Multi-site self-dispersing catalyst as well as preparation method and application thereof

Abstract

The invention discloses a multi-site self-dispersing catalyst as well as a preparation method and application thereof, and belongs to the technical field of multi-site catalyst preparation. The preparation method disclosed by the invention comprises the following steps: mixing a soluble reducing carbon precursor aqueous solution with a metal-ligand complex precursor emulsion to obtain a mixed solution; putting the mixed solution into a hydrothermal kettle for reaction, and obtaining a carbonized reaction product after the reaction is finished; and carrying out post-treatment on the carbonized reaction product to obtain the multi-site self-dispersing catalyst. Different from the traditional process, the method has the advantages that the raw material cost is remarkably reduced while the preparation process is simplified through the cooperative regulation and control of the precursor coordination chemistry and the carbon matrix reduction-anchoring effect.

Description

Technical Field

[0001] The present invention belongs to the technical field of multi-site catalyst preparation, and particularly relates to a multi-site self-dispersing catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] As a class of key industrial catalytic materials, multi-site catalysts have irreplaceable advantages in complex reaction systems that require the synergistic action of multiple active sites. Through the carefully designed spatial arrangement of active sites and electronic interactions, such catalysts can achieve the directional transfer and stepwise activation of reactant molecules between different functional sites, significantly improving the efficiency and selectivity of complex reactions. However, the controllable preparation of multi-site catalysts faces severe technical challenges, mainly reflected in the interaction and stability of active components. During the preparation process, the precursor active components with different functions (such as metal ions, acidic components, and basic components) are prone to spontaneous interaction. This interaction is mainly manifested as: the neutralization reaction between acidic sites and basic sites, resulting in the irreversible inactivation of the preset acid-base active centers; the strong interaction between metal active components and the carrier, causing a decrease in metal dispersion and a change in the coordination environment; and the uneven distribution of each component on the carrier surface, destroying the preset synergistic catalytic structure. Specifically, during the preparation of a typical acid-base-metal multi-active site catalyst, the acidic site precursor (such as ammonium sulfate) is prone to directly react with the basic site precursor (such as ammonia water) to form a neutral salt, resulting in a sharp reduction in the number of preset acid-base active centers. At the same time, the metal precursor (such as platinum ammonia complex) may undergo ion exchange with the acidic sites on the carrier surface to form a metal salt without catalytic activity, not only reducing the metal dispersion but also destroying the acidity of the carrier. This interaction also changes the electronic state of the metal and weakens its catalytic activity.

[0003] To avoid such problems, the existing technologies mostly rely on complex preparation processes or special structure carriers. For example, the molecular sieve confinement strategy is used to achieve spatial isolation of active components (Catal. Sci. Technol. 2021,11, 211-218; 2018,8, 4474-4484; New J. Chem. 2023,47, 891-899), or precursors with site isolation functions are designed and synthesized (Green Chem. 2023,25, 4090-4103). These methods generally have problems such as high preparation costs and complex processes, severely restricting their industrial applications. Summary of the Invention

[0004] The purpose of the present invention is to provide a multi-site self-dispersing catalyst, a preparation method thereof, and an application thereof, so as to solve the technical problems of high preparation costs and complex processes in the existing preparation methods.

[0005] To achieve the above object, the present invention is implemented by the following technical solutions: The present invention discloses a preparation method of a multi-site self-dispersing catalyst, comprising the following steps: Mix an aqueous solution of a soluble reducible carbon precursor with an emulsion of a metal-ligand complex precursor to obtain a mixed solution; Put the mixed solution into a hydrothermal autoclave for reaction, and after the reaction is completed, obtain a post-carbonization reaction product; After post-treating the post-carbonization reaction product, obtain a multi-site self-dispersing catalyst.

[0006] Further, the preparation method of the emulsion of the metal-ligand complex precursor is as follows: An acid / base property organic ligand and a metal precursor salt are respectively dissolved in an aqueous solution, and then mixed and stirred to obtain an emulsion of a metal-ligand complex precursor; The acid / base property organic ligand is one or more of 2-methylimidazole, pyridine, 5-sulfosalicylic acid, and p-toluenesulfonic acid; The metal precursor salt is one or more of ZrOCl2·8H2O, Zr(NO3)4·5H2O, and Zn(NO3)2·6H2O; The aqueous solution of the soluble reducible carbon precursor is obtained by mixing a soluble reducible carbon precursor and an aqueous solution.

