JP2007278099A - Purifying method of exhaust gas, and cogeneration method of vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a purifying method of exhaust gas for maintaining a high purifying rate, and a cogeneration method of a vehicle for efficiently utilizing energy recovered by the exhaust gas purifying method. <P>SOLUTION: In the purifying method of exhaust gas, a temperature control is performed so that a bed temperature of a catalyst is out of a temperature range of 250°C to 300°C, and the exhaust gas containing carbon monoxide is brought into contact with the catalyst so as to oxidatively-purify the exhaust gas. In a cogeneration method of a vehicle, waste heat recovered from the catalyst by the purifying method of the exhaust gas is used for air-conditioning, lighting of a light, or battery charge. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification method and a vehicle cogeneration method, and more particularly to an exhaust gas purification method and a vehicle cogeneration method capable of maintaining a high purification rate.

Combustion exhaust gas emitted from gasoline engines such as automobiles, diesel engines such as trucks and buses, etc. contains carbon monoxide, which is one of the harmful substances. Is a serious and urgent social issue.
Various catalysts have been developed to remove carbon monoxide in exhaust gases. For example, an exhaust gas purification catalyst having a carbon monoxide purification performance in which an active metal (such as copper or manganese) is supported on a crystalline silicate is disclosed (for example, refer to Patent Document 1).
Japanese Patent No. 2772117

However, exhaust gas discharge states are diverse, and it is extremely difficult to exhibit a constant and high purification performance.
The present invention has been made to solve the above problems, and an object of the present invention is to efficiently use the exhaust gas purification method capable of maintaining a high purification rate and the energy recovered by the exhaust gas purification method. It is to provide a vehicle cogeneration method.

That is, the present invention
<1> A method for purifying exhaust gas, wherein temperature control is performed so that the bed temperature of the catalyst is outside the temperature range of 250 ° C. to 300 ° C., and exhaust gas containing carbon monoxide is contacted with the catalyst to oxidatively purify.

When carbon monoxide is oxidized using an oxidation catalyst, carbon monoxide and oxygen are adsorbed on the catalyst, and these oxidation reactions occur to form carbon dioxide. However, since carbon monoxide exhibits strong adsorptivity to the catalyst in the temperature range of 250 ° C. to 300 ° C. and is difficult to desorb from the catalyst, CO poisoning that the catalyst surface is covered with carbon monoxide is not possible. Occur. As a result, it became clear that oxygen could not be adsorbed on the catalyst and oxidation reaction was difficult.
Therefore, in the invention <1>, by controlling the temperature so that the bed temperature of the catalyst is outside the temperature range of 250 ° C. to 300 ° C., CO poisoning of the catalyst is prevented and the oxidation reaction of carbon monoxide is inhibited. Not.
Therefore, according to the invention <1>, CO poisoning of the catalyst can be prevented, and a high purification rate of carbon monoxide can be maintained.

<2> The catalyst is a catalyst containing copper and manganese, a catalyst having gold supported on a carrier containing at least ceria and zirconia, a catalyst having gold supported on a carrier containing at least titania, a catalyst containing at least ceria, zirconia and silver. The exhaust gas according to <1>, wherein the exhaust gas is at least one selected from the group consisting of a catalyst containing at least ceria, zirconia and iron, and a catalyst containing at least ceria, zirconia, silver and iron. It is a purification method.

  In the above invention <2>, a catalyst that does not contain platinum, palladium, or rhodium as a main component is used. Even in this case, temperature control is performed so that the bed temperature of the catalyst is outside the temperature range of 250 ° C to 300 ° C. By doing so, the catalyst can be prevented from being poisoned by CO, and as a result, a high purification rate can be maintained.

<3> The exhaust gas purification method according to <1>, wherein the catalyst is a catalyst containing copper and manganese, or a catalyst in which gold is supported on a carrier containing at least ceria and zirconia.

  According to the invention <3>, since a highly active catalyst is used, a particularly high purification rate can be maintained.

<4> The above-mentioned <1>, wherein at least one of a heat absorbing material and a heating unit is disposed around the catalyst, and the temperature of the catalyst is controlled so that the bed temperature is outside the temperature range of 250 ° C to 300 ° C. The method for purifying exhaust gas according to any one of <1> to <3>.

  According to the above invention <4>, by disposing at least one of the heat absorbing material and the heating means around the catalyst such that the bed temperature of the catalyst is outside the temperature range of 250 ° C. to 300 ° C., the CO of the catalyst Poisoning can be prevented and a high purification rate of carbon monoxide can be maintained.

<5> The temperature of the exhaust gas when contacting the catalyst is controlled by at least one of a heat absorption material and a heating means, and the temperature of the catalyst is controlled to be outside the temperature range of 250 ° C to 300 ° C. The method for purifying exhaust gas according to any one of <1> to <4>, characterized in that:

According to the above invention <5>, the temperature of the exhaust gas is controlled by at least one of the heat absorbing material and the heating means so that the temperature-controlled exhaust gas contacts the catalyst. It can be controlled to be outside the temperature range of ° C., and a high purification rate of carbon monoxide can be maintained.
The exhaust gas temperature and the catalyst bed temperature are not necessarily the same, but as the exhaust gas continues to contact the catalyst, the catalyst temperature and the exhaust gas temperature become substantially the same. Therefore, the bed temperature of the catalyst can be achieved by controlling the temperature of the exhaust gas.

<6> The exhaust gas according to <4> or <5>, wherein the heat absorbing material is at least one selected from the group consisting of a thermoelectric element, cooling water, dry ice, and liquid nitrogen. It is a purification method.

