MnOx-modified integral activated carbon paper honeycomb catalyst as well as preparation method and application thereof

Abstract

The invention discloses a MnOx modified monolithic activated carbon paper honeycomb catalyst as well as a preparation method and application thereof, and belongs to the technical field of air purification. The invention provides a preparation method of a MnOx-modified monolithic activated carbon paper honeycomb catalyst. The MnOx-modified monolithic activated carbon paper honeycomb catalyst is generated in situ in one step according to a micro-electrochemical battery principle. The MnOx modified monolithic activated carbon paper honeycomb catalyst provided by the invention is mild in preparation condition and simple in process, and the shape of the substrate basically does not influence the preparation process; the manganese oxide active component in the prepared catalyst is firmly loaded on the paper honeycomb substrate and is uniformly distributed. The catalyst has a relatively large specific surface area, is beneficial to adsorption of formaldehyde, has rich oxygen vacancies by adjusting the pH value in the reaction process, and is beneficial to catalytic oxidation of formaldehyde.

Description

Technical Field

[0001] This invention belongs to the field of air purification technology, and specifically relates to a MnO x Modified monolithic activated carbon paper honeycomb catalyst, its preparation method and application. Background Technology

[0002] Formaldehyde (HCHO), a typical volatile organic compound (VOC) in indoor environments, mainly originates from building materials, furniture adhesives, and daily necessities. Studies have shown that long-term exposure to 0.1 mg / m³... 3 The formaldehyde environment described above can cause respiratory damage, decreased immune function, and even cancer. Therefore, developing efficient and stable formaldehyde purification technologies is a research hotspot in the field of environmental functional materials.

[0003] Currently, formaldehyde purification technologies mainly fall into two categories: physical adsorption (such as activated carbon and molecular sieves) and catalytic oxidation (such as precious metal / metal oxide catalysts). Among them, monolithic catalysts have become the mainstream carrier form for formaldehyde catalytic purification due to their advantages such as low fluid resistance (suitable for continuous flow scenarios such as air purifiers), high mechanical strength (impact resistance and wear resistance), and easy modular design.

[0004] However, the research and application of existing monolithic formaldehyde catalysts still face the following key technological bottlenecks:

[0005] First, the active components are not firmly supported, resulting in a short service life. Traditional monolithic catalysts mostly use physical loading methods (such as impregnation and spraying) to attach the active components to the substrate surface. This method relies on van der Waals forces or simple physical adsorption to achieve loading, resulting in weak bonding between the active components and the substrate. In practical applications, the active components are easily detached due to factors such as airflow erosion and humidity changes, leading to catalyst deactivation and requiring frequent replacement, significantly increasing operating costs.

[0006] Secondly, uneven distribution of active components limits catalytic efficiency. Physical loading methods struggle to achieve uniform dispersion of active components within the complex pores of monolithic substrates (such as honeycomb or foam structures). For instance, in impregnation methods, active components tend to accumulate on the substrate surface, while the deep pores suffer from insufficient solution penetration, resulting in extremely low loading and a distribution defect of high concentration on the outside and low concentration on the inside. This unevenness not only wastes active components but also causes the catalytic reaction to occur only on the substrate surface, failing to fully utilize the high specific surface area advantage of the monolithic structure.

[0007] Third, the preparation conditions are stringent and the process is highly complex. To improve the binding force between the active component and the substrate, some studies have attempted chemical loading methods (such as sol-gel methods and hydrothermal synthesis methods). However, these methods require high-temperature calcination or high-pressure reactions, which not only consume a lot of energy and require strict equipment, but also easily lead to the destruction of the substrate (such as activated carbon and molecular sieves) structure, weakening its adsorption performance. In addition, chemical loading methods usually require multiple pretreatment steps, which are cumbersome and difficult to meet the needs of large-scale industrial production. Summary of the Invention

[0008] To address the problems of unstable active component loading, uneven distribution, and demanding preparation conditions in existing monolithic formaldehyde catalysts, this invention proposes a MnO... x Modified monolithic activated carbon paper honeycomb catalyst, its preparation method and application.

[0009] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a MnO x A method for preparing modified monolithic activated carbon paper honeycomb catalysts is proposed, which generates MnOx-modified monolithic activated carbon paper honeycomb catalysts in situ in one step through the principle of micro-electrochemical cells.

[0011] Further, the preparation method includes the following steps: placing the pretreated activated carbon paper honeycomb in a potassium permanganate precursor solution, reacting at room temperature, washing the resulting activated carbon paper honeycomb until neutral, and drying to obtain the MnO. x Modified monolithic activated carbon paper honeycomb catalyst.

