JP2004161592A - Anatase type titania-silica composite and its production method - Google Patents
Anatase type titania-silica composite and its production method Download PDFInfo
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- JP2004161592A JP2004161592A JP2002367377A JP2002367377A JP2004161592A JP 2004161592 A JP2004161592 A JP 2004161592A JP 2002367377 A JP2002367377 A JP 2002367377A JP 2002367377 A JP2002367377 A JP 2002367377A JP 2004161592 A JP2004161592 A JP 2004161592A
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- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 title claims abstract description 244
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 title claims abstract description 164
- 239000000377 silicon dioxide Substances 0.000 title claims abstract description 76
- 239000002131 composite material Substances 0.000 title claims abstract description 28
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 17
- 239000013078 crystal Substances 0.000 claims abstract description 55
- 238000010438 heat treatment Methods 0.000 claims abstract description 44
- 230000001699 photocatalysis Effects 0.000 claims abstract description 44
- 238000000354 decomposition reaction Methods 0.000 claims abstract description 16
- 239000010936 titanium Substances 0.000 claims description 43
- CXKWCBBOMKCUKX-UHFFFAOYSA-M methylene blue Chemical compound [Cl-].C1=CC(N(C)C)=CC2=[S+]C3=CC(N(C)C)=CC=C3N=C21 CXKWCBBOMKCUKX-UHFFFAOYSA-M 0.000 claims description 34
- 229960000907 methylthioninium chloride Drugs 0.000 claims description 34
- 239000011259 mixed solution Substances 0.000 claims description 25
- 239000000843 powder Substances 0.000 claims description 24
- 239000002244 precipitate Substances 0.000 claims description 24
- 239000011941 photocatalyst Substances 0.000 claims description 22
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 20
- 239000003795 chemical substances by application Substances 0.000 claims description 19
- 239000000243 solution Substances 0.000 claims description 19
- 238000002835 absorbance Methods 0.000 claims description 18
- 229910052719 titanium Inorganic materials 0.000 claims description 17
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical class [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 16
- 238000001027 hydrothermal synthesis Methods 0.000 claims description 14
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 10
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 9
- 238000006243 chemical reaction Methods 0.000 claims description 8
- 230000007423 decrease Effects 0.000 claims description 8
- 230000007062 hydrolysis Effects 0.000 claims description 8
- 239000000463 material Substances 0.000 claims description 8
- 238000006460 hydrolysis reaction Methods 0.000 claims description 7
- 150000003377 silicon compounds Chemical class 0.000 claims description 7
- 150000003609 titanium compounds Chemical class 0.000 claims description 6
- 239000012153 distilled water Substances 0.000 claims description 5
- 238000010335 hydrothermal treatment Methods 0.000 claims description 5
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 4
- 239000002253 acid Chemical class 0.000 claims description 4
- 239000012736 aqueous medium Substances 0.000 claims description 4
- 230000008859 change Effects 0.000 claims description 4
- 238000002425 crystallisation Methods 0.000 claims description 4
- 230000008025 crystallization Effects 0.000 claims description 4
- 239000002781 deodorant agent Substances 0.000 claims description 4
- 238000011156 evaluation Methods 0.000 claims description 4
- 239000002609 medium Substances 0.000 claims description 4
- 239000003242 anti bacterial agent Substances 0.000 claims description 3
- 230000001098 anti-algal effect Effects 0.000 claims description 3
