Catalyst for promoting the decomposition reaction of ammonia and method for detoxifying a gas to be treated in the presence of this catalyst

Abstract

Provided are: a catalyst for promoting an ammonia decomposition reaction, which comprises a mixture of a first catalyst powder comprising at least one support selected from the group consisting of silica, titania and others and a noble metal supported on the support and a second catalyst powder comprising a product produced by the ion exchange of at least one ion selected from the group consisting of a Fe ion and others into zeolite; and a method for detoxifying a gas to be treated, the method comprising performing a chemical reaction for converting NH3 contained in the gas into nitrogen and water and a chemical reaction for converting NOX and N2O contained in the gas into nitrogen and water in the presence of the catalyst.

Description

[Technical Field]

[0001] The present invention relates to a catalyst for promoting the decomposition reaction of ammonia and a method for detoxifying the gas to be treated. More specifically, it relates to a catalyst that can efficiently promote the chemical reaction that decomposes ammonia (NH3) and to a method for detoxifying NO, which is produced as a by-product in the oxidation reaction of NH3. X It can also efficiently promote chemical reactions that decompose N2O, is hardly degraded by SO2 which is sometimes contained in combustion exhaust gases, has excellent high-temperature resistance, acts as a catalyst to promote the decomposition reaction of ammonia, and efficiently decomposes NH3 contained in the treated gas and also decomposes NO contained in the treated gas, which is produced as a by-product by the oxidation reaction of NH3. X The present invention relates to a method for detoxifying a gas to be treated, which can decompose N2O with high efficiency, and / or to a method for detoxifying a gas to be treated. [Background technology]

[0002] Carbon dioxide is known as a greenhouse gas. Therefore, ammonia fuel, which does not emit carbon dioxide when burned, is being considered. When ammonia fuel is burned, NH3 and NO are produced. X This also generates exhaust gas containing N2O. This exhaust gas can have adverse effects on the environment. Furthermore, in fields where ammonia is stored and utilized, such as ammonia-fueled ships, ammonia transport ships, ammonia fuel storage bases, ammonia tanks for denitrification equipment in power plants, and ammonia cooling and refrigeration equipment, large amounts of ammonia are released when tanks or pipes are purged with nitrogen, for example. In the treatment of ammonia-containing wastewater, such as wastewater from food and beverage production, chemical plants, plating, semiconductor parts manufacturing, and domestic wastewater, large amounts of ammonia are released, for example, in saturation towers. Ammonia is a malodorous substance that causes mucosal irritation, respiratory irritation, conjunctival edema, and corrosion.

[0003] Various catalysts or methods have been proposed to neutralize gases containing NH3 and other substances.

[0004] For example, Patent Document 1 discloses an ammonia decomposition catalyst for treating ammonia exhaust gas containing moisture, comprising a lower layer having a noble metal, an inorganic oxide, phosphorus, and a first proton-type zeolite or a first ion-exchange type zeolite that has been ion-exchanged with Cu, Co, or Fe ions, and an upper layer provided on the lower layer and having a second proton-type zeolite or a second ion-exchange type zeolite that has been ion-exchanged with Cu, Co, or Fe ions. The ammonia decomposition catalyst specifically disclosed in the examples of Patent Document 1 is obtained by coating a support with a mixture of platinum-supported titania and Cu ion-exchange beta-type zeolite, drying and calcining it to obtain a lower layer, coating it with an aqueous phosphoric acid solution, and then coating it with a mixture of silica sol and Cu ion-exchange beta-type zeolite to obtain an upper layer.

[0005] Patent Document 2 discloses a catalyst having carbon monoxide decomposition activity, ammonia decomposition activity, nitrous oxide decomposition activity, and nitric oxide decomposition activity, wherein the catalyst comprises an iron-supported zeolite as the first component and a precious metal composition of platinum or palladium, or the same precious metal composition pre-supported on a porous material such as zeolite, alumina, or silica, as the second component. In the examples disclosed in Patent Document 2, mordenite or pentasil-type zeolite is used as the first component.

[0006] Patent Document 3 discloses a method for producing a catalytic particulate filter, comprising the steps of: a) providing a porous filter body having a dispersion side and a permeate side; b) providing a catalytic wash coat containing together particles of a first catalyst composition active in the selective catalytic reduction of nitrogen oxides, particles of a second catalyst composition active in the oxidation of carbon monoxide and hydrocarbons and ammonia, and a third catalyst particle composition active in the selective oxidation of ammonia to nitrogen in combination with the second catalyst composition, wherein the particles of the first catalyst composition have a most frequent particle size smaller than the average pore diameter of the particulate filter, and the second and third catalyst compositions have a most frequent particle size larger than the average pore diameter of the particulate filter; c) covering the filter body with the catalytic wash coat by introducing the wash coat into the outlet end of the permeate side; and d) drying and heat-treating the covered filter body to obtain a catalytic particulate filter.

[0007] Patent documents 4 and 5 disclose catalysts containing titanium (Ti) oxide, oxides of one or more elements selected from tungsten (W), vanadium (V), and molybdenum (Mo), and silica, zeolite, and / or alumina supported with one or more noble metals selected from platinum (Pt), iridium (Ir), rhodium (Rh), and palladium (Pd).

[0008] Patent Document 6 discloses a catalyst for removing nitrogen oxides, characterized by containing a catalyst component obtained by calcining a precipitate obtained by precipitating an aqueous solution containing a soluble titanium compound, a soluble tungsten compound, and a soluble cerium compound in an aqueous medium.

[0009] Patent Document 7 discloses a catalyst for the reduction and removal of nitrous oxide in exhaust gas by ammonia, characterized by having iron supported on a β-type zeolite.

[0010] Patent Document 8 comprises a substrate, a first catalyst coating layer, and a second catalyst coating layer, wherein the first catalyst coating layer includes inorganic oxide particles and a catalyst noble metal supported on the inorganic oxide particles, and the second catalyst coating layer is NO X The invention discloses an ammonia oxidation catalyst apparatus comprising a selective reduction catalyst and a proton zeolite. The ammonia oxidation catalyst apparatus specifically disclosed in the examples of Patent Document 8 has a first catalyst coating layer made of platinum-supported alumina and a second catalyst coating layer made of ferrovanadium and BEA-type zeolite.

[0011] Patent Document 9 describes a diesel oxidation catalyst (DOC), a catalytic soot filter (CSF), a first reducing agent injector, an AEI zeolite-based selective catalytic reduction (SCR) catalyst, and a first ammonia oxidation catalyst (AMO) located downstream of the AEI zeolite-based SCR catalyst. X The present invention discloses an exhaust treatment system for a lean-burn engine, wherein the AEI zeolite has a molar ratio of silica to alumina of 10 to 19, preferably 14 to 18. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] WO2015 / 099024A1 [Patent Document 2] Japanese Patent Application Publication No. 9-884 [Patent Document 3] Japanese Patent Publication No. 2014-508631 [Patent Document 4] Japanese Patent Publication No. 2004-216300 [Patent Document 5] Japanese Patent Publication No. 2002-66538 [Patent Document 6] Japanese Patent Application Publication No. 8-257402 [Patent Document 7] Japanese Patent Application Publication No. 8-57262 [Patent Document 8] Japanese Patent Publication No. 2020-182898 [Patent Document 9] Japanese Patent Publication No. 2022-515962 [Overview of the Initiative] [Problems that the invention aims to solve]

[0013] The object of this invention is to efficiently promote the chemical reaction that decomposes ammonia (NH3), and to reduce NO, which is produced as a by-product by the oxidation reaction of NH3. X A catalyst for promoting the decomposition of ammonia, which can also efficiently promote chemical reactions that decompose N2O, is hardly degraded by SO2 which may be present in combustion exhaust gases, and has excellent high-temperature resistance, as well as efficiently decomposes NH3 contained in the treated gas and reduces NO contained in the treated gas, such as NO produced as a by-product by the oxidation reaction of NH3. X The objective is to provide a method for detoxifying a gas to be treated, which can also decompose N2O with high efficiency. [Means for solving the problem]

[0014] [1] A carrier containing silica and / or titania, and platinum and / or iridium and cerium supported on the carrier. A first catalyst powder comprising the following, Fe ions BEA type A second catalyst powder containing a substance obtained by ion exchange with zeolite, A catalyst for promoting the decomposition reaction of ammonia, containing a mixture of the following: And, In the first catalyst powder, the ratio of the mass of cerium to the mass of platinum and / or iridium is 1 or more and less than 10. A catalyst comprising 1 to 100 parts by mass of the second catalyst powder relative to 1 part by mass of the first catalyst powder. .

[0016] [ 2 ] The aforementioned First catalyst powder and The aforementioned Second catalyst powder and Titanium oxide, tungsten n Oxides, and cerium Mu A third catalyst powder containing an oxide and Contains a mixture of fruit , In the third catalyst powder, the ratio of cerium to titanium is 1 to 20% by weight as the weight percentage of cerium dioxide to titanium dioxide, and the ratio of tungsten to titanium is 1 to 50% by weight as the weight percentage of tungsten trioxide to titanium dioxide. The amount of the third catalyst powder is 0 to 70 parts by mass per 1 part by mass of the first catalyst powder, as described in [1]. Catalyst 。

[0019] 3 [1] or [2] The catalyst described in medium A method for detoxifying a gas to be treated, comprising, in the presence of a catalyst, carrying out a chemical reaction of converting NH3 contained in the gas to be treated into nitrogen and water, and a chemical reaction of converting NO X and N2O contained in the gas to be treated into nitrogen and water.

[0020] 4 The method according to [ [ 3 ], further comprising adding at least one reaction auxiliary selected from the group consisting of ammonia and urea to the gas to be treated. 5 The method according to [ [ X ], further comprising adjusting the amount of the reaction auxiliary added to the gas to be treated based on the temperature of the treated gas and the amounts of NO 4 and N2O contained in the treated gas.

[0021] 6 The method according to 〔3〕 , further comprising cooling the gas to be treated. 7 The method according to [ [ 6 ], further comprising adjusting the degree of cooling the gas to be treated based on the temperature of the treated gas. 。 Effects of the Invention

[0022] The catalyst of the present invention can promote the chemical reaction of decomposing ammonia (NH3) with high efficiency, and can also promote the decomposition reaction of NO X and / or N2O by-produced by the oxidation reaction of NH3 with high efficiency, has almost no deterioration caused by SO2 which may be contained in combustion exhaust gas, etc., and is excellent in high temperature resistance. The catalyst of the present invention is suitable for a chemical reaction for detoxifying exhaust gas containing NH3 and the like. ​​​​​The present invention provides a method for highly efficiently decomposing NH3 contained in the gas to be treated and for removing NO contained in the gas to be treated, such as NO produced as a by-product by the oxidation reaction of NH3. X And / or N2O can be decomposed with high efficiency. The method of the present invention is suitable for detoxifying exhaust gas containing NH3 and the like.

