JP2535790B2 - Method for producing tungsten bronze and coating composite thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to various tungsten bronzes and a method for producing an inorganic composite body obtained by coating them.

[0002]

2. Description of the Related Art Tungsten bronze has the general formula M _x WO
It is represented by ₃ (0 <x ≦ 1), and as M, there are known many substances such as alkali, alkaline earth, and rare earth metal elements. The method of reacting a mixture of metal oxide or metal tungstate, WO ₃ and metal W, which is a typical production method of these bronze, requires a high temperature and a long reaction time. For example, the production of rare earth bronze requires more than 100 hours at 1050 ° C (Inorg.
m., 5, P758 (1966)). In addition, in the case of producing an alkali metal bronze, there is a problem that metallic tungsten, which is difficult to separate and remove, easily remains as an unreacted material (“non-stoichiometric metal compound” (Basic Metal Property Course 15 ) P
68 (1975)). In addition, a high temperature reaction method using a metal halide, WO ₂ or a mixture of W and WO ₃ as a raw material (70
0-1050 ° C) has been reported (Inorg. Chem.,
7, P614 (1968)), a large amount of unstable tungsten oxyhalide is generated as a by-product, and orthotungstic acid which is difficult to separate and remove when an alkaline earth metal halide is used as a raw material. There is a problem that some salt is generated. On the other hand, there is almost no example of a method for manufacturing a tungsten bronze-coated composite, and sodium tungsten bronze (Na _x WO
_{3, 0 .7 0 <x <} 0.9 5) a method of coating has been proposed (JP-A-5-254843).

[0003]

DISCLOSURE OF THE INVENTION The present invention overcomes the problems found in the conventional methods and provides a method for easily producing various tungsten bronzes and a method for producing a coated inorganic composite of these tungsten bronzes. It is intended to be provided.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems of the prior art, the present inventors have used meta-type ammonium tungstate and various water-soluble metal salts as raw materials, It was found that the above object can be achieved and the above problems can be solved by subjecting the dry solid matter of the mixed aqueous solution to hydrogen reduction, and the present invention has been completed.

That is, according to the present invention, (1) meta-type ammonium tungstate (chemical formula (NH ₄ ) ₆ H ₂
W ₁₂ O ₄₀ ) and a metal salt are mixed with each other to give a dry solid which is hydrogenated to give a chemical formula M _x WO ₃ (where M is a metal element and x is a metal element).
Indicates a non-stoichiometric composition (0 <x <1). ), A method for producing a tungsten bronze characterized by producing a tungsten bronze, (2) applying a mixed aqueous solution of ammonium metatungstate and a metal salt to a support,
After drying, it is reduced with hydrogen and M _x WO ₃ (wherein
M represents a metal element, and x represents a nonstoichiometric composition (0 <x <1). (3) A method for producing a tungsten bronze-coated composite, which comprises forming a coating layer of tungsten bronze represented by (3), wherein (3) the metal salt is alkali, alkaline earth, rare earth, copper, tin, silver, nickel, indium. ,lead,
It is characterized in that it is selected from water-soluble tungstates, hydrochlorates, hydrobromides, nitrates and carbonates of metals selected from cobalt, iron, manganese, zinc, cadmium and mercury (1 ) And the method for producing the tungsten bronze-coated composite according to (2), and (4) the support is a carbonaceous material, a zirconia-based material, a magnesia-based material, a siliceous material, or a carrous material.
Characterized by being selected from a binder material, an alumina material, a titania material, and a corrosion-resistant / heat-resistant metal material (2)
Alternatively, there is provided a method for producing a tungsten bronze-coated composite according to item (3).

