A platinum-cobalt alloy catalyst supported on activated carbon, its preparation method and application

Abstract

This invention discloses an activated carbon-supported platinum-cobalt alloy catalyst, its preparation method, and its application. The method involves first carbonizing a biomass feedstock, followed by acid washing to remove impurities and high-temperature activation under the action of an ammonia activator to obtain activated carbon. A solution containing a cobalt source, oleic acid, oleylamine, and a reducing agent is mixed and dehydrated, then a platinum source and o-dichlorobenzene are added for a solvothermal reduction reaction to obtain platinum-cobalt alloy nanoparticles. The activated carbon and platinum-cobalt alloy nanoparticles are then ultrasonically mixed to obtain the final product. This invention features a simple and low-cost process, yielding a catalyst with uniform size and high catalytic activity, exhibiting excellent performance in the catalytic conversion of volatile organic compounds.

Description

Technical Field

[0001] This invention belongs to the field of inorganic nanomaterial chemistry and energy and environment technology, specifically relating to an activated carbon-supported platinum-cobalt alloy catalyst, its preparation method and application. Background Technology

[0002] Volatile organic compounds (VOCs) are a class of organic compounds with boiling points ranging from 50 to 250°C, which readily volatilize at room temperature. They are listed as major air pollutants, associated with atmospheric pollution and photochemical smog, and most VOCs are irritating, toxic, and carcinogenic to humans. VOC emission sources are widespread, including the chemical industry, petroleum refining, papermaking, wood processing, and carpet manufacturing. Current methods for treating VOCs include physical and chemical methods such as absorption, adsorption, membrane separation, condensation, combustion, catalytic oxidation, and biocatalysis to control and purify VOC emissions. Catalytic oxidation converts volatile organic compounds into less polluting compounds such as carbon dioxide and water. Compared to thermal oxidation, because catalysts lower the activation energy of the reaction, catalytic oxidation decomposition of VOCs can be achieved at 250–500°C, saving energy consumption under high-temperature conditions, reducing dioxin production, and treating waste gas with low VOC content (concentration less than 1%).

[0003] VOCs oxidation catalysts can be broadly classified into three categories: noble metal catalysts, non-noble metal catalysts, and mixed metal catalysts. However, all of these catalysts have some shortcomings. Although noble metal catalysts such as platinum and palladium exhibit excellent catalytic efficiency and stability, especially platinum-based catalysts which show significant effects on the treatment of aromatic compounds, their high price and short lifespan limit their widespread application. While non-noble metal catalysts such as manganese, cerium, and iron have cost advantages and better resistance to poisoning, their catalytic activity and selectivity are often lower than those of noble metal catalysts, which may affect the efficiency and thoroughness of VOCs treatment. Although mixed metal catalysts such as Pd-Au and Mn-Co exhibit superior catalytic performance, their preparation process is usually more complex and requires precise control of the metal ratio and distribution, which increases the difficulty and cost of catalyst preparation. In addition, the choice of catalyst support also has a significant impact on the catalytic effect. Although existing porous materials have high specific surface area and abundant pore structure, the support has failed to achieve synergistic effects with the active centers of nano-metal particles to further enhance the reaction active centers and lower the reaction activation energy. Therefore, its ability to protect the catalyst active sites in long-term use still has certain limitations. Meanwhile, existing methods for preparing platinum-cobalt alloy catalysts cannot simultaneously address the issues of catalyst particle size and uniformity, and nano-metal particles are prone to agglomeration during the loading process. Summary of the Invention

[0004] To address the shortcomings of existing technologies for platinum-cobalt alloy catalysts, the first objective of this invention is to provide a method for preparing activated carbon-supported platinum-cobalt alloy catalysts. This method employs a simple solvothermal reduction process, effectively controlling the particle size of platinum-cobalt alloy particles and preventing particle agglomeration through oleic acid and oleylamine ligand pairs. Simultaneously, the biochar is activated to obtain abundant amino functional groups on the activated carbon surface, resulting in a catalyst in which the support and platinum-cobalt alloy particles synergistically enhance the reactive centers.

[0005] The second objective of this invention is to provide an activated carbon-supported platinum-cobalt alloy catalyst. This catalyst uses activated biomass activated carbon as a support, which has a high specific surface area, well-developed pores, abundant nitrogen-containing functional groups, and uniformly supports platinum-cobalt alloy nanoparticles, thus inhibiting particle aggregation. Simultaneously, the abundant amino functional groups on the support can form more efficient reactive centers with the supported platinum-cobalt alloy particles, exhibiting high activity and high stability.

