Highly stable catalysts, methods for their preparation and use

Abstract

The application relates to the field of catalytic material preparation, and discloses a high-stability catalyst and a preparation method and application thereof. The catalyst comprises a metal organic framework material and a binder; wherein the metal organic framework material has an octahedron aggregate morphology, the edge length of the octahedron aggregate is 0.5-2 mu m, the octahedron aggregate is obtained by aggregation of microspheres, and the diameter of the microspheres is 20-100 nm. The catalyst has the characteristics of long service life, high activity, high polyester conversion rate and high yield of photocatalytic synthesis of ammonia.

Description

Technical Field

[0001] This invention relates to the field of catalytic material preparation, specifically to a highly stable catalyst, its preparation method, and its application. Background Technology

[0002] Currently, my country produces approximately 79 million tons of polyester annually, of which 80% is discarded, resulting in enormous economic and resource waste. Plastic additives continue to be released into the environment as they age and decompose, causing immeasurable and lasting environmental impacts. Therefore, recycling polyester to produce high-value-added chemicals is an important direction for resource recycling.

[0003] WO2022171029A1 discloses a polyester degradation catalyst that works in conjunction with a carboxylic acid to degrade polyester. The polyester used contains repeating units formed by dicarboxylic acids and diols, and the catalyst is a Lewis acid and / or a sulfonic acid. The catalyst of this invention is recyclable. The diol dicarboxylic ester obtained after polyester degradation using this catalyst can be hydrogenated and reduced to form a carboxylic acid, which is then repeatedly used with the catalyst in the degradation solution for polyester degradation.

[0004] CN103965509A discloses a zinc acetate polyester degradation catalyst. This invention treats the waste liquid generated from the degradation of PET polyester by ethylene glycol through vacuum distillation, and then uses the zinc acetate catalyst to reuse the treated waste liquid for further degradation of PET polyester. Using this catalyst to degrade polyester allows the treated waste liquid to be recycled for further degradation of waste polyester, thereby achieving the goal of comprehensive utilization of polyester degradation waste liquid.

[0005] Therefore, there is an urgent need to develop polyester degradation catalysts with high conversion rates, high strength, and high activity. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of short catalyst lifespan, low activity, insufficient exposure of surface active sites, low polyester conversion rate, and low photocatalytic ammonia synthesis yield in existing technologies, and to provide a highly stable catalyst, its preparation method, and its applications. This catalyst features long lifespan, high activity, high polyester conversion rate, and high photocatalytic ammonia synthesis yield.

[0007] During their research, the inventors of this invention discovered that the metal active sites of metal-organic frameworks (MOFs) attract electrons from the oxygen atoms of the carbonyl groups, thereby increasing the electropositivity of the carbonyl carbon. Some MOFs are photosensitive semiconductors; under illumination, these materials can generate photogenerated electrons and holes, collectively referred to as photogenerated charge carriers. These photogenerated charge carriers migrate to the active sites of the catalyst and react with substances such as water or alcohols to generate reactive free radicals such as hydroxyl radicals and superoxide radicals. These reactive free radicals attack the carbonyl groups in polyesters, enabling polyester degradation. When applied to photocatalytic nitrogen fixation, the surface microspheres of the MOFs increase the incident light absorption area, enhancing the generation of photogenerated charge carriers and thus improving the yield of photocatalytic ammonia synthesis. The inventors of this invention further discovered that when a metal-organic framework material with an octahedral aggregate morphology and composed of microspheres is mixed with a binder, it can greatly promote the generation of photogenerated charge carriers, increase the contact area between the catalyst and the polyester raw material during the reaction, and enhance the stability of the catalyst by introducing the binder. This effectively inhibits the degradation of the catalyst and the loss of active sites, prolongs the service life and activity of the catalyst, and improves the performance of the catalyst.

[0008] To achieve the above objectives, a first aspect of the present invention provides a catalyst, wherein the catalyst comprises a metal-organic framework material and a binder;

[0009] The metal-organic framework material has an octahedral aggregate morphology, the edge length of the octahedral aggregate is 0.5 to 2 μm, the octahedral aggregate is obtained by the aggregation of microspheres, and the diameter of the microspheres is 20 to 100 nm.

[0010] Preferably, Fe is present in the metal-organic framework material. II and Fe III Two forms, of which Fe II Fe III The ratio is 1:100 to 100:1, preferably 1:4 to 4:1, and more preferably 1:2 to 2:1.

[0011] Preferably, the adhesive is an aluminum-based adhesive.

[0012] A second aspect of the present invention provides a method for preparing the catalyst described in the first aspect, wherein the method includes the following steps:

[0013] The metal-organic framework material is mixed with a binder and / or a binder precursor, optionally shaped, and then calcined.

[0014] The third aspect of the present invention provides the application of the catalyst described in the first aspect or the catalyst prepared by the preparation method described in the second aspect in polyester degradation, preferably photocatalytic degradation of polyester or photocatalytic nitrogen fixation.

