A method for preparing bimetallic carbon catalysts by microwave-assisted hydrogen reduction

Abstract

This disclosure relates to the field of catalyst preparation technology, specifically a method for preparing a carbon catalyst supported on a bimetallic element using microwave-assisted hydrogen reduction. The method includes the following steps: preparing a raw material for forming a carbon substrate; then thoroughly mixing a first metal salt, a second metal salt, and the raw material for forming the carbon substrate, followed by spray drying to collect the solid; placing the obtained solid in a microwave tube furnace, turning on the microwave generator, and successively introducing an inert gas, a hydrogen-argon mixture, and another inert gas; and obtaining the carbon catalyst supported on a bimetallic element after heat treatment. In this disclosure, the raw material for forming the carbon substrate includes modified activated carbon. Through the preparation method provided in this disclosure, a carbon catalyst supported on a bimetallic element with high catalytic activity and high catalytic selectivity is obtained.

Description

Technical Field

[0001] This disclosure relates to the field of catalyst preparation technology, specifically a method for preparing a carbon catalyst supported on a bimetallic element by microwave-assisted hydrogen reduction. Background Technology

[0002] In existing technologies, the preparation of carbon catalysts with highly dispersed metals typically employs an impregnation method combined with high-temperature hydrogen reduction. However, traditional tubular furnaces suffer from low heating efficiency, high energy consumption, and long reduction times. Furthermore, existing methods tend to cause metal particle agglomeration, resulting in poor dispersion and affecting catalytic activity. Conventional hydrogen reduction requires a high hydrogen concentration in the hydrogen-argon mixture, posing safety risks. Additionally, in existing impregnation methods, the supported metal is easily covered by the substrate carbon structure, making it difficult to expose and leading to reduced catalytic activity. Therefore, there is an urgent need for a method for preparing metal-supported carbon catalysts. Summary of the Invention

[0003] This disclosure provides a method for preparing carbon catalysts supported on bimetallic elements by microwave-assisted hydrogen reduction, thereby addressing the shortcomings of related technologies.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] According to a first aspect of the present disclosure, a method for preparing a carbon catalyst supported on a bimetallic element by microwave-assisted hydrogen reduction is provided, the method comprising the following steps:

[0006] Step 1: Prepare the raw materials for forming the carbon substrate;

[0007] Step 2: Add the first metal salt, the second metal salt, and the raw materials used to form the carbon substrate to water, mix thoroughly, spray dry, and collect the solid;

[0008] Step 3: Place the solid obtained in Step 2 in a microwave tube furnace, introduce inert gas, turn on the microwave generator, raise the temperature to 200℃-300℃, and hold for 1-2 hours; then raise the temperature to 400℃-600℃ and hold for 2-3 hours; then raise the temperature to 700℃-900℃, switch to a hydrogen-argon mixture, and hold for 2-3 hours; then switch back to an inert gas and allow it to cool naturally to room temperature; thus obtaining the carbon catalyst supported on bimetallic elements.

[0009] In one aspect of this disclosure, the first metal salt is selected from nickel salts; the second metal salt is selected from copper salts.

[0010] In one aspect of this disclosure, the first metal salt is selected from nickel salts; the second metal salt is selected from iron salts.

[0011] In one aspect of this disclosure, the first metal salt is selected from nickel salts; the second metal salt is selected from cobalt salts.

[0012] In one aspect of this disclosure, the first metal salt is selected from nickel salts; the second metal salt is selected from zinc salts.

[0013] In one aspect of this disclosure, the first metal salt is selected from iron salts; the second metal salt is selected from copper salts.

[0014] In one aspect of this disclosure, the first metal salt is selected from cobalt salts; the second metal salt is selected from copper salts.

[0015] In one aspect of this disclosure, the first metal salt is selected from zinc salts; the second metal salt is selected from copper salts.

[0016] In one aspect of this disclosure, the first metal salt is selected from manganese salts; the second metal salt is selected from copper salts.

[0017] In one aspect of this disclosure, the copper salt is selected from at least one of copper formate, copper acetate, copper oxalate, copper citrate, copper nitrate, copper carbonate, copper sulfate, copper chloride, copper phosphate, and copper hydroxide.

[0018] In one aspect of this disclosure, the nickel salt is selected from at least one of nickel formate, nickel acetate, nickel oxalate, nickel citrate, nickel nitrate, nickel carbonate, nickel sulfate, nickel phosphate, and nickel hydroxide.

[0019] In one aspect of this disclosure, the iron salt is selected from ferrous sulfate, ferric sulfate, ferric chloride, ferrous chloride, ferric nitrate, ferrous nitrate, ferrous acetate, ferric acetate, or ferrous oxalate.

[0020] In one aspect of this disclosure, the cobalt salt is selected from cobalt sulfate, cobalt chloride, cobalt nitrate, cobalt oxalate, or cobalt fluoride.

[0021] In one aspect of this disclosure, the zinc salt is selected from zinc sulfate, zinc chloride, zinc nitrate, zinc acetate, or zinc citrate.

[0022] In one aspect of this disclosure, the manganese salt is selected from manganese sulfate, manganese chloride, manganese nitrate, manganese acetate, or manganese citrate.

[0023] In one aspect of this disclosure, the raw material used to form the carbon substrate includes modified activated carbon.

[0024] In one aspect of this disclosure, the modified activated carbon is obtained by modifying the activated carbon with ammonia water; the modification process includes: providing activated carbon; preparing ammonia water with a concentration selected from 20%-25%; adding the activated carbon to the ammonia water and letting it stand for 8-20 hours; and then washing and drying to obtain the modified activated carbon.

[0025] In one aspect of this disclosure, the raw material used to form the carbon substrate includes modified plant polysaccharides; the plant polysaccharides are selected from citrus peel polysaccharides, grapefruit peel polysaccharides, soybean polysaccharides, or fucoidan.

