A method for preparing a porous catalyst, a porous catalyst and applications thereof

Abstract

The application provides a preparation method of a porous catalyst, the porous catalyst and application thereof, and relates to the technical field of preparation of lithium ion battery electrolyte. The preparation method of the porous catalyst comprises the following steps: mixing a zirconium source, a surfactant and a first solvent to obtain a zirconium source solution; mixing urea and a second solvent to obtain a urea solution; mixing the urea solution and the zirconium source solution and stirring to obtain a mixed solution; and performing a solvothermal reaction and calcination on the mixed solution to obtain the porous catalyst. The application provides a preparation method of a porous catalyst, which solves the technical problems of low catalytic activity, insufficient selectivity, poor recycling rate, poor stability, complex preparation process and high cost of the zirconium oxide catalyst prepared by the existing method in the direct synthesis of dimethyl carbonate from CO2 and methanol.

Description

Technical Field

[0001] This invention relates to the technical field of lithium-ion battery electrolytes, and in particular to a method for preparing a porous catalyst, the porous catalyst itself, and its applications. Background Technology

[0002] As the global energy structure shifts towards green and low-carbon practices, the performance improvement and cost control of lithium-ion batteries, as the core energy storage carrier, have become the focus of industry competition. The electrolyte, as the "blood" of the battery, directly determines the battery's energy density, safety, low-temperature performance, and cycle life through its core solvent quality and cost.

[0003] Dimethyl carbonate (DMC) possesses excellent physicochemical properties. Its low viscosity (only 0.59 mPa·s at 25°C) effectively reduces the overall viscosity of the electrolyte system, significantly improving lithium-ion migration rate. As a chain carbonate, DMC, when combined with cyclic carbonates (such as ethylene carbonate EC), can create an ideal solvent environment with high dielectric constant and low viscosity, thereby achieving higher bulk ionic conductivity, reducing battery internal resistance, and improving rate performance. Its low melting point suppresses the tendency of electrolytes to crystallize at low temperatures, making it a key technology for addressing the pain points of reduced range and starting difficulties in electric vehicles during winter. It has become an indispensable key component of modern high-performance electrolytes.

[0004] Currently, mainstream industrial DMC production processes (such as transesterification and methanol oxidative carbonylation) generally suffer from problems such as reliance on fossil resources for raw materials, complex processes, high energy consumption, or the use of toxic media. Especially in the battery industry, where requirements for moisture, metallic impurities, and acidity are extremely stringent, traditional DMC production processes often require complex refining and purification steps, increasing costs and environmental burden. Meanwhile, converting the greenhouse gas carbon dioxide into high-value-added chemicals has significant environmental and economic value.

[0005] CN118320806A discloses a method for preparing cyclic carbonates via transesterification using zirconium oxide as a catalyst. The method for preparing the zirconium oxide catalyst includes: (1) mixing a zirconium source and an alkali separately with a solvent to obtain a zirconium source solution and an alkali solution; (2) adding the alkali solution dropwise to the zirconium source solution and mixing to obtain a slurry; (3) subjecting the slurry to a hydrothermal reaction, separating the solid and liquid, washing, drying, and then calcining to obtain the zirconium oxide catalyst. This method has at least the following drawbacks: First, the pore structure of the catalyst is uncontrollable, making it difficult to form a porous structure with a high specific surface area, resulting in insufficient exposure of catalytic active sites; second, the hydrothermal reaction is not conducive to the formation of a stable mesoporous structure; third, the zirconium oxide catalyst prepared by this method is only used for transesterification, rather than the direct synthesis of DMC from CO2 and methanol, and the reaction pathway is completely different, making it impossible to refer to its catalytic activity optimization strategy.

[0006] CN114939413A discloses a catalyst for the direct synthesis of dimethyl carbonate from methanol, its preparation method, and its application. The preparation method of the catalyst includes the following steps: (1) mixing the precursor salt of the active component, the precursor salt of the auxiliary agent, and the precursor salt of the support, then adding urea and water, and stirring until clear; (2) transferring to a polytetrafluoroethylene liner, then placing it in a microwave synthesis vessel, stirring, and reacting; (3) naturally cooling to room temperature, filtering, washing until the filtrate is neutral, then drying and calcining; (4) cooling, pressing into tablets, crushing, sieving, and passing through a sieve to obtain the target catalyst. The precursor salt of the active component is copper nitrate or copper acetate; the support is cerium oxide and / or zirconium oxide; the precursor salt of the auxiliary agent corresponds to at least one of nickel acetate, ferric nitrate, and palladium chloride. This method has at least the following drawbacks: First, the catalyst composition is complex, requiring the introduction of various active components and additives such as copper, nickel, iron, and palladium, which not only significantly increases the cost of raw materials but also easily introduces impurities that affect the purity of the product. Second, relying solely on hydrothermal reactions makes it difficult to form a porous structure with a high specific surface area. Third, the microwave synthesis process has high equipment investment and operating costs, which is not conducive to large-scale production.

[0007] Therefore, developing an efficient, low-energy-consumption, and green battery-grade DMC synthesis route is crucial for promoting the sustainable development of the new energy industry chain.

[0008] In view of this, the present invention is hereby proposed. Summary of the Invention

[0009] The purpose of this invention is to provide a method for preparing a porous catalyst, the porous catalyst itself, and its application, in order to solve the technical problems of low catalytic activity, insufficient selectivity, poor recycling rate, poor stability, complex preparation process, and high cost of existing catalysts in the direct synthesis of dimethyl carbonate from CO2 and methanol.

