Preparation method of nano rare earth oxide capable of recycling carbon dioxide

Abstract

The invention discloses a preparation method of a nano rare earth oxide capable of recycling carbon dioxide. The preparation method comprises the following steps: (1) proportionally adding an alkaline solution into a rare earth solution, and mixing and stirring to obtain nano rare earth hydroxide slurry; (2) spraying carbon dioxide into the nano rare earth hydroxide slurry to obtain nano basic rare earth carbonate slurry, and filtering to obtain nano basic rare earth carbonate; (3) adding an organic reagent into the nano basic rare earth carbonate, uniformly mixing, and drying to obtain dried nano basic rare earth carbonate; and (4) putting the dried nano basic rare earth carbonate particles into a reaction container, heating to a set temperature, roasting and decomposing to obtain the nano rare earth oxide, and returning the collected carbon dioxide to the step (2) for recycling. The carbon dioxide is introduced into the nano rare earth hydroxide slurry, so that the agglomeration problem is solved, and the decomposed carbon dioxide is collected and returned to convert the nano rare earth hydroxide so as to realize recycling of the carbon dioxide.

Description

Technical Field:

[0001] The present invention relates to the technical field of rare earths, and particularly to a preparation method of nano rare earth oxides for recycling carbon dioxide. Background Art:

[0002] Nanomaterials are the basis and forerunner of nanotechnology and also the most important part of nanotechnology. Nanomaterials have very small particle sizes and large surface curvatures, and are widely used in fields such as semiconductors, aerospace, metallurgy, sensors, micro - mechanical systems, cemented carbides, and biopharmaceuticals. Nano rare earth oxide particles exhibit the dual characteristics of size effect and rare earth, making them show better superiority in magnetism, electricity, light, heat, and chemical reactions. They have become the basis for the development of special functional materials and play an increasingly important and unique role in many technical fields, being widely used in many fields such as catalysts, fluorescence, waveguides, magnetism, and coatings.

[0003] The main preparation methods of nano rare earth oxides are: solid - phase method, gas - phase method, and liquid - phase precipitation method. The liquid - phase precipitation method has the simplest process, low economic cost, and wide popularity. This method is widely used in laboratory research and industrial production and is also the most mature method for synthesizing nano rare earth oxides. The precipitants of the liquid - phase precipitation method mainly include hydroxides, carbonates, etc. As is well known, the precipitate particles of hydroxide precipitation are fine, but rare earth hydroxides are prone to form bridging hydroxyl groups during the dehydration process, resulting in serious agglomeration phenomena, causing poor quality of nano rare earth oxides. Researchers have developed various methods for controlling powder agglomeration, mainly including mechanical force dispersion, organic matter washing, azeotropic distillation, drying methods, etc. Although they have certain effects, the cost is relatively high. The product of carbonate precipitation is rare earth carbonate. Rare earth carbonate is prone to crystallize to form large - particle crystalline rare earth carbonate during drying and calcination, resulting in relatively large particle sizes of nano rare earth oxides. Carbon dioxide gas is released during the thermal decomposition of rare earth carbonate, and the release of carbon dioxide increases the greenhouse effect, but the release of carbon dioxide can play a role in breaking particles to a certain extent. Therefore, exploring how to prevent or reduce the agglomeration of precipitation method powders and reduce carbon emissions is the main research direction at present. Summary of the Invention:

[0004] The present invention solves the problems of easy agglomeration and carbon emissions in the preparation of nano rare earth oxide powders by the wet precipitation method, and provides a preparation method of nano rare earth oxides for recycling carbon dioxide. The present invention utilizes the characteristics that the particles of rare earth hydroxide are fine and gas is released during the thermal decomposition of nanoparticles to play a role in breaking. Carbon dioxide is introduced into the nano rare earth hydroxide slurry, which not only solves the agglomeration problem, but also the decomposed carbon dioxide is collected and returned to convert nano rare earth hydroxide to realize the recycling of carbon dioxide.

[0005] The present invention provides a method for preparing nano rare earth oxides for recycling carbon dioxide, comprising the following steps:

[0006] (1) Adding an alkaline solution to the rare earth solution in proportion and mixing and stirring to obtain a nano rare earth hydroxide slurry;

[0007] (2) Spraying carbon dioxide into the nano rare earth hydroxide slurry obtained in step (1), starting stirring, to obtain a nano rare earth basic carbonate slurry, and filtering to obtain nano rare earth basic carbonate;

[0008] (3) Adding an organic reagent to the nano rare earth basic carbonate obtained in step (2), mixing evenly, and then spray drying to obtain dried nano rare earth basic carbonate, wherein the organic reagent is selected from one or two of polyethylene glycol and polyether;

[0009] (4) Putting the dried nano rare earth basic carbonate particles obtained in step (3) into a reaction vessel at 300°C to 900°C, heating to the set temperature for roasting and decomposition to obtain the nano rare earth oxide, and collecting the obtained carbon dioxide and returning it to step (2) for recycling.

