TWI474859B - An electro-catalytic honeycomb for controlling exhaust emissions - Google Patents

Description

Electrocatalyst honeycomb for controlling exhaust emissions

The invention relates to an electric catalyst honeycomb, in particular to an electric catalyst honeycomb which controls exhaust gas emission and effectively decomposes nitrogen oxides and oxidizes carbon monoxide, hydrocarbons and particles.

Fresh and clean air is one of the basic elements of human life. Breathing clean and pollution-free air ensures that human beings can survive in a stable and healthy manner. Although the technological excellence has promoted the rapid development of the economy, the emissions from vehicles and various forestry factories have also caused air pollution, which has a great impact on the air quality of human life. Among them, heavy factories and motor vehicles are the main sources of many pollutants.

Taking motor vehicles as an example, although the emission standards for motor vehicles continue to increase, the number of vehicles is increasing, and the problem of air pollution caused by vehicle emissions is still increasing. Generally speaking, the operation of a motor vehicle engine is to release different types of fuel through the internal combustion of the cylinder to release heat energy and generate transmission power; however, in the combustion process, the generated exhaust gas usually contains nitrogen oxides (NO _x ) and carbon monoxide (CO). ), hydrocarbons (HCs), particulate matter (PM) and other harmful pollutants, which not only form photochemical smog, but also destroy ozone and aggravate the deterioration of the greenhouse effect. It causes acid rain, etc., which destroys the ecological environment and endangers human health.

Among them, carbon monoxide comes from incomplete combustion of the engine, and its ability to combine with heme to form carbon monoxide hemoglobin (COHb) is 300 times that of heme and oxygen combined with oxygenated heme (HbO ₂ ), so the concentration of carbon monoxide in the air is too high. When it will affect the function of heme transporting oxygen; nitrogen oxides come from the combination of nitrogen and oxygen, mainly in the form of nitric oxide (NO) or nitrogen dioxide (NO ₂ ), and with hydrocarbons irradiated by ultraviolet light The reaction then forms toxic photochemical smog, has a special odor, irritates the eyes, damages plants, and reduces atmospheric visibility, and nitrogen oxides react with water in the air to form nitric acid and nitrous acid, which are components of acid rain; hydrocarbon Compounds can irritate the respiratory system at low concentrations. If the concentration is increased, it will affect the functioning of the central nervous system. Granules can also harm the health of the human body and even cause cancer.

Therefore, regardless of China or the EU, Japan, the United States and other advanced countries, we have set stricter emission standards (such as US BIN5 and Euro 6) for nitrogen oxides, carbon monoxide, hydrocarbons and pellets. Emissions such as emissions are set to control and reduce harmful emissions, while encouraging manufacturers to manufacture, develop, and introduce products that use the latest pollution prevention technologies.

"Electrochemical catalytic reduction cell for the reduction of NO _x in an O _{2 -} containing exhaust emission", as disclosed in U.S. Patent Publication No. 5,401,372, discloses a device for removing nitrogen oxides alone, in order to utilize an electrochemical catalyst reduction reaction, in combination with five Vanadium pentaoxide (V ₂ O ₅ ) catalyst catalyzes the conversion of nitrogen oxides to nitrogen. However, the device described above requires an additional power supply to cause an electrochemical cell in the device to operate, which is not only energy consuming but also unable to achieve the goal of simultaneously removing various harmful gases in the exhaust gas.

The "Electrocatalytic Tube of Electrochemical-Catalytic Converter for Exhaust Emissions Control" of the U.S. Patent Application No. 13362247 discloses an electrocatalyst tube for controlling exhaust gas emissions, which can be stacked into a honeycomb structure to form a An advanced honeycomb electrochemical converter can be used to purify nitrogen oxides, carbon monoxide, hydrocarbons and particulates in the exhaust gas, wherein the nitrogen oxides are decomposed into nitrogen and oxygen, the carbon monoxide, the hydrocarbon The compound and the granule are oxidized to carbon dioxide and water. Therefore, the electric catalyst tube can purify various pollutants without using extra energy and reducing gas.

