A hierarchical pore titanosilicate molecular sieve, a preparation method thereof and a method for ammoximation of cyclohexanone

Abstract

The present disclosure relates to a kind of level hole titanium silicalite molecular sieve and its preparation method and cyclohexanone ammoximation method.In the peak separation result of the spectrum peak in the wavelength range of 180~500nm in the UV-Vis spectrum of the titanium silicalite molecular sieve, the peak area of the peak separation peak in the spectrum peak in the peak position range of 205~215nm is recorded as A1, the peak area of the peak separation peak in the spectrum peak in the peak position range of 260~270nm is recorded as A2;The total area of the spectrum peak in the wavelength range of 180~500nm in the UV-Vis spectrum of titanium silicalite molecular sieve is recorded as A0;Q1 defined as follows (1) is 35~70%: Q1=A1 / A0×100% formula (1);Q2 defined as follows (2) is 30~50%: Q2=A2 / A0×100% formula (2).It has good catalytic activity and catalytic stability in cyclohexanone ammoximation reaction.

Description

Technical Field

[0001] This disclosure relates to the field of catalytic materials, specifically to a microporous titanium silicate molecular sieve, a method for its preparation, and a method for the ammoniation of cyclohexanone. Background Technology

[0002] Cyclohexanone oxime is an important intermediate in the preparation of caprolactam, the monomer of nylon-6. It is mainly obtained by the ammonoximation reaction of cyclohexanone, hydrogen peroxide, and ammonia via titanium silicate molecular sieve catalysis. Industrially, TS-1 molecular sieve is used as the main catalyst component. However, due to limitations in synthesis processes, crystal morphology, and microporous characteristics, TS-1 molecular sieves obtained by conventional methods have high anatase content and low pore volume, resulting in low conversion rates and poor lifespan in the ammonoximation reaction, thus affecting production efficiency. Therefore, improving the production process, increasing the framework titanium content and hexacoordinate titanium content of microporous TS-1, and reducing the anatase content, and further processing to obtain microporous TS-1 with high framework titanium content, high hexacoordinate titanium content, and low anatase content, is beneficial for improving the catalytic performance and lifespan of TS-1 molecular sieve in the cyclohexanone ammonoximation reaction.

[0003] The literature (Zhang J, Shi H, Song Y, et al. High-efficiency synthesis of enhanced-titanium and anatase-free TS-1zeolite by using a crystallization modifier[J]. Inorganic Chemistry Frontiers, 2021) reports a method for preparing microporous TS-1 with low anatase content using 1,3,5-benzenetricarboxylic acid as a growth regulator. By adding a certain amount of 1,3,5-benzenetricarboxylic acid to the precursor titanium silicate and crystallizing it for 24 hours, microporous TS-1 with low anatase content can be obtained, exhibiting good catalytic activity for the 1-hexene epoxidation.

[0004] The literature (Xu W, Zhang T, Bai R, et al. A one-step rapid synthesis of TS-1zeolites with highly catalytically active mononuclear TiO6 species[J]. Journal of Materials Chemistry A, 2020) reported a method for preparing microporous TS-1 with high hexacoordinate titanium content and low anatase content by using seed crystals and crystallizing under microwave heating. It also observed that its catalytic activity in the 1-hexene epoxidation reaction was superior to that of conventional microporous TS-1.

[0005] The literature (Yang G, Han J, Qiu Z, et al. An amino acid-assisted approach to fabricate nanosized hierarchical TS-1 zeolites for efficient oxidative desulfurization[J]. Inorganic Chemistry Frontiers, 2020) reports a method for preparing low anatase content microporous TS-1 using lysine as a mesoporous directing agent combined with segmented dynamic crystallization. The highest mesopore volume of the obtained microporous TS-1 reached 0.84 cm³. 3 / g also contains a certain amount of hexagonal titanium, but the detailed percentage of hexagonal titanium is not given.

[0006] The preparation method of hierarchical titanium-silicon molecular sieves is relatively complex. The generation of hierarchical pores leads to the conversion of a large amount of framework titanium into anatase, inhibiting further improvement of the molecular sieve's catalytic performance. Currently, a process for preparing hierarchical molecular sieves with high framework titanium and high hexacoordinate titanium content, and low anatase content, is not yet feasible. Summary of the Invention

[0007] The purpose of this disclosure is to provide a microporous titanium silicate molecular sieve and its preparation method, as well as a method for the ammoniation of cyclohexanone, which can increase the framework titanium content and the six-coordinate non-framework titanium content of the microporous titanium silicate molecular sieve, and reduce the anatase content, and exhibit good catalytic activity and catalytic stability in the ammoniation reaction of cyclohexanone.

[0008] To achieve the above objectives, the first aspect of this disclosure provides a microporous titanium silicate molecular sieve having the following UV-Vis characteristics:

[0009] In the peak division results of the UV-Vis spectrum of the titanium silicon molecular sieve in the wavelength range of 180 to 500 nm, the peak area of ​​the peak located in the range of 205 to 215 nm is recorded as A1, and the peak area of ​​the peak located in the range of 260 to 270 nm is recorded as A2.

[0010] The total area of ​​the spectral peaks in the UV-Vis spectrum of the titanium-silicon molecular sieve in the wavelength range of 180 to 500 nm is denoted as A0.

[0011] As defined in equation (1), Q1 is any value between 35% and 70%:

[0012] Q1 = A1 / A0 × 100% Equation (1);

[0013] As defined in equation (2), Q2 is any value between 30% and 50% in the following formula:

[0014] Q2 = A2 / A0 × 100% Equation (2).

[0015] Optionally, this grade of porous titanium silicate molecular sieve also possesses the following UV-Vis characteristics:

[0016] In the peak fractionation results of the UV-Vis spectrum of the titanium-silicon molecular sieve in the wavelength range of 180 to 500 nm, the peak area of ​​the peak located in the range of 320 to 330 nm is recorded as A3.

[0017] As defined in equation (3), Q3 is any value between 0 and 25%.

[0018] Q3=A3 / A0×100% formula (3).

[0019] Optionally, Q1 is any value between 40% and 60%; Q2 is any value between 30% and 45%; and Q3 is any value between 5% and 16%.

[0020] Optionally, the micropore volume of the microporous titanium-silicon molecular sieve is 0.15–0.21 cm³. 3 / g, mesopore volume is 0.14~0.20cm³ 3 / g, the proportion of mesoporous volume to total pore volume is 30-50%, the average particle size is 350-400 nm, and the BET specific surface area is 440-490 m². 2 / g;

[0021] Preferably, the micropore volume of the microporous titanium-silicon molecular sieve is 0.18–0.20 cm³. 3 / g, mesopore volume is 0.15~0.17cm³ 3 / g, the proportion of mesoporous volume to total pore volume is 40-50%, the average particle size is 370-390nm, and the BET specific surface area is 450-470m². 2 / g.

[0022] Optionally, the microporous titanium silicate molecular sieve is selected from one or more of the following: MFI structure molecular sieve, MEL structure molecular sieve, BEA structure molecular sieve, and MWW structure molecular sieve; preferably, it is an MFI structure molecular sieve.

[0023] The second aspect of this disclosure provides a method for preparing porous titanium-silicon molecular sieves, comprising the following steps:

[0024] S1. Mix the silicon source, titanium source, alkali source, polyamine compound and water to obtain a reaction mixture;

[0025] S2. The reaction mixture is subjected to crystallization treatment and first calcination treatment to obtain intermediate molecular sieve product;

[0026] S3. The intermediate molecular sieve product is contacted with an acid solution for acidification treatment; then it is contacted with an alkaline solution for recrystallization treatment to obtain a recrystallized product.

[0027] S4. The recrystallized product is subjected to a second calcination treatment.

[0028] Optionally, in step S1, the silicon source is SiO2, and the alkali source is OH. - The titanium source is calculated as TiO2, and the molar ratio of silicon source: alkali source: titanium source: polyamine: water is 1:(0.1~0.3):(0.01~0.1):(0.001~0.05):(3~40).

[0029] The preferred ratio is 1:(0.15~0.25):(0.03~0.06):(0.001~0.02):(10~25); and more preferably 1:(0.15~0.2):(0.03~0.05):(0.001~0.01):(10~20).

[0030] Optionally, in step S1, the polyamine compound is selected from at least one of the structures represented by the general formula (A):

[0031] H2N-CH2-(CH2-NH-CH2) n -CH2-NH2 formula (A); where n is a positive integer greater than or equal to 1; preferably, n is an integer between 1 and 6; more preferably, the polyamine compound is selected from one or more of diethylenetriamine, triethylenetetraamine, and tetraethylenepentamine;

[0032] The silicon source is selected from one or more of silica sol, silica gel, organosilicon ester and precipitated silica;

[0033] Optionally, the silica sol includes acidic silica sol and alkaline silica sol; preferably, the silica sol contains 5-40% by weight of silicon dioxide; the organosilicon ester is selected from one or more of tetraethyl silicate, tetrapropyl silicate, tetrabutyl silicate, trimethoxychlorosilane, triethoxyphenylsilane, and triethoxypropenylsilane; preferably, the silicon source is selected from one or more of organosilicon esters, more preferably tetraethyl silicate;

[0034] The titanium source is selected from one or more of organotitanium esters, titanium tetrachloride, titanium trichloride, and titanium sulfate; preferably, it is selected from one or more of organotitanium esters; the organotitanium ester is selected from one or more of tetraethyl titanate, tetrabutyl titanate, and tetraisopropyl titanate.

