TWI534080B - Porous carbon and a method for producing the same - Google Patents

Description

Porous carbon and method of producing the same

The present invention relates to a porous carbon and a method for producing the same, and particularly to a low-cost, safe, and specific boron-added porous carbon and a method for producing the same.

In recent years, with the increase in the integration of electronic circuits or the increase in the frequency of electrical signals, there has been a problem that electromagnetic waves or external leakage are generated from electronic devices. In order to suppress this electromagnetic wave, a method of coating an electronic device with an electromagnetic wave absorbing material in which a boron-containing carbon material is mixed with a resin, a rubber or the like is used. Further, a carbon material is used as the electrode material of the nonaqueous electrolyte battery or capacitor, but it is known at this time that boron is contained in the carbon material to improve the wettability to the electrolyte. The boron-containing carbon material is proposed as follows.

The cellulose-based material in which boric acid is mixed is subjected to papermaking, and finally fired at 2000 degrees or more to carry out black lead treatment. It is described that porous carbon containing 50 to 2000 ppm of boric acid can be obtained (see Patent Document 1 below).

However, the carbon material thus produced, as described in the document, has a pore diameter of several tens of μm and is almost completely free of micropores. Further, there is no description about the boron content and the specific surface area, but it is presumed that the carbon material produced is positively smaller than the surface area.

Further, carbon black having a boron solid capacity of 0.7 to 1.8% by weight has been proposed (see Patent Document 2 below), and the amount of solid solution boron is 0.5% by weight or more and soluble boron The amount of carbon black is 0.05% by weight or less (see Patent Document 3 below).

In these proposals, although the BET specific surface area is not clear, the general BET specific surface area of carbon black cannot satisfy 300 m ² /g even if it is the largest. Therefore, it is estimated that the porous carbon obtained by the above proposal has a BET specific surface area of less than 300 m ² /g. As described above, the carbon black produced by the above method cannot form high-performance porous carbon.

[Practical Technical Literature]

[Patent Literature]

Patent Document 1: Japanese Laid-Open Patent Publication No. Hei 10-237683

Patent Document 2: Japanese Laid-Open Patent Publication No. 2006-111791

Patent Document 3: Japanese Laid-Open Patent Publication No. 2006-265374

Therefore, the present invention has an object of providing porous carbon which can greatly improve performance by increasing the BET specific surface area even when boron is contained, and a method for producing the same.

In order to achieve the above object, the present invention is characterized in that a CBO bond structure is formed at least on the surface, and a BET specific surface area obtained by a nitrogen adsorption isotherm of 77 K is 300 m ² /g or more.

The carbon black shown by the prior art has little micropores or mesopores. Therefore, porous carbon having a large BET specific surface area cannot be obtained. On the other hand, in the porous carbon having the above configuration, since there are mesopores and micropores generated around the mesopores, porous carbon having a BET specific surface area of 300 m ² /g or more can be obtained.

Further, by the above configuration, a bond exists on the surface of the porous carbon The knot can improve the affinity of the hydrophilicity or the electrolyte. Further, in the porous carbon of the present invention, boron is chemically bonded to carbon due to the bonding, and can be stably held on the carbon surface (i.e., not only loaded in carbon). Further, since boron can be prevented from being detached from the porous carbon, the effect of improving hydrophilicity or affinity with the electrolytic solution (improvement in durability) is maintained for a long period of time.

As described above, for example, when the porous carbon of the present invention is used as an electrode material, since the electrolyte of the battery or the capacitor or the electrolyte dissolved in the electrolyte can be smoothly moved into the pores, the charge and discharge of the battery or the capacitor can be improved. characteristic. Further, when the porous carbon of the present invention is used as an adsorbent, the adsorption performance can be dramatically improved.

Here, the porous carbon of the present invention may be formed by a C-B-O bond structure on the surface of the porous carbon, irrespective of whether boron is present inside the porous carbon.

Further, the upper limit of the BET specific surface area is not limited. When the amount is too large, the shape of the carbon wall cannot be maintained, and the particles may be collapsed. Therefore, the BET specific surface area is preferably 1,500 m ² /g or less.

In addition, in the present specification, a pore having a pore diameter of less than 2 nm is referred to as a micropore, a pore having a pore diameter of 2 to 50 nm is referred to as a mesopores, and a pore having a diameter of 50 nm or more is a coarse pore.

