Solid acid catalyst for synthesizing cyclic peroxide and application of solid acid catalyst

Abstract

The invention discloses a solid acid catalyst for synthesizing cyclic peroxide and application of the solid acid catalyst, and belongs to the technical field of catalytic synthesis. The solid acid catalyst has a core-shell structure, and the core-shell structure sequentially comprises the following components from inside to outside: a) a core: ZSM-5 zeolite, the surface of which is grafted with an amino group, and the aperture of which is 0.54-0.58 nm; b) an intermediate layer: a phosphorylated titanium dioxide layer containing Ti-O-P bonds; and c) a shell: a nitrogen-doped sulfonated carbon layer, the surface sulfonic group density is 1.6 mmol / g-1. 8mmol / g, a temperature-sensitive polymer network is grafted in the shell layer, and the tail end of the temperature-sensitive polymer network is modified with a sulfonic group. The problems of harsh reaction conditions, low product purity, poor catalyst stability and insufficient environmental friendliness in the prior art are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalytic synthesis, and particularly relates to a solid acid catalyst for synthesizing cyclic peroxides and its application. Background Art

[0002] Cyclic peroxides (such as 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane) are a class of functional compounds with high oxidation activity, and are widely used in the fields of polymer crosslinking agents, pharmaceutical intermediates and energetic materials. Their synthesis needs to be completed through the synergistic two-step reactions of olefin epoxidation and ring closure. However, the coexistence of multiple peroxy bonds in the molecule leads to poor thermal stability and frequent side reactions. Traditional homogeneous acid catalysts (such as sulfuric acid, heteropolyacid) are prone to cause the cleavage of peroxy bonds or molecular rearrangement, and the product selectivity is less than 80%; while heterogeneous solid acids (such as Hβ zeolite, sulfonated resin) are difficult to match the large molecular size (about 1.2 nm) of the target product due to pore size limitation (<0.8 nm), and the problems of water molecule poisoning and carbon deposition lead to rapid deactivation of the catalyst (service life <200 h). The existing process also needs to strictly control the water content of raw materials (<5 ppm), further increasing energy consumption and operation complexity.

[0003] In the prior art, ZSM-5 / MCM-41 composite molecular sieves are often used to increase the acid density, but the single Brønsted acid type of this technology cannot adapt to the different requirements of epoxidation and ring closure reactions, and the product purity is lower than 90%. There is also a technology to improve the water resistance by loading sulfonic groups on the carbon carrier, but the fixed acid strength leads to the proportion of side reactions exceeding 15% at high temperatures. In addition, the above catalysts lack a dynamic response mechanism, are difficult to adjust the acid site distribution according to the reaction process, and have insufficient mechanical strength, making it difficult to cope with humidity fluctuations and mechanical stresses in industrial scenarios.

[0004] To solve the above problems, it is urgent to develop a new catalyst with gradient acid synergy, dynamic response regulation and environmental robustness. The defects of the prior art are concentrated in three points: firstly, a single acid type cannot match the different requirements of multi-step reactions; secondly, static acid sites lead to the accumulation of by-products; thirdly, mass transfer limitations and structural collapse restrict continuous production. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: to overcome the deficiencies of the prior art and provide a solid acid catalyst for synthesizing cyclic peroxides that is efficient, stable and highly adaptable, and its application.

[0006] A solid acid catalyst for synthesizing cyclic peroxides has a core-shell structure, and the core-shell structure from the inside to the outside is successively: a core, an intermediate layer and a shell; The core is an aluminosilicate molecular sieve with a SiO2 / Al2O3 molar ratio of 30 to 50 (preferably ZSM-5 zeolite), and amino groups are grafted on the surface; The intermediate layer is a phosphorylated titanium dioxide layer; The outer shell is a nitrogen-doped sulfonated carbon layer with a thickness of 10 nm to 50 nm, a surface sulfonic acid group density of 1.6 mmol / g to 1.8 mmol / g, a contact angle ≥ 150°, a thermosensitive polymer network is grafted on the outer shell, and sulfonic acid groups are grafted at the ends of the thermosensitive polymer network; There are interfacial metal nanoparticles between the core and the intermediate layer and / or between the intermediate layer and the outer shell. The interfacial metal nanoparticles include Pt, Pd or Ru nanoparticles with a particle size of 2 nm to 5 nm and a loading amount of 0.5% to 3% of the mass of the solid acid catalyst.

[0007] Preferably, for the above solid acid catalyst for synthesizing cyclic peroxides, the pore diameter of the aluminosilicate molecular sieve is 0.54 nm to 0.58 nm; the phosphorylated titanium dioxide layer contains Ti-O-P bonds, has a thickness of 3 nm to 8 nm, and a Brønsted acid density of 0.5 mmol / g to 0.8 mmol / g.

[0008] Preferably, for the above solid acid catalyst for synthesizing cyclic peroxides, the thermosensitive polymer is at least one of poly(N-isopropylacrylamide) (PNIPAM), polyacrylamide-co-acrylic acid or polyethylene glycol-co-methyl methacrylate, and the grafting rate of its sulfonic acid groups is 50% to 80%.

[0009] Preferably, for the above solid acid catalyst for synthesizing cyclic peroxides, the surface of the outer shell has fluorocarbon groups obtained by fluorination treatment with a fluorination depth of 3 nm to 8 nm, and the fluorocarbon groups include at least one of -CF2, -CF3 or -CF2-CF2-.

