Porous body and method for producing same

Abstract

The present invention addresses the problem of providing: a porous body that has a co-continuous structure formed of coarse pores and a ceramic framework including minute pores, and that has a high bulk density; and a method for producing the same. In order to solve the problem, the present invention provides: a porous body which has a co-continuous structure formed of coarse pores (2) and a ceramic framework (1) including minute pores (3), and in which the modal pore diameter of the minute pores of the porous body is not less than 1.0 nm but less than 200.0 nm, and the bulk density of the porous body is 0.50-2.00 g / cm3; and a method for producing the same.<sp / >

Description

Porous material and method for manufacturing the same

[0001] The present invention relates to a porous body having a co-continuous structure formed by a ceramic framework containing micropores and coarse pores, and a method for producing the same.

[0002] Porous materials having a co-continuous structure formed by a ceramic skeleton containing micropores and coarse pores are widely used in chromatography separation columns, enzyme supports, catalyst supports, adsorbents, and the like. Porous materials can be manufactured, for example, by the following method (for example, Patent Document 1). First, a reaction solution containing a ceramic precursor, a catalyst, a coarse pore forming agent, and other reagents is prepared, and hydrolysis and polycondensation reactions are carried out to produce a sol. Next, the hydrolysis and polycondensation reactions are carried out further to produce a gel having a co-continuous structure formed by a skeletal phase and a solvent phase. Next, the gel and a micropore forming agent (for example, urea, etc.) are reacted under heated reflux conditions to form micropores in the gel skeleton. Next, the gel is calcined to produce a porous material.

[0003] Patent No. 6924338

[0004] The reflux treatment, which involves reacting a gel with a micropore-forming agent under reflux conditions, is performed by immersing the gel in a solution containing the micropore-forming agent and then heating the solution under reflux. The porous material obtained through the reflux treatment has low bulk density and there is room for improvement in its mechanical strength.

[0005] The present invention aims to provide a porous body having a co-continuous structure formed by a ceramic skeleton containing micropores and coarse pores, having a high bulk density, and a method for producing the same.

[0006] To solve the above problems, the present invention provides the following method: [1] A porous body having a co-continuous structure formed by a ceramic skeleton containing micropores and coarse pores, wherein the most frequent pore diameter of the micropores in the porous body is 1.0 nm or more and less than 200.0 nm, and the bulk density of the porous body is 0.50 g / cm³ ３ 2.00g / cm or more ３The porous body is as follows: [2] The porous body according to [1], wherein the most frequent pore size of the coarse pores of the porous body is 200.0 nm or more and 10000.0 nm or less. [3] The specific surface area of ​​the porous body is 40 m² ２ / g or more 800m ２ A porous body according to [1] or [2], wherein the amount is less than or equal to / g. A method for producing a porous body according to any one of [4] [1] to [3], comprising the following steps: (a) impregnating a starting gel having a co-continuous structure formed by a skeletal phase and a solvent phase with an alkaline solution to obtain an impregnated gel; (b) heating the impregnated gel in a gas; (c) firing the impregnated gel after heating at a temperature higher than the heating temperature in step (b) to obtain the porous body, wherein in the impregnated gel obtained in step (a), the ratio of the mass of the alkaline solution contained in the impregnated gel to the dry mass of the impregnated gel is 0.01 or more and 1.50 or less.

[0007] The present invention provides a porous body having a co-continuous structure formed by a ceramic skeleton containing micropores and coarse pores, wherein the porous body has a high bulk density, and a method for manufacturing the same.

[0008] Figure 1 is an enlarged view of a part of the surface of a porous body according to one embodiment of the present invention.

[0009] The present invention relates to a porous body (hereinafter sometimes referred to as "ceramic monolith") having a co-continuous structure formed by a ceramic skeleton containing micropores and coarse pores, wherein the most frequent pore diameter of the micropores of the porous body is 1.0 nm or more and less than 200.0 nm, and the bulk density of the porous body is 0.50 g / cm³. ３ 2.00g / cm or more ３ The following relates to a porous material. The porous material of the present invention has improved mechanical strength due to its high bulk density.

[0010] <<Porous Material>> The porous material of the present invention will be described below. Two or more of the features of the porous material described below can be combined.

[0011] <Form and Shape of Porous Bodies> The form of a porous body is not particularly limited. Examples of forms of porous bodies include particles, lumps, molded bodies, etc. The shape of a porous body is also not particularly limited. Examples of shapes of porous bodies include columnar, spherical (e.g., perfect sphere, ellipsoid, etc.), needle-shaped, flaky (flake-shaped), polyhedral, flattened, crushed, and lumpy shapes. Examples of columnar shapes include cylindrical, elliptical, and polygonal prisms (e.g., quadrangular, hexagonal, and octagonal prisms). A columnar shape may also be a shape in which a part of a cylindrical, elliptical, or polygonal prism is missing.

[0012] <Structure of Porous Material> The structure of the porous material will be described below with reference to Figure 1. Two or more of the structural features of the porous material described below can be combined. Figure 1 is an enlarged view of a part of the surface of a porous material according to one embodiment.

[0013] As shown in Figure 1, the porous material has a co-continuous structure formed by a ceramic framework 1 containing micropores 3 and coarse pores 2.

[0014] In this invention, "micropores" refer to pores with a diameter of less than 200.0 nm calculated by the mercury intrusion method, and "coarse pores" refer to pores with a diameter of 200.0 nm or more calculated by the mercury intrusion method. The lower limit of the pore diameter for micropores is, for example, 1.0 nm or more. The upper limit of the pore diameter for coarse pores is, for example, 100.0 μm or less. "Pore diameter" refers to the diameter of the pore. The mercury intrusion method can be carried out under the conditions and procedures described in the examples.

[0015] In a porous material, the ceramic framework 1 and the coarse pores 2 each have a continuous three-dimensional network structure and are intertwined with each other, thereby forming a co-continuous structure between the ceramic framework 1 and the coarse pores 2. The presence of a co-continuous structure between the ceramic framework 1 and the coarse pores 2 in a porous material can be confirmed by observing the surface or cross-section of the porous material with a scanning electron microscope (SEM).

[0016] The most frequent pore diameter of the coarse pores 2 is preferably 200.0 nm to 10000.0 nm, more preferably 300.0 nm to 5000.0 nm, even more preferably 600.0 nm to 2500.0 nm, and particularly preferably 600.0 nm to 1000.0 nm. Each of the above lower limits may be combined with any of the above upper limits. When the most frequent pore diameter of the coarse pores 2 is within the above range, the bulk density of the porous material can be increased.

[0017] "The most frequent pore diameter of coarse pores" refers to the most frequent pore diameter of coarse pores analyzed based on the results measured by the mercury intrusion method in the range of pore diameters from 1.0 nm to 1,000,000.0 nm, as described in the examples.

[0018] The most frequent pore size of the micropores 3 is 1.0 nm or more and less than 200.0 nm. Preferably, the most frequent pore size of the micropores 3 is 1.1 nm or more and 100.0 nm or less, more preferably 1.2 nm or more and 50.0 nm or less, and even more preferably 1.3 nm or more and 10.0 nm or less. Each of the above lower limits may be combined with any of the above upper limits. When the most frequent pore size of the micropores 3 is within the above range, the bulk density of the porous material can be increased. Furthermore, when the most frequent pore size of the micropores 3 is within the above range, the porous material can be used in a wide range of applications such as chromatography separation columns, enzyme carriers, catalyst carriers, and adsorbents.

[0019] "The most frequent pore size of micropores" refers to the most frequent pore size of micropores analyzed based on the results measured by the BJH method in the range of pore size from 1.0 nm to 1000.0 nm, as described in the examples.

