Preparation method of fibrous nano cerium oxide

Abstract

The invention discloses a preparation method of fibrous nano cerium oxide, which belongs to the technical field of catalytic materials, and comprises the following steps: dropwise adding a cerium salt solution into an ammonia water solution under a stirring condition, and reacting until the pH value is 9 to obtain a reactant A; washing and filtering the obtained reactant A; putting the washed and filtered reactant A into a high-pressure reaction kettle, and reacting for 10-48 hours under the conditions that the temperature is 110-180 DEG C and the pressure is 0.4-5 MPa to obtain a reactant B; washing and filtering the obtained reactant B; putting the washed and filtered reactant B into a drying oven for drying to obtain cerium oxide precursor powder; and putting the cerium oxide precursor powder obtained in the previous step into a calcining furnace, and calcining to obtain the fibrous nano cerium oxide. According to the invention, the problem of small specific surface area of nano cerium oxide caused by serious particle aggregation in the production process of nano cerium oxide is solved.

Description

Technical Field

[0001] This invention belongs to the field of nano-cerium oxide production technology, specifically relating to a method for preparing fibrous nano-cerium oxide. Background Technology

[0002] Nano-cerium oxide (CeO2) is characterized by its unique fluorite-type cubic structure and the presence of cerium ions (Ce). 3+ / Ce 4+ The unique arrangement of cerium oxide with oxygen ions endows it with many excellent properties, such as good chemical stability, oxygen storage capacity, and catalytic activity. In the field of automotive exhaust purification, cerium oxide, as a key catalyst component, can catalyze the redox reactions of harmful gases such as nitrogen oxides, carbon monoxide, and hydrocarbons, converting them into harmless substances such as nitrogen, carbon dioxide, and water, thereby reducing the pollution of the environment by automotive exhaust. With the continuous growth of global car ownership and increasingly stringent environmental regulations, the role of cerium oxide in automotive exhaust purification is becoming increasingly crucial. However, during the preparation of nano-cerium oxide, the very fine powder particles and high surface energy lead to severe particle agglomeration, resulting in a small specific surface area in the produced nano-cerium oxide, which in turn affects the catalytic effect of nano-cerium oxide. Summary of the Invention

[0003] To address the above shortcomings, this invention discloses a method for preparing fibrous nano-cerium oxide, which solves the problem of small specific surface area of ​​nano-cerium oxide due to severe particle agglomeration during the production process.

[0004] This invention is achieved using the following technical solution: A method for preparing fibrous nano-cerium oxide includes the following steps: (1) Under stirring conditions of 300-500 r / min, cerium salt solution is added dropwise to ammonia solution to carry out the reaction until the pH value is 9 to obtain reactant A; the volume ratio of cerium salt solution to ammonia solution is (1-3):(3-6); (2) Wash and filter the reactant A obtained in step (1); (3) Place the washed and filtered reactant A into a high-pressure reactor and react for 10 to 48 hours at a temperature of 110 to 180°C and a pressure of 0.4 to 5 MPa to obtain reactant B; (4) Wash and filter the reactant B obtained in step (3); (5) The washed and filtered reactant B was placed in an oven and dried to obtain cerium oxide precursor powder; (6) The cerium oxide precursor powder obtained in step (5) is placed in a calcining furnace for calcination to obtain fibrous nano-cerium oxide. The calcination temperature is 300-600℃ and the calcination time is 2-8h.

[0005] In the preparation of nano-cerium oxide, the interactions between nanoparticles and molecules lead to particle aggregation, while the extremely high surface energy and large contact area facilitate the formation and growth of crystal nuclei. Therefore, this invention uses cerium salt and ammonia water to carry out a precipitation reaction to obtain a precipitate, which is then placed under high temperature and high pressure conditions for further reaction, thereby nucleation and directional growth to obtain fibrous cerium oxide grains. In this invention, the mixing ratio of cerium salt solution and ammonia water is adjusted to regulate the intensity of the reaction, thus facilitating crystal nuclei formation and growth. Subsequently, in the hydrothermal reaction process, the directional growth of grains is promoted by controlling the hydrothermal temperature and reaction pressure. Finally, by controlling the calcination temperature and time, fibrous nano-cerium oxide is obtained.

[0006] In a further preferred embodiment, in step (1), the concentration of cerium ions in the cerium salt solution is 0.5–2 mol / L, and the concentration of the ammonia solution is 3–10 mol / L.

