JP2015086119A - Method for producing crystalline titanium oxide and method for regenerating denitration catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing crystalline titanium oxide by effectively utilizing titanium oxide recovered from a waste material and to provide a method for regenerating a denitration catalyst.SOLUTION: There is provided a method for producing crystalline titanium oxide, which comprises: a melting step of mixing and heating a waste material containing titanium oxide (for example, a waste catalyst of a denitration catalyst containing titanium oxide, tungsten oxide, molybdenum oxide, and vanadium oxide) and an alkali compound; a step of adding water to a reaction product generated by the heating step to separate a soluble component containing an alkali salt of tungsten, molybdenum and vanadium from an insoluble component of the reaction product; an acid treatment step of mixing an insoluble component after separating the soluble component with an acid; and a firing process of firing the insoluble component obtained by mixing with the acid to produce crystalline titanium oxide. In addition, the denitration catalyst is regenerated using the crystalline titanium oxide produced.

Description

  The present invention relates to a method for producing crystalline titanium oxide and a method for regenerating a denitration catalyst. More specifically, the present invention relates to a method for separating and recovering titanium oxide contained in a waste material and producing crystalline titanium oxide using the separated titanium oxide, and a method for regenerating a denitration catalyst using the crystalline titanium oxide produced thereby.

In thermal power plants and the like, denitration treatment is performed to detoxify nitrogen oxides (NO _x ) in flue gas, which are causative substances such as photochemical smog and acid rain. The method currently used for denitration treatment is selective contact in which NO _x is converted into nitrogen (N ₂ ) and water (H ₂ O) by reacting with ammonia (NH ₃ ) in the presence of a denitration catalyst. The reduction method is mainly used, and as the denitration catalyst, a titanium oxide-based catalyst in which vanadium, molybdenum, tungsten or the like, which is a catalytic active component, is supported on titanium oxide is often used. In general, this type of denitration catalyst has a relatively long service life of 2 to 10 years, but an enormous amount ranging from several hundred to several thousand cubic meters is used per facility such as a thermal power plant. For this reason, it is desired to reuse the mineral resources contained in the spent spent catalyst whose service life has passed.

In particular, vanadium, molybdenum, and tungsten contained in the waste catalyst of such a denitration catalyst are considered to be rare valuable metals with a small production amount, and many uses such as superalloy materials are expected. In addition, in the exhaust gas treatment in oil fired boilers, etc., vanadium contained in oil may adhere to the catalyst during the treatment, so it is important from the viewpoint of resource recycling to recover vanadium from the waste catalyst. It is considered to be.
Therefore, a method for separating and recovering valuable metals such as vanadium, molybdenum, tungsten and the like from a used waste catalyst in a high yield has been proposed.

  For example, Patent Document 1 discloses a method for recovering a metal component from a spent catalyst of a denitration catalyst containing at least one metal component selected from the group of vanadium, tungsten, and molybdenum and titanium oxide. After impregnating an aqueous alkali metal hydroxide solution and calcining the obtained used alkali metal-containing catalyst, contact with water to extract the metal component, and then recover the metal component from the resulting extract A method for recovering a metal component from the spent catalyst is disclosed.

JP-A-4-114747

According to Patent Document 1, a high-purity metal component such as vanadium, tungsten, or molybdenum is increased from a spent catalyst of a denitration catalyst that contains at least one metal component selected from the group of vanadium, tungsten, and molybdenum and titanium oxide. It is said that it can be recovered economically in a yield.
However, a denitration catalyst generally has a composition containing titanium oxide at a high ratio as compared with valuable metals such as vanadium, tungsten, and molybdenum, and the content of titanium oxide is 60 mass per catalyst. % To about 80% by mass. Therefore, there is a need for a technique that effectively uses coarse titanium oxide recovered in large quantities from waste materials such as a denitration catalyst.
Accordingly, an object of the present invention is to provide a method for producing crystalline titanium oxide and a method for regenerating a denitration catalyst that effectively uses titanium oxide recovered from waste materials.

  In order to solve the above problems, a method for producing crystalline titanium oxide according to the present invention comprises at least one selected from the group consisting of a waste material containing titanium oxide, and an alkali hydroxide, an alkali carbonate, and an alkali nitrate. A step of mixing and heating with an alkali compound, a step of mixing an insoluble component contained in the reaction product generated by the heating with an acid, and a crystalline oxidation by firing the insoluble component obtained by mixing with the acid. It includes a step of producing titanium.

  Further, the method for regenerating a denitration catalyst according to the present invention includes a used denitration catalyst comprising titanium oxide and at least one metal oxide selected from the group consisting of tungsten, molybdenum and vanadium, and alkaline water. Mixing and heating at least one alkali compound selected from the group consisting of oxides, alkali carbonates and alkali nitrates, adding water to the reaction product produced by the heating, from tungsten, molybdenum and vanadium; Separating a soluble component comprising an alkali salt of at least one metal selected from the group from the insoluble component contained in the reaction product, and mixing the insoluble component from which the soluble component has been separated with an acid A process for producing crystalline titanium oxide by firing an insoluble component obtained by mixing with the acid. , The generated and the crystalline oxide of titanium formed of the metal metal compounds were mixed and baked to characterized in that it comprises a step of producing a denitration catalyst.

  According to the present invention, it is possible to provide a method for producing crystalline titanium oxide and a method for regenerating a denitration catalyst that effectively utilize titanium oxide recovered from waste materials.

It is a schematic diagram which shows the structure of the waste catalyst which is an example of the waste material containing a titanium oxide. It is process drawing which shows the outline of a machine selection process, a melting process, and a separation process. It is process drawing which shows the outline of an acid treatment process and a baking process. It is process drawing which shows the outline of a catalyst manufacturing process. It is process drawing which shows the outline of a separation collection process. It is a figure which shows the relationship between the acid concentration and alkali residual amount in an acid treatment process. It is a figure which shows an example of the X-ray-diffraction spectrum of the water-insoluble component collect | recovered at the isolation | separation process. It is a figure which shows an example of the X-ray-diffraction spectrum of the acid insoluble component collect | recovered at the acid treatment process. It is a figure which shows an example of the X-ray-diffraction spectrum of the titanium oxide collect | recovered at the baking process.

  Hereinafter, a method for producing crystalline titanium oxide and a method for regenerating a denitration catalyst according to an embodiment of the present invention will be described in detail.

In the method for producing crystalline titanium oxide according to the present embodiment, the titanium oxide is separated and recovered from the waste material containing titanium oxide (titanium dioxide; TiO ₂ ), and the recovered titanium oxide is crystallized to crystallize the crystalline titanium oxide. A method for producing titanium. This method has a side surface for separating other valuable metals contained in the waste material from the titanium oxide accompanying the production of the crystalline titanium oxide. Therefore, the titanium oxide contained in the waste material can be recovered with high purity and reused, which is an effective manufacturing method in terms of resource circulation.

