JP4053911B2 - Photocatalyst and method for producing photocatalyst - Google Patents
Photocatalyst and method for producing photocatalyst Download PDFInfo
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- JP4053911B2 JP4053911B2 JP2003075645A JP2003075645A JP4053911B2 JP 4053911 B2 JP4053911 B2 JP 4053911B2 JP 2003075645 A JP2003075645 A JP 2003075645A JP 2003075645 A JP2003075645 A JP 2003075645A JP 4053911 B2 JP4053911 B2 JP 4053911B2
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- photocatalyst
- oxide
- iron
- particles
- titanium
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- 239000011941 photocatalyst Substances 0.000 title claims description 74
- 238000004519 manufacturing process Methods 0.000 title description 15
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 claims description 105
- 239000002245 particle Substances 0.000 claims description 68
- QGZKDVFQNNGYKY-UHFFFAOYSA-N ammonia Natural products N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 39
- 229910052809 inorganic oxide Inorganic materials 0.000 claims description 29
- 230000003287 optical effect Effects 0.000 claims description 19
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 18
- 150000002505 iron Chemical class 0.000 claims description 17
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims description 12
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 10
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 10
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 10
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonium chloride Substances [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 claims description 9
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 9
- 239000002243 precursor Substances 0.000 claims description 9
- 239000012266 salt solution Substances 0.000 claims description 9
- 239000000377 silicon dioxide Substances 0.000 claims description 9
- 238000010304 firing Methods 0.000 claims description 8
- 238000001035 drying Methods 0.000 claims description 6
- 238000001914 filtration Methods 0.000 claims description 6
- 229910052742 iron Inorganic materials 0.000 claims description 5
- 238000005406 washing Methods 0.000 claims description 5
- 239000004065 semiconductor Substances 0.000 claims description 4
- 235000013980 iron oxide Nutrition 0.000 description 49
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 40
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 29
- 238000000034 method Methods 0.000 description 21
- 230000001699 photocatalysis Effects 0.000 description 19
- 239000010936 titanium Substances 0.000 description 18
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 17
- 239000000463 material Substances 0.000 description 17
- 229910052719 titanium Inorganic materials 0.000 description 17
- 239000011230 binding agent Substances 0.000 description 16
- 229910021529 ammonia Inorganic materials 0.000 description 15
- 239000002131 composite material Substances 0.000 description 14
- 230000000694 effects Effects 0.000 description 14
- 150000002506 iron compounds Chemical class 0.000 description 14
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 13
- 239000007864 aqueous solution Substances 0.000 description 11
- 230000006866 deterioration Effects 0.000 description 10
- 229910052710 silicon Inorganic materials 0.000 description 10
- 239000010703 silicon Substances 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 9
- 238000006460 hydrolysis reaction Methods 0.000 description 8
- 239000000243 solution Substances 0.000 description 8
- 239000000126 substance Substances 0.000 description 8
- 239000011248 coating agent Substances 0.000 description 7
- 238000000576 coating method Methods 0.000 description 7
- 239000007789 gas Substances 0.000 description 7
- 229910052751 metal Inorganic materials 0.000 description 7
- 239000002184 metal Substances 0.000 description 6
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 6
- -1 platinum group metals Chemical class 0.000 description 6
- 239000002244 precipitate Substances 0.000 description 6
- 229920005989 resin Polymers 0.000 description 6
- 239000011347 resin Substances 0.000 description 6
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 description 6
- 239000008279 sol Substances 0.000 description 6
- 239000000758 substrate Substances 0.000 description 6
- 239000004566 building material Substances 0.000 description 5
- 150000007530 organic bases Chemical class 0.000 description 5
- 239000003973 paint Substances 0.000 description 5
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 description 5
- 239000002344 surface layer Substances 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- IKHGUXGNUITLKF-UHFFFAOYSA-N Acetaldehyde Chemical compound CC=O IKHGUXGNUITLKF-UHFFFAOYSA-N 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 239000013078 crystal Substances 0.000 description 4
- 239000006185 dispersion Substances 0.000 description 4
- 239000000835 fiber Substances 0.000 description 4
- 230000007062 hydrolysis Effects 0.000 description 4
- 238000005470 impregnation Methods 0.000 description 4
- VCJMYUPGQJHHFU-UHFFFAOYSA-N iron(3+);trinitrate Chemical compound [Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VCJMYUPGQJHHFU-UHFFFAOYSA-N 0.000 description 4
- 238000011068 loading method Methods 0.000 description 4
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical group [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 4
- 230000004580 weight loss Effects 0.000 description 4
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 3
- 230000000844 anti-bacterial effect Effects 0.000 description 3
