JP2004154738A - Catalyst for combustion of hydrocarbon in exhaust gas and method of combusting hydrocarbon in exhaust gas - Google Patents
Catalyst for combustion of hydrocarbon in exhaust gas and method of combusting hydrocarbon in exhaust gas Download PDFInfo
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- JP2004154738A JP2004154738A JP2002325130A JP2002325130A JP2004154738A JP 2004154738 A JP2004154738 A JP 2004154738A JP 2002325130 A JP2002325130 A JP 2002325130A JP 2002325130 A JP2002325130 A JP 2002325130A JP 2004154738 A JP2004154738 A JP 2004154738A
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- exhaust gas
- catalyst
- composite oxide
- oxide
- manganese
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- 239000003054 catalyst Substances 0.000 title claims abstract description 70
- 229930195733 hydrocarbon Natural products 0.000 title claims abstract description 54
- 150000002430 hydrocarbons Chemical class 0.000 title claims abstract description 54
- 238000002485 combustion reaction Methods 0.000 title claims abstract description 22
- 239000004215 Carbon black (E152) Substances 0.000 title claims abstract description 19
- 238000000034 method Methods 0.000 title claims description 23
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 73
- 239000000203 mixture Substances 0.000 claims abstract description 32
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims abstract description 16
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 16
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 claims abstract description 16
- DOCYQLFVSIEPAG-UHFFFAOYSA-N [Mn].[Fe].[Li] Chemical compound [Mn].[Fe].[Li] DOCYQLFVSIEPAG-UHFFFAOYSA-N 0.000 claims abstract description 13
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims abstract description 12
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims abstract description 12
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims abstract description 8
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims abstract description 8
- 239000000395 magnesium oxide Substances 0.000 claims abstract description 8
- 239000011787 zinc oxide Substances 0.000 claims abstract description 8
- 229910044991 metal oxide Inorganic materials 0.000 claims abstract description 7
- 150000004706 metal oxides Chemical class 0.000 claims abstract description 7
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 6
- 229910000420 cerium oxide Inorganic materials 0.000 claims abstract description 4
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 claims abstract description 4
- 239000002131 composite material Substances 0.000 claims description 85
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 52
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 abstract description 16
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 abstract description 16
- 229910052763 palladium Inorganic materials 0.000 abstract description 8
- 229910052697 platinum Inorganic materials 0.000 abstract description 8
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 abstract description 7
- 229910052804 chromium Inorganic materials 0.000 abstract description 7
- 239000011651 chromium Substances 0.000 abstract description 7
- 230000007613 environmental effect Effects 0.000 abstract description 7
- 150000001875 compounds Chemical class 0.000 abstract description 5
- 229910000510 noble metal Inorganic materials 0.000 abstract description 5
- 235000002639 sodium chloride Nutrition 0.000 abstract description 3
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 abstract 1
- 229910052749 magnesium Inorganic materials 0.000 abstract 1
- 239000011777 magnesium Substances 0.000 abstract 1
- 239000011780 sodium chloride Substances 0.000 abstract 1
- 239000007789 gas Substances 0.000 description 51
- 239000011572 manganese Substances 0.000 description 47
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 43
- 238000006243 chemical reaction Methods 0.000 description 35
- 239000012153 distilled water Substances 0.000 description 32
- 239000007864 aqueous solution Substances 0.000 description 23
- 239000002245 particle Substances 0.000 description 23
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 22
- 239000007787 solid Substances 0.000 description 16
- 239000004810 polytetrafluoroethylene Substances 0.000 description 15
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 15
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 13
- 238000001027 hydrothermal synthesis Methods 0.000 description 13
- 229910052748 manganese Inorganic materials 0.000 description 13
- 239000000843 powder Substances 0.000 description 13
- 239000002002 slurry Substances 0.000 description 13
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 12
- 238000003756 stirring Methods 0.000 description 12
- 239000002244 precipitate Substances 0.000 description 11
- 150000002642 lithium compounds Chemical class 0.000 description 10
- 239000012495 reaction gas Substances 0.000 description 10
- 238000005406 washing Methods 0.000 description 10
- 229910052742 iron Inorganic materials 0.000 description 9
- 239000011259 mixed solution Substances 0.000 description 9
- 239000003513 alkali Substances 0.000 description 8
- 230000000694 effects Effects 0.000 description 8
- 230000003197 catalytic effect Effects 0.000 description 7
- 238000011056 performance test Methods 0.000 description 7
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 6
- 239000007795 chemical reaction product Substances 0.000 description 6
- 150000002506 iron compounds Chemical class 0.000 description 6
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 description 6
- IIPYXGDZVMZOAP-UHFFFAOYSA-N lithium nitrate Chemical compound [Li+].[O-][N+]([O-])=O IIPYXGDZVMZOAP-UHFFFAOYSA-N 0.000 description 6
- 229910003002 lithium salt Inorganic materials 0.000 description 6
- 159000000002 lithium salts Chemical class 0.000 description 6
- 150000002697 manganese compounds Chemical class 0.000 description 6
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 5
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 5
- PQVSTLUFSYVLTO-UHFFFAOYSA-N ethyl n-ethoxycarbonylcarbamate Chemical compound CCOC(=O)NC(=O)OCC PQVSTLUFSYVLTO-UHFFFAOYSA-N 0.000 description 5
- GLXDVVHUTZTUQK-UHFFFAOYSA-M lithium hydroxide monohydrate Substances [Li+].O.[OH-] GLXDVVHUTZTUQK-UHFFFAOYSA-M 0.000 description 5
- 229940040692 lithium hydroxide monohydrate Drugs 0.000 description 5
- 239000008188 pellet Substances 0.000 description 5
- VKJKEPKFPUWCAS-UHFFFAOYSA-M potassium chlorate Chemical compound [K+].[O-]Cl(=O)=O VKJKEPKFPUWCAS-UHFFFAOYSA-M 0.000 description 5
- 239000011541 reaction mixture Substances 0.000 description 5
- 239000000243 solution Substances 0.000 description 5
- 229910007499 Li1/3Mn2/3 Inorganic materials 0.000 description 4
