Solid acid catalyst and organic reaction method using said solid acid catalyst

Abstract

The present invention addresses the problem of providing: a solid acid catalyst having improved reaction efficiency and liquid permeability; and an organic reaction method using the solid acid catalyst. In order to solve the problem, the present invention provides a solid acid catalyst comprising a sulfo group-modified porous body that contains a porous body having a bicontinuous structure formed by macropores (2) and a ceramic framework (1) including mesopores (3), and a sulfo group that modifies the surface of the ceramic framework (1). The mode pore diameter of the macropores of the sulfo group-modified porous body is 200.0-5000.0 nm.

Description

Solid acid catalyst and organic reaction method using the solid acid catalyst

[0001] The present invention relates to a solid acid catalyst and an organic reaction method using the solid acid catalyst.

[0002] Non-patent document 1 discloses a method for the continuous production of butyl acetate and butyl lactate using a silica monolith modified with sulfo groups as a solid acid catalyst, and patent document 1 discloses a method for the continuous production of carboxylic acid esters using a porous silica gel modified with sulfo groups as a solid acid catalyst.

[0003] Applied Catalysis A: General, 489 (2015), pp. 203-208

[0004] Japanese Patent Publication No. 2017-197502

[0005] Methods for producing chemical substances using solid acid catalysts are broadly classified into batch methods and flow methods. The batch method involves adding reactants, a solid acid catalyst, and a solvent to a container, allowing the reaction to produce the target substance from the reactants to proceed within the container, and then recovering the target substance from the container. The flow method involves introducing a mixture containing reactants and a solvent into a reactor filled with a solid acid catalyst, allowing the reaction to produce the target substance from the reactants to proceed within the reactor, and then discharging the mixture containing the target substance and solvent from the reactor. Compared to the batch method, the flow method has advantages such as higher energy efficiency, lower waste generation, higher productivity of the target substance, and suitability for mass production of the target substance.

[0006] As disclosed in Non-Patent Document 1 and Patent Document 1, the use of sulfo-modified porous silica as a solid acid catalyst is known. However, conventional sulfo-modified porous silica had room for improvement in terms of reaction efficiency, whether used as a solid acid catalyst in batch or flow methods.

[0007] In addition, since conventional sulfonic acid group-modified porous silica has low liquid permeability, when performing a flow method using a reactor filled with conventional sulfonic acid group-modified porous silica, the pressure loss is large. When the pressure loss is large, the flow velocity and flow rate decrease, resulting in a decrease in energy efficiency, a decrease in the contact efficiency between the reactant and the sulfonic acid group, and a consequent decrease in reaction efficiency. Therefore, there was room for improvement in terms of liquid permeability for conventional sulfonic acid group-modified porous silica.

[0008] Therefore, an object of the present invention is to provide a solid acid catalyst with improved reaction efficiency and liquid permeability, and an organic reaction method using the solid acid catalyst.

[0009] To solve the above problems, the present invention provides the following inventions: [1] A solid acid catalyst comprising a porous body having a co-continuous structure formed by a ceramic skeleton containing mesopores and macropores, and a sulfogroup-modified porous body comprising sulfogroups modifying the surface of the ceramic skeleton, wherein the most frequent pore size of the macropores of the sulfogroup-modified porous body is 200.0 nm or more and 5000.0 nm or less. [2] The solid acid catalyst according to [1], wherein the most frequent pore size of the mesopores of the sulfogroup-modified porous body is 2.0 nm or more and 50.0 nm or less. [3] The solid acid catalyst according to [1] or [2], wherein the amount of sulfur atoms contained in the sulfogroup-modified porous body is 0.10 mmol / g or more and 5.00 mmol / g or less. [4] The solid acid catalyst according to any one of [1] to [3], wherein the ratio of the most frequent pore size of the macropores of the sulfogroup-modified porous body to the most frequent pore size of the mesopores of the sulfogroup-modified porous body is 15.0 or more and 300.0 or less. [5] The solid acid catalyst according to any one of [1] to [4], wherein the ceramic skeleton comprises one or more elements selected from silicon, aluminum, tin, cerium, titanium, and zirconium. [6] The solid acid catalyst according to any one of [1] to [5], wherein the solid acid catalyst is a solid acid catalyst for organic reactions. [7] The solid acid catalyst according to [6], wherein the organic reaction is selected from an esterification reaction, a trans-esterification reaction, an ester hydrolysis reaction, and a Ritter reaction. [8] An organic reaction method comprising the step of carrying out an organic reaction using the solid acid catalyst according to any one of [1] to [5]. [9] The organic reaction method according to [8], wherein the organic reaction is selected from an esterification reaction, a trans-esterification reaction, an ester hydrolysis reaction, and a Ritter reaction.

[10] Use as a solid acid catalyst for a sulfogroup-modified porous body comprising a porous body having a co-continuous structure formed by a ceramic skeleton including mesopores and macropores, and sulfogroups modifying the surface of the ceramic skeleton, wherein the most frequent pore size of the macropores of the sulfogroup-modified porous body is 200.0 nm or more and 5000.0 nm or less.

[11] Use according to

[10] , wherein the most frequent pore size of the mesopores of the sulfogroup-modified porous body is 2.0 nm or more and 50.0 nm or less.

[12] The use according to

[10] or

[11] , wherein the amount of sulfur atoms contained in the sulfo-modified porous body is 0.10 mmol / g or more and 5.00 mmol / g or less.

[13] The use according to any one of

[10] to

[12] , wherein the ratio of the most frequent pore diameter of the macropores of the sulfo-modified porous body to the most frequent pore diameter of the mesopores of the sulfo-modified porous body is 15.0 or more and 300.0 or less.

[14] The use according to any one of

[10] to

[13] , wherein the ceramic skeleton contains one or more elements selected from silicon, aluminum, tin, cerium, titanium and zirconium.

[15] The use according to any one of

[10] to

[14] , wherein the solid acid catalyst is a solid acid catalyst for organic reactions.

[16] The use according to

[15] , wherein the organic reaction is selected from esterification reactions, trans-esterification reactions, hydrolysis reactions of esters and Ritter reactions.

[17] A use for producing a solid acid catalyst of a sulfogroup-modified porous body comprising a porous body having a co-continuous structure formed by a ceramic skeleton containing mesopores and macropores, and sulfogroups modifying the surface of the ceramic skeleton, wherein the most frequent pore size of the macropores of the sulfogroup-modified porous body is 200.0 nm or more and 5000.0 nm or less.

[18] The use according to

[17] , wherein the most frequent pore size of the mesopores of the sulfogroup-modified porous body is 2.0 nm or more and 50.0 nm or less.

[19] The use according to

[17] or

[18] , wherein the amount of sulfur atoms contained in the sulfogroup-modified porous body is 0.10 mmol / g or more and 5.00 mmol / g or less.

[20] The use according to any one of

[17] to

[19] , wherein the ratio of the most frequent pore size of the macropores of the sulfogroup-modified porous body to the most frequent pore size of the mesopores of the sulfogroup-modified porous body is 15.0 or more and 300.0 or less.

[21] The use according to any one of

[17] to

[20] , wherein the ceramic skeleton comprises one or more elements selected from silicon, aluminum, tin, cerium, titanium, and zirconium.

[22] The use according to any one of

[17] to

[21] , wherein the solid acid catalyst is a solid acid catalyst for organic reactions.

[23] The use according to

[22] , wherein the organic reaction is selected from esterification reactions, trans-esterification reactions, hydrolysis reactions of esters, and Ritter reactions.

[0010] According to the present invention, there are provided a solid acid catalyst with improved reaction efficiency and liquid permeability, and an organic reaction method using the solid acid catalyst.

[0011] FIG. 1 is an enlarged view of a part of the surface of a porous body according to an embodiment. FIG. 2 is a schematic view showing the configuration of a flow reaction apparatus according to an embodiment.

[0012] <<Explanation of Terms>> The terms used in this specification will be explained below. The following explanations apply throughout this specification unless otherwise specified.

[0013] <Halogen Atom> The "halogen atom" includes a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0014] <Alkyl Group> The "alkyl group" is an alkyl group having, for example, 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, even more preferably 1 to 6 carbon atoms, still more preferably 1 to 5 carbon atoms, and particularly preferably 1 to 4 carbon atoms. The alkyl group may be linear or branched. The number of carbon atoms in the linear alkyl group is 1 or more, and the number of carbon atoms in the branched alkyl group is 3 or more.

[0015] <Aryl Group> The "aryl group" is, for example, a monocyclic or polycyclic (for example, bicyclic or tricyclic) aromatic hydrocarbon ring group. The number of carbon atoms in the aryl group is, for example, 6 to 14 carbon atoms, preferably 6 to 10 carbon atoms. The polycyclic may be a condensed ring type. Examples of the aryl group include a phenyl group, a naphthyl group, etc. The aryl group is preferably a phenyl group.