Examples of waste materials containing titanium oxide include metallic materials that should be disposed of, such as used molded products, and a collection of waste pieces mixed with multiple types of metallic materials and other materials. Used. The metallic material is, for example, a material made of a metal element-containing compound such as ceramic, a pure metal, an alloy, or a combination thereof.
The waste material containing titanium oxide is not limited to a waste material containing titanium oxide as a main composition component, and the content of titanium oxide may be less than 50% by mass per mass of the waste material. In particular, waste materials comprising at least one metal selected from the group consisting of tungsten, molybdenum and vanadium together with titanium oxide or oxides thereof are effectively separated and recovered in parallel with the production of crystalline titanium oxide. It is suitable at the point which can be performed.

  Specific examples of the waste material containing titanium oxide include used waste catalysts such as a denitration catalyst, a desulfurization catalyst, and a photocatalyst. In general, a denitration catalyst is mainly a catalyst in which vanadium oxide, which is a catalytically active component, is supported on titanium oxide, which is a catalyst carrier. In addition to vanadium oxide, tungsten oxide, molybdenum oxide or the like is often used as a catalyst active component in a denitration catalyst. In the desulfurization catalyst, a catalyst carrier made of titanium oxide may be used together with silica and alumina. In the desulfurization catalyst, molybdenum oxide, nickel oxide, cobalt oxide or the like is used as a catalyst active component. In photocatalysts, titanium oxide, which is a catalytically active component, is often supported on a carrier such as glass, quartz, or metal. Molybdenum, vanadium, or the like may be used in combination with the photocatalyst for the purpose of modifying photoresponsive characteristics.

In the method for producing crystalline titanium oxide according to the present embodiment, a waste material containing titanium oxide is alkali-melted, and the titanium oxide recovered as a residue is crystallized to produce crystalline titanium oxide. Therefore, in particular, it is preferable to use a waste material having a high content of titanium oxide and containing a valuable metal that forms a water-soluble alkali metal salt.
Therefore, hereinafter, a method for producing crystalline titanium oxide will be described by taking as an example a method for producing crystalline titanium oxide from a denitration catalyst waste catalyst containing titanium oxide, tungsten oxide, molybdenum oxide and vanadium oxide.

FIG. 1 is a schematic diagram showing a configuration of a waste catalyst which is an example of a waste material containing titanium oxide.
A waste catalyst 1 shown in FIG. 1 is a titanium oxide-based denitration catalyst, and includes a catalyst support base 2, titanium oxide 3, tungsten oxide 4, molybdenum oxide 5, and vanadium oxide 6. In the waste catalyst 1, the particles of tungsten oxide 4, molybdenum oxide 5, and vanadium oxide 6 that are catalytic active components are immobilized on the catalyst support base 2 while being supported on the particles of titanium oxide 3 that is a catalyst carrier. ing.
The waste catalyst 1 may further contain quartz sol 7 and inorganic fibers 8 together with these catalytically active components and catalyst carrier. This is because, when particles such as titanium oxide 3 are mixed with the quartz sol 7 and the inorganic fibers 8 and bonded to the catalyst support substrate 2, the sinterability is improved and the particles are firmly molded. The catalyst support base 2 is usually made of metal, glass, ceramics, or the like. Therefore, the waste catalyst 1 often contains silicon oxide, aluminum oxide and the like derived from these materials. Further, as the denitration catalyst, titanium oxide having an anatase type crystal structure with a large specific surface area is generally used. However, in the used waste catalyst 1 as shown in FIG. It may be transformed into a rutile crystal structure with a small specific surface area. Moreover, adsorption | suction of the dust 9 derived from flue gas, sulfur oxide, etc. is seen on the surface of the waste catalyst 1, and the element contained as an impurity in the waste catalyst 1 is various. Therefore, the titanium oxide contained in the waste catalyst 1 is in a very rough state in terms of crystallinity and purity.

  In the method for producing crystalline titanium oxide according to the present embodiment, a machine sorting step S10, a melting step S20, a separation step S30, and an acid treatment step are performed using waste materials containing titanium oxide as an example of the above-described waste catalyst. Through S40, firing step S50, etc., production of crystalline titanium oxide and separation of valuable metals are performed. However, in the production of crystalline titanium oxide, it is not always essential to perform the machine sorting step S10 and the separation step S30, depending on the purpose, one or more of these steps may be omitted or other purposes having an equivalent purpose may be used. It can be replaced with a known process.

  FIG. 2 is a process diagram showing an outline of the machine selection process, the melting process, and the separation process.

In the machine sorting step S10, a metallic material containing titanium oxide is mechanically separated from used various molded products to be discarded. That is, after the waste catalyst of the denitration catalyst is crushed into fine particles, it is separated into particles of catalyst components such as titanium oxide, tungsten oxide, molybdenum oxide, vanadium oxide, and particles of the substrate (catalyst supporting substrate). Thus, components other than titanium oxide and other valuable metals are appropriately removed from the waste material. Fine particles can be obtained by crushing various molded products using a shot blast type, shear type, impact type crusher, etc., so that catalyst components such as catalytic active components and catalyst carriers are powdered, flaky, granular, etc. It may be performed by a method of collecting as fine particles. In addition, the crushed fine particles may be separated by selecting the catalyst component with a sieve based on specific gravity, particle size, or the like.
By performing such a machine sorting step S10, only the catalyst component containing titanium oxide and other valuable metals can be used as a waste material for the post-process, and therefore used for the efficiency of the post-process and the production of crystalline titanium oxide. The purity of titanium oxide can be improved.
Note that the machine sorting step S10 is not necessarily performed when waste materials derived from used various molded products or the like are directly processed in a subsequent step. For example, if the catalyst component is not molded on the catalyst support substrate and exists independently, or if the catalyst component is molded in a fine powder form on the catalyst support substrate, Since the catalyst can be directly used in the subsequent process, the machine sorting process S10 can be omitted.

In the melting step S20, the waste material containing titanium oxide and the alkali compound are mixed and heated.
Mixing and homogenizing fine particle waste material containing catalyst components such as titanium oxide, tungsten oxide, molybdenum oxide, vanadium oxide with an alkali compound, heating the alkali compound into a molten salt, the catalyst component and the alkali compound become alkaline. By melting reaction, alkali metal oxyacid salts of valuable metals such as tungsten, molybdenum and vanadium are generated. For this reason, in the alkali melting reaction, a reaction product containing an oxyacid alkali salt of these valuable metals and titanium oxide remaining unreacted is obtained.

The alkali compound used in the melting step S20 is alkali metal hydroxide, alkali metal carbonate, alkali metal nitrate, alkali metal sulfate, alkali metal chloride, alkaline earth metal hydroxide, alkaline earth metal carbonate, alkali It is at least one selected from the group consisting of earth metal nitrates, alkaline earth metal sulfates and alkaline earth metal chlorides.
Alkali hydroxides and alkali nitrates have a feature that their melting point is lower than that of alkali carbonates and the like, so that the heating temperature for producing a molten salt can be lowered. Alkali hydroxides are more suitable for producing alkali salts of valuable metals because they are more efficient in alkali melting reactions than alkali nitrates. Therefore, the alkali compound is preferably at least one selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides, and more preferably alkali metal hydroxides.
In addition, you may use alkali nitrate and alkali sulfate as an oxidizing agent for making a valuable metal elute efficiently from a waste material. That is, as the alkali compound, alkali salts in the form of alkali persulfate, alkali nitrite or the like can be used.

