WO1999064151A1 - Catalyseur et procede de purification des gaz d'echappements - Google Patents

Catalyseur et procede de purification des gaz d'echappements Download PDF

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Publication number
WO1999064151A1
WO1999064151A1 PCT/JP1999/003020 JP9903020W WO9964151A1 WO 1999064151 A1 WO1999064151 A1 WO 1999064151A1 JP 9903020 W JP9903020 W JP 9903020W WO 9964151 A1 WO9964151 A1 WO 9964151A1
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Prior art keywords
catalyst
exhaust gas
zirconia
palladium
sulfate
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PCT/JP1999/003020
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English (en)
Japanese (ja)
Inventor
Hirofumi Ohtsuka
Takeshi Tabata
Masataka Masuda
Takenori Hirano
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Osaka Gas Company Limited
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Publication of WO1999064151A1 publication Critical patent/WO1999064151A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/8621—Removing nitrogen compounds
    • B01D53/8625—Nitrogen oxides
    • B01D53/8628—Processes characterised by a specific catalyst
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
    • B01J27/02—Sulfur, selenium or tellurium; Compounds thereof
    • B01J27/053—Sulfates
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
    • Y02C20/00—Capture or disposal of greenhouse gases
    • Y02C20/20—Capture or disposal of greenhouse gases of methane

Definitions

  • the present invention relates to a catalyst for decomposing nitrogen oxides (NO in a flue gas, which has an adverse effect on the environment) in a nitrogen atmosphere using an atmosphere, and a method for purifying nitrogen oxides using the catalyst.
  • the “oxygen-rich atmosphere” means that the gas to be treated brought into contact with the catalyst according to the present invention is necessary to completely oxidize the reducing components such as hydrocarbons and carbon monoxide contained therein. It means that it is a gas containing oxidizing components such as oxygen and nitrogen oxides in excess of the amount.
  • Catalysts for reducing nitrogen oxides in an oxygen-excess atmosphere using hydrocarbons as reducing agents are disclosed in Japanese Patent Laid-Open Publication Nos. 63-10091 and 1988. It is disclosed to others. These known documents do not disclose the use of methane as a carbon dioxide.
  • the methane is present in the exhaust gases generated when burning various fuels. Furthermore, since methane is a major component of natural gas that is widely supplied to households and factories, if it could be used to reduce nitrogen oxides, , 51
  • U.S. Pat. No. 5,149,512 and Japanese Unexamined Patent Publication No. 5-1952582 disclose a zeolite catalyst in which cobalt or rhodium is ion-exchanged in the presence of methane.
  • a method for reducing the nitrogen oxides in the exhaust gas by contacting the combustion exhaust gas with the exhaust gas is disclosed.
  • the activity of this catalyst is not sufficient, and furthermore, there is no mention of the activity of the catalyst in the coexistence of steam which is always contained in actual combustion exhaust gas.
  • steam reduces the catalytic activity in the reaction of reducing nitrogen oxides in an oxidizing atmosphere using hydrocarbons as a reducing agent. Does not describe the reduction of catalyst activity due to coexisting water vapor and there is no countermeasure to prevent it.
  • Japanese Patent Laid-Open Publication No. Hei 6-254352 discloses that a catalyst in which palladium is supported on a ZSM-5 type zeolite by nitrogen exchange using a methane as a reducing agent by ion exchange.
  • the activity of the catalyst is clearly evident, but there is no disclosure in this publication about the activity of the catalyst in the presence of steam.
  • Japanese Published Patent Application No. 8-500772 is based on the Ion Exchange.
  • Ri MF I type Zeorai bets on catalyst para Ji beam is from 0.3 to 2 wt 0/0 supported is, to the meta emission and the reducing agent, even in the presence of water vapor, reducing activity of high nitrogen oxides Is shown.
  • Satokawa and colleagues reported in the 1996 Preliminary Meeting on Catalyst Research (published on September 13, 1996) that the catalyst in which mordenite was ion-exchanged with palladium, even in the presence of steam, It discloses that it exhibits high nitrogen oxide reduction activity.
