Preparation method of cerium oxide with large specific gravity

Abstract

The invention provides a preparation method of large-specific-gravity cerium oxide, which comprises the following steps: mixing and precipitating an ammonium carbonate solution and cerium nitrate, and adding lemon triammonium and boric acid before reaction to regulate the crystal form, so that cerium carbonate crystals with high purity and granularity are generated, and the specific gravity of cerium oxide generated after calcination is directly influenced by the purity and granularity of the cerium carbonate crystals. Meanwhile, the growth of crystals in the reaction process is promoted by adopting microwave assistance, the crystal growth efficiency is improved through a heat effect generated by absorbing the microwaves by the crystals, the reaction speed is further improved, the reaction energy consumption is reduced by the microwaves, and the preparation cost of cerium oxide is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of rare earth material preparation, and particularly relates to a method for preparing high-density cerium oxide. Background Art

[0002] As the country pays more and more attention to environmental protection, the requirements for exhaust emissions are also increasing. As a cheap rare earth catalytic material, people are studying cerium oxide products with special properties. In the field of catalytic materials, the requirements for various physical properties of nano cerium oxide are increasing. More and more catalyst manufacturers are beginning to seek cerium oxide with a larger specific gravity to increase the density of cerium oxide on the catalyst surface and enhance the catalyst activity.

[0003] The conventional method for preparing cerium oxide is to react cerium salt with excess ammonia or carbon ammonia, filter the resulting precipitate and then burn it to finally obtain the cerium oxide product. However, the specific gravity of cerium oxide prepared by conventional methods is generally 0.5-0.8 g / cm 3 , which is far from meeting the needs of the current rare earth materials market. Summary of the invention

[0004] In view of the problem that the specific gravity of cerium oxide prepared by conventional methods is relatively low, the present invention provides a method for preparing cerium oxide with a high specific gravity, which can prepare cerium oxide with a high specific gravity under normal temperature and pressure.

[0005] The present invention is achieved through the following technical solutions: A method for preparing high-density cerium oxide comprises the following steps: S1: stirring a cerium nitrate solution having a concentration of 0.2-0.6 mol / L at 50-80 rpm, then adding an ammonium carbonate solution to the stirred cerium nitrate solution according to a molar ratio of cerium nitrate to ammonium carbonate of 1:(1.5-2.5), and simultaneously adding 0.1%-0.8% of triammonium citrate by mass fraction of the total solution, continuing to stir evenly, and aging until complete precipitation to obtain a precipitation slurry; S2: heating the obtained precipitation slurry by microwave for 2-5h to obtain the treated precipitation slurry; S3: preparing the treated precipitation slurry into a slurry with a mass percentage of 10-30% with deionized water, stirring at 60-100 rpm, and then adding a polyacrylamide precipitant with a mass percentage of 0.1%-1% of the slurry to carry out sedimentation to obtain a secondary sedimentation slurry; S4: transferring the secondary sedimentation slurry into a plate-frame filter press at 10 L / h, washing and filtering at room temperature and pressure at 100-300 rpm to obtain a cerium carbonate filter cake; S5: calcining the cerium carbonate filter cake at 500-650° C. to obtain cerium oxide with a high specific gravity.

[0006] The present invention adds an appropriate amount of triammonium citrate before ammonium carbonate precipitates cerium, and utilizes triammonium citrate and Ce to precipitate cerium. 3+ The strong coordination ability makes triammonium citrate and Ce 3+ The complexation increases the difficulty of the carbonate added subsequently to directly precipitate and crystallize Ce, thereby significantly reducing the crystallization rate of cerium carbonate, so that the cerium carbonate crystals can get more time to grow to generate more single crystal cerium carbonate, thereby improving the quality and particle size of the cerium carbonate crystals; at the same time, the addition of triammonium citrate adheres to the surface of the crystal, reducing the adsorption of nitrate ions by cerium ions, thereby reducing the entrainment and wrapping of nitrate ions by the crystal, thereby improving the purity of cerium carbonate crystals, and the purity of cerium carbonate directly affects the specific gravity of cerium oxide generated after calcination. At the same time, the present invention uses microwaves to assist the reaction of the precipitation slurry, and generates a thermal effect after absorbing microwaves from the inside of the crystal, thereby increasing the crystal growth rate, and can regulate the crystal to form hexagonal basic cerium carbonate, thereby reducing energy consumption for subsequent calcination to prepare cerium oxide.

