A carbon-based catalyst, its preparation method and application, and a formaldehyde-removing material

Abstract

The present invention provides a carbon-based catalyst, a preparation method and application thereof, and a formaldehyde-removing material, which relate to the technical fields of environmental functional materials and atmospheric treatment, and include the following steps: Step 1) Prepare activated carbon loaded with transition metal oxides; prepare activated carbon loaded with noble metals; Step 2) Mix the activated carbon loaded with transition metal oxides with the activated carbon loaded with noble metals to obtain a carbon-based catalyst. Through co-loading, the dosage of noble metal loading is reduced, the preparation cost of the catalyst is effectively reduced, and the economic benefits of the catalytic industry are improved; at the same time, by separately preparing activated carbon loaded with transition metal oxides and activated carbon loaded with noble metals, the problem that heavy metals in other raw and auxiliary materials are likely to cause heavy metal poisoning of noble metals during the loading process, resulting in the inactivation of the activated carbon loaded with noble metals and affecting the catalytic effect of the final carbon-based catalyst can be avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental functional materials and atmosphere treatment, and specifically relates to a carbon-based catalyst and a preparation method and application thereof, and a formaldehyde removal material. Background Art

[0002] Formaldehyde (HCHO) is a typical volatile organic compound (VOC). It is colorless and has a pungent odor. Indoor formaldehyde mainly comes from furniture decoration materials and building materials, mainly artificial board furniture, wall stickers, multi-layer solid wood floors, and wall paint. Exposure to formaldehyde can greatly damage human health. Studies have shown that when the formaldehyde concentration exceeds 0.5mg / m 3 The human body will feel strong stimulation and shed tears, even at a low concentration of 0.1 mg / m 3 Formaldehyde can also make the human body feel uncomfortable. More seriously, long-term exposure to formaldehyde can cause a series of serious diseases such as leukemia and chromosomal abnormalities, and in severe cases, can lead to a variety of cancers. Epidemiological studies have confirmed that exposure to formaldehyde can cause physical harm, such as asthma and dermatitis. 3 Exposure to low formaldehyde concentrations for 1-5 minutes may cause eye irritation. 3 Exposure to high concentrations of formaldehyde for 1 minute will affect the functional state of the cerebral cortex. Therefore, the problem of indoor formaldehyde needs to be solved urgently, which requires innovation in technology and materials. This is not only related to everyone's quality of life, but also to people's survival and health.

[0003] At present, the methods of removing indoor formaldehyde can be generally classified into two categories, namely, controlling the generation of formaldehyde from the source and eliminating the generated formaldehyde through a series of methods, including pollution source control, mechanical purification (such as opening windows for ventilation, air conditioning and exhaust fans, etc.), plant and biological purification, physical adsorption, catalytic oxidation, etc. The catalytic oxidation method relies on the catalytic action of a specific catalyst to react formaldehyde with oxygen to generate non-toxic small molecules of water (H2O) and carbon dioxide (CO2). Due to the special indoor environment, the catalytic oxidation of free formaldehyde in the room is mainly photocatalytic oxidation, thermal catalytic oxidation and room temperature catalytic oxidation. Electrocatalytic oxidation and other methods are difficult to apply due to the special indoor environment. Thermal catalytic oxidation requires a certain temperature to achieve good catalytic performance, which will be limited in daily application. Room temperature catalytic oxidation is more practical.

[0004] Carbon materials are excellent supported catalyst carriers. For example, activated carbon and graphene have been widely used in the preparation of polymer nanocomposites. As a porous material with more industrial applications, activated carbon has strong basic adsorption capacity. It has a large specific surface area and thermal stability, and the presence of a carbonized structure endows it with adjustable electron transfer and charge storage characteristics. Its electronic structure can be further adjusted by modifying with metal substances, thereby improving catalytic performance. Among them, supported noble metal catalysts can achieve relatively ideal conversion rates even at low temperatures or even at room temperature, realizing the rapid conversion of high-concentration formaldehyde at low temperatures. At present, among many noble metals, platinum (Pt), palladium (Pd), rhodium (Rh), gold (Au), and silver (Ag) have good catalytic effects and are widely studied. However, the disadvantages are that the cost of noble metals is high, and due to the easy agglomeration of noble metal particles, the atomic utilization rate is not high. Therefore, how to reduce the content of noble metals and improve the utilization rate is the top priority of the research.

[0005] However, the supported noble metal catalysts have the following problems: (1) Due to the high cost of noble metals, if the dosage is large, the preparation cost of the catalyst is relatively high; (2) Due to the easy agglomeration of noble metal particles, their atomic utilization rate is not high, resulting in low catalytic efficiency. Summary of the Invention

[0006] Therefore, the present invention provides a carbon-based catalyst, its preparation method and application, and a formaldehyde-removing material, which can solve the technical problem of high preparation cost of supported noble metal catalysts in the prior art.

[0007] To solve the above problems, the present invention provides a preparation method of a carbon-based catalyst, including the following steps:

[0008] Step 1) Prepare activated carbon loaded with transition metal oxides; prepare activated carbon loaded with noble metals;

[0009] Step 2) Mix the activated carbon loaded with transition metal oxides with the activated carbon loaded with noble metals to obtain a carbon-based catalyst.

[0010] Further, in the step 1), the preparation steps of the activated carbon loaded with transition metal oxides include:

[0011] Mix a transition metal salt solution with a buffer solution for a reaction to obtain a mixed solution; then use the mixed solution to impregnate activated carbon, and then perform filtration and drying treatments to obtain the activated carbon loaded with transition metal oxides.

[0012] Further, during the mixing reaction, stirring is performed; the stirring time is 5-10 min.

[0013] Further, the steps of impregnating the activated carbon with the mixed solution include:

[0014] Adding the activated carbon to the mixed solution at room temperature and stirring; the stirring time is 60 - 120 min.

[0015] Further, the temperature of the drying treatment is 60 - 80 °C; the drying time is 24 - 48 h.

[0016] Further, the transition metal salt is selected as potassium permanganate KMnO4; and / or

[0017] The buffer is selected as ammonium carbonate (NH4)2CO3; and / or

[0018] In the activated carbon loaded with transition metal oxide: the Mn 2+ content is 4.28% - 5.08%, the Mn 3+ content is 51.8% - 54.8%, the Mn 4+ content is 40.12% - 43.92%, the Mn 3+ / Mn 4+ ratio is 1.08 - 1.37; the crystal structure of manganese includes δ-MnO x and the δ-MnO x exists uniformly on the surface of the activated carbon; and / or

[0019] When the transition metal salt solution and the buffer solution are mixed and reacted, the weight ratio of the transition metal salt in the transition metal salt solution to the buffer in the buffer solution is 3.5:1 - 4.5:1; and / or

[0020] When the activated carbon is impregnated with the mixed solution, the weight ratio of the transition metal salt in the transition metal salt solution to the activated carbon is 2:1 - 3:1.

[0021] Further, the concentration of the transition metal salt solution is 65.7 - 67.7 mg / mL; and / or

[0022] The concentration of the buffer solution is 20 - 30 mg / mL.

[0023] Further, in the step 1), the steps of preparing the activated carbon loaded with noble metal include:

[0024] Step S1) Impregnating the activated carbon with the polyelectrolyte solution, then filtering and drying to obtain the activated carbon loaded with polyelectrolyte;

[0025] Step S2) Mixing and reacting the activated carbon loaded with polyelectrolyte with the noble metal salt solution and the reducing agent solution to obtain the activated carbon loaded with noble metal.

[0026] Further, in the step S1), the impregnation treatment includes:

[0027] Adding activated carbon into the polyelectrolyte solution at room temperature and stirring; wherein, the weight ratio of the activated carbon to the polyelectrolyte in the polyelectrolyte solution is 31.7:1 to 95.5:1; the stirring time is 60 - 120 min.

[0028] Further, in the step S1), the temperature of the drying treatment is 60 - 80 °C; the drying time is 24 - 48 h.

[0029] Further, the step S2) includes:

[0030] Step S21) Mixing the activated carbon loaded with polyelectrolyte with the noble metal salt solution to form a system to be reduced;

[0031] Step S22) Mixing the system to be reduced with the reducing agent solution to carry out a reduction reaction; after the reduction reaction is completed, filtration and drying treatments are carried out to obtain the once-loaded activated carbon;

[0032] Step S23) Mixing and reacting the once-loaded activated carbon with the noble metal salt solution and the reducing agent solution, and then carrying out secondary filtration and drying treatments to obtain the activated carbon loaded with noble metal.

[0033] Further, in the step S21), the mass ratio of the noble metal salt in the activated carbon loaded with polyelectrolyte to the noble metal salt is 312.5:1 to 937.5:1.

[0034] Further, in the step S22), the temperature of the drying treatment is 60 - 80 °C; the drying time is 24 - 48 h.

[0035] Further, in the step S23), the temperature of the drying treatment is 60 - 80 °C; the drying time is 24 - 48 h.

[0036] Further, the polyelectrolyte is selected as polydiallyldimethylammonium chloride PDDA; and / or

[0037] The noble metal salt is selected as chloroplatinic acid hexahydrate H2PtCl6·6H2O; and / or

[0038] The reducing agent solution is obtained by mixing sodium borohydride NaBH4 solution and sodium hydroxide NaOH solution; and / or

[0039] The mass fraction of the noble metal in the activated carbon loaded with noble metal is 0.18 - 0.22 wt%.