[0010] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: In a first aspect, the present invention provides a method for preparing a porous catalyst, the method comprising: A zirconium source, surfactant, and first solvent are mixed to obtain a zirconium source solution; Urea and the second solvent are mixed to obtain a urea solution; The urea solution and the zirconium source solution are mixed and stirred to obtain a mixed solution; The mixed solution was subjected to a solvothermal reaction and calcination to obtain the porous catalyst.

[0011] Furthermore, the molar ratio of the zirconium source to the surfactant is 1:(0.001~0.1).

[0012] Furthermore, the zirconium source includes any one or a combination of at least two of zirconium oxynitrate, zirconium tetrachloride, zirconium nitrate, and zirconium sulfate, preferably zirconium oxynitrate.

[0013] Furthermore, the surfactant comprises any one or a combination of at least two of sodium dodecyl sulfate, hexadecyltrimethylammonium bromide, and polyvinylpyrrolidone, preferably sodium dodecyl sulfate.

[0014] Furthermore, the molar ratio of the zirconium source to the first solvent is 1:(10~20).

[0015] Furthermore, the first solvent includes any one or a combination of at least two of methanol, ethanol, isopropanol, and water, preferably methanol.

[0016] Furthermore, the molar ratio of urea to the second solvent is (1~15):(1~20).

[0017] Furthermore, the second solvent includes any one or a combination of at least two of methanol, ethanol, isopropanol, and water, preferably methanol.

[0018] Furthermore, the mixing of the urea solution and the zirconium source solution includes: adding the urea solution dropwise into the zirconium source solution.

[0019] Furthermore, the stirring temperature is 10~40℃, and the stirring time is 1~3 h.

[0020] Further, in the mixed solution, the molar ratio of the zirconium source, surfactant, urea and total solvent is 1:(0.001~0.1):(1~20):(10~40); wherein the total solvent includes a first solvent and a second solvent.

[0021] Furthermore, the temperature of the solvothermal reaction is 110~130℃, and the time of the solvothermal reaction is 12~36h.

[0022] Furthermore, the calcination temperature is 480~520℃, and the calcination time is 4~6 h.

[0023] Furthermore, after the solvothermal reaction is completed and before calcination, the following post-treatment steps are also included: The reaction solution obtained from the solvothermal reaction is cooled, and the solid product is collected by centrifugation. Then, it is washed, dried and ground to obtain the powder to be calcined.

[0024] Furthermore, the centrifugation speed is 6000~10000 rpm, and the centrifugation time is 3~10 min.

[0025] Furthermore, the solvent used for washing includes water and / or ethanol; the washing is performed more than twice using each solvent.

[0026] Furthermore, the drying temperature is 50~70℃, and the drying time is 6~18 h.

[0027] Furthermore, the particle size of the powder to be calcined obtained by grinding is 5~15 μm.

[0028] In a second aspect, the present invention provides a porous catalyst, which is prepared by the method for preparing a porous catalyst as described in the first aspect.

[0029] Furthermore, the porous catalyst has a specific surface area of ​​60 m². 2 / g or more, preferably 95 m 2 / g or more.

[0030] Thirdly, the present invention provides the use of the porous catalyst according to the second aspect in the preparation of dimethyl carbonate.

[0031] Fourthly, the present invention provides a method for preparing dimethyl carbonate, the method comprising: The porous catalyst described in the second aspect is mixed with methanol, and carbon dioxide gas is introduced to carry out the reaction, thereby obtaining dimethyl carbonate.

[0032] Furthermore, the mass-to-volume ratio of the porous catalyst to methanol is (50~100) mg:(10~20) mL.

[0033] Furthermore, after introducing carbon dioxide gas, it needs to stand for 20 to 40 minutes.

[0034] Furthermore, the reaction temperature is 120~170℃, and the reaction time is 1~4 h.

[0035] Compared with the prior art, the present invention has the following beneficial effects: (1) The porous catalyst preparation method of the present invention involves the synergistic action of a zirconium source, a surfactant, and urea in a solvent, followed by a solvothermal reaction and calcination to prepare a porous zirconium oxide catalyst. The surfactant acts as a soft template agent to regulate the pore structure, forming abundant mesopores, increasing the specific surface area and active centers; urea slowly releases alkaline substances, achieving uniform precipitation, avoiding the aggregation of active components, and promoting the formation of a stable porous framework. This preparation method is simple and mild, and the resulting catalyst exhibits excellent catalytic activity, selectivity, and cycle stability in the direct synthesis of dimethyl carbonate from carbon dioxide and methanol. Furthermore, it is low in cost and easy to scale up for production.

[0036] (2) The method for preparing dimethyl carbonate described in this invention uses carbon dioxide and methanol as direct raw materials to synthesize battery-grade dimethyl carbonate in one step through a highly efficient and mild catalytic process. The core innovation of this technical route lies in the use of the above-mentioned high-performance heterogeneous catalyst, which can promote the reaction with high selectivity and high yield at low pressure and temperature. At the same time, the catalyst is easy to separate and can be recycled. The process of this invention has the characteristics of high atom economy, green process, and excellent natural product purity (the only byproduct is water). The obtained DMC product can directly meet the stringent standards of high-end lithium-ion battery electrolytes after simple processing. Attached Figure Description

[0037] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0038] Figure 1 This is a SEM image of the porous spherical particle catalyst prepared in Example 1 of the present invention.

