A catalyst for preparing fructose from glucose isomerization and its preparation method and application

Abstract

The application discloses a catalyst for preparing fructose from glucose isomerization and a preparation method and application thereof, and belongs to the technical field of catalysts. The preparation method of the catalyst for preparing fructose from glucose isomerization comprises the following steps: dispersing a molecular sieve into a solution of a first template agent, adding a solution of a first metal salt and a solution of a second metal salt, aging, and obtaining a gel precursor; dispersing a molecular sieve seed in a second template agent to form a suspension, adding the suspension into the gel precursor, and hydrothermally crystallizing to obtain a crystallized precursor; and calcining the crystallized precursor to obtain the catalyst for preparing fructose from glucose isomerization. The application can solve the technical problems of low glucose conversion rate, low fructose selectivity and low yield of the existing catalyst.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to a catalyst for the isomerization of glucose to fructose, its preparation method, and its application. Background Technology

[0002] The isomerization of glucose to fructose is an important reaction in biomass conversion and utilization. Fructose can be further converted into high-value chemicals such as hydroxymethylfurfural and lactic acid. Traditionally, glucose isomerase catalysis is used in industry, but enzymatic methods suffer from harsh reaction conditions, easy enzyme inactivation, and difficulties in product separation. In chemical catalysis, homogeneous alkaline catalysts exhibit numerous side reactions, corrode equipment, and cannot be recovered.

[0003] In recent years, heterogeneous catalysts, especially metal catalysts supported on molecular sieves, have attracted widespread attention. Studies have shown that metal-modified molecular sieves such as Sn and Mg, which possess Lewis acidity, can effectively catalyze the isomerization of glucose to fructose. However, existing preparation methods mostly employ impregnation or ion exchange methods, which suffer from problems such as low metal dispersion, easy aggregation, and uneven distribution of active sites. Furthermore, these methods tend to promote glucose degradation, resulting in low glucose conversion rates, fructose selectivity, and yields. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned technical deficiencies and propose a catalyst for the isomerization of glucose to fructose, its preparation method and application, aiming to solve the technical problems of low glucose conversion rate, low fructose selectivity and low yield of existing catalysts.

[0005] To achieve the above-mentioned technical objectives, a first aspect of the present invention provides a method for preparing a catalyst for the isomerization of glucose to fructose. The method comprises the following steps: dispersing a molecular sieve in a solution of a first template agent, adding a solution of a first metal salt and a solution of a second metal salt, aging the mixture to obtain a gel precursor; dispersing molecular sieve seed crystals in a second template agent to form a suspension, adding the suspension to the gel precursor, and hydrothermally crystallizing the suspension to obtain a crystallized precursor; and calcining the crystallized precursor to obtain the catalyst for the isomerization of glucose to fructose.

[0006] In some embodiments, the silica-to-alumina ratio of the molecular sieve is ≥150; and / or, the molecular sieve includes one or more of ZSM-5 molecular sieve, MCM-22 molecular sieve, Beta molecular sieve, and all-silica molecular sieve; and / or, the first template agent and the second template agent each independently include one or more of tetrapropylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium bromide, and hexamethyleneimine; and / or, the molar ratio of the first template agent to silicon in the molecular sieve is (0.1~0.8):1.

[0007] In some embodiments, the first metal salt includes one or more of tin salt, platinum salt, and lithium salt; and / or, the second metal salt includes one or more of magnesium salt, antimony salt, and indium salt; and / or, the molar ratio of the first metal salt to the second metal salt is 1:5 to 5:1; and / or, the sum of the masses of the first metal salt and the second metal salt as metal oxides is a, the mass of the molecular sieve as SiO2 is b, and a / b×100%=0.5‰ to 10‰.

[0008] In some embodiments, the first metal salt includes one or more of tin chloride, chloroplatinic acid, and lithium chloride; and / or, the second metal salt includes one or more of magnesium nitrate, antimony chloride, and indium chloride; and / or, the aging time is 6h to 12h.

[0009] In some embodiments, the molecular sieve seed crystals include one or more of ZSM-5 molecular sieve, MCM-22 molecular sieve, Beta molecular sieve, and all-silica molecular sieve; and / or, the mass of the molecular sieve seed crystals added is 1% to 3% of the mass of the molecular sieve in the gel precursor.

