WO2010114561A1 - Production of tailored metal oxide materials using a reaction sol-gel approach - Google Patents
Production of tailored metal oxide materials using a reaction sol-gel approach Download PDFInfo
- Publication number
- WO2010114561A1 WO2010114561A1 PCT/US2009/039510 US2009039510W WO2010114561A1 WO 2010114561 A1 WO2010114561 A1 WO 2010114561A1 US 2009039510 W US2009039510 W US 2009039510W WO 2010114561 A1 WO2010114561 A1 WO 2010114561A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- metal oxide
- oxide material
- solvent
- particles
- porous
- Prior art date
Links
- 150000004706 metal oxides Chemical class 0.000 title claims abstract description 92
- 229910044991 metal oxide Inorganic materials 0.000 title claims abstract description 89
- 239000000463 material Substances 0.000 title claims abstract description 71
- 238000006243 chemical reaction Methods 0.000 title description 7
- 238000004519 manufacturing process Methods 0.000 title description 3
- 238000013459 approach Methods 0.000 title description 2
- 239000002245 particle Substances 0.000 claims abstract description 42
- 150000003839 salts Chemical class 0.000 claims abstract description 42
- 238000006460 hydrolysis reaction Methods 0.000 claims abstract description 37
- 229910052751 metal Inorganic materials 0.000 claims abstract description 34
- 239000002184 metal Substances 0.000 claims abstract description 34
- 239000012702 metal oxide precursor Substances 0.000 claims abstract description 9
- 239000007795 chemical reaction product Substances 0.000 claims abstract description 4
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 101
- 238000000034 method Methods 0.000 claims description 79
- 239000011148 porous material Substances 0.000 claims description 67
- 239000002904 solvent Substances 0.000 claims description 64
- 229920000642 polymer Polymers 0.000 claims description 46
- 239000000243 solution Substances 0.000 claims description 33
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 30
- 239000002243 precursor Substances 0.000 claims description 26
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 24
- 238000001354 calcination Methods 0.000 claims description 21
- 239000002002 slurry Substances 0.000 claims description 20
- 238000010992 reflux Methods 0.000 claims description 19
- 239000007787 solid Substances 0.000 claims description 19
- 239000000203 mixture Substances 0.000 claims description 17
- 239000000758 substrate Substances 0.000 claims description 15
- 230000032683 aging Effects 0.000 claims description 14
- 239000002202 Polyethylene glycol Substances 0.000 claims description 13
- 229920001223 polyethylene glycol Polymers 0.000 claims description 13
- 239000004065 semiconductor Substances 0.000 claims description 13
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical class [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 12
- 238000009826 distribution Methods 0.000 claims description 12
- 238000001035 drying Methods 0.000 claims description 12
- 230000003750 conditioning effect Effects 0.000 claims description 10
- 239000002253 acid Substances 0.000 claims description 9
- 239000007864 aqueous solution Substances 0.000 claims description 9
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical group [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 9
- 239000003054 catalyst Substances 0.000 claims description 9
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 8
- 239000004094 surface-active agent Substances 0.000 claims description 8
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical class [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims description 6
- 239000002738 chelating agent Substances 0.000 claims description 6
- 238000001914 filtration Methods 0.000 claims description 6
- 229910052742 iron Inorganic materials 0.000 claims description 6
- 238000002156 mixing Methods 0.000 claims description 6
- 229910052718 tin Inorganic materials 0.000 claims description 6
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 5
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 claims description 5
- 238000010438 heat treatment Methods 0.000 claims description 5
- 229910052710 silicon Inorganic materials 0.000 claims description 5
- 239000010703 silicon Substances 0.000 claims description 5
- 229910052726 zirconium Inorganic materials 0.000 claims description 5
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 claims description 4
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 4
- 239000003125 aqueous solvent Substances 0.000 claims description 4
- 229910017052 cobalt Inorganic materials 0.000 claims description 4
- 239000010941 cobalt Substances 0.000 claims description 4
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 4
- 229910052733 gallium Inorganic materials 0.000 claims description 4
- 229910052732 germanium Inorganic materials 0.000 claims description 4
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 claims description 4
- 229910052735 hafnium Inorganic materials 0.000 claims description 4
- VBJZVLUMGGDVMO-UHFFFAOYSA-N hafnium atom Chemical compound [Hf] VBJZVLUMGGDVMO-UHFFFAOYSA-N 0.000 claims description 4
- 229910052746 lanthanum Inorganic materials 0.000 claims description 4
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 claims description 4
- 229910052750 molybdenum Inorganic materials 0.000 claims description 4
- 239000011733 molybdenum Substances 0.000 claims description 4
- 229910052759 nickel Inorganic materials 0.000 claims description 4
- 229910052758 niobium Inorganic materials 0.000 claims description 4
- 239000010955 niobium Substances 0.000 claims description 4
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 claims description 4
- 150000007524 organic acids Chemical class 0.000 claims description 4
- 229910052702 rhenium Inorganic materials 0.000 claims description 4
- WUAPFZMCVAUBPE-UHFFFAOYSA-N rhenium atom Chemical compound [Re] WUAPFZMCVAUBPE-UHFFFAOYSA-N 0.000 claims description 4
- 229910052706 scandium Inorganic materials 0.000 claims description 4
- SIXSYDAISGFNSX-UHFFFAOYSA-N scandium atom Chemical compound [Sc] SIXSYDAISGFNSX-UHFFFAOYSA-N 0.000 claims description 4
- 229910052715 tantalum Inorganic materials 0.000 claims description 4
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 claims description 4
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 4
- 229910052721 tungsten Inorganic materials 0.000 claims description 4
- 239000010937 tungsten Substances 0.000 claims description 4
- 229910052727 yttrium Inorganic materials 0.000 claims description 4
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 claims description 4
- 238000003618 dip coating Methods 0.000 claims description 3
- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical class [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 claims description 3
- 238000005507 spraying Methods 0.000 claims description 3
- 238000009503 electrostatic coating Methods 0.000 claims description 2
- 150000002367 halogens Chemical group 0.000 claims description 2
- 238000007669 thermal treatment Methods 0.000 claims description 2
- 238000007670 refining Methods 0.000 claims 3
- 229910052684 Cerium Chemical class 0.000 claims 2
- 229910052779 Neodymium Inorganic materials 0.000 claims 2
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical class [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims 2
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical class [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 claims 2
- 229910052738 indium Inorganic materials 0.000 claims 2
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical class [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 claims 2
- 229910052725 zinc Inorganic materials 0.000 claims 2
- 239000011701 zinc Chemical class 0.000 claims 2
- 230000001143 conditioned effect Effects 0.000 abstract 1
- 239000011941 photocatalyst Substances 0.000 description 29
- 239000004408 titanium dioxide Substances 0.000 description 19
- 230000001699 photocatalysis Effects 0.000 description 17
- 230000009849 deactivation Effects 0.000 description 16
- 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 16
- 230000007062 hydrolysis Effects 0.000 description 15
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 13
- 230000015572 biosynthetic process Effects 0.000 description 12
- 239000000843 powder Substances 0.000 description 11
- 125000002524 organometallic group Chemical group 0.000 description 10
- 230000008569 process Effects 0.000 description 10
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 description 10
- 229910052719 titanium Inorganic materials 0.000 description 10
- 239000010936 titanium Substances 0.000 description 10
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 9
- 239000011800 void material Substances 0.000 description 9
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 8
- 239000007789 gas Substances 0.000 description 8
- -1 siloxanes Chemical class 0.000 description 8
- 238000000576 coating method Methods 0.000 description 7
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 7
- 239000000047 product Substances 0.000 description 7
- YUOWTJMRMWQJDA-UHFFFAOYSA-J tin(iv) fluoride Chemical compound [F-].[F-].[F-].[F-].[Sn+4] YUOWTJMRMWQJDA-UHFFFAOYSA-J 0.000 description 7
- 239000011248 coating agent Substances 0.000 description 6
- 230000003993 interaction Effects 0.000 description 6
- 238000002955 isolation Methods 0.000 description 6
- 239000012528 membrane Substances 0.000 description 6
- 229910052760 oxygen Inorganic materials 0.000 description 6
- 239000001301 oxygen Substances 0.000 description 6
- 238000002360 preparation method Methods 0.000 description 6
- 229910001887 tin oxide Inorganic materials 0.000 description 6
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 5
- 239000012535 impurity Substances 0.000 description 5
- 230000000977 initiatory effect Effects 0.000 description 5
- 238000000926 separation method Methods 0.000 description 5
- 238000001179 sorption measurement Methods 0.000 description 5
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 description 4
- HGINCPLSRVDWNT-UHFFFAOYSA-N Acrolein Chemical compound C=CC=O HGINCPLSRVDWNT-UHFFFAOYSA-N 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- 229910052782 aluminium Inorganic materials 0.000 description 4
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 4
- 150000001768 cations Chemical class 0.000 description 4
- 229910000420 cerium oxide Inorganic materials 0.000 description 4
- 239000000356 contaminant Substances 0.000 description 4
- 238000002474 experimental method Methods 0.000 description 4
- 229910003437 indium oxide Inorganic materials 0.000 description 4
- PJXISJQVUVHSOJ-UHFFFAOYSA-N indium(iii) oxide Chemical compound [O-2].[O-2].[O-2].[In+3].[In+3] PJXISJQVUVHSOJ-UHFFFAOYSA-N 0.000 description 4
- 239000011572 manganese Substances 0.000 description 4
- 229910052757 nitrogen Inorganic materials 0.000 description 4
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 description 4
- 239000011343 solid material Substances 0.000 description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 239000000654 additive Substances 0.000 description 3
- 150000001450 anions Chemical class 0.000 description 3
- 239000000010 aprotic solvent Substances 0.000 description 3
- 239000012298 atmosphere Substances 0.000 description 3
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- PNOXNTGLSKTMQO-UHFFFAOYSA-L diacetyloxytin Chemical compound CC(=O)O[Sn]OC(C)=O PNOXNTGLSKTMQO-UHFFFAOYSA-L 0.000 description 3
- 238000010494 dissociation reaction Methods 0.000 description 3
- 230000005593 dissociations Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- UQEAIHBTYFGYIE-UHFFFAOYSA-N hexamethyldisiloxane Chemical compound C[Si](C)(C)O[Si](C)(C)C UQEAIHBTYFGYIE-UHFFFAOYSA-N 0.000 description 3
- 238000003837 high-temperature calcination Methods 0.000 description 3
- 238000010348 incorporation Methods 0.000 description 3
- 150000002500 ions Chemical class 0.000 description 3
- 235000013980 iron oxide Nutrition 0.000 description 3
- VBMVTYDPPZVILR-UHFFFAOYSA-N iron(2+);oxygen(2-) Chemical class [O-2].[Fe+2] VBMVTYDPPZVILR-UHFFFAOYSA-N 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 150000007522 mineralic acids Chemical class 0.000 description 3
- 229910052755 nonmetal Inorganic materials 0.000 description 3
- 238000000746 purification Methods 0.000 description 3
- 238000003980 solgel method Methods 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- POILWHVDKZOXJZ-ARJAWSKDSA-M (z)-4-oxopent-2-en-2-olate Chemical compound C\C([O-])=C\C(C)=O POILWHVDKZOXJZ-ARJAWSKDSA-M 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- NBBJYMSMWIIQGU-UHFFFAOYSA-N Propionic aldehyde Chemical compound CCC=O NBBJYMSMWIIQGU-UHFFFAOYSA-N 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 230000002378 acidificating effect Effects 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 239000011324 bead Substances 0.000 description 2
- 238000005119 centrifugation Methods 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 238000011109 contamination Methods 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 230000001186 cumulative effect Effects 0.000 description 2
- 238000003795 desorption Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000010790 dilution Methods 0.000 description 2
- 239000012895 dilution Substances 0.000 description 2
- KPUWHANPEXNPJT-UHFFFAOYSA-N disiloxane Chemical class [SiH3]O[SiH3] KPUWHANPEXNPJT-UHFFFAOYSA-N 0.000 description 2
- 238000004821 distillation Methods 0.000 description 2
- 239000002019 doping agent Substances 0.000 description 2
- 239000000839 emulsion Substances 0.000 description 2
- 239000012530 fluid Substances 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 2
- 238000005286 illumination Methods 0.000 description 2
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 229910003455 mixed metal oxide Inorganic materials 0.000 description 2
- 239000002105 nanoparticle Substances 0.000 description 2
- PLDDOISOJJCEMH-UHFFFAOYSA-N neodymium(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Nd+3].[Nd+3] PLDDOISOJJCEMH-UHFFFAOYSA-N 0.000 description 2
