Amino acid-mediated synthesis of amorphous rare earth oxides

Abstract

The application discloses a kind of amino acid-mediated amorphous rare earth oxide synthesis method, belong to rare earth oxide synthesis field.The application uses rare earth salt as raw material, amino acid is used as additive, and precursor system is prepared by adding alkali, then hydrothermal reaction is carried out, and then amorphous rare earth oxide is separated from hydrothermal reaction product.Compared with the traditional hydrothermal method for synthesizing crystalline rare earth oxide, the method utilizes the complexation of rare earth salt with amino acid during hydrothermal reaction, the formation of hydroxide is hindered, and it is easier to generate isotropic amorphous rare earth oxide particles, and the separation of crystalline and amorphous products can be achieved by decantation method, and various amorphous rare earth oxides can be prepared, with highly uniform morphology as microspheres.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of rare earth oxide synthesis, and particularly relates to a synthesis method of amino acid modified amorphous rare earth oxide. BACKGROUND

[0002] As a common state of rare earth metal, the synthesis and application of rare earth oxide have been studied. Rare earth oxide can be used as a catalyst and plays an important role in different catalytic fields such as thermal catalysis, electrocatalysis and photocatalysis. In the field of thermal catalysis, cerium oxide catalyst is applied to the catalyst of denitration technology, providing technical support for the field of atmospheric environmental protection (see CN119114059A). In the field of electrocatalytic reduction, rare earth oxide catalyst can reduce furfural to alcohol derivatives, providing important support for the field of biomass conversion and new energy industry (see CN103603008A).

[0003] At present, the synthesis and regulation technology of crystalline rare earth oxide is relatively mature, and the size and morphology of rare earth oxide are relatively mature. For example, octahedral cerium dioxide can be synthesized under non-burning conditions (CN118993127A). The synthesis of amorphous rare earth oxide has been studied to some extent, but it often needs to add some other inorganic additives (ceramic materials) to the final product, and the synthesis method needs to use programmed temperature and ball milling operations (CN118006157A, CN117185819A, CN118110047A). There is no better unified method for directly synthesizing amorphous rare earth oxide materials in one step. SUMMARY

[0004] In view of the problems existing in the above-mentioned synthesis process of amorphous rare earth oxide, the present application provides a method for synthesizing amorphous rare earth oxide.

[0005] The technical scheme of the present application is as follows:

[0006] A synthesis method of amorphous rare earth oxide, taking rare earth salt as raw material, amino acid as additive, and adding alkali to prepare a precursor system, then performing hydrothermal reaction, and then separating amorphous rare earth oxide from the hydrothermal reaction product.

[0007] In the above-mentioned synthesis method, the rare earth salt is preferably one or more of nitrate, hydrochloride, acetylacetone salt and acetate of rare earth element, and is further preferably nitrate of rare earth element. The rare earth element is selected from yttrium and all lanthanide elements. The amino acid is preferably aspartic acid, glutamic acid, asparagine, threonine or a corresponding amino acid salt, and is further preferably aspartic acid. The alkali is preferably alkali metal hydroxide or ammonia water, and is further preferably sodium hydroxide.

[0008] The solvent of the precursor system includes water and an organic solvent, and the volume ratio of water to the organic solvent is 5:1-1:5, preferably 1:1. The purpose of adding the organic solvent in the precursor system is to improve the solution polarity and the solubility of the organic solute, and the organic solvent is preferably an alcohol solvent, including but not limited to ethylene glycol, ethanol, isopropanol, methanol, propanol, glycerol.

[0009] In the precursor system, the concentration of the rare earth salt is 0.001-1 mmol / L, and in some embodiments of the present application, the concentration is 0.06 mmol / L; the concentration of the base is 0.01-10 mmol / L, and in some embodiments of the present application, the concentration is 0.1 mmol / L; the concentration of the amino acid is 0.001-1 mmol / L, and in some embodiments of the present application, the concentration is 0.06 mmol / L.

