WO2023084825A1 - 亜酸化窒素分解用触媒の再生方法および亜酸化窒素の分解方法 - Google Patents
亜酸化窒素分解用触媒の再生方法および亜酸化窒素の分解方法 Download PDFInfo
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- WO2023084825A1 WO2023084825A1 PCT/JP2022/024117 JP2022024117W WO2023084825A1 WO 2023084825 A1 WO2023084825 A1 WO 2023084825A1 JP 2022024117 W JP2022024117 W JP 2022024117W WO 2023084825 A1 WO2023084825 A1 WO 2023084825A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- nitrous oxide
- catalyst
- gas
- decomposition
- ruthenium
- Prior art date
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- GQPLMRYTRLFLPF-UHFFFAOYSA-N Nitrous Oxide Chemical compound [O-][N+]#N GQPLMRYTRLFLPF-UHFFFAOYSA-N 0.000 title claims abstract description 418
- 239000001272 nitrous oxide Substances 0.000 title claims abstract description 207
- 239000003054 catalyst Substances 0.000 title claims abstract description 186
- 238000000354 decomposition reaction Methods 0.000 title claims abstract description 124
- 238000000034 method Methods 0.000 title claims abstract description 95
- 230000001172 regenerating effect Effects 0.000 title claims abstract description 21
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims abstract description 59
- 238000011069 regeneration method Methods 0.000 claims abstract description 59
- 229910052707 ruthenium Inorganic materials 0.000 claims abstract description 38
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 claims abstract description 38
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 claims abstract description 30
- 150000003304 ruthenium compounds Chemical class 0.000 claims abstract description 22
- 239000007789 gas Substances 0.000 claims description 154
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 45
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 claims description 26
- 229910021529 ammonia Inorganic materials 0.000 claims description 22
- 230000001590 oxidative effect Effects 0.000 claims description 21
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 20
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 18
- 229910052760 oxygen Inorganic materials 0.000 claims description 17
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 16
- 239000001301 oxygen Substances 0.000 claims description 16
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 14
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims description 8
- 229910002091 carbon monoxide Inorganic materials 0.000 claims description 8
- 229910052757 nitrogen Inorganic materials 0.000 claims description 8
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 7
- 239000001569 carbon dioxide Substances 0.000 claims description 7
- JCXJVPUVTGWSNB-UHFFFAOYSA-N nitrogen dioxide Inorganic materials O=[N]=O JCXJVPUVTGWSNB-UHFFFAOYSA-N 0.000 claims description 6
- MGWGWNFMUOTEHG-UHFFFAOYSA-N 4-(3,5-dimethylphenyl)-1,3-thiazol-2-amine Chemical compound CC1=CC(C)=CC(C=2N=C(N)SC=2)=C1 MGWGWNFMUOTEHG-UHFFFAOYSA-N 0.000 claims description 5
- 229930195733 hydrocarbon Natural products 0.000 claims description 4
- 150000002430 hydrocarbons Chemical class 0.000 claims description 4
- 229910052739 hydrogen Inorganic materials 0.000 claims description 3
- 239000001257 hydrogen Substances 0.000 claims description 3
- 125000004435 hydrogen atom Chemical class [H]* 0.000 claims 1
- 238000010438 heat treatment Methods 0.000 abstract description 28
- 230000002378 acidificating effect Effects 0.000 abstract 1
- 238000006243 chemical reaction Methods 0.000 description 52
- 238000004519 manufacturing process Methods 0.000 description 28
- 230000008929 regeneration Effects 0.000 description 27
- 230000001603 reducing effect Effects 0.000 description 21
- 239000013078 crystal Substances 0.000 description 20
- 230000008569 process Effects 0.000 description 18
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 15
- 230000003197 catalytic effect Effects 0.000 description 13
- 229910052751 metal Inorganic materials 0.000 description 13
- 239000002184 metal Substances 0.000 description 12
- 229910001925 ruthenium oxide Inorganic materials 0.000 description 11
- WOCIAKWEIIZHES-UHFFFAOYSA-N ruthenium(iv) oxide Chemical compound O=[Ru]=O WOCIAKWEIIZHES-UHFFFAOYSA-N 0.000 description 11
- 229930195734 saturated hydrocarbon Natural products 0.000 description 11
- 239000000126 substance Substances 0.000 description 11
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 9
- 150000003839 salts Chemical class 0.000 description 9
- 239000003570 air Substances 0.000 description 8
- 229910001882 dioxygen Inorganic materials 0.000 description 8
- -1 ruthenium organic acid salts Chemical class 0.000 description 8
- 150000001875 compounds Chemical class 0.000 description 7
- 229910044991 metal oxide Inorganic materials 0.000 description 7
- 150000004706 metal oxides Chemical class 0.000 description 7
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 6
- 229910010413 TiO 2 Inorganic materials 0.000 description 6
- WNLRTRBMVRJNCN-UHFFFAOYSA-N adipic acid Chemical compound OC(=O)CCCCC(O)=O WNLRTRBMVRJNCN-UHFFFAOYSA-N 0.000 description 6
- JBKVHLHDHHXQEQ-UHFFFAOYSA-N epsilon-caprolactam Chemical compound O=C1CCCCCN1 JBKVHLHDHHXQEQ-UHFFFAOYSA-N 0.000 description 6
- 150000002739 metals Chemical class 0.000 description 6
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 6
- 229910017604 nitric acid Inorganic materials 0.000 description 6
- 239000008188 pellet Substances 0.000 description 6
- 230000033228 biological regulation Effects 0.000 description 5
- 229910052734 helium Inorganic materials 0.000 description 5
- 239000001307 helium Substances 0.000 description 5
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 5
- 239000011261 inert gas Substances 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- 229960003753 nitric oxide Drugs 0.000 description 5
- XJDNKRIXUMDJCW-UHFFFAOYSA-J titanium tetrachloride Chemical compound Cl[Ti](Cl)(Cl)Cl XJDNKRIXUMDJCW-UHFFFAOYSA-J 0.000 description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 4
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 4
- PCBMYXLJUKBODW-UHFFFAOYSA-N [Ru].ClOCl Chemical compound [Ru].ClOCl PCBMYXLJUKBODW-UHFFFAOYSA-N 0.000 description 4
- 238000001354 calcination Methods 0.000 description 4
- 239000002131 composite material Substances 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
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- 239000012495 reaction gas Substances 0.000 description 4
- 238000006722 reduction reaction Methods 0.000 description 4
- YBCAZPLXEGKKFM-UHFFFAOYSA-K ruthenium(iii) chloride Chemical compound [Cl-].[Cl-].[Cl-].[Ru+3] YBCAZPLXEGKKFM-UHFFFAOYSA-K 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 3
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- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 3
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- 239000001361 adipic acid Substances 0.000 description 3
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- 238000002360 preparation method Methods 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- WYRXRHOISWEUST-UHFFFAOYSA-K ruthenium(3+);tribromide Chemical compound [Br-].[Br-].[Br-].[Ru+3] WYRXRHOISWEUST-UHFFFAOYSA-K 0.000 description 3
- GTCKPGDAPXUISX-UHFFFAOYSA-N ruthenium(3+);trinitrate Chemical compound [Ru+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O GTCKPGDAPXUISX-UHFFFAOYSA-N 0.000 description 3
- 150000004684 trihydrates Chemical class 0.000 description 3
- 229930195735 unsaturated hydrocarbon Natural products 0.000 description 3
- OTMSDBZUPAUEDD-UHFFFAOYSA-N Ethane Chemical compound CC OTMSDBZUPAUEDD-UHFFFAOYSA-N 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical compound CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
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- 229910052786 argon Inorganic materials 0.000 description 2
- NQZFAUXPNWSLBI-UHFFFAOYSA-N carbon monoxide;ruthenium Chemical group [Ru].[Ru].[Ru].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-] NQZFAUXPNWSLBI-UHFFFAOYSA-N 0.000 description 2
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- VDRDGQXTSLSKKY-UHFFFAOYSA-K ruthenium(3+);trihydroxide Chemical compound [OH-].[OH-].[OH-].[Ru+3] VDRDGQXTSLSKKY-UHFFFAOYSA-K 0.000 description 2
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Classifications
-
- 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
-
- 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
- B01D53/96—Regeneration, reactivation or recycling of reactants
-
- 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
- B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
- B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
- B01J23/46—Ruthenium, rhodium, osmium or iridium
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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
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/90—Regeneration or reactivation
- B01J23/96—Regeneration or reactivation of catalysts comprising metals, oxides or hydroxides of the noble metals
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
- Y02C20/00—Capture or disposal of greenhouse gases
- Y02C20/10—Capture or disposal of greenhouse gases of nitrous oxide (N2O)
Definitions
- the present invention relates to a method for regenerating a nitrous oxide decomposition catalyst and a method for decomposing nitrous oxide.
- Nitrogen oxides (NOx) in exhaust gases have become a problem from the viewpoint of global environmental protection and air pollution prevention, and their emissions are being strictly regulated.
- nitrogen oxides subject to emission regulations are nitrogen dioxide (NO 2 ), which is harmful to the human body and causes photochemical smog and acid rain.
- NO 2 O nitrogen dioxide
- nitrous oxide (N 2 O) which is a type of nitrogen oxide, is currently not subject to emission regulations and is normally released into the atmosphere as it is.
- nitrogen monoxide and nitrogen dioxide are decomposed and removed by denitrification treatment in gases emitted from chemical manufacturing plants such as nitric acid manufacturing plants, ⁇ -caprolactam manufacturing plants, and adipic acid manufacturing plants.
- the by-produced nitrous oxide is often discharged (released) into the atmosphere without being decomposed and removed.
- Nitrous oxide is said to exhibit about 300 times the warming effect of carbon dioxide. Therefore, in recent years, there has been increasing interest in reducing emissions of nitrous oxide into the atmosphere, along with carbon dioxide, methane, and the like. Along with the growing awareness of sustainable environment, nitrous oxide is expected to be subject to emission regulations in the near future. A technique to suppress it is required.
- Patent Document 1 discloses ruthenium (Ru), rhodium (Rh), palladium (Pd), rhenium (Re), osmium (Os), iridium (Ir) Nitrous oxide decomposition by catalytically decomposing a gas containing nitrous oxide in the coexistence of a reducing gas using a catalyst characterized by supporting at least one noble metal selected from platinum (Pt). A method is described.
