A modified zsm-5 molecular sieve and a method for preparing the same

Abstract

The application provides a modified ZSM-5 molecular sieve and a preparation method thereof. The preparation method comprises the following steps: step 1, forming a gel from a silicon source, an alkali source, a metal salt solution and a cardanol polyoxyethylene ether sulfonate; step 2, adding ZSM-5 seeds into the gel, and then crystallizing, drying and calcining to obtain the modified ZSM-5 molecular sieve. The molecular sieve prepared by the method of the application does not use a template agent, the synthesis method is simple, and the crystallinity is high. The molecular sieve is used in catalytic cracking / partial oxidation reaction, and the yield of low-carbon olefins in the target product can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalysts, in particular to a modified ZSM-5 molecular sieve and a preparation method thereof. BACKGROUND

[0002] ZSM-5 molecular sieve is a kind of silicate molecular sieve with MFI channel structure, which has been widely used in petroleum chemical industry, coal chemical industry and fine chemical industry and many other fields. In particular, for the field of catalytic cracking / cracking, the unique channel structure of ZSM-5 molecular sieve enables it to selectively catalyze the alkylation, isomerization and aromatization reactions of gasoline components, thereby improving the quality of gasoline and increasing the yield of low-carbon olefins.

[0003] CN101332995A and CN1872415A developed an in-situ crystallization method of high-content ZSM-5 zeolite, including modification calcination of kaolin and in-situ crystallization of ZSM-5 zeolite. In the modification calcination step, the kaolin is mixed with the modified components or mechanically mixed into powder, or sprayed into balls, and the calcination temperature is preferably 800-1100℃, and the time is 2-5h. The preparation method needs to add a silicon source, an aluminum source, a template agent and seeds to stir the calcined kaolin at 20-70℃ for 1-5h to prepare a uniform gel, and the zeolite content of 30-80% of kaolin-based ZSM-5 zeolite can be obtained by crystallization at 140-180℃ in an autoclave for 10-48h. The patent believes that under the conditions described in the invention, the stirring mode greatly affects the in-situ crystallization. In the static crystallization process, a large proportion of non-in-situ zeolite is occupied, and it may be impossible to generate in-situ ZSM-5, and too fast or too slow stirring will directly affect the zeolite content of the crystallization product. The content of the kaolin-based ZSM-5 zeolite prepared by the invention can be controlled by adjusting the crystallization reaction conditions and changing the proportion of the binder and the filler. When used as a catalytic cracking aid, the total liquid yield is increased by more than 2 percentage points, and the propylene yield is increased by 1.7 percentage points, compared with domestic commercial aids and imported aids.

[0004] US5472594 discloses a catalyst containing phosphorus-modified ZSM-5 and Y, wherein the mass ratio of the phosphorus-modified ZSM-5 and Y is between 0.005 and 0.1, the catalyst / oil ratio is between 0.10 and 10, the reaction temperature is between 800 and 12000℃, and the pressure is between 0 and 150 pounds per square inch under the reaction conditions of catalytic cracking reaction, and it is found that the C4-C5 olefin yield is increased, but the loss of gasoline yield is also reduced.

[0005] US5380690 discloses a cracking catalyst for producing low carbon olefins, which is composed of 0-70wt.% of clay, 5-99wt.% of inorganic oxide, and 1-50wt.% of molecular sieve. The molecular sieve is composed of 0-25wt.% of REY or high-silica Y and 75-100wt.% of high-silica ZSM-5 containing phosphorus and rare earth. The catalyst shows better hydrothermal stability and higher yield of C2-C4 low carbon olefins in catalytic cracking reaction than the catalyst using only HZSM-5 molecular sieve as active component.

[0006] US3758403 also discloses that, under the reaction conditions of catalytic cracking, the catalyst using ZSM-5 molecular sieve and REY molecular sieve as active component has higher yield of low carbon olefins than the catalyst using only REY molecular sieve as active component.