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 4
- 238000010304 firing Methods 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- 239000010970 precious metal Substances 0.000 description 4
- JIPBPJZISZCBJQ-UHFFFAOYSA-N 1-[(2-methylpropan-2-yl)oxycarbonyl]-3-(pyridin-4-ylmethyl)piperidine-3-carboxylic acid Chemical compound C1N(C(=O)OC(C)(C)C)CCCC1(C(O)=O)CC1=CC=NC=C1 JIPBPJZISZCBJQ-UHFFFAOYSA-N 0.000 description 3
- 229910002551 Fe-Mn Inorganic materials 0.000 description 3
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- 238000001354 calcination Methods 0.000 description 3
- 238000009841 combustion method Methods 0.000 description 3
- 229910001873 dinitrogen Inorganic materials 0.000 description 3
- -1 hydrogen ions Chemical class 0.000 description 3
- SZQUEWJRBJDHSM-UHFFFAOYSA-N iron(3+);trinitrate;nonahydrate Chemical compound O.O.O.O.O.O.O.O.O.[Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O SZQUEWJRBJDHSM-UHFFFAOYSA-N 0.000 description 3
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 3
- 239000007800 oxidant agent Substances 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 2
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 2
- 229910005716 Li(Li1/3Mn2/3)O2 Inorganic materials 0.000 description 2
- 239000004480 active ingredient Substances 0.000 description 2
- 229910001038 basic metal oxide Inorganic materials 0.000 description 2
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 description 2
- 239000000292 calcium oxide Substances 0.000 description 2
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 2
- 239000000969 carrier Substances 0.000 description 2
- 238000006555 catalytic reaction Methods 0.000 description 2
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 description 2
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 description 2
- 239000000567 combustion gas Substances 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 239000000446 fuel Substances 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 230000007774 longterm Effects 0.000 description 2
- NUJOXMJBOLGQSY-UHFFFAOYSA-N manganese dioxide Chemical compound O=[Mn]=O NUJOXMJBOLGQSY-UHFFFAOYSA-N 0.000 description 2
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 239000001294 propane Substances 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- BZSXEZOLBIJVQK-UHFFFAOYSA-N 2-methylsulfonylbenzoic acid Chemical compound CS(=O)(=O)C1=CC=CC=C1C(O)=O BZSXEZOLBIJVQK-UHFFFAOYSA-N 0.000 description 1
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 description 1
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- 238000004438 BET method Methods 0.000 description 1
- OTMSDBZUPAUEDD-UHFFFAOYSA-N Ethane Chemical compound CC OTMSDBZUPAUEDD-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- 229910021380 Manganese Chloride Inorganic materials 0.000 description 1
- GLFNIEUTAYBVOC-UHFFFAOYSA-L Manganese chloride Chemical compound Cl[Mn]Cl GLFNIEUTAYBVOC-UHFFFAOYSA-L 0.000 description 1
- NIPNSKYNPDTRPC-UHFFFAOYSA-N N-[2-oxo-2-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)ethyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 NIPNSKYNPDTRPC-UHFFFAOYSA-N 0.000 description 1
- 229910002651 NO3 Inorganic materials 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- 229910002405 SrFeO3 Inorganic materials 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 229910021536 Zeolite Inorganic materials 0.000 description 1
- QSNQXZYQEIKDPU-UHFFFAOYSA-N [Li].[Fe] Chemical compound [Li].[Fe] QSNQXZYQEIKDPU-UHFFFAOYSA-N 0.000 description 1
- KLARSDUHONHPRF-UHFFFAOYSA-N [Li].[Mn] Chemical compound [Li].[Mn] KLARSDUHONHPRF-UHFFFAOYSA-N 0.000 description 1
- 150000001242 acetic acid derivatives Chemical class 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- QGZKDVFQNNGYKY-UHFFFAOYSA-N ammonia Natural products N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 1
- 150000008064 anhydrides Chemical class 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 239000001273 butane Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 150000001805 chlorine compounds Chemical class 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000003546 flue gas Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 239000003779 heat-resistant material Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 150000004679 hydroxides Chemical class 0.000 description 1
- 238000009616 inductively coupled plasma Methods 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 1
- SURQXAFEQWPFPV-UHFFFAOYSA-L iron(2+) sulfate heptahydrate Chemical compound O.O.O.O.O.O.O.[Fe+2].[O-]S([O-])(=O)=O SURQXAFEQWPFPV-UHFFFAOYSA-L 0.000 description 1
- 229910000359 iron(II) sulfate Inorganic materials 0.000 description 1
- 239000003949 liquefied natural gas Substances 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 229910001416 lithium ion Inorganic materials 0.000 description 1
- 239000011565 manganese chloride Substances 0.000 description 1
- 235000002867 manganese chloride Nutrition 0.000 description 1
- 229940099607 manganese chloride Drugs 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- IJDNQMDRQITEOD-UHFFFAOYSA-N n-butane Chemical compound CCCC IJDNQMDRQITEOD-UHFFFAOYSA-N 0.000 description 1
- OFBQJSOFQDEBGM-UHFFFAOYSA-N n-pentane Natural products CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 150000002823 nitrates Chemical class 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- XTQHKBHJIVJGKJ-UHFFFAOYSA-N sulfur monoxide Chemical class S=O XTQHKBHJIVJGKJ-UHFFFAOYSA-N 0.000 description 1
- 229910052815 sulfur oxide Inorganic materials 0.000 description 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- 239000010457 zeolite Substances 0.000 description 1
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- Exhaust Gas After Treatment (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、排ガス中の炭化水素燃焼用触媒及び排ガス中の炭化水素燃焼方法に関する。
【０００２】
【従来の技術】
自動車、火力発電所、各種工場等で用いられているガスエンジン、ガスタービン、ボイラー等では、燃焼ガスとして都市ガス、液化天然ガス、プロパンガス等を用いており、その燃焼効率や熱効率を高めるために、燃焼方式として、燃焼ガスに対して空気の比率を高めた希薄燃焼方式が採用されている。
【０００３】
かかる燃焼方式では、燃焼排ガスには、未燃焼炭化水素が僅かに含まれると共に水蒸気も含まれているため、このような排ガスを浄化するためには、水蒸気共存下において未燃焼炭化水素を燃焼させる必要がある。
【０００４】
従来、希薄炭化水素を燃焼除去するための触媒としては、例えば、パラジウム、白金又はその両方をゼオライト、アルミナ等の酸化物担体に担持したものが知られている。メザキ（Ｍｅｚａｋｉ）らは、これら貴金属を含む触媒は活性が高く、例えば、０．５％Ｐｄ−アルミナの場合には、燃焼開始温度が２１０℃と低いことを報告している（非特許文献１参照）。
【０００５】
しかしながら、パラジウム、白金等の貴金属は、資源量が少なく価格が高いという問題がある。例えば、１９９６年の白金及びパラジウム価格を基準に２０００年の価格を見ると、白金は１．５倍、パラジウムは９倍にまで高騰している。また、これら貴金属の産出国がロシアや南アフリカに極端に偏っているため、将来の長期にわたる安定供給にも不安がある。
【０００６】
このため、貴金属を含まない炭化水素燃焼用触媒の開発が進められており、例えば、ＳｒＦｅＯ３のようなペロブスカイト系触媒が報告されている（非特許文献２〜４参照）。
【０００７】
しかしながら、この触媒は、貴金属を含む触媒と比べて活性がかなり低く、点火温度（反応開始温度）を比較すると、白金又はパラジウムを含む触媒では２００℃前後であるのに対して、ペロブスカイト系触媒では３００℃以上である。このため、ペロブスカイト系触媒を高活性化するためには、環境負荷の大きなマンガン、クロム等の使用が不可欠である。更に、ペロブスカイト系触媒では、単位質量あたりの比表面積を高めることが困難である上、水蒸気存在下での反応活性について未だ十分に解明されていない。
【０００８】