The pore volume determined by the DR (Dubinin-Radushkevich) method from the nitrogen adsorption isotherm of 77K is preferably 0.3 ml/g or more, and all the pore volume obtained by the nitrogen adsorption isotherm of 77K is used. The difference from the micropore volume determined by the DR method from the nitrogen adsorption isotherm of 77K (this value is called the capacity of the mesopores) is preferably 1 ml/g or more.

When the volume of the micropores or the volume of the mesopores is larger, the function can be further exerted. The effect of the description.

The content of boron is preferably from 100 to 10,000 ppm by weight.

When the boron concentration is higher, the performance when porous carbon is used as the electromagnetic wave absorber can be dramatically improved.

When 0.03 wt% of porous carbon was added to 100 g of ion-exchanged water, ultrasonic waves of 40 kHz were applied for 3 minutes, and after leaving for 16 hours, the transmittance when light having a wavelength of 550 nm was used was preferably 80% or less.

When the hydrophilicity is better, the above-described effects can be more exerted.

Further, in order to achieve the above object, the present invention is characterized in that a boric acid and a magnesium citrate are mixed to form a mixture, and the mixture is heated and fired in a vacuum gas atmosphere, a non-oxidizing gas atmosphere, or a reducing gas atmosphere. The stage of producing the fired product and the stage of removing the above-mentioned mold in the fired product.

In the above production method, when a mixture of boric acid and magnesium citrate is heated and fired in a predetermined environment, magnesium citrate is first decomposed to form magnesium oxide and citric acid, and boron oxide formed from boric acid is dissolved. Next, the temperature is raised again, and a reaction product of magnesium oxide and boron oxide is formed on the outer periphery of the magnesium oxide, and the reaction product is formed into a mold with magnesium oxide, and carbon is disposed around the mold. Then, the above porous carbon can be obtained by removing the mold.

Here, the mechanism for introducing boron into carbon is considered to be (1) introduction of a carbon surface by reaction of magnesium oxide with boron oxide, or (2) introduction by direct reaction of molten boron oxide with carbon or carbon precursor. . In the case of this mechanism, the effect of selectively introducing boron onto the surface of the mesopores and uniformly introducing boron can be exerted. . In particular, when the mechanism of (1) is mainly used, the selected boron can be sufficiently introduced into the surface of the mesopores, and when the mechanism of (2) is the main component, boron can be sufficiently introduced uniformly.

Further, when boric acid is used as the boron source and boron metal is not used, the reason is as follows. In other words, when boric acid is more easily obtained at a lower price than boric acid, it is soluble in water or acid, so that it can be easily removed. Further, in addition to being a solid (powder) at a normal temperature, boric acid forms a molten state of boron oxide at a predetermined temperature or higher, so that fluidity can be improved and moved to various corners in the raw material. Therefore, in the introduction of the boron element represented by the above (1) and (2), since a uniform reaction can be performed, the boron element can be easily and uniformly introduced into the porous carbon. In this regard, the boron metal has a high melting point (2076 ° C) and is in a solid state, that is, as coarse particles. Further, since only the interface between the metal boron particles and the carbon (or carbon precursor) is reacted, it is considered that boron is not excessively introduced unevenly even if the reaction is carried out.

However, the boron source is not limited to boric acid, and may be other boron compounds such as boron oxide.

The ratio of boric acid to magnesium citrate is preferably more than 0% by weight and not more than 100% by weight.

The effect of the present invention can be exerted by the amount of boric acid, and it is sufficient that the above ratio exceeds 0% by weight. Further, when the boron content is too large, the pore volume is reduced, and it is preferably 100% by weight or less in the above ratio. Further, in order to sufficiently exert the effects of the present invention and sufficiently suppress the decrease in the pore volume, the ratio is preferably 1% by weight or more and 50% by weight or less.

The temperature at the time of the above heating and baking is 500 ° C or more and 1500 ° C or less. should.

When the temperature is less than 500 ° C, the carbonization is insufficient and the development of the pores is insufficient. When the temperature exceeds 1500 ° C, the oxide (magnesia or the like) of the pore mold is coarsened, and the pore size is increased. When it becomes larger, the specific surface area becomes smaller. In addition, when it exceeds 1500 ° C, the surface functional group having a CBO bond is decomposed. Further, there is a case where boron carbide (B ₄ C) is precipitated.

According to the present invention, even when boron is contained, the BET specific surface area can be increased, whereby an excellent effect of drastically improving the performance of porous carbon can be achieved.