[0006] The third objective of this invention is to provide an application of an activated carbon-supported platinum-cobalt alloy catalyst, which is applied to the low-temperature catalytic oxidation of VOCs-containing waste gas. It exhibits excellent catalytic oxidation capabilities and can efficiently catalytically oxidize and remove volatile organic compounds at a low temperature of 200°C, thereby reducing operating energy consumption.

[0007] To achieve the above-mentioned technical objectives, the present invention provides a method for preparing a platinum-cobalt alloy catalyst supported on activated carbon, the method comprising the following steps:

[0008] 1) After carbonization, biomass raw materials are successively subjected to acid washing to remove impurities and high-temperature activation treatment under the action of ammonia activator to obtain activated carbon;

[0009] 2) After removing water from a solution containing a cobalt source, oleic acid, oleylamine and a reducing agent, a platinum source and o-dichlorobenzene are added to carry out a solvothermal reduction reaction to obtain platinum-cobalt alloy nanoparticles.

[0010] 3) The activated carbon and platinum-cobalt alloy nanoparticles are ultrasonically mixed to obtain the final product.

[0011] The key to this invention lies in the high-temperature activation treatment of activated carbon after high-temperature carbonization with nitrogen, resulting in activated carbon with abundant amino functional groups on its surface. Small-diameter nano-platinum-cobalt alloy particles are then synthesized via solvothermal reduction and loaded onto the activated carbon surface. The resulting activated carbon-supported platinum-cobalt alloy catalyst possesses a high specific surface area and a well-developed pore structure. Simultaneously, this invention reduces the use of the precious metal platinum in the catalyst by introducing cobalt, thereby reducing the production cost. Furthermore, the rational addition of oleic acid, oleylamine, and o-dichlorobenzene during the preparation of the platinum-cobalt alloy nanoparticles stabilizes the reduced platinum and cobalt atoms during alloying, helping to control particle size and prevent excessive growth and agglomeration. This leads to the formation of a platinum-cobalt alloy at the nanoscale, thereby improving the catalyst's catalytic efficiency. In addition, the acid washing process between carbonization and high-temperature activation removes various impurity elements (mainly mineral ions) obtained from biomass carbon from the activated carbon, eliminating the inhibitory effect of these impurities and ensuring the stability of subsequent activation effects and catalytic performance.

[0012] The preparation principle of the cobalt-platinum alloy particles of this invention is as follows: During the reaction process, the dibenzyl ether solvent provides a relatively stable medium for the solvothermal reduction reaction. First, removing residual water from the solvent and introducing Ar gas ensures that the reaction proceeds under anaerobic conditions, preventing the oxidation of platinum and cobalt. Under the action of oleic acid and oleylamine ligands, the platinum and cobalt sources are formed into platinum-cobalt alloy nanoparticles by oleylamine and a reducing agent. Furthermore, oleic acid and oleylamine have a good controlling effect on the size of the platinum-cobalt nanoparticles.

[0013] The inventors discovered that even when biomass raw materials are carbonized without being activated by an ammonia activator, the catalytic activity of the prepared composite material is significantly reduced.

[0014] As a preferred option, the biomass raw material is derived from the bark of the cork oak tree, and in practice, cork stoppers or wine stoppers can be selected.

[0015] As a preferred embodiment, the solution also includes dibenzyl ether solvent.

[0016] As a preferred embodiment, the carbonization conditions are: temperature 700–1000℃, time 1–4 h, and nitrogen gas with a flow rate of 80–100 mL / min as a protective atmosphere; the high-temperature activation treatment conditions are: temperature 700–1000℃, time 1–4 h. This invention obtains a carrier with a high specific surface area and high porosity structure through carbonization, which is beneficial for the loading of platinum-cobalt alloy particles. Furthermore, the high-temperature activation in an ammonia activator followed by reaction etching with the porous carbon carrier results in activated carbon with well-developed pore sizes and abundant surface amino functional groups, thus facilitating the adsorption and catalytic decomposition of volatile organic compounds. The carbonization temperature affects the degree of biomass carbonization; excessively high carbonization temperatures increase equipment operating energy consumption, while lower temperatures result in incomplete carbonization. The high-temperature activation treatment temperature directly affects the adsorption performance of the carrier; within the scope of this invention, the adsorption performance of the carrier increases with increasing activation temperature. A further preferred activation temperature is 800–1000℃.

