Preparation method of cerium oxide

Abstract

The invention relates to the technical field of preparation of cerium oxide, in particular to a preparation method of cerium oxide. The invention provides a cerium oxide preparation method, which comprises: adding a pH buffer agent and a hydrogen peroxide solution to a cerium salt solution with a pH value of 4-5, carrying out an oxidation precipitation reaction, and sequentially carrying out filtration washing and drying to obtain cerium oxide, the purity of the cerium oxide is greater than or equal to 99.59%, and the pH value of a solution system subjected to the oxidation precipitation reaction is less than 6. The cerium oxide prepared by the preparation method is high in purity, the preparation method is simple, and industrial production is easy.

Description

Technical Field

[0001] The invention relates to the technical field of cerium oxide preparation, and in particular to a method for preparing cerium oxide. Background Art

[0002] Cerium oxide is a cheap and widely used light rare earth oxide. It has been used in luminescent materials, polishing agents, ultraviolet absorbers, automobile exhaust purification catalysts, chemical decolorizers for glass, radiation-resistant glass and electronic ceramics. With the development of science and technology, the market has higher and higher requirements for the purity of cerium oxide, and the demand for cerium oxide has also increased accordingly. The traditional method of preparing high-purity cerium oxide is mainly achieved through further purification, such as ion exchange, organic solvent extraction, etc., but the ion exchange method is only suitable for rare earth solutions with low solubility, and the organic solvent extraction method requires multiple extractions, which is time-consuming and intensive, and it is difficult to achieve industrialization. Summary of the invention

[0003] In view of this, an object of the present invention is to provide a method for preparing cerium oxide, wherein the cerium oxide prepared by the method has high purity, is simple in preparation, and is easy for industrial production.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: The present invention provides a method for preparing cerium oxide, comprising the following steps: Adding a pH buffer and a hydrogen peroxide solution to a cerium salt solution with a pH value of 4 to 5, performing an oxidation precipitation reaction, and then filtering, washing and drying in sequence to obtain the cerium oxide; The purity of the cerium oxide is ≥99.59%, and the pH of the solution system for the oxidation precipitation reaction is <6.

[0005] Preferably, the concentration of the cerium salt in the cerium salt solution with a pH value of 4 to 5 is 0.1 to 2.5 mol / L.

[0006] Preferably, the cerium salt in the cerium salt solution with a pH value of 4 to 5 is cerium chloride and / or cerium nitrate.

[0007] Preferably, the method for preparing the cerium salt solution having a pH value of 4 to 5 comprises: The cerium salt solution and ammonia water are mixed under stirring to obtain the cerium salt solution with a pH value of 4-5.

[0008] Preferably, the stirring speed is 50-300 rpm; The mass concentration of the ammonia water is 10% to 28%.

[0009] Preferably, the pH value after adding the pH buffer is 2-6.

[0010] Preferably, the pH buffer comprises hexamethylenetetramine or potassium hydrogen phthalate.

[0011] Preferably, the molar ratio of the pH buffer to the cerium salt in the cerium salt solution with a pH value of 4-5 is (1-10):100.

[0012] Preferably, the molar ratio of hydrogen peroxide in the hydrogen peroxide solution to the cerium salt in the cerium salt solution having a pH value of 4 to 5 is (2 to 5):1.

[0013] Preferably, the temperature of the oxidation precipitation reaction is 15°C to 25°C, and the time is 0.5 to 3 hours.

[0014] The invention provides a method for preparing cerium oxide, comprising the following steps: adding a pH buffer and a hydrogen peroxide solution to a cerium salt solution with a pH value of 4-5, performing an oxidation precipitation reaction, and then filtering, washing and drying in sequence to obtain the cerium oxide; the purity of the cerium oxide is ≥99.59%, and the pH of the solution system for the oxidation precipitation reaction is <6.

