A method for synthesizing a phosphorus-containing zsm-5 molecular sieve

Abstract

The application discloses a synthesis method of a phosphorus-containing ZSM-5 molecular sieve, which comprises the following steps: mixing a silicon source, an aluminum source, a template agent, alkali, water and a small amount of a phosphorus source in steps, moving into a stirring kettle for dynamic crystallization to obtain a crystallization intermediate product, further mixing slurry containing the crystallization intermediate product with a phosphorus-containing solution, adjusting the pH of the solution and performing hydrothermal treatment, then evaporating the solution to obtain a dry gel, crystallizing the dry gel under ammonia steam auxiliary conditions, and finally performing washing, filtering, drying and calcining in sequence to obtain the phosphorus-containing ZSM-5 molecular sieve. The method can efficiently introduce the phosphorus element into the ZSM-5 molecular sieve, inhibit the removal of framework aluminum, improve the acid properties, thereby improving the hydrothermal stability and catalytic reaction performance of the molecular sieve, and has important application value in the field of light hydrocarbon catalytic cracking for preparing low-carbon olefins and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of molecular sieves, in particular to a synthesis method of phosphorus-containing ZSM-5 molecular sieves. BACKGROUND

[0002] The framework of ZSM-5 molecular sieves is a typical MFI structure, which is composed of parallel straight channels and sinusoidal channels, and the two kinds of channels intersect with each other to form a three-dimensional channel system. Due to its unique channel structure, ZSM-5 molecular sieves have very wide application in the field of catalysis, and can be used as a main catalytic material in the fields of diesel hydrode-waxing, catalytic cracking / cracking to produce olefins, etc. The phosphorus element of phosphorus-modified ZSM-5 molecular sieves can combine with the aluminum element in the framework of the molecular sieve, improve the stability of aluminum in the framework, and inhibit the hydrothermal dealumination of the molecular sieve at high temperature, so as to achieve the purpose of enhancing the hydrothermal stability of the molecular sieve and adjusting the acid properties of the molecular sieve, and then make it obtain higher selectivity and yield of target products in catalytic cracking / cracking reactions.

[0003] CN113526519B discloses a preparation method of a phosphorus-containing hierarchical pore ZSM-5 molecular sieve, which is characterized in that the preparation method adopts an impregnation method to mix and contact a phosphorus-containing compound solution with a hydrogen-type hierarchical pore ZSM-5 molecular sieve at a certain temperature, and after drying treatment, a phosphorus-containing hierarchical pore ZSM-5 molecular sieve is obtained by hydrothermal calcination treatment under the external application of pressure and the external addition of water in an atmosphere environment.

[0004] CN105668586B discloses a preparation method of a nano ZSM-5 molecular sieve and a phosphorus-modified ZSM-5 molecular sieve thereof. The raw material transparent sol with a molar composition of (0.01-0.1) : 1 : (0.01-0.6) : (3-20) is prepared by uniformly mixing the required aluminum source, silicon source, template agent and water, and then crystallized at 100℃-175℃ for 24-48 hours. The prepared molecular sieve sol is neutralized by alkali and concentrated by thin film evaporation, and then the nano ZSM-5 molecular sieve raw powder is obtained by rake drying. The phosphorus-modified ZSM-5 molecular sieve raw powder is obtained by adding ammonium dihydrogen phosphate modifier into the molecular sieve raw powder, using salt effect and strong adsorption effect of nano molecular sieve to realize flocculation, and then drying the centrifuged product.