[0035] The alkali source is selected from an aqueous solution of an organic or inorganic alkali; preferably, the pH value of the alkali source is 10-14.

[0036] Optionally, the organic base is selected from one or more organic amine compounds; preferably, the organic amine compound is selected from one or more aliphatic amines, aromatic amines, alkanolamines, and organic quaternary ammonium bases; the organic quaternary ammonium base is selected from one or more tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide; the inorganic base is selected from one or more sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium phosphate, potassium phosphate, disodium hydrogen phosphate, dipotassium hydrogen phosphate, and ammonia water.

[0037] Preferably, the alkali source is selected from one or more of organic quaternary ammonium alkali and ammonia water; more preferably, it is selected from one or more of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide and ammonia water.

[0038] Optionally, step S1 includes the following steps:

[0039] (a) The silicon source, titanium source, alkali source, polyamine compound and water are mixed and hydrolyzed at 20-40°C for 2-12 hours to obtain an alcohol-containing hydrolysis product;

[0040] (b) The alcohol-containing hydrolysis product is subjected to alcohol removal at 60–110°C for 6–24 h to obtain a silicon-titanium gel as the raw material mixture.

[0041] Optionally, in step S2, the conditions for the crystallization treatment include: a crystallization temperature of 120–210°C, a crystallization time of 2–24 h, and an autogenous pressure; preferably, the temperature is 140–190°C and the crystallization time is 2–18 h.

[0042] The conditions for the first calcination treatment include: a calcination temperature of 250–750°C and a calcination time of 2–12 h; preferably, the calcination temperature is 350–750°C and the calcination time is 2–8 h.

[0043] Optionally, in step S2, before crystallization, a pre-crystallization treatment of the reaction mixture is further included; preferably, the conditions for the pre-crystallization treatment include: a crystallization temperature of 80-120°C and a crystallization time of 0.5-24h; preferably, the crystallization temperature is 80-100°C and the crystallization time is 0.5-12h.

[0044] Optionally, in step S3, the acid solution is an aqueous solution selected from inorganic acids, and the concentration of the acid solution is 0.5-3% by weight, preferably 0.5-2% by weight; the weight ratio of the acid solution to the intermediate molecular sieve product is (2-20):1, preferably (5-10):1; optionally, the inorganic acid is selected from one or more of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, hydrobromic acid and fluorosilicic acid;

[0045] The alkaline solution is an aqueous solution selected from inorganic or organic bases, and the concentration of the alkaline solution is 1-25% by weight, preferably 1-15% by weight; the pH value of the alkaline solution is 10-14; the weight ratio of the alkaline solution to the intermediate molecular sieve product is (1-10):1, preferably (2-5):1;

[0046] Preferably, the organic base is selected from one or more of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide; the inorganic base is selected from one or more of sodium hydroxide, potassium hydroxide, disodium hydrogen phosphate, dipotassium hydrogen phosphate, and ammonia water.

[0047] Optionally, in step S3, the acidification conditions include: an acidification temperature of 60–90°C and an acidification time of 2–12 h; preferably, the acidification temperature is 70–90°C and the acidification time is 2–6 h.

[0048] The recrystallization conditions include: a recrystallization temperature of 120–210°C and a recrystallization time of 2–36 h; preferably, the recrystallization temperature is 140–200°C and the recrystallization time is 2–24 h.

[0049] Optionally, in step S4, the conditions for the second calcination treatment include: a calcination temperature of 250–750°C and a calcination time of 2–12 h; preferably, the calcination temperature is 400–600°C and the calcination time is 3–6 h.

[0050] The third aspect of this disclosure provides a microporous titanium-silicon molecular sieve, prepared according to the method described in the second aspect of this disclosure.

[0051] The fourth aspect of this disclosure provides a method for the aminooximation of cyclohexanone, the method comprising reacting cyclohexanone with an oxidant in the presence of a catalyst, said catalyst containing the microporous titanium silicate molecular sieve described in the first and third aspects of this disclosure.

[0052] Optionally, the reaction conditions include: a molar ratio of oxidant to cyclohexanone of 0.5–2, a reaction temperature of 40–120°C, a reaction time of 0.5–6 h, and a mass ratio of catalyst to cyclohexanone of 0.05–0.5.

[0053] Through the above technical solutions, this disclosure provides a microporous titanium-silicon molecular sieve, its preparation method, and a method for the ammoniation of cyclohexanone. The microporous titanium-silicon molecular sieve has a high content of framework titanium atoms and six-coordinated non-framework titanium atoms, reducing the content of anatase-type non-framework titanium elements. Furthermore, the microporous molecular sieve simultaneously possesses micropores and mesopores, exhibiting high catalytic activity and good stability when used to catalyze the ammoniation of cyclohexanone. The method for preparing the microporous titanium-silicon molecular sieve provided by this disclosure further promotes the conversion of framework titanium to six-coordinated non-framework titanium during micropore formation, improving the catalytic performance of the microporous titanium-silicon molecular sieve in the cyclohexanone ammoniation reaction; simultaneously, it reduces crystallization time, improves the synthesis efficiency of the microporous titanium-silicon molecular sieve, and has good economic benefits.

[0054] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0055] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0056] Figure 1 This is a TEM image of the microporous titanium silicate molecular sieve obtained in Example 1;

[0057] Figure 2 The UV-Vis spectrum of the microporous titanium silicate molecular sieve obtained in Example 1 is shown.

[0058] Figure 3 This is a TEM image of the microporous titanium-silicon molecular sieve obtained in Comparative Example 1.

[0059] Figure 4 The UV-Vis spectrum of the microporous titanium silicate molecular sieve obtained in Comparative Example 1 is shown.

[0060] Figure 5 This is a TEM image of the hierarchical titanium-silicon molecular sieve obtained in Comparative Example 2;

[0061] Figure 6 The UV-Vis spectrum of the hierarchical titanium silicate molecular sieve obtained in Comparative Example 2 is shown. Detailed Implementation

[0062] The following provides a detailed description of specific embodiments of this disclosure. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit this disclosure.

[0063] In experiments, the inventors of this disclosure discovered that, in the UV-Vis spectrum of microporous titanium silicate molecular sieves, using the total area of ​​the peaks in the wavelength range of 180–500 nm as a benchmark, the peaks within this wavelength range are divided into two categories. Peaks in the wavelength range of 205–215 nm represent the framework titanium of the molecular sieve, while peaks in the wavelength range of 260–270 nm represent the six-coordinated titanium in the non-framework titanium form within the molecular sieve. The ratio of the peak area of ​​these two types of titanium to the total area of ​​the peaks in the entire wavelength range of 180–500 nm can respectively represent the mass percentage of these two types of titanium in the total titanium element of the molecular sieve. Furthermore, by controlling the ratio of the peak areas of the two types of peaks, the content of framework titanium atoms and six-coordinated non-framework titanium elements can be increased, while the content of anatase non-framework titanium elements can be decreased, thereby improving the catalytic activity and stability of the molecular sieve.

[0064] The first aspect of this disclosure provides a microporous titanium-silicon molecular sieve, which has the following UV-Vis characteristics:

[0065] In the peak division results of the UV-Vis spectrum of the titanium-silicon molecular sieve in the wavelength range of 180 to 500 nm, the peak area of ​​the peak located in the range of 205 to 215 nm is recorded as A1, and the peak area of ​​the peak located in the range of 260 to 270 nm is recorded as A2.

[0066] The total area of ​​the spectral peaks in the UV-Vis spectrum of the titanium-silicon molecular sieve in the wavelength range of 180 to 500 nm is denoted as A0.

[0067] As defined in equation (1), Q1 is any value between 35% and 70%:

[0068] Q1 = A1 / A0 × 100% Equation (1);

[0069] As defined in equation (2), Q2 is any value between 30% and 50% in the following formula:

[0070] Q2 = A2 / A0 × 100% Equation (2).

[0071] This disclosure provides a microporous titanium-silicon molecular sieve, which has a high content of framework titanium atoms and six-coordinated non-framework titanium elements, and a reduced content of anatase-type non-framework titanium elements; and when the microporous titanium-silicon molecular sieve is used to catalyze the ammonification reaction of pentanone, it has high catalytic activity and good stability.

[0072] In this disclosure, "mesoporous titanium-silicon molecular sieve" refers to a titanium-silicon molecular sieve that contains both mesopores and micropores. In this disclosure, mesopores of the molecular sieve refer to pores with a diameter of less than 50 nm, preferably pores with a diameter of 8 to 48 nm; micropores refer to pores with a diameter of less than 2 nm.

[0073] In this disclosure, the peak segmentation and peak area calculation of UV-Vis spectra are performed using software and methods conventional in the art.

