A photothermal catalyst for the photocatalytic depolymerization of lignin and a preparation method thereof

Abstract

The present invention discloses a photothermal catalyst for concentrating and depolymerizing lignin and a preparation method thereof, belonging to the technical field of biomass resource utilization. The above-mentioned photothermal catalyst uses a metal substrate as the base, and a photothermal conversion layer and a photothermal catalytic layer are sequentially constructed on the surface of the substrate, and it is a catalyst with an integral structure; the photothermal conversion layer includes MnFe2O4 nanosheets, and the photothermal catalytic layer includes a composite catalyst BiOBr@Cr2S3 and a bimetallic catalyst Ni-Re. Under the concentrating solar collector device, the photothermal conversion layer in the photothermal catalyst of the present invention can effectively absorb light in the infrared region and convert it into heat energy to provide sufficient energy for the reaction; the photothermal catalytic layer in it can efficiently promote the progress of the reaction after absorbing ultraviolet-visible light. Moreover, the recovery method of the catalyst is simple, the recycling performance is good, the raw material cost is low, and it has the advantages of environmental friendliness and ecological protection, which is of great significance for the industrial production of lignin.

Description

Technical Field

[0001] The present invention relates to the technical field of biomass resource utilization, and particularly relates to a photothermal catalyst for concentrating and depolymerizing lignin and a preparation method thereof. Background Art

[0002] The rapid development of human society's industry and economy severely depends on fossil resources, leading to the depletion of traditional fossil fuel reserves and increasingly serious environmental problems. This has prompted people to explore green and clean renewable resources to effectively replace fossil resources. Lignin is the most abundant renewable aromatic hydrocarbon resource in nature and has great application potential in replacing fossil fuels to produce high-value aromatic derivatives. Currently, the utilization methods of lignin mainly include direct combustion method, high-temperature pyrolysis method, acid-base catalysis method, etc. These methods usually require a large amount of energy consumption, and also lead to non-selective conversion of products and serious environmental pollution problems. Photocatalytic reactions driven by solar energy are capable of generating substances or reaction intermediates with oxidation-reduction properties under mild conditions. Usually, these intermediates have high reaction activities and can accelerate the promotion of reactions that are difficult to carry out kinetically. It is a new possibility beyond traditional thermal catalysis and enables lignin-based raw materials that are difficult to transform and utilize to be selectively converted into target products under mild conditions, which has attracted more and more interest in the academic community.

[0003] However, there are problems of low product selectivity and high energy consumption in the resource utilization of lignin by relying on traditional thermal catalysis methods. Although photocatalytic technology has the advantages of environmental friendliness and controllable product selectivity, various commonly used photocatalysts currently have problems such as low light utilization efficiency, difficult separation of photo-generated carriers, easy recombination of electron-hole pairs, and difficult effective control of reaction selectivity, which seriously hinder the large-scale value utilization of lignin. Summary of the Invention

[0004] Object of the Invention: To solve the technical problems existing in the prior art, the present invention aims to provide a photothermal catalyst for concentrating and depolymerizing lignin with high reactant selectivity, high reaction efficiency, and mild reaction conditions. Moreover, the present invention also provides a preparation method of the photothermal catalyst.

[0005] Technical Solution: The photothermal catalyst for concentrating and depolymerizing lignin according to the present invention uses a metal matrix as a substrate, and a photothermal conversion layer and a photothermal catalytic layer are sequentially constructed on the surface of the substrate; the photothermal conversion layer includes MnFe2O4 nanosheets, and the photothermal catalytic layer includes a composite catalyst BiOBr@Cr2S3 and a bimetallic catalyst Ni-Re.

[0006] Furthermore, the molar ratio of MnFe2O4, BiOBr, Cr2S3, Ni, and Re is 10:8:3 - 5:0.5 - 1:0.5

[0007] Further, the metal matrix is a metal fiber felt, and the metal fiber felt is a ferritic stainless steel fiber felt, an austenitic stainless steel fiber felt, or an austenitic-ferritic duplex stainless steel fiber felt. Preferably, the metal fiber felt is an austenitic-ferritic duplex stainless steel fiber felt.

[0008] The preparation method of the photothermal catalyst for concentrating solar lignin depolymerization according to the present invention comprises the following steps:

[0009] (1) The metal matrix is pretreated and placed in a solvent, then a manganese source and an iron source are added. After mixing evenly, an alkali solution is added. After adjusting the pH value, hydrothermal reaction and calcination treatment are carried out in sequence to obtain a metal matrix with MnFe2O4 nanosheets grown on the surface;

[0010] (2) Dissolve the bromine source in a solvent to obtain solution one, dissolve the bismuth source in a mixed solvent, and ultrasonically obtain solution two. Drop solution one into solution two to obtain a mixed solution. Place the material prepared in step (1) in the mixed solution, carry out hydrothermal reaction, and take it out and dry it after completion;

[0011] (3) Place the material prepared in step (2) in an aqueous solution of a chromium source, add a sulfur source and mix evenly, then carry out heat treatment, take it out and dry it after completion to obtain a metal matrix loaded with the composite catalyst BiOBr@Cr2S3 and MnFe2O4 nanosheets;

[0012] (4) Place the material prepared in step (3) in an aqueous solution of a nickel source and a rhenium source, ultrasonically disperse it, take it out and carry out a high-temperature reduction reaction in an argon-hydrogen mixed gas to obtain a metal matrix loaded with the bimetallic catalyst Ni-Re, the composite catalyst BiOBr@Cr2S3 and MnFe2O4 nanosheets, which is the photothermal catalyst for concentrating solar lignin depolymerization.

