JP2001321677A - Titanium oxide/carbon composite particle and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a titanium/carbon composite particle excellent in photocatalytic performance and suitable for a water treating material, a deodorant, an antibacterial material, a coating material, or the like. SOLUTION: The manufacturing method of the spherical titanium oxide/ carbon composite particle is implemented by carbonizing a spherical titanium oxide/carbon composite particle containing titanium oxide on the surface and inside, which is composed of carbonizable organic material such as cellulose.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to titanium oxide / carbon composite particles having excellent adsorption ability and photocatalytic ability, and a method for producing the same. The carbon composite particles of the present invention are spherical and are extremely excellent in immobilizing titanium oxide to carbon-based particles, and such carbon composite particles are used for water treatment materials, deodorizing materials, antibacterial materials, coating materials, and the like. It is preferably used.

[0002]

2. Description of the Related Art Conventional organic adsorbents include silica gel,
Activated carbon, zeolite, molecular sieves, etc., are particularly useful.Carbonaceous materials such as activated carbon have excellent adsorptive power to various organic substances, but are treated after adsorbing harmful substances such as environmental hormones after adsorption. It is very difficult to do this, and there is no choice but to perform incineration treatment at high temperature, treatment using a large-scale apparatus using high-temperature and high-pressure water, or treatment using special techniques such as plasma. Further, the adsorption power of NOx, SOx, and the like is small, and it is difficult to remove them.

[0003] On the other hand, titanium oxide has attracted special attention in recent years because it generates active oxygen by irradiating light, and the active oxygen decomposes and detoxifies environmental pollutants. Focusing on this point, there have been proposed some materials that attempt to share harmful substance adsorption capacity and harmful substance resolution by combining activated carbon with titanium oxide having photocatalytic ability.

[0004] For example, in Japanese Patent Application Laid-Open No. 6-315614,
The use of a mixture of titanium dioxide and activated carbon for the removal of pollutants is described. However, in this method, it is difficult to retain titanium oxide, and since activated carbon and titanium oxide are separately present, the effect of concentrating activated carbon cannot be expected, and it is difficult to sufficiently use the capacity of titanium oxide.

[0005] Therefore, composite activated carbon supporting titanium oxide has been proposed (JP-A-8-208211, JP-A-9-20509, and JP-A-9-67113). These are those in which titanium oxide is mixed during the activated carbon or activated carbon production process and immobilized on the surface of the activated carbon.However, according to the investigation by the present inventors, the supporting force is not so strong, and the titanium oxide used during use is not so strong. Discrete matters.

Japanese Patent Application Laid-Open No. 10-286456 discloses that titanium oxide is immobilized on the surface of activated carbon by a sol-gel method. However, the supporting force is weak, and a cumbersome chemical reaction process for obtaining a gel from the sol is performed. There is also the problem of having to go through. In addition, since any of the above activated carbons has an irregular shape, when used as a fixed bed in water treatment or the like, non-uniform diffusion of organic matter occurs in the fixed bed, and the efficiency of the fixed bed becomes poor.

On the other hand, some spherical titanium oxide composite activated carbons have been proposed (JP-A-8-295506,
JP-A-10-33989). These are all hollow particles and are intended for weight reduction, and are different from the present invention. In addition, since it is hollow, the mechanical strength is small, and a high specific surface area cannot be expected.

[0008]

SUMMARY OF THE INVENTION Accordingly, the present inventors
As a result of intensive studies to solve the above problems, the titanium oxide is firmly fixed on the surface and inside by carbonizing spherical composite particles made of carbonizable organic material containing titanium oxide on the surface and inside. It was found that spherical carbon composite particles were obtained. In the titanium oxide / carbon composite particles thus obtained, despite the titanium oxide being firmly fixed to the carbon particles, a large amount of titanium oxide is exposed on the particle surface due to the contraction of the particles themselves due to the carbonization treatment, and the photocatalyst Finding that it is a highly active material,
The present invention has been reached.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION As raw materials for spherical particles to be used, natural and synthetic carbonizable organic substances such as cellulose, phenolic resin, acrylic resin, and polyethylene can be used. It is necessary to form spherical particles having titanium oxide supported on the surface and inside. The particle size of the raw material particles is not particularly limited, but can be selected in consideration of the target particle size of the prepared titanium oxide / carbon particles. By carbonizing the organic particles carrying titanium oxide, spherical carbon particles carrying titanium oxide firmly on the surface and inside can be obtained. The carbonization treatment is appropriately performed under conditions according to the material. Usually, it is heated to a high temperature in an atmosphere of an inert gas, and the organic matter is changed to carbon. Particularly, titanium oxide / cellulose composite particles are more preferable because they are easily carbonized.

