Formaldehyde catalytic oxidation agent, preparation method and application thereof

Abstract

The application discloses a formaldehyde catalytic oxidation agent and a preparation method and application thereof, and aims at solving the technical problem of how to use copper manganese oxide with a spinel structure as an active component to efficiently and stably catalyze and oxidize formaldehyde at room temperature. The formaldehyde catalytic oxidation agent comprises the following components in percentage by mass: 70-94% of an activated carbon carrier with oxygen vacancy defects on the surface; 5-20% of an active component composed of copper manganese oxide with a spinel crystal phase structure; and 1-10% of an anti-poisoning auxiliary agent composed of an alkaline alkali metal salt; wherein, the active component and the anti-poisoning auxiliary agent are jointly loaded on the activated carbon carrier. The formaldehyde can be efficiently mineralized and decomposed at room temperature, and the service life is long.

Description

Technical Field

[0001] This invention relates to the field of formaldehyde catalytic oxidant technology, specifically to a formaldehyde catalytic oxidant, its preparation method, and its application. Background Technology

[0002] Formaldehyde (HCHO), a typical indoor volatile organic pollutant, poses a serious threat to human health. In formaldehyde treatment technologies, catalytic oxidation has attracted considerable attention due to its ability to completely mineralize formaldehyde into carbon dioxide and water under mild conditions. Among these, non-precious metal catalysts using copper-manganese oxide (CuMn2O4) with a spinel structure as the active component have become a research hotspot for replacing traditional precious metal catalysts (such as Pt and Pd) due to their low cost and excellent catalytic performance. Existing technologies show that the copper-manganese oxide possesses a unique copper-manganese bimetallic synergistic mechanism, utilizing the rapid electron transfer cycle between copper and manganese ions, combined with the large number of surface oxygen vacancies generated by lattice structure distortion, thereby greatly promoting the generation and migration of reactive oxygen species. Currently, the product forms of such formaldehyde catalysts mainly include pure-phase powders or nanoparticles supported on conventional supports such as alumina and titanium dioxide.

[0003] However, although existing copper-manganese oxide catalysts exhibit good performance under certain conditions, they still suffer from the following technical shortcomings in practical room-temperature applications: First, insufficient room-temperature activity of the catalysts. Existing copper-manganese oxide catalysts have low conversion efficiency for formaldehyde under normal temperature and pressure conditions, often failing to achieve complete oxidation of formaldehyde. To achieve the desired purification effect, additional heating devices are usually required to increase the reaction temperature, which not only increases the energy consumption and complexity of the equipment but also limits its convenient application in ordinary indoor environments. Second, poor resistance to poisoning and stability of the catalysts. During the formaldehyde oxidation process, acidic intermediates such as formate are produced. These acidic intermediates are difficult to decompose and desorb in a timely manner, easily covering the active sites, thus causing rapid "poisoning" and deactivation of the catalyst. Summary of the Invention

[0004] The purpose of this invention is to provide a formaldehyde catalytic oxidant, its preparation method, and its application, in order to solve the technical problem of how to use copper manganese oxide with a spinel structure as an active component to efficiently and stably catalyze the oxidation of formaldehyde at room temperature.

[0005] In a first aspect, a formaldehyde catalytic oxidant is provided, comprising the following components by mass percentage: 70%-94% of an activated carbon support with oxygen vacancy defects on its surface; 5%-20% of an active component composed of copper manganese oxide having a spinel crystal phase structure; and 1%-10% of an anti-poisoning agent composed of an alkaline alkali metal salt; wherein the active component and the anti-poisoning agent are co-loaded on the activated carbon support.

[0006] As an optimization and / or instantiation of the above-mentioned formaldehyde catalytic oxidant, further: the oxygen vacancy defects are formed by first subjecting the raw material activated carbon to inorganic acid etching treatment, and then subjecting it to thermal activation treatment.

[0007] As an optimization and / or instantiation of the above-mentioned formaldehyde catalytic oxidant, further: the specific manufacturing process of the oxygen vacancy defect is as follows: the raw material activated carbon is placed in an inorganic acid solution with a concentration of 3wt%-10wt%, and etched at 60℃-90℃ for 2-6 hours, then washed until neutral and dried. The inorganic acid solution is a nitric acid solution, a sulfuric acid solution, a hydrochloric acid solution, or a mixture of at least two of the above. Subsequently, under an inert atmosphere, it is thermally activated at 450℃-600℃ for 1-3 hours.