[0012] The core innovation of this invention lies in driving the in-situ growth of manganese oxide using a microbial electrochemical cell (MEC) mechanism. Specifically, activated carbon paper honeycomb is used as an electron donor (negative electrode), and potassium permanganate precursor solution is used as an oxidant (positive electrode). The microporous structure of the activated carbon paper honeycomb surface forms a microscale electrochemical interface with the potassium permanganate solution. Under room temperature conditions, the activated carbon substrate releases electrons from the active sites on the activated carbon surface through the MEC electron transfer mechanism, which are then transferred to the potassium permanganate solution via the microporous interface. This drives a controllable reduction reaction of potassium permanganate, resulting in the growth of MnO. x The active components grow slowly and uniformly in situ on the surface of activated carbon paper honeycomb to form a continuous coating. This process overcomes the limitation of traditional physical loading methods where the active components are adsorbed solely by van der Waals forces, and significantly enhances the MnO coating through the electronic coupling effect of MEC. x The chemical bonding with the activated carbon substrate ensures that the active components are not easily detached during long-term use.

[0013] The preparation method provided by this invention is simple to operate and highly applicable. It does not require complex equipment or high temperature and high pressure conditions. It only requires immersing activated carbon paper honeycomb in potassium permanganate precursor solution, optimizing the micro-electric field environment by pH adjustment, and utilizing the electron transfer mechanism of MEC to complete the MnO preparation. x The in-situ growth of activated carbon paper honeycomb is not limited by the shape of the substrate (flat, honeycomb, and irregular structures are all applicable), and fully retains the structural advantages of activated carbon paper honeycomb such as large specific surface area, low wind resistance, and high stability.

[0014] Furthermore, the mass concentration of potassium permanganate in the potassium permanganate precursor solution is 0.04-0.12 mol / L, and the pH of the potassium permanganate precursor solution is 6-11.

[0015] Furthermore, the volume ratio of the pretreated activated carbon paper honeycomb to the potassium permanganate precursor solution is (1:6) to (1:12); the mass ratio of the pretreated activated carbon paper honeycomb to potassium permanganate is (4:1) to (4:3).

[0016] Furthermore, the volume ratio of the pretreated activated carbon paper honeycomb to the potassium permanganate precursor solution is 1:6; the mass ratio of the pretreated activated carbon paper honeycomb to the potassium permanganate solution is 4:2.

[0017] Furthermore, the reaction time at room temperature is 6 hours.

[0018] Furthermore, the preparation method of the pretreated activated carbon paper honeycomb includes the following steps: placing the activated carbon paper honeycomb in a sodium carbonate solution, reacting it in a water bath, removing it, washing it until neutral, and drying it to obtain the pretreated activated carbon paper honeycomb.

[0019] Furthermore, the water bath reaction is carried out at a temperature of 50°C for 45 minutes.

[0020] Activated carbon paper honeycomb as an in-situ growth medium for MnO in MEC x The substrate, whose surface chemical properties and pore structure directly affect MnO x The loading effect of the original activated carbon, with its large number of acidic functional groups on the surface, neutralizes the electron release capacity of the activated carbon as a negative electrode in the MEC reaction, resulting in a slow reduction rate of potassium permanganate and MnO. x The amount produced is small; the pore distribution of the original activated carbon is mainly micropores, and potassium permanganate solution has difficulty penetrating into the deep pores, easily forming a "concentrated on the outside and dilute on the inside" MnO. x Loading defects; residual ash or uncarbonized organic matter on the surface can hinder electron transport in MECs. To optimize the in-situ growth of MnO in microelectrochemical cells (MECs)... xTo improve the uniformity and stability of active components, this invention employs alkaline pretreatment of activated carbon paper honeycomb (AC) with sodium carbonate solution, achieving the following key optimizations: First, by neutralizing acidic functional groups, alkaline sites are increased, enhancing the electron release capacity of activated carbon and thus regulating surface charge; Second, by gently etching amorphous carbon, micropores are enlarged and mesopores are formed, promoting the penetration of potassium permanganate solution into deeper pores and optimizing the pore structure; Third, by dissolving ash and organic matter, impurities on the carbon surface are cleaned, reducing obstacles to electron transfer and enhancing MnO. x Chemical bonding with activated carbon.

[0021] This invention optimizes the surface chemical properties and pore structure of activated carbon paper honeycomb through alkaline pretreatment with sodium carbonate, thus enabling the in-situ growth of uniform and robust MnO4 on MEC. x The active component provides crucial support, effectively solving the problems of uneven loading and weak binding force of active components in traditional monolithic catalysts.

[0022] Secondly, the present invention provides a MnO x The modified monolithic activated carbon paper honeycomb catalyst was prepared by the above-described method. The manganese oxide loading in the monolithic activated carbon paper honeycomb catalyst was 35%~39%, wherein the manganese oxide had a burnnssite (δ-MnO2) structure.

