JP4841768B2 - Nitrogen oxide adsorbent comprising chromium-containing oxide and method for producing the same - Google Patents
Nitrogen oxide adsorbent comprising chromium-containing oxide and method for producing the same Download PDFInfo
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- JP4841768B2 JP4841768B2 JP2001250310A JP2001250310A JP4841768B2 JP 4841768 B2 JP4841768 B2 JP 4841768B2 JP 2001250310 A JP2001250310 A JP 2001250310A JP 2001250310 A JP2001250310 A JP 2001250310A JP 4841768 B2 JP4841768 B2 JP 4841768B2
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- Prior art keywords
- chromium
- alkylamine
- adsorption
- oxide
- containing oxide
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- 239000011651 chromium Substances 0.000 title claims description 133
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 title claims description 106
- 229910052804 chromium Inorganic materials 0.000 title claims description 94
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 title claims description 85
- 239000003463 adsorbent Substances 0.000 title claims description 22
- 238000004519 manufacturing process Methods 0.000 title claims description 15
- 238000001179 sorption measurement Methods 0.000 claims description 74
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 42
- 150000003973 alkyl amines Chemical class 0.000 claims description 41
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 33
- 239000011148 porous material Substances 0.000 claims description 33
- 229910052751 metal Inorganic materials 0.000 claims description 28
- 239000002184 metal Substances 0.000 claims description 25
- 238000007254 oxidation reaction Methods 0.000 claims description 22
- 230000003647 oxidation Effects 0.000 claims description 21
- 239000002245 particle Substances 0.000 claims description 21
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 20
- 238000000034 method Methods 0.000 claims description 19
- 238000003756 stirring Methods 0.000 claims description 18
- 239000000203 mixture Substances 0.000 claims description 16
- 239000000377 silicon dioxide Substances 0.000 claims description 16
- 239000003960 organic solvent Substances 0.000 claims description 15
- -1 silicate ester Chemical class 0.000 claims description 15
- 238000000354 decomposition reaction Methods 0.000 claims description 14
- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical compound O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 claims description 13
- 230000002378 acidificating effect Effects 0.000 claims description 11
- 239000007864 aqueous solution Substances 0.000 claims description 11
- 229910000423 chromium oxide Inorganic materials 0.000 claims description 10
- 238000002441 X-ray diffraction Methods 0.000 claims description 7
- 239000002253 acid Substances 0.000 claims description 6
- 125000004432 carbon atom Chemical group C* 0.000 claims description 4
- 150000001845 chromium compounds Chemical class 0.000 claims description 4
- 229910044991 metal oxide Inorganic materials 0.000 claims description 4
- 150000004706 metal oxides Chemical class 0.000 claims description 4
- 230000008569 process Effects 0.000 claims description 2
- 150000005846 sugar alcohols Polymers 0.000 claims description 2
- 241000566146 Asio Species 0.000 claims 1
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 claims 1
- 239000000047 product Substances 0.000 description 16
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 15
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 description 15
- 238000010438 heat treatment Methods 0.000 description 14
- 238000005259 measurement Methods 0.000 description 14
- IOQPZZOEVPZRBK-UHFFFAOYSA-N octan-1-amine Chemical compound CCCCCCCCN IOQPZZOEVPZRBK-UHFFFAOYSA-N 0.000 description 14
- 239000007789 gas Substances 0.000 description 13
- 239000002243 precursor Substances 0.000 description 13
- 238000006243 chemical reaction Methods 0.000 description 12
- AFCARXCZXQIEQB-UHFFFAOYSA-N N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CCNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 AFCARXCZXQIEQB-UHFFFAOYSA-N 0.000 description 11
- 239000003054 catalyst Substances 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 11
- 239000011259 mixed solution Substances 0.000 description 11
- 230000008859 change Effects 0.000 description 10
- 229910021536 Zeolite Inorganic materials 0.000 description 9
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 9
- 238000002156 mixing Methods 0.000 description 9
- 239000000243 solution Substances 0.000 description 9
- 239000010457 zeolite Substances 0.000 description 9
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 8
- 238000009826 distribution Methods 0.000 description 8
- 230000001590 oxidative effect Effects 0.000 description 8
- 150000003839 salts Chemical class 0.000 description 8
- 239000000126 substance Substances 0.000 description 8
- 239000012265 solid product Substances 0.000 description 7
- 239000007858 starting material Substances 0.000 description 7
- 239000000725 suspension Substances 0.000 description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 6
- 150000001844 chromium Chemical class 0.000 description 6
- 238000001878 scanning electron micrograph Methods 0.000 description 6
- JMXKSZRRTHPKDL-UHFFFAOYSA-N titanium ethoxide Chemical compound [Ti+4].CC[O-].CC[O-].CC[O-].CC[O-] JMXKSZRRTHPKDL-UHFFFAOYSA-N 0.000 description 6
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical compound CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 description 5
- 230000015572 biosynthetic process Effects 0.000 description 5
- 239000002131 composite material Substances 0.000 description 5
- 239000012798 spherical particle Substances 0.000 description 5
- 150000001412 amines Chemical class 0.000 description 4
- 239000003795 chemical substances by application Substances 0.000 description 4
- QDOXWKRWXJOMAK-UHFFFAOYSA-N dichromium trioxide Chemical compound O=[Cr]O[Cr]=O QDOXWKRWXJOMAK-UHFFFAOYSA-N 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 230000007613 environmental effect Effects 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 230000007246 mechanism Effects 0.000 description 4
- 229910052757 nitrogen Inorganic materials 0.000 description 4
- 241000894007 species Species 0.000 description 4
- VZSRBBMJRBPUNF-UHFFFAOYSA-N 2-(2,3-dihydro-1H-inden-2-ylamino)-N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]pyrimidine-5-carboxamide Chemical compound C1C(CC2=CC=CC=C12)NC1=NC=C(C=N1)C(=O)NCCC(N1CC2=C(CC1)NN=N2)=O VZSRBBMJRBPUNF-UHFFFAOYSA-N 0.000 description 3
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 3
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- MKYBYDHXWVHEJW-UHFFFAOYSA-N N-[1-oxo-1-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propan-2-yl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(C(C)NC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 MKYBYDHXWVHEJW-UHFFFAOYSA-N 0.000 description 3
- 239000003513 alkali Substances 0.000 description 3
- 150000004703 alkoxides Chemical class 0.000 description 3
