CN113683097B - Preparation method of TS-1 molecular sieve rich in framework four-coordinate titanium - Google Patents

Preparation method of TS-1 molecular sieve rich in framework four-coordinate titanium Download PDF

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CN113683097B
CN113683097B CN202111114336.7A CN202111114336A CN113683097B CN 113683097 B CN113683097 B CN 113683097B CN 202111114336 A CN202111114336 A CN 202111114336A CN 113683097 B CN113683097 B CN 113683097B
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CN113683097A (en
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梁光华
任雅梅
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Shenzhen Keguan Huatai New Material Technology Co ltd
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Abstract

A preparation method of a TS-1 molecular sieve rich in framework four-coordinate titanium comprises the following steps: step 1, uniformly mixing organic silicon ester, deionized water and a hydrolysis speed regulator, hydrolyzing to obtain a hydrolysate, adding organic titanium ester into an alcohol solution, and uniformly stirring to obtain an alcohol mixture; step 2, adding the alcohol mixture into the hydrolysate, and quickly stirring; step 3, adding a template agent, uniformly stirring, and removing alcohol to obtain an initial crystallization liquid; step 4, crystallizing the initial crystallization liquid; and 5, after complete crystallization, sequentially filtering, washing, drying and roasting to obtain the TS-1 molecular sieve. The method adds the alcohol mixture into the hydrolysate, inhibits the hydrolysis of the organic titanium ester in an acidic environment, is favorable for matching the hydrolysis speed of the organic titanium ester with the hydrolysis speed of the organic silicon ester, and prepares the TS-1 molecular sieve rich in the tetradentate titanium.

Description

Preparation method of TS-1 molecular sieve rich in framework four-coordinate titanium
Technical Field
The invention relates to the field of molecular sieves, in particular to a preparation method of a TS-1 molecular sieve rich in framework four-coordinate titanium.
Background
The TS-1 molecular sieve is an isomorphous substituted derivative of pure silicon molecular sieve Silicate, which is prepared from Ti 4+ Substituting part of Si in the skeleton of the all-silicon molecular sieve 4+ Due to Ti 4+ The ion has the characteristic of six coordination, the energy of the titanium-oxygen tetrahedron is higher, the structure has electronic defects, and the potential of accepting electron pairs is provided, so the ion has the functions of shape-selective catalysis and catalytic oxidation, especially for H 2 O 2 The participated selective oxidation reactions of a series of organic matters, such as the epoxidation of olefin, phenol hydroxylation, benzene hydroxylation, cyclohexanone ammoxidation and the like have excellent shape-selective catalytic oxidation performance. Compared with other catalytic oxidation systems, TS-1/H 2 O 2 The catalytic oxidation system of the composition has very outstanding advantages, such as: the catalyst has the advantages of high atom utilization rate, high selectivity and yield of main products, no environmental pollution, mild reaction conditions, simple and safe process, and is called as a green catalyst with the most characteristic of 'atom economy'.
In 1983, marco Taramasso et al disclosed a hydrothermal synthesis of TS-1 molecular sieves in U.S. Pat. No. 5, 4410501, and through recent 40 years of development, the hydrothermal synthesis of TS-1 molecular sieves has now formed two systems: one is to adopt tetrapropyl ammonium hydroxide as a template agent to synthesize the TS-1 molecular sieve, which is called a classical system; the other method is to adopt cheap tetrapropylammonium bromide as a template agent to synthesize the TS-1 molecular sieve, which is called as a cheap system. However, because Ti-O bond is longer than Si-O bond, titanium atom is difficult to enter the framework, so TS-1 molecular sieve prepared by the existing synthetic method can generate non-framework titanium and has adverse effect on TS-1 molecular sieve. Firstly, the non-framework titanium does not have catalytic oxidation activity, but can cause a great deal of decomposition of hydrogen peroxide, thereby reducing the catalytic performance of the TS-1 molecular sieve; secondly, the content of non-skeleton titanium is difficult to control, and the activity stability of the TS-1 molecular sieve is generally poor, thereby restricting the industrial application of the TS-1 molecular sieve.