[0074] In one embodiment, the porous titanium silicate molecular sieve also possesses the following UV-Vis characteristics:

[0075] In the peak fractionation results of the UV-Vis spectrum of the titanium-silicon molecular sieve in the wavelength range of 180 to 500 nm, the peak area of ​​the peak located in the range of 320 to 330 nm is recorded as A3.

[0076] As defined in equation (3), Q3 is any value between 0 and 25%.

[0077] Q3 = A3 / A0 × 100% (3). In this disclosure, the peak position in the wavelength range of 320-330 nm in the peak separation results is taken as the non-framework titanium element in the form of anatase, and the ratio of the peak area of ​​this peak to the total peak area of ​​the microporous titanium silicate molecular sieve in the wavelength range of 180-500 nm is taken as the content of the anatase non-framework titanium element in all titanium elements of the molecular sieve. When Q3 is a value between 0 and 25%, the microporous titanium silicate molecular sieve has high catalytic activity and good stability.

[0078] In a preferred embodiment, Q1 is any value between 40% and 60%; Q2 is any value between 30% and 45%; and Q3 is any value between 5% and 16%. When the ratio between the peak areas of the three titanium elements in the microporous titanium-silicon molecular sieve and the total peak area meets the requirements of this embodiment, the catalytic activity and stability of the microporous titanium-silicon molecular sieve in the oximeation reaction of pentanone can be further improved.

[0079] In one embodiment, the micropore volume of the microporous titanium-silicon molecular sieve is 0.15–0.21 cm³. 3 / g, mesopore volume is 0.14~0.20cm³ 3 / g, the proportion of mesoporous volume to total pore volume is 30-50%, the average particle size is 350-400 nm, and the BET specific surface area is 440-490 m². 2 / g.

[0080] In a preferred embodiment, the micropore volume of the graded porous titanium-silicon molecular sieve is 0.18–0.20 cm³. 3 / g, mesopore volume is 0.15~0.17cm³ 3 / g, the proportion of mesoporous volume to total pore volume is 40-50%, the average particle size is 370-390nm, and the BET specific surface area is 450-470m². 2 / g. The hierarchical titanium silicate molecular sieve provided in this disclosure has a large proportion of mesopores in the total pore volume, resulting in superior performance of the hierarchical molecular sieve.

[0081] In one specific embodiment, the microporous titanium-silicon molecular sieve is selected from one or more of the following: MFI structure molecular sieve, MEL structure molecular sieve, BEA structure molecular sieve, and MWW structure molecular sieve; preferably, it is an MFI structure molecular sieve.

[0082] A second aspect of this disclosure provides a method for preparing porous titanium-silicon molecular sieves, comprising the following steps:

[0083] S1. Mix the silicon source, titanium source, alkali source, polyamine compound and water to obtain a reaction mixture;

[0084] S2. The reaction mixture is subjected to crystallization treatment and first calcination treatment to obtain intermediate molecular sieve product;

[0085] S3. The intermediate molecular sieve product is contacted with an acid solution for acidification treatment; then it is contacted with an alkaline solution for recrystallization treatment to obtain a recrystallized product.

[0086] S4. The recrystallized product is subjected to a second calcination treatment.

[0087] This disclosure provides a method for preparing microporous titanium-silicon molecular sieves. This method can increase the titanium content of the framework in the microporous titanium-silicon molecular sieve during synthesis and promote the conversion of framework titanium to six-coordinate titanium during microporous formation, further reducing the anatase content in the microporous titanium-silicon molecular sieve. This improves the catalytic performance of the microporous titanium-silicon molecular sieve in the cyclohexanone ammonium oxime reaction. Simultaneously, it can reduce crystallization time and improve the synthesis efficiency of the microporous titanium-silicon molecular sieve, resulting in good economic benefits.

[0088] The inventors of this disclosure discovered in experiments that introducing polyamines into the raw material mixture for preparing titanium-silicon molecular sieves can improve the performance of the final synthesized titanium-silicon molecular sieve. The reason for this is likely that the introduction of polyamines slows down the crystallization rate during the crystallization process, promoting the entry of titanium into the framework. In other words, by introducing polyamines, a microporous titanium-silicon molecular sieve with high framework titanium content, six-coordinated non-framework titanium content, and low anatase content can be obtained through a single crystallization process. Furthermore, after crystallization and calcination, the inventors of this disclosure continue with acid acidification and alkaline recrystallization. This effectively forms mesopores, ensuring the molecular sieve contains both micropores and mesopores. It also plays a crucial role in increasing the six-coordinated non-framework titanium content in the microporous titanium-silicon molecular sieve. Through the dissolution-recrystallization step, a portion of the framework titanium can be converted into six-coordinated non-framework titanium, further increasing the six-coordinated non-framework titanium content and obtaining a microporous titanium-silicon molecular sieve.

[0089] In one embodiment, in step S1, the silicon source is SiO2, and the alkali source is OH. - The titanium source is calculated as TiO2, and the molar ratio of silicon source: alkali source: titanium source: polyamine: water is 1:(0.1~0.3):(0.01~0.1):(0.001~0.05):(3~40).

[0090] In a preferred embodiment, the molar ratio of silicon source: alkali source: titanium source: polyamine: water is 1:(0.15-0.25):(0.03-0.06):(0.001-0.02):(10-25).

[0091] In a more preferred embodiment, the molar ratio of silicon source: alkali source: titanium source: polyamine: water is 1:(0.15-0.2):(0.03-0.05):(0.001-0.01):(10-20). Preparing molecular sieves according to the molar ratio of raw materials provided in this embodiment can further improve the catalytic performance of the molecular sieves.

[0092] In this disclosure, the term "polyamine compound" is used in the conventional understanding of the art, that is, a compound containing two or more amino groups in its molecule.

[0093] In one embodiment, in step S1, the polyamine compound is selected from at least one of the structures represented by the general formula (A):

[0094] H2N-CH2-(CH2-NH-CH2) n -CH2-NH2 formula (A); where n is a positive integer greater than or equal to 1; preferably, n is an integer between 1 and 6.

[0095] In a preferred embodiment, the polyamine compound is selected from one or more of diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

[0096] In one embodiment, the silicon source is selected from one or more of silica sol, silica gel, organosilicon esters, and precipitated silica. The silica sol includes acidic silica sol and alkaline silica sol; preferably, the silicon content in the silica sol, based on the weight of silica, is 5-40% by weight; the organosilicon ester is selected from one or more of tetraethyl silicate, tetrapropyl silicate, tetrabutyl silicate, trimethoxychlorosilane, triethoxyphenylsilane, and triethoxypropenylsilane; preferably, the silicon source is selected from one or more of organosilicon esters, more preferably tetraethyl silicate.

[0097] In one specific embodiment, the silica aggregates have a particle size of 200–1000 nm, a primary particle size of 5–70 nm, and a silicon content of not less than 99.8% by weight (based on silica weight).

[0098] In one embodiment, the titanium source is selected from one or more of organotitanium esters, titanium tetrachloride, titanium trichloride, and titanium sulfate.

[0099] In a preferred embodiment, the titanium source is selected from one or more organic titanium esters; the organic titanium ester is selected from one or more of tetraethyl titanate, tetrabutyl titanate, and tetraisopropyl titanate.

[0100] In one embodiment, the alkali source is selected from an aqueous solution of an organic or inorganic alkali; preferably, the pH value of the alkali source is 10-14. In this disclosure, the alkali source functions as an alkaline template agent.

[0101] In one specific embodiment, the organic base is selected from one or more organic amine compounds; preferably, the organic amine compound is selected from one or more aliphatic amines, aromatic amines, alkanolamines, and organic quaternary ammonium bases; the organic quaternary ammonium base is selected from one or more tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide; the inorganic base is selected from one or more sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium phosphate, potassium phosphate, disodium hydrogen phosphate, dipotassium hydrogen phosphate, and ammonia water.

[0102] In a preferred embodiment, the alkali source is selected from one or more of organic quaternary ammonium alkali and ammonia water; more preferably, it is selected from one or more of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide and ammonia water.

[0103] In one specific embodiment, step S1 includes the following steps:

[0104] (a) The silicon source, titanium source, alkali source, polyamine compound and water are mixed and hydrolyzed at 20-40°C for 2-12 hours to obtain an alcohol-containing hydrolysis product;

[0105] (b) The alcohol-containing hydrolysis product is subjected to alcohol removal at 60–110°C for 6–24 h to obtain a silicon-titanium gel as the raw material mixture. In this disclosure, the "alcohol removal" is carried out under stirring conditions, and the stirring rate can be adjusted according to actual experiments.

[0106] In one embodiment, in step S2, the conditions for the crystallization treatment include: a crystallization temperature of 120–210°C, a crystallization time of 2–24 h, and an autogenous pressure.

[0107] The conditions for the first calcination treatment include: a calcination temperature of 250–750°C and a calcination time of 2–12 hours.

[0108] In this disclosure, the crystallization process is carried out in a crystallization reactor.

[0109] In a preferred embodiment, in step S2, the conditions for the crystallization treatment include: a temperature of 140–190°C, a crystallization time of 2–18 h, and an autogenous pressure.

