CN108821304B - High-activity hierarchical pore titanium silicalite molecular sieve and preparation method and application thereof - Google Patents
High-activity hierarchical pore titanium silicalite molecular sieve and preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses a high-activity hierarchical pore titanium silicalite molecular sieve and a preparation method and application thereof, which mainly comprises the steps of slowly adding a silicon source into a template solution, uniformly mixing and hydrolyzing for a period of time; introducing a titanium source into an ice water bath, and stirring overnight to generate a gel solution; the high-activity hierarchical pore titanium silicalite molecular sieve has large mesopore volume and accurately adjustable silicon-titanium ratio, has good catalytic effect for selective oxidation of macromolecular olefin and micromolecular olefin compared with the traditional block titanium silicalite molecular sieve, greatly reduces mass transfer resistance, has good catalytic effect, and is suitable for industrialized popularization and application.
Description
Technical Field
The invention belongs to the technical field of catalyst preparation, and particularly relates to a high-activity hierarchical pore titanium silicalite molecular sieve, a preparation method thereof and application thereof in epoxidation reaction of olefin.
Background
TS-1 has the same MFI type structure as ZSM-5, has large pore volume and high specific surface area, and has unique catalytic oxidation performance due to the introduction of Ti atoms in the TS-1 framework, especially for H2O2The selective oxidation reaction of a series of organic matters involved can enable the reaction to have higher selectivity. In addition, due to the characteristics of mild reaction conditions, simple process, environmental friendliness and the like, the catalytic oxidation process meets the requirements of atomic economic reaction, green chemistry and chemical industry. Therefore, the synthesis and application of TS-1 have been rapidly developed.
The active center of the titanium-silicon molecular sieve mainly exists in a rich microporous pore channel (0.55nm), however, the smaller pore diameter is not beneficial to the diffusion of reactant and product molecules in the pore channel, and meanwhile, molecules with kinetic diameters larger than the pore channel diameter cannot enter the pore channel to be contacted with the active center, so that the catalytic performance and the application range of the titanium-silicon molecular sieve are greatly limited. Patent CN106115732A describes a modification method of titanium silicalite molecular sieve, which uses alkali metal salt solution to modify the conventional TS-1 molecular sieve, but the subsequent treatment method has a large loss of TS-1 to the molecular sieve raw material, and the conventional microporous titanium silicalite molecular sieve only has a catalytic effect on the epoxidation of small molecular olefins such as propylene, but has a poor catalytic effect on large molecular olefins. Patents CN1500004A and CN1248579A disclose methods for preparing Ti-MCM-41 mesoporous molecular sieve catalysts, but in order to improve the hydrophobicity of the catalysts, additional silylation treatment with a silylation reagent is required to be performed on the catalysts after the synthesis of the molecular sieve catalysts, which makes the production process of the catalysts complicated, inefficient, and costly.
Disclosure of Invention
Aiming at the problem that the catalytic effect of the conventional titanium silicalite molecular sieve is influenced by the diffusion of reactant and product molecules in the pore channel and the like because of small pore diameter, the invention provides a Bola type surfactant BC using a tetra-ammonium headph-12-6-6The prepared high-activity hierarchical-pore titanium silicalite molecular sieve not only has the catalytic oxidation effect of titanium, but also has the shape selection effect and excellent stability of an MFI type molecular sieve, can effectively reduce the ineffective decomposition of an oxidant, and improves the conversion rate of the epoxidation reaction of macromolecular olefin.
Meanwhile, the invention also provides a preparation method of the hierarchical pore titanium silicalite molecular sieve and application of the hierarchical pore titanium silicalite molecular sieve in small-molecule n-hexyl-rare epoxidation reaction and large-molecule olefin epoxidation reaction.
The technical scheme adopted by the invention for realizing the purpose is as follows:
a high-activity hierarchical pore titanium silicon molecular sieve is a petal-shaped structure stacked by three-dimensional symbiotic nano sheets, contains zeolite micropores, nano sheet interlayer mesopores and crystal grain stacking macropores, and has a Si/Ti atomic ratio of 25: 1-147: 1 is adjustable.