[0008] As an optimization and / or instantiation of the above-mentioned formaldehyde catalytic oxidant, further: in the copper-manganese oxide, the molar ratio of copper to manganese is 1:1.5-1:2.5.

[0009] As an optimization and / or instantiation of the above-mentioned formaldehyde catalytic oxidant, further: in the copper-manganese oxide, the molar ratio of copper to manganese is 1:2.

[0010] As an optimization and / or instantiation of the above-mentioned formaldehyde catalytic oxidant, further: the copper manganese oxide also contains a doping element, the doping element being selected from at least one of Co, Fe, and Zn; based on the total number of atoms of copper, manganese, and the doping element, the atomic percentage of the doping element is 1at%-10at.

[0011] As an optimization and / or instance of the above-mentioned formaldehyde catalytic oxidant, the alkaline alkali metal salt is further selected from one or more of the following: alkali metal carbonates, bicarbonates, nitrates, or acetates.

[0012] As an optimization and / or instantiation of the above-mentioned formaldehyde catalytic oxidant, further: the alkaline alkali metal salt is selected from one or more of potassium carbonate, sodium carbonate, and cesium carbonate.

[0013] As an optimization and / or instantiation of the above-mentioned formaldehyde catalytic oxidant, further: the content of the active component is 10%-12% by mass, the content of the anti-poisoning adjuvant is 3%-8% by mass, and the remainder is activated carbon carrier.

[0014] As an optimization and / or instantiation of the above-mentioned formaldehyde catalytic oxidant, further: the specific surface area of ​​the activated carbon support is 800 m². 2 / g-2000m 2 / g, pore volume 0.5cm 3 / g-1.5cm 3 / g.

[0015] The second aspect provides a method for preparing a formaldehyde catalytic oxidant, which is used to prepare the formaldehyde catalytic oxidant of the first aspect above, comprising: (1) etching the raw material activated carbon with inorganic acid and then performing thermal activation treatment to obtain an activated carbon support with oxygen vacancy defects on the surface; (2) immersing the activated carbon support in a precursor solution containing copper salt and manganese salt, drying it and then calcining it to generate an active component composed of copper manganese oxide with spinel crystal phase structure in situ; (3) immersing the product obtained in step (2) in an alkaline alkali metal salt solution and then drying it to obtain the formaldehyde catalytic oxidant.

[0016] As an optimization and / or instance of the above-mentioned method for preparing formaldehyde catalytic oxidant, further: Step (1) specifically includes: placing the raw material activated carbon in an inorganic acid solution with a concentration of 3wt%-10wt%, etching it at 60℃-90℃ for 2-6 hours, then washing it until neutral and drying it, wherein the inorganic acid solution is a nitric acid solution, a sulfuric acid solution, a hydrochloric acid solution, or a mixture of at least two of the above; subsequently, under an inert atmosphere, thermally activating it at 450℃-600℃ for 1-3 hours; Step (2) specifically includes: using an equal volume impregnation method, impregnating the activated carbon carrier in a precursor mixed solution with a total concentration of 0.5mol / L-2.0mol / L, wherein the precursor The catalyst mixture solution contains soluble copper salt and soluble manganese salt, and the molar ratio of copper to manganese is 1:1.5-1:2.5; after impregnation, it is dried at 100℃-120℃ for 4-12 hours, and then calcined at 300℃-600℃ for 2-5 hours in an inert atmosphere; the soluble copper salt is selected from one or more of copper nitrate, copper acetate, copper sulfate, and copper chloride, and the soluble manganese salt is selected from one or more of manganese nitrate, manganese acetate, manganese sulfate, and potassium permanganate; step (3) specifically includes: impregnating the product obtained in step (2) in an alkaline alkali metal salt solution with a concentration of 0.2mol / L-1.0mol / L, and then drying at 100℃-120℃ for 2-8 hours.

[0017] As an optimization and / or instance of the above-mentioned method for preparing formaldehyde catalytic oxidant, further: the calcination temperature is 480℃-520℃, and the calcination time is 3 hours.

[0018] The third aspect also provides the application of the formaldehyde catalytic oxidant mentioned in the first aspect in indoor air purification.