[In order to implement the invention]

In the following, embodiments of the invention will be described.

(1) First form

The carbide of the present invention is obtained by using an organic acid (for example, magnesium citrate, magnesium oxalate, calcium citrate or calcium oxalate) having a mold source and a carbon source, and boric acid as a boron source in a solution or a powder. Wet or dry mixing is carried out in a state, and the mixture is carbonized at a temperature of 500 ° C or more and 1500 ° C or less in a non-oxidizing atmosphere or under a reduced pressure [133 Pa (1 torr) or less] or a reducing atmosphere. The obtained carbide is subjected to a washing treatment to remove the mold. It can be produced through this step. By the manufacturing method, mesopores can be directly formed by a mold, and at least on the surface of the porous carbon The boron element is simultaneously introduced.

Specifically, the porous carbon is formed of a CBO bond structure at least on the surface, and the BET specific surface area obtained by a nitrogen adsorption isotherm of 77 K is 300 m ² /g or more. Further, the porous carbon is chemically reactive with an acid or a base, and is excellent in electrical conductivity.

Further, boron is introduced into at least the surface of the porous carbon (at least the surface of the mesopores), but is not limited to this portion, and may be introduced into the surface of the micropores or coarse pores or the carbon skeleton of the porous carbon.

Further, in order to adjust the ratio of the mold to the carbon, the ratio of the organic acid having both the mold source and the carbon source and the resin shown in the second embodiment described below can be adjusted.

When the mold is removed, the residual ratio of the mold after removal is preferably 0.5% or less. When the residual ratio of the mold after the removal exceeds 0.5%, the number of molds remaining in the mesopores increases, and the portion that does not exhibit the effect of the pores becomes wider. Further, a general inorganic acid such as hydrochloric acid, sulfuric acid, nitric acid, citric acid, acetic acid or formic acid is used as the washing liquid for removing the oxide, and it is preferably used as a dilute acid of 2 mol/l or less. In addition, hot water of 80 ° C or higher can also be used.

(2) The second form

The carbide of the present invention is a polyimine having at least one nitrogen or fluorine atom in a unit structure or a resin having a carbon yield of 40% by weight or more (for example, a phenol resin (polyvinyl alcohol) or pitch). a thermoplastic resin or the like, a mold and a boric acid as a boron source, in the same manner as described above, wet or dry mixing in a solution or powder state, and the mixture is allowed to be in a non-oxidizing environment, under reduced pressure or in a reducing environment. Carbonization is carried out at a temperature of 500 ° C or more and 1500 ° C or less, and the obtained carbide is subjected to a washing treatment. According to the production method, in the same manner as in the first embodiment, a CBO bond structure can be produced at least on the surface, and the BET specific surface area obtained by the nitrogen adsorption isotherm of 77 K is 300 m ² /g or more. Porous carbon.

Here, the polyimine containing at least one nitrogen or fluorine atom in the above unit structure can be obtained by polycondensing an acid component with a diamine component. However, at this time, it is necessary to contain one or more nitrogen atoms or fluorine atoms in either or both of the acid component and the diamine component.

Specifically, a polylysine film is obtained by forming a polylysine which is a precursor of a polyimide, and removing the solvent by heating. Next, the obtained polyaminic acid film can be thermally imidized at 200 ° C or higher to produce a polyimide.