- nitrous oxide decomposing catalysts Catalysts used to decompose nitrous oxide (nitrous oxide decomposing catalysts) become inactive as they are used, and the efficiency of decomposing nitrous oxide decreases. replaced and discarded. Disposal of the deactivated catalyst increases the nitrous oxide decomposition cost, and it is also important to reduce the amount of disposal from the viewpoint of global environmental protection. In the future, if nitrous oxide becomes a gas subject to emission regulations, it is expected that the demand for catalysts will increase. , the output (supply) is also insufficient. Therefore, there is a great advantage in reactivating the deactivated catalyst and reusing it to decompose nitrous oxide.
- a catalyst for decomposing nitrous oxide comprising a carrier containing titanium oxide and supporting a component containing at least one selected from the group consisting of ruthenium and ruthenium compounds, and used for the decomposition reaction of nitrous oxide.
- Nitrous oxide decomposition catalyst A method for regenerating a nitrous oxide decomposition catalyst, comprising a step of heat-treating at a temperature of 175 to 325° C. in an oxidizing gas atmosphere.
- ⁇ 3> The method for regenerating the nitrous oxide decomposition catalyst according to ⁇ 1> or ⁇ 2> above, followed by the nitrous oxide decomposition catalyst regenerated by the regeneration method, and a nitrous oxide-containing gas containing nitrous oxide.
- a method for decomposing nitrous oxide comprising the step of contacting with ⁇ 4>
- the nitrous oxide-containing gas contains at least one gas selected from the group consisting of nitrogen, carbon monoxide, carbon dioxide, water vapor, oxygen, hydrogen, ammonia, nitrogen monoxide, nitrogen dioxide and hydrocarbons. , the method for decomposing nitrous oxide according to ⁇ 3>.
- the present invention provides a method for regenerating a nitrous oxide decomposition catalyst capable of efficiently regenerating a deactivated nitrous oxide decomposition catalyst, and a method for decomposing nitrous oxide using the nitrous oxide decomposition catalyst regenerated by this regeneration method.
- a numerical range represented using “-" means a range including the numerical values described before and after "-" as lower and upper limits.
- the term “nitrous oxide decomposition catalyst” refers to a nitrous oxide decomposition catalyst (which is not used in the nitrous oxide decomposition reaction) unless otherwise specified. Also called unused catalyst, new catalyst, etc.), the nitrous oxide decomposition catalyst used for the decomposition reaction of nitrous oxide (also called used catalyst, deteriorated catalyst, etc.) It is used in the sense of including a regenerated catalyst for decomposing nitrogen oxides (also referred to as a regenerated catalyst).
- the method for regenerating a nitrous oxide decomposition catalyst of the present invention comprises is heat-treated at a temperature of 175 to 325° C. in an oxidizing gas atmosphere. As will be described later, this heat treatment step can efficiently recover or regenerate the catalytic activity of the deteriorated catalyst whose catalytic activity has been deactivated.
- the deteriorated catalyst used in the regeneration method of the present invention is a nitrous oxide decomposition catalyst comprising a support containing titanium oxide and a component containing at least one selected from the group consisting of ruthenium and ruthenium compounds supported on the support. It is a catalyst whose catalytic activity has been deactivated by using it in the cracking method.
- the method for decomposing nitrous oxide for deactivating the deteriorated catalyst is not particularly limited, and for example, the "step of contacting with nitrous oxide-containing gas" in the method for decomposing nitrous oxide of the present invention described later, etc. mentioned.
- the nitrous oxide decomposition catalyst is a catalyst in which a component containing at least one selected from the group consisting of ruthenium and ruthenium compounds is supported on a support containing titanium oxide.
- the term “catalyst in which a component containing at least one selected from the group consisting of ruthenium and ruthenium compounds is supported on a support containing titanium oxide” means the surface and/or pores of the support containing titanium oxide. It means a catalyst in which a component containing at least one selected from the group consisting of ruthenium and ruthenium compounds is attached.
- at least one selected from the group consisting of ruthenium and ruthenium compounds is selected as the component to be supported on the carrier from the viewpoint of the balance between catalytic activity and cost.
- the ruthenium compound is not particularly limited, and examples thereof include ruthenium oxide, ruthenium hydroxide, ruthenium nitrate, ruthenium chloride, chlororuthenate, chlororuthenate hydrate, salts of ruthenic acid, ruthenium oxychloride, and ruthenium oxychloride.
- ruthenium ammine complexes chlorides of ruthenium ammine complexes, ruthenium bromide, ruthenium carbonyl complexes, ruthenium organic acid salts, ruthenium nitrosyl complexes, and the like.
- Ruthenium oxide includes RuO 2 and the like.
- Ruthenium hydroxides include Ru(OH) 3 .
- Ruthenium nitrate includes Ru(NO 3 ) 3 .
- Ruthenium chloride includes RuCl 3 and RuCl trihydrate.
- Examples of the chlororuthenate include salts with [RuCl 6 ] 3- as an anion, such as K 3 RuCl 6 , and salts with [RuCl 6 ] 2- as an anion, such as K 2 RuCl 6 and (NH 4 ) 2 RuCl 6 . and salt.
- Examples of the chlororuthenate hydrate include a salt hydrate with [RuCl 5 (H 2 O) 4 ] 2 ⁇ as an anion and a salt hydrate with [RuCl 2 (H 2 O) 4 ] + as a cation. is mentioned.
- Salts of ruthenic acid include Na 2 RuO 4 , K 2 RuO 4 and the like.
- Ruthenium oxychlorides include Ru 2 OCl 4 , Ru 2 OCl 5 , Ru 2 OCl 6 and the like.
- Ruthenium oxychloride salts include K 2 Ru 2 OCl 10 , Cs 2 Ru 2 OCl 4 and the like.
- the ruthenium ammine complexes include complexes having complex ions such as [Ru(NH 3 ) 6 ] 2+ , [Ru(NH 3 ) 6 ] 3+ and [Ru(NH 3 ) 5 H 2 O] 2+ .
- the chlorides of the ruthenium ammine complexes include complexes with [Ru(NH 3 ) 5 Cl] 2+ as a complex ion, [Ru(NH 3 ) 6 ]Cl 2 , [Ru(NH 3 ) 6 ]Cl 3 , [Ru (NH 3 ) 6 ]Br 3 and the like.
- RuBr 3 and RuBr trihydrate are examples of ruthenium bromide.
- Ruthenium carbonyl complexes include Ru(CO) 5 and Ru 3 (CO) 12 .
- Ruthenium compounds are preferably ruthenium oxide, ruthenium nitrate, ruthenium chloride, ruthenium bromide, salts of ruthenic acid, and ruthenium nitrosyl complexes, more preferably ruthenium oxide.
- the component supported on the carrier containing titanium oxide may contain at least one selected from the group consisting of ruthenium and ruthenium compounds, and may further contain metals other than ruthenium and metal compounds other than ruthenium compounds. may contain.
- the catalyst for the purpose of inhibiting the adsorption of substances that cause catalyst poisoning on the catalyst surface, preventing the performance of the catalyst from deteriorating, or preventing the sintering of the catalyst active sites, the catalyst is: It is preferable that the catalyst is obtained by further supporting at least one selected from the group consisting of metals other than ruthenium and metal compounds other than ruthenium compounds on a support containing titanium oxide.
- Metals other than ruthenium are not particularly limited, and include silicon, zirconium, aluminum, niobium, tin, copper, iron, cobalt, nickel, vanadium, chromium, molybdenum, tungsten, manganese, antimony, and tellurium.
- the metal compound other than the ruthenium compound is not particularly limited, and includes compounds containing metals other than ruthenium, and oxides of metals other than ruthenium are preferred.
- the metal oxide may be a composite oxide of multiple metal species.
- the catalyst may also be a catalyst in which an alloy of ruthenium and a metal other than ruthenium or a composite oxide containing ruthenium and a metal other than ruthenium is further supported on a carrier.
- the catalyst contains at least one selected from the group consisting of silicon oxide, zirconium oxide, aluminum oxide, niobium oxide, manganese oxide, antimony oxide, tellurium oxide and tin oxide on a support containing rutile crystal form of titanium oxide.
- the metal salt used to obtain the metal oxide is not particularly limited.
- the content of at least one selected from the group consisting of ruthenium and ruthenium compounds in the catalyst is not particularly limited and is set appropriately. .5 to 10% by mass is more preferable, and 1 to 5% by mass is even more preferable.
- the content of at least one selected from the group consisting of ruthenium and ruthenium compounds is based on metal ruthenium when the total amount of the component containing at least one selected from the group consisting of ruthenium and ruthenium compounds and the support is 100% by mass. 0.1 to 20% by mass is preferable, 0.5 to 10% by mass is more preferable, and 1 to 5% by mass is even more preferable.
- the contents of metals other than ruthenium and metal compounds other than ruthenium compounds in the catalyst are not particularly limited and can be appropriately set according to the above purpose.
- the carrier may contain titanium oxide, and may contain other compounds described later.
- the crystal form of titanium oxide constituting the carrier is not particularly limited, and may be any of rutile crystal form, anatase crystal form, and brookite crystal form.
- the carrier is preferably composed of titanium oxide containing titanium oxide in rutile crystal form. From the viewpoint of catalytic activity, the content of rutile crystalline titanium oxide in the titanium oxide contained in the carrier is preferably 20% by mass or more, preferably 30% by mass, based on 100% by mass of the total amount of titanium oxide contained in the carrier. The above is more preferable, 80% by mass or more is more preferable, and 90% by mass or more is even more preferable.
- titanium oxide containing rutile crystalline titanium oxide refers to titanium oxide containing rutile crystals among which the ratio of rutile crystals and anatase crystals in titanium oxide is measured by X-ray diffraction analysis.
- Various radiation sources are used as X-ray sources.
- K ⁇ rays of copper can be used as X-ray sources.
- the carrier used in the present invention is a carrier having peak intensity of rutile crystals and peak intensity of anatase crystals, or a carrier having peak intensity of rutile crystals. That is, the carrier may have both diffraction peaks of rutile crystals and diffraction peaks of anatase crystals, or may have only diffraction peaks of rutile crystals.
- Other compounds that the support may contain include, for example, metal oxides other than titanium oxide, composite oxides of titanium oxide and other metal oxides, and mixtures of titanium oxide and other metal oxides. etc.
- metal oxides other than titanium oxide include aluminum oxide, silicon oxide, and zirconium oxide.
- titanium oxide one prepared by a known method can be used, and a commercially available product can also be used.
- examples of the method for preparing the rutile crystal form of titanium oxide include the following methods. Titanium tetrachloride is added dropwise to ice-cooled water and then neutralized with an aqueous ammonia solution at a temperature of 20° C. or higher to produce titanium hydroxide (orthotitanic acid). A method of removing ions and then firing at a temperature of 600° C.
