CN112125326B

CN112125326B - Preparation method for continuously producing nano cerium oxide

Info

Publication number: CN112125326B
Application number: CN202011153192.1A
Authority: CN
Inventors: 包中华; 李科; 李梅
Original assignee: Inner Mongolia University of Science and Technology
Current assignee: Inner Mongolia University of Science and Technology
Priority date: 2020-10-26
Filing date: 2020-10-26
Publication date: 2022-09-13
Anticipated expiration: 2040-10-26
Also published as: CN112125326A

Abstract

The invention provides a preparation method for continuously producing nano cerium oxide, which comprises the following steps: preparing a cerium salt solution with the concentration of 0.01-1mol/L and a precipitator solution with the concentration of 0.01-3mol/L by taking a dispersing agent as a medium, introducing the cerium salt solution and the precipitator solution into a supergravity rotating bed according to the molar ratio of 1:1-20 at a certain flow and pH, obtaining nano cerium oxide precursor slurry at a certain reaction temperature, reaction time and rotation speed, carrying out ultrasonic treatment on the precursor slurry, washing, carrying out centrifugal separation, carrying out freeze drying, and roasting the dried precursor to obtain the nano cerium oxide. The nano cerium oxide prepared by the method has the characteristics of high roundness, monodispersity and narrow distribution, and can be used for catalytic materials, polishing materials, hydrogen storage materials, luminescent materials and the like.

Description

Preparation method for continuously producing nano cerium oxide

Technical Field

The invention relates to the technical field of preparation of nano rare earth materials, in particular to a preparation method for continuously producing nano cerium oxide.

Background

The research on the preparation technology and performance of the nano cerium oxide particles has been started at home and abroad. Cerium oxide has a cubic fluorite structure. It has high thermal stability, strong oxygen storage capacity and can be in Ce ³⁺ And Ce ⁴⁺ The property of simple transitions between oxidation states, and therefore it has attracted the researchers' extensive interest. It has been widely used in the fields of catalysts, ultraviolet absorbing materials, oxygen sensitive materials, solid oxide cell materials, polishing materials, and the like.

The gravity technology is a new technology for strengthening the multiphase flow transmission and reaction process, and the super gravity machine has been widely regarded at home and abroad since the last century, and has the advantages of small volume, light weight, low energy consumption, easy operation, easy maintenance, safety, reliability, flexibility, environmental suitability and the like which are not possessed by the traditional equipment, so that the super gravity technology has wide commercial application prospect in the industrial fields of environmental protection, material biochemical industry and the like. However, the supergravity technology is mainly in the application and development stage at present, is mainly reflected in two aspects of the supergravity gas-solid fluidization technology and the supergravity gas-liquid mass transfer technology, is less applied to the liquid-liquid reaction technology, and is not popularized yet.

The precipitation method is a common method for liquid-phase synthesis of metal oxide nano-powder. It is generally prepared by adding precipitant into solution containing metal ions to generate precursors such as insoluble hydroxide, carbonate, sulfate and oxalate, and then heating and decomposing the precursors, i.e. the solution is preparedObtaining the nano oxide powder. The method comprises a coprecipitation method, a uniform precipitation method, a complex precipitation method, a hydrolysis precipitation method and the like. The rare earth oxide nanoparticles prepared by precipitation method contain CeO ₂ 、Tm ₂ O ₃ 、Y ₂ O ₃ 、Er ₂ O ₃ 、La ₂ O ₃ 。

Freeze drying is also known as sublimation drying. Drying processes in which an aqueous material is frozen below freezing to convert water to ice and then the ice is removed by converting it to a vapor under a relatively high vacuum. The material can be frozen in a freezing device and then dried. But can also be frozen directly in the drying chamber by rapidly drawing a vacuum. The water vapor formed by sublimation is removed by means of a condenser. The heat of vaporization required during sublimation is typically supplied by thermal radiation.

