JPH11292539A - Production of zirconia-ceria composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently produce a zirconia-ceria compsn. excellent in heat resistance by mixing basic zirconium sulfate with a soln. contg. cerium ions and then adding a base. SOLUTION: A dispersion prepd. by dispersing 5-20 pts.wt. basic zirconium sulfate of 0.5-20 μm average particle diameter in 100 pts.wt. medium such as water is mixed with a soln. having 5-25 wt.% concn. of a cerium salt such as cerium nitrate in a weight ratio of 1:10 to 1:0.7 (expressed in terms of ceria to zirconia), a third component such as lanthanum nitrate is, if necessary, added by 1-20 wt.% (expressed in terms of oxide) and a base such as an aq. soln. of potassium hydroxide having 5-25 wt.% concn. is added to form a layer of cerium hydroxide on the basic zirconium sulfate. This product is calcined at >=400 deg.C in the air or in an oxidizing atmosphere to obtain the objective zirconia- ceria compsn. having <60 wt.% ceria content, >=130 m<2> /g specific surface area at 400 deg.C and >=15 m<2> /g specific surface area at 1,000 deg.C and absorbing >=0.15 mmol/g oxygen.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a novel zirconia-ceria composition.

[0002]

2. Description of the Related Art The specific surface area of a single zirconia conventionally used as a catalyst carrier at 400 ° C. is at most about 100 m ² / g. Further, those having a specific surface area higher than that are generally amorphous having no fixed structure.
Therefore, even if zirconia alone is used as a catalyst carrier,
At a high temperature of 400 ° C. or higher, the specific surface area decreases, so that stable performance at a high temperature cannot be obtained. Therefore, in order to use it as a catalyst carrier, it is necessary to further improve heat resistance.

On the other hand, a zirconia-ceria composition comprising zirconium oxide and cerium oxide is generally 10%.
Even at a high temperature of 00 ° C., a relatively large specific surface area can be secured, and the catalyst is more advantageous in heat resistance than zirconia or the like. As a method for producing the zirconia-ceria composition, a method of adding cerium nitrate or the like to zirconium oxide and impregnating the same is generally used.

[0004]

However, also in this method, the specific surface area of the obtained composition depends on the physical properties of the starting material zirconium oxide. For this reason, 400 ° C
It is still impossible to obtain a carrier having a specific surface area of more than 100 m ² / g.

[0005] On the other hand, a method is also known in which a mixed solution of zirconium nitrate and cerium nitrate is used as a starting material and coprecipitated with ammonia, ammonium carbonate, or the like.

However, since the precipitate obtained by this method is a gel-like bulky mixed hydroxide having a high water content, the productivity is poor and cannot be said to be suitable for production on an industrial scale. .

That is, a filtration step for removing impurities in the gel precipitate is indispensable. In addition, since the precipitate is bulky, the processing speed per operation is necessarily reduced. In addition, since the water content is large, the energy required to convert the oxide is enormous.

Accordingly, it is a main object of the present invention to efficiently produce a zirconia-ceria composition having particularly excellent heat resistance.

[0009]

Means for Solving the Problems The present inventor has conducted intensive studies in view of the above-mentioned problems of the prior art, and as a result, has found that the above-mentioned object can be achieved by a production method using a specific method.
Finally, the present invention has been completed.

That is, the present invention relates to a method for producing a zirconia-ceria composition, which comprises mixing a basic zirconium sulfate with a solution containing cerium ions and then adding a base.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Basic zirconium sulfate is known, and commercially available products (reagents) and the like can be used as they are. Basic zirconium sulfate is generally poorly soluble in water, dilute acid and the like, and in the present invention, it is particularly preferable to use an anhydride. Although the form is not particularly limited, it is generally preferable to use particles (or powder). In this case, the average particle size may be usually about 0.5 to 20 μm. Note that other impurities may be contained within a range that does not impair the effects of the present invention.

The basic zirconium sulfate may be dispersed in an appropriate medium such as water before mixing. The amount of dispersion may be appropriately set according to, for example, the cerium ion-containing solution to be mixed and the amount of the cerium ion to be mixed, but is usually 5 to 20 parts by weight based on 100 parts by weight of the medium. In this case, a part of the basic zirconium sulfate may be dissolved within a range not to impair the effects of the present invention.

The solution containing cerium ions (III) is not particularly limited, and a solution obtained by dissolving a cerium salt in a suitable solvent can be used. Examples of the cerium salt include inorganic acid salts such as nitrate, sulfate and chloride, and organic acid salts such as acetate. The solvent is not particularly limited as long as it can dissolve the cerium salt to be used, but usually, water, alcohols (for example, methanol and ethanol) and the like can be used. The concentration of the solution is not particularly limited, but is usually about 5 to 25% by weight, preferably about 15% by weight.
It may be set to 25% by weight.

