the second gel to obtain a beta molecular sieve; wherein the molar ratio of the second aluminum source to the first aluminum source is (0.2-1.2):1. The method is simple to operate and can effectively improve the single-kettle yield of the template-free method for synthesizing a beta molecular sieve.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a method for synthesizing a β molecular sieve. BACKGROUND

[0002] The β molecular sieve was first synthesized by the U.S. Mobil Corporation in 1967 (US 3,308,069) and has a three-dimensional twelve-membered ring pore structure. Due to the unique topological structure and good thermal and hydrothermal stability of the molecular sieve, it exhibits excellent catalytic performance in reactions such as hydrocracking, hydroisomerization, hydrocarbon cracking, and alkylation, and has been industrialized.

[0003] The traditional β molecular sieve is synthesized in the presence of an organic template agent, and the synthesis cost is high, and the production and post-processing process is polluting, which limits its application prospect and application range. CN101249968A discloses a method for synthesizing a β molecular sieve without a template agent. This method is the first to synthesize a β molecular sieve without the presence of an organic template agent. Subsequently, a series of patents such as CN102910640A disclose a formula that broadens the synthesis formula, but all have the disadvantage of low silicon source utilization rate. In industry, the yield of ammonium synthesis of β molecular sieve is usually above 85%, but under the condition of no organic template agent, it is less than 30%. CN104649290B discloses a series of formulas for synthesizing β molecular sieve without a template agent, which achieves the purpose of improving the single-pot yield by reducing the H2O / SiO2 ratio, but the highest yield is still less than 30%, and the viscosity of white carbon black is extremely large in the low H2O / SiO2 system, which is very unfavorable for stirring and mixing. CN102285667A discloses a method for recycling the mother liquor of the synthesis of β molecular sieve without a template agent, i.e. the silicon-rich mother liquor is characterized to determine the silicon and aluminum content, and then the formula is adjusted to enter the next synthesis as raw material, thereby improving the utilization rate of silicon source. This method can to some extent solve the problem of low silicon source utilization rate, but the separation, determination and separate calculation of each batch of materials of the mother liquor process are complex, which increases the operation difficulty. SUMMARY

[0004] The purpose of the present disclosure is to provide a method for synthesizing a β molecular sieve, which is simple to operate and can effectively improve the single-pot yield of the synthesis of a β molecular sieve without a template agent.

[0005] In order to achieve the above-mentioned purpose, the present disclosure provides a method for synthesizing a β molecular sieve, which comprises:

[0006] mixing an inorganic alkali source, a first aluminum source, a silicon source and water to obtain a first gel;

[0007] mixing a first β molecular sieve seed with the first gel to perform a first crystallization to obtain a first crystallization product with obvious stratification;

[0008] adding a second aluminum source and a second beta molecular sieve seed into the supernatant of the first crystallization product to obtain a second gel;

[0009] crystallizing the second gel to obtain a beta molecular sieve;

[0010] The molar ratio of the second aluminum source to the first aluminum source is (0.2-1.2):1.

[0011] Optionally, the method further comprises: mixing the inorganic alkali source, the first aluminum source and the water first, then adding the silicon source, and stirring at a speed of not less than 200 r / min for 0.1-2 h to obtain the first gel.

[0012] Optionally, the molar ratio of the silicon source to the first aluminum source is (20-50):1, the molar ratio of the alkali source to the silicon source is (0.35-0.7):1, and the molar ratio of the water to the silicon source is (13-50):1, wherein the silicon source is calculated as SiO2, the first aluminum source is calculated as Al2O3, and the inorganic alkali source is calculated as OH - .

[0013] Optionally, the weight ratio of the first beta molecular sieve seed to the silicon source is (5-15):100, and the weight ratio of the second beta molecular sieve seed to the silicon source is (5-10):100.

[0014] Optionally, the conditions of the first crystallization include: a temperature of 110-160 ℃, a time of 8-48 h, static crystallization under self-pressure in a closed reactor or dynamic crystallization at a stirring speed of less than 15 rpm.

[0015] Optionally, the conditions of the second crystallization include: a temperature of 110-160 ℃, a time of 16-150 h, static crystallization under self-pressure in a closed reactor or dynamic crystallization at a stirring speed of less than 30 rpm.

[0016] Optionally, the silicon source is one or more selected from the group consisting of white carbon black, sodium silicate, silica sol and tetraethyl orthosilicate.

