Preparation method of Pd(OH)2 / ultra-thin spherical two-dimensional SiO2 catalyst and its products and applications

Abstract

The present invention discloses a method for preparing a Pd(OH)2 / ultra-thin spherical two-dimensional SiO2 catalyst, which belongs to the technical field of catalyst preparation. The method comprises the following steps: preparing a template solution, adding a silicon precursor and a morphology control agent dropwise thereto, stirring to obtain a composite precursor solution, dropping the composite precursor solution into an alkaline solution, reacting, centrifuging, washing and calcining to obtain an ultra-thin spherical SiO2 carrier, dispersing the carrier in deionized water and ultrasonically stirring to obtain a suspension, adding an acid solution of a palladium precursor to the suspension, stirring to obtain a target catalyst. The present invention also discloses a Pd(OH)2 / ultra-thin spherical two-dimensional SiO2 catalyst and its application. The method is simple in process, the carrier in the prepared catalyst has a large specific surface area, can stably load Pd(OH)2, exhibits high catalytic activity and low Pd loss rate in the HBIW hydrogenolysis benzyl reaction, and has good application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation. More specifically, the present invention relates to a preparation method of a Pd(OH)2 / ultra-thin spherical two-dimensional SiO2 catalyst, and its product and application. Background Art

[0002] Silicon dioxide (SiO2), as an oxide that is both economical and practical, has become an important choice for heterogeneous catalyst supports due to its strong controllable morphology and microstructure and excellent chemical stability. Among them, two-dimensional mesoporous SiO2 films have attracted much attention due to their unique structural advantages and functional properties, but their precise synthesis still faces significant challenges: traditional preparation relies on two-dimensional solid hard templates or special equipment, which not only has problems such as easy template shedding, cumbersome processes, and high costs, but also is accompanied by the generation of a large amount of waste acid, which limits its large-scale application. Furthermore, two-dimensional mesoporous SiO2 films loaded with SiO2 spheres can significantly promote the efficiency of catalytic reactions due to the synergistic effect of the two-dimensional substrate and the spheres, but their preparation often requires a complex two-step method, which undoubtedly increases the preparation cost and process difficulty, restricting its practical application value.

[0003] Benzyl and its derivatives are commonly used protecting groups in organic synthesis and the pharmaceutical industry, and their removal reactions (catalytic hydrogenolysis) are widely used. Among them, N-benzyl, as the most common type of protecting group, is significantly more difficult to remove than other benzyl derivatives. For hexabenzylhexaazaisowurtzitane (HBIW), which contains six N-benzyl groups, the debenzylation reaction places higher demands on the catalyst's activity. Firstly, HBIW has a unique three-dimensional cage structure that is easily damaged by high temperatures due to its high surface tension, so the reaction must be carried out at or near room temperature. Secondly, the simultaneous and efficient removal of multiple benzyl sites poses a dual challenge to the catalyst's activity and selectivity.

[0004] However, current catalysts for the hydrogenolysis of HBIW still suffer from significant shortcomings: either insufficient activity, resulting in low product yields, or weak binding between the support and the active component, leading to high precious metal loss and high operating costs. These issues make it difficult for existing technologies to meet the practical needs of HBIW debenzylation. The development of a catalyst that is highly efficient and stable under mild conditions has become a key challenge in this field. Summary of the Invention

[0005] The present invention provides a preparation method of a Pd(OH)2 / ultra-thin spherical two-dimensional SiO2 catalyst, as well as its product and application. By optimizing the specific surface area and microstructure, the catalyst achieves efficient loading and stable anchoring of Pd(OH)2, thereby simultaneously achieving high catalytic activity and low metal loss rate in the HBIW hydrogenolysis debenzylation reaction.

[0006] In order to achieve these purposes and other advantages according to the present invention, a method for preparing a Pd(OH)2 / ultra-thin spherical two-dimensional SiO2 catalyst is provided, comprising the following steps:

[0007] S1. Adding a template to an ethanol aqueous solution and stirring to obtain a template solution having a template concentration of 10-15 mg / mL; the template comprises one or more of cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, octadecyltrimethylammonium chloride, and octadecyltrimethylammonium bromide;

[0008] S2. Add a silicon precursor and a morphology control agent dropwise to the template solution, wherein the volume ratio of the silicon precursor, the morphology control agent and the ethanol aqueous solution is (1-4):(4-6):100, and stir at 30-50° C. for 10-60 min to obtain a composite precursor solution; the silicon precursor includes one or more of 1,2-bis(triethoxysilyl)ethane, triethoxy(ethyl)silane, (3-aminopropyl)triethoxysilane, triethoxymethylsilane, methyl orthosilicate, tetraethyl orthosilicate and (3-aminopropyl)trimethoxysilane, and the morphology control agent includes one or more of toluene, xylene, ethylbenzene and styrene;