  According to the invention <6>, the temperature of the catalyst or exhaust gas is cooled by at least one selected from the group consisting of a thermoelectric element, cooling water, dry ice and liquid nitrogen, so that the bed temperature of the catalyst is 250. The temperature can be lower than 0 ° C., and CO poisoning of the catalyst can be prevented.

<7> When the catalyst is provided in at least one of the plurality of exhaust gas channels provided in parallel, and the bed temperature of the catalyst in the channel including the catalyst becomes 250 ° C. to 300 ° C. The exhaust gas purifying method according to any one of <1> to <6>, wherein the exhaust gas is caused to flow into another flow path by a switching unit that switches inflow of the exhaust gas.

  According to the above <7>, the bed temperature of the catalyst provided in the flow path into which the exhaust gas has flowed is 250 by including the plurality of exhaust gas flow paths provided in parallel and the switching means for switching the inflow of the exhaust gas. Since it can be switched to another flow path when the temperature becomes from ℃ to 300 ℃, the catalyst bed temperature can be controlled to be outside the temperature range of 250 ℃ to 300 ℃, and a high purification rate of the catalyst can be maintained. it can.

<8> Disposing at least one of a heat absorbing material and a heating means in the other flow path, controlling the temperature so that the temperature of the exhaust gas is outside the temperature range of 250 ° C. to 300 ° C., and the heat absorbing material or the heating means The exhaust gas purification method according to <7>, wherein the catalyst is provided on the downstream side of the exhaust gas.

In the invention <8>, in the plurality of exhaust gas flow paths provided in parallel, one flow path includes the catalyst, and the other flow path includes at least one of a heat absorbing material and a heating unit. . When the bed temperature of the catalyst is outside the temperature range of 250 ° C. to 300 ° C., exhaust gas flows into one flow path, and when the bed temperature of the catalyst is within the temperature range of 250 ° C. to 300 ° C., the other 1 The exhaust gas flows into the flow path.
Therefore, according to the above invention <8>, when the temperature of the exhaust gas is in the temperature range of 250 ° C. to 300 ° C., the flow is switched to another flow path, so the bed temperature of the catalyst is outside the temperature range of 250 ° C. to 300 ° C. And a high purification rate of the catalyst can be maintained.

Further, since at least one of the heat absorbing material and the heating means is provided in the other one flow path, the temperature of the exhaust gas can be controlled outside the temperature range of 250 ° C to 300 ° C. The exhaust gas controlled outside the temperature range of 250 ° C. to 300 ° C. is purified by a catalyst provided downstream thereof.
Therefore, according to the above invention <8>, when the bed temperature of the catalyst becomes 250 ° C. to 300 ° C., the temperature of the exhaust gas is outside the temperature range of 250 ° C. to 300 ° C. by at least one of the heat absorbing material and the heating means. After the control, the exhaust gas is brought into contact with the catalyst to oxidize carbon monoxide, so that the content of carbon monoxide in the exhaust gas discharged after treatment can be lowered without depending on the temperature of the exhaust gas to be treated. .

<9> The exhaust gas purification method according to <7>, wherein an adsorbent is provided in the other channel.

In the above invention <9>, in the plurality of exhaust gas flow paths provided in parallel, one of the flow paths includes the catalyst, and the other one of the flow paths includes an adsorbent. When the bed temperature of the catalyst is outside the temperature range of 250 ° C. to 300 ° C., exhaust gas flows into one flow path, and when the bed temperature of the catalyst is within the temperature range of 250 ° C. to 300 ° C., the other 1 The exhaust gas flows into the flow path.
Therefore, according to the invention <9>, when the bed temperature of the catalyst is in the temperature range of 250 ° C. to 300 ° C., the flow is switched to another flow path, so the bed temperature of the catalyst is a temperature of 250 ° C. to 300 ° C. It can be controlled to be out of the region, and a high purification rate of the catalyst can be maintained.

Further, since the other one flow path is provided with the adsorbent, the exhaust gas can be adsorbed. The adsorbent can adsorb carbon monoxide even when the temperature of the exhaust gas is within a temperature range of 250 ° C to 300 ° C.
Therefore, according to the invention <9>, when the catalyst bed temperature is outside the temperature range of 250 ° C. to 300 ° C., the catalyst oxidizes carbon monoxide and discharges it as carbon dioxide. When the temperature becomes 250 ° C. to 300 ° C., the carbon monoxide in the exhaust gas is adsorbed by the adsorbent, so that the content of carbon monoxide in the exhaust gas after treatment can be lowered.

<10> The exhaust gas purification method according to <7>, wherein the catalyst is provided in the other flow path.

In the invention <10>, the catalyst is provided in a plurality of exhaust gas passages in a plurality of exhaust gas passages provided in parallel. First, exhaust gas is introduced into one flow path, and the exhaust gas is brought into contact with a catalyst in the flow path to oxidize carbon monoxide in the exhaust gas. The bed temperature of the catalyst rises due to the reaction heat of the oxidation reaction, and the bed temperature of the catalyst falls within a temperature range of 250 ° C to 300 ° C.
Here, the catalyst is also provided in the other channel, but since the exhaust gas did not flow into this channel, the bed temperature of the catalyst provided in the channel is about room temperature. The inflow of the exhaust gas is switched by the switching means, and the exhaust gas flows into the flow path having a catalyst at about room temperature. When the exhaust gas comes into contact with the catalyst, carbon monoxide in the exhaust gas reacts and is purified into carbon dioxide, while the bed temperature of the catalyst rises, and the bed temperature of the catalyst is also a temperature of 250 ° C to 300 ° C. Be in the region.
At this time, since the catalyst in the flow path into which the exhaust gas has flowed in does not generate an oxidation reaction because the oxidation reaction does not occur, the bed temperature of the catalyst is outside the temperature range of 250 ° C. to 300 ° C. by natural cooling. . Therefore, the inflow of the exhaust gas is returned to the original state, and the inflow of the exhaust gas is switched to the flow path into which the exhaust gas has been previously introduced. By repeating this operation, the catalyst bed temperature can always be outside the temperature range of 250 ° C. to 300 ° C., so that a high purification rate of the catalyst can be maintained.
When three or more flow paths are provided, switching may be performed so that the exhaust gas flows into another flow path.