【非特許文献１】
燃料協会編、「燃料協会誌」、１９７９年、第５８巻、第６２５号、ｐ．４２２−４３１
【０００９】
【非特許文献２】
エヌ．グナセカラン（Ｎ． Ｇｕｎａｓｅｋａｒａｎ）、外４名、「ソリッド ステート イオニクス（Ｓｏｌｉｄ Ｓｔａｔｅ Ｉｏｎｉｃｓ）」、オランダ、１９９５年、第８１巻、ｐ．２４３
【００１０】
【非特許文献３】
エル．エー．イスポバ（Ｌ． Ａ． Ｉｓｕｐｏｖａ）、外４名、「アプライド キャタリシス ビー−エンバイロメンタル（Ａｐｐｌｉｅｄ Ｃａｔａｌｙｓｉｓ Ｂ−Ｅｎｖｉｒｏｎｍｅｎｔａｌ）」、オランダ、１９９９年、第２１巻、ｐ．１７１
【００１１】
【非特許文献４】
ピー．サロモンソン（Ｐ． Ｓａｌｏｍｏｎｓｓｏｎ）、外２名、「アプライド キャタリシスエー−ジェネラル（Ａｐｐｌｉｅｄ Ｃａｔａｌｙｓｉｓ Ａ−Ｇｅｎｅｒａｌ）」、オランダ、１９９３年、第１０４巻、ｐ．１７５
【００１２】
【発明が解決しようとする課題】
本発明は、パラジウム、白金等の貴金属を含まず、環境負荷の大きなクロム、マンガン等の使用量も低減された、排ガス中の炭化水素の燃焼を促進できる高活性な触媒を提供することを主な目的とする。
【００１３】
【課題を解決するための手段】
本発明者は、上記した目的を達成すべく鋭意研究を重ねた結果、層状岩塩型構造を有する特定のリチウム−マンガン−鉄複合酸化物が上記目的を達成できることを見出し、本発明を完成するに至った。
【００１４】
即ち、本発明は、下記の排ガス中の炭化水素燃焼用触媒及び排ガス中の炭化水素燃焼方法に係るものである。
【００１５】
１．下記組成式：
Ｌｉ［（４−ｘ）／３］−ｙＭｎ（２−２ｘ）／３ＦｅｘＯ２
〔式中、ｘは０．０７≦ｘ≦０．６７であり、ｙは０≦ｙ≦０．４である。〕
で表され、Ｆｅ／（Ｆｅ＋Ｍｎ）のモル比が０．１〜０．７５の範囲内である層状岩塩型構造を有するリチウム−マンガン−鉄複合酸化物からなる排ガス中の炭化水素燃焼用触媒。
【００１６】
２．下記組成式：
Ｌｉ［（４−ｘ）／３］−ｙＭｎ（２−２ｘ）／３ＦｅｘＯ２
〔式中、ｘは０．０７≦ｘ≦０．６７であり、ｙは０≦ｙ≦０．４である。〕
で表され、Ｆｅ／（Ｆｅ＋Ｍｎ）のモル比が０．１〜０．７５の範囲内である層状岩塩型構造を有するリチウム−マンガン−鉄複合酸化物が、マグネシア、シリカ、チタニア、アルミナ、ジルコニア、酸化亜鉛及び酸化セリウムから選ばれる少なくとも１種の金属酸化物に担持された酸化物担持体からなる排ガス中の炭化水素燃焼用触媒。
【００１７】
３．炭化水素を含む排ガスを上記項１又は２に記載の炭化水素燃焼用触媒に接触させることを特徴とする排ガス中の炭化水素燃焼方法。
【００１８】
４．炭化水素がメタンである上記項３に記載の排ガス中の炭化水素燃焼方法。
【００１９】
【発明の実施の形態】
排ガス中の炭化水素燃焼用触媒
本発明の排ガス中の炭化水素燃焼用触媒は、下記組成式：
Ｌｉ［（４−ｘ）／３］−ｙＭｎ（２−２ｘ）／３ＦｅｘＯ２
〔式中、ｘは０．０７≦ｘ≦０．６７であり、ｙは０≦ｙ≦０．４である。〕
で表され、Ｆｅ／（Ｆｅ＋Ｍｎ）のモル比が０．１〜０．７５の範囲内である層状岩塩型構造を有するリチウム−マンガン−鉄複合酸化物を有効成分とするものである。このような複合酸化物は、排ガス中に含まれる炭化水素を燃焼させる反応に対して高活性を有し、排ガスを浄化するための触媒として有用性が高いものである。
【００２０】
当該複合酸化物は、Ｌｉ（Ｌｉ１／３Ｍｎ２／３）Ｏ２を基本構造とする層状岩塩型構造の複合酸化物における（Ｌｉ１／３Ｍｎ２／３）の一部がＦｅにより置換された置換型固溶体と考えることができる。当該複合酸化物は、Ｌｉ（Ｌｉ１／３Ｍｎ２／３）Ｏ２の（Ｌｉ１／３Ｍｎ２／３）の一部がＦｅに置換されていることにより、環境負荷の大きいマンガンの使用量が低減されており、更にクロム等の環境負荷の大きな成分も含まないものである。当該複合酸化物は、従来のマンガン、クロム等を添加して高活性化したペロブスカイト系触媒と同程度の温度域で排ガス中の炭化水素を燃焼させることが可能である点で、非常に有用性が高い触媒である。
【００２１】
上記組成式の概略について説明すると次のようになる。先ず、前記基本構造において、（Ｌｉ１／３Ｍｎ２／３）の一部がＦｅに置換された構造を、Ｆｅのモル比をｘとして表すと、Ｌｉ｛（Ｌｉ１／３Ｍｎ２／３）１−ｘＦｅｘ｝Ｏ２となる。式中、ｘは０．０７〜０．６７であり、０．０７〜０．４であることが好ましい。
【００２２】
次に、当該複合酸化物を合成する際の洗浄により、Ｌｉイオンが水素イオンやオキソニウムイオンと交換することにより生じ得るＬｉの欠損を考慮した構造について、欠損したＬｉのモル比をｙとして表すと、Ｌｉ１−ｙ｛（Ｌｉ１／３Ｍｎ２／３）１−ｘＦｅｘ｝Ｏ２となる。式中、ｙは０〜０．４である。この式を展開すると、上記組成式となる。
【００２３】
なお、本発明触媒としては、上記組成式で表される複合酸化物は、Ｆｅ／（Ｆｅ＋Ｍｎ）のモル比が０．１〜０．７５であることが必須であり、その中でも、０．３〜０．５であることが好ましい。Ｌｉ／（Ｆｅ＋Ｍｎ）のモル比は特に限定されないが、０．５〜２の範囲内であることが好ましい。
【００２４】
本発明触媒の有効成分であるリチウム−マンガン−鉄複合酸化物は、例えば、水熱反応法、焼成法等により製造できる。
【００２５】
複合酸化物を水熱反応法により製造する場合には、例えば、マンガン化合物と鉄化合物とを含む水溶液又は水−アルコール混合溶液をアルカリ性、例えば、ｐＨ１１以上にしてマンガン及び鉄を含む共沈物を得て、当該共沈物を酸化剤及びアルカリの共存下において、リチウム化合物と共に水熱反応させることにより製造できる。
【００２６】
このような水熱反応法において、マンガン化合物としては、例えば、マンガンの塩化物、硝酸塩、硫酸塩、酢酸塩、水酸化物等の水溶性化合物が使用でき、鉄化合物としては、例えば、鉄の塩化物、硝酸塩、硫酸塩、酢酸塩、水酸化物等の水溶性化合物が使用できる。これらの化合物は、水溶液又は水−アルコール混合溶液の状態で使用でき、アルコールとしては、メタノール、エタノール等が使用できる。
【００２７】
当該水溶液又は水−アルコール混合溶液における鉄及びマンガンの全濃度は、通常０．０１〜２ｍｏｌ／ｌ（無水物換算）程度、好ましくは０．１〜０．５ｍｏｌ／ｌ程度となるように調整すればよい。また、鉄化合物及びマンガン化合物の使用量は、目的とする複合酸化物中のＦｅ／（Ｆｅ＋Ｍｎ）のモル比となるように調整すればよい。
【００２８】
当該水溶液又は水−アルコール混合溶液をアルカリ性にするには、例えば、通常０．１〜２０ｍｏｌ／ｌ程度、好ましくは０．５〜１０ｍｏｌ／ｌ程度の水酸化カリウム、水酸化ナトリウム等を含むアルカリ水溶液を添加する方法が挙げられる。アルカリ水溶液の添加量は、当該水溶液又は水−アルコール混合溶液が完全にアルカリ性になるまで、例えば、ｐＨ１１以上となるまで添加すればよい。
【００２９】
上記方法によりマンガン及び鉄を含む共沈物が得られるが、必要に応じて、共沈物に、通常０〜１５０℃程度、好ましくは２０〜１００℃程度において、空気を吹き込みながら熟成処理を施してもよい。共沈物は、通常、蒸留水洗浄により過剰のアルカリ成分及び残留塩類を除去し、その後、溶液より濾別し、１００℃程度で乾燥させた後に、蒸留水と混合した状態で水熱反応させればよい。
【００３０】
共沈物を水熱反応させる際に用いる酸化剤としては、例えば、塩素酸カリウム、塩素酸ナトリウム、過酸化水素水等が使用できる。酸化剤の添加量は、添加後の溶液中において、通常０．１〜１０ｍｏｌ／ｌ程度、好ましくは１〜５ｍｏｌ／ｌ程度となるように設定すればよい。また、アルカリとしては、例えば、水酸化リチウム、水酸化ナトリウム、水酸化カリウム、アンモニア水等が使用できる。アルカリの添加量は、添加後の溶液中において、通常０．１〜１０ｍｏｌ／ｌ程度、好ましくは１〜５ｍｏｌ／ｌ程度となるように設定すればよい。水酸化リチウム以外のアルカリを用いることにより、硝酸リチウム、塩化リチウム等の中性又は酸性リチウム塩をリチウム源として用いることが可能となる。
【００３１】
リチウム化合物としては、例えば、水酸化リチウム（無水物でも水和物でもよい）、塩化リチウム、硝酸リチウム等が使用できる。リチウム化合物の使用量は、目的とする複合酸化物中のＬｉ／（Ｍｎ＋Ｆｅ）のモル比となるように調整すればよい。過剰なリチウム化合物の添加は経済的に不利であり工業的に好ましくない。
【００３２】
水熱反応は、上記の水熱反応原料を収容した容器を、例えば、オートクレーブのような水熱反応装置中に静置させて行うことができる。水熱反応条件は特に限定されないが、通常１００〜３００℃程度の温度で０．１〜１５０時間程度反応させればよく、好ましくは１５０〜２５０℃程度の温度で１〜１００時間程度反応させればよい。水熱反応は、例えば、大気等の酸化雰囲気下で行うことができる。反応終了後、残存する余分な塩類等を除去するために、必要に応じて、反応生成物を水洗、濾過、乾燥させてもよい。このようにして、リチウム−マンガン−鉄複合酸化物が得られる。
【００３３】
複合酸化物を焼成法により製造する場合には、例えば、マンガン化合物と鉄化合物とを含む水溶液又は水−アルコール混合溶液に、リチウム化合物を添加して沈殿物を得て、当該沈殿物を焼成することにより製造できる。また、当該水溶液又は水−アルコール混合溶液に、リチウム化合物を添加した後の溶液及び沈殿を蒸発乾固させることにより得た残渣を焼成することによっても製造できる。
【００３４】
上記の焼成法において、マンガン化合物及び鉄化合物としては、前記した水熱反応で使用できる化合物がそのまま使用でき、それらは水溶液又は水−アルコール混合溶液の状態で使用できる。当該水溶液又は水−アルコール混合溶液における鉄及びマンガンの全濃度も、前記した水熱反応の場合と同様でよい。
【００３５】
マンガン化合物及び鉄化合物の使用量は、目的とする複合酸化物中のＦｅ／（Ｆｅ＋Ｍｎ）のモル比となるように調整すればよい。
【００３６】
リチウム化合物としても、水熱反応法と同様に、水酸化リチウム（無水物でも水和物でもよい）、塩化リチウム、硝酸リチウム等が使用できる。リチウム化合物の使用量は、目的とする複合酸化物中のＬｉ／（Ｍｎ＋Ｆｅ）のモル比となるように調整すればよい。過剰なリチウム化合物の添加は経済的に不利であり工業的に好ましくない。
【００３７】
なお、リチウム化合物の添加により得られた沈殿物を焼成する場合には、沈殿物を溶液中から取り出したもの、例えば、水洗、濾過、乾燥させて取り出したものを焼成することができる。
【００３８】
沈殿又は残渣の焼成条件は特に限定されず、通常２００〜１０００℃程度で１〜１００時間程度、好ましくは３００〜８００℃程度で２０〜６０時間程度とすればよい。焼成雰囲気も特に限定されず、大気等の酸化雰囲気下でもよく、水素等の還元雰囲気下でもよい。焼成後、必要に応じて生成物を粉砕し、上記と同様の条件で焼成を繰り返してもよい。
【００３９】
このような製造方法により製造されたリチウム−マンガン−鉄複合酸化物は、そのまま本発明触媒として使用できる。この場合に、本発明触媒の形状は特に限定されず、例えば、粒子状、粉末状、ペレット状、板状、柱状、格子状等の任意の形状で使用できる。なお、複合酸化物を上記の形状に加工する際に、必要に応じて、本発明触媒の効果に影響を与えない範囲でバインダー等を添加することもできる。
【００４０】
上記した複合酸化物の大きさも特に限定されず、実際の使用態様を考慮して適宜設定できるが、例えば、粒子状で用いるのであれば、粒子の平均粒子径としては、通常０．１〜５ｍｍ程度が適当であり、１〜３ｍｍ程度が好ましい。また、粉末状で用いるのであれば、粉末の平均粒子径としては、通常０．１〜１０００ｎｍ程度が適当であり、１〜１００ｎｍ程度が好ましい。また、ペレット状で用いるのであれば、縦３０ｍｍ、横３０ｍｍ、高さ５ｍｍ程度、好ましくは縦１０ｍｍ、横１０ｍｍ、高さ３ｍｍ程度のペレットとすればよい。
【００４１】
本発明触媒の比表面積は、排ガスとの接触面積を広く確保できる範囲であればよいが、通常１０〜１０００ｍ２／ｇ程度が適当であり、５０〜１００ｍ２／ｇ程度が好ましい。なお、本明細書における比表面積の値は、測定対象物の表面に窒素を吸着させることを特徴とするＢＥＴ法により測定した値である。
【００４２】
本発明触媒としては、当該複合酸化物を担体に担持させて用いてもよい。担体に担持させる場合には、前記したように当該複合酸化物をそのまま触媒として用いる場合と比べて、複合酸化物と排ガスとの接触面積をより広く確保することができる。従って、当該複合酸化物をそのまま触媒として用いる場合と比べて、複合酸化物の使用量を少なくしても同等の炭化水素燃焼効果が発揮できるため、環境負荷の大きなマンガンの使用量をより低減できる点で有利である。
【００４３】
担体の種類は特に限定されないが、排ガスとの接触を考慮すると、耐熱性に優れたものが好ましい。担体としては、例えば、マグネシア、シリカ、チタニア、アルミナ、ジルコニア、酸化亜鉛、酸化セリウム、酸化カルシウム等の金属酸化物やこれらの複合酸化物等が挙げられる。この中でも、特に、マグネシア、酸化亜鉛、酸化カルシウム等の塩基性金属酸化物が好ましい。
【００４４】
担体の形状は特に限定されないが、排ガスとの接触を考慮すると、比表面積が大きな形状、例えば、粒子状、ペレット状、ハニカム状等が好ましい。担体の大きさは特に限定されず、実際の使用態様を考慮して適宜設定できるが、粒子状であれば、平均粒子径は通常０．５〜３ｍｍが適当であり、１〜２ｍｍ程度が好ましい。ペレット状であれば、縦３０ｍｍ、横３０ｍｍ、高さ３０ｍｍ程度が適当であり、縦１０ｍｍ、横１０ｍｍ、高さ１０ｍｍ程度が好ましい。
【００４５】
担体に対する複合酸化物の担持量は特に限定されないが、担体１００重量部に対して、通常１〜１０重量部程度が適当であり、３〜５重量部程度が好ましい。担持させる複合酸化物としては、例えば、平均粒子径が通常０．１〜１０００ｎｍ程度の粉末が好ましく、１〜１００ｎｍ程度の粉末がより好ましい。
【００４６】
担体に複合酸化物を担持させる方法は特に限定されず、例えば、担体と複合酸化物とを固体状態で混合する方法；担体と複合酸化物とを固体状態で混合したものに水を加えてよく撹拌した後、得られたスラリーを乾燥させる方法；担体又は複合酸化物のいずれか一方に水を加えたものに、他方を加えてよく撹拌した後、得られたスラリーを乾燥させる方法等により担持させることができる。また、複合酸化物と水からなるスラリーを、担体に塗布、噴霧等することによっても担持させることができる。
【００４７】
本発明触媒の使用方法
本発明触媒は、排ガス中の炭化水素を燃焼させる用途に使用できる。即ち、排ガス中の炭化水素を燃焼させて排ガスを浄化する用途に好適に使用できる。
【００４８】
本発明触媒が対象とする排ガスは、炭化水素を含むものであれば限定されず、例えば、ガスエンジン、ガスタービン、ボイラー、ガスファンヒーター、ガス湯沸かし器等から排出される排ガスを対象とできる。上記の排ガスには、炭化水素以外に、一般に水蒸気、窒素酸化物、硫黄酸化物、酸素等が含まれている。
【００４９】
燃焼対象とする炭化水素も特に限定されず、例えば、メタン、エタン、プロパン、ブタン等が挙げられる。本発明触媒は、炭化水素の中でも、特にメタン燃焼用として好適に使用できる。
【００５０】
本発明触媒が対象とする排ガス中の炭化水素濃度は特に限定されないが、炭化水素濃度１００００ｐｐｍ以下、特に２５００ｐｐｍ以下のような希薄炭化水素も対象とすることができる。従って、希薄燃焼方式を採用し、排ガス中の炭化水素濃度が低いガスエンジン、ガスタービン、ボイラー等の排ガスに含まれる炭化水素の燃焼用としても好適に使用できる。