[0009] S3, adding the composite precursor solution dropwise into the alkaline solution, stirring at 50-90°C for 2-6 hours, centrifuging and washing after the reaction, and calcining at 400-600°C in an air atmosphere for 3-6 hours to obtain an ultra-thin spherical SiO2 carrier;

[0010] S4, dispersing the ultrathin spherical SiO2 carrier in deionized water with ultrasonication and stirring to obtain a carrier suspension;

[0011] S5. Dissolve the palladium precursor in an acid solution to obtain a palladium precursor solution with a palladium concentration of 0.005-0.010 mol / L, add the solution to the carrier suspension, and the volume ratio of the palladium precursor solution to the carrier suspension is 1:(2-3). Stir at 20-30°C for 6-8h, adjust the pH to 9-10, and after the reaction is completed, centrifuge, wash, and dry to obtain a Pd(OH)2 / ultra-thin spherical two-dimensional SiO2 catalyst.

[0012] Preferably, the palladium precursor comprises one of sodium palladium (II) chloride, potassium palladium (II) chloride and palladium (II) chloride.

[0013] Preferably, the ethanol aqueous solution in S1 is prepared by anhydrous ethanol and water in a volume ratio of (5-10):12;

[0014] The concentration of the alkaline solution in S3 is 0.1-0.4 mol / L, the amount of the composite precursor solution added is 2-8 mL, and the rate of adding the composite precursor solution dropwise to the alkaline solution is 0.3-0.8 mL / s;

[0015] In S4, the ultrathin spherical SiO2 carrier is dispersed in deionized water, the mass ratio of the ultrathin spherical SiO2 carrier to deionized water is 1:(100-150), the ultrasonic power is 80-100 W, and the ultrasonic time is 10-20 min;

[0016] The concentration of the acid solution in S5 is 0.5-1 M, and the drying temperature is 30-40°C.

[0017] The Pd(OH)2 / ultra-thin spherical two-dimensional SiO2 catalyst is prepared by the preparation method.

[0018] Preferably, the specific surface area of ​​the ultra-thin spherical two-dimensional SiO2 carrier in the catalyst is 810-840 m 2 / g.

[0019] Preferably, the two-dimensional substrate thickness of the ultra-thin spherical two-dimensional SiO2 carrier is less than 50 nm, and the particle size of the SiO2 spheres loaded thereon is 1-2 μm.

[0020] Preferably, Pd(OH)2 is uniformly loaded on the surface of the ultra-thin spherical two-dimensional SiO2 in the form of particles with a particle size of 5-10 nm.

[0021] The invention discloses an application of a Pd(OH)2 / ultra-thin spherical two-dimensional SiO2 catalyst in catalyzing the hydrogenation debenzylation reaction of hexabenzylhexaazaisowurtzitane, and adopts the catalyst.

[0022] Preferably, the mass ratio of hexabenzylhexaazaisowurtzitane in the reaction system to the palladium element in the catalyst is 1000:1.

[0023] Preferably, the hydrogenolysis debenzylation reaction is carried out in a solvent comprising N,N-dimethylformamide and acetic anhydride, and the hydrogenolysis debenzylation reaction is carried out under a hydrogen atmosphere. The reaction conditions include a reaction temperature of 20-40° C., a reaction pressure of 0.2-0.3 MPa, and a reaction time of 18-22 h.

[0024] The present invention has at least the following beneficial effects:

[0025] First, the preparation method of the Pd(OH)2 / ultra-thin spherical two-dimensional SiO2 catalyst provided by the present invention can be achieved through a simple "one-pot method", with simple process and low cost.

[0026] Second, the ultra-thin spherical two-dimensional SiO2 prepared by the present invention has a rich pore structure, which has the advantages of large specific surface area and large pore volume. It can provide a large number of anchoring points for the loading of metal species, ensuring a low loss rate of metal species. At the same time, it can ensure effective mass transfer and avoid the enrichment of solid products on the catalyst.

[0027] Third, the present invention uniformly loads Pd(OH)2 nanoparticles on the carrier to obtain a Pd(OH)2 / ultra-thin spherical two-dimensional SiO2 catalyst, which helps to show high performance in the HBIW hydrogenolysis and debenzylation reaction and improve the yield of the target product.

