Photocatalyst and air cleaner using the same

The present invention relates to an air purifying filter for homes and offices, and an air purifier and an exhaust gas treatment device using the same.

Due to its strong oxidizing power, photocatalysts have been developed for various applications such as deodorization, antibacterial, antifouling, air purification, and water treatment. Air purifiers with photocatalytic filters, air conditioners, etc. are used to clean indoor spaces (trace amounts of formaldehyde, bacteria, tobacco odor, etc.) in homes, offices, hospitals, etc. Air purification with a photocatalyst is an excellent method as a maintenance-free method at room temperature. This method is based on the strong oxidizing power generated when a photocatalyst such as titanium oxide is irradiated with ultraviolet rays. When actually applied, it is often used in combination with an adsorbent such as zeolite or activated carbon in order to enhance the purification capacity. That is, in a hybrid photocatalyst in which a photocatalyst is mixed with these adsorbents, a target substance such as an organic substance is adsorbed on the adsorbent and gradually decomposed by the photocatalyst.

On the other hand, activated carbon, which is widely used as an adsorbent, usually has a specific surface area of several hundred meters.²It is about / g. The size of activated carbon is usually 10 μm above, and it has been devised to form nm-level pores on the surface, but since contaminated molecules do not reach the inside of the pores, there is a limit to increasing the adsorption surface area. There is.

In addition, harmful substances such as dioxins emitted from incinerators such as garbage incinerators and pyrolysis furnaces are social because of their various toxicities (for example, physiological toxicity, endocrine toxicity, carcinogenicity, etc.). It's a problem. Various measures have been taken to curb the emission of such harmful substances.

Figure 8 shows an example of an exhaust gas treatment system that has been improved in recent years. Gas cooling device 2 that cools high temperature (750 to 950 (C) exhaust gas discharged from incinerator 1 to about 200 (C) by water spraying, etc., and removal of harmful substances such as hydrogen chloride and sulfur oxides in the exhaust gas It is composed of a reaction tower 3 that performs chlorine and desulfurization treatment, a bag filter 4 that filters and collects soot and harmful substances in the exhaust gas with a filter cloth, and a chimney 6 that discharges the purified exhaust gas to the outside by an attracting blower. In order to improve the processing efficiency, a step of adding activated carbon in front of the bag filter to adsorb dioxin and heavy metals is added.

Due to the high toxicity of dioxins and toxic substances, their emission regulations are extremely strict, usually 1 ng / m.³It is necessary to control to a lower concentration.

In order to further improve the treatment efficiency for harmful substances such as dioxin, a method has been proposed in which a bug filter is installed separately in the front stage and the rear stage, and a dioxin decomposition catalyst is attached to the bug filter in the rear stage (see Patent Document 1). .. However, the current situation is that it is not always satisfactory.

Further, in recent years, a nanoscale carbon tube having an amorphous structure (amorphous structure) instead of a graphitic structure has been reported in Patent Document 2.<patcit num="1"><text>Japanese Unexamined Patent Publication No. 2001-137663 (paragraph number [0034], Fig. 1)</text></patcit><patcit num="2"><text>International Publication No. 00/40509 Pamphlet (pages 5-40)</text></patcit>

<p> As described above, the photocatalytic filter using zeolite or activated carbon in combination has a problem that the air purification performance is insufficient because the adsorption capacity is limited. The present invention solves the problems of a photocatalyst filter using conventional activated carbon and a photocatalyst, and provides a photocatalyst filter having excellent air purification performance and durability, and an air purifier and an exhaust gas treatment device using the same. The purpose.</p>