[0026] In one aspect of this disclosure, the orange peel polysaccharide is prepared by the following steps:

[0027] Step 1-a: Dry the orange peel at 60℃-80℃, pulverize and sieve through a 40-60 mesh sieve to obtain orange peel powder;

[0028] Step 2-a: Add the orange peel powder to 8-20 times its weight of water, then add the first compound enzyme, adjust the pH to 5.5-5.8, heat to 70℃-85℃, and perform reflux extraction for 2-4 hours; wherein, the first compound enzyme contains pectinase and cellulase;

[0029] Step 3-a: After extraction, the solution is obtained by filtration; the solution is concentrated by evaporation, 95% ethanol solution is added, and the mixture is allowed to stand for 4-8 hours to collect the precipitate; the precipitate is dried to obtain the orange peel polysaccharide.

[0030] In one aspect of this disclosure, specifically, the orange peel polysaccharide is prepared by the following steps:

[0031] Step 1-a: Dry the orange peel at 80℃, pulverize and sieve through a 40-mesh sieve to obtain orange peel powder;

[0032] Step 2-a: Add the orange peel powder to 16 times its weight of water, then add the first compound enzyme, adjust the pH to 5.5-5.8, heat to 80℃, and reflux for extraction for 3 hours; wherein, the first compound enzyme contains pectinase and cellulase, and the dosage of pectinase and cellulase is 50000U / L.

[0033] Step 3-a: After extraction, the solution is obtained by filtration; the solution is concentrated by evaporation to 1 / 5 of its original volume, and then 95% ethanol solution with an equal volume to the concentrated solution is added. The solution is allowed to stand for 6 hours and the precipitate is collected; the precipitate is dried to obtain the orange peel polysaccharide.

[0034] In one aspect of this disclosure, the fucoidan is prepared by the following steps:

[0035] Step 1-b: Provide brown algae raw material, dry it at 60℃-80℃, pulverize it and sieve it through a 60-80 mesh sieve to obtain brown algae powder; wherein, the brown algae raw material is selected from kelp, wakame, fucus vesiculosus or Sargassum fusiforme;

[0036] Step 2-b: Add the brown algae powder to 15-30 times its weight of water, then add cellulase, heat to 45℃-55℃, and simultaneously use ultrasound-assisted extraction. The ultrasound power is selected from 180-400W, and the ultrasound time is selected from 1-2h. Then stop the ultrasound, raise the temperature to 90℃-100℃, and reflux for extraction for 1-2h.

[0037] Step 3-b: After extraction, the solution is obtained by filtration; the solution is concentrated by evaporation, 95% ethanol solution is added, and the mixture is allowed to stand for 4-8 hours to collect the precipitate; the precipitate is dried to obtain the fucoidan.

[0038] In one aspect of this disclosure, specifically, the fucoidan is prepared by the following steps:

[0039] Step 1-b: Provide brown algae raw material, dry it at 60℃, pulverize it and sieve it through a 60-mesh sieve to obtain brown algae powder; wherein, the brown algae raw material is selected from wakame or hijiki.

[0040] Step 2-b: Add the brown algae powder to 25 times its weight of water, then add cellulase at a dosage of 80,000 U / L, heat to 50°C, and simultaneously use ultrasound-assisted extraction with an ultrasonic power of 200W and an ultrasonic time of 1.5h; then stop the ultrasound, raise the temperature to 98°C, and reflux for 2h.

[0041] Step 3-b: After extraction, the solution is obtained by filtration; the solution is concentrated by evaporation to 1 / 5 of its original volume, and then 95% ethanol solution with an equal volume to the concentrated solution is added. The solution is allowed to stand for 6 hours and the precipitate is collected; the precipitate is dried to obtain the fucoidan.

[0042] In one aspect of this disclosure, the soybean polysaccharide is prepared by the following steps:

[0043] Step 1-c: Provide soybean residue, dry it at 60℃-80℃, pulverize it and sieve it through a 60-80 mesh sieve to obtain soybean residue powder;

[0044] Step 2-c: Place the soybean residue powder in a hydrothermal reactor for hydrothermal reaction;

[0045] Step 3-c: Add all the products obtained after the hydrothermal reaction to the reaction vessel, cool to room temperature, add papain, and react for 2-5 hours;

[0046] Step 4-c: Take the supernatant after the reaction and adjust the pH to 5.5-6.0; add 15% of the volume of the supernatant in 95% ethanol solution, centrifuge, and collect the precipitate; after freeze-drying, obtain the soybean polysaccharide.

[0047] In one aspect of this disclosure, specifically, the soybean polysaccharide is prepared by the following steps:

[0048] Step 1-c: Provide soybean residue, dry it at 60℃, pulverize it and sieve it through an 80-mesh sieve to obtain soybean residue powder;

[0049] Step 2-c: Place the soybean residue powder in a hydrothermal reactor, add 10 times the weight of water, and then carry out a hydrothermal reaction at 120℃-160℃ for 2-6 hours;

[0050] Step 3-c: Add all the products obtained after the hydrothermal reaction to the reaction vessel, cool to room temperature, add papain, and react for 2-5 hours; the amount of papain used is 50000 U / L.

[0051] Step 4-c: Take the supernatant after the reaction and adjust the pH to 5.8; add 15% of the volume of the supernatant to 95% ethanol solution, centrifuge at 4000 r / min for 5 min, and collect the precipitate; after freeze drying, the soybean polysaccharide is obtained.

[0052] In one aspect of this disclosure, the modified plant polysaccharide is obtained by amination modification of the plant polysaccharide using an amino-containing compound; the amino-containing compound is selected from 3-methylaminopropylamine, 3-ethylaminopropylamine, or 3-ethoxypropylamine; the modification process includes: preparing the plant polysaccharide; the plant polysaccharide is selected from citrus peel polysaccharide, grapefruit peel polysaccharide, soybean polysaccharide, or fucoidan; dissolving the plant polysaccharide in n-propanol, isopropanol, or n-butanol, under nitrogen protection, while stirring, adding the amino-containing compound dropwise, and reacting at room temperature for 12-24 hours; finally, the reaction solution is dialyzed, evaporated and concentrated, and freeze-dried to obtain the modified plant polysaccharide.