[0017] As a preferred embodiment, the ammonia activator in the high-temperature activation process is ammonia gas and / or ammonia water. When ammonia gas is used as the activator, the flow rate is 25–100 mL / min; when ammonia water is used, the mass fraction is 5–25 wt%. Using ammonia gas and / or ammonia water as the activator in this invention allows the activated carbon surface to acquire abundant amino functional groups during the activation etching process. These amino functional groups on the activated carbon surface not only improve the dispersibility of platinum-cobalt alloy nanoparticles but also form more efficient reactive centers with the surface-supported platinum-cobalt alloy particles, reducing the activation energy and thus enhancing its catalytic activity. Increasing the amount of ammonia activator can, to some extent, increase the content of amino functional groups on the activated carbon surface, increase the specific surface area, and improve the pore structure, thereby facilitating the dispersion of platinum-cobalt alloy nanoparticles and the catalytic reaction. However, excessive use of ammonia activator can lead to over-etching, reducing the specific surface area of ​​the activated carbon support, which is detrimental to catalyst performance improvement and reduces the yield of activated carbon. Further, ammonia gas with a flow rate of 50-100 mL / min was preferred as the ammonia activator.

[0018] As a preferred embodiment, the molar ratio of the cobalt source to the platinum source is (8-16):1. In this invention, the amount of cobalt source is greater than that of platinum source, which reduces the amount of precious metal platinum while ensuring catalyst activity, resulting in a low-platinum catalyst, which can reduce the production and usage costs of the catalyst.

[0019] As a preferred embodiment, the cobalt source is one of cobalt acetylacetonate, cobalt chloride, cobalt nitrate, and cobalt acetate; the platinum source is one of platinum acetylacetonate, chloroplatinic acid, and diaminodinitroplatinum. More preferably, the cobalt source is cobalt acetylacetonate, and the platinum source is platinum acetylacetonate.

[0020] As a preferred embodiment, the reducing agent is tetraphenyl dipropylene glycol diphosphite (TDD). The TDD reducing agent used in this invention not only reduces platinum and cobalt sources into metal particles, but also acts as a surfactant, thereby improving the dispersibility of the particles.

[0021] As a preferred embodiment, the solvothermal reduction reaction conditions are: temperature 180–240°C and time 30–90 min. This invention controls the reduction reaction conditions during the preparation of platinum-cobalt alloy nanoparticles to control the size and uniformity of the particles. Excessively high temperatures may lead to excessively rapid diffusion of metal atoms, resulting in rapid nanoparticle formation and growth, but also increased particle size and uneven particle size distribution. This can lead to a decrease in the specific surface area of ​​the alloy nanoparticles, irregular crystal structure, and larger grain size. Excessively high reduction temperatures may also cause thermal decomposition or oxidation of the metal, reducing the synthesis yield of nanoparticles or even preventing their formation. Conversely, excessively low temperatures reduce the reaction rate, slowing down the reduction and synthesis of metal atoms, thus increasing the formation time of alloy nanoparticles. If the temperature is too low, the reduction reaction is ineffective, making it difficult for cobalt and platinum ions to be reduced to form low-platinum alloy nanoparticles. During the reduction reaction, metal ions are continuously reduced to metal atoms and undergo diffusion and grain growth. If the reduction time is too long, the grain size may increase, thereby reducing the specific surface area of ​​the nanoparticles and decreasing their catalytic performance and active site density. If the reduction time is too short, the cobalt and platinum sources may not be completely reduced to metal atoms, resulting in residues in the product. This affects the composition and crystal structure of the alloy nanoparticles, reducing their catalytic performance. Insufficient reduction time may also lead to poor dispersion of the alloy nanoparticles and uneven grain size distribution, affecting their catalytic activity and stability.

[0022] As a preferred embodiment, the dehydration process involves heating the mixture at 80–120°C in an argon atmosphere for 30–90 minutes. The argon atmosphere ensures the reaction proceeds under anaerobic conditions, preventing the oxidation of platinum and cobalt.

[0023] As a preferred embodiment, the ultrasonic mixing time is 10–60 minutes. Within the ultrasonic mixing time range of this invention, the loading of platinum-cobalt alloy particles can be effectively achieved.

