Cu-mn bimetallic catalyst, its preparation method and application

Abstract

The application belongs to the technical field of electrocatalytic hydrogenation of furfural, and discloses a Cu-Mn bimetallic catalyst and a preparation method and application thereof. The catalyst takes copper foam as a substrate, and Cu-P and Mn-MOF are loaded on the copper foam. The preparation method comprises the following steps: (1) dissolving copper sulfate, hypophosphite, a surfactant and an electrodeposition aid in water to prepare an electrodeposition solution; (2) placing the electrodeposition solution in a single-chamber electrolytic cell, performing electrochemical deposition on a copper foam working electrode, a platinum wire electrode as a counter electrode and a Hg / Hg2SO4 electrode as a reference electrode, the deposition potential is-1.8~‑2 V vs. Hg / Hg2SO4, the deposition time is 20~30 min, the working electrode is taken out, washed and dried to prepare Cu-P / CF; and (3) dissolving a manganese salt, an organic ligand and a surfactant in an organic solvent, then placing the Cu-P / CF in the organic solvent, performing a solvothermal reaction, and washing and drying to prepare the target catalyst. The Cu-Mn bimetallic catalyst has high catalytic activity, the whole process is simple to operate, the cost is low, and the catalyst has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of furfural electrocatalytic hydrogenation reaction technology, specifically relating to a Cu-Mn bimetallic catalyst, its preparation method, and its application. Background Technology

[0002] Biomass resources, as a renewable carbon-based resource inherent in nature, are widely regarded as an ideal alternative to traditional fossil resources due to their significant environmental friendliness and vast reserves. Electrochemical hydrogenation (ECH) of biomass-derived compounds such as furfural (FF) and 5-hydroxymethylfurfural (HMF) is an effective way to utilize biomass resources. It can efficiently convert biomass resources into high-quality fuels and high-value fine chemicals at ambient temperature and pressure, without relying on an external hydrogen supply, using water as a hydrogen source and employing economical catalysts. Therefore, developing biomass electrocatalytic reduction conversion methods driven by renewable energy has become a green and sustainable energy development solution. However, currently, several key issues remain regarding the selectivity of FF to furfuryl alcohol (FA) ECH process. First, there is a competing reaction between the hydrogen evolution reaction (HER) and the electrochemical hydrogen evolution reaction (ECH). HER is a common side reaction that consumes active hydrogen (Hads) on the electrode surface, thus reducing the selectivity and Faradaic efficiency of the ECH reaction. Second, due to the aforementioned competing reactions and other possible side reactions (such as furfural self-polymerization and the Cannizzaro reaction), current ECH processes often cannot effectively convert all input electrical energy into the target product, resulting in low furfuryl alcohol yields. Furthermore, the catalyst may lose its original catalytic activity during continuous reactions due to deactivation, corrosion, or structural changes, affecting the persistence and reliability of the catalytic effect. Therefore, achieving high selectivity, high conversion, and high Faradaic efficiency remains a significant challenge. Summary of the Invention

[0003] In view of the shortcomings of existing furfural electrocatalytic hydrogenation technology, such as low selectivity, low conversion rate and low Faraday efficiency, the purpose of this invention is to provide a Cu-Mn bimetallic catalyst, its preparation method and application.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A Cu-Mn bimetallic catalyst, wherein the catalyst is based on copper foam, and Cu-P and Mn-MOF are supported on the copper foam; wherein Cu-P is a copper-phosphorus complex, and Mn-MOF is an organic framework material of Mn.

[0006] A method for preparing a Cu-Mn bimetallic catalyst, comprising the following steps:

[0007] (1) Dissolve copper sulfate, hypophosphite, surfactant and electrodeposition additive in water to prepare an electrodeposition solution, which is stored for later use; the amount of copper sulfate and hypophosphite is determined to ensure Cu:P = 10: (1-2) in terms of molar ratio;

[0008] (2) Electrochemically deposit the electrodeposition solution in a single-chamber electrolytic cell, using foamed copper as a working electrode, a platinum wire electrode as a counter electrode and a Hg / Hg2SO4 electrode as a reference electrode, the deposition potential is -1.8 ~ -2 V vs. Hg / Hg2SO4, the deposition time is 20-30 min, the working electrode is taken out, washed and dried to prepare foamed copper with Cu-P deposited thereon, which is marked as Cu-P / CF;

[0009] (3) Dissolve a manganese salt, an organic ligand and a surfactant in an organic solvent, then put the Cu-P / CF into the organic solvent to perform a solvothermal reaction, and then wash and dry to prepare the target catalyst.

