JP2011062587A - Method for manufacturing fine particle composite - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a fine particle composite capable of manufacturing the fine particle composite having the almost same decomposition capacity as the decomposition speed of an organic substance such as an alcohol or an aldehyde due to titanium dioxide alone in a case that titanium dioxide is used as solid fine particles. <P>SOLUTION: The method for manufacturing the fine particle composite includes a process for coating the solid fine particles with carbon to obtain carbon coated solid fine particles, a process for adding a component capable of forming a porous material into a synthetic medium containing the carbon coated solid fine particles to mix the same with the synthetic medium to thereby compound the carbon coated solid fine particles with the component capable of forming the porous material to obtain a fine particle-containing composite precursor (a) and a process for baking the fine particle-containing composite precursor (a) to eliminate the carbon to obtain the fine particle composite containing the solid fine particles and the porous material. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a fine particle composite.

  Solid fine particles are industrially used in various aspects by utilizing their size and high surface area. In particular, solid fine particles having a diameter of micrometer or less have a large surface area per weight, and thus have various applications as a catalyst such as a photocatalyst.

  In the application of solid particulates to catalysts that convert or decompose organic or inorganic molecules, catalytic activity is improved by using catalytically active substances as solid particulates, regardless of whether they are metals, metal oxides, or metal nitrides. It is known to increase.

  Also in the photocatalyst, the performance is improved by making the active substance into solid fine particles. However, solid fine particles generally become unstable as the particle size decreases, and sufficient thermal stability cannot often be obtained alone. That is, various phenomena such as changes in the crystal phase of solid fine particles, particle growth, fusion between solid fine particles, and reduction in surface area occur due to heating, and the performance is deteriorated.

  In order to prevent these, solid fine particles such as titanium dioxide are dispersed and supported on a porous carrier having a high surface area such as mesoporous silica and zeolite. As a method for supporting solid fine particles on a porous material, for example, a patent There are methods disclosed in Documents 1 and 2.

  Patent Document 1 discloses a method of obtaining a fine particle composite by dispersing solid fine particles in a synthetic medium before the porous body is formed, and then generating the porous body in the synthetic medium.

  Patent Document 2 discloses a method of obtaining a fine particle composite of a crystalline porous material and solid fine particles using a so-called dry gel conversion method.

JP-A-2005-314208 JP 2009-155178 A

  In the fine particle composite obtained by using titanium dioxide as solid fine particles by the production methods of Patent Document 1 and Patent Document 2, when used as a catalyst for removing organic substances such as alcohol and aldehyde, the organic substance by titanium dioxide alone Compared to the decomposition rate, there was still room for improvement from the viewpoint of catalytic activity.

  The present invention has been made in view of the above matters, and the object of the present invention is that when titanium dioxide is used as the solid fine particles, the decomposition rate of organic substances such as alcohol and aldehyde by the titanium dioxide alone is almost the same. An object of the present invention is to provide a method for producing a fine particle composite capable of producing a fine particle composite having a resolution.

The method for producing a fine particle composite according to the first aspect of the present invention comprises:
Coating the solid fine particles with carbon to obtain carbon-coated solid fine particles;
A component capable of generating a porous body is added to and mixed with a synthetic medium containing the carbon-coated solid fine particles, and the carbon-coated solid fine particles and the component capable of generating the porous body are combined to form a composite containing fine particles. Obtaining a precursor (a);
Firing the fine particle-containing composite precursor (a), eliminating the carbon, and obtaining a fine particle composite containing the solid fine particles and a porous body;
It is characterized by including.

The method for producing a fine particle composite according to the second aspect of the present invention comprises:
Coating the solid fine particles with carbon to obtain carbon-coated solid fine particles;
A component capable of generating a porous body is added to and mixed with a synthetic medium containing the carbon-coated solid fine particles, and the carbon-coated solid fine particles and the component capable of generating the porous body are combined to form a composite containing fine particles. Obtaining a precursor (a);
A step of heating and aging the fine particle-containing composite precursor (a) in a heated steam atmosphere or in the presence of liquid water to obtain a fine particle-containing composite precursor (b);
Firing the fine particle-containing composite precursor (b) to eliminate the carbon to obtain a fine particle composite containing the solid fine particles and a crystalline porous body;
It is characterized by including.