The aforementioned diamine component, for example, 2,2-bis(4-aminophenyl)hexafluoropropane, 2,2-bis(trifluoromethyl)benzidine [ 2,2'-Bis(trifluoromethyl)-benzidine], 4,4'-diamino octafluorobiphenyl, or 3,3'-difluoro-4,4'-diaminodiphenylmethane, 3, 3'-Difluoro-4,4'-diaminodiphenyl ether, 3,3'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether, 3,3'-difluoro -4,4'-diaminodiphenylpropane, 3,3'-difluoro-4,4'-diaminodiphenylhexafluoropropane, 3,3'-difluoro-4,4'- Diaminobenzophenone, 3,3',5,5'-tetrafluoro-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetrakis(trifluoromethyl )-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetrafluoro-4,4'diaminodiphenylpropane, 3,3',5,5'- Tetrakis(trifluoromethyl)-4,4'-diaminodiphenylpropane, 3,3',5,5'-tetrafluoro-4,4-diamino Diphenylhexafluoropropane, 1,3-diamino-5-(perfluorodecyloxy)benzene, 1,3-diamino-4-methyl-5-(perfluorodecyloxy)benzene, 1,3-Diamino-4-methoxy-5-(perfluorodecyloxy)benzene, 1,3-diamino-2,4,6-trifluoro-5-(perfluorodecyloxy Benzene, 1,3-diamino-4-chloro-5-(perfluorodecyloxy)benzene, 1,3-diamino-4-bromo-5-(perfluorodecyloxy)benzene, 1 , 2-diamino-4-(perfluorodecyloxy)benzene, 1,2-diamino-4-methyl-5-(perfluorodecyloxy)benzene, 1,2-diamino- 4-methoxy-5-(perfluorodecyloxy)benzene, 1,2-diamino-3,4,6-trifluoro-5-(perfluorodecyloxy)benzene, 1,2-di Amino-4-chloro-5-(perfluorodecyloxy)benzene, 1,2-diamino-4-bromo-5-(perfluorodecyloxy)benzene, 1,4-diamino-3 -(perfluorodecyloxy)benzene, 1,4-diamino-2-methyl-5-(perfluorodecyloxy)benzene, 1,4-diamino-2-methoxy-5- (perfluorodecyloxy)benzene, 1,4-diamino-2,3,6-trifluoro-5-(perfluorodecyloxy)benzene, 1,4-diamino-2-chloro-5 -(perfluorodecyloxy)benzene, 1,4-diamino-2-bromo-5-(perfluorodecyloxy)benzene, 1,3-diamino-5-(perfluorohexyloxy) Benzene, 1,3-diamino 4-methyl-5-(perfluorohexyloxy)benzene, 1,3-diamino-4-methoxy-5-(perfluorohexyloxy)benzene 1,3-Diamino-2,4,6-trifluoro-5-(perfluorohexyloxy)benzene, 1,3-diamino-4-chloro-5-(perfluorohexyloxy)benzene , 1,3-diamino-4-bromo-5-(perfluorohexyloxy)benzene, 1,2-diamino-4-(perfluorohexyloxy)benzene, 1,2-diamine 4-methyl-5-(perfluorohexyloxy)benzene, 1,2-diamino-4-methoxy-5-(perfluorohexyloxy)benzene, 1,2-diamino- 3,4,6-trifluoro-5-(perfluorohexyloxy)benzene, 1,2-diamino-4-chloro-5-(perfluorohexyloxy)benzene, 1,2-diamine 4-bromo-5-(perfluorohexyloxy)benzene, 1,4-diamino-3-(perfluorohexyloxy)benzene, 1,4-diamino-2-methyl-5- (perfluorohexyloxy)benzene, 1,4-diamino-2-methoxy-5-(perfluorohexyloxy)benzene, 1,4-diamino-2,3,6-trifluoro -5-(perfluorohexyloxy)benzene, 1,4-diamino-2-chloro-5-(perfluorohexyloxy)benzene, 1,4-diamino-2-bromo- An aromatic diamine such as 5-(perfluorohexyloxy)benzene or a fluorine atom-free p-phenylenediamine (PPD) or dioxodiphenylamine. Further, the diamine component may be used in combination of two or more of the above aromatic diamines.

Further, the acid component is, for example, 4,4-hexafluoroisopropylidenedibenzoic anhydride (6FDA) containing a fluorine atom, and 3,4,3',4'-biphenyltetracarboxylic dianhydride containing no fluorine atom. (BPDA), trimellitic acid dianhydride (PMDA), and the like.

Further, an organic solvent used as a solvent of the polyimide precursor is, for example, N-methyl-2-pyrrolidone or dimethylformamide.

The method of imidization, such as the conventional method [for example, the reference to the Polymer Society, "New Polymer Experiment", published jointly, March 28, 1996, Volume 3, Polymer Synthesis, Reaction (2) 158 pages] It is indicated that any of the methods of heating or chemical imidization can be used, and the present invention is not affected by the method of imidization.

In addition, a resin having a carbon content of 40% by weight or more such as petroleum tar pitch or acrylic resin can be used as the resin other than the polyimide.