[0007] In a further preferred embodiment, in step (1), the cerium salt solution is obtained by diluting a cerium chloride solution with pure water; and the ammonia solution is obtained by diluting concentrated ammonia solution with pure water.

[0008] In a further preferred embodiment, in step (1), the cerium salt solution is added dropwise to the ammonia solution at a uniform rate to carry out the reaction until the pH value is 9 to obtain reactant A. The dropwise addition time of the cerium salt solution is 45-75 min. By controlling the dropwise addition rate of the cerium salt solution, the precipitation reaction process can be regulated to facilitate the formation of the target precipitate.

[0009] In a further preferred embodiment, in step (1), the cerium salt solution is added dropwise to the ammonia solution under stirring conditions of 300-500 r / min to carry out the reaction until the pH value is 9, and then the stirring is continued for 10-15 min under stirring conditions of 80-100 r / min, and then the reactant A is obtained by filtration.

[0010] In a further preferred embodiment, in step (2), reactant A is washed with pure water 3 to 5 times and filtered using a vacuum filter; in step (4), reactant B is washed with pure water 3 to 5 times and filtered using a centrifugal filter.

[0011] In a further preferred embodiment, in step (5), the drying temperature is 100–110°C, the drying time is 6–8 hours, and the moisture content of the dried cerium oxide precursor powder is below 5%. Controlling the moisture content of the dried cerium oxide precursor powder within a suitable range can prevent agglomeration and clumping in the early stage of calcination and is beneficial to obtaining materials with uniform particle size.

[0012] In a further preferred embodiment, in step (6), the cerium oxide precursor powder obtained in step (5) is placed in a calcining furnace, heated to 200–250°C and held at that temperature for 10–30 minutes, and then heated to 300–600°C and held at that temperature for 2–8 hours. Preheating the cerium oxide precursor powder to remove the water of crystallization not only improves the calcination efficiency and reduces energy consumption, but also promotes the directional growth of the cerium oxide crystal phase during the calcination stage.

[0013] Compared with existing technologies, this technical solution has the following advantages: 1. This invention can prepare fibrous nano-cerium oxide without adding a template agent during the preparation process, avoiding the introduction of impurities and the subsequent removal of the template agent, thus improving the purity of the product.

[0014] 2. The fibrous nano-cerium oxide powder prepared by this invention has the characteristics of good dispersibility and large specific surface area. The prepared cerium oxide powder is fibrous with good dispersibility, controllable specific surface area, and excellent adsorption performance, making it suitable for preparing high-end functional materials such as photocatalysts and ultraviolet absorbing materials.

[0015] 3. This invention directly uses cerium chloride precipitation-hydrothermal synthesis to prepare cerium oxide precursor. After washing and removing impurities, the cerium oxide precursor is dried and calcined to prepare fibrous nano-cerium oxide powder. Compared with using cerium nitrate as raw material, this shortens the process flow and helps control the preparation cost of cerium oxide. Attached Figure Description

[0016] Figure 1 This is an electron microscope image of the fibrous cerium oxide nanoparticles prepared by the method described in Example 1.

[0017] Figure 2 The image shows the XRD pattern of the fibrous cerium oxide nanoparticles prepared by the method described in Example 1.

[0018] Figure 3 This is a flowchart of the preparation method of fibrous nano-cerium oxide according to the present invention. Detailed Implementation

[0019] The present invention is further illustrated by the following examples, but these are not intended to limit the invention. Specific experimental conditions and methods not specified in the following examples are generally conventional methods well known to those skilled in the art.

[0020] Example 1: A method for preparing fibrous nano-cerium oxide, comprising the following steps: (1) Under stirring conditions of 300 r / min, the cerium salt solution was added dropwise to the ammonia solution at a uniform rate until the pH value was 9. Then, the stirring was continued for 10 min under stirring conditions of 80 r / min. The reaction was then filtered to obtain reactant A. The dropwise addition time of the cerium salt solution was 45 min. The volume ratio of the cerium salt solution to the ammonia solution was 1:3. The concentration of cerium ions in the cerium salt solution was 0.5 mol / L, and the concentration of the ammonia solution was 3 mol / L. The cerium salt solution was obtained by diluting the cerium chloride solution with pure water. The ammonia solution was obtained by diluting concentrated ammonia solution with pure water. (2) Wash reactant A obtained in step (1) three times with pure water and filter it with a vacuum filter. (3) The washed and filtered reactant A was placed in a high-pressure reactor and reacted for 15 h at a temperature of 150℃ and a pressure of 0.5MPa to obtain reactant B; (4) Wash the reactant B obtained in step (3) three times with pure water and filter it with a centrifugal filter. (5) The washed and filtered reactant B was placed in an oven to dry, and cerium oxide precursor powder was obtained. The drying temperature was 100℃ and the drying time was 8h. The moisture content of the dried cerium oxide precursor powder was 4%. (6) After the oxidant precursor powder obtained in step (5) is placed in the calcining furnace, it is first heated to 200℃ and kept at a constant temperature for 10 min, and then heated to 400℃ and kept at a constant temperature for h to obtain fibrous nano-cerium oxide.