[0028] Other advantages, objectives and features of the present invention will be reflected in part from the following description and will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a scanning electron microscope photograph of the ultrathin spherical two-dimensional SiO2 carrier prepared in Example 1 of the present invention;

[0030] Figure 2 This is a transmission electron microscope photograph of the ultrathin spherical two-dimensional SiO2 carrier prepared in Example 1 of the present invention;

[0031] Figure 3 The XRD curve of the catalyst Pd(OH)2 / SiO2-2 prepared in Example 2 of the present invention;

[0032] Figure 4 Element distribution diagram of the catalyst Pd(OH)2 / SiO2-3 prepared in Example 3 of the present invention;

[0033] Figure 5 This is a transmission electron microscope photograph of the SiO2 porous spheres in Comparative Example 3 of the present invention;

[0034] Figure 6 This is a transmission electron microscope photograph of the carrier SiO2-1' prepared in Comparative Example 5 of the present invention;

[0035] Figure 7 is the chemical reaction formula for the hydrogenolysis-debenzylacetylation of hexabenzylhexaazaisowurtzitane (HBIW) of the present invention. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can further explain the present invention with the accompanying drawings to enable those skilled in the art to specifically explain that all are conventional methods, and the reagents and materials, unless otherwise specified, can be obtained from commercial channels, and therefore cannot be understood as limiting the present invention.

[0037] <Example 1>

[0038] The preparation method of Pd(OH)2 / ultra-thin spherical two-dimensional SiO2 catalyst comprises the following steps:

[0039] S1. Dissolve 0.24 g of hexadecyltrimethylammonium bromide in a mixture of 6 mL of anhydrous ethanol and 12 mL of deionized water, and stir at 40°C and 800 rpm for 1 h.

[0040] S2, add 0.5 mL of 1,2-bis(triethoxysilyl)ethane and 1 mL of toluene, stir for 30 min at a speed of 800 r / min and a temperature of 30°C to obtain a composite precursor solution;

[0041] S3. Add 1 mL of concentrated ammonia water to 50 mL of deionized water and stir at 700 r / min for 30 min to form an alkaline solution. Add 5 mL of the composite precursor solution dropwise to the alkaline solution at a rate of 0.5 mL / s and react at 80°C and 700 r / min for 4 h. Collect the product by centrifugation and wash it with ethanol aqueous solution (the volume ratio of anhydrous ethanol to deionized water is 1:1). Dry it in a vacuum oven and calcine it in air at 500°C for 4 h to obtain an ultrathin spherical two-dimensional SiO2 carrier. The heating rate is 10°C / min.

[0042] S4. Disperse 0.5 g of ultrathin spherical two-dimensional SiO2 carrier uniformly in 60 mL of distilled water, ultrasonicate for 15 min, and stir to obtain a carrier suspension. The stirring time is 30 min and the stirring speed is 500 r / min.

[0043] S5. Dissolve 0.05 g of palladium (II) chloride in 30 mL of aqueous hydrochloric acid solution (0.6 M) by ultrasonication, then add the above suspension and stir for a certain period of time, add 6 wt% NaOH solution dropwise, adjust the pH to about 10, and stir the reaction for 6 h. The reaction temperature is 25°C and the stirring speed is 800 r / min. After the reaction is completed, the product is obtained by centrifugation and thorough washing, and then dried in a vacuum oven at a temperature of 35°C to obtain Pd(OH)2 / ultra-thin spherical two-dimensional SiO2 catalyst (abbreviated as Pd(OH)2 / SiO2-1).

[0044] <Example 2>

[0045] The preparation method of Pd(OH)2 / ultra-thin spherical two-dimensional SiO2 catalyst comprises the following steps:

[0046] S1. Dissolve 0.20 g of hexadecyltrimethylammonium bromide in a mixture of 6 mL of anhydrous ethanol and 11 mL of deionized water, and stir at 40°C and 800 rpm for 1 h.

[0047] S2, add 0.4 mL of 1,2-bis(triethoxysilyl)ethane and 0.8 mL of toluene, and stir for 20 min at a speed of 700 r / min and a temperature of 35°C to obtain a composite precursor solution;

[0048] S3. Add 0.9 mL of concentrated ammonia water to 45 mL of deionized water and stir at 700 r / min for 30 min to form an alkaline solution. Add 4 mL of the composite precursor solution dropwise to the alkaline solution at a rate of 0.4 mL / s and react at 70°C and 600 r / min for 3 h. Collect the product by centrifugation and wash it with ethanol aqueous solution (the volume ratio of anhydrous ethanol to deionized water is 0.8:1). Dry it in a vacuum oven and calcine it in air at 400°C for 5 h to obtain an ultrathin spherical two-dimensional SiO2 carrier. The heating rate is 8°C / min.