[0010] In some embodiments, the temperature of the hydrothermal crystallization is 150°C to 180°C; and / or, the time of the hydrothermal crystallization is 60h to 120h.

[0011] In some embodiments, the calcination temperature is 500°C to 600°C; and / or the calcination time is 4h to 6h.

[0012] In a second aspect, the present invention provides a catalyst for the isomerization of glucose to fructose, wherein the catalyst is prepared by the method for preparing the catalyst for the isomerization of glucose to fructose described in the first aspect of the present invention.

[0013] In a third aspect of the invention, the invention provides a method for the isomerization of glucose to fructose, wherein the reaction is carried out in the presence of the catalyst for the isomerization of glucose to fructose described in the second aspect of the invention.

[0014] In some embodiments, the reaction temperature is 60°C to 150°C; and / or, the solvent used in the reaction includes one or more of water, methanol, ethanol, and glycerol; and / or, the reactor used in the reaction includes any one of a reaction vessel, a fixed bed, and a slurry bed.

[0015] Compared with the prior art, the beneficial effects of the present invention include: This invention proposes a method for preparing a catalyst for the isomerization of glucose to fructose. Using a molecular sieve as a precursor, hydrothermal crystallization assisted by a template agent introduces two metal salt components. These metal components partially replace the T-sites of the molecular sieve framework via Si-O-Me bonds, or are embedded within the molecular sieve crystals or adjacent to the framework. This results in a bimetallic in-situ doped molecular sieve catalyst with uniform metal dispersion, excellent hydrothermal stability, and abundant catalytic active centers. The prepared catalyst, when applied to the isomerization of glucose to fructose, exhibits advantages such as high metal dispersion, good catalytic activity, and reusability. Compared to catalysts prepared by traditional impregnation methods, the catalyst obtained in this invention demonstrates higher glucose conversion, fructose selectivity, and yield in the isomerization of glucose to fructose, and possesses good reusability and stability, making it suitable for the high-value conversion of biomass sugar platform compounds. Attached Figure Description

[0016] Figure 1 This is a schematic flowchart illustrating the preparation method of the catalyst for the isomerization of glucose to fructose according to an embodiment of the present invention.

[0017] Figure 2 This is the XRD characterization diagram of the catalyst prepared in Example 1 of this invention for the isomerization of glucose to fructose. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] In a first aspect, the present invention provides a method for preparing a catalyst for the isomerization of glucose to fructose. Please refer to [link to relevant documentation]. Figure 1 The method for preparing the catalyst for the isomerization of glucose to fructose includes the following steps: S1. Molecular sieves are dispersed in a solution of the first template agent, and solutions of the first and second metal salts are added. The mixture is then aged to obtain a gel precursor. S2. Disperse molecular sieve seed crystals in the second template agent to form a suspension. Add the suspension to the gel precursor and perform hydrothermal crystallization to obtain the crystallized precursor. S3. The crystallized precursor is calcined to obtain a catalyst for the preparation of fructose from glucose isomerization.

[0020] Therefore, by using molecular sieves as a precursor and employing template-assisted hydrothermal crystallization to introduce two metal salt components, the metal components partially replace the T-sites of the molecular sieve framework via Si-O-Me bonds, or are embedded within the molecular sieve crystals and adjacent to the framework. This yields a bimetallic in-situ doped molecular sieve catalyst with uniform metal dispersion, excellent hydrothermal stability, and abundant catalytic active sites, avoiding agglomeration problems caused by subsequent loading and significantly improving the accessibility and stability of active sites. The prepared catalyst, applied to the isomerization of glucose to fructose, exhibits advantages such as high metal dispersion, good catalytic activity, and reusability. Compared to catalysts prepared by traditional impregnation methods, the catalyst obtained in this invention demonstrates higher glucose conversion rate, fructose selectivity, and yield in the isomerization of glucose to fructose, and possesses good reusability and stability, making it suitable for the high-value conversion of biomass sugar platform compounds.