[0021] The fibrous nano-cerium oxide powder prepared according to the method described in this embodiment has a width of 40-60 nm and a length of 180-300 nm.

[0022] Example 2: A method for preparing fibrous nano-cerium oxide, comprising the following steps: (1) Under stirring conditions of 400 r / min, the cerium salt solution was added dropwise to the ammonia solution at a uniform rate until the pH value was 9. Then, the stirring was continued for 12 min under stirring conditions of 90 r / min. The reaction was then filtered to obtain reactant A. The dropwise addition time of the cerium salt solution was 60 min. The volume ratio of the cerium salt solution to the ammonia solution was 1:5. The concentration of cerium ions in the cerium salt solution was 1 mol / L, and the concentration of the ammonia solution was 5 mol / L. The cerium salt solution was obtained by diluting the cerium chloride solution with pure water. The ammonia solution was obtained by diluting concentrated ammonia solution with pure water. (2) Wash reactant A obtained in step (1) with pure water 4 times and filter it using a vacuum filter. (3) The washed and filtered reactant A was placed in a high-pressure reactor and reacted for 12 h at a temperature of 120℃ and a pressure of 1MPa to obtain reactant B; (4) Wash the reactant B obtained in step (3) with pure water 4 times and filter it with a centrifugal filter. (5) The washed and filtered reactant B was placed in an oven to dry, and cerium oxide precursor powder was obtained. The drying temperature was 105℃ and the drying time was 7h. The moisture content of the dried cerium oxide precursor powder was 5%. (6) After the oxidant precursor powder obtained in step (5) is placed in the calcination furnace, it is first heated to 220℃ and kept at a constant temperature for 20 minutes, and then heated to 500℃ and kept at a constant temperature for 3 hours to obtain fibrous nano-cerium oxide.

[0023] The fibrous nano-cerium oxide powder prepared according to the method described in this embodiment has a width of 50-80 nm and a length of 230-400 nm.

[0024] Example 3: A method for preparing fibrous nano-cerium oxide, comprising the following steps: (1) Under stirring conditions of 300 r / min, the cerium salt solution was added dropwise to the ammonia solution at a uniform rate until the pH value was 9. Then, the stirring was continued for 15 min under stirring conditions of 100 r / min. The reaction was then filtered to obtain reactant A. The dropwise addition time of the cerium salt solution was 75 min. The volume ratio of the cerium salt solution to the ammonia solution was 2:3. The concentration of cerium ions in the cerium salt solution was 2 mol / L, and the concentration of the ammonia solution was 10 mol / L. The cerium salt solution was obtained by diluting the cerium chloride solution with pure water. The ammonia solution was obtained by diluting concentrated ammonia solution with pure water. (2) Wash reactant A obtained in step (1) five times with pure water and filter it using a vacuum filter. (3) The washed and filtered reactant A was placed in a high-pressure reactor and reacted for 18 hours at a temperature of 180℃ and a pressure of 0.4MPa to obtain reactant B; (4) Wash the reactant B obtained in step (3) with pure water 5 times and filter it with a centrifugal filter. (5) The washed and filtered reactant B was placed in an oven to dry, and cerium oxide precursor powder was obtained. The drying temperature was 110℃ and the drying time was 6h. The moisture content of the dried cerium oxide precursor powder was 5%. (6) After the oxidant precursor powder obtained in step (5) is placed in the calcination furnace, it is first heated to 250℃ and kept at a constant temperature for 30 min, and then heated to 400℃ and kept at a constant temperature for 5 h to obtain fibrous nano-cerium oxide.

[0025] The fibrous cerium oxide nanoparticles prepared according to the method described in this embodiment have a width of 30–60 nm and a length of 140–300 nm.