[0010] Preferably, the rare earth solution in step (1) is selected from one of rare earth chloride solution and rare earth nitrate solution, and the concentration of the rare earth solution is 0.1 to 1.0 mol / L.

[0011] Preferably, the alkaline solution in step (1) is selected from one of sodium hydroxide, ammonia water and potassium hydroxide, and the concentration of the alkaline solution is 1 to 6 mol / L.

[0012] Preferably, in step (1), the alkaline solution is added to the rare earth solution according to the molar ratio of rare earth:OH - of 1:3 to 4 to obtain a nano rare earth hydroxide slurry. In step (1), the stirring time is 1 to 5 hours.

[0013] Preferably, the flow rate of the carbon dioxide in step (2) is 0.2 - 50.0 L / min.

[0014] Preferably, in step (2), the stirring time is 1 to 5 hours.

[0015] Preferably, the addition amount of the organic reagent in step (3) is 0.1 to 3.0 wt% of the mass of the nano rare earth basic carbonate. Further preferably, the addition amount of the organic reagent is 2.25 wt% of the mass of the nano rare earth basic carbonate.

[0016] Preferably, the organic reagent in step (3) is a mixture of polyethylene glycol and polyether, and the mass ratio of polyethylene glycol to polyether is 1 to 6:1. Further preferably, the mass ratio of polyethylene glycol to polyether is 2:1.

[0017] Preferably, the spray drying temperature is 100°C to 250°C.

[0018] Preferably, the calcination conditions in step (4) are: calcination and decomposition at 650°C to 900°C for 1 - 5 hours.

[0019] Compared with the prior art, the present invention has the following advantages: By utilizing the characteristics that rare earth hydroxide particles are fine and gas is released during the thermal decomposition of nanoparticles, which plays a role in breaking, the rare earth in the rare earth solution is first precipitated as fine nano - rare earth hydroxide particles by an alkaline substance. To avoid the disadvantages that nano - rare earth hydroxide is prone to agglomeration during calcination and rare earth carbonate is prone to crystallize into large particles, carbon dioxide is introduced into the nano - rare earth hydroxide slurry to convert nano - rare earth hydroxide into nano - basic rare earth carbonate with gas release during thermal decomposition. Basic rare earth carbonate has the advantages of small particles of rare earth hydroxide and gas release during the decomposition of rare earth carbonate; To better solve the agglomeration problem, an organic reagent is added to the nano - basic rare earth carbonate and strongly stirred and mixed evenly to play a steric hindrance role between particles; Finally, the nano - basic rare earth carbonate is placed in a calcination furnace set at a certain temperature, heated to the set temperature for calcination and decomposition. Nano - rare earth basic carbonate can rapidly decompose and release a large amount of carbon dioxide, and these carbon dioxides play a role in breaking the powder. Then, the decomposed carbon dioxide is collected and returned to convert nano - rare earth hydroxide. The two work together to solve the problems of easy agglomeration and carbon dioxide emission in the preparation of nano - rare earth oxide powder by the existing wet precipitation method. Specific embodiments:

[0020] The following examples are further descriptions of the present invention rather than limitations thereof.

[0021] Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention. Unless otherwise specified, the experimental materials and reagents herein are all conventional commercially available products in this technical field. In the following examples, preferably, polyether, CAS No. 9003 - 11 - 6; polyethylene glycol 6000, CAS No. 25322 - 68 - 3, linear molecular formula H(OCH 2 CH 2 ) n OH.

