JP2010029796A - Carbon removal apparatus and method for removing carbon - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carbon removal apparatus showing a good carbon removal characteristic in a lower temperature range. <P>SOLUTION: The carbon removal apparatus comprises an anode 120, a cathode 130, and a proton conductive film 110 installed between both electrodes and having proton conductivity and is enabled to remove carbon by sticking carbon to the anode 120, applying electric current or voltage between both electrodes in a state that the anode 120 is exposed to environments containing steam, and thereby oxidizing carbon stuck to the anode 120 by oxygen dissociated from steam. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an apparatus for removing carbon. In particular, the present invention relates to an apparatus for oxidizing and removing carbon using an electrochemical technique, and such a method.

  In general, exhaust gas discharged from a diesel engine such as a vehicle contains a harmful substance mainly composed of carbon called particulate matter. Therefore, in order to prevent such particulate matter from being released to the outside, a filter such as a diesel particulate filter (DPF) is installed in the exhaust gas exhaust passage. Thereafter, the particulate matter collected in the DPF is removed by various methods such as high-temperature treatment.

Recently, apart from such a technique using a filter such as DPF, a method of removing particulate matter such as carbon using an electrochemical method has been studied. For example, it has been proposed to use an oxygen ion conductor sandwiched between two electrodes and to oxidize and remove carbon using oxygen ions passing through the oxygen ion conductor (Patent Documents 1 and 2).
JP 2008-110277 A JP 2008-119618 A

  However, in the conventional technology for removing carbon by oxidation, oxygen ions need to be circulated from the cathode electrode to the anode electrode through the oxygen ion conductor in order to generate an oxidation reaction of carbon. Generally, in order for an oxygen ion conductor to exhibit oxygen ion conductivity, a high temperature of 500 to 600 ° C. or higher is required. However, for example, the temperature of exhaust gas from a diesel engine is usually about 400 ° C. or lower. For this reason, even if the conventional technology is applied as it is to the exhaust gas environment of a diesel engine, it is extremely difficult to cause the carbon oxidation reaction properly. Therefore, in the case of the conventional technique, in order to appropriately cause the oxidation reaction of carbon, it is necessary to heat the reaction apparatus by applying energy from the outside. As described above, the conventional countermeasures have a problem that the energy consumption increases and an additional heating device is required, which complicates and increases the cost of the device.

  This invention is made | formed in view of such a problem, and it aims at providing the carbon removal apparatus which shows a favorable carbon removal characteristic in a lower temperature range. Another object of the present invention is to provide such a method for removing carbon.

In the present invention,
An anode electrode;
A cathode electrode;
A proton conductive film having proton conductivity disposed between the electrodes;
A carbon removal apparatus having the following is provided:

  Here, the carbon removing apparatus according to the present invention may further include a separation member capable of separating an environment to which the anode electrode is exposed and an environment to which the cathode electrode is exposed.

  In the carbon removing apparatus according to the present invention, the proton conductive film may contain a perovskite type material or a metal phosphate.

In particular, the perovskite type materials include BaCe _1-x Y _x O _{3 -α} , SrCe _1-x Yb _x O _{3 -α} , BaZr _1-x Y _x O _{3 -α} , and SrZr _1-x Y _x O _{3. It} may have at least one material selected from the group consisting of _-α (where X and α are in the range of 0 ≦ X ≦ 1 and 0 ≦ α ≦ 1, respectively).

Alternatively, the metal phosphate is made of at least one material selected from the group consisting of SnP ₂ O ₇ , SiP ₂ O ₇ , TiP ₂ O ₇ and ZrP ₂ O ₇ doped with In ³⁺ or Al ^3+. You may have.

  In the carbon removing apparatus according to the present invention, the anode electrode may be platinum (Pt), gold (Au), palladium (Pd), copper (Cu), silver (Ag), nickel (Ni), iron (Fe), You may have at least 1 material selected from the group which consists of carbon and these alloys.

  Alternatively, the anode electrode may be made of carbon deposited on the anode electrode during use of the carbon removal device.

  In the carbon removing apparatus according to the present invention, the cathode electrode may be platinum (Pt), gold (Au), palladium (Pd), copper (Cu), silver (Ag), nickel (Ni), iron (Fe), You may have at least 1 material selected from the group which consists of carbon and these alloys.

  In the carbon removing apparatus according to the present invention, the proton conductive film may have a thickness in the range of 0.1 mm to 10 mm.

Furthermore, the present invention is a method for removing carbon,
(A) preparing a carbon removal device having an anode electrode, a cathode electrode, and a proton conductive film having proton conductivity installed between the two electrodes;
(B) attaching carbon to the anode electrode of the carbon removal device;
(C) applying a current or voltage to the carbon removal device via the both electrodes while the anode electrode is exposed to an environment containing water vapor;
(D) the carbon adhering to the anode electrode is oxidized by the water vapor;
There is provided a method of removing carbon having

  Here, in the method according to the present invention, the steps (c) and (d) may be performed in a temperature range of room temperature to 500 ° C.