[0016] <Arylalkyl Group> The "arylalkyl group" is an alkyl group having one or more aryl groups, and the explanations regarding the "alkyl group" and the "aryl group" are as described above. The number of aryl groups contained in the arylalkyl group is, for example, 1 to 3, preferably 1 or 2, and more preferably 1.

[0017] <Alkylaryl Group> An "alkylaryl group" is an aryl group having one or more alkyl groups, and the explanations regarding "alkyl group" and "aryl group" are as described above. The number of alkyl groups contained in an alkylaryl group is, for example, 1 to 3, preferably 1 or 2, and more preferably 1.

[0018] <Alkyloxy Group> An "alkyloxy group" is a group represented by the formula: -O-alkyl group, and the explanation of "alkyl group" is as described above.

[0019] <Aryloxy group> The "aryloxy group" is a group represented by the formula: -O-aryl group, and the explanation of the "aryl group" is as described above.

[0020] <Arylalkyloxy group> The "arylalkyloxy group" is a group represented by the formula: -O-arylalkyl group, and the explanation of "arylalkyl group" is as described above.

[0021] <Alkylaryloxy Group> The "alkylaryloxy group" is a group represented by the formula: -O-alkylaryl group, and the explanation of the "alkylaryl group" is as described above.

[0022] <Alkylene Group and Arylene Group> The "alkylene group" and the "arylene group" are divalent functional groups produced by removing one hydrogen atom from an alkyl group and an aryl group, respectively. The explanations regarding the "alkyl group" and the "aryl group" are as described above.

[0023] <One or more substituents> "One or more substituents" preferably means one to three substituents, more preferably one or two substituents. Each of the one or more substituents can be independently selected from, for example, a hydroxyl group, a carboxyl group, a halogen atom, a phosphoric acid group, an oxo group, an alkyloxy group, an aryloxy group, an arylalkyloxy group, an alkylaryloxy group, etc.

[0024] ≪Sulfo-Modified Porous Materials≫ The following describes sulfo-modified porous materials. In this specification, a porous material before modification with sulfo groups is referred to as a "porous material" or "pre-modified porous material," and is distinguished from a porous material after modification with sulfo groups, which is a "sulfo-modified porous material."

[0025] The sulfo-modified porous material comprises a porous material having a co-continuous structure formed by a ceramic skeleton containing mesopores and macropores, and sulfo groups modifying the surface of the ceramic skeleton, wherein the most frequent pore size of the macropores in the sulfo-modified porous material is between 200.0 nm and 5000.0 nm.

[0026] Since sulfo groups function as acid catalysts, sulfo-modified porous materials can be used as solid acid catalysts or for manufacturing solid acid catalysts. Accordingly, according to one aspect of the present invention, a solid acid catalyst comprising a sulfo-modified porous material is provided; according to another aspect of the present invention, the use of a sulfo-modified porous material as a solid acid catalyst is provided; and according to yet another aspect of the present invention, the use of a sulfo-modified porous material for manufacturing solid acid catalysts is provided.

[0027] Reactions using a sulfo-modified porous material as a solid acid catalyst are not particularly limited, as long as the sulfo group can function as an acid catalyst in the reaction. In one embodiment, the reaction using the sulfo-modified porous material as a solid acid catalyst is an organic reaction. In an organic reaction, a target substance is produced from reactants under the influence of a solid acid catalyst. An organic reaction is a reaction in which at least one reactant is an organic compound. In one embodiment, the organic reaction is selected from esterification reactions, transesterification reactions, ester hydrolysis reactions, and Ritter reactions.

[0028] The presence of mesopores in the ceramic framework, the co-continuous structure of the porous material, and the most frequent pore size of the macropores in the sulfo-modified porous material being between 200.0 nm and 5000.0 nm improve the permeability of the reaction solution (a liquid containing components necessary for the reaction to produce the target substance, such as reactants) into the sulfo-modified porous material, thereby improving the contact efficiency between the reactants and the sulfo groups. Consequently, the reaction efficiency is improved whether the sulfo-modified porous material is used as a solid acid catalyst in either a batch or flow method. This improvement in reaction efficiency contributes to an increase in the yield of the target substance.

[0029] The co-continuous structure of the porous material and the most frequent pore size of the macropores in the sulfo-modified porous material being between 200.0 nm and 5000.0 nm improve the permeability of the sulfo-modified porous material, while preventing the reaction solution from passing through the material without sufficient contact with the sulfo groups due to excessive permeability. Therefore, when using a reactor packed with sulfo-modified porous material in a flow reaction, the pressure drop is small, thereby suppressing the decrease in energy efficiency, the decrease in contact efficiency between the reactants and the sulfo groups, and the resulting decrease in reaction efficiency that occur when the pressure drop is large. For this reason, sulfo-modified porous material is particularly suitable for use as a solid acid catalyst in flow reactions.

[0030] Due to the presence of mesopores in the ceramic framework and the co-continuous structure of the porous material, sulfo-modified porous materials have a large specific surface area. Therefore, sulfo-modified porous materials can adsorb water and remove it from the reaction system. For this reason, sulfo-modified porous materials are particularly useful as solid acid catalysts for reactions that produce a target substance and water from reactants. In reactions that produce a target substance and water from reactants, the removal of the generated water from the reaction system improves the reaction efficiency and increases the yield of the target substance. In particular, if the reaction that produces a target substance and water from reactants is a reversible reaction, the removal of the generated water from the reaction system suppresses the hydrolysis reaction of the generated target substance, thereby improving the reaction efficiency and increasing the yield of the target substance. An example of a reaction that produces a target substance and water from reactants is esterification. Esterification is a reaction that produces an ester and water from a carboxylic acid and an alcohol, but since this reaction is reversible, a hydrolysis reaction of the generated ester also occurs. In esterification reactions, the removal of water produced from the reaction system suppresses the hydrolysis of the resulting ester, thereby improving reaction efficiency and increasing the yield of the ester.

[0031] From the viewpoint of further improving reaction efficiency and liquid permeability, the most frequent pore size of the macropores in the sulfo-modified porous material is 200.0 nm or more and 5000.0 nm or less, preferably 400.0 nm or more and 4000.0 nm or less, more preferably 500.0 nm or more and 3000.0 nm or less, and even more preferably 600.0 nm or more and 2000.0 nm or less. Each of the above lower limits may be combined with any of the above upper limits.

[0032] The "most frequent pore size of the macropores in the sulfo-modified porous material" refers to the most frequent pore size of the macropores in the sulfo-modified porous material measured in the range of pore diameters from 50.0 nm to 500.0 μm by the mercury intrusion method, as described in the examples below.

[0033] The following describes other characteristics of sulfo-modified porous materials. The characteristic that the most frequent pore size of the macropores of the sulfo-modified porous material is within the above range can be combined with one or more of the other characteristics of sulfo-modified porous materials described below.

[0034] From the viewpoint of further improving reaction efficiency, the most frequent pore size of the mesopores in the sulfo-modified porous material is preferably 2.0 nm to 50.0 nm, more preferably 5.0 nm to 40.0 nm, and even more preferably 10.0 nm to 35.0 nm. Each of the above lower limits may be combined with any of the above upper limits.

[0035] The "most frequent pore size of mesopores in sulfo-modified porous material" refers to the most frequent pore size of mesopores in sulfo-modified porous material measured by the BJH method from nitrogen adsorption / desorption isotherms, as described in the examples below.

[0036] From the viewpoint of further improving reaction efficiency and liquid permeability, the ratio of the most frequent pore diameter of macropores in the sulfo-modified porous material to the most frequent pore diameter of mesopores is preferably 15.0 to 300.0, more preferably 20.0 to 200.0, and even more preferably 30.0 to 150.0. Each of the above lower limits may be combined with any of the above upper limits.

[0037] From the viewpoint of further improving reaction efficiency, the specific surface area of ​​the sulfo-modified porous material is preferably 100 m². ２ / g or more, more preferably 120m ２ / g or more, more preferably 130m ２ It is 1 / g or more. The upper limit of the specific surface area of ​​the sulfo-modified porous material is not particularly limited, but is typically 800 m ２ It is approximately / g. The specific surface area of ​​the sulfo-modified porous material is measured by the BET method from nitrogen adsorption / desorption isotherms, as described in the examples below.

[0038] From the viewpoint of further improving reaction efficiency and liquid permeability, the total pore volume of the sulfo-modified porous material is preferably 1.50 mL / g or more and 6.00 mL / g or less, more preferably 1.80 mL / g or more and 5.50 mL / g or less, and even more preferably 2.10 mL / g or more and 5.00 mL / g or less. Each of the above lower limits may be combined with any of the above upper limits. The total pore volume of the sulfo-modified porous material is measured by the mercury intrusion method as described in the examples below.

[0039] <Porous Materials> Porous materials will be described below. Two or more of the characteristics of porous materials described below can be combined.