[0026] Example 4: A method for preparing fibrous nano-cerium oxide, comprising the following steps: (1) Under stirring conditions of 500 r / min, the cerium salt solution was added dropwise to the ammonia solution at a uniform rate until the pH value was 9. Then, the stirring was continued for 12 min under stirring conditions of 80 r / min. The reaction was then filtered to obtain reactant A. The dropwise addition time of the cerium salt solution was 60 min. The volume ratio of the cerium salt solution to the ammonia solution was 1:6. The concentration of cerium ions in the cerium salt solution was 1.5 mol / L, and the concentration of the ammonia solution was 8 mol / L. The cerium salt solution was obtained by diluting the cerium chloride solution with pure water. The ammonia solution was obtained by diluting concentrated ammonia solution with pure water. (2) Wash reactant A obtained in step (1) five times with pure water and filter it using a vacuum filter. (3) The washed and filtered reactant A was placed in a high-pressure reactor and reacted for 18 hours at a temperature of 150°C and a pressure of 2MPa to obtain reactant B; (4) Wash the reactant B obtained in step (3) with pure water 5 times and filter it with a centrifugal filter. (5) The washed and filtered reactant B was placed in an oven to dry, and cerium oxide precursor powder was obtained. The drying temperature was 105℃ and the drying time was 8h. The moisture content of the dried cerium oxide precursor powder was 4.6%. (6) After the oxidant precursor powder obtained in step (5) is placed in the calcining furnace, it is first heated to 200℃ and kept at a constant temperature for 25 minutes, and then heated to 500℃ and kept at a constant temperature for 6 hours to obtain fibrous nano-cerium oxide.

[0027] The fibrous cerium oxide nanoparticles prepared according to the method described in this embodiment have a width of 70–90 nm and a length of 580–790 nm.

[0028] Example 5: A method for preparing fibrous nano-cerium oxide, comprising the following steps: (1) Under stirring conditions of 400 r / min, the cerium salt solution was added dropwise to the ammonia solution at a uniform rate until the pH value was 9. Then, the stirring was continued for 10 min under stirring conditions of 100 r / min. The reaction was then filtered to obtain reactant A. The dropwise addition time of the cerium salt solution was 55 min. The volume ratio of the cerium salt solution to the ammonia solution was 1:3. The concentration of cerium ions in the cerium salt solution was 0.8 mol / L, and the concentration of the ammonia solution was 4 mol / L. The cerium salt solution was obtained by diluting the cerium chloride solution with pure water. The ammonia solution was obtained by diluting concentrated ammonia solution with pure water. (2) Wash reactant A obtained in step (1) with pure water 4 times and filter it using a vacuum filter. (3) The washed and filtered reactant A was placed in a high-pressure reactor and reacted for 24 hours at a temperature of 180℃ and a pressure of 5MPa to obtain reactant B; (4) Wash the reactant B obtained in step (3) with pure water 4 times and filter it with a centrifugal filter. (5) The washed and filtered reactant B was placed in an oven to dry, and cerium oxide precursor powder was obtained. The drying temperature was 105℃ and the drying time was 8h. The moisture content of the dried cerium oxide precursor powder was 5%. (6) After the oxidant precursor powder obtained in step (5) is placed in the calcining furnace, it is first heated to 230℃ and kept at a constant temperature for 15 minutes, and then heated to 600℃ and kept at a constant temperature for 2 hours to obtain fibrous nano-cerium oxide.

[0029] The fibrous nano-cerium oxide powder prepared according to the method described in this embodiment has a width of 50-80 nm and a length of 480-610 nm.

[0030] Example 6: A method for preparing fibrous nano-cerium oxide, comprising the following steps: (1) Under stirring conditions of 300 r / min, the cerium salt solution was added dropwise to the ammonia solution at a uniform rate until the pH value was 9. Then, the stirring was continued for 15 min under stirring conditions of 80 r / min. The reaction was then filtered to obtain reactant A. The dropwise addition time of the cerium salt solution was 65 min. The volume ratio of the cerium salt solution to the ammonia solution was 1:6. The concentration of cerium ions in the cerium salt solution was 1 mol / L, and the concentration of the ammonia solution was 5 mol / L. The cerium salt solution was obtained by diluting the cerium chloride solution with pure water. The ammonia solution was obtained by diluting concentrated ammonia solution with pure water. (2) Wash reactant A obtained in step (1) three times with pure water and filter it using a vacuum filter. (3) The washed and filtered reactant A was placed in a high-pressure reactor and reacted for 24 hours at a temperature of 180℃ and a pressure of 0.8MPa to obtain reactant B; (4) Wash the reactant B obtained in step (3) three times with pure water and filter it with a centrifugal filter. (5) The washed and filtered reactant B was placed in an oven to dry, and cerium oxide precursor powder was obtained. The drying temperature was 105℃ and the drying time was 7h. The moisture content of the dried cerium oxide precursor powder was 5%. (6) After the oxidant precursor powder obtained in step (5) is placed in the calcining furnace, it is first heated to 250℃ and kept at a constant temperature for 10 min, and then heated to 600℃ and kept at a constant temperature for 8 h to obtain fibrous nano-cerium oxide.