[0020] The total pore volume of the coarse pores 2, as evaluated by the mercury intrusion method, is preferably 0.40 mL / g or more and 5.00 mL / g or less, more preferably 0.50 mL / g or more and 4.50 mL / g or less, and even more preferably 0.50 mL / g or more and 1.00 mL / g or less. Each of the above lower limits may be combined with any of the above upper limits. The evaluation of the total pore volume of the coarse pores 2 by the mercury intrusion method can be performed by the method described in the examples. Specifically, the total pore volume of the coarse pores 2 can be evaluated based on the results measured in a pore range having a diameter of 200.0 nm or more and 1,000,000.0 nm or less. When the total pore volume of the coarse pores 2 is within the above range, the porous material can be used in a wide range of applications such as chromatography separation columns, enzyme carriers, catalyst carriers, and adsorbents.

[0021] The total pore volume of the micropores 3 evaluated by the BJH method is preferably 0.05 mL / g or more and 1.00 mL / g or less, more preferably 0.10 mL / g or more and 0.80 mL / g or less, and even more preferably 0.15 mL / g or more and 0.45 mL / g or less. Each of the above lower limits may be combined with any of the above upper limits. The evaluation of the total pore volume of the micropores 3 by the BJH method can be performed by the method described in the examples. Specifically, the total pore volume of the micropores 3 can be evaluated based on the results measured in the pore range having a diameter of 1.0 nm or more and 1000.0 nm or less. When the total pore volume of the micropores 3 is within the above range, the bulk density of the porous material can be increased. Furthermore, when the total pore volume of the micropores 3 is within the above range, the porous material can be used in a wide range of applications such as chromatography separation columns, enzyme carriers, catalyst carriers, and adsorbents.

[0022] The total pore volume of the porous body evaluated by the mercury intrusion method is preferably 0.45 mL / g or more and 5.00 mL / g or less, more preferably 0.50 mL / g or more and 3.00 mL / g or less, and even more preferably 0.55 mL / g or more and 1.00 mL / g or less. Each of the above lower limit values may be combined with any of the above upper limit values. The evaluation of the total pore volume of the porous body by the mercury intrusion method can be performed by the method described in the examples. Specifically, the total pore volume of the porous body can be evaluated based on the results measured in the pore diameter range of 1.0 nm or more and 1000000.0 nm or less. When the total pore volume of the porous body is within the above range, the bulk density of the porous body can be increased. Further, when the total pore volume of the porous body is within the above range, the porous body can be used for a wide range of applications such as separation columns for chromatography, enzyme carriers, catalyst carriers, adsorbents, etc.

[0023] When calculating the most frequent pore diameter of the macropores 2 and evaluating the total pore volume of the macropores 2 and the total pore volume of the porous body by the mercury intrusion method, pores derived from peaks with a pore volume at the peak top in the obtained pore distribution diagram of less than 0.01 mL / g are not used for the calculation and evaluation.

[0024] The bulk density of the porous body is 0.50 g / cm ３ or more and 2.00 g / cm ３ or less. The bulk density of the porous body is preferably 0.60 g / cm ３ or more and 1.50 g / cm ３ or less, more preferably 0.70 g / cm ３ or more and 1.30 g / cm ３ or less, and even more preferably 0.75 g / cm ３ or more and 1.00 g / cm ３ or less. Each of the above lower limit values may be combined with any of the above upper limit values. The measurement of the bulk density of the porous body can be performed by the method described in the examples. When the bulk density of the porous body is within the above range, the mechanical strength of the porous body is improved compared with the conventional one, and it can be used for a wide range of applications such as separation columns for chromatography, enzyme carriers, catalyst carriers, adsorbents, etc.

[0025] The specific surface area of the porous body measured by the BET method is preferably 40 m ２ / g or more and 800 m ２ / g or less, more preferably 50 m ２ / g or more and 500 m ２ / g or less, even more preferably 60 m ２ / g or more and 350 m ２ / g or less. Each of the above lower limit values may be combined with any of the above upper limit values. The measurement of the specific surface area of the porous body by the BET method can be carried out by the method described in the examples. When the specific surface area of the porous body is within the above range, the porous body can be used for a wide range of applications such as separation columns for chromatography, enzyme carriers, catalyst carriers, adsorbents, etc.

[0026] In addition to the characteristics that the most frequent pore diameter of the micropores of the porous body is within the above range and the bulk density is within the above range, the porous body preferably has one or more characteristics selected from the characteristics that the most frequent pore diameter of the macropores is within the above range, the total pore volume of the macropores is within the above range, the total pore volume of the micropores is within the above range, the total pore volume is within the above range, and the specific surface area is within the above range.

[0027] <Material of the porous body> The ceramics constituting the ceramic skeleton 1 are, for example, oxide ceramics containing an element selected from the group consisting of semi-metal elements and metal elements. The ceramic skeleton 1 may contain one kind of element selected from the above group, or may contain two or more kinds of elements selected from the above group.

[0028] Examples of the semi-metal element include silicon. Examples of the oxide ceramics containing silicon include silica (SiO ２ ).

[0029] Examples of the metal element include aluminum, tin, transition metal elements (e.g., zinc, cerium, titanium, zirconium, vanadium, chromium, iron, cobalt, nickel, palladium, platinum, copper, silver, gold, etc.). Among these, from the viewpoint of ease of manufacturing the porous body, the metal element is preferably selected from the group consisting of aluminum, tin, cerium, titanium, and zirconium. Examples of the oxide ceramics containing aluminum, tin, cerium, titanium, or zirconium include, for example, alumina (Al ２ O ３ ), tin oxide (SnO ２ ), ceria (CeO ２ ), titania (TiO ２ ), zirconia (ZrO ２ ), etc.

[0030] The oxide ceramics may further contain an element selected from the group consisting of alkali metal elements such as lithium and sodium, alkaline earth metal elements such as magnesium and calcium, and rare earth elements such as lanthanum, scandium, yttrium, and gadolinium, in addition to the elements selected from silicon, aluminum, tin, and transition metal elements.

[0031] In one embodiment, the ceramic skeleton 1 is a silica skeleton.

[0032] In another embodiment, the ceramic skeleton 1 is an alumina skeleton, a tin oxide skeleton, a ceria skeleton, a titania skeleton, or a zirconia skeleton.

[0033] <<Method for manufacturing porous body>> The method of the present invention will be described below. Two or more of the features of the method of the present invention described below can be combined.

[0034] The method of the present invention includes steps (a) to (c). Steps (a) to (c) are performed sequentially. Steps (a) to (c) are described below. Two or more features from the features of each step described below can be combined. One or more features from step (a) described below can be combined with one or more features from step (b) described below and one or more features from step (c) described below.

[0035] <Step (a)> Step (a) is a step in which an alkaline solution is impregnated into a starting gel having a co-continuous structure formed by a skeletal phase and a solvent phase in order to obtain an impregnated gel.

[0036] <Departure Gel> The departure gel is described below. Two or more of the following features of the departure gel can be combined.

[0037] The starting gel has a co-continuous structure formed by the skeletal phase and the solvent phase.

[0038] The solid content of the starting gel is preferably 40.0% by mass or less, more preferably 38.0% by mass or less, and even more preferably 37.0% by mass or less. When the solid content of the starting gel is within the above range, a sufficient amount of alkaline solution can be impregnated into the starting gel in the impregnation treatment described later. The lower limit of the solid content of the starting gel is not particularly limited as long as a starting gel having a co-continuous structure can be obtained. The solid content of the starting gel is preferably 2.0% by mass or more, more preferably 5.0% by mass or more, and even more preferably 10.0% by mass or more. Each of the above lower limits may be combined with any of the above upper limits. The solid content of the starting gel can be measured by the method described in the examples.