  • these catalysts have a problem in that the activity of these catalysts greatly decreases with time in the presence of steam. For example, Hoshi et al.
  • the present invention provides an exhaust gas purification system that can stably purify nitrogen oxides over a long period of time by using methane as a reducing agent even in the presence of active inhibitors such as steam and sulfur oxides.
  • the main purpose is to provide a catalyst for use.
  • a catalyst containing an inorganic carrier supporting an active transition metal (hereinafter sometimes referred to as a “composite catalyst”) is used to decompose and remove nitrogen oxides using methane as a reducing agent. At this time, they found that they maintained high nitrogen oxide decomposition activity for a long time.
  • the present invention has been completed based on such new knowledge, and provides the following exhaust gas purifying catalyst and exhaust gas purifying method.
  • An oxygen excess comprising an inorganic carrier supporting a transition metal having an activity of oxidizing nitric oxide to nitrogen dioxide in the presence of oxygen and a sulfate group zirconia supporting palladium.
  • An exhaust gas purification catalyst that decomposes nitrogen oxides in the presence of methane in an atmosphere.
  • Item 7 The exhaust gas purifying catalyst according to any one of Items 1 to 6, wherein the carried amount of radium is 0.1 to 0.5% by weight based on the sulfated zirconia.
  • Item 8 The above item 6 wherein the amount of supported palladium is 0.1 to 0.5% by weight relative to sulfated zirconia and the content of platinum is 20 to 100% by weight relative to palladium. Exhaust gas purification catalyst.
  • the inorganic carrier is zirconia, sulfated zirconia, tan 99/4151 PT
  • Item 10 The method for purifying exhaust gas according to the above item 9 or 10, wherein at least one member is selected from the group consisting of gustened zirconia and titania.
  • the supported amount of palladium in the catalyst is 0.1 to 0.5% by weight based on the sulfated zirconia, and the content of platinum in the catalyst is 20 to 100% by weight based on palladium.
  • Item 14 The exhaust gas purification method according to Item 14 above.
  • the catalyst according to the present invention includes a sulfated zirconia carrier supporting palladium (hereinafter, this combination may be simply referred to as “first catalyst component”) and an inorganic carrier supporting a transition metal (hereinafter, referred to as “first catalyst component”).
  • first catalyst component a sulfated zirconia carrier supporting palladium
  • first catalyst component an inorganic carrier supporting a transition metal
  • second catalyst component The combination can be simply referred to as “second catalyst component”.
  • the sulfated zirconia itself used as a carrier in the first catalyst component is a known substance (for example, Makoto Hino and Kazushi Arata, "Surface", Vol. 28, No. 7, pp. 481 (1990), “Surface”, Vol. 34, No. 2, page 51 (1996)).
  • the sulfated zirconium is prepared, for example, by immersing commercially available zirconium hydroxide in dilute sulfuric acid, or impregnating zirconium hydroxide with an aqueous solution of ammonium sulfate, in air at a temperature of about 450 to 650 ° C. More preferably, it is obtained by firing at a temperature in the range of about 500 to 600 ° C.
  • the firing temperature is too high, a large amount of sulfate groups may be volatilized, whereas if it is too low, the effect of the firing becomes insufficient and unreacted hydroxylation in the carrier occurs. Zirconium remains or the fired product becomes amorphous Thus, stable zirconium hydroxide is not formed. Since part of the sulfate groups volatilize during the firing operation, it is preferable to add an excess amount of sulfate groups corresponding to the volatile matter to the zirconium hydroxide during the above immersion treatment or impregnation treatment. o
  • sulfate sulfate radical Jirukonia carrier (SO 4 2 -) content is referenced to Jirukonia weight, 1 to Ri about 20% der, rather then preferred Ri yo is 3 to about 10%.
  • the method of loading palladium on the sulfated zirconia carrier is not particularly limited as long as the latter is supported in a highly dispersed manner with respect to the former, but preferably the carrier is palladium nitrate or an amine complex. This is carried out by impregnating with an aqueous solution such as.
