High-silicon hydrophobic MFI type molecular sieve synthesized by polyvinylpyrrolidone modified composite template agent, and preparation method and application thereof

Abstract

The invention discloses a high-silicon hydrophobic MFI type molecular sieve synthesized by a polyvinylpyrrolidone modified composite template, and a preparation method and application thereof in the field of molecular sieve adsorption materials, and the synthesized high-silicon hydrophobic MFI type molecular sieve adopts a composite template composed of organic bases and organic amines to jointly guide the formation of a crystal nucleus of the molecular sieve. Furthermore, a surfactant polyvinylpyrrolidone is introduced, so that the reaction raw materials are uniformly dispersed in a solution system, a large number of crystal nucleuses are rapidly formed in the early stage, and crystal growth is induced. The microwave reaction avoids the generation of temperature gradient, materials in the medium are heated more uniformly, and the synthesis efficiency and purity of the molecular sieve can be obviously improved. The final result is that the adsorption capacity of the molecular sieve to VOCs is enhanced, the hydrophobicity is enhanced, and the competitive adsorption of water molecules and VOCs molecules is reduced. The device still has a good adsorption effect on VOCs waste gas with high humidity, large air volume and low concentration.

Description

Technical Field

[0001] The invention belongs to the technical field of molecular sieve material synthesis, and specifically relates to a high-silicon hydrophobic MFI type molecular sieve synthesized by a polyvinyl pyrrolidone modified composite template agent, a preparation method and application thereof. Background Art

[0002] VOCs, a general term for organic pollutants that are ubiquitous and complex in the air, refer to organic compounds with a boiling point of 50°C to 260°C under normal pressure. According to the chemical structure, they can be roughly divided into 8 categories: alkanes, aromatic hydrocarbons, olefins, halogenated hydrocarbons, lipids, aldehydes, ketones and other compounds. Adsorption is an effective way to control volatile organic compounds, and efficient adsorbents are the key to adsorption. Zeolite molecular sieve, as an inorganic aluminosilicate material, has a unique pore structure, a large specific surface area, and good stability, and is regarded as an excellent adsorption material.

[0003] VOCs waste gas treatment is usually accompanied by factors such as high humidity, large air volume, and low concentration. Therefore, the hydrophobicity and stability of molecular sieve adsorbents play an important role in VOCs waste gas treatment. Especially in high humidity environments, its adsorption capacity and stability will drop sharply. Therefore, how to improve the hydrothermal stability and hydrophobicity of molecular sieve products has become a key technology that needs to be solved urgently. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a high-silicon hydrophobic MFI type molecular sieve synthesized by a polyvinyl pyrrolidone modified composite template agent, a preparation method and use thereof. The obtained molecular sieve has the characteristics of high silicon-aluminum ratio, high hydrophobicity, high crystallinity and small grains, good hydrothermal stability and hydrophobicity, excellent VOCs adsorption effect, and the preparation process is easy to operate, low cost, and convenient for market promotion.

[0005] To this end, the object of the present invention is achieved as follows: a method for preparing a high-silicon hydrophobic MFI type molecular sieve synthesized by a polyvinyl pyrrolidone modified composite template agent, comprising the following steps:

[0006] (1) Mixing the raw materials silicon source, alkali source, composite template and water, adding polyvinyl pyrrolidone (PVP) to the mixture, stirring until clear, transferring to a reaction kettle, and using microwave reaction for 2 to 2.5 hours to obtain a gel precursor;

[0007] The silicon source, the alkali source, the composite template agent, and water are composed in a mass ratio of 1:(0.003-0.015):(0.1-0.4):(1-10); the composite template agent is composed of an organic base and an organic amine;

[0008] The amount of PVP added is 0.08-0.16% of the total mass of the mixture;

[0009] (2) transferring to a homogeneous reactor, crystallizing at a constant temperature, and cooling to obtain a crystallized material;

[0010] (3) adding an acid solution to the above-mentioned crystallized material, heating, stirring and acid treatment;

[0011] (4) filtering the flocculated material, washing it with water, drying it, roasting it, and crushing it to obtain a molecular sieve;

[0012] Furthermore, the silicon source in step (1) is liquid silica sol; the alkali source is sodium hydroxide; the organic base in the composite template includes at least one of tetraethylammonium bromide and tetrapropylammonium bromide; and the organic amine in the composite template includes at least one of n-butylamine, ethylamine and ethylenediamine.