[0007] US4.025.575 discloses that the low carbon oxygen-containing compounds can be converted into lower olefins ethylene and propylene using H-ZSM-5 zeolite as catalyst.

[0008] US5367100 discloses a ZSM-5-based zeolite catalyst containing at least 0.7wt.% of phosphorus and at least 0.97wt.% of rare earth elements doped in the structure of the catalyst for producing low carbon olefins.

[0009] CN102372555A discloses a method for producing light olefins by fluid catalytic cracking of naphtha. The naphtha and water are used as raw materials, and the raw materials are contacted with a fluidized bed catalyst under the conditions of a reaction temperature of 600-750℃, a weight space velocity of 0.1-2h -1 -1, and a water to oil weight ratio of 0.1-8:1 to generate ethylene and propylene. The catalyst contains the following components in percentage by weight: a) 15.0-60.0% of highland clay; b) 10.0-30.0% of at least one of silica or alumina; c) 0.5-15.0% of at least one of phosphorus, rare earth or alkaline earth oxide; and d) 25.0-70.0% of ZSM-5 zeolite with a crystal size of 200-1000nm prepared by a directing agent method.

[0010] In summary, the production of low carbon olefins using modified ZSM-5 molecular sieve is one of the research directions of the technical personnel, and the improvement of the crystallization rate in the preparation process, the non-use of template agent, and the suitable acidity are the research focuses of the researchers. SUMMARY

[0011] The main purpose of the present application is to provide a modified ZSM-5 molecular sieve and a preparation method thereof, so as to overcome the defects of low crystallinity, high cost caused by using a template agent, and unsuitable acidity in the preparation process of the modified ZSM-5 molecular sieve in the prior art.

[0012] In order to achieve the above-mentioned purpose, the present application provides a preparation method of a modified ZSM-5 molecular sieve, comprising the following steps:

[0013] Step 1: forming a gel from a silicon source, an alkali source, a metal salt solution and a cashew phenol polyoxyethylene ether sulfonate;

[0014] Step 2: adding ZSM-5 crystal seeds into the gel, and then crystallizing, drying and calcining to obtain the modified ZSM-5 molecular sieve;

[0015] In the metal salt solution, the metal is at least one of iron, titanium and silver.

[0016] The preparation method of the modified ZSM-5 molecular sieve provided by the present application, wherein the step of forming a gel in step 1 comprises:

[0017] Mixing the silicon source, the alkali source and water to form a solution A, and hydrolyzing for 15-40 minutes; adding the metal salt solution into the solution A, and then adding the cashew phenol polyoxyethylene ether sulfonate, and stirring to obtain the gel.

[0018] The preparation method of the modified ZSM-5 molecular sieve provided by the present application, wherein the silicon source is silica sol, tetraethyl orthosilicate, methyl orthosilicate or water glass; the alkali source is ethylamine or n-butylamine; and the cashew phenol polyoxyethylene ether sulfonate is sodium cashew phenol polyoxyethylene ether sulfonate, magnesium cashew phenol polyoxyethylene ether sulfonate or ammonium cashew phenol polyoxyethylene ether sulfonate.

[0019] The preparation method of the metal salt solution of the modified ZSM-5 provided by the present application, wherein the metal salt in the metal salt solution is at least one of ferric nitrate, ferric chloride, ferric sulfate, titanium nitrate, titanium sulfate, titanium chloride, silver nitrate and silver sulfate.

[0020] The preparation method of the modified ZSM-5 molecular sieve provided by the present application, wherein the silicon source is calculated as SiO2, the alkali source is calculated as OH - -, the metal salt solution is calculated as metal cation, the molar ratio of the silicon source, the alkali source, the metal salt solution and water is 1:2-10:0.01-0.05:4-10, and the molar ratio of the cashew phenol polyoxyethylene ether sulfonate and the silicon source is 0.005-0.03:1.

