Preparation method and application of titanium monatomic anchored silicon dioxide catalyst

Abstract

The invention discloses a preparation method and application of a titanium monatomic anchored silicon dioxide catalyst. In a silicon dioxide synthesis system, after silicon dioxide morphology construction is completed, a titanium source is introduced into a reaction system, the silicon dioxide with the morphology constructed is used as a carrier, titanium atoms are anchored to the silicon dioxide in the form of isolated metal monatomic through a one-step method, and the titanium monatomic anchored silicon dioxide catalyst is obtained. The catalyst has the remarkable advantages of simple and convenient preparation process, high titanium monatomic loading capacity, excellent structural stability and the like, shows excellent catalytic performance in catalytic oxidation desulfurization reaction, and has a good recycling characteristic; besides, the surface of the catalyst carrier is rich in a large number of polar functional groups (Si-OH and Ti-OH), oxidized sulfur-containing compounds with large polarity can be efficiently adsorbed, the catalytic system can achieve one-step efficient removal of dibenzothiophene without introduction of an extraction step, and the operation cost in the industrial application process is remarkably reduced.

Description

Technical Field

[0001] The invention relates to a titanium single atom anchored silicon dioxide catalyst, in particular to a preparation method and application of the titanium single atom anchored silicon dioxide catalyst. Background Art

[0002] Single-atom catalysts, characterized by atomic-scale catalytic centers, high atom utilization, and an excellent coordination environment, exhibit unique activity and selectivity in a variety of catalytic reactions and hold great promise for oxidative desulfurization. The anatase-free titanium silicalite TS-1 is a typical Ti-based single-atom catalyst (Ti-SAC) that exhibits excellent ODS catalytic performance. However, in heterogeneous solid-liquid catalytic systems, the Ti(OSi)4 sites of TS-1 are constrained by the rigid zeolite framework, resulting in a highly restricted coordination structure and low accessibility to the active sites, leading to suboptimal ODS catalytic efficiency. Furthermore, the micropore size of TS-1 (<0.56 nm) leads to significant mass transfer limitations, particularly for large sulfides, where diffusion resistance severely restricts the contact between reactants and the active sites, further reducing ODS performance.

[0003] In contrast, porous silica-based titanium single-atom catalysts exhibit greater flexibility in structure and composition, and can overcome the limitations encountered by molecular sieves in terms of accessibility to active centers. However, the surface area of ​​conventional silica supports is limited, resulting in insufficient titanium single-atom loading and easy agglomeration of titanium substances to form titanium dioxide, which causes a sharp drop in the catalytic activity and atomic utilization of the catalyst. Therefore, there is an urgent need to find silica materials with maximized surface area to grow titanium single atoms on their outer surface in order to overcome the interfacial resistance caused by the pores in heterogeneous catalysis and improve catalytic activity.

[0004] In summary, in order to solve the above technical problems, the present invention proposes a preparation method and application of a titanium single atom anchored silica catalyst. Summary of the Invention

[0005] The present invention aims to provide a method for preparing a titanium single-atom anchored silica catalyst and its application. The titanium single-atom anchored silica catalyst prepared by the present invention has significant advantages, including a simple preparation process, high titanium single-atom loading, and excellent structural stability. It exhibits excellent catalytic performance in catalytic oxidative desulfurization reactions and possesses good recyclability. Furthermore, the catalyst support surface is rich in polar functional groups (Si-OH and Ti-OH), which can efficiently adsorb highly polar oxidized sulfur-containing compounds. This catalytic system can achieve efficient, one-step removal of dibenzothiophene without the need for an extraction step, significantly reducing operating costs during industrial applications. The catalyst exhibits broad application prospects in the field of catalytic oxidative desulfurization of fuel oils.

[0006] The technical scheme of the present application: a preparation method of titanium monatomic anchored silica catalyst, in a silica synthesis system, after the morphology of the silica is constructed, a titanium source is introduced into the reaction system, the silica with completed morphology is used as a carrier to anchor titanium atoms in the form of isolated metal monatomic atoms on the silica by a one-step method, and the titanium monatomic anchored silica catalyst is obtained.

[0007] In the preparation method of the aforementioned titanium monatomic anchored silica catalyst, the silica with completed morphology is hierarchical hollow silica spheres (HHSS), fiber nanosilica spheres (KCC-1), hollow silica nanotubes (HSNT), or 2D channel silica (2D-CS).

[0008] In the preparation method of the aforementioned titanium monatomic anchored silica catalyst, the mass fraction of titanium monatomic atoms in the titanium monatomic anchored silica catalyst is 0.1-5%.

[0009] The preparation method of the aforementioned titanium monatomic anchored silica catalyst comprises the following steps: (1) in a silica synthesis system, after the morphology of the silica is constructed, the reaction system is A product; (2) 0.3-15 mL of peroxotitanium acid solution is added into 100 mL of A product, and stirring reaction is performed for 20-40 min to obtain B product; (3) B product is transferred into a Teflon-lined autoclave, and hydrothermal reaction is performed to obtain C product; (4) C product is suction filtered, the filter residue is vacuum dried, calcination is performed in air, and natural cooling is performed to obtain the titanium monatomic anchored silica catalyst.

[0010] In the preparation method of the aforementioned titanium monatomic anchored silica catalyst, in step (2), 0.3-15 mL of peroxotitanium acid solution is added into 100 mL of A product, and stirring reaction is performed for 20-40 min to obtain B product.

[0011] In the preparation method of the aforementioned titanium monatomic anchored silica catalyst, the peroxotitanium acid solution is prepared by the following method: 1-3 g of titanyl sulfate hydrate is completely dissolved in 20-30 mL of distilled water at 15-25 ℃, water bath is performed at 0-2 ℃, stirring is performed for 20-40 min, 3-6 mL of hydrogen peroxide solution is added under stirring, and stirring is continuously performed for 1-3 h to obtain the peroxotitanium acid solution.