[0019] The formaldehyde catalytic oxidant of the present invention, through an activated carbon support with oxygen vacancy defects on its surface, loads an active component composed of copper manganese oxide with a spinel crystal phase structure and an anti-poisoning auxiliary agent composed of alkaline alkali metal salts, and can produce the following technical effects:

[0020] First, this invention utilizes an activated carbon support with oxygen vacancy defects on its surface. On one hand, the large specific surface area of ​​the activated carbon support enables the efficient adsorption and enrichment of low-concentration formaldehyde molecules on the catalyst surface, forming a synergistic "adsorption-catalysis" effect. On the other hand, the oxygen vacancy defects on the surface of the activated carbon support can activate the adsorbed oxygen, converting it into highly active surface oxygen species. This activated carbon support, combined with the copper-manganese oxide active component (spinel structure) with excellent redox capabilities, effectively reduces the activation energy of the formaldehyde oxidation reaction, enabling this formaldehyde catalytic oxidant to achieve efficient mineralization and decomposition of formaldehyde at room temperature without the need for additional heating.

[0021] Secondly, to address the problem of acidic intermediates such as formates being generated during formaldehyde oxidation, which can cover active sites and lead to deactivation, this invention introduces an alkaline alkali metal salt as an anti-poisoning agent. This anti-poisoning agent can effectively neutralize acidic intermediates, promoting their rapid decomposition and desorption from the active sites, thus preventing blockage. This mechanism ensures that the copper-manganese oxide active component can remain exposed and participate in the reaction for a long time, thereby significantly extending the lifespan of the formaldehyde catalytic oxidant.

[0022] Third, the two-step process of inorganic acid etching followed by thermal activation not only removes impurities from the carbon surface but, more importantly, creates abundant oxygen vacancy defects on the carbon framework. These defect sites serve as activation centers for oxygen molecules and enhance the interaction between the activated carbon carrier and the active components, promoting the dispersion of the active components and further improving the overall performance of the formaldehyde catalytic oxidant.

[0023] Fourth, when elements such as Co, Fe, or Zn are doped into copper manganese oxide, lattice distortion can be induced, further increasing the oxygen vacancy concentration inside the active component and regulating the electron transfer rate between metal ions, thereby improving the catalytic degradation effect of formaldehyde by the formaldehyde catalytic oxidant.

[0024] Fifth, the raw materials used in the preparation method of the formaldehyde catalytic oxidant of this invention—activated carbon, copper salt, manganese salt, and alkaline alkali metal salt solution—are all readily available and inexpensive chemical raw materials. This makes the final cost of the formaldehyde catalytic oxidant of this invention far lower than that of catalysts using precious metals such as platinum and palladium, resulting in extremely high cost-effectiveness. Furthermore, the entire preparation process is conducted under mild conditions, with no emissions of toxic or harmful substances, meeting the requirements of green chemistry and sustainable development.

[0025] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Additional aspects and advantages provided by the present invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice. Attached Figure Description

[0026] The accompanying drawings, which form part of this specification, are used to aid in understanding the invention. The contents provided in the drawings and their related descriptions in this specification can be used to explain the invention, but do not constitute an undue limitation of the invention.

[0027] Figure 1 This is a schematic diagram of the experimental testing device for testing formaldehyde catalytic oxidant according to the present invention.

[0028] Figure 2 This is a scanning electron microscope (SEM) image of the formaldehyde catalytic oxidant of Example 1 of the present invention.

[0029] Figure 3 This is a scanning electron microscope (SEM) image of the formaldehyde catalytic oxidant of Example 1 of the present invention.

[0030] Figure 4 The image shows the X-ray diffraction (XRD) pattern of the formaldehyde catalytic oxidant in Example 1 of this invention.

[0031] Figure 5 It was conducted at 25℃, 50%RH, 1ppm formaldehyde, and a space velocity of 6000h. -1 Under the conditions described, the formaldehyde conversion rate of the catalyst of Example 1 of the present invention, Comparative Example 1 (without K2CO3 auxiliary agent), Comparative Example 2 (with γ-Al2O3 as support) and Comparative Example 3 (pure activated carbon support) are compared with the change of time, and the 120h long-term stability test results of the formaldehyde catalytic oxidant of Example 1 of the present invention are shown in the figure. Detailed Implementation

[0032] The present invention will now be clearly and completely described in conjunction with the accompanying drawings. Those skilled in the art will be able to implement the present invention based on these descriptions. Before describing the present invention in conjunction with the accompanying drawings, it should be particularly noted that:

[0033] The technical solutions and features provided in the various sections, including the following description, can be combined with each other without conflict. Furthermore, where possible, these technical solutions, features, and related combinations can be given specific technical subject matter and protected by relevant patents.

