Beta molecular sieve and preparation method thereof

Abstract

The invention relates to a Beta molecular sieve and a preparation method thereof, in the Beta molecular sieve, the volume of pores with the pore diameter of 2-10 nm accounts for 65-90% of the total pore volume; the method disclosed by the invention is simple in steps, and the Beta molecular sieve with large grain size and concentrated pore distribution can be prepared.

Description

Technical Field

[0001] The present disclosure relates to the field of molecular sieve synthesis, and in particular, to a Beta molecular sieve and a preparation method thereof. Background Art

[0002] In 1967, Wadlinger Digital Display of Mobile Company used sodium aluminate, silica gel, tetraethylammonium hydroxide (TEAOH) and water to synthesize Beta molecular sieve. Beta molecular sieve has the characteristics of high silicon-aluminum ratio and wide silicon-aluminum ratio modulation range. Marens et al. used decane as a probe reaction to reveal the 12-membered ring skeleton structure of Beta molecular sieve; in 1988, Newsam and Higgins et al. used the construction model and simulated powder diffraction to determine the stacking fault structure of Beta molecular sieve for the first time. Beta molecular sieve has a twelve-membered ring cross-channel structure. The pore size of the twelve-membered ring parallel to the (001) crystal plane is 0.57-0.75nm, and the pore size of the twelve-membered ring parallel to the (100) crystal plane is 0.56-0.65nm. Due to the unique pore structure, high acidity and good hydrothermal stability of Beta molecular sieve, its industrial application prospects are broad and it has been successfully used in petrochemical fields such as isomerization, catalytic cracking and alkylation of aromatics. However, due to the shape-selective effect of the molecular sieve, when the kinetic size of the reactant molecules exceeds the pore size of the microporous molecular sieve, the reactant molecules cannot diffuse into the interior of the molecular sieve, affecting the product distribution.

[0003] In order to overcome the weakness of small pore size of microporous materials, catalytic materials rich in mesopores have received increasing attention.

[0004] CN1769169 discloses a preparation method of a Beta molecular sieve with a multi-level pore structure, which mainly includes the following steps: directly treating the molecular sieve with low-temperature nucleation and high-temperature crystallization with ammonium salt, filtering and drying, and then performing three-stage temperature-controlled roasting and demolding, and then performing acid treatment under mild conditions and pressurized hydrothermal treatment. The obtained Beta molecular sieve has a silicon-aluminum ratio of 80-120 and has three pore size distributions of 0.1-1.7nm, 1.7-6.0nm and 10-90.0nm, thereby improving the surface utilization of the Beta molecular sieve.

[0005] CN102826564 discloses a method for preparing a Beta molecular sieve with a multi-level pore structure, which uses tetraethyl orthosilicate as a silicon source, sodium metaaluminate as an aluminum source, and a hexaammonium-based cationic quaternary ammonium salt surfactant as a template to prepare a Beta multi-level pore molecular sieve containing mesopores by a hydrothermal synthesis method under alkaline conditions.

[0006] CN103964458 discloses a Beta molecular sieve with a high silicon-aluminum ratio and a multi-level pore and a preparation method thereof. The pores of the molecular sieve have pore sizes below 2 nm, 5-11 nm and above 50 nm, and the micropore volume is 0.19 cm 3 / g or more, the total volume of mesopores and macropores is 0.35cm 3 / g or more, its silicon-aluminum ratio is more than 90, and its specific surface area is 400m 2 / g or more. The preparation method comprises the following steps: subjecting the raw material Beta zeolite to a first acid treatment; subjecting the Beta zeolite after the first acid treatment to a first calcination; subjecting the Beta zeolite after the first calcination to a second acid treatment to obtain the Beta zeolite with high silicon-aluminum ratio and multi-level pores.

[0007] The above-mentioned methods for preparing multi-level pore Beta all have problems such as the use of organic ammonium salt wastewater that is difficult to treat, a long preparation process, and molecular sieve mesoporous dispersion. Summary of the invention

[0008] The purpose of the present disclosure is to provide a Beta molecular sieve and a preparation method thereof.

