JP2011183280A - Co oxidation catalyst and exhaust gas cleaning method using the same - Google Patents

Co oxidation catalyst and exhaust gas cleaning method using the same Download PDF

Info

Publication number
JP2011183280A
JP2011183280A JP2010049474A JP2010049474A JP2011183280A JP 2011183280 A JP2011183280 A JP 2011183280A JP 2010049474 A JP2010049474 A JP 2010049474A JP 2010049474 A JP2010049474 A JP 2010049474A JP 2011183280 A JP2011183280 A JP 2011183280A
Authority
JP
Japan
Prior art keywords
oxidation catalyst
metal oxide
oxidation
catalyst
composite metal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
JP2010049474A
Other languages
Japanese (ja)
Other versions
JP5574222B2 (en
Inventor
Masashi Kikukawa
Kiyoshi Yamazaki
清 山崎
将嗣 菊川
Original Assignee
Toyota Central R&D Labs Inc
株式会社豊田中央研究所
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Toyota Central R&D Labs Inc, 株式会社豊田中央研究所 filed Critical Toyota Central R&D Labs Inc
Priority to JP2010049474A priority Critical patent/JP5574222B2/en
Publication of JP2011183280A publication Critical patent/JP2011183280A/en
Application granted granted Critical
Publication of JP5574222B2 publication Critical patent/JP5574222B2/en
Application status is Active legal-status Critical
Anticipated expiration legal-status Critical

Links

Images

Abstract

A sufficiently high CO oxidation performance can be exhibited from a low temperature of about 200 ° C., and even when exposed to a high temperature of about 800 ° C., a decrease in the CO oxidation performance of a catalyst can be sufficiently suppressed. In addition, a CO oxidation catalyst capable of achieving a sufficiently high CO conversion rate from a sufficiently low temperature is provided.
A support made of a composite metal oxide containing ceria, zirconia and alumina, wherein the content of ceria in the composite metal oxide is 50% by mass or more, copper oxide supported on the support, CO oxidation catalyst characterized by comprising.
[Selection figure] None

Description

  The present invention relates to a CO oxidation catalyst and an exhaust gas purification method using the same.

  Conventionally, various CO oxidation catalysts have been used to oxidize and purify carbon monoxide (CO) contained in gas discharged from internal combustion engines, etc., and improve CO oxidation performance under low temperature conditions Various studies have been made for the purpose. As such a CO oxidation catalyst, for example, a catalyst using a platinum group element as an active species is known. However, in the field of such CO oxidation catalyst, in recent years, it has been required to suppress the use of platinum group elements from the viewpoint of risk management of rare metals and the price. In particular, when a CO oxidation catalyst is used in an exhaust gas purification device for an automobile, it is often used in combination with a NOx reduction purification catalyst in the device. Since it is generally contained, when a platinum group element is also used for the CO oxidation catalyst, the total amount of the platinum group element contained in the apparatus becomes enormous. For this reason, research on CO oxidation catalysts having a structure that does not use platinum group elements such as Pt and Rh has been advanced.

For example, Haruta et al., Described in pages 177 to 195 of Journal of Catalysis (vol. 144) published in 1993, authors “Low-Temperature Oxidation of CO over Gold supported on TiO 2 , Fe 2 O 3 , and CO 3 O 4 (Non-patent Document 1) ”disclose a catalyst or the like in which gold (Au) is supported on a titania carrier or the like. Japanese Patent Application Laid-Open No. 1-266850 (Patent Document 1) discloses a CO oxidation catalyst comprising a mixture of copper oxide and cerium dioxide. Furthermore, Jian-Liang Cao et al., Described in pages 120-128 of Applied Catalysis B: Environmental (vol. 78) published in 2008, author “Preparation, Characterization and Catalytic behavior of nanostructured mesoporous CuO / Ce 0.8 “Zr 0.2 O 2 catalyst for low temperature CO oxidation (Non-patent Document 2)” discloses a CO oxidation catalyst in which copper oxide is supported on a solid solution of ceria and zirconia. Further, in Japanese Patent Application Laid-Open No. 2008-222501 (Patent Document 2), copper oxide is added to a carrier formed by mixing aluminum oxide with cerium oxide at a mixing ratio of 20 mol% or less in terms of a molar percentage converted to cerium and aluminum. A supported CO selective oxidation catalyst is disclosed. However, in the conventional CO oxidation catalysts as described in Patent Documents 1 and 2 and Non-Patent Documents 1 and 2, there is a problem that CO oxidation performance deteriorates when the catalyst is exposed to a high temperature of about 800 ° C. there were. Further, in such a conventional CO oxidation catalyst, a high CO conversion rate could not be achieved at a relatively low temperature.

JP-A-1-266850 JP 2008-222501 A

Haruta et al. , "Low-Temperature Oxidation of CO over Gold supported on TiO2, Fe2O3, and CO3O4", Journal of Catalysis, 1993, vol. 144, pp. 177-195 Jian-Liang Cao et al. , "Preparation, Characterization and Catalytic behavior of nanostructured mesoporous CuO / Ce0.8Zr0.2O2 catalyst for low temperature CO oxidation", Applied Catalysis B: Environmental, 2008, vol. 78, pp. 120-128

  The present invention has been made in view of the above-mentioned problems of the prior art, and can exhibit sufficiently high CO oxidation performance from a low temperature of about 200 ° C., and even when exposed to a high temperature of about 800 ° C. Provided is a CO oxidation catalyst capable of sufficiently suppressing a reduction in CO oxidation performance and capable of achieving a sufficiently high CO conversion rate from a sufficiently low temperature, and an exhaust gas purification method using the same. For the purpose.

  As a result of intensive studies to achieve the above object, the inventors of the present invention consisted of a composite metal oxide containing ceria, zirconia and alumina, and the content of ceria in the composite metal oxide was 50. Surprisingly, the structure is such that the active species of the catalyst supported on the carrier is copper oxide and the CO oxidation catalyst is supported on the carrier. A sufficiently high CO oxidation performance can be exhibited from a low temperature, the catalyst can sufficiently suppress a decrease in CO oxidation performance at a high temperature of about 800 ° C., and a sufficiently high CO conversion rate (for example, a conversion rate of 90%) Etc.) has been found to be achieved from a sufficiently low temperature, and the present invention has been completed.

  That is, the CO oxidation catalyst of the present invention is composed of a composite metal oxide containing ceria, zirconia, and alumina, and the content of ceria in the composite metal oxide is 50% by mass or more. And a supported copper oxide.

  In the composite metal oxide according to the present invention, it is preferable that the ceria, the zirconia, and the alumina are dispersed on the nm scale.

  In the composite metal oxide according to the present invention, it is preferable that the zirconia forms a ceria-zirconia solid solution in which the ceria is dissolved.

  Furthermore, in the CO oxidation catalyst of the present invention, the content of the copper oxide is preferably 0.5 to 30% by mass with respect to the total amount of the carrier and the copper oxide.

  The exhaust gas purification method of the present invention is a method characterized by bringing exhaust gas into contact with the CO oxidation catalyst of the present invention and oxidizing and removing carbon monoxide gas in the exhaust gas.