  Moreover, in the method according to the present invention, the environment containing water vapor in the step (c) may have a water vapor partial pressure of 0.01 vol% to 90 vol%.

  In the method according to the present invention, the carbon removal device may further include a separation member capable of separating an environment to which the anode electrode is exposed and an environment to which the cathode electrode is exposed. .

  In the method according to the present invention, the anode electrode of the carbon removing device may be formed by the step (b).

  According to the present invention, it is possible to provide a carbon removal apparatus that exhibits good carbon removal characteristics in a lower temperature range. Also provided is a method for providing such a carbon removal method.

  Before describing the carbon removal apparatus and method according to the present invention, a conventional carbon removal apparatus will first be described in order to better understand the features and effects of the present invention.

  FIG. 1 shows a schematic diagram of the operating principle of a conventional carbon removal apparatus. The conventional carbon removing apparatus 1 is configured by laminating an anode electrode 20, a solid electrolyte membrane 10 having oxygen ion conductivity, and a cathode electrode 30 in this order.

When the conventional carbon removing device 1 is connected to the power source V1, the cathode electrode 30

1 / 2O ₂ + 2e ⁻ → O ^{2 −} Formula (1)

Reaction occurs. O ²⁻ ions generated at the cathode electrode 30 pass through the solid electrolyte membrane 10 and reach the anode electrode 20. In the anode electrode 20,

_{^{O 2- + C → CO 2 +}} 2e - Formula (2)

Reaction occurs. Therefore, carbon adhering to the anode electrode can be removed by oxidation on the anode electrode.

  However, in general, the solid electrolyte membrane 10 exhibits oxygen ion conductivity in an extremely high temperature range such as about 500 ° C. or higher. On the other hand, the exhaust gas temperature of a general diesel engine is about 400 ° C. or less. For this reason, even if the conventional carbon removal apparatus 1 is installed in such an environment as it is, it is extremely difficult to properly remove the attached carbon. Therefore, in such a method, it is necessary to heat the apparatus by applying energy from the outside in order to appropriately generate the oxidation reaction of carbon. Such measures have problems that energy consumption increases and an additional heating device is required, which complicates and increases the cost of the device.

  In view of the above problems, the inventor of the present application has earnestly studied for the purpose of developing a carbon removing apparatus capable of oxidizing and removing carbon efficiently at a lower temperature. As a result, the inventors of the present application have found that carbon can be appropriately oxidized even in a low temperature range by using a proton conductor, and the present invention has been achieved.

  Hereinafter, a carbon removing apparatus according to the present invention will be described with reference to the drawings.

  FIG. 2 shows a schematic cross-sectional view of an example of the carbon removing apparatus according to the present invention. FIG. 3 shows the operating principle of the carbon removing apparatus according to the present invention. In both figures, it should be noted that the dimension of each member is not accurate, and each member and its relative dimension are exaggerated.

As shown in FIG. 2, the carbon removing apparatus 100 according to the present invention includes a proton conductive film 110 having proton conductivity, and an anode electrode 120 and a cathode electrode 130 installed on both surfaces of the proton conductive film 110. . The carbon removing apparatus 100 is configured by laminating an anode electrode 120, a proton conductive film 110, and a cathode electrode 130 in this order. The anode electrode 120 has a role of oxidizing and removing carbon adhering to the anode electrode. The cathode electrode 130 has a role of reducing H ⁺ ions that reach the cathode electrode through the proton conductive film 110. As will be described later, the anode electrode 120 may not be formed on the proton conductive film 110 immediately after the device is manufactured.

  Next, the operation principle of the carbon removing apparatus 100 according to the present invention will be described with reference to FIG. When the carbon removing apparatus 100 according to the present invention is connected to the power source V as shown in FIG. 3, the anode electrode 120 is anode-polarized and the cathode electrode 130 is cathode-polarized.

In the anode electrode 120, when water vapor is present in the surroundings, an oxidation reaction occurs in which the water vapor is decomposed into hydrogen ions and oxygen as shown in the following formula (3):

_{^{2H 2 O → 4H + + O}} * + 4e - Equation (3)

Here, the subscript “ ^* ” of O ^* is added to indicate that the generated oxygen is in an active state.

Hydrogen ions generated by the reaction of formula (3) move to the cathode 130 through the proton conductive film 110. On the cathode electrode 130, the hydrogen ions react with oxygen in the environment to become water vapor:

O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O Formula (4)

Here, when carbon adheres on the anode electrode 120, this carbon is oxidized by the active oxygen generated in the formula (3) to become carbon dioxide (CO ₂ ) and is released from the electrode. :

C + 2O * → CO ₂ formula (5)

Therefore, the carbon can be oxidized and removed by the carbon removing apparatus 100 according to the present invention.