[0013] In step (1), there is no special requirement for the silicon source, and at least one of liquid silica sol, silicon powder, solid silica gel, white carbon, water glass and ethyl orthosilicate can be selected. The inventors have found through a large number of experiments that the liquid silicon source that is easier to depolymerize after mixing with an alkali source is more conducive to the early generation of a large amount of gel precursor. Considering the cost of silicon source procurement, the silicon source is preferably selected as liquid silica sol with an effective ingredient of 25-35%.

[0014] In step (1), the alkali source can be at least one of sodium hydroxide, lithium hydroxide and potassium hydroxide, in order to provide a special alkalinity environment for the early generation of a large amount of gel precursor. The inventors have found through experimental comparison that the alkali source is preferably sodium hydroxide, and sodium ions are easier to remove by water washing.

[0015] Furthermore, the organic base and the organic amine in the composite template in step (1) are mixed in a mass ratio of 1:(1.2-1.6).

[0016] Furthermore, the average molecular weight of the PVP in step (1) is 8000 to 700000. Preferably, the average molecular weight of the PVP is one of 8000 (K17), 40000 (K30), 160000 (K60), and 360000 (K90).

[0017] Furthermore, the constant temperature crystallization in step (2) includes a first constant temperature of 110-120° C. for 15-16 hours and a second constant temperature of 180-190° C. for 12-13 hours.

[0018] Furthermore, the concentration of the acid solution is 0.2-0.5 mol / L; the acid treatment temperature is 70-80° C., and the stirring time is 2-3 hours; and the amount of the acid solution added is 0.3-0.5% of the total mass of the mixture.

[0019] In step (3), the acid solution is an aqueous solution of oxalic acid, acetic acid, hydrochloric acid, sulfuric acid, nitric acid, and citric acid.

[0020] Furthermore, in step (4), the calcination temperature is 530-630° C. and the time is 10-12 hours; and the pulverization includes mechanical pulverization and air flow pulverization.

[0021] A high-silicon hydrophobic MFI molecular sieve synthesized by a polyvinyl pyrrolidone modified composite template agent is prepared by the above preparation method. The use of the high-silicon hydrophobic MFI molecular sieve synthesized by a polyvinyl pyrrolidone modified composite template agent is that it can be used to adsorb VOCs waste gas.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] 1. The present invention adopts organic bases and organic amines to form a composite template agent, which jointly guides the nucleation of the molecular sieve. The template agent performs space filling in the molecular sieve framework, can stably form a specific structure, and makes a vital contribution to the size, shape, basicity, etc. of the crystal growth, and plays a structural guiding role. The organic amine template agent can stabilize the molecular sieve framework, the hydrophobic inner surface, and improve the thermodynamic stability of the molecular sieve framework. In addition, the cation in the template agent can affect the charge density of the molecular sieve framework and play a role in balancing the charge of the framework.

[0024] 2. The present invention adopts microwave reaction to avoid the generation of temperature gradient, and the material in the medium is heated more evenly. Conventional heating starts from the outside of the material, and the heat is transferred to the inside through the thermal radiation, thermal convection and thermal conduction of the material. Microwave heating is just the opposite. It starts from the inside of the material and then transfers the heat from the inside to the outside. Microwave reaction is conducive to the activation and decomposition of raw materials, greatly improving the nucleation speed and number of crystal nuclei in the induction period of the crystallization process, and inducing crystal growth.

[0025] 3. The present invention introduces the surfactant polyvinylpyrrolidone (PVP), which can make the reaction raw materials evenly dispersed in the solution system, quickly form a large number of crystal nuclei in the early stage, induce crystal growth, and significantly improve the synthesis efficiency and purity of the molecular sieve, while shortening the reaction time.

[0026] Experiments show that the above technical means enhance the adsorption capacity of molecular sieves for VOCs, enhance hydrophobicity, and reduce the competitive adsorption between water molecules and VOCs molecules. It still has a good adsorption effect for VOCs exhaust gas with high humidity, large air volume and low concentration. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0028] Example 1

[0029] A high-silicon hydrophobic MFI type molecular sieve synthesized by a polyvinyl pyrrolidone modified composite template agent, the preparation method of which comprises the following steps:

[0030] (1) The raw materials silicon source, alkali source, composite template and water are mixed in a mass ratio of 1:0.009:0.2:5, and then 0.12% polyvinyl pyrrolidone (PVP) with an average molecular weight of 40000 (K30) is added to the mixture; the mixture is stirred until clear, transferred into a reaction kettle, and microwaved for 2 to 2.5 hours to obtain a gel precursor; the silicon source is liquid silica sol; the alkali source is sodium hydroxide; the composite template is tetrapropylammonium bromide and n-butylamine, which are mixed in a mass ratio of 1:1.4;