[0021] The preparation method of the modified ZSM-5 molecular sieve provided by the present application, wherein the stirring is carried out at a temperature of 50-90℃, and the stirring time is 15-60 minutes.

[0022] The preparation method of the modified ZSM-5 molecular sieve also comprises the step of ammonium ion exchange of the modified ZSM-5 molecular sieve.

[0023] The preparation method of the modified ZSM-5 molecular sieve, wherein the mass ratio of the ZSM-5 seed crystal to the gel is 1:100-5:100; the temperature of the crystallization is 130-170 DEG C, and the time is 1-3 hours; the crystallization mode is microwave radiation heating; the drying temperature is 100-120 DEG C, and the drying time is 8-12 hours.

[0024] The preparation method of the modified ZSM-5 molecular sieve, wherein the synthesis step of the cardanol polyoxyethylene ether sulfonate is as follows:

[0025] Step a, cardanol and ethylene oxide are synthesized into cardanol polyoxyethylene ether under alkaline conditions;

[0026] Step b, using cardanol polyoxyethylene ether as raw material, adding t-butyl alcohol base, using alcohol as solvent, refluxing, then cooling the reaction system to room temperature, adding sulfonated lactone compound dropwise, refluxing, cooling, to obtain cardanol polyoxyethylene ether sulfonate.

[0027] The sulfonated lactone compound is 1,3-propane sulfonated lactone and / or 1,4-butane sulfonated lactone.

[0028] In order to achieve the above purpose, the application also provides the modified ZSM-5 molecular sieve prepared by the preparation method.

[0029] The application has the following beneficial effects:

[0030] (1) In the preparation process of the modified ZSM-5 molecular sieve, iron, titanium, silver and other metal elements are introduced, and the environment-friendly additive cardanol polyoxyethylene ether sulfonate is added, and the two have synergistic effect. In the process of crystal nucleation and growth, the solvent interface increases, a small amount of cardanol polyoxyethylene ether sulfonate is added, which can effectively reduce the surface tension of the solution, easily nucleate in energy, and form micelles in the gel. This effect increases the contact and action probability between silicon and metal elements, that is, the crystallization rate is improved by changing the thermodynamic properties of the sol, thereby improving the crystallinity of the modified ZSM-5 molecular sieve. At the same time, the metal elements are also successfully introduced into the molecular sieve framework. Due to the presence of metal elements in the molecular sieve, the oxidation is beneficial to the generation of carbanions, which makes the reaction more easily initiated, thereby improving the reaction activity and being beneficial to the improvement of olefin yield. In addition, the sulfonic acid group in the additive cardanol polyoxyethylene ether sulfonate can effectively neutralize the surface acidity of the molecular sieve, and can improve the reaction selectivity.

[0031] (2) The modified ZSM-5 molecular sieve synthesis process of the present application uses a seed crystal method, does not use an organic template agent, has a lower cost, and avoids environmental pollution caused by the use of an organic template agent. DETAILED DESCRIPTION

[0032] The technical solutions of the present application are described in detail below. The following embodiments are implemented on the premise of the technical solutions of the present application, and detailed implementation processes are given. However, the protection scope of the present application is not limited to the following embodiments. The structures or experimental methods not specified in the following embodiments are usually performed according to conventional conditions.

[0033] The present application provides a preparation method of a modified ZSM-5 molecular sieve, comprising the following steps:

[0034] Step 1: forming a gel from a silicon source, an alkali source, a metal salt solution and a cardanol polyoxyethylene ether sulfonate;

[0035] Step 2: adding ZSM-5 seeds to the gel, then crystallizing, drying and calcining to obtain the modified ZSM-5 molecular sieve.

