JP2994065B2 - Method for producing metal composite oxide powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a metal composite oxide powder used as a catalyst for oxidative decomposition of carbon monoxide and hydrocarbon compounds.

[0002]

2. Description of the Related Art Conventionally, many catalysts for oxidative decomposition of carbon monoxide and hydrocarbon compounds have been put into practical use. Considering oxidation catalysts, they can be roughly classified into noble metal-based and transition metal-based catalysts. Noble metal-based materials have been put to practical use as various catalysts because of their high catalytic activity, but they are inevitably expensive and have limited resources. On the other hand, transition metal oxides are also known as oxidation catalysts,
Metals such as r, Mn, Fe, Co, Ni, and Cu are used. In the case of an oxidative decomposition catalyst, these oxides have been studied for practical use, but their application is not much. Among them, mixed catalysts mainly composed of copper oxide and manganese dioxide are known to have good properties as a populite and as an oxidation catalyst for carbon monoxide, and are also interesting as hydrocarbon-based oxidation decomposition catalysts. It is. However, when these are used as catalysts, they are not as active as precious metals, so their application range is narrowed.

[0003]

Considering the application of the transition metal oxide according to the prior art as an oxidative decomposition catalyst, there is a problem that the activity of the oxide catalyst is low. In particular, when compared with precious metal catalysts, there was a difference in the catalytic activity in the low temperature range, and treatment such as heating was required to activate the catalyst, which made peripheral equipment complicated and hindered practical application. . The main cause of low catalytic activity is often that the specific surface area of the oxide catalyst is small and sufficient activity cannot be obtained. Conventional methods for producing a metal composite oxide include, for example, (1) each metal component is pulverized and mixed in the form of a powder of an oxide, a carbonate, an oxalate, and the like; A so-called dry method in which a metal composite oxide is obtained by pulverization. (2) Using a water-soluble salt such as nitrate, sulfate, hydrochloride or the like for each metal component to form a uniform aqueous solution, and adding a hydroxide ion, a carbonate ion, or an oxalate ion thereto to form a hydroxide, a carbonate. A coprecipitation in the form of oxalate, washing with water, drying and firing to obtain a metal composite oxide, a so-called wet method. Etc. In the method (1), since each powder is not fine particles after mixing in a powder state and then firing, the resulting powder does not become fine particles. Even if such a powder is used, sintering by firing has a large specific surface area. It's hard to get things. In the method (2), a large specific surface area can be obtained as compared with the method (1), but the control of the synthesis conditions such as the control of the precipitation conditions becomes strict. The present invention relates to a method for producing a metal composite oxide powder having a high specific surface area by applying the method (2) and synthesizing it under specific conditions.

[0004]

That is, the present invention comprises the following items. (1) In a method for producing CuMn ₂ O ₄ and a composite oxide in which a part of Mn of the CuMn ₂ O ₄ is substituted by Fe, Co or Ni, divalent as a water-soluble salt of a metal used in the production method is used. BET method by subjecting a water-soluble metal salt to neutralization and extrusion in an aqueous medium with an alkali agent at the time of or after the extrusion, oxidizing in an aqueous medium, and firing at a temperature of 500 ° C. or lower. A powder having a specific surface area of 80 m ² / g or more according to the above method. (2) 5-40% by weight of Mn of CuMn ₂ O ₄ is Fe, C
2. The method for producing a metal composite oxide powder according to claim 1, wherein the powder is substituted by o and Ni.

Next, the present invention will be described in detail. The present invention
A metal composite oxide is produced by a so-called wet method in which neutralization and precipitation are carried out with a water-soluble metal salt and an alkali agent. The above water-soluble metal salts include Cu, Mn, Fe, Co and Ni.
Are water-soluble metal salts of which are chloride,
Any water-soluble compound such as a nitrate, a sulfate or an acetate may be used. In the present invention, a divalent metal salt is particularly used. Examples of the alkaline agent for neutralizing and depositing the water-soluble metal salt include sodium hydroxide, potassium hydroxide, sodium carbonate, sodium hydrogen carbonate and the like. The amount of the alkaline agent used may be an amount capable of neutralizing each metal salt, but it is preferable to use a slightly excessive amount of the alkaline agent in order to complete neutralization and deposition.