[0049] S4. Disperse 0.5 g of ultrathin spherical two-dimensional SiO2 carrier uniformly in 50 mL of distilled water, ultrasonicate for 13 min, and stir to obtain a suspension. The stirring time is 30 min and the stirring speed is 500 r / min.

[0050] S5. Dissolve 0.04 g of palladium (II) chloride in 28 mL of aqueous hydrochloric acid solution (0.7 M) by ultrasonication, then add the above suspension and stir for a certain period of time, add 8 wt% NaOH solution dropwise, adjust the pH to about 9, and stir the reaction for 5 h. The reaction temperature is 20°C and the stirring speed is 700 r / min. After the reaction is completed, the product is obtained by centrifugation and thorough washing, and then dried in a vacuum oven at a temperature of 30°C to obtain Pd(OH)2 / ultra-thin spherical two-dimensional SiO2 catalyst (abbreviated as Pd(OH)2 / SiO2-2).

[0051] <Example 3>

[0052] The preparation method of Pd(OH)2 / ultra-thin spherical two-dimensional SiO2 catalyst comprises the following steps:

[0053] S1. Dissolve 0.26 g of hexadecyltrimethylammonium bromide in a mixture of 8 mL of anhydrous ethanol and 12 mL of deionized water, and stir at 40°C and 800 rpm for 1 h.

[0054] S2, add 0.6 mL of 1,2-bis(triethoxysilyl)ethane and 1.2 mL of toluene, and stir for 40 min at a speed of 1000 r / min and a temperature of 40°C to obtain a composite precursor solution;

[0055] S3. Add 1.2 mL of concentrated ammonia water to 60 mL of deionized water and stir at 700 r / min for 30 min to form an alkaline solution. Add 7 mL of the composite precursor solution dropwise to the alkaline solution at a rate of 0.7 mL / s and react at 85°C and 800 r / min for 5 h. Collect the product by centrifugation and wash it with ethanol aqueous solution (the volume ratio of anhydrous ethanol to deionized water is 1:1). Dry it in a vacuum oven and calcine it in air at 600°C for 6 h to obtain an ultrathin spherical two-dimensional SiO2 carrier. The heating rate is 15°C / min.

[0056] S4. Disperse 0.5 g of ultrathin spherical two-dimensional SiO2 carrier uniformly in 70 mL of distilled water, ultrasonicate for 15 min, and stir to obtain a suspension. The stirring time is 30 min and the stirring speed is 500 r / min.

[0057] S5. Dissolve 0.06 g of palladium (II) chloride in 30 mL of aqueous hydrochloric acid solution (0.7 M) by ultrasonication, then add the above suspension and stir for a certain period of time, add 8 wt% NaOH solution dropwise, adjust the pH to about 10, and stir the reaction for 8 h. The reaction temperature is 30°C and the stirring speed is 900 r / min. After the reaction is completed, the product is obtained by centrifugation and thorough washing, and then dried in a vacuum oven at a temperature of 40°C to obtain Pd(OH)2 / ultra-thin spherical two-dimensional SiO2 catalyst (abbreviated as Pd(OH)2 / SiO2-3).

[0058] Comparative Example 1

[0059] Pd(OH)2 / C catalyst, with a Pd content of 20%, was commercially available.

[0060] Comparative Example 2

[0061] The preparation method of Pd(OH)2 / diatomite catalyst comprises the following steps:

[0062] S1. The carrier is replaced with diatomaceous earth, which is commercially available.

[0063] S2 is the same as steps S4-S5 in Example 1.

[0064] Comparative Example 3

[0065] The preparation method of Pd(OH)2 / SiO2 porous spheres comprises the following steps:

[0066] S1. The carrier is replaced with SiO2 porous balls, which are commercially available.

[0067] S2 is the same as steps S4-S5 in Example 1.

[0068] Comparative Example 4

[0069] The preparation method of Pd(OH)2 / SiO2 two-dimensional sheet catalyst comprises the following steps:

[0070] S1. The carrier is replaced with a SiO2 two-dimensional sheet, which is commercially available.

[0071] S2 is the same as steps S4-S5 in Example 1.

[0072] Comparative Example 5

[0073] The preparation method of Pd(OH)2 / ultra-thin spherical two-dimensional SiO2 catalyst comprises the following steps:

[0074] Steps S1-S5 are the same as those in Example 1, except that toluene is not added in step S2.

[0075] Comparative Example 6

[0076] The preparation method of Pd(OH)2 / ultra-thin spherical two-dimensional SiO2 catalyst comprises the following steps:

[0077] Steps S1-S5 are the same as those in Example 1, except that the calcination temperature in step S3 is 100°C.

