A ceria fiber and a preparation method and application thereof

Abstract

The application relates to a cerium dioxide fiber and a preparation method and application thereof. A polyacetylacetone cerium precursor is synthesized by one-step coordination reaction of a cerium source and acetylacetone, an auxiliary spinning agent is added to mix with the cerium source precursor to obtain a precursor spinning solution, electrostatic spinning is carried out to obtain a cerium dioxide precursor fiber, and the cerium dioxide fiber is obtained through heat treatment. The obtained fiber is arranged in a network structure, has high porosity, has self-supporting property, has large specific surface area, can provide good contact efficiency for carbon smoke particles, exposes more active sites, shows excellent catalytic activity, and the carbon smoke catalytic performance of the cerium dioxide fiber calcined at 500 DEG C is optimal.

Description

Technical Field

[0001] This invention relates to a cerium dioxide fiber, its preparation method, and its application, belonging to the field of synthetic fiber technology. Background Technology

[0002] Diesel vehicle exhaust soot particles are a major contributor to smog. These particles often carry SO2 and carcinogens, which are inhaled and harmed to both humans and animals, potentially even causing cancer in severe cases. Therefore, eliminating soot particles is crucial for reducing environmental pollution and protecting human health. Installing a catalyst in the diesel engine particulate filter for catalytic combustion is the most thorough and effective way to eliminate soot particles.

[0003] Researchers have developed a wide variety of catalysts, such as alkali metal, transition metal oxides, noble metal, and rare earth-based catalysts. However, alkali metal catalysts are usually not in the form of a single oxide, but are often supported or doped into other catalysts; transition metal oxides have poor catalytic activity, high ignition temperature, and are easily poisoned; and noble metal oxides are expensive, limiting their use.

[0004] Among rare earth-based oxides, cerium dioxide has the most abundant raw material reserves (cerium is the most abundant of the rare earth elements). Cerium dioxide has wide applications in many fields. In environmental protection, it can be used as a catalyst for waste gas treatment, automobile exhaust purification, and catalytic combustion of volatile organic compounds (VOCs). In the energy sector, it can be used as an electrolyte and catalyst in solid oxide fuel cells to achieve efficient energy conversion and storage. Furthermore, cerium dioxide can also be used as a catalyst in the preparation of syngas, methanol production, and organic synthesis. Therefore, it has the advantages of low cost and high efficiency.

[0005] Cerium dioxide possesses excellent oxygen storage / release capacity, high oxygen vacancy concentration, and high ion mobility, making it an ideal catalyst for soot combustion. The role of cerium dioxide catalysts in soot combustion is to promote the transfer of oxygen from the gas phase to the surface of soot particles. This involves reversible redox reactions between different valence states (Ce...). 4+ / Ce 3+ The presence of certain conditions is a prerequisite for cerium dioxide catalysts to exhibit excellent catalytic performance. Therefore, cerium dioxide is an ideal catalyst material.

[0006] In catalytic reactions, the morphology of the catalyst significantly affects the reaction rate. This is because different morphologies result in varying specific surface areas and different contact rates with soot particles. Researchers have prepared catalysts in various shapes, including fibrous, powdered, three-dimensional self-assembled star-shaped, foam-like, cubic, flower-like, spherical, and rod-shaped fibers. Cerium dioxide fibers are one-dimensional materials with a polycrystalline structure. The fiber diameter and size effect have a significant impact on material properties. The fibrous morphology helps to obtain a larger specific surface area, exposing more active sites and thus improving contact with reactants. Compared to particles, fibrous materials are less prone to aggregation and can function more effectively.

[0007] Currently, precursors prepared using cerium salt precursors require the addition of large amounts of spinning aids to improve fiber tensile strength during electrospinning. Patent document CN113351211A discloses a cerium dioxide fibrous catalyst containing nickel particles. The cerium source used in its preparation (cerium nitrate) itself lacks spinnability, necessitating the addition of large amounts of spinning aids to provide spinnability. Furthermore, cerium acetate has poor solubility in various solvents, requiring large amounts of solvent for complete dissolution. The large amount of solvent used also increases the amount of spinning aids such as polyvinylpyrrolidone (PVP), resulting in a very low cerium content in the precursor fiber and significant sintering losses. Patent document CN114875658A describes an impregnation method to load cerium onto a silica fiber membrane to obtain silica fiber-loaded cerium dioxide. This method uses cerium nitrate as a raw material, and the nitrate ions undergo violent decomposition during sintering, damaging the fiber morphology.