[0023] The MnO provided by this invention x The modified monolithic activated carbon paper honeycomb catalyst achieves dual synergistic effects through "MEC-driven in-situ growth" and "structure-function synergy": on the one hand, the high specific surface area of ​​the activated carbon paper honeycomb efficiently adsorbs and enriches formaldehyde molecules; on the other hand, the uniformly loaded MnO x (By controlling the formation of a δ-MnO2 crystal form with high oxygen vacancy concentration via MEC) the catalyst can catalytically oxidize formaldehyde to CO2 and H2O at room temperature. The synergistic effect of both components enables the catalyst to exhibit excellent purification performance for low concentrations of formaldehyde at room temperature, significantly outperforming single activated carbon adsorption or traditional supported MnO2. x Its catalytic performance provides an efficient and stable solution for formaldehyde purification.

[0024] Thirdly, the present invention provides the above-mentioned MnO x Application of modified monolithic activated carbon paper honeycomb catalyst in formaldehyde purification.

[0025] Compared with the prior art, the present invention has the following advantages and technical effects:

[0026] The MnO provided by this invention xThe modified monolithic activated carbon paper honeycomb catalyst is prepared under mild conditions, with a simple process and no restrictions on substrate shape. The manganese oxide active component in the prepared catalyst is firmly supported and uniformly distributed on the paper honeycomb substrate. This catalyst has a large specific surface area, which is beneficial for formaldehyde adsorption. Furthermore, by adjusting the pH during the reaction, the catalyst has abundant oxygen vacancies, which is conducive to the catalytic oxidation of formaldehyde. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 MnO in Example 5 x XRD pattern of the modified monolithic activated carbon paper honeycomb catalyst;

[0029] Figure 2 The image shows the Raman diagram of the MnOx-modified monolithic activated carbon paper honeycomb catalyst in Example 5.

[0030] Figure 3 MnO in Example 5 x Scanning electron microscope image of the modified monolithic activated carbon paper honeycomb catalyst;

[0031] Figure 4 MnO in Example 5 x N2 adsorption-desorption isotherms of modified monolithic activated carbon paper honeycomb catalyst;

[0032] Figure 5 MnO in Example 5 x Pore ​​size distribution diagram of modified monolithic activated carbon paper honeycomb catalyst;

[0033] Figure 6 MnO in Example 5 x XPS test results of the modified monolithic activated carbon paper honeycomb catalyst;

[0034] Figure 7 MnO prepared in Example 5 x Comparison of saturated adsorption test results of modified monolithic activated carbon paper honeycomb catalyst and blank activated carbon paper honeycomb for different formaldehyde concentrations. Detailed Implementation

[0035] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0036] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0037] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0038] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0039] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0040] This embodiment provides a MnO x The preparation method of the modified monolithic activated carbon paper honeycomb catalyst involves a one-step in-situ generation of MnOx-modified monolithic activated carbon paper honeycomb catalyst using the principle of micro-electrochemical cells. The specific steps include: placing pretreated activated carbon paper honeycomb in a potassium permanganate precursor solution, reacting at room temperature, washing the resulting activated carbon paper honeycomb until neutral, and drying to obtain the MnOx-modified monolithic activated carbon paper honeycomb catalyst. x Modified monolithic activated carbon paper honeycomb catalyst.

[0041] The MnO provided by this invention xThe modified monolithic activated carbon paper honeycomb catalyst was prepared via a micro-electrochemical interfacial reaction between an activated carbon paper honeycomb substrate and a potassium permanganate precursor solution. Using the activated carbon paper honeycomb as the electron donor (negative electrode) and potassium permanganate as the oxidant (positive electrode), the controlled reduction of potassium permanganate was driven by the electron transfer mechanism of the micro-electrochemical cell, resulting in the slow, in-situ growth of uniform and robust MnO on the surface of the activated carbon paper honeycomb at room temperature. x The catalytic coating, after drying, yields the target catalyst. The innovation of this invention lies in the fact that the electron transfer process based on the MEC principle significantly enhances the binding force between the manganese oxide active component and the activated carbon substrate. Simultaneously, by optimizing the micro-electric field environment through pH control, the specific surface area of ​​the catalyst is effectively increased and oxygen vacancies are enriched, overcoming the technical bottlenecks of easy detachment and uneven distribution of active components in traditional physical loading methods. This catalyst integrates the high specific surface area adsorption advantages of activated carbon and MnO… x The catalytic oxidation performance of this material achieves a synergistic effect of "adsorption-enrichment-catalytic oxidation" in formaldehyde purification scenarios. It demonstrates significant purification effects on low-concentration formaldehyde at room temperature, outperforming single adsorption or catalytic materials. The preparation method provided by this invention is mild, simple, and unrestricted by substrate shape, making it suitable for large-scale industrial production.

[0042] In some preferred embodiments of the present invention, the concentration of potassium permanganate in the potassium permanganate precursor solution is 0.04-0.12 mol / L; the pH of the potassium permanganate precursor solution is 6-11. For example, the concentration of potassium permanganate is 0.04, 0.12, or 0.08 mol / L, and the pH of the potassium permanganate precursor solution is 6, 9, or 11.