[0078] <Carrier Performance Test>

[0079] The specific surface areas of the carriers in Examples 1-3 and Comparative Examples 2-6 were measured using the BET method. The results are shown in Table 1 below.

[0080] Table 1

[0081]

[0082] As shown in Table 1, the specific surface area of ​​the ultra-thin, spherical, two-dimensional SiO2 supports prepared in Examples 1-3 is significantly increased compared to the commercially available SiO2 supports in Comparative Examples 2-4 and the homemade SiO2 supports in Comparative Examples 5-6. This indicates that the SiO2 supports prepared in Examples 1-3 have more micropores and mesopores, which facilitates uniform loading of Pd species. A morphology modifier (such as toluene) ensures that the SiO2 forms a thin film and regulates the thickness of the SiO2 film. Without the addition of a morphology modifier, the prepared SiO2 is only spherical. The calcination temperature determines the number of pores in the SiO2 support. If the temperature is not high enough, the template may not be completely removed, resulting in a reduced number of pores and extremely poor mass transfer efficiency. Although a certain specific surface area is retained, the film-sphere synergistic structure is not formed, which directly limits the uniformity of Pd(OH)2 loading and the exposure of active sites. The high specific surface area comes from the unique structure of the ultra-thin spherical two-dimensional SiO2 carrier (ultra-thin two-dimensional substrate loaded with SiO2 small balls), which can provide more anchoring points for uniform loading of Pd(OH)2. At the same time, the rich pore structure can improve the mass transfer efficiency and avoid product enrichment on the catalyst surface, laying the foundation for subsequent catalytic activity improvement.

[0083] <Catalyst activity performance test>

[0084] The activity of the obtained catalyst was evaluated by hydrogenolysis of HBIW as a probe reaction. The reaction equation is as follows: Figure 7 As shown, the amount of catalyst used was calculated to ensure that the ratio of the mass of the Pd element in the catalyst to the mass of the substrate HBIW was 1:1000. The specific test conditions are as follows: 50 g of HBIW, 1.3 g of catalyst, 100 mL of N,N-dimethylformamide (DMF), 50 mL of acetic anhydride (Ac2O), and 1 mL of PhBr were mixed, evacuated, replaced with hydrogen 3-5 times, then hydrogen was introduced and stirred, and the mixture was reacted at room temperature and pressure until a solid hydrogenolysis product was precipitated. The temperature was raised to 40°C and the reaction was continued. The total reaction time was about 20 h. After the reaction, the solid obtained by filtration was washed and dried to obtain a crude hydrogenolysis debenzylation product. The activity data of each group of catalysts in the hydrogenolysis debenzylation reaction of HBIW were tested, wherein the catalysts were Pd(OH)2 / SiO2-1, Pd(OH)2 / SiO2-2, Pd(OH)2 / SiO2-3 catalysts prepared in Examples 1-3 and the catalysts of Comparative Examples 1-6, Pd / HBIW was the mass ratio of Pd element to HBIW, and the results were shown in Table 2 below.

[0085] Table 2

[0086]

[0087] According to the data in Table 2, the Pd(OH)2 / ultra-thin spherical two-dimensional SiO2 catalysts prepared in Examples 1-3 of the present invention exhibited comprehensive performance advantages far exceeding those of the comparative systems in the HBIW hydrogenolysis debenzylation reaction, which was specifically reflected in the dual breakthroughs in catalytic activity and metal stability:

[0088] From the yield of the target product TADB, the catalytic efficiency of Examples 1-3 is significantly better than that of Comparative Examples 2-6, all of which are stable at more than 90%, and completely avoids the problem of insufficient activity of the commercially available Pd(OH)2 / C catalyst in Comparative Example 1 (the Pd(OH)2 particles on the commercially available Pd(OH)2 / C catalyst are unevenly loaded and the particle size is inconsistent, resulting in the inability to efficiently contact with the substrate during the catalytic reaction at such a low catalyst dosage, thereby affecting the reaction). The specially designed support structure of the present invention can ensure uniform loading and small particle size of the Pd species, and the complete membrane-sphere synergy can provide sufficient active sites and efficient mass transfer, and can anchor Pd(OH)2 through multi-level pores to inhibit loss, fully demonstrating the efficient catalytic ability of the catalyst of the present invention for the hydrogenolysis debenzylation reaction of HBIW.