The alkali metal forming the alkali compound can be selected from lithium, sodium, potassium, rubidium, cesium and the like. The alkali metal is preferably at least one selected from the group consisting of lithium, sodium and potassium from the viewpoints of handling and availability.
The alkaline earth metal forming the alkali compound can be selected from beryllium, magnesium, calcium, strontium, barium and the like. The alkaline earth metal is preferably at least one selected from the group consisting of magnesium and calcium from the viewpoints of handling and availability.

Heating of the mixed waste material and the alkali compound is preferably performed by setting the heating temperature in the vicinity of the melting point of the alkali compound. Specifically, the heating temperature is preferably 150 ° C. or higher and 350 ° C. or lower.
If heating temperature is 150 degreeC or more, the waste material and titanium compound containing titanium oxide can fully be made to react by selecting an alkali compound seed | species appropriately. On the other hand, by setting the heating temperature to a low temperature of about 350 ° C. or less, the heating cost in the melting step S20 can be reduced. Moreover, if the heating temperature is a low temperature of about 350 ° C. or lower, it is not necessary to give an unintended thermal history to titanium oxide, which is suitable for producing crystalline titanium oxide.

The heating time of the waste material and the alkali compound may be a time to the extent that the mixed alkali compound is melted, and is usually about 30 minutes to 3 hours.
The heating temperature is not necessarily required to exceed the melting point as long as it is in the vicinity of the melting point of the alkali compound, but it is preferable to set the heating temperature to a temperature that is about 20 ° C. to 50 ° C. higher than the melting point of the alkali compound.
Therefore, from the viewpoint of suppressing the heating temperature in the melting step S20, the alkali compound is preferably melted at a low temperature. As a method of melting the alkali compound at a low temperature, a method of using an alkali compound having a low melting point alone or a method of lowering a freezing point (melting point) by using a combination of a plurality of types of alkali compounds can be used. For example, when lithium hydroxide (melting point: about 460 ° C.) is used alone, the heating temperature may be about 500 ° C., and when potassium hydroxide (melting point: about 380 ° C.) is used alone, heating is performed. The temperature may be about 420 ° C. On the other hand, when an equimolar mixture of sodium hydroxide and potassium hydroxide (melting point: about 170 ° C.) is used, the heating temperature may be about 200 ° C.

The addition amount of the alkali compound is preferably 0.6 to 10 times the total mass of the metal contained as the catalyst component, and more preferably 5 to 10 times the mass.
When the addition amount of the alkali compound is 5 to 10 times the total mass of the metal contained as the catalyst component, the alkali melting reaction proceeds with good efficiency, so that valuable metals such as tungsten, molybdenum, vanadium, etc. Separation and recovery can be performed in high yield. Moreover, the purity of the titanium oxide utilized for manufacture of crystalline titanium oxide can be improved. The amount of the alkali compound added depends on the elemental composition of the catalyst component and the alkali compound and other conditions. However, the reaction efficiency is large even if the amount exceeds 10 times the total mass of the metal contained as the catalyst component. There is a tendency not to improve.

In the alkali melting reaction, for example, when tungsten oxide (WO ₃ ) contained as a catalyst component reacts with an alkali metal hydroxide (ROH), an alkali metal tungstate (as shown in the following reaction formula 1) R ₂ WO ₄ ) is produced.
WO ₃ + 2ROH → R ₂ WO ₄ + H ₂ O (reaction formula 1)

In the reaction product of the alkali melting reaction, alkali metal oxyacids such as alkali tungstic acid, alkaline molybdate, and vanadic acid produced in accordance with such a reaction are soluble components (water Soluble component). On the other hand, titanium oxide, which is hardly reactive, partly reacts with an alkali compound to produce a slightly water-soluble alkali titanate such as Na ₂ Ti ₂ O ₄ (OH) ₂ , and the rest is unreacted. It remains as titanium oxide. In addition, silicon oxide, aluminum oxide, and the like contained in the waste catalyst partially react with an alkali compound to cause poorly water-soluble silica such as KAlSiO ₄ or Na ₅ Al ₅ Si ₅ O ₂₀ · 9H ₂ O. Acid alkali aluminate is produced. These titanium oxides and poorly water-soluble alkali salts are contained in the reaction product together with valuable metal water-soluble alkali salts as insoluble components (water-insoluble components).
Therefore, the reaction product obtained in the melting step S20 is subjected to the subsequent separation step S30, thereby performing solid-liquid separation utilizing the difference in water solubility.

In the separation step S30, water is added to the reaction product obtained in the melting step S20, and a water-soluble component containing an alkali salt of a valuable metal such as an alkali tungstate, an alkali molybdate, or an alkali vanadate, Separated from water-insoluble components such as titanium oxide contained in the reaction product. The water-insoluble component and water-soluble component are separated by mixing the reaction product and water, extracting the water-soluble component contained in the reaction product into the aqueous phase, and then the water-insoluble component contained in the reaction product. May be recovered from the aqueous phase using filtration or centrifugation.
The separation step S30 may be omitted or replaced with a simple water washing step or the like when the amount of valuable metals or other impurities expected to be separated as a water-soluble component is small. it can.
The recovered water-insoluble component is subjected to the subsequent acid treatment step S40. On the other hand, the water-soluble component containing valuable metals such as tungsten, molybdenum, vanadium can be further supplied to the separation and recovery step S70 as necessary.

  FIG. 3 is a process diagram showing an outline of an acid treatment process and a firing process.

In the acid treatment step S40, the water-insoluble component contained in the reaction product is mixed with the acid.
By mixing and reacting the water-insoluble component and the acid contained in the reaction product, the poorly water-soluble alkali component generated by the alkali melting reaction is dissolved and distributed to the liquid phase. Therefore, it is possible to separate titanium oxide, which is an insoluble component (acid-insoluble component), and alkali titanate, alkali aluminate silicate, etc., which are soluble components (acid-soluble component).

  The acid to be mixed can be selected from aqueous solutions of inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, perchloric acid, phosphoric acid, boric acid, hydrofluoric acid, hydrobromic acid and hydroiodic acid. As the acid, at least one selected from the group consisting of hydrochloric acid, sulfuric acid and nitric acid is preferable in that the solubility of the alkali component is excellent. Although dilute solutions can be used for hydrochloric acid, sulfuric acid, and nitric acid, in order to dissolve the acid-soluble component reliably, for example, hydrochloric acid is preferably at a concentration of 5% by mass or more, preferably 5% by mass to 10% by mass. More preferably, the concentration is as follows.

The acid treatment time and acid treatment temperature to be mixed with the acid are not particularly limited as long as the poorly water-soluble alkali component can be solubilized. For example, the acid treatment time is 2 to 24 hours, and the acid treatment temperature is normal temperature. It can be carried out.
By acid treatment, the poorly water-soluble alkali component is solubilized by reacting with an acid, and then an acid-insoluble component such as titanium oxide contained in the acid-treated reaction product is separated from the acid-soluble component. The acid-insoluble component and the acid-soluble component may be separated by distributing the solubilized acid-soluble component in the liquid phase and then collecting the acid-insoluble component from the liquid phase using filtration or centrifugation. .
The recovered acid-insoluble component is subjected to the subsequent firing step S50. The acid-insoluble component used in the firing step S50 is preferably washed with water or the like and then dried in order to remove unseparated acid-soluble components and acid. As a drying temperature at this time, the range of 80 degreeC or more and 100 degrees C or less is preferable.