[0039] Figure 2 The image shows an XRD pattern of the porous spherical particle catalyst provided in Example 1 of this invention.

[0040] Figure 3 This is a GC image of the porous spherical particle catalyst after catalysis in Example 1 of the present invention. Detailed Implementation

[0041] Unless otherwise defined herein, the scientific and technical terms used in conjunction with this invention shall have the meanings commonly understood by one of ordinary skill in the art. The meaning and scope of terms shall be clear; however, in any case of potential ambiguity, the definitions provided herein shall prevail over any dictionary or foreign definitions. In this application, unless otherwise stated, the use of "or" means "and / or". Furthermore, the use of the term "comprising" and other forms is non-limiting.

[0042] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] In a first aspect, the present invention provides a method for preparing a porous catalyst, the method comprising: A zirconium source, surfactant, and first solvent are mixed to obtain a zirconium source solution; Urea and the second solvent are mixed to obtain a urea solution; The urea solution and the zirconium source solution are mixed and stirred to obtain a mixed solution; The mixed solution was subjected to a solvothermal reaction and calcination to obtain the porous catalyst.

[0044] It is important to note that, firstly, the surfactant, acting as a soft template, self-assembles into micellar structures in solution, providing a spatial confinement effect for the directional growth of zirconia. During the solvothermal reaction, the zirconium source undergoes hydrolysis and condensation around these micellar templates, forming an ordered and abundant mesoporous channel structure. These channels not only significantly increase the specific surface area of ​​the catalyst but also provide more accessible active sites for reactants and promote the diffusion and transport of products within the channels. Secondly, urea, acting as a precipitant, exhibits unique slow-release characteristics, ensuring a uniform and controllable precipitation process for zirconium ions, avoiding the agglomeration of active components and pore blockage problems caused by rapid precipitation with strong alkalis. This uniform precipitation mechanism facilitates the formation of uniformly sized and well-dispersed zirconia nanoparticles, further ensuring the integrity and stability of the porous structure. Thirdly, the solvothermal reaction, compared to conventional hydrothermal reactions, provides a mild and uniform chemical environment for crystal nucleation and growth, contributing to the formation of a zirconia framework with appropriate crystallinity. The subsequent calcination treatment completely removes the organic template and transforms the amorphous precursor into a stable oxide crystalline phase, endowing the catalyst with excellent thermal stability and mechanical strength. Finally, the entire preparation process uses methanol as the solvent system, which facilitates the full dissolution and uniform mixing of the precursors, ensuring the homogeneity of the final catalyst composition and structure. The synergistic effect of these multiple factors results in the catalyst exhibiting high catalytic activity, excellent selectivity, and good cycle stability in the direct synthesis of dimethyl carbonate from carbon dioxide and methanol.

[0045] As an optional implementation, the molar ratio of the zirconium source to the surfactant is 1:(0.001~0.1), for example, it can be 1:0.001, 1:0.002, 1:0.004, 1:0.005, 1:0.006, 1:0.008, 1:0.01, 1:0.02, 1:0.04, 1:0.05, 1:0.06, 1:0.08, 1:0.1, etc.

[0046] It should be noted that within this range, the template agent can fully regulate the mesoporous structure while ensuring the effective exposure of zirconia active sites. In other words, this ratio range balances the pore-forming effect of the template with the exposure of active sites. If the ratio is too low, the surfactant is insufficient to form an effective micelle template, making it difficult to construct abundant pores; if the ratio is too high, it is easy to clog the pores or cover the active centers, resulting in a decrease in specific surface area and catalytic activity.

[0047] As an optional implementation, the zirconium source includes any one or a combination of at least two of zirconium oxynitrate, zirconium tetrachloride, zirconium nitrate, and zirconium sulfate.

[0048] In a preferred embodiment, the zirconium source is zirconium oxynitrate.

[0049] It should be noted that zirconium oxynitrate exhibits excellent solubility, enabling it to form a homogeneous and stable mixed solution with surfactants (such as sodium dodecyl sulfate). This ensures uniform dispersion of the zirconium source at the molecular level, laying a solid foundation for the subsequent template-controlled pore structure formation. Furthermore, after solvothermal reaction and high-temperature calcination, the nitrate ions readily decompose and volatilize, leaving no residue in the final product. This results in a high-purity zirconium oxide catalyst, preventing pore blockage or poisoning of active sites due to residual impurity anions, thus ensuring the catalyst's specific surface area and catalytic activity. Moreover, zirconium oxynitrate has a moderate hydrolysis rate, achieving uniform precipitation under alkaline conditions of slow urea release. This facilitates the formation of uniformly sized and well-dispersed zirconium oxide nanoparticles, promoting the stable construction of the porous framework.

[0050] As an optional embodiment, the surfactant includes any one or a combination of at least two of sodium dodecyl sulfate, hexadecyltrimethylammonium bromide, and polyvinylpyrrolidone.

[0051] In a preferred embodiment, the surfactant is sodium dodecyl sulfate.