- 230000003373 anti-fouling effect Effects 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- KDLHZDBZIXYQEI-UHFFFAOYSA-N palladium Substances [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 3
- 238000009832 plasma treatment Methods 0.000 description 3
- 239000004033 plastic Substances 0.000 description 3
- 229920003023 plastic Polymers 0.000 description 3
- 235000019353 potassium silicate Nutrition 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 239000004408 titanium dioxide Substances 0.000 description 3
- XJDNKRIXUMDJCW-UHFFFAOYSA-J titanium tetrachloride Chemical compound Cl[Ti](Cl)(Cl)Cl XJDNKRIXUMDJCW-UHFFFAOYSA-J 0.000 description 3
- 239000004925 Acrylic resin Substances 0.000 description 2
- 229920000178 Acrylic resin Polymers 0.000 description 2
- 239000004115 Sodium Silicate Substances 0.000 description 2
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 description 2
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 2
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 2
- VSCWAEJMTAWNJL-UHFFFAOYSA-K aluminium trichloride Chemical compound Cl[Al](Cl)Cl VSCWAEJMTAWNJL-UHFFFAOYSA-K 0.000 description 2
- 230000000843 anti-fungal effect Effects 0.000 description 2
- 239000012298 atmosphere Substances 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 239000011218 binary composite Substances 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- SZVJSHCCFOBDDC-UHFFFAOYSA-N ferrosoferric oxide Chemical compound O=[Fe]O[Fe]O[Fe]=O SZVJSHCCFOBDDC-UHFFFAOYSA-N 0.000 description 2
- 239000010408 film Substances 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 235000014413 iron hydroxide Nutrition 0.000 description 2
- MVFCKEFYUDZOCX-UHFFFAOYSA-N iron(2+);dinitrate Chemical compound [Fe+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O MVFCKEFYUDZOCX-UHFFFAOYSA-N 0.000 description 2
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 2
- NCNCGGDMXMBVIA-UHFFFAOYSA-L iron(ii) hydroxide Chemical compound [OH-].[OH-].[Fe+2] NCNCGGDMXMBVIA-UHFFFAOYSA-L 0.000 description 2
- 238000004898 kneading Methods 0.000 description 2
- 229910021645 metal ion Inorganic materials 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- SOQBVABWOPYFQZ-UHFFFAOYSA-N oxygen(2-);titanium(4+) Chemical compound [O-2].[O-2].[Ti+4] SOQBVABWOPYFQZ-UHFFFAOYSA-N 0.000 description 2
- 238000000746 purification Methods 0.000 description 2
- 238000005215 recombination Methods 0.000 description 2
- 230000006798 recombination Effects 0.000 description 2
- 229910052911 sodium silicate Inorganic materials 0.000 description 2
- 238000004544 sputter deposition Methods 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 238000010998 test method Methods 0.000 description 2
- 238000001771 vacuum deposition Methods 0.000 description 2
- 229910052720 vanadium Inorganic materials 0.000 description 2
- 239000002351 wastewater Substances 0.000 description 2
- 229910052726 zirconium Inorganic materials 0.000 description 2
- OERNJTNJEZOPIA-UHFFFAOYSA-N zirconium nitrate Chemical compound [Zr+4].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O OERNJTNJEZOPIA-UHFFFAOYSA-N 0.000 description 2
- BNGXYYYYKUGPPF-UHFFFAOYSA-M (3-methylphenyl)methyl-triphenylphosphanium;chloride Chemical compound [Cl-].CC1=CC=CC(C[P+](C=2C=CC=CC=2)(C=2C=CC=CC=2)C=2C=CC=CC=2)=C1 BNGXYYYYKUGPPF-UHFFFAOYSA-M 0.000 description 1
- WUPHOULIZUERAE-UHFFFAOYSA-N 3-(oxolan-2-yl)propanoic acid Chemical compound OC(=O)CCC1CCCO1 WUPHOULIZUERAE-UHFFFAOYSA-N 0.000 description 1
- VXEGSRKPIUDPQT-UHFFFAOYSA-N 4-[4-(4-methoxyphenyl)piperazin-1-yl]aniline Chemical compound C1=CC(OC)=CC=C1N1CCN(C=2C=CC(N)=CC=2)CC1 VXEGSRKPIUDPQT-UHFFFAOYSA-N 0.000 description 1
- DUFCMRCMPHIFTR-UHFFFAOYSA-N 5-(dimethylsulfamoyl)-2-methylfuran-3-carboxylic acid Chemical compound CN(C)S(=O)(=O)C1=CC(C(O)=O)=C(C)O1 DUFCMRCMPHIFTR-UHFFFAOYSA-N 0.000 description 1
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-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
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 239000004372 Polyvinyl alcohol Substances 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- OUUQCZGPVNCOIJ-UHFFFAOYSA-M Superoxide Chemical compound [O-][O] OUUQCZGPVNCOIJ-UHFFFAOYSA-M 0.000 description 1
- 239000005083 Zinc sulfide Substances 0.000 description 1
- CZNCTWNLEIFMDX-UHFFFAOYSA-N [Fe].O=O Chemical compound [Fe].O=O CZNCTWNLEIFMDX-UHFFFAOYSA-N 0.000 description 1
- UGACIEPFGXRWCH-UHFFFAOYSA-N [Si].[Ti] Chemical compound [Si].[Ti] UGACIEPFGXRWCH-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- NIXOWILDQLNWCW-UHFFFAOYSA-N acrylic acid group Chemical group C(C=C)(=O)O NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 229920000180 alkyd Polymers 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- DIZPMCHEQGEION-UHFFFAOYSA-H aluminium sulfate (anhydrous) Chemical compound [Al+3].[Al+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O DIZPMCHEQGEION-UHFFFAOYSA-H 0.000 description 1
- 229940121375 antifungal agent Drugs 0.000 description 1
- 239000012736 aqueous medium Substances 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 239000011449 brick Substances 0.000 description 1
- 229910052980 cadmium sulfide Inorganic materials 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000004332 deodorization Methods 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 238000007865 diluting Methods 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- VEPSWGHMGZQCIN-UHFFFAOYSA-H ferric oxalate Chemical compound [Fe+3].[Fe+3].[O-]C(=O)C([O-])=O.[O-]C(=O)C([O-])=O.[O-]C(=O)C([O-])=O VEPSWGHMGZQCIN-UHFFFAOYSA-H 0.000 description 1
