Preparation method of modified ts-1 catalyst and application thereof

Abstract

The application provides a preparation method of a modified TS-1 catalyst and application thereof. The preparation method of the modified TS-1 catalyst adopts a condensed ring aromatic hydrocarbon compound containing at least two hydroxyl substituents as a passivation agent, prepares a passivation solution, and performs impregnation treatment on TS-1 molecular sieve to obtain passivated TS-1 molecular sieve. Strong interaction between the hydroxyl functional groups in the passivation agent and the silicon hydroxyl functional groups on the surface of TS-1 is utilized to realize stable adsorption and loading of the passivation agent on the surface of TS-1. The passivated TS-1 molecular sieve is subjected to sintering treatment to obtain the modified TS-1 catalyst. The sintering treatment carbonizes the passivation agent adsorbed on the surface of TS-1, constructs a carbonaceous covering layer with selective passivation function on the surface of TS-1, realizes precise covering and passivation of the acidic silicon hydroxyl on the surface of TS-1, and inhibits the activity of the TS-1 in decomposing hydrogen peroxide and ring-opening of epichlorohydrin, thereby improving the conversion rate of hydrogen peroxide and further improving the selectivity of the target product.

Description

Technical Field

[0001] This application relates to the fields of catalytic materials and green chemical technology, and in particular to a method for preparing a modified TS-1 catalyst and its application. Background Technology

[0002] Epichlorohydrin is an important organic chemical raw material and fine chemical intermediate, widely used in the production of epoxy resins, synthetic glycerol, chlorohydrin rubber, and various surfactants. Traditional epichlorohydrin production processes, such as the chlorohydrin process and the glycerol process, suffer from severe equipment corrosion, significant environmental pollution, and poor atom economy. The direct epoxidation process using hydrogen peroxide as an oxidant, due to its mild reaction conditions, water as the only byproduct, and environmental friendliness, has become a research hotspot in the field of green chemistry.

[0003] In the epoxidation of allyl alcohol using hydrogen peroxide as an oxidant, the titanium-silicon molecular sieve TS-1 is one of the most widely studied and applied catalytic systems. Based on its unique titanium-oxygen active centers and molecular sieve pore structure, this catalyst can act on the reaction process of allyl alcohol and hydrogen peroxide. The application of the TS-1 catalytic system provides a technical route for the synthesis of epichlorohydrin that differs from the traditional chlorohydrin method. However, in the actual application of existing TS-1 catalysts in the preparation of epichlorohydrin from hydrogen peroxide, the selectivity of the target product has not yet reached the ideal expectations. Side reactions accompanying the reaction system, such as the ring-opening hydrolysis of the propylene oxide ring, the ineffective decomposition of hydrogen peroxide, and the formation of deep oxidation products, are often difficult to effectively suppress, resulting in low selectivity for epichlorohydrin. This increases the difficulty and energy consumption of subsequent separation and purification, thus affecting the overall economic efficiency of the process. Furthermore, the performance of the TS-1 catalyst may degrade due to micropore blockage or loss of titanium active centers during long-term operation, further exacerbating the problem of decreased selectivity.

[0004] Therefore, there is an urgent need to develop a new catalyst or optimize and modify the existing TS-1 catalytic system to improve its selectivity for the target product in the preparation of epichlorohydrin by hydrogen peroxide oxidation, and to promote the industrialization of this green synthesis route. Summary of the Invention

[0005] This application provides a method for preparing a modified TS-1 catalyst, which achieves the technical effect of improving the selectivity of epichlorohydrin.

[0006] This application also provides a modified TS-1 catalyst, which is prepared by the above preparation method and helps to improve the selectivity of epichlorohydrin.

[0007] This application also provides a method for preparing epichlorohydrin, achieving the technical effect of high selectivity of epichlorohydrin.

[0008] The first aspect of this application provides a method for preparing a modified TS-1 catalyst, comprising the following steps:

[0009] 1) TS-1 molecular sieve is impregnated with a passivation solution to obtain passivated TS-1 molecular sieve;

[0010] 2) The passivated TS-1 molecular sieve is sintered to obtain the modified TS-1 catalyst;

[0011] The passivation solution includes a passivating agent and a solvent, wherein the passivating agent includes a fused-ring aromatic compound containing at least two hydroxyl substituents.

[0012] In the preparation method described above, the passivating agent further includes graphene, and the mass ratio of the graphene to the fused-ring aromatic compound containing at least two hydroxyl substituents is 0.01~0.5:1.

[0013] The preparation method described above, wherein the fused-ring aromatic compound containing at least two hydroxyl substituents includes at least one selected from 1,2,4-trihydroxyanthraquinone, 1,8-dihydroxyanthraquinone, 3,4-phenanthroline, and alizarin (1,2-dihydroxyanthraquinone); and / or,

[0014] The silicon-to-titanium molar ratio of the TS-1 molecular sieve is 20-100.

[0015] In the preparation method described above, the concentration of the fused-ring aromatic compound containing at least two hydroxyl substituents in the passivation solution is 0.01~1 mol / L, and the mass-to-volume ratio of the TS-1 molecular sieve to the passivation solution is 1 g: 5~100 mL; and / or,

[0016] The immersion treatment is performed at a temperature of 20~80℃ for 1~24h.

[0017] The preparation method described above, wherein the impregnation treatment is a plasma impregnation treatment.

[0018] In the preparation method described above, the sintering temperature is 300~700℃ and the time is 1~12h.

[0019] In the preparation method described above, the heating rate of the sintering treatment is 1~5℃ / min.

