Cerium dioxide, preparation method thereof and application of ionic liquid

Abstract

The invention discloses cerium dioxide, a preparation method thereof and application of ionic liquid. The particle size of the cerium dioxide is 10-80 nm, and at least a part of cerium dioxide particles are square blocks. The cerium dioxide of the present invention has a specific particle size and form.

Description

Technical Field

[0001] The present invention relates to cerium dioxide, a preparation method thereof, and uses of an ionic liquid. Background Art

[0002] Cerium dioxide is a rare earth oxide, which has excellent physical and chemical properties and is widely used in fields such as chemical mechanical polishing of precision optical glass and silicon wafers for very large scale integrated circuits, tribochemical activity, catalysis, fuel cells, and solid electrolytes. The key factors affecting the performance of cerium dioxide are its morphology, size, and microstructure. Currently, the main methods for preparing cerium dioxide include coprecipitation method, high-temperature calcination method, hydrothermal method, microemulsion method, and sol-gel method.

[0003] Ionic liquids are ionic compounds that are liquid at room temperature. As a green chemical reagent and green organic salt, they have advantages such as low volatility, good solubility, and high thermal stability. They are a new type of functional material and can play their self-assembly ability in the synthesis of inorganic materials and can be used as templates to regulate the structure and morphology of samples.

[0004] CN118439646A discloses a method for preparing CeO 2 particles. An aqueous solution of a cerium salt is mixed with an ionic liquid to obtain a mixture; the mixture is reacted at 150-240°C, and after the reaction is completed, solid-liquid separation is carried out to obtain a precursor; the precursor is calcined to obtain CeO 2 particles. The particle size of the CeO 2 particles is 100-500 nm and is similar to a polyhedral sphere. Summary of the Invention

[0005] One object of the present invention is to provide a cerium dioxide, the particle size of which is 10-80 nm, and at least a part of the cerium dioxide particles are square-shaped. Another object of the present invention is to provide a preparation method of cerium dioxide, which can obtain cerium dioxide with good dispersibility, a specific particle size, and morphology. Further, the cerium dioxide obtained by this preparation method has a high crystallinity. Still another object of the present invention is to provide uses of an ionic liquid.

[0006] The present invention achieves the above objects through the following technical solutions.

[0007] On the one hand, the present invention provides a cerium dioxide, the particle size of which is 10-80 nm, and at least a part of the cerium dioxide particles are square-shaped.

[0008] The particle size of the cerium dioxide of the present invention is preferably 20-70 nm; more preferably 20-50 nm. The cerium dioxide of the present invention is cerium dioxide particles.

[0009] At least 5% or more of the cerium dioxide particles are square-shaped; preferably, at least 20% or more of the cerium dioxide particles are square-shaped; more preferably, at least 30% or more of the cerium dioxide particles are square-shaped. In some embodiments, at least 60% or less of the cerium dioxide particles are square-shaped. In some other embodiments, at least 50% or less of the cerium dioxide particles are square-shaped. In still some other embodiments, at least 40% or less of the cerium dioxide particles are square-shaped.

[0010] For the cerium dioxide according to the present invention, preferably, at least a part of the cerium dioxide particles are polygonal.

[0011] At least 5% or more of the cerium dioxide particles are polygonal; preferably, at least 20% or more of the cerium dioxide particles are polygonal; more preferably, at least 30% or more of the cerium dioxide particles are polygonal. In some embodiments, at least 60% or less of the cerium dioxide particles are polygonal. In some other embodiments, at least 50% or less of the cerium dioxide particles are polygonal. In still some other embodiments, at least 40% or less of the cerium dioxide particles are polygonal.

[0012] On the other hand, the present invention provides a method for preparing the above-mentioned cerium dioxide, comprising the following steps:

[0013] (1) Reacting a mixture containing an inorganic cerium salt and an ionic liquid at 150 - 240 °C to obtain a precursor;

[0014] The ionic liquid is selected from one or more of imidazole-based ionic liquids, pyridine-based ionic liquids, and piperidine-based ionic liquids, and the anion in the ionic liquid is iodide ion (I - );

[0015] The molar volume ratio of the inorganic cerium salt to the ionic liquid is (0.001 - 0.006) mol: 30 mL;

[0016] (2) Calcining the precursor at 650 - 850 °C to obtain cerium dioxide.

