CN107417812B

CN107417812B - Spherical double-mesoporous-structure composite material, supported polyethylene catalyst and preparation methods thereof

Info

Publication number: CN107417812B
Application number: CN201610348274.9A
Authority: CN
Inventors: 亢宇; 张明森
Original assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Current assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Priority date: 2016-05-24
Filing date: 2016-05-24
Publication date: 2020-06-09
Anticipated expiration: 2036-05-24
Also published as: CN107417812A

Abstract

The invention relates to the field of catalysts, in particular to a spherical double-mesoporous structure composite material, a preparation method of the spherical double-mesoporous structure composite material, the spherical double-mesoporous structure composite material prepared by the method, a supported polyethylene catalyst, a preparation method of the supported polyethylene catalyst and the supported polyethylene catalyst prepared by the method. The invention discloses a spherical double-mesoporous structure composite material which comprises a mesoporous molecular sieve material with a hollow spherical structure, a mesoporous molecular sieve material with a three-dimensional cubic cage-shaped structure and silica gel. The spherical double-mesoporous-structure composite material provided by the invention has a stable mesoporous structure, can still keep an ordered mesoporous structure after an active component is loaded, and has high catalytic activity when the supported polyethylene catalyst prepared by the spherical double-mesoporous-structure composite material is used for catalyzing ethylene polymerization.

Description

Spherical double-mesoporous-structure composite material, supported polyethylene catalyst and preparation methods thereof

Technical Field

The invention relates to the field of catalysts, in particular to a spherical double-mesoporous structure composite material, a preparation method of the spherical double-mesoporous structure composite material, the spherical double-mesoporous structure composite material prepared by the method, a supported polyethylene catalyst, a preparation method of the supported polyethylene catalyst and the supported polyethylene catalyst prepared by the method.

Background

Since the synthesis of a regular mesoporous material with highly ordered pore channels by the company Mobile in 1992, the application of the mesoporous material in the fields of catalysis, separation, medicine and the like has attracted much attention due to the high specific surface, the regular pore channel structure and the narrow pore size distribution. A novel mesoporous material SBA-15 is synthesized by Zhao Dongyuan et al in 1998, which has highly ordered pore diameter (6-30nm) and large pore volume (1.0 cm)³Per g), thicker pore walls (4-6nm), retainedHigh mechanical strength and good catalytic adsorption performance (see D.Y.ZHao, J.L.Feng, Q.S.Huo, et al Science 279(1998) 548-. CN1341553A discloses a preparation method of a mesoporous molecular sieve carrier material, and the mesoporous material prepared by the method is used as a heterogeneous reaction catalyst carrier, so that the separation of a catalyst and a product is easy to realize.

However, the conventional ordered mesoporous material SBA-15 has a rod-like microscopic morphology, the flowability of the material is poor, and the high specific surface area and the high pore volume of the material cause the material to have strong water and moisture absorption capacity, so that the agglomeration of the ordered mesoporous material is further aggravated, and the storage, transportation, post-processing and application of the ordered mesoporous material are limited.

The development and application of polyethylene catalysts is a major breakthrough in the field of olefin polymerization catalysts after traditional ziegler-natta catalysts, which makes the research of polyethylene catalysts enter a rapidly developing stage. The homogeneous phase polyethylene catalyst has high activity, needs large catalyst consumption and high production cost, and the obtained polymer has no granular shape and cannot be used in a polymerization process of a slurry method or a gas phase method which is widely applied. An effective method for overcoming the above problems is to carry out a supporting treatment of the soluble polyethylene catalyst. At present, a great number of researches on the loading of polyethylene catalysts are reported. In order to develop new support/catalyst/cocatalyst systems in depth, it is necessary to develop different supports to drive the further development of the supported catalyst and polyolefin industries.

The mesoporous material of the supported polyethylene catalyst reported in the previous literature is MCM-41, and the catalytic activity of the MCM-41 which is treated by Methylaluminoxane (MAO) and then supported by the polyethylene catalyst after ethylene polymerization is 10⁶gPE/(mol Zr h). The reason that the mesoporous material MCM-41 is low in ethylene polymerization activity after loading a catalyst is mainly that the thermal stability and the hydrothermal stability of a pore wall structure of the MCM-41 are low, partial collapse of the pore wall is caused in the loading process, the loading effect is influenced, and the catalytic activity is influenced. Therefore, there is a need for a mesoporous material with a stable mesoporous structure, which can maintain the ordered mesoporous structure after loading.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a spherical double-mesoporous-structure composite material which has a stable mesoporous structure, can still keep ordered mesoporous materials after loading active components and has high activity when loading a polyethylene catalyst to catalyze ethylene polymerization reaction.

In order to achieve the above objects, in one aspect, the present invention provides a spherical double mesoporous structure composite material, wherein the composite material comprises a mesoporous molecular sieve material having a hollow spherical structure, a mesoporous molecular sieve material having a three-dimensional cubic cage structure, and silica gel, the composite material has a pore volume of 0.3 to 1.8mL/g and a specific surface area of 50 to 650m²The average particle size is 20-60 mu m, the pore diameters are distributed in a trimodal mode, the trimodal corresponds to a first most probable pore size, a second most probable pore size and a third most probable pore size respectively, the first most probable pore size is smaller than the second most probable pore size, the second most probable pore size is smaller than the third most probable pore size, the first most probable pore size is 1-9nm, the second most probable pore size is 10-17nm, and the third most probable pore size is 20-50 nm.

In a second aspect, the present invention provides a method for preparing a spherical double mesoporous structure composite material, comprising the steps of:

(1) providing a mesoporous molecular sieve material with a hollow spherical structure or preparing a filter cake of the mesoporous molecular sieve material with the hollow spherical structure as a component a;

(2) providing a mesoporous molecular sieve material with a three-dimensional cubic cage-like structure or preparing a filter cake of the mesoporous molecular sieve material with the three-dimensional cubic cage-like structure as a component b;

(3) providing silica gel or preparing a filter cake of silica gel as component c;

(4) mixing and ball-milling the component a, the component b, the component c and a binder, pulping solid powder obtained after ball-milling with water, and then spray-drying the obtained slurry;

wherein the pore volume of the composite material is 0.3-1.8mL/g and the specific surface area is 50-650m²/g，The average particle size is 20-60 μm, the pore diameters are distributed in a trimodal manner, and the trimodal corresponds to a first most probable pore size, a second most probable pore size and a third most probable pore size respectively, the first most probable pore size is smaller than the second most probable pore size, the second most probable pore size is smaller than the third most probable pore size, the first most probable pore size is 1-9nm, the second most probable pore size is 10-17nm, and the third most probable pore size is 20-50 nm.