- 239000005357 flat glass Substances 0.000 description 1
- 238000009408 flooring Methods 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 238000004817 gas chromatography Methods 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 229910001922 gold oxide Inorganic materials 0.000 description 1
- 150000004677 hydrates Chemical class 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 230000003100 immobilizing effect Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 238000005468 ion implantation Methods 0.000 description 1
- 229910052741 iridium Inorganic materials 0.000 description 1
- FBAFATDZDUQKNH-UHFFFAOYSA-M iron chloride Chemical compound [Cl-].[Fe] FBAFATDZDUQKNH-UHFFFAOYSA-M 0.000 description 1
- 229910000358 iron sulfate Inorganic materials 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
- VBMVTYDPPZVILR-UHFFFAOYSA-N iron(2+);oxygen(2-) Chemical class [O-2].[Fe+2] VBMVTYDPPZVILR-UHFFFAOYSA-N 0.000 description 1
- PVFSDGKDKFSOTB-UHFFFAOYSA-K iron(3+);triacetate Chemical compound [Fe+3].CC([O-])=O.CC([O-])=O.CC([O-])=O PVFSDGKDKFSOTB-UHFFFAOYSA-K 0.000 description 1
- 230000001678 irradiating effect Effects 0.000 description 1
- 230000031700 light absorption Effects 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 1
- 229910052753 mercury Inorganic materials 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000003094 microcapsule Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 150000002823 nitrates Chemical class 0.000 description 1
- UJVRJBAUJYZFIX-UHFFFAOYSA-N nitric acid;oxozirconium Chemical compound [Zr]=O.O[N+]([O-])=O.O[N+]([O-])=O UJVRJBAUJYZFIX-UHFFFAOYSA-N 0.000 description 1
- QGLKJKCYBOYXKC-UHFFFAOYSA-N nonaoxidotritungsten Chemical compound O=[W]1(=O)O[W](=O)(=O)O[W](=O)(=O)O1 QGLKJKCYBOYXKC-UHFFFAOYSA-N 0.000 description 1
- 235000019645 odor Nutrition 0.000 description 1
- 239000005416 organic matter Substances 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 229910003445 palladium oxide Inorganic materials 0.000 description 1
- 239000000123 paper Substances 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 229910003446 platinum oxide Inorganic materials 0.000 description 1
- 229920002451 polyvinyl alcohol Polymers 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000011164 primary particle Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 230000002829 reductive effect Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 229910052703 rhodium Inorganic materials 0.000 description 1
- 239000010948 rhodium Substances 0.000 description 1
- 229910052707 ruthenium Inorganic materials 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
- 150000003377 silicon compounds Chemical class 0.000 description 1
- 239000005049 silicon tetrachloride Substances 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000011973 solid acid Substances 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 230000001954 sterilising effect Effects 0.000 description 1
- 238000004659 sterilization and disinfection Methods 0.000 description 1
- VEALVRVVWBQVSL-UHFFFAOYSA-N strontium titanate Chemical compound [Sr+2].[O-][Ti]([O-])=O VEALVRVVWBQVSL-UHFFFAOYSA-N 0.000 description 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 1
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 description 1
- 229910001887 tin oxide Inorganic materials 0.000 description 1
- PMTRSEDNJGMXLN-UHFFFAOYSA-N titanium zirconium Chemical compound [Ti].[Zr] PMTRSEDNJGMXLN-UHFFFAOYSA-N 0.000 description 1
- 229910052723 transition metal Inorganic materials 0.000 description 1
- 150000003624 transition metals Chemical class 0.000 description 1
- 229910001930 tungsten oxide Inorganic materials 0.000 description 1
- 238000004065 wastewater treatment Methods 0.000 description 1
- 239000013585 weight reducing agent Substances 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
- 239000011787 zinc oxide Substances 0.000 description 1
- 229910052984 zinc sulfide Inorganic materials 0.000 description 1
- DRDVZXDWVBGGMH-UHFFFAOYSA-N zinc;sulfide Chemical compound [S-2].[Zn+2] DRDVZXDWVBGGMH-UHFFFAOYSA-N 0.000 description 1
- DUNKXUFBGCUVQW-UHFFFAOYSA-J zirconium tetrachloride Chemical compound Cl[Zr](Cl)(Cl)Cl DUNKXUFBGCUVQW-UHFFFAOYSA-J 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
Description
【０００１】
【産業上の利用分野】
本発明は、蛍光灯のような微弱な光により空気中や廃水中の有害物質を浄化したり、汚れを分解除去したり、抗菌、防黴作用を発揮し、かつ繊維や塗料等の各種用途に適用可能な光触媒およびその製造方法に関するものである。
【０００２】
【従来の技術】
酸化チタン等光半導性を有した物質にバンドギャップ以上のエネルギーを有した光を照射すると電子と正孔が生成する。これによりスーパーオキサイドやＯＨラジカル等の強い酸化力を有した酸素種が光触媒の表面に生成して、接触する有害成分等を酸化分解することができる。そこで光触媒を建物の室内外に塗工して太陽光や蛍光灯の光を利用して大気や室内の環境浄化や脱臭、防汚、殺菌などへの応用が進められている。
【０００３】
光半導性を有する物質としては、一般に光触媒活性が高く化学的に安定な酸化チタンが使用されている。しかしながら、酸化チタンを励起するためには４００ｎｍ以下の紫外線を照射する必要があり、例えば室内では十分な効果を期待することができなかった。
【０００４】
そこで、光触媒の性能を向上するために酸化チタンにＰｔ、Ｐｄ、Ｒｈ、Ｒｕ、Ｉｒ 等の白金族金属やＦｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｚｎ、Ａｇ、Ｃｒ、Ｖ、Ｗ 等の各種遷移金属を添加することが検討されている。特に白金族金属の添加は光触媒の活性を高める効果が得られることがよく知られているが、高価な白金族金属を多量に使用することは光触媒の各種用途への適用性を損なうものであり好ましくない。
【０００５】
酸化チタンは、バンドギャップが大きく４００ｎｍ以下の紫外線しか利用できないため、可視光が利用できるバンドキャップが小さい酸化鉄などを光触媒として使用することが研究されている。例えば、金、白金、パラジウムあるいは二酸化チタンの表面に１０〜１００Åの粒径の酸化鉄を担持固定した光触媒が開示されている（特許文献１）。しかしながら、光触媒活性は低く実用レベルの効果が得られるものは見出されていない。
【０００６】
また、酸化チタン粒子の内部および／またはその表面に水酸化鉄等の鉄化合物を含有する光触媒用酸化チタンが開示されている（特許文献２）。しかしながら、紫外線照射下での効果が確認されているだけである。
【０００７】
最近では酸化チタンの光吸収帯を可視光領域までシフトさせ、可視光領域においても安定的に作用する可視光応答型光触媒に関する研究が行われている。例えば、Ｃｒ、Ｖ、Ｃｕ、Ｆｅ等の金属のイオンを３０ＫｅＶ以上の高エネルギーに加速して、酸化チタンに照射し該金属イオンを酸化チタンに導入する光触媒やその製造方法等が開示されている（特許文献３）。また、二酸化チタンを水素プラズマ処理または希ガス類元素プラズマ処理することによって、安定した酸素欠陥を有する可視光照射下で光触媒活性を示す二酸化チタンが得られることが開示されている（特許文献４）。しかし、これら金属元素のイオン注入やプラズマ処理には、大規模な装置が必要となり製造コストが非常に高くなるという問題があった。