Further limiting, the diameter of the medium pore of the high-activity hierarchical pore titanium silicalite molecular sieve is 4-6 nm, and the total specific surface area is 500-600m2·g-1The external specific surface area is 250-350m2·g-1The total pore volume is 0.6-0.8cm3·g-1The mesoporous volume is 0.4-0.6cm3·g-1。
The preparation method of the high-activity hierarchical pore titanium silicalite molecular sieve comprises the following steps:
(1) anion exchange resin and structure directing agent BCph-12-6-6Adding into deionized water, stirring at constant speed for 10-12 h, filtering, and taking the filtrate;
(2) slowly dripping the silicon source solution into the filtrate obtained in the step (1) under the ice-water bath condition, and uniformly stirring and hydrolyzing for 10-30 min to form a solution A;
(3) adding a titanium source solution into absolute ethyl alcohol, and stirring at room temperature to form a solution B;
(4) under the condition of ice-water bath, rapidly adding the solution B into the solution A, stirring at a constant speed for 0.5-2 h, removing the ice-water bath, stirring at room temperature in an open manner, aging for 8-15 h to form a gel solution, and using SiO as a silicon source2The titanium source is calculated as TiO2The molar ratio of each material is: SiO 22：BCph6-6-12：TiO2：H2O：EtOH＝1：0.04：0.0068～0.04：40：0.102～0.6；
(5) And (3) transferring the gel solution obtained in the step (4) to a high-pressure reaction kettle, raising the temperature for crystallization, adjusting the rotation speed to be 15-40 rpm and performing homogeneous crystallization at 120-150 ℃ for 5-7 d, and performing centrifugal separation, washing, drying and roasting on the obtained crystallized product to obtain the high-activity hierarchical pore titanium-silicon molecular sieve.
Further limiting, the silicon source is any one of silica sol, tetraethyl silicate, silicic acid and methyl orthosilicate, and the titanium source is any one of tetrabutyl titanate, tetraethyl titanate, titanium trichloride and titanium tetrachloride.
Further limiting, in the step (1), the stirring speed of the uniform stirring is 600-1000rpm, and the stirring time is 10-12 h.
Further limiting, the step (2) is to slowly drop the silicon source solution into the filtrate obtained in the step (1) under the ice-water bath condition at 0-10 ℃, and perform uniform stirring and hydrolysis at 600-.
Further limiting, in the step (4), under the ice-water bath condition, the solution B is rapidly added into the solution A, the mixture is stirred at a constant speed for 0.5 to 2 hours, then the ice-water bath is removed, the mixture is stirred in an open way at room temperature and aged for 10 to 12 hours to form a gel solution, and the silicon source is SiO2The titanium source is calculated as TiO2The molar ratio of each material is: SiO 22：BCph6-6-12：TiO2：H2O：EtOH＝1：0.04：0.0068～0.04：40：0.102～0.6。
And (3) further limiting, transferring the gel solution obtained in the step (4) into a high-pressure reaction kettle, heating for crystallization, adjusting the rotation speed to be 15-40 rpm and the temperature to be 120-150 ℃, performing homogeneous crystallization for 5-7 d, performing centrifugal separation and washing on the obtained crystallized product, performing vacuum drying at 100-120 ℃ for 8-12 h, and roasting at 500-600 ℃ for 8-12 h, wherein the heating rate is 1-6 ℃/min, and thus obtaining the high-activity hierarchical pore titanium-silicon molecular sieve.
The high-activity hierarchical-pore titanium silicalite molecular sieve is used as a catalyst in the epoxidation reaction of olefin.
Further limiting, in the epoxidation reaction of the small molecular olefin, the selectivity of the high-activity hierarchical pore titanium silicalite molecular sieve is not lower than 94%, and the conversion rate is not lower than 70%; in the epoxidation reaction of macromolecular olefin, the selectivity of the high-activity hierarchical pore titanium silicalite molecular sieve is not less than 90%, and the conversion rate is not less than 25%.