[0110] The conditions for the first calcination treatment include: a calcination temperature of 350–750°C and a calcination time of 2–8 hours. The microporous titanium-silicon molecular sieve prepared according to this embodiment exhibits better catalytic performance.

[0111] In one specific embodiment, step S2 further includes a pre-crystallization treatment of the reaction mixture before crystallization; preferably, the pre-crystallization conditions include: a crystallization temperature of 80–120°C and a crystallization time of 0.5–24 h; preferably, the crystallization temperature is 80–100°C and the crystallization time is 0.5–12 h. In this disclosure, the pre-crystallization is performed outside the crystallization vessel, for example, in a beaker. Pre-crystallization can improve the efficiency of subsequent crystallization and further reduce the crystallization time.

[0112] In one embodiment, in step S3, the acid solution is an aqueous solution selected from inorganic acids, and the concentration of the acid solution is 0.5-3% by weight, preferably 0.5-2% by weight; the weight ratio of the acid solution to the intermediate molecular sieve product is (2-20):1, preferably (5-10):1.

[0113] In one specific embodiment, the inorganic acid is selected from one or more of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, hydrobromic acid, and fluorosilicic acid.

[0114] In one embodiment, the alkaline solution is an aqueous solution selected from inorganic or organic bases, the concentration of the alkaline solution is 1-25% by weight, preferably 1-15% by weight; the pH value of the alkaline solution is 10-14; the weight ratio of the alkaline solution to the intermediate molecular sieve product is (1-10):1, preferably (2-5):1.

[0115] In one specific embodiment, the organic base is selected from one or more of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide; the inorganic base is selected from one or more of sodium hydroxide, potassium hydroxide, disodium hydrogen phosphate, dipotassium hydrogen phosphate, and ammonia water.

[0116] In one embodiment, in step S3, the acidification conditions include: an acidification temperature of 60–90°C and an acidification time of 2–12 h;

[0117] The recrystallization conditions include: a recrystallization temperature of 120–210°C and a recrystallization time of 2–36 h.

[0118] In a preferred embodiment, in step S3, the acidification conditions include: an acidification temperature of 70–90°C and an acidification time of 2–6 hours.

[0119] The recrystallization conditions include a recrystallization temperature of 140–200°C and a recrystallization time of 2–24 h. Following this embodiment of the dissolution-recrystallization process can further improve the hierarchical pore structure of the titanium-silicon molecular sieve and promote the conversion of more framework titanium into six-coordinate non-framework titanium.

[0120] In one embodiment, in step S4, the conditions for the second calcination treatment include: a calcination temperature of 250–750°C and a calcination time of 2–12 h; preferably, the calcination temperature is 400–600°C and the calcination time is 3–6 h.

[0121] The third aspect of this disclosure provides a microporous titanium-silicon molecular sieve, prepared according to the method described in the second aspect of this disclosure.

[0122] The fourth aspect of this disclosure provides a method for the aminooximation of cyclohexanone, the method comprising reacting cyclohexanone with an oxidant in the presence of a catalyst, said catalyst containing the microporous titanium silicate molecular sieve described in the first and third aspects of this disclosure.

[0123] In one embodiment, the reaction conditions include: a molar ratio of oxidant to cyclohexanone of 0.5 to 2, a reaction temperature of 40 to 120°C, a reaction time of 0.5 to 6 h, and a mass ratio of catalyst to cyclohexanone of 0.05 to 0.5.

[0124] In one specific embodiment, the catalyst may contain only the microporous titanium silicate molecular sieve provided in this disclosure, or the microporous titanium silicate molecular sieve provided in this disclosure may be combined with other molecular sieves and other materials, and may be adjusted according to actual needs.

[0125] In one specific embodiment, the method for the ammonium oximeation of cyclohexanone includes: contacting the aforementioned microporous titanium silicate molecular sieve, cyclohexanone, hydrogen peroxide, ammonia, and solvent under ammonium oximeation reaction conditions to obtain a product containing cyclohexanone oxime. The solvent is water or an alcohol with 1 to 6 carbon atoms. The ammonium oximeation reaction conditions include a molar ratio of cyclohexanone: ammonia: hydrogen peroxide: solvent preferably of 1:(1-5):(0.5-2.5):(1-10), more preferably 1:(2-5):(1-2):(2-4); a reaction temperature preferably of 40-90°C, more preferably 60-80°C; and a reaction pressure preferably of 0-1 MPa gauge pressure.

[0126] According to this disclosure, the microporous titanium silicate molecular sieve can be used for catalytic reactions in various reactors such as batch reactors, slurry bed reactors, fixed bed reactors, fluidized bed reactors, moving bed reactors, and microchannel reactors; the reaction raw materials and catalysts can be fed in one go, intermittently, or continuously; the separation of products and catalysts can be achieved in various ways, such as sedimentation, filtration, centrifugation, evaporation, and membrane separation, to achieve product separation and catalyst recovery and reuse.

[0127] The present disclosure will be further illustrated by the following examples, but these examples do not limit the scope of the disclosure.

[0128] The BET specific surface area and pore volume of the molecular sieve were characterized by a physical adsorption instrument, specifically a Micromeritics ASAP245 static nitrogen adsorption instrument, and were determined according to the ASTM D4222-98 standard method. The results were calculated using both the BET method and the t-plot method.

[0129] The average particle size of the molecular sieve was obtained by taking SEM images with a Hitachi 4800 microscope and counting the particle sizes of at least 100 particles.

[0130] The molecular sieves were characterized by high-resolution morphology analysis using transmission electron microscopy (TEM) with a JEM-ARM200F transmission electron microscope.

[0131] The titanium content of the molecular sieve framework was characterized by UV-Vis using a Cary 300 Agilent UV-Vis spectrometer with a test range of 180–800 nm. The results were obtained by Gaussian fitting and peak division, and the peak area was calculated as the integral of the spectral curve.

[0132] Unless otherwise specified, all raw materials used in the examples and comparative examples are analytical grade reagents.

[0133] The reaction products were analyzed by gas chromatography, and the results were quantified using the external standard method. The chromatographic conditions were as follows: Agilent-6890 chromatograph, HP-5 capillary column, injection volume 0.5 μL, injection port temperature 280℃. Column temperature was maintained at 45℃ for 5 min, then increased to 250℃ at a rate of 15℃ / min and held for 1 min. An FID detector was used, with a detector temperature of 280℃.

[0134] Example 1

[0135] Tetraethyl silicate (calculated as silicon dioxide), 25.5% by weight of tetrapropylammonium hydroxide aqueous solution (calculated as OH) -A mixture of tetraethyl titanate (calculated as titanium dioxide), triethylenetetramine, and water in a molar ratio of 1:0.15:0.03:0.005:20 was prepared and hydrolyzed at 30°C for 2 hours. The alcohol was then removed at 80°C for 6 hours to obtain a silica-titanium gel. This silica-titanium gel was pre-crystallized at 85°C for 6 hours, then transferred to a crystallization reactor and crystallized at 180°C for 18 hours to obtain a crystallized product. The crystallized product was recovered and calcined at 450°C for 6 hours to obtain the microporous titanium-silicon molecular sieve TS-1-a.

[0136] The obtained TS-1-a was dispersed in a 1.5 wt% nitric acid solution at a weight ratio of acid to TS-1-a of 10:1 and treated at 80°C for 2 h. The treated product was recovered and dispersed in a 15 wt% tetrapropylammonium hydroxide aqueous solution (pH 12) at a weight ratio of alkali to TS-1-a of 5:1, and recrystallized at 180°C for 12 h to obtain the recrystallized product. The recrystallized product was recovered and calcined at 550°C for 6 h to obtain the microporous titanium silicate molecular sieve TS-1-A.

[0137] TEM images of the microporous titanium silicate molecular sieve TS-1-A are shown below. Figure 1 As shown, the molecular sieve particles have regular shapes and a large number of pores.

[0138] The UV-Vis spectrum and peak fractionation results of the microporous titanium silicate molecular sieve TS-1-A are as follows: Figure 2 As shown, spectral peaks appeared at positions of 205–215 nm, 260–270 nm, and 330–340 nm, respectively, indicating that the microporous titanium-silicon molecular sieve provided in this embodiment contains three forms of titanium: framework titanium, six-coordinate non-framework titanium, and anatase non-framework titanium. The integral results of the peak areas of each peak in the UV-Vis spectrum of the titanium-silicon molecular sieve are as follows: the total area A0 of the peaks in the wavelength range of 180–500 nm is 70.57. In the peak segmentation results, the peak area A1 of the peak in the range of 205–215 nm is 28.65, the peak area A2 of the peak in the range of 260–270 nm is 32.18, and the peak area A3 of the peak in the range of 330–340 nm is 9.74. The results of Q1–Q3 calculated by equations (1)–(3) are listed in Table 1.

[0139] The structural data of the microporous titanium silica molecular sieve TS-1-A, including BET specific surface area, pore volume, and average particle size, are listed in Table 1.

