Carbon material having sulfo group, and method for producing carbon material

Abstract

The present invention pertains to a carbon material having sulfo groups, the carbon material being configured such that: the amount of the sulfo groups as calculated by titrating, with a 0.01 mol / L NaOH aqueous solution, a filtrate obtained by filtering a mixture resulting from agitating the carbon material and a 0.1 mol / L NaCl aqueous solution for 30 minutes is 0.55-5.0 mmol / g; and the ratio of the elemental sulfur molar content SXPS as determined by an XPS method to the elemental sulfur molar content SEA as determined by an elemental analysis (SXPS / SEA) is 0.90-2.0.

Description

Carbon material having sulfo group and method for producing carbon material

[0001] The present invention relates to a carbon material having a sulfo group and a method for producing the same.

[0002] Solid acids are used as catalysts in numerous chemical reactions, such as hydration, dehydration, polycondensation, alkylation, esterification, etherification, etc. For example, known examples of solid acids in which a sulfo group is attached to carbon include a catalyst for decomposing and carbonizing organic matter such as food waste, which is obtained by sulfonating activated carbon or the like with concentrated sulfuric acid or fuming sulfuric acid (Patent Document 1), a carbon-based solid acid having a specific BET specific surface area and amount of sulfonic acid groups, which is obtained by sulfonating porous carbon derived mainly from cellulose-containing raw materials in concentrated sulfuric acid, fuming sulfuric acid, or sulfur trioxide (Patent Document 2), and a carbon-based solid acid obtained by carbonizing organic matter such as cellulose or lignin, and sulfonating it with concentrated sulfuric acid or fuming sulfuric acid (Patent Document 3).

[0003] Patent No. 4894055 Patent No. 5528036 Patent No. 5152992

[0004] Various studies have been conducted on carbon-based solid acids containing sulfo groups, but further improvements in catalytic activity, such as carbonization at lower temperatures, are needed. However, conventional production methods that introduce sulfo groups into carbon-based materials by reacting them with concentrated sulfuric acid or fuming sulfuric acid have not been able to sufficiently improve catalytic activity. According to the inventors' studies, this is thought to be because the amount of sulfo groups contributing to the catalytic reaction in the carbon material is low or because sulfo groups are locally present in the carbon material. For example, Patent Document 1 discloses a catalyst for decomposing and carbonizing organic matter by sulfonating activated carbon particles with concentrated sulfuric acid, but it is difficult to sufficiently increase the amount of sulfo groups contributing to the catalytic reaction. Carbon materials sulfonated by reacting a cellulose-containing raw material (carbon source) with a strong acid such as concentrated sulfuric acid, as described in Patent Documents 2 and 3, contain a large amount of sulfur elements in forms other than sulfo groups, making it difficult to sufficiently increase the amount of sulfo groups contributing to the catalytic reaction.

[0005] Therefore, an object of the present invention is to provide a carbon material that has high reactivity and can be sufficiently carbonized even at low temperatures, for example.

[0006] In order to solve the above-mentioned problems, the present inventors have conducted extensive research into carbon materials, and as a result have found a carbon material that has sufficient sulfo groups that contribute to catalytic reactions, and that has high reactivity and can be carbonized sufficiently, for example, even at low temperatures, by adjusting the ratio of the molar content of sulfur element determined by elemental analysis to the molar content of sulfur element determined by XPS within a specific range. The present invention encompasses the following preferred embodiments. [1] A carbon material having sulfo groups, wherein the amount of sulfo groups calculated by titrating the filtrate obtained by stirring the carbon material with a 0.1 mol / L aqueous NaCl solution for 30 minutes and then filtering it with a 0.01 mol / L aqueous NaOH solution is 0.55 to 5.0 mmol / g, and the molar content S of sulfur element of the carbon material determined by elemental analysis is EA The molar content S of sulfur element determined by XPS method XPS The ratio (S XPS / S EA [2] The carbon interplanar spacing (d 002 [3] The carbon material according to [1], wherein the peak at 1230 cm in the Raman spectrum observed by laser Raman spectroscopy is 3.70 to 4.50 Å. －１ Nearby peaks and 1380cm －１ Intensity ratio I of the peaks near 1230 / I 1380 [4] The carbon material according to [1] or [2], wherein the value of 1380 cm in the Raman spectrum observed by laser Raman spectroscopy is 0.05 to 0.5. －１ The half-width of the peak in the vicinity is 150 cm －１ More than 350cm －１ [5] The carbon material according to any one of [1] to [4], wherein the sulfur content determined by elemental analysis is 1.8 to 16 mass %. [6] The carbon material according to any one of [1] to [5], wherein the carbon content determined by elemental analysis is 35 to 75 mass %. [7] The specific surface area determined by the BET method is 0.1 to 500 m２ / g of the carbon material according to any one of [1] to [6]. [8] The carbon material according to any one of [1] to [7], which is a carbon-based solid acid catalyst. [9] The carbon material according to [8], which is a catalyst used for carbonizing organic matter.

[10] A method for producing a carbon material, comprising preparing a mixed solution containing a carbon source, a compound containing a sulfo group, and a polar solvent, and adding the mixed solution to a heated nonpolar solvent to remove the polar solvent from the mixed solution, thereby producing a carbon material.

[11] The production method according to

[10] , wherein the compound containing a sulfo group further contains a hydroxyl group.

[12] The production method according to

[10] or

[11] , wherein the mixed solution is a mixed solution containing a carbon source, a compound containing a sulfo group, and sulfuric acid.

[13] The production method according to any one of

[10] to

[12] , wherein the carbon source is at least one selected from the group consisting of sugars and organic acids.

[0007] According to the present invention, it is possible to provide a carbon material that has high reactivity and can be sufficiently carbonized even at low temperatures, for example.

[0008] Hereinafter, embodiments of the present invention will be described in detail. Note that the following description is merely illustrative of embodiments of the present invention, and is not intended to limit the present invention to the following embodiments.

[0009] [Carbon Material] The carbon material of the present invention has sulfo groups, and the amount of sulfo groups calculated by titrating the filtrate obtained by stirring the carbon material and a 0.1 mol / L aqueous NaCl solution for 30 minutes and then filtering the resultant solution with a 0.01 mol / L aqueous NaOH solution is 0.55 to 5.0 mmol / g, and the molar content S of sulfur element of the carbon material determined by elemental analysis is 0.55 to 5.0 mmol / g. EA The molar content S of sulfur element determined by XPS method XPS The ratio (S XPS / S EA ) is 0.90 to 2.0.

[0010] In the carbon material of the present invention, the amount of sulfo groups calculated by titrating the filtrate obtained by stirring the carbon material and a 0.1 mol / L aqueous NaCl solution for 30 minutes and then filtering the mixture with a 0.01 mol / L aqueous NaOH solution (hereinafter, also referred to as the "amount of sulfo groups") is 0.55 to 5.0 mmol / g. The amount of sulfo groups calculated by the above method is the amount of sulfo groups that contribute to a catalytic reaction when the carbon material is used as a catalyst. This method calculates the amount of groups that have been salt-exchanged with NaCl, among the groups contained in the carbon material, by titrating with an aqueous NaOH solution, and therefore can accurately quantify the amount of groups present as strong acids in the carbon material.

[0011] When the carbon material and the 0.1 mol / L NaCl aqueous solution are stirred, the amount of the 0.1 mol / L NaCl aqueous solution per 0.1 g of the carbon material is preferably 10 to 30 mL. The stirring method is not particularly limited as long as they are sufficiently mixed.

[0012] After stirring, the solids and filtrate are separated by filtration, and the resulting filtrate is titrated with a 0.01 mol / L NaOH aqueous solution. A phenolphthalein solution is used as the indicator during titration. For example, 1 to 3 drops of the indicator are added to 5 ml of filtrate, and the sample is thoroughly stirred until it becomes homogeneous. The sample is then titrated with a 0.01 mol / L NaOH aqueous solution, and the titer is read when the indicator turns pink.

[0013] The method for calculating the amount of sulfo groups is not particularly limited. When the amount of the carbon material mixed with the NaCl aqueous solution is a [g], the amount of the NaCl aqueous solution is b [ml], the amount of the filtrate used in the titration is c [ml], and the titration amount of the 0.01 mol / L NaOH aqueous solution dropped onto the filtrate is X [ml], the following calculation can be performed: It is calculated as follows.

[0014] When the amount of sulfo groups is 0.55 mmol / g or more, the amount of sulfo groups contributing to the catalytic reaction is sufficient, resulting in high reactivity and sufficient carbonization even at low temperatures. When the amount of sulfo groups is less than 0.55 mmol / g, the amount of sulfo groups contributing to the catalytic reaction is insufficient, resulting in low reactivity and inability to achieve sufficient carbonization even at low temperatures. A larger amount of sulfo groups is preferable because it enhances catalytic function, but from the perspective of productivity and repeated use of the carbon material, the amount is 5.0 mmol / g or less. When the amount of sulfo groups exceeds 5.0 mmol / g, the solubility of the carbon material is likely to increase, which may make it difficult to produce the carbon material or to use it repeatedly.

[0015] In the carbon material of the present invention, the amount of sulfo groups is preferably 0.7 to 4.0 mmol / g, more preferably 1.0 to 3.0 mmol / g, even more preferably 1.3 to 2.5 mmol / g, and still more preferably 1.5 to 2.2 mmol / g.

[0016] The molar content S of sulfur element determined by elemental analysis of the carbon material of the present invention EA The molar content S of sulfur element determined by XPS method XPS The ratio of (hereinafter referred to as "S XPS / S EA The molar content of sulfur element S determined by elemental analysis is 0.90 to 2.0. EA is the amount of sulfur element contained in the entire carbon material. The molar content of sulfur element S determined by XPS method XPS corresponds to the amount of elemental sulfur contained in the surface region of the carbon material. XPS / S EA When S is 0.90 or more, there are sufficient sulfo groups present on the surface of the carbon material that can come into contact with the substrate, resulting in high reactivity. XPS / S EA If S is less than 0.90, the reactivity is low because there are few sulfo groups present on the surface of the carbon material that can come into contact with the substrate. XPS / S EA If the value exceeds 2.0, sulfo groups are too concentrated on the surface, which tends to increase the solubility of the carbon material, making it difficult to produce the carbon material or to use it repeatedly.

[0017] In the carbon material of the present invention, S XPS / S EA is preferably 0.90 to 1.5, more preferably 0.90 to 1.3, even more preferably 0.92 to 1.2, and still more preferably 0.95 to 1.1, from the viewpoints of the reactivity of the carbon material as a catalyst, the productivity of the carbon material, and repeated use.

[0018] Here, when sulfo groups are introduced into a carbon source using a strong acid such as concentrated sulfuric acid or fuming sulfuric acid, it is thought that carbonization due to a strong dehydration action proceeds in preference to sulfonation, particularly on the surface, and that there are fewer sites on the surface of the carbon material that can serve as reaction sites with sulfonic acid. Also, when sulfo groups are introduced after carbonization of the carbon source or after pre-carbonization of the carbon source, heat is more likely to be applied to the surface of the carbon source when the carbon source is carbonized, and the carbon structure develops more rapidly on the surface than inside the carbon source, which is thought to result in fewer sites on the surface of the carbon material that can serve as reaction sites with sulfonic acid. For this reason, there is a tendency for sulfo groups to be much more abundant inside the carbon material than on the surface, increasing the amount of sulfo groups and increasing the amount of S. XPS / S EA It is difficult to adjust the value to fall within the above range.

