JP3273820B2 - Cerium-containing composite oxide having oxygen absorbing / releasing ability and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention can be used for exhaust gas cleaning catalysts, ceramics, etc.
The present invention relates to a composite oxide having a releasing ability and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, cerium oxide has been used in large quantities as an exhaust gas purifying catalyst, ceramics and the like. For example, in the field of catalysts, cerium oxide absorbs oxygen in an oxidizing atmosphere,
Utilizing the property of cerium oxide that releases oxygen under a reducing atmosphere, the purification rate of exhaust gas components such as HC, CO, and NOx has been improved, and in the ceramics field, the cerium oxide has been improved. Utilizing its characteristics, it is used for conductive ceramics such as solid electrolytes. Such a conventional cerium oxide is usually produced, for example, by a method of adding oxalic acid or ammonium bicarbonate to a cerium nitrate solution or a hydrochloride solution, and filtering, washing, drying and calcining the obtained precipitate. Have been.

[0003] However, the conventional oxide containing cerium oxide as a main component produced by the above-described method or the like has oxygen absorbing / releasing ability, but has a drawback that it cannot absorb and release sufficient oxygen at 300 ° C or lower. is there.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a cerium-containing composite oxide having particularly excellent oxygen absorbing / releasing ability and a method for producing the same.

Another object of the present invention is to provide a production method capable of easily preparing a cerium-containing composite oxide having particularly excellent oxygen absorbing / releasing ability with good reproducibility.

[0006]

According to the present invention, there is provided a composite oxide containing cerium oxide as a main component, the composite oxide having an oxygen absorbing / releasing ability of 100 μmol / g or more at 300 ° C. or less. Have and noble metal 0.01-1
A cerium-containing composite oxide having an oxygen absorbing / releasing ability characterized by containing 0.0% by weight is provided.

Further, according to the present invention, cerium ions,
A solution containing a noble metal ion is mixed with an aqueous ammonia solution, an aqueous ammonium bicarbonate solution or an aqueous oxalic acid solution containing a reducing agent to prepare a composite salt precipitate, and then the composite salt precipitate is calcined at 250 ° C. or higher. A method for producing a cerium-containing composite oxide having the oxygen absorbing / releasing ability described above is provided.

Hereinafter, the present invention will be described in more detail.

The cerium-containing composite oxide having an oxygen absorbing / releasing ability of the present invention is at least 100 μmol / g, preferably at least 150 μmol, in a temperature range of 300 ° C. or less.
It has an oxygen absorption / release capacity of 1 / g or more.

The composite oxide of the present invention comprises cerium oxide as a main component, a noble metal such as palladium, platinum and rhodium as an essential component , and zirconium oxide if necessary .
It contains transition metal oxides such as titanium oxide, tungsten oxide, nickel oxide, copper oxide, iron oxide, aluminum oxide, and silicon oxide. The content ratio of the noble metal is 0.01 to 10.0% by weight, preferably 0.1 to 5% by weight, based on the total weight of the composite oxide. At this time, when the content ratio of the noble metal is less than 0.01% by weight, the amount of released oxygen is insufficient, and when the content exceeds 10.0% by weight, the amount of released oxygen decreases. On the other hand, when the transition metal oxide is used, its content is 0.01 to 10.0% by weight, preferably 0.1 to 5% by weight, based on the total weight of the composite oxide. At this time, when the content ratio of the transition metal oxide is less than 0.01% by weight,
Even if the amount of released oxygen is insufficient and exceeds 10.0% by weight, the amount of released oxygen decreases. Other precious metals is a further essential component,
Beryllium oxide, magnesium oxide, calcium oxide,
An alkaline earth metal oxide composed of strontium oxide, barium oxide, and radium oxide; a rare earth element oxide other than cerium oxide, or a mixture thereof may be contained.
The content ratio of the metal oxide other than the essential component and the transition metal oxide is 10% by weight based on the total weight of the composite oxide.
It is preferred that:

The composite oxide of the present invention is not particularly limited as long as it has the oxygen absorbing / releasing ability, and its shape is preferably, for example, spherical, cubic, or the like. The particle size is preferably from 0.1 to 0.5 μm. Further, the specific surface area at 800 ° C. is preferably 30 m ² /
g or more, particularly preferably 50 m ² / g or more.