In addition, the CO oxidation catalyst and the exhaust gas purification method of the present invention can exhibit sufficiently high CO oxidation performance from a low temperature of about 200 ° C., and even when exposed to a high temperature of about 800 ° C., the CO oxidation performance of the catalyst is reduced. However, the reason why it is possible to achieve a sufficiently high CO conversion rate from a sufficiently low temperature is not necessarily clear, but the present inventors speculate as follows: To do. That is, first, when examining the CO oxidation reaction in the CO oxidation catalyst in which CuO becomes an active species, the CO oxidation reaction is represented by the following reaction formulas (1) and (2):
[Reaction Formula (1)] 2CuO + CO → Cu 2 O + CO 2
[Reaction Formula (2)] Cu 2 O + O 2 → 2CuO
It progresses by reaction represented by. CuO in such reaction formulas (1) and (2) has a Cu valence of 2 and Cu 2 O has a monovalence of Cu. Moreover, it is inferred that the rate-limiting step in such CO oxidation reaction is the reaction described in the reaction formula (1). When such CuO is supported on a carrier containing ceria (CeO 2 ), CuO interacts with CeO 2 and is easily reduced by the oxygen storage / release function (OSC) of CeO 2 . In addition, in the case where CeO 2 and zirconia (ZrO 2 ) are contained in the support, if a solid solution of CeO 2 and ZrO 2 (CeO 2 —ZrO 2 solid solution) is formed, the OSC performance of the support is further improved. , CuO on the carrier is more easily reduced. Therefore, in the carrier comprising a carrier or CeO 2 -ZrO 2 solid solution consisting of CeO 2, there is a tendency that the reaction represented by the reaction formula of the CO oxidation reaction (1) (reaction rate-determining step) is promoted . However, carrier comprising a carrier or CeO 2 -ZrO 2 solid solution composed of CeO 2 is typically oxide particles when exposed to temperatures higher than 800 ° C. decreases the specific surface area and grain growth. Therefore, in conventional oxidation catalysts such as those described in Patent Documents 1 and 2 and Non-Patent Document 2 that use CuO as an active species, interaction with a carrier when exposed to a high temperature of 800 ° C. or higher. It is presumed that the CO oxidation activity is lowered because the amount of CuO in a state that is easily reduced by the decrease in the amount of active species (CuO) of the CO oxidation reaction on the support decreases. In addition, in the conventional CO oxidation catalyst as described in Non-Patent Document 1 using Au as an active species, Au particles grow when the catalyst is exposed to a high temperature of about 800 ° C. It is presumed that the catalytic activity is reduced.

In contrast, in the present invention, the support contains alumina (Al 2 O 3 ) together with CeO 2 and ZrO 2 . Such Al 2 O 3 does not dissolve in CeO 2 , ZrO 2 and CeO 2 —ZrO 2 solid solution. Therefore, the Al 2 O 3 particles and the CeO 2 particles, the ZrO 2 particles, and the CeO 2 —ZrO 2 solid solution particles act as a barrier that prevents the same oxide particles from aggregating with each other. When the Al 2 O 3 particles serve as partition walls and aggregation of the CeO 2 particles or CeO 2 —ZrO 2 solid solution particles is prevented, the solid-phase reaction between these particles is prevented, so that they are exposed to high temperatures. Even in such a case, grain growth of the support (complex metal oxide) is suppressed, and the specific surface area of the support is sufficiently maintained. As described above, when the growth of the support (composite metal oxide) at high temperatures is suppressed, the growth of the copper oxide supported on the support is also sufficiently suppressed. Furthermore, in the present invention, since CeO 2 is contained in the carrier at a ratio of 50% by mass or more, the number of active CuO species (number of active sites) interacting with CeO 2 in the carrier is sufficiently secured. And can exhibit sufficiently high CO oxidation performance. Therefore, in the present invention, a sufficiently high CO oxidation performance can be exhibited from a low temperature of about 200 ° C., and a sufficiently high CO catalyst activity can be maintained even when the catalyst is exposed to a high temperature of about 800 ° C. They guess.

Further, as the temperature of copper oxide increases, Cu 2 O tends to be more thermodynamically stabilized than CuO. When such copper oxide supported on a carrier consisting of a carrier or CeO 2 -ZrO 2 solid solution consisting of CeO 2, as described above, since the copper oxide by the interaction of the carrier is easily more reduced copper oxide The tendency to become Cu 2 O and stabilize becomes more prominent. Therefore, when a support made of CeO 2 or a support made of CeO 2 —ZrO 2 solid solution is used as a support for supporting copper oxide, usually, the higher the temperature, the more the reaction is represented by the reaction formula (1) in the CO oxidation reaction. Reaction is promoted while the reaction represented by the reaction formula (2) is suppressed, the temperature increases, and the number of active species (CuO) (number of active sites) decreases to reduce CO oxidation. The performance was degraded. Therefore, although the CO oxidation activity is sufficiently exhibited from a low temperature, it is difficult to reach a high CO conversion rate (for example, 90%) even if the temperature is slightly increased from there. On the other hand, in the present invention, since the composite metal oxide containing Al 2 O 3 together with CeO 2 and ZrO 2 is used as the copper oxide support, the surface of Al 2 O 3 in the support is used. And a part of CuO react with each other to form a spinel complex oxide CuAl 2 O 4 or a complex oxide similar thereto, and copper oxide is stabilized as CuO on Al 2 O 3 (spinel Even if the type complex oxide CuAl 2 O 4 is not completely formed, CuO tends to be stable on the Al 2 O 3 support. Therefore, on a support containing Al 2 O 3 together with CeO 2 and ZrO 2 , the valence of copper is not fixed to a monovalent regardless of the surrounding temperature conditions, and the bivalent and 1 It changes moderately between the price. Therefore, by supporting copper oxide on a support made of a composite metal oxide containing CeO 2 , ZrO 2 and Al 2 O 3 , the CO oxidation reaction (the above reaction formulas (1) and (2)) can be efficiently performed. This makes it possible to prevent the active species (CuO) from being reduced, so that stable high CO oxidation performance can be exhibited even at high temperatures, and a sufficiently high CO conversion rate even at sufficiently low temperatures. The present inventors speculate that this can be achieved.

  According to the present invention, a sufficiently high CO oxidation performance can be exhibited from a low temperature of about 200 ° C., and even when exposed to a high temperature of about 800 ° C., the deterioration of the CO oxidation performance of the catalyst can be sufficiently suppressed. In addition, it is possible to provide a CO oxidation catalyst capable of achieving a sufficiently high CO conversion rate from a sufficiently low temperature and an exhaust gas purification method using the same.

It is a graph which shows the 50-% CO conversion temperature of the CO oxidation catalyst obtained in Examples 1-2 of the initial state and Comparative Examples 1-7. It is a graph which shows 90% CO conversion temperature of the CO oxidation catalyst obtained in Examples 1-2 of the initial state, Comparative Example 1, and Comparative Examples 4-5. It is a graph which shows the 50-% CO conversion temperature of the CO oxidation catalyst obtained in Examples 1-2 and Comparative Examples 1-7 after a heat test. It is a graph which shows 90% CO conversion temperature of the CO oxidation catalyst obtained in Examples 1-2, Comparative Example 1, and Comparative Examples 4-5 after a heat test. Is H 2-TPR spectrum of CO oxidation catalyst obtained in Examples 1 and 2 and Comparative Examples 1 to 3 in the initial state (graph of concentration of H 2 in exit gas temperature). It is a graph which shows the specific surface area of the CO oxidation catalyst obtained by the initial state and the Examples 1-2 after the said heat test, and Comparative Examples 1-7.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.

  First, the CO oxidation catalyst of the present invention will be described. That is, the CO oxidation catalyst of the present invention is composed of a composite metal oxide containing ceria, zirconia, and alumina, and the content of ceria in the composite metal oxide is 50% by mass or more. And a supported copper oxide.

The composite metal oxide used as the carrier in the CO oxidation catalyst of the present invention contains ceria. The content of such ceria is 50% by mass or more with respect to the total amount of the composite metal oxide. When the content of ceria is less than the lower limit, CuO that is easily reduced by the interaction with CeO 2 is not sufficiently formed, and the CO oxidation performance of the catalyst is lowered. Moreover, as content of ceria in the said composite metal oxide, it is more preferable that it is 50-95 mass%, and it is still more preferable that it is 70-90 mass%. If the content of ceria is less than the lower limit, CuO that tends to be reduced tends not to be sufficiently formed. On the other hand, if the upper limit is exceeded, the oxide particles of the carrier easily grow when exposed to high temperatures. The heat resistance tends to decrease.

The composite metal oxide contains zirconia. Such zirconia is a carrier having a neutral property with respect to ceria and alumina, and by containing this, CuO can be reduced by higher OSC performance compared to the case where ceria is used alone. This can be facilitated. As content of such zirconia, it is more preferable that it is 2-45 mass% with respect to the total amount of composite metal oxide, and it is still more preferable that it is 5-20 mass%. When the content of zirconia is less than the lower limit, the effect of easily reducing CuO due to OSC performance tends to decrease. On the other hand, when the content exceeds the upper limit, CuO is easily reduced by interaction with CeO 2. The number of active species (number of active sites) tends to decrease. Further, in such a composite metal oxide, since higher OSC performance can be obtained, it is preferable that the ceria and the zirconia form a solid solution. That is, in such a composite metal oxide, it is preferable that at least a part of ceria and at least a part of zirconia form a cubic ceria-zirconia solid solution.