[0036] In the preparation process of the modified ZSM-5 molecular sieve, a metal element is introduced, and an environmentally friendly additive, cardanol polyoxyethylene ether sulfonate, is also added. The two components have a synergistic effect. During the crystal nucleation and growth process, the solvent interface increases. A small amount of cardanol polyoxyethylene ether sulfonate can effectively reduce the surface tension of the solution, easily nucleate from the energy, and form micelles in the gel. This effect increases the contact and interaction probability between silicon and metal elements, i.e., the crystallization rate is improved by changing the thermodynamic properties of the sol, thereby improving the crystallinity of the modified ZSM-5 molecular sieve. At the same time, the metal element is successfully introduced into the molecular sieve framework. Due to the presence of the metal element in the molecular sieve, its oxidation is beneficial to the generation of carbanions, making the reaction more easily initiated, thereby improving the reaction activity and being beneficial to the improvement of the olefin yield. In addition, the sulfonic acid group in the additive cardanol polyoxyethylene ether sulfonate can effectively neutralize the surface acidity of the molecular sieve, which can improve the reaction selectivity.

[0037] In an embodiment, the step of forming a gel in step 1 of the present application comprises:

[0038] Mixing the silicon source, the alkali source and water to form a solution A, and hydrolyzing for 15-40 minutes; adding the metal salt solution to the solution A, then adding the cardanol polyoxyethylene ether sulfonate, and stirring to obtain the gel.

[0039] In an embodiment, the silicon source is silica sol, tetraethyl orthosilicate, methyl orthosilicate or water glass; the alkali source is ethylamine or n-butylamine. The metal in the metal salt solution is at least one of iron, titanium and silver, the metal salt is at least one of ferric nitrate, ferric chloride, ferric sulfate, titanium nitrate, titanium sulfate, titanium chloride, silver nitrate and silver sulfate, and preferably silver nitrate. The cardanol polyoxyethylene ether sulfonate is sodium cardanol polyoxyethylene ether sulfonate, magnesium cardanol polyoxyethylene ether sulfonate or ammonium cardanol polyoxyethylene ether sulfonate.

[0040] In an embodiment, the silicon source is calculated in terms of SiO2, the alkali source is calculated in terms of OH - In an embodiment, the molar ratio of the silicon source, the alkali source, the metal salt solution calculated in terms of metal cation, the water and the cardanol polyoxyethylene ether sulfonate is 1:2-10:0.01-0.05:4-10:0.005-0.03:1.

[0041] In an embodiment, the stirring (hydrolysis) is performed at 50-90°C after the addition of the cardanol polyoxyethylene ether sulfonate, and the stirring time is 15-60 minutes to obtain the gel.

[0042] Then, the ZSM-5 seeds are added to the gel, and then crystallization, drying and calcination are performed to obtain the modified ZSM-5 molecular sieve.

[0043] In an embodiment, the mass ratio of the ZSM-5 seeds to the gel is 1:100-5:100, and after the addition of the seeds, the mixture is stirred again, and then crystallization, cooling to room temperature, centrifugal filtration, washing, drying and calcination are performed to obtain the modified ZSM-5 molecular sieve.

[0044] In an embodiment, in the preparation of the ZSM-5 molecular sieve, the temperature of the crystallization treatment is 130-170°C, and the time is 1-3 hours, the crystallization treatment is performed by microwave radiation heating, the drying temperature is 100-120°C, and the drying time is 8-12 hours. The calcination temperature is not particularly limited, and the conventional calcination temperature in the art can be used.

[0045] In an embodiment, the modified ZSM-5 molecular sieve needs to be further subjected to ammonium ion exchange treatment. Specifically, the ammonium salt, the modified ZSM-5 molecular sieve and deionized water can be mixed and uniformly beaten according to the weight ratio of ammonium salt: modified ZSM-5 molecular sieve: deionized water = 0.005-1:1:1-50, the pH value of the slurry is adjusted to 2.0-6.0, and the exchange is performed at 40-130°C for 0.5-4 hours. The ammonium salt can be one of ammonium chloride, ammonium sulfate, ammonium phosphate and ammonium nitrate.