  Moreover, it is preferable that the organic fine particles are adsorbed on the solid fine particles, and the organic matters are carbonized to obtain the carbon-coated solid fine particles.

  The organic material may be carbonized by heating in a non-oxygen atmosphere.

  Further, the organic substance may be carbonized using a dehydrating agent.

  Moreover, it is preferable to use titanium oxide as the solid fine particles.

  Moreover, it is preferable to use at least one selected from the group consisting of tetrahydrocarbonoxysilane, silica, silica alumina, silica gel, water glass, and fumed silica as the component capable of generating the porous body.

  In the method for producing a fine particle composite according to the first aspect of the present invention, a solid fine particle surface such as titanium dioxide is coated with carbon, and the fine particle-containing composite precursor (a) is formed using the carbon-coated solid fine particle. The fine particle-containing composite precursor (a) is baked to eliminate the coated carbon, thereby forming a fine particle composite containing solid fine particles and a porous material. In the method for producing a fine particle composite according to the second aspect of the present invention, the fine particle-containing composite precursor (b) is obtained by the so-called dry gel conversion method using the fine particle-containing composite precursor (a). By burning the carbon and disappearing the coated carbon, a fine particle composite containing solid fine particles and a crystalline porous material is formed. In the fine particle composite obtained in this way, the moving speed of harmful substances adsorbed on the porous body to titanium dioxide is high, and the adsorbed harmful substances are quickly carried to the solid fine particles and decomposed. As described above, the method for producing a fine particle composite according to the present invention has an advantage that a fine particle composite having a high catalytic activity can be obtained with almost the same resolution as the decomposition rate of harmful substances by titanium dioxide alone.

FIG. 3 is a process diagram of the method for producing a fine particle composite according to Embodiment 1. 6 is a process diagram of a method for producing a fine particle composite according to Embodiment 2. FIG. It is a conceptual diagram of the apparatus for performing the dry gel conversion method. In the decomposition experiment of 2-propanol of Example 1, (A) is a concentration change of 2-propanol, (B) is a concentration change of acetone, and (C) is a graph showing a concentration change of carbon dioxide. In the decomposition experiment of 2-propanol of Example 2, (A) is a concentration change of 2-propanol, (B) is a concentration change of acetone, (C) is a graph which shows a concentration change of carbon dioxide.

(Embodiment 1)
As shown in the process diagram of FIG. 1, the method for producing a fine particle composite according to Embodiment 1 includes a step of obtaining carbon-coated solid fine particles, a step of obtaining fine particle-containing composite precursor (a), and a fine particle composite. And obtaining a process. Hereinafter, each step will be described in detail.

(Step of obtaining carbon-coated solid fine particles)
First, a process for obtaining carbon-coated solid fine particles will be described. The method is not particularly limited as long as the surface of the solid fine particles can be coated with carbon. Examples of the method of coating the surface of the solid fine particles with carbon include the following methods.

  After the organic substance is adsorbed on the surface of the solid fine particles, the organic substance is converted to carbon, whereby the surface of the solid fine particles can be coated with carbon.

  In addition to oxygen-containing compounds such as alkanes, alkenes, alcohols, esters, and ethers, nitrogen-containing compounds such as pyridine, aniline, and amine can also be used as the organic substance. Alternatively, an organic substance in which nitrogen or oxygen is bonded to an aromatic compound including a benzene ring, a pyridine ring, a naphthalene ring, or the like may be used.

  The organic substance may be adsorbed on the surface of the solid fine particles in a molecular state, or may be polymerized on the surface of the solid fine particles and coated as a polymer. By polymerizing the organic monomer in the presence of the solid fine particles, the organic polymer can be coated on the solid fine particles.

  Alternatively, the surface of the solid fine particles may be coated with a solid fine particle by impregnating a solution obtained by dispersing or dissolving the organic polymer in a solvent. The solvent to be used may be an organic solvent or an aqueous solvent, and may be appropriately changed according to the organic substance. For example, when a polymer having an ether bond or an ester bond or a polymer having a hydroxyl group such as polyvinyl alcohol is used as the water-soluble polymer, an aqueous solvent may be used. As the polymer, a polymer obtained by polymerizing the organic material described above may be used.

  As a method for converting the organic substance adsorbed on the surface of the solid fine particles into carbon, any organic substance is carbonized by heating in the absence of oxygen, for example, in a nitrogen gas or inert gas stream or in a vacuum. Can do. Thereby, carbon-coated solid fine particles in which the solid fine particle surface is coated with carbon can be obtained.

