JP5737954B2 - Method for producing vanadate composite oxide - Google Patents

Description

The present invention is a magnetic material, a catalyst material, a fluorescent material, application to machinable ceramics, electrode material of lithium ion batteries, laser host materials, useful as electroluminescent materials, the general formula RVO ₄ or RVO ₃ (wherein , R is occupied by at least one element selected from rare earth elements, and V is a vanadium element.).

As a conventional method for synthesizing a vanadate-based composite oxide represented by RVO ₄ or RVO ₃ , taking LaVO ₄ as an example, the following synthesis methods are known:
A method of obtaining monoclinic LaVO ₄ by mixing La ₂ O ₃ and V ₂ O ₅ and heat-treating in air at 800 ° C. for 4 hours (Non-patent Document 1);
An aqueous solution of LaCl ₃ and a vanadate aqueous solution prepared by dissolving V ₂ O ₅ in dilute aqueous ammonia are mixed, adjusted to pH 8-9 with aqueous ammonia, and allowed to stand for several days and directly monoclinic LaVO without heat treatment ₄ (Non-Patent Document 2);
La (NO ₃ ) ₃ aqueous solution and NH ₄ VO ₃ aqueous solution are mixed, adjusted to pH 5-9 with aqueous ammonia, and hydrothermally treated at 160 ° C. using an autoclave, so that monoclinic LaVO ₄ is directly formed without heat treatment. Method to obtain (nonpatent literature 3).

Further, the applicants have the general formula ABO ₃ [wherein A is occupied by at least one element selected from rare earth elements, and B is at least one element selected from the group consisting of manganese, iron, and cobalt. Occupied by. A perovskite-type composite oxide represented by the following formula: a raw material containing at least one of oxides, hydroxides, oxide hydroxides and simple metals occupying the A site; A step of preparing a precursor of the perovskite complex oxide by mixing and pulverizing a raw material containing at least one of a hydroxide, an oxide hydroxide and a simple metal in an aqueous solvent; Has previously proposed a manufacturing method including a step of heat-treating (Patent Document 1). However, the manufacturing method described in Patent Document 1 is a perovskite complex oxide of rare earth elements and manganese, iron, or cobalt, and not a vanadate complex oxide.

  Note that “solvothermal” is a method for promoting the interaction of precursor materials by applying pressure and temperature in the solvent to the precursor material being synthesized and raising the temperature to the boiling point or higher of the solvent at atmospheric pressure. "The Law" is known. In the case of the solvothermal method using water as a solvent, it is said to be a hydrothermal synthesis method (Non-Patent Document 4).

JP 2008-007394 A

Bull. Chem. Soc. Jpn., 42, 3195 (1969) The Chemical Society of Japan NO.3, 455 (2002) J. Cryst. Growth, 310 (22), 4689 (2008) Part II Applied Technology of Fine Particle Engineering University (Fuji Techno System Co., Ltd., issued on January 18, 2002, page 32)

In the monoclinic complex oxide obtained by the method described in Non-Patent Document 1 (solid-phase reaction method in which each component oxide is mixed and heat-treated at high temperature), an impurity phase and unreacted substances remain. There is a problem that it is easy to do. A method as described in Non-Patent Document 2 or 3 (a coprecipitation method in which a coprecipitate of a component metal is obtained by adding a precipitating agent for adjusting pH to an aqueous solution of a salt of each component element) can be applied without LaVO. _Although a crystallized product of ₄ is obtained, a step of removing by-products such as ammonium nitrate and unreacted materials such as chloride raw materials is necessary. Furthermore, since the method as described in Non-Patent Document 3 performs hydrothermal treatment together with coprecipitation by-product such as ammonium nitrate, an apparatus such as an autoclave equipped with an expensive reaction vessel having corrosion resistance is required.

The present invention does not require a process for removing unreacted substances and impurities, which solves the problems as described above, and further eliminates the generation of corrosive by-products and the use of special solvents, and also requires stirring. A method for producing a vanadate-based composite oxide represented by the general formula RVO ₄ or RVO ₃ , capable of using a low-cost autoclave and obtaining a crystallized product without a heat treatment or a heat treatment step at a high temperature. The purpose is to provide.