<11> The exhaust gas purification method according to <7>, wherein the other channel includes a catalyst mainly composed of platinum, palladium, or rhodium.

Since the catalyst mainly composed of platinum, palladium or rhodium does not decrease the purification rate even when the bed temperature of the catalyst is in the temperature range of 250 ° C. to 300 ° C., the bed temperature of the other catalyst is 250 ° C. to 300 ° C. When the temperature falls within the temperature range, the inflow of the exhaust gas is switched to a flow path including a catalyst mainly composed of platinum, palladium, or rhodium.
As a result, according to the invention <11>, the content of carbon monoxide in the exhaust gas discharged after the treatment can be lowered without depending on the temperature of the exhaust gas to be treated.
In addition, in order to purify exhaust gas with a catalyst containing platinum, palladium or rhodium as a main component only when the bed temperature of the catalyst is in a temperature range of 250 ° C. to 300 ° C., platinum, palladium or rhodium is used as the main component. The life of the catalyst to be used can be prolonged, and the amount of valuable platinum, palladium or rhodium used can be suppressed.

<12> The above items <1> to <11>, wherein air is mixed upstream of the catalyst in the exhaust gas flow path, and the temperature of the exhaust gas contacting the catalyst is adjusted according to the amount of air mixed therein. It is a purification method of exhaust gas given in any 1 paragraph.

The temperature of the exhaust gas can be lowered by mixing air having a temperature lower than that of the exhaust gas into the exhaust gas. Further, by diluting the exhaust gas with air, the concentration of carbon monoxide contained is reduced, and the amount of heat generated on the catalyst can be suppressed. Therefore, in the invention <12>, the amount of air mixed in the exhaust gas is adjusted, and the temperature of the exhaust gas or the catalyst bed temperature is controlled to be lower than 250 ° C.
Therefore, according to the invention <12>, the bed temperature of the catalyst can be controlled to be outside the temperature range of 250 ° C. to 300 ° C. by adjusting the amount of air mixed in the exhaust gas, and the high purification rate of the catalyst is maintained. be able to.

<13> A vehicle cogeneration method in which exhaust heat from the catalyst recovered by the exhaust gas purification method according to any one of <1> to <12> is used for air conditioning, lighting of a light, or charging of a battery. is there.

  According to the invention <13>, energy can be efficiently used by using the waste heat recovered for controlling the bed temperature of the catalyst for air conditioning, lighting of a light, or charging of a battery. .

  According to the present invention, it is possible to provide an exhaust gas purification method capable of maintaining a high purification rate, and a vehicle cogeneration method that can efficiently use energy recovered by the exhaust gas purification method.

  Hereinafter, the exhaust gas purification method and vehicle cogeneration method of the present invention will be described in detail.

  In the exhaust gas purification method of the present invention, the temperature of the catalyst is controlled to be outside the temperature range of 250 ° C. to 300 ° C., and the exhaust gas containing carbon monoxide is contacted with the catalyst to oxidatively purify. It is.

The state of the oxidation reaction of carbon monoxide in the catalyst is shown in FIG.
As shown in FIG. 1A, in the oxidation reaction of carbon monoxide, first, carbon monoxide and oxygen are adsorbed on the active site of the catalyst, and the adsorbed carbon monoxide and oxygen react to form carbon dioxide and Become.
However, carbon monoxide gas has a property of exhibiting strong adsorptivity to the catalyst in a temperature range of 250 ° C. to 300 ° C. and being difficult to desorb from the catalyst. Therefore, as shown in FIG. 1B, in the temperature range of 250 ° C. to 300 ° C., the catalyst surface is covered with carbon monoxide and CO poisoning occurs. As a result, a phenomenon occurs in which oxygen cannot be adsorbed on the catalyst and carbon monoxide is hardly oxidized. In addition, when it exceeds 300 degreeC, even if carbon monoxide adsorb | sucks to a catalyst, it will become easy to detach | desorb from a catalyst by the molecular motion of carbon monoxide gas.

  If the state of CO poisoning continues, the oxidation reaction on the catalyst hardly occurs and the generation of reaction heat is reduced. As a result, the bed temperature of the catalyst is lowered and eventually departs from the temperature range of 250 ° C to 300 ° C. Then, as shown in FIG. 1C, CO poisoning is released, oxygen is adsorbed on the catalyst, and carbon monoxide begins to be oxidized again by the catalyst.

  However, when the oxidation reaction continues again, the bed temperature of the catalyst starts to rise due to the reaction heat and reaches a temperature range of 250 ° C to 300 ° C. In this temperature range, CO poisoning of the catalyst occurs, oxygen cannot be adsorbed on the catalyst, and carbon monoxide is hardly oxidized.

  Thus, since the CO poisoning and its release are repeated by the increase and decrease of the catalyst bed temperature, the exhaust gas purification rate cannot be kept constant, and the purification rate also decreases.

  Therefore, in the present invention, temperature control is performed so that the bed temperature of the catalyst is outside the temperature range of 250 ° C. to 300 ° C., and the purification rate of carbon monoxide is kept constant and high.

