JP2020142968A - Method for producing metal oxysulfide - Google Patents

Abstract

To provide a method for producing a metal oxysulfide, capable of producing the metal oxysulfide in which defects and contamination of by-products are prevented.SOLUTION: A method for producing a metal oxysulfide containing a component for preventing hydrogen sulfide from being decomposed or a mechanism for collecting hydrogen includes a step of reacting a metal oxide-containing raw material 16 with hydrogen sulfide in a reactor 10 to produce the metal oxysulfide, AaBbOcSd, wherein: A contains one or more selected from the group comprising Y, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, and La; B contains one or more selected from the group comprising Ti, Nb, Ta, and La; 1.7≤a≤2.3, 1.7≤b≤2.3, c=5, and 1.7≤d≤2.3.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing a metallic acid sulfide.

Metallic acid sulfide A ₂ B ₂ O ₅ S ₂ (A is Y, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, La, and B is one or a combination of two or more. One or a combination of two or more of Ti, Nb, Ta, and La) is a useful substance used for semiconductors, photocatalysts, reaction electrodes, and the like.

A ₂ B ₂ O ₅ S ₂ is a metallic acid sulfide, and a production method (Patent Document 1) in which hydrogen sulfide gas (H ₂ S) is used as a sulfur source at the time of production thereof is known, for example. Patent Document 1 discloses a technique for obtaining a Y · Er acid sulfide by heating a co-precipitate of Y and Er in a mixed atmosphere of hydrogen sulfide and nitrogen. Further, a production method (Patent Document 2) in which a metal sulfide and sulfur powder are used as a sulfur source for reaction is known. For example, in Patent Document 2, sulfur powder is added to a mixed oxide powder of Gd and Pr. A technique for obtaining Gd ₂ O ₂ S: Pr phosphor powder by calcining a mixture is disclosed.
When metal sulfide or sulfur powder is used as a sulfur source as in the latter method described above, the reaction is carried out in a vacuum, and in many cases, the reaction is carried out in a glass container or the like in a vacuum seal and fired. The possible amount is also limited due to the problem of pressure resistance of the glass container, and a long firing time of 2 to 10 days is required to obtain the desired acid sulfide A ₂ B ₂ O ₅ S _2. It is also known.
On the other hand, when hydrogen sulfide gas is used as a sulfur source as in the former method, the raw material is not vacuum-sealed by simply firing the flow gas of a normal atmosphere control furnace as hydrogen sulfide. In addition, it is known that the metallic acid sulfide A ₂ B ₂ O ₅ S ₂ can be obtained in an extremely short time of about several hours.

Japanese Unexamined Patent Publication No. 09-235547 Japanese Unexamined Patent Publication No. 2004-204503

In the method for producing a metal oxysulfide _{A 2 B} 2 _O 5 _S 2 using the above hydrogen sulfide gas to sulfur source, _{H 2} metal oxysulfide is obtained with _{H 2} produced by the decomposition of S _A 2 _{B 2} The B element of O ₅ S ₂ takes an electronic state in which it is partially reduced, for example, the B element is reduced, the valence of the cation becomes smaller, and a defect structure such as loss of anion (oxygen or sulfur) occurs. It ends up. Such a defect structure is not desirable because it hinders the transfer of electrons when considering the function as a semiconductor material.

Therefore, an object of the present invention is to provide a method for producing a metallic acid sulfide, which can produce a metallic acid sulfide in which the generation of defective structures is suppressed.

In the production of metallic acid sulfide A ₂ B ₂ O ₅ S ₂ using hydrogen sulfide gas as a sulfur source, the present inventors have generated metallic acid sulfide A ₂ by H ₂ produced by decomposition of H ₂ S. B ₂ O ₅ S ₂ was reduced, and as a result, it was found that a defective structure was generated and impurities were further generated, and the present invention was reached.
That is, the present invention provides a mechanism for suppressing hydrogen gas production or collecting hydrogen gas in the reaction atmosphere when producing metallic acid sulfide A ₂ B ₂ O ₅ S ₂ using hydrogen sulfide gas as a sulfur source. built, deficiency or anions, deterioration of crystallinity due to the reduction of H _2, prevents deviates from stoichiometry deviation from the composition, the valence should have the element B, or the photocatalytic higher than the reaction electrode performance We have found that it is possible to supply the metallic acid sulfide A ₂ B ₂ O ₅ S ₂ capable of exhibiting the above, and have reached the present invention.