[0052] It should be noted that sodium dodecyl sulfate (SDS), as an anionic surfactant, can self-assemble into micellar structures in solution. This serves as a soft template, effectively guiding the directional hydrolysis and condensation of the zirconium oxide precursor on the micelle surface. After calcination removal, abundant and ordered mesoporous channels remain, significantly increasing the catalyst's specific surface area. Its long-chain alkyl structure facilitates the construction of a stable porous framework, while the sulfonic acid groups can weakly interact with zirconium ions, promoting uniform dispersion of zirconium species and inhibiting particle aggregation. Furthermore, SDS exhibits good compatibility with methanol solvents and urea systems, is readily available and inexpensive, and is easily and completely decomposed and removed during subsequent calcination, without introducing residual impurities, thus ensuring the purity and activity of the catalyst.

[0053] As an optional implementation, the molar ratio of the zirconium source to the first solvent is 1:(10~20), for example, it can be 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, 1:20, etc.

[0054] As an optional implementation, the first solvent includes any one or a combination of at least two of methanol, ethanol, isopropanol, and water.

[0055] As an optional implementation, the molar ratio of urea to the second solvent is (1~15):(1~20); Among them, "1~15" can be, for example, 1, 2, 4, 5, 6, 8, 10, 12, 14, 15, etc.; Among them, "1~20" can be, for example, 1, 2, 4, 5, 6, 8, 10, 12, 14, 15, 16, 18, 20, etc.

[0056] As an optional implementation, the second solvent includes any one or a combination of at least two of methanol, ethanol, isopropanol, and water.

[0057] In a preferred embodiment, the second solvent is methanol.

[0058] As an optional implementation, the mixing of the urea solution and the zirconium source solution includes: adding the urea solution dropwise into the zirconium source solution.

[0059] As an optional implementation, the stirring temperature is 10~40℃, for example, it can be 10℃, 11℃, 12℃, 13℃, 14℃, 15℃, 16℃, 17℃, 18℃, 19℃, 20℃, 21℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, 29℃, 30℃, 31℃, 32℃, 33℃, 34℃, 35℃, 36℃, 37℃, 38℃, 39℃, 40℃, etc.; the stirring time is 1~3 h, for example, it can be 1 h, 1.2 h, 1.4 h, 1.6 h, 1.8 h, 2 h, 2.2 h, 2.4 h, 2.6 h, 2.8 h, 3 h, etc.

[0060] As an optional implementation, in the mixed solution, the molar ratio of the zirconium source, surfactant, urea and total solvent is 1:(0.001~0.1):(1~20):(10~40); wherein the total solvent includes a first solvent and a second solvent; Among them, "0.001~0.1" can be, for example, 0.001, 0.002, 0.004, 0.005, 0.006, 0.008, 0.01, 0.02, 0.04, 0.05, 0.06, 0.08, 0.1, etc.; Among them, "1~20" can be, for example, 1, 2, 4, 5, 6, 8, 10, 12, 14, 15, 16, 18, 20, etc.; Among them, "10~40" can be, for example, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40.

[0061] As an optional implementation, the temperature of the solvothermal reaction is 110~130℃, for example, 110℃, 112℃, 114℃, 116℃, 118℃, 120℃, 122℃, 124℃, 126℃, 128℃, 130℃, etc.; the time of the solvothermal reaction is 12~36 h, for example, 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, 24 h, 26 h, 28 h, 30 h, 32 h, 34 h, 36 h, etc.

[0062] As an optional implementation, the calcination temperature is 480~520℃, for example, it can be 480℃, 482℃, 484℃, 486℃, 488℃, 490℃, 492℃, 494℃, 496℃, 498℃, 500℃, 502℃, 504℃, 506℃, 508℃, 510℃, 512℃, 514℃, 516℃, 518℃, 520℃, etc.; the calcination time is 4~6 h, for example, it can be 4 h, 4.2 h, 4.4 h, 4.6 h, 4.8 h, 5 h, 5.2 h, 5.4 h, 5.6 h, 5.8 h, 6 h, etc.

[0063] As an optional implementation, the following post-treatment steps are included after the solvothermal reaction is completed and before calcination: The reaction solution obtained from the solvothermal reaction is cooled, and the solid product is collected by centrifugation. Then, it is washed, dried and ground to obtain the powder to be calcined.

[0064] As an optional implementation, the centrifugation speed is 6000~10000 rpm, for example, 6000 rpm, 6500 rpm, 7000 rpm, 7500 rpm, 8000 rpm, 8500 rpm, 9000 rpm, 9500 rpm, 10000 rpm, etc., and the centrifugation time is 3~10 min, for example, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, etc.

[0065] As an optional implementation, the solvent used for washing includes water and / or ethanol.

[0066] In a preferred embodiment, the washing process involves first washing with water, followed by washing with ethanol.

[0067] As an optional implementation, the washing is performed more than twice using each solvent, for example, 2 times, 3 times, 4 times, 5 times, 6 times, 7 times, 8 times, 9 times, 10 times, etc.

[0068] As an optional implementation, the drying temperature is 50~70℃, for example, it can be 50℃, 52℃, 54℃, 56℃, 58℃, 60℃, 62℃, 64℃, 66℃, 68℃, or 70℃, and the drying time is 6~18 h, for example, it can be 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, or 18 h.

[0069] As an optional implementation, the particle size of the powder to be calcined obtained by grinding is 5~15 μm, for example, it can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, etc.

[0070] As an optional implementation method, the water mentioned above includes, but is not limited to, deionized water, distilled water, and pure water.

[0071] In a second aspect, the present invention provides a porous catalyst, which is prepared by the method for preparing a porous catalyst as described in the first aspect.

