JP3985111B2 - Method for producing zirconia-ceria composition - Google Patents

Description

【００３７】
表１に示すように、実施例８〜３５の組成物は、４００℃での比表面積１３０ｍ²／ｇ以上、１０００℃での比表面積にあっては３０ｍ²／ｇ以上と大きく、また酸素吸着量も０．１５ｍｍｏｌ／ｇと優れていることがわかる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a novel zirconia-ceria composition.
[0002]
[Prior art]
The specific surface area at 400 ° C. of a single zirconia conventionally used as a catalyst carrier is at most about 100 m ² / g. Those having a specific surface area larger than that are generally amorphous having no fixed structure. For this reason, even when zirconia alone is used as a catalyst carrier, the specific surface area becomes small at a high temperature of 400 ° C. or higher, and stable performance at a high temperature cannot be obtained. Therefore, in order to use as a catalyst carrier, further improvement in heat resistance is necessary.
[0003]
On the other hand, a zirconia-ceria composition composed of zirconium oxide and cerium oxide can generally ensure a relatively large specific surface area even at a high temperature of 1000 ° C., and is advantageous in heat resistance as a catalyst compared to zirconia or the like. As a method for producing this zirconia-ceria composition, a method of adding cerium nitrate or the like to zirconium oxide and impregnating it is generally used.
[0004]
[Problems to be solved by the invention]
However, even in this method, the specific surface area of the resulting composition depends on the physical properties of the starting zirconium oxide. For this reason, it is still impossible to obtain a carrier having a specific surface area exceeding 400 m ² / g at 400 ° C.
[0005]
On the other hand, a method of coprecipitation with ammonia, ammonium carbonate or the like using a mixed solution of zirconium nitrate and cerium nitrate as a starting material is also known.
[0006]
However, since the precipitate obtained by this method is a gel-like bulky mixed hydroxide with a high water content, the productivity is poor and it cannot be said that the precipitate is suitable for production on an industrial scale.
[0007]
That is, a filtration step for removing impurities in the gel-like precipitate is indispensable. Moreover, since the sediment is bulky, the processing speed per time is inevitably slow. In addition, since the water content is high, the energy required to convert to an oxide becomes enormous.
[0008]
Therefore, the present invention mainly aims to efficiently produce a zirconia-ceria composition excellent in heat resistance.
[0009]
[Means for Solving the Problems]
As a result of intensive studies in view of the above-described problems of the prior art, the present inventor has found that the above object can be achieved by a production method using a specific method, and has finally completed the present invention.
[0010]
That is, the present invention relates to a method for producing a zirconia-ceria composition, wherein a base is added after mixing a basic zirconium sulfate and a solution containing cerium ions.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Basic zirconium sulfate is a known one, and commercially available products (reagents) can be used as they are. Basic zirconium sulfate is generally poorly soluble in water, dilute acid and the like, and it is particularly preferable to use an anhydride in the present invention. Although the form is not particularly limited, it is generally preferable to use a particulate (or powder) form. In this case, the average particle diameter is usually about 0.5 to 20 μm. It should be noted that other impurities may be contained within a range not impeding the effects of the present invention.
[0012]
The basic zirconium sulfate may be previously dispersed in an appropriate medium such as water prior to mixing. The dispersion amount may be appropriately set according to, for example, the solution containing cerium ions to be blended and the blending amount thereof, but is usually about 5 to 20 parts by weight with respect to 100 parts by weight of the medium. In this case, a part of the basic zirconium sulfate may be dissolved within a range not impeding the effects of the present invention.
[0013]
The solution containing cerium ion (III) is not particularly limited, and a solution obtained by dissolving a cerium salt in an appropriate solvent can be used. Examples of cerium salts include inorganic acid salts such as nitrates, sulfates and chlorides, and organic acid salts such as acetates. The solvent is not particularly limited as long as the cerium salt to be used can be dissolved, but water, alcohols (for example, methanol, ethanol) and the like can be usually used. The concentration of the solution is not particularly limited, but is usually about 5 to 25% by weight, preferably 15 to 25% by weight.
[0014]
In the production method of the present invention, in addition to these raw materials, a compound such as a rare earth element can be blended as a third component as required. For example, lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, and other inorganic acid salts (nitrates, sulfates, chlorides, 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, compounds such as cesium, magnesium, calcium, strontium, barium, manganese, tin, and yttrium (for example, inorganic acid salts and organic acid salts) may be added as necessary. These third components may be used alone or in combination of two or more. By adding the third component, the properties (specific surface area, etc.) of the obtained composition can be appropriately changed. In particular, in the present invention, it is preferable to add at least one kind of rare earth element compound, particularly at least one kind of lanthanum compound and neodymium compound. That is, it is preferable to contain at least one rare earth element, particularly at least one of lanthanum and neodymium, in the composition of the present invention.