Such a carbon removal apparatus 100 according to the present invention has the following features and advantages over the conventional apparatus:
(1) In the present invention, a proton conductive film is installed in the carbon removing device. The proton conductivity of the proton conductive film can be obtained at a lower temperature than the oxygen ion conductivity of the solid electrolyte membrane. Therefore, the carbon removing apparatus 100 according to the present invention can be used at a lower temperature than a conventional solid electrolyte membrane having oxygen ion conductivity.
(2) In the present invention, active oxygen is used as an oxidation source for oxidizing carbon. In a conventional apparatus using a solid electrolyte membrane having oxygen ion conductivity, an oxygen source that oxidizes carbon is oxygen ions that move through the solid electrolyte membrane and reach the anode (see FIG. 1). Since the reactivity of oxygen ions is relatively weak, the oxidation reaction rate of carbon is not so high. In contrast, in the present invention, active oxygen having extremely high reactivity is used for the oxidation reaction of carbon, so that the oxidation rate of carbon is large and the carbon can be oxidized relatively quickly.
(3) Oxygen (active oxygen) serving as a carbon oxidation source is provided by decomposition of water vapor. This means that the carbon removal characteristics of the carbon removal apparatus according to the present invention hardly depend on the oxygen partial pressure of the use environment. In general, the oxygen partial pressure in the exhaust gas of a diesel engine varies greatly depending on the operation mode. For example, in a reducing atmosphere such as the rich combustion operation mode, the oxygen partial pressure in the exhaust gas becomes extremely small. Therefore, in the conventional carbon removal apparatus using the solid electrolyte membrane having oxygen ion conductivity, the carbon removal characteristics depend on the oxygen partial pressure, and it is difficult to always exhibit good carbon removal characteristics. On the other hand, water vapor is always included in the exhaust gas environment of a diesel engine at a certain partial pressure in any operation mode. Therefore, in the present invention in which oxygen as a carbon oxidation source is supplied by decomposition of water vapor, it is possible to always exhibit good carbon removal characteristics without being affected by environmental conditions.

  Hereinafter, each member which comprises the carbon removal apparatus 100 of this invention is demonstrated in detail.

(Proton conductive film 110)
In the carbon removing apparatus 100 of the present invention, the proton conductive film 110 can be any film as long as it has proton conductivity. Proton conductive film 110 is, for _{example, BaCe 1-x Y x O} 3-α, SrCe 1-x Yb x O 3-α, BaZr 1-x Y x O 3-α, SrZr 1-x Y x O 3- It may be made of a perovskite type material such as _α . Here, X and α are ranges of 0 ≦ X ≦ 1 and 0 ≦ α ≦ 1, respectively, and may be, for example, X = 0.1. Generally, in the proton conductive film 110 made of a perovskite type material, the temperature range in which extremely good proton conductivity is obtained is about 300 ° C. to 800 ° C. Of course, it is obvious to those skilled in the art that it may be used in other temperature ranges.

Alternatively, the proton conductive film 110 may be a metal phosphate, for example. As the metal phosphate, _SnP 2 _O 7 doped with ^{In 3+} or ^{_{Al 3+, SiP 2 O 7,}} TiP 2 O 7 or _ZrP may be a 2 _{O 7,} for example, doped with ^{In 3+} or ^{Al 3+} SnP ₂ O ₇ . The doping amount of In ³⁺ and Al ³⁺ is not particularly limited, but may be in the range of approximately 5 mol% to 20 mol%, for example, 10 mol%. In addition, when the dope amount exceeds 20 mol%, phase separation may occur and there may be two phases. Generally, in the proton conductive film 110 made of a metal phosphate material, the temperature range in which extremely good proton conductivity is obtained is about 100 ° C. to 400 ° C. Of course, it is obvious to those skilled in the art that it may be used in other temperature ranges.

  The proton conductive film 110 may be a dense film with little gas permeability or a porous film with high gas permeability. The thickness of the proton conductive film 110 is not particularly limited, but may be in the range of 0.1 mm to 10 mm, for example, 1 mm.

(Anode electrode 120)
In the carbon removing apparatus 100 of the present invention, the anode electrode 120 may be of any material, form and size as long as it is a conductive member. The material of the anode electrode 120 is, for example, a metal such as platinum (Pt), gold (Au), palladium (Pd), copper (Cu), silver (Ag), nickel (Ni), iron (Fe) or the like. It is an alloy. Furthermore, carbon may be used as an electrode material.

  In another aspect, the anode electrode 120 may not be “positively” installed immediately after the device is manufactured. That is, in the carbon removing apparatus according to the present invention, carbon itself that is attached to the anode electrode during use and is subject to oxidation removal can be used as the anode electrode. In this case, since carbon is attached to the anode electrode during use of the apparatus, it is not necessary to install it "actively" before the apparatus is used.

  In addition, when the anode electrode 120 is installed “positively” on the proton conductive film 110, the thickness of the anode electrode 120 is not particularly limited. The thickness of the anode electrode 120 may be, for example, in the range of 0.01 mm to 1 mm, for example, 50 μm.