Here, the carbon source of the carbon source must be 40% by weight or more, and particularly preferably 40% by weight or more and 85% by weight or less, as described below. When the carbon yield is too small or too large (specifically, the carbon yield of the fluid material is less than 40% by weight or more than 85% by weight), a carbon powder which cannot be maintained in the ternary mesh structure is formed, but the carbon yield is used. When the carbon source is 40% by weight or more and 85% by weight or less, after removing the mold, it is possible to surely obtain porous carbon having a three-dimensional network structure in which continuous pores are formed at the mold. Further, when the carbon yield of the fluid material is in the above range, since the micropores are extremely developed, the specific surface area becomes large.

The above mold is preferably an alkaline earth metal compound such as magnesium oxide or calcium oxide. Since the alkaline earth metal compound can be removed by weak acid or water (that is, the mold can be removed without using a strong acid), the change in the properties of the porous carbon itself can be suppressed in the stage of removing the mold. Moreover, even if it is within the high temperature range of the carbonization step, it is not easily reduced to form a metal. For the carbon source, the ratio of the above mold is preferably 10 to 90% by weight.

The diameter of the pores, the pore distribution of the porous material, and the thickness of the carbonaceous wall can be adjusted by changing the diameter of the mold or the type of the organic resin. Further, by appropriately adjusting the diameter of the mold and the type of the organic resin, it is possible to produce porous carbon having a more uniform pore diameter and having a larger pore volume.

[Examples] (Example 1)

First, magnesium citrate (monohydrate) and boric acid (H ₃ BO ₃ , forming a powdery solid at room temperature) having both a mold source and a carbon source are used, and in the mortar, relative to the above magnesium citrate The above ratio of boric acid was 4% by weight, and as shown in Fig. 1(a), a mixture of magnesium citrate 1 and boric acid 2 was obtained. Then, the mixture was heated to 900 ° C at a temperature elevation rate of 10 ° C / min, and kept at 900 ° C for 1 hour. Next, the obtained carbon diluted sulfuric acid solution was added at a ratio of 1 mol/l to be washed, and magnesium oxide (MgO) or a reaction product of magnesium oxide and boron oxide was completely dissolved in sulfuric acid. Finally, by washing with water, porous carbon made of a bond structure of at least CBO is formed on the surface.

Here, in the heat treatment step, when the temperature of the mixture is raised to 169 ° C, the boronic acid 2 is decomposed to form boron oxide 3 as shown in Fig. 1(b). Then, when the temperature is raised to reach 480 ° C, as shown in Fig. 1 (c), magnesium citrate 1 is decomposed to form magnesium oxide 4 and magnesium citrate 6 in the middle of decomposition, and boron oxide 3 is melted. Then, when the temperature is raised again, a reaction product of magnesium oxide and boron oxide is formed on the outer periphery of the magnesium oxide, and as shown in FIG. 1(d), the mold 7 is formed by the reaction product and the magnesium oxide, and at the same time, the mold 7 is formed. Carbon 8 formed by carbonization of a citric acid component is disposed around the periphery. Finally, the mold 7 is removed by washing with a dilute sulfuric acid solution, and as shown in Fig. 1(e), a porous carbon 8 having a C-B-O bond structure at least on the surface can be obtained.

The porous carbon thus produced is hereinafter referred to as carbon A1 of the present invention.

(Example 2)

Porous carbon was produced in the same manner as in Example 1 except that the ratio of boric acid to magnesium citrate was 20% by weight.

The porous carbon thus produced is hereinafter referred to as carbon A2 of the present invention.

(Example 3)

Porous carbon was produced in the same manner as in Example 1 except that the proportion of boric acid was 50% by weight based on the magnesium citrate.

The porous carbon thus produced is hereinafter referred to as carbon A3 of the present invention.

(Comparative Example 1)

Porous carbon was produced in the same manner as in Example 1 except that boric acid was not added.

The porous carbon thus produced is referred to as comparative carbon Z1 in the following.

(Comparative Example 2)

Porous carbon was produced in the same manner as in Example 1 except that boronic acid was used instead of boric acid and the ratio of boron metal was 5% by weight based on magnesium citrate.

The porous carbon thus produced is referred to as comparative carbon Z2 in the following.

(Experiment 1)

The yields of carbon and the yield of carbon of the carbon A1, A3 and comparative carbon Z1 of the present invention were observed. The results are shown in Table 1.

As is clear from Table 1, the higher the proportion of boric acid added, the lower the yield of magnesium oxide or carbon. When the amount of boric acid added is increased, magnesium citrate The amount of the magnesium oxide source or the carbonic acid source is reduced.