[0039] The specific surface area of ​​the dried starting gel, as measured by the BET method, is preferably 1.0 m². ２ / g or more, more preferably 1.2m ２ / g or more, more preferably 1.5m ２ The value is greater than or equal to / g. There is no particular upper limit. For example, the specific surface area of ​​the dried starting gel measured by the BET method is 10.0 m². ２The specific surface area of ​​the dried starting gel is less than or equal to / g. When the specific surface area of ​​the dried starting gel is within the above range, the alkaline solution is more easily impregnated into the starting gel in the impregnation treatment described later. The dried starting gel can be prepared, for example, by drying the starting gel in a drying oven. The drying temperature may be, for example, 70°C, 80°C, 90°C, or 100°C. The drying time may be, for example, 12 hours or more, 15 hours or more, or 20 hours or more. The preparation of the dried starting gel and the measurement of the specific surface area of ​​the dried starting gel by the BET method can be carried out by the methods described in the examples.

[0040] The ratio of the specific surface area of ​​the porous body obtained in step (c) to the specific surface area of ​​the dried starting gel is preferably 10 to 1000, more preferably 20 to 500, and even more preferably 30 to 300. Each of the above lower limits may be combined with any of the above upper limits. This ratio being within the above range means that the desired micropores are formed in the porous body obtained in step (c). In the present invention, the "desired micropores" formed in the porous body means micropores suitable for obtaining a porous body having a bulk density within the above range, and includes micropores whose most frequent pore diameter and / or total pore volume are within the above range.

[0041] While it is not necessary to heat-treat the starting gel before using it for impregnation, it is preferable to heat-treat the starting gel before using it for impregnation. This is because heat-treating the starting gel allows the polycondensation reaction described later to proceed, stabilizing the gel's framework and making it easier to form the desired micropores in the gel's framework. In this invention, the "desired micropores" formed in the gel's framework refer to micropores that are suitable for obtaining a porous body with increased bulk density. In the heat-treating of the starting gel before impregnation, the heating temperature and heating time are preferably adjusted so that the solid content of the starting gel falls within the above range. The heating temperature is preferably 30°C to 200°C, more preferably 60°C to 100°C, and even more preferably 70°C to 90°C. Each of the above lower limits may be combined with any of the above upper limits. The heating time is preferably 30 minutes to 750 minutes, more preferably 120 minutes to 730 minutes, and even more preferably 300 minutes to 720 minutes. Each of the above lower limits may be combined with any of the above upper limits. The heating method is not particularly limited. Heat treatment can be carried out, for example, using a dryer.

[0042] In one embodiment, the starting gel is a polymetalloxane gel produced by the sol-gel method.

[0043] The following describes a method for producing polymetalloxane gel using the sol-gel method. Two or more of the features described below can be combined.

[0044] Polymetalloxanes are inorganic polymers whose main chain structure consists of metalloxane bonds. A metalloxane bond is a bond between a metalloid or metallic element and an oxygen atom, i.e., an M-O bond (where M represents a metalloid or metallic element).

[0045] Examples of metalloid elements represented by M include silicon. Examples of metallic elements represented by M include aluminum, tin, cerium, titanium, zirconium, vanadium, chromium, iron, cobalt, nickel, palladium, platinum, copper, silver, gold, and zinc. However, from the viewpoint of ease of manufacturing porous materials, aluminum, tin, cerium, titanium, or zirconium are preferred.

[0046] The sol-gel method can be performed according to conventional procedures. An example of the sol-gel method is as follows:

[0047] The sol-gel method includes a sol manufacturing step and a gel manufacturing step.

[0048] In the sol manufacturing process, a reaction solution containing a ceramic precursor, a catalyst, and a coarse pore-forming agent is stirred to produce the sol.

[0049] The ceramic precursor is not particularly limited as long as it can form a polymetalloxane gel.

[0050] The ceramic precursor can be selected from, for example, metalloid compounds having hydroxyl groups and / or hydrolyzable functional groups (e.g., silicon compounds), metal compounds having hydroxyl groups and / or hydrolyzable functional groups (e.g., aluminum compounds, tin compounds, cerium compounds, titanium compounds, zirconium compounds, etc.). The total number of hydroxyl groups and hydrolyzable functional groups in each of the metalloid and metal compounds may be 1 or 2, but from the viewpoint of producing a polymetalloxane gel having a highly crosslinked structure by metalloxane bonds (M-O bonds), it is preferable to have 3 or more, and more preferably 4. When each of the metalloid and metal compounds has 2 or more hydrolyzable functional groups, the types of the 2 or more hydrolyzable functional groups may be the same or different.

[0051] Hydrolyzable functional groups are functional groups that are converted to hydroxyl groups by hydrolysis. Examples of hydrolyzable functional groups include alkoxy groups, acetoxy groups, halogen groups, and hydride groups, but alkoxy groups are preferred. The alkoxy group is preferably an alkoxy group having 1 to 10 carbon atoms, more preferably an alkoxy group having 1 to 5 carbon atoms, and even more preferably a methoxy group, an ethoxy group, or a propyl group. The alkoxy group may be linear or branched.

[0052] The semimetallic compound and the metal compound may each have functional groups other than hydroxyl groups and hydrolyzable functional groups. Examples of functional groups other than hydroxyl groups and hydrolyzable functional groups include alkyl groups, alkenyl groups, phenyl groups, phenoxy groups, carboxyl groups, epoxy groups, aldehyde groups, thiol groups, amino groups, acryloyl groups, and methacryloyl groups. The alkyl group is preferably a C1-C10 alkyl group, more preferably a C1-C5 alkyl group, and even more preferably a methyl group, an ethyl group, or a propyl group. The alkyl group may be linear or branched. The alkenyl group is preferably a C2-C10 alkenyl group, more preferably a C2-C5 alkenyl group, and even more preferably a vinyl group. The alkenyl group may be linear or branched.

[0053] The silicon compound having a hydroxyl group and / or a hydrolyzable functional group is preferably an alkoxysilane. Examples of alkoxysilanes include tetraalkoxysilane, trialkoxysilane, dialkoxysilane, and monoalkoxysilane, but among these, tetraalkoxysilane is preferred from the viewpoint of facilitating hydrolysis and polycondensation reactions. Examples of tetraalkoxysilanes include tetramethoxysilane and tetraethoxysilane.

[0054] The aluminum compound having a hydroxyl group and / or a hydrolyzable functional group is preferably aluminum hydroxide, aluminum alkoxide, etc.

[0055] The tin compound having a hydroxyl group and / or a hydrolyzable functional group is preferably tin hydroxide, tin alkoxide, etc.

[0056] The cerium compound having a hydroxyl group and / or a hydrolyzable functional group is preferably cerium hydroxide, cerium alkoxide, etc.

[0057] The titanium compound having a hydroxyl group and / or a hydrolyzable functional group is preferably a titanium alkoxide. Examples of titanium alkoxides include titanium monoalkoxide, titanium dialkoxide, titanium trialkoxide, and titanium tetraalkoxide, but among these, titanium tetraalkoxide is preferred from the viewpoint of facilitating hydrolysis and polycondensation reactions. Examples of titanium tetraalkoxides include titanium tetraisopropoxide.

[0058] The zirconium compound having a hydroxyl group and / or a hydrolyzable functional group is preferably a zirconium alkoxide. Examples of zirconium alkoxides include zirconium monoalkoxide, zirconium dialkoxide, zirconium trialkoxide, and zirconium tetraalkoxide, but among these, zirconium tetraalkoxide is preferred from the viewpoint of facilitating hydrolysis and polycondensation reactions. Examples of zirconium tetraalkoxides include zirconium tetraisopropoxide.

[0059] The ceramic precursor may be a metal salt (e.g., aluminum salt, tin salt, cerium salt, etc.) that is converted to a hydroxide by hydrolysis. Examples of aluminum salts include aluminum nitrate, aluminum sulfate, and aluminum chloride. Examples of tin salts include tin nitrate, tin sulfate, and tin chloride. Examples of cerium salts include cerium nitrate, cerium sulfate, and cerium chloride. Of these, aluminum chloride, tin chloride, or cerium chloride are preferred from the viewpoint of facilitating the hydrolysis and polycondensation reactions.