- Catalyst Preparation Chemistry, 1989, p.211, Kodansha A method of preparing a reaction gas by passing an oxygen-nitrogen mixed gas through a titanium tetrachloride evaporator, introducing it into a reactor, and reacting it at 900 ° C. or higher (Catalyst Preparation Chemistry, 1989, p.
- the carrier can be obtained by molding titanium oxide or the like into a desired shape.
- the carrier contains a compound or the like other than titanium oxide, it can be obtained by molding a mixture of titanium oxide and other compound or the like into a desired shape.
- the shape of the catalyst (carrier) is not particularly limited, and may be spherical granules, cylindrical pellets, rings, honeycombs, monoliths, corrugates, or moderately sized granules or fine particles obtained by crushing and classifying after molding. is mentioned.
- the diameter of the catalyst is preferably 10 mm or less from the viewpoint of catalytic activity.
- the diameter of the catalyst as used herein means the diameter of the sphere in the case of spherical particles, the diameter of the cross section in the case of cylindrical pellets, and the maximum diameter of the cross section in the case of other shapes.
- the catalyst is selected from the group consisting of ruthenium and ruthenium compounds, for example, by impregnating a carrier containing titanium oxide with a solution containing at least one component selected from the group consisting of ruthenium and ruthenium compounds. It can be prepared by a method of drying after attaching a component containing at least one of the following.
- the solvent in the solution containing the component containing at least one selected from the group consisting of ruthenium and ruthenium compounds is not particularly limited, but water, ethanol and the like can be used. You may bake after drying.
- the catalyst contains ruthenium oxide
- a step of impregnating a support containing titanium oxide with a solution containing ruthenium halide to support the ruthenium halide on the support It can be obtained by a method comprising a step of drying the supported material and a step of calcining the dried material.
- the catalyst can be used by diluting it with an inert substance.
- the deteriorated catalyst used in the regeneration method of the present invention may be one that has been used in the method for decomposing nitrous oxide and whose catalytic activity has been deactivated. be done.
- the "regeneration rate" ratio of reaction rate constants for the decomposition reaction of nitrous oxide
- the details (chemical structure, structural change, physical properties, etc.) of the catalyst deactivated by the decomposition reaction of nitrous oxide are not yet clear, as they are considered to be inconsistent depending on the type of catalyst (compound type) and the like.
- ruthenium oxide ruthenium oxide particles poisoned by adsorption of its reduced form, components in nitrous oxide-containing gas, etc., ruthenium oxide particles whose degree of dispersion is reduced by sintering of ruthenium oxide particles, etc. , and those that have lost the function of promoting the decomposition of nitrous oxide.
- the oxidizing gas used in the regeneration method of the present invention may be any gas that oxidizes a specific substance and is itself reduced. Examples thereof include gases containing oxidizing substances, typically oxygen contained gas.
- the oxygen-containing gas may generally contain oxygen gas, and examples thereof include air and a gas obtained by diluting oxygen gas with an inert gas or the like, with air being preferred.
- the oxygen gas is not particularly limited, but usually includes air, pure oxygen, and the like.
- the inert gas may be any gas that does not substantially contain oxidizing substances. Examples include rare earth gases such as helium, neon, and argon, nitrogen gas, carbon monoxide gas, carbon dioxide gas, hydrocarbon gas, and the like. and preferably nitrogen gas.
- the oxidizing gas may contain moisture.
- the oxygen concentration in the oxygen-containing gas is appropriately determined depending on the regeneration conditions, etc., and is usually 0.1 to 100 mol%, preferably 2 to 50 mol%, and 4 to 30 mol. % is more preferable.
- the above-described deteriorated catalyst is heat-treated at a temperature of 175 to 325° C. in an oxidizing gas atmosphere.
- the deactivated catalyst activity can be recovered and the deteriorated catalyst can be regenerated.
- the heat treatment step is performed in an oxidizing gas atmosphere, preferably in an oxidizing gas stream.
- this step can be carried out in an atmosphere of an oxidizing gas, it may be of a batch type or a continuous type, and the continuous type is preferred in terms of workability, regeneration efficiency, and the like.
- the continuous type includes, for example, a fixed bed type and a fluidized bed type.
- the heat treatment temperature is appropriately determined within the range of 175 to 325°C, preferably 180 to 320°C, more preferably 185 to 315°C, from the viewpoint of regeneration efficiency of the deteriorated catalyst.
- the heating method is not particularly limited, and conventional heating methods using various heaters and the like can be mentioned.
- the oxidizing gas may be heated in advance and brought into contact with the deteriorated catalyst.
- the heat treatment temperature of the present invention allows the heat source used in the contacting step to be used for heating the oxidizing gas, thereby reducing the cost of the regeneration step and efficiently regenerating the deteriorated catalyst.
- the heat treatment time is appropriately determined according to the oxidizing substance concentration or supply rate of the oxidizing gas, the heat treatment temperature, etc., and can be, for example, 0.5 to 100 hours, or 1 to 50 hours. , 1.5 to 25 hours.
- the supply rate of the oxidizing gas relative to the weight of the catalyst is not particularly limited, and is appropriately determined according to the type or concentration of the oxidizing substance.
- the flow rate at 0° C. and 0.1013 MPa (absolute) with respect to 1 g of catalyst is preferably 1 to 350 cm 3 /min, more preferably 3.5 to 300 cm 3 /min.
- the pressure during the heat treatment can be appropriately determined in consideration of the heat treatment temperature, the supply rate of the oxidizing gas, the pressure of the ambient air, and the like.
- the absolute pressure can be 0.08 to 1 MPa (absolute), preferably 0.09 to 0.7 MPa (absolute).
- the regeneration method of the present invention can recover the catalytic activity of the deteriorated catalyst and regenerate the deteriorated catalyst with high efficiency even if the heat treatment is performed in a relatively short time.
- the regeneration efficiency of the catalyst in the regeneration method of the present invention cannot be uniquely determined by the above-described heat treatment conditions, heat treatment scale, etc., but for example, the "regeneration rate" in the examples described later is up to 0.90 or more. , preferably up to 0.93 or higher.
- the regeneration method of the present invention may have steps other than the heat treatment step. For example, when the heat treatment process is performed in a continuous manner, the process of circulating an inert gas until the heat treatment temperature is reached, the process of removing the deteriorated catalyst from the nitrous oxide decomposition device, and the crushing and crushing of the removed deteriorated catalyst. a step of reshaping the catalyst, a step of charging the regenerated catalyst into the cracker, and the like.
- the nitrous oxide decomposition method of the present invention (hereinafter sometimes simply referred to as the "decomposition method of the present invention") comprises a regenerated catalyst regenerated by the above-described regeneration method of the present invention and nitrous oxide (gas). and a nitrous oxide-containing gas.
- the decomposition method of the present invention includes the regeneration method of the present invention as a step of regenerating the deteriorated catalyst, and a contacting step of contacting the regenerated catalyst regenerated by this regeneration method with the nitrous oxide-containing gas.
- the decomposition method of the present invention may be any method as long as it includes the regeneration method of the present invention and the contact step, and the regeneration method and the contact step may be alternately repeated multiple times.
- the contacting step and the regeneration method are alternately repeated multiple times, there is a method in which the catalyst that has deteriorated in the contacting step is regenerated in the regeneration step, which is the next step, and the resulting regenerated catalyst is used in the contacting step, which is the next step. preferable.
- the regeneration method and the contacting step can each be performed multiple times before proceeding to the next step.
- a nitrous oxide decomposition step prior to the regeneration method, can be performed using an unused catalyst.
- This cracking step is the same as the contacting step, which will be described later, except that an unused catalyst is used.
- the timing of performing the regeneration method is not particularly limited, and may be performed at an appropriate time, including when the contact step and the regeneration method can be performed with the same device (equipment). can be switched with For example, regardless of the amount of deactivation of the catalyst in the contacting step, it is possible to switch to the regeneration method during or after the contacting step. Once the volume is reached, it is preferred to switch from the contacting step to the regeneration process.
- the regenerated catalyst used in the contacting step is the catalyst regenerated by the above-described regeneration method of the present invention, and the details thereof are as described above.
- the nitrous oxide-containing gas used in the contact step may contain nitrous oxide, and may contain an inert gas as a diluent gas.
- Nitrous oxide-containing gases include nitrous oxide, nitrogen, carbon monoxide, carbon dioxide, water vapor, oxygen, hydrogen, ammonia, nitric oxide, nitrogen dioxide, and hydrocarbons (including saturated and unsaturated hydrocarbons). including). It may also contain an inert gas.
- the contents (concentrations) of these gases in the nitrous oxide-containing gas are not particularly limited and can be set appropriately. For example, it can be the same content as a suitable nitrous oxide-containing gas described later.
- the nitrous oxide containing gas may include liquids. In the decomposition method of the present invention, the nitrous oxide-containing gas may be gaseous at least while in contact with the catalyst (reaction conditions), and even if it is liquid before contacting, it may be a mixture of gas and liquid. may be
- the nitrous oxide-containing gas (sometimes referred to as a suitable nitrous oxide-containing gas) used in the preferable contacting step described later is a gas containing nitrous oxide, water vapor and ammonia, and one kind of gas other than these Or two or more kinds may be included.
- gases include various gases such as oxygen, helium, argon, nitrogen, and carbon dioxide, as well as reducing gases to be described later.
- the content (concentration) of each component in suitable nitrous oxide-containing gas is not particularly limited and can be set as appropriate. For unique values, it is efficient to use almost as is. Therefore, for example, the molar concentration of nitrous oxide in a suitable nitrous oxide-containing gas is generally and preferably 0.002 to 10 mol %.
- the molar concentration of water vapor is generally and preferably 0.1 to 10 mol %.
- the molar concentration of ammonia in a suitable nitrous oxide-containing gas is preferably 0.0002 mol % or more and preferably 1 mol % or less from the viewpoint of nitrous oxide decomposition efficiency.
- the molar concentration of ammonia is more preferably 0.0002 to 0.5 mol %, even more preferably 0.0002 to 0.2 mol %.
- the content ratio of ammonia to water vapor [ammonia/steam] contained in the preferred nitrous oxide-containing gas is not particularly limited and can be set as appropriate. 0010 or more is preferable.
- the molar ratio is more preferably 0.0010 to 0.050, and 0.0010 to 0.030 in terms of suppressing or avoiding the problem of remaining ammonia (emission into the atmosphere, implementation of removal work). is more preferably 0.0010 to 0.010.
- the content ratio of ammonia to nitrous oxide contained in a suitable nitrous oxide-containing gas [ammonia/nitrous oxide] is not particularly limited and can be set as appropriate, but the molar ratio is 0.005 to 10. Preferably.
