阅读说明：本技术 改性介孔分子筛及其制备方法 (Modified mesoporous molecular sieve and preparation method thereof ) 是由 夏长久 林民 郑爱国 彭欣欣 朱斌 舒兴田 于 2019-10-29 设计创作，主要内容包括：本发明涉及分子筛制备领域,具体涉及一种改性介孔分子筛及其制备方法。所述分子筛包括：介孔分子筛、氟元素和金属元素,所述金属元素选自IVB族金属元素和IVA族金属元素中的至少一种；金属元素、氟元素和介孔分子筛的摩尔比为1：(0.1-10)：(10-100),其中,所述改性介孔分子筛的表面金属元素含量与体相金属元素含量的比在2以上。采用本发明提供的方法制得的改性介孔分子筛活性好,有利于提高催化反应转化率和产物选择性。(The invention relates to the field of molecular sieve preparation, in particular to a modified mesoporous molecular sieve and a preparation method thereof. The molecular sieve comprises: a mesoporous molecular sieve, fluorine and a metal element selected from at least one of group IVB metal elements and group IVA metal elements; the molar ratio of the metal element to the fluorine element to the mesoporous molecular sieve is 1: (0.1-10): (10-100), wherein the ratio of the surface metal element content to the bulk metal element content of the modified mesoporous molecular sieve is more than 2. The modified mesoporous molecular sieve prepared by the method provided by the invention has good activity and is beneficial to improving the conversion rate of catalytic reaction and the selectivity of products.)

1. A modified mesoporous molecular sieve, the molecular sieve comprising: a mesoporous molecular sieve, fluorine and a metal element selected from at least one of group IVB metal elements and group IVA metal elements; the molar ratio of the metal element to the fluorine element to the mesoporous molecular sieve is 1: (0.1-10): (10-100), wherein the ratio of the surface metal element content to the bulk metal element content of the modified mesoporous molecular sieve is more than 2.

2. The molecular sieve according to claim 1, wherein the ratio of the surface metal element content to the bulk metal element content of the modified mesoporous molecular sieve is 2-6, preferably 2.1-5.1;

preferably, the modified mesoporous molecular sieve has an average radial diameter of 7 to 35 μm, preferably 7 to 30 μm.

3. The molecular sieve of claim 1, wherein the modified mesoporous molecular sieve satisfies I₉₆₀/I₈₀₀Above 3, preferably 3.4 to 6, wherein I₉₆₀The infrared absorption spectrum of the molecular sieve is 960cm^-1Absorption intensity in the vicinity, I₈₀₀The infrared absorption spectrum of the molecular sieve is 800cm^-1Absorption strength in the vicinity.

4. The molecular sieve of any one of claims 1-3, wherein the mesoporous molecular sieve is selected from at least one of SBA-15, MCM-41, MCM-48, HMS, KIT-6, and MSU;

preferably, the metal element is at least one selected from the group consisting of Ti element, Zr element, Sn element, and Ge element;

preferably, the molar ratio of the metal element, the fluorine element and the mesoporous molecular sieve is 1: (0.2-5): (40-75).

5. A method for preparing a modified mesoporous molecular sieve, comprising:

(1) mixing a metal source, a fluorine source, an organic matter and optionally a silicon source to obtain a first material;

(2) mixing the first material with a mesoporous molecular sieve to obtain a second material;

(3) aging the second material under conditions comprising: the temperature is 20-100 ℃, and the time is 0.5-24 h;

(4) drying and roasting the aged product;

the organic matter is organic polycarboxylic acid and/or organic acyl ketone;

the metal is at least one selected from a group IVB metal element and a group IVA metal element.

6. The method according to claim 5, wherein the molar ratio of the metal source, the fluorine source, the organic substance, and the silicon source is 1: (0.1-12): (0.1-12): (0-12), preferably 1: (0.4-6): (0.4-6): (0.4-6), the silicon source is SiO₂And (6) counting.

7. The production method according to claim 5 or 6, wherein the metal is at least one selected from a Ti element, a Zr element, a Sn element, and a Ge element;

preferably, the metal source is selected from TiCl₄、TiOSO₄、TiCl₃、TiF₄、H₂TiF₆、(NH₄)₂TiF₆、SnCl₄、ZrCl₄And ZrF₄At least one of;

preferably, the fluorine source is selected from NH₄F. At least one of NaF, KF, and HF;

preferably, the silicon source is an organic silicon source and/or an inorganic silicon source;

further preferably, the silicon source is selected from H₂SiF₆、SiF₄、SiCl₄、(NH₄)₂SiF₆And ethyl orthosilicate.