[0060] In one embodiment, M is silicon, the polymetalloxane gel is a polysiloxane gel, and the ceramic precursor is a silica precursor.

[0061] Silica precursors are, for example, silicon compounds having a hydroxyl group and / or a hydrolyzable functional group.

[0062] The silica precursor may be sodium silicate or water glass. The water glass is a concentrated aqueous solution of sodium silicate. The type of water glass, the concentration of sodium silicate, etc., are not particularly limited, but from the viewpoint of availability and handling, the sodium silicate concentration of the water glass is preferably 20% by mass or more and 40% by mass or less.

[0063] Catalysts function as catalysts for hydrolysis and / or polycondensation reactions. Examples of catalysts include acids and bases. Examples of acids include inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid; and organic acids such as formic acid, acetic acid, oxalic acid, and citric acid. Examples of bases include amines such as sodium hydroxide, potassium hydroxide, aqueous ammonia, sodium carbonate, sodium bicarbonate, and trimethylammonium; ammonium hydroxides such as tert-butylammonium hydroxide; and alkali metal alkoxides such as sodium methoxide.

[0064] Coarse pore-forming agents contribute to the formation of coarse pores in ceramic monoliths. Examples of coarse pore-forming agents include water-soluble polymers and surfactants, of which water-soluble polymers are preferred. Water-soluble polymers induce a sol-gel transition accompanied by a phase separation process (typically spinodal decomposition), contributing to the formation of a co-continuous structure between the skeletal phase and the solvent phase in the gel, and consequently, the formation of coarse pores in the ceramic monolith.

[0065] Examples of water-soluble polymers include polyalkylene glycols such as polyethylene glycol and polypropylene glycol, polyacrylic acid, polyethylene glycol-polypropylene glycol block copolymers, polyvinylpyrrolidone, sodium polystyrene sulfonate, and polyallylamine hydrochloride.

[0066] The weight-average molecular weight of the water-soluble polymer is preferably between 8,000 and 150,000, from the viewpoint of efficiently carrying out the phase separation process (typically spinodal decomposition). The weight-average molecular weight is measured by GPC (gel permeation chromatography). In this invention, "weight-average molecular weight" means the weight-average molecular weight measured by a GPC analysis method based on polystyrene.

[0067] Examples of surfactants include cationic surfactants such as cetyltrimethylammonium chloride, anionic surfactants such as sodium dodecyl sulfate, and nonionic surfactants such as polyoxyethylene alkyl ethers.

[0068] The reaction solution may contain one or more solvents. Examples of solvents include water, organic solvents, and mixed solvents of water and organic solvents. Examples of organic solvents include alcohols such as methanol, ethanol, propanol, and butanol; and ketones such as acetone and methyl ethyl ketone. When the solvent is a mixed solvent of water and organic solvent, the content of the organic solvent is preferably 65% ​​by mass or less, based on the mass of the mixed solvent.

[0069] From the viewpoint of appropriately controlling the reaction initiation time, it is preferable to prepare the reaction solution by adding a ceramic precursor to a mixture containing a catalyst and a coarse pore-forming agent. The reaction is initiated by adding a ceramic precursor to a mixture containing a catalyst and a coarse pore-forming agent.

[0070] When stirring the reaction solution, it may be cooled. The reaction solution can be cooled so that its temperature is below a temperature at which the sol-gel transition, accompanied by a phase separation process (typically spinodal decomposition), is likely to proceed. For example, below 60°C. The lower limit is a temperature at which the reaction solution does not freeze, for example, around 1°C.

[0071] The reaction solution becomes sol-like as the hydrolysis and polycondensation reactions proceed. If the ceramic precursor does not have hydrolyzable functional groups (for example, if the ceramic precursor is sodium silicate or water glass), the hydrolysis reaction does not occur, and the reaction solution becomes sol-like as the polycondensation reaction proceeds.

[0072] In the hydrolysis reaction, the hydrolyzable functional groups of the ceramic precursor are hydrolyzed, forming hydroxyl groups. In the polycondensation reaction, metalloxane oligomers are formed by dehydration condensation between hydroxyl groups and dealcoholization condensation between hydroxyl groups and unhydrolyzed hydrolyzable functional groups. For example, if the ceramic precursor is a silicon compound having hydrolyzable functional groups, siloxane oligomers are formed by the dehydration condensation reaction shown in formula (1) below and the dealcoholization condensation reaction shown in formula (2) below. In formula (2) below, -OR represents an unhydrolyzed hydrolyzable functional group. ≡Si-OH + HO-Si≡ → ​​≡Si-O-Si≡ + H ２ O...(1) ≡Si-OR + HO-Si≡ → ​​≡Si-O-Si≡ + ROH...(2)

[0073] As the hydrolysis and polycondensation reactions proceed further, nanometer-sized primary metalloxane oligomer particles are formed, and secondary particles are formed by the aggregation of these primary particles. As a result, the reaction solution becomes sol-like.

[0074] In the gel manufacturing process, a molding mold (a mold for shaping the gel into a desired form) is added to the sol obtained in the sol manufacturing process, as needed, and then heated to the gelation temperature to produce a polymetalloxane gel. In the gelation process, hydrolysis and polycondensation reactions proceed further to form a metalloxane polymer, and a sol-gel transition accompanied by a phase separation process (typically spinodal decomposition) is induced to produce a polymetalloxane gel (wet gel). The produced polymetalloxane gel has a co-continuous structure of a skeletal phase and a solvent phase. The skeletal phase is rich in metalloxane polymers produced by hydrolysis and polycondensation reactions, and the solvent phase is rich in solvent. The skeletal phase and the solvent phase each have a continuous three-dimensional network structure and are intertwined with each other, thereby forming the co-continuous structure of the skeletal phase and the solvent phase.

[0075] The gelation temperature is preferably 20°C to 80°C, more preferably 25°C to 40°C, from the viewpoint of appropriately forming a co-continuous structure between the skeletal phase and the solvent phase in the gel. Each of the above lower limits may be combined with any of the above upper limits. The heating time at the gelation temperature is preferably 10 minutes or more. There is no particular upper limit to the heating time, but from the viewpoint of manufacturing efficiency, it is preferably 24 hours or less.

[0076] To remove any alkali metals remaining in the gel, it is preferable to wash the gel obtained in the gel manufacturing process before using it as a starting gel. Examples of washing solutions used for washing include water, organic solvents, mixed solvents of water and organic solvents, and aqueous solutions containing acids or bases. Examples of organic solvents include alcohols such as methyl alcohol, ethyl alcohol, n-propanol, and 2-propanol. Examples of acids include hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, acetic acid, formic acid, carbonic acid, citric acid, and phosphoric acid. Examples of bases include sodium hydroxide, potassium hydroxide, ammonia, water-soluble amines, sodium carbonate, and sodium bicarbonate.

[0077] If the gel obtained in the gel manufacturing process contains alkali metals (for example, if sodium silicate or water glass is used as the ceramic precursor), the concentration of alkali metals in the gel after washing is preferably 500 ppm or less, more preferably 100 ppm or less, and even more preferably 0 ppm. When the concentration of alkali metals in the gel after washing is within the above range, the strength of the porous body obtained in step (c) can be improved.

[0078] The gel obtained in the gel manufacturing process may be ground to the desired size before being used as the starting gel. Grinding may be performed before or after washing the gel obtained in the gel manufacturing process. Grinding can be carried out according to conventional methods. Grinding can be carried out using, for example, a mortar and pestle, hammer mill, ball mill, bead mill, jet mill, roller mill, etc.

[0079] <Alkaline Solutions> The alkaline solutions used in the impregnation process are described below. Two or more of the characteristics of the alkaline solutions described below can be combined.

[0080] The alkaline solution used in the impregnation process contains an alkaline and an aqueous solvent.

