JP2008230950A - N- and/or s-doped tubular titanium oxide particle and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide N- and/or S-doped tubular titanium oxide particles which exhibit high photocatalytic performance under natural light including visible light or under irradiation with light from an artificial light source. <P>SOLUTION: The N- and/or S-doped tubular titanium oxide particles are characterized in that the content of N is within a range of 0.1-5 wt.% expressed in terms of N, the content of S is within a range of 0.2-6 wt.% expressed in terms of S, the average outer tube diameter (D<SB>out</SB>) is within a range of 5-40 nm, the average inner tube diameter (D<SB>in</SB>) is within a range of 4-20 nm, the average tube thickness is within a range of 0.5-10 nm, the average length (L<SB>p</SB>) is within a range of 25-1,000 nm, and the aspect ratio (L<SB>p</SB>/D<SB>out</SB>) is within a range of 5-200. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to tubular titanium oxide-based particles doped with nitrogen (N) and / or sulfur (S) and a method for producing the same. The present invention also relates to tubular titanium oxide-based particles doped with nitrogen (N) and / or sulfur (S) containing iron oxide and a method for producing the same.
More specifically, N- and / or S-doped tubular titanium oxide particles that have high photocatalytic activity in the visible light region and can be suitably used for environmental catalysts, deodorizing catalysts, semiconductor films for solar cells, and the like. It relates to the manufacturing method. The present invention also relates to N- and / or S-doped tubular titanium oxide particles further improved in photocatalytic activity due to containing iron oxide and a method for producing the same.

  Titanium oxide has a wide range of uses that make use of its chemical properties. For example, it has an appropriate bond strength with oxygen and has acid resistance, so it can be used as a redox catalyst or carrier, as a surface coating agent for cosmetic materials or plastic materials using the shielding ability of ultraviolet rays, and also as a high dielectric material, high refractive index. As an anti-reflective coating material that utilizes slag, reduced titanium oxide is used as an antistatic material that utilizes electrical conductivity. In addition, these properties are used in combination for functional hard coat materials, and further used for antibacterial agents, antifouling agents, superhydrophilic coatings and the like using photocatalysis.

  In recent years, titanium oxide has been suitably used as a photocatalyst because it has a high band gap, and also as a so-called photoelectric conversion material that converts light energy into electric energy. Moreover, it has come to be used also for secondary batteries such as lithium batteries, hydrogen storage materials, proton conductive materials, and the like.

  Thus, titanium oxide is used in many applications, but depending on the application, the UV activity is high, the photocatalytic activity is too strong, and the light resistance may be inferior. In order to suppress this, Si or the like is doped. Or as a composite oxide with other oxides.

The applicant of the present application is that N-doped tubular titanium oxide particles having excellent conductivity, photocatalytic performance, visible light absorption ability, chemical resistance, and the like, and an aqueous dispersion of titanium oxide particles in the presence of an alkali metal hydroxide. A method for producing N-doped tubular titanium oxide particles that is subjected to a reduction treatment in the presence of ammonia, amine or the like after hydrothermal treatment is disclosed (Patent Document 1: Japanese Patent Application Laid-Open No. 2004-35362).
However, the N-doped tubular titanium oxide particles do not necessarily have sufficient visible light absorption (shielding) performance, and have problems in photocatalytic activity and durability.

Patent Document 2 (Japanese Patent Application Laid-Open No. 2001-205103) discloses a photocatalyst that is a titanium compound doped with nitrogen atoms or sulfur atoms between the lattices of a titanium oxide crystal and has a charge separation substance supported on the surface thereof. Is disclosed.
This photocatalyst is exemplified by a sputtering method. In nitrogen doping, a TiO ₂ target is set in a vacuum chamber, N ₂ gas and Ar gas are introduced, and sputtering is performed in N ₂ and Ar plasma. An N-doped titanium oxide film is obtained by heat treatment (annealing) in a nitrogen atmosphere. In addition, in sulfur doping, a method is described in which Ti, TiO ₂ or TiS (titanium sulfide) is used as a target, sputtering is performed in SO ₂ + O ₂ + Ar gas, and heat treatment is performed. However, in any case, a large amount of oxygen defects are generated simultaneously with doping, and this defect becomes a recombination center. Therefore, there is a problem that when the doping concentration is increased, the catalytic activity is greatly reduced.

  One of the inventors of the present application discloses a sulfur-containing metal oxide useful as a photo-oxidation catalyst and a method for producing the same (Patent Document 3: Japanese Patent Application Laid-Open No. 2004-143032). However, this photo-oxidation catalyst also has an amorphous metal oxide, and the photocatalytic activity is not always sufficient.

  Under such circumstances, the present inventors have conducted further earnest studies, and as a result, N-doped tubular titanium oxide having excellent photocatalytic activity while maintaining crystallinity when tubular titanium oxide is treated with urea or thiourea, The inventors have found that S-doped tubular titanium oxide can be obtained and have completed the present invention.

JP 2004-35362 A JP 2001-205103 A JP 2004-143032 A

  An object of the present invention is to provide N and / or S-doped tubular titanium oxide particles that exhibit high photocatalytic performance under irradiation of natural light including visible light or an artificial light source, and a method for producing the same.