(Experiment 2)

X-ray diffraction of the carbon material (specifically, the carbon material before washing with a sulfuric acid solution) in the stage of producing the carbon A1, A3 and the comparative carbon Z1 of the present invention was carried out, and the results are shown in Fig. 2.

As can be seen from Fig. 2, in the comparison of the carbon material in the production stage of the carbon Z1, the peak of the magnesium oxide can not be confirmed, and in the production stage of the carbon A1 of the present invention, the peak of the carbon material in addition to the magnesium oxide can also be confirmed as Mg ₃ (BO ₃ ) ₂ peak. Further, in the production stage of the carbon A3 of the present invention, the carbon material showed almost no peak of the magnesium oxide, but the peak of Mg ₃ (BO ₃ ) _{2 and} the peak of Mg ₂ B ₂ O _{5 were} confirmed. Thus, it can be seen that the original mold magnesium oxide reacts with boric acid.

Specifically, it is considered to generate a responder represented by the following (1) and (2). Further, when the amount of boric acid added is small, the reaction of (1) occurs, and when the amount of boric acid added is large, the reaction of (2) is produced in addition to the reaction of (1). In the case of the carbon material in the production stage of the carbon A1 of the present invention, since the amount of the boric acid added is small, only the reaction of (1) is produced. When the carbon material in the production stage of the carbon A3 of the present invention is used, since the amount of boric acid added is large, The reaction of (2) is produced in addition to the reaction of (1).

3MgO+2H ₃ BO ₃ → Mg ₃ (BO ₃ ) ₂ +3H ₂ O. . . (1)

2Mg ₃ (BO ₃ ) ₂ +2H ₃ BO ₃ → 3Mg ₂ B ₂ O ₅ +3H ₂ O. . . (2)

(Experiment 3)

X-ray diffraction of carbon A1~A3 and comparative carbon Z1 of the present invention The results are shown in Fig. 3.

As is clear from Fig. 3, the carbon A1 to A3 and the comparative carbon Z1 of the present invention did not greatly change, and even when boron was added, the crystallinity and the like did not significantly change.

(Experiment 4)

Since the X-ray diffraction measurement of the carbon Z2 was performed, the results are shown in Fig. 4.

As is clear from Fig. 4, even if it was washed with a sulfuric acid solution, the metal boron could not be removed, and it was confirmed that a large amount of metal boron remained (see A of Fig. 4).

(Experiment 5)

Since the carbon A1, A3 and the comparative carbon Z1 of the present invention were observed by TEM (transmission electron microscope), the results are as shown in Figs. 5 to 7 (Fig. 5 is a photograph of the carbon A1 of the present invention, and Fig. 6 is a carbon of the present invention. The photograph of A3 and the photograph of Fig. 7 are compared with the photograph of carbon Z1). Further, since the carbon A3 of the present invention was observed using SEM (Scanning Electron Microscope), the results are shown in Fig. 8.

As can be seen from Fig. 5 to Fig. 7, the obtained carbon nanostructure can be changed by changing the amount of boric acid added. In summary, it is considered that the carbon nanostructure can be controlled by the amount of boric acid added. As shown in Fig. 1, in the present invention, after coating with carbon, a mold is removed to form a mesopores, and a reaction product of magnesium oxide and boric acid is used as a mold. As described above, the carbon A1 and A3 of the present invention are oxygen which is directly formed from magnesium citrate by being melted by molten boron oxide and magnesium citrate. Magnesium is formed into a mold with a reaction product formed around the magnesium oxide (a reaction product formed by magnesium oxide and boric acid). Further, without adding boric acid (i.e., formed only of magnesium citrate), the carbon Z1 was compared, and only magnesium oxide directly formed from magnesium citrate was used to form a mold. Further, the molds of the carbons A1 and A3 of the present invention are larger than those of the molds of the comparative carbon Z1. As a result, when the mold is removed and the mesopores are formed, when the carbons A1 and A3 of the present invention are compared with the comparative carbon Z1, it is confirmed that the mesopores are large (compared from the comparison of Fig. 5 and Fig. 6 and Fig. 7). ). Further, from Fig. 5 and Fig. 6, it was confirmed that the primary particles of the carbon A1 and A3 of the present invention have a particle diameter of about 10 nm. Further, it can be confirmed from Fig. 8 that the carbon A3 of the present invention has mesopores remarkably.

(Experiment 6)

The XPS (X-ray photoelectron spectroscopy) analysis of the carbon A3 of the present invention described above was carried out, and the results are shown in Fig. 9. Moreover, since the XPS analysis of the comparative carbon Z1 was performed, the results are shown in Fig. 10.