[0007] Further, the molar ratio of the metal precursor salt to the acid / base property organic ligand is 1:(0.8 - 4); the molar ratio of the soluble reducible carbon precursor to the metal precursor salt is 1:(1 - 0.25).

[0008] Further, the soluble reducible carbon precursor is one or more of ascorbic acid, glucose, fructose, and sucrose.

[0009] Further, the concentrations of the aqueous solution of the soluble reducible carbon precursor, the aqueous solution of the acid / base property organic ligand, and the aqueous solution of the metal precursor salt are 0.25 - 1 mol / L; The post-treatment is washing and drying treatments carried out in sequence.

[0010] The present invention also discloses a multi-site self-dispersing catalyst prepared by the above preparation method.

[0011] Further, the multi-site self-dispersing catalyst is a heterogeneous catalyst.

[0012] The present invention also discloses the application of the above multi-site self-dispersing catalyst in the catalytic HMF transfer hydrogenation reaction for preparing 2,5-furandimethanol, and the reaction temperature is 90 - 130°C.

[0013] The present invention also discloses the application of the above multi-site self-dispersing catalyst in the catalytic etherification reaction of HMF in the preparation of 5-isopropoxymethylfurfural, and the reaction temperature is 70-120 °C.

[0014] The present invention also discloses the application of the above multi-site self-dispersing catalyst in the catalytic etherification and transfer hydrogenation reactions of HMF in the preparation of 2,5-bis(isopropoxymethyl)furan, and the reaction temperature is 110-140 °C.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a preparation method of a multi-site self-dispersing catalyst. First, a stable precursor complex is constructed by metal-organic ligand directional complexation and dispersed in a carbon precursor solution with reduction characteristics. The in-situ reduction dissociation effect of the hydrothermal process is utilized to achieve uniform dispersion of the active components. During the subsequent carbonization process, the carbon-based carrier effectively fixes the dissociated active sites through the coordination anchoring effect, and finally a carbon-based catalyst with multiple active sites is constructed. Different from the traditional process, this method realizes the synergistic regulation of precursor coordination chemistry and carbon matrix reduction-anchoring effect, simplifies the preparation process, and significantly reduces the raw material cost.

[0016] The present invention also discloses the application of the above multi-site self-dispersing catalyst. Taking the catalytic conversion of the biomass platform molecule 5-hydroxymethylfurfural (HMF) as a verification system, by adjusting the types and ratios of the precursors, the efficient directional synthesis of 2,5-furandimethanol, 5-isopropoxymethylfurfural, and 2,5-bis(isopropoxymethyl)furan can be respectively achieved. The present invention has the advantages of simplified preparation process, controllable raw material cost, and adjustable product selectivity, providing an innovative solution for the large-scale preparation of industrial heterogeneous catalysts. Detailed Embodiments

[0017] To enable those skilled in the art to understand the features and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meanings understood by those skilled in the art for the present invention. In case of conflict, the definition in this specification shall prevail.

[0018] The theories or mechanisms described and disclosed herein, whether correct or incorrect, shall not limit the scope of the present invention in any way, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0019] In this text, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values within the ranges (including integers and fractions).

[0020] In this text, unless otherwise specified, terms such as "comprise", "include", "contain", "have", or similar terms cover the meanings of "consist of" and "consist essentially of". For example, "A comprises a" covers the meanings of "A comprises a and others" and "A consists only of a".

[0021] In this text, for the sake of concise description, all possible combinations of all technical features in each embodiment or example are not described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered to be within the scope described in this specification.

[0022] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught in the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0023] Conventional instruments and equipment in the art are used in the following examples. For the experimental methods without specific conditions noted in the following examples, they are usually carried out under conventional conditions or according to the conditions recommended by the manufacturers. Various raw materials are used in the following examples. Unless otherwise stated, commercially available products are used, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" represents weight percentage, "parts" represents weight parts, and the ratio represents weight ratio.

[0024] Example 1 A preparation method of a multi-site self-dispersing catalyst, comprising the following steps: Step 1: Dissolve 3.28 g of 2-methylimidazole in 40 mL of aqueous solution, dissolve 3.22 g of ZrOCl2·8H2O in 40 mL of aqueous solution, and then quickly mix and stir them until a uniform metal-ligand complex precursor emulsion is obtained; Step 2: Dissolve 7.2 g of glucose in 40 mL of aqueous solution to obtain an aqueous solution of a soluble reducing carbon precursor; add it to the above metal-ligand complex precursor emulsion, stir to obtain a mixed solution; transfer the mixed solution to a stainless-steel hydrothermal reactor with a polytetrafluoroethylene lining, react at 180 °C for 12 h. After the hydrothermal process is completed, filter and wash the resulting carbonized solid until the pH of the filtrate is neutral, and dry the filtered and washed solid to obtain a multi-site self-dispersing catalyst.