[0046] In an embodiment, the application further provides a synthesis step of the cardanol polyoxyethylene ether sulfonate, comprising:

[0047] Step a, synthesis of cardanol polyoxyethylene ether from cardanol and ethylene oxide under alkaline condition;

[0048] Step b, cardanol polyoxyethylene ether sulfonate was obtained by adding tert-butyl alcohol base, alcohol as solvent, reflux, then the reaction system was cooled to room temperature, dropwise addition of sulfonic acid lactone compound, reflux, cooling.

[0049] The sulfonic acid lactone compound is a compound containing sulfonic acid lactone group, in an embodiment, the sulfonic acid lactone compound is 1,3-propane sulfonic acid lactone and / or 1,4-butane sulfonic acid lactone.

[0050] In an embodiment, the mass ratio of cardanol to ethylene oxide is 1:10-1:40.

[0051] In an embodiment, the synthesis step of cardanol polyoxyethylene ether sulfonate can also be: cardanol polyoxyethylene ether was synthesized from cardanol and ethylene oxide under alkaline condition; under argon protection, in a three-necked flask, cardanol polyoxyethylene ether (EON value: n≈5, 6, 10, 12, 18) was used as raw material, sodium tert-butoxide was used as base, anhydrous ethanol was used as solvent, refluxed for 30 min, the reaction system was cooled to room temperature, 1,3-propane sulfonic acid lactone or 1,4-butane sulfonic acid lactone was slowly added dropwise, refluxed, cooled, excess ethanol was removed by vacuum distillation, petroleum ether was added, grinded to obtain white solid, centrifuged, vacuum dried to obtain the final product, which is white deliquescent solid cardanol polyoxyethylene ether sodium sulfonate.

[0052] In an embodiment, the solvent alcohol can be ethanol.

[0053] Therefore, the present application provides a preparation method of modified ZSM-5 molecular sieve, the molecular sieve prepared by the method does not use a template agent, the synthesis method is simple, and the crystallinity is high, and the molecular sieve is used for catalytic cracking / cracking reaction, so that the yield of low-carbon olefins in the target product is improved.

[0054] The following detailed description of the embodiments of the present application is based on the premise of the technical solutions of the present application, and detailed implementation methods and processes are given, but the protection scope of the present application is not limited to the following embodiments, and the experimental methods not specified in the following embodiments are usually carried out under conventional conditions. If the following ratio is not specially specified, it is mass ratio.

[0055] Source of raw materials:

[0056] 1) ZSM-5 molecular sieve: industrial product, produced by Lanzhou Petrochemical Company, crystallinity 84%, silicon-aluminum ratio (molar ratio of silicon dioxide and aluminum oxide) 5, Na2O content 14.3wt%;

[0057] 2) Silica sol, tetraethyl orthosilicate, methyl orthosilicate or water glass, ethylamine, n-butylamine, ferric nitrate, ferric chloride, ferric sulfate, titanium nitrate, titanium sulfate, titanium chloride, silver nitrate, silver sulfate, cardanol, oxirane, t-butyl alcohol alkali, anhydrous ethanol, 1,3-propane sulfonate lactone, 1,4-butane sulfonate lactone, ammonium chloride, ammonium sulfate, ammonium phosphate, ammonium nitrate: analytical pure, all are chemical reagents;

[0058] Evaluation method used in the examples

[0059] Catalytic cracking reaction selectivity evaluation: the catalytic reaction selectivity evaluation was carried out in a small fixed fluidized bed (FFB) test device (XGL-2, origin Luoyang). The catalyst was pretreated at 800℃ under 100% steam for 10h. The reaction raw oil was Lanzhou Petrochemical light gasoline, the specific properties were as shown in Table 1, the reaction temperature was 600-685℃, the space velocity was 12-15h-1, and the catalyst to oil ratio was 4-12. -1