  Alternatively, the adsorbed organic substance may be carbonized by chemical reaction with various chemicals by heating or non-heating. For example, when an organic substance such as saccharide such as sucrose is adsorbed on the surface of the solid fine particles, it can be easily carbonized without heating by reacting the organic substance with a dehydrating agent such as concentrated sulfuric acid at room temperature. .

  Solid fine particles include magnesia, alumina, silica, aluminum phosphate, boron, carbon, silicon nitride, aluminum nitride and other inorganic oxides, chlorides, nitrides, borides, carbides, sulfides, polyethylene, etc. Although organic substances such as resin particles can be used, fine particles having a photocatalytic function are particularly preferable.

Any fine particles having a photocatalytic function (hereinafter referred to as photocatalyst fine particles) may be used as long as they have characteristics as a semiconductor and have photocatalytic characteristics. Of these, metal sulfides and metal oxides are preferable, and metal oxides such as titania, zirconia, niobium oxide, and tungsten oxide are most preferable. Specific examples include TiO ₂ , SrTiO ₃ , WO ₃ , Fe ₂ O ₃ , Bi ₂ O ₃ , MoS ₂ , CdS, CdSe, GaP, GaAs, MoSe ₂ , CdTe, Nb ₂ O ₅ , Ta ₂ O. ₅ , heteropolyacids such as H ₃ PW ₁₂ O ₄₀ and H ₃ PMo ₁₂ O _40, and salts thereof, in addition to complex oxides of N, Nb and Ta. Of these, TiO ₂ (titanium dioxide), which is known to have high photocatalytic activity, is preferable. As the photocatalyst fine particles, it is preferable to use fine particles that are not aggregated (for example, P-25 manufactured by Degussa, Germany).

  The solid fine particles preferably form pores having an average particle diameter of 2 nm or more and 50000 nm or less. As a minimum, 5 nm or more is more preferable, and 10 nm or more is further more preferable. As an upper limit, 50000 nm or less is more preferable, and 1000 nm or less is further more preferable. When the average particle size of the solid fine particles is smaller than the above range, the crystallinity of the solid fine particles is poor and the photocatalytic activity is lowered. In addition, if the average particle size is larger than the above range, the surface area of the solid fine particles becomes small, so that the catalytic activity becomes low.

(Step of obtaining fine particle-containing composite precursor (a))
Then, the process of obtaining a fine particle containing composite precursor (a) is demonstrated.

  A component capable of forming a porous material is added to and mixed in the synthesis medium containing the carbon-coated solid fine particles obtained as described above. As a result, the fine particles-containing composite precursor (a) can be obtained by combining the carbon-coated solid fine particles and the component capable of generating a porous material.

  The synthesis medium is preferably an aqueous medium. Examples of the aqueous medium include a medium in which ammonia, sodium hydroxide, or the like is added to water for the purpose of adjusting pH. The pH of the synthesis medium is preferably 9-12, or 1-5. Silica easily precipitates when the pH is within the above range.

  The component capable of forming the porous body is not particularly limited as long as it forms a porous body, but a silicon compound is preferably used. The silicon compound is preferably at least one silicon compound selected from the group consisting of tetrahydrocarbon oxysilane, silica, silica alumina, silica gel, water glass and fumed silica. Specific examples include tetraalkoxysilane and tetrahalogenated silane. Other metal alkoxides and chlorides may be added thereto. Of these, tetraethoxysilane is preferred. This is because these silicon compounds easily produce silica.

  Further, a surfactant may be contained in the synthesis medium. As the surfactant, at least one surfactant selected from the group consisting of polyoxyethylene / polyoxypropylene block copolymer, tetraalkylammonium hydroxide and tetraalkylammonium halide may be used.

  Among these, tetraalkylammonium bromide, tetraalkylammonium chloride, and polyoxyethylene / polyoxypropylene block copolymer are more preferable, but any of those generally used for the synthesis of mesoporous silica can be preferably used. Specifically, cetyltrimethylammonium bromide, dodecyltrimethylammonium bromide, and the like are preferable. This is because these surfactants efficiently generate mesopores.