[0017] Optionally, the first aluminum source is one or more selected from the group consisting of sodium aluminate, aluminum sulfate and aluminum nitrate; and the second aluminum source is one or more selected from the group consisting of sodium aluminate, aluminum sulfate and aluminum nitrate.

[0018] Optionally, the inorganic alkali source is sodium hydroxide and / or potassium hydroxide.

[0019] Optionally, the first beta molecular sieve seed and the second beta molecular sieve seed are each hydrogen-type beta molecular sieve or ammonium-type beta molecular sieve, and the silicon-aluminum molar ratio of the first beta molecular sieve seed and the second beta molecular sieve seed is each (20-30):1.

[0020] By the technical scheme, the first crystallization is performed by the template-free method, the aluminum source and the seed crystal are added in the supernatant of the obtained crystallization product again, so that the gel is formed again and the second crystallization is performed, and finally the β molecular sieve is synthesized, which can significantly improve the single-pot yield of the product, without increasing the complexity of the operation and the burden on the equipment, and has higher practical value.

[0021] Other features and advantages of the present disclosure will be described in detail in the following specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0022] The accompanying drawings are included to provide a further understanding of the present disclosure and constitute a part of the specification, and are used together with the following specific embodiments to explain the present disclosure, but do not constitute a limitation on the present disclosure. In the drawings:

[0023] Figure 1 is an XRD spectrum of the β molecular sieve used as the seed crystal in Example 1.

[0024] Figure 2 is an SEM photograph of the β molecular sieve used as the seed crystal in Example 1.

[0025] Figure 3 is an XRD spectrum of the β molecular sieve prepared in Example 1.

[0026] Figure 4 is an SEM photograph of the β molecular sieve prepared in Example 1.

[0027] Figure 5 is an SEM photograph of the β molecular sieve prepared in Example 1. 27 is an Al MAS NMR spectrum of the β molecular sieve prepared in Example 1.

[0028] Figure 6 is an XRD spectrum of the β molecular sieve prepared in Comparative Example 1.

[0029] Figure 7 is an SEM photograph of the β molecular sieve prepared in Comparative Example 1.

[0030] Figure 8 is an XRD spectrum of the molecular sieve prepared in Comparative Example 2.

[0031] Figure 9 is an SEM photograph of the molecular sieve prepared in Comparative Example 2.

[0032] Figure 10 is an XRD spectrum of the molecular sieve prepared in Comparative Example 3.

[0033] Figure 11 is an SEM photograph of the molecular sieve prepared in Comparative Example 3.

[0034] Figure 12 is an XRD spectrum of the beta molecular sieve prepared in Example 2. DETAILED DESCRIPTION

[0035] The specific embodiments of the present disclosure are described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely intended to illustrate and explain the present disclosure, and are not intended to limit the present disclosure.

[0036] The present disclosure provides a method for synthesizing a beta molecular sieve, which comprises:

[0037] mixing an inorganic base source, a first aluminum source, a silicon source and water to obtain a first gel;

[0038] mixing the first beta molecular sieve seed with the first gel to perform a first crystallization to obtain a first crystallization product with obvious stratification;

[0039] adding a second aluminum source and a second beta molecular sieve seed to the supernatant of the first crystallization product to obtain a second gel;

[0040] performing a second crystallization on the second gel to obtain a beta molecular sieve;

[0041] wherein the molar ratio of the second aluminum source to the first aluminum source is (0.2-1.2):1.

[0042] The inventors of the present disclosure found in research that, in the process of synthesizing a beta molecular sieve in a template-free system, after forming an initial gel and hydrothermal crystallization for a certain period of time, the gel sinks to the bottom of the reactor, and the silicon in the supernatant is in a state similar to that of an alkaline silica sol. Then, the aluminum source and the seed are added again to the supernatant, so that the silicon in the supernatant is gelled again, which can improve the single-pot yield of the beta molecular sieve.

[0043] The inorganic base source, the first aluminum source, the silicon source and water in the method of the present disclosure can be mixed uniformly according to a conventional method to obtain the first gel. In a preferred embodiment of the present disclosure, in order to further improve the single-pot yield of the beta molecular sieve, the method can further comprise: mixing the inorganic base source, the first aluminum source and the water first, then adding the silicon source, and stirring at a speed of not less than 200 r / min for 0.1-2 h to obtain the first gel.

