A solid acid catalyst for synthesizing cyclic peroxides and its application

Abstract

A solid acid catalyst for synthesizing cyclic peroxides and its application belong to the field of catalytic synthesis technology. The solid acid catalyst has a core-shell structure, which is sequentially as follows from the inside to the outside: a) core: ZSM-5 zeolite, with amino groups grafted on the surface and a pore size of 0.54nm~0.58nm; b) middle layer: phosphated titanium dioxide layer, containing Ti-O-P bonds; c) outer shell: nitrogen-doped sulfonated carbon layer, with a surface sulfonic acid group density of 1.6mmol / g~1.8mmol / g, and a thermosensitive polymer network grafted in the outer shell, wherein the end of the thermosensitive polymer network is modified with sulfonic acid groups. The problem of harsh reaction conditions, low product purity, poor catalyst stability and insufficient environmental friendliness in the prior art is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of catalytic synthesis, and in particular relates to a solid acid catalyst for synthesizing cyclic peroxides and application thereof. 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 oxidative activity, widely used in polymer crosslinkers, pharmaceutical intermediates, and energetic materials. Their synthesis requires a two-step olefin epoxidation and ring closure reaction. However, the coexistence of multiple peroxide bonds in the molecule leads to poor thermal stability and frequent side reactions. Traditional homogeneous acid catalysts (such as sulfuric acid and heteropolyacids) are prone to peroxide bond cleavage or molecular rearrangement, resulting in product selectivity of less than 80%. Heterogeneous solid acids (such as Hβ zeolite and sulfonated resins) are difficult to match the large molecular size of the target product (approximately 1.2 nm) due to pore size limitations (<0.8 nm). Furthermore, water poisoning and carbon deposition lead to rapid catalyst deactivation (lifetime <200 h). Existing processes also require strict control of the water content of the feedstock (<5 ppm), further increasing energy consumption and operational complexity.

[0003] Existing technologies often use ZSM-5 / MCM-41 composite molecular sieves to increase acid density, but the single Brønsted acid type of this technology cannot adapt to the differentiated needs of epoxidation and ring closure reactions, and the product purity is less than 90%. Other technologies use carbon carriers to load sulfonic acid groups to improve water resistance, but the fixed acid strength causes side reactions to account for more than 15% at high temperatures. In addition, these catalysts lack a dynamic response mechanism, making it difficult to adjust the distribution of acid sites according to the reaction progress. Their insufficient mechanical strength makes it difficult to cope with humidity fluctuations and mechanical stress in industrial scenarios.

[0004] To address these issues, there is an urgent need to develop a new catalyst that combines gradient acid synergy, dynamic response regulation, and environmental robustness. Existing technologies suffer from three key shortcomings: first, a single acid type cannot meet the diverse needs of multi-step reactions; second, static acid sites lead to byproduct accumulation; and third, mass transfer limitations and structural collapse hinder 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 highly efficient, stable and adaptable solid acid catalyst for synthesizing cyclic peroxides and its application.

[0006] The technical solution adopted by the present invention to solve the technical problem is: a solid acid catalyst for synthesizing cyclic peroxides, having a core-shell structure, wherein the core-shell structure comprises, from the inside to the outside, a core, an intermediate layer and an outer shell;

[0007] The core is an aluminosilicate molecular sieve (preferably ZSM-5 zeolite) with a SiO2 / Al2O3 molar ratio of 30 to 50, with amino groups grafted onto the surface;

[0008] The middle layer is a phosphated titanium dioxide layer;

[0009] 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, and a contact angle of ≥150°. A thermosensitive polymer network is grafted onto the shell, and a sulfonic acid group is grafted onto the end of the thermosensitive polymer network;

[0010] Interfacial metal nanoparticles are provided between the core and the intermediate layer or / and between the intermediate layer and the shell. The interfacial metal nanoparticles comprise Pt, Pd or Ru nanoparticles with a particle size of 2nm to 5nm and a loading amount of 0.5% to 3% of the mass of the solid acid catalyst.

[0011] Preferably, in the solid acid catalyst for synthesizing cyclic peroxides, the pore size of the aluminosilicate molecular sieve is 0.54 nm to 0.58 nm; the phosphated titanium dioxide layer contains Ti-OP 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.

[0012] Preferably, in the 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 sulfonic acid group grafting rate thereof is 50% to 80%.

[0013] Preferably, the surface of the shell of the solid acid catalyst for synthesizing cyclic peroxides has fluorocarbon groups obtained by fluorination treatment, the fluorination depth is 3nm~8nm, and the fluorocarbon groups include at least one of -CF2, -CF3 or -CF2-CF2-.

[0014] The present invention provides a multi-layer composite catalytic system with gradient acidity. Its core is an ordered pore material with a surface modified to enhance its adsorption capacity for target reactants. The system comprises, from the inside out, the following:

[0015] The inner layer substrate utilizes aluminosilicate molecular sieves (SiO2 / Al2O3 molar ratio of 30-50, pore size range of 0.54nm-0.58nm). The aluminum-oxygen bonds in the framework form Lewis acid sites, promoting the initial reaction. The surface is modified with organic amines to introduce amino functional groups, further enhancing the adsorption capacity of intermediates.