[0043] In some preferred embodiments of the present invention, the volume ratio of the pretreated activated carbon paper honeycomb to the potassium permanganate precursor solution is (1:6) to (1:12); the mass ratio of the pretreated activated carbon paper honeycomb to potassium permanganate is (4:1) to (4:3). Exemplarily, the volume ratio of the pretreated activated carbon paper honeycomb to the potassium permanganate precursor solution is 1:6 or 1:12; the mass ratio of the pretreated activated carbon paper honeycomb to potassium permanganate is 4:1, 4:3, or 4:2.

[0044] In some preferred embodiments of the present invention, the reaction time at room temperature is 6-12 hours, the drying temperature is 80-100°C, and the drying time is 6-12 hours. For example, the reaction time at room temperature is 6 hours, the drying temperature is 80°C, and the drying time is 8 hours.

[0045] In some preferred embodiments of the present invention, the preparation method of the pretreated activated carbon paper honeycomb includes the following steps: weighing anhydrous sodium carbonate, adding it to deionized water, stirring until completely dissolved, and preparing a sodium carbonate solution of 0.1~0.3 mol / L. The activated carbon paper honeycomb is ultrasonically cleaned in deionized water for 10~20 minutes to remove surface dust and loose particles; then transferred to a forced-air drying oven and dried at 60℃ to ensure no moisture residue remains on the surface. The dried activated carbon paper honeycomb is completely immersed in the sodium carbonate solution prepared in the above step, and the solution temperature is controlled at 50℃ using a constant-temperature water bath, and allowed to stand for 30~60 minutes. The treated activated carbon paper honeycomb is removed, and the surface and pores are repeatedly rinsed with deionized water until the pH of the rinsing solution is neutral to avoid residual sodium carbonate affecting the subsequent MEC reaction. The washed activated carbon paper honeycomb is transferred to a vacuum drying oven and vacuum dried at 60℃ (to avoid high-temperature oxidation of the activated carbon surface). After drying, it is sealed and stored to prevent the adsorption of moisture or impurities from the environment. For example, the concentration of the sodium carbonate solution is 0.2 mol / L; the water bath reaction temperature is 50°C and the time is 45 min.

[0046] This embodiment also provides a MnO x The modified monolithic activated carbon paper honeycomb catalyst was prepared by the above preparation method.

[0047] This embodiment also provides the above-mentioned MnO x Application of modified monolithic activated carbon paper honeycomb catalyst in formaldehyde purification.

[0048] The room temperature in this invention refers to 25±2℃.

[0049] The anhydrous sodium carbonate used in the embodiments of this invention is of analytical grade.

[0050] Example 1

[0051] S1. Weigh anhydrous sodium carbonate, add it to deionized water, and stir until completely dissolved to prepare a 0.2 mol / L sodium carbonate solution. Place the activated carbon paper honeycomb in deionized water and ultrasonically clean for 15 min to remove surface dust and loose particles. Then transfer it to a forced-air drying oven and dry at 60℃ for 6 h to ensure no moisture residue remains on the surface. Completely immerse the dried activated carbon paper honeycomb in the above sodium carbonate solution, using a constant-temperature water bath to control the solution temperature at 50℃, and let it stand for 45 min. Remove the treated activated carbon paper honeycomb and repeatedly rinse the surface and pores with deionized water until the pH of the rinsing solution is neutral. Transfer the washed activated carbon paper honeycomb to a vacuum drying oven and vacuum dry at 60℃ for 12 h to obtain the pretreated activated carbon paper honeycomb.

[0052] S2. Potassium permanganate was added to water, and the pH of the solution was adjusted to 6 using ammonium chloride and ammonia water to prepare a potassium permanganate precursor solution (concentration of 0.04 mol / L). The pretreated activated carbon paper honeycomb from S1 was added to the obtained potassium permanganate precursor solution, and the reaction was carried out slowly in situ at room temperature for 6 hours. The mass ratio of the pretreated activated carbon paper honeycomb to potassium permanganate was 4:1; the volume ratio of the pretreated activated carbon paper honeycomb to the potassium permanganate precursor solution was 1:6. After the reaction, the activated carbon paper honeycomb was removed and washed with deionized water until the pH was neutral. It was then dried in a forced-air drying oven at 80°C for 8 hours to obtain MnO. x Modified monolithic activated carbon paper honeycomb catalyst.