[0024] As a preferred embodiment, the volume ratio of oleic acid to oleylamine is (0.8–1.2):1, and the total amount of oleic acid and oleylamine relative to the amount of cobalt source is (0.2–1) L / mol. Oleic acid and oleylamine play important roles in the formation of platinum-cobalt alloy nanoparticles. The carboxyl groups in oleic acid can undergo complexation reactions with platinum-cobalt metal ions to form stable complexes, while oleylamine has good reducing properties, thus platinum-cobalt nanoparticles are obtained through oleylamine reduction. Furthermore, the ligand pair of oleic acid and oleylamine can control the size and shape of platinum-cobalt alloy nanoparticles and prevent their aggregation.

[0025] This invention provides a method for preparing a platinum-cobalt alloy catalyst supported on activated carbon, specifically including the following steps:

[0026] 1) After drying the biomass raw material, it is crushed into powder and carbonized under a nitrogen atmosphere to obtain carbonized material. The carbonized material is acid-washed to remove impurities, washed with water until neutral, and dried to obtain biochar. The biochar is then activated at high temperature using ammonia activator to obtain activated carbon.

[0027] 2) Dissolve the cobalt source, oleic acid, oleylamine, and reducing agent in dibenzyl ether, and heat at 80–120°C under argon atmosphere for 30–90 min to remove moisture from the system. Raise the temperature to 180–240°C, add the platinum source and o-dichlorobenzene, and maintain this temperature for 30–90 min. Allow to cool naturally to room temperature, add ethanol to a three-necked flask, and centrifuge at 10,000 rpm to obtain platinum-cobalt alloy particles.

[0028] 3) Place activated carbon and platinum-cobalt alloy particles in n-hexane and sonicate for 10–60 min. Dry in a vacuum drying oven at 40–60 °C to obtain a black powder, which is the activated carbon-supported platinum-cobalt alloy catalyst.

[0029] The present invention also provides an activated carbon-supported platinum-cobalt alloy catalyst, which has nanoscale particle size, high specific surface area and well-developed pore structure, and exhibits excellent catalytic activity when catalyzing volatile organic compound gases.

[0030] As a preferred embodiment, the activated carbon-supported platinum-cobalt alloy catalyst has a honeycomb-like three-dimensional porous structure, and the activated carbon is uniformly loaded with platinum-cobalt alloy nanoparticles.

[0031] Finally, this invention also provides an application of an activated carbon-supported platinum-cobalt alloy catalyst, which is used in the low-temperature catalytic oxidation of VOCs-containing waste gas. When applied to the low-temperature catalytic oxidation reaction of VOCs waste gas, the catalyst of this invention exhibits excellent catalytic oxidation capability, enabling efficient catalytic oxidation and removal of volatile organic compounds at a low temperature of 200℃, thus reducing operating energy consumption.

[0032] The principle behind the catalyst of this invention exhibiting high catalytic activity for VOCs waste gas under low-temperature conditions lies in the following: On the one hand, the amino functional groups enhance the adsorption effect of the catalyst on toluene, thereby facilitating the catalytic reaction process; on the other hand, the amino nitrogen functional groups on the surface of activated carbon interact with the platinum-cobalt alloy nanoparticles. The presence of the amino functional groups adjusts the electronic structure of the platinum-cobalt alloy, reduces the activation energy of the toluene catalytic oxidation reaction, and thus optimizes the toluene catalytic reaction capability of the catalytic active center, forming a highly efficient reactive active center of amino functional groups-platinum-cobalt alloy.

[0033] As a preferred embodiment, the catalyst can be used in the reaction of toluene to CO2 at temperatures below 200°C. The amount of catalyst used during the reaction is less than 15000 h⁻¹ based on a gas hourly space velocity (GHSV). -1 Accounting.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1) The catalyst of this invention uses activated biomass activated carbon as a support, which has a high specific surface area, well-developed pores, abundant nitrogen-containing functional groups, and uniformly loaded platinum-cobalt alloy nanoparticles, thus inhibiting particle aggregation. At the same time, the abundant amino functional groups on the support can form more efficient reactive centers with the loaded platinum-cobalt alloy particles, exhibiting high activity and high stability.

[0036] 2) The process of this invention is simple, uses readily available biomass raw materials as carriers, and has high economic benefits. At the same time, the introduction of cobalt synthesizes low-platinum nanocatalysts, which reduces the use of precious metal platinum and reduces the production cost of catalysts.