[0072] As an optional embodiment, the porous catalyst has a specific surface area of ​​60 m². 2 / g or more, for example, 60m 2 / g、62 m 2 / g、64 m 2 / g、66 m 2 / g、68 m 2 / g、70 m 2 / g、72 m 2 / g、74 m 2 / g、76 m 2 / g、78 m 2 / g、80m 2 / g、82 m 2 / g、84 m 2 / g、86 m 2 / g、88 m 2 / g、90 m 2 / g、92 m 2 / g、94 m 2 / g、96 m 2 / g、98 m 2 / g, 100m 2 / g etc.

[0073] In a preferred embodiment, the porous catalyst has a specific surface area of ​​95 m². 2 / g or more.

[0074] Thirdly, the present invention provides the use of the porous catalyst according to the second aspect in the preparation of dimethyl carbonate.

[0075] Fourthly, the present invention provides a method for preparing dimethyl carbonate, the method comprising: The porous catalyst described in the second aspect is mixed with methanol, and carbon dioxide gas is introduced to carry out the reaction, thereby obtaining dimethyl carbonate.

[0076] As an optional embodiment, the mass-to-volume ratio of the porous catalyst to methanol is (50~100) mg:(10~20) mL; Among them, "(50~100) mg" can be, for example, 50 mg, 55 mg, 60 mg, 65 mg, 70 mg, 75 mg, 80 mg, 85 mg, 90 mg, 95 mg, 100 mg, etc. Among them, “(10~20) mL” can be, for example, 10 mL, 11 mL, 12 mL, 13 mL, 14 mL, 15 mL, 16 mL, 17 mL, 18 mL, 19 mL, 20 mL, etc.

[0077] As an optional implementation method, after introducing carbon dioxide gas, it is necessary to let it stand for 20 to 40 minutes, for example, 20 minutes, 22 minutes, 24 minutes, 25 minutes, 26 minutes, 28 minutes, 30 minutes, 32 minutes, 34 minutes, 36 minutes, 38 minutes, 40 minutes, etc.

[0078] As an optional implementation, the reaction temperature is 120~170℃, for example, it can be 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, 150℃, 155℃, 160℃, 165℃, 170℃, etc., and the reaction time is 1~4h, for example, it can be 1h, 1.2h, 1.4h, 1.6h, 1.8h, 2h, 2.2h, 2.4h, 2.6h, 2.8h, 3h, 3.2h, 3.4h, 3.6h, 3.8h, 4h, etc.

[0079] The present invention will be further illustrated by the following examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0080] Example 1 This embodiment provides a method for preparing and applying a porous catalyst, including the following steps: (1) Dissolve zirconium oxynitrate and sodium dodecyl sulfate in methanol solution and stir rapidly for 30 min to ensure complete dissolution; the molar ratio of zirconium oxynitrate, sodium dodecyl sulfate and methanol is 1:0.02:14; (2) Dissolve urea in methanol solution and stir rapidly for 30 min to ensure complete dissolution; the molar ratio of urea to methanol is 5:14. (3) Under continuous stirring, the urea solution obtained in step (2) is slowly added dropwise to the zirconium oxynitrate solution obtained in step (1), and stirred at room temperature for 2 h to obtain a mixed solution; at this time, the molar ratio of zirconium oxynitrate, sodium dodecyl sulfate, urea and methanol is 1:0.02:5:28. (4) Transfer the mixed solution obtained in step (3) to a 100 mL polytetrafluoroethylene-lined high-pressure reactor, place it in an oven, and heat it at 120°C for 24 h. After the reaction is completed, cool it naturally to room temperature, separate and collect the solid product by high-speed centrifugation (8000 rpm, 5 min), wash it 3 times with deionized water, and then wash it 3 times with anhydrous ethanol. Subsequently, place the collected sample in a 60°C constant temperature oven to dry for 12 h. Finally, grind the dried solid powder (particle size of 5~15 μm), place it in a crucible, and calcine it in a muffle furnace at 500°C for 5 h to obtain a white powdered catalyst. (5) Add 50 mg of the powdered catalyst obtained in step (4) and 20 mL of anhydrous methanol to a 100 mL micro high-pressure reactor, purge with carbon dioxide gas, and let stand for 30 min; set the reaction parameters: reaction time 2 h, reaction temperature 160℃, rotation speed 400 r / min, and start the reaction by heating and stirring. (6) After the reaction is completed, the solid-liquid mixture is centrifuged and separated. The liquid part is analyzed by GC, and the solid part is washed and dried to obtain the porous catalyst. Take 50 mg for later use and repeat step (5) 5 times to evaluate the stability of the catalyst.

[0081] Example 2 This embodiment provides a method for preparing and applying a porous catalyst. The only difference from Example 1 is that the molar ratio of zirconium oxynitrate, sodium dodecyl sulfate and methanol in step (1) is adjusted to 1:0.01:14; the molar ratio of zirconium oxynitrate, sodium dodecyl sulfate, urea and methanol in step (3) is 1:0.01:5:28; and the other steps are the same as in Example 1.

[0082] Example 3 This embodiment provides a method for preparing and applying a porous catalyst. The only difference from Example 1 is that the molar ratio of zirconium oxynitrate, sodium dodecyl sulfate and methanol in step (1) is adjusted to 1:0.05:14; the molar ratio of zirconium oxynitrate, sodium dodecyl sulfate, urea and methanol in step (3) is 1:0.05:5:28; and the other steps are the same as in Example 1.