<p> As a result of diligent research to solve the above problems, the present inventions have solved the above problems by using a filter containing an adsorbent containing a nanoscale carbon tube having an extremely high adsorption ability and a photocatalyst. The invention was completed.</p><p> That is, the present invention provides the following photocatalytic filter, and an air purifier and an exhaust gas treatment device using the same.</p><p> Item 1 Photocatalytic filter containing a filter substrate, an adsorbent containing a nanoscale carbon tube, and a photocatalyst.</p><p> Item 2 Nanoscale carbon tubes are carbon nanotubes (CNT), or (i) amorphous nanoscale carbon tubes, (ii) nanoflake carbon tubes, (iii) (a) nanoflake carbon tubes, and (b) iron and nickel. And a metal selected from the group consisting of cobalt or an alloy thereof, and the metal or an alloy thereof is present in a range of 10 to 90% of the space inside the tube of the nanoflake carbon tube (a). Item 2. The photocatalyst filter according to Item 1, wherein the carbon composite or (iv) is a mixture of two or more of the above (i) to (iii).</p><p> Item 3 The nanoscale carbon tube is selected from the group consisting of (i) amorphous nanoscale carbon tube, (ii) nanoflake carbon tube, (iii) (a) nanoflake carbon tube, and (b) iron, nickel and cobalt. A metal-carbon composite consisting of a metal or an alloy thereof, in which the metal or an alloy thereof is present in a range of 10 to 90% of the space inside the tube of the nanoflake carbon tube (a), or (iv. ) The photocatalyst filter according to Item 1, wherein the photocatalyst filter is a mixture of two or more of the above (i) to (iii).</p><p> Item 4 The photocatalyst filter according to Item 1, wherein the photocatalyst is at least one selected from the group consisting of titanium dioxide, zinc oxide, cadmium sulfide, and strontium titanate.</p><p> Item 5 The photocatalyst filter according to Item 1, wherein at least one metal selected from the group consisting of Pt, Pd, Cu, and Ag is supported on the surface of the photocatalyst.</p><p> Item 6. The photocatalyst filter according to Item 1, wherein the photocatalyst is supported on an adsorbent.</p><p> Item 7. A photocatalyst filter unit including the photocatalyst filter and a light source according to any one of Items 1 to 6.</p><p> Item 8 The photocatalyst filter unit according to Item 7, wherein the light source is at least one selected from the group consisting of a high-pressure mercury lamp, a low-pressure mercury lamp, a black light, an excimer laser, a deuterium lamp, a xenon lamp, and an Hg-Zn-Pb lamp. ..</p><p> Item 9 Air purifier equipped with the photocatalytic filter unit of item 8.</p><p> Exhaust gas treatment device equipped with the photocatalytic filter unit of item 10 item 8.</p><p> Item 11 A method for producing a photocatalyst filter, which comprises coating a filter substrate with a slurry containing an adsorbent containing a nanoscale carbon tube, a photocatalyst, a binder, and a dispersant as main components.</p><p> The photocatalytic filter of the present invention, and an air purifier and an exhaust gas treatment device using the same will be described in detail.<u style="single">I. Photocatalytic filter</u> The present invention provides a photocatalytic filter containing a filter substrate, an adsorbent containing a nanoscale carbon tube, and a photocatalyst. In this photocatalyst filter, even if the adsorbent containing the nanoscale carbon tube and the photocatalyst are supported on the filter substrate, the adsorbent containing the nanoscale carbon tube and the photocatalyst are supported by being sandwiched between the filter substrates. You may. The photocatalytic filter of the present invention is characterized in that a nanoscale carbon tube having extremely high adsorptivity is used as an adsorbent.</p><p> Examples of the photocatalytic filter of the present invention include the filter shown in FIG.</p><p><u style="single">Filter substrate</u> The filter substrate is not particularly limited as long as it is a material capable of supporting an adsorbent and a dioxin decomposition catalyst, and examples thereof include ceramics, metals, carbon, glass, paper, and non-woven fabrics.</p><p> Ceramics include aluminum oxide, beryllium oxide, cerium oxide, chromium oxide, cobalt oxide, iron oxide, nickel oxide, silicon oxide, tantalum oxide, tarium oxide, titanium oxide, vanadium oxide, yttrium oxide, zinc oxide, zirconium oxide, and oxidation. Magnesium and composite metal oxides thereof are exemplified, and silicon oxide and aluminum oxide are preferable from the viewpoint of cost.</p><p> Examples of the metal include zinc, tin, aluminum, chromium, titanium, magnesium, beryllium, copper, manganese, tungsten and the like, and aluminum is preferable from the viewpoint of light weight and cost.</p><p> Examples of carbon include graphite, calvin, coke, charcoal, carbon black, diamond-like carbon, carbon fiber, and glassy carbon, and carbon fiber is preferable from the viewpoint of processability and specific surface area.</p><p> Examples of the glass include soda-lime glass, potash lime glass, water glass, quartz glass, glass fiber and the like, and glass fiber is preferable from the viewpoint of cost, air permeability and the like.</p><p> Examples of the paper include fluororesin fiber paper, functional paper impregnated with synthetic resin, and paper made of inorganic fibers.</p><p> Ceramic is preferably used because of the ease of supporting the adsorbent and the photocatalyst, durability, heat resistance, and the like.</p><p> Examples of the shape of the filter substrate include a honeycomb shape, a mesh shape, a tubular shape, and a box shape. From the viewpoint of breathability and surface area, a honeycomb shape is preferable. Examples of the shape of the honeycomb include a hexagon honeycomb composed of hexagonal cells, a honeycomb composed of square cells, a honeycomb composed of triangular cells, and a honeycomb formed by assembling hollow cylindrical cells. Here, the cell shape such as a hexagon or a square is not a formal polygon, but may be a deformed shape such as a corner, a round shape, or a curved side.</p><p><u style="single">Adsorbent containing nanoscale carbon tubes</u> The adsorbent used in the present invention comprises an adsorbent containing a nanoscale carbon tube. Here, the nanoscale carbon tubes are carbon nanotubes (CNT), or (i) amorphous nanoscale carbon tubes, (ii) nanoflake carbon tubes, (iii) (a) nanoflake carbon tubes, and (b) iron. It is composed of a metal selected from the group consisting of nickel and cobalt or an alloy thereof, and the metal or an alloy thereof is present in a range of 10 to 90% of the space inside the tube of the nanoflake carbon tube (a). Examples include a metal-carbon composite, or (iv) a mixture of two or more of the above (i) to (iii). Above all, the nanoscale carbon tube according to any one of (i) to (iv) above is preferably selected.</p><p> Conventionally known carbon nanotubes (CNTs) are used. The CNT has a completely continuous graphite structure in which the wall portion is composed of a completely continuous carbon network surface and the arrangement of carbon atoms on the outermost surface is regular.</p><p> Further, among the above nanoscale carbon tubes, the amorphous nanoscale carbon tube of (i) has an amorphous structure in which a large number of fine graphene sheets (carbon mesh surfaces) are irregularly distributed instead of a graphite structure in the wall portion. Therefore, the carbon mesh surface forming the outermost layer is not continuous over the entire length in the longitudinal direction of the tube, and is discontinuous.</p><p> Similarly, even in the nanoflake carbon tube of (ii) and the metal-carbon composite of (iii) above, the outermost layer of the nanoflake carbon tube constituting the wall portion is continuous over the entire length in the longitudinal direction of the tube. It is formed from a discontinuous graphene sheet that is not.</p><p> As described above, in the above-mentioned amorphous nanoscale carbon tube, nanoflake carbon tube and metal-carbon composite, the outermost surface of the wall portion is formed because the graphene sheet constituting the wall portion, particularly the outermost surface thereof has discontinuity. The arrangement of the constituent carbon atoms is irregular. Perhaps because of this, the nanoscale carbon tubes used in the present invention have a high affinity for other substances such as resins and solvents. Further, since the nanoscale carbon tube used in the present invention has a linear shape, it is possible to form a network for obtaining conductivity or antistatic property (that is, charge transfer between nanoscale carbon tubes is possible). It is also easy to form a dispersed state that exhibits conductivity or antistatic property over the entire system by contacting or approaching to such an extent. Perhaps because of such high affinity and high linearity, charge transfer due to contact between nanoscale carbon tubes or charge transfer due to tunneling effect due to mutual approach between nanoscale carbon tubes, even in small amounts. It is presumed that the desired conductivity or antistatic property can be achieved.</p><p> In addition, the nanoscale carbon tube is in the form of nanoscale fibers, and it is possible to suppress particle contamination to an extremely low level with almost no dropout from the resin, and these are physically firmly bonded to the resin of the matrix. It is presumed that this is due to the fact that it has an excellent affinity with the resin of the matrix.</p><p> Hereinafter, the amorphous nanoscale carbon tube (i), the metal-carbon composite (iii), and the nanoflake carbon tube (ii) will be described in this order.</p><p><u style="single">&lt;Amorphous nanoscale carbon tube&gt;</u> The amorphous nanoscale carbon tube is described in WO00 / 40509 (Patent No. 3355442 = Patent Document 2 above), and has a main skeleton made of carbon, a diameter of 0.1 to 1000 nm, and a nanoscale having an amorphous structure. It is a carbon tube, has a linear morphology, and in the X-ray diffraction method (incident X-ray: CuKα), the plane spacing (d002) of the carbon net plane (002) measured by the amorphous method is 3.54 Å. As described above, it is characterized in that the diffraction angle (2θ) is 25.1 degrees or less, particularly 24.1 degrees or less, and the half-value width of the 2θ band is 3.2 degrees or more, particularly 7.0 degrees or more. ..