Low-temperature-resistant active carbon for vehicle and preparation method thereof

Abstract

The application provides a low-temperature-resistant and long-acting purification vehicle-mounted activated carbon and a preparation method thereof, and belongs to the technical field of activated carbon. The application constructs a self-driven chemical regeneration purification system by compounding two functional materials on the activated carbon. The gallium-doped zinc oxide nanorod utilizes the enhanced thermoelectric effect to generate an instantaneous thermoelectric surface potential difference when the ambient temperature changes, which serves as the internal electrochemical driving force of the system. The cerium dioxide particles coated with cesium phosphotungstate, which is a pollutant oxidant, improves the long-term stability in a humid environment by converting the easily soluble phosphotungstate into insoluble cesium salt. The thermoelectric surface potential difference induced by temperature fluctuation is distributed and conducted in the conductive network, which helps to extract electrons from the reduced center and restore its high valence state, completing its online regeneration. The synergistic effect enables the material to maintain the catalytic activity by utilizing the ambient temperature difference, thereby realizing long-acting and long-keeping purification under the conditions of no light and low temperature.

Description

Technical Field

[0001] This invention belongs to the field of activated carbon technology, and relates to a low-temperature resistant, long-lasting purification vehicle-mounted activated carbon and its preparation method. Background Technology

[0002] In-vehicle air quality, due to the continuous release of volatile organic compounds (VOCs) such as formaldehyde and benzene from the enclosed space and interior materials, has become a significant health hazard for drivers and passengers. Currently, air purification technologies for in-vehicle environments mainly include physical adsorption, chemical oxidation, and catalytic decomposition. While physical adsorption materials, such as activated carbon, are inexpensive, their adsorption capacity is limited; once saturated, they become ineffective or even undergo secondary desorption, failing to fundamentally remove pollutants. To overcome the limitations of physical adsorption, chemically modified activated carbon impregnated with strong oxidants such as potassium permanganate has been developed. However, these materials are essentially consumable purifiers; their oxidant is rapidly depleted through reaction with pollutants, resulting in a very limited lifespan. Furthermore, under the high humidity conditions common in in-vehicle environments, water-soluble oxidants are at risk of migration and loss, severely affecting their performance stability and durability.

[0003] While photocatalysis can mineralize pollutants, its activation requires continuous ultraviolet light irradiation, which is blocked by most ultraviolet rays inside vehicle windows, resulting in extremely low efficiency in practical automotive applications. Although some catalysts that can operate at low temperatures (such as precious metal or manganese-based catalysts) have been developed in recent years, they still face the challenge of catalytic active sites being poisoned by intermediate products or moisture over time, gradually losing activity and being unable to self-recover, making it difficult to meet the requirements for long-lasting efficacy. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a low-temperature resistant, long-lasting activated carbon for vehicle purification and its preparation method. This application constructs a self-driven chemical regeneration purification system by composited two functional materials onto activated carbon. Gallium-doped zinc oxide nanorods utilize their enhanced pyroelectric effect to generate an instantaneous pyroelectric surface potential difference when the ambient temperature changes, serving as the internal electrochemical driving force of the system. Meanwhile, cesium phosphotungstic acid-coated cerium dioxide particles, acting as pollutant oxidants, improve long-term stability in humid environments by converting easily soluble phosphotungstic acid into insoluble cesium salts. Finally, through a charge transport network constructed from conductive carbon black, the pyroelectric surface potential difference induced by temperature fluctuations is distributed and conducted within the conductive network, facilitating the extraction of electrons from the reduced centers and the restoration of their high valence state, thus completing online regeneration. This synergistic effect enables the material to maintain its catalytic activity using ambient temperature differences, thereby achieving long-lasting and sustained purification under light-free and low-temperature conditions.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing low-temperature resistant and long-lasting activated carbon for vehicle purification, the method comprising:

[0007] S1: Coconut shell activated carbon particles are immersed in zinc acetate ethanol solution, and the immersion-drying process is repeated. The carbon is then placed under a nitrogen atmosphere and heat-treated to obtain an activated carbon substrate with seed crystals. Zinc nitrate, gallium nitrate and hexamethylenetetramine are dispersed in deionized water to obtain a modification solution. The activated carbon substrate with seed crystals is immersed in the modification solution to obtain reaction solution A. The reaction is carried out hydrothermally, washed, and dried to obtain activated carbon loaded with gallium-doped zinc oxide nanorods.

[0008] S2: Prepare a cerium nitrate solution, add ammonia water to adjust the pH, stir continuously to react, centrifuge, wash to obtain a cerium hydroxide precursor, calcine the cerium hydroxide precursor to obtain cerium dioxide nanoparticles, disperse the cerium dioxide nanoparticles in a mixed solvent to obtain suspension B, add phosphotungstic acid solution to adjust the pH to obtain reaction solution C, stir to adsorb, add cesium chloride solution to obtain reaction solution D, stir to react, centrifuge, wash, dry to obtain cesium phosphotungstic acid-coated cerium dioxide nanoparticles, wherein the mixed solvent is a mixture of deionized water and anhydrous ethanol;

[0009] S3: Cesium phosphotungsten-coated cerium dioxide nanoparticles are dispersed in a mixed solvent to obtain a loaded suspension. Activated carbon loaded with gallium-doped zinc oxide nanorods and conductive carbon black are added, and the mixture is ultrasonically stirred. The impregnated activated carbon loaded with gallium-doped zinc oxide nanorods is then removed and vacuum dried to obtain low-temperature resistant, long-lasting purification vehicle-mounted activated carbon.