In the production method of the present invention, a compound such as a rare earth element can be blended as a third component, if necessary, in addition to these raw materials. For example, lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium,
An inorganic acid salt such as erbium, thulium, ytterbium, and lutetium (nitrate, sulfate, chloride, etc.) or an organic acid salt (acetate, etc.) may be blended. More specifically,
It can be added in the form of lanthanum nitrate, neodymium nitrate, praseodymium nitrate or the like. In addition to rare earth elements,
If necessary, compounds such as cesium, magnesium, calcium, strontium, barium, manganese, tin, and yttrium (for example, inorganic acid salts and organic acid salts) may be added. One or more of these third components may be used. By adding the third component, the properties (specific surface area and the like) of the obtained composition can be appropriately changed. In particular, in the present invention, it is preferable to add at least one kind of a compound of a rare earth element, particularly, at least one kind of a lanthanum compound and a neodymium compound. That is, the composition of the present invention preferably contains at least one rare earth element, particularly at least one of lanthanum and neodymium.

The amount of the third component is usually 1 in terms of oxide.
It may be about 20% by weight, preferably 1% to 10% by weight. The addition time of the third component is as long as it can be blended uniformly.
It may be added at any stage. For example, the step may be a step of mixing basic zirconium sulfate and a solution containing cerium ions, or a step of adding a base. In addition,
The third component is preferably added in advance as a solution (particularly an aqueous solution).

Next, the basic zirconium sulfate and a solution containing cerium ions are mixed. The mixing ratio of both is
It may be appropriately set according to the use of the final product, etc., and is usually 1:10 to 1: 1 in terms of ceria: zirconia (weight ratio).
It may be about 0.7, preferably 1: 5 to 1: 2.
When both are blended, it is preferable to mix uniformly while stirring. The temperature of the mixed solution is usually 10 to
The temperature may be set to about 50 ° C.

After blending both, a base is added to the resulting mixture. Addition of the base mainly produces a cerium hydroxide on the basic zirconium sulfate, and also hydroxylates the basic zirconium sulfate. The base is not particularly limited and includes, for example, sodium hydroxide,
Known alkalis such as potassium hydroxide, ammonia, sodium carbonate and ammonium carbonate can be used. The concentration of the base to be used is not particularly limited as long as the mixture can be neutralized, but may be usually about 5 to 25% by weight, preferably 15 to 25% by weight.

The obtained product may be collected by filtration and washing with water, followed by solid-liquid separation in accordance with a recovery method employed in a known coprecipitation method or the like. After collection, it may be dried if necessary.

In the present invention, the zirconia-ceria composition obtained by the above method may be further fired. The firing temperature is usually 400 ° C. or higher, preferably 400 to 800 ° C.
It is good. The firing time can be appropriately set according to the firing temperature and the like. The firing atmosphere may be air or an oxidizing atmosphere.

The zirconia-ceria composition according to the present invention preferably has a ceria content in the zirconia-ceria composition which usually does not exceed 60% by weight. Preferably, the ceria content is between 1 and 49% by weight, most preferably between 20 and 30% by weight. This content can be adjusted by the amount of basic zirconium sulfate or the like used as a starting material.

The zirconia-ceria composition of the present invention has a specific surface area at 400 ° C. of 130 m ^2.
/ G or more, the specific surface area at 1000 ° C. is 15 m ² / g
It has the above characteristics. The form is not particularly limited as long as it has such a specific surface area, and has a form such as powder, particle, and granule. In addition, the oxygen adsorption amount of the composition obtained by the present invention is usually 0.15 mmol / g or more.

[0022]

According to the production method of the present invention, in particular, basic zirconium sulfate is used as a precursor, cerium hydroxide is deposited on the precursor, and the precursor itself is hydroxylated. A composition having excellent heat resistance can be efficiently produced. Further, since relatively inexpensive materials such as basic zirconium sulfate can be effectively used as a starting material, production costs can be reduced accordingly. Further, the process can be simplified as compared with the prior art. The cerium content in the composition can also be easily changed. Thus, the production method of the present invention
Suitable for industrial scale production of zirconia-ceria compositions that exhibit excellent heat resistance.

The zirconia-ceria composition according to the production method of the present invention has a specific surface area at 400 ° C. of 130 m ² /
g, the specific surface area at 1000 ° C. is 15 m ² / g or more (especially 30 m ² / g or more), and the oxygen adsorption amount is 0.15 mmol / g or more. It can exhibit heat resistance and the like.