[0010] The present invention provides a multi-layer composite catalytic system with gradient acidity characteristics. Its core is an ordered pore material, and the surface is modified to enhance the adsorption capacity for target reactants. The system sequentially includes from the inside to the outside: Inner layer substrate: An aluminosilicate molecular sieve (SiO2 / Al2O3 molar ratio of 30 to 50, pore diameter range of 0.54 nm to 0.58 nm) is used. Lewis acid sites are formed through the aluminum-oxygen bonds in its framework to promote the initiation of the initial reaction. The surface is modified with organic amines to introduce amino functional groups to further enhance the adsorption capacity of intermediates.

[0011] Intermediate layer regulation unit: Deposit a titanium-containing compound (Ti-O-P bond, preferably with a pore size of 1.2 nm and an acid density of 0.7 mmol / g) on the surface of the inner layer substrate. Control the thickness to 5 nm by atomic layer deposition (ALD), and activate it with phosphoric acid solution to adjust the diffusion rate of reaction intermediates and inhibit the occurrence of side reactions.

[0012] Outer active shell: Use a sulfonated carbon material doped with nitrogen elements (preferably with an N-SO3H density of 1.8 mmol / g, a mesopore size of 3 nm, and a contact angle > 150°). Coating by chemical vapor deposition (CVD) method, with a thickness of 10 nm to 50 nm. The surface is treated by fluorination to form a hydrophobic channel, enhancing the anti-water poisoning performance, and at the same time providing a super-strong acidic environment (H0 = -9.1) to promote the progress of the closed-loop reaction.

[0013] To achieve temperature-controlled acidic regulation, the present invention introduces a thermosensitive polymer segment in the outer shell and grafts sulfonic acid groups. Specifically: Under low-temperature conditions (< 40 °C), the exposure amount of sulfonic acid groups increases, and the acid density reaches 1.6 mmol / g, effectively activating hydrogen peroxide; Under high-temperature conditions (> 60 °C), the sulfonic acid groups contract, and the acid density drops to 1.2 mmol / g, avoiding the occurrence of over-oxidation reactions.

[0014] In addition, noble metal nanoparticles (particle size 2 - 3 nm) are embedded between the inner layer substrate and the outer active shell. Through the electron transfer effect, the acid strength of the sulfonic acid groups is enhanced, and its H0 (Hammett acidity) value is reduced from -8.2 to -9.1, significantly increasing the generation rate of epoxy intermediates.

[0015] A preparation method of a solid acid catalyst for synthesizing the above cyclic peroxide, comprising the following steps: Core modification: Calcinate the aluminosilicate molecular sieve and then impregnate it with an amino-silane coupling agent, and dry to obtain an amino-functionalized zeolite; Intermediate layer construction: Grow a titanium dioxide layer on the surface of the core layer by atomic layer deposition, and impregnate and activate it with phosphoric acid to form a Ti-O-P bond to obtain a phosphorylated titanium dioxide layer; Outer shell coating: Use glucose-citric acid as the carbon source, and coat a nitrogen-doped carbon layer by chemical vapor deposition method to form a carbon shell; After sulfonation treatment of the carbon shell, free radical polymerization is initiated on the surface of the carbon shell to form a thermosensitive polymer network, and the thermosensitive polymer network is selectively sulfonated and modified at the chain ends to obtain the outer shell; It also includes metal nanoparticle loading: Use the impregnation reduction method to deposit Pt, Pd or Ru nanoparticles on the surface after the core modification step or / and the intermediate layer construction step.

[0016] Preferably, in the preparation method of the solid acid catalyst, the specific operation of impregnating the aminosilane coupling agent is: in anhydrous toluene or a mixed solvent of toluene / ethanol (volume ratio 1-3:1), 2.5mL-3mL of aminosilane coupling agent is added to each 1g of molecular sieve for batching, and then refluxed at 70℃-80℃ for 18-24 hours to promote the covalent bonding of silane molecules with the hydroxyl groups on the surface of the substrate, and after the reaction is completed, it is washed with toluene, ethanol and deionized water in sequence to remove the physically adsorbed unreacted silane, and finally the surface modification layer is cured by vacuum drying at 80℃. The aminosilane coupling agent is at least one of aminopropyltriethoxysilane (APTES), aminoethylaminopropylmethyldimethoxysilane (AEAPMDS) and 3-aminopropyltrimethoxysilane (APTS).

[0017] Preferably, in the preparation method of the above-mentioned solid acid catalyst, the number of deposition cycles of the atomic layer deposition is 30 to 60 times, and the phosphoric acid immersion activation adopts 0.3 mol / L to 0.8 mol / L H3PO4 solution at 60°C to 90°C for 4h to 8h.

[0018] Preferably, in the preparation method of the above-mentioned solid acid catalyst, the carrier gas of the chemical vapor deposition method is a mixture of nitrogen and hydrogen in a volume ratio of 5 to 10:1, the deposition pressure is 0.1 MPa to 0.3 MPa, the heating rate is 3°C / min to 8°C / min, and the deposition temperature is 550°C to 650°C; the carbon source is a compound of glucose and citric acid in a mass ratio of 2 to 4:1.

[0019] Preferably, in the preparation method of the above-mentioned solid acid catalyst, the sulfonation treatment is carried out step by step by liquid phase sulfonation and gas phase sulfonation strengthening: the liquid phase sulfonation is treated with fuming sulfuric acid at 110°C~130°C for 10h~15h; the gas phase sulfonation strengthening is treated in SO3 vapor at 180°C~220°C for 1h~3h.