However, in the honeycomb electrochemical converter described above, half of the channels must be sealed to form the dielectric catalyst tube, thus reducing the reaction area and manufacturing more than the honeycomb catalytic converter of the existing vehicle. Cost, therefore, there is still room for improvement.

The main object of the present invention is to solve the problem of a conventional honeycomb electrochemical converter having a small reaction area and a high manufacturing cost.

To achieve the above object, the present invention provides an electric catalyst honeycomb for controlling exhaust gas emissions for purifying an oxy-combustion combustion exhaust gas, the electric catalyst honeycomb comprising a honeycomb structure, a solid oxide layer and a cathode layer. The honeycomb structure comprises an anode and a plurality of gas flow channels, the anode forming a skeleton of the honeycomb structure, consisting of a first porous material and having a reducing environment, wherein the gas flow channel is formed in the skeleton Providing the oxy-combustion exhaust gas to circulate; the solid oxide layer coating a surface of the anode and having a uniform dense structure and having a tube wall facing the gas flow passage; the cathode layer is attached to the tube wall The solid oxide layer is located between the anode and the cathode layer, and the cathode layer is composed of a second porous material, which is used to purify the oxy-combusted combustion exhaust gas to have an oxidizing environment.

Wherein, the reducing environment and the oxidizing environment generate an electromotive force between the anode and the cathode layer to drive nitrogen oxides in the oxyfuel combustion exhaust gas to undergo a decomposition reaction in the cathode layer to form nitrogen gas and oxygen gas.

In summary, in the present invention, all of the gas flow passages of the electric catalyst honeycomb are used for reacting with the oxy-combustion exhaust gas, and the electric catalyst honeycomb is compared with the conventional honeycomb electrochemical touch. The media converter is easier to manufacture, and accordingly, the present invention has a larger reaction area and a lower manufacturing cost than conventional honeycomb electrochemical converters.

The detailed description and technical content of the present invention will now be described as follows:

1 is a schematic perspective view of the first embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view of the first embodiment of the present invention, and FIG. 3 is a schematic view of the first embodiment of the present invention. A partially enlarged schematic cross-sectional view of a first embodiment of the present invention, the present invention is an electric catalyst honeycomb for controlling exhaust gas emissions for purifying an oxy-combustion combustion exhaust gas, which may include nitrogen oxides (NO _x ), Carbon monoxide (CO), hydrocarbons (HCs), and particulate matter (PM), the electrocatalyst honeycomb comprises a honeycomb structure 10, a solid oxide layer 20, and a cathode layer 30. The honeycomb structure 10 includes an anode 11 and a plurality of gas flow channels 12, and the anode 11 forms a skeleton of the honeycomb structure 10. In this embodiment, the anode 11 is composed of a first porous material and has A large number of holes, the material of the anode 11 may be metal and fluorite structure metal oxides of ceramsite, fluorite metal oxides, perovskite metal oxides, plus a metal fluorite structure metal oxide or a metal-added perovskite structure metal oxide such as nickel (Ni) and yttria-stabilized zirconia (YSZ) pottery (Ni-YSZ cermet); The air flow passage 12 is formed in the frame and penetrates opposite ends of the honeycomb structure 10 for circulating the oxygen-enriched combustion exhaust gas.

The solid oxide layer 20 covers a surface of the anode 11 to completely seal the anode 11 so that the anode 11 can be a reducing environment. The solid oxide layer 20 has a side of the gas flow channel 12 The wall 21, and the solid oxide layer 20 has a uniform dense structure and may have oxygen ion conductivity, and the material thereof may be a fluorite structure metal oxide or a perovskite structure metal oxide; for example, fluorite Structure of yttria-stabilized zirconia, stabilized zirconia, fluorite-structured yttrium-doped ceria (GDC), doped yttria, perovskite-structured yttrium and magnesium-doped gallic acid Stro (strontium/magnesium-doped lanthanum gallate, LSGM), doped with barium gallate.