- 239000012298 atmosphere Substances 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 230000006378 damage Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 239000002114 nanocomposite Substances 0.000 description 3
- 239000007800 oxidant agent Substances 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 239000011164 primary particle Substances 0.000 description 3
- 229910052815 sulfur oxide Inorganic materials 0.000 description 3
- 238000003786 synthesis reaction Methods 0.000 description 3
- 238000002076 thermal analysis method Methods 0.000 description 3
- 229910018516 Al—O Inorganic materials 0.000 description 2
- 229910052684 Cerium Inorganic materials 0.000 description 2
- 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 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 2
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 230000001133 acceleration Effects 0.000 description 2
- 125000000217 alkyl group Chemical group 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- 230000003197 catalytic effect Effects 0.000 description 2
- 238000001311 chemical methods and process Methods 0.000 description 2
- ZCDOYSPFYFSLEW-UHFFFAOYSA-N chromate(2-) Chemical class [O-][Cr]([O-])(=O)=O ZCDOYSPFYFSLEW-UHFFFAOYSA-N 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 229910052748 manganese Inorganic materials 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 239000002905 metal composite material Substances 0.000 description 2
- 150000002736 metal compounds Chemical class 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 229910017604 nitric acid Inorganic materials 0.000 description 2
- KMUONIBRACKNSN-UHFFFAOYSA-N potassium dichromate Chemical compound [K+].[K+].[O-][Cr](=O)(=O)O[Cr]([O-])(=O)=O KMUONIBRACKNSN-UHFFFAOYSA-N 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 238000000746 purification Methods 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 239000012495 reaction gas Substances 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 229910052718 tin Inorganic materials 0.000 description 2
- 229910052725 zinc Inorganic materials 0.000 description 2
- 229910052726 zirconium Inorganic materials 0.000 description 2
- JHWIEAWILPSRMU-UHFFFAOYSA-N 2-methyl-3-pyrimidin-4-ylpropanoic acid Chemical compound OC(=O)C(C)CC1=CC=NC=N1 JHWIEAWILPSRMU-UHFFFAOYSA-N 0.000 description 1
- PNWJTIFZRHJYLK-UHFFFAOYSA-N CC(C)(C)O[Cr](=O)(=O)OC(C)(C)C Chemical compound CC(C)(C)O[Cr](=O)(=O)OC(C)(C)C PNWJTIFZRHJYLK-UHFFFAOYSA-N 0.000 description 1
- DNNANASOSZKKIS-UHFFFAOYSA-N CC(C)(O[Cr](=O)(=O)OC(C)(C)c1ccccc1)c1ccccc1 Chemical compound CC(C)(O[Cr](=O)(=O)OC(C)(C)c1ccccc1)c1ccccc1 DNNANASOSZKKIS-UHFFFAOYSA-N 0.000 description 1
- QEYLDKWOZQLWNL-UHFFFAOYSA-N CCC(C)(C)O[Cr](=O)(=O)OC(C)(C)CC Chemical compound CCC(C)(C)O[Cr](=O)(=O)OC(C)(C)CC QEYLDKWOZQLWNL-UHFFFAOYSA-N 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- 229910020647 Co-O Inorganic materials 0.000 description 1
- 229910020704 Co—O Inorganic materials 0.000 description 1
- 229910002480 Cu-O Inorganic materials 0.000 description 1
- 229910002588 FeOOH Inorganic materials 0.000 description 1
- 230000010718 Oxidation Activity Effects 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 239000004113 Sepiolite Substances 0.000 description 1
- 241000705939 Shortia uniflora Species 0.000 description 1
- 229910009203 Y-Ba-Cu-O Inorganic materials 0.000 description 1
- MCMNRKCIXSYSNV-UHFFFAOYSA-N ZrO2 Inorganic materials O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 1
- 229910007746 Zr—O Inorganic materials 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- YOGFUEYUFUYXLT-UHFFFAOYSA-N acetyl acetate;chromium Chemical compound [Cr].CC(=O)OC(C)=O YOGFUEYUFUYXLT-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 239000003242 anti bacterial agent Substances 0.000 description 1
- FPCJKVGGYOAWIZ-UHFFFAOYSA-N butan-1-ol;titanium Chemical compound [Ti].CCCCO.CCCCO.CCCCO.CCCCO FPCJKVGGYOAWIZ-UHFFFAOYSA-N 0.000 description 1
- BSDOQSMQCZQLDV-UHFFFAOYSA-N butan-1-olate;zirconium(4+) Chemical compound [Zr+4].CCCC[O-].CCCC[O-].CCCC[O-].CCCC[O-] BSDOQSMQCZQLDV-UHFFFAOYSA-N 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 229910010293 ceramic material Inorganic materials 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 238000013375 chromatographic separation Methods 0.000 description 1
- UZEDIBTVIIJELN-UHFFFAOYSA-N chromium(2+) Chemical compound [Cr+2] UZEDIBTVIIJELN-UHFFFAOYSA-N 0.000 description 1
- WFOOTRPLCMPWIP-UHFFFAOYSA-K chromium(3+) pentanoate Chemical compound [Cr+3].CCCCC([O-])=O.CCCCC([O-])=O.CCCCC([O-])=O WFOOTRPLCMPWIP-UHFFFAOYSA-K 0.000 description 1
- LJAOOBNHPFKCDR-UHFFFAOYSA-K chromium(3+) trichloride hexahydrate Chemical compound O.O.O.O.O.O.[Cl-].[Cl-].[Cl-].[Cr+3] LJAOOBNHPFKCDR-UHFFFAOYSA-K 0.000 description 1
- PYXSPTLIBJZHQW-UHFFFAOYSA-K chromium(3+);propanoate Chemical compound [Cr+3].CCC([O-])=O.CCC([O-])=O.CCC([O-])=O PYXSPTLIBJZHQW-UHFFFAOYSA-K 0.000 description 1
- WYYQVWLEPYFFLP-UHFFFAOYSA-K chromium(3+);triacetate Chemical compound [Cr+3].CC([O-])=O.CC([O-])=O.CC([O-])=O WYYQVWLEPYFFLP-UHFFFAOYSA-K 0.000 description 1
- QOWZHEWZFLTYQP-UHFFFAOYSA-K chromium(3+);triformate Chemical compound [Cr+3].[O-]C=O.[O-]C=O.[O-]C=O QOWZHEWZFLTYQP-UHFFFAOYSA-K 0.000 description 1
- JOPOVCBBYLSVDA-UHFFFAOYSA-N chromium(6+) Chemical class [Cr+6] JOPOVCBBYLSVDA-UHFFFAOYSA-N 0.000 description 1
- GRWVQDDAKZFPFI-UHFFFAOYSA-H chromium(III) sulfate Chemical compound [Cr+3].[Cr+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O GRWVQDDAKZFPFI-UHFFFAOYSA-H 0.000 description 1
- 229910052681 coesite Inorganic materials 0.000 description 1
- 238000004040 coloring Methods 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 229910052593 corundum Inorganic materials 0.000 description 1
- 229910052906 cristobalite Inorganic materials 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- JRBPAEWTRLWTQC-UHFFFAOYSA-N dodecylamine Chemical compound CCCCCCCCCCCCN JRBPAEWTRLWTQC-UHFFFAOYSA-N 0.000 description 1
- 238000000921 elemental analysis Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 230000005281 excited state Effects 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 238000010304 firing Methods 0.000 description 1
- 238000005469 granulation Methods 0.000 description 1
- 230000003179 granulation Effects 0.000 description 1
- 230000005283 ground state Effects 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 150000004677 hydrates Chemical class 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 229910001507 metal halide Inorganic materials 0.000 description 1
- 150000005309 metal halides Chemical class 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 239000002808 molecular sieve Substances 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 150000002823 nitrates Chemical class 0.000 description 1
- 230000018537 nitric oxide storage Effects 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical compound CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000012552 review Methods 0.000 description 1