In the N and / or S-doped tubular titanium oxide particles according to the present invention, the N content is in the range of 0.1 to 5% by weight as N, and the S content is 0.2 to 6% by weight as S. It is characterized by being in range.
The tubular titanium oxide particles have an average tube outer diameter (D _out ) in the range of 5 to 40 nm, an average tube inner diameter (D _in ) in the range of 4 to 20 nm, and an average tube thickness of 0.5 to 10 nm. The average length (L _p ) is in the range of 25 to 1000 nm, and the aspect ratio (L _p ) / (D _out ) is preferably in the range of 5 to 200.
The crystal form of the N and / or S doped tubular titanium oxide particles is preferably an anatase type.
In the N and / or S-doped tubular titanium oxide particles according to the present invention, iron oxide is supported in the range of 0.01 to 5% by weight as Fe ₂ O _{3 on the} N and / or S-doped tubular titanium oxide particles. It is characterized by that.

The method for producing N- and / or S-doped tubular titanium oxide particles according to the present invention comprises the tubular titanium oxide particles at 200 to 700 ° C., one or more nitrogen compounds selected from urea and amino acids and / or elemental sulfur. , Thiourea, mercaptan, decanethiol, and thioacetamide, which are contacted with one or more sulfur compounds.
The nitrogen compound and / or sulfur compound is preferably contacted in an air atmosphere.

The tubular titanium oxide particles have an average tube outer diameter (D _out ) in the range of 5 to 40 nm, an average tube inner diameter (D _in ) in the range of 4 to 20 nm, and an average tube thickness of 0.5 to 10 nm. The average length (L _p ) is in the range of 25 to 1000 nm, and the aspect ratio (L _p ) / (D _out ) is preferably in the range of 5 to 200.
The N content in the N and / or S-doped tubular titanium oxide particles is in the range of 0.1 to 5% by weight as N, and the S content is in the range of 0.2 to 6% by weight as S. Is preferred.
The crystal form of the N and / or S doped tubular titanium oxide particles is preferably an anatase type.

In the method for producing N and / or S-doped tubular titanium oxide particles according to the present invention, the dispersion of N and / or S-doped tubular titanium oxide particles obtained by the production method is prepared by adding second nitric acid in the presence of an ion exchange resin. An aqueous iron solution is mixed, then dried, and heat-treated as necessary.
In the method for producing N and / or S-doped tubular titanium oxide particles according to the present invention, the ferric nitrate aqueous solution is absorbed in the N and / or S-doped tubular titanium oxide particles obtained by the production method, and then dried. The heat treatment is performed as necessary.

INDUSTRIAL APPLICABILITY According to the present invention, N- and / or S-doped tubes useful as raw materials for functional materials such as photocatalysts, photoelectric conversion materials, cosmetic materials, and optical materials obtained by treating tubular titanium oxide with specific nitrogen compounds and sulfur compounds. Titanium oxide particles and a method for producing the same can be provided.
Moreover, in the N and / or S-doped tubular titanium oxide particles containing iron oxide according to the present invention, the photocatalytic activity is further improved.

N and / or S-doped tubular titanium oxide particles The N and / or S-doped tubular titanium oxide particles according to the present invention have a content of N in the range of 0.1 to 5% by weight as N, and a content of S. S is in the range of 0.2 to 6% by weight.
In the present invention, conventionally known tubular titanium oxide particles can be used as the tubular titanium oxide particles. Examples thereof include tubular titanium oxide particles disclosed in JP-A-10-152323 and JP-A-2004-35362 (Patent Document 1). Since such tubular titanium oxide particles have pores penetrating inside, the effective surface is larger than that of rod-like or fiber-like titanium oxide, and the contact efficiency with the reactants is improved, resulting in high photocatalytic activity. Can be expressed. It is also considered that this is a factor that enables uniform N and / or S doping to the inside of the particle.

  Among them, the tubular titanium oxide particles before the reduction treatment disclosed in Patent Document 1 have a small residual amount of alkali, and even when the N and / or S doping treatment described later is at a high temperature or when used as a catalyst. N- and / or S-doped tubular titanium oxide particles excellent in photocatalytic activity and the like can be obtained without being easily sintered (sintered) or producing sodium titanate even at a high temperature.

The average tube outer diameter (D _out ) of the tubular titanium oxide particles is preferably in the range of 5 to 40 nm, more preferably 5 to 20 nm.
When the average tube outer diameter (D _out ) of the tubular titanium oxide particles is less than 5 nm, it is difficult to obtain, and even if obtained, the crystallinity of the tubular titanium oxide particles is insufficient, and the photocatalytic performance is insufficient. It may become. When the average tube outer diameter (D _out ) of the tubular titanium oxide particles exceeds 40 nm, the doping of N and / or S may become non-uniform, or the doping amount may decrease and the photocatalytic performance may become insufficient.

The average tube inner diameter (D _in ) of tubular titanium oxide is preferably in the range of 4 to 20 nm, more preferably 4 to 15 nm.
When the average tube inner diameter (D _in ) of the tubular titanium oxide particles is less than 4 nm, the crystallinity of the tubular titanium oxide particles may be insufficient, and the photocatalytic performance and the like may be insufficient. When the average tube inner diameter (D _in ) of the tubular titanium oxide particles exceeds 20 nm, the average tube outer diameter (D _out ) of the tubular titanium oxide particles exceeds 40 nm, and N and / or S doping becomes non-uniform, Doping amount may decrease and photocatalytic performance may become insufficient.