【０００８】
一方、上記のように光触媒の性能向上を図るのとは別に、光触媒を各種用途に適用するに際して樹脂塗料等の有機バインダーを用いて基材に塗布したり、プラスチックスや繊維等の有機基材に練りこんだりした場合に光触媒の強力な酸化力により有機バインダーや有機基材を分解することが問題となっている。
【０００９】
この問題を解決するために、光触媒粒子を有機系バインダーを含む有機基材との接触を防止するために光触媒をマイクロカプセル状にする方法が知られている。例えば、チタニア粒子の表面に孔径が１ｎｍ 〜１０ μｍ の細孔を有する、光触媒として不活性なセラミックス膜をコートした光触媒が開示されている（特許文献５）。しかしながら、このような光触媒を製造するために有機溶媒や有機金属が使用されており、環境への負荷が大きくコスト的に割高となり工業的な量産には適していない。
【００１０】
さらに、本発明者等は光半導性物質に、例えば含浸法等により酸化鉄を高分散に担持することによって窒素酸化物除去等に適した光触媒が得られることを既に出願している（特許文献６）。
【特許文献１】
特開平６−３９２８５号公報
【特許文献２】
特開平７−３０３８３５号公報（特許第２９０９４０３号公報）
【特許文献３】
特開平９−２６２４８２公報
【特許文献４】
特許第３２５２１３６号公報
【特許文献５】
特許第２９４５９２６号公報
【特許文献６】
特願２００１−２８９６２２号明細書
【発明が解決しようとする課題】
このように従来の光触媒は２つの大きな課題があり十分に利用されていないのが現状である。すなわち、第一に酸化チタンは太陽光や紫外線ランプの照射により環境浄化、防汚等の機能を発揮することができるが、室内のような微弱な光照射下においては十分な光触媒効果が得られない。第二に光触媒は有害成分だけではなく接触する有機バインダーや有機基材まで分解するため適用可能な用途が限定されている。
【００１１】
本発明は上記の点に鑑み、微弱な光により悪臭の除去や、空気中の有害物質または汚れの分解除去、廃水処理や浄水処理、抗菌や防黴等の光触媒の優れた機能を効果的に発揮し、しかも樹脂塗料やコーティング剤に分散させて使用したり、プラスチックスや繊維等の練りこんで使用した場合でも、有機バインダーや有機基材の劣化が抑制される耐久性の優れた特性を有する光触媒およびその製造方法の提供を目的とするものである。
【００１２】
【課題を解決するための手段】
本発明は微弱な光で作用し各種用途に適用可能な光触媒に関するものであり、光半導性を有する粒子の表面に酸化鉄が０．３〜５質量％被覆されていることを特徴としている。光半導性を有する物質としては酸化チタンを使用することが好ましい。
【００１３】
粒子の表層部に酸化鉄を担持するものであるが、酸化鉄以外に０．５〜１０質量％の多孔質無機酸化物を光半導性を有する粒子の表面に被覆させてもよい。上記多孔質無機酸化物としてはシリカ、アルミナおよびジルコニアからなる群から選ばれる少なくとも1種であることが好ましい。
【００１４】
また、光触媒の製造方法として、光半導性を有する粒子をアンモニア水溶液に接触させた後に、鉄塩水溶液を添加し、次いで、ろ過、洗浄してから乾燥、焼成して粒子の表面に酸化鉄を０．３〜５質量％被覆せしめることにより上記特性を有した光触媒を得ることが出来る。
【００１５】
また、上記製造方法において、鉄塩水溶液とともに、多孔質無機酸化物の前駆体を添加して、次いで、ろ過、洗浄してから乾燥、焼成して粒子の表面に酸化鉄を０．３〜５質量％および多孔質無機酸化物を０．５〜１０質量％被覆せしめてもよい。
【００１６】
要するに、前記目的は、次の発明によって達成される。
（１）比表面積が３０〜２００ｍ ２ ／ｇ、平均粒子経が０．１〜５０μｍの光半導性を有する粒子の表面に酸化鉄が０．３〜５質量％被覆された光触媒であって、該酸化鉄が、上記光半導性を有する粒子をアンモニア水溶液に接触させた後に、鉄塩水溶液を添加し、次いでろ過、洗浄してから乾燥、焼成して得られたものであることを特徴とする光触媒。
（２）比表面積が３０〜２００ｍ ２ ／ｇ、平均粒子経が０．１〜５０μｍの光半導性を有する粒子の表面に酸化鉄が０．３〜５質量％、多孔質無機酸化物が０．５〜１０質量％被覆された光触媒であって、該酸化鉄および多孔質無機酸化物が、上記光半導性を有する粒子をアンモニア水溶液に接触させた後に、鉄塩水溶液と多孔質無機酸化物の前駆体とを添加し、次いでろ過、洗浄してから乾燥、焼成して得られたものであることを特徴とする光触媒。
（３）多孔質無機酸化物がシリカ、アルミナおよびジルコニアから選ばれる少なくとも１種である請求項１または２記載の光触媒。
【００１７】
【発明の実施の形態】
本発明の光触媒は、光半導性を有する粒子の表面に酸化鉄が０．３〜５質量％被覆されていることを特徴としている。本発明の光触媒は酸化チタン等の光半導性物質に含浸法等により酸化鉄が単に分散担持されているのではなく、光半導性を有した粒子を覆うように表層部に酸化鉄が担持されている光触媒である。このように光半導性を有した粒子の表面に酸化鉄を被覆することによって、微弱な光照射に対して量子効率が高まり優れた光触媒活性が得られると共に接触する有機バインダーや有機基材の劣化を抑制することができる。
【００１８】
本発明者等は光半導性物質に例えば含浸法等により酸化鉄を高分散に担持することによって窒素酸化物除去等に適した光触媒が得られることを既に出願している（特許文献６参照）。しかし、このように粒子の内部にまで酸化鉄を担持する場合は酸化鉄の含有率が高くなると光触媒性能が大幅に低下する場合があることが判った。原因としては電子と正孔の再結合が促進されるため性能が低下すると考えられる。一方、本発明に開示するように酸化鉄を光半導性粒子の表面に被覆せしめることにより、光触媒性能の低下を招くことなく含有率を高めることが可能となり微弱な光を利用して優れた光触媒効果が得られ、かつ従来問題となっていた、接触する有機バインダーや有機基材の劣化を抑制する効果が得られることを見出し本発明は完成するにいたっている。
【００１９】
粒子状の光半導性物質としては、酸化チタン、酸化スズ、酸化亜鉛や酸化タングステン等の酸化物、チタン酸ストロンチウム等の複合酸化物や硫化カドミウム、硫化亜鉛、炭化ケイ素等の化合物やそれらの混合物が使用可能である。特に化学的に安定である酸化チタンを使用することが好ましい。
【００２０】
光半導性物質の凝集粒子の平均粒子径は０．１〜５０μｍであり、比表面積が３０〜２００ｍ２／ｇであるものが好ましい。平均粒子径が０．１μｍより小さい場合や比表面積が２００ｍ２／ｇを超える場合は光触媒を調製することが難しくなり好ましくない。また平均粒子径が５０μｍを超える場合や比表面積が３０ｍ２／ｇ未満である場合は十分な光触媒性能が得られず好ましくない。
【００２１】
また、特公平５−５５１８４号公報に示されるチタン−ケイ素、チタン−ジルコニウム等のチタン系複合酸化物も、本発明の光半導性を有する粒子として使用することができる。チタン系複合酸化物も酸化チタンと同様に優れた光触媒特性を有し化学的に安定であり、且つ比表面積が高く耐熱性が優れているため酸化チタンより更に好ましい。チタン系複合酸化物は上記チタン系複合酸化物を用いる場合はチタンの含有率が５０〜８５モル％の範囲であることが好ましい。
【００２２】
上記チタン系複合酸化物は既知の手法により調製することが可能であるが、例えばチタンとケイ素からなる２元系複合酸化物を調製する方法として、以下の方法を例示する。
▲１▼四塩化チタンをシリカゾルと共に混合し、アンモニアを添加して沈殿を生成せしめ、この沈殿を洗浄、乾燥後に焼威する方法。
▲２▼四塩化チタンに珪酸ナトリウム水溶液（水ガラス）を添加して沈殿（共沈物）を生成させ、これを洗浄、乾燥後に焼成する方法。
▲３▼四塩化チタンの水一アルコール溶液にテトラエチルシリケートを添加して加水分解により沈殿を生成させ、これを洗浄、乾燥後に焼成する方法。
【００２３】
上記各方法において、得られた共沈物を３００〜６５０℃で１〜１０時間焼成することによって容易にチタンおよびケイ素からなる二元系複合酸化物を得ることができる。
【００２４】
上記調製方法において、▲１▼の方法が特に好ましいものであり、安価で容易な製造方法により優れた光半導性を有するチタン系複合酸化物を得ることができる。またチタン源、ケイ素源およびジルコニウム源のモル比を所定量とすることにより、同様にしてチタン系各複合酸化物よりなる光半導性を有した粒子を得ることができる。
【００２５】
本発明の光半導性粒子の表面に被覆せしめる酸化鉄の担持率は、光半導性粒子を基準として、０．３〜５質量％の範囲であり、より好ましくは０．５〜３質量％である。上記担持率は酸化鉄をＦｅ２Ｏ３に換算した値であり、酸化鉄の担持率が０．３質量％未満である場合は、量子効率が低くなり微弱な光に対する応答性が不十分となったり接触する有機物の劣化抑制効果が弱まる。また酸化鉄の担持率が５質量％より大きくなる場合は、光半導性物質に光が十分に到達しなくなり光触媒性能の低下を招く。
【００２６】
酸化鉄の結晶形態としてはＦｅＯ、Ｆｅ３Ｏ４、α−Ｆｅ２Ｏ３、γ−Ｆｅ２Ｏ３等の各種結晶形態があることが知られているが、本発明の光半導性粒子の表面に固定化されている酸化鉄の結晶形としてはα−Ｆｅ２Ｏ３であることが好ましい。また酸化鉄の一次粒子径は５〜１００ｎｍであることが好ましい。
【００２７】
酸化鉄は上記光半導性を有する粒子の表面に被覆する必要があり、例えばゾルとして被覆する方法や真空蒸着法やイオンスパッタリング法等により製造することができる。特に好ましくは加水分解反応により光半導性を有する粒子の表面に鉄化合物を沈着させた後に加熱して酸化鉄として固定する方法等が挙げられる。
【００２８】
次に、酸化鉄に加えて０．５〜１０質量％の多孔質無機酸化物を光半導性を有する粒子の表面に被覆してもよい。これにより光触媒と接触する有機バインダーや有機基材の劣化を更に抑制することができる。
【００２９】
酸化鉄を光半導性粒子に被覆してから更にその表面に多孔質無機酸化物を被覆してもよいし、酸化鉄と同時に多孔質無機酸化物を粒子の表面に被覆せしめてもよい。多孔質無機酸化物を被覆する方法としてはゾル付着法、界面反応法、真空蒸着法やイオンスパッタリング法等により実施することができる。多孔質無機酸化物が１０質量％を超える場合は光触媒性能が阻害されて微弱な光に対する反応性が低下するため好ましくない。
【００３０】
上記多孔質無機酸化物としては各種無機酸化物を使用することができ、例えば光触媒として不活性なシリカ、アルミナ、ジルコニア等を使用することができる。特に光透過性を有するシリカを使用することが好ましい。
【００３１】
本発明の光触媒の製造方法によれば、光半導性を有する粒子をアンモニア水溶液に接触させた後に、鉄塩水溶液を添加し、次いで、ろ過、洗浄してから乾燥、焼成して粒子の表面に酸化鉄を、好ましくは０．３〜５質量％の割合で、被覆せしめる。
【００３２】
鉄塩としては、硝酸鉄、硫酸鉄、塩化鉄、シュウ酸鉄、酢酸鉄等の、加水分解により不溶性の鉄化合物を生成するものを原料として使用することができる。
【００３３】
このように加水分解反応を用いることにより安価な原料を用いて、特別な製造装置を用いることなく簡易に優れた機能を有する光触媒を製造することができる。上記において接触させるアンモニアは被覆しようとする鉄塩のモル数に対して１．５〜１０倍程度の過剰となるようにアンモニア濃度を調整することが好ましい。
【００３４】
アンモニアの添加量は水溶液のｐＨを確認しながら滴下することが好ましい。アンモニア量が多過ぎると鉄塩を添加する際に溶液中に加水分解物が析出するため本発明の光触媒が得られない可能性がある。そこで、アンモニアに接触させてから一度ろ過して過剰なアンモニアは除去してから次の工程に進んでもよい。例えば、光半導性粒子をアンモニア水溶液と接触させた後、ろ過分離し、分離した粒子を水性媒体に分散させて分散液として使用してもよい。
【００３５】
このようにしてアンモニア処理された光半導性物質の分散液を攪拌しながら、徐々に鉄塩水溶液を滴下して鉄化合物を粒子の表面に沈着せしめる。加水分解反応により粒子の表面に付着する鉄化合物としては、水酸化鉄やオキシ酸化鉄のいずれかや、これらの混合物が生成しているものと考えられる。
【００３６】
上記製造方法において、鉄塩水溶液に、アンモニアと接触させた光半導性粒子の分散液を徐々に添加して、粒子の表面に鉄化合物を付着させてもよい。
【００３７】
本発明において使用することが好ましい光半導性物質である酸化チタンやチタン系複合酸化物は固体酸点を有しているためアンモニアと接触させた際に粒子が多量のアンモニウムイオンを吸着することができる。これにより次に分散液に鉄塩水溶液を滴下する際に液相で鉄化合物の沈殿が生成することが防止され、アンモニウムイオンが付着している粒子の表面にて加水分解反応が起こり選択的に鉄化合物を光半導性物質の表面に沈着することができる。