The tungsten bronze in the present invention is
To an aqueous solution of ammonium metatungstate prepared by a known method, an aqueous solution of a metal salt corresponding to x mol relative to 1/12 mol of ammonium metatungstate is added, and this mixed aqueous solution is preferably 80 to 250 ° C.
It is manufactured by subjecting the product to dryness under reduced pressure and then reducing with hydrogen while heating. Hydrogen reduction is preferably performed at 300 to 700 ° C. in a state where the reducing power of hydrogen is adjusted by adding an inert gas or steam to the supplied hydrogen gas. The approximate concentration of meta-type ammonium tungstate in the mixed aqueous solution as WO ₃ is preferably 0.1 to 5 mm.
1 to 3 mmol / ml, more preferably 0.01 to 5 mmo as metal ions in the metal salt aqueous solution.
It is preferably about 0.1 to 3 mmol / ml, more preferably 1 / ml. Although the concentration of each of these is not limited, the amount of the meta-type ammonium tungstate added to the metal salt is preferably 0.005 to 0.98, more preferably the molar ratio of metal ion / WO _{3 in} the liquid. 0.0
It should be 1 to 0.95. In addition, when preparing this mixed aqueous solution, a powdery metal salt may be added directly to the aqueous meta-type ammonium tungstate solution, but addition of the aqueous solution is more preferable from the viewpoint of easiness of mixing and the like. Drying of the mixed aqueous solution is preferably carried out at 80 to 250 ° C, more preferably 80 to 170 ° C. If the heating temperature is too low, some water will remain, and if the heating temperature is too high, a decomposition reaction will occur and WO _3, etc. will be produced.
Preferred metal salts in the present invention are alkali, alkaline earth, rare earth, copper, tin, silver, nickel, indium,
Examples thereof include water-soluble tungstates, halogenates, nitrates and carbonates composed of metal elements such as lead, cobalt, iron, manganese, zinc, cadmium and mercury. The anion components of these metal salts are ammonium salts (NH ₄ Cl (sublimable), NH ₄ Br (sublimable), NH ₄ NO ₃ etc.), HCl, HBr, NO _x during the reduction treatment operation.
Also, there is no danger of remaining in the generated solid phase since it will be emitted from the reaction system as CO ₂ and CO ₂ . On the other hand, the concentration of the supplied hydrogen gas is 300 to 500 in the case of adding the inert gas.
The hydrogen concentration is about 50 vol% or less, preferably 20 vol% or less at the reduction temperature of ℃, about 10 vol% at 500-700 ℃.
%, Preferably 5 vol% or less, the by-products such as metal W and W ₃ O, which are difficult to separate and remove, can be avoided. Further, in the case of adding steam, it is 300 to 70.
The amount of water vapor in hydrogen gas is about 15 with respect to the reduction temperature of 0 ° C.
If the supply is controlled to less than vol%, the same will be achieved for metal W and W ₃ O.
By-products such as can be avoided. Examples of the inert gas in the case of adding the inert gas include helium, argon and nitrogen gas. The content may be added so that the hydrogen gas concentration is the above.

Next, the production of the tungsten bronze-coated composite will be described. As in the case of the above-mentioned production of tungsten bronze, a mixed aqueous solution prepared by adding a predetermined amount of an aqueous metal salt solution to an aqueous solution of ammonium metatungstate is applied to the support material by a method such as dipping, preferably at 80 to 250 ° C. Then, the same hydrogen reduction treatment may be performed. In this case, the preferable aqueous solution concentrations of the meta-type ammonium tungstate and the metal salt, and the preferable water-soluble metal salt are the same as those in the above-mentioned production of tungsten bronze. In the case of a plate material, the coating amount of this mixed aqueous solution is, for example, preferably 0.001 to 0.05 m per unit cm ^2.
1 and more preferably 0.003 to 0.03 ml. Further, for those having a fine structure such as carbon fiber cloth, preferably 0.003 to 0.3 ml, more preferably 0.005 to 0.2 m.
It is l. On the other hand, the material used as the support is not limited to a plate material, a rod material, or a woven cloth or a porous material having a fine structure as long as it is a material having heat resistance, hydrogen reduction resistance and alkali resistance at a temperature of 700 ° C. or lower. There is no such thing. In the tungsten bronze-coated composite obtained by the method of the present invention, the coating layer of tungsten bronze is:
It can be of any thickness, from thin to thick, depending on the application of the composite. The thickness of the coating layer is preferably in the range of about 0.1 μm to 10 μm, but is not limited thereto.