[0040] The form of the porous body is not particularly limited. Examples of porous body forms include particles, lumps, molded bodies, etc. Furthermore, the shape of the porous body is not particularly limited. Examples of porous body shapes include columnar, spherical (e.g., perfect sphere, ellipsoid, etc.), needle-shaped, flaky (flake-like), polyhedral, flattened, fragmented, and lumpy. Examples of columnar shapes include cylindrical, elliptical, and polygonal prisms (e.g., quadrangular, hexagonal, octagonal, etc.). The columnar shape may also be a shape in which a part of a cylindrical, elliptical, or polygonal prism is missing.

[0041] When the porous material is in the form of particles, the particle diameter is, for example, between 0.5 μm and 7.0 mm. "Particle diameter" refers to the equivalent diameter of a circle, that is, the diameter of a circle assumed to have an area equal to the area of ​​the particle in an observation image of the particle (e.g., a SEM image). The particle diameter can be adjusted, for example, by classification.

[0042] When the porous body is columnar, its length is, for example, 1.0 mm to 500 mm, and its diameter is, for example, 1.5 mm to 20 mm. "Length" refers to the dimension in the direction in which the columnar body extends. "Diameter" refers to the diameter of the end face located at the end of the columnar body in the direction of extension. If the end face is circular, the diameter refers to the diameter of the circle. If the end face has a shape other than circular, the diameter refers to the diameter of the circle circumscribing the end face. It is preferable that the diameters of the end faces located at both ends of the columnar body in the direction of extension are within the above ranges.

[0043] The structure of the porous material before modification with sulfo groups 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.

[0044] As shown in Figure 1, the porous material has a co-continuous structure formed by a ceramic skeleton 1 containing mesopores 3 and macropores 2.

[0045] In a porous material, the ceramic framework 1 and macropores 2 each have a continuous three-dimensional network structure and are intertwined with each other, thereby forming a co-continuous structure. The presence of a co-continuous structure in a porous material can be confirmed by observing the surface or cross-section of the porous material with a scanning electron microscope (SEM).

[0046] From the viewpoint of adjusting the most frequent pore size of the macropores in the sulfo-modified porous material to a desired range, the most frequent pore size of the macropores in the porous material is preferably 200.0 nm or more and 5000.0 nm or less, more preferably 400.0 nm or more and 4500.0 nm or less, even more preferably 500.0 nm or more and 4000.0 nm or less, and particularly preferably 600.0 nm or more and 3000.0 nm or less. Each of the above lower limits may be combined with any of the above upper limits.

[0047] The "most frequent pore size of macropores in a porous material" refers to the most frequent pore size of macropores measured in the range of 50.0 nm to 500.0 μm by the mercury intrusion method, as described in the examples below.

[0048] From the viewpoint of adjusting the most frequent pore size of the mesopores in the sulfo-modified porous material to a desired range, the most frequent pore size of the mesopores in the porous material is preferably 2.0 nm to 50.0 nm, more preferably 5.0 nm to 40.0 nm, even more preferably 10.0 nm to 35.0 nm, and particularly preferably 15.0 nm to 30.0 nm. Each of the above lower limits may be combined with any of the above upper limits.

[0049] The "most frequent pore size of mesopores in a porous material" refers to the most frequent pore size of mesopores measured by the BJH method from nitrogen adsorption / desorption isotherms, as described in the examples below.

[0050] From the viewpoint of adjusting the ratio of the most frequent pore diameter of the macropores of the sulfonic acid group-modified porous body to the most frequent pore diameter of the mesopores of the sulfonic acid group-modified porous body within a desired range, the ratio of the most frequent pore diameter of the macropores of the porous body to the most frequent pore diameter of the mesopores of the porous body is preferably 15.0 or more and 300.0 or less, more preferably 20.0 or more and 200.0 or less, still more preferably 30.0 or more and 150.0 or less, and particularly preferably 50.0 or more and 100.0 or less. Each of the above lower limit values may be combined with any of the above upper limit values.

[0051] From the viewpoint of adjusting the specific surface area of the sulfonic acid group-modified porous body within a desired range, the specific surface area of the porous body is preferably 100 m ２ / g or more, more preferably 120 m ２ / g or more, and still more preferably 130 m ２ / g or more. The upper limit of the specific surface area of the porous body is not particularly limited, but is typically about 800 m ２ / g. The specific surface area of the porous body is measured by the BET method from the nitrogen adsorption / desorption isotherm as described in the examples below.

[0052] From the viewpoint of adjusting the total pore volume of the sulfonic acid group-modified porous body within a desired range, the total pore volume of the porous body is preferably 1.50 mL / g or more and 6.00 mL / g or less, more preferably 1.80 mL / g or more and 5.50 mL / g or less, and still more preferably 2.50 mL / g or more and 5.00 mL / g or less. Each of the above lower limit values may be combined with any of the above upper limit values. The total pore volume of the porous body is measured by the mercury intrusion method as described in the examples below.

[0053] The ceramics constituting the ceramic skeleton of the porous body are, for example, oxide ceramics containing a semi-metal element or a metal element. The ceramic skeleton may contain one element selected from semi-metal elements and metal elements, or may contain two or more elements selected from semi-metal elements and metal elements.

[0054] Examples of the semi-metal element include silicon. Examples of the oxide ceramics containing silicon include silica (SiO ２ ).

[0055] Examples of metallic elements include aluminum, tin, and transition metal elements such as cerium, titanium, zirconium, vanadium, chromium, iron, cobalt, nickel, palladium, platinum, copper, silver, gold, and zinc. Among these, from the viewpoint of ease of manufacturing porous materials, it is preferable to select the metallic element from aluminum, tin, cerium, titanium, and zirconium. Examples of oxide ceramics containing aluminum, tin, cerium, titanium, or zirconium include alumina (Al ２ O ３ ), tin oxide (SnO ２ ), Celia (CeO ２ ), Titania (TiO ２ ), Zirconia (ZrO ２ Examples include:

[0056] In addition to silicon, aluminum, tin, or transition metal elements, oxide ceramics may further contain elements selected from 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.

[0057] Porous materials can be manufactured, for example, by the method described in International Publication No. 2022 / 163834, specifically, by a method comprising the following steps: (a) a step of producing a polymetalloxane gel by a sol-gel method; (b) a step of forming pores in the framework of the polymetalloxane gel produced in step (a); and (c) a step of washing and / or drying the polymetalloxane gel subjected to step (b) as necessary, and then firing it to produce a ceramic monolith (porous material).

[0058] In one embodiment, the ceramic monolith is preferably a silica monolith. The silica monolith has a co-continuous structure formed by a silica skeleton containing mesopores and macropores.

[0059] In another embodiment, the ceramic monolith may be a monolith of alumina, tin oxide, ceria, titania, or zirconia. In this case as well, the monolith has a co-continuous structure formed by a mesopore-containing alumina, tin oxide, ceria, titania, or zirconia framework and macropores.

[0060] The manufactured ceramic monolith may be molded and used as a porous body, or a molded ceramic monolith may be manufactured using a mold, and then used as is or molded as needed and used as a porous body. For example, in the gel manufacturing process, a molded ceramic monolith can be manufactured by using a mold to shape the gel into a desired shape. The average diameter of the molded ceramic monolith will be smaller than the average diameter of the mold.

[0061] The manufactured ceramic monolith may be pulverized and used as a porous body. Pulverization can be carried out according to conventional methods. Pulverization can be carried out using, for example, a mortar and pestle, hammer mill, ball mill, bead mill, jet mill, roller mill, etc. The particle size of the porous body after pulverization is preferably 0.5 μm to 7.0 mm, more preferably 2.0 μm to 5.0 mm, and even more preferably 5.0 μm to 3.0 mm. Each of the above lower limits may be combined with any of the above upper limits. Note that "particle size" refers to the equivalent circle diameter, that is, the diameter of a circle assumed to have an area equal to the area of ​​the porous body after pulverization in an observation image (e.g., SEM image) of the porous body after pulverization.

[0062] <Sulfo Group Modification> The following describes sulfo group modification in sulfo group-modified porous materials. Two or more of the sulfo group modification characteristics described below can be combined.

[0063] In a sulfo-modified porous material, the surface of the ceramic skeleton is composed of sulfo groups (-SO ３It is modified with H). The surface of the ceramic skeleton may be modified with sulfo groups only, or it may be modified with sulfo groups in addition to one or more functional groups other than sulfo groups. The sulfo groups may be directly bonded to the surface of the ceramic skeleton, or they may be bonded to the surface of the ceramic skeleton via a linker.

[0064] The surface of the ceramic skeleton includes the inner and outer surfaces of the ceramic skeleton. The inner surface of the ceramic skeleton includes the inner surfaces of macropores and mesopores that are located inside the ceramic skeleton (i.e., not exposed on the outer surface of the ceramic skeleton), and the outer surface of the ceramic skeleton includes the inner surfaces of macropores and mesopores that are exposed on the outer surface of the ceramic skeleton. Preferably, at least the inner surface of the ceramic skeleton is modified with sulfo groups.