【００５１】
排ガス中の炭化水素を燃焼させるには、例えば、本発明触媒を充填した反応管に排ガスを流通させることにより、排ガスに含まれる炭化水素を燃焼させることができる。反応管の形状、大きさ等は、実際の使用態様を考慮して適宜設定できる。このような反応管は、例えば、石英製ガラス、ステンレス等の耐熱性材料で作製されたものが使用できる。
【００５２】
触媒使用量は特に限定されないが、ガス時間当たり空間速度（ＳＶ）に換算して、１０００〜１０００００ｍｌ／ｈ・ｇ−ｃａｔの範囲が適当であり、１０００〜１００００ｍｌ／ｈ・ｇ−ｃａｔの範囲が好ましい。触媒使用量が少なすぎる場合には、炭化水素燃焼率が不十分となる。触媒使用量が多すぎる場合には、炭化水素燃焼率は向上するが、使用量に見合った触媒性能の向上が得られないため経済的に不利となる。
【００５３】
本発明触媒の高い活性を有効利用するためには、排ガス処理温度としては、通常２００〜１０００℃が適当であり、３００〜５００℃程度が好ましい。排ガス処理温度が低すぎる場合には、炭化水素燃焼率が不十分となる。排ガス処理温度が高すぎる場合には、触媒の耐久性が低下し易くなる。
【００５４】
【発明の効果】
本発明触媒は、排ガス中の炭化水素の燃焼を促進できる。特に、希薄燃焼方式により排出される炭化水素濃度の低い排ガスを対象とする場合にも、炭化水素の燃焼を促進できる点で、非常に有用性が高い触媒である。このような本発明触媒は、特にメタン燃焼用として好適に使用できる。
【００５５】
本発明触媒は、パラジウム、白金等の貴金属や環境負荷の大きなクロムを含まず、しかもマンガン使用量も低減されている。このような本発明触媒は、より少量のマンガンしか用いずに、従来のマンガン又はクロムを多く含むペロブスカイト系触媒とほぼ同程度の温度域で、燃焼排ガス中の炭化水素を燃焼させることができる。また、貴金属を含まない点において、製造コストを削減でき、しかも原料を安定供給できるという利点もある。
【００５６】
また、本発明触媒は十分な耐久性を有しており、触媒の交換頻度を抑えることもでき、排ガス処理システム自体を低コスト化することもできる。更に、その酸化により発熱を伴うため、熱回収が可能である。
【００５７】
【実施例】
以下、実施例及び比較例を示し、本発明をより具体的に説明する。但し、本発明はこれらの実施例に限定されるものではない。
【００５８】
実施例１
硝酸マンガン（ＩＩ）六水和物６４．５８ｇ及び硝酸鉄（ＩＩＩ）九水和物１０．１ｇを蒸留水４００ｍｌに溶解させてＦｅ−Ｍｎ混合水溶液（全量０．２５ｍｏｌ、Ｆｅ／（Ｆｅ＋Ｍｎ）のモル比０．１）を調製した。
【００５９】
混合水溶液に、室温まで冷却した水酸化カリウム水溶液４００ｍｌ（水酸化カリウム５０ｇを蒸留水４００ｍｌに溶解したもの）を２〜３時間かけて、水溶液がｐＨ１１以上となるまで撹拌しながら滴下してＦｅ−Ｍｎ共沈物を得た。共沈物を撹拌しつつ空気酸化した後、密閉容器に入れて５０℃で２〜３日熟成させた。
【００６０】
次いで、共沈物を蒸留水で洗浄濾過して残留アルカリ成分を除去後、共沈物を１００℃で乾燥させた。ＰＴＦＥ製ビーカーに乾燥させた共沈物、蒸留水２００ｍｌ、水酸化リチウム一水和物４０ｇ及び塩素酸カリウム４０ｇを入れてよく撹拌した。ＰＴＦＥ製ビーカーをオートクレーブ内に静置し、内容物を２２０℃で５時間水熱反応させた。
【００６１】
反応終了後、室温まで自然冷却してからＰＴＦＥ製ビーカーを取り出し、反応生成物を蒸留水で洗浄濾過して過剰のリチウム塩を除去した。固形分を１００℃で乾燥させて粒子状のリチウム−マンガン−鉄複合酸化物を得た。
【００６２】
複合酸化物は、Ｌｉ／（Ｆｅ＋Ｍｎ）のモル比が１．６９であり、Ｆｅ／（Ｆｅ＋Ｍｎ）のモル比が０．１であった。組成式は、Ｌｉ１．１６Ｆｅ０．０７Ｍｎ０．６２Ｏ２であった。複合酸化物の形状は粒子状であり、ＢＥＴ比表面積は２２ｍ２／ｇであり、粒子径は１０〜５００ｎｍであった。なお、本明細書における複合酸化物の組成は、誘導結合プラズマ（ＩＣＰ）測定により決定した結果である。
【００６３】
実施例２
硝酸マンガン（ＩＩ）六水和物５０．２３ｇ及び硝酸鉄（ＩＩＩ）九水和物３０．３ｇを蒸留水４００ｍｌに溶解させてＦｅ−Ｍｎ混合水溶液（全量０．２５ｍｏｌ、Ｆｅ／（Ｆｅ＋Ｍｎ）のモル比０．３）を調製した。
【００６４】
混合水溶液に、室温まで冷却した水酸化カリウム水溶液４００ｍｌ（水酸化カリウム５０ｇを蒸留水４００ｍｌに溶解したもの）を２〜３時間かけて、水溶液がｐＨ１１以上となるまで撹拌しながら滴下してＦｅ−Ｍｎ共沈物を得た。共沈物を撹拌しつつ空気酸化した後、密閉容器にいれて５０℃で２〜３日熟成させた。
【００６５】
次いで、共沈物を蒸留水で洗浄濾過して残留アルカリ成分を除去後、共沈物を１００℃で乾燥させた。ＰＴＦＥ製ビーカーに乾燥させた共沈物、蒸留水２００ｍｌ、水酸化リチウム一水和物４０ｇ及び塩素酸カリウム４０ｇを入れてよく撹拌した。ＰＴＦＥ製ビーカーをオートクレーブ内に静置し、内容物を２２０℃で５時間水熱反応させた。
【００６６】
反応終了後、室温まで自然冷却してからＰＴＦＥ製ビーカーを取り出し、反応生成物を蒸留水で洗浄濾過して過剰のリチウム塩を除去した。固形分を１００℃で乾燥させて粒子状のリチウム−マンガン−鉄複合酸化物を得た。
【００６７】
複合酸化物は、Ｌｉ／（Ｆｅ＋Ｍｎ）のモル比が１．４であり、Ｆｅ／（Ｆｅ＋Ｍｎ）のモル比が０．３であった。組成式は、Ｌｉ１．０４（Ｆｅ０．２２Ｍｎ０．５２）Ｏ２であった。複合酸化物の形状は粒子状であり、ＢＥＴ比表面積は４４ｍ２／ｇであり、粒子径は１０〜５００ｎｍであった。
【００６８】
実施例３
硝酸マンガン（ＩＩ）六水和物３５．８８ｇ及び硝酸鉄（ＩＩＩ）九水和物５０．５ｇを蒸留水４００ｍｌに溶解させてＦｅ−Ｍｎ混合水溶液（全量０．２５ｍｏｌ、Ｆｅ／（Ｆｅ＋Ｍｎ）のモル比０．５）を調製した。
【００６９】
混合水溶液に、室温まで冷却した水酸化カリウム水溶液４００ｍｌ（水酸化カリウム５０ｇを蒸留水４００ｍｌに溶解したもの）を２〜３時間かけて、水溶液がｐＨ１１以上となるまで撹拌しながら滴下してＦｅ−Ｍｎ共沈物を得た。共沈物を撹拌しつつ空気酸化した後、密閉容器に入れて５０℃で２〜３日間熟成させた。
【００７０】
次いで、共沈物を蒸留水で洗浄濾過して残留アルカリ成分を除去後、共沈物を１００℃で乾燥させた。ＰＴＦＥ製ビーカーに乾燥させた共沈物、蒸留水２００ｍｌ、水酸化リチウム一水和物４０ｇ及び塩素酸カリウム４０ｇを入れてよく撹拌した。ＰＴＦＥ製ビーカーをオートクレーブ内に静置し、内容物を２２０℃で５時間水熱反応させた。
【００７１】
反応終了後、室温まで自然冷却してからＰＴＦＥ製ビーカーを取り出し、反応生成物を蒸留水で洗浄濾過して過剰のリチウム塩を除去した。固形分を１００℃で乾燥させて粒子状のリチウム−マンガン−鉄複合酸化物を得た。
【００７２】
複合酸化物は、Ｌｉ／（Ｆｅ＋Ｍｎ）のモル比が１．２８であり、Ｆｅ／（Ｆｅ＋Ｍｎ）のモル比が０．４７であった。組成式は、Ｌｉ１．０１（Ｆｅ０．３７Ｍｎ０．４２）Ｏ２であった。複合酸化物の形状は粒子状であり、ＢＥＴ比表面積は５３ｍ２／ｇであり、粒子径は５０〜１００ｎｍであった。
【００７３】
実施例４
実施例３で得られた複合酸化物５０ｍｇと平均粒子径０．０５ｍｍの粉末状マグネシア１ｇとを固体状態で混合した。
【００７４】
混合物に蒸留水１ｍｌを加えて超音波洗浄機槽中で３０分間よく混合した。得られたスラリーを１００℃で一晩乾燥させた後、得られた粉末を６００℃で５時間焼成し、複合酸化物を５重量部担持したマグネシアを得た。
【００７５】
実施例５
実施例３で得られた複合酸化物５０ｍｇと平均粒子径０．０５ｍｍの粉末状ジルコニア１ｇとを固体状態で混合した。
【００７６】
混合物に蒸留水１ｍｌを加えて超音波洗浄機槽中で３０分間よく混合した。得られたスラリーを１００℃で一晩乾燥させた後、得られた粉末を６００℃で５時間焼成し、複合酸化物を５重量部担持したジルコニアを得た。
【００７７】
実施例６
実施例２で得られた複合酸化物を５０ｍｇと平均粒子径０．０５ｍｍの粉末状セリア１ｇとを固体状態で混合した。
【００７８】
混合物に蒸留水１ｍｌを加えて超音波洗浄機槽中で３０分間よく混合した。得られたスラリーを１００℃で一晩乾燥させた後、得られた粉末を６００℃で５時間焼成し、複合酸化物を５重量部担持したセリアを得た。
【００７９】
実施例７
実施例２で得られた複合酸化物を５０ｍｇと平均粒子径０．１ｍｍの粉末状アルミナ１ｇとを固体状態で混合した。
【００８０】
混合物に蒸留水１ｍｌを加えて超音波洗浄機槽中で３０分間よく混合した。得られたスラリーを１００℃で一晩乾燥させた後、得られた粉末を６００℃で５時間焼成し、複合酸化物を５重量部担持したアルミナを得た。
【００８１】
実施例８
実施例２で得られた複合酸化物を５０ｍｇと平均粒子径０．２ｍｍの粉末状酸化亜鉛１ｇとを固体状態で混合した。
【００８２】
混合物に蒸留水１ｍｌを加えて超音波洗浄機槽中で３０分間よく混合した。得られたスラリーを１００℃で一晩乾燥させた後、得られた粉末を６００℃で５時間焼成し、複合酸化物を５重量部担持した酸化亜鉛を得た。
【００８３】
実施例９
実施例２で得られた複合酸化物を５０ｍｇと平均粒子径０．１ｍｍの粉末状チタニア１ｇとを固体状態で混合した。
【００８４】
混合物に蒸留水１ｍｌを加えて超音波洗浄機槽中で３０分間よく混合した。得られたスラリーを１００℃で一晩乾燥させた後、得られた粉末を６００℃で５時間焼成し、複合酸化物を５重量部担持したチタニアを得た。
【００８５】
実施例１０
実施例２で得られた複合酸化物を５０ｍｇと粒子径０．０６３〜０．２ｍｍの粉末状アモルファスシリカ１ｇとを固体状態で混合した。
【００８６】
混合物に蒸留水１ｍｌを加えて超音波洗浄機槽中で３０分間よく混合した。得られたスラリーを１００℃で一晩乾燥させた後、得られた粉末を６００℃で５時間焼成し、複合酸化物を５重量部担持したアモルファスシリカを得た。
【００８７】
実施例１１
実施例２で得られた複合酸化物を５０ｍｇと平均粒子径０．３ｍｍの粉末状メソポーラスシリカ１ｇとを固体状態で混合した。
【００８８】
混合物に蒸留水１ｍｌを加えて超音波洗浄機槽中で３０分間よく混合した。得られたスラリーを１００℃で一晩乾燥させた後、得られた粉末を６００℃で５時間焼成し、複合酸化物を５重量部担持したメソポーラスシリカを得た。
【００８９】
比較例１
二酸化マンガン３ｇをＰＴＦＥ製ビーカーに入れ、蒸留水２００ｍｌを加えてよく分散させ、更に水酸化リチウム一水和物５０ｇを加えてよく撹拌した。
【００９０】
ＰＴＦＥ製ビーカーをオートクレーブ内に静置し、内容物を２２０℃で７時間水熱反応させた。
【００９１】
反応終了後、室温まで自然冷却してからＰＴＦＥ製ビーカーを取り出し、反応生成物を蒸留水で洗浄濾過して過剰のリチウム塩を除去した。固形分を１００℃で乾燥させてリチウム−マンガン複合酸化物を得た。
【００９２】
複合酸化物のＬｉ／Ｍｎのモル比は１．３５であった。組成式は、Ｌｉ０．９Ｍｎ０．６７Ｏ２であった。複合酸化物の形状は粒子状であり、ＢＥＴ比表面積は３０ｍ２／ｇであった。
【００９３】
比較例２
硫酸鉄（ＩＩ）七水和物６９．５１ｇを蒸留水４００ｍｌに溶解させて硫酸鉄（ＩＩ）水溶液を調製した。
【００９４】
水溶液に、室温まで冷却した水酸化カリウム水溶液４００ｍｌ（水酸化カリウム５０ｇを蒸留水４００ｍｌに溶解したもの）を２〜３時間かけて、水溶液がｐＨ１１以上となるまで撹拌しながら滴下して水酸化鉄の沈殿を得た。沈殿物を撹拌しながら空気酸化した後、密閉容器に入れて５０℃で２〜３日熟成させた。
【００９５】
次いで、沈殿物を蒸留水で洗浄濾過して残留アルカリ成分を除去後、沈殿物を１００℃で乾燥させた。ＰＴＦＥ製ビーカーに乾燥させた沈殿物、蒸留水２００ｍｌ、水酸化リチウム一水和物４０ｇ及び塩素酸カリウム４０ｇを入れてよく撹拌した。ＰＴＦＥ製ビーカーをオートクレーブ内に静置し、内容物を２２０℃で５時間水熱反応させた。
【００９６】
反応終了後、室温まで自然冷却してからＰＴＦＥ製ビーカーを取り出し、反応生成物を蒸留水で洗浄濾過して過剰のリチウム塩を除去した。固形分を１００℃で乾燥させて粒子状のリチウム−鉄複合酸化物を得た。
【００９７】
複合酸化物は、Ｘ線回折分析によりα−ＬｉＦｅＯ２であった。複合酸化物の形状は粒子状であり、ＢＥＴ比表面積は６ｍ２／ｇであった。
【００９８】
触媒性能試験１
実施例１〜３及び比較例１〜２で得られたそれぞれの複合酸化物の触媒性能を確認した。触媒性能の確認は、５種類の複合酸化物それぞれについて、複合酸化物３００ｍｇを内径１２ｍｍの石英製ガラス管に充填し、常圧下、固定床流通式反応装置を用いてガラス管に反応ガスを流通させ、反応ガス中に含まれるメタンの転化率を調べることにより確認した。
【００９９】
反応ガスとしては、２５００ｐｐｍ（容積）のメタン及び２０％の酸素を含む窒素ガスを用いた。反応ガスの流通速度は、毎分５０ｍｌとした（ＳＶ＝１０，０００ｍｌ／ｈ・ｇ−ｃａｔ）。反応温度は３００℃から５０℃づつ昇温させて５５０℃まで変化させた。
【０１００】
触媒性能の指標となるメタン転化率の値は、ガスクロマトグラフ分析装置により反応ガス中に含まれるメタン、一酸化炭素及び二酸化炭素の濃度を測定した上で、下記式に基づいて算出した。
メタン転化率（％）＝（Ｃ０−Ｃ１）／Ｃ０×１００
Ｃ０：反応開始前のメタン濃度
Ｃ１：反応後のメタン濃度。
【０１０１】
５種類の複合酸化物それぞれの反応温度とメタン転化率との関係を示すグラフを図１に示す。
【０１０２】
図１の結果からは、マンガンに対する鉄の割合が増加するにつれてメタン転化率が大きくなり、触媒性能が高くなることが分かる。
【０１０３】
また、マンガン又は鉄しか含まない複合酸化物と比較して、Ｆｅ／（Ｆｅ＋Ｍｎ）のモル比０．５である複合酸化物は、より良好な触媒性能を発揮することも分かる。
【０１０４】
なお、触媒性能の長期安定性を確認するため、Ｆｅ／（Ｆｅ＋Ｍｎ）のモル比０．５である複合酸化物からなる触媒を４５０℃で１３時間連続反応させたが、メタン添加率の低下は認められなかった。
【０１０５】
触媒性能試験２
実施例４〜１１で得られた金属酸化物担体に実施例３で得られた複合酸化物を担持した材料の触媒性能を確認した。性能試験の方法は、触媒性能試験１と同じである。
【０１０６】
各材料それぞれの反応温度とメタン転化率との関係を示すグラフを図２に示す。
【０１０７】
図２の結果からは、マグネシア、酸化亜鉛等の塩基性金属酸化物担体に複合酸化物を担持した場合に、特に触媒性能が向上することが分かる。これらの金属酸化物担体に担持することにより、マンガンの使用量を抑制することができる。
【０１０８】
触媒性能試験３
反応ガスとして２４００ｐｐｍ（容積）のメタン及び１９．２％の酸素を含む窒素ガスを用いた他は、触媒性能試験１と同じ条件にて、実施例３で得られた複合酸化物の触媒性能を確認した。反応ガスは乾燥状態である。反応温度とメタン転化率との関係を示すグラフを図３に示す。
【０１０９】
また、反応ガスとして４％水蒸気、２４００ｐｐｍ（容積）のメタン及び１９．２％の酸素を含む窒素ガスを用いた他は、触媒性能試験１と同じ条件にて、実施例３で得られた複合酸化物の触媒性能を確認した。反応ガスは水蒸気を含んでいる。反応温度とメタン転化率の関係を示すグラフを図３に示す。
【０１１０】
図３の結果からは、実施例３で得られた複合酸化物は、水蒸気存在下でも高いメタン転化率を確保できることが分かる。
【図面の簡単な説明】
【図１】実施例１〜３及び比較例１〜２で得られた複合酸化物を炭化水素燃焼用触媒として用いてメタンを燃焼させた場合における、反応温度とメタン転化率との関係を示すグラフである。