That is, the gist of the present invention is as follows.
[1] One or more selected from the group consisting of A _a B _{b Oc} S _d (A is Y, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er and La) which is _a metallic acid sulfide. B comprises one or more selected from the group consisting of Ti, Nb, Ta and La, 1.7 ≦ a ≦ 2.3, 1.7 ≦ b ≦ 2.3, c = 5, 1.7 ≦ d ≦ 2.3) is produced by reacting a metal oxide-containing raw material with hydrogen sulfide in a reaction furnace, and the step is at least one of the following M1 to M4. A method for producing a metallic acid sulfide, including one.
M1: The metal oxide-containing raw material contains a component that suppresses the decomposition of hydrogen sulfide.
M2: The atmospheric gas introduced into the reactor contains a component that suppresses the decomposition of hydrogen sulfide.
M3: In the reactor, there is a substance that generates a component that suppresses the decomposition of hydrogen sulfide, in addition to the metal oxide-containing raw material.
M4: A mechanism for collecting hydrogen is provided in the reactor separately from the metal oxide-containing raw material.
[2] The metal acid sulfide according to [1], wherein the metal oxide-containing raw material contains a metal oxide-containing raw material having a stoichiometric composition having less sulfur than the stoichiometric composition of the metal acid sulfide. Manufacturing method.
[3] The method for producing a metallic acid sulfide according to [1] or [2], wherein the atmospheric gas in M2 is a mixed gas containing hydrogen sulfide and sulfur.
[4] The method for producing a metallic acid sulfide according to any one of [1] to [3], wherein A contains Y.
[5] The method for producing a metallic acid sulfide according to any one of [1] to [4], wherein the B contains Ti.
[6] The A contains Y and the content of Y in A is 80 mol% or more, and the B contains Ti and the content of Ti in B is 80 mol% or more. 1] The method for producing a metallic acid sulfide according to any one of [5].

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a method for producing a metallic acid sulfide, which can produce a metallic acid sulfide in which the generation of defective structures is suppressed.

This is an example of a reaction system to which the method for producing a metallic acid sulfide according to an embodiment of the present invention can be applied. It is a graph which showed the measurement result of the ultraviolet-visible diffuse reflection spectrum of each powder sample in Examples 1 and 2 and Comparative Example 1.

The embodiments of the present invention will be described in detail below, but these descriptions are examples (representative examples) of the embodiments of the present invention, and the present invention is not limited to these contents as long as the gist thereof is not exceeded.
In the present invention, all the materials used for producing the metallic acid sulfide, including the metal oxide-containing raw material and hydrogen sulfide, may be collectively referred to as "raw material".

The method for producing a metallic acid sulfide according to an embodiment of the present invention (hereinafter, also simply referred to as “method for producing a metallic acid sulfide”) is A _a B _{b Oc} S _d (A) which is a metallic acid sulfide. Contains one or more selected from the group consisting of Y, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er and La, and B is selected from the group consisting of Ti, Nb, Ta and La. 1.7 ≦ a ≦ 2.3, 1.7 ≦ b ≦ 2.3, c = 5, 1.7 ≦ d ≦ 2.3), including one or more of them, in a reactor. A metal comprising a step of reacting a metal oxide-containing raw material with hydrogen sulfide (hereinafter, also referred to as a “reaction step”), and the step including at least one of the following M1 to M4. This is a method for producing acid sulfide.
M1: The metal oxide-containing raw material contains a component that suppresses the decomposition of hydrogen sulfide.
M2: The atmospheric gas introduced into the reactor contains a component that suppresses the decomposition of hydrogen sulfide.
M3: In the reactor, there is a substance that generates a component that suppresses the decomposition of hydrogen sulfide, in addition to the metal oxide-containing raw material.
M4: A mechanism for collecting hydrogen is provided in the reactor separately from the metal oxide-containing raw material.

In the method for producing a metallic acid sulfide according to the above embodiment, hydrogen sulfide gas (H ₂ S) has the following reaction formula at a place where a reaction for producing the metallic acid sulfide A _a B _b O _c S _d is occurring. By the reaction represented by (1), a mechanism for suppressing the reaction in which hydrogen sulfide gas produces reducing hydrogen gas or for collecting hydrogen gas is introduced, and the target product, A _a B _{b Oc} S, is introduced. _This is to prevent defects and by-products from being mixed in _d .

Suppressing the reaction of hydrogen sulfide gas to produce reducing hydrogen gas or introducing a mechanism for collecting hydrogen gas corresponds to including at least one of M1 to M4 shown below.
M1: The metal oxide-containing raw material contains a component that suppresses the decomposition of hydrogen sulfide.
M2: The atmospheric gas introduced into the reactor contains a component that suppresses the decomposition of hydrogen sulfide.
M3: In the reactor, there is a substance that generates a component that suppresses the decomposition of hydrogen sulfide, in addition to the metal oxide-containing raw material.
M4: A mechanism for collecting hydrogen is provided in the reactor separately from the metal oxide-containing raw material.
The details of the metallic acid sulfide, the reaction process, the above M1 to 4 and the like will be described below.