【００３８】
鉄塩を加水分解により粒子の表面に沈着させた後、ろ過して十分に水洗してから乾燥して焼成する。焼成温度としては１５０〜６００℃の範囲であり、好ましくは３００〜５００℃で実施することが好ましい。焼成温度が、１５０℃以下では酸化鉄になっていない鉄化合物が残存し発明の効果が十分得られない。また６００℃以上で焼成すると比表面積の低下を招くため好ましくない。
【００３９】
酸化鉄と多孔質無機酸化物とを被覆した光触媒を製造するに好適な方法としては、前述のように光半導性を有する粒子をアンモニア水溶液に接触させた後に鉄塩水溶液を添加する際に、鉄塩水溶液と多孔質無機酸化物の前駆体とを添加する方法が挙げられる。これにより鉄化合物とともに、多孔質無機酸化物の前駆体の加水分解生成物などが光半導性を有する粒子の表面に付着され以下同様にして、ろ過、洗浄してから乾燥、焼成して粒子の表面に酸化鉄および多孔質無機酸化物を被覆せしめることができる。
【００４０】
これら多孔質無機酸化物の前駆体は、アンモニア処理された光半導性粒子と接触することにより、粒子の表面で加水分解したり、不安定となって、鉄化合物と同様に粒子の表面に沈着（共沈）する。
上記製造方法を用いることにより、酸化鉄と多孔質無機酸化物とを同時に粒子の表面に被覆することが可能であり、安価な原料を用いて特別な製造装置を用いることなく簡易に優れた特性を有した光触媒を製造することができる。また、鉄塩水溶液を添加して鉄化合物を付着させた後に、多孔質無機酸化物の前駆体を添加してもよい。
【００４１】
多孔質無機酸化物の前駆体とは、焼成により多孔質無機酸化物を生成する、各金属、好ましくはケイ素、アルミニウムおよびジルコニウムの硝酸塩、硫酸塩、塩化物、酢酸塩、アルコキシド化合物などの化合物と、これら金属酸化物の水和物がコロイド状に分散したゾルを意味する。これらは単独でも、あるいは混合して使用してもよい。なお、上記各金属の硝酸塩、硫酸塩などの化合物は溶液、通常、水溶液の形態で用いられる。
【００４２】
多孔質無機酸化物の前駆体の代表例としては、例えば、シリカ源としては四塩化ケイ素、水ガラス、珪酸ナトリウム、エチルシリケートなどやシリカゾル等、アルミナ源としては硝酸アルミニウム、硫酸アルミニウム、塩化アルミニウムなどやアルミナゾル等、そしてジルコニア源としては硝酸ジルコニウム、オキシ硝酸ジルコニウム、塩化ジルコニウム、酢酸ジルコニウムなどやジルコニアゾル等を挙げることができる。
【００４３】
本発明の光触媒は室内外の建材等に塗工したりすることにより太陽光や室内照明を使用して、大気中の有害物質や臭気物質を分解除去したり、廃水浄化、防汚、抗菌、防黴等の優れた機能を得ることができる。特に微弱な光に対して敏感に作用し室内の蛍光灯照射下においても良好な光触媒効果が得られる。光触媒を塗工する建材としては室外では路面、ブロック、レンガ、防音壁、遮光壁、ビル側壁、屋根、窓ガラス、ガードレール、道路標識、自動車ボディ、船底等が挙げられる。また室内では天井材、壁紙、カーテン、絨毯、カーペット、床材、照明器具、家具、タイル等の光が当る部分に適用することができる。
【００４４】
光触媒を建材等の表面に被覆する方法としては、無機系および／または有機系のバインダーと共に各種建材に吹き付けたり、塗料化して各種建築物に塗布したり、プラスチックス、繊維、フィルム、紙に練り込んで利用する方法等がある。本発明の光触媒は有機バインダーや接触する有機基材の劣化を抑制することが可能であり各種用途に適用することができる。本発明における、光触媒を建材等に固定化するバインダーとしては、アクリル系樹脂、アルキド系樹脂、フッ素系樹脂、シリコン系樹脂やポリビニルアルコール等の有機系バインダーおよびシリカゾル、アルミナゾル、セメント、水ガラスやりん酸塩等の無機系バインダーを使用することができる。
【００４５】
【実施例】
以下の示す方法により実施例の光触媒Ａ〜Ｈ及び比較例の光触媒ａ〜ｂを調製し、その組成を表１に示した。
実施例１
光半導性を有した粒子として結晶形がアナターゼの市販の酸化チタン（比表面積７５ｍ２／ｇ、平均粒子径５．５μｍ）を用いて以下の光触媒を調製した。濃度１．２質量％に調整したアンモニア水溶液２５０ｇに上記酸化チタン１５０ｇを添加して１時間攪拌してアンモニアと接触させる。このアンモニア処理した酸化チタンの分散液に硝酸第二鉄１５ｇを溶解した水溶液１００ｇを徐々に滴下して酸化チタン粒子の表面に鉄化合物を沈着させる。５時間静置後、ろ過して洗浄を数回繰り返す。その後、１００℃で１２時間乾燥してから３５０℃で４時間焼成し酸化鉄が２．０質量％表層に担持されている光触媒Ａを得た。
実施例２〜４
実施例１において、添加する酸化チタンの量を変更した以外は実施例１と同様にして酸化鉄の担持量の異なる光触媒ＢからＥを調製した。
実施例５
アンモニア濃度２質量％の水溶液３００ｇに市販の酸化チタン２００ｇを分散し２時間攪拌した。このアンモニア処理した酸化チタンの分散液に硝酸第二鉄５ｇおよびシリカゾル（日産化学ＮＣＳ−Ｏ）４０ｇを溶解して水溶液１００ｇを徐々に滴下して粒子の表面に鉄化合物およびケイ素化合物を沈着させる。５時間静置後、ろ過して洗浄を数回繰り返す。その後、１００℃で１２時間乾燥してから３５０℃で４時間焼成し酸化鉄０．５質量％、シリカ４．０質量％が表層に担持されている光触媒Ｆを得た。
実施例６
チタンおよびケイ素からなる二元系複合酸化物を以下に述べる方法で調製した。シリカゾル２０ｋｇ（日産化学製ＮＣＳ−３０）にアンモニア水３００ｋｇ（濃度２５％）と水４００ｋｇを添加して溶液ａを得た。次に硫酸チタニルの硫酸水溶液１８０Ｌ（ＴｉＯ２濃度２５０ｇ／Ｌ，全硫酸濃度１１００ｇ／Ｌ）を水２５０ｋｇで希釈して溶液ｂを得た。溶液ａを攪拌しながら徐々に溶液ｂを滴下して共沈ゲルを生成し１５時間静置した。得られたゲルを濾過、水洗後２００℃で１０時間乾燥し、５５０℃で６時間焼成した後にハンマーミルにて粉砕し複合酸化物ＴＳ−１を得た。複合酸化物ＴＳ−１はチタンとケイ素がモル比でＴｉ／Ｓｉ＝８５／１５であり、比表面積は１５５ｍ２／ｇで平均粒子径が２０μｍであった。
【００４６】
次に実施例１において市販の酸化チタンの代わりに上記ＴＳ−１を用いた以外は実施例１と同様にしてチタンとケイ素の複合酸化物の粒子に酸化鉄が２．０質量％表層に担持されている光触媒Ｇを得た。
実施例７
実施例５において光半導性を有した粒子として実施例６で得られた複合酸化物ＴＳ−１を用い、シリカゾルの代わりにアルミナゾル（日産化学ＮＣＡ−５２０）を用いた以外は実施例５と同様にして酸化鉄０．５質量％、アルミナ４．０％が表層に担持されている光触媒Ｈを得た。
比較例１
実施例１において酸化鉄を担持しない市販の酸化チタンを比較例１（光触媒ａ）とした。
比較例２
通常の含浸法を用いて粒子の内部にまで酸化鉄が担持された比較触媒を以下のようにして調製した。硝酸鉄１５ｇを溶解した水溶液１００ｇを実施例１で用いたものと同じ酸化チタン７５ｇに添加して十分に混合してから乾燥焼成することにより酸化鉄が４質量％担持された光触媒ｂを得た。
【００４７】
【表１】
＜試験例１＞
実施例１〜７および比較例１〜２の光触媒を以下に示す閉鎖系試験方法でアセトアルデヒド分解性能を測定した。試験片は光触媒をＰＷＣ８０％でアクリル系樹脂を用いて塗料化し、塗布量５０ｇ／ｍ２となるように１５０×７０ｍｍのアクリル板の片面に塗布して６０℃で乾燥し作成した。上記試験片を５Ｌ反応器に設置し初期ガス濃度を１００ｐｐｍになるようにアセトアルデヒドを注入して光を照射し経時後のガス濃度をガスクロマトグラフィで測定して光触媒性能を比較した。
【００４９】
試験条件Ａでは光源に４Ｗのブラックライト（東芝ＦＬ４ＢＬＢ）を２本照射して３０分経過後の反応器内のガス濃度を測定し結果を表２に示した。試料に照射されている３６５ｎｍ付近の紫外線強度は３００μＷ／ｃｍ２であった。また試験条件Ｂでは光源に４Ｗの昼光色蛍光灯（東芝ＦＬ４Ｄ）を２本照射して１２０分経過後のガス濃度を測定し結果を表２に示した。試験条件Ｂの紫外線強度は１５μＷ／ｃｍ２であった。
【００５０】
【表２】
上記閉鎖系試験は光触媒の反応速度を比較するものであり、経時後のガス濃度が低いほど優れた光触媒性能を有していると判断される。また試験方法は室内の天井や壁に光触媒を塗工することを想定しており、これによりＶＯＣ等の有害性ガスに対する光触媒の効果を見積ることも可能である。
【００５２】
比較例１の酸化チタンに、実施例１〜５のように表面に酸化鉄を被覆することにより著しく光触媒性能が向上して優れた処理効率が得られている。特に光強度が弱い蛍光灯照射下において、その効果は顕著であり単に酸化鉄を含浸担持した比較例２と比較しても大幅に反応速度が促進されている。単に含浸して鉄を内部にまで担持する場合は光触媒により生成した電子と正孔の再結合を招くのに対して、表面に酸化鉄を担持した場合は電荷分離が促進され量子効率が高まっていると考えられる。またチタンとケイ素の複合酸化物を用いたり、表面にシリカやアルミナを酸化鉄と同時に添加した実施例５〜７のものも良好な光触媒性能を有している。
＜試験例２＞
試験例１で作成した試験片を紫外線でエージングして樹脂の減量率から有機バインダに対する劣化抑制効果を調べた。重量減少量が大きいほどバインダーの劣化が大きく、使用時に剥がれたり外観等に悪影響が出ると判断される。４００Ｗの水銀ランプ（東芝Ｈ４００ＢＬ）で紫外線を１００時間照射して塗料の減量率を測定した結果を表２に示した。試料面の紫外線強度は３．０ｍＷ／ｃｍ２であった。
【００５３】
表２に示す比較例１及び実施例１〜４の結果より酸化鉄を表面に被覆することにより塗料の減量が抑制される効果が得られることは明確である。チタンとケイ素の複合酸化物を用いた実施例６は酸化チタン系と比較して重量減少率は更に少ない。また実施例５及び実施例７の酸化鉄と同時にシリカやアルミナを粒子の表面に被覆したものは大幅に樹脂の劣化を抑制することができている。
【００５４】
【発明の効果】
本発明の光触媒は、酸化チタンと比較して反応速度の大幅な向上があり、特に微弱な紫外線照射下においても優れた光触媒効果を得ることができる。また光触媒性能は高いにもかかわらず接触する有機バインダーや有機基材の劣化を抑制する効果を有しており各種用途に適用することができる。本発明の光触媒は特殊な装置を使用することなく簡易な装置で安価に生産することが可能であり量産性も優れている。[0001]
[Industrial application fields]
The present invention purifies harmful substances in the air and wastewater with weak light such as a fluorescent lamp, decomposes and removes dirt, exhibits antibacterial and antifungal effects, and is used in various applications such as fibers and paints. The present invention relates to a photocatalyst that can be applied to the above and a production method thereof.
[0002]
[Prior art]
When a material having photoconductivity such as titanium oxide is irradiated with light having energy higher than the band gap, electrons and holes are generated. As a result, oxygen species having strong oxidizing power such as superoxide and OH radicals are generated on the surface of the photocatalyst, and harmful components and the like that come into contact can be oxidatively decomposed. Thus, photocatalysts are applied to the interior and exterior of buildings, and sunlight and fluorescent light are used to purify the atmosphere and indoor environments, and to apply to deodorization, antifouling, sterilization, and the like.