[0060] Table 1 Properties of raw oil

[0061] Percent content / % n-alkanes 6.97 iso-alkanes 44.18 olefins 43.61 naphthenes 4.27 aromatics 0.97 MON 84.37 RON 92.9

[0062] Preparation method of the examples:

[0063] (1) mixing the silicon source, the alkali source and H2O to form solution A; adding the metal salt solution to the above solution A, then adding the additive cardanol polyoxyethylene ether sulfonate, uniformly stirring at 50℃-90℃ for 15-60 minutes to form a mixed gel B;

[0064] (2) adding ZSM-5 seeds to the above mixed gel B, stirring uniformly for 1-3h to obtain a mixture C;

[0065] (3) sequentially subjecting the mixture C to crystallization, cooling to room temperature, then centrifugal filtration, washing, drying and calcination to obtain the modified ZSM-5 molecular sieve, and subjecting the metal-modified ZSM-5 molecular sieve to ammonium salt exchange to obtain the final modified ZSM-5 molecular sieve.

[0066] According to the above method, the specific selection of raw materials and the implementation process conditions are referred to in Table 2 below to prepare the samples.

[0067] Table 2 Selection and ratio of each raw material

[0068]

[0069]

[0070] Comparative Example 1 was Lanzhou Petrochemical ZSM-5 molecular sieve.

[0071] Comparative Example 2​

[0072] The modified ZSM-5 molecular sieve is prepared by the method of CN 108238837 B, specifically as follows: the ZSM-5 type nano molecular sieve raw powder with a particle size distribution of 190-210 nm and a silicon-aluminum ratio of 62 is placed in a crucible; a lanthanum nitrate solution with a concentration of 20-30 wt% and a phosphoric acid solution with a concentration of 30-40 wt% are prepared, and the lanthanum nitrate solution and the phosphoric acid solution are mixed in a volume ratio of 1:1; the mixed solution of the lanthanum nitrate and the phosphoric acid is poured into the crucible, and the molecular sieve is fully impregnated by stirring with a glass rod while pouring the mixed solution until the solution surface exceeds the molecular sieve raw powder; then the solution is sent into a constant-temperature water bath for impregnation at 60℃ for 8 hours, and then the molecular sieve solution is filtered, and the filtered molecular sieve powder is sent into a muffle furnace for staged calcination, with a calcination temperature of 120℃ for 2 hours, 350℃ for 4 hours, and 450℃ for 6 hours, so that the modification treatment of the molecular sieve is completed, and the modified ZSM-5 molecular sieve is obtained.

[0073] Comparative Example 3

[0074] Similar to the method of Example 2, the difference is that no cardanol polyoxyethylene ether sulfonate is added, and the modified molecular sieve is obtained under the same conditions.

[0075] The crystallinity of the modified ZSM-5 molecular sieves obtained in each example and comparative example is shown in Table 3.

[0076] The modified ZSM-5 molecular sieves obtained in Example 1-Example 5, Comparative Example 1 and Comparative Example 2 are evaluated on a fixed fluidized bed, and the reaction conditions are as follows: a reaction temperature of 630℃, a space velocity of 15h-1, a catalyst / oil ratio of 8, and a reaction pressure of 130kpa (gauge pressure). The evaluation results are shown in Table 4. -1

[0077] Table 3 Crystallinity of Examples and Comparative Examples

[0078]

[0079] As shown in Table 3, the crystallinity of the modified ZSM-5 molecular sieve synthesized in the examples of the present application is higher than that of the ZSM-5 molecular sieves synthesized in Comparative Examples 1-3.

[0080] Table 4 Evaluation results of samples

[0081]

[0082] As shown in Table 4, compared with the catalysts of the comparative examples, the modified ZSM-5 molecular sieve prepared from the examples of the present application has a higher yield of low-carbon olefins in the target product when used in a light gasoline catalytic cracking reaction.