FIG. 2 shows the relationship between the catalyst bed temperature and the purification rate. In the graph of FIG. 2, A is a case where a catalyst having gold supported on a CeO ₂ —ZrO ₂ solid solution is used, and B is a case where CuO-2.7MnO ₂ is used as a catalyst. In any case, it can be seen that when the catalyst bed temperature is 250 ° C. to 300 ° C., the purification rate is lowered.

The catalyst bed temperature for avoiding a reduction in the purification rate is outside the temperature range of 250 ° C. to 300 ° C., and it is practically preferable to set it to 150 ° C. or more and less than 250 ° C. or more than 300 ° C. and 600 ° C. From the viewpoint of achieving a high purification rate, it is more preferably 200 ° C. or higher and 240 ° C. or lower or 350 ° C. or higher and 500 ° C. or lower.
In addition, when the bed temperature of the catalyst is 150 ° C. to 180 ° C., the purification rate is about 60% to 80%, which is about the same as or lower than about 80% of the purification rate at 250 ° C. to 300 ° C. However, as a result of suppressing the deterioration of the catalyst due to the low temperature, the case of 150 ° C. to 180 ° C. is more preferable than the case of 250 ° C. to 300 ° C. from the viewpoint of extending the catalyst life.

  The catalyst applicable to the present invention is not particularly limited as long as it is an oxidation catalyst capable of oxidizing carbon monoxide in exhaust gas to carbon dioxide. Specifically, a catalyst containing copper and manganese, a catalyst having gold supported on a support containing at least ceria and zirconia, a catalyst supporting gold on a support containing at least titania, a catalyst containing at least ceria, zirconia and silver, A catalyst containing ceria, zirconia and iron, a catalyst containing at least ceria, zirconia, silver and iron, etc. can be applied. Among them, a catalyst containing copper and manganese, and at least gold on a support containing ceria and zirconia. Supported catalyst, catalyst having gold supported on a carrier containing at least titania, catalyst containing at least ceria, zirconia and silver, catalyst containing at least ceria, zirconia and iron, or at least containing ceria, zirconia, silver and iron CO oxidation activity is at least one selected from the group consisting of catalysts Preferably a high point of view, particularly in view of catalytic activity, the catalyst comprising copper and manganese, it is preferable that a catalyst supported with gold carrier including at least ceria, and zirconia.

  In addition, if a catalyst mainly composed of platinum, palladium, or rhodium is used, it is difficult to cause CO poisoning even if the bed temperature of the catalyst is in the temperature range of 250 ° C to 300 ° C. However, it is desired not to use platinum, palladium, or rhodium as much as possible because of resource problems.

  In the present invention, the shape of the catalyst is not particularly limited, and particles or pellets may be filled with a part of the gas flow path as a column, or may have a honeycomb structure. A catalyst having a honeycomb structure can be obtained by coating the surface of a commercially available honeycomb carrier with a catalyst powder and then firing the catalyst powder.

  Next, the temperature control method in which the bed temperature of the catalyst is outside the temperature range of 250 ° C. to 300 ° C. will be described with reference to the drawings from the first aspect to the seventh aspect. It is not limited by the control method. In the first to seventh aspects described below, the method for controlling the bed temperature of the catalyst is roughly divided by controlling the temperature of the catalyst itself or controlling the temperature of the exhaust gas contacting the catalyst.

<First aspect>
FIG. 3 shows a first embodiment of the temperature control method for the catalyst bed temperature.
As shown in FIG. 3, in the first embodiment, at least one of the heat absorbing material 12 and the heating means 14 is arranged around the catalyst 10. In this method, the bed temperature of the catalyst is controlled by controlling the temperature of the catalyst itself. In addition, the bed temperature of a catalyst means what measured the temperature inside filling in the filled catalyst. Such temperature can be measured by a temperature measuring instrument such as a thermocouple.

As the heat absorbing material 12, a thermoelectric element, cooling water, dry ice, liquid nitrogen, or a combination thereof can be applied. Among these, it is preferable to apply a thermoelectric element or cooling water from the viewpoint of easy temperature control.
When the temperature control of the catalyst bed temperature is performed by the thermoelectric element, the temperature of the catalyst bed temperature is detected by the temperature measuring device 16 such as a thermocouple, and the control can be performed by turning on / off the thermoelectric element based on this temperature. it can.
When the temperature of the catalyst bed temperature is controlled by the cooling water, it can be controlled by detecting the bed temperature of the catalyst by the thermocouple 16 or the like and opening and closing the cooling water valve based on this temperature.
Turning on / off the power supply of the thermoelectric element and opening / closing the cooling water valve may be performed manually, but may be automatically controlled using a central processing unit (CPU) 18 or the like.

A heater or the like can be applied as the heating means 14, but is not limited thereto.
Hereinafter, also in the second and subsequent embodiments, when the heat absorbing material or the heating means is provided, the temperature can be controlled by the same method as in the first embodiment.

<Second aspect>
FIG. 4 shows a second embodiment of the temperature control method for the catalyst bed temperature.
In the second embodiment, the temperature of the exhaust gas in contact with the catalyst is controlled. As shown in FIG. 4, in the second mode, in the exhaust gas flow, at least one of the heat absorbing material 24 and the heating means 26 is arranged in the exhaust gas flow path 22 upstream of the catalyst 20. The temperature of the exhaust gas is controlled by the arranged heat absorbing material 24 and the heating means 26, and the temperature is controlled so that the bed temperature of the catalyst is outside the temperature range of 250 ° C to 300 ° C.