8. The production method according to claim 5 or 6, wherein the organic polycarboxylic acid is selected from at least one of oxalic acid, citric acid, EDTA, and tartaric acid;

the organic acyl ketone is at least one of acetylacetone, bicyclohexanoneoxalyl dihydrazone, sulfonyl triazolone and 3-carbethoxy-4-piperanone.

9. The production method according to any one of claims 5 to 8, wherein the mesoporous molecular sieve is selected from at least one of SBA-15, MCM-41, MCM-48, HMS, KIT-6, and MSU;

preferably, the molar ratio of the metal source to the mesoporous molecular sieve is 1: (10-100), more preferably 1: (20-60), wherein the mesoporous molecular sieve is SiO₂And (6) counting.

10. The production method according to any one of claims 5 to 9, wherein the aging conditions include: the temperature is 20-80 ℃, and the time is 0.5-18 h;

preferably, the aging conditions include: aging at 25-70 deg.C for 1-12 h;

preferably, the calcination in step (4) is carried out at a temperature of 350-880 ℃, preferably 350-700 ℃, more preferably 400-600 ℃.

11. The production method according to any one of claims 5 to 10, wherein the method further comprises: introducing an acid to adjust the pH in step (1) and/or step (2), preferably in step (2);

preferably, the pH of the first and second materials is 1 to 7, more preferably 3 to 6.5, independently of each other.

12. The modified mesoporous molecular sieve prepared by the preparation method of any one of claims 5 to 11.

Technical Field

The invention relates to the field of molecular sieve preparation, in particular to a modified mesoporous molecular sieve and a preparation method thereof.

Background

Along with the need of people for catalytic oxidation of macromolecular organic matters, research on inserting heteroatoms into mesoporous molecular sieves is underway, and significant breakthroughs are made for titanium-containing mesoporous molecular sieves, Sn-MCM-41, Zr-SBA-15, Nb-SBA-15, mesoporous molecular sieves doped with other metals and the like.

The titanium-containing molecular sieve uniformly inserts four-coordinate titanium atoms into a molecular sieve framework space matrix through isomorphous substitution, and unique catalytic oxidation performance is endowed. At present, a plurality of titanium-containing microporous materials TS-1, Ti-beta, ETS, Ti-Y and the like are widely concerned by researchers, wherein the TS-1 molecular sieve realizes the development from a laboratory to industrialization and is successfully applied to a plurality of hydrocarbon selective catalytic oxidation processes. However, all microporous titanium-containing molecular sieves have small pore sizes and cannot meet the requirement that macromolecular reactants are diffused to be close to active sites, so researchers are constantly striving to develop catalytic materials with larger pore sizes. Researchers of Mobil corporation in 1992 adopt alkyl quaternary ammonium salt cationic surfactant to synthesize M41s series mesoporous molecular sieve materials, the mesoporous molecular sieve materials have the advantages of large specific surface area and pore size and the like, the development of large-pore-size titanium-containing catalytic oxidation materials is possible, and successively proposed preparation schemes comprise direct hydrothermal synthesis, grafting or secondary synthesis. Corma et al firstly insert Ti atoms into the amorphous pore walls of MCM-41 molecular sieves by direct hydrothermal synthesis, not only leaving the mesoporous structure well, but also the Ti atoms exist in a tetradentate form and can react with H₂O₂The activity of the catalyst in the catalytic epoxidation reaction of 1-hexene is better than that of the TS-1 molecular sieve. One then surrounds the alkaline water hot standThe Ti-MCM-41 molecular sieve is synthesized or secondarily synthesized, and a large amount of research on synthesis and application is carried out, but the application of the Ti-MCM-41 molecular sieve in catalytic oxidation is greatly limited due to the influence of the inherent poor hydrothermal stability of the MCM-41 molecular sieve. Compared with MCM-41 molecular sieves, SBA-15 molecular sieves directly synthesized in strong acid environments such as Zhao Dongyuan and the like have higher wall thickness and hydrothermal stability, and the pore diameter is easy to modulate (5-30nm), so that the SBA-15 molecular sieves are widely applied to the fields of catalysis, biology, medical treatment, adsorption separation and the like.