In a third aspect, the invention provides a spherical double-mesoporous-structure composite material prepared by the preparation method.

In a fourth aspect, the present invention provides a supported polyethylene catalyst, which contains a carrier and a magnesium salt and/or a titanium salt supported on the carrier, wherein the carrier is the spherical double mesoporous structure composite material provided by the present invention.

In a fifth aspect, the present invention provides a method for preparing a supported polyethylene catalyst, the method comprising: in the presence of inert gas, the carrier is soaked in mother liquor containing magnesium salt and/or titanium salt, and then filtration and spray drying are sequentially carried out; wherein, the carrier is the spherical double-mesoporous structure composite material provided by the invention.

In a sixth aspect, the present invention provides a supported polyethylene catalyst prepared by the above process.

The mesoporous structure of the spherical double-mesoporous structure composite material provided by the invention is stable, the ordered mesoporous structure can be still maintained after the active component is loaded, the supported polyethylene catalyst prepared by the mesoporous structure has high catalytic activity when being used for catalyzing ethylene polymerization reaction, and a polyethylene product which has low bulk density and melt index and is not easy to break can be obtained at the same time, specifically, the bulk density of the prepared polyethylene product is below 0.42g/mL, the melt index is below 0.55g/10min, and the powder breaking rate is less than 3%.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

FIG. 1 is an X-ray diffraction pattern of a spherical double mesoporous composite material D1 according to example 1 of the present invention;

FIG. 2 is an SEM scanning electron micrograph of the micro-morphology of the spherical double mesoporous composite material D1 in example 1 of the invention;

fig. 3 is a pore size distribution diagram of the spherical double mesoporous structure composite material D1 according to example 1 of the present invention.

Detailed Description

The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

In a first aspect, the invention provides a spherical double-mesoporous structure composite material, wherein the composite material comprises a mesoporous molecular sieve material with a hollow spherical structure, a mesoporous molecular sieve material with a three-dimensional cubic cage-shaped structure and silica gel, the pore volume of the composite material is 0.3-1.8mL/g, and the specific surface area of the composite material is 50-650m²The average particle size is 20-60 mu m, the pore diameters are distributed in a trimodal mode, and the trimodal corresponds to a first most probable pore diameter, a second most probable pore diameter and a third most probable pore diameter respectively, wherein the first most probable pore diameter is 1-9nm, the second most probable pore diameter is 10-17nm, and the third most probable pore diameter is 20-50 nm.

In the invention, the average particle size of the spherical double-mesoporous structure composite material is measured by a laser particle size distribution instrument, the specific surface area, the pore volume and the most probable pore diameter are measured by a nitrogen adsorption method, and the surface morphology of the spherical double-mesoporous structure composite material is measured by a Scanning Electron Microscope (SEM). In the present invention, the average particle diameter is an average particle diameter.

In the invention, the particle size of the spherical double-mesoporous structure composite material is controlled within the range, so that the spherical double-mesoporous structure composite material is not easy to agglomerate, and the conversion rate of reaction raw materials in the ethylene polymerization reaction process can be improved by using the supported catalyst prepared by using the spherical double-mesoporous structure composite material as a carrier. When the specific surface area of the spherical double mesoporous structure composite material is less than 50m²When the volume/g and/or pore volume is less than 0.3mL/g, the catalytic activity of the supported catalyst prepared by using the supported catalyst is remarkably reduced; when the specific surface area of the spherical double mesoporous structure composite material is more than 650m²When the volume/g and/or pore volume is more than 1.8mL/g, the supported catalyst prepared by using the supported catalyst as a carrier is easy to agglomerate in the ethylene polymerization process, thereby influencing the monomer conversion rate in the ethylene polymerization process.

Preferably, the pore volume of the spherical double mesoporous structure composite material is 0.3-1.5mL/g, and the specific surface area is 60-500m²(iv) g, an average particle diameter of 40 to 60 μm, a first mode pore diameter of 2 to 8nm, a second mode pore diameter of 10 to 16nm, and a third mode pore diameter of 20 to 45 nm.

Further preferably, the pore volume of the spherical double mesoporous structure composite material is 0.3-0.9mL/g, and the specific surface area is 70-200m²(ii)/g, average particle diameter of 45-55 μm, first mode pore diameter of 3-8nm, second mode pore diameter of 10-16nm, and third mode pore diameter of 20-40 nm.

According to the present invention, the contents of the molecular sieve material having a hollow spherical structure and the silica gel in the spherical double mesoporous structure composite material are not particularly limited as long as the microscopic size of the spherical double mesoporous structure composite material satisfies the above conditions. Preferably, the weight ratio of the mesoporous molecular sieve material with the hollow spherical structure, the mesoporous molecular sieve material with the three-dimensional cubic cage-shaped structure and the silica gel is 1: 0.5-2: 0.5-2, preferably 1: 0.5-1.5: 0.5-1.5.

In a second aspect, the present invention provides a method for preparing a spherical double mesoporous structure composite material, which may include the steps of:

1) providing a mesoporous molecular sieve material with a hollow spherical structure or preparing a filter cake of the mesoporous molecular sieve material with the hollow spherical structure as a component a;

wherein the pore volume of the composite material is 0.3-1.8mL/g and the specific surface area is 50-650m²The average particle size is 20-60 mu m, the pore diameters are distributed in a trimodal mode, and the trimodal corresponds to a first most probable pore diameter, a second most probable pore diameter and a third most probable pore diameter respectively, wherein the first most probable pore diameter is 1-9nm, the second most probable pore diameter is 10-17nm, and the third most probable pore diameter is 20-50 nm.

In the step (1), the process of preparing a filter cake of the mesoporous molecular sieve material having a hollow spherical structure may include: in an acidic aqueous solution, in the presence of trimethylpentane and ethanol, a template agent is contacted with a silicon source, and a mixture obtained after the contact is crystallized and filtered.

In the step (1), the molar ratio of the template agent, the ethanol, the trimethylpentane and the silicon source is 1: 100-500: 200-500: 50-200, preferably 1: 180-400: 250-400: 70-150.

In step (1), the templating agent may be various templating agents conventionally used in the art. Preferably, the templating agent is a triblock copolymer polyethylene glycol-polyglycerol-polyethylene glycol, which is commercially available (e.g., from Aldrich under the trade name P123, formula EO)₂₀PO₇₀EO₂₀₂And Mn of 5800) or can be prepared by various conventional methods. When the template agent is polyethylene glycol-polyglycerol-polyethylene glycol, the mole number of the template agent is calculated according to the average molecular weight of the polyethylene glycol-polyglycerol-polyethylene glycol.