[0015] Through the above technical solution, the catalyst provided by this invention combines a metal-organic framework material with a special structure and morphology with a binder, fully exposing the active sites and increasing the number of free radicals generated during the reaction. It exhibits strong catalytic performance, high activity, and long service life when applied to polyester degradation or photocatalytic nitrogen fixation. For example, when applied to polyester degradation, the metal-organic framework is photoexcited, generating photogenerated electrons and holes at the active sites. These electrons and holes react with water to generate strong oxidizing free radicals, which can degrade polyester. The addition of the binder increases the structural stability of the catalyst, making the active component, the metal-organic framework, less susceptible to photodecomposition and improving the catalyst's service life. When applied to photocatalytic nitrogen fixation, the active sites of the metal-organic framework can rapidly adsorb and reduce nitrogen gas, and the binder similarly enhances the catalyst's stability. Attached Figure Description

[0016] Figure 1 These are scanning electron microscope (SEM) images of the metal-organic framework material in Example 1;

[0017] Figure 2 The image shows the X-ray diffraction (XRD) curve of the metal-organic framework material in Example 1. Detailed Implementation

[0018] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0019] Unless otherwise specified, all percentages, parts, ratios, etc. mentioned in this invention are based on weight, unless being based on weight would not be in accordance with the common understanding of those skilled in the art.

[0020] In this invention, unless otherwise stated, room temperature or normal temperature refers to 25±2℃.

[0021] In this invention, unless otherwise stated, all pressures are gauge pressures.

[0022] A first aspect of the present invention provides a catalyst, wherein the catalyst comprises a metal-organic framework material and a binder;

[0023] The metal-organic framework material has an octahedral aggregate morphology, the edge length of the octahedral aggregate is 0.5 to 2 μm, the octahedral aggregate is obtained by the aggregation of microspheres, and the diameter of the microspheres is 20 to 100 nm.

[0024] Preferably, the edge length of the regular octahedral aggregate is 1 to 1.5 μm, and more preferably 1 to 1.2 μm.

[0025] Preferably, the diameter of the microspheres is 40–80 nm, and more preferably 50–60 nm.

[0026] The metal-organic framework (MOF) material in the catalyst provided by this invention not only possesses an octahedral morphology, but the octahedral aggregates are also formed by the aggregation of microspheres. The microsphere morphology of the MOF material exposes more active sites, increasing the contact area between the active sites and reactants, enhancing reactant adsorption. Furthermore, under illumination, the MOF material generates photogenerated carriers, which react with the solvent to generate active free radicals. These active free radicals attack the carbonyl groups in the polyester, thereby achieving polyester degradation and improving polyester conversion rate. Mixing the MOF material with a binder allows the binder and ligands in the MOF material to enhance the catalyst's stability, effectively inhibiting catalyst degradation and loss of active sites, extending the catalyst's lifespan and activity, and improving catalyst performance.

[0027] In this invention, the term "regular octahedron" has a broad meaning, including both regular octahedrons and quasi-regular octahedrons.

[0028] In this invention, the term "octahedral aggregate obtained by microsphere aggregation" has a broad meaning, and it is not required that all primary particles be microspheres. A scheme in which more than 90% of the primary particles are microspheres is also within the scope of protection of this invention.

[0029] In this invention, the octahedral aggregate obtained by microsphere aggregation means that the metal-organic framework material has secondary particles formed by the aggregation of primary microsphere particles, and the secondary particles are in the shape of octahedrons.

[0030] In this invention, the morphology of the metal-organic framework material, the edge length of the octahedral aggregates, and the diameter of the microspheres are obtained by SEM characterization. Specifically, the edge length of the octahedral aggregates and the diameter of the microspheres in 50 different regions of the material are statistically analyzed using 20 SEM images, and then the average value is calculated.

[0031] According to the present invention, preferably, based on the total amount of catalyst, the content of the metal-organic framework material is 55-98% by weight, more preferably 60-95% by weight, and even more preferably 65-80% by weight; the content of the binder is 2-45% by weight, more preferably 5-40% by weight, and even more preferably 20-35% by weight.

[0032] The preferred embodiments described above are more conducive to improving the service life and stability of the catalyst.

[0033] In this invention, the content of metal-organic framework materials and binders in the catalyst is obtained by X-ray fluorescence spectroscopy analysis.

[0034] The present invention does not particularly limit the type of binder, as long as it can improve the stability of the catalyst. Those skilled in the art can select according to actual needs. Preferably, the binder is an aluminum-based binder, and more preferably, it is alumina.

[0035] In this invention, aluminum-based binders are preferred, as they are more conducive to the bonding of aluminum with ligands in metal-organic framework materials, extending the lifespan and activity of the catalyst, and improving the conversion rate of polyester and the yield of photocatalytic ammonia synthesis.

[0036] According to the present invention, preferably, the specific surface area of ​​the catalyst is 50 to 450 cm². 2 / g, more preferably 300-450cm 2 / g.

[0037] The specific surface area of ​​the catalyst described in this invention was obtained by nitrogen adsorption-desorption experiments. The methods for measuring specific surface area are well known to those skilled in the art, and will not be described in detail here.

[0038] The present invention does not particularly limit the particle size distribution of the catalyst, as long as it can meet the requirements of the catalytic reaction. Those skilled in the art can select according to actual needs. Preferably, the particle size distribution of the catalyst is 0.09-4 mm, and more preferably 0.5-1 mm.

