JP2011213572A - Iron oxide porous body, air purifying material obtained by using the same and method for producing iron oxide porous body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an iron oxide porous body which has sufficiently high purifying performance with respect to reactive molecules such as a volatile organic compound (for example, acetaldehyde) contained in the air when used as an air purifying material.SOLUTION: The iron oxide porous body comprises an agglomerate in which primary particles of iron oxide agglomerate, wherein the average particle diameter of the primary particles is 2-8 nm and the median pore diameter of pores of the agglomerate is 2-10 nm. The iron oxide porous body has a two-line ferrihydride phase which shows two peaks comprising one peak derived from the (110) plane of a crystal and the other peak derived from the (300) plane of the crystal in an X-ray diffraction pattern, and the content ratio of the two-line ferrihydride phase to the whole crystal phase of the iron oxide is ≥40 mass%. The total amount of impurities comprising oxides of silicon, aluminum, tin, zinc and titanium is ≤0.1 mass%.

Description

  The present invention relates to an iron oxide porous body, an air purification material using the same, and a method for producing an iron oxide porous body.

In a wide-angle X-ray pattern, a peak at a position where the d value is 2.6 angstroms (a peak derived from the (110) plane of the crystal) and a peak at a position where the d value is 1.5 angstroms (on the (300) plane of the crystal) iron oxide having 2 line ferrihydrite phases having two broad peaks with a derived peak) is Fe ³⁺ ions less tetrahedral the correct coordination besides octahedral Fe ³⁺ ion species on the surface It has the property of being present and is expected to be applied in various fields.

  As a method for producing such an iron oxide having a two-line ferrihydrite phase, for example, “Occurrence and Constitution of Natural and Synthetic” described in pages 2549 to 2586 of Chemical Review vol. In “Ferrihydrite, a Widespread Iron Oxyhydroxide” (Non-Patent Document 1), a base is introduced into a solution containing an iron salt to form a precipitate, and then the precipitate is filtered and dried to form a two-line ferrihydrite. A method for obtaining iron oxide having a phase is disclosed. In Non-Patent Document 1, iron oxide having a two-line ferrihydrite phase can be used in fields such as wastewater treatment for adsorbing organic impurities, arsenic, manganese, copper, zinc, and other toxic elements. Are listed.

In JP 2005-2888439 (Patent Document 1), Fe (III) salts (for example, FeCl ₃ , Fe ₂ (SO ₄ ) ₃ , FeClSO ₄ , Fe (NO ₃ ) ₃ ) and an alkaline solution ( Fe (OH) ₃ was quantitatively precipitated using a reaction (Fe ³⁺ + 3OH ⁻ → Fe (OH) ₃ ) with NaOH, KOH, NH ₃ , Na ₂ CO ₃ , Ca (OH) ₂ ) A method for obtaining ferrihydrite by performing filtration and washing later and obtaining ferrihydrite is disclosed, and the obtained ferrihydrite is used to adsorb undesired components such as hydrogen sulfide, mercaptan, SOx, and NOx in exhaust gas. It is described that it is used.

Further, JP-in 2007-509832 (Patent Document 2), after the iron (III) nitrate _{(Fe (NO 3) 3 ·} 9H 2 O) was precipitated by NaOH in water, at 105 ° C. in an oven Disclosed is a method of obtaining mesoporous iron oxide by heating for 14 hours to produce ferrihydrite and goethite, washing with water, filtering, and drying at 60 ° C. under vacuum. It is disclosed that such iron oxide is used as a catalyst for removing NO, SO ₂ or the like, or is used as a filter for water containing organic chemical species, bacteria, heavy metals and other pollutants.

Furthermore, in “Synthesis and magnetic investigations of ordered mesoporous two-line ferrihydrite” (Non-Patent Document 2) described in pages 280 to 287 of vol.130 of the Journal of American Chemical Society published in 2008, using mesoporous silica (mesoporous silica KIT-6 mesoporous silica SBA-15 or three-dimensional cubic two-dimensional hexagonal), nitrate _{(Fe (NO 3) 3 ·} 9H 2 O) iron (III) in ethanol template after both stirring, ethanol was evaporated, after calcination for 6 hours at 200 ° C., the resulting solid contains nitrates of iron (III) in ethanol _{(Fe (NO 3) 3 ·} 9H 2 O) Add to the solution, stir, evaporate the ethanol again and calcine the resulting solid at 200 ° C. for 6 hours After obtaining the porous body precursor, the mesoporous silica as a template is removed from the porous body precursor using NaOH to obtain an iron oxide porous body having a 2-line ferrihydrite and having a mesoporous structure. A method of obtaining is disclosed.

JP 2005-2888439 A JP 2007-509832 A

Chemical Review, “Occurrence and Constitution of Natural and Synthetic Ferrihydrite, a Widespread Iron Oxyhydroxide”, vol. 98, 1998, 2549-2586 Harun Tuysuz et al., Journal of American Chemical Society, “Synthesis and magnetic investigations of ordered mesoporous two-line ferrihydrite”, vol. 130, 2008, 280-287.

  However, the iron oxide obtained by using the conventional methods for producing iron oxide as described in Patent Documents 1 and 2 and Non-Patent Documents 1 and 2 is a volatile organic compound when used as an air purification material. The performance of purifying reactive molecules such as (VOC: acetaldehyde, for example) has not always been sufficient.

  The present invention has been made in view of the above-mentioned problems of the prior art, and is sufficiently advanced with respect to reactive molecules such as volatile organic compounds (for example, acetaldehyde) contained in the air when used as an air purification material. Iron oxide porous body capable of having high purification performance, air purification material using the iron oxide porous body, and iron oxide porous body capable of efficiently producing the iron oxide porous body in a simple process It aims at providing the manufacturing method of.

  In order to achieve the above object, the present inventors first studied the above prior art (Patent Documents 1 and 2 and Non-Patent Documents 1 and 2). First, in the conventional methods for producing iron oxide as described in Patent Document 1 and Non-Patent Document 1, a porous body having a mesoporous structure cannot be obtained, and the structure of iron oxide serves as an air purification material. It was found that a sufficiently high purification performance could not be obtained when used. Next, when the above Patent Document 2 was examined, a mesoporous iron oxide porous body was obtained in the conventional method for producing iron oxide as described in this document, but such an iron oxide porous body is The primary particles have an irregularly aggregated structure due to very high wettability, and it is assumed that the pores are formed as spaces between the particles, the uniformity of the pores is low, and the central pore diameter is 35 nm. Furthermore, the pore volume is extremely low such as 0.09 to 0.18 cc / g. In addition, in such an iron oxide porous body, the size of the primary particles constituting the porous body cannot be made sufficiently small, and the average particle diameter of the primary particles exceeds 8 nm, and sufficiently small particles are not formed. An agglomerated structure could not be obtained. And when such an iron oxide porous body as described in Patent Document 2 is used as an air purification material, volatile organic compounds in the air cannot be sufficiently diffused into the pores, and are not necessarily limited. It was found that sufficient purification performance could not be obtained. In addition, when such an iron oxide porous body as described in Patent Document 2 is fired at a temperature of 200 ° C. or higher, there is no mesoporous structure. Next, when non-patent document 2 was examined, in the conventional method for producing iron oxide as described in this document, a mesoporous iron oxide porous body was obtained, but the mesoporous silica used as a template at the time of production was obtained. 2% by weight or more of the derived silicon oxide (silicon dioxide) is contained, and further, the surface of the iron oxide porous body obtained by Na derived from NaOH used for removing the template is unsaturated. It turns out that the coordination site is poisoned. And in such an iron oxide porous body as described in Non-Patent Document 2, when it is used as an air purification material, it is not necessarily derived from impurities (such as silicon dioxide) contained in the iron oxide porous body. It was found that sufficient volatile organic compound removal performance could not be obtained. In addition, in such a conventional iron oxide porous body as described in Non-Patent Document 2, when silicon dioxide is not included, the 2-line ferrihydrite phase is not sufficiently formed, and hematite is mainly formed. Will be. Further, the conventional method for producing iron oxide as described in Non-Patent Document 2 requires not only a very complicated process but also is not necessarily sufficient in terms of cost.

  Next, as a result of further earnest studies to achieve the above object, the present inventors based on the above examination results, the iron oxide porous body is composed of an aggregate in which primary particles of iron oxide are aggregated. The average particle diameter of the primary particles is 2 to 8 nm, the center pore diameter of the pores of the aggregate is 2 to 10 nm, and the content ratio of the two-line ferrihydrite phase in the iron oxide is 40 mass. %, And the total amount of impurities composed of oxides of silicon, aluminum, tin, zinc and titanium was 0.1% by mass or less, and surprisingly, the iron oxide porous body was used as an air purification material. In some cases, it has been found that sufficiently high purification performance can be obtained for reactive molecules such as volatile organic compounds (for example, acetaldehyde) contained in the air, and the present invention has been completed. Furthermore, the present inventors comprise polyoxyethylene alkyl ether in which the number of ethoxy groups (hydrophilic groups) is 2 to 200 and the alkyl group (hydrophobic group) has 6 to 20 carbon atoms in the alcohol. A surfactant and an iron salt are added to prepare a reaction solution, and then a base is added to the reaction solution, and the pH of the reaction solution is adjusted to 4.5 to 13 to adjust the surfactant and the After forming a complex with iron hydroxide, the reaction solution containing the complex is introduced into a sealed container and heat-aged at a temperature of 20 to 125 ° C., and the reaction solution after heat-aged The composite is taken out of the product, and the composite is washed with a polar solvent to remove the surfactant from the composite to produce an iron hydroxide porous body in which primary particles of iron hydroxide are aggregated. 200-45 after drying the iron oxide porous body By firing at a temperature of ° C., to complete the present invention found that it becomes possible to efficiently produce the iron oxide porous body.

That is, the iron oxide porous body of the present invention comprises an aggregate in which primary particles of iron oxide are aggregated,
The average particle diameter of the primary particles is 2 to 8 nm,
The central pore diameter of the pores of the aggregate is 2 to 10 nm,
The iron oxide has a two-line ferrihydrite phase showing two peaks of a peak derived from the (110) plane of the crystal and a peak derived from the (300) plane of the crystal in the X-ray diffraction pattern;
The content ratio of the two-line ferrihydrite phase to the total crystal phase of the iron oxide is 40% by mass or more, and
The total amount of impurities composed of oxides of silicon, aluminum, tin, zinc and titanium is 0.1% by mass or less;
It is characterized by.

In the iron oxide porous body of the present invention, the aggregate preferably has a pore volume of 0.25 to 0.45 cm ³ / g.

In the iron oxide porous body of the present invention, the specific surface area of the aggregate is preferably 140 to 350 m ² / g.

  Furthermore, the iron oxide porous body of the present invention preferably further contains a transition metal (excluding zinc and titanium), and the transition metal is selected from manganese, cerium, silver, zirconium, yttrium and gallium. More preferably, it is at least one element.

  The air purification material of the present invention comprises the iron oxide porous body of the present invention.

The method for producing an iron oxide porous body of the present invention is a polyoxygen in which the number of ethoxy groups as hydrophilic groups is 2 to 200 and the number of carbon atoms of alkyl groups as hydrophobic groups is 6 to 20 in alcohol. Adding a surfactant made of ethylene alkyl ether and an iron salt to obtain a reaction solution;
By adjusting the pH of the reaction solution to 4.5 to 13 by adding a base to the reaction solution, iron hydroxide is precipitated around the surfactant in the reaction solution, so that the surface activity is increased. Obtaining a complex of the agent and the iron hydroxide;
Introducing the reaction solution containing the complex into a sealed container and heating and aging at a temperature of 20 to 125 ° C .;
After the complex is taken out of the reaction solution after the heat aging, the complex is washed with a polar solvent to remove the surfactant from the complex, thereby aggregating water of primary particles of iron hydroxide. Obtaining an iron oxide porous body;
A step of obtaining the iron oxide porous body of the present invention by baking the iron hydroxide porous body after drying at a temperature condition of 200 to 450 ° C .;
It is the method characterized by including.

  Moreover, in the manufacturing method of the iron oxide porous body of the said invention, it is preferable that the addition amount of the said surfactant is 0.02-50 mass% with respect to the total amount of the said alcohol.

  In the method for producing a porous iron oxide of the present invention, the base comprises an alkali metal hydroxide, ammonia, an alkyl carbonate, an alkyl bicarbonate, an alkylamine, an alkoxide, and a tetraalkylammonium hydroxide. It is preferably at least one selected from the group.

  Furthermore, in the method for producing a porous iron oxide of the present invention, in the step of obtaining the reaction solution, it is preferable to further add a salt of a transition metal (excluding zinc and titanium) to the alcohol. Is more preferably at least one element selected from manganese, cerium, silver, zirconium, yttrium and gallium.

