A nitrogen-doped carbon-coated trimetallic catalyst, a preparation method and application thereof

Abstract

The application discloses a nitrogen-doped carbon-coated three-metal catalyst and a preparation method and application thereof, and belongs to the field of catalyst preparation and application. The method adopts sucrose, melamine and metal salt as low-cost raw materials, and forms an alkaline environment with the assistance of sodium hydroxide. In the environment, melamine is hydrolyzed into cyanuric acid, which is complexed with sucrose metal ions to form a stable supramolecular aggregate precursor containing metal, and then realizes effective encapsulation of the metal in a high-temperature pyrolysis process. The synergistic effect of the three metal elements Co, Ni and Zn significantly improves the performance of the catalyst, so that CoNiZnO@NC-600 not only exhibits high conversion rate (98.4%) and selectivity (99%) in the reaction of hydrogenation conversion of furfural to furfuryl alcohol, but also has excellent cycle stability, thereby providing a new efficient method for the hydrogenation conversion of biomass-derived compounds.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation and application, specifically relating to a nitrogen-doped carbon-encapsulated trimetallic catalyst, its preparation method, and its application. This catalyst is mainly used for the efficient hydrogenation of furfural to furfuryl alcohol and is applicable to the fields of chemical engineering and renewable resource conversion technology. Background Technology

[0002] In the current energy and chemical industries, biomass and its derivative platform molecules are widely considered to be highly promising sustainable resources for the production of various value-added chemicals. Furfural (FAL), as an important biomass-derived platform molecule, is typically extracted from xylan-rich hemicellulose biomass. In particular, the catalytic hydrogenation conversion of furfural to furfuryl alcohol (FOL) is a key step in the biomass conversion process, as furfuryl alcohol is an important intermediate in the preparation of various chemical products such as biofuels, resins, fibers, and vitamin C. However, due to the presence of active C=O bonds and furan rings in furfural, various competing reactions (such as decarbonylation, hydrogenation, and ring-opening reactions) can occur, which can significantly reduce the selectivity of furfuryl alcohol.

[0003] Traditionally, copper chromate catalysts have been used industrially to catalyze the conversion of furfural to furfuryl alcohol under harsh conditions. However, the use of these catalysts is limited by the complexity of their processing and the environmental pollution risks posed by the high toxicity of chromium. In recent years, although the introduction of precious metals such as platinum, lead, and ruthenium can improve catalytic performance, their high cost limits their widespread application. Currently, non-precious metal-based catalysts are showing promise due to their abundant sources, lower cost, and improved catalytic activity or product selectivity. However, most non-precious metal catalysts suffer from insufficient stability and excessively high reaction temperatures. Therefore, developing a non-toxic, non-precious metal-based catalyst with high catalytic efficiency and stability has become the future direction for industrial applications. Summary of the Invention

[0004] The purpose of this invention is to provide a nitrogen-doped carbon-encapsulated trimetallic catalyst, its preparation method, and its application. This catalyst is used for the efficient and environmentally friendly hydrogenation conversion of furfural to furfuryl alcohol. This invention improves the environmental friendliness, economy, activity, and stability of the catalyst under complex reaction conditions through a unique combination of non-precious metals and nitrogen-doped carbon materials.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A method for preparing a nitrogen-doped carbon-encapsulated trimetallic catalyst includes the following steps:

[0007] (1) Weigh a certain amount of sucrose, zinc nitrate hexahydrate (Zn(NO3)2·6H2O), nickel nitrate hexahydrate (Ni(NO3)2·6H2O) and cobalt nitrate hexahydrate (Co(NO3)2·6H2O), dissolve them, and heat and stir at 50-100℃ for 0.5-4 hours to obtain mixture A;

[0008] In this step, the mixture is stirred at a certain temperature (50-100℃) to allow the nitrate and sucrose to react fully, and the metal salt ions are evenly distributed in the sucrose to form a sucrose metal ion complex.