[0010] As a preferred technical solution of the present invention, in step S1, the concentration of the zinc acetate ethanol solution is 5-15 mmol / L, for example, it can be 5 mmol / L, 6 mmol / L, 7 mmol / L, 8 mmol / L, 9 mmol / L, 10 mmol / L, 11 mmol / L, 12 mmol / L, 13 mmol / L, 14 mmol / L or 15 mmol / L, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0011] In some optional embodiments, the volume ratio of the zinc acetate ethanol solution to the mass ratio of the coconut shell activated carbon particles is (0.8-1.2) mL:1g, for example, it can be 0.8mL:1g, 0.84mL:1g, 0.88mL:1g, 0.92mL:1g, 0.96mL:1g, 1mL:1g, 1.04mL:1g, 1.08mL:1g, 1.12mL:1g, 1.16mL:1g, or 1.2mL:1g, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0012] In some alternative embodiments, the soaking-drying process is repeated 3-4 times, for example, 3 or 4 times, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0013] In some optional embodiments, the heat treatment temperature is 280-320°C, for example, 280°C, 284°C, 288°C, 292°C, 296°C, 300°C, 304°C, 308°C, 312°C, 316°C or 320°C, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0014] In some optional embodiments, the heat treatment time is 1-2 hours, for example, it can be 1.0 hours, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours or 2.0 hours, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0015] In some optional embodiments, the total concentration of zinc nitrate and gallium nitrate in the modified solution is 0.02-0.05M, for example, it can be 0.020M, 0.023M, 0.026M, 0.029M, 0.032M, 0.035M, 0.038M, 0.041M, 0.044M, 0.047M or 0.050M, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0016] In some optional embodiments, the molar ratio of zinc nitrate to gallium nitrate is (99-98):(1-2), for example, it can be (98.0, 98.1, 98.2, 98.3, 98.4, 98.5, 98.6, 98.7, 98.8, 98.9 or 99.0):(1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2.0), but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0017] The total molar ratio of zinc nitrate and gallium nitrate to hexamethylenetetramine is 1:1.

[0018] In some optional embodiments, the mass-to-volume ratio of the seeded activated carbon substrate to the modified solution is 1g:(100-200)mL, for example, it can be 1g:100mL, 1g:110mL, 1g:120mL, 1g:130mL, 1g:140mL, 1g:150mL, 1g:160mL, 1g:170mL, 1g:180mL, 1g:190mL or 1g:200mL, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0019] In some optional embodiments, the temperature of the hydrothermal reaction of the reaction solution A is 90-100°C, for example, it can be 90°C, 91°C, 92°C, 93°C, 94°C, 95°C, 96°C, 97°C, 98°C, 99°C or 100°C, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0020] In some optional embodiments, the hydrothermal reaction time of the reaction solution A is 8-12 hours, for example, it can be 8.0 hours, 8.4 hours, 8.8 hours, 9.2 hours, 9.6 hours, 10.0 hours, 10.4 hours, 10.8 hours, 11.2 hours, 11.6 hours or 12.0 hours, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0021] As a preferred technical solution of the present invention, in step S2, the concentration of the cerium nitrate solution is 0.1-0.3M, for example, it can be 0.10M, 0.12M, 0.14M, 0.16M, 0.18M, ​​0.20M, 0.22M, 0.24M, 0.26M, 0.28M or 0.30M, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0022] In some alternative embodiments, the concentration of the ammonia water is 1-3M, for example, it can be 1.0M, 1.2M, 1.4M, 1.6M, 1.8M, 2.0M, 2.2M, 2.4M, 2.6M, 2.8M or 3.0M, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0023] In some alternative embodiments, the addition of ammonia to adjust the pH of the cerium nitrate solution to 9-10, for example, to 9.0, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9 or 10.0, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0024] In some optional embodiments, the reaction time after pH adjustment by cerium nitrate is 1-2 hours, for example, 1.0 hours, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours, or 2.0 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0025] In some optional embodiments, the calcination temperature of the cerium hydroxide precursor is 350-450°C, for example, 350°C, 360°C, 370°C, 380°C, 390°C, 400°C, 410°C, 420°C, 430°C, 440°C or 450°C, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0026] In some optional embodiments, the calcination time of the cerium hydroxide precursor is 2-4 hours, for example, 2.0 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, 3.0 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours, or 4.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0027] In some optional embodiments, the volume ratio of deionized water to anhydrous ethanol in the mixed solvent is (3:7)-(5:5), for example, it can be 3.0:7.0, 3.2:6.8, 3.4:6.6, 3.6:6.4, 3.8:6.2, 4.0:6, 4.2:5.8, 4.4:5.6, 4.6:5.4, 4.8:5.2 or 5.0:5.0, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0028] In some optional embodiments, the concentration of the phosphotungstic acid solution is 0.05-0.1M, for example, it can be 0.050M, 0.055M, 0.060M, 0.065M, 0.070M, 0.075M, 0.080M, 0.085M, 0.090M, 0.095M or 0.100M, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0029] In some alternative embodiments, the suspension B is adjusted to pH 2-3 by adding phosphotungstic acid solution, for example, to 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9 or 3.0, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0030] In some optional embodiments, the reaction solution C is stirred and adsorbed for 4-8 hours, for example, 4.0 hours, 4.4 hours, 4.8 hours, 5.2 hours, 5.6 hours, 6.0 hours, 6.4 hours, 6.8 hours, 7.2 hours, 7.6 hours or 8.0 hours, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0031] In some alternative embodiments, the concentration of the cesium chloride solution is 0.1-0.2M, for example, it can be 0.10M, 0.11M, 0.12M, 0.13M, 0.14M, 0.15M, 0.16M, 0.17M, 0.18M, ​​0.19M or 0.20M, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0032] In some optional embodiments, the molar ratio of cesium chloride to phosphotungstic acid in the reaction solution D is (1.2-1.5):1, for example, it can be 1.20:1, 1.23:1, 1.26:1, 1.29:1, 1.32:1, 1.35:1, 1.38:1, 1.41:1, 1.44:1, 1.47:1 or 1.50:1, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0033] In some optional embodiments, the reaction time of the reaction solution D is 2-4 hours, for example, it can be 2.0 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, 3.0 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours or 4.0 hours, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0034] As a preferred technical solution of the present invention, in step S3, the concentration of the loaded suspension is 10-20 mg / mL, for example, it can be 10 mg / mL, 11 mg / mL, 12 mg / mL, 13 mg / mL, 14 mg / mL, 15 mg / mL, 16 mg / mL, 17 mg / mL, 18 mg / mL, 19 mg / mL or 20 mg / mL, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0035] In some optional embodiments, the ultrasonic stirring time is 30-60 min, for example, it can be 30 min, 33 min, 36 min, 39 min, 42 min, 45 min, 48 min, 51 min, 54 min, 57 min or 60 min, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0036] In some optional embodiments, the mass ratio of the cesium phosphotungstenate-coated cerium dioxide nanoparticles to the activated carbon loaded with gallium-doped zinc oxide nanorods is 1:(10-15), for example, it can be 1:10.0, 1:10.5, 1:11.0, 1:11.5, 1:12.0, 1:12.5, 1:13.0, 1:13.5, 1:14.0, 1:14.5 or 1:15.0, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0037] In some optional embodiments, the amount of conductive carbon black fed is 0.02-0.05% of the mass of activated carbon loaded with gallium-doped zinc oxide nanorods, for example, it can be 0.020%, 0.023%, 0.026%, 0.029%, 0.032%, 0.035%, 0.038%, 0.041%, 0.044%, 0.047% or 0.050%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0038] In some optional embodiments, the vacuum drying temperature is 60-80°C, for example, it can be 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C, 78°C or 80°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0039] In some optional embodiments, the vacuum drying time is 6-12 hours, for example, 6.0 hours, 6.6 hours, 7.2 hours, 7.8 hours, 8.4 hours, 9.0 hours, 9.6 hours, 10.2 hours, 10.8 hours, 11.4 hours, or 12.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0040] Secondly, the present invention provides a low-temperature resistant, long-lasting purifying activated carbon for vehicles.