[0009] In order to achieve the above object, the first aspect of the present disclosure provides a Beta molecular sieve, in which the volume of pores with a pore diameter of 2-10 nm accounts for 65-90% of the total pore volume.

[0010] Optionally, in the Beta molecular sieve, the volume ratio of pores with 2 nm≤a≤4 nm to pores with 4 nm<a≤10 nm is 0.01-0.75, preferably 0.08-0.70, where a is the pore diameter.

[0011] Optionally, the Beta molecular sieve has a crystal size of 0.3-2 μm, preferably 0.35-1.5 μm.

[0012] Optionally, the mesoporous specific surface area of ​​the Beta molecular sieve is 300-550m 2 / g.

[0013] A second aspect of the present disclosure provides a method for preparing Beta molecular sieve, the method comprising the following steps:

[0014] a. contacting a phosphorus source, a template, an aluminum source, water, and an optional first alkali source to obtain a first mixture;

[0015] b. contacting a silicon source with the first mixture to obtain a second mixture;

[0016] c. subjecting the second mixture to a hydrothermal crystallization treatment, and subjecting the hydrothermal crystallization product to a heat treatment to obtain a heat-treated product;

[0017] d. subjecting the heat-treated product to alkali treatment.

[0018] Optionally, the phosphorus source includes one or more of diethyl phosphine oxide, triethyl phosphine oxide, dibutyl phosphine oxide, tributyl phosphine oxide, diphenyl phosphine oxide and triphenyl phosphine oxide;

[0019] The first alkali source includes one or more of sodium hydroxide, sodium oxide, potassium hydroxide and potassium oxide;

[0020] The template agent includes one or more of tetraethylammonium hydroxide, n-butylamine, tetraethylammonium bromide and tetraethylammonium chloride;

[0021] The aluminum source includes one or more of sodium aluminate, SB powder, aluminum alcoholate, aluminum oxide, aluminum hydroxide, aluminum sulfate and gibbsite;

[0022] The silicon source includes one or more of silica sol, silicon dioxide, white carbon black, silicate and solid silica gel.

[0023] Optionally, the template is Al 2 O 3 Aluminum in terms of SiO 2 The molar ratio of silicon element calculated as silicon, water and alkali metal element calculated as metal oxide is (0.01-0.20): (0.01-0.066): 1: (5-30): (0-0.1), preferably (0.04-0.19): (0.01-0.066): 1: (6-25): (0.01-0.1);

[0024] P 2 O 5 Phosphorus in terms of Al 2 O 3 The molar ratio of the aluminum element is (0.4-1.5):1, preferably (0.6-1.0):1.

[0025] Optionally, in step c, the conditions of the hydrothermal crystallization treatment include: time of 18-168h and temperature of 140-200°C.

[0026] Optionally, in step c, the heat treatment method includes calcination, and the heat treatment conditions include: time of 0.5-8h and temperature of 400-800°C.

[0027] Optionally, step d comprises: contacting the heat-treated product and a second alkali source with water to perform alkali treatment;

[0028] The weight ratio of the heat-treated product, the second alkali source and the water is 1:(0.04-0.25):(5-10), preferably 1:(0.10-0.20):(6-9);

[0029] The second alkali source includes one or more of sodium hydroxide, potassium hydroxide, cesium hydroxide, ammonia water, sodium carbonate, potassium carbonate, potassium bicarbonate and sodium bicarbonate;

[0030] The conditions of the alkali treatment include: time of 0.5-2h and temperature of 50-80°C.

[0031] The third aspect of the present disclosure provides a Beta molecular sieve prepared by the method described in the second aspect of the present disclosure.

[0032] Through the above technical scheme, the present invention prepares a multi-level pore Beta molecular sieve by adding a phosphorus source during the in-situ synthesis of Beta molecular sieve and subsequent alkali treatment. The method disclosed in the present invention has simple steps, and the prepared Beta molecular sieve has a larger grain size and a more concentrated pore distribution.