Hereinafter, the present invention will be described in detail with reference to specific examples in which the raw material spherical particles are limited to titanium oxide / cellulose composite particles, but the present invention is not limited thereto. The spherical titanium oxide / cellulose composite particles referred to in the present invention may be any as long as they contain titanium oxide having photocatalytic ability on the surface and inside, and are described in, for example, JP-A-63-92603. What was manufactured by the method can be used. According to this method, fine spherical titanium oxide / cellulose composite particles having an average particle diameter of 3 to 10 μm from a large one having an average particle diameter of 600 to 1000 μm can be obtained by selecting appropriate production conditions. The particle size can be properly adjusted by classification as needed. In addition, a molded article in which raw cellulose such as pulp is once dissolved in a solvent and coagulated into cellulose with a coagulant is generally called particularly regenerated cellulose.
This is preferable in that the shape and structure can be highly controlled.

The content of titanium oxide in the prepared titanium oxide / carbon composite particles is roughly controlled by the content of titanium oxide in the starting titanium oxide / cellulose composite particles. It is necessary to prepare raw materials. The content of titanium oxide in the titanium oxide / cellulose composite particles is preferably 0.02 to 5 parts by weight, more preferably 0.05 to 1.0 part by weight, per 1 weight of cellulose. If the content is less than 0.02 parts by weight,
If the titanium oxide / carbon composite particles to be adjusted have a poor photocatalytic function and exceed 5 parts by weight, the morphology of the cellulose composite particles will not be stable and the titanium oxide will not only fall off easily, but also the resulting titanium oxide / carbon The strength of the particles becomes weak, which is not preferable.

[0012] If necessary, the cellulose composite particles as a raw material may be subjected to a porous treatment. When titanium oxide / cellulose composite particles having a high degree of porosity are used as a raw material, the resulting titanium oxide / carbon composite particles also have a generally rough structure, the surface area is improved, and the bulk specific gravity is reduced.
The method of the porous treatment is not particularly limited, and for example, a method described in JP-A-63-90501 or JP-A-63-92602 can be used. Another method for improving the surface area and bulk specific gravity of the particles of the present invention can be achieved by previously including a foaming agent that foams in the carbonization treatment step of the present invention together with titanium oxide in the cellulose particles. Any foaming agent may be used as long as it expands in volume by decomposition or vaporization due to heat.For example, an inorganic foaming agent or an azo compound which generates a gas by thermal decomposition, a hydrazine derivative, a semicarbazide compound,
Organic foaming agents such as azimuth compounds, nitroso compounds, and triazole compounds can be used.

The titanium oxide used in the present invention is not particularly limited, and any one of anatase type and rutile type crystal forms can be used. However, the anatase type is generally more preferable because of its higher photocatalytic activity. Generally, the particle diameter of titanium oxide is about 0.001 to 1.0 μm, and it is preferable that the particle diameter be as small as possible from the viewpoint of photocatalytic ability. In particular, it is particularly preferable to use titanium oxide in the form of ultrafine particles (usually 2 to 200 nm) which has been developed in recent years. The titanium oxide actually used is the titanium oxide to be produced.
It is 1/20 or less, and preferably 1/50 or less, of the target particle size of the carbon composite particles. If it is larger than 1/20, the morphology of the titanium oxide / carbon composite particles will not be stable and will not be spherical, and the carrying capacity of titanium oxide will be weak. The shape of the photocatalyst is not particularly limited. According to the method of adding titanium dioxide, carbon spherical particles in which agglomerated photocatalysts are composited and dispersed photocatalysts are composited are obtained.