[0023] The chemical reaction that can convert NH3 into nitrogen and water (the direct decomposition reaction of ammonia) is represented by equation (4). 4NH3 + 3O2 → 2N2 + 6H2O (4) This chemical reaction is exothermic. If large amounts of ammonia and oxygen are supplied to the catalyst layer, the chemical reaction may proceed too quickly, causing hot spots to form in the catalyst layer and leading to thermal degradation of the catalyst. The catalyst of the present invention promotes the direct decomposition reaction of ammonia. In particular, the catalyst of the present invention described in [3] promotes the direct decomposition reaction of ammonia without thermal degradation even at high temperatures of 500°C or higher.

[0024] NO X A chemical reaction that can change (NO) into nitrogen and water. X The decomposition reaction of is represented by equations (6), (7), and (8). 4NO + 4NH3+ O2→ 4N2+ 6H2O (6) 6NO2 + 8NH3 → 7N2 + 12H2O (7) NO + NO2+ 2NH3→ 2N2+ 3H2O (8) The chemical reaction that can convert N2O into nitrogen and water (the decomposition reaction of N2O) is represented by equation (9). 3N2O + 2NH3 → 4N2 + 3H2O (9) The catalyst of the present invention is NO X It also promotes the decomposition reaction of and the decomposition reaction of N2O.

[0025] In parallel with the chemical reaction represented by equation (4), the chemical reactions (side reactions) represented by equations (1), (2), and (3) may proceed. 4NH3 + 5O2 → 4NO + 6H2O (1) 4NH3 + 7O2 → 4NO2 + 6H2O (2) 2NH3 + 2O2 → N2O + 3H2O (3) NO produced by these side reactions X And N2O are harmful substances that affect the environment, etc. As mentioned above, the catalyst of the present invention is NO X Since it also promotes the decomposition reaction of NH3 and the decomposition reaction of N2O, as a result, the catalyst of the present invention converts NH3 into an intermediate (NO X This facilitates a chemical reaction (indirect decomposition of ammonia) that can convert ammonia into nitrogen and water via N2O. [Brief explanation of the drawing]

[0026] [Figure 1] This figure shows the change in NH3 concentration at the reactor outlet at 550°C. [Figure 2] This figure shows the change in NOX concentration at the reactor outlet at 550°C. [Figure 3] This figure shows the change in N2O concentration at the reactor outlet at 550°C. [Figure 4] This figure compares the NH3 concentrations at the reactor outlet at 550°C. [Figure 5] This figure compares the NOx concentrations at the reactor outlet at 550°C. [Figure 6] This figure compares the N2O concentrations at the reactor outlet at 550°C. [Figure 7] This figure shows the temperature dependence of the NH3 decomposition rate. [Figure 8] This is an enlarged view of the main part of Figure 7. [Figure 9] This figure shows the temperature dependence of the NOx decomposition rate (denitrification rate). [Figure 10] This figure shows the temperature dependence of the N2O concentration at the reactor outlet. [Figure 11] This is a diagram comparing the NH3 decomposition rates. [Figure 12] This is a graph comparing denitrification rates. [Figure 13] This graph compares the N2O concentrations at the reactor outlet. [Figure 14] This figure shows an example of an apparatus for detoxifying high-temperature NH3-containing gases. [Figure 15] This figure shows an example of an apparatus for detoxifying low-temperature NH3-containing gases. [Figure 16] This figure shows an example of an apparatus for detoxifying high-temperature NH3-containing gases. [Figure 17] This figure shows an example of an apparatus for detoxifying high-temperature NH3-containing gases. [Figure 18] This figure shows an example of an apparatus for detoxifying high-temperature NH3-containing gases. [Modes for carrying out the invention]

[0027] The catalyst of the present invention is a catalyst for promoting the decomposition reaction of ammonia. The catalyst of the present invention comprises a mixture of a first catalyst powder and a second catalyst powder, or a mixture of the first catalyst powder, the second catalyst powder, and a third catalyst powder.

[0028] The first catalyst powder comprises a carrier and a noble metal.

[0029] The support is a support containing at least one selected from the group consisting of ceria, silica, alumina, titania, zirconia, and zeolite. A support containing silica and / or titania is preferably used. The support is preferably porous. The specific surface area of ​​the support is not particularly limited, for example, 10 to 1,000 m². 2 / g is preferred, and 100-500m 2 / g is more preferable. Specific examples of the carrier include: ceria powder, silica powder, alumina powder, titania powder, zirconia powder, or zeolite powder; a mixture of two or more powders selected from the group consisting of ceria powder, silica powder, alumina powder, titania powder, zirconia powder, and zeolite powder; powder of two or more composites selected from the group consisting of ceria, silica, alumina, titania, zirconia, and zeolite (e.g., silica-titania, alumina-titania, ceria-titania, silica-alumina, silica-zirconia, alumina-zirconia, etc.); powder in which at least one powder selected from the group consisting of ceria powder, silica powder, alumina powder, titania powder, zirconia powder, and zeolite powder is doped, supported, or compounded with at least one element selected from the group consisting of cerium, silicon, aluminum, titanium, and zirconium and different from the elements constituting the powder, and / or other metallic elements such as molybdenum, tungsten, and vanadium; and so on. Doping, supported, or compounded powders tend to have high resistance to hydrothermal aging.

[0030] The precious metal is at least one selected from the group consisting of gold, silver, platinum, ruthenium, rhodium, palladium, osmium, iridium, and rhenium. Platinum and / or iridium are particularly preferred as the precious metal.

[0031] The first catalyst powder has a noble metal supported on a carrier. The ratio of the noble metal to the carrier in the first catalyst powder is preferably 0.01 to 10% by mass, more preferably 0.02 to 5% by mass, and even more preferably 0.05 to 2% by mass.

[0032] The first catalyst powder may have metal elements other than noble metals supported on the carrier. Examples of other metal elements include rare earth elements such as cerium (Ce), and metallic elements such as molybdenum, tungsten, and vanadium. The ratio of rare earth elements to the carrier in the first catalyst powder is not particularly limited as long as it does not hinder the effects of the present invention. For example, the ratio of the mass of rare earth elements to the mass of noble metals in the first catalyst powder is preferably 1 or more and less than 10, more preferably 3 or more and 7 or less, and even more preferably 4 or more and 6 or less. The first catalyst powder having metal elements other than noble metals supported on the carrier tends to have high resistance to hydrothermal aging.

[0033] The preparation of the first catalyst powder includes, for example, supporting a noble metal on a carrier, and then, if necessary, crushing or pulverizing it to produce a powder. Supporting can be done, for example, by immersing the carrier in a solution, suspension, or emulsion containing the noble metal. Supporting other metal elements besides noble metals can be done in the same manner. After immersion, kneading, evaporation to dryness, drying, calcination, etc., can be performed. The drying temperature should be a temperature at which the liquid can be removed, for example, 100 to 150°C. The calcination temperature should be below the heat resistance temperature of the carrier, for example, 350 to 550°C. The calcination time is, for example, 1 to 5 hours.

[0034] The first catalyst powder is preferably porous. The pore size distribution of the first catalyst powder is not particularly limited. The first catalyst powder is not particularly limited in terms of particle size distribution as long as it is in the form of a fine powder. The particle size distribution can be adjusted by grinding / crushing, classification, etc.

[0035] The second catalyst powder comprises a zeolite and metal ions that can be ion-exchanged with it.

[0036] Examples of zeolites include amicite, analcime, barrerite, bellbergite, bikitaite, boggsite, brewsterite, strontium brewsterite (Sr), brewsterite (Ba), chabazite, chabazite (Ca), chabazite (Na), chabazite (K), chiavennite, and clinoptyryl zeolite. clinoptilolite, clinoptilolite-K, clinoptilolite-Na, clinoptilolite-Ca, cowlesite, dachiardite, dachiardite-Ca, clinoptilolite-Ca (dachiardite-Na), edingtonite, edingtonite (epistilbite), erionite, sodaerionite (Na), carieerionite (K), erionite (Ca), faujasite, soda faujasite (Na), faujasite (Ca), magnesi faujasite (Mg), ferrierite, magnesi ferrierite (Mg), carieferrierite (K), sodaferrierite (Na), garronite, gaultite, gismondine, gmelinite, sodagmelinite (gmelinite-Na), gmelinite-Ca, gmelinite-K, gobbinsite, gonnardite,Goosecreekite, gottardiite, harmome, heulandite, heulandite-Ca, strontium heulandite-Sr, soda heulandite-Na, potassium heulandite-K, hsianghualite, kalborsite, laumontite, levyne, and levitite. (levyne-Ca), levyne-Na, lovdarite, maricopaite, mazzite, merlinoite, mesolite, Monteson montesommaite, mordenite, mutinaite, natrolite, offretite, pahasapaite, partheit e), paulingite, paulingite-Na, paulingite-K, paulingite-Ca, perlialite, perlialite phillipsite, phillipsite-Na, phillipsite-K, phillipsite-Ca, pollucite, roggianite, scole Scolecite, stellerite, stilbite, stilbite-Ca, stilbite-Na, terranovaite, thomsonite, tschernichite, tschortnerite, wairakite, weinebeneite, willhendersonite,Natural zeolites such as yugawaralite; A-type (LTA-type) zeolite, X-type (FAU-type) zeolite, LSX-type (FAU-type) zeolite, Beta-type (BEA-type) zeolite, ZSM-5-type (MFI-type) zeolite, Ferrielite-type (FER-type) zeolite, Mordenite-type (MOR-type) zeolite, L-type (LTL-type) zeolite, Y-type (FAU-type) zeolite, MCM-22-type (MWW-type) zeolite, Ofletite / Erionite-type (O / E-type) zeolite, AEI-type zeolite Synthetic zeolites such as olite, AEL-type zeolite, AFT-type zeolite, AFX-type zeolite, CHA-type zeolite, EAB-type zeolite, ERI-type zeolite, KFI-type zeolite, LEV-type zeolite, LTN-type zeolite, MSO-type zeolite, RHO-type zeolite, SAS-type zeolite, SAT-type zeolite, SAV-type zeolite, SFW-type zeolite, TON-type zeolite, and TSC-type zeolite can be mentioned. Of these, BEA-type zeolite is preferred. The ratio of SiO2 to Al2O3 in the zeolite (SiO2 / Al2O3 ratio) is preferably 5 to 100, more preferably 7 to 50, and even more preferably 9 to 30. The higher the proportion of SiO2, the higher the durability of the catalyst tends to be, but the higher the proportion of Al2O3, the greater the amount of ion-exchangeable metal ions, so there is an optimal value for the SiO2 / Al2O3 ratio. The zeolite is preferably porous. The pore size of the zeolite is not particularly limited; for example, 0.01 to 10 nm is preferred, and 0.2 to 2 nm is more preferred.