(Cathode electrode 130)
In the carbon removing apparatus 100 of the present invention, the cathode electrode 130 can be basically made of the same material, shape and dimensions as the anode electrode 120. However, when carbon is used for the cathode electrode 130, it is necessary to install such a carbon electrode in advance, unlike the carbon of the anode electrode.

  Although not shown in FIG. 2, the carbon removing apparatus according to the present invention may have additional members in addition to the proton conductive film 110, the anode electrode 120, and the cathode electrode 130. For example, a current collecting member such as a metal mesh may be further disposed on the anode electrode 120 and / or the cathode electrode 130. As a result, electrons or current generated by the electrochemical reaction at each electrode can be recovered more reliably. Further, lead wires are led out from the metal mesh on both electrodes or the respective electrodes, and by using these lead wires, an external power source and the carbon removing apparatus according to the present invention are connected to each other. An electrochemical reaction at the electrode may be caused.

(Second carbon removal device)
Next, another carbon removing apparatus according to the present invention will be described. FIG. 4 shows a schematic cross-sectional view of an example of the second carbon removing apparatus 200 according to the present invention. The second carbon removing device 200 has the same components as the carbon removing device 100 shown in FIG. Therefore, in FIG. 4, the same reference numerals are given to the same members as those in FIG.

  The second carbon removing apparatus 200 includes a proton conductive film 110 and an anode electrode 120 and a cathode electrode 130 installed on both surfaces thereof. As described above, the anode electrode 120 may not be installed at a stage before the use of the apparatus.

  The second carbon removing apparatus 200 further includes a tubular member 250 installed on the upper part of the cathode electrode 130. The tubular member 250 is arranged so that one end opened is in contact with the cathode electrode 130, and the other end is sealed with a sealing member 255 such as a rubber plug. The sealing member 255 has two through holes, one of which has an inlet pipe 260 inserted therein and the other of which has an outlet pipe 270 inserted therein. The inlet tube 260 is preferably installed so that one end thereof is closer to the surface of the cathode electrode 130 than the outlet tube 270. This makes it possible to more reliably supply a gas (for example, air) necessary for the reaction to the surface of the cathode electrode. The material of the inlet pipe 260 and the outlet pipe 270 is not particularly limited. On the other hand, since the tubular member 250 is in direct contact with the cathode electrode 130, the tubular member 250 is made of an insulating material. The tubular member 250, the inlet pipe 260, and the outlet pipe 270 may be made of a ceramic member such as alumina. The method for fixing the tubular member 250 and the cathode electrode 130 is not particularly limited. For example, both may be fixed by inserting the cathode electrode 130 into the tip of the tubular member 250 along the inner diameter of the tubular member 250, although they are different from the state shown in the figure.

  In the second carbon removing apparatus 200 configured in this way, the environment to which the anode electrode 120 is exposed and the environment to which the cathode electrode 130 is exposed can be separated. Thus, for example, it is possible to supply a separate controlled gas to the cathode electrode 130 side while leaving the anode electrode 120 side exposed to an environment that requires oxidative removal of carbon. Become.

  In the example of FIG. 4, the tubular member 250 is installed to separate the environment to which the anode electrode 120 is exposed and the environment to which the cathode electrode 130 is exposed. However, this tubular member is only an example. That is, the second carbon removing apparatus according to the present invention is not limited to the configuration shown in FIG. 4, and it is obvious to those skilled in the art that another separating member for separating both electrodes may be used. It is.

(Method of oxidizing and removing carbon)
Next, a method for oxidizing and removing carbon will be described in more detail. FIG. 5 shows a flowchart of a method for oxidizing and removing carbon.

  In the method for oxidizing and removing carbon according to the present invention, a step of preparing a carbon removing device comprising an anode electrode, a cathode electrode, and a proton conductive film sandwiched between both electrodes (step S110), and a step of attaching carbon to the anode electrode (step S110) Step S120), applying an electric current or voltage to both electrodes of the carbon removing device in a state where the anode electrode is exposed to an environment containing water vapor (Step S130), and carbon adhering to the anode electrode by the water vapor Is performed by the step of oxidizing (step S140).

  First, in step S110, a carbon removing apparatus having an anode electrode, a cathode electrode, and a proton conductive film as shown in FIG. 2 or FIG. 4 is prepared.

  Next, in step S120, for example, a carbon removal device is installed in an environment that requires carbon removal, and carbon is deposited on the anode electrode.

  As a matter of course, the environment in which the anode electrode is installed may be an environment of exhaust gas of a normal diesel engine.

  Next, in step S130, a current or voltage is applied to both electrodes of the carbon removal device in a state where the anode electrode is exposed to an environment containing water vapor. Note that this step may be performed in the reverse order of step S120 described above.