[0053] Example 2

[0054] S1. Same as Example 1;

[0055] S2. Potassium permanganate was added to water, and the pH was adjusted to 6 using ammonium chloride and ammonia water to prepare a potassium permanganate precursor solution (concentration of 0.12 mol / L). The pretreated activated carbon paper honeycomb from S1 was added to the obtained potassium permanganate precursor solution, and the reaction was carried out slowly in situ at room temperature for 6 hours. The mass ratio of the pretreated activated carbon paper honeycomb to potassium permanganate was 4:3; the volume ratio of the pretreated activated carbon paper honeycomb to the potassium permanganate precursor solution was 1:6. After the reaction, the activated carbon paper honeycomb was removed, washed with deionized water until the pH was neutral, and dried in a forced-air drying oven at 80°C for 8 hours to obtain MnO. x Modified monolithic activated carbon paper honeycomb catalyst.

[0056] Example 3

[0057] S1. Same as Example 1;

[0058] S2. Potassium permanganate was added to water, and the pH was adjusted to 9 using ammonium chloride and ammonia water to prepare a potassium permanganate precursor solution (concentration of 0.08 mol / L). The pretreated activated carbon paper honeycomb from S1 was added to the obtained potassium permanganate precursor solution, and the reaction was carried out slowly in situ at room temperature for 6 hours. The mass ratio of the pretreated activated carbon paper honeycomb to potassium permanganate was 2:1; the volume ratio of the pretreated activated carbon paper honeycomb to the potassium permanganate precursor solution was 1:6. After the reaction, the activated carbon paper honeycomb was removed and washed with deionized water until the pH was neutral. It was then dried in a forced-air drying oven at 80°C for 8 hours to obtain MnO. x Modified monolithic activated carbon paper honeycomb catalyst.

[0059] Example 4

[0060] S1. Same as Example 1;

[0061] S2. Potassium permanganate was added to water, and the pH was adjusted to 11 using ammonium chloride and ammonia water to prepare a potassium permanganate precursor solution (concentration of 0.08 mol / L). The pretreated activated carbon paper honeycomb from S1 was added to the obtained potassium permanganate precursor solution, and the reaction was carried out slowly in situ at room temperature for 6 hours. The mass ratio of the pretreated activated carbon paper honeycomb to potassium permanganate was 2:1; the volume ratio of the pretreated activated carbon paper honeycomb to the potassium permanganate precursor solution was 1:6. After the reaction, the activated carbon paper honeycomb was removed and washed with deionized water until the pH was neutral. It was then dried in a forced-air drying oven at 80°C for 8 hours to obtain MnO. x Modified monolithic activated carbon paper honeycomb catalyst.

[0062] Example 5

[0063] S1. Same as Example 1;

[0064] S2. Potassium permanganate was added to water, and the pH was adjusted to 6 using ammonium chloride and ammonia water to prepare a potassium permanganate precursor solution (concentration of 0.08 mol / L). The pretreated activated carbon paper honeycomb from S1 was added to the obtained potassium permanganate precursor solution, and the reaction was carried out slowly in situ at room temperature for 6 hours. The mass ratio of the pretreated activated carbon paper honeycomb to potassium permanganate was 2:1; the volume ratio of the pretreated activated carbon paper honeycomb to the potassium permanganate precursor solution was 1:6. After the reaction, the activated carbon paper honeycomb was removed and washed with deionized water until the pH was neutral. It was then dried in a forced-air drying oven at 80°C for 8 hours to obtain MnO. x Modified monolithic activated carbon paper honeycomb catalyst.

[0065] Figure 1 MnO prepared in Example 5 x XRD pattern of the modified monolithic activated carbon paper honeycomb catalyst. The XRD pattern of this catalyst shows two broad and weak diffraction peaks at 36.2° and 65.5°, which correspond to the characteristic peak positions of δ-MnO2 (JCPDS 80-1098), indicating that δ-MnO2 was successfully loaded onto the activated carbon paper honeycomb. Manganese, as the most active catalyst among transition metal oxides, has been widely used for HCHO oxidation due to its rich valence states and structural flexibility. Among various crystal structures (α-, β-, γ-, and δ-), δ-MnO2, due to its easy release of lattice oxygen and its two-dimensional layered structure, is the preferred choice with the highest catalytic activity, which is one of the reasons for the excellent formaldehyde purification performance of the catalyst.

[0066] MnO was further analyzed by Raman spectroscopy. x The structural properties of the modified monolithic activated carbon paper honeycomb catalyst are shown in the following results. Figure 2 As shown. Figure 2 The Raman spectroscopy plot of the MnOx-modified monolithic activated carbon paper honeycomb catalyst in Example 5 shows that at 572 cm⁻¹...-1 and 649cm -1 Two main characteristic peaks can be identified at 649 cm⁻¹, which are characteristic Raman bands of the stretching vibration of Mn-O in δ-MnO₂. -1 A distinct peak can be observed, indicating that MnO2 is more enriched on the surface of activated carbon.

