Nano cerium oxide synthesized based on Taylor vortex reactor as well as preparation method and application of nano cerium oxide

Abstract

The invention discloses nano cerium oxide synthesized based on a Taylor vortex reactor as well as a preparation method and application of the nano cerium oxide. The specific method comprises the following steps: dissolving cerium salt and a dispersing agent in water to form a reaction solution A, transferring the reaction solution A into a Taylor vortex reactor, dropwise adding an alkali solution, regulating and controlling the temperature of the Taylor vortex reactor and the material retention time to obtain a precursor, and burning out the precursor to obtain the cubic and / or rod-like nano cerium oxide. The cubic and / or rod-like nano cerium oxide prepared by the method has smaller particle size and better uniformity, and has wide application value.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterial preparation technology, specifically relating to a nano-cerium oxide synthesized based on a Taylor vortex reactor, its preparation method, and its application. Background Technology

[0002] As a metal semiconductor oxide, nano-cerium oxide is widely used in many fields, including fuel cells and solar cells. Because Ce... 4f and Ce 5d The electron states of these electrons have the same energy, and the potential energy barrier of their electron density distributions is very low, which makes it relatively easy for them to undergo reversible Ce transitions. 3+ / Ce 4+ This transformation allows for better oxygen storage or oxygen vacancy generation. Furthermore, cerium oxide exhibits excellent thermal and chemical stability, maintaining catalytic activity even under high temperatures and harsh environments, thus finding wide application in the chemical industry and environmental protection fields.

[0003] Methods for preparing nano-cerium oxide include hydrothermal synthesis, co-precipitation, and sol-gel methods. Among these, hydrothermal synthesis is the most effective and popular method, but it usually requires complex operations to form a uniform nanostructure. For example, patent application CN120057973A discloses a highly stable nano-cerium oxide dispersion and its preparation method, which involves mixing cerium salt, alkaline solution, and plant extracts, followed by steps such as ultrasonication, stirring, oxidation, and sedimentation to obtain cubic nano-cerium oxide, but this method is cumbersome. Patent application CN120573738A discloses a method for preparing a highly suspended and easily dispersible nano-cerium oxide liquid using ammonium chloride as an aid, yielding nano-cerium oxide with a primary particle size of 50-100 nm, but its morphology control is poor and its uniformity is poor.

[0004] Existing morphologies of cerium oxide nanoparticles include spherical, cubic, and rod-shaped forms. Different shapes expose varying proportions of crystal facets, which possess drastically different surface atomic arrangements, unsaturated chemical bonds, and electronic structures. This results in significant differences in their catalytic activity, adsorption capacity, and interaction with other substances. While existing spherical cerium oxide nanoparticles have a large specific surface area and can achieve relatively stable and uniform distribution, they are typically mixtures of multiple stable crystal facets with low surface energy (such as {111}), resulting in a low proportion of active crystal facets and thus lower activity for applications in catalysis and other fields (such as automotive exhaust purification catalysts). Cubic cerium oxide nanoparticles primarily expose the {100} crystal facets, exhibiting the highest activity. This makes them suitable for catalysis (e.g., automotive exhaust purification catalysts, catalytic combustion of VOCs in industrial waste gas treatment, hydrogen production via water-gas shift reaction) and applications requiring a low-defect background, such as stable supports or polishing / transparent slurries. Interface engineering is more controllable, and constructing smooth interfaces with conductive agents / binders in alkaline electrocatalysis and electrochemical systems is easier. However, they suffer from wide particle size distribution and poor particle size uniformity. Rod-shaped cerium oxide nanoparticles primarily expose the {110} and {100} crystal facets, with {110} being one of the most active facets, also exhibiting high catalytic activity. Furthermore, their defects are similar to those of Ce. 3+ With higher oxygen content and more abundant oxygen vacancies, it has stronger low-temperature reducibility and oxygen storage capacity (OSC), making it suitable for reactions mainly involving lattice oxygen. However, it also has problems such as wide particle size distribution and poor particle size uniformity.

[0005] Therefore, it is necessary to study how to solve the problems of wide particle size distribution, poor uniformity, poor stability, and long synthesis time of cubic and rod-shaped cerium oxide nanoparticles synthesized by existing methods. Summary of the Invention

[0007] To address the shortcomings and deficiencies of existing technologies, the primary objective of this invention is to provide a method for preparing cubic and rod-shaped cerium oxide nanoparticles based on a Taylor vortex reactor. The cubic and rod-shaped cerium oxide nanoparticles prepared by this invention have smaller particle sizes and better uniformity and stability, thus solving the problems of wide particle size distribution, poor uniformity, poor stability, and long synthesis time of cubic and rod-shaped cerium oxide nanoparticles synthesized by existing methods.