In step (1), the silicon source may be various silicon sources conventionally used in the art, and preferably the silicon source is tetramethoxysilane.

In step (1), the acidic aqueous solution may be various acidic aqueous solutions conventionally used in the art, and preferably, the acidic aqueous solution is a buffer solution of acetic acid and sodium acetate having a pH value of 1 to 6.

In step (1), the conditions for contacting the templating agent with the silicon source may include: the temperature is 10-60 ℃, the time is 10-72h, and the pH value is 1-7; preferably, the conditions under which the templating agent is contacted with the silicon source may include: the temperature is 10-20 deg.C, and the time is 10-30 h. In order to further facilitate uniform mixing between the substances, the contacting of the templating agent and the silicon source is preferably performed under stirring conditions. The dosage of the acidic aqueous solution is preferably such that the pH value of the contact reaction system of the template agent and the silicon source is 1-7.

In the step (1), the crystallization conditions may include: the temperature is 30-150 ℃, and the time is 10-40 h; preferably, the temperature is 40-80 ℃ and the time is 20-30 h. Further preferably, the crystallization is performed by a hydrothermal crystallization method.

In the step (1), in the above-described process of preparing a filter cake of the mesoporous molecular sieve material having a hollow spherical structure, the process of obtaining the filter cake by filtration may include: after filtration, repeated washing with deionized water (washing times may be 2 to 10) and suction filtration.

In the step (1), "providing the mesoporous molecular sieve material having a hollow spherical structure" may be a product obtained by directly weighing or selecting the mesoporous molecular sieve material having a hollow spherical structure, or may be a product obtained by preparing the mesoporous molecular sieve material having a hollow spherical structure. The preparation method of the mesoporous molecular sieve material having a hollow spherical structure may be performed according to a conventional method, and for example, the preparation method may include: a filter cake of mesoporous molecular sieve material having a hollow spherical structure is prepared according to the above method, and the resulting filter cake is then dried.

In the step (2), the process of preparing a filter cake of the mesoporous molecular sieve material having a three-dimensional cubic cage-like structure may include: in an acidic aqueous solution, in the presence of potassium sulfate, a template agent is contacted with a silicon source, and a mixture obtained after the contact is crystallized and filtered.

In the step (2), the molar ratio of the template to the silicon source may be 1: 20-200, preferably 1: 100-200. More preferably, the molar ratio of the template agent to the potassium sulfate can be 1: 100-800, more preferably 1: 200-400.

In step (2), the templating agent may be various templating agents conventionally used in the art. Preferably, the templating agent is a triblock copolymer polyoxyethylene-polyoxypropylene-polyoxyethylene, which is commercially available (e.g., from Fuka corporation under the trade name

F108, molecular formula EO₁₃₂PO₆₀EO₁₃₂And Mn is 14600), or can be prepared by a conventional method. When the template is polyoxyethylene-polyoxypropylene-polyoxyethylene, the number of moles of the template is calculated from the average molecular weight of polyoxyethylene-polyoxypropylene-polyoxyethylene.

In the step (2), the silicon source may be various silicon sources conventionally used in the art, preferably the silicon source is at least one of tetraethoxysilane, methyl orthosilicate, propyl orthosilicate, sodium orthosilicate and silica sol, more preferably tetraethoxysilane.

In step (2), the acidic aqueous solution may be various acidic aqueous solutions conventionally used in the art, and for example, may be an aqueous solution of at least one of hydrochloric acid, sulfuric acid, nitric acid, and hydrobromic acid, and is preferably an aqueous hydrochloric acid solution.

In step (2), the conditions for contacting the templating agent with the silicon source may include: the temperature is 25-60 ℃, the time is 10-72h, and the pH value is 1-7; preferably, the conditions under which the templating agent is contacted with the silicon source may include: the temperature is 35-45 deg.C, and the time is 20-30 h. In order to further facilitate uniform mixing between the substances, the contacting of the templating agent and the silicon source is preferably performed under stirring conditions. The dosage of the acidic aqueous solution is preferably such that the pH value of the contact reaction system of the template agent and the silicon source is 1-7.

In the step (2), the crystallization conditions may include: the temperature is 90-150 ℃, and the time is 10-40 h; preferably, the temperature is 90-120 ℃ and the time is 20-30 h. Further preferably, the crystallization is performed by a hydrothermal crystallization method.

In the step (2), in the above-described process of preparing a filter cake of a mesoporous molecular sieve material having a three-dimensional cubic cage-like structure, the process of obtaining the filter cake by filtration may include: after filtration, repeated washing with deionized water (washing times may be 2 to 10) and suction filtration.

In the step (2), "providing the mesoporous molecular sieve material having a three-dimensional cubic cage structure" may be a product obtained by directly weighing or selecting the mesoporous molecular sieve material having a three-dimensional cubic cage structure, or may be a product obtained by preparing the mesoporous molecular sieve material having a three-dimensional cubic cage structure. The preparation method of the mesoporous molecular sieve material having a three-dimensional cubic cage structure may be performed according to a conventional method, and for example, the preparation method may include: a filter cake of a mesoporous molecular sieve material having a three-dimensional cubic cage-like structure is prepared according to the above method, and the resulting filter cake is then dried.

In the step (3), the process of preparing the filter cake of silica gel may include: the water glass is contacted with the polyhydric alcohol in the presence of the mineral acid, and the mixture obtained after the contact is filtered.

In the step (3), the polyol is not particularly limited in the present invention, and preferably the polyol is at least one of ethylene glycol, propylene glycol and glycerin, preferably ethylene glycol and/or glycerin, and more preferably glycerin.

In the step (3), the conditions for contacting the water glass with the polyol in the present invention are not particularly limited, and may be appropriately determined according to the conventional process for preparing silica gel. Preferably, the contacting conditions include: the temperature is 10-60 ℃, preferably 30-45 ℃; the time is 1 to 5 hours, preferably 1 to 3 hours; the pH value is 2-4, preferably 2.5-3.5.

In order to facilitate the uniform mixing of the materials, the contact reaction of the water glass and the polyol is preferably carried out under stirring.

Preferably, the weight ratio of the water glass, the inorganic acid and the polyhydric alcohol is 3-6: 2-3: 1; more preferably 3 to 5: 1: 1.

the water glass is an aqueous solution of sodium silicate, and the concentration thereof may be 3 to 20% by weight, preferably 10 to 20% by weight.

The inorganic acid may be various inorganic acids conventionally used in the art, and for example, may be at least one of sulfuric acid, nitric acid, and hydrochloric acid. The inorganic acid may be used in a pure form or in the form of an aqueous solution thereof. The inorganic acid is preferably used in such an amount that the pH of the contact reaction system of water glass and a polyhydric alcohol is 2 to 4.