  • the supported amount of palladium is usually about 0.05 to 1%, more preferably about 0.1 to 0.5%, by weight based on the sulfated zirconia after the calcination treatment described later. If the supported amount of palladium is too small, the nitrogen oxide decomposing activity becomes low, while if it is too high, the nitrogen oxide decomposing activity is rather impaired by aggregation.
  • the calcination temperature for preparing the first catalyst component is usually in the range of about 300 to 600 ° C, more preferably in the range of about 450 to 550 ° C.
  • the second catalyst component for oxidizing nitric oxide to nitrogen dioxide in the presence of oxygen needs to have high activity to oxidize nitric oxide to nitrogen dioxide, while If the activity of methane in the combustion reaction is too high, the reducing agent, methane, will be consumed by the combustion reaction, thus reducing the nitrogen oxide reduction performance of the entire catalyst. Let it. In view of such conflicting performance requirements, platinum and rhodium are more preferred as transition metals, and platinum is particularly preferred.
  • the inorganic carrier for supporting the transition metal includes, for example, zirconia, titania, tungsten stainless, sulphate zirconia, alumina, silica, silica and alumina. Alternatively, crystalline aluminosilicate or the like can be used.
  • zirconia, titania, tungsten zirconia, sulfate zirconia, and the like are more preferable in terms of activity and durability.
  • zirconia, titania, alumina, and the like those commercially available as catalyst carriers can be used as they are.
  • the zirconium carrier is obtained by firing zirconium hydroxide. Thus, it can be easily prepared.
  • Tungsten zirconia is a known substance that may be described as WO 3 / ZrO 2 (for example, Makoto Hino and Kazushi Arata, “Surface”, Vol. 34, No. 2, page 51 (1996)) Etc.), and can be prepared according to known methods.
  • the method for supporting the transition metal on the inorganic carrier is not particularly limited as long as the transition metal is highly dispersed on the inorganic carrier.
  • the inorganic carrier is an aqueous solution of a transition metal nitrate, an amine complex, or the like. This is done by impregnating the material.
  • the inorganic support supporting the transition metal is dried and then calcined.
  • the firing condition may be selected at an appropriate temperature according to the type of the transition metal and the type of the carrier.
  • the platinum is supported on a carrier such as zirconia, titania, or sulfated zirconia, the firing temperature is usually about 300 to 600 ° C.
  • the composite catalyst according to the present invention preferably has a temperature in the range of 450 to 550 ° C. It is prepared by mixing a supported sulfated zirconia carrier (first catalyst component) and a transition metal-supported inorganic carrier (second catalyst component).
  • the composite catalyst according to the present invention may be mixed with the dried first catalyst component and the second catalyst component, and then calcined, if necessary. Or, After the molding step described below is performed using the dry mixture, baking may be performed. Regardless of the method of mixing, in order to achieve the desired effect of the present invention, it is desirable that mixing is sufficiently performed to obtain a mixture as uniform as possible.
  • the content of transition metal (for example, platinum) in the composite catalyst according to the present invention is usually about 10 to 200% by weight relative to palladium, and more preferably 20 to 100%. is there.
  • the composite catalyst of the present invention can also be used in the form of a “single-supported catalyst” in which both palladium and a transition metal are supported on the same sulfated zirconia carrier. Also in this case, after carrying out the loading operation on the sulfated zirconia carrier using the same solution of the palladium compound and the transition metal compound as described above, if necessary, drying and firing are performed.
  • the support on the carrier may be performed by a single operation using a solution in which the palladium compound and the transition metal compound are dissolved, or using a solution in which the palladium compound is dissolved.
  • the transition metal may be loaded using a solution in which the transition metal compound is dissolved, or conversely, after loading the transition metal, Palladium may be supported.
  • the amount of palladium supported on the support and the amount of transition gold on palladium are also determined.
  • the amount of metal used, the sintering conditions for the palladium / transition metal-carrying carrier, and the like are the same as those described above.
  • the catalyst according to the present invention may be used in the form of a pellet in accordance with a conventional method, or may be used as a fire-coated honeycomb support. In either case, binders can be added as needed.