[0041] This application constructs gallium-doped zinc oxide nanorods and cesium phosphotungstenate-coated cerium dioxide nanoparticles on a porous activated carbon carrier in coconut shells to solve the problems of low activity and short lifespan of traditional vehicle purification materials under low temperature and no light conditions. Through a self-driven chemical cycle, it achieves continuous decomposition of pollutants and online regeneration of catalytic materials.

[0042] First, this application prepared gallium-doped zinc oxide nanorods on activated carbon via an in-situ hydrothermal method. The non-centrosymmetric crystal structure of zinc oxide alters its spontaneous polarization intensity upon temperature changes, generating transient charges on its surface. Gallium doping in the zinc oxide lattice introduces free electrons, improving the material's conductivity and facilitating rapid charge separation and transport. Furthermore, it causes lattice distortion, enhancing the material's pyroelectricity. The driving force originates from the amount of temperature change, rather than the absolute temperature difference. Therefore, when the ambient temperature fluctuates, the gallium-doped zinc oxide nanorods can convert the thermal energy change into locally occurring transient high-potential and low-potential regions, providing an electrochemical driving force for subsequent chemical reactions.

[0043] Secondly, this application prepared cesium phosphotungstenate-coated cerium dioxide nanoparticles. These composite particles are responsible for the oxidative decomposition of pollutants. The cerium dioxide core within these particles, after high-temperature calcination, forms a structure rich in oxygen vacancies and Ce. 3+ / Ce 4+ The structure of the redox couple enables the provision of lattice oxygen to participate in deep oxidation reactions and stabilize reaction intermediates. The externally coated phosphotungstic acid is a molecular cluster with strong oxidizing capabilities, exhibiting high reactivity towards pollutants such as formaldehyde, and is itself reduced during oxidation. To avoid the loss of activity due to the water solubility of phosphotungstic acid, this application employs cesium chloride for in-situ ion exchange, generating cesium phosphotungstic acid with low water solubility. This cesium phosphotungstic acid is then fixed onto the cerium dioxide surface, ensuring the structural stability and functional durability of the composite particles in humid environments.