[0034] The embodiments of the present invention described below are generally only some embodiments and not all embodiments. Based on these embodiments, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of patent protection.

[0035] The term "comprising" and any variations thereof in this specification, the corresponding claims, and related sections are intended to cover a non-exclusive inclusion. Other related terms and units can be reasonably interpreted based on the relevant content provided in this specification.

[0036] Unless otherwise stated, all reagents used in the embodiments of this invention are commercially available analytical grade chemicals, and the activated carbon used is commercially available coal-based activated carbon (specific surface area 1240 m²). 2 / g, pore volume 0.68cm 3 / g).

[0037] Example 1: Preparation, characterization and performance testing of a formaldehyde catalytic oxidant (Cat-E1).

[0038] A formaldehyde catalytic oxidant was prepared, comprising, by mass percentage: 85% activated carbon carrier with oxygen vacancy defects on its surface, 10% active component (CuMn2O4) composed of copper manganese oxide with spinel crystal phase structure, and 5% anti-poisoning auxiliary composed of alkaline alkali metal salt (specifically potassium carbonate).

[0039] The specific preparation steps of the formaldehyde catalytic oxidant are as follows: (1) The raw activated carbon is first etched with inorganic acid and then thermally activated to obtain an activated carbon carrier with oxygen vacancy defects on the surface. Specifically, 100g of raw activated carbon is weighed and added to 500mL of 6wt% nitric acid solution (inorganic acid). The solution is shaken and stirred in an 80℃ water bath for 4h for acid etching treatment. After the treatment, the activated carbon is repeatedly filtered and washed with deionized water until the pH value of the filtrate is close to 7. The washed activated carbon is dried in an oven at 110℃ for 12h. Then, the dried acid-etched activated carbon is placed in a tube furnace and heated to 500℃ at a heating rate of 5℃ / min under nitrogen atmosphere (flow rate 200mL / min) protection. It is then thermally activated at this temperature for 2h. After cooling to room temperature, an activated carbon carrier with oxygen vacancy defects on the surface is obtained, denoted as AC-M.

[0040] (2) The activated carbon support is impregnated in a precursor solution containing copper and manganese salts, dried, and then calcined to generate an active component composed of copper-manganese oxides with a spinel crystal phase structure in situ. Specifically, 85g of the activated carbon support AC-M with oxygen vacancy defects on its surface prepared above is weighed, and its saturated water absorption rate is measured to be approximately 1.0 mL / g. 10.28g of copper nitrate and 30.14g of a 50wt% manganese nitrate solution are weighed and dissolved in 50.74g of deionized water to prepare a precursor solution, wherein the molar ratio of copper to manganese is 1:2. This solution is then uniformly impregnated dropwise onto the AC-M support while stirring, followed by ultrasonic treatment for 30 minutes, and then allowed to stand for 4 hours. The impregnated sample is dried in an oven at 110℃ for 6 hours. Then, it is transferred to a tube furnace and calcined at 500℃ for 3 hours under a nitrogen atmosphere at a rate of 2℃ / min. In this process, an active component consisting of copper manganese oxide (CuMn2O4) with a spinel crystal phase structure is generated in situ, and this active component is loaded on the activated carbon support. The resulting intermediate product is denoted as AC-CuMn2O4.

[0041] (3) The product obtained in step (2) is impregnated in an alkaline alkali metal salt solution and then dried to obtain the formaldehyde catalytic oxidant. Specifically, 5g of potassium carbonate (as an alkaline alkali metal salt) is weighed and prepared into an 85mL aqueous solution. This solution is then loaded onto the AC-CuMn2O4 sample prepared above using an equal-volume impregnation method. The impregnated sample is dried at 110℃ for 4 hours until constant weight is achieved. The final product obtained is the formaldehyde catalytic oxidant of this embodiment, labeled Cat-E1.