[0020] The second aspect of this application provides a modified TS-1 catalyst, which is prepared by the method of the first aspect.

[0021] The modified TS-1 catalyst as described above, wherein the mass fraction of titanium is 0.5%~4.0%, the mass fraction of silicon is 33%~55%, the mass fraction of oxygen is 40%~63%, and the mass fraction of carbon is 1.0%~4.0%.

[0022] The third aspect of this application provides a method for preparing epichlorohydrin, which uses 3-chloropropene and hydrogen peroxide as raw materials to carry out a catalytic reaction to obtain the epichlorohydrin; the catalytic reaction includes the modified TS-1 catalyst of the second aspect.

[0023] The method for preparing the modified TS-1 catalyst of this application involves using a polycyclic aromatic hydrocarbon compound containing at least two hydroxyl substituents as a passivating agent, preparing a passivation solution to impregnate a TS-1 molecular sieve, and obtaining a passivated TS-1 molecular sieve. The strong interaction between the hydroxyl functional groups in the passivating agent and the silanol functional groups on the TS-1 surface is utilized to achieve stable adsorption and loading of the passivating agent on the TS-1 surface. The passivated TS-1 molecular sieve is then sintered to obtain the modified TS-1 catalyst. The sintering process carbonizes the passivating agent adsorbed on the TS-1 surface, constructing a carbonaceous capping layer with selective passivation function on the TS-1 surface. This achieves precise coverage and passivation of the acidic silanol groups on the TS-1 surface, inhibiting their catalytic activity in hydrogen peroxide decomposition and epichlorohydrin ring-opening, thereby improving the conversion rate of hydrogen peroxide and further enhancing the selectivity of the target product. Attached Figure Description

[0024] Figure 1 The structural formula is 1,2,4-trihydroxyanthraquinone;

[0025] Figure 2 The structural formula is 1,8-dihydroxyanthraquinone;

[0026] Figure 3 The structural formula of 3,4-phenanthrenediol;

[0027] Figure 4 The structural formula of alizarin (1,2-dihydroxyanthraquinone);

[0028] Figure 5 The bar chart shows the conversion of hydrogen peroxide and the selectivity of epichlorohydrin in the preparation of epichlorohydrin using the modified TS-1 catalysts of Examples 1, 2, 3, and 4 of this application and the TS-1 catalyst of Comparative Example 1.

[0029] Figure 6 The bar chart shows the conversion of hydrogen peroxide and the selectivity of epichlorohydrin in the preparation of epichlorohydrin using the modified TS-1 catalyst Cat-1 in Example 1 of this application after 4 cycles. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0031] Epichlorohydrin is an important intermediate in the chemical industry, widely used in the synthesis of epoxy resins, chlorohydrin rubbers, glycerol derivatives, and surfactants. Traditional production processes, such as the chlorohydrin and glycerol processes, suffer from severe equipment corrosion, large wastewater discharges, and poor atom economy, making it difficult to meet the requirements of modern green chemistry for environmental friendliness and efficient resource utilization.

[0032] Direct epoxidation using hydrogen peroxide as an oxidant has become a research hotspot in the field of green chemistry due to its mild reaction conditions and the fact that water is the only byproduct. This process uses 3-chloropropene and hydrogen peroxide as raw materials, and generates epichlorohydrin through an epoxidation reaction in the presence of a titanium-silicon molecular sieve (TS-1) catalyst. However, the presence of acidic silanol groups (Si-OH) on the surface of TS-1 not only causes hydrogen peroxide to decompose into water and oxygen, reducing its conversion rate, but may also trigger a ring-opening side reaction of epichlorohydrin, leading to a decrease in the selectivity of the target product.

[0033] The inventors conducted research on this and believe that by introducing a polycyclic aromatic hydrocarbon compound containing at least two hydroxyl substituents, and utilizing the strong interaction between the hydroxyl functional group and the silanol functional group, a carbonaceous capping layer with selective passivation function can be constructed on the surface of TS-1. This can precisely cover the acidic silanol groups on the surface of TS-1, inhibiting their catalytic activity in hydrogen peroxide decomposition and epichlorohydrin ring opening, thereby improving the conversion rate of hydrogen peroxide and further enhancing the selectivity of the target product.

[0034] Based on this, the first aspect of this application provides a method for preparing a modified TS-1 catalyst, comprising the following steps:

[0035] 1) TS-1 molecular sieve is impregnated with a passivation solution to obtain passivated TS-1 molecular sieve;

[0036] 2) The passivated TS-1 molecular sieve was sintered to obtain the modified TS-1 catalyst;

[0037] The passivation solution includes a passivating agent and a solvent, wherein the passivating agent includes a fused-ring aromatic compound containing at least two hydroxyl substituents.

[0038] Titanium-silicon molecular sieve (TS-1) is a heteroatom molecular sieve formed by doping titanium atoms into the all-silicon MFI topological molecular sieve framework. The four-coordinate titanium species in its framework are effective active centers for olefin epoxidation reactions. Fused ring aromatic compounds containing at least two hydroxyl substituents include a fused ring aromatic framework and at least two hydroxyl functional groups. The fused ring aromatic framework is selected from one or more of anthracene, phenanthrene, pyrene, and naphthalene.