The mesoporous SBA-15 molecular sieve is synthesized in a strong acid environment, but the system is not beneficial to realizing the direct synthesis of the metal mesoporous molecular sieve. For example, the mesoporous Ti-SBA-15 molecular sieve has the hydrolysis rate of the titanium source far higher than that of the silicon source in the strong acid environment, and the titanium source is hydrolyzed into TiO before the molecular sieve structure is formed₂And cannot be inserted into the molecular sieve framework. Aiming at the defects, a means of introducing various organic matters into an acidic synthesis method as a protective agent of a titanium source can be adopted, and the purpose is to draw the hydrolysis rates of the titanium source and a silicon source to be matched, so that a part of Ti atoms can be inserted into the walls of mesoporous pores to synthesize the Ti-SBA-15 molecular sieve with certain activity, but the method still has a plurality of defects. Meanwhile, the secondary synthesis method for preparing Ti-SBA-15 molecular sieve attracts wide attention, for example, Tatsumi and the like perform secondary crystallization treatment in hydrothermal environment after statically mixing titanium silicon nanocluster sol prepared in TPAOH solution and SBA-15 molecular sieve. The Ti-SBA-15 molecular sieve prepared in the way shows good activity in the epoxidation reaction of cyclohexene, but the preparation process of the method is complicated.

From the above, the existing modified mesoporous molecular sieve has the problems of difficult direct synthesis, low efficiency of metal insertion into the molecular sieve framework, complex preparation process and the like, and a more effective novel process for directly synthesizing the modified mesoporous molecular sieve still needs to be developed.

Disclosure of Invention

The invention aims to solve the problems of difficult direct synthesis of a modified mesoporous molecular sieve, low efficiency of metal insertion into a molecular sieve framework and complex preparation process in the prior art, and provides a modified mesoporous molecular sieve and a preparation method thereof. The modified mesoporous molecular sieve prepared by the method provided by the invention has good activity and is beneficial to improving the conversion rate of catalytic reaction and the selectivity of products.

In order to achieve the above object, a first aspect of the present invention provides a modified mesoporous molecular sieve comprising: a mesoporous molecular sieve, fluorine and a metal element selected from at least one of group IVB metal elements and group IVA metal elements; the molar ratio of the metal element to the fluorine element to the mesoporous molecular sieve is 1: (0.1-10): (10-100), wherein the ratio of the surface metal element content to the bulk metal element content of the modified mesoporous molecular sieve is more than 2.

Preferably, the ratio of the surface metal element content to the bulk metal element content of the modified mesoporous molecular sieve is 2-6, preferably 2.1-5.1.

Preferably, the modified mesoporous molecular sieve satisfies I₉₆₀/I₈₀₀Above 3, preferably 3.4 to 6, wherein I₉₆₀The infrared absorption spectrum of the molecular sieve is 960cm^-1Absorption intensity in the vicinity, I₈₀₀The infrared absorption spectrum of the molecular sieve is 800cm^-1Absorption strength in the vicinity.

Preferably, the mesoporous molecular sieve is selected from at least one of SBA-15, MCM-41, MCM-48, HMS, KIT-6 and MSU.

In a second aspect, the present invention provides a method for preparing a modified mesoporous molecular sieve, comprising:

(1) mixing a metal source, a fluorine source, an organic matter and optionally a silicon source to obtain a first material;

(2) mixing the first material with a mesoporous molecular sieve to obtain a second material;

(3) aging the second material under conditions comprising: the temperature is 20-100 ℃, and the time is 0.5-24 h;

(4) drying and roasting the aged product;

the organic matter is organic polycarboxylic acid and/or organic acyl ketone;

the metal is at least one selected from a group IVB metal element and a group IVA metal element.

In a third aspect, the present invention provides a modified mesoporous molecular sieve prepared by the preparation method described above.

The modified mesoporous molecular sieve provided by the invention has the advantages of simple preparation process, low raw material cost, mild conditions and no harm to the environment, metal atoms can be effectively inserted into the amorphous pore wall of the mesoporous molecular sieve in a four-coordination form, the metal atoms are enriched on the surface, and the non-framework metal content is low. Preferably, in an acidic environment during the preparation process, the soluble low-polymer silicon atoms and the metal atoms form a copolymer, so that the generation of chemical bonds between the metal atoms and oxygen atoms is reduced, and the generation of metal oxides is avoided. The results of the examples show that the modified mesoporous molecular sieve provided by the invention has smaller average radial diameter of particles, the minimum average radial diameter is 7 μm, and the modified mesoporous molecular sieve has higher conversion rate of reaction raw materials and product selectivity during phenol hydroxylation reaction, the highest utilization rate of hydrogen peroxide can reach 99%, the highest conversion rate of phenol can reach 99%, and the highest total selectivity of products catechol and hydroquinone can reach 90%.