[0042] The prepared formaldehyde catalytic oxidant Cat-E1 was characterized. SEM characterization (e.g., ...) Figure 2 , Figure 3 As shown in the figure): The results show that the formaldehyde catalytic oxidant retains the original porous structure of the activated carbon support. Uniformly distributed, tiny white nanoparticles can be observed on its surface and pore walls. These particles are copper manganese oxide crystals with a spinel crystal phase structure generated in situ. XRD characterization (e.g.) Figure 4 As shown in the diagram: The characteristic diffraction peak at 2θ≈35.6° in the spectrum corresponds to the (311) crystal plane of CuMn2O4 with a spinel structure (standard card JCPDS#84-0543), confirming that the active component successfully exists in the spinel phase. At the same time, the characteristic diffraction peak at 2θ≈26.5° corresponds to the (002) crystal plane of the graphitized structure of activated carbon (standard card JCPDS#75-2078), reflecting the characteristics of the activated carbon support.

[0043] Figure 1This invention demonstrates an experimental testing apparatus for testing formaldehyde catalytic oxidants. Its working principle involves precisely controlling the gas path to simulate a formaldehyde-polluted environment under specific temperature and humidity conditions. At the start of the experiment, nitrogen, oxygen, and formaldehyde gases are precisely metered from gas cylinders using mass flow meters. One nitrogen stream is humidified to introduce moisture and adjust the relative humidity. All gases are then thoroughly mixed in a mixing bottle to form a reaction feed gas with constant flow rate, concentration, and humidity. The mixed gas enters a U-shaped tube fixed-bed reactor placed in a constant-temperature water bath, passing through a bed filled with the formaldehyde catalytic oxidant to undergo a catalytic oxidation reaction. The resulting exhaust gas is introduced through a three-way valve into a formaldehyde detector to monitor the residual formaldehyde concentration in real time and calculate the conversion rate. Finally, the waste gas is absorbed by an exhaust gas treatment device before being discharged, thus achieving a quantitative evaluation of the activity and stability of the formaldehyde catalytic oxidant.

[0044] use Figure 1 The experimental setup shown involves filling a U-shaped tube fixed-bed reactor with an inner diameter of 15 mm with 10 mL (approximately 5.0 g) of Cat-E1 formaldehyde catalytic oxidant, crushed to 10-20 mesh. The test conditions were: reaction temperature 25±3℃, relative humidity 50%±5%, and inlet formaldehyde concentration 1±0.1 mg / m³. 3 With an oxygen concentration of 20% vol% and a total gas flow rate of 1.0 L / min, the corresponding gas space velocity (GHSV) is 6000 h⁻¹. -1 The inlet gas is a mixture of humidified nitrogen, oxygen, and standard formaldehyde gas (100 ppm HCHO / N2) precisely controlled by a mass flow meter. Relative humidity is controlled by adjusting the ratio of dry to humid air. Formaldehyde concentrations before and after the reaction are measured using a British PPM formaldehyde detector. The formaldehyde conversion rate (η) is calculated using the following formula: Where η: formaldehyde conversion rate (%), C0: initial concentration (mg / m³). 3 Ct: outlet concentration (mg / m³) 3 ).

[0045]

[0046] like Figure 5 As shown, under conditions of 25°C and 50% relative humidity, the formaldehyde catalytic oxidant Cat-E1 of Example 1 of the present invention rapidly reaches very high activity after the reaction begins, with the initial formaldehyde conversion rate (within 4 hours) stabilizing at over 99%, and the formaldehyde conversion rate still being higher than 95% after 120 hours.

[0047] Examples 2-4: Investigating the effect of CuMn2O4 loading.

[0048] Except for changing the CuMn2O4 loading, the other preparation steps and conditions were exactly the same as in Example 1.

[0049] Example 2 (Cat-E2): CuMn2O4 loading was 5 wt%.

[0050] Example 3 (Cat-E3): CuMn2O4 loading was 15wt%.

[0051] Example 4 (Cat-E4): CuMn2O4 loading was 20wt%.

[0052] Cat-E1, Cat-E2, Cat-E3, and Cat-E4 were tested under the same conditions as in Example 1, and the results are shown in Table 1.