The nano powder has some problems in the practical application process because the nano particles have small particle size and high surface activity, and are easy to agglomerate to form aggregates with larger size; because the particle size of the product is not uniform and the particle size distribution is wide, continuous mass production becomes an industrial problem; because the interference factors are too many in the preparation process of the nano powder, the influence of human factors, equipment factors and the like is very important, and further, the reproducibility of products among each batch is poor, and the product quality is unstable.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides the preparation method for continuously producing the nano cerium oxide, and the nano cerium oxide prepared by the method has the advantages of high roundness, monodispersity, narrow distribution, simple equipment, easiness in reaction control and easiness in industrial continuous production.

A preparation method for continuously producing nano cerium oxide comprises the following steps:

step 1) preparing raw materials: respectively preparing a cerium salt solution with the concentration of 0.01-1mol/L and a precipitator solution with the concentration of 0.01-3mol/L, PH of 6-12 by taking a dispersant solution as a medium; preheating the prepared cerium salt solution and precipitator solution by an external heating device, wherein the preheating temperature is 25-150 ℃;

step 2) reaction: respectively adding the preheated cerium salt solution and the precipitant solution into a super-gravity rotating bed, and reacting under the action of high-speed shearing to obtain precursor slurry;

step 3) ultrasonic treatment: carrying out ultrasonic treatment on the precursor slurry;

step 4) washing and centrifuging: placing the precursor slurry after ultrasonic treatment into a centrifuge for centrifugal separation, taking the lower layer concentrated solution, washing with distilled water, repeatedly carrying out centrifugal washing for 1-5 times until the solution is neutral, and finally obtaining precursor viscous liquid;

step 5), freeze drying: freeze-drying the precursor viscous liquid to obtain a cerium oxide precursor;

step 6) roasting: and oxidizing and roasting the cerium oxide precursor at the high temperature of 350-950 ℃ to obtain the nano cerium oxide powder.

Further, the cerium salt solution in step 1) is any one of cerium nitrate, ammonium cerium nitrate, cerium chloride, cerium sulfate and cerium formate.

Further, the precipitant in step 1) is at least one of ammonium bicarbonate, urea, ammonia water and polyacrylamide hydroximic acid; the dispersing agent is at least one of polyethylene glycol, polyoxyethylene octyl phenol ether, sodium dodecyl sulfate and fatty alcohol polyoxyethylene ether phosphate; the concentration of the dispersant contained in the cerium salt solution and the precipitant solution is 0.001-1 mol/L.

Further, the flow rate of the cerium salt solution entering the super-gravity rotating bed in the step 2) is 0.1-5L/min, and the flow rate of the precipitator entering the super-gravity rotating bed is 0.1-10L/min.

Further, the rotating speed of the super-gravity rotating bed in the step 2) is 10-3000r/min, 10-10000g of centrifugal force can be generated, and under the conditions of high-speed centrifugation and shearing, the salt solution of cerium and the precipitator solution generate 0.01-100um of liquid drops and 0.001-0.5cm ² The liquid film of (2) is reacted.

Further, the high-gravity rotating bed in the step 2) is a vertical high-gravity rotating bed, the cerium salt solution and the precipitator solution are added from the middle part of the vertical high-gravity rotating bed in a uniform mixing mode, and the average reaction time in the rotating bed is 0.1-10 seconds.

Further, the pH value of the precursor slurry obtained after the reaction in the step 2) is 6-10.

Further, in the ultrasonic treatment process in the step 3), the ultrasonic time of the ultrasonic equipment is 10-600 seconds, the ultrasonic power is 0.1-15KW, and the ultrasonic medium is water or alcohol.

Further, the working pressure of the freeze drying equipment in the process of freeze drying treatment in the step 5) is 0.1-5MPa, and the drying time is 1-48 h.

Further, the time of high-temperature oxidizing roasting in the step 6) is 0.5-4 h.