<1. Metallic acid sulfide>
The metallic acid sulfide produced by the above embodiment is a metallic acid sulfide represented by A _a B _{b Oc} S _d .
A is Y (yttrium), Pr (placeodium), Nd (neodymium), Sm (samarium), Gd (gadolinium), Tb (terbium), Dy (dysprosium), Ho (holmium), Er (erbium), La ( It is one or a combination of two or more from lantern).
In particular, among these, it is preferable to include Y, Sm, Gd, Tb, Ho, Er, more preferably Y, Sm, and most preferably Y.
The content of Y in A is preferably 60 mol% or more, more preferably 70 mol% or more, and particularly preferably 80 mol% or more. The stability of the compound is most preferably 100 mol%, but another element may be added to improve the properties such as the life as a catalyst, in which case the addition amount is 20 mol. % Or less, more preferably 10 mol% or less. Further, from the viewpoint of crystal stability, a is 1.7 ≦ a ≦ 2.3, but most preferably 1.8 ≦ a ≦ 2.2.
Further, when A is a combination of two or more kinds of metal elements, it can be expressed as A1 _a1 A2 _a2 , and the value of a can be specified for each metal element, and each of them can be specified. The range of a above can be specified with respect to the total value (a1 + a2) of a. For example, A _a can be expressed as Y _1.5 Pr _0.5 .

B is one or a combination of two or more of Ti (titanium), Nb (niobium), Ta (tantalum), and La (lanthanum). In particular, among these, it is preferable to contain Ti. This is because Ti is likely to change from the original tetravalence to trivalence due to the influence of excessive H ⁺ , and thus the effect of the production method of the present invention is particularly remarkable. The content of Ti in B is preferably 60 mol% or more, more preferably 70 mol% or more, and particularly preferably 80 mol% or more. The stability of the compound is most preferably 100 mol%, but another element may be added to improve the properties such as the life as a catalyst, in which case the addition amount is 20 mol. % Or less, more preferably 10 mol% or less.
La can be used as both A and B. Therefore, when La is contained, it is sufficient to look at the cation element and the anion element that are contained at the same time and determine how much of the cation element is contained from the balance of the electric charges.

It is particularly preferable that A contains Y and B contains Ti, and the content of Y in A is high from the viewpoint of stabilizing the crystal structure that a certain amount or more of elements forming a matrix are contained. It is preferable that the content is 80 mol% or more and the Ti content in B is 80 mol% or more.

Further, b is 1.7 ≦ b ≦ 2.3, more preferably 1.8 ≦ b ≦ 2.2.
Further, similarly to A above, when B is a combination of two or more kinds of metal elements, it can be expressed as B1 _b1 B2 _b2 , and the value of b is specified for each metal element. It is also possible to specify the range of b above for the total value (b1 + b2) of each b. For example, B _b can be expressed as Ti _1.5 Nb _0.5 .

c is the amount of oxygen, which is a reference in the general formula of the present invention. Let this value be 5.
d is the amount of sulfur and bears the charge on the anion side together with oxygen. Since the standard with oxygen of 5 is used, some fluctuation is allowed, and 1.7 ≦ d ≦ 2.3, but 1.8 ≦ d ≦ 2.2 is more preferable.
Regarding these compositions, ICP (inductively coupled plasma) emission spectroscopic analysis may be used for cations, and an ONH meter (oxygen / nitrogen / hydrogen analyzer) or carbon / sulfur analyzer may be used for anions.

The use of the metallic acid sulfide A _a B _{b Oc} S _d is not particularly limited, but it can be used, for example, as a magnetic material, a dielectric, a phosphor, a photocatalyst, a reaction electrode, a conductor, a filter pigment, or the like.

<2. Characteristics of metallic acid sulfides>
<2-1. Ultraviolet / visible diffuse reflection spectrum measurement>
By measuring the ultraviolet / visible diffuse reflection spectrum of the above metallic acid sulfide, it is possible to confirm the difference from the metallic acid sulfide produced by the conventional method.
The measurement conditions are not particularly limited, but can be, for example, the following conditions.
Measuring device: V-670 Spectrophotometer (manufactured by JASCO)
・ Measurement range: 300 to 800 mm
-Data interval: 1.0 nm
-Scanning speed: 10000 nm / min-Light source switching: 340.0 nm
-Data analysis software: Spectra Manager version 2
Analysis: Vertical axis is Kbelka-Munch (KM) conversion
Kubelkar-Munch conversion formula f (R _∞ ) = (1-R _∞ ) ² / 2R _∞ = K / S
Here, f (R _∞ ) is K.I. M. The function, R _∞ is the absolute reflectance, K is the molecular extinction coefficient, and S is the scattering coefficient.
It is difficult to measure the absolute reflectance R _∞ of a sample, and in practice, it is common to use the relative reflectance r _∞ using a standard sample. Therefore,
r _∞ = r (measurement sample) / r (standard sample) (BaSO ₄ is used as the standard sample)
The relative reflectance r _∞ was measured using
f (r _∞ ) = (1-r _∞ ) ² / 2r _∞ = K / S
May be derived from.

Metal oxysulfide produced by the above embodiment _{Y a Ti b O c S d} (1.7 ≦ a ≦ 2.3,1.7 ≦ b ≦ 2.3, c = 5,1.7 ≦ If a d ≦ 2.3), the metal oxysulfide, are manufactured by a conventional manufacturing method the _{Y a Ti b O c S d} (1.7 ≦ a ≦ 2.3,1.7 ≦ b ≦ Compared with 2.3, c = 5, 1.7 ≦ d ≦ 2.3), there is a difference on the long wavelength side of the diffuse reflection spectrum. It is presumed that this is because the local reduction of the Ti element was suppressed. Thus, photoactivation of the manufactured in the above embodiment _Y a _Ti b _O c _{S d} becomes excellent.