[0040] Furthermore, the weight ratio of NaOH in the sodium hydroxide NaOH solution to NaBH4 in the sodium borohydride NaBH4 solution is 5:1 to 5.4:1; and / or

[0041] The concentration of the polydiallyldimethylammonium chloride PDDA solution is 2.10 - 6.30 mg / mL; and / or

[0042] The concentration of the chloroplatinic acid hexahydrate H2PtCl6·6H2O solution is 0.96 - 2.88 mg / mL; and / or

[0043] The concentration of the sodium borohydride NaBH4 solution is 3.0 - 9.1 mg / mL; and / or

[0044] The concentration of the sodium hydroxide NaOH solution is 16 - 48 mg / mL.

[0045] Furthermore, in the step 2): the mass ratio of the activated carbon loaded with transition metal oxide to the activated carbon loaded with noble metal is 6.5 - 7.5:2.5 - 3.5.

[0046] Furthermore, before the step 1), it further includes a purification step of activated carbon:

[0047] Add the original activated carbon to deionized water for soaking, then filter and dry it to obtain the purified activated carbon.

[0048] Furthermore, in the activated carbon loaded with noble metal: the noble metal is loaded in the activated carbon in the form of nanoparticles; preferably, the particle size of the nanoparticles is 1 - 5 nm.

[0049] On the other hand, the present invention also provides a carbon-based catalyst, and the carbon-based catalyst is obtained by mixing the activated carbon loaded with transition metal oxide and the activated carbon loaded with noble metal.

[0050] Preferably, the transition metal oxide is manganese oxide; in the activated carbon loaded with transition metal oxide: the Mn 2+ content is 4.28% - 5.08%, the Mn 3+ content is 51.8% - 54.8%, the Mn 4+ content is 40.12% - 43.92%, the ratio of Mn 3+ / Mn 4+ is 1.08 - 1.37; the crystal structure of the transition metal includes δ-MnO x and the δ-MnO x exists uniformly on the surface of the activated carbon;

[0051] Preferably, in the activated carbon loaded with noble metal: the noble metal is loaded in the activated carbon in the form of nanoparticles; preferably, the particle size of the nanoparticles is 1-5 nm;

[0052] Preferably, the carbon-based catalyst is obtained by the preparation method described in any one of the above.

[0053] On the other hand, the present invention provides an application of the above carbon-based catalyst, and the carbon-based catalyst is used for removing indoor formaldehyde at room temperature.

[0054] On the other hand, the present invention also provides a formaldehyde removal material, and the formaldehyde removal material is the above-mentioned carbon-based catalyst.

[0055] Compared with the prior art, the present invention has at least the following beneficial effects:

[0056] 1. The present invention provides a preparation method of a carbon-based catalyst, which mixes activated carbon loaded with transition metal oxide and activated carbon loaded with noble metal to obtain a carbon-based catalyst; based on the above method, the loading amount of noble metal is reduced; the preparation cost of the catalyst is effectively reduced, and the economic benefit of the catalytic industry is improved; at the same time, by separately preparing activated carbon loaded with transition metal oxide and activated carbon loaded with noble metal, the problem that heavy metals in other raw and auxiliary materials are likely to cause noble metal poisoning during the loading process (for example, when preparing a carbon-based catalyst, if transition metal oxide and noble metal are loaded simultaneously, the transition metal existing in the surrounding environment of the noble metal is likely to deactivate the noble metal), resulting in the inactivation of the activated carbon loaded with noble metal and affecting the catalytic effect of the final carbon-based catalyst.

[0057] 2. Further, the present invention separately prepares activated carbon loaded with transition metal oxide and activated carbon loaded with noble metal, and then mixes them. Reducing agents can be respectively selected based on the chemical properties of transition metal and noble metal to fully reduce transition metal salt and noble metal salt, ensuring the loading effect after impregnation treatment, and thus ensuring the catalytic effect of the final carbon-based catalyst.

[0058] 3. Further, when loading noble metal on the activated carbon, at least two loadings are carried out. Then the loading amount each time is small, the concentration of the reactant and the ionic strength of the impregnation solution can be regulated, the particle size of the noble metal nanoparticles can be reduced, and the dispersion of the noble metal can be enhanced; at the same time, it can be avoided that the loading amount at one time is too large, resulting in agglomeration between noble metal particles, low utilization rate of the reduced noble metal, high preparation cost and low catalytic efficiency.

[0059] 4. On the other hand, the present invention provides a carbon-based catalyst, which is prepared by the above method and is a carbon-based catalyst with synergistic loading of transition metal oxide and noble metal. It can reduce the preparation cost of the loaded catalyst and improve the catalytic efficiency. The above carbon-based catalyst of the present invention is used for removing indoor formaldehyde at room temperature and can remove more than 85% of indoor formaldehyde. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. The drawings in the following description are only exemplary, and for those of ordinary skill in the art, without creative efforts, other implementation drawings can be obtained according to the provided drawings.

[0061] Figure 1 It is a graph of the removal efficiency of formaldehyde by platinum and activated carbon with different ratios in the present invention;

[0062] Figure 2 It is a graph of the removal efficiency of formaldehyde by carbon-based catalysts with different addition amounts in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0063] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. The drawings in the following description are only exemplary, and for those of ordinary skill in the art, without creative efforts, other implementation drawings can be obtained according to the provided drawings.

[0064] According to an embodiment of the present invention, a preparation method of a carbon-based catalyst is provided, including the following steps:

[0065] Step 1) Purification step of activated carbon: Add the original activated carbon to deionized water for soaking, then filter and dry to obtain purified activated carbon; the activated carbon used in the following methods is all purified activated carbon (AC); the ash content of the purified AC ≤ 10%, and the particle size is 30 - 60 mesh;

[0066] Step of preparing activated carbon loaded with transition metal oxide: Mix and react the transition metal salt solution with the buffer solution to obtain a mixed solution; then add the activated carbon to the mixed solution at room temperature, and at the same time perform secondary stirring, filtering, and drying treatments (i.e., impregnate the activated carbon with the mixed solution), and obtain the activated carbon loaded with transition metal oxide after drying;

[0067] Among them, the transition metal salt is potassium permanganate KMnO4, and the concentration of the potassium permanganate KMnO4 solution is 65.7 - 67.7 mg / mL; the buffer is ammonium carbonate (NH4)2CO3, and the concentration of the ammonium carbonate (NH4)2CO3 solution is 20 - 30 mg / mL; when the transition metal salt solution and the buffer solution are mixed and reacted, the weight ratio of KMnO4 (i.e., the solute) in the potassium permanganate KMnO4 solution to (NH4)2CO3 (i.e., the solute) in the ammonium carbonate (NH4)2CO3 solution is 3.5:1 - 4.5:1; when the activated carbon is impregnated with the said mixed solution, the weight ratio of KMnO4 in the potassium permanganate KMnO4 solution to the activated carbon is 2:1 - 3:1; one stirring is carried out during the process of the mixed reaction; preferably, the time of one stirring is 5 - 10 min; preferably, the time of the second stirring is 60 - 120 min; the temperature of the drying treatment is 60 - 80 °C; the time of the drying treatment is 24 - 48 h;

[0068] Steps for preparing activated carbon loaded with noble metal:

[0069] Step S1) Add activated carbon into the polyelectrolyte solution at room temperature, and carry out stirring, filtration, and drying treatment to obtain activated carbon loaded with polyelectrolyte; among them, the weight ratio of the activated carbon to the polyelectrolyte (i.e., the solute) in the polyelectrolyte solution is 31.7:1 - 95.5:1; preferably, the stirring time is 60 - 120 min; the temperature of the drying treatment is 60 - 80 °C; the time of the drying treatment is 24 - 48 h;

[0070] Step S21) Mix the activated carbon loaded with polyelectrolyte with the noble metal salt solution to form a system to be reduced; among them, the mass ratio of the activated carbon loaded with polyelectrolyte to the noble metal salt (i.e., the solute) in the noble metal salt solution is 312.5:1 - 937.5:1.

[0071] Step S22) Mix the system to be reduced with the reducing agent solution (reduction solution) to carry out a reduction reaction; after the reduction reaction is completed, carry out filtration and drying treatment to obtain the once-loaded activated carbon; preferably, the temperature of the drying treatment is 60 - 80 °C; the time of the drying treatment is 24 - 48 h;

[0072] Step S23) Carry out a mixed reaction on the once-loaded activated carbon with the noble metal salt solution and the reducing agent solution, and then carry out filtration and drying treatment once;

[0073] Among them, the polyelectrolyte is poly(diallyldimethylammonium chloride) PDDA; the noble metal salt is hexachloroplatinic acid hexahydrate H2PtCl6·6H2O; the reducing agent solution is obtained by mixing sodium borohydride NaBH4 solution and sodium hydroxide NaOH solution; the obtained activated carbon loaded with noble metal is platinum (Pt)-modified activated carbon, wherein platinum is loaded in the activated carbon in the form of platinum nanoparticles, and the particle size of the platinum nanoparticles is 1-5 nm;

[0074] Step 2) Mix the activated carbon loaded with transition metal oxide and the activated carbon loaded with noble metal to obtain a carbon-based catalyst with synergistic loading of transition metal oxide and noble metal; among them, the mass ratio of the activated carbon loaded with transition metal oxide to the activated carbon loaded with noble metal is 6.5-7.5:2.5-3.5.

[0075] Among them, the weight ratio of NaOH (i.e., the solute) in the sodium hydroxide NaOH solution to NaBH4 (i.e., the solute) in the sodium borohydride NaBH4 solution is 5:1-5.4:1; the concentration of the poly(diallyldimethylammonium chloride) PDDA solution is 2.10-6.30 mg / mL; the concentration of the hexachloroplatinic acid hexahydrate H2PtCl6·6H2O solution is 0.96-2.88 mg / mL; the concentration of the sodium borohydride NaBH4 solution is 3.0-9.1 mg / mL; the concentration of the sodium hydroxide NaOH solution is 16-48 mg / mL.