In step (3), "providing silica gel" may be directly weighing or selecting the silica gel product, or preparing the silica gel. The method for preparing silica gel may be carried out according to conventional methods, and may include, for example: a filter cake of silica gel was prepared according to the above method and the resulting filter cake was then dried.

According to the present invention, in step (4), the amount and type of the binder are not particularly limited, and in order to improve the strength of the spherical mesoporous composite material and further improve the performance of the polyethylene product, the amount of the component b may be 50 to 150 parts by weight, the amount of the component c may be 50 to 150 parts by weight, and the amount of the binder may be 1 to 10 parts by weight, relative to 100 parts by weight of the component a. Preferably, the binder is polyvinyl alcohol and/or polyethylene glycol, more preferably polyvinyl alcohol.

In the step (4), the ball milling may be performed in a ball mill, the inner wall of a ball milling pot in the ball mill is preferably agate lining, and the diameter of the milling balls in the ball mill may be 2-3 mm; the number of the grinding balls can be reasonably selected according to the size of the ball milling tank, and for the ball milling tank with the size of 50-150mL, 1 grinding ball can be generally used; the material of the grinding ball can be agate, polytetrafluoroethylene and the like, and agate is preferred. The ball milling conditions may include: the rotation speed of the grinding ball is 200-; preferably, the rotation speed of the grinding balls is 300-.

In the step (4), the process of slurrying the solid powder obtained after ball milling with water may be performed at 25 to 60 ℃. In the pulping process, the weight ratio of the solid powder to the amount of water may be 1:0.1-5, preferably 1: 0.5-3.5.

In step (4), the spray drying may be carried out according to conventional means, for example in an atomizer. The conditions of the spray drying may include: the temperature is 150-; preferably, the spray drying conditions include: the temperature is 150-250 ℃, and the rotating speed is 11000-13000 r/min.

In the step (4), when the component a is a filter cake of a mesoporous molecular sieve material having a hollow spherical structure and the component b is a filter cake of silica gel, that is, when the step (1) is a process of preparing a filter cake of a mesoporous molecular sieve material having a hollow spherical structure and the step (2) is a process of preparing a filter cake of silica gel, the method for preparing a spherical double mesoporous structure composite material may further include: after the spray-drying process of step (3), the template is removed from the spray-dried product. Preferably, the conditions for removing the template agent include: the temperature is 90-600 ℃, and more preferably 400-600 ℃; the time is 10 to 80 hours, more preferably 10 to 24 hours.

In a third aspect, the invention also provides the spherical double-mesoporous-structure composite material prepared by the method.

In a fourth aspect, the invention further provides a supported polyethylene catalyst, which comprises a carrier and magnesium salt and/or titanium salt supported on the carrier, wherein the carrier is the spherical double mesoporous structure composite material provided by the invention.

According to the present invention, in the supported catalyst, the content of the magnesium salt and/or the titanium salt is not particularly limited, and may be suitably determined according to the supported catalyst which is conventional in the art, for example, the content of the carrier is 90 to 99% by weight, and the sum of the contents of the magnesium salt and the titanium salt in terms of magnesium element and titanium element, respectively, is 1 to 10% by weight, based on the total weight of the catalyst; preferably, the content of the carrier is 91-98 wt%, and the sum of the contents of the magnesium salt and the titanium salt calculated by magnesium element and titanium element respectively is 2-9 wt%; further preferably, the content of the carrier is 91.5 to 95% by weight, and the sum of the contents of the magnesium salt and the titanium salt in terms of magnesium element and titanium element, respectively, is 5 to 8.5% by weight.

In the present invention, the catalyst may be prepared according to various methods conventionally used in the art, as long as a magnesium salt and/or a titanium salt is supported on the spherical double mesoporous structure composite material.

In a fifth aspect, the present invention also provides a method for preparing a supported polyethylene catalyst, comprising: in the presence of inert gas, the carrier is soaked in mother liquor containing magnesium salt and/or titanium salt, and then is sequentially filtered and dried; wherein, the carrier is the spherical double-mesoporous structure composite material provided by the invention.

According to the invention, the impregnation conditions may include: the temperature is 25-100 ℃, and the time is 0.1-5 h; preferably, the impregnation conditions include: the temperature is 40-60 ℃ and the time is 1-3 h.

In the present invention, the amount of the magnesium salt and the titanium salt is not particularly limited, and preferably, the amount of the carrier, the magnesium salt and the titanium salt is such that the content of the carrier is 90 to 99 wt% and the sum of the contents of the magnesium salt and the titanium salt in terms of magnesium element and titanium element, respectively, is 1 to 10 wt% in the prepared supported polyethylene catalyst, based on the total weight of the catalyst; more preferably, the content of the carrier is 91-98 wt%, and the sum of the contents of the magnesium salt and the titanium salt calculated by magnesium element and titanium element is 2-9 wt%; further preferably, the content of the carrier is 91.5 to 95% by weight, and the sum of the contents of the magnesium salt and the titanium salt in terms of magnesium element and titanium element, respectively, is 5 to 8.5% by weight.

In a preferred embodiment of the present invention, the magnesium salt and the titanium salt are used in a weight ratio of 1:0.1 to 2, preferably 1: 0.5-2.

In the present invention, the magnesium salt may be various magnesium salts conventionally used in the art, for example, may be one or more of magnesium chloride, magnesium sulfate, magnesium nitrate and magnesium bromide, and is preferably magnesium chloride.

In the present invention, the titanium salt may be various titanium salts conventionally used in the art, and for example, titanium tetrachloride and/or titanium trichloride may be mentioned.

In the invention, the content of the elements in the catalyst can be measured by adopting an X-ray fluorescence spectrum analysis method.

The mother liquor may preferably further contain an organic solvent for dissolving the magnesium salt and the titanium salt, and the organic solvent is not particularly limited in the present invention as long as the magnesium salt and the titanium salt can be dissolved, and for example, isopropanol and tetrahydrofuran may be used, and the volume ratio of isopropanol to tetrahydrofuran may be 1: 1-3, preferably 1: 1-1.5.

In the present invention, the drying conditions for the preparation of the catalyst in the present invention are not particularly limited, and may be various conditions commonly used in the art; preferably, the preparation of the catalyst also comprises a washing process after filtration and before drying, and/or a milling process after drying. The washing and milling conditions can be selected by the person skilled in the art according to the practical circumstances and will not be described in detail here.

In the present invention, the inert gas is a gas which does not react with the raw materials and the product, and may be, for example, nitrogen gas or at least one of group zero element gases in the periodic table, preferably nitrogen gas, which is conventional in the art.