[0031] (2) Transfer to a homogeneous reactor and perform constant temperature crystallization, the first stage is constant temperature of 110-120°C for 15-16 hours; the second stage is constant temperature of 180-190°C for 12-13 hours; cool down to obtain a crystallized material;

[0032] (3) adding 0.35 mol / L oxalic acid solution to the above crystallized material, heating, stirring and acid treatment; the treatment temperature is 70-80° C., and the stirring time is 2-3 h; the amount of acid solution added is 0.03-0.05% of the total mass of the mixture;

[0033] (4) The flocculated material is subjected to filter pressing, water washing, drying, roasting and pulverizing to obtain a molecular sieve; the roasting temperature is 530-630° C. and the time is 10-12 hours; the pulverizing includes mechanical pulverization and air flow pulverization.

[0034] Example 2-1

[0035] The composite template is tetrapropylammonium bromide and ethylamine, and the rest is the same as in Example 1;

[0036] Example 2-2

[0037] The composite template agent is tetrapropylammonium bromide and ethylenediamine, and the rest is the same as in Example 1; Example 2-3

[0038] Instead, "the composite template agent is tetraethylammonium bromide and n-butylamine", and the rest is the same as in Example 1; Example 2-4

[0039] The composite template agent is tetraethylammonium bromide and ethylamine, and the rest is the same as in Example 1;

[0040] Embodiment 2-5

[0041] The composite template agent is tetraethylammonium bromide and ethylenediamine, and the rest is the same as in Example 1; Comparative Example 2-a

[0042] The composite template is tetraethylammonium bromide, tetrapropylammonium bromide and n-butylamine, and the rest is the same as in Example 1;

[0043] Comparative Example 2-b

[0044] The composite template is tetraethylammonium bromide, tetrapropylammonium bromide, n-butylamine and ethylamine, and the rest is the same as in Example 1;

[0045] Comparative Example 2-c

[0046] The composite template is tetraethylammonium bromide, tetrapropylammonium bromide, n-butylamine, ethylamine and ethylenediamine, and the rest is the same as in Example 1;

[0047] Comparative Example 2-d

[0048] The composite template is tetrapropylammonium bromide, n-butylamine, ethylamine and ethylenediamine, and the rest is the same as in Example 1;

[0049] Comparative Example 2-e

[0050] The composite template is a single template containing only tetrapropylammonium bromide, and the rest is the same as in Example 1;

[0051] Comparative Example 2-f

[0052] The composite template agent is a single template agent, which is only n-butylamine, and the rest is the same as in Example 1;

[0053] Table 1 Comparison of crystallization results of different composite templates

[0054]

[0055]

[0056] According to the crystallization comparison of different composite templates in Table 1, the composite template is preferably a mixture of tetrapropylammonium bromide and n-butylamine.

[0057] Example 3-1

[0058] Instead, "the composite template is mixed in a mass ratio of 1:1.2", and the rest is the same as in Example 1; Example 3-2

[0059] Instead, "the composite template is mixed in a mass ratio of 1:1.3", and the rest is the same as in Example 1; Example 3-3

[0060] Instead, "the composite template is mixed in a mass ratio of 1:1.5", and the rest is the same as in Example 1; Example 3-4

[0061] Instead, "the composite template is mixed in a mass ratio of 1:1.6", and the rest is the same as in Example 1; Comparative Example 3-a

[0062] The composite template is mixed in a mass ratio of 1:1.0, and the rest is the same as in Example 1; Comparative Example 3-b

[0063] The composite template is mixed in a mass ratio of 1:1.1, and the rest is the same as in Example 1; Comparative Example 3-c

[0064] The composite template is mixed in a mass ratio of 1:1.7, and the rest is the same as in Example 1; Comparative Example 3-d

[0065] The composite template is mixed in a mass ratio of 1:1.9, and the rest is the same as in Example 1;

[0066] Table 2 Comparison of crystallization results of composite templates with different mass ratios

[0067]

[0068] According to the comparison of composite templates with different mass ratios in Table 2, as the mass ratio increases, the relative crystallinity first increases and then decreases. Therefore, the composite template tetrapropylammonium bromide and n-butylamine are selected in a mass ratio of 1:1.2 to 1.6, preferably 1:1.4.