[0019] In the carbon material of the present invention, the molar content S of sulfur element determined by elemental analysis EA is preferably 1.0 to 7.0 mol%, more preferably 2.0 to 6.0 mol%, even more preferably 3.0 to 5.0 mol%, and even more preferably 3.5 to 4.5 mol%. XPS is preferably 1.2 to 7.0 mol%, more preferably 2.5 to 6.0 mol%, even more preferably 3.5 to 5.5 mol%, and still more preferably 4.0 to 5.0 mol%.

[0020] In the carbon material of the present invention, the amount of sulfo groups is 0.55 to 5.0 mmol / g, and the molar content S of sulfur element determined by elemental analysis EA The molar content of sulfur element S obtained by XPS method XPS The ratio (S XPS / S EA) is 0.90 to 2.0, a sufficient amount of sulfo groups is present in the carbon material, and these sulfo groups are present on the surface and inside the carbon material at a predetermined ratio relative to the entire carbon material, and are considered to be relatively uniformly distributed. The presence of a predetermined amount or more of sulfo groups, as detected in the titration described above, allows them to come into contact with the substrate, contributing to improved reactivity with the substrate. Therefore, for example, when the carbon material is used as a carbonization catalyst, organic matter can be sufficiently carbonized at low temperatures. Although the reason for the improved reactivity is unclear, the presence of such sulfo groups inside the carbon material is considered to enable the carbon material to maintain its high reactivity as a catalyst. Furthermore, since catalytic action can be obtained through the internal sulfo groups even if the surface is scraped, repeated use is also considered advantageous.

[0021] S EA and S XPS can be measured, for example, by an organic trace element analyzer and a scanning X-ray photoelectron spectrometer, respectively, as described below.

[0022] The amount of sulfo groups in the carbon material of the present invention and S XPS / S EA There are no particular limitations on the method for adjusting the value to fall within the above range. For example, when a carbon material is produced by a carbon material production method described below, the value can be adjusted by adjusting the amount of the compound containing a sulfo group, the reaction temperature, and, when sulfuric acid is used, the concentration and amount of sulfuric acid.

[0023] Carbon interplanar spacing (d ００２ ) is preferably 3.70 to 4.50 Å, more preferably 3.85 to 4.40 Å, even more preferably 3.90 to 4.30 Å, and still more preferably 3.95 to 4.20 Å, from the viewpoint of lowering the crystallinity of the carbon material and increasing the number of sites into which a sulfo group can be introduced.

[0024] Carbon interplanar spacing (d ００２ ) can be calculated by the Bragg equation based on the peak position (diffraction angle 2θ) observed by X-ray diffraction, and specifically, is measured by the method described in the Examples.

[0025] Carbon interplanar spacing (d００２ The method for adjusting the sulfo group-containing compound (C) to fall within the above range is not particularly limited. However, when a carbon material is produced by the carbon material production method described below, the sulfo group-containing compound (C) can be adjusted by adjusting the type and amount of the carbon source and the sulfo group-containing compound, as well as the reaction temperature.

[0026] In a preferred embodiment, the carbon material has a Raman spectrum of 1230 cm observed by laser Raman spectroscopy. －１ Nearby peaks and 1380cm －１ The intensity ratio of the peaks in the vicinity of the Raman peak (hereinafter referred to as "Raman peak intensity ratio I") 1230 / I 1380 ") is preferably 0.05 to 0.5, more preferably 0.1 to 0.4, and even more preferably 0.2 to 0.3. －１ The peak around 1380 cm is a Raman peak generally called the D band, which is caused by disorder and defects in the graphite structure, and indicates that the carbon structure is amorphous. －１ The peak around 1365 cm －１ ~1395cm －１ , preferably 1370 cm －１ ~1390cm －１ On the other hand, it is observed in the range of 1230 cm －１ The peak in the Raman spectrum around 1380 cm －１ The Raman peak intensity ratio I is a peak due to an amorphous carbon structure with a higher degree of amorphousness than the carbon structure due to the peaks in the vicinity. 1230 / I 1380 A large value of α can be said to characterize the high non-crystallinity of the amorphous structure of the carbon material, and indicates that there are many sites to which sulfo groups can be introduced due to the low crystallinity.

[0027] In a preferred embodiment of the present invention, a carbon material is characterized by a Raman spectrum of 1380 cm in a Raman spectrum observed by laser Raman spectroscopy. －１ The half-width value of the peak in the vicinity is preferably 150 to 350 cm －１ , more preferably 200 to 300 cm －１ , more preferably 230 to 280 cm －１ It is 1380 cm－１ The half-width value of the peak in the vicinity falling within the above range indicates that the carbon structure is sufficiently amorphous, and that there are many sites into which a sulfo group can be introduced due to low crystallinity.

[0028] 1230 cm of the Raman spectrum －１ Peak intensity I near 1230 , 1380 cm －１ Peak intensity I near 1380 , and 1380 cm in the Raman spectrum －１ The half-width of the peak in the vicinity can be measured, for example, by the method described in the Examples below.

[0029] Raman peak intensity ratio I 1230 / I 1380 , and 1380 cm －１ There are no particular limitations on the method for adjusting the half-width of the peak in the vicinity to the above range. However, when a carbon material is produced by the carbon material production method described below, the half-width can be adjusted by adjusting the type and amount of the carbon source and the compound containing a sulfo group, as well as the reaction temperature.

[0030] In a preferred embodiment, the sulfur content of the carbon material determined by elemental analysis is preferably 1.8 to 16% by mass, more preferably 2.7 to 14% by mass, and even more preferably 7.0 to 12% by mass. Generally, the sulfur content of a carbon material includes sulfur in forms other than the sulfo group content, such as sulfide bonds (RSR) and sulfoxide bonds (R2-(S=O)), and therefore cannot be considered equivalent to the sulfo group content. For example, in the case of a carbon material sulfonated using a strong acid such as concentrated sulfuric acid or fuming sulfuric acid, the reactivity of concentrated sulfuric acid or fuming sulfuric acid is high, and side reactions other than sulfonation are likely to proceed, which tends to produce functional groups other than sulfo groups. As a result, the proportion of sulfur in forms other than sulfo groups increases, and it cannot be said that sulfo groups are sufficiently introduced. Therefore, when the sulfo group content of a carbon material is 0.55 to 5.0 mmol / g, and the molar sulfur content S of the carbon material determined by elemental analysis is 0.55 to 5.0 mmol / g, the sulfo group content of the carbon material is 0.55 to 5.0 mmol / g. EA The molar content S of sulfur element determined by XPS method XPS The ratio (S XPS / SEA ) is 0.90 to 2.0, and the sulfur element content is preferably within the above range.

[0031] In a preferred embodiment, the carbon content of the carbon material determined by elemental analysis is preferably 35 to 75 mass%, more preferably 40 to 70 mass%, and even more preferably 45 to 60 mass%, from the viewpoint of maintaining the carbon skeleton while having a sufficient amount of sulfo groups in the carbon skeleton. A low carbon content determined by elemental analysis indicates the presence of a large amount of elements other than carbon, i.e., the presence of a large amount of sulfo groups in the carbon material of the present invention.

[0032] The sulfur element content and carbon element content determined by elemental analysis can be measured, for example, by an organic trace elemental analyzer, as described below.

[0033] There are no particular limitations on the method for adjusting the sulfur element content and carbon element content determined by elemental analysis to fall within the above ranges. When a carbon material is produced by a carbon material production method described below, the sulfur element content and carbon element content can be adjusted by adjusting the type and amount of the carbon source and the compound containing a sulfo group, the reaction temperature, and, when sulfuric acid is used, the concentration and amount of sulfuric acid.

[0034] In a preferred embodiment, the specific surface area of ​​the carbon material calculated by the BET method from the nitrogen adsorption isotherm is preferably 0.1 to 500 m ２ / g, more preferably 0.5 to 400 m ２ / g, more preferably 1 to 300 m ２ / g. The specific surface area is 500 m ２ When the specific surface area is 0.1 m / g or less, the contact area between the air and the carbon material is reduced, which reduces the hygroscopicity of the carbon material and the amount of water present in the carbon material. As a result, it is thought that hydrolysis of sulfo groups due to water is suppressed, and the resulting decrease in catalytic function can be suppressed. ２ / g or more, it is believed that the contact area with the substrate can be increased, and the catalytic function can be further improved.

[0035] The specific surface area can be calculated by measuring the adsorption isotherm of the carbon material and analyzing the adsorption isotherm by a multipoint method using the BET equation, as described in the Examples below.

[0036] There are no particular limitations on the method for adjusting the specific surface area to the above range. However, when a carbon material is produced by the carbon material production method described below, the specific surface area can be adjusted by adjusting the type and amount of the carbon source and the compound containing a sulfo group, as well as the reaction temperature.

[0037] The shape and size of the carbon material are not particularly limited. The carbon material may be, for example, particulate, flaky, layered, etc., and is preferably particulate from the viewpoint of the reactivity of the carbon material as a catalyst. In this case, the average particle size (diameter) of the carbon material is preferably 10 to 200 μm, more preferably 30 to 100 μm. The average particle size (diameter) of the carbon material can be measured by a laser scattering method as described in the Examples below.

[0038] [Method for Producing Carbon Material] The carbon material of the present invention may be produced by any production method as long as it satisfies the above-mentioned characteristics. For example, the carbon material of the present invention can be produced by a method comprising the steps of: (1) preparing a mixed solution containing a carbon source, a compound containing a sulfo group, and a polar solvent; and (2) adding the mixed solution to a heated nonpolar solvent to remove the polar solvent from the mixed solution, thereby producing a carbon material. The present invention also provides a method for producing the above-mentioned carbon material.

[0039] In step (1), a mixture containing a carbon source, a compound containing a sulfo group, and a polar solvent is prepared. The carbon source is not particularly limited, and examples include sugars, organic acids, hydrophilic polymers, etc. These carbon sources can be used alone or in combination of two or more. Examples of sugars include monosaccharides such as glucose, galactose, mannose, fructose, ribose, and glucosamine; disaccharides such as sucrose, trehalose, maltose, cellobiose, maltitol, lactobionic acid, and lactosamine; and polysaccharides such as starch, cellulose, glycogen, pectin, curdlan, and guar gum. When the carbon source is a sugar, the hydroxyl groups in the sugar serve as reaction sites for introducing sulfo groups, allowing for the introduction of many sulfo groups. Examples of organic acids include aliphatic carboxylic acids such as propionic acid, butyric acid, valeric acid, caproic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, palmitic acid, stearic acid, succinic acid, linoleic acid, oleic acid, and adipic acid; aromatic carboxylic acids such as benzoic acid, salicylic acid, phthalic acid, and terephthalic acid; and hydroxycarboxylic acids such as lactic acid, tartaric acid, citric acid, and malic acid. When the carbon source is an organic acid, the carboxyl groups in the organic acid serve as reaction sites for introducing sulfo groups, allowing for the introduction of many sulfo groups. Examples of hydrophilic polymers include polyvinyl alcohol, polyacrylic acid, and polyvinylpyrrolidone. When the carbon source is a monosaccharide, oligosaccharide (a sugar formed by the bonding of 2 to 10 monosaccharides) or organic acid, which have lower molecular weights than polysaccharides, it is believed that sulfo groups can be introduced relatively uniformly into the carbon material. From the viewpoint of carbon formation and introduction of sulfo groups, the carbon source is preferably a sugar or an organic acid, more preferably a monosaccharide, an oligosaccharide or an organic acid, and even more preferably glucose or citric acid.