  The reason why the above object is achieved by the iron oxide porous body of the present invention, the air purification material using the same, and the method for producing the iron oxide porous body is not necessarily clear, but the present inventors speculate as follows. To do. That is, the iron oxide porous body of the present invention comprises an aggregate in which primary particles of iron oxide having an average particle diameter of 2 to 8 nm are aggregated, and the content ratio of the two-line ferrihydrite phase in the iron oxide is 40. It is at least mass%. Thus, the iron oxide porous body of the present invention has a structure in which fine particles are aggregated. A combination of such fine nanoparticles (primary particles) having an average particle diameter of 2 to 8 nm and a porous body (secondary particles) having a porous structure in which mesopores are formed by aggregation of the nanoparticles is Thus, since the function when used as an air purification material becomes dual-functional, it is very effective in improving adsorption performance and catalytic reaction activity for volatile organic compounds such as acetaldehyde. That is, first, in the iron oxide porous body of the present invention, a very high specific surface area is ensured by fine nanoparticles (primary particles) having an average particle diameter of 2 to 8 nm, and functions as an active site for adsorption and catalytic functions. Therefore, it is possible to have a sufficient number of unsaturated coordination sites on the surface of the ferrihydrite. Further, in the iron oxide porous body of the present invention, the inside of the aggregate is formed by a high specific surface area specific to the nanoparticles and a large number of grain boundary regions (boundary surfaces between crystal grains) formed by the aggregation of the particles. In this case, charge transfer is facilitated, and adsorption and catalysis occur synchronously on the unsaturated coordination site on the surface of the two-line ferrihydrite, so that a large amount of harmful gas can be quickly removed. In addition, in such an aggregate (secondary particle) in which nanoparticles (primary particles) are aggregated, pores having a central pore diameter of 2 to 10 nm are formed, so that the guest entering the pores A space with less diffusion hindrance is provided for molecules, and volatile organic compounds in the air can be sufficiently diffused into the pores. Thus, in the present invention, the presence of mesopores in the iron oxide porous body not only provides a large number of surface adsorption sites for adsorbing a large amount of reactive molecules such as volatile organic compounds, but also a catalyst. The diffusion hindrance of the reaction molecule into the pore, which is extremely important in the action, is also sufficiently suppressed. Therefore, in the iron oxide porous body of the present invention, the reaction molecules that enter the pores of the iron oxide porous body can be sufficiently dispersed and adsorbed, and the adsorption removal performance becomes very high. Accordingly, the present inventors speculate that the iron oxide porous body of the present invention exhibits a sufficiently high purification performance for volatile organic compounds (for example, acetaldehyde) when used as an air purification material.

In the method for producing an iron oxide porous body of the present invention, first, iron hydroxide is precipitated around the surfactant in the alcohol using the surfactant as a template. When iron hydroxide is precipitated in this way, the iron hydroxide and the hydrophilic group in the template interact to form a hydrogen bond, thereby forming a complex of iron hydroxide and a surfactant. . For this reason, in the present invention, by depositing iron hydroxide, a structure is formed in which the precipitated particles of iron hydroxide cover the periphery of the surfactant. In the present invention, since alcohol is used as a solvent, the formation of a hydrogen bond interaction between iron hydroxide and a template is sufficiently suppressed by the solvent. On the other hand, when water generally used in the conventional precipitation method of iron hydroxide is used as a solvent, the precipitated and precipitated iron hydroxide (the type is mainly ferric hydroxide (Fe (OH) ₃ ) and iron oxyhydroxide (FeOOH)) tend to strongly adsorb H ₂ O molecules due to their strong hydrogen bonding ability. Therefore, when water is used as the solvent, water molecules are strongly adsorbed through the hydrogen bond to the outer sphere of iron hydroxide in which the water molecules are precipitated and precipitated. The water molecules strongly adsorbed on the outer sphere of iron hydroxide in this way inhibit the interaction between iron hydroxide and the template. Therefore, when water is used as the solvent, it is difficult to form a complex with the template itself, and the iron hydroxide nanoparticles produced by the precipitation are agglomerated. And when water is used as a solvent, when the template is removed or the calcination is performed at a very low temperature on the obtained aggregate, there is no iron oxide having high crystallinity or mesoporous structure. Iron oxyhydroxide is formed. As described above, in the present invention, an alcohol having a low hydrogen bonding ability with respect to iron hydroxide as compared with water molecules is used as a solvent. Therefore, the hydrogen bonding between the iron hydroxide and the template is caused by the solvent. Inhibition of the formation is sufficiently suppressed, and a complex of iron hydroxide and a surfactant is efficiently formed, the formed nanoparticles are stabilized, and non-uniform aggregation does not occur. Therefore, when the surfactant is removed from the composite thus obtained, water in which very uniform mesopores (so-called single pore distribution mesopores) derived from the shape of the surfactant is formed. An iron oxide porous body is obtained. In addition, since such a surfactant is bonded by a weak hydrogen bond interaction as compared with a direct covalent bond, it can be easily removed from the complex by washing with a polar solvent such as water. Removed. Furthermore, it becomes possible to obtain a higher surface area by thus forming the pores by removing the surfactant by washing with a polar solvent. In addition, the agglomerates (iron hydroxide porous bodies) obtained by agglomerating nanoparticles obtained in this manner retain the mesopore structure even when fired to at least 450 ° C. Therefore, in this invention, after obtaining an iron hydroxide porous body in this way, the iron hydroxide porous body can be dried and baked. By firing the iron hydroxide porous body in this way, a two-line ferrihydrite phase of iron oxide can be formed while maintaining the pore structure and the like, and the primary particles of iron oxide have an average particle size of 2 It becomes sufficiently fine nanoparticles of ˜8 nm. Furthermore, by firing in this way, it is assumed that the obtained iron oxide is in a sufficiently dehydrated state. That is, normally, iron oxide in which a two-line ferrihydrite phase is formed is generally expressed by a molecular formula: 5Fe ₂ O ₃ .9H ₂ O (about 17% by mass of the whole is a water molecule) (for example, Chemical Review, vol.98, published 1998, pages 2549-2586). However, in the present invention, since iron oxide having a two-line ferrihydrite phase is obtained through the firing step as described above, water molecules hydrated to iron oxide at the time of firing are removed by evaporation. While the line ferrihydrite phase is formed, the iron oxide is in a sufficiently dried state. Therefore, the amount of water molecules hydrated to the obtained iron oxide is derived from the amount of water contained in the atmosphere, and the water molecule content is estimated to be about 5% by mass or less. In the two-line ferrihydrite phase of iron oxide dehydrated in this way, it is possible to adsorb reactive molecules such as volatile organic compounds on the surface site where water has been coordinated, and more It is inferred that an adsorption active site is obtained. In addition, according to the method for producing a porous iron oxide of the present invention, basically, a raw material capable of forming silicon, aluminum, tin, zinc and titanium oxides is not used in the production process. In the resulting iron oxide porous body, since the impurities composed of such oxides are not contained in the iron oxide, catalytic activity is caused by the impurities composed of oxides of silicon, aluminum, tin, zinc and titanium. Will not drop. In addition, such a method for producing a porous iron oxide according to the present invention is a simple synthetic method with high reproducibility, and an inexpensive inorganic iron salt can be used as an iron salt and a surfactant used for a template is also available. This is a method that is sufficiently superior in terms of workability and cost as compared with conventional methods for producing iron oxide porous bodies.

  According to the present invention, when used as an air purification material, an iron oxide porous body capable of having a sufficiently high purification performance for reactive molecules such as volatile organic compounds (for example, acetaldehyde) contained in air. It is possible to provide an air purification material using the iron oxide porous body, and a method for producing an iron oxide porous body capable of efficiently producing the iron oxide porous body by a simple process.

2 is a graph showing an X-ray diffraction pattern in a low angle region of the iron oxide porous body obtained in Example 1. FIG. It is a graph which shows the X-ray-diffraction pattern of the wide angle area | region of the iron oxide porous body obtained in Example 1, and the powder before baking. 3 is a graph showing nitrogen adsorption / desorption isotherms of the iron oxide porous material obtained in Example 1. FIG. 2 is a pore size distribution curve of a porous iron oxide obtained in Example 1. FIG. 2 is a transmission electron microscope (TEM) photograph of the iron oxide porous material obtained in Example 1. FIG. 6 is a graph showing an X-ray diffraction pattern in a low angle region of the iron oxide porous body obtained in Example 6. 6 is a graph showing an X-ray diffraction pattern in a wide angle region of the iron oxide porous body obtained in Example 6. FIG. It is a graph which changes and shows the scale of the X-ray diffraction pattern shown in FIG. 10 is a graph showing nitrogen adsorption / desorption isotherms of the iron oxide porous material obtained in Example 6. 6 is a pore size distribution curve of the iron oxide porous material obtained in Example 6. 10 is a graph showing an X-ray diffraction pattern in a low angle region of the iron oxide porous body obtained in Example 7. 6 is a graph showing an X-ray diffraction pattern in a wide angle region of the iron oxide porous body obtained in Example 7. FIG. 7 is a graph showing nitrogen adsorption / desorption isotherms of the iron oxide porous material obtained in Example 7. 6 is a pore diameter distribution curve of the iron oxide porous material obtained in Example 7. 4 is a graph showing an X-ray diffraction pattern in a low angle region of iron oxide obtained in Comparative Example 1. 4 is a graph showing an X-ray diffraction pattern of a wide-angle region of iron oxide obtained in Comparative Example 1. 2 is a graph showing nitrogen adsorption / desorption isotherms of iron oxide obtained in Comparative Example 1. FIG. 3 is a pore diameter distribution curve of iron oxide obtained in Comparative Example 1. 6 is a graph showing an X-ray diffraction pattern in a low angle region of iron oxide obtained in Comparative Example 2. 6 is a graph showing an X-ray diffraction pattern in a wide angle region of iron oxide obtained in Comparative Example 2. 6 is a graph showing nitrogen adsorption / desorption isotherms of iron oxide obtained in Comparative Example 2. 3 is a pore diameter distribution curve of iron oxide obtained in Comparative Example 2. 10 is a graph showing an X-ray diffraction pattern in a low angle region of iron oxide obtained in Comparative Example 3. 6 is a graph showing an X-ray diffraction pattern in a wide angle region of iron oxide obtained in Comparative Example 3. 4 is a graph showing nitrogen adsorption / desorption isotherms of iron oxide obtained in Comparative Example 3. 6 is a pore diameter distribution curve of iron oxide obtained in Comparative Example 3.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.

First, the iron oxide porous body of the present invention will be described. That is, the iron oxide porous body of the present invention comprises an aggregate in which primary particles of iron oxide are aggregated,
The average particle diameter of the primary particles is 2 to 8 nm,
The central pore diameter of the pores of the aggregate is 2 to 10 nm,
The iron oxide has a two-line ferrihydrite phase showing two peaks of a peak derived from the (110) plane of the crystal and a peak derived from the (300) plane of the crystal in the X-ray diffraction pattern;
The content ratio of the two-line ferrihydrite phase to the total crystal phase of the iron oxide is 40% by mass or more, and
The content of impurities composed of oxides of silicon, aluminum, tin, zinc and titanium is 0.1% by mass or less,
It is characterized by.

Thus, the iron oxide porous body of the present invention has an aggregate structure in which primary particles of iron oxide are aggregated. Such primary particles of iron oxide have an average particle diameter of 2 to 8 nm. When the average particle diameter of such primary particles is less than the lower limit, it becomes difficult to prepare an iron oxide porous body. On the other hand, when the upper limit is exceeded, the specific surface area decreases, and there are few correct coordinations present on the iron oxide surface. The amount of active sites (unsaturated coordination sites) of the catalyst derived from tetrahedral Fe ³⁺ ions becomes insufficient, and a sufficiently high purification performance cannot be obtained when used as an air purification material. In addition, the average particle diameter of such primary particles is more preferably 2 to 6 nm from the viewpoint of easy preparation and obtaining a desired pore structure. Note that the “particle diameter” referred to here means, in principle, an average value of the minimum diameter and the maximum diameter of the particles when the particles are not spherical. The “average particle size of primary particles” is measured by X-ray diffraction (XRD), and Scherrer's formula:
D = 0.9λ / βcos θ
(In the formula, D represents the particle diameter, λ represents the used X-ray wavelength, β represents the diffraction line width of the sample, and θ represents the diffraction angle)
Is obtained by calculating As a method of X-ray diffraction measurement in confirming the particle size of such primary particles, a scan step of 0.01 °, a divergence and a scattering slit, using a trade name “RINT2100” manufactured by Rigaku Corporation as a measuring device. A method of measuring under the conditions of 1/2 deg, light receiving slit 0.15 mm, CuKα line, 40 kV, 30 mA, scan speed 2θ = 4 ° / min is adopted. Further, the particle diameter is calculated from the diffraction line width of the peak (around 2θ = 35 °) derived from the (110) plane of the crystal. Such a particle size can be confirmed by observation with a transmission electron microscope (TEM).