[0039] In this invention, the particle size distribution of the catalyst is obtained by sieving.

[0040] The present invention does not particularly limit the shape of the catalyst, as long as it can meet the requirements of the catalytic reaction. Those skilled in the art can select according to actual needs. Preferably, the shape of the catalyst is at least one of spherical, cylindrical, flake and strip, and more preferably spherical.

[0041] According to a preferred embodiment of the present invention, the metal in the metal-organic framework material is Fe.

[0042] The present invention allows for a wide range of selections of organic ligands in the metal-organic framework material. Preferably, the organic ligands in the metal-organic framework material are selected from at least one of terephthalic acid, 2-aminoterephthalic acid, 2,4-diaminoterephthalic acid, 2-hydroxyterephthalic acid, 2,4-dihydroxyterephthalic acid, 2-carboxyterephthalic acid, and 2,4-dicarboxyterephthalic acid. More preferably, at least one of terephthalic acid, 2-aminoterephthalic acid, and 2,4-diaminoterephthalic acid is selected, and more preferably, terephthalic acid and / or 2-aminoterephthalic acid is selected.

[0043] According to a preferred embodiment of the present invention, the metal-organic framework material is at least one of MIL-101(Fe), MIL-53(Fe), and MIL-88(Fe). The above-mentioned structure of the metal-organic framework material can be confirmed by XRD. The confirmation of the structures of MIL-101(Fe), MIL-53(Fe), and MIL-88(Fe) is well known to those skilled in the art and will not be described in detail here.

[0044] According to a preferred embodiment of the present invention, Fe is present in the metal-organic framework material. II and Fe III Two forms, of which Fe II Fe III The ratio is 1:100 to 100:1, preferably 1:4 to 4:1, and more preferably 1:2 to 2:1. This preferred embodiment is more conducive to the exposure of active sites and the stability of the framework structure.

[0045] In this invention, Fe II This refers to ferrous iron, Fe. III This refers to ferric iron (Fe3+). II and Fe III The presence and ratio of Fe2p were determined by XPS characterization; specifically, Fe2p orbitals in high-resolution Fe2p orbital XPS spectra were detected using X-ray photoelectron spectroscopy. 1 / 2 and Fe 2p 3 / 2 The presence of the peak proves that Fe II and Fe III The presence of Fe; calculated in high-resolution Fe 2p orbital XPS spectra. II and Fe III The corresponding peak area S FeII and S FeIII Calculate S FeII / S FeIII Fe II and Fe III The ratio of .

[0046] According to the present invention, preferably, the specific surface area of ​​the metal-organic framework material is 50-500 cm². 2 / g, preferably 300-500cm 2 / g, more preferably 400-500cm 2 / g. The specific surface area described in this invention was obtained by nitrogen adsorption-desorption experiment. The method for testing specific surface area is well known to those skilled in the art, and will not be described in detail here.

[0047] The present invention does not impose any particular limitation on the preparation method of the catalyst, as long as the above-mentioned product can be obtained.

[0048] A second aspect of the present invention provides a method for preparing the catalyst described in the first aspect, wherein the method includes the following steps:

[0049] The metal-organic framework material is mixed with a binder and / or a binder precursor, optionally shaped, and then calcined.

[0050] According to the present invention, preferably, the amount of metal-organic framework material and binder and / or binder precursor is such that the content of metal-organic framework material in the prepared catalyst is 55-98% by weight, more preferably 60-95% by weight, and even more preferably 65-80% by weight; and the content of binder is 2-45% by weight, more preferably 5-40% by weight, and even more preferably 20-35% by weight.

[0051] In this invention, the binder precursor refers to a substance that can be converted into the binder through a subsequent calcination step. Those skilled in the art, knowing the types of binders, know which binder precursor to choose.

[0052] The present invention does not particularly limit the types of binders and binder precursors, as long as they can improve the stability of the catalyst, and can be conventional choices in the art. Preferably, the binder and / or binder precursor is selected from at least one of alumina, boehmite, kaolinite, dickite, perlite, refractory stone and halloysite, more preferably alumina.

[0053] In this invention, the adhesive or adhesive precursor can be commercially available or prepared using methods known in the art.

[0054] In this invention, "optional" means that those skilled in the art can select the molding method of the catalyst according to actual needs. According to a preferred embodiment of the present invention, the molding method is ball forming.

[0055] This invention does not particularly limit the specific implementation method of the spheroidizing process, as long as the catalyst can be shaped. Those skilled in the art can choose according to actual needs. Preferably, this invention involves placing the catalyst in a rotating device and spraying water while it is rolling to cause the catalyst to adhere and agglomerate into small balls. Based on the total amount of catalyst, the amount of water used is 2-20% by weight, more preferably 5-15% by weight.

[0056] The present invention does not particularly limit the equipment for spherical forming, as long as it can form the catalyst. Those skilled in the art can select according to actual needs, such as at least one of a turntable, a sugar coating pan and a roller.

[0057] The present invention also includes sieving the catalyst after spheroidization.

[0058] In this invention, preferably, the method further includes drying after molding.