[0040] The sulfo group-containing compound is not particularly limited, and examples thereof include organic sulfonic acids. Organic sulfonic acids are organic compounds having a sulfo group, and examples of organic sulfonic acids include aromatic sulfonic acids and aliphatic sulfonic acids. Aromatic sulfonic acids include those in which a sulfo group is bonded to an aromatic ring such as a benzene ring or a naphthalene ring. Aliphatic sulfonic acids include linear and cyclic sulfonic acids. The sulfo group-containing compound preferably further contains a hydroxyl group, since the hydroxyl group serves as a reaction site with the carbon source. Examples of sulfo group-containing compounds that contain a hydroxyl group include phenolic sulfonic acids and hydroxyl alkyl sulfonic acids. From the viewpoint of high reactivity with the carbon source, the sulfo group-containing compound is preferably at least one selected from the group consisting of phenolic sulfonic acids and hydroxyl alkyl sulfonic acids, and more preferably at least one selected from the group consisting of paraphenol sulfonic acid and hydroxyethyl sulfonic acid.

[0041] The polar solvent is not particularly limited, and any solvent can be used as long as it can disperse or dissolve the carbon source and the compound containing a sulfo group, and is incompatible with the nonpolar solvent. Examples of polar solvents include water or alcohol. The polar solvents can be used alone or in combination of two or more. Examples of alcohols include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, ethylene glycol, and glycerin. In this specification, the polar solvent is preferably water or ethanol, and more preferably water.

[0042] The mixture may be a solution or a suspension containing a polar solvent, but is preferably a solution from the viewpoint of uniformly mixing the carbon source and the compound containing a sulfo group.

[0043] The amount of the carbon source in the mixed solution is preferably 10 to 60 parts by mass, more preferably 15 to 55 parts by mass, and even more preferably 20 to 50 parts by mass, relative to 100 parts by mass of the solid content of the mixed solution. When the amount of the carbon source in the solid content of the mixed solution is within the above range, it is possible to maintain the carbon skeleton while having a sufficient number of sulfo groups in the carbon skeleton, which is preferable.

[0044] The amount of the compound containing a sulfo group in the mixed solution is preferably 80 to 500 parts by mass, more preferably 130 to 450 parts by mass, and even more preferably 180 to 400 parts by mass, relative to 100 parts by mass of the carbon source. When the amount of the compound containing a sulfo group is within the above range, the amount of sulfo groups and the amount of elemental sulfur in the resulting carbon material can be adjusted to suitable ranges.

[0045] The amount of the polar solvent in the mixed solution is preferably 300 to 1,200 parts by mass, more preferably 350 to 1,150 parts by mass, and even more preferably 400 to 1,000 parts by mass, relative to 100 parts by mass of the carbon source. When the amount of the polar solvent is within the above range, the carbon source, the compound containing a sulfo group, and the like can be sufficiently dissolved or dispersed and homogenized.

[0046] In a preferred embodiment of the present invention, the mixed solution contains a carbon source, a compound containing a sulfo group, and sulfuric acid. In this embodiment, the sulfuric acid contained in the mixed solution may be dilute or concentrated sulfuric acid, but is preferably dilute sulfuric acid with a concentration of 5 to 20% by mass, and particularly preferably 10% by mass. When concentrated sulfuric acid is used, the reaction may not proceed smoothly because the strong dehydrating effect of concentrated sulfuric acid may cause carbonization of the carbon source to occur preferentially over sulfonation at room temperature, or because the carbon source and the compound containing a sulfo group do not completely dissolve in concentrated sulfuric acid and a homogeneous mixture is not formed. When dilute sulfuric acid is contained in the mixture, sulfate ions in the dilute sulfuric acid react with the carbon source, thereby facilitating the introduction of sulfo groups. In this embodiment, the amount of sulfuric acid contained in the mixed solution is preferably 300 to 1200 parts by mass, more preferably 350 to 1150 parts by mass, and even more preferably 400 to 1000 parts by mass per 100 parts by mass of the carbon source. The water contained in the sulfuric acid corresponds to a polar solvent.

[0047] The method for mixing the carbon source, the compound containing a sulfo group, and the polar solvent, and the method for mixing the carbon source, the compound containing a sulfo group, and the sulfuric acid are not particularly limited, and any mixing method can be used. Heating may be performed during mixing.

[0048] In step (2), the mixed solution obtained in step (1) is added to a heated nonpolar solvent, thereby removing the nonpolar solvent from the mixed solution and producing a carbon material. In this specification, a nonpolar solvent refers to a solvent that is incompatible with a polar solvent. Examples of nonpolar solvents include nonaromatic hydrocarbons, aromatic hydrocarbons, silicone oil, ethers, and esters. More specific examples include nonane, decane, dodecane, tetradecane, ethylcyclohexane, isopropylcyclohexane, silicone oil, p-cymene, phenyl ether, and diethyl phthalate. One type of nonpolar solvent may be used alone, or two or more types may be used in combination. Decane, dodecane, and tetradecane are preferred nonpolar solvents from the viewpoints of their high boiling point and low reactivity with the carbon source and the compound containing a sulfo group.

[0049] When the mixed solution obtained in step (1) is added dropwise to the nonpolar solvent described above, the nonpolar solvent is insoluble in the polar solvent in the mixed solution, and therefore, it is believed that the polar solvent is removed from the mixed solution. By adding the mixed solution dropwise to the heated nonpolar solvent, the polar solvent is removed and the carbon source and the compound containing sulfo groups are carbonized by heating, thereby obtaining the carbon material of the present invention. At this time, carbonization proceeds in a state in which the organic substance serving as the carbon source and the compound containing sulfo groups are mixed, i.e., in a state in which the sulfo groups are distributed relatively uniformly throughout the carbon material, and therefore, it is believed that many sulfo groups that can contribute to the catalytic reaction are introduced both on the surface and inside of the carbon skeleton.

[0050] In the step (2), the size of the droplets of the mixed liquid dropped into the non-polar solvent is preferably 0.1 to 5 mm from the viewpoint of uniform heating throughout.

[0051] In the step (2), the dropwise addition rate when the mixed solution is added to the heated non-polar solvent is preferably 0.1 to 1.0 ml / min from the viewpoints of productivity and dispersibility of the carbon material.

[0052] The heating temperature of the non-polar solvent is preferably 170 to 250°C, more preferably 190 to 230°C, from the viewpoint of forming a carbon skeleton and introducing a sufficient amount of sulfo groups.

[0053] Taking the heating temperature into consideration, the boiling point of the non-polar solvent is preferably 170° C. or higher, more preferably 200° C. or higher, and even more preferably 230° C. or higher.

[0054] The heating time after the completion of dropwise addition of the mixed solution may be appropriately selected depending on the type or amount of the non-polar solvent and mixed solution used, but is preferably 0 to 5 hours, more preferably 0.5 to 3 hours.

[0055] An oil bath can be used as a device for heating the non-polar solvent.

[0056] It is also preferable to remove the polar solvent from the system. The apparatus used in step (2) is not particularly limited, but may be, for example, a Dean-Stark apparatus, a reflux condenser, a syringe pump, a separable flask, or the like.

[0057] The step (2) is preferably carried out in an inert gas atmosphere, such as nitrogen or argon.

[0058] After step (2), the resulting mixture is cooled to room temperature, and the non-polar solvent is removed by filtration to obtain a carbon material. The resulting carbon material may be washed with water and / or dried, as necessary. When drying the carbon material after washing with water, it may be subjected to a drying treatment using a known dryer such as a hot air dryer or a reduced pressure dryer. Drying is preferably carried out at a temperature of 80 to 150°C for 4 to 8 hours. It is preferable that the drying temperature and drying time are within the above ranges, because water and the non-polar solvent can be sufficiently removed without decomposing the carbon material.

[0059] The obtained carbon material may be pulverized. The pulverization step is a step for controlling the shape, particle size, etc. of the finally obtained carbon material to a desired shape, particle size, etc. The pulverization method is not particularly limited, and known pulverizers such as a ball mill, centrifugal roll mill, ring roll mill, centrifugal ball mill, jet mill, cone crusher, double roll crusher, disc crusher, rotary crusher, etc., can be used alone or in combination.

[0060] The method for producing a carbon material may further include a classification step after the pulverization step. For example, by removing particles that are significantly smaller or larger than the desired particle size, porous carbon with a narrow particle size distribution can be obtained. The classification method is not particularly limited, but examples include classification using a sieve, wet classification, and dry classification. Examples of wet classifiers include classifiers that utilize the principles of gravity classification, inertial classification, hydraulic classification, and centrifugal classification. Examples of dry classifiers include classifiers that utilize the principles of sedimentation classification, mechanical classification, and centrifugal classification. From an economical standpoint, it is preferable to use a dry classification device. Furthermore, to prevent surface oxidation during pulverization, it is preferable to perform the pulverization and classification steps in an inert gas atmosphere.

[0061] Pulverization and classification can also be performed using a single device. For example, pulverization and classification can be performed using a jet mill equipped with a dry classification function. Furthermore, devices having a pulverizer and a classifier independent from each other can also be used. In this case, pulverization and classification can be performed continuously, or pulverization and classification can be performed discontinuously.

[0062] [Carbon-based Solid Acid Catalyst] The carbon material of the present invention can be used as a carbon-based solid acid, and can be used, for example, as a dehydration catalyst and a catalyst for various chemical reactions.

[0063] The carbon material of the present invention may be, for example, a catalyst (carbonization catalyst) used for carbonizing organic matter. Conventionally, when food waste or the like is disposed of, it is burned in a waste treatment facility or the like, resulting in CO ２However, by carbonizing food waste and the like using the carbon material of the present invention, it is possible to obtain valuable carbon. Examples of organic matter include wood chips, sawdust, bark, pruned branches, rice husks, aquatic plants, sludge, food waste, and waste plastic. The method for carbonizing organic matter using the carbon material of the present invention as a catalyst is not particularly limited, but includes a method in which the organic matter, such as the wood chips, is mixed with a carbon material and heated under stirring in an inert gas atmosphere. When carbonizing organic matter, water may or may not be added to the organic matter. It is also preferable that moisture is present in the organic matter.

[0064] In the above method, the mixing ratio of the carbon material to the organic substance is preferably 1 to 100 parts by mass, more preferably 10 to 50 parts by mass, of the carbon material per 100 parts by mass of the organic substance.