The structure directing agent used in the invention is a tetra-ammonium head Bola type surfactant BCph-12-6-6The method comprises the following steps:
(1) 2g of 4, 4' -Biphenyl phenol are dissolved in 80ml of hot ethanol containing 1.28g of potassium hydroxide, and 16.2g of 1, 12-dibromododeca [ Br (CH) are slowly added dropwise under nitrogen protection2)12Br]Refluxing at 80 deg.C for 20 h. Filtering while the solution is hot, repeatedly washing a solid sample with a hot ethanol solution for many times, and carrying out vacuum drying at 50 ℃ for 12h to obtain an intermediate product 1;
(2) 2g of product 1 and 11g N, N, N, N-tetramethyl-1, 6-hexanediamine were dissolved in 50ml of a 1:1 by volume mixture of acetonitrile and toluene at 70 ℃ (N)2Protection), cooling the product in an ice-water bath, adding diethyl ether for precipitation, filtering, washing with diethyl ether, and drying in a vacuum drying oven at 50 ℃ for 12 hours to obtain an intermediate product 2;
(3) 2.326g of product 2 and 1.587g of 1-bromohexane were dissolved in 30ml of acetonitrile at 88 ℃ (N)2Protection) heating reaction and stirring for 10h, placing the product in ice-water bath for cooling, adding ether for precipitation, filtering, washing with ether, placing in a vacuum drying oven at 50 ℃ for drying for 12h after filtering, and obtaining the final product, namely the tetraammonium head Bola type surfactant, which is marked as BCph-12-6-6。
The high-activity hierarchical pore titanium silicalite molecular sieve is mainly prepared from a tetra-ammonium head Bola type surfactant BCph-12-6-6As a structure directing agent, toThe invention relates to a hierarchical pore titanium-silicon molecular sieve which takes silica sol, tetraethyl silicate, silicic acid, methyl orthosilicate and the like as silicon sources, tetrabutyl titanate, tetraethyl titanate, titanium trichloride, titanium tetrachloride and the like as titanium sources, and adopts a sol-gel method to obtain the hierarchical pore titanium-silicon molecular sieve containing zeolite micropores, interlayer mesopores of nano-sheet layers and large crystal grain accumulation macropores, compared with the prior art, the invention has the beneficial effects that:
(1) the high-activity hierarchical pore titanium silicalite molecular sieve contains zeolite micropores, interlayer mesopores of nanosheets and crystal grain stacking macropores, has larger specific surface area and pore volume, is beneficial to the dispersion of active site titanium, and has the Si/Ti atomic ratio of 25: 1-147: can be accurately regulated and controlled within the range of 1.
(2) The invention adopts a tetra-ammonium head Bola type surfactant as a structure directing agent, the aggregation of long carbon chain alkyl groups at two ends of the surfactant forms mesopores, and a short chain can form micropores; the aromatic-aromatic or pi-pi stacking interaction in the structure can promote the self-assembly or molecular recognition process, the MFI nanosheets synthesized by using the long-chain template agent with the double quaternary ammonium head groups and the biphenyl groups have a card-shaped 90-degree rotating boundary morphology, the card-shaped 90-degree rotating boundary can enable MFI sheets to keep a certain mesopore degree after roasting, the prepared molecular sieve is of an MFI type zeolite structure and has a sheet structure with mesopore and micropore gaps, and the synthesized molecular sieve has a high specific surface area.
(3) The hierarchical pore titanium silicalite molecular sieve prepared by the method greatly reduces mass transfer resistance by utilizing the advantages of the hierarchical pore channels, has wide application in separation and absorption, is particularly suitable for catalytic oxidation reaction of various olefins, has larger pore size due to the addition of titanium atoms, is particularly suitable for selective oxidation of macromolecular olefins, and can obviously improve the activity and stability of olefin epoxidation reaction compared with the conventional TS-1 by using the hierarchical pore titanium silicalite molecular sieve catalyst prepared by the method.
(4) The hierarchical pore titanium silicalite molecular sieve can remove alcohol along with the aging process of gel without removing alcohol in the synthesis process, thereby simplifying the reaction steps, saving resources, reducing cost and being suitable for industrialized popularization and application.
Drawings
FIG. 1 is a wide angle X-ray diffraction pattern of example 2 and comparative example 1.
FIG. 2 is a scanning electron micrograph of example 2.
Fig. 3 is a scanning electron micrograph of comparative example 1 as a comparison.
FIG. 4 is a TEM photograph of example 2.
Fig. 5 is a transmission electron micrograph of comparative example 1 as a comparison.
Fig. 6 is a uv spectrum of example 2 and comparative example 1.
FIG. 7 shows N in example 2 and comparative example 12Adsorption and desorption curves.
Detailed Description
The technical solution of the present invention is further illustrated by experimental data and specific examples, but the present invention is not limited to the following examples.