[0044] The amounts of the inorganic base source, the first aluminum source, the silicon source and water in the first gel can be the common ratios for synthesizing beta molecular sieve. According to one specific embodiment of the present disclosure, the molar ratio of the silicon source to the first aluminum source can be (20-50): 1, preferably (20-40): 1; the molar ratio of the base source to the silicon source can be (0.35-0.7): 1, preferably (0.45-0.65): 1; the molar ratio of water to the silicon source can be (13-50): 1, preferably (20-35): 1; wherein the silicon source is calculated as SiO2, the first aluminum source is calculated as Al2O3, the inorganic base source is calculated as OH - In one preferred embodiment of the present disclosure, the molar ratio of the second aluminum source to the first aluminum source is (0.5-1.2): 1, which is advantageous for further improving the single-pot yield of beta molecular sieve.

[0045] After the first gel is formed, the first-stage crystallization is performed, and the obtained first crystallization product is obviously layered, i.e., comprising a lower layer gel and an upper layer clear solution. The conditions of the first crystallization can be the common crystallization conditions for synthesizing beta molecular sieve. In one specific embodiment of the present disclosure, the conditions of the first crystallization can include: temperature of 110-160°C, time of 8-48h, and static crystallization under self-pressure in a closed reactor or dynamic crystallization with stirring speed lower than 15rpm for better obtaining the first crystallization product which is obviously layered.

[0046] Next, after the first crystallization product is cooled to room temperature, the second-stage gel formation and crystallization are performed. The first crystallization product is obviously layered after standing, and the operation of separating the lower layer gel from the upper layer clear solution can not be necessary, but the second aluminum source and the second beta molecular sieve seed can be directly added to the upper layer clear solution of the first crystallization product without affecting the state of the lower layer gel. The second aluminum source and the second beta molecular sieve seed can be added to the upper layer clear solution of the first crystallization product and mixed uniformly according to the conventional method (for example, the upper layer clear solution can be stirred at a speed of 60-350r / min after the second aluminum source and the second beta molecular sieve seed are added), and then the second gel is obtained. The conditions of the second crystallization of the second gel can be the common crystallization conditions for synthesizing beta molecular sieve. In one specific embodiment of the present disclosure, the conditions of the second crystallization can include: temperature of 110-160°C, time of 16-150h, and static crystallization under self-pressure in a closed reactor or dynamic crystallization with stirring speed lower than 30rpm for not affecting the state of the first gel.

[0047] The amount of the first and second beta molecular sieve seeds can be the common ratio for synthesizing beta molecular sieve. For example, the total amount of the first and second beta molecular sieve seeds to the amount of the silicon source can be (10-25):100; further, the amount of the first beta molecular sieve seeds to the amount of the silicon source can be (5-15):100, and the amount of the second beta molecular sieve seeds to the amount of the silicon source can be (5-10):100.

[0048] According to the present disclosure, the silicon source can be the commonly used silicon source for synthesizing beta molecular sieve known to those skilled in the art, and the present disclosure does not have a particular limitation. Preferably, the silicon source is one or more selected from the group consisting of white carbon black, sodium silicate, silica sol and tetraethyl orthosilicate.

[0049] The first and second aluminum sources can be the commonly used substances capable of providing aluminum elements in the art, and preferably, the first and second aluminum sources are each one or more selected from the group consisting of sodium aluminate, aluminum sulfate and aluminum nitrate. The first and second aluminum sources can be the same substance or different, and preferably are the same kind of aluminum source.

[0050] The inorganic alkali source can be the commonly used inorganic alkali substance in the art, and the kind thereof is not particularly limited, and preferably, the inorganic alkali source is sodium hydroxide and / or potassium hydroxide.

[0051] The water can be the commonly used water for synthesizing molecular sieve, and preferably, deionized water is used in the present disclosure to avoid the introduction of heteroatoms.

[0052] According to the present disclosure, the first and second beta molecular sieve seeds can be various types of beta molecular sieve seeds commonly used, for example, hydrogen type beta molecular sieve or ammonium type beta molecular sieve. The silicon-aluminum molar ratio of the first and second beta molecular sieve seeds can each be (20-30):1. The crystal type and silicon-aluminum molar ratio of the first and second beta molecular sieve seeds can be the same or different, and preferably are the same beta molecular sieve.

[0053] After the second crystallization is completed, the beta molecular sieve can be obtained by the commonly used method in the art. For example, the crystallization product is washed with water, filtered and dried to obtain the beta molecular sieve, and the drying conditions can be, for example, a temperature of 70-100°C and a time of 12-24h.

[0054] Compared with the conventional beta molecular sieve synthesis technology, the beta molecular sieve synthesized by the present disclosure has a higher single-pot yield, and the single-pot yield of the template-free method for synthesizing beta molecular sieve can be increased by more than 60%.

