Alkali metal modified manganese metal oxide catalyst as well as preparation method and application thereof

Abstract

The invention discloses an alkali metal modified manganese metal oxide catalyst and a preparation method and application thereof, and the preparation method of the catalyst comprises the following steps: dissolving manganese metal salt in ionized water to obtain a solution A; dissolving permanganate in ionized water to obtain a solution B; dropwise adding the solution B into the solution A, and stirring for coprecipitation reaction; and collecting a precipitate obtained by the reaction, filtering, washing and drying to obtain the alkali metal modified manganese metal oxide catalyst. According to the method, soluble manganese metal salt and soluble permanganate are taken as raw materials, water is taken as a solvent, the alkali metal ion intercalated manganese oxide catalyst is obtained through a coprecipitation reaction, and the catalyst has high catalytic efficiency and high selectivity on a reaction path for oxidizing HMF into FFCA and FDCA.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and in particular to an alkali metal modified manganese metal oxide catalyst and a preparation method and application thereof. Background Art

[0002] 5-Hydroxymethylfurfural (HMF) is an important platform compound extracted from biomass. It is a key bridge between biomass and high-value chemicals / fuels. The preparation of HMF and its derivatives 5-formyl-2-furancarboxylic acid (FFCA) and 2,5-furandicarboxylic acid (FDCA) has attracted widespread attention. These compounds have important applications in bioplastics, solvents, drugs and other fine chemical products.

[0003] HMF can be converted into FFCA and FDCA by catalytic oxidation reaction. The catalysts currently used can be divided into two categories, namely precious metal catalysts (such as palladium or platinum) and non-precious metal catalysts (such as manganese or iron-based catalysts). These catalysts can effectively oxidize the hydroxymethyl group of HMF to carboxyl groups to obtain FFCA. Further oxidation can convert FFCA into FDCA. The preparation of FDCA usually involves stronger oxidation conditions or more effective catalytic systems.

[0004] Although existing catalysts can convert HMF into FFCA and FDCA, they generally have problems with low conversion efficiency and selectivity. Therefore, studying a new catalyst to improve the conversion efficiency and product selectivity of HMF is of great significance to the development of HMF catalytic oxidation technology. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to develop a highly efficient catalyst to improve the conversion efficiency and selectivity of HMF.

[0006] In order to solve the above technical problems, the first aspect of the present invention provides a method for preparing an alkali metal-modified manganese metal oxide catalyst, comprising the following steps:

[0007] S1. dissolving a manganese metal salt in ionized water to obtain a solution A, wherein the manganese metal salt is selected from one or more of MnCl2, MnBr2, Mn(NO3)2, MnSO4, and Mn(CH3COO)2;

[0008] S2, dissolving permanganate in ionized water to obtain solution B, wherein the permanganate is selected from one or more of KMnO4, NaMnO4, and LiMnO4;

[0009] S3, adding solution B dropwise to solution A, stirring to carry out coprecipitation reaction;

[0010] S4. Collect the precipitate obtained by the reaction, filter, wash and dry to obtain the alkali metal modified manganese metal oxide catalyst.

[0011] The present invention uses soluble manganese metal salt and soluble permanganate as raw materials and water as solvent to obtain an alkali metal ion intercalated manganese oxide catalyst through a coprecipitation reaction. The manganese oxide catalyst has high catalytic efficiency and high selectivity for the reaction path of HMF oxidation to FFCA and FDCA, and the addition of alkali metal ions can enhance the stability of the catalyst under reaction conditions, making it more resistant to high temperature and corrosive environment.

[0012] Furthermore, in the solution A, the concentration of the manganese metal salt is 1 to 10 mol / L.

[0013] Furthermore, in the solution B, the concentration of permanganate is 1 to 10 mol / L.

[0014] Furthermore, in step S3, the volume ratio of solution A to the added solution B is 1:0.5 to 1:2.

[0015] By reacting a manganese metal salt solution with a permanganate solution at a specific solubility and ratio, the product structure can be controlled to obtain an alkali metal ion (Li + 、Na + , K + ) intercalated manganese oxide nanoflower catalyst.

[0016] Furthermore, in step S3, the reaction time is 1 to 6 hours.

[0017] Furthermore, in step S4, the drying temperature is 60-100° C. and the drying time is 6-12 hours.

[0018] The second aspect of the present invention provides an alkali metal-modified manganese metal oxide catalyst, which is prepared by the above-mentioned preparation method, and the alkali metal-modified manganese metal oxide catalyst is a nano flower spherical structure. The nano flower spherical structure enables the catalyst to have a very high specific surface area, increases the number of active sites, and thus improves the catalytic efficiency; the intercalation of alkali metal ions further optimizes the electronic environment of these active sites, which is conducive to enhancing the activity of the catalyst.