[0013] Further, in step (1), the manganese source is manganese chloride tetrahydrate, the iron source is iron nitrate nonahydrate, the molar ratio of the manganese source to the iron source is 1:2, the solvent is deionized water, and the concentration of the manganese source in the solvent is 0.15 - 0.55 mol / L; the alkali solution is an aqueous solution of sodium hydroxide, an aqueous solution of potassium hydroxide, or ammonia water, the pH value is adjusted to 9 - 11, and the concentration of the alkali solution is 0.15 - 0.5 mol / L; the conditions of the hydrothermal reaction are: reacting at 95 - 150 °C for 6 - 12 h; the conditions of the calcination treatment are: reacting at 300 - 450 °C for 5 - 8 h.

[0014] Further, in step (2), the bromine source is potassium bromide, the bismuth source is bismuth nitrate pentahydrate, the molar ratio of the bromine source to the bismuth source is 1:1, the solvent is water, and the concentration of the bromine source in the solvent is 0.1 - 0.5 mol / L; the mixed solvent is an acetic acid aqueous solution, in the acetic acid aqueous solution, the mass fraction of ethanol is 20 - 40%, and the time of ultrasonic treatment is 1 - 2 h; the conditions of the hydrothermal reaction are: reacting at 120 - 200 °C for 12 - 24 h, and the conditions of drying are: drying by blowing air at 100 - 150 °C for 5 - 8 h.

[0015] Further, in step (3), the chromium source is chromium nitrate nonahydrate, the sulfur source is sodium sulfide, the molar ratio of the chromium source to the sulfur source is 2:3, and the concentration of the chromium source in the aqueous solution of the chromium source is 0.1 - 0.3 mol / L; the method of mixing evenly is: ultrasonic treatment for 30 - 90 min; the conditions of the heat treatment are: reacting at 50 - 100 °C for 15 - 90 min.

[0016] Further, in step (4), the nickel source is nickel nitrate hexahydrate, the rhenium source is ammonium perrhenate, and the molar ratio of the nickel source to the rhenium source is 1 - 2:1; in the aqueous solutions of the nickel source and the rhenium source, the concentration of the rhenium source is 0.005 - 0.05 mol / L; the conditions of the high-temperature reduction reaction are: reacting at 150 - 300 °C for 2 - 5 h.

[0017] The present invention provides an application of the above-mentioned photothermal catalyst for concentrating solar depolymerization of lignin in concentrating solar depolymerization of lignin.

[0018] Further, the method of the application is: using lignin as a reaction raw material, using an aqueous solution of methanol as a solvent, placing the photothermal catalyst in a high-pressure reaction device, using a concentrating solar collector device to focus the simulated sunlight generated by a xenon lamp on the surface of the photothermal catalyst, adjusting the distance between the condenser lens and the catalyst, and performing a depolymerization reaction; the conditions of the depolymerization reaction are: the light intensity is 500 - 3500 mW·cm -2 , the hydrogen pressure is 1 - 3 bar, and the reaction time is 5 - 10 h.

[0019] Principle of the invention: The present invention constructs a photothermal catalyst for concentrating solar depolymerization of lignin. By combining thermal catalysis with photocatalysis, under a concentrating solar collector device, the photocatalytic conversion of lignin is efficiently promoted. The condenser lens can converge the irradiated sunlight onto the monolithic photothermal catalyst, and a local high-temperature environment and a high-throughput light intensity can be simultaneously generated on its surface. Utilizing this amplified photothermal effect under concentration to provide sufficient energy for the catalytic reaction of lignin enables the reaction to proceed under mild and controllable conditions, which helps to improve product selectivity and reaction efficiency.

[0020] The photothermal catalyst for concentrating and depolymerizing lignin in the present invention uses a corrosion-resistant metal fiber felt as the substrate, and a photothermal conversion layer and a photothermal catalytic layer are sequentially constructed on the surface of the substrate. Among them, the photothermal conversion layer uses magnetic MnFe2O4 nanosheets, and the magnetic characteristics are beneficial to the adsorption of the catalyst on the surface of the metal substrate to prevent shedding. MnFe2O4 can effectively absorb light in the infrared region and convert it into heat energy, generating a local high-temperature environment on the surface of the catalyst to provide energy for the reaction; the composite catalyst BiOBr@Cr2S3 and the bimetallic catalyst Ni-Re are used as the photothermal catalytic layer. BiOBr@Cr2S3 has a Z-type heterojunction structure, which can effectively promote the separation and transmission of photogenerated carriers (electrons - holes). Ni-Re can be used as the active site for hydrogenolysis reduction reaction, and can catalyze the redox reaction of lignin under mild and controllable conditions.

[0021] Advantages: Compared with the prior art, the present invention has the following remarkable advantages:

[0022] (1) The present invention studies the concentrated photothermal depolymerization of lignin to obtain low-molecular-weight products, which can effectively alleviate the environmental pollution problems brought by fossil fuel resources and at the same time deepen the research on the resource utilization of biomass;

[0023] (2) The monolithic photothermal catalyst prepared in the present invention can fit with the concentrating and heat-collecting reaction device, can locally heat the catalyst to provide heat for the reaction, and the photothermal conversion layer (magnetic material manganese ferrite) of the catalyst can effectively perform photothermal conversion to realize the energy supply for the lignin catalytic reaction system;

[0024] (3) The preparation method of the monolithic photothermal catalyst prepared in the present invention is simple and efficient, the recovery cost is low, and the recycling performance is excellent, which is beneficial to large-scale industrial production. Description of the Drawings

[0025] Figure 1 It is the scanning electron microscope image of the photothermal catalyst prepared in Example 1 of the present invention. Detailed Embodiments

[0026] Next, the present invention will be further described in conjunction with specific embodiments and drawings.