[0005] The above method is a traditional preparation method of phosphorus-containing ZSM-5 molecular sieves, that is, phosphorus modification operation is performed on the basis of ZSM-5 molecular sieve raw powder to obtain phosphorus-containing ZSM-5 molecular sieves, but this method has the problems of poor phosphorus dispersion effect and unobvious improvement of hydrothermal stability of the molecular sieve. SUMMARY

[0006] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method for synthesizing phosphorus-containing ZSM-5 molecular sieves, which can improve the dispersibility of phosphorus, enhance the interaction between phosphorus and skeletal aluminum, and thus improve the hydrothermal stability of ZSM-5 molecular sieves.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for synthesizing phosphorus-containing ZSM-5 molecular sieve includes the following steps;

[0009] (1) After mixing silicon source, water and template agent evenly, stir to form solution A; mix aluminum source, alkaline substance, diammonium hydrogen phosphate and water evenly to form solution B; slowly add solution B and solution A dropwise to obtain mixed solution C. During the mixing process, the pH of mixed solution C is controlled within a certain range; after mixing mixed solution C in a closed container, transfer it to a hydrothermal stirring tank and stir at 150℃~180℃ for 2~12h to precrystallize and obtain a slurry containing precrystallized intermediate products; the purpose of setting such parameters is to enhance the interaction between aluminum and phosphorus by using aluminum and phosphorus pretreatment; compared with the traditional ZSM-5 crystallization (crystallization temperature ≥180℃, crystallization time ≥24h), the low temperature and short time dynamic crystallization method is used to obtain small ZSM-5 crystals while preventing excessive growth of crystals, creating favorable conditions for the next step of fully dispersed addition of phosphorus.

[0010] (2) Add a certain amount of diammonium hydrogen phosphate solution to the slurry containing the pre-crystallized intermediate product in step (1), adjust the pH of the mixed solution system, and stir in a closed manner for 2 to 6 hours at 40 to 70°C until the mixture is evaporated to dryness under open conditions to obtain a gel; after drying the obtained gel, grind it thoroughly and crystallize it at 180°C to 230°C under the self-generated pressure of ammonia water vapor for 12 to 48 hours to obtain a crystallized product; (The purpose of setting such parameters is to ensure that after the ZSM-5 small crystals are fully mixed with the phosphorus source, the ammonia water vapor is used to help ensure that the ZSM-5 molecular sieve crystals are further crystallized and grown, and the dry crystallization method can be used to inhibit the formation of phosphorus-oxygen tetrahedral molecular sieve framework structure by phosphorus element.)

[0011] (3) After washing, filtering, drying and calcining the crystallization product of step (2), phosphorus-containing ZSM-5 molecular sieve can be obtained.

[0012] Preferably, in step (1), the molar ratio of silicon source (calculated as SiO2), template agent, and water is SiO2:template agent:H2O = (30-80):(20-60):(400-650); the molar ratio of aluminum source (calculated as Al2O3), alkaline substance, and water is Al2O3:alkaline substance:H2O = 1:(0.1-3.0):(15-75); and the molar ratio of silicon source to aluminum source is SiO2:Al2O3 = (30-80):1. (The purpose of such ratios is to define the application of this technology to the preparation of phosphorus-containing ZSM-5 molecular sieves with a silicon-to-aluminum ratio in the range of 30-80, and to specify its acidity / alkalinity, template agent dosage, and water usage.)

[0013] Preferably, the template agent in step (1) is at least one of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrapropylammonium bromide, and ammonia.

[0014] Preferably, the silicon source in step (1) is at least one of tetraethyl orthosilicate, silica sol, and water glass;

[0015] Preferably, the aluminum source in step (1) is at least one of sodium aluminate, aluminum sulfate, and aluminum isopropoxide;

[0016] Preferably, the alkaline substance in step (1) is at least one of sodium hydroxide, potassium hydroxide and ammonia.

[0017] Preferably, in step (1), the dripping rates of solution B and solution A are adjusted to ensure that the pH of the mixed solution C system is 10-12 during the mixing process;

[0018] Preferably, the total amount of phosphorus used in steps (1) and (2) is proportional to the mass ratio of silicon dioxide in the silicon source, P:SiO2 = (0.01~0.05):1, wherein the ratio of phosphorus used in steps (1) and (2) is 1:(4~9); and the volume ratio of the slurry containing the crystallization intermediate product to the diammonium hydrogen phosphate solution is (10~50):1.