[0053] In one aspect of this disclosure, specifically, the modification process includes:

[0054] Step 1-e: Dissolve the plant polysaccharide in n-butanol, under nitrogen protection, and add 3-methylaminopropylamine dropwise while stirring, and react at room temperature for 16 hours;

[0055] Step 2-e: Disperse the reaction solution obtained in step 1-e in deionized water to prepare a 2% aqueous solution. Then, dialyze the solution using a dialysis bag with a molecular weight cutoff of 3000 Da for 12 hours. After evaporation, concentration and freeze-drying, the modified plant polysaccharide is obtained.

[0056] In one aspect of this disclosure, specifically, the modification process includes:

[0057] Step 1-e: Dissolve orange peel polysaccharide in n-butanol, use nitrogen protection, add 3-methylaminopropylamine dropwise while stirring, and react at room temperature for 16 hours;

[0058] Step 2-e: Disperse the reaction solution obtained in step 1-e in deionized water to prepare a 2% aqueous solution. Then, dialyze the solution using a dialysis bag with a molecular weight cutoff of 3000 Da for 12 hours. After evaporation, concentration and freeze-drying, the modified orange peel polysaccharide is obtained.

[0059] In one aspect of this disclosure, specifically, the modification process includes:

[0060] Step 1-e: Dissolve fucoidan in n-butanol, use nitrogen protection, add 3-methylaminopropylamine dropwise while stirring, and react at room temperature for 16 hours;

[0061] Step 2-e: Disperse the reaction solution obtained in step 1-e in deionized water to prepare a 2% aqueous solution. Then, dialyze the solution using a dialysis bag with a molecular weight cutoff of 3000 Da for 12 hours. After evaporation, concentration and freeze-drying, the modified fucoidan is obtained.

[0062] In one aspect of this disclosure, the raw material used to form the carbon substrate is a mixture of modified activated carbon and modified plant polysaccharides; the modified activated carbon is obtained by modifying the activated carbon with ammonia water; the modified plant polysaccharides are obtained by amylating the plant polysaccharides with an amino-containing compound; the mass ratio of the modified activated carbon to the modified plant polysaccharides is selected from 1:(0.25-0.5).

[0063] In one aspect of this disclosure, step 2 includes:

[0064] Step 2-1: Dissolve the first metal salt, the second metal salt, and the modified plant polysaccharide in water to obtain a solution; the ratio of the sum of the masses of the first metal salt and the second metal salt to the mass of the modified plant polysaccharide is selected from 1:(15-50); stir for 2-4 hours; then add the modified activated carbon, the mass ratio of the modified activated carbon to the modified plant polysaccharide is selected from 1:(0.25-0.5); continue stirring for 2-4 hours, and then let stand for 8-12 hours;

[0065] Step 2-2: The dispersion obtained in Step 2-1 is spray-dried to collect particulate solids; wherein the inlet temperature of the spray dryer is 105℃-115℃ and the feed rate is 5-10mL / min.

[0066] In one aspect of this disclosure, specifically, step 2 includes:

[0067] Step 2-1: Dissolve nickel chloride, copper chloride, and modified plant polysaccharide in water to obtain a solution; the ratio of the sum of the masses of nickel chloride and copper chloride to the mass of the modified plant polysaccharide is selected from 1:(25-30); the molar ratio of nickel chloride to copper chloride is selected from 1:(0.15-5); stir for 2-4 hours; then add the modified activated carbon, the mass ratio of the modified activated carbon to the modified plant polysaccharide is selected from 1:(0.25-0.5); continue stirring for 2-4 hours, then let stand for 8-12 hours;

[0068] Step 2-2: The dispersion obtained in Step 2-1 is spray-dried to collect particulate solids; wherein the inlet temperature of the spray dryer is 105℃-115℃ and the feed rate is 5-10mL / min.

[0069] In one aspect of this disclosure, step 3 includes:

[0070] Step 3-1: Place the solid obtained in step 2 in a microwave tube furnace, introduce nitrogen gas, turn on the microwave generator, select 1200-1800W microwave power, heat from room temperature to 200℃-250℃ at a heating rate of 1℃ / min, and keep at this temperature for 1-2 hours.

[0071] Step 3-2: After the heat preservation ends, increase the temperature to 400℃-500℃ at a heating rate of 5℃ / min and hold for 2-3 hours; then increase the temperature to 700℃-900℃ at a heating rate of 10℃ / min, switch to hydrogen-argon mixture, and hold for 2-3 hours; then switch to nitrogen and cool naturally to room temperature; thus obtaining the carbon catalyst supported on bimetallic elements.

[0072] In one aspect of this disclosure, specifically, step 3 includes:

[0073] Step 3-1: Place the solid obtained in step 2 in a microwave tube furnace, introduce nitrogen gas, turn on the microwave generator, select 1500W microwave power, heat from room temperature to 220℃ at a heating rate of 1℃ / min, and hold at that temperature for 1.5h.

[0074] Step 3-2: After the heat preservation is completed, the temperature is increased to 450℃ at a heating rate of 5℃ / min and held for 2 hours; then the temperature is increased to 800℃ at a heating rate of 10℃ / min, the nitrogen atmosphere is switched to a hydrogen-argon mixture, and held for 2 hours; then the hydrogen-argon mixture is switched back to nitrogen and the mixture is allowed to cool naturally to room temperature; the carbon catalyst loaded with bimetallic elements is obtained.

[0075] In this disclosure, the proportion of hydrogen in the hydrogen-argon mixture is 5%.

[0076] The technical solutions provided by the embodiments of this disclosure may include the following beneficial effects:

[0077] As can be seen from the above embodiments, a carbon catalyst with high catalytic activity and high catalytic selectivity supported on bimetallic elements is obtained through the preparation method provided in this disclosure.