【図２】実施例３で得られた、Ｆｅ／（Ｆｅ＋Ｍｎ）のモル比０．４７である複合酸化物を各種金属酸化物担体に担持してなる酸化物担持体を、炭化水素燃焼用触媒として用いてメタンを燃焼させた場合における、反応温度とメタン転化率との関係を示すグラフである。
【図３】実施例３で得られた、Ｆｅ／（Ｆｅ＋Ｍｎ）のモル比０．４７である複合酸化物を炭化水素燃焼用触媒として用いてメタンを燃焼させた場合において、反応ガスが乾燥している場合と水蒸気を含む場合とを比較した、反応温度とメタン転化率との関係を示すグラフである。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a catalyst for burning hydrocarbons in exhaust gas and a method for burning hydrocarbons in exhaust gas.
[0002]
[Prior art]
Gas engines, gas turbines, boilers, etc. used in automobiles, thermal power plants, various factories, etc. use city gas, liquefied natural gas, propane gas, etc. as the combustion gas to improve their combustion efficiency and thermal efficiency. In addition, as a combustion method, a lean combustion method in which the ratio of air to combustion gas is increased is employed.
[0003]
In such a combustion method, since the combustion exhaust gas contains a small amount of unburned hydrocarbons and also contains steam, in order to purify such exhaust gas, unburned hydrocarbons are burned in the presence of steam. There is a need.
[0004]
Conventionally, as a catalyst for burning and removing a dilute hydrocarbon, for example, a catalyst in which palladium, platinum, or both are supported on an oxide carrier such as zeolite or alumina is known. Mezaki et al. Report that catalysts containing these noble metals have high activity, for example, in the case of 0.5% Pd-alumina, the combustion start temperature is as low as 210 ° C. (Non-Patent Document 1). reference).
[0005]
However, noble metals such as palladium and platinum have a problem in that the amount of resources is small and the price is high. For example, looking at the price of platinum and palladium in 1996 and the price in 2000, platinum has soared 1.5 times and palladium has soared 9 times. In addition, since the producing countries of these precious metals are extremely biased toward Russia and South Africa, there is concern about long-term stable supply in the future.
[0006]
For this reason, the development of a catalyst for hydrocarbon combustion containing no noble metal has been promoted. For example, SrFeO3Such perovskite-based catalysts have been reported (see Non-Patent Documents 2 to 4).
[0007]
However, the activity of this catalyst is considerably lower than that of a catalyst containing a noble metal. When the ignition temperature (reaction initiation temperature) is compared, the catalyst containing platinum or palladium is around 200 ° C., whereas the catalyst containing perovskite is about 200 ° C. 300 ° C. or higher. Therefore, in order to highly activate the perovskite-based catalyst, it is indispensable to use manganese, chromium, or the like that has a large environmental load. Furthermore, in the case of perovskite-based catalysts, it is difficult to increase the specific surface area per unit mass, and the reaction activity in the presence of steam has not yet been sufficiently elucidated.
[0008]
[Non-patent document 1]
Japan Fuel Association, "Fuel Association Journal", 1979, Vol. 58, No. 625, p. 422-431
[0009]
[Non-patent document 2]
N. N. Gunasekaran, 4 others, "Solid State Ionics", The Netherlands, 1995, Vol. 81, p. 243
[0010]
[Non-Patent Document 3]
El. A. LA Isupova, 4 others, "Applied Catalysis B-Environmental", Netherlands, 1999, Vol. 21, p. 171
[0011]
[Non-patent document 4]
P. P. Salomonsson, two others, "Applied Catalysis A-General", Netherlands, 1993, vol. 104, p. 175
[0012]
[Problems to be solved by the invention]
The present invention mainly provides a highly active catalyst which does not contain precious metals such as palladium and platinum and has a reduced amount of chromium and manganese which have a large environmental load and can promote combustion of hydrocarbons in exhaust gas. Purpose.
[0013]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to achieve the above object, and as a result, have found that a specific lithium-manganese-iron composite oxide having a layered rock-salt structure can achieve the above object, and completed the present invention. Reached.
[0014]
That is, the present invention relates to the following catalyst for combustion of hydrocarbons in exhaust gas and a method for burning hydrocarbons in exhaust gas.
[0015]
1. The following composition formula:
Li[(4-x) / 3] -yMn(2-2x) / 3FexO2
[Where x is 0.07 ≦ x ≦ 0.67, and y is 0 ≦ y ≦ 0.4. ]
And a catalyst for burning hydrocarbons in exhaust gas comprising a lithium-manganese-iron composite oxide having a layered rock-salt structure having a molar ratio of Fe / (Fe + Mn) in the range of 0.1 to 0.75.
[0016]
2. The following composition formula:
Li[(4-x) / 3] -yMn(2-2x) / 3FexO2
[Where x is 0.07 ≦ x ≦ 0.67, and y is 0 ≦ y ≦ 0.4. ]
And a lithium-manganese-iron composite oxide having a layered rock-salt structure in which the molar ratio of Fe / (Fe + Mn) is in the range of 0.1 to 0.75 is magnesia, silica, titania, alumina, zirconia A catalyst for burning hydrocarbons in exhaust gas, comprising an oxide carrier supported on at least one metal oxide selected from zinc oxide and cerium oxide.
[0017]
3. 3. A method for burning hydrocarbons in exhaust gas, comprising contacting an exhaust gas containing hydrocarbons with the hydrocarbon combustion catalyst according to item 1 or 2.
[0018]
4. Item 4. The method for combusting hydrocarbons in exhaust gas according to the above item 3, wherein the hydrocarbon is methane.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Catalyst for combustion of hydrocarbons in exhaust gas
The hydrocarbon combustion catalyst in the exhaust gas of the present invention has the following composition formula:
Li[(4-x) / 3] -yMn(2-2x) / 3FexO2
[Where x is 0.07 ≦ x ≦ 0.67, and y is 0 ≦ y ≦ 0.4. ]
And a lithium-manganese-iron composite oxide having a layered rock-salt structure having a molar ratio of Fe / (Fe + Mn) in the range of 0.1 to 0.75 as an active ingredient. Such a composite oxide has high activity against a reaction of burning hydrocarbons contained in exhaust gas, and is highly useful as a catalyst for purifying exhaust gas.
[0020]
The composite oxide is Li (Li1/3Mn2/3) O2(Li) in complex oxides with a layered rock-salt structure based on1/3Mn2/3) Can be considered as a substitutional solid solution in which part of the substitution is replaced by Fe. The composite oxide is Li (Li1/3Mn2/3) O2(Li1/3Mn2/3By substituting a part of ()) with Fe, the amount of manganese having a large environmental load is reduced, and further, a component having a large environmental load such as chromium is not contained. The composite oxide is extremely useful in that it can burn hydrocarbons in exhaust gas in the same temperature range as conventional perovskite-based catalysts that have been activated by adding manganese, chromium, etc. Is a high catalyst.