[0019] The third aspect of the present invention provides an application, in which the above-mentioned alkali metal-modified manganese metal oxide catalyst is used for catalytic oxidation of 5-hydroxymethylfurfural.

[0020] Furthermore, persulfate (PMS) and an alkali metal-modified manganese metal oxide catalyst are added to the 5-hydroxymethylfurfural aqueous solution, and the mixed solution is heated or irradiated with light to convert the 5-hydroxymethylfurfural into the target product, wherein the target product is 5-formyl-2-furancarboxylic acid and / or 2,5-furandicarboxylic acid.

[0021] Furthermore, the reaction time required for catalytic oxidation of 5-hydroxymethylfurfural to generate the target product is 0.5 to 12 hours.

[0022] Under alkali-free conditions, using PMS as an oxidant and adding an alkali metal-modified manganese metal oxide catalyst can achieve efficient conversion of HMF, and the catalyst is highly selective for the reaction path of HMF oxidation to FFCA and FDCA.

[0023] In summary, compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention prepares a manganese metal oxide catalyst through a coprecipitation reaction, introduces a certain amount of alkali metal ions, can increase the oxygen vacancy content in the catalyst, change the morphology, material structure and electronic environment of the catalyst, increase the number of active sites, and improve the catalytic ability of the catalyst. The catalyst has a high conversion rate and high selectivity for the reaction path of HMF oxidation to FFCA and FDCA. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is the X-ray diffraction pattern of the catalyst prepared in Example 1, Example 2 and Example 3 of the present invention.

[0026] Figure 2 It is the electron paramagnetic resonance spectrum of the catalyst prepared in Example 1, Example 2 and Example 3 of the present invention.

[0027] Figure 3 It is a transmission electron microscope image of the catalyst prepared in Example 1 of the present invention.

[0028] Figure 4 It is a transmission electron microscope image of the catalyst prepared in Example 2 of the present invention.

[0029] Figure 5 It is a transmission electron microscope image of the catalyst prepared in Example 3 of the present invention.

[0030] Figure 6 The diagrams show the photocatalytic (left) and thermal catalytic (right) effects of the catalyst prepared in Example 1 of the present invention on HMF.

[0031] Figure 7 The diagram shows the photocatalytic (left) and thermal catalytic (right) effects of the catalyst prepared in Example 2 of the present invention on HMF.

[0032] Figure 8 The diagrams show the photocatalytic (left) and thermal catalytic (right) effects of the catalyst prepared in Example 3 of the present invention on HMF. DETAILED DESCRIPTION

[0034] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0035] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0036] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present application description and examples are exemplary only.

[0037] A specific embodiment of the present invention provides a method for preparing an alkali metal modified manganese metal oxide catalyst, comprising the following steps:

[0038] S1. Dissolve a soluble manganese metal salt in ionized water to obtain solution A. In a specific embodiment, the manganese metal salt can be selected from MnCl2, MnBr2, Mn(NO3)2, MnSO4, Mn(CH3COO)2, etc.; in solution A, the concentration of the manganese metal salt is 1 to 10 mol / L.

[0039] S2. Dissolve soluble permanganate in ionized water to obtain solution B. In a specific embodiment, the permanganate can be KMnO4, NaMnO4, LiMnO4, which has alkali metal ions; in solution B, the concentration of permanganate is 1-10 mol / L.

[0040] S3, adding solution B dropwise to solution A, stirring to perform a coprecipitation reaction. In a specific embodiment, the volume ratio of solution A to the added solution B is 1:0.5 to 1:2, and the reaction time is 1 to 6 hours.

[0041] S4, collecting the precipitate obtained by the reaction, filtering, washing and drying to obtain the alkali metal modified manganese metal oxide catalyst. The preferred drying conditions are a temperature of 60 to 100° C. and a time of 6 to 12 hours.

[0042] The catalyst prepared by the above method is a nano-flower ball structure, which increases the number of active sites and has alkali metal ion intercalation, which optimizes the electronic environment of the active sites and makes the catalyst highly active. The addition of alkali metal ions can enhance the stability of the catalyst under reaction conditions and make it more resistant to high temperature and corrosive environments.

[0043] The above catalyst is used for catalytic oxidation of 5-hydroxymethylfurfural, and persulfate is used as an oxidant. Under alkali-free conditions, efficient conversion of HMF can be achieved, and the reaction time required to generate the target product is 0.5 to 12 hours. At the same time, the catalyst is highly selective for the reaction path of HMF oxidation to FFCA and FDCA.

[0044] The technical effects of the present invention are described below in conjunction with specific embodiments. Unless otherwise specified, the raw materials in the embodiments of the present application are purchased through commercial channels.