  In the second aspect, the bed temperature of the catalyst 20 is controlled by controlling the temperature of the exhaust gas in contact with the catalyst 20. The temperature of the exhaust gas and the bed temperature of the catalyst are not necessarily the same, but as the exhaust gas continues to contact the catalyst 20, the temperature of the catalyst 20 and the temperature of the exhaust gas become substantially the same. Therefore, the catalyst bed temperature can be controlled by controlling the temperature of the exhaust gas.

<Third embodiment>
FIG. 5 shows a third embodiment of the temperature control method for the catalyst bed temperature.
In the third aspect, the temperature of the exhaust gas contacting the catalyst is controlled. In a 3rd aspect, the flow path of the some exhaust gas provided in parallel is provided. 5A and 5B show a case where two parallel exhaust gas flow paths 30, 31 are provided, but three or more parallel exhaust gas flow paths may be provided.
5A and 5B, the catalyst 32 is provided in the flow path 30. When the bed temperature of the catalyst 32 in the flow path 30 becomes 250 ° C. to 300 ° C., the switching means 34 such as a valve for switching the flow of the exhaust gas is switched so that the exhaust gas flows into the flow path 31. By this switching, the bed temperature of the catalyst 32 can be controlled to be outside the temperature range of 250 ° C. to 300 ° C., and a high purification rate of the catalyst 32 can be maintained.
Switching of the flow paths 30 and 31 by the switching means 34 is performed by detecting the bed temperature of the catalyst 32 by a temperature measuring device 33 such as a thermocouple, and automatically or manually by a central processing unit (CPU) 35 based on this temperature data. Perform by control.

Furthermore, in the third aspect, at least one of the heat absorbing material 36 and the heating means 37 is disposed in the flow path 31, and the catalyst 39 is provided downstream of the heat absorbing material 36 and the heating means 37 in the exhaust gas flow path. . Since at least one of the heat absorbing material 36 and the heating means 37 is provided in the flow path 31, the temperature of the exhaust gas contacting the catalyst 39 can be controlled outside the temperature range of 250 ° C. to 300 ° C. High purification rate can be maintained.
Therefore, in the third aspect, a high purification rate can be maintained for both the catalyst 32 and the catalyst 39.
5A, the catalyst 39 is provided in the flow path 31, and in FIG. 5B, the catalyst 39 is provided after the flow path 30 and the flow path 31 are merged. In either case, the exhaust gas temperature in contact with the catalyst 39 is outside the temperature range of 250 ° C. to 300 ° C., so that CO poisoning of the catalyst 39 can be prevented.

<Fourth aspect>
FIG. 6 shows a fourth embodiment of the temperature control method for the catalyst bed temperature.
In the fourth aspect, the temperature of the exhaust gas in contact with the catalyst is controlled. In a 4th aspect, the flow path of the some exhaust gas provided in parallel is provided. Although FIG. 6 shows a case where two parallel exhaust gas flow paths 40 and 41 are provided, three or more parallel exhaust gas flow paths may be provided.
The flow path 40 includes the catalyst 42. When the bed temperature of the catalyst 42 in the flow path 40 reaches 250 ° C. to 300 ° C., the switching means 44 such as a valve for switching the flow of the exhaust gas is switched so that the exhaust gas flows into the flow path 41. By this switching, the bed temperature of the catalyst 42 can be controlled to be outside the temperature range of 250 ° C. to 300 ° C., and a high purification rate of the catalyst 42 can be maintained. Switching of the flow paths 40 and 41 by the switching means 44 is performed by detecting the bed temperature of the catalyst 42 by a temperature measuring device 45 such as a thermocouple, and automatically or automatically by a central processing unit (CPU) 46 based on this temperature data. Perform by control.

Furthermore, in the fourth aspect, the adsorbent 48 is provided in the flow path 41. The adsorbent 48 can adsorb carbon monoxide even when the exhaust gas temperature is 250 ° C to 300 ° C.
Therefore, in the fourth aspect, when the bed temperature of the catalyst is outside the temperature range of 250 ° C. to 300 ° C., carbon monoxide is oxidized by the catalyst 42 and discharged as carbon dioxide, while the bed temperature of the catalyst 42 is When the temperature reaches 250 ° C. to 300 ° C., the carbon monoxide in the exhaust gas is adsorbed by the adsorbent 48, so that the content of carbon monoxide in the exhaust gas after treatment can be lowered.

  As the adsorbent 48, for example, known materials such as zeolite, activated carbon, Pt, Pd, Rh, Ce, Ba, K, Li, and Ne can be appropriately applied.

<Fifth aspect>
FIG. 7 shows a fifth embodiment of the temperature control method for the catalyst bed temperature.
In the fifth aspect, the temperature of the exhaust gas in contact with the catalyst is controlled. In a 5th aspect, the flow path of the some exhaust gas provided in parallel is provided. Although FIG. 7 shows a case where two parallel exhaust gas flow paths 50 and 51 are provided, three or more parallel exhaust gas flow paths may be provided.
The flow path 50 includes the catalyst 52. When the bed temperature of the catalyst 52 in the flow channel 50 becomes 250 ° C. to 300 ° C., the switching is performed so that the exhaust gas flows into the flow channel 51 by the switching means 54 such as a valve for switching the inflow of the exhaust gas. By this switching, the bed temperature of the catalyst 52 can be controlled to be outside the temperature range of 250 ° C. to 300 ° C., and a high purification rate of the catalyst 52 can be maintained. Switching of the flow paths 50 and 51 by the switching means 54 is performed by detecting the bed temperature of the catalyst 52 by a temperature measuring device 55 such as a thermocouple, and automatically or manually by a central processing unit (CPU) 56 based on the temperature data. Perform by control.

