JP2014066243A - Electro-catalytic honeycomb for exhaust emission control - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electro-catalytic honeycomb for exhaust emission control.SOLUTION: The electro-catalytic honeycomb for exhaust emission control is used for controlling oxygen-rich combustion emission, and includes a honeycomb structure, solid oxide layer and cathode layer. The honeycomb structure includes an anode, a plurality of gas channels and a shell. The anode forms a backbone of the honeycomb structure. The gas channel is formed in the backbone and causes the oxygen-rich combustion emission to pass. The shell covers one outer surface of the anode. The solid oxide layer adheres to one inner surface of the anode and is connected to the shell to encapsulate the anode. The shell has a tube wall facing the gas channel. The cathode layer adheres to the tube wall, the anode has reduction atmosphere and the cathode layer has oxidation atmosphere. With this arrangement, the reduction atmosphere and the oxidation atmosphere generate electromotive force between the anode layer and the cathode layer, nitrogen oxide in the oxygen-rich combustion emission is decomposed with the anode layer.

Description

  The present invention relates to a kind of electrocatalyst honeycomb, and more particularly to a kind of electrocatalyst honeycomb which controls exhaust gas emission and effectively decomposes nitrogen oxides and oxidizes carbon monoxide, carbon hydrogen compounds and particulate matter. .

  Clean air is one of the basic requirements of human life. Breathing clean and uncontaminated air ensures that mankind is stable and healthy. Although the economy has developed rapidly due to the outstanding advancement of science and technology, exhaust emissions from transportation tools and various forested factories cause air pollution and the impact on the air quality of human life is enormous. Among them, heavy industry factories and automobiles are the main sources of many pollutants.

  In the case of automobiles, although the emission standards for automobiles are constantly being raised, the number of vehicles is constantly increasing, so the problem of air pollution caused by exhaust gas emitted from vehicles is still increasing day by day. In general, the operation of an automobile engine burns different types of fuel in a cylinder to release heat energy and transmit power. However, exhaust gas generated during the combustion process includes harmful pollutants such as nitrogen oxides (NOx), carbon monoxide (CO), carbon hydrogen compounds (hydrocarbons, HCs), and particulate matter (particulate matter, PM). However, these substances not only form photochemical smog, but also destroy the ozone layer, worsen the greenhouse effect, cause acid rain, and thus destroy the ecological environment, thereby damaging human health.

  Among them, carbon monoxide is generated by incomplete combustion of the engine, and the ability to combine with its hemoglobin to form carbon monoxide hemoglobin (COHb) is the ability for oxygen to combine with hemoglobin to form oxidized hemoglobin (HbO2). Therefore, when the concentration of carbon monoxide in the air is too high, the oxygen transport function of hemoglobin is affected. Nitrogen oxide is formed by the combination of nitrogen gas and oxygen gas, and is emitted mainly in the form of nitrogen monoxide (NO) or nitrogen dioxide (NO2). It reacts with carbon hydrogen compounds by UV irradiation and is a toxic photochemical smog. , Has a special odor, irritate eyes, damage plants, and reduce atmospheric transparency, and nitrogen oxides react with water in the air to form nitric acid and nitrous acid, which is acidic It is a component of rain. Carbon hydrogen compounds stimulate the respiratory system at low concentrations, and higher concentrations affect the function of the central nervous system. Particulate matter can also be harmful to human health, which in turn causes cancer.

  As a result, Taiwan, Europe, Japan, the United States, and other advanced countries all have strict exhaust gas standards (for example, US standard BIN5 and European standard EURO6), nitrogen oxides, carbon monoxide, and hydrocarbon compounds. Standards are set for the emission of exhaust gases such as particulate matter, etc., thereby controlling and reducing the emission of harmful gases, and contractors promote the manufacture, research and development, and use of the latest pollution control technology products. Is encouraged.