The cathode layer 30 is attached to the tube wall 21 such that the solid oxide layer 20 is located between the anode 11 and the cathode layer 30. In this embodiment, the cathode layer 30 is composed of a second porous material. , and has a large number of pores, such as a perovskite structure metal oxide, a fluorite structure metal oxide, a metal-added perovskite structure metal oxide or a metal-added fluorite structure metal oxide, for example: calcium titanium a combination of samarium cobalt copper oxide, lanthanum manganese copper oxide, samarium cobalt copper oxide and yttrium oxide doped yttrium oxide, a combination of lanthanum manganese copper oxide and yttrium oxide doped yttrium oxide Silver samarium cobalt copper oxide, silver-added lanthanum manganese copper oxide, silver-added samarium cobalt copper oxide and yttria-doped yttrium oxide combination, silver-added lanthanum manganese copper oxide and cerium oxide A combination of doped cerium oxide.

In the present invention, the anode 11 comprises a metal oxide during preliminary preparation, and the metal oxide is reduced to a metal by a treatment using a reducing gas when the anode 11 is formed, for example, by nickel oxide. Reduction to nickel; or, the metal oxide may be reduced to an oxygen-deficient metal oxide to form the reducing environment of the anode 11. In addition, carbon monoxide or hydrocarbon may be added to the anode 11 before the anode 11 is completely sealed, for example, the anode 11 is allowed to pass through a pore diffusion, such as methane, ethane, propylene or propane. A carbon species attached to the pores of the anode 11 is formed to enhance the reducing environment in which the anode 11 is formed. In addition, before completely sealing the anode 11, the gas in the hole of the anode 11 can be extracted to lower the gas pressure to below atmospheric pressure or to a vacuum, thereby reducing the honeycomb structure 10 in the exhaust gas treatment. Structural damage that may occur due to thermal expansion and contraction.

Please refer to FIG. 4 for a partial enlarged view of a cross section according to a second embodiment of the present invention. In the second embodiment, compared with the first embodiment, the photocatalyst honeycomb may further include An interface layer 40 is disposed between the cathode layer 30 and the solid oxide layer 20 to facilitate connection between the cathode layer 30 and the solid oxide layer 20, wherein the interface layer 40 is made of a material It is a fluorite structure metal oxide, or a perovskite structure metal oxide, such as yttrium oxide doped yttrium oxide having a fluorite structure.

Furthermore, in the second embodiment, the electrocatalyst honeycomb may further comprise an oxidation catalyst layer 50 for promoting oxidation of a component of the oxy-combustion combustion exhaust gas which is not easily oxidized by the cathode layer 30, the oxidation catalyst The layer 50 is connected to the cathode layer 30 and adhered to the cathode layer 30. The material of the oxidation catalyst layer 50 may be metal, alloy, metal oxide, fluorite structure metal oxide, perovskite structure metal oxide. For example, palladium, fluorite-structured cerium oxide-doped cerium oxide, and lanthanum-strontium-manganese oxide.

The process of purifying the exhaust gas of the present invention will be described. First, the electric catalyst honeycomb is placed in an exhaust gas environment, and the exhaust gas has an oxidizing environment for the oxygen-enriched combustion exhaust gas, or may be added to the secondary air to make it richer. Oxygen, the working temperature of the electric catalyst honeycomb is from normal temperature to 800 ° C, and the oxy-combustion exhaust gas mainly comprises nitrogen oxides, carbon monoxide, hydrocarbons and granular components, and the invention purifies the oxyfuel combustion exhaust gas In terms of reaction, it can be mainly divided into two parts: removal of nitrogen oxides and removal of carbon monoxide, hydrocarbons, and granules.

In terms of nitrogen oxide removal, nitrogen oxides are mainly nitrogen monoxide (NO) and nitrogen dioxide (NO ₂ ). Nitric oxide can be decomposed in the cathode layer 30 to generate nitrogen and oxygen. The reaction formula is as follows. (1).

2NO → N ₂ + O ₂ (1)

Nitrogen dioxide can be decomposed in the cathode layer 30 to produce nitric oxide, and the reaction formula is the following formula (2).