The zirconia-ceria composition having such characteristics can be widely used in the field of catalysts and the like. In particular, it is useful as an application requiring a high heat-resistant temperature, for example, as a catalyst carrier for purifying exhaust gas.

[0025]

EXAMPLES Examples and comparative examples are shown below to further clarify the features of the present invention. The oxygen adsorption amount was determined for the sample treated at 1000 ° C. for 3 hours.
It measured at 600 degreeC by the oxygen pulse method using "multitask TPD (TPD-1-AT)" (made by Japan Bell).

Example 1 Basic zirconium sulfate (Zr content: 7 as zirconia)
5 g) was dispersed in water, and a cerium nitrate solution (Ce content: containing 25 g as ceria) was added thereto, followed by neutralization with a sodium hydroxide solution. Next, after filtration and washing with water, solid-liquid separation was performed to collect a hydroxide. This was fired at 400 ° C. to obtain an oxide. The specific surface area of the obtained oxide is represented by B
It was measured by the ET method. The specific surface area of the oxide is 134.5
m ² / g. Furthermore, the specific surface area after treating this oxide at 1000 ° C. for 3 hours was measured in the same manner. As a result, it was 28.3 m ² / g. Oxygen adsorption amount is 0.18
mmol / g.

Example 2 Basic zirconium sulfate (Zr content: 5 as zirconia)
1 g) was dispersed in water, and a cerium nitrate solution (Ce content: containing 49 g as ceria) was added thereto, followed by neutralization with a sodium hydroxide solution. Next, after filtration and washing with water, solid-liquid separation was performed to collect a hydroxide. This was fired at 400 ° C. to obtain an oxide. The specific surface area of the obtained oxide is represented by B
It was measured by the ET method. The specific surface area of the oxide is 138.2
m ² / g. Furthermore, the specific surface area after treating this oxide at 1000 ° C. for 3 hours was measured in the same manner. As a result, it was 17.5 m ² / g. Oxygen adsorption amount is 0.25
mmol / g.

Example 3 Basic zirconium sulfate (Zr content: 7 as zirconia)
4 g) was dispersed in water, and a cerium nitrate solution (amount of Ce: contained 24 g as ceria) and a lanthanum nitrate solution (amount of La: contained 2 g as lantana) were added thereto, followed by neutralization with a sodium hydroxide solution. Then, filtration
After washing with water, solid-liquid separation was performed to collect a hydroxide. This is 40
Calcination was performed at 0 ° C. to obtain an oxide. The specific surface area of the obtained oxide was measured by the BET method. The specific surface area of the oxide is 13
2.1 m ² / g. In addition, this oxide
The specific surface area after the treatment at 0 ° C. for 3 hours was measured in the same manner. As a result, it was 37.5 m ² / g. The oxygen adsorption amount is 0.
It was 20 mmol / g.

Example 4 Basic zirconium sulfate (Zr content: 6 as zirconia)
0 g) was dispersed in water, and a cerium nitrate solution (amount of Ce: contained 30 g as ceria) and a lanthanum nitrate solution (amount of La: contained 10 g as lantana) were added thereto, followed by neutralization with a sodium hydroxide solution. Then, filtration
After washing with water, solid-liquid separation was performed to collect a hydroxide. This is 40
Calcination was performed at 0 ° C. to obtain an oxide. The specific surface area of the obtained oxide was measured by the BET method. The specific surface area of the oxide is 14
It was 3.7 m ² / g. In addition, this oxide
The specific surface area after the treatment at 0 ° C. for 3 hours was measured in the same manner and found to be 42.1 m ² / g. The oxygen adsorption amount is 0.
It was 31 mmol / g.

Example 5 Basic zirconium sulfate (Zr content: 5 as zirconia)
0 g) was dispersed in water, and a cerium nitrate solution (Ce content: containing 42 g as ceria) and a lanthanum nitrate solution (La content: containing 8 g as lantana) were added thereto, followed by neutralization with a sodium hydroxide solution. Then, filtration
After washing with water, solid-liquid separation was performed to collect a hydroxide. This is 40
Calcination was performed at 0 ° C. to obtain an oxide. The specific surface area of the obtained oxide was measured by the BET method. The specific surface area of the oxide is 14
It was 8.1 m ² / g. In addition, this oxide
The specific surface area after the treatment at 0 ° C. for 3 hours was measured in the same manner and found to be 22.1 m ² / g. The oxygen adsorption amount is 0.
27 mmol / g.