[0076] Based on the above method, the amount of noble metal used can be reduced, effectively reducing the preparation cost of the catalyst and enhancing the economic benefits of the catalytic industry; at the same time, by separately preparing the activated carbon loaded with transition metal oxide and the activated carbon loaded with noble metal, the problem that heavy metals in other raw and auxiliary materials are likely to cause noble metal poisoning during the loading process, resulting in the inactivation of the activated carbon loaded with noble metal and affecting the catalytic effect of the final carbon-based catalyst can be avoided; in addition, reducing agents can be selected respectively based on the chemical properties of transition metals and noble metals to fully reduce transition metal salts and noble metal salts, ensuring the loading effect after impregnation treatment, and thus ensuring the catalytic effect of the final carbon-based catalyst.

[0077] When the mass ratio of the activated carbon loaded with transition metal oxide to the activated carbon loaded with noble metal is higher than the above range value, the long-term stability of the final carbon-based catalyst will be weakened. Through experiments, it is obtained that under the condition of keeping other experimental conditions the same, the stable formaldehyde removal ability of single manganese oxide can only be maintained for 24 h; as the mass ratio of the two gradually decreases, the stable formaldehyde removal period gradually extends, and when the mass ratio of the two is within the range value of 6.5-7.5:2.5-3.5, the optimal peak value of formaldehyde removal effect is reached; when the mass ratio of the two is lower than the above range value, it will lead to the overuse and waste of noble metal catalysts, resulting in an increase in cost.

[0078] The reduction products of KMnO4 are diverse, which affect the adsorption and conversion of HCHO and O2 by the catalyst. The manganese species with formaldehyde catalytic function are Mn 3+ and Mn 4+ and δ-MnO x . In this application, ammonium carbonate (NH4)2CO3 solution is used as a buffer to ensure the conversion rate of KMnO4 to Mn 3+ and Mn 4+ , the formation rate of δ-MnO x , and the loading amount and distribution uniformity on the AC surface. In this application, the solution impregnation method at room temperature is selected to prepare the manganese oxide catalyst, and ammonium carbonate (NH4)2CO3 is used as a mild reducing agent to synthesize the carbon-based manganese oxide modified catalyst in one step. Among them, the catalytic activity of the manganese-based catalyst for formaldehyde depends on the content of Mn 3+ and Mn 4+ , the ratio of Mn 3+ / Mn 4+ , and the existing crystal form state of MnO x . In the manganese oxide catalyst obtained in this application (i.e., activated carbon loaded with transition metal oxide), the content of Mn 2+ is 4.28% - 5.08%, the content of Mn 3+ is 51.8% - 54.8%, the content of Mn 4+ is 40.12% - 43.92%, and the ratio of Mn 3+ / Mn 4+ is 1.08 - 1.37; preferably, the content of Mn 2+ is 4.68%, the content of Mn 3+ is 53.8%, the content of Mn 3+ is 41.5%, and the ratio of Mn 3+ / Mn 4+ is 1.30. Compared with the existing manganese-based catalyst, the ratio of Mn 3+ / Mn 4+ is further improved, and the crystal structure of manganese is mainly δ-MnO x and uniformly exists on the surface of activated carbon.

[0079] Among them, Mn 2+ and Mn 3+ and Mn 4+The sum of the contents is 100%; According to the natural law of known redox reactions, the reduction of potassium permanganate is extremely susceptible to the influence of the environmental pH value and will exhibit different decreased valence states under different conditions. Potassium permanganate is likely to gain 5 electrons under acidic conditions and thus can be reduced to manganese ions with a valence of +2. Under strongly alkaline conditions, it is likely to be reduced to manganese ions with a valence of +6, both of which are not conducive to the catalytic removal of formaldehyde; while under weakly alkaline conditions, it is likely to gain three electrons to generate manganese ions with a valence of +4, that is, MnO₂, which is conducive to the removal of formaldehyde. Therefore, in this application, ammonium carbonate (NH₄)₂CO₃ is selected as the temperature buffer and at the same time as the reducing agent, providing a suitable acid-base environment for the reduction of potassium permanganate and avoiding the generation of manganese ions with a valence of +2 and +6 that are not conducive to the formaldehyde catalysis;

[0080] Manganese oxide crystal resources are abundant, and manganese oxides with different crystal forms can be obtained by controlling the preparation method, raw materials and preparation conditions. Compared with thermal decomposition method, hydrothermal method, sol-gel method, precipitation method, etc. which require high-temperature experiments and special difficult-to-control conditions such as isothermal and low-pressure, this application adopts a solution impregnation redox method at room temperature. However, the anions in the manganese salt solution in the redox method will affect the growth of the crystal form of manganese oxide. Therefore, a suitable reducing agent needs to be selected. Sulfate ions and nitrate ions, etc. are likely to promote the formation of β-MnO x which is not conducive to the progress of the formaldehyde catalytic reaction, while ammonium carbonate (NH₄)₂CO₃ is conducive to the formation of δ-MnO with a lamellar structure x ; At the same time, the concentration of reactants in the redox reaction is also an important factor. In this application, the formation of δ-MnO can be achieved by strictly controlling the concentration of potassium permanganate KMnO₄ solution and the concentration of ammonium carbonate (NH₄)₂CO₃ solution x , that is, the concentration of potassium permanganate KMnO₄ solution is 65.7 - 67.7 mg / mL, and the concentration of ammonium carbonate (NH₄)₂CO₃ solution is 20 - 30 mg / mL.

[0081] In addition, compared with the simultaneous loading of transition metals and noble metals, the platinum nanoparticles in this application are loaded on the surface of activated carbon in a more appropriate particle size range and more uniformly, ensuring the stability of the catalytic active center and the best utilization rate of platinum; Preferably, the particle size of the nanoparticles is 1 - 5 nm.

[0082] In the process of constructing a catalyst with uniformly dispersed noble metal active sites, an alkaline environment is often required to achieve the successful loading of noble metals. During the preparation of the catalyst using the impregnation method, after impregnating with a chloride salt or acid solution of the noble metal and then neutralizing with an alkali solution, it will be converted into a hydroxide precipitate on the pore surface of the support, which is conducive to the removal of chloride ions, thereby improving the activity of the catalyst. Therefore, an appropriate pH value is crucial for the preparation of the catalyst. In this application, sodium borohydride (NaBH4) and sodium hydroxide (NaOH) create a suitable alkaline environment to reduce hexachloroplatinic acid hexahydrate (H2PtCl6·6H2O) to elemental Pt. Due to the interaction between noble metal particles, the elemental Pt agglomerates and the particle size increases to form nanoparticles with a certain particle size. To ensure an appropriate particle size range and avoid a one-time accumulation exceeding the range value of 1 - 5 nm, which would cause a decrease in the utilization rate of noble metals, this application successfully prepared nanoparticles with a particle size range of 1 - 5 nm through two low-concentration loadings.

[0083] On the other hand, the present invention also provides a carbon-based catalyst, which is obtained by mixing activated carbon loaded with transition metal oxide and activated carbon loaded with noble metal to obtain the carbon-based catalyst;

[0084] Preferably, the transition metal oxide is manganese oxide; in the activated carbon loaded with the transition metal oxide: the content of Mn 2+ is 4.28% - 5.08%, the content of Mn 3+ is 51.8% - 54.8%, the content of Mn 4+ is 40.12% - 43.92%, and the ratio of Mn 3+ / Mn 4+ is 1.08 - 1.37; the crystal structure of the transition metal includes δ-MnO x , and the δ-MnO x exists uniformly on the surface of the activated carbon; further preferably, the content of Mn 2+ is 4.68%, the content of Mn 3+ is 53.8%, the content of Mn 4+ is 41.5%, and the ratio of Mn 3+ / Mn 4+ is 1.30;

[0085] Preferably, in the activated carbon loaded with the noble metal: the noble metal is loaded in the activated carbon in the form of nanoparticles; preferably, the particle size of the nanoparticles is 1 - 5 nm;

[0086] Preferably, the carbon-based catalyst is obtained by using the preparation method described in any one of the above.

[0087] On the other hand, the present invention provides an application of the above carbon-based catalyst, and the carbon-based catalyst is used for removing indoor formaldehyde at room temperature. The above carbon-based catalyst can also be used for removing other volatile organic pollutants (such as aromatic hydrocarbon pollutants) in the room except HCHO.

[0088] On the other hand, the present invention provides an application of the above carbon-based catalyst, and the carbon-based catalyst is used for removing indoor formaldehyde at room temperature.

[0089] The present invention will be further described below in conjunction with specific examples and comparative examples.