[0015] Compared with the prior art, the preparation method of the present invention has the following beneficial effects: 1) The inventive addition of a pH buffer in the present invention can ensure that the pH value of the solution system for the oxidation precipitation reaction is stable below 6, reduce the effect of the hydrogen peroxide solution on the pH of the system, and ensure the separation of tetravalent cerium ions and other trivalent rare earth ions; 2) The inventive addition of a pH buffer in the present invention can ensure that the solution system for the oxidation precipitation reaction is stable below 6, which can ensure that the reaction system will not be locally over-concentrated, making the precipitation particles smaller and more uniform, reducing entrainment, and facilitating the purification of Ce; 3) The inventive addition of a pH buffer in the present invention can ensure that the solution system for the oxidation precipitation reaction is stable below 6, and can ensure that the hydrogen peroxide slowly oxidizes the trivalent cerium ions to form a cerium precipitate without causing local overconcentration to entrain the trivalent rare earth ions; 4) The preparation method can complete purification and separation in one step of precipitation, has a short process flow and simple process operation, and is expected to achieve industrial production. DETAILED DESCRIPTION

[0016] The present invention provides a method for preparing cerium oxide, comprising the following steps: Adding a pH buffer and a hydrogen peroxide solution to a cerium salt solution with a pH value of 4 to 5, performing an oxidation precipitation reaction, and then filtering, washing and drying in sequence to obtain the cerium oxide; The purity of the cerium oxide is ≥99.59%, and the pH of the solution system for the oxidation precipitation reaction is <6.

[0017] In the present invention, unless otherwise specified, all preparation raw materials are commercially available products well known to those skilled in the art.

[0018] In the present invention, the concentration of the cerium salt in the cerium salt solution with a pH value of 4 to 5 is preferably 0.1 to 2.5 mol / L, more preferably 0.5 to 2.0 mol / L. In an embodiment of the present invention, the concentration of the cerium salt in the cerium salt solution with a pH value of 4 to 5 may be 2.25 mol / L, 0.35 mol / L or 2.2 mol / L.

[0019] In the present invention, the pH value of the cerium salt solution with a pH value of 4 to 5 is preferably 4.3 to 4.6. In an embodiment of the present invention, the pH value of the cerium salt solution with a pH value of 4 to 5 may be 4, 4.5 or 5.

[0020] In the present invention, the cerium salt in the cerium salt solution with a pH value of 4 to 5 is preferably cerium chloride and / or cerium nitrate, and more preferably cerium chloride; when the cerium salt is two or more of the above-mentioned specific options, the present invention has no special limitation on the ratio of the above-mentioned specific substances, and they can be mixed in any ratio.

[0021] In the present invention, the preparation method of the cerium salt solution with a pH value of 4 to 5 preferably comprises: mixing the cerium salt solution and ammonia water under stirring to obtain the cerium salt solution with a pH value of 4 to 5. In the present invention, the stirring speed is preferably 50 to 300 rpm, more preferably 100 to 250 rpm, and most preferably 150 to 200 rpm. In an embodiment of the present invention, the stirring speed may be 100 rpm, 50 rpm or 300 rpm. In the present invention, the mass concentration of the ammonia water is preferably 10% to 28%, more preferably 25% to 28%. In an embodiment of the present invention, the mass concentration of the ammonia water may be 28%.

[0022] In the present invention, the pH value after adding the pH buffer is preferably 2 to 6, more preferably 3 to 5. In an embodiment of the present invention, the pH value after adding the pH buffer may be 4.5, 5 or 4.

[0023] In the present invention, the pH buffer preferably includes hexamethylenetetramine or potassium hydrogen phthalate, and more preferably includes hexamethylenetetramine. In an embodiment of the present invention, the pH buffer may be hexamethylenetetramine or potassium hydrogen phthalate.

[0024] In the present invention, the molar ratio of the pH buffer to the cerium salt in the cerium salt solution with a pH value of 4 to 5 is preferably (1 to 10): 100, more preferably (2 to 8): 100, and most preferably (3 to 5): 100. In an embodiment of the present invention, the molar ratio of the pH buffer to the cerium salt in the cerium salt solution with a pH value of 4 to 5 may be 1:100, 3:100 or 9:100.