As a result of diligent investigation to solve such problems, the present inventors have found that the vanadate-based composite oxide represented by the general formula RVO ₄ is an oxide, hydroxide or oxidized water of an element occupying an R site. Using raw materials containing at least one of oxides and at least one of vanadium oxides, hydroxides or oxide hydroxides, and using these raw materials with an organic solvent compatible with water The composite of RVO ₄ is obtained by wet mixing and pulverizing in an aqueous solvent containing a controlled amount of water including the amount of water generated by reaction in the pulverizing process depending on the type of the organic solvent. A composite hydroxide or composite oxide hydroxide that is a precursor of oxide is prepared, and a slurry obtained by wet mixing and pulverizing in the above aqueous solvent is subjected to solvothermal treatment to obtain a crystallized product without heat treatment. In other words, the present inventors have found that a crystallized product can be obtained without heat treatment at a high temperature.

  If desired, the same effect as the solvothermal treatment can be obtained by heating (refluxing) the slurry that has been wet-mixed and pulverized in an aqueous solvent at normal pressure instead of the solvothermal treatment as described above. The present inventors have found a further aspect of the present invention.

On the other hand, for the vanadate-based composite oxide represented by RVO ₃ , the raw material containing the oxide of the element occupying the R site and the oxide of vanadium is used as an organic solvent compatible with water that does not substantially contain water. By preparing a precursor of the vanadate composite oxide by wet mixing and pulverizing in the process, and then subjecting this wet mixed and pulverized slurry to a solvothermal process, a crystallized product can be obtained without heat treatment at a high temperature. The present inventors have found that the present invention can be accomplished and have completed the present invention.

In the production method of the present invention, the element occupying the R site is at least one element of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, or Lu. It is suitable for a case where an industrially useful complex oxide such as a rare earth vanadate complex oxide, particularly a rare earth vanadate complex oxide represented by LaVO ₄ or LaVO ₃ , is used.

  The production method of the present invention (wet mixing and grinding treatment step, solvothermal treatment step or heating (reflux) treatment step, and optionally heat treatment step) can be performed without using special equipment or expensive raw materials, Further, since only water is produced as a by-product, no special removal step is required. Therefore, a high-quality vanadate-based complex oxide crystallized product that does not contain impurities that cause performance degradation in various applications can be produced inexpensively and efficiently without a treatment or a heat treatment step at a high temperature.

X-ray diffraction pattern of crystallized LaVO ₄ composite oxide single phase after vacuum drying (no heat treatment) in Example 1 (in Comparative Example 1, it is La (OH) ₃ or an impurity phase other than LaVO ₄ It is included.) X-ray diffraction pattern of LaVO ₄ composite oxide after heat treatment in Example 1 (in air, 200 to 1200 ° C., both LaVO ₄ single phase) X-ray diffraction pattern of crystallized LaVO ₄ composite oxide single phase after vacuum drying (no heat treatment) in Example 2 X-ray diffraction pattern of crystallized LaVO ₄ composite oxide after vacuum drying (no heat treatment) in Example 3 (La (OH) _{3 in} Comparative Example 2) X-ray diffraction pattern of LaVO ₄ composite oxide after heat treatment in Example 3 (in the atmosphere, 200 to 600 ° C., both LaVO ₄ single phase) LaVO ₃ complex oxide X-ray diffraction pattern after heat treatment in Example 4 (in 1% H ₂ / N ₂ , 800 ° C., as Comparative Example 3, in air and argon, 800 ° C.)

Vanadate-based complex oxide The vanadate-based complex oxide that is the object of the production method of the present invention has a general formula RVO ₄ or RVO ₃ (wherein R is occupied by at least one element selected from rare earth elements, and V is Vanadium element).

In the production method of the present invention, the element occupying the R site is at least one element of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, or Lu. This is suitable for rare earth vanadate composite oxides, particularly vanadate composite oxides represented by LaVO ₄ or LaVO ₃ (R site is La).