[0010] The preparation process of the precursor system can be: dissolving the rare earth salt in deionized water, adding an organic solvent and stirring to obtain solution A; dissolving the amino acid in a base solution to obtain solution B; slowly adding solution B to solution A under stirring, and continuing to stir for a period of time to obtain the precursor system.

[0011] The above process first dissolves the rare earth salt in water, and then adds an organic solvent, which can ensure that the rare earth salt is completely dissolved to form a homogeneous solution, while avoiding premature reaction with other materials added to form a difficult-to-dissolve solid coating, or precipitation with organic components, or premature hydrolysis with a base to lose activity. Dissolving the amino acid in a base solution can convert the organic substance into a corresponding salt in advance, enhance its solubility, and allow it to fully interact with the rare earth salt. Sequentially adding materials in the above manner can maximize the homogeneous and full reaction.

[0012] Preferably, the reaction temperature for the hydrothermal reaction of the precursor is 80-200 ℃, and the reaction time is 2-24 h. In some embodiments of the present application, the reaction is carried out at 180 ℃ for 5 h.

[0013] The synthesis method of the present application only needs general hydrothermal heating reaction conditions, is suitable for various rare earth elements, and has good synthesis repeatability. The rare earth salt undergoes complexation with the amino acid during the hydrothermal reaction process, and the hydroxide formation process is hindered, which is different from the traditional reaction of the rare earth salt with the base to form a crystalline rare earth oxide, and is more likely to generate isotropic amorphous rare earth oxide particles.

[0014] During the separation process after the hydrothermal reaction, attention should be paid to the fact that the alkali and the rare earth nitrate itself can produce a part of crystalline product of rare earth oxide, which has a large difference from the amorphous product. In the experiment, the two kinds of solids can be separated by the decantation method. In order to avoid the introduction of the crystalline impurities, the crystalline impurities need to be discarded in the separation process to improve the purity of the synthesized product. The specific separation method can be as follows: the suspension liquid with precipitate generated after the hydrothermal reaction is taken out, the upper suspension liquid is obtained by the decantation method, and the lower large particle solid precipitate is discarded; then the upper suspension liquid is washed with water and ethanol, and the solid-liquid separation is realized by centrifugation, and the obtained solid is dried to obtain the required product.

[0015] The present application uses rare earth salt and alkali as initial raw materials, adds amino acid and organic solvent for modification, and adopts a hydrothermal method to synthesize amorphous rare earth oxide. Compared with the traditional method for synthesizing crystalline rare earth oxide by the hydrothermal method, the present application can prepare various amorphous rare earth oxides, and the morphology is highly uniform as microspheres. The amorphous rare earth oxide is widely used and plays an important role in various catalytic fields. Compared with the crystalline rare earth oxide catalyst, the amorphous rare earth oxide catalyst has better adsorption capacity and catalytic selectivity, and plays an important role in the fields of electrocatalysis, thermal catalysis, photocatalysis and the like. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The flowchart of the synthesis method used in the embodiments of the present application, and the appearance of the product after washing and drying (top) and further calcination (bottom).

[0017] Figure 2 The XRD image of the rare earth oxide microspheres prepared in Examples 1-6.

[0018] Figure 3 The SEM image of the rare earth oxide microspheres prepared in Examples 1-6.

[0019] Figure 4 The TEM image (left), HRTEM image (middle) and SAED image (right) of the rare earth oxide microspheres prepared in Examples 1-5 and 7.

[0020] Figure 5 The EDS characterization results of the rare earth oxide microspheres prepared in Examples 1-5 and 7.

[0021] Figure 6 The IR image of the rare earth oxide microspheres prepared in Examples 1-5 and 7, wherein "A-" represents an amorphous sample; "C-" represents a crystalline sample, which is a standard sample for comparison; and "calcination" represents a sample calcined at 300 degrees Celsius for 4 hours. DETAILED DESCRIPTION

[0022] The technical solutions of the present application are described in detail below through examples, but the present application can be implemented by other methods and is not limited to the following examples, and therefore the protection scope of the present application is not limited by the following examples.