[0037] Synthetic zeolites can be obtained by mixing a silica source, alumina source, alkali source, solvent, organic structure-directing agent (OSDA), surfactant, etc., to obtain a starting reaction mixture, which is then subjected to a hydrothermal reaction under high temperature and pressure in an autoclave. The synthetic zeolite obtained by this method contains organic components derived from OSDA. However, it appears that these organic components can be removed by subsequent calcination.

[0038] Certain synthetic zeolites can be obtained by hydrothermal reaction without using OSDA. Furthermore, certain synthetic zeolites can be obtained by utilizing mechanochemical treatment and steam synthesis methods without using OSDA. Synthetic zeolites obtained without using OSDA (hereinafter sometimes referred to as OSDA-free zeolites) do not contain organic matter derived from OSDA. In the present invention, OSDA-free zeolites can be preferably used. The SiO2 / Al2O3 molar ratio in OSDA-free zeolite is preferably 1 or more, more preferably 5 or more, and even more preferably 8 or more. The upper limit of the SiO2 / Al2O3 molar ratio in OSDA-free zeolite is, for example, preferably 50, more preferably 45, and even more preferably 40.

[0039] The ion-exchangeable metal ion is preferably at least one ion selected from the group consisting of Fe ions, Ce ions, Co ions, and Cu ions, with Fe ions being more preferred.

[0040] The second catalyst powder is obtained by exchanging (ion-exchanging) the cations of the elements that constituted the zeolite for cations of Fe, Ce, Co, or Cu. The second catalyst powder may also contain zeolite to which at least one selected from the group consisting of Fe, Ce, Co, and Cu is attached (supported). The proportion of ion-exchangeable metal ions to the zeolite in the second catalyst powder is preferably 0.1 to 10% by mass, more preferably 0.7 to 7% by mass. The proportion of Fe ions to the zeolite is preferably 0.1 to 10% by weight, more preferably 0.7 to 7% by weight.

[0041] Ion exchange can be performed by immersing zeolite in a liquid containing ion-exchangeable metal ions, and then filtering / drying / calcining as necessary. It is preferable to adjust the pH of the solution containing ion-exchangeable metal ions into which the zeolite is immersed. The pH of the solution containing ion-exchangeable metal ions is, for example, 1 to 8, preferably 3.5 to 7.5, and more preferably 5.5 to 7.0. Basic compounds such as sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, sodium carbonate, potassium carbonate, or acidic compounds such as hydrochloric acid or nitric acid can be used to adjust the pH. The drying temperature should be any temperature that can remove the liquid, for example, 100-150°C. The firing temperature should be any temperature below the heat resistance temperature of the zeolite, for example, 350-800°C. The firing time can be set appropriately according to the firing temperature, for example, 1-10 hours. After ion exchange, the material can be powdered by grinding or crushing as needed.

[0042] The second catalyst powder is preferably porous. The pore size distribution of the second catalyst powder is not particularly limited. The second catalyst powder is not particularly limited in terms of particle size distribution as long as it is in the form of a fine powder. The particle size distribution can be adjusted by grinding / crushing, classification, etc.

[0043] The second catalyst powder has acid sites derived from OH groups, etc. The properties of the acid sites can generally be observed using a method known as the pyridine-TPD method. In the pyridine-TPD method, for example, a flame ionization detector (FID) can be used as a detector. Pyridine is adsorbed at the acid sites. Pyridine can be adsorbed at acid sites on the outer surface of the catalyst pores and at acid sites on the inner surface of the pores. It is generally understood that the higher the temperature at which the adsorbed pyridine is desorbed, the stronger the acidity of the acid sites. It is also said that the pyridine desorbed at high temperatures comes from acid sites affected by diffusion, i.e., acid sites located on the inner surface of the pores (Nakano et al., "Measurement of Acid Properties of Zeolites by Temperature-Increased Desorption Method," Toyo Soda Research Reports, Vol. 29, No. 1 (1985), pp. 3-11). The effective molecular diameter of pyridine is said to be 5.8 Å (see Anderson et al. J. Catal., 58, 114 (1979)). Furthermore, the total amount of acid sites can be determined by the saturation adsorption amount of pyridine. The acid intensity distribution of acid sites can be determined by the distribution of the amount of pyridine desorbed at each temperature when pyridine is adsorbed and then the temperature is raised at a constant rate (20°C / min) (this distribution is sometimes called the TPD spectrum). In this invention, pyridine adsorption can be carried out at room temperature to 150°C, preferably at 150°C.

[0044] The second catalyst powder has a TPD spectrum in which the ratio of the total amount of pyridine removed in the range of 150°C to less than 450°C to the total amount of pyridine removed in the range of 450°C to 800°C is preferably 0.9 or higher, more preferably 0.98 or higher, even more preferably 1 or higher, and even more preferably 1.1 or higher. The upper limit of the ratio of the total amount of pyridine removed in the range of 150°C to less than 450°C to the total amount of pyridine removed in the range of 450°C to 800°C is not particularly limited, as long as it can be manufactured.

[0045] The second catalyst powder has a TPD spectrum in which the total amount of pyridine released in the range of 150°C to less than 450°C is preferably 100 μmol or more, more preferably 200 μmol or more, even more preferably 250 μmol or more, and even more preferably 300 μmol or more per gram of catalyst. The upper limit of the total amount of pyridine released in the range of 150°C to less than 450°C is not particularly limited, as long as it can be manufactured.

[0046] The second catalyst powder has a TPD spectrum in which the total amount of pyridine removed in the range of 450°C to 800°C is preferably 1000 μmol or less, more preferably 800 μmol or less, and even more preferably 500 μmol or less per gram of catalyst. The lower limit of the total amount of pyridine removed in the range of 450°C to 800°C is not particularly limited, as long as it can be manufactured.

[0047] In the TPD spectrum of the second catalyst powder, the value of the L peak (amount of pyridine elimination at the maximum peak top within the range of 150°C to less than 450°C) is greater than the value of the H peak (amount of pyridine elimination at the maximum peak top within the range of 450°C to 800°C). That is, the ratio of the L peak value to the H peak value is preferably greater than 1, more preferably 1.12 or more, even more preferably 1.2 or more, even more preferably 1.4 or more, and most preferably 1.6 or more. The upper limit of the ratio of the L peak value to the H peak value is not particularly limited, as long as it is feasible to manufacture.

[0048] In the second catalyst powder, the lower limit of the temperature at which the H peak appears in the TPD spectrum (temperature at the maximum peak top within the range of 450°C to 800°C) is preferably 490°C, more preferably 510°C, even more preferably 530°C, and the upper limit is 650°C, more preferably 620°C, even more preferably 600°C, and even more preferably 580°C.

[0049] The second catalyst powder is preferably one that has a high saturation adsorption capacity for pyridine. The saturation adsorption capacity of pyridine in the second catalyst powder is preferably 100 μmol or more, more preferably 200 μmol or more, even more preferably 500 μmol or more, and even more preferably 700 μmol or more per gram of catalyst. The upper limit of the saturation adsorption capacity of pyridine in the second catalyst powder is not particularly limited as long as it can be manufactured, for example, preferably 2000 μmol and more preferably 1500 μmol per gram of catalyst. The saturation adsorption capacity of pyridine can be measured at 150°C.

[0050] The second catalyst powder is preferably one with a large crystallite size. The crystallite size of the second catalyst powder is preferably 5 nm or larger, more preferably 10 nm or larger, even more preferably 20 nm or larger, and even more preferably 30 nm or larger. The upper limit of the crystallite size of the second catalyst powder is not particularly limited as long as it can be manufactured, for example, preferably 100 nm, more preferably 80 nm. The crystallite size can be measured by X-ray diffraction (see, for example, JIS H 7805 or JIS R 7651).

[0051] Preferably, the second catalyst powder maintains high NO2 decomposition rates and NO decomposition rates even after exposure to a 530°C gas containing 20% ​​H2O and 20 ppm SO2 for 70 hours. Preferably, the second catalyst powder maintains a NO2 decomposition rate of 60% or more and an NO decomposition rate of 90% or more under 450°C conditions, even after exposure to a 530°C gas containing 20% ​​H2O and 20 ppm SO2 for 70 hours.

[0052] The third catalyst powder comprises titanium oxide, tungsten and / or molybdenum oxide, and cerium and / or vanadium oxide, preferably comprising titanium oxide, tungsten oxide, and cerium oxide.

[0053] The ratio of Ce and / or V elements to Ti is preferably 1 to 20% by weight, more preferably 3 to 15% by weight, as a weight percentage of (CeO2 + V2O5) / TiO2. The ratio of Mo and / or W to Ti is preferably 1 to 50% by weight, more preferably 10 to 40% by weight, as a weight percentage of (MoO3 + WO3) / TiO2.

[0054] In the preparation of the third catalyst powder, titanium oxide powder or titanium oxide precursors can be used as raw materials for titanium oxide. Examples of titanium oxide precursors include titanium oxide slurry, titanium oxide sol; titanium sulfate, titanium tetrachloride, titanates, and titanium alkoxides. In the present invention, materials that form anatase-type titanium oxide are preferably used as raw materials for titanium oxide. Vanadium compounds such as vanadium pentoxide, ammonium metavanadate, and vanadyl sulfate can be used as raw materials for vanadium oxide. Ammonium paratungstate, ammonium metatungstate, tungsten trioxide, and tungsten chloride can be used as raw materials for tungsten oxide. Ammonium molybdate and molybdenum trioxide can be used as raw materials for molybdenum oxide. Cerium nitrate, cerium nitrate, cerium carbonate, cerium sulfate, cerium sulfate, and cerium acetate can be used as raw materials for cerium oxide.

[0055] The third catalyst powder may contain, as a co-catalyst or additive, oxides of P, S, Al (e.g., alumina), Si (e.g., glass fiber), Zr (e.g., zirconia), gypsum (e.g., dihydrate gypsum), zeolite, etc. These can be used in the form of powder, sol, slurry, or fiber during catalyst preparation.

[0056] The preparation of the third catalyst powder includes, for example, adding a solvent (e.g., water) to the raw materials of each oxide and, if necessary, a co-catalyst or additive, kneading the mixture, evaporating the resulting mixture to dryness, drying, calcining, and then, if necessary, grinding or crushing it to produce a powder. The drying temperature should be a temperature at which the liquid can be removed, for example, 100 to 150°C. The calcination temperature should be below the heat resistance temperature of the oxide, for example, 350 to 550°C. The calcination time is, for example, 1 to 5 hours.

[0057] The third catalyst powder is preferably porous. The pore size distribution of the third catalyst powder is not particularly limited. As long as the third catalyst powder is in the form of a fine powder, its particle size distribution is not particularly limited. The particle size distribution can be adjusted by grinding / crushing, classification, etc.