[0140] Example 2

[0141] Tetraethyl silicate (calculated as silicon dioxide), 25.5% by weight of tetrapropylammonium hydroxide aqueous solution (calculated as OH) -A mixture of titanium dioxide (calculated as titanium dioxide), tetrabutyl titanate (calculated as titanium dioxide), and water was prepared in a molar ratio of 1:0.15:0.04:20. The mixture was hydrolyzed at 30°C for 2 hours, followed by alcohol removal at 80°C for 6 hours to obtain a titanium silicate gel. This titanium silicate gel was pre-crystallized at 80°C for 0.5 hours, then transferred to a crystallization reactor and crystallized at 170°C for 4 hours to obtain a crystallized product. The crystallized product was recovered and calcined at 550°C for 3 hours to obtain the microporous titanium silicate molecular sieve TS-1-b.

[0142] The obtained TS-1-b was dispersed in a 1.5 wt% hydrochloric acid solution at a weight ratio of acid to TS-1-b of 8:1 and treated at 80°C for 2 h. The treated product was recovered and dispersed in a 5 wt% tetrapropylammonium hydroxide aqueous solution (pH 11) at a weight ratio of alkali to TS-1-b of 3:1, and recrystallized at 170°C for 24 h to obtain the recrystallized product. The recrystallized product was recovered and calcined at 550°C for 3 h to obtain the microporous titanium silicate molecular sieve TS-1-B.

[0143] TEM images of the microporous titanium silicate molecular sieve TS-1-B and Figure 1 Similarly, UV-Vis results are the same as Figure 2 Similarly, the data on the framework titanium content, six-coordinate non-framework titanium content, anatase non-framework titanium content, BET specific surface area, pore volume, and average particle size of the microporous titanium silicate molecular sieve TS-1-B are listed in Table 1.

[0144] Example 3

[0145] Tetraethyl silicate and silica were mixed at a molar ratio of 1:1 as a silicon source (based on silica). This silicon source was then mixed with a 25.5% by weight aqueous solution of tetrapropylammonium hydroxide (based on OH). - A mixture of titanium dioxide (calculated as titanium dioxide), tetrabutyl titanate (calculated as titanium dioxide), diethylenetriamine, and water in a molar ratio of 1:0.3:0.03:0.01:40 was prepared and hydrolyzed at 40°C for 12 hours. The alcohol was then removed at 90°C for 12 hours to obtain a silica-titanium gel. This silica-titanium gel was pre-crystallized at 120°C for 12 hours, then transferred to a crystallization reactor and crystallized at 180°C for 2 hours to obtain a crystallized product. The crystallized product was recovered and calcined at 450°C for 3 hours to obtain the microporous titanium-silicon molecular sieve TS-1-c.

[0146] The obtained TS-1-c was dispersed in a 3% wt% nitric acid solution at a weight ratio of acid to TS-1-c of 10:1 and treated at 80°C for 6 hours. The treated product was recovered and dispersed in a 10% wt% tetrapropylammonium hydroxide aqueous solution (pH 12) at a weight ratio of alkali to TS-1-c of 5:1, and recrystallized at 180°C for 24 hours to obtain the recrystallized product. The recrystallized product was recovered and calcined at 550°C for 3 hours to obtain the microporous titanium silicate molecular sieve TS-1-C.

[0147] TEM images of microporous titanium silicate molecular sieve TS-1-C and Figure 1 Similarly, UV-Vis results are the same as Figure 2 Similarly, the data on the framework titanium content, six-coordinate non-framework titanium content, anatase non-framework titanium content, BET specific surface area, pore volume, and average particle size of the microporous titanium silicate molecular sieve TS-1-C are listed in Table 1.

[0148] Example 4

[0149] Tetraethyl silicate (calculated as silicon dioxide) and a 20% by weight aqueous solution of tetrabutylammonium hydroxide (calculated as OH) - The following mixtures were prepared: titanium dioxide (calculated as titanium dioxide), tetraisopropyl titanate (calculated as titanium dioxide), diethylenetriamine, and water in a molar ratio of 1:0.15:0.04:0.01:20. The mixture was hydrolyzed at 40°C for 6 hours, followed by alcohol removal at 80°C for 8 hours to obtain a titanium silicate gel. This titanium silicate gel was pre-crystallized at 80°C for 6 hours, then transferred to a crystallization reactor and crystallized at 170°C for 12 hours to obtain a crystallized product. The crystallized product was recovered and calcined at 550°C for 6 hours to obtain the microporous titanium silicate molecular sieve TS-1-d.

[0150] The obtained TS-1-d was dispersed in a 1.5 wt% sulfuric acid solution at a weight ratio of acid to TS-1-d of 5:1 and treated at 80°C for 4 h. The treated product was recovered and dispersed in a 10 wt% tetrabutylammonium hydroxide aqueous solution (pH 12) at a weight ratio of alkali to TS-1-d of 4:1, and recrystallized at 170°C for 12 h to obtain the recrystallized product. The recrystallized product was recovered and calcined at 500°C for 6 h to obtain the microporous titanium silicate molecular sieve TS-1-D.

[0151] TEM images of the microporous titanium silicate molecular sieve TS-1-D and Figure 1 Similarly, UV-Vis results are the same as Figure 2 Similarly, the data on the framework titanium content, six-coordinate non-framework titanium content, anatase non-framework titanium content, BET specific surface area, pore volume, and average particle size of the microporous titanium silicate molecular sieve TS-1-D are listed in Table 1.

[0152] Example 5

[0153] Tetrapropyl silicate (calculated as silicon dioxide), 25.5% by weight of tetrapropylammonium hydroxide aqueous solution (calculated as OH) - A mixture of tetrabutyl titanate, tetraethylenepentamine, and water in a molar ratio of 1:0.2:0.06:0.01:25 was hydrolyzed at 30°C for 2 hours, followed by alcohol removal at 100°C for 12 hours to obtain a silica-titanium gel. This silica-titanium gel was pre-crystallized at 100°C for 6 hours, then transferred to a crystallization reactor and crystallized at 170°C for 12 hours to obtain a crystallized product. The crystallized product was recovered and calcined at 550°C for 3 hours to obtain the microporous titanium-silicon molecular sieve TS-1-e.

[0154] The obtained TS-1-e was dispersed in a 1.5 wt% nitric acid solution at a weight ratio of acid to TS-1-e of 3:1 and treated at 80°C for 6 h. The treated product was recovered and dispersed in a 15 wt% tetrapropylammonium hydroxide aqueous solution (pH 12) at a weight ratio of alkali to TS-1-e of 5:1, and recrystallized at 180°C for 12 h to obtain the recrystallized product. The recrystallized product was recovered and calcined at 600°C for 3 h to obtain the microporous titanium silicate molecular sieve TS-1-E.

[0155] TEM images of microporous titanium silicate molecular sieve TS-1-E and Figure 1 Similarly, UV-Vis results are the same as Figure 2 Similarly, the data on the framework titanium content, six-coordinate non-framework titanium content, anatase non-framework titanium content, BET specific surface area, pore volume, and average particle size of the microporous titanium silicate molecular sieve TS-1-E are listed in Table 1.

[0156] Example 6

[0157] Tetraethyl silicate (calculated as silicon dioxide), 25.5% by weight of tetrapropylammonium hydroxide aqueous solution (calculated as OH) - A mixture of tetrabutyl titanate (calculated as titanium dioxide), triethylenetetramine, and water in a molar ratio of 1:0.15:0.04:0.005:20 was prepared and hydrolyzed at 30°C for 2 hours. The mixture was then heated to 80°C to remove the alcohol for 6 hours, yielding a silica-titanium gel. This silica-titanium gel was pre-crystallized at 80°C for 4 hours, then transferred to a crystallization reactor and crystallized at 180°C for 6 hours to obtain a crystallized product. The crystallized product was recovered and calcined at 500°C for 4 hours to obtain the microporous titanium-silicon molecular sieve TS-1-f.

[0158] The obtained TS-1-f was dispersed in a 2% (w / w) hydrochloric acid solution at a weight ratio of acid to TS-1-f of 5:1, and treated at 80°C for 6 h. The treated product was recovered and dispersed in a 15% (w / w) tetrapropylammonium hydroxide aqueous solution (pH 12) at a weight ratio of alkali to TS-1-f of 5:1, and recrystallized at 170°C for 18 h to obtain the recrystallized product. The recrystallized product was recovered and calcined at 550°C for 3 h to obtain the microporous titanium silicate molecular sieve TS-1-F.

[0159] TEM images of microporous titanium silicate molecular sieve TS-1-F and Figure 1 Similarly, UV-Vis results are the same as Figure 2 Similarly, the data on the framework titanium content, six-coordinate non-framework titanium content, anatase non-framework titanium content, BET specific surface area, pore volume, and average particle size of the microporous titanium silicate molecular sieve TS-1-F are listed in Table 1.

[0160] Example 7

[0161] An aqueous solution prepared by mixing silica sol (calculated as silicon dioxide), hexamethylenediamine, and potassium hydroxide in a 1:1 molar ratio (calculated as OH) - A mixture of tetrabutyl titanate (calculated as titanium dioxide), triethylenetetramine, and water in a molar ratio of 1:0.3:0.06:0.01:25 was prepared and hydrolyzed at 40°C for 2 hours. The alcohol was then removed at 80°C for 6 hours to obtain a silica-titanium gel. This silica-titanium gel was pre-crystallized at 90°C for 12 hours, then transferred to a crystallization reactor and crystallized at 170°C for 12 hours to obtain a crystallized product. The crystallized product was recovered and calcined at 550°C for 3 hours to obtain microporous titanium-silicon molecular sieve TS-1-g.