In a sixth aspect, the present invention also provides a supported polyethylene catalyst prepared by the above process.

The present invention will be described in detail below by way of examples.

In the following examples and comparative examples, polyethylene glycol-polyglycerol-polyethylene glycol was purchased from Aldrich under the trade name P123 and the formula EO₂₀PO₇₀EO₂₀₂The molecular weight Mn was 5800.

Polyoxyethylene-polyoxypropylene-polyoxyethylene is available from Fuka under the trade name

F108, molecular formula EO₁₃₂PO₆₀EO₁₃₂Abbreviated as F108, and an average molecular weight Mn of 14600

In the following examples and comparative examples, X-ray diffraction analysis was carried out on an X-ray diffractometer, model D8Advance, available from Bruker AXS, Germany; scanning electron microscopy analysis was performed on a scanning electron microscope, model XL-30, available from FEI, USA; pore structure parameter analysis was performed on a nitrogen desorption apparatus model Autosorb-1 available from corna, usa, wherein the sample was degassed at 200 ℃ for 4 hours before testing; the X-ray fluorescence analysis was carried out on an X-ray fluorescence analyzer of the Netherlands company, model Axios-Advanced.

The bulk density of the polyolefin powder was determined by the method specified in GB/T1636-2008.

Polymer melt index: measured according to ASTM D1238-99.

Polyethylene pulverization rate: determined by sieving through a 800 mesh screen.

Example 1

This example is used to illustrate the spherical double mesoporous composite material and supported catalyst of the present invention and their preparation methods.

(1) Preparation of spherical double-mesoporous structure composite material

Adding 1g (0.00017mol) of template P123 and 1.69g (0.037mol) of ethanol into 28mL of acetic acid and sodium acetate buffer solution with pH value of 4.4, stirring at 15 ℃ until the template is completely dissolved, adding 6g (0.05mol) of trimethylpentane into the solution, stirring at 15 ℃ for 8h, adding 2.13g (0.014mol) of tetramethoxysilane into the solution, stirring at 15 ℃ for 20h, transferring the solution into an agate-lined reaction kettle, oven-crystallizing at 60 ℃ for 24h, filtering, washing with deionized water for 4 times, and suction-filtering to obtain a filter cake A1 of mesoporous molecular sieve material with a hollow spherical structure.

1.46g (0.0001mol) of template F108 and 5.24g (0.03mol) of K₂SO₄Stirring with 60g hydrochloric acid solution with equivalent concentration of 2 at 38 ℃ until F108 is completely dissolved; adding 4.2g (0.02mol) of tetraethoxysilane into the solution, stirring for 15min at 38 ℃, and standing for 24h at 38 ℃; then transferring the mixture into an agate-lined reaction kettle, crystallizing the mixture for 24 hours at the temperature of 100 ℃, then filtering the mixture, washing the mixture for 4 times by using deionized water, and then carrying out suction filtration to obtain a filter cake B1 of the mesoporous molecular sieve material with the three-dimensional cage-shaped structure.

Mixing 15 wt% of water glass, 12 wt% of sulfuric acid solution and glycerol in a weight ratio of 5: 1: 1, then adjusting the pH value to 3 with 98 wt% sulfuric acid, then carrying out suction filtration on the obtained reaction mass, and washing with distilled water until the content of sodium ions is 0.02 wt%, thus obtaining a filter cake C1 of silica gel.

And (2) putting 10g of the prepared filter cake A1, 10g of the prepared filter cake B1, 10g of the prepared filter cake C1 and 0.5g of polyvinyl alcohol into a 100mL ball milling tank together, wherein the ball milling tank is made of agate, grinding balls are made of agate, the diameter of each grinding ball is 3mm, the number of the grinding balls is 1, and the rotating speed is 400 r/min. Sealing the ball milling tank, and carrying out ball milling for 5 hours in the ball milling tank at the temperature of 25 ℃ to obtain solid powder; dissolving the solid powder in 25g of deionized water, and spray-drying at 200 ℃ at a rotating speed of 12000 r/min; and calcining the product obtained after spray drying in a muffle furnace at 550 ℃ for 10h, and removing the template agent to obtain the spherical double-mesoporous-structure composite material D1.

The spherical double-mesoporous structure composite material D1 is characterized by an XRD, a scanning electron microscope and a nitrogen adsorption instrument.

FIG. 1 is an X-ray diffraction pattern, and it can be seen that the spherical double mesoporous composite material D1 has a hollow spherical structure unique to mesoporous materials.

FIG. 2 is a SEM image of the spherical double mesoporous structure composite material D1, which shows that the spherical double mesoporous structure composite material D1 has a micro-sphere with a particle size of 20-60 μm and good dispersibility.

Fig. 3 is a pore size distribution diagram of the spherical double mesoporous composite material D1, and it can be seen from the diagram that the spherical double mesoporous composite material D1 has a three-pore structure distribution and uniform pore channels.

The pore structure parameters of the spherical double mesoporous structure composite material D1 are shown in table 1 below.

TABLE 1

*: the first most probable aperture, the second most probable aperture and the third most probable aperture are separated by commas.

(2) Preparation of the catalyst

0.1g of magnesium chloride and 0.1g of titanium tetrachloride were dissolved in 10mL of a composite solvent of tetrahydrofuran and isopropanol (the volume ratio of tetrahydrofuran to isopropanol was 1: 1.2) to form a catalyst mother liquor. 1g of the spherical double mesoporous structure composite material D1 was added to the mother liquor at 45 ℃ for immersion for 1h, then filtered, and washed with n-hexane for 4 times, dried at 75 ℃ and ground to obtain the catalyst E1.

As a result of X-ray fluorescence analysis, in the catalyst E1 described in this example, the content of magnesium was 7.17% by weight and the content of titanium was 1.3% by weight, in terms of element.

Comparative example 1

Commercially available ES955 silica Gel (GRACE) was calcined under nitrogen at 400 deg.C for 10h to remove hydroxyl groups and residual moisture, thereby obtaining heat-activated ES955 silica gel.

A catalyst was prepared by following the procedure of step (2) of example 1, except that the same parts by weight of the above-mentioned activated ES955 silica gel was used instead of the spherical mesoporous composite material D1, thereby preparing a comparative catalyst DE 1.

As a result of X-ray fluorescence analysis, in comparative catalyst DE1, the content of magnesium was 3.0% by weight and the content of titanium was 1.2% by weight in terms of element.

