Y / beta composite double micro-porous material and preparation method thereof

Abstract

The present disclosure relates to a Y / Beta composite dual-microporous material and a preparation method thereof, the method comprising the following steps: obtaining a Beta molecular sieve precursor and a small crystal NaY molecular sieve, respectively; mixing the Beta molecular sieve precursor, the small crystal NaY molecular sieve, a dual-microporous material synthesis template agent, a dual-microporous material synthesis alkali source and water to obtain a synthesis mixture; and performing dual-microporous material synthesis crystallization on the synthesis mixture. The Y / Beta composite dual-microporous material has a high specific surface area and pore volume.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a Y / Beta composite dual-microporous material and a preparation method thereof. BACKGROUND

[0002] Among the hundreds of molecular sieves that have been developed, the Y-type molecular sieve is the most widely used in industry. At present, the synthesis of NaY molecular sieve in industry mainly adopts the seed gel method. Due to the use and improvement of the seed gel, the crystallization time of the Y-type molecular sieve is greatly shortened, which lays the foundation for the industrialization of the Y-type molecular sieve. Beta zeolite is the only large-pore high-silicon zeolite with a three-dimensional cross twelve-membered ring pore structure discovered so far, and exhibits excellent catalytic performance in hydrocracking, hydroisomerization, alkane aromatization, alkylation and transalkylation reactions of hydrocarbons.

[0003] Y and Beta type molecular sieves have different characteristics due to different crystal structures, microporous texture properties and element compositions: Y-type molecular sieves have supercage structure and three-dimensional pore system, have good adsorption performance, rich micropore channels and uniform pore size, etc.; Beta type molecular sieves have good hydrothermal stability, exhibit good carbon deposition resistance and long service life in catalysis, etc. In addition, the basic structural units of Y-type molecular sieves and Beta-type molecular sieves are different, which belong to different topological structure molecular sieve systems, and there are significant differences in the composition of the crystallization liquid and the crystallization conditions during the synthesis process. It is impossible to synthesize them in one step by "co-crystallization method". The existing synthesis method of Y / Beta composite molecular sieve is usually difficult to ensure the composite of Y-type molecular sieve and Beta-type molecular sieve at the micro level, and the specific surface area and pore volume of the obtained composite molecular sieve product are low, which affects the catalytic activity. SUMMARY

[0004] The purpose of the present disclosure is to provide a Y / Beta composite dual-microporous material and a preparation method thereof, so as to improve the specific surface area and pore volume of the Y / Beta composite dual-microporous material.

[0005] In order to achieve the above-mentioned purpose, the first aspect of the present disclosure provides a preparation method of a Y / Beta composite dual-microporous material, which comprises the following steps:

[0006] Beta molecular sieve precursor and small crystal NaY molecular sieve are obtained respectively;

[0007] The Beta molecular sieve precursor, the small crystal NaY molecular sieve, the optional dual-microporous material synthesis template agent, the optional dual-microporous material synthesis alkali source and the optional water are mixed to obtain a synthesis mixture;

[0008] The synthesis mixture is subjected to dual-microporous material synthesis crystallization.

[0009] Optionally, the preparation step of the Beta molecular sieve precursor comprises:

[0010] mixing a first aluminum source, a first silicon source, a first template agent and a first alkali source to obtain a first mixture;

[0011] crystallizing the first mixture to obtain the Beta molecular sieve precursor;

[0012] wherein, in terms of oxides and in terms of moles, the first mixture has a composition of M:Al2O3:SiO2:R:H2O=(2-9):1:(15-40):(2-5):(100-400), M represents an alkali metal oxide, and R represents the first template agent.

[0013] Optionally, the first aluminum source is one or more selected from aluminum sulfate, aluminum chloride, aluminum nitrate, sodium metaaluminate and pseudo-boehmite;

[0014] the first silicon source is one or more selected from water glass, colloidal silicon dioxide, silica sol and white carbon black;

[0015] the first template agent is one or more selected from tetraethylammonium hydroxide, tetrapropylammonium hydroxide and tetrabutylammonium hydroxide;

[0016] the first alkali source is one or more selected from sodium hydroxide, potassium hydroxide, sodium oxide and potassium oxide.

[0017] Optionally, the first crystallization has a temperature of 110-155℃ and a time of 12-72 hours.

[0018] Optionally, the small-grained NaY molecular sieve has a particle size of 100-500nm.