The production method of the present invention _{also, Y a Ti b O c S} d (1.7 ≦ a ≦ 2.3,1.7 ≦ b ≦ 2.3, c = 5,1.7 ≦ a ≦ 2.3 ), And a metallic acid sulfide having a ratio of the spectral intensity at a wavelength of 600 nm to the maximum value of the spectral intensity at a wavelength of 300 nm or more and less than 600 nm of the ultraviolet / visible diffuse reflection spectrum of 1.7 or more was obtained. However, the photoactivity is excellent.

Hereinafter, the reaction process and details of the above M1 to 4 and the like will be described with reference to FIG. 1 showing a reaction system to which the present embodiment can be applied. However, the reaction system to which the embodiment can be applied is not limited to the embodiment shown in FIG.

<3. Process of reacting a metal oxide-containing raw material with hydrogen sulfide in a reaction furnace to produce>
The above metal acid sulfide is produced by reacting the metal oxide-containing raw material 16 with hydrogen sulfide in the reaction furnace 10.

<3-1. Metal oxide-containing raw materials>
The metal oxide-containing raw material is not particularly limited as long as it contains the above-mentioned elements A and B and O (oxygen), but for example, an oxide (A _a3 O _c3 ) containing an element A and a sulfide (A). _{One or more of a3} S _d3 ) and acid sulfide (A _a3 O _c3 S _d3 ), oxides containing B element (B _b3 O _c3 ), sulfides (B _b3 S _d3 ), acid sulfide One or more of the substances (B _b3 O _c3 S _d3 ), oxides containing A element and B element (A _a3 B _b3 O _c3 ), sulfides (A _a3 B _b3 S _d3 ), acid sulfide A co-precipitation composition containing one or more of the substances (A _a3 B _{b3 Oc3} S _d3 ), A element and B element can be arbitrarily used.
The amounts of the elements A, B, and O in the stoichiometric composition of the metal oxide-containing raw material, that is, the above-mentioned a3, b3, and c3 are not particularly limited, and the above-mentioned target product, a, the metal acid sulfide. It does not have to be the same as b and c, but it is preferable from the viewpoint that a desired metallic acid sulfide can be obtained. Further, the amount of the element S in the stoichiometric composition of the metal oxide-containing raw material, that is, d3 described above is not particularly limited, but is preferably smaller than d of the metal acid sulfide which is the target product.

The method for producing the metal oxide-containing raw material is not particularly limited, and a general method for producing a metal oxide can be adopted. For example, titanium tetraisopropoxide, yttrium nitrate, and citric acid are mixed at 1: 1: 1. The mixture was mixed in an ethylene glycol methanol solution at a ratio of 15, heated to 200 ° C. for polymerization, and then fired in two steps of 350 ° C. and 500 ° C. for 1 hour, respectively, to obtain the precursor oxide Y ₂ Ti _2. O ₇ can be obtained. Moreover, a commercially available product can be used.

The "metal oxide-containing raw material" in the present invention may be a single substance or a mixture of a plurality of substances.
Further, the metal oxide-containing raw material preferably contains a metal oxide-containing raw material having a stoichiometric composition having less sulfur than the stoichiometric composition of the target metal acid sulfide from the viewpoint of suppressing the generation of defect structures. ..
In the present invention, the metal oxide-containing material with a word of the precursor, for example, also referred to as a _{A a} B _b O _c precursor oxide.

From the viewpoint of easy availability, Y ₂ O ₃ or Y ₂ S ₃ Y ₂ S ₂ O is preferable when the A element is Y, and TiO ₂ is preferable when the B element is Ti. .. Further, in the case of an oxide containing an element A and an element B, Y ₂ Ti ₂ O ₇ or the like is used.

The particle size of the metal oxide-containing raw material is not particularly limited, but in general, a smaller particle size is preferable from the viewpoint of improving reactivity and uniformity, and the average particle size on a volume basis is preferably 1 mm or less. It is particularly preferably 5 mm or less, and on the other hand, if it is too small, it becomes difficult to handle. Therefore, the average particle size is preferably 5 nm or more, more preferably 10 nm or more, and particularly preferably 20 nm or more. ..
The volume-based average particle size is a value measured by a laser particle size meter. Here, the volume-based average particle size is a volume-based relative particle when a sample is measured using a particle size distribution measuring device based on the laser diffraction / scattering method and the particle size distribution (cumulative distribution) is obtained. It is defined as the particle size (d50) at which the amount is 50%.

<3-2. Hydrogen sulfide>
The mode of hydrogen sulfide is not particularly limited and may be a gas or a liquid, but from the viewpoint of stability at normal temperature and pressure, a gas, that is, hydrogen sulfide gas is preferable. Regardless of the embodiment, a commercially available product can be used.