The catalytic activity of the TS-1 molecular sieve is closely related to the preparation method thereof, generally, the hydrolysis speeds of a silicon source and a titanium source are not matched in the synthesis process of the TS-1 molecular sieve, and the hydrolysis speed of the titanium source is far higher than that of the silicon source, so that titanium is rapidly hydrolyzed without entering a silicon framework to generate anatase-type titanium dioxide, and thus the catalytic reaction is not favorable, and therefore, only when the hydrolysis speeds of the two are the same, more titanium atoms can be promoted to enter the molecular sieve framework to form a catalytic activity center, namely four-coordinate titanium. In order to solve the problem that titanium atoms are difficult to enter the framework of the molecular sieve, researchers at home and abroad carry out a great deal of work.
Thangaraj et al (Zeolite, 1992, vol.12, p 943-950) optimizes the synthesis process based on the synthesis mechanism, specifically, tetrabutyl titanate with weak hydrolysis activity is used to replace tetraethyl titanate with strong hydrolysis activity, isopropanol solution is introduced to dilute the tetrabutyl titanate so as to delay the hydrolysis speed, and tetraethyl silicate is subjected to pre-hydrolysis treatment so that the hydrolysis speeds of the tetrabutyl titanate and the tetraethyl silicate are matched, so that the content of tetra-coordinated titanium of the TS-1 molecular sieve is increased. However, the TS-1 molecular sieve synthesized by the method has large mass difference, unstable performance and poor repeatability.
The Chinese patent CN108793182B takes metatitanic acid or orthotitanic acid as a brand-new titanium source, and the metatitanic acid or the orthotitanic acid is complexed with peroxide and tetrapropylammonium hydroxide to form peroxide salt instead of being rapidly hydrolyzed into titanium dioxide, so that the generation of non-framework titanium in the synthesis process is avoided. However, the TS-1 molecular sieve prepared by the method has too large (14 mu m) crystal grains, and the catalytic performance needs to be further improved.
The application CN1475442A of the Chinese invention hydrolyzes alkoxy silicon under acidic or alkaline conditions, then mixes the alkoxy silicon with alcoholic solution of a titanium source, and adds a template agent to prepare the TS-1 molecular sieve, thereby effectively solving the problem of titanium polymerization in the synthesis process. However, strong acid or weak acid is adopted to provide an acidic condition, hydrogen ions in an acidic environment are gradually consumed along with the gradual hydrolysis of the silicon source, the hydrolysis speed promoting effect on the silicon source is gradually weakened, the problem of titanium polymerization in the TS-1 molecular sieve is limited, and the optimized sample in the invention application does not provide any representation of titanium atom distribution in the molecular sieve framework.
Disclosure of Invention
The technical scheme of the invention is to solve the above problems and provide a preparation method of a TS-1 molecular sieve rich in framework four-coordinate titanium, which is characterized by comprising the following steps: the preparation method comprises the following steps:
step 1, uniformly mixing organic silicon ester, deionized water and a hydrolysis speed regulator, hydrolyzing to obtain a hydrolysate, adding organic titanium ester into an alcohol solution, and uniformly stirring to obtain an alcohol mixture;
step 2, adding the alcohol mixture into the hydrolysate, and quickly stirring;
step 3, adding a template agent, and removing alcohol to prepare an initial crystallization liquid;
step 4, crystallizing the initial crystallization liquid;
and 5, after complete crystallization, sequentially filtering, washing, drying and roasting to obtain the TS-1 molecular sieve.
The organic silicon ester contains SiO 2 Organic titanium ester containing TiO 2 Alcohol solution containing alcohol, siO 2 、TiO 2 Template agent, H 2 The molar ratio of O to alcohol is: 1:0.01 to 0.05:0.1 to 0.5:15 to 30:2.5 to 6.0.
Further, in the step 1, the organic silicon ester is one or more of methyl orthosilicate, ethyl orthosilicate and propyl orthosilicate; the hydrolysis speed regulator is ammonium fluoride-hydrogen fluoride buffer solution; the organic titanium ester is one or a mixture of tetrabutyl titanate and tetraisopropyl titanate; in the step 1, the alcoholic solution is one or more of absolute ethyl alcohol, isopropanol and tert-butanol.
Further, in the step 1, the pH value of the hydrolysis speed regulator is 4~5, and the mass of the added hydrolysis speed regulator is 2% -10% of that of the organic silicon ester.