Drawings

FIG. 1 is a SEM representation of the Ti-SBA-15 mesoporous molecular sieve prepared in example 1;

FIG. 2 is a SEM representation of the Ti-SBA-15 mesoporous molecular sieve prepared in comparative example 1.

Detailed Description

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 the present invention, "radial direction" is relative to the modified mesoporous molecular sieve, that is, the direction extending along the length direction of the modified mesoporous molecular sieve is an axial direction, and the direction perpendicular to the axial direction is a radial direction, and it should be noted that these terms are only used for illustrating the present invention, and are not used for limiting the present invention. In the present invention, "optionally" means that the technical feature connected with "optionally" may be included, or the technical feature connected with "optionally" may not be included. The numerical ranges appearing in the present invention each include the two endpoints that make up the numerical range.

In a first aspect, the present invention provides a modified mesoporous molecular sieve comprising: a mesoporous molecular sieve, fluorine and a metal element selected from at least one of group IVB metal elements and group IVA metal elements; the molar ratio of the metal element to the fluorine element to the mesoporous molecular sieve is 1: (0.1-10): (10-100), wherein the ratio of the surface metal element content to the bulk metal element content of the modified mesoporous molecular sieve is more than 2.

According to the present invention, the molar ratio of the metal element, the fluorine element and the mesoporous molecular sieve can be measured by an XRF method.

In the invention, the content of the surface metal element is determined by adopting an X-ray photoelectron spectroscopy method, and the content of the bulk metal element is determined by adopting an X-ray fluorescence spectroscopy method. The test methods are carried out according to conventional methods without special requirements and are well known to those skilled in the art.

In a preferable case, the ratio of the surface metal element content to the bulk metal element content of the modified mesoporous molecular sieve is 2 to 6, preferably 2.1 to 5.1. The metal elements of the modified mesoporous molecular sieve provided by the invention are enriched on the surface, and under the preferable condition, the modified mesoporous molecular sieve has better catalytic performance.

According to the present invention, preferably, the modified mesoporous molecular sieve has an average radial diameter of 7 to 35 μm, preferably 7 to 30 μm. The average radial diameter of the modified mesoporous molecular sieve is measured by a TEM method.

According to the present invention, preferably, the modified mesoporous molecular sieve satisfies I₉₆₀/I₈₀₀Above 3, preferably 3.4 to 6, wherein I₉₆₀The infrared absorption spectrum of the molecular sieve is 960cm^-1Absorption intensity in the vicinity, I₈₀₀The infrared absorption spectrum of the molecular sieve is 800cm^-1Absorption strength in the vicinity.

In the present invention, the absorption intensity of the infrared absorption spectrum of the molecular sieve at a specific wave number refers to the absorption intensity of the fourier transform infrared absorption spectrum of the molecular sieve at a specific wave number, which is well known to those skilled in the art and will not be described herein.

In the invention, the absorption intensity of the infrared absorption spectrum of the molecular sieve at a specific wave number is measured by adopting an infrared spectroscopy (IR), the test method can be carried out according to a conventional method, the invention has no special requirement, is well known by the technical personnel in the field, and is not described herein again.

According to the present invention, preferably, the mesoporous molecular sieve is selected from at least one of SBA-15, MCM-41, MCM-48, HMS, KIT-6 and MSU. The adoption of the optimal selection mode is more beneficial to improving the catalytic performance of the modified mesoporous molecular sieve.

In the invention, the mesoporous molecular sieve can be obtained by commercial products or can be prepared by the existing method.

According to the present invention, the modifying metal element is selected from at least one of a group IVB metal element and a group IVA metal element, preferably, the modifying metal element is selected from at least one of a Ti element, a Zr element, a Sn element, and a Ge element, more preferably, at least one of a Ti element, a Zr element, and a Sn element, and most preferably, a Ti element.

According to a preferred embodiment of the present invention, the molar ratio of the metal element, the fluorine element and the mesoporous molecular sieve is 1: (0.2-5): (40-75). In such a preferable ratio, it is more advantageous to increase the reaction conversion rate and the product selectivity.

In a second aspect, the present invention provides a method for preparing a modified mesoporous molecular sieve, comprising:

(1) mixing a metal source, a fluorine source, an organic matter and optionally a silicon source to obtain a first material;

(2) mixing the first material with a mesoporous molecular sieve to obtain a second material;

(3) aging the second material under conditions comprising: the temperature is 20-100 ℃, and the time is 0.5-24 h;

(4) drying and roasting the aged product;

the metal is at least one selected from a group IVB metal element and a group IVA metal element.