[0010] Preferably, in step (1), the hypophosphite is NaH2PO2 or KH2PO2, the surfactant is SDS, and the electrodeposition additive is Na2SO4 or K2SO4.

[0011] Preferably, in step (1), the amount of copper sulfate, hypophosphite, surfactant and electrodeposition additive is determined to be 10: (1-2): 1: 1 in terms of molar ratio, and the amount of copper sulfate and hypophosphite is determined in terms of Cu and P therein, respectively; the concentration of copper sulfate in the electrodeposition solution is 0.2-0.4 M.

[0012] Preferably, in step (2), the foamed copper is sequentially ultrasonically cleaned in 1-3 M HCl solution, acetone, water, ethanol and water before use, and then dried.

[0013] Preferably, in step (3), the manganese salt is MnCl2, Mn(NO3)2 or MnSO4, the organic ligand is terephthalic acid, the surfactant is SDS, and the organic solvent is DMF.

[0014] Preferably, in step (3), the amount of manganese salt, organic ligand and surfactant is determined to be 1: 1: (0.5-1) in terms of molar ratio, and the amount of manganese salt is determined in terms of Mn therein; the concentration of manganese salt in the organic solvent is 1-3 mM.

[0015] Preferably, in step (3), the temperature of the solvothermal reaction is 110-120 ℃, and the time of the solvothermal reaction is 8-10 h.

[0016] Application of a Cu-Mn bimetallic catalyst in electrocatalytic hydrogenation of aldehyde biomass derivatives to alcohol biomass derivatives.

[0017] Preferably, the aldehyde biomass derivative is preferably furfural, 5-hydroxymethylfurfural, benzaldehyde or cinnamaldehyde.

[0018] Preferably, the catholyte is a 1-2 M, pH=6-7.5 phosphate buffer containing 10-70 mM aldehyde biomass derivative, and the anolyte is a 1-2 M, pH=6-7.5 phosphate buffer, a platinum wire electrode is used as a counter electrode and placed in the anolyte, a Cu-Mn bimetallic catalyst is used as a working electrode and a silver / silver chloride electrode is used as a reference electrode and placed in the catholyte, the working electrode is first activated by CV, then an external voltage of -0.3 to -0.5 V vs. RHE is applied, and a constant voltage coulombic electrolysis reaction is carried out until the charge reaches 200-220 C, the reaction is stopped, the catholyte is removed, and high-phase liquid chromatography is used to separate and obtain the alcohol biomass derivative.

[0019] Preferably, during CV activation, the voltage range is 0.6-0.9 V vs. RHE, the scanning speed is 150-250 mv / s, and the CV scanning is 10-20 times.

[0020] Advantages:

[0021] (1) The application develops a preparation method of a Cu-Mn bimetallic catalyst. First, Cu-P is deposited on a foamed copper by an electrodeposition method, then Mn-MOF is grown on the surface of Cu-P / CF by a solvothermal method, and the electrohydrogenation process is further regulated. The reaction has high catalytic activity, the whole process is simple to operate, and the cost is low.

[0022] (2) The Cu-Mn bimetallic catalyst prepared by the application belongs to a non-noble metal supported catalyst, and the raw materials for preparing the catalyst are inexpensive.

[0023] (3) The Cu-Mn bimetallic catalyst prepared by the application can be applied to catalyze furfural, 5-hydroxymethylfurfural, benzaldehyde or cinnamaldehyde, and has a broad application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 : Relationship between charge and concentration of furfural and furfuryl alcohol in catholyte during constant voltage coulombic electrolysis reaction. DETAILED DESCRIPTION

[0025] The technical solutions of the present application will be described clearly and completely in combination with specific embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of the present application.

[0026] The foam copper used in the following examples, comparative examples and application examples is commercially available foam copper (thickness 1 mm). After being purchased, the foam copper is pretreated according to the following process: cut into 1 cm x 1 cm (length x width), sequentially ultrasonic in 1 M HCl solution, acetone, ultrapure water, anhydrous ethanol, ultrapure water for 10 min, to clean the foam copper thoroughly, and dried in a 60 ℃ oven, and stored for use.