[0058] The catalyst of the present invention can be obtained by mixing a first catalyst powder and a second catalyst powder, or by mixing a first catalyst powder, a second catalyst powder, and a third catalyst powder. The mixing may be dry or wet. After mixing, drying or calcination, crushing / disintegration, granulation, and classification can be performed as needed. The drying temperature should be a temperature at which the liquid can be removed, for example, 100 to 150°C. The calcination temperature should be below the heat resistance temperature of the oxide, for example, preferably 350 to 650°C, more preferably 450 to 600°C, and even more preferably 480 to 570°C. The calcination time can be appropriately set according to the calcination temperature, for example, 1 to 5 hours. The catalyst of the present invention is not particularly limited by the particle size distribution. The particle size distribution can be adjusted by crushing / disintegration, granulation, classification, etc.

[0059] The mixing ratio of the first catalyst powder to the second catalyst powder, or the mixing ratio of the first catalyst powder, the second catalyst powder, and the third catalyst powder, is determined, for example, by the NH3 concentration and NO concentration in the gas effluent from the catalyst layer or reactor. X The concentration and N2O concentration can be set so that they are within a predetermined range.

[0060] The amount of the first catalyst powder contained in the catalyst of the present invention is preferably 0.01 to 10% by mass, more preferably 0.1 to 5% by mass, and even more preferably 0.5 to 3% by mass. The amount of noble metal contained in the catalyst of the present invention is preferably 0.05 to 1000 ppm, more preferably 0.1 to 500 ppm, and even more preferably 5 to 200 ppm. For every 1 part by mass of the first catalyst powder, the amount of the second catalyst powder is preferably 1 to 100 parts by mass, more preferably 10 to 70 parts by mass, and even more preferably 20 to 55 parts by mass.

[0061] The third catalyst powder can be mixed in when heat resistance is required. The amount of the third catalyst powder is preferably 0 to 70 parts by mass, more preferably 0 to 50 parts by mass, and even more preferably 0 to 30 parts by mass, per 1 part by mass of the first catalyst powder. The higher the proportion of the third catalyst powder, the lower the NH3 outlet concentration can be in reactions at high temperatures, such as 500°C or above.

[0062] The catalyst of the present invention may be formed by attaching (supporting) the above mixture to a support, or by molding the above mixture. Examples of support materials include honeycomb supports, corrugated supports, and plate-shaped supports (lath plates) such as expanded metal and perforated metal (punching metal). The amount of catalyst attached to the support can be set appropriately, taking into consideration the improvement of the catalyst packing efficiency. The mixture can be molded into shapes such as honeycomb, corrugated, cone, frustum, ellipsoid, spindle, Raschig ring, Dixon, saddle, and McMahon, taking into consideration factors such as improving catalyst packing efficiency and suppressing increased head loss. After being supported or molded onto a support, drying or firing can be performed as needed. The drying temperature should be any temperature that can remove the liquid, for example, 100 to 150°C. The firing temperature should be any temperature below the heat resistance temperature of the oxide, for example, preferably 350 to 650°C, more preferably 450 to 600°C, and even more preferably 480 to 570°C. The firing time can be set appropriately according to the firing temperature, for example, 1 to 5 hours.

[0063] The present invention provides a method for detoxifying a gas to be treated. Here, the gas to be treated refers to the gas flowing into the catalyst layer (where the catalyst of the present invention is located) or the gas passing through the catalyst layer. When the catalyst layers are arranged in a series of multiple stages, the gas to be treated includes not only the gas flowing into or passing through the preceding catalyst layer, but also the gas flowing into or passing through the subsequent catalyst layer.

[0064] The gas to be treated is a gas containing NH3 and O2. For example, if the O2 concentration of the NH3-containing gas is high, the NH3-containing gas can be used as the gas to be treated as is. Otherwise, a gas obtained by mixing the NH3-containing gas and the O2-containing gas can be used as the gas to be treated. Examples of NH3-containing gases include exhaust gas produced by the combustion of ammonia fuel, exhaust gas released during purging of ammonia-related equipment, or exhaust gas released during the treatment of ammonia-containing wastewater. NH3-containing gases can also be used from fields that store and utilize ammonia, such as ammonia-fueled ships, ammonia transport ships, ammonia fuel storage bases, ammonia tanks for denitrification equipment in power plants, and ammonia cooling / refrigeration equipment; and from fields that treat ammonia-containing wastewater, such as wastewater from food and beverage production, chemical plants, plating wastewater, semiconductor component manufacturing wastewater, and domestic wastewater. If NH3 is dissolved in a liquid or adsorbed on a solid, vaporized NH3 can be used, obtained by using a decontamination tower, vaporizer, etc. As the O2-containing gas, for example, air can be used. The mass ratio of O2 to NH3 and the temperature of the gas to be treated are, for example, the NH3 concentration and NO in the gas effluent from the catalyst layer or reactor. X The concentration and N2O concentration can be set to be within predetermined ranges. Temperature control can be performed by known methods, for example, using temperature control devices such as heaters, heat exchangers, and coolers. The gas flowing out of the catalyst layer may be used as the heat transfer medium for temperature control of the gas to be treated. The exhaust gas produced by the combustion of ammonia fuel is NO X It contains or / and N2O. The gas being treated is NO X Or / and may further contain N2O.

[0065] The method of the present invention involves a chemical reaction in the presence of the catalyst of the present invention that converts NH3 contained in the gas to be treated into nitrogen and water, and NO contained in the gas to be treated. X and a chemical reaction that converts N2O into nitrogen and water. X The N2O may be present in the gas flowing into the catalyst layer from the beginning, or it may be generated while passing through the catalyst layer.

[0066] Chemical reactions are preferably carried out in a continuous flow reactor. A catalyst layer is present inside the reactor. In a continuous flow reactor, gas adjusted to a predetermined temperature is introduced from the reactor inlet, the chemical reaction takes place in the catalyst layer inside the reactor, and the gas is discharged from the reactor outlet. The catalyst of the present invention can be installed in a reactor in the form of a fixed bed, a fluidized bed, a moving bed, a pseudo-moving bed, and preferably in the form of a fixed bed or a pseudo-moving bed. The space velocity of the gas flowing inside the reactor [1 / hr] (= volumetric flow rate (m³) 3 / hr) / catalyst volume (m 3 )) for example, the NH3 concentration and NO concentration in the gas effluent from the catalyst layer or reactor. XThe concentration and N2O concentration can be set to be within predetermined ranges. The gas temperature at the reactor inlet is preferably 300 to 600°C, more preferably 350 to 550°C.

[0067] The method of the present invention preferably involves adding at least one reaction aid selected from the group consisting of ammonia and urea to the gas to be treated. Urea decomposes into carbon dioxide and ammonia by an endothermic reaction. The addition of the reaction aid is due to the NO contained in the gas to be treated. X This is preferably done when the amount of N2O is large.

[0068] The method of the present invention preferably further includes cooling the gas to be treated. Gases discharged from combustion devices such as furnaces and internal combustion engines are often at high temperatures. The inflow of high-temperature gas to be treated raises the temperature of the catalyst layer. An excessive rise in the temperature of the catalyst layer increases the risk of catalyst degradation. If the temperature of the gas to be treated is too high, it is preferable to cool the gas to be treated to prevent catalyst degradation. Cooling of the gas to be treated can be achieved by adding a low-temperature gas such as air to the gas to be treated, or by heat exchange between the gas to be treated and a refrigerant.

[0069] The method of the present invention involves adjusting the amount of reaction aid added to the gas to be treated, the temperature of the treated gas, and the amount of NO contained in the treated gas. XPreferably, the method further includes adjusting based on the amount of N2O. Furthermore, preferably, the method of the present invention further includes adjusting the degree of cooling of the gas to be treated based on the temperature of the treated gas. The temperature of the treated gas is a substitute value for the temperature of the catalyst layer. The temperature of the treated gas is preferably measured near the outlet of the catalyst layer or near the outlet of the reactor. If the temperature of the catalyst layer can be measured directly, that temperature may be used. Here, the treated gas refers to the gas that has flowed out from the catalyst layer (where the catalyst of the present invention is located). When the catalyst layers are arranged in a series of multiple stages, the treated gas includes not only the gas that has flowed out from the preceding catalyst layer but also the gas that has flowed out from the subsequent catalyst layer. However, when adjusting the amount of reaction aid or the degree of cooling, it is preferable that the gas to be treated to which the reaction aid is added or which is cooled is the gas to be treated that is located earlier than the treated gas to which the temperature etc. is measured.

[0070] The amount of reaction aid added and the degree to which the gas to be treated is cooled can be adjusted by considering, for example, the following points. The direct decomposition reaction of ammonia is an exothermic reaction. As the amount of ammonia used in the direct decomposition reaction increases, the temperature of the catalyst layer rises, and consequently, the temperature of the treated gas increases. In other words, the addition of reaction aids can increase the temperature of the treated gas. Furthermore, the inflow of high-temperature gas to be treated also increases the temperature of the catalyst layer. The higher the temperature of the catalyst layer, the faster the rates of the direct decomposition reaction of ammonia and the decomposition reaction of N2O tend to be. However, the higher the temperature of the catalyst layer, the greater the risk of catalyst degradation. (Direct decomposition reaction of ammonia, NO) X The decomposition reaction of NO and the decomposition reaction of N2O reduce the ammonia in the treated gas. When ammonia is reduced, NO X The decomposition reaction of and the decomposition reaction of N2O become less likely to proceed, and NO in the treated gas X Alternatively, the amount of N2O may increase.

[0071] The temperature of the treated gas at each stage is, for example, preferably 400 to 600°C, more preferably 450 to 550°C. NO in the treated gas at the final stage. XThe concentration of is preferably 500 ppm or less, more preferably 200 ppm or less. The concentration of N2O in the treated gas of the final stage is preferably 100 ppm or less, more preferably 10 ppm or less.

[0072] The apparatus for detoxifying the gas to be treated, as shown in Figure 14, includes a reactor 11 and a catalyst layer 12. The apparatus shown in Figure 14 can be suitably used for processing high-temperature NH3-containing gases, such as NH3 fuel combustion exhaust gas.