[0083] Example 4 This embodiment provides a method for preparing and applying a porous catalyst. The only difference from Example 1 is that the molar ratio of zirconium oxynitrate, sodium dodecyl sulfate and methanol in step (1) is adjusted to 1:0.1:14; the molar ratio of zirconium oxynitrate, sodium dodecyl sulfate, urea and methanol in step (3) is 1:0.1:5:28; and the other steps are the same as in Example 1.

[0084] Example 5 This embodiment provides a method for preparing and applying a porous catalyst. The only difference from Example 1 is that the molar ratio of urea to methanol in step (2) is 1:14; the molar ratio of zirconium oxynitrate, sodium dodecyl sulfate, urea and methanol in step (3) is 1:0.02:1:28; and the other steps are the same as in Example 1.

[0085] Example 6 This embodiment provides a method for preparing and applying a porous catalyst. The only difference from Example 1 is that the molar ratio of urea to methanol in step (2) is 3:14; the molar ratio of zirconium oxynitrate, sodium dodecyl sulfate, urea and methanol in step (3) is 1:0.02:3:28; and the other steps are the same as in Example 1.

[0086] Example 7 This embodiment provides a method for preparing and applying a porous catalyst. The only difference from Example 1 is that the molar ratio of urea to methanol in step (2) is 7:14; the molar ratio of zirconium oxynitrate, sodium dodecyl sulfate, urea and methanol in step (3) is 1:0.02:7:28; and the other steps are the same as in Example 1.

[0087] Example 8 This embodiment provides a method for preparing and applying a porous catalyst. The only difference from Example 1 is that the molar ratio of urea to methanol in step (2) is 9:14; the molar ratio of zirconium oxynitrate, sodium dodecyl sulfate, urea and methanol in step (3) is 1:0.02:9:28; and the other steps are the same as in Example 1.

[0088] Example 9 This embodiment provides a method for preparing and applying a porous catalyst. The only difference from Example 1 is that the molar ratio of urea to methanol in step (2) is 15:14; the molar ratio of zirconium oxynitrate, sodium dodecyl sulfate, urea and methanol in step (3) is 1:0.02:15:28; and the other steps are the same as in Example 1.

[0089] Example 10 This embodiment provides a method for preparing and applying a porous catalyst. The only difference from Example 1 is that sodium dodecyl sulfate is replaced with an equimolar amount of hexadecyltrimethylammonium bromide; the other steps are the same as in Example 1.

[0090] Example 11 This embodiment provides a method for preparing and applying a porous catalyst. The only difference from Example 1 is that sodium dodecyl sulfate is replaced with an equimolar amount of polyvinylpyrrolidone; the other steps are the same as in Example 1.

[0091] Example 12 This embodiment provides a method for preparing and applying a porous catalyst. The only difference from Example 1 is that methanol in steps (1) and (2) is replaced with an equimolar amount of ethanol; the other steps are the same as in Example 1.

[0092] Example 13 This embodiment provides a method for preparing and applying a porous catalyst. The only difference from Example 1 is that methanol in steps (1) and (2) is replaced with an equimolar amount of isopropanol; the other steps are the same as in Example 1.

[0093] Example 14 This embodiment provides a method for preparing and applying a porous catalyst. The only difference from Example 1 is that the temperature of the solvothermal reaction is 110°C and the time of the solvothermal reaction is 36 h; the other steps are the same as in Example 1.

[0094] Example 15 This embodiment provides a method for preparing and applying a porous catalyst. The only difference from Example 1 is that the temperature of the solvothermal reaction is 130°C and the time of the solvothermal reaction is 12 h; the other steps are the same as in Example 1.

[0095] Comparative Example 1 This comparative example provides a method for preparing and applying a catalyst, which differs from Example 1 only in that: in step (1), the molar ratio of zirconium oxynitrate, sodium dodecyl sulfate and methanol is adjusted to 1:0:14 (i.e., sodium dodecyl sulfate is not added); in step (3), the molar ratio of zirconium oxynitrate, sodium dodecyl sulfate, urea and methanol is 1:0:5:28; the other steps are the same as in Example 1.

[0096] Comparative Example 2 This comparative example provides a method for preparing and applying a catalyst. The only difference from Example 1 is that the solvothermal reaction is replaced with a hydrothermal reaction, that is, the methanol in steps (1) and (2) is replaced with an equimolar amount of deionized water; the other steps are the same as in Example 1.

[0097] Comparative Example 3 This comparative example provides a method for preparing and applying a catalyst, which differs from Example 1 only in that urea is replaced with an equimolar amount of ammonia; the other steps are the same as in Example 1.

[0098] Test case Test method: (1) Catalyst specific surface area: Measured using a Micromeritics (USA) specific surface area analyzer. 0.2 g of the catalyst provided in this invention was placed at 1 / 2 of the bulb in the sample tube to ensure sufficient adsorption and thermal equilibrium. A degassing process was then performed, requiring degassing at 250°C for 4 hours under a vacuum or inert gas atmosphere. The instrument software automatically calculated the specific surface area based on the BET equation.