  Furthermore, the composite metal oxide contains alumina. Such alumina has a property that it does not dissolve in ceria, zirconia and their solid solutions. Therefore, alumina in the carrier and ceria, zirconia, and their solid solutions serve as diffusion barriers, thereby suppressing aggregation of the same kind of oxides and further suppressing grain growth of the supported copper oxide. It becomes possible to do. As content of such an alumina, it is preferable that it is 2-45 mass% with respect to the total amount of complex metal oxide, and it is more preferable that it is 5-20 mass%. When the content of alumina is less than the lower limit, the thermal stability of the composite metal oxide (support) tends to decrease. On the other hand, when the upper limit is exceeded, the number of CuO active species that are easily reduced (activity) The number of sites) tends to decrease.

  In such a composite metal oxide, it is preferable that the ceria, the zirconia, and the alumina are dispersed on the nm scale from the viewpoint of achieving both high CO oxidation activity and high heat resistance. Here, “nm-scale dispersion” means that the composite metal oxide is divided into a plurality of minute regions having a cross-sectional diameter of 1 nm or less and the composition is measured using a microanalyzer having high resolution. It means a state in which most of the minute region (preferably 90% or more of all measurement points) is formed by a plurality of components. As an apparatus capable of such microanalysis, for example, a field emission scanning transmission microscope (FE-STEM) such as “HD-2000” manufactured by Hitachi, Ltd. may be mentioned. Furthermore, the “microscopic area having a cross-sectional diameter of 1 nm or less” as used herein refers to a composite in which this beam is transmitted when the composite metal oxide is irradiated with a beam having a diameter of 1 nm or less in measurement using a microanalyzer. It means the region in the metal oxide. Moreover, in the measurement using such a microanalyzer, it is preferable to measure at any five or more measurement points on the composite metal oxide.

  Further, as such a composite metal oxide, when the composite metal oxide is divided into a plurality of microregions having a cross-sectional diameter of 1 nm or less, the contents of cerium, zirconium, and aluminum in the microregions are respectively The ratio of cerium, zirconium and aluminum is within the range of ± 20% (preferably ± 10%), and such a micro area exists at a ratio of 90% or more of the total micro area (all measurement points). Is preferred. In this way, the composite metal oxide in which the composition of most of the microregions is almost the same as the charged composition has a substantially uniform composition (each metal oxide is uniformly dispersed), and has a higher degree of CO. It tends to show oxidative activity. In addition, “the charge ratio of cerium, aluminum and zirconium” means the ratio of the respective charge amounts of cerium, aluminum and zirconium to the total charge amount of metal atoms forming the composite metal oxide (ratio of the number of elements, unit:%) ). Moreover, “within the range of the preparation ratio ± 20%” means, for example, 50 to 90% when the preparation ratio is 70%.

  Further, in such a composite metal oxide, an aggregate of ceria particles, zirconia particles, and alumina particles (in the aggregate, a part or all of the ceria particles and the zirconia particles are ceria-zirconia solid solution particles. It is also possible that Such agglomerates of particles provide a higher specific surface area, and pores are formed as voids between the particles. CO can be diffused into the pores to efficiently oxidize and purify CO. It becomes possible.

Although such is not particularly limited as specific surface area of the composite metal oxide is preferably from 10 to 1000 m 2 / g, and more preferably 20 to 500 m 2 / g. When the specific surface area exceeds the upper limit, the support tends to sinter, and the heat resistance of the resulting catalyst tends to decrease. On the other hand, when the specific surface area is lower than the lower limit, CuO that interacts with CeO 2 is sufficiently formed. There is a tendency not to be. In addition, the specific surface area of such a composite metal oxide is 2 to 200 m 2/5 even after calcination at 800 ° C. for 5 hours from the viewpoint of sufficiently maintaining the CO oxidation activity even after being exposed to a high temperature. It is preferable to be in the range of g. Such a specific surface area can be calculated as a BET specific surface area from an adsorption isotherm using a BET isotherm adsorption formula.

  Furthermore, when pores are formed in such a composite metal oxide, the pores are preferably mesopores. As used herein, “mesopore” means a pore having a pore diameter ranging from a lower limit of 3.5 nm to 100 nm that can be measured using a mercury porosimeter.

Further, in such a composite metal oxide, the pore volume of the mesopores is 0.07 cm 3 / g or more even after calcination for 5 hours at 600 ° C. and even after calcination for 5 hours at 800 ° C. preferably has at 0.04 cm 3 / g or more, 0.10 cm 3 / g or more even after the firing of 0.13 cm 3 / g or more in it and 5 hours at 800 ° C. even after firing for 5 hours at 600 ° C. And more preferably 0.19 cm 3 / g or more even after baking at 600 ° C. for 5 hours and 0.15 cm 3 / g or more even after baking at 800 ° C. for 5 hours. . Thus, by supporting copper oxide on a carrier containing a composite metal oxide having a sufficiently secured pore volume, it becomes possible to support copper oxide in a highly dispersed state in mesopores. And in the catalyst which supported copper oxide in this way, since a mesopore becomes a reaction field of CO oxidation reaction, it becomes possible to achieve a higher degree of CO oxidation activity. In the composite metal oxide, the grain growth due to aggregation of the same metal oxide in the composite metal oxide is sufficiently suppressed even after being exposed to a high temperature due to the barrier action of the alumina particles. Therefore, the pore volume and the like of the pores can be sufficiently maintained.

In such a composite metal oxide, the crystallite diameter of ceria calculated from the half width of the peak of CeO 2 (220) by X-ray diffraction is 5 to 10 nm after baking at 600 ° C. for 5 hours. A film having a thickness of 10 to 20 nm after baking at 800 ° C. for 5 hours is preferable. When the ceria crystallite diameter is in the above range, sintering at high temperatures is further suppressed, and a sufficient pore volume tends to be ensured even after exposure to high temperatures.

  Further, when such a composite metal oxide is in a powder form, the average particle diameter of the powder (secondary particles when the composite metal oxide is an aggregate) is not particularly limited. .1 to 100 μm is preferable, and 1 to 10 μm is more preferable. When the average particle size is less than the lower limit, the support tends to be easily sintered under high temperature conditions. On the other hand, when the upper limit is exceeded, CO hardly diffuses and the CO oxidation catalytic activity tends to decrease. It is in. In addition, the average particle diameter of such a composite metal oxide can be appropriately changed by a usual method (for example, a method of pulverizing with a mortar or a cold isostatic pressing method (CIP)). Further, after the production of the CO oxidation catalyst, the average particle size of the powder of the composite metal oxide (support) in the catalyst may be changed by changing the average particle size of the catalyst by a usual method.

  In addition, the method for producing such a composite metal oxide support is not particularly limited. For example, the composite is obtained by sufficiently stirring a solid solution powder of commercially available ceria and zirconia and a commercially available alumina powder. Method (I) for obtaining a carrier comprising a metal oxide, an aqueous solution in which a cerium compound, a zirconium compound and an aluminum compound are dissolved, or a solution containing water, and then adding an alkaline solution to the aqueous solution or solution to add a ceria precursor A method (II) for obtaining a support made of a composite metal oxide by precipitating a solid body, a zirconia precursor and an alumina precursor as a precipitate, and firing the obtained precipitate (precipitate precipitate) Can do. Among the methods for producing a carrier comprising such a composite metal oxide, it is possible to obtain a carrier comprising a composite metal oxide in which ceria, zirconia and alumina are dispersed on the nm scale. It is preferable to employ method (II). In the case of adopting the method (II), after the ceria precursor and the zirconia precursor are simultaneously precipitated as a precipitate (precipitate precipitate), the coprecipitate is baked, so that at least the ceria A solid solution of ceria and zirconia is formed by a part of the material and a part of the zirconia. Hereinafter, the method (II) for obtaining a carrier composed of such a composite metal oxide will be specifically described.

  As the cerium compound, aluminum compound and zirconium compound used in the method (II), salts of sulfate, nitrate, chloride, acetate, etc. of the metal can be used. Moreover, water and alcohol are mentioned as a solvent which melt | dissolves such a salt. Further, for example, an aqueous solution containing aluminum nitrate may be a mixture of aluminum hydroxide, nitric acid and water. The amount of such cerium compound, aluminum compound, and zirconium compound used is not particularly limited except that the content of ceria in the obtained carrier is 50% by mass or more, depending on the intended design. The usage amount can be changed as appropriate.

