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• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
  • B01J27/14—Phosphorus; Compounds thereof
  • B01J27/186—Phosphorus; Compounds thereof with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
  • B01J27/195—Phosphorus; Compounds thereof with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium with vanadium, niobium or tantalum
  • B01J27/198—Vanadium
  • B01J27/199—Vanadium with chromium, molybdenum, tungsten or polonium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/46—Removing components of defined structure
  • B01D53/64—Heavy metals or compounds thereof, e.g. mercury
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
  • B01D53/86—Catalytic processes
  • B01D53/8621—Removing nitrogen compounds
  • B01D53/8625—Nitrogen oxides
  • B01D53/8628—Processes characterised by a specific catalyst
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
  • B01D53/86—Catalytic processes
  • B01D53/8665—Removing heavy metals or compounds thereof, e.g. mercury
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
  • B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
  • B01J21/063—Titanium; Oxides or hydroxides thereof
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
  • B01J23/20—Vanadium, niobium or tantalum
  • B01J23/22—Vanadium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
  • B01J23/24—Chromium, molybdenum or tungsten
  • B01J23/28—Molybdenum
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
  • B01J23/24—Chromium, molybdenum or tungsten
  • B01J23/30—Tungsten
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/02—Impregnation, coating or precipitation
  • B01J37/0215—Coating
  • B01J37/0225—Coating of metal substrates
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/28—Phosphorising
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/20—Metals or compounds thereof
  • B01D2255/207—Transition metals
  • B01D2255/20707—Titanium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/20—Metals or compounds thereof
  • B01D2255/207—Transition metals
  • B01D2255/20723—Vanadium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/20—Metals or compounds thereof
  • B01D2255/207—Transition metals
  • B01D2255/20769—Molybdenum
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/20—Metals or compounds thereof
  • B01D2255/207—Transition metals
  • B01D2255/20776—Tungsten
• • B01J35/58—
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/04—Mixing

Definitions

• the present invention relates to an exhaust gas purification catalyst, and more particularly to, a catalyst used for oxidizing elemental mercury (Hg) as well as reducing nitrogen oxides (NOx) contained in coal combustion exhaust gas by ammonia, which can maintain to a very low level an activity of oxidizing SO 2 contained in the exhaust gas to SO 3 for a long period of time by suppressing an increase in the activity of oxidizing SO 2 with the lapse of time by an increase in Fe compound, and a method of producing the same.
• Hg oxidizing elemental mercury
• NOx nitrogen oxides
• the denitration catalyst for ammonia catalytic reduction containing titanium oxide as a main component has high activity and favorable durability, it is generally used worldwide for the treatment of exhaust gas such as gas released from a boiler and constitutes the mainstream denitration catalyst (Patent Document 1).
• Patent Document 1 Japanese Patent Application Laid-Open (JP-A) No. 50-128681
• Patent Document 2 JP-A No. 2-184342
• Patent Document 3 JP-A No. 09-220468
• SO 2 oxidation active site of a denitration catalyst there are SO 2 oxidation active site that is intrinsic to the catalyst component and SO 2 oxidation active site that is newly formed by adhesion of a Fe component contained in combustion ash to the catalyst or by migration of a Fe component accompanied with corrosion of a substrate to the catalyst, when a metal substrate is used for the catalyst.
• SO 2 oxidation active site that is intrinsic to the catalyst component
• SO 2 oxidation active site that is newly formed by adhesion of a Fe component contained in combustion ash to the catalyst or by migration of a Fe component accompanied with corrosion of a substrate to the catalyst, when a metal substrate is used for the catalyst.
• a dramatic increase in SO 2 oxidizing activity is caused when the degree of forming SO 2 active site in the catalyst is huge.
• Fe 2 O 3 is contained at high concentration of 20 to 30% by weight in combustion ash of high S coals that are produced in the United States, etc., for the treatment of combustion exhaust gas of such high S coals, it is necessary to suppress an increase in SO 2 oxidizing activity caused by adhesion of Fe 2 O 3 to the catalyst.
• SO 2 oxidation rate of the catalyst component itself can be suppressed to a low level, and therefore sufficiently low initial SO 2 oxidation rate is obtained for the catalyst.