[0065] The temperature for carbonizing the organic material is not particularly limited as long as it is a temperature at which the carbon-based solid acid functions as a catalyst, but may be, for example, 80 to 200° C., and from the viewpoint of high activation and long-term maintenance of catalytic function, it is preferably 90 to 150° C. The time for carbonizing the organic material is preferably 0.5 to 3 hours from the viewpoint of productivity.

[0066] The carbon material of the present invention is believed to act as a dehydration catalyst in the carbonization reaction, and is believed to be able to catalyze the carbonization reaction more efficiently. Therefore, carbonization can be carried out at a lower temperature. Furthermore, since the carbon material has a large amount of sulfo groups, it is possible to reduce the amount of catalyst used for carbonization.

[0067] The carbonized material obtained as a result of the carbonization reaction can be used for biochar, biocoke, concrete, solid fuel, etc.

[0068] In addition to the above, the carbon material of the present invention can also be used as a catalyst in reactions such as the cleavage of carbon-carbon bonds in molecules, the formation of new carbon-carbon bonds, and the conversion of linear hydrocarbons into branched hydrocarbons (isomerization) by changing the position of carbon-carbon bonds in molecules. For example, the carbon material exhibits catalytic activity in various reactions such as the synthesis of olefins and ethers by dehydration of alcohols, the synthesis of aldehydes and ketones by dehydrogenation of alcohols, the hydration and isomerization of olefins, alkylation, esterification, amidation, acetalization, amination, hydrogen transfer reactions, aldol condensation reactions, hydrolysis reactions, and polymerization reactions.

[0069] The carbonized product obtained by carbonizing an organic substance using the carbon material of the present invention as a carbon-based solid acid catalyst (hereinafter also referred to as a carbon solid acid) is a semi-carbonized product. Therefore, the present invention also relates to a semi-carbonized product obtained by carbonizing an organic substance using the carbon material of the present invention as a carbon-based solid acid catalyst, and a method for producing the semi-carbonized product.

[0070] In order to promote the replacement of fossil fuels with renewable energy, attempts have been made to produce semi-charred materials from waste materials such as wood chips, agricultural residues, and food waste, and use them as fuel. One example of such semi-charred materials is a biomass solid fuel (Japanese Patent No. 7467577), which is obtained by molding woody biomass powder and heating it at 230-275°C, and which reaches a maximum temperature of less than 200°C in a self-heating test. It is also known to use a solid acid as a catalyst when producing semi-charred materials. For example, Japanese Patent No. 4894055 describes the decomposition and carbonization of organic matter such as food waste using a catalyst (solid acid) prepared by sulfonating activated carbon with concentrated sulfuric acid or fuming sulfuric acid.

[0071] Various studies have been conducted on semi-charred materials produced from waste materials, but further improvements in combustibility, such as high calorific value and combustion at lower temperatures, are needed. However, semi-charred materials obtained by heating organic materials such as biomass powder at relatively high temperatures above 230°C and semi-charred materials obtained by sulfonating activated carbon with concentrated sulfuric acid or fuming sulfuric acid have not been able to achieve sufficient combustibility. According to the inventors' research, this is because, in the case of Patent Document 4, semi-charred materials obtained by heating organic materials at relatively high temperatures above 230°C require temperatures above that temperature for combustion, while in the case of Patent Document 4, carbonization is insufficient due to the use of a catalyst (solid acid) with a low amount of sulfo groups contributing to the catalytic reaction. This results in a low density of carbon usable for combustion and a low calorific value.

[0072] Therefore, an object of one aspect of the present invention is to provide a torrefied material having excellent combustibility, for example, a high calorific value, and capable of being combusted at a lower temperature.

[0073] In order to solve the above-mentioned problems, the present inventors conducted extensive research on semi-carbide materials, and as a result, discovered semi-carbide materials that have excellent combustibility, for example, a high calorific value, and can be burned at lower temperatures, by lowering the weight loss onset temperature under a nitrogen atmosphere and increasing the residual rate at 600°C. The present invention encompasses the following preferred embodiments.

[14] A method for producing semi-carbide materials, comprising mixing an organic substance with the carbon material described in any one of [1] to [9] above, and heating the mixture.

[15] The method for producing semi-carbide described in

[14] , wherein the heating temperature is 50°C or higher and lower than 230°C.

[16] Semi-carbide materials, wherein the temperature at which weight loss begins when heated at a rate of 10°C / min under a nitrogen atmosphere by thermogravimetry is 150 to 220°C, and the residual rate at 600°C is 22 to 65% by mass.

[17] An intensity I at 290°C in a DTG curve determined by thermogravimetry under a nitrogen atmosphere. ２９０ Strength I at 360 ° C ３６０ The ratio (I ３６０ / I ２９０

[18] The semi-carbide according to

[16] or

[17] , wherein the ash content is 0 to 2 mass% based on the mass of the semi-carbide.

[19] The semi-carbide according to any one of

[16] to

[18] , wherein the sulfur element content is 10 to 5000 ppm.

[0074] In the above-described aspect of the present invention, it is possible to provide a torrefied product having excellent combustibility, for example, a high calorific value, and capable of being combusted at a lower temperature.

[0075] Hereinafter, embodiments of the present invention will be described in detail. Note that the following description is merely illustrative of embodiments of the present invention, and is not intended to limit the present invention to the following embodiments.

[0076] [Semi-carbonized Product] When the semi-carbonized product of the present invention is heated at a rate of 10°C / min in a nitrogen atmosphere by thermogravimetry, the temperature at which the weight loss begins is 150 to 220°C, and the residual ratio at 600°C is 22 to 65% by mass.

[0077] In the case of the semi-carbide of the present invention, the temperature at which weight loss begins when heated at a rate of 10°C / min in a nitrogen atmosphere by thermogravimetry is 150-220°C. To distinguish the temperature at which weight loss begins from the weight of the semi-carbide at 150°C, the temperature at which the weight loss reaches 0.5% by weight was used as the reference weight, to clearly distinguish it from the amount of moisture loss. According to the above measurement, because the semi-carbide is thermogravimetred in a nitrogen atmosphere without the presence of oxygen, no combustion reaction occurs, and only the pyrolysis reaction can be accurately evaluated. The lower the temperature at which weight loss begins in the pyrolysis reaction, the lower the temperature at which combustion can occur. For example, if the temperature at which weight loss begins is 220°C or below, the semi-carbide can be burned at a temperature as low as 220°C or below. In the semi-carbonized material of the present invention, the temperature at which weight loss begins is preferably 150 to 215°C, for example, 160 to 215°C, 165 to 215°C, more preferably 150 to 210°C, for example, 160 to 210°C, 165 to 210°C, and even more preferably 150 to 200°C, for example, 160 to 200°C, 165 to 200°C.

[0078] The semi-carbonized material of the present invention has a residual fraction of 22 to 65% by mass at 600°C when heated at a rate of 10°C / min in a nitrogen atmosphere by thermogravimetry. The residual fraction at 600°C serves as an index of the degree of carbonization of the semi-carbonized material. The more carbonized the semi-carbonized material, the smaller its weight becomes. Therefore, when heated, the weight loss from the weight before heating is smaller, and the residual fraction at 600°C tends to be higher. When the residual fraction at 600°C is 22% by mass or more, the semi-carbonized material is adequately carbonized, and the density of carbon required for heat generation is high, resulting in a high calorific value upon combustion. When the residual fraction at 600°C exceeds 65% by mass, the semi-carbonized material is considered to be over-carbonized or completely carbonized. In this case, most of the energy contained in the organic material is consumed, resulting in a decrease in the overall energy efficiency obtained from the organic material. In the semi-carbide of the present invention, the residual ratio at 600°C is preferably 24 to 40 mass%, more preferably 25 to 35 mass%, even more preferably 26 to 34 mass%, still more preferably 28 to 33 mass%, and extremely preferably 28 to 32 mass%, from the viewpoints of a high calorific value as a semi-carbide and overall energy efficiency.

[0079] Here, in the case of semi-carbonized materials obtained by heating a carbon source such as biomass powder at a relatively high temperature of 230°C or higher, it is thought that high temperatures of, for example, 230°C or higher are required for thermal decomposition. Therefore, the thermal decomposition onset temperature tends to be high, making it difficult to adjust the temperature at which weight loss begins to occur within the above range. Furthermore, in the case of semi-carbonized materials obtained by a production method in which activated carbon or the like is sulfonated with concentrated sulfuric acid or fuming sulfuric acid, it is thought that carbonization does not proceed sufficiently because the carbonization is performed using a catalyst (solid acid) with a small amount of sulfo groups that contribute to the catalytic reaction. Therefore, it is difficult to adjust the residual ratio at 600°C within the above range.

[0080] When the semi-carbonized material of the present invention is heated at a rate of 10°C / min in a nitrogen atmosphere by thermogravimetry, the temperature at which weight loss begins is 150 to 220°C, and the residual ratio at 600°C is 22 to 65% by mass. This indicates that the semi-carbonized material can be burned at a low temperature and has a high calorific value because the density of the carbon required for heat generation is high due to sufficient semi-carbonization. Therefore, when the semi-carbonized material is used as a solid fuel, for example, it has a high calorific value and can be burned at a lower temperature, allowing the same amount of fuel to generate more heat for a longer period of time, resulting in high combustion efficiency and excellent combustibility.

[0081] There are no particular limitations on the method for adjusting the temperature at which the weight loss of the semi-carbonized product of the present invention begins and the residual rate at 600°C to fall within the above ranges. For example, the temperature and amount of the organic substance when obtaining the semi-carbonized product, the heating temperature and time, and when producing the semi-carbonized product by the semi-carbonized product production method described below, the temperature and amount of the organic substance, the amount of the carbon solid acid, the amount of sulfo groups in the carbon solid acid, and the reaction temperature and reaction time of the organic substance and the carbon solid acid can be adjusted.

[0082] The temperature at which weight loss begins and the residual ratio at 600°C can be measured by thermogravimetry using a simultaneous differential thermal and thermogravimetry analyzer, specifically by the method described in the examples below.

[0083] Intensity I at 290 ° C. in the DTG curve of semi-carbide obtained by thermogravimetry under a nitrogen atmosphere ２９０ Strength I at 360 ° C ３６０ The ratio (I ３６０ / I ２９０ ) is preferably 2.5 or less. The intensity I at 360 ° C in the DTG curve ３６０ is the strength resulting from the decomposition of lignin in the semi-carbonized material. Semi-carbonized material usually contains lignin resulting from the organic wood-based raw material. When semi-carbonized material is heated in a nitrogen atmosphere, the lignin decomposes at 360°C, and a peak usually appears around 360°C. The peak around 360°C is usually observed in the range of 350 to 370°C, preferably 355 to 365°C. On the other hand, the strength I at 290°C in the DTG curve is ２９０is the strength due to the decomposition of hemicellulose and cellulose in the semi-carbonized material. Semi-carbonized material is usually obtained by heating at a relatively high temperature of 230°C or higher, for example, 270°C, so hemicellulose and cellulose, which have low thermal decomposition temperatures, are thermally decomposed to some extent, and the strength I due to the decomposition of lignin is not observed in the DTG curve. ３６０ Intensity I due to the degradation of hemicellulose and cellulose compared to ２９０ However, in the case of semi-carbonized materials obtained by carbonization at low temperatures, for example, below 230°C, hemicellulose and cellulose remain without being thermally decomposed, so a peak is usually observed around 290°C in the DTG curve, and the intensity I at 290°C is ２９０ The peak around 290°C is usually observed in the range of 280 to 300°C, preferably 285 to 295°C. ２９０ The larger the peak ratio (I) in the DTG curve, the lower the temperature at which the torrefied material can begin to thermally decompose, for example, at 220°C or lower. ３６０ / I ２９０ ) characterizes the thermal decomposition behavior of the constituents in the microstructure of the torrefied material, and indicates that the torrefied material is more likely to burn at a lower temperature.