[0162] The obtained TS-1-g was dispersed in a 1.5 wt% hydrochloric acid solution at a weight ratio of acid to TS-1-g of 15:1 and treated at 80℃ for 4 h. The treated product was recovered and dispersed in an aqueous solution prepared with hexamethylenediamine and potassium hydroxide in a 1:1 molar ratio of alkali to TS-1-g at a weight ratio of 8:1 (hexamethylenediamine mass fraction 5 wt%, alkali solution pH 10). The solution was recrystallized at 180℃ for 12 h to obtain the recrystallized product. The recrystallized product was recovered and calcined at 550℃ for 6 h to obtain the microporous titanium silicate molecular sieve TS-1-G.

[0163] TEM images of microporous titanium silicate molecular sieve TS-1-G and Figure 1 Similarly, UV-Vis results are the same as Figure 2 Similarly, the data on the framework titanium content, six-coordinate non-framework titanium content, anatase non-framework titanium content, BET specific surface area, pore volume, and average particle size of the microporous titanium silicate molecular sieve TS-1-G are listed in Table 1.

[0164] Example 8

[0165] An aqueous solution of tetraethyl silicate (calculated as silicon dioxide), tetrapropylammonium hydroxide and tetraethylammonium hydroxide in a 1:1 molar ratio (calculated as OH) - A mixture of tetraethyl titanate (calculated as titanium dioxide), triethylenetetramine, and water in a molar ratio of 1:0.2:0.03:0.005:20 was prepared and hydrolyzed at 30°C for 2 hours. The alcohol was then removed at 80°C for 6 hours to obtain a silica-titanium gel. This silica-titanium gel was pre-crystallized at 85°C for 2 hours, then transferred to a crystallization reactor and crystallized at 180°C for 6 hours to obtain a crystallized product. The crystallized product was recovered and calcined at 550°C for 6 hours to obtain the microporous titanium-silicon molecular sieve TS-1-h.

[0166] The obtained TS-1-h was dispersed in a 1.5 wt% nitric acid solution at a weight ratio of acid to TS-1-h of 20:1 and treated at 80°C for 2 hours. The treated product was recovered and dispersed in an aqueous solution of tetrapropylammonium hydroxide and tetraethylammonium hydroxide in a 1:1 molar ratio of alkali to TS-1-h (based on a total mass fraction of 15 wt% for the combined tetrapropylammonium hydroxide and tetraethylammonium hydroxide, and a pH of 12 for the alkali solution) at a weight ratio of 10:1. The solution was recrystallized at 180°C for 12 hours to obtain the recrystallized product. The recrystallized product was recovered and calcined at 550°C for 6 hours to obtain the microporous titanium silicate molecular sieve TS-1-H.

[0167] TEM images of the microporous titanium silicate molecular sieve TS-1-H and Figure 1 Similarly, UV-Vis results are the same as Figure 2 Similarly, the data on the framework titanium content, six-coordinate non-framework titanium content, anatase non-framework titanium content, BET specific surface area, pore volume, and average particle size of the microporous titanium silicate molecular sieve TS-1-H are listed in Table 1.

[0168] Example 9

[0169] Tetraethyl silicate (calculated as silicon dioxide), 25.5% by weight of tetrapropylammonium hydroxide aqueous solution (calculated as OH) - A titanium source (calculated as titanium dioxide) was prepared by mixing tetraethyl titanate and titanium sulfate in a 1:1 ratio, along with triethylenetetramine and water in a molar ratio of 1:0.2:0.06:0.005:30. The mixture was hydrolyzed at 30°C for 2 hours, followed by alcohol removal at 80°C for 6 hours to obtain a titanium silicate gel. This titanium silicate gel was pre-crystallized at 100°C for 24 hours, then transferred to a crystallization reactor and crystallized at 180°C for 24 hours to obtain a crystallized product. The crystallized product was recovered and calcined at 550°C for 6 hours to obtain the microporous titanium silicate molecular sieve TS-1-i.

[0170] The obtained TS-1-i was dispersed in a 1.5 wt% nitric acid solution at a weight ratio of acid to TS-1-i of 10:1 and treated at 80°C for 4 h. The treated product was recovered and dispersed in a 15 wt% tetrapropylammonium hydroxide aqueous solution (pH 12) at a weight ratio of alkali to TS-1-i of 2:1, and recrystallized at 180°C for 12 h to obtain the recrystallized product. The recrystallized product was recovered and calcined at 550°C for 6 h to obtain the microporous titanium silicate molecular sieve TS-1-I.

[0171] TEM images of the microporous titanium silicate molecular sieve TS-1-I and Figure 1 Similarly, UV-Vis results are the same as Figure 2 Similarly, the data on the framework titanium content, six-coordinate non-framework titanium content, anatase non-framework titanium content, BET specific surface area, pore volume, and average particle size of the microporous titanium silicate molecular sieve TS-1-I are shown in Table 1.

[0172] Example 10

[0173] Tetrabutyl silicate (calculated as silicon dioxide), 25.5% by weight of tetrabutylammonium hydroxide aqueous solution (calculated as OH) - A mixture of tetrabutyl titanate (calculated as titanium dioxide), tetraethylenepentamine, and water in a molar ratio of 1:0.15:0.05:0.002:25 was prepared and hydrolyzed at 30°C for 4 hours. The alcohol was then removed at 80°C for 9 hours to obtain a silica-titanium gel. This silica-titanium gel was pre-crystallized at 90°C for 9 hours, then transferred to a crystallization reactor and crystallized at 180°C for 12 hours to obtain a crystallized product. The crystallized product was recovered and calcined at 550°C for 6 hours to obtain the microporous titanium-silicon molecular sieve TS-1-j.

[0174] The obtained TS-1-j was dispersed in a 1.5 wt% nitric acid solution at a weight ratio of acid to TS-1-j of 10:1 and treated at 80°C for 2 h. The treated product was recovered and dispersed in a 10 wt% tetrabutylammonium hydroxide aqueous solution (pH 12) at a weight ratio of alkali to TS-1-j of 5:1, and recrystallized at 180°C for 12 h to obtain the recrystallized product. The recrystallized product was recovered and calcined at 550°C for 6 h to obtain the microporous titanium silicate molecular sieve TS-1-J.

[0175] TEM images of the microporous titanium silicate molecular sieve TS-1-J and Figure 1 Similarly, UV-Vis results are the same as Figure 2 Similarly, the data on the framework titanium content, six-coordinate non-framework titanium content, anatase non-framework titanium content, BET specific surface area, pore volume, and average particle size of the microporous titanium silicate molecular sieve TS-1-J are listed in Table 1.

[0176] Example 11

[0177] The preparation method is the same as that in Example 10, except that:

[0178] The pre-crystallization temperature was 120℃ and the time was 24h; the crystallization temperature in the crystallization kettle was 140℃ and the time was 24h; the first calcination temperature was 500℃ and the time was 10h.

[0179] The acidification temperature was 60℃ for 10 hours; the recrystallization temperature was 140℃ for 12 hours; and the second calcination temperature was 450℃ for 6 hours. This yielded a microporous titanium silicate molecular sieve, TS-1-K.

[0180] TEM images of the microporous titanium silicate molecular sieve TS-1-K and Figure 1 Similarly, UV-Vis results are the same as Figure 2 Similarly, the data on the framework titanium content, six-coordinate non-framework titanium content, anatase non-framework titanium content, BET specific surface area, pore volume, and average particle size of the microporous titanium silicate molecular sieve TS-1-K are listed in Table 1.

[0181] Example 12

[0182] The preparation method is the same as in Example 1, but differs from that in that:

[0183] The molar ratio of silicon source: alkali source: titanium source: polyamine: water is 1:0.1:0.1:0.05:40;

[0184] The pre-crystallization temperature was 120℃ and the time was 24h; the crystallization temperature in the crystallization kettle was 140℃ and the time was 24h; the first calcination temperature was 500℃ and the time was 10h.

[0185] The acidification temperature was 60℃ for 10 hours; the recrystallization temperature was 140℃ for 12 hours; and the second calcination temperature was 450℃ for 6 hours. This yielded a microporous titanium silicate molecular sieve, TS-1-L.

[0186] TEM images of microporous titanium silicate molecular sieve TS-1-L and Figure 1 Similarly, UV-Vis results are the same as Figure 2 Similarly, the data on the framework titanium content, six-coordinate non-framework titanium content, anatase non-framework titanium content, BET specific surface area, pore volume, and average particle size of the microporous titanium silicate molecular sieve TS-1-L are listed in Table 1.

[0187] Comparative Example 1

[0188] Microporous titanium silicalite D-TS-1 was synthesized according to the method described in the literature (Thangaraj A, Eapen M J, Sivasanker S, et al. Studies on the synthesis of titanium silicalite, TS-1[J]. Zeolites, 1992).