To prepare the composite oxide of the present invention, first, cerium ions, noble metal ions , and, if necessary, transition gold
The solution containing the genus ions, containing a reducing agent, aqueous ammonia, mixed with ammonium bicarbonate solution or oxalic acid solution, cerium, a noble metal and a transition necessary metals
And preparing a complex salt precipitate comprising: The solution containing the cerium ion, the noble metal ion, and if necessary, the transition metal ion can be obtained by, for example, a method of mixing an aqueous cerium nitrate solution and an aqueous nitric acid solution in which the noble metal or the transition metal is dissolved. Further , if necessary, a solution containing a rare earth metal ion other than the alkaline earth metal ion and the cerium ion or a mixed ion thereof may be mixed. The concentration of the solution containing the cerium ion and the noble metal ion is preferably 10% in terms of total ion concentration.
~300g / l, particularly preferably area by Der of 30~100g / l. Further, the mixing ratio of the cerium ion, the noble metal ion and the transition metal ion, and other metal ions to be added and mixed as necessary, is 99.99 to 70.0% by weight as an oxide. : 0.01 to 20.0: 0 to 1
It is preferably 0.0.

Examples of the reducing agent contained in the aqueous ammonia solution, the aqueous ammonium bicarbonate solution or the aqueous oxalic acid solution include, for example, NH ₂ NH ₂ (hydrazine), NH ₂ NH ₂ 2H
Examples thereof include Cl (hydrazine hydrochloride) and HCOOH (formic acid), and the amount thereof is preferably 1 to 30 moles, more preferably 5 to 15 moles with respect to the noble metal. If the amount is outside the above range, the noble metal is not sufficiently blended, and the amount of oxygen released from the obtained oxide is insufficient. When the aqueous ammonia solution is used, the concentration is preferably 1 to 2N, particularly preferably 1 to 1.5N.
N, the concentration when using an aqueous solution of ammonium bicarbonate is
Preferably 50 to 200 g / l, particularly preferably 100
To 150 g / l, the concentration when using an oxalic acid aqueous solution is 50 to 100 g / l, particularly preferably 50 to 60 g / l.
Range.

The mixing ratio of the solution containing the cerium ion and the noble metal ion and the aqueous ammonia solution, the aqueous ammonium bicarbonate solution or the aqueous oxalic acid solution containing the reducing agent is 1: 1 by weight, respectively. １ ： 1: 2 is preferred. The composite salt precipitate obtained at this time is, for example, a composite hydroxide.

Next, the complex salt precipitate is heated at 250 ° C. or higher,
Preferably, the composite oxide of the present invention can be produced by firing at 300 to 400 ° C. Further, in the production method of the present invention, if necessary, before firing the complex salt precipitate, a hydrothermal treatment or the like may be performed before the firing step. The hydrothermal treatment can be performed by a usual autoclave or the like, and the temperature at that time is 100 to 1
It is desirable that the treatment time is 35 ° C. and the treatment time is in the range of 0.5 to 1 hour. When the firing temperature is lower than 250 ° C., the oxide hardly becomes an oxide. The firing time is preferably 1 to 10 hours.

The composite oxide obtained by the production method of the present invention can be used as it is, but it can also be used after adding a rare earth nitrate or the like.

[0017]

Cerium-containing composite oxide of the present invention exhibits, because it contains a noble <br/> metals as an essential component, in the temperature range of 300 ° C. or less, an oxygen absorbing and desorbing capability over 100 [mu] mol / g. Therefore, it is extremely useful in the field of catalysts, ceramics, and the like. Further, according to the production method of the present invention, the composite oxide of the present invention having excellent oxygen absorbing / releasing ability can be easily produced with good reproducibility.

[0018]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

[0019]

Example 1 A high-purity cerium nitrate solution (manufactured by Santoku Metal Industry Co., Ltd., purity 99.9%) was prepared by dissolving in water.
Cerium nitrate aqueous solution 1 with a cerium oxide concentration of 300 g / l
To 65 ml, 6 ml of an aqueous palladium nitrate solution prepared by dissolving a palladium nitrate solution (purity 99.9%, manufactured by Wako Pure Chemical Industries, Ltd.) in water was mixed to make Ce: Pd = 99: 1 (weight ratio), A solution containing cerium ions and palladium ions having a composite oxide concentration of 50 g / l was prepared. Next, 1 liter of the obtained solution was mixed with 1 liter of a 1N aqueous ammonia solution containing 5 mol of (NH ₂ ) ₂ 2HCl as a separately prepared reducing agent to obtain a precipitate of a composite hydroxide containing cerium and palladium. The obtained composite hydroxide was calcined at 300 ° C. for 4 hours to have a specific surface area of 110 m ² /
After recalcination at 900 ° C., 50 g of a cerium- and palladium-containing composite oxide having a specific surface area of 5 m ² / g was obtained. In order to measure the amount of oxygen absorption and release of the obtained composite oxide, 1 g of the composite oxide was charged into a cylindrical furnace, and the mixture was measured by gas chromatography while flowing hydrogen gas and oxygen gas. -The release ability was 100 mol / g at 150 to 250C. The content of palladium in the composite oxide was 1% by weight.