The H ₂ O partial pressure contained in the environment to which the anode electrode is exposed is not particularly limited, but may be, for example, in the range of 0.01 vol% to 90%. The H ₂ O partial pressure is, for example, 1 vol% to 10 vol%. As a matter of course, this environment may be an environment of exhaust gas of a normal diesel engine.

In the next step S140, the reaction of the above formulas (3) and (5) occurs on the anode electrode by the current or voltage applied in step S130, and the reaction of the above formula (4) occurs on the cathode electrode. Occurs. Thereby, carbon adhering on the anode electrode is oxidized, and carbon is removed as CO ₂ .

  As described above, in the present invention, oxygen (activity), which is a carbon oxidation source, is provided by decomposition of water vapor, so oxygen present in the use environment hardly participates in the reaction. Normally, water vapor is always included in the exhaust gas environment of a diesel engine at a certain partial pressure. Therefore, in the present invention in which oxygen as a carbon oxidation source is supplied by decomposition of water vapor, even in the exhaust gas environment of a diesel engine, it always exhibits good carbon removal characteristics without being affected by engine operating conditions. can do.

  Further, as described above, in the conventional method using a solid electrolyte membrane having oxygen ion conductivity, the oxygen source for oxidizing carbon is oxygen ions. Therefore, the oxidation reaction rate of carbon is not so great. On the other hand, in the present invention, since highly reactive oxygen is used for the oxidation reaction of carbon, the oxidation rate of carbon is large and the oxidation reaction of carbon can be caused relatively quickly. .

  Further, in the present invention, a proton conductive film is installed between the electrodes instead of the solid electrolyte having oxygen ion conductivity. For this reason, in the method of the present invention, carbon removal can be carried out in a wide temperature range from room temperature to 800 ° C. The treatment temperature may be, for example, in the range of room temperature to 500 ° C., which is a temperature range that is significantly lower than the use temperature for conventional carbon removal.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

Example 1
(Preparation of proton conductive film)
SnO ₂ powder (purity 98%, manufactured by Wako Pure Chemical Industries) 13.6 g, In ₂ O ₃ powder (purity 99.9%, manufactured by Wako Pure Chemical Industries) 1.39 g, and H ₃ PO ₄ (purity 85%, 31.1 g of Wako Pure Chemical Industries, Ltd.) was mixed, and this mixed powder was added to 80 ml of distilled water and stirred at 300 ° C. The obtained slurry-like mixture was transferred to an alumina crucible and kept in an atmospheric firing furnace at 650 ° C. for 2.5 hours to fire the slurry-like mixture. Next, the obtained calcined body was pulverized using a mortar, and this was put into a mold (diameter 14 mm) to produce a pellet. Then, this pellet was vacuum-packed with vinyl and pressurized with a pressure of 1000 kgfcm ⁻² using an isostatic press, and an Sn _0.9 In _0.1 P ₂ O ₇ proton conductive film was obtained. The proton conductive film had a diameter of 13 mm and a thickness of 1.0 mm.

(Production of carbon removal equipment sample)
Next, a sample of a carbon removal apparatus was produced using the Sn _0.9 In _0.1 P ₂ O ₇ proton conductive film prepared by the above-described method. First, an anode electrode was installed on one surface of the proton conductive film. For the anode electrode, a mixed powder of platinum black and carbon was used (carbon is also an object to be removed by this apparatus). First, 2 mg of platinum black powder (manufactured by Wako Pure Chemical Industries) and 5 mg of carbon powder (black pearl) were sufficiently mixed to prepare a mixed powder.

Next, this mixed powder was dispersed substantially uniformly on the proton conductive film. Next, pressure was applied by hand from above the mixed powder, and the mixed powder and the proton conductive film were pressure bonded. Thereby, the anode electrode was installed on the proton conductive film. Further, the above-described platinum black powder (manufactured by Wako Pure Chemical Industries, Ltd.) was used for the cathode electrode. The powder was pressed on the other surface of the proton conductive film in the same manner as in the case of the anode electrode described above to form a cathode electrode. Each electrode area was 0.5 cm ² .

  Next, a gold mesh (mesh # 100) was placed on each electrode as a current collector, and a gold wire (diameter 0.2 mmφ) connected to each gold mesh was used as a lead wire for energization. . A carbon removal device sample was prepared by such a method.

(Configuration of measuring device for measuring carbon removal characteristics)
A measurement apparatus for evaluating the carbon removal characteristics of the sample was configured using the sample prepared by the above-described method. FIG. 6 shows a schematic configuration of the measuring apparatus.