[0053] As shown in Table 1, the formaldehyde catalytic oxidant exhibited excellent room-temperature formaldehyde catalytic activity within the CuMn2O4 loading range of 5wt%-20wt%. When the CuMn2O4 loading increased from 5wt% to 10%, the formaldehyde conversion rate significantly improved, attributed to the increase in the number of active sites. The formaldehyde catalytic oxidant activity reached its peak at a CuMn2O4 loading of 10%. Further increasing the CuMn2O4 loading to 15wt% resulted in a slight decrease in activity, which became more pronounced at 20wt%. This may be because excessively high loading caused the CuMn2O4 nanoparticles to aggregate, reducing the specific surface area and potentially clogging some of the micropores of the activated carbon, thus affecting the mass transfer process of formaldehyde molecules. Therefore, the optimal CuMn2O4 loading range is 8wt%-15wt%, with approximately 10wt% being particularly preferred.

[0054] Table 1: Initial formaldehyde conversion rate of formaldehyde catalytic oxidants in different embodiments

[0055] Example number <![CDATA[CuMn2O4(wt%)]]> <![CDATA[K2CO3(wt%)]]> Initial formaldehyde conversion rate (%) Cat-E2 5 5 91.2 Cat-E1 10 5 99.1 Cat-E3 15 5 97.5 Cat-E4 20 5 92.3

[0056] Examples 5-7: Investigating the effect of K2CO3 loading

[0057] Except for changing the K2CO3 loading, the other preparation steps and conditions (CuMn2O4 loading was fixed at 10wt%) were exactly the same as in Example 1.

[0058] Example 5 (Cat-E5): K2CO3 loading was 1 wt%.

[0059] Example 6 (Cat-E6): K2CO3 loading was 8 wt%.

[0060] Example 7 (Cat-E7): K2CO3 loading was 10 wt%.

[0061] Cat-E1, Cat-E5, Cat-E6, and Cat-E7 were subjected to long-term stability testing under the following conditions: 25℃, 1ppm HCHO, 50%RH, 20vol%O2, GHSV=6000h. -1 It ran continuously for 120 hours. The results are shown in Table 2.

[0062] Table 2 shows that the addition of K2CO3 plays a decisive role in the long-term stability of the catalyst. When the K2CO3 loading is 5 wt%, the formaldehyde catalytic oxidant exhibits the best stability, retaining over 95% of its activity after 120 hours of continuous operation. Stability decreases when the K2CO3 content is low (1 wt%) or high (8 wt%-10 wt%). This indicates the existence of an optimal amount of anti-poisoning agent. Too little anti-poisoning agent is insufficient to completely neutralize and promote the decomposition of all generated acidic intermediates; while too much anti-poisoning agent may cover some CuMn2O4 active sites or affect formaldehyde adsorption or subsequent oxidation steps due to excessive alkalization of the catalyst surface. Therefore, the optimal K2CO3 loading range is 3 wt%-8 wt%, particularly preferably around 5 wt%.

[0063] Table 2: Formaldehyde conversion rate of formaldehyde catalytic oxidants from different embodiments after 120 h

[0064] Example number <![CDATA[CuMn2O4(wt%)]]> <![CDATA[K2CO3(wt%)]]> Formaldehyde conversion rate (%) after 120 hours Cat-E5 10 1 88 Cat-E1 10 5 ＞95 Cat-E6 10 8 92 Cat-E7 10 10 85

[0065] Examples 8-10: Optimization of surface treatment for activated carbon raw materials.

[0066] Except for changing the inorganic acid solution, the other preparation steps and conditions are exactly the same as in Example 1.

[0067] Example 8 (Cat-E8): Untreated.

[0068] Example 9 (Cat-E9): 6 wt% sulfuric acid solution.

[0069] Example 10 (Cat-E10): 6 wt% hydrochloric acid solution.

[0070] Cat-E1, Cat-E8, Cat-E9, and Cat-E10 were tested under the same conditions as in Example 1, and the results are shown in Table 3.