[0007] As a further improvement of the present invention, in step S1, a boric acid solution having a mass fraction of 0.1% to 0.2% of the total solution is added simultaneously with the addition of triammonium citrate.

[0008] Boric acid can effectively regulate the particle size of cerium carbonate crystals. Boric acid can adsorb and bond cerium carbonate particles. Combined with the effect of triammonium citrate in inhibiting the C-axis growth of particles, cerium carbonate particles can be stacked along the C-axis direction, so that cerium carbonate crystals can generate large-size crystals during the crystallization process. Finally, after calcination, high-density cerium oxide can be obtained.

[0009] Preferably, the aging temperature of the cerium nitrate solution in step S1 is 60-80° C., and the reaction time is 0.5-2 h.

[0010] Preferably, the microwave power in step S2 is 100-1000W.

[0011] Preferably, the precipitant in step S3 is one of polyethyleneimine, starch and chitosan, and the added amount is 0.1%-1% of the mass of the slurry.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. In the present invention, an appropriate amount of triammonium citrate and boric acid are added as regulators before precipitating cerium with ammonium carbonate to improve the purity and particle size of cerium carbonate crystals, and the purity and particle size of cerium carbonate directly affect the specific gravity of cerium oxide generated after calcination.

[0013] 2. The present invention uses microwaves to promote crystal growth, generating a thermal effect from within the material to improve reaction efficiency. Compared with the conventional method of preparing cerium carbonate crystals at high pressure and high temperature, it effectively reduces the reaction environment conditions, thereby reducing energy consumption and costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is the XRD structure diagram of cerium carbonate prepared in Example 1.

[0015] Figure 2 This is the XRD structure diagram of cerium oxide prepared in Example 1.

[0016] Figure 3 This is the TEM image of cerium oxide prepared in Example 1. DETAILED DESCRIPTION

[0017] The present invention will be further described below in conjunction with the embodiments.

[0018] Embodiment 1: A method for preparing high specific gravity cerium oxide, comprising the following steps: S1: stirring a 0.2 mol / L cerium nitrate solution at 50 rpm, then adding ammonium carbonate solution to the stirring cerium nitrate solution according to a molar ratio of cerium nitrate to ammonium carbonate of 1:1.5, and adding 0.1% of triammonium citrate by mass fraction of the total solution, continuing to stir evenly, aging at 60° C. for 0.5 h until complete precipitation, to obtain a precipitation slurry; S2: The obtained precipitation slurry was subjected to microwave heating for 5 h at a microwave power of 100 W to obtain a treated precipitation slurry; S3: preparing the treated precipitation slurry into a slurry with a mass percentage of 10% with deionized water, stirring at 60 rpm, and then adding 0.1% polyacrylamide by mass of the slurry for sedimentation to obtain a secondary sedimentation slurry; S4: transferring the secondary sedimentation slurry into a plate-frame filter press at 10 L / h, washing and filtering at room temperature and pressure at 100 rpm to obtain a cerium carbonate filter cake; S5: calcining the cerium carbonate filter cake at 500° C. to obtain cerium oxide with a high specific gravity.

[0019] The cerium carbonate prepared in this example has a crystal particle size of 100 μm, and the bulk density of the cerium oxide obtained after calcination is 0.9 g / cm 3 , the tap density is 1.2g / cm 3 .

[0020] Embodiment 2: A method for preparing high specific gravity cerium oxide, comprising the following steps: S1: stirring a 0.4 mol / L cerium nitrate solution at 70 rpm, then adding ammonium carbonate solution to the stirring cerium nitrate solution according to a molar ratio of cerium nitrate to ammonium carbonate of 1:2.0, and adding triammonium citrate with a mass fraction of 0.4% of the total solution, continuing to stir evenly, aging at 70° C. for 1 h until complete precipitation, to obtain a precipitation slurry; S2: The obtained precipitation slurry was subjected to microwave heating for 3.5 h at a microwave power of 500 W to obtain a treated precipitation slurry; S3: preparing the treated precipitation slurry into a slurry with a mass percentage of 20% with deionized water, stirring at 80 rpm, and then adding chitosan with a mass percentage of 0.6% of the slurry for sedimentation to obtain a secondary sedimentation slurry; S4: The secondary sedimentation slurry was transferred into a plate-frame filter press at 10 L / h, and washed and filtered at normal temperature and pressure at 200 rpm to obtain a cerium carbonate filter cake; S5: calcining the cerium carbonate filter cake at 600° C. to obtain cerium oxide with a high specific gravity.