[0020]

Example 2 Cerium nitrate aqueous solution 1 prepared in Example 1
50 ml and 60 ml of an aqueous solution of palladium nitrate were mixed to make Ce: Pd = 90: 10 (weight ratio), and a cerium ion and palladium ion-containing solution having a composite oxide concentration of 50 g / l was prepared. Next, a composite oxide was produced in the same manner as in Example 1, and the amount of oxygen absorption / release was measured. The resulting composite oxide has an oxygen absorption / release capacity of 15
At 0 to 250 ° C, it was 130 µmol / g.
The content of palladium in the composite oxide was 10% by weight.

[0021]

Example 3 Cerium nitrate aqueous solution 1 prepared in Example 1
65 ml of platinum nitrate (purity 99.9, manufactured by Wako Pure Chemical Industries, Ltd.)
%) Dissolved in water and mixed with 10 ml of an aqueous solution of platinum nitrate to prepare a solution containing cerium ions and platinum ions with a composite oxide concentration of 50 g / l at a Ce: Pt = 99: 1 (weight ratio). did. Next, a composite oxide was produced in the same manner as in Example 1, and the amount of oxygen absorption / release was measured. The resulting composite oxide has an oxygen absorption / release capacity of 150
At 〜250 ° C., it was 120 μmol / g. The content of platinum in the composite oxide was 1% by weight.

[0022]

Example 4 Cerium nitrate aqueous solution 1 prepared in Example 1
65 ml, and rhodium nitrate (purity 99.
9%) in water.
Then, a solution containing cerium ions and rhodium ions having a composite oxide concentration of 50 g / l was prepared by mixing Ce: Rh = 99: 1 (weight ratio). Next, a composite oxide was produced in the same manner as in Example 1, and the amount of oxygen absorption / release was measured. The resulting composite oxide has an oxygen absorption / release capacity of 110 μmol / g at 150 to 250 ° C.
Met. The content of rhodium in the composite oxide is
It was 1% by weight.

[0023]

Example 5 Cerium nitrate aqueous solution 1 prepared in Example 1
65 ml, 30 ml of an aqueous solution of palladium nitrate, and 25 ml of an aqueous solution of neodymium nitrate having a neodymium oxide concentration of 100 g / l prepared by dissolving neodymium nitrate (manufactured by Santoku Metal Industry Co., Ltd., purity 99.9%) in water, Ce: Pd: Nd =
90: 5: 5 (weight ratio), and a composite oxide concentration of 50 g /
A solution containing cerium ion, palladium ion and neodymium ion was prepared. Next, a composite oxide was produced in the same manner as in Example 1, and the amount of oxygen absorption / release was measured.
The resulting composite oxide has an oxygen absorption / release capacity of 1
At 50 to 250 ° C, it was 112 µmol / g. The contents of palladium and neodymium oxide in the composite oxide were 5% by weight and 5% by weight, respectively.

[0024]

Example 6 Cerium nitrate aqueous solution 1 prepared in Example 1
34 ml, an aqueous solution of palladium nitrate 30 ml, and europium nitrate (purity 99.9%, manufactured by Santoku Metal Industry Co., Ltd.) dissolved in water to prepare a europium oxide concentration 100 g / l.
5 ml of an aqueous solution of europium nitrate and 25 ml of an aqueous solution of aluminum nitrate (100 g / l) prepared by dissolving aluminum nitrate (purity: 99.9%, manufactured by Wako Pure Chemical Industries, Ltd.) in water were mixed with Ce: Pd: Eu: A
l = 89: 5: 1: 5 (weight ratio), cerium ion, palladium ion at a composite oxide concentration of 50 g / l,
A solution containing europium ions and aluminum ions was prepared. Next, a composite oxide was produced in the same manner as in Example 1, and the amount of oxygen absorption / release was measured. The resulting composite oxide had an oxygen absorbing / releasing ability of 112 µmol / g at 150 to 250 ° C. The contents of palladium, europium oxide and aluminum oxide in the composite oxide were 5% by weight, 1% by weight and 5% by weight, respectively.