[0069] Example 4-1

[0070] Instead, "0.08% polyvinyl pyrrolidone is added to the total mass of the mixture", and the rest is the same as in Example 1; Example 4-2

[0071] Instead, "0.10% polyvinyl pyrrolidone is added to the total mass of the mixture", and the rest is the same as in Example 1; Example 4-3

[0072] Instead, "0.14% polyvinyl pyrrolidone is added to the total mass of the mixture", and the rest is the same as in Example 1; Example 4-4

[0073] Instead, "0.16% polyvinyl pyrrolidone was added to the total mass of the mixture", and the rest was the same as in Example 1; Comparative Example 4-a

[0074] Instead, "0.05% polyvinyl pyrrolidone was added to the total mass of the mixture", and the rest was the same as in Example 1; Comparative Example 4-b

[0075] The method was changed to "add 0.20% polyvinyl pyrrolidone based on the total mass of the mixture", and the other parts were the same as those in Example 1;

[0076] Table 3 Comparison of crystallization results of adding different proportions of polyvinyl pyrrolidone

[0077]

[0078] According to the comparison results of adding polyvinyl pyrrolidone in different proportions according to Table 3, when 0.08-0.16% polyvinyl pyrrolidone of the total mass of the mixture is added, the relative crystallinity is greater than 99%, preferably 0.12%.

[0079] Example 5-1

[0080] Use "polyvinyl pyrrolidone average molecular weight 8000 (K17)" instead, and the rest is the same as in Example 1; Example 5-2

[0081] Use "polyvinyl pyrrolidone with an average molecular weight of 160,000 (K60)" instead, and the rest is the same as in Example 1; Example 5-3

[0082] Use "polyvinyl pyrrolidone with an average molecular weight of 360,000 (K90)" instead, and the rest is the same as in Example 1; Comparative Example 5-a

[0083] Using "no polyvinyl pyrrolidone", the rest is the same as in Example 1;

[0084] Table 4 Comparison of crystallization results of adding polyvinyl pyrrolidone with different molecular weights

[0085]

[0086] Adding polyvinyl pyrrolidone is conducive to the uniform dispersion of raw materials in the solution system, accelerating the formation of crystal nuclei and inducing crystal growth. Generally speaking, as the molecular weight increases, the solubility and stability of polyvinyl pyrrolidone become better, but its viscosity and cost will also increase accordingly.

[0087] Therefore, according to the comparison results of adding polyvinyl pyrrolidone with different molecular weights in Table 3, the relative crystallinity of crystallization is >98% and the silicon-aluminum ratio is >3200. It is preferred that the average molecular weight of the PVP is one of 8000 (K17), 40000 (K30), 160000 (K60), and 360000 (K90). Further, K30 is preferred, which is economical and practical.

[0088] Example 6

[0089] A high-silicon hydrophobic MFI type molecular sieve synthesized by a polyvinyl pyrrolidone modified composite template agent, the preparation method of which comprises the following steps:

[0090] (1) The raw materials silicon source, alkali source, composite template and water are mixed in a mass ratio of 1:0.003:0.1:1, and then 0.08% polyvinyl pyrrolidone (PVP) with an average molecular weight of 40000 (K30) is added to the mixture; the mixture is stirred until clear, transferred into a reaction kettle, and microwaved for 2 to 2.5 hours to obtain a gel precursor; the silicon source is liquid silica sol; the alkali source is sodium hydroxide; the composite template is tetrapropylammonium bromide and n-butylamine, which are mixed in a mass ratio of 1:1.2;

[0091] (2) Transfer to a homogeneous reactor and perform constant temperature crystallization, the first stage is constant temperature of 110-120°C for 15-16 hours; the second stage is constant temperature of 180-190°C for 12-13 hours; cool down to obtain a crystallized material;

[0092] (3) adding 0.03-0.05 mol / L oxalic acid solution to the above crystallized material, heating, stirring and acid treatment; the treatment temperature is 70-80° C., and the stirring time is 2-3 hours; the amount of acid solution added is 0.03-0.05% of the total mass of the mixture;

[0093] (4) The flocculated material is subjected to filter pressing, water washing, drying, roasting and pulverizing to obtain a molecular sieve; the roasting temperature is 530-630° C. and the time is 10-12 hours; the pulverizing includes mechanical pulverization and air flow pulverization.