[0016] Intermediate layer control unit: A layer of titanium-containing compound (Ti-OP bond, preferably with a pore size of 1.2 nm and an acid density of 0.7 mmol / g) is deposited on the surface of the inner substrate. The thickness is controlled to 5 nm by atomic layer deposition (ALD) technology, and activated with phosphoric acid solution to regulate the diffusion rate of the reaction intermediates and inhibit the occurrence of side reactions.

[0017] The outer active shell is a nitrogen-doped sulfonated carbon material (preferred N-SO₃H₃ density 1.8 mmol / g, mesopore size 3 nm, contact angle >150°) coated via chemical vapor deposition (CVD) to a thickness of 10 nm to 50 nm. The surface is fluorinated to form hydrophobic channels, enhancing resistance to water poisoning while also providing a highly acidic environment (H₀ = -9.1) to promote the ring-closing reaction.

[0018] To achieve temperature-controlled acidity regulation, the present invention introduces a thermosensitive polymer segment into the shell and grafts a sulfonic acid group. Specifically:

[0019] Under low temperature conditions (<40°C), the exposure of sulfonic acid groups is increased, and the acid density reaches 1.6mmol / g, effectively activating hydrogen peroxide;

[0020] Under high temperature conditions (>60°C), the sulfonic acid groups shrink and the acid density drops to 1.2 mmol / g, avoiding excessive oxidation reactions.

[0021] In addition, precious metal nanoparticles (particle size 2-3 nm) are embedded between the inner substrate and the outer active shell to enhance the acid strength of the sulfonic acid group through the electron transfer effect, reducing its H0 (Hamimett acidity) value from -8.2 to -9.1, significantly increasing the generation rate of epoxy intermediates.

[0022] A method for preparing the solid acid catalyst for synthesizing cyclic peroxides comprises the following steps:

[0023] Core modification: calcining aluminosilicate molecular sieve, impregnating it with aminosilane coupling agent, and drying it to obtain amino-functionalized zeolite;

[0024] Intermediate layer construction: A titanium dioxide layer is grown on the surface of the core layer by atomic layer deposition, and phosphoric acid immersion activation forms Ti-OP bonds to obtain a phosphated titanium dioxide layer;

[0025] Shell coating: Glucose-citric acid is used as the carbon source, and a nitrogen-doped carbon layer is coated by chemical vapor deposition to form a carbon shell; the carbon shell is sulfonated, and then free radical polymerization is initiated on the surface of the carbon shell to form a thermosensitive polymer network. The thermosensitive polymer network is selectively sulfonated to modify the chain ends to obtain the shell;

[0026] It also includes metal nanoparticle loading: using an impregnation reduction method to deposit Pt, Pd or Ru nanoparticles on the surface after the core modification step and / or the intermediate layer construction step.

[0027] Preferably, in the above-mentioned method for preparing a solid acid catalyst, the specific operation of impregnating the aminosilane coupling agent is as follows: 2.5 mL to 3 mL of aminosilane coupling agent is added to 1 g of molecular sieve in anhydrous toluene or a toluene / ethanol (volume ratio of 1 to 3:1) solvent mixture, followed by refluxing at 70°C to 80°C for 18 to 24 hours to promote covalent bonding between the silane molecules and the hydroxyl groups on the substrate surface. After the reaction, the substrate is washed sequentially with toluene, ethanol, and deionized water to remove physically adsorbed unreacted silane, and finally, the surface modification layer is cured by vacuum drying at 80°C. The aminosilane coupling agent is at least one of aminopropyltriethoxysilane (APTES), aminoethylaminopropylmethyldimethoxysilane (AEAPMDS), and 3-aminopropyltrimethoxysilane (APTS).

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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:

[0032] 1. Use metal salts as precursors, such as H2PtCl6 (platinum source), PdCl2 (palladium source) or RuCl3 (ruthenium source);

[0033] 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;

[0034] 3. Depending on the catalyst structure, choose the core (amino-functionalized ZSM-5 zeolite) or the middle layer (phosphorylated TiO2) as the support;

[0035] 4. Immerse the carrier in a metal salt solution and allow the metal ions to be evenly adsorbed on the carrier surface by stirring or ultrasonic treatment for 2 to 4 hours. After impregnation, dry at 80°C to 120°C for 4 to 6 hours to remove the solvent.

[0036] 5. Reduction includes chemical reduction and thermal reduction:

[0037] Chemical reduction: Use NaBH4, hydrazine hydrate or ethanol as a reducing agent and react at room temperature for 1-2 hours (applicable to Pd and Ru);

[0038] Thermal reduction: heating at 200℃~400℃ in H2 atmosphere for 1~3 hours (applicable to Pt and Ru, the heating rate needs to be controlled to prevent particle agglomeration);

[0039] 6. After reduction, wash with deionized water or ethanol to remove residual ions and dry in an inert atmosphere.

[0040] An application of the solid acid catalyst for synthesizing cyclic peroxides comprises the following steps:

[0041] 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 cyclic peroxides. After the reaction, an oil phase separated from the system is 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane.