[0008]

Next, the present invention will be described in more detail with reference to examples. Example 1 Ammonia water (2 to 4 wt%) and tungstic acid (H ₂ W)
5 ml of an aqueous solution of ammonium metatungstate (WO ₃ concentration in the liquid; 2 mmol / ml) prepared from O ₄ ) and 5 kinds of salts of potassium, which is a typical alkali metal (potassium metatungstate, potassium chloride, odor) Potassium iodide,
1.35 ml of an aqueous solution of potassium nitrate and potassium carbonate (both potassium ion concentrations in the solution are 2 mmol / ml) were mixed and prepared so that the K / WO ₃ molar ratio in the solution was 0.27. (About 5 ml) was dried in a drier at 150 ° C. to obtain 2.27 g, 2.13 g, 2.22 g, 2.19 g of dried products corresponding to the above 5 kinds of salts.
2.12 g each was obtained. These dry solids were
2.5 vol in a quartz reaction tube (diameter 25 mm) at 550 ° C
% (In argon) hydrogen gas was supplied at a flow rate of about 350 ml / min to carry out a reduction treatment for 3 hours. Thus, the desired products (potassium tungsten bronze) corresponding to the above-mentioned five kinds of dry solids were respectively 1.96 g, 1.94 g, 1.
95 g, 1.94 g and 1.93 g were obtained. The obtained solid product was examined by X-ray diffraction, X-ray elemental analysis and chemical analysis. As a result, it was found that only Hexagonal type potassium tungsten bronze represented by K _x WO ₃ (x = 0.27) was used. Not only the ammonium component but also the anion component of the added metal salt was not detected. Almost the same result was obtained by the reduction treatment using hydrogen gas added with 10 vol% of steam instead of the above-mentioned supply gas.

[0009] Example 2 the alkaline earth chlorides two metals in place of the potassium salt of Example _{1 (BaC 2 · 2 H 2} O, Sr Cl 2 · 6 H 2
O) and chloride two rare earth metals (La Cl ₃ · 7 H
₂ O, Nd Cl ₃ .6 H ₂ O) in an aqueous solution of 2 ml and the molar ratio of metal ion to WO ₃ component in the solution is 0.1.
(Alkaline earth type) and 0.2 (rare earth type), and dried products of these were subjected to hydrogen reduction treatment (heating temperature: 475 ° C., hydrogen concentration (in argon) in the same manner as in Example 1. ); 20 vol%, time; 3 hours) and tungsten bronze 1.97 corresponding to the above-mentioned two kinds of alkaline earth metal chlorides and two kinds of rare earth metal chlorides, respectively.
g, 1.93 g, 2.08 g, 2.09 g were obtained. The obtained solid products were all single-phase tungsten bronze, and no ammonium or chlorine components were detected in them. Bronze composition produced: Ba _x WO ₃ (x = 0.1),
Sr _x WO ₃ (x = 0.1), La _x WO ₃ (x = 0.2), Nd _x WO
₃ (x = 0.2). When the amount of chlorine ions in the mixed aqueous solution of the raw materials was more than the amount of ammonium ions as in the case of the rare earth type, HCl was partially formed together with NH ₄ Cl.

Example 3 Nickel was used instead of the aqueous potassium salt solution of Example 1 above.
When 2 ml of an aqueous solution of copper and tin chloride was used and the molar ratio of the metal ion and the WO ₃ component in the solution was nickel and copper, it was 0.1.
In the case of tin, it was adjusted to 0.21, and the dried solids thereof were reduced with hydrogen in the same manner as in Example 1 (heating temperature; 475 ° C., hydrogen concentration (in argon); 10 vol%, time). 3 hours) to obtain 1.87 g, 1.88 g, and 2.05 g of the above-mentioned products corresponding to nickel, copper, and tin, respectively.
The obtained solid products were all single phases of tungsten bronze, and no ammonium or chlorine components were detected in them. Product bronze composition: Ni _x WO ₃ (x = 0.06
), Cu _x WO ₃ (x = 0.06), Sn _x WO ₃ (x = 0.21)
).