[0065] In one embodiment, the surface of a ceramic skeleton is modified with a sulfo group by fixing a compound having a sulfo group (hereinafter referred to as "the first compound") to the surface of the ceramic skeleton. Methods for introducing the first compound to the surface of the ceramic skeleton include, for example, chemically fixing the first compound to the surface of the ceramic skeleton via covalent bonds, and physically fixing the first compound to the surface of the ceramic skeleton via physical interactions such as ionic bonds and hydrophobic interactions. A method for chemically introducing the first compound to the surface of the ceramic skeleton includes, for example, reacting the first compound with a functional group (e.g., a hydroxyl group) on the surface of the ceramic skeleton to chemically fix the first compound to the surface of the ceramic skeleton. The first compound may also be fixed to the surface of the ceramic skeleton via a linker. For example, a functional group that reacts with the first compound may be introduced to the surface of the ceramic skeleton, and then the introduced functional group may be reacted with the first compound to chemically fix the first compound to the surface of the ceramic skeleton. One method for introducing a functional group that reacts with the first compound to the surface of a ceramic skeleton is to react a functional group (e.g., a hydroxyl group) on the surface of the ceramic skeleton with a silane coupling agent having a functional group that reacts with the first compound, thereby chemically fixing the silane coupling agent to the surface of the ceramic skeleton. Examples of silane coupling agents having a functional group that reacts with the first compound include silane coupling agents having an epoxy group and / or a haloalkyl group. Examples of silane coupling agents having an epoxy group include 3-glycidyloxypropyltrimethoxysilane. Examples of silane coupling agents having a haloalkyl group include 3-chloropropyltrimethoxysilane.

[0066] As a method for modifying the surface of a ceramic skeleton with sulfo groups, a method may be employed in which a compound containing a thiol group (-SH) (hereinafter referred to as "the second compound") is fixed to the surface of the ceramic skeleton, and then the thiol group contained in the second compound is converted to a sulfo group. The second compound can be fixed to the surface of the ceramic skeleton in the same manner as the first compound. The conversion of the thiol group to a sulfo group can be carried out according to a conventional method. Even if the compound fixed to the surface of the ceramic skeleton does not initially contain a sulfo group, if the compound is ultimately converted to contain a sulfo group by derivatization, as in the case where the thiol group contained in the second compound is fixed to the surface of the ceramic skeleton and then converted to a sulfo group, this is included in the statement "the surface of the ceramic skeleton is modified with sulfo groups by fixing a compound containing a sulfo group to the surface of the ceramic skeleton."

[0067] The portion of the first compound other than the sulfo group and the portion of the second compound other than the thiol group may each consist of hydrogen atoms and carbon atoms, or may contain one or more other elements (e.g., oxygen atoms, nitrogen atoms, halogen atoms, silicon atoms, etc.) in addition to hydrogen atoms and carbon atoms. One or more compounds may be used as the first compound and the second compound, or two or more compounds may be used. The first compound and the second compound may be used in combination. Silane coupling agents may be used as the first compound and the second compound, respectively.

[0068] It is preferable that the sulfo groups introduced onto the surface of the ceramic skeleton are fixed to the surface of the ceramic skeleton via a linker such as a silane coupling agent. When the linker is, for example, a silane coupling agent, the carbon skeleton of the silane coupling agent allows the sulfo groups to move flexibly while fixed to the surface of the ceramic skeleton. As a result, each sulfo group becomes more readily able to act on the reactants, and multiple sulfo groups cooperate to act on the reactants more readily, improving reaction efficiency compared to when the sulfo groups are directly introduced onto the surface of the ceramic skeleton.

[0069] Examples of silane coupling agents containing a sulfo group include silane coupling agents represented by formula A or B. Formula A: R ａ -R ｄ -Si(-R ｂ ) ｎ (-R ｃ ) ３－ｎ Formula B: R ａ -R ｄ -Si(-O-(R ｅ -O) ｍ -R ｆ ) ｎ (-R ｃ ) ３－ｎ

[0070] Examples of silane coupling agents containing a thiol group include silane coupling agents represented by formula C or D. Formula C: R ｇ -R ｄ -Si(-R ｂ ) ｎ (-R ｃ ) ３－ｎ Formula D:R ｇ -R ｄ -Si(-O-(R ｅ -O) ｍ -R ｆ ) ｎ (-R ｃ ) ３－ｎ

[0071] In equation A, R ａ represents a sulfo group, R ｂ Each of these independently represents an alkyl group, R ｃ Each of these independently represents an alkyloxy group or a halogen atom, R ｄ represents an alkylene group, an arylene group, or a combination thereof, and n represents an integer between 0 and 2.

[0072] In equation B, R ａ , R ｃ , R ｄ And n is equivalent to equation A, and R ｅ Each of these independently represents an alkylene group, R ｆ Each of these independently represents an alkyl group, and m represents an integer from 1 to 5, preferably an integer from 1 to 3, more preferably an integer from 1 to 2.

[0073] In equation C, R ｂ , R ｃ , R ｄ And n is equivalent to equation A, and R ｇ The symbol represents a thiol group.

[0074] In equation D, R ｃ , R ｄ And n is equivalent to equation A, and R ｅ , R ｆ And m is synonymous with equation B, and R ｇ This is equivalent to equation C.

[0075] R ｂ or R ｆ Examples of alkyl groups represented by this symbol include methyl, ethyl, propyl, and butyl groups.

[0076] R ｃ Examples of alkyloxy groups or halogen atoms represented by include methoxy groups, ethoxy groups, propoxy groups, butoxy groups, chlorine atoms, bromine atoms, iodine atoms, etc. ｃ The alkyloxy group represented is preferably a methoxy group or an ethoxy group. ｃ The halogen group represented is preferably a chlorine atom.

[0077] R ｄ or R ｅ Examples of alkylene groups represented by this formula include methylene, ethylene, propylene, and butylene groups.

[0078] R ｄ Examples of arylene groups represented by this formula include phenylene groups, naphthylene groups, and biphenylene groups.

[0079] R ｄ Examples of combinations of alkylene and arylene groups represented by the formulas: -X-Y-, -Y-X-, -X-Y-X-, or -Y-X-Y-. In the formulas, X represents an alkylene group and Y represents an arylene group.

[0080] R ｄ The alkylene group, arylene group, or combination thereof represented by may have one or more substituents.

[0081] Examples of silane coupling agents represented by formula A include 3-(trimethoxysilyl)-1-propanesulfonic acid.

[0082] Examples of silane coupling agents represented by formula B include 3-(dimethoxy(2-methoxyethoxy)silyl)-1-propanesulfonic acid.

[0083] Examples of silane coupling agents represented by formula C include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, and 3-mercaptopropyltriethoxysilane.

[0084] Examples of silane coupling agents represented by formula D include ethoxy(3-mercaptopropyl)bis(3,6,9,12,15-pentaoxacosan-1-yloxy)silane.

[0085] The greater the amount of sulfo groups contained in the sulfo-modified porous material, the higher the reaction efficiency. From the viewpoint of improving reaction efficiency, the amount of sulfur atoms contained in the sulfo-modified porous material is preferably 0.10 mmol / g or more, more preferably 0.20 mmol / g or more, even more preferably 0.30 mmol / g or more, particularly preferably 0.40 mmol / g or more, and most preferably 0.50 mmol / g or more, based on the mass of the sulfo-modified porous material. On the other hand, if the amount of sulfo groups contained in the sulfo-modified porous material is too high, the amount of dehydration sites (e.g., hydroxyl groups derived from silanol groups) in the sulfo-modified porous material decreases, and the water produced in the reaction is not sufficiently removed from the reaction system, which may reduce the reaction efficiency. From the viewpoint of suppressing a decrease in reaction efficiency, the amount of sulfur atoms contained in the sulfo-modified porous material is preferably 5.00 mmol / g or less, more preferably 4.50 mmol / g or less, and even more preferably 4.00 mmol / g or less, based on the mass of the sulfo-modified porous material. Each of the above lower limits may be combined with any of the above upper limits.

[0086] When thiol groups are converted to sulfo groups during the production of a sulfo-modified porous material, some thiol groups may remain. Therefore, in this invention, the amount of sulfur atoms contained in the sulfo-modified porous material is used as an indicator of the amount of sulfo groups contained in the sulfo-modified porous material. When thiol groups are converted to sulfo groups during the production of the sulfo-modified porous material, the "amount of sulfur atoms contained in the sulfo-modified porous material" means the sum of the amount of sulfur atoms derived from sulfo groups and the amount of sulfur atoms derived from remaining thiol groups. When thiol groups are not converted to sulfo groups during the production of the sulfo-modified porous material, the "amount of sulfur atoms contained in the sulfo-modified porous material" means the amount of sulfur atoms derived from sulfo groups. In other words, the sulfo-modified porous material does not contain any sulfur atom sources other than sulfo groups and thiol groups. Therefore, in either case, the amount of sulfur atoms contained in the sulfo-modified porous material reflects the amount of sulfo groups contained in the sulfo-modified porous material. The amount of sulfur atoms contained in the sulfo-modified porous material can be measured according to conventional methods. For example, the amount of sulfur atoms contained in the sulfo-modified porous material can be measured by the method described in the examples below.