  The precursor precipitate is added to the aqueous solution or the solution containing water in which the cerium compound, the zirconium compound and the aluminum compound are dissolved, and the pH of the aqueous solution or the solution containing water is adjusted by adding the alkaline solution. Can be deposited. Also, in this way, when depositing the precursor precipitates, a method of depositing the precursor precipitates almost simultaneously so that the precursor precipitates are more uniformly dispersed. As such a method, for example, a method of instantly adding an alkaline solution to the aqueous solution or the solution and stirring vigorously, or a peroxidation of the aqueous solution or the solution is used. A method of adding the alkaline solution after adding hydrogen water or the like to adjust the pH of the aqueous solution or the solution to a pH at which each precursor starts to precipitate can be employed. Further, when depositing the precursor precipitate, a method of depositing the alumina precursor precipitate before the other precursor precipitate (or vice versa) may be employed, In this case, for example, it takes a long time (preferably a time of 10 minutes or more) to add the alkaline solution, and the pH of the aqueous solution or the solution is monitored to monitor each precursor. Adopting a method that adjusts the pH stepwise so that the precipitate of the body precipitates, or a method in which a buffer solution is added so that the pH of the aqueous solution or the solution is kept at the pH at which the precipitate of each precursor is precipitated. May be.

  Moreover, as an alkaline solution used for such a method (II), the aqueous solution or alcohol solution which ammonia water, ammonium carbonate, sodium hydroxide, potassium hydroxide, sodium carbonate etc. melt | dissolved is mentioned. Among these alkaline solutions, ammonia water, an aqueous solution of ammonium carbonate, or an alcohol solution is more preferable because it is easy to volatilize and remove the composite metal oxide when firing. Further, from the viewpoint of promoting the precipitation reaction of the precursor precipitate, the pH of the alkaline solution is preferably adjusted to 9 or more.

  Further, in the method (II) for producing such a carrier, a step of aging the precursor precipitate may be performed as necessary before firing the precursor precipitate. As such an aging step, the step of heating the aqueous solution or the solution in which the precursor precipitate is deposited to an aging temperature of room temperature or higher (more preferably 100 to 200 ° C., more preferably 100 to 150 ° C.). It is preferable to adopt. Thus, when the precursor precipitate is aged, the heating heat promotes dissolution and reprecipitation of the precipitate in the aqueous solution or the solution, and ceria in the obtained composite metal oxide. It is possible to obtain a composite metal oxide in which particles of each metal oxide having relatively high crystallinity and an appropriate particle diameter (preferably 5 to 10 nm) are aggregated. Here, when the aging temperature is less than the lower limit, the accelerating effect by aging is small, and the time required for aging tends to be long.On the other hand, when the upper limit is exceeded, the water vapor pressure becomes extremely high. It becomes necessary and the manufacturing cost tends to increase. Further, the heating time at such an aging temperature is preferably about 0.5 to 10 hours.

  Furthermore, in the method (II) for producing such a carrier, after obtaining the precursor precipitate, the precipitate is fired. Such firing may be performed in the air. Moreover, as a baking temperature in such a baking process, 300-800 degreeC is preferable. When the calcination temperature is less than the lower limit, the heat stability of the resulting composite metal oxide carrier tends to decrease. On the other hand, when the upper limit is exceeded, the specific surface area of the resulting composite metal oxide decreases. Tend to.

  As described above, the method (II) for producing the support made of the composite metal oxide has been specifically described as a preferred method for producing the support made of the composite metal oxide used in the present invention. The method for producing a support made of an oxide is not limited to the above embodiment. For example, after obtaining a solution containing a precursor precipitate in the same manner as in the above method (II), the solution is heated as it is to evaporate the solvent to dry the precipitate, and then fired. May be. In this case, in order to allow the precipitate to age during the drying of the precipitate, it is preferable to dry the precipitate at the aging temperature. Moreover, you may utilize separately another component which can be utilized for a CO oxidation catalyst in the range which does not impair the effect of this invention.

  In addition, the CO oxidation catalyst of the present invention includes copper oxide supported on the carrier together with the carrier. The amount of copper oxide supported is not particularly limited, but is preferably 0.5 to 30% by mass, particularly preferably 1 to 20% by mass, based on the total amount of the carrier and the copper oxide. . If the amount of the copper oxide supported is less than the lower limit, sufficient activity may not be imparted to the resulting CO oxidation catalyst. On the other hand, if the amount exceeds the upper limit, the support containing the composite metal oxide may not be provided. There is an increase in the number of coarse CuO particles not supported on the surface, and the activity tends to decrease.

  As such a method for supporting copper oxide, for example, a predetermined amount of a copper compound is included by impregnating a support containing the composite metal oxide with a solution containing a copper (Cu) compound at a predetermined concentration. A method in which the solution is supported on the carrier and then baked can be employed. At this time, the support containing the composite metal oxide may be used in the form of powder such as pellets, or the support containing the composite metal oxide is known in advance such as a cordierite honeycomb substrate. You may use it in the form fix | immobilized by the coating etc. to the base material. Moreover, it does not restrict | limit especially as such a compound of copper (Cu), Salts, such as copper nitrate, acetate, a chloride, a sulfate, can be used.

  Moreover, you may implement in the air | atmosphere the baking process in such a copper oxide loading method. Moreover, as a baking temperature in such a baking process, 200-600 degreeC is preferable. When such a calcination temperature is less than the lower limit, the copper compound is not sufficiently thermally decomposed, it becomes difficult to support copper oxide on the support, and there is a tendency that sufficient CO oxidation activity cannot be obtained. When the upper limit is exceeded, the supported copper oxide grows and the CO oxidation activity tends to decrease. The firing time is preferably 0.1 to 100 hours. When the calcination time is less than the lower limit, the copper compound is not sufficiently thermally decomposed, and it becomes difficult to support copper oxide, and the resulting catalyst tends to have low CO oxidation activity. Even if the upper limit is exceeded, no further effect is obtained, leading to an increase in the cost for preparing the catalyst.

  Further, the form of the CO oxidation catalyst of the present invention is not particularly limited, and can be used by appropriately forming into various forms according to the application, for example, pellet form, monolith form, honeycomb form, foam form, etc. These may be used after being molded into various forms (may be supported on a known base material such as a cordierite honeycomb base material).

  In addition, such a CO oxidation catalyst of the present invention can be appropriately used for applications that require oxidation and removal of CO, and in particular, high CO oxidation performance can be obtained from a low temperature and high temperature conditions can be obtained. Since deterioration of the CO oxidation performance below is sufficiently suppressed, it can be suitably used as a catalyst for purifying exhaust gas from an automobile internal combustion engine (particularly preferably a diesel engine).

  Although the CO oxidation catalyst of the present invention has been described above, the exhaust gas purification method of the present invention will be described below.

  The exhaust gas purification method of the present invention is a method characterized by bringing exhaust gas into contact with the CO oxidation catalyst of the present invention and oxidizing and removing carbon monoxide gas (CO gas) in the exhaust gas.

  Such an exhaust gas purification method is a method of using the CO oxidation catalyst of the present invention to purify the CO gas in the exhaust gas. By contacting the exhaust gas with the CO oxidation catalyst of the present invention, the CO oxidation catalyst In this method, carbon monoxide gas (CO gas) is oxidized and removed using the oxidation activity of the. Further, the method for contacting the exhaust gas is not particularly limited. For example, the CO oxidation catalyst of the present invention is disposed in the exhaust gas pipe through which the gas discharged from the internal combustion engine circulates. The exhaust gas from the internal combustion engine may be contacted. Further, in such an exhaust gas purification method, since the CO oxidation catalyst of the present invention is used, CO can be sufficiently purified even under relatively low temperature conditions.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

Example 1
First, 0.2 mol (75.1 g) of aluminum nitrate nonahydrate was added to 2000 ml of ion-exchanged water, and dissolved by stirring for 5 minutes with a propeller stirrer. Next, the concentration of CeO 2 in terms to obtain a mixed aqueous solution was stirred for 5 minutes added (corresponding to 0.43 mol in terms of CeO 2) 28 wt% of aqueous cerium nitrate solution 265g to the solution. Next, an aqueous solution in which 0.068 mol (18.1 g) of zirconyl nitrate dihydrate was dissolved in 30 g of ion-exchanged water was added to the mixed aqueous solution and stirred for 5 minutes to obtain a mixed aqueous solution. And 177 g of 25 mass% ammonia water was added to the obtained mixed aqueous solution instantaneously, and it stirred for 10 minutes to precipitate the precipitate, and obtained the aqueous solution containing a precipitate. Next, the aqueous solution containing the precipitate was heated at 120 ° C. for 2 hours under a pressure of 2 atm to age the precipitate. Next, the aqueous solution containing the precipitate thus aged is heated to 400 ° C. at a heating rate of 100 ° C./hour, pre-baked at that temperature (400 ° C.) for 5 hours, and then further heated at 600 ° C. for 5 hours. By firing for a time, a powder of a composite metal oxide containing ceria, zirconia and alumina was obtained. The composite metal oxide powder (support) thus obtained is composed of about 80% by mass of CeO 2 , about 9% by mass of ZrO 2 and about 11% by mass of Al 2 O 3 . .