[0021] Furthermore, before adding the molecular sieve to the gel precursor, it is first dispersed to form a suspension, which can avoid uneven distribution of molecular sieve seeds in the gel precursor. Dispersing the molecular sieve seeds in the second template agent allows the surface of the molecular sieve seeds to fully adsorb the second template agent, effectively avoiding the problem of uneven distribution of molecular sieve seeds in the gel precursor. Combined with static hydrothermal crystallization, a highly active catalyst with uniform grains and few defects can be obtained.

[0022] In some embodiments, the silica-to-alumina ratio of the molecular sieve is ≥150, for example, it can be 150, 160, 170, 180, 190, 200 or any two of the above values. Thus, the high silica-to-alumina ratio of the molecular sieve can avoid residual acidic sites from easily promoting glucose degradation and improve the selectivity and conversion rate of glucose to fructose.

[0023] It can be understood that the silicon-to-aluminum ratio of a molecular sieve refers to the molar ratio of SiO2 / Al2O3 within the molecular sieve framework.

[0024] In some embodiments, the molecular sieve includes one or more of ZSM-5 molecular sieve, MCM-22 molecular sieve, Beta molecular sieve, and all-silica molecular sieve. These molecular sieves exhibit high stability and numerous active sites, which can further enhance the activity of the resulting catalyst for the isomerization of glucose to fructose.

[0025] In some embodiments, the first template agent and the second template agent each independently comprise one or more of tetrapropylammonium hydroxide (TPAOH), tetraethylammonium hydroxide (TEAOH), tetrapropylammonium bromide (TPABr), and hexamethyleneimine (HMI). The aforementioned template agents can further improve the dispersion of the two metals in the molecular sieve, thereby enhancing the activity of the resulting catalyst for the isomerization of glucose to fructose.

[0026] In some embodiments, the solution of the first template agent may be an aqueous solution of the first template agent. The present invention does not limit the concentration; for example, the mass concentration of the first template agent may be 25%.

[0027] In some embodiments, the molar ratio of the first template agent to silicon in the molecular sieve is (0.1~0.8):1. For example, the molar ratio of the first template agent to silicon in the molecular sieve can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, or any range of two of the above values. This can further improve the dispersion of the two metals in the molecular sieve and enhance the activity of the resulting catalyst for the isomerization of glucose to fructose.

[0028] In some embodiments, the first metal salt includes one or more of tin salt, platinum salt, and lithium salt; the second metal salt includes one or more of magnesium salt, antimony salt, and indium salt. Thus, experiments show that the first and second metal salts can provide metal components with synergistic effects (such as combinations of Mg / Sn, Sn / In, Sn / Li, etc.), which can further improve glucose conversion rate, fructose selectivity, and yield.

[0029] Preferably, the first metal salt and the second metal salt are soluble salts.

[0030] Preferably, in some embodiments, the first metal salt includes one or more of tin chloride, chloroplatinic acid, and lithium chloride; the second metal salt includes one or more of magnesium nitrate, antimony chloride, and indium chloride.

[0031] In some embodiments, the molar ratio of the first metal salt to the second metal salt is 1:5 to 5:1. For example, it can be 1:1, 1:3, 1:5, 3:1, 3:5, 5:1, 5:3, or any range of two of the above values. This can further enhance the synergistic effect of the two metal components and further improve the glucose conversion rate, fructose selectivity, and yield.

[0032] In some embodiments, the sum of the masses of the first metal salt and the second metal salt, calculated as metal oxides, is 'a', and the mass of the molecular sieve, calculated as SiO2, is 'b', where a / b × 100% = 0.5‰ to 10‰. For example, a / b × 100% can be 0.5‰, 1‰, 2‰, 3‰, 5‰, 8‰, 10‰, or any range of two of the above values. This can further enhance the synergistic effect of the two metal components, and further improve the glucose conversion rate, fructose selectivity, and yield.

[0033] In some embodiments, the aging time is 6h to 12h. For example, it can be 6h, 7h, 8h, 9h, 10h, 11h, 12h or any two of the above values. This can further ensure that the metal ions are fully dispersed into the molecular sieve, more effectively stabilize the active components and exert the confinement effect, and further improve the glucose conversion rate, fructose selectivity and yield.

[0034] In some embodiments, aging can be a static process.