[0087] <Method for Manufacturing Sulfo-Modified Porous Materials> The method for manufacturing sulfo-modified porous materials is described below. Two or more of the features of the method for manufacturing sulfo-modified porous materials described below can be combined.

[0088] In one embodiment, a sulfo-modified porous body can be produced by a method comprising the following steps: (1) modifying the surface of the ceramic skeleton of the porous body with thiol groups; and (2) converting the thiol groups into sulfo groups. This method is advantageous in that it allows for easy adjustment of the amount of sulfo groups contained in the sulfo-modified porous body.

[0089] Step (1) can be carried out by bringing a porous body and a reagent for modifying the surface of the ceramic skeleton of the porous body with thiol groups (hereinafter referred to as "the first reagent") into contact in a first solvent.

[0090] As the first reagent, for example, a compound having a thiol group, preferably a silane coupling agent having a thiol group, and more preferably a silane coupling agent represented by formula C or D can be used.

[0091] As the first solvent, for example, water, aqueous solution, a mixed solution of an organic solvent and an aqueous solution or water can be used.

[0092] An aqueous solution can be prepared by adding an acid to water. The acid can be selected from, for example, acetic acid, hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, etc. Of these, acetic acid is preferred. The concentration of acetic acid in the aqueous solution is, for example, 0.01% by mass or more and 5.0% by mass or less.

[0093] Examples of organic solvents that can be used include alcohol-based solvents such as methanol, ethanol, and propanol; ether-based solvents such as tetrahydrofuran and 2-methyltetrahydrofuran; ketone-based solvents such as acetone and methyl ethyl ketone; ester-based solvents such as methyl acetate and ethyl acetate; halogenated hydrocarbon-based solvents such as dichloromethane and chloroform; aromatic hydrocarbon-based solvents such as toluene and xylene; and aliphatic hydrocarbon-based solvents such as hexane and heptane.

[0094] The temperature at which the porous material and the first reagent are brought into contact in the first solvent is, for example, between 60°C and 100°C. The time at which the porous material and the first reagent are brought into contact in the first solvent is, for example, between 2 hours and 24 hours.

[0095] After modifying the surface of the porous ceramic skeleton with thiol groups, the thiol-modified porous material is separated from the reaction mixture using a solid-liquid separation method such as filtration. The separated porous material is washed with a washing solution such as pure water, dried, and then used in step (2).

[0096] Step (2) can be carried out by contacting the thiol-modified porous body obtained in step (1) with a reagent for converting thiol groups to sulfo groups (hereinafter referred to as the "second reagent") in a second solvent.

[0097] As the second reagent, for example, an oxidizing agent such as hydrogen peroxide, nitric acid, or metachloroperbenzoic acid can be used. An aqueous solution containing the oxidizing agent may also be used as the second reagent. An aqueous solution containing the oxidizing agent can be prepared by adding the oxidizing agent to water. When an aqueous solution containing hydrogen peroxide is used as the second reagent, the concentration of hydrogen peroxide in the aqueous solution is, for example, 10.0% by mass or more and 60.0% by mass or less.

[0098] As the second solvent, for example, water can be used. When hydrogen peroxide or an aqueous solution containing hydrogen peroxide is used as the second reagent, the concentration of hydrogen peroxide in the second solvent after mixing with the second reagent is, for example, 5.0% by mass or more and 30.0% by mass or less.

[0099] The temperature at which the thiol-modified porous material and the second reagent are brought into contact in the second solvent is, for example, 40°C to 80°C. The time at which the thiol-modified porous material and the second reagent are brought into contact in the solvent is, for example, 0.5 hours to 12 hours.

[0100] After converting the thiol groups in the thiol-modified porous material to sulfo groups, the sulfo-modified porous material is separated from the reaction mixture using a solid-liquid separation method such as filtration. The separated porous material is washed with a washing solution such as pure water and then dried. In this way, a sulfo-modified porous material can be obtained.

[0101] In another embodiment, a sulfo-modified porous body can be produced by a method that includes a step of directly modifying the surface of the ceramic skeleton of the porous body with sulfo groups. Such a method can be found, for example, in RSC Adv. 2017, 7, pp. 56559-56565. According to the method described in this document, the surface of the ceramic skeleton of the porous body can be directly modified with sulfo groups by adding chlorosulfonic acid to the porous body and stirring.

[0102] <<Organic Reaction Method>> The following describes an organic reaction method using a sulfo-modified porous material as a solid acid catalyst. Two or more of the features of the organic reaction methods described below can be combined.

[0103] The organic reaction method includes a step of carrying out an organic reaction using a sulfo-modified porous material as a solid acid catalyst.

[0104] In organic reactions, a target substance is produced from reactants in the presence of a solid acid catalyst. An organic reaction is a reaction in which at least one reactant is an organic compound. An organic reaction is not particularly limited as long as the sulfo group can function as an acid catalyst. In one embodiment, the organic reaction is selected from esterification reactions, transesterification reactions, ester hydrolysis reactions, and Ritter reactions.

[0105] As described above, the mesopores present in the ceramic framework can adsorb water and remove it from the reaction system; therefore, sulfo-modified porous materials are particularly useful as solid acid catalysts for reactions that produce the target substance and water from the reactants. Accordingly, the organic reaction is preferably an esterification reaction.

[0106] The organic reaction can be carried out according to conventional methods, except that the sulfo-modified porous material is used as a solid acid catalyst.

[0107] Organic reactions may be carried out by batch or flow methods. In the batch method, reactants, a sulfo-modified porous material (solid acid catalyst), and a solvent are added to a container, the reaction to produce the target substance from the reactants proceeds in the container, and the target substance is recovered from the container. In the flow method, a mixture containing the reactants and solvent is introduced into a reactor filled with a sulfo-modified porous material (solid acid catalyst) from one end, the reaction to produce the target substance from the reactants proceeds in the reactor, and the mixture containing the target substance and solvent is discharged from the other end of the reactor. The solvent used in the batch or flow method is appropriately selected from water, organic solvents, mixed solvents of water and organic solvents, etc., depending on the type of organic reaction. Compared to the batch method, the flow method has advantages such as higher energy efficiency, lower waste generation, higher productivity of the target substance, and suitability for mass production of the target substance.

[0108] The flow method can be performed, for example, using the flow reactor 10 shown in Figure 2.

[0109] The flow reactor 10 will be described below. Two or more of the features of the flow reactor 10 described below can be combined.

[0110] The flow reaction apparatus 10 is a device for carrying out a reaction to produce a target substance from a first reactant and a second reactant using a flow method. For example, in the case of an esterification reaction, the first reactant is a carboxylic acid, the second reactant is an alcohol, and the target substance is an ester.

[0111] The flow reactor 10 comprises a mixer 11, a first supply unit 12, a second supply unit 13, a reactor 14, a temperature controller 15, and a recovery container 16.

[0112] The first supply unit 12 supplies the raw material liquid L1 containing the first reactant to the mixer 11. The first supply unit 12 supplies the raw material liquid L1 to the mixer 11 at a flow rate of, for example, 0.1 mL / min or more and 10 mL / min or less. The raw material liquid L1 may contain a solvent.

[0113] In one embodiment, the first supply unit 12 includes a storage tank 121 for storing a raw material liquid L1 containing a first reactant, a supply pipe 122 for supplying the raw material liquid L1 from the storage tank 121 to the mixer 11, and a pump 123 provided on the supply pipe 122. The first supply unit 12 uses the suction and discharge forces of the pump 123 to supply the raw material liquid L1 from the storage tank 121 to the mixer 11 through the supply pipe 122.

[0114] The supply pipe 122 may be equipped with a flow meter (not shown) for detecting the flow rate of the raw material liquid L1, a flow regulator (not shown) for adjusting the flow rate of the raw material liquid L1, etc. The flow regulator may adjust the flow rate of the raw material liquid L1 flowing through the supply pipe 122 based on the flow rate of the raw material liquid L1 detected by the flow meter. The flow regulator may be omitted by using a pump 123 that also has a flow rate adjustment function.

[0115] The second supply unit 13 supplies the raw material liquid L2 containing the second reactant to the mixer 11. The second supply unit 13 supplies the raw material liquid L2 to the mixer 11 at a flow rate of, for example, 0.1 mL / min or more and 10 mL / min or less. The raw material liquid L2 may contain a solvent.

[0116] In one embodiment, the second supply unit 13 includes a storage tank 131 for storing a raw material liquid L2 containing a second reactant, a supply pipe 132 for supplying the raw material liquid L2 from the storage tank 131 to the mixer 11, and a pump 133 provided on the supply pipe 132. The second supply unit 13 uses the suction and discharge forces of the pump 133 to supply the raw material liquid L2 from the storage tank 131 to the mixer 11 through the supply pipe 132.