The invention has the following beneficial effects:

1. the invention provides a preparation method for continuously producing nano cerium oxide, which comprises the steps of firstly preparing a cerium salt solution with the concentration of 0.01-1mol/L and a precipitator solution with the concentration of 0.01-3mol/L, introducing the cerium salt solution and the precipitator solution into a super-gravity rotating bed according to the molar ratio of 1:1-20 at a certain flow rate and pH, obtaining nano cerium oxide precursor slurry at a certain reaction temperature, reaction time and rotation speed, carrying out ultrasonic treatment on the precursor slurry, washing, carrying out centrifugal separation, carrying out freeze drying, and roasting the dried precursor to obtain the nano cerium oxide. The nano cerium oxide prepared by the method has the characteristics of high roundness, monodispersity and narrow distribution, and can be used for catalytic materials, polishing materials, hydrogen storage materials, luminescent materials and the like.

2. The particle size of the nano cerium dioxide powder prepared by the traditional precipitation ball-milling method is about 2 microns, while the particle size of the nano cerium dioxide powder prepared by the method is below 0.2 micron, and the particle size of the prepared powder is improved by one order of magnitude. In the process of preparing the nano cerium dioxide, the nano cerium dioxide with the characteristics of high roundness, monodispersity and narrow distribution can be prepared by researching parameters such as material concentration, pH, dispersant dosage, parameters of a super-gravity rotating bed, ultrasonic dispersion, drying mode, roasting temperature, roasting time and the like.

3. Compared with other methods, the preparation method has the advantages of simple process, less used raw materials, short reaction time, short period, low energy consumption, small powder granularity and good dispersibility, and meanwhile, the method adopts simple equipment, is easy to control the reaction and is easy to realize industrial continuous production. Meanwhile, the method has the advantages of simple equipment, easy control of reaction and easy realization of industrial continuous batch production. By analogy, the invention can expand the preparation process of other two-phase liquid in the same way.

In addition to the objects, features and advantages described above, other objects, features and advantages of the present invention are also provided. The present invention will be described in further detail below with reference to the drawings.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 is a process flow diagram for preparing nano cerium oxide;

FIG. 2 is a schematic structural diagram of an apparatus for continuously producing nano cerium oxide according to the present invention; the device comprises a high-gravity rotating bed 1, an ultrasonic device 2, a centrifuge 4, a freeze dryer 5, a roasting furnace 11, a filler 12, a motor 13, liquid heaters A and 14 and a liquid heater B, wherein the high-gravity rotating bed is connected with the ultrasonic device 3;

FIG. 3 is a graph showing a wettability analysis of the preferred embodiment 2 of the present invention;

FIG. 4 is a graph showing the relationship between the calcination temperature and the calcination time and the particle size of cerium oxide in preferred embodiment 2 of the present invention;

FIG. 5 is an XRD pattern of preferred embodiment 2 of the present invention;

FIG. 6 is a transmission electron microscope image of cerium oxide powder according to preferred embodiment 2 of the present invention.

Detailed Description

Embodiments of the invention will be described in detail below with reference to the drawings, but the invention can be implemented in many different ways as defined and covered by the claims.

The method adopted by the invention comprises the following steps: by utilizing the characteristic of rapid reaction of two liquids, simultaneously adding a proper amount of dispersant, synthesizing a nanoparticle precursor under the action of high-speed centrifugal force, and preparing the nano powder by ultrasonic treatment, washing, centrifugation, freeze drying and roasting. The matched equipment used in the method disclosed by the invention is shown in figure 2 and consists of a supergravity rotating bed 1, an ultrasonic device 2, a centrifuge 3, a freeze dryer 4 and a roasting furnace 5 which are sequentially connected, wherein the supergravity rotating bed 1 consists of a liquid heater, a filler 11 and a motor 12, the liquid heater is used for heating liquid externally and conveying the liquid into the filler, the filler 11 can enable reaction liquid to stay in the filler for a period of time and form tiny liquid drops and liquid films, and the motor 12 provides adjustable shearing force. The liquid heaters include liquid heater a13 and liquid heater B14. Liquid heater a13 is used to preheat the cerium salt solution and liquid heater B14 is used to preheat the precipitant solution.