[0189] Tetraethyl orthosilicate (based on silicon dioxide) was pre-hydrolyzed in a tetrapropylammonium hydroxide aqueous solution at pH 14 for 30 min. Tetrabutyl titanate (based on titanium dioxide) dissolved in a small amount of isopropanol was added, and the mixture was stirred until homogeneous. Water was then added, and the hydrolysis was further performed. The alcohol was removed at 80°C for 3 h to obtain a silicon-titanium gel. This silicon-titanium gel consists of a silicon source (based on silicon dioxide) and an alkali source (based on OH... - The molar ratio of titanium dioxide (calculated as titanium dioxide) to water was 1:0.4:0.03:40. This titanium dioxide silica gel was transferred to a crystallization reactor and crystallized at 170℃ for 24 hours. After recovering the crystallized product, it was calcined at 520℃ for 16 hours to obtain microporous titanium silica molecular sieve D-TS-1.

[0190] TEM images of microporous titanium silicate molecular sieve D-TS-1 are shown below. Figure 3 As shown; UV-Vis results are as follows Figure 4 As shown.

[0191] The skeleton titanium content, six-coordinate non-skeleton titanium content, anatase non-skeleton titanium content, specific surface area, and pore volume of microporous titanium silicate molecular sieve D-TS-1 are listed in Table 1.

[0192] Comparative Example 2

[0193] Grade porous titanium silicate molecular sieve D-TS-2 was synthesized according to the literature method (Wang Y, Lin M, Tuel A. Hollow TS-1 crystals formed via adissolution–recrystallization process[J]. Microporous and mesoporous materials, 2007).

[0194] Take 1 g of the microporous titanium-silicon molecular sieve obtained in Comparative Example 1, disperse it in 4.167 mL of tetrapropylammonium hydroxide aqueous solution with pH 14, and add 3.32 mL of water. Transfer the mixture to a crystallization reactor and recrystallize at 170 °C for 24 h. After recovering the crystallized product, calcine at 520 °C for 16 h to obtain microporous titanium-silicon molecular sieve D-TS-2.

[0195] TEM images of the microporous titanium silicate molecular sieve D-TS-2 are shown below. Figure 5 As shown; UV-Vis results are as follows Figure 6 As shown.

[0196] Table 1 lists the data on the framework titanium content, six-coordinate non-framework titanium content, anatase non-framework titanium content, BET specific surface area, pore volume, and average particle size of the microporous titanium silicate molecular sieve D-TS-2.

[0197] Comparative Example 3

[0198] The preparation method in Example 1 is the same as in Example 1, except that no polyamine is added. The rest of the process and conditions are the same as in Example 1. The resulting titanium silicate molecular sieve product is denoted as D-TS-3.

[0199] Comparative Example 4

[0200] The preparation method is the same as in Example 1, except that acidification and recrystallization are not performed, and the intermediate product microporous titanium silicon molecular sieve TS-1-a is designated as D-TS-4.

[0201] In Table 1, the skeletal titanium content is represented by Q1, which is calculated according to formula (1); the six-coordinate non-skeletal titanium content is represented by Q2, which is calculated according to formula (2); and the anatase non-skeletal titanium content is represented by Q3, which is calculated according to formula (3).

[0202] Table 1

[0203]

[0204]

[0205] Test case

[0206] This test example illustrates the effect of using the microporous titanium-silicon molecular sieve obtained by the method of this disclosure to catalyze the amination reaction of cyclohexanone.

[0207] The cyclohexanone amination reaction was carried out in a 250 ml three-necked flask reaction apparatus equipped with an automatic temperature-controlled water bath, magnetic stirring, and reflux condenser. Samples prepared in the above examples and comparative examples were added to a three-necked flask at a ratio of 1.03 g of sample, 20 g of solvent tert-butanol, and 9.8 g of cyclohexanone (catalyst to cyclohexanone mass ratio of 0.1). The flask was then placed in a water bath at a preset reaction temperature of 80 °C. Using a peristaltic pump, 13.7 g of 30 wt% hydrogen peroxide and 28.1 g of 25 wt% ammonia were simultaneously added dropwise, with a molar ratio of cyclohexanone:ammonia:hydrogen peroxide:solvent of 1:2:1.2:2.7. The reaction was stopped after 0.5 h, rapidly cooled, and the liquid product was obtained by filtration and composition determination. The results are listed in Table 2.

[0208] For the long-cycle reaction, 1.03 g of the obtained sample was placed in a 100 mL slurry bed reactor equipped with continuous feed and membrane separation device. Under stirring, 30% hydrogen peroxide (w / w) was added at a rate of 24.7 mL / h, 25% ammonia (w / w) at a rate of 61.7 mL / h, and a mixture of cyclohexanone and tert-butanol (cyclohexanone to tert-butanol volume ratio 1:2.5) was added at a rate of 72.2 mL / h, while simultaneously being discharged continuously at the same rate. The reaction temperature was maintained at 80 °C for 120 h, and samples were taken for analysis every 12 h thereafter. The data in the "Long-cycle Reaction Results" column of Table 2 are the average of the five sampling results after 120 h of reaction.

[0209] Cyclohexanone conversion rate (%) = (moles of cyclohexanone in the feed - moles of cyclohexanone in the product) / moles of cyclohexanone in the feed × 100%;

[0210] Cyclohexanone oxime selectivity (%) = number of moles of cyclohexanone oxime generated in the product / number of moles of cyclohexanone consumed to generate all products × 100%.

[0211] Table 2

[0212]

[0213] According to the data in Tables 1 and 2 above, compared with the molecular sieves D-TS-1 to D-TS-4 prepared by Comparative Examples 1 to 4, the molecular sieves TS-1-A to TS-1-J prepared by the method provided in this application meet the requirements of Q1 being 35 to 70%, Q2 being 30 to 50%, and Q3 being 0 to 25%. Molecular sieves TS-1-A to TS-1-J have higher cyclohexanone conversion rate, higher cyclohexanone oxime selectivity, and better catalytic stability in the catalytic cyclohexanone amination oxime reaction.

[0214] Comparing molecular sieves TS-1-A to TS-1-K with TS-1-L, it can be seen that the microporous titanium silicate molecular sieves TS-1-A to TS-1-K satisfy the requirements of "Q1 in the range of 40-60%, Q2 in the range of 30-45%, and Q3 in the range of 5-16%". Compared with TS-1-L, the microporous titanium silicate molecular sieves TS-1-A to TS-1-K have higher cyclohexanone conversion, higher cyclohexanone oxime selectivity, and better catalytic stability in the catalytic cyclohexanone amination oxime reaction.

[0215] Comparing molecular sieves TS-1-D, TS-1-E, TS-1-F, TS-1-H, and TS-1-J with other molecular sieves, it can be seen that molecular sieves TS-1-D, TS-1-F, TS-1-H, TS-1-E, and TS-1-J satisfy the following molar ratio of silicon source: alkali source: titanium source: polyamine: water during the preparation process: 1:(0.15~0.25):(0.03~0.06):(0.001~0.02):(10~25). Molecular sieves TS-1-D, TS-1-E, TS-1-F, TS-1-H, and TS-1-J have higher cyclohexanone conversion rates in the catalytic amination reaction of cyclohexanone.

[0216] Comparing molecular sieves TS-1-J and TS-1-K, it can be seen that molecular sieve TS-1-J adopts the process conditions in the preferred embodiment of this disclosure during its preparation. Molecular sieve TS-1-J has higher cyclohexanone conversion rate, higher cyclohexanone oxime selectivity and better catalytic stability in the catalytic cyclohexanone amination oxime reaction.

[0217] The preferred embodiments of this disclosure have been described in detail above. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0218] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0219] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A microporous titanium-silicon molecular sieve, characterized in that, This grade of porous titanium silicate molecular sieve exhibits the following UV-Vis characteristics: In the peak division results of the UV-Vis spectrum of the titanium-silicon molecular sieve in the wavelength range of 180~500nm, the peak area of ​​the peak located in the range of 205~215nm is recorded as A1, and the peak area of ​​the peak located in the range of 260~270nm is recorded as A2. The total area of ​​the spectral peaks in the UV-Vis spectrum of the titanium-silicon molecular sieve in the wavelength range of 180~500nm is denoted as A0. As defined in equation (1), Q1 is any value between 35% and 70%: Q1 = A1 / A0 × 100% (1); As defined in equation (2), Q2 is any value between 30% and 50% in the following formula: Q2 = A2 / A0 × 100% (2).

2. The microporous titanium-silicon molecular sieve according to claim 1, characterized in that, This grade of porous titanium silicate molecular sieve also exhibits the following UV-Vis characteristics: In the peak fractionation results of the UV-Vis spectrum of the titanium-silicon molecular sieve in the wavelength range of 180~500nm, the peak area of ​​the peak located in the range of 320~330nm is recorded as A3. As defined in equation (3), Q3 is any value between 0 and 25%: Q3=A3 / A0×100% formula (3).

3. The microporous titanium-silicon molecular sieve according to claim 2, characterized in that, Q1 is any value between 40% and 60%; Q2 is any value between 30% and 45%; Q3 is any value between 5% and 16%.