[0022] Example 1

[0023] A rare earth chloride solution with a rare earth concentration of 0.15 mol / L, with the ratio of rare earth: OH -The sodium hydroxide solution with a concentration of 1.2 mol / L was slowly added at a molar ratio of 1:3.1. After mixing and stirring for 1.5 hours, a nano rare earth hydroxide slurry was obtained. Carbon dioxide was sprayed into the nano rare earth hydroxide slurry at a flow rate of 0.2 L / min, and stirring was started for 5 hours to generate a nano rare earth basic carbonate slurry. After filtering the nano rare earth basic carbonate slurry, nano rare earth basic carbonate was obtained. Polyethylene glycol accounting for 2 wt% of the mass of the nano rare earth basic carbonate was added and strongly stirred evenly. It was spray-dried at 120 °C to obtain dried nano rare earth basic carbonate. Then it was put into a calcination furnace at 400 °C and calcined and decomposed at 650 °C for 5 hours to obtain nano rare earth oxide, and carbon dioxide was collected and returned to convert nano rare earth hydroxide. After analysis, the particle size distribution D50 of the nano rare earth oxide was 190 nm.

[0024] Comparative Example 1

[0025] The nano rare earth hydroxide slurry in Example 1 was filtered to obtain a nano rare earth slurry. Polyethylene glycol 6000 accounting for 2 wt% of the mass of the nano rare earth slurry was added and strongly stirred evenly. It was dried in a drying device at 70 °C for 12 hours to obtain dried nano rare earth hydroxide. Then it was put into a calcination furnace at 400 °C and calcined and decomposed at 650 °C for 5 hours to obtain nano rare earth oxide. After analysis, the particle size distribution D50 of the nano rare earth oxide was 6.8 μm.

[0026] Comparative Example 2

[0027] Carbon dioxide was sprayed into the nano rare earth hydroxide slurry in Example 1 at a flow rate of 0.2 L / min, and stirring was started for 5 hours to generate a nano rare earth basic carbonate slurry. Stirring was continued for 15 hours to generate a rare earth carbonate slurry. After filtering the rare earth carbonate slurry, rare earth carbonate was obtained. It was dried in a drying device at 70 °C for 12 hours to obtain dried rare earth carbonate. Then it was put into a calcination furnace at 400 °C and calcined and decomposed at 650 °C for 5 hours to obtain nano rare earth oxide. After analysis, the particle size distribution D50 of the nano rare earth oxide was 870 nm.

[0028] Comparing Example 1 with Comparative Examples 1 and 2, it can be seen that when only an organic reagent (Comparative Example 1) or only carbon dioxide (Comparative Example 2) was added, the particle size of the obtained rare earth oxide was not as good as that in Example 1. In the present invention, carbon dioxide was used to convert rare earth hydroxide into rare earth carbonate, and an organic reagent was added and strongly stirred and mixed evenly to play a steric hindrance effect between particles. The synergistic effect of carbon dioxide and the organic reagent produced an unexpected technical effect.

[0029] Example 2

[0030] The rare earth nitrate solution with a rare earth concentration of 0.9 mol / L, with the rare earth solution and the alkaline solution in terms of rare earth:OH -The ammonia water solution with a concentration of 6 mol / L was slowly added at a molar ratio of 1:4. After mixing and stirring for 5 hours, a nano rare earth hydroxide slurry was obtained; carbon dioxide was sprayed into the nano rare earth hydroxide slurry at a flow rate of 50 L / min, and stirring was started for 1.5 hours to generate a nano rare earth basic carbonate slurry; after filtering the nano rare earth basic carbonate slurry, polyether accounting for 0.2 wt% of the mass of the nano rare earth basic carbonate was added and strongly stirred evenly, and then spray-dried at 240 °C to obtain dry nano rare earth basic carbonate. Then it was put into a calcination furnace at 900 °C and calcined and decomposed at 900 °C for 1 hour to obtain nano rare earth oxide, and the carbon dioxide was collected and returned to convert rare earth hydroxide. After analysis, the particle size distribution D50 of the nano rare earth oxide was 110 nm.

[0031] Example 3

[0032] The rare earth chloride solution with a rare earth concentration of 0.5 mol / L, according to the rare earth solution and the alkaline solution in terms of rare earth: OH - The potassium hydroxide solution with a concentration of 3 mol / L was slowly added at a molar ratio of 1:3.5. After mixing and stirring for 3 hours, a nano rare earth hydroxide slurry was obtained; carbon dioxide was sprayed into the nano rare earth hydroxide slurry at a flow rate of 20 L / min, and stirring was started for 3 hours to generate a nano rare earth basic carbonate slurry; after filtering the nano rare earth basic carbonate slurry, polyethylene glycol accounting for 1.5 wt% and polyether accounting for 0.75 wt% of the mass of the nano rare earth basic carbonate were added and strongly stirred evenly, and then spray-dried at 180 °C to obtain dry nano rare earth basic carbonate. Then it was put into a calcination furnace at 700 °C and calcined and decomposed at 800 °C for 3 hours to obtain nano rare earth oxide, and the carbon dioxide was collected and returned to convert rare earth hydroxide. After analysis, the particle size distribution D50 of the nano rare earth oxide was 140 nm.