[0019] The preparation step of the small-grained NaY molecular sieve comprises:

[0020] mixing sodium metaaluminate and water glass at a temperature of 15-60℃ and under stirring to obtain a second mixture, wherein, in terms of oxides and in terms of moles, the second mixture has a composition of Na2O:Al2O3:SiO2=(6-25):1:(6-25);

[0021] stirring and aging the second mixture at 15-60℃ for 5-48 hours, and then statically aging the second mixture at 15-60℃ for 5-48 hours to obtain a third mixture;

[0022] adding water to the third mixture under stirring to obtain a directing agent, wherein the directing agent has a composition of Na2O:Al2O3:SiO2:H2O=(6-25):1:(6-25):(200-400) in terms of oxide and in terms of mole;

[0023] mixing the second silicon source, the second aluminum source and the directing agent to obtain a fourth mixture, wherein the fourth mixture has a composition of Na2O:Al2O3:SiO2:H2O=(6-25):1:(6-25):(200-400) in terms of oxide and in terms of mole, and the number of moles of aluminum in the directing agent accounts for 3-30% of the total number of moles of aluminum in the fourth mixture;

[0024] crystallizing the fourth mixture at 90-100°C for 15-48 hours, and washing and filtering to obtain the small-grained NaY molecular sieve.

[0025] Optionally, the second silicon source is one or more selected from water glass, silica sol, silica gel and white carbon black.

[0026] The second aluminum source is one or more selected from sodium metaaluminate, aluminum sulfate, aluminum chloride, aluminum nitrate, aluminum hydroxide and pseudo-boehmite.

[0027] Optionally, the weight ratio of the Beta molecular sieve precursor, the small-grained NaY molecular sieve, the synthesis template of the dual-microporous material, the synthesis alkali source of the dual-microporous material and the water is 1:(0.1-10):(0-0.4):(0-1):(0-10).

[0028] Optionally, the synthesis template of the dual-microporous material is one or more selected from tetraethylammonium hydroxide, tetrapropylammonium hydroxide and tetrabutylammonium hydroxide.

[0029] The synthesis alkali source of the dual-microporous material is one or more selected from sodium hydroxide, potassium hydroxide, sodium oxide and potassium oxide.

[0030] Optionally, the conditions of the synthesis crystallization of the dual-microporous material include a temperature of 110-155°C and a time of 12-60 hours.

[0031] In a second aspect, the present disclosure provides a Y / Beta composite dual-microporous material prepared by the method of the first aspect.

[0032] By the above technical solution, the present disclosure uses a nano-sized Beta molecular sieve precursor and a small-grained NaY as a combination unit to synthesize a Y / Beta composite dual-microporous material, realizes the combination of two different crystal molecular sieve particles at a nano level, and the obtained Y / Beta composite dual-microporous material has a high specific surface area and pore volume.

[0033] Other features and advantages of the present disclosure will be illustrated in detail in the following specific embodiments section. BRIEF DESCRIPTION OF DRAWINGS

[0034] The accompanying drawings are included to provide a further understanding of the present disclosure and constitute a part of the specification, which together with the specific embodiments below, serve to explain the present disclosure but do not limit the present disclosure. In the drawings:

[0035] Figure 1 is an XRD spectrum of the Y / Beta composite dual-microporous material prepared in Example 1.

[0036] Figure 2 is an SEM image of the Y / Beta composite dual-microporous material prepared in Example 1.

[0037] Figure 3 is an SEM image of the Y / Beta composite dual-microporous material prepared in Comparative Example 1. DETAILED DESCRIPTION

[0038] 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 only used to illustrate and explain the present disclosure, and do not limit the present disclosure.

[0039] In a first aspect, the present disclosure provides a preparation method of a Y / Beta composite dual-microporous material, which comprises the following steps:

[0040] Beta molecular sieve precursor and small crystal NaY molecular sieve are obtained respectively;

[0041] The Beta molecular sieve precursor, the small crystal NaY molecular sieve, optional dual-microporous material synthesis template agent, optional dual-microporous material synthesis alkali source and water are mixed to obtain a synthesis mixture;

[0042] The synthesis mixture is subjected to dual-microporous material synthesis crystallization.

[0043] According to the present disclosure, the Beta molecular sieve precursor has a nanoscale size, and specifically, the particle size of the Beta molecular sieve precursor can be 50-100 nm.