- the content of oxygen gas in the suitable nitrous oxide-containing gas is not particularly limited and can be set as appropriate. It is preferably 0.01 to 10,000 mol times the content of When a suitable nitrous oxide-containing gas does not contain oxygen gas, it can be obtained, for example, by mixing a suitable nitrous oxide-containing gas and an oxygen-containing gas.
- Oxygen-containing gas includes air.
- a suitable nitrous oxide-containing gas may also contain a reducing gas to further enhance the efficiency of nitrous oxide decomposition.
- a raw material that reacts with oxygen contained in the nitrous oxide-containing gas or generated in the reactor to generate a reducing gas such as carbon monoxide gas
- a saturated hydrocarbon gas such as carbon monoxide gas
- a method in which a suitable nitrous oxide-containing gas contains a reducing gas is preferred.
- the reducing gas any reducing gas other than ammonia may be used, and any reducing gas used in a general catalytic reduction method can be used without particular limitation.
- Examples include unsaturated hydrocarbon gases such as ethylene, propylene, ⁇ -butylene and ⁇ -butylene, carbon monoxide gas, hydrogen gas, and alcohol compound gases such as methanol, ethanol, propanol and butanol. Among them, at least one of carbon monoxide gas, unsaturated hydrocarbon gas and hydrogen gas is preferred.
- Methane, ethane, propane, n-butane, and the like are examples of saturated hydrocarbon gases that are raw materials for generating reducing gases such as carbon monoxide gas.
- Preferred saturated hydrocarbon gases include ethane, propane and n-butane.
- Mixtures such as natural gas, liquefied natural gas, and liquefied petroleum gas may be used to include saturated hydrocarbon gases.
- the content of reducing gas or saturated hydrocarbon gas in suitable nitrous oxide-containing gas is not particularly limited and can be set as appropriate.
- the molar concentration of reducing gas or saturated hydrocarbon gas in suitable nitrous oxide-containing gas is 0.001 to 1 mol %.
- the molar ratio of the reducing gas or saturated hydrocarbon gas to steam [reducing gas or saturated hydrocarbon gas/steam] in the suitable nitrous oxide-containing gas is preferably 0.0003 to 0.03.
- the content ratio of reducing gas or saturated hydrocarbon gas to nitrous oxide contained in suitable nitrous oxide-containing gas [reducing gas or saturated hydrocarbon gas/nitrous oxide] is 0.00 in terms of molar ratio. 01-100 is preferred.
- the nitrous oxide-containing gas can be prepared by appropriately mixing nitrous oxide, water vapor, ammonia, and other gases mentioned above.
- various exhaust gases discharged from chemical manufacturing plants can also be used.
- gases discharged from chemical manufacturing plants such as nitric acid manufacturing plants, ⁇ -caprolactam manufacturing plants, and adipic acid manufacturing plants contain water vapor, ammonia, and oxygen gas in addition to nitrous oxide.
- it can be effectively used in the preferable contacting step described later.
- the exhaust gas satisfies the above range of content, content ratio, etc., it is preferable in that it can be applied to the preferred contacting step as it is without adjusting the content.
- the contacting step may be a step of contacting the nitrous oxide decomposition catalyst and a nitrous oxide-containing gas containing nitrous oxide, and the nitrous oxide decomposition catalyst used is the above-mentioned regenerated catalyst.
- can be applied to the contacting step in the nitrous oxide decomposition method of Examples of the contacting step in a known method for decomposing nitrous oxide include a method (step) of contacting a catalyst and nitrous oxide in the presence of a reducing gas, described in Patent Document 1, for example.
- the contacting step in the present invention is preferably a step of contacting the regenerated nitrous oxide decomposition catalyst with a nitrous oxide-containing gas containing nitrous oxide, water vapor and ammonia (sometimes referred to as a “preferred contacting step”).
- a nitrous oxide-containing gas containing nitrous oxide, water vapor and ammonia sometimes referred to as a “preferred contacting step”.
- the nitrous oxide-containing gas is brought into contact with the regenerated catalyst.
- the contacting method is not particularly limited, and may be, for example, a batch method or a continuous method, preferably a continuous method in terms of reaction efficiency.
- the continuous type includes, for example, a fixed bed type and a fluidized bed type.
- the nitrous oxide contained in the nitrous oxide-containing gas comes into contact with the regenerated catalyst, so that the decomposition reaction of nitrous oxide represented by the following formula occurs even in the presence of water vapor, resulting in nitrous oxide. is efficiently decomposed into nitrogen molecules and oxygen molecules.
- Decomposition reaction of nitrous oxide N 2 O ⁇ N 2 + 1/2O 2
- the ammonia in the nitrous oxide-containing gas further promotes the decomposition reaction of nitrous oxide.
- a catalyst that exhibits a reducing action such as a ruthenium-supported catalyst
- ammonia reacts with nitrous oxide on the surface of the catalyst to decompose nitrous oxide into nitrogen molecules and water molecules. It is presumed that the decomposition reaction of nitric oxide can be further accelerated.
- a catalyst that does not exhibit a reducing action such as a catalyst supporting ruthenium oxide
- the oxygen atoms are removed from the catalyst surface by reacting with the oxygen atoms remaining on the catalyst surface to maintain the catalytic activity. It is presumed that the deactivation of the catalyst can be suppressed and the decomposition reaction can be promoted.
- the contacting method and contacting conditions can be appropriately adopted in each step.
- Preferred contact conditions in the contact step are not particularly limited, but include, for example, the following conditions.
- the contact temperature (reaction temperature) is appropriately determined, but is preferably 500° C. or lower from the viewpoint of catalyst activity deterioration, and preferably 100° C. or higher from the viewpoint of reaction rate.
- the contact temperature is preferably 200-450°C, more preferably 250-400°C.
- the feed rate of the nitrous oxide-containing gas relative to the weight of the catalyst is not particularly limited and is determined appropriately. It is preferably 10000 cm 3 /min, more preferably 50 to 5000 cm 3 /min.
- the contact time is appropriately determined according to the concentration of nitrous oxide in the nitrous oxide-containing gas, the supply rate, the contact temperature, and the like.
- the reaction pressure varies depending on the contact temperature, the supply rate of the nitrous oxide-containing gas, the pressure of the ambient air around the reactor, etc., but is preferably higher than the ambient pressure, preferably 0.08 to 1 MPa (absolute) in terms of absolute pressure. and more preferably 0.09 to 0.7 MPa (absolute) in terms of absolute pressure.
- the decomposition method of the present invention may have steps other than the regeneration method and the contact step.
- the above-described contact step using an unused catalyst, the step of adjusting the component content of the nitrous oxide-containing gas, the step of introducing oxygen gas or reducing gas into the nitrous oxide-containing gas, and the like can be mentioned.
- the regeneration method and the contact step can be performed in the same device (reactor) or in different devices.
- the regeneration method and the contacting step are performed continuously, it is preferable to perform them in the same apparatus in that they can be easily transferred by changing the gas to be supplied.
- a tubular or tower-type reactor such as a metal tube or a column tower can be used, and more specifically, various fixed bed reactors can be used.
- the decomposition method of the present invention has a step of recovering the catalytic activity deactivated by the nitrous oxide decomposition step, and the nitrous oxide decomposition catalyst can be reused in the nitrous oxide decomposition step. Therefore, the decomposition method of the present invention makes it possible to reduce the decomposition cost of nitrous oxide and further reduce the waste amount of the catalyst. In addition, since the degraded catalyst can be efficiently regenerated by the regeneration method, it is possible to decompose nitrous oxide while suppressing the decrease in decomposition efficiency in the decomposition process, and it is possible to perform multiple decomposition processes in succession. Become.
- the nitrous oxide in the continuous system, by circulating (passing) the nitrous oxide-containing gas through the catalyst, the nitrous oxide can be efficiently decomposed and the emission of nitrous oxide can be suppressed.
- ammonia in the nitrous oxide-containing gas in the preferred contacting step, can also be efficiently decomposed, and the emission of ammonia can be suppressed.
- the decomposition method of the present invention can be used in various fields and applications for decomposing and removing nitrous oxide, such as chemical manufacturing plants.
- it can be suitably used in chemical manufacturing plants such as nitric acid manufacturing plants, ⁇ -caprolactam manufacturing plants, and adipic acid manufacturing plants that discharge gases containing nitrous oxide, ammonia and water vapor.
- the installation position of the apparatus for performing the decomposition method of the present invention is not particularly limited, but it is usually installed in the last stage in the flow direction of the exhaust gas, for example, the front stage of the discharge tower. be Specifically, if it is a nitric acid production plant, it is incorporated after the denitrification reactor.
- the space velocity GHSV (h ⁇ 1 ) of the decomposition reaction of nitrous oxide is obtained by dividing the reaction gas supply rate (cm 3 (0° C., 0.1013 MPa (absolute))/hour) by the catalyst volume (cm 3 ).
- reaction rate constant (s ⁇ 1 ) was calculated from the nitrous oxide reduction rate X (%) and the space velocity GHSV (h ⁇ 1 ) of the reaction gas by the following formula.
- Reaction rate constant (s ⁇ 1 ) ⁇ ln(1 ⁇ X/100)/(3600/GHSV)
- ln(1 ⁇ X/100) represents the natural logarithm of (1 ⁇ X/100).
- a RuO 2 /TiO 2 catalyst was produced as a nitrous oxide decomposition catalyst in the following manner, used for a nitrous oxide decomposition reaction, and deteriorated.
- the internal temperature of the quartz glass tube was 275°C when the temperature of the electric tubular furnace was 250°C.
- 20.9 g of RuO 2 /TiO 2 catalyst containing 4.0% by mass of ruthenium oxide (3.0% by mass of Ru content, in the form of cylindrical pellets) was obtained.
- the obtained RuO 2 /TiO 2 catalyst in the form of cylindrical pellets was pulverized and sieved into granules of 1.0 to 1.7 mm to obtain a new catalyst (a), which was used in the following examples.
- the gas brought into contact with the new catalyst (a) was 0.10 mol % nitrous oxide, 1.50 mol % oxygen and the remainder nitrogen (flow rate: 24.6 cm 3 (0 ° C.,
- the mixed gas was switched to 0.1013 MPa (absolute)/min), and the decomposition reaction of nitrous oxide was performed.
- the reaction rate constant when the decomposition reaction started to stabilize was 5.8 s -1 .
- the time when the decomposition reaction started to stabilize was defined as the time when the variation in the reaction rate constant became ⁇ 1% or less.