[0044] Synergistic effects also exist in this application. In the final composite material, the introduced conductive carbon black constructs a three-dimensional, highly efficient charge transport network. When the gallium-doped zinc oxide nanorods generate a transient pyroelectric surface potential difference due to temperature changes, this potential difference is distributed along the charge conduction network established by the conductive carbon black, causing the reduced active sites to transport electrons outward, thereby restoring them to a high valence state. Since this regeneration process is driven by the pyroelectric surface potential difference induced by temperature fluctuations, rather than relying on overall heating to a high temperature for thermal regeneration, in-situ reactivation of deactivated sites can be achieved under low-temperature, light-free conditions, overcoming the limitations of traditional automotive catalytic materials that require high-temperature "burn-back" or external energy input. This process completes the online regeneration of catalytically active oxide species. Simultaneously, the electrons generated by the gallium-doped zinc oxide nanorods can activate adsorbed oxygen, forming another oxidation pathway. In this way, a passive adsorption material is transformed into a purification system that can self-maintain catalytic activity using environmental temperature differences, achieving long-term, sustained purification under light-free, low-temperature conditions.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] This application describes the fabrication of gallium-doped zinc oxide nanorods on activated carbon. Utilizing the pyroelectric effect of zinc oxide, surface charges are generated in response to changes in ambient temperature. Gallium doping enhances the efficiency of this process: on the one hand, it improves the conductivity of the material to facilitate charge separation; on the other hand, it strengthens the pyroelectric properties. This transforms environmental thermal fluctuations into locally occurring transient regions of high and low potential, providing an electrochemical driving force for subsequent chemical reactions.

[0047] This application describes the preparation of cesium phosphotungstenate-coated cerium dioxide composite particles, which can be used as a stable and efficient pollutant oxidant. The internal cerium dioxide core is rich in oxygen vacancies and Ce. 3+ / Ce 4+ The redox pair provides active sites and lattice oxygen for deep oxidation reactions. The strong oxidant phosphotungstic acid on the outside is converted into water-insoluble cesium phosphotungstate through ion exchange with cesium ions, avoiding the problem of phosphotungstic acid being easily soluble in water and thus being lost. It is fixed on the surface of cerium dioxide, thereby ensuring the long-term and stable oxidative decomposition capability of the composite particles in humid environments.

[0048] In this application, conductive carbon black constructs a highly efficient charge transport network that connects two functional components in the system. When the ambient temperature changes, the gallium-doped zinc oxide nanorods generate a transient pyroelectric surface potential difference. This potential difference is distributed along the charge conduction network established by the conductive carbon black, causing the reduced active sites to transport electrons outward, thereby restoring them to a high valence state. This enables the online regeneration of the deactivated catalyst, restoring its high oxidation activity, thus achieving long-term purification under light-free and low-temperature conditions. Detailed Implementation

[0049] The technical solution of the present invention will be described in detail below with reference to specific embodiments. The embodiments described herein are specific implementations of the present invention and are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be construed as limiting the implementation of the present invention or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the content disclosed in the claims and the specification of this application. These technical solutions include technical solutions that employ any obvious substitutions and modifications made to the embodiments described herein.

[0050] The chemical reagents used in the embodiments and comparative examples of this invention are all commercially available products and have not undergone further purification or processing.

[0051] Example 1

[0052] This embodiment provides a low-temperature resistant, long-lasting purification vehicle-mounted activated carbon and its preparation method. The preparation method of the low-temperature resistant, long-lasting purification vehicle-mounted activated carbon specifically includes the following steps:

[0053] S1: Coconut shell activated carbon particles are immersed in a 10 mmol / L zinc acetate ethanol solution, wherein the volume ratio of the zinc acetate ethanol solution to the mass ratio of the coconut shell activated carbon particles is 1.1 mL:1 g. The immersion-drying process is repeated 3 times. The solution is then placed under a nitrogen atmosphere and heat-treated at 310 °C for 1.8 h to obtain a seeded activated carbon substrate. Zinc nitrate, gallium nitrate, and hexamethylenetetramine are dispersed in deionized water to obtain a modification solution, wherein the total concentration of zinc nitrate and gallium nitrate is 0.04 M, the molar ratio of zinc nitrate to gallium nitrate is 98.5:1.5, and the molar ratio of the total molar amount of zinc nitrate and gallium nitrate to hexamethylenetetramine is 1:1. The seeded activated carbon substrate is immersed in the modification solution to obtain reaction solution A, wherein the mass-volume ratio of the seeded activated carbon substrate to the modification solution is 1 g:180 mL. The solution is then hydrothermally reacted at 98 °C for 11 h. After washing and drying, activated carbon loaded with gallium-doped zinc oxide nanorods is obtained.

[0054] S2: Prepare a 0.25M cerium nitrate solution, add 2.5M ammonia water to adjust the pH to 9.8, and continue stirring for 1.8h. Centrifuge and wash to obtain cerium hydroxide precursor. Calcinate the cerium hydroxide precursor at 420℃ for 3.5h to obtain cerium dioxide nanoparticles. Disperse the cerium dioxide nanoparticles in a mixed solvent to obtain suspension B, wherein the volume ratio of deionized water to anhydrous ethanol in the mixed solvent is 4:6. Add a 0.08M phosphotungstic acid solution to adjust the pH to 2.8 to obtain reaction solution C. Stir and adsorb for 7h, add a 0.18M cesium chloride solution to obtain reaction solution D, wherein the molar ratio of cesium chloride to phosphotungstic acid in reaction solution D is 1.4:1. Stir and react for 3.2h, centrifuge, wash, and dry to obtain cesium phosphotungstic acid-coated cerium dioxide nanoparticles.