- 235000019355 sepiolite Nutrition 0.000 description 1
- 229910052624 sepiolite Inorganic materials 0.000 description 1
- 150000004760 silicates Chemical class 0.000 description 1
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000002594 sorbent Substances 0.000 description 1
- 229910052682 stishovite Inorganic materials 0.000 description 1
- 239000011232 storage material Substances 0.000 description 1
- XTQHKBHJIVJGKJ-UHFFFAOYSA-N sulfur monoxide Chemical class S=O XTQHKBHJIVJGKJ-UHFFFAOYSA-N 0.000 description 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- UQMOLLPKNHFRAC-UHFFFAOYSA-N tetrabutyl silicate Chemical compound CCCCO[Si](OCCCC)(OCCCC)OCCCC UQMOLLPKNHFRAC-UHFFFAOYSA-N 0.000 description 1
- LFQCEHFDDXELDD-UHFFFAOYSA-N tetramethyl orthosilicate Chemical compound CO[Si](OC)(OC)OC LFQCEHFDDXELDD-UHFFFAOYSA-N 0.000 description 1
- ZUEKXCXHTXJYAR-UHFFFAOYSA-N tetrapropan-2-yl silicate Chemical compound CC(C)O[Si](OC(C)C)(OC(C)C)OC(C)C ZUEKXCXHTXJYAR-UHFFFAOYSA-N 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- VXUYXOFXAQZZMF-UHFFFAOYSA-N titanium(IV) isopropoxide Chemical compound CC(C)O[Ti](OC(C)C)(OC(C)C)OC(C)C VXUYXOFXAQZZMF-UHFFFAOYSA-N 0.000 description 1
- WOZZOSDBXABUFO-UHFFFAOYSA-N tri(butan-2-yloxy)alumane Chemical compound [Al+3].CCC(C)[O-].CCC(C)[O-].CCC(C)[O-] WOZZOSDBXABUFO-UHFFFAOYSA-N 0.000 description 1
- 229910052905 tridymite Inorganic materials 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- 229910001845 yogo sapphire Inorganic materials 0.000 description 1
Images
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- Exhaust Gas Treatment By Means Of Catalyst (AREA)
- Inorganic Compounds Of Heavy Metals (AREA)
- Solid-Sorbent Or Filter-Aiding Compositions (AREA)
- Silicon Compounds (AREA)
- Catalysts (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は、窒素酸化物吸着剤として用いられる多孔質含クロム酸化物粒子及びその製造方法に関するものである。
【０００２】
【従来の技術】
種々の燃焼器、エンジン、化学プロセスから環境中に排出される窒素酸化物は、健康被害や光化学スモッグ等様々な環境被害を引き起こしている。排ガス処理技術としては触媒を用いた分解技術が主に検討されているが、現状では反応ガス中のＳＯxや水分等の共存物質による触媒の機能低下や、反応により生成する酸素や反応ガス中に含まれる酸素によって触媒活性が大きく阻害されてしまう等の理由から実用的な浄化プロセスへの適用が困難となっている。
この課題を克服し、低コストで革新的な環境浄化プロセスを開発するための一つの方法として、選択的・高効率な吸着現象を積極的に組み入れ、窒素酸化物を分離濃縮できる吸着材料を用いることが考えられる。
【０００３】
ＮＯ吸着剤として、これまでに活性炭、ゼオライト、種々の酸化物並びに複合酸化物等が知られているが、実用化には多くの克服すべき課題が残されている。
例えば、最近の総説（Machida, M.「Solid Sorbents for Catalytic NOx Removal」，In Catalysis，The Royal Society of Chemistry，Cambridge, 2000, Vol.15, pp.73-97.）等によれば、（１）活性炭では、アルカリを担持したものを使用して、予めＯ３でＮＯをＮＯ２かそれ以上の高次酸化物に酸化して、中和吸収させる方法が検討されてきた。しかし、Ｏ３添加の制御、過剰Ｏ３の除去等の煩雑さが克服すべき課題である。また、繊維状活性炭のマイクロ孔入り口付近にＦｅＯＯＨやＦｅ２Ｏ３を分散させたものは常温付近で高いＮＯ吸着能を示すことが報告されているが、酸化能力は有していない。
また、（２）ゼオライトではＣｕや種々の金属イオンでイオン交換したＺＳＭ型が良く知られているが、空気中、特に水蒸気存在下ではＮＯ吸着能は認められていない。
さらに、（３）Ｙ−Ｂａ−Ｃｕ−Ｏ系、Ｂａ−Ｃｕ−Ｏ系、Ｙ−Ｓｒ−Ｃｏ−Ｏ系、Ｂａ−Ａｌ−Ｏ等では酸素雰囲気下でＮＯ吸着能を有するが、レア・アース金属やアルカリ（土類）金属がＣＯ２と反応して表面に炭酸塩が生じ失活してしまう。
一方、（４）Ｍｎ−Ｚｒ−Ｏ系、Ｐｔ/Ｚｒ−Ａｌ−Ｏ系、Ｐｄ/ＺｒＯ２系等ではＣＯ２による障害は無く、ＮＯは容易にＮＯ２として吸着されるが、ＮＯ吸着能試験は１５０℃以上の高温でのみ行われている。
最近では、（５）Ｍｎ−Ｃｅ−Ｏ系酸化物が室温で高ＮＯ吸着能を示すことが報告されているが、比表面積等が１００ｍ２／ｇ以下と小さく、実用化に向けては更なる検討が必要である。
【０００４】
上記の通り、これまでにＮＯ吸着剤に関しては、多くの研究成果が公表されているが、常温付近の低温吸着に関する研究例は極めて少なく、また空気と混合したＮＯガスを対象とした吸着試験もほとんど行われていない。
上記の中で比較的高ＮＯ吸着能を示す（３）〜（５）の酸化物系ＮＯ吸着剤では、２種類以上の金属元素の組合せによって高い吸着性能が認められている。当該酸化物の表面に存在する金属元素がＮＯの吸着サイトであるが、比表面積が小さく、原料である金属元素を多量に必要とする。また、従来のＮＯ吸着剤は、製造方法から粉末状で得られる場合がほとんどで、実際に吸着剤として用いるには造粒操作等の２次加工が必要である。
【０００５】
更に、特開２００１−２４０９号公報には、球形状含シリカ多孔体を製造するに当たり、アルコキシランと１−アルキルアミンとの混合液に、撹拌しながら、酸性水溶液を添加し、次いで生成した球形状粒子／１−アルキルアミン複合物を取り出し、その後この複合体より１−アルキルアミンを除去することを特徴とする球形状含シリカ多孔体の製造方法及び多数のシリカ微粒子の集合体から構成される直径５ミクロン以上３００ミクロン以下の球形状粒子よりなり、多数の細孔を有することを特徴とする球形状含シリカ多孔体が記載されている。
【０００６】
更にまた、本発明者は、水混和性有機溶媒、アルキルアミン及びケイ酸エステル或いはケイ酸エステルと水混和性有機溶媒に可溶な金属塩との組合せを含む混合液に、攪拌下に水或いは酸性水溶液を添加し、生成するシリカ−アルキルアミン複合生成物を球状粒子に成長させ、球状粒子中のアルキルアミンを除去して得られる球状多孔質シリカ乃至シリカ金属複合体粒子を合成した。（特許出願中）
【０００７】
【発明が解決しようとする課題】
本発明者らは、全く新規な特性、即ち窒素酸化物に対して吸着性を有し、一酸化窒素に対して酸化性を有する含クロム酸化物の合成に成功した。本発明の目的は、多孔性であり、比較的大きい比表面積と微細孔とを有し、吸着性と酸化性とを有する含クロム酸化物からなる窒素酸化物吸着剤及び、この含クロム酸化物の製造方法を提供することにある。
【０００８】
【課題を解決するための手段】
アルキルアミンとこのアルキルアミンを取り囲むクロム酸化物或いは更にシリカ及び／又は他の多価金属酸化物の規則的配列とからなり且つ回折角２θ＝１．０乃至５．０度にＸ線回折（ＣｕＫα）ピークを有する複合体からアルキルアミンの少なくとも一部を除去することにより得られる含クロム酸化物であって、下記式（１）
ａＳｉＯ２・ｂＭ１Ｏｍ／２・Ｍ２Ｏｎ／２ ‥（１）
式中、
Ｍ２はＣｒを表し、
Ｍ１はＳｉ，Ｃｒ以外の多価金属元素を表し、
ｎはＣｒの価数であり、
ｍは多価金属の価数であり、
ａはゼロを含む４８５以下の数であり、
ｂはゼロを含む２未満の数である、
で表される金属酸化物基準組成を有し、更に５ｍ ２ ／ｇ以上のＢＥＴ比表面積と微細孔とを有する含クロム酸化物からなることを特徴とする窒素酸化物吸着剤が提供される。本発明で用いる含クロム酸化物は、ＮＯ吸着性を有すること、及びＮＯのＮＯ２への酸化性を有することも顕著な特徴である。
本発明で用いる含クロム酸化物（以下、本発明の含クロム酸化物と呼ぶことがある）においては、
１．アルキルアミンもしくはその分解生成物の含有量が０．２重量％以下であること、
２．前記微細孔がマイクロポア及び／又はメソポアであること、
３．細孔径１０乃至５０オングストロームに０．０５ｍｌ／ｇ以上の細孔容積を有すること、
４．前記式（１）において、ａが０乃至２５０の数であること、
が好ましい。
本発明によればまた、水混和性有機溶媒、アルキルアミン及び水混和性有機溶媒に可溶なクロム化合物或いは更にケイ酸エステルを含む混合液に、攪拌下に水或いは酸性水溶液を添加し、生成するアルキルアミン複合分解生成物粒子を成長させ、粒子中のアルキルアミンを除去することを特徴とする、窒素酸化物吸着剤として用いられる含クロム酸化物の製造方法が提供される。
本発明の製造方法においては、
１．ケイ酸エステルをＣｒ元素１モル当たり０乃至４８５のモル比で用いること、
２．アルキルアミンをＣｒ元素１モル当たり４乃至１６６モルの量で用いること、
３．水混和性有機溶媒をＣｒ元素１モル当たり１５乃至５７２モルの量で用いること、
４．水をＣｒ元素１モル当たり８０乃至１８３００モルの量で添加すること、
５．酸をＣｒ元素１モル当たり３３モル以下の量で用いること、
６．水混和性有機溶媒が１価乃至多価のアルコールであること、
７．ケイ酸エステルが炭素数が１乃至４のアルコールのケイ酸エステルであること、
が好ましい。
【０００９】
【発明の実施の形態】
酸化クロムとしては、２価、３価、６価クロムの化合物が最も普通に知られ、そのほか４価、５価化合物及び混合酸化物が知られているが、本発明者らの知る限り、ＮＯに対して吸着性を示し、またＮＯのＮＯ２への酸化作用を示すクロム酸化物は知られていない。また、公知のクロム酸化物は、比表面積が非常に小さく、ＢＥＴ比表面積は測定不能な程度である。
【００１０】
これに対して、本発明の金属酸化物基準組成で表した含クロム酸化物は、下記式（１）
ａＳｉＯ２・ｂＭ１Ｏｍ／２・Ｍ２Ｏｎ／２ ‥（１）
式中、Ｍ２はＣｒを表し、Ｍ１ はＳｉ，Ｃｒ以外の多価金属元素を表
し、
ｎはＣｒの価数であり、ｍは多価金属の価数であり、
ａはゼロを含む４８５以下の数、好適には０乃至２５０、最も好適には０
乃至１１０であり、
ｂはゼロを含む２未満の数である、
で表され、クロムの価数は、３乃至６の値をとる。
１．ａ＞０の場合は、クロムの含有量が少ない時（１０＜ａ≦４８５）には球形状を示し（実施例１）、特に窒素酸化物検知用のインジケータ素材として有用である。一方、クロムの含有量が多くなるに従って（０＜ａ≦１０）形状の規則性は低下する傾向であるが、窒素酸化物に対する吸着性に関して、最も好適となる（その一例として実施例２）。それぞれの粒子形態を図１のＳＥＭ像に示す。また、アルキルアミン等の有機成分を完全に除去した場合、シリカ成分が共存することで細孔構造は破壊されず、比表面積は６００乃至１２００ｍ２／ｇと大きいことが特徴である。
２．ａ＝０の場合、ＢＥＴ比表面積が５ｍ２／ｇ以上、特に１０ｍ２／ｇ以上が好ましい。また、アルキルアミン等の有機成分の大部分を除去することによって２００ｍ２／ｇ以上のＢＥＴ比表面積を有することが特徴である。有機成分あるいはその分解生成物、具体的にはアルキルアミンあるいはその分解生成物は０．２重量％以下、好ましくは０．１重量％以下で、ＤＴＡ曲線上４００℃付近に発熱ピークとして認められる場合もある。（図８；実施例３）また、形状に関しては、シリカ成分を含まないため、上記同様規則性はほとんど失われてしまう。
以上の特徴により、本発明の含クロム酸化物は、ＮＯに対して優れた吸着性を示し、また吸着したＮＯのＮＯ２への酸化作用にも優れている。更に、本発明の含クロム酸化物に窒素酸化物を吸着させた後、それを３５０℃以上の温度、特に本発明のクロム酸化物の合成加熱処理の温度で焼成することにより再生でき繰り返し使用することができる。また、窒素酸化物は、硝酸等として回収することができる。
ＮＯに対する吸着性能は、次の方法で評価することができる。
【００１１】
本発明の含クロム酸化物のＮＯ吸着性能の評価は、島津 NOA-7000型ＮＯx分析計を少流量用に改良したものを使用した。本分析装置は、ＮＯとオゾンによる化学発光反応を利用してＮＯ濃度を測定する装置である。具体的には、ＮＯとオゾンを反応させて励起状態となったＮＯ２ ＊が再び基底状態に戻るときに発生する光（波長590〜2500nm）の強度を半導体光電素子で測定し、この光強度をＮＯ濃度に換算する。またＮＯ２を等しいモル数のＮＯに変換できるＮＯ２−ＮＯコンバーターを備えており、間接的にＮＯ２濃度の測定も可能である。分析対象ガスはＮＯおよびＮＯx（ＮＯ＋ＮＯ２）の二種類であり、どちらか一方の測定モードを選択して別々に測定する。
マスフロー制御ガス混合器を用いて、０．１％ ＮＯに乾燥空気を混合して作製した約１００ｐｐｍのＮＯガスを、約１００ｍｌ／ｍｉｎの流量に調製した流通反応系で、サンプルカラムに０．０４ｇ充填した試料のＮＯ吸着特性並びにＮＯ２への酸化特性を室温下において破過曲線測定によって評価した。
図２にその一例を示す。本発明の含クロム酸化物は室温においてＮＯ吸着能を示し、測定開始からある一定時間ＮＯ濃度は０ppmを保つことが分かる。この０ｐｐｍを保持する吸着挙動を初期吸着と定義する。一方、ＮＯ濃度が上昇するより前に、ＮＯｘ（ＮＯ+ＮＯ２）の発生が認められ、さらにＮＯｘ濃度は急激に上昇して、ＮＯ濃度を大きく上回る。このことは、吸着されたＮＯがＮＯ２に酸化されることを示しており、本発明の含クロム酸化物が窒素酸化物に対して吸着能と酸化能を併せ持つことを明示するものである。
更に、本発明による含クロム酸化物（式（１））で、ａ＞０の場合は実施例１（図６）から明らかなようにクロム含有量が多くなるほどＮＯの吸着容量が大きくなることが分かる。また、ａ＝０の場合、実施例３（図９）のＮＯ破過曲線から１５分後においてもＮＯは検出されず、ＮＯ２への酸化が長時間持続することが分かる。