[0078] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Detailed Implementation

[0079] The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0080] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with embodiments. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. The embodiments described herein are illustrative in nature and are used to provide a basic understanding of this application. The embodiments of this application should not be construed as limiting this application.

[0081] For the sake of brevity, this article only discloses a few specific numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0082] In this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0083] In this description, unless otherwise stated, "above" and "below" include the stated number.

[0084] Unless otherwise stated, the terms used in this disclosure have their common meanings as commonly understood by those skilled in the art. Unless otherwise stated, the values ​​of the parameters mentioned in this disclosure can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this disclosure).

[0085] The term "about" is used to describe and indicate small variations. When used in conjunction with an event or situation, the term may refer to examples in which the event or situation occurred precisely or in examples in which the event or situation occurred very approximately. For example, when used in conjunction with numerical values, the term may refer to a range of variation less than or equal to ±10% of the numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. Additionally, quantities, ratios, and other numerical values ​​are sometimes presented in range format herein. It should be understood that such range format is for convenience and brevity and should be interpreted flexibly to include not only numerical values ​​explicitly specified as range limits but also all individual numerical values ​​or subranges covered within the range, as if each numerical value and subrange were explicitly specified.

[0086] The list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another instance, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single component or multiple components. Item B may contain a single component or multiple components. Item C may contain a single component or multiple components.

[0087] The present disclosure is further illustrated below with reference to embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the disclosure.

[0088] Examples and comparative examples:

[0089] Example 1

[0090] Example 1 includes the following steps:

[0091] 1. Preparation of modified plant polysaccharides:

[0092] 300g of orange peel was dried at 80℃, pulverized, and sieved through a 40-mesh sieve to obtain orange peel powder. The orange peel powder was added to 4800mL of water, and then a first complex enzyme was added to adjust the pH to 5.7. The mixture was heated to 80℃ and refluxed for 3 hours. The first complex enzyme contained pectinase and cellulase, each at a concentration of 50,000 U / L. After extraction, the solution was filtered. The solution was concentrated by evaporation to 1 / 5 of its original volume, and then an equal volume of 95% ethanol solution was added. The mixture was allowed to stand for 6 hours, and the precipitate was collected. The precipitate was dried to obtain 18.21g of orange peel polysaccharide. The above steps were repeated to obtain sufficient orange peel polysaccharide for the next reaction.

[0093] Weigh 25g of citrus peel polysaccharide and dissolve it in 100mL of n-butanol. Under nitrogen protection, add 12mL of 3-methylaminopropylamine dropwise while stirring. React at room temperature for 16h. After the reaction is complete, disperse the reaction solution in deionized water to prepare a 2% aqueous solution. Then dialyze the solution using a dialysis bag with a molecular weight cutoff of 3000Da for 12h. After evaporation, concentration and freeze-drying, the modified citrus peel polysaccharide is obtained.

[0094] 2. Preparation of modified activated carbon:

[0095] Weigh 100g of activated carbon; prepare 300mL of 25% ammonia solution; add the activated carbon to the ammonia solution and let it stand for 12h; then wash with deionized water and dry in a 60℃ oven to obtain the modified activated carbon.

[0096] 3. Catalyst preparation:

[0097] Weigh 25g of modified orange peel polysaccharide, add it, 0.65g of copper chloride dihydrate and 0.35g of nickel chloride hexahydrate to 100mL of water, mix thoroughly to obtain a solution, and stir for 4h; then weigh 100g of modified activated carbon and add it; continue stirring for 2h, and then let stand for 12h; then spray dry the dispersion and collect the particulate solids; wherein the inlet temperature of the spray dryer is 110℃ and the feed rate is 10mL / min.

[0098] The obtained solid was placed in a microwave tube furnace, nitrogen gas was introduced, and the microwave generator was turned on. The microwave power was selected as 1500W, and the temperature was increased from room temperature to 220°C at a heating rate of 1°C / min, and held for 1.5 hours. After the holding period, the temperature was increased to 450°C at a heating rate of 5°C / min, and held for 2 hours. Then, the temperature was increased to 800°C at a heating rate of 10°C / min, and the nitrogen atmosphere was switched to a hydrogen-argon mixture, and held for 2 hours. Then, the hydrogen-argon mixture was switched back to nitrogen, and the mixture was allowed to cool naturally to room temperature. The carbon catalyst with bimetallic elements supported in Example 1 was obtained.

[0099] Comparative Example 1

[0100] Comparative Example 1 includes the following steps:

[0101] 1. Preparation of modified plant polysaccharides:

[0102] 300g of orange peel was dried at 80℃, pulverized, and sieved through a 40-mesh sieve to obtain orange peel powder. The orange peel powder was added to 4800mL of water, and then a first complex enzyme was added to adjust the pH to 5.7. The mixture was heated to 80℃ and refluxed for 3 hours. The first complex enzyme contained pectinase and cellulase, each at a concentration of 50,000 U / L. After extraction, the solution was filtered. The solution was concentrated by evaporation to 1 / 5 of its original volume, and then an equal volume of 95% ethanol solution was added. The mixture was allowed to stand for 6 hours, and the precipitate was collected. The precipitate was dried to obtain orange peel polysaccharide. The above steps were repeated to obtain sufficient orange peel polysaccharide for the next reaction.

[0103] Weigh 25g of citrus peel polysaccharide and dissolve it in 100mL of n-butanol. Under nitrogen protection, add 12mL of 3-methylaminopropylamine dropwise while stirring. React at room temperature for 16h. After the reaction is complete, disperse the reaction solution in deionized water to prepare a 2% aqueous solution. Then dialyze the solution using a dialysis bag with a molecular weight cutoff of 3000Da for 12h. After evaporation, concentration and freeze-drying, the modified citrus peel polysaccharide is obtained.