  For example, Patent Document 1 describes an apparatus for removing a kind of nitrogen oxide alone, which uses an electrochemical catalytic reduction reaction, and converts nitrogen oxide to nitrogen with a vanadium pentoxide (V2O5) catalyst. Assists the reaction with gas. However, the above-mentioned device has to supply extra power and operate the electrochemical cell in this device, so that the target is to consume energy and remove many kinds of harmful hazards in the exhaust gas at the same time Cannot be achieved.

  Therefore, Patent Document 2 discloses a kind of electrocatalyst tube that controls exhaust gas emission, and the electrocatalyst tube is stacked to form a honeycomb-like structure to form an advanced honeycomb electrochemical catalyst converter. It can be used to purify nitrogen oxides, carbon monoxide, carbon hydrogen compounds and particulate matter in exhaust gas. Of these, the nitrogen oxides are decomposed into nitrogen gas and oxygen gas, and the carbon monoxide, carbon compound and particulate matter are oxidized into carbon dioxide and water. Thereby, the electrocatalyst tube can purify many kinds of pollutants without consuming excess energy and reducing gas.

  However, the above-mentioned honeycomb electrochemical catalyst converter requires that half of the channels be sealed in order to form the electrocatalyst tube. Not only does the area decrease, but the manufacturing costs increase, so there is still room for improvement.

US Patent Publication No. 5401372 US Patent Application No. 13362247

  The main object of the present invention is to solve the problem that the known honeycomb electrochemical catalytic converter has a relatively small reaction area and a relatively high production cost.

  To achieve the above objective, the present invention provides an electrocatalytic honeycomb for controlling exhaust gas emissions, which includes a honeycomb structure, a solid oxide layer and a cathode layer. The honeycomb structure includes an anode, a plurality of air flow channels and a casing, the anode forming a skeleton of the honeycomb structure, formed of a first porous material, and having a reducing environment, the air flow channel Is formed in the skeleton to circulate the oxygen-rich combustion exhaust gas, and the casing covers one outer surface of the anode and has a first dense microstructure. The solid oxide layer adheres to the inner surface of the anode opposite the outer surface, has a second dense microstructure, and includes a tube wall facing the air flow channel, and the solid oxide layer comprises the Joined to the casing to seal the anode. The cathode layer is deposited on the tube wall, the solid oxide layer is located between the anode and the cathode layer, the cathode layer is formed of a second porous material and has an oxidizing environment.

  Among these, the reducing environment and the oxidizing environment generate an electromotive force between the anode and the cathode layer, promote the decomposition reaction of nitrogen oxides in the oxygen-rich combustion exhaust gas at the cathode layer, Gas and oxygen gas are generated.

Overall, in the present invention, all the air flow channels of the electrocatalyst honeycomb are used for the reaction of the oxygen-rich combustion exhaust gas, and the electrocatalyst honeycomb is manufactured more than the known honeycomb type electrochemical catalyst converter. As a result, the present invention has the following advantages over the known honeycomb type electrochemical catalyst converter.
1. It has a relatively large reaction area.
2. It can be manufactured at a relatively low cost.

1 is an external perspective view of a first embodiment of the present invention. It is sectional drawing of 1st Example of this invention. It is a cross-sectional local enlarged view of 1st Example of this invention. It is a section local enlarged view of the 2nd example of the present invention. It is a front view of 3rd Example of this invention.

  The technical contents, structural features, objects to be achieved, and operational effects of the present invention will be described in detail below with reference to examples and drawings.

  Please refer to FIG. 1 to FIG. FIG. 1 is an external perspective view of a first embodiment of the present invention. FIG. 2 is a cross-sectional view of the first embodiment of the present invention. FIG. 3 is a partially enlarged cross-sectional view of the first embodiment of the present invention. The present invention is an electrocatalyst honeycomb for controlling exhaust gas emission, which is used to purify oxygen-rich combustion exhaust gas, and the oxygen-rich combustion exhaust gas contains nitrogen oxide (NOx), carbon monoxide (CO), carbon Hydrogen compounds (HCs) and particulate matter (PM) may be included.