2NO ₂ → 2NO + O ₂ (2)

Nitric oxide can be decomposed in the cathode layer 30 to generate nitrogen and oxygen.

By the reducing environment of the anode 11 and the oxidizing environment of the cathode layer 30 generating different oxygen partial pressures between the anode 11 and the cathode layer 30, an electromotive force between the cathode layer 30 and the anode 11 can be promoted. (electromotive force, emf), and driving promotes decomposition of nitrogen oxides in the oxy-combustion exhaust gas to the cathode layer 30 to form nitrogen and oxygen, and the electromotive force is generated according to the following principle:

Emf=[(RT)/(4F)]‧ln[(P _O2|Cathode )/(P _O2|Anode )] (3)

Where R is the gas constant, T is the absolute temperature, F is the Faradic constant, and P _O2 is the oxygen partial pressure. The anode 11 formed by the metal or the oxygen-deficient metal oxide, or the anode 11 to which the carbon species is attached, which is a reducing compound, will result in a relatively low oxygen partial pressure. The environment is on the anode side, thus creating a large electromotive force. Different reducing gases and different reducing compounds will cause different partial pressures of oxygen on the anode side, and different electromotive forces will be generated; different oxygen concentrations on the cathode side will also correspond to different oxygen partial pressure values. Different electromotive forces are generated, that is, the higher the oxygen content in the oxy-combustion exhaust gas on the cathode side, the larger the electromotive force, and the larger the electromotive force, the higher the reaction rate of the nitrogen oxide of the present invention by electrochemical promotion decomposition. According to this, although the oxy-combustion exhaust gas can generate an electromotive force in an oxidizing environment, adding the secondary air to the oxy-combustion combustion exhaust gas can cause a larger electromotive force. In a certain temperature range, the decomposition reaction rate will be larger as the working temperature is lower, and the decomposition reaction at normal temperature can be as effective as at higher temperatures.

In the reaction for removing carbon monoxide, hydrocarbons and granules in the oxy-combustion exhaust gas, the oxy-combusted combustion exhaust gas is in an oxygen-rich state, or secondary air is added to make it more oxygen-rich, and the cathode layer 30 can be used. And oxidizing the oxidation catalyst layer 50 to form a harmless gas, wherein the carbon monoxide in the oxy-combustion exhaust gas can be oxidized to carbon dioxide, and the hydrocarbons and granules (carbon-containing (C) substances) can be oxidized to carbon dioxide and water. The reaction formulas are as follows (4) to (6):

2CO + O ₂ → 2CO ₂ (4)

HCs + O ₂ → H ₂ O + CO ₂ (5)

C + O ₂ → CO ₂ (6)

Therefore, in the first embodiment of the present invention, the removal of nitrogen oxides is mainly performed by electrochemically promoting the decomposition reaction, and the carbon monoxide, hydrocarbons and particulate matter are removed by an oxidation reaction, thereby effectively removing the oxyfuel combustion. Harmful components in the exhaust gas.

Referring to FIG. 5, a front view of a third embodiment of the present invention. In this embodiment, the cross-sectional appearance of the honeycomb structure 10 is hexagonal, and the cross-sectional appearance of the airflow passage 12 is shown. The circular shape is formed, but is not limited thereto. The shape of the cross-sectional surface of the honeycomb structure 10 and the air flow passage 12 may vary depending on the needs and forms of use.

In summary, since the present invention generates the electromotive force by forming different oxygen partial pressures between the anode side and the cathode side, respectively, to promote the catalyst decomposition reaction, not only the structure is simplified, but the production cost is reduced. The invention can achieve the purifying effect by using a minimum volume, for example, disposed in the exhaust pipe of the vehicle engine, eliminating harmful substances in the oxyfuel combustion exhaust gas discharged by the engine, reducing air pollution, and finally, the present invention and the known honeycomb Compared with the electrochemical converter, all of the gas flow channels are used for reacting with the oxy-combustion exhaust gas, and have a large reaction area and better reaction efficiency, so the invention is highly advanced and conforms to the application. The essentials of the invention patent, the application of the law in accordance with the law, the prayer bureau to grant the patent as soon as possible, the real sense of virtue.