[0020] Preferably, in the preparation method of the solid acid catalyst, the specific process of depositing Pt, Pd or Ru nanoparticles on the surface by the impregnation reduction method after the core modification step and / or the intermediate layer construction step is: 1. Use metal salts as precursors, such as H2PtCl6 (platinum source), PdCl2 (palladium source) or RuCl3 (ruthenium source); 2. Dissolve the precursor in deionized water or an organic solvent (such as ethanol) to prepare a metal salt solution with a concentration range of 0.1 mol / L to 0.5 mol / L; 3. Depending on the catalyst structure, choose the core (amino-functionalized ZSM-5 zeolite) or the middle layer (phosphorylated TiO2) as the carrier; 4. Immerse the carrier in a metal salt solution, and make metal ions uniformly adsorbed on the surface of the carrier by stirring or ultrasonic treatment. The impregnation time is 2 to 4 hours. After impregnation, dry at 80°C to 120°C for 4 to 6 hours to remove the solvent; 5. Reduction includes chemical reduction and thermal reduction: Chemical reduction: Use NaBH4, hydrazine hydrate or ethanol as a reducing agent and react at room temperature for 1 - 2 hours (applicable to Pd, Ru); Thermal reduction: Heat in an H2 atmosphere at 200°C to 400°C for 1 to 3 hours (applicable to Pt, Ru, and the heating rate needs to be controlled to prevent particle agglomeration); 6. After reduction, wash with deionized water or ethanol to remove residual ions, and dry in an inert atmosphere to obtain the product.

[0021] An application of the solid acid catalyst for synthesizing the above cyclic peroxide, comprising the following steps: In a reactor, carry out a synthesis reaction of an organic ketone and hydrogen peroxide under the catalysis of the solid acid catalyst for synthesizing the above cyclic peroxide. The separated oil phase in the reaction system is 3,6,9 - triethyl - 3,6,9 - trimethyl - 1,4,7 - triperoxynonane.

[0022] The reaction temperature is 10°C to 30°C; the reaction time is 1 h to 2 h; the feed molar ratio of the organic ketone to hydrogen peroxide is 0.5 to 2.5:1; the organic ketone is selected from one or more of methyl ethyl ketone and its homologues.

[0023] Compared with the prior art, the beneficial effects of the solid acid catalyst for synthesizing cyclic peroxide and its application in the present invention are as follows: Through the innovative design of the core - shell structure, the present invention breaks through the technical bottleneck of traditional catalysts and realizes the efficient and green synthesis of cyclic peroxide. With an amino - functionalized aluminosilicate molecular sieve as the core, a phosphorylated titanium dioxide intermediate layer and a nitrogen - doped sulfonated carbon shell are constructed to form a gradient acid system, which precisely adapts to the different requirements of epoxidation / ring - closing reactions and improves the product selectivity. The first - created temperature - sensitive polymer grafted with sulfonic acid groups realizes the dynamic regulation of acid density and effectively inhibits side reactions. The synergistic effect of the fluorination treatment of the shell and the hierarchical pore design improves the anti - water poisoning ability, and the tolerance of the water content of the raw material is relaxed to 50 ppm, greatly improving the catalyst life. The interfacial Pt / Ru nanoparticles enhance the acid strength through the electronic effect, and the generation rate of epoxy intermediates is increased by more than 2.3 times, greatly improving the utilization rate of hydrogen peroxide. The core - shell composite structure and wide - temperature - range adaptability significantly reduce energy consumption, and the yield of cyclic peroxide is increased, providing an efficient and stable solution for industrial - scale continuous production. Description of the Drawings

[0024] Figure 1The infrared chromatogram comparison of the oil phase separated during the catalytic synthesis of cyclic peroxide using the solid acid catalyst of the present invention and the oil phase separated during the catalytic synthesis of cyclic peroxide using 60% sulfuric acid and hydrochloric acid.

[0025] Figure 2 The liquid phase diagram of the cyclic peroxide catalytically synthesized using the solid acid catalyst of the present invention.

[0026] Figure 3 The liquid phase diagram of the cyclic peroxide catalytically synthesized using 60% sulfuric acid.

[0027] From Figure 1 it can be seen that the peak positions of the three chromatograms are the same, indicating that the solid acid catalyst of the present invention can catalyze the synthesis of cyclic peroxide.

[0028] Figure 2 In [specific reference], the peak at 5.7607 min is the product 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane with a purity of 98.09%.

[0029] Figure 3 In [specific reference], the peak at 5.76811 min is the product 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane with a purity of 82.10%. Detailed Embodiments

[0030] The present invention relates to a multifunctional catalyst for the synthesis of cyclic peroxide, its preparation method and application, and the core lies in achieving high catalytic performance through the design and combination of a multi-layer composite structure. The following is a detailed description.

[0031] The overall structure of the catalyst of the present invention sequentially includes a core, an intermediate layer, and a shell from the inside to the outside. These functional layers are tightly combined through chemical bonding and physical deposition techniques to form a gradient acid distribution and a synergistic mechanism. The inner layer uses an aluminosilicate molecular sieve material with a SiO2 / Al2O3 molar ratio of 30 - 50 and a pore size range of 0.54 nm - 0.58 nm. This material provides Lewis acid sites through the aluminum-oxygen bonds in the framework, and at the same time, the surface is modified with organic amines to introduce amino functional groups to enhance the adsorption ability of the target reactants. Preferably, the preparation process of the core includes calcining at 550 °C for 4 hours to remove the template agent, and then depositing a titanium compound layer with a thickness of 5 nm on its surface through atomic layer deposition technology (ALD), and activating it with 0.5 mol / L phosphoric acid solution at 80 °C for 6 hours. This treatment step ensures that the inner layer substrate has stable acidity and good mechanical strength.