Furthermore, in the fifth aspect, the catalyst 58 is provided in the flow path 51. Since the exhaust gas has not flowed into the flow channel 51 so far, the bed temperature of the catalyst 58 provided in the flow channel 51 is about room temperature, and the catalyst 58 is not poisoned with CO. Therefore, when the exhaust gas comes into contact with the catalyst 58, carbon monoxide in the exhaust gas reacts and is purified into carbon dioxide.
However, as the reaction of the catalyst 58 proceeds, the bed temperature of the catalyst rises and eventually reaches 250 ° C to 300 ° C.

At this time, since the catalyst 52 of the flow path 50 into which the exhaust gas has been flown is switched, the oxidation reaction does not occur and no reaction heat is generated. Therefore, the bed temperature of the catalyst 52 is reduced by natural cooling. Outside the temperature range of 250 ° C to 300 ° C.
Therefore, the inflow of the exhaust gas is returned to the original state by the switching means 54, and the inflow of the exhaust gas is switched to the flow path 50 in which the exhaust gas has been previously introduced. The switching of the flow paths 50 and 51 by the switching means 54 is carried out by detecting the bed temperature of the catalyst 58 by a temperature measuring device 59 such as a thermocouple, and automatically or automatically by a central processing unit (CPU) 56 based on this temperature data. Perform by control.
By repeating this operation, the bed temperature of the catalysts 52 and 58 can always be outside the temperature range of 250 ° C. to 300 ° C., so that a high purification rate of the catalyst can be maintained.

  In the fifth aspect, when three or more flow paths are provided, the switching means 54 may switch so that the exhaust gas flows into another flow path without returning the flow of the exhaust gas back to the original state.

  Since the temperature control method of the catalyst bed temperature of the fifth aspect uses the principle of natural cooling, it can be applied when the temperature of the exhaust gas is lower than 250 ° C.

<Sixth aspect>
FIG. 8 shows a sixth embodiment of the temperature control method for the catalyst bed temperature.
In the sixth aspect, the temperature of the exhaust gas in contact with the catalyst is controlled. In the sixth aspect, a plurality of exhaust gas flow paths provided in parallel are provided. Although FIG. 8 shows a case where two parallel exhaust gas flow paths 60 and 61 are provided, three or more parallel exhaust gas flow paths may be provided.
The catalyst 62 is provided in the flow path 60. When the bed temperature of the catalyst 62 in the flow path 60 reaches 250 ° C. to 300 ° C., the switching means 64 such as a valve for switching the flow of the exhaust gas is switched so that the exhaust gas flows into the flow path 61. By this switching, the bed temperature of the catalyst 62 can be controlled to be outside the temperature range of 250 ° C. to 300 ° C., and a high purification rate of the catalyst 62 can be maintained. Switching of the flow paths 60 and 61 by the switching means 64 is performed by detecting the bed temperature of the catalyst 62 by a temperature measuring device 65 such as a thermocouple, and automatically or manually by a central processing unit (CPU) 66 based on this temperature data. Perform by control.

Furthermore, in the sixth embodiment, the flow path 61 is provided with a catalyst 68 mainly composed of platinum, palladium, or rhodium. Since the catalyst 68 mainly composed of platinum, palladium, or rhodium does not decrease the purification rate even if the bed temperature of the catalyst is in the temperature range of 250 ° C. to 300 ° C., the bed temperature of the catalyst 62 is 250 ° C. to 300 ° C. When the temperature is within the temperature range, the inflow of the exhaust gas is switched to the flow path 61 including the catalyst 68 mainly composed of platinum, palladium, or rhodium.
The catalyst 68 mainly composed of platinum, palladium, or rhodium is used when the bed temperature of the catalyst 62 falls within a temperature range of 250 ° C. to 300 ° C., and the catalyst 62 is used outside this temperature range. Can extend the lifetime of As a result, it is possible to reduce the amount of valuable metals such as platinum used.

<Seventh aspect>
FIG. 9 shows a seventh embodiment of the temperature control method for the catalyst bed temperature.
In the seventh aspect, the temperature of the exhaust gas in contact with the catalyst is controlled. In the seventh aspect, the mixed air amount adjusting means 72 for adjusting the amount of mixed air by mixing air is provided upstream of the catalyst 70 in the exhaust gas flow path. By mixing air having a temperature lower than the temperature of the exhaust gas into the exhaust gas, the temperature of the exhaust gas can be lowered. Moreover, since the concentration of carbon monoxide is reduced by mixing air with the exhaust gas, the amount of heat generated on the catalyst can be suppressed.

  When the bed temperature of the catalyst 70 reaches 250 ° C. to 300 ° C., the mixed air amount adjusting means 72 introduces air into the exhaust gas. Depending on the amount of air introduced, the bed temperature of the catalyst 70 can be controlled to be outside the temperature range of 250 ° C. to 300 ° C., and a high purification rate of the catalyst 70 can be maintained. The introduction of air by the mixed air amount adjusting means 72 detects the bed temperature of the catalyst 70 by a temperature measuring device 74 such as a thermocouple, and is automatically controlled manually or by a central processing unit (CPU) 76 based on this temperature data. Do by.

The methods for controlling the bed temperature of the catalyst according to the first to seventh aspects can be applied in an appropriate combination.
In the first to seventh aspects, the catalyst bed temperature is measured by a temperature measuring instrument such as a thermocouple, and the temperature of the catalyst bed temperature is controlled based on this data. If the exhaust gas keeps in contact with the catalyst, the exhaust gas temperature and the catalyst bed temperature almost coincide with each other. Therefore, it is possible to measure the temperature of the exhaust gas with a temperature measuring instrument and control the temperature based on the data. .