[0059] This invention does not impose any particular requirements on the mixing method, as long as it facilitates thorough mixing of the metal-organic framework material with the binder and / or binder precursor. Those skilled in the art can select the appropriate method based on actual needs. Preferably, the mixing conditions include: a mixing time of 0.5–48 h, more preferably 12–24 h; and a mixing temperature of 0–50 °C, more preferably 20–30 °C.

[0060] According to the present invention, preferably, the drying conditions include: a drying time of 0.5 to 48 hours, more preferably 12 to 24 hours; and a drying temperature of 50 to 150°C, more preferably 100 to 120°C.

[0061] According to the present invention, preferably, the calcination conditions include: a calcination temperature of 200–420°C, more preferably 250–350°C; and a calcination time of 2–12 h, more preferably 6–10 h.

[0062] This invention does not particularly limit the preparation method of the metal-organic framework material, as long as the product with the above-described morphology can be obtained. According to a specific embodiment of this invention, preferably, the preparation method of the metal-organic framework material includes:

[0063] (1) Mix alcohol compounds with organic solvents at a volume ratio of 1:8 to 100 to obtain a mixed solvent;

[0064] (2) The mixed solvent is mixed with the organic ligand and the metal precursor to obtain a precursor solution;

[0065] (3) Crystallize the precursor solution.

[0066] The inventors of this invention accidentally discovered during their research that mixing alcohol compounds with organic solvents in a specific volume ratio, and then adding organic ligands and metal precursors, could prepare metal-organic framework materials with specific morphologies.

[0067] In this invention, the organic solvent refers to various organic solvents conventionally used in the synthesis of metal-organic framework materials, excluding alcohols. Preferably, the organic solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, and N,N-diethylacetamide, and more preferably N,N-dimethylformamide.

[0068] This invention allows for a wide range of selection of alcohol compounds. Preferably, the alcohol compounds are selected from C1-C5 alcohols. The alcohols can be monohydric or dihydric. According to a preferred embodiment of the invention, the alcohol compounds are selected from at least one of methanol, ethanol, ethylene glycol, and isopropanol, preferably methanol and / or ethylene glycol, and more preferably ethylene glycol. This preferred embodiment is more conducive to the competitive adsorption of alcohol compounds and organic ligands, thereby forming octahedral aggregates.

[0069] According to the present invention, preferably, the volume ratio of the alcohol compound to the organic solvent is 1:25 to 3:50. Using the volume ratio of the alcohol compound to the organic solvent within the above-preferred range is more conducive to preparing metal-organic framework materials with better catalytic performance.

[0070] Preferably, the mixing conditions in step (1) include: a mixing temperature of 10-80°C, more preferably 20-30°C, and even more preferably 25-30°C; and a mixing time of 10-120 min, more preferably 20-40 min, and even more preferably 15-25 min.

[0071] The present invention does not have any particular limitation on the specific mixing method of the mixed solvent, organic ligand and metal precursor in step (2), as long as the three are mixed evenly. In order to further improve the catalytic performance of the prepared material, preferably, step (2) includes: mixing the mixed solvent and organic ligand in a first mixing to obtain an organic ligand solution; and then mixing the organic ligand solution with the metal precursor in a second mixing to obtain the precursor solution.

[0072] The present invention allows for a wide range of choices regarding the amount of organic ligands and metal precursors to be added, and those skilled in the art can make adaptive choices based on specific needs to prepare metal-organic framework materials.

[0073] Preferably, the concentration of the organic ligand in the organic ligand solution is 3-15 g / L, more preferably 3.6-14.5 g / L, and most preferably 10.2-12.5 g / L.

[0074] Preferably, the concentration of the metal precursor in the precursor solution is 3-40 g / L, more preferably 3.3-38.9 g / L, and most preferably 20.5-25.5 g / L.

[0075] Preferably, the metal precursor is selected from at least one of anhydrous ferric chloride, ferric chloride hexahydrate, and ferric nitrate nonahydrate.

[0076] The first mixing in this invention only requires that the organic ligand dissolves in the mixed solvent. Preferably, the conditions for the first mixing include: a mixing temperature of 10–80°C, more preferably 20–30°C, and even more preferably 25–30°C; and a mixing time of 10–120 min, more preferably 20–40 min, and even more preferably 15–25 min.

[0077] In the method provided by this invention, the range of organic ligands selected is the same as that described in the first aspect above, and will not be repeated here.

[0078] The second mixing in this invention only requires that the metal precursor and the organic ligand solution be mixed uniformly. Preferably, the conditions for the second mixing include: a mixing temperature of 10–80°C, more preferably 20–30°C, and even more preferably 25–30°C; and a mixing time of 10–120 min, more preferably 50–100 min, and even more preferably 50–70 min.

[0079] The crystallization step (3) of this invention allows the metal precursor to react with the organic ligand to prepare a metal-organic framework material. The crystallization conditions are designed to produce the product with the aforementioned morphology. Preferably, the crystallization conditions include: a crystallization temperature of 120–180°C, more preferably 140–160°C, and even more preferably 145–155°C; and a crystallization time of 4–72 h, more preferably 10–48 h, and even more preferably 12–24 h.