In the firing step S50, the insoluble component obtained by mixing with the acid is fired to produce crystalline titanium oxide.
The acid insoluble component obtained in the acid treatment step S40 has a composition mainly composed of titanium oxide contained in the waste catalyst by separating valuable metals, silicon and aluminum. In general, titanium oxide contained in the catalyst before use is anatase type crystalline titanium oxide, whereas most of the spent catalyst after use is transformed into rutile type. However, these crystalline titanium oxides often lose their crystallinity when mixed with an alkali compound in the melting step S20 and change to amorphous.
Therefore, in this firing step S50, the acid-insoluble component is heat-treated, whereby the amorphous titanium oxide forming the acid-insoluble component is fired to form crystalline titanium oxide.

The heating temperature in firing is preferably 400 ° C. or higher, more preferably 400 ° C. or higher and 700 ° C. or lower, and further preferably 500 ° C. or higher and 700 ° C. or lower.
By setting the heating temperature to 400 ° C. or higher, preferably 500 ° C. or higher, crystallization of amorphous titanium oxide forming an acid-insoluble component proceeds, so that titanium oxide with good crystallinity can be produced. On the other hand, if the heating temperature is 700 ° C. or lower, the heating cost required for crystallization can be reduced.

The heating temperature in firing may further limit the temperature range according to the structure of the crystalline titanium oxide to be produced.
For example, when the heating temperature in firing is in the range of 650 ° C. or higher (heating (1) in FIG. 3), rutile crystalline titanium oxide can be produced. Further, when the heating temperature in the baking is in the range of 400 ° C. or more and 600 ° C. or less (heating (2) in FIG. 3), anatase type crystalline titanium oxide can be produced.

According to the method for producing crystalline titanium oxide according to the above-described embodiment, it is possible to produce crystalline titanium oxide using high-purity titanium oxide efficiently recovered from the waste material containing titanium oxide. it can. In addition, through the separation step S30, the valuable metal contained in the waste material can be integrally separated in parallel with the production of the crystalline titanium oxide. Therefore, titanium oxide and other valuable metals contained in the waste material can be effectively used in a resource circulation compatible manner. Furthermore, the cost of the entire process can be reduced by integrating manufacturing and separation.
In addition, the crystalline titanium oxide produced by using such a method is fired after being separated from the valuable metal in the process, so that the production cost is low but the purity is good. In addition, since it is fired through an amorphous state following a process having a small influence of thermal history, it can be produced as a crystalline titanium oxide closer to a single phase regardless of the properties of titanium oxide contained in the waste material. For example, rutile type crystalline titanium oxide has uses as a colorant, paint, pigment, and the like, and anatase type crystalline titanium oxide is useful as a catalyst material such as a denitration catalyst. A catalyst comprising titanium oxide can be remanufactured using the produced crystalline titanium oxide.

  Next, the regeneration method of the denitration catalyst according to this embodiment will be described.

  The method for regenerating a denitration catalyst according to the present embodiment is performed using the above-described method for producing crystalline titanium oxide using a denitration catalyst waste catalyst as a waste material. That is, in the denitration catalyst regeneration method according to the present embodiment, in addition to the machine selection step S10, the melting step S20, the separation step S30, the acid treatment step S40, the calcining step S50, etc. that are performed in the method for producing crystalline titanium oxide. Further, the denitration catalyst is regenerated by passing through the catalyst manufacturing step S60. This regeneration method uses a crystalline titanium oxide produced from a denitration catalyst waste catalyst as a raw material of the catalyst, and substantially corresponds to a production method of a denitration catalyst.

  FIG. 4 is a process diagram showing an outline of the catalyst production process.

  In the catalyst manufacturing step S60, the crystalline titanium oxide produced in the firing step S50 and a metal compound made of at least one metal selected from the group consisting of tungsten, molybdenum and vanadium are mixed and fired to produce a denitration catalyst. To do. Crystalline titanium oxide is used as a raw material for a catalyst carrier of a denitration catalyst, and a metal compound of tungsten, molybdenum, or vanadium is used as a raw material for a catalytic active component. However, in the catalyst manufacturing step S60, the selection of the catalyst raw material is excluded. Thus, it is possible to employ a conventional method for producing a general denitration catalyst known in the art.

As a raw material for the catalyst carrier supporting the catalytically active component of the denitration catalyst, it is preferable to use anatase type crystalline titanium oxide produced by setting the heating temperature in the range of 400 ° C. to 600 ° C. in the firing step S50. High catalytic activity can be obtained by using anatase-type crystalline titanium oxide having a relatively large specific surface area as a catalyst carrier.
On the other hand, as the catalytically active component, it is preferable to support vanadium oxide, preferably at least one of tungsten oxide and molybdenum oxide, on crystalline titanium oxide. Therefore, a metal compound containing tungsten, molybdenum or vanadium is used as a raw material for the catalytically active component. Examples of such a metal compound include a metal oxide itself serving as a catalytically active component, or a heat-decomposable metal compound that is converted into these metal oxides by heat oxidation. Specifically, examples of the metal compound as a raw material of vanadium oxide include divanadium pentoxide, ammonium metavanadate, vanadium oxalate, and vanadium sulfate. Examples of the metal compound as a raw material of tungsten oxide include tungsten trioxide, tungstic acid, ammonium metatungstate, and ammonium paratungstate. In addition, examples of the metal compound as a raw material of molybdenum oxide include molybdenum trioxide, molybdic acid, and ammonium paramolybdate. These metal compounds may be metal compounds composed of valuable metals recovered in the separation and recovery step S70 described later, or may be procured as new raw materials.

  In the production of a denitration catalyst, for example, crystalline titanium oxide serving as a catalyst carrier and a metal compound serving as a catalytically active component are mixed with a dispersion medium such as water, and additives such as quartz sol and inorganic fibers are added as necessary. Kneaded to make a paste. Then, the paste is molded on a catalyst support base having a lath shape, honeycomb shape or the like, dried and fired to produce a denitration catalyst molded product. The firing is preferably performed in an oxidizing gas atmosphere, and the firing temperature is preferably in the range of 300 ° C. or more and 600 ° C. or less, for example.

  According to the denitration catalyst regeneration method according to the present embodiment described above, the denitration catalyst can be remanufactured by effectively using titanium oxide recovered from the waste material containing titanium oxide. In particular, if the heating temperature in the melting step S20 is 150 ° C. or higher and 350 ° C. or lower, the denitration catalyst can be regenerated using titanium oxide having high purity and good crystal state at low heating cost. In addition, when the heating temperature in the firing step S50 is set to 500 ° C. or more and 600 ° C. or less, the surface area of titanium oxide as a raw material for the catalyst carrier is further increased, so that the catalytic activity of the regenerated denitration catalyst can be improved. it can. Therefore, as compared with a catalyst regeneration method that eliminates poisoning due to adsorption of ash or the like by washing or the like, it is a method that achieves both a reduction in the amount of resources discarded and a recovery of high catalyst activity.