4. The microporous titanium-silicon molecular sieve according to claim 1, characterized in that, The micropore volume of the microporous titanium-silicon molecular sieve is 0.15~0.21 cm³. 3 / g, mesopore volume is 0.14~0.20cm³ 3 / g, mesoporous volume accounts for 30-50% of the total pore volume, average particle size is 350-400 nm, and BET specific surface area is 440-490 m². 2 / g.

5. The microporous titanium-silicon molecular sieve according to claim 4, characterized in that, The micropore volume of the microporous titanium-silicon molecular sieve is 0.18~0.20 cm³. 3 / g, mesopore volume is 0.15~0.17cm³ 3 / g, mesoporous volume accounts for 40-50% of the total pore volume, average particle size is 370-390nm, and BET specific surface area is 450-470m². 2 / g.

6. The microporous titanium-silicon molecular sieve according to claim 1, characterized in that, The microporous titanium-silicon molecular sieve is selected from one or more of the following: MFI structure molecular sieve, MEL structure molecular sieve, BEA structure molecular sieve, and MWW structure molecular sieve.

7. The microporous titanium-silicon molecular sieve according to claim 6, characterized in that, The microporous titanium silicate molecular sieve is an MFI structure molecular sieve.

8. A method for preparing the microporous titanium-silicon molecular sieve as described in claim 1, characterized in that, Includes the following steps: S1. Mix the silicon source, titanium source, alkali source, polyamine compound and water to obtain a reaction mixture; S2. The reaction mixture is subjected to crystallization treatment and first calcination treatment to obtain intermediate molecular sieve product; S3. The intermediate molecular sieve product is contacted with an acid solution for acidification treatment; then it is contacted with an alkaline solution for recrystallization treatment to obtain a recrystallized product. S4. The recrystallized product is subjected to a second calcination treatment.

9. The method according to claim 8, characterized in that, In step S1, the silicon source is SiO2, and the alkali source is OH. - The titanium source is calculated as TiO2, and the molar ratio of silicon source: alkali source: titanium source: polyamine: water is 1: (0.1~0.3): (0.01~0.1): (0.001~0.05): (3~40).

10. The method according to claim 9, characterized in that, The molar ratio of silicon source: alkali source: titanium source: polyamine: water is 1: (0.15~0.25): (0.03~0.06): (0.001~0.02): (10~25).

11. The method according to claim 10, characterized in that, The molar ratio of silicon source: alkali source: titanium source: polyamine: water is 1: (0.15~0.2): (0.03~0.05): (0.001~0.01): (10~20).

12. The method according to claim 8, characterized in that, In step S1, the polyamine compound is selected from at least one of the structures represented by the general formula (A): H2N-CH2-(CH2-NH-CH2) n -CH2-NH2 formula (A); where n is a positive integer greater than or equal to 1; The silicon source is selected from one or more of silica sol, silica gel, organosilicon ester and precipitated silica; The titanium source is selected from one or more of organic titanium esters, titanium tetrachloride, titanium trichloride, and titanium sulfate; the alkali source is selected from an aqueous solution of an organic alkali or an inorganic alkali.

13. The method according to claim 12, characterized in that, In equation (A), n is an integer between 1 and 6.

14. The method according to claim 12, characterized in that, The polyamine compound is selected from one or more of diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

15. The method according to claim 12, characterized in that, The silica sol includes acidic silica sol and alkaline silica sol.

16. The method according to claim 12, characterized in that, The silica sol contains 5-40% silicon by weight, based on silica weight; the organosilicon ester is selected from one or more of tetraethyl silicate, tetrapropyl silicate, tetrabutyl silicate, trimethoxychlorosilane, triethoxyphenylsilane, and triethoxypropenylsilane.

17. The method according to claim 12, characterized in that, The silicon source is selected from one or more organosilicon esters.

18. The method according to claim 12, characterized in that, The silicon source is tetraethyl silicate.

19. The method according to claim 12, characterized in that, The titanium source is selected from one or more organic titanium esters; the organic titanium ester is selected from one or more of tetraethyl titanate, tetrabutyl titanate, and tetraisopropyl titanate.

20. The method according to claim 12, characterized in that, The pH value of the alkali source is 10-14.

21. The method according to claim 12, characterized in that, The organic base is selected from one or more organic amine compounds.

22. The method according to claim 21, characterized in that, The organic amine compound is selected from one or more of aliphatic amines, aromatic amines, alkanolamines, and organic quaternary ammonium bases; the organic quaternary ammonium base is selected from one or more of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide; the inorganic base is selected from one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium phosphate, potassium phosphate, disodium hydrogen phosphate, dipotassium hydrogen phosphate, and ammonia water.

23. The method according to claim 12, characterized in that, The alkali source is selected from one or more of organic quaternary ammonium alkali and ammonia water.

24. The method according to claim 23, characterized in that, The alkali source is selected from one or more of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, and ammonia water.

25. The method according to claim 8, characterized in that, Step S1 includes the following steps: (a) The silicon source, titanium source, alkali source, polyamine compound and water are mixed and hydrolyzed at 20~40℃ for 2~12h to obtain alcohol-containing hydrolysis products; (b) The alcohol-containing hydrolysis product is subjected to alcohol removal at 60~110℃ for 6~24h to obtain silicon-titanium gel as the raw material mixture.

26. The method according to claim 8, characterized in that, In step S2, the conditions for the crystallization treatment include: a crystallization temperature of 120~210℃, a crystallization time of 2~24h, and an autogenous pressure. The conditions for the first calcination treatment include: a calcination temperature of 250~750℃ and a calcination time of 2~12.

27. The method according to claim 26, characterized in that, In step S2, the conditions for the crystallization treatment include: a temperature of 140~190℃ and a crystallization time of 2~18h.

28. The method according to claim 26, characterized in that, The conditions for the first calcination treatment include: calcination temperature of 350~750℃ and calcination time of 2~8h.

29. The method according to claim 8, characterized in that, Step S2 further includes a pre-crystallization treatment of the reaction mixture before crystallization.

30. The method according to claim 29, characterized in that, The conditions for the pre-crystallization treatment include: a crystallization temperature of 80~120℃ and a crystallization time of 0.5~24h.

31. The method according to claim 30, characterized in that, The conditions for the pre-crystallization treatment include: a crystallization temperature of 80~100℃ and a crystallization time of 0.5~12h.

32. The method according to claim 8, characterized in that, In step S3, the acid solution is an aqueous solution selected from inorganic acids, the concentration of the acid solution is 0.5~3% by weight; the weight ratio of the acid solution to the intermediate molecular sieve product is (2~20):1; The alkaline solution is an aqueous solution selected from inorganic or organic bases, with a concentration of 1-25% by weight; the pH value of the alkaline solution is 10-14; and the weight ratio of the alkaline solution to the intermediate molecular sieve product is (1-10):

1.

33. The method according to claim 32, characterized in that, The concentration of the acid solution is 0.5~2% by weight.

34. The method according to claim 32, characterized in that, The weight ratio of the acid solution to the intermediate molecular sieve product is (5~10):

1.

35. The method according to claim 32, characterized in that, The inorganic acid is selected from one or more of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, hydrobromic acid, and fluorosilicic acid.

36. The method according to claim 32, characterized in that, The concentration of the alkaline solution is 1-15% by weight.

37. The method according to claim 32, characterized in that, The weight ratio of the alkaline solution to the intermediate molecular sieve product is (2~5):

1.

38. The method according to claim 32, characterized in that, The organic base is selected from one or more of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide; the inorganic base is selected from one or more of sodium hydroxide, potassium hydroxide, disodium hydrogen phosphate, dipotassium hydrogen phosphate, and ammonia water.

39. The method according to claim 8, characterized in that, In step S3, the acidification conditions include: an acidification temperature of 60~90℃ and an acidification time of 2~12h; The conditions for recrystallization include: recrystallization temperature of 120~210℃ and recrystallization time of 2~36h.

40. The method according to claim 39, characterized in that, In step S3, the acidification conditions include: an acidification temperature of 70~90℃ and an acidification time of 2~6h; The conditions for recrystallization include: recrystallization temperature of 140~200℃ and recrystallization time of 2~24 h.

41. The method according to claim 8, characterized in that, In step S4, the conditions for the second calcination treatment include: a calcination temperature of 250~750℃ and a calcination time of 2~12h.

42. The method according to claim 41, characterized in that, In step S4, the conditions for the second calcination treatment include: a calcination temperature of 400~600℃ and a calcination time of 3~6h.

43. A method for the aminooximation of cyclohexanone, the method comprising reacting cyclohexanone with an oxidizing agent in the presence of a catalyst, characterized in that, The catalyst contains the microporous titanium-silicon molecular sieve as described in any one of claims 1 to 7.

44. The method according to claim 43, characterized in that, The reaction conditions include: a molar ratio of oxidant to cyclohexanone of 0.5 to 2, a reaction temperature of 40 to 120°C, a reaction time of 0.5 to 6 h, and a mass ratio of catalyst to cyclohexanone of 0.05 to 0.5.

Images