[0025] In the present invention, the molar ratio of hydrogen peroxide in the hydrogen peroxide solution to the cerium salt in the cerium salt solution with a pH value of 4 to 5 is preferably (2 to 5): 1, more preferably (3 to 4): 1. In an embodiment of the present invention, the molar ratio of hydrogen peroxide in the hydrogen peroxide solution to the cerium salt in the cerium salt solution with a pH value of 4 to 5 may be 2.7: 1, 2.8: 1 or 5: 1.

[0026] In the present invention, the mass concentration of the hydrogen peroxide solution is preferably 10% to 50%, more preferably 30%. In an embodiment of the present invention, the mass concentration of the hydrogen peroxide solution can be 30wt%.

[0027] In the present invention, the process of adding the pH buffer and the hydrogen peroxide solution is preferably to add the hydrogen peroxide solution and the pH buffer in sequence, or preferably to add the pH buffer and the hydrogen peroxide solution in sequence. More preferably, the pH buffer and the hydrogen peroxide solution are added in sequence. In the present invention, adjusting the pH value first and then adding the hydrogen peroxide can further allow the hydrogen peroxide to slowly oxidize the trivalent cerium to form a cerium precipitate, without causing the problem of local over-concentration of trivalent cerium and rare earth entrainment.

[0028] In the present invention, the temperature of the oxidation precipitation reaction is preferably 15-25°C, more preferably 20°C; the time is preferably 0.5-3h, more preferably 1-2h. In the present invention, the oxidation precipitation reaction is preferably carried out under stirring, and the stirring speed is preferably 50-300rpm. In an embodiment of the present invention, the temperature of the oxidation precipitation reaction can be 20°C, the time can be 1.5h, 0.5h or 3h; the stirring speed can be 100rpm, 50rpm or 300rpm.

[0029] In the present invention, the reaction formula of the oxidation precipitation reaction is: 2Ce 3+ +H2O2+6H2O→2Ce(OH)4↓+6H + ;Ce(OH)4→CeO2+2H2O.

[0030] The present invention does not have any special limitation on the filtering, washing and drying process, and the filtering, washing and drying process may be carried out using a process well known to those skilled in the art.

[0031] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Example 1 Using 28% ammonia water, under stirring (speed of 100 rpm), 0.8 L of 2.25 mol / L cerium chloride solution was adjusted to pH 4, 5 g of potassium hydrogen phthalate (the amount of substance was 0.025 mol, and the molar ratio of potassium hydrogen phthalate to cerium chloride was 1.389:100) was added, and then 0.5 L of 30% hydrogen peroxide (pH was 4.5, and the molar ratio of hydrogen peroxide to cerium chloride was 2.7:1) was added, and the reaction was stirred at 20° C. at a speed of 100 rpm for 1.5 hours, and the obtained precipitate was filtered, washed and dried in turn to obtain cerium oxide.

[0033] Comparative Example 1 Referring to Example 1, the difference is that potassium hydrogen phthalate is not added. After the oxidation precipitation reaction is completed, less precipitate is generated and the purification effect is not obvious.

[0034] Table 1 The mass percentage of each element in the cerium chloride solution (raw material), the cerium oxide described in Example 1 and the cerium oxide described in Comparative Example 1.

[0035]

[0036] Note: The mass percentage of the above elements is calculated based on the corresponding oxides of the elements.

[0037] Example 2 Using 28% ammonia water, under stirring (speed of 50 rpm), 1L of 0.35mol / L cerium chloride solution was adjusted to pH 5, 1g of hexamethylenetetramine (the amount of substance was 0.01mol, and the molar ratio of hexamethylenetetramine to cerium chloride was 3:100) was added, and then 0.1L of 30% hydrogen peroxide (pH was 4.6, and the molar ratio of hydrogen peroxide to cerium chloride was 2.8:1) was added, and the reaction was stirred at 20°C at a speed of 50 rpm for 0.5h, and the obtained precipitate was filtered, washed and dried in turn to obtain cerium oxide.