[0033] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0035] Figure 1 It is the X-ray diffraction spectrum of Beta molecular sieve A prepared in Example 1 of the present disclosure.

[0036] Figure 2 This is a transmission electron microscope (TEM) image of Beta molecular sieve A prepared in Example 1 of the present disclosure.

[0037] Figure 3 It is a pore size distribution curve diagram of Beta molecular sieve A prepared in Example 1 of the present disclosure.

[0038] Figure 4 It is a transmission electron microscope (TEM) image of Beta molecular sieve D1 prepared in Comparative Example 1 of the present disclosure.

[0039] Figure 5 It is a pore size distribution curve diagram of Beta molecular sieve D1 prepared in Comparative Example 1 of the present disclosure. DETAILED DESCRIPTION

[0040] The specific implementation of the present disclosure is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the present disclosure, and is not used to limit the present disclosure.

[0041] A first aspect of the present disclosure provides a Beta molecular sieve, in which the volume of pores with a pore diameter of 2-10 nm accounts for 65-90% of the total pore volume.

[0042] In the present disclosure, pore parameters are tested by nitrogen physical adsorption.

[0043] According to one embodiment of the present disclosure, in the Beta molecular sieve, the mesopores are concentrated in the range of 2-10 nm, specifically, the volume of pores with a pore size of 2-10 nm accounts for more than 99% of the total volume of the mesopores, preferably 100%.

[0044] According to one embodiment of the present disclosure, in the Beta molecular sieve, the volume ratio of pores with 2nm≤a≤4nm to pores with 4nm<a≤10nm is 0.01-0.75, preferably 0.08-0.70, where a is the pore diameter.

[0045] According to one embodiment of the present disclosure, the crystal size of the molecular sieve is 0.3-2 μm, preferably 0.35-1.5 μm.

[0046] According to one embodiment of the present disclosure, the mesoporous specific surface area of ​​the Beta molecular sieve is 300-550m 2 / g, preferably 315-500m 2 / g.

[0047] A second aspect of the present disclosure provides a method for preparing Beta molecular sieve, the method comprising the following steps:

[0048] a. contacting a phosphorus source, a template, an aluminum source, water, and an optional first alkali source to obtain a first mixture;

[0049] b. contacting a silicon source with the first mixture to obtain a second mixture;

[0050] c. subjecting the second mixture to a hydrothermal crystallization treatment, and subjecting the hydrothermal crystallization product to a heat treatment to obtain a heat-treated product;

[0051] d. subjecting the heat-treated product to alkali treatment.

[0052] The present invention prepares a Beta molecular sieve with a larger grain size by adding a phosphorus source during the in-situ synthesis process, and adjusts the pore structure parameters of the molecular sieve through the final alkali treatment step to obtain a Beta molecular sieve with a more concentrated pore distribution and more mesopores.

[0053] According to one embodiment of the present disclosure, the phosphorus source includes phosphorus-containing organic matter, for example, it may include one or more of diethyl phosphine oxide, triethyl phosphine oxide, dibutyl phosphine oxide, tributyl phosphine oxide, diphenyl phosphine oxide and triphenyl phosphine oxide. When the phosphorus source includes more than two substances, there is no specific limitation on their ratio.

[0054] According to one embodiment of the present disclosure, the type of template is conventional in the art, for example, it may include one or more of tetraethylammonium hydroxide, n-butylamine, tetraethylammonium bromide and tetraethylammonium chloride. When the template includes more than two substances, there is no specific restriction on their ratio; the template can be added in the form of an aqueous solution, for example, the present disclosure does not specifically limit the concentration of the aqueous solution, for example, the concentration of the tetrabutylammonium hydroxide aqueous solution can be 15-30% by weight.

[0055] According to an embodiment of the present disclosure, the silicon source includes one or more of silica sol, silicon dioxide, white carbon black, silicate and solid silica gel. When the silicon source includes two or more substances, there is no specific limitation on their ratio.