In the present invention, a water-soluble salt of each of the above metals,
Any method may be used for mixing and extracting with an alkali agent. For example, (1) a water-soluble metal salt is dissolved in water to prepare an aqueous solution,
A method in which an alkali agent or an aqueous solution thereof is added thereto for neutralization. (2) A method in which an aqueous solution is prepared by dissolving an alkali agent in water, and a water-soluble salt of a metal is added thereto for neutralization. (3) A method in which an aqueous solution in which a water-soluble salt of a metal is dissolved and an aqueous solution of an alkali agent are prepared, and these are simultaneously added to water for neutralization. And the like. However, the method is not necessarily limited to the method described above, and a method in which hydroxides of each metal and oxide carbonates can be obtained in a uniformly mixed state,
Any method may be used.

Further, in the present invention, a bivalent metal salt is used as a water-soluble salt of each metal and oxidized in a liquid phase to obtain a metal composite oxide having a high specific surface area. Is being found. Therefore, the divalent metal in the slurry mixed and extracted with the water-soluble metal salt and the alkali agent is oxidized. Here, a method of oxidizing in the liquid phase using an oxidizing agent is employed. As the oxidizing agent to be used, any oxidizing agent such as aqueous hydrogen peroxide, oxygen gas, and sodium chlorate may be used. The amount of the oxidizing agent used may be an amount sufficient to oxidize the divalent metal, but it is preferable to use the oxidizing agent in a somewhat excessive ratio in order to complete the oxidation.
Such oxidation may be performed after removing unnecessary cations and anions such as cations such as sodium and potassium, or anions such as various acid ions such as chlorine from the slurry. When the slurry is used as it is, an oxidizing agent may be allowed to coexist at the time of neutralization and / or the oxidizing agent may be added after the neutralization and / or completion. At this time, it is necessary to remove various unnecessary ions by a method such as decantation after completion of the oxidation. The slurry obtained in this manner is filtered, dried, baked and pulverized to obtain a target metal composite oxide powder.

[0008]

The metal composite oxide powder according to the production method of the present invention as described above has a higher specific surface area than the conventional method. Further, a part of Mn of the composite oxide of CuMn ₂ O ₄ is
Substitution with e, Co, and Ni is preferable because the specific surface area further increases. In particular, those fired at 500 ° C. or less have a small reduction in specific surface area due to firing, and have excellent catalytic activity as an oxidative decomposition catalyst in a medium to low temperature range.

Further, the production method does not require special expensive equipment and can provide the above-mentioned excellent metal composite oxide powder at a low production cost. Next, the present invention will be described specifically with reference to examples.

[0010]

EXAMPLE 1 Water was added to and dissolved in 29 g of copper nitrate and 68.9 g of manganese nitrate to make the total amount 250 cc. On the other hand, sodium hydroxide 3
Water is added to 5 g and dissolved to make the total amount 250 cc. Prepare 35cc of 20% hydrogen peroxide water and prepare 600g
The above three solutions are simultaneously poured into a vessel equipped with a stirrer and containing cc of water. During this time, the pH of the slurry is maintained at around 10. After the end of the deposition reaction, the entire amount of excess aqueous sodium hydroxide solution is added dropwise. The pH of the liquid in this state is 12.5.
Met. Next, the slurry is heated and aged at 80 ° C. for 1 hour. The obtained black-brown product is washed with decantation to remove impurities such as unnecessary cations and anions, and then filtered and dried sufficiently at 120 ° C. This is 45
Calcination was performed for 1 hour at each of 0 ° C. and 600 ° C. to obtain a metal composite oxide powder. BET specific surface area of the resulting powder, respectively 92m ² / g, was 40 m ² / g.