  When obtaining a synthetic medium containing carbon-coated solid fine particles, it is preferable to add the carbon-coated solid fine particles to the synthetic medium and irradiate ultrasonic waves to disperse the carbon-coated solid fine particles in the synthetic medium.

  The temperature at the time of mixing after adding the component which can produce | generate a porous body to the synthetic | combination medium containing a carbon covering solid fine particle is preferably 0-90 degreeC, and it is more preferable that it is 20-50 degreeC. The time required for mixing is usually 0.5 seconds to 5 hours, and the aging time after mixing is usually 0 to 10 hours, preferably 0.5 to 3 hours. This is because silica is efficiently produced and aged within the above range.

  After completion of the reaction, the fine particle-containing composite precursor (a) can be obtained by removing the product from the synthesis medium by filtration or the like, washing with ion exchange water or the like, and drying.

(Step of obtaining a fine particle composite)
Next, a process for obtaining a fine particle composite will be described. By firing the fine particle-containing composite precursor (a) obtained as described above, the carbon covering the surface of the solid fine particles can be eliminated, and a fine particle composite can be obtained.

  The temperature during firing is preferably 400 to 700 ° C, and more preferably 450 to 600 ° C. Moreover, baking time is 1 to 20 hours normally, and it is more preferable to set it as 2 to 8 hours. By calcination under the above conditions, carbon covering the surface of the solid fine particles and the surfactant can be eliminated, and chemical bonds that create the skeleton of the porous body can be efficiently generated. .

(Embodiment 2)
Subsequently, a method for producing the fine particle composite according to Embodiment 2 will be described. As shown in FIG. 2, the method for producing a fine particle composite according to Embodiment 2 includes a step of obtaining carbon-coated solid fine particles, a step of obtaining a fine particle-containing composite precursor (a), and a fine particle-containing composite precursor (b). And a step of obtaining a fine particle complex. Hereinafter, each step will be described in detail.

  Since the step of obtaining the carbon-coated solid fine particles and the step of obtaining the fine particle-containing composite precursor (a) are the same as those in the first embodiment, the description thereof is omitted.

(Step of obtaining fine particle-containing composite precursor (b))

  The fine particle-containing composite precursor (b) can be obtained by heat aging the fine particle-containing composite precursor (a) in a heated steam atmosphere or in the presence of liquid water. This step may be performed by a so-called dry gel conversion method. The dry gel conversion method is a method of crystallizing zeolite by treating a dry gel obtained by drying a raw material mixture for zeolite synthesis with water vapor or the like.

  In the fine particle composite obtained through this step, the porous body is formed as a crystalline porous body. An example of a conceptual diagram of an apparatus for performing the dry gel conversion method is shown in FIG.

  In this step, the temperature at which the heat aging is performed is preferably 100 to 250 ° C, and more preferably 120 to 200 ° C. Moreover, the time for performing heat aging is usually 0 to 1000 hours, and more preferably 2 to 200 hours.

  Moreover, it is preferable to carry out the heat aging in the presence of an organic substance that serves as a templating agent for the porous body. When heat aging is performed in the presence of an organic substance serving as a templating agent, a porous body is easily generated.

  It is preferable to use at least one organic substance selected from the group consisting of tetrahydrochloric ammonium ammonium and halogenated tetrahydrocarbon ammonium as the templating agent, and comprises tetraalkylammonium bromide and tetraalkylammonium hydroxide. It is more preferable to use at least one organic substance selected from the group. Specifically, it is particularly preferable to use at least one organic material selected from the group consisting of tetrapropylammonium bromide and tetrapropylammonium hydroxide.

  In this step, as a method for allowing the organic material that serves as the templating agent to coexist, for example, the fine particle-containing composite precursor (a) is added to an aqueous solution containing the organic material that serves as the templating agent, and then irradiated with ultrasonic waves to form fine particles There is a method in which the composite precursor (a) is dispersed in a solution and then the solution is evaporated to dryness.

  Moreover, when a surfactant is used in the step of obtaining the fine particle-containing composite precursor (a), a step of removing this surfactant may be added before this step. For example, the surfactant can be removed by adding the fine particle-containing composite precursor (a) to a solvent capable of extracting the surfactant and stirring the mixture.