[0021] The cerium carbonate prepared in this example has a crystal particle size of 150 μm, and the bulk density of the cerium oxide obtained after calcination is 0.96 g / cm 3 , the tap density is 1.3g / cm 3 .

[0022] Embodiment 3: A method for preparing high specific gravity cerium oxide, comprising the following steps: S1: stirring a 0.6 mol / L cerium nitrate solution at 80 rpm, then adding ammonium carbonate solution to the stirring cerium nitrate solution according to a molar ratio of cerium nitrate to ammonium carbonate of 1:2.5, and adding triammonium citrate with a mass fraction of 0.8% of the total solution, continuing to stir evenly, aging at 80° C. for 2 h until complete precipitation, to obtain a precipitation slurry; S2: The obtained precipitation slurry was subjected to microwave heating for 2 h at a microwave power of 1000 W to obtain a treated precipitation slurry; S3: preparing the treated precipitation slurry into a slurry with a mass percentage of 30% with deionized water, stirring at 100 rpm, and then adding polyethyleneimine with a mass percentage of 1% of the slurry for sedimentation to obtain a secondary sedimentation slurry; S4: The secondary sedimentation slurry was transferred into a plate-frame filter press at 10 L / h, and washed and filtered at room temperature and pressure at 300 rpm to obtain a cerium carbonate filter cake; S5: calcining the cerium carbonate filter cake at 650° C. to obtain cerium oxide with a high specific gravity.

[0023] The cerium carbonate prepared in this example has a crystal particle size of 168 μm, and the bulk density of the cerium oxide obtained after calcination is 1.0 g / cm3 , the tap density is 1.3g / cm 3 .

[0024] Example 4: A method for preparing high specific gravity cerium oxide, comprising the following steps: S1: stirring a 0.4 mol / L cerium nitrate solution at 60 rpm, then adding ammonium carbonate solution to the stirring cerium nitrate solution according to a molar ratio of cerium nitrate to ammonium carbonate of 1:2.2, and adding 0.4% of triammonium citrate and 0.4% of boric acid by mass fraction of the total solution, continuing to stir evenly, aging at 65° C. for 2 h until complete precipitation, to obtain a precipitated slurry; S2: The obtained precipitation slurry was subjected to microwave heating for 2 h at a microwave power of 1000 W to obtain a treated precipitation slurry; S3: preparing the treated precipitation slurry into a slurry with a mass percentage of 10-30% with deionized water, stirring at 60-100 rpm, and then adding 1% starch by mass of the slurry for sedimentation to obtain a secondary sedimentation slurry; S4: The secondary sedimentation slurry was transferred into a plate-frame filter press at 10 L / h, and washed and filtered at normal temperature and pressure at 200 rpm to obtain a cerium carbonate filter cake; S5: calcining the cerium carbonate filter cake at 620° C. to obtain cerium oxide with a high specific gravity.

[0025] The cerium carbonate prepared in this example has a crystal particle size of 300 μm, and the bulk density of the cerium oxide obtained after calcination is 1.2 g / cm 3 , the tap density is 1.4g / cm 3 .

[0026] Example 5: A method for preparing high specific gravity cerium oxide, comprising the following steps: S1: stirring a 0.6 mol / L cerium nitrate solution at 80 rpm, then adding ammonium carbonate solution to the stirring cerium nitrate solution according to a molar ratio of cerium nitrate to ammonium carbonate of 1:2.5, and adding 0.8% of triammonium citrate and 0.1% of boric acid in the total solution by mass fraction, continuing to stir evenly, and aging at 70° C. for 2 h until complete precipitation, to obtain a precipitated slurry; S2: The obtained precipitation slurry is subjected to microwave heating for 2 h at a microwave power of 800 W to obtain a treated precipitation slurry; S3: preparing the treated precipitation slurry into a slurry with a mass percentage of 15% with deionized water, stirring at 80 rpm, and then adding 0.6% polyacrylamide by mass of the slurry for sedimentation to obtain a secondary sedimentation slurry; S4: The secondary sedimentation slurry was transferred into a plate-frame filter press at a rate of 10 L / h, and washed and filtered at room temperature and pressure at 120 rpm to obtain a cerium carbonate filter cake; S5: calcining the cerium carbonate filter cake at 600° C. to obtain cerium oxide with a high specific gravity.