[0055] The present disclosure is further disclosed by the following examples, but not limited to the content of the present disclosure.

[0056] In the following examples and comparative examples, the crystal phase pattern of X-ray diffraction (XRD) is determined by Philips Panalytical X'pert device, and the test conditions are as follows: Cu target, Kα radiation, Ni filter, super power detector, tube voltage 30 KV, and tube current 40 mA. The scanning electron microscope (SEM) picture is measured by FEI Company Quanta 200F type scanning electron microscope. The solid nuclear magnetic result is measured by Bruker Company AVANCE III 600WB type nuclear magnetic resonance spectrometer.

[0057] Single-pot yield (%) = weight of SiO2 in dry basis of molecular sieve / weight of SiO2 in raw material × 100%

[0058] Example 1

[0059] Under stirring, 18.29 g of sodium metaaluminate solution (sodium oxide 287 g / L, aluminum oxide 159.7 g / L) is added into 350 g of deionized water, 11 g of sodium hydroxide is added, after dissolution, 37.6 g of white carbon black (silicon dioxide 93.0 wt%, water 7.0 wt%) is added into the above solution, and a first gel is formed after stirring at a speed of ≥200 r / min for about 10-30 min, and the molar composition of the raw material mixture is as follows: SiO2 / Al2O3=40, H2O / SiO2=35, NaOH / SiO2=0.60, and 3.0 g of β molecular sieve seed crystals (Sinopec Changling Catalyst Subsidiary, hydrogen type β molecular sieve, SiO2 / Al2O3(molar ratio)=22, SEM picture and XRD spectrum are shown in Figure 1 Figure 2 respectively) is added into the above first gel, and continues to be stirred at a speed of ≥200 r / min for about 10-30 min, and is transferred into a reaction kettle, and is statically crystallized at 120°C for 30 h, and is cooled. After standing and layering, the lower gel is kept still, the upper clear liquid is stirred at a speed of 60-350 r / min, and 18.29 g of sodium metaaluminate solution (the molar ratio of the second aluminum source to the first aluminum source is 1:1) is added, and 3.0 g of the above β molecular sieve seed crystals is added, and a second gel is formed after mixing uniformly, and continues to be statically crystallized at 120°C for 100 h, and is cooled, and the solid product is separated after filtration at room temperature, and is washed, and is dried at 80°C for 12 h, and the β molecular sieve product is obtained. The single-pot yield is 61.1% after the collection and weighing of the solid product.

[0060] The XRD spectrum of the β molecular sieve prepared in the example is shown in Figure 3 (having the characteristic diffraction peak of β molecular sieve), the SEM picture is shown in Figure 4 (having the morphology characteristics of β molecular sieve), 27 ​The Al MAS NMR spectrum is shown in Figure 1. Figure 5 (To show that all of the aluminum source added twice enters the framework of the molecular sieve).

[0061] Comparative Example 1

[0062] The β molecular sieve was synthesized according to the method of Example 1, except that the second aluminum supplement was not performed, and specifically:

[0063] Under stirring, 18.29 g of a sodium metaaluminate solution (sodium oxide 287 g / L, aluminum oxide 159.7 g / L) was added to 350 g of deionized water, 11 g of sodium hydroxide was added, and after dissolution, 37.6 g of white carbon black (silicon dioxide 93.0 wt%, water 7.0 wt%) was added to the above solution. After stirring at a speed of ≥200 r / min for about 10-30 min, a gel was formed, and the molar composition of the raw material mixture was SiO2 / Al2O3=40, H2O / SiO2=35, NaOH / SiO2=0.60. 3.0 g of β molecular sieve seeds were added to the above gel, and stirring was continued for about 10-30 min, and then transferred to a reaction kettle. After crystallization at 120°C for 120 h, it was cooled, and the solid product was separated by filtration at room temperature, washed, and dried at 80°C for 12 h to obtain the β molecular sieve product. The single-pot yield was 25.7% after the solid product was collected and weighed.

[0064] The XRD spectrum of the β molecular sieve prepared in this comparative example is shown in Figure 2. Figure 6 , and the SEM photograph is shown in Figure 3. Figure 7 .