Example 4 Graphite fiber cloth (thickness 0.4 ^mm , length 15 ^mm , width 4) was prepared as a support for each mixed aqueous solution of ammonium metatungstate and potassium salt prepared by the same method as in Example 1 above.
0 ^mm ) 3 pieces dipped (impregnation amount 0.05 ml / cm ² ), 1
After drying at 50 ° C, 2.5 vol% (in argon) of hydrogen gas in a quartz reaction tube (diameter 25 mm) at about 550 ° C, about 350 ml /
It was supplied at a flow rate of min and reduction treatment was performed for 2 hours. When the obtained samples were analyzed in the same manner, K
Only the Hexagonal type potassium tungsten bronze represented by _x WO ₃ (x = 0.27) was formed (coverage 2
5 mg / cm ² ). When these samples were observed with a scanning electron microscope, formation of a coating layer made of fine crystals of potassium tungsten bronze (particle size: 0.5 μm or less) was observed. Also, instead of the graphite fiber cloth as a support, yttria-stabilized zirconia plate and Hastelloy-based corrosion-resistant, heat-resistant alloy plate having almost the same dimensions were subjected to the same operation to analyze and observe the product after hydrogen reduction treatment. , And almost the same result was obtained.

[0012]

INDUSTRIAL APPLICABILITY The present invention uses, as raw materials, easily produced or available meta-type ammonium tungstate and various water-soluble metal salts. Various tungsten bronzes represented by M _x WO ₃ (M is a metal element such as alkali, alkaline earth and rare earth, 0 <x <1) can be produced in a short time only by controlling and supplying. . INDUSTRIAL APPLICABILITY The present invention facilitates the production of tungsten bronze, which has been reported to be successful in electrode catalysts for fuel cells and the like, organic synthesis catalysts and electrochromic materials. Also,
In the present invention, various tungsten bronze coatings can be formed not only on the plate material and the rod material but also on the surface of the woven cloth or porous material having a fine structure by performing the same operation as above on the support. . The composite thus obtained is suitable for the production of electrode materials for electrolytic devices and fuel cells, and catalyst materials for organic synthesis.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C04B 35/80 C04B 41/87 A 41/87 35/80 L (72) Inventor Toshiya Kumagai Ibaraki Prefecture Tsukuba City Higashi 1-1, Industrial Technology Institute, Institute of Materials Engineering and Industrial Technology (72) Inventor Susumu Susumu, Susumu Mizuta Ibaraki Prefecture, Tsukuba City East 1-1, Industrial Technology Institute, Institute of Materials Engineering (56) Reference JP-A-5-254843 (JP, A)

Claims (4)

(57) [Claims] 1. A dry product of a mixed aqueous solution of meta-type ammonium tungstate (chemical formula (NH ₄ ) ₆ H ₂ W ₁₂ O ₄₀ ) and a metal salt is hydrogen-reduced to give a chemical formula M _x WO ₃ (wherein, M is A method for producing a tungsten bronze, which comprises producing a tungsten bronze represented by a metal element and x by a non-stoichiometric composition (0 <x <1). 2. A mixed aqueous solution of ammonium metatungstate and a metal salt is applied to a support, dried and hydrogen reduced to give M _x WO ₃ (wherein M is a metal element and x is a metal oxide) on the surface of the support. A method for producing a tungsten bronze-coated composite body, which comprises forming a tungsten bronze coating layer represented by a nonstoichiometric composition (indicating 0 <x <1). 3. A water-soluble tungsten whose metal salt is a metal selected from alkali, alkaline earth, rare earth, copper, tin, silver, nickel, indium, lead, cobalt, iron, manganese, zinc, cadmium and mercury. 3. The method for producing a tungsten bronze-coated composite according to claim 1, wherein the tungsten bronze is selected from the group consisting of acid salts, hydrochloric acid salts, hydrobromic acid salts, nitrates and carbonates. 4. A support having a carbonaceous material, a zirconia-based material, a magnesia-based material, a siliceous material, a carbide material,
The method for producing a tungsten bronze-coated composite according to claim 2 or 3, wherein the material is selected from an alumina-based material, a titania-based material, and a corrosion-resistant / heat-resistant metal material.