[0003]
In general, titanium oxide having high photocatalytic activity and being chemically stable is used as the material having photo-conductivity. However, in order to excite titanium oxide, it is necessary to irradiate ultraviolet rays of 400 nm or less, and for example, a sufficient effect cannot be expected indoors.
[0004]
Therefore, in order to improve the performance of the photocatalyst, a platinum group metal such as Pt, Pd, Rh, Ru, and Ir and various transition metals such as Fe, Co, Ni, Cu, Zn, Ag, Cr, V, and W are added to titanium oxide. The addition of is being considered. In particular, it is well known that the addition of platinum group metals has the effect of enhancing the activity of the photocatalyst, but the use of large amounts of expensive platinum group metals impairs the applicability of the photocatalyst to various uses. It is not preferable.
[0005]
Since titanium oxide has a large band gap and can only use ultraviolet rays having a wavelength of 400 nm or less, the use of iron oxide having a small band cap that can use visible light as a photocatalyst has been studied. For example, a photocatalyst is disclosed in which iron oxide having a particle size of 10 to 100 mm is supported and fixed on the surface of gold, platinum, palladium, or titanium dioxide (Patent Document 1). However, a photocatalytic activity is low and no practical effect has been found.
[0006]
Moreover, the titanium oxide for photocatalysts which contains iron compounds, such as iron hydroxide, in the inside and / or the surface of a titanium oxide particle is disclosed (patent document 2). However, only the effect under ultraviolet irradiation has been confirmed.
[0007]
Recently, studies have been conducted on visible light responsive photocatalysts that shift the light absorption band of titanium oxide to the visible light region and that stably operate in the visible light region. For example, a photocatalyst that accelerates metal ions such as Cr, V, Cu, and Fe to a high energy of 30 KeV or more, irradiates titanium oxide, and introduces the metal ions into titanium oxide, a manufacturing method thereof, and the like are disclosed. (Patent Document 3). Further, it is disclosed that titanium dioxide exhibiting photocatalytic activity under visible light irradiation having stable oxygen defects can be obtained by subjecting titanium dioxide to hydrogen plasma treatment or rare gas element plasma treatment (Patent Document 4). However, ion implantation and plasma treatment of these metal elements have a problem that a large-scale apparatus is required and the manufacturing cost becomes very high.
[0008]
On the other hand, apart from improving the performance of the photocatalyst as described above, when applying the photocatalyst to various uses, it is applied to the substrate using an organic binder such as a resin paint, or an organic substrate such as plastics or fibers. It is a problem that the organic binder or organic base material is decomposed by the strong oxidizing power of the photocatalyst when it is kneaded into the base.
[0009]
In order to solve this problem, a method is known in which the photocatalyst particles are made into microcapsules in order to prevent the photocatalyst particles from coming into contact with an organic substrate containing an organic binder. For example, a photocatalyst having a pore diameter of 1 nm to 10 μm on the surface of titania particles and coated with an inactive ceramic film as a photocatalyst is disclosed (Patent Document 5). However, an organic solvent or an organic metal is used to produce such a photocatalyst, which is not suitable for industrial mass production because it has a large environmental load and is expensive.
[0010]
Furthermore, the present inventors have already filed an application that a photocatalyst suitable for removal of nitrogen oxides can be obtained by supporting iron oxide in a highly dispersed manner by, for example, an impregnation method on a photoconductive substance (patent) Reference 6).
[Patent Document 1]
JP-A-6-39285
[Patent Document 2]
Japanese Patent Laid-Open No. 7-303835 (Japanese Patent No. 2909403)
[Patent Document 3]
Japanese Patent Laid-Open No. 9-262482
[Patent Document 4]
Japanese Patent No. 3252136
[Patent Document 5]
Japanese Patent No. 2945926
[Patent Document 6]
Japanese Patent Application No. 2001-289622
[Problems to be solved by the invention]
As described above, the conventional photocatalyst has two major problems and is not fully utilized. That is, firstly, titanium oxide can exert functions such as environmental purification and antifouling by irradiation with sunlight or an ultraviolet lamp, but a sufficient photocatalytic effect can be obtained under weak light irradiation such as indoors. Absent. Secondly, the photocatalyst decomposes not only harmful components but also organic binders and organic substrates that come into contact with them, so that applicable applications are limited.
[0011]
In view of the above points, the present invention effectively removes bad odors by faint light, decomposes and removes harmful substances or dirt in the air, effectively treats the excellent functions of photocatalysts such as wastewater treatment and water purification, antibacterial and antifungal. Even when used by dispersing in resin paints or coating agents, or by kneading plastics or fibers, it has excellent durability characteristics that suppress deterioration of organic binders and organic substrates. The object is to provide a photocatalyst having the same and a method for producing the same.
[0012]
[Means for Solving the Problems]
The present invention relates to a photocatalyst that works with weak light and can be applied to various uses, and is characterized in that the surface of particles having photo-semiconductivity is coated with 0.3 to 5% by mass of iron oxide. . It is preferable to use titanium oxide as the substance having optical semiconductivity.
[0013]
The iron oxide is supported on the surface layer of the particles. In addition to iron oxide, 0.5 to 10% by mass of a porous inorganic oxide may be coated on the surface of the particles having photoconductivity. The porous inorganic oxide is preferably at least one selected from the group consisting of silica, alumina and zirconia.
[0014]
In addition, as a photocatalyst production method, after bringing a photo-semiconductive particle into contact with an aqueous ammonia solution, an aqueous iron salt solution is added, and then filtered, washed, dried and baked to form iron oxide on the particle surface. A photocatalyst having the above characteristics can be obtained by coating 0.3 to 5% by mass of.
[0015]
Moreover, in the said manufacturing method, the precursor of a porous inorganic oxide is added with an iron salt aqueous solution, Then, it filters and wash | cleans, Then, it dries and bakes, and iron oxide is 0.3-5 on the particle | grain surface. You may coat 0.5 to 10% by mass of a porous inorganic oxide with a mass%.
[0016]
In short, the object is achieved by the following invention.
(1)Specific surface area of 30-200m 2 / G, a photocatalyst in which 0.3 to 5% by mass of iron oxide is coated on the surface of a particle having an optical semiconductivity with an average particle diameter of 0.1 to 50 μm,It is obtained by contacting the particles having optical semiconductivity with an aqueous ammonia solution, adding an aqueous iron salt solution, then filtering, washing, drying and firing.IsA photocatalyst characterized by the above.
(2)Specific surface area of 30-200m 2 / G, the surface of particles having an optical semiconductivity with an average particle diameter of 0.1 to 50 μm was coated with 0.3 to 5 mass% of iron oxide and 0.5 to 10 mass% of porous inorganic oxide A photocatalyst, wherein the iron oxide and the porous inorganic oxide areIt is obtained by bringing the particles having photo-semiconductivity into contact with an aqueous ammonia solution, adding an aqueous iron salt solution and a precursor of a porous inorganic oxide, then filtering, washing, drying and firing.IsA photocatalyst characterized by the above.
(3) The porous inorganic oxide is at least one selected from silica, alumina and zirconia.1 or 2The photocatalyst described.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
The photocatalyst of the present invention is characterized in that iron oxide is coated on the surface of particles having optical semiconductivity in an amount of 0.3 to 5% by mass. In the photocatalyst of the present invention, iron oxide is not simply dispersed and supported on a photoconductive material such as titanium oxide by an impregnation method or the like, but iron oxide is formed on the surface layer so as to cover the particles having photoconductive properties. It is a supported photocatalyst. Oxidation on the surface of the particles having photo-conductivity in this wayironBy covering the surface, the quantum efficiency is increased with respect to weak light irradiation, and excellent photocatalytic activity can be obtained, and at the same time, deterioration of the organic binder or organic base material in contact can be suppressed.
[0018]
The present inventors have already filed an application that a photocatalyst suitable for removing nitrogen oxides can be obtained by supporting iron oxide in a highly dispersed manner by, for example, an impregnation method on a photoconductive material (see Patent Document 6). ). However, it has been found that when the iron oxide is supported even inside the particles as described above, the photocatalytic performance may be significantly lowered as the iron oxide content increases. The cause is thought to be a decrease in performance because the recombination of electrons and holes is promoted. On the other hand, as disclosed in the present invention, by coating iron oxide on the surface of the photoconductive particles, it is possible to increase the content without deteriorating the photocatalytic performance, and it is excellent by using weak light. The present invention has been completed by finding that a photocatalytic effect can be obtained and an effect of suppressing deterioration of a contacting organic binder or organic base material, which has been a problem in the past, can be obtained.
[0019]
Particulate photoconductive materials include oxides such as titanium oxide, tin oxide, zinc oxide and tungsten oxide, composite oxides such as strontium titanate, compounds such as cadmium sulfide, zinc sulfide and silicon carbide, and their Mixtures can be used. It is particularly preferable to use titanium oxide that is chemically stable.
[0020]
The average particle diameter of the aggregated particles of the light semiconductive material is 0.1 to 50 μm, and the specific surface area is 30 to 200 m.2/ G is preferable. When the average particle size is smaller than 0.1 μm and the specific surface area is 200 m2If it exceeds / g, it is difficult to prepare a photocatalyst, which is not preferable. In addition, when the average particle diameter exceeds 50 μm, the specific surface area is 30 m.2When it is less than / g, sufficient photocatalytic performance cannot be obtained, which is not preferable.