[0009] (2) Add melamine to mixture A and stir for 10 minutes to ensure uniform mixing, forming mixture B;

[0010] (3) Under vigorous stirring, slowly add sodium hydroxide solution to mixture B to adjust the pH value to 10-12, and continue stirring at 50-100℃ for 1-6 hours to prepare reaction slurry;

[0011] In an alkaline environment with a pH of 10-12, melamine can undergo hydrolysis, and the resulting cyanuric acid reacts with sucrose metal salts to form supramolecular aggregate precursors.

[0012] (4) The obtained slurry is transferred to a stainless steel autoclave lined with polytetrafluoroethylene and reacted at 150-200℃ for 6-12 hours for hydrothermal treatment.

[0013] This alkaline, high-temperature hydrothermal environment further promoted the conversion of melamine to cyclocyanuric acid and its complexation with sucrose metal ions.

[0014] (5) After the hydrothermal reaction is completed, the product is collected by centrifugation; the collected solid is washed with deionized water and then dried in air at 100°C for 12 hours; after drying, it is pyrolyzed in an argon atmosphere, and the resulting solid product is the nitrogen-doped porous carbon-coated trimetallic catalytic material.

[0015] Furthermore, the mass ratio of sucrose, zinc nitrate hexahydrate, nickel nitrate hexahydrate and cobalt nitrate hexahydrate in step (1) is 2:1:0.5:1.

[0016] Furthermore, the amount of melamine used in step (2) is 0.25-2 times the mass of sucrose.

[0017] Furthermore, the concentration of the sodium hydroxide solution added in step (3) is 2-6 mol / L.

[0018] Furthermore, the hydrothermal treatment described in step (4) is carried out at a temperature of 200°C for 12 hours.

[0019] Furthermore, the pyrolysis step in step (5) includes preliminary pyrolysis at 200–400°C for 0.5 hours, followed by further treatment at 600–900°C for 1 hour.

[0020] Another object of the present invention is to provide a catalyst prepared by the above method, the catalyst having a carbon-coated trimetallic structure and containing microporous and mesoporous structures.

[0021] Furthermore, the catalyst can be used for the efficient hydrogenation conversion of furfural to furfuryl alcohol, and it achieves a conversion rate of up to 98.4% and a selectivity of 99% in the hydrogenation reaction of furfural, and still exhibits excellent cycle stability and reusability after multiple reaction cycles.

[0022] The beneficial effects of this invention are:

[0023] The core innovation of this invention lies in the preparation of a nitrogen-doped porous carbon-encapsulated trimetallic catalyst, CoNiZnO@NC-600, via NaOH-induced self-assembly. The preparation process involves promoting the hydrolysis of melamine to cyanuric acid in an alkaline environment constructed with NaOH, followed by a reaction with a sucrose metal ion complex to form a metal-containing supramolecular polymer. These polymers, acting as stable precursors, effectively encapsulate the metal after high-temperature pyrolysis, significantly improving the catalyst's dispersibility and stability. The catalyst of this invention exhibits superior catalytic performance and excellent cycling stability in the hydrogenation conversion of furfural to furfuryl alcohol. CoNiZnO@NC-600 achieves a furfural conversion rate of 98.4% and a furfuryl alcohol selectivity of up to 99%, significantly outperforming traditional single-metal catalysts. By precisely controlling the pyrolysis temperature, this invention further optimizes the catalyst's pore structure and surface properties, enhancing its activity and stability in the reaction. In particular, even after six consecutive cycles, the catalyst maintains a high conversion rate and selectivity close to its initial level, demonstrating its potential value in industrial applications. Attached Figure Description

[0024] The invention will now be further described with reference to the accompanying drawings.

[0025] Figure 1 This is the XRD pattern of the carbon-encapsulated trimetallic material obtained in Example 1;

[0026] Figure 2 The image shows the SEM image and elemental distribution of the carbon-encapsulated trimetallic material obtained in Example 1.