[0045] The performance test methods of the catalysts in the following embodiments and comparative examples are as follows:

[0046] 1. Photocatalytic effect test: Add 9 ml of 20 mmol HMF aqueous solution and 1 ml of 100 mmol potassium persulfate aqueous solution to the reaction container, and then add 50 mg of catalyst. Provide 500 mW / cm2 full-spectrum light, turn on the light source, start timing and carry out catalytic reaction. Every 20 minutes, take 10 μl of the reaction solution, add 990 μl of water to dilute and filter, and analyze the sample using liquid chromatography. The whole reaction process lasts for 2 hours.

[0047] 2. Thermal catalytic effect test: Add 9 ml of 20 mmol HMF aqueous solution and 1 ml of 100 mmol potassium persulfate aqueous solution to the reaction container, and then add 50 mg of catalyst. Heat the reaction solution to 55°C, start timing and perform catalytic reaction. Every 20 minutes, take 10 μl of the reaction solution, add 990 μl of water to dilute and filter, and analyze the sample using liquid chromatography. The entire reaction process lasts for 2 hours.

[0048] Example 1

[0049] (1) Dissolve 30 mmol of Mn(NO3)2·4H2O in 100 ml of deionized water and stir to make it fully dissolved to obtain solution A.

[0050] (2) Dissolve 20 mmol KMnO4 in 100 ml deionized water and stir evenly to fully dissolve it to obtain solution B.

[0051] (3) Solution B was added dropwise into solution A and stirred for 2 hours to obtain a brown precipitate.

[0052] (4) The obtained brown precipitate was filtered, washed, and dried at 60° C. for 12 hours to obtain a potassium ion-modified manganese metal oxide catalyst.

[0053] In order to confirm the composition and morphology of the catalyst prepared in Example 1, X-ray diffraction and transmission electron scanning microscopy analysis were performed. The results are as follows: Figure 1 and Figure 3 As shown in Figure 1, the catalyst synthesized according to Example 1 has a low-crystallinity MnO2 phase state, and the image in the transmission electron scanning microscope shows a nano-flower ball structure. The catalyst was analyzed by electron paramagnetic resonance spectroscopy, and the results are as follows: Figure 2 As shown, it can be seen that the catalyst has a high concentration of oxygen vacancies.

[0054] The performance of the catalyst was tested, and its photocatalytic effect on HMF was as follows: Figure 6 As shown in (left), within 2 hours of catalytic reaction, the conversion rate of HMF was 93.7%, the yield of FFCA was 81.6%, and the yield of FDCA was 10.1%; the thermal catalytic reaction effect of HMF was as follows Figure 6 As shown in (right), within 2 hours of catalytic reaction time, the conversion rate of HMF was 97.6%, the yield of FFCA was 85.5%, and the yield of FDCA was 10.9%.

[0055] Example 2

[0056] (1) Dissolve 20 mmol of MnSO4·4H2O in 100 ml of deionized water and stir to make it fully dissolved to obtain solution A.

[0057] (2) Take 30 mmol of NaMnO4 and dissolve it in 100 ml of deionized water. Stir evenly to make it fully dissolved to obtain solution B.

[0058] (3) Solution B was added dropwise into solution A and stirred for 3 hours to obtain a brown precipitate.

[0059] (4) The obtained brown precipitate was filtered, washed, and dried at 80° C. for 10 hours to obtain a sodium ion-modified manganese metal oxide catalyst.

[0060] In order to confirm the composition and morphology of the catalyst prepared in Example 2, X-ray diffraction and transmission electron scanning microscopy analysis were performed. The results are as follows: Figure 1 and Figure 4 As shown in Figure 2, the catalyst synthesized according to Example 2 has a MnO2 phase state with low crystallinity, and the image in the transmission electron scanning microscope shows a nano-flower ball structure. The catalyst was analyzed by electron paramagnetic resonance spectroscopy, and the results are as follows: Figure 2 As shown, it can be seen that the catalyst has a high concentration of oxygen vacancies.

[0061] The performance of the catalyst was tested, and its photocatalytic effect on HMF was as follows: Figure 7As shown in (left), within 2 hours of catalytic reaction, the conversion rate of HMF was 98.8%, the yield of FFCA was 90.6%, and the yield of FDCA was 8.7%; the thermal catalytic reaction effect of HMF was as follows Figure 7 As shown in (right), within 2 hours of catalytic reaction time, the conversion rate of HMF was 99.9%, the yield of FFCA was 93.1%, and the yield of FDCA was 4.4%.

[0062] Example 3

[0063] (1) Dissolve 50 mmol of MnCl2·4H2O in 100 ml of deionized water and stir to make it fully dissolved to obtain solution A.

[0064] (2) Take 40 mmol LiMnO4 and dissolve it in 80 ml deionized water. Stir evenly to make it fully dissolved to obtain solution B.