Example 2 Synthesis was carried out in the same manner as in Example 1 except that 68.9 g of manganese nitrate in Example 1 was changed to 62 g, and 6.9 g of iron nitrate was added. To obtain a metal composite oxide powder. BET at this time
Each specific surface area 121m ² / g, was 54m ² / g.

Example 3 Synthesis was performed in the same manner as in Example 1 except that 68.9 g of manganese nitrate in Example 1 was changed to 62 g, and 7 g of nickel nitrate was added, and calcined at 450 ° C. and 600 ° C. in the same manner. Thus, a metal composite oxide powder was obtained. BET at this time
Each specific surface area 110m ² / g, was 48m ² / g.

Example 4 Synthesis was performed in the same manner as in Example 1 except that 68.9 g of manganese nitrate in Example 1 was changed to 62 g, and 7 g of cobalt nitrate was added, and calcined at 450 ° C. and 600 ° C. in the same manner. Thus, a metal composite oxide powder was obtained. BET at this time
Each specific surface area 102m ² / g, was 45 m ² / g.

Example 5 Synthesis was performed in the same manner as in Example 4 except that the amount of manganese nitrate in Example 4 was changed to 55.1 g, and 14 g of cobalt nitrate was added, and calcined at 450 ° C. and 600 ° C. in the same manner. Thus, a metal composite oxide powder was obtained. Each BET specific surface area at this time 113m ² / g, was 48m ² / g.

Comparative Example 1 Except that no hydrogen peroxide solution was used in Example 1,
Synthesized in the same manner as in Example 1,
The mixture was calcined at ℃ to obtain a metal composite oxide powder. B at this time
Each ET specific surface area of 56m ² / g, was 26m ² / g.

Example 6 To determine the catalytic activity of the metal composite oxide powders obtained in Examples 1 to 5 and Comparative Example 1 as an oxidative decomposition catalyst, the decomposition rate of propane was measured. The decomposition rate of propane was determined by a conventional fixed bed flow system with propane 0.7% air balance.
The space velocity at this time was set to 7000 hr ^-1 . Table 1 shows the results.

[0017]

[0018]

Since the metal composite oxide powder obtained by the production method of the present invention has a large specific surface area, it exhibits excellent effects when applied as an oxidative decomposition catalyst. Especially 500
The metal composite oxide powder of the present invention obtained by firing at a temperature of not more than ℃ has a small decrease in specific surface area and is excellent in oxidative decomposition characteristics at low temperatures.

────────────────────────────────────────────────── (5) Continuation of the front page (51) Int.Cl. ⁶ Identification symbol FI C01G 53/00 B01J 23/84 311A (56) Reference Proc. Nucl. Phys. Solid State Phys. Sym p. (1984), Volume Date 1982, 25C, 257-8 (58) Fields investigated (Int. Cl. ⁶ , DB name) C01G 45/00 C01G 53/00 B01J 23/889 B01J 37/03 B01J 37/12 CA (STN)

Claims (2)

(57) [Claims] 1. A of CuMn ₂ O ₄ and the CuMn ₂ O ₄ of the Mn
Production of composite oxide partially substituted with Fe, Co or Ni
A water-soluble salt of a metal used in the production method
Using a divalent water-soluble metal salt as
During or after neutralization in an aqueous medium
Is subjected to an oxidation treatment in an aqueous medium at a temperature of 500 ° C. or less.
By firing, 80m ² / g or more by BET method
Metal composite characterized by being a powder having a specific surface area
A method for producing an oxide powder. _2. 5 to 40% by weight of Mn of CuMn ₂ O ₄ is F
2. The metal composite according to claim 1, wherein said metal composite is substituted with
Method for producing composite oxide powder.