[0039] This application employs a polycyclic aromatic hydrocarbon compound containing at least two hydroxyl substituents as a passivating agent. A passivation solution is prepared and impregnated with TS-1 molecular sieve to obtain a passivated TS-1 molecular sieve. The strong interaction between the hydroxyl functional groups in the passivating agent and the silanol functional groups on the TS-1 surface is utilized to achieve stable adsorption and loading of the passivating agent on the TS-1 surface. By sintering the passivated TS-1 molecular sieve, a modified TS-1 catalyst is obtained. The sintering process carbonizes the passivating agent adsorbed on the TS-1 surface, constructing a carbonaceous capping layer with selective passivation function on the TS-1 surface. This achieves precise coverage and passivation of the acidic silanol groups on the TS-1 surface, inhibiting their catalytic activity in hydrogen peroxide decomposition and epichlorohydrin ring opening, thereby improving the conversion rate of hydrogen peroxide and further enhancing the selectivity of the target product.

[0040] In one specific embodiment, after the impregnation treatment in step 1), the solid-liquid mixture is further subjected to solid-liquid separation, and the solid is washed and dried to obtain passivated TS-1 molecular sieve. The washing is performed 1 to 3 times, and the washing solution includes at least one of methanol, ethanol, isopropanol, acetone, N,N-dimethylformamide, and tetrahydrofuran; the drying temperature is 80 to 120°C, and the drying time is 2 to 12 hours.

[0041] This application does not limit the solvent. In one specific embodiment, the solvent includes at least one selected from alcohols, ketones, and ethers. Further, the solvent includes at least one selected from methanol, ethanol, isopropanol, acetone, N,N-dimethylformamide, and tetrahydrofuran.

[0042] In one specific embodiment, the passivating agent further includes graphene, wherein the mass ratio of graphene to a fused-ring aromatic compound containing at least two hydroxyl substituents is 0.01 to 0.5:1. The graphene includes at least one of graphene oxide and reduced graphene oxide.

[0043] Graphene possesses a high specific surface area and strong adsorption capacity, enabling it to adsorb and disperse polycyclic aromatic hydrocarbons (PAHs), preventing their aggregation and ensuring uniform dispersion of the passivating agent on the TS-1 surface. This lays the foundation for subsequent precise passivation of acidic silanol groups. Simultaneously, graphene exhibits excellent thermal conductivity and mechanical strength, serving as an auxiliary component of the carbonaceous precursor during sintering. It co-carbonizes with PAHs to form a denser and more stable carbonaceous coating, enhancing the wear resistance and longevity of the passivation layer. This effectively inhibits the ineffective decomposition of hydrogen peroxide and the ring-opening of epichlorohydrin, improving the selectivity of epichlorohydrin.

[0044] Limiting the mass ratio of graphene to polycyclic aromatic hydrocarbons (PAHs) containing at least two hydroxyl substituents ensures that graphene can fully function, effectively adsorbing and dispersing PAHs and preventing their aggregation on the TS-1 surface. This ensures uniform distribution of the passivating agent, providing a structural basis for subsequent precise coverage and passivation of acidic silanol groups. Furthermore, it allows graphene and PAHs to synergistically carbonize during sintering, forming a dense and stable carbonaceous covering layer. This layer continuously suppresses the ineffective decomposition of hydrogen peroxide and the ring-opening side reaction of epichlorohydrin induced by acidic silanol groups, further improving the selectivity of epichlorohydrin while maintaining high hydrogen peroxide conversion.

[0045] This application does not limit the scope of fused-ring aromatic compounds containing at least two hydroxyl substituents. In one specific embodiment, the fused-ring aromatic compound containing at least two hydroxyl substituents includes at least one of 1,2,4-trihydroxyanthraquinone, 1,8-dihydroxyanthraquinone, 3,4-phenanthroline, and alizarin (1,2-dihydroxyanthraquinone).

[0046] All of the above compounds contain two or more hydroxyl groups, which can form strong hydrogen bonds with the acidic silanol groups on the TS-1 surface. This enables stable adsorption and uniform loading of the passivating agent on the TS-1 surface, providing a structural basis for the subsequent sintering to form a carbonaceous capping layer and precisely passivate the acidic silanol groups. This effectively suppresses the ineffective decomposition of hydrogen peroxide and the ring-opening side reaction of epichlorohydrin, improving the selectivity of epichlorohydrin. Simultaneously, all of these compounds use fused-ring aromatic hydrocarbons such as anthracene, phenanthrene, pyrene, and naphthalene as their framework. During sintering, they can stably carbonize to form a dense carbon layer, ensuring selective passivation of silanol groups while minimizing clogging of molecular sieve channels and obscuring the active centers of the titanium framework. This balances passivation effectiveness with epoxidation catalytic activity, further improving the selectivity of epichlorohydrin.

[0047] It should be added that the silicon-to-titanium molar ratio of TS-1 molecular sieve is 20~100. By controlling the silicon-to-titanium molar ratio of TS-1 molecular sieve within the above range, it is possible to ensure that an appropriate amount of tetracoordinated titanium active centers are introduced into the molecular sieve framework, providing sufficient and effective catalytic sites for the epoxidation reaction of 3-chloropropene and hydrogen peroxide. At the same time, the number of silanol groups on the surface of the molecular sieve is kept within an appropriate range, thus balancing the overall structural stability of the catalyst, the passivation effect, and the conversion rate and selectivity of the epoxidation reaction.

[0048] Furthermore, the silicon-to-titanium molar ratio of the TS-1 molecular sieve is 30~60. Further limiting the silicon-to-titanium molar ratio of the TS-1 molecular sieve can provide more sufficient and effective catalytic sites for the epoxidation reaction of 3-chloropropene and hydrogen peroxide, and make the number of silanol groups on the molecular sieve surface within a more precise and suitable range, thereby further improving the selectivity of epichlorohydrin.