• sufficient consideration regarding the suppression of an increase in SO 2 oxidation rate of the catalyst that is caused by an increase in a Fe component in the latter case was not made, and therefore the SO 2 oxidation rate of the catalyst with the lapse of time is still big and improvements are needed in several aspects.
• An object of the present invention is to provide, considering the problems of the conventional technology above, an exhaust gas purification catalyst that can suppress an increase in SO 2 oxidation with an increase in a Fe component in the denitration catalyst with the lapse of time attributable to internal and external causes and, even in exhaust gases of fuels having a high Fe content such as high S coals, can realize operation at a low SO 2 oxidation rate for a long period of time, and a method of producing the same.
• An exhaust gas purification catalyst containing titanium oxide as a main component and an oxide of one element or two or more elements selected from the group consisting of tungsten (W), molybdenum (Mo), and vanadium (V) as an active component, in which the catalyst contains phosphoric acid or a water soluble phosphoric acid compound so that the atomic ratio of phosphorus (P) to a catalytically active component represented by the following formula is more than 0 and 1.0 or less;
• P/catalytically active component (atomic ratio) number of moles of P/(number of moles of W+number of moles of Mo+number of moles of V).
• a method of producing an exhaust gas purification catalyst including: adding an oxide or an oxo-acid salt of one element or two or more elements selected from the group consisting of tungsten (W), molybdenum (Mo), and vanadium (V) to titanium oxide; adding water; and kneading followed by drying and calcination, wherein phosphoric acid or a water soluble phosphoric acid compound is added to the oxide or the oxo-acid salt thereof for a reaction so that the atomic ratio of P to a catalytically active component represented by the following formula is more than 0 and 1.0 or less;
• a method of producing an exhaust gas purification catalyst including: adding an oxide or an oxo-acid salt of one element or two or more elements selected from the group consisting of tungsten (W), molybdenum (Mo), and vanadium (V) to titanium oxide; adding water; kneading followed by drying and calcination; and immersing the resultant in a solution that is prepared separately in advance by adding phosphoric acid or a water soluble phosphoric acid compound to an oxide or an oxo-acid salt of one element or two or more elements selected from the group consisting of tungsten (W), molybdenum (Mo), and vanadium (V) to be reacted so that the atomic ratio of P to a catalytically active component represented by the following formula is more than 0 and 1.0 or less;
• the atomic ratio of P to a catalytically active component in the catalyst to be within the range described above, formation of SO 2 oxidation active site in the catalyst that is caused by the adhesion of a Fe component comprised in ash from gas to be treated is suppressed, and therefore SO 2 oxidation rate can be maintained at a low level for a long period of time.
• formation of SO 2 active site caused by corrosion product containing a Fe component, that is generated when the catalyst is used in harsh condition is prevented so that even for the catalyst using a metal substrate as a carrier the SO 2 oxidation rate can be maintained at a low level for a long period of time.
• the catalyst of the invention has not only high denitrating performance and Hg oxidizing performance but also low SO 2 oxidation rate, when it is used for denitration of exhaust gas from a high S coal boiler used in the United States, etc., generation of SO 3 can be suppressed to a low level. Furthermore, since it is difficult for SO 2 oxidation rate to increase even when the Fe component contained in ash or the like migrates into the catalyst, problems such as generation of purple smoke due to SO 3 resulting from oxidation of SO 2 can be avoided when it is applied for exhaust gas of high S coals containing a great amount of a Fe component.
• Fe component such as iron oxide or the like adheres on the surface of a catalyst or corrosion of a metal substrate occurs at the interface between the metal substrate and the catalyst component, but no increase in SO 2 oxidation rate occurs during this step.
• the Fe component in the catalyst is sulphated by SOx present in exhaust gas.
• the sulphate is dissolved in water which is absorbed when operation of a combustion furnace is on hold, and as a result, it migrates as a Fe ion to the inside of the catalyst.
• the migrated Fe ion is adsorbed onto titanium oxide to form SO 2 oxidation active site.
• part of the catalytically active component is present as a complex resulting from a qualitative reaction with phosphoric acid/phosphoric acid compound, and it is believed that Fe ion and the complex of phosphoric acid and the active component undergo the reaction as follows.
• the Fe ion forms insoluble iron phosphate by which absorption onto TiO 2 is inhibited, and therefore an increase in SO 2 oxidation rate is prevented.
