A method for preparing an electrochemical catalyst from solid humin

Abstract

The application discloses a method for preparing an electrochemical catalyst from solid humin, and first, solid humin is obtained, then pretreated humin powder, mixed metal salt and thiourea are added into a zirconium oxide or agate ball mill jar, then ethanol solution is added until the powder is just wet; subsequently, grinding balls are added, the jar cover is tightly covered, and the jar is placed in a planetary ball mill for ball milling; after the ball milling is completed, ethanol aqueous solution is used to wash out the slurry in the jar, the mixed solution is thinly spread in a container and transferred to an oven for drying; after drying, flaky particles are formed, which are ground into powder using a mortar and transferred to a porcelain boat and placed in a tube furnace for precalcination under a nitrogen flow; after the calcination is completed, the solid powder is collected, which is the humin derivative carbon supported transition metal sulfide electrocatalyst to be prepared; compared with a traditional carbon supported metal catalyst, the application has multiple advantages of high intrinsic activity, strong structural stability and excellent electronic adjustability in HMF oxidation, and provides an ideal material platform for efficient electrocatalytic conversion of high-purity biomass platform molecules.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a method for preparing an electrochemical catalyst from solid humin. Background Technology

[0002] Biorefining technology for producing high-value-added platform chemicals (such as 5-hydroxymethylfurfural, HMF, furfural, and levulinic acid) from biomass has attracted widespread attention. However, during the acid-catalyzed hydrothermal conversion of biomass, a large amount of dark brown, structurally complex polymer byproducts—humins—are inevitably generated. Statistics show that humins can be produced at yields of 10-30 wt% in HMF production. The lack of resource utilization methods and the resulting additional waste treatment costs increase the cost of HMF production, becoming a significant bottleneck restricting the economic viability of biorefining.

[0003] Huminol is a highly cross-linked macromolecular polymer formed from sugars, HMF, and their degradation products through reactions such as aldol condensation, etherification, and furan ring-opening. It is characterized by high aromaticity, abundant oxygen-containing functional groups, and good thermal stability, and typically exists as a black solid or a high-viscosity liquid. Low-polymerization liquid humulone can be dissolved in solvents and chemically modified for high-value utilization. However, the utilization of highly polymerized solid humulone remains limited, with the vast majority being directly burned as low-value fuel, resulting in resource waste and carbon emissions. A few studies have shown that solid humulone can utilize its self-crosslinking polymerization under heat, controlling the pore structure by temperature control, to prepare thermosetting materials. Other studies have modified it with alkaline solution (3–5 mol / L NaOH) at 200–210 °C, converting it into a product containing phenolic aromatic functional groups, which can then be polycondensed with formaldehyde to prepare wood adhesives. Therefore, exploring high-value-added resource utilization pathways for solid humulone is of great significance for improving the economic efficiency and environmental friendliness of the entire biorefining process.

[0004] It is worth noting that the unique structure of humin gives it the potential to be a precursor for carbon-based catalysts. Solid humin has a high carbon content and its surface is rich in oxygen-containing functional groups such as carboxyl, carbonyl, and hydroxyl groups. These functional groups can form coordination bonds with metal ions, serving as anchoring sites for metal nanoparticles. This facilitates high dispersion of the active component and avoids the problem of metal agglomeration in traditional impregnation methods. By controlling the carbonization temperature and activation method, carbon materials with different pore structures (micropores, mesopores, macropores) and degrees of graphitization can also be obtained. Summary of the Invention

[0005] In view of the problems existing in the prior art, the purpose of this invention is to provide a method for preparing an electrochemical catalyst from solid humin. This invention transforms solid humin from waste into a valuable resource, using it as a carbon source support for the catalyst. This catalyst combines a highly conductive carbon framework with highly active bimetallic sulfide nanoparticles.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: A method for preparing an electrochemical catalyst from solid humin includes the following steps: 1) Solid humins pretreatment: The solid humins obtained by washing and filtering the HMF concentrate with water are washed with deionized water to remove soluble substances, drained in a tray with a pore size, and then the black humins are transferred to an oven for drying. After the black humins have a moisture content of less than 10%, they are crushed and sieved to obtain black powder. 2) Preparation of Huminin-derived carbon-supported transition metal sulfide electrocatalyst: First, the humin powder, mixed metal salt, and thiourea pretreated in step 1) are added to a zirconium oxide or agate ball mill jar. Then, an ethanol solution is added until the powder is just wetted. Grinding balls are then added, the jar is sealed, and the jar is placed in a planetary ball mill for ball milling. After ball milling, the slurry in the jar is washed out completely with an ethanol-water solution. The mixture is spread thinly in a container and transferred to an oven for drying. After drying, it becomes flaky particles, which are then ground into powder using a mortar and pestle. The powder is transferred to a ceramic boat and placed in a tube furnace for pre-calcination under a nitrogen atmosphere. After calcination, the solid powder is collected, which is the huminin-derived carbon-supported transition metal sulfide electrocatalyst to be prepared.