As a raw material component of the rare earth element occupying the raw material R site [Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu], an oxide of these rare earth elements [R ₂ O ₃ , RO ₂ ], hydroxide [R (OH) ₃ , R (OH) ₄ ], and oxide hydroxide [RO (OH), ROOH]. In addition, the above compounds include those containing crystal water [R ₂ O ₃ · nH ₂ O, RO ₂ · nH ₂ O, R (OH) ₃ · nH ₂ O, R (OH) ₄ · nH ₂ O, n is a positive number], and for rare earth hydroxides and rare earth oxide hydroxides, non-stoichiometric rare earth oxide hydrates [R ₂ O ₃ .XH ₂ O, RO ₂ .XH ₂ O and X are arbitrary positive numbers]. These substances may be crystalline or amorphous. Any one of the rare earth element occupying the R site may be used alone, or two or more may be used in combination.

As a raw material component of V (vanadium element), vanadium oxide [VO, V ₂ O ₃ , VO ₂ , V ₂ O ₅ , V ₃ O ₄ , V ₃ O ₇ , V ₄ O ₉ ], hydroxide [V (OH) ₅ , V (OH) ₄ , V (OH) ₃ , V (OH) ₂ ], oxide hydroxide [VO (OH), VO (OH) ₂ , VO (OH) ₃ , VO ₂ (OH)]. The above compound contains water of crystallization [V ₂ O ₅ · nH ₂ O, VO ₂ · nH ₂ O, V ₂ O ₃ · nH ₂ O, VO · nH ₂ O, V ₃ O ₄ · nH ₂ O, V (OH) ₅ · nH ₂ O, V (OH) ₄ · nH ₂ O, V (OH) ₃ · nH ₂ O, V (OH) ₂ · nH ₂ O, n is a positive number] In addition, non-stoichiometric oxide hydrates [V ₂ O ₅ · XH ₂ O, VO ₂ · XH ₂ O, V ₂ O ₃ · XH ₂ O, V ₃ O ₄ .XH ₂ O, where X is an arbitrary positive number] is also included. These substances may be crystalline or amorphous. As the raw material component of the element occupying the V site, any one kind may be used alone, or two or more kinds may be used in combination.

The particle size of the material used as the raw material is preferably 100 μm or less, more preferably 50 μm or less, and still more preferably 10 μm or less. When an oxide is used as a raw material, hydration or hydroxide formation occurs in the process of wet mixed pulverization and the particle size becomes small, so there is no problem even if the initial particle size is large.
Moreover, the compounding quantity of each component of a raw material should just make the quantitative ratio in the raw material of R site and vanadium (V) the same as the quantitative ratio in the target complex oxide.

Wet mixed pulverization treatment The wet mixed pulverization treatment in the present invention is generally carried out in an aqueous solvent using a mixing pulverizer.

  An aqueous solvent is a solvent (grinding medium) that is placed in a grinding container together with raw materials when preparing a hydrated precursor (composite hydroxide or composite oxide hydroxide) by a mixed grinding process, and is compatible with water. A solvent in which water is mixed with an organic solvent.

  The organic solvent compatible with water is not particularly limited, but alcohols (methanol, ethanol, propanol, butanol, etc.), ethers (diethyl ether, tetrahydrofuran, etc.), ketones (acetone, methyl ethyl ketone, diethyl) Ketone) and the like. Any one of these organic solvents may be used alone, or two or more thereof may be used in combination.

  As the organic solvent compatible with water, it is desirable to employ an organic solvent having an appropriate relative dielectric constant depending on the raw material and the processing conditions of wet mixing and pulverization. If the relative permittivity of the organic solvent is in an appropriate range, the dispersibility of the pulverized product in the aqueous solvent will not be too high, and a uniform hydrated precursor of the vanadate composite oxide can be obtained.

  If a mixed liquid of water and organic solvent (benzene, toluene, xylene, etc.) that is not compatible with water is used as the grinding fluid, the raw material powder will adhere to the inside of the mixing and grinding machine, and the mixing and grinding process Although the efficiency may be significantly reduced, an organic solvent that is not compatible with water can be blended with an aqueous solvent if it is used in combination with an organic solvent that is compatible with water.