</p><p> The amorphous nanoscale carbon tube is a thermosetting resin having a decomposition temperature of 200 to 900 ° C., for example, in the presence of a catalyst composed of at least one chloride of a metal such as magnesium, iron, cobalt, and nickel. It is obtained by excitation-treating polytetrafluoroethylene, polyvinylidene chloride, polyvinylidene fluoride, polyvinyl alcohol and the like.</p><p> The shape of the pyrolytic resin as a starting material may be any shape such as a film shape, a sheet shape, a powder shape, and a lump shape. For example, in the case of obtaining a carbon material in which a thin filmed amorphous nanoscale carbon tube is formed on a substrate, a thermosetting resin may be coated or placed on the substrate and subjected to excitation treatment under appropriate conditions. ..</p><p> The excitation treatment includes, for example, heating in an inert atmosphere, preferably in a temperature range of about 450 to 1800 ° C and above the thermal decomposition temperature of the raw material, in a temperature range of about room temperature to 3000 ° C and heat of the raw material. Examples of treatments such as plasma treatment at a decomposition temperature or higher can be exemplified.</p><p> The amorphous nanoscale carbon tube used in the present invention is a nanoscale carbon nanotube having an amorphous structure (amorphous structure), has a hollow linear shape, and has highly controlled pores. Its shape is mainly a cylinder, a quadrangular prism, etc., and at least one of the tips often does not have a cap (opens). When the tip is closed, the shape is often flat.</p><p> The outer diameter of the amorphous nanoscale carbon tube is usually in the range of about 1 to 1000 nm, preferably in the range of about 1 to 200 nm, and more preferably in the range of about 1 to 100 nm. Its aspect ratio (tube length / diameter) is more than twice, preferably more than five times.</p><p> Here, the "amorphous structure" does not mean a graphitic structure composed of continuous carbon layers of regularly arranged carbon atoms, but a carbonaceous structure composed of irregular carbon network planes, and a large number of fine particles. The graphene sheets are arranged irregularly, and the arrangement of atoms is irregular. From the image obtained by a transmission electron microscope (TEM), which is a typical analysis method, the nanoscale carbon tube having an amorphous structure according to the present invention has a spread in the plane direction of the carbon network plane of the diameter of the amorphous nanoscale carbon tube. It can be specified that it is smaller than 1 time. Therefore, the length of the carbon mesh surface constituting the outermost surface of the wall portion of the amorphous nanoscale carbon tube is less than 20 nm, particularly less than 5 nm.</p><p> Amorphous carbon generally does not exhibit X-ray diffraction, but exhibits broad reflection. In the graphitic structure, the carbon network planes are regularly stacked, so the carbon network plane spacing (d)₀₀₂) Narrows, the broad reflection shifts to the high angle side (2θ), gradually becomes sharper (the half width of the 2θ band becomes narrower), and d₀₀₂It can be observed as a diffraction line (d if it is regularly stacked due to the graphite-like positional relationship.₀₀₂= 3.354 Å).</p><p> Amorphous structures, on the other hand, generally do not exhibit X-ray diffraction as described above, but partially exhibit very weak coherent scattering. In the X-ray diffraction method (incident X-ray = CuKα), the theoretical crystallographic properties of the amorphous nanoscale carbon tube according to the present invention measured by the diffractometer method are defined as follows: Carbon mesh plane. Interval (d₀₀₂) Is 3.54 Å or more, more preferably 3.7 Å or more; the diffraction angle (2θ) is 25.1 degrees or less, more preferably 24.1 degrees or less; the half width of the 2θ band is 3.2 degrees. It is more than that, more preferably 7.0 degrees or more.</p><p> Typically, the amorphous nanoscale carbon tubes used in the present invention have a diffraction angle (2θ) due to X-ray diffraction in the range of 18.9 to 22.6 degrees, and a carbon network plane spacing (d).₀₀₂) Is in the range of 3.9 to 4.7 Å, and the half width of the 2θ band is in the range of 7.6 to 8.2 degrees.</p><p> The term "straight", which is one term for the shape of the amorphous nanoscale carbon tube of the present invention, is defined as follows. That is, the length of the amorphous nanoscale carbon tube image obtained by the transmission electron microscope is L, and the length when the amorphous nanoscale carbon tube is extended is L.₀When, L / L₀It shall mean a shape characteristic in which is 0.9 or more.</p><p> The tube wall portion of such an amorphous nanoscale carbon tube has an amorphous structure composed of a plurality of fine carbon mesh planes (graphene sheets) oriented in all directions, and the active points are formed by the carbon plane spacing of these carbon mesh planes. It has an advantage that it is excellent in compatibility with a thermoplastic polymer resin or a thermosetting polymer resin which is a medium.</p><p><u style="single">&lt;Metal-carbon complex&gt;</u> In the metal-carbon composite used in the present invention, the metal or alloy is completely filled over the entire length of the space inside the nanoscale carbon tube, that is, 100% of the space inside the tube. It is characterized in that the metal or alloy is filled (that is, partially filled) in a range of 10 to 90% of the space inside the tube.</p><p> The wall is a patchwork-like or papier-mache-like (so-called paper mache-like) nanoflake carbon tube. In the claims and specification of the present application, the "nanoflake carbon tube" is composed of a plurality of (usually a large number) flake-shaped graphite sheets assembled in a patchwork-like or papier-mache-like shape. Refers to a carbon tube made of an aggregate of graphite sheets.</p><p> In this nanoflake carbon tube, a single-walled carbon nanotube (single-wall carbon nanotube) in which one graphite sheet is closed in a cylindrical shape or a plurality of graphite sheets are closed in a cylindrical shape to form a concentric cylindrical or nested shape. It is a tubular carbon material with a completely different structure from the multi-walled carbon nanotubes (multi-wall carbon nanotubes).</p><p> Further, the metal contained in the space inside the tube may be one kind of metal or an alloy. Examples of the metal contained in the space inside the tube include iron, nickel, and cobalt. The alloy contained in the space inside the tube is an alloy composed of two or more of the above metals, for example, a metal such as an iron-nickel alloy, an iron-cobalt alloy, a nickel-cobalt alloy, or an iron-nickel-cobalt alloy. Examples of alloys between each other can be given. Further, a metal such as iron, nickel and cobalt, an alloy containing carbon in an alloy of these metals, iron carbide, nickel carbide, cobalt carbide and the like can also be exemplified. Of these, iron or iron carbide is preferable.</p><p> The metal-encapsulating carbon tube used in the present invention is composed of (a) nanoflake carbon tube and (b) encapsulating metal or alloy (preferably iron or iron carbide), and the space inside the carbon tube (that is, that is, iron carbide). , The space surrounded by the tube wall) is not completely filled, but a part of the space, more specifically about 10 to 90%, particularly about 30 to 80%, preferably 40. About 70% is filled with an encapsulated metal or alloy (preferably iron or iron carbide). Hereinafter, the carbon tube containing iron carbide or iron is referred to as "iron-carbon composite". Such an iron-carbon composite is described in JP-A-2002-338220.</p><p> The iron-carbon composite has a pressure of 10 in an inert gas atmosphere according to the production method described in JP-A-2002-338220.^-5Adjusting to Pa ~ 200kPa, the ratio B / A of the oxygen concentration in the reactor is 1 × 10 when the reactor volume is A (liter) and the oxygen amount is B (Ncc).^-10~1×10^-1The process of heating iron halide to 600 to 900 ° C in the reactor by adjusting the concentration to the above, and (2) creating an inert gas atmosphere in the reactor and increasing the pressure to 10.^-5It is obtained by a manufacturing method including a step of adjusting to Pa to 200 kPa, introducing a pyrolytic carbon source, and performing a heat treatment at 600 to 900 ° C.</p><p> Hereinafter, the iron or iron carbide-encapsulating carbon tube (iron-carbon composite) of the present invention will be described.</p><p> In the iron-carbon composite used in the present invention, the carbon portion becomes a nanoflake carbon tube when cooled at a specific rate after performing the manufacturing steps (1) and (2), and becomes a nanoflake carbon tube, and the manufacturing steps (1) and (2) After performing 2), heat treatment is performed in an inert gas, and the carbon nanotubes are cooled at a specific cooling rate to obtain a multi-walled carbon nanotube having a nested structure.</p><p> &lt;(a-1) Nanoflake carbon tube&gt; The nanoflake carbon tube of the present invention and an iron-carbon composite composed of iron carbide or iron are typically columnar, but such columnar iron- A transmission electron microscope (TEM) photograph of a cross section substantially perpendicular to the longitudinal direction of the carbon composite (obtained in Reference Example 2 described later) is shown in FIG. 6, and a side TEM photograph is shown in FIG.</p><p> Further, (a-1) of FIG. 7 shows a schematic diagram of a TEM image of such a columnar nanoflake carbon tube. In FIG. 7 (a-1), 100 schematically shows a TEM image in the longitudinal direction of the nanoflake carbon tube, and 200 indicates a TEM image of a cross section substantially perpendicular to the longitudinal direction of the nanoflake carbon tube. It is shown schematically.