[0008] Another object of the present invention is to provide a cubic and rod-shaped cerium oxide nanoparticle synthesized based on a Taylor vortex reactor obtained by the above preparation method.

[0009] Another object of the present invention is to provide an application of the cubic and rod-shaped cerium oxide nanoparticles synthesized based on a Taylor vortex reactor.

[0010] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing nano-cerium oxide based on a Taylor vortex reactor, comprising the following steps: (1) Dissolve cerium salt and dispersant in water to obtain a mixed solution. Transfer the mixed solution to a Taylor vortex reactor and rotate the inner cylinder. After adding alkaline solution, adjust the temperature of the Taylor vortex reactor and control the material residence time. Discharge the material and dry it to obtain the precursor. (2) The precursor is calcined to obtain cubic and / or rod-shaped nano-cerium oxide.

[0011] Preferably, the cerium salt in step (1) includes at least one of cerium nitrate hexahydrate, cerium nitrate trihydrate, cerium chloride, cerium chloride hexahydrate, cerium carbonate, cerium oxalate, and cerium sulfate.

[0012] Preferably, the dispersant in step (1) includes at least one of citric acid, urea, polyethylene glycol and ethylenediaminetetraacetic acid.

[0013] Preferably, the molar ratio of cerium salt and dispersant in step (1) is 1:3-1:5.

[0014] Preferably, in the mixed solution of step (1), the concentration of cerium salt is 0.025-0.3 mol / L.

[0015] Preferably, the rotational speed of the inner cylinder in step (1) is 100-1000 rpm; more preferably 200-800 rpm.

[0016] Preferably, the alkaline solution in step (1) includes at least one of sodium hydroxide solution, potassium hydroxide solution, calcium hydroxide solution, barium hydroxide solution, ammonia solution, ethylenediamine solution, and triethylamine solution.

[0017] Preferably, the concentration of the alkaline solution in step (1) is 5-20 mol / L.

[0018] Preferably, the molar ratio of cerium in the cerium salt and alkali in the alkaline solution in step (1) is 1: (50-300).

[0019] Preferably, the temperature of the Taylor vortex reactor in step (1) is 80-200℃, more preferably 100-180℃; the material residence time is 1-36 h, more preferably 3-12 h.

[0020] Specifically, by adjusting the temperature of the Taylor vortex reactor to 80-140℃ and the residence time to 1-36 h, rod-shaped cerium oxide nanoparticles were obtained; by adjusting the temperature of the Taylor vortex reactor to 140-200℃ and the residence time to 1-36 h, cubic cerium oxide nanoparticles were obtained.

[0021] Preferably, the calcination temperature in step (2) is 300-600℃ and the calcination time is 3-8 h.

[0022] Preferably, the calcination process in step (2) is carried out in an air atmosphere.

[0023] Preferably, the Taylor vortex reactor in step (1) includes a material reactor, wherein an inner cylinder for stirring materials is arranged along the central axis of the material reactor; A heating layer for heating the material is provided on the outside of the material reactor. The material reactor is provided with an inlet and an outlet on its side wall.

[0024] More preferably, the inner cylinder is connected to the outer motor.

[0025] More preferably, the heating layer sidewall is provided with a heat transfer oil inlet and a heat transfer oil outlet; the heat transfer oil inlet and the heat transfer oil outlet are connected to the heating circulator.

[0026] More preferably, the heat transfer oil inlet is an axial heat transfer oil inlet; and the heat transfer oil outlet is an axial heat transfer oil outlet.

[0027] More preferably, the feed inlet is a biaxial feed inlet connected to a feed pump.

[0028] More preferably, the discharge port is an axial discharge port.

[0029] Secondly, the present invention provides a cubic and / or rod-shaped cerium oxide nanoparticle obtained by the above preparation method.

[0030] Thirdly, the present invention provides the application of the above-mentioned cubic and / or rod-shaped nano-cerium oxide.

[0031] Preferably, the application areas include catalysts, fuel cells, and solar cells.

[0032] More preferably, the catalyst includes an automotive exhaust purification catalyst, an industrial waste gas VOCs combustion catalyst, and a water-gas shift reaction hydrogen production catalyst.

[0033] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) The Taylor vortex reactor of the present invention has high shear stress and mixing efficiency, which can accelerate the nucleation time of nano-cerium oxide and reduce the hydrothermal reaction time.