Further, in the step 3, the template agent is tetrapropylammonium hydroxide.
Further, in the step 1, the hydrolysis temperature is 35-65 ℃, and the hydrolysis time is 4-8h.
Further, in the step 2, the stirring time is 15 to 30min.
Further, in the step 3, the temperature of alcohol removal is 82-95 ℃, and the time of alcohol removal is 2h-5h.
Further, in the step 4, the crystallization temperature is 170-190 ℃, and the crystallization time is 15h-30h.
Further, in the step 5, the baking temperature is 500 to 600 ℃, and the baking time is 4 to 6h.
After the technical scheme is adopted, the invention has the effects that:
1. the silicon atoms in the silicone ester molecules are bonded to the silicon atoms by four alkoxy groups-OR, which are small in size and insufficient to completely surround the silicon ions, and theoretical voids exist. The hydrolysis speed regulator is ammonium fluoride-hydrogen fluoride buffer solution, fluorine ions have strong electronegativity, the radius is smaller than a theoretical gap, and nucleophilic attack can be directly initiated on silicon atoms, so that the hydrolysis speed of the organic silicon ester is effectively accelerated.
2. Under acidic conditions, due to H + By the action of water molecules attacking and decomposing the organosilyl ester directly, but H + The concentration is too low, so that the accelerating effect on the hydrolysis of the organic silicon ester is small; h + Too high a concentration results in more consumption of the synthetic template agent. The hydrolysis speed regulator is ammonium fluoride-hydrogen fluoride buffer solution and can ensure H + On the premise of supply, the aims of accelerating the hydrolysis of the organic silicon ester and reducing the synthesis cost are fulfilled at the same time.
3. The hydrolysis speed of the organic titanium ester in the alcoholic solution is greatly reduced, the alcoholic solution of the titanium source is added into the acidic hydrolysis solution of the organic silicon ester, the hydrolysis of the organic titanium ester is further inhibited by the acidic environment, and finally the hydrolysis speed of the organic titanium ester is matched with the hydrolysis speed of the organic silicon ester to prepare the TS-1 molecular sieve rich in the four-coordinate titanium.
Drawings
FIG. 1 is an X-ray powder diffraction XRD spectrum of the TS-1 molecular sieve of example 1 of the present invention;
FIG. 2 is a SEM image of the TS-1 molecular sieve in example 1 of the present invention;
FIG. 3 is a diagram of the UV-vis absorption spectrum of the TS-1 molecular sieve of example 1 of the present invention;
FIG. 4 is an X-ray powder diffraction XRD spectrum of the TS-1 molecular sieve of example 2 of the present invention;
FIG. 5 is a SEM image of the TS-1 molecular sieve in example 2 of the present invention;
FIG. 6 is a diagram of the UV-vis absorption spectrum of the TS-1 molecular sieve in accordance with example 2 of the present invention;
FIG. 7 is an X-ray powder diffraction XRD spectrum of the TS-1 molecular sieve of example 3 of the present invention;
FIG. 8 is a SEM image of the TS-1 molecular sieve in example 3 of the present invention;
FIG. 9 is a diagram of the UV-vis absorption spectrum of the TS-1 molecular sieve in accordance with example 3 of the present invention;
FIG. 10 is an X-ray powder diffraction XRD spectrum of the TS-1 molecular sieve of example 4 of the present invention;
FIG. 11 is a SEM image of a TS-1 molecular sieve in example 4 of the present invention;
FIG. 12 is a diagram of the UV-vis absorption spectrum of the TS-1 molecular sieve in accordance with example 4 of the present invention;
FIG. 13 is an X-ray powder diffraction XRD spectrum of the TS-1 molecular sieve of comparative example 1 of the present invention;
FIG. 14 is a SEM image of a TS-1 molecular sieve of comparative example 1 of the present invention;
FIG. 15 is a diagram showing the UV-vis absorption spectrum of the TS-1 molecular sieve of comparative example 1 according to the present invention.