  Further, such an aggregate of primary particles of iron oxide (iron oxide porous body) has a pore having a central pore diameter of 2 to 10 nm. When the diameter of the central pore is within the above range, when used as an air purification material, the reaction molecules easily diffuse in the pores, so that not only the active sites on the outer surface of the aggregate but also the activity inside the pores. At the site, the decomposition reaction of the reactive molecules easily proceeds, and the purification performance is sufficiently improved. Here, when the diameter of the central pore is less than the lower limit, the reactive molecules are not diffused at a sufficient rate inside the pore, and the ozonolysis performance is lowered. On the other hand, when the above upper limit is exceeded, the specific surface area decreases, the catalytic activity decreases, and the air purification performance decreases. From this point of view, the center pore diameter of the carrier is more preferably 2 to 8 nm, and further preferably 3 to 6 nm.

  Here, the “center pore diameter” is a value obtained by differentiating the pore volume (Vp) by the pore radius (Rp) (d (Vp) / d (Rp)) to the pore radius (Rp). This is a value obtained by doubling the pore radius at the maximum peak of the curve plotted against the pore size (pore diameter distribution curve). The pore size distribution curve can be obtained by the method described below. That is, first, the aggregate is cooled to a liquid nitrogen temperature (−196 ° C.), nitrogen gas is introduced, the adsorption amount is determined by a constant volume method or a gravimetric method, and then the pressure of the introduced nitrogen gas is gradually increased. Increase and plot the amount of nitrogen gas adsorbed against each equilibrium pressure to obtain an adsorption isotherm. Then, using the adsorption isotherm, a pore diameter distribution curve can be obtained by employing a calculation method such as Cranston-Inklay method, Pollimore-Heal method, BJH method and the like.

In addition, in such an aggregate, an IV type hysteresis loop defined by IUPAC is confirmed in the nitrogen adsorption / desorption isotherm between relative pressures (P / P ₀ ) of 0.4 to 1. It is preferable that it is a thing. It is possible to confirm that the aggregate has a mesopore structure by the IV type hysteresis loop defined by IUPAC.

  Furthermore, the pores formed in such an aggregate are secondary pores formed by agglomerating primary particles. Since the pores are formed as secondary pores in this way, in such aggregates, the pore diameter, specific surface area and pore volume are sufficiently increased and diffused when the reaction molecules are diffused into the pores. The resistance becomes very small and the reactive molecules diffuse quickly into the pores. Therefore, it is possible to cause adsorption and decomposition reactions of more reactive molecules inside the pores, and sufficiently high performance can be obtained when used as an air purification material. Furthermore, since the iron oxide porous body of the present invention takes the structure of an aggregate in which primary particles are aggregated, the pore structure becomes a three-dimensional pore structure, and more pores are formed and the specific surface area is increased. Thus, when used as an air purification material, the purification activity becomes higher.

  The pores formed in such an aggregate are within the range of ± 40% (more preferably ± 30%) of the central pore diameter in the pore size distribution curve, and 60% of the total pore volume (more preferably 75%) or more is preferable. When these conditions are satisfied, the aggregate can be said to be an aggregate having a very uniform pore diameter. In such an aggregate having uniform pores, there are more active sites for adsorption (unsaturated coordination sites). In addition, when the iron oxide porous body of the present invention is obtained using the iron oxide porous body manufacturing method of the present invention described later, the pores are derived from the surfactant as a template. Since it is formed, the above-mentioned conditions are satisfied.

As the pore volume of such aggregates is preferably 0.25~0.45cm ³ / g, more preferably 0.25~0.41cm ³ / g, 0.3 More preferably, it is -0.41 cm < ³ > / g. When the pore volume of such an aggregate is less than the lower limit, it tends to be difficult to diffuse the reaction substrate into the pores at a sufficient rate, while when the upper limit is exceeded, the reaction substrate is adsorbed. Performance tends to decrease and reaction efficiency tends to decrease. As the pore volume of such an aggregate, the aggregate is cooled to liquid nitrogen temperature (−196 ° C.), nitrogen gas is introduced, and the saturated adsorption amount is obtained by a constant volume method or a gravimetric method, The value obtained by converting the volume from the amount of adsorption is adopted.

As the specific surface area of such agglomerates is preferably 140~350cm ² / g, more preferably 150~325m ² / g. If the specific surface area is less than the lower limit, the amount of unsaturated sites in the iron oxide porous body is not sufficient, and when used as an air purification material, there is a tendency that sufficient purification performance cannot be obtained, On the other hand, when the upper limit is exceeded, not only mesopore structures but also micropores tend to be formed. The specific surface area of such an aggregate is calculated as a BET specific surface area using the BET isotherm adsorption equation from the adsorption isotherm.

  Moreover, it is preferable that the particle diameter of such an aggregate (secondary particle) is 600 nm or less. When the particle diameter of such an aggregate (secondary particle) exceeds the upper limit, gas diffusion from the particle surface to the inside of the particle is delayed, and the air purification performance tends to be deteriorated. In addition, the particle diameter of such an aggregate (secondary particle) can be measured with a transmission electron microscope.

  Further, in such an aggregate, one peak is observed when 2θ is between 0.5 ° and 3 ° in the X-ray diffraction (XRD) pattern.

  Further, the iron oxide forming such an aggregate has a peak derived from the (110) plane of the crystal in an X-ray diffraction pattern (a peak at a position where the d value is 2.6 angstroms), and (300) of the crystal. The presence of a two-line ferrihydrite phase having two peaks originating from the surface (peak at a position where the d value is 2.6 angstroms) is confirmed. That is, “a peak derived from the (110) plane of the crystal” refers to a peak at a position where 2θ is 35.1 ° in the X-ray diffraction pattern, and “a peak derived from the (300) plane of the crystal” is an X-ray diffraction pattern. 2θ is a peak at a position of 60.4 °, and in such an X-ray diffraction pattern, there are two peaks, a peak derived from the (110) plane of the crystal and a peak derived from the (300) plane of the crystal. It can be confirmed that a two-line ferrihydrite phase is present in the iron oxide. In addition, as a method of X-ray diffraction measurement when confirming the presence of such a two-line ferrihydrite phase in iron oxide, a scanning range is used by using a trade name “RINT2100” manufactured by Rigaku Corporation as a measuring device. Employs measurement method under the conditions of 10 ° -80 °, scan step 0.01 °, divergence and scattering slit 1/2 deg, light receiving slit 0.15 mm, CuKα ray, 40 kV, 30 mA, scan speed 2θ = 4 ° / min. To do. Further, the “peak” referred to here is one having a height from the baseline to the peak top of 100 cps or more.

  Moreover, in such an aggregate, the content ratio of the 2-line ferrihydrite phase to the total crystal phase of iron oxide is 40% by mass or more. When the content ratio of such a two-line ferrihydrite phase is less than 40% by mass, the particle diameter of the primary particles becomes larger than 8 nm (which tends to be 15 nm or more). The amount of active sites (unsaturated coordination sites) to be produced is not sufficient, and when used as an air purification material, sufficient purification performance cannot be obtained. Moreover, as a content rate of such a 2 line ferrihydrite phase, it is more preferable that it is 40-100 mass%, and it is more preferable that it is 80-100 mass%. In addition, the iron oxide exceeding the upper limit tends to be difficult to produce. In the present invention, “the content ratio of the two-line ferrihydrite phase to the total crystal phase of iron oxide” is determined as follows. That is, first, the product name “D8 Advance” manufactured by Bruker is used as the measuring device, the scanning range is 15 ° to 145 °, the scanning step is 0.05 ° / step, the divergence slit is 0.3 °, the CoKα ray, and the CoKβ ray are removed. An X-ray diffraction pattern of CoKα is measured under the conditions of 40 kV, 35 mA, and scan speed of 3 ° / min. Next, after identifying the crystal phase of each peak in the CoKα X-ray diffraction pattern using the Rietan-2000 software and determining the peak area, the sum of the peak areas of each crystal phase (total area) The ratio of the peak area of the 2-line ferrihydrite phase relative to is calculated. Then, the value of the ratio of the peak area of the two-line ferrihydrite phase calculated as described above is directly adopted as the content ratio of the two-line ferrihydrite phase. The “peak” of the CoKα X-ray diffraction pattern referred to here is one having a height from the base line to the peak top of 100 cps or more.

  In the iron oxide porous body of the present invention, the total amount (total content) of impurities composed of oxides of silicon, aluminum, tin, zinc and titanium is 0.1% by mass or less. When the total amount of such impurities exceeds the upper limit, not only cannot sufficient performance be obtained when used in an air purification material, but the heat resistance of the ferrihydrite phase is reduced. In addition, as an oxide of the said element as such an impurity, silicon dioxide etc. are mentioned, for example. Furthermore, as a method for measuring the content of such impurities, a method of elemental analysis using a high frequency plasma emission spectroscopic analyzer (ICPS) can be employed.

  Further, in the iron oxide porous body of the present invention, using TG / DTA (differential thermogravimetric simultaneous measurement device: trade name “Thermo plus TG8120” manufactured by Rigaku Co., Ltd.) It is preferable that the moisture content obtained by heating from 100 ° C. to 300 ° C. to measure the weight change of the sample and calculating the weight change rate before and after the heating is 5% by mass or less. With such a water content aggregate (iron oxide porous body), higher air purification activity tends to be obtained. In addition, the iron oxide porous body having such a water content can be easily manufactured by utilizing the method for manufacturing an iron oxide porous body of the present invention in which a firing step as described below is performed.

  Moreover, in the iron oxide porous body of this invention, it is preferable to further contain a transition metal (except zinc and titanium). Thus, by containing transition metals (excluding zinc and titanium), in the firing step during preparation, aggregation of ferrihydrite particles and enlargement of the particle size are prevented, compared to the case of ferrihydrite alone. Since it is possible to increase the specific surface area, when used as an air purification material, higher purification performance tends to be obtained. As described above, when the transition metal (excluding zinc and titanium) is contained in the iron oxide porous body, the form of the transition metal is not particularly limited. For example, the atom of the transition metal is iron oxide. It may be contained in the iron oxide porous body so as to form a skeleton of iron oxide primary particles by isomorphous substitution with iron atoms in the primary particles, or the transition metal on the surface of the iron oxide primary particles It may be contained in the iron oxide porous material by being dispersed as an oxide.

  Moreover, as such transition metals (excluding zinc and titanium), manganese, cerium, silver, zirconium, yttrium, and gallium are preferable, manganese and cerium are more preferable, and manganese is particularly preferable from the viewpoint of improving air purification performance. . Such transition metals may be contained alone or in combination of two or more in the iron oxide porous body.

  Thus, when the iron oxide porous body of the present invention further contains a transition metal (except for zinc and titanium), the content of the transition metal in the iron oxide porous body is a molar ratio ([transition Metal] / [Iron]) is preferably from 0.01 to 2, and more preferably from 0.2 to 1. When the molar ratio of iron to the transition metal is less than the lower limit, the air purification performance of the obtained iron oxide porous body is compared with the air purification performance of the iron oxide porous body not containing the transition metal. There is a tendency that sufficient improvement cannot be expected. On the other hand, even if the upper limit is exceeded, there is no further improvement in air purification performance, and there is a tendency that it is negative in terms of resource utilization and manufacturing cost. As a method for measuring the content of such a transition metal, an elemental analysis method using a high-frequency plasma emission spectrometer (ICPS) can be employed.

  Such an iron oxide porous body of the present invention can quickly diffuse an adsorbent and a reaction substrate into pores, and can be suitably used as an absorbent, a catalyst, a catalyst carrier, and the like. It can be suitably used for an air purification material that removes harmful substances such as volatile organic compounds (VOC).

  Next, the manufacturing method of the iron oxide porous body of this invention which can be employ | adopted suitably as a method of manufacturing the iron oxide porous body of this invention is demonstrated.

The method for producing an iron oxide porous body of the present invention is a polyoxygen in which the number of ethoxy groups as hydrophilic groups is 2 to 200 and the number of carbon atoms of alkyl groups as hydrophobic groups is 6 to 20 in alcohol. A step of adding a surfactant made of ethylene alkyl ether and an iron salt to obtain a reaction solution (first step);
By adjusting the pH of the reaction solution to 4.5 to 13 by adding a base to the reaction solution, iron hydroxide is precipitated around the surfactant in the reaction solution, so that the surface activity is increased. A step of obtaining a complex of the agent and the iron hydroxide (second step);
Introducing the reaction solution containing the complex into a sealed container and heating and aging at a temperature of 20 to 125 ° C. (third step);
After the complex is taken out of the reaction solution after the heat aging, the complex is washed with a polar solvent to remove the surfactant from the complex, thereby aggregating water of primary particles of iron hydroxide. A step of obtaining a porous iron oxide (fourth step);
The step of obtaining the iron oxide porous body of the present invention by calcination at a temperature of 200 to 450 ° C. after drying the iron hydroxide porous body,
It is the method characterized by including. Hereinafter, the first to fifth steps will be described separately.