[0042] 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; and the organic ketone is selected from one or more of butanone and its homologues.

[0043] Compared to existing technologies, the present invention's solid acid catalyst for synthesizing cyclic peroxides and its application offer the following advantages: Through its innovative core-shell structure design, the present invention overcomes the bottleneck of conventional catalyst technology, enabling efficient and green synthesis of cyclic peroxides. A gradient acid system is constructed, consisting of an amino-functionalized aluminosilicate molecular sieve core, a phosphated titanium dioxide intermediate layer, and a nitrogen-doped sulfonated carbon shell. This precisely tailors the differentiated requirements of epoxidation and ring-closure reactions, enhancing product selectivity. The innovative grafting of sulfonic acid groups onto a thermosensitive polymer enables dynamic regulation of acid density, effectively suppressing side reactions. The shell fluorination and hierarchical pore design synergistically enhance resistance to water poisoning, extending the raw material moisture tolerance to 50 ppm and significantly extending catalyst life. Interfacial Pt / Ru nanoparticles enhance acid strength through electronic effects, increasing the epoxy intermediate formation rate by over 2.3 times and significantly improving hydrogen peroxide utilization. The core-shell composite structure and wide temperature range adaptability significantly reduce energy consumption and improve cyclic peroxide yield, providing an efficient and stable solution for industrial-scale continuous production. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 The infrared chromatogram is a comparison chart of the oil phase separated when the solid acid catalyst of the present invention is used to catalyze the synthesis of cyclic peroxide and the oil phase separated when the cyclic peroxide is catalyzed by 60% sulfuric acid or hydrochloric acid.

[0045] Figure 2 The liquid phase diagram of the cyclic peroxide synthesized by using the solid acid catalyst of the present invention.

[0046] Figure 3 This is a liquid phase diagram of cyclic peroxide synthesized using 60% sulfuric acid as a catalyst.

[0047] from Figure 1 It can be seen that the peak positions of the three spectra are the same, indicating that the solid acid catalyst of the present invention can catalyze the synthesis of cyclic peroxides.

[0048] Figure 2 The peak at 5.7607 min was the product 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane with a purity of 98.09%.

[0049] Figure 3 The peak at 5.76811 min was the product 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane with a purity of 82.10%. DETAILED DESCRIPTION

[0050] The present invention relates to a multifunctional catalyst for synthesizing cyclic peroxides, its preparation method, and its application. The core of the invention is to achieve high catalytic performance through a multi-layer composite structure design. A detailed description is provided below.

[0051] The overall structure of the catalyst of the present invention comprises, from the inside out, a core, an intermediate layer, and an outer shell. These functional layers are tightly bonded together through chemical bonding and physical deposition techniques, creating a gradient acidity distribution and a synergistic mechanism. The inner layer utilizes an aluminosilicate molecular sieve material with a SiO2 / Al2O3 molar ratio of 30-50 and a pore size range of 0.54-0.58 nm. This material provides Lewis acid sites through aluminum-oxygen bonds within the framework, while the surface is modified with organic amines to introduce amino functional groups to enhance adsorption of target reactants. Preferably, the core is prepared by calcining at 550°C for 4 hours to remove the template. A 5 nm thick titanium compound layer is then deposited on the surface via atomic layer deposition (ALD), followed by activation with a 0.5 mol / L phosphoric acid solution at 80°C for 6 hours. This treatment ensures stable acidity and good mechanical strength in the inner layer substrate.

[0052] The interlayer is primarily composed of a titanium-containing compound with a Ti-OP bond structure, a pore size of approximately 1.2 nm, and an acid density of approximately 0.7 mmol / g. This layer is deposited using atomic layer deposition to a thickness of approximately 5 nm and activated with phosphoric acid solution to regulate the diffusion rate of reaction intermediates. The interlayer suppresses side reactions while providing a transitional acid environment for subsequent reactions. Precious metal nanoparticles with a particle size of 2 to 3 nm and a loading of 2 wt% are embedded outside the interlayer. These precious metal nanoparticles are prepared by an impregnation reduction method, where a 0.1 mol / L chloroplatinic acid ethanol solution is uniformly impregnated onto the interlayer surface and reduced at 300°C in a hydrogen atmosphere for 2 hours. The presence of the precious metal nanoparticles enhances electron transfer, thereby increasing the acid strength of the sulfonic acid groups, reducing their H0 value from -8.2 to -9.1.

[0053] The shell is made of nitrogen-doped sulfonated carbon, with an optimal N-SO₃H₄ density of 1.8 mmol / g, a mesopore size of 3 nm, and a contact angle greater than 150°. The shell is coated by chemical vapor deposition (CVD) with a thickness of 10 to 50 nm. During the coating process, glucose and citric acid are used as carbon sources, with the precursor partial pressure controlled within the range of 0.15 MPa to 0.25 MPa, and the deposition time is approximately 4 hours. This is followed by liquid-phase sulfonation using fuming sulfuric acid at 120°C for 12 hours, followed by vapor-phase fluorination (C₄F₃ plasma for 30 minutes) to form hydrophobic channels. The shell is designed to enhance resistance to water poisoning while providing a superacidic environment to promote ring closure. Furthermore, thermosensitive polymer segments are introduced into the shell and grafted with sulfonic acid groups, generating a PNIPAM network structure via free radical polymerization. This process preferably uses N-isopropylacrylamide as the monomer and AIBN as the initiator, with the reaction taking place at 70°C for 6 hours. The introduction of thermosensitive polymer chain segments increases the exposure of sulfonic acid groups in the catalyst under low temperature conditions, with the acid density reaching 1.6 mmol / g, while under high temperature conditions, the sulfonic acid groups shrink and the acid density drops to 1.2 mmol / g, thus achieving temperature-controllable acidity regulation.