- 239000002519 antifouling agent Substances 0.000 claims description 3
- 239000003429 antifungal agent Substances 0.000 claims description 3
- 229940121375 antifungal agent Drugs 0.000 claims description 3
- 230000015572 biosynthetic process Effects 0.000 claims description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 claims description 2
- 150000003839 salts Chemical class 0.000 claims description 2
- 238000012360 testing method Methods 0.000 claims description 2
- 239000012629 purifying agent Substances 0.000 claims 2
- 238000001556 precipitation Methods 0.000 claims 1
- 238000002360 preparation method Methods 0.000 claims 1
- 239000000203 mixture Substances 0.000 abstract description 43
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 abstract description 18
- 238000007146 photocatalysis Methods 0.000 abstract description 4
- 239000005416 organic matter Substances 0.000 abstract description 3
- 230000001476 alcoholic effect Effects 0.000 abstract 1
- 150000001875 compounds Chemical class 0.000 abstract 1
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- 230000007704 transition Effects 0.000 description 16
- 238000002441 X-ray diffraction Methods 0.000 description 13
- 230000000052 comparative effect Effects 0.000 description 13
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 12
- 238000000034 method Methods 0.000 description 11
- DCKVFVYPWDKYDN-UHFFFAOYSA-L oxygen(2-);titanium(4+);sulfate Chemical compound [O-2].[Ti+4].[O-]S([O-])(=O)=O DCKVFVYPWDKYDN-UHFFFAOYSA-L 0.000 description 11
- VKYKSIONXSXAKP-UHFFFAOYSA-N hexamethylenetetramine Chemical compound C1N(C2)CN3CN1CN2C3 VKYKSIONXSXAKP-UHFFFAOYSA-N 0.000 description 10
- 239000000126 substance Substances 0.000 description 10
- 239000007864 aqueous solution Substances 0.000 description 9
- 239000002245 particle Substances 0.000 description 9
- 230000000694 effects Effects 0.000 description 8
- 239000000499 gel Substances 0.000 description 8
- 239000011159 matrix material Substances 0.000 description 8
- 229910002027 silica gel Inorganic materials 0.000 description 8
- 239000000741 silica gel Substances 0.000 description 8
- 229910010413 TiO 2 Inorganic materials 0.000 description 7
- 229910000349 titanium oxysulfate Inorganic materials 0.000 description 7
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 6
- 238000001069 Raman spectroscopy Methods 0.000 description 6
- 229910004298 SiO 2 Inorganic materials 0.000 description 6
- 238000000862 absorption spectrum Methods 0.000 description 6
- 238000005259 measurement Methods 0.000 description 6
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 5
- 238000005169 Debye-Scherrer Methods 0.000 description 5
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 5
- 235000011114 ammonium hydroxide Nutrition 0.000 description 5
- 239000004202 carbamide Substances 0.000 description 5
- 239000004312 hexamethylene tetramine Substances 0.000 description 5
- 235000010299 hexamethylene tetramine Nutrition 0.000 description 5
- 238000000746 purification Methods 0.000 description 5
- 239000004065 semiconductor Substances 0.000 description 5
- 238000001179 sorption measurement Methods 0.000 description 5
- 230000002195 synergetic effect Effects 0.000 description 5
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 description 4
- 238000004887 air purification Methods 0.000 description 4
- 230000000844 anti-bacterial effect Effects 0.000 description 4
- 230000003373 anti-fouling effect Effects 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 239000010419 fine particle Substances 0.000 description 4
- 229910021645 metal ion Inorganic materials 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- 239000010703 silicon Substances 0.000 description 4
- 229910052710 silicon Inorganic materials 0.000 description 4