  As shown in FIG. 6, the measuring apparatus 600 includes a sample 605 manufactured by the above-described method, outer and inner alumina tubes 610A and 615A installed on the anode electrode 605A side of the sample 605, and a cathode electrode 605C of the sample 605. And outer and inner alumina tubes 610C and 615C installed on the side. The outer alumina tubes 610A and 610C are installed so as to surround the inner alumina tubes 615A and 615C, respectively. The outer alumina tube 610A is installed so as to contact the sample 605, whereas the inner alumina tube 615A is installed so as not to contact the sample 605. Similarly, the outer alumina tube 610C is installed so as to contact the sample 605, and the inner alumina tube 615C is installed so as not to contact the sample 605. By installing these alumina pipes, an anode supply gas flow path 630A is formed between the outer alumina pipe 610A and the inner alumina pipe 615A, and an anode exhaust gas flow path 635A is formed inside the inner alumina pipe 615A. The Similarly, a cathode supply gas channel 630C is formed between the outer alumina tube 610C and the inner alumina tube 615C, and a cathode exhaust gas channel 635C is formed inside the inner alumina tube 615C.

In such a measuring apparatus 600, when a mixed gas (argon gas containing 3 vol% of water vapor in this embodiment) is supplied to the anode supply gas flow path 630A from the outside, this mixed gas becomes the anode of the sample 605. When carbon dioxide gas (CO ₂ ) is generated by the reaction after being supplied onto the electrode 605A, it is discharged together with the CO ₂ gas through the anode exhaust gas flow path 635A. On the other hand, when a mixed gas (air in this embodiment) is supplied to the cathode supply gas flow path 630C from the outside, this mixed gas is supplied onto the cathode electrode 605C of the sample 605, and then water ( When the water vapor (or water vapor) is generated, the water (or water vapor) is discharged through the cathode exhaust gas flow path 635C. Therefore, the amount of CO ₂ discharged from the sample 605 can be measured by introducing the mixed gas discharged through the anode exhaust gas flow path 635A into a gas chromatography device (CP2002; manufactured by Varian).

(Measurement of carbon removal characteristics of sample: Experiment 1)
Using such a measuring apparatus 600, the CO ₂ concentration in the mixed gas discharged from the anode exhaust gas flow path 635A was measured by the following method. Sample 605 was set at 25 ° C. The respective mixed gas flow rates supplied to the anode and cathode supply gas flow paths 630A and 630C were 30 ml / min.

First, two lead wires derived from the sample are connected to a galvanostat (HA501; manufactured by Hokuto Denko). A current is supplied from the galvanostat to the sample 605 so that the anode electrode 605A of the sample 605 is polarized to the anode side. The current density applied first is about 3 mA / cm ² . After the current application, the state is maintained until the CO ₂ concentration in the mixed gas discharged from the anode exhaust gas flow path 635A is stabilized. Obtain the value of the CO ₂ concentration when it becomes stable. Next, the current density is increased and the same measurement is performed. Such measurement was continued until the current density reached a maximum of 10 mA / cm ² .

As a result of the measurement, it was found that the concentration of CO ₂ discharged increases linearly as the applied current density increases.

Next, from the obtained results, the current efficiency η _eff of carbon removal at each current was obtained by the following (i) to (iii).

(I) The net anodic reaction occurring at the anode electrode of the sample is represented by the sum of the above formulas (3) and (5),

_{C + 2H 2 O → CO 2} + 4H + + 4e - formula (6)

It becomes.

The theoretical amount of CO ₂ produced by this reaction n (mol) is

n (mol) = I (A) x t (sec)
/ {Z × F (C / mol)} Formula (7)

It is represented by Here, I (A) is a current, t (sec) is time, and F (C / mol) is a Faraday constant. z is the number of electrons in the electrochemical reaction (ie, formula (6)), and is 4.

(Ii) As an example, assuming that the current I is 10 mA, the gas flow rate is 30 ml / min. Therefore, the theoretical CO ₂ production amount n per minute is n (mol / min) from the equation (7). = 1.554 μmol.

When this value is converted into gas concentration C (vol%), per unit area,

C (vol%) = n (mol / min) × 2.24 × 10 ⁴ (mL / mol) / 30 (ml / min) × 100 = 0.116 (vol%) Formula (8)

It becomes.

(Iii) Therefore, the current efficiency η _eff is obtained from the following equation (9) from the measurement result P (vol%) of the CO ₂ concentration obtained by the measurement.

η _eff (%) = (measurement result P (vol%) / C (vol%)) × 100 Formula (9)

The current efficiency η _eff calculated using this equation (9) was 42%. (The calculated current efficiency η _eff was the same regardless of the measurement result at any current.) From this, the carbon removal apparatus according to the present invention has good carbon removal characteristics even at room temperature level. Was found to be obtained.

(Measurement of carbon removal characteristics of sample: Experiments 2 to 7)
Next, Experiments 2 to 7 similar to Experiment 1 were performed by changing the temperature of the sample in the range of 50 ° C to 300 ° C. In Experiment 2, the sample temperature was 50 ° C., in Experiment 3, the sample temperature was 100 ° C., in Experiment 4, the sample temperature was 150 ° C., in Experiment 5, the sample temperature was 200 ° C., and in Experiment 6, the sample temperature was Was 250 ° C., and in Experiment 7, the sample temperature was 300 ° C. In Experiment 3, the maximum current density measured as 30 mA / cm ² or so, in Experiment 4, the maximum current density measured as 40 mA / cm ² or so, in Experiment 5-7, the maximum current density 50 mA / cm ² The degree.