In the RVO ₄ production method, in order to obtain an RVO ₄ composite oxide single phase without heat treatment by a wet mixing and pulverization step and a solvothermal treatment step or a heating step, among the above organic solvents, organic solvents other than alcohols And an amount of water in the aqueous solvent is not less than 0.25 times the stoichiometric molar amount necessary to produce the RV (OH) ₈ composite hydroxide. Therefore, it is necessary to limit the amount to 1.0 times or less. Below the 0.25 molar amount, only the R (OH) ₃ phase is produced, and no RVO ₄ is produced. _{On the} other hand, when the molar amount is more than 1.0 times, an impurity phase that is considered to be a hydrate of RVO ₄ is mixed in addition to RVO ₄ .

It is considered that the solvothermal treatment step or the heat treatment step has an effect of promoting dehydration from RV (OH) ₈ composite hydroxide to RVO ₄ . In addition, although the said heat processing process is typically performed by recirculation | reflux, it is not limited to this. For example, in the following hydroxylation reaction of La ₂ O ₃ , since the free energy change is −60 kJ / mol or more, the hydroxide is very stable, and in order to suppress the formation of RVO ₄ hydrate, It is necessary to limit the amount of water added (1.0 times the molar amount or less). However, it is necessary to add water to such an extent that no unreacted La ₂ O ₃ remains in the wet mixing and pulverization step (0.25 molar amount or more).
La ₂ O ₃ + 3H ₂ O → 2La (OH) ₃

In addition, when using an aqueous solvent (alcohol aqueous solvent) mixed with alcohols, the amount of water in the aqueous solvent is the chemical amount necessary to produce RV (OH) ₈ composite hydroxide. by increasing the pudding molar amount (1.0-fold molar amount), it is possible to obtain the LaVO ₄ composite oxide single phase RVO ₄ without the heat treatment by a wet mixing and grinding process and solvothermal process. Below 1.0 molar amount, only the R (OH) ₃ phase is produced and no RVO ₄ is produced.

In the case of using an alcohol-based aqueous solvent, it is considered that the following reaction proceeds between V ₂ O ₅ and the alcohol-based solvent in the wet mixing and pulverizing step, and vanadium oxyalkoxide is generated (J. Phys. Chem., 64, 1756 (1960)).

このバナジウムオキシアルコキシドを、湿式混合粉砕工程で生成するＲ(ＯＨ)₃と共に加水分解して、熱処理なしにＲＶＯ₄複合酸化物単一相を得るためには、ソルボサーマル処理工程での加水分解を促進のために上記１．０倍モル量より多い水が必要であると考えている。

In order to hydrolyze this vanadium oxyalkoxide together with R (OH) ₃ produced in the wet mixing and pulverizing step to obtain an RVO ₄ composite oxide single phase without heat treatment, hydrolysis in the solvothermal treatment step is performed. We believe that more water than the above 1.0-fold molar amount is required for promotion.

On the other hand, in order to obtain a RVO ₃ composite oxide crystallized product by a wet mixing and pulverization step, a solvothermal treatment step, and a low-temperature heat treatment step, water that does not substantially contain water (the amount of water is reduced to 0). It is necessary to carry out wet mixing and pulverization in an organic solvent compatible with. It is substantially free of water (the amount of water is reduced to 0) means that an oxide is used as a raw material and no hydroxide, oxide hydroxide, crystal water content or hydrate is used, It means that water is not added to the organic solvent, and that the oxide raw material to be used may contain moisture slightly absorbed, or moisture slightly absorbed in the organic solvent. In addition, it is not excluded that water generated as a by-product in the course of the wet mixing and pulverizing treatment described below is added to an organic solvent compatible with water.

When water such as crystallization water is included in the material used as a raw material, the amount of water is also taken into account, and the amount of water initially added to the aqueous solvent is adjusted (from the predetermined amount to the above crystal It is necessary to first add an amount of water minus the amount of water etc.). On the other hand, water by-produced by the reaction of the raw material and the organic solvent in the course of the wet mixing and pulverizing treatment [for example, when vanadium pentoxide (V ₂ O ₅ ) is used as the raw material and acetone or 2-propanol is used as the organic solvent]. As for the amount of, the above considerations shall not be taken.