[0055] S3: Cesium phosphotungsten-coated cerium dioxide nanoparticles were dispersed in a mixed solvent to obtain a loaded suspension with a concentration of 18 mg / mL. Activated carbon loaded with gallium-doped zinc oxide nanorods and conductive carbon black were added, and the mixture was ultrasonically stirred for 50 min. The mass ratio of cesium phosphotungsten-coated cerium dioxide nanoparticles to activated carbon loaded with gallium-doped zinc oxide nanorods was 1:14, and the amount of conductive carbon black added was 0.04% of the mass of activated carbon loaded with gallium-doped zinc oxide nanorods. The activated carbon loaded with gallium-doped zinc oxide nanorods was taken out after impregnation and vacuum dried at 75 °C for 10 h to obtain low-temperature resistant and long-lasting purification vehicle activated carbon.

[0056] Example 2

[0057] This embodiment provides a low-temperature resistant, long-lasting purification vehicle-mounted activated carbon and its preparation method. The preparation method of the low-temperature resistant, long-lasting purification vehicle-mounted activated carbon specifically includes the following steps:

[0058] S1: Coconut shell activated carbon particles are immersed in a 5 mmol / L zinc acetate ethanol solution, wherein the volume ratio of the zinc acetate ethanol solution to the mass ratio of the coconut shell activated carbon particles is 1.0 mL:1 g. The immersion-drying process is repeated 4 times. The solution is then placed under a nitrogen atmosphere and heat-treated at 280°C for 1 h to obtain a seeded activated carbon substrate. Zinc nitrate, gallium nitrate, and hexamethylenetetramine are dispersed in deionized water to obtain a modification solution, wherein the total concentration of zinc nitrate and gallium nitrate is 0.02 M, the molar ratio of zinc nitrate to gallium nitrate is 99:1, and the molar ratio of the total molar amount of zinc nitrate and gallium nitrate to hexamethylenetetramine is 1:1. The seeded activated carbon substrate is immersed in the modification solution to obtain reaction solution A, wherein the mass-volume ratio of the seeded activated carbon substrate to the modification solution is 1 g:100 mL. The solution is then hydrothermally reacted at 90°C for 8 h. After washing and drying, activated carbon loaded with gallium-doped zinc oxide nanorods is obtained.

[0059] S2: Prepare a 0.1M cerium nitrate solution, add 1M ammonia water to adjust the pH to 9, and continue stirring for 1 hour. Centrifuge and wash to obtain cerium hydroxide precursor. Calcinate the cerium hydroxide precursor at 350℃ for 2 hours to obtain cerium dioxide nanoparticles. Disperse the cerium dioxide nanoparticles in a mixed solvent to obtain suspension B, wherein the volume ratio of deionized water to anhydrous ethanol in the mixed solvent is 5:5. Add a 0.05M phosphotungstic acid solution to adjust the pH to 2 to obtain reaction solution C. Stir and adsorb for 4 hours. Add a 0.1M cesium chloride solution to obtain reaction solution D, wherein the molar ratio of cesium chloride to phosphotungstic acid in reaction solution D is 1.2:1. Stir and react for 2 hours, centrifuge, wash, and dry to obtain cesium phosphotungstic acid-coated cerium dioxide nanoparticles.

[0060] S3: Cesium phosphotungsten-coated cerium dioxide nanoparticles were dispersed in a mixed solvent to obtain a loaded suspension with a concentration of 10 mg / mL. Activated carbon loaded with gallium-doped zinc oxide nanorods and conductive carbon black were added, and the mixture was ultrasonically stirred for 30 min. The mass ratio of cesium phosphotungsten-coated cerium dioxide nanoparticles to activated carbon loaded with gallium-doped zinc oxide nanorods was 1:10, and the amount of conductive carbon black added was 0.02% of the mass of activated carbon loaded with gallium-doped zinc oxide nanorods. The activated carbon loaded with gallium-doped zinc oxide nanorods was taken out after impregnation and vacuum dried at 60 °C for 6 h to obtain low-temperature resistant and long-lasting purification vehicle activated carbon.

[0061] Example 3

[0062] This embodiment provides a low-temperature resistant, long-lasting purification vehicle-mounted activated carbon and its preparation method. The preparation method of the low-temperature resistant, long-lasting purification vehicle-mounted activated carbon specifically includes the following steps:

[0063] S1: Coconut shell activated carbon particles are immersed in a 12 mmol / L zinc acetate ethanol solution, wherein the volume ratio of the zinc acetate ethanol solution to the mass ratio of the coconut shell activated carbon particles is 0.8 mL:1 g. The immersion-drying process is repeated 3 times. The solution is then placed under a nitrogen atmosphere and heat-treated at 290°C for 1.2 h to obtain a seeded activated carbon substrate. Zinc nitrate, gallium nitrate, and hexamethylenetetramine are dispersed in deionized water to obtain a modification solution, wherein the total concentration of zinc nitrate and gallium nitrate is 0.03 M, the molar ratio of zinc nitrate to gallium nitrate is 98.2:1.8, and the molar ratio of the total molar amount of zinc nitrate and gallium nitrate to hexamethylenetetramine is 1:1. The seeded activated carbon substrate is immersed in the modification solution to obtain reaction solution A, wherein the mass-volume ratio of the seeded activated carbon substrate to the modification solution is 1 g:120 mL. The solution is then hydrothermally reacted at 92°C for 9 h. After washing and drying, activated carbon loaded with gallium-doped zinc oxide nanorods is obtained.