It can be seen from Fig. 9 that in the surface state analysis, it was confirmed that there was almost no BO bond [caused by boron oxide (BO ₃ ) bonding], BC bonding [caused by bonding of boron carbide (B ₄ C)] However, it was confirmed that there was a significant peak due to the CBO bond. Further, it can be seen that the state of boron on the surface of the carbon A3 of the present invention is not simply adhered, loaded, adsorbed, nor exists in the state of boron oxide or boron carbide, but is bonded in a state called CBO on the carbon surface. presence.

In addition, it can be confirmed from Fig. 10 that the comparative carbon Z1 is not caused by the peak of boron.

(Experiment 7)

The carbon adsorption isotherm was determined by subjecting the carbon A1 to A3 and the comparative carbon Z1 of the present invention to nitrogen adsorption at 77 K, and the results are shown in Fig. 11. Further, since the nitrogen adsorption isotherm of the comparative carbon Z2 was obtained by the same method, the results are shown in Fig. 12. Further, a nitrogen adsorption isotherm for comparing carbon Z1 is also shown in Fig. 12.

It can be confirmed from Fig. 11 that in the low pressure region, when the carbon A1 to A3 of the present invention is compared with the comparative carbon Z1, the adsorption isotherm moves downward, but in the high pressure region, the adsorption isothermal of the carbon A1 to A3 of the present invention is high. The line moves up. From the results, it is understood that when the carbon A1 to A3 of the present invention is compared with the comparative carbon Z1, the micropores are reduced, and the larger mesopores or coarse pores are increased.

Further, it can be confirmed from Fig. 12 that the comparative carbon Z2 moves downward in the adsorption isotherm in all regions than the comparative carbon Z1. This is due to the reasons given below. The reaction of metal boron with carbon is negligible due to the slight contact area of carbon with the metal boron powder. Further, the solubility of the metal boron to the acid is remarkably lowered, and the unreacted person cannot be sufficiently removed. Further, there was no significant change in the pore structure of the comparative carbon Z2 and the comparative carbon Z1. As a result, when the comparative carbon Z2 is compared with the comparative carbon Z1, only the weight component of boron is considered, and the adsorption isotherm moves downward.

(Experiment 8)

The boron content (weight ratio) of the carbon A1 to A3 and the comparative carbon Z1 of the present invention was measured using a fluorescent X-ray apparatus. Moreover, by the above 77K nitrogen suction With the isotherm, the BET specific surface area and the total pore volume were determined, and the pore volume was determined by the DR method from the nitrogen adsorption line of 77K. Further, the mesopore volume was obtained by subtracting the above pore volume from all of the above pore volumes. The results of these are shown in Table 2.

As can be seen from Table 2, the ratio of boric acid was increased with respect to magnesium citrate, and the boron content was also increased. Therefore, it was confirmed that the boron content was increased and the BET specific surface area was small. However, even in the carbon A3 of the present invention having the highest boron content, the BET specific surface area was 890 m ² /g, which was a great value when compared with carbon black.

Further, as is clear from Table 2, as the boron content increases, the pore volume also decreases. This has the same tendency as the BET specific surface area. Even the carbon A3 of the present invention having the highest boron content has a micropore volume of 0.34 ml/g and has a micropore volume which can be referred to as a sufficient porous material.

Further, as is clear from Table 2, even if the carbon A1 of the present invention having the smallest mesopore volume is 1.22 ml/g, it can be maintained at a high level as compared with the conventional porous carbon containing activated carbon or the like.

(Experiment 9)

The pore diameter distribution of the mesopores of the carbon A1 to A3 and the comparative carbon Z1 of the present invention is as shown in Fig. 13.

It can be confirmed from Fig. 13 that the proportion of large mesopores increases as the amount of boric acid added increases. By reacting the magnesium oxide forming the mesoporous mold with boric acid, there is a possibility that the volume of the mold becomes large and the mesopore capacity increases.

(Experiment 10)

In the carbons A1 to A3 and the comparative carbon Z1 of the present invention, the dispersibility to water was confirmed, and the results shown below were shown in Table 3. In the experiment, 0.03 wt% of each porous carbon was added to 100 g of ion-exchanged water, and ultrasonic waves of 40 kHz were applied for 3 minutes, and then left for 16 hours, and then the transmittance at a wavelength of 550 nm was measured. The measurement was carried out using a UV-Vis spectrophotometer using a unit cell having an optical path length of 1 cm.