  The electrocatalyst honeycomb includes a honeycomb structure (10), a solid oxide layer (20), and a cathode layer (30). The honeycomb structure (10) includes an anode (11), a plurality of air flow channels (12), and a casing (13), and the anode (11) forms a skeleton of the honeycomb structure (10). In this embodiment, the anode (11) is made of a first porous material and has a large number of pores, and the material of the anode (11) is made of a metal and a fluorite-type structural metal oxide. (Cermet), fluorite-type metal oxides, perovskite-metal oxides, fluorite-type metal oxides added with metal or perovskite-type metal oxides added with metal, For example, nickel (Ni) and yttria-stabilized zirconia (YSZ) cermet (Ni-YSZ cermet).

  The air flow channel (12) is formed in the skeleton, penetrates through the corresponding both ends of the honeycomb structure (10), and is used for circulation of the oxygen-rich combustion exhaust gas.

  The casing (13) covers one outer surface (111) of the anode (11) and has a first dense microstructure, which is made of metal, ceramics or glass such as stainless steel, oxidized Aluminum and quartz glass.

  The solid oxide layer (20) adheres to the inner surface (112) of the anode (11) opposite the outer surface (111), and correspondingly on the casing (13) and the anode (11). A tube joined at two ends, completely sealing the anode (11), creating a reducing environment in the anode (11), the solid oxide layer (20) as well as a tube facing the air flow channel (12) The solid oxide layer (20) has a wall (21), and the structure of the solid oxide layer (20) is a second dense microstructure, and has oxygen ion conductivity, and the material is a fluorite structure metal oxide or perovskite. Type metal oxide. For example, fluorite-type structural metal oxides include yttria-stabilized zirconia (YSZ), stabilized zirconia, gadolinia-doped cerium oxide (gadolinia-doped ceria, GDC), doped cerium oxide, Perovskite-type strontium and magnesium-doped lanthanum gallate (LSGM) and doped lanthanum gallate.

  The cathode layer (30) is attached to the tube wall (21), and the solid oxide layer (20) is positioned between the anode (11) and the cathode layer (30). The cathode layer (30) is formed of the second porous material and has a large amount of pores, for example, a perovskite type metal oxide, a fluorite type structure metal oxide, and a perovskite type metal oxide added with a metal. Is a metal-added fluorite-type structure metal oxide, for example, perovskite-type lanthanum strontium cobalt copper oxide, lanthanum strontium manganese copper oxide, lanthanum strontium cobalt copper oxide and gadolinia-doped ceria, GDC ), A combination of lanthanum strontium manganese copper oxide and gadolinia-doped cerium oxide, Lanthanum strontium cobalt copper oxide with addition of silver, lanthanum strontium manganese copper oxide with addition of silver, combination of lanthanum strontium cobalt copper oxide with addition of silver and gadolinia-doped cerium oxide, lanthanum strontium manganese copper oxide with addition of silver and It is a combination of gadolinia-doped cerium oxide.

  In the present invention, the anode (11) includes a metal oxide during initial fabrication, and the metal oxide is first treated with a reducing gas and reduced to a metal when the anode (11) is manufactured. For example, nickel oxide is reduced to nickel. Alternatively, the metal oxide is reduced to an oxygen-deficient metal oxide to form the reducing environment of the anode (11).

  In addition, before the solid oxide layer (20) is joined to the casing (13) to completely seal the anode (11), carbon monoxide or a carbon hydrogen compound is first applied to the anode (11). For example, methane, ethane, propylene, propane or the like is introduced into the anode (11) by pore diffusion, and carbonaceous species attached to the pores of the anode (11) are added. Forming, thereby enhancing the formation of the reducing environment of the anode (11).

  In addition to this, before the anode (11) is completely sealed, the gas in the hole of the anode (11) is extracted, whereby the gas pressure is reduced to atmospheric pressure or less, Thereby, the damage of the structure which may be generated by the thermal expansion / cooling shrinkage in the exhaust gas treatment operation of the honeycomb structure (10) can be reduced.