Before synthesizing the high-activity hierarchical-pore titanium silicalite molecular sieve, the structure directing agent tetraammonio head Bola type surfactant BC used by the invention needs to be prepared according to the methodph-12-6-6Then, the high-activity hierarchical pore titanium silicalite molecular sieve is prepared according to the following steps:
(1) adding anion exchange resin and a structure directing agent into deionized water, stirring at a constant speed, and filtering to obtain filtrate;
(2) slowly dripping a silicon source into the filtrate obtained in the step (1) under the ice-water bath condition, and stirring at a constant speed for hydrolysis to form a solution A;
(3) adding a titanium source reagent into absolute ethyl alcohol, and stirring at room temperature to form a solution B;
(4) under the condition of ice-water bath, quickly adding the solution B into the solution A, stirring at a constant speed, removing the ice-water bath, stirring at room temperature in an open manner, and aging for a certain time to form a gel solution;
(5) and (3) transferring the gel solution obtained in the step (4) into a stainless steel high-pressure reaction kettle, then carrying out homogeneous crystallization in a homogeneous reactor for a certain time under a hydrothermal condition, or directly completing temperature rise and homogeneous crystallization in the high-pressure reaction kettle, and sequentially carrying out conventional centrifugal separation, washing, vacuum drying and roasting on the obtained crystallization product to obtain the high-activity hierarchical pore titanium silicalite molecular sieve.
According to the method, the high-activity hierarchical-pore titanium silicalite molecular sieve is prepared by referring to the selection of the specific raw materials and the implementation process conditions in the following table 1.
Table 1 shows the selection and proportion of each raw material
Note: SDA is quaternary ammonium head Bola type surfactant BCph-12-6-6TBOT is titanium tetrabutyl titanate.
Taking the high activity hierarchical pore titanium silicalite molecular sieve prepared in example 2 as an example, the analysis result is as follows:
comparative example 1: the mol ratio of each component oxide, organic template agent and solvent in the initial gel mixture is as follows: 1SiO2：0.25SDA：0.0215TiO2：16.44H2O: 0.3225 EtOH. SDA is tetrapropylammonium hydroxide.
(1) 3.75g of silica sol (containing 40 wt% aqueous silica) was weighed and mixed with 3.1776g of tetrapropylammonium hydroxide, and 3.244g of deionized water was added thereto and stirred in an ice-water bath to form solution A.
(2) 0.47ml of absolute ethanol was measured, and 0.1864ml of tetrabutyltitanate was added to the absolute ethanol to form a solution B.
(3) Under the condition of ice-water bath, the solution B is quickly added into the solution A, the water bath is removed after stirring for 0.5h, and the solution B is stirred and aged at room temperature for 10h to remove alcohol, so that clear gel is formed.
(4) And transferring the mixture into a stainless steel reaction kettle with a polytetrafluoroethylene lining after room temperature aging is finished, carrying out hydrothermal constant temperature crystallization on the initial gel mixture for 4-6 days at 140 ℃ under autogenous pressure, and sequentially carrying out centrifugal separation, washing, drying and roasting on the finally obtained product for multiple times to obtain the TS-1 titanium silicalite molecular sieve, wherein the label is comparative example 1.
Firstly, the crystal structures of the high-activity hierarchical pore titanium silicalite molecular sieve are characterized compared with the crystal structures of the conventional TS-1 molecular sieve of the comparative example, and the hierarchical pore titanium silicalite molecular sieve of the example 2 is compared with the conventional TS-1 molecular sieve serving as the comparative material, namely the comparative example 1, and the results are shown in figure 1.
As can be seen from fig. 1, the hierarchical pore titanium silicalite molecular sieve prepared in example 2 of the present invention has typical characteristic diffraction peaks of MFI-type molecular sieve, and has similar crystallinity and purity to those of comparative example 1, and compared with conventional TS-1 molecular sieve, the characteristic diffraction peaks of the hierarchical pore titanium silicalite molecular sieve in some crystal planes are not obvious or adjacent peaks are fused, and the reason for analyzing the characteristic diffraction peaks is mainly that the crystal planes of MFI framework zeolite nanosheets with single cell thickness are incomplete.
Secondly, the high-activity hierarchical pore titanium silicalite molecular sieve is compared with the crystal structure and the morphological characteristics of the conventional TS-1 molecular sieve of the comparative example, and is observed and analyzed by a scanning electron microscope, which is respectively shown in figures 2 and 3.
As can be seen from the comparison of FIGS. 2 and 3, the hierarchical pore titanium silicalite molecular sieve has the shape characteristics of a card sheet like a flower, and is a petal-shaped structure formed by stacking three-dimensional symbiotic nano sheets; and the conventional titanium silicalite TS-1 is a block particle with regular geometric shape and smooth surface.