[0019] Preferably, in step (2), the mass ratio of 25% ammonia water used for crystallization to the dry gel after gel drying is (0.2~0.6):1; (The purpose of setting such parameters is: by heating the crystallization kettle, the ammonia water evaporates into alkaline vapor, and the alkaline vapor atmosphere is conducive to the crystallization of the dry gel, thereby promoting the growth of dry gel crystals.)

[0020] The phosphorus-containing ZSM-5 molecular sieve is polymerized from 100nm to 200nm nanoscale particles.

[0021] The beneficial effects of this invention are:

[0022] (1) This invention is based on a two-stage crystallization method, which introduces phosphorus element into the ZSM-5 molecular sieve preparation and synthesis process in stages, realizing the one-step synthesis of phosphorus-containing ZSM-5 molecular sieves. This solves the problem of poor phosphorus modification effect in the traditional phosphorus-containing ZSM-5 molecular sieves after molecular sieve synthesis. The phosphorus-containing ZSM-5 molecular sieve obtained by this invention has high relative crystallinity, does not produce impurity crystals, is polymerized from 100-200nm crystal grains, and has highly dispersed phosphorus element. The molecular sieve has abundant Brønsted acid sites, high specific surface area, and good high-temperature hydrothermal stability.

[0023] (2) When the ZSM-5 molecular sieve prepared by the method of the present invention is used for the catalytic cracking of light hydrocarbons to produce low-carbon olefins, the conversion rate of light hydrocarbons is high, the selectivity and yield of dienes are significantly improved, and the catalyst’s resistance to carbon deposition is significantly enhanced, thereby improving the reaction activity, diene yield and resistance to deactivation of light hydrocarbons.

[0024] (3) The method provided by the present invention is simple to operate, has good repeatability, uses little water in the synthesis process and can be recycled, has good economic benefits and is relatively environmentally friendly. Attached Figure Description

[0025] Figure 1 The images show the SEM spectra of the ZSM-5 zeolite molecular sieves prepared in Example 1 and the comparative example of this invention.

[0026] Figure 2 XRD pattern of ZSM-5 zeolite molecular sieve prepared for Example 1 of this invention.

[0027] Figure 3 The nitrogen adsorption-desorption curve of the ZSM-5 zeolite molecular sieve prepared in Example 1 of this invention. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings.

[0029] Example 1

[0030] (1) Acidic silica sol with a solid content of 30 wt%, water, and tetraethylammonium hydroxide are mixed evenly and stirred at 40°C for 4 hours to form solution A. The molar ratio of silica sol (calculated as SiO2), tetraethylammonium hydroxide, and water is SiO2:tetraethylammonium hydroxide:H2O = 40:30:450. Sodium aluminate, sodium hydroxide, diammonium hydrogen phosphate, and water are mixed evenly to form solution B. The molar ratio of sodium aluminate (calculated as Al2O3), sodium hydroxide, and water is... The molar ratio of Al2O3:sodium hydroxide:H2O is 1:0.5:25, and the molar ratio of silica sol to sodium aluminate is SiO2:Al2O3 = 40:1. Solution B and solution A are added dropwise to obtain mixed solution C. During the mixing process, the pH of mixed solution C is kept at 12. Mixed solution C is stirred in a closed container at 50°C for 4 hours. Then, mixed solution C is transferred to a hydrothermal stirred tank and stirred at 160°C for 6 hours to precrystallize, resulting in a slurry containing precrystallized intermediate products.