[0007] Furthermore, in step 1), the pretreatment of black rot has a moisture content of 5-10% and a drying temperature of 40-60℃.

[0008] Furthermore, in step 1), the sieve has a mesh size of 200.

[0009] Further, in step 2), the mass ratio of the hydrated metal salt to thiourea and solid humic acid powder is 0.5~1:2~3:2~5; wherein the hydrated metal salt is one or more of nickel chloride hexahydrate, cobalt chloride hexahydrate, manganese chloride tetrahydrate, copper chloride dihydrate, and ferric chloride hexahydrate.

[0010] Furthermore, in step 2), the ball-to-material ratio is 10:1; the ball milling speed is 300-400 rpm; the ball milling time is 2 hours; during the ball milling process, the milling is paused for 10 minutes every 30 minutes to cool down, and the temperature of the tank wall is controlled at 40-60℃.

[0011] Further, in step 4), under a nitrogen atmosphere, the temperature is heated to 350~400°C at a heating rate of 5-10°C / min for 2-4 hours for pre-calcination, and then the heating rate is controlled at 2-5°C / min to 600°C~700°C and held for 3-4 hours.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) This invention transforms solid humic acid from waste into a valuable resource, using it as a carbon source support for a catalyst. This catalyst combines a highly conductive carbon framework with highly active bimetallic sulfide nanoparticles. Compared to traditional carbon-supported metal catalysts, this invention has multiple advantages in HMF oxidation, including high intrinsic activity, strong structural stability, and excellent electronic tunability, providing an ideal material platform for the efficient electrocatalytic conversion of high-purity biomass platform molecules. 2) Research on the application of humin-derived carbon-supported transition metal sulfides to the electro-oxidation reaction of organic molecules (especially HMF electro-oxidation) is still rarely reported. Compared with conventional carbon supports, humin-derived carbon has unique structural advantages: abundant oxygen-containing functional groups can serve as anchoring sites for sulfide nanoparticles, achieving high dispersion and stable loading of active components. The multi-doped carbon support not only provides abundant mesoporous channels, but its heteroatom (N, O, S) regulated electronic structure can also optimize the adsorption energy of HMF molecules and promote the desorption of key intermediates, thereby achieving high Faradaic efficiency and FDCA selectivity under alkaline conditions. Attached Figure Description

[0013] Figure 1 A schematic diagram of the multi-atom-doped carbon-supported metal sulfide catalyst prepared in this invention; Figure 2 This is a schematic diagram of a single electrolytic cell three-electrode system; Figure 3 The LSV curves are for catalyst-supported nickel foam as the working electrode under strongly alkaline conditions. Figure 4 It is an H-type electrolytic cell device; Figure 5 This is a spectrum used to detect changes in products during charge transfer in the electrolysis process; Figure 6 The images show the liquid phase detection spectra in the electrolyte before and after electrolysis. Detailed Implementation

[0014] The present invention will be further described below with reference to embodiments and accompanying drawings, but the scope of protection of the present invention is not limited to the scope described.

[0015] Example 1 Catalyst Preparation 4.5g of humins powder after sieving, 3.2g of thiourea, and 2g of nickel chloride hexahydrate were added to a zirconia ball mill jar. 5g of ethanol aqueous solution was added to wet the powder, and the mixture was ball-milled for 2 hours. After ball milling, the powder was passed through a 200-mesh sieve, washed with 20% ethanol aqueous solution, and dried in a 105°C oven for 4 hours. The powder was then transferred to a ceramic boat and placed in a tube furnace under fume hood, with the exhaust end directed to alkaline absorption. The furnace was pre-calcined at 350°C for 2 hours at a nitrogen atmosphere with a heating rate of 5°C / min, followed by a heating rate of 5°C / min to 700°C and holding for 4 hours. After cooling, the solid powder was collected to obtain a multi-atom-doped carbon-supported metal sulfide catalyst, denoted as Ni. x S y / NSOC.

[0016] Example 2 Catalyst Preparation 4.5 g of sieved humins powder, 3.2 g of thiourea, and 2 g of cobalt chloride hexahydrate were added to a zirconia ball mill jar. 5 g of ethanol aqueous solution was added to wet the powder, and the mixture was ball-milled for 2 hours. After ball milling, the powder was passed through a 200-mesh sieve, washed with 20% ethanol aqueous solution, and dried in a 105°C oven for 4 hours. The powder was then transferred to a ceramic boat and placed in a tube furnace under fume hood, with the exhaust end directed to alkaline absorption. The furnace was pre-calcined at 350°C for 2 hours at a nitrogen atmosphere with a heating rate of 5°C / min, followed by a heating rate of 5°C / min to 700°C and holding for 4 hours. After cooling, the solid powder was collected to obtain a multi-atom-doped carbon-supported metal sulfide catalyst, denoted as Co. x S y / NSOC.