[0044] In an embodiment, the preparation step of the Beta molecular sieve precursor can comprise:

[0045] The first aluminum source, the first silicon source, the first template agent and the first alkali source are mixed to obtain a first mixture;

[0046] The first mixture is subjected to first crystallization to obtain the Beta molecular sieve precursor;

[0047] wherein the composition of the first mixture is M:Al203:Si02:R:H20 = (2-9):1:(15-40):(2-5):(100-400) in terms of oxides and in terms of moles, M represents an alkali metal oxide, and R represents the first template.

[0048] wherein the first aluminum source, the first silicon source, the first template, and the first base source can be common types for synthesizing Beta molecular sieve; specifically, the first aluminum source can be one or more selected from the group consisting of aluminum sulfate, aluminum chloride, aluminum nitrate, sodium metaaluminate, and pseudo-boehmite, preferably one or more selected from the group consisting of aluminum sulfate, sodium metaaluminate, and pseudo-boehmite; the first silicon source can be one or more selected from the group consisting of water glass, colloidal silicon dioxide, silica sol, and white carbon black, preferably colloidal silicon dioxide and / or white carbon black; the first template can be one or more selected from the group consisting of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide, preferably tetraethylammonium hydroxide and / or tetrapropylammonium hydroxide; and the first base source can be one or more selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium oxide, and potassium oxide, preferably sodium hydroxide and / or potassium hydroxide.

[0049] The first crystallization can be carried out under a closed condition, and specifically, the conditions of the first crystallization can include a temperature of 110-155°C and a time of 12-72 hours.

[0050] According to the present disclosure, the small-grained NaY molecular sieve can have a particle size of 100-500 nm.

[0051] The small-grained NaY molecular sieve can be synthesized by a method well known to those skilled in the art. In one embodiment, the preparation of the small-grained NaY molecular sieve comprises:

[0052] The sodium metaaluminate and the water glass are mixed at a temperature of 15-60°C and under stirring to obtain a second mixture, wherein the composition of the second mixture is Na20:Al203:Si02 = (6-25):1:(6-25) in terms of oxides and in terms of moles;

[0053] The second mixture is stirred at a temperature of 15-60°C for 5-48 hours, and then is statically aged at a temperature of 15-60°C for 5-48 hours to obtain a third mixture;

[0054] Water is added to the third mixture under stirring to obtain a directing agent, wherein the composition of the directing agent is Na20:Al203:Si02:H20 = (6-25):1:(6-25):(200-400) in terms of oxides and in terms of moles;

[0055] mixing the second silicon source, the second aluminum source and the directing agent to obtain a fourth mixture, wherein the fourth mixture has a composition of Na2O:Al2O3:SiO2:H2O=(6-25):1:(6-25):(200-400) in terms of oxide and in terms of mole, and the number of moles of aluminum element in the directing agent accounts for 3-30% of the total number of moles of aluminum element in the fourth mixture;

[0056] carrying out second crystallization on the fourth mixture at 90-100°C for 15-48 hours, and washing and filtering to obtain the small-grained NaY molecular sieve.

[0057] The second silicon source and the second aluminum source can be common types for synthesizing NaY molecular sieve. Specifically, the second silicon source can be one or more selected from water glass, silica sol, silica gel and white carbon black; and the second aluminum source can be one or more selected from sodium aluminate, aluminum sulfate, aluminum chloride, aluminum nitrate, aluminum hydroxide and pseudo-boehmite. The water can be deionized water or distilled water.

[0058] According to the present disclosure, the weight ratio of the Beta molecular sieve precursor, the small-grained NaY molecular sieve, the synthesis template of the dual-microporous material, the synthesis alkali source of the dual-microporous material and the water in the synthesis mixture can be 1:(0.1-10):(0-0.4):(0-1):(0-10), and preferably, the weight ratio of the Beta molecular sieve precursor, the small-grained NaY molecular sieve, the synthesis template of the dual-microporous material, the synthesis alkali source of the dual-microporous material and the water is 1:(1-9):(0.04-0.4):(0.0001-1):(0.09-10). The synthesis template of the dual-microporous material can be one or more selected from tetraethylammonium hydroxide, tetrapropylammonium hydroxide and tetrabutylammonium hydroxide; and the synthesis template of the dual-microporous material and the first template can be the same template or different templates, and preferably the same template. The synthesis alkali source of the dual-microporous material can be one or more selected from sodium hydroxide, potassium hydroxide, sodium oxide and potassium oxide; and the synthesis alkali source of the dual-microporous material and the first alkali source can be the same alkali source or different alkali sources, and preferably the same alkali source.