  • the exhaust gas purification method of the present invention is characterized by using the composite catalyst obtained above. If the amount of the catalyst used is too small, an effective nitrogen oxide purification rate cannot be obtained, whereas if it is too large, the performance corresponding to the amount of the catalyst used cannot be obtained. Therefore, it is preferable that the catalyst be used in a range where the gas space velocity per hour (GHSV) is 2,000 to 200,000 h— 1 and 2,000 to 60,000 h — It is more preferable to use within the range of 1 .
  • GHSV gas space velocity per hour
  • the catalyst of the present invention has high activity, but if the temperature of exhaust gas is too low, effective purification performance may not be exhibited. On the other hand, if the temperature of the exhaust gas is too high, the durability of the catalyst may be impaired. Therefore, the catalyst according to the invention is preferably used in the range of about 350-500 ° C, more preferably in the range of about 375-475 ° C.
  • Nitrogen oxide concentration of exhaust gas to be purified by the method of the present invention is usually in the range of 10 to 5000 vol. Ppm.
  • the methane concentration during the decomposition of nitrogen oxides varies depending on the required denitrification rate and other reaction conditions, but in order to obtain a high denitration rate, it is usually more than 1 times that of nitrogen oxides in exhaust gas, More preferably, it should be about 5 times or more. If the amount of methane contained in the exhaust gas is smaller than that required for the reduction of nitrogen oxides, add an appropriate amount of methane-containing gas such as methane or natural gas-based city gas to the exhaust gas. Is also good.
  • the oxygen concentration in the exhaust gas is not particularly limited as long as it contains excessive oxygen.However, when the oxygen concentration is extremely low, for example, 1% or less by volume, sufficient reaction activity can be obtained. May not be. When the oxygen concentration in the exhaust gas is too low If the temperature of the exhaust gas is high and there is a possibility that the temperature of the catalyst may exceed the above-mentioned preferred temperature range, the temperature of the exhaust gas may not fall below the preferred range. After mixing the amount of air, the air mixed gas may be brought into contact with the catalyst.
  • the concentration of methane remaining in the gas to be treated can be kept low.
  • Example 1 in the case of performing the cleaning process of the simulated exhaust gas, NO chi and time of conversion of meta emissions This is a graph showing the change.
  • Figure 2 shows the case where the simulated exhaust gas was purified using the 0.5% PdZ sulfate zirconia catalyst (1) according to Comparative Example 1.
  • 5 is a graph showing the change over time in the conversion of NO ⁇ and methane in FIG.
  • Fig. 3 is a graph showing the change over time in the conversion rates of NO and male when the simulated exhaust gas was purified using 0.5% PtZ sulfate zirconia catalyst according to Comparative Example 2. It is.
  • Figure 4 is a graph showing with that by the comparative example 3 P d Z Morudenai Bok catalyst (1), when the purification process of the simulated exhaust gas having conducted, the time course of conversion of NO chi and meta emissions It is.
  • FIG. 7 is a graph showing the change over time of the conversion rates of NO and methane when the simulated exhaust gas was purified in the presence of sulfur oxide using the mixed catalyst 1 according to Example 7 of the present invention. is there. 8, using a mixed catalyst 2 according to the present invention Example 8, in the case of performing the purification process of the simulated exhaust gas under sulfur oxides coexist, a graph showing the time course of vo chi and conversion of meta emissions is there.
  • a 150 ml aqueous solution in which 15 g of ammonium sulfate was dissolved was impregnated with 50 g of zirconium hydroxide I for 10 hours. After drying the impregnated body, it was calcined at 550 ° C for 3 hours to obtain sulfated zirconia.
  • Example 2 In a solution obtained by diluting 1.25 g to 20 ml with pure water, 25 g of sulfated zirconia prepared in the same manner as in Example 1 was immersed for 10 hours. After drying the impregnated sulfate zirconia, the mixture was calcined at 500 ° C for 9 hours to obtain a 0.5% PdZ sulfate zirconia catalyst (1).
  • 35 g of sulfated zirconia prepared in the same manner as in Example 2 was immersed for 15 hours in a solution prepared by diluting 3.0 g of a tetrauramin platinum nitrate aqueous solution containing 5.8% by weight of Pt with pure water to 30 ml. . After drying the impregnated sulfate zirconia, it was baked at 500 ° C for 9 hours to obtain a 0.5% Pt / sulfate zirconia catalyst.