[0067] Figure 3 MnO prepared in Example 5 x Scanning electron microscopy (SEM) images of the modified monolithic activated carbon paper honeycomb catalyst reveal its surface microstructure, showing a uniform and firmly adhered MnO layer on the surface of the activated carbon paper honeycomb substrate. x The successful loading of manganese oxides onto the surface of activated carbon fibers indicates a greater number of active sites, which is more conducive to the efficient purification of formaldehyde. Furthermore, the surface manganese oxide active layer contains abundant pores, which facilitates the adsorption and accumulation of formaldehyde gas on the catalyst surface, providing sufficient contact for subsequent formaldehyde catalysis. The synergistic effect of adsorption and catalysis effectively promotes the catalytic oxidation of HCHO.

[0068] Figure 4 MnO in Example 5 x N2 adsorption-desorption isotherms of modified monolithic activated carbon paper honeycomb catalyst; Figure 5 MnO in Example 5 x Pore ​​size distribution diagram of modified monolithic activated carbon paper honeycomb catalyst; analysis Figure 4 and Figure 5 It can be seen that the catalyst isotherm is type IV, with an H4 type hysteresis loop, and MnO x The modified monolithic activated carbon paper honeycomb has a rich BET specific surface area, reaching 379.6 m². 2 / s, the pore size distribution of the catalyst shows that there are a large number of pores of 3-10nm, with a rich mesoporous structure. The rich mesoporous structure can provide more pores and surface area, which will increase the adsorption of gas and make it more conducive to formaldehyde gas entering the interior of the catalyst channel and fully contacting the active sites.

[0069] Surface chemical analysis of the catalyst was performed using XPS, and the results are as follows: Figure 6 As shown; Figure 6 MnO in Example 5 x XPS spectra of modified monolithic activated carbon paper honeycomb catalyst; in Mn2p 3 / 2 The spectrum shows that this catalyst has a higher Mn content. 3+ / Mn 4+ The ratio, i.e., the catalyst with a higher Mn content 3+ Content, of which Mn 3+ The proportion is often considered to be closely related to the oxygen vacancy concentration in the material. Because Mn3+ relative to Mn 4+ It has a lower valence state and is more easily formed in MnO. x Oxygen vacancies are formed in the crystal lattice, and these vacancies can act as active sites to adsorb and activate oxygen molecules in the air, transforming them into more active adsorbed oxygen species, thereby enhancing the oxidative decomposition of pollutants such as formaldehyde.

[0070] MnO in Example 5 x The surface chemical composition of the modified monolithic activated carbon paper honeycomb catalyst is shown in Table 1.

[0071] Table 1

[0072]

[0073] As shown in Table 1, MnO in Example 5 x Surface Mn of modified monolithic activated carbon paper honeycomb catalyst 3+ The content is 49.01%, indicating that the active layer of manganese oxide in the catalyst has a high proportion of Mn. 3+ ;and Mn 3+ The increase in oxygen vacancies leads to the formation of more oxygen vacancies in the active layer. In order to maintain the surface electrical balance, a higher concentration of oxygen vacancies in the active layer will be more conducive to the adsorption, activation and electron transfer of O2 molecules, thereby forming more active oxygen species and improving the catalytic purification activity of formaldehyde.

[0074] Example 6

[0075] S1. Same as Example 1;

[0076] S2. Potassium permanganate was added to water, and the pH was adjusted to 6 using ammonium chloride and ammonia water to prepare a potassium permanganate precursor solution (concentration of 0.04 mol / L). The pretreated activated carbon paper honeycomb from S1 was added to the obtained potassium permanganate precursor solution, and the reaction was carried out slowly in situ at room temperature for 6 hours. The mass ratio of the pretreated activated carbon paper honeycomb to potassium permanganate was 2:1; the volume ratio of the pretreated activated carbon paper honeycomb to the potassium permanganate precursor solution was 1:12. After the reaction, the activated carbon paper honeycomb was removed and washed with deionized water until the pH was neutral. It was then dried in a forced-air drying oven at 80°C for 8 hours to obtain MnO. x Modified monolithic activated carbon paper honeycomb catalyst.

[0077] Table 2 shows the MnO prepared in Examples 1-6. x Manganese oxide loading in modified monolithic activated carbon paper honeycomb catalyst.

[0078] Table 2

[0079]

[0080] Comparative Example 1

[0081] S1. Same as Example 1;

[0082] S2. Potassium permanganate was added to water, and the pH was adjusted to 6 using ammonium chloride and ammonia water to prepare a potassium permanganate precursor solution (concentration of 0.02 mol / L). The pretreated activated carbon paper honeycomb from S1 was added to the obtained potassium permanganate precursor solution, and the reaction was carried out slowly in situ at room temperature for 6 hours. The mass ratio of the pretreated activated carbon paper honeycomb to potassium permanganate was 8:1; the volume ratio of the pretreated activated carbon paper honeycomb to the potassium permanganate precursor solution was 1:6. After the reaction, the activated carbon paper honeycomb was removed and washed with deionized water until the pH was neutral. It was then dried in a forced-air drying oven at 80°C for 8 hours to obtain MnO. x Modified monolithic activated carbon paper honeycomb catalyst.