- 239000012454 non-polar solvent Substances 0.000 description 2
- 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 2
- 239000011368 organic material Substances 0.000 description 2
- 239000002798 polar solvent Substances 0.000 description 2
- 239000011164 primary particle Substances 0.000 description 2
- 239000003586 protic polar solvent Substances 0.000 description 2
- 239000010453 quartz Substances 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 125000006850 spacer group Chemical group 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- YJGJRYWNNHUESM-UHFFFAOYSA-J triacetyloxystannyl acetate Chemical compound [Sn+4].CC([O-])=O.CC([O-])=O.CC([O-])=O.CC([O-])=O YJGJRYWNNHUESM-UHFFFAOYSA-J 0.000 description 2
- 229910001930 tungsten oxide Inorganic materials 0.000 description 2
- 238000001291 vacuum drying Methods 0.000 description 2
- HRSADIZPZPRZEI-UHFFFAOYSA-L zinc;diacetate;hydrate Chemical compound O.[Zn+2].CC([O-])=O.CC([O-])=O HRSADIZPZPRZEI-UHFFFAOYSA-L 0.000 description 2
- MBWMIEZHOLGJBM-UHFFFAOYSA-N 3-(4-methylphenyl)-3-[(2-methylpropan-2-yl)oxycarbonylamino]propanoic acid Chemical compound CC1=CC=C(C(CC(O)=O)NC(=O)OC(C)(C)C)C=C1 MBWMIEZHOLGJBM-UHFFFAOYSA-N 0.000 description 1
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 1
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- FBPFZTCFMRRESA-FSIIMWSLSA-N D-Glucitol Natural products OC[C@H](O)[C@H](O)[C@@H](O)[C@H](O)CO FBPFZTCFMRRESA-FSIIMWSLSA-N 0.000 description 1
- FBPFZTCFMRRESA-JGWLITMVSA-N D-glucitol Chemical compound OC[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO FBPFZTCFMRRESA-JGWLITMVSA-N 0.000 description 1
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- IAYPIBMASNFSPL-UHFFFAOYSA-N Ethylene oxide Chemical compound C1CO1 IAYPIBMASNFSPL-UHFFFAOYSA-N 0.000 description 1
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 1
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 1
- DAOANAATJZWTSJ-UHFFFAOYSA-N N-Decanoylmorpholine Chemical compound CCCCCCCCCC(=O)N1CCOCC1 DAOANAATJZWTSJ-UHFFFAOYSA-N 0.000 description 1
- 239000004372 Polyvinyl alcohol Substances 0.000 description 1
- GOOHAUXETOMSMM-UHFFFAOYSA-N Propylene oxide Chemical compound CC1CO1 GOOHAUXETOMSMM-UHFFFAOYSA-N 0.000 description 1
- DKGAVHZHDRPRBM-UHFFFAOYSA-N Tert-Butanol Chemical compound CC(C)(C)O DKGAVHZHDRPRBM-UHFFFAOYSA-N 0.000 description 1
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 238000007259 addition reaction Methods 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 150000001298 alcohols Chemical class 0.000 description 1
- 150000004703 alkoxides Chemical class 0.000 description 1
- 239000000908 ammonium hydroxide Substances 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 239000007900 aqueous suspension Substances 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 229920001400 block copolymer Polymers 0.000 description 1
- YHWCPXVTRSHPNY-UHFFFAOYSA-N butan-1-olate;titanium(4+) Chemical compound [Ti+4].CCCC[O-].CCCC[O-].CCCC[O-].CCCC[O-] YHWCPXVTRSHPNY-UHFFFAOYSA-N 0.000 description 1
- 239000004202 carbamide Substances 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000012159 carrier gas Substances 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000007806 chemical reaction intermediate Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000013626 chemical specie Substances 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 239000007859 condensation product Substances 0.000 description 1
- 238000006482 condensation reaction Methods 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 239000000645 desinfectant Substances 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 229910001882 dioxygen Inorganic materials 0.000 description 1
- 238000002845 discoloration Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 239000002803 fossil fuel Substances 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 150000004820 halides Chemical class 0.000 description 1
- 229910052736 halogen Inorganic materials 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- AQBLLJNPHDIAPN-LNTINUHCSA-K iron(3+);(z)-4-oxopent-2-en-2-olate Chemical compound [Fe+3].C\C([O-])=C\C(C)=O.C\C([O-])=C\C(C)=O.C\C([O-])=C\C(C)=O AQBLLJNPHDIAPN-LNTINUHCSA-K 0.000 description 1
- 229910001416 lithium ion Inorganic materials 0.000 description 1
- 238000003760 magnetic stirring Methods 0.000 description 1
- AMWRITDGCCNYAT-UHFFFAOYSA-L manganese oxide Inorganic materials [Mn].O[Mn]=O.O[Mn]=O AMWRITDGCCNYAT-UHFFFAOYSA-L 0.000 description 1
- PPNAOCWZXJOHFK-UHFFFAOYSA-N manganese(2+);oxygen(2-) Chemical class [O-2].[Mn+2] PPNAOCWZXJOHFK-UHFFFAOYSA-N 0.000 description 1
- 238000010907 mechanical stirring Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000003801 milling Methods 0.000 description 1
- LZWCWYLKIKTIEH-UHFFFAOYSA-N neodymium;pentane-2,4-dione Chemical compound [Nd].CC(=O)CC(C)=O LZWCWYLKIKTIEH-UHFFFAOYSA-N 0.000 description 1
- 238000006384 oligomerization reaction Methods 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
- 229920001983 poloxamer Polymers 0.000 description 1
- 229920001296 polysiloxane Polymers 0.000 description 1
- 229920002689 polyvinyl acetate Polymers 0.000 description 1
- 239000011118 polyvinyl acetate Substances 0.000 description 1
- 229920002451 polyvinyl alcohol Polymers 0.000 description 1
- 238000000634 powder X-ray diffraction Methods 0.000 description 1
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical compound CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 description 1
- 238000010926 purge Methods 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000013557 residual solvent Substances 0.000 description 1
- 238000001223 reverse osmosis Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 238000000527 sonication Methods 0.000 description 1
- 229960002920 sorbitol Drugs 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 125000001424 substituent group Chemical group 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000002411 thermogravimetry Methods 0.000 description 1
- 229910001432 tin ion Inorganic materials 0.000 description 1
- QHGNHLZPVBIIPX-UHFFFAOYSA-N tin(ii) oxide Chemical class [Sn]=O QHGNHLZPVBIIPX-UHFFFAOYSA-N 0.000 description 1
- XJDNKRIXUMDJCW-UHFFFAOYSA-J titanium tetrachloride Chemical compound Cl[Ti](Cl)(Cl)Cl XJDNKRIXUMDJCW-UHFFFAOYSA-J 0.000 description 1
- 239000002341 toxic gas Substances 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 238000003828 vacuum filtration Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
- 239000011787 zinc oxide Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B13/00—Oxygen; Ozone; Oxides or hydroxides in general
- C01B13/14—Methods for preparing oxides or hydroxides in general
- C01B13/32—Methods for preparing oxides or hydroxides in general by oxidation or hydrolysis of elements or compounds in the liquid or solid state or in non-aqueous solution, e.g. sol-gel process
- C01B13/326—Methods for preparing oxides or hydroxides in general by oxidation or hydrolysis of elements or compounds in the liquid or solid state or in non-aqueous solution, e.g. sol-gel process of elements or compounds in the liquid state
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
- B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
- B01J21/063—Titanium; Oxides or hydroxides thereof
-
- B01J35/39—
-
- B01J35/613—
-
- B01J35/69—
-
- B01J35/695—
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/02—Impregnation, coating or precipitation
- B01J37/03—Precipitation; Co-precipitation
- B01J37/031—Precipitation
- B01J37/033—Using Hydrolysis
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G15/00—Compounds of gallium, indium or thallium
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G23/00—Compounds of titanium
- C01G23/04—Oxides; Hydroxides
- C01G23/047—Titanium dioxide
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G49/00—Compounds of iron
- C01G49/02—Oxides; Hydroxides
- C01G49/04—Ferrous oxide (FeO)
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G49/00—Compounds of iron
- C01G49/02—Oxides; Hydroxides
- C01G49/06—Ferric oxide (Fe2O3)
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G9/00—Compounds of zinc
- C01G9/02—Oxides; Hydroxides
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
- B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/60—Compounds characterised by their crystallite size
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/10—Solid density
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/12—Surface area
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/14—Pore volume
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/16—Pore diameter
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/16—Pore diameter
- C01P2006/17—Pore diameter distribution
Definitions
- This invention relates generally to the preparation of porous metal oxides. More specifically, the present invention relates to a modified sol gel method of making metal oxides containing a tailored pore structure.
- Porous materials are commonly used in catalyses, separation technologies, electrode applications and sensor applications.
- the preparation of porous materials can be accomplished mainly by two different routes: thermally treating hydrous metal oxides; and the removal of surfactant, oligomeric and polymeric templates.
- a metal oxide powder comprised of porous particles is formed from a modified sol gel process.
- the sol gel process includes template creation, template conditioning, template refinement, and coating application.
- the template creation utilizes a hydrolysis reaction using a metal oxide precursor within an aqueous solution that includes a polymer, surfactant, oligomer, or chelating agent.
- the solution may also include an organic or inorganic acid, and a metal salt that when combined with oxygen forms a metal oxide.
- the ions from the solvated metal salt may form an organometallic species from reaction with the organic or inorganic acid.
- the sol may be aged to achieve the desired surface area and pore size.
- Template conditioning of the metal oxide material produced by the hydrolysis reaction results in the isolation, purification and "locking in” of the solid material with a specific template.
- Template conditioning may include filtering and refluxing with a solvent having a lower surface tension than water.
- Template refinement transforms the template structure into a material having a specific phase composition, crystallinity, surface area and pore size distribution.
- Template refinement may include an optional low temperature drying step followed by a high temperature calcination step.
- Coating application is performed by mixing the powder obtained from calcination with dispersing fluid to form a slurry. The slurry is then applied to a substrate.
- FIG. 1 is a diagrammatic illustration of a metal oxide film formed of porous particles.
- FIG. 2 is a flow diagram of a process for making large surface area metal oxide particles and coatings.
- FIG. 3 is a flow diagram illustrating a specific example of the process of FIG. 2.
- FIG. 4 is a graph showing deactivation rate as a function of surface area of pores having a diameter of equal to or greater than 4 nm for different UV photocatalysts.
- FIG. 5 is a graph showing a desorption hysteresis loop for a titanium dioxide based photocatalyst material formed with neodymium acetylacetone as a metal salt additive.
- FIG. 6 is a graph showing a desorption hysteresis loop for a titanium dioxide based photocatalyst material formed with zinc (II) acetate hydrate as a metal salt additive.
- Tailored porous metal oxide particles may be used in many different applications including catalysis, separation technology, electrodes and sensors.
- deactivation resistant photocatalysts can be formulated by layering one or more photocatalysts on a suitable substrate such as, but not limited to, an aluminum honeycomb. These deactivation resistant photocatalysts may also be used in so-called backside illumination designs where the photocatalyst is deposited on light pipes, light carrying fibers or structures, where the photons enter from the photocatalytic layer opposite that which is exposed to the fluid flow.
- Metal oxides include but are not limited to metal oxides of cobalt, gallium, germanium, hafnium, iron, nickel, niobium, molybdenum, lanthanum, rhenium, scandium, silicon, tantalum, titanium, tungsten, yttrium and zirconium; suitably doped titanium dioxide where the dopant increases the photocatalytic activity; metal oxide grafted titanium dioxide catalysts such as, but not limited, to tungsten oxide grafted TiO 2; and mixed metal oxides such as, but not limited to, tin oxide (SnO 2 ), indium oxide (In 2 O 3 ), zinc oxide (ZnO), iron oxides (FeO and Fe 2 O 3 ), neodymium oxide (Nd 2 O 3 ) and cerium oxide (CeO 2 ).
- FIG. 1 illustrates one exemplarily structure of a tailored porous metal oxide.
- metal oxide film 10 is deposited on substrate 12 made up of clusters 14 of porous particles 16.
- Crystallites 18 and pores 20 form the porous structure of porous particles 16.
- crystallites 18 are formed of wide band gap semiconductor material, for example, having a band gap of greater than about 3.1 eV.
- Pores 20 are interconnected to form a three-dimensional pore network within porous particles 16.
- crystallites 18 are greater than about 2 nm in diameter, and pores 20 are about 4 nm or greater in diameter. In another example, there are about 10 4 crystallites 18 per porous particle 16, and the diameter of porous particle 16 is approximately 100 nm. In a further example, clusters 14 of porous particles 16 have a diameter on the order of about 1 micron to about 2 microns.
- the overall thickness of film 10 depends on the application. In one example where film 10 was a photocatalyst film, the overall thickness of film 10 was between about 2 to about 12 microns. In another example where film 10 was a photocatalyst film, the overall thickness of film 10 was about 3 to about 6 microns.
- the porous structure of particle 16 provides a large surface area, large pore metal oxide.