[0027] Figure 3 This is a cyclic test of the furfural hydrogenation reaction of the carbon material obtained in Example 1. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1

[0030] First, dissolve 2g of sucrose, 1g of zinc nitrate hexahydrate (Zn(NO3)2·6H2O), 0.5g of nickel nitrate hexahydrate (Ni(NO3)2·6H2O), and 1g of cobalt nitrate hexahydrate (Co(NO3)2·6H2O) in 30ml of deionized water and stir at 75℃. Add 1g of melamine to the solution and stir continuously for 0.5 hours to ensure thorough mixing. Under vigorous stirring, slowly add 4mol / L NaOH solution to adjust the pH to 12, and continue stirring at 75℃ for 2 hours. Then transfer the reaction slurry to a stainless steel autoclave lined with polytetrafluoroethylene and react at 200℃ for 12 hours. After the reaction is complete, collect the solid product by centrifugation, wash with deionized water, and air-dry at 100℃ for 12 hours. The dried sample was calcined at 400℃ for 0.5 hours, followed by heat treatment at 600℃ for 1 hour under an argon flow (flow rate 5 ml / min) to obtain a black solid powder with uniform trimetallic distribution (XRD pattern of the sample is shown in [reference]). Figure 1 SEM images and elemental distributions of the samples are shown below. Figure 2 The black solid powder was used as a catalyst in the hydrogenation of furfural in a 50 ml high-pressure reactor. The reaction mixture consisted of 10 mg of catalyst, 1 mmol of furfural, and 20 ml of ethanol solvent. The reaction was carried out at 140 °C, with a hydrogen pressure of 2 MPa and a reaction time of 2 hours, and a magnetic stirring speed of 360 rpm. The experimentally measured furfural conversion rate reached 98.4%, and the selectivity of furfuryl alcohol was as high as 99%, demonstrating the high efficiency and selectivity of the catalyst. The recyclability of the prepared catalyst was evaluated. The used catalyst was separated and reused under the same conditions without any activation treatment. After six cycles, the catalyst still exhibited excellent catalytic performance (see the catalytic performance cycle test of the sample for details). Figure 3 ).

[0031] Example 2

[0032] Following the operating steps and conditions of Example 1, the difference lies in changing the amount of NaOH solution and adjusting the pH of the solution to 11. The final product obtained is a porous carbon material encapsulating metal nanoparticles. The prepared porous carbon material was tested for furfural hydrogenation performance, showing a furfural conversion rate of 97% and a furfuryl alcohol selectivity of 98.7%.

[0033] Example 3

[0034] Following the operating steps and conditions of Example 1, the difference lies in changing the amounts of the three metals: adding 0.5 g of zinc nitrate hexahydrate (Zn(NO3)2·6H2O), 1 g of nickel nitrate hexahydrate (Ni(NO3)2·6H2O), and 0.3 g of cobalt nitrate hexahydrate (Co(NO3)2·6H2O). The final product is a porous carbon material encapsulating cobalt-nickel bimetallic nanoparticles. The prepared porous carbon material was tested for furfural hydrogenation performance, showing a furfural conversion rate of 50.7% and a furfuryl alcohol selectivity of 88.3%.

[0035] Example 4

[0036] Following the operating steps and conditions of Example 1, the difference lies in changing the type of metal; instead of adding zinc salt, only 0.5 g of nickel nitrate hexahydrate (Ni(NO3)2·6H2O) and 1 g of cobalt nitrate hexahydrate (Co(NO3)2·6H2O) were added. The final product obtained was a porous carbon material encapsulating cobalt-nickel bimetallic nanoparticles. The prepared porous carbon material was tested for furfural hydrogenation performance, showing a furfural conversion rate of 81.8% and a furfuryl alcohol selectivity of 79.7%.

[0037] Example 5

[0038] Following the operating steps and conditions of Example 1, the difference lies in changing the type of metal; instead of adding nickel salt, only 1g of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and 1g of cobalt nitrate hexahydrate (Co(NO3)2·6H2O) are added. The final product is a porous carbon material encapsulating cobalt-zinc bimetallic nanoparticles. The prepared porous carbon material was tested for furfural hydrogenation performance, showing a furfural conversion rate of 5.2% and a furfuryl alcohol selectivity of 44%.