[0081] Alkali have the effect of forming micropores in the gel framework. These micropores formed in the gel framework become the micropores in the ceramic monolith. Therefore, alkali contributes to the formation of micropores in the ceramic monolith.

[0082] The alkali can be selected from, for example, alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide; alkali metal carbonates such as lithium carbonate, sodium carbonate, potassium carbonate, and cesium carbonate; alkali metal bicarbonates such as sodium bicarbonate and potassium bicarbonate; alkaline earth metal hydroxides such as calcium hydroxide; alkaline earth metal carbonates such as calcium carbonate; alkaline earth metal bicarbonates such as calcium bicarbonate; ammonia; ammonium carbonate; ammonium bicarbonate; metal alkoxides such as sodium methoxy, potassium methoxy, sodium ethoxy, potassium ethoxy, and tert-butoxysodium. One alkali may be used alone, or two or more alkalis may be used in combination.

[0083] From the viewpoint of availability and ease of handling, the alkali is preferably selected from alkali metal hydroxides and alkaline earth metal hydroxides, more preferably from alkali metal hydroxides, and even more preferably from sodium hydroxide.

[0084] The aqueous solvent can be selected from, for example, water, hydrophilic organic solvents, or mixed solvents of water and hydrophilic organic solvents. The hydrophilic organic solvent can be selected from, for example, lower alcohols having 1 to 5 carbon atoms such as methyl alcohol, ethyl alcohol, n-propanol, and 2-propanol; lower aliphatic ketones such as acetone and methyl ethyl ketone; and polyhydric alcohols having 2 to 5 carbon atoms such as 1,3-butylene glycol, propylene glycol, and glycerin. One type of hydrophilic organic solvent may be used alone, or two or more types of hydrophilic organic solvents may be used in combination.

[0085] From the viewpoint of ease of handling, the aqueous solvent is preferably water or a mixed solvent of water and a hydrophilic organic solvent, and more preferably water.

[0086] From the viewpoint of suppressing the dissolution of the gel's constituent skeleton, the alkali concentration in the alkaline solution is preferably 0.01 mol / L or more and 10 mol / L or less, more preferably 0.05 mol / L or more and 5 mol / L or less, and even more preferably 0.1 mol / L or more and 1 mol / L or less. Each of the above lower limits may be combined with any of the above upper limits.

[0087] In one embodiment, the alkaline solution is an aqueous solution of an alkali metal hydroxide (preferably sodium hydroxide).

[0088] <Impregnation Treatment> The impregnation treatment will be explained below. Two or more of the features of the impregnation treatment described below can be combined.

[0089] In step (a), the starting gel is impregnated with an alkaline solution, thereby obtaining an impregnated gel.

[0090] In the impregnation-treated gel obtained in step (a), the ratio of the mass of the alkaline solution contained in the impregnation-treated gel to the dry mass of the impregnation-treated gel (hereinafter referred to as the "solid-liquid ratio of the impregnation-treated gel") is 0.01 or more and 1.50 or less. Preferably, the solid-liquid ratio of the impregnation-treated gel is 0.05 or more and 1.40 or less, more preferably 0.08 or more and 1.30 or less, and even more preferably 0.10 or more and 1.20 or less. Each of the above lower limits may be combined with any of the above upper limits. The solid-liquid ratio of the impregnation-treated gel can be calculated by the method described in the examples. In the impregnation treatment, all or most of the water contained in the starting gel is replaced with the alkaline solution, so a solid-liquid ratio of the impregnation-treated gel being within the above range means that the impregnation-treated gel contains a sufficient amount of alkaline solution to form the desired micropores in the gel skeleton. Therefore, when the solid-liquid ratio of the impregnation-treated gel is within the above range, a porous body with desired micropores and increased bulk density can be obtained in step (c). Furthermore, unlike the reflux treatment, if the solid-liquid ratio of the impregnated gel is within the above range, no large amount of waste liquid is generated. The solid-liquid ratio of the impregnated gel can be controlled, for example, by adjusting the contact time between the starting gel and the alkaline solution, the mass of the alkaline solution impregnated into the starting gel, etc.

[0091] The impregnation treatment can be carried out, for example, by immersing the starting gel in an alkaline solution, or by dropping, coating, or spraying the starting gel with an alkaline solution. The impregnation treatment may also be carried out by combining two or more methods.

[0092] When obtaining an impregnated gel by immersing the starting gel in an alkaline solution, the alkaline solution used for immersion (the alkaline solution remaining after the impregnated gel has been separated) can be used for another new impregnation treatment. Therefore, unlike the reflux treatment, no large amount of waste liquid is generated.

[0093] When an impregnated gel is obtained by dropping, coating, or spraying an alkaline solution onto a starting gel, the remaining alkaline solution that was not dropped, coated, or sprayed can be used for another new impregnation treatment. Therefore, unlike the reflux treatment, no large amount of waste liquid is generated.

[0094] The impregnation treatment is carried out so that the starting gel is impregnated with an amount of alkaline solution sufficient to form micropores in the gel's framework. Specifically, the impregnation treatment is carried out so that the solid-liquid ratio of the impregnated gel falls within the range described above.

[0095] When immersing the starting gel in an alkaline solution, the immersion time is adjusted so that the starting gel is impregnated with a sufficient amount of alkaline solution to form micropores in the gel's framework. Specifically, the immersion time is adjusted so that the solid-liquid ratio of the impregnated gel falls within the above range. The immersion time is preferably 30 minutes or more, more preferably 60 minutes or more, and even more preferably 120 minutes or more. The upper limit of the immersion time can be adjusted as appropriate. From the viewpoint of manufacturing efficiency, the upper limit of the immersion time is, for example, 200 minutes or less.

[0096] When adding, coating, or spraying an alkaline solution onto a starting gel, the amount of alkaline solution added, coated, or sprayed is adjusted so that the starting gel is impregnated with a sufficient amount of alkaline solution to form micropores in the gel's framework. Specifically, the amount of alkaline solution added, coated, or sprayed is adjusted so that the solid-liquid ratio of the impregnated gel falls within the above range.

[0097] <Step (b)> Step (b) is a step in which the impregnation-treated gel obtained in step (a) is heated in a gas.

[0098] The heat treatment of the impregnation-treated gel must be performed while the impregnation-treated gel is in a gaseous state. For example, in step (a), when an impregnation-treated gel is obtained by immersing the starting gel in an alkaline solution, it is necessary to separate the impregnation-treated gel from the alkaline solution, leave the separated impregnation-treated gel in a gaseous state, and then perform the heat treatment on the impregnation-treated gel.

[0099] Embodiments in which the impregnated gel is in a liquid during the heat treatment are not included in step (b). In conventional methods, a reflux treatment is performed in which the gel and a micropore-forming agent (e.g., urea) are reacted under reflux conditions to form micropores in the gel's framework. During the reflux treatment, the gel is in a liquid. Therefore, the reflux treatment in conventional methods is not included in step (b).

[0100] Porous materials obtained through reflux heating have low bulk density. In contrast, the present invention makes it possible to obtain porous materials with high bulk density by going through step (b). Furthermore, in conventional reflux heating methods, the entire solution, including the solution portion that does not actually contribute to the reaction (and therefore does not need to be heated), must be heated, resulting in low energy efficiency. In contrast, step (b) heats the alkaline solution contained in the impregnation gel (i.e., the alkaline solution that actually contributes to the reaction), resulting in high energy efficiency.

[0101] In the heat treatment of the impregnation-treated gel, the heating temperature is preferably 50°C to 250°C, more preferably 70°C to 230°C, and even more preferably 80°C to 200°C. Each of the above lower limits may be combined with any of the above upper limits. The heating time can be appropriately adjusted according to the conditions of the heat treatment. When the heating temperature of the impregnation-treated gel is within the above range, the desired micropores are formed, and a porous body with increased bulk density can be obtained.