And (III) the hierarchical pore titanium silicalite molecular sieve of the example 2 and the conventional TS-1 molecular sieve as the comparative example 1 are subjected to transmission electron microscope observation and analysis, and are respectively shown in FIGS. 4 and 5.
As can be seen from the comparison of FIGS. 4 and 5, the thickness of the nanosheet layer of the hierarchical pore titanium silicalite molecular sieve prepared by the method is about 2nm, and the hierarchical pore titanium silicalite molecular sieve has an intracrystalline mesoporous structure; and the conventional titanium silicalite TS-1 only has a micropore structure.
(IV) the hierarchical pore titanium silicalite molecular sieve of example 2 and the conventional TS-1 molecular sieve as the comparative material, comparative example 1, were subjected to UV spectrogram analysis, as shown in FIG. 6.
As can be seen from FIG. 6, the hierarchical pore titanium silicalite molecular sieve prepared in example 2 and the conventional TS-1 molecular sieve in comparative example 1 both have a strong absorption peak near 210nm in the ultraviolet characterization wavelengthNo absorption peak appears near 330nm, which indicates that four-coordinated framework titanium exists and six-coordinated anatase TiO is not contained2It is further explained that the hierarchical pore molecular sieve prepared by the invention is a titanium-silicon molecular sieve doped with a titanium atom framework.
(V) the hierarchical pore titanium silicalite molecular sieve of example 2 and the conventional TS-1 molecular sieve as a comparative material, i.e., comparative example 1, were subjected to pore structure property analysis, the results of which are shown in FIG. 7;
FIG. 7 shows the hierarchical pore titanium silicalite molecular sieve prepared in example 2 of the present invention and a conventional TS-1 molecular sieve as a comparative material, i.e., N of comparative example 12Adsorption and desorption isotherms. It is shown that the hierarchical pore titanium silicalite molecular sieve prepared in preparation example 2 of the invention has a medium-micro double-pore structure and a low N2Partial pressure (p/p 0)<0.01) a jump occurs, which embodies the adsorption characteristics of a typical microporous molecular sieve and shows that a sample contains a large amount of microporous structures; the general form of the hysteresis loop of type a occurs at medium to high pressures, which means that the material consists of good cylindrical channels, whereas conventional TS-1 molecular sieves, as a comparative material, only exhibit a sudden transition in the low pressure region, no hysteresis loop occurs, indicating that there are only micropores. The specific surface area and pore volume results of the hierarchical pore titanium silicalite molecular sieve of preparation example 2 of the present invention and the conventional TS-1 molecular sieve as a comparative material are shown in table 2.
TABLE 2 specific surface area and pore volume parameters of the hierarchical pore titanium silicalite molecular sieve of preparative example 2 of the present invention and conventional TS-1 molecular sieve as a comparative material
| Sample (I) | SBET(m2/g) | Sext(m2/g) | Vtot(cm3/g) | Vmicro(cm3/g) | Sext/SBET |
| Example 2 | 590 | 308 | 0.75 | 0.16 | 0.52 |
| Comparative example 1 | 448 | 60 | 0.22 | 0.06 | 0.13 |
As can be seen from Table 2, the multi-stage pore titanium silicalite molecular sieve prepared by the invention in preparation example 2 has the typical characteristics of a microporous zeolite molecular sieve with both a large external specific surface area and a large mesoporous pore volume, and Sext/SBETThe numerical value of (A) is 4 times of that of the conventional TS-1 molecule, which shows that the hierarchical pore titanium silicalite molecular sieve prepared by the invention has higher external specific surface area and possibly excellent performance when being applied to the epoxidation of macromolecular olefin.
In order to verify the catalytic effect of the high activity hierarchical pore titanium silicalite molecular sieve prepared by the invention, 500mg of each of example 2 and comparative example 1 was taken and subjected to epoxidation reaction test in a 250ml three-neck flask. Adding 0.5g of molecular sieve and 100ml of solvent acetonitrile into a 250ml round-bottom flask with condensation reflux, and then adding 0.1mol of n-hexane (cyclooctene) and 0.1mol of oxidant H2O2(30 wt% aqueous solution). Stirring was carried out at 60 ℃ for 2 h. After the reaction is finished, the reaction solution isFiltration was performed and detection was performed by gas chromatography (GC 9790), FID detector, column KB-1Q (30 m.times.0.25 mm.times.0.5. mu.m). The results of the reaction tests are shown in Table 3.