[0037] 3) The activated carbon-supported platinum-cobalt nanocatalyst synthesized in this invention has excellent VOCs catalytic oxidation ability, achieving efficient catalytic oxidation and removal of toluene under low temperature conditions, which can reduce operating energy consumption.

[0038] 4) The method of the present invention uses a simple solvothermal reduction method to effectively control the particle size of platinum-cobalt alloy particles and prevent particle agglomeration through the pairing of oleic acid and oleylamine. At the same time, the biochar is activated so that the surface of the activated carbon is rich in amino functional groups, resulting in a catalyst in which the support and platinum-cobalt alloy particles can synergistically enhance the reaction activity center. Attached Figure Description

[0039] Figure 1 This is a comparison chart of the adsorption capacity of toluene on biochar C800 and catalyst supports N700, N800 and N900 prepared in Example 1.

[0040] Figure 2TEM images of the catalyst supports NQ25(a), NQ50(b), and NQ100(c) prepared in Example 2.

[0041] Figure 3 The image shows an SEM image of the catalyst support N900 prepared in Example 3.

[0042] Figure 4 The image shows a TEM image of the platinum-cobalt alloy catalyst PtCo3@N900 prepared in Example 3.

[0043] Figure 5 SEM image of biochar C800 prepared in Comparative Example 1.

[0044] Figure 6 The particle size distribution diagram is shown for the PtCo3 alloy nanoparticles of the platinum-cobalt alloy catalyst prepared in Example 3.

[0045] Figure 7 The graph shows the toluene catalytic oxidation conversion efficiency of the platinum-cobalt alloy catalyst PtCo3@N900 prepared in Example 3.

[0046] Figure 8 The graph shows the toluene catalytic oxidation conversion efficiency of the catalyst PtCo3@C800 prepared for Comparative Example 1.

[0047] Figure 9 The graph shows the toluene catalytic oxidation conversion efficiency of the catalysts PtCo3@NQ25, PtCo3@NQ50, and PtCo3@NQ100 prepared in Example 2. Detailed Implementation

[0048] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments. Obviously, the embodiments described below are only a part of the embodiments, and all other embodiments obtained by those skilled in the art without creative effort are still within the scope of protection of the present invention.

[0049] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0050] Example 1 (Activation Temperature Investigation Experiment)

[0051] (1) Carbonization process:

[0052] The biomass raw material, cork (cork oak material), was dried and crushed into powder. It was then carbonized at 800℃ for 2 hours under a nitrogen atmosphere of 100mL / min to obtain carbonized material. After removing impurities by acid washing with HCl, the carbonized material was washed with water until neutral and dried at 60℃ to obtain biochar, which was named C800.

[0053] (2) Activation process:

[0054] Biochar C800 was activated at high temperatures of 700℃, 800℃ and 900℃ respectively, using NH3 at a rate of 100 mL / min for 1 h. After cooling to room temperature, activated carbon, i.e. catalyst support, was obtained and named N700, N800 and N900 respectively.

[0055] The toluene adsorption performance of C800, N700, N800, and N900 was tested at 25℃ and 3kPa (carrier amount: 30g). The results are as follows: Figure 1 As shown.

[0056] Depend on Figure 1 The results showed that, compared with biochar support C800, the activated supports after ammonia activation all improved the adsorption capacity for toluene; and with the increase of activation temperature, the adsorption performance of the catalyst support also increased. Among them, N900 showed outstanding toluene adsorption effect, which is attributed to the developed pore structure, large specific surface area and abundant amino functional groups of N900. The activation temperature was further optimized to be 800-900℃.

[0057] Example 2 (Experiment to Investigate the Dosage of Activator)

[0058] (1) Carbonization process:

[0059] The biomass raw material, cork, was dried and crushed into powder. It was then carbonized at 800℃ for 2 hours under a nitrogen atmosphere of 100mL / min to obtain carbonized material. The carbonized material was then acid-washed with HCl to remove impurities, washed with water until neutral, and dried at 60℃ to obtain biochar, which was named C800.

[0060] (2) Activation process:

[0061] Biochar C800 was activated at a high temperature of 900℃ using NH3 at flow rates of 25 mL / min, 50 mL / min, and 100 mL / min for 1 h, respectively. After cooling to room temperature, activated carbon, i.e. catalyst support, was obtained and named NQ25, NQ50, and NQ100 (i.e., N900), respectively.