[0102] The heat treatment of the impregnation-treated gel is carried out in a gaseous environment. That is, the heat treatment of the impregnation-treated gel is carried out in an environment filled with gas (hereinafter referred to as "atmosphere"). Examples of atmospheres include an oxidizing atmosphere and an inert atmosphere. An oxidizing atmosphere is an atmosphere containing one or more oxidizing gases. In addition to one or more oxidizing gases, an oxidizing atmosphere may also contain one or more other gases (for example, one or more inert gases). An inert atmosphere is an atmosphere composed of one or more inert gases. Examples of oxidizing gases include air (atmosphere), oxygen, water vapor, and mixtures of two or more of these. Examples of inert gases include nitrogen gas, carbon dioxide gas, argon gas, and mixtures of two or more of these.

[0103] The heat treatment of the impregnated gel may be carried out while humidifying the impregnated gel. For example, the heat treatment of the impregnated gel may be carried out while supplying water vapor to the impregnated gel, or the heat treatment of the impregnated gel may be carried out with water present in the container containing the impregnated gel (however, the water is not in contact with the impregnated gel).

[0104] From the viewpoint of efficiently obtaining a porous body in which desired micropores are formed and bulk density is increased, it is preferable that the heating of the impregnation-treated gel in a gas is carried out in such a way that the rate of mass change of the impregnation-treated gel before and after heating (hereinafter referred to as "mass change rate G") is small (i.e., the evaporation of the alkaline solution from the impregnation-treated gel is suppressed).

[0105] The mass change rate G is preferably 85.00% or less, more preferably 50.00% or less, even more preferably 25.00% or less, and particularly preferably 2.00% or less. The lower limit of the mass change rate G is not particularly limited. For example, the mass change rate G is 0.05% or more. When the mass change rate G is within the above range, a porous body with desired micropores and increased bulk density can be efficiently obtained. The mass change rate G can be calculated from the following formula: Mass change rate G = ((Mass of impregnated gel before heating) - (Mass of impregnated gel after heating)) / (Mass of impregnated gel before heating) × 100

[0106] Heat treatment of impregnated gel is usually performed with the impregnated gel contained in a container. In this case, the atmosphere inside the container corresponds to the atmosphere in which the heat treatment of the impregnated gel is performed. As containers, gas barrier containers, autoclaves with liners, etc., can be used. Examples of materials for gas barrier containers include plastic, metal, and glass. Examples of plastics include polyethylene, polypropylene, polyvinylidene chloride, ethylene vinyl alcohol copolymer, polyacrylonitrile, and nylon. When using an autoclave with a liner, the heat treatment of the impregnated gel is performed with the impregnated gel contained in the liner. In this case, the atmosphere inside the liner corresponds to the atmosphere in which the heat treatment of the impregnated gel is performed. Examples of liner materials include heat-resistant materials such as polytetrafluoroethylene (PTFE).

[0107] The heat treatment of the impregnated gel is preferably carried out under conditions that maintain the presence of the alkaline solution in the impregnated gel.

[0108] In one embodiment, the heat treatment of the impregnation gel is performed with the impregnation gel contained in a sealed container (hereinafter sometimes referred to as "sealed container"). For example, the container containing the impregnation gel can be sealed by placing a sealed lid on it. Specific examples of the material of the sealed lid are the same as specific examples of the material of the container. The pressure inside the sealed container during the heat treatment is usually the saturated vapor pressure of the alkaline solution contained in the impregnation gel corresponding to the heat treatment temperature, or a pressure exceeding that. As a sealed container, for example, an autoclave with a liner can be used. When using an autoclave with a liner, the heat treatment of the impregnation gel is performed with the impregnation gel contained in a sealed liner. The pressure inside the liner during the heat treatment is usually the saturated vapor pressure of the alkaline solution contained in the impregnation gel corresponding to the heat treatment temperature, or a pressure exceeding that.

[0109] In another embodiment, the heat treatment of the impregnation-treated gel is performed with the impregnation-treated gel contained in an open container (hereinafter sometimes referred to as "open container"). For example, the container can be made open by not covering the container containing the impregnation-treated gel, or by covering the container containing the impregnation-treated gel with a lid having holes. The holes in the lid function as holes for releasing vapor from inside the container. Examples of lids with holes include airtight lids with holes formed in them, porous lids (e.g., paper), and the like.

[0110] The heat treatment of the impregnated gel can be carried out, for example, using a heating furnace. The type of heating furnace is not particularly limited, and examples of heating furnaces include kilns and belt furnaces.

[0111] <Step (c)> Step (c) is a step in which the impregnated gel after heating is fired at a temperature higher than the heating temperature in step (b) to obtain a porous body.

[0112] The impregnated gel after heating may be washed before firing. Alternatively, the impregnated gel after heating may be dried after washing.

[0113] Specific examples of cleaning solutions used to clean impregnated gels after heating are similar to the specific examples of cleaning solutions used to clean gels obtained in the gel manufacturing process.

[0114] Examples of drying methods include natural drying, heat drying, drying using low surface tension solvents, drying by freeze-sublimation, and supercritical drying.

[0115] In the firing of the impregnated gel after heating, the firing temperature is higher than the heating temperature in step (b). From the viewpoint of sufficiently removing water contained in the impregnated gel, the difference between the firing temperature and the heating temperature in step (b) (firing temperature - heating temperature in step (b)) is preferably 10°C or more, more preferably 20°C or more, and even more preferably 40°C or more. From the viewpoint of suppressing pore blockage due to sintering, the difference between the firing temperature and the heating temperature in step (b) is preferably 700°C or less, more preferably 600°C or less, and even more preferably 500°C or less. Each of the above lower limits may be combined with any of the above upper limits. In one embodiment, the firing temperature is preferably 200°C or more and 700°C or less, more preferably 300°C or more and 650°C or less. In one embodiment, the firing time is preferably 3 hours or more and 12 hours or less. Firing is usually carried out in an air atmosphere.

[0116] The porous body (ceramic monolith) obtained in step (c) has a co-continuous structure formed by a ceramic skeleton containing micropores and coarse pores. The ceramic skeleton of the porous body is formed from the skeletal phase of the gel, and the coarse pores of the porous body are formed from the solvent phase of the gel.

[0117] Examples of ceramic monoliths include silica monoliths, alumina monoliths, tin oxide monoliths, ceria monoliths, titania monoliths, and zirconia monoliths. Each of these ceramic monoliths has a ceramic framework containing micropores, such as a silica framework, alumina framework, tin oxide framework, ceria framework, titania framework, and zirconia framework, and also has a co-continuous structure formed by the ceramic framework containing micropores and coarse pores.

[0118] The porous material obtained in step (c) may be subjected to processes such as molding and grinding. Grinding can be carried out according to conventional methods. Grinding can be carried out using, for example, a mortar and pestle, hammer mill, ball mill, bead mill, jet mill, roller mill, etc.

[0119] The porous material of the present invention can be used in a wide range of applications, such as chromatography separation columns, enzyme carriers, catalyst carriers, and adsorbents.

[0120] Examples and comparative examples are described below. Unless otherwise specified, the operations in the examples and comparative examples were carried out at room temperature.

[0121] [Example 1] (1) In a starting gel preparation container (150 mL stainless steel can), polyacrylic acid (Fujifilm Wako Pure Chemical Industries) with a weight-average molecular weight of 25,000 (hereinafter referred to as "HPAA") was dissolved in water, then concentrated nitric acid was added and the mixture was stirred. Water glass (sodium silicate concentration: approximately 38 wt%) was added to the resulting solution and stirred to obtain a homogeneous sol. The composition of the preparation was water:concentrated nitric acid:HPAA:water glass = 97:37:6.5:55 by weight ratio. The sol was allowed to stand at 30°C for 1 hour to gel and obtain a polysiloxane gel. The obtained polysiloxane gel was pulverized and classified using a sieve with a mesh size of 850 μm to obtain pulverized polysiloxane gel with a particle size of 1 to 2 cm. The obtained pulverized polysiloxane gel was washed with water until the Na concentration of the washing solution reached 500 ppm, and then immersed in water for 24 hours. After immersion, the gel was collected using a sieve to remove excess liquid adhering to the gel, thereby obtaining a starting gel having a co-continuous structure formed by the skeletal phase and the solvent phase. The obtained starting gel was subjected to heat treatment (80°C for 720 minutes) and then used in (2) below.