  Please refer to FIG. It is a cross-sectional local enlarged view of the second embodiment of the present invention. In the second embodiment, compared with the first embodiment, the feature is that the electrocatalyst honeycomb further includes an interface layer (40), and the interface layer (40) includes the cathode layer (30) and the solid oxide. It is provided between the physical layers (20), thereby promoting the connection between the cathode layer (30) and the solid oxide layer (20). The material of the interface layer (40) can be a fluorite-type structure metal oxide or a perovskite-type metal oxide, such as gadolinia-doped cerium oxide with a fluorite structure.

  Further, in the second embodiment, the electrocatalyst honeycomb further includes an oxidation catalyst layer (50), which oxidizes components of the oxygen-rich combustion exhaust gas that are not easily oxidized by the cathode layer (30). The catalyst layer (50) is connected to the cathode layer (30) and adhered onto the cathode layer (30), and the material of the oxidation catalyst layer (50) is metal, alloy, metal oxide, fluorite type Structural metal oxides, perovskite-type metal oxides such as palladium, gadolinia-doped cerium oxide having a fluorite-type structure, and lanthanum-strontium-manganese oxide.

  Next, the process of exhaust gas purification according to the present invention will be described. First, the electrocatalyst honeycomb is placed in an exhaust gas environment. The exhaust gas is regarded as the oxygen-rich combustion exhaust gas and has an oxidizing environment, or secondary air is added to make it further oxygen-rich. The working temperature of the electrocatalyst honeycomb is from room temperature to 800 ° C., and the oxygen-rich combustion exhaust gas contains nitrogen oxide, carbon monoxide or carbon hydrogen compound and particulate matter as main components. The present invention proceeds to the purification reaction surface of the oxygen-rich combustion exhaust gas in two parts: removal of nitrogen oxides and removal of carbon monoxide or carbon hydrogen compounds and particulate matter.

  In terms of removing nitrogen oxides, nitrogen oxides are mainly made of nitric oxide (NO) and nitrogen dioxide (NO2), and nitrogen monoxide generates a decomposition reaction in the cathode layer (30) to generate nitrogen gas and oxygen gas. The reaction formula is represented by the following general formula (1).

  Nitrogen dioxide generates a decomposition reaction in the cathode layer (30) to generate nitric oxide, and the reaction formula is represented by the following general formula (2).

  The nitric oxide further undergoes a decomposition reaction in the cathode layer (30) to generate nitrogen gas and oxygen gas.

  Due to the reducing environment of the anode (11) and the oxidizing environment of the cathode layer (30), different partial pressures of oxygen are generated in the anode (11) and the cathode layer (30), thereby the cathode layer. An electromotive force (emf) is generated between the anode (11) and the anode (11), the decomposition reaction of the nitrogen oxide in the oxygen-rich combustion exhaust gas at the cathode layer (30) is promoted, and nitrogen gas Oxygen gas is formed and the electromotive force is generated according to the following principle.

そのうち、Ｒは気体定数であり、Ｔは絶対温度、Ｆはファラデー定数（Ｆａｒａｄｉｃ ｃｏｎｓｔａｎｔ）、ＰＯ２は酸素分圧とされる。該金属或いは該酸素欠乏の金属酸化物で形成される該陽極（１１）、或いは該炭素質種が付着した該陽極（１１）は、還元性化合物とされ、相当に低い酸素分圧の環境を陽極（Ａｎｏｄｅ）側にもたらし、これにより、比較的大きな起電力を発生する。異なる還元性化合物は陽極側で異なる酸素分圧をもたらし得て、異なる起電力を発生し得る。陰極（Ｃａｔｈｏｄｅ）側の異なる酸素濃度も異なる酸素分圧値に対応し、異なる起電力を発生し得て、すなわち、陰極側の該富酸素燃焼排ガス中の酸素含有量が高くなるほど、起電力は大きくなり、起電力が大きいほど、本発明の窒素酸化物は電気化学促進（ｅｌｅｃｔｒｏｃｈｅｍｉｃａｌ ｐｒｏｍｏｔｉｏｎ）分解の反応速度が速くなる。これにより、該富酸素燃焼排ガスは酸化性環境で起電力を発生できるが、該二次空気を添加して該富酸素燃焼排ガスに進入させることで、さらに大きな起電力をもたらし得る。一定温度範囲内で、分解反応速度は作業温度が低くなるほど大きくなり、常温の分解反応は比較的高い温度のときと同様に有効である。