[0062] (3) Preparation of platinum-cobalt alloy nanoparticles:

[0063] In a three-necked flask, 1.16 g of cobalt acetylacetonate, 0.4 mL of oleic acid, 0.4 mL of oleylamine, and 200 mg of reducing agent tetraphenyldipropylene glycol diphosphite (TDD) were dissolved in 30 mL of dibenzyl ether. The air in the three-necked flask was purged with an argon gas flow of 100 mL / min, and the solution was heated at 100 °C for 1 h under argon atmosphere to remove moisture. The three-necked flask was then heated to 200 °C, and 0.2 mmol of platinum acetylacetonate and 1.4 mL of o-dichlorobenzene were added. The mixture was kept at this temperature for 1 h. After cooling to room temperature, 50 mL of anhydrous ethanol was added, and the mixture was centrifuged to obtain platinum-cobalt alloy nanoparticles (PtCo3).

[0064] (4) Catalyst Synthesis: PtCo3 nanoparticles and catalyst supports NQ25, NQ50, and NQ100 (N900) were added to 30 mL of n-hexane and sonicated for 30 min to uniformly load the PtCo3 nanoparticles onto the biomass activated carbon support. After washing several times, the catalysts were placed in a vacuum drying oven and dried at 60 °C for 18 h to finally obtain low-platinum catalysts PtCo3@NQ25, PtCo3@NQ50, and PtCo3@NQ100 (PtCo3@N900).

[0065] The catalyst supports NQ25, NQ50, and NQ100 prepared in Example 2 were subjected to transmission electron microscopy (TEM) tests, and the results are as follows: Figure 2 As shown. By Figure 2 This indicates that increasing the amount of activator modulates the microporous structure on the surface of activated carbon.

[0066] Example 3

[0067] (1) Preparation of catalyst support:

[0068] Biomass feedstock, cork, was dried and crushed into powder. The powder was then carbonized at 800℃ for 2 hours under a nitrogen atmosphere (nitrogen flow rate 100 mL / min) to obtain carbonized material. This carbonized material was then removed by acid washing with HCl, washed with water until neutral, and dried at 60℃ to obtain biochar, named C800. Biochar C800 was then activated at 900℃ using NH3 at a flow rate of 100 mL / min for 1 hour. After cooling to room temperature, activated carbon, i.e., the catalyst support, was obtained and named N900.

[0069] (2) Preparation of platinum-cobalt alloy nanoparticles:

[0070] In a three-necked flask, 1.16 g of cobalt acetylacetonate, 0.4 mL of oleic acid, 0.4 mL of oleylamine, and 200 mg of reducing agent TDD were dissolved in 30 mL of dibenzyl ether. The air in the three-necked flask was purged with an argon gas flow of 100 mL / min, and the solution was heated at 100 °C for 1 h under argon atmosphere to remove moisture. The three-necked flask was then heated to 200 °C, and 0.2 mmol of platinum acetylacetonate and 1.4 mL of o-dichlorobenzene were added. The mixture was kept at this temperature for 1 h. After cooling to room temperature, 50 mL of anhydrous ethanol was added, and the mixture was centrifuged to obtain platinum-cobalt alloy nanoparticles (PtCo3). The particle size distribution of the platinum-cobalt alloy prepared in this invention is shown in the figure. Figure 6 ,like Figure 6 As shown, the platinum-cobalt alloy prepared by this invention has a small particle size and narrow distribution, and is uniformly distributed in the range of 2-3 nm.

[0071] (3) Synthesis catalyst:

[0072] PtCo3 nanoparticles and N900 biomass activated carbon were added to 30 mL of n-hexane and sonicated for 30 min to uniformly load the PtCo3 nanoparticles onto the biomass activated carbon support. After washing several times, the mixture was placed in a vacuum drying oven and dried at 60 °C for 18 h to finally obtain the low-platinum catalyst PtCo3@N900.

[0073] Meanwhile, the N700 and N800 catalyst supports prepared at 700℃ and 800℃ in Example 1, loaded with the platinum-cobalt alloy nanoparticles prepared in this example under the same conditions, yielded PtCo3@N700 and PtCo3@N800, which also exhibited higher activity than the unactivated catalysts.