(First step)
The first step is a surface activity comprising polyoxyethylene alkyl ether in which the number of ethoxy groups as hydrophilic groups is 2 to 200 and the alkyl group as hydrophobic groups is 6 to 20 carbon atoms in alcohol. In this step, a reaction liquid is obtained by adding an agent and an iron salt.

  Such alcohol is used as a solvent in the reaction solution. In the present invention, by using alcohol as the solvent in the reaction solution, it is prevented that the surfactant and iron hydroxide are combined by hydrogen bonds when iron hydroxide is precipitated in the second step described later. This makes it possible to more efficiently produce a complex of a surfactant and iron hydroxide. As such an alcohol, from the viewpoint that the complex can be produced more efficiently, an alkyl alcohol having 2 to 6 carbon atoms (more preferably 2 to 4 carbon atoms), 3 to 6 (more preferably The alkene alcohol of 3-4) is preferable, and ethanol, 1-propanol, 2-propanol, allyl alcohol, 2-propanol, and butanol are particularly preferable. Such alcohols may be used alone or in combination of two or more.

  The surfactant is a polyoxyethylene alkyl ether having 2 to 200 ethoxy groups as hydrophilic groups and 6 to 20 carbon atoms in an alkyl group as hydrophobic groups. When the number of ethoxy groups contained in such a polyoxyethylene alkyl ether is less than the lower limit, a mesopore structure cannot be obtained. On the other hand, when the upper limit is exceeded, iron oxide having a two-line ferrihydrite phase is obtained. It becomes impossible. Further, the number of ethoxy groups contained in such polyoxyethylene alkyl ether is more preferably 2 to 100 from the same viewpoint. Further, when the number of carbon atoms of the alkyl group contained in the polyoxyethylene alkyl ether is less than the lower limit, a mesopore structure cannot be obtained. On the other hand, when the upper limit is exceeded, iron oxide having a two-line ferrihydrite phase is obtained. It becomes impossible. As carbon number of such an alkyl group, it is more preferable that it is 12-18 from the same viewpoint.

  Such a surfactant may be any polyoxyethylene alkyl ether having 2 to 200 ethoxy groups and 6 to 20 carbon atoms in the alkyl group, and is not particularly limited. An agent may be used. As such a surfactant, for example, polyoxyethylene (20) cetyl ether (trade name “Brij 58” manufactured by Sigma-Aldrich): the number of ethoxy groups is 20, and the number of carbon atoms in the alkyl group is The number is 16.), polyoxyethylene (4) lauryl ether (trade name “Brij 30” manufactured by Sigma-Aldrich), polyoxyethylene (23) lauryl ether (trade name “Brij” manufactured by Sigma-Aldrich) 35 "), polyoxyethylene (2) cetyl ether (trade name" Brij 52 "manufactured by Sigma-Aldrich), polyoxyethylene (10) cetyl ether (trade name" Brij 56 "manufactured by Sigma-Aldrich), Polyoxyethylene (2) stearyl ether (Si (trade name “Brij 72” manufactured by gma-Aldrich), polyoxyethylene (10) stearyl ether (trade name “Brij 76” manufactured by Sigma-Aldrich), polyoxyethylene (20) stearyl ether (Sigma-Aldrich) Product name “Brij 78”), polyoxyethylene (2) oleyl ether (trade name “Brij 92” manufactured by Sigma-Aldrich), polyoxyethylene (10) oleyl ether (trade name manufactured by Sigma-Aldrich) “Brij 97”, polyoxyethylene (20) oleyl ether (trade name “Brij 98” manufactured by Sigma-Aldrich), polyoxyethylene (100) stearyl ether (trade name “Bri” manufactured by Sigma-Aldrich) 700 "), and the like.

As the iron salt, a trivalent iron salt is used. Examples of such iron salts include iron nitrate (Fe (NO ₃ ) ₃ ), iron halide (eg, iron bromide (FeBr ₃ ), iron chloride (FeCl ₃ )), and organic iron (eg, iron acetate). (III), iron (III) oxalate, iron (III) alkoxide (iron ethoxide, iron isopropoxide, iron butoxide, etc.)) and the like. Among these iron salts, iron chloride (FeCl ₃ ) and iron nitrate (Fe (NO ₃ ) ₃ ) are preferable from the viewpoint that it is possible to form aggregates having more uniform pores. (Fe (NO ₃ ) ₃ ) is particularly preferred. In addition, it is possible to change the content ratio of the 2-line ferrihydrite phase in the oxide finally obtained by changing the kind of iron salt suitably. For example, although it varies depending on the type and amount of alcohol and surfactant used, when FeCl ₃ .9H ₂ O is used as the iron salt, α-Fe ₂ O ₃ together with the 2-line ferrihydrite phase. And iron oxide containing γ-Fe ₂ O ₃ tends to be obtained. When Fe (NO ₃ ) ₃ is used as the iron salt, iron oxide composed of almost 100% by mass of a two-line ferrihydrite phase is obtained. It tends to be obtained.

  The reaction solution is obtained by adding the surfactant and the iron salt to the alcohol. The method for preparing such a reaction liquid is not particularly limited. For example, after adding the surfactant in alcohol and stirring to obtain a mixed liquid, an iron salt is added to the mixed liquid, A method of obtaining a reaction liquid by stirring may be employed, or a method of obtaining a reaction liquid by simultaneously mixing and stirring all components may be employed. In preparing the reaction solution, the components are introduced into the alcohol and sufficiently stirred so that the surfactant and the iron salt are more uniformly mixed (dispersed) in the alcohol. Is preferred. Moreover, it does not restrict | limit especially as temperature conditions at the time of preparing a reaction liquid in this way, It is preferable to set it as 20-40 degreeC, and it is more preferable that it is about room temperature.

  Furthermore, the amount of the surfactant added to the reaction solution is preferably 0.02 to 50% by mass, more preferably 1 to 50% by mass with respect to the total amount of the alcohol. It is especially preferable to set it to -45 mass%. When the content of such a surfactant is less than the lower limit, the surfactant is not sufficiently introduced into the iron salt, the formation of pores is incomplete, and further, a nonuniform pore structure tends to be formed. On the other hand, when the upper limit is exceeded, the surfactant tends to not be completely dissolved.

  Further, the amount of the iron salt added to the reaction solution is preferably such that the molar ratio to the surfactant ([iron salt] / [surfactant]) is 0.3 to 60. It is more preferable that the amount is -55. If the amount of the iron salt added is less than the lower limit, the amount of the surfactant with respect to the iron salt becomes excessively large and the amount of the unreacted surfactant increases, so that micropores are partially formed and uniform. On the other hand, when the upper limit is exceeded, the amount of the surfactant relative to the iron salt is excessively reduced, and the surfactant is sufficiently contained in the iron salt. It is not introduced and the particles tend to be non-uniform.

  The amount of alcohol in the reaction solution is preferably 50 to 300 ml with respect to 0.01 to 0.06 mol of iron salt in the reaction solution. If the amount of such alcohol is less than the lower limit, the iron salt and the surfactant are not sufficiently dispersed, and instead of 2-line ferrihydrite, goethite tends to be formed, On the other hand, when the upper limit is exceeded, the surfactant is not sufficiently introduced into the iron salt, and the pores tend to be non-uniform.

  Moreover, you may further add the salt of a transition metal (except zinc and titanium) to the said reaction liquid. That is, in the present invention, a salt of a transition metal (excluding zinc and titanium) may be further added to the alcohol together with the surfactant and the iron salt. Thus, when the salt of a transition metal (except zinc and titanium) is contained, the transition metal can be contained in the obtained iron oxide porous body.

  There are no particular restrictions on the salts of such transition metals (excluding zinc and titanium), but the transition metal nitrates (manganese nitrate, cerium nitrate, etc.), halides, organic salts (eg, acetates, oxalates, Alkoxide) and the like. Moreover, as such transition metals (excluding zinc and titanium), manganese, cerium, silver, zirconium, yttrium, and gallium are preferable, manganese and cerium are more preferable, and manganese is particularly preferable from the viewpoint of improving air purification performance. . Such transition metal salts (excluding zinc and titanium) may be contained alone or in combination of two or more in the iron oxide porous body.

  In addition, the method for preparing the reaction liquid is not particularly limited even when the salt of transition metal (except for zinc and titanium) is contained in the reaction liquid as described above. For example, the surfactant is added to alcohol. , After obtaining a mixed solution by stirring, an iron salt may be added to the mixed solution, and a method of obtaining a reaction solution by adding and stirring a transition metal salt may be adopted. You may employ | adopt the method of obtaining a reaction liquid by mixing and stirring a component simultaneously. In addition, even when a salt of a transition metal (excluding zinc and titanium) is contained in the reaction solution as described above, the amount of the surfactant added to the reaction solution is 0. 0% with respect to the total amount of the alcohol. It is preferable to set it as 02-50 mass%, It is more preferable to set it as 1-50 mass%, It is especially preferable to set it as 5-45 mass%.

  In addition, when a salt of a transition metal (excluding zinc and titanium) is contained in the reaction solution, the total amount of the iron salt and the transition metal salt added to the reaction solution is a molar ratio to the surfactant ( The amount of ([iron salt] + [transition metal salt]) / [surfactant]) is preferably 0.3 to 60, and more preferably 1 to 55. When the total amount of the iron salt and the transition metal salt is less than the lower limit, the amount of the surfactant relative to the total amount of the iron salt and the transition metal salt is excessively increased, and the unreacted surfactant is present. Therefore, when the upper limit is exceeded, the iron salt and the transition metal tend to be unable to be obtained. The amount of the surfactant relative to the total amount of the salt is excessively small, the surfactant is not sufficiently introduced into the iron salt, and the particles tend to be non-uniform.

  In addition, in the case where a transition metal salt (excluding zinc and titanium) is contained in the reaction solution, the amount of the transition metal salt is a molar ratio ([transition metal salt] to the iron salt in the reaction solution). / [Iron salt]) is preferably in an amount of 0.01 to 2, more preferably 0.2 to 1. When the amount of the transition metal salt added is less than the lower limit, the air purification performance of the obtained iron oxide porous body is sufficient as compared with the air purification performance of the iron oxide porous body not containing the transition metal. On the other hand, there is a tendency that improvement cannot be expected. On the other hand, even if the upper limit is exceeded, there is no further improvement in the air purification performance of the obtained iron oxide porous body, which tends to be negative in terms of resource utilization and production cost.

  In the case where a transition metal salt (excluding zinc and titanium) is contained in the reaction liquid, the amount of alcohol in the reaction liquid is the amount of the iron salt and the transition metal salt in the reaction liquid. It is preferable to be 50 to 300 ml with respect to the total number of moles of 0.01 to 0.06 mol. If the amount of the alcohol is less than the lower limit, the iron salt, the transition metal salt, and the surfactant are not sufficiently dispersed, and not a two-line ferrihydrite but a goethite. On the other hand, when the upper limit is exceeded, the surfactant is not sufficiently introduced into the iron salt, and the pores tend to be non-uniform.

(Second step)
In the second step, iron hydroxide is precipitated around the surfactant in the reaction solution by adding a base to the reaction solution and adjusting the pH of the reaction solution to 4.5 to 13. And obtaining a complex of the surfactant and the iron hydroxide.

Such a base is not particularly limited as long as the pH of the reaction solution can be adjusted to 4.5 to 13, and the pH can be more efficiently set to 10 or more. Therefore, alkali metal hydroxides, ammonia, alkyl carbonates, alkyl hydrogen carbonates, alkylamines, alkoxides and tetraalkylammonium hydroxides are preferred. Among them, they are derived from unreacted substances and their bases in the washing process and firing process. From the viewpoint that it is possible to easily remove the by-product (for example, NH ₄ NO ₃ ), it is more preferable to use a metal-free base, and it is more preferable to use ammonia. Such a base may be used as an aqueous solution. In addition, you may use such a base individually by 1 type or in combination of 2 or more types. Moreover, the method in particular of adding such a base in a reaction liquid is not restrict | limited, For example, you may employ | adopt the method of adding by dripping the aqueous solution of the said base in the said reaction liquid. In the case of using an aqueous solution in this way, it is preferable to make the water content smaller in order to sufficiently prevent the formation of the complex by water, and the amount of water in the aqueous solution Is more preferably less than 20% by mass.