  The mixing pulverizer may be any material that can mechanically pulverize and grind the raw material. For example, the raw material and a pulverizing medium (rod, cylinder, ball, bead, etc.) are placed in a pulverization container. A ball mill such as a rolling ball mill, a vibration ball mill, a stirring ball mill, or a planetary ball mill that pulverizes the raw material by stirring is suitable. Crushers with such a ball mill as a continuous type (for example, “SC Mill” manufactured by Mitsui Mining Co., Ltd., “Dyno Mill” manufactured by Shinmaru Enterprises Co., Ltd.), and very small balls (beads) having a diameter of 1 mm or less. A ball mill that can be used is also recommended.

As balls (beads) which are typical grinding media, ZrO ₂ (zirconia), Si ₃ N ₄ (silicon nitride), SiC (silicon carbide), WC (tungsten carbide), having a diameter of about 0.1 to 10 mm, For example, a zirconia ball “YTZ” (registered trademark) manufactured by Tosoh Corporation is preferable.

  What is necessary is just to adjust the process conditions of wet-mixing grinding suitably according to the kind of mixing-grinding machine. For example, when a planetary ball mill is used, the filling amount of balls (beads) as a grinding medium is 15 to 60 mL, the total filling amount of the aqueous solvent and the raw material is 10 to 30 mL per 100 mL of the container volume, and the aqueous solvent It is preferable that the concentration of the raw material in the mixture of the raw material is 2 to 30% by volume. Further, the revolution speed of the planetary ball mill is usually 1 to 10 Hz, preferably 4 to 6 Hz, and the processing time for the mixing and grinding is preferably 1 to 10 hours.

Solvothermal treatment or heating (reflux) treatment step The method for producing a composite oxide of the present invention is obtained by a step of preparing a composite hydroxide or a composite oxide hydroxide which is a precursor of the composite oxide as described above. The aqueous solvent slurry (in the case of RVO ₄ ) or the slurry (in the case of RVO ₃ ) obtained by wet mixing and pulverization in an organic solvent compatible with water substantially free of water is subjected to solvothermal treatment. Process or heating (reflux) treatment process.

  As the solvent for the solvothermal treatment, the conditions of the aqueous solvent used for the mixing and grinding treatment can be applied as they are. The treatment temperature is suitably maintained at the boiling point or higher of the aqueous solvent at atmospheric pressure, usually 200 ° C. or lower, preferably 150 ° C. or lower, for reaction. If the reaction temperature is too low, a crystalline product may not be obtained. On the other hand, if the reaction temperature is too high, the solvothermal treatment container becomes expensive and not industrial. The normal processing pressure is the vapor pressure of the aqueous solvent at the processing temperature. It is desirable to appropriately select temperature conditions and pressure conditions suitable for the composition of the target compound. The treatment time is usually 4 to 48 hours, preferably 8 to 24 hours.

  Although a reaction vessel used for solvothermal treatment, when a batch-type mixing and grinding machine is used, the grinding vessel can be sealed and used as it is, and heated. When a continuous mixing and grinding machine is used, the slurry can be transferred to an autoclave and subjected to solvothermal treatment. It will not specifically limit if the said processing temperature and processing pressure are obtained.

  When performing a heating (refluxing) treatment step at normal pressure instead of the solvothermal treatment step, it is desirable that the heating (refluxing) temperature be 60 ° C. or more and 200 ° C. or less, preferably 150 ° C. or less. If the heating (reflux) temperature is too low, a crystalline product cannot be obtained, and heating (refluxing) for a long time is required to obtain a crystalline product, which is not industrial. For example, when the mixture is pulverized and vacuum-dried at 120 ° C. after suction filtration, the crystallinity is low even if it is ventilated for 4 days or more for crystallization. For example, when a heating (refluxing) treatment step at normal pressure in a solvent of acetone (boiling point: 56 ° C.) is performed, crystallization starts after heating (refluxing) for 16 hours, but the crystallinity is low. In such a case, an organic solvent having a high boiling point [for example, toluene (boiling point: 110 ° C.)] is added to the aqueous slurry after the mixing and pulverizing treatment, and a heating (refluxing) treatment step at normal pressure is performed. Is preferably increased. On the other hand, if the heating (refluxing) temperature is too high, the heating medium and the like are expensive and not industrial.