According to the method provided by the present invention, the selection of the metal can be as described above, and is not described herein again.

The metal source of the present invention can be selected from a wide range of metals as long as the metal source can provide the metal, for example, a soluble salt containing a metal. Preferably, the metal source is selected from TiCl₄、TiOSO₄、TiCl₃、TiF₄、H₂TiF₆、(NH₄)₂TiF₆、SnCl₄、ZrCl₄And ZrF₄At least one of (1).

In the present invention, the fluorine source may be selected from a wide range as long as it can provide fluorine, for example, hydrofluoric acid and/or a fluorine-containing soluble salt. Preferably, the fluorine source is selected from NH₄F. At least one of NaF, KF and HF.

In the present invention, the term "soluble" means that the solvent can be dissolved directly or dissolved in a solvent under the action of a cosolvent.

In the present invention, the organic substance is selected from a wide range, and is preferably an organic polycarboxylic acid and/or an organic acyl ketone. The organic substance may be the organic polycarboxylic acid alone, the organic acyl ketone alone, or a mixture of the organic polycarboxylic acid and the organic acyl ketone. Further preferably, the organic substance is an organic polycarboxylic acid or an organic acyl ketone.

According to the present invention, the organic polycarboxylic acid may be a dicarboxylic or higher polycarboxylic acid. In the present invention, the number of carbon atoms of the organic polycarboxylic acid is selected from a wide range, and for example, the number of carbon atoms may be 2 to 10.

According to the present invention, preferably, the organic polycarboxylic acid is selected from at least one of oxalic acid, citric acid, EDTA and tartaric acid.

According to the present invention, the organic acyl ketone refers to an organic compound containing an acyl group and a ketone group, preferably, the organic acyl ketone is at least one selected from the group consisting of acetylacetone, bicyclohexanoneoxalyl dihydrazone, sulfonitriazolone and 3-ethoxycarbonyl-4-piperanone, preferably acetylacetone.

In the present invention, the optional silicon source in step (1) means that the silicon source may or may not be introduced when the first material is obtained by mixing. Preferably, the silicon source is introduced while mixing in step (1).

The silicon source selection range of the invention is wider, and the silicon source can be various silicon sources which are conventionally used in the field. Specifically, the silicon source is an organic silicon source and/or an inorganic silicon source. Preferably, the silicon source is selected from H₂SiF₆、SiF₄、SiCl₄、(NH₄)₂SiF₆And ethyl orthosilicate. The adoption of the preferred embodiment is more beneficial to improving the catalytic performance of the prepared molecular sieve.

According to the present invention, the fluorine source and the silicon source may be introduced in the form of a solution (e.g., an aqueous solution).

According to the present invention, the mixing process in step (1) may optionally further include a solvent, if the metal source, the fluorine source, the organic substance and optionally the silicon source satisfy the requirement of uniform mixing, i.e. the solvent does not need to be introduced, and the solvent (preferably water) needs to be introduced otherwise. The amount of the solvent to be introduced in the present invention is not particularly limited, and may be appropriately selected depending on the amounts of the metal source, the fluorine source, the organic substance, and optionally the silicon source to be introduced, as long as the requirement of sufficient mixing can be satisfied.

According to a preferred embodiment of the present invention, the step (1) comprises: and mixing a metal source, a fluorine source, an organic matter, a solvent and a silicon source to obtain the first material.

In the present invention, the mixing in the step (1) is not particularly limited, and may be performed under stirring conditions or ultrasonic conditions. Preferably, the mixing in step (1) is carried out under ultrasound, which is more favorable for material mixing.

According to a preferred embodiment of the present invention, the metal source, the fluorine source and the mesoporous molecular sieve are used in such amounts that the modified mesoporous molecular sieve is obtained in which the molar ratio of the modified metal element, the fluorine element and the mesoporous molecular sieve is 1: (0.1-10): (10-100), preferably 1: (0.2-5): (40-75). It should be noted that, if the metal source and the silicon source contain F element during the preparation process, which can provide part of F element, the amount of the fluorine source can be reduced accordingly. The person skilled in the art knows how to select the metal source, the fluorine source and the ratio of the amount of mesoporous molecular sieve based on the above disclosure.

According to the present invention, it is preferable that the molar ratio of the metal source, the fluorine source, the organic substance, and the silicon source is 1: (0.1-12): (0.1-12): (0-12), preferably 1: (0.4-6): (0.4-6): (0.4-6), the silicon source is SiO₂And (6) counting.

According to the method provided by the invention, the selection of the mesoporous molecular sieve is as described above, and details are not repeated here.