• WO 3 , MoO 3 and V 2 O 5 are also formed as an active component along with the generation of FePO 4 . As such, it is also expected to obtain the effect of maintaining the denitration activity or Hg oxidation activity at a high level.
• the catalyst of the invention it is important to have the atomic ratio of P to a catalytically active component in the catalyst to be more than 0 and 1.0 or less.
• P reacts with the catalytically active component to lower the denitration activity, there is a tendency that denitration activity is reduced by excessive P.
• the atomic ratio of P to a catalytically active component is more than 0 and 0.5 or less.
• any one of the oxides, salts or the like of the corresponding component may be used.
• the P compound needs to react with a Mo compound or a W compound and a V compound
• soluble salts of the corresponding compound for example, oxo acid or ammonium salts of the corresponding element and mixing them with titanium oxide in the presence of water
• Phosphoric acid/phosphoric acid compound i.e., P compound
• P compound may be directly added during the process of producing the catalyst as described above.
• a method in which a compound obtained by reacting in advance phosphoric acid/P compound (i.e., complex) or a solution containing the compound is added during a process of kneading raw materials for producing the catalyst, aside from the W, Mo, and V compounds that are added as an active component, or it is immersed after producing the catalyst or the like may be adopted.
• the latter method is preferable in that the influence of P on catalytic activity can be easily controlled.
• the water soluble phosphoric acid compound include ammonium dihydrogen phosphate and diammonium hydrogen phosphate.
• a reducing agent like ammonia is injected and reacted by contact with the catalyst according to the method known per se in the art.
• Titanium oxide (specific surface area: 290 m 2 /g, manufactured by Ishihara Sangyo K.K.) (900 g), ammonium molybdate (107 g), ammonium metavanadate (28.3 g), 85% phosphoric acid (68.3 g), silica sol (trade name: OS SOL, manufactured by Nissan Chemical Industries, Ltd.) (404 g), and water (50 g) were placed in a kneader, and then kneaded for 60 minutes.
• silica-alumina ceramic fiber manufactured by Toshiba Fine Flex K.K.
• 151 g silica-alumina ceramic fiber
• the mixture was kneaded for 30 minutes, to thereby yield a catalyst paste having a water content of 27% by weight.
• the paste obtained was applied onto a base material (thickness: 0.7 mm) produced by subjecting a SUS 430 stainless steel plate (thickness: 0.2 mm) to a metal-lath processing; the base material was sandwiched between two polyethylene sheets; and the thus-sandwiched base material was passed through a pair of pressure rollers so that the meshes of the metal lath base were filled with the paste.
• the paste-filled base material was air-dried, and then calcined at 500° C. for two hours, to thereby obtain a catalyst of the invention.
• Composition of the catalyst of this invention was found to have a Ti/Mo/V (atomic proportions) of 93/5/2, and a P/(Mo+V) (atomic ratio) of 0.5.
• the catalyst of the invention was obtained in the same manner as Example 1, except that ammonium molybdate used in Example 1 was replaced by an equimolar amount of ammonium metatungstate, to thereby obtain a catalyst of the invention.
• Composition of the catalyst of this invention was found to have a Ti/WN (atomic proportions) of 93/5/2, and a P/(Mo+V) (atomic ratio) of 0.5.
• the catalyst was prepared in the same manner as Example 1 and Example 2, except that no phosphoric acid was added.
• Titanium oxide (specific surface area: 290 m 2 /g, manufactured by Ishihara Sangyo K.K.) (900 g), ammonium molybdate (113 g), ammonium metavanadate (105 g), 85% phosphoric acid (18 g (Example 3), 53 g (Example 4), 88 g (Example 5), 124 g (Example 6) and 177 g (Example 7)) and silica sol (trade name: OS SOL, manufactured by Nissan Chemical Industries, Ltd.) (404 g) were placed in a kneader, and then kneaded for 60 minutes.
• OS SOL silica sol
• silica-alumina ceramic fiber manufactured by Toshiba Fine Flex K.K.
• 151 g silica-alumina ceramic fiber
• the mixture was kneaded for 30 minutes, to thereby obtain a catalyst paste having a water content of 27% by weight.
