CN100387522C - Preparation process of high oxygen storage nanometer cerium-based composite oxide material - Google Patents

Abstract

The invention relates to the technical field of composite oxide manufacturing methods, in particular to the preparation process of high oxygen storage nanometer cerium-based composite oxide materials. The invention provides a preparation process of a high-oxygen-storage nanometer cerium-based composite oxide material aiming at the defect that the existing composite oxide preparation method will cause serious pollution to the environment. The preparation process of the present invention is: dissolving a certain ratio of high oxygen storage nano-composite oxide material precursor with a solvent, adding a precipitant for co-precipitation, filtering and washing the precipitate, mixing the precipitate with an organic acid solution, and then drying and roasting High oxygen storage nanocomposite oxide materials. The composite oxide material obtained by the method of the invention has high oxygen recovery ability. In the preparation process of the present invention, no nitrogen oxides will be produced due to the use of nitrates and other substances, only water and carbon dioxide will be discharged, and the salts contained in the filtrate after the precipitation is filtered and washed can be recycled, and will not cause serious pollution to the environment. It is environmentally friendly.

Description

Preparation process of nano-cerium-based composite oxide material with high oxygen storage

technical field

The invention relates to the technical field of composite oxide manufacturing methods, in particular to the preparation process of high oxygen storage nanometer cerium-based composite oxide materials.

Background technique

CeO ₂ is an excellent additive for oxidation-type catalysts with a fluorite structure. It has a high ability to store and release oxygen, and conducts redox reactions on Ce ⁴⁺ /Ce ³⁺ through redox. The role of chemical regulators. Adding transition metal oxides such as ZrO ₂ to CeO ₂ can form a cerium-based composite oxide, which greatly improves its ability to store and release oxygen and anti-sintering performance, and has excellent chemical reaction performance and catalytic efficiency. It is widely used in automobile exhaust Three-way catalyst and oxidation of CO, _CH4 , etc. Existing composite oxide materials are usually prepared by methods such as sol-gel method and co-precipitation method. Among them, the composite oxide materials prepared by sol-gel method have small powder particle size, high purity and chemical uniformity. However, it has the disadvantages of high price of precursor raw materials, rapid agglomeration of particles under high temperature treatment, and the possible use of nitrates to discharge nitrogen oxides during the preparation of composite oxides, causing environmental pollution; although the co-precipitation method has The reaction process is simple and the cost is low, but it is easy to introduce impurities; someone has prepared Ce _0.5 Zr _0.5 O ₂ composite oxide by high-energy ball milling method, but its specific surface area is small, between 16-20m ² /g.

Contents of the invention

Aiming at the above-mentioned shortcomings in the existing composite oxide preparation methods, the present invention provides a preparation process of a high oxygen storage nanometer cerium-based composite oxide material.

The preparation process of the high oxygen storage nano cerium-based composite oxide material of the present invention is as follows: dissolving a certain ratio of high oxygen storage nano composite oxide material precursor with a solvent, adding a precipitant for co-precipitation, filtering and washing the precipitate, and separating the precipitate and The organic acid solutions are mixed, then dried and calcined to obtain a high oxygen storage nanometer composite oxide material. Among them, the precursors include one or more of the soluble salts and oxides of cerium and one or more of transition elements, alkaline earth metal elements, and soluble salts, hydroxides and oxides of aluminum, gallium, silicon, tin and bismuth. one or more; the solvent is water or acid; the precipitant is one or more of ammonium carbonate, ammonium bicarbonate, ammonia water, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium hydroxide, More than one kind, the total substance amount of the precipitant used is 0.5 to 6 times the total substance amount of the composite oxide precursor; the organic acid is one or more of citric acid, malic acid and tartaric acid, and the used The total substance amount of the organic acid is 0.5 to 20 times that of the composite oxide precursor.

The steps of the preparation process of the high oxygen storage nanometer cerium-based composite oxide material of the present invention are as follows:

(1) Dissolve the precursor, add a precipitating agent, filter and wash the precipitate;

(2) Mix the precipitate with the organic acid solution to obtain a sol, and then dry it at room temperature to 140°C to obtain a xerogel;

(3) Roasting the xerogel in a high-temperature furnace at 400-1000° C. for 1-8 hours to produce a finished high-oxygen-storage nano-cerium-based composite oxide material.

During the preparation process of the high-oxygen-storage nano-cerium-based composite oxide material of the present invention, no nitrogen oxides will be produced due to the use of nitrate and other substances, and only water and carbon dioxide will be discharged; the salts contained in the filtrate after the precipitation is filtered and washed can be recovered Utilization, will not cause serious pollution to the environment, and has the characteristics of environmental friendliness.

In addition, the preparation process of the high oxygen storage nanometer cerium-based composite oxide material of the present invention is also applicable to the preparation of copper-manganese-based transition metal composite oxides.

Description of drawings

Accompanying drawing 1 is the TPR spectrum of _{CexZr1 -xO2 composite} oxide material.

Figure 2 is the TPR spectrum of Ce _0.8 Zr _0.2 O ₂ composite oxide material after reduction at 920°C and then oxidation.

Detailed ways

The preparation process of the high oxygen storage nanometer cerium-based composite oxide material of the present invention will be further illustrated by examples below, but the present invention is not limited to these examples.