[0027] Example 1: The photothermal catalyst for concentrating and depolymerizing lignin in the present invention uses an austenitic-ferritic duplex stainless steel fiber felt as the substrate, and a photothermal conversion layer with magnetic MnFe2O4 nanosheets and a photothermal catalytic layer containing the composite catalyst BiOBr@Cr2S3 and the bimetallic catalyst Ni-Re are sequentially constructed on the surface of the substrate. The preparation method includes the following steps:

[0028] (1) Using an austenite-ferrite duplex stainless steel fiber felt with an area of 1.5 cm × 1.5 cm as the substrate, ultrasonic washing with a 0.5 mol / L hydrochloric acid solution for 1 h to remove surface oxides and impurities, then taking it out and drying for standby;

[0029] (2) Weigh 8.08 g of ferric nitrate nonahydrate and 1.98 g of manganese chloride tetrahydrate and dissolve them in 50 mL of deionized water; then add the above stainless steel fiber felt and slowly dropwise add an aqueous potassium hydroxide solution with a concentration of 0.15 mol / L to adjust the pH value to 9; after the solution is evenly dispersed, transfer it to a high-pressure reaction kettle and react at 95 °C for 12 h; then take out the stainless steel fiber felt, wash it and place it in a muffle furnace, heat it up to 300 °C at a heating rate of 5 °C / min in an air atmosphere and keep it warm for 8 h. After the reaction is completed, a stainless steel fiber felt with magnetic MnFe2O4 nanosheets grown on the surface as a photothermal conversion layer can be prepared;

[0030] (3) Weigh 0.95 g of potassium bromide and 3.88 g of bismuth nitrate pentahydrate, and add them to 30 mL of deionized water and 40 mL of acetic acid aqueous solution with a mass fraction of 40% respectively. After being evenly dispersed, slowly dropwise add the potassium bromide aqueous solution to the bismuth nitrate acetic acid aqueous solution under vigorous stirring, add the material prepared in step (2) to this solution, transfer it to a hydrothermal reaction kettle and react at 200 °C for 12 h; take it out, wash it and dry it in a blast dryer at 100 °C for 5 h;

[0031] (4) Weigh 2.40 g of chromium nitrate nonahydrate and dissolve it in 20 mL of deionized water and put the material prepared in step (3) into it; weigh 0.71 g of sodium sulfide and dissolve it in 40 mL of deionized water, and ultrasonic it for 30 min; then slowly dropwise add the sodium sulfide solution to the chromium nitrate solution. After mixing evenly, place the solution in an oil bath at 100 °C and react for 15 min to load Cr2S3. After the reaction is completed, wash and dry it;

[0032] (5) Weigh 0.29 g of nickel nitrate hexahydrate and 0.13 g of ammonium perrhenate and add them to 50 mL of deionized water. After complete dissolution, place the material prepared in step (4) in the solution and let it stand and age for 12 h; finally, react at 150 °C for 5 h in an atmosphere of 5% hydrogen and 95% argon. After the reaction, wash and dry it to obtain a photothermal catalyst for concentrating solar lignin depolymerization, denoted as 10MnFe2O4 / 8BiOBr@3Cr2S3@1Ni-0.5Re. Its scanning electron microscope image is as Figure 1 shown. It can be seen from the figure that MnFe2O4 nanosheet structures with a thickness of about 5 - 10 nm grow on the surface of the stainless steel metal fiber felt, spherical BiOBr nanoflowers with a diameter of about 0.5 - 1 μm and Cr2S3 nanoparticles with a size of about 200 nm are loaded on the surface of the nanosheet layer, and Ni and Re nanoparticles are smaller in size and deposited on the surface of the catalyst.

[0033] Example 2: The photothermal catalyst for concentrating and depolymerizing lignin in the present invention uses an austenite-ferrite duplex stainless steel fiber felt as the substrate. A photothermal conversion layer of magnetically functional MnFe₂O₄ nanosheets and a photothermal catalytic layer containing the composite catalyst BiOBr@Cr₂S₃ and the bimetallic catalyst Ni-Re are sequentially constructed on the surface of the substrate. The preparation method includes the following steps:

[0034] (1) Using an austenite-ferrite duplex stainless steel fiber felt with an area of 1.5 cm × 1.5 cm as the substrate, ultrasonic washing with a 0.5 mol / L hydrochloric acid solution for 1 h to remove surface oxides and impurities, and taking it out for drying and standby;

[0035] (2) Weigh 8.08 g of ferric nitrate nonahydrate and 1.98 g of manganese chloride tetrahydrate and dissolve them in 50 mL of deionized water; then add the above-mentioned stainless steel fiber felt and slowly dropwise add a 0.15 mol / L aqueous potassium hydroxide solution to adjust the pH value to 9; after the solution is evenly dispersed, transfer it to a high-pressure reaction kettle and react at 120 °C for 10 h; then take out the stainless steel fiber felt, wash it and place it in a muffle furnace, heat it up to 350 °C at a heating rate of 5 °C / min in an air atmosphere and keep it warm for 6 h. After the reaction is completed, a stainless steel fiber felt with magnetic MnFe₂O₄ nanosheets grown on the surface as the photothermal conversion layer can be prepared;