[0025] Example 2 A method for preparing a multi-site self-dispersing catalyst, comprising the following steps: Step 1: Dissolve 0.82 g of 2-methylimidazole in 40 mL of aqueous solution, dissolve 3.22 g of ZrOCl2·8H2O in 40 mL of aqueous solution, and then quickly mix and stir them until a uniform metal-ligand complex precursor emulsion is obtained; Step 2: Dissolve 3.42 g of sucrose in 50 mL of aqueous solution to obtain an aqueous solution of a soluble reducing carbon precursor; add it to the above metal-ligand complex precursor emulsion, stir to obtain a mixed solution; transfer the mixed solution to a stainless-steel hydrothermal reactor with a polytetrafluoroethylene lining, react at 130 °C for 24 h. After the hydrothermal process is completed, filter and wash the resulting carbonized solid until the pH of the filtrate is neutral, and dry the filtered and washed solid to obtain a multi-site self-dispersing catalyst.

[0026] Example 3 A method for preparing a multi-site self-dispersing catalyst, comprising the following steps: Step 1: Dissolve 2.54 g of 5-sulfosalicylic acid in 40 mL of aqueous solution, dissolve 2.97 g of Zn(NO3)2·6H2O in 40 mL of aqueous solution, and then quickly mix and stir them until a uniform metal-ligand complex precursor emulsion is obtained; Step 2: Dissolve 3.6 g of fructose in 40 mL of aqueous solution to obtain an aqueous solution of a soluble reducing carbon precursor; add it to the above metal-ligand complex precursor emulsion, stir to obtain a mixed solution; transfer the mixed solution to a stainless-steel hydrothermal reactor with a polytetrafluoroethylene lining, react at 180 °C for 12 h. After the hydrothermal process is completed, filter and wash the resulting carbonized solid until the pH of the filtrate is neutral, and dry the filtered and washed solid to obtain a multi-site self-dispersing catalyst.

[0027] Example 4 A method for preparing a multi-site self-dispersing catalyst, comprising the following steps: Step 1: Dissolve 1.72 g of p-toluenesulfonic acid in 40 mL of aqueous solution, and dissolve 2.97 g of Zn(NO3)2·6H2O in 40 mL of aqueous solution. Then mix and stir them rapidly until a uniform metal-ligand complex precursor emulsion is obtained; Step 2: Dissolve 3.52 g of ascorbic acid in 40 mL of aqueous solution to obtain a soluble reducing carbon precursor aqueous solution. Add it to the above metal-ligand complex precursor emulsion, stir to obtain a mixed solution. Transfer the mixed solution to a stainless-steel hydrothermal autoclave with a polytetrafluoroethylene liner, react at 180 °C for 18 h. After the hydrothermal process is completed, filter and wash the obtained carbonized solid until the pH value of the filtrate is neutral, and dry the filtered and washed solid to obtain a multi-site self-dispersing catalyst.

[0028] Example 5 A preparation method of a multi-site self-dispersing catalyst, comprising the following steps: Step 1: Dissolve 1.64 g of 2-methylimidazole and 1.27 g of 5-sulfosalicylic acid in 40 mL of aqueous solution, and dissolve 3.22 g of ZrOCl2·8H2O in 40 mL of aqueous solution. Then mix and stir them rapidly until a uniform metal-ligand complex precursor emulsion is obtained; Step 2: Dissolve 3.6 g of fructose in 40 mL of aqueous solution to obtain a soluble reducing carbon precursor aqueous solution. Add it to the above metal-ligand complex precursor emulsion, stir to obtain a mixed solution. Transfer the mixed solution to a stainless-steel hydrothermal autoclave with a polytetrafluoroethylene liner, react at 180 °C for 12 h. After the hydrothermal process is completed, filter and wash the obtained carbonized solid until the pH value of the filtrate is neutral, and dry the filtered and washed solid to obtain a multi-site self-dispersing catalyst.