[0038] Comparative Example 2 Referring to Example 2, the difference is that when 0.01 L of 30% hydrogen peroxide was added, the amount of precipitate (cerium oxide) generated was small and the purification effect was not obvious.

[0039] Table 2 The mass percentage of each element in the cerium chloride solution (raw material), the cerium oxide described in Example 2 and the cerium oxide described in Comparative Example 2.

[0040]

[0041] Note: The mass percentage of the above elements is calculated based on the corresponding oxides of the elements.

[0042] Example 3 Using 28% ammonia water, under stirring (rotation speed of 300 rpm), 1L of 2.2mol / L cerium chloride solution was adjusted to pH 4.5, 1.1L of 30% hydrogen peroxide (the molar ratio of hydrogen peroxide to cerium chloride is 5:1) was added, and then 28g of hexamethylenetetramine (the amount of substance is 0.2mol) (pH is 4, the molar ratio of hexamethylenetetramine to cerium chloride is 9:100) was added, and the reaction was stirred at 20°C for 3h at a rotation speed of 300rpm, and the obtained precipitate was filtered, washed and dried in turn to obtain cerium oxide.

[0043] Comparative Example 3 Refer to Example 3, except that the pH value of the cerium chloride solution is adjusted to 6.5, 1 g of hexamethylenetetramine is added, and cerium oxide powder is obtained (trivalent rare earth precipitation is produced, and the purification effect is poor).

[0044] Table 3 The mass percentage of each element in the cerium chloride solution (raw material), the cerium oxide described in Example 3 and the cerium oxide described in Comparative Example 3.

[0045]

[0046] Note: The mass percentage of the above elements is calculated based on the corresponding oxides of the elements.

[0047] Comparative Example 4 Refer to Example 1, except that the pH value of the cerium chloride solution was adjusted to 0.26, potassium hydrogen phthalate was not added, and no precipitate was produced during the reaction.

[0048] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing cerium oxide, characterized in that: The following steps are involved: Adding a pH buffer and a hydrogen peroxide solution to a cerium salt solution with a pH value of 4 to 5, performing an oxidation precipitation reaction, and then filtering, washing and drying in sequence to obtain the cerium oxide; The purity of the cerium oxide is ≥99.59%, and the pH of the solution system for the oxidation precipitation reaction is <6.

2. The preparation method according to claim 1, characterized in that The concentration of the cerium salt in the cerium salt solution with a pH value of 4-5 is 0.1-2.5 mol / L.

3. The preparation method according to claim 1 or 2, characterized in that: The cerium salt in the cerium salt solution with a pH value of 4-5 is cerium chloride and / or cerium nitrate.

4. The preparation method according to claim 3, characterized in that: The preparation method of the cerium salt solution with a pH value of 4 to 5 comprises: The cerium salt solution and ammonia water are mixed under stirring to obtain the cerium salt solution with a pH value of 4-5.

5. The preparation method according to claim 4, characterized in that: The stirring speed is 50-300 rpm; The mass concentration of the ammonia water is 10% to 28%.

6. The preparation method according to claim 1, characterized in that: The pH value after adding the pH buffer is 2-6.

7. The preparation method according to claim 6, characterized in that: The pH buffer includes hexamethylenetetramine or potassium hydrogen phthalate.

8. The preparation method according to claim 7, characterized in that: The molar ratio of the pH buffer to the cerium salt in the cerium salt solution with a pH value of 4-5 is (1-10):

100.

9. The preparation method according to claim 1, characterized in that: The molar ratio of hydrogen peroxide in the hydrogen peroxide solution to the cerium salt in the cerium salt solution having a pH value of 4 to 5 is (2 to 5):

1.

10. The preparation method according to claim 1, characterized in that: The temperature of the oxidation precipitation reaction is 15-25° C. and the time is 0.5-3 h.

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