[0008] Therefore, it is of great significance to develop a cerium dioxide fiber with stable spinning sol, high content of target elements, good fiber morphology, uniform grains, fine diameter, and large specific surface area. Summary of the Invention

[0009] To address the shortcomings of existing technologies, especially the fact that the preparation of existing cerium dioxide fibers requires a large amount of spinning aids for electrospinning, and that the target element content in the precursor sol is low, resulting in poor fiber quality, this invention provides a cerium dioxide fiber, its preparation method, and its applications.

[0010] This invention uses acetylacetone as the ligand for cerium salt and cerium chloride as the cerium source, replacing the cerium salt used in the prior art. The resulting spinning sol is stable, and electrospinning technology is used to successfully produce cerium dioxide precursor fibers, which greatly increases the cerium content in the precursor fibers. The resulting fibers have good morphology, with uniform cerium dioxide fiber grains, fine diameter, and large specific surface area, which can better contact carbon soot particles in the catalytic reaction.

[0011] The technical solution of the present invention is as follows:

[0012] A method for preparing cerium dioxide fiber includes the following steps:

[0013] (1) Dissolve the cerium source fully in the solvent, add acetylacetone for coordination, stir evenly, and then add the spinning aid to the cerium dioxide precursor solution according to the mass ratio of the spinning aid to the cerium source as (1-17.6):100, stir until completely dissolved, and obtain cerium dioxide precursor sol.

[0014] (2) Electrospinning of cerium dioxide precursor spinning sol to obtain cerium dioxide precursor fibers;

[0015] (3) Heat treatment of cerium dioxide precursor fibers in air atmosphere at 500-800℃ to obtain cerium dioxide fibers.

[0016] According to the present invention, preferably, in step (1), the cerium source is a cerium chloride.

[0017] According to the present invention, preferably, in step (1), the cerium source is anhydrous cerium trichloride and / or cerium trichloride heptahydrate.

[0018] According to the present invention, preferably, in step (1), the molar ratio of cerium source to acetylacetone is 1:(0.5-10).

[0019] More preferably, in step (1), the molar ratio of cerium source to acetylacetone is 1:(1 to 1.3).

[0020] According to the present invention, preferably, in step (1), the stirring speed is 100-350 r / min.

[0021] According to the present invention, preferably, in step (1), the stirring time after adding the spinning aid is 0.5 to 2 hours.

[0022] According to the present invention, preferably, in step (1), the solvent is a low-carbon alcohol.

[0023] According to the present invention, preferably, in step (1), the weight ratio of cerium source to solvent is 1:(1-2).

[0024] According to the present invention, preferably, in step (1), the lower alcohol is methanol, ethanol or isopropanol.

[0025] According to the present invention, preferably, in step (1), the stirring reaction temperature is 0 to 70°C, the stirring reaction time is 1 to 2 hours, and the stirring speed is 200 to 350 r / min.

[0026] According to the present invention, preferably, in step (1), the spinning aid is one or a combination of two or more of polyethylene oxide (PEO), PVP, polyvinyl butyral (PVB), and polyvinyl alcohol (PVA).

[0027] According to the present invention, preferably, in step (1), the mass ratio of the spinning aid to the cerium source is (1-8):100.

[0028] The selection and dosage of acetylacetone, as well as the choice of the sol system, are crucial for obtaining a high-cerium-content, highly spinnable, and stable spinning sol. Insufficient acetylacetone leads to poor coordination between the acetylacetone and the cerium source, resulting in an unstable and spinnable precursor. Excessive acetylacetone results in residual free acetylacetone in the system and poor spinnability of the sol. The solvent system of this invention ensures a highly soluble, spinnable, and homogeneous stable sol. Due to the special nature of the cerium source, other systems are prone to precipitation, failing to form a homogeneous and highly spinnable sol. The precursor sol obtained by this invention has a high content of the target element, exhibiting strong spinnability and homogeneity. This invention successfully achieves the simple method to obtain stable spinning sols with high target element content, good fiber morphology, uniform grain size, fine diameter, and large specific surface area of ​​cerium dioxide fibers.