[0029] Example 6 A preparation method of a multi-site self-dispersing catalyst, comprising the following steps: Step 1: Dissolve 1.58 g of pyridine and 1.27 g of 5-sulfosalicylic acid in 40 mL of aqueous solution, and dissolve 3.22 g of ZrOCl2·8H2O in 40 mL of aqueous solution. Then mix and stir them rapidly until a uniform metal-ligand complex precursor emulsion is obtained; Step 2: Dissolve 3.6 g of fructose in 40 mL of aqueous solution to obtain an aqueous solution of soluble reducing carbon precursor; add it to the above metal-ligand complex precursor emulsion, stir to obtain a mixed solution; transfer the mixed solution to a stainless-steel hydrothermal autoclave with a polytetrafluoroethylene liner, react at 180 °C for 12 h. After the hydrothermal process is completed, filter and wash the obtained carbonized solid until the pH value of the filtrate is neutral, and dry the filtered and washed solid to obtain a multi-site self-dispersing catalyst.

[0030] The multi-site self-dispersing catalyst is used as a catalyst for the transfer hydrogenation reaction of HMF when preparing 2,5-furandimethanol, and as a catalyst for the etherification reaction of HMF when preparing 5-isopropoxymethylfurfural; the multi-site self-dispersing catalyst is used as a catalyst for the etherification and transfer hydrogenation reactions of HMF when preparing 2,5-bis(isopropoxymethyl)furan.

[0031] Application Example 1 When the multi-site self-dispersing catalyst prepared in Example 1 is used as a catalyst for the transfer hydrogenation reaction of HMF in the preparation of 2,5-furandimethanol, the reaction temperature is 130 °C and maintained for 0.5 h, obtaining a 99.5% HMF conversion rate and a 98.0% 2,5-furandimethanol selectivity.

[0032] Application Example 2 When the multi-site self-dispersing catalyst prepared in Example 2 is used as a catalyst for the transfer hydrogenation reaction of HMF in the preparation of 2,5-furandimethanol, the reaction temperature is 90 °C and maintained for 12 h, obtaining a 37.6% HMF conversion rate and a 95.3% 2,5-furandimethanol selectivity.

[0033] Application Example 3 When the multi-site self-dispersing catalyst prepared in Example 3 is used as a catalyst for the etherification reaction of HMF in the preparation of 5-isopropoxymethylfurfural, the reaction temperature is 120 °C and maintained for 0.33 h, obtaining a 99.9% HMF conversion rate and an 85.5% 5-isopropoxymethylfurfural selectivity.

[0034] Application Example 4 When the multi-site self-dispersing catalyst prepared in Example 4 is used as a catalyst for the etherification reaction of HMF in the preparation of 5-isopropoxymethylfurfural, the reaction temperature is 70 °C and maintained for 6 h, obtaining a 90.1% HMF conversion rate and an 84.9% 5-isopropoxymethylfurfural selectivity.

[0035] Application Example 5 When the multi-site self-dispersing catalyst prepared in Example 5 was used for the preparation of 2,5-bis(isopropoxymethyl)furan, it was a catalyst for the etherification and transfer hydrogenation reactions of HMF. The reaction temperature was 140 °C and it was maintained for 0.25 h, obtaining a 99.9% HMF conversion rate and a 95.6% selectivity for 2,5-bis(isopropoxymethyl)furan.

[0036] Application Example 6 When the multi-site self-dispersing catalyst prepared in Example 6 was used for the preparation of 2,5-bis(isopropoxymethyl)furan, it was a catalyst for the etherification and transfer hydrogenation reactions of HMF. The reaction temperature was 110 °C and it was maintained for 7.5 h, obtaining a 99.8% HMF conversion rate and a 92.7% selectivity for 2,5-bis(isopropoxymethyl)furan.

[0037] From the experimental results of each example and application example, it can be seen that: For the transfer hydrogenation reaction system that requires Lewis acid-base as the effective catalytic active site (Examples 1-2), a catalytic system constructed from a Lewis acidic metal salt and a basic organic ligand was used. Through the metal-ligand complexation and synergistic carbon matrix reduction-anchoring effect, the effective dispersion of dual functional sites (Lewis acid-base) in the catalyst was successfully achieved. The experimental data show that under the corresponding reaction conditions (Application Examples 1-2), this dual-functional catalyst can achieve the efficient conversion of HMF to 2,5-furandimethanol.