[0083] ​Of course, the present application can have other various embodiments, and those skilled in the art can make various corresponding changes and modifications according to the present application without departing from the spirit and essence of the present application, and these corresponding changes and modifications shall all belong to the protection scope of the claims of the present application.

Claims

1. A method for preparing modified ZSM-5 molecular sieve, characterized in that, Includes the following steps: Step 1: Form a gel by combining silicon source, alkali source, metal salt solution and cashew phenol polyoxyethylene ether sulfonate; Step 2: Add ZSM-5 seed crystals to the gel, then crystallize, dry, and calcine to obtain modified ZSM-5 molecular sieve; The metal in the metal salt solution is at least one of iron, titanium, and silver.

2. The method for preparing modified ZSM-5 molecular sieve according to claim 1, characterized in that, Step 1, the gel formation process, includes: A solution A is formed by mixing a silicon source, an alkaline source, and water, and hydrolyzing for 15–40 minutes. A metal salt solution is added to solution A, followed by the addition of cashew phenol polyoxyethylene ether sulfonate, and the mixture is stirred to obtain the gel.

3. The method for preparing modified ZSM-5 molecular sieve according to claim 1, characterized in that, The silicon source is silica sol, tetraethyl silicate, methyl orthosilicate, or water glass; the alkali source is ethylamine or n-butylamine; and the cashew phenol polyoxyethylene ether sulfonate is sodium cashew phenol polyoxyethylene ether sulfonate, magnesium cashew phenol polyoxyethylene ether sulfonate, or ammonium cashew phenol polyoxyethylene ether sulfonate.

4. The method for preparing modified ZSM-5 molecular sieve according to claim 1, characterized in that, The metal salt in the metal salt solution is at least one of ferric nitrate, ferric chloride, ferric sulfate, titanium nitrate, titanium sulfate, titanium chloride, silver nitrate, and silver sulfate.

5. The method for preparing modified ZSM-5 molecular sieve according to claim 1, characterized in that, The silicon source is SiO2, and the alkali source is OH. - The ion meter is used, the metal salt solution is measured as metal cations, the molar ratio of the silicon source, alkali source, metal salt solution and water is 1:2~10:0.01~0.05:4~10, and the molar ratio of cashew phenol polyoxyethylene ether sulfonate to silicon source is 0.005~0.03:

1.

6. The method for preparing modified ZSM-5 molecular sieve according to claim 2, characterized in that, The stirring is carried out at a temperature of 50℃ to 90℃ for a duration of 15 to 60 minutes.

7. The method for preparing modified ZSM-5 molecular sieve according to claim 1, characterized in that, It also includes the step of ammonium ion exchange of the modified ZSM-5 molecular sieve.

8. The method for preparing modified ZSM-5 molecular sieve according to claim 1, characterized in that, The mass ratio of the ZSM-5 seed crystals added to the gel is 1:100 to 5:100; the crystallization temperature is 130℃ to 170℃, the time is 1h to 3h, and the crystallization method is microwave radiation heating; the drying temperature is 100℃ to 120℃, and the drying time is 8h to 12h.

9. The method for preparing modified ZSM-5 molecular sieve according to claim 1, characterized in that, The synthesis steps of the cashew phenol polyoxyethylene ether sulfonate are as follows: Step a: Cashew nut phenol and ethylene oxide are reacted under alkaline conditions to synthesize cashew nut phenol polyoxyethylene ether; Step b: Using cashew phenol polyoxyethylene ether as raw material, add tert-butanol base, use alcohol as solvent, reflux, then cool the reaction system to room temperature, add sulfonate lactone compound dropwise, reflux, cool, and obtain cashew phenol polyoxyethylene ether sulfonate.

10. The method for preparing the modified ZSM-5 molecular sieve according to claim 9, characterized in that, The sulfonyl lactone compound is 1,3-propanesulfonyl lactone and / or 1,4-butanesulfonyl lactone.

11. The modified ZSM-5 molecular sieve prepared by the preparation method according to any one of claims 1-10.

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