Comparative example 2

A spherical double mesoporous structure composite material and a catalyst were prepared according to the same method as in example 1, except that, in the preparation of the spherical double mesoporous structure composite material in the step (1), 10g of the filter cake a1, 10g of the filter cake B1, and 10g of the filter cake C1 were put together in a 100mL ball mill pot, that is, polyvinyl alcohol was not added as a binder. Thus, comparative catalyst DE2 was prepared.

As a result of X-ray fluorescence analysis, in comparative catalyst DE2, the content of magnesium element was 2.1% by weight and the content of titanium element was 1.3% by weight in terms of element.

Example 2

(1) Preparation of spherical double-mesoporous structure composite material

Adding 1g (0.00017mol) of template P123 and 1.4g (0.03mol) of ethanol into 28mL of acetic acid and sodium acetate buffer solution with the pH value of 4.4, stirring at 10 ℃ until the template is completely dissolved, adding 4.56g (0.04mol) of trimethylpentane into the solution, stirring at 10 ℃ for 8 hours, adding 1.83g (0.012mol) of tetramethoxysilane into the solution, stirring at 10 ℃ for 30 hours, transferring the solution into an agate-lined reaction kettle, oven-crystallizing at 80 ℃ for 20 hours, filtering, washing with deionized water for 6 times, and suction-filtering to obtain a filter cake A2 of mesoporous molecular sieve material with a hollow spherical structure.

1.46g (0.0001mol) of template F108 and 6.96g (0.04mol) of K₂SO₄Stirring with 60g hydrochloric acid solution with equivalent concentration of 2 at 38 ℃ until F108 is completely dissolved; adding 3.1g (0.015mol) of tetraethoxysilane into the solution, stirring for 15min at 45 ℃, and standing for 30h at 45 ℃; then transferring the mixture into an agate-lined reaction kettle, crystallizing the mixture for 30 hours at 120 ℃, then filtering the mixture, washing the mixture for 4 times by using deionized water, and performing suction filtration to obtain a filter cake B2 of the mesoporous molecular sieve material with the three-dimensional cage-shaped structure.

Mixing 20 wt% of water glass, 12 wt% of sulfuric acid solution and propylene glycol in a weight ratio of 4: 1: 1, and then the reaction was carried out for 3 hours at 40 ℃, followed by adjusting the pH to 4 with sulfuric acid having a concentration of 98% by weight, then the resulting reaction mass was subjected to suction filtration, and washed with distilled water until the sodium ion content was 0.02% by weight, to obtain a filter cake C2 of silica gel.

10g of the filter cake A2, 15g of the filter cake B2, 15g of the filter cake C2 and 0.9g of polyvinyl alcohol are put into a 100mL ball milling tank together, wherein the ball milling tank is made of agate, grinding balls are made of agate, the diameter of each grinding ball is 3mm, the number of the grinding balls is 1, and the rotating speed is 500 r/min. Sealing the ball milling tank, and carrying out ball milling for 10 hours in the ball milling tank at the temperature of 30 ℃ to obtain solid powder; dissolving the solid powder in 100g of deionized water, and spray-drying at 150 ℃ at the rotating speed of 13000 r/min; calcining the product obtained after spray drying in a muffle furnace at 600 ℃ for 15h, and removing the template agent to obtain the spherical double-mesoporous-structure composite material D2.

The pore structure parameters of the spherical double mesoporous structure composite material D2 are shown in table 2 below.

TABLE 2

(2) Preparation of the catalyst

0.1g of magnesium chloride and 0.2g of titanium tetrachloride were dissolved in 10mL of a composite solvent of tetrahydrofuran and isopropanol (the volume ratio of tetrahydrofuran to isopropanol was 1: 1.5) to form a catalyst mother liquor. 1g of the spherical double mesoporous structure composite material D2 was added to the mother liquor at 60 ℃ for immersion for 1h, then filtered, and washed with n-hexane for 4 times, dried at 75 ℃ and ground to obtain catalyst E2.

The catalyst E2 in this example had a magnesium content of 6.0 wt.% and a titanium content of 1.7 wt.% as measured by X-ray fluorescence analysis.

Example 3

(1) Preparation of spherical double-mesoporous structure composite material

Adding 1g (0.00017mol) of template P123 and 3.13g (0.068mol) of ethanol into 28mL of acetic acid and sodium acetate buffer solution with the pH value of 4.4, stirring at 20 ℃ until the template is completely dissolved, adding 7.75g (0.068mol) of trimethylpentane into the solution, stirring at 20 ℃ for 8h, adding 3.8g (0.025mol) of tetramethoxysilane into the solution, stirring at 20 ℃ for 10h, transferring the solution into an agate-lined reaction kettle, oven-crystallizing at 40 ℃ for 30h, filtering, washing with deionized water for 6 times, and suction-filtering to obtain a filter cake A3 of the mesoporous molecular sieve material with a hollow spherical structure.

1.46g (0.0001mol) of template F108 and 3.48g (0.02mol) of K₂SO₄Stirring with 60g hydrochloric acid solution with equivalent concentration of 2 at 38 ℃ until F108 is completely dissolved; adding 2.1g (0.01mol) of tetraethoxysilane into the solution, stirring at 35 ℃ for 15min, and standing at 35 ℃ for 20 h; then transferring the mixture into a reaction kettle with an agate inner lining, crystallizing the mixture for 20 hours at 90 ℃, then filtering the mixture, washing the mixture for 4 times by using deionized water, and then carrying out suction filtration to obtain a filter cake B3 of the mesoporous molecular sieve material with the three-dimensional cage-shaped structure.

Mixing water glass with the concentration of 10 weight percent, sulfuric acid solution with the concentration of 12 weight percent and ethylene glycol according to the weight ratio of 3: 1: 1, then adjusting the pH value to 2 with sulfuric acid with the concentration of 98 weight percent, then carrying out suction filtration on the obtained reaction material, and washing the reaction material with distilled water until the content of sodium ions is 0.02 weight percent to obtain a filter cake C3 of silica gel.

10g of the filter cake A3, 5g of the filter cake B3, 5g of the filter cake C3 and 0.2g of polyethylene glycol are put into a 100mL ball milling tank together, wherein the ball milling tank is made of agate, grinding balls are made of agate, the diameter of each grinding ball is 3mm, the number of the grinding balls is 1, and the rotating speed is 300 r/min. Sealing the ball milling tank, and carrying out ball milling for 20 hours in the ball milling tank at the temperature of 50 ℃ to obtain solid powder; dissolving the solid powder in 50g of deionized water, and spray-drying at 250 ℃ at the rotating speed of 11000 r/min; and calcining the product obtained after spray drying in a muffle furnace at 400 ℃ for 24h, and removing the template agent to obtain the spherical double-mesoporous-structure composite material D3.