[0083] Comparative Example 2

[0084] S1. Same as Example 1;

[0085] S2. Potassium permanganate was added to water, and the pH was adjusted to 6 using ammonium chloride and ammonia water to prepare a potassium permanganate precursor solution (concentration of 0.008 mol / L). The pretreated activated carbon paper honeycomb from S1 was added to the obtained potassium permanganate precursor solution, and the reaction was carried out slowly in situ at room temperature for 6 hours. The mass ratio of the pretreated activated carbon paper honeycomb to potassium permanganate was 20:1; the volume ratio of the pretreated activated carbon paper honeycomb to the potassium permanganate precursor solution was 1:6. After the reaction, the activated carbon paper honeycomb was removed and washed with deionized water until the pH was neutral. It was then dried in a forced-air drying oven at 80°C for 8 hours to obtain MnO. x Modified monolithic activated carbon paper honeycomb catalyst.

[0086] Comparative Example 3

[0087] S1. Same as Example 1;

[0088] S2. Potassium permanganate was added to water, and the pH was adjusted to 6 using ammonium chloride and ammonia water to prepare a potassium permanganate precursor solution (concentration of 0.16 mol / L). The pretreated activated carbon paper honeycomb from S1 was added to the obtained potassium permanganate precursor solution, and the reaction was carried out slowly in situ at room temperature for 6 hours. The mass ratio of the pretreated activated carbon paper honeycomb to potassium permanganate was 2:1; the volume ratio of the pretreated activated carbon paper honeycomb to the potassium permanganate precursor solution was 1:3. After the reaction, the activated carbon paper honeycomb was removed and washed with deionized water until the pH was neutral. It was then dried in a forced-air drying oven at 80°C for 8 hours to obtain MnO. x Modified monolithic activated carbon paper honeycomb catalyst.

[0089] Comparative Example 4

[0090] S1. Same as Example 1;

[0091] S2. Potassium permanganate was added to water, and the pH was adjusted to 6 using ammonium chloride and ammonia water to prepare a potassium permanganate precursor solution (concentration of 0.028 mol / L). The pretreated activated carbon paper honeycomb from S1 was added to the obtained potassium permanganate precursor solution, and the reaction was carried out slowly in situ at room temperature for 6 hours. The mass ratio of the pretreated activated carbon paper honeycomb to potassium permanganate was 2:1; the volume ratio of the pretreated activated carbon paper honeycomb to the potassium permanganate precursor solution was 1:18. After the reaction, the activated carbon paper honeycomb was removed and washed with deionized water until the pH was neutral. It was then dried in a forced-air drying oven at 80°C for 8 hours to obtain MnO. x Modified monolithic activated carbon paper honeycomb catalyst.

[0092] Comparative Example 5

[0093] S1. Same as Example 1;

[0094] S2. Potassium permanganate was added to water, and the pH was adjusted to 3 using ammonium chloride and ammonia water to prepare a potassium permanganate precursor solution (concentration of 0.08 mol / L). The pretreated activated carbon paper honeycomb from S1 was added to the obtained potassium permanganate precursor solution, and the reaction was carried out slowly in situ at room temperature for 6 hours. The mass ratio of the pretreated activated carbon paper honeycomb to potassium permanganate was 2:1; the volume ratio of the pretreated activated carbon paper honeycomb to the potassium permanganate precursor solution was 1:6. After the reaction, the activated carbon paper honeycomb was removed and washed with deionized water until the pH was neutral. It was then dried in a forced-air drying oven at 80°C for 8 hours to obtain MnO. x Modified monolithic activated carbon paper honeycomb catalyst.

[0095] Performance testing

[0096] 1) Formaldehyde conversion rate evaluation test

[0097] The catalysts (160×160×10mm) prepared in Examples 1-6 and Comparative Examples 1-5 were mounted on a homemade air purifier and then placed in a formaldehyde-simulated purification environment chamber (700×700×500mm, with an internal enclosed space of approximately 0.245m²) while wearing operating gloves. 3 Formaldehyde purification performance was tested. Specific test conditions were as follows: solid paraformaldehyde was used as the gas source, and formaldehyde gas was generated by heating and volatilizing it on a heating platform. The initial formaldehyde concentration in the chamber was controlled at 1.0 ± 0.1 mg / m³. 3 A built-in fan was used to achieve rapid diffusion of formaldehyde gas in the chamber. A formaldehyde detector was used to test the real-time formaldehyde concentration in the chamber every 2 minutes, and the formaldehyde conversion rate was calculated using the following formula. Table 3 shows the formaldehyde conversion rate measurement results after 1 hour.