[0117] The supply pipe 132 may be equipped with a flow meter (not shown) for detecting the flow rate of the raw material liquid L2, a flow regulator (not shown) for adjusting the flow rate of the raw material liquid L2, etc. The flow regulator may adjust the flow rate of the raw material liquid L2 flowing through the supply pipe 132 based on the flow rate of the raw material liquid L2 detected by the flow meter. The flow regulator may be omitted by using a pump 133 that also has a flow rate adjustment function.

[0118] The mixer 11 mixes the raw material liquid L1 supplied by the first supply unit 12 and the raw material liquid L2 supplied by the second supply unit 13 to prepare the mixed liquid M1.

[0119] If raw material liquids L1 and L2 are miscible, the mixer 11 may or may not have a function to stir raw material liquids L1 and L2. If raw material liquids L1 and L2 are miscible, it is preferable that the mixer 11 has a function to stir raw material liquids L1 and L2.

[0120] Examples of a mixer 11 that does not have the function of stirring the raw material liquids L1 and L2 include containers such as flasks.

[0121] Examples of mixers 11 that have the function of stirring raw material liquids L1 and L2 include line mixers (also called in-line mixers). Examples of line mixers include static mixers and dynamic mixers.

[0122] Reactor 14 is filled with a sulfo-modified porous material (solid acid catalyst).

[0123] In one embodiment, the reactor 14 is a column packed with a sulfo-modified porous material (solid acid catalyst).

[0124] The temperature controller 15 adjusts the temperature of the reactor 14 to a temperature suitable for the reaction that produces the target substance from the first reactant and the second reactant.

[0125] In one embodiment, the temperature controller 15 is a heat block.

[0126] The mixed liquid M1 is discharged from the mixer 11. The supply pipe 17 supplies the mixed liquid M1 discharged from the mixer 11 to the reactor 14. The mixed liquid M1 is supplied to the reactor 14 at a flow rate of, for example, 0.1 mL / min or more and 10 mL / min or less. When the mixed liquid M1 is supplied to the reactor 14, a reaction to produce the target substance from the first reactant and the second reactant proceeds in the reactor 14, producing a mixed liquid M2 containing the target substance. The mixed liquid M2 is discharged from the reactor 14. The supply pipe 18 supplies the mixed liquid M2 discharged from the reactor 14 to the recovery container 16.

[0127] The present invention will be described in more detail below based on examples and comparative examples, but the scope of the present invention is not limited in any way by the examples and comparative examples. Items that have not been evaluated in Tables 1 and 2 are indicated with "-".

[0128] [Production Example 1] (1) Preparation of silica monolith (porous material before sulfo group modification) 8.67 g of polyethylene glycol 10000 (manufactured by SIGMA-ALDRICH), 7.80 g of urea, and 86.7 g of aqueous acetic acid solution (acetic acid concentration: 6.06% by mass) were added to a 150 mL reaction vessel and stirred at room temperature for 10 minutes. The reaction vessel was placed in an ice bath and the reaction solution was cooled while stirring for 15 minutes. 44.7 g of tetramethoxysilane was added to the cooled reaction solution and stirred while cooling in an ice bath for 30 minutes. After warming the reaction solution in a 30°C bath, it was left to stand overnight in a 30°C incubator to prepare a polysiloxane gel.

[0129] Next, the obtained polysiloxane gel was added to another reaction vessel containing 30 mL of 3 mol / L urea solution and heated under reflux for 12 hours. After the reaction was complete, the obtained polysiloxane gel was washed with water and dried in a dryer set to 60°C for 12 hours. After drying, it was calcined at 600°C for 5 hours under an air atmosphere to produce silica monoliths. The prepared silica monoliths were crushed and classified to obtain silica monoliths with a particle size of 100 μm to 300 μm.

[0130] (2) Observation by Scanning Electron Microscope (SEM) When the surface structure of the silica monolith obtained in (1) above was observed with an SEM (JSM-7900F manufactured by JEOL), it was confirmed that the silica monolith has a co-continuous structure formed by a silica skeleton and macropores.

[0131] (3) Measurement of specific surface area and most frequent pore diameter of mesopores of silica monoliths The specific surface area and most frequent pore diameter of mesopores of the silica monoliths obtained in (1) above were measured using a specific surface area and pore distribution analyzer (BELSORP-miniX, manufactured by Microtrac-Bell). For silica monoliths that had been degassed under reduced pressure at 110°C for 0.5 hours, the amount of nitrogen adsorption and desorption at a temperature of 77K was measured using a multipoint method with liquid nitrogen, and adsorption / desorption isotherms were determined. Based on these adsorption / desorption isotherms, the specific surface area and most frequent pore diameter were calculated. The specific surface area was calculated using the BET method, and the most frequent pore diameter was calculated using the BJH method.

[0132] 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 this invention, the analysis was performed on pores with diameters ranging from 2 to 200 nm.

[0133] Table 1 shows the measurement results for the specific surface area and the most frequent pore diameter of the mesopores of the silica monolith.

[0134] (4) Measurement of total pore volume and most frequent pore diameter of macropores in silica monoliths The total pore volume and most frequent pore diameter of macropores in silica monoliths obtained in (1) above were measured using a mercury porosimeter (AutoPore IV 9520, manufactured by Micromeritics) by the mercury intrusion method. In the mercury intrusion method, pressure was applied to the pores of the silica monolith to infiltrate mercury, and the pore volume and specific surface area were determined from the pressure and the amount of mercury injected. The pore diameter was calculated from the relationship between the pore volume and specific surface area assuming the pores are cylindrical. In this invention, the mercury intrusion method was used to analyze pores with diameters from 50 nm to 500 μm. The measurements were performed under the following conditions and procedures.

[0135] (Measurement conditions) ・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: 0.0035 MPa Equilibrium time: 10 seconds ・High pressure parameters: Equilibrium time: 10 seconds ・Injection volume: Adjusted to be between 25% and 90% ・Measurement environment: 20℃

[0136] (Measurement Procedure) (i) Weigh approximately 0.5 g of the 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 0.2068 to 255.1060 MPa. Steps (ii) and (iii) were performed automatically using the software provided with the device.

[0137] Table 1 shows the measurement results for the total pore volume and the most frequent pore diameter of the silica monolith.

[0138] (5) Preparation of thiol-modified silica monoliths In a reaction vessel, 8.2 g of 3-mercaptopropyltrimethoxysilane and 17.5 mL of aqueous acetic acid solution (acetic acid concentration: 0.1% by mass) were mixed and vigorously stirred until clear. Then, 2.5 g of the silica monolith obtained in (1) above was added and heated at 80°C for 4 hours to prepare thiol-modified silica monoliths. After separating the thiol-modified silica monoliths from the solution by filtration, they were washed with pure water and dried overnight at room temperature to obtain 5.1 g of thiol-modified silica monoliths.

[0139] (6) Preparation of sulfo-modified silica monolith (sulfo-modified porous body) In a reaction vessel, 4.0 g of the thiol-modified silica monolith obtained in (5) above and 25 mL of hydrogen peroxide solution (hydrogen peroxide concentration: 15% by mass) were mixed and heated at 60°C for 1 hour to convert the thiol groups to sulfo groups and prepare a sulfo-modified silica monolith. After separating the sulfo-modified silica monolith from the solution by filtration, it was washed with pure water and dried at 60°C for 24 hours to obtain 2.1 g of sulfo-modified silica monolith.

[0140] (7) Measurement of sulfur atom content The amount of sulfur atoms contained in the sulfo-modified silica monolith obtained in (6) above was measured using a carbon-sulfur analyzer (EMIA-Expert, Horiba, Ltd.). The measurement results are shown in Table 1.

[0141] (8) Measurement of specific surface area and most frequent pore diameter of mesopores of sulfogroup-modified silica monolith The specific surface area and most frequent pore diameter of mesopores of the sulfogroup-modified silica monolith obtained in (6) above were measured in the same manner as in (3) above. The measurement results are shown in Table 1.

[0142] (9) Measurement of total pore volume and most frequent pore diameter of macropores of sulfogroup-modified silica monolith The total pore volume and most frequent pore diameter of macropores of the sulfogroup-modified silica monolith obtained in (6) above were measured in the same manner as in (4) above. The measurement results are shown in Table 1.

[0143] [Production Example 2] (1) Preparation of silica monolith (porous material before sulfo group modification) A polysiloxane gel prepared in the same manner as in Production Example 1 (1) was added to another reaction vessel containing 30 mL of 3 mol / L urea solution and heated under reflux for 1 hour. After the reaction was complete, the obtained polysiloxane gel was washed with water and dried in a dryer set to 80°C for 12 hours. After drying, it was calcined at 600°C for 3 hours under an air atmosphere to produce silica monoliths. The prepared silica monoliths were crushed and classified to obtain silica monoliths with a particle size of 100 μm or more and 300 μm or less.

[0144] (2) Observation using a scanning electron microscope (SEM) In the same manner as in Manufacturing Example 1 (2), it was confirmed that the silica monolith has a co-continuous structure formed by a silica skeleton and macropores.