The pore structure parameters of the spherical double mesoporous structure composite material D3 are shown in table 3 below.

TABLE 3

(2) Preparation of the catalyst

0.2g of magnesium chloride and 0.1g of titanium tetrachloride were dissolved in 10mL of a composite solvent of tetrahydrofuran and isopropanol (the volume ratio of tetrahydrofuran to isopropanol was 1: 1) to form a catalyst mother liquor. 1g of the spherical double mesoporous structure composite material D3 was added to the mother liquor at 40 ℃ for immersion for 3h, then filtered, and washed with n-hexane for 4 times, dried at 75 ℃ and ground to obtain the catalyst E3.

The catalyst E3 in this example had a magnesium content of 6.2 wt% and a titanium content of 1.32 wt% calculated as element, as determined by X-ray fluorescence analysis.

Example 4

A spherical double mesoporous structure composite material and a catalyst were prepared according to the same method as in example 1, except that, in the preparation of the spherical double mesoporous structure composite material in the step (1), glycerol was not added in the preparation of the filter cake of silica gel, to obtain a spherical double mesoporous structure composite material D4 and a catalyst E4.

The pore structure parameters of the spherical double mesoporous structure composite material D4 are shown in table 4 below.

TABLE 4

The catalyst E4 in this example had a magnesium content of 5.9 wt% and a titanium content of 1.1 wt% calculated as element, as determined by X-ray fluorescence analysis.

Experimental example 1

This experimental example is used to illustrate the application of the supported catalyst provided by the present invention.

In a 2L stainless steel high pressure polymerization reactor, nitrogen and ethylene were each replaced three times, then 200mL of hexane was added, the reactor was warmed to 80 ℃ and 800mL of hexane was added, 2mL of a 1mol/L Triethylaluminum (TEA) solution in hexane was added with the addition of hexane, then 0.5g of catalyst component E1 was added, ethylene gas was introduced, the pressure was raised to 1.0MPa and maintained at 1.0MPa, and after 1 hour of reaction at 70 ℃, separation by suction filtration was carried out to obtain a polyethylene pellet powder. The polyethylene granular powder was measured to have a Bulk Density (BD) of 0.41g/mL and a melt index MI_2.16The powder grinding rate is less than 2 percent when the powder is 0.4g/10 min. The efficiency of the catalyst was found by calculation to be 2715gPE/gcat h.

Experimental comparative example 1

Polymerization of ethylene was carried out in accordance with the procedure of experimental example 1, except that the catalyst E1 prepared from example 1 was replaced with the same parts by weight of comparative catalyst DE1 prepared from comparative example 1. The polyethylene granular powder obtained had a Bulk Density (BD) of 0.4g/mL and a melt index MI_2.16Pulverizing into pieces of 0.87g/10minThe powder rate is more than 8 percent. The efficiency of the catalyst was found by calculation to be 1767g PE/gcat h.

Experimental comparative example 2

Polymerization of ethylene was carried out in accordance with the procedure of experimental example 1, except that the catalyst E1 prepared from example 1 was replaced with the same parts by weight of comparative catalyst DE2 prepared from comparative example 2. The polyethylene granular powder obtained had a Bulk Density (BD) of 0.45g/mL and a melt index MI_2.16When the powder is equal to 0.67g/10min, the crushing rate is more than 8 percent. The efficiency of the catalyst was determined by calculation to be 1050g PE/gcat h.

Experimental example 2

In a 2L stainless steel high pressure polymerization reactor, nitrogen and ethylene were each replaced three times, then 200mL of hexane was added, the reactor was warmed to 75 ℃ and 900mL of hexane was added, 2mL of a 1mol/L Triethylaluminum (TEA) solution in hexane was added with the addition of hexane, then 0.1g of catalyst component E2 was added, ethylene gas was introduced, the pressure was raised to 1MPa and maintained at 1MPa, and after 1.5 hours of reaction at 75 ℃ the reaction solution was separated by suction filtration to obtain polyethylene pellet powder. The polyethylene granular powder obtained had a Bulk Density (BD) of 0.4g/mL and a melt index MI_2.16When the powder is equal to 0.55g/10min, the crushing rate is less than 3 percent. The efficiency of the catalyst was found by calculation to be 2150g PE/gcat h.

Experimental example 3

In a 2L stainless steel high pressure polymerization reactor, nitrogen and ethylene were each replaced three times, then 200mL of hexane was added, the reactor was warmed to 85 ℃ and 700mL of hexane was added, 2mL of a 1mol/L Triethylaluminum (TEA) solution in hexane was added with the addition of hexane, then 1g of catalyst component E3 was added, ethylene gas was introduced, the pressure was raised to 1MPa and maintained at 1MPa, and after reacting at 85 ℃ for 2 hours, separation by suction filtration, a polyethylene pellet powder was obtained. The polyethylene pellet powder obtained had a Bulk Density (BD) of 0.42g/mL and a melt index MI_2.16When the powder is equal to 0.47g/10min, the crushing rate is less than 3 percent. Warp gaugeThe catalyst efficiency was determined to be 2200g PE/gcat h.

Experimental example 4

Polymerization of ethylene was carried out in accordance with the procedure of Experimental example 1, except that the same parts by weight of comparative catalyst E4 prepared in example 4 was used in place of catalyst E1 prepared in example 1. The polyethylene granular powder obtained had a Bulk Density (BD) of 0.4g/mL and a melt index MI_2.16The powder grinding rate is less than 3 percent when the powder is 0.4g/10 min. The efficiency of the catalyst was found by calculation to be 2050g PE/gcat h.

From the results of comparing the experimental examples 1 to 4 with the experimental comparative examples 1 to 2, it can be seen that when the spherical double mesoporous structure composite material and the supported catalyst provided by the present invention are used in an ethylene polymerization reaction, the catalyst has high catalytic activity, and a polyethylene product with low bulk density and melt index and not easy to break can be obtained, specifically, the bulk density of the prepared polyethylene product is below 0.42g/mL, the melt index is below 0.55g/10min, and the powder breaking rate is less than 3%.

The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.

It should be noted that the various features described in the above embodiments may be combined in any suitable manner without departing from the scope of the invention. The invention is not described in detail in order to avoid unnecessary repetition.

In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.