Table 3 results of n-hexylene epoxidation reaction of example 2 and comparative example 1
TABLE 4 results of cyclooctene epoxidation reaction of example 2 and comparative example 1
It can be seen from table 3 that, in the reaction process of catalyzing the oxidation of n-hexene to generate 1, 2-epoxyhexane, compared with the conventional TS-1 molecular sieve, the catalyst prepared by the present invention has a conversion rate significantly better than that of the conventional TS-1 molecular sieve under the condition that the selectivity of the main product, epoxycyclohexane, is equivalent, and the conversion rate is improved by about 10 times while the selectivity is maintained. As can be seen from Table 4, in the reaction process of catalyzing the oxidation of cyclooctene to generate 1, 2-epoxycyclooctane, compared with the conventional TS-1 molecular sieve, the conversion rate and selectivity of the hierarchical pore titanium silicalite molecular sieve prepared by the invention are obviously superior to those of the conventional TS-1 titanium silicalite molecular sieve, and are respectively increased by 84% and 30%. Therefore, the hierarchical pore titanium silicalite molecular sieve catalyst prepared by the invention can be widely used in industrial production.
The experimental results of other examples 1, 3 and 5 by the same method are similar to the results of example 2, the mesoporous diameter of the mesoporous titanium silicalite molecular sieve with high activity is 4-6 nm, and the total specific surface area is 500-600m2·g-1The external specific surface area is 250-350m2·g-1The total pore volume is 0.6-0.8cm3·g-1The mesoporous volume is 0.4-0.6cm3·g-1. The selectivity of the catalyst in the epoxidation reaction of micromolecular olefin is more than 94 percent, and the conversion rate can be more than 70 percent; in a macromolecular alkeneIn the hydrocarbon epoxidation reaction, the selectivity can reach more than 90 percent, and the conversion rate can reach more than 25 percent.
Experimental data also show that the high-activity hierarchical pore titanium silicalite molecular sieve prepared by the invention has a good catalytic effect on common small-molecule n-hexane epoxidation reaction, and also has high selectivity and conversion rate in macromolecular cyclooctene epoxidation reaction, namely the high-activity hierarchical pore titanium silicalite molecular sieve has a good catalytic effect on selective oxidation of olefin, and can be popularized and applied in the epoxidation reaction of olefin.
Claims (10)
1. A high-activity hierarchical pore titanium silicalite molecular sieve is characterized in that: the molecular sieve is a petal-shaped structure stacked by three-dimensional symbiotic nano sheets, contains zeolite micropores, nano sheet interlayer mesopores and crystal grain stacking macropores, and has a Si/Ti atomic ratio of 25: 1-147: 1 is adjustable within the range;
the molecular sieve is prepared by the following steps:
(1) anion exchange resin and structure directing agent BCph-12-6-6Adding into deionized water, stirring at constant speed for 10-12 h, filtering, and taking the filtrate;
(2) slowly dripping the silicon source solution into the filtrate obtained in the step (1) under the ice-water bath condition, and uniformly stirring and hydrolyzing for 10-30 min to form a solution A;
(3) adding a titanium source solution into absolute ethyl alcohol, and stirring at room temperature to form a solution B;
(4) under the condition of ice-water bath, rapidly adding the solution B into the solution A, stirring at a constant speed for 0.5-2 h, removing the ice-water bath, stirring at room temperature in an open manner, aging for 8-15 h to form a gel solution, and using SiO as a silicon source2The titanium source is calculated as TiO2The molar ratio of each material is: SiO 22：BCph6-6-12：TiO2：H2O：EtOH＝1：0.04：0.0068～0.04：40：0.102～0.6；
(5) And (3) transferring the gel solution obtained in the step (4) to a high-pressure reaction kettle, raising the temperature for crystallization, adjusting the rotation speed to be 15-40 rpm and performing homogeneous crystallization at 120-150 ℃ for 5-7 d, and performing centrifugal separation, washing, drying and roasting on the obtained crystallized product to obtain the high-activity hierarchical pore titanium-silicon molecular sieve.