[0017] In the present invention, the molar volume ratio of the inorganic cerium salt to the ionic liquid is preferably (0.002 - 0.005) mol: 30 mL; more preferably (0.002 - 0.0035) mol: 30 mL. This helps to form cerium dioxide with a specific particle size and shape and improve the dispersibility.

[0018] According to the preparation method of the present invention, preferably, the cation of the imidazole-based ionic liquid is as shown in formula (I):

[0019]

[0020] Wherein, R 1 and R 2independently selected from C1-C6 alkyl groups and C2-C6 alkenyl groups; R 3 selected from H, C1-C6 alkyl groups, and C2-C6 alkenyl groups;

[0021] The cation of the pyridine-based ionic liquid is shown in formula (II):

[0022]

[0023] wherein, R 4 is selected from C1-C6 alkyl groups and C2-C6 alkenyl groups;

[0024] The cation of the piperidine-based ionic liquid is shown in formula (III):

[0025]

[0026] wherein, R 5 and R 6 are independently selected from C1-C6 alkyl groups and C2-C6 alkenyl groups.

[0027] R 1 is preferably selected from C1-C4 alkyl groups and C2-C3 alkenyl groups. Preferably, the alkyl group is a linear alkyl group; more preferably, the alkyl group is a straight-chain alkyl group. The alkenyl group is preferably a linear alkenyl group; more preferably, it is a straight-chain alkenyl group. For example, R 1 can be selected from methyl, ethyl, propyl, butyl, vinyl, propenyl, and allyl.

[0028] R 2 is preferably selected from C1-C6 alkyl groups; more preferably, it is selected from C1-C3 alkyl groups. Preferably, the alkyl group is a linear alkyl group; more preferably, the alkyl group is a straight-chain alkyl group. The alkenyl group is preferably a linear alkenyl group; more preferably, it is a straight-chain alkenyl group. For example, R 2 can be selected from methyl, ethyl, propyl, butyl, pentyl, and hexyl.

[0029] R 3 is preferably selected from H and C1-C6 alkyl groups; more preferably, it is selected from H and C1-C3 alkyl groups. Preferably, the alkyl group is a linear alkyl group; more preferably, the alkyl group is a straight-chain alkyl group. The alkenyl group is preferably a linear alkenyl group; more preferably, it is a straight-chain alkenyl group. For example, R 3 can be selected from H, methyl, ethyl, and propyl.

[0030] R 4 is preferably selected from C1-C6 alkyl groups; more preferably, it is selected from C1-C4 alkyl groups. Preferably, the alkyl group is a linear alkyl group; more preferably, the alkyl group is a straight-chain alkyl group. The alkenyl group is preferably a linear alkenyl group; more preferably, it is a straight-chain alkenyl group. For example, R 4 can be selected from methyl, ethyl, propyl, and butyl.

[0031] Preferably, R 5 and R 6 are each independently selected from C1-C6 alkyl groups; more preferably, R 5 and R 6 are each independently selected from C1-C3 alkyl groups. Preferably, the alkyl group is a linear alkyl group; more preferably, the alkyl group is a straight-chain alkyl group. The alkenyl group is preferably a linear alkenyl group; more preferably, it is a straight-chain alkenyl group. For example, R 5 can be selected from methyl, ethyl, and propyl. For example, R 6 can be selected from methyl, ethyl, and propyl.

[0032] According to the preparation method of the present invention, preferably, the cation in the ionic liquid is selected from one or more of 1-butyl-3-methylimidazole, 1-ethyl-3-methylimidazole, 1-vinyl-3-methylimidazole, 1,2,3-trimethylimidazole, N-propyl-N-methylpiperidine, and N-butylpyridine.