[0012] In the preparation method of the aforementioned titanium monatomic anchored silica catalyst, in step (3), B product is transferred into a Teflon-lined autoclave, hydrothermal reaction is performed at 80-120 ℃ for 20-28 h to obtain C product.

[0013] In the preparation method of the aforementioned titanium monatomic-anchored silica catalyst, in step (4), the C product is suction filtered, the filter residue is vacuum dried at 60-80 ℃ for 10-14 h, calcined in air at a temperature increasing rate of 4-6 ℃ / min and at 400-600 ℃ for 7-8 h, and naturally cooled to 15-30 ℃, to obtain the titanium monatomic-anchored silica catalyst.

[0014] The aforementioned titanium monatomic-anchored silica catalyst is used for removing sulfur-containing compounds, i.e. dibenzothiophene, in fuel oil.

[0015] In the aforementioned application of the titanium monatomic-anchored silica catalyst, the catalyst is dispersed in a n-octane solution containing dibenzothiophene, and used for fuel oil desulfurization at 40-70 ℃ with tert-butyl hydroperoxide as an oxidant; the catalyst needs to be washed with acetonitrile or high-temperature calcined at 400-600 ℃ for repeated use.

[0016] Compared with the prior art, the application has the following beneficial effects: 1. The application innovatively introduces a titanium source directly into the original reaction system after the morphology of the silica is constructed and shaped, and precisely fixes titanium atoms in a highly isolated monatomic form on the shaped silica carrier by an in-situ anchoring strategy. The preparation strategy introduces the titanium source after the morphology of the silica is constructed, thereby maintaining the structural integrity of the silica template micelles and ensuring the effective retention of the morphology characteristics of the silica. Meanwhile, the method significantly simplifies the lengthy process flow of the traditional supported titanium catalyst involving carrier pre-synthesis, separation, drying, calcination, re-impregnation loading, secondary drying and calcination, and effectively avoids the irreversible hard agglomeration of silica particles easily caused by the multiple separation, drying and high-temperature calcination processes, thereby maintaining the inherent high specific surface area, fine morphology and high dispersion characteristics of the carrier to the greatest extent, and laying a structural foundation for obtaining titanium monatomic catalytic sites with high exposure and high activity.

[0017] 2. The application innovatively selects a silica carrier (including hierarchical hollow silica spheres (HHSS, 687 m 2 / g), fiber nanosilica spheres (KCC-1, 641 m 2 / g), hollow nanosilica tubes (HSNT, 601 m 2 / g) and two-dimensional channel silica (2D-CS, 525 m 2 / g), which is significantly different from conventional amorphous silica or common mesoporous silica support. The unique "hollow small sphere building hollow large sphere" hierarchical structure of HHSS provides excellent external specific surface area; the dendritic silica fibers and internal channels of KCC-1 are the source of its ultra-high specific surface area; HSNT realizes efficient functionalization of the inner and outer walls and excellent mass transfer performance due to its hollow tubular structure, nanoscale channel diameter and quasi-one-dimensional characteristics; 2D-CS exhibits unique advantages in heterogeneous solid-liquid catalysis due to its completely open and accessible transport channel structure. The common core value of these carriers lies in their unique structural characteristics. The rich multi-level pores provide a large number of titanium atom anchoring sites, the ultra-large specific surface area (especially the effective external surface area) significantly improves the loadable amount of titanium monatomic, and the highly open pore system greatly optimizes the mass transfer efficiency of reactants / products. The synergistic effect of the above structural advantages not only provides an ideal carrier platform for the dispersion of high-density and high-stability titanium monatomic, but also lays a solid material foundation for the catalyst to achieve excellent catalytic performance in the oxidation desulfurization reaction by maximizing the exposure and utilization efficiency of active sites.

[0018] 3. The present application introduces 0.3-15 mL of peroxotitanium acid solution as a titanium source in 100 mL of A product (silica preparation system) and stirs for 20-40 min to prepare a titanium monatomic-anchored silica catalyst. The peroxotitanium monomer (Ti(OH)3OOH) in the peroxotitanium acid solution ionizes to form peroxotitanium anions (Ti(OH)3OO - ) under the alkaline silica preparation system, and the electrostatic repulsion effect and steric hindrance effect between the anion monomers can effectively inhibit the tendency of titanium species to agglomerate. Subsequently, the Ti-OH of Ti(OH)3OO - reacts with the Si-OH of SiO2 to undergo dehydration, so that the titanium metal atom is anchored on the surface of the silica in the form of an isolated monatomic. The unique dual stabilization mechanism of this peroxotitanium species plays a decisive role in the preparation of titanium monatomic-anchored silica catalysts with high dispersity, high titanium content (0.1-5%) and high catalytic activity. Traditional titanium source precursors (such as tetrabutyl titanate and titanyl sulfate) exhibit extremely high reactivity during hydrolysis, which leads to easy agglomeration of titanium monomers and formation of low-activity titanium dioxide. This characteristic makes it difficult to anchor atomically dispersed titanium species in amorphous SiO2 carriers when using tetrabutyl titanate and titanyl sulfate as the titanium source.

[0019] 4. This invention uses inexpensive and relatively stable titanyl sulfate as a titanium precursor. 1-3 g of titanyl sulfate hydrate is completely dissolved in 20-30 mL of distilled water at 15-25°C. Stirring is performed in a water bath at 0-2°C for 20-40 minutes to produce titanium monomer (Ti(OH)₄). 3-6 mL of hydrogen peroxide solution is then added and stirred for 1-3 hours. During this process, H₂O₂ oxidizes Ti(OH)₄ to produce titanium peroxide monomer (Ti(OH)₃OOH), resulting in a peroxytitanic acid solution. This peroxytitanic acid solution exhibits excellent stability and dispersibility in aqueous systems. This unique property provides a new technical path for the development of high-performance titanium single-atom catalysts.