[0034] (2) This invention utilizes the high shear mixing characteristics of the Taylor vortex reactor to solve the particle size dispersion problem caused by uneven mass transfer in the reaction system in the traditional hydrothermal method, and can controllably synthesize cubic and rod-shaped nano-cerium oxide. The prepared nano-cerium oxide particles have smaller particle size and better uniformity and stability.

[0035] (3) Cubic cerium oxide nanoparticles have {100} crystal faces as the main exposed facets, exhibiting relatively good thermal / morphological stability. The {100} facets have higher vacancy formation energy and lower defect density, resulting in more uniform surface adsorption / activation sites, facilitating the controlled deposition of noble metals. They are suitable as stable supports or for polishing / transparent pastes and other applications requiring a low-defect background. Interface engineering is more controllable, and it is easier to construct smooth interfaces with conductive agents / binders in alkaline electrocatalysis and electrochemical systems. Rod-shaped cerium oxide nanoparticles typically expose {110} / {100} crystal faces, with defects and Ce... 3+ With higher oxygen vacancy content and richer oxygen content, it has stronger low-temperature reducibility and oxygen storage and release (OSC) capacity, making it suitable for reactions in which lattice oxygen is the main participant, such as CO oxidation, soot / VOC oxidation, WGS / CO-PROX and other reactions in which lattice oxygen is the main participant; the one-dimensional structure provides continuous transport channels, shortens the migration path of electrons / holes and oxygen ions, and reduces the recombination probability, thereby achieving more efficient carrier separation in photocatalysis / thermal catalysis. Attached Figure Description

[0036] Figure 1 The X-ray diffraction patterns are those of nano-cerium oxide obtained by the preparation methods in Examples 1-5 of this invention.

[0037] Figure 2 The X-ray diffraction patterns are those of nano-cerium oxide obtained by the preparation methods in Examples 6-11 of this invention.

[0038] Figure 3 The image shown is a TEM image of the product obtained in Example 1, where the nano-cerium oxide is cubic.

[0039] Figure 4 The image shown is a TEM image of the product obtained in Example 6. The nano-cerium oxide is rod-shaped (short rod).

[0040] Figure 5 The X-ray diffraction patterns are of nano-cerium oxide obtained by the preparation methods of Comparative Examples 1-2 of this invention.

[0041] Figure 6 The image shown is a TEM image of the product obtained in Comparative Example 1.

[0042] Figure 7 The image shown is a TEM image of the product obtained in Comparative Example 2.

[0043] Figure 8This is a schematic diagram of the Taylor vortex reactor structure, where 1 is an external motor, 2 is a feed pump, 3 is a feed pump, 4 is a heating circulator, 5 is an axial feed port, 6 is an axial feed port, 7 is an axial heating oil inlet, 8 is an axial heating oil outlet, 9 is an axial discharge port, 10 is an inner cylinder, 11 is a material reactor, and 12 is a heating layer. Detailed Implementation

[0044] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the implementation of the present invention is not limited thereto.

[0045] Unless otherwise specified in the embodiments of this invention, the conditions shall be performed according to conventional conditions or conditions recommended by the manufacturer. All raw materials and reagents used, unless otherwise specified, are commercially available conventional products.

[0046] The structure of the Taylor vortex reactor used in the embodiments of the present invention is as follows: Figure 8 The structure includes a material reactor (11), with an inner cylinder (10) for stirring materials arranged along the central axis of the material reactor (11); the inner cylinder (10) is connected to an external motor (1); The material reactor (11) is provided with a heating layer (12) for heating the material on the outside; the heating layer (12) is provided with an axial heat-guiding oil inlet (7) and an axial heat-guiding oil outlet (8) on the side wall; the axial heat-guiding oil inlet (7) and the axial heat-guiding oil outlet (8) are connected to the heating circulator (4); The material reactor (11) is provided with a double axial feed port (5) and (6) and an axial discharge port (9) on its side wall; the axial feed port (5) is connected to the feed pump (2), and the axial feed port (6) is connected to the feed pump (3).