[0094] Example 7

[0095] A high-silicon hydrophobic MFI type molecular sieve synthesized by a polyvinyl pyrrolidone modified composite template agent, the preparation method of which comprises the following steps:

[0096] (1) The raw materials silicon source, alkali source, composite template and water are mixed in a mass ratio of 1:0.015:0.4:10, and then 0.16% polyvinyl pyrrolidone (PVP) with an average molecular weight of 40000 (K30) is added to the mixture; the mixture is stirred until clear, transferred into a reaction kettle, and microwaved for 2 to 2.5 hours to obtain a gel precursor; the silicon source is liquid silica sol; the alkali source is sodium hydroxide; the composite template is tetrapropylammonium bromide and n-butylamine, which are mixed in a mass ratio of 1:1.6;

[0097] (2) Transfer to a homogeneous reactor and perform constant temperature crystallization, the first stage is constant temperature of 110-120°C for 15-16 hours; the second stage is constant temperature of 180-190°C for 12-13 hours; cool down to obtain a crystallized material;

[0098] (3) adding 0.03-0.05 mol / L oxalic acid solution to the above crystallized material, heating, stirring and acid treatment; the treatment temperature is 70-80° C., and the stirring time is 2-3 hours; the amount of acid solution added is 0.03-0.05% of the total mass of the mixture;

[0099] (4) The flocculated material is subjected to filter pressing, water washing, drying, roasting and pulverizing to obtain a molecular sieve; the roasting temperature is 530-630° C. and the time is 10-12 hours; the pulverizing includes mechanical pulverization and air flow pulverization.

[0100] Example 8

[0101] A high-silicon hydrophobic MFI type molecular sieve synthesized by a polyvinyl pyrrolidone modified composite template agent, the preparation method of which comprises the following steps:

[0102] (1) The raw materials silicon source, alkali source, composite template and water are mixed in a mass ratio of 1:0.008:0.3:6, and then 0.08% polyvinyl pyrrolidone (PVP) with an average molecular weight of 160000 (K60) is added to the mixture; the mixture is stirred until clear, transferred into a reaction kettle, and microwaved for 2 to 2.5 hours to obtain a gel precursor; the silicon source is liquid silica sol; the alkali source is sodium hydroxide; the composite template is tetrapropylammonium bromide and n-butylamine, which are mixed in a mass ratio of 1:1.2;

[0103] (2) Transfer to a homogeneous reactor and perform constant temperature crystallization, the first stage is constant temperature of 110-120°C for 15-16 hours; the second stage is constant temperature of 180-190°C for 12-13 hours; cool down to obtain a crystallized material;

[0104] (3) adding 0.03-0.05 mol / L oxalic acid solution to the above crystallized material, heating, stirring and acid treatment; the treatment temperature is 70-80° C., and the stirring time is 2-3 hours; the amount of acid solution added is 0.03-0.05% of the total mass of the mixture;

[0105] (4) The flocculated material is subjected to filter pressing, water washing, drying, roasting and pulverizing to obtain a molecular sieve; the roasting temperature is 530-630° C. and the time is 10-12 hours; the pulverizing includes mechanical pulverization and air flow pulverization.

[0106] According to the above example, a high-silicon super-hydrophobic MFI type molecular sieve was prepared, and the relevant data are as follows:

[0107]

[0108]

[0109] According to the above examples, the adsorption performance was evaluated after calcination: static saturated adsorption of water and toluene; dynamic saturated adsorption time of xylene and ethyl acetate.

[0110]

[0111] When the static water contact angle θ is greater than 90°, the surface is considered to be hydrophobic; when θ is less than 90°, the surface is considered to be hydrophilic. In addition, when the static contact angle θ is greater than 150°, the surface is considered to be superhydrophobic. According to the results in the table, it can be seen that the molecular sieve prepared by the method of the present invention has a high silicon-aluminum ratio, high hydrophobicity, and excellent adsorption performance.

[0112] Considering the fact that VOCs waste gas is accompanied by high humidity, large air volume, low concentration and other influencing factors in practical applications, it is very important to study the hydrophobicity and stability of the molecular sieve adsorbent. The molecular sieve prepared in Example 1 was applied to the saturated adsorption of xylene and ethyl acetate at different temperatures and humidities. At a temperature of 100°C and a humidity of 90%, it still has a high saturated adsorption capacity, so the hydrophobic effect and adsorption effect of the adsorption catalyst are excellent.