[0015]
The compounding amount of the third component is usually about 1 to 20% by weight, preferably 1 to 10% by weight in terms of oxide. The third component may be added at any stage as long as it can be blended uniformly. For example, it may be a step of mixing basic zirconium sulfate and a solution containing cerium ions, or a step of adding a base. The third component is preferably added in advance as a solution (particularly an aqueous solution).
[0016]
Next, basic zirconium sulfate and a solution containing cerium ions are mixed. The mixing ratio of the two may be appropriately set according to the use of the final product, but is usually about 1:10 to 1: 0.7, preferably 1: 5 to 1 in terms of ceria: zirconia (weight ratio). : 2 When mixing both, it is preferable to mix uniformly, stirring. Moreover, what is necessary is just to make the temperature of a liquid mixture into about 10-50 degreeC normally.
[0017]
After blending both, a base is added to the resulting mixture. By adding a base, a hydroxide of cerium is mainly formed on basic zirconium sulfate, and further, hydroxylation of basic zirconium sulfate is also performed. It does not specifically limit as a base, For example, well-known alkalis, such as sodium hydroxide, potassium hydroxide, ammonia, sodium carbonate, ammonium carbonate, can be used. The concentration of the base to be used is not particularly limited as long as the mixed solution can be neutralized, but it is usually about 5 to 25% by weight, preferably 15 to 25% by weight.
[0018]
The obtained product may be recovered by solid-liquid separation after filtration and water washing according to a recovery method employed in a known coprecipitation method or the like. After collection, it may be dried as necessary.
[0019]
In the present invention, the zirconia-ceria composition obtained by the above method may be further baked. The firing temperature is usually 400 ° C. or higher, preferably 400 to 800 ° C. 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.
[0020]
In the zirconia-ceria composition according to the present invention, it is preferable that the ceria content in the zirconia-ceria composition usually does not exceed 60% by weight. Preferably, the ceria content is 1 to 49% by weight, most preferably 20 to 30% by weight. This content can be adjusted by the amount of basic zirconium sulfate used as a starting material.
[0021]
Such a zirconia-ceria composition in the present invention has a characteristic that the specific surface area at 400 ° C. is 130 m ² / g or more and the specific surface area at 1000 ° C. is 15 m ² / g or more. The form is not particularly limited as long as it has such a specific surface area, and has a powder form, a particulate form, a granular form or the like. The oxygen adsorption amount of the composition obtained by the present invention is usually 0.15 mmol / g or more.
[0022]
【The invention's effect】
According to the production method of the present invention, particularly basic zirconium sulfate is used as a precursor, and cerium hydroxide is deposited on the precursor and the precursor itself is hydroxylated. The composition which has it can be produced efficiently. Further, since a relatively inexpensive material such as basic zirconium sulfate can be used effectively as a starting material, the production cost can be reduced accordingly. Furthermore, the process can be simplified as compared with the prior art. The cerium content in the composition can also be easily varied. As described above, the production method of the present invention is suitable for production on an industrial scale of a zirconia-ceria composition exhibiting excellent heat resistance.
[0023]
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 or more, a specific surface area at 1000 ° C. of 15 m ² / g or more (particularly 30 m ² / g or more), The amount is 0.15 mmol / g or more, and particularly excellent heat resistance and the like as a catalyst carrier can be exhibited.
[0024]
The zirconia-ceria composition having such characteristics can be widely used in the catalyst field and the like. In particular, it is useful for applications requiring a high heat-resistant temperature, such as an exhaust gas purification catalyst carrier.
[0025]
【Example】
Hereinafter, examples and comparative examples will be shown to further clarify the features of the present invention. The oxygen adsorption amount was measured at 600 ° C. by an oxygen pulse method using “Multitask TPD (TPD-1-AT)” (manufactured by Nippon Bell) for a sample treated at 1000 ° C. for 3 hours.
[0026]
Example 1
Basic zirconium sulfate (Zr content: containing 75 g as zirconia) 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 recover the hydroxide. This was baked 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 134.5 m ² / g. Furthermore, as a result of measuring the specific surface area after treating this oxide at 1000 ° C. for 3 hours in the same manner, it was 28.3 m ² / g. The oxygen adsorption amount was 0.18 mmol / g.
[0027]
Example 2
Basic zirconium sulfate (Zr content: containing 51 g as zirconia) was dispersed in water, a cerium nitrate solution (Ce content: containing 49 g as ceria) was added thereto, and then neutralized with a sodium hydroxide solution. Next, after filtration and washing with water, solid-liquid separation was performed to recover the hydroxide. This was baked 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 138.2 m ² / g. Further, the specific surface area after the oxide was treated at 1000 ° C. for 3 hours was measured in the same manner, and as a result, it was 17.5 m ² / g. The oxygen adsorption amount was 0.25 mmol / g.
[0028]
Example 3