[0065] Comparative Example 2

[0066] The β molecular sieve was synthesized according to the method of Example 1, except that the operation method of the second aluminum supplement process was changed, and specifically:

[0067] Under stirring, 18.29 g of sodium aluminate solution (sodium oxide 287 g / L, aluminum oxide 159.7 g / L) was added into 350 g of deionized water, 11 g of sodium hydroxide was added, after dissolution, 37.6 g of white carbon black (silicon dioxide 93.0 wt%, water 7.0 wt%) was added into the above solution, after stirring at a speed of ≥200 r / min for about 10-30 min, a gel was formed, the molar composition of the raw material mixture was: SiO2 / Al2O3=40, H2O / SiO2=35, NaOH / SiO2=0.60, 3.0 g of β molecular sieve seed was added into the above gel, and stirring was continued for about 10-30 min, and then it was transferred into a reaction kettle, and crystallization was carried out at 120°C for 30 h, and then it was cooled. After standing and layering, 15 g of sodium aluminate solution was added, the lower layer gel was stirred to mix with the gel after the second aluminum addition, 3.0 g of β molecular sieve seed was added, and the mixture was uniformly mixed, and then crystallization was continued at 120°C for 100 h, and then it was cooled. After cooling, the solid product was separated by filtration at room temperature, washed, and dried at 80°C for 12 h to obtain a molecular sieve product. The single-pot yield was 60.3% after the solid product was collected and weighed.

[0068] The XRD spectrum and SEM photograph of the molecular sieve product prepared in the present comparative example are shown in Figure 8 and Figure 9 It can be seen that in addition to the characteristic peaks of β molecular sieve, a mixed phase appears, and the SEM morphology does not have the characteristics of β molecular sieve.

[0069] Comparative Example 3

[0070] The β molecular sieve was synthesized according to the method of Example 1, except that the aluminum source and the seed were added into the initial gel at one time, specifically:

[0071] Under stirring, 36.58 g of sodium aluminate solution (sodium oxide 287 g / L, aluminum oxide 159.7 g / L) was added into 350 g of deionized water, 11 g of sodium hydroxide was added, after dissolution, 37.6 g of white carbon black (silicon dioxide 93.0 wt%, water 7.0 wt%) was added into the above solution, after stirring at a speed of ≥200 r / min for about 10-30 min, a gel was formed, the molar composition of the raw material mixture was: SiO2 / Al2O3=40, H2O / SiO2=35, NaOH / SiO2=0.78, 6.0 g of β molecular sieve seed was added into the above gel, and stirring was continued at a speed of ≥200 r / min for about 10-30 min, and then it was transferred into a reaction kettle, and crystallization was carried out at 120°C for 100 h, and then it was cooled. After cooling, the solid product was separated by filtration at room temperature, washed, and dried at 80°C for 12 h to obtain a molecular sieve product. The single-pot yield was 58.3% after the solid product was collected and weighed.

[0072] The XRD spectrum of the molecular sieve product prepared in the present comparative example is shown in Figure 10 , and the SEM photograph is shown inFigure 11 The characteristic peaks of the molecular sieve show that its structure does not belong to β molecular sieve, and the SEM morphology does not have the characteristics of β molecular sieve.

[0073] Example 2

[0074] The β molecular sieve was synthesized according to the method of Example 1, except that the amount of sodium hydroxide added was changed to 13 g, and the molar composition of the raw material mixture was SiO2 / Al2O3=40, H2O / SiO2=35, and NaOH / SiO2=0.67. 3.5 g of β molecular sieve seeds were added to the first gel, and stirring was continued at a rotation speed of ≥200 r / min for about 10-30 min. The mixture was then transferred to a reaction kettle, and static crystallization was carried out at 140°C for 10 h. After cooling, the mixture was allowed to stand and separate into layers. The lower layer of the gel was maintained stationary, and the upper layer of the clear solution was stirred at a rotation speed of 60-350 r / min and 0.7 times the first amount of sodium metaaluminate solution (the molar ratio of the second aluminum source to the first aluminum source was 0.7:1) was added. Then, 3.0 g of the β molecular sieve seeds were added, and the mixture was mixed uniformly to form a second gel. Static crystallization was continued at 120°C for 80 h. After cooling, the solid product was separated by filtration at room temperature, washed, and dried at 80°C for 12 h to obtain the β molecular sieve product. The single-kettle yield was 53.5% after the solid product was collected and weighed.

[0075] The XRD spectrum of the β molecular sieve prepared in this example is shown in Figure 12 (Characteristic diffraction peaks of β molecular sieve).