[0059] The mixing of the Beta molecular sieve precursor, the small-grained NaY molecular sieve, the synthesis template of the dual-microporous material, the synthesis alkali source of the dual-microporous material and the water is preferably carried out under stirring.

[0060] According to the present disclosure, the conditions of the synthesis crystallization of the dual-microporous material can include a temperature of 110-155°C and a time of 12-60 hours.

[0061] According to the present disclosure, the method further comprises the steps of filtering, washing, drying and calcining the crystallization product obtained by synthesizing and crystallizing the dual-microporous material, wherein the drying and calcining conditions can be conventional in the art.

[0062] The Y / Beta composite dual-microporous material of the present disclosure uses nanoscale Beta molecular sieve precursor and small-grained NaY molecular sieve as combined units, realizes the composite of different crystal type molecular sieve particles at the nanometer level, and also ensures relatively high grain integrity and relative crystallinity of the two molecular sieves.

[0063] In a second aspect, the present disclosure provides a Y / Beta composite dual-microporous material prepared by the method of the first aspect of the present disclosure. The weight percentage of Y molecular sieve can be randomly adjusted between 5-95% as needed. The present disclosure realizes the composite of two different crystal type molecular sieve particles at the nanometer level, and the Y / Beta composite dual-microporous material has a relatively high specific surface area and pore volume. Specifically, the specific surface area of the Y / Beta composite dual-microporous material can be 720-750 m 2 / g, and the pore volume can be 0.34-0.39 cm 3 / g.

[0064] The present disclosure will be further described below in conjunction with examples and comparative examples, but the scope of the present disclosure is not limited only to these examples.

[0065] In each example and comparative example, the specific surface area and pore structure are measured by using an ASAP2420 automatic adsorption instrument and an ASAP2020 automatic adsorption instrument of American Micromeritics Company, the total pore volume and secondary pore volume of the molecular sieve are calculated according to the BET method, and the specific steps are as follows: the BET specific surface is specified in the range of 0.05-0.35 MPa of nitrogen partial pressure, 3-5 pressures are selected, the actual nitrogen adsorption amount is measured, and then the specific surface area is calculated by using the BET equation. The micropore volume and total pore volume are calculated according to the t-plot curve, and the secondary pore volume is calculated by the BJH formula.

[0066] Example 1

[0067] (1) Preparation of Beta molecular sieve precursor

[0068] 18.4g TEAOH (Aladdin, analytical grade, 25% aqueous solution, the same below), 5.4g sodium aluminate (provided by Sinopec Catalyst Changling Branch, Al2O3 content 101.5g / L, Na2O content 142.5g / L, specific gravity 1.17, the same below), 0.50g NaOH (Shanghai Test, analytical grade, ≥96%, the same below), and 0.70g aluminum sulfate (Sinopharm Chemical Reagent Co., Ltd., analytical grade) were added. 10g of precipitated silica (Shanghai test, analytical grade, ≥99%) and 10g of precipitated silica (Shanghai test, analytical grade, ≥99%) were mixed and stirred into a uniform white gel. The mixture was then placed in a 100mL stainless steel reactor and crystallized at 110℃ for 72h. The mixture was then removed and set aside for use. The original material molar ratio of the Beta molecular sieve precursor was 2.5Na2O:Al2O3:25.2SiO2:4.7(TEA)2O:149.5H2O. The particle size of the Beta molecular sieve precursor was 100nm.

[0069] (2) Preparation of small-crystal NaY molecular sieves

[0070] 50.39 g of high-alkali sodium aluminate solution (provided by Sinopec Catalyst Changling Branch, Al2O3 content 40.2 g / L, Na2O content 255 g / L, specific gravity 1.324, the same below) was added to 65.56 g of water glass (provided by Sinopec Catalyst Changling Branch, SiO2 content 260.6 g / L, Na2O content 81.6 g / L, specific gravity 1.2655, modulus 3.3, the same below). The solution was stirred and aged at room temperature for 48 hours, then statically aged at 60℃ for 5 hours. Finally, 15 g of deionized water was added under stirring. The final molar ratio of the resulting directing agent was 15Na2O:Al2O3:15SiO2:320H2O. All of the prepared directing agent was used in the preparation of the following reaction mixture. The amount of directing agent added was calculated based on the molar number of aluminum in the directing agent accounting for 3% of the total molar number of aluminum.