[0073] The apparatus for detoxifying the gas to be treated, as shown in Figure 15, includes a temperature control mechanism, a reactor 11, a catalyst layer 12, and a control device 17. The temperature control mechanism in the apparatus shown in Figure 15 is configured to raise the gas to be treated to a predetermined temperature. The apparatus shown in Figure 15 includes a heat exchanger 9 configured to exchange heat between the gas to be treated and the treated gas, and a heater 10h configured to exchange heat between the gas to be treated and an external heat source. The apparatus shown in Figure 15 is suitable for treating low-temperature NH3-containing gases, such as purge gases in NH3-related equipment. The apparatus is configured to obtain the gas to be treated by mixing NH3-containing gas A and O2-containing gas B in a mixer 5. The supply amounts of NH3-containing gas A and O2-containing gas B can be adjusted by the opening of their respective control valves. The supply amount of treated gas to the heat exchanger 9 can be adjusted by the opening of a control valve installed in the heat exchanger bypass pipe 3, thereby adjusting the amount of heat exchanged in the heat exchanger 9. If the temperature of the gas to be treated is controlled, there is no need to provide the heat exchanger 9 and / or heater 10h. The catalyst layer 12 consists of the catalyst or catalytic body of the present invention and is fixed inside the reactor 11. The amount of gas to be treated flowing into the catalyst layer can also be adjusted by the opening of a control valve installed in the catalyst layer inlet pipe 2. It is preferable that the amount of gas to be treated flowing in through the catalyst layer inlet pipe 2 be substantially constant in order to ensure that the chemical reaction in the catalyst layer 12 is carried out stably.

[0074] The measurement mechanism measures physical properties necessary to monitor the operating status of the device. In the device shown in Figure 15, multiple measuring instruments 14 measure the gas temperature of the mixer; the gas temperature at the inlet of the catalyst layer; the NH3 concentration; the O2 concentration; and NO X Concentration, N2O concentration, etc.; gas temperature at the outlet of the catalyst layer, NH3 concentration, O2 concentration, NO X It is configured to measure concentrations, N2O concentrations, and other parameters. Based on the measurement values ​​from the measuring device, the supply amount of NH3-containing gas A 、 The control device 17 is configured to control the amount of O2-containing gas B supplied, the amount of gas to be treated flowing into the catalyst layer, and the temperature of the gas to be treated flowing into the catalyst layer. The control objective of the control device 17 is, for example, to prevent high-temperature conditions such as hot spots from occurring in the catalyst layer and to prevent N2O and NO from being present in the exhaust gas 13. X And / or reduce NH3.

[0075] The apparatus for detoxifying the gas to be treated, as shown in Figure 16, includes a reactor 11, a catalyst layer 12, and a control device 17. The apparatus shown in Figure 16 can be suitably used for processing high-temperature NH3-containing gases, such as NH3 fuel combustion exhaust gas. The supply amounts of each reaction aid C can be adjusted by the opening of the control valve. The measuring mechanism measures physical properties necessary to monitor the operating state of the apparatus. In the apparatus shown in Figure 16, multiple measuring instruments 14 measure the gas temperature of the mixer; the gas temperature at the inlet of the catalyst layer; the NH3 concentration; the O2 concentration; and NO X Concentration, N2O concentration, etc.; gas temperature at the outlet of the catalyst layer, NH3 concentration, O2 concentration, NO X It is configured to measure concentrations, N2O concentrations, and other parameters. The control device 17 is configured to control the supply amount of reaction aid C and other parameters based on measurements taken by the measurement mechanism. The control objective of the control device 17 is, for example, to prevent high-temperature conditions such as hot spots from occurring in the catalyst layer and to ensure that N2O and NO are not present in the exhaust gas 13. X And / or reducing NH3. Otherwise, the configuration is the same as the apparatus shown in Figure 14.

[0076] The apparatus for detoxifying the gas to be treated, as shown in Figure 17, includes a temperature control mechanism, a reactor 11, a catalyst layer 12, and a control device 17. The temperature control mechanism in the apparatus shown in Figure 17 is configured to lower the temperature of the gas to be treated to a predetermined level. The apparatus shown in Figure 17 is equipped with a cooling air supply device to lower the temperature of the gas to be treated. The apparatus shown in Figure 17 is particularly suitable for treating high-temperature NH3-containing gases, such as exhaust gas from combustion systems. Supplying air at a lower temperature than the gas to be treated has the effect of lowering the temperature of the gas to be treated. The same effect as supplying cooling air can be obtained by providing a cooler configured to exchange heat with an external cooling source. Otherwise, the configuration is the same as the apparatus shown in Figure 14.

[0077] The apparatus for detoxifying the gas to be treated, as shown in Figure 18, includes a temperature control mechanism, a reactor 11, catalyst layers 12a and 12b, and a control device 17. The temperature control mechanism in the apparatus shown in Figure 18 is configured to lower the temperature of the gas flowing out of the catalyst layer 12a to a predetermined temperature before it flows into the catalyst layer 12b. The apparatus shown in Figure 18 is equipped with a cooler configured to supply cooling air to lower the temperature of the gas flowing out of the catalyst layer 12a. The apparatus shown in Figure 18 can be suitably used to treat high-temperature NH3-containing gases, such as exhaust gas from a combustion system. The same effect as supplying cooling air can be obtained by providing a cooler configured to exchange heat with an external cooling source. Otherwise, the configuration is the same as the apparatus shown in Figure 14.

[0078] Next, examples illustrating the effects of the present invention will be described. However, the scope of the present invention is not limited by these examples.

[0079] [Example 1: Honeycomb catalyst A] (Preparation of the first catalyst powder (1)) 100 g of amorphous silica powder was added to an aqueous solution of hexahydrate chlorplatinic acid (H2PtCl6·6H2O) and stirred, then evaporated to dryness on a sand bath. The dry product was calcined in air at 500°C for 2 hours. The resulting calcined product was pulverized to obtain a first catalyst powder (1) consisting of amorphous silica powder supported with 0.05% by mass of platinum.

[0080] (Preparation of the second catalyst powder (1)) 60 g of BEA-type zeolite powder (SiO2 / Al2O3 ratio = 25) was added to 2000 ml of an aqueous solution containing 9.1 g of iron(II) sulfate heptahydrate (FeSO4·7H2O) heated to 80°C. The mixture was then stirred for 2 hours while maintaining the temperature at 80°C to obtain a slurry. The slurry was dehydrated using a suction funnel fitted with filter paper (No. 5C). Pure water was poured over the cake on the filter paper and washed. The washed cake was dried at 110°C for 12 hours. The dried cake was placed in a furnace and the temperature was increased at 100°C / h, and it was fired at 500°C for 5 hours. The fired material was crushed to obtain a second catalyst powder (1) in which Fe ions were exchanged with the zeolite.

[0081] (Preparation of the third catalyst powder) Dissolve 110g of cerium(III) nitrate hexahydrate (Ce(NO3)3·6H2O), 385g of ammonium metatungstate, and 55g of oxalic acid in 700g of water. This aqueous solution was then prepared in 300ml solution. 2 715g of anatase-type titanium dioxide with a specific surface area of ​​90m² or more 2 The mixture was poured into a powder containing 385 g of anatase-type titanium dioxide (less than 1 g) and kneaded for at least 1 hour. The resulting mixture was granulated. The granulated material was dried at 120°C for 4 hours. The dried product was calcined in air at 500°C for 2 hours. The resulting calcined material was pulverized to obtain a third catalyst powder containing titanium oxide, tungsten oxide, and cerium oxide.

[0082] (Manufacturing of catalysts) A slurry was obtained by adding 2 parts by mass of the first catalyst powder (1), 78 parts by mass of the second catalyst powder (1), and 20 parts by mass of the third catalyst powder to pure water. This slurry was applied to a coating area of ​​140 g / m². 2The material was applied to a honeycomb substrate (which had an outer diameter such that the outer surface of the honeycomb catalyst was in contact with the inner surface of the tube wall of a tubular reactor). This was dried at 120°C for 2 hours. Then it was calcined at 500°C for 2 hours to obtain honeycomb catalyst A. The amount of platinum contained in the catalyst of honeycomb catalyst A was 10 ppm.

[0083] (Evaluation of catalysts (1)) A honeycomb catalyst A was fitted and fixed inside a tubular reactor. Simulated gas A containing the components shown in Table 1 was flowed into the tubular reactor at AV = 13 Nm / hr (AV = gas volume / geometric surface area of ​​the honeycomb catalyst), and the temperature of the tubular reactor was set to 550°C. The NH3 concentration and NO at the reactor outlet were measured. X The concentrations of the solution and N2O were measured. The results are shown in Figures 1-6.

[0084] [Table 1]

[0085] [Example 2: Honeycomb catalyst B] Honeycomb catalyst B was obtained in the same manner as in Example 1, except that 2 parts by mass of first catalyst powder (1), 78 parts by mass of second catalyst powder (1), and 20 parts by mass of third catalyst powder were replaced with 2 parts by mass of first catalyst powder (1), 88 parts by mass of second catalyst powder (1), and 10 parts by mass of third catalyst powder. Honeycomb catalyst A was replaced with honeycomb catalyst B in the same manner as in Example 1, and the NH3 concentration and NO at the reactor outlet were measured. X The concentrations of the solution and N2O were measured. The results are shown in Figures 1-6.

[0086] [Example 3: Honeycomb catalyst C] Honeycomb catalyst C was obtained in the same manner as in Example 1, except that 2 parts by mass of the first catalyst powder (1), 78 parts by mass of the second catalyst powder (1), and 20 parts by mass of the third catalyst powder were replaced with 2 parts by mass of the first catalyst powder (1) and 98 parts by mass of the second catalyst powder (1). The NH3 concentration and NO at the reactor outlet were measured in the same manner as in Example 1, except that honeycomb catalyst A was replaced with honeycomb catalyst C. X The concentrations of the solution and N2O were measured. The results are shown in Figures 1-6.

[0087] [Example 4: Honeycomb catalyst D] Honeycomb catalyst D was obtained in the same manner as in Example 1, except that 2 parts by mass of first catalyst powder (1), 78 parts by mass of second catalyst powder (1), and 20 parts by mass of third catalyst powder were replaced with 2 parts by mass of first catalyst powder (1), 70 parts by mass of second catalyst powder (1), and 28 parts by mass of third catalyst powder. Honeycomb catalyst A was replaced with honeycomb catalyst D in the same manner as in Example 1, and the NH3 concentration and NO at the reactor outlet were measured. X The concentrations of the solution and N2O were measured. The results are shown in Figures 1-6.

[0088] [Example 5: Honeycomb catalyst E] Honeycomb catalyst E was obtained in the same manner as in Example 1, except that 2 parts by mass of first catalyst powder (1), 78 parts by mass of second catalyst powder (1), and 20 parts by mass of third catalyst powder were replaced with 2 parts by mass of first catalyst powder (1), 50 parts by mass of second catalyst powder (1), and 48 parts by mass of third catalyst powder. Honeycomb catalyst A was replaced with honeycomb catalyst E in the same manner as in Example 1, and the NH3 concentration and NO at the reactor outlet were measured. X The concentrations of the solution and N2O were measured. The results are shown in Figures 1-6.