[0035] In some embodiments, the molecular sieve seed crystals include one or more of ZSM-5 molecular sieves, MCM-22 molecular sieves, Beta molecular sieves, and all-silica molecular sieves. These molecular sieve seed crystals can act as guides, uniformly dispersing in the gel precursor and efficiently inducing the crystallization of the active components in the gel precursor, facilitating the formation of a catalyst with high crystallinity and a complete structure.

[0036] In some embodiments, the molecular sieve seed crystals may be the same as the molecular sieve in the gel precursor.

[0037] In some embodiments, the mass of the added molecular sieve seed crystals is 1% to 3% of the mass of the molecular sieve in the gel precursor. For example, it can be 1%, 2%, 3%, or any combination of two of the above values. Thus, the above-mentioned amount of added molecular sieve seed crystals is more conducive to the formation of a catalyst with high crystallinity and complete structure.

[0038] In some embodiments, the hydrothermal crystallization temperature is 150°C to 180°C. For example, it can be 150°C, 160°C, 170°C, 180°C, or any combination of two of the above values. Thus, the above crystallization temperature is more conducive to forming a catalyst with high crystallinity and complete structure.

[0039] In some embodiments, the hydrothermal crystallization time is 60h to 120h. For example, the crystallization time can be 60h, 70h, 80h, 90h, 100h, 110h, 120h, or any combination of two of the above values. Therefore, within the above-mentioned crystallization time range, it is further beneficial to form a catalyst with high crystallinity and a complete structure.

[0040] In some embodiments, the calcination temperature is 500°C to 600°C, for example, it can be 500°C, 550°C, 600°C or any combination of two of the above values, thereby facilitating the generation of a highly stable catalyst for the isomerization of glucose to fructose and avoiding damage to the catalyst caused by high temperature.

[0041] In some embodiments, the calcination time is 4 to 6 hours. For example, it can be 4 hours, 5 hours, 6 hours, or any combination of two of these values. This facilitates the generation of a highly stable catalyst for the isomerization of glucose to fructose and avoids damage to the catalyst caused by high temperatures.

[0042] In summary, the in-situ synthesis method provided by this invention uses a high silica-to-alumina ratio molecular sieve as a precursor, employs template-assisted hydrothermal crystallization, in-situ loads two synergistic metal components, and optimizes process parameters such as seed dispersion, aging time, and calcination procedure. The prepared catalyst, when applied to the isomerization reaction of glucose to fructose, exhibits advantages such as high metal dispersion, good catalytic activity, and reusability.

[0043] In a second aspect, the present invention provides a catalyst for the isomerization of glucose to fructose, wherein the catalyst is prepared by the method for preparing the catalyst for the isomerization of glucose to fructose described in the first aspect of the present invention.

[0044] Therefore, the catalyst proposed in this invention for the isomerization of glucose to fructose has advantages such as high metal dispersion, good catalytic activity, and reusability. In the glucose isomerization reaction to fructose, it exhibits higher glucose conversion rate, fructose selectivity, and yield, and has good reusability and stability, making it suitable for the high-value conversion of biomass sugar platform compounds.

[0045] In a third aspect of the invention, the invention provides a method for the isomerization of glucose to fructose, wherein the reaction is carried out in the presence of the catalyst for the isomerization of glucose to fructose described in the second aspect of the invention.

[0046] In some embodiments, the reaction temperature is 60°C to 150°C. For example, it can be 60°C, 80°C, 100°C, 120°C, 150°C, or any combination of two of the above values, thereby achieving high glucose conversion rate and high fructose selectivity and yield.

[0047] In some embodiments, the solvent used in the reaction includes one or more of water, methanol, ethanol, and glycerol. Therefore, these solvents are low-cost, easy to recycle, and do not pollute the environment, while achieving high glucose conversion and high fructose selectivity and yield.

[0048] In some embodiments, the reactor used for the reaction includes any one of a reaction vessel, a fixed bed, and a slurry bed.

[0049] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0050] Unless otherwise specified, all raw materials and reagents used in the following examples and comparative examples were purchased from commercially available sources from Raodong New Materials Co., Ltd.