According to the present invention, preferably, the molar ratio of the metal source to the mesoporous molecular sieve is 1: (10-100), more preferably 1: (20-60), wherein the mesoporous molecular sieve is SiO₂And (6) counting.

In the present invention, the mixing in the step (2) is not particularly limited, and may be performed under stirring conditions as long as the mesoporous molecular sieve and the first material are uniformly mixed.

In the present invention, in order to further optimize the aging effect, it is preferable that the aging in step (3) is performed under stirring conditions. The stirring is preferably carried out using a magnetic stirrer.

Preferably, the aging conditions include: the temperature is 20-80 ℃ and the time is 0.5-18 h.

Further preferably, the aging conditions include: the aging temperature is 25-70 ℃, and the aging time is 1-12 h. Under the preferable condition, the prepared modified mesoporous molecular sieve is more beneficial to obtaining high material conversion rate and product selectivity.

According to an embodiment of the present invention, the method may further include: filtering and washing the aged product to obtain an aged product before the drying in the step (4). The filtration and washing are all operations well known to those skilled in the art, and the present invention is not particularly limited.

The conditions for the drying in step (4) are particularly limited in the present invention, and may be those well known to those skilled in the art. For example, the drying conditions may include: the temperature is 80-180 ℃ and the time is 1-20 hours.

Preferably, the calcination in step (4) is carried out at a temperature of 350-. The selection range of the roasting time is wide, and the roasting time is preferably 1 to 10 hours, more preferably 2 to 6 hours.

According to the present invention, preferably, the method further comprises: introducing acid to adjust the pH in the step (1) and/or the step (2). It should be noted that, in this preferred embodiment, the acid may be introduced separately in step (1) to adjust the pH of the first material, may be introduced separately in step (2) to adjust the pH of the second material, or may be introduced in both step (1) and step (2) to adjust the pH of the first material and the second material. As long as the pH of the material to be aged (the second material) can be adjusted. It is preferred to introduce an acid to adjust the pH in step (2).

The acid may be at least one of various acids conventionally used in the art, such as nitric acid, hydrochloric acid, acetic acid, and carbonic acid.

In the conventional preparation method, the hydrolysis rate of the metal source is higher than that of the silicon source under acidic conditions, and the metal source is hydrolyzed into corresponding metal oxide before being combined with the mesoporous molecular sieve, so that the metal source cannot be inserted into the molecular sieve framework. The preparation method of the modified mesoporous molecular sieve overcomes the defects, the addition of the fluorine source influences the occurrence state of metal atoms, the formation of chemical bonds between the metal atoms and oxygen atoms is reduced, and the production of metal oxides is avoided.

Preferably, the pH of the first and second materials is 1 to 7, more preferably 3 to 6.5, independently of each other. In the preferable case, the conversion rate and the product selectivity of the obtained modified mesoporous molecular sieve are more favorably improved.

The modified mesoporous molecular sieve provided by the invention is easier to directly synthesize, and the efficiency of inserting the metal into the molecular sieve framework is high, so that the third aspect of the invention provides the modified mesoporous molecular sieve prepared by the preparation method.

The modified mesoporous molecular sieve material prepared by the invention has the advantages that metal atoms are enriched on the surface, the ratio of the content of surface metal elements to the content of bulk metal elements is more than 2, the activity is better, the average radial diameter is smaller, and the high catalytic reaction rate and the product selectivity can be obtained.

The present invention will be described in detail with reference to examples, but the scope of the present invention is not limited thereto.

In the following examples and comparative examples, the reagents used were all commercially available analytical reagents.

Hydrochloric acid, silicon tetrachloride, Tetraethoxysilane (TEOS), titanium trichloride and titanium tetrachloride are analytically pure and purchased from chemical reagents of national medicine group, Inc.;

the SBA-15 mesoporous molecular sieve is produced by Hunan Jianchang petrochemical company; MCM-41, HMS, KIT-6 and MCM-48 all-silicon mesoporous molecular sieves were synthesized according to the monograph (Zhao Dongyuan et al, ordered mesoporous molecular sieve materials [ M ]. higher education publishers, 2012).

The average radial diameter of the particles of the modified mesoporous molecular sieve prepared in the embodiment is measured by a TEM method; the molar ratio of the metal element, the fluorine element and the mesoporous molecular sieve is measured by an XRF method.

In the present invention, the surface metal element content was measured by an ESCALab250 type X-ray photoelectron spectrometer of Thermo Scientific, and the bulk metal element content was measured by a 3271E type X-ray fluorescence spectrometer of japan physical electrical machinery corporation, and the ratio of the surface metal element content/the bulk metal element content of the modified mesoporous molecular sieves prepared in examples and comparative examples is shown in table 2.