[0036] (3) Weigh 0.95 g of potassium bromide and 3.88 g of bismuth nitrate pentahydrate, and add them to 30 mL of deionized water and 40 mL of acetic acid aqueous solution with a mass fraction of 35%, respectively. After being evenly dispersed, slowly drop the potassium bromide aqueous solution into the bismuth nitrate acetic acid aqueous solution under vigorous stirring, add the material prepared in step (2) to this solution, transfer it to a hydrothermal reaction kettle, and react at 180 °C for 15 h. Take it out, wash it and dry it in a blast dryer at 120 °C for 6 h;

[0037] (4) Weigh 3.20 g of chromium nitrate nonahydrate and dissolve it in 20 mL of deionized water and put the material prepared in step (3); weigh 0.94 g of sodium sulfide and dissolve it in 40 mL of deionized water, and ultrasonicate for 30 min; then slowly drop the sodium sulfide solution into the chromium nitrate solution. After mixing evenly, place the solution in an oil bath at 85 °C and react for 30 min to load Cr₂S₃. After the reaction is completed, wash and dry it;

[0038] (5) Weigh 0.29 g of nickel nitrate hexahydrate and 0.13 g of ammonium perrhenate and add them to 50 mL of deionized water. After complete dissolution, place the material prepared in step (4) in the solution and let it stand for aging for 12 h; finally, react at 150 °C for 5 h in an atmosphere of 5% hydrogen and 95% argon. After the reaction, wash and dry it to obtain a photothermal catalyst for concentrating and depolymerizing lignin, denoted as 10MnFe₂O₄ / 8BiOBr@4Cr₂S₃@1Ni-0.5Re.

[0039] Example 3: The photothermal catalyst for the photocatalytic depolymerization of lignin in the present invention uses an austenite-ferrite duplex stainless steel fiber felt as the substrate, and a photothermal conversion layer of magnetically active MnFe2O4 nanosheets and a photothermal catalytic layer containing the composite catalyst BiOBr@Cr2S3 and the bimetallic catalyst Ni-Re are sequentially constructed on the surface of the substrate. The preparation method includes the following steps:

[0040] (1) Use an austenite-ferrite duplex stainless steel fiber felt with an area of 1.5 cm × 1.5 cm as the substrate, and ultrasonically wash it with a 0.5 mol / L hydrochloric acid solution for 1 h to remove surface oxides and impurities, then take it out and dry it for later use;

[0041] (2) Weigh 8.08 g of ferric nitrate nonahydrate and 1.98 g of manganese chloride tetrahydrate and dissolve them in 50 mL of deionized water; then add the above stainless steel fiber felt and slowly dropwise add a 0.3 mol / L aqueous potassium hydroxide solution to adjust the pH value to 10; after the solution is evenly dispersed, transfer it to a high-pressure reaction kettle and react at 130 °C for 12 h; then take out the stainless steel fiber felt, wash it and place it in a muffle furnace, heat it up to 400 °C at a heating rate of 5 °C / min in an air atmosphere and keep it warm for 5.5 h. After the reaction is completed, a stainless steel fiber felt with magnetically grown MnFe2O4 nanosheets on the surface as the photothermal conversion layer can be prepared;

[0042] (3) Weigh 0.95 g of potassium bromide and 3.88 g of bismuth nitrate pentahydrate, and add them to 30 mL of deionized water and 40 mL of acetic acid aqueous solution with a mass fraction of 30%, respectively. After being evenly dispersed, slowly drop the potassium bromide aqueous solution into the bismuth nitrate acetic acid aqueous solution under vigorous stirring, add the material prepared in step (2) to this solution, transfer it to a hydrothermal reaction kettle, and react at 150 °C for 20 h; take out the stainless steel fiber felt, wash it and dry it in a blast dryer at 150 °C for 6.5 h;

[0043] (4) Weigh 4.01 g of chromium nitrate nonahydrate and dissolve it in 20 mL of deionized water and put the material prepared in step (3) into it; weigh 1.17 g of sodium sulfide and dissolve it in 40 mL of deionized water, and ultrasonically treat it for 30 min; then slowly drop the sodium sulfide solution into the chromium nitrate solution, and after mixing evenly, place the solution in an oil bath at 90 °C and react for 15 min to load Cr2S3. After the reaction is completed, wash and dry it;

[0044] (5) Weigh 0.29 g of nickel nitrate hexahydrate and 0.13 g of ammonium perrhenate, add them to 50 mL of deionized water. After complete dissolution, place the material prepared in step (4) into the solution and let it stand and age for 12 h. Finally, react at 200 °C for 3 h in an atmosphere of 5% hydrogen and 95% argon. After the reaction, wash and dry to obtain a photothermal catalyst for concentrating solar lignin depolymerization, denoted as 10MnFe2O4 / 8BiOBr@5Cr2S3@1Ni-0.5Re.

[0045] Example 4: The photothermal catalyst for concentrating solar lignin depolymerization of the present invention uses an austenite-ferrite duplex stainless steel fiber felt as the substrate, and a photothermal conversion layer of magnetically active MnFe2O4 nanosheets and a photothermal catalytic layer containing the composite catalyst BiOBr@Cr2S3 and the bimetallic catalyst Ni-Re are successively constructed on the substrate surface. The preparation method includes the following steps:

[0046] (1) Use an austenite-ferrite duplex stainless steel fiber felt with an area of 1.5 cm × 1.5 cm as the substrate, and ultrasonically wash it with a 0.5 mol / L hydrochloric acid solution for 1 h to remove surface oxides and impurities, then take it out and dry it for standby.