[0084] In a preferred embodiment of the present invention, a peak I in the vicinity of 290 ° C. in a DTG curve of a semi-carbide obtained by thermogravimetry under a nitrogen atmosphere is ２９０ Peak I at around 360 ° C. ３６０ The ratio (I ３６０ / I ２９０ ) is preferably 0.1 to 2.5, more preferably 0.2 to 2.2, and even more preferably 0.3 to 2.0.

[0085] Intensity I at 290°C in the DTG curve determined by thermogravimetry under a nitrogen atmosphere ２９０ Strength I at 360 ° C ３６０ The ratio (I ３６０ / I ２９０The method for adjusting the carbon content of the organic material to fall within the above range is not limited in any way. For example, the carbon content can be adjusted by adjusting the type and amount of the organic material, the heating temperature and time when obtaining the semi-carbonized material, or, when producing the semi-carbonized material by the semi-carbonized material production method described below, the type and amount of the organic material, the amount of the carbon solid acid, the amount of sulfo groups in the carbon solid acid, and the reaction temperature and reaction time of the organic material and the carbon solid acid.

[0086] Intensity I at 290° in the DTG curve determined by thermogravimetry under a nitrogen atmosphere ２９０ Strength I at 360 ° C ３６０ The ratio (I ３６０ / I ２９０ ) can be measured, for example, by the method described in the Examples below.

[0087] The ash content of the semi-carburized material is preferably 0 to 2 mass %, more preferably 0 to 1.9 mass %, based on the mass of the semi-carburized material. In the semi-carburized material, ash is a component that does not contribute to combustion. When the ash content of the semi-carburized material is within the above range, the semi-carburized material has a high carbon purity, which tends to be excellent in combustibility and to suppress the generation of clinker.

[0088] The ash includes inorganic components such as potassium, sodium, iron, and calcium. The potassium content in the semi-carbide is preferably 0 to 1500 ppm, more preferably 0 to 1300 ppm, and even more preferably 0 to 1000 ppm based on the mass of the semi-carbide. The sodium content in the semi-carbide is preferably 0 to 5 ppm, more preferably 0 to 3 ppm, even more preferably 0 to 2 ppm, and particularly preferably 0 to 1.5 ppm based on the mass of the semi-carbide. When a semi-carbide is obtained using the solid carbon acid of the present invention, hydrogen in the sulfo groups contained in the solid carbon acid undergoes ion exchange with metals such as sodium and potassium contained in the organic material that is the raw material for the semi-carbide, and the sodium and potassium contents in the resulting semi-carbide can be within the above-mentioned ranges. When the potassium content and sodium content in the semi-carbide are within the above-mentioned ranges, the semi-carbide has a high carbon purity, tends to have excellent combustibility, and tends to suppress clinker generation.

[0089] There are no particular limitations on the method for adjusting the ash content, potassium content, and sodium content in the semi-carbonized material to fall within the above ranges. For example, these contents can be adjusted by adjusting the type and amount of the organic substance, the heating temperature and time when obtaining the semi-carbonized material, or, when producing the semi-carbonized material by the semi-carbonized material production method described below, the type and amount of the organic substance, the amount of the carbon solid acid, the amount of sulfo groups in the carbon solid acid, and the reaction temperature and reaction time of the organic substance and the carbon solid acid.

[0090] The ash content in the semi-carbonized material can be calculated based on the thermogravimetric residual fraction measured by thermogravimetry under air using a differential thermal and thermogravimetry simultaneous measuring apparatus, and specifically, it is measured by the method described in the examples.

[0091] The potassium content and sodium content in the semi-carbide can be measured by ICP mass spectrometry, specifically by the method described in the Examples.

[0092] The sulfur element content in the semi-carbide is preferably 10 to 5,000 ppm, more preferably 20 to 4,000 ppm, even more preferably 50 to 2,500 ppm, still more preferably 100 to 2,000 ppm, particularly preferably 200 to 1,800 ppm, even more particularly preferably 500 to 1,600 ppm, and extremely preferably 750 to 1,500 ppm. The sulfur element in the semi-carbide is attributable to sulfo groups contained in the catalyst used to obtain the semi-carbide, and this means that the semi-carbide was carbonized using a solid acid catalyst, such as a carbon solid acid. When the semi-carbide is obtained using the solid acid catalyst (carbon solid acid) of the present invention, which has a large amount of sulfo groups that contribute to the catalytic reaction, the sulfur element content in the semi-carbide can be within the above-mentioned range. When the sulfur element content in the semi-carbide is within the above-mentioned range, the semi-carbide tends to have excellent combustibility.

[0093] There are no particular limitations on the method for adjusting the sulfur element content in the semi-carbide to fall within the above range, but when the semi-carbide is produced by the semi-carbide production method described below, the sulfur element content can be adjusted by adjusting the type and amount of organic substance, the amount of carbon solid acid, the amount of sulfo groups in the carbon solid acid, and the reaction temperature and reaction time of the carbon source and the carbon solid acid. The sulfur element content in the semi-carbide can also be adjusted to fall within the above range by removing the carbon solid acid used in producing the semi-carbide after production of the semi-carbide. Methods for removing the carbon solid acid include using a solid acid molded into pellets (on the order of millimeters) as the carbon solid acid and separating it by sieving after production, or loading a magnetic substance such as iron oxide onto the carbon solid acid and separating it by magnetic force.

[0094] The sulfur element content in the semi-carbide can be measured by an organic trace element analyzer, specifically by the method described in the examples.

[0095] [Method for Producing Semi-Carbonized Material] The semi-carbonized material of the present invention may be produced by any method as long as it satisfies the above-mentioned characteristics. For example, the semi-carbonized material of the present invention can be produced by a method including mixing an organic substance with the carbon material of the present invention as a carbon solid acid, and heating the mixture. The heating temperature is preferably 50°C or higher and lower than 230°C. The present invention also provides a method for producing the semi-carbonized material.

[0096] In one embodiment of the present invention, an organic material and a carbon solid acid are mixed to prepare a mixture. The organic material is not particularly limited, and examples thereof include wood chips, sawdust, bark, pruned branches, rice husks, aquatic plants, sludge, food waste, and waste plastic. These organic materials can be used alone or in combination of two or more. From the viewpoint of ease of semi-carbonization, the organic material is preferably wood chips, sawdust, and bark.

[0097] The solid carbon acid is, for example, a catalyst (carbonization catalyst) used to carbonize organic matter. Conventionally, when food waste or the like is disposed of, it is burned in a waste treatment facility or the like, resulting in CO ２However, by carbonizing food waste and the like using a carbon solid acid, it is possible to obtain carbon, which is a valuable material. The carbon solid acid used in the method for producing a semi-carbonized product is preferably the carbon material of the present invention.

[0098] The carbon material (carbon solid acid) of the present invention is thought to act as a dehydration catalyst in the heating (carbonization reaction) and is thought to be able to catalyze the carbonization reaction more efficiently. Therefore, sufficient carbonization can be achieved at a lower temperature, for example, at least 50°C and less than 230°C. It is thought that the semi-carbonized material obtained using the carbon solid acid of the present invention can be burned at a low temperature and has a high calorific value. Therefore, when the semi-carbonized material is used as a solid fuel, for example, it has a high calorific value and can be burned at a lower temperature, so that the same amount of fuel can generate more heat for a longer period of time, resulting in high combustion efficiency and excellent combustibility.

[0099] In one embodiment of the present invention, the mixing ratio of the organic substance and the carbon solid acid in the method for producing a semi-carbonized material is preferably 1 to 100 parts by mass, more preferably 10 to 50 parts by mass, of the carbon solid acid per 100 parts by mass of the organic substance.

[0100] In one embodiment of the present invention, an organic substance and a carbon solid acid are mixed and heated to carbonize the organic substance. The method for mixing the organic substance and the carbon solid acid is not particularly limited, and any mixing method can be used. Heating may also be performed during mixing. When carbonizing the organic substance, water may or may not be added to the organic substance. If water is added, the amount added is such that the water content of the organic substance is preferably 30 to 60 mass %, more preferably 40 to 50 mass %. It is also preferable that moisture is present in the organic substance. From the viewpoint of uniformly absorbing moisture, it is preferable that the organic substance absorbs moisture in advance. In a preferred embodiment of the present invention, the water content of the organic substance is preferably 30 to 60 mass %, more preferably 40 to 50 mass %.

[0101] In one embodiment of the present invention, the temperature at which the organic substance and the carbonaceous solid acid are heated is not particularly limited as long as the carbonaceous solid acid functions as a catalyst. However, from the viewpoint of the combustibility of the obtained semi-carbonized material at low temperatures and the viewpoint of reducing energy consumption, a lower temperature is preferable, and the temperature is preferably 50°C or higher and lower than 230°C, for example, 60°C or higher and lower than 230°C, 65°C or higher and lower than 230°C, 70°C or higher and lower than 230°C, more preferably 50 to 220°C, for example, 60 to 220°C, 65 to 220°C, 70 to 220°C, even more preferably 50 to 200°C, for example, 60 to 200°C, 65 to 200°C, 70 to 200°C, particularly preferably 50 to 150°C, for example, 60 to 150°C, 65 to 150°C, 70 to 150°C, more particularly preferably 50 to 100°C, for example, 50 to 100°C, 65 to 100°C, 70 to 100°C.

[0102] In one embodiment of the present invention, the time for heating the organic substance and the carbon solid acid may be appropriately selected depending on the type or amount of the organic substance and the carbon solid acid used, but from the viewpoint of productivity, it is preferably 0.5 to 3 hours, more preferably 1 to 2 hours.

[0103] An oil bath can be used as a device for heating the organic substance and the carbon solid acid.

[0104] <Uses of Semi-Charred Material> The semi-charred material of the present invention can be used for biochar, bio-coke, concrete, solid fuel, and the like. The semi-charred material of the present invention is sufficiently carbonized at lower temperatures; when heated at a rate of 10°C / min in a nitrogen atmosphere, the temperature at which weight loss begins is 150-220°C, and the residual ratio at 600°C is 22-65% by mass. Semi-charred materials with the above characteristics are believed to be combustible at low temperatures and have a high calorific value. Therefore, when semi-charred materials are used as solid fuel, for example, they have a high calorific value and can be combusted at a lower temperature, allowing the same amount of fuel to generate more heat for a longer period of time, resulting in high combustion efficiency and excellent combustibility.