[0071] The guiding agent (prepared in the previous step), 1682.6 g of water glass, 134.19 g of low-alkali sodium metaaluminate solution (provided by Sinopec Catalyst Changling Branch Co., Ltd., Al2O3 content of 194 g / L, Na2O content of 286.2 g / L, and specific gravity of 1.413, same below), 448.02 g of aluminum sulfate (provided by Sinopec Catalyst Changling Branch Co., Ltd., Al2O3 content of 88.9 g / L, and specific gravity of 1.2829, same below), and 150.4 g of water were sequentially added into a mixing tank under the condition of room temperature and high-speed stirring, and the total molar ratio of the reaction mixture was 7Na2O:Al2O3:12SiO2:209H2O. After being uniformly stirred, it was loaded into a stainless steel reaction kettle, statically crystallized at 100 ℃ for 24 h, and then filtered, washed, and dried to obtain a small-grained NaY molecular sieve product, and the particle size of the small-grained NaY molecular sieve product was 500 nm.

[0072] (3) Preparation of Y / Beta composite bimicroporous material

[0073] The 18.4 g of TEAOH, 0.42 g of NaOH, 4.5 g of deionized water, 50 g of the Beta molecular sieve precursor prepared in step (1), and 50 g of the small-grained NaY molecular sieve prepared in step (2) were mixed and stirred into a uniform white gel, loaded into a 100 mL stainless steel reaction kettle, crystallized at 120 ℃ for 48 h, and then filtered, washed, dried at 110 ℃ for 6 h, and calcined at 560 ℃ for 4 h to obtain a Y / Beta composite bimicroporous material, and the XRD spectrum is shown in Figure 1 , and Figure 1 It can be seen that the Y / Beta composite bimicroporous material has the spectral characteristics of both Y molecular sieve and Beta molecular sieve, and the SEM image of the Y / Beta composite bimicroporous material is shown in Figure 2 , and the specific surface area and pore volume are listed in Table 1.

[0074] Example 2

[0075] The Y / Beta composite bimicroporous material was prepared according to the method of Example 1, and the sources of the raw materials were the same as those of Example 1. The difference lies in that in step (1), the crystallization condition was crystallization at 145 ℃ for 58 h; and in step (3), the amounts of the materials were as follows: 2.1 g of TEAOH, 0.05 g of NaOH, 5.0 g of deionized water, 49.95 g of the Beta molecular sieve precursor prepared in step (1), and 5.55 g of the small-grained NaY molecular sieve prepared in step (2). The Y / Beta composite bimicroporous material was prepared, and the XRD spectrum was similar to Figure 1 , and the specific surface area and pore volume of the Y / Beta composite bimicroporous material are listed in Table 1.

[0076] Example 3

[0077] A Y / Beta composite dual-microporous material was prepared according to the method of Example 1, and the sources of the raw materials were the same as in Example 1. The difference was that in step (1), the crystallization condition was 125°C for 20h; in step (3), the amounts of the materials were 18.4g TEAOH, 37.8g NaOH, 405g deionized water, 50g of the Beta molecular sieve precursor prepared in step (1), and 450g of the small crystal NaY molecular sieve prepared in step (2). A Y / Beta composite dual-microporous material was prepared, and the XRD spectrum thereof was similar to that of Figure 1, wherein the weight ratio of Beta / Y was 1:9, and the specific surface area and pore volume of the Y / Beta composite dual-microporous material are listed in Table 1. Figure 1

[0078] Example 4

[0079] A Y / Beta composite dual-microporous material was prepared according to the method of Example 1, and the sources of the raw materials were the same as in Example 1. The difference was that in step (1), 10.6g TEAOH, 8.25g sodium metaaluminate, and 40g water glass were mixed and stirred into a uniform white gel, which was loaded into a 100mL stainless steel reaction kettle, and crystallized at 140°C for 40h, and then taken out for use. The molar ratio of the original materials of the Beta molecular sieve precursor was 8.3Na2O:Al2O3:19.5SiO2:2.6(TEA)2O:346.2H2O. In step (3), 49.93g of the Beta molecular sieve precursor prepared in step (1) and 21.4g of the small crystal NaY molecular sieve prepared in step (2) were mixed and stirred into a uniform white gel, which was loaded into a 100mL stainless steel reaction kettle, and crystallized at 130°C for 36h, and then filtered, washed, and dried to obtain a Y / Beta composite dual-microporous material, wherein the weight ratio of Beta / Y was 7:3, and the specific surface area and pore volume of the Y / Beta composite dual-microporous material are listed in Table 1.