[0029] According to the present invention, preferably, in step (2), the electrospinning conditions are: spinning voltage 10-25kV, feed speed 0.5-2mL / h, receiving distance 15-25cm, spinning humidity 20-45%, and spinning temperature 20-40℃.

[0030] According to the present invention, preferably, in step (3), the temperature is raised to the heat treatment temperature at a heating rate of 1℃ / min and held for 1h to obtain cerium dioxide fiber;

[0031] According to the present invention, preferably, in step (3), the heat treatment temperature is 500-600°C, and most preferably 500°C.

[0032] This invention achieves excellent catalytic performance from cerium dioxide fibers using relatively low heat treatment temperatures. However, excessively low heat treatment temperatures prevent complete removal of organic matter, thus affecting catalytic performance. Conversely, excessively high heat treatment temperatures lead to larger cerium dioxide fiber grains, reduced specific surface area, and decreased catalytic performance.

[0033] A cerium dioxide fiber, prepared by the above method, has a diameter of 700-2000 nm, belongs to the cubic phase, and has uniform grain size.

[0034] This invention employs electrospinning to prepare cerium dioxide fibers. Because the reaction occurs in solution to form a spinning sol, molecular-level uniformity is achieved. The product boasts high purity and a low crystallization temperature, eliminating the need for excessively high-temperature heat treatment and prolonged heat preservation, thus saving energy. Compared to fibers obtained through centrifugal spinning, these fibers have finer diameters, larger specific surface areas, and a loose, porous structure and morphology. Furthermore, it overcomes the tendency for particle-based materials to agglomerate, thereby better leveraging the performance of cerium dioxide as a catalyst or catalyst support. Simultaneously, the preparation method employed in this invention is simple, yielding a cerium dioxide precursor with a high degree of polymerization in the spinning solution. This method significantly reduces the addition of spinning aids. The coordination and dosage of acetylacetone, along with the sol system, enhance the spinning ability, resulting in a uniform, stable, highly spinnable spinning sol with a high cerium content.

[0035] According to the present invention, cerium dioxide fibers are used for carbon soot catalysis.

[0036] According to a preferred embodiment of the present invention, the specific application method is as follows:

[0037] The above-mentioned cerium dioxide fiber and soot particle powder are mixed and ground, diluted with inert silica, loaded into a reactor, heated, and a reaction gas is introduced to carry out the soot catalytic reaction.

[0038] According to the present invention, the preferred mass ratio of cerium dioxide fiber to carbon soot particle powder is (5-20):1, and the preferred mass ratio of cerium dioxide fiber to carbon soot particle powder is 10:1, and the grinding time is 3-40 min.

[0039] According to a preferred embodiment of the present invention, the heating is performed from room temperature to 650-750°C at a heating rate of 5-15°C / min, and the reaction gas is synthetic air with 21% O2 / N2.

[0040] Applications have shown that cerium dioxide fibers obtained by heat treatment at 500℃ reduce the ignition temperature from 465.6℃ during pure soot combustion to 307.2℃, and the burnout temperature from 597.7℃ during pure soot combustion to 443.5℃, effectively improving the catalytic activity of soot combustion.

[0041] Technical features and superior effects of the present invention:

[0042] 1. This invention uses a one-step reaction to prepare cerium dioxide fiber precursors. The cerium dioxide precursor fibers are prepared by electrospinning and then heat-treated. The resulting fibers have high crystallinity, uniform grain size, fine diameter, and large specific surface area, allowing for more thorough contact with the reactants and overcoming the problem of easy agglomeration of particle materials.