[0027] Example 1

[0028] The preparation method of the Cu-P@Mn-MOF / CF catalyst is as follows:

[0029] (1) An electrolyte containing 0.3 M CuSO4·5H2O, 0.03 M NaH2PO2·H2O, 0.03 M SDS and 0.03 M Na2SO4 is prepared with water as the solvent, and the total volume of the electrolyte is 40 mL;

[0030] (2) The electrolyte obtained in step (1) is placed in a 100 mL single-chamber electrolytic cell, and foam copper is used as the working electrode, a platinum wire electrode is used as the counter electrode, and a Hg / Hg2SO4 electrode is used as the reference electrode. The working electrode is taken out after electrodeposition at a deposition potential of -2 V vs. Hg / Hg2SO4 for 30 min, and then washed and dried to obtain foam copper with deposited Cu-P, which is marked as Cu-P / CF;

[0031] (3) A solvothermal solution containing 2 mM MnCl2·H2O, 2 mM terephthalic acid and 2 mM SDS is prepared with DMF as the solvent, and the total volume of the solvothermal solution is 30 mL. Then, the Cu-P / CF is placed in the solvothermal solution and subjected to solvothermal reaction at 120 ℃ for 10 h. The foam copper is taken out, washed and dried to obtain the target catalyst, which is marked as Cu-P@Mn-MOF / CF.

[0032] Comparative Example 1

[0033] The preparation method of the Cu-P / CF catalyst is as follows:

[0034] (1) Using water as the solvent, an electrolyte containing 0.3 M CuSO4·5H2O, 0.03 M NaH2PO2·H2O, 0.03 M SDS, and 0.03 M Na2SO4was prepared, and the total volume of the electrolyte was 40 mL;

[0035] (2) The electrolyte obtained in step (1) was placed in a 100 mL single-chamber electrolytic cell, and a copper foam was used as the working electrode, a platinum wire electrode was used as the counter electrode, and a Hg / Hg2SO4 electrode was used as the reference electrode. The copper foam was electrodeposited at a deposition potential of -2 V vs. Hg / Hg2SO4for 30 min. The working electrode was taken out, washed, and dried to obtain a copper foam on which Cu-P was deposited, which was marked as Cu-P / CF.

[0036] Comparative Example 2

[0037] The preparation method of the Cu / CF catalyst was as follows:

[0038] (1) Using water as the solvent, an electrolyte containing 0.3 M CuSO4·5H2O, 0.03 M SDS, and 0.03 M Na2SO4was prepared, and the total volume of the electrolyte was 40 mL;

[0039] (2) The electrolyte obtained in step (1) was placed in a 100 mL single-chamber electrolytic cell, and a copper foam was used as the working electrode, a platinum wire electrode was used as the counter electrode, and a Hg / Hg2SO4 electrode was used as the reference electrode. The copper foam was electrodeposited at a deposition potential of -2 V vs. Hg / Hg2SO4for 30 min. The working electrode was taken out, washed, and dried to obtain a copper foam on which Cu was deposited, which was marked as Cu / CF.

[0040] Comparative Example 3

[0041] The preparation method of the Mn-MOF / CF catalyst was as follows: DMF was used as the solvent to prepare a solvothermal solution containing 2 mM MnCl2·4H2O, 2 mM terephthalic acid, and 2 mM SDS, and the total volume of the solvothermal solution was 30 mL. Then, the copper foam was placed in the solvothermal solution and subjected to a solvothermal reaction at 120 ℃ for 10 h. The copper foam was taken out, washed, and dried to obtain a copper foam on which Mn-MOF was deposited, which was marked as Mn-MOF / CF.

[0042] Application Example 1

[0043] The catalyst prepared in the above Example 1, the catalyst prepared in Comparative Examples 1 to 3, and the copper foam (after pretreatment) were respectively used as the cathode electrode in the reaction of electrocatalytic hydrogenation of furfural, and the specific steps were as follows:

[0044] (1) Add 25 mL of an anolyte and a catholyte into a H-type electrolytic cell with a Nafion-117 proton exchange membrane, the anolyte is PBS solution (pH=6.7, 1M), and the catholyte is PBS solution containing 50 mM furfural (pH=6.7, 1M);

[0045] (2) Put a platinum wire electrode into the anolyte as a counter electrode, and put the catalyst prepared in Example 1, the catalyst prepared in Comparative Examples 1-3 or copper foam as a working electrode into the catholyte, and put a silver / silver chloride electrode as a reference electrode into the catholyte;