[0080] According to a specific embodiment of the present invention, the method further includes a separation and drying step after crystallization in step (3), wherein the separation and drying can be carried out using conventional techniques in the art. Preferably, the separation is centrifugal separation, the centrifugation speed is preferably 4000-10000 r / min, more preferably 8000-12000 r / min; the centrifugation time is preferably 1-20 min, more preferably 5-10 min. The drying temperature is preferably 60-120℃, more preferably 90-110℃; the drying time is preferably 3-30 h, more preferably 20-24 h.

[0081] The third aspect of the present invention provides the application of the catalyst described in the first aspect or the catalyst prepared by the preparation method described in the second aspect in polyester degradation, preferably photocatalytic degradation of polyester or photocatalytic nitrogen fixation.

[0082] The catalyst provided by this invention exhibits excellent catalytic performance in polyester degradation or photocatalytic nitrogen fixation. It offers the advantage of high polyester conversion rate in polyester degradation and high ammonia synthesis yield in photocatalytic nitrogen fixation.

[0083] This invention does not impose any particular limitations on the specific application methods and conditions for polyester degradation or photocatalytic nitrogen fixation, and can be carried out in accordance with conventional technical means in this field.

[0084] Preferably, the polyester degradation is either thermocatalytic degradation or photocatalytic degradation, more preferably photocatalytic degradation. The material provided by this invention is more suitable for the photocatalytic degradation of polyester.

[0085] The present invention will be described in detail below through embodiments. In the following embodiments, the characterization methods of XRD, SEM, and XPS are as described above and will not be repeated here.

[0086] In the following examples and comparative examples, the characterization methods for the content of metal-organic framework materials and binders in the catalyst, the specific surface area of ​​the catalyst, and the particle size distribution of the catalyst are as described above, and will not be repeated here.

[0087] In the following examples and comparative examples, the catalyst is spherical in shape.

[0088] Example 1

[0089] (1) Under stirring conditions, 2.5 mL of ethylene glycol and 42.5 mL of N,N-dimethylformamide were added to a glass and stirred at 25°C for 20 min.

[0090] (2) Add 0.498 g of terephthalic acid to the above mixed solvent and continue stirring at 25°C for 20 min.

[0091] (3) Add 0.973 g of anhydrous ferric chloride to the above solution and continue stirring at 25 °C for 60 min. Then transfer the stirred solution to a reaction vessel and heat at 150 °C for 24 h. Centrifuge the product at 10000 r / min for 8 min. Dry the obtained solid product at 100 °C for 24 h.

[0092] SEM images of the prepared metal-organic framework materials are shown below. Figure 1 XRD pattern can be found Figure 2 .from Figure 1As can be seen, the metal-organic framework material prepared in this embodiment has an octahedral aggregate morphology, and the octahedral aggregates are formed by the aggregation of microspheres. The morphological characteristics of the metal-organic framework material and the morphology of Fe obtained by SEM characterization are listed in Table 1. Figure 2 It can be seen that the metal-organic framework material prepared in this embodiment is MIL-101(Fe).

[0093] (4) The prepared metal-organic framework material was mixed evenly with alumina, wherein the content of metal-organic framework material was 70% by weight and the content of alumina was 30% by weight. Then, the mixture was rolled into balls, and the particle size distribution of the catalyst was 0.85-1.00 mm. The mixture was dried at 120°C for 12 h and finally calcined at 250°C for 12 h. The relevant parameters of the metal-organic framework material are shown in Table 1, and the other parameters of the catalyst are shown in Table 2.

[0094] Example 2

[0095] The catalyst was prepared according to the method of Example 1, except that the volume of ethylene glycol added in step (1) was 2 mL. The morphology of the metal-organic framework material and the morphology of Fe, as well as the parameters of other metal-organic framework materials, obtained by SEM characterization, are shown in Table 1, and the remaining parameters of the catalyst are shown in Table 2.

[0096] Example 3

[0097] The catalyst was prepared according to the method of Example 1, except that in step (1), ethylene glycol was replaced with an equal volume of methanol. The morphology of the metal-organic framework material and the morphology of Fe, as well as the parameters of other metal-organic framework materials, obtained by SEM characterization, are shown in Table 1, and the remaining parameters of the catalyst are shown in Table 2.

[0098] Example 4

[0099] Metal-organic framework materials were prepared according to the method of Example 1, except that the mass of terephthalic acid added in step (2) was 0.597 g. The morphological characteristics of the metal-organic framework materials obtained by SEM characterization, the morphology of Fe, and other parameters of the metal-organic framework materials are shown in Table 1, and the remaining parameters of the catalyst are shown in Table 2.

[0100] Example 5

[0101] Metal-organic framework materials were prepared according to the method of Example 1, except that the solvothermal temperature (crystallization temperature) in step (3) was 130°C. The morphological characteristics of the metal-organic framework materials obtained by SEM characterization, the morphology of Fe, and other parameters of the metal-organic framework materials are shown in Table 1, and the remaining parameters of the catalyst are shown in Table 2.

[0102] Example 6

[0103] Metal-organic framework materials were prepared according to the method of Example 1, except that in step (2), terephthalic acid was replaced with 0.543 g of 2-amino-terephthalic acid. The morphological characteristics of the metal-organic framework materials obtained by SEM characterization, the morphology of Fe, and other parameters of the metal-organic framework materials are shown in Table 1, and the remaining parameters of the catalyst are shown in Table 2.