[0049] In one specific embodiment, the concentration of the fused-ring aromatic compound containing at least two hydroxyl substituents in the passivation solution is 0.01~1 mol / L. Limiting the concentration of the fused-ring aromatic compound containing at least two hydroxyl substituents in the passivation solution ensures that the fused-ring aromatic compound is fully dissolved in the solvent, allowing it to contact and form a stable interaction with the acidic silanol groups on the TS-1 surface during impregnation. This effectively suppresses the decomposition of hydrogen peroxide and the ring-opening side reaction of epichlorohydrin, improving the selectivity of epichlorohydrin.

[0050] Furthermore, the concentration of fused-ring aromatic compounds containing at least two hydroxyl substituents in the passivation solution is 0.01~0.5 mol / L. Further limiting the concentration of fused-ring aromatic compounds containing at least two hydroxyl substituents in the passivation solution ensures that the fused-ring aromatic compounds are fully dissolved and uniformly dispersed in the solvent, allowing for sufficient contact with the acidic silanol groups on the TS-1 surface and the formation of more stable interactions, thereby further improving the selectivity of epichlorohydrin.

[0051] Furthermore, the mass-to-volume ratio of TS-1 molecular sieve to passivation solution is 1g:5~100mL. Limiting this ratio ensures, on the one hand, that TS-1 is fully wetted and uniformly dispersed in the passivation solution, allowing the acidic silanol groups on the TS-1 surface to fully contact and interact with the passivating agent, thus guaranteeing the inhibition of hydrogen peroxide decomposition and epichlorohydrin ring-opening side reactions. On the other hand, it avoids excessive adsorption of the passivating agent due to an excessively large passivation solution volume, ensuring a moderate, uniform, and dense carbonaceous coating layer, further improving the conversion rate of hydrogen peroxide and the selectivity of epichlorohydrin.

[0052] It should be added that the impregnation treatment temperature is 20~80℃ and the time is 1~24h. By controlling the temperature and time of the impregnation treatment within the above range, suitable kinetic conditions can be provided for the hydrogen bonding interaction between the polycyclic aromatic hydrocarbon compound and the silanol groups on the TS-1 surface, ensuring more sufficient and uniform coverage of the acidic silanol groups. This better suppresses the decomposition of hydrogen peroxide and the ring-opening side reaction of epichlorohydrin, improving the selectivity of epichlorohydrin. At the same time, the passivating agent structure is not damaged, and the MFI topology of TS-1 and the four-coordinate titanium active center are not damaged, thus balancing the conversion rate of hydrogen peroxide and the selectivity of epichlorohydrin.

[0053] In one specific embodiment, the impregnation treatment is a plasma impregnation treatment. The plasma impregnation treatment enhances the interaction between the passivating agent and the TS-1 surface through high-energy bombardment, strengthening the diffusion of polycyclic aromatic hydrocarbon compounds containing at least two hydroxyl substituents into the molecular sieve channels and their precise binding with silanol groups. This significantly improves the uniformity and density of the passivating agent adsorption load, achieving more efficient selective passivation of acidic silanol groups, thereby effectively suppressing hydrogen peroxide decomposition and epichlorohydrin ring-opening side reactions, and improving the selectivity of epichlorohydrin.

[0054] It should be added that the power of plasma impregnation treatment is 50~500W, the time is 10~60min, and the atmosphere is argon, nitrogen or air; the plasma includes at least one of dielectric barrier discharge plasma, radio frequency plasma and microwave plasma.

[0055] In addition, the sintering temperature is 300~700℃, the time is 1~12h, and the atmosphere is nitrogen, argon, or helium. Limiting the sintering temperature and time ensures, on the one hand, that the passivating agent adsorbed on the TS-1 surface is fully carbonized, forming a continuous and dense carbonaceous coating layer. This achieves precise coating and passivation of the acidic silanol groups, effectively suppressing their activity in catalyzing the decomposition of hydrogen peroxide and the ring-opening side reaction of epichlorohydrin, thereby improving the utilization rate of hydrogen peroxide and the selectivity of the target product. On the other hand, it avoids damage to the molecular sieve framework, pore collapse, and destruction of the four-coordinate titanium active centers, ensuring the passivation effect while maximizing the preservation of the epoxidation activity and structural stability of the TS-1 catalyst.

[0056] Furthermore, the sintering temperature is 350–500℃, the time is 2–4 hours, and the atmosphere is nitrogen, argon, or helium. Further limiting the sintering temperature and time allows for the complete carbonization of the passivating agent adsorbed on the TS-1 surface, forming a more continuous and dense carbonaceous coating layer, further improving the utilization rate of hydrogen peroxide and the selectivity of the target product. Simultaneously, it effectively avoids damage to the molecular sieve framework, pore collapse, and destruction of the four-coordinate titanium active centers, further ensuring the epoxidation activity and structural stability of the catalyst.

[0057] It should be added that the heating rate of the sintering process is 1~5℃ / min. By controlling the heating rate of the sintering process within the above range, the passivating agent adsorbed on the TS-1 surface can undergo slow and uniform pyrolysis and carbonization reactions, forming a carbonaceous coating layer with uniform thickness, dense structure and strong adhesion. This achieves stable and precise passivation of acidic silanol groups, continuously suppresses hydrogen peroxide decomposition and epichlorohydrin ring-opening side reactions, and improves the selectivity of epichlorohydrin. At the same time, it can reduce the impact of thermal stress on the molecular sieve, avoid local collapse and pore blockage of the molecular sieve, and balance the stability of the catalyst and the selectivity of the epoxidation reaction.