  Using 40 g of the composite metal oxide powder thus obtained, an aqueous solution (about 200 mL) in which 9.9 g of copper (II) nitrate trihydrate was dissolved in the composite metal oxide powder was used. After impregnation, the aqueous solution was supported on the composite metal oxide powder to obtain a copper nitrate supporting carrier. Next, the copper nitrate-supported carrier was heated on a hot stirrer at about 200 ° C. for about 5 hours to evaporate the water in the aqueous solution supported on the carrier to dry the copper nitrate-supported carrier. Next, the copper nitrate-supported carrier after the evaporation to dryness is further dried at 110 ° C. overnight (about 16 hours), and then calcined in the atmosphere at a temperature of 350 ° C. for 3 hours. A CO oxidation catalyst in which copper oxide (CuO) was supported on the powder was obtained. The amount of CuO supported in such a CO oxidation catalyst was 7.5% by mass. The CO oxidation catalyst thus obtained was compacted by a conventional method and then crushed and formed into pellets having a diameter of 0.5 to 1 mm.

  Hereinafter, characteristics (specific surface area, dispersibility of each metal atom) of the carrier produced in Example 1 will be described.

<Specific surface area>
The specific surface area of the mixed metal oxide powder obtained in Example 1 was measured at a liquid nitrogen temperature (−196 ° C.) using a fully automatic specific surface area measuring device (trade name “MICRO SORP4232II” manufactured by MICRO DATA Corporation). It was calculated by the BET single point method using N 2 adsorption. As a result, it was confirmed that the specific surface area of the composite metal oxide powder thus obtained was 100 m 2 / g.

<Pore distribution>
When the pore distribution of the composite metal oxide powder obtained in Example 1 was measured using a mercury porosimeter, the composite metal oxide powder had mesopores (average pore diameter of 30 nm). The volume was found to be 0.20 mL / g.

<Average particle size of primary particles>
The average particle diameter of each metal oxide particle (primary particle) in the composite metal oxide powder obtained in Example 1 was calculated from the half width of the peak of CeO 2 (220) by X-ray diffraction. It was found that the average particle diameter of ceria particles (primary particles) in the metal oxide was 7 nm.

<Dispersibility of each metal atom in powder of composite metal oxide>
The dispersibility of the metal atoms in the powder of the composite metal oxide obtained in Example 1 was measured using a field emission scanning transmission microscope (FE-STEM, “HD-2000” manufactured by Hitachi, Ltd.) as follows. Observed by the method. That is, in the FE-STEM, one non-overlapping particle (primary particle of ceria) in the composite metal oxide powder is irradiated with an electron beam with a diameter of 0.5 nm at an acceleration voltage of 200 kV, and the characteristic X generated from the sample The line is detected by an EDX detector (“VATAGE EDX system” manufactured by NCRAN) attached to the FE-STEM, and elemental analysis in a micro region having a cross-sectional diameter of 0.5 nm is performed on the composite metal oxide particles. Was done. Such elemental analysis was carried out on arbitrary five minute regions. Note that “a microscopic region having a cross-sectional diameter of 0.5 nm” means a region in the composite metal oxide through which an electron beam with a diameter of 0.5 nm irradiated to the composite metal oxide particles is transmitted. As a result of the elemental analysis in the minute region having a cross-sectional diameter of 0.5 nm, the obtained composite metal oxide powder contains Ce, Zr and Al in any minute region subjected to the elemental analysis. It was confirmed that the ratios were within the ranges of these charging ratios (Ce = 61%, Zr = 10%, Al = 29%) ± about 10%. That is, the composite metal oxide powder contains a metal element having a substantially charged ratio in any of the minute regions having a cross-sectional diameter of 0.5 nm, and ceria, zirconia, and alumina are dispersed on the nm scale. It was confirmed.

(Example 2)
First, CeO 2 —ZrO 2 solid solution powder (manufactured by JGC Corporation: CeO 2 content 87 wt%, ZrO 2 content 13 wt%, specific surface area 150 m 2 / g, average particle size 9 nm) 35 to ion exchange water 200 g 0.6 g and 4.4 g of Al 2 O 3 powder (manufactured by JGC Universal Co., Ltd .: specific surface area 150 m 2 / g, average particle size 10 nm) were added and stirred with a magnetic stirrer for 1 hour, and then copper (II) nitrate was further added. 9.9 g of trihydrate was added and stirred for 1 hour to obtain a mixed solution. Next, the mixed solution is heated on a hot stirrer at about 200 ° C. for about 5 hours to evaporate the water and dry the solid content in the mixed solution. And then dried overnight (about 16 hours) and calcined in the atmosphere at a temperature of 350 ° C. for 3 hours to obtain a CO oxidation catalyst. In such a CO oxidation catalyst, the support is formed of a mixture (complex metal oxide) of CeO 2 —ZrO 2 solid solution and Al 2 O 3 powder, and the supported amount of CuO in the catalyst is 7.5% by mass. It was. Further, the CO oxidation catalyst thus obtained was compacted by a conventional method, then crushed and formed into pellets having a diameter of 0.5 to 1 mm.

(Comparative Example 1)
40 g of CeO 2 powder (manufactured by Anan Kasei Co., Ltd .: specific surface area 150 m 2 / g, average particle diameter 16 nm) was used as the carrier, and an aqueous solution (about 9.9 g) of the copper (II) nitrate trihydrate dissolved in the carrier. 200 mL) is impregnated and supported to obtain a copper nitrate supported carrier, and then the copper nitrate supported carrier is heated on a hot stirrer at about 200 ° C. for about 5 hours to evaporate water in the aqueous solution and The copper support was dried. Next, the copper nitrate-supported carrier after the evaporation to dryness is further dried at 110 ° C. overnight (about 16 hours), and then calcined in the atmosphere at 350 ° C. for 3 hours to obtain the CeO 2 powder ( A CO oxidation catalyst for comparison, in which copper oxide (CuO) was supported on the support, was obtained. The amount of CuO supported in such a CO oxidation catalyst was 7.5% by mass. The CO oxidation catalyst thus obtained was compacted by a conventional method and then crushed and formed into pellets having a diameter of 0.5 to 1 mm.

(Comparative Example 2)
For comparison, in the same manner as in Comparative Example 1, except that ZrO 2 powder (manufactured by Daiichi Rare Element Chemical Industry Co., Ltd .: specific surface area 100 m 2 / g, 40 g) was used as the carrier instead of CeO 2 powder (40 g). A CO oxidation catalyst was obtained. The amount of CuO supported in such a CO oxidation catalyst was 7.5% by mass. The CO oxidation catalyst thus obtained was compacted by a conventional method and then crushed and formed into pellets having a diameter of 0.5 to 1 mm.

(Comparative Example 3)
Comparison was made in the same manner as in Comparative Example 1 except that Al 2 O 3 powder (manufactured by JGC Universal Co., Ltd .: specific surface area 150 m 2 / g, average particle size 10 nm, 40 g) was used as the carrier instead of CeO 2 powder (40 g). A CO oxidation catalyst for was obtained. The amount of CuO supported in such a CO oxidation catalyst was 7.5% by mass. The CO oxidation catalyst thus obtained was compacted by a conventional method and then crushed and formed into pellets having a diameter of 0.5 to 1 mm.

(Comparative Example 4)
Instead of CeO 2 powder (40 g), CeO 2 —ZrO 2 solid solution powder (manufactured by JGC Corporation: CeO 2 content 87 wt%, ZrO 2 content 13 wt%, specific surface area 150 m 2 / g, average particle diameter 9 nm, A CO oxidation catalyst for comparison was obtained in the same manner as in Comparative Example 1 except that 40 g) was used as the carrier. The amount of CuO supported in such a CO oxidation catalyst was 7.5% by mass. The CO oxidation catalyst thus obtained was compacted by a conventional method and then crushed and formed into pellets having a diameter of 0.5 to 1 mm.