[0047] Example 1 Solution A was prepared by dissolving Ce(NO3)3•6H2O and citric acid in deionized water, with Ce(NO3)3•6H2O concentration of 0.1 mol / L and citric acid concentration of 0.4 mol / L. The solution was stirred for 30 min to ensure complete dissolution. The solution was then fed into a Taylor vortex reactor using a peristaltic pump, and the inner cylinder was rotated. The stirring was started and maintained at 500 rpm. Solution B was prepared by dissolving NaOH in deionized water, with an initial NaOH concentration of 15.0 mol / L. After solution B cooled to room temperature, it was added dropwise to solution A, with a Ce to NaOH molar ratio of 1:290. After all solution B was added, the valve was closed, and the temperature was raised to 180℃ and maintained for 3 h (i.e., the Taylor vortex reactor temperature was controlled at 180℃, and the material residence time was controlled at 3 h). After the mixed solution cooled to room temperature, the valve was opened, and the mixed solution was transferred to a centrifuge tube. After centrifugation, the solution was dried at 80℃ for 12 hours. h; After drying, the powder was pre-treated by grinding in a mortar and then placed in a crucible. It was then transferred to a muffle furnace and calcined at 400℃ for 4 h in air, finally yielding yellow cerium oxide nanoparticles. Cubic cerium oxide nanoparticles were obtained, and XRD patterns were as follows. Figure 1 As shown, TEM Figure 3 As shown in Table 1, the particle size is as follows.

[0048] Example 2 A method for synthesizing nano-cerium oxide using a Taylor vortex reactor, the steps of which are basically the same as those in Example 1, with the difference being: The reaction time of the Taylor vortex reactor is 6 h.

[0049] The XRD of the obtained powder is as follows Figure 1 As shown in Table 1, the particle size is as follows.

[0050] Example 3 A method for synthesizing nano-cerium oxide using a Taylor vortex reactor, the steps of which are basically the same as those in Example 1, with the difference being: The reaction time of the Taylor vortex reactor is 12 h.

[0051] The XRD of the obtained powder is as follows Figure 1 As shown in Table 1, the particle size is as follows.

[0052] Example 4 A method for synthesizing nano-cerium oxide using a Taylor vortex reactor, the steps of which are basically the same as those in Example 1, with the difference being: The inner cylinder of the Taylor vortex reactor rotates at 200 rpm.

[0053] The XRD of the obtained powder is as follows Figure 1 As shown in Table 1, the particle size is as follows.

[0054] Example 5 A method for synthesizing nano-cerium oxide using a Taylor vortex reactor, the steps of which are basically the same as those in Example 1, with the difference being: The inner cylinder of the Taylor vortex reactor rotates at 800 rpm.

[0055] The XRD of the obtained powder is as follows Figure 1 As shown in Table 1, the particle size is as follows.

[0056] Example 6 A method for synthesizing nano-cerium oxide using a Taylor vortex reactor, the steps of which are basically the same as those in Example 1, with the difference being: The reaction temperature of the Taylor vortex reactor is 100℃.

[0057] The XRD of the obtained powder is as follows Figure 2 As shown, TEM Figure 4 As shown in Table 1, the particle size is as follows.

[0058] Example 7 A method for synthesizing nano-cerium oxide using a Taylor vortex reactor, the steps of which are basically the same as those in Example 6, with the difference being: The reaction time of the Taylor vortex reactor is 6 h.

[0059] The XRD of the obtained powder is as follows Figure 2 As shown in Table 1, the particle size is as follows.

[0060] Example 8 A method for synthesizing nano-cerium oxide using a Taylor vortex reactor, the steps of which are basically the same as those in Example 6, with the difference being: The reaction time of the Taylor vortex reactor is 12 h.

[0061] The XRD of the obtained powder is as follows Figure 2 As shown in Table 1, the particle size is as follows.

[0062] Example 9 A method for synthesizing nano-cerium oxide using a Taylor vortex reactor, the steps of which are basically the same as those in Example 6, with the difference being: The inner cylinder of the Taylor vortex reactor rotates at 200 rpm.

[0063] The XRD of the obtained powder is as follows Figure 2 As shown in Table 1, the particle size is as follows.

[0064] Example 10 A method for synthesizing nano-cerium oxide using a Taylor vortex reactor, the steps of which are basically the same as those in Example 6, with the difference being: The inner cylinder of the Taylor vortex reactor rotates at 800 rpm.

[0065] The XRD of the obtained powder is as follows Figure 2 As shown in Table 1, the particle size is as follows.

[0066] Example 11 A method for synthesizing nano-cerium oxide using a Taylor vortex reactor, the steps of which are basically the same as those in Example 6, with the difference being: The reaction temperature of the Taylor vortex reactor is 140℃.

[0067] The XRD of the obtained powder is as follows Figure 2 As shown in Table 1, the particle size is as follows.

