JP6269693B2 - Method for producing porous carbon material - Google Patents

Description

  The present invention relates to a method for producing a porous carbon material.

In Patent Document 1, in a method for producing a porous carbon material by heat-treating a carbide such as silicon or titanium in a chlorine-containing atmosphere, the generated chloride such as silicon or titanium (SiCl ₄ , TiCl ₄ or the like) is converted into Zn. , By catalytic reaction reduction with a metal element such as Mg, thereby generating Si or Ti as a simple metal, metal element such as Zn or Mg becomes a chloride, and chlorine generated by electrolyzing the metal chloride is generated. It is described that it is reused in the porous carbon material manufacturing process.
Further, in Patent Document 2, in a method for producing a porous carbon material by heat-treating a carbide such as silicon or titanium in a chlorine-containing atmosphere, SiCl ₄ and TiCl ₄ produced are reacted with oxygen, whereby silicon Alternatively, it is described that an oxide such as titanium (SiO ₂ , TiO ₂ or the like) and chlorine are generated and the generated chlorine is reused in a porous carbon material generating step.

International Publication No. 2013/150941 Pamphlet JP 2014-80325 A

However, in the technique described in Patent Document 1, not only chlorine but also simple metals such as Zn and Mg can be recovered and reused, but the electrolysis of chloride must be performed in a molten salt state at a high temperature. Therefore, there is a problem that the equipment load is large and the equipment cost is high.
Further, in the technique described in Patent Document 2, an oxidation reaction using oxygen is performed for recovery of chlorine. However, not all oxygen added for use in the reaction is used for the reaction, and a part of it is used. Remains. If oxygen remains, the porous carbon material from which the oxygen is obtained is burned, so that it is necessary to separate chlorine gas and oxygen gas. However, the separation operation of chlorine gas and oxygen gas is very complicated. In addition, in the oxidation reaction, oxide ultrafine particles (0.05 to 0.2 μm in diameter) are generated, so that further contrivance is required for the recovery.

  Accordingly, the present invention provides a technique for producing a porous carbon material by heat-treating a metal carbide such as silicon or titanium in a chlorine-containing atmosphere, and simultaneously recovering chlorine and the like from by-products generated in the production process and reusing them in the production process. An object of the present invention is to provide a technique that does not require additional equipment or complicated operations.

A method for producing a porous carbon material according to an aspect of the present invention includes:
A first step of generating a metal chloride containing the first metal and a porous carbon material by exposing a metal carbide containing the first metal in a heated atmosphere of the first gas containing chlorine gas; ,
A second step of neutralizing the metal chloride with an aqueous alkali hydroxide solution to produce an aqueous alkali chloride solution and at least one of a metal oxide and a metal hydroxide containing a first metal;
A third step of electrolyzing the alkali chloride aqueous solution to produce chlorine gas and an alkali hydroxide aqueous solution;
The chlorine gas generated in the third step and the aqueous alkali hydroxide solution are used in the first step and the second step, respectively.

  According to the method for producing a porous carbon material of the present invention, in the technique of recovering chlorine and the like from a by-product generated in the production process and reusing it in the production process, further facilities and complicated operations are not required.

It is a flowchart which shows the outline | summary of the manufacturing method of the porous carbon material which concerns on 1 aspect of this invention. It is the schematic of the electrolytic cell which can be used for the 3rd process of the manufacturing method of the porous carbon material which concerns on 1 aspect of this invention.

[Description of Embodiment of the Present Invention]
In the method for producing a porous carbon material according to one aspect of the present invention, (1) a metal carbide containing a first metal is exposed to a heated atmosphere of a first gas containing chlorine gas, and the first metal is exposed. A first step of producing a metal chloride containing a porous carbon material, and neutralizing the metal chloride with an aqueous alkali hydroxide solution to obtain a metal oxide containing the aqueous alkali chloride solution and the first metal And a second step of producing at least one of the metal hydroxide and a third step of electrolyzing the aqueous alkali chloride solution to produce chlorine gas and an aqueous alkali hydroxide solution, Chlorine gas and alkali hydroxide aqueous solution generated in the step are used for the first step and the second step, respectively.