[0104] Example 7

[0105] The method of Example 1 was followed, except that in step (1), the amount of N,N-dimethylformamide used was 37.5 mL. The morphological characteristics of the metal-organic framework material and the morphology of Fe, as well as other parameters of the metal-organic framework material, obtained by SEM characterization, are shown in Table 1, and the remaining parameters of the catalyst are shown in Table 2.

[0106] Example 8

[0107] The method is the same as in Example 1, except that the amount of terephthalic acid added in step (2) is 0.675 g, and the amount of anhydrous ferric chloride added in step (3) is 1.8 g. The morphological characteristics of the metal-organic framework material and the morphology of Fe obtained by SEM characterization, as well as the parameters of other metal-organic framework materials, are shown in Table 1, and the remaining parameters of the catalyst are shown in Table 2.

[0108] Example 9

[0109] The method is the same as in Example 1, except that in step (4), the content of the metal-organic framework is 95% by weight and the content of alumina is 5% by weight. The remaining parameters of the catalyst are shown in Table 2.

[0110] Example 10

[0111] The method is the same as in Example 1, except that in step (4), the content of the metal-organic framework is 55% by weight and the content of alumina is 45% by weight. The remaining parameters of the catalyst are shown in Table 2.

[0112] Example 11

[0113] The method is the same as in Example 1, except that in step (4), alumina is replaced with an equal amount of boehmite (calculated as alumina). The remaining parameters of the catalyst are shown in Table 2.

[0114] Example 12

[0115] The catalyst was prepared according to the method of Example 1, except that the catalyst particle size distribution in step (4) was 3.35-4.00 mm. The remaining parameters of the catalyst are shown in Table 2.

[0116] Comparative Example 1

[0117] The catalyst was prepared according to the method of Example 1, except that ethylene glycol was not added in step (1) and zirconium chloride was added in step (3). The metal-organic framework material prepared was UiO-66. The morphology of the metal-organic framework material obtained by SEM characterization was octahedral, with a smooth surface and no microsphere structure. The parameters of other metal-organic framework materials are shown in Table 1, and the remaining parameters of the catalyst are shown in Table 2.

[0118] Comparative Example 2

[0119] The catalyst was prepared according to the method of Example 1, except that the solvothermal temperature in step (3) was 110°C. The metal-organic framework material prepared was MIL-101. The morphology of the metal-organic framework material obtained by SEM characterization was octahedral, with a smooth surface and no microsphere structure. The morphology of Fe and other parameters of the metal-organic framework material are shown in Table 1. The remaining parameters of the catalyst are shown in Table 2.

[0120] Comparative Example 3

[0121] The catalyst was prepared according to the method of Example 1, except that in step (1), only 42.5 mL of N,N-dimethylformamide was added and no alcohol compound was added, and in step (3), after anhydrous ferric chloride was stirred evenly, 2.5 mL of ethylene glycol was added, and stirring was continued at 25 °C for 60 min. The metal-organic framework material prepared in this way was MIL-101(Fe). The morphology of the metal-organic framework material was characterized by SEM. The morphology was spindle-shaped with a major axis of 2 μm and a minor axis of 0.5 μm. The surface was smooth and there was no microsphere structure. The morphology of Fe and the parameters of other metal-organic framework materials are shown in Table 1, and the remaining parameters of the catalyst are shown in Table 2.

[0122] Comparative Example 4

[0123] The method of Example 1 was followed, except that ethylene glycol was not added in step (1). The metal-organic framework material prepared in this way was MIL-101(Fe). The morphology of the metal-organic framework material obtained by SEM characterization was octahedral, with a smooth surface and no microsphere structure. The morphology of Fe and the parameters of other metal-organic framework materials are shown in Table 1, and the remaining parameters of the catalyst are shown in Table 2.

[0124] Comparative Example 5

[0125] The catalyst was prepared according to the method of Example 1, except that in step (1), ethylene glycol was replaced with an equal amount of acetic acid. The metal-organic framework material prepared was MIL-101(Fe). The morphological characteristics of the metal-organic framework material and the morphology of Fe, as well as the parameters of other metal-organic framework materials, obtained by SEM characterization, are shown in Table 1, and the remaining parameters of the catalyst are shown in Table 2.

[0126] Table 1

[0127]

[0128] Note: Fe in Table 1 of this invention II Fe III A value of 0 indicates that the catalyst contains only Fe. III In Table 1 of this invention, " / " indicates that the catalyst does not contain this feature.