[0064] S2: Prepare a 0.15M cerium nitrate solution, add 1.5M ammonia water to adjust the pH to 9.2, and stir continuously for 1.2h. Centrifuge and wash to obtain cerium hydroxide precursor. Calcinate the cerium hydroxide precursor at 380℃ for 2.5h to obtain cerium dioxide nanoparticles. Disperse the cerium dioxide nanoparticles in a mixed solvent to obtain suspension B, wherein the volume ratio of deionized water to anhydrous ethanol in the mixed solvent is 3:7. Add a 0.06M phosphotungstic acid solution to adjust the pH to 2.2 to obtain reaction solution C. Stir and adsorb for 5h, add a 0.12M cesium chloride solution to obtain reaction solution D, wherein the molar ratio of cesium chloride to phosphotungstic acid in reaction solution D is 1.3:1. Stir and react for 2.8h, centrifuge, wash, and dry to obtain cesium phosphotungstic acid-coated cerium dioxide nanoparticles.

[0065] S3: Cesium phosphotungsten-coated cerium dioxide nanoparticles were dispersed in a mixed solvent to obtain a loaded suspension with a concentration of 12 mg / mL. Activated carbon loaded with gallium-doped zinc oxide nanorods and conductive carbon black were added, and the mixture was ultrasonically stirred for 40 min. The mass ratio of cesium phosphotungsten-coated cerium dioxide nanoparticles to activated carbon loaded with gallium-doped zinc oxide nanorods was 1:11, and the amount of conductive carbon black added was 0.03% of the mass of activated carbon loaded with gallium-doped zinc oxide nanorods. The activated carbon loaded with gallium-doped zinc oxide nanorods was taken out after impregnation and vacuum dried at 65 °C for 8 h to obtain low-temperature resistant and long-lasting purification vehicle activated carbon.

[0066] Example 4

[0067] This embodiment provides a low-temperature resistant, long-lasting purification vehicle-mounted activated carbon and its preparation method. The preparation method of the low-temperature resistant, long-lasting purification vehicle-mounted activated carbon specifically includes the following steps:

[0068] S1: Coconut shell activated carbon particles are immersed in a 15 mmol / L zinc acetate ethanol solution, wherein the volume ratio of the zinc acetate ethanol solution to the mass ratio of the coconut shell activated carbon particles is 1.2 mL: 1 g. The immersion-drying process is repeated 4 times. The solution is then placed under a nitrogen atmosphere and heat-treated at 320°C for 2 h to obtain a seeded activated carbon substrate. Zinc nitrate, gallium nitrate, and hexamethylenetetramine are dispersed in deionized water to obtain a modification solution, wherein the total concentration of zinc nitrate and gallium nitrate is 0.05 M, the molar ratio of zinc nitrate to gallium nitrate is 98:2, and the molar ratio of the total molar amount of zinc nitrate and gallium nitrate to hexamethylenetetramine is 1:1. The seeded activated carbon substrate is immersed in the modification solution to obtain reaction solution A, wherein the mass-volume ratio of the seeded activated carbon substrate to the modification solution is 1 g: 200 mL. The solution is then hydrothermally reacted at 100°C for 12 h. After washing and drying, activated carbon loaded with gallium-doped zinc oxide nanorods is obtained.

[0069] S2: Prepare a 0.3M cerium nitrate solution, add 3M ammonia water to adjust the pH to 10, and continue stirring for 2 hours. Centrifuge and wash to obtain cerium hydroxide precursor. Calcinate the cerium hydroxide precursor at 450℃ for 4 hours to obtain cerium dioxide nanoparticles. Disperse the cerium dioxide nanoparticles in a mixed solvent to obtain suspension B, wherein the volume ratio of deionized water to anhydrous ethanol in the mixed solvent is 4.5:5.5. Add a 0.1M phosphotungstic acid solution to adjust the pH to 3 to obtain reaction solution C. Stir and adsorb for 8 hours. Add a 0.2M cesium chloride solution to obtain reaction solution D, wherein the molar ratio of cesium chloride to phosphotungstic acid in reaction solution D is 1.5:1. Stir and react for 4 hours, centrifuge, wash, and dry to obtain cesium phosphotungstic acid-coated cerium dioxide nanoparticles.

[0070] S3: Cesium phosphotungsten-coated cerium dioxide nanoparticles were dispersed in a mixed solvent to obtain a loaded suspension with a concentration of 20 mg / mL. Activated carbon loaded with gallium-doped zinc oxide nanorods and conductive carbon black were added, and the mixture was ultrasonically stirred for 60 min. The mass ratio of cesium phosphotungsten-coated cerium dioxide nanoparticles to activated carbon loaded with gallium-doped zinc oxide nanorods was 1:15, and the amount of conductive carbon black added was 0.05% of the mass of activated carbon loaded with gallium-doped zinc oxide nanorods. The activated carbon loaded with gallium-doped zinc oxide nanorods was taken out after impregnation and vacuum dried at 80 °C for 12 h to obtain low-temperature resistant and long-lasting purification vehicle activated carbon.