- pores 20 are believed to provide available void space for deposition or location of non-volatile compounds of silicon and oxygen resulting from a conversion of the volatile silicone-containing species, so that the nonvolatile products do not block active sites on the photocatalyst. As a result, the deactivation of the photocatalyst is reduced.
- the pore diameter may be measured by the BJH technique that is well known to those skilled in the art and is typically an option on automated surface area determination equipment.
- the original reference describing the BJH technique is E.P. Barrett, L. G. Joyner, P.P. Halenda, J. Am. Chem. Soc. 73, (1951), 373-380.
- P25 titania has a BET surface area of 50 m 2 /g and consists of aggregated primary particles with an average size of 21 nm. Of these primary particles, 80% are anatase, and 20% are rutile.
- P25 titania based photocatalytic material has a measured BET specific surface area of between about 44 m 2 /g and about 55 m /g. BET surface area is described in S. Brunauer, P.H. Emmett, and E. Teller, J.
- the surface area has to be corrected for the potentially different densities of different metal oxides.
- the anatase form of TiO 2 has a density of 3.84 m 2 /g
- rutile form has a density of
- an 80% anatase 20% rutile mix has a surface area per cm of skeletal volume of
- FIG. 2 illustrates process 30 for forming a film having porous metal oxide particles made up of nano-sized crystallites in a large pore, high surface area structure.
- Process 30 makes use of sol-gel chemistry to create porous particles with the desired crystallite and pore structure and the desired population of pore sizes.
- Process 30 includes four basic steps: template creation 32, template conditioning 34, template refinement 36 and coating application 38. Although process 30 is discussed with respect to titanium dioxide and titanium precursors, other metal oxides may be formed as will be discussed later.
- Template creation 32 of the nano-engineered porous metal oxide particles is dependent upon several factors, which include the choice of an organometallic precursor, composition of solvent medium, control of the hydrolysis of an organometallic precursor, control of condensation reactions that occur concurrently or after hydrolysis of the organometallic precursor, and the time needed to age a sol to create a template for a material that has a surface area greater than 50m 2 /g with well defined pores.
- Substituents on the organometallic precursor are expected to contribute to the hydrolysis reaction in the following manner in an aqueous solvent with no additives: halogens will hydrolyze faster than isoproxide which will hydrolyze faster than t- butoxide.
- Coordination of the organometallic precursor can affect the amount of oligomerization than could occur after hydrolysis and ultimately will affect the gel structure.
- the concentration of the precursor should decrease the rate of hydrolysis when the precursor is diluted with a solvent that does not interact with the precursor.
- the organometallic precursor has not been observed to be critical in the synthesis.
- the titanium organometallic precursor has not been observed to be critical in the synthesis of about 100 to about 130 m 2 /g titanium oxide with a controlled pore distribution. Titanium isopropoxide of 97% to 99.999% purity has been used with no differences in the overall reaction product.
- the rate of addition of the organometallic precursor can also control the hydrolysis reaction in such a manner that the faster the addition, the faster the hydrolysis in an aqueous solution.
- a rate of 4 drops/ 5 sec has been found to produce a titanium oxide material with a surface area >100m /g and the incremental surface area was greater than 15 m 2 /g. Increasing the rate of addition produces a lower surface area titanium oxide.
- the rate of hydrolysis is also affected by the medium in which the hydrolysis reaction occurs.
- aqueous or protic or polar solvents are used as the bulk medium, hydrolysis would be expected to occur, whereas non-aqueous or aprotic or non-polar solvents would not participate in hydrolysis.
- a combination of small aliquot of aqueous, protic or polar solvent rapidly mixed with large volume of nonaqueous, aprotic or non- polar solvent would result in a medium where a controlled hydrolysis could occur due to the dilution of the reactive medium.
- the pH of a medium will also affect the rate of hydrolysis of the organometallic precursor such that the hydrolysis reaction will occur at a faster rate in acidic environments.
- the pH of the medium can be critical to the concentration, shape, and size of the dynamic entanglements that result from the polymer interactions with the medium.
- the choice of polymer present in the bulk medium may affect the hydrolysis rate if the polymer changes the pH or viscosity of the bulk medium.
- the choice of polymer and solvent will result in the formation of dynamic entanglements of the polymer that will influence the size and shape of the hydrolysis and condensation products.
- polymers interact with solvent by either an attraction to the solvent, repulsion to a solvent, or the polymer chain reaches an equilibrium state with the solvent. When the polymer is attracted to solvent, the polymer chains are extended away from other polymer chains and large void spaces within the polymer chains result.
- the polymer chains are more attracted to other polymer chains, and the void spaces are smaller than those void spaces that would exist if polymer chains were more attracted to a solvent.
- Another means of phrasing the previous example is that the polymer chains collapse on and amongst other polymer chains. Under equilibrium conditions, or theta solvent conditions, the void spaces of the polymer chains result from the balance of attractive and repulsive forces existing in the polymer solvent solution. All of the above described scenarios are affected by temperature.
- metal salts to an aqueous solution would be expected to provide additional interaction with the polymer solvent interactions, and thus contribute to changes in the resulting void space which ultimately affects phase, shape, surface area, particle size and pore size distribution of the end material.
- the dissociation of the metal salt results in the separation of the cation and anion species.
- further reaction with the solvent e.g., acid
- the solvent e.g., acid
- tin fluoride when tin fluoride is added to an aqueous IM acetic acid solution containing polyethylene glycol (PEG), the dissociation of the salt results in the formation of tin and fluoride ions.
- PEG polyethylene glycol
- the hydrolysis reaction that occurs also initiates an addition reaction where the tin ions combine with acetate ions to form tin(II) acetate.
- Acetate ions are much larger than tin or fluoride ions, the size of tin(II) acetate would be the equivalent of the diameter of one tin atom plus two acetate molecules.
- the tin(II) acetate is a large bulky spacer group that can interact and hence orient the PEG in solution.
- the type of salt can also influence the final material. If the salt contains the cation of a known semiconductor oxide, then incorporation of the salt into metal vacancies of the main metal oxide material may result in a material with a band gap that is altered from both the parent metal oxide (material being produced) and cation-based metal oxide. A similar scenario would exist for non-oxide based metal salts as long as the necessary anion was incorporated into the parent material.
- the aging of the sol is critical for formation of the polymer network and the crystallization of the metal oxide particles formed. Differences in surface area and pore size distribution result when aging time varies from 0 hours to 3 weeks. For example for titanium dioxide particles, aging times under 72 hours result in materials with lower surface areas ( ⁇ 100 m /g) and incremental pore areas under 15 m 2 /g, and aging times over 168 hours do not produce dramatic improvements in surface area or incremental pore area compared to aging for 72 hours. Higher surface areas and incremental pore areas are obtained when the sol is gently stirred over the duration of aging. In the absence of stirring during the aging process, a material with lower surface area and incremental pore area is obtained i.e., less than 100 m 2 /g and incremental pore area under 15 m 2 /g for titanium dioxide particles.
- the pore diameter may be measured by the BJH technique that is well known to those skilled in the art and is typically an option on automated surface area determination equipment.
- Template conditioning 34 results in the isolation, purification and a "locking in” of the solid material with a specific template after the template creation step. After isolation of the solid from the liquid sol, residual water and potentially other impurities from the sol are removed and the solid is isolated under reduced pressure.
- Isolation of the solid produced in the sol during template formation may be accomplished for example, by vacuum filtration, gravity filtration, or centrifugation.
- the resulting solid may also be isolated under reduced pressure e.g., rotoevaporation, however the affect of pressure will alter the template of the solid such that in the case of titanium oxide, materials with lower surface areas ( ⁇ 100 m /g) and incremental pore areas under 15 m 2 /g will result.
- the isolated solid may need to be washed with small aliquots of solvent several times to remove potential contaminants or undesirable materials that could ultimately prevent the formation of a desired phase, structure, crystallinity, etc.
- Reflux of the isolated solid with a solvent that has a lower surface tension than water results in the removal of water and water-based impurities trapped internally within the solid providing that the solvent is protic or aprotic.
- solvents that have a higher surface tension than water it is believed that solvent would become trapped within vacant pores and limit the surface area and pore size distribution of the resulting material.
- Time of reflux is proportional to the amount of water removed. For example a one hour reflux time will remove more water than a reflux time of 15 min. After reflux times of one hour or greater, the solid particles form an emulsion within the solvent water mixture and solid particles do not appear to settle up to 24 hours post reflux.
- the volume of solvent used for reflux should always be in excess of the amount of water or water-based impurities that are predicted to be removed. For 1Og of solid material, 300ml of solvent would be appropriate to perform a successful reflux. A repeat reflux step can ultimately result in additional removal of water and/or water based impurities. In order to repeat reflux, the solid must be isolated by filtration or centrifugation means. Solvent removal at reduced pressure prior to reflux would negatively alter the template and result in material with lower surface areas ( ⁇ 100 m 2 /g) and incremental pore areas under 15 m 2 /g in the case of titanium oxide materials.
- the solid in the emulsion created in the reflux step must be isolated under reduced pressure to "lock-in" a structure template.
- a suitable template is produced that after refinement can result in a material having a surface area greater than 100 m 2 /g and an incremental pore area of 15 m 2 /g or greater.
- Template refinement 36 of the template structure may include an optional low temperature drying step followed by a high temperature calcination step.
- a low temperature drying step is critical for removal of residual solvent vapors.
- a high temperature calcination step will transform the template structure into a material with a specific phase composition, crystallinity, particle size, surface area, and pore size distribution.
- a low temperature i.e., 100 0 C or less
- reduced pressure drying step may be necessary to remove residual contaminants.
- preparations that used polymer amounts greater than 4g or preparations that did not use a metal salt had higher surface areas when a 12 hours vacuum drying step was employed prior to calcination.
- a vacuum drying step resulted in lower surface area after calcination.
- Calcination is done either following the isolation of the material by rotoevaporation or after a low temperature drying step is implemented. Calcination temperature is critical to produce a desired phase. For titanium oxide, temperatures above 700 0 C typically produce a photochemically inactive rutile phase, and temperatures between 300 0 C to 600 0 C will produce an anatase phase which is regarded to be photochemically active.
- Coupled with temperature are the rate of heating, duration of heating, and atmosphere of calcination. All of the mentioned variables are critical for control of phase, crystallinity, surface area, and pore size.
- the resulting surface area was less than 100 m2/g and the incremental surface area was less than 15 m 2 /g.
- the presence of organic material was evident by the brown discoloration on the powder (powder should be white) and verified by thermogravimetric analysis.
- the resulting surface area was greater than 100m 2 /g and the incremental surface area was greater than 15 m 2 /g.
- the resulting surface area is under 50 m 2 /g, incremental pore area is less than 5 m 2 /g.
- five pore size distributions exist over a range of
- the major phase for this material is expected to be anatase.
- Crystallite size is predicted to be greater than 13nm.
- the atmosphere in which the calcination occurs can influence the phase, crystallinity, surface area, and pore size.
- it is conducive to have an oxygen rich environment.
- 500 0 C there is no substantial difference in surface area or incremental pore area when using air compared to using a 50/50 mixture of CVN 2 .
- surface area there is no substantial difference in surface area or incremental pore area when using air compared to using a 50/50 mixture of CVN 2 .
- Coating application 38 uses the powder obtained after calcinations.
- the powder is mixed with a solvent to prepare a slurry.
- This slurry is applied to a substrate, and can be further dried.
- the critical steps in the preparation of the slurry pertain to the reduction of agglomerates within the solution and the extent of incorporation of the solid powder into a solvent. Agglomerates in the powder may be reduced by sonication in a desired solvent or centrifugal mixing with appropriate milling media. Critical to all agglomeration methods is the ability to not introduce additional contamination.
- Incorporation of the solid into the solvent may be accomplished by the use of but not limited to mechanical stirring, centrifugal mixing, magnetic stirring, high shear mixing.
- the slurry can be applied to a substrate by spray coating, dip coating, electrostatic coating or thermal treatment to a substrate.
- the coated substrate can be dried at room temperature, dried on hot contact, or vacuum dried at either room or elevated temperature.
- FIG. 3 illustrates a specific example of process 30.
- Template creation 32 begins with the addition of a metal oxide precursor A to a solution B to produce controlled hydrolysis reaction 40.
- metal oxide precursor A is a titanium precursor that may be, for example, a titanium alkoxide or halide such as titanium isopropoxide, titanium butoxide, or titanium tetrachloride or other such compounds.
- Solution B includes one or more low molecular weight polymer component, one or more solvents and one or more metal salts.
- the polymer component may be, for example, polyethylene glycol with a number average molecular weight (Mn) such as 200, 500, 2000, 4600, or 10,000.
- the polymer component may also include surfactants and chelating agents, such as citric acid, urea, poloxyethyleneglycol (e.g. Brij®) surfactants, an ethylene oxide/propylene oxide block copolymer (e.g. Pluronic 123®), polyvinyl alcohol, polyvinyl acetate, D-sorbitol and other hydroxyl-containing compounds.