[0076] Example 3

[0077] The β molecular sieve was synthesized according to the method of Example 1, except that the silicon source was changed from white carbon black to basic silicon sol (silicon dioxide 30% by weight), and the molar composition of the raw material mixture was SiO2 / Al2O3=40, H2O / SiO2=35, and NaOH / SiO2=0.60. 4.0 g of β molecular sieve seeds were added to the first gel, and stirring was continued at a rotation speed of ≥200 r / min for about 10-30 min. The mixture was then transferred to a reaction kettle, and static crystallization was carried out at 120°C for 30 h. After cooling, the mixture was allowed to stand and separate into layers. The lower layer of the gel was maintained stationary, and the upper layer of the clear solution was stirred at a rotation speed of 60-350 r / min and 0.7 times the first amount of sodium metaaluminate solution (the molar ratio of the second aluminum source to the first aluminum source was 0.7:1) was added. Then, 4.0 g of the β molecular sieve seeds were added, and the mixture was mixed uniformly to form a second gel. Static crystallization was continued at 120°C for 100 h. After cooling, the solid product was separated by filtration at room temperature, washed, and dried at 80°C for 12 h to obtain the β molecular sieve product. The single-kettle yield was 51.5% after the solid product was collected and weighed.

[0078] The XRD spectrum of the β molecular sieve prepared in this example is similar to Figure 3 .

[0079] Example 4

[0080] The β molecular sieve was synthesized according to the method of Example 1, except that the seed crystals were changed to ammonium-type β molecular sieve. The molar composition of the raw material mixture was: SiO2 / Al2O3=40, H2O / SiO2=35, NaOH / SiO2=0.60, 3.3 g of β molecular sieve seed crystals (Sinopec Changling Catalyst Co., ammonium-type β molecular sieve, SiO2 / Al2O3=22) were added to the first gel, and stirring was continued at a rotation speed of ≥200 r / min for about 10-30 min, and then the mixture was transferred to the reaction kettle, and static crystallization was carried out at 120°C for 30 h, and then the mixture was cooled. After standing and layering, the lower layer of the gel was maintained stationary, the upper layer of the clear solution was stirred at a rotation speed of 60-350 r / min, and an amount of sodium metaaluminate solution equal to the first amount was added (the molar ratio of the second aluminum source to the first aluminum source was 1:1), and then 3.3 g of the above β molecular sieve seed crystals were added, and the mixture was mixed uniformly to form a second gel, and static crystallization was continued at 120°C for 100 h, and then the mixture was cooled, and the solid product was separated by filtration at room temperature, washed, and dried at 80°C for 12 h to obtain a β molecular sieve product. The single-kettle yield was 57.3% after the solid product was collected and weighed.

[0081] The XRD spectrum of the β molecular sieve prepared in this example was similar to that of Figure 3 .

[0082] Example 5

[0083] The β molecular sieve was synthesized according to the method of Example 1, except that the amount of the second aluminum source added was changed. The molar composition of the raw material mixture was: SiO2 / Al2O3=40, H2O / SiO2=35, NaOH / SiO2=0.60, 3.0 g of β molecular sieve seed crystals were added to the first gel, and stirring was continued at a rotation speed of ≥200 r / min for about 10-30 min, and then the mixture was transferred to the reaction kettle, and static crystallization was carried out at 120°C for 30 h, and then the mixture was cooled. After standing and layering, the lower layer of the gel was maintained stationary, the upper layer of the clear solution was stirred at a rotation speed of 60-350 r / min, and an amount of sodium metaaluminate solution equal to 1.2 times the first amount was added (the molar ratio of the second aluminum source to the first aluminum source was 1.2:1), and then 3.0 g of the above β molecular sieve seed crystals were added, and the mixture was mixed uniformly to form a second gel, and static crystallization was continued at 120°C for 100 h, and then the mixture was cooled, and the solid product was separated by filtration at room temperature, washed, and dried at 80°C for 12 h to obtain a β molecular sieve product. The single-kettle yield was 62.2% after the solid product was collected and weighed.

[0084] The XRD spectrum of the β molecular sieve prepared in this example was similar to that of Figure 3 .

[0085] Example 6

[0086] The β molecular sieve was synthesized according to the method of Example 1, except that the molar composition of the raw material mixture was changed to SiO2 / Al2O3= 35, H2O / SiO2= 25, NaOH / SiO2= 0.55, 2.5 g of β molecular sieve seeds were added to the first gel, stirring was continued at a rotation speed of ≥ 200 r / min for about 10-30 min, and then the mixture was transferred into a reaction kettle, and static crystallization was carried out at 120°C for 30 h, and then the mixture was cooled. After standing and layering, the lower gel was maintained still, the upper clear solution was stirred at a rotation speed of 60-350 r / min, and a sodium metaaluminate solution (second aluminum source) was added in an amount of 0.9 times the first addition amount (the molar ratio of the second aluminum source to the first aluminum source was 0.9:1), 2.5 g of β molecular sieve seeds were added, and a second gel was formed by mixing uniformly, static crystallization was continued at 120°C for 100 h, and then the mixture was cooled, the solid product was separated by filtration at room temperature, washed, and dried at 80°C for 12 h to obtain a β molecular sieve product. The single-kettle yield was 55.2% after the solid product was collected and weighed.