- 229910000348 titanium sulfate Inorganic materials 0.000 description 4
- XJDNKRIXUMDJCW-UHFFFAOYSA-J titanium tetrachloride Chemical compound Cl[Ti](Cl)(Cl)Cl XJDNKRIXUMDJCW-UHFFFAOYSA-J 0.000 description 4
- GETQZCLCWQTVFV-UHFFFAOYSA-N trimethylamine Chemical compound CN(C)C GETQZCLCWQTVFV-UHFFFAOYSA-N 0.000 description 4
- 239000004115 Sodium Silicate Substances 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 3
- 230000009471 action Effects 0.000 description 3
- 150000004703 alkoxides Chemical class 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N ammonia Natural products N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 3
- 230000000536 complexating effect Effects 0.000 description 3
- 230000003247 decreasing effect Effects 0.000 description 3
- 238000004332 deodorization Methods 0.000 description 3
- 238000004993 emission spectroscopy Methods 0.000 description 3
- -1 for example Chemical compound 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 230000031700 light absorption Effects 0.000 description 3
- 239000011148 porous material Substances 0.000 description 3
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 description 3
- 229910052911 sodium silicate Inorganic materials 0.000 description 3
- 239000002904 solvent Substances 0.000 description 3
- 238000004627 transmission electron microscopy Methods 0.000 description 3
- ATRRKUHOCOJYRX-UHFFFAOYSA-N Ammonium bicarbonate Chemical compound [NH4+].OC([O-])=O ATRRKUHOCOJYRX-UHFFFAOYSA-N 0.000 description 2
- 238000004438 BET method Methods 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 2
- 230000002378 acidificating effect Effects 0.000 description 2
- 239000001099 ammonium carbonate Substances 0.000 description 2
- 235000012501 ammonium carbonate Nutrition 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 239000003054 catalyst Substances 0.000 description 2
- 238000005119 centrifugation Methods 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 235000011118 potassium hydroxide Nutrition 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 235000012239 silicon dioxide Nutrition 0.000 description 2
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Chemical compound [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 description 2
- 235000011121 sodium hydroxide Nutrition 0.000 description 2
- 238000003980 solgel method Methods 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 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 2
- 238000000108 ultra-filtration Methods 0.000 description 2
- 239000005796 Ipconazole Substances 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N Phenol Chemical compound OC1=CC=CC=C1 ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 description 1
- 229910003902 SiCl 4 Inorganic materials 0.000 description 1
- IKHGUXGNUITLKF-XPULMUKRSA-N acetaldehyde Chemical compound [14CH]([14CH3])=O IKHGUXGNUITLKF-XPULMUKRSA-N 0.000 description 1
- 150000008043 acidic salts Chemical class 0.000 description 1
- 239000003929 acidic solution Substances 0.000 description 1
- 239000003463 adsorbent Substances 0.000 description 1
- 239000000443 aerosol Substances 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- ROOXNKNUYICQNP-UHFFFAOYSA-N ammonium persulfate Chemical compound [NH4+].[NH4+].[O-]S(=O)(=O)OOS([O-])(=O)=O ROOXNKNUYICQNP-UHFFFAOYSA-N 0.000 description 1
- 239000012935 ammoniumperoxodisulfate Substances 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- FPCJKVGGYOAWIZ-UHFFFAOYSA-N butan-1-ol;titanium Chemical compound [Ti].CCCCO.CCCCO.CCCCO.CCCCO FPCJKVGGYOAWIZ-UHFFFAOYSA-N 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 235000013877 carbamide Nutrition 0.000 description 1
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 239000008199 coating composition Substances 0.000 description 1