また、本発明による含クロム酸化物は、窒素酸化物中にイオウ酸化物（SOx)が含まれていても、窒素酸化物の吸着及び酸化能に影響を及ぼさない。具体的には、100ppmのNOガスに20ppmのSO２を含むガスに本発明による含クロム酸化物（実施例１−２）のものを接触させた場合、NO破過曲線はSO２を含まない場合とほぼ重なり窒素酸化物に対する選択性が大きいことが分かった（図１５）。更にまた本発明の含クロム酸化物は、大気中の水分にも影響されない。
本吸着及び酸化現象は、空気中室温下で適度に吸湿した試料でも認められ、このような雰囲気下ではＣｕ-ＺＳＭ型ゼオライトがＮＯ吸着能を全く示さないことと大きな相違点となっている（比較例２；図１１）。
【００１２】
また、市販の酸化クロム（Ｃｒ２Ｏ３）は窒素酸化物に対して全く吸着性を示さないのに対して（比較例３；図１２）、本発明のシリカを含まない含クロム酸化物は優れた吸着性を示しており（実施例３；図９）、本発明による予想外の効果が明らかとなる。
【００１３】
本発明の含クロム酸化物が１次粒子内に微細孔を有しており、この微細孔が吸着活性及び酸化活性のサイトとなることは既に指摘したが、本発明の含クロム酸化物は細孔径１０乃至５０オングストロームに０．０５ｍｌ／ｇ以上、好ましくは０．０７ｍｌ／ｇ以上の細孔容積を有することが、吸着性や酸化作用の点で望ましい。
【００１４】
本発明の含クロム酸化物は、アルキルアミンとこのアルキルアミンを取り囲むクロム酸化物或いは更にシリカや他の多価金属との複合体が規則的配列を有し且つ回折角２θ＝１．０乃至５．０度にＸ線回折（ＣｕＫα）ピークを有する複合体（前駆体或いはナノ複合体とも呼ぶ）の脱アルキルアミン物（例えば前駆体を直接加熱処理して得られる焼成物、あるいは前駆体を酸性水溶液乃至エタノールと酸性水溶液との混合溶液により抽出処理して得られる生成物）からなることが、微細孔の形成及び保持のために好ましい。
【００１５】
本発明の含クロム酸化物の前駆体となるアルキルアミンとのナノ複合粒子は、回折角２θ＝１．０乃至５．０度にＸ線回折（ＣｕＫα）ピークを有するメソ構造体であることが特徴であり、この特徴により、本発明の含クロム酸化物は微細孔を保持しているのである。
【００１６】
図３は、本発明の含クロム酸化物の前駆体である（ａ）Ｃｒを含むシリカメソ構造体（実施例１−２）と、（ｂ）Ｓｉを含まないクロム酸化物メソ構造体（実施例３）のＸ線回折図であり、底面反射の存在は細孔を与える無機骨格の配列が規則的であることを示している。
また、図４は、図３（ａ）の６００℃加熱処理生成物、（ｂ）の３５０℃加熱処理生成物に対応する窒素吸着等温線である。前者にはHorvath-Kawazoe法、後者にはＢＪＨ法を適用して求めた細孔系分布曲線から、細孔直径のピーク値は（ａ）２ｎｍ、（ｂ）２．４ｎｍであり、シャープな分布を示すことが分かった。
本発明の含クロム酸化物は、アルキルアミンと無機溶存種との協調的秩序形成能により生成するメソ構造体を前駆体とすることによって、前駆体に含まれる有機化合物を加熱処理等により除去し、多孔性を賦与したことが特徴である。
【００１７】
本発明の含クロム酸化物は、水混和性有機溶媒、アルキルアミン及び水混和性有機溶媒に可溶なクロム化合物或いは更にケイ酸エステルを含む混合液を攪拌したり、あるいは攪拌下に水或いは酸性水溶液を添加し、アルキルアミンと無機イオン種との協調的秩序形成能により生成するメソ構造体であるアルキルアミン複合分解生成物を前駆体として成長させ、アルキルアミンを除去することにより得られる。
【００１８】
本発明の含クロム酸化物の製造法の概略機構は以下の様に推定され、その生成機構モデルを図５に示す。
例えば、塩化クロム・６水和物をアルコールに溶解すると、Ｃｒ元素がアルコールと反応して一部アルコキシド化すると同時にプロトンが生成して正電荷を有するクロム溶存種（Ｉ＋）が生成する。
この溶液にアルキルアミンを添加すると、アミン中のＮＨ２基は瞬時にＮＨ３ ＋（Ｓ＋）に変化して、塩素イオン（Ｘ−）を媒介としてＳ＋Ｘ−Ｉ＋の規則構造体が生成する。なお、Ｓｉを含む系ではＩ＋がＳｉと金属元素との複合化した溶存種となる。Ｓ＋Ｘ−Ｉ＋が核となって成長する１次粒子はＳ＋Ｘ−Ｉ＋の集合したメソ構造体であり、さらにこの１次粒子間の衝突により粒子成長して最終的に、金属元素の添加割合が低い場合にはミクロンオーダーのマクロ形態を有する球状粒子が生成し易くなる。
無機骨格を取巻く有機成分を加熱等の処理により除去することで得られる最終生成物は、メソ構造体に由来した細孔構造を有する多孔性粒子となる。ＮＯの吸着サイトはＣｒ元素であり、ＮＯに対する高吸着性能を達成するためには、無機骨格中にＣｒを高分散させＮＯとの接触を効率的に行うことが必要である。
上記生成機構に基づいて製造された本ＮＯ吸着剤は、粒子内部に生成する細孔に基づいた多孔性物質であり、ＮＯを効果的に吸着する能力を発する。
【００１９】
本製造法は、用いるアルキルアミン中の炭素数によって細孔径が容易にコントロール可能なことはもとより、窒素酸化物吸着剤の前駆体となるメソ構造体を、常温常圧下、８０分以内で製造できる。
また、攪拌速度、酸濃度あるいはアルコールの添加割合により粒子径の制御が可能となる。
【００２０】
本発明で使用される水混和性有機溶媒、アルキルアミン及び水混和性有機溶媒に可溶な金属化合物（金属塩並びに金属アルコキシド）或いは更にケイ酸エステルについて更に説明する。
【００２１】
本発明で使用するシリカ原料としてのケイ酸エステルとしては、Ｓi-アルコキシドで、テトラメチルオルトシリケート、テトラエチルオルトシリケート、テトライソプロピルオルトシリケート、テトラ-ｎ-ブチルオルトシリケート等を用いることが可能で好ましくはテトラエチルオルトシリケート（以下ＴＥＯＳと略す）を使用する。
【００２２】
アルコールとしては、メタノール、エタノール、プロパノール、ブタノール等を用いることができ、好ましくはエタノールを使用する。
【００２３】
アルキルアミンとしては、直鎖アルキルアミンが好ましく、カーボン数８〜１８のものが使用され、比較的廉価で常温において溶液状態にあるオクチルアミンとドデシルアミンが好ましい。
【００２４】
金属種としては、Ｃｒ或いはＳｉの他に、Ｔｉ、Ｚｒ、Ａｌ、Ｆｅ、Ｚｎ、Ｍｎ、Ｃｏ、Ｃｕ、Ｎｉ、Ｖ、Ｓｎ、Ｃｅ等の１種類あるいは複数を同時に用いることができる。
水混和性有機溶媒に可溶な金属塩としては、上記金属のハロゲン化物、硝酸塩、硫酸塩、炭酸塩やその水和物等アルコールに可溶な全ての金属塩を使用することができる。
また、金属アルコキシドとしては、Ｔｉではテトラエチルオルトチタネート、テトライソプロピルオルトチタネート、テトラ-ｎ-ブチルオルトチタネート等の使用が可能であり、好ましくはテトラエチルオルトチタネートを用いる。Ｚｒの場合には、ジルコニウムテトラ-ｎ-ブトキシド溶液（１-ブタノールに８０ｗｔ％溶解させた溶液；ＴＢＯＺと略す）、また、Ａｌの場合にはアルミニウム-トリ-sec-ブトキシド等を使用できる。
【００２５】
また、クロム化合物としては、クロム塩、クロム酸塩、あるいはクロムカルボン酸塩、クロム−１,３−ジケト化合物、クロム酸エステル、クロム酸アミド等が挙げられ、具体的には、塩化クロム、硝酸クロム、硫酸クロム、重クロム酸カリウム、重クロム酸ナトリウム、酢酸クロム、ギ酸クロム、プロピオン酸クロム、ペンタン酸クロム、ヘキサカルボニルクロム、クロムアセチルアセテート、クロム−１,３−ブタンジオネート、ビス（tert-ブチル)クロメート、ビス（1,1-ジメチルプロピル）クロメート、ビス（2-フェニル-2-プロピル）クロメート、ビス（ビストリメチルシリルアミド）クロム（II)-THF錯体等が挙げられる。
【００２６】
酸としては、塩酸、硝酸、硫酸、酢酸等を使用することができる。
【００２７】
本発明の含クロム酸化物の合成において、出発原料の混合モル比は、金属元素：ＴＥＯＳ：１−アルキルアミン：アルコール：酸：水＝１：０〜４８５：４〜１６６：１５〜５７２：０〜３３：８０〜１８３００である。
さらに出発原料の混合方式を詳細に記述すると、ＴＥＯＳを使用する場合には、▲１▼ＴＥＯＳとアルコールに溶解した金属塩との混合溶液に、アルキルアミンを加えるか、あるいは▲２▼ＴＥＯＳとアルキルアミンとの混合溶液に、アルコールに溶解した金属塩を加え、いずれの場合も１分から２０分間攪拌し、さらに攪拌を続けながら水あるいは酸性水溶液を添加し、充分な混合状態を保持しながら、室温で８０分以内好ましくは１０〜６０分程度反応させる。また、ＴＥＯＳを用いない場合には、予めアルコールに溶解した金属塩を攪拌しながら溶液状態を保持した状態で、アルキルアミンを加え１分から２０分間攪拌し、さらに攪拌を続けながら水あるいは酸性水溶液を添加し、充分な混合状態を保持しながら、室温で８０分以内好ましくは１０〜６０分程度反応させる。
出発原料の混合モル比は、好ましくは、金属元素：ＴＥＯＳ：１−アルキルアミン：アルコール：酸：水＝１：０〜２５０：４〜９０：１５〜３００：０〜１０：８０〜９５００である。
【００２８】
上記いずれの場合も、反応後懸濁液から固体生成物を分離し、室温〜１００℃で充分乾燥させる。
最後に有機成分を除去して含クロム酸化物を作製するために、例えば３００℃以上で３０分間以上、好ましくは３２０℃以上で１時間加熱処理する。
【００２９】
（用途）
本発明の含クロム酸化物は、必要に応じて顆粒状、棒状、ペレット状、ハニカム状にして、窒素酸化物の吸着・吸蔵剤また酸化剤や分解除去剤、あるいは窒素酸化物検知用のインジケータ用素材（具体的には、２０ppm以下のＮＯガスを接触させることにより本発明の含クロム酸化物は、淡黄色から褐色に変化する）、さらには種々の形状選択性酸化触媒、例えば、ポリエチレン製造用酸化触媒等として、また有用イオン・分子の吸着・分離・貯蔵剤、また有害イオン・分子の吸着・分離さらには分解用触媒或いは触媒担体として、工業および環境保全に有用な材料などに適している。
本発明の含クロム酸化物は、種々の酸化触媒として使用され、用途に応じてゼオライト、セピオライト、抗菌剤、光反応性半導体、等を組み合わせて使用できる。また、塗料に添加して窒素酸化物吸着能をもつ塗料、更にはディーゼルエンジン排ガス中の窒素酸化物の処理、コージェネレーション、トンネル等での排ガス処理等に用いることができる。
【００３０】
【実施例】
次に、本発明を実施例によって更に具体的に説明するが、本発明はこの実施例によって限定されない。
尚、実施例で行った各試験方法は次の方法により行った。
【００３１】
（測定法）
（１）走査型電子顕微鏡：日本電子製ＪＳＭ５３００を使用し、加速電圧１０ｋＶ、ＷＤ１０ｍｍで観察した。
（２）比表面積・細孔径分布：日本ベル製ＢＥＬＳＯＲＰ２８を使用し、液体窒素温度で測定した窒素吸着等温線からＢＥＴ比表面積を求め、細孔径分布はＭＰ法、Horvath-Kawazoe法並びにＢＪＨ法により解析した。
（３）粒径：ベックマン・コールター製粒度分布測定装置コールターＬＳ２３０によって測定した。
（４）形状：走査型電子顕微鏡写真から観察した。
（５）Ｘ線回折：リガク製ロータフレックスＲＵ−３００を使用し、ＣｕＫα線源、加速電圧４０ｋＶ、８０ｍＡで測定した。
（６）ＮＯ破過曲線測定：島津NOA-7000型NOx分析計を使用し測定した。
（７）化学組成分析：シリカ（ＳｉＯ２）分はアルカリ溶融法により測定し、Ｃｒについてはアルカリ溶融後原子吸光法により測定した。
（８）熱分析：リガク製熱分析装置ＴＧ８１２０を用いて、ＴＧ−ＤＴＡ測定を行った。
（９）元素分析：住化分析センター製ＮＣＨ定量装置スミグラフＮＣＨ−２１型を使用した。
【００３２】
（実施例１）
ＴＥＯＳを６００rpmで攪拌し、エタノールに溶解したＣｒＣｌ３・６Ｈ２Ｏを添加後、オクチルアミンを加え１０分間攪拌した後、塩酸水溶液を加え、さらにそのまま１時間攪拌する。混合溶液のモル比は表１にそれぞれ示したとおりである。反応後懸濁液から固体生成物を濾別し、５０℃で充分乾燥させた後、６００℃で１時間加熱して有機成分を除去して含クロム酸化物を作製する。
表１に出発原料組成、及び表２にそれぞれの合成条件で作製した含クロム酸化物のＣｒ／Ｓｉモル比、比表面積と細孔形分布曲線から求めたピーク値を細孔径として示す。なお、実施例１−４では明確な細孔径分布曲線は得られず表２は空欄とした。また、粒子はいずれも球形で実施例１−２及び実施例１−３の中位径はそれぞれ３７、４２μｍであった。実施例１−２のＳＥＭ像を図１ａに示した。
ＮＯx分析計(島津製作所製 NOA-7000)を使用して、０．１％ ＮＯに乾燥空気をマスフロー制御ガス混合器で約１００ｐｐｍ に濃度調整したＮＯガスを、室温下約１００ｍｌ／ｍｉｎの流通反応系で、サンプルカラムに、実施例１-２、実施例１-３、実施例１-４の含クロム酸化物試料０．０４ｇを充填し、ＮＯ吸着特性並びにＮＯ２酸化特性を破過曲線測定によって評価した。（なお、測定に当たって各サンプルは加熱処理後空気中に放置し充分に吸湿させた後使用した。）図６にその結果を示す。なお、実施例１−１のＮＯ吸着特性並びにＮＯ２酸化特性に関する破過曲線は図２に示した。
本実施例で記載した含クロム酸化物はいずれも室温において優れたＮＯ吸着能を示し、測定開始からある一定時間ＮＯ濃度は０ppmを保持し（この０ｐｐｍを保持する吸着挙動を初期吸着と呼ぶ）、この保持時間はＣｒの含有量が多いほど長いことが分かる。
さらに、本含クロム酸化物はＣｒ／Ｓｉ比、また前処理条件によって、ＮＯ吸着前には橙色、黄色あるいは鶯色等を呈し、いずれの場合もＮＯ濃度に拠らずＮＯの吸着によって接触部分は瞬時に褐色に変化する。このＮＯ吸着前後の着色の変化を利用して、本含クロム酸化物はＮＯ検知剤あるいはＮＯモニター用インジケータとして使用することが可能である。
【００３３】
（実施例２）
エタノールに溶解したＣｒＣｌ３・６Ｈ２ＯにＴＥＯＳを添加し、さらにオクチルアミンを加え１０分間攪拌した後、水を加え、そのまま１時間攪拌する。混合溶液のモル比はＣｒ：Ｓｉ：オクチルアミン：エタノール：ＨＣｌ：Ｈ２Ｏ ＝ １：１．０２：５．５：１８．６：０：１９７である。反応後懸濁液から固体生成物を遠心分離後、５０℃で充分乾燥させた後、３００℃以上で１時間加熱して有機成分を除去して含クロム酸化物を作製する。表１に出発原料組成、及び表２に４００℃で１時間加熱して得られた含クロム酸化物ののＣｒ／Ｓｉモル比とオクチルアミンもしくはその分解生成物割合、及び比表面積と細孔形分布曲線から求めたピーク値を細孔径として示す。本実施例の含クロム酸化物は図１ｂのＳＥＭ像に示す通り、球形ではなく不規則な形状を呈している。
本実施例の含クロム酸化物のＮＯ破過曲線と、ＮＯx濃度変化を図７に示す。本サンプルは前駆体であるメソ構造体を４００℃、１時間加熱したもので、ＸＲＤ測定の結果Ｃｒ２Ｏ３のピークと、低角（２θ＝５°以下）にはメソ構造の痕跡を示す大きな立ち上がりが認められた。ＮＯ破過曲線から、ＮＯ吸着はＳｉを含む実施例１のサンプル同様、初期吸着挙動を経て極めて徐々に進行し、顕著なＮＯ吸蔵挙動を示すと共に、ＮＯ２の発生も緩慢で、本サンプルは酸化能力も極めて高いことが分かる。（測定に当たっては、特に吸湿させることなく空気中に放置したものを使用した。）
また、図７中には、加熱処理温度がＮＯ破過曲線に及ぼす影響を示した。前駆体であるメソ構造体を３５０℃と６００℃でそれぞれ１時間加熱したもので、６００℃では細孔構造の破壊によって著しく機能低下することが明らかである。この結果が示すように、メソ構造体から有機物を取り除くための適切な加熱処理温度はＣｒ含有量に依存することが分かる。
【００３４】
（実施例３）
エタノールに溶解したＣｒＣｌ３・６Ｈ２Ｏに、オクチルアミンを加え１０分間攪拌した後、水を加え、さらにそのまま１時間攪拌する。混合溶液のモル比はＣｒ：Ｓｉ：オクチルアミン：エタノール：ＨＣｌ：Ｈ２Ｏ ＝ １：０：５．４：１８．６：０：１９７である。反応後懸濁液から固体生成物を遠心分離後、５０℃で充分乾燥させた後、有機成分を加熱除去して含クロム酸化物を作製する。
表１に出発原料組成、及び表２に３５０℃で１時間加熱して得られた含クロム酸化物のオクチルアミンもしくはその分解生成物と、比表面積及び細孔形分布曲線から求めたピーク値を細孔径として示す。なお、図８の熱分析曲線上４００℃付近に発熱ピークが認められることから、本含クロム酸化物中の残留分はアミン等の有機物あるいはその分解生成物等として存在すると考えられる。