[0056] According to one embodiment of the present disclosure, the first alkali source includes one or more of sodium hydroxide, sodium oxide, potassium hydroxide and potassium oxide. When the first alkali source includes two or more substances, there is no specific limitation on their ratio.

[0057] According to one embodiment of the present disclosure, the template is Al 2 O 3 Aluminum in terms of SiO 2 The molar ratio of silicon element calculated as water to alkali metal element calculated as metal oxide is (0.01-0.20): (0.01-0.066): 1: (5-30): (0-0.1), preferably (0.04-0.19): (0.01-0.066): 1: (6-25): (0.01-0.1); wherein the molar amount of "alkali metal element" includes the molar amount of alkali metal element in all raw materials, for example, NaOH is used as the first alkali source, sodium aluminate is used as the aluminum source, tetraethylammonium hydroxide is used as the template, and solid silica gel is used as the silicon source, the molar amount of alkali metal element includes the total molar amount of sodium element in sodium aluminate and NaOH, and Na 2 O plan.

[0058] According to one embodiment of the present disclosure, 2 O 5 Phosphorus in terms of Al 2 O 3 The molar ratio of the aluminum element is (0.4-1.5):1, preferably (0.6-1.0):1.

[0059] According to one embodiment of the present disclosure, the hydrothermal crystallization treatment can be carried out in a hydrothermal kettle, and the method and conditions are conventional in the art. For example, the conditions of the hydrothermal crystallization treatment include: a time of 18-168h and a temperature of 140-200°C.

[0060] According to one embodiment of the present disclosure, the heat treatment method includes roasting, and the heat treatment conditions include: time is 0.5-8h, temperature is 400-800°C, and the heat treatment can be carried out in an air atmosphere or an oxygen atmosphere, wherein the definitions of air atmosphere and oxygen atmosphere are conventional in the art.

[0061] According to one embodiment of the present disclosure, step a comprises: mixing a phosphorus source, water and an alkali source under stirring for 0.1-2 hours, and then mixing the obtained mixture, a template and an aluminum source for 0.5-2 hours.

[0062] According to one embodiment of the present disclosure, step b comprises: contacting the silicon source with the first mixture under stirring for 0.5-2 hours to obtain a second mixture.

[0063] According to one embodiment of the present disclosure, the method further comprises: drying the solid product obtained by the hydrothermal crystallization treatment to obtain the hydrothermal crystallization product, and the method and conditions for the drying treatment are conventional in the art.

[0064] According to one embodiment of the present disclosure, the method further includes: performing solid-liquid separation on the mixture obtained by hydrothermal crystallization treatment, and washing the obtained solid with water; the solid-liquid separation method may be, for example, filtration, and the water washing method is conventional in the art; further, the liquid containing the template obtained by solid-liquid separation can be used in step b to further reduce costs, and the amount of the liquid containing the template is calculated based on water.

[0065] According to one embodiment of the present disclosure, step d includes: contacting the heat-treated product and a second alkali source with water for alkali treatment; specifically, it may include: slurrying the heat-treated product with water to obtain a slurry with a solid content of 10-20 weight %, and then contacting the slurry with a second alkali source for alkali treatment.

[0066] According to one embodiment of the present disclosure, the weight ratio of the heat-treated product, the second alkali source and water is 1:(0.04-0.25):(5-10), preferably 1:(0.10-0.20):(6-9). The above ratio can obtain a Beta molecular sieve with a more concentrated pore distribution.

[0067] According to one embodiment of the present disclosure, the second alkali source includes one or more of ammonia water, alkaline hydroxides, alkaline carbonates and alkaline bicarbonates; specifically, it may include one or more of sodium hydroxide, potassium hydroxide, cesium hydroxide, ammonia water, sodium carbonate, potassium carbonate, potassium bicarbonate and sodium bicarbonate. When the second alkali source includes more than two substances, there is no specific limitation on their ratio, wherein the concentration of ammonia water is conventional in the art.