In the invention, the Fourier transform infrared absorption spectrum of a sample is measured on a Nicolet 8210 type Fourier infrared spectrometer, KBr tablets (the sample accounts for 1 wt%) are adopted under vacuum, and the test range is 400-1400cm^-1. I of the modified mesoporous molecular sieves prepared in the examples and comparative examples was measured₉₆₀And I₈₀₀And is combined with₉₆₀/I₈₀₀The ratio data are shown in Table 2, I₉₆₀The infrared absorption spectrum of the molecular sieve is 960cm^-1Absorption intensity in the vicinity, I₈₀₀The infrared absorption spectrum of the molecular sieve is 800cm^-1Absorption strength in the vicinity.

The room temperature means 25 ℃ without particular limitation.

In the following examples, the silicon source and the molecular sieve are both SiO₂And (6) counting.

Example 1

(1) Mixing a metal source, a fluorine source, an organic matter and a silicon source in an ultrasonic environment to form a colorless transparent solution; the proportions and types of the metal source, fluorine source, organic substance and silicon source used are shown in Table 1;

(2) adding the colorless transparent solution into a suspension containing the SBA-15 molecular sieve which is continuously stirred, and then adding 0.1mol/L hydrochloric acid to adjust the pH value to 6.1-6.2;

(3) continuously stirring and aging the suspension obtained in the step (2) for 2 hours at the temperature of 40 ℃;

(4) and (4) sequentially filtering and washing the product obtained in the step (3) to obtain an aged product, drying at 120 ℃ for 4 hours, and roasting at 550 ℃ for 3 hours to obtain the Ti-SBA-15 mesoporous molecular sieve S-1. Of the mesoporous molecular sieve S-1, the mesoporous molecular Sieve (SiO)₂Calculated), the molar ratio of fluorine and the modifying metal element are listed in table 2.

FIG. 1 is a SEM characteristic spectrum of Ti-SBA-15 mesoporous molecular sieve S-1, and it can be seen from the graph that Ti-SBA-15 mesoporous molecular sieve S-1 has a smaller average radial diameter, and the average radial diameter of the modified mesoporous molecular sieve S-1 is shown in Table 2.

Examples 2 to 31

Modified mesoporous molecular sieves S-2 to S-31 were prepared according to the method of example 1, except that the metal source, fluorine source, organic substance and silicon source used in step (1) were different in the ratio and kind of the used amount and the aging condition in step (3), and the specific conditions of the respective examples are shown in Table 1.

Average radial diameter of modified mesoporous molecular sieves S-2 to S-31 and mesoporous molecular sieves (in SiO)₂Calculated), the molar ratio of fluorine and the modifying metal element are listed in table 2.

Comparative example 1

The Ti-SBA-15 mesoporous molecular sieve material is directly synthesized according to the method reported in the Applied Catalysis A, General,2004,273(1-2), 185-191. TEOS and titanium trichloride are respectively used as a silicon source and a metal titanium source, a triblock copolymer P123 (molecular weight is 5800) is used as a structure directing agent, a concentrated hydrochloric acid aqueous solution is used as an acid source, and the specific synthesis steps are as follows:

(1) 2g P123 was dissolved in 60ml of hydrochloric acid solution at pH 5;

(2) after 4.25g of tetraethyl orthosilicate (TEOS) had been prehydrolyzed at 40 ℃ for a period of time, 0.02g of TiCl was added to the acidic solution with vigorous stirring₃Mixing with 2ml hydrogen peroxide solution, and stirring for 24 hours;

(3) the resulting mixture was statically aged at 60 ℃ for 24 hours;

(4) the resulting aged product was recovered, washed, and dried at 100 ℃ overnight. Calcining for 6h at 550 ℃ in the air to obtain the Ti-SBA-15 mesoporous molecular sieve D-1.

FIG. 2 is a SEM representation of Ti-SBA-15 mesoporous molecular sieve D-1, and it can be seen from a comparison of FIG. 2 and FIG. 1 that Ti-SBA-15 mesoporous molecular sieve D-1 has a larger average radial diameter and that the average radial diameter of mesoporous molecular sieve D-1 is shown in Table 2.