[0099] (2) Initial yield: After the reaction in Example 1 (6), the solid-liquid mixture was centrifuged, and the liquid fraction was analyzed by GC. In this application, a gas chromatograph (GC 9160) was used to quantitatively analyze the liquid product after the reaction. A PEG 20 M capillary column (Φ 0.32 mm × 0.33 μm × 30 m, quartz capillary column) was used, with a hydrogen-air generator (HA-300A) providing stable gas for the chromatography, and high-purity N2 as the carrier gas to determine the product content. Initial yield of dimethyl carbonate (mmol / g) = Dimethyl carbonate production (mmol) / Catalyst dosage (g).

[0100] (3) Initial selectivity: Initial selectivity (%) = amount of dimethyl carbonate × 2 / (amount of methanol before reaction - amount of methanol after reaction) × 100%.

[0101] (4) Yield of the fifth cycle: Yield of reactants after the fifth cycle (mmol / g) = Amount of dimethyl carbonate produced in the fifth reaction (mmol) / Amount of catalyst used (g).

[0102] The specific test results are shown in Table 1, and Figures 1-3 As shown: Table 1

[0103] Note: Dimethyl carbonate yield (mmol / g) = Dimethyl carbonate produced (mmol) / Catalyst amount (g); Initial selectivity (%) = Amount of dimethyl carbonate * 2 / (Amount of methanol before reaction - Amount of methanol after reaction) * 100%.

[0104] As shown in Table 1, the catalyst provided by this invention has a high specific surface area (60 m²). 2 / g or more, preferably 95 m 2 With its abundant porous structure and high concentration of active sites (above 10 mmol / g), the catalyst exhibits a high level of catalytic activity, exceeding 10 mmol / g. It can efficiently catalyze the direct reaction of carbon dioxide and methanol to produce dimethyl carbonate electrolyte under mild conditions (160℃, 2 h). During preparation, the catalyst is calcined at 500℃ to form a stable white crystalline oxide, ensuring structural stability and allowing for multiple uses. After five cycles, the yield reaches 96.2%, with a selectivity greater than 99%.

[0105] The comparison between Examples 1 and Examples 2-4 shows that the amount of surfactant has a certain impact on the pore structure and catalytic performance of the catalyst. If the amount of surfactant is too low, there will be insufficient micelle template, making it difficult to form abundant mesopores, resulting in a decrease in specific surface area and insufficient exposure of active sites. If the amount of surfactant is too high, it will easily clog the pores or cover the active centers, which will also reduce the catalytic performance. Therefore, the amount of surfactant needs to be controlled within an appropriate range to balance the pore-forming effect of the template with the effective exposure of active sites, thereby obtaining a porous catalyst with high specific surface area and high catalytic activity.

[0106] The comparison between Examples 1 and Examples 5-9 shows that the amount of urea has a certain impact on the pore structure and catalytic performance of the catalyst. If the amount of urea is too low, the release of alkaline substances is insufficient, the precipitation of zirconium ions is incomplete, and it is difficult to form abundant mesopores, resulting in a decrease in specific surface area and catalytic activity. If the amount of urea is too high, it may lead to excessive precipitation, affecting the optimization of the pore structure. Therefore, the amount of urea needs to be controlled within an appropriate range to achieve uniform and controllable precipitation of zirconium ions, construct a porous framework with a high specific surface area, and thus obtain excellent catalytic activity and cycle stability.

[0107] A comparison between Example 1 and Examples 10-11 shows that the type of surfactant has a certain influence on the pore structure and catalytic performance of the catalyst. Example 1 uses sodium dodecyl sulfate as an anionic surfactant, which has good compatibility with the system and can effectively guide the directional hydrolysis and polycondensation of the zirconium oxide precursor, forming abundant and ordered mesoporous channels, thereby obtaining high specific surface area and high catalytic activity. In contrast, Examples 10-11 use hexadecyltrimethylammonium bromide and polyvinylpyrrolidone, respectively. At the same dosage, both significantly inferior to sodium dodecyl sulfate in terms of pore-forming effect and catalytic performance.

[0108] A comparison of Examples 1 and 12-13 shows that the type of solvent has a certain influence on the pore structure and catalytic performance of the catalyst. When methanol is used as a solvent, it facilitates the full dissolution and uniform mixing of the precursors and has good compatibility with the surfactant and urea system, effectively promoting micellar template formation and uniform precipitation of zirconium ions, thereby constructing a porous framework with a high specific surface area. However, ethanol and isopropanol, due to differences in polarity, viscosity, or molecular size, result in weakened precursor dispersion and template effect, less perfect pore structure, and consequently, decreased catalytic activity.

[0109] As can be seen from the comparison between Example 1 and Examples 14-15, the temperature and time of the solvothermal reaction need to be controlled in a coordinated manner to maintain abundant mesoporous channels while ensuring crystallinity, so as to obtain a porous catalyst with high specific surface area and high catalytic activity.

[0110] The comparison between Example 1 and Comparative Example 1 shows that surfactants are a key element in constructing porous catalysts. Without surfactants, the zirconium source lacks template guidance during the solvothermal reaction, failing to form an ordered mesoporous structure. This results in a significant reduction in the catalyst's specific surface area and insufficient exposure of active sites, leading to a substantial decrease in catalytic activity. This clearly demonstrates that surfactants, acting as soft templates, form micellar structures through self-assembly, providing a spatial confinement effect for the directional growth of zirconium oxide. After removal by calcination, abundant mesoporous channels remain, thereby significantly increasing the specific surface area and improving catalytic performance.