- surfactants and chelating agents such as citric acid, urea, poloxyethyleneglycol (e.g. Brij®) surfactants, an ethylene oxide/propylene oxide block copolymer (e.g. Pluronic 123®), polyvinyl alcohol, polyvinyl acetate, D-sorbitol and other hydroxyl-containing compounds.
- polymers, oligomers, surfactants, or chelating agents that contain chemical functionalities that can interact with the reaction contituents may be used as it is believed that the polymer, oligomer, surfactant or chelating agent contributes to the initial gel structure which contributes to (directs or creates a template for) the resulting particle morphology and structure during calcination.
- Solvents may include, but are not limited to water, alcohols or organic -based solvents or mixtures thereof.
- the solvent is water with controlled concentrations of added acid, base or salt.
- the acid may be an organic acid such as acetic acid (e.g. IM, 4M, 0.5M, 0.25M) or an inorganic acid such as hydrochloric acid (IM).
- the base may be sodium hydroxide (IM) or other metal oxide bases or ammonium bases such as ammonium hydroxide.
- the salt may be sodium chloride (IM) or other salts.
- the solution may also include one or more additional metal salts, wherein the metal is one that, when combined with oxygen, forms a wide band gap metal oxide semiconductor.
- metal salts include tin(IV) fluoride, iron(II) acetylacetonate, iron(III) acetylacetonate, neodymium(III) acetylacetonate, zinc(II) acetate hydrate, and cerium(IV) fluoride. It is believed that the addition of a metal salt contributes to the formation of a discrete porous network, and may also contribute to increased photocatalytic activity compared to commercial titanium oxide materials.
- salts, acids and bases may be used as long as the interaction between the salt, solvent and polymer results in less than 5 populations of discrete pore size distributions in the isolated photocatalyst, which is material isolated following removal of the salt, solvent and polymer.
- the combination of polymer, salt, and solvent is important as the interactions between the solvent and the polymer are believed to control initial formation and structure of the gel network.
- polymer chains in solution will adopt dynamic random conformations that will result in regions varying in polymer concentration. These regions may be defined by globules or coils. Globules are regions of high polymer concentration where polymer chains are dense, compact and possess minimal void spaces. Coils are more relaxed regions of polymer chains where void spaces are present. It is believed that the hydrolysis reaction of the metal precursor occurs within the confines of the polymer void spaces.
- a metal salt, such as tin fluoride, in the solution can dissociate into ions and further interact with other components in solution or titanium dioxide produced by the hydrolysis of the initial titanium precursor. The resulting chemical species formed from the dissociation of the metal salt can either act as spacers or as crystal surface control agents.
- the resulting tin oxide semiconductor in conjunction with the titanium dioxide semiconductor, may yield enhanced photocatalytic activity.
- tin fluoride When tin fluoride is introduced into an aqueous acetic acid solution, it dissociates, and tin acetate is formed.
- the addition of titanium-based precursors into this aqueous solution starts a chemical reaction and forms oxidized titanium products, such as titanium dioxide.
- a typical example of the above described catalyst would be when 20ml of titanium isopropoxide, 99%, is hydrolyzed in a solution containing 100ml of aqueous IM Acetic acid, 4.00 g of 4400-4800 M n polyethylene glycol, and 1.5 g of tin(II) fluoride, 99%.
- the combination of the polymer, the acetic acid, and the tin acetate form a dynamic entanglement, and the voids within the entanglement are most likely where the crystallites of titanium dioxide form.
- the titanium dioxide is surrounded by regions of polyethylene glycol, acetate, and hydroxyl groups from water and from polyethylene glycol.
- the sol is aged (step 42). Aging times range from about 0 hours to about 3 weeks, and preferably are in a range of about 72 hours to about 168 hours. The sol may be stirred during the aging process.
- Template conditioning 34 isolates, purifies and locks in the catalyst material with a specific template. It includes filtration (step 44), reflux (step 46) and rotoevaporation (step 48).
- the hydrolysis reaction (step 40) and subsequent aging (step 42) produces a dispersion or mixture of powder and solution.
- the mixture is filtered (step 44), and is then refluxed in the presences of alcohol or aprotic solvent to remove some of the water that remains in the material, most likely inside the pores (step 46).
- Water has a high surface energy, and is expected to cause some of the pores to collapse as the solid structure is dried.
- Alcohol typically has a lower surface tension, and is expected to readily evaporate without collapsing the pore structure of particle 16.
- Reflux of the mixture (step 46) is then followed by solvent removal, preferably using reduced pressure methods, such as rotoevaporation process (step 48).
- Template refinement 36 includes optional drying (step 50) and calcination (step 50
- the product may be dried, preferably at pressures below one atmosphere, to remove most of the non-metal oxide material (step 50). Drying takes place under reduced pressures at a temperature typically between about 25° C and about 100° C. In one embodiment, drying is performed for about 2 days at about 75° C, under conditions in which low vapor pressure impurities are removed. Various desirable combinations of time, temperature and pressure can be used to carefully control the drying and to remove the non-metal oxide materials to a content below about 10% by weight.
- Calcination is performed at temperatures in a range of about 350° C to about 700° C (step 52).
- the product is heated from room temperature to about 500° C at a rate of about 3° C per minute.
- the temperature is then held at about 500° C for about four to about 18 hours, and then is reduced back to room temperature.
- the calcination step removes any residual non-metal oxide materials, so that the resulting porous particles are about 100 nm in diameter and are made up of crystallites, such as wide band gap oxide semiconductor crystallites, in a pore structure having pores of diameter 4 nm or larger.
- oxygen enrichment may be used to assist in the removal of organic materials.
- the oxygen enrichment is controlled so that it does not for example trigger an exothermic oxidation and cause a transition from the anatase phase of TiO 2 to the rutile phase.
- the product is in the form of a white powder, with porous particles forming clusters of about 1 micron to about 2 micron diameter.
- Coating application 38 includes aqueous slurry formation (step 54) and application to a substrate (step 56).
- the powder is mixed with water or organic solvent to form a slurry having approximately 1-20 wt% solids (step 54).
- the slurry is then applied to substrate by spraying, dip coating, or other application technique (step 56).
- Solvent evaporates, leaving the film.
- the film is a photocatalyst film having a thickness on the order of about 3 microns to about 6 microns thickness.
- the film is a photocatalyst film having approximately 1 milligram catalyst per square centimeter. Greater than about 1 milligram per square centimeter does not significantly increase the photocatalytic properties of the film. An amount significantly less 1 milligram per square centimeter will result in a lower photocatalytic effect.
- FIG. 4 is a graph showing deactivation rate, in relative units, as a function of cumulative surface area in pores of greater than 4 nm diameter for conventional P25 photocatalyst and for photocatalysts (designated UVl 14, UV139, 2UV45, 2UV59, 2UV91, 2UV106 and 2UVl 17) made using the process shown in FIG. 2.
- the deactivation rate was determined by the comparison of single pass activity exposing each photocatalyst to propenal, and then to hexamethyldisiloxate.
- the data point for conventional P25 titanium dioxide photocatalyst shows a deactivation rate of slightly greater than 2 and a cumulative surface area of less than 20 m 2 /g in pores of greater than 4 nm in diameter.
- all of the other photocatalyst exhibited a deactivation rate of 1.5 or lower and the surface area of 40 m /g or greater in pores of greater than 4 nm diameter.
- These represent show a deactivation rate greater than 2, where deactivation rate is defined as the % single pass efficiency decrease per hour.
- the aqueous solution used in making UV139 did not include a metal salt.
- photocatalyst 2UV45, 2UV59, and UVl 14 were formed using the method with polyethylene glycol, acetic acid, titanium isopropoxide, and with tin fluoride as the metal salt in the aqueous solution.
- a reduced pressure was used for each of samples 2UV45, 2UV59, and UVl 14.
- All of the synthesized photocatalysts had increased photocatalytic efficiency compared to Degussa P25 titania as a result of surface area greater than 50 m 2 /g, a discrete number of high population pore diameters, e.g., one, two or three different pore diameter populations as opposed to Degussa P25 that has greater than five populations of pore diameters.
- the synthesized photocatalysts also exhibited improved resistance to siloxane contamination compared to the commercial P25 titanium oxide photocatalyst.
- the P25 titania would drop to 50% of its initial activity in about 24 hours at 90 ppb, or 90 days a 1 ppb.
- the UV 114 activity would reach 50% of its initial activity in 550 days of continuous operation when challenged with 1 ppb hexamethyldisiloxane if the deactivation rate is proportional to the siloxane concentration.
- the photocatalyst has a skeletal or crystallite density of 3.84 g/cm 3 and a surface area of greater than 50 m 2 /gram in pores 4 nm or greater diameter as measured with nitrogen by adsorption.
- the surface area in pores greater than or equal to 4 nm diameter be greater than 50 m 2 /gram where the surface area and pore diameter is measured with nitrogen by adsorption and the data analyzed by the BJH method.
- this can be expressed as greater than about 190 m /gram of photocatalytic skeletal volume.
- the conventional BET specific surface area measurement of m /g is used for convenience.
- High-purity nitrogen gas was passed through a water bubbler to set the desired humidity level.
- the contaminants were generated either from a compressed gas cylinder such as Propenal/N 2 , or a temperature controlled bubbler.
- An oxygen gas flow was then combined with the nitrogen and contaminant flows to produce the desired carrier gas mixture (15% oxygen, 85% nitrogen).
- the titania-coated aluminum or gas slides were placed in a well milled from an aluminum block, and covered by a quartz window (96 percent UVA transparent). Gaskets between the quartz window and aluminum block created a flow passage of 25.4 mm (width) by 2 mm (height) above the titania-coated slides.
- Contaminated gas entered the reactor by first passing through a bed of glass mixing beads. Next, the gas flow entered a 25.4 mm by 2 mm entrance region of sufficient length (76.2 mm) to produce a fully-developed laminar velocity profile. The gas flow then passed over the surface of the titania-coated glass-slides. Finally, the gas passed through a 25.4 mm by 2 mm exit region (76.2 mm long) and a second bed of glass beads before exiting the reactor. The longevity of various TiO 2 based photocatalysts in the presence of 90 ppb hexamethyldisiloxane was determined using the above reactor. The deactivation rate was determined by the slope of a straight line best representing the catalyst performance during its initial stages of operation.
- the P25 value represents the average results from multiple tests.
- the rate of activity loss expressed in % initial activity per hour becomes smaller, that is tends towards zero as the surface area in m 2 /g in pores greater than or equal to 6 nm becomes larger. This is not the case with the BET surface area, or the surface area in pores greater than 4 nm in diameter as determined by N 2 adsorption and
- photocatalyst may also be formed, such as suitably doped titanium dioxide where the dopant increases the photocatalytic activity, and metal oxide grafted titanium dioxide catalysts, such as, but not limited to tungsten oxide grafted TiO 2
- metal oxide grafted titanium dioxide catalysts such as, but not limited to tungsten oxide grafted TiO 2
- the present invention also contemplates the formation of photocatalytic mixed metal oxides such as, but not limited to, tin oxide (SnO 2 ), indium oxide (In 2 O 3 ), zinc oxide (ZnO), iron oxides (FeO and Fe 2 O 3 ), neodymium oxide (Nd 2 O 3 ) and cerium oxide (CeO 2 ).
- porous metal oxide materials may be used in many other applications.
- porous metal oxides may be used in separation technology applications, electrode applications and sensor applications.
- Porous metal oxides may be formed into membranes that selectively separate one or more materials from a liquid or a gas. These membranes may be resistant to corrosive liquids and gases, and are stable at temperatures ranging from 500-800 0 C. For example, membranes may be used to capture iron oxides, carbon dioxide and other undesirable fossil fuel combustion products, and membranes may be used to separate chemicals and wastes from pulp and paper manufacturing process water.
- Porous metal oxides may also be used as water purification filter materials.
- metal oxides are used in reverse osmosis membranes. These membranes are resistant to disinfectants such as chlorine and may be steam treated to reduce biofouling.
- Porous metal oxides may also be used as electrodes in battery systems.
- manganese oxides may be used in battery systems
- tin oxides or titanium oxide/tin oxide mixtures may be used in lithium ion battery systems.
- Porous metal oxides may also be used in sensor applications.
- sensors formed of metal oxides may be used to detect combustible and toxic gases. The performance (i.e. the sensitivity, selectivity and stability) of such sensors is directly related to the exposed surface volume. Therefore, the tailored porous metal oxide particles may improve the performance of metal oxide sensors because of the pore structure and increased surface area.
- Porous metal oxides also may be used as a catalyst. Porous metal oxides can interact with atoms, ions and molecules throughout the bulk of the material because of the pore structure. The pores may control the diffusion of reagents and products into and out of the porous metal oxide. The pores also may control the reaction intermediates that may form within the pores. Metal oxides such as, but not limited to, titanium and zirconium based metal oxides may be used in catalyst applications.