[0032] The middle layer is mainly composed of titanium-containing compounds. Its Ti-O-P bond structure has a pore diameter of about 1.2 nm and an acid density of about 0.7 mmol / g. The thickness of this layer is controlled to be about 5 nm by atomic layer deposition technology, and the diffusion rate of reaction intermediates is adjusted by activation treatment with phosphoric acid solution. The role of the middle layer is to inhibit the occurrence of side reactions and provide a transitional acidic environment for subsequent reactions. Noble metal nanoparticles with a particle size of 2 nm - 3 nm and a loading of 2 wt% are embedded outside the middle layer. These noble metal particles are prepared by the impregnation reduction method. For example, a 0.1 mol / L ethanol solution of chloroplatinic acid is uniformly impregnated on the surface of the middle layer and reduced at 300 °C for 2 hours in a hydrogen atmosphere. The presence of noble metal particles enhances the electron transfer effect, thereby increasing the acid strength of the sulfonic acid group and reducing its H0 value from -8.2 to -9.1.

[0033] The outer shell is prepared from sulfonated carbon materials doped with nitrogen elements. The preferred N-SO3H density is 1.8 mmol / g, the mesopore size is 3 nm, and the contact angle is greater than 150°. The outer shell is coated by chemical vapor deposition (CVD) method with a thickness of 10 nm - 50 nm. During the coating process, glucose and citric acid are used as carbon sources, the precursor partial pressure is controlled within the range of 0.15 MPa - 0.25 MPa, and the deposition time is about 4 hours. Subsequently, liquid-phase sulfonation treatment is carried out, reacting with fuming sulfuric acid at 120 °C for 12 hours, and then hydrophobic channels are formed through gas-phase fluorination treatment (C4F8 plasma, 30 minutes). The design of the outer shell aims to enhance the anti-water poisoning performance and provide a super-strong acidic environment to promote the closed-loop reaction. In addition, a thermosensitive polymer segment is introduced into the outer shell, grafted with sulfonic acid groups, and a PNIPAM network structure is generated through free radical polymerization reaction. This process preferably uses N-isopropylacrylamide as the monomer and AIBN as the initiator, and the reaction is completed at 70 °C for 6 hours. The introduction of the thermosensitive polymer segment enables the catalyst to have an increased exposure amount of sulfonic acid groups and an acid density of 1.6 mmol / g at low temperatures, while the sulfonic acid groups contract and the acid density drops to 1.2 mmol / g at high temperatures, thus achieving temperature-controlled acidic regulation.

[0034] In order to enable relevant personnel in the technical field to better understand and implement the present invention, the following further describes the present invention in combination with specific embodiments. For the convenience of comparison, only the key technical points are listed in the embodiments, and the process route can be referred to the above introduction. Example 1

[0035] 1. Core modification Material: ZSM-5 zeolite (SiO2 / Al2O3 molar ratio 40, pore diameter 0.54 - 0.58 nm) Steps: Calcination: Calcinate at 550 °C for 4 hours to remove the template agent; Amino functionalization: Solvent system: Toluene / ethanol (volume ratio 2:1); Aminosilane coupling agent: Add 2.8 mL of APTES to 1 g of ZSM-5 zeolite; Reaction conditions: Reflux at 75 °C for 20 hours, wash (toluene → ethanol → deionized water), vacuum dry at 90 °C for 7 hours.

[0036] 2. Loading of metal nanoparticles Method: Impregnation reduction method: Metal salt solution: H2PtCl6 (concentration 0.3 mol / L, solvent is water); Carrier selection: Core (aminated ZSM-5); Impregnation time: 3 hours, dry (100 °C, 5 hours); Reduction method: Thermal reduction: In H2 atmosphere, heat at 300 °C for 2 hours; Loading control: 2.1 wt%, average particle size 3 nm.

[0037] 3. Intermediate layer construction (phosphorylated TiO2) ALD deposition: Precursors: TiCl4 and H2O; Number of deposition cycles: 45 times, control the average thickness at 5 nm; Phosphoric acid activation: Activating solution: 0.5 mol / L H3PO4 solution; Conditions: Immerse at 75 °C for 6 hours, form Ti-O-P bonds, Brønsted acid density 0.6 mmol / g.

[0038] 4. Loading of metal nanoparticles Perform the process operations in step 2 on the intermediate layer (phosphorylated TiO2).

[0039] 5. Outer shell coating (nitrogen-doped sulfonated carbon layer) Steps: CVD deposition of carbon shell: Carbon source: Glucose and citric acid (mass ratio 3:1); Carrier gas: N2 / H2 (volume ratio 8:1), pressure 0.2 MPa; Deposition temperature: 600 °C, heating rate 6 °C / min, time 4 hours; Sulfonation treatment: Liquid-phase sulfonation: Fuming sulfuric acid, treat at 120 °C for 12 hours; Gas-phase strengthening: SO3 vapor, treat at 200 °C for 2 hours; Sulfonic acid group density: 1.7 mmol / g; Fluorination treatment: C4F8 plasma treatment, average depth 6 nm, contact angle ≥150°; Thermosensitive polymer grafting: Monomer: PNIPAM; Initiator: AIBN (1.0 wt%), reaction temperature 70 °C, time 6 hours; Grafting rate of sulfonic acid group: 65%. Example 2

[0040] 1. Core modification Material: ZSM-5 zeolite (SiO2 / Al2O3 molar ratio 40, pore diameter 0.54 - 0.58 nm) Steps: Calcination: Calcined at 550 °C for 4 hours to remove the template agent; Amino functionalization: Solvent system: Toluene / ethanol (volume ratio 2:1); Amino silane coupling agent: 2.8 mL of APTES was added to 1 g of ZSM-5 zeolite; Reaction conditions: Reflux at 75 °C for 20 hours, wash (toluene → ethanol → deionized water), vacuum dry at 90 °C for 7 hours.