  Waste heat is recovered from the catalyst by the exhaust gas purification method of the present invention. By using this waste heat for air conditioning, lighting of lights, or charging of a battery, energy can be used efficiently. In particular, the vehicle exhaust gas purification method is a vehicle cogeneration method.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, raw materials, amounts used, operations, and the like can be appropriately changed without departing from the gist of the present invention. Therefore, the scope of the present invention is not limited to the following examples.

[Example 1]
<Preparation of catalyst 1>
Preparation liquid-1 was prepared by adding 19.0 g of CeO ₂ —ZrO ₂ solid solution to 300 ml of water and then adding 5.08 × 10 ⁻³ mol of 1% by mass of HAuCl ₄ .4H ₂ O aqueous solution.
To this preparation liquid-1, 1.23 × 10 ⁻² mol of 0.5 mol / L Na ₂ CO ₃ aqueous solution was dropped at a dropping rate of 4.00 × 10 ⁻⁵ mol / sec until pH = 7. did. Thereafter, it was centrifuged, washed 5 times with water at 80 ° C., and then dried. This was fired at 400 ° C. for 4 hours in an air atmosphere to prepare CeO ₂ —ZrO ₂ supporting 5% by mass of Au.

The preparation of the CeO ₂ —ZrO ₂ catalyst supporting 5% by mass of Au can be obtained in the same manner even if each raw material is changed to the following amounts.
・ Water: 300ml
CeO ₂ —ZrO ₂ solid solution: 28.5 g
1 mass% HAuCl ₄ .4H ₂ O aqueous solution: 7.62 × 10 ⁻³ mol
・ 0.5 mol / L Na ₂ CO ₃ aqueous solution: 1.93 × 10 ⁻² mol

<Preparation of catalyst 2>
Preparation liquid-2 was prepared by adding 0.100 mol of Cu (NO ₃ ) ₂ .H ₂ O and 0.270 mol of Mn (NO ₃ ) .3H ₂ O 19.0 g to 300 ml of water.
This preparation was -2 to 0.594mol of aqueous Na ₂ CO ₃ 0.5 mol / L, it was added dropwise until pH = 7 at a dropping rate of 4.00 × 10 ^-5 mol / sec. Thereafter, it was centrifuged, washed 5 times with water at 80 ° C., and then dried. This was calcined at 500 ° C. for 4 hours in an air atmosphere to prepare CuO-2.7MnO ₂ .

<Evaluation method>
Evaluation was carried out using 3 g of the pellet-shaped catalyst 1 or catalyst 2 prepared above in the apparatus of FIG. 3 equipped with a thermoelectric element. Further, in FIG. 3, metal powder was spread on the surface so that heat conduction was uniform from the center of the catalyst to the end. The size of the device of FIG. 3 is about 3 cm wide and about 4 cm high.
The composition of the inflowing gas is as follows.
(Rich)
C ₃ H ₆ : 2500 ppmC, NO: 2200 ppm, CO ₂ : 10 vol%, H ₂ O: 10 vol%, CO: 2.8 vol%, O ₂ : 0.77 vol%, H ₂ : 2700 ppm, N ₂ : residue ( Lean)
C ₃ H ₆ : 2500 ppmC, NO: 2200 ppm, CO ₂ : 10 vol%, H ₂ O: 10 vol%, CO: 0.81 vol%, O ₂ : 1.7 vol%, H ₂ : 0 ppm, N ₂ : balance

The gas temperatures to be introduced were 200 ° C., 260 ° C., 290 ° C., and 350 ° C., the gas inflow rate was 20 L / min, and Rich gas and Lean gas were introduced for 1 second each.
When the gas temperatures to be introduced were 200 ° C. and 350 ° C., the gas was allowed to flow without controlling the bed temperature of the catalyst by the thermoelectric element.
When the inflowing gas temperature is 260 ° C., the thermoelectric element controls the catalyst bed temperature to be a constant temperature of 220 ° C., and when the inflowing gas temperature is 290 ° C., the thermoelectric element controls the catalyst bed temperature. The temperature was controlled to be a constant temperature of 240 ° C.

  The composition of the gas after passing through the catalyst was measured, and the CO purification rate (%) [(1-CO content after passing through catalyst / CO content of inflow gas) × 100] was determined from the CO content.

<Evaluation results>
It was found that when the gas temperature to be introduced was 200 ° C., the bed temperature of the catalyst was constant at 200 ° C. The CO purification rate (%) was 85% for catalyst 1 and 90% for catalyst 2, and both catalysts showed a constant purification rate with respect to the inflow time.
When the temperature of the gas to be introduced is 260 ° C. and the temperature is controlled so that the bed temperature of the catalyst is constant at 220 ° C., the CO purification rate (%) is 87% for catalyst 1 and 91% for catalyst 2. Both catalysts showed a certain purification rate with respect to the inflow time.
When the inflowing gas temperature is 290 ° C. and the temperature is controlled so that the catalyst bed temperature is constant at 240 ° C., the CO purification rate (%) is 90% for catalyst 1 and 92% for catalyst 2. Both catalysts showed a certain purification rate with respect to the inflow time.
When the gas temperature to be introduced was 350 ° C., the bed temperature of the catalyst was constant at 350 ° C. without temperature control. The CO purification rate (%) was 90% for catalyst 1 and 95% for catalyst 2, and both catalysts showed a constant purification rate with respect to the inflow time.

When a CuO-2.7MnO ₂ catalyst is used, the calorific value due to the oxidation reaction is 104 W when the CO purification rate is 90%, and the calorific value is 105 W when the CO purification rate is 91%. When the CO purification rate was 92%, the heat generation amount was 107 W, and when the CO purification rate was 95%, the heat generation amount was 110 W. Therefore, the amount of heat that can be recovered from the heat-absorbing material seems to be about 100W to 150W.