[0021]
The outline of the above composition formula is as follows. First, in the basic structure, (Li1/3Mn2/3) Is replaced by Fe, and the molar ratio of Fe is represented by x, Li ｛(Li1/3Mn2/3)1-xFex｝ O2Becomes In the formula, x is 0.07 to 0.67, preferably 0.07 to 0.4.
[0022]
Next, with respect to a structure in which Li ions can be exchanged with hydrogen ions or oxonium ions by washing when synthesizing the composite oxide, a loss ratio of Li which has been taken into consideration is expressed as y. And Li1-y｛(Li1/3Mn2/3)1-xFex｝ O2Becomes In the formula, y is 0 to 0.4. When this equation is developed, it becomes the above composition equation.
[0023]
As the catalyst of the present invention, it is essential that the composite oxide represented by the above composition formula has a molar ratio of Fe / (Fe + Mn) of 0.1 to 0.75. It is preferably from 0.5 to 0.5. The molar ratio of Li / (Fe + Mn) is not particularly limited, but is preferably in the range of 0.5 to 2.
[0024]
The lithium-manganese-iron composite oxide, which is an active ingredient of the catalyst of the present invention, can be produced, for example, by a hydrothermal reaction method, a calcination method, or the like.
[0025]
In the case where the composite oxide is produced by a hydrothermal reaction method, for example, an aqueous solution containing a manganese compound and an iron compound or a water-alcohol mixed solution is made alkaline, for example, a coprecipitate containing manganese and iron at pH 11 or higher. Then, the coprecipitate can be produced by a hydrothermal reaction with a lithium compound in the presence of an oxidizing agent and an alkali.
[0026]
In such a hydrothermal reaction method, as the manganese compound, for example, water-soluble compounds such as manganese chloride, nitrate, sulfate, acetate, and hydroxide can be used, and as the iron compound, for example, iron Water-soluble compounds such as chlorides, nitrates, sulfates, acetates and hydroxides can be used. These compounds can be used in the form of an aqueous solution or a mixed solution of water and alcohol, and as the alcohol, methanol, ethanol and the like can be used.
[0027]
The total concentration of iron and manganese in the aqueous solution or the water-alcohol mixed solution is usually adjusted to be about 0.01 to 2 mol / l (in terms of anhydride), preferably about 0.1 to 0.5 mol / l. Just fine. Further, the amounts of the iron compound and the manganese compound to be used may be adjusted so as to have a molar ratio of Fe / (Fe + Mn) in the target composite oxide.
[0028]
To make the aqueous solution or the water-alcohol mixed solution alkaline, for example, an alkaline aqueous solution containing usually about 0.1 to 20 mol / l, preferably about 0.5 to 10 mol / l, containing potassium hydroxide, sodium hydroxide, or the like Is added. The amount of the alkaline aqueous solution added may be added until the aqueous solution or the water-alcohol mixed solution becomes completely alkaline, for example, until the pH becomes 11 or more.
[0029]
A coprecipitate containing manganese and iron can be obtained by the above method. If necessary, the coprecipitate is usually subjected to an aging treatment while blowing air at about 0 to 150 ° C, preferably about 20 to 100 ° C. You may. The coprecipitate is usually washed with distilled water to remove excess alkali components and residual salts, then filtered off from the solution, dried at about 100 ° C., and then subjected to a hydrothermal reaction in a state mixed with distilled water. Just do it.
[0030]
As the oxidizing agent used when the coprecipitate is subjected to a hydrothermal reaction, for example, potassium chlorate, sodium chlorate, aqueous hydrogen peroxide and the like can be used. The amount of the oxidizing agent to be added may be set so as to be usually about 0.1 to 10 mol / l, preferably about 1 to 5 mol / l, in the solution after the addition. In addition, as the alkali, for example, lithium hydroxide, sodium hydroxide, potassium hydroxide, aqueous ammonia and the like can be used. The amount of the alkali added may be set so as to be usually about 0.1 to 10 mol / l, preferably about 1 to 5 mol / l, in the solution after the addition. By using an alkali other than lithium hydroxide, a neutral or acidic lithium salt such as lithium nitrate or lithium chloride can be used as a lithium source.
[0031]
As the lithium compound, for example, lithium hydroxide (which may be anhydrous or hydrate), lithium chloride, lithium nitrate and the like can be used. The amount of the lithium compound to be used may be adjusted so as to be a molar ratio of Li / (Mn + Fe) in the target composite oxide. Excessive addition of a lithium compound is economically disadvantageous and industrially undesirable.
[0032]
The hydrothermal reaction can be carried out by leaving the container containing the above hydrothermal reaction raw materials in a hydrothermal reactor such as an autoclave, for example. The hydrothermal reaction conditions are not particularly limited, but the reaction may be usually performed at a temperature of about 100 to 300 ° C for about 0.1 to 150 hours, preferably at a temperature of about 150 to 250 ° C for about 1 to 100 hours. Just fine. The hydrothermal reaction can be performed, for example, in an oxidizing atmosphere such as air. After the completion of the reaction, the reaction product may be washed with water, filtered, and dried as necessary in order to remove the remaining excess salts and the like. Thus, a lithium-manganese-iron composite oxide is obtained.
[0033]
When the composite oxide is produced by a firing method, for example, an aqueous solution containing a manganese compound and an iron compound or a water-alcohol mixed solution, a lithium compound is added to obtain a precipitate, and the precipitate is fired. It can be manufactured by Further, it can also be produced by baking the residue obtained by evaporating the solution and the precipitate after adding the lithium compound to the aqueous solution or the water-alcohol mixed solution to dryness.
[0034]
In the above-mentioned firing method, as the manganese compound and the iron compound, the compounds that can be used in the above-described hydrothermal reaction can be used as they are, and they can be used in the form of an aqueous solution or a water-alcohol mixed solution. The total concentration of iron and manganese in the aqueous solution or the mixed solution of water and alcohol may be the same as in the case of the above-described hydrothermal reaction.
[0035]
The amounts of the manganese compound and the iron compound may be adjusted so that the molar ratio of Fe / (Fe + Mn) in the target composite oxide is obtained.
[0036]
As the lithium compound, lithium hydroxide (which may be anhydrous or hydrated), lithium chloride, lithium nitrate and the like can be used as in the case of the hydrothermal reaction method. The amount of the lithium compound to be used may be adjusted so as to be a molar ratio of Li / (Mn + Fe) in the target composite oxide. Excessive addition of a lithium compound is economically disadvantageous and industrially undesirable.
[0037]
When the precipitate obtained by adding the lithium compound is baked, a precipitate obtained by taking out the precipitate from the solution, for example, a product obtained by washing with water, filtering and drying can be baked.
[0038]
The conditions for firing the precipitate or the residue are not particularly limited, and may be generally about 200 to 1000 ° C. for about 1 to 100 hours, preferably about 300 to 800 ° C. for about 20 to 60 hours. The firing atmosphere is not particularly limited, and may be an oxidizing atmosphere such as the air or a reducing atmosphere such as hydrogen. After the calcination, the product may be pulverized, if necessary, and the calcination may be repeated under the same conditions as described above.
[0039]
The lithium-manganese-iron composite oxide produced by such a production method can be used as it is as the catalyst of the present invention. In this case, the shape of the catalyst of the present invention is not particularly limited, and for example, it can be used in any shape such as a particle, a powder, a pellet, a plate, a column, and a lattice. When processing the composite oxide into the above-described shape, a binder or the like can be added as needed, as long as the effect of the catalyst of the present invention is not affected.
[0040]
The size of the composite oxide is not particularly limited, and can be appropriately set in consideration of an actual use mode. For example, if the composite oxide is used in the form of particles, the average particle diameter of the particles is usually 0.1 to 5 mm. The degree is appropriate, and preferably about 1 to 3 mm. When used in the form of a powder, the average particle diameter of the powder is usually about 0.1 to 1000 nm, and preferably about 1 to 100 nm. In the case of using pellets, pellets having a length of about 30 mm, a width of about 30 mm, and a height of about 5 mm, preferably about 10 mm in length, about 10 mm in width, and about 3 mm in height may be used.
[0041]
The specific surface area of the catalyst of the present invention may be any range as long as it can secure a wide contact area with the exhaust gas.2/ G is appropriate, and 50-100 m2/ G is preferred. In addition, the value of the specific surface area in the present specification is a value measured by a BET method characterized in that nitrogen is adsorbed on the surface of an object to be measured.
[0042]
The catalyst of the present invention may be used by supporting the composite oxide on a carrier. When the composite oxide is supported on a carrier, a wider contact area between the composite oxide and the exhaust gas can be secured than in the case where the composite oxide is used as a catalyst as described above. Therefore, compared to the case where the composite oxide is used as it is as a catalyst, the same hydrocarbon combustion effect can be exhibited even if the amount of the composite oxide is reduced, so that the amount of manganese having a large environmental load can be further reduced. This is advantageous.
[0043]
The type of the carrier is not particularly limited, but a carrier having excellent heat resistance is preferable in consideration of contact with exhaust gas. Examples of the carrier include magnesia, silica, titania, alumina, zirconia, zinc oxide, cerium oxide, calcium oxide, and other metal oxides, and composite oxides thereof. Among them, basic metal oxides such as magnesia, zinc oxide and calcium oxide are particularly preferable.
[0044]
Although the shape of the carrier is not particularly limited, a shape having a large specific surface area, for example, a particle shape, a pellet shape, a honeycomb shape, or the like is preferable in consideration of contact with exhaust gas. The size of the carrier is not particularly limited, and can be appropriately set in consideration of the actual use mode. If it is particulate, the average particle size is usually 0.5 to 3 mm, and preferably about 1 to 2 mm. . If it is in the form of a pellet, it is suitably about 30 mm long, 30 mm wide and about 30 mm high, and preferably about 10 mm long, 10 mm wide and about 10 mm high.
[0045]
The amount of the composite oxide supported on the carrier is not particularly limited, but usually about 1 to 10 parts by weight, and preferably about 3 to 5 parts by weight, per 100 parts by weight of the carrier. As the composite oxide to be supported, for example, a powder having an average particle diameter of usually about 0.1 to 1000 nm is preferable, and a powder having an average particle diameter of about 1 to 100 nm is more preferable.
[0046]
The method for supporting the composite oxide on the carrier is not particularly limited, for example, a method of mixing the carrier and the composite oxide in a solid state; water may be added to a mixture of the carrier and the composite oxide in a solid state. After stirring, a method of drying the obtained slurry; a method in which water is added to either the carrier or the composite oxide, the other is added, and the resulting slurry is thoroughly stirred, and then the obtained slurry is dried. Can be done. Further, the slurry can also be supported by applying, spraying, or the like, a slurry composed of the composite oxide and water.
[0047]
Method for using the catalyst of the present invention
The catalyst of the present invention can be used for burning hydrocarbons in exhaust gas. That is, it can be suitably used for purifying exhaust gas by burning hydrocarbons in the exhaust gas.
[0048]
The exhaust gas targeted by the catalyst of the present invention is not limited as long as it contains hydrocarbons, and can be, for example, exhaust gas discharged from a gas engine, a gas turbine, a boiler, a gas fan heater, a gas water heater or the like. The above-mentioned exhaust gas generally contains water vapor, nitrogen oxides, sulfur oxides, oxygen and the like in addition to hydrocarbons.