[0020] 5. In this method, the intermediate (Product B) after the titanium source addition reaction is placed in a Teflon-lined autoclave and treated under mild hydrothermal conditions at 80-120°C for 20-28 hours. This hydrothermal process, through the high temperature and high pressure, synergistically promotes two key transformations: first, it significantly enhances the dehydration condensation reaction between the titanium source and the silanol groups on the silica surface, achieving high-density and stable anchoring of titanium atoms via Ti-O-Si bonds; second, it drives deep deoxidation of peroxotitanium species to form highly active Ti(IV) single-atom sites. Simultaneously, the hydrothermal environment promotes rearrangement and strengthening of the silica support skeleton, effectively eliminating structural defects and resulting in significantly superior morphology and pore structure stability compared to supports obtained by conventional direct drying / calcination methods. This targeted, optimized hydrothermal strategy simultaneously achieves efficient construction of active sites and enhanced support mechanical strength, laying the structural foundation for the long-term operation of the catalyst.

[0021] 6. In this method, the hydrothermal product C is filtered, and the residue is vacuum-dried at 60-80°C for 10-14 hours. The residue is then calcined in air at 400-600°C for 7-8 hours at a precisely controlled heating rate (4-6°C / min). This process maximizes the integrity of the support pores during the low-temperature drying phase, while achieving targeted removal of surfactants and trace adsorbed water molecules during the high-temperature calcination. The critical calcination phase, conducted at a moderate temperature well below the silica phase transition temperature (>1000°C), thoroughly decomposes organic residues and eliminates surface ligand shielding, while effectively minimizing the risk of titanium species migration and aggregation caused by high temperatures. The result is a catalyst with fully exposed titanium single-atom active sites and an intact support skeleton.

[0022] 7. The titanium single-atom-anchored silica catalyst prepared in this invention was dispersed in an n-octane solution containing dibenzothiophene and subjected to catalytic oxidative desulfurization at 40-70°C using tert-butyl hydroperoxide as the oxidant. The results demonstrated that the titanium single-atom catalyst exhibited excellent catalytic performance, achieving 100% removal of 500 ppm of dibenzothiophene in simulated oil within 5 minutes. The titanium single atoms are anchored to the silica support via covalent crosslinking between titanium hydroxyl (Ti-OH) and silicon hydroxyl (Si-OH) groups, demonstrating excellent recyclability. After 10 cycles, the catalyst maintained a DBT removal rate of 95.53%, and its catalytic activity was restored to the level of fresh catalyst after high-temperature calcination and recovery.

[0023] 8. The titanium single-atom-anchored silica catalyst prepared in this work has surface polar groups (Si-OH and Ti-OH) that specifically adsorb dibenzothiophene oxidation products (DBTO2). After eluting the adsorbed oxidation products with acetonitrile, the catalyst can be regenerated and recycled. Due to the adsorption of sulfur-containing compounds by the catalyst after oxidation, this system can remove dibenzothiophene (DBT) in a single step without secondary treatment, thus eliminating the extraction step and significantly reducing industrial application costs. This catalyst shows potential application value in the catalytic oxidation desulfurization of fuel oils.

[0024] In summary, the titanium single atom anchored silica catalyst prepared by the present invention has significant advantages such as simple preparation process, high titanium single atom loading and excellent structural stability. It exhibits excellent catalytic performance in catalytic oxidation desulfurization reactions and has good recycling characteristics. In addition, the surface of the catalyst carrier is rich in a large number of polar functional groups (Si-OH and Ti-OH), which can efficiently adsorb oxidized sulfur-containing compounds with high polarity. The catalytic system can achieve one-step and efficient removal of dibenzothiophene without introducing an extraction step, significantly reducing the operating cost in the industrial application process, and showing beneficial effects with broad application prospects in the field of catalytic oxidation desulfurization of fuel. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 TEM images of titanium single atom anchored silica catalysts prepared in Examples 1-4 of the present invention; wherein, Figure 1 a is a titanium single atom anchored hierarchical hollow silica sphere catalyst (Ti SA-HHSS), Figure 1 b is titanium single atom anchored fiber nano-silica sphere catalyst (Ti SA-KCC-1), Figure 1 c is titanium single atom anchored hollow silica nanotube catalyst (Ti SA-HSNT), Figure 1 d: Titanium single atom anchored 2D channel silica catalyst (Ti SA-2D-CS).

[0026] Figure 2 : EDS element distribution diagram of the Ti SA-HHSS catalyst prepared in Examples 5-8 of the present invention; Figure 3 (a) UV–Vis and (b) XPS spectra of the Ti SA-HHSS catalysts prepared in Examples 5-8 of the present invention; Figure 4 Ti K-edge XANES spectra (a) and Fourier transform (FT) EXAFS spectra (b) of Ti SA-HHSS prepared in Examples 5-8 of the present invention and the reference sample; k 3 Wavelet transform of weighted EXAFS; Figure 5 The oxidative desulfurization performance of the Ti SA-HHSS catalysts with different titanium contents prepared in Examples 5-8 of the present invention; Figure 6 The oxidative desulfurization performance of the 2% Ti SA-HHSS catalyst prepared in Example 8 of the present invention at different oxygen-sulfur ratios (O / S); Figure 7 The oxidative desulfurization performance of the 2% Ti SA-HHSS catalyst prepared in Example 8 of the present invention at different catalyst dosages; Figure 8 The oxidative desulfurization performance of the 2% Ti SA-HHSS catalyst prepared in Example 8 of the present invention at different ODS reaction temperatures; Figure 9 The oxidative desulfurization performance of the 2% Ti SA-HHSS catalyst prepared in Example 8 of the present invention under different organic sulfur compounds; Figure 10 The oxidative desulfurization performance of the 2% Ti SA-HHSS catalyst prepared in Example 8 of the present invention at different sulfur concentrations; Figure 11 This is the cyclic stability of the 2%Ti SA-HHSS catalyst prepared in Example 8 of the present invention.