[0089] [Example 6: Honeycomb catalyst F] Honeycomb catalyst F was obtained in the same manner as in Example 1, except that 2 parts by mass of first catalyst powder (1), 78 parts by mass of second catalyst powder (1), and 20 parts by mass of third catalyst powder were replaced with 2 parts by mass of first catalyst powder (1), 30 parts by mass of second catalyst powder (1), and 68 parts by mass of third catalyst powder. Honeycomb catalyst A was replaced with honeycomb catalyst F in the same manner as in Example 1, and the NH3 concentration and NO at the reactor outlet were measured. X The concentrations of the solution and N2O were measured. The results are shown in Figures 1-6.

[0090] [Example 7: Honeycomb catalyst G] Honeycomb catalyst G was obtained in the same manner as in Example 1, except that 2 parts by mass of first catalyst powder (1), 78 parts by mass of second catalyst powder (1), and 20 parts by mass of third catalyst powder were replaced with 2 parts by mass of first catalyst powder (1) and 98 parts by mass of third catalyst powder. Honeycomb catalyst A was replaced with honeycomb catalyst G in the same manner as in Example 1, and the NH3 concentration and NO at the reactor outlet were measured. XThe concentrations of the solution and N2O were measured. The results are shown in Figures 1-6.

[0091] As described above, the honeycomb catalyst using the catalyst of the present invention can decompose NH3 with high efficiency (approximately 97% or more) even at high temperatures of 500°C or higher. In particular, honeycomb catalysts A, B, C, and D decompose NH3 and NO X Furthermore, it enables highly efficient removal of N2O.

[0092] [Example 8: Honeycomb catalyst C] (Manufacturing of catalysts) Two parts by mass of the first catalyst powder (1) and ninety-eight parts by mass of the second catalyst powder (1) were added to pure water to obtain a slurry. This slurry was used to coat an area of ​​140 g / m². 2 The material was applied to a honeycomb substrate. This was dried at 120°C for 2 hours. Then, it was fired at 500°C for 2 hours to obtain honeycomb catalyst C. The amount of platinum contained in the catalyst of honeycomb catalyst C was 10 ppm.

[0093] (Evaluation of catalysts (2)) A honeycomb catalyst C was fixed inside a tubular reactor. Simulated gas B containing the components shown in Table 2 was flowed into the tubular reactor at AV = 13 Nm / hr (AV = gas volume / geometric surface area of ​​the honeycomb catalyst), and the temperature of the tubular reactor was set to 350°C, 400°C, or 450°C. At each set temperature, the NH3 concentration and NO concentration at the reactor outlet were measured. X The concentration and N2O concentration were measured. NH3 decomposition rate, NO X The decomposition rate (denitrification rate) was calculated. The results are shown in Figures 7-13.

[0094] [Table 2]

[0095] [Example 9: Honeycomb catalyst H] Honeycomb catalyst H was obtained in the same manner as in Example 8, except that 2 parts by mass of the first catalyst powder (1) and 98 parts by mass of the second catalyst powder (1) were replaced with 4 parts by mass of the first catalyst powder (1) and 96 parts by mass of the second catalyst powder (1). The amount of platinum contained in the catalyst of honeycomb catalyst H was 20 ppm. The NH3 concentration and NO at the reactor outlet were measured in the same manner as in Example 8, except that honeycomb catalyst C was replaced with honeycomb catalyst H. X The concentration and N2O concentration were measured. NH3 decomposition rate, NO X The decomposition rate (denitrification rate) was calculated. The results are shown in Figures 7-13.

[0096] [Example 10: Honeycomb catalyst I] (NO X Preparation of reduction catalyst powder) 300m 2 715g of anatase-type titanium dioxide powder with a specific surface area of ​​90m² or more. 2 385g of anatase-type titanium dioxide powder (less than 1g / g), 194g of ammonium metatungstate, 80g of ammonium metavanadate, 103g of oxalic acid, and 560g of water were mixed to make a paste. The resulting paste was granulated. The granules were dried at 120°C for 4 hours, and then calcined at 500°C for 2 hours. The resulting calcined material was crushed and NO X A reduction catalyst powder was obtained.

[0097] 2 parts by mass of the first catalyst powder (1) and 98 parts by mass of the second catalyst powder (1) are mixed with 1 part by mass of the first catalyst powder (1) and NO X Honeycomb catalyst I was obtained in the same manner as in Example 8, except that 99 parts by mass of reduction catalyst powder was used. The amount of platinum contained in the catalyst of honeycomb catalyst I was 5 ppm. The NH3 concentration and NO concentration at the reactor outlet were measured in the same manner as in Example 8, except that honeycomb catalyst C was replaced with honeycomb catalyst I. X The concentration and N2O concentration were measured. NH3 decomposition rate, NO X The decomposition rate (denitrification rate) was calculated. The results are shown in Figures 7-13.

[0098] [Example 11: Honeycomb catalyst J] 2 parts by mass of the first catalyst powder (1) and 98 parts by mass of the second catalyst powder (1) are mixed with 4 parts by mass of the first catalyst powder (1) and NO XHoneycomb catalyst J was obtained in the same manner as in Example 8, except that 96 parts by mass of reduction catalyst powder was used. The amount of platinum contained in the catalyst of honeycomb catalyst J was 20 ppm. The NH3 concentration and NO concentration at the reactor outlet were measured in the same manner as in Example 8, except that honeycomb catalyst C was replaced with honeycomb catalyst J. X The concentration and N2O concentration were measured. NH3 decomposition rate, NO X The decomposition rate (denitrification rate) was calculated. The results are shown in Figures 7-13.

[0099] [Example 12: Honeycomb catalyst K] Honeycomb catalyst K was obtained using the same method as in Example 8, except that BEA-type zeolite powder was replaced with MOR (mordenite)-type zeolite powder (SiO2 / Al2O3 ratio = 25). Honeycomb catalyst C was replaced with honeycomb catalyst K, and the NH3 concentration and NO at the reactor outlet were obtained using the same method as in Example 8. X The concentration and N2O concentration were measured. NH3 decomposition rate, NO X The decomposition rate (denitrification rate) was calculated. The results are shown in Figures 7-13.

[0100] [Example 13: Honeycomb catalyst L] Honeycomb catalyst L was obtained using the same method as in Example 8, except that BEA-type zeolite powder was replaced with MFI (pentasil)-type zeolite powder (SiO2 / Al2O3 ratio = 30). The NH3 concentration and NO at the reactor outlet were obtained using the same method as in Example 8, except that honeycomb catalyst C was replaced with honeycomb catalyst L. X The concentration and N2O concentration were measured, and the NH3 decomposition rate and NO were determined. X The decomposition rate (denitrification rate) was calculated. The results for honeycomb catalyst L were similar to those for honeycomb catalyst K.

[0101] [Example 14: Honeycomb catalyst M] (Preparation of N2O decomposition catalyst powder) 60 g of BEA-type zeolite powder (SiO2 / Al2O3 ratio = 25) was added to 2000 ml of an aqueous solution containing 7.3 g of copper(II) sulfate pentahydrate (CuSO4·5H2O) heated to 80°C. The mixture was then stirred for 2 hours while maintaining the temperature at 80°C to obtain a slurry. The slurry was dehydrated using a suction funnel fitted with filter paper (No. 5C). Pure water was poured over the cake on the filter paper and washed. The washed cake was dried at 110°C for 12 hours. The dried cake was placed in a furnace and the temperature was increased at 100°C / h, and it was fired at 500°C for 5 hours. The fired material was crushed to obtain an N2O decomposition catalyst powder in which Cu ions were exchanged with zeolite.

[0102] Honeycomb catalyst M was obtained in the same manner as in Example 8, except that 2 parts by mass of first catalyst powder (1) and 98 parts by mass of second catalyst powder (1) were replaced with 2 parts by mass of first catalyst powder (1) and 98 parts by mass of N2O decomposition catalyst powder. The NH3 concentration and NO concentration at the reactor outlet were obtained in the same manner as in Example 8, except that honeycomb catalyst C was replaced with honeycomb catalyst M. X The concentration and N2O concentration were measured, and the NH3 decomposition rate and NO were determined. X The decomposition rate (denitrification rate) was calculated. The results for honeycomb catalyst M were similar to those for honeycomb catalyst K. The N2O concentration at the reactor outlet was low immediately after the start of the reaction, but gradually increased due to degradation, presumably caused by SO2, and eventually reached the same level as that of honeycomb catalyst K.

[0103] The honeycomb catalyst C,H using the catalyst of the present invention shows almost no degradation due to SO2, and even in situations where the NH3 concentration is high, it does not degrade due to NO in the exhaust gas. X And while suppressing the increase of N2O, NH3, NO X Furthermore, N2O can be simultaneously decomposed into H2O and N2, rendering it harmless.

[0104] [Example 15: Honeycomb catalyst N] (Preparation of the first catalyst powder (2)) 100 g of amorphous silica powder was added to an aqueous solution of cerium nitrate hexahydrate (Ce(NO3)3·6H2O) and chlorplatinic acid hexahydrate (H2PtCl6·6H2O) and stirred, then evaporated to dryness on a sand bath. The dry product was calcined in air at 500°C for 2 hours. The resulting calcined product was pulverized to obtain a first catalyst powder (2), which consisted of amorphous silica powder supported with 0.25% by mass of cerium and 0.05% by mass of platinum.

[0105] Two parts by mass of the first catalyst powder (2) and ninety-eight parts by mass of the second catalyst powder (1) were added to pure water to obtain a slurry. This slurry was used to coat an area of ​​140 g / m². 2 The material was applied to a honeycomb substrate (which had an outer diameter such that the outer surface of the honeycomb catalyst was in contact with the inner surface of the tube wall of a tubular reactor). This was dried at 120°C for 2 hours. Then it was calcined at 500°C for 2 hours to obtain honeycomb catalyst N. The amount of platinum contained in the catalyst of honeycomb catalyst N was 10 ppm.

[0106] (Evaluation of catalysts (3)) A honeycomb catalyst N was fitted and fixed inside a tubular reactor. Simulated gas C containing the components shown in Table 3 was flowed into the tubular reactor at AV = 13 Nm / hr (AV = gas volume / geometric surface area of ​​honeycomb catalyst), and the temperature of the tubular reactor was set to 359°C, 415°C, 467°C, or 500°C. The NH3 concentration and NO at the reactor outlet were measured. X The concentrations of the solution and N2O were measured. The results are shown in Table 5.

[0107] [Table 3]

[0108] (Catalyst evaluation (4)) A honeycomb catalyst N was fitted and fixed inside a tubular reactor. Simulated gas D containing the components shown in Table 4 was flowed into the tubular reactor at AV = 13 Nm / hr (AV = gas volume / geometric surface area of ​​the honeycomb catalyst), the reactor temperature was set to 530°C, and it was left for 50 hours (hydrothermal aging). Subsequently, simulated gas C containing the components shown in Table 3 was flowed into the tubular reactor at AV = 13 Nm / hr (AV = gas volume / geometric surface area of ​​the honeycomb catalyst), and the reactor temperature was set to 359°C, 415°C, 467°C, or 500°C. The NH3 concentration and NO at the reactor outlet were measured. X The concentrations of the solution and N2O were measured. The results are shown in Table 5.