</p><p> The nanoflake carbon tube constituting the iron-carbon composite used in the present invention typically has a hollow cylindrical shape, and when the cross section thereof is observed by TEM, arc-shaped graphene sheet images are concentrically assembled. A few arc-shaped graphene sheet images are gathered to form a discontinuous ring, and when the longitudinal direction is observed by TEM, the substantially linear graphene sheet images are almost parallel to the longitudinal direction. The individual graphene sheet images are not continuous over the entire length of the longitudinal direction (shorter than the total length of the longitudinal direction), and several short graphene sheet images are gathered together to form a discontinuous linear line. It is characterized in that an image of the shape is formed over the entire length in the longitudinal direction of the tube.</p><p> The nanoflake carbon tube constituting the iron-carbon composite used in the present invention has a cross section substantially perpendicular to the longitudinal direction thereof, as is clear from 200 in (a-1) of FIGS. 6 and 7. When observed by TEM, a large number of arc-shaped graphene sheet images are gathered concentrically (in the form of a multi-layered tube), but the individual graphene sheet images are completely closed and continuous, as shown in, for example, 210 and 214. It does not form a ring, but forms a discontinuous ring that is interrupted in the middle. Some graphene sheet images may be branched, as shown in 211. At the discontinuity point, the plurality of arc-shaped TEM images constituting one discontinuity ring may have a partially disturbed layer structure as shown in 222 of FIG. 7 (a-1). Although there may be a gap between adjacent graphene sheet images as shown in 223, the large number of arcuate graphene sheet images observed by TEM form a multi-layered tube structure as a whole. There is.</p><p> Further, as is clear from 100 in (a-1) of FIGS. 2 and 7, when the longitudinal direction of the nanoflake carbon tube is observed by TEM, a large number of substantially linear graphene sheet images are used in the present invention. Although they are arranged in multiple layers almost parallel to the longitudinal direction of the iron-carbon composite, the individual graphene sheet images 110 are not continuous over the entire longitudinal length of the iron-carbon composite and are discontinuous in the middle. It has become. Some graphene sheet images may be branched, as shown in 111 in (a-1) of FIG. Further, at the discontinuity point, among the TEM images arranged in layers, the TEM image of one discontinuous layer is at least a part of the adjacent graphene sheet image as shown in 112 of (a-1) of FIG. In some cases, they overlap with each other, and in some cases, they are slightly separated from the adjacent graphene sheet images as shown in 113, but a large number of substantially linear TEM images form a multi-layer structure as a whole.</p><p> The structure of the nanoflake carbon tube of the present invention is significantly different from that of conventional multi-walled carbon nanotubes. That is, as shown in (a-2) 400 of FIG. 7, the nested multi-walled carbon nanotube has a TEM image of a cross section perpendicular to the longitudinal direction thereof, and a completely circular TEM image as shown in 410. It is a concentric tube, and as shown in 300 in (a-2) of FIG. 7, a structure in which linear graphene sheet images 310 and the like continuous over the entire length in the longitudinal direction are arranged in parallel. (Concentric cylindrical or nested structure).</p><p> From the above, although the details have not been completely clarified yet, in the nanoflake carbon tube constituting the iron-carbon composite used in the present invention, a large number of flake-shaped graphene sheets are overlapped in a patchwork-like or papier-mache shape. It seems to form a tube as a whole.</p><p> When the nanoflake carbon tubes constituting the iron-carbon composite used in the present invention are observed by TEM, individual graphene sheet images are obtained with respect to a large number of substantially linear graphene sheet images oriented in the longitudinal direction thereof. The length of is usually about 2 to 500 nm, particularly about 10 to 100 nm. That is, as shown by 100 in (a-1) of FIG. 7, a large number of TEM images of the substantially linear graphene sheet shown by 110 are gathered to form a TEM image of the wall portion of the nanoflake carbon tube. The length of each substantially linear graphene sheet image is usually about 2 to 500 nm, particularly about 10 to 100 nm.</p><p> As described above, the length of the carbon network surface forming the outermost surface of the nanoflake carbon tube constituting the iron-carbon composite is 500 nm or less, particularly 2 to 500 nm, and particularly 10 to 100 nm.</p><p> As described above, the carbon portion of the wall portion of the nanoflake carbon tube constituting the iron-carbon composite used in the present invention has a large number of flake-shaped graphene sheets oriented in the longitudinal direction to form a tube as a whole. However, when measured by the X-ray diffractometry, it has a graphitic structure with an average distance (d002) between carbon network surfaces of 0.34 nm or less.</p><p> Further, the thickness of the wall portion made of the nanoflake carbon tube of the iron-carbon composite used in the present invention is 75 nm or less, particularly about 1 to 40 nm, preferably about 1 to 30 nm, and is substantially over the entire length. Uniform.</p><p> &lt;(b) Contained Iron Carbide or Iron&gt; In the present specification, the filling rate (10 to 90%) of the space inside the carbon tube with iron or iron is the iron-carbon composite obtained by the present invention. The body is observed with a transmission electron microscope, and the area of the image of the iron-carbonized or iron-filled portion with respect to the area of the image of the space of each carbon tube (that is, the space surrounded by the tube wall of the carbon tube). Is the ratio of.</p><p> The form of containing iron carbide or iron includes a form of being continuously contained in the space inside the carbon tube, a form of being intermittently contained in the space inside the carbon tube, and the like, but basically it is intermittent. It is included. Therefore, the iron-carbon composite used in the present invention should also be referred to as a metal-encapsulating carbon composite or an iron compound-encapsulating carbon composite, iron carbide or an iron-encapsulating carbon composite.</p><p> Further, the iron carbide or iron contained in the iron-carbon composite used in the present invention is oriented in the longitudinal direction of the carbon tube, has high crystallinity, and is in the range of being filled with iron or iron carbide. The ratio of the area of the crystalline iron or iron TEM image to the area of the TEM image (hereinafter referred to as crystallization rate) is generally about 90 to 100%, particularly about 95 to 100%.</p><p> The high crystallinity of the contained iron carbide or iron is clear from the fact that the TEM images of the inclusions are arranged in a grid pattern when TEM observation is performed from the side surface of the iron-carbon composite of the present invention. It is clear from the fact that a clear diffraction pattern can be obtained in electron diffraction.</p><p> Further, it can be easily confirmed by an electron microscope and EDX (energy dispersive X-ray detector) that iron carbide or iron is contained in the iron-carbon composite used in the present invention.</p><p> &lt;Overall shape of iron-carbon composite&gt; The iron-carbon composite used in the present invention has little curvature and is linear, and the wall thickness has a substantially constant uniform thickness over the entire length. Therefore, it has a uniform shape over the entire length. Its shape is columnar, mainly columnar.</p><p> The outer diameter of the iron-carbon composite according to the present invention is usually in the range of about 1 to 150 nm, particularly in the range of about 3 to 100 nm, preferably in the range of about 5 to 80 nm. The aspect ratio (L / D) of the length (L) of the tube to the outer diameter (D) is about 5 to 10000, and particularly about 10 to 1000.</p><p> The term "straight line", which is one of the terms used in the present invention to describe the shape of an iron-carbon composite, is defined as follows. That is, when the carbonaceous material containing the iron-carbon composite used in the present invention is observed with a transmission electron microscope in the range of 200 to 2000 nm square, the length of the image is W, and the image is stretched linearly. When the length of Wo is taken as Wo, it means a shape characteristic in which the ratio W / Wo is 0.8 or more, particularly 0.9 or more.</p><p> The iron-carbon composite used in the present invention has the following properties when viewed as a bulk material. That is, in the present invention, the iron-carbon composite in which iron or iron carbide is filled in the range of 10 to 90% of the inner space of the nanoflake carbon tube as described above can be barely observed by microscopic observation. A large amount in the form of a bulk material containing a large number of the iron-carbon composites, not a trace amount of the above, and a carbonaceous material containing the iron-carbon composite, or a material which can be called iron carbide or an iron-encapsulating carbonaceous material. Obtained in.</p><p> FIG. 3 shows an electron micrograph of the carbonaceous material of the present invention composed of the nanoflake carbon tube manufactured in Reference Example 2 described later and the carbon carbide partially filled in the space inside the tube.</p><p> As can be seen from FIG. 3, in the carbonaceous material containing the iron-carbon composite used in the present invention, basically all (especially 99% or more) carbon tubes have a space (that is, a space portion) thereof. , The space surrounded by the tube wall of the carbon tube) is filled with iron carbide or iron in the range of 10 to 90%, and there is usually virtually no carbon tube in which the space is not filled. However, in some cases, a small amount of iron carbide or carbon tubes not filled with iron may be mixed.