The average tube thickness of the tubular titanium oxide particles is preferably in the range of 0.5 to 10 nm, more preferably 0.5 to 5 nm.
When the average tube thickness of the tubular titanium oxide particles is less than 0.5 nm, when the doping treatment of N and / or S becomes a high temperature, the crystallinity is lowered or the voids cannot be maintained and the rod-like or fiber-like titanium oxide It may become particles and the photocatalytic performance and the like may be insufficient. If the average tube thickness of the tubular titanium oxide particles exceeds 10 nm, the doping of N and / or S may become non-uniform, or the amount of doping may decrease, resulting in insufficient photocatalytic performance.

The average length (L _p ) of the tubular titanium oxide particles is preferably in the range of 25 to 1000 nm, more preferably 50 to 500 nm. It is difficult to obtain a tubular titanium oxide particle having an average length (L _p ) outside the above range.
The aspect ratio (L _p ) / (D _out ) of the tubular titanium oxide particles is preferably 5 to 200, more preferably 10 to 100.
It is difficult to obtain an aspect ratio (L _p ) / (D _out ) outside the above range.

The outer diameter (D _out ), inner diameter (D _in ), length (L _p ) and the like are obtained by taking a transmission electron micrograph, measuring each value for 100 particles, and obtaining the average value. The inner diameter (D _in ) can be obtained from a line that forms a boundary of contrast recognized inside the line for obtaining the outer diameter.

  The tubular titanium oxide particles used in the present invention are preferably crystalline tubular titanium oxide, and anatase type titanium oxide, brookite type titanium oxide and rutile type titanium oxide are preferably used. Among these, anatase-type tubular titanium oxide particles are suitable because they are relatively easy to synthesize and have excellent photocatalytic activity.

Further, the tubular titanium oxide particles used in the present invention have an alkali content (residual amount) such as Na or K that may be used during synthesis, which varies depending on the application, but is 0.2 as Na ₂ O or K ₂ O. It is preferably 1% by weight or less, more preferably 0.05% by weight or less, and particularly preferably 0.01% by weight or less. If alkali content is 0.1 weight% or less, it can use suitably as a photocatalyst, a photoelectric conversion material, etc.

Next, the N content in the N and / or S-doped tubular titanium oxide particles is preferably 0.1 to 5% by weight, more preferably 0.2 to 3% by weight as N. Moreover, it is preferable that content of S exists in the range of 0.2-6 weight% as S, and also 0.5-5 weight%.
When the content of N is less than 0.1% by weight as N, the generation density of the impurity rank accompanying the doping of the N element is small, so the light absorption in the visible light region is extremely small, and the photocatalytic activity under visible light Is hardly expressed. On the other hand, when the content of N exceeds 5 wt% as N, the elemental N is excessively doped into the tubular titanium oxide particles, so that the crystal structure of titanium oxide is distorted. Further, by replacing the N (3-) element with the O (2-) element, the electrical neutrality in the titanium oxide crystal lattice is destroyed. Due to these changes, the catalyst activity of the catalyst doped with N element exceeding 5% by weight in the tubular titanium oxide particles is remarkably lowered.

  Further, when the S content is less than 0.2% by weight as S, since the generation density of the impurity rank accompanying the doping of the S element is small, the light absorption in the visible light region is extremely small, and under visible light. Almost no photocatalytic activity is exhibited. On the other hand, when the S content exceeds 6% by weight as S, the elemental S is excessively doped into the tubular titanium oxide particles, thereby causing distortion in the crystal structure of titanium oxide. Due to this change, the catalyst activity of the catalyst doped with S element exceeding 6 wt% in the tubular titanium oxide particles is remarkably lowered.

When N and / or S-doped tubular titanium oxide particles contain both N and S, the total content is 0.1 to 6% by weight as N and S, and further 0.2 to 5% by weight. It is preferable that it exists in the range.
The average tube outer diameter (D _out ), average tube inner diameter (D _in ), average tube thickness, average length (L _p ) and aspect ratio (L _p ) of such N and / or S-doped tubular titanium oxide particles / (D _out ) is the same as the tubular titanium oxide particles.

  The N and / or S doped tubular titanium oxide particles are preferably crystalline N and / or S doped tubular titanium oxide, and anatase type titanium oxide, brookite type titanium oxide and rutile type titanium oxide are preferably used. Among these, anatase-type N and / or S-doped tubular titanium oxide particles are excellent in photocatalytic activity and can be suitably used.

In the N and / or S-doped tubular titanium oxide particles of the present invention, iron oxide is preferably supported in the range of 0.01 to 5% by weight, more preferably 0.02 to 2% by weight as Fe ₂ O _3. .
When the supported amount of iron oxide is less than 0.01% by weight as Fe ₂ O ₃ , the effect of improving the photocatalytic activity may not be sufficiently obtained. When the amount exceeds 5% by weight, the reason is not necessarily clear, but oxidation The photocatalytic activity may be lower than when no iron is supported.

Method for Producing N and / or S Doped Tubular Titanium Oxide Particles Next, a method for producing N and / or S doped tubular titanium oxide particles according to the present invention will be described.
The method for producing N- and / or S-doped tubular titanium oxide particles according to the present invention comprises the tubular titanium oxide particles at 200 to 700 ° C., one or more nitrogen compounds selected from urea and amino acids and / or elemental sulfur. , Thiourea, mercaptan, decanethiol, and thioacetamide, which are contacted with one or more sulfur compounds.
As the tubular titanium oxide particles, the same tubular titanium oxide particles as described above are used.