Comparative example 2

Ti-MCM-41 was synthesized by microwave hydrothermal method according to the method reported in Journal of Environmental Sciences,2016,44: 76-87. Cationic surfactant Cetyl Trimethyl Ammonium Bromide (CTAB) is used as template agent. Titanium isopropoxide and sodium silicate (Na)₂SiO₃) The method is used as a metal titanium source and a silicon source respectively, and comprises the following specific synthetic steps:

(1) 4.25g CTAB and 5.32g Na were added₂SiO₃Dissolving the two solutions in 30mL and 15mL of deionized water respectively, mixing the two solutions, and then stirring vigorously for 30 minutes at room temperature;

(2) adding 0.45g of titanium isopropoxide into the mixture, stirring for 180min, and adjusting the pH value of the mixed solution to 9.5-10.0 by using 0.1mol/L hydrochloric acid;

(3) heating the mixed solution at 100 ℃ for 180 minutes under the 120W microwave hydrothermal condition, then washing with deionized water and drying;

(4) sintering the obtained product for 6 hours at 823K to obtain Ti-MCM-41 molecular sieve D-2, wherein the average radial diameter of the mesoporous molecular sieve D-2 is shown in Table 2.

Comparative example 3

Neutral S was used according to the method reported in the Journal of Molecular Catalysis A: Chemical,2015,397:26-35⁰I⁰Synthesizing the HMS-Ti molecular sieve material by a template method. The process is based on a neutral primary amine surfactant S⁰(dodecylamine) with a neutral inorganic precursor I⁰(tetraethoxysilane: TEOS) hydrogen bond and self-assembly, and mesitylene and tetrabutyl orthotitanate are respectively used as Ti⁴⁺Cationic swelling agent and precursor, filtering the product obtained by the reaction and washing the product with distilled water. Then dried at room temperature for 24h and at 100 ℃ for 2h, and then calcined in air at 550 ℃ for 3.5h to obtain the HMS-Ti molecular sieve D-3, wherein the average radial diameter of the modified mesoporous molecular sieve D-3 is shown in Table 2.

Comparative examples 4 to 5

Modified mesoporous molecular sieves D-4 and D-5 were prepared according to the method of example 1, except that the metal source, fluorine source, organic material and silicon source used in step (1) were used in different ratios and types and the aging conditions in step (3), and the details of each ratio are shown in Table 1.

Average radial diameter of the metal mesoporous molecular sieves D-4 and D-5 and the mesoporous molecular sieves (in SiO)₂Calculated), the molar ratio of fluorine and the modifying metal element are listed in table 2.

Test example 1

The modified mesoporous molecular sieves prepared in examples 1 to 31 and comparative examples 1 to 5 were subjected to a catalytic phenol hydroxylation reaction to evaluate the properties of the modified mesoporous molecular sieves:

the reaction conditions include: the reaction raw material is phenol, the dosage is 6.25g, the dosage of the modified molecular sieve is 0.31g, the dosage of the solvent acetone is 5g, and the molar ratio of the phenol to the hydrogen peroxide is 1: 1. The reaction temperature was 80 ℃ and the reaction time was 2 hours under normal pressure. After the reaction is finished, analyzing the product by using a gas chromatography, quantifying by using an internal standard method, measuring the content of hydrogen peroxide, phenol, catechol and hydroquinone in the obtained reaction product, and respectively calculating to obtain the data of the hydrogen peroxide utilization rate, the phenol conversion rate, the catechol selectivity and the hydroquinone selectivity. The data results are shown in table 2.

Wherein: reaction conversion rate ═ (amount of raw material phenol substance-amount of phenol substance remaining after the reaction)/amount of raw material phenol substance × 100%;

the product selectivity is the amount of catechol or hydroquinone substance/(amount of raw material phenol substance-amount of phenol substance remaining after reaction) × 100%;

H₂O₂utilization rate ═ initial H₂O₂Amount of substance-remaining H after reaction₂O₂Amount of material)/initial H₂O₂Amount of substance × 100%.

TABLE 1

TABLE 2

The modified mesoporous molecular sieve provided by the invention has the advantages of simple preparation process, low raw material cost, mild conditions and no harm to the environment, metal atoms can be effectively inserted into the amorphous pore wall of the mesoporous molecular sieve in a four-coordination mode, and the content of non-framework metals is low.

The data in table 2 show that the modified mesoporous molecular sieve prepared by the method provided by the invention has a smaller average radial diameter, the minimum average radial diameter is 7 μm, and the modified mesoporous molecular sieve has higher raw material conversion rate and product selectivity when catalyzing phenol hydroxylation reaction, the highest raw material phenol conversion rate is 99%, the highest hydrogen peroxide utilization rate is 99%, and the highest total selectivity of the products catechol and hydroquinone is 90%.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.