It can be confirmed from Table 3 that the transmittance of the carbon A1 to A3 of the present invention is 19 to 74% with respect to the transmittance of the comparative carbon Z1 to which no boric acid is added, and the transmittance is lower than that of the comparative carbon Z1. . This is the carbon A1 of the present invention. ~A3, carbon is purely dispersed without precipitation, and continues to maintain the state of the suspended wave. From this, it is understood that the present invention has an effect of improving the wettability to water and improving the dispersibility.

[Industry use value]

The present invention can be used as an electromagnetic wave absorbing material, an electrode material of a capacitor, an electrode material of a fuel cell or a battery, a gas absorbing material, a filter, a heat insulating material, a catalyst carrier, and the like.

1‧‧‧Magnesium citrate

2‧‧‧ Boric acid

3‧‧‧Boron Oxide

4‧‧‧Magnesium oxide

6‧‧‧Magnesium citrate on the way to decomposition

7‧‧‧Molding

8‧‧‧Porous carbon

[Fig. 1] is an explanatory view showing a manufacturing step of carbon of the present invention.

[Fig. 2] is a graph showing the results of X-ray diffraction of a carbon material (specifically, a carbon material before being washed with a sulfuric acid solution) in the stage of producing the carbon A1, A3 and the comparative carbon Z1 of the present invention.

[Fig. 3] is a graph showing the results of X-ray diffraction of carbon A1 to A3 and comparative carbon Z1 of the present invention.

[Fig. 4] is a graph showing the results of X-ray diffraction of comparative carbon Z2.

[Fig. 5] A TEM (transmission electron microscope) photograph of the carbon A1 of the present invention.

[Fig. 6] A TEM photograph of the carbon A3 of the present invention.

[Fig. 7] is a TEM photograph comparing carbon Z1.

[Fig. 8] A SEM (Scanning Electron Microscope) photograph of the carbon A3 of the present invention.

[Fig. 9] XPS (X-ray photoelectron spectroscopy) measurement of carbon A3 of the present invention fruit.

[Fig. 10] is a comparison of XPS measurement results of carbon Z1.

[Fig. 11] is a diagram showing the nitrogen adsorption isotherm of the carbon A1 to A3 and the comparative carbon Z1 of the present invention.

[Fig. 12] shows a nitrogen adsorption isotherm chart comparing carbons Z1 and Z2.

[Fig. 13] is a graph showing the pore diameter distribution of the mesopores of the carbon A1 to A3 and the comparative carbon Z1 of the present invention.

Claims (7)

A porous carbon characterized by having a bond structure of CBO at least on the surface, and a BET specific surface area determined by a nitrogen adsorption isotherm of 77K is 300 m ² /g or more, wherein the adsorption is isothermal by 77 K of nitrogen. The difference between the total pore volume obtained by the line and the nitrogen adsorption isotherm of 77 K and the micropore volume obtained by the DR (Dubinin-Radushkevich) method was 1 ml/g or more. The porous carbon according to the first aspect of the patent application, wherein the pore volume of the nitrogen adsorption adsorption line of 77K and the DR method is 0.3 ml/g or more. For example, the porous carbon of claim 1 or 2, wherein the boron content is 100 to 10000 ppm. The porous carbon according to claim 1 or 2, wherein 0.03 wt% of porous carbon is added to 100 g of ion-exchanged water, ultrasonic waves of 40 kHz are applied for 3 minutes, and after being left for 16 hours, light having a wavelength of 550 nm is used. The transmittance is below 80%. A method for producing porous carbon, characterized in that a mixture of boric acid and magnesium citrate is mixed to prepare a mixture, and the mixture is heated and fired in a vacuum gas atmosphere, a non-oxidizing gas atmosphere or a reducing gas atmosphere to produce a stage in which a fired product of a mold composed of a reaction product of boron oxide and magnesium oxide produced by boric acid is contained, and a stage in which the above-mentioned mold is removed in the fired product. A method for producing porous carbon according to item 5 of the patent application, The ratio of boric acid is specified to be more than 0% by weight and 100% by weight or less relative to magnesium citrate. The method for producing porous carbon according to the fifth or sixth aspect of the invention, wherein the temperature during the heating and baking is 500 ° C or more and 1500 ° C or less.