In addition, the amount of base used in this way is the amount of base used itself from the viewpoint of further reducing the amount of by-products formed from the base (for example, NaNO ₃ , NH ₄ NO ₃ ). The amount is preferably smaller, and more preferably 1 to 1.2 equivalents of the cation derived from the base relative to the anion derived from the iron salt.

  In the second step, the pH of the reaction solution is adjusted to 4.5 to 13 by adding the base. Thus, iron hydroxide can be deposited by adjusting the pH of the reaction solution. When the pH value is less than 4.5, it is difficult to sufficiently precipitate iron hydroxide. On the other hand, when the above upper limit is exceeded, instead of 2-line ferrihydrite, goethite is present. It tends to be partly formed. In addition, the pH value of the reaction solution to be adjusted in this way is more preferably 5 to 13 from the viewpoint of depositing iron hydroxide more efficiently. Further, in the baking step described later, the pH value of the reaction solution is adjusted to 7.5 to 10.5 from the viewpoint that baking at a higher temperature (more preferably baking at 300 ° C. or higher) is possible. It is more preferable. Thus, as temperature of the reaction liquid when adding a base, it is preferable to set it as 10-80 degreeC, It is more preferable to set it as 20-40 degreeC, About room temperature is especially preferable.

In the second step, iron hydroxide is precipitated around the surfactant in the reaction solution to obtain a complex of the surfactant and the iron hydroxide. In addition, it is guessed that such a composite_body | complex is formed as follows. That is, in the second step, when iron hydroxide is precipitated in the reaction solution, an interaction works between the iron hydroxide and the hydrophilic group of the surfactant present in the surrounding area to form a hydrogen bond, A complex in which iron hydroxide binds around the surfactant is formed by hydrogen bonding. Here, by precipitating and precipitating iron hydroxide in a solvent composed of an alcohol having less polarity than water, the type of iron hydroxide mainly contains iron oxyhydroxide (Fe ₅ HO ₈ 4H ₂ O). It is assumed that primary particles of iron oxyhydroxide having an average particle diameter of 2 to 8 nm are formed. When the precipitation of iron hydroxide proceeds, the primary particles of iron hydroxide (iron oxyhydroxide) aggregate (aggregate) so as to cover the periphery of the surfactant by hydrogen bonding interaction. It is presumed that a complex aggregated by being stabilized by hydrogen bond interaction is obtained.

  In addition, when the said reaction liquid contains the salt of a transition metal (except zinc and titanium), such a composite_body | complex will contain the said transition metal. The form of the transition metal contained in the composite is not particularly limited in this way. For example, the transition metal atom is replaced by the same shape as the iron atom in the primary particle of iron hydroxide so as to be hydroxylated. It may be contained in the composite so as to form a skeleton of primary particles of iron, or the composite by being dispersed as a hydroxide of the transition metal on the surface of primary particles of iron hydroxide It may be contained in.

(Third step)
The reaction solution containing the complex is introduced into a sealed container and aged by heating under a temperature condition of 20 to 125 ° C.

  Thus, after forming a composite_body | complex by a 2nd process, the reaction liquid containing the composite_body | complex is heated in an airtight container. Thus, by heating and aging the reaction solution containing the complex in a sealed container, it becomes possible to sufficiently precipitate iron hydroxide, and the primary particles of iron hydroxide (iron oxyhydroxide) are more A complex that is uniformly and more densely assembled (in the case where the reaction solution contains a salt of a transition metal (excluding zinc and titanium), the transition metal is included) is formed, It becomes possible to improve the yield of the iron oxide porous body having a two-line ferrihydrite phase which is the final object.

  The heating temperature at the time of heat aging of the reaction solution in such a closed container is 20 to 125 ° C. If the heating temperature is less than the lower limit, aging tends to hardly occur. On the other hand, if the heating temperature exceeds the upper limit, the micelle structure in the mixed solution is broken, not the two-line ferrihydrite phase, but other crystals. Phases (eg, hematite, 6 line ferrihydrite) tend to form. Such a heating temperature is preferably 35 to 120 ° C., more preferably 40 to 110 ° C., because higher effects are obtained from the same viewpoint.

  Further, the heat aging time in the heat aging in such a closed container is preferably 1 hour or more, and more preferably 1 hour or more and 6 days or less. If the heating time is less than the lower limit, aging is not sufficient, and the micelle structure (aggregate structure) formed by the fine particles of 2-line ferrihydrite and the surfactant (template) is unstable. On the other hand, when the upper limit is exceeded, the 2-line ferrihydrite tends to partially change to 6-line ferrihydrite or goethite. The gas atmosphere in the sealed container when introducing such a reaction solution into the sealed container is preferably air from the viewpoint that oxygen is required for aging to proceed. In addition, the pressure conditions for heating in such a closed container are not particularly limited, but from the viewpoint of preventing solvent scattering and maintaining the formed micelle structure, it is performed under natural pressure in the closed container. Are preferred.

(4th process)
In the fourth step, the complex is taken out from the reaction solution after the heat aging, and then the complex is washed with a polar solvent to remove the surfactant from the complex. This is a step of obtaining an iron hydroxide porous body in which particles are aggregated.

  Thus, the method of taking out the complex from the reaction solution after heating is not particularly limited, and a known filtration method can be employed. In the fourth step, the complex thus taken out from the reaction solution is washed with a polar solvent to remove the surfactant from the complex. Such a polar solvent is not particularly limited, and examples thereof include water, dimethyl sulfoxide, sulfolane, N-methylpyrrolidone, etc. Among them, from the viewpoint that the surfactant can be sufficiently removed and is inexpensive. Water is particularly preferred.

The surfactant is removed from the complex by the washing with the polar solvent as follows. That is, the oxyhydroxide species (including FeO ⁻ ) in the iron hydroxide contained in the composite is the leading group (C ₂ H ₅ OH) of the hydrophilic group (C ₂ H ₅ O) of the surfactant. ) And a relatively weak hydrogen bond. Therefore, by using a polar solvent in the washing step, a relatively weak hydrogen between the iron oxyhydroxide species (FeO ⁻ ) and the template hydrophilic head (ROH) group due to the strong hydrogen bonding ability of the polar solvent. The binding interaction can be easily broken, thereby easily removing the surfactant from the complex. Further, in such a cleaning process, other salts which are produced as a by-product _(e.g., NaNO _{3, NH} 4 NO 3, etc.) can be together removed. NH ₄ NO _{3 and the} like can be removed also in the firing step described later, but since it is difficult to remove NaNO _{3 and the} like containing a metal by firing, a material containing a metal as a base was used. In some cases, it is preferable to perform sufficient washing using a large amount of polar solvent.

Further, in such a cleaning step, in the iron hydroxide porous body in which primary particles of iron hydroxide obtained after cleaning are aggregated, the content of the surfactant is 20% by mass with respect to the total amount of the iron hydroxide porous body. It is preferable to wash so as to be less than. If the content of such a surfactant exceeds the upper limit, it is difficult to obtain a desired material in the subsequent steps, and γ-Fe ₂ O ₃ tends to be formed after firing in the final step. Moreover, in order to achieve such a washing | cleaning state, what is necessary is just to change suitably the kind of polar solvent to be used, its usage-amount, etc.

  In the porous body obtained by such a washing step, pores are formed at the positions where the surfactant has been introduced, and the shape of the pores (pore diameter, pore volume, etc.) is the interface. Since it is derived from the shape of the activator, it has very uniform pores. When the reaction solution used in the second step contains a transition metal salt (excluding zinc and titanium), the resulting iron hydroxide porous body contains the transition metal.

  In addition, before carrying out the fifth step, the porous iron hydroxide obtained in this way removes organic compound impurities such as carbon components derived from the surfactant remaining in the pores. From this point of view, it is preferable to stir the mixture again in the alcohol. Further, the time for such stirring is preferably 6 to 24 hours. If the stirring time is less than the lower limit, the removal of organic compound impurities such as carbon components tends to be insufficient. On the other hand, even if the upper limit is exceeded, the effect of removing organic compound impurities such as carbon components does not change. There is no tendency. Moreover, the same alcohol as the alcohol used for the solvent of the reaction solution can be used as such an alcohol.

In addition, the iron hydroxide porous body thus obtained has a peak derived from the (110) plane of the crystal in the X-ray diffraction pattern (a peak at a position where the d value is 2.6 angstroms), and (300) of the crystal. Iron hydroxide (formula: iron oxyhydroxide represented by Fe ₅ HO ₈ 4H ₂ O) in which two peaks derived from the plane (peak at a position where the d value is 2.6 angstroms) is confirmed It will contain. Such an X-ray diffraction pattern can be measured by employing the same method as the X-ray diffraction measurement method for confirming the presence of the two-line ferrihydrite phase in the iron oxide.

(5th process)
The fifth step is a step of obtaining the iron oxide porous body of the present invention by baking the iron hydroxide porous body at a temperature of 200 to 450 ° C. after drying.

  The method for drying such an iron hydroxide porous body is not particularly limited, and a known method can be employed as appropriate. For example, a method of leaving at room temperature, a method of blowing hot air, and the like can be appropriately employed. it can.

  Moreover, the baking temperature conditions at the time of baking the said iron hydroxide porous body are 200 degreeC-450 degreeC. When such a calcination temperature is lower than the lower limit, organic compound impurities such as a carbon component derived from the surfactant cannot be sufficiently removed. On the other hand, when the upper limit is exceeded, 2 in the obtained iron oxide The content ratio of the line ferrihydrite phase is less than 40% by mass. From the same viewpoint, the firing temperature is more preferably 250 ° C. to 450 ° C., and particularly preferably 300 to 400 ° C.

Moreover, it is preferable to set it as 1-6 hours as a baking time in such a baking process, and it is more preferable to set it as 2-3 hours. When the firing time is less than the lower limit, organic compound impurities such as a carbon component derived from the surfactant tend not to be sufficiently removed. On the other hand, when the upper limit is exceeded, the mesopore structure There is a tendency that α-Fe ₂ O ₃ is formed from a part of the two-line ferrihydrite and the particle diameter of the obtained particles is increased.

  In addition, when such a baking process is implemented in the manufacturing method of the iron oxide porous body which has the conventional 2 line ferrihydrite phase as described in the said nonpatent literature 2, in iron oxide obtained, for example The content of the 2-line ferrihydrite phase cannot be 40% by mass or more. On the other hand, in the present invention, since the iron hydroxide porous body used for firing has a structure in which fine iron hydroxide primary particles are aggregated, the firing step as described above was performed. Even later, the content of the two-line ferrihydrite phase in the obtained iron oxide can be 40% by mass or more.

By carrying out the first step to the fifth step in this way, the iron oxide primary particles consist of aggregates, the primary particles have an average particle diameter of 2 to 8 nm, and the pores of the aggregates And the iron oxide has the two-line ferrihydrite phase, and the content ratio of the two-line ferrihydrite phase to the total crystal phase of the iron oxide is 40 mass. %, And the total amount of impurities composed of oxides of silicon, aluminum, tin, zinc, and titanium is 0.1% by mass or less. In addition, when such a method for producing an iron oxide porous body of the present invention is used, what has been described as suitable as the iron oxide porous body of the present invention (for example, the pore volume in the numerical range as described above) Or having a specific surface area, or in the case where the reaction solution contains a salt of a transition metal (excluding zinc and titanium), it can be obtained. Since the pores are formed from the above-mentioned surfactant, the center pore diameter of the obtained porous body can be made 2 to 10 nm, and the obtained porous body can be adsorbed and desorbed with nitrogen. It is also possible to confirm the IV type hysteresis loop defined by IUPAC when the relative pressure (P / P ₀ ) is between 0.4 and ₁ in the isotherm. Further, when such a method for producing a porous iron oxide according to the present invention is used, since the porous iron oxide is obtained through a firing step, the water content of the obtained porous iron oxide is extremely low. It is also possible to obtain an iron oxide porous body having a water content of 5% by mass or less when the TG-DTA analysis as described above is performed. The shape of the iron oxide porous body thus obtained is not particularly limited, but may be powdered by pulverization or the like, or may be molded into various shapes (for example, pellets). Further, in the stage before firing (in the state of the iron hydroxide porous body obtained in the fourth step), it may be pulverized in advance to be powdered.

  As mentioned above, although the iron oxide porous body of this invention and the manufacturing method of the iron oxide porous body of this invention were demonstrated, hereafter, an air purification material is demonstrated.

  The air purification material of the present invention comprises the iron oxide porous body of the present invention. Such an air purification material is provided with the iron oxide porous body of the present invention, and can rapidly diffuse the adsorbed substance and the reaction substrate into the pores of the iron oxide porous body. It is possible to quickly remove harmful substances such as volatile organic compounds (VOC) and to quickly oxidize CO.