[0031] The fibrous nano-cerium oxide powder prepared according to the method described in this embodiment has a width of 30-70 nm and a length of 280-530 nm.

[0032] Experimental Example 1: Fibrous nano-cerium oxide powder was prepared according to the method described in Example 1, wherein in step (1), the volume ratio of cerium salt solution to ammonia water was 1:2, 1:3, 1:4, 2:1, 3:1, 2:5, 2:7. The crystal structure of the prepared cerium oxide nano-powder was detected, and the specific structure is shown in Table 1.

[0033] Table 1. Crystal structures of cerium oxide nanopowders prepared under different ratios of cerium salt solution and ammonia.

[0034] As can be seen from the data in Table 1, the crystal structure of cerium oxide nanopowder obtained under different ratios of cerium salt solution and ammonia water is different. Only by following the ratio of cerium salt solution and ammonia water specified by the method described in this invention can stable fibrous cerium oxide nanopowder be obtained.

[0035] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing fibrous nano-cerium oxide, characterized in that: Includes the following steps: (1) Under stirring conditions of 300-500 r / min, cerium salt solution is added dropwise to ammonia solution to carry out the reaction until the pH value is 9 to obtain reactant A; the volume ratio of cerium salt solution to ammonia solution is (1-3):(3-6); (2) Wash and filter the reactant A obtained in step (1); (3) Place the washed and filtered reactant A into a high-pressure reactor and react for 10 to 48 hours at a temperature of 110 to 180°C and a pressure of 0.4 to 5 MPa to obtain reactant B; (4) Wash and filter the reactant B obtained in step (3); (5) The washed and filtered reactant B was placed in an oven and dried to obtain cerium oxide precursor powder; (6) The cerium oxide precursor powder obtained in step (5) is placed in a calcining furnace for calcination to obtain fibrous nano-cerium oxide. The calcination temperature is 300-600℃ and the calcination time is 2-8h.

2. The method for preparing fibrous nano-cerium oxide according to claim 1, characterized in that: In step (1), the concentration of cerium ions in the cerium salt solution is 0.5 to 2 mol / L, and the concentration of the ammonia solution is 3 to 10 mol / L.

3. The method for preparing fibrous nano-cerium oxide according to claim 1, characterized in that: In step (1), the cerium salt solution is obtained by diluting the cerium chloride solution with pure water; the ammonia solution is obtained by diluting concentrated ammonia solution with pure water.

4. The method for preparing fibrous nano-cerium oxide according to claim 1, characterized in that: In step (1), the cerium salt solution is added dropwise to the ammonia solution at a constant rate to carry out the reaction until the pH value is 9 to obtain reactant A. The dropwise addition time of the cerium salt solution is 45 to 75 minutes.

5. The method for preparing fibrous nano-cerium oxide according to claim 4, characterized in that: In step (1), the cerium salt solution is added dropwise to the ammonia solution under stirring conditions of 300-500 r / min to carry out the reaction until the pH value is 9. Then, the stirring is continued for 10-15 min under stirring conditions of 80-100 r / min, and then the reactant A is obtained by filtration.

6. The method for preparing fibrous nano-cerium oxide according to claim 1, characterized in that: In step (2), reactant A is washed with pure water 3 to 5 times and filtered using a vacuum filter; in step (4), reactant B is washed with pure water 3 to 5 times and filtered using a centrifugal filter.

7. The method for preparing fibrous nano-cerium oxide according to claim 1, characterized in that: In step (5), the drying temperature is 100-110℃, the drying time is 6-8h, and the moisture content of the dried cerium oxide precursor powder is below 5%.

8. The method for preparing fibrous nano-cerium oxide according to claim 1, characterized in that: In step (6), the oxidant precursor powder obtained in step (5) is placed in a calcining furnace, heated to 200-250℃ and held for 10-30 minutes, and then heated to 300-600℃ and held for 2-8 hours.

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