Description of the preferred embodiment
The technical solution of the present invention is further described by the following examples:
the invention provides a preparation method of a TS-1 molecular sieve rich in framework four-coordinate titanium, which comprises the following steps:
step 1, uniformly mixing organic silicon ester, deionized water and a hydrolysis speed regulator, hydrolyzing to obtain a hydrolysate, adding organic titanium ester into an alcohol solution, and uniformly stirring to obtain an alcohol mixture;
step 2, adding the alcohol mixture into the hydrolysate, and quickly stirring;
step 3, adding a template agent, uniformly stirring, and removing alcohol to obtain an initial crystallization liquid;
step 4, crystallizing the initial crystallization liquid;
and 5, after complete crystallization, sequentially filtering, washing, drying and roasting to obtain the TS-1 molecular sieve.
Specifically, the organic silicon ester contains SiO 2 Organic titanium ester containing TiO 2 Alcohol solution containing alcohol, siO 2 、TiO 2 Template agent, H 2 The molar ratio of O to alcohol is: 1:0.01 to 0.05:0.1 to 0.5:15 to 30:2.5 to 6.0.
More specifically, in step 1, the organosilicon ester is one or more of methyl orthosilicate, ethyl orthosilicate, and propyl orthosilicate.
More specifically, in step 1, the hydrolysis rate regulator is ammonium fluoride-hydrogen fluoride buffer solution, the pH value is 4~5, and the mass of the added hydrolysis rate regulator is 2% -10% of that of the organic silicon ester.
More specifically, in step 1, the organic titanium ester is one or more of tetrabutyl titanate and tetraisopropyl titanate.
More specifically, in step 1, the alcohol solution is one or more of absolute ethyl alcohol, isopropyl alcohol and tert-butyl alcohol.
More specifically, in step 3, the templating agent is tetrapropylammonium hydroxide.
Specifically, in the step 1, the hydrolysis temperature is 35-65 ℃, and the hydrolysis time is 4-8h.
Specifically, in the step 2, the stirring time is 15 to 30min.
Specifically, in the step 3, the temperature of alcohol removal is 82-95 ℃, and the time of alcohol removal is 2h-5h.
Specifically, in the step 4, the crystallization temperature is 170-190 ℃, and the crystallization time is 15h-30h.
Specifically, in the step 5, the baking temperature is 500 to 600 ℃, and the baking time is 4 to 6 hours.
The TS-1 molecular sieve skeleton is rich in four-coordinate titanium, the body appearance is similar to a sphere, and the grain size is about 200 nm.
Specifically, in step 3, the alcohol removal is carried out in a water bath; in the step 4, transferring the initial crystallization liquid into a 100mL high-pressure kettle with a polytetrafluoroethylene lining, and placing the high-pressure kettle into an oven to crystallize the initial crystallization liquid; in step 5, a high-speed centrifuge (separation factor 9900) is used for separation and washing, then the filter cake is put into an oven for drying, and finally the filter cake is put into a muffle furnace for roasting after grinding.
Compared with the prior art, the TS-1 molecular sieve has the following remarkable advantages:
1. the silicon atoms in the silicone ester molecules are bonded by four alkoxy groups-OR, which are small in size and are not enough to completely surround the silicon ions, and theoretical voids exist. The hydrolysis speed regulator is ammonium fluoride-hydrogen fluoride buffer solution, fluorine ions have strong electronegativity, the radius is smaller than a theoretical gap, and nucleophilic attack can be directly initiated on silicon atoms, so that the hydrolysis speed of the organic silicon ester is effectively increased.
2. Under acidic conditions, due to H + By the action of water molecules attacking and decomposing the organosilyl ester directly, but H + The concentration is too low, so that the accelerating effect on the hydrolysis of the organic silicon ester is small; h + Too high a concentration results in more consumption of the synthetic template agent. The hydrolysis speed regulator is ammonium fluoride-hydrogen fluoride buffer solution and can ensure H + On the premise of supply, at the same timeThe aims of accelerating the hydrolysis of the organic silicon ester and reducing the synthesis cost are fulfilled.
3. The hydrolysis speed of the organic titanium ester in the alcoholic solution is greatly reduced, the alcoholic solution of the titanium ester is added into the acidic hydrolysis solution of the organic silicon ester, the hydrolysis of the organic titanium ester is further inhibited under the acidic environment, and finally the hydrolysis speed of the organic titanium ester is matched with the hydrolysis speed of the organic silicon ester, so that the TS-1 molecular sieve rich in the four-coordinate titanium is prepared.