  In such an air purification material of the present invention, the iron oxide porous body of the present invention itself may constitute the air purification material, or the iron oxide porous body of the present invention is supported on another substrate. At least, it may be configured as the air purification material of the present invention. Moreover, in the air purification material of this invention, you may use what carried catalyst fine particles, such as a noble metal, in the iron oxide porous body of the said invention. The shape of the air purification material of the present invention is not particularly limited, and for example, it may be formed into a pellet shape, or may be supported on a honeycomb-like or corrugated substrate.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

Example 1
First, 34.04 g of polyoxyethylene (20) cetyl ether (surfactant: trade name “Brij 58” manufactured by Sigma-Aldrich) was added to 300 ml of 1-propanol, mixed and mixed with 1-propanol. A liquid mixture containing 12.42% by mass of a surfactant was obtained. Then, it was added _{Fe (NO 3) 3 · 9H} 2 O to the mixed solution, and stirred for 2 hours to obtain a reaction solution. The amount of Fe (NO ₃ ) ₃ · 9H ₂ O added to the mixed solution is the molar ratio of Fe (NO ₃ ) ₃ · 9H ₂ O to the surfactant in the obtained reaction solution ([ _{Fe (NO 3) 3 · 9H} 2 O]: [ surfactant]) is 0.06: it was set at 0.03. Next, while stirring the reaction solution, a 28% by mass aqueous ammonia solution is added dropwise to the reaction solution, the pH of the reaction solution is adjusted to 7.5, and further stirred for 3 hours. A precipitate was deposited. Subsequently, after putting the reaction liquid in which the precipitate has been deposited into a sealed container having a capacity of 1 L, the container is introduced into an oven, and is subjected to a temperature condition of 50 ° C. under a natural pressure condition in the container. For 3 days. Next, the precipitate was filtered out from the reaction solution after the heat aging, and then the precipitate was washed with 2.5 L of distilled water and dried. The precipitate thus dried was pulverized in an agate mortar to obtain a powder. Thereafter, 3 g of the powder was added to 100 ml of ethanol and stirred for 24 hours. Next, the powder was taken out from the ethanol by filtration, dried, and then fired at 300 ° C. for 3 hours to obtain a porous iron oxide. In such an iron oxide porous body, the total amount of impurities composed of oxides of silicon, aluminum, tin, zinc and titanium is clearly 0% by mass from the production method.

<XRD measurement>
The X-ray diffraction pattern of the iron oxide porous material obtained in Example 1 was measured using an X-ray diffractometer (manufactured by Rigaku Corporation, model number “RINT2100”), and a low angle region with a scanning range of 0.5 ° to 5 °. In this case, the scanning speed is 1 ° per minute, the scanning step is 0.01 °, the divergence and scattering slit is 1/6 deg, the light receiving slit is 0.15 mm, CuKα ray, 40 kV, 30 mA, and the scanning range is 10 ° to 80 °. In the wide-angle region, the measurement was performed under the conditions of a scanning speed of 4 ° per minute, a scanning step of 0.01 °, a divergence and scattering slit of 1/2 deg, a light receiving slit of 0.15 mm, CuKα rays, 40 kV, and 30 mA. Further, the X-ray diffraction pattern in the wide-angle region was measured in the same manner for the unfired powder obtained in Example 1. The low-angle X-ray diffraction pattern of the iron oxide porous material obtained in Example 1 is shown in FIG. 1, and the wide-angle X-ray diffraction pattern of the iron oxide porous material obtained in Example 1 and the powder before firing is shown in FIG. Is shown in FIG.

  As is clear from the low-angle XRD pattern shown in FIG. 1, a peak was observed in the range of 2θ of 0.5 ° to 3 °, and it was confirmed to have a mesopore structure. In addition, when the average particle diameter of primary particles of iron oxide was determined from the peak at a position where 2θ was around 33.1 ° based on the XRD measurement data shown in FIG. It was confirmed to be 0.0 nm. Furthermore, from the result shown in FIG. 2, in the iron oxide porous body obtained in Example 1, two peaks, a peak derived from the (110) plane of the crystal and a peak derived from the (300) plane of the crystal, were obtained. It was confirmed to contain the 2-line ferrihydrite phase shown. Further, from the XRD measurement data shown in FIG. 2, it was confirmed that the 2-line ferrihydrite phase was sufficiently maintained before and after firing.

<Measurement of content ratio of 2-line ferrihydrite phase>
The CoKα X-ray diffraction pattern of the iron oxide porous body obtained in Example 1 was measured using the product name “D8 Advance” manufactured by Bruker as a measuring device, with a scanning range of 15 ° to 145 ° and a scanning step of 0.05 °. / Step, divergence slit 0.3 °, using CoKα ray, CoKβ ray removal Fe filter, measured at 40 kV, 35 mA, scan speed 3 ° / min, based on the obtained CoKα X-ray diffraction pattern After identifying the crystal phase of each peak using the Rietan-2000 software and determining the peak area, the peak area of the two-line ferrihydrite phase relative to the total peak area of each crystal phase (total area) The ratio was calculated and the content ratio of the 2-line ferrihydrite phase was determined. As a result of such measurement, it was confirmed that the content ratio of the two-line ferrihydrite phase was 100% by mass in the crystals of total iron oxide.

<Measurement of pore size distribution curve>
With respect to the iron oxide porous body obtained in Example 1, a nitrogen adsorption / desorption isotherm was measured using a gas adsorption method pore distribution measuring device (manufactured by Nippon Bell Co., Ltd., model number “BELSORP18”), and BJH ( The pore size distribution curve was determined by the Barrett-Joyner-Halenda method. The obtained nitrogen adsorption / desorption isotherm is shown in FIG. 3, and the pore size distribution curve is shown in FIG. In FIG. 4, rp represents the radius of the pore, and Vp represents the pore volume.

The center pore diameter, specific surface area, and pore volume were determined based on the measurement data shown in FIGS. 3 and 4, respectively. The center pore diameter was 4.8 nm, and the specific surface area was 189 m ² / g. It was confirmed that the pore volume was 0.37 cm ³ / g. Moreover, when the particle diameter of the secondary particle was calculated | required based on the measurement data shown in FIG.3 and FIG.4, it turned out that it is a particle | grain of 20 nm-600 nm. Further, from the results shown in FIG. 4, it is confirmed that the pores have a very uniform pore diameter because 70% or more of the total pore volume is included in the range of ± 30% of the central pore diameter. It was done. Further, as is apparent from the nitrogen adsorption / desorption isotherm shown in FIG. 3, the IV type hysteresis defined by IUPAC at a position where the value of the relative pressure P / P ₀ is in the range of 0.4 to 1.0. It was confirmed to show a curve, and it was confirmed that the iron oxide porous body had a mesopore structure.

<Measurement by transmission electron microscope>
The iron oxide porous body obtained in Example 1 was observed with a transmission electron microscope (trade name “JEM200CX” manufactured by JEOL Ltd.). The obtained transmission electron microscope (TEM) photograph is shown in FIG.

  As is clear from the results shown in FIG. 5, the iron oxide porous body was composed of an aggregate in which primary particles of iron oxide were aggregated, and it was confirmed that secondary pores were formed thereby. . Moreover, from the TEM photograph shown in FIG. 5, it can be confirmed that the iron oxide porous body obtained in Example 1 is an aggregate of primary particles of iron oxide of about 2 to 6 nm.

<TG / DTA analysis>
Using 13.071 mg of the iron oxide porous material obtained in Example 1, TG / DTA (differential thermothermal gravimetric simultaneous measurement apparatus: trade name “Thermo plus TG8120” manufactured by Rigaku Corporation) was used to change the iron oxide porous material to 100 ° C. From 300 to 300 ° C., the weight change was measured, and the water content of the iron oxide porous body was measured by calculating the weight change rate before and after the heating. As a result of such measurement, the water content of the iron oxide porous material obtained in Example 1 was 2.8% by mass.

(Examples 2 to 5)
Example 1 except that the temperature conditions during firing were changed to 250 ° C. (Example 2), 350 ° C. (Example 3), 400 ° C. (Example 4), and 450 ° C. (Example 5), respectively. Similarly, an iron oxide porous body was obtained.

For the iron oxide porous bodies obtained in Examples 2 to 5, XRD measurement, measurement of pore diameter distribution curve, measurement by transmission electron microscope, and TG / DTA analysis were performed in the same manner as in Example 1. As a result of such measurement, in each of the iron oxide porous bodies obtained in Examples 2 to 5, the peak derived from the (110) plane of the crystal and the (300) plane of the crystal in the XRD pattern in the wide angle region. Two peaks of the derived peak were confirmed, and it was confirmed that a two-line ferrihydrite phase was contained. Moreover, in the iron oxide porous bodies obtained in Examples 2 to 5, in each of the low angle XRD patterns, a peak was confirmed in the range of 2θ of 0.5 ° to 3 °, and nitrogen adsorption and In the desorption isotherm, at the position where the value of the relative pressure P / P ₀ is in the range of 0.4 to 1.0, an IV type hysteresis curve defined by IUPAC is confirmed, and the iron oxide porous body has a mesoporous structure. It was confirmed to have In addition, as a result of measurement with a transmission electron microscope, the iron oxide porous bodies obtained in Examples 2 to 5 are each composed of an aggregate obtained by agglomerating primary particles of iron oxide. It was confirmed that a hole was formed. Further, Table 1 shows the results of the average particle diameter of the primary particles, the content ratio of the two-line ferrihydrite phase, the center pore diameter, the pore volume, and the specific surface area obtained by such measurement. As a result of TG / DTA analysis, the iron oxide porous bodies obtained in Examples 2 to 5 each had a water content of 5% by mass or less.

(Example 6)
First, 46.7 g of polyoxyethylene (100) stearyl ether (surfactant: trade name “Brij 700” manufactured by Sigma-Aldrich) in 100 ml of 1-propanol, the number of ethylene groups is 100, The number of carbon atoms 18) was added and mixed to obtain a mixed solution containing 16.3% by mass of a surfactant in 1-propanol. Then added FeCl ₃ · 9H ₂ O to the mixed solution, and stirred for 2 hours to obtain a reaction solution. The addition amount of FeCl ₃ · 9H ₂ O to the mixture in the molar ratio of FeCl ₃ · 9H ₂ O with a surfactant in a reaction solution obtained _{([FeCl 3 · 9H 2 O} ]: [Surfactant]) was set to 0.06: 0.03. Next, while stirring the reaction solution, a 28% by mass aqueous ammonia solution is added dropwise to the reaction solution to adjust the pH of the reaction solution to 7.5, and further stirred for 3 hours. A precipitate was deposited. Subsequently, after putting the reaction liquid in which the precipitate has been deposited into a sealed container having a capacity of 1 L, the container is introduced into an oven, and is subjected to a temperature condition of 50 ° C. under a natural pressure condition in the container. For 3 days. Next, after the precipitate was filtered out from the reaction solution after the heating, the precipitate was washed with 2.5 L of distilled water and dried. The precipitate thus dried was pulverized in an agate mortar to obtain a powder. Thereafter, 3 g of the powder was added to 100 ml of ethanol and stirred for 24 hours. Next, the powder was taken out from the ethanol by filtration, dried, and then fired at 300 ° C. for 3 hours to obtain a porous iron oxide. In such an iron oxide porous body, the total amount of impurities composed of oxides of silicon, aluminum, tin, zinc and titanium is apparently 0% by mass from the production method.

For the iron oxide porous body obtained in Example 6, XRD measurement, measurement of the content ratio of the two-line ferrihydrite phase, measurement of the pore size distribution curve, measurement by transmission electron microscope, and TG / DTA analysis was performed. As a result of such a measurement, the X-ray diffraction pattern of the low-angle region of the iron oxide porous material obtained in Example 6 is shown in FIG. A line diffraction pattern is shown in FIG. In addition, the X-ray diffraction pattern in which 2θ of the X-ray diffraction pattern in the wide-angle region of FIG. 7 is described on a different scale and the X-ray diffraction pattern indicated by α-Fe ₂ O ₃ and γ-Fe ₂ O ₃ is described as a reference line. FIG. 8 shows a nitrogen adsorption / desorption isotherm, and FIG. 10 shows a pore diameter distribution curve.