</p><p> Further, in the carbonaceous material of the present invention, an iron-carbon composite in which iron or iron carbide is filled in 10 to 90% of the space inside the carbon tube as described above is a main component, but the present invention In addition to the iron-carbonaceous complex of, soot and the like may be contained. In such a case, the components other than the iron-carbonaceous composite of the present invention are removed to improve the purity of the iron-carbonaceous composite in the carbonaceous material of the present invention, which is substantially used in the present invention. It is also possible to obtain a carbonaceous material consisting only of an iron-carbon composite.</p><p> In addition, unlike conventional materials that can only be confirmed in trace amounts by microscopic observation, the carbonaceous material containing the iron-carbon composite used in the present invention can be synthesized in large quantities, so its weight can be easily reduced to 1 mg or more. can do. The material of the present invention can be produced infinitely by scaling up the production method of the present invention described later or repeating the process many times.</p><p> The carbonaceous material of the present invention is 25 mm with respect to 1 mg of the carbonaceous material.²In the powder X-ray diffraction measurement by irradiating CuKα with X-rays in the above irradiation area, it shows the strongest integrated intensity among the peaks of 40 ° &lt;2θ &lt;50 ° attributable to the contained iron or iron carbide. When the integrated intensity of the peak is Ia and the integrated intensity of the peak of 26 ° &lt;2θ &lt;27 °, which is attributed to the average distance (d002) between the carbon mesh surfaces of the carbon tube, is Ib, the ratio R of Ia to Ib ( = Ia / Ib) is preferably about 0.35 to 5, particularly about 0.5 to 4, and more preferably about 1 to 3.</p><p> In the claims and specification of the present application, the ratio of Ia / Ib is referred to as an R value. This R value is 25 mm in the X-ray diffraction method for the carbon material containing the iron-carbon composite used in the present invention.²When observed in the above X-ray irradiation area, the peak intensity is observed as the average value of the entire carbonic material, so it is not the inclusion rate or filling rate in one iron-carbon composite that can be measured by TEM analysis. , Indicates the average value of iron carbide or iron filling rate or inclusion rate of the entire carbonaceous material, which is an aggregate of iron-carbon composites.</p><p> The average filling rate of the entire carbonaceous material containing a large number of iron-carbon composites of the present invention is determined by observing a plurality of fields of view with TEM and iron carbide or iron carbide in the plurality of iron-carbon composites observed in each field of view. It can also be obtained by measuring the average filling rate of iron and further calculating the average value of the average filling rate of a plurality of fields of view. When measured by such a method, the average filling rate of iron carbide or iron as a whole carbonic material composed of the iron-carbon composite used in the present invention is about 10 to 90%, particularly about 40 to 70%.</p><p> Further, in the present invention, instead of iron halide, for example, (a) a halide of a metal selected from the group consisting of nickel, cobalt, etc., or (b) a halide of the metal of (a) above and others. A metal selected from the group consisting of nickel, cobalt, etc. of (a) above, or the above, in the same manner as in the above method for producing an iron-carbon composite, using a mixture of the metal (for example, iron) with a halide. An alloy composed of the constituent elements of the mixture of (b) or a metal-carbon composite in which the above-mentioned carbides such as nickel and cobalt are present in the range of 10 to 90% of the space inside the tube of the nanoflake carbon tube. Obtainable.</p><p><u style="single">&lt;Nanoflake carbon tube&gt;</u> By acid-treating the metal-carbon composite in which the above metal is partially contained in the inner space of the nanoflake carbon tube, the contained metal is dissolved and removed, and the hollow space in which no metal is present in the inner space of the tube. Nanoflake carbon tubes can be obtained. Examples of the acid include hydrochloric acid and nitric acid, and the concentration thereof is preferably about 1 to 10% by weight. The acid treatment method can be carried out by various methods. For example, 5 g of the metal-carbon composite is stirred at room temperature for 24 hours with 500 ml of hydrochloric acid specified in 1 and washed with ethanol after the stirring is completed. Allows the isolation of hollow nanoflake carbon tubes.</p><p> The basic composition of the nanoflake carbon tube is not particularly changed by this acid treatment. Therefore, even in a hollow nanoflake carbon tube in which no metal exists in the space inside the tube, the length of the carbon mesh surface constituting the outermost surface is 500 nm or less, particularly 2 to 500 nm, particularly 10 to 100 nm. ..</p><p> Further, other adsorbent components can be added to the adsorbent made of the above nanoscale carbon tube to the extent that the dioxin removing ability of the dioxin removing filter of the present invention is not impaired. Other adsorbed components may be those capable of adsorbing dioxin, for example, activated carbon such as coal charcoal, palm charcoal, resin charcoal, wood charcoal, or peat charcoal; volcanic ash, silica gel, silas, chromosolve, etc. Silica-based substances; Clay minerals such as zeolite and mordenite; Phosphoric compounds such as apatite, bone charcoal and magnesium ammonium phosphate granules; Carbonated compounds such as coral fossils and calcium carbonate; Alumina; Crystalline silicate; Silica-alumina, etc. Is used. In particular, silica gel, crystalline silicate, magnesium ammonium phosphate granules, coral fossils, zeolites, volcanic ash and the like are preferably used. The other adsorbed component may be usually contained in an amount of about 0 to 50 parts by weight with respect to 100 parts by weight of the nanoscale carbon tube. If there are too many other adsorbed components, the effect will be reduced, which is not preferable.</p><p><u style="single">photocatalyst</u> Examples of the photocatalyst include titanium dioxide (TiO).₂), Zinc oxide (ZnO), Cadmium sulfide (CdS), Strontium titanate (SrTiO)₃) Etc. can be mentioned. In addition, at least one selected from the group consisting of these can be mentioned. In particular, titanium dioxide is preferable from the viewpoint of safety and cost. The photocatalyst may be produced by a known method such as a chlorine method or a sulfuric acid method, and examples thereof include anatase type photocatalysts. The photocatalyst is preferably in the form of powder or fine particles in terms of enhancing the catalytic activity. For example, those having an average primary particle diameter of about 2 to 400 nm are preferable, and those having an average diameter of about 5 to 80 nm are more preferable. Further, as the surface shape of the photocatalyst particles, a porous one having a large contact surface is preferable.</p><p> Further, from the viewpoint of the decomposition efficiency of the photocatalyst, at least one metal selected from the group consisting of Pt, Pd, Cu, and Ag may be supported on the surface of the photocatalyst. The amount of the metal supported may be about 0.01 to 10 parts by weight, preferably about 0.1 to 5 parts by weight, based on 100 parts by weight of the photocatalyst. As a method of supporting the metal on the surface of the photocatalyst, a known method may be used.</p><p><u style="single">Manufacture of photocatalytic filters</u> When the photocatalyst filter is a filter substrate on which an adsorbent containing a nanoscale carbon tube and a photocatalyst are supported, a method of supporting the adsorbent and the photocatalyst on the filter substrate is a known method depending on the material of the filter. It can be appropriately selected and used.</p><p> For example, when the material of the filter is ceramic, metal, glass, paper, non-woven fabric, etc., a slurry containing an adsorbent, a photocatalyst, and an appropriate binder is coated on the filter substrate and supported by heat treatment as necessary. be able to.</p><p> The slurry contains an adsorbent, a photocatalyst, a binder and a dispersant as main components. Examples of the dispersant constituting the slurry include water, methanol, ethanol, toluene, isopropanol and the like, and at least one selected from the group consisting of them can be adopted. The binder used in the present invention is not particularly limited, but an inorganic or organic binder usually used can be used. Examples of the inorganic binder include a silicate-based binder, a phosphate-based binder, an inorganic colloid, a metal alkoxide, a molten frit, and the like, and examples of the organic-based binder include a fluororesin and a silicon resin.</p><p> Examples of the silicate-based binder include aluminosilicate and tetraalkyl orthosilicate, examples of the phosphate-based binder include calcium phosphate and the like, examples of the inorganic colloid include silica colloid, and examples of the metal alkoxide include silica colloid. , Titanium alkoxide and the like, and examples of the molten frit include frit glass and the like. Examples of the fluororesin include polytetrafluoroethylene. Examples of the silicone resin include phenylmethylpolysiloxane.</p><p> The ratio of each component constituting the slurry is about 1 to 200 parts by weight (preferably about 10 to 100 parts by weight) of the adsorbent, about 5 to 100 parts by weight of the binder, and 50 parts by weight of the dispersant with respect to 100 parts by weight of the photocatalyst. It is about 800 parts by weight (preferably about 100 to 400 parts by weight).