[ example 1]
Preparing raw materials:
SiO in silicon source 2 TiO in the titanium source 2 Template agent, H 2 The molar ratio of O to alcohol is 1:0.05:0.5:15:6; the mass of the ammonium fluoride-hydrogen fluoride buffer solution is 10% of the mass of the silicon source.
Step 1, preparing a reaction mixed solution: uniformly mixing ethyl orthosilicate, deionized water and an ammonium fluoride-hydrogen fluoride buffer solution (11 wt%), heating to 65 ℃, hydrolyzing for 4 hours, cooling to room temperature to obtain hydrolysate containing ethyl orthosilicate, adding tetrabutyl titanate into isopropanol, and uniformly stirring to obtain an alcohol mixture containing tetrabutyl titanate;
step 2, adding the alcohol mixture into the hydrolysate of the tetraethoxysilane under the condition of maintaining the stirring of the hydrolysate, and quickly stirring for 30min;
step 3, adding 25wt% of tetrapropyl ammonium hydroxide, uniformly stirring, and then placing the solution in a water bath kettle at the temperature of 95 ℃ for dealcoholization for 5 hours to obtain initial crystallization liquid;
step 4, transferring the initial crystallization liquid into a crystallization kettle, and crystallizing for 30 hours at 170 ℃;
and step 5, sequentially filtering, washing and drying the crystallized product, and roasting at 550 ℃ for 5 hours to obtain the TS-1 molecular sieve.
The characterization result of X-ray powder diffraction (XRD) is shown in figure 1, and the result shows that the molecular sieve is pure phase TS-1; the Scanning Electron Microscope (SEM) results are shown in FIG. 2, and show that the crystal morphology is approximately spherical, and the grain size is about 200 nm; the ultraviolet-visible absorption spectrum (UV-vis) result is shown in FIG. 3, and the result shows that an absorption peak appears only near 210nm, which indicates that the prepared TS-1 molecular sieve is rich in the four-coordinate titanium.
[ example 2]
Preparing raw materials:
SiO in silicon source 2 TiO in a titanium source 2 Template agent, H 2 The molar ratio of O to alcohol is 1:0.01:0.1:30:2.5; the mass of the ammonium fluoride-hydrogen fluoride buffer solution is 2% of the mass of the silicon source.
Step 1, preparing a reaction mixed solution: uniformly mixing n-propyl silicate, deionized water and 11wt% of ammonium fluoride-hydrogen fluoride buffer solution, heating to 35 ℃, hydrolyzing for 8 hours, cooling to room temperature to obtain hydrolysate containing the n-propyl silicate, adding the tetraisopropyl titanate into absolute ethyl alcohol, and uniformly stirring to obtain an alcohol mixture containing the tetraisopropyl titanate;
step 2, adding the alcohol-containing mixture into the hydrolysate containing propyl orthosilicate under the condition of maintaining the hydrolysate to be stirred, and quickly stirring for 15min;
step 3, adding 25wt% of tetrapropyl ammonium hydroxide, uniformly stirring, and then placing the solution in a 82 ℃ water bath kettle for dealcoholization for 2 hours to obtain initial crystallization liquid;
step 4, transferring the initial crystallization liquid into a crystallization kettle, and crystallizing for 15 hours at 190 ℃;
and step 5, sequentially filtering, washing and drying the crystallized product, and roasting at 550 ℃ for 5 hours to obtain the TS-1 molecular sieve.
The characterization result of X-ray powder diffraction (XRD) is shown in FIG. 4, and the result shows that the molecular sieve is pure phase TS-1; the Scanning Electron Microscope (SEM) results are shown in FIG. 5, which shows that the crystal morphology is approximately spherical, and the grain size is about 200 nm; the ultraviolet-visible absorption spectrum (UV-vis) result is shown in FIG. 6, and the result shows that an absorption peak appears only near 210nm, which indicates that the prepared TS-1 molecular sieve is rich in the four-coordinate titanium.