The nitrogen compound is preferably one or more nitrogen compounds selected from urea and amino acids. Examples of amino acids include glycine, alanine, valine, leucine, tyrosine and the like.
When such a nitrogen compound is used, tubular titanium oxide particles uniformly doped with N can be obtained without substantially impairing the crystallinity of the tubular titanium oxide particles. In addition, since the decrease in crystallinity can be suppressed, doping treatment can be performed at a higher temperature, and tubular titanium oxide particles with a large amount of N doping can be obtained.
In addition, the nitrogen compounds such as ammonia, amine, hydrazine, and pyridine used in the method for producing reduced tubular titanium oxide disclosed in Patent Document 1 are strongly basic, or the crystallinity of the obtained N-doped tubular titanium oxide particles is low. The photocatalytic performance and the like were not always satisfactory.

The sulfur compound is preferably one or more sulfur compounds selected from thiourea (sometimes referred to as thiourea, (NH ₂ ) ₂ CS), mercaptan, decanethiol, and thioacetamide. Such a sulfur compound can be physically mixed with the tubular titanium oxide particles at room temperature as compared with other sulfur compounds such as H ₂ S, CS ₂ and SO ₂ . Moreover, since it is also possible to control the addition amount, it is preferable.

Such a nitrogen compound and sulfur compound are brought into contact with the tubular titanium oxide particles at 200 to 700 ° C, and further at 300 to 650 ° C.
As a contacting method, a nitrogen compound or a sulfur compound and tubular titanium oxide particles can be mixed and heated, and the nitrogen compound and / or the sulfur compound can also be contacted in a gas atmosphere.

  At this time, rare gas, nitrogen gas, oxygen gas, air, or the like can be used as the gas, but air is preferred in the method for producing N and / or S-doped tubular titanium oxide particles of the present invention. When only an inert gas such as a rare gas or nitrogen gas is used, depending on the contact temperature, reduction (deoxygenation) of the tubular titanium oxide particles may occur and many lattice defects may occur. In addition, when the doping nitrogen compound and the sulfur compound are compounds containing carbon, carbon may be deposited on the surface of the tubular titanium oxide particles. For this reason, the obtained N and / or S doped tubular titanium oxide particles Even when used as a photocatalyst, sufficient activity may not be obtained.

The concentration of the nitrogen compound and / or sulfur compound in the air is not particularly limited, but is generally in the range of 10 ppm to 50% by volume, more preferably 50 ppm to 10% by volume.
When the concentration is less than 10 ppm, N and / or S may be insufficiently doped, or it may take a long time to dope desired N and / or S.
When the concentration exceeds 50% by volume, the inner surface or the outer surface of the tubular titanium oxide is selectively doped with N and / or S, and uneven doping occurs, or the doping amount exceeds the upper limit described above. In some cases, the photocatalytic activity may become insufficient with phase separation and a decrease in crystallinity.

  Moreover, although the usage-amount of a nitrogen compound and / or a sulfur compound changes also with process temperature, it is preferable that it is the same or more thru | or 5 times or less substantially as desired content. Further, the above-described processing can be repeated as necessary. In this way, tubular titanium oxide particles doped with N and / or S in the desired content described above are obtained.

First method for producing iron oxide-supported N and / or S-doped tubular titanium oxide particles Further, iron oxide is supported on the N and / or S-doped tubular titanium oxide particles of the present invention, but iron oxide is supported. As a first method for producing N and / or S-doped tubular titanium oxide particles, the dispersion of N and / or S-doped tubular titanium oxide particles obtained as described above is mixed with nitric acid in the presence of an ion exchange resin. It is preferable to mix a two-iron aqueous solution, then dry, and heat-treat as necessary.

The concentration of the N and / or S-doped tubular titanium oxide particle dispersion is not particularly limited as long as the ion exchange resin described later can be dispersed and the dispersion can be uniformly stirred, but the solid content is 1 to 30% by weight, It is preferably in the range of 20% by weight.
If the concentration of the N- and / or S-doped tubular titanium oxide particle dispersion is less than 1% by weight as the solid content, the productivity decreases, and if it exceeds 30% by weight, the iron oxide loading becomes non-uniform, In some cases, the effect of supporting the iron oxide is reduced, and the effect of improving the photocatalytic activity is not sufficiently obtained.

As the ion exchange resin, a conventionally known anion exchange resin can be used to remove the nitrate radical of ferric nitrate.
The amount of the ion exchange resin used can be varied depending on the ion exchange capacity of the ion exchange resin and the amount of ferric nitrate used, but it is preferable that the amount of nitrate radicals be removed substantially.
Although ferric nitrate is used in the method of the present invention, ferrous nitrate can also be used, and ferric sulfate and ferric chloride can also be used. However, although the reason is not clear, ferric nitrate can be suitably used because it has the most excellent effect of improving photocatalytic activity. Furthermore, in the method of the present invention, ferric nitrate and other salts can be mixed and used.