[0041] 2. Metal nanoparticle loading Method: Impregnation reduction method: Metal salt solution: H2PtCl6 (concentration 0.3 mol / L, solvent is water); Carrier selection: Core (aminated ZSM-5); Impregnation time: 3 hours, dry (100 °C, 5 hours); Reduction method: Thermal reduction: In H2 atmosphere, heated at 300 °C for 2 hours; Loading control: 2.1 wt%, average particle size 3 nm.

[0042] 3. Intermediate layer construction (phosphorylated TiO2) ALD deposition: Precursors: TiCl4 and H2O; Number of deposition cycles: 45 times, controlling the average thickness of 5 nm; Phosphoric acid activation: Activation solution: 0.5 mol / L H3PO4 solution; Conditions: Impregnated at 75 °C for 6 hours to form Ti-O-P bonds, Brønsted acid density 0.6 mmol / g.

[0043] 4. Shell Coating (Nitrogen-Doped Sulfonated Carbon Layer) Steps: CVD Deposition of Carbon Shell: Carbon Source: Glucose and Citric Acid (mass ratio 3:1); Carrier Gas: N2 / H2 (volume ratio 8:1), pressure 0.2 MPa; Deposition Temperature: 600 °C, heating rate 6 °C / min, time 4 hours; Sulfonation Treatment: Liquid-Phase Sulfonation: Fuming Sulfuric Acid, treatment at 120 °C for 12 hours; Gas-Phase Enhancement: SO3 Vapor, treatment at 200 °C for 2 hours; Density of Sulfonic Acid Groups: 1.7 mmol / g; Fluorination Treatment: C4F8 Plasma Treatment, average depth 6 nm, contact angle ≥150°; Thermosensitive Polymer Grafting: Monomer: PNIPAM; Initiator: AIBN (1.0 wt%), reaction temperature 70 °C, time 6 hours; Grafting Rate of Sulfonic Acid Groups: 65%. Example 3

[0044] 1. Core Modification Material: ZSM-5 Zeolite (SiO2 / Al2O3 molar ratio 40, pore diameter 0.54 - 0.58 nm) Steps: Calcination: Calcination at 550 °C for 4 hours to remove the template agent; Amino Functionalization: Solvent System: Toluene / Ethanol (volume ratio 2:1); Aminosilane Coupling Agent: Add 2.8 mL APTES to 1 g ZSM-5 zeolite; Reaction Conditions: Reflux at 75 °C for 20 hours, wash (toluene → ethanol → deionized water), vacuum dry at 90 °C for 7 hours.

[0045] 2. Intermediate Layer Construction (Phosphorylated TiO2) ALD Deposition: Precursors: TiCl4 and H2O; Number of Deposition Cycles: 45 times, control the average thickness at 5 nm; Phosphoric Acid Activation: Activation Solution: 0.5 mol / L H3PO4 Solution; Conditions: Immersion at 75 °C for 6 hours to form Ti - O - P bonds, Brønsted acid density 0.6 mmol / g.

[0046] 3. Metal nanoparticle loading Method: Impregnation reduction method: Metal salt solution: H2PtCl6 (concentration 0.3 mol / L, solvent is water); Support selection: middle layer (phosphorylated TiO2); Impregnation time: 3 hours, drying (100 °C, 5 hours); Reduction method: Thermal reduction: in H2 atmosphere, heated at 300 °C for 2 hours; Loading control: 2.1 wt%, average particle size 3 nm.

[0047] 4. Shell coating (nitrogen-doped sulfonated carbon layer) Steps: CVD deposition of carbon shell: Carbon source: glucose and citric acid (mass ratio 3:1); Carrier gas: N2 / H2 (volume ratio 8:1), pressure 0.2 MPa; Deposition temperature: 600 °C, heating rate 6 °C / min, time 4 hours; Sulfonation treatment: Liquid-phase sulfonation: fuming sulfuric acid, treated at 120 °C for 12 hours; Gas-phase strengthening: SO3 vapor, treated at 200 °C for 2 hours; Sulfonic acid group density: 1.7 mmol / g; Fluorination treatment: C4F8 plasma treatment, average depth 6 nm, contact angle ≥150°; Thermosensitive polymer grafting: Monomer: PNIPAM; Initiator: AIBN (1.0 wt%), reaction temperature 70 °C, time 6 hours; Grafting rate of sulfonic acid group: 65%. Example 4

[0048] 1. Core modification Material: ZSM-5 zeolite (SiO2 / Al2O3 molar ratio 35, pore size 0.55 nm) Steps: Calcination: calcined at 52 °C for 4.5 hours to remove the template agent; Amino functionalization: Solvent system: toluene / ethanol (volume ratio 2:1); Amino silane coupling agent: 2.8 mL of AEAPMDS is added to 1 g of molecular sieve; Reaction conditions: reflux at 72 °C for 22 hours, wash (toluene → ethanol → deionized water), vacuum dry at 95 °C for 6.5 hours.