[0104] 2. Preparation of modified activated carbon:

[0105] Weigh 100g of activated carbon; prepare 300mL of 25% ammonia solution; add the activated carbon to the ammonia solution and let it stand for 12h; then wash with deionized water and dry in a 60℃ oven to obtain the modified activated carbon.

[0106] 3. Catalyst preparation:

[0107] Weigh 25g of modified orange peel polysaccharide, add it, 0.65g of copper chloride dihydrate and 0.35g of nickel chloride hexahydrate to 100mL of water, mix thoroughly to obtain a solution, and stir for 4h; then weigh 100g of modified activated carbon and add it; continue stirring for 2h, and then let stand for 12h; then spray dry the dispersion and collect the particulate solids; wherein the inlet temperature of the spray dryer is 110℃ and the feed rate is 10mL / min.

[0108] The obtained solid was placed in a microwave tube furnace, nitrogen gas was introduced, and the temperature was increased from room temperature to 220℃ at a heating rate of 1℃ / min, and held for 1.5 h. After the holding period, the temperature was increased to 450℃ at a heating rate of 5℃ / min, and held for 2 h. Then the temperature was increased to 800℃ at a heating rate of 10℃ / min, the nitrogen atmosphere was switched to a hydrogen-argon mixture, the microwave generator was turned on, the microwave power was selected as 1500W, and the temperature was held for 2 h. Then the hydrogen-argon mixture was switched back to nitrogen gas, and the mixture was allowed to cool naturally to room temperature, thus obtaining the carbon catalyst with bimetallic elements supported in Comparative Example 1.

[0109] The difference between Comparative Example 1 and Example 1 is that the microwave generator was turned on only after the gas was converted into a hydrogen-argon mixture during the heat treatment process.

[0110] Comparative Example 2

[0111] Comparative Example 2 includes the following steps:

[0112] 1. Preparation of modified plant polysaccharides:

[0113] 300g of orange peel was dried at 80℃, pulverized, and sieved through a 40-mesh sieve to obtain orange peel powder. The orange peel powder was added to 4800mL of water, and then a first complex enzyme was added to adjust the pH to 5.7. The mixture was heated to 80℃ and refluxed for 3 hours. The first complex enzyme contained pectinase and cellulase, each at a concentration of 50,000 U / L. After extraction, the solution was filtered. The solution was concentrated by evaporation to 1 / 5 of its original volume, and then an equal volume of 95% ethanol solution was added. The mixture was allowed to stand for 6 hours, and the precipitate was collected. The precipitate was dried to obtain orange peel polysaccharide. The above steps were repeated to obtain sufficient orange peel polysaccharide for the next reaction.

[0114] Weigh 25g of citrus peel polysaccharide and dissolve it in 100mL of n-butanol. Under nitrogen protection, add 12mL of 3-methylaminopropylamine dropwise while stirring. React at room temperature for 16h. After the reaction is complete, disperse the reaction solution in deionized water to prepare a 2% aqueous solution. Then dialyze the solution using a dialysis bag with a molecular weight cutoff of 3000Da for 12h. After evaporation, concentration and freeze-drying, the modified citrus peel polysaccharide is obtained.

[0115] 2. Preparation of modified activated carbon:

[0116] Weigh 100g of activated carbon; prepare 300mL of 25% ammonia solution; add the activated carbon to the ammonia solution and let it stand for 12h; then wash with deionized water and dry in a 60℃ oven to obtain the modified activated carbon.

[0117] 3. Catalyst preparation:

[0118] Weigh 25g of modified orange peel polysaccharide, add it, 0.65g of copper chloride dihydrate and 0.35g of nickel chloride hexahydrate to 100mL of water, mix thoroughly to obtain a solution, and stir for 4h; then weigh 100g of modified activated carbon and add it; continue stirring for 2h, and then let stand for 12h; then spray dry the dispersion and collect the particulate solids; wherein the inlet temperature of the spray dryer is 110℃ and the feed rate is 10mL / min.

[0119] The obtained solid was placed in a microwave tube furnace, nitrogen gas was introduced, and the temperature was increased from room temperature to 220℃ at a heating rate of 1℃ / min, and held for 1.5h. After the holding period, the temperature was increased to 450℃ at a heating rate of 5℃ / min, and held for 2h. Then the temperature was increased to 800℃ at a heating rate of 10℃ / min, the nitrogen atmosphere was switched to a hydrogen-argon mixture, and held for 2h. Then the hydrogen-argon mixture was switched back to nitrogen, and the mixture was naturally cooled to room temperature to obtain the carbon catalyst with bimetallic elements of Comparative Example 2.

[0120] The difference between Comparative Example 2 and Example 1 is that the microwave generator was not turned on during the heat treatment process.

[0121] Comparative Example 3

[0122] Comparative Example 3 includes the following steps:

[0123] 1. Preparation of modified plant polysaccharides:

[0124] 300g of orange peel was dried at 80℃, pulverized, and sieved through a 40-mesh sieve to obtain orange peel powder. The orange peel powder was added to 4800mL of water, and then a first complex enzyme was added to adjust the pH to 5.7. The mixture was heated to 80℃ and refluxed for 3 hours. The first complex enzyme contained pectinase and cellulase, each at a concentration of 50,000 U / L. After extraction, the solution was filtered. The solution was concentrated by evaporation to 1 / 5 of its original volume, and then an equal volume of 95% ethanol solution was added. The mixture was allowed to stand for 6 hours, and the precipitate was collected. The precipitate was dried to obtain 18.21g of orange peel polysaccharide. The above steps were repeated to obtain sufficient orange peel polysaccharide for the next reaction.

[0125] 2. Preparation of modified activated carbon:

[0126] Weigh 100g of activated carbon; prepare 300mL of 25% ammonia solution; add the activated carbon to the ammonia solution and let it stand for 12h; then wash with deionized water and dry in a 60℃ oven to obtain the modified activated carbon.