  The method for producing crystalline titanium oxide and the method for regenerating a denitration catalyst according to the present embodiment can further include a separation and recovery step S70. The separation and recovery step S70 is a step performed after the separation step S30, and is a step of further separating and recovering the valuable metal separated from the titanium oxide in the separation step S30. In the regeneration method of the denitration catalyst, it is performed after the separation step S30 and before the catalyst production step S60, and the recovered metal compound is used as a catalyst raw material for the catalyst production step S60.

  FIG. 5 is a process diagram showing an outline of the separation and recovery process.

  In the separation and recovery step S70, these valuable metals are separated and recovered as solids from the water-soluble components containing alkali salts of valuable metals such as tungsten, molybdenum and vanadium extracted in the aqueous phase in the separation step S30. The separation / recovery is not necessarily performed completely for each metal element type, and may be performed only on a metal element contained in a relatively large amount, such as vanadium.

  The separation / recovery method may be a general chemical or physical separation method, but is preferably a precipitation separation. For example, when an aqueous phase such as a filtrate or a supernatant containing a water-soluble component is adjusted to pH 6 or more and 8 or less, precipitation of ammonium metavanadate is generated by adding an ammonium salt such as ammonium chloride. By separating and recovering the precipitate, vanadium can be separated from tungsten and molybdenum.

  The liquid phase from which the vanadate precipitate was recovered can be subjected to further precipitation separation to recover tungsten and molybdenum. For example, calcium tungstate and calcium molybdate precipitates are formed by adding calcium chloride to the liquid phase from which ammonium metavanadate precipitates are collected and adjusting the pH appropriately. Tungsten and molybdenum can be recovered by solid-liquid separation of the precipitate. Alternatively, the liquid phase from which the ammonium metavanadate precipitate is collected is adjusted to pH 8 or more and 10 or less, and after adding sodium hydrogen sulfide or the like to generate thiomolybdate, the acid is adjusted to pH 2 or more and 3 or less. The treatment produces a precipitate of molybdenum trisulfide. By separating and collecting the precipitate, tungsten and molybdenum can be further separated.

  In the separation and recovery step S70, valuable metals such as tungsten, molybdenum, and vanadium contained as water-soluble components can be recovered after being converted into a desired metal compound. For example, ammonium metavanadate recovered as a precipitate is suitable in that it can be directly used as a starting metal compound in the catalyst production step S60, but may be converted to divanadium pentoxide by thermal decomposition. Further, calcium tungstate, calcium molybdate and the like may be converted into molybdic acid, tungstic acid and the like by boiling and washing with hot concentrated nitric acid or the like. Furthermore, these molybdic acid, tungstic acid, molybdenum trisulfide, and the like may be converted into molybdenum oxide or tungsten oxide by thermal oxidation.

According to the method for producing crystalline titanium oxide including the separation and recovery step S70 described above, separation and collection of valuable metals contained in the waste material can be performed integrally with the production of crystalline titanium oxide. For this reason, valuable metals contained in the waste material can be effectively used in a resource circulation compatible manner, and furthermore, the cost of the entire process can be suppressed by integrating production and separation / recovery. The valuable metal separated and recovered can also be used as a superalloy material or the like as a material for a cemented carbide tool or the like.
Moreover, according to the regeneration method of the denitration catalyst provided with the above separation / recovery step S70, a metal compound of tungsten, molybdenum or vanadium derived from valuable metals separated and recovered from the waste catalyst of the denitration catalyst is used as a raw material of the catalyst active component It can be used in the catalyst production step S60. For this reason, it is possible to remanufacture the denitration catalyst by utilizing valuable metals contained in the waste catalyst in a resource circulation compatible manner.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using the Example of this invention, the technical scope of this invention is not limited to this.

Using the method for producing crystalline titanium oxide according to the present invention, crystalline titanium oxide was produced from a waste material containing titanium oxide, and valuable metals contained in the waste material were recovered.
The waste material comprising titanium oxide, 80 wt% of titanium oxide (TiO _2), 8 wt% tungsten oxide (WO _3), 0.5 wt% of molybdenum oxide (MoO _3), vanadium pentoxide ( A waste catalyst of a denitration catalyst having a composition containing 1.5% by mass of V ₂ O ₅ ), 4% by mass of aluminum oxide (Al ₂ O ₃ ), and 6% by mass of silicon dioxide (SiO ₂ ) was used. This denitration catalyst is a molded product that is applied to a catalyst support base made of stainless steel and then sintered, and is formed into a plate-like catalyst.

  First, the spent catalyst was subjected to the machine sorting step S10. The waste catalyst was recovered as a powdery waste material by mechanical separation from the catalyst support substrate by shot blasting. Subsequently, the obtained powdery waste material was subjected to a melting step S20. The waste materials and the alkali compounds were subjected to alkali fusion reactions by carrying out the following Examples 1 to 15 in which the composition and amount of the alkali compound used and the heating temperature were changed.

[Example 1]
In Example 1, lithium hydroxide (LiOH) and sodium hydroxide (NaOH) were used as the alkali compounds so that the mass ratio was 0.2: 0.8. This mass ratio corresponds to about 5:12 in terms of molar ratio.
The alkali compound was homogenized by adjusting the concentration in advance so that the total addition amount was 1 kg to obtain an alkaline compound aqueous solution, adding 8 kg of this alkaline compound aqueous solution to 1 kg of waste material, and stirring for 2 hours. Subsequently, the obtained mixture was put into an alumina evaporating dish and dried at 80 ° C. to 100 ° C. for 15 hours. The dried mixture was mixed using a crusher and heated in the atmosphere at a heating temperature of 250 ° C. for 5 hours to obtain a reaction product of an alkali melting reaction.

  The obtained reaction product was subjected to separation step S30. After adding 20 L of water to the reaction product, the reaction product was stirred for 3 hours, and water-soluble components contained in the reaction product were extracted into the aqueous phase. Subsequently, by filtration, the water-soluble component and the water-insoluble component contained in the reaction product were subjected to solid-liquid separation, and the filtrate and the residue were recovered.

The filtrate from which the water-soluble component contained in the reaction product of the alkali melting reaction was extracted was subjected to the separation and recovery step S70. When the filtrate was adjusted to pH 7 by adding a pH adjuster, a composite oxide containing silicon, aluminum, titanium, alkali, etc. was precipitated, and thus the composite oxide precipitate was removed by filtration. . Subsequently, 250 g of ammonium chloride (NH ₄ Cl) was added and stirred for 30 minutes to form a precipitate of ammonium metavanadate. Then, the precipitate was separated by filtration and washed with 50 mL of a 2 wt% aqueous ammonium chloride solution and 50 mL of water, respectively, to recover the vanadate.

On the other hand, with respect to the filtrate remaining after the precipitate was filtered off, 80 g of calcium chloride (CaCl ₂ ) was added and stirred for 10 minutes to generate precipitates of calcium tungstate and calcium molybdate. The precipitate was filtered off, boiled in 1 L of hot concentrated nitric acid for 30 minutes, washed with an aqueous ammonium chloride solution and water, dried at 100 ° C., and molybdate and tungstate. The mixture was collected.