A method for preparing spherical titanium oxide / carbon composite particles by carbonizing the spherical titanium oxide / cellulose composite particles will be described below. First, the obtained titanium oxide / cellulose composite particles need to be dried, and the water content is preferably about 3 to 10% by weight. The drying method is not particularly limited, but a hot air drying method, use of a cylindrical dryer, infrared drying, high frequency drying, freeze drying, drying from an organic solvent, drying under reduced pressure, air drying and the like can be used (drying process).

It is necessary to remove adsorbed water in order to suppress aggregation and maintain a spherical shape in the obtained titanium oxide / carbon composite spherical particles. Therefore, in order to remove the adsorbed water of the titanium oxide / cellulose composite spherical particles, 100 ° C. to 250 ° C.
Heating at 150 ° C., preferably at 150 ° C. to 220 ° C. under vacuum (adsorbed water removal process).

After that, dry air or oxygen is passed under air.
Dehydration-condensation is performed at 0 ° C to 350 ° C, preferably at 270 ° C to 330 ° C (dehydration condensation process). Since many tar substances are generated at the time of dehydration condensation, after the dehydration condensation, the product is successively washed with an organic solvent such as water, methanol, ethanol, tetrahydrofuran, N, N-dimethylformamide, hexane, etc. to remove tar substances (tar). Object removal process).

Next, carbonization is performed. 350 carbonization
C. to 1300.degree. C., preferably 500.degree. C. to 900.degree. C., for a predetermined time in an atmosphere of an inert gas such as nitrogen (carbonization process). It is preferable to select carbonization conditions that increase the anatase crystal form having high photocatalytic ability, and the conditions are appropriately selected. Thereby, titanium oxide / carbon composite particles can be obtained. The existence state of titanium oxide depends on the existence state of titanium oxide in the raw titanium oxide / cellulose composite particles, and if the titanium oxide is uniformly dispersed in the raw material, the titanium oxide is uniformly prepared in the prepared carbon particles. Is carried. In addition, as the carbonation process proceeds, the particles shrink, and a large amount of titanium oxide appears on the particle surface, resulting in particles having high photocatalytic activity.

If necessary, an activation treatment can be performed to increase the pore area. The activation treatment is carried out in a carbon dioxide gas, steam or other oxidizing gas atmosphere after the carbonization treatment.
50 ° C to 1300 ° C, preferably 500 ° C to 1000 ° C
Do with. As for the activation, it is preferable to select conditions that increase the number of anatase crystal forms having high photocatalytic ability, as in the carbonization treatment.

The photocatalytic activity of the obtained titanium oxide / carbon composite particles will be described as one of uses. However, in the present invention,
It is not limited to these uses. Titanium oxide / carbon composite spherical particles are filled in a glass column that does not absorb in the ultraviolet region, such as quartz, synthetic quartz, or Pyrex, and a UV light such as a xenon lamp, a mercury lamp, or a black light, or a light that can also emit visible light. Use and irradiate from around the glass column. On this occasion,
The shape of the light includes a spiral light and a cylindrical light. The number of lights may be one or more. In addition, a reflector such as a mirror can be attached to the side of the box for irradiating the light from all sides into the box for light irradiation. Water contaminated with organic substances such as formaldehyde is fed into the column by a pump by a pump, and the lamp is irradiated by the lamp so that the titanium oxide / carbon composite spherical particles exhibit photocatalytic activity. During the elution, disappearance and reduction of formaldehyde in water are performed. At this time, the length and number of the column may be appropriately adjusted according to the decomposition stability of the organic substance. When used in such a fixed bed, the spherical particles of the present invention are particularly suitable. Compared to irregular shaped particles, the dead space is small due to the spherical shape, uneven diffusion of the processing liquid is unlikely to occur, and the processing efficiency is high. In addition, the pressure loss in the packed tower is small, and processing can be performed at a high flow rate.

[0020]

EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples. Example 1 Titanium oxide having photocatalytic ability (manufactured by Nippon Aerosil: P-
25) 23g and ion-exchanged water are mixed with a homomixer 8000r
The mixture was stirred and mixed at pm to obtain a titanium oxide dispersion in which titanium oxide was dispersed as secondary particles of about 1 μm. The dispersion and 1300 g of viscose (5.5% by weight of caustic soda, 8.9% by weight of cellulose) obtained by a conventional method were mixed with a three-one motor at 300 rpm to obtain viscose containing titanium oxide.