[0127] 3. Catalyst preparation:

[0128] Weigh 25g of citrus peel polysaccharide, add it, 0.65g of copper chloride dihydrate, and 0.35g of nickel chloride hexahydrate to 100mL of water, mix thoroughly to obtain a solution, and stir for 4h; then weigh 100g of modified activated carbon and add it; continue stirring for 2h, and then let it stand for 12h; then spray dry the dispersion and collect the particulate solids; wherein the inlet temperature of the spray dryer is 110℃ and the feed rate is 10mL / min.

[0129] The obtained solid was placed in a microwave tube furnace, nitrogen gas was introduced, and the microwave generator was turned on. The microwave power was selected as 1500W, and the temperature was increased from room temperature to 220℃ at a heating rate of 1℃ / min, and held for 1.5h. After the holding period, the temperature was increased to 450℃ at a heating rate of 5℃ / min, and held for 2h. Then the temperature was increased to 800℃ at a heating rate of 10℃ / min, and the nitrogen atmosphere was switched to a hydrogen-argon mixture, and held for 2h. Then the hydrogen-argon mixture was switched back to nitrogen, and the mixture was naturally cooled to room temperature. The carbon catalyst with a bimetallic element supported in Comparative Example 3 was obtained.

[0130] The difference between Comparative Example 3 and Example 1 is that Comparative Example 3 did not involve amination modification of the plant polysaccharides.

[0131] Example 2

[0132] Example 2 includes the following steps:

[0133] 1. Preparation of modified plant polysaccharides:

[0134] Weigh 300g of wakame seaweed, dry it at 60℃, pulverize it, and sieve it through a 60-mesh sieve to obtain brown algae powder. Add the brown algae powder to 25 times its weight of water, then add cellulase at a concentration of 80,000 U / L. Heat to 50℃ and simultaneously use ultrasound-assisted extraction with an ultrasound power of 200W for 1.5 hours. Then stop the ultrasound, raise the temperature to 98℃, and reflux for 2 hours. After extraction, filter to obtain a solution. Evaporate and concentrate the solution to 1 / 5 of its original volume, then add an equal volume of 95% ethanol solution. Let it stand for 6 hours and collect the precipitate. Dry the precipitate to obtain fucoidan (14.18g). Repeat the above steps to obtain sufficient fucoidan for the next reaction.

[0135] Weigh 25g of fucoidan and dissolve it in 100mL of n-butanol. Under nitrogen protection, add 12mL of 3-methylaminopropylamine dropwise while stirring. React at room temperature for 16h. After the reaction is complete, disperse the reaction solution in deionized water to prepare a 2% aqueous solution. Then dialyze the solution using a dialysis bag with a molecular weight cutoff of 3000Da for 12h. After evaporation, concentration and freeze-drying, the modified fucoidan is obtained.

[0136] 2. Preparation of modified activated carbon:

[0137] Weigh 100g of activated carbon; prepare 300mL of 25% ammonia solution; add the activated carbon to the ammonia solution and let it stand for 12h; then wash with deionized water and dry in a 60℃ oven to obtain the modified activated carbon.

[0138] 3. Catalyst preparation:

[0139] Weigh 25g of modified fucoidan, add it, 0.65g of copper chloride dihydrate and 0.35g of nickel chloride hexahydrate to 100mL of water, mix thoroughly to obtain a solution, and stir for 4h; then weigh 100g of modified activated carbon and add it; continue stirring for 2h, and then let stand for 12h; then spray dry the dispersion and collect the particulate solids; wherein the inlet temperature of the spray dryer is 110℃ and the feed rate is 10mL / min.

[0140] The obtained solid was placed in a microwave tube furnace, nitrogen gas was introduced, and the microwave generator was turned on. The microwave power was selected as 1500W, and the temperature was increased from room temperature to 220°C at a heating rate of 1°C / min, and held for 1.5 hours. After the holding period, the temperature was increased to 450°C at a heating rate of 5°C / min, and held for 2 hours. Then the temperature was increased to 800°C at a heating rate of 10°C / min, and the nitrogen atmosphere was switched to a hydrogen-argon mixture, and held for 2 hours. Then the hydrogen-argon mixture was switched back to nitrogen, and the mixture was allowed to cool naturally to room temperature. The carbon catalyst with bimetallic elements supported in Example 2 was obtained.

[0141] The difference between Example 2 and Example 1 lies in the different plant polysaccharides used.

[0142] Example 3

[0143] Example 3 includes the following steps:

[0144] 1. Preparation of modified plant polysaccharides:

[0145] Weigh 300g of soybean residue, dry it at 60℃, pulverize it, and sieve it through an 80-mesh sieve to obtain soybean residue powder. Place the soybean residue powder in a hydrothermal reactor, add 10 times its weight of water, and then carry out a hydrothermal reaction at 150℃ for 3 hours. Add all the products obtained after the hydrothermal reaction to a reaction vessel, cool to room temperature, add papain, and react for 3 hours. The amount of papain used is 50000 U / L. Take the supernatant after the reaction and adjust the pH to 5.8. Add 15% of the volume of the supernatant to 95% ethanol solution, centrifuge at 4000 r / min for 5 min, and collect the precipitate. After freeze-drying, obtain soybean polysaccharide (12.95g). Repeat the above steps to obtain sufficient soybean polysaccharide for the next reaction.

[0146] Weigh 25g of soybean polysaccharide and dissolve it in 100mL of n-butanol. Under nitrogen protection, add 12mL of 3-methylaminopropylamine dropwise while stirring. React at room temperature for 16h. After the reaction is complete, disperse the reaction solution in deionized water to prepare a 2% aqueous solution. Then dialyze the solution using a dialysis bag with a molecular weight cutoff of 3000Da for 12h. After evaporation, concentration and freeze-drying, the modified soybean polysaccharide is obtained.