ＸＲＤ測定の結果、本含クロム酸化物試料には、Ｃｒ２Ｏ３のピークと、低角（２θ＝５°以下）にはメソ構造の痕跡を示す大きな立ち上がりが認められた。
本実施例の含クロム酸化物のＮＯ破過曲線と、ＮＯx濃度変化を図９に示す。（測定に当たっては、特に吸湿させることなく空気中に放置したものを使用した。）ＮＯ破過曲線から、ＮＯ吸着はＳｉを含む実施例１、実施例２のサンプル同様、初期吸着挙動を経て徐々に進行すると同時に、ＮＯ２の発生も認められることから、本サンプルは酸化能力も極めて高いことが分かる。
【００３５】
（実施例４）
ＴＥＯＳとＴｉ-アルコキシド（テトラエチルオルトチタネート；ＴＥＯＴと略す）とを混合して６００rpmで攪拌し、エタノールに溶解したＣｒＣｌ３・６Ｈ２Ｏを添加後、オクチルアミンを加え１０分間攪拌した後、塩酸水溶液を加え、さらにそのまま１時間攪拌する。混合溶液のモル比はＣｒ：Ｔｉ：Ｓｉ：オクチルアミン：エタノール：ＨＣｌ：Ｈ２Ｏ ＝ １：０．２３：４２．０：１４．４：５０．０：０．７１：１５９３である。反応後懸濁液から固体生成物を濾別し、５０℃で充分乾燥させた後、６００℃で１時間加熱して有機成分を除去して含クロム酸化物を作製する。生成物は球形を呈し、中位径は５１μｍで、ＢＥＴ比表面積は７９５ｍ２／ｇであった。
Ｔｉを含む球形含クロム酸化物のＮＯ破過曲線を測定した結果を図１０に示す。Ｔｉ以外ほぼ同一の出発物質混合比である実施例１-２の結果も図１０に示した。Ｔｉの添加により、初期吸着時間は短縮されるものの、室温において優れたＮＯ吸着能を示し、またＮＯ２への酸化能力を減じる作用をもたらす事が分かる。
【００３６】
（比較例１）
実施例１と同様な方法で製造した、Ｃｒ以外の金属元素、Ａｌ、Ｚｒ、Ｆｅ、Ｍｎ、Ｃｏ、Ｃｕ、Ｎｉ、Ｚｎ、Ｓｎ、Ｃｅを含む多孔質シリカ金属複合体粒子のＮＯ吸着特性を実施例１と同一方法で検討した結果、Ｃｒの場合と顕著な差異が認められ、ＮＯ吸着能を有しないことが分かった。
【００３７】
（比較例２）
４００℃で４時間加熱脱水したＣｕ-ＺＳＭ型ゼオライトのＮＯ破過曲線を図１１に示す。ゼオライトの化学組成はＣｕＯ３．７ｗｔ％、ＳｉＯ２／Ａｌ２Ｏ３モル比３９である。空気と混合した室温条件下においては、Ｃｕ-ＺＳＭ型ゼオライトはＮＯをほとんど吸着することなく、ＮＯ２の発生も全く認められない。また、吸着温度を２００℃及び４００℃とした場合には、初期吸着並びに酸化能は認められず、ＮＯ吸着能だけを有することことが分かった。
本発明の窒素酸化物吸着剤並びに酸化剤が、室温、空気混合条件下で、ＮＯ吸着能と酸化能を併せ持つことと、Ｃｕ-ＺＳＭ型ゼオライトがＮＯ吸着能および酸化能を全く示さないことは顕著な相違点である。
【００３８】
（比較例３）
ＸＲＤ粉末測定でＣｒ２Ｏ３と同定され、さらにそのＢＥＴ比表面積は極めて小さく上記装置では測定不能である市販試薬Ｃｒ２Ｏ３に対するＮＯ破過曲線の結果を図１２に示す。ＮＯ吸着は僅かに認められるものの、初期吸着は認められずしかも酸化能も有していないことが分かった。
本発明の実施例３の窒素酸化物吸着剤並びに酸化剤のＸＲＤ回折パターンは市販酸化第二クロム同様Ｃｒ２Ｏ３の回折ピークが認められるが、図３に示すメソ構造体である中間体を加熱処理して製造しており、表２の通り比表面積280ｍ２／ｇと多孔性を有すること、さらには表面クロム元素の存在状態が市販Ｃｒ２Ｏ３とは異なるものと考えられる。
【００３９】
（比較例４）
実施例１と全く同様の手法、ＴＥＯＳを６００rpmで攪拌し、エタノールに溶解したＣｒＣｌ３・６Ｈ２Ｏを添加後、オクチルアミンを加え１０分間攪拌した後、塩酸水溶液を加え、さらにそのまま１時間攪拌する。ただし、Ｃｒ量が極めて少ない条件で、混合溶液のモル比はＣｒ：Ｓｉ：オクチルアミン：エタノール：ＨＣｌ：Ｈ２Ｏ ＝ １：４８８：１６６：５７５：３３：１８３９０である。反応後懸濁液から固体生成物を濾別し、５０℃で充分乾燥させた後、６００℃で１時間加熱して有機成分を除去して含クロム酸化物を作製する。
図１３に本サンプルのＮＯ破過曲線を実施例１−１と比較して示す。本含クロム酸化物はＮＯ吸着能を全く有しないことはないが、初期吸着はほとんど認められないことが分かる。また、本含クロム酸化物は淡黄色でＮＯ吸着によって僅かに変色が認められるが、本含クロム酸化物単独ではＮＯ検知剤あるいはＮＯモニター用インジケータとして使用することは難しい。
【００４０】
（比較例５）
ＴＥＯＳとＴＥＯＴとを混合して６００rpmで攪拌し、エタノールに溶解したＣｒＣｌ３・６Ｈ２Ｏを添加後、オクチルアミンを加え１０分間攪拌した後、塩酸水溶液を加え、さらにそのまま１時間攪拌する。ただし、実施例４よりもＴｉ量を増加し、混合溶液のモル比はＣｒ：Ｔｉ：Ｓｉ：オクチルアミン：エタノール：ＨＣｌ：Ｈ２Ｏ ＝ １：２：４６：１５．９：５５：０．７９：１７５６である。反応後懸濁液から固体生成物を濾別し、５０℃で充分乾燥させた後、６００℃で１時間加熱して有機成分を除去して含クロム酸化物を作製する。
本Ｔｉを含む球形含クロム酸化物のＮＯ破過曲線を実施例４と比較して図１４に示す。Ｔｉの添加により、ＮＯ吸着能を全く示さないことが分かる。
【００４１】
【表１】
含クロム酸化物の合成条件
【表２】
生成物である含クロム酸化物の特性
【発明の効果】
本発明によれば、高い比表面積と微細孔とを有し、窒素酸化物に対して吸着性を有し、一酸化窒素に対して酸化性を有する含クロム酸化物の合成に成功した。
本発明は、細孔構造の制御剤としてアルキルアミンを使用し、ＴＥＯＳ、アルコールに溶解した金属化合物、および水あるいは酸性水溶液を添加し、反応物質の混合割合、酸性度、またアルキル鎖のカーボン数を変化させることにより、常温、常圧下で含クロム酸化物の前駆体となる界面活性剤を含んだ有機無機ナノ複合体（メソ構造体）を短時間で作製し、最終的に有機物を取除くことにより、Ｓｉの一部をＣｒで置換したり、また骨格外にＣｒ酸化物等として存在する含クロム酸化物の製造方法を提供する。
さらに、アルコールに溶解した金属塩の溶液相に、攪拌下でアルキルアミンと水或いは酸性水溶液を添加し、生成するアルキルアミン複合分解生成物粒子を成長させ、粒子中のアルキルアミンを除去することを特徴とする含クロム酸化物の製造方法を提供する。
しかも、本含クロム酸化物は、窒素酸化物に対する吸着能と酸化能を有することから、窒素酸化物の環境汚染防止対策に有用な反応プロセスに用いることが可能で、さらに種々の酸化反応プロセスにも適用でき、工業および環境保全の両面で有用な分子篩い、触媒担体、触媒さらにはセンサー等の機能性セラミックス素材として活用できる。特に、本発明は、ミクロンオーダーの球状粒子の特性を活かし、固定床ばかりでなく、流動床反応用の化学プロセス用触媒・触媒担体やクロマト分離用カラム充填剤の製造法として価値が高い。さらに、本含クロム酸化物はＣｒ／Ｓｉ比、また前処理条件によって、ＮＯ吸着前には橙色、黄色あるいは鶯色等を呈し、いずれの場合もＮＯ濃度に拠らず、ＮＯの吸着によって接触部分は瞬時に褐色に変化することから、この着色変化を利用した、ＮＯ検知剤あるいはＮＯモニター用インジケータとして使用することが可能である。
【図面の簡単な説明】
【図１】含クロム酸化物粒子、（ａ）実施例１-２、（ｂ）実施例２の走査型電子顕微鏡写真（ＳＥＭ）である。
【図２】実施例１-１の含クロム酸化物のＮＯ吸着特性を示す破過曲線と、ＮＯｘ濃度変化特性を示すグラフである。
【図３】実施例１-２の含クロム酸化物、および実施例３の含クロム酸化物の前駆体であるメソ構造体のＸ線回折パターン図である。
【図４】実施例１-２の含クロム酸化物、および実施例３の含クロム酸化物多孔性粒子の窒素吸着等温線である。
【図５】本発明の含クロム酸化物の生成機構を示す概念図である。
【図６】実施例１-２、実施例１-３、実施例１-４の含クロム酸化物のＮＯ吸着特性を示す破過曲線と、それぞれに対応するＮＯｘ濃度変化特性を示すグラフである。
【図７】実施例２の含クロム酸化物のＮＯ吸着特性を示す破過曲線と、ＮＯｘ濃度変化特性を示すグラフである。
【図８】実施例３の含クロム酸化物の熱分析曲線である。
【図９】実施例３の含クロム酸化物のＮＯ吸着特性を示す破過曲線と、ＮＯｘ濃度変化特性を示すグラフである。
【図１０】実施例４のＴｉを含む含クロム酸化物のＮＯ吸着特性を示す破過曲線と、ＮＯｘ濃度変化特性を示すグラフである。（実施例１-２との比較）
【図１１】比較例２のＣｕ-ＺＳＭ５型ゼオライトのＮＯ吸着特性を示す破過曲線と、ＮＯｘ濃度変化特性を示すグラフである。
【図１２】比較例３の市販酸化第二クロムＣｒ２Ｏ３のＮＯ吸着特性を示す破過曲線である。（実施例３との比較）
【図１３】比較例４の含クロム酸化物のＮＯ吸着特性を示す破過曲線である。（実施例１−１との比較）
【図１４】比較例５のＴｉを含む含クロム酸化物のＮＯ吸着特性を示す破過曲線である。（実施例４との比較）
【図１５】含クロム酸化物（実施例１−２）のＮＯ＋ＳＯ２混合ガス中のＮＯ吸着特性を示す破過曲線である。[0001]
BACKGROUND OF THE INVENTION
The present inventionUsed as nitrogen oxide adsorbentThe present invention relates to porous chromium-containing oxide particles and a method for producing the same.
[0002]
[Prior art]
Nitrogen oxides discharged into the environment from various combustors, engines, and chemical processes cause various environmental damages such as health damage and photochemical smog. As the exhaust gas treatment technology, the decomposition technology using a catalyst is mainly studied. However, at present, the function of the catalyst is deteriorated due to coexisting substances such as SOx and moisture in the reaction gas, and in the oxygen and reaction gas generated by the reaction. Application to a practical purification process is difficult because the catalytic activity is greatly hindered by the contained oxygen.
One method for overcoming this problem and developing an innovative environmental purification process at low cost is to use an adsorption material that can actively incorporate selective and highly efficient adsorption phenomena and separate and concentrate nitrogen oxides. It is possible.
[0003]
As NO adsorbents, activated carbon, zeolite, various oxides and composite oxides have been known so far, but many problems to be overcome remain in practical use.
For example, according to a recent review (Machida, M. “Solid Sorbents for Catalytic NOx Removal”, In Catalysis, The Royal Society of Chemistry, Cambridge, 2000, Vol. 15, pp. 73-97.) ) For activated carbon, use an alkali-supported one in advance.3NO to NO2A method of oxidizing to higher-order oxides and absorbing and absorbing them has been studied. But O3Addition control, excess O3This is a problem that should be overcome. In addition, FeOOH and Fe near the micropore entrance of fibrous activated carbon2O3It is reported that those in which NO is dispersed show a high NO adsorption ability at around room temperature, but do not have an oxidation ability.
In addition, (2) ZSM type ion-exchanged with Cu or various metal ions is well known as zeolite, but NO adsorption ability is not recognized in the air, particularly in the presence of water vapor.
Further, (3) Y—Ba—Cu—O, Ba—Cu—O, Y—Sr—Co—O, Ba—Al—O and the like have NO adsorption ability in an oxygen atmosphere. Earth metals and alkali (earth) metals are CO2Reacts with and forms carbonate on the surface and deactivates.
On the other hand, (4) Mn—Zr—O, Pt / Zr—Al—O, Pd / ZrO2CO2There is no obstacle caused by NO, NO is easily NO2However, the NO adsorption capacity test is conducted only at a high temperature of 150 ° C. or higher.
Recently, it has been reported that (5) Mn—Ce—O-based oxides exhibit high NO adsorption ability at room temperature, but the specific surface area and the like are 100 m.2/ G or less, and further study is necessary for practical use.
[0004]
As described above, a lot of research results have been published so far regarding NO adsorbents, but there are very few examples of low temperature adsorption near normal temperature, and adsorption tests for NO gas mixed with air are also available. Almost never done.