The amount of ferric nitrate used is 0.01 to 5% by weight as the Fe ₂ O ₃ content of iron oxide in the finally obtained N and / or S-doped tubular titanium oxide particles supporting iron oxide, Is used in a range of 0.02 to 2% by weight.
Next, after adding the ferric nitrate aqueous solution, stirring is continued as necessary, and then a dispersion of N and / or S-doped tubular titanium oxide particles carrying iron oxide is obtained by separating the ion exchange resin. Can do. The obtained iron oxide-supported N and / or S-doped tubular titanium oxide particle dispersion can be used as it is, but can be concentrated or diluted as necessary. Furthermore, it can be dried and heat-treated as necessary to form a powder, or the powder can be molded and used as a molded body.

At this time, the drying temperature is not particularly limited as long as moisture can be substantially removed, but is preferably in the range of 80 to 250 ° C, more preferably 95 to 200 ° C.
The heating temperature at the time of heat treatment as necessary is generally in the range of 200 to 650 ° C, and further 300 to 600 ° C. When the heating temperature is less than 200 ° C., decomposition and desorption of nitrate radicals are insufficient, and a sufficient effect of improving photocatalytic activity may not be obtained. When the heating temperature exceeds 650 ° C., the crystal form of titanium oxide may change from anatase type to rutile type, and the photocatalytic activity may decrease, or the N and / or S-doped tubular titanium oxide particles carrying iron oxide may be strong. Aggregation may require pulverization, or sufficient photocatalytic activity may not be obtained.

Second Production Method of Iron Oxide-Supported N and / or S-Doped Tubular Titanium Oxide Particles As a second production method of N and / or S-doped tubular titanium oxide particles carrying iron oxide, the above-described N and It is also possible to absorb the ferric nitrate aqueous solution in the S-doped tubular titanium oxide particles, then dry and heat-treat as necessary.
When the ferric nitrate aqueous solution is absorbed by the powdered N and / or S-doped tubular titanium oxide particles, the amount of the ferric nitrate aqueous solution depends on the average particle diameter of the N and / or S-doped tubular titanium oxide particles. Although different, it is preferable that the N- and / or S-doped tubular titanium oxide particles absorb the aqueous solution uniformly and become a paste. The concentration of the N and / or S-doped tubular titanium oxide particles in the paste-like mixture at this time is about 25 to 60% by weight as the solid content.

When the concentration of the N and / or S-doped tubular titanium oxide particles in the paste-like mixture is less than 25% by weight as a solid content, the total amount of iron oxide may not be supported. In some cases, iron oxide cannot be uniformly supported on the S-doped tubular titanium oxide particles, and the effect of improving the photocatalytic activity may not be sufficiently obtained.
The amount of ferric nitrate used is 0.01 to 5% by weight as the Fe ₂ O ₃ content of iron oxide in the finally obtained N and / or S-doped tubular titanium oxide particles supporting iron oxide, Is used in a range of 0.02 to 2% by weight.

Next, the paste-like mixture is dried. There is no restriction | limiting in particular in the drying method, A conventionally well-known method is employable. Although there will be no restriction | limiting in particular if a drying temperature can remove a water | moisture content substantially, It is preferable that it exists in the range of 80-250 degreeC, Furthermore, 95-200 degreeC.
Next, heat treatment is performed as necessary, but the heating temperature is generally in the range of 200 to 650 ° C., more preferably 300 to 600 ° C. When the heating temperature is less than 200 ° C., decomposition and desorption of nitrate radicals are insufficient, and a sufficient effect of improving photocatalytic activity may not be obtained. When the heating temperature exceeds 650 ° C., the crystal form of titanium oxide may change from anatase type to rutile type, and the photocatalytic activity may decrease, or the N and / or S-doped tubular titanium oxide particles carrying iron oxide may be strong. Aggregation may require pulverization, or sufficient photocatalytic activity may not be obtained.

  Hereinafter, although an example explains, the present invention is not limited by these examples.

[Example 1]
Preparation of tubular titanium oxide particles (PT) A titanium chloride aqueous solution was diluted with pure water to prepare a titanium chloride aqueous solution having a concentration of 5% by weight as TiO ₂ . This aqueous solution was neutralized and hydrolyzed by adding it to 15% by weight ammonia water whose temperature was adjusted to 5 ° C. The pH after addition of the aqueous titanium chloride solution was 10.5. Next, the produced gel was washed by filtration to obtain an orthotitanic acid gel having a concentration of 9% by weight as TiO ₂ .
After 1000 g of this orthotitanic acid gel was dispersed in 29000 g of pure water, 800 g of hydrogen peroxide having a concentration of 35% by weight was added and heated at 85 ° C. for 3 hours with stirring to prepare a peroxotitanic acid aqueous solution. The concentration of the resulting aqueous peroxotitanic acid solution as TiO ₂ was 0.5% by weight.

Then, the mixture was heated at 95 ° C. for 10 hours to obtain a titanium oxide particle dispersion, and tetramethylammonium hydroxide (molecular weight: 149.m.) was added to the titanium oxide particle dispersion so that the molar ratio to TiO ₂ in the dispersion was 0.016. 2) was added. The pH of the dispersion at this time was 11. Next, hydrothermal treatment was performed at 230 ° C. for 5 hours to prepare a titanium oxide particle dispersion. The average particle diameter of the titanium oxide particles was 20 nm.