[0109] [Table 4]

[0110] [Example 16: Honeycomb catalyst O] (Preparation of the first catalyst powder (3)) 100 g of amorphous silica powder was added to an aqueous solution of cerium nitrate hexahydrate (Ce(NO3)3·6H2O) and chlorplatinic acid hexahydrate (H2PtCl6·6H2O) and stirred, and then evaporated to dryness on a sand bath. The dry product was calcined in air at 500°C for 2 hours. The resulting calcined product was pulverized to obtain a first catalyst powder (3) consisting of amorphous silica powder supported with 0.5 mass% cerium and 0.05 mass% platinum.

[0111] Two parts by mass of the first catalyst powder (3) and ninety-eight parts by mass of the second catalyst powder (1) were added to pure water to obtain a slurry. This slurry was applied to a coating area of ​​140 g / m². 2 The material was applied to a honeycomb substrate (which had an outer diameter such that the outer surface of the honeycomb catalyst was in contact with the inner surface of the tube wall of the tubular reactor). This was dried at 120°C for 2 hours. Then it was calcined at 500°C for 2 hours to obtain honeycomb catalyst O. The amount of platinum contained in the catalyst of honeycomb catalyst O was 10 ppm. The NH3 concentration and NO at the reactor outlet were measured using the same method as in Example 15. X The concentrations of the solution and N2O were measured. The results are shown in Table 5.

[0112] [Example 17: Honeycomb catalyst P] (Preparation of the first catalyst powder (4)) 100 g of amorphous silica powder was added to an aqueous solution of cerium nitrate hexahydrate (Ce(NO3)3·6H2O) and chlorplatinic acid hexahydrate (H2PtCl6·6H2O) and stirred, then evaporated to dryness on a sand bath. The dry product was calcined in air at 500°C for 2 hours. The resulting calcined product was pulverized to obtain a first catalyst powder (4) consisting of amorphous silica powder supported with 3% by mass of cerium and 0.05% by mass of platinum.

[0113] Two parts by mass of the first catalyst powder (4) and ninety-eight parts by mass of the second catalyst powder (1) were added to pure water to obtain a slurry. This slurry was used to coat an area of ​​140 g / m². 2 The material was applied to a honeycomb substrate (which had an outer diameter such that the outer surface of the honeycomb catalyst was in contact with the inner surface of the tube wall of the tubular reactor). This was dried at 120°C for 2 hours. Then it was calcined at 500°C for 2 hours to obtain honeycomb catalyst P. The amount of platinum contained in the catalyst of honeycomb catalyst P was 10 ppm. The NH3 concentration and NO at the reactor outlet were measured using the same method as in Example 15. X The concentrations of the solution and N2O were measured. The results are shown in Table 5.

[0114] [Example 18: Honeycomb catalyst A] For honeycomb catalyst A, the NH3 concentration and NO at the reactor outlet were measured using the same method as in Example 15. X The concentrations of the solution and N2O were measured. The results are shown in Table 5.

[0115] [Table 5]

[0116] As shown in Table 5, honeycomb catalysts N and O showed higher NH3 decomposition rates compared to honeycomb catalyst A under evaluations (3) and (4), which were under conditions of ammonia concentration of 20,000 ppm and NO concentration of 3,000 ppm. Honeycomb catalyst P showed a low NH3 decomposition rate in evaluation (3), so evaluation (4) was not performed. Therefore, improvement in durability can be expected with the addition of cerium, and there is an optimal amount of cerium to add.

[0117] [Example 19: Honeycomb catalyst Q] (Preparation of the first catalyst powder (5)) 100 g of amorphous silica powder was added to an aqueous solution of cerium nitrate hexahydrate (Ce(NO3)3·6H2O) and chlorplatinic acid hexahydrate (H2PtCl6·6H2O) and stirred, and then evaporated to dryness on a sand bath. The dry product was calcined in air at 500°C for 2 hours. The resulting calcined product was pulverized to obtain a first catalyst powder (5) consisting of amorphous silica powder supported with 1.25% by mass of cerium and 0.25% by mass of platinum.

[0118] Two parts by mass of the first catalyst powder (5) and ninety-eight parts by mass of the second catalyst powder (1) were added to pure water to obtain a slurry. This slurry was applied to a coating area of ​​140 g / m². 2 The material was applied to a honeycomb substrate (which had an outer diameter such that the outer surface of the honeycomb catalyst was in contact with the inner surface of the tube wall of a tubular reactor). This was dried at 120°C for 2 hours. Then it was calcined at 500°C for 2 hours to obtain honeycomb catalyst Q. The amount of platinum contained in the catalyst of honeycomb catalyst Q was 50 ppm.

[0119] (Evaluation of catalysts (5)) A honeycomb catalyst Q was fitted and fixed inside a tubular reactor. A simulated gas E containing the components shown in Table 6 was flowed into the tubular reactor at AV = 13 Nm / hr (AV = gas volume / geometric surface area of ​​the honeycomb catalyst), and the temperature of the tubular reactor was set to 350°C, 400°C, 450°C, or 500°C. The NH3 concentration and NO at the reactor outlet were measured. X The concentrations of the solution and N2O were measured. The results are shown in Table 7.

[0120] [Table 6]

[0121] (Evaluation of catalysts (6)) A honeycomb catalyst N was fitted and fixed inside a tubular reactor. Simulated gas D containing the components shown in Table 4 was flowed into the tubular reactor at AV = 13 Nm / hr (AV = gas volume / geometric surface area of ​​the honeycomb catalyst), the reactor temperature was set to 530°C, and it was left for 70 hours (hydrothermal aging). Subsequently, simulated gas E containing the components shown in Table 6 was flowed into the tubular reactor at AV = 13 Nm / hr (AV = gas volume / geometric surface area of ​​the honeycomb catalyst), and the reactor temperature was set to 350°C, 400°C, 450°C, or 500°C. The NH3 concentration and NO at the reactor outlet were measured. X The concentrations of the solution and N2O were measured. The results are shown in Table 7.

[0122] [Example 20: Honeycomb catalyst R] (Preparation of the first catalyst powder (6)) 100 g of amorphous silica powder was added to an aqueous solution of cerium nitrate hexahydrate (Ce(NO3)3·6H2O) and chlorplatinic acid hexahydrate (H2PtCl6·6H2O) and stirred, and then evaporated to dryness on a sand bath. The dry product was calcined in air at 500°C for 2 hours. The resulting calcined product was pulverized to obtain a first catalyst powder (6) consisting of amorphous silica powder supported with 2.5% by mass of cerium and 0.5% by mass of platinum.

[0123] Two parts by mass of the first catalyst powder (6) and ninety-eight parts by mass of the second catalyst powder (1) were added to pure water to obtain a slurry. This slurry was used to coat an area of ​​140 g / m². 2 The material was applied to a honeycomb substrate (which had an outer diameter such that the outer surface of the honeycomb catalyst was in contact with the inner surface of the tube wall of the tubular reactor). This was dried at 120°C for 2 hours. Then it was calcined at 500°C for 2 hours to obtain honeycomb catalyst R. The amount of platinum contained in the catalyst of honeycomb catalyst R was 100 ppm. The NH3 concentration and NO at the reactor outlet were measured using the same method as in Example 19. X The concentrations of the solution and N2O were measured. The results are shown in Table 7.

[0124] [Example 21: Honeycomb catalyst S] Amorphous silica powder was replaced with titania powder (anatase crystal type, specific surface area = 65.8 m 2 / g, 50% particle diameter = 0.024 μm, TiO2 = 97.3%, SO4 = 2.43%, Na2O = 0.003%), and a honeycomb catalyst S was obtained in the same manner as in Example 15. The amount of platinum contained in the catalyst of honeycomb catalyst S was 10 ppm. In the same manner as in Example 19, the NH3 concentration and NO concentration at the reactor outlet were X measured along with the N2O concentration. The results are shown in Table 7.

[0125] [Example 22: Honeycomb catalyst T] Amorphous silica powder was replaced with titania powder (anatase crystal type, specific surface area = 65.8 m 2 / g, 50% particle diameter = 0.024 μm, TiO2 = 97.3%, SO4 = 2.43%, Na2O = 0.003%), and a honeycomb catalyst T was obtained in the same manner as in Example 19. The amount of platinum contained in the catalyst of honeycomb catalyst T was 50 ppm. In the same manner as in Example 19, the NH3 concentration and NO concentration at the reactor outlet were X measured along with the N2O concentration. The results are shown in Table 7.

[0126] [Example 23: Honeycomb catalyst U] Amorphous silica powder was replaced with titania powder (anatase crystal type, specific surface area = 65.8 m 2 / g, 50% particle diameter = 0.024 μm, TiO2 = 97.3%, SO4 = 2.43%, Na2O = 0.003%), and a honeycomb catalyst U was obtained in the same manner as in Example 20. The amount of platinum contained in the catalyst of honeycomb catalyst U was 100 ppm. In the same manner as in Example 19, the NH3 concentration and NO concentration at the reactor outlet were X measured along with the N2O concentration. The results are shown in Table 7.

[0127] [Example 24: Honeycomb catalyst N] For honeycomb catalyst N, in the same manner as in Example 19, the NH3 concentration and NO concentration at the reactor outlet were X measured along with the N2O concentration. The results are shown in Table 7.

[0128] [Example 25: Honeycomb Catalyst V] Honeycomb Catalyst V was obtained by the same method as in Example 20, except that the amorphous silica powder was replaced with silica-titania powder (powder of composite oxide composed of titanium dioxide and silicon dioxide (main component: titanium dioxide), manufactured by Tronox, GX-550). The amount of platinum contained in the catalyst of Honeycomb Catalyst V was 100 ppm. By the same method as in Example 19, the NH3 concentration, NO X concentration and N2O concentration at the reactor outlet were measured. The results are shown in Table 7.

[0129] [Example 26: Honeycomb Catalyst W] 110 g of cerium(III) nitrate hexahydrate (Ce(NO3)3·6H2O), 385 g of ammonium metatungstate, and 55 g of oxalic acid were dissolved in 700 g of water. This aqueous solution had a specific surface area of 300 m 2 / g or more of anatase-type titanium oxide 715 g and 90 m specific surface area 2 / g or less of anatase-type titanium oxide 385 g, poured into the mixed powder, and kneaded for 1 hour or more. The obtained kneaded product was granulated. The granulated product was dried at 120°C for 4 hours. The dried product was calcined in air at 500°C for 2 hours. The obtained calcined product was pulverized to obtain a titania-containing support (powder comprising titania, an oxide of tungsten and an oxide of cerium).