[0047] (2) Weigh 8.08 g of ferric nitrate nonahydrate and 1.98 g of manganese chloride tetrahydrate, dissolve them in 50 mL of deionized water. Then add the above stainless steel fiber felt and slowly dropwise add a 0.45 mol / L aqueous potassium hydroxide solution to adjust the pH value to 11. After the solution is evenly dispersed, transfer it to a high-pressure reaction kettle and react at 150 °C for 6 h. Then take out the stainless steel fiber felt, wash it and place it in a muffle furnace. Heat it to 450 °C at a heating rate of 5 °C / min in an air atmosphere and keep it warm for 5 h. After the reaction, a stainless steel fiber felt with magnetically grown MnFe2O4 nanosheets as the photothermal conversion layer can be prepared.

[0048] (3) Weigh 0.95 g of potassium bromide and 3.88 g of bismuth nitrate pentahydrate, and add them to 30 mL of deionized water and 40 mL of acetic acid aqueous solution with a mass fraction of 40% respectively. After uniform dispersion, slowly drop the potassium bromide aqueous solution into the bismuth nitrate acetic acid aqueous solution under vigorous stirring, and add the material prepared in step (2) to this solution. Transfer it to a hydrothermal reaction kettle and react at 120 °C for 24 h. Take it out, wash it and dry it in a blast dryer at 130 °C for 6 h.

[0049] (4) Weigh 3.20 g of chromium nitrate nonahydrate, dissolve it in 20 mL of deionized water and put the material prepared in step (3) into it. Weigh 0.94 g of sodium sulfide, dissolve it in 40 mL of deionized water, and ultrasonically treat it for 30 min. Then slowly drop the sodium sulfide solution into the chromium nitrate solution. After mixing evenly, place the solution in an oil bath at 100 °C and react for 15 min to load Cr2S3. After the reaction, wash and dry.

[0050] (5) Weigh 0.145 g of nickel nitrate hexahydrate and 0.13 g of ammonium perrhenate and add them to 50 mL of deionized water. After complete dissolution, place the material prepared in step (4) into the solution and let it stand for aging for 12 h. Finally, react at 200 °C for 3 h in an atmosphere of 5% hydrogen and 95% argon. After the reaction, wash and dry to obtain a photothermal catalyst for concentrating solar lignin depolymerization, the 10MnFe2O4 / 8BiOBr@4Cr2S3@0.5Ni-0.5Re monolithic photothermal catalyst.

[0051] Comparative Example 1: The preparation method of the 8BiOBr@4Cr2S3@1Ni-0.5Re monolithic photothermal catalyst in this comparative example is as follows:

[0052] (1) Use an austenite-ferrite duplex stainless steel fiber felt with an area of 1.5 cm × 1.5 cm as the substrate, and ultrasonically wash it with 0.5 mol / L hydrochloric acid solution for 1 h to remove surface oxides and impurities, then take it out and dry it for standby;

[0053] (2) Weigh 0.95 g of potassium bromide and 3.88 g of bismuth nitrate pentahydrate, and add them to 30 mL of deionized water and 40 mL of acetic acid aqueous solution with a mass fraction of 35% respectively. After uniform dispersion, slowly drop the potassium bromide aqueous solution into the bismuth nitrate acetic acid aqueous solution under vigorous stirring. Add the material prepared in step (1) to this solution, transfer it to a hydrothermal reaction kettle, and react at 180 °C for 15 h. Take it out, wash it, and then dry it in a blast dryer at 120 °C for 6 h;

[0054] (3) Weigh 3.20 g of chromium nitrate nonahydrate and dissolve it in 20 mL of deionized water, and put the material prepared in step (2) into it; weigh 0.94 g of sodium sulfide and dissolve it in 40 mL of deionized water, and ultrasonically treat it for 30 min; then slowly drop the sodium sulfide solution into the chromium nitrate solution. After mixing evenly, place the solution in an oil bath at 85 °C and react for 30 min to load Cr2S3. After the reaction, wash and dry;

[0055] (4) Weigh 0.29 g of nickel nitrate hexahydrate and 0.13 g of ammonium perrhenate and add them to 50 mL of deionized water. After complete dissolution, place the stainless steel fiber felt into the solution and let it stand for aging for 12 h. Finally, react at 150 °C for 5 h in an atmosphere of 5% hydrogen and 95% argon to obtain the 8BiOBr@4Cr2S3@1Ni-0.5Re monolithic photothermal catalyst.

[0056] Comparative Example 2: The preparation method of the 10MnFe2O4 / 8BiOBr@4Cr2S3@1Ni monolithic photothermal catalyst in this comparative example is as follows:

[0057] (1) Using an austenite-ferrite duplex stainless steel fiber felt with an area of 1.5 cm × 1.5 cm as the substrate, it was washed ultrasonically with a 0.5 mol / L hydrochloric acid solution for 1 h to remove surface oxides and impurities, taken out and dried for standby;

[0058] (2) Weigh 8.08 g of ferric nitrate nonahydrate and 1.98 g of manganese chloride tetrahydrate and dissolve them in 50 mL of deionized water; then add the above-mentioned stainless steel fiber felt and slowly dropwise add an aqueous potassium hydroxide solution with a concentration of 0.15 mol / L to adjust the pH value to 9; after the solution is dispersed evenly, transfer it to a high-pressure reaction kettle and react at 120 °C for 10 h; then take out the stainless steel fiber felt, wash it and place it in a muffle furnace, heat it up to 350 °C at a heating rate of 5 °C / min in an air atmosphere and keep it warm for 6 h. After the reaction is completed, a stainless steel fiber felt with magnetic MnFe2O4 nanosheets grown on the surface as a photothermal conversion layer can be prepared;