[0046] (3) Before the reaction starts, activate the working electrode by CV: the voltage range is 0.6-0.9 V vs. RHE, the scanning speed is 250 mv / s, and the CV scanning is 20 cycles;

[0047] (4) Use the CHI 760E electrochemical workstation, apply a voltage of -0.4 V vs. RHE, and electrolyze the reaction by constant voltage coulomb method (furfural is electrohydrogenated to furfuryl alcohol at the cathode side), until the charge reaches 210 C, and then stop the reaction;

[0048] (5) After the reaction ends, take out the catholyte, and perform qualitative and quantitative analysis by using a high-performance liquid chromatograph, the chromatographic conditions are as follows: the detector is an ultraviolet detector, the chromatographic column is an SB-C18 chromatographic column (4.6x150 mm, 5 μm), the mobile phase is acetonitrile: ultrapure water=50:50 (v / v), the flow rate is 1.0 mL / min, the injection amount is 5 μL, the chromatographic column temperature is 30 ℃, and the ultraviolet detector wavelength is 220 nm.

[0049] The activity results of different catalysts are shown in Table 1.

[0050]

[0051] As shown in Table 1, the copper foam has the lowest FF conversion rate, FA selectivity and Faraday efficiency, and the performance of the copper foam is greatly improved after being loaded with Cu / Mn, because the reduction of furfural involves the reduction of a complex C=O bond and the selective generation of the target product furfuryl alcohol. The catalysts in Comparative Examples 1, 2 and 3 not only have high activity of Cu / Mn to furfural, but also improve the selectivity of Cu / Mn to electrocatalytic hydrogenation (ECH) of furfural. In addition, the catalyst in Comparative Example 1 is doped with a heteroatom (P), which not only makes the material have a high specific surface area, but also can effectively adjust the electronic structure of Cu. Therefore, the catalyst in Example 1 (Cu-P@Mn-MOF / CF) has double active sites, and has higher activity for electrocatalytic hydrogenation of furfural.

[0052] In addition, in step (4), the relationship between the amount of charge and the concentration of furfural (FF) and furfuryl alcohol (FA) in the catholyte during the constant voltage coulombic electrolysis reaction is shown in Figure Figure 1 As can be seen from Figure 1 , as the amount of charge increases, the concentration of furfural decreases and the concentration of furfuryl alcohol increases, indicating that an electrohydrogenation reaction occurs and furfuryl alcohol is the only product.

[0053] Application Example 2

[0054] The catalyst prepared in Example 1 was used as the working electrode, and the difference from Application Example 1 was that in step (1), the concentration of the reaction substrate furfural in the catholyte was changed from 10 mM to 70 mM; and the other steps were the same as in Application Example 1.

[0055] The activity results of the catalyst at different concentrations of furfural are shown in Table 2. As can be seen from Table 2, the conversion rate of furfural increases as the concentration increases, while the selectivity of furfuryl alcohol and the Faraday efficiency reach a maximum at 50 mM, and the activity of the catalyst is the highest at a furfural concentration of 50 mM.

[0056]

[0057] Application Example 3

[0058] The catalyst prepared in Example 1 was used as the working electrode, and the difference from Application Example 1 was that in step (4), the electrolysis voltage was adjusted from -0.3 V to -0.5 V vs. RHE, and electrolysis tests were performed at every 0.05 V potential interval; and the other steps were the same as in Application Example 1.

[0059] The activity results of the catalyst at different potentials are shown in Table 3. As can be seen from Table 3, when the potential is -0.4 V vs. RHE, the conversion rate of furfural, the selectivity of furfuryl alcohol, and the Faraday efficiency reach the highest.

[0060]

[0061] Application Example 4

[0062] The catalyst prepared in Example 1 was used as the working electrode, and the difference from Application Example 1 was that in step (1), the PBS solution was replaced with a weakly acidic acetate buffer solution (1 M, PH=4.6) and a weakly basic carbonate buffer solution (1 M, PH=8.6) in sequence; and the other steps were the same as in Application Example 1.

[0063] The activity results of the catalyst at different pH values are shown in Table 4. As can be seen from Table 4, furfural exhibits better catalytic performance in a near-neutral phosphate buffer solution (1 M, PH=6.7).