Each of the recovered vanadate, molybdate, and tungstate is subjected to X-ray Fluorescence Analysis (XRF) to confirm the composition, and extracted vanadium, molybdenum, and tungsten elements. The mass of was determined. Moreover, about the filtrate, it used for the inductively coupled plasma emission spectrometry (Inductively Coupled Plasma-Atomic Emission Spectrometry; ICP-AES), and confirmed the composition. And about each element collect | recovered as a valuable metal, the extraction rate (mass%) with respect to the mass contained in the waste material was computed.
As a result, the extraction rate of valuable metals was 94.9% for tungsten, 95.0% for molybdenum, and 90.1% for vanadium.

[Example 2]
In Example 2, sodium hydroxide (NaOH) and potassium hydroxide (KOH) were used as the alkali compounds so that the mass ratio was 0.42: 0.58. This mass ratio corresponds to about 1: 1 when converted to a molar ratio.
In Example 2, the heating temperature in the melting step was 200 ° C., and the other conditions were the same as in Example 1.
As a result, the extraction rate of valuable metals was 99.9% for tungsten, 96.3% for molybdenum, and 97.3% for vanadium.

[Example 3]
In Example 3, sodium hydroxide (NaOH) and potassium hydroxide (KOH) were used as the alkali compounds so that the mass ratio was 0.74: 0.26. This mass ratio corresponds to about 4: 1 in terms of molar ratio.
In Example 3, the heating temperature in the melting step was 250 ° C., and the other conditions were the same as in Example 2.
As a result, the extraction rate of valuable metals was 96.5% for tungsten, 94.5% for molybdenum, and 93.9% for vanadium.

[Example 4]
In Example 4, sodium hydroxide (NaOH) and potassium hydroxide (KOH) were used as the alkali compounds so that the mass ratio was 0.42: 0.58.
In Example 4, an alkali compound whose concentration was adjusted so that the total amount of alkali compound added was 0.8 kg was added to 1 kg of waste material to cause an alkali melting reaction, and the other conditions were the same as in Example 2. went.
As a result, the extraction rate of valuable metals was 99.4% for tungsten, 92.5% for molybdenum, and 97.7% for vanadium.

[Example 5]
In Example 5, sodium hydroxide (NaOH) and potassium hydroxide (KOH) were used as the alkali compounds so that the mass ratio was 0.42: 0.58.
In Example 5, an alkali compound whose concentration was adjusted so that the total addition amount of the alkali compound was 0.6 kg was added to 1 kg of waste material to cause an alkali melting reaction, and the other conditions were the same as in Example 2. went.
As a result, the extraction rate of valuable metals was 98.0% for tungsten, 90.3% for molybdenum, and 95.3% for vanadium.

[Example 6]
In Example 6, as the alkali compound, sodium hydroxide (NaOH) and potassium hydroxide (KOH) were used in a mass ratio of 0.42: 0.58.
In Example 6, the heating temperature in the melting step was set to 170 ° C., and the other conditions were the same as in Example 2.
As a result, the extraction rate of valuable metals was 98.5% for tungsten, 95.0% for molybdenum, and 97.1% for vanadium.

[Example 7]
In Example 7, sodium hydroxide (NaOH) and potassium hydroxide (KOH) were used as the alkali compounds so that the mass ratio was 0.42: 0.58.
In Example 7, the heating temperature in the melting step was 150 ° C., and the other conditions were the same as in Example 2.
As a result, the extraction rate of valuable metals was 99.0% for tungsten, 90.0% for molybdenum, and 96.4% for vanadium.

[Example 8]
In Example 8, sodium hydroxide (NaOH), potassium hydroxide (KOH), and lithium hydroxide (LiOH) are used as the alkali compound so that the mass ratio is 0.34: 0.46: 0.20. It was. This mass ratio corresponds to about 1: 1: 1 in terms of molar ratio.
In Example 8, an alkali compound whose concentration was adjusted so that the total amount of alkali compound added was 1 kg was added to 1 kg of waste material to cause an alkali melting reaction, the heating temperature in the melting step was 170 ° C., and other conditions Was carried out in the same manner as in Example 2.
As a result, the extraction rate of valuable metals was 99.7% for tungsten, 90.8% for molybdenum, and 95.9% for vanadium.

[Example 9]
In Example 9, sodium hydroxide (NaOH), potassium hydroxide (KOH), and sodium nitrate (NaNO ₃ ) are used as alkali compounds so that the mass ratio is 0.34: 0.46: 0.20. It was. This mass ratio corresponds to about 4: 4: 1 in terms of molar ratio.
In Example 9, an alkali compound whose concentration was adjusted so that the total amount of the alkali compound added was 1 kg was added to 1 kg of waste material to cause an alkali melting reaction, the heating temperature in the melting step was 150 ° C., and other conditions Was carried out in the same manner as in Example 2.
As a result, the extraction rate of valuable metals was 99.4% for tungsten, 93.3% for molybdenum, and 98.0% for vanadium.

[Example 10]
In Example 10, as an alkali compound, sodium hydroxide (NaOH), potassium hydroxide (KOH), and calcium hydroxide (Ca (OH) ₂ ) were used in a mass ratio of 0.34: 0.46: 0.20. Used to be. This mass ratio corresponds to about 1: 1: 3 in terms of molar ratio.
In Example 10, an alkali compound whose concentration was adjusted so that the total amount of alkali compound added was 1 kg was added to 1 kg of waste material to cause an alkali melting reaction, the heating temperature in the melting step was 150 ° C., and other conditions Was carried out in the same manner as in Example 2.
As a result, the extraction rate of valuable metals was 98.8% for tungsten, 92.8% for molybdenum, and 97.6% for vanadium.

[Example 11]
In Example 11, magnesium hydroxide (Mg (OH) ₂ ) and calcium carbonate (CaCO ₃ ) were used as the alkali compound so that the mass ratio was 0.8: 0.2. This mass ratio corresponds to about 7: 1 in terms of molar ratio.
In Example 11, a 1 kg waste material is added with an alkali compound whose concentration is adjusted so that the total addition amount of the alkali compound is 1 kg to cause an alkali melting reaction, the heating temperature in the melting step is 250 ° C., and other conditions Was carried out in the same manner as in Example 2.
As a result, the extraction rate of valuable metals was 94.5% for tungsten, 95.0% for molybdenum, and 93.6% for vanadium.

[Example 12]
In Example 12, sodium hydroxide (NaOH) and sodium sulfate (Na ₂ SO ₄ ) were used as the alkali compound so that the mass ratio was 0.95: 0.05.
In Example 12, an alkali compound whose concentration was adjusted so that the total amount of alkali compound added was 1 kg was added to 1 kg of waste material to cause an alkali melting reaction, the heating temperature in the melting step was set to 300 ° C., and other conditions Was carried out in the same manner as in Example 1.
As a result, the extraction rate of valuable metals was 98.1% for tungsten, 96.6% for molybdenum, and 97.2% for vanadium.

[Example 13]
In Example 13, sodium hydroxide (NaOH) was used alone as the alkali compound.
In Example 13, an alkali compound whose concentration was adjusted so that the total amount of alkali compound added was 1 kg was added to 1 kg of waste material, the heating temperature in the melting step was 350 ° C., and other conditions were the same as in Example 1. The same was done.
As a result, the extraction rate of valuable metals was 97.2% for tungsten, 95.3% for molybdenum, and 93.5% for vanadium.