[0059] (3) Weigh 0.95 g of potassium bromide and 3.88 g of bismuth nitrate pentahydrate, and add them to 30 mL of deionized water and 40 mL of acetic acid aqueous solution with a mass fraction of 35%, respectively. After being dispersed evenly, slowly dropwise add the potassium bromide aqueous solution to the bismuth nitrate acetic acid aqueous solution under vigorous stirring, and add the material prepared in step (2) to this solution; transfer it to a hydrothermal reaction kettle and react at 180 °C for 15 h; take it out, wash it and dry it in a blast dryer at 120 °C for 6 h;

[0060] (4) Weigh 3.20 g of chromium nitrate nonahydrate and dissolve it in 20 mL of deionized water and put the material prepared in step (3) into it; weigh 0.94 g of sodium sulfide and dissolve it in 40 mL of deionized water, and ultrasonicate it for 30 min; then slowly dropwise add the sodium sulfide solution to the chromium nitrate solution, and after mixing evenly, place the solution in an oil bath at 85 °C and react for 30 min to load Cr2S3. After the reaction is completed, wash and dry it;

[0061] (5) Weigh 0.29 g of nickel nitrate hexahydrate and add it to 50 mL of deionized water. After complete dissolution, place the material prepared in step (4) in the solution and let it stand and age for 12 h; finally, react at 150 °C for 5 h in an atmosphere of 5% hydrogen and 95% argon to obtain a 10MnFe2O4 / 8BiOBr@4Cr2S3@1Ni monolithic photothermal catalyst.

[0062] Comparative Example 3: The preparation method of the 10MnFe2O4 / 8BiOBr@4Cr2S3@0.5Re monolithic photothermal catalyst in this comparative example is as follows:

[0063] (1) Using an austenite-ferrite duplex stainless steel fiber felt with an area of 1.5 cm × 1.5 cm as the substrate, it was washed ultrasonically with a 0.5 mol / L hydrochloric acid solution for 1 h to remove surface oxides and impurities, taken out and dried for standby;

[0064] (2) Weigh 8.08 g of iron(III) nitrate nonahydrate and 1.98 g of manganese(II) chloride tetrahydrate and dissolve them in 50 mL of deionized water; then add the above-mentioned stainless steel fiber felt and slowly dropwise add an aqueous potassium hydroxide solution with a concentration of 0.15 mol / L to adjust the pH value to 9; after the solution is evenly dispersed, transfer it to a high-pressure reaction kettle and react at 120 °C for 10 h; then take out the stainless steel fiber felt, wash it and place it in a muffle furnace, heat it up to 350 °C at a heating rate of 5 °C / min in an air atmosphere and keep it warm for 6 h. After the reaction is completed, a stainless steel fiber felt with magnetic MnFe₂O₄ nanosheets grown on the surface as a photothermal conversion layer can be prepared.

[0065] (3) Weigh 0.95 g of potassium bromide and 3.88 g of bismuth(III) nitrate pentahydrate, and add them to 30 mL of deionized water and 40 mL of acetic acid aqueous solution with a mass fraction of 35% respectively. After being evenly dispersed, slowly dropwise add the potassium bromide aqueous solution to the bismuth(III) nitrate acetic acid aqueous solution under vigorous stirring, and add the material prepared in step (2) to this solution; transfer it to a hydrothermal reaction kettle and react at 180 °C for 15 h; take out the stainless steel fiber felt, wash it and dry it in a blast dryer at 120 °C for 6 h;

[0066] (4) Weigh 3.20 g of chromium(III) nitrate nonahydrate and dissolve it in 20 mL of deionized water and put the material prepared in step (3) into it; weigh 0.94 g of sodium sulfide and dissolve it in 40 mL of deionized water, and ultrasonicate it for 30 min; then slowly dropwise add the sodium sulfide solution to the chromium(III) nitrate solution. After mixing evenly, place the solution in an oil bath at 85 °C and react for 30 min to load Cr₂S₃. After the reaction is completed, wash and dry it;

[0067] (5) Weigh 0.13 g of ammonium perrhenate and add it to 50 mL of deionized water. After it is completely dissolved, place the material prepared in step (4) in the solution and let it stand and age for 12 h; finally, react at 150 °C for 5 h in an atmosphere of 5% hydrogen and 95% argon to obtain the 10MnFe₂O₄ / 8BiOBr@4Cr₂S₃@0.5Re monolithic photothermal catalyst.

[0068] Comparative Example 4: The preparation method of the 10MnFe₂O₄ / 8BiOBr@4Cr₂S₃ monolithic photothermal catalyst in this comparative example is as follows:

[0069] (1) Use an austenite-ferrite duplex stainless steel fiber felt with an area of 1.5 cm × 1.5 cm as the substrate, and wash it with a 0.5 mol / L hydrochloric acid solution by ultrasonication for 1 h to remove surface oxides and impurities, then take it out and dry it for standby;

[0070] (2) Weigh 8.08 g of iron(III) nitrate nonahydrate and 1.98 g of manganese(II) chloride tetrahydrate and dissolve them in 50 mL of deionized water; then add the above-mentioned stainless steel fiber felt and slowly dropwise add an aqueous potassium hydroxide solution with a concentration of 0.15 mol / L to adjust the pH value to 9; after the solution is evenly dispersed, transfer it to a high-pressure reaction kettle and react at 120 °C for 10 h; then take out the stainless steel fiber felt, wash it and place it in a muffle furnace, heat it up to 350 °C at a heating rate of 5 °C / min in an air atmosphere and keep it warm for 6 h. After the reaction is completed, a stainless steel fiber felt with magnetic MnFe₂O₄ nanosheets grown on its surface as a photothermal conversion layer can be prepared;