1200 g of titanium oxide-containing viscose, 4800 g of an aqueous solution of sodium polyacrylate (average molecular weight: 200,000, concentration: 10% by weight) and 200 g of calcium carbonate powder were mixed at room temperature for 10 minutes at a rotation speed of 400 rpm. Was obtained. 80 over 30 minutes
The liquid was solidified at 80 ° C. for 30 minutes. The coagulated particles were separated by filtration using a glass filter, neutralized with 1% by weight hydrochloric acid, and washed with water to obtain cellulose containing titanium oxide. A scanning electron micrograph (SEM) of the obtained titanium oxide / cellulose composite particles is shown in FIG.
a. In the spherical particles, a peak derived from cellulose and a peak derived from titanium dioxide (anatase type) were confirmed by X-ray diffraction (FIG. 2A). Further, the content of titanium oxide measured by the residue on ignition was 19.5% by weight per cellulose. Next, the titanium oxide
The cellulose composite particles were dried by a freeze-drying method to a water content of 3.0%.

To remove the adsorbed water, 40 g of titanium oxide / cellulose composite particles were added at 0.05 torr at room temperature.
The temperature was held for 0 minutes, then the temperature was raised to 200 ° C. in 2 hours, and the temperature was held for 5 hours, followed by natural cooling. Yield 37.0 g, carbon content 4
7.7%. In the composite particles at this stage, a peak derived from cellulose and a peak derived from titanium dioxide (anatase type) were confirmed by X-ray diffraction (FIG. 2).
b).

Spherical particles from which adsorbed water has been removed (FIG. 1-b)
In order to dehydrate and condense 37.0 g, the temperature was raised to 300 ° C. in 5 hours and maintained for 1 hour. The yield was 20.7 g and the carbon content was 54%. In the spherical particles after the dehydration condensation, the peak derived from cellulose disappeared and the peak derived from titanium dioxide (anatase type) was confirmed by X-ray diffraction (FIG. 2-c). Further, the carbonization treatment was performed by heating at 600 ° C. for 3 hours in an atmosphere of an inert gas such as nitrogen. The yield of the spherical particles after the carbonization treatment was 13.2 g. Further, the peak derived from cellulose disappeared from X-ray diffraction, and a peak derived from titanium dioxide (anatase type) was confirmed (FIG. 2-d). The BET specific surface area of the obtained data (spherical particles after carbonization treatment) was 251 m ² / g. Thereafter, in order to further increase the surface area, heating was performed at 900 ° C. for 0.5 hour in a carbon dioxide gas atmosphere to perform an activation treatment. The yield was 12.4 g. In addition, peaks derived from carbon and titanium oxide (anatase type) were confirmed by X-ray diffraction (FIG. 2B). BE of particles after activation treatment
The T specific surface area was 1000 m ² / g. SEM observation was performed to confirm the existence state of titanium oxide in the carbon particles. FIG. 1-c shows an SEM photograph. From FIG. 1-c, it can be seen that a large amount of titanium oxide is present on the surface of the carbon particles and is buried, and that the titanium oxide is firmly fixed to carbon.

The photocatalytic activity of the titanium oxide / carbon composite spherical particles thus obtained was investigated. Figure 3 shows the photocatalytic ability test.
This was performed using an apparatus as shown in FIG. The titanium oxide / carbon composite spherical particles 1 are filled in a Pyrex (registered trademark) glass column 2 of 10 × 300 mm, and deaerated water (mobile phase) is first sent by a pump 4, and black around the glass column 2. Light was emitted from Light 3. Thereafter, 20 ml of a 10% by weight aqueous solution of acetaldehyde (flow rate 0.50 ml / min.) Was injected into the column 2 by the injector 6 for liquid chromatography. Black light 3
And the liquid eluted from the column 2 during the irradiation was guided to the detector 7, and the ultraviolet (UV) absorption spectrum of the compound in the liquid was measured. As a result, decomposition of acetaldehyde was observed. FIG. 4 shows the results. In FIG. 3, reference numeral 5 denotes an irradiation box provided with a black light 3 and a glass column 2, 8 denotes a recorder, 9 denotes a mobile phase storage tank, and 10 denotes a waste liquid tank.