[0071] Comparative Example 1

[0072] This comparative example provides a low-temperature resistant, long-lasting activated carbon for vehicle purification. The difference from Example 1 is that it uses untreated raw coconut shell activated carbon particles.

[0073] Comparative Example 2

[0074] This comparative example provides a low-temperature resistant and long-lasting activated carbon for vehicle purification. The difference from Example 1 is that it uses the traditional equal-volume impregnation method, in which the original coconut shell activated carbon is impregnated in a potassium permanganate aqueous solution and then dried to obtain the traditional modified activated carbon.

[0075] Comparative Example 3

[0076] This comparative example provides a low-temperature resistant, long-lasting activated carbon for vehicle purification. The difference between this example and Example 1 is that conductive carbon black is not added, while the other operating steps and process parameters are exactly the same as in Example 1.

[0077] Comparative Example 4

[0078] This comparative example provides a low-temperature resistant and long-lasting activated carbon for vehicle purification. The difference from Example 1 is that gallium-doped zinc oxide nanorods are not loaded on the coconut shell activated carbon particles. Other operating steps and process parameters are exactly the same as in Example 1.

[0079] Comparative Example 5

[0080] This comparative example provides a low-temperature resistant, long-lasting activated carbon for vehicle purification. The difference between this example and Example 1 is that cesium chloride solution is not added in step S2, while the other operating steps and process parameters are exactly the same as in Example 1.

[0081] The performance of the low-temperature resistant and long-lasting activated carbon for vehicle purification in Examples 1-4 and Comparative Examples 1-5 was tested, and the specific process is as follows:

[0082] Single-pass purification rate test: The purification material sample to be tested was placed in a sealed quartz glass reactor equipped with a built-in fan. A fixed amount of formaldehyde and toluene was injected into the reactor, and the mixture was kept in the dark and static condition for 1 hour to reach adsorption-desorption equilibrium. Subsequently, the built-in fan was turned on to simulate air circulation inside a car, and the reaction was carried out for 4 hours under standard conditions (constant temperature 25℃) and low-temperature conditions (constant temperature 5℃), respectively. After the reaction, samples were taken from the reactor, and the final pollutant concentration was measured using gas chromatography-mass spectrometry (GC-MS) to calculate the single-pass degradation rate of formaldehyde and toluene.

[0083] Cyclic Regeneration Performance Test: After completing the initial single-cycle purification rate test, the "used" sample was removed and placed in a temperature-controlled chamber. Ten cycles of temperature increases and decreases were performed at a rate of 0.5℃ / min under standard conditions (between 25℃ and 50℃) and low-temperature conditions (between 5℃ and 20℃) to simulate temperature fluctuations inside the vehicle. After completing the temperature cycle "regeneration" treatment, the sample was placed back into the reactor, and the entire process of the "single-cycle purification rate test" was repeated. This "purification-regeneration" process was repeated a total of 10 times.

[0084] High humidity environment stability test: Unused purification material samples were placed at a constant temperature of 25℃ and a constant humidity of 85% for 48 hours for aging treatment. After aging, the purification rates for formaldehyde and toluene were tested under the standard conditions of the "Single Purification Rate Test" mentioned above.

[0085] The test results are shown in Table 1.

[0086] Table 1. Performance test results of low-temperature resistant, long-lasting purification vehicle-mounted activated carbon prepared in Examples 1-4 and Comparative Examples 1-5

[0087]

[0088] As shown in Table 1, the test results of Example 1 and Comparative Example 1 reveal that the purification mechanism of untreated raw coconut shell activated carbon particles is purely physical adsorption, lacking the pyroelectric regeneration driven by gallium-doped zinc oxide nanorods and the catalytic oxidation function of cesium phosphotungstenate-coated cerium dioxide nanoparticles. Therefore, its single-cycle purification efficiency is limited, and once the adsorption sites are occupied by pollutants and water molecules, they become saturated and cannot be regenerated through temperature cycling, leading to a sharp decline in cycling performance and performance under high humidity.

[0089] As shown in Table 1, the test results of Example 1 and Comparative Example 2 reveal that the conventional modified activated carbon, prepared by impregnating raw coconut shell activated carbon in a potassium permanganate aqueous solution using the traditional equal-volume impregnation method and then drying it, exhibits some initial oxidation capacity against formaldehyde under standard conditions. However, this oxidation reaction is a typical thermochemical process, highly temperature-dependent, leading to activity decay at low temperatures. Furthermore, potassium permanganate, as a consumable oxidant, is reduced during the reaction and cannot be regenerated, resulting in poor cycle performance. Its water solubility also makes it prone to loss and deactivation in humid environments, exhibiting extremely weak moisture resistance.

[0090] As shown in Table 1, the test results of Example 1 and Comparative Example 3 indicate that the absence of conductive carbon black disrupts the efficient charge transport network within the system. Although the material still possesses pyroelectric effect and initial catalytic oxidation capability, the surface charge generated by the gallium-doped zinc oxide nanorods due to temperature changes cannot be effectively transferred to the catalytic sites of the cesium phosphotungstenate-coated cerium dioxide nanoparticles that have become deactivated by the reaction. This disrupts the pyroelectric-driven chemical regeneration cycle, preventing the catalyst from being regenerated online and leading to irreversible activity degradation after multiple cycles.