[ example 3]
SiO in silicon source 2 TiO in a titanium source 2 Template agent, H 2 The molar ratio of O to alcohol is 1:0.03:0.3:25:5; the mass of the ammonium fluoride-hydrogen fluoride buffer solution is 2% of the mass of the silicon source.
Step (1), preparing a reaction mixed solution: uniformly mixing methyl orthosilicate, deionized water and an ammonium fluoride-hydrogen fluoride buffer solution (11 wt%), heating to 45 ℃, hydrolyzing for 6 hours, cooling to room temperature to prepare hydrolysate containing methyl orthosilicate, adding tetraethyl titanate into tert-butyl alcohol, and uniformly stirring to prepare an alcohol mixture containing tetraethyl titanate;
adding the alcohol mixture into the hydrolysate containing propyl orthosilicate while maintaining the hydrolysate to be stirred, and quickly stirring for 15min;
step (3), adding 25wt% of tetrapropyl ammonium hydroxide, uniformly stirring, and then placing the solution in a water bath kettle at 90 ℃ for dealcoholization for 4 hours to obtain initial crystallization liquid;
step (4), transferring the initial crystallization liquid into a crystallization kettle, and crystallizing for 25 hours at 180 ℃;
and (5) sequentially filtering, washing and drying the crystallized product, and roasting at 550 ℃ for 5 hours to obtain the TS-1 molecular sieve.
The characterization result of X-ray powder diffraction (XRD) is shown in FIG. 7, and the result shows pure phase TS-1 molecular sieve; the Scanning Electron Microscope (SEM) results are shown in fig. 8, and show that the crystal morphology is approximately spherical, and the grain size is about 200 nm; the ultraviolet-visible absorption spectrum (UV-vis) result is shown in FIG. 9, and the result shows that an absorption peak appears only near 210nm, which indicates that the prepared TS-1 molecular sieve is rich in the four-coordinate titanium.
[ example 4]
SiO in silicon source 2 TiO in a titanium source 2 Template agent, H 2 The molar ratio of O to alcohol is 1:0.02:0.25:20:4; the mass of the ammonium fluoride-hydrogen fluoride buffer solution is 6% of the mass of the silicon source.
Step (1), preparing a reaction mixed solution: uniformly mixing ethyl orthosilicate, deionized water and an ammonium fluoride-hydrogen fluoride buffer solution (11 wt%), heating to 50 ℃, hydrolyzing for 4 hours, cooling to room temperature to obtain hydrolysate containing ethyl orthosilicate, adding tetrabutyl titanate into tert-butyl alcohol, and uniformly stirring to obtain an alcohol mixture containing tetrabutyl titanate;
adding the alcohol mixture into the hydrolysate containing propyl orthosilicate while maintaining the hydrolysate to be stirred, and quickly stirring for 15min;
step (3), adding 25wt% of tetrapropylammonium hydroxide, uniformly stirring, and then placing the solution in a 92 ℃ water bath to remove alcohol for 3 hours to obtain an initial crystallization liquid;
step (4), transferring the initial crystallization liquid into a crystallization kettle, and crystallizing for 24 hours at 183 ℃;
and (5) sequentially filtering, washing and drying the crystallized product, and roasting at 550 ℃ for 5 hours to obtain the TS-1 molecular sieve.
The characterization result of X-ray powder diffraction (XRD) is shown in FIG. 10, and the result shows pure phase TS-1 molecular sieve; the Scanning Electron Microscope (SEM) results are shown in fig. 11, which shows that the crystal morphology is approximately spherical, and the grain size is about 200 nm; the ultraviolet-visible absorption spectrum (UV-vis) result is shown in FIG. 12, and the result shows that an absorption peak appears only near 210nm, which indicates that the prepared TS-1 molecular sieve is rich in the four-coordinate titanium.