(Step of obtaining a fine particle composite)
By firing the fine particle-containing composite precursor (b) obtained as described above, a fine particle composite containing solid fine particles and a crystalline porous material can be obtained. The firing temperature for producing the fine particle-containing composite precursor (b) is preferably 400 to 700 ° C, more preferably 450 to 600 ° C. Moreover, baking time is 0.5 to 30 hours, and it is more preferable that it is 1 to 10 hours. By firing under the above conditions, the carbon coated on the surface of the solid fine particles and the organic substance serving as the templating agent can be removed efficiently, and chemical bonds that form the skeleton of the crystalline porous body can be efficiently generated. .

  In the method for producing a fine particle composite described in the first and second embodiments, solid crystalline fine particles having good crystallinity, that is, solid fine particles having high catalytic activity can be used as they are, so that a fine particle composite having high catalytic activity is formed. be able to.

  The obtained fine particle composite can be used as various catalysts, and the fine particle composite may be used alone or in combination with a carrier such as a metal oxide.

The catalyst containing the fine particle composite can be suitably used as a photolysis reaction catalyst when the solid fine particles contain a metal compound, more preferably TiO ₂ . As an aspect using the catalyst containing such a fine particle complex, for example, an aspect of holding the catalyst in a state in which the catalyst can come into contact with a gas containing a sample such as an organic substance such as alcohol or aldehyde can be cited. By irradiating the catalyst with light having a wavelength that activates the solid fine particles while the porous body adsorbs organic substances and the like, the solid fine particles quickly convert and decompose the organic substance. Specific examples of the organic substance include acetaldehyde and 2-propanol.

  Further, the catalyst containing the fine particle composite is suitably used as a hydrogen reduction reaction catalyst, a denitration reaction catalyst, a decarbonization reaction catalyst, etc. when it contains metal fine particles as solid fine particles. The solid fine particles contained in the fine particle composite are generally used as catalysts such as metal particles such as Pt, Pd, Ru, Rh, Ir, Ni, Cu, Zn, Co, and Mo, oxides thereof, titanium oxide-supported vanadium oxide, and the like. Therefore, the catalyst including the fine particle composite obtained by using such solid fine particles has a catalytic activity derived from each solid fine particle, and has a variety of properties depending on the solid fine particles. It can be used as a reaction catalyst.

  Using titanium dioxide as the solid fine particles, a fine particle composite was manufactured by the method for manufacturing a fine particle composite according to Embodiment 1, and a 2-propanol decomposition experiment was performed.

(Manufacture of fine particle composite)
TiO ₂ (product name: P-25, manufactured by Degussa, particle diameter 20-30 nm) (hereinafter referred to as P-25) was vacuum dried for 2 hours.

  Surfactant sodium dodecyl sulfate (4.61 g) was dissolved in 1 M aqueous hydrochloric acid solution (200 mL), and P-25 (3.0 g) and aniline (3.68 g) were added and stirred. To this solution, ammonium peroxodisulfate (2.28 g) was added as a polymerization initiator and stirred for 2 hours. Due to the formation of polyaniline, the color of the solution changed from white to blue to green. The product was collected by centrifugation, washed with ethanol, and dried at 70 ° C. to obtain a powder.

  The obtained powder was heated at 450 ° C. for 12 hours under a nitrogen stream to carbonize the polyaniline adsorbed on P-25 to obtain carbon-coated solid fine particles of black powder. Hereinafter, the obtained black powder is referred to as Carbon P25.

  Surfactant hexadecyltrimethylammonium bromide (0.86 g) was dissolved in ion-exchanged water (46 g) with heating, and 28% aqueous ammonia was added to adjust the pH to 11.8. To this solution, 1.54 g of carbon-coated Carbon P25 was added, and ultrasonic waves were dispersed for 20 minutes.

While this solution was vigorously stirred, tetraethoxysilane (Si (OC ₂ H ₅ ) ₄ ) (3.38 g) was added all at once. As a result, hydrolysis of tetraethoxysilane occurred and silica was formed around the micelles of the surfactant.

  After stirring this mixed solution for 1 hour, the product was collected by filtration, washed with ion-exchanged water, and then dried at 70 ° C. to obtain a fine particle-containing composite precursor (a).

This fine particle-containing composite precursor (a) is baked at 450 ° C. for 6 hours to eliminate the surfactant and the carbon coated on the surface of P-25, and the white powder fine particle composite is mesoporous silica-TiO ₂ composite. Got the body. Hereinafter, this is referred to as CarbonNC. Carbon NC had a surface area of 424 m ² g ⁻¹ .