[0090] Example 1

[0091] This example provides a preparation method of a carbon-based catalyst, including the following steps:

[0092] Step 1) Purification step of activated carbon: Add 40 g of raw activated carbon into 400 mL of deionized water, soak for 5 min and then filter, and then place it in an oven at a constant temperature of 80 °C and dry for 24 h to obtain purified activated carbon AC;

[0093] Preparation step of activated carbon loaded with transition metal oxide: Rapidly inject 100 mL of ammonium carbonate (NH4)2CO3 solution (concentration 25 mg / mL) into 150 mL of potassium permanganate KMnO4 solution (concentration 66.7 mg / mL) (the weight ratio of KMnO4 in potassium permanganate KMnO4 solution to (NH4)2CO3 in ammonium carbonate (NH4)2CO3 solution is about 4:1), and stir for 5 min, then add 25 g of AC (the weight ratio of KMnO4 in potassium permanganate KMnO4 solution to activated carbon is 2.5:1), carry out a secondary stirring reaction at room temperature, and the time of secondary stirring is 60 min and then filter, and then place it in an oven at a constant temperature of 80 °C and dry for 24 h to obtain activated carbon loaded with manganese oxide (MnO x / AC);

[0094] Preparation step of activated carbon loaded with noble metal:

[0095] Step S1) After adding 15 g of AC into 75 mL of polydiallyldimethylpropylammonium chloride PDDA (polyelectrolyte) solution (concentration 2.1 mg / mL) (the weight ratio of activated carbon to polyelectrolyte in the polyelectrolyte solution is 95.5:1), continuously stir and react at room temperature for 60 min and then filter, and then place it in an oven at a constant temperature of 80 °C and dry for 24 h to obtain activated carbon loaded with PPDA (PDDA / AC);

[0096] Step S21) Mix 15 g of PDDA / AC with 16.65 mL of a solution of hexahydrate chloroplatinic acid H2PtCl6·6H2O (i.e., precious metal salt) (concentration: 0.96 mg / mL) to obtain a system to be reduced (suspension) (the mass ratio of the activated carbon loaded with polyelectrolyte to the precious metal salt in the precious metal salt solution is 937.5:1);

[0097] Step S22) Take 7.5 mL of sodium borohydride (NaBH4) solution (concentration: 3.0 mg / mL) and 7.5 mL of sodium hydroxide (NaOH) solution (concentration: 16 mg / mL) respectively (the weight ratio of NaOH in the sodium hydroxide NaOH solution to NaBH4 in the sodium borohydride NaBH4 solution is approximately 5.3:1), mix them evenly to obtain 15 mL of reducing solution; quickly inject this reducing solution into the system to be reduced, continuously stir and react for 30 min, then filter, and then place it in an oven at a constant temperature of 80 °C and dry for 24 h to obtain the once-loaded activated carbon;

[0098] Step S23) Take 7.5 mL of sodium borohydride (NaBH4) solution (concentration: 3.0 mg / mL) and 7.5 mL of sodium hydroxide (NaOH) solution (concentration: 16 mg / mL) respectively (the weight ratio of NaOH in the sodium hydroxide NaOH solution to NaBH4 in the sodium borohydride NaBH4 solution is approximately 5.3:1), mix them evenly to obtain 15 mL of reducing solution; mix 15 g of the once-loaded activated carbon and 16.65 mL of H2PtCl6·6H2O solution (concentration: 0.96 mg / mL) (the mass ratio of the once-loaded activated carbon to the precious metal salt in the precious metal salt solution is 937.5:1) to obtain a suspension; quickly inject this reducing solution into the above suspension, continuously stir and react for 30 min, then filter, and then place it in an oven at a constant temperature of 80 °C and dry for 24 h to obtain platinum-modified activated carbon (Pt / AC); the mass fraction of platinum in the Pt / AC obtained in this example is 0.08 wt% (denoted as 0.08 wt% Pt / AC);

[0099] Step 2) Take 21 g of the above-mentioned MnO x / AC and 9 g of the above-mentioned Pt / AC (i.e., the mass ratio of MnO x / AC to Pt / AC is 7:3), and stir evenly by physical rotation mixing to obtain a carbon-based catalyst.

[0100] In this example, in the activated carbon of manganese oxide (MnO x / AC): the content of Mn 2+ is 4.68%, the content of Mn 3+ is 53.8%, the content of Mn 4+ is 41.5%, and the ratio of Mn 3+ / Mn 4+The ratio is 1.30; the crystal structure of the transition metal includes δ-MnO x , δ-MnO x is uniformly present on the surface of the activated carbon;

[0101] In Pt / AC: platinum is loaded in the activated carbon in the form of nanoparticles; the particle size of the nanoparticles is 1 - 5 nm.

[0102] Example 2

[0103] This example provides a preparation method of a carbon-based catalyst, including the following steps:

[0104] Step 1) Purification step of activated carbon: Add 40 g of raw activated carbon to 400 mL of deionized water, soak for 5 min and then filter, and then place it in an oven at a constant temperature of 80 °C and dry for 24 h to obtain purified activated carbon AC;

[0105] Preparation step of activated carbon loaded with transition metal oxide: Rapidly inject 100 mL of ammonium carbonate (NH4)2CO3 solution (concentration 25 mg / mL) into 150 mL of potassium permanganate KMnO4 solution (concentration 66.7 mg / mL) (the weight ratio of KMnO4 in the potassium permanganate KMnO4 solution to (NH4)2CO3 in the ammonium carbonate (NH4)2CO3 solution is about 4:1), and stir for 5 min once, then add 25 g of AC, (the weight ratio of KMnO4 in the potassium permanganate KMnO4 solution to the activated carbon is 2.5:1), carry out a secondary stirring reaction at room temperature, the time of the secondary stirring is 60 min and then filter, and then place it in an oven at a constant temperature of 80 °C and dry for 24 h to obtain activated carbon loaded with manganese oxide (MnO x / AC);

[0106] Preparation step of activated carbon loaded with noble metal:

[0107] Step S1) After adding 15 g of AC to 75 mL of polydiallyldimethylpropylammonium chloride PDDA (polyelectrolyte) solution (concentration 3.15 mg / mL), (the weight ratio of the activated carbon to the polyelectrolyte in the polyelectrolyte solution is 63.5:1), continuously stir and react at room temperature for 60 min and then filter, and then place it in an oven at a constant temperature of 80 °C and dry for 24 h to obtain activated carbon loaded with PPDA (PDDA / AC);

[0108] Step S21) Mix 15 g of PDDA / AC with 16.65 mL of hexahydrate chloroplatinic acid H2PtCl6·6H2O (noble metal salt) solution (concentration 1.44 mg / mL) to obtain a system to be reduced (suspension) (the mass ratio of the activated carbon loaded with the polyelectrolyte to the noble metal salt in the noble metal salt solution is 625:1);

[0109] Step S22) Take 7.5 mL of sodium borohydride (NaBH4) solution (concentration: 4.6 mg / mL) and 7.5 mL of sodium hydroxide (NaOH) solution (concentration: 24 mg / mL) respectively (the weight ratio of NaOH in the sodium hydroxide (NaOH) solution to NaBH4 in the sodium borohydride (NaBH4) solution is about 5.2:1), mix them evenly to obtain 15 mL of reduction solution; quickly inject this reduction solution into the system to be reduced, continuously stir and react for 30 min, then filter, and then place it in an oven at a constant temperature of 80 °C to dry for 24 h to obtain the once-loaded activated carbon;

[0110] Step S23) Take 7.5 mL of sodium borohydride (NaBH4) solution (concentration: 4.6 mg / mL) and 7.5 mL of sodium hydroxide (NaOH) solution (concentration: 24 mg / mL) respectively (the weight ratio of NaOH in the sodium hydroxide (NaOH) solution to NaBH4 in the sodium borohydride (NaBH4) solution is about 5.2:1), mix them evenly to obtain 15 mL of reduction solution; mix 15 g of the once-loaded activated carbon and 16.65 mL of H2PtCl6·6H2O solution (concentration: 1.44 mg / mL) (the mass ratio of the once-loaded activated carbon to the precious metal salt in the precious metal salt solution is 625:1) to obtain a suspension; quickly inject this reduction solution into the above suspension, continuously stir and react for 30 min, then filter, and then place it in an oven at a constant temperature of 80 °C to dry for 24 h to obtain platinum-modified activated carbon (Pt / AC); the mass fraction of platinum in the Pt / AC obtained in this example is 0.12 wt% (denoted as 0.12 wt% Pt / AC);

[0111] Step 2) Take 21 g of the above-mentioned MnO x / AC and 9 g of the above-mentioned Pt / AC (i.e., the mass ratio of MnO x / AC to Pt / AC is 7:3), and stir evenly by physical rotation mixing to obtain a carbon-based catalyst.

[0112] In this example, in the activated carbon of manganese oxide (MnO x / AC): the content of Mn 2+ is 4.68%, the content of Mn 3+ is 53.8%, the content of Mn 4+ is 41.5%, and the ratio of Mn 3+ / Mn 4+ is 1.30; the crystal structure of the transition metal includes δ-MnO x , and δ-MnO x uniformly exists on the surface of the activated carbon;

[0113] In Pt / AC: platinum is loaded in the activated carbon in the form of nanoparticles; the particle size of the nanoparticles is 1 - 5 nm.

[0114] Example 3

[0115] This example provides a preparation method of a carbon-based catalyst, which includes the following steps:

[0116] Step 1) Purification step of activated carbon: Add 40 g of raw activated carbon into 400 mL of deionized water, soak for 5 min and then filter, and then place it in an oven at a constant temperature of 80 °C for drying for 24 h to obtain purified activated carbon AC;

[0117] Preparation step of activated carbon loaded with transition metal oxide: Rapidly inject 100 mL of ammonium carbonate (NH4)2CO3 solution (concentration: 25 mg / mL) into 150 mL of potassium permanganate KMnO4 solution (concentration: 66.7 mg / mL) (the weight ratio of KMnO4 in the potassium permanganate KMnO4 solution to (NH4)2CO3 in the ammonium carbonate (NH4)2CO3 solution is about 4:1), stir for 5 min once, then add 25 g of AC, (the weight ratio of KMnO4 in the potassium permanganate KMnO4 solution to the activated carbon is 2.5:1), carry out a secondary stirring reaction at room temperature, the time of the secondary stirring is 60 min and then filter, and then place it in an oven at a constant temperature of 80 °C for drying for 24 h to obtain activated carbon loaded with manganese oxide (MnO x / AC);

[0118] Preparation step of activated carbon loaded with noble metal:

[0119] Step S1) After adding 15 g of AC into 75 mL of polydiallyldimethylammonium chloride PDDA (polyelectrolyte) solution (concentration: 4.2 mg / mL), (the weight ratio of the activated carbon to the polyelectrolyte in the polyelectrolyte solution is 47.6:1), continuously stir and react at room temperature for 60 min and then filter, and then place it in an oven at a constant temperature of 80 °C for drying for 24 h to obtain activated carbon loaded with PPDA (PDDA / AC);

[0120] Step S21) Mix 15 g of PDDA / AC with 16.65 mL of hexahydrate chloroplatinic acid H2PtCl6·6H2O (noble metal salt) solution (concentration: 1.92 mg / mL) to obtain a system to be reduced (suspension) (the mass ratio of the activated carbon loaded with polyelectrolyte to the noble metal salt in the noble metal salt solution is 468.6:1);

[0121] Step S22) Take 7.5 mL of sodium borohydride (NaBH4) solution (concentration: 6.1 mg / mL) and 7.5 mL of sodium hydroxide (NaOH) solution (concentration: 32 mg / mL) respectively (the weight ratio of NaOH in the sodium hydroxide (NaOH) solution to NaBH4 in the sodium borohydride (NaBH4) solution is about 5.2:1), mix them evenly to obtain 15 mL of reducing solution; quickly inject this reducing solution into the system to be reduced, continuously stir and react for 30 min, then filter, and then place it in an oven at a constant temperature of 80 °C to dry for 24 h to obtain the once-loaded activated carbon;

[0122] Step S23) Take 7.5 mL of sodium borohydride (NaBH4) solution (concentration: 6.1 mg / mL) and 7.5 mL of sodium hydroxide (NaOH) solution (concentration: 32 mg / mL) respectively (the weight ratio of NaOH in the sodium hydroxide (NaOH) solution to NaBH4 in the sodium borohydride (NaBH4) solution is about 5.2:1), mix them evenly to obtain 15 mL of reducing solution; mix 15 g of the once-loaded activated carbon and 16.65 mL of H2PtCl6·6H2O solution (concentration: 1.92 mg / mL) (the mass ratio of the once-loaded activated carbon to the precious metal salt in the precious metal salt solution is 468.6:1) to obtain a suspension; quickly inject this reducing solution into the above suspension, continuously stir and react for 30 min, then filter, and then place it in an oven at a constant temperature of 80 °C to dry for 24 h to obtain platinum-modified activated carbon (Pt / AC); the mass fraction of platinum in the Pt / AC obtained in this example is 0.16 wt% (denoted as 0.16 wt% Pt / AC);

[0123] Step 2) Take 21 g of the above-mentioned MnO x / AC and 9 g of the above-mentioned Pt / AC (i.e., the mass ratio of MnO x / AC to Pt / AC is 7:3), and stir evenly by physical rotation mixing to obtain a carbon-based catalyst.

[0124] In this example, in the activated carbon of manganese oxide (MnO x / AC): the content of Mn 2+ is 4.68%, the content of Mn 3+ is 53.8%, the content of Mn 4+ is 41.5%, and the ratio of Mn 3+ / Mn 4+ is 1.30; the crystal structure of the transition metal includes δ-MnO x , and δ-MnO x exists uniformly on the surface of the activated carbon;

[0125] In Pt / AC: platinum is loaded in the activated carbon in the form of nanoparticles; the particle size of the nanoparticles is 1 - 5 nm.

[0126] Example 4

[0127] This example provides a method for preparing a carbon-based catalyst, which includes the following steps:

[0128] Step 1) Purification step of activated carbon: Add 40 g of raw activated carbon into 400 mL of deionized water, soak for 5 min and then filter, and then place it in an oven at a constant temperature of 80 °C for drying for 24 h to obtain purified activated carbon AC;

[0129] Preparation step of activated carbon loaded with transition metal oxide: Rapidly inject 100 mL of ammonium carbonate (NH4)2CO3 solution (concentration: 25 mg / mL) into 150 mL of potassium permanganate KMnO4 solution (concentration: 66.7 mg / mL) (the weight ratio of KMnO4 in the potassium permanganate KMnO4 solution to (NH4)2CO3 in the ammonium carbonate (NH4)2CO3 solution is about 4:1), and perform a first stirring for 5 min, then add 25 g of AC, (the weight ratio of KMnO4 in the potassium permanganate KMnO4 solution to the activated carbon is 2.5:1), perform a second stirring reaction at room temperature, filter after the second stirring for 60 min, and then place it in an oven at a constant temperature of 80 °C for drying for 24 h to obtain activated carbon loaded with manganese oxide (MnO x / AC);

[0130] Preparation step of activated carbon loaded with noble metal:

[0131] Step S1) Add 15 g of AC into 75 mL of polydiallyldimethylammonium chloride PDDA (polyelectrolyte) solution (concentration: 5.25 mg / mL) (the weight ratio of the activated carbon to the polyelectrolyte in the polyelectrolyte solution is 38.1:1), continuously stir and react at room temperature for 60 min and then filter, and then place it in an oven at a constant temperature of 80 °C for drying for 24 h to obtain activated carbon loaded with PPDA (PDDA / AC);

[0132] Step S21) Mix 15 g of PDDA / AC with 16.65 mL of hexahydrate chloroplatinic acid H2PtCl6·6H2O (noble metal salt) solution (concentration: 2.4 mg / mL) to obtain a system to be reduced (suspension) (the mass ratio of the activated carbon loaded with polyelectrolyte to the noble metal salt in the noble metal salt solution is 375:1);

[0133] Step S22) Take 7.5 mL of sodium borohydride (NaBH4) solution (concentration: 7.6 mg / mL) and 7.5 mL of sodium hydroxide (NaOH) solution (concentration: 40 mg / mL) respectively (the weight ratio of NaOH in the sodium hydroxide (NaOH) solution to NaBH4 in the sodium borohydride (NaBH4) solution is about 5.3:1), mix them evenly to obtain 15 mL of reducing solution; quickly inject this reducing solution into the system to be reduced, continuously stir and react for 30 min, then filter, and then place it in an oven at a constant temperature of 80 °C to dry for 24 h to obtain the once-loaded activated carbon;

[0134] Step S23) Take 7.5 mL of sodium borohydride (NaBH4) solution (concentration: 7.6 mg / mL) and 7.5 mL of sodium hydroxide (NaOH) solution (concentration: 40 mg / mL) respectively (the weight ratio of NaOH in the sodium hydroxide (NaOH) solution to NaBH4 in the sodium borohydride (NaBH4) solution is about 5.3:1), mix them evenly to obtain 15 mL of reducing solution; mix 15 g of the once-loaded activated carbon and 16.65 mL of H2PtCl6·6H2O solution (concentration: 2.4 mg / mL) (the mass ratio of the once-loaded activated carbon to the precious metal salt in the precious metal salt solution is 375:1) to obtain a suspension; quickly inject this reducing solution into the above suspension, continuously stir and react for 30 min, then filter, and then place it in an oven at a constant temperature of 80 °C to dry for 24 h to obtain platinum-modified activated carbon (Pt / AC); the mass fraction of platinum in the Pt / AC obtained in this example is 0.2 wt% (denoted as 0.2 wt% Pt / AC);

[0135] Step 2) Take 21 g of the above-mentioned MnO x / AC and 9 g of the above-mentioned Pt / AC (i.e., the mass ratio of MnO x / AC to Pt / AC is 7:3), stir evenly by physical rotation mixing to obtain a carbon-based catalyst.

[0136] In this example, in the activated carbon of manganese oxide (MnO x / AC): the content of Mn 2+ is 4.68%, the content of Mn 3+ is 53.8%, the content of Mn 4+ is 41.5%, and the ratio of Mn 3+ / Mn 4+ is 1.30; the crystal structure of the transition metal includes δ-MnO x , and δ-MnO x exists uniformly on the surface of the activated carbon;

[0137] In Pt / AC: platinum is loaded in the activated carbon in the form of nanoparticles; the particle size of the nanoparticles is 1 - 5 nm.

[0138] Example 5

[0139] This example provides a method for preparing a carbon-based catalyst, which includes the following steps:

[0140] Step 1) Purification step of activated carbon: Add 40 g of raw activated carbon to 400 mL of deionized water, soak for 5 min and then filter, and then place it in an oven at a constant temperature of 80 °C and dry for 24 h to obtain purified activated carbon AC;

[0141] Preparation step of activated carbon loaded with transition metal oxide: Rapidly inject 100 mL of ammonium carbonate (NH4)2CO3 solution (concentration 25 mg / mL) into 150 mL of potassium permanganate KMnO4 solution (concentration 66.7 mg / mL) (the weight ratio of KMnO4 in the potassium permanganate KMnO4 solution to (NH4)2CO3 in the ammonium carbonate (NH4)2CO3 solution is about 4:1), and stir for 5 min once, then add 25 g of AC, (the weight ratio of KMnO4 in the potassium permanganate KMnO4 solution to the activated carbon is 2.5:1), carry out a secondary stirring reaction at room temperature, and after the secondary stirring time of 60 min, filter, and then place it in an oven at a constant temperature of 80 °C and dry for 24 h to obtain activated carbon loaded with manganese oxide (MnO x / AC);

[0142] Preparation step of activated carbon loaded with noble metal:

[0143] Step S1) After adding 15 g of AC to 75 mL of polydiallyldimethylammonium chloride PDDA (polyelectrolyte) solution (concentration 6.3 mg / mL), (the weight ratio of the activated carbon to the polyelectrolyte in the polyelectrolyte solution is 31.7.1:1), continuously stir and react at room temperature for 60 min, then filter, and then place it in an oven at a constant temperature of 80 °C and dry for 24 h to obtain activated carbon loaded with PPDA (PDDA / AC);