[0025]

Example 7 Cerium nitrate aqueous solution 1 prepared in Example 1
34 ml, an aqueous solution of palladium nitrate 6 ml, and a zirconium nitrate solution (manufactured by Daiichi Kagaku Kabushiki Kaisha, purity 99.9%) diluted with water to prepare a zirconium oxide concentration of 375 g / l
And 12 ml of an aqueous solution of zirconium nitrate, Ce:
A solution containing cerium ion, palladium ion and zirconium ion with a Pd: Zr = 89: 1: 10 (weight ratio) and a composite oxide concentration of 50 g / l was prepared. Next, a composite oxide was produced in the same manner as in Example 1,
The release was measured. The resulting composite oxide has an oxygen absorbing / releasing ability of 113 μm at 150 to 250 ° C.
mol / g. The contents of palladium and zirconium oxide in the composite oxide were 1% by weight and 10% by weight, respectively.

[0026]

Example 8 Cerium nitrate aqueous solution 1 prepared in Example 1
34 ml, a palladium nitrate aqueous solution 20 ml, and praseodymium nitrate (purity: 99.9%, manufactured by Santoku Metal Industry Co., Ltd.) dissolved in water to prepare praseodymium oxide at a concentration of 100 g / l.
Of a praseodymium nitrate aqueous solution of 5 ml and an aluminum nitrate aqueous solution of 25 ml were mixed, and Ce: Pd: Pr: Al =
89: 5: 1: 5 (weight ratio) and a composite oxide concentration of 50
A solution containing cerium ion, palladium ion, praseodymium ion, and aluminum ion at g / l was prepared. Next, a composite oxide was produced in the same manner as in Example 1,
The amount of oxygen absorption / release was measured. The resulting composite oxide had an oxygen absorbing / releasing ability of 111 μmol / g at 150 to 250 ° C. The contents of palladium, praseodymium oxide and aluminum oxide in the composite oxide were 5% by weight, 1% by weight and 5% by weight, respectively.
Met.

[0027]

Example 9 Cerium nitrate aqueous solution 1 prepared in Example 1
50 ml, an aqueous solution of palladium nitrate 30 ml, and an aqueous solution of silicon nitrate 25 having a silicon oxide concentration of 100 g / l prepared by dissolving silicon nitrate (Wako Pure Chemical Industries, purity 99.9%) in water.
and mixed with Ce: Pd: Si = 90: 5: 5 (weight ratio) to prepare a solution containing cerium ion, palladium ion and silicon ion at a composite oxide concentration of 50 g / l. Next, a composite oxide was produced in the same manner as in Example 1, and the amount of oxygen absorption / release was measured. The resulting composite oxide had an oxygen absorbing / releasing ability of 105 µmol / g at 150 to 250 ° C. The contents of palladium and silicon oxide in the composite oxide were 5% by weight and 5% by weight, respectively.

[0028]

Example 10 A barium oxide concentration of 100 g was prepared by dissolving 165 ml of the cerium nitrate aqueous solution prepared in Example 1, 30 ml of the palladium nitrate aqueous solution, and barium nitrate (purity 99.9%, manufactured by Wako Pure Chemical Industries, Ltd.) in water. / L nitric acid burr
And 25 ml of an aqueous solution of Ce: Pd: Ba = 9.
0: 5: 5 (weight ratio), composite oxide concentration 50 g / l
A solution containing cerium ion, palladium ion and barium ion was prepared. Next, a composite oxide was produced in the same manner as in Example 1, and the amount of oxygen absorption / release was measured. The resulting composite oxide has an oxygen absorption / release capacity of 15
At 0 to 250 ° C, it was 111 µmol / g.
The contents of palladium and barium oxide in the composite oxide were 5% by weight and 5% by weight, respectively.

[0029]

Comparative Example 1 Cerium nitrate aqueous solution 1 prepared in Example 1
50 ml and 13 ml of an aqueous solution of zirconium nitrate were mixed to prepare Ce: Zr = 90: 10 (weight ratio), and a solution containing cerium ions and zirconium ions having a composite oxide concentration of 50 g / l was prepared. Next, a composite oxide was produced in the same manner as in Example 1 except that no reducing agent was used, and the amount of oxygen absorption / release was measured. The oxygen absorption / desorption ability of the resulting composite oxide is 0 at 150 to 250 ° C.
μmol / g. The content of zirconium oxide in the composite oxide was 10% by weight.