After the wet mixing and pulverizing treatment as described above, the product after the solvothermal treatment or heating (refluxing) treatment is filtered and dried, so that a single phase of the crystallized RVO ₄ composite oxide or a low temperature The precursor that crystallizes into the RVO ₃ composite oxide by heat treatment can be recovered.

  The filtration method may be appropriately selected from general methods such as pressure filtration, suction filtration, and centrifugal separation. The drying method may be any method such as normal ventilation drying and vacuum drying. In the wet mixed pulverization treatment of the present invention, no by-products other than water (salts, etc.) are generated in the aqueous solvent. Therefore, after the wet mixed pulverization treatment, the slurry after the solvothermal treatment or heating (reflux) treatment is evaporated to dryness. It is also possible to dry by spray drying or the like. Although drying temperature is not specifically limited, 50-200 degreeC is preferable.

The crystallized RVO ₄ composite oxide prepared by solvothermal treatment or heat (reflux) treatment after the heat treatment wet mixing and pulverization treatment has high crystallinity without heat treatment, and the heat treatment can be omitted. It is possible to further improve the crystallinity or change the crystal phase by heat treatment in the medium. Whether or not heat treatment is required may be determined as desired.

The precursor that crystallizes into the RVO ₃ composite oxide by low-temperature heat treatment requires heat treatment in a reducing atmosphere such as H ₂ or CO. This is because the heat treatment in the atmosphere or an inert gas atmosphere such as argon or nitrogen causes crystallization to RVO ₄ instead of RVO ₃ .

  As described above, the heat treatment conditions (temperature, atmosphere, time, etc.) need to be adjusted as appropriate according to the desired aspect of the vanadate composite oxide (composite oxide composition, crystallization rate, specific surface area, etc.). is there. The temperature of the heat treatment is preferably 200 to 1000 ° C. Note that the crystallinity of the vanadate complex oxide can be confirmed by an X-ray diffraction pattern (presence or absence of a predetermined peak).

[Example 1] LaVO ₄ solvothermal process
To Kurimoto Seiko planetary ball mill (stainless steel pot, volume 420 mL), raw powder La ₂ O ₃ 10.3 g and V ₂ O ₅ 5.7 g, ₂ mmφYTZ ^(R) ball (Tosoh Corp.) 168 mL, Acetone 67 mL, water 2.3 mL (corresponding to 0.5 molar amount of stoichiometric mole) or 4.5 mL (corresponding to 1.0 molar amount of stoichiometric molar amount) (Comparative Example 1; water 0 mL) Alternatively, 6.8 mL (corresponding to 1.5 times the molar amount of the stoichiometric molar amount)) was filled, and the treatment for 3 hours was performed at the revolution and rotation speed of 6 Hz. The mixing and pulverizing vessel was sealed, and solvothermal treatment was performed at 120 ° C. for 16 hours. (The pressure in the sealed container at this time is a self-generated pressure due to heating of the aqueous solvent.) After suction-filtering the solvothermally treated product, vacuum drying is performed at 85 ° C. for 12 hours to crystallize into a monoclinic system. LaVO ₄ single phase was obtained. (Comparative Example 1;. A small amount of LaVO ₄ hydrate was mixed to obtain a LaVO ₄ crystallized in the monoclinic system) specific surface area, when the water 2.3mL added 27m ² / g, water 54. It was 54 m ² / g when 5 mL was added. (Comparative Example 1;. Water 0mL was 52m ² / g when 18m ² /g,6.8mL when) as compared with Comparative Example 1 The X-ray diffraction pattern after vacuum drying shown in FIG. [La (OH) ₃ phase is observed in the X-ray diffraction pattern when 0 mL of water is added, because water partially contained in the oxide raw material or organic solvent and V ₂ O ₅ and acetone partially react (CH ₃ COCH ₃ + 4V ₂ O ₅ → 3CO ₂ + 3H ₂ O + 4V ₂ O ₃ ) is considered to be due to the hydroxylation of La ₂ O ₃ . FIG. 2 shows the heating change of the X-ray diffraction pattern when heat treatment is performed for 1 hour at various temperatures in the atmosphere when 4.5 mL of water is added. At any heating temperature, it was a monoclinic LaVO ₄ single phase.