As shown in fig. 1, a method for continuously producing nano cerium oxide, the process adopts the supporting equipment as shown in fig. 2, and the specific steps are as follows:

step 1) preparing raw materials: respectively preparing a cerium salt solution with the concentration of 0.01-1mol/L and a precipitator solution with the concentration of 0.01-3mol/L, PH of 6-12 by taking a dispersant solution as a medium; preheating the prepared cerium salt solution and the precipitator solution by an external heating device, wherein the preheating temperature is 25-150 ℃;

step 2) reaction: respectively adding the preheated cerium salt solution and the precipitant solution into a super-gravity rotating bed, and generating precipitates under the action of high-speed shearing to prepare precursor slurry;

step 6) roasting: oxidizing and roasting the cerium oxide precursor at the high temperature of 350-950 ℃ to obtain the nano cerium oxide powder.

The present invention will be described and explained in detail with reference to specific examples.

Example 1

A method for continuously producing nano cerium oxide, comprising the following steps:

(1) preparing raw materials: respectively preparing a cerium nitrate solution with the concentration of 0.01mol/L and an ammonium bicarbonate precipitant solution with the concentration of 0.6mol/L, PH of 6-12 by taking a polyethylene glycol solution with the concentration of 0.2mol/L as a dispersing agent; preheating the prepared solution by a liquid heater, wherein the preheating temperature is 25-150 ℃.

(2) Reaction: adding the preheated cerium salt solution and the precipitant solution into a vertical super-gravity rotating bed at a certain flow rate, and reacting under the action of high-speed shearing to generate precursor slurry.

(3) Ultrasonic: and carrying out ultrasonic treatment on the precursor slurry.

(4) Washing and centrifuging: and (3) putting the precursor slurry after ultrasonic treatment into a centrifuge for centrifugal separation, taking the lower layer concentrated solution, washing with distilled water, repeatedly carrying out centrifugal washing for 1-5 times until the solution is neutral, and finally obtaining the precursor viscous liquid.

(5) And (3) freeze drying: and (4) freeze-drying the precursor viscous liquid obtained after washing and centrifugal treatment to obtain the cerium oxide precursor. The working pressure of the freeze drying process is 0.1-5MPa, and the drying time is 1-48 h.

(6) Roasting: and (3) oxidizing and roasting the precursor obtained after freezing treatment at the high temperature of 450 ℃ for 0.5h to obtain the nano cerium oxide powder.

The nano cerium oxide powder D50 prepared in this example was 60-100nm, and the average particle size was 80 nm.

Example 2

(1) preparing raw materials: using OP-10 solution with the concentration of 0.2mol/L as a dispersant to respectively prepare cerium chloride solution with the concentration of 1mol/L and urea precipitant solution with the concentration of 0.8mol/L, PH of 6-12; preheating the prepared solution by a liquid heater, wherein the preheating temperature is 25-150 ℃.

(3) Ultrasonic: and carrying out ultrasonic treatment on the precursor slurry.

(4) Washing and centrifuging: and (3) putting the precursor slurry into a centrifuge for centrifugal separation, taking the lower layer concentrated solution, washing with distilled water, repeatedly carrying out centrifugal washing for 1-5 times until the solution is neutral, and finally obtaining the precursor viscous liquid.

(5) And (3) freeze drying: and (4) freeze-drying the precursor viscous liquid to obtain a cerium oxide precursor. The working pressure of the freeze drying process is 0.1-5MPa, and the drying time is 1-48 h.

(6) Roasting: the precursor is oxidized and roasted for 1.5h at the high temperature of 650 ℃ to obtain the nano cerium oxide powder.

The nano cerium oxide powder D50 prepared in this example was 40-60nm, and had an average particle size of 60 nm.

FIG. 4 is a graph showing the relationship between the calcination temperature and the calcination time and the particle size of cerium oxide in preferred embodiment 2 of the present invention. As can be seen from FIG. 4, the particle size gradually decreases with the increase of the calcination time within the temperature range of 350-650 ℃, but the variation range of the particle size is not very large, the particle size of the powder obtained by calcination at 650 ℃ for 1.5h is the smallest, and when the calcination temperature is higher than 650 ℃, the particle size becomes significantly larger with the increase of the calcination time, and the sintering agglomeration of the powder occurs. From the results of XRD analysis, it is found that the best crystallization of cerium oxide is obtained after calcination at 650 deg.C, and thus the optimum calcination condition is 650 deg.C, calcination for 1.5 h. The optimum grain size for calcination is 60 nm.