(Comparative Example 5)
First, 0.2 mol (75.1 g) of aluminum nitrate nonahydrate was added to 2000 ml of ion-exchanged water, and dissolved by stirring for 5 minutes with a propeller stirrer. Next, the concentration of CeO 2 in terms to obtain a mixed aqueous solution was stirred for 5 minutes adding (corresponding to 0.5 mol terms of CeO 2) 28 wt% of aqueous cerium nitrate solution 304g to the solution. And 177 g of 25 mass% ammonia water was added to the obtained mixed aqueous solution, and it stirred for 10 minutes, and obtained the aqueous solution containing a deposit. Next, the aqueous solution containing the precipitate was heated at 120 ° C. for 2 hours under a pressure of 2 atm to age the precipitate. Next, the aqueous solution containing the precipitate thus aged is heated to 400 ° C. at a heating rate of 100 ° C./hour, pre-baked at that temperature (400 ° C.) for 5 hours, and then further heated at 600 ° C. for 5 hours. A composite metal oxide powder containing ceria and alumina was obtained by firing for a period of time. The composite metal oxide powder (support) for comparison obtained in this manner is composed of about 89% by mass of CeO 2 and about 11% by mass of Al 2 O 3 .

  Using 40 g of the composite metal oxide powder thus obtained, the composite metal oxide powder was impregnated with an aqueous solution (about 200 mL) in which 9.9 g of copper nitrate trihydrate was dissolved. The aqueous solution was supported on the powder of the composite metal oxide to obtain a copper nitrate supporting carrier. Next, the copper nitrate carrier was heated on a hot stirrer at about 200 ° C. for about 5 hours to evaporate the water in the aqueous solution and dry the copper nitrate carrier. Next, the copper nitrate-supported carrier after the evaporation to dryness is further dried overnight at 110 ° C., and then calcined in the atmosphere at a temperature condition of 350 ° C. for 3 hours, and copper oxide ( A CO oxidation catalyst carrying CuO) was obtained. The amount of CuO supported in such a CO oxidation catalyst was 7.5% by mass. The CO oxidation catalyst thus obtained was compacted by a conventional method and then crushed and formed into pellets having a diameter of 0.5 to 1 mm.

Further, in Comparative Example 5, the same method as the evaluation method of the characteristics (specific surface area, pore volume, pore distribution, average particle size, dispersibility of each metal atom) of the carrier adopted in Example 1 was adopted. When the characteristics of the manufactured composite metal oxide powder (support) for comparison were evaluated, the specific surface area was 90 m 2 / g, and mesopores (average pore diameter of 30 nm) were formed in the support. In addition, it is confirmed that the average particle diameter of the primary particles is 7 nm, the pore volume is 0.20 mL / g, and the dispersibility of each metal atom is in any minute region where the elemental analysis is performed. The charging ratio (Ce = 71%, Al = 29%) ± about 10%, and it was found that ceria and alumina were dispersed in nm scale in the support.

(Comparative Example 6)
After dissolving 1.48 g of chloroauric acid aqueous solution (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) having a gold (Au) content of 30% by weight in about 90 ° C. ion-exchanged water (3000 mL), a solution was obtained. While stirring with a stirrer, 1N NaOH aqueous solution was added dropwise to adjust the pH to about 9.0. Next, after adding 11.8 g of titania (TiO 2 ) powder (manufactured by Degussa: anatase-rutile mixed phase, specific surface area 60 m 2 / g) to the solution, 1N NaOH aqueous solution is further added. The mixture was stirred for 1 hour while maintaining the pH at about 9.0. Subsequently, after filtering the said solution and taking out solid content, the said solid content was dried under reduced pressure on the temperature conditions of room temperature (25 degreeC). The solid content after drying was calcined in the atmosphere at a temperature of 350 ° C. for 3 hours to obtain a CO oxidation catalyst for comparison in which Au was supported on TiO 2 powder. The amount of Au supported in such a CO oxidation catalyst was 3.6% by mass. The CO oxidation catalyst thus obtained was compacted by a conventional method and then crushed and formed into pellets having a diameter of 0.5 to 1 mm.

(Comparative Example 7)
40 g of Al 2 O 3 powder (manufactured by JGC Universal Co., Ltd .: specific surface area 150 m 2 / g, average particle diameter 10 nm) was used as a carrier, and a predetermined amount of dinitrodiammine platinum aqueous solution with respect to the carrier had a Pt loading of 1% by mass After impregnating and supporting to obtain a platinum-supported carrier, the platinum-supported carrier is heated on a hot stirrer at about 200 ° C. for about 5 hours, so that the platinum-supported Water was evaporated to dry the platinum-supported carrier. Next, the platinum-supported carrier after the evaporation to dryness was further dried at 110 ° C. overnight, and then calcined in the atmosphere at 500 ° C. for 3 hours, whereby Pt was supported on the Al 2 O 3 powder. A CO oxidation catalyst for comparison was obtained. The amount of Pt supported in such a CO oxidation catalyst is 1% by mass. The CO oxidation catalyst thus obtained was compacted by a conventional method and then crushed and formed into pellets having a diameter of 0.5 to 1 mm.

[Evaluation of CO oxidation catalyst performance obtained in Examples 1-2 and Comparative Examples 1-7]
<Heat resistance test>
Each of the CO oxidation catalysts (initial states) obtained in Examples 1 and 2 and Comparative Examples 1 to 7 was used in an amount of 2.5 g, and each catalyst was separately placed in a 15 ml magnetic crucible, and air was supplied at 1000 ml / min. The catalyst after the heat test was manufactured by heating for 5 hours at 800 ° C. while supplying.

<Measurement of CO oxidation activity>
Using each of the CO oxidation catalysts obtained in Examples 1-2 and Comparative Examples 1-7 in the initial state and each of the CO oxidation catalysts obtained in Examples 1-2 and Comparative Examples 1-7 of the heat resistance test, respectively. The CO oxidation activity of each catalyst was measured (the “initial state” here refers to a state in which the heat resistance test was not performed after the catalyst was manufactured). That is, first, using a fixed bed flow type reactor, CO (0.4% by volume), O 2 (10% by volume), CO 2 ( 10% by volume), H 2 O (10% by volume) and N 2 (balance) while supplying a model gas at 7000 ml / min, the catalyst bed temperature (gas temperature entering the catalyst) was 10 ° C./min. The temperature was raised to 350 ° C. at a rate of temperature rise, heated at 350 ° C. for 10 minutes, and then subjected to a treatment (pretreatment) for cooling until the bed temperature of the catalyst (the temperature of the gas entering the catalyst) reached 70 ° C. Next, while supplying the model gas to the pretreated catalyst at 7000 ml / min, the catalyst bed temperature (temperature of the gas entering the catalyst) is increased from 70 ° C. to 520 ° C. at a rate of 10 ° C./min. The temperature was raised to. Then, the CO concentration in the gas emitted from the catalyst during such temperature rise (the gas discharged from the quartz reaction tube after contacting the catalyst) is measured using a continuous gas analyzer, and the CO concentration in the model gas is measured. The CO conversion rate is calculated from the CO concentration in the output gas and the temperature when the CO conversion rate reaches 50% (50% CO conversion temperature) and the temperature when the CO conversion rate reaches 90% (90 % CO conversion temperature). Of the obtained results, the 50% CO conversion temperature of each CO oxidation catalyst obtained in Examples 1-2 in the initial state and Comparative Examples 1-7 is shown in FIG. 2, 90% CO conversion temperature of each CO oxidation catalyst obtained in Comparative Example 1 and Comparative Examples 4 to 5 is shown in FIG. 2 and obtained in Examples 1-2 and Comparative Examples 1-7 after the heat resistance test. The 50% CO conversion temperature of each CO oxidation catalyst is shown in FIG. 3, and the 90% CO conversion temperature of each CO oxidation catalyst obtained in Examples 1-2, Comparative Example 1 and Comparative Examples 4-5 after the heat resistance test is shown. As shown in FIG.