[0031] (2) Add diammonium hydrogen phosphate solution to the slurry containing the pre-crystallized intermediate product in step (1), adjust the pH of the mixed solution system to 12, stir in a closed manner at 50°C for 2 hours, and then stir and evaporate to dryness at 85°C to obtain gel; dry the obtained gel and grind it thoroughly, crystallize it at 220°C under the self-generated pressure of ammonia vapor for 36 hours to obtain crystallized product, wherein the total amount of phosphorus used to the mass ratio of silicon dioxide in the silicon source P:SiO2=0.03:1, the mass ratio of 25% ammonia water used to dry gel is 0.6:1, and the ratio of phosphorus used in step (1) to step (2) is 1:9;

[0032] (3) Wash and filter the crystallization product from step (2), dry the obtained filter cake, and calcine it at 550°C for 6 hours to obtain phosphorus-containing ZSM-5 molecular sieve.

[0033] Example 2

[0034] (1) After mixing tetraethyl orthosilicate, water, and n-butylamine evenly, the mixture is stirred at 50°C for 4 hours to form solution A, wherein the molar ratio of tetraethyl orthosilicate (as SiO2), n-butylamine, and water is SiO2:n-butylamine:H2O = 60:60:450; and sodium aluminate, sodium hydroxide, diammonium hydrogen phosphate, and water are mixed evenly to form solution B, wherein the molar ratio of sodium aluminate (as Al2O3), sodium hydroxide, and water is Al2O3: Sodium hydroxide:H2O = 1:0.5:25, the molar ratio of silica sol to sodium aluminate is SiO2:Al2O3 = 60:1; solution B and solution A are added dropwise to obtain mixed solution C, ensuring that the pH of mixed solution C is 11.5 during the mixing process. Mixed solution C is stirred in a closed container at 50℃ for 4 hours, and then mixed solution C is transferred to a hydrothermal stirred tank and stirred at 170℃ for 4 hours to precrystallize, resulting in a slurry containing precrystallized intermediate products.

[0035] (2) Add diammonium hydrogen phosphate solution to the slurry containing the pre-crystallized intermediate product in step (1), adjust the pH of the mixed solution system to 12, stir in a closed manner at 50°C for 2 hours, and then stir and evaporate to dryness at 85°C to obtain gel; dry the obtained gel and grind it thoroughly, crystallize it at 230°C under the self-generated pressure of ammonia vapor for 36 hours to obtain crystallized product, wherein the total amount of phosphorus used to the mass ratio of silicon dioxide in the silicon source P:SiO2=0.03:1, the mass ratio of 25% ammonia water used to dry gel is 0.5:1, and the ratio of phosphorus used in step (1) to step (2) is 1:4;

[0036] (3) Wash and filter the crystallization product from step (2), dry the obtained filter cake, and calcine it at 550°C for 6 hours to obtain phosphorus-containing ZSM-5 molecular sieve.

[0037] Example 3

[0038] (1) Mix 30 wt% acidic silica sol, water, and tetrapropylammonium hydroxide evenly, and stir at 40°C for 4 hours to form solution A. The molar ratio of silica sol (as SiO2), tetrapropylammonium hydroxide, and water is SiO2:tetrapropylammonium hydroxide:H2O = 50:25:500. Mix sodium aluminate, sodium hydroxide, and water evenly to form solution B. The molar ratio of sodium aluminate (as Al2O3), sodium hydroxide, and water is A. L2O3: Sodium hydroxide: H2O = 1:1.0:40, and the molar ratio of silica sol to sodium aluminate is SiO2:Al2O3 = 50:1. Solution B and solution A are added dropwise to obtain mixed solution C. During the mixing process, the pH of mixed solution C is kept at 10. Mixed solution C is stirred in a closed container at 50°C for 4 hours. Then, mixed solution C is transferred to a hydrothermal stirred tank and stirred at 180°C for 6 hours to precrystallize, resulting in a slurry containing precrystallized intermediate products.