[0071] Table 3: Effect of different inorganic acid solutions on the initial conversion rate of formaldehyde

[0072] Example acid etching solution <![CDATA[Specific surface area (m 2 / g)]]> Initial formaldehyde conversion rate (%) Cat-E8 Unprocessed 850 72% Cat-E9 6wt% sulfuric acid solution 1200 91% Cat-E10 6wt% hydrochloric acid solution 1100 89% Cat-E1 6wt% nitric acid solution 1350 96%

[0073] Results analysis: Inorganic acid etching generally increased the specific surface area (+29%-59%), but nitric acid showed significantly better optimization than hydrochloric acid and sulfuric acid (Cat-E1 had a 12.5%-22.7% higher specific surface area than Cat-E9 / Cat-E10). This is because the strong oxidizing properties of nitric acid can deeply etch the carbon skeleton, while introducing oxygen-containing functional groups such as carboxyl and phenolic hydroxyl groups, forming a hierarchical porous structure.

[0074] Comparative Example 1: The preparation method was the same as in Example 1, but without K2CO3 loading, i.e., a catalyst AC-M supported on 10wt% CuMn2O4 was prepared, denoted as Cat-C1. Cat-C1 had high initial activity, but its activity decreased rapidly with the passage of reaction time, with a decrease of more than 40% after 60 hours. This fully demonstrates the key role of K2CO3 promoter in inhibiting the accumulation of intermediate products and maintaining the long-term stability of the catalyst.

[0075] Comparative Example 2: The same impregnation, calcination, and anti-poisoning agent loading as Example 1 were used, but the activated carbon support was replaced with commercial γ-Al₂O₃. The resulting catalyst was designated Cat-C2. Cat-C2 exhibited an initial formaldehyde conversion rate of only about 45% at 25°C. This contrasts sharply with the high conversion rate of Cat-E1 (up to 99%), demonstrating that the specially pretreated activated carbon support used in this invention, for example, with acid-etched enhanced oxygen vacancy concentration, generates a strong synergistic effect with the active components through its unique surface chemistry and pore structure, which is a crucial prerequisite for achieving high room temperature activity.

[0076] Comparative Example 3: The pretreated activated carbon carrier AC-M prepared in Example 1 was used as a comparative example, denoted as Cat-C3. Cat-C3 initially showed some formaldehyde removal capacity, which is a result of physical adsorption. However, its outlet formaldehyde concentration rose rapidly, reaching the same level as the inlet concentration after about 5 hours, indicating that its adsorption sites were saturated and it completely lost its formaldehyde purification capacity. This proves that the formaldehyde catalytic oxidant of this invention continuously removes formaldehyde through catalytic oxidation rather than physical adsorption.

[0077] 50g of the catalyst Cat-E1 prepared in Example 1 was filled into a self-made air purifier filter and placed in a 30m... 3 Inside the sealed test chamber, formaldehyde was released to initially raise the formaldehyde concentration inside the chamber to 1.0 mg / m³. 3 (Approximately 0.8 ppm). Turn on the built-in fan to circulate air through the catalytic filter. Monitor the formaldehyde concentration inside the chamber every hour. Results showed that after 4 hours, the formaldehyde concentration inside the chamber dropped to the safe limit of 0.08 mg / m³ according to the new national standard "Indoor Air Quality Standard" (GB / T 18883-2022). 3Below, after 24 hours, the formaldehyde concentration was below the instrument detection limit of 0.01 ppm. The device was run continuously for 30 days, with a small amount of formaldehyde added daily during this period; its purification efficiency did not decrease significantly, demonstrating the high efficiency and durability of the catalyst of this invention in practical applications.

[0078] The foregoing has described the relevant content of the present invention. Those skilled in the art will be able to implement the present invention based on these descriptions. All other embodiments obtained by those skilled in the art based on the foregoing content of this specification without inventive effort should fall within the scope of the present invention.

Claims

1. A formaldehyde catalytic oxidant, characterized in that: Includes the following components by mass percentage: Activated carbon carriers with 70%-94% of their surface having oxygen vacancy defects; 5%-20% of the active component is composed of copper manganese oxides with a spinel crystal phase structure; 1%-10% of anti-poisoning adjuvants composed of alkaline alkali metal salts; The active component and the anti-poisoning adjuvant are jointly loaded onto the activated carbon carrier.

2. The formaldehyde catalytic oxidant as described in claim 1, characterized in that: The oxygen vacancy defects are formed by first etching the raw activated carbon with inorganic acid and then thermally activating it.