[0023] The reagents and materials described in the examples, such as no special instructions, are conventional reagents and materials, or can be purchased by commercial channels. The experimental instruments and equipment involved in the experimental methods in the examples, such as no special instructions, are implemented according to the recommended parameters of the manufacturer.

[0024] Example 1

[0025] Preparation of amorphous cerium oxide:

[0026] 1. Weigh 1.30 g of cerous nitrate hexahydrate, dissolve in 15 mL of deionized water, and after fully dissolving, add 18 mL of ethylene glycol, stir uniformly and reserve;

[0027] 2. Weigh 0.40 g of aspartic acid, fully dissolve in 3 mL of 2 mol / L sodium hydroxide solution, and reserve;

[0028] 3. Slowly add the solution of step 2 to the solution of step 1 under stirring, a milky white precipitate appears, and continue stirring for 1 h;

[0029] 4. Transfer the suspension obtained in step 3 to a 50 mL hydrothermal reactor, heat at a temperature of 180 ℃ for 5 h to obtain a suspension with precipitate;

[0030] 5. Take out the precipitated suspension obtained in step 4, and use the decanting method to obtain the upper suspension, and discard the lower large particle solid precipitate;

[0031] 6. Centrifuge the suspension obtained in step 5 (11000 r / min), and wash with water and ethanol alternately for 3 times, then dry at 40 ℃ for 12 h to obtain the final product.

[0032] Example 2

[0033] Preparation of amorphous neodymium oxide:

[0034] 1. Weigh 1.32 g of neodymium nitrate hexahydrate, dissolve in 15 mL of deionized water, and after fully dissolving, add 18 mL of ethylene glycol, stir uniformly and reserve;

[0035] 2. Weigh 0.40 g of aspartic acid, fully dissolve in 3 mL of 2 mol / L sodium hydroxide solution, and reserve;

[0036] 3. Slowly add the solution of step 2 to the solution of step 1 under stirring, a milky white precipitate appears, and continue stirring for 1 h;

[0037] 4. The suspension obtained in step 3 was transferred to a 50 mL hydrothermal reactor, heated at a temperature of 180 °C for 5 h to obtain a precipitated suspension;

[0038] 5. The precipitated suspension obtained in step 4 was taken out, and the upper layer suspension was obtained by decantation, and the lower layer large particle solid precipitate was discarded;

[0039] 6. The suspension obtained in step 5 was centrifuged (11000 r / min), and washed with water and ethanol alternately for 3 times, and then dried at 40 °C for 12 h to obtain the final product.

[0040] Example 3

[0041] Preparation of amorphous lanthanum oxide:

[0042] 1. 1.30 g of lanthanum nitrate hexahydrate was weighed and dissolved in 15 mL of deionized water, and after fully dissolved, 18 mL of ethylene glycol was added, stirred uniformly and reserved;

[0043] 2. 0.40 g of aspartic acid was weighed and fully dissolved in 3 mL of 2 mol / L sodium hydroxide solution, reserved;

[0044] 3. The solution of step 2 was slowly added to the solution of step 1 under stirring, a milky white precipitate appeared, and stirring was continued for 1 h;

[0045] 4. The suspension obtained in step 3 was transferred to a 50 mL hydrothermal reactor, heated at a temperature of 180 °C for 5 h to obtain a precipitated suspension;

[0046] 5. The precipitated suspension obtained in step 4 was taken out, and the upper layer suspension was obtained by decantation, and the lower layer large particle solid precipitate was discarded;

[0047] 6. The suspension obtained in step 5 was centrifuged (11000 r / min), and washed with water and ethanol alternately for 3 times, and then dried at 40 °C for 12 h to obtain the final product.