[0147] 2. Preparation of modified activated carbon:

[0148] Weigh 100g of activated carbon; prepare 300mL of 25% ammonia solution; add the activated carbon to the ammonia solution and let it stand for 12h; then wash with deionized water and dry in a 60℃ oven to obtain the modified activated carbon.

[0149] 3. Catalyst preparation:

[0150] Weigh 25g of modified soybean polysaccharide, add it, 0.65g of copper chloride dihydrate, and 0.35g of nickel chloride hexahydrate to 100mL of water, mix thoroughly to obtain a solution, and stir for 4h; then weigh 100g of modified activated carbon and add it; continue stirring for 2h, and then let it stand for 12h; then spray dry the dispersion and collect the particulate solids; wherein the inlet temperature of the spray dryer is 110℃ and the feed rate is 10mL / min.

[0151] The obtained solid was placed in a microwave tube furnace, nitrogen gas was introduced, and the microwave generator was turned on. The microwave power was selected as 1500W, and the temperature was increased from room temperature to 220°C at a heating rate of 1°C / min, and held for 1.5 hours. After the holding period, the temperature was increased to 450°C at a heating rate of 5°C / min, and held for 2 hours. Then the temperature was increased to 800°C at a heating rate of 10°C / min, and the nitrogen atmosphere was switched to a hydrogen-argon mixture, and held for 2 hours. Then the hydrogen-argon mixture was switched back to nitrogen, and the mixture was allowed to cool naturally to room temperature. The carbon catalyst with bimetallic elements supported in Example 3 was obtained.

[0152] The difference between Example 3 and Example 1 lies in the different plant polysaccharides used.

[0153] Comparative Example 4

[0154] Comparative Example 4 includes the following steps:

[0155] Weigh 100g of activated carbon; prepare 300mL of 25% ammonia solution; add the activated carbon to the ammonia solution and let it stand for 12h; then wash with deionized water and dry in a 60℃ oven to obtain the modified activated carbon.

[0156] Add 20g of chitosan and 5g of sodium alginate to 200mL of water and heat to 60℃. Then add 0.65g of copper chloride dihydrate, 0.35g of nickel chloride hexahydrate, 0.15g of citric acid solid and 100g of modified activated carbon. After stirring thoroughly, evaporate and concentrate to 100mL at 60℃ while stirring. Then spray dry the solution directly while it is hot and collect the particulate solid. The inlet temperature of the spray dryer is 110℃ and the feed rate is 10mL / min.

[0157] The obtained solid was placed in a microwave tube furnace, nitrogen gas was introduced, and the microwave generator was turned on. The microwave power was selected as 1500W, and the temperature was increased from room temperature to 220℃ at a heating rate of 1℃ / min, and held for 1.5h. After the holding period, the temperature was increased to 450℃ at a heating rate of 5℃ / min, and held for 2h. Then the temperature was increased to 800℃ at a heating rate of 10℃ / min, and the nitrogen atmosphere was switched to a hydrogen-argon mixture, and held for 2h. Then the hydrogen-argon mixture was switched back to nitrogen, and the mixture was naturally cooled to room temperature. The carbon catalyst with bimetallic elements supported in Comparative Example 4 was obtained.

[0158] Comparative Example 5

[0159] Comparative Example 5 includes the following steps:

[0160] Weigh 100g of activated carbon; prepare 300mL of 25% ammonia solution; add the activated carbon to the ammonia solution and let it stand for 12h; then wash with deionized water and dry in a 60℃ oven to obtain the modified activated carbon.

[0161] 25g of carbon nanotubes were dispersed in 100mL of water, and then 0.65g of copper chloride dihydrate, 0.35g of nickel chloride hexahydrate and 100g of modified activated carbon were added. The mixture was stirred and sonicated for 12h. The solution was then spray-dried to collect particulate solids. The inlet temperature of the spray dryer was 110℃ and the feed rate was 10mL / min.

[0162] The obtained solid was placed in a microwave tube furnace, nitrogen gas was introduced, and the microwave generator was turned on. The microwave power was selected as 1500W, and the temperature was increased from room temperature to 220℃ at a heating rate of 1℃ / min, and held for 1.5h. After the holding period, the temperature was increased to 450℃ at a heating rate of 5℃ / min, and held for 2h. Then the temperature was increased to 800℃ at a heating rate of 10℃ / min, and the nitrogen atmosphere was switched to a hydrogen-argon mixture, and held for 2h. Then the hydrogen-argon mixture was switched back to nitrogen, and the mixture was naturally cooled to room temperature. The carbon catalyst with a bimetallic element supported in Comparative Example 5 was obtained.

[0163] Catalytic activity test:

[0164] The examples and comparative examples of this disclosure were used to catalyze the synthesis of 2-pentanone from ethanol and acetone. 0.05 g of each sample from the examples and comparative examples were added to a 100 mL high-pressure reactor, followed by the addition of 20 mL of ethanol and 20 mL of acetone to each. The reaction was carried out at 175 °C for 2 h, with the stirring speed maintained at 500 r / min throughout the reaction. After the reaction, the conversion and selectivity were obtained by gas chromatography analysis. Specific results are shown in Table 1.