[0039] Example 6

[0040] Following the operating steps and conditions of Example 1, the difference lies in changing the product's thermal temperature to 700°C. Specifically, the dried sample was calcined at 400°C for 0.5 hours, followed by heat treatment at 700°C for 1 hour under an argon flow (flow rate 5 ml / min) to obtain a black porous carbon material encapsulating trimetallic nanoparticles. The prepared porous carbon material was tested for furfural hydrogenation performance, showing a furfural conversion rate of 26.5% and a furfuryl alcohol selectivity of 98.1%.

[0041] Example 7

[0042] Following the operating steps and conditions of Example 1, the difference lies in changing the product's thermal temperature to 500°C. Specifically, the dried sample was calcined at 400°C for 0.5 hours, followed by heat treatment at 500°C for 1 hour under an argon flow (5 ml / min) to obtain a black porous carbon material encapsulating trimetallic nanoparticles. The prepared porous carbon material was tested for furfural hydrogenation performance, showing a furfural conversion rate of 73.7% and a furfuryl alcohol selectivity of 36.1%.

[0043] The above detailed embodiments provide a specific description of the analytical methods involved in this invention. It should be noted that the above description is only intended to help those skilled in the art better understand the methods and ideas of this invention, and is not intended to limit the scope of the invention. Without departing from the principles of this invention, those skilled in the art can make appropriate adjustments or modifications to this invention, and such adjustments and modifications should also fall within the protection scope of this invention.

Claims

1. A method for preparing a nitrogen-doped carbon-coated trimetallic catalyst, characterized in that, The method comprises the following steps: (1) a certain amount of sucrose, zinc nitrate hexahydrate, nickel nitrate hexahydrate and cobalt nitrate hexahydrate are weighed and dissolved, and heated and stirred at 50-100℃ for 0.5-4 hours to obtain a mixed solution A; (2) melamine is added to the mixed solution A, and stirred for 10 minutes to ensure uniform mixing, to form a mixed solution B; (3) under intense stirring, sodium hydroxide solution is slowly added to the mixed solution B to adjust the pH value to 10-12, and continue to stir at 50-100℃ for 1-6 hours to prepare a reaction slurry; (4) the obtained slurry is transferred to a stainless steel autoclave lined with polytetrafluoroethylene, and subjected to hydrothermal treatment at 150-200℃ for 6-12 hours; (5) after the hydrothermal treatment, the reaction product is collected by centrifugal separation; the collected solid is washed with deionized water, and then air dried at 100℃ for 12 hours; after drying, pyrolysis is carried out in an argon atmosphere, and the obtained solid product is a nitrogen-doped porous carbon-coated three-metal catalytic material; The catalyst has a carbon-coated three-metal structure and contains microporous and mesoporous structures.

2. The method for preparing a nitrogen-doped carbon-coated trimetallic catalyst according to claim 1, characterized in that, The amount of the sucrose, zinc nitrate hexahydrate, nickel nitrate hexahydrate and cobalt nitrate hexahydrate in step (1) is 2:1:0.5:1 by mass ratio.

3. The method for preparing a nitrogen-doped carbon-coated trimetallic catalyst according to claim 1, characterized in that, The amount of the melamine in step (2) is 0.25-2 times the mass of the sucrose.

4. The method for preparing a nitrogen-doped carbon-encapsulated trimetallic catalyst according to claim 1, characterized in that, The concentration of the sodium hydroxide solution added in step (3) is 2-6 mol / L.

5. The method for preparing a nitrogen-doped carbon-encapsulated trimetallic catalyst according to claim 1, characterized in that, The hydrothermal treatment in step (4) is carried out at 200℃ for 12 hours.

6. The method for preparing a nitrogen-doped carbon-encapsulated trimetallic catalyst according to claim 1, characterized in that, The pyrolysis step in step (5) includes preliminary pyrolysis at 200-400℃ for 0.5 hours, and further treatment at a temperature of 600-900℃ for 1 hour.

7. A nitrogen-doped carbon-encapsulated trimetallic catalyst, characterized in that, Prepared according to any one of claims 1-6.

8. The catalyst according to claim 7 for use in high-efficiency hydrogenation conversion of furfural to furfuryl alcohol.

9. Use according to claim 8, characterized in that, The conversion rate of furfural reaches 98.4%, and the selectivity of furfuryl alcohol reaches 99%.

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