[0039] (2) Add diammonium hydrogen phosphate solution to the slurry containing the pre-crystallized intermediate product in step (1), adjust the pH of the mixed solution system to 12, stir in a closed manner at 50°C for 4 hours, and then stir and evaporate to dryness at 90°C to obtain gel; dry the obtained gel and grind it thoroughly, crystallize it at 230°C under the self-generated pressure of ammonia vapor for 48 hours to obtain crystallized product, wherein the total amount of phosphorus used to the mass ratio of silicon dioxide in the silicon source P:SiO2=0.03:1, the mass ratio of 25% ammonia water used to dry gel is 0.4:1, and the ratio of phosphorus used in step (1) to step (2) is 1:6;

[0040] (3) Wash and filter the crystallization product from step (2), dry the obtained filter cake, and calcine it at 550°C for 6 hours to obtain phosphorus-containing ZSM-5 molecular sieve.

[0041] Example 4

[0042] (1) After mixing water glass, water and tetraethylammonium hydroxide evenly, stir at 60°C for 4 hours to form solution A, wherein the molar ratio of water glass, tetraethylammonium hydroxide and water is SiO2:tetraethylammonium hydroxide:H2O=80:50:650; mix aluminum sulfate, sodium hydroxide, diammonium hydrogen phosphate and water evenly to form solution B, wherein the molar ratio of aluminum sulfate, sodium hydroxide and water is Al2O3:sodium hydroxide:H2O=1:2.0:25, and the molar ratio of water glass to aluminum sulfate is SiO2:Al2O3=80:1; add solution B and solution A dropwise to obtain mixed solution C, ensuring that the pH of mixed solution C is 12 during the mixing process. After mixing mixed solution C in a closed container at 50°C for 4 hours, transfer mixed solution C into a hydrothermal stirring tank and stir at 180°C for 12 hours to crystallize, to obtain a slurry containing crystallization intermediate products;

[0043] (2) Add diammonium hydrogen phosphate solution to the slurry containing the pre-crystallized intermediate product in step (1), adjust the pH of the mixed solution system to 12, stir in a closed manner at 50°C for 2 hours, and then stir and evaporate to dryness at 90°C to obtain gel; dry the obtained gel and grind it thoroughly, crystallize it at 220°C under the self-generated pressure of ammonia vapor for 48 hours to obtain crystallized product, wherein the total amount of phosphorus used to the mass ratio of silicon dioxide in the silicon source P:SiO2=0.03:1, the mass ratio of 25% ammonia water used to dry gel is 0.6:1, and the ratio of phosphorus used in step (1) to step (2) is 1:9;

[0044] (3) Wash and filter the crystallization product from step (2), dry the obtained filter cake, and calcine it at 550°C for 6 hours to obtain phosphorus-containing ZSM-5 molecular sieve.

[0045] Comparative Example 1

[0046] (1) Mix 30wt% acidic silica sol, water and tetraethylammonium hydroxide evenly and stir at 40℃ for 4 hours to form solution A, wherein the molar ratio of silica sol, tetraethylammonium hydroxide and water is SiO2:tetraethylammonium hydroxide:H2O=40:30:450; mix sodium aluminate, sodium hydroxide and water evenly to form solution B, wherein the molar ratio of sodium aluminate, sodium hydroxide and water is Al2O3:sodium hydroxide:H2O=1:0.5:25 and the molar ratio of silica sol to sodium aluminate is SiO2:Al2O3=40:1; slowly add solution B dropwise to continuously stirred solution A to obtain mixed solution C. After complete mixing, adjust the pH of the system to 12 using sodium hydroxide. After mixing solution C in a sealed environment at 50℃ for 4 hours, then transfer mixed solution C into a hydrothermal stirring tank and stir at 160℃ for 6 hours to crystallize, to obtain a slurry containing crystallization intermediate products;

[0047] (2) Adjust the pH of the slurry containing the crystallization intermediate product in step (1) to 12, stir it in a closed container at 50°C for 2 hours, and then stir and evaporate it at 85°C to obtain a gel. After drying the gel, grind it thoroughly and crystallize it at 220°C under the self-generated pressure of ammonia vapor for 36 hours to obtain the crystallized product. The mass ratio of 25% ammonia water to dry gel is 0.6:1.