[0071] (3) Weigh 0.95 g of potassium bromide and 3.88 g of bismuth(III) nitrate pentahydrate, and add them to 30 mL of deionized water and 40 mL of acetic acid aqueous solution with a mass fraction of 35%, respectively. After being evenly dispersed, slowly dropwise add the potassium bromide aqueous solution to the bismuth(III) nitrate acetic acid aqueous solution under vigorous stirring, add the material prepared in step (2) to this solution, transfer it to a hydrothermal reaction kettle, and react at 180 °C for 15 h; take it out, wash it and dry it in a blast dryer at 120 °C for 6 h;

[0072] (4) Weigh 3.20 g of chromium(III) nitrate nonahydrate and dissolve it in 20 mL of deionized water and put the material prepared in step (3) into it; weigh 0.94 g of sodium sulfide and dissolve it in 40 mL of deionized water, and after ultrasonic treatment for 30 min; then slowly dropwise add the sodium sulfide solution to the chromium(III) nitrate solution. After mixing evenly, place the solution in an oil bath at 85 °C and react for 30 min to load Cr₂S₃. After the reaction is completed, wash and dry it to obtain a 10MnFe₂O₄ / 8BiOBr@4Cr₂S₃ monolithic photothermal catalyst.

[0073] Comparative Example 5: The preparation method of the 10MnFe₂O₄ / 8BiOBr monolithic photothermal catalyst in this comparative example is as follows:

[0074] (1) Use an austenite-ferrite duplex stainless steel fiber felt with an area of 1.5 cm × 1.5 cm as the substrate, and ultrasonically wash it with a 0.5 mol / L hydrochloric acid solution for 1 h to remove surface oxides and impurities, take it out and dry it for standby;

[0075] (2) Weigh 8.08 g of iron(III) nitrate nonahydrate and 1.98 g of manganese(II) chloride tetrahydrate and dissolve them in 50 mL of deionized water; then add the above-mentioned stainless steel fiber felt and slowly dropwise add an aqueous potassium hydroxide solution with a concentration of 0.15 mol / L to adjust the pH value to 9; after the solution is evenly dispersed, transfer it to a high-pressure reaction kettle and react at 120 °C for 10 h; then take out the stainless steel fiber felt, wash it and place it in a muffle furnace, heat it up to 350 °C at a heating rate of 5 °C / min in an air atmosphere and keep it warm for 6 h. After the reaction is completed, a stainless steel fiber felt with magnetic MnFe₂O₄ nanosheets grown on its surface as a photothermal conversion layer can be prepared;

[0076] (3) Weigh 0.95 g of potassium bromide and 3.88 g of bismuth nitrate pentahydrate, and add them to 30 mL of deionized water and 40 mL of acetic acid aqueous solution with a mass fraction of 35% respectively. After uniform dispersion, slowly add the potassium bromide aqueous solution dropwise to the bismuth nitrate acetic acid aqueous solution under vigorous stirring, and add the material prepared in step (2) to this solution; transfer it to a hydrothermal reaction kettle, react at 180 °C for 15 h; take it out, wash it, and then dry it in a blast dryer at 120 °C for 6 h to obtain the 10MnFe2O4 / 8BiOBr monolithic photothermal catalyst.

[0077] Application Example 1: Application of the MnFe2O4 / BiOBr@Cr2S3@Ni-Re monolithic photothermal catalyst with stainless steel fiber felt as the substrate in the photothermal depolymerization and liquefaction of lignin, and the application steps are as follows:

[0078] Place the 10MnFe2O4 / 8BiOBr@4Cr2S3@1Ni-0.5Re catalyst prepared in Example 1 in a high-pressure reaction kettle with a conical quartz liner, use a two-stage concentrating and heat-collecting reaction device to focus the simulated sunlight generated by the xenon lamp on the surface of the catalyst, and adjust the distance between the two-stage condenser and the catalyst until the light intensity is 2500 mW·cm -2 , the hydrogen pressure is 1.5 bar, the solvent is methanol and water, and the volume ratio is 5 mL:10 mL. Use 100 mg of alkaline lignin as the reaction raw material, the reaction time is 10 h, and the stirring speed is 8000 r / min.

[0079] Application Examples 2 - 4 and Comparative Application Examples 1 - 5:

[0080] The differences from Application Example 1 are as follows: In Application Examples 2, 3, and 4, the catalysts prepared in Example 2, Example 3, and Example 4 are used respectively; in Comparative Application Examples 1, 2, 3, 4, and 5, the catalysts prepared in Comparative Examples 1 - 5 are used respectively.

[0081] The catalytic performances of the catalysts prepared in Application Examples 1 - 4 and Application Comparative Examples 1 - 5 in the photothermal depolymerization and liquefaction of alkaline lignin are shown in Table 1 below. It can be seen from Table 1 that the photothermal catalysts prepared in Examples 1 - 4 show good photocatalytic activity in the photothermal depolymerization and liquefaction of alkaline lignin. Among them, the photothermal catalyst 10MnFe2O4 / 8BiOBr@4Cr2S3@1Ni-0.5Re prepared in Example 2 has the best photocatalytic performance and can effectively promote the photothermal catalytic conversion of alkaline lignin into high-value aromatic monomer products.