[0033] According to an embodiment of the present invention, the ionic liquid is 1-butyl-3-methylimidazolium iodide ionic liquid.

[0034] The above ionic liquid helps to form cerium dioxide with a specific particle size and shape and improves the dispersibility.

[0035] The purity of the ionic liquid of the present invention is greater than or equal to 99 wt%; preferably, the purity is greater than or equal to 99.5 wt%.

[0036] According to the preparation method of the present invention, preferably, no additional water is added to the mixture.

[0037] Preferably, the mixture of the present invention may contain trace amounts of water brought in by the ionic liquid, but no additional water is added to the mixture of the present invention. More preferably, the mixture of the present invention is composed of an ionic liquid and an inorganic cerium salt.

[0038] In step (1), the reaction temperature can be 150-240 °C; preferably 180-220 °C.

[0039] In step (1), the reaction time can be 10-20 h; preferably 15-18 h.

[0040] The mixture can be reacted in a polytetrafluoroethylene reaction kettle.

[0041] The reaction can be carried out under anhydrous, surfactant-free, and dispersant-free conditions. The "anhydrous" means that no additional water is added, but trace amounts of water brought in by the ionic liquid are not excluded.

[0042] The above reaction conditions help to form cerium dioxide with good dispersibility and a specific particle size and morphology.

[0043] In some embodiments, the following steps are further included: separating the solid and liquid of the reaction product obtained from the reaction to obtain a solid product. Washing the solid product and then drying it to obtain a precursor.

[0044] The reaction product can be separated into solid and liquid by centrifugation or filtration. Preferably, centrifugation is used. Before the solid-liquid separation, the reaction product can be first cooled to 20-35 °C; preferably, it is cooled to 25-30 °C.

[0045] The purpose of washing is to clean the impurities attached to the solid product. The washing method is not limited herein, and conventional methods in the art can be used. The detergent used for washing can be selected from monohydric alcohols containing 1-6 carbon atoms. For example, methanol, ethanol, propanol, isopropanol.

[0046] The purpose of drying is to remove the liquid attached to the surface of the washed solid product. Preferably, the drying temperature is 60-95 °C; more preferably, it is 70-85 °C. Preferably, the drying time is 7-15 h; preferably, it is 9-12 h. Drying can be carried out in an oven.

[0047] According to the preparation method of the present invention, preferably, the following steps are further included:

[0048] Mixing the solid inorganic cerium salt and the ionic liquid to obtain a mixture;

[0049] The inorganic cerium salt is selected from one or more of cerium chloride, cerium carbonate, cerium nitrate, and cerium sulfate.

[0050] According to an embodiment of the present invention, the inorganic cerium salt is cerium nitrate.

[0051] The mixing can be carried out under stirring conditions. The stirring time can be 30-100 min; preferably, it is 30-60 min.

[0052] The solid inorganic cerium salt and the ionic liquid can be mixed at 20-45 °C, preferably at 35-45 °C.

[0053] According to the preparation method of the present invention, preferably, in step (1), the reaction time is 10-20 h; in step (2), the calcination time is 1-5 h.

[0054] In the present invention, the calcination temperature can be 650-850 °C; preferably, it is 700-800 °C. This helps to obtain cerium dioxide with a specific morphology and particle size and improve the dispersion of cerium dioxide.

[0055] In the present invention, the calcination time can be 1-5 h; preferably, it is 2-3 h.

[0056] Calcination can be carried out in a muffle furnace.

[0057] In some embodiments, the following steps are further included: after cooling the calcined product, grinding is carried out to obtain cerium dioxide.

[0058] Grinding disperses the cerium dioxide particles that are partially adhered or agglomerated together, and does not change the shape and particle size of the cerium dioxide particles.

[0059] On the other hand, the present invention provides a use of an ionic liquid in regulating the particle size and / or morphology of cerium dioxide, and the ionic liquid is selected from one or more of imidazole-based ionic liquids, pyridine-based ionic liquids, and piperidine-based ionic liquids, and the anion in the ionic liquid is an iodide ion.