In the titanium oxide particle dispersion liquid, a KOH aqueous solution 700g of concentration 40 wt%, TiO ₂ molar number (T _M) and the number of moles of potassium hydroxide (A _M) and the molar ratio of (A _M) / (T _M ) Was added to 10 and hydrothermally treated at 150 ° C. for 2 hours to synthesize tubular titanium oxide particles.
The obtained particles were sufficiently washed with pure water. At this time, the residual amount of K ₂ O was 0.9% by weight. After washing with pure water, an aqueous dispersion of tubular titanium oxide particles (concentration 5% by weight as TiO ₂ ) was added, and the same amount of cation exchange resin and anion exchange resin as tubular titanium oxide particles were added thereto. The resulting solution was treated at 60 ° C. for 24 hours to achieve high purity such as alkali removal.

Subsequently, it dried at 100 degreeC for 3 hours, and the tubular titanium oxide particle (PT) was prepared.
The obtained tubular titanium oxide particles (PT) were anatase-type titanium oxide. The average particle length obtained by taking a TEM photograph of the particles was 180 nm, the average tube outer diameter was 10 nm, and the average tube inner diameter was 7.5 nm.

Preparation of N-doped tubular titanium oxide particles (NPT-1) 20 g of tubular titanium oxide particles (PT) and 10.5 g of urea were mixed, placed in an alumina boat, and placed in an electric furnace set at 300 ° C. in an air atmosphere. Was heated for 3 hours to prepare N-doped tubular titanium oxide particles (NPT-1).
The obtained N-doped tubular titanium oxide particles (NPT-1) were analyzed for crystal form, N-doping amount and K ₂ O residual amount, and the results are shown in Table 1. Moreover, when the TEM photograph of particle | grains was image | photographed and the average particle length (L), the average pipe outer diameter (Dout), and the average pipe inner diameter (Din) were calculated | required, it was the same as a tubular titanium oxide particle (PT).

Evaluation of activity A solution prepared by mixing 2-propanol in acetonitrile solvent so as to have a concentration of 50 mmol / L was prepared, and 5 ml of this solution, 100 mg of N-doped tubular titanium oxide particles (NPT-1) and a stirrer were added to a test tube. And sealed with Parafilm (registered trademark). Irradiate the test tube with ultrasonic waves to fully disperse the N-doped tubular titanium oxide particles (NPT-1), stir the test tube with a magnetic stirrer, and simultaneously cool the air with an air blower to light the Xe lamp 1 Irradiated for hours. At this time, the light having a wavelength of 350 nm or less was blocked by the UV-35 filter and irradiated.
After irradiation, the solution was taken out, N-doped tubular titanium oxide particles (NPT-1) were separated with a centrifuge, and the amount of 2-propanol and produced acetone in the solution after the reaction was measured by gas chromatography. Table 1 shows the amount of 2-propanol reduced and the amount of acetone produced.