[0165] Table 1

[0166] Ethanol conversion rate (%) Acetone conversion rate (%) Selectivity of 2-pentanone (%) Example 1 93.4 90.6 91.4 Comparative Example 1 74.4 75.6 73.2 Comparative Example 2 60.1 63.9 62.9 Comparative Example 3 83.8 82.4 80.1 Example 2 91.7 86.8 87.4 Example 3 90.8 87.1 84.3 Comparative Example 4 72.1 73.9 71.0 Comparative Example 5 58.1 55.6 56.2

[0167] Comparing Examples 1 to 3 and Comparative Examples 1, 4, and 5, it can be seen that when the temperature is raised from room temperature to 220°C and the microwave generator is turned on, the activity and selectivity of the obtained catalyst are significantly improved. This is because: plant polysaccharide molecules contain various functional groups, such as hydroxyl and amino groups, which can coordinate with metal ions in metal salts to form complexes. This complexation can fix metal ions in the molecular structure of polysaccharides, providing a relatively stable system for subsequent processing. Microwave radiation can cause rapid polarization and orientation movement of polar functional groups in polysaccharide molecules, such as hydroxyl groups, thereby causing the glycosidic bonds inside the polysaccharide molecules to break under microwave radiation, destroying the molecular chain of polysaccharides, and thus weakening the binding force between metal atoms and polysaccharides, further exposing the metal atoms. When the metal atoms are exposed, hydrogen gas, as a reducing agent, can reduce the metal atoms from their oxidized state to a more reactive elemental state. This elemental state of metal atoms has higher activity and can participate in chemical reactions as a catalyst, thereby improving the activity and selectivity of the catalyst. Comparing Examples 1 to 3 with Comparative Examples 1, 4, and 5, it can be seen that the activity and selectivity of the catalysts prepared from polysaccharides after amination modification were improved. This is because amination modification further increases the density of amino groups in the molecular structure of plant polysaccharides, which can better complex metal ions, thereby stabilizing the structure of the precursor and improving the activity and selectivity of the catalyst.

[0168] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This disclosure is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein.

Claims

1. A method for preparing a carbon catalyst supported on a bimetallic element by microwave-assisted hydrogen reduction, characterized in that, The method includes the following steps: Step 1: Prepare the raw materials for forming the carbon substrate; Step 2: Add nickel salt, copper salt and the raw materials used to form the carbon substrate to water, mix thoroughly, spray dry, and collect the solid; Step 3: Place the solid obtained in Step 2 in a microwave tube furnace, introduce inert gas, turn on the microwave generator, raise the temperature to 200℃-300℃, and hold for 1-2 hours; then raise the temperature to 400℃-600℃ and hold for 2-3 hours; then raise the temperature to 700℃-900℃, switch to a hydrogen-argon mixture, and hold for 2-3 hours; then switch back to an inert gas and allow to cool naturally to room temperature; thus obtaining the carbon catalyst supported on the bimetallic element; wherein, The raw materials used to form the carbon substrate include modified activated carbon or modified plant polysaccharides. The modified activated carbon is obtained by modifying the activated carbon with ammonia water; the modification process includes: providing activated carbon; preparing ammonia water with a concentration selected from 20%-25%; adding the activated carbon to the ammonia water and letting it stand for 8-20 hours; and then washing and drying to obtain the modified activated carbon; The modified plant polysaccharide is obtained by amination modification of the plant polysaccharide using an amino-containing compound; the amino-containing compound is selected from 3-methylaminopropylamine, 3-ethylaminopropylamine, or 3-ethoxypropylamine; the modification process includes: preparing plant polysaccharide; the plant polysaccharide is selected from citrus peel polysaccharide, grapefruit peel polysaccharide, soybean polysaccharide, or fucoidan; dissolving the plant polysaccharide in n-propanol, isopropanol, or n-butanol, using nitrogen protection, and adding the amino-containing compound dropwise while maintaining stirring, reacting at room temperature for 12-24 hours; finally, the reaction solution is dialyzed, evaporated and concentrated, and freeze-dried to obtain the modified plant polysaccharide.

2. The method for preparing a carbon catalyst supported on a bimetallic element by microwave-assisted hydrogen reduction according to claim 1, characterized in that, The copper salt is selected from at least one of copper formate, copper acetate, copper oxalate, copper citrate, copper nitrate, copper carbonate, copper sulfate, copper chloride, and copper phosphate; the nickel salt is selected from at least one of nickel formate, nickel acetate, nickel oxalate, nickel citrate, nickel nitrate, nickel carbonate, nickel sulfate, and nickel phosphate.

3. The method for preparing a carbon catalyst supported on a bimetallic element by microwave-assisted hydrogen reduction according to claim 1, characterized in that, The raw material used to form the carbon substrate is a mixture of modified activated carbon and modified plant polysaccharides; the modified activated carbon is obtained by modifying the activated carbon with ammonia water. The modified plant polysaccharide is obtained by amylating the plant polysaccharide with an amino-containing compound. The mass ratio of the modified activated carbon to the modified plant polysaccharide is selected from 1:(0.25-0.5).

4. The method for preparing a carbon catalyst supported on a bimetallic element by microwave-assisted hydrogen reduction according to claim 1, characterized in that, Step 2 includes: Step 2-1: Dissolve the nickel salt, copper salt, and the modified plant polysaccharide in water to obtain a solution; the ratio of the sum of the masses of the nickel salt and copper salt to the mass of the modified plant polysaccharide is selected from 1:(15-50); stir for 2-4 hours; then add the modified activated carbon, the mass ratio of the modified activated carbon to the modified plant polysaccharide is selected from 1:(0.25-0.5); continue stirring for 2-4 hours, and then let stand for 8-12 hours; Step 2-2: The dispersion obtained in Step 2-1 is spray-dried to collect particulate solids; wherein the inlet temperature of the spray dryer is 105℃-115℃ and the feed rate is 5-10mL / min.

5. The method for preparing a carbon catalyst supported on a bimetallic element by microwave-assisted hydrogen reduction according to claim 1, characterized in that, Step 3 includes: Step 3-1: Place the solid obtained in step 2 in a microwave tube furnace, introduce nitrogen gas, turn on the microwave generator, select 1200-1800W microwave power, heat from room temperature to 200℃-250℃ at a heating rate of 1℃ / min, and keep at this temperature for 1-2 hours. Step 3-2: After the heat preservation ends, increase the temperature to 400℃-500℃ at a heating rate of 5℃ / min and hold for 2-3 hours; then increase the temperature to 700℃-900℃ at a heating rate of 10℃ / min, switch to hydrogen-argon mixture, and hold for 2-3 hours; then switch to nitrogen and cool naturally to room temperature; thus obtaining the carbon catalyst supported on bimetallic elements.