[0144] Step S21) Mix 15 g of PDDA / AC with 16.65 mL of hexahydrate chloroplatinic acid H2PtCl6·6H2O (noble metal salt) solution (concentration 2.88 mg / mL) to obtain a system to be reduced (suspension) (the mass ratio of the activated carbon loaded with polyelectrolyte to the noble metal salt in the noble metal salt solution is 312.5:1);

[0145] Step S22) Take 7.5 mL of sodium borohydride (NaBH4) solution (concentration: 9.1 mg / mL) and 7.5 mL of sodium hydroxide (NaOH) solution (concentration: 48 mg / mL) respectively (the weight ratio of NaOH in the sodium hydroxide (NaOH) solution to NaBH4 in the sodium borohydride (NaBH4) solution is about 5.3:1), mix them evenly to obtain 15 mL of reducing solution; quickly inject this reducing solution into the system to be reduced, continuously stir and react for 30 min, then filter, and then place it in an oven at a constant temperature of 80 °C to dry for 24 h to obtain the once-loaded activated carbon;

[0146] Step S23) Take 7.5 mL of sodium borohydride (NaBH4) solution (concentration: 9.1 mg / mL) and 7.5 mL of sodium hydroxide (NaOH) solution (concentration: 48 mg / mL) respectively (the weight ratio of NaOH in the sodium hydroxide (NaOH) solution to NaBH4 in the sodium borohydride (NaBH4) solution is about 5.3:1), mix them evenly to obtain 15 mL of reducing solution; mix 15 g of the once-loaded activated carbon and 16.65 mL of H2PtCl6·6H2O solution (concentration: 2.88 mg / mL) (the mass ratio of the once-loaded activated carbon to the precious metal salt in the precious metal salt solution is 312.5:1) to obtain a suspension; quickly inject this reducing solution into the above suspension, continuously stir and react for 30 min, then filter, and then place it in an oven at a constant temperature of 80 °C to dry for 24 h to obtain platinum-modified activated carbon (Pt / AC); the mass fraction of platinum in the Pt / AC obtained in this example is 0.24 wt% (denoted as 0.24 wt% Pt / AC);

[0147] Step 2) Take 21 g of the above-mentioned MnO x / AC and 9 g of the above-mentioned Pt / AC (i.e., the mass ratio of MnO x / AC to Pt / AC is 7:3), and stir evenly by physical rotation mixing to obtain a carbon-based catalyst.

[0148] In this example, in the activated carbon of manganese oxide (MnO x / AC): the content of Mn 2+ is 4.68%, the content of Mn 3+ is 53.8%, the content of Mn 4+ is 41.5%, and the ratio of Mn 3+ / Mn 4+ is 1.30; the crystal structure of the transition metal includes δ-MnO x , and δ-MnO x exists uniformly on the surface of the activated carbon;

[0149] In Pt / AC: platinum is loaded in the activated carbon in the form of nanoparticles; the particle size of the nanoparticles is 1 - 5 nm.

[0150] For the carbon-based catalysts with different Pt loadings prepared in Examples 1 to 5 of the present invention, the following experiments were carried out to obtain the influence of different Pt loadings on the HCHO removal efficiency.

[0151] The experimental conditions were as follows: 0.3 g of the carbon-based catalyst in the example was placed in the middle of quartz wool in a stainless-steel thermocouple tube with a diameter of 5 mm; a stable HCHO gas stream with a concentration of 100 ppm was generated from a formalin solution (37 vol% HCHO) and a carrier gas (balanced with 21 vol% O2 and 79 vol% N2, relative humidity (RH) of 25%); the total flow rate was 100 mL / min, the corresponding weight hourly space velocity (WHSV) was 60 L / (gcath), and the reaction time was 12 h. The initial concentration and outlet concentration of HCHO and CO2 at the outlet were measured by a real-time photoacoustic infrared multi-gas detector (LumaSense INNOVA, model 1512, with detection limits of 0.02 and 5.1 ppm for HCHO and CO2, respectively), and the degradation efficiency was calculated.

[0152] The test results are as Figure 1 shown. It can be seen that as the Pt loading in the platinum-modified activated carbon increases, the catalytic effect gradually improves. However, when a certain ratio is reached, the Pt nanoparticles begin to agglomerate and the exposed surface area becomes smaller, so the catalytic efficiency will also decrease. Therefore, the preferred Pt loading in the carbon-based catalyst of the present invention is 0.18 - 0.22 wt% (i.e., the mass fraction of platinum in Pt / AC is preferably 0.18 - 0.22 wt%).

[0153] Comparative Example 1

[0154] This comparative example provides a preparation method of a carbon-based catalyst, including the following steps:

[0155] Step 1) Purification step of activated carbon: 40 g of raw activated carbon was added to 400 mL of deionized water, soaked for 5 min and then filtered, and then dried in an oven at a constant temperature of 80 °C for 24 h to obtain purified activated carbon AC;

[0156] Preparation steps of activated carbon loaded with transition metal oxide: Rapidly inject 100 mL of ammonium carbonate (NH4)2CO3 solution (concentration: 25 mg / mL) into 150 mL of potassium permanganate KMnO4 solution (concentration: 66.7 mg / mL) (the weight ratio of KMnO4 in the potassium permanganate KMnO4 solution to (NH4)2CO3 in the ammonium carbonate (NH4)2CO3 solution is about 4:1), and perform stirring for 5 min. Then add 25 g of AC (the weight ratio of KMnO4 in the potassium permanganate KMnO4 solution to the activated carbon is 2.5:1), and carry out secondary stirring reaction at room temperature for 60 min, then filter, and then place it in an oven at a constant temperature of 80 °C and dry for 24 h to obtain activated carbon loaded with manganese oxide (MnO x / AC);

[0157] Preparation steps of activated carbon loaded with noble metal:

[0158] Step S1) Add 15 g of AC to 75 mL of polydiallyldimethylammonium chloride PDDA (polyelectrolyte) solution (concentration: 5.25 mg / mL) (the weight ratio of the activated carbon to the polyelectrolyte in the polyelectrolyte solution is 38.1:1), and then continuously stir and react at room temperature for 60 min, then filter, and then place it in an oven at a constant temperature of 80 °C and dry for 24 h to obtain activated carbon loaded with PPDA (PDDA / AC);

[0159] Step S21) Mix 15 g of PDDA / AC with 16.65 mL of hexahydrate chloroplatinic acid H2PtCl6·6H2O (noble metal salt) solution (concentration: 2.4 mg / mL) to obtain a system to be reduced (suspension) (the mass ratio of the activated carbon loaded with the polyelectrolyte to the noble metal salt in the noble metal salt solution is 375:1);

[0160] Step S22) Respectively take 7.5 mL of sodium borohydride (NaBH4) solution (concentration: 7.6 mg / mL) and 7.5 mL of sodium hydroxide (NaOH) solution (concentration: 40 mg / mL) (the weight ratio of NaOH in the sodium hydroxide NaOH solution to NaBH4 in the sodium borohydride NaBH4 solution is about 5.3:1), mix them evenly to obtain 15 mL of reducing solution; rapidly inject the reducing solution into the system to be reduced, continuously stir and react for 30 min, then filter, and then place it in an oven at a constant temperature of 80 °C and dry for 24 h to obtain the once-loaded activated carbon;

[0161] Step S23) Take 7.5 mL of sodium borohydride (NaBH4) solution (concentration: 7.6 mg / mL) and 7.5 mL of sodium hydroxide (NaOH) solution (concentration: 40 mg / mL) respectively (the weight ratio of NaOH in the sodium hydroxide (NaOH) solution to NaBH4 in the sodium borohydride (NaBH4) solution is about 5.3:1), mix them evenly to obtain 15 mL of reduction solution; mix 15 g of once-loaded activated carbon and 16.65 mL of H2PtCl6·6H2O solution (concentration: 2.4 mg / mL) (the mass ratio of once-loaded activated carbon to the precious metal salt in the precious metal salt solution is 375:1) to obtain a suspension; quickly inject the reduction solution into the above suspension, continuously stir and react for 30 min, then filter, and then place it in an oven at a constant temperature of 80 °C to dry for 24 h to obtain platinum-modified activated carbon (Pt / AC); the mass fraction of platinum in the Pt / AC obtained in this example is 0.2 wt% (denoted as 0.2 wt% Pt / AC);

[0162] Step 2) Take 15 g of the above MnO x / AC and 15 g of the above Pt / AC (i.e., the mass ratio of MnO x / AC to Pt / AC is 1:1), and stir evenly by physical rotation mixing to obtain a carbon-based catalyst.

[0163] In this comparative example, in the activated carbon of manganese oxide (MnO x / AC): the content of Mn 2+ is 4.68%, the content of Mn 3+ is 53.8%, the content of Mn 4+ is 41.5%, and the ratio of Mn 3+ / Mn 4+ is 1.30; the crystal structure of the transition metal includes δ-MnO x and δ-MnO x exists uniformly on the surface of the activated carbon;

[0164] In Pt / AC: platinum is loaded in the activated carbon in the form of nanoparticles; the particle size of the nanoparticles is 1 - 5 nm.

[0165] Under the above experimental conditions, the formaldehyde removal rate of the carbon-based catalyst in this comparative example is calculated to be 63.4%. Compared with the formaldehyde removal rate of 87.6% of the carbon-based catalyst in Example 4, it decreases significantly. This is because the content of MnO x / AC in the carbon-based catalyst of this comparative example is relatively high, and the stable formaldehyde removal ability of MnO x / AC can only be maintained for 24 h, so the formaldehyde removal rate is relatively low.