[0021]
In addition, titanium-based composite oxides such as titanium-silicon and titanium-zirconium disclosed in JP-B-5-55184 can also be used as the particles having optical semiconductivity of the present invention. Similar to titanium oxide, titanium-based composite oxides are more preferable than titanium oxide because they have excellent photocatalytic properties, are chemically stable, and have a high specific surface area and excellent heat resistance. When the titanium composite oxide is used, the titanium composite oxide preferably has a titanium content in the range of 50 to 85 mol%.
[0022]
The titanium composite oxide can be prepared by a known method. For example, the following method is exemplified as a method of preparing a binary composite oxide composed of titanium and silicon.
(1) A method in which titanium tetrachloride is mixed with silica sol, ammonia is added to form a precipitate, and this precipitate is washed and dried and then burned.
(2) A method in which an aqueous sodium silicate solution (water glass) is added to titanium tetrachloride to form a precipitate (coprecipitate), which is washed and dried and then fired.
(3) A method in which tetraethyl silicate is added to a water-alcohol solution of titanium tetrachloride to form a precipitate by hydrolysis, which is washed, dried and then fired.
[0023]
In each of the above methods, a binary composite oxide composed of titanium and silicon can be easily obtained by firing the obtained coprecipitate at 300 to 650 ° C. for 1 to 10 hours.
[0024]
In the above preparation method, the method (1) is particularly preferable, and a titanium-based composite oxide having excellent optical semiconductivity can be obtained by an inexpensive and easy production method. In addition, by setting the molar ratio of the titanium source, silicon source and zirconium source to a predetermined amount, particles having optical semiconductivity composed of titanium-based composite oxides can be obtained in the same manner.
[0025]
The supporting rate of iron oxide to be coated on the surface of the optical semiconductor particles of the present invention is in the range of 0.3 to 5% by mass, more preferably 0.5 to 3% by mass, based on the optical semiconductor particles. %. The above loading ratio is obtained by converting iron oxide into Fe.2O3When the iron oxide loading is less than 0.3% by mass, the quantum efficiency is low, the response to weak light is insufficient, and the effect of suppressing deterioration of organic matter in contact is weakened. . On the other hand, when the iron oxide loading is larger than 5% by mass, the light does not reach the photoconductive material sufficiently and the photocatalytic performance is lowered.
[0026]
The crystal form of iron oxide is FeO, Fe3O4, Α-Fe2O3, Γ-Fe2O3It is known that there are various crystal forms such as, but the crystal form of iron oxide immobilized on the surface of the optical semiconductor particles of the present invention is α-Fe.2O3It is preferable that The primary particle diameter of iron oxide is preferably 5 to 100 nm.
[0027]
Iron oxide must be coated on the surface of the particles having the above-mentioned optical semiconductivity, and can be produced by, for example, a coating method as a sol, a vacuum deposition method, an ion sputtering method, or the like. Particularly preferred is a method in which an iron compound is deposited on the surface of a particle having a light semiconductivity by a hydrolysis reaction and then heated and fixed as iron oxide.
[0028]
Next, in addition to iron oxide, 0.5 to 10% by mass of a porous inorganic oxide may be coated on the surface of the particles having optical semiconductivity. Thereby, deterioration of the organic binder and organic base material which contact a photocatalyst can further be suppressed.
[0029]
The surface of the particles may be coated with the porous inorganic oxide after the iron oxide is coated on the optical semiconductive particles, or the surface of the particles may be coated with the porous inorganic oxide simultaneously with the iron oxide. The porous inorganic oxide can be coated by a sol deposition method, an interface reaction method, a vacuum deposition method, an ion sputtering method, or the like. When the porous inorganic oxide exceeds 10% by mass, the photocatalytic performance is hindered and the reactivity to weak light is lowered, which is not preferable.
[0030]
Various inorganic oxides can be used as the porous inorganic oxide. For example, inert silica, alumina, zirconia, or the like can be used as a photocatalyst. In particular, it is preferable to use silica having optical transparency.
[0031]
According to the method for producing a photocatalyst of the present invention, after bringing photoconductive semiconductive particles into contact with an aqueous ammonia solution, an aqueous iron salt solution is added, and then filtered, washed, dried and fired to obtain the surface of the particles. Is coated with iron oxide, preferably at a ratio of 0.3 to 5% by mass.
[0032]
As an iron salt, iron nitrate, iron sulfate, iron chloride, iron oxalate, iron acetate, or the like that generates an insoluble iron compound by hydrolysis can be used as a raw material.
[0033]
Thus, by using a hydrolysis reaction, a photocatalyst having an excellent function can be easily produced without using a special production apparatus, using an inexpensive raw material. In the above, it is preferable to adjust the ammonia concentration so that the ammonia to be contacted is in excess of about 1.5 to 10 times the number of moles of iron salt to be coated.
[0034]
The ammonia is preferably added dropwise while confirming the pH of the aqueous solution. If the amount of ammonia is too large, a hydrolyzate precipitates in the solution when the iron salt is added, so that the photocatalyst of the present invention may not be obtained. Therefore, after contacting with ammonia, it may be filtered once to remove excess ammonia and then proceed to the next step. For example, the photoconductive particles may be contacted with an aqueous ammonia solution and then separated by filtration, and the separated particles may be dispersed in an aqueous medium and used as a dispersion.
[0035]
While stirring the dispersion of the photoconductive material treated with ammonia in this manner, an iron salt aqueous solution is gradually dropped to deposit the iron compound on the surface of the particles. As the iron compound adhering to the surface of the particles by the hydrolysis reaction, it is considered that either iron hydroxide or iron oxyoxide or a mixture thereof is generated.
[0036]
In the above production method, the dispersion of the light semiconductive particles brought into contact with ammonia may be gradually added to the iron salt aqueous solution to adhere the iron compound to the surface of the particles.
[0037]
Titanium oxide and titanium-based composite oxides, which are preferable photoconductive materials to be used in the present invention, have solid acid sites, so that particles adsorb a large amount of ammonium ions when brought into contact with ammonia. Can do. This prevents the precipitation of an iron compound in the liquid phase when the aqueous iron salt solution is subsequently added dropwise to the dispersion, and a hydrolysis reaction occurs selectively on the surface of the particles to which ammonium ions are attached. An iron compound can be deposited on the surface of the photoconductive material.
[0038]
The iron salt is deposited on the surface of the particles by hydrolysis, then filtered, washed thoroughly with water, dried and fired. As a calcination temperature, it is the range of 150-600 degreeC, It is preferable to implement at 300-500 degreeC preferably. When the firing temperature is 150 ° C. or less, iron compounds that are not iron oxide remain and the effects of the invention cannot be sufficiently obtained. Further, firing at 600 ° C. or higher is not preferable because the specific surface area is reduced.
[0039]
As a suitable method for producing a photocatalyst coated with iron oxide and a porous inorganic oxide, as described above, when an aqueous iron salt solution is added after bringing the photoconductive particles into contact with an aqueous ammonia solution, And a method of adding an aqueous iron salt solution and a precursor of a porous inorganic oxide. As a result, the hydrolysis product of the precursor of the porous inorganic oxide together with the iron compound is adhered to the surface of the particle having photo-semiconductivity, and thereafter, filtered, washed, dried and fired to obtain particles. The surface can be coated with iron oxide and porous inorganic oxide.
[0040]
These porous inorganic oxide precursors are hydrolyzed or unstable on the surface of the particles when in contact with the ammonia-treated photoconductive particles, and on the surface of the particles as with iron compounds. Deposit (co-precipitate).
By using the above manufacturing method, it is possible to coat iron oxide and porous inorganic oxide on the surface of the particles at the same time, and easily and excellent characteristics using inexpensive raw materials without using special manufacturing equipment Can be produced. Moreover, after adding an iron salt aqueous solution and making an iron compound adhere, you may add the precursor of a porous inorganic oxide.
[0041]
The porous inorganic oxide precursor is a compound such as nitrate, sulfate, chloride, acetate, alkoxide compound of each metal, preferably silicon, aluminum and zirconium, which forms a porous inorganic oxide by firing. In addition, it means a sol in which hydrates of these metal oxides are colloidally dispersed. These may be used alone or in combination. The compounds such as nitrates and sulfates of the above metals are used in the form of a solution, usually an aqueous solution.
[0042]
Typical examples of porous inorganic oxide precursors include, for example, silicon tetrachloride, water glass, sodium silicate, ethyl silicate, and silica sol as the silica source, and aluminum nitrate, aluminum sulfate, and aluminum chloride as the alumina source. Examples of the zirconia source include zirconium nitrate, zirconium oxynitrate, zirconium chloride, zirconium acetate, and zirconia sol.