[0060] According to the use of the present invention, preferably, the cation of the imidazole-based ionic liquid is as shown in formula (I):

[0061]

[0062] Wherein, R 1 and R 2 are each independently selected from C1-C6 alkyl groups and C2-C6 alkenyl groups; R 3 is selected from H, C1-C6 alkyl groups, and C2-C6 alkenyl groups;

[0063] The cation of the pyridine-based ionic liquid is as shown in formula (II):

[0064]

[0065] Wherein, R 4 is selected from C1-C6 alkyl groups and C2-C6 alkenyl groups;

[0066] The cation of the piperidine-based ionic liquid is as shown in formula (III):

[0067]

[0068] Wherein, R 5 and R 6 are each independently selected from C1-C6 alkyl groups and C2-C6 alkenyl groups.

[0069] The selection of the ionic liquid is as specifically described above and will not be elaborated herein.

[0070] Specifically, the following steps may be included:

[0071] (1) React a mixture containing an inorganic cerium salt and an ionic liquid at 150-240 °C to obtain a precursor;

[0072] The ionic liquid is selected from one or more of imidazole-based ionic liquids, pyridine-based ionic liquids, and piperidine-based ionic liquids, and the anion in the ionic liquid is an iodide ion;

[0073] The molar volume ratio of the inorganic cerium salt to the ionic liquid is (0.001 - 0.006) mol: 30 mL;

[0074] (2) Calcinate the precursor at 650 - 850 °C to obtain cerium dioxide.

[0075] The above steps are as described in the previous text and will not be elaborated here.

[0076] The preparation method of the present invention can obtain cerium dioxide with good dispersibility, specific particle size and morphology. The cerium dioxide of the present invention has a high crystallinity and regular morphology. The preparation method of the present invention does not require the use of surfactants or dispersants during the preparation process. Description of the Drawings

[0077] Figure 1 It is the TEM image of the cerium dioxide obtained in Example 1.

[0078] Figure 2 It is the XRD image of the cerium dioxide obtained in Example 1.

[0079] Figure 3 It is the TEM image of the cerium dioxide obtained in Example 2.

[0080] Figure 4 It is the TEM image of the cerium dioxide obtained in Comparative Example 1.

[0081] Figure 5 It is the TEM image of the cerium dioxide obtained in Comparative Example 2.

[0082] Figure 6 It is the TEM image of the cerium dioxide obtained in Comparative Example 3. Detailed Embodiments

[0083] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0084] The following introduces the test methods:

[0085] XRD: Test is carried out using an X'Pert PRO X-ray diffractometer. Use a mortar to crush the sample into fine particles, and use an X'Pert PRO X-ray diffractometer, with a Cu target and Kα rays, The scanning speed is 2° per second, and the test angle range is 5 - 80°, for analyzing the crystal structure of the sample.

[0086] TEM: The test was carried out using a Thermo Fisher Talos F200i transmission electron microscope. The sample was placed in an absolute ethanol solution and ultrasonically dispersed for 5 min, then dropped onto a copper grid. After drying, the Thermo Fisher Talos F200i transmission electron microscope was used to observe the microscopic morphology and elemental distribution of the sample.

[0087] Example 1

[0088] 1.085 g of cerium nitrate was added to 30 mL of 1-butyl-3-methylimidazolium iodide ionic liquid (purity 99.5 wt%), and then stirred at 40 °C for 60 min to obtain a mixture.

[0089] The mixture was placed in a high-temperature reactor with a polytetrafluoroethylene liner and reacted at 180 °C for 16 h to obtain a reaction product. The reaction product was cooled to 25 °C and then centrifuged to obtain a solid product. The solid product was washed three times with absolute ethanol; then placed in an oven and dried at 80 °C for 10 h to obtain a precursor.

[0090] The precursor was placed in a muffle furnace and calcined at 700 °C for 2 h. After cooling, it was ground to obtain cerium dioxide.