Figure 5 is an XRD pattern of preferred embodiment 2 of the present invention. In the whole reaction process, the products obtained at different stages are different, qualitative analysis is respectively carried out on the powder dried at 50 ℃, 100 ℃ and calcined at 350-650 ℃, and as can be seen from FIG. 5, the product obtained by drying the precursor at 50 ℃ is Ce ₂ (CO ₃ ) ₃ ·8H ₂ O, decomposition of the precursor to Ce at 100 ℃ drying ₂ O(CO ₃ ) ₂ ·H ₂ O and Ce (CO) ₃ ) ₂ O·H ₂ O, when the temperature is higher than 350 ℃, the cerium dioxide powder is obtained,however, the diffraction peak intensity of the obtained powder is low and is widened to a certain extent, and the diffraction peak is sharp along with the increase of the temperature, so that the crystallization effect is good. The cerium dioxide powder with good crystallization condition is obtained at 650 ℃. From Scherrer formula D _hkl K λ/(β COS θ) where k is 0.89, λ is 0.154056nm, θ is the diffraction angle, β is the half-peak width (radian) of the strongest peak, and the average grain size D perpendicular to the (111) crystal plane is calculated ₁₁₁ The average particle size was 65nm, which is consistent with the results of particle size testing.

FIG. 6 is a transmission electron microscope image of cerium oxide powder according to preferred embodiment 2 of the present invention. It can be seen from fig. 6 that the cerium oxide powder particles prepared in example 2 were relatively uniform.

Example 3

(1) preparing raw materials: respectively preparing a cerium chloride solution with the concentration of 0.05mol/L and an ammonia water precipitator solution with the concentration of 3mol/L, PH of 6-12 by taking a polyethylene glycol solution with the concentration of 0.4mol/L as a dispersing agent; preheating the prepared solution by a liquid heater, wherein the preheating temperature is 25-150 ℃.

(3) Ultrasonic: and carrying out ultrasonic treatment on the precursor slurry.

(6) Roasting: the precursor is oxidized and roasted for 2 hours at the high temperature of 450 ℃ to obtain the nano cerium oxide powder.

The nano cerium oxide powder D50 prepared in this example was 40-70nm, and the average particle size was 70 nm.

Example 4

(1) preparing raw materials: 1mol/LAEO solution is taken as a dispersant, and 0.2mol/L cerium formate solution and 0.8mol/L, PH polyacrylamide hydroximic acid precipitator solution with the concentration of 6-12 are respectively prepared; preheating the prepared solution by a liquid heater, wherein the preheating temperature is 25-150 ℃.

(3) Ultrasonic treatment: and carrying out ultrasonic treatment on the precursor slurry.

(4) Washing and centrifuging: and (3) placing the precursor slurry after ultrasonic treatment into a centrifuge for centrifugal separation, taking the lower-layer concentrated solution, washing with distilled water, repeatedly carrying out centrifugal washing for 1-5 times until the solution is neutral, and finally obtaining the precursor viscous liquid.

(6) Roasting: and (3) oxidizing and roasting the precursor obtained after freezing treatment at the high temperature of 850 ℃ for 2h to obtain the nano cerium oxide powder.

The nano cerium oxide powder D50 prepared in this example was 66-76nm, and had an average particle size of 85 nm.

Comparative example 1: (without using a dispersant)

Comparative example 1 differs from example 1 in that: respectively preparing a cerous nitrate solution with the concentration of 0.01mol/L and an ammonium bicarbonate precipitator solution with the concentration of 0.6mol/L, PH of 6-12 by directly using distilled water in the step (1); preheating the prepared solution by a liquid heater, wherein the preheating temperature is 25-150 ℃. The other steps are the same as in example 1.