[0089] From the perspective of Pd element stability, the Pd loss rate of Examples 1-3 is significantly lower than that of Comparative Examples 2-6. This may be due to the high specific surface area of ​​the ultrathin spherical two-dimensional SiO2 (813.8-831.7 m 2 / g) provides abundant anchoring sites, and the confinement effect brought by the synergistic structure of the two-dimensional substrate and the support sphere can effectively inhibit the agglomeration and leaching of Pd(OH)2 nanoparticles, thus achieving stable loading of Pd metal species. 2 / g), unable to provide sufficient binding sites for Pd, resulting in a large amount of metal species agglomeration or a large amount of metal loss and insufficient active sites; although the SiO2 porous spheres in comparative example 3 and the SiO2 two-dimensional sheets in comparative example 4 have a higher specific surface area than diatomite, they lack the synergistic structure of the ultra-thin two-dimensional substrate and the carrier ball, and their mass transfer efficiency and metal anchoring ability are inferior to those of the carrier of the present invention, which ultimately manifests as a double disadvantage in yield and stability; although the carrier of comparative example 5 does not form an ultra-thin carrier ball-type two-dimensional structure, it can still provide a small amount of anchoring sites (such as mesoporous channels and surface hydroxyl groups), which inhibit the dissolution of Pd(OH)2 to a certain extent, but because the force on Pd metal is weaker than that in Example 1, the Pd loss rate is higher than that in Example 1. At the same time, since the catalysts are all spherical, the mass transfer efficiency and enrichment of substrates, intermediates and products are low, which is not conducive to the catalytic reaction process; the carrier in comparative example 6 may have less pore structure due to the incomplete removal of the template agent, which in turn causes a significant decrease in specific surface area, insufficient anchoring and confinement effect on Pd(OH)2, and ultimately affects the effective exposure of active sites and the mass transfer process in the reaction, resulting in a high Pd loss rate and a decrease in the yield of the target product.

[0090] The Pd(OH)2 / ultra-thin spherical two-dimensional SiO2 catalysts prepared in Examples 1-3 of the present invention achieve efficient loading and stable anchoring of Pd(OH)2 by optimizing the specific surface area and microstructure, thereby simultaneously achieving high catalytic activity and low metal loss rate in the HBIW hydrogenolysis debenzylation reaction. Its performance advantages are far beyond the comparison of existing conventional carrier systems, highlighting the key regulatory role of carrier structure innovation on catalytic performance.

[0091] Figure 1 The figure shows a scanning electron microscope image of the ultrathin spherical two-dimensional SiO2 carrier of Example 1. A large continuous thin film structure can be observed in the figure, showing a translucent feature, that is, the substrate is an ultrathin two-dimensional sheet. The thickness of the two-dimensional substrate of the ultrathin spherical two-dimensional SiO2 carrier is less than 50 nm. The surface of the ultrathin two-dimensional sheet substrate is densely distributed with spherical protrusions, and the particle size distribution is uniform, that is, the structure of SiO2 spheres with a particle size of 1-2 μm. The spheres and the film surface form mesoporous channels, providing a high specific surface area (831.7 m 2 / g), the graded pores are conducive to mass transfer, and it is characterized that Pd(OH)2 is uniformly loaded on the ultra-thin spherical two-dimensional SiO2 surface in the form of particles with a particle size of 5-10 nm.

[0092] Figure 2 Shown is a transmission electron microscope photograph of Pd(OH)2 / SiO2-1 of Example 1. It can be observed that the light-colored area in the figure is a two-dimensional SiO2 membrane substrate with evenly distributed mesoporous channels on the surface. The dark spherical structure is the loaded SiO2 spheres, which are several microns in diameter and dispersed without agglomeration, reflecting the precise control of the in-situ growth and dispersion of the spheres by the morphology regulator in the "one-pot method". Due to the in-situ growth, the interaction between the spheres and the membrane substrate is strong, ensuring the structural stability of the catalyst. This stable synergistic structure can significantly reduce the Pd loss rate and accelerate the diffusion and mass transfer of reactants / products. The mesoporous channels and the surface of the spheres synergistically increase the specific surface area, provide sufficient anchoring points for Pd(OH)2 loading, and avoid agglomeration of active components.

[0093] Figure 3 Shown is the XRD curve of Pd(OH)2 / SiO2-2 from Example 2. The characteristic diffraction peaks of Pd(OH)2 are not clearly observed in the figure, indicating that the Pd(OH)2 is uniformly dispersed in the form of nanoparticles on the SiO2 support (without obvious agglomeration). Furthermore, characteristic amorphous peaks (broadened peaks) of the SiO2 support are observed in the figure, indicating an amorphous structure, consistent with the characteristics of mesoporous SiO2. The high catalytic activity of Pd(OH)2 / SiO2-2 is likely due to the uniform loading and good dispersion of Pd(OH)2.