[0130] Honeycomb Catalyst W was obtained by the same method as in Example 20, except that the amorphous silica powder was replaced with the titania-containing support (powder comprising titania, an oxide of tungsten and an oxide of cerium). The amount of platinum contained in the catalyst of Honeycomb Catalyst W was 100 ppm. By the same method as in Example 19, the NH3 concentration, NO X concentration and N2O concentration at the reactor outlet were measured. The results are shown in Table 7.

[0131] [Example 27: Honeycomb Catalyst X] (Preparation of first catalyst powder (7)) 100 g of silica titania powder was added to an aqueous solution of cerium nitrate hexahydrate (Ce(NO3)3·6H2O) and chlorplatinic acid hexahydrate (H2PtCl6·6H2O) and stirred, then evaporated to dryness on a sand bath. The dry product was calcined in air at 500°C for 2 hours. The resulting calcined product was pulverized to obtain a first catalyst powder (7) consisting of silica titania powder supported with 5.0% by mass of cerium and 1.0% by mass of platinum.

[0132] Two parts by mass of the first catalyst powder (7) and ninety-eight parts by mass of the second catalyst powder (1) were added to pure water to obtain a slurry. This slurry was used to coat an area of ​​140 g / m². 2 The material was applied to a honeycomb substrate (which had an outer diameter such that the outer surface of the honeycomb catalyst was in contact with the inner surface of the tube wall of the tubular reactor). This was dried at 120°C for 2 hours. Then it was calcined at 550°C for 2 hours to obtain honeycomb catalyst X. The amount of platinum contained in the catalyst of honeycomb catalyst X was 200 ppm. The NH3 concentration and NO at the reactor outlet were measured using the same method as in Example 19. X The concentrations of the solution and N2O were measured. The results are shown in Table 7.

[0133] [Example 28: Honeycomb catalyst Y] (Preparation of the second catalyst powder (2)) 2000 ml of an aqueous solution containing 9.1 g of iron(II) sulfate heptahydrate (FeSO4·7H2O) was mixed with 0.1 N sodium hydroxide solution to adjust the pH to approximately 6, and then heated to 80°C. 60 g of BEA-type zeolite powder (SiO2 / Al2O3 ratio = 25) was added, and the mixture was stirred for 2 hours while maintaining the temperature at 80°C to obtain a slurry. The slurry was dehydrated using a suction funnel fitted with filter paper (No. 5C). Pure water was poured over the cake on the filter paper and washed. The washed cake was dried at 110°C for 12 hours. The dried cake was placed in a furnace and the temperature was increased at 100°C / h, and it was fired at 500°C for 5 hours. The fired material was crushed to obtain a second catalyst powder (2) in which Fe ions were exchanged with the zeolite.

[0134] Two parts by mass of the first catalyst powder (7) and ninety-eight parts by mass of the second catalyst powder (2) were added to pure water to obtain a slurry. This slurry was applied to a coating area of ​​140 g / m². 2The material was applied to a honeycomb substrate (which had an outer diameter such that the outer surface of the honeycomb catalyst was in contact with the inner surface of the tube wall of the tubular reactor). This was dried at 120°C for 2 hours. Then it was calcined at 500°C for 2 hours to obtain honeycomb catalyst Y. The amount of platinum contained in the catalyst of honeycomb catalyst Y was 200 ppm. The NH3 concentration and NO at the reactor outlet were measured using the same method as in Example 19. X The concentrations of the solution and N2O were measured. The results are shown in Table 7.

[0135] [Example 29: Honeycomb catalyst Z] (Preparation of the second catalyst powder (3)) 60 g of BEA-type zeolite powder (SiO2 / Al2O3 ratio = 12), synthesized without the use of an organic structure-regulating agent (OSDA), was added to 2000 ml of an aqueous solution containing 26.6 g of iron(III) sulfate notahydrate (Fe(NO3)3·9H2O) heated to 80°C. The mixture was then stirred for 2 hours while maintaining the temperature at 80°C to obtain a slurry. The slurry was dehydrated using a suction funnel fitted with filter paper (No. 5C). Pure water was poured over the cake on the filter paper and washed. The washed cake was dried at 110°C for 12 hours. The dried cake was placed in a furnace and the temperature was increased at 100°C / h, and it was fired at 600°C for 5 hours. The fired material was crushed to obtain a second catalyst powder (3) in which Fe ions were exchanged with the zeolite.

[0136] Two parts by mass of the first catalyst powder (7) and ninety-eight parts by mass of the second catalyst powder (3) were added to pure water to obtain a slurry. This slurry was used to coat an area of ​​140 g / m². 2 The material was applied to a honeycomb substrate (which had an outer diameter such that the outer surface of the honeycomb catalyst was in contact with the inner surface of the tube wall of the tubular reactor). This was dried at 120°C for 2 hours. Then it was calcined at 500°C for 2 hours to obtain honeycomb catalyst Z. The amount of platinum contained in the catalyst of honeycomb catalyst Z was 200 ppm. The NH3 concentration and NO at the reactor outlet were measured using the same method as in Example 19. X The concentrations of the solution and N2O were measured. The results are shown in Table 7.

[0137] [Example 30: Honeycomb catalyst AA] (Preparation of the first catalyst powder (8)) 100 g of silica titania powder was added to an aqueous solution containing cerium nitrate hexahydrate (Ce(NO3)3·6H2O), chlorplatinic acid hexahydrate (H2PtCl6·6H2O), and iridium nitrate, and the mixture was stirred. The mixture was then evaporated to dryness on a sand bath. The dry product was calcined in air at 500°C for 2 hours. The resulting calcined product was pulverized to obtain a first catalyst powder (8) consisting of silica titania powder supported with 2.5% by mass of cerium, 0.5% by mass of platinum, and 0.25% by mass of iridium.

[0138] Two parts by mass of the first catalyst powder (8) and ninety-eight parts by mass of the second catalyst powder (1) were added to pure water to obtain a slurry. This slurry was used to coat an area of ​​140 g / m². 2 The material was applied to a honeycomb substrate (which had an outer diameter such that the outer surface of the honeycomb catalyst was in contact with the inner surface of the tube wall of the tubular reactor). This was dried at 120°C for 2 hours. Then it was calcined at 500°C for 2 hours to obtain honeycomb catalyst AA. The amount of platinum contained in the catalyst of honeycomb catalyst AA was 100 ppm. The NH3 concentration and NO at the reactor outlet were measured using the same method as in Example 19. X The concentrations of the solution and N2O were measured. The results are shown in Table 7.

[0139] [Table 7]

[0140] As shown in Table 7, when comparing honeycomb catalysts N, Q, and R, honeycomb catalysts S, T, and U, or honeycomb catalysts V and X, increasing the amount of platinum and cerium supported improves the NH3 decomposition rate, slightly decreases the denitrification rate, slightly increases the outlet N2O concentration, and reduces the effect of hydrothermal aging on the NH3 decomposition rate under evaluations (5) and (6) with an ammonia concentration of 8000 ppm and an NO concentration of 5000 ppm. Furthermore, honeycomb catalysts S, T, and U using titania-containing supports, or honeycomb catalyst V using silica-titania-containing supports, show slightly lower or almost the same NH3 decomposition rate, higher denitrification rate, and lower outlet N2O concentration compared to honeycomb catalysts N, Q, and R using silica-containing supports in evaluations (5) and (6). Also, as shown in Table 7, honeycomb catalysts V and W are almost equivalent to honeycomb catalyst U in evaluations (5) and (6).

[0141] Honeycomb catalyst Y, obtained by adjusting the pH to approximately 6 during ion exchange, and honeycomb catalyst Z, which was calcined at 600°C using OSDA-free zeolite, showed a higher 350°C denitrification rate in evaluation (6) after hydrothermal aging compared to the 350°C denitrification rate in evaluation (5) before hydrothermal aging. Honeycomb catalyst AA, which contains iridium, showed a higher denitrification rate compared to honeycomb catalyst V.

[0142] As shown above, the catalyst of the present invention is NH3, NO X And NH3 and NO in exhaust gas containing N2O X Furthermore, it can efficiently promote the reaction that decomposes N2O, and the NO produced as a by-product in the oxidation reaction of NH3. X Furthermore, it can suppress N2O emissions, does not degrade even when exposed to SO2 which may be present in combustion exhaust gases, and has excellent high-temperature resistance. [Explanation of symbols]

[0143] A: NH3-containing gas B: O2-containing gas C: Reaction aid (ammonia or urea) D: Cooling air 2: Gas inlet pipe 3: Heat exchanger bypass tube 5: Mixer 9: Heat exchanger 10h: Heater 10c,10c2: Cooler 11, 11a, 11b: Reactor 12,12a,12b: Catalyst layer 13: Processed gas 14: Measuring instrument (thermometer / densitometer) 17: Control device

Claims

1. A first catalyst powder comprising a carrier containing silica and / or titania, and platinum and / or iridium and cerium supported on the carrier, A second catalyst powder comprising Fe ions obtained by ion exchange with BEA-type zeolite, and A catalyst for promoting the decomposition reaction of ammonia, comprising a mixture of the following: In the first catalyst powder, the ratio of the mass of cerium to the mass of platinum and / or iridium is 1 or more and less than 10. A catalyst wherein the second catalyst powder is present in an amount of 1 to 100 parts by mass per 1 part by mass of the first catalyst powder.

2. The first catalyst powder, The second catalyst powder and, A third catalyst powder comprising titanium oxide, tungsten oxide, and cerium oxide It contains a mixture of, In the third catalyst powder, the ratio of cerium to titanium is 1 to 20% by weight as the weight percentage of cerium dioxide to titanium dioxide, and the ratio of tungsten to titanium is 1 to 50% by weight as the weight percentage of tungsten trioxide to titanium dioxide. The catalyst according to claim 1, wherein the amount of the third catalyst powder is 0 to 70 parts by mass per 1 part by mass of the first catalyst powder.

3. In the presence of the catalyst according to claim 1 or 2, NH contained in the gas to be treated ３ A chemical reaction that turns into nitrogen and water, NO contained in the gas to be treated Ｘ and N ２ Chemical reaction that converts oxygen into nitrogen and water Including doing, A method for rendering the gas to be treated harmless.

4. The method according to claim 3, further comprising adding at least one reaction aid selected from the group consisting of ammonia and urea to the gas to be treated.

5. The amount of reaction aid added to the gas to be treated, the temperature of the treated gas, and the NO content in the treated gas are all considered. Ｘ and N ２ The method according to claim 4, further comprising adjusting based on the amount of O.

6. The method according to claim 3, further comprising cooling the gas to be treated.

7. The method according to claim 6, further comprising adjusting the degree to which the gas to be treated is cooled based on the temperature of the treated gas.

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