[0145] (3) Measurement of specific surface area and most frequent pore diameter of mesopores of silica monoliths In the same manner as in Manufacturing Example 1 (3), the specific surface area and most frequent pore diameter of mesopores of silica monoliths were measured using a specific surface area and pore distribution analyzer (BELSORP-miniX, manufactured by Microtrac-Bell). The measurement results are shown in Table 2.

[0146] (4) Measurement of total pore volume and most frequent pore diameter of macropores of silica monoliths The total pore volume and most frequent pore diameter of macropores of silica monoliths were measured using a mercury porosimeter (AutoPore IV 9520, Micromeritics) by mercury intrusion method, in the same manner as in Manufacturing Example 1 (4). The measurement results are shown in Table 2.

[0147] (5) Preparation of thiol-modified silica monoliths In a reaction vessel, 8.2 g of 3-mercaptopropyltrimethoxysilane and 17.0 mL of aqueous acetic acid solution (acetic acid concentration: 0.1% by mass) were mixed and vigorously stirred until clear. Then, 2.5 g of the silica monolith obtained in Production Example 2 (1) was added and heated at 80°C for 4 hours to prepare thiol-modified silica monoliths. After separating the thiol-modified silica monoliths from the solution by filtration, they were washed with pure water and dried overnight at room temperature to obtain 3.0 g of thiol-modified silica monoliths.

[0148] (6) Preparation of sulfo-modified silica monolith (sulfo-modified porous body) In a reaction vessel, 4.0 g of the thiol-modified silica monolith obtained in Production Example 2 (5) and 25 mL of hydrogen peroxide solution (hydrogen peroxide concentration: 15% by mass) were mixed and heated at 60°C for 1 hour to convert the thiol groups to sulfo groups and prepare a sulfo-modified silica monolith. After separating the sulfo-modified silica monolith from the solution by filtration, it was washed with pure water and dried at 60°C for 24 hours to obtain 2.6 g of sulfo-modified silica monolith.

[0149] (7) Measurement of sulfur atom content In the same manner as in Production Example 1 (7), the amount of sulfur atoms contained in the sulfo-modified silica monolith obtained in Production Example 2 (6) was measured using a carbon-sulfur analyzer (EMIA-Expert, Horiba, Ltd.). The measurement results are shown in Table 2.

[0150] (8) Measurement of specific surface area and most frequent pore diameter of mesopores of sulfogroup-modified silica monolith The specific surface area and most frequent pore diameter of mesopores of the sulfogroup-modified silica monolith obtained in Production Example 2 (6) were measured in the same manner as in Production Example 1 (8). The measurement results are shown in Table 2.

[0151] (9) Measurement of total pore volume and most frequent pore diameter of macropores of sulfo-modified silica monolith The total pore volume and most frequent pore diameter of macropores of the sulfo-modified silica monolith obtained in Production Example 2 (6) were measured in the same manner as in Production Example 1 (9). The measurement results are shown in Table 2.

[0152] [Example 1] The sulfo-modified silica monolith obtained in Production Example 1 (6) was used as an acid catalyst to carry out the following reaction to produce benzyl acetate (3a) from acetic acid (1a) and benzyl alcohol (2a) by batch method. The following reaction is an example of an esterification reaction.

[0153]

[0154] A stirring bar, acetic acid (2 mmol), benzyl alcohol (10 mmol, 5 equivalents), and sulfo-modified silica monolith (sulfur atom content: 0.009 mmol) obtained in Production Example 1 (6) were added to a 30 mL vial. The resulting mixture was heated at 50°C for 15 hours with stirring (600 rpm), and then cooled to room temperature. After cooling, an internal standard (naphthalene) was added to the mixture, followed by ethyl acetate (10 mL) and water (10 mL). The resulting mixture was filtered through a syringe filter (pore size: 0.45 μm). The obtained filtrate was analyzed by high-performance liquid chromatography (HPLC). The HPLC peak area ratio of benzyl acetate to the internal standard was determined, and the yield of benzyl acetate was determined from a calibration curve showing the relationship between the HPLC peak area ratio of benzyl acetate to the internal standard and the concentration ratio of benzyl acetate to the internal standard. The yield of benzyl acetate was 100%. The data for Example 1 are shown in Table 1. HPLC was performed under the following conditions.

[0155] <HPLC Analysis Conditions> Instrument: Shimadzu HPLC, LC-2050C Column: InertSustainSwift C18 (5 mm, 250 x 4.6 mm I.D.) Column Temperature: 40°C Eluent: Acetonitrile / Water = 7 / 3 (volume ratio) Flow Rate: 1 mL / min Sample Injection Volume: 2 μL Detection Wavelength: 254 nm

[0156] [Example 2] The above reaction for producing benzyl acetate (3a) from acetic acid (1a) and benzyl alcohol (2a) was carried out by the flow method using the flow reactor 10 shown in Figure 2.

[0157] Acetic acid (0.083 mmol) was used as the raw material solution L1. Benzyl alcohol (0.83 mmol, 10 equivalents) was used as the raw material solution L2. A flask was used as the mixer 11. A column (diameter: 10 mm, length: 100 mm) packed with sulfo-modified silica monolith (sulfur atom content: 2.04 mmol) obtained in Production Example 1 (6) was used as the reactor 14. A heat block was used as the temperature controller 15. Raw material solutions L1 and L2 were supplied to the mixer 11 at a flow rate of 0.2 mL / min for 1 hour from the first supply unit 12 and the second supply unit 13, respectively. The mixed solution M1 containing acetic acid and benzyl alcohol prepared in the mixer 11 was supplied to the reactor 14 at a flow rate of 0.2 mL / min for 1 hour. The temperature of the reactor 14 was adjusted to 90°C using the temperature controller 15. The mixed liquid M2 containing benzyl acetate flowing out of reactor 14 was collected in recovery container 16 and cooled to room temperature.

[0158] After cooling, 12 mL of the mixed solution M2 was mixed with an internal standard (naphthalene), followed by ethyl acetate (15 mL). The resulting mixture was filtered through a syringe filter (pore size: 0.45 μm). The resulting filtrate was analyzed by high-performance liquid chromatography (HPLC), and the yield of benzyl acetate was determined in the same manner as in Example 1. The yield of benzyl acetate was 94.0%. The data for Example 2 is shown in Table 1.

[0159] [Example 3] The same procedure as in Example 2 was followed, except that raw material liquids L1 and L2 were supplied to the mixer 11 at a flow rate of 0.2 mL / min for 172 hours through the first supply unit 12 and the second supply unit 13, respectively, and the mixed solution M1 containing acetic acid and benzyl alcohol prepared in the mixer 11 was supplied to the reactor 14 at a flow rate of 0.2 mL / min for 172 hours, and the mixed solution M2 collected in the recovery container 16 was taken out every 3 hours, and the yield of benzyl acetate was determined every 3 hours. The average yield of benzyl acetate determined every 3 hours was 94.0%. The data for Example 3 is shown in Table 1.

[0160] [Example 4] The same procedure as in Example 1 was followed, except that the sulfo-modified silica monolith obtained in Production Example 2(6) (sulfur atom content: 0.009 mmol) was used instead of the sulfo-modified silica monolith obtained in Production Example 1(6). The yield of benzyl acetate was 64.1%. The data for Example 4 is shown in Table 2.

[0161] [Example 5] The sulfo-modified silica monolith obtained in Production Example 1 (6) was used as an acid catalyst to carry out the following reaction to produce methyl benzoate (3b) from ethyl benzoate (1b) and methanol (2b) by batch method. The following reaction is an example of a transesterification reaction.

[0162]

[0163] A stirring bar, ethyl benzoate (3 mmol), methanol (20 mmol, 6.7 equivalents), and sulfo-modified silica monolith (sulfur atom content: 0.15 mmol) obtained in Preparation Example 1 (6) were added to a 30 mL vial. The resulting mixture was heated at 90°C for 48 hours with stirring (600 rpm), and then cooled to room temperature. After cooling, an internal standard (naphthalene) was added to the mixture, followed by ethyl acetate (10 mL) and water (10 mL). The resulting mixture was filtered through a syringe filter (pore size: 0.45 μm). The obtained filtrate was analyzed by high-performance liquid chromatography (HPLC). The HPLC peak area ratio of methyl benzoate to the internal standard was determined, and the conversion rate (molar basis) from ethyl benzoate to methyl benzoate was determined from a calibration curve showing the relationship between the HPLC peak area ratio of ethyl benzoate to the internal standard and the concentration ratio of ethyl benzoate to the internal standard. The conversion rate (molar basis) from ethyl benzoate to methyl benzoate was 70.3%. The data for Example 5 is shown in Table 2. HPLC was performed under the same conditions as in Example 1.

[0164] [Example 6] The sulfo-modified silica monolith obtained in Production Example 1 (6) was used as an acid catalyst to carry out the following reaction to produce N-tert-butylbenzamide (3c) from benzonitrile (1c) and tert-butyl alcohol (2c) by batch method. The following reaction is an example of a Ritter reaction.