Comparative example 1
The preparation of the TS-1 molecular sieve is substantially the same as in example 1, except that no ammonium fluoride-hydrogen fluoride buffer solution is added in step 1. As shown in FIGS. 13 and 14, the X-ray powder diffraction (XRD) and Scanning Electron Microscope (SEM) results are similar to those of example 1, and the ultraviolet-visible absorption spectrum (UV-vis) characterization results are shown in FIG. 15, which shows that the sample has two absorption peaks near 210nm and 340nm, indicating that the prepared TS-1 molecular sieve framework contains titanium in a form of not only tetracoordinate titanium but also a large amount of non-framework anatase TiO 2 。
Therefore, the TS-1 molecular sieves prepared in the example 1~4 are pure-phase TS-1 molecular sieves, the crystal morphologies of the TS-1 molecular sieves are similar to spherical shapes, the crystal grain sizes of the TS-1 molecular sieves are all about 200nm, and an absorption peak appears only near 210nm, so that the TS-1 molecular sieves prepared in the example 1~4 are rich in four-coordinate titanium. While comparative example 1Although the obtained TS-1 molecular sieve is also a pure-phase TS-1 molecular sieve, the crystal morphology is similar to a sphere, the grain size is about 200nm, two absorption peaks appear near 210nm and 340nm, and the obtained TS-1 molecular sieve contains a large amount of non-framework anatase TiO under the condition that an ammonium fluoride-hydrogen fluoride buffer solution is not added in the preparation process 2 。
The above-described embodiments are merely preferred examples of the present invention, and not intended to limit the scope of the invention, so that equivalent changes or modifications in the structure, features and principles of the invention described in the claims should be included in the claims.

Claims (8)

1. A preparation method of a TS-1 molecular sieve rich in framework four-coordinate titanium is characterized by comprising the following steps: the preparation method comprises the following steps:
step 1, uniformly mixing organic silicon ester, deionized water and a hydrolysis speed regulator, hydrolyzing to obtain a hydrolysate, adding organic titanium ester into an alcohol solution, and uniformly stirring to obtain an alcohol mixture;
step 2, adding the alcohol mixture into the hydrolysate, and quickly stirring;
step 3, adding a template agent, uniformly stirring, and removing alcohol to obtain an initial crystallization liquid;
step 4, crystallizing the initial crystallization liquid;
step 5, after complete crystallization, sequentially filtering, washing, drying and roasting to prepare the TS-1 molecular sieve;
the organic silicon ester contains SiO 2 Organic titanium ester containing TiO 2 Alcohol solution containing alcohol, siO 2 、TiO 2 Template agent, H 2 The molar ratio of O to alcohol is: 1:0.01 to 0.05:0.1 to 0.5:15 to 30:2.5 to 6.0 percent, wherein the hydrolysis rate regulator is ammonium fluoride-hydrogen fluoride buffer solution, the pH value of the hydrolysis rate regulator is 4~5, and the mass of the added hydrolysis rate regulator is 2 to 10 percent of the mass of the organic silicon ester.
2. The method for preparing the TS-1 molecular sieve rich in framework tetradentate titanium as claimed in claim 1, characterized in that: in the step 1, the organic silicon ester is one or more of methyl orthosilicate, ethyl orthosilicate and propyl orthosilicate; the organic titanium ester is one or a mixture of tetrabutyl titanate and tetraisopropyl titanate; in the step 1, the alcohol solution is one or more of absolute ethyl alcohol, isopropanol and tert-butanol.
3. The method for preparing the TS-1 molecular sieve rich in framework tetracoordinate titanium according to claim 1, characterized in that: in the step 3, the template agent is tetrapropylammonium hydroxide.
4. The method for preparing the TS-1 molecular sieve rich in framework tetradentate titanium as claimed in claim 1, characterized in that: in the step 1, the hydrolysis temperature is 35-65 ℃, and the hydrolysis time is 4-8h.
5. The method for preparing the TS-1 molecular sieve rich in framework tetracoordinate titanium according to claim 1, characterized in that: in the step 2, the stirring time is 15 to 30min.
6. The method for preparing the TS-1 molecular sieve rich in framework tetracoordinate titanium according to claim 1, characterized in that: in the step 3, the temperature of alcohol removal is 82-95 ℃, and the time of alcohol removal is 2h-5h.
7. The method for preparing the TS-1 molecular sieve rich in framework tetracoordinate titanium according to claim 1, characterized in that: in the step 4, the crystallization temperature is 170-190 ℃, and the crystallization time is 15h-30h.
8. The method for preparing the TS-1 molecular sieve rich in framework tetracoordinate titanium according to claim 1, characterized in that: in the step 5, the baking temperature is 500 to 600 ℃, and the baking time is 4 to 6h.
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