FIG. 4 is a graph showing the solute residence time in the column and the change in the ultraviolet absorption spectrum of the eluted substrate (acetaldehyde). The retention time of the solute in the column 2 was set to five steps of 0, 54.9, 88.0, 147.3 and 442.6 minutes (min.), And the UV absorption spectrum of the compound in the eluted liquid was measured. It can be seen that UV absorption by acetaldehyde decreases as the residence time increases, and acetaldehyde is decomposed and converted to acetic acid. In the figure, the absorption around 210 nm (upward arrow point) indicates the presence of acetic acid, and 280 nm (downward arrow point).
Near absorption indicates the presence of acetaldehyde.

Comparative Example 1 An acetaldehyde decomposition removal test was performed in the same manner as in the example except that the black light was not irradiated and the photocatalytic function was not used. as a result,
The ultraviolet absorption spectrum representing acetaldehyde hardly changed (corresponding to a residence time of 0 in FIG. 4). Thus, it was found that the carbon particles provided with the photocatalytic function had excellent ability to decompose and remove acetaldehyde.

[0027]

According to the present invention, the raw material particles are prepared into spherical particles containing fine titanium oxide, and the resulting particles are dried, adsorbed water removed, dehydrated and condensed, and carbonized so that the surface and the inside are firmly formed. Spherical titanium oxide-carbon composite particles containing the immobilized titanium oxide are obtained. Since the composite particles of the present invention are spherical particles, the size of the particle size distribution can be easily adjusted by classification. Therefore, when used in a fixed bed, compared with amorphous particles, there is less dead space, more dense and reproducible packing is possible, so that the average distance for solute molecules to move between particles becomes shorter, and the processing solution becomes more inefficient. It has the advantage that uniform diffusion hardly occurs and the processing efficiency of the column is increased. In addition, since there is little pressure loss in the filling building, processing can be performed at a high flow rate, and the fluidity is high, when used as a fluidized bed, there are advantages such as easy recovery. The composite particles of the present invention can be used in various fields as a photocatalyst and the like, and since they have fluidity, they can also be used as coating materials and powder coatings.

[Brief description of the drawings]

FIG. 1 is a scanning electron micrograph of titanium oxide composite particles in each processing step.

FIG. 2 is an X-ray diffraction graph of titanium oxide composite particles in each processing step.

FIG. 3 is a schematic diagram of a function evaluation device.

FIG. 4 is a graph showing the retention time of a solute in a column and the change in ultraviolet absorption spectrum of an eluted substrate (acetaldehyde).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Titanium oxide / carbon composite spherical particle 2 Glass column 3 Black light 4 Pump 5 Irradiation box 6 Injector

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C01G 23/04 B01D 53/36 J (72) Inventor Hideaki Mukaiyama 5595 Ueyanagi Motomachi, Yatsushiro-shi, Kumamoto (72) Inventor Shoji Nagaoka 3-11-38 Higashicho, Kumamoto City, Kumamoto Prefecture Inside the Kumamoto Prefectural Industrial Technology Center (72) Inventor Masanori Nagata 3-11-38 Higashicho, Kumamoto City, Kumamoto Prefecture In the Kumamoto Prefectural Industrial Technology Center (72) Inventor Naga Nagasawa Hachiro 1-1, Higashi, Tsukuba, Ibaraki Prefecture F-term (Reference) 4M048 AA19 AB03 BA05X BA05Y BA07X BA07Y BB01 EA01 4G046 CA04 CB02 CB08 CC01 HA10 4G047 CA02 CC03 CD03 4G069 AA02 BA04A08A08B08 BA48A BC50A BC50B BD04A BD04B CA05 CA11 CA17 DA06 FA01 FA02 FB06

Claims (3)

[Claims] 1. Spherical titanium oxide / carbon composite particles containing titanium oxide on the surface and inside. 2. A method for producing spherical titanium oxide / carbon composite particles comprising carbonizing spherical titanium oxide / organic composite particles comprising a carbonizable organic substance containing titanium oxide on the surface and inside. 3. The method for producing spherical titanium oxide / carbon composite particles according to claim 1, comprising carbonizing spherical titanium oxide / cellulose composite particles containing titanium oxide on the surface and inside.