</p><p> Additives may be added to the slurry in addition to the above components as needed. For example, a surfactant, a pH adjuster, an antifoaming agent and the like can be mentioned. Examples of the surfactant include a cationic surfactant, an anionic surfactant, a nonionic surfactant, and an amphoteric surfactant. The total amount of these additives used may be about 0 to 50 parts by weight (preferably about 1 to 10 parts by weight) with respect to 100 parts by weight of the photocatalyst.</p><p> A known method may be adopted for both the method of coating the slurry on the substrate of the filter and the method of heat-treating the coated product, and there is no particular limitation. As the coating method, for example, dip coating, spray coating, brush coating, electrostatic coating and the like can be adopted. In addition, the heat treatment is usually about 80 to 500 ° C, and may be heated in about 0.5 to 5 hours. By the above coating and heat treatment steps, the adsorbent and the photocatalyst are supported on the substrate of the filter.</p><p> In addition to the above method, the method of supporting the adsorbent and the photocatalyst on the filter substrate is to support the photocatalyst on the adsorbent containing the nanoscale carbon tube in advance, and then support the catalyst-supporting adsorbent on the filter substrate. May be good.</p><p> In the filter of the present invention, the total amount of the adsorbent and the photocatalyst supported on the filter substrate is 10 to 200 g / m in dry weight per filtration area of the filter substrate.²Degree, preferably 20-100 g / m²Degree. 10 g / m²If it is less than or equal to, the activity of the catalyst tends to decrease, and it is 200 g / m.²If the above is done, the filtration pressure loss is large and it is not economical.</p><p> Further, the photocatalyst filter of the present invention may be one in which an adsorbent containing a nanoscale carbon tube and a photocatalyst are supported by being sandwiched between filter substrates. For example, a bag-shaped air filter is filled with an adsorbent and a photocatalyst, and the adsorbent and the photocatalyst are dispersed inside the filter so as to be in uniform contact with the passing air.<u style="single">II. Light source</u> The light source to be used may be an ultraviolet light source having a functioning photocatalyst. A light source or two types of light sources having different wavelength ranges can be used. In particular, from a practical point of view, black light is preferable.<u style="single">III. Photocatalytic filter unit</u> The present invention also provides a photocatalytic filter unit including the above photocatalytic filter and a light source. A specific example is shown in FIG. Specifically, the outside of the photocatalyst filter is provided with an intake port 8, a dust collection filter 9, a photocatalyst filter 10, a light source 11, a blower 12, and an exhaust port 13. It is preferable that the photocatalyst filter 10 is arranged so as to sandwich the light source 11 from the viewpoint of light utilization efficiency.</p><p> Examples of the dust collecting filter 9 include known ones such as HEPA and ULPA. One or two or more dust collecting filters may be provided.</p><p> As the photocatalyst filter 10, the above-mentioned one can be adopted. The photocatalyst filter may be used by bundling one or two to five sheets, or may provide about two to five photocatalyst filters in which one or several sheets are bundled via a light source.</p><p> The light source 11 may employ the above. One or two or more light sources may be provided depending on the size of the filter.</p><p> The filtration rate of air passing through the photocatalytic filter of the present invention can be adjusted by the blower 12, and the filtration rate of air is usually 0.2 to 3.0 m.³It should be about / minute.</p><p> The temperature of the air passing through the photocatalytic filter of the present invention can be selected depending on the intended use, but is usually 0 to 300 ° C, preferably 0 to 250 ° C, and more preferably 0 to 230 ° C.</p><p> Examples of substances that can be treated by the photocatalytic filter of the present invention include substances that cause malodor in the atmosphere, dust, microorganisms, viruses, substances that cause sick house syndrome (formaldehyde, etc.), odorous components (tobacco odor, etc.), chemical substances, etc. (hereinafter, "" (Called "pollutant") is exemplified. According to the photocatalytic filter of the present invention, these can be efficiently adsorbed, decomposed and removed. It also includes dioxins and PCBs, which will be described later.</p><p> Since the photocatalyst filter of the present invention supports the adsorbent and the photocatalyst on the filter, the pollutants adsorbed on the adsorbent are rapidly decomposed by the photocatalyst. While the amount of adsorbed material reaches a plateau due to the adsorption equilibrium with the adsorbent alone, the filter of the present application can efficiently adsorb and decompose pollutants. In addition, since it contains a nanoscale carbon tube as an adsorbent, it has extremely high adsorption power. Further, since the nanoscale carbon tube has an extremely high adsorption capacity, the amount of the adsorbent used can be reduced, and the filter itself can be made compact while maintaining the adsorption performance.<u style="single">IV. Air purifier</u> The present invention also provides an air purifier equipped with the above photocatalytic filter unit. The air purifier is a pre-filter that removes rough dust; an ionization unit that uses static electricity to facilitate collecting dirt; electricity with an antibacterial / deodorizing filter. It may be a dust collecting roll filter; a photocatalytic filter unit of the present invention; and an intake (or exhaust) fan or the like. Other than the photocatalytic filter unit of the present invention, known members can be used. The air purifier of the present invention may be incorporated inside an air conditioner or the like.<u style="single">V. Exhaust gas treatment equipment</u> The present invention also provides an exhaust gas treatment device provided with the above photocatalytic filter unit. An example is shown in FIG. The exhaust gas treatment device of FIG. 11 includes the incinerator 1, the gas cooling tower 2, the reaction tower 3, the bug filter 4, the photocatalyst filter unit 7, the attracting blower 5, and the chimney 6. Further, an operation of treating the exhaust gas with activated carbon is included between the reaction tower 3 and the bag filter 4. Among the configurations of this exhaust gas treatment apparatus, any known configuration other than the photocatalyst filter unit 7 of the present invention can be adopted.</p><p> The incinerator 1 is an incinerator that incinerates dust, which is an object to be treated.</p><p> In the gas cooling tower 2, the high temperature (750 to 950 ° C) exhaust gas discharged from the incinerator 1 is cooled to about 200 ° C by water spraying or the like.</p><p> In the reaction tower 3, harmful substances such as hydrogen chloride (HCl) and sulfur oxides (SOx) (X is an integer of 1 to 3) in the exhaust gas are desulfurized and desalted. Specifically, slaked lime (Ca (OH)) as a neutralizing agent₂) Powder is sprayed in a considerable amount (dry type) or washed with an alkaline aqueous solution (NaOH aqueous solution, etc.) (wet) to contain hydrogen chloride (HCl) and sulfur oxide (SOx), which are acidic components of the exhaust gas. Be summed. Then soot and neutralized reaction products (CaCl)₂, CaSO₄) Is collected by the filter cloth installed in the bug filter 4.</p><p> The bug filter 4 filters and collects soot and dust in the exhaust gas with a filter cloth. That is, unreacted acidic components, unreacted slaked lime, dioxins, and heavy metals that did not react in the reaction tower 3 are removed to some extent in the bag filter 4.</p><p> Further, the photocatalytic filter unit 7 of the present invention efficiently removes pollutants, particularly dioxins, in the exhaust gas from the exhaust gas.</p><p> The purified exhaust gas is attracted by the attracting blower 5 and discharged to the outside from the chimney 6.</p><p> Here, examples of dioxins that can be treated by the exhaust gas treatment apparatus of the present invention include harmful halogenated aromatic compounds typified by dioxins and PXB (X represents halogen). The aromatic halogen compound is not limited to harmful substances such as dioxins and PCBs (for example, environmental hormones). Here, the dioxin is a general term for polyhalogenated dibenzo-p-dioxins (PXDDs) and polyhalogenated dibenzofurans (PXDFs) (X indicates halogen), and halogen-based compounds and certain organic halogens. It is said that a small amount is generated when the compound is burned. Depending on the number of halogens, there are monohalides to octahalides, of which dibenzo-p-dioxin tetrachloride (T) is particularly important.₄CDD) is known to be the most toxic. That is, the dioxins represent not only chlorinated dioxins but also halogenated dioxins such as brominated dioxins. In addition, PXBs (polyhalogenated biphenyls) are a general term for compounds in which several halogen atoms are added to biphenyls, and there are isomers depending on the number of halogen substitutions and substitution positions, but in the case of PCBs (polychlorinated biphenyls). , 2,6-dichlorobiphenyl, 2,2'-dichlorobiphenyl, 2,3,5-trichlorobiphenyl, etc. are typical and highly toxic, and dioxins may be generated when incinerated. Known as a thing, it needs to be removed. Needless to say, the PXBs also include the coplanar PXB.</p><p> The filtration rate of the exhaust gas passing through the photocatalyst filter unit 7 of the present invention is usually about 0.4 m / min to 1.5 m / min. As a result, the dioxin concentration in the treated gas is reduced to 0.1ng-TEQ / Nm.³It can be reduced as follows.</p><p> The photocatalyst filter included in the photocatalyst filter unit 7 of the present invention may be composed of one or a plurality of photocatalyst filters as described above.</p>