[0054] In order to better enable relevant personnel in this technical field to fully understand and implement the present invention, the present invention is further described below in conjunction with specific embodiments. For the sake of comparison, only key technical points are listed in the embodiments, and the process route refers to the above introduction. Example 1

[0055] 1. Core modification

[0056] Material: ZSM-5 zeolite (SiO2 / Al2O3 molar ratio 40, pore size 0.54~0.58 nm)

[0057] step:

[0058] Calcination: Calcination at 550℃ for 4 hours to remove the template;

[0059] Amino functionalization:

[0060] Solvent system: toluene / ethanol (volume ratio 2:1);

[0061] Aminosilane coupling agent: add 2.8 mL of APTES to 1 g of ZSM-5 zeolite;

[0062] Reaction conditions: reflux at 75°C for 20 hours, washing (toluene → ethanol → deionized water), and vacuum drying at 90°C for 7 hours.

[0063] 2. Metal Nanoparticle Loading

[0064] method:

[0065] Impregnation reduction method:

[0066] Metal salt solution: H2PtCl6 (concentration 0.3 mol / L, solvent is water);

[0067] Support selection: core (aminated ZSM-5);

[0068] Immersion time: 3 hours, drying (100°C, 5 hours);

[0069] Restore method:

[0070] Thermal reduction: H2 atmosphere, heating at 300℃ for 2 hours;

[0071] Loading control: 2.1wt%, average particle size 3nm.

[0072] 3. Intermediate layer construction (phosphorylated TiO2)

[0073] ALD deposition:

[0074] Precursors: TiCl4 and H2O;

[0075] Deposition cycle number: 45 times, controlling the average thickness to 5nm;

[0076] Phosphate activation:

[0077] Activation solution: 0.5 mol / L H3PO4 solution;

[0078] Conditions: immersion at 75°C for 6 hours, formation of Ti-OP bonds, Brønsted acid density 0.6 mmol / g.

[0079] 4. Metal Nanoparticle Loading

[0080] The middle layer (phosphorylated TiO2) was subjected to the process of step 2.

[0081] 5. Shell coating (nitrogen-doped sulfonated carbon layer)

[0082] step:

[0083] CVD deposited carbon shell:

[0084] Carbon source: glucose and citric acid (mass ratio 3:1);

[0085] Carrier gas: N2 / H2 (volume ratio 8:1), pressure 0.2 MPa;

[0086] Deposition temperature: 600°C, heating rate 6°C / min, time 4 hours;

[0087] Sulfonation treatment:

[0088] Liquid phase sulfonation: fuming sulfuric acid, 120℃ for 12 hours;

[0089] Gas phase strengthening: SO3 vapor, 200℃ treatment for 2 hours;

[0090] Sulfonic acid group density: 1.7mmol / g;

[0091] Fluorination treatment: C4F8 plasma treatment, average depth 6 nm, contact angle ≥150°;

[0092] Thermosensitive polymer grafting:

[0093] Monomer: PNIPAM;

[0094] Initiator: AIBN (1.0 wt%), reaction temperature 70°C, time 6 hours;

[0095] Sulfonic acid group grafting rate: 65%. Example 2

[0096] 1. Core modification

[0097] Material: ZSM-5 zeolite (SiO2 / Al2O3 molar ratio 40, pore size 0.54~0.58 nm)

[0098] step:

[0099] Calcination: Calcination at 550℃ for 4 hours to remove the template;

[0100] Amino functionalization:

[0101] Solvent system: toluene / ethanol (volume ratio 2:1);

[0102] Aminosilane coupling agent: add 2.8 mL of APTES to 1 g of ZSM-5 zeolite;

[0103] Reaction conditions: reflux at 75°C for 20 hours, washing (toluene → ethanol → deionized water), and vacuum drying at 90°C for 7 hours.

[0104] 2. Metal Nanoparticle Loading

[0105] method:

[0106] Impregnation reduction method:

[0107] Metal salt solution: H2PtCl6 (concentration 0.3 mol / L, solvent is water);

[0108] Support selection: core (aminated ZSM-5);

[0109] Immersion time: 3 hours, drying (100°C, 5 hours);

[0110] Restore method:

[0111] Thermal reduction: H2 atmosphere, heating at 300℃ for 2 hours;

[0112] Loading control: 2.1wt%, average particle size 3nm.