[0051] Example 1 Catalyst preparation: 10g of Beta molecular sieve with a silicon-to-aluminum ratio of 150 was uniformly dispersed in a 25wt% TEAOH aqueous solution (template agent to Si molar ratio 0.5:1). Then, 0.1M Mg(CH2COO)2·4H2O aqueous solution and 0.1M SnCl4 aqueous solution were prepared and added to the above mixture at 3‰ of the total metal content (a / b×100%, Mg:Sn molar ratio 1:1). The mixture was stirred evenly and aged for 8 hours to prepare a gel precursor. Further, 2wt% Beta molecular sieve (with a silicon-to-aluminum ratio of 150) was added as a seed crystal. This seed crystal was pre-soaked in a small amount of TEAOH aqueous solution (TEAOH mass percentage 25%) for 10 minutes followed by stirring for 30 minutes to allow the template agent to be fully adsorbed onto the seed crystal surface. Finally, this seed crystal suspension was slowly added dropwise to the gel precursor under vigorous stirring, and the mixture was crystallized in an autoclave at 160℃ for 110 hours. Finally, the catalyst was filtered, washed, dried, and calcined at 550°C for 5 hours at a rate of 2°C / min to obtain the desired catalyst. Figure 2 The image shows the XRD characterization of the prepared catalyst. Only the characteristic peaks of beta molecular sieves are visible in the image, while the characteristic peaks of tin oxide and magnesium oxide are not. It is speculated that this is because the metals are in situ doped into the framework, thus their characteristic peaks cannot be characterized.

[0052] Catalyst evaluation: 5g of the catalyst prepared in Example 1 was used to evaluate the performance of the glucose isomerization reaction to fructose in a fixed-bed reactor. The reaction temperature was 90℃, the reaction pressure was 1MPa, and the mass hourly space velocity was set to 1.0 h⁻¹. 1 Under certain conditions, a 30% glucose aqueous solution was introduced to carry out an isomerization reaction to obtain glucose / fructose syrup. The product was analyzed by HPLC (high performance liquid chromatography), and the conversion rate and selectivity of glucose and the yield of fructose were calculated. The results are shown in Table 1.

[0053] Example 2 Catalyst preparation: 10 g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 180 was dispersed in a 25 wt% TPAOH solution (template agent to Si molar ratio 0.3:1). A 0.1 M SnCl4 solution was prepared with pure water, and a 0.05 M SbCl3 solution was prepared with 0.1 M dilute nitric acid. These solutions were added to the above mixture at 2‰ of the total metal content (Sn:Sb molar ratio 1:0.5), stirred evenly, and aged for 8 h to prepare a gel precursor. 3 wt% ZSM-5 seed crystals were added. These seed crystals were pre-ultrasonicated in a small amount of TPAOH for 10 min and stirred for 30 min to allow the template agent to be fully adsorbed on the seed crystal surface. Finally, this seed crystal suspension was slowly added dropwise to the gel precursor under vigorous stirring, and crystallized at 165 °C for 96 h. The remaining steps were the same as in Example 1.

[0054] Catalyst evaluation: 100g of glucose was dissolved in 100g of water, and then 134g of ethanol was added to prepare a 30 wt% glucose solution. This solution was then added to a high-pressure reactor, followed by 15g of the catalyst from Example 2. The reactor was sealed, and the temperature was raised. After the temperature inside the reactor reached 100℃ and stabilized, a magnetic stirrer was started at 300 rpm, and the reaction time was initiated. After reacting for 2 hours, the mixture was cooled to room temperature, the pressure was released, and the resulting glucose / fructose syrup was analyzed by liquid chromatography. The results are shown in Table 1.

[0055] Example 3 Catalyst preparation: 10 g of MCM-22 molecular sieve with a silicon-to-aluminum ratio of 200 was dispersed in a 25 wt% HMI solution (template agent to Si molar ratio 0.7:1). A 0.1 M LiNO3 solution was prepared with pure water, and a 0.02 M InCl3·4H2O solution was prepared with 0.1 M dilute hydrochloric acid. The mixture was added at 4‰ of the total metal content (Sb:Li molar ratio 1:1.2), stirred thoroughly, and aged for 8 h to prepare a gel precursor. 1 wt% MCM-22 seed crystals were added. These seed crystals were pre-ultrasonicated in a small amount of HMI for 10 min and stirred for 30 min to ensure sufficient adsorption of the template agent on the seed surface. Finally, this seed crystal suspension was slowly added dropwise to the gel precursor under vigorous stirring. 3 wt% MCM-22 seed crystals were added, and the mixture was crystallized at 155 °C for 100 h. The rest of the process was the same as in Example 1.