[0027] Example 1. A method for preparing a titanium single atom anchored silica catalyst comprises the following steps: (1) In the silica synthesis system, when the hierarchical hollow silica sphere (HHSS) morphology is completed, the reaction system is Grade A; (2) Add 0.3-15 mL of peroxytitanic acid solution to 100 mL of product A and stir for 20-40 minutes to obtain product B. The peroxytitanic acid solution is prepared by the following method: 1-3 g of titanyl sulfate hydrate is completely dissolved in 20-30 mL of distilled water at 15-25° C., the mixture is placed in a water bath at 0-2° C., stirred for 20-40 minutes, and then 3-6 mL of hydrogen peroxide solution is added under stirring, and stirring is continued for 1-3 hours to obtain the peroxytitanic acid solution; (3) Transfer product B to a Teflon-lined autoclave and perform a hydrothermal reaction at 80-120 °C for 20-28 h to obtain product C; (4) Product C was filtered, and the residue was vacuum dried at 60-80 °C for 10-14 h, calcined in air at 400-600 °C at a heating rate of 4-6 °C / min for 7-8 h, and naturally cooled to 15-30 °C to obtain titanium single atom anchored hierarchical hollow silica sphere catalyst (Ti SA-HHSS). The mass fraction of titanium single atoms in Ti SA-HHSS was 0.1-5%.

[0028] Example 2. A method for preparing a titanium single atom anchored silica catalyst comprises the following steps: (1) In the silica synthesis system, when the morphology of the fiber nano-silica sphere (KCC-1) is completed, the reaction system is product A; (2) Add 0.3-15 mL of peroxytitanic acid solution to 100 mL of product A and stir for 20-40 minutes to obtain product B. The peroxytitanic acid solution is prepared by the following method: 1-3 g of titanyl sulfate hydrate is completely dissolved in 20-30 mL of distilled water at 15-25° C., the mixture is placed in a water bath at 0-2° C., stirred for 20-40 minutes, and then 3-6 mL of hydrogen peroxide solution is added under stirring, and stirring is continued for 1-3 hours to obtain the peroxytitanic acid solution; (3) Transfer product B to a Teflon-lined autoclave and perform a hydrothermal reaction at 80-120 °C for 20-28 h to obtain product C; (4) Product C was filtered, and the residue was vacuum dried at 60-80 °C for 10-14 h, calcined in air at 400-600 °C at a heating rate of 4-6 °C / min for 7-8 h, and naturally cooled to 15-30 °C to obtain titanium single atom anchored fiber nanosilica sphere catalyst (Ti SA-KCC-1). The mass fraction of titanium single atoms in Ti SA-KCC-1 was 0.1-5%.

[0029] Example 3. A method for preparing a titanium single atom anchored silica catalyst comprises the following steps: (1) In the silica synthesis system, after the hollow silica nanotube (HSNT) morphology is completed, the reaction system is product A; (2) Add 0.3-15 mL of peroxytitanic acid solution to 100 mL of product A and stir for 20-40 minutes to obtain product B. The peroxytitanic acid solution is prepared by the following method: 1-3 g of titanyl sulfate hydrate is completely dissolved in 20-30 mL of distilled water at 15-25° C., the mixture is placed in a water bath at 0-2° C., stirred for 20-40 minutes, and then 3-6 mL of hydrogen peroxide solution is added under stirring, and stirring is continued for 1-3 hours to obtain the peroxytitanic acid solution; (3) Transfer product B to a Teflon-lined autoclave and perform a hydrothermal reaction at 80-120 °C for 20-28 h to obtain product C; (4) Product C was filtered, and the residue was vacuum dried at 60-80 °C for 10-14 h, calcined in air at 400-600 °C at a heating rate of 4-6 °C / min for 7-8 h, and naturally cooled to 15-30 °C to obtain titanium single atom anchored hollow silica nanotube catalyst (Ti SA-HSNT). The mass fraction of titanium single atoms in Ti SA-HSNT was 0.1-5%.

[0030] Example 4. A method for preparing a titanium single atom anchored silica catalyst comprises the following steps: (1) In the silica synthesis system, when the 2D channel silica (2D-CS) morphology is completed, the reaction system is Grade A; (2) Add 0.3-15 mL of peroxytitanic acid solution to 100 mL of product A and stir for 20-40 minutes to obtain product B. The peroxytitanic acid solution is prepared by the following method: 1-3 g of titanyl sulfate hydrate is completely dissolved in 20-30 mL of distilled water at 15-25° C., the mixture is placed in a water bath at 0-2° C., stirred for 20-40 minutes, and then 3-6 mL of hydrogen peroxide solution is added under stirring, and stirring is continued for 1-3 hours to obtain the peroxytitanic acid solution; (3) Transfer product B to a Teflon-lined autoclave and perform a hydrothermal reaction at 80-120 °C for 20-28 h to obtain product C; (4) Product C was filtered, and the residue was vacuum dried at 60-80 °C for 10-14 h, calcined in air at 400-600 °C at a heating rate of 4-6 °C / min for 7-8 h, and naturally cooled to 15-30 °C to obtain a titanium single atom anchored 2D channel silica catalyst (Ti SA-2D-CS). The mass fraction of titanium single atoms in Ti SA-2D-CS was 0.1-5%.

[0031] Example 5: A method for preparing a titanium single atom anchored silica catalyst, comprising the following steps: (1) In the silica synthesis system, when the hierarchical hollow silica sphere morphology is completed, the reaction system is product A; (2) Add 1.5 mL of peroxytitanic acid solution to 100 mL of product A and stir for 20 min to obtain product B. The peroxotitanic acid solution is prepared by the following method: 2 g of titanyl sulfate hydrate is completely dissolved in 25 mL of distilled water at 20° C., the mixture is stirred in a water bath at 1° C. for 30 minutes, 4.5 mL of hydrogen peroxide solution is added under stirring, and stirring is continued for 2 hours to obtain the peroxotitanic acid solution; (3) Transfer product B to a Teflon-lined autoclave and perform a hydrothermal reaction at 80 °C for 20 h to obtain product C. (4) Product C was filtered, and the residue was vacuum dried at 60 °C for 10 h, calcined in air at 400 °C at a heating rate of 4 °C / min for 7 h, and naturally cooled to 15 °C to obtain a titanium single atom anchored hierarchical hollow silica sphere catalyst, which was recorded as 0.5%Ti SA-HHSS.