- Example precursors include but are not limited to: cobalt, gallium, germanium, hafnium, iron, nickel, niobium, molybdenum, lanthanum, rhenium, scandium, silicon, tantalum, tungsten, yttrium and zirconium based precursors and mixtures thereof.
Abstract
A porous metal oxide is formed by creating a metal oxide material with a hydrolysis reaction in solution. The hydrolysis reaction or reaction products of a metal oxide precursor react simultaneously or in conjunction with a metal salt or a disassociation species of a metal salt. The metal oxide material is conditioned, and is refined to produce metal oxide particles having a porous structure containing crystallites.
Description
PRODUCTION OF TAILORED METAL OXIDE MATERIALS USING A REACTION SOL-GEL APPROACH
FIELD OF THE INVENTION
This invention relates generally to the preparation of porous metal oxides. More specifically, the present invention relates to a modified sol gel method of making metal oxides containing a tailored pore structure.
BACKGROUND
Porous materials are commonly used in catalyses, separation technologies, electrode applications and sensor applications. The preparation of porous materials can be accomplished mainly by two different routes: thermally treating hydrous metal oxides; and the removal of surfactant, oligomeric and polymeric templates.
SUMMARY
A metal oxide powder comprised of porous particles is formed from a modified sol gel process. The sol gel process includes template creation, template conditioning, template refinement, and coating application.
The template creation utilizes a hydrolysis reaction using a metal oxide precursor within an aqueous solution that includes a polymer, surfactant, oligomer, or chelating agent. The solution may also include an organic or inorganic acid, and a metal salt that when combined with oxygen forms a metal oxide. The ions from the solvated metal salt may form an organometallic species from reaction with the organic or inorganic acid. Following the hydrolysis reaction, the sol may be aged to achieve the desired surface area and pore size.
Template conditioning of the metal oxide material produced by the hydrolysis reaction results in the isolation, purification and "locking in" of the solid material with a specific template. Template conditioning may include filtering and refluxing with a solvent having a lower surface tension than water.
Template refinement transforms the template structure into a material having a specific phase composition, crystallinity, surface area and pore size distribution. Template refinement may include an optional low temperature drying step followed by a high temperature calcination step.
Coating application is performed by mixing the powder obtained from calcination with dispersing fluid to form a slurry. The slurry is then applied to a substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagrammatic illustration of a metal oxide film formed of porous particles.
FIG. 2 is a flow diagram of a process for making large surface area metal oxide particles and coatings.
FIG. 3 is a flow diagram illustrating a specific example of the process of FIG. 2. FIG. 4 is a graph showing deactivation rate as a function of surface area of pores having a diameter of equal to or greater than 4 nm for different UV photocatalysts.
FIG. 5 is a graph showing a desorption hysteresis loop for a titanium dioxide based photocatalyst material formed with neodymium acetylacetone as a metal salt additive.
FIG. 6 is a graph showing a desorption hysteresis loop for a titanium dioxide based photocatalyst material formed with zinc (II) acetate hydrate as a metal salt additive. DETAILED DESCRIPTION
Tailored porous metal oxide particles may be used in many different applications including catalysis, separation technology, electrodes and sensors. In one application, deactivation resistant photocatalysts can be formulated by layering one or more photocatalysts on a suitable substrate such as, but not limited to, an aluminum honeycomb. These deactivation resistant photocatalysts may also be used in so-called backside illumination designs where the photocatalyst is deposited on light pipes, light carrying fibers or structures, where the photons enter from the photocatalytic layer opposite that which is exposed to the fluid flow.
Metal oxides include but are not limited to metal oxides of cobalt, gallium, germanium, hafnium, iron, nickel, niobium, molybdenum, lanthanum, rhenium, scandium, silicon, tantalum, titanium, tungsten, yttrium and zirconium; suitably doped titanium dioxide where the dopant increases the photocatalytic activity; metal oxide grafted titanium dioxide catalysts such as, but not limited, to tungsten oxide grafted TiO2; and mixed metal oxides such as, but not limited to, tin oxide (SnO2), indium oxide (In2O3), zinc oxide (ZnO), iron oxides (FeO and Fe2O3), neodymium oxide (Nd2O3) and cerium oxide (CeO2).
FIG. 1 illustrates one exemplarily structure of a tailored porous metal oxide. In FIG. 1, metal oxide film 10 is deposited on substrate 12 made up of clusters 14 of porous particles 16. Crystallites 18 and pores 20 form the porous structure of porous particles
16. In one example, crystallites 18 are formed of wide band gap semiconductor material, for example, having a band gap of greater than about 3.1 eV. Pores 20 are interconnected to form a three-dimensional pore network within porous particles 16.
In one example, crystallites 18 are greater than about 2 nm in diameter, and pores 20 are about 4 nm or greater in diameter. In another example, there are about 104 crystallites 18 per porous particle 16, and the diameter of porous particle 16 is approximately 100 nm. In a further example, clusters 14 of porous particles 16 have a diameter on the order of about 1 micron to about 2 microns. The overall thickness of film 10 depends on the application. In one example where film 10 was a photocatalyst film, the overall thickness of film 10 was between about 2 to about 12 microns. In another example where film 10 was a photocatalyst film, the overall thickness of film 10 was about 3 to about 6 microns.
The porous structure of particle 16 provides a large surface area, large pore metal oxide. In photocatalytic applications, pores 20 are believed to provide available void space for deposition or location of non-volatile compounds of silicon and oxygen resulting from a conversion of the volatile silicone-containing species, so that the nonvolatile products do not block active sites on the photocatalyst. As a result, the deactivation of the photocatalyst is reduced.
The pore diameter may be measured by the BJH technique that is well known to those skilled in the art and is typically an option on automated surface area determination equipment. The original reference describing the BJH technique is E.P. Barrett, L. G. Joyner, P.P. Halenda, J. Am. Chem. Soc. 73, (1951), 373-380.
For titanium dioxide, higher surface area in pores substantially less than 4 nm in diameter did not increase the resistance to deactivation by siloxanes. For adequate photocatalytic activity, the crystallites of the wide band gap semiconductor (or semiconductors) that make up this porous structure must possess sufficient size (typically greater than about 2 nm in diameter) and the appropriate degree of crystallite perfection to allow adequate electron-hole separation to occur. According to Degussa Technical Information TI 1243, March 2002, P25 titania has a BET surface area of 50 m2/g and consists of aggregated primary particles with an average size of 21 nm. Of these primary particles, 80% are anatase, and 20% are rutile. The anatase particles tend to be somewhat smaller and the rutile somewhat larger. In practice P25 titania based photocatalytic material has a measured BET specific surface area of between about 44 m2/g and about
55 m /g. BET surface area is described in S. Brunauer, P.H. Emmett, and E. Teller, J.
Am. Chem. Soc. 60, (1938), 309-319.
Since specific surface area is measured in m2/gram, the surface area has to be corrected for the potentially different densities of different metal oxides. For example, the anatase form of TiO2 has a density of 3.84 m2/g, while rutile form has a density of
4.26 m2/g. In contrast, tin oxide (SnO2) as cassiterite has a density of 6.95 m2/g, while zinc oxide (zincite) has a density of 5.61 m2/g. Thus, to convert to m2/cm3 of skeletal volume, an 80% anatase 20% rutile mix has a surface area per cm of skeletal volume of
[(0.8 x 3.84 g/cm3) + (0.2 x 4.26 g/cm3)] * 50 m2/g = 196.2 mW. FIG. 2 illustrates process 30 for forming a film having porous metal oxide particles made up of nano-sized crystallites in a large pore, high surface area structure.
The process makes use of sol-gel chemistry to create porous particles with the desired crystallite and pore structure and the desired population of pore sizes. Process 30 includes four basic steps: template creation 32, template conditioning 34, template refinement 36 and coating application 38. Although process 30 is discussed with respect to titanium dioxide and titanium precursors, other metal oxides may be formed as will be discussed later.
Template creation 32 of the nano-engineered porous metal oxide particles is dependent upon several factors, which include the choice of an organometallic precursor, composition of solvent medium, control of the hydrolysis of an organometallic precursor, control of condensation reactions that occur concurrently or after hydrolysis of the organometallic precursor, and the time needed to age a sol to create a template for a material that has a surface area greater than 50m2/g with well defined pores.
Substituents on the organometallic precursor are expected to contribute to the hydrolysis reaction in the following manner in an aqueous solvent with no additives: halogens will hydrolyze faster than isoproxide which will hydrolyze faster than t- butoxide.
Coordination of the organometallic precursor can affect the amount of oligomerization than could occur after hydrolysis and ultimately will affect the gel structure.
The concentration of the precursor should decrease the rate of hydrolysis when the precursor is diluted with a solvent that does not interact with the precursor.
Interaction with the dilution solvent would mean that hydrolysis has started prematurely before contact with the intended solution.
Purity of the organometallic precursor has not been observed to be critical in the synthesis. For example, the titanium organometallic precursor has not been observed to be critical in the synthesis of about 100 to about 130 m2/g titanium oxide with a controlled pore distribution. Titanium isopropoxide of 97% to 99.999% purity has been used with no differences in the overall reaction product.
The rate of addition of the organometallic precursor can also control the hydrolysis reaction in such a manner that the faster the addition, the faster the hydrolysis in an aqueous solution. For example, using titanium isopropoxide and conditions described for the standard example, a rate of 4 drops/ 5 sec has been found to produce a titanium oxide material with a surface area >100m /g and the incremental surface area was greater than 15 m2/g. Increasing the rate of addition produces a lower surface area titanium oxide.
The rate of hydrolysis is also affected by the medium in which the hydrolysis reaction occurs. When aqueous or protic or polar solvents are used as the bulk medium, hydrolysis would be expected to occur, whereas non-aqueous or aprotic or non-polar solvents would not participate in hydrolysis. A combination of small aliquot of aqueous, protic or polar solvent rapidly mixed with large volume of nonaqueous, aprotic or non- polar solvent would result in a medium where a controlled hydrolysis could occur due to the dilution of the reactive medium. The pH of a medium will also affect the rate of hydrolysis of the organometallic precursor such that the hydrolysis reaction will occur at a faster rate in acidic environments. The pH of the medium can be critical to the concentration, shape, and size of the dynamic entanglements that result from the polymer interactions with the medium. The choice of polymer present in the bulk medium may affect the hydrolysis rate if the polymer changes the pH or viscosity of the bulk medium. The choice of polymer and solvent will result in the formation of dynamic entanglements of the polymer that will influence the size and shape of the hydrolysis and condensation products. In general, polymers interact with solvent by either an attraction to the solvent, repulsion to a solvent, or the polymer chain reaches an equilibrium state with the solvent. When the polymer is attracted to solvent, the polymer chains are extended away from other polymer chains and large void spaces within the polymer chains result. In a solvent that lacks attraction to a polymer chain, the polymer chains are more attracted to other polymer chains, and the void spaces are smaller than those void spaces that would exist
if polymer chains were more attracted to a solvent. Another means of phrasing the previous example is that the polymer chains collapse on and amongst other polymer chains. Under equilibrium conditions, or theta solvent conditions, the void spaces of the polymer chains result from the balance of attractive and repulsive forces existing in the polymer solvent solution. All of the above described scenarios are affected by temperature.
The addition of metal salts to an aqueous solution would be expected to provide additional interaction with the polymer solvent interactions, and thus contribute to changes in the resulting void space which ultimately affects phase, shape, surface area, particle size and pore size distribution of the end material. In an aqueous solution, the dissociation of the metal salt results in the separation of the cation and anion species. Depending on the nature of the ionic species and the reactivity of the anion and cation, further reaction with the solvent (e.g., acid) can result in the formation of a new chemical present in solution that can interact with the existing polymer. For example, when tin fluoride is added to an aqueous IM acetic acid solution containing polyethylene glycol (PEG), the dissociation of the salt results in the formation of tin and fluoride ions. When the initial drop of an organometallic precursor is added, the hydrolysis reaction that occurs also initiates an addition reaction where the tin ions combine with acetate ions to form tin(II) acetate. Acetate ions are much larger than tin or fluoride ions, the size of tin(II) acetate would be the equivalent of the diameter of one tin atom plus two acetate molecules. The tin(II) acetate is a large bulky spacer group that can interact and hence orient the PEG in solution.
The type of salt can also influence the final material. If the salt contains the cation of a known semiconductor oxide, then incorporation of the salt into metal vacancies of the main metal oxide material may result in a material with a band gap that is altered from both the parent metal oxide (material being produced) and cation-based metal oxide. A similar scenario would exist for non-oxide based metal salts as long as the necessary anion was incorporated into the parent material.