As is clear from the results shown in FIG. 1 (50% CO conversion temperature of the catalyst in the initial state), the CO oxidation catalyst obtained in Examples 1 and 2 in the initial state, Comparative Example 1 and Comparative Example 4 in the initial state. It was confirmed that the CO oxidation catalyst obtained in ˜5 had higher CO oxidation activity than the CO oxidation catalyst obtained in Comparative Examples 2, 3, and 7 in the initial state. From these results, in the CO oxidation catalyst (Examples 1-2, Comparative Example 1, and Comparative Examples 4-5) using a carrier containing CeO 2 with CuO as an active species, when a ZrO 2 carrier is used ( It was found that higher CO oxidation activity was obtained under low temperature conditions as compared with the catalyst obtained in Comparative Example 2) and when using the Al 2 O 3 support (Comparative Example 3).

Further, as is apparent from the results shown in FIG. 2 (90% CO conversion temperature of the catalyst in the initial state), the CO oxidation catalyst of the present invention (Examples 1 and 2) is a CO oxidation catalyst for comparison (comparison). Compared to Example 1 and Comparative Examples 4 to 5), it was confirmed that the 90% CO conversion temperature was sufficiently low, and a high CO oxidation activity was obtained from a lower temperature. From such a result, CO oxidation catalyst of the present invention that among the carrier containing CeO 2 with a carrier comprising a CeO 2, ZrO 2 and Al 2 O 3 (Examples 1-2), the carrier containing only CeO 2 Is obtained (Comparative Example 1), a support containing CeO 2 and ZrO 2 (Comparative Example 4), or a support containing CeO 2 and Al 2 O 3 (Comparative Example 5). It can be seen that, compared with the catalyst, a high CO oxidation activity is obtained from a low temperature, and a sufficiently high CO oxidation activity is exhibited even in a temperature range (usually about 180 to 250 ° C.) where the CO conversion rate is higher.

Further, as is clear from the results shown in FIG. 3 (50% CO conversion temperature of the catalyst after the heat test), after the heat test at 800 ° C., the CO oxidation catalyst of the present invention (Examples 1 to 2) is superior in heat resistance because the 50% CO conversion temperature is lower than the CO oxidation catalyst for comparison (Comparative Examples 1 to 7), and the 50% CO conversion temperature is sufficiently low. It has been found that it has sufficiently high CO oxidation performance even when exposed to high temperatures. Further, the CO oxidation catalyst (Au / TiO 2 ) obtained in Comparative Example 6 exhibits very high activity in the initial state (see FIG. 1), but its activity is significantly reduced when exposed to a high temperature of 800 ° C. As a result, it was found that this was insufficient for practical use. The decrease in the activity of the CO oxidation catalyst obtained in Comparative Example 6 is due to the fact that the Au particles grow and the 2-3 nm Au fine particles necessary for the expression of the CO oxidation activity disappear. They guess. Moreover, from the results shown in FIGS. 1 and 3, the CO oxidation catalyst of the present invention (Examples 1 and 2) was more in the initial state and after the heat resistance test at 800 ° C. than the CO oxidation catalyst obtained in Comparative Example 7. In any case, it was confirmed that the 50% CO conversion temperature was low. From these results, the CO oxidation catalyst of the present invention using CuO which is a base metal oxide (Examples 1 and 2) is superior to the catalyst using Pt which is a noble metal (Comparative Example 7). It was found that the CO oxidation catalyst of the present invention is very significant in terms of cost.

From the results shown in FIG. 4 (the 90% CO conversion temperature of the catalyst after the heat test), the CO oxidation catalyst of the present invention (Examples 1 and 2) is the CO oxidation catalyst for comparison (comparison) even after the heat test. Compared to Example 1 and Comparative Examples 4 to 5), the 90% CO conversion temperature is sufficiently low, and the 90% CO conversion temperature is sufficiently low. 2) was confirmed to have sufficiently high CO oxidation performance even when exposed to a high temperature of 800 ° C. Further, as apparent from the results shown in FIGS. 3 and 4, after the heat resistance test, the CO oxidation catalyst of the present invention in which CuO was supported on a support containing CeO 2 , ZrO 2 and Al 2 O 3 (Examples) 1-2) when a support containing only CeO 2 is used (Comparative Example 1), when using a support containing CeO 2 and ZrO 2 (Comparative Example 4), or a support containing CeO 2 and Al 2 O 3 As compared with the catalyst obtained in the case of using (Comparative Example 5), high CO oxidation activity is obtained from a low temperature, and even in a temperature range where the CO conversion rate is higher (usually about 200 to 350 ° C.) sufficiently. It turns out that high CO oxidation activity is expressed.

<Hydrogen heating reduction (H 2-TPR) Test>
An H 2 -TPR test was performed on each CO oxidation catalyst (initial state) obtained in Examples 1-2 and Comparative Examples 1-3. That is, using a fixed bed flow reactor, gas (A) composed of O 2 (60% by volume) / Ar (remainder) was 50 ml / min with respect to 0.080 g of catalyst packed in a quartz reaction tube having an inner diameter of 10 mm. The catalyst was heated to 350 ° C. at a rate of temperature increase of 20 ° C./min and subjected to a treatment for 20 minutes at 350 ° C. (pre-oxidation treatment). Cooling until the bed temperature reaches 30 ° C., then switching the supply gas species to gas (B) made of Ar (100% by volume) and supplying gas (B) at a supply rate of 50 ml / min for 30 minutes (Purge process) was performed. Next, the supply gas species is switched to gas (C) composed of H 2 (1%) / Ar (remainder), and after supplying gas (C) at a supply rate of 50 ml / min for 5 minutes, gas (C) The temperature of the catalyst was raised from 30 ° C. to 600 ° C. at a rate of temperature increase of 20 ° C./min. Then, to measure the concentration of H 2 in exit gas during such heated using a mass spectrometer. A graph showing the relationship between the H 2 concentration in the outgas and the temperature is shown in FIG. The easiness of reduction of the CuO active species in the catalyst is known from the temperature at which the consumption of H 2 is started, and the reduction amount of the CuO active species is known from the amount of consumption of H 2 .

As is clear from the results shown in FIG. 5, the CO oxidation catalyst of the present invention (Examples 1-2: initial state) and the CO oxidation catalyst (initial state) obtained in Comparative Example 1 are Comparative Examples 2-3. Compared with the CO oxidation catalyst (initial state) obtained in Step 1, it was confirmed that H 2 was consumed sufficiently from a low temperature, and it was found that CuO in the catalyst was more easily reduced. Based on these results and the results of the 50% CO conversion temperature of the catalyst in the initial state shown in FIG. 1, the CO oxidation catalyst obtained in the CO oxidation catalyst of the present invention (Examples 1 and 2) and Comparative Example 1 were used. The present inventors speculate that the sufficiently high oxidation activity of the catalyst in the initial state is due to the fact that CuO in the catalyst is easily reduced. That is, the present inventors speculate that CuO in the catalyst is more likely to be reduced as one of the factors for achieving high CO oxidation activity.

<Measurement of specific surface area>
About each CO oxidation catalyst obtained in Examples 1-2 and Comparative Examples 1-7, the specific surface area of the catalyst of an initial state and the specific surface area of the catalyst after the said heat test are fully automatic specific surface area measuring apparatus (MICRO * DATA). The product name “MICRO SORP4232II”) manufactured by the company was used, and the BET one-point method using N 2 adsorption at a liquid nitrogen temperature (−196 ° C.) was used. The obtained result is shown in FIG.

As is clear from the results shown in FIG. 6, the CO oxidation catalyst of the present invention (Examples 1 and 2) was compared with the CO oxidation catalyst obtained in Comparative Example 1 and Comparative Examples 4 to 5 after the heat resistance test. It was confirmed that the specific surface area was sufficiently large. Considering the case where a CO oxidation catalyst is produced using a support containing CeO 2 based on such results, the CO oxidation of the present invention in which CuO is supported on a support containing CeO 2 , ZrO 2 and Al 2 O 3. The catalysts (Examples 1 and 2) were prepared using a support containing only CeO 2 (Comparative Example 1), using a support containing CeO 2 and ZrO 2 (Comparative Example 4), or CeO 2 and Al 2 O. It can be seen that the rate of decrease in the specific surface area of the carrier when exposed to a high temperature of 800 ° C. is sufficiently small compared to the catalyst obtained when the carrier containing 3 is used (Comparative Example 5). From these results and the results shown in FIGS. 3 to 4, the CO oxidation catalyst of the present invention (Examples 1 and 2) is one of the factors that exhibit sufficiently high oxidation activity even after the heat resistance test. The present inventors speculate that even if the CO oxidation catalyst (Examples 1 and 2) is exposed to a high temperature of 800 ° C., the decrease in specific surface area is sufficiently suppressed.