[Examples 2 to 5]
Preparation of N-doped tubular titanium oxide particles (NPT-2) to (NPT-5) N-doped tubular titanium oxide particles (NPT- ) were prepared in the same manner as in Example 1, except that 15 g, 30 g, 45 g and 60 g of urea were mixed. 2) to (NPT-5) were prepared.
The obtained N-doped tubular titanium oxide particles (NPT-2) to (NPT-5) were measured for crystal type, N-doped amount, and K ₂ O residual amount, and the results are shown in Table 1. The average particle length (L), average tube outer diameter (Dout), and average tube inner diameter (Din) of these N-doped tubular titanium oxide particles were the same as the tubular titanium oxide particles (PT). The activity was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Examples 6 and 7]
Preparation of N-doped tubular titanium oxide particles (NPT-6) and (NPT-7) N-doped tubular titanium oxide particles (NPT-6) were prepared in the same manner as in Example 2, except that the processing temperatures were 450 ° C. and 600 ° C. , (NPT-7) was prepared.
The obtained N-doped tubular titanium oxide particles (NPT-6) and (NPT-7) were measured for crystal type, N-doped amount, and K ₂ O residual amount, and the results are shown in Table 1. The average particle length (L), average tube outer diameter (Dout), and average tube inner diameter (Din) of these N-doped tubular titanium oxide particles were the same as the tubular titanium oxide particles (PT). The activity was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Examples 8 to 10]
Preparation of N / S doped tubular titanium oxide particles (NSPT-8) to (NSPT-10 ) 20 g of tubular titanium oxide particles (PT) and 5.7 g, 19 g and 76 g of thiourea were mixed, and this was mixed into an alumina boat. Then, heat treatment was performed in an electric furnace set at 300 ° C. under an air atmosphere for 3 hours to prepare N / S-doped tubular titanium oxide particles (NSPT-8) to (NSPT-10).
The obtained N / S-doped tubular titanium oxide particles (NSPT-8) to (NSPT-10) were measured for crystal type, N-doped amount, and K ₂ O residual amount, and the results are shown in Table 1. The average particle length (L), average tube outer diameter (Dout), and average tube inner diameter (Din) of these N / S-doped tubular titanium oxide particles were the same as the tubular titanium oxide particles (PT). The activity was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Examples 11 to 13]
Preparation of N / S-doped tubular titanium oxide particles (NSPT-11) to (NSPT-13) N / S-doped tubular oxidation in the same manner as in Example 10, except that the processing temperatures were 350 ° C., 400 ° C., and 450 ° C. Titanium particles (NSPT-11) to (NSPT-13) were prepared.
The obtained N / S-doped tubular titanium oxide particles (NSPT-11) to (NSPT-13) were measured for crystal type, N-doped amount, and K ₂ O residual amount, and the results are shown in Table 1. The average particle length (L), average tube outer diameter (Dout), and average tube inner diameter (Din) of these N / S-doped tubular titanium oxide particles were the same as the tubular titanium oxide particles (PT). The activity was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Example 14]
Preparation of S-doped tubular titanium oxide particles (SPT-14) 20 g of tubular titanium oxide particles (PT) and 3.2 g of simple sulfur as a sulfur compound were mixed, put in an alumina boat, and set in an electric furnace set at 300 ° C. S-doped tubular titanium oxide particles (SPT-14) were prepared by heat treatment in an air atmosphere for 3 hours.
The obtained S-doped tubular titanium oxide particles (SPT-14) were measured for crystal type, N-doped amount, and K ₂ O residual amount, and the results are shown in Table 1. The average particle length (L), average tube outer diameter (Dout), and average tube inner diameter (Din) of the S-doped tubular titanium oxide particles were the same as the tubular titanium oxide particles (PT). The activity was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Example 15]
Preparation of N-doped tubular titanium oxide particles (NPT-15 ) 20 g of N-doped tubular titanium oxide particles (NPT-1) prepared in the same manner as in Example 1 were dispersed in 180 g of water, stirred sufficiently, and then anion exchange resin. (Mitsubishi Chemical Corporation: SA20A) 5 g was mixed, and then the temperature was adjusted to 50 ° C., and then 2 g of ferric nitrate aqueous solution having a concentration of 1 wt% as Fe ₂ O ₃ was added and stirred for 2 hours. After that, the ion exchange resin was separated to obtain a dispersion of N-doped tubular titanium oxide particles (NPT-15) carrying iron oxide.
Subsequently, it was dried at 200 ° C. for 3 hours to prepare N-doped tubular titanium oxide particles (NPT-15) carrying iron oxide. The amount of iron oxide supported is shown in the table. The activity was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Example 16]
Preparation of N-doped tubular titanium oxide particles (NPT-16 ) 20 g of N-doped tubular titanium oxide particles (NPT-1) prepared in the same manner as in Example 1 were dispersed in 180 g of water, stirred well, and then anion exchange resin. (Mitsubishi Chemical Corporation: SA20A) 10 g was mixed, and then the temperature was adjusted to 50 ° C., and then 20 g of ferric nitrate aqueous solution having a concentration of 1% by weight as Fe ₂ O ₃ was added and stirred for 2 hours. After that, the ion exchange resin was separated to obtain a dispersion of N-doped tubular titanium oxide particles (NPT-16) carrying iron oxide.
Subsequently, N-doped tubular titanium oxide particles (NPT-16) supporting iron oxide were prepared by drying at 200 ° C. for 3 hours. The amount of iron oxide supported is shown in the table. The activity was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Example 17]
Preparation of N-doped tubular titanium oxide particles (NPT-17 ) 20 g of N-doped tubular titanium oxide particles (NPT-1) prepared in the same manner as in Example 1 were dispersed in 180 g of water, stirred sufficiently, and then anion exchange resin. (Mitsubishi Chemical Corporation: SA20A) 20 g was mixed, and after adjusting the temperature to 50 ° C., 40 g of ferric nitrate aqueous solution having a concentration of 1 wt% as Fe ₂ O ₃ was added and stirred for 2 hours. After that, the ion exchange resin was separated to obtain a dispersion of N-doped tubular titanium oxide particles (NPT-17) carrying iron oxide.
Subsequently, N-doped tubular titanium oxide particles (NPT-17) supporting iron oxide were prepared by drying at 200 ° C. for 3 hours. The amount of iron oxide supported is shown in the table. The activity was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Example 18]
Preparation of N-doped tubular titanium oxide particles (NPT-18 ) 20 g of N-doped tubular titanium oxide particles (NPT-1) prepared in the same manner as in Example 1 and ferric nitrate at a concentration of 1% by weight as Fe ₂ O ₃ 20 g of aqueous solution was mixed to make a paste.
Subsequently, it was dried at 200 ° C. for 3 hours to prepare N-doped tubular titanium oxide particles (NPT-18) carrying iron oxide. The amount of iron oxide supported is shown in the table. The activity was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Comparative Example 1]
The tubular titanium oxide particles (PT) before being doped with N and / or S as the tubular titanium oxide particles were evaluated for activity in the same manner as in Example 1, and the results are shown in Table 1.