[0068] According to one embodiment of the present disclosure, the conditions for the alkali treatment include: a time of 0.5-2h and a temperature of 50-80°C.

[0069] According to one embodiment of the present disclosure, the method further comprises: separating the solid-liquid mixture obtained by the alkali treatment, and washing the obtained solid until the washing liquid is neutral (test value at 25° C. under standard atmospheric pressure).

[0070] According to one embodiment of the present disclosure, the method further comprises: exchanging the alkali-treated product with ammonium, and drying the obtained solid; the steps and conditions of the ammonium exchange and drying are conventional in the art and will not be elaborated herein.

[0071] The third aspect of the present disclosure provides a Beta molecular sieve prepared by the method described in the second aspect of the present disclosure.

[0072] The Beta molecular sieve described in the third aspect of the present disclosure has the same characteristics as the Beta molecular sieve described in the first aspect of the present disclosure, which will not be described in detail here.

[0073] The present invention will be further described below by way of examples, but the contents of the present invention are not limited thereby.

[0074] Unless otherwise specified, the instruments and reagents used in the embodiments of the present invention are commonly used by those skilled in the art.

[0075] The Beta molecular sieve synthesized by the method of Example 1 in USP 3,308,069 was used as a standard sample, and its crystallinity was determined to be 100%.

[0076] The X-ray diffraction spectra were measured on a Rigaku TTR-3 powder X-ray diffractometer with the following instrument parameters: copper target (tube voltage 40 kV, tube current 250 mA), scintillation counter, step width 0.02°, and scanning rate 0.4° / min.

[0077] The crystal size of the molecular sieve was characterized by transmission electron microscopy (TEM) produced by FEI Company.

[0078] The method for determining the molecular sieve pore structure is as follows:

[0079] The nitrogen adsorption was measured using an AS-6 static nitrogen adsorption instrument produced by Quantachrome Instruments.

[0080] Instrument parameters: The sample was placed in the sample handling system and vacuumed to 1.33×10 -2 Pa, keep the temperature and pressure for 4 hours, and purify the sample. Test the purified sample at different pressure ratios P / P at a liquid nitrogen temperature of -196°C. 0 The adsorption and desorption of nitrogen under the conditions were obtained. 2 Adsorption-desorption isotherms.

[0081] Then the two-parameter BET formula was used to calculate the total specific surface area and the mesopore specific surface area, and the specific pressure P / P was taken. 0 The adsorption amount below =0.98 is the total pore volume of the sample. The pore size distribution of the mesoporous part is calculated using the BJH formula, and the pore volume is calculated using the integration method.

[0082] Example 1

[0083] Beta molecular sieve A was prepared by the following steps:

[0084] 24.60 g of diphenylphosphine oxide and 6.96 g of NaOH were added to 280.59 g of deionized water, and the mixture was stirred for 0.5 h. 145.69 g of tetraethylammonium hydroxide solution (concentration: 25 wt%) and 12.52 g of sodium aluminate were added to the solution and stirred for 0.5 h to obtain a first mixture. 200 g of solid silica gel (SiO 2 The content is 77.4 wt %), stirred and dispersed at room temperature for 1 hour, the obtained second mixture was transferred to a hydrothermal kettle, hydrothermally crystallized at 160°C for 60 hours, the hydrothermally crystallized product was dried at 120°C for 12 hours, and then calcined at 600°C for 2 hours. The heat-treated product was slurried with water to obtain a molecular sieve slurry with a solid content of 10 wt %, 25 g of NaOH (purity 96 wt %) was added, the temperature was raised to 65°C and stirred at a constant temperature for 1 hour, the sample was filtered and washed after the reaction until the washing liquid was neutral, and phosphorus-containing Beta molecular sieve A was obtained. The parameters of molecular sieve A are listed in Table 1.