<3-3. Reaction furnace ＞
The reaction furnace 10 is not particularly limited as long as it can react the metal oxide-containing raw material with hydrogen sulfide, and a general reaction furnace can be used. For example, a quartz tube furnace or an electric muffle furnace can be used.
Further, the arrangement mode of the metal oxide-containing raw material in the reaction furnace is not particularly limited, but for example, a table or a vessel (for example, the alumina board 14 shown in FIG. 1) or the like is installed in the reaction furnace, and metal oxidation is performed on the table or the device. Material-containing raw materials can also be arranged.

The reaction furnace can be equipped with equipment used for the reaction between the metal oxide-containing raw material and hydrogen sulfide, for example, a heater for accelerating the reaction, a table for placing the metal oxide-containing raw material, and the like. Examples include vessels (for example, alumina boards, platinum boats, etc.).

<3-4. Reaction conditions>
The reaction conditions for reacting the metal oxide-containing raw material 16 placed in the reaction furnace 10 with hydrogen sulfide are shown below.
The reaction pressure in the reactor is not particularly limited, but it is usually 0 because no special equipment is required.
It is 001 MPa or more, preferably 0.005 MPa or more, and most preferably normal pressure. However, due to heating and heat generation during the reaction, the pressure may be higher than normal pressure without any special equipment. The upper limit is usually 100 MPa or less, preferably 50 MPa or less, and most preferably normal pressure as described above.
The reaction temperature in the reaction furnace is not particularly limited, but from the viewpoint of obtaining the target metallic acid sulfide with high purity, it is usually 300 ° C. or higher, preferably 500 ° C. or higher, and preferably 700 ° C. or higher. Is more preferably 800 ° C. or higher, particularly preferably 900 ° C. or higher, while usually 2000 ° C. or lower, preferably 1800 ° C. or lower, and 1400 ° C. or lower. It is more preferably 1300 ° C. or lower, and particularly preferably 1200 ° C. or lower.
As a means for controlling the reaction temperature, a reaction heater 13 can be provided in the reaction furnace as shown in FIG.

When gaseous hydrogen sulfide is used, its flow rate is not particularly limited, but from the viewpoint of advancing a sufficient reaction, it is usually 0.01 l / hour or more, preferably 0.02 l / hour or more, and 0. It is more preferably 03 l / hour or more, further preferably 0.04 l / hour or more, particularly preferably 0.05 l / hour or more, while it is usually 50 l / hour or less, 45 l / hour. It is preferably less than an hour, more preferably 40 l / hour or less, further preferably 30 l / hour or less, and particularly preferably 20 l / hour or less.

When gaseous hydrogen sulfide is used, the flow velocity of the gas containing hydrogen sulfide is not particularly limited, but is usually 0.1 m / S or more from the viewpoint of suppressing the formation of the impurity phase and the scattering of the target sample, which is 0. .2 m / S or more is preferable, 0.3 m / S or more is more preferable, 0.4 m / S or more is further preferable, and 0.5 m / S or more is particularly preferable. On the other hand, it is usually 500 m / S or less, preferably 400 m / S or less, more preferably 300 m / S or less, further preferably 250 m / S or less, and more preferably 200 m / S or less. Is particularly preferable.

The atmosphere in the reaction furnace is not particularly limited, but an inert gas such as nitrogen gas or argon gas can be used for the purpose of improving the yield and uniformity of the target metallic acid sulfide.
In addition, in the above-mentioned M2, the condition of atmospheric gas in the description of M2 described later can be applied.

<4. M1-4>
<4-1. M1>
M1 is that the metal oxide-containing raw material 16 contains a component that suppresses the decomposition of hydrogen sulfide.
The component that suppresses the decomposition of hydrogen sulfide is not particularly limited, and examples thereof include elemental sulfur (S) and metal sulfide. By adding a single sulfur, in the chemical equilibrium in the following formula (1), that is, in the chemical equilibrium between hydrogen sulfide and sulfur and hydrogen which are decomposition products of the hydrogen sulfide, the equilibrium is on the side where hydrogen sulfide is generated. Since it moves, the decomposition of hydrogen sulfide can be suppressed. Addition means, for example, mixing a metal oxide-containing raw material and a component that suppresses the decomposition of hydrogen sulfide.

The amount of sulfur added as a simple substance is not particularly limited, but the total amount of sulfur combined with sulfur in the metal oxide-containing raw material is theoretically required to be calculated from the chemical composition of the target metal acid sulfide. It is preferable that the amount of sulfur is larger than the amount of sulfur. Specifically, the amount of sulfur contained in the metallic acid sulfide when all the metal oxide-containing raw materials are metallic acid sulfides having the chemical quantitative composition of the desired metallic acid sulfide (hereinafter, "metal"). More than the total amount of sulfur (hereinafter, also referred to as "amount of sulfur in the raw material"), which is the sum of the sulfur alone and the sulfur in the metal oxide-containing raw material, than the amount of sulfur in the acid sulfide). It is necessary to become.
The ratio of the amount of sulfur in the raw material to the amount of sulfur in the above metallic acid sulfide is not particularly limited, but is usually 1.05 times or more and 1.5 times or less from the viewpoint of suppressing the formation of the impurity phase. It is preferably 0.05 times or more and 1.2 times or less.