- ⁇ Production Example 2> (Contact process using new catalyst) 1.24 g (1.0 cm 3 ) of the cylindrical pellet-shaped RuO 2 /TiO 2 catalyst obtained in Production Example 1 above was placed in a stainless steel reaction tube (inner diameter 156 mm) equipped with a stainless sheath tube for measuring internal temperature. filled to This reaction tube is placed in an electric furnace, and the temperature inside the stainless steel reaction tube is 300 under normal pressure (0.1 MPa (absolute)), 500 cm 3 (0 ° C., 0.1013 MPa (absolute)) / min nitrogen gas flow. The temperature was raised to °C.
- the gas to be brought into contact with the RuO 2 /TiO 2 catalyst was switched to the exhaust gas from the nitric acid production plant to decompose nitrous oxide.
- Exhaust gas from a nitric acid production plant was collected in a gas sampling bag, and the exhaust gas was analyzed using gas chromatography and a gas detector tube (water vapor 6, ammonia 3M). 1.50 mol % oxygen, 0.40 mol % water vapor, and 0.05 mol % ammonia.
- the gases brought into contact with the degraded catalyst (b) were 0.10 mol % nitrous oxide, 1.50 mol % oxygen, and the remainder nitrogen (flow rate: 24.6 cm 3 (0° C., The mixed gas was switched to 0.1013 MPa (absolute)/min), and the second decomposition reaction of nitrous oxide was performed.
- the reaction rate constant when the decomposition reaction started to stabilize was 5.1 s ⁇ 1 .
- the time when the decomposition reaction started to stabilize was defined as the time when the variation in the reaction rate constant became ⁇ 1% or less.
- Example 1 (regeneration process) 0.06 g (0.05 cm 3 ) of the deteriorated catalyst (b) obtained in Production Example 2 above was filled in a quartz glass reaction tube (inner diameter 26.5 mm) equipped with a quartz glass sheath tube for measuring the internal temperature. .
- This reaction tube was installed in an electric furnace, normal pressure (0.1 MPa (absolute)), 6.8 cm 3 (0 ° C., 0.1013 MPa (absolute)) / min air was circulated, and the electric furnace temperature was 200 After the temperature was raised to 200° C., a heat treatment was performed at a temperature of 200° C. for 3 hours to obtain a regenerated catalyst 1.
- the obtained regenerated catalyst 1 was filled in a quartz glass reaction tube (inner diameter 8 mm) equipped with a quartz glass sheath tube for measuring the internal temperature.
- This reaction tube was installed in an electric furnace, normal pressure (0.1 MPa (absolute)), 100 cm 3 (0 ° C., 0.1013 MPa (absolute)) / min helium gas was circulated, and the inside of the quartz glass reaction tube was The temperature was raised until the temperature reached 300°C.
- the gas brought into contact with the regenerated catalyst 1 was composed of 0.10 mol % nitrous oxide, 1.50 mol % oxygen, and the balance nitrogen (flow rate: 24.6 cm 3 (at 0° C., 0.5 mol %).
- the mixed gas was switched to 1013 MPa (absolute)/min), and the decomposition reaction of nitrous oxide was performed.
- the reaction rate constant was 7.0 s ⁇ 1 when the decomposition reaction started to stabilize.
- the time when the decomposition reaction started to stabilize was defined as the time when the variation in the reaction rate constant became ⁇ 1% or less.
- Table 1 shows the regeneration rate of regenerated catalyst 1 when the reaction rate constant (5.8 s -1 ) of the nitrous oxide decomposition reaction using the new catalyst (a) in Production Example 1 is set to 1. shown in
- Example 2 In the regeneration step of Example 1, the procedure was the same as in Example 1, except that the temperature of the electric furnace was raised to 250° C., and then heat treatment was performed at a temperature of 250° C. for 3 hours to obtain a regenerated catalyst 2. A regeneration step and a nitrous oxide contact step were carried out.
- the reaction rate constant was 6.9 s ⁇ 1 when the decomposition reaction started to stabilize.
- the time when the decomposition reaction started to stabilize was defined as the time when the variation in the reaction rate constant became ⁇ 1% or less.
- Table 1 shows the regeneration rate of the regenerated catalyst 2 when the reaction rate constant of the nitrous oxide decomposition reaction using the new catalyst (a) in Production Example 1 is set to 1.
- Example 3 In the regeneration step of Example 1, the procedure was the same as in Example 1, except that the temperature of the electric furnace was raised to 300° C., and then heat treatment was performed at a temperature of 300° C. for 3 hours to obtain a regenerated catalyst 3. A regeneration step and a nitrous oxide contact step were carried out.
- the reaction rate constant was 7.9 s ⁇ 1 when the decomposition reaction started to stabilize.
- the time when the decomposition reaction started to stabilize was defined as the time when the variation in the reaction rate constant became ⁇ 1% or less.
- Table 1 shows the regeneration rate of the regenerated catalyst 3 when the reaction rate constant of the nitrous oxide decomposition reaction using the new catalyst (a) in Production Example 1 is set to 1.
- Example 1 In the regeneration step of Example 1, the procedure was the same as in Example 1, except that after the electric furnace temperature was raised to 150° C., heat treatment was performed at a temperature of 150° C. for 3 hours to obtain a regenerated catalyst C1. A regeneration step and a nitrous oxide contact step were carried out.
- the reaction rate constant was 5.1 s ⁇ 1 when the decomposition reaction started to stabilize.