Among them, R is a gas constant, T is an absolute temperature, F is a Faraday constant, and PO2 is an oxygen partial pressure. The anode (11) formed of the metal or the oxygen-deficient metal oxide, or the anode (11) to which the carbonaceous species is attached, is a reducing compound, and has a considerably low oxygen partial pressure environment. This is provided on the anode side, thereby generating a relatively large electromotive force. Different reducible compounds can result in different oxygen partial pressures on the anode side and generate different electromotive forces. Different oxygen concentrations on the cathode side also correspond to different oxygen partial pressure values and can generate different electromotive forces, that is, the higher the oxygen content in the oxygen-rich combustion exhaust gas on the cathode side, the more the electromotive force The larger the electromotive force, the higher the reaction rate of the electrochemical promotion decomposition of the nitrogen oxide of the present invention. Thereby, although the oxygen-rich combustion exhaust gas can generate an electromotive force in an oxidizing environment, adding the secondary air to enter the oxygen-rich combustion exhaust gas can bring about a larger electromotive force. Within a certain temperature range, the decomposition reaction rate increases as the working temperature decreases, and the decomposition reaction at normal temperature is as effective as at a relatively high temperature.

  In the reaction direction in which carbon monoxide, carbon hydrogen compounds and particulate matter are removed from the oxygen-rich combustion exhaust gas, the oxygen-rich combustion exhaust gas is in an oxygen-rich state, or secondary air is added to the reaction. Because it is oxygen-rich, harmless gas is formed by oxidation of the cathode layer (30) and the oxidation catalyst layer (50), and carbon monoxide in the oxygen-rich combustion exhaust gas is oxidized. Carbon dioxide, carbon hydrogen compound and particulate matter (substance containing C) are oxidized to carbon dioxide and water, and their reaction formulas are as shown in the following general formulas (4) to (6). is there.

  Thereby, for the first embodiment of the present invention, nitrogen oxide is mainly removed by electrochemically promoted decomposition reaction, and carbon monoxide, carbon hydrogen compound and particulate matter are removed by oxidation reaction, Effectively remove harmful components in the oxygen-rich combustion exhaust gas.

  Please refer to FIG. It is a front view of the third embodiment of the present invention. In this embodiment, the cross-sectional appearance of the honeycomb structure (10) forms a hexagon, and the cross-sectional appearance of the air flow channel (12) forms a circle, but is not limited thereto. The cross-sectional shape of the honeycomb structure (10) and the air flow channel (12) can vary depending on the need and type of use.

  In summary, the present invention forms different oxygen partial pressures between the anode side and the cathode side, generates the electromotive force and promotes the catalytic decomposition reaction, and has a simple structure as well as production. Further, the present invention can achieve a purification effect with a minimum volume. For example, it is installed in a vehicle engine exhaust pipe and removes harmful substances in the oxygen-rich combustion exhaust gas discharged from the engine. Can be reduced. Finally, when compared to the well-known honeycomb electrochemical catalytic converter, the present invention uses all the air flow channels for the progress of the reaction with the oxygen-rich flue gas, has a relatively large reaction area, and Has a relatively good reaction efficiency. As a result, the present invention has an inventive step, meets the requirements of the patent, and it is up to the patent application here.

  The foregoing is only a description of the preferred embodiment of the present invention, and is not intended to limit the present invention. Other equivalent effect modifications or substitutions that may be accomplished without departing from the spirit of the present invention are not Are also within the scope of the claims of the present invention.