• the obtained paste was applied onto a base material (thickness: 0.7 mm) produced by subjecting a SUS 430 stainless steel plate (thickness: 0.2 mm) to a metal-lath processing; the base material was sandwiched between two polyethylene sheets; and the thus-sandwiched base material was passed through a pair of pressure rollers so that the meshes provided in the metal lath base were filled with the paste.
• the paste-filled base material was air-dried, and then calcined at 500° C. for two hours, to thereby obtain a catalyst of the invention.
• Composition of the catalyst of this invention was found to have a Ti/MoN (atomic proportions) of 88/5/7 and a P/(Mo+V) (atomic ratio) of 0.1, 0.3, 0.5, 0.7 and 1.0 for Example 3 to 7, respectively.
• the catalyst was prepared in the same manner as Example 3, except that no phosphoric acid/phosphoric acid compound was added.
• Titanium oxide (specific surface area: 290 m 2 /g, manufactured by Ishihara Sangyo K.K.) (900 g), ammonium molybdate (113 g), ammonium metavanadate (42.9 g), ammonium dihydrogen phosphate (110 g), silica sol (trade name: OS SOL, manufactured by Nissan Chemical Industries, Ltd.) (404 g) and water (50 g) were placed in a kneader, and then kneaded for 60 minutes.
• silica-alumina ceramic fiber manufactured by Toshiba Fine Flex K.K.
• 151 g silica-alumina ceramic fiber
• the mixture was kneaded for 30 minutes, to thereby obtain a catalyst paste having a water content of 27% by weight.
• the obtained paste was applied onto a base material (thickness: 0.7 mm) produced by subjecting a SUS 430 stainless steel plate (thickness: 0.2 mm) to a metal-lath processing; the base material was sandwiched between two polyethylene sheets; and the thus-sandwiched base material was passed through a pair of pressure rollers so that the meshes provided in the metal lath base were filled with the paste.
• the paste-filled base material was air-dried, and then calcined at 500° C. for two hours, to thereby obtain a catalyst of the invention.
• Composition of the catalyst of this invention was found to have a Ti/MoN (atomic proportions) of 93/5/3 and a P/(Mo+V) (atomic ratio) of 0.4.
• Titanium oxide (specific surface area: 290 m 2 /g, manufactured by Ishihara Sangyo K.K.) (900 g), molybdenum trioxide (88 g), ammonium metavanadate (42.9 g), ammonium dihydrogen phosphate (110 g), silica sol (trade name: OS SOL, manufactured by Nissan Chemical Industries, Ltd.) (404 g) and water (50 g) were placed in a kneader, and then kneaded for 60 minutes.
• silica-alumina ceramic fiber manufactured by Toshiba Fine Flex K.K.
• 151 g silica-alumina ceramic fiber
• the mixture was kneaded for 30 minutes, to thereby obtain a catalyst paste having a water content of 27%.
• the obtained paste was applied onto a base material (thickness: 0.7 mm) produced by subjecting a SUS 430 stainless steel plate (thickness: 0.2 mm) to a metal-lath processing; the base material was sandwiched between two polyethylene sheets; and the thus-sandwiched base material was passed through a pair of pressure rollers so that the meshes provided in the metal lath base were filled with the paste.
• the paste-filled base material was air-dried, and then calcined at 500° C. for two hours, to thereby obtain a catalyst of the invention.
• Composition of the catalyst of this invention was found to have a Ti/MoN (atomic proportions) of 93/5/3 and a P/(Mo +V) (atomic ratio) of 0.4.
• the catalyst was prepared in the same manner as Examples 8 and Examples 9, except that no ammonium dihydrogen phosphate was added.
• Ammonium metavanadate (42.9 g) was dispersed in water (100 ml) and added with 85% phosphoric acid (45 g). According to the reaction between them, a red slurry-like product was obtained.
• titanium oxide (specific surface area: 290 m 2 /g, manufactured by Ishihara Sangyo K.K.) (900 g), ammonium molybdate (117 g), ammonium metavanadate (103 g), and silica sol (trade name: OS SOL, manufactured by Nissan Chemical Industries, Ltd.) (404 g) were placed in a kneader, and then kneaded for 30 minutes to obtain a past. To the paste, the red slurry obtained from the above was added and kneaded further for 30 minutes.