[Example 14]
In Example 14, sodium carbonate (Na ₂ CO ₃ ) and lithium carbonate (Li ₂ CO ₃ ) were used as the alkali compound so that the mass ratio was 0.65: 0.35. This mass ratio corresponds to about 4: 3 in terms of molar ratio.
In Example 14, an alkali compound whose concentration was adjusted so that the total amount of alkali compound added was 1 kg was added to 1 kg of waste material to cause an alkali melting reaction, the heating temperature in the melting step was 550 ° C., and other conditions Was carried out in the same manner as in Example 1.
As a result, the extraction rate of valuable metals was 62.6% for tungsten, 54.1% for molybdenum, and 57.8% for vanadium.

[Example 15]
In Example 15, lithium nitrate (LiNO ₃ ) and potassium nitrate (KNO ₃ ) were used as the alkali compound so that the mass ratio was 0.2: 0.8. This mass ratio corresponds to about 2: 5 when converted to a molar ratio.
In Example 15, an alkali compound whose concentration was adjusted so that the total addition amount of the alkali compound was 1 kg was added to 1 kg of waste material to cause an alkali melting reaction, the heating temperature in the melting step was 150 ° C., and other conditions Was carried out in the same manner as in Example 1.
As a result, the extraction rate of valuable metals was 6.5% for tungsten, 0.8% for molybdenum, and 0.1% for vanadium.

  The composition and addition amount of the alkali compound and the heating temperature in Examples 1 to 15 are shown in the following Table 1 together with the extraction rate (%) of the valuable metal.

As shown in Table 1, in Example 13 in which an alkali compound that melts at a low temperature alone was used, and in Examples 1 to 12 in which a plurality of types of alkali compounds were used in combination, the heating temperature in the melting step S20 was set to a low temperature. Nevertheless, it was confirmed that the extraction rate of valuable metals is sufficiently secured. Therefore, according to the conditions as shown in Examples 1 to 13, the heating cost in the melting step S20 can be reduced. Further, it is possible to separate the titanium oxide used for the production of crystalline titanium oxide with high purity from other valuable metals without being exposed to a high temperature.
Regarding the addition amount of the alkali compound in the melting step S20, also in Example 5 where the mass ratio of the addition amount of the alkali compound is 0.6, the extraction rate of the valuable metal was 90% or more. Therefore, it was confirmed that if the amount of alkali compound added is about 0.6 times or more of the total mass of metals contained as the catalyst component, the extraction rate of valuable metals can be sufficiently secured. In addition, when the addition amount of the alkali compound was further increased, the extraction rate of valuable metals further increased.
On the other hand, in Example 14 using an alkali carbonate and Example 15 using an alkali nitrate, the extraction rate of valuable metals was low.

  Next, the water-insoluble component contained in the reaction product of the alkali melting reaction was subjected to the acid treatment step S40. Concentration conditions for the acid mixed with the water-insoluble component in the acid treatment step S40 were separately examined in advance.

FIG. 6 is a diagram showing the relationship between the acid concentration and the remaining alkali amount in the acid treatment step.
The horizontal axis of FIG. 6 represents the concentration of hydrochloric acid (wt%) added to the water-insoluble component in the acid treatment step S40, and the vertical axis represents the residual amount of alkali (%) remaining in the residue after the acid treatment step S40. It represents. The remaining amount of alkali (%) is the fraction of element mass for each alkali element.
In the residue according to Example 4 shown in FIG. 6, the total mass of potassium and sodium confirmed as a result of elemental analysis was about 20% by mass and 4% by mass, respectively, with respect to the total mass of the residue of the water-insoluble component. For potassium, when the hydrochloric acid concentration was 2.5% or more, and for potassium, the residual alkali amount was reduced to about 0.4% or less when the hydrochloric acid concentration was 5% or more.
Therefore, it can be seen from the above results that the acid concentration in the acid treatment step S40 is preferably equivalent to or higher than 5% hydrochloric acid. With 10% hydrochloric acid, the remaining alkali amount was approximately 0%, and no remaining alkali salt was confirmed.

Therefore, the residue consisting of the water-insoluble component recovered in the separation step S30 is washed with water, dried to a powder, mixed with 10% hydrochloric acid and acid-treated for 15 hours, and the alkali salt is sufficiently removed. Dissolved. And after acid treatment, the residue which consists of an acid insoluble component was collect | recovered by filtering, and it was made into powder form by washing with water and drying.
The recovered residual powder of the water-insoluble component before acid treatment and the residual powder of the acid-insoluble component after acid treatment were each subjected to powder X-ray diffraction measurement.

FIG. 7 is a diagram showing an example of an X-ray diffraction spectrum of a water-insoluble component recovered in the separation step.
The residue of the water-insoluble component recovered in the separation step S30 is 2θ = 10 ° to 15 °, 2θ = 25 ° to 40 °, and 2θ = as shown by the residue according to Example 4 shown in FIG. A halo pattern was exhibited around 55 ° to 70 °. Further, alkali silicate aluminates such as KAlSiO ₄ (represented by ▲ in the figure), Na ₅ Al ₅ Si ₅ O ₂₀ · 9H ₂ O (represented by ♦ in the figure) and Na ₂ Ti ₂ O ₄ A peak corresponding to alkali salt of titanic acid such as (OH) ₂ (indicated by ■ in the figure) or other complex oxide alkaline salt is shown, and rutile type titanium oxide (indicated by ● in the figure). The peak corresponding to is shown weakly.

FIG. 8 is a diagram showing an example of an X-ray diffraction spectrum of the acid-insoluble component recovered in the acid treatment step.
The residue of the acid-insoluble component recovered in the acid treatment step S40 shows a halo pattern centering around 2θ = 20 ° to 40 ° as shown by the residue according to Example 4 shown in FIG. A peak corresponding to titanium oxide (represented by ● in the figure) was shown. On the other hand, peaks corresponding to various alkali salts disappeared. In the residue according to Example 4, the element content of potassium and sodium was about 24% by mass with respect to the total mass of the residue, but decreased to about 0.4% by mass, and silicon remained as an impurity, Similarly, the content of elements such as aluminum, magnesium, iron, and carbon was also decreased. On the other hand, the elemental content of titanium was about 82% by mass with respect to the total mass of the residue, and the purity of titanium was improved.

  From the results of these analyses, the residue of the acid-insoluble component recovered in the acid treatment step S40 is mainly composed of amorphous titanium oxide, and a small amount of rutile-type titanium oxide is added to amorphous titanium oxide. It was judged to have a mixed composition.

Next, the residue of the acid-insoluble component recovered in the acid treatment step S40 was baked to produce crystalline titanium oxide.
Firing was performed under a plurality of temperature conditions including a heating time of 4 hours and a heating temperature in the range of 300 ° C to 650 ° C. The recovered titanium oxide powder was subjected to powder X-ray diffraction measurement.