(10) honeycomb structure (11) anode (111) outer surface (112) inner surface (12) air flow channel (13) casing (20) solid oxide layer (21) tube wall (30) cathode layer (40) interface Layer (50) oxidation catalyst layer

Claims (10)

In the electrocatalyst honeycomb that controls the exhaust gas emission used to purify the oxygen-rich combustion exhaust gas,
A honeycomb structure (10), a skeleton anode (11) forming the honeycomb structure (10), a plurality of air flow channels (12) formed in the skeleton and circulating the oxygen-rich combustion exhaust gas, And a casing (13) covering one outer surface (111) of the anode (11), the anode (11) being composed of a first porous material and having a reducing environment, The casing (13) has the first dense microstructure, the honeycomb structure (10),
A solid oxide layer (20) attached to an inner surface (112) opposite to the outer surface (111) of the anode (11), the solid oxide layer (20) having a second dense microstructure; The solid oxide comprising a tube wall (21) facing the air flow channel (12), and the solid oxide layer (20) being joined to the casing (13) to seal the anode (11) Layer (20);
A cathode layer (30) attached to the tube wall (21), wherein the solid oxide layer (20) is located between the anode (11) and the cathode layer (30), and the cathode layer (30 ) Is composed of the second porous material and has an oxidizing environment, the cathode layer (30),
Wherein the reducing environment and the oxidizing environment generate an electromotive force between the anode (11) and the cathode layer (30), and the cathode layer of nitrogen oxides in the oxygen-rich combustion exhaust gas. An electrocatalyst honeycomb for controlling exhaust gas emission, wherein the decomposition reaction in (30) is promoted to generate nitrogen gas and oxygen gas.   The electrocatalyst honeycomb for controlling exhaust gas emission according to claim 1, wherein the anode (11) includes a plurality of holes for adhering carbonaceous species.   The electrocatalyst honeycomb for controlling exhaust gas emission according to claim 1, wherein the material of the anode (11) is a cermet, a perovskite type metal oxide, a fluorite type structural metal composed of a metal and a fluorite type structural metal oxide. An electrocatalyst honeycomb for controlling exhaust gas emission, which is freely selected from the group consisting of oxides, perovskite-type metal oxides added with metals, fluorite-structured metal oxides added with metals, and combinations thereof.   The electrocatalyst honeycomb for controlling exhaust gas emission according to claim 1, wherein the material of the casing (13) is freely selected from the group consisting of metal, ceramic, glass and a combination thereof. Electrocatalytic honeycomb to be controlled.   The electrocatalyst honeycomb for controlling exhaust gas emission according to claim 1, wherein the material of the solid oxide layer (20) is freely selected from the group consisting of a fluorite-type structure metal oxide, a perovskite-type metal oxide, and a combination thereof. An electrocatalyst honeycomb that controls exhaust gas emission.   The electrocatalyst honeycomb for controlling exhaust gas emission according to claim 1, wherein the material of the cathode layer (30) is a perovskite type metal oxide, a fluorite type structure metal oxide, a perovskite type metal oxide added with a metal, a metal An electrocatalyst honeycomb for controlling exhaust gas emission, which is freely selected from the group consisting of a fluorite-type structural metal oxide to which is added and a combination thereof.   The electrocatalyst honeycomb for controlling exhaust gas emission according to claim 1, wherein the cathode layer (30) and the solid oxide layer (20) are disposed between the cathode layer (30) and the solid oxide layer (20). An electrocatalyst honeycomb for controlling exhaust gas emission, further comprising an interface layer (40) that promotes connection of   The electrocatalyst honeycomb for controlling exhaust gas emission according to claim 7, wherein a material of the interface layer (40) is freely selected from the group consisting of a fluorite type structure metal oxide, a perovskite type metal oxide, and a combination thereof. An electrocatalyst honeycomb that controls exhaust gas emission.   The electrocatalyst honeycomb for controlling exhaust gas emission according to claim 1, further comprising an oxidation catalyst layer (50) attached on the cathode layer (30).   The electrocatalyst honeycomb for controlling exhaust gas emission according to claim 9, wherein the material of the oxidation catalyst layer (50) is selected from the group consisting of metals, alloys, fluorite-type structural metal oxides, perovskite-type metal oxides, and combinations thereof. An electrocatalyst honeycomb for controlling exhaust gas emission, which is freely selected.

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