[0111] A comparison of Example 1 and Comparative Example 2 shows that solvothermal reactions using alcohol as a solvent are more conducive to constructing porous catalysts with high specific surface areas than hydrothermal reactions using water. Under hydrothermal reaction conditions, crystal nucleation and growth are not conducive to the formation of stable and abundant mesoporous structures, resulting in incomplete pore construction, insufficient exposure of active sites, and a significant reduction in catalytic activity. In contrast, solvothermal reactions provide a milder and more uniform chemical environment for the nucleation and growth of zirconia, which is beneficial for the complete dissolution and uniform mixing of precursors, promoting the effective guidance of pore formation by the micelle template, thereby obtaining porous catalysts with high specific surface areas and high catalytic activity.

[0112] A comparison of Example 1 and Comparative Example 3 shows that urea, as a precipitant, is more conducive to constructing porous catalysts with high specific surface area than ammonia. Ammonia is a strong alkali, and its rapid release of alkaline substances leads to a violent and uneven precipitation process of zirconium ions, easily causing agglomeration of active components and pore blockage, making it difficult to form a stable porous framework, thus reducing catalytic activity. Urea, on the other hand, has the characteristic of slowly releasing alkaline substances, enabling uniform and controllable precipitation of zirconium ions, avoiding particle agglomeration, and facilitating the formation of uniformly sized and well-dispersed zirconium oxide nanoparticles. This ensures the integrity and stability of the porous structure, resulting in higher specific surface area and catalytic activity.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention 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; and these 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 the present invention.

Claims

1. A method for preparing a porous catalyst, characterized in that, The method for preparing the porous catalyst includes: A zirconium source, surfactant, and first solvent are mixed to obtain a zirconium source solution; Urea and the second solvent are mixed to obtain a urea solution; The urea solution and the zirconium source solution are mixed and stirred to obtain a mixed solution; The mixed solution was subjected to a solvothermal reaction and calcination to obtain the porous catalyst.

2. The method for preparing the porous catalyst according to claim 1, characterized in that, The molar ratio of the zirconium source to the surfactant is 1:(0.001~0.1); Preferably, the zirconium source includes any one or a combination of at least two of zirconium oxynitrate, zirconium tetrachloride, zirconium nitrate, and zirconium sulfate, with zirconium oxynitrate being the most preferred. Preferably, the surfactant comprises any one or a combination of at least two of sodium dodecyl sulfate, hexadecyltrimethylammonium bromide, and polyvinylpyrrolidone, with sodium dodecyl sulfate being the most preferred. Preferably, the molar ratio of the zirconium source to the first solvent is 1:(10~20); Preferably, the first solvent includes any one or a combination of at least two of methanol, ethanol, isopropanol, and water, with methanol being the most preferred.

3. The method for preparing the porous catalyst according to claim 1, characterized in that, The molar ratio of urea to the second solvent is (1~15):(1~20); Preferably, the second solvent includes any one or a combination of at least two of methanol, ethanol, isopropanol, and water, with methanol being the most preferred.

4. The method for preparing the porous catalyst according to claim 1, characterized in that, The mixing of the urea solution and the zirconium source solution includes: adding the urea solution dropwise into the zirconium source solution; Preferably, the stirring temperature is 10~40℃, and the stirring time is 1~3 h; Preferably, in the mixed solution, the molar ratio of the zirconium source, surfactant, urea and total solvent is 1:(0.001~0.1):(1~20):(10~40); wherein the total solvent includes a first solvent and a second solvent.

5. The method for preparing the porous catalyst according to claim 1, characterized in that, The temperature of the solvothermal reaction is 110~130℃, and the time of the solvothermal reaction is 12~36 h; Preferably, the calcination temperature is 480~520℃, and the calcination time is 4~6 h; Preferably, after the solvothermal reaction is completed and before calcination, the following post-treatment steps are further included: The reaction solution obtained from the solvothermal reaction is cooled, and the solid product is collected by centrifugation. Then, it is washed, dried and ground in sequence to obtain the powder to be calcined. Preferably, the centrifugation speed is 6000~10000 rpm, and the centrifugation time is 3~10 min; Preferably, the solvent used for washing includes water and / or ethanol; the washing is performed more than twice using each solvent; Preferably, the drying temperature is 50~70℃, and the drying time is 6~18 h; Preferably, the particle size of the powder to be calcined obtained by grinding is 5~15 μm.

6. A porous catalyst, characterized in that, The porous catalyst is prepared by the method for preparing porous catalysts as described in any one of claims 1 to 5.

7. The porous catalyst according to claim 6, characterized in that, The porous catalyst has a specific surface area of ​​60 m². 2 / g or more, preferably 95 m 2 / g or more.

8. The use of a porous catalyst according to claim 6 or 7 in the preparation of dimethyl carbonate.

9. A method for preparing dimethyl carbonate, characterized in that, The method for preparing the dimethyl carbonate includes: The porous catalyst described in claim 6 or 7 is mixed with methanol, and carbon dioxide gas is introduced to carry out the reaction, thereby obtaining dimethyl carbonate.

10. The method for preparing dimethyl carbonate according to claim 9, characterized in that, The mass-to-volume ratio of the porous catalyst to methanol is (50~100) mg:(10~20) mL; Preferably, after introducing carbon dioxide gas, the mixture should be allowed to stand for 20 to 40 minutes. Preferably, the reaction temperature is 120~170℃ and the reaction time is 1~4 h.

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