[0033] Comparative Example 3

[0034] The rare earth chloride solution with a rare earth concentration of 0.5 mol / L, according to the rare earth solution and the alkaline solution in terms of rare earth: OH - The potassium hydroxide solution with a concentration of 3 mol / L was slowly added at a molar ratio of 1:3.5. After mixing and stirring for 3 hours, a nano rare earth hydroxide slurry was obtained; carbon dioxide was sprayed into the nano rare earth hydroxide slurry at a flow rate of 20 L / min, polyethylene glycol accounting for 1.5 wt% and polyether accounting for 0.75 wt% of the mass of the nano rare earth hydroxide slurry were added, and stirring was started for 3 hours to generate a nano rare earth basic carbonate slurry; after filtering the nano rare earth basic carbonate slurry, it was strongly stirred evenly and spray-dried at 180 °C to obtain dry nano rare earth basic carbonate. Then it was put into a calcination furnace at 700 °C and calcined and decomposed at 800 °C for 3 hours to obtain nano rare earth oxide, and the carbon dioxide was collected and returned to convert rare earth hydroxide. After analysis, the particle size distribution D50 of the nano rare earth oxide was 1100 nm.

[0035] Comparative Example 4

[0036] A rare earth chloride solution with a rare earth concentration of 0.5 mol / L was slowly added to a potassium hydroxide solution with a concentration of 3 mol / L at a ratio of rare earth solution to alkaline solution of rare earth:OH - The molar ratio was 1:3.5, and after mixing and stirring for 3 hours, a nano rare earth hydroxide slurry was obtained; carbon dioxide was sprayed into the nano rare earth hydroxide slurry at a flow rate of 20 L / min, and stirring was started for 3 hours to generate a nano basic rare earth carbonate slurry; after filtering the nano basic rare earth carbonate slurry, polyether with a mass of 2.25 wt% of the nano basic rare earth carbonate was added and strongly stirred, and then spray-dried at 180 °C to obtain dry nano basic rare earth carbonate. Then it was put into a calcination furnace at 700 °C and calcined and decomposed at 800 °C for 3 hours to obtain nano rare earth oxide, and carbon dioxide was collected and returned to convert rare earth hydroxide. After analysis, the particle size distribution D50 of the nano rare earth oxide was 920 nm.

[0037] Comparative Example 5

[0038] A rare earth chloride solution with a rare earth concentration of 0.5 mol / L was slowly added to a potassium hydroxide solution with a concentration of 3 mol / L at a ratio of rare earth solution to alkaline solution of rare earth:OH- molar ratio of 1:3.5, and after mixing and stirring for 3 hours, a nano rare earth hydroxide slurry was obtained; carbon dioxide was sprayed into the nano rare earth hydroxide slurry at a flow rate of 20 L / min, and stirring was started for 3 hours to generate a nano basic rare earth carbonate slurry; after filtering the nano basic rare earth carbonate slurry, polyethylene glycol with a mass of 2.25 wt% of the nano basic rare earth carbonate was added and strongly stirred, and then spray-dried at 180 °C to obtain dry nano basic rare earth carbonate. Then it was put into a calcination furnace at 700 °C and calcined and decomposed at 800 °C for 3 hours to obtain nano rare earth oxide, and carbon dioxide was collected and returned to convert rare earth hydroxide. After analysis, the particle size distribution D50 of the nano rare earth oxide was 815 nm.

[0039] Comparing Example 3 with Comparative Example 4 and Comparative Example 5, the particle sizes of the nano rare earth oxides obtained by adding polyethylene glycol or polyether alone were not as good as those of Example 3. The synergistic effect of polyethylene glycol and polyether made the particle sizes of the obtained rare earth oxides uniform.

[0040] Example 4

[0041] Add a sodium hydroxide solution with a concentration of 1 mol / L slowly to a rare earth chloride solution with a rare earth concentration of 0.1 mol / L at a ratio of rare earth:OH⁻ molar ratio of 1:3. After mixing and stirring for 1 hour, a nano rare earth hydroxide slurry is obtained; spray carbon dioxide into the nano rare earth hydroxide slurry at a flow rate of 0.2 L / min, start stirring for 1 hour, and a nano basic rare earth carbonate slurry is generated; filter the nano basic rare earth carbonate slurry to obtain nano basic rare earth carbonate, add an organic reagent accounting for 0.1 wt% of the mass of the nano basic rare earth carbonate, with the mass ratio of polyethylene glycol to polyether being 1:1, stir strongly, and obtain dried nano basic rare earth carbonate through spray drying at 100 °C. Then place it in a calcination furnace at 400 °C and roast and decompose it at 650 °C for 5 hours to obtain nano rare earth oxide, collect carbon dioxide and return it to convert nano rare earth hydroxide. Through analysis, the particle size distribution D50 of the nano rare earth oxide is 160 nm.