  • H-type mordenite manufactured by Tosoichi Co., Ltd., silica / alumina ratio: 16
  • tetraamine minpalladium nitrate 20 g
  • the mixture was ion-exchanged at 60 ° C for 18 hours using 300 ml of an aqueous solution in which acetic acid and ammonium lg were dissolved.
  • the ion-exchanged H-type mordenite is separated by filtration, washed, dried at 110 ° C for 5 hours, and calcined in air at 500 ° C for 9 hours to obtain a PdZ mordenite catalyst (1).
  • Preparation of Pd / ZSM-5 catalyst Dissolve 14g of ZSM-5 zeolite (manufactured by Swiss Helicopter, Inc., silica / alumina ratio: 30g), 0.2g of tetramethylamparadium nitrate and 2g of ammonium acetate Ion exchange was performed at 60 ° C for 18 hours using an additional 300 ml of the aqueous solution.
  • the ZSM-5 zeolite is separated by filtration, washed, dried at 110 ° C for 3 hours and at 150 ° C for 2 hours, and calcined in air at 500 ° C for 9 hours to obtain PdZZSM- Got 5
  • the amount of Pd supported on the PdZZSM-5 was 0.6%. Comparative Example 6
  • H-type mordenite manufactured by Tosoichi Co., Ltd., silica / alumina ratio 16
  • Pt. / 25 g of H-type mordenite (manufactured by Tosoichi Co., Ltd., silica / alumina ratio 16) is 6.3 weight as Pt. /.
  • the obtained ion-exchanged H-type mordenite was separated by filtration, washed, dried at 110 ° C for 5 hours, and further calcined in air at 500 ° C for 9 hours to obtain a Pd-PtZ mordenite.
  • the catalyst was obtained.
  • Each of the catalysts obtained with the catalysts of Examples 1, 2, and 3 and Comparative Examples 1 and 2 was tablet-formed, pulverized, and sized to a particle size of l to 2 mm.
  • Each of the obtained catalysts was filled with 4 ml, and a gas consisting of 150 ppm of nitric oxide, 10% of oxygen, 9% of water vapor, and the balance of hydrogen was used for a gas time using a reactor.
  • GHSV space velocity
  • the NO oxidation activity test was carried out by changing the temperature of the catalyst layer in the range of 350 to 500 ° C and circulating it.
  • the NO ⁇ concentration at the outlet of the catalyst layer was measured by a chemical emission type NO ⁇ analyzer.
  • the Pd / sulfate radical zirconia catalyst has substantially no NO oxidation activity (similar to the gas flow in the non-catalytic state). It is clear that the Pt / sulfuric acid zirconia catalyst has high NO oxidation activity. Also, it can be seen that the NO oxidation activity of the catalyst supporting both Pd and Pt also has a high NO oxidation activity due to the presence of Pt.
  • the catalysts of Examples 1 and 2 and Comparative Examples 1, 2, 3, and 5 were After tablet compression, crushed and sized to 1-2 mm particle size.
  • a simulated exhaust gas consisting of 150 ppm of nitrogen monoxide, 2000 ppm of methane, 10% of oxygen, 9% of steam and the balance of helium was used.
  • the catalyst was subjected to a catalytic activity test by flowing it under the conditions of a space velocity per gas hour (GHSV) of 15,000 h- 1 and a catalyst layer temperature of 450 ° C.
  • GHSV space velocity per gas hour
  • Catalyst layer outlet of meta emissions, carbon monoxide and carbon dioxide concentrations are shorted with a Gasuku Loma preparative graph, also NO chi concentration of the catalyst layer inlet and outlet are shorted with a chemiluminescence NO chi analyzer, measuring Specified.
  • the actual combustion exhaust gas usually contains 5 to 15% carbon dioxide in addition to the above components, but it was separately confirmed that this did not substantially affect the reaction activity.
  • the NO ⁇ conversion rate (%) and methane conversion rate (%) indicate values calculated by the following formulas.