After dispersing basic zirconium sulfate (Zr content: 74 g as zirconia) in water and adding cerium nitrate solution (Ce content: 24 g as ceria) and lanthanum nitrate solution (La content: 2 g as Lantana) And neutralized with sodium hydroxide solution. Next, after filtration and washing with water, solid-liquid separation was performed to recover the hydroxide. This was baked 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 132.1 m ² / g. Further, the specific surface area after the oxide was treated at 1000 ° C. for 3 hours was also measured and found to be 37.5 m ² / g. The oxygen adsorption amount was 0.20 mmol / g.
[0029]
Example 4
After dispersing basic zirconium sulfate (Zr content: 60 g as zirconia) in water, and adding cerium nitrate solution (Ce content: 30 g as ceria) and lanthanum nitrate solution (La content: 10 g as Lantana) And neutralized with sodium hydroxide solution. Next, after filtration and washing with water, solid-liquid separation was performed to recover the hydroxide. This was baked 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 143.7 m ² / g. Furthermore, the specific surface area after the oxide was treated at 1000 ° C. for 3 hours was measured in the same manner, and was found to be 42.1 m ² / g. The oxygen adsorption amount was 0.31 mmol / g.
[0030]
Example 5
After basic zirconium sulfate (Zr content: containing 50 g as zirconia) is dispersed in water, a cerium nitrate solution (Ce content: containing 42 g as ceria) and a lanthanum nitrate solution (La content: containing 8 g as Lantana) are added thereto. And neutralized with sodium hydroxide solution. Next, after filtration and washing with water, solid-liquid separation was performed to recover the hydroxide. This was baked 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 148.1 m ² / g. Further, the specific surface area after the oxide was treated at 1000 ° C. for 3 hours was also measured and found to be 22.1 m ² / g. The oxygen adsorption amount was 0.27 mmol / g.
[0031]
Example 6
Basic zirconium sulfate (Zr amount: containing 67 g as zirconia) is dispersed in water, and cerium nitrate solution (Ce amount: containing 21 g as ceria), lanthanum nitrate solution (La amount: containing 2 g as lantana), neodymium nitrate solution (Nd amount: containing 5 g as neodia) and praseodymium nitrate solution (Pr amount: containing 5 g as praseodya) were added, and then neutralized with sodium hydroxide solution. Next, after filtration and washing with water, solid-liquid separation was performed to recover the hydroxide. This was baked 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, as a result of measuring the specific surface area after treating this oxide at 1000 ° C. for 3 hours in the same manner, it was 54.1 m ² / g. The oxygen adsorption amount was 0.24 mmol / g.
[0032]
Example 7
Basic zirconium sulfate (Zr content: containing 42 g as zirconia) 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 recover the hydroxide. This was baked 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 138.2 m ² / g. Further, the specific surface area after the oxide was treated at 1000 ° C. for 3 hours was measured in the same manner. As a result, it was 16.8 m ² / g. The oxygen adsorption amount was 0.28 mmol / g.
[0033]
Comparative Example 1
A zirconium nitrate solution (Zr amount: containing 75 g as zirconia) and a cerium nitrate solution (Ce amount: containing 25 g as ceria) were mixed and neutralized with aqueous ammonia. Next, after filtration and washing with water, solid-liquid separation was performed to recover the hydroxide. This was baked 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. Further, the specific surface area after the oxide was treated at 1000 ° C. for 3 hours was measured in the same manner, and as a result, it was 19.5 m ² / g. The oxygen adsorption amount was 0.16 mmol / g.
[0034]
Comparative Example 2
Zirconium oxide (Zr content: containing 75 g as zirconia) was dispersed in water, mixed with a cerium nitrate solution (Ce content: containing 25 g as ceria), and then dried to obtain a hydrous oxide. This was baked 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. Further, the specific surface area after the oxide was treated at 1000 ° C. for 3 hours was also measured and found to be 5.4 m ² / g. The oxygen adsorption amount was 0.10 mmol / g.
[0035]
Examples 8-35
An oxide was prepared in the same manner as in Example 3 with the composition shown in Table 1 (as oxide). About the obtained oxide, it carried out similarly to Example 3, and measured the specific surface area (400 degreeC and 1000 degreeC) and oxygen adsorption amount. The results are shown in Table 1. All the third components were blended as nitrates.
[0036]
[Table 1]

[0037]
As shown in Table 1, the compositions of Examples 8 to 35 have a specific surface area of 130 m ² / g or more at 400 ° C., a specific surface area of 1000 ° C. is as large as 30 m ² / g, and oxygen adsorption. It can be seen that the amount is also excellent at 0.15 mmol / g.

Claims (6)

A method for producing a zirconia-ceria composition, comprising mixing a basic zirconium sulfate and a solution containing cerium ions, and then adding a base. The production method according to claim 1, wherein at least one kind of rare earth element compound is further added. The manufacturing method of Claim 1 which further adds at least 1 sort (s) of a lanthanum compound and a neodymium compound. The manufacturing method according to any one of claims 1 to 3, wherein the zirconia-ceria composition is further fired at 400 ° C or higher. The production method according to claim 1, wherein the ceria content in the zirconia-ceria composition does not exceed 60% by weight. The manufacturing method according to any one of claims 1 to 3, wherein the zirconia-ceria composition has a specific surface area at 400 ° C of 130 m ² / g or more and a specific surface area at 1000 ° C of 15 m ² / g or more.