[0113] 3. Intermediate layer construction (phosphorylated TiO2)

[0114] ALD deposition:

[0115] Precursors: TiCl4 and H2O;

[0116] Deposition cycle number: 45 times, controlling the average thickness to 5nm;

[0117] Phosphate activation:

[0118] Activation solution: 0.5 mol / L H3PO4 solution;

[0119] Conditions: immersion at 75°C for 6 hours, formation of Ti-OP bonds, Brønsted acid density 0.6 mmol / g.

[0120] 4. Shell coating (nitrogen-doped sulfonated carbon layer)

[0121] step:

[0122] CVD deposited carbon shell:

[0123] Carbon source: glucose and citric acid (mass ratio 3:1);

[0124] Carrier gas: N2 / H2 (volume ratio 8:1), pressure 0.2 MPa;

[0125] Deposition temperature: 600°C, heating rate 6°C / min, time 4 hours;

[0126] Sulfonation treatment:

[0127] Liquid phase sulfonation: fuming sulfuric acid, 120℃ for 12 hours;

[0128] Gas phase strengthening: SO3 vapor, 200℃ treatment for 2 hours;

[0129] Sulfonic acid group density: 1.7mmol / g;

[0130] Fluorination treatment: C4F8 plasma treatment, average depth 6 nm, contact angle ≥150°;

[0131] Thermosensitive polymer grafting:

[0132] Monomer: PNIPAM;

[0133] Initiator: AIBN (1.0 wt%), reaction temperature 70°C, time 6 hours;

[0134] Sulfonic acid group grafting rate: 65%. Example 3

[0135] 1. Core modification

[0136] Material: ZSM-5 zeolite (SiO2 / Al2O3 molar ratio 40, pore size 0.54~0.58 nm)

[0137] step:

[0138] Calcination: Calcination at 550℃ for 4 hours to remove the template;

[0139] Amino functionalization:

[0140] Solvent system: toluene / ethanol (volume ratio 2:1);

[0141] Aminosilane coupling agent: add 2.8 mL of APTES to 1 g of ZSM-5 zeolite;

[0142] Reaction conditions: reflux at 75°C for 20 hours, washing (toluene → ethanol → deionized water), and vacuum drying at 90°C for 7 hours.

[0143] 2. Intermediate layer construction (phosphorylated TiO2)

[0144] ALD deposition:

[0145] Precursors: TiCl4 and H2O;

[0146] Deposition cycle number: 45 times, controlling the average thickness to 5nm;

[0147] Phosphate activation:

[0148] Activation solution: 0.5 mol / L H3PO4 solution;

[0149] Conditions: immersion at 75°C for 6 hours, formation of Ti-OP bonds, Brønsted acid density 0.6 mmol / g.

[0150] 3. Metal Nanoparticle Loading

[0151] method:

[0152] Impregnation reduction method:

[0153] Metal salt solution: H2PtCl6 (concentration 0.3 mol / L, solvent is water);

[0154] Support selection: middle layer (phosphorylated TiO2);

[0155] Immersion time: 3 hours, drying (100°C, 5 hours);

[0156] Restore method:

[0157] Thermal reduction: H2 atmosphere, heating at 300℃ for 2 hours;

[0158] Loading control: 2.1wt%, average particle size 3nm.

[0159] 4. Shell coating (nitrogen-doped sulfonated carbon layer)

[0160] step:

[0161] CVD deposited carbon shell:

[0162] Carbon source: glucose and citric acid (mass ratio 3:1);

[0163] Carrier gas: N2 / H2 (volume ratio 8:1), pressure 0.2 MPa;

[0164] Deposition temperature: 600°C, heating rate 6°C / min, time 4 hours;

[0165] Sulfonation treatment:

[0166] Liquid phase sulfonation: fuming sulfuric acid, 120℃ for 12 hours;

[0167] Gas phase strengthening: SO3 vapor, 200℃ treatment for 2 hours;

[0168] Sulfonic acid group density: 1.7mmol / g;

[0169] Fluorination treatment: C4F8 plasma treatment, average depth 6 nm, contact angle ≥150°;

[0170] Thermosensitive polymer grafting:

[0171] Monomer: PNIPAM;

[0172] Initiator: AIBN (1.0 wt%), reaction temperature 70°C, time 6 hours;

[0173] Sulfonic acid group grafting rate: 65%. Example 4

[0174] 1. Core modification

[0175] Material: ZSM-5 zeolite (SiO2 / Al2O3 molar ratio 35, pore size 0.55nm)

[0176] step:

[0177] Calcination: Calcination at 52°C for 4.5 hours to remove the template;

[0178] Amino functionalization:

[0179] Solvent system: toluene / ethanol (volume ratio 2:1);

[0180] Aminosilane coupling agent: add 2.8 mL AEAPMDS to 1 g molecular sieve;

[0181] Reaction conditions: reflux at 72°C for 22 hours, washing (toluene → ethanol → deionized water), and vacuum drying at 95°C for 6.5 hours.

[0182] 2. Intermediate layer construction (phosphorylated TiO2)

[0183] ALD deposition:

[0184] Precursors: TiCl4 and H2O;

[0185] Deposition cycle number: 40 times, controlled thickness 5nm;

[0186] Phosphate activation:

[0187] Activation solution: 0.5 mol / L H3PO4 solution;

[0188] Conditions: immersion at 70°C for 7 hours, formation of Ti-OP bonds, Brønsted acid density 0.7 mmol / g.