  • NO ⁇ -in is a vo chi concentration inlet the catalyst layer
  • NO x -out is a NO chi concentration of the catalyst layer outlet
  • C0 2 -ou exits catalyst layer
  • the carbon dioxide concentration at the mouth and “CH 4 -oi” represent the concentration at the outlet of the catalyst layer.
  • Figure 1 is a graph showing a first embodiment in accordance os Pd-o.So/oPtZ the sulfate Gilles Konia catalyst (1) Test results conducted with (time course of NO chi and conversion of meta emissions) is there. 52% after 30 hours from the start of the test, 45 percent after 50 hours, Oite after 88 hours Ri Contact show high NO chi conversion rate of 35%, Ri cotton Yu nitrogen oxide decomposing properties for long-term, maintenance are doing. Although not shown, the 0.25% Pd-0.1% Pt / zirconium sulfate zirconia catalyst according to Example 2 also exhibited high NO conversion rates of 55% 30 hours after the start of the test, 45% after 50 hours, and 40% after 86 hours. The methane conversion was 48%, 45% and 42% after 30, 50 and 86 hours, respectively.
  • Figures 2, 3 and 4 show the 0.5% PdZ sulfate zirconia catalyst (1) of Comparative Example 1, the 0.5% Pt / sulfate zirconia catalyst of Comparative Example 2, and the 0.5% PdZ mordenite catalyst (1) of Comparative Example 3, respectively.
  • 0.5% PDZ Morudenai preparative catalyst (1) shows high activity levels initially for any vo chi conversion and meta down conversion, cause this to markedly correct degradation over time are doing. That is, the NO ⁇ conversion rate decreased to 44% after 30 hours, 22% after 50 hours, and 14% after 65 hours (Fig. 4).
  • PdZZSM-5 catalyst by Comparative Example 5 NO chi conversion to 3 hours after start of the test Ri 73% der, but meta down conversion been filed in 43%, respectively, after 10 hours They dropped to 58% and 40%, and after 18 hours to 32% and 30%, respectively.
  • the catalyst according to the present invention has remarkably high durability even in the coexistence of steam as compared with a known catalyst. Further, the catalyst according to the present invention also exhibits a high methane conversion over a long period of time.
  • the gas composition was 150 ppm for nitric oxide, 2000 ppm for methane, 10% for oxygen, 9% for steam, 3 ppm for sulfur dioxide, and the balance for lithium.
  • the catalyst activity test was performed in the same manner as in Example 5 except that Test was carried out.
  • Figure 5 is a view to graph the time course of vo chi and meta down conversion of 0.25% Pd-0.1% PtZ sulfate group Gilles Konia catalyst according to Example 2.
  • NO conversion was 61%, 61% and 60%, respectively, and the methane conversion was extremely high at 54%, 50% and 46%, respectively. stable.
  • sulfur oxides sulfur disulfide
  • the catalyst activity was hardly affected, but rather the catalyst activity tended to be stable.
  • Figure 6 is a graph showing the time course of NO chi conversion Oyobime data down conversion of that by the comparative example 4 PDZ Morudenai preparative catalyst (2).
  • Example 2 35 g of sulfated zirconia prepared in the same manner as in Example 2 was immersed in a solution obtained by diluting 1.75 g of a palladium nitrate solution containing 10% by weight of Pd with pure water to 30 ml for 15 hours, and dried. The mixture was calcined at 500 ° C for 9 hours to obtain 0.5% PdZ sulfate zirconia (2).
  • Mizusani ⁇ Jinorekoniumu 160 g and data Ngusute phosphate (H 2 W0 4) was mixed with 20g of water 200 ml, was stirred for 6 hours, the or or maintained is et to 10 hours. Next, the product was dried and calcined at 800 ° C for 6 hours to obtain tungsten zirconia.
  • Zirconium hydroxide was calcined at 700 ° C for 6 hours to obtain zirconia. 15 g of this zirconia was immersed in a solution of 1.3 g of tetrauramin platinum nitrate aqueous solution containing 5.8% by weight of Pt diluted with pure water to 15 ml for 15 hours, dried, and dried at 500 ° C. By baking with C for 9 hours, 0.5% Pt nozirconia was obtained.