<p> Since the photocatalyst filter of the present invention supports an adsorbent containing a nanoscale carbon tube and a photocatalyst on the filter, the adsorption performance is dramatically improved.</p><p> Further, since the nanoscale carbon tube has extremely high durability, the durability of the photocatalytic filter of the present invention is also improved.</p>

Hereinafter, the present invention will be described in detail with reference to Examples. The present invention is not limited to the examples.

<u style="single">Reference Example 1 (Manufacturing of amorphous nanoscale carbon tube)</u> Amorphous nanoscale carbon nanotubes were prepared by the methods shown below.

Anhydrous iron chloride powder (particle size 500 μm or less) of 10 mg was uniformly sprinkled on a 60 μm × 10 mm × 10 mm PTFE film, and then plasma-excited. The conditions for plasma excitation were as follows: Atmosphere: Argon (Ar) Internal pressure: 0.01torr Input power: 300W RF frequency: 13.56MHz.

After completion of the reaction, it was confirmed by scanning electron microscopy (SEM) and X-ray diffraction that an amorphous nanoscale carbon tube (outer diameter; 10 to 60 nm, length; 5 to 6 μm) was formed.

The X-ray diffraction angle (2θ) of the obtained amorphous nanoscale carbon tube was 19.1 degrees, the carbon network plane spacing (d002) calculated from it was 4.6 Å, and the half width of the 2θ band was 8.1 degrees. It was.

<u style="single">Reference Example 2 (Manufacturing of iron-carbon composite)</u> Using the reactor as shown in FIG. 1, the iron-carbon composite of the present invention was obtained as follows. In FIG. 1, 1'indicates a reactor, 2'indicates a heating device, and 10'indicates a porcelain boat.

<u style="single">Process (1)</u> Anhydrous FeCl₃(Made by Kanto Chemical Co., Inc.) Spread 0.5g thinly in a porcelain boat and spread it. This is installed in the center of the furnace made of quartz tube, and the pressure inside the furnace is reduced to 50 Pa. At this time, argon gas containing 5000 ppm of oxygen is supplied at a rate of 30 ml / min from the side opposite to the reaction furnace end (the left side of the reaction tube in FIG. 1) to which the vacuum suction line is attached. As a result, the ratio B / A when the reactor volume is A (liter) and the oxygen content is B (Ncc) is 2.5 × 10.^-3And said. Then, the temperature is raised to a reaction temperature of 800 ° C. with reduced pressure.

<u style="single">Process (2)</u> When it reaches 800 ° C, argon is introduced and the pressure is 6.7 × 10.⁴Control to Pa. On the other hand, as a pyrolyzable carbon source, argon gas is bubbled in a benzene tank, and a mixed gas of volatilized benzene and argon is introduced into the furnace at a flow rate of 30 ml / min per liter of the reactor volume to dilute the gas. As a result, argon gas is introduced at a flow rate of 20 ml / min.

The carbonaceous material containing the iron-carbon composite of the present invention was obtained by reacting at a reaction temperature of 800 ° C for 30 minutes, lowering the temperature to 500 ° C in 20 minutes, removing the heater, and air-cooling to room temperature in 20 minutes. 200 mg was obtained.

From the results of SEM observation, the obtained iron-carbon composite had an outer diameter of 15 to 40 nm and a length of 2 to 3 microns, and was highly linear. The thickness of the wall made of carbon was 2 to 10 nm, which was substantially uniform over the entire length. Further, it was confirmed from TEM observation and X-ray diffraction method that the wall portion was a nanoflake carbon tube having a graphite structure with an average distance (d002) between carbon mesh surfaces of 0.34 nm or less.

Further, it was confirmed by X-ray diffraction and EDX that iron carbide was contained in the iron-carbon composite of the present invention.

When a large number of iron-carbon composites constituting the obtained carbonaceous material of the present invention were observed with an electron microscope (TEM), they were surrounded by the space of the nanoflake carbon tube (that is, the tube wall of the nanoflake carbon tube). Iron-carbon composites having various filling rates in which the filling rate of carbonized iron in the space) was in the range of 10 to 80% were mixed.

Incidentally, the average filling rate of iron carbide in the nanoflake carbon tube or the space inside the carbon nanotube of the large number of iron-carbon composites was 40%. Table 1 below shows the average filling rate of iron carbide calculated by observing multiple fields of view of the obtained TEM observation image of the iron-carbon composite. The R value calculated from X-ray diffraction was 0.56.

<tables num="1"><img file="JP2004148305A_D0001.tif" /></tables> Figure 2 shows an electron microscope (TEM) photograph of one iron-carbon composite that constitutes the carbonaceous material obtained in Reference Example 2.

Figure 3 shows an electron microscope (TEM) photograph showing the presence of a large number of iron-carbon complexes in the carbonaceous material obtained in Reference Example 2.