[0098]

[0099] Table 3

[0100]

[0101] Table 3 shows that adjusting the pH value of the potassium permanganate solution, the volume ratio of activated carbon paper honeycomb substrate to potassium permanganate precursor solution, the mass ratio of activated carbon paper honeycomb to potassium permanganate, and the amount of MnO in the catalyst can significantly improve the effectiveness of the drug. x The loading amount was determined to obtain catalyst samples for Comparative Examples 1-5, and their formaldehyde conversion rates were tested. Comparison with the formaldehyde conversion rate test data of the catalysts obtained in Examples 1-5 confirmed that the preparation of MnO... x When modifying activated carbon paper honeycomb catalysts, the pH of the potassium permanganate solution, the volume ratio of activated carbon paper honeycomb to potassium permanganate precursor solution, and the mass ratio of activated carbon paper honeycomb to potassium permanganate jointly determine the performance of the resulting catalyst, and control the MnO content in the catalyst. x The load is 35%-39%.

[0102] 2) Catalyst loading robustness test

[0103] The catalyst prepared in Example 5 was placed in 50 mL of deionized water and ultrasonicated in an ultrasonic cleaner for 30 min. The sample weight was measured before and after ultrasonication, and the mass loss was calculated. The results are shown in Table 4.

[0104] Table 4

[0105]

[0106] As can be seen from Table 4, the MnO prepared by this invention x The modified monolithic activated carbon paper honeycomb catalyst exhibits high loading stability.

[0107] 3) MnO x Performance Study of Modified Monolithic Activated Carbon Paper Honeycomb Catalyst

[0108] MnO prepared according to the procedure in Example 5 x The modified monolithic activated carbon paper honeycomb catalyst (160×160×10mm) and blank activated carbon paper honeycomb were compared in saturated adsorption tests with different formaldehyde concentrations. The results are as follows: Figure 7 As shown, the blank activated carbon paper honeycomb exhibits a certain adsorption effect on formaldehyde, but when the formaldehyde concentration increases, the formaldehyde removal rate of the blank activated carbon paper honeycomb begins to decrease rapidly. When the formaldehyde concentration reaches 10 ppm, its formaldehyde removal rate is already below 50%. In contrast, as the formaldehyde concentration gradually increases, MnO... xAlthough the formaldehyde removal rate of the modified monolithic activated carbon paper honeycomb catalyst also decreased, the reduction was small; when the formaldehyde concentration increased to 270 ppm, its formaldehyde removal rate still remained above 50%, exhibiting a higher formaldehyde saturation adsorption capacity. This can be attributed in part to the MnO content in the composite material. x The abundant mesoporous structure of the active layer is more conducive to formaldehyde adsorption and accumulation; on the other hand, the MnO of the composite material... x The large number of oxygen vacancies in the active layer also makes it more conducive to the oxidation and decomposition of formaldehyde.

[0109] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A MnO x A method for producing a modified monolithic activated carbon paper honeycomb catalyst, characterized by, One-step in-situ generation of MnO by micro-electrochemical cell principle x Modified monolithic activated carbon paper honeycomb catalyst.

2. The production method according to claim 1, characterized by, The method comprises the following steps: The pretreated activated carbon paper honeycomb is placed in a potassium permanganate precursor solution, and after reaction at room temperature, the activated carbon paper honeycomb is washed to neutral, and after drying, the MnO x Modified monolithic activated carbon paper honeycomb catalyst.

3. The production method according to claim 2, characterized by, The concentration of potassium permanganate in the potassium permanganate precursor solution is 0.04-0.12 mol / L; and the pH of the potassium permanganate precursor solution is 6-11.

4. The production method according to claim 3, characterized by, The volume ratio of the pretreated activated carbon paper honeycomb and the potassium permanganate precursor solution is 1: (6-12) ; and the mass ratio of the pretreated activated carbon paper honeycomb and the potassium permanganate is 4: (1-3).

5. The preparation method according to claim 4, characterized in that, The volume ratio of the pretreated activated carbon paper honeycomb and the potassium permanganate precursor solution is 1:6; and the mass ratio of the pretreated activated carbon paper honeycomb and the potassium permanganate is 4:

2.

6. The preparation method according to claim 2, characterized in that, The reaction time at room temperature is 6 h.

7. The preparation method according to claim 2, characterized in that, The preparation method of the pretreated activated carbon paper honeycomb comprises the following steps: placing an activated carbon paper honeycomb in a sodium carbonate solution, taking out after water bath reaction, washing to neutral, drying, and obtaining the pretreated activated carbon paper honeycomb.

8. The method of claim 7, wherein, The temperature of the water bath reaction is 50 ℃, and the time is 45 min.

9. A MnO x Modified monolithic activated carbon paper honeycomb catalyst characterized by The method is prepared by the preparation method in any one of claims 1-8.

10. A MnO of claim 9 x Use of modified monolithic activated carbon paper honeycomb catalysts in the purification of formaldehyde.

Images