- the time when the decomposition reaction started to stabilize was defined as the time when the variation in the reaction rate constant became ⁇ 1% or less.
- Table 1 shows the regeneration rate of the regenerated catalyst C1 when the reaction rate constant of the nitrous oxide decomposition reaction using the new catalyst (a) in Production Example 1 is set to 1.
- Example 2 In the regeneration step of Example 1, the procedure was the same as in Example 1, except that after the electric furnace temperature was raised to 350° C., heat treatment was performed at a temperature of 350° C. for 3 hours to obtain a regenerated catalyst C2. A regeneration step and a nitrous oxide contact step were carried out.
- the reaction rate constant was 1.7 s ⁇ 1 when the decomposition reaction started to stabilize.
- the time when the decomposition reaction started to stabilize was defined as the time when the variation in the reaction rate constant became ⁇ 1% or less.
- Table 1 shows the regeneration rate of the regenerated catalyst C2 when the reaction rate constant of the nitrous oxide decomposition reaction using the new catalyst (a) in Production Example 1 is set to 1.
- the reaction rate constant of the regenerated catalysts 1 to 3 was 5.0 in the second nitrous oxide decomposition reaction that was continuously performed without performing the regeneration step of the deteriorated catalyst (b) in Production Example 2. It is larger than 1 s ⁇ 1 and it can be seen that the catalytic activity of the deteriorated catalyst (b) can be recovered.
- the regeneration process can restore the catalytic activity of the nitrous oxide decomposition catalyst. It can be seen that the cost of decomposition of nitrogen oxides and the amount of waste of the deteriorated catalyst can be reduced. In addition, nitrous oxide can be decomposed while suppressing a decrease in decomposition efficiency in the decomposition process, and it is possible to continuously perform a plurality of decomposition processes.
- the present invention provides a method for regenerating a nitrous oxide decomposition catalyst capable of efficiently regenerating a deactivated nitrous oxide decomposition catalyst, and a method for decomposing nitrous oxide using the nitrous oxide decomposition catalyst regenerated by this regeneration method.
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Abstract
Description
<1>酸化チタンを含む担体に、ルテニウムおよびルテニウム化合物からなる群から選ばれる少なくとも1種を含有する成分が担持されてなる亜酸化窒素分解用触媒であって亜酸化窒素の分解反応に使用した亜酸化窒素分解用触媒を、
酸化性ガスの雰囲気下、温度175~325℃の条件で熱処理する工程を含む、亜酸化窒素分解用触媒の再生方法。
<2>前記酸化性ガスが空気である、<1>に記載の亜酸化窒素分解用触媒の再生方法。
<3>上記<1>または<2>に記載の亜酸化窒素分解用触媒の再生方法に次いで、該再生方法で再生した亜酸化窒素分解用触媒と、亜酸化窒素を含む亜酸化窒素含有ガスとを接触させる工程を含む、亜酸化窒素の分解方法。
<4>前記亜酸化窒素含有ガスが、窒素、一酸化炭素、二酸化炭素、水蒸気、酸素、水素、アンモニア、一酸化窒素、二酸化窒素および炭化水素からなる群から選ばれる少なくとも1種のガスを含む、<3>に記載の亜酸化窒素の分解方法。
本発明において、「亜酸化窒素分解用触媒」(単に「触媒」ということもある。)というときは、特に断らない限り、亜酸化窒素の分解反応に使用していない亜酸化窒素分解用触媒(未使用触媒、新品触媒等ともいう。)と、亜酸化窒素の分解反応に使用した亜酸化窒素分解用触媒(使用済触媒、劣化触媒等ともいう。)と、更に、劣化触媒を再生した亜酸化窒素分解用再生触媒(再生触媒ともいう。)とを含む意味で用いる。
本発明の亜酸化窒素分解用触媒の再生方法(以下、単に「本発明の再生方法」ということがある。)は、亜酸化窒素の分解反応(分解方法)に使用した亜酸化窒素分解用触媒を、酸化性ガスの雰囲気下、温度175~325℃の条件で熱処理する工程を含んでいる。この熱処理工程により、後述するように、触媒活性が失活した劣化触媒の触媒活性を効率よく回復もしくは再生することができる。
本発明の再生方法に用いる劣化触媒は、酸化チタンを含む担体にルテニウムおよびルテニウム化合物からなる群から選ばれる少なくとも1種を含有する成分が担持されてなる亜酸化窒素分解用触媒を亜酸化窒素の分解方法に使用することにより、触媒活性が失活した触媒である。ここで、劣化触媒を失活させる亜酸化窒素の分解方法等は、特に制限されず、例えば、後述する本発明の亜酸化窒素の分解方法における「亜酸化窒素含有ガスと接触させる工程」等が挙げられる。
本発明において、「酸化チタンを含む担体にルテニウムおよびルテニウム化合物からなる群から選ばれる少なくとも1種を含有する成分が担持されてなる触媒」とは、酸化チタンを含む担体の表面および/または細孔内に、ルテニウムおよびルテニウム化合物からなる群から選ばれる少なくとも1種を含有する成分が付着している触媒を意味する。
本発明においては、担体に担持する成分として、触媒活性およびコストのバランスなどの点で、ルテニウムおよびルテニウム化合物からなる群から選ばれる少なくとも1種を選択する。
ルテニウム化合物としては、特に制限されず、例えば、酸化ルテニウム、水酸化ルテニウム、硝酸ルテニウム、塩化ルテニウム、クロロルテニウム酸塩、クロロルテニウム酸塩水和物、ルテニウム酸の塩、ルテニウムオキシ塩化物、ルテニウムオキシ塩化物の塩、ルテニウムアンミン錯体、ルテニウムアンミン錯体の塩化物、臭化ルテニウム、ルテニウムカルボニル錯体、ルテニウム有機酸塩、ルテニウムニトロシル錯体などが挙げられる。
酸化ルテニウムとしては、RuO2などが挙げられる。
水酸化ルテニウムとしては、Ru(OH)3が挙げられる。
硝酸ルテニウムとしては、Ru(NO3)3が挙げられる。
塩化ルテニウムとしては、RuCl3、RuCl3水和物などが挙げられる。
クロロルテニウム酸塩としては、K3RuCl6など、〔RuCl6〕3-を陰イオンとする塩、K2RuCl6や(NH4)2RuCl6など、〔RuCl6〕2-を陰イオンとする塩が挙げられる。
クロロルテニウム酸塩水和物としては、〔RuCl5(H2O)4〕2-を陰イオンとする塩水和物、〔RuCl2(H2O)4〕+を陽イオンとする塩水和物などが挙げられる。
ルテニウム酸の塩としては、Na2RuO4、K2RuO4などが挙げられる。
ルテニウムオキシ塩化物としては、Ru2OCl4、Ru2OCl5、Ru2OCl6などが挙げられる。
ルテニウムオキシ塩化物の塩としては、K2Ru2OCl10、Cs2Ru2OCl4などが挙げられる。
ルテニウムアンミン錯体としては、〔Ru(NH3)6〕2+、〔Ru(NH3)6〕3+、〔Ru(NH3)5H2O〕2+などを錯イオンとする錯体などが挙げられる。
ルテニウムアンミン錯体の塩化物としては、〔Ru(NH3)5Cl〕2+を錯イオンとする錯体、〔Ru(NH3)6〕Cl2、〔Ru(NH3)6〕Cl3、〔Ru(NH3)6〕Br3などが挙げられる。
臭化ルテニウムとしては、RuBr3、RuBr3水和物などが挙げられる。
ルテニウムカルボニル錯体としては、Ru(CO)5、Ru3(CO)12などが挙げられる。
ルテニウム有機酸塩としては、[Ru3O(OCOCH3)6(H2O)3]OCOCH3水和物、Ru2(RCOO)4Cl(R=炭素数1~3のアルキル基)などが挙げられる。
ルテニウムニトロシル錯体としては、K2〔RuCl5NO)〕、〔Ru(NH3)5(NO)〕Cl3、〔Ru(OH)(NH3)4(NO)〕(NO3)2、Ru(NO)(NO3)3などが挙げられる。
ルテニウム化合物は、酸化ルテニウム、硝酸ルテニウム、塩化ルテニウム、臭化ルテニウム、ルテニウム酸の塩、ルテニウムニトロシル錯体が好ましく、酸化ルテニウムがより好ましい。
本発明において、触媒被毒の原因となる物質が触媒表面に吸着することを阻害し、触媒の性能が低下することを防ぐ、あるいは触媒活性点のシンタリングを防ぐなどの目的で、触媒は、酸化チタンを含む担体に、ルテニウム以外の金属およびルテニウム化合物以外の金属化合物からなる群から選択される少なくとも1種がさらに担持された触媒であることが好ましい。
ルテニウム以外の金属としては、特に制限されず、ケイ素、ジルコニウム、アルミニウム、ニオブ、スズ、銅、鉄、コバルト、ニッケル、バナジウム、クロム、モリブデン、タングステン、マンガン、アンチモン、テルルなどが挙げられる。ルテニウム化合物以外の金属化合物としては、特に制限されず、上記ルテニウム以外の金属を有する化合物が挙げられ、上記ルテニウム以外の金属の酸化物が好ましい。金属酸化物は、複数の金属種の複合酸化物であってもよい。また、触媒は、担体に、ルテニウムとルテニウム以外の金属との合金や、ルテニウムとルテニウム以外の金属とを含む複合酸化物がさらに担持された触媒でもよい。
触媒は、より好ましくは、ルチル結晶形の酸化チタンを含有する担体に、酸化ケイ素、酸化ジルコニウム、酸化アルミニウム、酸化ニオブ、酸化マンガン、酸化アンチモン、酸化テルルおよび酸化スズからなる群から選ばれる少なくとも一種の酸化物がさらに担持された触媒である。
金属の酸化物を得るために用いられる金属塩は、特に限定されない。
ルテニウムおよびルテニウム化合物からなる群から選ばれる少なくとも1種の含有量は、ルテニウムおよびルテニウム化合物からなる群から選ばれる少なくとも1種を含む成分と担体との合計量を100質量%とすると、金属ルテニウム基準で、0.1~20質量%が好ましく、0.5~10質量%がより好ましく、1~5質量%がさらに好ましい。
触媒中の、ルテニウム以外の金属、およびルテニウム化合物以外の金属化合物などの含有量は、特に制限されず、上記目的に応じて適宜に設定できる。