[0189] 3. Metal Nanoparticle Loading

[0190] method:

[0191] Impregnation reduction method:

[0192] Metal salt solution: PdCl2 (concentration 0.2 mol / L, solvent: water);

[0193] Support selection: core (aminated ZSM-5);

[0194] Immersion time: 2.5 hours, drying (90°C, 5.5 hours);

[0195] Restore method:

[0196] Chemical reduction: 0.2 mol / L NaBH4 solution, room temperature for 2 hours;

[0197] Loading control: 1wt%, particle size 2nm.

[0198] 4. Shell coating (nitrogen-doped sulfonated carbon layer)

[0199] step:

[0200] CVD deposited carbon shell:

[0201] Carbon source: glucose and citric acid (mass ratio 3:1);

[0202] Carrier gas: N2 / H2 (volume ratio 6:1), pressure 0.2 MPa;

[0203] Deposition temperature: 680°C, heating rate 7°C / min, time 4.5 hours;

[0204] Sulfonation treatment:

[0205] Liquid phase sulfonation: fuming sulfuric acid, 115℃ for 11 hours;

[0206] Gas phase strengthening: SO3 vapor, 190℃ for 2.5 hours;

[0207] Sulfonic acid group density: 1.7mmol / g;

[0208] Fluorination treatment: C4F8 plasma treatment, depth 5 nm, contact angle ≥150°;

[0209] Thermosensitive polymer grafting:

[0210] Monomer: acrylamide-co-acrylic acid;

[0211] Initiator: AIBN (0.8 wt%), reaction temperature 75 °C, time 5 hours;

[0212] Sulfonic acid group grafting rate: 60%. Example 5

[0213] 1. Core modification

[0214] Material: ZSM-5 zeolite (SiO2 / Al2O3 molar ratio 30, pore size 0.54nm)

[0215] step:

[0216] Calcination: Calcination at 500 ° C for 5 hours to remove the template;

[0217] Amino functionalization:

[0218] Solvent system: toluene / ethanol (volume ratio 1:1);

[0219] Aminosilane coupling agent: add 2.5mL APTS to 1g molecular sieve;

[0220] Reaction conditions: reflux at 70°C for 24 hours, washing (toluene → ethanol → deionized water), and vacuum drying at 80°C for 8 hours.

[0221] 2. Intermediate layer construction (phosphorylated TiO2)

[0222] ALD deposition:

[0223] Precursors: TiCl4 and H2O;

[0224] Deposition cycle number: 30 times, controlled thickness 3nm;

[0225] Phosphate activation:

[0226] Activation solution: 0.3 mol / L H3PO4 solution;

[0227] Conditions: immersion at 60°C for 8 hours, formation of Ti-OP bonds, Brønsted acid density 0.5 mmol / g.

[0228] 3. Metal Nanoparticle Loading

[0229] method:

[0230] Impregnation reduction method:

[0231] Metal salt solution: RuCl3·3H2O (concentration 0.5 mol / L, solvent: ethanol);

[0232] Support selection: middle layer (phosphorylated TiO2);

[0233] Immersion time: 2 hours, drying (80°C, 6 hours);

[0234] Restore method:

[0235] Thermal reduction: H2 atmosphere, heating at 400℃ for 1 hour;

[0236] Loading amount control: 0.5wt%, particle size 2nm.

[0237] 4. Shell coating (nitrogen-doped sulfonated carbon layer)

[0238] step:

[0239] CVD deposited carbon shell:

[0240] Carbon source: glucose and citric acid (mass ratio 2:1);

[0241] Carrier gas: N2 / H2 (volume ratio 5:1), pressure 0.3 MPa;

[0242] Deposition temperature: 550°C, heating rate 3°C / min, time 5 hours;

[0243] Sulfonation treatment:

[0244] Liquid phase sulfonation: fuming sulfuric acid, 110℃ for 15 hours;

[0245] Gas phase strengthening: SO3 vapor, 180℃ for 3 hours;

[0246] Sulfonic acid group density: 1.6mmol / g;

[0247] Fluorination treatment: C4F8 plasma treatment, depth 3nm, contact angle ≥150°;

[0248] Thermosensitive polymer grafting:

[0249] Monomer: ethylene glycol-co-methyl methacrylate;

[0250] Initiator: AIBN (0.5 wt%), reaction temperature 60°C, time 8 hours;

[0251] Sulfonic acid group grafting rate: 50%. Example 6

[0252] 1. Core modification

[0253] Material: ZSM-5 zeolite (SiO2 / Al2O3 molar ratio 50, pore size 0.58 nm)

[0254] step:

[0255] Calcination: Calcination at 600℃ for 3 hours to remove the template;

[0256] Amino functionalization:

[0257] Solvent system: anhydrous toluene;

[0258] Aminosilane coupling agent: add 3 mL APTES to 1 g molecular sieve;

[0259] Reaction conditions: reflux at 80°C for 18 hours, washing (toluene → ethanol → deionized water), and vacuum drying at 100°C for 6 hours.