The present invention has been described in detail above, but the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the scope of the invention. That is, the equivalent changes and modifications made by the scope of the present application should remain within the scope of the patent of the present invention.

10. . . Honeycomb structure

11. . . anode

12. . . Air flow channel

20. . . Solid oxide layer

twenty one. . . Wall

30. . . Cathode layer

40. . . Interface layer

50. . . Oxidation catalyst layer

FIG. 1 is a perspective view showing the appearance of a first embodiment of the present invention.

Figure 2 is a cross-sectional view showing the first embodiment of the present invention.

Fig. 3 is a partially enlarged schematic cross-sectional view showing the first embodiment of the present invention.

Fig. 4 is a partially enlarged schematic cross-sectional view showing a second embodiment of the present invention.

Figure 5 is a front elevational view showing a third embodiment of the present invention.

10. . . Honeycomb structure

11. . . anode

12. . . Air flow channel

20. . . Solid oxide layer

30. . . Cathode layer

Claims (9)

An electric catalyst honeycomb for controlling exhaust gas emissions for purifying an oxyfuel combustion exhaust gas, the electric catalyst honeycomb comprising:
a honeycomb structure comprising an anode forming a skeleton of the honeycomb structure and a plurality of gas flow channels formed in the skeleton for circulating the oxygen-enriched combustion exhaust gas, the anode being composed of a first porous material, and Have a reducing environment;
a solid oxide layer covering a surface of the anode, the solid oxide layer having a uniform dense structure and having a tube wall facing the gas flow passage; and a cathode layer attached to the tube wall, a solid oxide layer is disposed between the anode and the cathode layer, the cathode layer is composed of a second porous material and has an oxidizing environment;
Wherein, the reducing environment and the oxidizing environment generate an electromotive force between the anode and the cathode layer to drive nitrogen oxides in the oxyfuel combustion exhaust gas to undergo a decomposition reaction in the cathode layer to form nitrogen gas and oxygen gas. The electrocatalyst honeycomb for controlling exhaust gas emissions according to claim 1, wherein the anode has a plurality of holes attached to a carbon species. The electrocatalyst honeycomb for controlling exhaust gas emissions according to claim 1, wherein the material of the anode is selected from the group consisting of metal and fluorite structure metal oxides, gold oxide, perovskite structure metal oxide, fluorite structure. A group of metal oxides, metal-added perovskite structure metal oxides, metal-added fluorite structure metal oxides, and combinations thereof. The electrocatalyst honeycomb for controlling exhaust gas emissions according to claim 1, wherein the material of the solid oxide layer is selected from the group consisting of fluorite structure metal oxides, perovskite structure metal oxides, and combinations thereof. group. The electrocatalyst honeycomb for controlling exhaust gas emissions according to claim 1, wherein the material of the cathode layer is selected from the group consisting of a perovskite structure metal oxide, a fluorite structure metal oxide, and a metal-added perovskite structure metal. A group of oxides, metal-added fluorite structure metal oxides, and combinations thereof. The electrocatalyst honeycomb for controlling exhaust gas emissions according to claim 1, further comprising an interface disposed between the cathode layer and the solid oxide layer to promote connection between the cathode layer and the solid oxide layer. Floor. The electrocatalyst honeycomb for controlling exhaust gas emissions according to claim 6, wherein the material of the interface layer is selected from the group consisting of fluorite structure metal oxides, perovskite structure metal oxides, and combinations thereof. The electrocatalyst honeycomb for controlling exhaust gas emissions according to claim 1, further comprising an oxidation catalyst layer attached to the cathode layer. The electrocatalyst honeycomb for controlling exhaust gas emissions according to claim 8, wherein the material of the oxidation catalyst layer is selected from the group consisting of metals, alloys, fluorite structure metal oxides, perovskite structure metal oxides, and combinations thereof. The group formed.