[0048] Example 4

[0049] Preparation of amorphous praseodymium oxide:

[0050] 1. 1.30 g of praseodymium nitrate hexahydrate was weighed and dissolved in 15 mL of deionized water, and after fully dissolved, 18 mL of ethylene glycol was added, stirred uniformly and reserved;

[0051] 2. 0.40 g of aspartic acid was weighed and fully dissolved in 3 mL of 2 mol / L sodium hydroxide solution, reserved;

[0052] 3. Slowly add the solution of step 2 into the solution of step 1 under stirring, a milky white precipitate appears, and continue stirring for 1 h;

[0053] 4. Transfer the suspension obtained in step 3 into a 50 mL hydrothermal reactor, heat at 180 °C for 5 h to obtain a suspension with precipitate;

[0054] 5. Take out the suspension with precipitate obtained in step 4, and obtain the upper suspension by decantation, and discard the lower large particle solid precipitate;

[0055] 6. Centrifuge the suspension obtained in step 5 (11000 r / min), and wash with water and ethanol alternately for 3 times, and then dry at 40 °C for 12 h to obtain the final product.

[0056] Example 5

[0057] Preparation of amorphous ytterbium oxide:

[0058] 1. Weigh 1.08 g of ytterbium nitrate hexahydrate, dissolve in 15 mL of deionized water, and after fully dissolving, add 18 mL of ethylene glycol, stir uniformly and reserve;

[0059] 2. Weigh 0.40 g of aspartic acid, fully dissolve in 3 mL of 2 mol / L sodium hydroxide solution, and reserve;

[0060] 3. Slowly add the solution of step 2 into the solution of step 1 under stirring, a milky white precipitate appears, and continue stirring for 1 h;

[0061] 4. Transfer the suspension obtained in step 3 into a 50 mL hydrothermal reactor, heat at 180 °C for 5 h to obtain a suspension with precipitate;

[0062] 5. Take out the suspension with precipitate obtained in step 4, and obtain the upper suspension by decantation, and discard the lower large particle solid precipitate;

[0063] 6. Centrifuge the suspension obtained in step 5 (11000 r / min), and wash with water and ethanol alternately for 3 times, and then dry at 40 °C for 12 h to obtain the final product.

[0064] Example 6

[0065] Preparation of amorphous yttrium oxide:

[0066] 1. Weigh 1.32 g of yttrium nitrate hexahydrate, dissolve in 15 mL of deionized water, and after fully dissolving, add 18 mL of ethylene glycol, stir uniformly and reserve;

[0067] 2. Weigh 0.40 g aspartic acid, dissolve in 3 mL 2 mol / L sodium hydroxide solution, and reserve;

[0068] 3. Slowly add the solution of step 2 to the solution of step 1 under stirring, a milky white precipitate appears, and continue stirring for 1 h;

[0069] 4. Transfer the suspension obtained in step 3 to a 50 mL hydrothermal reactor, heat at 180 °C for 5 h, and obtain a suspension with precipitate;

[0070] 5. Take out the suspension with precipitate obtained in step 4, obtain the upper suspension by decantation, and discard the lower large-particle solid precipitate;

[0071] 6. Centrifuge the suspension obtained in step 5 (11000 r / min), wash with water and ethanol alternately for 3 times, and dry at 40 °C for 12 h to obtain the final product.

[0072] Example 7

[0073] Preparation of amorphous samarium oxide:

[0074] 1. Weigh 1.32 g samarium nitrate hexahydrate, dissolve in 15 mL deionized water, after complete dissolution, add 18 mL ethylene glycol, stir uniformly, and reserve;

[0075] 2. Weigh 0.40 g aspartic acid, dissolve in 3 mL 2 mol / L sodium hydroxide solution, and reserve;

[0076] 3. Slowly add the solution of step 2 to the solution of step 1 under stirring, a milky white precipitate appears, and continue stirring for 1 h;

[0077] 4. Transfer the suspension obtained in step 3 to a 50 mL hydrothermal reactor, heat at 180 °C for 5 h, and obtain a suspension with precipitate;

[0078] 5. Take out the suspension with precipitate obtained in step 4, obtain the upper suspension by decantation, and discard the lower large-particle solid precipitate;

[0079] 6. Centrifuge the suspension obtained in step 5 (11000 r / min), wash with water and ethanol alternately for 3 times, and dry at 40 °C for 12 h to obtain the final product.