3. The formaldehyde catalytic oxidant as described in claim 2, characterized in that: The specific manufacturing process of the oxygen vacancy defect is as follows: the raw activated carbon is placed in an inorganic acid solution with a concentration of 3wt%-10wt%, and etched at 60℃-90℃ for 2-6 hours. After that, it is washed until neutral and dried. The inorganic acid solution is a nitric acid solution, a sulfuric acid solution, a hydrochloric acid solution, or a mixture of at least two of the above. Then, under an inert atmosphere, it is thermally activated at 450℃-600℃ for 1-3 hours.

4. The formaldehyde catalytic oxidant as described in claim 1, characterized in that: In the copper-manganese oxide, the molar ratio of copper to manganese is 1:1.5 to 1:2.

5.

5. The formaldehyde catalytic oxidant as described in claim 4, characterized in that: In the copper-manganese oxide, the molar ratio of copper to manganese is 1:

2.

6. The formaldehyde catalytic oxidant as described in claim 1, characterized in that: The copper-manganese oxide further comprises a doping element selected from at least one of Co, Fe, and Zn; the percentage of the number of atoms of the doping element is 1 at% to 10 at, based on the total number of atoms of copper, manganese, and the doping element.

7. The formaldehyde catalytic oxidant as described in claim 1, characterized in that: The alkaline alkali metal salt is selected from one or more of the carbonates, bicarbonates, or acetates of alkali metals.

8. The formaldehyde catalytic oxidant as described in claim 7, characterized in that: The alkaline alkali metal salt is selected from one or more of potassium carbonate, sodium carbonate, and cesium carbonate.

9. The formaldehyde catalytic oxidant as described in claim 1, characterized in that: The content of the active component is 10%-12% by mass, the content of the anti-poisoning adjuvant is 3%-8% by mass, and the remainder is activated carbon carrier.

10. The formaldehyde catalytic oxidant as described in claim 1, characterized in that: The specific surface area of ​​the activated carbon carrier is 800 m². 2 / g-2000m 2 / g, pore volume 0.5cm 3 / g-1.5cm 3 / g.

11. A method for preparing a formaldehyde catalytic oxidant, characterized in that: A method for preparing the formaldehyde catalytic oxidant as described in any one of claims 1-10, comprising: (1) The raw activated carbon is first etched with inorganic acid and then thermally activated to obtain an activated carbon carrier with oxygen vacancy defects on the surface. (2) The activated carbon carrier is immersed in a precursor solution containing copper and manganese salts, dried and then calcined to generate an active component composed of copper and manganese oxides with a spinel crystal phase structure in situ. (3) The product obtained in step (2) is immersed in an alkaline alkali metal salt solution and then dried to obtain the formaldehyde catalytic oxidant.

12. The method for preparing the formaldehyde catalytic oxidant as described in claim 11, characterized in that: Step (1) specifically includes: placing the raw activated carbon in an inorganic acid solution with a concentration of 3wt%-10wt%, etching it at 60℃-90℃ for 2-6 hours, then washing it until neutral and drying it. The inorganic acid solution is a nitric acid solution, a sulfuric acid solution, a hydrochloric acid solution, or a mixture of at least two of the above. Subsequently, under an inert atmosphere, it is thermally activated at 450℃-600℃ for 1-3 hours. Step (2) specifically includes: using an equal-volume impregnation method, impregnating the activated carbon carrier in a precursor mixed solution with a total concentration of 0.5 mol / L-2.0 mol / L, wherein the precursor mixed solution contains soluble copper salt and soluble manganese salt, and the molar ratio of copper to manganese is 1:1.5-1:2.5; after impregnation, drying at 100℃-120℃ for 4-12 hours, and then calcining at 300℃-600℃ for 2-5 hours in an inert atmosphere; wherein the soluble copper salt is selected from one or more of copper nitrate, copper acetate, copper sulfate, and copper chloride, and the soluble manganese salt is selected from one or more of manganese nitrate, manganese acetate, manganese sulfate, and potassium permanganate; Step (3) specifically includes: immersing the product obtained in step (2) in an alkaline alkali metal salt solution with a concentration of 0.2 mol / L-1.0 mol / L, and then drying it at 100℃-120℃ for 2-8 hours.

13. The method for preparing the formaldehyde catalytic oxidant as described in claim 12, characterized in that: The roasting temperature is 480℃-520℃, and the roasting time is 3 hours.

14. The application of the formaldehyde catalytic oxidant as described in any one of claims 1-10 in indoor air purification.

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