[0105] The present invention will be specifically described below with reference to examples, but these examples are not intended to limit the scope of the present invention.

[0106] [Analysis Method] <Amount of Sulfo Groups> 0.1 g of carbon material was weighed into a 50 cc sample tube, and 20 mL of a 0.1 mol / L aqueous NaCl solution was added and stirred for 30 minutes. The resulting mixture was filtered through a 0.45 μm filter, and 5 mL of the filtrate was weighed into a beaker, to which three drops of a 10 g / L phenolphthalein solution were added. 0.01 mol / L NaOH was added dropwise until the color of the phenolphthalein changed from clear to pink, and the amount of sulfo groups was calculated from the amount of NaOH added (X ml) using the following formula:

[0107] <Sulfur element content and carbon element content determined by elemental analysis> Elemental analysis was performed using an organic trace elemental analyzer ("FLASH2000" manufactured by Thermo Fisher Scientific) to obtain the sulfur element content (mass % and mol %) and carbon element content (mass %) in the carbon material. (Measurement conditions) Combustion furnace temperature: 950°C Oven temperature: 65°C Gas: He 140 ml / min, O ２ 250 ml / min. Standard: Sulfanilamide (2, 2.5, 3 mg). Sample container: Tin foil. Sample: 1.0 to 1.5 mg (n=3). Detection method: Thermal conductivity detector (TCD).

[0108] <Sulfur element content S determined by XPS method XPS > Using a scanning X-ray photoelectron spectrometer ("PHI Quantera SXM" manufactured by ULVAC-PHI, Inc.), peaks derived from C1s, S2p, and O1s of each carbon material were analyzed, and the sulfur content S was calculated from the elemental composition ratio. XPS (Measurement conditions) X-ray source: Monochromated Al Kα (1486.6 eV) X-ray beam diameter: 100 μmφ (100 W, 20 kV) Measurement range: 1000 μm (horizontal) × 300 μm (vertical) Signal acceptance angle: 45° Charge neutralization conditions: Neutralization electron gun, Ar+ ion gun pressure: 1×10 －６ Pa measurement method: normal measurement

[0109] <S EA / S XPS The sulfur element content (mol %) contained in each carbon material measured by elemental analysis is expressed as S EAThe sulfur element content (mol%) determined by the XPS method was defined as S XPS Then, S EA S against XPS The ratio (S XPS / S EA ) was sought.

[0110] <Carbon interplanar spacing (d ００２ )> The carbon material to be measured was loaded into a sample holder ("MiniFlex II" manufactured by Rigaku Corporation), and an X-ray diffraction pattern was obtained using CuKα radiation monochromatized by a Ni filter as the radiation source. The peak positions of the X-ray diffraction pattern were determined by the centroid method (a method in which the centroid position of the diffraction line is determined and the peak position is determined using the corresponding 2θ value), and correction was performed using the diffraction peak of the (111) plane of high-purity silicon powder for standard material. The wavelength λ of CuKα radiation was set to 0.15418 nm, and d was calculated using the Bragg formula shown below. ００２ was calculated.

[0111] <Raman Spectrum> The Raman spectrum of each carbon material was measured using a Raman spectrometer (Laser Raman Microscope Ramanforce, manufactured by Nanophoton Inc.). The carbon material to be measured was set on the observation stage, the magnification of the objective lens was set to 20 times, the focus was adjusted, and the Raman spectrum was measured while irradiating the sample with argon ion laser light. The detailed measurement conditions are as follows: (Measurement Conditions) Wavelength of argon ion laser light: 532 nm Laser power on sample: 5 kW / cm ２ ND filter: 0.04% Resolution: 5-7cm －１ Measurement range: 150-4000 cm －１ Measurement mode: Point Exposure time: 1 second Number of integrations: 60 Peak intensity measurement: Baseline correction Polynom-3rd order automatic correction Peak search & fitting processing Gauss Lorentz 1230 cm －１ , 1380 cm －１ Near 1530 cm －１ and 1600 cm －１ For the peak in the vicinity, the peak position is 1230 cm －１ and 1530 cm －１The peaks were fixed and peak fitting was performed using the analysis software "LabSpec 5 Spectroscopy Suite Software" to obtain four peaks. From the results of the peak fitting, －１ , 1380 cm －１ The intensity of the peak around 1380 cm －１ The half-width of the peak in the vicinity was determined.

[0112] <Raman peak intensity ratio I 1230 / I 1380 > 1230 cm of the Raman spectrum determined above －１ The peak intensity near I 1230 and 1380 cm －１ The intensity of the peak near I 1380 and the intensity ratio I 1230 / I 1380 asked for.

[0113] <Specific surface area determined by nitrogen adsorption BET method> A carbon material serving as a measurement sample was filled into a sample tube. This sample tube was placed in a "BERSORP-MINI" (manufactured by Microtrackbell Co., Ltd.), cooled to -196°C, and once depressurized. Thereafter, nitrogen (purity 99.999%) was adsorbed onto the measurement sample at a predetermined relative pressure. The amount of nitrogen adsorbed onto the sample when equilibrium pressure was reached at each predetermined relative pressure was measured and defined as the amount of adsorbed gas v. The BET approximation formula shown below was applied to the predetermined relative pressure (p / p) obtained as described above by the multipoint method using nitrogen adsorption. ０ ) and substitute the amount of adsorbed gas (v) in ｍ The approximate formula derived from the BET formula is shown below. The obtained v ｍ Using this, the specific surface area (SSA: unit is m ２ g －１ ) was calculated. In the above formula, v ｍ is the amount of adsorption required to form a monolayer on the sample surface (cm ３ / g), v is the measured adsorption amount (cm ３ / g), p ０ is the saturated vapor pressure, p is the absolute pressure, c is a constant (reflecting the heat of adsorption), and N is Avogadro's number 6.022 × 10 ２３ , a (nm２ ) is the area occupied by the adsorbate molecule on the sample surface (molecular occupied cross-sectional area).

[0114] <Average particle size of carbon material> The average particle size (diameter) of the carbon material was measured by a laser scattering method using a particle size / particle size distribution measuring device (Microtrac MT3300EXII manufactured by Microtrac Bell Co., Ltd.). The sample was placed in an aqueous solution containing 5% by mass of a surfactant (Toriton X100 manufactured by Wako Pure Chemical Industries, Ltd.), treated with an ultrasonic cleaner for 2 minutes or more, and dispersed in the aqueous solution. The particle size distribution was measured using this dispersion. D ５０ is the particle size at which the cumulative volume becomes 50%, and this value was used as the average particle size.

[0115] <Production of Carbon Material> [Example 1] 2 g of glucose, 8 g of paraphenolsulfonic acid, and 20 g of 10% by weight sulfuric acid were mixed to form an aqueous solution. A 300 ml separable flask was equipped with a Dean-Stark tube, a reflux tube, a thermometer, and a magnetic stirrer. 150 ml of dodecane was measured out as a nonpolar solvent, and the system was purged with nitrogen. The flask was immersed in an oil bath adjusted to 210°C. The dodecane in the flask was heated to 200°C, and the aqueous solution was added at a rate of 0.5 ml / min. The reaction proceeded while removing the released water using a Dean-Stark tube. The entire aqueous solution was continuously fed over approximately 50 minutes, and the system was then dewatered for an additional 60 minutes. The nitrogen gas flow rate during the reaction was 1 NL / min. After the flask was cooled to room temperature, the nonpolar solvent was removed by filtration to obtain the product. The resulting product was washed twice with 100 ml of ion-exchanged water under reflux (approximately 100°C) and filtered, and the pH of the filtrate was confirmed to be 5 or higher. The product was then dried in a vacuum dryer at 120°C for 5 hours to obtain a carbon material. The carbon material was in the form of particles and had an average particle size of 53 μm.

[0116] [Example 2] A carbon material was obtained in the same manner as in Example 1, except that an aqueous solution obtained by mixing 0.5 g of glucose, 4.5 g of citric acid, 5 g of paraphenolsulfonic acid, and 20 g of 10% by mass sulfuric acid was used. The carbon material was in the form of particles, and had an average particle size of 38 μm.

[0117] [Example 3] A carbon material was obtained in the same manner as in Example 1, except that an aqueous solution obtained by mixing 5 g of glucose, 5 g of hydroxyethylsulfonic acid, and 20 g of 10 mass % sulfuric acid was used. The carbon material was in the form of particles, and had an average particle size of 59 μm.

[0118] Example 4 A carbon material was obtained in the same manner as in Example 1, except that an aqueous solution obtained by mixing 5 g of citric acid, 5 g of paraphenolsulfonic acid, and 20 g of 10% by mass sulfuric acid was used, tetradecane was used instead of dodecane, the temperature in the oil bath was adjusted to 240° C., and the temperature of the tetradecane in the reaction vessel was raised to 230° C. The carbon material was in the form of particles, and had an average particle size of 83 μm.

[0119] [Example 5] A carbon material was obtained in the same manner as in Example 1, except that an aqueous solution obtained by mixing 2 g of glucose, 4 g of hydroxyethylsulfonic acid, 4 g of paraphenolsulfonic acid, and 20 g of 10 mass % sulfuric acid was used. The carbon material was in the form of particles, and had an average particle size of 176 μm.

[0120] [Example 6] A carbon material was obtained in the same manner as in Example 1, except that an aqueous solution obtained by mixing 0.5 g of glucose, 4.5 g of citric acid, 5 g of paraphenolsulfonic acid, and 20 g of ion-exchanged water was used. The carbon material was in the form of particles, and had an average particle diameter of 39 μm.

[0121] Comparative Example 1: A 300 ml three-neck flask was equipped with a reflux condenser, a thermometer, and a magnetic stirrer. 10 g of commercially available granular activated carbon (average particle size 1.2 mm) and 150 g of concentrated sulfuric acid were added to the flask, and the system was purged with nitrogen. The flask was immersed in an oil bath adjusted to 210°C, and the temperature inside the flask was raised to 200°C. After stirring for 5 hours, sulfonation was carried out. The nitrogen gas flow rate during the reaction was 1 NL / min. After the flask was cooled to room temperature, the concentrated sulfuric acid was removed by filtration. The resulting product was washed twice with 100 ml of ion-exchanged water under reflux (approximately 100°C) and filtered, and the pH of the filtrate was confirmed to be 5 or higher. The product was then dried in a vacuum dryer at 120°C for 5 hours to obtain a carbon material.