[0058] The second aspect of this application provides a modified TS-1 catalyst, which is prepared by the method of the first aspect.

[0059] In one specific embodiment, the modified TS-1 catalyst contains 0.5% to 4.0% titanium by mass, 33% to 55% silicon by mass, 40% to 63% oxygen by mass, and 1.0% to 4.0% carbon by mass.

[0060] Limiting the mass fraction of titanium ensures that the TS-1 catalyst contains sufficient four-coordinated titanium active centers, providing ample and effective catalytic sites for the epoxidation reaction of 3-chloropropene and hydrogen peroxide, thereby improving the conversion rate of hydrogen peroxide and further enhancing the selectivity of epichlorohydrin. Limiting the mass fraction of silicon ensures that the TS-1 catalyst possesses a complete MFI topology, providing a stable porous system and good hydrothermal stability, balancing catalyst stability with the selectivity of the epoxidation reaction.

[0061] Limiting the mass fraction of oxygen ensures the integrity of the oxygen structure in the TS-1 catalyst, stabilizes the coordination environment of the four-coordinate titanium active centers, guarantees epoxidation catalytic activity, and further improves the selectivity of epichlorohydrin. Simultaneously, it maintains the overall charge balance and structural stability of the TS-1 catalyst, improving its long-term stability. Limiting the mass fraction of carbon ensures a moderate, uniform, and dense carbonaceous capping layer, effectively suppressing hydrogen peroxide decomposition and epichlorohydrin ring-opening side reactions, significantly improving the selectivity of the target product. It also avoids pore blockage and excessive coating of the titanium active centers, thus achieving efficient and selective passivation while ensuring the mass transfer efficiency between reactants and products and the epoxidation catalytic activity.

[0062] The third aspect of this application provides a method for preparing epichlorohydrin, which uses 3-chloropropene and hydrogen peroxide as raw materials to carry out a catalytic reaction to obtain epichlorohydrin; the catalytic reaction includes the modified TS-1 catalyst of the second aspect.

[0063] This application utilizes 3-chloropropene and hydrogen peroxide as raw materials and a modified TS-1 catalyst as the catalyst to catalyze the reaction to obtain epichlorohydrin. The modified TS-1 catalyst employs tetracoordinated titanium as the active center to catalyze the epoxidation reaction of 3-chloropropene and hydrogen peroxide. Simultaneously, the carbonaceous capping layer on the surface of the modified TS-1 catalyst selectively passivates acidic silanol groups, effectively inhibiting hydrogen peroxide decomposition and the ring-opening side reaction of epichlorohydrin, significantly improving the selectivity of epichlorohydrin. Furthermore, the modified TS-1 catalyst exhibits structural stability and a long service life, making this preparation method more in line with the requirements of green chemical engineering for high efficiency and environmental protection.

[0064] It should be added that the catalytic reaction also includes a solvent, which includes at least one of methanol, ethanol, tert-butanol, and water; further, the solvent includes methanol or methanol-water; the catalytic reaction temperature is 20~60℃, the pressure is 0.1~0.5MPa, and the time is 0.5~6h; further, the catalytic reaction temperature is 30~50℃, the pressure is 0.1~0.3MPa, and the time is 1~3h; the hydrogen peroxide is a 10~50% (w / w) aqueous solution of hydrogen peroxide; the modified TS-1 catalyst is used in 3-chloropropene, The mass fraction of hydrogen peroxide, modified TS-1 catalyst, and solvent in the total mass is 0.2-10%. Further, the mass fraction of modified TS-1 catalyst in the total mass of 3-chloropropene, hydrogen peroxide, modified TS-1 catalyst, and solvent is 0.2-5%. The molar ratio of solvent to hydrogen peroxide is 1:1-12:1, the molar ratio of 3-chloropropene to hydrogen peroxide is 1:1-4:1, further, the molar ratio of solvent to hydrogen peroxide is 1:1-10:1, and the molar ratio of 3-chloropropene to hydrogen peroxide is 1:1-3:1.

[0065] The present application will be further described below through specific embodiments.

[0066] Example 1

[0067] This embodiment provides a method for preparing a modified TS-1 catalyst, including the following steps:

[0068] 1) Weigh 5.0g of TS-1 molecular sieve (Xi'an Ruilijie Experimental Instrument Co., Ltd.). The silicon-titanium molar ratio of TS-1 molecular sieve is 40. Place it in a 150mL beaker for later use.

[0069] 2) Weigh 1.281 g (5.0 mmol) of 1,2,4-trihydroxyanthraquinone (analytical grade, Xi'an Ruilijie Experimental Instrument Co., Ltd., structural formula as shown). Figure 1 The sample (shown) and 0.064 g of graphene oxide (powder, Xi'an Ruilijie Experimental Instrument Co., Ltd.) were dispersed together in 50 mL of N,N-dimethylformamide (analytical grade, Xi'an Ruilijie Experimental Instrument Co., Ltd.), and the passivation solution was obtained after ultrasonic treatment for 1 h.

[0070] The concentration of 1,2,4-trihydroxyanthraquinone in the passivation solution was 0.1 mol / L.

[0071] 3) Add the TS-1 molecular sieve from step 1) to the passivation solution from step 2), place it in a dielectric barrier discharge plasma reactor, and treat it at 200W power for 30 minutes under an argon atmosphere (high purity gas ≥99.999%, Shaanxi Xinyuanda Gas Co., Ltd.). Then, keep magnetic stirring for impregnation treatment. The impregnation treatment temperature is 25℃ and the time is 6 hours to obtain a solid-liquid mixture.