  • Amorphous titanium oxide (manufactured by Wako Pure Chemical Industries, Ltd.) was calcined at 600 ° C for 9 hours to obtain titania. 6 g of this titania was immersed in a solution prepared by diluting 0.5 g of an aqueous solution of tetranamine platinum nitrate containing 5.8% by weight of Pt with pure water to 10 ml for 15 hours, dried, and then dried at 500 ° C. For 9 hours to obtain 0.5% Pt / titania.
  • Example 8 20 g of tungsten zirconia prepared in the same manner as in Example 8 was immersed in a solution prepared by diluting a solution of lg palladium nitrate containing 10% by weight of Pd to 15 ml with pure water for 15 hours, and dried. The mixture was calcined at 500 ° C. for 9 hours to obtain 0.5% PdZ stainless steel.
  • a 0.5% Pt / tungsten zirconia 2.5g was mixed in a mortar to obtain a comparative mixed catalyst (2).
  • Example ? Each of the catalysts according to Comparative Examples 10 to 10, 0.5% PdZ sulfate Zirconia according to Comparative Example 7 (2), and the catalysts according to Comparative Examples 8 and 9 were tableted, crushed and sized to l to 2 mm in particle size. did. Using a reactor filled with 4 ml of each of the obtained catalysts, a gas consisting of 150 ppm of nitric oxide, 10% of oxygen, 9% of water vapor, and the balance of helium was charged at a space velocity per gas hour. (GHSV) 15,000 h- 1
  • Table 2 shows the ratio of the concentration of nitrogen dioxide in the total gas in the catalyst layer outlet gas and the sum of the concentration of nitric oxide and the concentration of nitrogen dioxide.
  • the NO ⁇ concentration was measured by a chemiluminescent NO ⁇ analyzer. The results are as shown in Table 3.
  • the catalyst used in combination with P d and Pt is the catalyst of Comparative Example 7 consisting of sulfate ion Jirukonia you carrying pd only In comparison, it is clear that the compound exhibits a higher nitrogen oxide decomposition activity. Furthermore, as with the catalyst of the present invention, a transition with excellent NO oxidation activity Even if the inorganic support carrying the transfer metal coexist, carriers other than the sulfate Jirukonia as a carrier of P d (e.g., motor ring stainless zirconate Nia) when used, the NO chi degradation activity, It is clear that there is not much improvement.
  • FIGS. 7 and 8 are graphs showing the change over time of the NO and the conversion of the monomers obtained in the tests using the catalysts of Example 7 and Example 8, respectively.
  • catalyst is the maintenance child TogaAkira et or higher NO chi conversion rate Ri stable cotton long term.

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Abstract

L'invention concerne un catalyseur de purification des gaz d'échappement permettant de décomposer les oxydes d'azote en présence de méthane dans une atmosphère à excès d'oxygène. Le catalyseur est caractérisé en ce qu'il comprend un support inorganique sur lequel est déposé un métal de transition actif quant à l'oxydation du monoxyde d'azote en dioxyde d'azote en présence d'oxygène, et un zircone sulfaté sur lequel est déposé du palladium. L'invention concerne également un procédé de purification des gaz d'échappement utilisant ledit catalyseur.
PCT/JP1999/003020 1998-06-08 1999-06-07 Catalyseur et procede de purification des gaz d'echappements WO1999064151A1 (fr)

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EP10/158763 1998-06-08

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JPH0671181A (ja) * 1992-08-31 1994-03-15 Mitsubishi Heavy Ind Ltd 排ガス処理方法
JPH0768180A (ja) * 1993-09-01 1995-03-14 Sekiyu Sangyo Kasseika Center 窒素酸化物接触還元用触媒
JPH10156145A (ja) * 1996-11-29 1998-06-16 Ford Global Technol Inc 捕捉性及び硫黄許容度を改良したジルコニア及び硫酸塩使用ＮＯｘトラップ
JPH11123331A (ja) * 1997-08-22 1999-05-11 Nissan Motor Co Ltd 排気ガス浄化用触媒

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