[0260] 2. Metal Nanoparticle Loading

[0261] method:

[0262] Impregnation reduction method:

[0263] Metal salt solution: H2PtCl6 (concentration 0.5 mol / L, solvent is water);

[0264] Support selection: core (aminated ZSM-5);

[0265] Immersion time: 4 hours, drying (120°C, 4 hours);

[0266] Restore method:

[0267] Thermal reduction: H2 atmosphere, heating at 400℃ for 1 hour;

[0268] Loading amount control: 3wt%, particle size 5nm.

[0269] 3. Intermediate layer construction (phosphorylated TiO2)

[0270] ALD deposition:

[0271] Precursors: TiCl4 and H2O;

[0272] Deposition cycle number: 60 times, controlled thickness 8nm;

[0273] Phosphate activation:

[0274] Activation solution: 0.8 mol / L H3PO4 solution;

[0275] Conditions: immersion at 90°C for 4 hours, formation of Ti-OP bonds, Brønsted acid density 0.8 mmol / g.

[0276] 4. Shell coating (nitrogen-doped sulfonated carbon layer)

[0277] step:

[0278] CVD deposited carbon shell:

[0279] Carbon source: glucose and citric acid (mass ratio 4:1);

[0280] Carrier gas: N2 / H2 (volume ratio 10:1), pressure 0.3 MPa;

[0281] Deposition temperature: 650°C, heating rate 8°C / min, time 3 hours;

[0282] Sulfonation treatment:

[0283] Liquid phase sulfonation: fuming sulfuric acid, 130℃ for 10 hours;

[0284] Gas phase strengthening: SO3 vapor, 220℃ for 1 hour;

[0285] Sulfonic acid group density: 1.8mmol / g;

[0286] Fluorination treatment: C4F8 plasma treatment, depth 8 nm, contact angle ≥150°;

[0287] Thermosensitive polymer grafting:

[0288] Monomer: PNIPAM;

[0289] Initiator: AIBN (1.5 wt%), reaction temperature 80 °C, time 4 hours;

[0290] Sulfonic acid group grafting rate: 80%.

[0291] The catalysts obtained in each example were used to synthesize cyclic peroxides for performance testing. The synthesis process was as follows: butanone and hydrogen peroxide were added in a molar ratio of 1.5:1 in a fixed-bed reactor, and 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 and the reaction time was 1.5 hours. After the reaction, the oil phase separated from the 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.

[0292] Table 1

[0293]

[0294] The stability in Table 1 is the percentage of activity decay after the catalyst has been running continuously for 500 hours.

[0295] The basic process and material ratio in the comparative example are the same as those in Example 1, except that:

[0296] Comparative Example 1 does not have an intermediate layer (phosphorylated TiO2 layer)

[0297] Preparation method:

[0298] The core amino-modified ZSM-5 is directly coated with a nitrogen-doped sulfonated carbon layer, skipping the ALD deposition of TiO2 and phosphoric acid activation steps.

[0299] Test results:

[0300] By-product (ketone peroxide decomposition product) content: 25%;

[0301] The diffusion rate of the reaction intermediates was reduced, and the reaction time was extended to 4 hours (1.5 hours in Example 1).

[0302] Conclusion: The intermediate layer regulates the diffusion of intermediates and inhibits side reactions.

[0303] Comparative Example 2 without thermosensitive polymer (static acid density)

[0304] Preparation method:

[0305] The outer sulfonated carbon layer was not grafted with PNIPAM, and the sulfonic acid group density was fixed at 1.6 mmol / g.

[0306] Test results:

[0307] At high temperature (60°C), the product overoxidation rate reaches 30%;

[0308] At low temperature (20°C), the reaction rate decreases by 20%.

[0309] Conclusion: Thermosensitive polymers achieve dynamic regulation of acid density and break through thermodynamic limitations.

[0310] Comparative Example 3: No interface metal nanoparticles

[0311] Preparation method:

[0312] No Pt / Ru / Pd nanoparticles are loaded between the core and the middle layer, or between the middle layer and the shell.

[0313] Test results:

[0314] Sulfonic acid strength (H0 value): -8.2;

[0315] The rate of epoxidation intermediate formation was reduced by 40%.

[0316] Conclusion: Metal nanoparticles enhance acidity and improve reaction efficiency through electronic effects.

[0317] Comparative Example 4: Non-fluorinated shell (low hydrophobicity)

[0318] Preparation method:

[0319] The C4F8 plasma fluorination step of the carbon shell was omitted, and the contact angle was 100° (Examples ≥ 150°).

[0320] Test results:

[0321] In a high humidity environment (relative humidity 80%), the catalyst activity decreases by 60%;

[0322] The decomposition rate of hydrogen peroxide is increased and the utilization rate is reduced to 70%.

[0323] Conclusion: Fluorination treatment enhances hydrophobicity and inhibits water poisoning effect.

[0324] Non-precious metal substitution (Fe nanoparticles) in Comparative Example 5

[0325] Preparation method:

[0326] The interfacial metal nanoparticles used Fe instead of Pt with a loading of 2 wt%.