[0166] Comparative Example 2

[0167] This comparative example provides a method for preparing a carbon-based catalyst, comprising the following steps:

[0168] Step 1) 40 g of the original activated carbon was added to 400 mL of deionized water, soaked for 5 min, filtered, and then placed in an oven at a constant temperature of 80° C. for 24 h to obtain purified activated carbon AC;

[0169] Step S1) adding 15 g AC to 75 mL polydiallyl dimethylpropyl ammonium chloride PDDA (polyelectrolyte) solution (concentration of 5.25 mg / mL) (the weight ratio of activated carbon to polyelectrolyte in the polyelectrolyte solution is 38.1:1), stirring and reacting at room temperature for 60 min, filtering, and then drying in an oven at a constant temperature of 80° C. for 24 h to obtain activated carbon loaded with PPDA (PDDA / AC);

[0170] Step S21) 15 g of PDDA / AC was mixed with 33.3 mL of chloroplatinic acid hexahydrate (H2PtCl6·6H2O) solution (concentration of 2.4 mg / mL) to obtain a system (suspension) to be reduced (the mass ratio of the activated carbon loaded with polyelectrolyte to the noble metal salt in the noble metal salt solution was 187.7:1);

[0171] Step S22) Take 15 mL of sodium borohydride (NaBH4) solution (concentration of 7.6 mg / mL) and 15 mL of sodium hydroxide (NaOH) solution (concentration of 40 mg / mL) (the weight ratio of NaOH in the sodium hydroxide NaOH solution to NaBH4 in the sodium borohydride NaBH4 solution is about 5.3:1), mix them evenly to obtain 15 mL of reducing solution; quickly inject the reducing solution into the system to be reduced, continue stirring to react for 30 minutes, then filter, and then place it in a constant temperature oven at 80°C for 24 hours to obtain platinum-modified activated carbon (Pt / AC), that is, the carbon-based catalyst of this comparative example.

[0172] In the Pt / AC of this comparative example: platinum is loaded in the activated carbon in the form of nanoparticles; the particle size of the nanoparticles is 4 to 17 nm.

[0173] The one-time loading of precious metals leads to more serious agglomeration of precious metal nanoparticles on the catalyst surface. The larger particle size of the nanoparticles reduces the relative area of ​​precious metal exposure, reduces atomic utilization, and reduces the contact area with formaldehyde molecules, which is not conducive to catalysis.

[0174] Using the above experimental conditions, the formaldehyde removal rate of the carbon-based catalyst in this comparative example was calculated to be 85.3%, which is a significant decrease compared to the 99.8% formaldehyde removal rate of Pt / AC obtained by double loading. At the same time, since only platinum-loaded activated carbon is used, the preparation cost is relatively high.

[0175] Comparative Example 3

[0176] This comparative example provides a method for preparing a carbon-based catalyst, including the following steps:

[0177] Add 40 g of raw activated carbon to 400 mL of deionized water, soak for 5 min, filter, and then place in an oven at a constant temperature of 80 °C for 24 h to obtain purified activated carbon AC;

[0178] Mix 150 mL of potassium permanganate KMnO4 solution (concentration 66.7 mg / mL) and 33.3 mL of chloroplatinic acid hexahydrate H2PtCl6·6H2O solution (concentration 2.4 mg / mL) evenly (the weight ratio of KMnO4 in the potassium permanganate KMnO4 solution to the solute in the chloroplatinic acid hexahydrate H2PtCl6·6H2O solution is about 125.2:1) to obtain a mixed solution; then quickly inject 100 mL of ammonium oxalate (NH4)2C2O4 solution (concentration 25 mg / mL, as a reducing agent) into the above mixed solution (the weight ratio of KMnO4 in the potassium permanganate KMnO4 solution to (NH4)2C2O4 in the ammonium oxalate (NH4)2C2O4 solution is about 4:1) and continuously stir for 5 - 10 min, then add 25 g of AC and continuously stir and react at room temperature for 60 - 120 min, filter, and then place in an oven at a constant temperature of 60 - 80 °C for 24 - 48 h to obtain modified activated carbon, which is the carbon-based catalyst of this comparative example.

[0179] In this comparative example, in the activated carbon with manganese oxide (MnO x / AC): the content of Mn 2+ is 40.26%, the content of Mn 3+ is 20.7%, the content of Mn 4+ is 39.04%, and the ratio of Mn 3+ / Mn 4+ is 0.53; in Pt / AC: platinum is loaded on the activated carbon in the form of nanoparticles; the particle size of the nanoparticles is 2 - 7 nm.

[0180] Mn 3+ and Mn 4+ can promote the chemisorption, activation, and dissociation of O2 on the catalyst surface, thereby generating more active free radical oxygen vacancies OVs that enter the lattice of the oxide, and further mineralizing formaldehyde molecules into non-toxic H2O and CO2. However, in this method, the proportion of Mn 2+ is the largest, and the ratio of Mn 3+ / Mn 4+ is relatively small;

[0181] The formaldehyde purification performance of the modified activated carbon (carbon-based catalyst) obtained in this comparative example was evaluated under the following test conditions: 0.3 g of the obtained carbon-based catalyst was placed in the middle of quartz wool in a stainless-steel thermocouple tube with a diameter of 5 mm. A stable HCHO gas stream with a concentration of 100 ppm was generated from a formalin solution (37 vol% HCHO) and a carrier gas (balanced with 21 vol% O2 and 79 vol% N2, relative humidity (RH) of 25%). The total flow rate was 100 mL / min, and the corresponding weight hourly space velocity (WHSV) was 60 L / (g cat h). The reaction time was 12 h.

[0182] The formaldehyde removal rate of the modified activated carbon in this comparative example was 80.4%. Compared with the 87.6% formaldehyde removal rate of the carbon-based catalyst in Example 4, it decreased significantly. In order to simultaneously reduce the noble metal salt and permanganate under safe conditions to avoid explosion, ammonium oxalate with weak reducing property and certain weak acidity was selected as the reducing agent in this comparative example. However, due to the different chemical properties of the noble metal salt and permanganate, weak acidic reducing agents such as ammonium oxalate are only more suitable for reducing permanganate. In the process of constructing a catalyst with uniformly dispersed noble metal active sites, an alkaline environment is often required to achieve the successful loading of noble metals. During the preparation of the catalyst, different pH values provide different environments, which have certain effects on the protonation, crystal structure, and electron distribution of some catalysts. As shown in formula (1), during the preparation of the catalyst using the impregnation method, after impregnating the chloride salt or acid solution of the noble metal and then neutralizing with an alkali solution, it will be converted into hydroxide precipitation on the pore surface of the carrier, which is beneficial to the removal of chloride ions, thereby improving the activity of the catalyst. Therefore, an appropriate pH value is crucial for the preparation of the catalyst.

[0183] (1)

[0184] Therefore, ammonium oxalate with weak acidity was used as the reducing agent in this comparative example, and the formaldehyde removal rate of the obtained modified activated carbon was relatively low. In addition, during the preparation process, transition metal manganese and noble metal platinum coexisted in the raw and auxiliary materials. The presence of metal manganese occupied the noble metal active center to a certain extent, causing the temporary inactivation of the noble metal that plays a major catalytic role, thereby affecting the catalytic performance of the catalyst.

[0185] The applicant also studied the effect of different addition amounts of the carbon-based catalyst on the HCHO degradation efficiency. The carbon-based catalyst used was the MnO x carbon-based catalyst co-loaded with platinum.

[0186] Specifically, 0.05 g, 0.1 g, 0.2 g, 0.25 g, and 0.3 g of the co-loaded carbon-based catalyst were respectively placed in the quartz wool in a stainless-steel thermocouple tube with a diameter of 5 mm. The effect of different addition amounts of the catalyst on the HCHO removal efficiency was studied. Other experimental conditions: A stable HCHO gas stream with a concentration of 100 ppm was generated from a formalin solution (37 vol% HCHO) and a carrier gas (balanced with 21 vol% O2 and 79 vol% N2, relative humidity (RH) of 25%). The total flow rate was 100 mL / min, and the corresponding weight hourly space velocity (WHSV) was 60 L / (gcath). The reaction time was 12 h.

[0187] The test results are as Figure 2 shown. It can be seen that as the addition amount of the carbon-based catalyst increases, the catalytic effect gradually improves. On the premise of keeping other experimental conditions consistent, when the addition amount of the catalyst is 0.25 g and the reaction time is 12 h, the HCHO removal efficiency can reach 87.6% at room temperature. Further increasing the addition amount does not result in a significant improvement in the catalytic effect. Therefore, the addition amount of the carbon-based catalyst prepared in this application is preferably 0.25 - 0.30 g.

[0188] The applicant selected the carbon-based catalyst co-loaded with MnO x prepared in Example 4 and platinum to conduct the following experiments to study the effect of different reaction times on the removal efficiency of formaldehyde (HCHO). Experimental conditions: 0.3 g of the carbon-based catalyst was placed in the quartz wool in a stainless-steel thermocouple tube with a diameter of 5 mm. A stable HCHO gas stream with a concentration of 100 ppm was generated from a formalin solution (37 vol% HCHO) and a carrier gas (21 vol% O2 and 79 vol% N2 balanced, relative humidity (RH) of 25%). The total flow rate was 100 mL / min, and the corresponding weight hourly space velocity (WHSV) was 60 L / (gcath). The reaction times were respectively controlled at 3 h, 6 h, 12 h, 18 h, and 24 h.

[0189] For the carbon-based catalyst obtained in Example 4, the HCHO removal efficiency can reach over 98% within the shortest 1 min, and the current long-term test lasts for 21 days, with the HCHO removal efficiency stably remaining > 80% for a long time. Therefore, compared with the prior art, the catalyst in this application allows for a longer reaction time.

[0190] In addition, the carbon-based catalyst of the present invention can also be used to remove other volatile organic pollutants (such as aromatic hydrocarbon pollutants) in the room besides HCHO.