[0165]

[0166] A stirring bar, benzonitrile (3 mmol), tert-butyl alcohol (15 mmol, 5 equivalents), and sulfo-modified silica monolith (sulfur atom content: 0.09 mmol) obtained in Preparation Example 1 (6) were added to a 30 mL vial. The resulting mixture was heated at 90°C for 15 hours with stirring (600 rpm), and then cooled to room temperature. After cooling, an internal standard (naphthalene) was added to the mixture, followed by ethyl acetate (10 mL) and water (10 mL). The resulting mixture was filtered through a syringe filter (pore size: 0.45 μm). The obtained filtrate was analyzed by high-performance liquid chromatography (HPLC). The HPLC peak area ratio of N-tert-butylbenzamide to the internal standard was determined, and the yield of N-tert-butylbenzamide was determined from a calibration curve showing the relationship between the HPLC peak area ratio of N-tert-butylbenzamide to the internal standard and the concentration ratio of N-tert-butylbenzamide to the internal standard. The yield of N-tert-butylbenzamide was 56.8%. The data for Example 6 is shown in Table 2. HPLC was performed under the same conditions as in Example 1.

[0167] [Example 7] The sulfo-modified silica monolith obtained in Production Example 1 (6) was used as an acid catalyst to carry out the following reaction to produce benzyl alcohol (3d) from benzyl acetate (1d) and water (2d) by batch method. The following reaction is an example of an ester hydrolysis reaction.

[0168]

[0169] A stirring bar, benzyl acetate (2 mmol), water (200 mol), and sulfo-modified silica monolith (sulfur atom content: 0.06 mmol) obtained in Production Example 1 (6) were added to a 30 mL vial. The resulting mixture was heated at 100 °C for 24 hours with stirring (600 rpm), and then cooled to room temperature. After cooling, an internal standard (naphthalene) was added to the mixture, followed by ethyl acetate (10 mL) and water (10 mL). The resulting mixture was filtered through a syringe filter (pore size: 0.45 μm). The obtained filtrate was analyzed by high-performance liquid chromatography (HPLC). The HPLC peak area ratio of benzyl alcohol to the internal standard was determined, and the yield of benzyl alcohol was determined from a calibration curve showing the relationship between the HPLC peak area ratio of benzyl alcohol to the internal standard and the concentration ratio of benzyl alcohol to the internal standard. The yield of benzyl alcohol was 88.6%. The data for Example 7 is shown in Table 2. The HPLC was performed under the same conditions as in Example 1.

[0170] [Comparative Example 1] The same procedure as in Example 1 was performed, except that the ion exchange resin Amberlite 200CTH (manufactured by Organo Corporation) (sulfur atom content: 0.009 mmol) was used instead of the sulfo-modified silica monolith (sulfur atom content: 0.009 mmol), and the yield of benzyl acetate was determined. The yield of benzyl acetate was 21.0%. The data for Comparative Example 1 is shown in Table 1. Since Amberlite 200CTH is an ion exchange resin modified with sulfo groups, the porous material before modification was not evaluated. Also, since Amberlite 200CTH does not have macropores, the macropore size was not evaluated.

[0171] [Comparative Example 2] The same procedure as in Example 1 was performed, except that Amberlyst-15 hydroxyl form dry (manufactured by Merck) (sulfur atom content: 0.025 mmol) was used instead of sulfo-modified silica monolith (sulfur atom content: 0.009 mmol), and the yield of benzyl acetate was determined. The yield of benzyl acetate was 50.8%. The data for Comparative Example 2 is shown in Table 1. Since Amberlyst-15 hydroxyl form dry is an ion exchange resin modified with sulfo groups, the porous material before modification was not evaluated. Also, since Amberlyst-15 hydroxyl form dry does not have macropores, the macropore size was not evaluated.

[0172] [Comparative Example 3] The same procedure as in Example 2 was followed, except that Amberlyst-15 hydroxyl form dry (manufactured by Merck) (sulfur atom content: 13.96 mmol) was used instead of sulfo-modified silica monolith (sulfur atom content: 2.04 mmol). The data for Comparative Example 3 are shown in Table 1. Mixture M1 solidified in reactor 14, and benzyl acetate could not be obtained, so the yield in Table 1 is indicated as "-". Since Amberlyst-15 hydroxyl form dry is an ion exchange resin modified with sulfo groups, the porous body before modification was not evaluated. Also, since Amberlyst-15 hydroxyl form dry does not have macropores, the macropore size was not evaluated.

[0173] [Comparative Example 4] The same procedure as in Example 1 was followed, except that a sulfo-modified material (sulfur atom content: 0.009 mmol) obtained by modifying Wako Gel R Q-12 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) with sulfo groups was used instead of sulfo-modified silica monolith (sulfur atom content: 0.009 mmol), and the yield of benzyl acetate was determined. Wako Gel R Q-12 was used after its particle size was adjusted to 100 μm or more and 300 μm or less by classification. The yield of benzyl acetate was 4.1%. The data for Comparative Example 4 is shown in Table 1. Since Wako Gel R Q-12 does not have macropores, the macropore size was not evaluated.

[0174] [Comparative Example 5] The same procedure as in Example 1 was followed, except that a sulfo-modified material (sulfur atom content: 0.009 mmol) obtained by modifying WakoSil RC-300 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) with sulfo groups was used instead of sulfo-modified silica monolith (sulfur atom content: 0.009 mmol), and the yield of benzyl acetate was determined. WakoSil RC-300 was used after its particle size was adjusted to 100 μm or more and 210 μm or less by classification. The yield of benzyl acetate was 35.0%. The data for Comparative Example 5 is shown in Table 1. Since WakoSil RC-300 does not have macropores, the macropore size was not evaluated.

[0175] [Comparative Example 6] The same procedure as in Example 5 was performed, except that Amberlyst-15 hydroxyl form dry resin (manufactured by Merck) (sulfur atom content: 0.15 mmol) was used instead of sulfo-modified silica monolith (sulfur atom content: 0.15 mmol), and the conversion rate (molar basis) from ethyl benzoate to methyl benzoate was determined. The conversion rate (molar basis) from ethyl benzoate to methyl benzoate was 29.1%. The data for Comparative Example 6 is shown in Table 2.

[0176] [Comparative Example 7] The same procedure as in Example 6 was followed, except that Amberlite 200CTH (manufactured by Organo Corporation) (sulfur atom content: 0.09 mmol) was used instead of sulfo-modified silica monolith (sulfur atom content: 0.09 mmol), and the yield of N-tert-butylbenzamide was determined. The yield of N-tert-butylbenzamide was 31.0%. The data for Comparative Example 7 is shown in Table 2.

[0177] [Comparative Example 8] The same procedure as in Example 7 was followed, except that Amberlyst-15 hydroxyl form dry resin (manufactured by Merck) (sulfur atom content: 0.06 mmol) was used instead of sulfo-modified silica monolith (sulfur atom content: 0.06 mmol), and the yield of benzyl alcohol was determined. The yield of benzyl alcohol was 51.4%. The data for Comparative Example 8 is shown in Table 2.

[0178]

[0179]

[0180] 1...Ceramic framework 2...Macropores 3...Mesopores 10...Flow reactor 11...Mixer 12...First supply unit 13...Second supply unit 14...Reactor 15...Temperature controller 16...Recovery container

Claims

1. A solid acid catalyst comprising a porous body having a co-continuous structure formed by a ceramic skeleton containing mesopores and macropores, and a sulfo-group modified porous body comprising sulfo groups modifying the surface of the ceramic skeleton, wherein the most frequent pore size of the macropores in the sulfo-group modified porous body is 200.0 nm or more and 5000.0 nm or less.

2. The solid acid catalyst according to claim 1, wherein the most frequent pore size of the mesopores in the sulfo-modified porous body is 2.0 nm or more and 50.0 nm or less.

3. The solid acid catalyst according to claim 1, wherein the amount of sulfur atoms contained in the sulfo-modified porous body is 0.10 mmol / g or more and 5.00 mmol / g or less.

4. The solid acid catalyst according to claim 1, wherein the ratio of the most frequent pore diameter of the macropores of the sulfo-modified porous material to the most frequent pore diameter of the mesopores of the sulfo-modified porous material is 15.0 or more and 300.0 or less.

5. The solid acid catalyst according to claim 1, wherein the ceramic skeleton comprises one or more elements selected from silicon, aluminum, tin, cerium, titanium, and zirconium.

6. The solid acid catalyst according to any one of claims 1 to 5, wherein the solid acid catalyst is a solid acid catalyst for organic reactions.

7. The solid acid catalyst according to claim 6, wherein the organic reaction is selected from esterification, transesterification, hydrolysis of esters, and Ritter reaction.

8. An organic reaction method comprising the step of carrying out an organic reaction using a solid acid catalyst according to any one of claims 1 to 5.

9. The organic reaction method according to claim 8, wherein the organic reaction is selected from an esterification reaction, a transesterification reaction, an ester hydrolysis reaction, and a Ritter reaction.

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