[0082] Comparing Example 2 with Comparative Examples 1 - 5, it can be seen that the overall photothermal catalyst with both the MnFe2O4 photothermal conversion layer and the BiOBr@Cr2S3@Ni-Re photothermal catalytic layer has the best reaction performance. This is because MnFe2O4 can effectively convert infrared light into heat to provide energy for the reaction; the photocatalyst BiOBr@Cr2S3 with a good Z-scheme heterojunction structure can effectively promote the migration and transport of photogenerated carriers; the bimetallic Ni-Re cocatalyst is a good active site for the hydrogenation reaction, enhancing the photocatalytic hydrogenolysis reaction of lignin.

[0083] Table 1 Summary of the catalytic performance of the catalysts prepared in Application Examples 1 - 4 and Application Comparative Examples 1 - 5 in the photocatalytic pyrolysis and liquefaction of alkaline lignin under concentrated sunlight

[0084]

Claims

1. A photothermal catalyst for the photodegradation of lignin by condensation, characterized in that, The catalyst uses a metal matrix as the substrate, and a photothermal conversion layer and a photothermal catalytic layer are sequentially constructed on the surface of the substrate; the photothermal conversion layer includes MnFe₂O₄ nanosheets, and the photothermal catalytic layer includes a composite catalyst BiOBr@Cr₂S₃ and a bimetallic catalyst Ni-Re.

2. The catalyst according to claim 1, characterized in that, The molar ratio of MnFe₂O₄, BiOBr, Cr₂S₃, Ni, and Re is 10:8:3 - 5:0.5 - 1:0.

5.

3. The catalyst according to claim 2, characterized in that, The metal matrix is a metal fiber felt, and the metal fiber felt is a ferritic stainless steel fiber felt, an austenitic stainless steel fiber felt, or an austenitic-ferritic duplex stainless steel fiber felt.

4. A preparation method of the photothermal catalyst for concentrating and depolymerizing lignin according to claim 1, characterized in that, It includes the following steps: (1) The metal matrix is pretreated and placed in a solvent, then a manganese source and an iron source are added. After mixing evenly, an alkali solution is added, and after adjusting the pH value, a hydrothermal reaction and a calcination treatment are carried out in sequence to obtain a metal matrix with MnFe₂O₄ nanosheets grown on the surface; (2) Dissolve the bromine source in a solvent to obtain solution one, dissolve the bismuth source in a mixed solvent, and ultrasonically obtain solution two. Drop solution one into solution two to obtain a mixed solution. Place the material prepared in step (1) in the mixed solution, carry out a hydrothermal reaction, and take it out and dry it after completion; (3) Place the material prepared in step (2) in an aqueous solution of a chromium source, add a sulfur source and mix evenly, then carry out a heat treatment, and take it out and dry it after completion to obtain a metal matrix loaded with the composite catalyst BiOBr@Cr₂S₃ and MnFe₂O₄ nanosheets; (4) Place the material prepared in step (3) in an aqueous solution of a nickel source and a rhenium source, ultrasonically disperse it, take it out and carry out a high-temperature reduction reaction in an argon-hydrogen mixed gas to obtain a metal matrix loaded with the bimetallic catalyst Ni-Re, the composite catalyst BiOBr@Cr₂S₃, and MnFe₂O₄ nanosheets, which is the photothermal catalyst for concentrating solar lignin depolymerization.

5. The preparation method according to claim 4, characterized in that, In step (1), the manganese source is manganese chloride tetrahydrate, and the iron source is iron nitrate nonahydrate; the alkali solution is an aqueous solution of sodium hydroxide, an aqueous solution of potassium hydroxide, or ammonia water, and the pH value is adjusted to 9 - 11; the conditions for the hydrothermal reaction are: reacting at 95 - 150 °C for 6 - 12 h; the conditions for the calcination treatment are: reacting at 300 - 450 °C for 5 - 8 h.

6. The preparation method according to claim 4, characterized in that, In step (2), the bromine source is potassium bromide, the bismuth source is bismuth nitrate pentahydrate, the mixed solvent is an aqueous acetic acid solution, and in the aqueous acetic acid solution, the mass fraction of ethanol is 20 - 40%; the conditions for the hydrothermal reaction are: reacting at 120 - 200 °C for 12 - 24 h.

7. The preparation method according to claim 4, characterized in that, In step (3), the chromium source is chromium nitrate nonahydrate, and the sulfur source is sodium sulfide; the conditions for the heat treatment are: reacting at 50 - 100 °C for 15 - 90 min.

8. The preparation method according to claim 4, characterized in that, In step (4), the nickel source is nickel nitrate hexahydrate, the rhenium source is ammonium perrhenate, and the molar ratio of the nickel source to the rhenium source is 1 - 2:1; the conditions for the high-temperature reduction reaction are: reacting at 150 - 300 °C for 2 - 5 h.

9. Application of the photothermal catalyst for concentrating solar lignin depolymerization according to claim 1 in concentrating solar lignin depolymerization.

10. The application according to claim 9, wherein The method of the application is as follows: Using lignin as a reaction raw material, an aqueous solution of methanol as a solvent, placing a photothermal catalyst in a high-pressure reaction device, using a concentrating and heat-collecting reaction device to focus the simulated sunlight generated by a xenon lamp on the surface of the photothermal catalyst, adjusting the distance between the condenser lens and the catalyst, and carrying out a depolymerization reaction; the conditions of the depolymerization reaction are: the light intensity is 500 - 3500 mW·cm -2 , the hydrogen pressure is 1 - 3 bar, and the reaction time is 5 - 10 h.

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