[0017] Example 3 Catalyst Preparation 4.5 g of sieved humins powder, 3.2 g of thiourea, 0.8 g of nickel chloride hexahydrate, and 1.2 g of cobalt chloride hexahydrate were added to a zirconia ball mill jar. 5 g of ethanol aqueous solution was added to wet the powder, and the mixture was ball-milled for 2 hours. After ball milling, the powder was passed through a 200-mesh sieve, washed with 20% ethanol aqueous solution, and dried in a 105°C oven for 4 hours. The powder was then transferred to a ceramic boat and placed in a tube furnace. The furnace was then subjected to fume hood operation, with the exhaust end directed to alkaline absorption. The furnace was pre-calcined at 350°C for 2 hours at a heating rate of 5°C / min under a nitrogen atmosphere, followed by a heating rate of 5°C / min to 700°C and holding for 4 hours. After cooling, the solid powder was collected to obtain a multi-atom-doped carbon-supported metal sulfide catalyst, such as... Figure 1 As shown, denoted as Ni 0.8 Co 1.2 S / NSOC.

[0018] Example 4 Catalyst Preparation Carbon nanotubes were refluxed in concentrated HNO3 at 80°C for 3 hours to introduce oxygen-containing functional groups. 0.8 g of nickel chloride hexahydrate, 1.2 g of cobalt chloride hexahydrate, and 3.2 g of thiourea were first dissolved in ethanol-water mixture, and then the treated carbon nanotubes were added. The mixture was transferred to a PTFE-lined autoclave and reacted at 160°C for 12 hours. After natural cooling, the precipitate was collected by centrifugation and filtration, and washed three times alternately with deionized water and ethanol. The precipitate was then vacuum-dried at 60-80°C for 12 hours, transferred to a ceramic boat, and placed in a tube furnace. The reaction was carried out in a fume hood, with the exhaust end directed to an alkaline solution for absorption. The mixture was heated to 500°C at a nitrogen atmosphere with a heating rate of 5°C / min, annealed for 2 hours, cooled, and the solid powder was collected to obtain an oxygen-doped carbon-supported metal sulfide catalyst, denoted as Ni. 0.8 Co 1.2 S / OC.

[0019] Example 5 Catalyst Preparation Activated carbon was dried in an oven at 100°C for 12 hours to remove adsorbed moisture. 0.8 g of nickel chloride hexahydrate, 1.2 g of cobalt chloride hexahydrate, and 3.2 g of thiourea were first dissolved in ethanol-water mixture, then added to the treated activated carbon. The mixture was ultrasonically dispersed for 30 minutes, magnetically stirred for 2 hours, and dried in an oven at 80°C for 12-24 hours to completely remove the solvent. The powder was then ground in an agate mortar for 10 minutes, passed through a 200-mesh sieve, and transferred to a porcelain boat placed in a tube furnace. The furnace was then operated in a fume hood, with the exhaust end directed to the alkaline solution for absorption. The mixture was pre-calcined at 350°C for 2 hours at a nitrogen atmosphere with a heating rate of 5°C / min, followed by a heating rate of 2-5°C / min to 600°C-700°C and holding for 4 hours. After cooling, the solid powder was collected to obtain the carbon-supported metal sulfide catalyst, denoted as Ni. 0.8 Co 1.2 S / C.

[0020] Example 6 Electrochemical Performance Testing Using the catalyst-added nickel foam electrode as the working electrode, denoted as Ni x S y / NSOC / NF electrode; Co x S y / NSOC / NF electrode; Ni 0.8 Co 1.2 S / NSOC / NF electrode; Ni 0.8 Co 1.2 S / OC / NF electrode; Ni 0.8 Co 1.2 An S / C / NF electrode, a carbon rod as the counter electrode, and mercury / mercury oxide as the reference electrode are assembled to obtain a three-electrode system for a single electrolytic cell, such as... Figure 2As shown, the electrolyte was 1M KOH (pH ≈ 14). Linear voltammetry LSV was performed using 20ml of electrolyte or 20ml of (1M KOH + 10mM HMF) reaction solution. No IR compensation was performed during the electrochemical test.