[0191] The applicant selected the MnO xThe carbon-based catalyst co-loaded with platinum was studied for its removal effect on other volatile organic pollutants in the air (except HCHO). Specifically, taking the aromatic hydrocarbon pollutant toluene (C6H5CH3) as an example. 0.3 g of the carbon-based catalyst was placed in the middle of the quartz wool in a self-made English tube (high-temperature resistant) reactor with a diameter of 5 mm. A stable C7H8 gas stream with a concentration of 1000 mg / m3 was generated from an analytical pure C7H8 solution and a carrier gas (balanced with 21 vol% O2 and 79 vol% N2, relative humidity (RH) of 50%). The total flow rate was 120 mL / min. The reaction time was 12 h. The initial concentration and outlet concentration of C6H5CH3 and CO2 at the outlet were measured by a real-time photoacoustic infrared multi-gas detector (LumaSense INNOVA, model 1512, with detection limits of 0.02 and 5.1 ppm for C6H5CH3 and CO2 respectively), and the degradation efficiency was calculated accordingly.

[0192] Compared with the unmodified purification activated carbon (AC), the catalytic reaction activity of the carbon-based catalyst in Example 4 of the present invention for C6H5CH3 was significantly improved. At 152 °C and 172 °C, the removal rates of C6H5CH3 increased from 45% and 79% to 50% and 92% respectively.

[0193] The applicant also tested the stability of the carbon-based catalyst of the present invention. It selected the MnO prepared in Example 4 x For the carbon-based catalyst co-loaded with platinum, after each reaction (i.e., after the catalytic reaction), the carbon-based catalyst was washed with pure water and ethanol respectively, dried and then used again as a room-temperature catalyst for the degradation of HCHO for reaction. The above process was regarded as a cycle, and the previous reaction cycle was repeated multiple times. After each reaction, the degradation efficiency was calculated, and the relative change amount of the HCHO removal efficiency in each reaction cycle was used as the evaluation standard for evaluating the stability of the co-loaded carbon-based catalyst of the present invention.

[0194] After repeating the above reaction cycle 5 times, with a catalyst addition amount of 0.30 g and a reaction time of 12 h, the HCHO removal efficiency could still reach 75% at room temperature. It was proved that the carbon-based catalyst of the present invention had good practical application stability and reliability.

[0195] It is easy for those skilled in the art to understand that, on the premise of no conflict, the advantageous technical features of the above various methods can be freely combined and superimposed.

[0196] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention. The above is only the preferred implementation manner of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and variations can still be made, and these improvements and variations should also be regarded as within the protection scope of the present invention.

Claims

1. A method for preparing a carbon-based catalyst, characterized in that: The following steps are involved: Step 1) preparing activated carbon loaded with transition metal oxides; preparing activated carbon loaded with noble metals; Step 2) mixing the activated carbon loaded with transition metal oxides with the activated carbon loaded with noble metals to obtain a carbon-based catalyst; Wherein, the mass ratio of the activated carbon loaded with transition metal oxide and the activated carbon loaded with precious metal is (6.5-7.5): (2.5-3.5); In the activated carbon loaded with transition metal oxides: Mn 2+ The content is 4.28%~5.08%, Mn 3+ The content is 51.8%~54.8%, Mn 4+ The content is 40.12%~43.92%, wherein the Mn 2+ , Mn 3+ , Mn 4+ The sum of the contents of Mn is 100%; 3+ / Mn 4+ The ratio is 1.08~1.37; the crystal structure of manganese includes δ-MnO x , the δ-MnO x Uniformly present on the surface of activated carbon; The step of preparing activated carbon loaded with transition metal oxides comprises: mixing a transition metal salt solution with a buffer solution to obtain a mixed solution; then using the mixed solution to impregnate the activated carbon, then filtering and drying to obtain the activated carbon loaded with transition metal oxides; wherein the transition metal oxide is manganese oxide; when the transition metal salt solution and the buffer solution are mixed, the weight ratio of the transition metal salt in the transition metal salt solution to the buffer in the buffer solution is 3.5:1 to 4.5:1; when the mixed solution is used to impregnate the activated carbon, the weight ratio of the transition metal salt in the transition metal salt solution to the activated carbon is 2:1 to 3:1; The steps of preparing the activated carbon loaded with precious metals include: step S1) impregnating the activated carbon with a polyelectrolyte solution, filtering, and drying to obtain the activated carbon loaded with the polyelectrolyte; step S2) mixing the activated carbon loaded with the polyelectrolyte with a precious metal salt solution and a reducing agent solution to obtain the activated carbon loaded with precious metals; Wherein, the step S2) comprises: step S21) mixing the activated carbon loaded with polyelectrolyte with a noble metal salt solution to form a system to be reduced; step S22) mixing the system to be reduced with the reducing agent solution to perform a reduction reaction; after the reduction reaction is completed, filtering and drying are performed to obtain a primary loaded activated carbon; step S23) mixing the primary loaded activated carbon with a noble metal salt solution and the reducing agent solution, and then filtering and drying are performed to obtain activated carbon loaded with noble metals; The reducing agent solution is obtained by mixing a sodium borohydride NaBH4 solution with a sodium hydroxide NaOH solution; the mass fraction of the noble metal in the noble metal-loaded activated carbon is 0.18-0.22 wt%.

2. The method for preparing a carbon-based catalyst according to claim 1, characterized in that: Stirring is performed during the mixing reaction of the transition metal salt solution and the buffer solution; the stirring time is 5 to 10 minutes.

3. The method for preparing a carbon-based catalyst according to claim 1, characterized in that: The step of impregnating the activated carbon with the mixed solution comprises: Add activated carbon to the mixed solution at room temperature and stir; the stirring time is 60 to 120 minutes.

4. The method for preparing a carbon-based catalyst according to claim 1, characterized in that: In the step of preparing activated carbon loaded with transition metal oxides, the temperature of the drying treatment is 60 to 80° C. and the time of the drying treatment is 24 to 48 hours.

5. The method for preparing a carbon-based catalyst according to any one of claims 1 to 4, characterized in that: The transition metal salt solution is potassium permanganate KMnO4 solution; and / or The buffer solution is ammonium carbonate (NH4)2CO3 solution.

6. The method for preparing a carbon-based catalyst according to claim 5, characterized in that: The concentration of the transition metal salt solution is 65.7 to 67.7 mg / mL; and / or The concentration of the buffer solution is 20-30 mg / mL.

7. The method for preparing a carbon-based catalyst according to claim 1, characterized in that: In the step S1), the immersion treatment includes: Add activated carbon to the polyelectrolyte solution at room temperature and stir; The weight ratio of the activated carbon to the polyelectrolyte in the polyelectrolyte solution is 31.7:1 to 95.5:1; and the stirring time is 60 to 120 minutes.

8. The method for preparing a carbon-based catalyst according to claim 1, characterized in that: In the step S1), the drying temperature is 60 to 80° C. and the drying time is 24 to 48 hours.

9. The method for preparing a carbon-based catalyst according to claim 1, characterized in that: In the step S21), the mass ratio of the activated carbon loaded with polyelectrolyte to the noble metal salt in the noble metal salt solution is 312.5:1 to 937.5:

1.

10. The method for preparing a carbon-based catalyst according to claim 1, characterized in that: In the step S22), the drying temperature is 60 to 80° C. and the drying time is 24 to 48 hours.

11. The method for preparing a carbon-based catalyst according to claim 1, characterized in that: In the step S23), the drying temperature is 60 to 80° C. and the drying time is 24 to 48 hours.

12. The method for preparing a carbon-based catalyst according to claim 1, characterized in that: The polyelectrolyte is polydiallyl dimethyl propyl ammonium chloride (PDDA); and / or The noble metal salt is selected from chloroplatinic acid hexahydrate H2PtCl6·6H2O.

13. The method for preparing a carbon-based catalyst according to claim 12, characterized in that: The weight ratio of NaOH in the sodium hydroxide NaOH solution to NaBH4 in the sodium borohydride NaBH4 solution is 5:1 to 5.4:1; and / or The concentration of the polydiallyl dimethyl propyl ammonium chloride (PDDA) solution is 2.10 to 6.30 mg / mL; and / or The concentration of the hexahydrate chloroplatinic acid H2PtCl6·6H2O solution is 0.96 to 2.88 mg / mL; and / or The concentration of sodium borohydride NaBH4 solution is 3.0-9.1 mg / mL; and / or The concentration of the sodium hydroxide NaOH solution is 16-48 mg / mL.

14. The method for preparing a carbon-based catalyst according to claim 1, characterized in that: Before step 1), a purification step of activated carbon is also included: The original activated carbon is added into deionized water for soaking, and then filtered and dried to obtain purified activated carbon.

15. The method for preparing a carbon-based catalyst according to claim 1, characterized in that: In the activated carbon loaded with precious metals: the precious metals are loaded in the activated carbon in the form of nanoparticles.

16. The method for preparing a carbon-based catalyst according to claim 15, characterized in that: The particle size of the nanoparticles is 1 to 5 nm.

17. A carbon-based catalyst, characterized in that The carbon-based catalyst is obtained by mixing activated carbon loaded with transition metal oxides and activated carbon loaded with precious metals; The carbon-based catalyst is obtained by the preparation method according to any one of claims 1 to 16.

18. The carbon-based catalyst according to claim 17, characterized in that In the activated carbon loaded with precious metals: the precious metals are loaded in the activated carbon in the form of nanoparticles; the particle size of the nanoparticles is 1 to 5 nm.

19. Use of the carbon-based catalyst according to any one of claims 17 to 18, characterized in that: The carbon-based catalyst is used for removing indoor formaldehyde at room temperature.

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