[Example 2] LaVO ₄ heating (reflux) treatment
To Kurimoto Seiko planetary ball mill (stainless steel pot, volume 420 mL), raw powder La ₂ O ₃ 10.3 g and V ₂ O ₅ 5.7 g, ₂ mmφYTZ ^(R) ball (Tosoh Corp.) 168 mL, 70 mL of acetone and 4.5 mL of water (corresponding to 1.0 times the molar amount of the stoichiometric amount) were filled, and a revolution and a rotational speed of 6 Hz were performed for 3 hours. The mixed and pulverized slurry was transferred to a 4-diameter round bottom flask, 225 mL of toluene was added, heat (reflux) treatment was performed at 110 ° C. for 16 hours, suction filtration, and vacuum drying at 85 ° C. for 12 hours. Single-phase LaVO ₄ crystallized in a monoclinic system was obtained. The specific surface area after vacuum drying was 48 m ² / g. FIG. 3 shows X-ray diffraction patterns when heat treatment is performed for 1 hour at various temperatures in the atmosphere. At any heating temperature, it was a monoclinic LaVO ₄ single phase.

[Example 3] LaVO ₄ solvothermal process
To a planetary ball mill manufactured by Kurimoto Seiko Co., Ltd. (stainless steel pot, capacity 420 mL), 10.3 g of raw material powder La ₂ O ₃ and 5.7 g of V ₂ O ₅ , ₂ mmφYTZ® ball (Tosoh Corp.) 168 mL, 2-propanol 67 mL, water 6.8 mL (corresponding to 1.5 times the molar amount of stoichiometric amount) (Comparative Example 2; 0 mL, 2.3 mL (corresponding to 0.5 times the molar amount of stoichiometric amount) ) Or 4.5 mL (corresponding to 1.0 times the stoichiometric molar amount)), and subjected to revolution and rotational speed of 6 Hz for 3 hours. The mixing and pulverizing vessel was sealed, and solvothermal treatment was performed at 120 ° C. for 16 hours. (The pressure in the sealed container at this time is a self-generated pressure due to heating of the aqueous solvent.) After suction-filtering the solvothermally treated product, vacuum drying is performed at 85 ° C. for 12 hours to crystallize into a monoclinic system. A single phase of LaVO ₄ was obtained (FIG. 4). The specific surface area was 71 m ² / g. (Comparative Example 2; both are amorphous lanthanum hydroxide [La (OH) ₃ ] crystalline phase. The La (OH) ₃ phase is observed in the X-ray diffraction pattern when 0 mL of water is added. Moisture slightly contained in organic solvent and V ₂ O ₅ and 2-propanol partially react [V ₂ O ₅ +6 (CH ₃ ) ₂ CHOH → 2 ((CH ₃ ) ₂ CH) ₃ VO ₄ + 3H It is thought that the water generated by ₂ O)] hydroxylates La ₂ O ₃ . )
FIG. 5 shows changes in the X-ray diffraction pattern when heat-treated at various temperatures in the atmosphere for 1 hour. Each was a single phase of LaVO ₄ crystallized in a monoclinic system and had a specific surface area of 47 m ² / g when heated at 600 ° C. for 1 hour.

[Example 4] LaVO ₃ solvothermal process
Kurimoto Yokosho planetary ball mill (stainless steel pot, capacity 420 mL), raw material powder La ₂ O ₃ 10.3 g and V ₂ O ₅ 5.7 g, ₂ mmφYTZ ^(R) ball (Tosoh Corporation) 168 mL, Acetone 74 mL was charged, and the revolution and rotation speed were 6 Hz, and the treatment was performed for 3 hours. The mixing and pulverizing vessel was sealed, and solvothermal treatment was performed at 120 ° C. for 16 hours. The treated product was subjected to suction filtration, and then vacuum dried at 85 ° C. for 12 hours to obtain a LaVO ₃ composite oxide precursor.