[0074] Comparative Example 1

[0075] (1) Preparation of catalyst support: The biomass raw material cork was dried and crushed into powder. It was carbonized at 800℃ for 2h under a nitrogen atmosphere of 100mL / min to obtain carbonized material. The carbonized material was removed by acid washing with HCl, washed with water until neutral, and dried at 60℃ to obtain biochar, named C800.

[0076] (2) Preparation of platinum-cobalt alloy nanoparticles: In a three-necked flask, 1.16 g of cobalt acetylacetonate, 0.4 mL of oleic acid, 0.4 mL of oleylamine, and 200 mg of reducing agent TDD were dissolved in 30 mL of dibenzyl ether. The air in the three-necked flask was purged with an argon gas flow of 100 mL / min, and the mixture was heated at 100 °C for 1 h under argon atmosphere to remove moisture from the solution. The three-necked flask was then heated to 200 °C, and 0.2 mmol of platinum acetylacetonate and 1.4 mL of o-dichlorobenzene were added. The mixture was kept at this temperature for 1 h. After cooling to room temperature, 50 mL of anhydrous ethanol was added, and the mixture was centrifuged to obtain platinum-cobalt alloy nanoparticles (PtCo3).

[0077] (3) Catalyst synthesis: PtCo3 nanoparticles and biomass activated carbon C800 were added to 30 mL of n-hexane and ultrasonically treated for 30 min to uniformly load the PtCo3 nanoparticles onto the biomass activated carbon support. After washing several times, the mixture was placed in a vacuum drying oven and dried at 60 °C for 18 h to finally obtain the low-platinum catalyst PtCo3@C800.

[0078] The activated catalyst support N900 prepared in Example 3 and the unactivated catalyst support C800 prepared in Comparative Example 1 were subjected to scanning electron microscopy (SEM) analysis. The results are as follows: Figure 3 and Figure 5 As shown, from Figure 5 As can be seen, biomass carbonized at high temperatures has a honeycomb-like porous structure. Figure 3 It can be seen that it still retains its unique honeycomb-like structure after high-temperature activation.

[0079] The activated carbon-supported platinum-cobalt alloy catalyst PtCo3@N900 prepared in Example 3 was subjected to transmission electron microscopy (TEM) analysis, and the results are as follows: Figure 4 ,Depend on Figure 4 It can be seen that platinum-cobalt nanoparticles are uniformly loaded on the surface of the activated carbon support.

[0080] Catalyst activity assessment

[0081] The catalytic oxidation effects of the low-platinum catalysts PtCo3@NQ25, PtCo3@NQ50, and PtCo3@NQ100 from Example 2, the low-platinum catalyst PtCo3@N900 from Example 3, and the catalyst prepared in Comparative Example 1 were evaluated as follows: The catalysts were mixed with an appropriate amount of quartz sand (30 mg of catalyst and 0.8 cm... 3 The quartz sand was thoroughly mixed and placed into the catalytic reaction vessel. During the catalytic activity experiment, a reaction gas with a total flow rate of 160 mL / min was introduced, including: three types of toluene with concentrations of 400, 700, and 1000 ppm, 20% oxygen, and nitrogen as a balance gas. The gas hourly space velocity (GHSV) was 12000 h⁻¹. -1 The toluene concentration in the exhaust gas was recorded at each temperature during the programmed heating process, and the toluene conversion rate was calculated (in this invention, toluene is converted to CO2, and the conversion rate is calculated by measuring the toluene concentration and CO2 content before and after the reaction. Gas chromatography can simultaneously detect the concentrations of toluene and CO2, thereby calculating the toluene conversion rate).

[0082] The conversion results of toluene are as follows: Figure 7 , Figure 8 and Figure 9 , Figure 7The figure shows the conversion efficiency of toluene catalytic oxidation of the catalyst prepared in Example 3. As can be seen from the figure, toluene gradually begins to oxidize and decompose under the action of PtCo3@N900 catalyst starting from 160℃. The conversion efficiency of toluene also increases as the concentration decreases. At 210℃, the conversion rate of toluene at all concentrations reaches more than 99%. Figure 8 The graph shows the toluene catalytic oxidation conversion efficiency of the catalyst prepared in Comparative Example 1. Figure 8 It can be seen that toluene requires 200℃ to gradually oxidize and decompose under the action of PtCo3@C800 catalyst, and the toluene conversion efficiency increases as the concentration decreases. Figure 9 The catalytic performance of PtCo3@NQ25, PtCo3@NQ50, and PtCo3@NQ100 prepared in Example 2 was compared (where the concentration of toluene was 1000 ppm). Figure 9 It is evident that the PtCo3@NQ100 catalyst exhibits the best catalytic effect on toluene, gradually initiating oxidation and decomposition from 160℃, and achieving a toluene conversion rate of over 99% at 205℃. In contrast, toluene, under the action of PtCo3@NQ50 and PtCo3@NQ25 catalysts, requires 180℃ to gradually begin oxidation and decomposition, with a toluene conversion rate exceeding 99% at 230℃. The examples demonstrate the promoting effect of catalyst support activation on the catalytic cracking of toluene, with a further preferred activation rate of 50–100 mL / min.