As a result of the experiment, it was confirmed that the applied current and the generated CO ₂ concentration were in a proportional relationship at any sample temperature.

Table 1 shows the sample temperature in Experiments 1 to 7 and the measurement results of the current efficiency η _eff for removing carbon. FIG. 7 shows the relationship between the temperature of the sample and the current efficiency η _eff for removing carbon.

表１および図７から明らかなように、サンプル温度の上昇とともに、カーボン除去の電流効率η_ｅｆｆは、上昇した。特に、サンプル温度が２００℃を超えると、カーボン除去の電流効率η_ｅｆｆは、１００％となり（実験５〜７）、投与したエネルギーがカーボン除去に有効に利用されていることがわかった。

As is apparent from Table 1 and FIG. 7, the current efficiency η _eff of carbon removal increased with increasing sample temperature. In particular, when the sample temperature exceeded 200 ° C., the current efficiency η _eff of carbon removal became 100% (Experiments 5 to 7), and it was found that the administered energy was effectively used for carbon removal.

(Example 2)
A sample of a carbon removal device having a Sn _0.9 In _0.1 P ₂ O ₇ proton conductive film was produced in the same manner as in Example 1. However, in Example 2, acetylene black powder (manufactured by DENKA) was installed as carbon contained in the anode electrode of the sample instead of black pearl powder. The installation amount of acetylene black was 5 mg.

  Using this sample, the carbon removal characteristics were evaluated in the same manner as in Example 1 (referred to as Experiment 8). In addition, the measurement temperature of the sample was 200 degreeC.

(Example 3)
A sample of a carbon removal device having a Sn _0.9 In _0.1 P ₂ O ₇ proton conductive film was produced in the same manner as in Example 1. However, in Example 3, carbon black powder (manufactured by Sigma-Aldrich Japan) was installed as carbon contained in the anode electrode of the sample, instead of black pearl powder. The installation amount of carbon black was 5 mg.

  Using this sample, the carbon removal characteristics were evaluated in the same manner as in Example 1 (referred to as Experiment 9). In addition, the measurement temperature of the sample was 200 degreeC.

The results of Experiments 8 and 9 are summarized in FIG. 7 and Table 1 described above. From these results, even if the type of carbon installed in the anode electrode is changed to acetylene black (Example 2) or carbon black (Example 3), the current efficiency η _eff of carbon removal does not change, It was found that at 200 ° C., a high current efficiency η _eff of 100% can be obtained.

Example 4
A sample of a carbon removal device having a Sn _0.9 In _0.1 P ₂ O ₇ proton conductive film was produced in the same manner as in Example 1. However, in Example 4, only black pearl powder was used as the anode electrode of the sample, and platinum black was not used. Therefore, in this embodiment, the constituent material of the anode electrode itself is the object to be removed. The installation amount of black pearl powder was 5 mg.

  Using this sample, the sample temperature was changed in the range of 25 ° C. to 300 ° C., and the carbon removal characteristics were evaluated by the same method as in Example 1 (respectively, Experiments 10 to 16).

(Example 5)
A sample of a carbon removal device having a Sn _0.9 In _0.1 P ₂ O ₇ proton conductive film was produced in the same manner as in Example 4. However, in Example 5, acetylene black powder (manufactured by DENKA) was used as the anode electrode of the sample instead of black pearl powder. The installation amount of acetylene black is 5 mg.

  Using this sample, the carbon removal characteristics were evaluated in the same manner as in Example 1 (referred to as Experiment 17). In addition, the measurement temperature of the sample was 200 degreeC.

(Example 6)
A sample of a carbon removal device having a Sn _0.9 In _0.1 P ₂ O ₇ proton conductive film was produced in the same manner as in Example 4. However, in Example 6, carbon black powder (manufactured by Sigma Aldrich Japan) was used as the anode electrode instead of black pearl powder. The installation amount of carbon black is 5 mg.

  Using this sample, the carbon removal characteristics were evaluated in the same manner as in Example 1 (referred to as Experiment 18). In addition, the measurement temperature of the sample was 200 degreeC.

The results of Experiments 10 to 18 are summarized in Table 2. Moreover, in FIG. 8, the relationship between the temperature of the sample which concerns on Examples 4-6 and carbon removal efficiency (eta) _eff is shown.

表２の実験１０の結果から、前述の実施例１の実験１の場合と同様、アノード電極としてカーボンのみを使用したサンプルにおいても、２５℃の低温域において、３９％の高い電流効率η_ｅｆｆが得られることがわかった。

From the results of Experiment 10 in Table 2, as in the case of Experiment 1 of Example 1 described above, even in the sample using only carbon as the anode electrode, a high current efficiency η _{eff of} 39% was obtained at a low temperature range of 25 ° C. It turns out that it is obtained.