[0056] Catalyst evaluation: 100g of glucose was dissolved in 100g of water, and then 300g of methanol was added to prepare a 20 wt% glucose solution. This solution was added to a high-pressure reactor, followed by 15g of the catalyst from Example 3. The reactor was sealed, and the temperature was raised. After the temperature inside the reactor reached 100℃ and stabilized, a magnetic stirrer was started at 300 rpm, and the reaction time was initiated. After reacting for 2 hours, the mixture was cooled to room temperature, the pressure was released, and the resulting glucose / fructose syrup was analyzed by liquid chromatography. The results are shown in Table 1.

[0057] Example 4 Catalyst preparation: Same as in Example 3, except that crystallization was carried out in a high-pressure reactor for only 48 hours, while the remaining steps were the same as in Example 3.

[0058] Catalyst evaluation: Same as in Example 3.

[0059] Comparative Example 1 Catalyst preparation: Same as in Example 1, except that only Mg metal is supported in situ and Sn metal is not added. The remaining steps are the same as in Example 1.

[0060] Catalyst evaluation: Same as in Example 1.

[0061] Comparative Example 2 Catalyst preparation: Same as in Example 1, except that Sn metal is supported in situ and Mg metal is not added. The remaining steps are the same as in Example 1.

[0062] Catalyst evaluation: Same as in Example 1.

[0063] Comparative Example 3 Catalyst preparation: 10g of the same molecular sieve used in Example 1 was used as a support. A 0.1M Mg(CH3COO)2·4H2O aqueous solution and a 0.1M SnCl4 aqueous solution were loaded using an equal-volume impregnation method (the water absorption rate of the support was first calculated, and a solution of the corresponding volume was prepared based on the water absorption rate before impregnation). The total metal content was 3‰ (Mg:Sn molar ratio 1:1), and the mixture was stirred for 2 hours. The mixture was first dried at 100℃, and then calcined at 550℃ for 5 hours with a heating rate of 2℃ / min to obtain the desired catalyst.

[0064] Catalyst evaluation: Same as in Example 1.

[0065] Comparative Example 4 Catalyst preparation: Same as in Example 2, except that ZMS-5 is not added as a seed crystal to induce crystallization, and the remaining steps are the same as in Example 2.

[0066] Catalyst evaluation: Same as in Example 2.

[0067] Comparative Example 5 Catalyst preparation: Same as in Example 2, except that ZMS-5, which was added as a seed sieve, was added directly without being wetted with TEAOH solution. The rest of the steps were the same as in Example 2.

[0068] Catalyst evaluation: Same as in Example 2.

[0069] Comparative Example 6 Catalyst preparation: Same as in Example 3, except that after adding metal salt to make a gel precursor, no aging was performed. The remaining steps were the same as in Example 3.

[0070] Catalyst evaluation: Same as in Example 3.

[0071] The catalysts for the isomerization of glucose to fructose obtained in each embodiment and comparative example, when used to prepare fructose from glucose, show the conversion rate, selectivity and fructose yield of glucose as shown in Table 1.

[0072] Table 1

[0073] As shown in Table 1, the catalysts for the isomerization of glucose to fructose synthesized in situ using the method of this invention exhibit excellent performance in the glucose isomerization to fructose reaction. First, the performance of Example 1 is significantly better than that of Comparative Example 2 (Sn only) and Comparative Example 3 (Mg only), demonstrating that the synergistic catalysis of bimetals can significantly improve reaction efficiency. Second, the in-situ synthesis method has significant advantages over the traditional impregnation method: a comparison of the results of Example 1 and Comparative Example 3 shows that Example 1, by encapsulating the metal inside the molecular sieve crystal in situ, is more effective in stabilizing the active component and exerting a confinement effect than the impregnation method (Comparative Example 3), which loads the metal on the outer surface. Third, seed induction and activation are key control steps in the crystallization process. The performance of Example 2 is better than that of Comparative Example 4 without seeds, confirming the structure-directing role of seeds; while seeds must be pre-wetted and activated with a template agent solution (Example 2 vs. Comparative Example 5) to ensure uniform dispersion in the gel and efficient crystallization induction. Finally, precise control of synthesis parameters is crucial for catalyst performance. The results of Example 3 indicate that aging (vs. Comparative Example 6) prior to gel precursor formation is essential for obtaining a catalyst with high crystallinity and intact structure. Compared to Example 3, the reduced hydrothermal crystallization time in Example 4 resulted in decreased purity and structural integrity of the catalyst obtained for the isomerization of glucose to fructose, thus reducing its catalytic effect.