[0065] (3) Solution B was added dropwise into solution A and stirred for 4 hours to obtain a brown precipitate.

[0066] (4) The obtained brown precipitate was filtered, washed, and dried at 100° C. for 6 hours to obtain a lithium ion-modified manganese metal oxide catalyst.

[0067] In order to confirm the composition and morphology of the catalyst prepared in Example 3, X-ray diffraction and transmission electron scanning microscopy analysis were performed. The results are as follows: Figure 1 and Figure 5 As shown in Figure 2, the catalyst synthesized according to Example 3 has a low crystallinity MnO2 phase state, and the image in the transmission electron scanning microscope shows a nano-flower ball structure. The catalyst was analyzed by electron paramagnetic resonance spectroscopy, and the results are as follows: Figure 2 As shown, it can be seen that the catalyst has a high concentration of oxygen vacancies.

[0068] The performance of the catalyst was tested, and its photocatalytic effect on HMF was as follows: Figure 8 As shown in (left), within 2 hours of catalytic reaction, the conversion rate of HMF was 93.3%, the yield of FFCA was 74.7%, and the yield of FDCA was 11.1%; the thermal catalytic reaction effect of HMF was as follows Figure 8 As shown in (right), within 2 hours of catalytic reaction time, the conversion rate of HMF was 93.5%, the yield of FFCA was 75.7%, and the yield of FDCA was 15.9%.

[0069] Comparative Example 1 The commercial MnO2 catalyst purchased was used as a comparative example, and HMF photocatalysis and thermal catalysis experiments were carried out under the same conditions. The experimental results of the photocatalytic reaction showed that within 2 hours of catalytic reaction time, the conversion rate of HMF was 66.2%, the yield of FFCA was 35.7%, and the yield of FDCA was 4.9%; the effect of the thermal catalytic reaction showed that within 2 hours of catalytic reaction time, the conversion rate of HMF was 71.3%, the yield of FFCA was 47.0%, and the yield of FDCA was 6.0%. It can be seen that the catalyst prepared in the above embodiment has greatly improved conversion efficiency and selectivity relative to the catalyst of the comparative example.

[0071] Although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A method for preparing an alkali metal modified manganese metal oxide catalyst, It is characterized in that The following steps are involved: S1. Dissolving a manganese metal salt in ionized water to obtain solution A, wherein the manganese metal salt is selected from MnCl 2 、MnBr 2 、Mn(NO 3 ) 2 、MnSO 4 、Mn(CH 3 COO 2 One or more of; S2, dissolving permanganate in ionized water to obtain solution B, wherein the permanganate is selected from KMnO 4 、NaMnO 4 、LiMnO 4 One or more of; S3, adding solution B dropwise to solution A, stirring to carry out coprecipitation reaction; S4. Collect the precipitate obtained by the reaction, filter, wash and dry to obtain the alkali metal modified manganese metal oxide catalyst.

2. The method for preparing the alkali metal modified manganese metal oxide catalyst according to claim 1, It is characterized in that In the solution A, the concentration of the manganese metal salt is 1 to 10 mol / L.

3. The method for preparing the alkali metal modified manganese metal oxide catalyst according to claim 2, It is characterized in that In the solution B, the concentration of permanganate is 1-10 mol / L.

4. The method for preparing the alkali metal modified manganese metal oxide catalyst according to claim 3, It is characterized in that In the step S3, the volume ratio of solution A to the added solution B is 1:0.5 to 1:

2.

5. The method for preparing the alkali metal modified manganese metal oxide catalyst according to claim 1, It is characterized in that In the step S3, the reaction time is 1 to 6 hours.

6. The method for preparing the alkali metal modified manganese metal oxide catalyst according to any one of claims 1 to 5, It is characterized in that In step S4, the drying temperature is 60-100° C. and the drying time is 6-12 hours.

7. An alkali metal modified manganese metal oxide catalyst, It is characterized in that Prepared by the preparation method according to any one of claims 1 to 6, the alkali metal-modified manganese metal oxide catalyst is a nano-flower spherical structure.

8. An application, It is characterized in that The alkali metal-modified manganese metal oxide catalyst according to claim 7 is used for catalytic oxidation of 5-hydroxymethylfurfural.

9. The use according to claim 8, It is characterized in that Persulfate and alkali metal-modified manganese metal oxide catalyst are added to a 5-hydroxymethylfurfural aqueous solution, and the mixed solution is heated or irradiated with light to convert the 5-hydroxymethylfurfural into a target product, wherein the target product is 5-formyl-2-furancarboxylic acid and / or 2,5-furandicarboxylic acid.

10. The use according to claim 9, It is characterized in that The reaction time required for catalytic oxidation of 5-hydroxymethylfurfural to produce the target product is 0.5 to 12 hours.

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