[Comparative Example 2]
Preparation of N-doped tubular titanium oxide particles (RNPT-2) N-doped tubular titanium oxide particles (RNPT-2) were prepared in the same manner as in Example 1 except that 0.75 g of urea was mixed.
The obtained N-doped tubular titanium oxide particles (RNPT-2) were measured for crystal type, N-doped amount, and K ₂ O residual amount, and the results are shown in Table 1. The average particle length (L), average tube outer diameter (Dout), and average tube inner diameter (Din) of the N-doped tubular titanium oxide particles were the same as the tubular titanium oxide particles (PT). The activity was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Comparative Example 3]
Preparation of N-doped tubular titanium oxide particles (RNPT-3) N-doped tubular titanium oxide particles (RNPT-3) were prepared in the same manner as in Example 1 except that 72.6 g of urea was mixed.
The obtained N-doped tubular titanium oxide particles (RNPT-3) were measured for crystal type, N-doped amount, and K ₂ O residual amount, and the results are shown in Table 1. The average particle length (L), average tube outer diameter (Dout), and average tube inner diameter (Din) of the N-doped tubular titanium oxide particles were the same as the tubular titanium oxide particles (PT). The activity was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Comparative Example 4]
Preparation of S-doped tubular titanium oxide particles (RSPT-4) In Example 14, S-doped tubular titanium oxide particles (RSPT-4) were prepared in the same manner except that 0.8 g of elemental sulfur was mixed.
The obtained S-doped tubular titanium oxide particles (RSPT-4) were measured for crystal type, N-doped amount, and K ₂ O residual amount, and the results are shown in Table 1. The average particle length (L), average tube outer diameter (Dout), and average tube inner diameter (Din) of the S-doped tubular titanium oxide particles were the same as the tubular titanium oxide particles (PT). The activity was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Comparative Example 5]
Preparation of S-doped tubular titanium oxide particles (RSPT-5) In Example 14, S-doped tubular titanium oxide particles (RSPT-5) were prepared in the same manner except that 40 g of elemental sulfur was mixed.
The obtained S-doped tubular titanium oxide particles (RSPT-5) were measured for crystal type, N-doped amount, and K ₂ O residual amount, and the results are shown in Table 1. The average particle length (L), average tube outer diameter (Dout), and average tube inner diameter (Din) of the S-doped tubular titanium oxide particles were the same as the tubular titanium oxide particles (PT). The activity was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Comparative Example 6]
Preparation of N-doped tubular titanium oxide particles (RNPT-6) In an electric furnace adjusted to 400 ° C, tubular titanium oxide particles (PT) were supplied with ammonia gas (NH ₃ : 10% by volume) diluted with nitrogen for 2 hours. Thus, N-doped tubular titanium oxide particles (RNPT-6) were prepared.
The obtained N-doped tubular titanium oxide particles (RNPT-6) were measured for crystal type, N-doped amount, and K ₂ O residual amount, and the results are shown in Table 1. The average particle length (L), average tube outer diameter (Dout), and average tube inner diameter (Din) of the N-doped tubular titanium oxide particles were the same as the tubular titanium oxide particles (PT). The activity was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Claims (11)

  Tubular titanium oxide particles doped with N and / or S, wherein the content of N in the tubular titanium oxide particles is in the range of 0.1 to 5% by weight as N, and the content of S is as S N and / or S doped tubular titanium oxide particles in the range of 0.2 to 6% by weight. The tubular titanium oxide particles have an average tube outer diameter (D _out ) in the range of 5 to 40 nm, an average tube inner diameter (D _in ) in the range of 4 to 20 nm, and an average tube thickness of 0.5 to 10 nm. The average length (L _p ) is in the range of 25 to 1000 nm, and the aspect ratio (L _p ) / (D _out ) is in the range of 5 to 200. N and / or S doped tubular titanium oxide particles.   3. The N and / or S-doped tubular titanium oxide particles according to claim 1 or 2, wherein the N and / or S-doped tubular titanium oxide particles have an anatase crystal type. N and / or S-doped tubular titanium oxide particles according to any one of claims 1 to 3, characterized in that the iron oxide was loaded in a range of 0.01 to 5% by weight Fe ₂ O _3.   Tubular titanium oxide particles at 200 to 700 ° C., one or more nitrogen compounds selected from urea and amino acids, and / or one or more selected from elemental sulfur, thiourea, mercaptan, decanethiol, and thioacetamide A method for producing N- and / or S-doped tubular titanium oxide particles, characterized by contacting with a sulfur compound.   The method for producing N and / or S-doped tubular titanium oxide particles according to claim 5, wherein the nitrogen compound and / or the sulfur compound are contacted in an air atmosphere. The tubular titanium oxide particles have an average tube outer diameter (D _out ) in the range of 5 to 40 nm, an average tube inner diameter (D _in ) in the range of 4 to 20 nm, and an average tube thickness of 0.5 to 10 nm. The average length (L _p ) is in the range of 25 to 1000 nm, and the aspect ratio (L _p ) / (D _out ) is in the range of 5 to 200. The manufacturing method of the N and / or S dope tubular titanium oxide particle in any one.   The N content in the N and / or S-doped tubular titanium oxide particles is in the range of 0.1 to 5% by weight as N, and the S content is in the range of 0.2 to 6% by weight as S. The method for producing N and / or S-doped titanium oxide particles according to any one of claims 5 to 7.   The method for producing N and / or S doped tubular titanium oxide particles according to any one of claims 5 to 8, wherein the crystal form of the N and / or S doped tubular titanium oxide particles is an anatase type.   A ferric nitrate aqueous solution is mixed with the dispersion of N and / or S doped tubular titanium oxide particles obtained by the production method according to claim 5 in the presence of an ion exchange resin, and then necessary The method for producing N- and / or S-doped tubular titanium oxide particles is characterized by drying according to the above and heat treatment.   The N and / or S-doped tubular titanium oxide particles obtained by the production method according to claim 5 absorb the ferric nitrate aqueous solution, and then dry and heat-treat as necessary. A process for producing N and / or S doped tubular titanium oxide particles characterized by