[0048] (3) Wash and filter the crystallization product from step (2), dry the obtained filter cake, and calcine it at 550°C for 6 hours to obtain ZSM-5 molecular sieve.

[0049] (4) After hydrogenating ZSM-5 molecular sieve, H-ZSM-5 molecular sieve is obtained. Diammonium hydrogen phosphate is loaded onto H-ZSM-5 molecular sieve by equal volume impregnation. After standing for 24 hours, it is dried and calcined to obtain phosphorus-containing ZSM-5 molecular sieve. The total amount of phosphorus used is P:SiO2 = 0.03:1 with the mass ratio of silicon dioxide in silicon source.

[0050] Specific implementation results:

[0051] 1. The phosphorus-containing ZSM-5 molecular sieve prepared in Example 1 was subjected to scanning electron microscopy (SEM), and its SEM image is shown below. Figure 1 As shown. By Figure 1 It can be seen that the ZSM-5 molecular sieve prepared in Example 1 is formed by the aggregation and stacking of small crystals with a particle size of 100-200 nm.

[0052] 2. X-ray diffraction analysis was performed on the ZSM-5 molecular sieve prepared in Example 1, and the results are as follows: Figure 2 As shown, the prepared ZSM-5 molecular sieve has typical ZSM-5 molecular sieve characteristic diffraction peaks, good crystallinity, and no obvious impurity peaks.

[0053] 3. Nitrogen adsorption-desorption experiments were conducted on the ZSM-5 molecular sieves of Examples 1-4 and Comparative Example 1 to analyze their pore structure properties. The results are shown in Table 1. The nitrogen adsorption-desorption curve of the ZSM-5 molecular sieve prepared in Example 1 is shown below. Figure 3 As shown in Table 1 and Figure 3 It can be seen that all embodiments have a high specific surface area, which is around 400m². 2 The specific surface area of ​​the phosphorus-containing ZSM-5 molecular sieve obtained by two-step equal-volume impregnation in Comparative Example 1 was slightly lower than that in Example 1. This is because the two-step impregnation process of phosphorus-containing compounds causes partial blockage of the micropores of the molecular sieve, resulting in a certain degree of loss of the pore structure of the molecular sieve.

[0054] Table 1. Pore structure data of ZSM-5 molecular sieve

[0055]

[0056] 4. Table 2 shows that the phosphorus-containing ZSM-5 molecular sieve prepared by this method still has a high degree of crystallinity retention after hydrothermal treatment at 800℃ and 100% steam for 24 hours. Compared with the comparative example, the crystallinity retention of the example is increased by more than 3.9 percentage points.

[0057] Table 2 Effect of hydrothermal treatment on the crystallinity of phosphorus-containing molecular sieves

[0058] Pre-hydrothermal crystallinity (%) Post-hydrothermal crystallinity (%) Crystal form retention (%) Example 1 85.2 68.3 80.2 Example 2 82.4 66.7 80.9 Example 3 86.5 70.9 82.0 Example 4 81.9 68.6 83.8 Comparative Example 1 Comparative Example 2 79.5 61.2 77.0

[0059] 5. Light hydrocarbon catalytic cracking catalysts were prepared using the H-ZSM-5 molecular sieves from Examples 1-4 and Comparative Example 1. These catalysts were applied to light hydrocarbon catalytic cracking reactions. The fixed-bed catalyst bed loading was 15 g, the reactant was stable light hydrocarbons, the feed flow rate was 1.678 ml / min, the reaction temperature was 650 °C, and the space velocity was 4 h⁻¹. -1 The stable conversion rate and the selectivity / yield of diolefins are shown in Table 3.

[0060] Table 3. Catalytic cracking performance data of phosphorus-containing ZSM-5 molecular sieves for light hydrocarbons.