The electron diffraction pattern of one iron-carbon complex obtained in Reference Example 2 is shown in FIG. From FIG. 4, a clear electron diffraction pattern is observed, and it can be seen that the inclusions have high crystallinity. As a result of TEM observation, the crystallinity of the inclusions (the ratio of the area of the TEM image of crystalline iron carbide to the area of the TEM image in the range filled with iron carbide) was about 100%.

Figure 5 shows an X-ray diffraction pattern of the carbonaceous material (aggregate of iron-carbon composite material) containing the iron-carbon composite obtained in Reference Example 2.

FIG. 6 shows an electron microscope (TEM) photograph of one iron-carbon composite obtained in Reference Example 2 in a slice shape.

As can be seen from FIG. 6, in the carbonaceous material obtained in Reference Example 2, the carbon wall surface is not nested or scrolled, but is patchwork-like (so-called paper mache-like or papier-mache-like). It looked like a nanoflake carbon tube.

As can be seen from FIG. 6, the shape of the nanoflake carbon tube constituting the iron-carbon composite obtained in this example is cylindrical and is observed in the TEM photograph of the cross section crossing the longitudinal direction thereof. The graphene sheet image was not a closed ring, but a discontinuous ring with many discontinuities.

Further, when the nanoflake carbon tube constituting the iron-carbon composite of the present invention is observed by TEM, individual graphene sheet images are obtained with respect to a large number of substantially linear graphene sheet images oriented in the longitudinal direction thereof. The length of was generally in the range of 2 to 30 nm (Fig. 2).

Furthermore, from the EDX measurement results measured at points 1 to 20 in the tube of FIG. 6, it was found that the carbon: iron atomic ratio was 5: 5 and a nearly uniform compound was contained.

<u style="single">Example 1</u> The photocatalytic filter unit of the present invention shown in FIG. 10 was manufactured as follows.

The dust collection filter 9 in FIG. 10 uses high-performance HEPA pleated so as to collect fine particles such as cigarette smoke and Aerosil.

An amorphous nanoscale carbon tube (manufactured based on Reference Example 1) was used as the adsorbent used for the photocatalyst filter 10. As the photocatalyst, anatase titanium oxide having a primary particle size of about 20 nm was used. The amount of adsorbent used is 30 g / m with respect to the surface of the filter substrate.²Also, the amount of photocatalyst is 30 g / m with respect to the filter area.²As a photocatalytic filter was manufactured.

The filter of the present invention was manufactured as follows. 50 parts by weight of the adsorbent, 100 parts by weight of titanium oxide, and 50 parts by weight of the binder (tetramethyl orthosilicate) were dispersed in 200 parts by weight of ethanol to form a slurry. This slurry was applied to a ceramic honeycomb (material: silica) composed of square cells by an impregnation method. By adjusting the number of impregnations, the total amount of the adsorbent, photocatalyst and binder supported on the filter substrate is 70 g / m by dry weight.²(Corresponding to the filtration area of the filter substrate).

As shown in FIG. 10, the filter of the present invention has four filters stacked in a photocatalyst filter unit, and two filters are installed with four light sources in between.

<u style="single">Example 2</u> A photocatalytic filter was prepared in the same manner as in Example 1 except that the iron-carbon composite obtained in Reference Example 2 was used as the adsorbent.

<u style="single">Comparative example 1</u> A photocatalyst filter unit was manufactured by the same operation as in Example 1 except that only activated carbon (M-30, manufactured by Osaka Gas Co., Ltd.) was used instead of the amorphous nanoscale carbon tube as the adsorbent.

<u style="single">Experimental example 1</u> The photocatalytic filter unit obtained in Examples 1 and 2 and Comparative Example 1 was 1 m.³It was installed in the test box of the above and tested. The air volume of the blower installed in the filter unit is 2.5 m.³It was set to / min. The test gas used was acetaldehyde with an initial concentration of 80 ppm. Light source is 3mW / cm²I used 4 black lights. The change in the concentration of acetaldehyde and carbon dioxide gas in the test box after the operation of the photocatalytic filter unit was started was measured by gas chromatography. The results are shown in Table 2.

As can be seen from Table 2, when the filter unit of the example of the present invention was used, the time required to decompose the acetaldehyde concentration in the reaction system to 0.01 ppm or less was shorter than that of the conventional filter.

<tables num="2"><img file="JP2004148305A_D0002.tif" /></tables><u style="single">Experimental example 2</u> In order to evaluate the dioxin removing effect of the photocatalyst filter of the present invention, exhaust gas treatment is performed using the conventional exhaust gas treatment device shown in FIG. 8 and the exhaust gas treatment device using the photocatalyst filter unit of Example 1 shown in FIG. , The incinerator outlet and the dioxin concentration after treatment were measured. The exhaust gas filtration rate was set to about 1.0 m / min. The results are shown in Table 3.

<tables num="3"><img file="JP2004148305A_D0003.tif" /></tables> As is clear from Table 3, it was found that dioxin can be almost completely removed when the exhaust gas treatment apparatus of FIG. 11 provided with the photocatalytic filter unit of the present invention is used. In addition, it can be seen that the ability to remove dioxins has improved dramatically compared to the conventional exhaust gas treatment device.

<figref num="1">It is the schematic which shows an example of the manufacturing apparatus for manufacturing the metal-carbon composite used in this invention.</figref><figref num="2">It is an electron microscope (TEM) photograph of one iron-carbon composite constituting the carbonaceous material obtained in Reference Example 2.</figref><figref num="3">It is an electron microscope (TEM) photograph showing the existence state of the iron-carbon complex in the carbonaceous material obtained in Reference Example 2.</figref><figref num="4">It is an electron diffraction diagram of one iron-carbon complex obtained in Reference Example 2.</figref><figref num="5">It is an X-ray diffraction pattern of the carbonaceous material (aggregate of iron-carbon composite) containing the iron-carbon composite obtained in Reference Example 2.</figref><figref num="6">It is an electron microscope (TEM) photograph of one iron-carbon complex obtained in Reference Example 2 in a slice shape. The black triangle () shown in the photograph of FIG. 6 indicates the EDX measurement point for composition analysis.</figref><figref num="7">A schematic diagram of the TEM image of the carbon tube is shown, (a-1) is a schematic diagram of the TEM image of the columnar nanoflake carbon tube, and (a-2) is a schematic diagram of the TEM image of the nested multi-walled carbon nanotube. It is a schematic diagram.</figref><figref num="8">It is a figure which shows an example of the conventional exhaust gas treatment apparatus.</figref><figref num="9">It is a figure which shows an example of the photocatalytic filter of this invention.</figref><figref num="10">It is a figure which shows an example of the photocatalyst filter unit of this invention.</figref><figref num="11">It is a figure which shows an example of the exhaust gas treatment apparatus of this invention.</figref>

Code description

1'Reactor 2'Heating device 10'Magnetic boat 100 Longitudinal TEM image of nanoflake carbon tube 110 Approximately linear graphene sheet image 200 TEM image of cross section almost perpendicular to the longitudinal direction of nanoflake carbon tube 210 Arc Graphene sheet image 300 Linear graphene sheet image continuous over the entire length of the nested multi-walled carbon nanotubes 400 TEM image of the cross section of the nested multi-walled carbon nanotubes perpendicular to the longitudinal direction 1 Incinerator 2 Gas cooling tower 3 Catalytic reaction Tower 4 Bug filter 5 Attracting blower 6 Chimney 7 Photocatalyst filter unit 8 Intake port 9 Dust collection filter 10 Photocatalyst filter 11 Light source 12 Blower 13 Exhaust port