[0085] Tetraethylammonium hydroxide, Al 2 O 3 Aluminum in terms of SiO 2 Silicon, water and Na 2 The molar ratio of NaOH in O is 0.096:0.0295:1:8.39:0.063;

[0086] P 2 O 5 Phosphorus in terms of Al 2 O 3The molar ratio of aluminum element is 0.797:1;

[0087] The weight ratio of the heat-treated product, NaOH and water is 1:0.13:9.

[0088] The XRD test results of molecular sieve A are as follows: Figure 1 As shown, according to Figure 1 It can be seen that molecular sieve A is Beta molecular sieve.

[0089] The TEM test results of molecular sieve A are as follows: Figure 2 shown.

[0090] The pore size distribution test of molecular sieve A was carried out, and the results were as follows: Figure 3 shown.

[0091] Example 2

[0092] Beta molecular sieve B was prepared by the following steps:

[0093] 6.04 g of diethylphosphine oxide and 6.29 g of NaOH were added to 600 g of deionized water, and the mixture was stirred for 0.25 h. 238.24 g of tetraethylammonium hydroxide solution (concentration of 25 wt%) and 10.82 g of SB powder (alumina content of 67%) were added to the solution and stirred for 0.5 h to obtain a first mixture. 156 g of white carbon black (SiO 2 The obtained second mixture was transferred to a hydrothermal reactor, and hydrothermally crystallized at 140°C for 100h. The hydrothermally crystallized product was dried at 120°C for 12h, and then calcined at 650°C for 3h in an air atmosphere. The heat-treated product was slurried with water to obtain a molecular sieve slurry with a solid content of 20% by weight, 45.88g of KOH (purity 85% by weight) was added, and the temperature was raised to 50°C and stirred at a constant temperature for 2h. After the reaction, the sample was filtered and washed until the washing liquid was neutral to obtain phosphorus-containing Beta molecular sieve B. The parameters of molecular sieve B are listed in Table 1.

[0094] Tetraethylammonium hydroxide, Al 2 O 3 Aluminum in terms of SiO 2 Silicon, water and Na 2 The molar ratio of sodium element in terms of O is 0.157:0.0276:1:18:0.031;

[0095] P 2 O 5 Phosphorus in terms of Al 2 O 3 The molar ratio of aluminum element is 0.4:1;

[0096] The weight ratio of the heat-treated product, KOH and water is 1:0.24:4.

[0097] XRD test on molecular sieve B shows that it is Beta molecular sieve.

[0098] Example 3

[0099] Beta molecular sieve C was prepared by the following steps:

[0100] 6.31 g of triethylphosphine oxide and 0.28 g of NaOH were added to 90 g of deionized water and stirred for 1 h. 20.29 g of tetraethylammonium hydroxide solution (concentration of 25 wt%) and 2.62 g of SB powder (alumina content of 67%) were added to the solution and stirred for 0.5 h to obtain a first mixture. 69 g of alkaline silica sol (SiO 2 The obtained second mixture was transferred to a hydrothermal reactor, and hydrothermally crystallized at 190°C for 72h. The hydrothermally crystallized product was dried at 120°C for 12h, and then calcined at 500°C for 6h in an air atmosphere. The heat-treated product was slurried with water to obtain a molecular sieve slurry with a solid content of 13% by weight, 1.88g of CsOH (purity 95% by weight) was added, and the temperature was raised to 80°C and stirred at a constant temperature for 0.5h. After the reaction, the sample was filtered and washed until the washing liquid was neutral to obtain phosphorus-containing Beta molecular sieve C. The parameters of molecular sieve C are listed in Table 1.

[0101] Tetraethylammonium hydroxide, Al 2 O 3 Aluminum in terms of SiO 2 Silicon, water and Na 2 The molar ratio of sodium element in O is 0.1:0.05:1:24.7:0.01;

[0102] P 2 O 5 Phosphorus in terms of Al 2 O 3 The molar ratio of aluminum element is 1.37:1;

[0103] The weight ratio of the heat-treated product, CsOH and water is 1:0.08:6.7.

[0104] XRD test on molecular sieve C shows that it is Beta molecular sieve.