[0038] In the Brønsted acid-catalyzed etherification reaction system (Examples 3-4), a metal Zn salt and a Brønsted acidic organic ligand were selected to construct a composite acid catalyst. The results of Application Examples 3-4 show that under the corresponding reaction conditions and catalytic system, the efficient conversion of HMF to 5-isopropoxymethylfurfural was successfully achieved, indicating that the Brønsted acid was successfully dispersed in the catalyst. For the multi-step continuous transfer hydrogenation etherification reaction system that requires Lewis acid-base and Brønsted acid sites (Examples 5-6), through the precise regulation of the ternary components (Lewis acid metal salt / basic ligand / Brønsted acidic ligand), a multi-functional catalyst integrating Lewis acid-base and Brønsted acid was successfully constructed. Under the corresponding reaction conditions (Application Examples 5-6), this catalyst can achieve the efficient conversion of HMF to 2,5-bis(isopropoxymethyl)furan in one step.

[0039] The above research results fully verify that the preparation strategy of the multi-site self-dispersing catalyst proposed by the present invention has the following advantages: the catalyst preparation has strong flexibility and can be applied to the preparation of a variety of different multifunctional catalysts; the reaction has wide applicability and can meet the catalytic requirements of transfer hydrogenation, etherification and multi-step continuous reaction systems. In addition, the precursors required for the preparation of the multi-site self-dispersing catalyst in this application are cheap and the preparation process is simple, which can save the production cost of the catalyst to a certain extent. This also provides an important technical reference for the development of new multifunctional heterogeneous catalysts.

[0040] The above content is only to illustrate the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A preparation method of a multi-site self-dispersing catalyst, characterized in that, It includes the following steps: Mix an aqueous solution of a soluble reducible carbon precursor with an emulsion of a metal-ligand complex precursor to obtain a mixed solution; Put the mixed solution into a hydrothermal autoclave for reaction. After the reaction ends, obtain a post-carbonization reaction product; After post-treating the post-carbonization reaction product, obtain a multi-site self-dispersing catalyst.

2. The preparation method of a multi-site self-dispersing catalyst according to claim 1, characterized in that, The preparation method of the metal-ligand complex precursor emulsion is as follows: An acid / base property organic ligand and a metal precursor salt are respectively dissolved in an aqueous solution, and then mixed and stirred to obtain a metal-ligand complex precursor emulsion; The acid / base property organic ligand is one or more of 2-methylimidazole, pyridine, 5-sulfosalicylic acid, and p-toluenesulfonic acid; The metal precursor salt is one or more of ZrOCl2·8H2O, Zr(NO3)4·5H2O, and Zn(NO3)2·6H2O; The aqueous solution of the soluble reducible carbon precursor is obtained by mixing a soluble reducible carbon precursor and an aqueous solution.

3. The preparation method of a multi-site self-dispersing catalyst according to claim 2, characterized in that, The molar ratio of the metal precursor salt to the acid / base property organic ligand is 1:(0.8 - 4); the molar ratio of the soluble reducible carbon precursor to the metal precursor salt is 1:(1 - 0.25).

4. The preparation method of a multi-site self-dispersing catalyst according to claim 2, characterized in that, The soluble reducible carbon precursor is one or more of ascorbic acid, glucose, fructose, and sucrose.

5. The preparation method of a multi-site self-dispersing catalyst according to claim 2, characterized in that, The concentrations of the aqueous solution of the soluble reducible carbon precursor, the aqueous solution of the acid / base property organic ligand, and the aqueous solution of the metal precursor salt are 0.25 - 1 mol / L; The post-treatment is washing and drying treatments carried out in sequence.

6. A multi-site self-dispersing catalyst, characterized in that, Prepared by using the preparation method described in any one of claims 1 to 5.

7. The multi-site self-dispersing catalyst according to claim 6, characterized in that, The multi-site self-dispersing catalyst is a heterogeneous catalyst.

8. Use of a multi-site self-dispersing catalyst according to claim 6 or 7 in the catalytic transfer hydrogenation reaction of HMF to prepare 2,5-furandimethanol, characterized in that, The reaction temperature is 90 - 130 °C.

9. Use of a multi-site self-dispersing catalyst according to claim 6 or 7 in the catalytic etherification reaction of HMF in the preparation of 5-isopropoxymethylfurfural, characterized in that, The reaction temperature is 70 - 120 °C.

10. Use of a multi-site self-dispersing catalyst according to claim 6 or 7 in the catalytic etherification and transfer hydrogenation reactions of HMF in the preparation of 2,5-bis(isopropoxymethyl)furan, characterized in that, The reaction temperature is 110 - 140 °C.