[0032] Example 6. A method for preparing a titanium single atom anchored silica catalyst comprises the following steps: (1) In the silica synthesis system, when the hierarchical hollow silica sphere morphology is completed, the reaction system is product A; (2) Add 3 mL of peroxytitanic acid solution to 100 mL of product A and stir for 30 min to obtain product B. The peroxotitanic acid solution is prepared by the following method: 2 g of titanyl sulfate hydrate is completely dissolved in 25 mL of distilled water at 20° C., the mixture is stirred in a water bath at 1° C. for 30 minutes, 4.5 mL of hydrogen peroxide solution is added under stirring, and stirring is continued for 2 hours to obtain the peroxotitanic acid solution; (3) Transfer product B to a Teflon-lined autoclave and perform a hydrothermal reaction at 100 °C for 24 h to obtain product C. (4) Product C was filtered, and the residue was vacuum dried at 70 °C for 12 h, calcined in air at 500 °C at a heating rate of 5 °C / min for 7.5 h, and naturally cooled to 20 °C to obtain a titanium single atom anchored hierarchical hollow silica sphere catalyst, which was recorded as 1%Ti SA-HHSS.

[0033] Example 7. A method for preparing a titanium single atom anchored silica catalyst comprises the following steps: (1) In the silica synthesis system, when the hierarchical hollow silica sphere morphology is completed, the reaction system is product A; (2) Add 4.5 mL of peroxytitanic acid solution to 100 mL of product A and stir for 30 min to obtain product B. The peroxotitanic acid solution is prepared by the following method: 2 g of titanyl sulfate hydrate is completely dissolved in 25 mL of distilled water at 20° C., the mixture is stirred in a water bath at 1° C. for 30 minutes, 4.5 mL of hydrogen peroxide solution is added under stirring, and stirring is continued for 2 hours to obtain the peroxotitanic acid solution; (3) Transfer product B to a Teflon-lined autoclave and perform a hydrothermal reaction at 100 °C for 26 h to obtain product C. (4) Product C was filtered, and the residue was vacuum dried at 70 °C for 13 h, calcined in air at 550 °C at a heating rate of 5 °C / min for 8 h, and naturally cooled to 25 °C to obtain a titanium single atom anchored hierarchical hollow silica sphere catalyst, which was recorded as 1.5%Ti SA-HHSS.

[0034] Example 8. A method for preparing a titanium single atom anchored silica catalyst comprises the following steps: (1) In the silica synthesis system, when the hierarchical hollow silica sphere morphology is completed, the reaction system is product A; (2) Add 6 mL of peroxytitanic acid solution to 100 mL of product A and stir for 40 min to obtain product B. The peroxotitanic acid solution is prepared by the following method: 2 g of titanyl sulfate hydrate is completely dissolved in 25 mL of distilled water at 20° C., the mixture is stirred in a water bath at 1° C. for 30 minutes, 4.5 mL of hydrogen peroxide solution is added under stirring, and stirring is continued for 2 hours to obtain the peroxotitanic acid solution; (3) Transfer product B to a Teflon-lined autoclave and perform a hydrothermal reaction at 120 °C for 28 h to obtain product C. (4) Product C was filtered, and the residue was vacuum dried at 80 °C for 14 h, calcined in air at 600 °C at a heating rate of 6 °C / min for 8 h, and naturally cooled to 30 °C to obtain a titanium single atom anchored hierarchical hollow silica sphere catalyst, which was recorded as 2%TiSA-HHSS.

[0035] Application Example 1: The titanium single-atom-anchored hierarchical hollow silica sphere catalysts (0.5-2% Ti SA-HHSS) prepared in Examples 5-8 were used to study the oxidative desulfurization of DBT. Sulfide concentration was analyzed using a WK-2D microcoulometric sulfur analyzer. A calculated amount of an organic sulfur compound (DBT) was dissolved in n-octane to prepare a sulfur-containing simulated oil with a concentration of approximately 500 ppm. A typical oxidative desulfurization reaction was carried out at 60°C, with 10 mL of simulated oil, 60 mg of the catalyst, and 43 µL of TBHP (O / S = 2:1) added to a 25 mL single-necked flask with a reflux condenser. The reaction lasted 10 minutes, with samples taken at regular intervals. The samples were centrifuged at 10,000 rpm for 5 minutes, and the supernatant was removed and transferred to a WK-2D microcoulometric sulfur analyzer for determination of sulfur content. The desulfurization rate was calculated using the following formula: η=[(C0-C0) / C0]×100% Where η is the desulfurization rate, C0 is the initial simulated oil concentration, and C is the final simulated oil concentration. The solid separated by centrifugation was washed 2-3 times with acetonitrile and then centrifuged and dried for use in subsequent recycling experiments.

[0036] Application Example 2: The titanium single-atom-anchored hierarchical hollow silica sphere catalyst (2% Ti SA-HHSS) prepared in Example 8 was used to investigate the effect of the oxygen / sulfur ratio (O / S) on the oxidative desulfurization of DBT. A typical oxidative desulfurization reaction was conducted at 60°C in a 25 mL single-necked flask equipped with a reflux condenser. 10 mL of 500 ppm DBT simulated oil, 60 mg of catalyst, and a specific amount of TBHP were added. The reaction lasted 10 minutes, with samples collected at regular intervals. The samples were centrifuged at 10,000 rpm for 5 minutes, and the supernatant was removed and used to determine the sulfur content in a WK-2D microcoulometric sulfur analyzer.

[0037] Application Example 3: The titanium single-atom-anchored hierarchical hollow silica sphere catalyst (2% Ti SA-HHSS) prepared in Example 8 was used to investigate the effect of catalyst dosage on the oxidative desulfurization of DBT. A typical oxidative desulfurization reaction was conducted at 60°C using 10 mL of 500 ppm DBT simulated oil, a predetermined amount of catalyst, and 43 µL of TBHP (O / S = 2:1) in a 25 mL single-necked flask with a reflux condenser. The reaction lasted 10 minutes, with samples collected at regular intervals. The samples were centrifuged at 10,000 rpm for 5 minutes, and the supernatant was removed and used to determine the sulfur content in a WK-2D microcoulometric sulfur analyzer.