[0080] Example 5

[0081] ​A Y / Beta composite dual-microporous material was prepared according to the method of Example 1, and the sources of the raw materials were the same as in Example 1. The difference was that in step (1), 10.6 g of TEAOH, 8.25 g of sodium metaaluminate and 40 g of silica sol (SiO2mass fraction 40%, Na2O mass fraction 0.5%) were mixed and stirred into a uniform white gel, which was then loaded into a 100 mL stainless steel autoclave and crystallized at 140°C for 40 h. The original raw material molar ratio of the Beta molecular sieve precursor was 2.8 Na2O:Al2O3:38.5 SiO2:2.6 (TEA)2O:242.2 H2O. In step (3), 18.4 g of TEAOH, 37.8 g of NaOH, 405 g of deionized water, 192.86 g of the Beta molecular sieve precursor prepared in step (1) and 450 g of the small crystal NaY molecular sieve prepared in step (2) were mixed and stirred into a uniform white gel, which was then loaded into a 100 mL stainless steel autoclave and crystallized at 120°C for 48 h. Then the product was filtered, washed, dried at 110°C for 6 h and calcined at 540°C for 4 h to obtain the Y / Beta composite dual-microporous material. The XRD spectrum of the Y / Beta composite dual-microporous material was similar to that of the Y / Beta composite dual-microporous material of Example 1, and the specific surface area and pore volume of the Y / Beta composite dual-microporous material were 650 m2 / g and 0.45 cm3 / g, respectively. Figure 1 The specific surface area and pore volume of the Y / Beta composite dual-microporous material were 650 m2 / g and 0.45 cm3 / g, respectively.

[0082] Comparative Example 1

[0083] First, 70 ml of distilled water, 2 ml of concentrated sulfuric acid, 25 ml of a sodium silicate solution ([SiO2]=4.85 mol / L, [OH]=2.75 mol / L), 11.5 ml of a sodium metaaluminate solution ([Al2O3]=2.09 mol / L, [OH]=8.25 mol / L) and 3 ml of a directing agent (molar ratio of components: 16 Na2O: 15 SiO2: Al2O3: 320 H2O) were sequentially added and mixed into a gel, which was then loaded into a 100 mL stainless steel autoclave and crystallized at 90°C for 27 h to obtain a Y-type zeolite. Then, 35 ml of distilled water, 15 g of TEABr (tetraethylammonium bromide), 5 ml of NH3.H2O (concentrated ammonia water), the Y-type zeolite obtained above, 45 ml of a silica sol ([SiO2]=6.05 mol / L) and 45 ml of deionized water were sequentially added and mixed into a uniform white gel, which was then loaded into three 50 mL stainless steel autoclaves and crystallized at 140°C for 5 days. After washing until the solution was neutral, the product was dried and then calcined at 550°C for 5 h. The SEM image of the Y / Beta composite dual-microporous material is shown in FIG. 2. Figure 3 The specific surface area and pore volume of the Y / Beta composite dual-microporous material were 650 m2 / g and 0.45 cm3 / g, respectively.

[0084] Comparative Example 2

[0085] A mixture of 26.4 g of TEABr (tetraethylammonium bromide), 9 mL of concentrated ammonia, 5.6 mL of sodium metaaluminate solution ([Al2O3]=2.45 mol / L, [OH]=10.37 mol / L), 45 mL of silica sol ([SiO2]=6.05 mol / L), and 50 mL of distilled water was stirred to form a uniform white gelatinous substance, which was then charged into a 100 mL stainless steel autoclave and crystallized at 140°C for 7 days. After washing until the solution was neutral, the product was dried. The product was calcined at 550°C for 5 h to remove the organic amine. A mixture of 3.2 g of the calcined product, 8 mL of sodium metaaluminate solution ([Al2O3]=0.25 mol / L, [OH]=1.04 mol / L), 1.2 g of sodium hydroxide, 37 mL of distilled water, and 1.5 mL of a directing agent (molar ratio: 16 Na2O: 15 SiO2: Al2O3: 320 H2O) was stirred to form a uniform white substance, which was then charged into a 50 mL stainless steel autoclave and crystallized at 90°C for 24 h. After washing until the solution was neutral, the product was dried. The specific surface area and pore volume of the Y / Beta composite bimicroporous material are shown in Table 1.