[0091] Figure 1 This is the TEM image of the cerium dioxide in this example. From Figure 1 it can be seen that the particle size of the cerium dioxide in this example is 20 - 50 nm, the shape is polygonal and square, and the dispersion is good.

[0092] Figure 2 This is the XRD pattern of the cerium dioxide in this example. From Figure 2 it can be seen that the crystallinity of the cerium dioxide in this example is good. The X-ray diffraction peaks correspond to the standard diffraction pattern of cerium dioxide, and there are no impurity peaks, indicating that the product prepared in this example is pure cerium dioxide.

[0093] Example 2

[0094] 1.085 g of cerium nitrate was added to 30 mL of 1-butyl-3-methylimidazolium iodide ionic liquid (purity 99.5 wt%), and then stirred at 40 °C for 60 min to obtain a mixture.

[0095] The mixture was placed in a high-temperature reactor with a polytetrafluoroethylene liner and reacted at 200 °C for 16 h to obtain a reaction product. The reaction product was cooled to 25 °C and then centrifuged to obtain a solid product. The solid product was washed three times with absolute ethanol; then placed in an oven and dried at 80 °C for 10 h to obtain a precursor.

[0096] The precursor was placed in a muffle furnace and calcined at 700 °C for 2 h. After cooling, it was ground to obtain cerium dioxide.

[0097] Figure 3 This is the TEM image of the cerium dioxide in this example. As Figure 3 can be seen, the particle size of the cerium dioxide in this example is 10 - 50 nm, and the shape is square or polygonal, with good dispersibility.

[0098] Comparative Example 1

[0099] 2.17 g of cerium nitrate was added to 30 mL of 1-butyl-3-methylimidazolium iodide ionic liquid (purity 99.5 wt%). Then, it was stirred at 25 °C for 60 min to obtain a mixture.

[0100] The mixture was placed in a high-temperature reactor with a polytetrafluoroethylene liner and reacted at 200 °C for 24 h to obtain a reaction product. The reaction product was cooled to 25 °C and then centrifuged to obtain a solid product. The solid product was washed three times with absolute ethanol; then it was placed in an oven and dried at 80 °C for 10 h to obtain a precursor.

[0101] The precursor was placed in a muffle furnace and calcined at 700 °C for 2 h. After cooling, it was ground to obtain cerium dioxide.

[0102] Figure 4 This is the TEM image of the cerium dioxide in this comparative example. As Figure 4 can be seen, the particle size of the cerium dioxide in this comparative example is 20 - 50 nm, with serious agglomeration, a high degree of particle stacking, unclear boundaries, and a small amount of cerium dioxide particles being square, while most are irregular in shape.

[0103] Comparative Example 2

[0104] 1.085 g of cerium nitrate was added to 30 mL of 1-butyl-3-methylimidazolium iodide ionic liquid (purity 99.5 wt%). Then, it was stirred at 25 °C for 60 min to obtain a mixture.

[0105] The mixture was placed in a high-temperature reactor with a polytetrafluoroethylene liner and reacted at 200 °C for 16 h to obtain a reaction product. The reaction product was cooled to 25 °C and then centrifuged to obtain a solid product. The solid product was washed three times with absolute ethanol; then it was placed in an oven and dried at 80 °C for 10 h to obtain a precursor.

[0106] The precursor was placed in a muffle furnace and calcined at 600 °C for 2 h. After cooling, it was ground to obtain cerium dioxide.

[0107] Figure 5TEM image of cerium dioxide in this comparative example. Figure 5 It can be seen that the particle size of the cerium dioxide in this comparative example is less than 30 nm, the shape is block-shaped and irregular, there are agglomerated particles, and the dispersion is uneven.

[0108] Comparative Example 3

[0109] 4.34 g of cerium nitrate was added to 30 mL of 1-butyl-3-methylimidazolium iodide ionic liquid (purity: 99.5 wt%), followed by stirring at 25° C. for 60 min to obtain a mixture.