[0113]

[0114]

[0115] In summary, the present invention adopts organic bases and organic amines to form a composite template agent, which jointly guides the nucleus formation of the molecular sieve. Further, the surfactant polyvinyl pyrrolidone (PVP) is introduced, which can make the reaction raw materials uniformly dispersed in the solution system, quickly form a large number of nuclei in the early stage, and induce crystal growth. Microwave reaction avoids the generation of temperature gradients, heats the materials in the medium more evenly, and can significantly improve the synthesis efficiency and purity of the molecular sieve. Therefore, the adsorption capacity of the molecular sieve for VOCs is enhanced, the hydrophobicity is further enhanced, and the competitive adsorption of water molecules and VOCs molecules is reduced.

[0116] The present invention is not limited to the above-mentioned embodiments. On the basis of the technical solution disclosed in the present invention, technicians in this field can make some substitutions and deformations to some technical features therein according to the disclosed technical content without creative labor, and these substitutions and deformations are all within the protection scope of the present invention.

Claims

1. A method for preparing a high-silicon hydrophobic MFI type molecular sieve synthesized by a polyvinyl pyrrolidone modified composite template agent, characterized in that The following steps are involved: (1) Mixing the raw materials silicon source, alkali source, composite template and water, adding polyvinyl pyrrolidone to the mixture, stirring until clear, transferring to a reaction kettle, and using microwave reaction for 2 to 2.5 hours to obtain a gel precursor; The silicon source, the alkali source, the composite template agent, and water are composed in a mass ratio of 1:(0.003-0.015):(0.1-0.4):(1-10); the composite template agent is composed of an organic base and an organic amine; The amount of PVP added is 0.08-0.16% of the total mass of the mixture; (2) transferring to a homogeneous reactor, crystallizing at a constant temperature, and cooling to obtain a crystallized material; (3) adding an acid solution to the above-mentioned crystallized material, heating, stirring and acid treatment; (4) The flocculated material is subjected to filter pressing, water washing, drying, roasting and crushing to obtain a molecular sieve.

2. The method for preparing a high-silicon hydrophobic MFI type molecular sieve synthesized by a polyvinyl pyrrolidone modified composite template according to claim 1, characterized in that: In step (1), the silicon source is liquid silica sol; the alkali source is solid sodium hydroxide; the organic base in the composite template includes at least one of tetraethylammonium bromide and tetrapropylammonium bromide; the organic amine in the composite template includes at least one of n-butylamine, ethylamine and ethylenediamine.

3. The method for preparing a high-silicon hydrophobic MFI type molecular sieve synthesized by a polyvinyl pyrrolidone modified composite template according to claim 1, characterized in that: The organic base and the organic amine in the composite template of step (1) are mixed in a mass ratio of 1:(1.2-1.6).

4. The method for preparing a high-silicon hydrophobic MFI type molecular sieve synthesized by a polyvinyl pyrrolidone modified composite template according to claim 1, characterized in that: The average molecular weight of the polyvinyl pyrrolidone in step (1) is 8,000 to 700,000.

5. The method for preparing a high-silicon hydrophobic MFI type molecular sieve synthesized by a polyvinyl pyrrolidone modified composite template according to claim 4, characterized in that: The average molecular weight of the polyvinyl pyrrolidone is one of 8000, 40000, 160000 and 360000.

6. The method for preparing a high-silicon hydrophobic MFI type molecular sieve synthesized by a polyvinyl pyrrolidone modified composite template according to claim 1, characterized in that: The constant temperature crystallization in step (2) includes a first constant temperature of 110-120° C. for 15-16 hours and a second constant temperature of 180-190° C. for 12-13 hours.

7. The method for preparing a high-silicon hydrophobic MFI type molecular sieve synthesized by a polyvinyl pyrrolidone modified composite template according to claim 1, characterized in that: The concentration of the acid solution in step (3) is 0.2-0.5 mol / L; the acid treatment temperature is 70-80° C., and the stirring time is 2-3 h; and the amount of the acid solution added is 0.3-0.5% of the total mass of the mixture.

8. The method for preparing a high-silicon hydrophobic MFI type molecular sieve synthesized by a polyvinyl pyrrolidone modified composite template according to claim 1, characterized in that: The calcination temperature in step (4) is 530-630° C. and the time is 10-12 hours; the pulverization includes mechanical pulverization and air flow pulverization.

9. A high-silicon hydrophobic MFI molecular sieve synthesized by a polyvinyl pyrrolidone modified composite template agent, characterized in that: The method is prepared according to any one of claims 1 to 8.

10. The use of a high-silicon hydrophobic MFI type molecular sieve synthesized by a polyvinyl pyrrolidone modified composite template according to claim 9, characterized in that: Used to adsorb VOCs waste gas.

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