[0021] The results show that... Figure 3 As shown, Ni 0.8 Co 1.2 The HMF oxidation onset potential (1.32V) of the S / NSOC / NF electrode is higher than that of other Ni electrodes. 0.8 Co 1.2 S / OC / NF electrode (1.42V) and Ni 0.8 Co 1.2 The oxidation initiation potential of the S / C / NF (1.42V) electrode shifted negatively by 100 mV, and the peak current density increased by three times. This indicates that the multi-atom-doped carbon-supported metal sulfide catalyst prepared by humulin pyrolysis has higher intrinsic activity for HMF oxidation than carbon-supported metal sulfide catalysts prepared from other carbon sources. This is attributed to the abundant oxygen-containing functional groups on humulin serving as anchoring sites for sulfide nanoparticles, achieving high dispersion and stable loading of the active component. In contrast, traditional carbon supports lack anchoring sites, resulting in uneven metal particle distribution and significant agglomeration. Furthermore, the electronic structure is regulated by heteroatoms (N, O, S). In addition, Ni... 0.8 Co 1.2 The HMF oxidation initiation potential of the S / NSOC / NF electrode is also higher than that of other Ni electrodes. x S y The oxidation initiation potentials of the / NSOC / NF and CoxSy / NSOC / NF electrodes are earlier, mainly because the bimetallic synergistic effect between Ni and Co also promotes electron transfer.

[0022] Example 7 Ni 0.8 Co 1.2 S / NSOC / NF working electrode HMF electrolytic oxidation performance test Replace the three-electrode system with an H-type electrolytic cell, such as Figure 4 As shown, the cathode contains 20 ml of electrolyte, and the anode contains 20 ml of (1 M KOH + 10 mM HMF). A constant voltage electrolysis method is used, with a constant voltage of 1.4 V. Ni 0.8 Co 1.2 An electrocatalytic oxidation of HMF to FDCA occurs at the S / NSOC / NF working electrode, while water reduction to H2 occurs at the counter electrode. HPLC analysis of the products yields the following results: Figure 5-6As shown in the figure. HPLC results showed that HMF was basically completely converted, with a certain amount of FFCA, HMFCA and a small amount of HMF and DFF present. The final HMF conversion rate was approximately 99%, the molar yield of FDCA was approximately 98.30%, and the Faraday efficiency was 98%.

Claims

1. A method for preparing an electrochemical catalyst from solid humin, characterized in that... Includes the following steps: 1) Solid humins pretreatment: The solid humins obtained by washing and filtering the HMF concentrate with water are washed with deionized water to remove soluble substances, drained in a tray with a pore size, and then the black humins are transferred to an oven for drying. After the black humins have a moisture content of less than 10%, they are crushed and sieved to obtain black powder. 2) Preparation of Huminin-derived carbon-supported transition metal sulfide electrocatalyst: First, the humin powder, mixed metal salt, and thiourea pretreated in step 1) are added to a zirconium oxide or agate ball mill jar. Then, an ethanol solution is added until the powder is just wetted. Grinding balls are then added, the jar is sealed, and the jar is placed in a planetary ball mill for ball milling. After ball milling, the slurry in the jar is washed out completely with an ethanol-water solution. The mixture is spread thinly in a container and transferred to an oven for drying. After drying, it becomes flaky particles, which are then ground into powder using a mortar and pestle. The powder is transferred to a ceramic boat and placed in a tube furnace for pre-calcination under a nitrogen atmosphere. After calcination, the solid powder is collected, which is the huminin-derived carbon-supported transition metal sulfide electrocatalyst to be prepared.

2. The method for preparing an electrochemical catalyst from solid humin according to claim 1, characterized in that... In step 1), the pretreatment of black rot has a moisture content of 5~10% and a drying temperature of 40~60℃.

3. The method for preparing an electrochemical catalyst from solid humin according to claim 1, characterized in that... In step 1), the sieve has a mesh size of 200.

4. The method for preparing an electrochemical catalyst from solid humin according to claim 1, characterized in that... In step 2), the mass ratio of the hydrated metal salt to thiourea and solid humic acid powder is 0.5~1:2~3:2~5; wherein the hydrated metal salt is one or more of nickel chloride hexahydrate, cobalt chloride hexahydrate, manganese chloride tetrahydrate, copper chloride dihydrate, and ferric chloride hexahydrate.

5. The method for preparing an electrochemical catalyst from solid humin according to claim 1, characterized in that... In step 2), the ball-to-material ratio is 10:1; the ball milling speed is 300-400 rpm; the ball milling time is 2 hours; during the ball milling process, pause for 10 minutes every 30 minutes to cool down, and control the tank wall temperature to 40-60℃.

6. The method for preparing an electrochemical catalyst from solid humin according to claim 1, characterized in that... In step 2), under a nitrogen atmosphere, the temperature is raised to 350-400°C at a rate of 5-10°C / min for 2-4 hours for pre-calcination. Then, the temperature is raised to 600-700°C at a rate of 2-5°C / min and held for 3-4 hours.

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