[0072] The mass-to-volume ratio of TS-1 molecular sieve to passivation solution is 1g:10mL;

[0073] 4) The solid-liquid mixture was subjected to solid-liquid separation. The solid was washed twice with 20 mL of acetone and then transferred to a petri dish. It was then dried in a 100℃ forced-air drying oven for 6 h to obtain passivated TS-1 molecular sieve.

[0074] 5) The passivated TS-1 molecular sieve was placed in a quartz boat in a tube furnace and heated from room temperature to 400℃ at a rate of 2℃ / min under the protection of argon gas (high purity gas ≥99.999%, Shaanxi Xinyuanda Gas Co., Ltd.) at a flow rate of 100mL / min. It was then sintered at 400℃ for 3h and then naturally cooled to room temperature in an argon flow to obtain the modified TS-1 catalyst Cat-1.

[0075] In the modified TS-1 catalyst Cat-1, the mass fraction of titanium is 2.1%, the mass fraction of silicon is 44.7%, the mass fraction of oxygen is 50.2%, and the mass fraction of carbon is 3.0%.

[0076] Example 2

[0077] The preparation method in this embodiment is basically the same as that in Example 1, except that in step 2), 5.0 mmol of 1,2,4-trihydroxyanthraquinone is replaced with 5.0 mmol of 1,8-dihydroxyanthraquinone (structural formula as shown). Figure 2 As shown in the figure, the modified TS-1 catalyst Cat-2 was obtained.

[0078] Example 3

[0079] The preparation method in this embodiment is basically the same as that in Example 1, except that in step 2), 5.0 mmol of 1,2,4-trihydroxyanthraquinone is replaced with 5.0 mmol of 3,4-phenanthrenediol (structural formula as shown). Figure 3 As shown in the figure, the modified TS-1 catalyst Cat-3 was obtained.

[0080] Example 4

[0081] The preparation method in this embodiment is basically the same as that in Example 1, except that in step 2), 5.0 mmol of 1,2,4-trihydroxyanthraquinone is replaced with 5.0 mmol of alizarin (1,2-dihydroxyanthraquinone) (structural formula as shown in the figure). Figure 4 As shown in the figure, the modified TS-1 catalyst Cat-4 was obtained.

[0082] Example 5

[0083] The preparation method of this embodiment is basically the same as that of Example 1, except that the concentration of 1,2,4-trihydroxyanthraquinone in the passivation solution in step 2) is 0.2 mol / L, and the modified TS-1 catalyst Cat-5 is obtained.

[0084] Example 6

[0085] The preparation method of this embodiment is basically the same as that of Example 1, except that the sintering temperature in step 5) is 700℃, and the modified TS-1 catalyst Cat-6 is obtained.

[0086] Example 7

[0087] The preparation method of this embodiment is basically the same as that of Example 1, except that the impregnation treatment time in step 3) is 24h, and the modified TS-1 catalyst Cat-7 is obtained.

[0088] Example 8

[0089] The preparation method of this embodiment is basically the same as that of Example 1, except that in step 2), N,N-dimethylformamide is replaced with acetone to obtain the modified TS-1 catalyst Cat-8.

[0090] Example 9

[0091] The preparation method of this embodiment is basically the same as that of Example 1. The difference is that after obtaining the modified TS-1 catalyst Cat-1, 1.0 g of modified TS-1 catalyst Cat-1, 1.3 mol of 3-chloropropene, 1 mol of hydrogen peroxide and 240 mL of methanol are placed in a high-pressure reactor for epoxidation reaction to obtain a reaction solution. The reaction solution is centrifuged to separate the catalyst, washed with methanol 3 times and dried at 100°C for 2 h to obtain the modified TS-1 catalyst Cat-9.

[0092] Example 10

[0093] The preparation method of this embodiment is basically the same as that of Example 9. The difference is that after obtaining the modified TS-1 catalyst Cat-9, 1.0 g of modified TS-1 catalyst Cat-9, 1.3 mol of 3-chloropropene, 1 mol of hydrogen peroxide and 240 mL of methanol are placed in a high-pressure reactor for epoxidation reaction to obtain a reaction solution. The reaction solution is centrifuged to separate the catalyst, washed with methanol 3 times and dried at 100°C for 2 h to obtain the modified TS-1 catalyst Cat-10.

[0094] Example 11

[0095] The preparation method of this embodiment is basically the same as that of Example 10. The difference is that after obtaining the modified TS-1 catalyst Cat-10, 1.0 g of modified TS-1 catalyst Cat-10, 1.3 mol of 3-chloropropene, 1 mol of hydrogen peroxide and 240 mL of methanol are placed in a high-pressure reactor for epoxidation reaction to obtain a reaction solution. The reaction solution is centrifuged to separate the catalyst, washed with methanol 3 times and dried at 100°C for 2 h to obtain the modified TS-1 catalyst Cat-11.

[0096] Example 12

[0097] The preparation method of this embodiment is basically the same as that of Example 1, except that graphene oxide is not used in step 2) and dielectric barrier discharge plasma treatment is not used in step 3) to obtain the modified TS-1 catalyst Cat-12.

[0098] Example 13

[0099] The preparation method of this embodiment is basically the same as that of Example 1, except that there is no dielectric barrier discharge plasma treatment in step 3) to obtain the modified TS-1 catalyst Cat-13.

[0100] Example 14

[0101] The preparation method of this embodiment is basically the same as that of Example 1, except that graphene oxide is not used in step 2), and the modified TS-1 catalyst Cat-14 is obtained.