[0086] Comparative Example 3

[0087] A beaker was charged with 11.3 g of sodium hydroxide, 65 mL of distilled water, 5.8 mL of sodium aluminate solution (2.88 mol / L), and 33 mL of water glass (SiO2 content 34 wt%), which were stirred and aged at 30°C for 24 h to obtain a Y structure directing agent. A beaker was charged with 0.8 g of sodium hydroxide, 1.5 mL of sodium aluminate (2.88 mol / L), 24 g of white carbon black, and 100 mL of tetraethylammonium hydroxide (25 wt%), which were stirred for 3 h, charged into a synthesis bomb, and crystallized at 140°C for 5 h to obtain β seeds. A beaker was charged with 100 mL of distilled water, 4.6 g of sodium hydroxide, 1.1 mL of sodium aluminate (2.88 mol / L), 12 g of white carbon black, and 6 mL of β seeds, which were stirred for 30 min, charged into a synthesis bomb, and crystallized at 140°C for 2 d to obtain a β molecular sieve slurry. A 100 mL portion of the β molecular sieve slurry obtained above (dry β molecular sieve 4.6 g or so) was charged into a beaker, and 300 mL of distilled water, 3 mL of sodium aluminate (2.88 mol / L), and 1 g of sodium hydroxide were added, which were stirred for 10 min. Finally, 6.5 mL of the Y structure directing agent was added, and the mixture was stirred for 30 min, charged into a synthesis bomb, and crystallized at 80°C for 35 h. The product was washed with distilled water until the solution was neutral, and dried at 100°C for 2 h. The weight content of the Beta molecular sieve in the composite molecular sieve was 55%. The specific surface area and pore volume of the Y / Beta composite bimicroporous material are shown in Table 1.

[0088] Comparative Example 4

[0089] Take 4.9ml deionized water in a 25ml beaker. Weigh 0.226g sodium aluminate slowly into the above beaker under magnetic stirring to dissolve it. Weigh 0.84g sodium hydroxide into the beaker, stir to dissolve it, and after it cools, slowly add 1.7ml silica sol, stir until uniform, continue stirring for 5min, seal and store for 18h to obtain the seed gel. Take 3.2ml deionized water in a 25ml beaker. Weigh 0.226g sodium aluminate slowly into the above beaker under magnetic stirring to dissolve it. Weigh 0.25g sodium hydroxide into the beaker, stir to dissolve it, and after it cools, slowly add 0.9ml silica sol, stir for 30min. Take 1.0ml of the seed gel prepared in the previous step, and stir for 25min. Then transfer this solution into a self-pressing autoclave with a polytetrafluoroethylene liner, seal it, and place it in a 90℃ oven to crystallize for 2h to obtain a gel containing Y-type zeolite structural units. Take 5.0ml deionized water in a 100ml beaker. Weigh 0.50g sodium hydroxide into the beaker under magnetic stirring to dissolve it, and after it cools, slowly add 14.70ml tetraethylammonium hydroxide solution, the gel containing Y-type zeolite structural units, and 9.1ml silica sol, and continue stirring for 30min. Then transfer this solution into a self-pressing autoclave with a polytetrafluoroethylene liner, seal it, and place it in a 120℃ oven to crystallize for 12d. After crystallization, cool to room temperature, suction filter, wash with deionized water until pH=7, dry at 100℃ for 2h, and then calcine at 350℃ for 6h in an air atmosphere, and cool to room temperature. The specific surface area and pore volume of the Y / Beta composite bimicroporous material are listed in Table 1.

[0090] Table 1

[0091] Specific surface area (m 2 / g) Pore volume (cm 3 / g) Example 1 745.18 0.3849 Example 2 733.45 0.3514 Example 3 733.74 0.3674 Example 4 720.93 0.3472 Example 5 749.48 0.3760 Comparative Example 1 626.49 0.3277 Comparative Example 2 613.52 0.3242 Comparative Example 3 605.83 0.3387 Comparative Example 4 627.62 0.3197

[0092] As can be seen from Table 1, the Y / Beta composite bimicroporous material prepared by the method of the present disclosure has a high specific surface area and pore volume.

[0093] The preferred embodiments of the present disclosure are described in detail above with reference to 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 solutions of the present disclosure, and these simple modifications all belong to the protection scope of the present disclosure.

[0094] 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 describe various possible combinations again.