[0327] Test results:

[0328] Acid strength (H0 value): -7.5;

[0329] The activation energy of the reaction increases, and the temperature needs to be raised to 50°C to achieve the same conversion rate.

[0330] Conclusion: The electron transfer effect of precious metals is irreplaceable.

[0331] The core SiO2 / Al2O3 ratio in Comparative Example 6 is out of range (compared to the molar ratio)

[0332] Preparation method:

[0333] Use ZSM-5 with SiO2 / Al2O3=20.

[0334] Test results:

[0335] The Lewis acid sites are overloaded, and the intermediate adsorption is too strong, resulting in reaction stagnation;

[0336] The hydrogen peroxide conversion rate is only 35%.

[0337] Conclusion: The acid density of core aluminosilicates needs to be precisely controlled.

[0338] Comparative Example 7: Unaminated Core (Insufficient Adsorption Capacity)

[0339] Preparation method:

[0340] The ZSM-5 zeolite was not grafted with amino groups and was directly subjected to subsequent coating.

[0341] Test results:

[0342] The adsorption of ketone reactants is reduced by 50%, and the reaction rate is halved;

[0343] Additional catalysts (such as acid regulators) are required.

[0344] Conclusion: Amino functionalization enhances the adsorption of reactants and reduces the dependence on additives.

[0345] Evaluation indicators:

[0346] Hydrogen peroxide conversion rate (iodine titration);

[0347] Product selectivity (GC-MS analysis);

[0348] Catalyst life (activity retention after 10 cycles);

[0349] Acid strength (H0 value, Hammett indicator method);

[0350] Environmental adaptability test: Repeat the reaction under 80% humidity to evaluate activity decay.

[0351] By comparing the data of the embodiments and comparative examples, the core-shell structure design, temperature-sensitive acid density adjustment, noble metal enhancement effect and hydrophobic treatment of the present invention synergistically achieve the efficient synthesis of cyclic peroxides, solving the problems of low activity, multiple side reactions and poor environmental adaptability of traditional catalysts.

[0352] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other manner. Any person skilled in the art may utilize the above-disclosed technical content to modify or modify the present invention into equivalent embodiments. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present invention and are based on the technical essence of the present invention remain within the scope of protection of the present invention.

Claims

1. A solid acid catalyst for synthesizing cyclic peroxides, characterized in that It has a core-shell structure, which consists of a core, an intermediate layer and an outer shell from the inside to the outside. 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 middle layer is a phosphated 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, and a contact angle of ≥150°. A thermosensitive polymer network is grafted onto the shell, and a sulfonic acid group is grafted onto the end of the thermosensitive polymer network; Interfacial metal nanoparticles are provided between the core and the intermediate layer or / and between the intermediate layer and the shell, wherein the interfacial metal nanoparticles comprise 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; The surface of the shell has fluorocarbon groups obtained by fluorination treatment, the fluorination depth is 3nm~8nm, and the fluorocarbon groups include at least one of -CF2, -CF3 or -CF2-CF2-.

2. A solid acid catalyst for synthesizing cyclic peroxide according to claim 1, characterized in that, The pore size of the aluminosilicate molecular sieve is 0.54 nm to 0.58 nm; the thickness of the phosphated 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. A 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 grafting rate of the sulfonic acid group is 50% to 80%.

4. A solid acid catalyst for synthesizing cyclic peroxide according to claim 1, characterized in that, The preparation method comprises the following steps: Core modification: Aluminosilicate molecular sieve is calcined and then impregnated with aminosilane coupling agent and dried to obtain 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 immersion activation forms Ti-OP bonds to obtain a phosphated titanium dioxide layer; Shell coating: Using glucose-citric acid as the carbon source, a nitrogen-doped carbon layer is coated by chemical vapor deposition to form a carbon shell; the carbon shell is sulfonated and then fluorinated to form hydrophobic channels. Free radical polymerization is then initiated on the surface of the carbon shell to form a thermosensitive polymer network. The thermosensitive polymer network is selectively sulfonated to modify the chain ends to obtain the shell; It also includes metal nanoparticle loading: using an impregnation reduction method to deposit Pt, Pd or Ru nanoparticles on the surface after the core modification step and / or the intermediate layer construction step.

5. A solid acid catalyst for synthesizing cyclic peroxide according to claim 4, characterized in that, The atomic layer deposition cycle number 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.

6. A solid acid catalyst for synthesizing cyclic peroxide according to claim 4, characterized in that, 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 mixture of glucose and citric acid in a mass ratio of 2 to 4:

1.

7. A solid acid catalyst for synthesizing cyclic peroxide according to claim 4, characterized in that, The sulfonation treatment is carried out in steps of liquid phase sulfonation and gas phase sulfonation strengthening: the liquid phase sulfonation is carried out using fuming sulfuric acid at 110°C to 130°C for 10h to 15h; the gas phase sulfonation strengthening is carried out in SO3 vapor at 180°C to 220°C for 1h to 3h.

8. Use of a solid acid catalyst for synthesizing cyclic peroxides according to any one of claims 1 to 7, characterized in that: The following steps are involved: 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 cyclic peroxides according to any one of claims 1 to 7; and the oil phase separated from the system after the reaction is 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane.

Images