When the amount of elemental sulfur added is excessive, the unreacted component of the sulfur volatilizes, and in the chemical equilibrium in the above formula (1), the equilibrium shifts to the side where hydrogen sulfide is generated. Since sulfur in the reaction furnace is mixed with the metal oxide-containing raw material at this stage, the impurity concentration of elemental sulfur is preferably as low as possible, and the purity is preferably 95% by weight or more, preferably 99% by weight or more. Is more preferable. If the impurities volatilize at the temperature at the time of the reaction and immediately move from the place where the reaction occurs, or if the impurities are stable at the reaction temperature, there is no problem with this degree of purity.

The mode of elemental sulfur is not particularly limited and can be used as a powder (sulfur powder), and a commercially available product can be used for this.

<4-2. M2>
M2 is that the atmospheric gas introduced into the reactor 10 contains a component that suppresses the decomposition of hydrogen sulfide.
The atmospheric gas is not particularly limited, and an inert gas such as nitrogen to which sulfur is added may be used, but a mixed gas of hydrogen sulfide and sulfur is preferable. The mixing ratio of the mixed gas is not particularly limited as long as it contains even a small amount of sulfur, so that it is effective in principle, but it is preferably 5 to 20 vlo% with respect to the sulfur content. The purity of hydrogen sulfide used is preferably 95 vol% or more from the viewpoint of suppressing the formation of an impurity phase. Similarly, when an inert gas is used, 95 vol% or more is preferable.
The gas containing sulfur may be introduced intermittently, or may be continuously introduced during or after the reaction.
Further, the flow rate, the flow velocity, and the like of the atmospheric gas can be the same as the conditions of hydrogen sulfide of the gas in the reaction furnace described above.

<4-3. M3>
M3 means that a substance that generates a component that suppresses the decomposition of hydrogen sulfide is present in the reaction furnace 10 in addition to the metal oxide-containing raw material 16.
As the substance that generates the component, elemental sulfur is preferable, and for example, sulfur powder can be used. In the M3, even if the purity of the sulfur itself is slightly low, the sulfur volatilizes first and remains in the atmosphere as a gas, which is preferable in that impurities are less likely to enter the metal oxide-containing raw material.
The position of the substance that generates the component is not particularly limited, but it is necessary that the substance is present on the gas inflow side of the metal oxide-containing raw material. The mode of "existing" is not particularly limited, and the metal oxide-containing raw material is placed on, for example, a reactor or a table or vessel installed in the reactor (for example, the alumina board 14 shown in FIG. 1). Indicates the state of being.
Further, as shown in FIG. 1, by providing the heater 12 in the reactor 10, the volatilization of sulfur can be promoted.

<4-4. M4>
M4 is to provide a mechanism for collecting hydrogen in the reaction furnace 10 separately from the metal oxide-containing raw material 16.
In the M4, as the substance that collects hydrogen, in addition to a hydrogen storage alloy or the like, a membrane or the like that separates hydrogen gas or a combination thereof may be used.
The hydrogen storage alloy is not particularly limited, and is, for example, AB2 type based on transition elements such as titanium, manganese, zirconium, and nickel, AB5 type based on transition elements such as nickel, cobalt, and aluminum, and Ti-Fe type. , V-based, Mg alloy, Pd-based, Ca-based alloy and the like can be used.
As the membrane for separating hydrogen gas, for example, a palladium membrane, a silica membrane, a zeolite membrane, a polymer membrane and the like can be used, and in particular, considering the temperature of the gas to be separated, a palladium membrane, a silica membrane and a zeolite membrane are preferable. Can be used.

<5. Other processes>
The above-described embodiment may include a step other than the above-mentioned reaction step, for example, the following step. <5-1. Preparation process of metal oxide-containing raw materials>
A step of preparing a metal oxide-containing raw material may be included before the reaction step. The preparation method is not particularly limited, and examples thereof include preparation by a complex polymerization method. For example, a metal oxide-containing raw material Y ₂ Ti ₂ O ₇ is prepared by mixing titanium tetraisopropoxide, yttrium nitrate and citric acid in an ethylene glycol methanol solution and heating them at a specific temperature for complex polymerization. can do.
<5-2. Firing process of metal oxide-containing raw materials>
A firing step of firing the metal oxide-containing raw material may be included before the reaction step.
The firing temperature is not particularly limited, but is usually 60 ° C. or higher, and 80 ° C. or higher, from the viewpoint of being able to remove water adsorbed on the particle surface that inhibits the reaction with hydrogen sulfide while suppressing excessive growth of the particles. It is preferably 100 ° C. or higher, and on the other hand, it is usually 1000 ° C. or lower, 900 ° C. or lower, and 850 ° C. or lower.