As is clear from the low-angle XRD pattern shown in FIG. 6, a peak was observed in the range of 2θ of 0.5 ° to 3 °, confirming the mesopore structure. Further, based on the results shown in FIG. 7, when the average particle diameter of primary particles of iron oxide was determined from the peak at a position where 2θ was near 33.1 ° by the Scherrer equation, the average particle diameter of the primary particles was 3. It was confirmed to be 1 nm. Further, from the results shown in FIGS. 7 to 8, in the iron oxide porous body obtained in Example 6, the peak derived from the (110) plane of the crystal and the peak derived from the (300) plane of the crystal in the XRD pattern. It was confirmed that it contained a two-line ferrihydrite phase having two peaks, and contained α-Fe ₂ O ₃ and γ-Fe ₂ O ₃ . Moreover, from the measurement result of the content ratio of the 2-line ferrihydrite phase with respect to the iron oxide porous body obtained in Example 6, the content ratio of the 2-line ferrihydrite phase was 90% by mass in the crystals of total iron oxide. And the remainder was confirmed to be α-Fe ₂ O ₃ and γ-Fe ₂ O ₃ . Further, from the data of nitrogen adsorption / desorption isotherm (FIG. 9) and pore diameter distribution curve (FIG. 10), the central pore diameter is 5.6 nm, the pore volume is 0.27 cm ³ / g, the ratio It is confirmed that the surface area is 162 m ² / g and the secondary particle diameter is in the range of 100 to 600 nm, and more than 70% of the total pore volume is in the range of ± 40% of the central pore diameter. It was confirmed that it was contained, and it was found to have a very uniform pore diameter. Further, in the nitrogen adsorption / desorption isotherm, a IV type hysteresis curve defined by IUPAC was confirmed at a position where the value of the relative pressure P / P ₀ was in the range of 0.4 to 1.0, and the iron oxide porous body was It was confirmed to have a mesopore structure. Furthermore, as a result of measurement with a transmission electron microscope, the iron oxide porous material obtained in Example 6 is composed of an aggregate obtained by agglomerating primary particles of iron oxide, whereby secondary pores are formed. It was confirmed. As a result of TG / DTA analysis, the iron oxide porous material obtained in Example 6 had a water content of 7.7 mass% or less.

(Example 7)
Instead of adding only Fe (NO ₃ ) ₃ · 9H ₂ O to the mixed solution in the step of obtaining the reaction solution, Fe (NO ₃ ) ₃ · 9H ₂ O and Mn (NO ₃ ) ₃ · 6H are added to the mixed solution. ₂ O is added, and the molar ratio of Fe (NO ₃ ) ₃ · 9H ₂ O to Mn (NO ₃ ) ₃ · 6H ₂ O and the surfactant in the reaction solution ([FeCl ₃ · 9H ₂ O]: [Mn (NO ₃ ) ₃ · 6H ₂ O]: [surfactant]) was the same as in Example 1 except that the ratio was 0.04: 0.02: 0.03. Got the body.

  In the iron oxide porous body thus prepared, it is apparent from the manufacturing method that the total amount of impurities composed of oxides of silicon, aluminum, tin, zinc and titanium is 0% by mass. Moreover, it turns out that the iron oxide porous body prepared in this way contains manganese (Mn) from the manufacturing method. In addition, when elemental analysis was performed using a high-frequency plasma emission spectrometer (ICPS) using such an iron oxide porous body, the content of manganese (Mn) was a molar ratio ([Mn]: [ Fe]) was 0.508: 1.

  Further, for the iron oxide porous body obtained in Example 7 in this manner, the XRD measurement, the measurement of the content ratio of the two-line ferrihydrite phase, the measurement of the pore diameter distribution curve, and the transmission are performed in the same manner as in Example 1. Measurement with a scanning electron microscope and TG / DTA analysis were performed. As a result of such a measurement, the X-ray diffraction pattern of the low-angle region of the iron oxide porous material obtained in Example 7 is shown in FIG. The line diffraction pattern is shown in FIG. Further, a nitrogen adsorption / desorption isotherm is shown in FIG. 13, and a pore diameter distribution curve is shown in FIG.

As is clear from the low-angle XRD pattern shown in FIG. 11, a peak was observed in the range of 2θ of 0.5 ° to 3 °, confirming the mesopore structure. Further, based on the results shown in FIG. 12, when the average particle diameter of primary particles of iron oxide was obtained from the peak at a position where 2θ was near 33.1 ° by the Scherrer equation, the average particle diameter of the primary particles was 2. It was confirmed to be 0 nm. Furthermore, from the result of the XRD measurement, in the iron oxide porous body obtained in Example 7, two peaks of the peak derived from the (110) plane of the crystal and the peak derived from the (300) plane of the crystal in the XRD pattern were obtained. It was confirmed to contain a two-line ferrihydrite phase having a peak. Moreover, when the content ratio of the 2-line ferrihydrite phase was calculated | required about the iron oxide porous body obtained in Example 7 based on the result of the XRD measurement, the content ratio of the 2-line ferrihydrite phase was the total iron oxide. It was confirmed that it was 100% by mass in the crystal. Further, from the data of nitrogen adsorption / desorption isotherm (FIG. 13) and pore diameter distribution curve (FIG. 14), the center pore diameter is 4.8 nm, the pore volume is 0.41 cm ³ / g, the ratio The surface area is 291 m ² / g, and it is confirmed that 71% or more of the total pore volume is included in the range of ± 40% of the central pore diameter, and has a very uniform pore diameter. I understood. Further, in the nitrogen adsorption / desorption isotherm, a IV type hysteresis curve defined by IUPAC was confirmed at a position where the value of the relative pressure P / P ₀ was in the range of 0.4 to 1.0, and the iron oxide porous body was It was confirmed to have a mesopore structure. Furthermore, as a result of measurement by a transmission electron microscope and a high-resolution transmission electron microscope, the iron oxide porous body obtained in Example 7 is composed of an aggregate in which primary particles of iron oxide are aggregated. It was confirmed that pores were formed, and the primary primary particle size was in the range of 4 to 6 nm, and the secondary particle size was in the range of 20 to 300 nm. As a result of TG / DTA analysis, the iron oxide porous material obtained in Example 7 had a water content of 2.8% by mass or less.

(Comparative Example 1)
An iron oxide having a ferrihydrite phase was prepared according to the method described in JP-A-2005-288439. That is, _{first, Fe (NO 3) 3 ·} 9H 2 O (0.06 mol: 24.24g) were dissolved in distilled water 300 ml, to obtain a solution of an iron salt and stirred for 2 hours. Next, while stirring the iron salt solution, a 1M NaOH aqueous solution was added dropwise to the iron salt solution at a speed of 2 mL / min until the pH was 7.5, and the mixture was further stirred for 1 hour. Thereafter, the precipitate deposited in the solution was filtered, washed with distilled water, and then dried at 75 ° C. for 12 hours to obtain iron oxide for comparison.

  The iron oxide obtained in Comparative Example 1 was subjected to XRD measurement, measurement of the content ratio of the two-line ferrihydrite phase, and measurement of the pore size distribution curve in the same manner as in Example 1. As a result of such measurement, FIG. 15 shows a low-angle X-ray diffraction pattern of the iron oxide obtained in Comparative Example 1, and a wide-angle X-ray diffraction pattern of the iron oxide obtained in Comparative Example 1 is shown in FIG. FIG. 16 shows a nitrogen adsorption / desorption isotherm, and FIG. 18 shows a pore diameter distribution curve.

Based on the X-ray diffraction pattern in the wide-angle region shown in FIG. 16, the average particle size of primary particles of iron oxide was determined from the peak at a position where 2θ was near 33.1 ° by the Scherrer equation. The diameter was confirmed to be 1.7 nm. Moreover, from FIG. 16, it was confirmed that the iron oxide obtained in Comparative Example 1 has a 2-line ferrihydrite phase. Furthermore, it was confirmed that the content ratio of the 2-line ferrihydrite phase was 100% by mass. However, in the iron oxide obtained in Comparative Example 1, no peak indicating mesoporosity was confirmed in the XRD pattern in the low angle region shown in FIG. 15, and further, in the nitrogen adsorption / desorption isotherm (FIG. 17). The hysteresis was not confirmed, and the mesopore distribution was not confirmed even in the pore distribution curve by BJH (FIG. 18). Thus, the iron oxide obtained in Comparative Example 1 did not have a mesoporous structure. Further, the iron oxide thus obtained was confirmed to have a specific surface area of 226 m ² / g and a pore volume of 0.13 cm ³ / g from the data shown in FIGS.

(Comparative Example 2)
In accordance with the method described in “Synthesis and magnetic investigations of ordered mesoporous two-line ferrihydrite” on pages 280-287 of Journal of American Chemical Society vol. 130 published in 2008. Iron oxide was prepared. That is, first, 2 g of KIT-6 (silica) was added to a mixed solution obtained by dissolving 0.8 M Fe (NO ₃ ) ₃ .9H ₂ O in 20 mL of ethanol, and room temperature (25 ) For 1 hour to obtain a first reaction solution. Next, after the ethanol in the first reaction solution was evaporated at a temperature of 50 ° C., the solid was obtained by baking at 200 ° C. for 6 hours. Then, the solid was added to a mixed solution obtained by dissolving 0.8M of _{Fe (NO 3) 3 · 9H} 2 O in ethanol 20 mL, and stirred for 1 hour at room temperature (25 ° C.) To obtain a second reaction solution. Thereafter, the ethanol in the second reaction solution was evaporated under a temperature condition of 50 ° C. and then calcined at 200 ° C. for 6 hours to obtain a complex of KIT-6 (silica) and iron oxide. In addition, content of the iron oxide in this composite_body | complex was 50 mass%. Next, after removing KIT-6 (silica) present in the composite by immersing it in an aqueous NaOH solution (using an amount such that 2M NaOH aqueous solution is 150 ml per 5 g of iron oxide in the composite), The process of adding the obtained iron oxide to 2 L of water, washing, and filtering was repeated several times until the pH of the filtrate reached 7 (total amount of water used 2 L), filtered, and 50 ° C. To obtain iron oxide for comparison.

  Thus, with respect to the iron oxide obtained in Comparative Example 2, the XRD measurement, the measurement of the content ratio of the 2-line ferrihydrite phase, and the measurement of the pore size distribution curve were performed in the same manner as in Example 1. As a result of such measurement, FIG. 19 shows the low-angle X-ray diffraction pattern of the iron oxide obtained in Comparative Example 2, and the wide-angle X-ray diffraction pattern of the iron oxide obtained in Comparative Example 2 is shown in FIG. FIG. 20 shows a nitrogen adsorption / desorption isotherm, and FIG. 22 shows a pore diameter distribution curve.

From the XRD pattern in the wide-angle region shown in FIG. 20, when the average particle size of primary particles of iron oxide was determined by Scherrer's equation, it was confirmed that the average particle size of primary particles was 2.7 nm. Moreover, from FIG. 20, it was confirmed that the iron oxide obtained in Comparative Example 2 has a 2-line ferrihydrite phase. Further, it was confirmed that the content ratio of the 2-line ferrihydrite phase was 100% by mass. Further, in the XRD pattern in the low angle region shown in FIG. 19, a peak at 2θ of 0.5 ° to 3 ° is confirmed, and the value of the relative pressure P / P ₀ is shown in the nitrogen adsorption / desorption isotherm (FIG. 21). A type IV hysteresis curve defined by IUPAC was confirmed at a position in the range of 0.4 to 1.0, and it was confirmed that the iron oxide obtained in Comparative Example 2 was a porous body having a mesoporous structure. It was done. Further, from the data of nitrogen adsorption / desorption isotherm (FIG. 21) and pore distribution curve by BJH (FIG. 22), the central pore diameter is 3.8 nm, the specific surface area is 177 m ² / g, It was confirmed that the volume was 0.33 cm ³ / g. The iron oxide porous body obtained in Comparative Example 2 uses KIT-6 (silica) as a pore template, and is subjected to elemental analysis using a high-frequency plasma emission spectrometer (ICPS). It was confirmed that the content of silica (silicon dioxide: acid oxide) in the total amount of iron oxide measured by the above was 1.5% by mass.

(Comparative Example 3)
Iron oxide for comparison was obtained in the same manner as in Example 1 except that the temperature condition during firing was changed from 300 ° C to 500 ° C.

  Thus, with respect to the iron oxide obtained in Comparative Example 3, the XRD measurement, the measurement of the content ratio of the two-line ferrihydrite phase, and the measurement of the pore size distribution curve were performed in the same manner as in Example 1. As a result of such measurement, the X-ray diffraction pattern of the iron oxide obtained in Comparative Example 3 is shown in FIG. 23, and the X-ray diffraction pattern of the iron oxide obtained in Comparative Example 3 is shown in FIG. 24, a nitrogen adsorption / desorption isotherm is shown in FIG. 25, and a pore diameter distribution curve is shown in FIG.