[0043]
The photocatalyst of the present invention is applied to indoor and outdoor building materials, etc. by using sunlight and indoor lighting to decompose and remove harmful substances and odorous substances in the atmosphere, purifying wastewater, antifouling, antibacterial, Excellent functions such as fendering can be obtained. In particular, it works sensitively to weak light, and a good photocatalytic effect can be obtained even under indoor fluorescent lamp irradiation. Examples of building materials to which the photocatalyst is applied include road surfaces, blocks, bricks, soundproof walls, light shielding walls, building side walls, roofs, window glass, guardrails, road signs, automobile bodies, ship bottoms, and the like. In addition, the present invention can be applied to portions that are exposed to light such as ceiling materials, wallpaper, curtains, carpets, carpets, flooring materials, lighting equipment, furniture, and tiles.
[0044]
The photocatalyst can be coated on the surface of building materials by spraying it on various building materials with inorganic and / or organic binders, coating it on various buildings, and kneading it on plastics, fibers, films and papers. There are methods to use it. The photocatalyst of the present invention can suppress deterioration of an organic binder or an organic base material in contact with the photocatalyst, and can be applied to various uses. In the present invention, the binder for immobilizing the photocatalyst on building materials and the like includes organic binders such as acrylic resins, alkyd resins, fluorine resins, silicon resins and polyvinyl alcohol, silica sol, alumina sol, cement, water glass and phosphorus. An inorganic binder such as an acid salt can be used.
[0045]
【Example】
The photocatalysts A to H of Examples and the photocatalysts a to b of Comparative Examples were prepared by the following method, and the compositions thereof are shown in Table 1.
Example 1
Commercially available titanium oxide having a crystal form of anatase as a particle having optical semiconductivity (specific surface area 75 m2/ G, average particle diameter of 5.5 μm) was used to prepare the following photocatalyst. 150 g of the above titanium oxide is added to 250 g of an aqueous ammonia solution adjusted to a concentration of 1.2% by mass, stirred for 1 hour and brought into contact with ammonia. 100 g of an aqueous solution in which 15 g of ferric nitrate is dissolved is gradually added dropwise to the ammonia-treated titanium oxide dispersion to deposit an iron compound on the surface of the titanium oxide particles. After standing for 5 hours, filtration and washing are repeated several times. Then, after drying at 100 degreeC for 12 hours, it baked at 350 degreeC for 4 hours, and obtained the photocatalyst A by which iron oxide was carry | supported by 2.0 mass% surface layer.
Examples 2-4
In Example 1, E was prepared from photocatalysts B to E having different loadings of iron oxide in the same manner as in Example 1 except that the amount of titanium oxide to be added was changed.
Example 5
200 g of commercially available titanium oxide was dispersed in 300 g of an aqueous solution having an ammonia concentration of 2% by mass and stirred for 2 hours. In this ammonia-treated titanium oxide dispersion, 5 g of ferric nitrate and 40 g of silica sol (Nissan Chemical NCS-O) are dissolved, and 100 g of an aqueous solution is gradually added dropwise to deposit an iron compound and a silicon compound on the surface of the particles. After standing for 5 hours, filtration and washing are repeated several times. Then, after drying at 100 degreeC for 12 hours, it baked at 350 degreeC for 4 hours, and obtained the photocatalyst F by which 0.5 mass% of iron oxides and 4.0 mass% of silica were carry | supported by the surface layer.
Example 6
A binary complex oxide composed of titanium and silicon was prepared by the method described below. A solution a was obtained by adding 300 kg of ammonia water (concentration 25%) and 400 kg of water to 20 kg of silica sol (NCS-30 manufactured by Nissan Chemical Co., Ltd.). Next, 180 L (TiO2) aqueous solution of titanyl sulfate2A solution b was obtained by diluting a concentration of 250 g / L and a total sulfuric acid concentration of 1100 g / L with 250 kg of water. While stirring the solution a, the solution b was gradually added dropwise to form a coprecipitated gel, which was allowed to stand for 15 hours. The obtained gel was filtered, washed with water, dried at 200 ° C. for 10 hours, calcined at 550 ° C. for 6 hours, and then pulverized with a hammer mill to obtain composite oxide TS-1. The composite oxide TS-1 has a molar ratio of titanium / silicon of Ti / Si = 85/15 and a specific surface area of 155 m.2The average particle size was 20 μm at / g.
[0046]
Next, in the same manner as in Example 1 except that TS-1 was used in place of the commercially available titanium oxide in Example 1, 2.0% by mass of iron oxide was supported on the surface of the composite oxide of titanium and silicon. The photocatalyst G being obtained was obtained.
Example 7
Example 5 is the same as Example 5 except that the composite oxide TS-1 obtained in Example 6 was used as the particle having optical semiconductivity in Example 5 and alumina sol (Nissan Chemical NCA-520) was used instead of silica sol. Similarly, a photocatalyst H in which 0.5% by mass of iron oxide and 4.0% of alumina were supported on the surface layer was obtained.
Comparative Example 1
In Example 1, a commercially available titanium oxide not supporting iron oxide was used as Comparative Example 1 (photocatalyst a).
Comparative Example 2
A comparative catalyst in which iron oxide was supported inside the particles using a normal impregnation method was prepared as follows. 100 g of an aqueous solution in which 15 g of iron nitrate was dissolved was added to 75 g of the same titanium oxide used in Example 1, mixed thoroughly, and then dried and fired to obtain a photocatalyst b carrying 4% by mass of iron oxide. .
[0047]
[Table 1]
<Test Example 1>
The acetaldehyde decomposition performance of the photocatalysts of Examples 1 to 7 and Comparative Examples 1 and 2 was measured by the closed system test method described below. The test piece was made from a photocatalyst with a PWC of 80% using an acrylic resin, and the coating amount was 50 g / m.2It was applied to one side of a 150 × 70 mm acrylic plate so as to be dried at 60 ° C. The test piece was placed in a 5 L reactor, acetaldehyde was injected so that the initial gas concentration was 100 ppm, light was irradiated, the gas concentration after aging was measured by gas chromatography, and the photocatalytic performance was compared.
[0049]
Under test condition A, two 4 W black lights (Toshiba FL4BLB) were irradiated to the light source and the gas concentration in the reactor after 30 minutes was measured. The results are shown in Table 2. The UV intensity around 365 nm irradiated on the sample is 300 μW / cm2Met. In test condition B, the light concentration was irradiated with two 4 W daylight fluorescent lamps (Toshiba FL4D) and the gas concentration after 120 minutes was measured. The results are shown in Table 2. UV intensity of test condition B is 15 μW / cm2Met.
[0050]
[Table 2]
The above closed system test compares the reaction rate of the photocatalyst, and it is judged that the lower the gas concentration after time, the better the photocatalytic performance. In addition, the test method assumes that a photocatalyst is applied to the ceiling or wall of the room, so that the effect of the photocatalyst on harmful gases such as VOC can be estimated.
[0052]
By coating the surface of the titanium oxide of Comparative Example 1 with iron oxide as in Examples 1 to 5, the photocatalytic performance is remarkably improved and excellent processing efficiency is obtained. The effect is particularly remarkable under the irradiation of a fluorescent lamp having a low light intensity, and the reaction rate is greatly accelerated compared with Comparative Example 2 in which iron oxide is simply impregnated and supported. In the case of simply impregnating and supporting iron inside, recombination of electrons and holes generated by the photocatalyst is caused, whereas in the case of supporting iron oxide on the surface, charge separation is promoted and quantum efficiency is increased. It is thought that there is. Moreover, the thing of Examples 5-7 which used the complex oxide of titanium and silicon, or added silica and alumina to the surface simultaneously with iron oxide also has favorable photocatalytic performance.
<Test Example 2>
The test piece prepared in Test Example 1 was aged with ultraviolet rays, and the deterioration inhibiting effect on the organic binder was examined from the resin weight loss rate. It is determined that the greater the weight loss, the greater the deterioration of the binder, causing peeling during use and adverse effects on the appearance and the like. Table 2 shows the results of measuring the weight loss rate of the paint by irradiating ultraviolet rays with a 400 W mercury lamp (Toshiba H400BL) for 100 hours. UV intensity of sample surface is 3.0mW / cm2Met.
[0053]
From the results of Comparative Example 1 and Examples 1 to 4 shown in Table 2, it is clear that the effect of suppressing the weight loss of the paint can be obtained by coating the surface with iron oxide. In Example 6 using the composite oxide of titanium and silicon, the weight reduction rate is still smaller than that of the titanium oxide system. Moreover, the thing which coat | covered the surface of the particle | grains with silica and alumina simultaneously with the iron oxide of Example 5 and Example 7 has suppressed the deterioration of resin significantly.
[0054]
【The invention's effect】
The photocatalyst of the present invention has a significant improvement in the reaction rate as compared with titanium oxide, and an excellent photocatalytic effect can be obtained even under weak ultraviolet irradiation. Moreover, although it has high photocatalytic performance, it has an effect of suppressing deterioration of the organic binder and organic substrate that are in contact with each other, and can be applied to various applications. The photocatalyst of the present invention can be produced inexpensively with a simple apparatus without using a special apparatus, and is excellent in mass productivity.
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