Further, as a reference example, a white powder microparticle composite was obtained in the same manner as above except that carbon coating was not performed. Hereinafter, this fine particle composite is referred to as NC. The specific surface area of this NC was 409 m ² g ⁻¹ .

(2-propanol decomposition experiment)
2-propanol was decomposed | disassembled using CarbonNC, NC produced | generated above, and P-25 single-piece | unit, respectively.

  Carbon NC and 2-propanol (initial concentration 568 ppm) were introduced into a sealed container that shields light from the outside. CarbonNC was introduced so that the amount of P-25 contained was 20 mg.

  After 90 minutes from introduction of Carbon NC, ultraviolet rays were irradiated with a xenon lamp (500 W).

  Since 2-propanol is decomposed into carbon dioxide through acetone, the change with time of each concentration of 2-propanol, acetone, and carbon dioxide was measured by gas chromatography.

  Similarly, NC and P-25 alone are introduced into a sealed container so that the amount of P-25 is 20 mg, respectively, and 2-propanol is decomposed to give 2-propanol, acetone, and carbon dioxide. The time course of each concentration of was measured.

  Each concentration change is shown in FIG. 4A shows the change in 2-propanol concentration, FIG. 4B shows the change in acetone concentration, and FIG. 4C shows the change in carbon dioxide concentration.

  FIG. 4A shows that Carbon NC and NC both have high adsorption ability due to porous mesoporous silica, and almost adsorb 2-propanol in the gas phase before ultraviolet irradiation.

  4B shows that acetone produced during the reaction is almost adsorbed without being released to the outside.

  Moreover, when FIG.4 (C) is seen, the production | generation speed | rate of carbon dioxide of CarbonNC shows the speed | rate substantially equivalent to P-25 single-piece | unit, and shows the activity higher than NC manufactured without carbon coating. I understand.

  From this result, due to the effect of carbon coating, close complexation of P-25 and mesoporous silica was realized, the speed of movement of adsorbed organic molecules to the P-25 surface was increased, and the same catalyst as P-25 alone It is thought that it shows activity.

  Using titanium dioxide as the solid fine particles, a fine particle composite was manufactured by the method of manufacturing a fine particle composite according to Embodiment 2, and a 2-propanol decomposition experiment was performed.

(Manufacture of fine particle composite)
First, a fine particle-containing composite precursor (a) was obtained in the same manner as in Example 1.

  Glacial acetic acid (0.30 g) was added to 39.2 g of ethanol to prepare a 0.1 M acetic acid / ethanol solution, and the dried fine particle-containing composite precursor (a) was added thereto, followed by stirring at 80 ° C. for 2 hours.

  This was filtered, washed with ethanol, and dried at 70 ° C. This operation was repeated once more to remove the surfactant hexadecyltrimethylammonium bromide.

  0.1 g of tetrapropylammonium bromide was dissolved in 10 mL of ion-exchanged water, and 0.5 g of the fine particle-containing composite precursor (a) from which the surfactant was removed by solvent extraction was added thereto and treated with ultrasonic waves for 20 minutes.

  This solution was dried at 70 ° C. to obtain a powder. This powder is placed on the polytetrafluoroethylene cup 2 in the autoclave 6 shown in the conceptual diagram of the apparatus in FIG. 3, and 9.5 mL of ion-exchanged water and 0. 0 ethylenediamine are placed on the bottom of the polytetrafluoroethylene inner cylinder 5. 5 mL was added and aged at 175 ° C. for 7 days. Thereafter, the product was collected by centrifugation, washed with ion exchange water, and dried at 70 ° C.

This was calcined at 450 ° C. for 6 hours to eliminate the carbon and surfactant coated on the surface of P-25, and a silicalite (zeolite) -TiO ₂ composite, which is a white powder microparticle composite, was obtained. It was. Hereinafter, this white powder is referred to as DGC-CarbonNC. The specific surface area of DGC-CarbonNC was 184 cm ² g ⁻¹ and the micropore volume was 0.052 cm ³ g ⁻¹ .

Further, as a reference example, a white powder microparticle composite was obtained in the same manner as above except that carbon coating was not performed. Hereinafter, this fine particle composite is referred to as DGC-NC. This DGC-NC had a specific surface area of 51 cm ² g ⁻¹ and a micropore volume of 0.009 cm ³ g ⁻¹ .