FIG. 9 is a diagram showing an example of an X-ray diffraction spectrum of titanium oxide recovered in the firing step.
As shown in FIG. 9, the titanium oxide fired at a heating temperature of 500 ° C. showed a strong peak corresponding to anatase-type titanium oxide (indicated by ◯ in the figure). Compared with the X-ray diffraction spectrum before firing as shown in FIG. 8, a peak corresponding to rutile type titanium oxide (indicated by ● in the figure) remained slightly, but amorphous titanium oxide. The halo pattern indicating decreased. At a heating temperature of 500 ° C., the integrated intensity ratio (I _A / I _R ) between the integrated intensity (I _A ) of the peak showing the anatase type crystal structure and the integrated intensity (I _R ) of the peak showing the rutile type crystal structure is 48.1. In addition, in titanium oxide fired at a heating temperature of 400 ° C., a peak indicating anatase-type crystal structure was confirmed and the halo pattern indicating amorphous titanium oxide was reduced, as in 500 ° C. It was. At a heating temperature of 400 ° C., the integrated intensity ratio (I _A / I _R ) was 24.0.

The peak showing the anatase type crystal structure as shown in FIG. 9 was observed in the titanium oxide fired under the condition where the heating temperature was in the range of 400 ° C. to 600 ° C. Therefore, it was confirmed that crystalline titanium oxide having an anatase type crystal structure as a main phase can be produced by setting the heating temperature in the firing step to 400 ° C. or more and 600 ° C. or less.
On the other hand, in titanium oxide fired at a heating temperature of 300 ° C., a halo pattern indicating amorphous titanium oxide remained, and no peak indicating an anatase type crystal structure was confirmed.
On the other hand, in titanium oxide fired at a heating temperature set to 650 ° C. or higher, the peak indicating the rutile crystal structure is the center, the peak indicating the anatase crystal structure is small, and the halo indicating amorphous titanium oxide. The pattern was not confirmed. Therefore, it was confirmed that by setting the heating temperature in the firing step to 650 ° C. or higher, crystalline titanium oxide having a rutile crystal structure as a main phase can be produced.

Next, the BET specific surface area of the titanium oxide contained in the denitration catalyst and the produced crystalline titanium oxide was measured.
The BET specific surface area was measured based on a constant volume method using nitrogen gas as an adsorbed gas, using a surface area analyzer “NOVA-1200” (manufactured by Quantachrome).

As a result of measuring the BET specific surface area, the BET specific surface area in the denitration catalyst before use was 100 m ² / g, and the BET specific surface area in the used denitration catalyst was 22 m ² / g. Moreover, the BET specific surface area in the titanium oxide recovered in the acid treatment step was further reduced to 17.5 m ² / g.
On the other hand, the BET specific surface area in the titanium oxide baked by setting the heating temperature to 500 ° C. in the baking step was increased to 46 m ² / g. Moreover, the BET specific surface area in the titanium oxide baked by setting the heating temperature to 400 ° C. was increased to 40 m ² / g.
Therefore, the titanium oxide having become amorphous by being mixed with an alkali compound and having a significantly reduced BET specific surface area is subjected to a firing step at a heating temperature of 400 ° C. or higher, preferably 500 ° C. or higher. It can be seen that it is regenerated to crystalline titanium oxide whose surface area has been recovered.

S10 Machine selection step S20 Melting step S30 Separation step S40 Acid treatment step S50 Firing step S60 Catalyst production step S70 Separation and recovery step 1 Waste catalyst (waste material)
2 catalyst support substrate 3 titanium oxide 4 tungsten oxide 5 molybdenum oxide 6 vanadium oxide 7 quartz sol 8 inorganic fiber 9 dust

Claims (14)

Mixing and heating the waste material comprising titanium oxide and at least one alkali compound selected from the group consisting of alkali hydroxide, alkali carbonate, and alkali nitrate;
Mixing an insoluble component contained in the reaction product generated by the heating with an acid;
Calcination of the insoluble component obtained by mixing with the acid to produce crystalline titanium oxide,
A method for producing crystalline titanium oxide, comprising: Waste material comprising at least one metal oxide selected from the group consisting of titanium oxide and tungsten, molybdenum and vanadium, and at least selected from the group consisting of alkali hydroxide, alkali carbonate and alkali nitrate Mixing and heating a kind of alkali compound,
Water is added to the reaction product produced by the heating, and the reaction product contains a soluble component comprising an alkali salt of at least one metal selected from the group consisting of tungsten, molybdenum and vanadium. Separating from insoluble components,
Mixing an insoluble component separated from the soluble component with an acid;
Calcination of the insoluble component obtained by mixing with the acid to produce crystalline titanium oxide,
A method for producing crystalline titanium oxide, comprising: The heating temperature in the firing is 400 ° C. or more and 600 ° C. or less,
The method for producing crystalline titanium oxide according to claim 1 or 2, wherein the produced crystalline titanium oxide is of anatase type. The heating temperature in the firing is 650 ° C. or higher,
The method for producing crystalline titanium oxide according to claim 1, wherein the produced crystalline titanium oxide is a rutile type. The production of crystalline titanium oxide according to claim 1 or 2, wherein the alkali compound is at least one selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides. Method. The method for producing crystalline titanium oxide according to claim 1 or 2, wherein the alkali compound comprises at least one alkali metal selected from the group consisting of lithium, sodium and potassium. The method for producing crystalline titanium oxide according to claim 1 or 2, wherein the mixed acid is at least one selected from the group consisting of hydrochloric acid, sulfuric acid and nitric acid. The method for producing crystalline titanium oxide according to claim 1 or 2, wherein a heating temperature in the mixing and heating step is 150 ° C or higher and 350 ° C or lower. The method for producing crystalline titanium oxide according to claim 1 or 2, wherein the waste material is a used denitration catalyst. The method for producing crystalline titanium oxide according to claim 9, further comprising a step of separating the used denitration catalyst from the catalyst support substrate prior to the mixing and heating step. A used denitration catalyst comprising titanium oxide, and an oxide of at least one metal selected from the group consisting of tungsten, molybdenum and vanadium; and a group consisting of alkali hydroxide, alkali carbonate and alkali nitrate Mixing and heating at least one selected alkali compound;
Water is added to the reaction product produced by the heating, and the reaction product contains a soluble component comprising an alkali salt of at least one metal selected from the group consisting of tungsten, molybdenum and vanadium. Separating from insoluble components,
Mixing an insoluble component separated from the soluble component with an acid;
Calcination of the insoluble component obtained by mixing with the acid to produce crystalline titanium oxide,
A step of mixing the produced crystalline titanium oxide and a metal compound composed of the metal and calcining to produce a denitration catalyst,
A method for regenerating a denitration catalyst comprising: further,
Separating and recovering the metal from a soluble component comprising the alkali salt of the metal,
The method for regenerating a denitration catalyst according to claim 11, wherein the produced crystalline titanium oxide and the metal compound composed of the separated and recovered metal are mixed and calcined to produce a denitration catalyst. The heating temperature in the firing is 400 ° C. or more and 600 ° C. or less,
The method for regenerating a denitration catalyst according to claim 11, wherein the produced crystalline titanium oxide is of anatase type. The method for regenerating a denitration catalyst according to claim 11, wherein a heating temperature in the mixing and heating step is 150 ° C or higher and 350 ° C or lower.

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