<5-3. Acid treatment process>
The metal oxide-containing raw material after sulfurization may include a step of performing an acid treatment for the purpose of removing the reduction product on the surface layer of the particles.
The acidic substance used for the acid treatment is not particularly limited, and for example, sulfuric acid, hydrochloric acid, nitric acid, aqua regia, organic acid and the like can be used.

<6. Reaction system>
FIG. 1 is an example of a reaction system according to an embodiment of the present invention to which the above method for producing a metallic acid sulfide can be applied. The reaction system to which the production method can be applied is not limited to the embodiment shown in FIG.

The reaction system of FIG. 1 includes an alumina board 14 on which a silicon oxide mesh 11 and a sulfur powder 15 are placed, an alumina board 14 on which a metal oxide-containing raw material is placed, and a reaction furnace 10 provided on the outside of the reaction furnace 10. It has a heater 12 for volatilizing sulfur powder and a reaction heater 13 for accelerating the reaction of a raw material compound with sulfur such as hydrogen sulfide. In FIG. 1, the sulfur powder 15 can be a substance that generates other components that suppress the decomposition of hydrogen sulfide, and the silicon oxide mesh is a pipe in which excess sulfur in the system is connected to the outside of the furnace. It is installed for the purpose of avoiding blockage inside.

In FIG. 1, the alumina board 14, the heater 12, and the reaction heater 13 may or may not be used. Further, the mechanism for suppressing the decomposition of hydrogen sulfide such as sulfur powder 15 may or may not be used, but if it is not used, the metal oxide-containing raw material contains a component that suppresses the decomposition of hydrogen sulfide. It is necessary to be.

When the reaction system of FIG. 1 is used, for example, nitrogen gas is first passed through the reaction furnace 10 to perform gas replacement, and then hydrogen sulfide gas, which is a reaction gas, is passed through and gas replacement is performed again. Further, the sulfur powder as a facility for generating sulfur, which is placed in the front stage (gas inflow side) of the gas introduction portion, is heated by the heater 12 to generate sulfur gas. The amount of hydrogen sulfide can be increased by the generation of sulfur gas. Then, while heating with the reaction heater 13, the sulfur gas and hydrogen sulfide gas are reacted with the metal oxide-containing raw material placed in the latter stage (gas discharge side) of the gas introduction portion to obtain the target metal acid sulfide. Obtainable.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

<Preparation of metal oxide-containing raw materials>
Precursor oxide Y ₂ Ti ₂ O ₇ was used as the metal oxide-containing raw material. The precursor oxide Y ₂ Ti ₂ O ₇ was prepared by a complex polymerization method. Specifically, titanium tetraisopropoxide, yttrium nitrate, and citric acid are mixed at a ratio of 1: 1: 15 in an ethylene glycol methanol solution, heated to 200 ° C. for polymerization, and then 350 ° C. And, each of them was calcined at 500 ° C. for 1 hour to obtain precursor oxide Y ₂ Ti ₂ O ₇ .

<Reaction with sulfur>
[Example 1: Sulfur vapor addition sulfurization method]
The precursor oxide Y ₂ Ti ₂ O ₇ was placed on an alumina boat, sealed in a quartz tube furnace, nitrogen gas was circulated, and gas replacement was performed. After that, hydrogen sulfide gas, which is a reaction gas, was circulated and gas replacement was performed again. Further, as a component for generating the above-mentioned sulfur gas in the front stage (gas inflow side) of the gas introduction portion, 10 mol times the amount of sulfur powder is sealed with respect to the precursor oxide, and the sulfur gas is generated by heating and holding at 150 ° C. It was. The sulfur gas and hydrogen sulfide are circulated at 50 mL / min, heated to 1050 ° C. at 10 ° C./min, and then held for 60 minutes to obtain a powder sample A of metallic acid sulfide Y ₂ Ti ₂ O ₅ S _2. It was.

[Example 2: Sulfur powder addition sulfurization method]
After mixing 10 mol times the amount of sulfur powder with the precursor, the precursor oxide Y ₂ Ti ₂ O ₇ is placed on an alumina boat, sealed in a quartz tube furnace, and nitrogen gas is circulated for gas substitution. went. After that, hydrogen sulfide gas, which is a reaction gas, was circulated and gas replacement was performed again. Further, hydrogen sulfide was heated to 1050 ° C. at 10 ° C./min while flowing at 50 mL / min, and then held for 60 minutes to obtain a powder sample B of metallic acid sulfide Y ₂ Ti ₂ O ₅ S ₂ . ..

[Comparative example 1: Conventional method]
The precursor oxide Y ₂ Ti ₂ O ₇ was placed on an alumina boat, sealed in a quartz tube furnace, nitrogen gas was circulated, and gas replacement was performed. After that, hydrogen sulfide gas, which is a reaction gas, was circulated and gas replacement was performed again. A powder sample C of metallic acid sulfide Y ₂ Ti ₂ O ₅ S ₂ was obtained by raising the temperature to 1050 ° C. at 10 ° C./min while circulating hydrogen sulfide at 50 mL / min and then holding it for 60 minutes.