[0110] The mixture was placed in a high-temperature reactor with a polytetrafluoroethylene liner and reacted at 140°C for 16 hours to obtain a reaction product. The reaction product was cooled to 25°C and then centrifuged to obtain a solid product. The solid product was washed three times with anhydrous ethanol; then placed in an oven and dried at 80°C for 10 hours to obtain a precursor.

[0111] The precursor was placed in a muffle furnace, calcined at 900° C. for 2 h, and ground after cooling to obtain cerium dioxide.

[0112] Figure 6 TEM image of cerium dioxide in this comparative example. Figure 6 It can be seen that the particle size of cerium dioxide in this comparative example is 50 to 150 nm, the particle size is uneven, the shape is irregular, and the dispersibility is poor.

[0113] The present invention is not limited to the above-mentioned embodiments. Without departing from the essential content of the present invention, any deformation, improvement and substitution that can be conceived by those skilled in the art shall fall within the scope of the present invention.

Claims

1. A cerium dioxide, characterized in that: The particle size of the cerium dioxide is 10 to 80 nm, and at least a portion of the cerium dioxide particles are in a block shape.

2. Ceria according to claim 1, characterized in that: At least a portion of the cerium oxide particles are polygonal.

3. The method for preparing cerium dioxide according to claim 1 or 2, characterized in that: The steps include: (1) reacting a mixture containing an inorganic cerium salt and an ionic liquid at 150 to 240° C. to obtain a precursor; The ionic liquid is selected from one or more of imidazole ionic liquids, pyridine ionic liquids, and piperidine ionic liquids, and the anion in the ionic liquid is an iodide ion; The molar volume ratio of the inorganic cerium salt and the ionic liquid is (0.001-0.006) mol:30 mL; (2) The precursor is calcined at 650-850°C to obtain cerium dioxide.

4. The preparation method according to claim 3, characterized in that: The cation of the imidazole ionic liquid is shown in formula (I): Wherein, R1 and R2 are independently selected from C1-C6 alkyl and C2-C6 alkenyl; R3 is selected from H, C1-C6 alkyl and C2-C6 alkenyl; The cation of the pyridine ionic liquid is shown in formula (II): Wherein, R4 is selected from C1-C6 alkyl, C2-C6 alkenyl; The cation of the piperidine ionic liquid is shown in formula (III): Wherein, R5 and R6 are independently selected from C1-C6 alkyl and C2-C6 alkenyl.

5. The preparation method according to claim 3, characterized in that: The cation in the ionic liquid is selected from one or more of 1-butyl-3-methylimidazole, 1-ethyl-3-methylimidazole, 1-vinyl-3-methylimidazole, 1,2,3-trimethylimidazole, N-propyl-N-methylpiperidine, and N-butylpyridine.

6. The preparation method according to claim 3, characterized in that: No additional water was added to the mixture.

7. The preparation method according to claim 3, characterized in that: The following steps are also included: mixing a solid inorganic cerium salt and an ionic liquid to obtain a mixture; The inorganic cerium salt is selected from one or more of cerium chloride, cerium carbonate, cerium nitrate and cerium sulfate.

8. The preparation method according to claim 3, characterized in that: In step (1), the reaction time is 10 to 20 hours; in step (2), the calcination time is 1 to 5 hours.

9. Use of an ionic liquid in regulating the particle size and / or morphology of cerium dioxide, characterized in that: The ionic liquid is selected from one or more of imidazole ionic liquids, pyridine ionic liquids, and piperidine ionic liquids, and the anions in the ionic liquid are iodide ions.

10. The use according to claim 9, characterized in that The cation of the imidazole ionic liquid is shown in formula (I): Wherein, R1 and R2 are independently selected from C1-C6 alkyl and C2-C6 alkenyl; R3 is selected from H, C1-C6 alkyl and C2-C6 alkenyl; The cation of the pyridine ionic liquid is shown in formula (II): Wherein, R4 is selected from C1-C6 alkyl, C2-C6 alkenyl; The cation of the piperidine ionic liquid is shown in formula (III): Wherein, R5 and R6 are independently selected from C1-C6 alkyl and C2-C6 alkenyl.

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