After the hydrolysis reaction is complete, the aging of the sol is critical for formation of the polymer network and the crystallization of the metal oxide particles formed. Differences in surface area and pore size distribution result when aging time varies from 0 hours to 3 weeks. For example for titanium dioxide particles, aging times under 72 hours result in materials with lower surface areas (<100 m /g) and incremental pore areas under 15 m2/g, and aging times over 168 hours do not produce dramatic
improvements in surface area or incremental pore area compared to aging for 72 hours. Higher surface areas and incremental pore areas are obtained when the sol is gently stirred over the duration of aging. In the absence of stirring during the aging process, a material with lower surface area and incremental pore area is obtained i.e., less than 100 m2/g and incremental pore area under 15 m2/g for titanium dioxide particles.
The pore diameter may be measured by the BJH technique that is well known to those skilled in the art and is typically an option on automated surface area determination equipment.
Template conditioning 34 results in the isolation, purification and a "locking in" of the solid material with a specific template after the template creation step. After isolation of the solid from the liquid sol, residual water and potentially other impurities from the sol are removed and the solid is isolated under reduced pressure.
Isolation of the solid produced in the sol during template formation, may be accomplished for example, by vacuum filtration, gravity filtration, or centrifugation. The resulting solid may also be isolated under reduced pressure e.g., rotoevaporation, however the affect of pressure will alter the template of the solid such that in the case of titanium oxide, materials with lower surface areas (<100 m /g) and incremental pore areas under 15 m2/g will result. Depending on the composition of the sol, the isolated solid may need to be washed with small aliquots of solvent several times to remove potential contaminants or undesirable materials that could ultimately prevent the formation of a desired phase, structure, crystallinity, etc.
Reflux of the isolated solid with a solvent that has a lower surface tension than water results in the removal of water and water-based impurities trapped internally within the solid providing that the solvent is protic or aprotic. For solvents that have a higher surface tension than water, it is believed that solvent would become trapped within vacant pores and limit the surface area and pore size distribution of the resulting material.
Time of reflux is proportional to the amount of water removed. For example a one hour reflux time will remove more water than a reflux time of 15 min. After reflux times of one hour or greater, the solid particles form an emulsion within the solvent water mixture and solid particles do not appear to settle up to 24 hours post reflux.
The volume of solvent used for reflux should always be in excess of the amount of water or water-based impurities that are predicted to be removed. For 1Og of solid material, 300ml of solvent would be appropriate to perform a successful reflux. A repeat
reflux step can ultimately result in additional removal of water and/or water based impurities. In order to repeat reflux, the solid must be isolated by filtration or centrifugation means. Solvent removal at reduced pressure prior to reflux would negatively alter the template and result in material with lower surface areas (<100 m2/g) and incremental pore areas under 15 m2/g in the case of titanium oxide materials.
The solid in the emulsion created in the reflux step must be isolated under reduced pressure to "lock-in" a structure template. In the case of titanium oxide, by removing solvent so that the solvent is distilled off at 400C, a suitable template is produced that after refinement can result in a material having a surface area greater than 100 m2/g and an incremental pore area of 15 m2/g or greater.
It is believed that under reduced pressure, the organic and polymer components "lock" the placement of the titanium oxide network. The application of higher distillation temperatures and pressures result in a collapse of the network for titanium dioxide, while the use of lower temperatures and pressures may not effectively remove solvent from the solid material. Failure to remove solvent will result in a decrease of surface area and incremental pore area.
Template refinement 36 of the template structure may include an optional low temperature drying step followed by a high temperature calcination step. For some preparations a low temperature drying step is critical for removal of residual solvent vapors. A high temperature calcination step will transform the template structure into a material with a specific phase composition, crystallinity, particle size, surface area, and pore size distribution.
Depending on the polymer type, polymer concentration and reflux solvent, a low temperature (i.e., 1000C or less), reduced pressure drying step may be necessary to remove residual contaminants. For examples where titanium oxide was produced, preparations that used polymer amounts greater than 4g or preparations that did not use a metal salt had higher surface areas when a 12 hours vacuum drying step was employed prior to calcination. When 4g of polymer, and 1.5g of metal salt were used, a vacuum drying step resulted in lower surface area after calcination. Calcination is done either following the isolation of the material by rotoevaporation or after a low temperature drying step is implemented. Calcination temperature is critical to produce a desired phase. For titanium oxide, temperatures above 7000C typically produce a photochemically inactive rutile phase, and temperatures
between 3000C to 6000C will produce an anatase phase which is regarded to be photochemically active.
Coupled with temperature are the rate of heating, duration of heating, and atmosphere of calcination. All of the mentioned variables are critical for control of phase, crystallinity, surface area, and pore size.
The following calcination examples apply to a titanium oxide material prepared by the hydrolysis of titanium isopropoxide in an aqueous acidic PEG 4600, tin fluoride medium and worked up by isolation of the solid, 1 hour reflux, removal of solvent by at 400C under reduced pressure. For calcination experiments of 4 hours (at temperature) with a constant air purge at a heating rate of 3°C/min:
At 4000C, the resulting surface area was less than 100 m2/g and the incremental surface area was less than 15 m2/g. The presence of organic material was evident by the brown discoloration on the powder (powder should be white) and verified by thermogravimetric analysis.
At 5000C and 550 0C, the resulting surface area was greater than 100m2/g and the incremental surface area was greater than 15 m2/g. Two to three pore size distributions exist from Onm to 50nm. Materials produced are greater than 95% anatase with 5% rutile. Crystallite size has been measured using powder X-ray diffraction at approximately 13nm.
At 7000C, the resulting surface area is under 50 m2/g, incremental pore area is less than 5 m2/g. Compared to the above calcination experiments where there are two distinct pore size distributions, at 7000C, five pore size distributions exist over a range of
Onm to lOOnm. The major phase for this material is expected to be anatase. Crystallite size is predicted to be greater than 13nm.
The atmosphere in which the calcination occurs can influence the phase, crystallinity, surface area, and pore size. Ideally for the decomposition of organic matter, it is conducive to have an oxygen rich environment. At 5000C, there is no substantial difference in surface area or incremental pore area when using air compared to using a 50/50 mixture of CVN2. Despite the lack of change in surface area, one may expect changes in crystal size and phase.
Coating application 38 uses the powder obtained after calcinations. The powder is mixed with a solvent to prepare a slurry. This slurry is applied to a substrate, and can be further dried.
The critical steps in the preparation of the slurry pertain to the reduction of agglomerates within the solution and the extent of incorporation of the solid powder into a solvent. Agglomerates in the powder may be reduced by sonication in a desired solvent or centrifugal mixing with appropriate milling media. Critical to all agglomeration methods is the ability to not introduce additional contamination.
Incorporation of the solid into the solvent may be accomplished by the use of but not limited to mechanical stirring, centrifugal mixing, magnetic stirring, high shear mixing.
The slurry can be applied to a substrate by spray coating, dip coating, electrostatic coating or thermal treatment to a substrate. The coated substrate can be dried at room temperature, dried on hot contact, or vacuum dried at either room or elevated temperature.
FIG. 3 illustrates a specific example of process 30. Template creation 32 begins with the addition of a metal oxide precursor A to a solution B to produce controlled hydrolysis reaction 40. When the metal oxide is a wide band gap oxide semiconductor containing titanium dioxide, metal oxide precursor A is a titanium precursor that may be, for example, a titanium alkoxide or halide such as titanium isopropoxide, titanium butoxide, or titanium tetrachloride or other such compounds. Solution B includes one or more low molecular weight polymer component, one or more solvents and one or more metal salts.
The polymer component may be, for example, polyethylene glycol with a number average molecular weight (Mn) such as 200, 500, 2000, 4600, or 10,000. The polymer component may also include surfactants and chelating agents, such as citric acid, urea, poloxyethyleneglycol (e.g. Brij®) surfactants, an ethylene oxide/propylene oxide block copolymer (e.g. Pluronic 123®), polyvinyl alcohol, polyvinyl acetate, D-sorbitol and other hydroxyl-containing compounds. Other polymers, oligomers, surfactants, or chelating agents that contain chemical functionalities that can interact with the reaction contituents may be used as it is believed that the polymer, oligomer, surfactant or chelating agent contributes to the initial gel structure which contributes to (directs or creates a template for) the resulting particle morphology and structure during calcination.
Solvents may include, but are not limited to water, alcohols or organic -based solvents or mixtures thereof. In one example, the solvent is water with controlled concentrations of added acid, base or salt. For example, the acid may be an organic acid such as acetic acid (e.g. IM, 4M, 0.5M, 0.25M) or an inorganic acid such as
hydrochloric acid (IM). The base may be sodium hydroxide (IM) or other metal oxide bases or ammonium bases such as ammonium hydroxide. The salt may be sodium chloride (IM) or other salts.
The solution may also include one or more additional metal salts, wherein the metal is one that, when combined with oxygen, forms a wide band gap metal oxide semiconductor. Examples of metal salts include tin(IV) fluoride, iron(II) acetylacetonate, iron(III) acetylacetonate, neodymium(III) acetylacetonate, zinc(II) acetate hydrate, and cerium(IV) fluoride. It is believed that the addition of a metal salt contributes to the formation of a discrete porous network, and may also contribute to increased photocatalytic activity compared to commercial titanium oxide materials.
Other salts, acids and bases (and combinations thereof) may be used as long as the interaction between the salt, solvent and polymer results in less than 5 populations of discrete pore size distributions in the isolated photocatalyst, which is material isolated following removal of the salt, solvent and polymer. The combination of polymer, salt, and solvent is important as the interactions between the solvent and the polymer are believed to control initial formation and structure of the gel network.
Depending on the choice of solvent, polymer chains in solution will adopt dynamic random conformations that will result in regions varying in polymer concentration. These regions may be defined by globules or coils. Globules are regions of high polymer concentration where polymer chains are dense, compact and possess minimal void spaces. Coils are more relaxed regions of polymer chains where void spaces are present. It is believed that the hydrolysis reaction of the metal precursor occurs within the confines of the polymer void spaces. A metal salt, such as tin fluoride, in the solution, can dissociate into ions and further interact with other components in solution or titanium dioxide produced by the hydrolysis of the initial titanium precursor. The resulting chemical species formed from the dissociation of the metal salt can either act as spacers or as crystal surface control agents. In addition, the resulting tin oxide semiconductor, in conjunction with the titanium dioxide semiconductor, may yield enhanced photocatalytic activity. When tin fluoride is introduced into an aqueous acetic acid solution, it dissociates, and tin acetate is formed. The addition of titanium-based precursors into this aqueous solution starts a chemical reaction and forms oxidized titanium products, such as titanium dioxide.
A typical example of the above described catalyst would be when 20ml of titanium isopropoxide, 99%, is hydrolyzed in a solution containing 100ml of aqueous IM
Acetic acid, 4.00 g of 4400-4800 Mn polyethylene glycol, and 1.5 g of tin(II) fluoride, 99%. The combination of the polymer, the acetic acid, and the tin acetate form a dynamic entanglement, and the voids within the entanglement are most likely where the crystallites of titanium dioxide form. As a result, the titanium dioxide is surrounded by regions of polyethylene glycol, acetate, and hydroxyl groups from water and from polyethylene glycol.
When the hydrolysis reaction is complete, the sol is aged (step 42). Aging times range from about 0 hours to about 3 weeks, and preferably are in a range of about 72 hours to about 168 hours. The sol may be stirred during the aging process. Template conditioning 34 isolates, purifies and locks in the catalyst material with a specific template. It includes filtration (step 44), reflux (step 46) and rotoevaporation (step 48).
The hydrolysis reaction (step 40) and subsequent aging (step 42) produces a dispersion or mixture of powder and solution. The mixture is filtered (step 44), and is then refluxed in the presences of alcohol or aprotic solvent to remove some of the water that remains in the material, most likely inside the pores (step 46). Water has a high surface energy, and is expected to cause some of the pores to collapse as the solid structure is dried. Alcohol, on the other hand, typically has a lower surface tension, and is expected to readily evaporate without collapsing the pore structure of particle 16. Reflux of the mixture (step 46) is then followed by solvent removal, preferably using reduced pressure methods, such as rotoevaporation process (step 48). It is desirable to control the pressure used to remove the solvent, such that the solvent vapor distillation will occur at a controlled temperature. In one example, the pressure during solvent removal was controlled so that solvent vapor was distilled at 40° C. Template refinement 36 includes optional drying (step 50) and calcination (step
52). The product may be dried, preferably at pressures below one atmosphere, to remove most of the non-metal oxide material (step 50). Drying takes place under reduced pressures at a temperature typically between about 25° C and about 100° C. In one embodiment, drying is performed for about 2 days at about 75° C, under conditions in which low vapor pressure impurities are removed. Various desirable combinations of time, temperature and pressure can be used to carefully control the drying and to remove the non-metal oxide materials to a content below about 10% by weight.
Calcination is performed at temperatures in a range of about 350° C to about 700° C (step 52). In one embodiment, the product is heated from room temperature to about
500° C at a rate of about 3° C per minute. The temperature is then held at about 500° C for about four to about 18 hours, and then is reduced back to room temperature. The calcination step removes any residual non-metal oxide materials, so that the resulting porous particles are about 100 nm in diameter and are made up of crystallites, such as wide band gap oxide semiconductor crystallites, in a pore structure having pores of diameter 4 nm or larger.