[Example 2]
Using the catalyst 1 and the catalyst 2 prepared in Example 1, the purification rate when the catalyst bed temperature was changed from 100 ° C. to 500 ° C. was measured. The gas composition and gas inflow conditions used are the same as in the case of Example 1.
The result is shown in FIG. In the graph of FIG. 2, A is the result using the catalyst 1, and B is the result when using the catalyst 2. In any catalyst, it is understood that the purification rate is lowered when the bed temperature of the catalyst is in the temperature range of 250 ° C to 300 ° C.

[Comparative Example 1]
Using the catalyst 1 and the catalyst 2 prepared in Example 1, the CO purification rate was measured. The condition different from that in Example 1 was that the gas was allowed to pass through without temperature control even when the inflowing gas temperature was 260 ° C. and 290 ° C., and the other conditions were the same as in Example 1. Evaluation was performed.

  The obtained result is shown in FIG. FIG. 10 shows the CO purification rate (%) with respect to the inflow elapsed time. When the gas temperature to be introduced was 260 ° C. and 290 ° C., the CO purification rate was not constant with respect to time. This seems to be due to CO poisoning of the catalyst.

It is a figure which shows the mode of the oxidation reaction of the carbon monoxide in a catalyst. 1A shows how carbon monoxide and oxygen are adsorbed on the catalyst, FIG. 1B shows the state of CO poisoning of the catalyst, and FIG. 1C shows that CO poisoning has been released. Show the state. It is a graph which shows the relationship between the bed temperature of a catalyst, and a purification rate. It is a figure which shows the 1st aspect of the temperature control method of the bed temperature of a catalyst. It is a figure which shows the 2nd aspect of the temperature control method of the bed temperature of a catalyst. It is a figure which shows the 3rd aspect of the temperature control method of the bed temperature of a catalyst. It is a figure which shows the 4th aspect of the temperature control method of the bed temperature of a catalyst. It is a figure which shows the 5th aspect of the temperature control method of the bed temperature of a catalyst. It is a figure which shows the 6th aspect of the temperature control method of the bed temperature of a catalyst. It is a figure which shows the 7th aspect of the temperature control method of the bed temperature of a catalyst. 6 is a graph showing the CO purification rate (%) with respect to the inflow elapsed time in Comparative Example 1.

Explanation of symbols

10, 20, 32, 39, 42, 52, 58, 62, 68, 70 Catalyst 16, 33, 45, 55, 59, 65, 74 Temperature measuring device 18, 35, 46, 56, 66, 76 CPU
12, 24, 36 Heat absorbing material 14, 26, 37 Heating means 34, 44, 54, 64 Switching means 48 Adsorbent 72 Mixed air amount adjusting means

Claims (13)

  A method for purifying exhaust gas, wherein temperature control is performed so that the bed temperature of the catalyst is outside a temperature range of 250 ° C to 300 ° C, and exhaust gas containing carbon monoxide is contacted with the catalyst to oxidatively purify.   The catalyst is a catalyst containing copper and manganese, a catalyst having gold supported on a carrier containing at least ceria and zirconia, a catalyst having gold supported on a carrier containing at least titania, a catalyst containing at least ceria, zirconia and silver, at least ceria. 2. The exhaust gas purification method according to claim 1, wherein the exhaust gas purification method is at least one selected from the group consisting of a catalyst containing at least one of ceria, zirconia, iron, and a catalyst containing at least ceria, zirconia, silver, and iron.   2. The exhaust gas purification method according to claim 1, wherein the catalyst is a catalyst containing copper and manganese, or a catalyst in which gold is supported on a carrier containing at least ceria and zirconia.   The temperature control is performed by arranging at least one of a heat absorbing material and a heating means around the catalyst so that the bed temperature of the catalyst is outside the temperature range of 250 ° C to 300 ° C. 4. The exhaust gas purification method according to any one of 3 above.   The temperature of the exhaust gas when contacting the catalyst is controlled by at least one of a heat absorbing material and a heating means, and the temperature of the catalyst is controlled to be outside the temperature range of 250 ° C to 300 ° C. The exhaust gas purification method according to any one of claims 1 to 4.   6. The exhaust gas purification method according to claim 4, wherein the heat absorbing material is at least one selected from the group consisting of a thermoelectric element, cooling water, dry ice, and liquid nitrogen.   The catalyst is provided in at least one of the plurality of exhaust gas passages provided in parallel, and when the bed temperature of the catalyst in the passage including the catalyst becomes 250 ° C. to 300 ° C., the exhaust gas The exhaust gas purification method according to any one of claims 1 to 6, wherein the exhaust gas is caused to flow into another flow path by a switching means for switching inflow.   At least one of the heat absorbing material and the heating means is disposed in the other flow path, and the temperature is controlled so that the temperature of the exhaust gas is outside the temperature range of 250 ° C. to 300 ° C. The exhaust gas purification method according to claim 7, comprising the catalyst on a side.   The exhaust gas purification method according to claim 7, wherein an adsorbent is provided in the other flow path.   The exhaust gas purification method according to claim 7, wherein the catalyst is provided in the other flow path.   The exhaust gas purification method according to claim 7, wherein a catalyst having platinum, palladium, or rhodium as a main component is provided in the other channel.   12. The air according to claim 1, wherein air is mixed upstream of the catalyst in the exhaust gas flow path, and the temperature of the exhaust gas contacting the catalyst is adjusted according to the amount of mixed air. 2. A method for purifying exhaust gas according to 1.   A vehicle cogeneration method using exhaust heat from the catalyst recovered by the exhaust gas purification method according to any one of claims 1 to 12 for air conditioning, lighting of a light, or charging of a battery.

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