Example 6 Basic zirconium sulfate (Zr content: 6 as zirconia)
7 g) was dispersed in water, and a cerium nitrate solution (Ce content: 21 g as ceria), a lanthanum nitrate solution (La content: 2 g as lantana), a neodymium nitrate solution (Nd content: 5 g as neodia) and After adding a praseodymium nitrate solution (Pr amount: containing 5 g as praseodysia), the mixture was neutralized with a sodium hydroxide solution.
Next, after filtration and washing with water, solid-liquid separation was performed to collect a hydroxide. This was fired at 400 ° C. to obtain an oxide. The specific surface area of the obtained oxide was measured by the BET method. The specific surface area of the oxide was 132.2 m ² / g. Furthermore, the specific surface area after treating this oxide at 1000 ° C. for 3 hours was measured in the same manner. As a result, it was 54.1 m ² / g. The oxygen adsorption amount was 0.24 mmol / g.

Example 7 Basic zirconium sulfate (Zr content: 4 as zirconia)
2 g) was dispersed in water, and a cerium nitrate solution (Ce content: containing 58 g as ceria) was added thereto, followed by neutralization with a sodium hydroxide solution. Next, after filtration and washing with water, solid-liquid separation was performed to collect a hydroxide. This was fired at 400 ° C. to obtain an oxide. The specific surface area of the obtained oxide is represented by B
It was measured by the ET method. The specific surface area of the oxide is 138.2
m ² / g. Furthermore, the specific surface area after treating this oxide at 1000 ° C. for 3 hours was measured in the same manner. As a result, it was 16.8 m ² / g. Oxygen adsorption amount is 0.28
mmol / g.

Comparative Example 1 Zirconium nitrate solution (Zr content: 75 as zirconia)
g) and a cerium nitrate solution (Ce content: 2 as ceria)
(Containing 5 g) and neutralized with aqueous ammonia. Next, after filtration and washing with water, solid-liquid separation was performed to collect a hydroxide.
This was fired at 400 ° C. to obtain an oxide. The specific surface area of the obtained oxide was measured by the BET method. The specific surface area of the oxide was 112.2 m ² / g. Furthermore, the specific surface area after treating this oxide at 1000 ° C. for 3 hours was measured in the same manner. As a result, it was 19.5 m ² / g. The oxygen adsorption amount was 0.16 mmol / g.

Comparative Example 2 Zirconium oxide (Zr content: 75 g as zirconia) was dispersed in water, and a cerium nitrate solution (Ce content:
(Containing 25 g of ceria) and dried to obtain a hydrated oxide. This was fired at 400 ° C. to obtain an oxide. The specific surface area of the obtained oxide was measured by the BET method. The specific surface area of the oxide was 57 m ² / g. Furthermore, the specific surface area after treating this oxide at 1000 ° C. for 3 hours was measured in the same manner. As a result, it was 5.4 m ² / g. The oxygen adsorption amount was 0.10 mmol / g.

Examples 8 to 35 Oxides were prepared in the same manner as in Example 3 with the composition (in terms of oxide) shown in Table 1. About the obtained oxide, Example 3
The specific surface area (400 ° C. and 1000 ° C.) and the amount of adsorbed oxygen were measured in the same manner as described above. Table 1 shows the results. All the third components were compounded as nitrates.

[0036]

[Table 1]

As shown in Table 1, the compositions of Examples 8 to 35 had a specific surface area at 400 ° C. of 130 m ² / g or more.
It can be seen that the specific surface area at 00 ° C. is as large as 30 m ² / g or more, and the oxygen adsorption amount is as excellent as 0.15 mmol / g.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI B01J 35/10 301 B01J 35/10 301J B01D 53/36 ZABC

Claims (6)

[Claims] 1. A method for producing a zirconia-ceria composition, comprising mixing a basic zirconium sulfate with a solution containing cerium ions and then adding a base. 2. The method according to claim 1, wherein at least one compound of a rare earth element is further added. 3. The method according to claim 1, wherein at least one of a lanthanum compound and a neodymium compound is further added. 4. The method according to claim 1, wherein the zirconia-ceria composition is further added to 400 parts.
The method according to any one of claims 1 to 3, wherein the firing is performed at a temperature of not less than C. 5. The method according to claim 1, wherein the ceria content in the zirconia-ceria composition does not exceed 60% by weight. 6. A zirconia-ceria composition having a specific surface area at 400 ° C. of 130 m ² / g or more,
The production method according to any one of claims 1 to 3, wherein the specific surface area at 0 ° C is 15 m ² / g or more.