During calcination, oxygen enrichment may be used to assist in the removal of organic materials. The oxygen enrichment, however, is controlled so that it does not for example trigger an exothermic oxidation and cause a transition from the anatase phase of TiO2 to the rutile phase.
As a result of calcination, the product is in the form of a white powder, with porous particles forming clusters of about 1 micron to about 2 micron diameter.
Coating application 38 includes aqueous slurry formation (step 54) and application to a substrate (step 56). The powder is mixed with water or organic solvent to form a slurry having approximately 1-20 wt% solids (step 54). The slurry is then applied to substrate by spraying, dip coating, or other application technique (step 56). Solvent evaporates, leaving the film. In one example the film is a photocatalyst film having a thickness on the order of about 3 microns to about 6 microns thickness. In another example the film is a photocatalyst film having approximately 1 milligram catalyst per square centimeter. Greater than about 1 milligram per square centimeter does not significantly increase the photocatalytic properties of the film. An amount significantly less 1 milligram per square centimeter will result in a lower photocatalytic effect.
EXAMPLES The following examples illustrate the benefits a photocatalyst formed from tailored porous titanium dioxide particles.
FIG. 4 is a graph showing deactivation rate, in relative units, as a function of cumulative surface area in pores of greater than 4 nm diameter for conventional P25 photocatalyst and for photocatalysts (designated UVl 14, UV139, 2UV45, 2UV59, 2UV91, 2UV106 and 2UVl 17) made using the process shown in FIG. 2. The deactivation rate was determined by the comparison of single pass activity exposing each photocatalyst to propenal, and then to hexamethyldisiloxate.
The data point for conventional P25 titanium dioxide photocatalyst shows a deactivation rate of slightly greater than 2 and a cumulative surface area of less than 20
m2/g in pores of greater than 4 nm in diameter. In contrast, all of the other photocatalyst exhibited a deactivation rate of 1.5 or lower and the surface area of 40 m /g or greater in pores of greater than 4 nm diameter. These represent show a deactivation rate greater than 2, where deactivation rate is defined as the % single pass efficiency decrease per hour.
UV139 is a photocatalyst according to the process shown in FIG. 2 using polyethylene glycol with Mn = 4600, acetic acid, and titanium isopropoxide. The aqueous solution used in making UV139 did not include a metal salt.
In separate experiments, photocatalyst 2UV45, 2UV59, and UVl 14 were formed using the method with polyethylene glycol, acetic acid, titanium isopropoxide, and with tin fluoride as the metal salt in the aqueous solution. For each of samples 2UV45, 2UV59, and UVl 14, during solvent removal using rotoevaporation, a reduced pressure was used.
In separate experiments for preparing samples 2UV91, 2UV106, and 2UVl 17, the vacuum during rotoevaporation was controlled to 137 millibar. Sample 2UV91 was a batch using four grams of polyethylene glycol (Mn = 4600); 1.5 grams tin fluoride; 100 milliliters acetic acid (IM); and 20 milliliters titanium isopropoxide (97% solution). Samples 2UV106 and 2UVl 17 used the same components in twice the quantity.
All of the synthesized photocatalysts had increased photocatalytic efficiency compared to Degussa P25 titania as a result of surface area greater than 50 m2/g, a discrete number of high population pore diameters, e.g., one, two or three different pore diameter populations as opposed to Degussa P25 that has greater than five populations of pore diameters. In addition to improved photocatalytic activity, the synthesized photocatalysts also exhibited improved resistance to siloxane contamination compared to the commercial P25 titanium oxide photocatalyst.
1 ppm propanal was oxidized by UV-A light at 50% relative humidity under conditions where initially about 20% of the propanol was oxidized. The deactivation agent was 90 ppb hexamethyldisiloxane. Under these conditions increasing the surface area of pores greater than 4 nm from 18.5 m2/g (-72.6 m2/cm3 by BJH N2 adsorption in P25 titania) to 77.8 m2/g, (i.e., -298.8 m2/cm3) in tin doped anatase TiO2 (designated UVl 14) decreased the rate of deactivation from 2.05% initial activity/hr for P25 to 0.335% initial activity/hr for UVl 14. Thus the P25 titania would drop to 50% of its initial activity in about 24 hours at 90 ppb, or 90 days a 1 ppb. In contrast, the UV 114 activity would reach 50% of its initial activity in 550 days of continuous operation when
challenged with 1 ppb hexamethyldisiloxane if the deactivation rate is proportional to the siloxane concentration.
In one example, the photocatalyst has a skeletal or crystallite density of 3.84 g/cm3 and a surface area of greater than 50 m2/gram in pores 4 nm or greater diameter as measured with nitrogen by adsorption. In another example the surface area in pores greater than or equal to 4 nm diameter be greater than 50 m2/gram where the surface area and pore diameter is measured with nitrogen by adsorption and the data analyzed by the BJH method. As other photocatalytic oxides with different densities may be used, this can be expressed as greater than about 190 m /gram of photocatalytic skeletal volume. In these examples, the conventional BET specific surface area measurement of m /g is used for convenience.
Further experimental details are described herein for typical measurements of photocatalyst deactivation. Substrates were coated with an aqueous suspension of P25 Degussa titania and allowed to dry. The P25 coating was positioned to absorb 100% of the incident light when used in a flat plate photocatalytic reactor with UV illumination provided by two black- light lamps (SpectroLine XX- 15A). The spectral distribution was symmetric about a peak intensity located at 352 nm and extended from 300 nm to 400 nm. The intensity was selected by adjusting the distance between the lamp and the titania-coated substrate. UV intensity at the reactor surface was measured by a UVA power meter (Oriel UVA Goldilux). High-purity nitrogen gas was passed through a water bubbler to set the desired humidity level. The contaminants were generated either from a compressed gas cylinder such as Propenal/N2, or a temperature controlled bubbler. An oxygen gas flow was then combined with the nitrogen and contaminant flows to produce the desired carrier gas mixture (15% oxygen, 85% nitrogen). The titania-coated aluminum or gas slides were placed in a well milled from an aluminum block, and covered by a quartz window (96 percent UVA transparent). Gaskets between the quartz window and aluminum block created a flow passage of 25.4 mm (width) by 2 mm (height) above the titania-coated slides.
Contaminated gas entered the reactor by first passing through a bed of glass mixing beads. Next, the gas flow entered a 25.4 mm by 2 mm entrance region of sufficient length (76.2 mm) to produce a fully-developed laminar velocity profile. The gas flow then passed over the surface of the titania-coated glass-slides. Finally, the gas passed through a 25.4 mm by 2 mm exit region (76.2 mm long) and a second bed of glass beads before exiting the reactor.
The longevity of various TiO2 based photocatalysts in the presence of 90 ppb hexamethyldisiloxane was determined using the above reactor. The deactivation rate was determined by the slope of a straight line best representing the catalyst performance during its initial stages of operation. The P25 value represents the average results from multiple tests. The rate of activity loss expressed in % initial activity per hour becomes smaller, that is tends towards zero as the surface area in m2/g in pores greater than or equal to 6 nm becomes larger. This is not the case with the BET surface area, or the surface area in pores greater than 4 nm in diameter as determined by N2 adsorption and
BJH analysis of this adsorption as performed by a Micromeritics ASAP 2010 surface area determination unit.
Although the foregoing examples refer to titanium dioxide, other photocatalyst may also be formed, such as suitably doped titanium dioxide where the dopant increases the photocatalytic activity, and metal oxide grafted titanium dioxide catalysts, such as, but not limited to tungsten oxide grafted TiO2 The present invention also contemplates the formation of photocatalytic mixed metal oxides such as, but not limited to, tin oxide (SnO2), indium oxide (In2O3), zinc oxide (ZnO), iron oxides (FeO and Fe2O3), neodymium oxide (Nd2O3) and cerium oxide (CeO2).
In addition to photocatalytic applications, porous metal oxide materials may be used in many other applications. For example, porous metal oxides may be used in separation technology applications, electrode applications and sensor applications.
Porous metal oxides may be formed into membranes that selectively separate one or more materials from a liquid or a gas. These membranes may be resistant to corrosive liquids and gases, and are stable at temperatures ranging from 500-8000C. For example, membranes may be used to capture iron oxides, carbon dioxide and other undesirable fossil fuel combustion products, and membranes may be used to separate chemicals and wastes from pulp and paper manufacturing process water.
Porous metal oxides may also be used as water purification filter materials. In one example, metal oxides are used in reverse osmosis membranes. These membranes are resistant to disinfectants such as chlorine and may be steam treated to reduce biofouling.
Porous metal oxides may also be used as electrodes in battery systems. For example, manganese oxides may be used in battery systems, and tin oxides or titanium oxide/tin oxide mixtures may be used in lithium ion battery systems.
Porous metal oxides may also be used in sensor applications. For example, sensors formed of metal oxides may be used to detect combustible and toxic gases. The performance (i.e. the sensitivity, selectivity and stability) of such sensors is directly related to the exposed surface volume. Therefore, the tailored porous metal oxide particles may improve the performance of metal oxide sensors because of the pore structure and increased surface area.
Porous metal oxides also may be used as a catalyst. Porous metal oxides can interact with atoms, ions and molecules throughout the bulk of the material because of the pore structure. The pores may control the diffusion of reagents and products into and out of the porous metal oxide. The pores also may control the reaction intermediates that may form within the pores. Metal oxides such as, but not limited to, titanium and zirconium based metal oxides may be used in catalyst applications.
Further, although the forgoing examples refer to using titanium precursors, other metals precursors may be used. Any metal that may be prepared as an alkoxide is a suitable precursor to create porous metal oxide nanoparticles. Example precursors include but are not limited to: cobalt, gallium, germanium, hafnium, iron, nickel, niobium, molybdenum, lanthanum, rhenium, scandium, silicon, tantalum, tungsten, yttrium and zirconium based precursors and mixtures thereof.
Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.
Claims
1. A method of forming a porous metal oxide, the method comprising: creating a metal oxide material with a controlled surface area and pore size distribution with a hydrolysis reaction in solution, where the hydrolysis reaction or reaction products of a metal oxide precursor react simultaneously or in conjunction with a metal salt or a disassociation species of a metal salt; conditioning the metal oxide material; and refining the metal oxide material to produce metal oxide particles having a porous structure containing crystallites.
2. The method of claim 1, wherein the solution includes an aqueous solvent.
3. The method of claim 1, wherein the solution includes a mixture of aqueous solvent and nonaqueous solvent.
4. The method of claim 1, wherein the solution includes a polymer.
5. The method of claim 4, wherein the polymer comprises polyethylene glycol.
6. The method of claim 1, wherein the solution further includes at least one of an acid, a salt, and a base.
7. The method of claim 6, wherein the solution includes an acid.
8. The method of claim 7, wherein the acid comprises acetic acid.
9. The method of claim 1, wherein the solution further includes an oligomer.
10. The method of claim 1, wherein the solution further includes a surfactant.
11. The method of claim 1 , wherein the solution further includes a chelating agent.
12. The method of claim 1, wherein the solution further includes a metal salt of a metal that when combined with oxygen forms a metal oxide semiconductor.
13. The method of claim 12, wherein the metal salt comprises at least one of salts of tin, indium, zinc, iron, neodymium, and cerium.
14. The method of claim 1, wherein the metal oxide precursor includes halogen substituents.
15. The method of claim 1, wherein the metal oxide precursor comprises at least one selected from the group consisting of cobalt, gallium, germanium, hafnium, iron, nickel, niobium, molybdenum, lanthanum, rhenium, scandium, silicon, tantalum, tungsten, yttrium and zirconium precursors, and mixtures thereof.
16. The method of claim 1, wherein the crystallites are semiconductor crystallites.
17. The method of claim 1 and further comprising: aging the metal oxide material after the hydrolysis reaction is complete.
18. The method of claim 17, wherein aging is for a period of about 0 hours to about 3 weeks.
19. The method of claim 18, wherein aging is for a period of about 72 hours to about 168 hours.
20. The method of claim 1, wherein conditioning the metal oxide material comprises: filtering the metal oxide material.
21. The method of claim 1, wherein conditioning the metal oxide material comprises: refluxing the metal oxide material with a solvent.
22. The method of claim 21, wherein the solvent has a lower surface tension then water.
23. The method of claim 21, wherein conditioning the metal oxide material further comprises: removing the solvent by rotoevaporation.
24. The method of claim 23, wherein removal of the solvent is performed at reduced pressure so that the solvent vapor temperature is 400C.
25. The method of claim 1, wherein refining the metal oxide material comprises: drying the metal oxide material in a vacuum at a temperature of between about
25°C and about 1000C.