[0122] (2) Impregnation treatment of the starting gel: 0.70 g of alkaline solution was added to a polypropylene container, then 67.06 g of the starting gel was added and the starting gel was immersed in the alkaline solution. By immersing at room temperature for 30 minutes, the starting gel was impregnated with the alkaline solution and an impregnated gel was obtained. A 0.25 mol / L aqueous sodium hydroxide solution was used as the alkaline solution.

[0123] (3) Heat treatment of impregnation gel The sodium hydroxide aqueous solution was removed from the polypropylene container, leaving only the impregnation gel inside the polypropylene container. After sealing the polypropylene container with a polypropylene lid, the impregnation gel inside the polypropylene container was heated at 90°C for 3 hours in an air atmosphere inside the polypropylene container, i.e., in a gaseous state.

[0124] The rate of change in mass of the impregnated gel before and after heating was calculated from the difference between the mass of the impregnated gel before heating and the mass of the impregnated gel after heating (= (mass of impregnated gel before heating - mass of impregnated gel after heating) / mass of impregnated gel before heating × 100).

[0125] (4) Preparation of silica monoliths (porous material) The impregnated gel after heating was washed with water and then dried using a dryer. The purpose of this drying process is to remove water adhering to the gel after washing and is not included in the heating process of the impregnated gel. The dried impregnated gel was fired at 600°C for 3 hours in an air atmosphere to obtain silica monoliths.

[0126] Observation of the surface structure of the obtained silica monolith using a scanning electron microscope (JSM-7900F from JEOL) confirmed that the silica monolith has a co-continuous structure formed by a silica framework and coarse pores.

[0127] (5) Measurement of micropore volume, coarse pore volume, and total pore volume in silica monoliths The pore volume of micropores in the silica monoliths obtained in (4) above was calculated using the BJH method. The calculation was performed by determining the adsorption isotherm using a specific surface area and pore distribution analyzer (BELSORP-miniX, Microtrac-Bell), and then using the determined adsorption isotherm as the basis. Specifically, for silica monolith samples that had been degassed under reduced pressure at 400°C for 3 hours, the amount of nitrogen adsorbed at a temperature of 77K using liquid nitrogen was measured using the multipoint method, and the adsorption isotherm was determined. Based on the adsorption isotherm, the pore volume of micropores was calculated. The BJH method is a method for analyzing the distribution of pore volume with respect to the diameter of pores assumed to be cylindrical according to the Barrett-Joyner-Halenda standard model (see J. Amer. Chem. Soc., 73, 373, 1951, etc. for details). In the BJH method, analysis was performed on pores with a diameter of 1.0 nm to 1000.0 nm, the pore volume of the micropores was calculated, and the total pore volume of the micropores (mL / g) was defined as the "micropore volume."

[0128] Using a mercury porosimeter (AutoPore IV 9520, Micromeritics), the coarse pore volume and total pore volume of the silica monolith obtained in (4) above were evaluated by the mercury intrusion method. In the mercury intrusion method, pressure was applied to the pores of the sample to infiltrate mercury, and the pore volume and specific surface area were calculated from the pressure and the amount of mercury injected. Assuming the pores were cylindrical, the pore diameter was calculated from the relationship between the calculated pore volume and specific surface area. The evaluation of the coarse pore volume and total pore volume was performed using the results measured in the pore range having a diameter of 1.0 nm to 1,000,000.0 nm. The pore volume of coarse pores was evaluated based on the results measured in the pore range having a diameter of 200.0 nm to 1,000,000.0 nm, and the total pore volume of coarse pores (mL / g) was defined as the "coarse pore volume". The total pore volume was evaluated based on measurements taken within the pore range having a diameter of 1.0 nm to 1,000,000.0 nm, and the total pore volume (mL / g) was defined as the "total pore volume." The mercury intrusion method was performed under the following conditions and procedure. When evaluating the coarse pore volume and total pore volume using the mercury intrusion method, pores originating from peaks with a peak volume of less than 0.01 mL / g in the obtained pore distribution map were not used in the evaluation, considering the measurement accuracy.

[0129] (Conditions for the mercury intrusion method) ・Mercury parameters: Forward contact angle: 130.0° Reverse contact angle: 130.0° Surface tension: 485.0 mN / m (485.0 dynes / cm) Mercury density: 13.5335 g / mL ・Low pressure parameters: Exhaust pressure: 50 μmHg Exhaust time: 5.0 min Mercury injection pressure: 0.0034 MPa Equilibrium time: 10 seconds ・High pressure parameters: Equilibrium time: 10 seconds ・Injection volume: Adjusted to be between 25% and 90% ・Measurement environment: 25℃

[0130] (Procedure for mercury intrusion method) (i) Weigh approximately 0.05 to 0.1 g of sample and place it in the sample cell, then input the weighed value. (ii) Measure the low-pressure section in the range of 0.0048 to 0.2068 MPa. (iii) Measure the high-pressure section in the range of 0.2241 to 255.1060 MPa. (ii) and (iii) were performed automatically using the software attached to the device.

[0131] (6) Measurement of the most frequent pore size of micropores and coarse pores in silica monoliths The most frequent pore size of micropores was calculated using the BJH method. The calculation was performed by determining the adsorption isotherm using a specific surface area and pore distribution analyzer (BELSORP-miniX, Microtrac-Bell), and then using the obtained adsorption isotherm as the basis. Specifically, for silica monolith samples that had been degassed under reduced pressure at 400°C for 3 hours, the amount of nitrogen adsorbed at a temperature of 77K using liquid nitrogen was measured using a multipoint method, and the adsorption isotherm was determined. Based on the adsorption isotherm, the most frequent pore size of micropores was calculated. The BJH method is a method for analyzing the distribution of pore volume with respect to pore diameter, assuming a cylindrical shape according to the Barrett-Joyner-Halenda standard model (see J. Amer. Chem. Soc., 73, 373, 1951, etc. for details). In the BJH method, analysis was performed on pores with diameters between 1.0 nm and 1000.0 nm, and the most frequent pore diameter of the micropores was calculated.

[0132] The most frequent pore diameter of coarse pores was calculated using the mercury intrusion method. In the mercury intrusion method, assuming the pores were cylindrical, the pore diameter was measured from the relationship between the pore volume and specific surface area measured in (5) above. In the mercury intrusion method, analysis was performed on pores with diameters between 1.0 nm and 1,000,000.0 nm to calculate the most frequent pore diameter of coarse pores. When calculating the most frequent pore diameter of coarse pores using the mercury intrusion method, pores originating from peaks with a peak volume of less than 0.01 mL / g in the obtained pore distribution map were not used in the calculation, considering the measurement accuracy.

[0133] (7) Measurement of the bulk density of the silica monolith The bulk density of the silica monolith was calculated using the mercury intrusion method. The bulk density of the silica monolith (g / cm³) was calculated by dividing the mass of the silica monolith measured by a weighing scale by the volume of the silica monolith calculated from the total pore volume of the silica monolith and the amount of mercury intruded. ３ The following was calculated. Pores originating from peaks with a peak volume of less than 0.01 mL / g at the top of the obtained pore distribution map were not used in the calculation, taking into consideration the measurement accuracy.