Claims

1. A spherical composite material with dual mesoporous structure is characterized by thatThe composite material contains mesoporous molecular sieve material with a hollow spherical structure, mesoporous molecular sieve material with a three-dimensional cubic cage-like structure and silica gel, wherein the pore volume of the composite material is 0.3-1.8mL/g, and the specific surface area is 50-650m²The average particle size is 20-60 mu m, the pore diameters are distributed in a trimodal mode, and the trimodal corresponds to a first most probable pore diameter, a second most probable pore diameter and a third most probable pore diameter respectively, wherein the first most probable pore diameter is 1-9nm, the second most probable pore diameter is 10-17nm, and the third most probable pore diameter is 20-50 nm;

the preparation method of the spherical double-mesoporous structure composite material comprises the following steps:

wherein, in the step (4), the component b is used in an amount of 50 to 150 parts by weight, the component c is used in an amount of 50 to 150 parts by weight, and the binder is used in an amount of 1 to 10 parts by weight, relative to 100 parts by weight of the component a.

2. The composite material according to claim 1, wherein the weight ratio of the mesoporous molecular sieve material having a hollow spherical structure, the mesoporous molecular sieve material having a three-dimensional cubic cage structure, and the silica gel is 1: 0.5-1.5: 0.5-1.5.

3. A method for preparing a spherical double mesoporous structure composite material comprises the following steps:

4. The method as set forth in claim 3, wherein, in the step (4), the component b is used in an amount of 50-150 parts by weight, the component c is used in an amount of 50-150 parts by weight, and the binder is used in an amount of 1-10 parts by weight, relative to 100 parts by weight of the component a.

5. The method of claim 3, wherein the binder is polyvinyl alcohol and/or polyethylene glycol.

6. The method of claim 3, wherein the binder is polyvinyl alcohol.

7. The method according to claim 3, wherein, in the step (1), the process of preparing the filter cake of the mesoporous molecular sieve material having the hollow spherical structure comprises: in an acidic aqueous solution, in the presence of trimethylpentane and ethanol, a template agent is contacted with a silicon source, and a mixture obtained after the contact is crystallized and filtered.

8. The method of claim 7, wherein the molar ratio of the templating agent, ethanol, trimethylpentane, and silicon source is 1: 100-500: 200-500: 50-200.

9. The method of claim 7, wherein the molar ratio of the templating agent, ethanol, trimethylpentane, and silicon source is 1: 180-400: 250-400: 70-150.

10. The method of claim 7, wherein the templating agent is a triblock copolymer polyethylene glycol-polyglycerol-polyethylene glycol; the silicon source is tetramethoxysilane; the acidic aqueous solution is acetic acid and sodium acetate buffer solution with pH value of 1-6.

11. The method of claim 7, wherein the conditions of the contacting comprise: the temperature is 10-60 ℃, the time is 10-72 hours, and the pH value is 1-7; the crystallization conditions include: the temperature is 30-150 ℃ and the time is 10-72 hours.

12. The method of claim 3, wherein, in step (2), the process of preparing a filter cake of mesoporous molecular sieve material having a three-dimensional cubic cage structure comprises: in an acidic aqueous solution, in the presence of a template agent and potassium sulfate, the template agent is contacted with a silicon source, and a mixture obtained after the contact is crystallized and filtered.

13. The method as claimed in claim 12, wherein, in step (2), the molar ratio of the template to the silicon source is 1: 20-200.

14. The method of claim 12, wherein the templating agent is a triblock copolymer polyoxyethylene-polyoxypropylene-polyoxyethylene; the silicon source is at least one of ethyl orthosilicate, methyl orthosilicate, propyl orthosilicate, sodium orthosilicate and silica sol; the acidic aqueous solution is at least one aqueous solution of hydrochloric acid, sulfuric acid, nitric acid and hydrobromic acid.

15. The method of claim 12, wherein the conditions of the contacting comprise: the temperature is 25-60 ℃, the time is 10-72 hours, and the pH value is 1-7; the crystallization conditions include: the temperature is 90-150 ℃ and the time is 10-40 hours.

16. The method according to claim 3, wherein, in the step (3), the process of preparing the filter cake of silica gel comprises: the water glass is contacted with the polyhydric alcohol in the presence of the mineral acid, and the mixture obtained after the contact is filtered.

17. The method of claim 16, wherein in step (3), the polyol is at least one of ethylene glycol, propylene glycol, and glycerol.

18. The method of claim 16, wherein the polyol is ethylene glycol and/or glycerol.

19. The method of claim 16, wherein the weight ratio of the water glass, the inorganic acid, and the polyol is 3-6: 2-3: 1.

20. the method of claim 16, wherein in step (3), the conditions of the contacting comprise: the temperature is 10-60 ℃, the time is 1-5 hours, and the pH value is 2-4; the inorganic acid is at least one of sulfuric acid, nitric acid and hydrochloric acid.

21. The method of claim 3, wherein, in step (4), the ball milling conditions comprise: the rotation speed of the grinding ball is 300-; the conditions of the spray drying include: the temperature is 150-600 ℃, and the rotating speed is 10000-15000 r/min.

22. The method of any one of claims 3-6, wherein component a is a filter cake of a mesoporous molecular sieve material having a hollow sphere-like structure, component b is a filter cake of a mesoporous molecular sieve material having a three-dimensional cubic cage-like structure, and component c is a filter cake of silica gel, the method further comprising: after the spray-drying process of step (3), the template is removed from the spray-dried product.

23. The method of claim 22, wherein the conditions to remove the templating agent comprise: the temperature is 90-600 ℃, and the time is 10-80 hours.

24. A spherical dual mesoporous structure composite material prepared by the method of any of claims 3-23.

25. A supported polyethylene catalyst comprising a carrier and a magnesium salt and/or a titanium salt supported on the carrier, wherein the carrier is the spherical double mesoporous structure composite material according to any one of claims 1 to 2 and 24.

26. The catalyst according to claim 25, wherein the carrier is contained in an amount of 90 to 99% by weight, and the sum of the contents of the magnesium salt and the titanium salt is 1 to 10% by weight, in terms of magnesium element and titanium element, respectively, based on the total weight of the catalyst.

27. A method for preparing a supported polyethylene catalyst, the method comprising: in the presence of inert gas, the carrier is soaked in mother liquor containing magnesium salt and/or titanium salt, and then filtration and spray drying are sequentially carried out; wherein the carrier is the spherical double mesoporous structure composite material according to any one of claims 1-2 and 24.

28. The method of claim 27, wherein the conditions of the impregnation comprise: the temperature is 25-100 ℃ and the time is 0.1-5 h.

29. The process of claim 27, wherein the support, magnesium salt and titanium salt are used in amounts such that the support is present in an amount of 90 to 99 wt%, and the sum of the amounts of the magnesium salt and titanium salt, calculated as magnesium and titanium, respectively, is 1 to 10 wt%, based on the total weight of the catalyst, in the preparation of the supported polyethylene catalyst.

30. A supported polyethylene catalyst prepared by the process of any one of claims 27-29.