(2-propanol decomposition experiment)
Using the DGC-CarbonNC, DGC-NC, and P-25 alone produced above, 2-propanol was decomposed, respectively.

  The fine particle composite and 2-propanol (initial concentration 568 ppm) were introduced into a sealed container that shields light from the outside. DGC-CarbonNC was introduced so that the amount of P-25 contained was 20 mg each.

  After 90 minutes from the introduction, ultraviolet rays were irradiated with a xenon lamp (500 W). As in Example 1, changes with time in the concentrations of 2-propanol, acetone, and carbon dioxide were measured by gas chromatography.

  Similarly, DGC-NC and P-25 alone are introduced into a sealed container so that the amount of P-25 contained is 20 mg, 2-propanol is decomposed, 2-propanol, acetone, And the change with time of each concentration of carbon dioxide was measured.

  Each concentration change is shown in FIG. FIG. 5A shows the change in 2-propanol concentration, FIG. 5B shows the change in acetone concentration, and FIG. 5C shows the change in carbon dioxide concentration.

  As shown in FIG. 5 (A), DGC-CarbonNC and DGC-NC both show high adsorbability due to silicalite, which is a crystalline porous material, and almost adsorb 2-propanol in the gas phase before UV irradiation. You can see that Moreover, when FIG.5 (B) is seen, it turns out that the acetone which arises by decomposition | disassembly of 2-propanol is also almost adsorb | sucked.

  5C, the carbon dioxide production rate of DGC-CarbonNC is almost the same as that of P-25 alone, indicating a higher activity than DGC-NC without carbon coating. I understand that.

  From this result, due to the effect of carbon coating, close complexation of P-25 and silicalite was realized, and the moving speed of the adsorbed organic molecules to the P-25 surface was increased. It is thought that it shows activity.

  Since the fine particle composite obtained by the above production method has a high decomposition rate of organic substances and the like, harmful organic substances can be rapidly decomposed, and extremely low concentrations of harmful substances can be removed from water and air. This technology can be used for purification and removal of harmful substances in all fields. In particular, harmful substances in the air can be adsorbed and removed from the air and decomposed efficiently under light irradiation.

1 Fine particle-containing composite precursor (a)
2 Polytetrafluoroethylene cup 3 Stainless mesh 4 Ion exchange water, ethylenediamine 5 Inner cylinder 6 Autoclave

Claims (7)

Coating the solid fine particles with carbon to obtain carbon-coated solid fine particles;
A component capable of generating a porous body is added to and mixed with a synthetic medium containing the carbon-coated solid fine particles, and the carbon-coated solid fine particles and the component capable of generating the porous body are combined to form a composite containing fine particles. Obtaining a precursor (a);
Firing the fine particle-containing composite precursor (a), eliminating the carbon, and obtaining a fine particle composite containing the solid fine particles and a porous body;
A process for producing a fine particle composite comprising: Coating the solid fine particles with carbon to obtain carbon-coated solid fine particles;
A component capable of generating a porous body is added to and mixed with a synthetic medium containing the carbon-coated solid fine particles, and the carbon-coated solid fine particles and the component capable of generating the porous body are combined to form a composite containing fine particles. Obtaining a precursor (a);
A step of heating and aging the fine particle-containing composite precursor (a) in a heated steam atmosphere or in the presence of liquid water to obtain a fine particle-containing composite precursor (b);
Firing the fine particle-containing composite precursor (b) to eliminate the carbon to obtain a fine particle composite containing the solid fine particles and a crystalline porous body;
A process for producing a fine particle composite comprising:   The method for producing a fine particle composite according to claim 1 or 2, wherein an organic substance is adsorbed on the solid fine particles, and the organic substance is carbonized to obtain the carbon-coated solid fine particles.   The method for producing a fine particle composite according to claim 3, wherein the organic substance is heated and carbonized in a non-oxygen atmosphere.   4. The method for producing a fine particle composite according to claim 3, wherein the organic substance is carbonized using a dehydrating agent.   The method for producing a fine particle composite according to claim 1 or 2, wherein titanium oxide is used as the solid fine particles.   The component capable of generating the porous body is at least one selected from the group consisting of tetrahydrocarbonoxysilane, silica, silica alumina, silica gel, water glass, and fumed silica. 3. A method for producing a fine particle composite according to 2.

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