Among the above, in the oxide-based NO adsorbents (3) to (5) that exhibit a relatively high NO adsorption capacity, high adsorption performance is recognized by a combination of two or more metal elements. Although the metal element present on the surface of the oxide is an adsorption site for NO, the specific surface area is small and a large amount of metal element as a raw material is required. Further, most of the conventional NO adsorbents are obtained in powder form from the production method, and secondary processing such as granulation operation is necessary to actually use them as adsorbents.
[0005]
Furthermore, in JP-A-2001-2409, in producing a spherical silica-containing porous material, an acidic aqueous solution is added to a mixed liquid of alkoxylane and 1-alkylamine while stirring, and then the produced spheres are produced. It is composed of a method for producing a spherical silica-containing porous material characterized by removing a shaped particle / 1-alkylamine composite and then removing 1-alkylamine from the composite and an aggregate of a large number of silica fine particles. There is described a spherical silica-containing porous material comprising spherical particles having a diameter of 5 microns or more and 300 microns or less and having a large number of pores.
[0006]
Furthermore, the present inventor has added water or water under stirring to a mixed solution containing a water-miscible organic solvent, an alkylamine and a silicate ester or a combination of a silicate ester and a metal salt soluble in the water-miscible organic solvent. An acidic aqueous solution was added, and the resulting silica-alkylamine composite product was grown into spherical particles, and spherical porous silica or silica metal composite particles obtained by removing the alkylamine in the spherical particles were synthesized. (Patent pending)
[0007]
[Problems to be solved by the invention]
The present inventors have succeeded in synthesizing chromium-containing oxides having completely new characteristics, that is, adsorptivity to nitrogen oxides and oxidizing properties to nitric oxide. An object of the present invention is a chromium-containing oxide which is porous, has a relatively large specific surface area and fine pores, and has adsorptivity and oxidation propertiesNitrogen oxide adsorbent comprisingas well asOf this chromium-containing oxideProvide manufacturing methodThere is.
[0008]
[Means for Solving the Problems]
X-ray diffraction (CuKα) consisting of an alkylamine and a regular arrangement of chromium oxide surrounding this alkylamine or further silica and / or other polyvalent metal oxide and having a diffraction angle of 2θ = 1.0 to 5.0 degrees. ) A chromium-containing oxide obtained by removing at least part of the alkylamine from the complex having a peak,Following formula (1)
aSiO2・ BM1Om / 2・ M2On / 2(1)
Where
M2Represents Cr,
M1Represents a polyvalent metal element other than Si and Cr,
n is the valence of Cr;
m is the valence of the polyvalent metal,
a is a number of 485 or less including zero,
b is a number less than 2 including zero,
The metal oxide standard composition represented byAnd 5m 2 Nitrogen oxide adsorbent comprising a chromium-containing oxide having a BET specific surface area of not less than / g and fine poresIs provided. The present inventionUsed inChromium-containing oxides have NO adsorption and NO NO2It is also a prominent feature that it has an oxidizing property.
The present inventionUsed inChromium-containing oxide(Hereafter, it may be called the chromium-containing oxide of this invention.)In
1.The content of alkylamine or its decomposition product is 0.2% by weight or less,
2.The micropores are micropores and / or mesopores;
3.Having a pore volume of 0.05 ml / g or more in a pore diameter of 10 to 50 angstroms;
4).In the formula (1), a is a number from 0 to 250,
Is preferred.
According to the present invention, water or an acidic aqueous solution is also added to a mixed solution containing a water-miscible organic solvent, an alkylamine and a chromium compound soluble in the water-miscible organic solvent or further containing a silicate ester with stirring. Characterized by growing alkylamine complex decomposition product particles to remove alkylamine in the particlesUsed as nitrogen oxide adsorbentA method for producing a chromium-containing oxide is provided.
In the production method of the present invention,
1. Using silicate esters in a molar ratio of 0 to 485 per mole of Cr element;
2. Using alkylamine in an amount of 4 to 166 moles per mole of Cr element;
3. Using a water miscible organic solvent in an amount of 15 to 572 moles per mole of Cr element;
4). Adding water in an amount of 80 to 18300 moles per mole of Cr element;
5. Using an acid in an amount of not more than 33 moles per mole of Cr element;
6). The water-miscible organic solvent is a monohydric to polyhydric alcohol,
7). The silicate ester is a silicate ester of an alcohol having 1 to 4 carbon atoms,
Butpreferable.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
As the chromium oxide, divalent, trivalent and hexavalent chromium compounds are most commonly known, and in addition, tetravalent, pentavalent compounds and mixed oxides are known. However, as far as the present inventors know, NO is known. Adsorbent to NO and NO NO2There is no known chromium oxide that exhibits an oxidative action. In addition, the known chromium oxide has a very small specific surface area, and the BET specific surface area is not measurable.
[0010]
In contrast, the chromium-containing oxide represented by the metal oxide reference composition of the present invention has the following formula (1):
aSiO2・ BM1Om / 2・ M2On / 2 (1)
Where M2Represents Cr, M1Indicates polyvalent metal elements other than Si and Cr
And
n is the valence of Cr, m is the valence of the polyvalent metal,
a is a number of 485 or less including zero, preferably 0 to 250, most preferably 0.
To 110,
b is a number less than 2 including zero,
The valence of chromium takes a value of 3 to 6.
1. In the case of a> 0, when the content of chromium is small (10 <a ≦ 485), it shows a spherical shape (Example 1) and is particularly useful as an indicator material for detecting nitrogen oxides. On the other hand, the regularity of the shape tends to decrease as the chromium content increases (0 <a ≦ 10), but it is most suitable in terms of adsorptivity to nitrogen oxides (example 2 as an example). Each particle morphology is shown in the SEM image of FIG. Further, when organic components such as alkylamine are completely removed, the pore structure is not destroyed by the coexistence of the silica component, and the specific surface area is 600 to 1200 m.2The characteristic is as large as / g.
2. When a = 0, the BET specific surface area is 5 m2/ G or more, especially 10m2/ G or more is preferable. Also, by removing most of the organic components such as alkylamines, 200m2It is characterized by having a BET specific surface area of at least / g. When organic components or decomposition products thereof, specifically alkylamines or decomposition products thereof are 0.2% by weight or less, preferably 0.1% by weight or less, and are observed as an exothermic peak around 400 ° C. on the DTA curve. There is also. (FIG. 8; Example 3) Moreover, since the shape does not contain a silica component, the regularity is almost lost as described above.
Due to the above characteristics, the chromium-containing oxide of the present invention exhibits excellent adsorptivity to NO, and NO adsorbed NO.2Also excellent in oxidizing action. Further, after nitrogen oxide is adsorbed on the chromium-containing oxide of the present invention, it can be regenerated and repeatedly used by firing at a temperature of 350 ° C. or higher, particularly at the temperature of the synthetic heat treatment of the chromium oxide of the present invention. be able to. Nitrogen oxides can be recovered as nitric acid or the like.
The adsorption performance for NO can be evaluated by the following method.
[0011]
For the evaluation of the NO adsorption performance of the chromium-containing oxide of the present invention, a Shimadzu NOA-7000 type NOx analyzer improved for low flow rate was used. This analyzer is an apparatus for measuring NO concentration using a chemiluminescence reaction by NO and ozone. Specifically, NO is in an excited state by reacting NO with ozone.2 *The intensity of light (wavelength 590 to 2500 nm) generated when the light returns to the ground state again is measured with a semiconductor photoelectric device, and this light intensity is converted into NO concentration. NO2NO can be converted to NO with the same number of moles2-Equipped with NO converter, indirectly NO2Concentration measurement is also possible. Analyzed gases are NO and NOx (NO + NO2), Select either one of the measurement modes and measure separately.
Using a mass flow control gas mixer, about 100 ppm NO gas produced by mixing dry air with 0.1% NO was prepared at a flow rate of about 100 ml / min. NO adsorption characteristics and NO of packed sample2The oxidation characteristics were evaluated by breakthrough curve measurement at room temperature.
An example is shown in FIG. It can be seen that the chromium-containing oxide of the present invention exhibits NO adsorption ability at room temperature, and the NO concentration is kept at 0 ppm for a certain period from the start of measurement. This adsorption behavior holding 0 ppm is defined as initial adsorption. On the other hand, before the NO concentration increases, NOx (NO + NO2) Is observed, and the NOx concentration rapidly increases and greatly exceeds the NO concentration. This means that the adsorbed NO is NO2It is clearly shown that the chromium-containing oxide of the present invention has both adsorption ability and oxidation ability for nitrogen oxides.
Furthermore, in the case of a chromium-containing oxide according to the present invention (formula (1)), when a> 0, as is clear from Example 1 (FIG. 6), as the chromium content increases, the NO adsorption capacity increases. I understand. Further, when a = 0, NO is not detected even after 15 minutes from the NO breakthrough curve of Example 3 (FIG. 9), and it can be seen that the oxidation to NO2 lasts for a long time.
Further, the chromium-containing oxide according to the present invention does not affect the adsorption and oxidation ability of nitrogen oxides even if sulfur oxides (SOx) are contained in the nitrogen oxides. Specifically, 20 ppm SO in 100 ppm NO gas.2When a chromium-containing oxide according to the present invention (Example 1-2) is brought into contact with a gas containing NO, the NO breakthrough curve is SO2It was found that the selectivity to nitrogen oxides was large, almost overlapping with the case of not containing (FIG. 15). Furthermore, the chromium-containing oxide of the present invention is not affected by moisture in the atmosphere.
This adsorption and oxidation phenomenon is observed even in samples moderately absorbed at room temperature in air, which is a major difference from the fact that Cu-ZSM type zeolite does not show NO adsorption ability at all in such an atmosphere ( Comparative Example 2; FIG. 11).
[0012]
In addition, commercially available chromium oxide (Cr2O3) Does not show any adsorptivity to nitrogen oxides (Comparative Example 3; FIG. 12), whereas the chromium-containing oxides not containing silica of the present invention show excellent adsorptivity (Examples). 3; FIG. 9), the unexpected effect of the present invention becomes clear.
[0013]
It has already been pointed out that the chromium-containing oxide of the present invention has fine pores in the primary particles, and these fine pores become sites of adsorption activity and oxidation activity. It is desirable in terms of adsorptivity and oxidation action to have a pore volume of 0.05 ml / g or more, preferably 0.07 ml / g or more in a pore diameter of 10 to 50 angstroms.
[0014]
The chromium-containing oxide of the present invention has a regular arrangement of a complex of alkylamine and chromium oxide surrounding the alkylamine, or further silica or other polyvalent metal, and a diffraction angle 2θ = 1.0 to 5 Dealkylated amines of composites (also referred to as precursors or nanocomposites) that have an X-ray diffraction (CuKα) peak at 0 ° (for example, calcined products obtained by direct heat treatment of precursors, or acidic precursors) It is preferable for the formation and retention of micropores to be composed of an aqueous solution or a product obtained by extraction with a mixed solution of ethanol and an acidic aqueous solution.
[0015]
The nanocomposite particles with an alkylamine serving as a precursor of the chromium-containing oxide of the present invention should be a mesostructure having an X-ray diffraction (CuKα) peak at a diffraction angle 2θ = 1.0 to 5.0 degrees. This is a feature, and the chromium-containing oxide of the present invention retains micropores due to this feature.
[0016]
FIG. 3 shows (a) a silica mesostructure containing Cr (Example 1-2), which is a precursor of a chromium-containing oxide of the present invention, and (b) a chromium oxide mesostructure containing no Si (Example). It is an X-ray diffraction diagram of 3), and the presence of bottom reflection shows that the arrangement of the inorganic skeleton that gives pores is regular.
4 is a nitrogen adsorption isotherm corresponding to the 600 ° C. heat treatment product of FIG. 3A and the 350 ° C. heat treatment product of FIG. 3B. From the pore distribution curve obtained by applying the Horvath-Kawazoe method to the former and the BJH method to the latter, the peak values of the pore diameter are (a) 2 nm, (b) 2.4 nm, and a sharp distribution It was found that
The chromium-containing oxide of the present invention removes the organic compound contained in the precursor by heat treatment or the like by using the mesostructure formed by the cooperative order-forming ability of the alkylamine and the inorganic dissolved species as a precursor. It is characterized by imparting porosity.
[0017]
The chromium-containing oxide of the present invention is prepared by stirring a water-miscible organic solvent, alkylamine and a mixture containing a chromium compound soluble in a water-miscible organic solvent or further a silicate ester, or water or acidic under stirring. It is obtained by adding an aqueous solution, growing an alkylamine complex decomposition product, which is a mesostructure formed by the cooperative order formation ability of alkylamine and inorganic ionic species, as a precursor, and removing the alkylamine.