[0105] Example 4

[0106] Beta molecular sieve D was prepared by the following steps:

[0107] 24.26 g of dibutylphosphine oxide and 7.06 g of KOH were added to 390.74 g of deionized water, and the mixture was stirred for 0.25 h. 39.8 g of tetraethylammonium bromide and 11.48 g of SB (alumina content 67%) were added to the solution and stirred for 1.5 h to obtain a first mixture. 150 g of solid silica gel (SiO 2 The obtained second mixture was transferred to a hydrothermal reactor, and hydrothermally crystallized at 170°C for 60h. The hydrothermally crystallized product was dried at 120°C for 12h, and then calcined at 450°C for 8h in an air atmosphere. The heat-treated product was slurried with water to obtain a molecular sieve slurry with a solid content of 13% by weight, 25g of NaOH (purity 95% by weight) was added, and the temperature was raised to 60°C and stirred at a constant temperature for 0.5h. After the reaction, the sample was filtered and washed until the washing liquid was neutral to obtain phosphorus-containing Beta molecular sieve D. The parameters of molecular sieve D are listed in Table 1.

[0108] Tetraethylammonium bromide, Al 2 O 3 Aluminum in terms of SiO 2 The molar ratio of silicon element, water and alkali metal element calculated as alkali metal oxide is 0.098:0.039:1:11:0.033;

[0109] P 2 O 5 Phosphorus in terms of Al 2 O 3 The molar ratio of aluminum element is 1:1;

[0110] The weight ratio of the heat-treated product, NaOH and water is 1:0.19:6.7.

[0111] XRD test on molecular sieve D shows that it is Beta molecular sieve.

[0112] Example 5

[0113] Beta molecular sieve E was prepared by the steps of Example 1, except that the weight ratio of the heat-treated product, NaOH and water was 1:0.25:8.

[0114] XRD test on molecular sieve E shows that it is Beta molecular sieve.

[0115] Comparative Example 1

[0116] Beta molecular sieve D1 was prepared by the following steps:

[0117] 6.96 g of NaOH was added to 280.59 g of deionized water, and the mixture was stirred for 0.5 h. 145.69 g of tetraethylammonium hydroxide solution (concentration: 25 wt%) and 12.52 g of sodium aluminate were added to the solution and stirred for 0.5 h to obtain a first mixture. 200 g of solid silica gel (SiO 2 The obtained second mixture was transferred to a hydrothermal reactor, crystallized at 160°C for 60h, dried at 120°C for 12h, and then calcined at 600°C for 6h in an air atmosphere. The heat-treated product was slurried with water to obtain a molecular sieve slurry with a solid content of 10% by weight, 25g of NaOH (purity 96% by weight) was added, the temperature was raised to 65°C and stirred at a constant temperature for 1h, and the sample was filtered and washed after the reaction until the washing liquid was neutral to obtain Beta molecular sieve D1. The parameters of molecular sieve D1 are listed in Table 1.

[0118] XRD test on molecular sieve D1 shows that it is Beta molecular sieve.

[0119] The TEM test results of molecular sieve D1 are as follows: Figure 4 shown.

[0120] The pore size distribution test of molecular sieve D1 was carried out, and the results were as follows: Figure 5 shown.

[0121] Table 1

[0122] serial number A / ％ B Grain size / μm <![CDATA[Mesoporous specific surface area / m 2 / g]]> Example 1 A 67 0.69 0.36 319 Example 2 B 86 0.01 0.30 410 Example 3 C 65 0.75 0.31 300 Example 4 D 83 0.11 0.60 451 Example 5 E 85 0.07 0.36 520 Comparative Example 1 D1 3.15 - 0.10 159

[0123] In Table 1, A represents: the proportion of the volume of pores with a pore size of 2-10 nm to the total pore volume in the phosphorus-containing Beta molecular sieve; B represents: the volume ratio of pores with a pore size of 2 nm ≤ a ≤ 4 nm to pores with a pore size of 4 nm < a ≤ 10 nm.