[0102] Example 15

[0103] The preparation method of this embodiment is basically the same as that of Example 1, except that the concentration of 1,2,4-trihydroxyanthraquinone in the passivation solution in step 2) is 2 mol / L, so as to obtain the modified TS-1 catalyst Cat-15.

[0104] Example 16

[0105] The preparation method of this embodiment is basically the same as that of Example 1, except that the sintering temperature in step 5) is 200℃, and the modified TS-1 catalyst Cat-16 is obtained.

[0106] Example 17

[0107] The preparation method of this embodiment is basically the same as that of Example 1, except that the impregnation time in step 3) is 10 min, and the modified TS-1 catalyst Cat-17 is obtained.

[0108] Comparative Example 1

[0109] This comparative example does not modify the TS-1 molecular sieve to obtain the TS-1 catalyst Cat-Ref.

[0110] Comparative Example 2

[0111] The preparation method of this comparative example is basically the same as that of Example 1, except that in step 2), 5.0 mmol of 1,2,4-trihydroxyanthraquinone is replaced with 5.0 mmol of the monohydroxy compound 1-naphthol to obtain the modified TS-1 catalyst Cat-Comp2.

[0112] Comparative Example 3

[0113] The preparation method of this comparative example is basically the same as that of Example 1, except that in step 2), 5.0 mmol of 1,2,4-trihydroxyanthraquinone is replaced with 5.0 mmol of ethylene glycol to obtain the modified TS-1 catalyst Cat-Comp3.

[0114] Comparative Example 4

[0115] Take 5.0 g of TS-1 molecular sieve and add it to 50 mL of toluene. Stir well. Under nitrogen protection, add 2.0 mL of hexamethyldisilazane (HMDS) dropwise. Heat to 110 °C and reflux for 6 h. After the reaction is complete, cool, filter, wash with toluene, and then dry at 120 °C for 4 h to obtain silanized modified TS-1 catalyst Cat-Comp4.

[0116] Experimental Example 1

[0117] Epichlorohydrin was prepared by using the modified TS-1 catalyst from all examples and comparative examples as the catalyst, and 3-chloropropene and hydrogen peroxide as the raw materials for the catalytic reaction, according to the following method.

[0118] The reaction was carried out in a 1000 mL autoclave reactor equipped with a magnetic stirrer, thermometer, pressure gauge, and condenser. 1.0 g of modified TS-1 catalyst, 240 mL of methanol, 1.3 mol (approximately 99.45 g) of 3-chloropropene, and 1 mol of hydrogen peroxide (equivalent to approximately 113.3 g of a 30% hydrogen peroxide aqueous solution) were added. The reactor was placed in a constant temperature jacket, the stirring was started, and the temperature was raised to 30 °C. The stirring speed was 500 rpm, and the pressure in the reactor was maintained at 0.1 MPa. The reaction was continued at 30 °C for 2 h. After the reaction was completed, the reactor was quickly placed in an ice-water bath to cool and terminate the reaction. A nitrogen atmosphere was used for protection throughout the process.

[0119] The conversion rate of hydrogen peroxide and the selectivity of epichlorohydrin were tested, and the results are shown in Table 1. Figure 5 , Figure 6 After the reaction is complete, take a small amount of the clear reaction solution and calculate the conversion rate of hydrogen peroxide by potassium permanganate titration or iodometric titration. Calculate the selectivity of epichlorohydrin by internal standard method (internal standard is bromobenzene or n-decane).

[0120] 1) Conversion rate of hydrogen peroxide

[0121] The conversion rate of hydrogen peroxide was calculated by the amount of residual hydrogen peroxide after the reaction (using potassium permanganate titration or iodometric titration).

[0122] The conversion rate of hydrogen peroxide = (number of moles of hydrogen peroxide consumed in the reaction / initial number of moles of hydrogen peroxide) × 100%.

[0123] 2) Selectivity of epichlorohydrin

[0124] Selectivity of epichlorohydrin = (moles of epichlorohydrin produced / moles of hydrogen peroxide consumed in the reaction) × 100%.

[0125] Table 1

[0126]

[0127] The results of Examples 1-4 show that when modified TS-1 catalysts were prepared using 1,2,4-trihydroxyanthraquinone, 1,8-dihydroxyanthraquinone, 3,4-phenanthroline, alizarin, and graphene oxide as passivating agents, the conversion rate of hydrogen peroxide exceeded 96%, and the selectivity of epichlorohydrin reached over 96%. Compared with the results of the catalytic oxidation reaction using TS-1 molecular sieve in Comparative Example 1 (hydrogen peroxide conversion rate 81.1%, epichlorohydrin selectivity 93.3%), both the conversion rate of hydrogen peroxide and the selectivity of epichlorohydrin were significantly improved.

[0128] The results of Examples 1 and 5 show that when the concentrations of 1,2,4-trihydroxyanthraquinone in the passivation solution are 0.1 mol / L and 0.2 mol / L, respectively, the conversion rate of hydrogen peroxide exceeds 96%, and the selectivity of epichlorohydrin reaches over 96%. However, in Example 15, the concentration of 1,2,4-trihydroxyanthraquinone in the passivation solution is 2 mol / L, resulting in a hydrogen peroxide conversion rate of 81.6% and an epichlorohydrin selectivity of 96.3%, indicating a significant decrease in both. This suggests that excessively high concentrations of 1,2,4-trihydroxyanthraquinone may affect mass transfer or cover some effective active sites, leading to a severe decrease in conversion rate, although selectivity remains high.