[0018]
The schematic mechanism of the method for producing a chromium-containing oxide according to the present invention is estimated as follows, and its production mechanism model is shown in FIG.
For example, when chromium chloride hexahydrate is dissolved in alcohol, the Cr element reacts with the alcohol to partially alkoxide, and at the same time, protons are generated and positively charged chromium dissolved species (I+) Is generated.
When alkylamine is added to this solution, NH in the amine is added.2The group is instantly NH3 +(S+) And chlorine ions (X−) Through S+X−I+The rule structure is generated. In systems containing Si, I+Becomes a dissolved species in which Si and a metal element are combined. S+X−I+Primary particles that grow with nuclei as S+X−I+The mesostructures are aggregated, and the particles grow by collision between the primary particles, and finally, when the addition ratio of the metal element is low, spherical particles having a macro form of micron order are easily generated. .
The final product obtained by removing the organic components surrounding the inorganic skeleton by a treatment such as heating becomes porous particles having a pore structure derived from the mesostructure. The adsorption site of NO is Cr element, and in order to achieve high adsorption performance for NO, it is necessary to highly disperse Cr in the inorganic skeleton and to efficiently make contact with NO.
The present NO adsorbent manufactured based on the above generation mechanism is a porous substance based on pores generated inside the particles, and emits an ability to effectively adsorb NO.
[0019]
In this production method, not only the pore diameter can be easily controlled by the number of carbon atoms in the alkylamine to be used, but also a mesostructure that is a precursor of the nitrogen oxide adsorbent can be produced within 80 minutes at room temperature and normal pressure. .
Further, the particle size can be controlled by the stirring speed, the acid concentration, or the alcohol addition ratio.
[0020]
The water-miscible organic solvent, alkylamine and metal compound (metal salt and metal alkoxide) soluble in the water-miscible organic solvent or silicate ester used in the present invention will be further described.
[0021]
As a silicate ester as a silica raw material used in the present invention, it is possible to use Si-alkoxide, such as tetramethyl orthosilicate, tetraethyl orthosilicate, tetraisopropyl orthosilicate, tetra-n-butyl orthosilicate and the like. Tetraethylorthosilicate (hereinafter abbreviated as TEOS) is used.
[0022]
As the alcohol, methanol, ethanol, propanol, butanol and the like can be used, and ethanol is preferably used.
[0023]
As the alkylamine, a linear alkylamine is preferable, an alkylamine having 8 to 18 carbon atoms is used, and octylamine and dodecylamine which are relatively inexpensive and in a solution state at normal temperature are preferable.
[0024]
As the metal species, in addition to Cr or Si, one or more of Ti, Zr, Al, Fe, Zn, Mn, Co, Cu, Ni, V, Sn, Ce and the like can be used simultaneously.
As the metal salt soluble in the water-miscible organic solvent, all metal salts soluble in alcohol such as the above-mentioned metal halides, nitrates, sulfates, carbonates and hydrates thereof can be used.
As the metal alkoxide, for Ti, tetraethyl orthotitanate, tetraisopropyl orthotitanate, tetra-n-butyl orthotitanate, etc. can be used, and tetraethyl orthotitanate is preferably used. In the case of Zr, zirconium tetra-n-butoxide solution (80% by weight dissolved in 1-butanol; abbreviated as TBOZ), and in the case of Al, aluminum-tri-sec-butoxide or the like can be used.
[0025]
Examples of chromium compounds include chromium salts, chromate salts, or chromium carboxylates, chromium-1,3-diketo compounds, chromate esters, chromate amides, and the like. Chromium, chromium sulfate, potassium dichromate, sodium dichromate, chromium acetate, chromium formate, chromium propionate, chromium pentanoate, hexacarbonyl chromium, chromium acetyl acetate, chromium-1,3-butanedionate, bis (tert -Butyl) chromate, bis (1,1-dimethylpropyl) chromate, bis (2-phenyl-2-propyl) chromate, bis (bistrimethylsilylamido) chromium (II) -THF complex and the like.
[0026]
As the acid, hydrochloric acid, nitric acid, sulfuric acid, acetic acid and the like can be used.
[0027]
In the synthesis of the chromium-containing oxide of the present invention, the mixing molar ratio of the starting materials is as follows: metal element: TEOS: 1-alkylamine: alcohol: acid: water = 1: 0 to 485: 4 to 166: 15 to 572: 0. ~ 33: 80-18300.
Furthermore, the mixing method of the starting materials is described in detail. When TEOS is used, (1) alkylamine is added to a mixed solution of TEOS and a metal salt dissolved in alcohol, or (2) TEOS and alkyl are mixed. Add a metal salt dissolved in an alcohol to a mixed solution with an amine, and in each case, stir for 1 to 20 minutes, add water or an acidic aqueous solution while continuing to stir, and maintain a sufficiently mixed state at room temperature. Within 80 minutes, preferably about 10 to 60 minutes. In addition, when TEOS is not used, while maintaining the solution state while stirring the metal salt previously dissolved in alcohol, the alkylamine is added and stirred for 1 to 20 minutes, and water or acidic aqueous solution is added while continuing stirring. The mixture is added and allowed to react at room temperature within 80 minutes, preferably for about 10 to 60 minutes while maintaining a sufficient mixing state.
The mixing molar ratio of the starting materials is preferably metal element: TEOS: 1-alkylamine: alcohol: acid: water = 1: 0 to 250: 4 to 90:15 to 300: 0 to 10:80 to 9500. .
[0028]
In any of the above cases, the solid product is separated from the suspension after the reaction and sufficiently dried at room temperature to 100 ° C.
Finally, in order to remove the organic component and produce a chromium-containing oxide, for example, heat treatment is performed at 300 ° C. or higher for 30 minutes or longer, preferably 320 ° C. or higher for 1 hour.
[0029]
(Use)
The chromium-containing oxide of the present invention may be granulated, rod-shaped, pellet-shaped, or honeycomb-shaped as necessary, and adsorbing / occluding agent for nitrogen oxide, oxidizing agent, decomposition / removing agent, or indicator for detecting nitrogen oxide Materials (specifically, the chromium-containing oxide of the present invention changes from pale yellow to brown by contact with NO gas of 20 ppm or less), and various shape-selective oxidation catalysts such as polyethylene Suitable for materials useful for industrial and environmental conservation, such as oxidation catalysts for use, adsorption / separation / storage agent for useful ions / molecules, adsorption / separation of harmful ions / molecules, and decomposition catalyst or catalyst carrier Yes.
The chromium-containing oxide of the present invention is used as various oxidation catalysts, and can be used in combination with zeolite, sepiolite, antibacterial agent, photoreactive semiconductor, etc. depending on the application. Further, it can be added to paints and have a nitrogen oxide adsorption ability, and further can be used for treatment of nitrogen oxides in diesel engine exhaust gas, cogeneration, exhaust gas treatment in tunnels, and the like.
[0030]
【Example】
EXAMPLES Next, although an Example demonstrates this invention further more concretely, this invention is not limited by this Example.
In addition, each test method performed in the Example was performed by the following method.
[0031]
(Measurement method)
(1) Scanning electron microscope: JSM5300 manufactured by JEOL Ltd. was used and observed at an acceleration voltage of 10 kV and a WD of 10 mm.
(2) Specific surface area / pore size distribution: BEL specific surface area was determined from nitrogen adsorption isotherm measured at liquid nitrogen temperature using BELSORP28 manufactured by Nippon Bell. Analyzed.
(3) Particle size: measured by a particle size distribution measuring device Coulter LS230 manufactured by Beckman Coulter.
(4) Shape: Observed from scanning electron micrograph.
(5) X-ray diffraction: Rigaku Rotorflex RU-300 was used and measured with a CuKα radiation source, an acceleration voltage of 40 kV, and 80 mA.
(6) NO breakthrough curve measurement: Measured using a Shimadzu NOA-7000 NOx analyzer.
(7) Chemical composition analysis: silica (SiO2) Content was measured by an alkali melting method, and Cr was measured by an atomic absorption method after alkali melting.
(8) Thermal analysis: TG-DTA measurement was performed using a Rigaku thermal analyzer TG8120.
(9) Elemental analysis: NCH quantitative apparatus Sumigraph NCH-21 type manufactured by Sumika Chemical Analysis Center was used.
[0032]
Example 1
Stir TEOS at 600 rpm, CrCl dissolved in ethanol3・ 6H2After adding O, octylamine is added and stirred for 10 minutes, then an aqueous hydrochloric acid solution is added, and the mixture is further stirred for 1 hour. The molar ratio of the mixed solution is as shown in Table 1. After the reaction, the solid product is filtered off from the suspension, sufficiently dried at 50 ° C., and then heated at 600 ° C. for 1 hour to remove organic components to produce a chromium-containing oxide.
Table 1 shows the starting material composition, and Table 2 shows the peak value obtained from the Cr / Si molar ratio, specific surface area and pore shape distribution curve of the chromium-containing oxide prepared under each synthesis condition as the pore diameter. In Example 1-4, a clear pore size distribution curve was not obtained, and Table 2 was left blank. The particles were all spherical, and the median diameters of Examples 1-2 and 1-3 were 37 and 42 μm, respectively. The SEM image of Example 1-2 is shown in FIG.
Using NOx analyzer (NOA-7000, manufactured by Shimadzu Corporation), NO gas with 0.1% NO and dry air adjusted to a concentration of about 100 ppm with a mass flow control gas mixer is used for a flow reaction of about 100 ml / min at room temperature. In this system, a sample column is packed with 0.04 g of the chromium-containing oxide sample of Example 1-2, Example 1-3, and Example 1-4, and the NO adsorption characteristics and NO2The oxidation characteristics were evaluated by breakthrough curve measurement. (In the measurement, each sample was left in the air after heat treatment and used after sufficiently absorbing moisture.) The results are shown in FIG. In addition, the NO adsorption characteristics and NO of Example 1-12The breakthrough curve for oxidation properties is shown in FIG.
All of the chromium-containing oxides described in this example show excellent NO adsorption capacity at room temperature, and the NO concentration is maintained at 0 ppm for a certain period of time from the start of measurement (this adsorption behavior holding 0 ppm is referred to as initial adsorption). The retention time is longer as the Cr content is higher.
Further, the present chromium-containing oxide exhibits orange, yellow, or amber color before NO adsorption depending on the Cr / Si ratio and pretreatment conditions, and in any case, the contact part by NO adsorption regardless of the NO concentration. Changes to brown instantly. Using this change in coloring before and after NO adsorption, the present chromium-containing oxide can be used as an NO detector or an NO monitor indicator.
[0033]
(Example 2)
CrCl dissolved in ethanol3・ 6H2Add TEOS to O, add octylamine and stir for 10 minutes, then add water and stir for 1 hour. The molar ratio of the mixed solution is Cr: Si: octylamine: ethanol: HCl: H2O = 1: 1.02: 5.5: 18.6: 0: 197. After the reaction, the solid product is centrifuged from the suspension, sufficiently dried at 50 ° C., and then heated at 300 ° C. or higher for 1 hour to remove organic components to produce a chromium-containing oxide. Table 1 shows the starting material composition, and Table 2 shows the Cr / Si molar ratio and octylamine or decomposition product ratio of the chromium-containing oxide obtained by heating at 400 ° C. for 1 hour, and the specific surface area and pore shape. The peak value obtained from the distribution curve is shown as the pore diameter. As shown in the SEM image of FIG. 1b, the chromium-containing oxide of this example has an irregular shape instead of a spherical shape.
FIG. 7 shows the NO breakthrough curve and the change in NOx concentration of the chromium-containing oxide of this example. This sample is a mesostructure which is a precursor heated at 400 ° C. for 1 hour. The result of XRD measurement is Cr2O3A large rise indicating a trace of a mesostructure was observed at the peak and the low angle (2θ = 5 ° or less). From the NO breakthrough curve, like the sample of Example 1 containing Si, NO adsorption progresses very gradually through the initial adsorption behavior, showing a remarkable NO storage behavior, and NO.2It can be seen that this sample is slow and the oxidation ability of this sample is extremely high. (In the measurement, a sample left in the air without absorbing moisture was used.)
Further, FIG. 7 shows the influence of the heat treatment temperature on the NO breakthrough curve. It is apparent that the mesostructure which is a precursor is heated at 350 ° C. and 600 ° C. for 1 hour, respectively, and at 600 ° C., the function is remarkably deteriorated due to the destruction of the pore structure. As this result shows, the appropriate heat treatment temperature for removing the organic substance from the mesostructure depends on the Cr content.