[0134] (8) Measurement of specific surface area in silica monoliths Using a specific surface area and pore distribution measuring device (BELSORP-miniX manufactured by Microtrac-Bel), measure the specific surface area (m²) of the silica monolith obtained in (4) above. ２ The nitrogen adsorption amount (per g) was measured. For silica monolith samples degassed under reduced pressure at 400°C for 3 hours, the nitrogen adsorption amount at a temperature of 77 K was measured using a multipoint method with liquid nitrogen, and the adsorption isotherm was determined. Based on the adsorption isotherm, the specific surface area was calculated. The specific surface area was calculated using the BET method.

[0135] (9) Preparation of the dried starting gel The starting gel was obtained in the same manner as in (1) above. The starting gel was dried at 80°C for 12 hours using a drying oven to obtain the dried starting gel.

[0136] (10) Measurement of the specific surface area of ​​the dried starting gel The specific surface area (m²) of the dried starting gel obtained in (9) above ２ The amount ( / g) was measured in the same manner as in (8) above.

[0137] (11) Measurement of moisture content and solid content of the starting gel A starting gel was obtained in the same manner as in (1) above. The moisture content of the starting gel was measured by the dry weight method using a heat drying type moisture meter (MX-50, manufactured by A&D Co., Ltd.). The measurement was performed on the gel that was collected by sieving after being immersed in water for 30 minutes. Specifically, 0.5 g of the starting gel after being immersed in water was heated at 180°C, and the moisture content (= ((initial mass of the starting gel) - (dry mass of the starting gel)) / (initial mass of the starting gel) × 100) and solid content (= ((dry mass of the starting gel) / (initial mass of the starting gel) × 100) were determined from the mass of the starting gel before drying (hereinafter referred to as the "initial mass of the starting gel") and the mass of the starting gel after drying (hereinafter referred to as the "dry mass of the starting gel"). The mass at which the weight change rate detected by the moisture meter became 0.05% / min or less was taken as the dry mass of the starting gel.

[0138] (12) Calculation of the solid-liquid ratio of the impregnated gel The ratio of the mass of the alkaline solution contained in the impregnated gel to the dry mass of the impregnated gel (hereinafter referred to as the "solid-liquid ratio of the impregnated gel") was determined. When determining the solid-liquid ratio of the impregnated gel, the mass obtained from the formula: (initial mass of the starting gel) × (solid content of the starting gel / 100) was used as the "dry mass of the impregnated gel". In addition, assuming that all the water contained in the starting gel is replaced with the alkaline solution during the impregnation process, the mass obtained from the formula: (initial mass of the starting gel) × (moisture content of the starting gel / 100) × (specific gravity of the alkaline solution (25°C)) was used as the "mass of the alkaline solution contained in the impregnated gel".

[0139] The results of Example 1 are shown in Tables 1 to 3. In Table 1, "SSA" is the specific surface area (m²) of the silica monolith. ２ ( / g), "SSA ratio" represents the ratio of the specific surface area of ​​the silica monolith to the specific surface area of ​​the dried starting gel. In Table 2, "SSA" represents the specific surface area (m²) of the dried starting gel. ２ This represents the volume per gram ( / g). Note that the micropore volume was below the detection limit of the measuring device, so it is indicated as "0.00".

[0140] [Example 2] The same procedure as in Example 1 was followed, except that in "(1) Preparation of the starting gel" and "(2) Impregnation treatment of the starting gel," the amount of alkaline solution added to the polypropylene container was changed to 3.70 g. The results of Example 2 are shown in Tables 1 to 3.

[0141] [Example 3] In Example 3, the same procedure as in Example 1 was followed, except that in "(1) Preparation of the starting gel" and "(2) Impregnation treatment of the starting gel," the amount of alkaline solution added to the polypropylene container was changed to 5.85 g. The results of Example 3 are shown in Tables 1 to 3.

[0142] [Comparative Example 1] The same procedure as in Example 1 was followed, except that steps (2) Impregnation treatment of the starting gel and (3) Heat treatment of the impregnated gel were not performed, and instead a reflux treatment of the starting gel was performed; in (4) Preparation of silica monolith (porous body), the gel after reflux treatment was used instead of the impregnated gel after heating; the rate of change of the gel before and after reflux treatment (= (mass of starting gel - mass of gel after reflux treatment) / mass of starting gel × 100) was determined from the difference between the mass of the starting gel and the mass of the gel after reflux treatment; in (11) Measurement of moisture content and solid content of the starting gel, the moisture content and solid content of the starting gel were measured without immersing the starting gel in water; and the solid-liquid ratio of the gel in reflux treatment was calculated as follows instead of the solid-liquid ratio of the impregnated gel. The reflux treatment was carried out by adding 20.16 g of the starting gel to a reaction vessel containing 30.0 mL of alkaline solution and heating under reflux at 90°C for 3 hours. A 0.50 mol / L aqueous sodium hydroxide solution was used as the alkaline solution. The results for Comparative Example 1 are shown in Tables 1 to 3. The mass change rate of the gel before and after the reflux treatment was 48.27% by mass.

[0143] The ratio of the mass of the alkaline solution used in the reflux treatment to the dry mass of the starting gel was determined and used as the solid-liquid ratio of the gel during the reflux treatment. The mass obtained from the formula: (initial mass of starting gel) × (solid content of starting gel / 100) was used as the "dry mass of the starting gel". The mass of the alkaline solution used in the reflux treatment was calculated using the specific gravity of the alkaline solution at 25°C.

[0144] [Comparative Example 2] The same procedure as in Example 1 was followed, except that in "(1) Preparation of the starting gel," no heat treatment was performed on the starting gel; in "(2) Impregnation treatment of the starting gel," a 0.10 mol / L aqueous sodium hydroxide solution was used as the alkaline solution; and in "(11) Measurement of the moisture content and solid content of the starting gel," the moisture content and solid content of the starting gel were measured without immersing the starting gel in water. The results of Comparative Example 2 are shown in Tables 1 to 3.

[0145] [Comparative Example 3] The same procedure as in Example 1 was followed, except that in "(1) Preparation of the starting gel," no heat treatment was performed on the starting gel, and in "(11) Measurement of the moisture content and solid content of the starting gel," the moisture content and solid content of the starting gel were measured without immersing the starting gel in water. The results of Comparative Example 3 are shown in Tables 1 to 3.

[0146] [Comparative Example 4] The same procedure as in Comparative Example 3 was performed, except that the heating time was changed to 1 hour in "(3) Heat treatment of impregnated gel". The results of Comparative Example 4 are shown in Tables 1 to 3.

[0147] [Comparative Example 5] The same procedure as in Comparative Example 3 was performed, except that the heating temperature was changed to 60°C in "(3) Heat treatment of impregnated gel". The results of Comparative Example 5 are shown in Tables 1 to 3.

[0148]

[0149]

[0150]

[0151] 1...Ceramic framework 2...Coarse pores 3...Micropores

Claims

1. A porous body having a co-continuous structure formed by a ceramic framework containing micropores and coarse pores, wherein the most frequent pore size of the micropores in the porous body is 1.0 nm or more and less than 200.0 nm, and the bulk density of the porous body is 0.50 g / cm³. ３ 2.00g / cm or more ３ The porous body is as follows:

2. The porous body according to claim 1, wherein the most frequent pore size of the coarse pores in the porous body is 200.0 nm or more and 10000.0 nm or less.

3. The specific surface area of ​​the porous body is 40 m². ２ / g or more 800m ２ A porous body according to claim 1 or 2, wherein the amount is less than or equal to / g.

4. A method for producing a porous body according to claim 1 or 2, comprising the following steps: (a) impregnating a starting gel having a co-continuous structure formed by a skeletal phase and a solvent phase with an alkaline solution to obtain an impregnated gel; (b) heating the impregnated gel in a gas; (c) firing the impregnated gel after heating at a temperature higher than the heating temperature in step (b) to obtain the porous body, wherein in the impregnated gel obtained in step (a), the ratio of the mass of the alkaline solution contained in the impregnated gel to the dry mass of the impregnated gel is 0.01 or more and 1.50 or less.

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