[0068] Comparative Example 1 Solution A was prepared by dissolving Ce(NO3)3•6H2O and citric acid in deionized water, with Ce(NO3)3•6H2O concentration of 0.1 mol / L and citric acid concentration of 0.4 mol / L. The solution was stirred for 30 min to ensure complete dissolution. Solution B was prepared by dissolving NaOH in deionized water, with an initial NaOH concentration of 15.0 mol / L. After solution B cooled to room temperature, it was added dropwise to solution A, with a Ce to NaOH molar ratio of 1:290. Magnetic stirring was maintained at 500 rpm during the addition process, and stirring continued for 30 min after the addition was complete. The mixed solution was transferred to a polytetrafluoroethylene (PTFE) bottle and placed in a hydrothermal synthesis reactor equipped with PTFE. The reaction was carried out at 180℃ in an oven for 3 h. After the hydrothermal synthesis reactor cooled, the reaction solution was centrifuged and dried at 80℃ for 12 hours. h; After drying, the powder was pre-treated by grinding in a mortar and then placed in a crucible. It was then transferred to a muffle furnace and calcined at 400℃ for 4 h in air, finally yielding yellow cerium oxide nanoparticles. Cubic cerium oxide nanoparticles were obtained, and XRD patterns were as follows. Figure 5 As shown, TEM Figure 6 As shown in Table 1, the particle size is as follows.

[0069] Comparative Example 2 A method for synthesizing nano-cerium oxide using a Taylor vortex reactor, the steps of which are basically the same as those in Comparative Example 1, the difference being: The hydrothermal reaction temperature is 100℃.

[0070] The XRD of the obtained powder is as follows Figure 5 As shown, TEM Figure 7 As shown in Table 1, the particle size is as follows.

[0071] Table 1. Particle size and morphology of cerium oxide nanoparticles obtained in the examples and comparative examples.

[0072] In summary, under the conditions of consistent reaction temperature, reaction time, and stirring rate, the cubic and rod-shaped cerium oxide nanoparticles obtained in the embodiments of the present invention have smaller particle sizes and better uniformity.

[0073] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing nano-cerium oxide based on a Taylor vortex reactor, characterized in that, Includes the following steps: (1) Dissolve cerium salt and dispersant in water to obtain a mixed solution. Transfer the mixed solution to a Taylor vortex reactor and rotate the inner cylinder. After adding alkaline solution, adjust the temperature of the Taylor vortex reactor and control the material residence time. Discharge the material and dry it to obtain the precursor. (2) The precursor is calcined to obtain cubic and / or rod-shaped nano-cerium oxide.

2. The preparation method according to claim 1, characterized in that, In step (1), the temperature of the Taylor vortex reactor is adjusted to 80-200℃, more preferably 100-180℃; And / or, the controlled material residence time in step (1) is 1-36 h, more preferably 3-12 h.

3. The preparation method according to claim 1 or 2, characterized in that, In the mixed solution described in step (1), the concentration of cerium salt is 0.025-0.3 mol / L; And / or, the rotational speed of the inner cylinder in step (1) is 100-1000 rpm; more preferably 200-800 rpm; And / or, the concentration of the alkaline solution in step (1) is 5-20 mol / L.

4. The preparation method according to claim 1 or 2, characterized in that, The molar ratio of cerium salt and dispersant in step (1) is 1:3-1:

5.

5. The preparation method according to claim 1 or 2, characterized in that, In step (1), the molar ratio of cerium in the cerium salt to alkali in the alkaline solution is 1:(50-300).

6. The preparation method according to claim 1 or 2, characterized in that, The cerium salt in step (1) includes at least one of cerium nitrate hexahydrate, cerium nitrate trihydrate, cerium chloride, cerium chloride hexahydrate, cerium carbonate, cerium oxalate, and cerium sulfate; And / or, the dispersant in step (1) includes at least one of citric acid, urea, polyethylene glycol and ethylenediaminetetraacetic acid.

7. The preparation method according to claim 1 or 2, characterized in that, The calcination temperature in step (2) is 300-600℃; And / or, the calcination treatment in step (2) takes 3-8 hours; And / or, the calcination process described in step (2) is carried out in an air atmosphere.

8. The preparation method according to claim 1 or 2, characterized in that, The alkaline solution in step (1) includes at least one of sodium hydroxide solution, potassium hydroxide solution, calcium hydroxide solution, barium hydroxide solution, ammonia solution, ethylenediamine solution, and triethylamine solution.

9. The preparation method according to any one of claims 1-8 yields a nano-cerium oxide synthesized based on a Taylor vortex reactor.

10. The application of the nano-cerium oxide synthesized based on the Taylor vortex reactor as described in claim 9.

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