2. The highly active hierarchical pore titanium silicalite molecular sieve of claim 1, wherein: the high-activity hierarchical pore titanium silicalite molecular sieve has a medium pore diameter of 4-6 nm and a total specific surface area of 500-600m2·g-1The external specific surface area is 250-350m2·g-1The total pore volume is 0.6-0.8cm3·g-1The mesoporous volume is 0.4-0.6cm3·g-1。
3. The method of preparing a highly active hierarchical pore titanium silicalite molecular sieve of claim 1, comprising the steps of:
(1) anion exchange resin and structure directing agent BCph-12-6-6Adding into deionized water, stirring at constant speed for 10-12 h, filtering, and taking the filtrate;
(2) slowly dripping the silicon source solution into the filtrate obtained in the step (1) under the ice-water bath condition, and uniformly stirring and hydrolyzing for 10-30 min to form a solution A;
(3) adding a titanium source solution into absolute ethyl alcohol, and stirring at room temperature to form a solution B;
(4) under the condition of ice-water bath, rapidly adding the solution B into the solution A, stirring at a constant speed for 0.5-2 h, removing the ice-water bath, stirring at room temperature in an open manner, aging for 8-15 h to form a gel solution, and using SiO as a silicon source2The titanium source is calculated as TiO2The molar ratio of each material is: SiO 22：BCph6-6-12：TiO2：H2O：EtOH＝1：0.04：0.0068～0.04：40：0.102～0.6；
(5) And (3) transferring the gel solution obtained in the step (4) to a high-pressure reaction kettle, raising the temperature for crystallization, adjusting the rotation speed to be 15-40 rpm and performing homogeneous crystallization at 120-150 ℃ for 5-7 d, and performing centrifugal separation, washing, drying and roasting on the obtained crystallized product to obtain the high-activity hierarchical pore titanium-silicon molecular sieve.
4. The method of claim 3, wherein the step of preparing the high activity hierarchical pore titanium silicalite molecular sieve comprises: the silicon source is any one of silica sol, tetraethyl silicate, silicic acid and methyl orthosilicate, and the titanium source is any one of tetrabutyl titanate, tetraethyl titanate, titanium trichloride and titanium tetrachloride.
5. The method of claim 3, wherein the step of preparing the high activity hierarchical pore titanium silicalite molecular sieve comprises: in the step (1), the stirring speed of uniform stirring is 600-1000rpm, and the stirring time is 10-12 h.
6. The method of claim 3, wherein the method comprises: the step (2) is specifically that under the condition of ice water bath at 0-10 ℃, the silicon source solution is slowly dripped into the filtrate obtained in the step (1), and the mixture is stirred at the uniform speed of 1000rpm for hydrolysis for 10-30 min at 600-.
7. The method of claim 3, wherein the step of preparing the high activity hierarchical pore titanium silicalite molecular sieve comprises: in the step (4), under the ice-water bath condition, the solution B is rapidly added into the solution A, the ice-water bath is removed after the uniform stirring for 0.5 to 2 hours, the mixture is stirred in an open way at room temperature and aged for 10 to 12 hours to form a gel solution, and the silicon source is SiO2The titanium source is calculated as TiO2The molar ratio of each material is: SiO 22：BCph6-6-12：TiO2：H2O：EtOH＝1：0.04：0.0068～0.04：40：0.102～0.6。
8. The method of claim 3, wherein the step of preparing the high activity hierarchical pore titanium silicalite molecular sieve comprises: and (3) transferring the gel solution obtained in the step (4) to a high-pressure reaction kettle, heating for crystallization, adjusting the rotation speed to be 15-40 rpm and the temperature to be 120-150 ℃, performing homogeneous crystallization for 5-7 d, performing centrifugal separation and washing on the obtained crystallized product, performing vacuum drying at 100-120 ℃ for 8-12 h, and roasting at 500-600 ℃ for 8-12 h, wherein the heating rate is 1-6 ℃/min, so as to obtain the high-activity hierarchical pore titanium-silicon molecular sieve.
9. The use of the high activity, hierarchical pore titanium silicalite molecular sieve of claim 1 as a catalyst in olefin epoxidation reactions.
10. Use according to claim 9, characterized in that: in the epoxidation reaction of small molecular olefin, the selectivity of the high-activity hierarchical pore titanium silicalite molecular sieve of claim 1 is not lower than 94%, and the conversion rate is not lower than 70%; in the epoxidation reaction of macromolecular olefin, the high activity hierarchical pore titanium silicalite molecular sieve of claim 1 has a selectivity of not less than 90% and a conversion of not less than 25%.
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