[0124] According to the above data, it can be seen that the phosphorus-containing Beta molecular sieve prepared by the method disclosed in the present invention has a larger grain size, a more concentrated mesopore distribution and a larger mesopore specific surface area.

[0125] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings; however, the present disclosure is not limited to the specific details in the above embodiments. Within the technical concept of the present disclosure, a variety of simple modifications can be made to the technical solution of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0126] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0127] In addition, various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A Beta molecular sieve, characterized in that: In the Beta molecular sieve, the volume of pores with a pore diameter of 2-10 nm accounts for 65-90% of the total pore volume.

2. The Beta molecular sieve according to claim 1, wherein In the Beta molecular sieve, the volume ratio of pores with 2nm≤a≤4nm to pores with 4nm<a≤10nm is 0.01-0.75, preferably 0.08-0.70, where a is the pore diameter.

3. The Beta molecular sieve according to claim 1, wherein The crystal size of the Beta molecular sieve is 0.3-2 μm, preferably 0.35-1.5 μm.

4. The Beta molecular sieve according to claim 1, wherein The mesoporous specific surface area of ​​the Beta molecular sieve is 300-550m 2 / g.

5. A method for preparing Beta molecular sieve, characterized in that: The method comprises the following steps: a. contacting a phosphorus source, a template, an aluminum source, water, and an optional first alkali source to obtain a first mixture; b. contacting a silicon source with the first mixture to obtain a second mixture; c. subjecting the second mixture to a hydrothermal crystallization treatment, and subjecting the hydrothermal crystallization product to a heat treatment to obtain a heat-treated product; d. subjecting the heat-treated product to alkali treatment.

6. The method according to claim 5, wherein: The phosphorus source includes one or more of diethyl phosphine oxide, triethyl phosphine oxide, dibutyl phosphine oxide, tributyl phosphine oxide, diphenyl phosphine oxide and triphenyl phosphine oxide; The first alkali source includes one or more of sodium hydroxide, sodium oxide, potassium hydroxide and potassium oxide; The template agent includes one or more of tetraethylammonium hydroxide, n-butylamine, tetraethylammonium bromide and tetraethylammonium chloride; The aluminum source includes one or more of sodium aluminate, SB powder, aluminum alcoholate, aluminum oxide, aluminum hydroxide, aluminum sulfate and gibbsite; The silicon source includes one or more of silica sol, silicon dioxide, white carbon black, silicate and solid silica gel.

7. The method according to claim 5, wherein: The molar ratio of the template, the aluminum element calculated as Al2O3, the silicon element calculated as SiO2, the water and the alkali metal element calculated as metal oxide is (0.01-0.20): (0.01-0.066): 1: (5-30): (0-0.1), preferably (0.04-0.19): (0.01-0.066): 1: (6-25): (0.01-0.1); The molar ratio of phosphorus element calculated as P2O5 to aluminum element calculated as Al2O3 is (0.4-1.5):1, preferably (0.6-1.0):

1.

8. The method according to claim 5, wherein: In step c, the conditions of the hydrothermal crystallization treatment include: time of 18-168h and temperature of 140-200°C.

9. The method according to claim 5, wherein: In step c, the heat treatment method includes roasting, and the heat treatment conditions include: time is 0.5-8h, and temperature is 400-800°C.

10. The method according to claim 5, wherein: Step d comprises: contacting the heat-treated product, a second alkali source and water to perform alkali treatment; The weight ratio of the heat-treated product, the second alkali source and the water is 1:(0.04-0.25):(5-10), preferably 1:(0.10-0.20):(6-9); The second alkali source includes one or more of sodium hydroxide, potassium hydroxide, cesium hydroxide, ammonia water, sodium carbonate, potassium carbonate, potassium bicarbonate and sodium bicarbonate; The conditions of the alkali treatment include: time of 0.5-2h and temperature of 50-80°C.

11. Beta molecular sieve prepared by the method according to any one of claims 5 to 10.

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