[0129] Table 2

[0130]

[0131] Test Example 1

[0132] This test example uses a temperature-controlled reactor to determine the polyester conversion rate of the catalysts prepared in the above examples and comparative examples. The reactor consists of a heating platform, reaction vessel, thermometer, pressure control valve, circulating water jacket, xenon lamp head, and xenon lamp power supply. The reaction vessel is made of stainless steel and has a sapphire skylight at the top, with a thickness of 1 cm. The polyester reaction evaluation method is as follows: 2g of polyester, 0.2g of catalyst, and 100g of water are added to the reaction vessel; stirring is started and the stirring speed is increased to 300 rpm; then the system temperature is increased to 25°C; and the system pressure is increased to 1 MPa. The xenon lamp power supply is turned on, and the xenon lamp head is directed at the skylight of the reaction vessel, with a xenon lamp density of 750 mW / cm³. 2 (mW / cm³), the light source was full-spectrum light with wavelengths of 200-800nm. After reacting for 2 hours, the reaction solution was collected, filtered using Ф7 medium-speed qualitative filter paper, washed and filtered with 50g / L sodium hydroxide solution, and then washed and filtered with deionized water. The filtered product was dried in an oven at 100℃ for 24 hours, and finally the mass of the solid product was weighed. The polyester conversion rate was calculated using the following formula:

[0133]

[0134] Where, m A m represents the total mass of the catalyst and polyester before the reaction. B This represents the total mass of the dried catalyst and polyester after the reaction.

[0135] The stability of the catalyst was tested through a cyclic experiment. The specific method was as follows: a catalytic cycle was defined as 2 hours. After one catalytic cycle, the catalyst was filtered using Ф7 medium-speed qualitative filter paper, washed and filtered with 50 g / L sodium hydroxide solution, and then washed and filtered again with deionized water to separate the catalyst. Then, the raw material was added for the next reaction cycle. After 10 cycles, the polyester conversion rate was measured, and the results are listed in Table 3 below.

[0136] Table 3

[0137]

[0138]

[0139] Test Example 2

[0140] This test example uses a temperature-controlled reactor to determine the ammonia synthesis yield of the catalysts prepared in the examples and comparative examples. The reactor consists of a heating platform, reaction vessel, thermometer, pressure control valve, circulating water jacket, xenon lamp head, and xenon lamp power supply. The reaction vessel is made of stainless steel and has a sapphire skylight at the top, with a thickness of 1 cm. The nitrogen fixation reaction evaluation method is as follows: 0.2 g of catalyst and 100 g of water are added to the reaction vessel, nitrogen gas is introduced, and the system pressure is increased to 1 MPa using nitrogen gas. The stirring speed is increased to 300 r / min; then the system temperature is increased to 25°C. The xenon lamp power supply is turned on, and the xenon lamp head is directed towards the skylight of the reaction vessel, with a xenon lamp density of 750 mW / cm³. 2 (mW / cm³), the light source is full-spectrum light with wavelengths of 200-800nm. After reacting for 2 hours, the reaction solution is collected and filtered using a 0.22μm water-based syringe filter. The catalyst-removed reaction solution is then analyzed by ion chromatography, and the ammonia production is calculated by calculating the peak area. The ammonia synthesis yield is calculated using the following formula:

[0141]

[0142] Where, n NH3 The reaction time is t, where m represents the amount of ammonia produced, t represents the mass of catalyst added, and t represents the reaction time. The stability of the catalyst was tested through a cyclic experiment. Specifically, each catalytic cycle lasted 2 hours. After each cycle, the catalyst was filtered using Ф7 medium-speed qualitative filter paper, washed and filtered with 50 g / L sodium hydroxide solution, and then washed and filtered again with deionized water to separate the catalyst. The starting material was then added for the next reaction cycle. After 10 cycles, the ammonia yield was measured, and the results are shown in Table 4 below.

[0143] Table 4

[0144] serial number <![CDATA[Synthesis ammonia yield, μmol g -1 h -1 > <![CDATA[Synthesis ammonia yield after 10 cycles, μmol g -1 h -1 > Example 1 217 198 Example 2 201 182 Example 3 182 163 Example 4 174 155 Example 5 163 141 Comparative Example 1 67 34 Comparative Example 2 52 21

[0145] The results in the table above show that, compared with the comparative example, the examples using the catalyst provided by this invention exhibit higher polyester conversion and ammonia synthesis yield, longer catalyst lifespan, higher activity, and better stability. This indicates that the metal-organic framework material with an octahedral aggregate morphology, composed of microspheres, prepared by this invention, when mixed with a binder, can significantly promote the generation of photogenerated carriers and increase the contact area between the catalyst and the polyester raw material during the reaction. When applied to photocatalytic nitrogen fixation, the surface microspheres of the metal-organic framework material increase the incident light absorption area, enhancing the generation of photogenerated carriers and thus improving the photocatalytic ammonia synthesis yield. The introduction of the binder enhances the catalyst's stability, effectively inhibiting catalyst degradation and loss of active sites, extending the catalyst's lifespan and activity, and improving its performance. This solves the problems of short catalyst lifespan, low activity, insufficient exposure of surface active sites, low polyester conversion, and low photocatalytic ammonia synthesis yield.

[0146] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A catalyst, characterized in that, The catalyst comprises a metal-organic framework material and a binder; The metal-organic framework material has an octahedral aggregate morphology, the edge length of the octahedral aggregate is 0.5 to 2 μm, the octahedral aggregate is obtained by the aggregation of microspheres, and the diameter of the microspheres is 20 to 100 nm.