FIG. 6 shows the X-ray diffraction pattern of the LaVO ₃ composite oxide precursor heated at 800 ° C. for 1 hour in a 1% H ₂ / N ₂ atmosphere at 800 ° C. in air and argon as Comparative Example 3. X-ray diffraction pattern when heated for 1 hour is shown.) It was a tetragonal single phase of LaVO ₃ composite oxide. The specific surface area was 7.0 m ² / g.

Claims (7)

A method for producing a vanadate-based composite oxide represented by a general formula RVO ₄ (wherein R is occupied by at least one element selected from rare earth elements and V is a vanadium element),
A raw material containing at least one of an oxide, hydroxide or oxide hydroxide of an element occupying an R site, and at least one of vanadium oxide, hydroxide or oxide hydroxide , Which is compatible with water other than alcohol and 0.25 to 1.0 mole amount of the stoichiometric mole amount required to produce RV (OH) ₈ composite hydroxide. By including a step of preparing the precursor of the vanadate-based composite oxide by wet mixing and pulverizing in a non-alcohol-based aqueous solvent containing an organic solvent, and a step of solvothermally treating the aqueous solvent slurry. A method for producing a vanadate composite oxide, which directly obtains a crystallized product of the vanadate composite oxide. A method for producing a vanadate-based composite oxide represented by a general formula RVO ₄ (wherein R is occupied by at least one element selected from rare earth elements and V is a vanadium element),
A raw material containing at least one of an oxide, hydroxide or oxide hydroxide of an element occupying an R site, and at least one of vanadium oxide, hydroxide or oxide hydroxide , Which is compatible with water other than alcohol and 0.25 to 1.0 mole amount of the stoichiometric mole amount required to produce RV (OH) ₈ composite hydroxide. Including a step of preparing a precursor of the vanadate-based composite oxide by wet mixing and pulverizing in a non-alcohol-based aqueous solvent containing an organic solvent, and a step of heat-treating the aqueous solvent slurry at normal pressure Thus, a method for producing a vanadate-based composite oxide, wherein the crystallized product of the vanadate-based composite oxide is directly obtained. A method for producing a vanadate-based composite oxide represented by a general formula RVO ₄ (wherein R is occupied by at least one element selected from rare earth elements and V is a vanadium element),
A raw material containing at least one of an oxide, hydroxide or oxide hydroxide of an element occupying an R site, and at least one of vanadium oxide, hydroxide or oxide hydroxide , by wet mixing and pulverizing treatment with alcoholic aqueous solvent containing stoichiometric molar amount greater than water and water-compatible with certain alcohols required to generate the RV (OH) ₈ complex hydroxide, Including the step of preparing a precursor of the vanadate-based composite oxide, and the step of solvothermally treating the alcohol-based aqueous solvent slurry, to obtain a crystallized product of the vanadate-based composite oxide directly. A method for producing a vanadate composite oxide. A method for producing a vanadate-based composite oxide represented by a general formula RVO ₃ (wherein R is occupied by at least one element selected from rare earth elements and V is a vanadium element),
A raw material consisting of oxides of elements occupying R sites (excluding crystallization water-containing substances and hydrates) and vanadium oxides (excluding crystallization water-containing substances and hydrates) , substantially containing water Including a step of preparing a precursor of the vanadate-based composite oxide by wet mixing and pulverizing in an organic solvent compatible with water, and a step of solvothermally processing the wet mixed pulverizing slurry. A method for producing a vanadate-based composite oxide, which is characterized.   Any one of Claims 1-4 including the process of heat-processing the non-crystallized thing or crystallized thing of the vanadate type complex oxide obtained by the processing process in any one of Claims 1-4. The manufacturing method of vanadate type complex oxide as described in 2.   The element occupying the R site is at least one element of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, or Lu. The manufacturing method of the vanadate type complex oxide in any one of. Manufacturing method of the vanadate-based composite oxide is represented by LaVO ₄ or LaVO _3, vanadate-based composite oxide according to claim 1.

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