[0049]
The hydrocarbon to be burned is not particularly limited, and examples thereof include methane, ethane, propane, and butane. The catalyst of the present invention can be suitably used especially for methane combustion among hydrocarbons.
[0050]
The hydrocarbon concentration in the exhaust gas targeted by the catalyst of the present invention is not particularly limited, but a lean hydrocarbon having a hydrocarbon concentration of 10,000 ppm or less, particularly 2500 ppm or less can also be targeted. Therefore, it can be suitably used for combustion of hydrocarbons contained in exhaust gas from gas engines, gas turbines, boilers, and the like that employ a lean burn system and have a low hydrocarbon concentration in the exhaust gas.
[0051]
In order to burn hydrocarbons in the exhaust gas, for example, the hydrocarbons contained in the exhaust gas can be burned by flowing the exhaust gas through a reaction tube filled with the catalyst of the present invention. The shape, size, and the like of the reaction tube can be appropriately set in consideration of the actual use mode. As such a reaction tube, for example, a tube made of a heat-resistant material such as quartz glass or stainless steel can be used.
[0052]
The amount of the catalyst used is not particularly limited, but is preferably in the range of 1000 to 100000 ml / hg-cat, and in the range of 1000 to 10000 ml / hg-cat in terms of gas hourly space velocity (SV). preferable. If the amount of the catalyst used is too small, the hydrocarbon combustion rate will be insufficient. If the amount of catalyst used is too large, the combustion rate of hydrocarbons is improved, but it is economically disadvantageous because catalyst performance cannot be improved in proportion to the amount used.
[0053]
In order to effectively utilize the high activity of the catalyst of the present invention, the exhaust gas treatment temperature is usually 200 to 1000 ° C, and preferably about 300 to 500 ° C. If the exhaust gas treatment temperature is too low, the hydrocarbon combustion rate will be insufficient. If the exhaust gas treatment temperature is too high, the durability of the catalyst tends to decrease.
[0054]
【The invention's effect】
The catalyst of the present invention can promote the combustion of hydrocarbons in exhaust gas. In particular, it is a very useful catalyst in that it can promote the combustion of hydrocarbons even in the case of exhaust gas with a low hydrocarbon concentration discharged by the lean burn method. Such a catalyst of the present invention can be suitably used particularly for methane combustion.
[0055]
The catalyst of the present invention does not contain precious metals such as palladium and platinum and chromium, which has a large environmental load, and has a reduced amount of manganese. Such a catalyst of the present invention can burn hydrocarbons in flue gas in a temperature range substantially the same as that of a conventional perovskite-based catalyst containing a large amount of manganese or chromium, using a smaller amount of manganese. In addition, since no precious metal is contained, there is an advantage that the production cost can be reduced and the raw material can be stably supplied.
[0056]
Further, the catalyst of the present invention has sufficient durability, the frequency of catalyst replacement can be suppressed, and the cost of the exhaust gas treatment system itself can be reduced. Furthermore, heat is generated by the oxidation, so that heat can be recovered.
[0057]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. However, the present invention is not limited to these examples.
[0058]
Example 1
64.58 g of manganese (II) nitrate hexahydrate and 10.1 g of iron (III) nitrate nonahydrate were dissolved in 400 ml of distilled water, and a mixed aqueous solution of Fe—Mn (total amount: 0.25 mol, Fe / (Fe + Mn)) was dissolved. A molar ratio of 0.1) was prepared.
[0059]
To the mixed aqueous solution, 400 ml of an aqueous potassium hydroxide solution (50 g of potassium hydroxide dissolved in 400 ml of distilled water) cooled to room temperature was added dropwise over 2 to 3 hours while stirring until the pH of the aqueous solution became 11 or more. An Mn coprecipitate was obtained. The coprecipitate was air-oxidized while stirring, then placed in a closed container and aged at 50 ° C for 2 to 3 days.
[0060]
Next, the coprecipitate was washed and filtered with distilled water to remove residual alkali components, and then the coprecipitate was dried at 100 ° C. The dried coprecipitate, 200 ml of distilled water, 40 g of lithium hydroxide monohydrate and 40 g of potassium chlorate were placed in a PTFE beaker, followed by thorough stirring. The PTFE beaker was left in an autoclave, and the contents were hydrothermally reacted at 220 ° C. for 5 hours.
[0061]
After the reaction was completed, the reaction mixture was naturally cooled to room temperature, taken out of the PTFE beaker, and the reaction product was washed with distilled water and filtered to remove excess lithium salt. The solid content was dried at 100 ° C. to obtain a particulate lithium-manganese-iron composite oxide.
[0062]
In the composite oxide, the molar ratio of Li / (Fe + Mn) was 1.69, and the molar ratio of Fe / (Fe + Mn) was 0.1. The composition formula is Li1.16Fe0.07Mn0.62O2Met. The shape of the composite oxide is particulate, and the BET specific surface area is 22 m2/ G, and the particle size was 10 to 500 nm. Note that the composition of the composite oxide in this specification is a result determined by inductively coupled plasma (ICP) measurement.
[0063]
Example 2
50.23 g of manganese (II) nitrate hexahydrate and 30.3 g of iron (III) nitrate nonahydrate were dissolved in 400 ml of distilled water, and a mixed aqueous solution of Fe-Mn (total amount 0.25 mol, Fe / (Fe + Mn) A molar ratio of 0.3) was prepared.
[0064]
To the mixed aqueous solution, 400 ml of an aqueous potassium hydroxide solution (50 g of potassium hydroxide dissolved in 400 ml of distilled water) cooled to room temperature was added dropwise over 2 to 3 hours while stirring until the pH of the aqueous solution became 11 or more. An Mn coprecipitate was obtained. The coprecipitate was air-oxidized while stirring, and then placed in a closed container and aged at 50 ° C. for 2 to 3 days.
[0065]
Next, the coprecipitate was washed and filtered with distilled water to remove residual alkali components, and then the coprecipitate was dried at 100 ° C. The dried coprecipitate, 200 ml of distilled water, 40 g of lithium hydroxide monohydrate and 40 g of potassium chlorate were placed in a PTFE beaker, followed by thorough stirring. The PTFE beaker was left in an autoclave, and the contents were hydrothermally reacted at 220 ° C. for 5 hours.
[0066]
After the reaction was completed, the reaction mixture was naturally cooled to room temperature, taken out of the PTFE beaker, and the reaction product was washed with distilled water and filtered to remove excess lithium salt. The solid content was dried at 100 ° C. to obtain a particulate lithium-manganese-iron composite oxide.
[0067]
In the composite oxide, the molar ratio of Li / (Fe + Mn) was 1.4, and the molar ratio of Fe / (Fe + Mn) was 0.3. The composition formula is Li1.04(Fe0.22Mn0.52) O2Met. The composite oxide has a particle shape and a BET specific surface area of 44 m.2/ G, and the particle size was 10 to 500 nm.
[0068]
Example 3
35.88 g of manganese (II) nitrate hexahydrate and 50.5 g of iron (III) nitrate nonahydrate were dissolved in 400 ml of distilled water, and a mixed aqueous solution of Fe-Mn (total amount 0.25 mol, Fe / (Fe + Mn)) was dissolved. A molar ratio of 0.5) was prepared.
[0069]
To the mixed aqueous solution, 400 ml of an aqueous potassium hydroxide solution (50 g of potassium hydroxide dissolved in 400 ml of distilled water) cooled to room temperature was added dropwise over 2 to 3 hours while stirring until the pH of the aqueous solution became 11 or more. An Mn coprecipitate was obtained. The coprecipitate was air-oxidized while stirring, then placed in a closed container and aged at 50 ° C for 2 to 3 days.
[0070]
Next, the coprecipitate was washed and filtered with distilled water to remove residual alkali components, and then the coprecipitate was dried at 100 ° C. The dried coprecipitate, 200 ml of distilled water, 40 g of lithium hydroxide monohydrate and 40 g of potassium chlorate were placed in a PTFE beaker, followed by thorough stirring. The PTFE beaker was left in an autoclave, and the contents were hydrothermally reacted at 220 ° C. for 5 hours.
[0071]
After the reaction was completed, the reaction mixture was naturally cooled to room temperature, taken out of the PTFE beaker, and the reaction product was washed with distilled water and filtered to remove excess lithium salt. The solid content was dried at 100 ° C. to obtain a particulate lithium-manganese-iron composite oxide.
[0072]
In the composite oxide, the molar ratio of Li / (Fe + Mn) was 1.28, and the molar ratio of Fe / (Fe + Mn) was 0.47. The composition formula is Li1.01(Fe0.37Mn0.42) O2Met. The composite oxide is in the form of particles and has a BET specific surface area of 53 m.2/ G, and the particle size was 50 to 100 nm.
[0073]
Example 4
50 mg of the composite oxide obtained in Example 3 and 1 g of powdered magnesia having an average particle diameter of 0.05 mm were mixed in a solid state.
[0074]
1 ml of distilled water was added to the mixture, and the mixture was mixed well in an ultrasonic washing tank for 30 minutes. After the obtained slurry was dried at 100 ° C. overnight, the obtained powder was fired at 600 ° C. for 5 hours to obtain magnesia supporting 5 parts by weight of the composite oxide.
[0075]
Example 5
50 mg of the composite oxide obtained in Example 3 and 1 g of powdery zirconia having an average particle diameter of 0.05 mm were mixed in a solid state.
[0076]
1 ml of distilled water was added to the mixture, and the mixture was mixed well in an ultrasonic washing tank for 30 minutes. After the obtained slurry was dried at 100 ° C. overnight, the obtained powder was fired at 600 ° C. for 5 hours to obtain zirconia supporting 5 parts by weight of the composite oxide.
[0077]
Example 6
50 mg of the composite oxide obtained in Example 2 and 1 g of powdered ceria having an average particle diameter of 0.05 mm were mixed in a solid state.
[0078]
1 ml of distilled water was added to the mixture, and the mixture was mixed well in an ultrasonic washing tank for 30 minutes. After the obtained slurry was dried at 100 ° C. overnight, the obtained powder was fired at 600 ° C. for 5 hours to obtain ceria supporting 5 parts by weight of the composite oxide.
[0079]
Example 7
50 mg of the composite oxide obtained in Example 2 and 1 g of powdery alumina having an average particle diameter of 0.1 mm were mixed in a solid state.
[0080]
1 ml of distilled water was added to the mixture, and the mixture was mixed well in an ultrasonic washing tank for 30 minutes. After the obtained slurry was dried at 100 ° C. overnight, the obtained powder was fired at 600 ° C. for 5 hours to obtain alumina supporting 5 parts by weight of the composite oxide.
[0081]
Example 8
50 mg of the composite oxide obtained in Example 2 and 1 g of powdered zinc oxide having an average particle diameter of 0.2 mm were mixed in a solid state.
[0082]
1 ml of distilled water was added to the mixture, and the mixture was mixed well in an ultrasonic washing tank for 30 minutes. After the obtained slurry was dried at 100 ° C. overnight, the obtained powder was fired at 600 ° C. for 5 hours to obtain zinc oxide supporting 5 parts by weight of the composite oxide.
[0083]
Example 9
50 mg of the composite oxide obtained in Example 2 and 1 g of powdered titania having an average particle diameter of 0.1 mm were mixed in a solid state.
[0084]
1 ml of distilled water was added to the mixture, and the mixture was mixed well in an ultrasonic washing tank for 30 minutes. After the obtained slurry was dried at 100 ° C. overnight, the obtained powder was fired at 600 ° C. for 5 hours to obtain titania supporting 5 parts by weight of the composite oxide.