[0064]

Claims

1. A Cu-Mn bimetallic catalyst characterized in that: The catalyst takes foamed copper as a substrate, and Cu-P is loaded on the foamed copper, and Mn-MOF grows on the surface of the Cu-P; In the formula, Cu-P is a copper-phosphorus composite, Mn-MOF is an organic framework material of Mn, and the organic ligand of the Mn-MOF is terephthalic acid.

2. A method for preparing the Cu-Mn bimetallic catalyst according to claim 1, characterized by, The steps are as follows: (1) Dissolve copper sulfate, hypophosphite, a surfactant and an electrodeposition additive in water to prepare an electrodeposition solution, and store for later use; the amounts of copper sulfate and hypophosphite are determined to ensure that the molar ratio of Cu to P is 10: (1-2); (2) Place the electrodeposition solution in a single-chamber electrolytic cell, and perform electrochemical deposition on a foamed copper substrate as a working electrode, a platinum wire electrode as a counter electrode and a Hg / Hg2SO4 electrode as a reference electrode, the deposition potential is -1.8 to -2 V vs. Hg / Hg2SO4, and the deposition time is 20-30 min, then take out the working electrode, wash and dry to obtain foamed copper with Cu-P deposited thereon, marked as Cu-P / CF; (3) Dissolve a manganese salt, an organic ligand and a surfactant in an organic solvent, then place the Cu-P / CF in the solvent, and perform a solvothermal reaction to grow Mn-MOF on the surface of the Cu-P, and then wash and dry to obtain the target catalyst; the organic ligand is terephthalic acid.

3. The method for preparing the Cu-Mn bimetallic catalyst as described in claim 2, characterized in that: In step (1), the hypophosphite is NaH2PO2 or KH2PO2, the surfactant is SDS, and the electrodeposition additive is Na2SO4 or K2SO4.

4. The method for preparing the Cu-Mn bimetallic catalyst as described in claim 2, characterized in that: In step (1), the amounts of copper sulfate, hypophosphite, surfactant and electrodeposition additive are determined to ensure that the molar ratio of Cu to P is 10: (1-2); the concentration of copper sulfate in the electrodeposition solution is 0.2-0.4 M.

5. The method for preparing the Cu-Mn bimetallic catalyst as described in claim 2, characterized in that: In step (2), the foamed copper is sequentially ultrasonically cleaned in 1-3 M HCl solution, acetone, water, ethanol and water before use, and then dried.

6. The method for preparing the Cu-Mn bimetallic catalyst according to claim 2, characterized in that: In step (3), the manganese salt is MnCl2, Mn(NO3)2 or MnSO4, and the surfactant is SDS; the organic solvent is DMF.

7. The method for preparing the Cu-Mn bimetallic catalyst according to claim 2, characterized in that: In step (3), the amounts of manganese salt, organic ligand and surfactant are determined to ensure that the molar ratio of Mn to the organic ligand is 1:1: (0.5-1); the concentration of the manganese salt in the organic solvent is 1-3 mM.

8. The method for preparing the Cu-Mn bimetallic catalyst as described in claim 2, characterized in that: In step (3), the temperature of the solvothermal reaction is 110-120 ℃, and the time is 8-10 h.

9. Application of the Cu-Mn bimetallic catalyst of claim 1 in electrocatalytic hydrogenation of an aldehyde biomass derivative to an alcohol biomass derivative, wherein the aldehyde biomass derivative is furfural, and the alcohol biomass derivative is furfuryl alcohol.

10. The use of the Cu-Mn bimetallic catalyst according to claim 9, characterized in that: In a double-chamber H-type electrolytic cell, a cathode electrolyte and an anode electrolyte are added respectively, and a proton exchange membrane is used to separate the cathode electrolyte and the anode electrolyte, wherein the cathode electrolyte is a 1-2 M, pH=6-7.5 phosphate buffer solution containing 10-70 mM aldehyde biomass derivatives, the anode electrolyte is a 1-2 M, pH=6-7.5 phosphate buffer solution, a platinum wire electrode is used as a counter electrode and is placed in the anode electrolyte, a Cu-Mn bimetallic catalyst is used as a working electrode and a silver / silver chloride electrode is used as a reference electrode and is placed in the cathode electrolyte, the working electrode is first activated by CV, then an external voltage of -0.3 to -0.5 V vs. RHE is applied, and a constant voltage coulomb method is used for electrolysis until the charge reaches 200-220 ℃, the reaction is stopped, the cathode electrolyte is taken out, and high-phase liquid chromatography is used for separation to obtain alcohol biomass derivatives.

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