担体は、酸化チタンを含むものであればよく、後述する他の化合物などを含んでいてもよい。担体を構成する酸化チタンの結晶形は、特に制限されず、ルチル結晶形、アナターゼ結晶形、ブルッカイト結晶形のいずれもでもよい。本発明において、担体は、ルチル結晶形の酸化チタンを含有する酸化チタンで構成されていることが好ましい。触媒活性の観点から、担体に含まれる酸化チタン中の、ルチル結晶形の酸化チタンの含有率は、担体に含まれる酸化チタンの全量を100質量%として、20質量%以上が好ましく、30質量%以上がより好ましく、80質量%以上がさらに好ましく、90質量%以上がさらに好ましい。
ルチル結晶形の酸化チタンの調製方法としては、以下の方法が挙げられる。
四塩化チタンを氷冷した水に滴下溶解した後、20℃以上の温度で、アンモニア水溶液で中和し、水酸化チタン(オルトチタン酸)を生成させ、次いで、生成した沈殿を水洗して塩素イオンを除去した後、600℃以上の温度で焼成する方法(触媒調製化学、1989年、211頁、講談社);
四塩化チタン蒸発器に酸素-窒素混合ガスを通じて反応ガスを調製し、これを反応器に導入し、900℃以上で反応させる方法(触媒調製化学、1989年、89頁、講談社);
四塩化チタンを硫酸アンモニウムの存在下に加水分解した後、焼成する方法(例えば、触媒工学講座10元素別触媒便覧、1978年、254頁、地人書館);
アナターゼ結晶形の酸化チタンを焼成する方法(例えば、金属酸化物と複合酸化物、1980年、107頁、講談社);
塩化チタン水溶液を加熱加水分解する方法;および
硫酸チタンや塩化チタンなどのチタン化合物水溶液とルチル結晶形の酸化チタン粉末を混合した後、加熱加水分解やアルカリ加水分解し、次いで、500℃前後の温度で焼成する方法
触媒が酸化ルテニウムを含有する場合、例えば、ハロゲン化ルテニウムを含む溶液に、酸化チタンを含有する担体を含侵させて、担体にハロゲン化ルテニウムを担持させる工程と、ハロゲン化ルテニウムが担体に担持された担持物を乾燥させる工程と、乾燥物を焼成する工程とを有する方法により得ることができる。
亜酸化窒素の分解反応により失活した触媒の詳細(化学構造、構造変化、物性等)は、触媒の種類(化合物種)等により一義的ではないと考えられ、まだ明らかではない。例えば、酸化ルテニウムである場合、その還元体、亜酸化窒素含有ガス中の成分等が吸着して被毒された酸化ルテニウム粒子、酸化ルテニウム粒子のシンタリングによって分散度が低下した酸化ルテニウム粒子等の、亜酸化窒素の分解促進機能を失ったものが考えられる。
本発明の再生方法に用いる酸化性ガスは、特定の物質を酸化するとともに自身は還元される特性を示すガスであればよく、例えば、酸化性物質を含むガスが挙げられ、典型的には酸素含有ガスが挙げられる。酸素含有ガスとしては、通常、酸素ガスを含有していればよく、例えば、空気、または酸素ガスを不活性ガス等で希釈したガスが挙げられ、空気が好ましい。酸素ガスとしては、特に制限されないが、通常、空気、純酸素等が挙げられる。不活性ガスとしては、実質的に酸化性物質を含有しないガスであればよく、例えば、ヘリウム、ネオン、アルゴン等の希土類ガス、窒素ガス、一酸化炭素ガス、二酸化炭素ガス、炭化水素ガス等が挙げられ、好ましくは窒素ガスである。また、酸化性ガスには水分が含まれていてもよい。
酸素含有ガス中の酸素濃度は、再生条件等に応じて適宜に決定され、通常、0.1~100モル%とすることができ、2~50モル%とすることが好ましく、4~30モル%とすることがより好ましい。
本発明の再生方法においては、上記の劣化触媒を、酸化性ガスの雰囲気下、温度175~325℃の条件で熱処理する。この熱処理工程により、失活した触媒活性を回復させて、劣化触媒を再生することができる。例えば、触媒の劣化が還元反応によるものである場合、この触媒を酸化反応させることによって再生することができると考えられる。
熱処理工程は、酸化性ガスの雰囲気下、好ましくは酸化性ガスの気流下で行う。この工程は、酸化性ガスの雰囲気下で行うことができれば、バッチ式でも連続式でもよく、作業性、再生効率等の点で、連続式が好ましい。連続式としては、例えば、固定床形式、流動床形式が挙げられる。
熱処理時間は、酸化性ガスの酸化性物質濃度もしくは供給速度、熱処理温度等に応じて適宜に決定され、例えば、0.5~100時間とすることができ、1~50時間とすることもでき、1.5~25時間という比較的短時間に設定することもできる。
連続式で熱処理を行う場合、触媒重量に対する酸化性ガスの供給速度は、特に制限されず、酸化性物質の種類もしくは濃度等に応じて適宜に決定される。例えば、触媒1gに対する、0℃、0.1013MPa(absolute)での流量として、1~350cm3/分であることが好ましく、3.5~300cm3/分であることがより好ましい。
熱処理時の圧力は、熱処理温度、酸化性ガスの供給速度や周辺の外気の圧力などを考慮して適宜に決定することができる。例えば、絶対圧で、0.08~1MPa(absolute)とすることができ、0.09~0.7MPa(absolute)とすることが好ましい。
本発明の再生方法は、熱処理工程以外の工程を有していてもよい。例えば、連続式で熱処理工程を行う場合、熱処理温度に到達するまで不活性ガスを流通させる工程、また、亜酸化窒素の分解装置から劣化触媒を取り出す工程、取り出した劣化触媒を粉砕、解砕等する工程、触媒を再成形する工程、更に再生触媒を分解装置に充填する工程などが挙げられる。
本発明の亜酸化窒素の分解方法(以下、単に「本発明の分解方法」ということがある。)は、上述の本発明の再生方法で再生された再生触媒と、亜酸化窒素(ガス)を含む亜酸化窒素含有ガスとを接触させる工程を行う方法である。本発明の分解方法は、劣化触媒を再生する工程としての本発明の再生方法と、この再生方法で再生した再生触媒、および亜酸化窒素含有ガスとを接触させる接触工程とを含む。
本発明の分解方法は、本発明の再生方法と接触工程と行う方法であればよく、再生方法と接触工程とを交互に複数回繰り返し行うこともできる。接触工程と再生方法とを交互に複数回繰り返し行う方法としては、接触工程で劣化した触媒を次工程となる再生工程で再生し、得られた再生触媒を次工程となる接触工程で用いる方法が好ましい。本発明において、再生方法および接触工程は、それぞれ、次工程に移行する前に、複数回行うこともできる。本発明においては、再生方法に先立って、未使用触媒を用いて亜酸化窒素の分解工程(接触工程)を行うこともできる。この分解工程は未使用触媒を用いること以外は後述する接触工程と同じである。
本発明において、再生方法を行う時期(接触工程から再生方法に切り替えるタイミング)は、特に制限されず、接触工程と再生方法とを同じ装置(設備)で実施可能な場合を含めて、適宜の時期で切り替えることができる。例えば、接触工程による触媒の失活量に関わらず接触工程の途中もしくは終了後に再生方法に切り替えることができ、好ましくは、接触工程の実施により触媒の活性低下が認められた時点、例えば上記失活量に到達した時点で、接触工程から再生方法に切り替えることが好ましい。
接触工程に用いる再生触媒は、上述の本発明の再生方法により再生された触媒であり、その詳細は上述の通りである。
接触工程に用いる亜酸化窒素含有ガスとしては、亜酸化窒素を含んでいればよく、希釈ガスとして不活性ガスを含んでいてもよい。亜酸化窒素含有ガスは、亜酸化窒素と、窒素、一酸化炭素、二酸化炭素、水蒸気、酸素、水素、アンモニア、一酸化窒素、二酸化窒素、および、炭化水素(飽和炭化水素、不飽和炭化水素を含む。)の少なくとも1種のガスを含んでいることが好ましい。また不活性ガスを含んでいてもよい。これらのガスについて、亜酸化窒素含有ガス中の含有量(濃度)は、特に制限されず、適宜に設定できる。例えば、後述する好適な亜酸化窒素含有ガスと同じ含有量とすることができる。
亜酸化窒素含有ガスは、液体を含んでもよい。本発明の分解方法において、亜酸化窒素含有ガスは、少なくとも触媒と接触している間(反応条件下)に気体となっていればよく、接触前は液体であっても、気体と液体の混合物であってもよい。
好適な亜酸化窒素含有ガスに含まれる水蒸気に対するアンモニアの含有量比[アンモニア/水蒸気]は、特に制限されず適宜に設定できるが、亜酸化窒素の分解効率の点から、モル比で、0.0010以上であることが好ましい。モル比で、0.0010~0.050であることがより好ましく、残存するアンモニアの問題(大気中への排出、除去作業の実施)を抑制または回避できる点で、0.0010~0.030であることがより好ましく、0.0010~0.010であることがさらに好ましい。また、好適な亜酸化窒素含有ガスに含まれる亜酸化窒素に対するアンモニアの含有量比[アンモニア/亜酸化窒素]は、特に制限されず適宜に設定できるが、モル比で、0.005~10であることが好ましい。
好適な亜酸化窒素含有ガス中の還元性ガスまたは飽和炭化水素ガスの含有量は、特に制限されず、適宜に設定できる。例えば、好適な亜酸化窒素含有ガス中の還元性ガスまたは飽和炭化水素ガスのモル濃度は、0.001~1モル%である。好適な亜酸化窒素含有ガス中の、水蒸気に対する還元性ガスまたは飽和炭化水素ガスのモル比[還元性ガスまたは飽和炭化水素ガス/水蒸気]は、0.0003~0.03であることが好ましい。また、好適な亜酸化窒素含有ガスに含まれる亜酸化窒素に対する還元性ガスまたは飽和炭化水素ガスの含有量比[還元性ガスまたは飽和炭化水素ガス/亜酸化窒素]は、モル比で、0.01~100であることが好ましい。
接触工程は、亜酸化窒素分解用触媒と、亜酸化窒素を含む亜酸化窒素含有ガスとを接触させる工程であればよく、用いる亜酸化窒素分解用触媒が上記再生触媒であること以外は、公知の亜酸化窒素の分解方法における接触工程を適用できる。公知の亜酸化窒素の分解方法における接触工程としては、例えば、特許文献1に記載の、還元性ガスの共存下で触媒と亜酸化窒素を接触させる方法(工程)が挙げられる。本発明における接触工程は、亜酸化窒素分解用再生触媒と、亜酸化窒素、水蒸気およびアンモニアを含む亜酸化窒素含有ガスとを接触させる工程が好ましい(「好ましい接触工程」ということがある。)。
接触工程においては、亜酸化窒素含有ガスと上記再生触媒とを接触させる。
接触させる方法は、特に制限されず、例えば、バッチ式でも連続式でもよく、反応効率の点で連続式が好ましい。連続式としては、例えば、固定床形式、流動床形式が挙げられる。
亜酸化窒素の分解反応:N2O → N2 + 1/2O2
上記好ましい接触工程において、亜酸化窒素含有ガス中のアンモニアは、亜酸化窒素の分解反応をさらに促進させる。その作用メカニズムの詳細はまだ明らかではないが、次のように考えられる。例えば、ルテニウムを担持した触媒などのように還元作用を示す触媒の存在下においては、アンモニアが触媒表面で亜酸化窒素と反応することにより、亜酸化窒素を窒素分子と水分子に分解して亜酸化窒素の分解反応をさらに促進できると推定される。一方、酸化ルテニウムを担持した触媒などのように還元作用を示さない触媒の存在下においては、触媒表面に残存する酸素原子と反応することにより触媒表面から酸素原子を除去して触媒活性を持続させ(触媒の失活を抑制し)、上記分解反応を促進できると推定される。
好ましい接触工程における接触条件としては、特に制限されないが、例えば、下記条件が挙げられる。接触温度(反応温度)は、適宜に決定されるが、触媒活性劣化の観点から500℃以下が好ましく、反応速度の観点から100℃以上が好ましい。接触温度は、好ましくは200~450℃であり、より好ましくは250~400℃である。連続式接触方法における、触媒重量に対する亜酸化窒素含有ガスの供給速度は、特に制限されず適宜に決定され、例えば、触媒1gに対する、0℃、0.1013MPa(absolute)での流量として、10~10000cm3/分であることが好ましく、50~5000cm3/分であることがより好ましい。接触時間は、亜酸化窒素含有ガス中の亜酸化窒素濃度もしくは供給速度、接触温度等に応じて適宜に決定される。反応圧力は、接触温度、亜酸化窒素含有ガスの供給速度や反応器周辺の外気の圧力などによって変動するが、外気より高い圧力が好ましく、好ましくは絶対圧で0.08~1MPa(absolute)であり、より好ましくは絶対圧で0.09~0.7MPa(absolute)である。
本発明の分解方法は、再生方法および接触工程以外の工程を有していてもよい。例えば、上述の未使用触媒を用いた接触工程、亜酸化窒素含有ガスの成分含有量を調整する工程、亜酸化窒素含有ガスに酸素ガスまたは還元性ガスを導入する工程などが挙げられる。
特に、連続式では、亜酸化窒素含有ガスを触媒中に流通(通過)させることにより、亜酸化窒素を効率よく分解でき、亜酸化窒素の排出を抑制できる。また、好ましい接触工程では、亜酸化窒素含有ガス中のアンモニアも効率よく分解することができ、アンモニアの排出を抑制できる。
本発明の分解方法を既存の製造プラントに適用する場合、本発明の分解方法を行う装置の設置位置は、特に制限されないが、通常、排ガスの流通方向の最後段、例えば排出塔の前段に組み込まれる。具体的には、硝酸の製造プラントであれば、脱硝反応器の後段に組み込まれる。