[0091] As shown in Table 1, the test results of Example 1 and Comparative Example 4 reveal that without loading gallium-doped zinc oxide nanorods onto the coconut shell activated carbon particles, the entire composite material system loses its source of pyroelectric effect, i.e., it loses its self-regeneration capability. Although the stable cesium phosphotungstenate-coated cerium dioxide nanoparticles provide excellent initial purification performance and moisture resistance, once their active sites are consumed or covered by intermediate products in the first reaction, the entire system cannot drive its regeneration. Therefore, the material's performance degrades with increasing cycle number.

[0092] As shown in Table 1, the test results of Example 1 and Comparative Example 5 reveal that the absence of cesium chloride solution in step S2, and the lack of an ion exchange solidification step for cesium chloride, allows the supported strong oxidant phosphotungstic acid to exist in its original water-soluble form. While this does not affect its initial high catalytic activity under dry conditions, in high humidity environments, water molecules cause a significant amount of phosphotungstic acid to dissolve, migrate, and escape from the support surface, resulting in a physical loss of the core active component of the catalyst. Therefore, this material exhibits poor moisture resistance, and its performance deteriorates after aging in high humidity.

[0093] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing low-temperature resistant, long-lasting activated carbon for vehicle purification, characterized in that, The preparation method includes: S1: Coconut shell activated carbon particles are immersed in zinc acetate ethanol solution, and the immersion-drying process is repeated. The carbon is then placed under a nitrogen atmosphere and heat-treated to obtain an activated carbon substrate with seed crystals. Zinc nitrate, gallium nitrate and hexamethylenetetramine are dispersed in deionized water to obtain a modification solution. The activated carbon substrate with seed crystals is immersed in the modification solution to obtain reaction solution A. The reaction is carried out hydrothermally, washed, and dried to obtain activated carbon loaded with gallium-doped zinc oxide nanorods. S2: Prepare a cerium nitrate solution, add ammonia water to adjust the pH, stir continuously to react, centrifuge, wash to obtain a cerium hydroxide precursor, calcine the cerium hydroxide precursor to obtain cerium dioxide nanoparticles, disperse the cerium dioxide nanoparticles in a mixed solvent to obtain suspension B, add phosphotungstic acid solution to adjust the pH to obtain reaction solution C, stir to adsorb, add cesium chloride solution to obtain reaction solution D, stir to react, centrifuge, wash, dry to obtain cesium phosphotungstic acid-coated cerium dioxide nanoparticles, wherein the mixed solvent is a mixture of deionized water and anhydrous ethanol; S3: Cesium phosphotungsten-coated cerium dioxide nanoparticles are dispersed in a mixed solvent to obtain a loaded suspension. Activated carbon loaded with gallium-doped zinc oxide nanorods and conductive carbon black are added, and the mixture is ultrasonically stirred. The impregnated activated carbon loaded with gallium-doped zinc oxide nanorods is then removed and vacuum dried to obtain low-temperature resistant, long-lasting purification vehicle-mounted activated carbon.

2. The method for preparing low-temperature resistant, long-lasting activated carbon for vehicle purification according to claim 1, characterized in that, In S1: The volume ratio of the zinc acetate ethanol solution to the mass ratio of the coconut shell activated carbon particles is (0.8-1.2) mL:1 g.

3. The method for preparing a low-temperature resistant, long-lasting activated carbon for vehicle purification according to claim 1, characterized in that, In S1: The total concentration of zinc nitrate and gallium nitrate in the modified solution is 0.02-0.05 M; The molar ratio of zinc nitrate to gallium nitrate is (99-98):(1-2); The total molar ratio of zinc nitrate and gallium nitrate to hexamethylenetetramine is 1:

1.

4. The method for preparing low-temperature resistant, long-lasting activated carbon for vehicle purification according to claim 1, characterized in that, In S1: The mass-to-volume ratio of the seeded activated carbon substrate to the modified solution is 1 g:(100-200) mL.

5. The method for preparing a low-temperature resistant, long-lasting activated carbon for vehicle purification according to claim 1, characterized in that, In S2: The volume ratio of deionized water to anhydrous ethanol in the mixed solvent is (3:7)-(5:5); The pH of the suspension B was adjusted to 2-3 by adding phosphotungstic acid solution.

6. The method for preparing a low-temperature resistant, long-lasting activated carbon for vehicle purification according to claim 1, characterized in that, In S2: The concentration of the cesium chloride solution is 0.1-0.2M; The molar ratio of cesium chloride to phosphotungstic acid in the reaction solution D is (1.2-1.5):

1.

7. The method for preparing low-temperature resistant, long-lasting activated carbon for vehicle purification according to claim 1, characterized in that, In S3: The concentration of the loaded suspension is 10-20 mg / mL.

8. The method for preparing low-temperature resistant, long-lasting activated carbon for vehicle purification according to claim 1, characterized in that, In S3: The mass ratio of the cesium phosphotungsten-coated cerium dioxide nanoparticles to the activated carbon loaded with gallium-doped zinc oxide nanorods is 1:(10-15).

9. The method for preparing low-temperature resistant, long-lasting activated carbon for vehicle purification according to claim 1, characterized in that, In S3: The amount of conductive carbon black fed is 0.02-0.05% of the mass of activated carbon loaded with gallium-doped zinc oxide nanorods.

10. A low-temperature resistant, long-lasting activated carbon for vehicle purification prepared by the preparation method according to any one of claims 1-9.

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