[0122] Comparative Example 2: Lignin was heat-treated at 400°C for 1 hour under a nitrogen atmosphere to obtain lignin charcoal. The nitrogen gas flow rate was 1 NL / min. The obtained lignin charcoal was pulverized in a ball mill to obtain pulverized lignin charcoal with an average particle size of 29 μm. A 300 ml three-neck flask was equipped with a reflux condenser, a thermometer, and a magnetic stirrer. 10 g of pulverized lignin charcoal and 150 g of concentrated sulfuric acid were added to the flask, and the system was purged with nitrogen. The flask was immersed in an oil bath adjusted to a temperature of 160°C, and the temperature inside the flask was raised to 150°C. After stirring for 5 hours, sulfonation was carried out. The nitrogen gas flow rate during the reaction was 1 NL / min. After the flask was cooled to room temperature, the concentrated sulfuric acid was removed by filtration. The obtained product was washed twice with 100 ml of ion-exchanged water under reflux (about 100°C) and filtered, and it was confirmed that the pH of the filtrate was not less than 5. Thereafter, the product was dried in a vacuum dryer at 120°C for 5 hours to obtain a carbon material.

[0123] Comparative Example 3: Lignin was heat-treated at 300°C for 1 hour under a nitrogen atmosphere to obtain lignin charcoal. The nitrogen gas flow rate was 1 NL / min. The obtained lignin charcoal was pulverized in a ball mill to obtain pulverized lignin charcoal with an average particle size of 43 μm. A 300 ml three-neck flask was equipped with a reflux condenser, a thermometer, and a magnetic stirrer. 10 g of pulverized lignin charcoal and 150 g of concentrated sulfuric acid were added to the flask, and the system was purged with nitrogen. The flask was immersed in an oil bath adjusted to a temperature of 160°C, and the temperature inside the flask was raised to 150°C. After stirring for 5 hours, sulfonation was carried out. The nitrogen gas flow rate during the reaction was 1 NL / min. The flask was cooled to room temperature, and the concentrated sulfuric acid was removed by filtration. The obtained product was washed twice with 100 ml of ion-exchanged water under reflux (about 100°C) and filtered, and it was confirmed that the pH of the filtrate was not less than 5. Thereafter, the product was dried in a vacuum dryer at 120°C for 5 hours to obtain a carbon material.

[0124] Comparative Example 4: A 300 ml three-neck flask was equipped with a reflux condenser, a thermometer, and a magnetic stirrer. 10 g of glucose and 150 g of concentrated sulfuric acid were added to the flask, and the system was purged with nitrogen. The flask was immersed in an oil bath adjusted to 210°C, and the temperature inside the flask was raised to 200°C. After stirring for 5 hours, sulfonation was carried out. The nitrogen gas flow rate during the reaction was 1 NL / min. After the flask was cooled to room temperature, the concentrated sulfuric acid was removed by filtration. The resulting product was washed twice with 100 ml of ion-exchanged water under reflux (approximately 100°C) and filtered, and the pH of the filtrate was confirmed to be 5 or higher. The product was then dried in a vacuum dryer at 120°C for 5 hours to obtain a carbon material.

[0125] Table 1 shows the physical properties of the carbon materials in the examples and comparative examples.

[0126]

[0127] The carbon materials obtained in the examples and comparative examples were subjected to the following performance evaluations.

[0128] <Carbonization Treatment Evaluation> A separable flask was equipped with a thermometer, a dropping funnel, and a mechanical stirrer. 10 g of wood chips and 1 g of carbon material were charged into the flask and stirred at 100 rpm under a nitrogen gas flow rate of 0.5 NL / min. The flask was immersed in an oil bath with the temperature adjusted to 150°C, and the flask was heated to 100°C. 5 ml of ion-exchanged water was then dropped into the flask and stirred for 30 minutes. Another 5 ml of ion-exchanged water was then dropped and stirred for 30 minutes to obtain a charcoal product. The charcoal product was semi-carbonized.

[0129] <Oxygen Element Content of Carbide> The above carbide was subjected to elemental analysis based on the inert gas dissolution method using an oxygen, nitrogen, and hydrogen analyzer "EMGA-30E (manufactured by Horiba, Ltd.)" to obtain the oxygen element content in the carbonized product. The detection methods used by the analyzer were: oxygen: inert gas fusion-non-dispersive infrared absorption (NDIR), nitrogen: inert gas fusion-thermal conduction (TCD), and hydrogen: inert gas fusion-non-dispersive infrared absorption (NDIR). Calibration was performed using a Sn capsule, TiH ２ (H standard sample), SUS-10, Fe２ O ３ The moisture content of the carbide was measured after pretreatment at 100°C for approximately 30 minutes using SS-3 (O standard sample), SS-3, and SiN (N standard sample). 2 mg of the carbide was placed in a Sn capsule and degassed for 25 seconds in an elemental analyzer before measurement. Three samples were analyzed, and the average value was used as the analytical value. The lower the oxygen element content in the carbide, the more advanced the carbonization.

[0130] <Thermogravimetric measurement> 10 mg of the carbonized material was weighed into an alumina pan and subjected to thermogravimetric measurement using a differential thermal and thermogravimetric simultaneous measurement device "STA 2500 Regulus (manufactured by NETZSCH)". The larger the thermal decomposition residue in the carbonized material, the more advanced the carbonization of the wood chips. (Measurement conditions) Maximum temperature: 600°C Heating condition: 10°C / min Atmosphere: N ２ 20 mL / min. Measurement container: Alumina pan. Measurement sample amount: Approximately 10 mg.

[0131] Table 3 shows the measurement results of the oxygen element content and the residue after TG pyrolysis of the carbonized products in the examples and comparative examples.

[0132] <Production of Carbon Solid Acid> [Solid Acid 1] 2 g of glucose, 8 g of paraphenolsulfonic acid, and 20 g of 10% by weight sulfuric acid were mixed to form an aqueous solution. A 300 ml separable flask was equipped with a Dean-Stark tube, a reflux tube, a thermometer, and a magnetic stirrer. 150 ml of dodecane was measured out as a nonpolar solvent, and the system was purged with nitrogen. The flask was immersed in an oil bath adjusted to 210°C. The dodecane in the flask was heated to 200°C, and the aqueous solution was added at a rate of 0.5 ml / min. The reaction proceeded while removing the water discharged using a Dean-Stark tube. The entire aqueous solution was continuously fed over approximately 50 minutes, and the water in the system was removed for an additional 60 minutes. The nitrogen gas flow rate during the reaction was 1 NL / min. After the flask was cooled to room temperature, the nonpolar solvent was removed by filtration to obtain the product. The obtained product was washed twice with 100 ml of ion-exchanged water under reflux (about 100°C) and filtered, and it was confirmed that the pH of the filtrate was 5 or higher. Thereafter, the product was dried in a vacuum dryer at 120°C for 5 hours to obtain carbon solid acid 1. Carbon solid acid 1 was in the form of particles, and the average particle diameter was 53 μm.

[0133] [Solid acid 2] Carbon solid acid 2 was obtained in the same manner as solid acid 1, except that an aqueous solution obtained by mixing 2 g of glucose, 4 g of hydroxyethylsulfonic acid, 4 g of paraphenolsulfonic acid, and 20 g of 10 mass % sulfuric acid was used. Carbon solid acid 2 was in the form of particles, and the average particle diameter was 176 μm.

[0134] [Solid Acid 3] A 300 ml three-neck flask was equipped with a reflux condenser, a thermometer, and a mechanical stirrer. 10 g of activated carbon (Kuraray Co., Ltd., 4GS, particle diameter 4 mm) and 200 g of concentrated sulfuric acid were added to the flask, and the system was purged with nitrogen. The flask was immersed in an oil bath adjusted to 210 °C, and the temperature inside the flask was raised to 200 °C. After stirring for 3 hours, sulfonation was carried out. The nitrogen gas flow rate during the reaction was 1 NL / min. After the flask was cooled to room temperature, the concentrated sulfuric acid was removed by filtration. The resulting product was washed twice with 100 ml of ion-exchanged water under reflux (approximately 100 °C) and filtered, and the pH of the filtrate was confirmed to be 5 or higher. The product was then dried in a vacuum dryer at 120 °C for 5 hours to obtain carbon solid acid 3.

[0135] [Method for Analyzing Carbon Solid Acid] <Amount of Sulfo Groups in Carbon Solid Acid> 0.1 g of carbon solid acid was weighed into a 50 cc sample tube, and 20 mL of a 0.1 mol / L NaCl aqueous solution was added and stirred for 30 minutes. The resulting mixture was filtered through a 0.45 μm filter, and 5 mL of the filtrate was weighed into a beaker, to which three drops of a 10 g / L phenolphthalein solution were added. 0.01 mol / L NaOH was added dropwise until the color of the phenolphthalein changed from clear to pink. The amount of sulfo groups was calculated from the amount of NaOH added (X ml) using the following formula: [Mathematical Formula 6] Amount of sulfo groups [mmol / g] = (X [mL] × NaOH concentration [mol / L] / carbon solid acid weight [g]) × (20 [mL] / 5 [mL]) = (X × 0.01 / 0.1) × (20 / 5)

[0136] <Sulfur element content S determined by elemental analysis of carbon solid acid ＥＡ Elemental analysis was performed using an organic trace elemental analyzer ("FLASH2000" manufactured by Thermo Fisher Scientific) to determine the sulfur element content S in the carbon solid acid. ＥＡ (% by mass and % by mole) were obtained. (Measurement conditions) Combustion furnace temperature: 950°C Oven temperature: 65°C Gas: He 140 ml / min, O ２ 250 ml / min. Standard: Sulfanilamide (2, 2.5, 3 mg). Sample container: Tin foil. Sample: 1.0 to 1.5 mg (n=3). Detection method: Thermal conductivity detector (TCD).

[0137] <Sulfur element content S of carbon solid acid determined by XPS method XPS > Using a scanning X-ray photoelectron spectrometer ("PHI Quantera SXM" manufactured by ULVAC-PHI, Inc.), peaks derived from C1s, S2p, and O1s of each carbon solid acid were analyzed, and the sulfur element content S XPS (Measurement conditions) X-ray source: Monochromated Al Kα (1486.6 eV) X-ray beam diameter: 100 μmφ (100 W, 20 kV) Measurement range: 1000 μm (horizontal) × 300 μm (vertical) Signal acceptance angle: 45° Charge neutralization conditions: Neutralization electron gun, Ar+ ion gun pressure: 1×10 －６Pa measurement method: normal measurement

[0138] <Carbon solid acid S EA / S XPS The sulfur element content (mol%) contained in each carbon solid acid measured by elemental analysis was expressed as S EA The sulfur element content (mol%) determined by the XPS method was defined as S XPS Then, S EA S against XPS The ratio (S XPS / S EA ) was sought.

[0139] <Average particle size of carbon solid acid> The average particle size (diameter) of carbon solid acid was measured by a laser scattering method using a particle size / particle size distribution measuring device (Microtrac MT3300EXII manufactured by Microtrac Bell Co., Ltd.). The sample was placed in an aqueous solution containing 5% by mass of a surfactant (Toriton X100 manufactured by Wako Pure Chemical Industries, Ltd.), treated with an ultrasonic cleaner for 2 minutes or more, and dispersed in the aqueous solution. The particle size distribution was measured using this dispersion. D ５０ is the particle size at which the cumulative volume becomes 50%, and this value was used as the average particle size.