[0027] The cerium carbonate prepared in this example has a crystal particle size of 328 μm, and the bulk density of the cerium oxide obtained after calcination is 1.1 g / cm 3 , the tap density is 1.3g / cm 3 .

[0028] Example 6: A method for preparing high specific gravity cerium oxide, comprising the following steps: S1: stirring a 0.4 mol / L cerium nitrate solution at 80 rpm, then adding ammonium carbonate solution to the stirring cerium nitrate solution according to a molar ratio of cerium nitrate to ammonium carbonate of 1:2.0, and adding 0.7% triammonium citrate and 0.3% boric acid of the total solution by mass fraction, continuing to stir evenly, aging at 70° C. for 1 h until complete precipitation, to obtain a precipitated slurry; S2: The obtained precipitation slurry was subjected to microwave heating for 4 h at a microwave power of 600 W to obtain a treated precipitation slurry; S3: preparing the treated precipitation slurry into a slurry with a mass percentage of 15% with deionized water, stirring at 100 rpm, and then adding polyethyleneimine with a mass percentage of 1% of the slurry for sedimentation to obtain a secondary sedimentation slurry; S4: The secondary sedimentation slurry was transferred into a plate-frame filter press at 10 L / h, and washed and filtered at room temperature and pressure at 300 rpm to obtain a cerium carbonate filter cake; S5: calcining the cerium carbonate filter cake at 650° C. to obtain cerium oxide with a high specific gravity.

[0029] The cerium carbonate prepared in this example has a crystal particle size of 400 μm, and the bulk density of the cerium oxide obtained after calcination is 1.2 g / cm 3 , the tap density is 1.5g / cm 3 .

[0030] The above embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention. The protection scope of the present invention is defined by the claims. Those skilled in the art may make various modifications or equivalent substitutions to the present invention within the essence and protection scope of the present invention, and such modifications or equivalent substitutions shall also be deemed to fall within the protection scope of the present invention.

Claims

1. A method for preparing high specific gravity cerium oxide, characterized in that: The following steps are involved: S1: stirring a cerium nitrate solution having a concentration of 0.2-0.6 mol / L at 50-80 rpm, then adding an ammonium carbonate solution to the stirred cerium nitrate solution according to a molar ratio of cerium nitrate to ammonium carbonate of 1:(1.5-2.5), and simultaneously adding 0.1%-0.8% of triammonium citrate by mass fraction of the total solution, continuing to stir evenly, and aging until complete precipitation to obtain a precipitation slurry; S2: heating the obtained precipitation slurry by microwave for 2-5h to obtain the treated precipitation slurry; S3: preparing the treated precipitation slurry into a slurry with a mass percentage of 10-30% with deionized water, stirring at 60-100 rpm, and then adding a polyacrylamide precipitant with a mass percentage of 0.1%-1% of the slurry to carry out sedimentation to obtain a secondary sedimentation slurry; S4: transferring the secondary sedimentation slurry into a plate-frame filter press at 10 L / h, washing and filtering at room temperature and pressure at 100-300 rpm to obtain a cerium carbonate filter cake; S5: calcining the cerium carbonate filter cake at 500-650° C. to obtain cerium oxide with a high specific gravity.

2. The method for preparing high specific gravity cerium oxide according to claim 1, characterized in that: In step S1, while adding triammonium citrate, a boric acid solution having a mass fraction of 0.1% to 0.2% of the total solution is added.

3. The method for preparing high specific gravity cerium oxide according to claim 1, characterized in that: The cerium nitrate solution in step S1 is aged at a temperature of 60-80° C. and a reaction time of 0.5-2 h.

4. The method for preparing high specific gravity cerium oxide according to claim 1, characterized in that: The microwave power in step S2 is 100-1000W.

5. The method for preparing high specific gravity cerium oxide according to claim 1, characterized in that: The precipitant in step S3 may be one of polyethyleneimine, starch and chitosan, and the amount added is 0.1%-1% of the mass of the slurry.

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