[0083] Meanwhile, the conversion temperatures of the catalyst at different toluene concentrations (50% and 90% toluene conversion) were statistically analyzed, and the results are listed in Table 1. According to the data in Table 1, the toluene catalytic efficiency of the ammonia-activated biomass activated carbon supported catalyst PtCo3@N900 is significantly better than that of the unactivated biomass carbon supported catalyst. Benefiting from the activated support and the excellent distribution characteristics of platinum-cobalt nanoparticles, the PtCo3@N900 catalyst prepared in Example 3 achieved a toluene conversion efficiency of 90% at a concentration of 400 ppm only at 193 °C, demonstrating higher catalytic activity.

[0084] Table 1 shows the T values ​​of the catalysts prepared in Example 3 and Comparative Example 1 at different toluene concentrations. 50 T 90 Conversion temperature

[0085]

Claims

1. The application of an activated carbon-supported platinum-cobalt alloy catalyst, characterized in that: It is applied to the low-temperature catalytic oxidation of VOCs-containing waste gas; The preparation method of the activated carbon-supported platinum-cobalt alloy catalyst includes the following steps: 1) After carbonization, biomass raw materials are successively subjected to acid washing to remove impurities and high-temperature activation treatment under the action of ammonia activator to obtain activated carbon; 2) After removing water from a solution containing a cobalt source, oleic acid, oleylamine and a reducing agent, a platinum source and o-dichlorobenzene are added to carry out a solvothermal reduction reaction to obtain platinum-cobalt alloy nanoparticles. 3) The activated carbon and platinum-cobalt alloy nanoparticles are ultrasonically mixed to obtain the final product; In the high-temperature activation process, the ammonia activator is ammonia gas; The biomass raw material is cork oak wood.

2. The application of the activated carbon-supported platinum-cobalt alloy catalyst according to claim 1, characterized in that: The carbonization conditions are: temperature 700~1000℃, time 1~4h, and nitrogen gas with a flow rate of 80~100mL / min as a protective atmosphere; the high-temperature activation conditions are: temperature 700~1000℃, time 1~4h.

3. The application of the activated carbon-supported platinum-cobalt alloy catalyst according to claim 1 or 2, characterized in that: The flow rate of the ammonia gas is 25~100 mL / min.

4. The application of the activated carbon-supported platinum-cobalt alloy catalyst according to claim 1, characterized in that: The molar ratio of the cobalt source to the platinum source is (8~16):

1.

5. The application of the activated carbon-supported platinum-cobalt alloy catalyst according to claim 1 or 4, characterized in that: The cobalt source is one of cobalt acetylacetonate, cobalt chloride, cobalt nitrate, and cobalt acetate; The platinum source is one of platinum acetylacetonate, chloroplatinic acid, and diaminodinitroplatinum. The reducing agent is tetraphenyldipropylene glycol diphosphite.

6. The application of the activated carbon-supported platinum-cobalt alloy catalyst according to claim 5, characterized in that: The conditions for the solvothermal reduction reaction are: temperature 180~240℃, time 30~90min; The mixture for dehydration is heated in an argon atmosphere at 80-120°C for 30-90 minutes.

7. The application of the activated carbon-supported platinum-cobalt alloy catalyst according to claim 1, characterized in that: The volume ratio of oleic acid to oleylamine is (0.8~1.2):1, and the total amount of oleic acid and oleylamine relative to the amount of cobalt source is (0.2~1) L / mol.

8. The application of the activated carbon-supported platinum-cobalt alloy catalyst according to claim 1, characterized in that: The catalyst has a honeycomb-like three-dimensional porous structure, and the activated carbon is uniformly loaded with platinum-cobalt alloy nanoparticles.

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