[0038] Application Example 4, the titanium monatomic anchoring hierarchical hollow silica sphere catalyst (2%Ti SA-HHSS) prepared in Example 8 was taken as the research object, and the influence of ODS reaction temperature on the oxidation desulfurization of DBT was studied. In a 25 mL single-neck flask with a reflux condenser, 10 mL of 500 ppm DBT simulated oil, 60 mg of catalyst and 43 μL of TBHP (O / S = 2:1) were added to perform a typical oxidation desulfurization reaction at a certain temperature. The reaction time was 10 min, and samples were taken at intervals, the obtained samples were centrifuged at 10000 r / min for 5 min, the supernatant was taken out and sent to WK-2D microcoulometric sulfur determination instrument to determine the sulfur content.

[0039] Application Example 5, the titanium monatomic anchoring hierarchical hollow silica sphere catalyst (2%Ti SA-HHSS) prepared in Example 8 was taken as the research object, and the influence of different sulfur-containing compounds on the oxidation desulfurization was studied. A calculated amount of organic sulfur-containing compound (DBT, 4,6-DMDBT or BT) was dissolved in n-octane to prepare a sulfur-containing simulated oil with a concentration of about 500 ppm. In a 25 mL single-neck flask with a reflux condenser, 10 mL of simulated oil, 60 mg of catalyst and 43 μL of TBHP (O / S = 2:1) were added to perform a typical oxidation desulfurization reaction at 60 ℃. The reaction time was 10 min, and samples were taken at intervals, the obtained samples were centrifuged at 10000 r / min for 5 min, the supernatant was taken out and sent to WK-2D microcoulometric sulfur determination instrument to determine the sulfur content.

[0040] Application Example 6, the titanium monatomic anchoring hierarchical hollow silica sphere catalyst (2%Ti SA-HHSS) prepared in Example 8 was taken as the research object, and the influence of different S concentrations on the oxidation desulfurization of DBT was studied. A calculated amount of DBT was dissolved in n-octane to prepare sulfur-containing simulated oil with a concentration of about 300, 500 and 1000 ppm. In a 25 mL single-neck flask with a reflux condenser, 10 mL of simulated oil, 60 mg of catalyst and a certain amount of TBHP (O / S = 2:1) were added to perform a typical oxidation desulfurization reaction at 60 ℃. The reaction time was 10 min, and samples were taken at intervals, the obtained samples were centrifuged at 10000 r / min for 5 min, the supernatant was taken out and sent to WK-2D microcoulometric sulfur determination instrument to determine the sulfur content.

[0041] Example 7, the titanium monatomic anchoring hierarchical hollow silica sphere catalyst (2% Ti SA-HHSS) prepared in Example 8 was taken as the research object, and the cycle stability of the catalyst was studied. After the oxidative desulfurization reaction, the recovered catalyst adsorbing the oxidation products of sulfur-containing compounds was obtained by centrifugation. After washing with acetonitrile, the regenerated catalyst was obtained by drying at 60 ℃. Then, the simulated oil was added, and the next step of catalytic oxidative desulfurization reaction was carried out under the same reaction conditions. In a single-mouth flask with a reflux condenser, 10 mL of 500 ppm DBT simulated oil, 60 mg of recovered regenerated catalyst and 43 μL of TBHP (O / S = 2:1) were added to carry out a typical oxidative desulfurization reaction at 60 ℃. The reaction time was 10 min, and samples were taken at intervals. The obtained samples were centrifuged at 10000 r / min for 5 min, and the supernatant was taken and sent to a WK-2D microcoulomb sulfur tester for determination of sulfur content. After repeating the above steps for 10 times, the recovered catalyst was calcined at 550 ℃ for 6 h to completely remove the organic compounds adsorbed by the catalyst, and then the 11th cycle reaction was carried out.

[0042] 1、 Figure 1 TEM images of the titanium monatomic anchoring silica catalysts prepared in Examples 1-4 of the present application; wherein, Figure 1 a is a titanium monatomic anchoring hierarchical hollow silica sphere catalyst (Ti SA-HHSS), and the TEM image shows that the Ti SA-HHSS nanoparticles are porous hierarchical hollow nanospheres with a double side size of 100 nm, which are large hollow silica sphere structures assembled by small hollow silica spheres. The ultra-high outer surface greatly reduces the pore diffusion resistance in solid-liquid catalysis. Figure 1 b is a titanium monatomic anchoring fiber nanosilica sphere catalyst (Ti SA-KCC-1), which exhibits a special spherical structure formed by three-dimensionally arranged dendritic polymer fibers (at an angle of 8-10 nm in thickness), which can allow easy access to a high surface area available. Figure 1 c is a titanium monatomic anchoring hollow silica nanotube catalyst (Ti SA-HSNT), which is a hollow rectangular nanotube structure, and nanopore structures are observed on the tube wall. The ultra-thin tube wall thickness makes the pore structure highly accessible to the outside world. The hollow tube diameter of about 100 nm does not have capillary phenomenon, and both the inner and outer surfaces of the nanotube are fully utilized. Figure 1 d is a titanium monatomic anchoring 2D channel silica catalyst (Ti SA-2D-CS), which has an axial layered structure and a high specific surface area, which is beneficial to the dispersion of active components and molecular diffusion.

[0043] 2、 Figure 2 EDS element distribution map of the Ti SA-HHSS catalyst prepared in Examples 5-8 of the present application. From the EDS element distribution map of the Ti SA-HHSS catalyst prepared in Examples 5-8 of the present application, Figure 2The uniform spatial distribution of Si and O clearly identifies the silica support, and the titanium species exhibits a uniform dispersion without detectable aggregation.