[0043] 2. The cerium dioxide fiber precursor spinning sol of this invention is a stable sol prepared by the sol-gel method, rather than simply mixing cerium inorganic salts, spinning aids, and solvents. The coordination, dosage, and sol system of acetylacetone enhance the spinning ability, resulting in a uniform and stable spinning sol with strong spinnability and high cerium content. This significantly reduces the amount of spinning aid required, allowing for the formation of a spinning sol with excellent spinnability with minimal aid usage. The preparation method is simple and suitable for industrial production. During use, it is uniform, transparent, free of sediment, impurities, and bubbles.

[0044] 3. The cerium dioxide fiber of this invention can be used for catalytic combustion of carbon soot, and has broad application prospects in automobile exhaust treatment. The ignition temperature of catalytic combustion of carbon soot is reduced from 465.6℃ in pure carbon soot combustion to 307.2℃, and the burnout temperature is reduced from 597.7℃ in pure carbon soot combustion to 443.5℃, effectively improving the catalytic activity of carbon soot. Attached Figure Description

[0045] Figure 1 This is a photograph of the cerium dioxide precursor fiber obtained in Example 1 of the present invention.

[0046] Figure 2 This is a photograph of cerium dioxide fibers obtained after heat treatment at 500℃ in Example 1 of the present invention.

[0047] Figure 3 This is a SEM image of cerium dioxide fibers obtained after heat treatment at 500℃ in Example 1 of the present invention.

[0048] Figure 4 This is a SEM image of the cerium dioxide fibers obtained after heat treatment at 800℃ in Comparative Example 10 of this invention.

[0049] Figure 5 The XRD patterns are those of cerium dioxide fibers obtained after heat treatment at different temperatures in Examples 1 and 4, and Comparative Examples 9 and 10 of this invention.

[0050] Figure 6 This is the temperature programmed oxidation (TPO) curve obtained in Example 1 of the present invention.

[0051] Figure 7 This is the CO2 generation curve obtained in Example 1 of the present invention.

[0052] Figure 8 This is a photograph showing the solubility of the raw materials in Comparative Example 11 of this invention.

[0053] Figure 9 This is a photograph of the precursor solution prepared in Example 1. Detailed Implementation

[0054] The present invention will be further described below with reference to embodiments, but is not limited thereto.

[0055] All raw materials used in the examples are conventional raw materials, and all equipment used are conventional equipment and commercially available products.

[0056] Example 1:

[0057] A method for preparing cerium dioxide fiber, comprising the following steps:

[0058] (1) Preparation of cerium dioxide fiber spinning sol

[0059] Weigh 50.0g of cerium trichloride heptahydrate, dissolve it in 60.0g of methanol, stir until fully dissolved, then add 13.42g of acetylacetone, stir thoroughly for 20min to obtain a precursor solution; weigh 2.9g of PVP and add it to the precursor solution, stir until dissolved at room temperature to obtain cerium dioxide precursor spinning sol.

[0060] (2) The cerium dioxide precursor spinning sol obtained in step (1) was electrospun at a temperature of 25°C and a humidity of 30%. The electrospinning voltage was 12kV, the feed speed was 1.0mL / h, and the receiving distance was 18cm to obtain cerium dioxide precursor fibers.

[0061] (3) The cerium dioxide precursor fiber is heated to 500℃ at a heating rate of 1℃ / min, then kept at the temperature for 1h, and then cooled naturally to obtain pure cerium dioxide fiber.

[0062] The cerium dioxide precursor fiber obtained in step (2) of the embodiment is shown in the following image. Figure 1 As shown; a photograph of the high-cerium-content cerium dioxide fiber obtained after heat treatment at 500℃ in step (3) is shown. Figure 2 As shown, the SEM image of cerium dioxide fiber with high cerium content is as follows: Figure 3 As shown. Figure 1 , Figure 2 This indicates that both the cerium dioxide precursor fibers and the cerium dioxide fibers possess complete fiber morphology. Figure 2-3 It is known that the diameter of the cerium dioxide fiber of the present invention is 700-2000 nm.

[0063] Example 2:

[0064] The preparation method of cerium dioxide fiber is the same as that described in Example 1, except that:

[0065] In step (1), the amount of PVP is replaced with 3.6g, and the rest is carried out as in Example 1.