[0061]

[0062] As shown in Table 3, the phosphorus-containing ZSM-5 molecular sieve prepared in this invention exhibits excellent catalytic cracking performance for light hydrocarbons. Compared to Comparative Example 1, the diolefin selectivity of the light hydrocarbon catalytic cracking catalyst prepared in Example 1 is 3.71 percentage points higher. The main reason for this is that the phosphorus element in Example 1 effectively modulates the acidity of the ZSM-5 molecular sieve, thereby shifting the light hydrocarbon catalytic cracking reaction towards a direction favorable to diolefin formation and reducing the formation of byproducts such as methane and coke.

Claims

1. A method for synthesizing phosphorus-containing ZSM-5 molecular sieves, characterized in that, Includes the following steps; (1) Mix the silicon source, water and template agent evenly and stir to form solution A; A certain proportion of aluminum source, alkaline substance, diammonium hydrogen phosphate and water are mixed evenly to form solution B; solution B and solution A are simultaneously and slowly added dropwise to obtain mixed solution C. During the mixing process, the pH of the mixed solution C system is controlled within a certain range; after mixing mixed solution C in a sealed container, it is transferred to a hydrothermal stirring tank and stirred at 150℃~180℃ for 2~12h for pre-crystallization to obtain a slurry containing pre-crystallization intermediate products. (2) Add a certain amount of diammonium hydrogen phosphate solution to the slurry containing the pre-crystallized intermediate product in step (1), adjust the pH of the mixed solution system, stir in a closed environment at 40-70℃ for 2-6 hours, stir and evaporate to dryness under open conditions to obtain a gel; dry the obtained gel and grind it thoroughly, crystallize it at 180℃-230℃ under the self-generated pressure of ammonia vapor for 12-48 hours to obtain the crystallized product; (3) After washing, filtering, drying and calcining the crystallization product of step (2), phosphorus-containing ZSM-5 molecular sieve can be obtained. The total amount of phosphorus used in steps (1) and (2) is proportional to the mass ratio of silicon dioxide in the silicon source, P:SiO2 = (0.01~0.05):1, where the mass ratio of diammonium hydrogen phosphate used in steps (1) and (2) is 1:(4~9); the volume ratio of the slurry containing the crystallization intermediate product to the diammonium hydrogen phosphate solution is (10~50):

1. In step (2), the mass ratio of 25% ammonia water used for crystallization to the dry glue after drying is (0.2-0.6):

1.

2. The method for synthesizing a phosphorus-containing ZSM-5 molecular sieve according to claim 1, characterized in that, In step (1), the molar ratio of silicon source (calculated as SiO2), template agent and water is SiO2: template agent: H2O = (30~80): (20~60): (400-650); the molar ratio of aluminum source (calculated as Al2O3), alkaline substance and water is Al2O3: alkaline substance: H2O = 1: (0.1~3.0): (15-75); the molar ratio of silicon source to aluminum source is SiO2: Al2O3 = (30~80):

1.

3. The method for synthesizing a phosphorus-containing ZSM-5 molecular sieve according to claim 1, characterized in that, The template agent mentioned in step (1) is at least one of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrapropylammonium bromide, and ammonia. The silicon source mentioned in step (1) is at least one of tetraethyl orthosilicate, silica sol, and water glass; In step (1), the aluminum source is at least one of sodium aluminate, aluminum sulfate, and aluminum isopropoxide; The alkaline substance mentioned in step (1) is at least one of sodium hydroxide, ammonia or potassium hydroxide.

4. The method for synthesizing a phosphorus-containing ZSM-5 molecular sieve according to claim 1, characterized in that, In step (1), the pH of the mixed solution C is controlled to be 10-12 by adjusting the dripping rates of solution B and solution A.

5. A phosphorus-containing ZSM-5 molecular sieve prepared according to the synthesis method of a phosphorus-containing ZSM-5 molecular sieve according to any one of claims 1-4, characterized in that, The phosphorus-containing ZSM-5 molecular sieve is polymerized from 100nm to 200nm nanoscale particles.

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