[0044] 3、 Figure 3 (a) UV-Vis and (b) XPS spectra of Ti SA-HHSS catalysts prepared in Examples 5-8 of the present invention. Generally, in the UV-Vis spectra of titanium species, the peaks near 200-220 nm, 250-280 nm, and 310-330 nm are attributed to tetrahedrally coordinated Ti04(Ti(OSi)4or Ti(OSi)3OH), octahedrally coordinated Ti06(Ti(OH2)2(OH)2(OSi)2or Ti(OH)4(OSi)2), and anatase Ti02species, respectively. As shown in Figure 3 a, the titanium species of Ti SA-HHSS catalysts are Ti04sites and Ti06sites, with no apparent anatase titania formation, which indicates that the titanium monatomic species exist in the form of mononuclear Ti04and Ti06sites. The XPS spectra of Figure 3 b further analyze the type of Ti species in Ti SA-HHSS catalysts, with 460.6 eV and 459.4 eV corresponding to tetrahedrally coordinated Ti04and hexahedrally coordinated Ti06, respectively, which corresponds to the UV-Vis spectral analysis.

[0045] 4、 Figure 4 Ti K-edge XANES spectra (a) and Fourier-transformed (FT) EXAFS spectra (b) of Ti SA-HHSS and reference samples prepared in Examples 5-8 of the present invention; k 3 Wavelet transform of weighted EXAFS. To further investigate the coordination environment of Ti atoms, the X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) of Ti SA-HHSS materials and reference samples (Ti foil and anatase Ti02) were tested. Figure 4 The XANES spectra in a can reflect the symmetry of Ti coordination structure in the pre-edge peak range (about 4960-4980 eV). Generally, the symmetric structure of Ti foil results in a strong pre-edge peak, while the asymmetric Ti coordination structure of anatase Ti02presents three peaks at A1, A2, and A3. For Ti SA-HHSS, only one peak at A2 is observed, indicating the absence of anatase phase, which is consistent with the results of UV-Vis and XPS analysis. As shown in Figure 4Ti SA-HHSS, as shown in FIG. b, the Fourier transform extended X-ray absorption fine structure (FT-EXAFS) spectrum shows a main peak corresponding to Ti-O bonds, but no significant Ti-Ti bonds are detected, which directly confirms that almost all Ti atoms in the sample exist in the form of isolated Ti monomers. Wavelet transform (WT-EXAFS) is an effective method for separating backscattering atoms, which provides radial distance resolution and k-space resolution, and has the advantage of directly showing the type of coordination atoms, while showing the bond length of the coordination environment. As shown in FIG. Figure 4 c, for anatase TiO2, WT maxima corresponding to Ti-O and Ti-Ti shells can be observed in the ranges of 1-2 Å and 2-4 Å, respectively, indicating the presence of Ti-O and Ti-Ti coordination environments in TiO2. Notably, no significant Ti-Ti shell is observed in Ti SA-HHSS ( Figure 4 d), further confirming the existence of TiO4 and TiO6 species as isolated monomers.

[0046] 5、 Figure 5 The oxidative desulfurization performance of Ti SA-HHSS catalysts with different titanium contents prepared in Examples 5-8 of the present application. Specifically, the atomic utilization rate of titanium monomers is high, and has excellent ODS reaction activity, so the higher the content of titanium monomers, the higher the oxidative desulfurization catalytic activity. When the titanium content is 2%, the activity of the Ti SA-HHSS catalyst reaches the optimum (5 min DBT conversion rate reaches 100%), and then decreases with the decrease of titanium content, resulting in a decrease in active TiO4 and TiO6 sites, and a decrease in desulfurization efficiency.

[0047] 6、 Figure 6 The oxidative desulfurization performance of 2% Ti SA-HHSS catalyst prepared in Example 8 of the present application under different oxygen-sulfur ratios (O / S). Since the theoretical O / S of oxidized sulfur compounds is 2:1, when O / S = 1:1, the highest DBT conversion rate can only reach 59%, at this time the amount of oxidant added does not reach the theoretical standard, and a small amount of DBT is oxidized to DBTO and removed from the oil phase. When O / S = 2:1, DBT can be completely removed. Since the Ti SA-HHSS catalyst is a hydrophilic nanomaterial rich in hydroxyl groups (Si-OH and Ti-OH), an excess of oxidant can reduce the accessibility of active sites by covering the surface of the catalyst. Therefore, when O / S continues to increase (O / S = 3:1 and O / S = 4:1), the desulfurization reaction rate continues to decrease.

[0048] 7、 Figure 7The oxidative desulfurization performance of the 2% Ti SA-HHSS catalyst prepared in Example 8 under different catalyst dosages. The results show that 40 mg of the Ti SA-HHSS catalyst can achieve 97% ODS efficiency in 15 min, and 60 and 80 mg of the catalyst only need 5 and 4 min, respectively. Therefore, in order to balance the desulfurization efficiency and desulfurization cost, 60 mg is selected as the optimal dosage of the Ti SA-HHSS catalyst.

[0049] 8、 Figure 8 The oxidative desulfurization performance of the 2% Ti SA-HHSS catalyst prepared in Example 8 under different ODS reaction temperatures. It can be seen from the results that the DBT removal rate of the catalyst increases with the increase of the temperature. At 40 ℃ and 50 ℃, the catalyst removes 56% and 95% of the sulfur-containing compound DBT in 15 min, respectively. With the temperature rising to 60 ℃, the catalyst only needs 5 min to complete the deep oxidative desulfurization. When the reaction temperature is 70 ℃, the reaction rate continues to rise, but still needs 5 min to complete the complete oxidative desulfurization. Therefore, considering the desulfurization efficiency and desulfurization cost, 60 ℃ is selected as the optimal temperature for the oxidative desulfurization of the catalyst. Figure 8

[0050] 9、 Figure 9 The oxidative desulfurization performance of the 2% Ti SA-HHSS catalyst prepared in Example 8 under different organic sulfur-containing compounds. Model oils with different sulfur-containing compounds are used to simulate fuel oil in actual application. The Ti SA-HHSS catalyst completely removes 500 ppm DBT and 500 ppm 4,6-DMDBT in 5 min and 15 min, respectively, and removes 88% of 500 ppm BT in 15 min, showing excellent adaptability to different sulfur-containing compounds. The desulfurization capacity of the catalyst to sulfur-containing compounds is in the order of DBT > 4,6-DMDBT > BT, which depends on the electron density and steric hindance of sulfur atoms in the reactants.