[0087] The XRD spectrum of the β molecular sieve prepared in this example was similar to Figure 3 .

[0088] Example 7

[0089] The β molecular sieve was synthesized according to the method of Example 1, except that the molar composition of the raw material mixture was changed to SiO2 / Al2O3= 40, H2O / SiO2= 20, NaOH / SiO2= 0.45, 2.5 g of β molecular sieve seeds were added to the first gel, stirring was continued at a rotation speed of ≥ 200 r / min for about 10-30 min, and then the mixture was transferred into a reaction kettle, and static crystallization was carried out at 120°C for 30 h, and then the mixture was cooled. After standing and layering, the lower gel was maintained still, the upper clear solution was stirred at a rotation speed of 60-350 r / min, and a sodium metaaluminate solution (second aluminum source) was added in an amount of 0.2 times the first addition amount (the molar ratio of the second aluminum source to the first aluminum source was 0.2:1), 2.5 g of β molecular sieve seeds were added, and a second gel was formed by mixing uniformly, static crystallization was continued at 120°C for 100 h, and then the mixture was cooled, the solid product was separated by filtration at room temperature, washed, and dried at 80°C for 12 h to obtain a β molecular sieve product. The single-kettle yield was 43.9% after the solid product was collected and weighed.

[0090] The XRD spectrum of the β molecular sieve prepared in this example was similar to Figure 3 .

[0091] Example 8

[0092] The β molecular sieve was synthesized according to the method of Example 1, except that the molar composition of the raw material mixture was changed to Si02 / Al203= 45, H20 / Si02= 50, NaOH / Si02= 0.7, 3.0 g of β molecular sieve seeds were added to the first gel, stirring was continued at a rotation speed of ≥ 200 r / min for about 10-30 min, and then the mixture was transferred into a reaction kettle, and static crystallization was carried out at 120°C for 30 h, and then the mixture was cooled. After standing and layering, the lower gel was kept still, the upper clear solution was stirred at a rotation speed of 60-350 r / min, and a sodium metaaluminate solution (the molar ratio of the second aluminum source to the first aluminum source was 1:1) in an amount equal to the first addition was added, 3.0 g of β molecular sieve seeds were further added, and a second gel was formed after mixing uniformly, and then dynamic crystallization was carried out at 140°C for 50 h at a rotation speed of 30 r / min, and then the mixture was cooled. The solid product was separated by filtration at room temperature after cooling, washed, and dried at 80°C for 12 h to obtain the β molecular sieve product. The single-kettle yield was 47.5% after the solid product was collected and weighed.

[0093] The XRD spectrum of the β molecular sieve prepared in this example was similar to Figure 3 .

[0094] Example 9

[0095] The β molecular sieve was synthesized according to the method of Example 1, except that the molar composition of the raw material mixture was changed to Si02 / Al203= 45, H20 / Si02= 50, NaOH / Si02= 0.7, 3.0 g of β molecular sieve seeds were added to the first gel, stirring was continued at a rotation speed of ≥ 200 r / min for about 10-30 min, and then the mixture was transferred into a reaction kettle, and static crystallization was carried out at 120°C for 30 h, and then the mixture was cooled. After standing and layering, the lower gel was kept still, the upper clear solution was stirred at a rotation speed of 60-350 r / min, and a sodium metaaluminate solution (the molar ratio of the second aluminum source to the first aluminum source was 1:1) in an amount equal to the first addition was added, 3.0 g of β molecular sieve seeds were further added, and a second gel was formed after mixing uniformly, and then dynamic crystallization was carried out at 140°C for 50 h at a rotation speed of 30 r / min, and then the mixture was cooled. The solid product was separated by filtration at room temperature after cooling, washed, and dried at 80°C for 12 h to obtain the β molecular sieve product. The single-kettle yield was 47.5% after the solid product was collected and weighed.

[0096] The XRD spectrum of the β molecular sieve prepared in this example was similar to Figure 3 .