• silica-alumina ceramic fiber manufactured by Toshiba Fine Flex K.K.
• 151 g silica-alumina ceramic fiber
• the obtained paste was applied onto a base material (thickness: 0.7 mm) produced by subjecting a SUS 430 stainless steel plate (thickness: 0.2 mm) to a metal-lath processing; the base material was sandwiched between two polyethylene sheets; and the thus-sandwiched base material was passed through a pair of pressure rollers so that the meshes provided in the metal lath base were filled with the paste, to thereby obtain a catalyst of the invention.
• Composition of the catalyst of this invention was found to have a Ti/Mo/V (atomic proportions) of 85/5/10 and a P/(Mo+V) (atomic ratio) of 0.2.
• Titanium oxide (specific surface area: 290 m 2 /g, manufactured by Ishihara Sangyo K.K.) (900 g), ammonium metavanadate (105 g), and silica sol (trade name: OS SOL, manufactured by Chemical Industries, Ltd.) (404 g) were placed in a kneader, and then kneaded for 60 minutes. Thereafter, while silica-alumina ceramic fiber (manufactured by Toshiba Fine Flex K.K.) (151 g) was gradually added to the mixture, the mixture was kneaded for 30 minutes, to thereby obtain a catalyst paste having a water content of 27% by weight.
• silica-alumina ceramic fiber manufactured by Toshiba Fine Flex K.K.
• the obtained paste was applied onto a base material (thickness: 0.7 mm) produced by subjecting a SUS 430 stainless steel plate (thickness: 0.2 mm) to a metal-lath processing; the base material was sandwiched between two polyethylene sheets; and the thus-sandwiched base material was passed through a pair of pressure rollers so that the meshes provided in the metal lath base were filled with the paste.
• the resulting catalyst was air-dried, and then calcined at 500° C. for two hours, to thereby obtain a catalyst of the invention.
• ammonium molybdate (112 g) was dispersed in water (200 ml) and added with 85% phosphoric acid (89 g) to obtain a solution in which the two components are reacted with each other.
• the catalyst obtained from the above was immersed, the liquid was removed, and then the catalyst was air-dried at room temperature or calcined at 350° C. for one hour, to thereby obtain a catalyst of the invention.
• Composition of the catalyst of this invention was found to have a Ti/Mo/V (atomic proportions) of 88/5/7 and a P/(Mo+V) (atomic ratio) of 0.5.
• Each of the catalysts prepared in Examples 1 to 11 and Comparative examples 1 to 5 was cut into test pieces, each having a rectangular shape with a size of 100 mm ⁇ 20 mm.
• the test pieces of each catalyst were brought into contact with the gas under the condition shown in Table 1 to measure the denitrating performance and the Hg oxidation rate of the catalyst. Furthermore, they were brought into contact with the gas under the condition shown in Table 2 to measure the SO 2 oxidizing performance of each catalyst, and the initial activity was also determined.
• combustion ash of bituminous coal known as high S coals was pulverized with a ball mill until 200 mesh pass ratio is at least 95% to prepare simulated ash.
• This simulated ash was applied to a vat, added with the catalyst of Examples 1 to 11 and Comparative examples 1 to 5, and added further with the simulated ash to have thickness of about 1 mm.
• the vessel was placed in a calcination furnace in which atmosphere is adjusted to have SO 2 of 500 ppm, humidity of 10% and air for the remainder, and the vessel was kept at 400° C. for 50 hours. After that, the vessel was kept for 100 hours under the condition including the temperature of 35° C.
• the Fe components included in the ash were forced to move into the catalyst.
• the Fe 2 O 3 concentration on the surface of the catalyst was increased about 2.6% by weight on average.
• the Fe 2 O 3 was increased up to 0.38% by weight on average compared to the whole components of the catalyst.
• the catalyst of the invention has higher denitration rate and Hg oxidation rate with much lower SO 2 oxidation rate compared to the catalyst of the Comparative examples.
• the SO 2 oxidation rate has dramatically increased with the catalyst of the Comparative examples, while the increase in the SO 2 oxidation rate was minor for the catalyst of the present invention.
• the catalyst of the invention is resistant to the adhesion of a Fe component.

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• 2009
  • 2009-03-25 EP EP09725440.3A patent/EP2269732B1/en active Active
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