Chlorine gas is recovered by electrolyzing the aqueous alkali chloride solution produced in the second step in the third step, and this chlorine gas can be used as the chlorine gas in the first step. Thereby, in the production of the porous carbon material, the chlorine gas can be reused by reusing the chlorine gas. Thus, chlorine gas can be used efficiently and the environmental load of chlorine gas can be reduced.
Moreover, the intermediate product produced | generated by a 1st process and a 2nd process is a thing with easy piping transport and reaction operation, such as gas, a slurry, and aqueous solution. Furthermore, the reaction in each of the second and third steps proceeds in a room temperature region of about 0 to 50 ° C. This eliminates the need for further equipment and complicated operations in the method of the present invention. In addition, since the electrolysis of the aqueous alkali chloride solution in the third step is widely used as a caustic soda manufacturing process, it is easy to use existing facilities.
Moreover, since the metal chloride produced | generated in the 1st process can be neutralized and preserve | saved, even when a manufacturing facility stops, compared with the technique of patent document 1, the safety | security at the time of operation is high.
Furthermore, not only the method according to one aspect of the present invention is used alone, but also the method according to one aspect of the present invention is incorporated into a part of known processes described in Patent Documents 1 and 2, etc., so It can also be used for safe exclusion and recovery of

(2) The metal carbide used in the first step preferably includes at least one of aluminum carbide, boron carbide, silicon carbide, titanium carbide, tungsten carbide, and molybdenum carbide. All of these metal chlorides produced by reacting with chlorine have a boiling point of 300 ° C. or lower, a high vapor pressure, and are easily in the form of a gas at normal temperature and pressure. Thereby, the piping operation of the metal chloride produced | generated and reaction operation in the following process can be made easier.
(3) It is preferable that the metal carbide is silicon carbide in terms of handleability, availability, and cost performance.
(4) It is preferable that the first gas is heated to a temperature of 500 to 1500 ° C. in terms of the certainty of the reaction and the heating energy cost.
(5) It is more preferable that the first gas is heated to a temperature of 1000 to 1300 ° C. in terms of the certainty of the reaction and the heating energy cost.
(6) In the second step, the alkali hydroxide is NaOH, and the concentration of the aqueous solution is preferably 5 to 20% by mass. By using NaOH, a general industrial process for producing NaOH and chlorine can be diverted in the third step.
(7) The electrolysis is preferably performed via a cation exchange membrane. Equipment and the like used in a general industrial process for producing NaOH and chlorine can be easily diverted.

[Details of the embodiment of the present invention]
Hereinafter, embodiments of the present invention will be described in detail.
[Outline of porous carbon material]
The method for producing a porous carbon material according to one embodiment of the present invention includes a first step, a second step, and a third step, as shown in the flowchart of FIG. In the first step, the metal carbide containing the first metal is exposed to the heated atmosphere of the first gas containing chlorine gas to produce the metal chloride containing the first metal and the porous carbon material. To do. In the second step, the metal chloride is neutralized with an aqueous alkali hydroxide solution to produce an aqueous alkali chloride solution and at least one of a metal oxide containing a first metal and a metal hydroxide. In the third step, the alkali chloride aqueous solution is electrolyzed to produce chlorine gas and an alkali hydroxide aqueous solution. Further, the chlorine gas and the alkali hydroxide aqueous solution generated in the third step are used in the first step and the second step, respectively.

[First step]
In the first step, the metal carbide containing the first metal is exposed to a heated atmosphere of the first gas containing chlorine gas to cause the metal carbide to react with the first gas. Metal carbide includes carbon and metal elements as constituent elements. In the first step, in detail, the metal constituting the metal carbide is reacted with chlorine contained in the first gas. By this reaction, a metal chloride containing the first metal and a porous carbon material are generated.
For example, when silicon carbide (SiC) is used as the metal carbide, silicon tetrachloride (SiCl ₄ ) and a porous carbon material (C) are generated. This reaction is represented by the following chemical reaction formula (1).