[0094] Figure 4Shown is the elemental distribution diagram of Pd(OH)2 / SiO2-3 of Example 3. The figure shows the spatial distribution of O, Si, and Pd in ​​the catalyst. O and Si are evenly distributed (corresponding to the SiO2 support), and the distribution trend of Pd is consistent with that of O and Si. This indicates that Pd(OH)2 is uniformly loaded on the support surface without localized aggregation. This uniformity ensures full exposure of catalytic active sites and is the structural reason for the high catalyst activity and low Pd loss rate.

[0095] Figure 5 The following is a transmission electron microscope photo of the SiO2 porous spheres in comparative example 3. It can be observed that the carrier is an independent spherical structure with pores inside the spheres, but without the characteristics of an ultra-thin two-dimensional substrate and loaded spheres. The whole is a single spherical particle accumulation. Figure 1 Compared with SiO2-1, its pore size is uneven, resulting in a high Pd loss rate (1.34%), and its structure leads to a low specific surface area (625.3 m in Table 1). 2 / g), thereby affecting the loading efficiency and stability of Pd(OH)2.

[0096] Figure 6 Shown is a transmission electron microscope photograph of the carrier SiO2-1' of comparative example 5. A large number of independent spherical SiO2 particles can be observed in the figure, and there is no synergistic structure of the two-dimensional membrane substrate + carrier sphere in the embodiment. Due to the lack of toluene, the silicon precursor loses its interface guiding effect and cannot be assembled into a two-dimensional membrane in a direction. It only grows into a pure sphere through free nucleation. Compared with the continuous mesoporous network of the embodiment, the secondary pores and particle voids in its pore system have limited contribution to the increase in specific surface area, resulting in insufficient anchoring points and confinement for Pd(OH)2; due to the lack of the dispersion effect of the two-dimensional membrane, Pd(OH)2 is easy to agglomerate on the spherical surface, reducing the catalytic activity. The gaps between the spherical particles are large but the pores are single, the mass transfer efficiency is poor, the product is easy to enrich, and Pd is easy to leach and lose.

[0097] Figure 7 The core chemical process of the hydrogenolysis debenzylation of hexabenzylhexaazaisowurtzitane (HBIW) is shown. The reactant, HBIW, contains six benzyl groups (Bn). During the hydrogenolysis debenzylation, four of the Bn groups are removed, and acetylation occurs simultaneously, with acetyl groups (Ac) replacing the active hydrogens on the nitrogen atoms. This generates the intermediate tetraacetyldibenzylhexaazaisowurtzitane (TADBIW). The remaining two benzyl groups can then be removed by other means, ultimately leading to nitration to hexanitrohexaazaisowurtzitane (CL-20), which contains six nitro groups (NO2).

[0098] The ultra-thin spherical silica support structure significantly improves catalyst performance through multiple synergistic mechanisms.

[0099] First, the carrier's unique two-dimensional, ultra-thin substrate significantly shortens the diffusion path of reactant molecules, while the uniformly loaded silica spheres on the surface create a hierarchical pore system. This unique, two-dimensional, hierarchical mass transfer structure ensures effective contact between the hexabenzylhexaazaisowurtzitane macromolecule and the active sites, while also ensuring efficient mass transfer between intermediates and products. This overcomes the problem of substrate and product blockage caused by molecular size effects in traditional carriers, significantly improving the catalytic reaction rate.

[0100] Secondly, the high density of hydroxyl groups enriched on the support surface form a strong chemical interaction with the active component, palladium hydroxide. This chemical anchoring effect not only stabilizes the palladium species but also significantly reduces the hydrogen dissociation energy barrier through electronic synergy, while simultaneously polarizing the carbon-nitrogen bond of the target reaction, thereby reducing the reaction activation energy through a dual pathway. The nanoscale dispersion of palladium hydroxide on the support surface further exposes abundant active sites, enabling the catalyst to achieve reaction efficiencies unattainable with traditional systems under mild reaction conditions.

[0101] Finally, the dual stabilization mechanism of chemical bonding and physical confinement imparts remarkable durability to the catalyst. The strong interaction between the support and the active component effectively reduces the leaching of palladium metal species within a specific size range during the reaction. The catalyst structure maintains its intact morphology after the reaction, exhibiting no structural collapse, demonstrating its stability. This intrinsic stability enables the catalyst to maintain high activity during continuous operation, significantly reducing the cost of active component replenishment in industrial applications.