[0074] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a catalyst for the isomerization of glucose to fructose, characterized in that, Includes the following steps: Molecular sieves are dispersed in a solution of a first template agent, and solutions of a first metal salt and a second metal salt are added. After aging, a gel precursor is obtained. Molecular sieve seed crystals are dispersed in a second template agent to form a suspension. The suspension is then added to the gel precursor and hydrothermally crystallized to obtain a crystallized precursor. The crystallized precursor was calcined to obtain a catalyst for the preparation of fructose from glucose isomerization.

2. The method for preparing the catalyst for the isomerization of glucose to fructose according to claim 1, characterized in that, The molecular sieve has a silica-to-alumina ratio ≥150; and / or, The molecular sieve includes one or more of ZSM-5 molecular sieve, MCM-22 molecular sieve, Beta molecular sieve, and all-silica molecular sieve; and / or, The first template agent and the second template agent each independently comprise one or more of tetrapropylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium bromide, and hexamethyleneimine; and / or, The molar ratio of the first template agent to the silicon element in the molecular sieve is (0.1~0.8):

1.

3. The method for preparing the catalyst for the isomerization of glucose to fructose according to claim 1, characterized in that, The first metal salt includes one or more of tin salts, platinum salts, and lithium salts; and / or, The second metal salt includes one or more of magnesium salts, antimony salts, and indium salts; and / or, The molar ratio of the first metal salt to the second metal salt is 1:5 to 5:1; and / or, The sum of the masses of the first metal salt and the second metal salt, calculated as metal oxides, is a, and the mass of the molecular sieve, calculated as SiO2, is b. a / b×100%=0.5‰~10‰.

4. The method for preparing the catalyst for the isomerization of glucose to fructose according to claim 1, characterized in that, The first metal salt includes one or more of tin chloride, chloroplatinic acid, and lithium chloride; and / or, The second metal salt includes one or more of magnesium nitrate, antimony chloride, and indium chloride; and / or, The aging time is 6h to 12h.

5. The method for preparing the catalyst for the isomerization of glucose to fructose according to claim 1, characterized in that, The molecular sieve seed crystals include one or more of ZSM-5 molecular sieve, MCM-22 molecular sieve, Beta molecular sieve, and all-silica molecular sieve; and / or, The mass of the added molecular sieve seed crystals is 1% to 3% of the mass of the molecular sieve in the gel precursor.

6. The method for preparing the catalyst for the isomerization of glucose to fructose according to claim 1, characterized in that, The hydrothermal crystallization temperature is 150℃~180℃; and / or, The hydrothermal crystallization time is 60h~120h.

7. The method for preparing the catalyst for the isomerization of glucose to fructose according to claim 1, characterized in that, The calcination temperature is 500℃~600℃; and / or, The roasting time is 4 to 6 hours.

8. A catalyst for the isomerization of glucose to fructose, characterized in that, The catalyst for the isomerization of glucose to fructose is prepared by the method described in any one of claims 1 to 7.

9. A method for preparing fructose via glucose isomerization, characterized in that, The reaction is carried out in the presence of the catalyst for the isomerization of glucose to fructose as described in claim 8.

10. The method for preparing fructose by glucose isomerization according to claim 9, characterized in that, The reaction temperature is 60℃~150℃; and / or, The solvent used in the reaction includes one or more of water, methanol, ethanol, and glycerol; and / or, The reactor used for the reaction includes any one of a reaction vessel, a fixed bed, or a slurry bed.

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