亜酸化窒素濃度の減少率X(%)=[(CB-CA)/CB]×100
反応速度定数(s-1)=-ln(1-X/100)/(3600/GHSV)
ここで、ln(1-X/100)は、(1-X/100)の自然対数を表す。
以下のようにして、亜酸化窒素分解用触媒としてRuO2/TiO2触媒を製造し、亜酸化窒素の分解反応に使用し、劣化させた。
酸化チタン粉末(昭和電工社製)が押出成形された酸化チタン成形体(直径3mm、長さ4~6mmの円柱形ペレット状)を触媒の担体とした。
塩化ルテニウム水和物1.6g(フルヤ金属社製、RuCl3・nH2O、Ru含有量40%)を、イオン交換水4.0gに溶解させた。得られた溶液を、インシピエントウェットネス法により、酸化チタンで形成された担体20.0gに含浸させた後、空気雰囲気下、室温(25℃)で一晩風乾することで、塩化ルテニウム水和物を担持した酸化チタン固体を得た。
得られた固体を、内温測定用のさや管を具備した石英製ガラス管に充填した後、電気管状炉を用いて、200cm3(0℃、0.1013MPa(absolute))/分の空気流通下、炉温250℃まで昇温し、次いで、同温度で2時間保持することで焼成した。電気管状炉温250℃における石英製ガラス管内温は275℃であった。焼成により、酸化ルテニウムを4.0質量%含むRuO2/TiO2触媒20.9g(Ru含有量3.0質量%、円柱形ペレット状)を得た。得られた円柱形ペレット状のRuO2/TiO2触媒を粉砕し、1.0~1.7mmの顆粒に篩い分けることで得られた新品触媒(a)を以下の例で使用した。
得られた新品触媒(a)0.06g(0.05cm3)を、内温測定用の石英ガラス製さや管を具備した石英ガラス製反応管(内径8mm)に充填した。この反応管を電気炉に設置し、常圧(0.1MPa(absolute))、100cm3(0℃、0.1013MPa(absolute))/分のヘリウムガスを流通し、石英ガラス製反応管の内温が300℃になるまで昇温した。次いで、同圧力および同温度で、新品触媒(a)に接触させるガスを、亜酸化窒素0.10モル%、酸素1.50モル%および残分窒素(流量:24.6cm3(0℃、0.1013MPa(absolute))/分)の混合ガスに切り替えて、亜酸化窒素の分解反応を行った。この分解反応において、分解反応が安定しはじめた時の反応速度定数は、5.8s-1であった。分解反応が安定しはじめた時は、反応速度定数のばらつきが±1%以下となった時とした。
(新品触媒を用いた接触工程)
上記製造例1で得られた円柱形ペレット状のRuO2/TiO2触媒1.24g(1.0cm3)を、内温測定用のステンレス製さや管を具備したステンレス製反応管(内径156mm)に充填した。この反応管を電気炉内に設置し、常圧(0.1MPa(absolute))、500cm3(0℃、0.1013MPa(absolute))/分の窒素ガス流通下、ステンレス製反応管内温が300℃になるまで昇温した。次いで、同圧力および同温度で、RuO2/TiO2触媒に接触させるガスを、硝酸製造プラントの排ガスに切り替えて、亜酸化窒素の分解を行った。
硝酸製造プラントの排ガスをガスサンプリングバッグに採取し、排ガスをガスクロマトグラフィおよびガス検知管(水蒸気6、アンモニア3M)を用いて分析した結果、排ガスの主成分は窒素であり、亜酸化窒素0.01モル%、酸素1.50モル%、水蒸気0.40モル%、アンモニア0.05モル%を含んでいた。
亜酸化窒素の分解反応開始から400時間後に反応管から取り出した円柱形ペレット状のRuO2/TiO2触媒を粉砕し、1.0~1.7mmの顆粒に篩い分けることで劣化触媒(b)を得た。
得られた劣化触媒(b)0.06g(0.05cm3)を、内温測定用の石英ガラス製さや管を具備した石英ガラス製反応管(内径8mm)に充填した。この反応管を電気炉に設置し、常圧(0.1MPa(absolute))、100cm3(0℃、0.1013MPa(absolute))/分のヘリウムガスを流通し、石英ガラス製反応管の内温が300℃になるまで昇温した。次いで、同圧力および同温度で、劣化触媒(b)に接触させるガスを、亜酸化窒素0.10モル%、酸素1.50モル%、残分窒素(流量:24.6cm3(0℃、0.1013MPa(absolute))/分)の混合ガスに切り替えて、2回目の、亜酸化窒素の分解反応を行った。この分解反応において、分解反応が安定しはじめた時の反応速度定数は、5.1s-1であった。分解反応が安定しはじめた時は、反応速度定数のばらつきが±1%以下となった時とした。
(再生工程)
上記製造例2で得た劣化触媒(b)0.06g(0.05cm3)を、内温測定用の石英ガラス製さや管を具備した石英ガラス製反応管(内径26.5mm)に充填した。この反応管を電気炉内に設置し、常圧(0.1MPa(absolute))、6.8cm3(0℃、0.1013MPa(absolute))/分の空気を流通し、電気炉温度が200℃になるまで昇温した後、温度200℃にて3時間熱処理を実施して再生触媒1を得た。
(接触工程)
得られた再生触媒1を、内温測定用の石英ガラス製さや管を具備した石英ガラス製反応管(内径8mm)に充填した。この反応管を電気炉に設置し、常圧(0.1MPa(absolute))、100cm3(0℃、0.1013MPa(absolute))/分のヘリウムガスを流通し、石英ガラス製反応管の内温が300℃になるまで昇温した。次いで、同圧力および同温度で、再生触媒1に接触させるガスを、亜酸化窒素0.10モル%、酸素1.50モル%、残分窒素(流量:24.6cm3(0℃、0.1013MPa(absolute))/分)の混合ガスに切り替えて、亜酸化窒素の分解反応を行った。この分解反応において、分解反応が安定しはじめた時の反応速度定数は7.0s-1であった。分解反応が安定しはじめた時は、反応速度定数のばらつきが±1%以下となった時とした。この反応速度定数について、製造例1における新品触媒(a)を用いた亜酸化窒素の分解反応の反応速度定数(5.8s-1)を1とした場合の再生触媒1の再生率を表1に示す。
実施例1の再生工程において、電気炉温度が250℃になるまで昇温した後、温度250℃にて3時間熱処理を実施して再生触媒2を得たこと以外は、実施例1と同様にして、再生工程および亜酸化窒素の接触工程を行った。この分解反応において、分解反応が安定しはじめた時の反応速度定数は6.9s-1であった。分解反応が安定しはじめた時は、反応速度定数のばらつきが±1%以下となった時とした。この反応速度定数について、製造例1における新品触媒(a)を用いた亜酸化窒素の分解反応の反応速度定数を1とした場合の再生触媒2の再生率を表1に示す。
実施例1の再生工程において、電気炉温度が300℃になるまで昇温した後、温度300℃にて3時間熱処理を実施して再生触媒3を得たこと以外は、実施例1と同様にして、再生工程および亜酸化窒素の接触工程を行った。この分解反応において、分解反応が安定しはじめた時の反応速度定数は7.9s-1であった。分解反応が安定しはじめた時は、反応速度定数のばらつきが±1%以下となった時とした。この反応速度定数について、製造例1における新品触媒(a)を用いた亜酸化窒素の分解反応の反応速度定数を1とした場合の再生触媒3の再生率を表1に示す。
実施例1の再生工程において、電気炉温度が150℃になるまで昇温した後、温度150℃にて3時間熱処理を実施して再生触媒C1を得たこと以外は、実施例1と同様にして、再生工程および亜酸化窒素の接触工程を行った。この分解反応において、分解反応が安定しはじめた時の反応速度定数は5.1s-1であった。分解反応が安定しはじめた時は、反応速度定数のばらつきが±1%以下となった時とした。この反応速度定数について、製造例1における新品触媒(a)を用いた亜酸化窒素の分解反応の反応速度定数を1とした場合の再生触媒C1の再生率を表1に示す。
実施例1の再生工程において、電気炉温度が350℃になるまで昇温した後、温度350℃にて3時間熱処理を実施して再生触媒C2を得たこと以外は、実施例1と同様にして、再生工程および亜酸化窒素の接触工程を行った。この分解反応において、分解反応が安定しはじめた時の反応速度定数は1.7s-1であった。分解反応が安定しはじめた時は、反応速度定数のばらつきが±1%以下となった時とした。この反応速度定数について、製造例1における新品触媒(a)を用いた亜酸化窒素の分解反応の反応速度定数を1とした場合の再生触媒C2の再生率を表1に示す。
これに対して、酸化性ガスの雰囲気下において200~300℃の温度範囲で劣化触媒(b)を熱処理すると、3時間の熱処理であっても、劣化触媒(b)を効率よく再生することができ、得られた再生触媒1~3を亜酸化窒素の分解反応に供すると、反応速度定数が大きく亜酸化窒素を効率よく分解できる(亜酸化窒素分解用触媒の再生率が高い)。また、再生触媒1~3の反応速度定数は、製造例2において、劣化触媒(b)の再生工程を行わずに連続して行った2回目の亜酸化窒素の分解反応における反応速度定数5.1s-1よりも大きく、劣化触媒(b)の触媒活性を回復できていることが分かる。
上述の結果から、亜酸化窒素の分解工程に用いて触媒活性が一旦低下した触媒であっても、再生工程を行うことにより、亜酸化窒素分解用触媒の触媒活性を回復することができ、亜酸化窒素の分解コスト及び劣化触媒の廃棄量を低減できることが分かる。また、分解工程における分解効率の低下を抑えながらも亜酸化窒素を分解することができ、複数回の分解工程を連続実施も可能となる。
Claims (4)
- 酸化チタンを含む担体に、ルテニウムおよびルテニウム化合物からなる群から選ばれる少なくとも1種を含有する成分が担持されてなる亜酸化窒素分解用触媒であって亜酸化窒素の分解反応に使用した亜酸化窒素分解用触媒を、
酸化性ガスの雰囲気下、温度175~325℃の条件で熱処理する工程を含む、亜酸化窒素分解用触媒の再生方法。 - 前記酸化性ガスが空気である、請求項1に記載の亜酸化窒素分解用触媒の再生方法。
- 請求項1または2に記載の亜酸化窒素分解用触媒の再生方法に次いで、該再生方法で再生した亜酸化窒素分解用触媒と、亜酸化窒素を含む亜酸化窒素含有ガスとを接触させる工程を含む、亜酸化窒素の分解方法。
- 前記亜酸化窒素含有ガスが、窒素、一酸化炭素、二酸化炭素、水蒸気、酸素、水素、アンモニア、一酸化窒素、二酸化窒素および炭化水素からなる群から選ばれる少なくとも1種のガスを含む、請求項3に記載の亜酸化窒素の分解方法。
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JPH06218232A (ja) | 1993-01-26 | 1994-08-09 | Sakai Chem Ind Co Ltd | 亜酸化窒素含有排ガスの浄化方法 |
JP2002253967A (ja) * | 2001-02-28 | 2002-09-10 | Showa Denko Kk | 亜酸化窒素分解触媒、その製造方法および亜酸化窒素の分解方法 |
JP2002320863A (ja) * | 2001-04-24 | 2002-11-05 | Nippon Shokubai Co Ltd | 触媒の再生方法 |
JP2020520797A (ja) * | 2017-05-19 | 2020-07-16 | コベストロ、ドイチュラント、アクチエンゲゼルシャフトCovestro Deutschland Ag | ルテニウムまたはルテニウム化合物を含有する被毒した触媒を再生する方法 |
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JPH05305219A (ja) * | 1992-04-28 | 1993-11-19 | Babcock Hitachi Kk | 排ガス中の亜酸化窒素除去方法および装置 |
JPH06218232A (ja) | 1993-01-26 | 1994-08-09 | Sakai Chem Ind Co Ltd | 亜酸化窒素含有排ガスの浄化方法 |
JP2002253967A (ja) * | 2001-02-28 | 2002-09-10 | Showa Denko Kk | 亜酸化窒素分解触媒、その製造方法および亜酸化窒素の分解方法 |
JP2002320863A (ja) * | 2001-04-24 | 2002-11-05 | Nippon Shokubai Co Ltd | 触媒の再生方法 |
JP2020520797A (ja) * | 2017-05-19 | 2020-07-16 | コベストロ、ドイチュラント、アクチエンゲゼルシャフトCovestro Deutschland Ag | ルテニウムまたはルテニウム化合物を含有する被毒した触媒を再生する方法 |
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