[0102] In summary, the ultra-thin spherical two-dimensional Pd(OH)2 / SiO2 carrier designed in the present invention achieves efficient loading and stable anchoring of Pd(OH)2 by optimizing the specific surface area and microstructure, thereby simultaneously achieving high catalytic activity and low metal loss rate in the HBIW hydrogenolysis debenzylation reaction. Its performance advantages are far beyond the comparison of existing conventional carrier systems, highlighting the key regulatory role of carrier structure innovation on catalytic performance.

[0103] The number of devices and processing scales described herein are intended to simplify the description of the present invention. Applications, modifications, and variations of the present invention will be readily apparent to those skilled in the art.

[0104] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for preparing a Pd(OH)2 / ultra-thin spherical two-dimensional SiO2 catalyst, characterized in that: The following steps are involved: S1, adding a template agent to an ethanol aqueous solution and stirring to obtain a template agent solution with a template agent concentration of 10-15 mg / mL; the template agent is hexadecyltrimethylammonium bromide; S2. Add a silicon precursor and a morphology control agent dropwise to the template solution. The volume ratio of the silicon precursor, the morphology control agent, and the ethanol aqueous solution is (1-4):(4-6):

100. Stir at 30-50° C. for 10-60 min to obtain a composite precursor solution. The silicon precursor is 1,2-bis(triethoxysilyl)ethane, and the morphology control agent is toluene. S3, adding the composite precursor solution dropwise into the alkaline solution, stirring at 50-90°C for 2-6 hours, centrifuging and washing after the reaction, and calcining at 400-600°C in an air atmosphere for 3-6 hours to obtain an ultra-thin spherical SiO2 carrier; S4, dispersing the ultrathin spherical SiO2 carrier in deionized water with ultrasonication and stirring to obtain a carrier suspension; S5, dissolving a palladium precursor in an acid solution to obtain a palladium precursor solution having a palladium concentration of 0.005-0.010 mol / L, adding the solution to the support suspension, wherein the volume ratio of the palladium precursor solution to the support suspension is 1:2-3, stirring at 20-30° C. for 6-8 h, adjusting the pH to 9-10, and obtaining a Pd(OH)2 / ultra-thin spherical two-dimensional SiO2 catalyst after completion of the reaction by centrifugation, washing, and drying, wherein the palladium precursor comprises one of sodium palladium chloride (II), potassium palladium chloride (II), and palladium chloride (II); In the Pd(OH)2 / ultra-thin spherical two-dimensional SiO2 catalyst, the specific surface area of ​​the ultra-thin spherical two-dimensional SiO2 carrier is 810-840m 2 / g, the two-dimensional substrate thickness of the ultra-thin spherical two-dimensional SiO2 carrier is less than 50 nm, the particle size of the SiO2 beads loaded on it is 1-2 μm, and Pd(OH)2 is uniformly loaded on the surface of the ultra-thin spherical two-dimensional SiO2 in the form of particles with a particle size of 5-10 nm.

2. The preparation method according to claim 1, characterized in that The ethanol aqueous solution in S1 is prepared by mixing anhydrous ethanol and water in a volume ratio of 5-10:12; The concentration of the alkaline solution in S3 is 0.1-0.4 mol / L, the amount of the composite precursor solution added is 2-8 mL, and the rate of adding the composite precursor solution dropwise to the alkaline solution is 0.3-0.8 mL / s; In S4, the ultrathin spherical SiO2 carrier is dispersed in deionized water, the mass ratio of the ultrathin spherical SiO2 carrier to deionized water is 1:100-150, the ultrasonic power is 80-100 W, and the ultrasonic time is 10-20 min; The concentration of the acid solution in S5 is 0.5-1 M, and the drying temperature is 30-40°C.

3. Pd(OH)2 / ultra-thin spherical two-dimensional SiO2 catalyst, characterized by: The preparation method according to claim 1 or 2 is used for preparation.

4. Application of Pd(OH)2 / ultra-thin spherical two-dimensional SiO2 catalyst in the hydrogenolysis of hexabenzylhexaazaisowurtzitane, characterized in that: The catalyst according to claim 3 is used.

5. The use according to claim 4, characterized in that The mass ratio of hexabenzylhexaazaisowurtzitane in the reaction system to the palladium element in the catalyst is 1000:

1.

6. The use according to claim 4, characterized in that The hydrogenolysis debenzylation reaction is carried out in a solvent comprising N,N-dimethylformamide and acetic anhydride. The hydrogenolysis debenzylation reaction is carried out under a hydrogen atmosphere. The reaction conditions include a reaction temperature of 20-40° C., a reaction pressure of 0.2-0.3 MPa, and a reaction time of 18-22 h.

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