[0095] Furthermore, the various embodiments of the present disclosure can be arbitrarily combined with each other unless they contradict each other, and it should be understood that the same should be construed as being included in the disclosure of the present disclosure.

Claims

1. A method for preparing a Y / Beta composite dual-microporous material, characterized in that, The method comprises the following steps: Beta molecular sieve precursor and small-grained NaY molecular sieve are respectively obtained; The Beta molecular sieve precursor, the small-grained NaY molecular sieve, optional bimodal material synthesis template agent, optional bimodal material synthesis alkali source and optional water are mixed to obtain a synthesis mixture; The synthesis mixture is subjected to bimodal material synthesis crystallization.

2. The method of claim 1, wherein, The preparation steps of the Beta molecular sieve precursor comprise: A first aluminum source, a first silicon source, a first template agent and a first alkali source are mixed to obtain a first mixture; The first mixture is subjected to first crystallization to obtain the Beta molecular sieve precursor; The first mixture is composed of M:Al2O3:SiO2:R:H2O=(2-9):1:(15-40):(2-5):(100-400) in terms of oxides and in terms of moles, wherein M represents alkali metal oxide, and R represents the first template agent.

3. The method of claim 2, wherein, The first aluminum source is one or more selected from aluminum sulfate, aluminum chloride, aluminum nitrate, sodium metaaluminate and pseudo-boehmite; The first silicon source is one or more selected from water glass, colloidal silicon dioxide, silica sol and white carbon black; The first template agent is one or more selected from tetraethylammonium hydroxide, tetrapropylammonium hydroxide and tetrabutylammonium hydroxide; The first alkali source is one or more selected from sodium hydroxide, potassium hydroxide, sodium oxide and potassium oxide.

4. The method of claim 2, wherein, The first crystallization is performed at a temperature of 110-155 ℃ for 12-72 hours.

5. The method of claim 1, wherein, The small-grained NaY molecular sieve has a particle size of 100-500 nm.

6. The method of claim 1 or 5, wherein, The preparation steps of the small-grained NaY molecular sieve comprise: Sodium metaaluminate and water glass are mixed at a temperature of 15-60 ℃ under stirring to obtain a second mixture, wherein the second mixture is composed of Na2O:Al2O3:SiO2=(6-25):1:(6-25) in terms of oxides and in terms of moles; The second mixture is stirred and aged at 15-60 ℃ for 5-48 hours, and then is statically aged at 15-60 ℃ for 5-48 hours to obtain a third mixture; Water is added to the third mixture under stirring to obtain a directing agent, wherein the directing agent is composed of Na2O:Al2O3:SiO2:H2O=(6-25):1:(6-25):(200-400) in terms of oxides and in terms of moles; A second silicon source and a second aluminum source are mixed with the directing agent to obtain a fourth mixture, wherein the fourth mixture is composed of Na2O:Al2O3:SiO2:H2O=(6-25):1:(6-25):(200-400) in terms of oxides and in terms of moles, and the number of moles of aluminum elements in the directing agent accounts for 3-30% of the total number of moles of aluminum elements in the fourth mixture; The fourth mixture is subjected to second crystallization at 90-100 ℃ for 15-48 hours, and then is washed and filtered to obtain the small-grained NaY molecular sieve.

7. The method of claim 6, wherein, The second silicon source is one or more selected from water glass, silica sol, silica gel and white carbon black; The second aluminum source is one or more selected from sodium metaaluminate, aluminum sulfate, aluminum chloride, aluminum nitrate, aluminum hydroxide and pseudoboehmite.

8. The method of claim 1, wherein, The weight ratio of the Beta molecular sieve precursor, the small crystal NaY molecular sieve, the synthesis template of the dual-microporous material, the synthesis alkali source of the dual-microporous material and the water is 1:(0.1-10):(0-0.4):(0-1):(0-10).

9. The method of claim 1, wherein, The synthesis template of the dual-microporous material is one or more selected from tetraethylammonium hydroxide, tetrapropylammonium hydroxide and tetrabutylammonium hydroxide. The synthesis alkali source of the dual-microporous material is one or more selected from sodium hydroxide, potassium hydroxide, sodium oxide and potassium oxide.

10. The method of claim 1, wherein, The conditions of the synthesis crystallization of the dual-microporous material include that the temperature is 110-155 ℃ and the time is 12-60 hours. 11.A Y / Beta composite dual-microporous material prepared by the method of any one of claims 1-10.

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