SiC + 2Cl ₂ → SiCl ₄ + C (1)

As the metal carbide used in the first step, aluminum carbide, boron carbide, titanium carbide, tungsten carbide, and molybdenum carbide are preferable in addition to the silicon carbide described above, and these are used alone or in combination. be able to.
When these metal carbides are produced as metal chlorides by the reaction shown in the above chemical reaction formula (1), the metal chlorides have a boiling point of 300 ° C. or lower and become gaseous or liquid at room temperature. It is. If it is in the state of gas or liquid at normal temperature, it is suitable for the piping transportation to the place of the 2nd process and reaction operativity which are explained in full detail later.
From the viewpoints of handleability, availability, and cost performance, it is preferable to use silicon carbide.

The first gas used in the first step is a gas containing chlorine gas as a constituent element. The first gas is a mixed gas of chlorine gas and an inert gas, or a gas consisting essentially of 100% chlorine gas. The inert gas is nitrogen gas (N ₂ ), argon gas (Ar), helium gas (He), neon gas (Ne), xenon gas (Xe), or the like.

  The reaction in the first step is performed in a heated atmosphere, and specifically, a temperature range of 500 to 1500 ° C. is preferable. If it is 500 degreeC or more, reaction rate will become reliable conditions. Moreover, when it exceeds 1500 degreeC, it is unpreferable at the point of a heating energy cost. In addition, the production equipment may be damaged, the generated metal chloride or porous carbon material may be destroyed, or a by-product may be generated. A more preferable heating atmosphere is a temperature range of 1000 to 1300 ° C.

  The metal chloride and porous carbon material produced in the first step are gas and solid particles, respectively. The metal chloride and porous carbon material produced in the first step are separated by an appropriate gas-solid particle separation means.

[Second step]
In the second step, the metal chloride produced in the first step is added to the aqueous alkali hydroxide solution to neutralize the metal chloride by hydrolysis. By this neutralization reaction, a metal oxide or metal hydroxide and an aqueous alkali chloride solution are generated.
For example, when the metal chloride produced in the first step is SiCl ₄ and the alkali hydroxide is sodium hydroxide (NaOH), silicon oxide (SiO ₂ ) and sodium chloride (NaCl) are produced. . This reaction is represented by the following chemical reaction formula (2).

SiCl ₄ + 4NaOH → SiO ₂ + 4NaCl + 2H ₂ O
... (2)

  Since the reaction in the second step is performed in a range of normal temperature of 0 to 50 ° C., the energy cost for heating the reaction apparatus can be reduced.

As the alkali hydroxide used in the second step, potassium hydroxide, calcium hydroxide, aluminum hydroxide, magnesium hydroxide and the like are preferable in addition to the sodium hydroxide already exemplified, and these may be used alone or in combination. Can be used.
Sodium hydroxide is preferably used from the viewpoints of handleability, availability, cost performance, and the advantage that a general industrial process for producing caustic soda and chlorine can be introduced. Moreover, it is preferable that the density | concentration of the sodium hydroxide aqueous solution in that case is 5-20 mass%.

  For separation of the metal oxide or metal hydroxide generated in the second step and the aqueous alkali chloride solution, a method of precipitation filtering the generated oxide or the like can be used. In some cases, a method may be used in which a polymer flocculant or the like is added to facilitate precipitation.

  The aqueous alkali chloride solution produced in the second step is subjected to a third step which will be described in detail later. On the other hand, the metal oxide or metal hydroxide may be discarded, may be used for another purpose, or may be made into a carbide by reacting with carbon and reused in the first step.

[Third step]
In the third step, the alkaline chloride aqueous solution generated in the second step is electrolyzed. By this reaction, chlorine gas and an aqueous alkali hydroxide solution are generated.
For example, when the alkali chloride aqueous solution generated in the second step is a sodium chloride (NaCl) aqueous solution, chlorine gas (Cl ₂ ) and a sodium hydroxide (NaOH) aqueous solution are generated. This reaction is represented by the following chemical reaction formula (3).