[0085]
Example 10
50 mg of the composite oxide obtained in Example 2 and 1 g of powdery amorphous silica having a particle diameter of 0.063 to 0.2 mm were mixed in a solid state.
[0086]
1 ml of distilled water was added to the mixture, and the mixture was mixed well in an ultrasonic washing tank for 30 minutes. After the obtained slurry was dried at 100 ° C. overnight, the obtained powder was fired at 600 ° C. for 5 hours to obtain amorphous silica carrying 5 parts by weight of the composite oxide.
[0087]
Example 11
50 mg of the composite oxide obtained in Example 2 and 1 g of powdery mesoporous silica having an average particle diameter of 0.3 mm were mixed in a solid state.
[0088]
1 ml of distilled water was added to the mixture, and the mixture was mixed well in an ultrasonic washing tank for 30 minutes. After the obtained slurry was dried at 100 ° C. overnight, the obtained powder was calcined at 600 ° C. for 5 hours to obtain mesoporous silica supporting 5 parts by weight of the composite oxide.
[0089]
Comparative Example 1
3 g of manganese dioxide was placed in a PTFE beaker, 200 ml of distilled water was added to disperse well, and 50 g of lithium hydroxide monohydrate was further added and stirred well.
[0090]
The PTFE beaker was left in an autoclave, and the contents were hydrothermally reacted at 220 ° C. for 7 hours.
[0091]
After the reaction was completed, the reaction mixture was naturally cooled to room temperature, taken out of the PTFE beaker, and the reaction product was washed with distilled water and filtered to remove excess lithium salt. The solid was dried at 100 ° C. to obtain a lithium-manganese composite oxide.
[0092]
The molar ratio of Li / Mn of the composite oxide was 1.35. The composition formula is Li0.9Mn0.67O2Met. The shape of the composite oxide is particulate, and the BET specific surface area is 30 m2/ G.
[0093]
Comparative Example 2
69.51 g of iron (II) sulfate heptahydrate was dissolved in 400 ml of distilled water to prepare an aqueous solution of iron (II) sulfate.
[0094]
To the aqueous solution, 400 ml of an aqueous potassium hydroxide solution (50 g of potassium hydroxide dissolved in 400 ml of distilled water) cooled to room temperature was added dropwise over 2 to 3 hours while stirring until the aqueous solution became pH 11 or higher. Was obtained. The precipitate was air-oxidized while stirring, then placed in a closed container and aged at 50 ° C for 2 to 3 days.
[0095]
Next, the precipitate was washed and filtered with distilled water to remove residual alkaline components, and then the precipitate was dried at 100 ° C. The dried precipitate, 200 ml of distilled water, 40 g of lithium hydroxide monohydrate and 40 g of potassium chlorate were put in a PTFE beaker, and the mixture was thoroughly stirred. The PTFE beaker was left in an autoclave, and the contents were hydrothermally reacted at 220 ° C. for 5 hours.
[0096]
After the reaction was completed, the reaction mixture was naturally cooled to room temperature, taken out of the PTFE beaker, and the reaction product was washed with distilled water and filtered to remove excess lithium salt. The solid content was dried at 100 ° C. to obtain a particulate lithium-iron composite oxide.
[0097]
The composite oxide was converted to α-LiFeO by X-ray diffraction analysis.2Met. The composite oxide has a particle shape and a BET specific surface area of 6 m.2/ G.
[0098]
Catalyst performance test 1
The catalytic performance of each of the composite oxides obtained in Examples 1 to 3 and Comparative Examples 1 and 2 was confirmed. To confirm the catalyst performance, for each of the five types of composite oxides, 300 mg of the composite oxide was filled into a quartz glass tube having an inner diameter of 12 mm, and the reaction gas was passed through the glass tube under normal pressure using a fixed-bed flow reactor. It was confirmed by examining the conversion of methane contained in the reaction gas.
[0099]
As a reaction gas, a nitrogen gas containing 2,500 ppm (volume) of methane and 20% of oxygen was used. The flow rate of the reaction gas was 50 ml per minute (SV = 10,000 ml / hg-cat). The reaction temperature was increased from 300 ° C. by 50 ° C. to 550 ° C.
[0100]
The value of the methane conversion rate, which is an index of the catalyst performance, was calculated based on the following equation after measuring the concentrations of methane, carbon monoxide and carbon dioxide contained in the reaction gas with a gas chromatograph analyzer.
Methane conversion (%) = (C0-C1) / C0× 100
C0: Methane concentration before the start of the reaction
C1: Methane concentration after reaction.
[0101]
FIG. 1 is a graph showing the relationship between the reaction temperature of each of the five types of composite oxides and the methane conversion.
[0102]
From the results of FIG. 1, it can be seen that as the ratio of iron to manganese increases, the methane conversion increases and the catalyst performance increases.
[0103]
Also, it can be seen that the composite oxide having a Fe / (Fe + Mn) molar ratio of 0.5 exhibits better catalytic performance than the composite oxide containing only manganese or iron.
[0104]
In order to confirm the long-term stability of the catalyst performance, a composite oxide catalyst having a molar ratio of Fe / (Fe + Mn) of 0.5 was continuously reacted at 450 ° C. for 13 hours. I was not able to admit.
[0105]
Catalyst performance test 2
The catalytic performance of a material in which the composite oxide obtained in Example 3 was supported on the metal oxide supports obtained in Examples 4 to 11 was confirmed. The method of the performance test is the same as the catalyst performance test 1.
[0106]
FIG. 2 is a graph showing the relationship between the reaction temperature of each material and the methane conversion.
[0107]
From the results shown in FIG. 2, it can be seen that the catalytic performance is particularly improved when the composite oxide is supported on a basic metal oxide carrier such as magnesia or zinc oxide. By supporting on these metal oxide carriers, the amount of manganese used can be suppressed.
[0108]
Catalyst performance test 3
Except for using a nitrogen gas containing 2400 ppm (volume) of methane and 19.2% oxygen as a reaction gas, the catalytic performance of the composite oxide obtained in Example 3 was measured under the same conditions as in the catalytic performance test 1. confirmed. The reaction gas is in a dry state. FIG. 3 is a graph showing the relationship between the reaction temperature and the methane conversion.
[0109]
The composite obtained in Example 3 under the same conditions as in the catalyst performance test 1 except that a nitrogen gas containing 4% steam, 2400 ppm (volume) of methane and 19.2% of oxygen was used as a reaction gas. The catalytic performance of the oxide was confirmed. The reaction gas contains water vapor. FIG. 3 is a graph showing the relationship between the reaction temperature and the methane conversion.
[0110]
The results in FIG. 3 indicate that the composite oxide obtained in Example 3 can secure a high methane conversion even in the presence of steam.
[Brief description of the drawings]
FIG. 1 shows the relationship between reaction temperature and methane conversion when methane is combusted using the composite oxides obtained in Examples 1 to 3 and Comparative Examples 1 and 2 as a catalyst for burning hydrocarbons. It is a graph.
FIG. 2 shows an oxide carrier obtained by supporting a composite oxide obtained in Example 3 having a molar ratio of Fe / (Fe + Mn) of 0.47 on various metal oxide carriers, as a hydrocarbon combustion catalyst. 4 is a graph showing the relationship between the reaction temperature and the methane conversion when methane is burned by using the method.
FIG. 3 is a diagram showing a reaction gas dried when methane is burned using the composite oxide having a molar ratio of Fe / (Fe + Mn) of 0.47 obtained in Example 3 as a catalyst for burning hydrocarbons. 6 is a graph showing the relationship between the reaction temperature and the methane conversion, comparing the case where the temperature is higher than the case where the water vapor is included.
Claims (4)
Ｌｉ［（４−ｘ）／３］−ｙＭｎ（２−２ｘ）／３ＦｅｘＯ２
〔式中、ｘは０．０７≦ｘ≦０．６７であり、ｙは０≦ｙ≦０．４である。〕
で表され、Ｆｅ／（Ｆｅ＋Ｍｎ）のモル比が０．１〜０．７５の範囲内である層状岩塩型構造を有するリチウム−マンガン−鉄複合酸化物からなる排ガス中の炭化水素燃焼用触媒。The following composition formula:
Li [(4-x) / 3] -y Mn (2-2x) / 3 Fe x O 2
[Where x is 0.07 ≦ x ≦ 0.67, and y is 0 ≦ y ≦ 0.4. ]
And a catalyst for burning hydrocarbons in exhaust gas comprising a lithium-manganese-iron composite oxide having a layered rock salt structure having a molar ratio of Fe / (Fe + Mn) in the range of 0.1 to 0.75.
Ｌｉ［（４−ｘ）／３］−ｙＭｎ（２−２ｘ）／３ＦｅｘＯ２
〔式中、ｘは０．０７≦ｘ≦０．６７であり、ｙは０≦ｙ≦０．４である。〕
で表され、Ｆｅ／（Ｆｅ＋Ｍｎ）のモル比が０．１〜０．７５の範囲内である層状岩塩型構造を有するリチウム−マンガン−鉄複合酸化物が、マグネシア、シリカ、チタニア、アルミナ、ジルコニア、酸化亜鉛及び酸化セリウムから選ばれる少なくとも１種の金属酸化物に担持された酸化物担持体からなる排ガス中の炭化水素燃焼用触媒。The following composition formula:
Li [(4-x) / 3] -y Mn (2-2x) / 3 Fe x O 2
[Where x is 0.07 ≦ x ≦ 0.67, and y is 0 ≦ y ≦ 0.4. ]
And a lithium-manganese-iron composite oxide having a layered rock-salt structure in which the molar ratio of Fe / (Fe + Mn) is in the range of 0.1 to 0.75 is magnesia, silica, titania, alumina, zirconia A catalyst for burning hydrocarbons in exhaust gas, comprising an oxide carrier supported on at least one metal oxide selected from zinc oxide and cerium oxide.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007160297A (en) * | 2005-11-21 | 2007-06-28 | Kumamoto Univ | Oxidation catalyst for burning pm and cleaning method for diesel engine exhaust gas, filter and cleaning device using the same |
| KR20090091754A (en) * | 2006-11-15 | 2009-08-28 | 바스프 카탈리스트 엘엘씨 | Catalysts for dual oxidation of ammonia and carbon monoxide with low to no nox formation |
| JP2012091982A (en) * | 2010-10-28 | 2012-05-17 | National Institute Of Advanced Industrial Science & Technology | Lithium-manganese compound oxide having cubic rock salt structure and process for producing the same |
-
2002
- 2002-11-08 JP JP2002325130A patent/JP3940794B2/en not_active Expired - Lifetime
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007160297A (en) * | 2005-11-21 | 2007-06-28 | Kumamoto Univ | Oxidation catalyst for burning pm and cleaning method for diesel engine exhaust gas, filter and cleaning device using the same |
| KR20090091754A (en) * | 2006-11-15 | 2009-08-28 | 바스프 카탈리스트 엘엘씨 | Catalysts for dual oxidation of ammonia and carbon monoxide with low to no nox formation |
| JP2010510049A (en) * | 2006-11-15 | 2010-04-02 | ビーエーエスエフ、カタリスツ、エルエルシー | NOx forming catalyst with little or no ammonia and carbon monoxide double oxidation catalyst |
| KR101634390B1 (en) * | 2006-11-15 | 2016-06-28 | 바스프 카탈리스트 엘엘씨 | CATALYSTS FOR DUAL OXIDATION OF AMMONIA AND CARBON MONOXIDE WITH LOW TO NO NOx FORMATION |
| JP2012091982A (en) * | 2010-10-28 | 2012-05-17 | National Institute Of Advanced Industrial Science & Technology | Lithium-manganese compound oxide having cubic rock salt structure and process for producing the same |
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