Example 1

The detailed preparation process of Ce _0.3 Zr _0.7 O ₂ : Weigh 1.42g Ce(NO ₃ ) ₃ ·6H ₂ O and 3.27g Zr(NO ₃ ) ₄ ·5H ₂ O to dissolve in water, then add 2.13g Na ₂ CO Co-precipitate the aqueous solution of ₃ , filter and wash the precipitate, dissolve the precipitate in a solution containing 16.92g of citric acid to obtain a gel, evaporate to a gel at 95-100°C, bake at 120°C for 12 hours, and finally bake at 650°C 4 hours. The Ce _0.3 Zr _0.7 O ₂ composite oxide prepared by this method has a specific surface area of 32 m ² /g, an oxygen storage capacity of 571 μmol/g at 920° C., and a grain size of 11.3 nm.

Example 2

The detailed preparation process of Ce _0.5 Zr _0.5 O ₂ : Weigh 2.20g Ce(NO ₃ ) ₃ 6H ₂ O and 2.18g Zr(NO ₃ ) ₄ 5H ₂ O and dissolve them in water, then add 1.88g Na ₂ CO Co-precipitate the aqueous solution of ₃ , filter and wash the precipitate, dissolve the precipitate in a solution containing 14.94g of citric acid to obtain a gel, evaporate to a gel at 95-100°C, bake at 120°C for 12 hours, and finally bake at 650°C 4 hours. The Ce _0.5 Zr _0.5 O ₂ composite oxide prepared by the method has a specific surface area of 55 m ² /g, an oxygen storage capacity of 599 μmol/g at 920° C., and a grain size of 4.0 nm.

Example 3

The detailed preparation process of Ce _0.6 Zr _0.4 O ₂ : Weigh 2.56g Ce(NO ₃ ) ₃ 6H ₂ O and 1.69g Zr(NO ₃ ) ₄ 5H ₂ O and dissolve them in water, then add 1.77g Na ₂ CO Co-precipitate the aqueous solution of ₃ , filter and wash the precipitate, dissolve the precipitate in a solution containing 14.04g of citric acid to obtain a gel, evaporate to a gel at 95-100°C, bake at 120°C for 12 hours, and finally bake at 650°C 4 hours. The Ce _0.6 Zr _0.4 O ₂ composite oxide prepared by the method has a specific surface area of 36 m ² /g, an oxygen storage capacity of 700 μmol/g at 920° C., and a grain size of 4.9 nm.

Example 4

The detailed preparation process of Ce _0.8 Zr _0.2 O ₂ : Weigh 3.21g Ce(NO ₃ ) ₃ ·6H ₂ O and 0.79g Zr(NO ₃ ) ₄ ·5H ₂ O to dissolve in water, then add 1.57g Na ₂ CO Co-precipitate the aqueous solution of ₃ , filter and wash the precipitate, dissolve the precipitate in a solution containing 12.42g of citric acid to obtain a gel, evaporate to a gel at 95-100°C, bake at 120°C for 12 hours, and finally bake at 650°C 4 hours. The Ce _0.8 Zr _0.2 O ₂ composite oxide prepared by this method has a specific surface area of 31 m ² /g, an oxygen storage capacity of 496 μmol/g at 920° C., and a grain size of 11.8 nm.

Example 5

Under the H ₂ -N ₂ mixed gas containing 5% H ₂ , the reduction performance of the _Cex Zr _1-x O ₂ composite oxide material was investigated by TPR technique, and the results are shown in Figure 1.

Example 6

The Ce _0.8 Zr _0.2 O ₂ composite oxide material was reduced at 920°C and re-oxidized in air at different temperatures for 30 minutes before TPR experiment. The results are shown in Figure 2. It can be seen from Fig. 2 that the Ce _0.8 Zr _0.2 O ₂ composite oxide material obtained by the preparation process of the present invention has a very high oxygen recovery ability, and can basically recover even at a temperature of 50°C.

Claims (2)

1. the preparation technology of a high oxygen storage nanometer cerium base composite oxide material, it is characterized in that high oxygen storage nanometer composite oxide material precursor dissolution with solvents with certain proportioning, add the precipitation agent co-precipitation, the filtration washing precipitation, to precipitate and the organic acid soln mixing, drying, roasting make the high oxygen storage nanometer composite oxide material then; Wherein:

(1), the high oxygen storage nanometer composite oxide material precursor that is adopted comprises one or more in soluble salt, oxyhydroxide and the oxide compound of the soluble salt of cerium and one or more and transition element, alkali earth metal and aluminium in the oxide compound, gallium, silicon, tin, bismuth;

(2), the solvent that is adopted is water or acid;

(3), the precipitation agent that adopted is in volatile salt, bicarbonate of ammonia, ammoniacal liquor, yellow soda ash, salt of wormwood, sodium bicarbonate, saleratus, sodium hydroxide, the potassium hydroxide one or more, the total amount of substance of precipitation agent is 0.5～6 times of the total amount of substance of composite oxides precursor;

(4), the organic acid that adopted is in citric acid, oxysuccinic acid and the tartrate one or more, the total amount of substance of used organic acid is 0.5～20 times of the total amount of substance of composite oxides precursor.

2. the preparation technology of high oxygen storage nanometer cerium base composite oxide material according to claim 1 is characterized in that preparation technology's the step of composite oxide material is as follows:

(1) with the dissolving of composite oxides precursor, adds precipitation agent, filtration, washing precipitation;

(2) will precipitate and organic acid soln mixes, obtain colloidal sol, ℃ dry down in room temperature to 140 again, xerogel;

(3) with xerogel 400～1000 ℃ of roastings 1～8 hour in High Temperature Furnaces Heating Apparatus, promptly make the high oxygen storage nanometer cerium base composite oxide finished material.

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