Based on the result of the XRD pattern shown in FIG. 24, when the average particle diameter of primary particles of iron oxide was obtained from the peak at a position where 2θ was near 33.1 ° by the Scherrer equation, the average particle size of primary particles of iron oxide was determined. The diameter was confirmed to be 17.3 nm. Moreover, from FIG. 24, it was confirmed that the iron oxide obtained in Comparative Example 3 contains α-Fe ₂ O ₃ . Furthermore, from the measurement result of the content ratio of the 2-line ferrihydrite phase, it was confirmed that the content ratio of α-Fe ₂ O ₃ was 100% by mass. Further, in the XRD pattern in the low angle region shown in FIG. 23, a peak is confirmed at a position where 2θ is 0.5 ° to 3 °, and the relative pressure P / P ₀ is shown in the nitrogen adsorption / desorption isotherm (FIG. 25). The IV type hysteresis curve defined by IUPAC is confirmed at a position where the value is in the range of 0.4 to 1.0, and the iron oxide obtained in Comparative Example 3 is a porous body having a mesoporous structure. Was confirmed. Further, from the data of nitrogen adsorption / desorption isotherm (FIG. 25) and pore distribution curve by BJH (FIG. 26), the center pore diameter is 7.2 nm, the specific surface area is 97 m ² / g, It was confirmed that the volume was 0.30 cm ³ / g.

(Comparative Example 4)
34.04 g of polyoxyethylene (20) cetyl ether (surfactant: trade name “Brij 58” manufactured by Sigma-Aldrich) was added to 300 ml of 1-propanol, mixed and mixed in 1-propanol. A liquid mixture containing 12.42% by mass of a surfactant was obtained. Then, it was added _{Fe (NO 3) 3 · 9H} 2 O to the mixed solution, and stirred for 2 hours to obtain a reaction solution. The amount of Fe (NO ₃ ) ₃ · 9H ₂ O added to the mixed solution is the molar ratio of Fe (NO ₃ ) ₃ · 9H ₂ O to the surfactant in the obtained reaction solution ([ _{Fe (NO 3) 3 · 9H} 2 O]: [ surfactant]) is 0.06: it was set at 0.03. Next, while stirring the reaction solution, a 46% by mass aqueous KOH solution is added dropwise to the reaction solution, the pH of the reaction solution is adjusted to 7.5, and further stirred for 3 hours. A precipitate was deposited. Subsequently, after putting the reaction liquid in which the precipitate has been deposited into a sealed container having a capacity of 1 L, the container is introduced into an oven, and is subjected to a temperature condition of 50 ° C. under a natural pressure condition in the container. For 3 days. Next, the precipitate was filtered out from the reaction solution after the heat aging, and the precipitate was washed with 2.5 L of distilled water and dried. The precipitate thus dried was pulverized in an agate mortar to obtain a powder. Thereafter, 3 g of the powder was added to 100 ml of ethanol and stirred for 24 hours. Next, the powder was taken out from the ethanol by filtration and dried, and then calcined at 475 ° C. for 3 hours to obtain an iron oxide porous body.

Thus, with respect to the iron oxide porous body obtained in Comparative Example 4, the XRD measurement, the measurement of the content ratio of the two-line ferrihydrite phase, and the measurement of the pore diameter distribution curve were performed in the same manner as in Example 1. From such measurement results, it was confirmed that the average particle diameter of the primary particles of iron oxide obtained in Comparative Example 4 was 8.5 nm. Further, in the iron oxide obtained in Comparative Example 4, it was confirmed that the content ratio of the two-line ferrihydrite phase was 90% by mass, and the remainder was α-Fe ₂ O ₃ and γ-Fe ₂ O _3. It was done. In addition, a peak is confirmed at 2θ of 0.5 ° to 3 ° in the XRD pattern in the low angle region, and the relative pressure P / P ₀ is 0.4 to 1.0 on the nitrogen adsorption / desorption isotherm. An IV type hysteresis curve defined by IUPAC was confirmed at a position in the range, and the iron oxide porous material obtained in Comparative Example 4 was confirmed to be a porous material having a mesoporous structure. Furthermore, from the data of the nitrogen adsorption / desorption isotherm and the pore distribution curve by BJH, the central pore diameter is 6.2 nm, the specific surface area is 153 m ² / g, and the pore volume is 0.33 cm ³ / g. It was confirmed that there was.

(Comparative Example 5)
In 200 ml of 1-propanol, 34.04 g of polyoxyethylene (20) cetyl ether (surfactant: trade name “Brij 58” manufactured by Sigma-Aldrich) was added, mixed and mixed in 1-propanol. A liquid mixture containing 17.54% by mass of a surfactant was obtained. Then, it was added _{Fe (NO 3) 3 · 9H} 2 O to the mixed solution, and stirred for 2 hours to obtain a reaction solution. The amount of Fe (NO ₃ ) ₃ · 9H ₂ O added to the mixed solution is the molar ratio of Fe (NO ₃ ) ₃ · 9H ₂ O to the surfactant in the obtained reaction solution ([ _{Fe (NO 3) 3 · 9H} 2 O]: [ surfactant]) is 0.06: it was set at 0.03. Next, while stirring the reaction solution, a 28% by mass NH ₃ aqueous solution was added dropwise to the reaction solution, the pH of the reaction solution was adjusted to 7.5, and the reaction solution was further stirred for 3 hours. A precipitate was precipitated. Subsequently, after putting the reaction liquid in which the precipitate has been deposited into a sealed container having a capacity of 1 L, the container is introduced into an oven, and is subjected to a temperature condition of 50 ° C. under a natural pressure condition in the container. For 3 days. Next, the precipitate was filtered out from the reaction solution after the heat aging, and the precipitate was washed with 2.5 L of distilled water and dried. The precipitate thus dried was pulverized in an agate mortar to obtain a powder. Thereafter, 3 g of the powder was added to 100 ml of ethanol and stirred for 24 hours. Next, the powder was taken out from the ethanol by filtration and dried, and then calcined at 475 ° C. for 3 hours to obtain an iron oxide porous body.

Thus, with respect to the iron oxide porous body obtained in Comparative Example 5, the XRD measurement, the measurement of the content ratio of the two-line ferrihydrite phase, and the measurement of the pore size distribution curve were performed in the same manner as in Example 1. From such measurement results, it was confirmed that the average particle diameter of the primary particles of iron oxide obtained in Comparative Example 5 was 7.0 nm. In the iron oxide obtained in Comparative Example 5, the content ratio of 2 lines ferrihydrite phase is 65 wt%, it remains an alpha-Fe ₂ O ₃ was confirmed. In addition, a peak is confirmed at 2θ of 0.5 ° to 3 ° in the XRD pattern in the low angle region, and the relative pressure P / P ₀ is 0.4 to 1.0 on the nitrogen adsorption / desorption isotherm. An IV type hysteresis curve defined by IUPAC was confirmed at a position in the range, and the iron oxide porous material obtained in Comparative Example 5 was confirmed to be a porous material having a mesoporous structure. Furthermore, from the data of the nitrogen adsorption / desorption isotherm and the pore distribution curve by BJH, the central pore diameter is 10.2 nm, the specific surface area is 145 m ² / g, and the pore volume is 0.30 cm ³ / g. It was confirmed that there was.

[Evaluation of air purification performance]
The air purification performance was measured using the iron oxide porous bodies obtained in Example 1 and Examples 6 to 7 and the iron oxide obtained in Comparative Examples 1 to 5 as 0.1 g samples, respectively. That is, first, after introducing a sample (0.1 g) into a gas container (5 L), the gas atmosphere in the gas container is composed of 31.67 ppm acetaldehyde, 20 vol% oxygen and nitrogen (balance). A gas atmosphere was used. And the acetaldehyde density | concentration in the gas in the gas container after 3 hours passed at room temperature (25 degreeC) was measured with the gas chromatograph (Shimadzu GC-14B). Similarly, for the gas container (5 L) into which no sample was introduced, the gas atmosphere was similarly a gas atmosphere composed of 31.67 ppm acetaldehyde, 20 vol% oxygen and nitrogen (balance), and room temperature (25 ° C. The concentration of acetaldehyde in the gas in the gas container after 3 hours was measured. And the following formula:
[Removal rate (%)] = (1− [Concentration of acetaldehyde in the gas container into which the sample was introduced] / [Concentration of acetaldehyde in the gas container into which the sample was not introduced]) × 100
The removal rate of acetaldehyde before, 1 hour, 3 hours, 5 hours, and 24 hours before the reaction was determined. The results are shown in Table 2.

  As is clear from the results shown in Table 2, in the iron oxide porous body of the present invention (Example 1 and Examples 6 to 7), sufficiently high acetaldehyde removal performance was obtained, and the air purification material It was confirmed that it showed sufficiently high performance when trying to do so. On the other hand, none of the iron oxides for comparison (Comparative Examples 1 to 5) had sufficient acetaldehyde removal performance. From these results, even when the iron oxide mesoporous material having a two-line ferrihydrite phase contains 1.5% by mass of impurities (silicon dioxide) (Comparative Example 2), acetaldehyde removal performance It turns out that is not enough. Moreover, even in the case of an iron oxide mesoporous material having a two-line ferrihydrite phase, the average particle diameter of the primary particles exceeds 8 nm (Comparative Example 4) or the central pore diameter exceeds 10 nm. In the case (Comparative Example 5), it was found that the removal performance of acetaldehyde was not sufficient.

  Further, as is clear from the results shown in Table 2, in the iron oxide porous material containing the transition metal obtained in Example 7, the removal rate of acetaldehyde becomes 100% after 1 hour from the start of the reaction. Was confirmed. From such a result, in the iron oxide porous body of the present invention, it was confirmed that a higher acetaldehyde removal performance can be obtained by including a transition metal.

As described above, according to the present invention, when used as an air purification material, it has a sufficiently high purification performance for reactive molecules such as volatile organic compounds (for example, acetaldehyde) contained in the air. An iron oxide porous body, an air purification material using the iron oxide porous body, and a method for producing an iron oxide porous body capable of efficiently producing the iron oxide porous body by a simple process Is possible. Such an iron oxide porous body of the present invention can quickly diffuse the adsorbed substance and the reaction substrate into the pores, and thus can be suitably used as an absorbent, a catalyst, a catalyst carrier, etc. Useful.

Claims (11)

Consists of aggregates of iron oxide primary particles,
The average particle diameter of the primary particles is 2 to 8 nm,
The central pore diameter of the pores of the aggregate is 2 to 10 nm,
The iron oxide has a two-line ferrihydrite phase showing two peaks of a peak derived from the (110) plane of the crystal and a peak derived from the (300) plane of the crystal in the X-ray diffraction pattern;
The content ratio of the two-line ferrihydrite phase to the total crystal phase of the iron oxide is 40% by mass or more, and
The total amount of impurities composed of oxides of silicon, aluminum, tin, zinc and titanium is 0.1% by mass or less;
Iron oxide porous material characterized by Iron oxide porous body according to claim 1, the pore volume of the aggregate is characterized by a 0.25~0.45cm ³ / g. The iron oxide porous body according to claim 1, wherein the aggregate has a specific surface area of 140 to 350 m ² / g.   The iron oxide porous body according to any one of claims 1 to 3, further comprising a transition metal (excluding zinc and titanium).   The iron oxide porous body according to claim 4, wherein the transition metal is at least one element selected from manganese, cerium, silver, zirconium, yttrium and gallium.   An air purification material comprising the iron oxide porous body according to any one of claims 1 to 5. A surfactant comprising an alcohol, a polyoxyethylene alkyl ether having 2 to 200 ethoxy groups as hydrophilic groups and 6 to 20 carbon atoms in an alkyl group as hydrophobic groups, and an iron salt And a step of obtaining a reaction solution by adding
By adjusting the pH of the reaction solution to 4.5 to 13 by adding a base to the reaction solution, iron hydroxide is precipitated around the surfactant in the reaction solution, so that the surface activity is increased. Obtaining a complex of the agent and the iron hydroxide;
Introducing the reaction solution containing the complex into a sealed container and heating and aging at a temperature of 20 to 125 ° C .;
After the complex is taken out of the reaction solution after the heat aging, the complex is washed with a polar solvent to remove the surfactant from the complex, thereby aggregating water of primary particles of iron hydroxide. Obtaining an iron oxide porous body;
The step of obtaining the iron oxide porous body according to claim 1, by drying the iron hydroxide porous body after baking at a temperature condition of 200 to 450 ° C.
The manufacturing method of the iron oxide porous body characterized by including.   8. The method for producing a porous iron oxide according to claim 7, wherein the addition amount of the surfactant is 0.02 to 50 mass% with respect to the total amount of the alcohol.   The base is at least one selected from the group consisting of alkali metal hydroxides, ammonia, alkyl carbonates, alkyl hydrogencarbonates, alkylamines, alkoxides, and tetraalkylammonium hydroxides. Item 9. A method for producing a porous iron oxide according to Item 7 or 8.   The iron oxide porous material according to any one of claims 7 to 9, wherein in the step of obtaining the reaction solution, a salt of a transition metal (excluding zinc and titanium) is further added to the alcohol. Body manufacturing method.   11. The iron oxide porous body according to claim 10, wherein the transition metal is at least one element selected from manganese, cerium, silver, zirconium, yttrium, and gallium.