[0049] 2. Intermediate layer construction (phosphorylated TiO2) ALD deposition: Precursors: TiCl4 and H2O; Number of deposition cycles: 40 times, controlled thickness 5 nm; Phosphoric acid activation: Activating solution: 0.5 mol / L H3PO4 solution; Conditions: impregnate at 70 °C for 7 hours to form Ti-O-P bonds, Brønsted acid density 0.7 mmol / g.

[0050] 3. Loading of metal nanoparticles Method: Impregnation reduction method: Metal salt solution: PdCl2 (concentration 0.2 mol / L, solvent is water); Carrier selection: core (aminated ZSM-5); Impregnation time: 2.5 hours, dry (90 °C, 5.5 hours); Reduction method: Chemical reduction: 0.2 mol / L NaBH4 solution, at room temperature for 2 hours; Loading amount control: 1 wt%, particle size 2 nm.

[0051] 4. Outer shell coating (nitrogen-doped sulfonated carbon layer) Steps: CVD deposition of carbon shell: Carbon source: glucose and citric acid (mass ratio 3:1); Carrier gas: N2 / H2 (volume ratio 6:1), pressure 0.2 MPa; Deposition temperature: 680 °C, heating rate 7 °C / min, time 4.5 hours; Sulfonation treatment: Liquid-phase sulfonation: fuming sulfuric acid, treat at 115 °C for 11 hours; Gas-phase strengthening: SO3 vapor, treat at 190 °C for 2.5 hours; Sulfonic acid group density: 1.7 mmol / g; Fluorination treatment: C4F8 plasma treatment, depth 5 nm, contact angle ≥150°; Thermosensitive polymer grafting: Monomer: acrylamide-co-acrylic acid; Initiator: AIBN (0.8 wt%), reaction temperature 75 °C, time 5 hours; Sulfonic acid group grafting rate: 60%. Example 5

[0052] 1. Core modification Material: ZSM-5 zeolite (SiO2 / Al2O3 molar ratio 30, pore diameter 0.54 nm) Steps: Calcination: Calcinate at 500 °C for 5 hours to remove the template agent; Amino functionalization: Solvent system: Toluene / ethanol (volume ratio 1:1); Aminosilane coupling agent: Add 2.5 mL of APTS to 1 g of molecular sieve; Reaction conditions: Reflux at 70 °C for 24 hours, wash (toluene → ethanol → deionized water), vacuum dry at 80 °C for 8 hours.

[0053] 2. Intermediate layer construction (phosphorylated TiO2) ALD deposition: Precursors: TiCl4 and H2O; Number of deposition cycles: 30 times, control the thickness at 3 nm; Phosphoric acid activation: Activation solution: 0.3 mol / L H3PO4 solution; Conditions: Immerse at 60 °C for 8 hours to form Ti-O-P bonds, Brønsted acid density 0.5 mmol / g.

[0054] 3. Loading of metal nanoparticles Method: Impregnation reduction method: Metal salt solution: RuCl3·3H2O (concentration 0.5 mol / L, solvent is ethanol); Carrier selection: Intermediate layer (phosphorylated TiO2); Impregnation time: 2 hours, dry (80 °C, 6 hours); Reduction method: Thermal reduction: In H2 atmosphere, heat at 400 °C for 1 hour; Loading amount control: 0.5 wt%, particle size 2 nm.

[0055] 4. Outer shell coating (nitrogen-doped sulfonated carbon layer) Steps: CVD deposition of carbon shell: Carbon source: Glucose and citric acid (mass ratio 2:1); Carrier gas: N2 / H2 (volume ratio 5:1), pressure 0.3 MPa; Deposition temperature: 550 °C, heating rate 3 °C / min, time 5 hours; Sulfonation treatment: Liquid-phase sulfonation: Oleum, treated at 110 °C for 15 hours; Gas-phase strengthening: SO3 vapor, treated at 180 °C for 3 hours; Sulfonic acid group density: 1.6 mmol / g; Fluorination treatment: Treated with C4F8 plasma, depth 3 nm, contact angle ≥ 150°; Thermosensitive polymer grafting: Monomer: Ethylene glycol-co-methyl methacrylate; Initiator: AIBN (0.5 wt%), reaction temperature 60 °C, time 8 hours; Grafting rate of sulfonic acid group: 50%. Example 6

[0056] 1. Core modification Material: ZSM-5 zeolite (SiO2 / Al2O3 molar ratio 50, pore diameter 0.58 nm) Steps: Calcination: Calcined at 600 °C for 3 hours to remove the template agent; Amino functionalization: Solvent system: Anhydrous toluene; Aminosilane coupling agent: 1 g of molecular sieve added with 3 mL of APTES; Reaction conditions: Reflux at 80 °C for 18 hours, washed (toluene → ethanol → deionized water), vacuum dried at 100 °C for 6 hours.

[0057] 2. Loading of metal nanoparticles Method: Impregnation reduction method: Metal salt solution: H2PtCl6 (concentration 0.5 mol / L, solvent is water); Carrier selection: Core (aminated ZSM-5); Impregnation time: 4 hours, dried (120 °C, 4 hours); Reduction method: Thermal reduction: In H2 atmosphere, heated at 400 °C for 1 hour; Loading control: 3 wt%, particle size 5 nm.

[0058] 3. Intermediate layer construction (phosphorylated TiO2) ALD deposition: Precursors: TiCl4 and H2O; Number of deposition cycles: 60 times, controlled thickness 8 nm; Phosphoric acid activation: Activation solution: 0.8 mol / L H3PO4 solution; Condition: Impregnation at 90 °C for 4 hours to form Ti-O-P bonds, Brønsted acid density of 0.8 mmol / g.