[0080] Figure 1 The above is a schematic diagram of the synthesis process of the example, and the appearance of the product. The upper part is the appearance of the product after washing and drying, and the lower part is the appearance of the product after further burning at 300 °C for 4 h. Figure 2XRD (X-ray diffraction) characterization of the rare earth oxide microspheres prepared in Examples 1-6, and no absorption peak in the figure indicates its amorphous nature. Figure 3 SEM (scanning electron microscope) morphology characterization of the amorphous rare earth oxide microspheres prepared in Examples 1-6, and the synthesis method of the present application produces microspheres of similar size for various rare earth elements. Figure 4 TEM (transmission electron microscope), HRTEM (high-resolution transmission electron microscope), and SAED (selected area electron diffraction) characterization results of the amorphous rare earth oxide microspheres prepared in Examples 1-5 and 7. Figure 5 EDS (energy dispersive X-ray spectroscopy) characterization of the amorphous rare earth oxide microspheres prepared in Examples 1-5 and 7, indicating uniform distribution of rare earth elements. Figure 6 Infrared (IR) characterization results, and by comparing the infrared spectra of standard rare earth oxides and hydroxides, it can be concluded that the product is an oxide containing part of a hydroxide.

[0081] The above detailed the preferred embodiments of the present application and the experimental verification. It should be understood that those skilled in the art can make many modifications and changes without creative labor according to the concept of the present application. Therefore, any technical solution that can be obtained by logical analysis, reasoning or limited experiment on the basis of the prior art according to the concept of the present application shall be within the scope of protection of the present application.

Claims

1. A method for synthesizing amorphous rare earth oxides, characterized by, The rare earth salt is dissolved in deionized water, and an organic solvent is added to stir uniformly to obtain solution A; an amino acid is dissolved in an alkali solution to obtain solution B; solution B is slowly added to solution A under stirring, and the stirring is continued for a period of time to obtain a precursor system; then a hydrothermal reaction is performed, the suspension with precipitate generated after the hydrothermal reaction is taken out, the upper layer suspension is obtained by a decantation method, and the lower layer large particle solid precipitate is discarded; then the upper layer suspension is washed with water and ethanol, and solid-liquid separation is realized by centrifugation, and the obtained solid is dried to obtain an amorphous rare earth oxide.

2. The method of synthesis of claim 1, wherein, The rare earth salt is one or more of nitrate, hydrochloride, acetylacetone salt and acetate of a rare earth element, wherein the rare earth element is selected from yttrium and lanthanide elements.

3. The method of synthesis of claim 1, wherein, The amino acid is one or more of aspartic acid, glutamic acid, asparagine and threonine or corresponding amino acid salt; and the alkali is alkali metal hydroxide or ammonia water.

4. The method of synthesis of claim 1, wherein, The solvent of the precursor system comprises water and an organic solvent, and the volume ratio of water to the organic solvent is 5:1-1:

5.

5. The method of synthesis of claim 4, wherein, The organic solvent is an alcohol solvent, and is one or more of ethylene glycol, ethanol, isopropyl alcohol, methanol, propanol and glycerol.

6. The method of synthesis of claim 1, wherein, In the precursor system, the concentration of the rare earth salt is 0.001-1 mmol / L, the concentration of the alkali is 0.01-10 mmol / L, and the concentration of the amino acid is 0.001-1 mmol / L.

7. The method of synthesis of claim 1, wherein, The reaction temperature of the hydrothermal reaction is 80-200 DEG C, and the reaction time is 2-24 h.

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