2. The catalyst according to claim 1, wherein, Based on the total amount of catalyst, the content of the metal-organic framework material is 55-98% by weight, preferably 60-95% by weight, more preferably 65-80% by weight; the content of the binder is 2-45% by weight, preferably 5-40% by weight, more preferably 20-35% by weight. Preferably, the adhesive is an aluminum-based adhesive, and more preferably aluminum oxide; And / or, the specific surface area of ​​the catalyst is 50–450 cm². 2 / g, preferably 300-450cm 2 / g; And / or, the particle size distribution of the catalyst is 0.09–4 mm, preferably 0.5–1 mm; Preferably, the catalyst is at least one of spherical, cylindrical, flake, and strip shapes, with spherical being the most preferred.

3. The catalyst according to claim 1 or 2, wherein, The edge length of the octahedral aggregate is 1 to 1.5 μm, preferably 1 to 1.2 μm; And / or, the diameter of the microspheres is 40-80 nm, preferably 50-60 nm; And / or, the metal in the metal-organic framework material is Fe; The organic ligand in the metal-organic framework material is selected from at least one of terephthalic acid, 2-aminoterephthalic acid, 2,4-diaminoterephthalic acid, 2-hydroxyterephthalic acid, 2,4-dihydroxyterephthalic acid, 2-carboxyterephthalic acid, and 2,4-dicarboxyterephthalic acid, preferably at least one of terephthalic acid, 2-aminoterephthalic acid, and 2,4-diaminoterephthalic acid; Preferably, the metal-organic framework material is at least one of MIL-101(Fe), MIL-53(Fe), and MIL-88(Fe).

4. The catalyst according to any one of claims 1-3, wherein, The metal-organic framework material contains Fe. II and Fe III Two forms, of which Fe II Fe III The ratio is 1:100 to 100:1, preferably 1:4 to 4:1, and more preferably 1:2 to 2:1; And / or, the specific surface area of ​​the metal-organic framework material is 50–500 cm². 2 / g, preferably 300-500cm 2 / g.

5. A method for preparing the catalyst according to any one of claims 1-4, wherein, The method includes the following steps: The metal-organic framework material is mixed with a binder and / or a binder precursor, optionally shaped, and then calcined.

6. The preparation method according to claim 5, wherein, The amount of metal-organic framework material and binder and / or binder precursor in the prepared catalyst is such that the content of metal-organic framework material in the prepared catalyst is 55-98% by weight, preferably 60-95% by weight, more preferably 65-80% by weight; and the content of binder is 2-45% by weight, preferably 5-40% by weight, more preferably 20-35% by weight. And / or, the binder and / or binder precursor is selected from at least one of alumina, boehmite, kaolinite, dickite, perlite, refractory stone and halloysite, preferably alumina; And / or, the method further includes drying after molding; And / or, the forming method is ball forming; And / or, the mixing conditions include: a mixing time of 0.5 to 48 hours; and a mixing temperature of 0 to 50°C. And / or, the drying conditions include: a drying time of 0.5 to 48 hours; and a drying temperature of 50 to 150°C. And / or, the calcination conditions include: a calcination temperature of 200–420°C, preferably 250–350°C; and a calcination time of 2–12 h, preferably 6–10 h.

7. The preparation method according to claim 5 or 6, wherein, The preparation method of the metal-organic framework material includes: (1) Mix alcohol compounds with organic solvents at a volume ratio of 1:8 to 100 to obtain a mixed solvent; (2) The mixed solvent is mixed with the organic ligand and the metal precursor to obtain a precursor solution; (3) Crystallize the precursor solution.

8. The preparation method according to claim 7, wherein, The alcohol compound is selected from C1-C5 alcohols, preferably selected from at least one of methanol, ethanol, ethylene glycol and isopropanol, more preferably methanol and / or ethylene glycol, and most preferably ethylene glycol; And / or, the organic solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide and N,N-diethylacetamide, preferably N,N-dimethylformamide; Preferably, the volume ratio of the alcohol compound to the organic solvent is 1:25 to 3:50; Preferably, the mixing conditions in step (1) include: a mixing temperature of 10-80°C, preferably 20-30°C, more preferably 25-30°C; and a mixing time of 10-120 min, preferably 20-40 min, more preferably 15-25 min. And / or, the crystallization conditions include: a crystallization temperature of 120–180°C and a crystallization time of 4–72 h.

9. The preparation method according to claim 7, wherein, Step (2) includes: first mixing the mixed solvent with the organic ligand to obtain an organic ligand solution; then second mixing the organic ligand solution with the metal precursor to obtain the precursor solution; Preferably, the concentration of the organic ligand in the organic ligand solution is 3–15 g / L; Preferably, the concentration of the metal precursor in the precursor solution is 3-40 g / L; Preferably, the metal precursor is selected from at least one of anhydrous ferric chloride, ferric chloride hexahydrate, and ferric nitrate nonahydrate; Preferably, the conditions for the first mixing include: a mixing temperature of 10–80°C and a mixing time of 10–120 min; Preferably, the conditions for the second mixing include: a mixing temperature of 10–80°C and a mixing time of 10–120 min.

10. The application of the catalyst according to any one of claims 1-4 or the catalyst prepared by any one of claims 5-9 in polyester degradation, preferably photocatalytic degradation of polyester or photocatalytic nitrogen fixation.

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