[0059] 4. Shell Coating (Nitrogen-Doped Sulfonated Carbon Layer) Steps: CVD Deposition of Carbon Shell: Carbon Source: Glucose and Citric Acid (mass ratio 4:1); Carrier Gas: N2 / H2 (volume ratio 10:1), pressure 0.3 MPa; Deposition Temperature: 650 °C, heating rate 8 °C / min, time 3 hours; Sulfonation Treatment: Liquid-Phase Sulfonation: Fuming Sulfuric Acid, treatment at 130 °C for 10 hours; Gas-Phase Enhancement: SO3 Vapor, treatment at 220 °C for 1 hour; Sulfonic Acid Group Density: 1.8 mmol / g; Fluorination Treatment: C4F8 Plasma Treatment, depth 8 nm, contact angle ≥ 150°; Thermosensitive Polymer Grafting: Monomer: PNIPAM; Initiator: AIBN (1.5 wt%), reaction temperature 80 °C, time 4 hours; Sulfonic Acid Group Grafting Rate: 80%.

[0060] The catalysts obtained in each example were used for the performance test of synthesizing cyclic peroxides. The synthesis process was as follows: After feeding methyl ethyl ketone and hydrogen peroxide in a molar ratio of 1.5:1 into a fixed-bed reactor, the synthesis reaction was carried out under the catalysis of the solid acid catalyst for synthesizing cyclic peroxides of the present invention. The reaction temperature was 20 °C; the reaction time was 1.5 h; the oil phase separated from the reaction system was 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane. The catalyst performance and catalytic effect are shown in Table 1.

[0061] Table 1

[0062] The stability in Table 1 is the percentage of the activity decay amount after the catalyst has been continuously operated for 500 hours.

[0063] In the comparative example, the basic process and material ratio were the same as in Example 1, except that: In Comparative Example 1, there was no intermediate layer (phosphorylated TiO2 layer) Preparation Method: The core amino-functionalized ZSM-5 was directly coated with a nitrogen-doped sulfonated carbon layer, skipping the ALD deposition of TiO2 and the phosphoric acid activation step.

[0064] Test results: Content of by - products (ketone peroxide decomposition products): 25%; The diffusion rate of reaction intermediates decreases, and the reaction time is extended to 4 hours (1.5 hours in Example 1).

[0065] Conclusion: The intermediate layer regulates the diffusion of intermediates and inhibits side reactions.

[0066] No thermosensitive polymer in Comparative Example 2 (static acid density) Preparation method: The sulfonated carbon layer of the outer shell is not grafted with PNIPAM, and the sulfonic acid group density is fixed at 1.6 mmol / g.

[0067] Test results: The over - oxidation rate of the product reaches 30% at high temperature (60 °C); The reaction rate decreases by 20% at low temperature (20 °C).

[0068] Conclusion: The thermosensitive polymer realizes the dynamic regulation of acid density and breaks through the thermodynamic limit.

[0069] No interfacial metal nanoparticles in Comparative Example 3 Preparation method: The core and the intermediate layer, and between the intermediate layer and the outer shell are not loaded with Pt / Ru / Pd nanoparticles.

[0070] Test results: Sulfonic acid group acid strength (H0 value): - 8.2; The generation rate of epoxy intermediates decreases by 40%.

[0071] Conclusion: Metal nanoparticles enhance acidity through electronic effects and improve reaction efficiency.

[0072] The outer shell in Comparative Example 4 is not fluorinated (low hydrophobicity) Preparation method: Omit the C4F8 plasma fluorination step of the carbon shell, and the contact angle is 100° (≥150° in the example).

[0073] Test results: The catalyst activity decreases by 60% in a high - humidity environment (relative humidity 80%); The decomposition rate of hydrogen peroxide increases, and the utilization rate decreases to 70%.

[0074] Conclusion: Fluorination treatment enhances hydrophobicity and inhibits the water poisoning effect.

[0075] Non - noble metal substitution in Comparative Example 5 (Fe nanoparticles) Preparation method: The interfacial metal nanoparticles use Fe instead of Pt, with a loading of 2 wt%.

[0076] Test results: Acid strength (H0 value): -7.5; The reaction activation energy increases, and the temperature needs to be raised to 50 °C to achieve the same conversion rate.

[0077] Conclusion: The electron transfer effect of noble metals is irreplaceable.

[0078] In Comparative Example 6, the ratio of the core SiO2 / Al2O3 exceeds the range (compared molar ratio) Preparation method: Use ZSM-5 with SiO2 / Al2O3 = 20.

[0079] Test results: The Lewis acid sites are overloaded, and the adsorption of intermediates is too strong, resulting in the reaction stagnation; The conversion rate of hydrogen peroxide is only 35%.

[0080] Conclusion: The acid density of the core aluminosilicate needs to be precisely controlled.

[0081] In Comparative Example 7, the core is not aminated (insufficient adsorption capacity) Preparation method: The ZSM-5 zeolite is not grafted with amino groups and is directly coated subsequently.

[0082] Test results: The adsorption amount of ketone reactants is reduced by 50%, and the reaction rate is halved; An additional cocatalyst (such as an acid regulator) is required.

[0083] Conclusion: Amino functionalization enhances the adsorption of reactants and reduces the dependence on additives.