[0129] The results of Examples 1 and 6 show that when the sintering temperatures are 400℃ and 700℃, respectively, the conversion rates of hydrogen peroxide are 97.2% and 96.1%, both exceeding 96%, and the selectivity of epichlorohydrin is 96.5% and 97.1%, both exceeding 96%. However, in Example 16, where the sintering temperature is 200℃, the conversion rates of hydrogen peroxide and epichlorohydrin selectivity are 80.9% and 92.9%, respectively. This indicates that excessively low sintering temperatures may lead to incomplete pyrolysis and conversion of the carbon precursor, resulting in poor stability and shielding effect of the formed capping layer, and unsatisfactory conversion rates and selectivity.

[0130] The results of Examples 1 and 7 show that when the impregnation treatment time is 6 h and 24 h, respectively, the conversion rate of hydrogen peroxide is 97.2% and 97.1%, and the selectivity of epichlorohydrin is 96.5% and 96.2%, respectively. However, in Example 17, the impregnation treatment time is 10 min, and the conversion rate of hydrogen peroxide and the selectivity of epichlorohydrin are 81.3% and 93.5%, respectively. This indicates that impregnation for 10 min may result in insufficient adsorption equilibrium, inadequate and uneven passivation, and poor performance.

[0131] The results of Examples 1 and 8 show that common polar solvents such as N,N-dimethylformamide and acetone can effectively dissolve 1,2,4-trihydroxyanthraquinone and be used for impregnation, and the performance of the resulting modified TS-1 catalyst is similar.

[0132] The results of Examples 9, 10, and 11 show that after four reuses, the activity and selectivity of the modified TS-1 catalyst Cat-1 decreased slightly, but remained at a high level, demonstrating good stability. Deactivation may originate from the adsorption of trace amounts of organic matter on the catalyst surface or a very small amount of carbon deposition during the reaction. Appropriate high-temperature regeneration treatment (such as low-temperature calcination in air or oxygen dilution gas) is expected to restore most of the activity.

[0133] The above examples and comparative examples fully demonstrate that this application successfully prepared a high-performance epichlorohydrin synthesis catalyst by using a polycyclic aromatic hydrocarbon compound containing at least two hydroxyl substituents to composite with graphene and modifying TS-1 molecular sieves through impregnation-sintering under plasma assistance. This catalyst can precisely and effectively passivate harmful silanol sites on the TS-1 surface, strongly suppressing ineffective hydrogen peroxide decomposition and epichlorohydrin ring-opening side reactions without significantly affecting mass transfer and the activity of the framework titanium. Under optimized process conditions, it achieves excellent performance with a hydrogen peroxide conversion rate of 97.2% and an epichlorohydrin selectivity of 96.5%, significantly superior to unmodified TS-1 and catalysts modified with monohydroxyl or non-aromatic polyhydroxyl compounds, and comparable to or even better than those modified with expensive silanizing reagents. The method of this application is simple, mild, cost-controllable, and environmentally friendly, and has good prospects for industrial application.

[0134] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing a modified TS-1 catalyst, characterized in that, Includes the following steps: 1) TS-1 molecular sieve is impregnated with a passivation solution to obtain passivated TS-1 molecular sieve; 2) The passivated TS-1 molecular sieve is sintered to obtain the modified TS-1 catalyst; The passivation solution includes a passivating agent and a solvent, wherein the passivating agent includes a fused-ring aromatic compound containing at least two hydroxyl substituents.

2. The preparation method according to claim 1, characterized in that, The passivating agent further includes graphene, and the mass ratio of the graphene to the polycyclic aromatic hydrocarbon compound containing at least two hydroxyl substituents is 0.01~0.5:

1.

3. The preparation method according to claim 1 or 2, characterized in that, The fused-ring aromatic compound containing at least two hydroxyl substituents includes at least one selected from 1,2,4-trihydroxyanthraquinone, 1,8-dihydroxyanthraquinone, 3,4-phenanthroline, and alizarin (1,2-dihydroxyanthraquinone); and / or, The silicon-to-titanium molar ratio of the TS-1 molecular sieve is 20-100.

4. The preparation method according to any one of claims 1-3, characterized in that, The concentration of polycyclic aromatic hydrocarbons containing at least two hydroxyl substituents in the passivation solution is 0.01~1 mol / L, and the mass-to-volume ratio of the TS-1 molecular sieve to the passivation solution is 1 g: 5~100 mL; and / or, The immersion treatment is performed at a temperature of 20~80℃ for 1~24h.

5. The preparation method according to any one of claims 1-4, characterized in that, The impregnation treatment is a plasma impregnation treatment.

6. The preparation method according to any one of claims 1-5, characterized in that, The sintering process is carried out at a temperature of 300~700℃ for 1~12 hours.

7. The preparation method according to claim 6, characterized in that, The heating rate of the sintering process is 1~5℃ / min.

8. A modified TS-1 catalyst, characterized in that, It is prepared by the preparation method according to any one of claims 1-7.

9. The modified TS-1 catalyst according to claim 8, characterized in that, In the modified TS-1 catalyst, the mass fraction of titanium is 0.5%~4.0%, the mass fraction of silicon is 33%~55%, the mass fraction of oxygen is 40%~63%, and the mass fraction of carbon is 1.0%~4.0%.

10. A method for preparing epichlorohydrin, characterized in that, The epichlorohydrin is obtained by catalytic reaction using 3-chloropropene and hydrogen peroxide as raw materials; the catalytic reaction includes the modified TS-1 catalyst as described in claim 8 or 9.

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