[0066] Example 3:

[0067] The preparation method of cerium dioxide fiber is the same as that described in Example 1, except that:

[0068] In step (1), 60g of methanol was replaced with 120g of methanol, and the rest was carried out as in Example 1. The resulting fiber diameter was finer than that in Example 1.

[0069] Example 4:

[0070] The preparation method of cerium dioxide fiber is the same as that described in Example 1, except that:

[0071] In step (3), the cerium dioxide precursor fiber is heated to 600°C at a heating rate of 1°C / min, kept at that temperature for 1 hour, and then cooled naturally. The rest is carried out as in Example 1. Compared with Example 1, the fiber crystallinity is slightly increased, but the catalytic performance is slightly reduced.

[0072] Example 5:

[0073] The preparation method of cerium dioxide fiber is the same as that described in Example 1, except that:

[0074] In step (1), 2.9g PVP is replaced with 1.0g PEO, and the rest is carried out as in Example 1.

[0075] Example 6:

[0076] The preparation method of cerium dioxide fiber is the same as that described in Example 1, except that:

[0077] In step (1), 2.9g PVP is replaced with 4.5g PVA, and the rest is carried out as in Example 1.

[0078] Example 7:

[0079] Application of the cerium dioxide fiber prepared in Example 1: for carbon soot catalysis;

[0080] The cerium dioxide fiber and carbon soot particle powder obtained in Example 1 were mixed and ground, diluted with inert silica, loaded into a reactor, heated, and a reaction gas was introduced to carry out the carbon soot catalytic reaction. The mass ratio of cerium dioxide fiber to carbon soot particle powder was 10:1, the grinding time was 3 to 40 min, the heating was carried out at a heating rate of 10 °C / min from room temperature to 700 °C, and the reaction gas was synthetic air with 21% O2 / N2.

[0081] Comparative Example 1:

[0082] The preparation method of cerium dioxide fiber is the same as that described in Example 1, except that:

[0083] In step (1), after dissolving cerium trichloride heptahydrate in methanol and adding acetylacetone, PVP is first dissolved in water and then mixed with the cerium precursor solution. The resulting precursor fiber has poor volatility.

[0084] Comparative Example 2:

[0085] The preparation method of cerium dioxide fiber is the same as that described in Example 1, except that:

[0086] In step (1), cerium trichloride heptahydrate is dissolved in water. The precursor fibers obtained by using water as the solvent are adhered, and the solvent has poor volatility.

[0087] Comparative Example 3:

[0088] The preparation method of cerium dioxide fiber is the same as that described in Example 1, except that:

[0089] In step (1), cerium trichloride heptahydrate is dissolved in n-propanol. The precursor fibers obtained by using n-propanol as a solvent are bonded together, and the solvent has poor volatility.

[0090] Comparative Example 4:

[0091] The preparation method of cerium dioxide fiber is the same as that described in Example 1, except that:

[0092] In step (1), after dissolving cerium trichloride heptahydrate in methanol, acetylacetone is not added. Without the coordination of acetylacetone with cerium trichloride heptahydrate, the resulting fibers suffer severe burn-off.

[0093] Comparative Example 5:

[0094] The preparation method of cerium dioxide fiber is the same as that described in Example 1, except that:

[0095] In step (1), 13.42g of acetylacetone was replaced with 6.23g of acetylacetone. Too little acetylacetone resulted in poor coordination and significant fiber loss.

[0096] Comparative Example 6:

[0097] The preparation method of cerium dioxide fiber is the same as that described in Example 1, except that:

[0098] In step (1), 13.42g of acetylacetone was replaced with 28.97g of acetylacetone. The excess of acetylacetone resulted in poor fiber morphology.

[0099] Comparative Example 7:

[0100] The preparation method of cerium dioxide fiber is the same as that described in Example 1, except that:

[0101] In step (1), 60g of methanol was replaced with 200g of methanol. The methanol solvent was in excess, and there were droplets in the fiber.