[0140] <Production of Semi-Carbonized Product> [Example 7] A separable flask was equipped with a thermometer, a dropping funnel, and a mechanical stirrer. 10 g of wood chips with a water content of 50% (manufactured by Sansei Shoji Co., Ltd.: Quercus arabescens size 6 mm or less) and 1 g of solid acid 1 were added to the flask and stirred at 40 rpm. The flask was immersed in an oil bath adjusted to a temperature of 150°C, and the temperature inside the flask was raised to 100°C. The mixture was heated and stirred for 90 minutes to obtain semi-carbonized product 1.

[0141] Example 8 A separable flask was equipped with a thermometer, a dropping funnel, and a mechanical stirrer. 10 g of wood chips with a water content of 50% and 1 g of solid acid 2 were added to the flask and stirred at 40 rpm. The flask was immersed in an oil bath adjusted to a temperature of 180°C, and the temperature inside the flask was raised to 150°C. The mixture was heated and stirred for 90 minutes to obtain semi-carbonized product 2.

[0142] Comparative Example 5 10 g of wood chips was heat-treated at 270° C. for 1 hour in a nitrogen atmosphere to obtain semi-carbonized material 3. At that time, the flow rate of nitrogen gas was set to 5 NL / min.

[0143] Comparative Example 6 A separable flask was equipped with a thermometer, a dropping funnel, and a mechanical stirrer. 10 g of wood chips with a water content of 50% and 5 g of solid acid 3 were added to the flask and stirred at 40 rpm. The flask was immersed in an oil bath adjusted to a temperature of 230°C, and the temperature inside the flask was raised to 200°C. The mixture was heated and stirred for 90 minutes to obtain semi-carbonized product 4.

[0144] [Method for Analyzing Semi-Carbonized Material] <Thermogravimetric Measurement of Semi-Carbonized Material under Nitrogen> 10 mg of semi-carbonized material was weighed into an alumina pan and subjected to thermogravimetric measurement using a differential thermal and thermogravimetric simultaneous analyzer "STA 2500 Regulus (manufactured by NETZSCH)" to obtain a TG curve. (Measurement conditions) Maximum temperature: 600°C Heating condition: 10°C / min Atmosphere: N ２ 20 mL / min, measurement container: alumina pan, measurement sample amount: about 10 mg. The above TG curve was differentiated to obtain a differential curve. The intensity of the differential curve at 290 ° C. was calculated as I ２９０ , the strength at 360 ° C is I ３６０ The temperature at which weight loss began was the temperature at which the weight of the semi-carbide was reduced by 0.5% by weight from the weight at 150°C. The weight remaining at 600°C was taken as the 600°C residual rate.

[0145] <Half-carbide I ３６０ / I ２９０ The intensity at 290 ° C. in the differential curve of the TG curve for each semi-carbide measured by thermogravimetry under nitrogen is expressed as I ２９０ and the strength at 360 ° C is I ３６０ And I ２９０ I against ３６０ The ratio (I ３６０ / I ２９０ ) was sought.

[0146] <Thermogravimetric Measurement of Semi-Carbonized Material under Air> Five mg of semi-carbonized material was weighed into an alumina pan and subjected to thermogravimetric and differential thermal analysis using a STA 2500 Regulus (manufactured by NETZSCH) simultaneous differential thermal analysis and thermogravimetry analyzer. (Measurement Conditions) Maximum temperature: 815°C, Maximum temperature hold time: 10 minutes, Heating conditions: 20°C / min, Atmosphere: Air 20 mL / min, Measurement container: Alumina pan, Sample size: Approximately 5 mg. The thermogravimetric residue after measurement was calculated as ash content. Three samples were analyzed, and the average value was used as the ash content. The decomposition onset temperature was defined as the temperature at which the weight of the semi-carbonized material at 150°C decreased by 0.5 wt%. The ignition temperature was defined as the temperature at which the baseline of the differential thermal analysis curve intersected with the extrapolated maximum slope of the first peak.

[0147] <Sulfur Element Content in Semi-Carbonized Material> Elemental analysis was performed using an organic trace elemental analyzer ("FLASH2000" manufactured by Thermo Fisher Scientific) to obtain the sulfur element content (ppm) in the semi-carbonized material. (Measurement Conditions) Combustion furnace temperature: 950°C Oven temperature: 65°C Gas: He 140 ml / min, O ２ 250 ml / min. Standard: Sulfanilamide (2, 2.5, 3 mg). Sample container: Tin foil. Sample: 1.0 to 1.5 mg (n=3). Detection method: Thermal conductivity detector (TCD).

[0148] <Potassium and Sodium Contents in Semi-Carbonized Material> After vacuum drying the semi-carbonized material at 60°C for 3 hours, 0.01 g was weighed into a PTFE decomposition vessel, 8 ml of nitric acid (1.42) was added, and microwave decomposition was performed using a microwave decomposition apparatus ("Multiwave5000" manufactured by Anton Paar). After cooling, the mixture was filled up to 50 ml with ion-exchanged water in a PFA measuring flask, filtered through a hydrophilic PTFE filter with a pore size of 0.45 μm, and then subjected to elemental analysis using an ICP mass spectrometer ("Agilent7900" manufactured by Agilent Technologies) to obtain the potassium and sodium content (ppm) in the semi-carbonized material. (Microwave decomposition conditions) Method: H_max230 Heat from initial temperature to 110°C in 15 minutes, hold at 110°C for 10 minutes, then heat to 230°C in 25 minutes, hold at 230°C for 20 minutes Temperature limit: 250°C Cooling temperature: 55°C Control pressure: Automatic vent at 40 bar (ICP mass spectrometry conditions) RF output: 1500 W Carrier gas flow rate: 0.7 L / min Plasma mode: Cool plasma, hot plasma Cool mode measurement elements: Na, K H2 mode measurement elements: K

[0149] <Calorific Value of Semi-Charred Material> The calorific value (HHV) of solid fuel is calculated empirically using the Channiwala equation: HHV = 0.3491C + 1.1783H + 0.1005S - 0.1034O - 0.0151N - 0.0211A. In this equation, C, H, S, O, N, and A represent the mass fractions (%) of carbon, hydrogen, sulfur, oxygen, nitrogen, and ash on a dry basis. Since semi-charred material is primarily composed of carbon, hydrogen, oxygen, and ash, the oxygen content (mass fraction) and hydrogen content (mass fraction) were measured using an oxygen, nitrogen, and hydrogen analyzer, and the ash content (mass fraction) was measured using a simultaneous differential thermal and thermogravimetric analyzer under air, as shown below. The calorific value was calculated using the above equation, using the mass fraction obtained by subtracting the oxygen content, hydrogen content, and ash content from 100% as the carbon content. It is believed that the calorific value increases when the carbon purity is improved by pyrolysis, and therefore, the fact that the calorific value is about the same despite the lower temperature treatment is believed to indicate that the carbon purity is about the same despite the lower temperature treatment.

[0150] <Oxygen Content and Hydrogen Element Content of Semi-Carbide> The semi-carbide was subjected to elemental analysis based on the inert gas dissolution method using an oxygen, nitrogen, and hydrogen analyzer "EMGA-30E (manufactured by Horiba, Ltd.)" to obtain the oxygen and hydrogen element contents in the carbonized product. The detection methods used by this device were: oxygen: inert gas fusion-non-dispersive infrared absorption (NDIR), and hydrogen: inert gas fusion-non-dispersive infrared absorption (NDIR). Calibration was performed using a Sn capsule, TiH ２ (H standard sample), SUS-10, Fe ２ O ３ The moisture content of the carbide was measured after pretreatment at 100°C for about 30 minutes using an O2 standard sample. 2 mg of the carbide was placed in a Sn capsule and degassed for 25 seconds in an elemental analyzer before measurement. Three samples were analyzed for each test, and the average values ​​were used to determine the oxygen content and hydrogen content.

[0151] Table 4 shows the physical properties of the carbon solid acids and the physical properties and performance evaluations of the semi-carbonized products in the examples and comparative examples.

Claims

1. A carbon material having a sulfo group, wherein the carbon material and a 0.1 mol / L aqueous NaCl solution are stirred for 30 minutes, followed by filtration, and the filtrate is titrated with a 0.01 mol / L aqueous NaOH solution to obtain a sulfo group amount of 0.55 to 5.0 mmol / g; and the molar content S of sulfur element of the carbon material determined by elemental analysis is 0.55 to 5.0 mmol / g. EA The molar content S of sulfur element determined by XPS method XPS The ratio (S XPS / S EA ) is 0.90 to 2.

0.

2. Carbon interplanar spacing (d 002 2. The carbon material according to claim 1, wherein the surface roughness (f) of the carbon material is 3.70 to 4.50 Å.

3. 1230 cm of the Raman spectrum observed by laser Raman spectroscopy －１ Nearby peaks and 1380cm －１ Intensity ratio I of the peaks near 1230 / I 1380 The carbon material according to claim 1 or 2, wherein is 0.05 to 0.

5.

4. 1380 cm of the Raman spectrum observed by laser Raman spectroscopy －１ The half-width of the peak in the vicinity is 150 cm －１ More than 350cm －１ The carbon material according to claim 3, wherein:

5. The carbon material according to any one of claims 1 to 4, wherein the sulfur content determined by elemental analysis is 1.8 to 16 mass%.

6. The carbon material according to any one of claims 1 to 5, wherein the carbon element content determined by elemental analysis is 35 to 75 mass %.

7. The specific surface area determined by the BET method is 0.1 to 500 m ２ The carbon material according to any one of claims 1 to 6, wherein the carbon content is 1 / g.

8. The carbon material according to any one of claims 1 to 7, which is a carbon-based solid acid catalyst.

9. The carbon material according to claim 8, which is a catalyst used for carbonizing organic matter.

10. A method for producing a carbon material, comprising preparing a mixed solution containing a carbon source, a compound containing a sulfo group, and a polar solvent, and adding the mixed solution to a heated nonpolar solvent to remove the polar solvent from the mixed solution, thereby producing a carbon material.

11. The method of claim 10, wherein the compound containing a sulfo group further contains a hydroxyl group.

12. The method according to claim 10 or 11, wherein the mixture contains a carbon source, a compound containing a sulfo group, and sulfuric acid.

13. The method of any one of claims 10 to 12, wherein the carbon source is at least one selected from the group consisting of sugars and organic acids.

14. A method for producing a semi-carbonized material, comprising mixing an organic substance with the carbon material according to any one of claims 1 to 9 and heating the mixture.

15. The method of claim 14, wherein the heating temperature is 50°C or higher and lower than 230°C.

16. A semi-carbide whose weight loss begins at 150-220°C when heated at a rate of 10°C / min in a nitrogen atmosphere by thermogravimetry, and whose residual weight at 600°C is 22-65% by mass.

17. Intensity I at 290°C in the DTG curve obtained by thermogravimetry under a nitrogen atmosphere ２９０ Strength I at 360 ° C ３６０ The ratio (I ３６０ / I ２９０ 17. The torrefied material according to claim 16, wherein σ is 2.5 or less.

18. The torrefied product according to claim 16 or 17, wherein the ash content is 0 to 2% by mass based on the mass of the torrefied product.

19. The torrefied material according to any one of claims 16 to 18, wherein the sulfur element content is 10 to 5000 ppm.

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