[0051] 10、 Figure 10 The oxidative desulfurization performance of the 2% Ti SA-HHSS catalyst prepared in Example 8 under different sulfur concentrations. Figure 9 The desulfurization efficiency of the Ti SA-HHSS catalyst for different sulfur content model oils is shown, and 100% DBT removal rate is achieved in 4 min, 5 min and 25 min for 300 ppm, 500 ppm and 1000 ppm model oils, respectively, indicating that the catalyst also has superior ODS capacity for high concentration model oils.

[0052] 11、 Figure 11 ​The cyclic stability of the 2% Ti SA-HHSS catalyst prepared in Example 8 of the present invention is shown in FIG. As a key factor in practical application, the stability of the Ti SA-HHSS catalyst in the solvent-free ODS reaction is of vital importance. Figure 10 As shown in the figure, the catalyst exhibits excellent cyclic stability. After 10 cycles, the catalyst, which has undergone recovery and polar solvent regeneration, still maintains a DBT conversion rate of 95.53%. The 11th cycle shows the ODS activity of the catalyst recovered by high-temperature calcination. The desulfurization activity has recovered to the catalytic level before the cycle, indicating that the Ti SA-HHSS catalyst has excellent thermal and cyclic stability.

[0053] Comprehensive application examples 1-7 show that the optimal conditions for removing DBT from fuel oil using the titanium single-atom anchored silica catalyst prepared by the present invention are an O / S ratio of 2:1, 60 mg of catalyst, and 60°C. In a 10 mL 500 ppm ODS reaction system, 2% TiSA-HHSS rapidly achieved 100% removal of the organic sulfide DBT within 5 minutes. Furthermore, after 10 cycles, 2% Ti SA-HHSS still removed 95.53% of DBT, demonstrating its excellent operational stability. The 11th cycle, the ODS activity of the catalyst recovered after high-temperature calcination, showed that the desulfurization activity had returned to the catalytic level before the cycle, demonstrating the excellent thermal stability and regenerative properties of the 2% Ti SA-HHSS catalyst.

[0054] The applicant also conducted the experimental tests and analyses described in Experimental Proofs 2-11 above on the titanium single atom anchored silica catalysts prepared in other examples, and the results obtained were comparable to the above test and analysis results.

Claims

1. A method for preparing a titanium single atom anchored silica catalyst, characterized in that: In the silica synthesis system, after the silica morphology is completed, a titanium source is introduced into the reaction system. The silica with completed morphology is used as a carrier to anchor the titanium atoms on the silica in the form of isolated metal single atoms through a one-step method to obtain a titanium single atom anchored silica catalyst.

2. The method for preparing a titanium single atom anchored silica catalyst according to claim 1, wherein: The silica with a complete morphology is hierarchical hollow silica spheres, fiber nano silica spheres, hollow silica nanotubes or 2D channel silica.

3. The method for preparing a titanium single atom anchored silica catalyst according to claim 1, wherein: The mass fraction of titanium atoms in the titanium single atom anchored silica catalyst is 0.1-5%.

4. The method for preparing a titanium single atom anchored silica catalyst according to claim 1, wherein: The following steps are included: (1) In the silica synthesis system, when the silica morphology is completed, the reaction system is product A; (2) Add peroxytitanic acid solution to product A and stir to react to obtain product B; (3) Transfer product B to a Teflon-lined autoclave and perform a hydrothermal reaction to obtain product C; (4) Product C was filtered, the filter residue was vacuum dried, calcined in air, and naturally cooled to obtain a titanium single atom anchored silica catalyst.

5. The method for preparing a titanium single atom anchored silica catalyst according to claim 4, wherein: In step (2), 0.3-15 mL of peroxytitanic acid solution is added to 100 mL of product A, and the mixture is stirred and reacted for 20-40 min to obtain product B.

6. The method for preparing a titanium single atom anchored silica catalyst according to claim 4, wherein: The peroxytitanic acid solution is prepared by the following method: 1-3 g of titanyl sulfate hydrate is completely dissolved in 20-30 mL of distilled water at 15-25° C., the mixture is placed in a water bath at 0-2° C., stirred for 20-40 minutes, and then 3-6 mL of hydrogen peroxide solution is added under stirring, and stirring is continued for 1-3 hours to obtain the peroxytitanic acid solution.

7. The method for preparing a titanium single atom anchored silica catalyst according to claim 4, wherein: In step (3), product B is transferred to a Teflon-lined autoclave and subjected to a hydrothermal reaction at 80-120°C for 20-28 hours to obtain product C.

8. The method for preparing a titanium single atom anchored silica catalyst according to claim 4, wherein: In the step (4), product C is filtered, and the filter residue is vacuum dried at 60-80°C for 10-14 h, air calcined at 400-600°C at a heating rate of 4-6°C / min for 7-8 h, and naturally cooled to 15-30°C to obtain a titanium single atom anchored silica catalyst.

9. Use of the titanium single atom anchored silica catalyst according to any one of claims 1 to 8, characterized in that: The titanium single atom anchored silica catalyst is used to remove the sulfur-containing compound dibenzothiophene in fuel oil.

10. Use of the titanium single atom anchored silica catalyst according to any one of claims 1 to 8, characterized in that: The titanium single atom anchored silica catalyst is dispersed in an n-octane solution containing dibenzothiophene, and tert-butyl hydroperoxide is used as an oxidant to perform fuel oil desulfurization at 40-70°C. The catalyst needs to be washed with acetonitrile or calcined at a high temperature of 400-600°C for repeated use.

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