[0084] Evaluation indicators: Hydrogen peroxide conversion rate (iodometric method); Product selectivity (GC-MS analysis); Catalyst life (activity retention rate after 10 cycles of use); Acid strength (H0 value, Hammett indicator method); Environmental adaptability test: Repeat the reaction under the condition of 80% humidity to evaluate the activity decay.

[0085] By comparing the data of the examples and comparative examples, the core-shell structure design, temperature-sensitive acid density regulation, noble metal enhancement effect, and hydrophobic treatment and other features of the present invention have synergistically achieved the efficient synthesis of cyclic peroxides, solving the problems of low activity, many side reactions, and poor environmental adaptability of traditional catalysts.

[0086] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention in any other form. Any person skilled in the relevant art may use the technical content disclosed above to make changes or modifications into equivalent embodiments with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A solid acid catalyst for synthesizing cyclic peroxides, characterized in that, It has a core-shell structure, and the core-shell structure is successively from the inside to the outside: a core, an intermediate layer, and a shell; The core is an aluminosilicate molecular sieve with a SiO2 / Al2O3 molar ratio of 30 to 50, and amino groups are grafted on the surface; The intermediate layer is a phosphorylated titanium dioxide layer; The shell is a nitrogen-doped sulfonated carbon layer with a thickness of 10 nm to 50 nm, a surface sulfonic acid group density of 1.6 mmol / g to 1.8 mmol / g, a contact angle ≥ 150°, a thermosensitive polymer network is grafted on the shell, and sulfonic acid groups are grafted at the ends of the thermosensitive polymer network; There are interfacial metal nanoparticles between the core and the intermediate layer or / and between the intermediate layer and the shell. The interfacial metal nanoparticles include Pt, Pd, or Ru nanoparticles; the particle size of the interfacial metal nanoparticles is 2 nm to 5 nm, and the loading amount is 0.5% to 3% of the mass of the solid acid catalyst.

2. The solid acid catalyst for synthesizing cyclic peroxide according to claim 1, wherein The pore diameter of the aluminosilicate molecular sieve is 0.54 nm to 0.58 nm; the thickness of the phosphorylated titanium dioxide layer is 3 nm to 8 nm, and the Brønsted acid density is 0.5 mmol / g to 0.8 mmol / g.

3. The solid acid catalyst for synthesizing cyclic peroxide according to claim 1, characterized in that, The thermosensitive polymer is at least one of poly(N-isopropylacrylamide), polyacrylamide-co-acrylic acid, or polyethylene glycol-co-methyl methacrylate, and the sulfonic acid group grafting rate is 50% to 80%.

4. The solid acid catalyst for synthesizing cyclic peroxide according to claim 1, characterized in that, There are fluorocarbon groups obtained by fluorination treatment on the surface of the shell, the fluorination depth is 3 nm to 8 nm, and the fluorocarbon groups include at least one of -CF2, -CF3, or -CF2-CF2-; 5. The solid acid catalyst for synthesizing cyclic peroxide according to claim 1, characterized in that, The preparation method includes the following steps: Core modification: The aluminosilicate molecular sieve is calcined and then impregnated with an amino silane coupling agent, and dried to obtain an amino-functionalized zeolite; Intermediate layer construction: A titanium dioxide layer is grown on the surface of the core layer by atomic layer deposition, and phosphoric acid impregnation activation is carried out to form a Ti-O-P bond to obtain a phosphorylated titanium dioxide layer; Shell coating: Using glucose-citric acid as a carbon source, a nitrogen-doped carbon layer is coated by chemical vapor deposition to form a carbon shell; after the carbon shell is sulfonated, radical polymerization is initiated on the surface of the carbon shell to form a thermosensitive polymer network, and the thermosensitive polymer network is selectively sulfonated and modified at the chain ends to obtain the shell; It also includes the loading of metal nanoparticles: The impregnation reduction method is used to deposit Pt, Pd, or Ru nanoparticles on the surface after the core modification step or / and the intermediate layer construction step.

6. The solid acid catalyst for synthesizing cyclic peroxide according to claim 5, characterized in that, The number of deposition cycles of the atomic layer deposition is 30 to 60 times, and the phosphoric acid impregnation activation is carried out with a 0.3 mol / L to 0.8 mol / L H3PO4 solution at 60 °C to 90 °C for 4 h to 8 h.

7. The solid acid catalyst for synthesizing cyclic peroxide according to claim 5, characterized in that, The carrier gas of the chemical vapor deposition method is a mixed gas of nitrogen and hydrogen with a volume ratio of 5 to 10:1, the deposition pressure is 0.1 MPa to 0.3 MPa, the heating rate is 3 °C / min to 8 °C / min, and the deposition temperature is 550 °C to 650 °C; the carbon source is a compound of glucose and citric acid with a mass ratio of 2 to 4:

1.

8. A solid acid catalyst for synthesizing cyclic peroxide according to claim 5, characterized in that, The sulfonation treatment is carried out by stepwise liquid-phase sulfonation and gas-phase sulfonation enhancement: the liquid-phase sulfonation is carried out with fuming sulfuric acid at 110°C to 130°C for 10 h to 15 h; the gas-phase sulfonation enhancement is carried out in SO3 vapor at 180°C to 220°C for 1 h to 3 h.

9. Use of the solid acid catalyst for synthesizing cyclic peroxide according to any one of claims 1 to 8, characterized in that, It includes the following steps: In a reactor, an organic ketone and hydrogen peroxide are subjected to a synthesis reaction under the catalysis of the solid acid catalyst for synthesizing a cyclic peroxide according to any one of claims 1 to 8. The oil phase separated from the reaction system after the reaction is 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane.

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