[0034]
(Example 3)
CrCl dissolved in ethanol3・ 6H2After adding octylamine to O and stirring for 10 minutes, water is added and the mixture is further stirred for 1 hour. The molar ratio of the mixed solution is Cr: Si: octylamine: ethanol: HCl: H2O = 1: 0: 5.4: 18.6: 0: 197. After the reaction, the solid product is centrifuged from the suspension and sufficiently dried at 50 ° C., and then the organic components are removed by heating to produce a chromium-containing oxide.
Table 1 shows the starting material composition, and Table 2 shows the peak value obtained from octylamine or its decomposition product of chromium-containing oxide obtained by heating at 350 ° C. for 1 hour, and the specific surface area and pore shape distribution curve. It shows as a pore diameter. In addition, since the exothermic peak is recognized by 400 degreeC vicinity on the thermal analysis curve of FIG. 8, it is thought that the residue in this chromium-containing oxide exists as organic substances, such as an amine, or its decomposition product.
As a result of XRD measurement, this chromium-containing oxide sample contains Cr2O3A large rise indicating a trace of a mesostructure was observed at the peak and the low angle (2θ = 5 ° or less).
FIG. 9 shows the NO breakthrough curve and the change in NOx concentration of the chromium-containing oxide of this example. (In the measurement, a sample that was left in the air without absorbing moisture was used.) From the NO breakthrough curve, NO adsorption was gradually performed through the initial adsorption behavior as in the samples of Examples 1 and 2 containing Si. NO at the same time2From this, it can be seen that this sample also has extremely high oxidation ability.
[0035]
Example 4
CrCl dissolved in ethanol by mixing TEOS and Ti-alkoxide (tetraethylorthotitanate; abbreviated as TEOT) and stirring at 600 rpm3・ 6H2After adding O, octylamine is added and stirred for 10 minutes, then an aqueous hydrochloric acid solution is added, and the mixture is further stirred for 1 hour. The molar ratio of the mixed solution is Cr: Ti: Si: octylamine: ethanol: HCl: H2O = 1: 0.23: 42.0: 14.4: 50.0: 0.71: 1593. After the reaction, the solid product is filtered off from the suspension, sufficiently dried at 50 ° C., and then heated at 600 ° C. for 1 hour to remove organic components to produce a chromium-containing oxide. The product has a spherical shape, the median diameter is 51 μm, and the BET specific surface area is 795 m.2/ G.
The result of measuring the NO breakthrough curve of the spherical chromium-containing oxide containing Ti is shown in FIG. The results of Example 1-2, which have almost the same starting material mixing ratio except Ti, are also shown in FIG. Although the initial adsorption time is shortened by the addition of Ti, it exhibits excellent NO adsorption capacity at room temperature, and NO2It can be seen that it has the effect of reducing the ability to oxidize.
[0036]
(Comparative Example 1)
NO adsorption characteristics of porous silica metal composite particles produced by the same method as in Example 1 and containing metallic elements other than Cr, including Al, Zr, Fe, Mn, Co, Cu, Ni, Zn, Sn, and Ce As a result of examining the same method as in Example 1, it was found that there was a significant difference from the case of Cr, and it did not have NO adsorption ability.
[0037]
(Comparative Example 2)
FIG. 11 shows an NO breakthrough curve of Cu—ZSM type zeolite dehydrated by heating at 400 ° C. for 4 hours. The chemical composition of zeolite is 3.7 wt% CuO, SiO2/ Al2O3The molar ratio is 39. Under room temperature conditions mixed with air, the Cu-ZSM zeolite hardly adsorbs NO,2Occurrence is not recognized at all. Moreover, when adsorption temperature was 200 degreeC and 400 degreeC, initial stage adsorption and oxidation ability were not recognized, but it turned out that it has only NO adsorption ability.
The nitrogen oxide adsorbent and the oxidant of the present invention have both NO adsorption ability and oxidation ability at room temperature under air mixing conditions, and that the Cu-ZSM type zeolite does not show NO adsorption ability and oxidation ability at all. This is a significant difference.
[0038]
(Comparative Example 3)
Cr by XRD powder measurement2O3In addition, the BET specific surface area is extremely small and cannot be measured with the above apparatus.2O3FIG. 12 shows the result of NO breakthrough curve for. Although NO adsorption was slightly observed, it was found that initial adsorption was not observed and it did not have oxidation ability.
The XRD diffraction pattern of the nitrogen oxide adsorbent and the oxidant in Example 3 of the present invention is similar to that of commercially available chromic oxide.2O3The diffraction peak is observed, but it is manufactured by heat-treating the intermediate that is the mesostructure shown in FIG.2/ G, and the presence state of surface chromium element is commercially available Cr2O3Is considered to be different.
[0039]
(Comparative Example 4)
Exactly the same method as in Example 1, TEOS stirred at 600 rpm, CrCl dissolved in ethanol3・ 6H2After adding O, octylamine is added and stirred for 10 minutes, then an aqueous hydrochloric acid solution is added, and the mixture is further stirred for 1 hour. However, the molar ratio of the mixed solution is Cr: Si: octylamine: ethanol: HCl: H under the condition that the amount of Cr is extremely small.2O = 1: 488: 166: 575: 33: 18390. After the reaction, the solid product is filtered off from the suspension, sufficiently dried at 50 ° C., and then heated at 600 ° C. for 1 hour to remove organic components to produce a chromium-containing oxide.
FIG. 13 shows the NO breakthrough curve of this sample in comparison with Example 1-1. This chromium-containing oxide does not have NO adsorption ability at all, but it is understood that initial adsorption is hardly recognized. The chromium-containing oxide is light yellow and slightly discolored by NO adsorption. However, it is difficult to use the chromium-containing oxide alone as a NO detector or an NO monitor indicator.
[0040]
(Comparative Example 5)
Mix the TEOS and TEOT, stir at 600 rpm, CrCl dissolved in ethanol3・ 6H2After adding O, octylamine is added and stirred for 10 minutes, then an aqueous hydrochloric acid solution is added, and the mixture is further stirred for 1 hour. However, the Ti amount was increased as compared with Example 4, and the molar ratio of the mixed solution was Cr: Ti: Si: octylamine: ethanol: HCl: H.2O = 1: 2: 46: 15.9: 55: 0.79: 1756. After the reaction, the solid product is filtered off from the suspension, sufficiently dried at 50 ° C., and then heated at 600 ° C. for 1 hour to remove organic components to produce a chromium-containing oxide.
FIG. 14 shows the NO breakthrough curve of the spherical chromium-containing oxide containing Ti in comparison with Example 4. It can be seen that the addition of Ti does not show any NO adsorption capacity.
[0041]
[Table 1]
Conditions for the synthesis of chromium-containing oxides
[Table 2]
Properties of the product chromium oxide
【The invention's effect】
According to the present invention, a chromium-containing oxide having a high specific surface area and fine pores, adsorbing to nitrogen oxides, and oxidizing to nitric oxide has been successfully synthesized.
In the present invention, alkylamine is used as a pore structure control agent, TEOS, a metal compound dissolved in alcohol, and water or an acidic aqueous solution are added, and the mixing ratio of the reactants, the acidity, and the carbon number of the alkyl chain. By changing the temperature, organic-inorganic nanocomposites (mesostructures) containing surfactants that become chromium-containing oxide precursors at room temperature and normal pressure can be produced in a short time, and finally organic substances are removed. Thus, a method for producing a chromium-containing oxide in which a part of Si is substituted with Cr or exists as a Cr oxide or the like outside the skeleton is provided.
Furthermore, an alkylamine and water or an acidic aqueous solution are added to a solution phase of a metal salt dissolved in an alcohol with stirring to grow the resulting alkylamine complex decomposition product particles, and to remove the alkylamine in the particles. A method for producing a chromium-containing oxide is provided.
Moreover, since this chromium-containing oxide has adsorption ability and oxidation ability for nitrogen oxides, it can be used in reaction processes useful for measures to prevent nitrogen oxides from being contaminated by the environment, and in various oxidation reaction processes. It can also be used as a functional ceramic material for molecular sieves, catalyst carriers, catalysts, and sensors that are useful in both industrial and environmental conservation. In particular, the present invention is highly valuable as a method for producing not only a fixed bed but also a chemical process catalyst / catalyst support for fluidized bed reactions and a column filler for chromatographic separation by utilizing the characteristics of micron-order spherical particles. Furthermore, the chromium-containing oxide exhibits orange, yellow, or amber before NO adsorption, depending on the Cr / Si ratio and pretreatment conditions, and in any case, contacted by NO adsorption, regardless of the NO concentration. Since the portion changes to brown instantly, it can be used as a NO detection agent or a NO monitoring indicator using this color change.
[Brief description of the drawings]
1 is a scanning electron micrograph (SEM) of chromium-containing oxide particles, (a) Example 1-2, and (b) Example 2. FIG.
FIG. 2 is a breakthrough curve showing NO adsorption characteristics of the chromium-containing oxide of Example 1-1 and a graph showing NOx concentration change characteristics.
3 is an X-ray diffraction pattern diagram of a mesostructure that is a precursor of the chromium-containing oxide of Example 1-2 and the chromium-containing oxide of Example 3. FIG.
4 is a nitrogen adsorption isotherm of the chromium-containing oxide of Example 1-2 and the chromium-containing oxide porous particles of Example 3. FIG.
FIG. 5 is a conceptual diagram showing a mechanism for producing chromium-containing oxides of the present invention.
6 is a breakthrough curve showing NO adsorption characteristics of chromium-containing oxides of Example 1-2, Example 1-3, and Example 1-4, and a graph showing NOx concentration change characteristics corresponding to each of the breakthrough curves. FIG. .
7 is a breakthrough curve showing NO adsorption characteristics of the chromium-containing oxide of Example 2 and a graph showing NOx concentration change characteristics. FIG.
8 is a thermal analysis curve of the chromium-containing oxide of Example 3. FIG.
9 is a breakthrough curve showing NO adsorption characteristics of the chromium-containing oxide of Example 3 and a graph showing NOx concentration change characteristics. FIG.
10 is a breakthrough curve showing NO adsorption characteristics of a chromium-containing oxide containing Ti of Example 4 and a graph showing NOx concentration change characteristics. FIG. (Comparison with Example 1-2)
11 is a breakthrough curve showing NO adsorption characteristics of the Cu—ZSM5 type zeolite of Comparative Example 2 and a graph showing NOx concentration change characteristics. FIG.
12 is a commercially available chromic oxide Cr of Comparative Example 3. FIG.2O3It is a breakthrough curve which shows NO adsorption characteristics. (Comparison with Example 3)
13 is a breakthrough curve showing NO adsorption characteristics of the chromium-containing oxide of Comparative Example 4. FIG. (Comparison with Example 1-1)
14 is a breakthrough curve showing NO adsorption characteristics of the chromium-containing oxide containing Ti of Comparative Example 5. FIG. (Comparison with Example 4)
FIG. 15 shows NO + SO of chromium-containing oxide (Example 1-2).2It is a breakthrough curve which shows the NO adsorption characteristic in mixed gas.
Claims (14)
ａＳｉＯ２・ｂＭ１Ｏｍ／２・Ｍ２Ｏｎ／２ ‥（１）
式中、
Ｍ２はＣｒを表し、
Ｍ１はＳｉ，Ｃｒ以外の多価金属元素を表し、
ｎはＣｒの価数であり、
ｍは多価金属の価数であり、
ａはゼロを含む４８５以下の数であり、
ｂはゼロを含む２未満の数である、
で表される金属酸化物基準組成を有し、更に５ｍ ２ ／ｇ以上のＢＥＴ比表面積と微細孔とを有する含クロム酸化物からなることを特徴とする窒素酸化物吸着剤。 X-ray diffraction (CuKα) consisting of an alkylamine and a regular arrangement of chromium oxide surrounding this alkylamine or further silica and / or other polyvalent metal oxide and having a diffraction angle of 2θ = 1.0 to 5.0 degrees. ) A chromium-containing oxide obtained by removing at least a part of an alkylamine from a complex having a peak, which has the following formula (1):
aSiO 2 · bM 1 O m / 2 · M 2 On / 2 (1)
Where
M 2 represents Cr,
M 1 represents a polyvalent metal element other than Si and Cr;
n is the valence of Cr;
m is the valence of the polyvalent metal,
a is a number of 485 or less including zero,
b is a number less than 2 including zero,
A nitrogen oxide adsorbent comprising a chromium oxide having a BET specific surface area of 5 m 2 / g or more and a fine pore.
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