Positive electrode 2NaCl → Cl ₂ + 2Na ⁺ + 2e ⁻
Negative electrode 2Na ⁺ + 2H ₂ O + 2e ⁻ → 2NaOH + H ₂
... (3)

The conditions for the electrolysis in the third step are not particularly limited, but it is preferably carried out via a cation exchange membrane. Specifically, there is an electrolytic cell 1 as shown in FIG. 2 used in a general industrial process for producing caustic soda and chlorine.
The electrolytic cell 1 shown in FIG. 2 includes an anode 2 and a cathode 3, and the anode chamber 4 and the cathode chamber 5 are formed by separating the anode 2 and the cathode 3 by a cation exchange membrane 6. ing. Electrolysis is performed by supplying saline (NaClsoln.) From the lower part of the anode chamber 4 and water (H ₂ O) from the lower part of the cathode chamber 5 and applying a direct current between the anode 2 and the cathode 3.
In the anode chamber 4, chlorine ions (Cl ⁻ ) are electrically attracted to the anode 2 by electrolysis, and become gaseous chlorine molecules (Cl ₂ ) on the surface of the anode 2. In addition, sodium ions (Na ⁺ ) in the anode chamber 4 are electrically attracted to the cathode 3, pass through the cation exchange membrane 6, and move to the cathode chamber 5. In the cathode chamber 5, H ₂ O is decomposed into hydrogen ions (H ⁺ ) and hydroxide ions (OH ⁻ ), H ⁺ is electrically attracted to the cathode 3, and gaseous hydrogen molecules (H ₂ ). An aqueous NaOH solution is generated by OH ⁻ decomposed from H ₂ O and Na ⁺ that has moved from the anode chamber 4 through the cation exchange membrane 6.
In the electrolytic cell 1, Na ⁺ passes through the cation exchange membrane 6 and moves from the anode chamber 4 to the cathode chamber 5, but Cl ⁻ and OH ⁻ cannot pass through the cation exchange membrane 6. Remain without moving from the anode chamber 4 and the cathode chamber 5, respectively.
Cl ₂ generated in the anode chamber 4 is reused in the first step, and the aqueous NaOH solution generated in the cathode chamber 5 is reused in the second step.

[Others]
In this embodiment, the reaction temperatures of the second and third steps are low, and the substances produced in the steps are also easy to handle, so that chlorine gas can be efficiently recovered and reused while keeping the manufacturing cost low. . On the other hand, the techniques described in Patent Documents 1 and 2 have a higher reaction temperature in each process than in the present embodiment, and the materials generated in each process are more complicated to handle. Can be efficiently recovered and reused, and there is an advantage different from the present embodiment.
Therefore, as a method and equipment for producing a porous carbon material, and recovering and reusing a prepared material used therefor, the technology described in Patent Documents 1 and 2 is a main configuration, and a method of the main configuration, When the equipment is stopped, the method and equipment of this embodiment may be operated as a preliminary or emergency avoidance processing method and equipment.

DESCRIPTION OF SYMBOLS 1 Electrolysis cell 2 Anode 3 Cathode 4 Anode chamber 5 Cathode chamber 6 Cation exchange membrane

Claims (7)

A first step of generating a metal chloride containing the first metal and a porous carbon material by exposing a metal carbide containing the first metal in a heated atmosphere of the first gas containing chlorine gas; ,
A second step of neutralizing the metal chloride with an aqueous alkali hydroxide solution to produce an aqueous alkali chloride solution and at least one of a metal oxide and a metal hydroxide containing a first metal;
A third step of electrolyzing the alkali chloride aqueous solution to produce chlorine gas and an alkali hydroxide aqueous solution;
A method for producing a porous carbon material, wherein the chlorine gas and the alkali hydroxide aqueous solution generated in the third step are used in the first step and the second step, respectively.   The method for producing a porous carbon material according to claim 1, wherein the metal carbide includes at least one of aluminum carbide, boron carbide, silicon carbide, titanium carbide, tungsten carbide, and molybdenum carbide.   The method for producing a porous carbon material according to claim 1, wherein the metal carbide is silicon carbide.   The method for producing a porous carbon material according to claim 1 or 2, wherein, in the first step, the first gas is heated to a temperature of 500 to 1500 ° C.   The method for producing a porous carbon material according to claim 4, wherein in the first step, the first gas is heated to a temperature of 1000 to 1300 ° C.   The porous carbon material according to any one of claims 1 to 5, wherein in the second step, the alkali hydroxide is NaOH and the concentration of the aqueous solution is 5 to 20% by mass. Method.   The method for producing a porous carbon material according to any one of claims 1 to 6, wherein the electrolysis is performed via a cation exchange membrane.

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