[0102] Comparative Example 8:

[0103] The preparation method of cerium dioxide fiber is the same as that described in Example 1, except that:

[0104] In step (3), the cerium dioxide precursor fiber is heated to 450°C at a heating rate of 1°C / min, kept at that temperature for 1 hour, and then cooled naturally.

[0105] Compared to Example 1, the carbon soot catalysis (the minimum temperature of this process is higher than 450°C) ends at a temperature exceeding the fiber's own heat treatment temperature, making the fiber unrecyclable.

[0106] Comparative Example 9:

[0107] The preparation method of cerium dioxide fiber is the same as that described in Example 1, except that:

[0108] In step (3), the cerium dioxide precursor fiber is heated to 700°C at a heating rate of 1°C / min, held at that temperature for 1 hour, and then allowed to cool naturally. Compared with Example 1, the heat treatment temperature is too high, resulting in reduced fiber crystallinity and decreased catalytic performance.

[0109] Comparative Example 10:

[0110] The preparation method of cerium dioxide fiber is the same as that described in Example 1, except that:

[0111] Step (3): The obtained cerium dioxide precursor fiber is heated to 800℃ at a heating rate of 1℃ / min, kept at the temperature for 1h, and then cooled naturally.

[0112] SEM images of cerium dioxide fibers obtained after heat treatment at 800℃ are shown below. Figure 4 Compared with Example 1, the fiber crystallinity is increased and the catalytic performance of the fiber is reduced.

[0113] Comparative Example 11:

[0114] The preparation method of cerium dioxide fiber is the same as that described in Example 1, except that:

[0115] In step (1), cerium trichloride heptahydrate is replaced with cerium acetylacetone. The raw materials used in this method have poor solubility in solvents and cannot be fully dissolved with a small amount of solvent, thus failing to form a homogeneous and stable sol. (See...) Figure 8 .

[0116] Experimental Example 1:

[0117] The XRD patterns of cerium dioxide fibers obtained after heat treatment at different temperatures in Examples 1 and 4, and Comparative Examples 9 and 10 are shown in the figure. Figure 5 This indicates that the present invention has successfully obtained cerium dioxide fibers.

[0118] Experimental Example 2:

[0119] The cerium dioxide fibers obtained in Examples 1-5 were arranged according to... Figure 6 The steps for conducting a temperature-programmed oxidation experiment are as follows:

[0120] 200 mg of cerium dioxide fiber and 20 mg of carbon soot particles were weighed, mixed, and ground for 10 min. Before being loaded into the reactor, the mixture was diluted with inert silica. All data were obtained by increasing the temperature from room temperature to 700 °C at a rate of 5 °C / min. The reaction gas was syngas containing 21% O2 and 79% N2. The resulting curves are shown below. Figure 7 As shown, the cerium dioxide fiber treated at 500℃ in Example 1 exhibits the best catalytic effect in the soot catalytic test, and can meet the combustion requirements of soot within the diesel engine exhaust temperature range.

Claims

1. An application of cerium dioxide fiber, comprising the following steps: (1) Preparation of cerium dioxide fiber spinning sol Weigh 50.0g of cerium trichloride heptahydrate, dissolve it in 60.0g of methanol, stir until fully dissolved, then add 13.42g of acetylacetone, stir thoroughly for 20min to obtain a precursor solution; weigh 2.9g of PVP and add it to the precursor solution, stir until dissolved at room temperature to obtain cerium dioxide precursor spinning sol. (2) The cerium dioxide precursor spinning sol obtained in step (1) was electrospun at a temperature of 25°C and a humidity of 30%. The electrospinning voltage was 12kV, the feed speed was 1.0mL / h, and the receiving distance was 18cm to obtain cerium dioxide precursor fibers. (3) The cerium dioxide precursor fiber is heated to 500℃ at a heating rate of 1℃ / min, then kept at the temperature for 1h, and then cooled naturally to obtain pure cerium dioxide fiber. Weigh 200mg of cerium dioxide fiber and 20mg of carbon soot particles, mix and grind for 10min. Before loading into the reactor, dilute with inert silica and heat from room temperature to 700℃ at 5℃ / min. The reaction gas is synthetic air with 21% O2 / 79% N2.

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