26. The method of claim 1, wherein refining the metal oxide material comprises: calcining the metal oxide material.
27. The method of claim 1, wherein calcining the metal oxide material comprises heating the metal oxide material to a temperature between about 3500C and about 7000C.
28. The method of claim 1 and further comprising: applying the metal oxide particles to a substrate surface to form a film.
29. The method of claim 28, wherein applying the metal oxide particles comprises: forming a slurry containing the metal oxide particles; and applying the slurry to the substrate surface.
30. The method of claim 29, wherein forming a slurry comprises mixing the particles with a solvent.
31. The method of claim 29, wherein applying the slurry comprises one of spray coating, dip coating, electrostatic coating, or thermal treatment.
32. The method of claim 29 and further comprising: drying the slurry on the substrate surface.
33. The method of claim 29, wherein the slurry includes about 1% to about 20% solids.
34. The method of claim 29, wherein the slurry is applied as a film of about 1 milligram of porous metal oxide material per square centimeter.
35. The method of claim 1, wherein the metal oxide particles comprise semiconductor crystallites of a diameter of about 2 nm or greater.
36. The method of claim 35, wherein the particles have a diameter of about 100 nm.
37. The method of claim 1, wherein the metal oxide particles have a surface area of greater than about 50 m /g at a skeletal density of 3.84.
38. The method of claim 37, wherein the metal oxide particles have pores of a diameter of 4 nm or greater.
39. The method of claim 37, wherein the crystallites are anatase particles.
40. A method of forming a porous metal oxide, the method comprising: forming a metal oxide material with a hydrolysis reaction in solution, where the hydrolysis reaction or reaction products of a metal oxide precursor react simultaneously or in conjunction with a metal salt or the disassociation species of a metal salt; aging of a metal oxide material produced by the hydrolysis reaction; filtering a metal oxide material produced by the hydrolysis reaction; refluxing the metal oxide material with a solvent having a lower surface tension than water; removing the solvent from the metal oxide material; calcining the metal oxide material; forming an aqueous slurry of the porous metal oxide material; and applying the aqueous slurry to a surface of a substrate to form a metal oxide film.
41. The method of claim 40, wherein the aqueous solution further includes at least one of an acid, a salt, and a base.
42. The method of claim 41, wherein the aqueous solution includes an organic acid.
43. The method of claim 42, wherein the acid comprises acetic acid.
44. The method of claim 40, wherin the solution further includes an oligomer.
45. The method of claim 40, wherein the solution further includes a surfactant.
46. The method of claim 40, wherein the solution further includes a chelating agent.
47. The method of claim 40, wherein the solution further includes polyethylene glycol.
48. The method of claim 40, wherein the solution further includes a metal salt of a metal that when combined with oxygen forms a metal oxide semiconductor.
49. The method of claim 46, wherein the metal salt comprises at least one of salts of tin, indium, zinc, iron, neodymium, and cerium.
50. The method of claim 40, wherein removal of the solvent is done at reduced pressure so that the solvent vapor temperature is 400C.
51. The method of claim 40, wherein the metal oxide precursor comprises a precursor selected from the group consisting of cobalt, gallium, germanium, hafnium, iron, nickel, niobium, molybdenum, lanthanum, rhenium, scandium, silicon, tantalum, tungsten, yttrium and zirconium based precursors, and mixtures thereof.
52. The method of claim 40, wherein removing the solvent comprises rotoevaporation.
53. The method of claim 40, wherein removing the solvent comprises drying the porous metal oxide material in a vacuum at a temperature between about 25°C and about 1000C.
54. The method of claim 40, wherein calcining the metal oxide material comprises heating the catalyst material to a temperature between about 3500C and about 7000C.
55. The method of claim 40, wherein the aqueous slurry of the porous metal oxide material includes about 1% to about 20% solids.
56. The method of claim 40, wherein the aqueous slurry is applied as a film of about 1 milligram of porous metal oxide material per square centimeter.
57. The method of claim 56, wherein the particles have a surface area of at least about 50 m2/gm.
58. The method of claim 40, wherein the porous metal oxide material comprises particles having crystallites of a diameter of about 2 nm or greater, forming porous structure with pores of a diameter of about 4 nm or greater.
59. The method of claim 58, wherein the particles have a diameter of about 12 nm.
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
PCT/US2009/039510 WO2010114561A1 (en) | 2009-04-03 | 2009-04-03 | Production of tailored metal oxide materials using a reaction sol-gel approach |
EP09842828.7A EP2276694A4 (en) | 2009-04-03 | 2009-04-03 | Production of tailored metal oxide materials using a reaction sol-gel approach |
CN2009801213021A CN102105393A (en) | 2009-04-03 | 2009-04-03 | Production of tailored metal oxide materials using a reaction sol-gel approach |
US12/876,642 US20110003085A1 (en) | 2008-04-04 | 2010-09-07 | Production Of Tailored Metal Oxide Materials Using A Reaction Sol-Gel Approach |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
PCT/US2009/039510 WO2010114561A1 (en) | 2009-04-03 | 2009-04-03 | Production of tailored metal oxide materials using a reaction sol-gel approach |
Related Child Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US12/876,642 Continuation US20110003085A1 (en) | 2008-04-04 | 2010-09-07 | Production Of Tailored Metal Oxide Materials Using A Reaction Sol-Gel Approach |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2010114561A1 true WO2010114561A1 (en) | 2010-10-07 |
Family
ID=42828602
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US2009/039510 WO2010114561A1 (en) | 2008-04-04 | 2009-04-03 | Production of tailored metal oxide materials using a reaction sol-gel approach |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP2276694A4 (en) |
CN (1) | CN102105393A (en) |
WO (1) | WO2010114561A1 (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN102248737A (en) * | 2011-04-14 | 2011-11-23 | 天津大学 | Cr2O3 or NiO porous film material using WO3 as base material and method for manufacturing air-sensitive sensor |
WO2014023680A1 (en) * | 2012-08-06 | 2014-02-13 | Westfälische Wilhelms-Universität Münster | Method for producing carbon-coated metal-doped zinc oxide particles and the use thereof |
EP3409640A4 (en) * | 2016-01-21 | 2019-12-04 | Fujimi Incorporated | Method for producing porous metallic oxide |
US10689739B2 (en) | 2013-12-13 | 2020-06-23 | Constellium Issoire | Aluminium-copper-lithium alloy products with improved fatigue properties |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR3061210B1 (en) * | 2016-12-22 | 2021-12-24 | Electricite De France | SOL-GEL PROCESS FOR MANUFACTURING AN ANTICORROSION COATING ON METALLIC SUBSTRATE |
CN108821326B (en) * | 2018-06-27 | 2020-05-12 | 五邑大学 | ZnO nano material and preparation method thereof |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4585752A (en) * | 1984-08-15 | 1986-04-29 | W. R. Grace & Co. | Catalyst composition for ultra high temperature operation |
US5534468A (en) * | 1990-08-13 | 1996-07-09 | The Boeing Company | Ceramic oxide compounds |
US20040026324A1 (en) * | 2000-10-31 | 2004-02-12 | Victor Luca | Transition metal oxide compositions |
US6752979B1 (en) * | 2000-11-21 | 2004-06-22 | Very Small Particle Company Pty Ltd | Production of metal oxide particles with nano-sized grains |
JP2006027933A (en) * | 2004-07-13 | 2006-02-02 | Toyota Motor Corp | Method for producing multiple oxide |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2008147359A1 (en) * | 2007-05-31 | 2008-12-04 | Carrier Corporation | Deactivation resistant photocatalyst and method of preparation |
-
2009
- 2009-04-03 WO PCT/US2009/039510 patent/WO2010114561A1/en active Application Filing
- 2009-04-03 CN CN2009801213021A patent/CN102105393A/en active Pending
- 2009-04-03 EP EP09842828.7A patent/EP2276694A4/en not_active Withdrawn
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4585752A (en) * | 1984-08-15 | 1986-04-29 | W. R. Grace & Co. | Catalyst composition for ultra high temperature operation |
US5534468A (en) * | 1990-08-13 | 1996-07-09 | The Boeing Company | Ceramic oxide compounds |
US20040026324A1 (en) * | 2000-10-31 | 2004-02-12 | Victor Luca | Transition metal oxide compositions |
US6752979B1 (en) * | 2000-11-21 | 2004-06-22 | Very Small Particle Company Pty Ltd | Production of metal oxide particles with nano-sized grains |
JP2006027933A (en) * | 2004-07-13 | 2006-02-02 | Toyota Motor Corp | Method for producing multiple oxide |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN102248737A (en) * | 2011-04-14 | 2011-11-23 | 天津大学 | Cr2O3 or NiO porous film material using WO3 as base material and method for manufacturing air-sensitive sensor |
CN102248737B (en) * | 2011-04-14 | 2013-08-14 | 天津大学 | Cr2O3 or NiO porous film material using WO3 as base material and method for manufacturing air-sensitive sensor |
WO2014023680A1 (en) * | 2012-08-06 | 2014-02-13 | Westfälische Wilhelms-Universität Münster | Method for producing carbon-coated metal-doped zinc oxide particles and the use thereof |
US9620775B2 (en) | 2012-08-06 | 2017-04-11 | Westfälische Wilhelms-Universität Münster | Method for producing carbon-coated metal-doped zinc oxide articles and the use thereof |
US10689739B2 (en) | 2013-12-13 | 2020-06-23 | Constellium Issoire | Aluminium-copper-lithium alloy products with improved fatigue properties |
EP3409640A4 (en) * | 2016-01-21 | 2019-12-04 | Fujimi Incorporated | Method for producing porous metallic oxide |
US11554967B2 (en) | 2016-01-21 | 2023-01-17 | Fujimi Incorporated | Method for producing porous metal oxide |
Also Published As
Publication number | Publication date |
---|---|
EP2276694A4 (en) | 2013-12-04 |
EP2276694A1 (en) | 2011-01-26 |
CN102105393A (en) | 2011-06-22 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US20100190643A1 (en) | Deactivation resistant photocatalyst and method of preparation | |
US20110003085A1 (en) | Production Of Tailored Metal Oxide Materials Using A Reaction Sol-Gel Approach | |
TWI651269B (en) | Titanium dioxide particles and preparation method thereof | |
Li et al. | Photodecolorization of Rhodamine B on tungsten-doped TiO2/activated carbon under visible-light irradiation | |
Sayılkan | Improved photocatalytic activity of Sn4+-doped and undoped TiO2 thin film coated stainless steel under UV-and VIS-irradiation | |
Mousavi et al. | Green synthesis of ZnO hollow sphere nanostructures by a facile route at room temperature with efficient photocatalytic dye degradation properties | |
US7863215B2 (en) | Photocatalyst, method for producing same, liquid dispersion containing photocatalyst and photocatalyst coating composition | |
EP2276694A1 (en) | Production of tailored metal oxide materials using a reaction sol-gel approach | |
WO2007037321A1 (en) | Titanium oxide photocatalyst, method for producing same and use thereof | |
KR20020041604A (en) | Novel titania photocatalyst and its manufacturing method | |
Wolski et al. | The effect of the preparation procedure on the morphology, texture and photocatalytic properties of ZnO | |
Kitsou et al. | ZnO-coated SiO2 nanocatalyst preparation and its photocatalytic activity over nitric oxides as an alternative material to pure ZnO | |
Mori et al. | Titanium dioxide nanoparticles produced in water-in-oil emulsion | |
JP4507066B2 (en) | Tungsten oxide-containing titanium oxide sol, production method thereof, coating agent and optical functional body | |
KR100225342B1 (en) | Method for preparing titanium oxide photocatalyst | |
Vasić et al. | Degradation of crystal violet over heterogeneous TiO2-based catalysts: The effect of process parameters | |
Miyake et al. | Photocatalytic degradation of methylene blue with metal-doped mesoporous titania under irradiation of white light | |
EP3012022A1 (en) | Visible light responsive photocatalyst material | |
Luan et al. | Research on different preparation methods of new photocatalysts | |
Tehrani et al. | Characterization and photocatalytic activities of nanosized titanium dioxide thin films | |
JP2739128B2 (en) | Decomposition method of organic chemicals by titanium ceramic membrane | |
KR20190117875A (en) | Method for preparing TiO2 using underwater plasma | |
JP2007117999A (en) | Titanium oxide-based photocatalyst and its use | |
Hattab et al. | Photocatalytic degradation of methylene blue by modified nanoparticles titania catalysts | |
KR20120069093A (en) | Manufacturing method of super hydrophilic titanium oxide thin film and titanium oxide thin film manufactured by the method |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
WWE | Wipo information: entry into national phase |
Ref document number: 200980121302.1 Country of ref document: CN |
|
WWE | Wipo information: entry into national phase |
Ref document number: 2009842828 Country of ref document: EP |
|
121 | Ep: the epo has been informed by wipo that ep was designated in this application |
Ref document number: 09842828 Country of ref document: EP Kind code of ref document: A1 |
|
NENP | Non-entry into the national phase |
Ref country code: DE |