[0042] Example 5

[0043] Add a sodium hydroxide solution with a concentration of 6 mol / L slowly to a rare earth chloride solution with a rare earth concentration of 1.0 mol / L at a ratio of rare earth:OH⁻ molar ratio of 1:4. After mixing and stirring for 5 hours, a nano rare earth hydroxide slurry is obtained; spray carbon dioxide into the nano rare earth hydroxide slurry at a flow rate of 50 L / min, start stirring for 5 hours, and a nano basic rare earth carbonate slurry is generated; filter the nano basic rare earth carbonate slurry to obtain nano basic rare earth carbonate, add an organic reagent accounting for 3 wt% of the mass of the nano basic rare earth carbonate, with the mass ratio of polyethylene glycol to polyether being 6:1, stir strongly, and obtain dried nano basic rare earth carbonate through spray drying at 250 °C. Then place it in a calcination furnace at 400 °C and roast and decompose it at 900 °C for 1 hour to obtain nano rare earth oxide, collect carbon dioxide and return it to convert nano rare earth hydroxide. Through analysis, the particle size distribution D50 of the nano rare earth oxide is 174 nm.

[0044] The descriptions of the above embodiments are only used to help understand the technical solutions and their core ideas of the present invention. It should be pointed out that for those skilled in the art of this technology, without departing from the principle of the present invention, several improvements and modifications can still be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing nano rare earth oxides for recycling carbon dioxide, characterized in that: The steps include: (1) adding alkaline solution to the rare earth solution in proportion, mixing and stirring, to obtain nano rare earth hydroxide slurry; (2) spraying carbon dioxide into the nano rare earth hydroxide slurry obtained in step (1), starting stirring to obtain nano basic rare earth carbonate slurry, and filtering to obtain nano basic rare earth carbonate; (3) adding an organic reagent to the nano-basic rare earth carbonate obtained in step (2), mixing, and spray drying to obtain dry nano-basic rare earth carbonate, wherein the organic reagent is selected from one or two of polyethylene glycol and polyether; (4) placing the dried nano-sized basic rare earth carbonate particles obtained in step (3) into a reaction vessel at 300° C. to 900° C., heating the vessel to a set temperature, calcining and decomposing the nano-sized rare earth oxide, and collecting the obtained carbon dioxide and returning it to step (2) for recycling.

2. The preparation method according to claim 1, characterized in that: The rare earth solution described in step (1) is selected from one of rare earth chloride solution and rare earth nitrate solution, and the concentration of the rare earth solution is 0.1-1.0 mol / L.

3. The preparation method according to claim 1, characterized in that: The alkaline solution described in step (1) is selected from one of sodium hydroxide, ammonia water and potassium hydroxide, and the concentration of the alkaline solution is 1-6 mol / L.

4. The preparation method according to any one of claims 1 to 3, characterized in that In step (1), the rare earth solution and the alkaline solution are prepared according to the rare earth: OH - An alkaline solution is added at a molar ratio of 1:3 to 4 to obtain a nano rare earth hydroxide slurry.

5. The preparation method according to claim 1, characterized in that: The flow rate of the carbon dioxide in step (2) is 0.2-50.0 L / min.

6. The preparation method according to claim 1, characterized in that: In step (2), the stirring time is 1 to 5 hours.

7. The preparation method according to claim 1, characterized in that: The amount of the organic reagent added in step (3) is 0.1 to 3.0 wt % of the mass of the nano-basic rare earth carbonate.

8. The preparation method according to claim 1, characterized in that: The organic reagent described in step (3) is a mixture of polyethylene glycol and polyether, and the mass ratio of polyethylene glycol to polyether is 1 to 6:

1.

9. The preparation method according to claim 1, characterized in that: The spray drying temperature is 100°C to 250°C.

10. The preparation method according to claim 1, characterized in that: The calcination conditions in step (4) are: calcination and decomposition at 650°C to 900°C for 1 to 5 hours.