[0030]

Comparative Example 2 Cerium nitrate aqueous solution 1 prepared in Example 1
A cerium ion-containing solution having an oxide concentration of 50 g / l was prepared from 67 ml. Next, a cerium oxide was produced in the same manner as in Example 1 except that no reducing agent was used, and the amount of oxygen absorption / release was measured. The resulting cerium oxide has the ability to absorb and release oxygen at 150-250 ° C.
It was 0 μmol / g.

[0031]

Example 11 used in Example 1 (NH ₂₎ 1N aqueous ammonia containing 5mol a ₂ 2HCl (NH _{2) 2} 2HC
A cerium oxide was produced in the same manner as in Example 1 except that an aqueous solution of 1 mol / l ammonium bicarbonate containing 5 mol of 1 was prepared, and the amount of oxygen absorption / release was measured. The resulting cerium oxide has an oxygen absorption / release capacity of 150-250.
At 108 ° C., it was 108 μmol / g.

[0032]

Example 12 used in Example 1 (NH ₂₎ 1N aqueous ammonia containing 5mol a ₂ 2HCl (NH _{2) 2} 2HC
A cerium oxide was produced in the same manner as in Example 1 except that an aqueous solution of 1 mol / l oxalic acid containing 1 mol of 1 was prepared, and the amount of oxygen absorption / release was measured. The resulting cerium oxide had an oxygen absorbing / releasing ability of 105 μmol / g at 150 to 250 ° C.

[0033]

Example 13 A palladium nitrate solution was added to 165 ml of an aqueous cerium nitrate solution having a cerium oxide concentration of 300 g / l prepared by dissolving a high-purity cerium nitrate solution (purity: 99.9%, manufactured by Santoku Metal Industry Co., Ltd.) in water. Wako Pure Chemical Co., Ltd.
(99.9% purity) dissolved in water and mixed with 6 ml of an aqueous solution of palladium nitrate, and Ce: Pd = 99: 1.
(Weight ratio), a solution containing cerium ions and palladium ions with a composite oxide concentration of 50 g / l was prepared.
Then, 1 liter of a 1N aqueous ammonia solution containing 5 mol of HCOOH as a separately prepared reducing agent was added to 1 liter of the obtained solution and mixed to obtain a precipitate of a composite hydroxide containing cerium and palladium. The obtained composite hydroxide is calcined at 300 ° C. for 4 hours to have a specific surface area of 115 m ² / g,
After reheating at 900 ° C., 55 g of a cerium and palladium-containing composite oxide having a specific surface area of 8 m ² / g was obtained. In order to measure the amount of oxygen absorbed and released from the obtained composite oxide, 1 g of the composite oxide was charged into a cylindrical furnace, and the mixture was measured by gas chromatography while flowing hydrogen gas and oxygen gas. -Release ability was 104 micromol / g at 150-250 degreeC. The content of palladium in the composite oxide was 1% by weight.

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Claims (4)

(57) [Claims] 1. A composite oxide containing cerium oxide as a main component, wherein the composite oxide has an oxygen absorbing / releasing ability of 100 μmol / g or more at 300 ° C. or less, and a noble metal of 0.01 to 10 mol / g. A cerium-containing composite oxide having an oxygen absorbing / releasing ability, wherein the cerium-containing composite oxide contains 0.1 % by weight. 2. The method according to claim 1, wherein the transition metal oxide is 0.01 to 10.0.
2. Oxygen absorption according to claim 1, characterized in that it contains% by weight.
-A cerium-containing composite oxide having a releasing ability. Wherein the composite oxide, and claim 1 further comprising an alkaline earth metal oxides and / or other than cerium oxide a rare earth element oxide 10 wt% or less
Is a cerium-containing composite oxide having oxygen absorbing / releasing ability according to 2 . 4. A mixed salt precipitate is prepared by mixing a solution containing cerium ions and noble metal ions with an aqueous ammonia solution, aqueous ammonium bicarbonate solution or aqueous oxalic acid solution containing a reducing agent. 2. The method according to claim 1, wherein the composite salt precipitate is calcined at 250 ° C. or higher.
A method for producing a cerium-containing composite oxide having a releasing ability.