  As described above, according to the present invention, sufficiently high CO oxidation performance can be exhibited from a low temperature of about 200 ° C., and even when exposed to a high temperature of about 800 ° C., the CO oxidation performance of the catalyst is sufficiently lowered. It is possible to provide a CO oxidation catalyst that can be suppressed to a sufficiently low level, and that can achieve a sufficiently high CO conversion rate from a sufficiently low temperature, and an exhaust gas purification method using the same. Therefore, the CO oxidation catalyst of the present invention is particularly useful as a catalyst for purifying exhaust gas from an internal combustion engine (particularly preferably a diesel engine) of an automobile.

Claims (4)

  1.   Comprising a support made of a composite metal oxide containing ceria, zirconia and alumina, wherein the content of ceria in the composite metal oxide is 50% by mass or more, and copper oxide supported on the support. Characteristic CO oxidation catalyst.
  2.   2. The CO oxidation catalyst according to claim 1, wherein in the composite metal oxide, the ceria, the zirconia, and the alumina are dispersed on a nanometer scale.
  3.   The CO oxidation catalyst according to claim 1 or 2, wherein a content of the copper oxide is 0.5 to 30% by mass with respect to a total amount of the carrier and the copper oxide.
  4. An exhaust gas purification method comprising contacting an exhaust gas with the CO oxidation catalyst according to any one of claims 1 to 3, and oxidizing and removing carbon monoxide gas in the exhaust gas.
JP2010049474A 2010-03-05 2010-03-05 CO oxidation catalyst and exhaust gas purification method using the same Active JP5574222B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP2010049474A JP5574222B2 (en) 2010-03-05 2010-03-05 CO oxidation catalyst and exhaust gas purification method using the same

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP2010049474A JP5574222B2 (en) 2010-03-05 2010-03-05 CO oxidation catalyst and exhaust gas purification method using the same

Publications (2)

Publication Number Publication Date
JP2011183280A true JP2011183280A (en) 2011-09-22
JP5574222B2 JP5574222B2 (en) 2014-08-20

Family

ID=44790207

Family Applications (1)

Application Number Title Priority Date Filing Date
JP2010049474A Active JP5574222B2 (en) 2010-03-05 2010-03-05 CO oxidation catalyst and exhaust gas purification method using the same

Country Status (1)

Country Link
JP (1) JP5574222B2 (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2014028994A (en) * 2012-07-31 2014-02-13 Furukawa Electric Co Ltd:The Copper fine particle dispersion and conductive material
JP2015083295A (en) * 2013-09-17 2015-04-30 ダイハツ工業株式会社 Catalyst for exhaust gas purification
JP2016068038A (en) * 2014-09-30 2016-05-09 ダイハツ工業株式会社 Exhaust gas purification catalyst
JP2016068039A (en) * 2014-09-30 2016-05-09 ダイハツ工業株式会社 Exhaust gas purification catalyst

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH04371231A (en) * 1991-06-18 1992-12-24 N E Chemcat Corp Catalyst for purification of exhaust gas
JPH0947661A (en) * 1995-08-04 1997-02-18 Babcock Hitachi Kk Process and catalyst for purifying exhaust gas
JP2004230223A (en) * 2003-01-28 2004-08-19 Fujitsu Ltd Co oxidation catalyst and production method therefor
WO2009158008A1 (en) * 2008-06-27 2009-12-30 Catalytic Solutions, Inc. Zero platinum group metal catalysts

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH04371231A (en) * 1991-06-18 1992-12-24 N E Chemcat Corp Catalyst for purification of exhaust gas
JPH0947661A (en) * 1995-08-04 1997-02-18 Babcock Hitachi Kk Process and catalyst for purifying exhaust gas
JP2004230223A (en) * 2003-01-28 2004-08-19 Fujitsu Ltd Co oxidation catalyst and production method therefor
WO2009158008A1 (en) * 2008-06-27 2009-12-30 Catalytic Solutions, Inc. Zero platinum group metal catalysts

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2014028994A (en) * 2012-07-31 2014-02-13 Furukawa Electric Co Ltd:The Copper fine particle dispersion and conductive material
JP2015083295A (en) * 2013-09-17 2015-04-30 ダイハツ工業株式会社 Catalyst for exhaust gas purification
JP2016068038A (en) * 2014-09-30 2016-05-09 ダイハツ工業株式会社 Exhaust gas purification catalyst
JP2016068039A (en) * 2014-09-30 2016-05-09 ダイハツ工業株式会社 Exhaust gas purification catalyst

Also Published As

Publication number Publication date
JP5574222B2 (en) 2014-08-20

Similar Documents

Publication Publication Date Title
CN1457921B (en) Catalyst for reducing nitrogen oxide content in waste gas of fuel-lean engine
JP4625173B2 (en) Method for producing nitrogen oxide-occlusion material and occlusion material produced thereby
JP4567120B2 (en) Nitric oxide-accumulating substance and nitric oxide-accumulating catalyst produced therefrom
US8202819B2 (en) Catalyst system to be used in automobile exhaust gas purification apparatus, exhaust gas purification apparatus using the same and exhaust gas purification method
CN101610844B (en) NOx storage materials and traps resistant to thermal aging
JP5538237B2 (en) Exhaust gas purification catalyst, exhaust gas purification device using the same, and exhaust gas purification method
JP3797313B2 (en) Method for producing metal oxide particles and catalyst for exhaust gas purification
JP3741303B2 (en) Exhaust gas purification catalyst
US6933259B2 (en) Composite oxide powder, a method for producing the same and a catalyst using the same
JP3858625B2 (en) Composite oxide and its production method, exhaust gas purification catalyst and its production method
KR101688850B1 (en) Nitrogen oxide storage catalytic converter for use in a motor vehicle in a position near the engine
JP3861647B2 (en) Exhaust gas purification catalyst
JP2659796B2 (en) The catalyst and its manufacturing method for exhaust gas purification
KR101010070B1 (en) Exhaust gas purifying catalyst and method for producing the same
KR100989224B1 (en) Exhaust gas purifying catalyst and manufacturing method thereof
JP2014522726A (en) Catalysts containing lanthanide-doped zirconia and methods of manufacture
EP0718028B1 (en) Heat-resistant support for catalysts and the production thereof
JP5194397B2 (en) Exhaust gas purification catalyst and method for producing the same
JP6120309B2 (en) Exhaust gas purification catalyst
WO2002066155A1 (en) Exhaust gas clarification catalyst
JP4959129B2 (en) Exhaust gas purification catalyst
JP4165442B2 (en) Metal oxide particles, production method thereof, and exhaust gas purification catalyst
JP4977467B2 (en) Cerium-zirconium composite oxide, method for producing the same, oxygen storage / release material using the same, exhaust gas purification catalyst, and exhaust gas purification method
WO2013022958A1 (en) Palladium solid solution castalyst and methods of making
DE60031258T2 (en) Catalyst for purifying exhaust gas

Legal Events

Date Code Title Description
A621 Written request for application examination

Free format text: JAPANESE INTERMEDIATE CODE: A621

Effective date: 20130212

A977 Report on retrieval

Free format text: JAPANESE INTERMEDIATE CODE: A971007

Effective date: 20131209

A131 Notification of reasons for refusal

Free format text: JAPANESE INTERMEDIATE CODE: A131

Effective date: 20131213

A601 Written request for extension of time

Free format text: JAPANESE INTERMEDIATE CODE: A601

Effective date: 20140205

A602 Written permission of extension of time

Free format text: JAPANESE INTERMEDIATE CODE: A602

Effective date: 20140210

A521 Written amendment

Free format text: JAPANESE INTERMEDIATE CODE: A523

Effective date: 20140227

A521 Written amendment

Free format text: JAPANESE INTERMEDIATE CODE: A821

Effective date: 20140227

TRDD Decision of grant or rejection written
A01 Written decision to grant a patent or to grant a registration (utility model)

Free format text: JAPANESE INTERMEDIATE CODE: A01

Effective date: 20140606

A61 First payment of annual fees (during grant procedure)

Free format text: JAPANESE INTERMEDIATE CODE: A61

Effective date: 20140619