Comparative example 1 no dispersant was used in the preparation process, which resulted in a decrease in the dispersion effect of the prepared nano-powder, particle agglomeration, and an increase in the particle size. While the addition of dispersants optimizes the process flow. The effect of the dispersant can be measured by the magnitude of the contact angle. Because the contact angle of the liquid on the surface of the solid material is an important parameter for measuring the wettability of the liquid on the surface of the material. Many information of the interaction of solid-liquid and solid-gas interface on the surface of the material can be obtained by measuring the contact angle. As can be seen from the wetting property analysis of example 2, FIG. 3 shows that the precursor has different contact angles in water and a dispersant solution, the wetting ability of the solution is changed by adding the dispersant OP-10, the complete wetting time of the precursor in water is 40s, and the time in the dispersant solution is 12 s, which indicates that the wetting time of the precursor in water is greatly shortened by adding the dispersant, and good hydrophilicity is shown. The addition of the dispersant allows the precursor to be better dispersed in the solution, preventing liquid phase agglomeration. While the use of no dispersant in comparative example 1 resulted in a deterioration in the dispersion effect of the nano cerium oxide powder, and thus agglomeration resulted in an increase in particle size.

Comparative example 2: (the prepared solution was not subjected to heat treatment)

Comparative example 2 differs from example 1 in that: respectively preparing a cerium nitrate solution with the concentration of 0.01mol/L and an ammonium bicarbonate precipitant solution with the concentration of 0.6mol/L, PH of 6 to 12 by taking a polyethylene glycol solution with the concentration of 0.2mol/L as a dispersing agent; and then directly adding the prepared cerium salt solution and precipitator solution into a vertical supergravity rotating bed, and generating precipitate under the action of high-speed shearing to generate precursor slurry. The other steps are the same as in example 1.

Comparative example 2 the pre-heating treatment of the prepared solution was not performed, which resulted in insufficient reaction and increased particle size of the prepared nano-powder. The raw material liquid is heated, so that the reaction rate of the two liquid phases can be effectively improved, the mass transfer capacity of the two liquid phases is increased along with the rise of the temperature in a microscopic state, and the characteristic is just suitable for the process of the supergravity reaction. The hypergravity reaction is suitable for the rapid reaction of two liquid phases, the faster the mass transfer speed is, the better the hypergravity reaction effect is, and therefore, the material needs to be heated. The principle of preheating treatment is the same as that of heating treatment in a high-gravity rotating bed, but the preheating treatment has better effect because the unheated solution has a heating process after entering the high-gravity rotating bed, and the reaction time wasted by the heating process is critical at high rotating speed, so that the reaction is incomplete or the particle size of a precursor is increased, and the whole reaction needs preheating treatment.

Comparative example 3: (without freeze-drying directly into the ordinary drying treatment)

Comparative example 3 differs from example 1 in that: in the step (5), the precursor viscous liquid obtained after washing and centrifugal treatment is subjected to common drying treatment. The other steps are the same as in example 1.

Comparative example 3 common drying treatment is not performed with freeze drying, but common drying treatment is performed, the common drying treatment can not reduce a precursor phase with original taste, heating can cause the precursor to be decomposed into another intermediate phase, meanwhile, if an organic dispersant is added, a part of organic matters can be decomposed along with the drying process by using a common drying method, the decomposition process of the organic matters is exothermic, the local temperature of a sample can be overhigh, the kinetic energy of the precursor with small particle size can be increased, agglomeration can be spontaneously caused, moisture in the sample can be directly sublimated from ice under the condition of high vacuum through freeze drying to achieve the purpose of drying, at the moment, the organic matters can not be decomposed and emit heat, small particle powder can not be agglomerated, and the particle size of the prepared nano powder is uniform and fine.

Comparative example 4: (without sonication)

Comparative example 4 differs from example 1 in that: and (3) directly and tightly washing and centrifuging the precursor slurry generated in the step (2) for ultrasonic treatment. The other steps are the same as in example 1.