[0097] Example 10

[0098] The β molecular sieve was synthesized according to the method of Example 1, except that the crystallization conditions of the second crystallization were changed to dynamic crystallization at 140°C for 50 h at a rotation speed of 30 r / min, and then the mixture was cooled. The solid product was separated by filtration at room temperature after cooling, washed, and dried at 80°C for 12 h to obtain the β molecular sieve product. The single-kettle yield was 60.4% after the solid product was collected and weighed.

[0099] The XRD spectrum of the beta molecular sieve prepared in the embodiment is similar to Figure 3

[0100] From the results of the above embodiments and comparative examples, it can be seen that the beta molecular sieve can be synthesized by using the scheme of the present disclosure, and the single-pot yield of the product can be effectively improved. Specifically, the single-pot yield of Comparative Example 1 is only 25.7% by using the prior art scheme without secondary aluminum supplementation; the single-pot yield of Examples 1-7 can reach 43.3-62.2% by using the scheme of the present disclosure; which is increased by 68.5-142% compared with the prior art; although Comparative Example 2 and Comparative Example 3 are supplemented with secondary aluminum, the secondary aluminum is not added to the supernatant, and the molecular sieve finally prepared does not belong to the structure of the beta molecular sieve.

[0101] The preferred embodiments of the present disclosure are described in detail above in combination with the drawings, but the present disclosure is not limited to the specific details in the above-described embodiments. Within the technical concept of the present disclosure, various simple modifications can be made to the technical scheme of the present disclosure, and these simple modifications all belong to the protection scope of the present disclosure.

[0102] In addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combination manners.

[0103] Furthermore, any combination of various different embodiments of the present disclosure can also be made as long as it does not deviate from the idea of the present disclosure, and it should also be considered as the disclosed content of the present disclosure.​

Claims

1. A method for synthesizing a β molecular sieve, characterized by, The method comprises: mixing an inorganic alkali source, a first aluminum source, a silicon source and water to obtain a first gel; mixing a first beta molecular sieve seed with the first gel to perform a first crystallization to obtain a first crystallization product with obvious stratification; adding a second aluminum source and a second beta molecular sieve seed to an upper clear liquid of the first crystallization product to obtain a second gel; crystallizing the second gel to obtain a beta molecular sieve; wherein a molar ratio of the second aluminum source to the first aluminum source is (0.2-1.2):

1.

2. The method of claim 1, wherein, The method further comprises: mixing the inorganic alkali source, the first aluminum source and the water first, then adding the silicon source, and stirring at a speed not lower than 200 r / min for 0.1-2 h to obtain the first gel.

3. The method of claim 1, wherein, the molar ratio of the silicon source to the first aluminum source is (20-50): 1, the molar ratio of the base source to the silicon source is (0.35-0.7): 1, and the molar ratio of the water to the silicon source is (13-50): 1, wherein the silicon source is calculated as Si02, the first aluminum source is calculated as Al203, and the inorganic base source is calculated as OH - .

4. The method of claim 1, wherein, A weight ratio of the first beta molecular sieve seed to the silicon source is (5-15):100, and a weight ratio of the second beta molecular sieve seed to the silicon source is (5-10):

100.

5. The method of claim 1, wherein, The first crystallization is performed at a temperature of 110-160 ℃ for 8-48 h in a static crystallization under self-pressure in a closed reactor or a dynamic crystallization with a stirring speed lower than 15 rpm.

6. The method of claim 1, wherein, The second crystallization is performed at a temperature of 110-160 ℃ for 16-150 h in a static crystallization under self-pressure in a closed reactor or a dynamic crystallization with a stirring speed lower than 30 rpm.

7. The method of claim 1, wherein, The silicon source is one or more selected from the group consisting of white carbon black, sodium sesquicarbonate, silica sol and tetraethyl orthosilicate.

8. The method of claim 1, wherein, The first aluminum source is one or more selected from the group consisting of sodium aluminate, aluminum sulfate and aluminum nitrate; and the second aluminum source is one or more selected from the group consisting of sodium aluminate, aluminum sulfate and aluminum nitrate.

9. The method of claim 1, wherein, The inorganic alkali source is sodium hydroxide and / or potassium hydroxide.

10. The method of claim 1, wherein, The first beta molecular sieve seed and the second beta molecular sieve seed are each hydrogen-type beta molecular sieve or ammonium-type beta molecular sieve, and a silicon-aluminum molar ratio of the first beta molecular sieve seed and the second beta molecular sieve seed is each (20-30):1.

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