  Further, from the results of Experiments 10 to 16 in Table 2 and FIG. 8, it is understood that the current efficiency increases as the sample temperature increases, and at 200 ° C. or higher, the current efficiency becomes 100%, and good carbon removal characteristics can be obtained. It was. Further, from the results of Experiments 17 (Example 5) and 18 (Example 6), the current efficiency at 200 ° C. shows 100% even when the carbon to be removed is changed to acetylene black or carbon black. I understood it.

  The present invention can be used, for example, in an exhaust gas purification device that suppresses release of particulate matter contained in exhaust gas discharged from a diesel engine to the outside.

It is the figure which showed the principle of operation of the conventional carbon removal apparatus. It is a schematic sectional drawing of an example of the carbon removal apparatus by this invention. It is the figure which showed the operating principle of the carbon removal apparatus by this invention. It is a schematic sectional drawing of an example of another carbon removal apparatus by this invention. 3 is a flowchart of a carbon removal method according to the present invention. It is the figure which showed roughly the measuring apparatus for evaluating a carbon removal characteristic. It is the graph which showed the relationship between the temperature of the sample which concerns on Examples 1-3, and the current efficiency of carbon removal. It is the graph which showed the relationship between the temperature of the sample which concerns on Examples 4-6, and the current efficiency of carbon removal.

Explanation of symbols

V1, V Power supply 1 Conventional carbon removal device 10 Solid electrolyte membrane 20 Anode electrode 30 Cathode electrode 100 Carbon removal device according to the present invention 110 Proton conductive film 120 Anode electrode 130 Cathode electrode 200 Another carbon removal device according to the present invention 250 Tubular member 255 Sealing member 260 Inlet tube 270 Outlet tube 600 Measuring device 605 Sample 605A Anode electrode 605C Cathode electrode 610A Outer alumina tube 615A Inner alumina tube 610C Outer alumina tube 615C Inner alumina tube 630A Anode supply gas channel 635A Anode exhaust gas channel 630C Cathode Supply gas flow path 635C Cathode exhaust gas flow path.

Claims (14)

An anode electrode;
A cathode electrode;
A proton conductive film having proton conductivity disposed between the electrodes;
A carbon removing device having   The carbon removing apparatus according to claim 1, further comprising a separation member capable of separating an environment to which the anode electrode is exposed and an environment to which the cathode electrode is exposed.   The carbon removing apparatus according to claim 1, wherein the proton conductive film includes a perovskite type material or a metal phosphate. The perovskite type materials include BaCe _1-x Y _x O _3-α , SrCe _1-x Yb _x O _3-α , BaZr _1-x Y _x O _3-α , and SrZr _1-x Y _x O _3-α. The carbon removing apparatus according to claim 3, wherein X and α are 0 ≦ X ≦ 1 and 0 ≦ α ≦ 1, respectively, comprising at least one material selected from the group consisting of Range). The metal phosphate has at least one material selected from the group consisting of SnP ₂ O ₇ , SiP ₂ O ₇ , TiP ₂ O ₇ and ZrP ₂ O ₇ doped with In ³⁺ or Al ^3+. The carbon removing apparatus according to claim 3.   The anode electrode is selected from the group consisting of platinum (Pt), gold (Au), palladium (Pd), copper (Cu), silver (Ag), nickel (Ni), iron (Fe), carbon, and alloys thereof. The carbon removing apparatus according to claim 1, comprising at least one material.   6. The carbon removing apparatus according to claim 1, wherein the anode electrode is made of carbon deposited on the anode electrode during use of the carbon removing apparatus.   The cathode electrode is selected from the group consisting of platinum (Pt), gold (Au), palladium (Pd), copper (Cu), silver (Ag), nickel (Ni), iron (Fe), carbon, and alloys thereof. The carbon removing apparatus according to claim 1, comprising at least one material.   The carbon removing apparatus according to claim 1, wherein the proton conductive film has a thickness in a range of 0.1 mm to 10 mm. A method of removing carbon,
(A) preparing a carbon removal device having an anode electrode, a cathode electrode, and a proton conductive film having proton conductivity installed between the two electrodes;
(B) attaching carbon to the anode electrode of the carbon removal device;
(C) applying a current or voltage to the carbon removal device via the both electrodes while the anode electrode is exposed to an environment containing water vapor;
(D) the carbon adhering to the anode electrode is oxidized by the water vapor;
A method for removing carbon having a surface.   The method for removing carbon according to claim 10, wherein the steps (c) and (d) are performed in a temperature range of room temperature to 500 ° C.   The method for removing carbon according to claim 10 or 11, wherein the environment containing water vapor in step (c) has a water vapor partial pressure of 0.01 vol% to 90 vol%.   The carbon removal apparatus further includes a separation member capable of separating an environment to which the anode electrode is exposed and an environment to which the cathode electrode is exposed. The method of removing carbon as described in any one.   The method for removing carbon according to claim 10, wherein the anode electrode of the carbon removing device is formed by the step (b).

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