Comparative example 4 was not sonicated and the particle size produced was larger. The dispersion of ultrasonic waves in liquid mainly depends on the ultrasonic cavitation of the liquid. Ultrasonic dispersion may be to the nanoparticles. When ultrasonic vibration is transmitted into liquid, strong cavitation effect is excited in the liquid due to the high sound intensity, so that a large amount of cavitation bubbles are generated in the liquid. As these cavitation bubbles are generated and burst, micro-jets will be generated, which act to break up liquid-heavy solid particles. Meanwhile, due to the vibration and dispersion of ultrasonic waves, solid and liquid are mixed more fully, and most of chemical reactions are promoted. After the cerium salt solution reacts with the precipitant, the generated precursor is agglomerated in a liquid phase, agglomerated particles can be dispersed through ultrasonic treatment, and the dispersed particles are wrapped by the dispersant, so that re-agglomeration can be avoided. The precursor has good dispersion effect, and the particle size of the powder prepared by corresponding roasting at the later stage is reduced, so that the effect after ultrasonic treatment is better.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A preparation method for continuously producing nano cerium oxide is characterized by comprising the following steps:

step 1) preparing raw materials: respectively preparing a cerium salt solution with the concentration of 0.01-1mol/L and a precipitator solution with the concentration of 0.01-3mol/L, PH of 6-12 by taking a dispersing agent as a medium; preheating the prepared cerium salt solution and the precipitator solution by an external heating device, wherein the preheating temperature is 150 ℃;

step 5) freeze drying: freeze-drying the precursor viscous liquid to obtain a cerium oxide precursor;

step 6) roasting: oxidizing and roasting the cerium oxide precursor at the high temperature of 350-650 ℃ to obtain nano cerium oxide powder;

wherein the dispersing agent is at least one of polyethylene glycol, polyoxyethylene octyl phenol ether, sodium dodecyl sulfate and fatty alcohol-polyoxyethylene ether phosphate;

the concentration of the dispersant contained in the cerium salt solution and the precipitant solution in the step 1) is 0.001-1 mol/L;

in the step 2), the flow rate of the cerium salt solution entering the super-gravity rotating bed is 0.1-5L/min, and the flow rate of the precipitator solution entering the super-gravity rotating bed is 0.1-10L/min;

the rotating speed of the super-gravity rotating bed is 10-3000r/min, 10-10000g of centrifugal force can be generated, and under the conditions of high-speed centrifugation and shearing, the cerium salt solution and the precipitator solution generate 0.01-100um of liquid drops and 0.001-0.5cm ² The liquid membrane of (2) is reacted; the average reaction time of the cerium salt solution and the precipitant solution in the rotating bed is 0.1-10 seconds; the PH value of the precursor slurry obtained after the reaction is 6-10;

the time of high-temperature oxidizing roasting in the step 6) is 0.5-4 h;

the matched equipment used by the method consists of a supergravity rotating bed, an ultrasonic device, a centrifuge, a freeze dryer and a roasting furnace which are sequentially connected, wherein the supergravity rotating bed consists of a liquid heater, a filler and a motor, the liquid heater is used for heating liquid externally and conveying the liquid into the filler, the filler can enable the reaction liquid to stay in the liquid heater for a period of time and form tiny liquid drops and a liquid film, and the motor provides adjustable shearing force; the liquid heater includes a heater for preheating a salt solution of cerium and a heater for preheating a precipitant solution.

2. The method of claim 1, wherein the cerium salt solution in step 1) is any one of cerium nitrate, ammonium cerium nitrate, cerium chloride, cerium sulfate and cerium formate.

3. The method of claim 1, wherein the precipitating agent in step 1) is at least one of ammonium bicarbonate, urea, ammonia water and polyacrylamide hydroximic acid.

4. The method as claimed in claim 1, wherein the high-gravity rotating bed in step 2) is a vertical high-gravity rotating bed, and the cerium salt solution and the precipitant solution are added in a uniform mixture from the middle of the vertical high-gravity rotating bed.

5. The method for continuously producing nano cerium oxide according to claim 1, wherein the ultrasonic time of the ultrasonic equipment in the ultrasonic treatment process in the step 3) is 10-600 seconds, the ultrasonic power is 0.1-15KW, and the ultrasonic medium is water or alcohol.

6. The method for preparing nano cerium oxide continuously as claimed in claim 1, wherein the drying time in the process of freeze-drying in step 5) is 1-48 h.