<Acid treatment>
For each of the above-mentioned powder samples after sulfurization, the following operation was carried out for the purpose of removing the reduction product on the particle surface layer. Each powder sample was immersed in a 9 mol / L sulfuric acid solution and stirred for 2 hours to etch the particle surface. Then, after thoroughly washing each powder sample with water, it was dried overnight at 40 ° C. and under reduced pressure.

<Ultraviolet / visible diffuse reflection spectrum measurement>
Ultraviolet / visible diffuse reflection spectra were measured for each powder sample after the above acid treatment.
The measurement conditions are not particularly limited, but can be, for example, the following conditions.
Measuring device: V-670 Spectrophotometer (manufactured by JASCO)
・ Measurement range: 300 to 800 mm
-Data interval: 1.0 nm
-Scanning speed: 10000 nm / min-Light source switching: 340.0 nm
-Data analysis software: Spectra Manager version 2
Analysis: Vertical axis is Kbelka-Munch (KM) conversion
Kubelkar-Munch conversion formula f (R _∞ ) = (1-R _∞ ) ² / 2R _∞ = K / S
Here, f (R _∞ ) is K.I. M. The function, R _∞ is the absolute reflectance, K is the molecular extinction coefficient, and S is the scattering coefficient.
It is difficult to measure the absolute reflectance R _∞ of a sample, and in practice, it is common to use the relative reflectance r _∞ using a standard sample. Therefore,
r _∞ = r (measurement sample) / r (standard sample) (BaSO ₄ is used as the standard sample)
The relative reflectance r _∞ was measured using
f (r _∞ ) = (1-r _∞ ) ² / 2r _∞ = K / S
Was derived from.

The results of the ultraviolet / visible magnifying reflection spectrum measurement of the powder samples A to C (Examples 1 and 2 and Comparative Example 1) after the acid treatment are shown in FIG. From FIG. 2, it can be seen that in Examples 1 and 2, the decrease in the components having absorption at 600 nm or more is large as compared with Comparative Example 1. Specifically, when the ratio of the spectral intensity (S ₆₀₀ ) at the wavelength of 600 nm to the maximum value (S _max ) of the spectral intensity at the wavelength of 300 nm or more and less than 600 nm of the spectrum was calculated, Example 1 was 2.47 (S _max :). 2.696, S ₆₀₀ : 1.091), Example 2 is 2.64 (S _max : 2.987, S ₆₀₀ : 1.131), Comparative Example 1 is 1.65 (S _max : 2.583, S ₆₀₀ : 1.563). This indicates that the local reduction of the Ti element in the above-mentioned metallic acid sulfide can be suppressed in Examples 1 and 2, and the reducibility from the hydrogen sulfide gas in Comparative Example 1 which is the prior art. It is considered that the decomposition reaction of hydrogen sulfide into hydrogen gas is suppressed in Examples 1 and 2.

1 Reaction system 10 Reaction furnace 11 Silicon oxide mesh 12 Heater 13 Reaction heater 14 Alumina board 15 Sulfur powder 16 Metal oxide-containing raw material

Claims (6)

A _a B _{b Oc} S _d (A is one or more selected from the group consisting of Y, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er and La, which are metallic acid sulfides. B includes one or more selected from the group consisting of Ti, Nb, Ta and La, 1.7 ≦ a ≦ 2.3, 1.7 ≦ b ≦ 2.3, c = 5, 1.7. ≦ d ≦ 2.3) includes a step of reacting a metal oxide-containing raw material with hydrogen sulfide in a reaction furnace, and the step comprises at least one of the following M1 to M4. A method for producing metallic acid sulfide, including.
M1: The metal oxide-containing raw material contains a component that suppresses the decomposition of hydrogen sulfide.
M2: The atmospheric gas introduced into the reactor contains a component that suppresses the decomposition of hydrogen sulfide.
M3: In the reactor, there is a substance that generates a component that suppresses the decomposition of hydrogen sulfide, in addition to the metal oxide-containing raw material.
M4: A mechanism for collecting hydrogen is provided in the reactor separately from the metal oxide-containing raw material. The method for producing a metal acid sulfide according to claim 1, wherein the metal oxide-containing raw material contains a metal oxide-containing raw material having a stoichiometric composition having less sulfur than the stoichiometric composition of the metal acid sulfide. .. The method for producing a metallic acid sulfide according to claim 1 or 2, wherein the atmospheric gas in M2 is a mixed gas containing hydrogen sulfide and sulfur. The method for producing a metallic acid sulfide according to any one of claims 1 to 3, wherein A contains Y. The method for producing a metallic acid sulfide according to any one of claims 1 to 4, wherein B contains Ti. Claims 1 to 1, wherein A contains Y and the content of Y in A is 80 mol% or more, and the B contains Ti and the content of Ti in B is 80 mol% or more. 5. The method for producing a metallic acid sulfide according to any one of 5.