- 238000010668 complexation reaction Methods 0.000 description 1
- 229910052906 cristobalite Inorganic materials 0.000 description 1
- 229910002026 crystalline silica Inorganic materials 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000010304 firing Methods 0.000 description 1
- 239000010881 fly ash Substances 0.000 description 1
- 238000010574 gas phase reaction Methods 0.000 description 1
- 238000007429 general method Methods 0.000 description 1
- 150000004679 hydroxides Chemical class 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- QTYCMDBMOLSEAM-UHFFFAOYSA-N ipconazole Chemical compound C1=NC=NN1CC1(O)C(C(C)C)CCC1CC1=CC=C(Cl)C=C1 QTYCMDBMOLSEAM-UHFFFAOYSA-N 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
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- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 239000000575 pesticide Substances 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 230000008569 process Effects 0.000 description 1
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- 230000009467 reduction Effects 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 229910021487 silica fume Inorganic materials 0.000 description 1
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 235000019795 sodium metasilicate Nutrition 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 208000024891 symptom Diseases 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 238000009283 thermal hydrolysis Methods 0.000 description 1
- LLZRNZOLAXHGLL-UHFFFAOYSA-J titanic acid Chemical compound O[Ti](O)(O)O LLZRNZOLAXHGLL-UHFFFAOYSA-J 0.000 description 1
- 150000003608 titanium Chemical class 0.000 description 1
- 229910052905 tridymite Inorganic materials 0.000 description 1
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- Disinfection, Sterilisation Or Deodorisation Of Air (AREA)
- Physical Water Treatments (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
- Silicon Compounds (AREA)
- Treatment Of Water By Oxidation Or Reduction (AREA)
- Catalysts (AREA)
Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は，高い光触媒作用を有し，アナターゼ相の相安定性に優れ，有機物分解性に優れ，水質浄化，脱臭，抗菌，防汚，大気浄化用として好適に用いられ，物質吸着性にも優れるアナターゼ型チタニア−シリカ複合体及びその製造法に関する。
【０００２】
【従来の技術】
酸化チタン（チタニア，ＴｉＯ２）はｎ型半導体に属し，三種類の結晶相（アナターゼ，ルチル，ブルッカイト）のなかでもアナターゼ型のチタニアは優れた光触媒作用を示す。チタニアの熱力学的安定相はルチルであり，アナターゼは準安定相であるので，一般に，大気中における熱処理により容易にアナターゼ型からルチル型への相転移を生じる。高温では，アナターゼ型のチタニアは極めて不安定である。アナターゼ型からルチル型への相転移は動力学的検討から約６３５℃付近で生じるとされるが，アナターゼ相の安定性は，粒子径，不純物，組成，製造法などに大きく依存し，調製法，使用する前駆体によっては５００℃付近からアナターゼ型からルチル型への相転移が生じ始める。
【０００３】
酸化チタンの製法には，チタンのアルコキシドを原料に使用したゾルーゲル法，四塩化チタンあるいは硫酸チタン，オキシ硫酸チタン等のチタン塩水溶液の加熱分解や，加水分解による方法等が一般的手法として知られている。
【０００４】
シリカは，石英，トリジマイト，クリストバライトの３種の多形があり，多方面で工業的に利用されているが，ガラスの主成分であって，比較的容易にガラス状態（非晶質）として存在しうる。工業的なシリカ原料にも非晶質のものが多々使用されている。非晶質シリカとして，例えば，シリカゲルは高い比表面積とその無数に発達した細孔を利用して，吸着剤，脱臭剤，触媒坦体などに応用されている。
【０００５】
シリカを含有するチタニアについては，純粋なアナターゼ型ＴｉＯ２について，アナターゼ型からルチル型への相転移に及ぼすシリカ添加の影響について，（１）ＴｉＣｌ４−ＳｉＣｌ４−Ｏ２系気相反応により合成されたＣＶＤ−ＴｉＯ２・ＳｉＯ２粉体において調べられ，アナターゼ型からルチル型への相転移が抑制されることが見いだされている（９８０℃までアナターゼ相で存在）。（陶山容子，加藤昭夫，窯業協会誌８６［３］１１９（１９７８））また，（２）アナターゼ型チタニア粒子にシリカ添加して，１０００℃の焼成でもルチル型に相転移する割合が少なく，光触媒活性の高い，光触媒機能を有する陶磁器及びその製造方法が開示されている。（特開平１１−１５７９６６）さらには，（３）チタニウムテトライソプロポキシドとオルトケイ酸テトラエチルを用いて，ゾル−ゲル法により合成された粉末について報告があり，チタニアに対するシリカの固溶について議論されており，アナターゼ型からルチル型への相転移温度約３００℃上昇させる効果が示されている（１００％がアナターゼ相で約８２５℃まで存在）。（Ｋ．Ｏｋａｄａら，Ｊ．Ａｍ．Ｃｅｒａｍ．Ｓｏｃ．，８４［７］１５９１（２００１）．）
【０００６】
シリカゲルなどとチタニア光触媒の複合化については，多孔性ゲル光触媒（特開平１０−３２３５６８）が，また半導体光触媒含有球状シリカゲル体および製造方法並びに塗料組成物（特開２００１−１０４７９９）があるが，これら製法によるチタニアの相安定性は高くはなく，しかもチタニア光触媒とシリカ成分との複合化による光触媒能の向上効果に関する実験データに基づいた具体的かつ客観的証拠は示されていない。しかも，これら前記の出願以前において，すでにシリカゲルなどへのチタニア光触媒の複合化（チタニア光触媒とシリカのゾルーゲル混合物についての開示，Ｘ．Ｆｕら，Ｅｎｖｉｒｏｎ．Ｓｃｉ．Ｔｅｃｈｎｏｌ，３０［２］６４７−６５３（１９９６）．）あるいは，シリカゲル−チタニア触媒（チタニア−シリカエーロゲルの構造と触媒特性に及ぼす前加水分解の影響，Ｊ．Ｂ．Ｍｉｌｌｅｒら，Ｊ．Ｃａｔａｌ，１５０［２］３１１−３２０（１９９４））等が文献により開示されており，類似技術がすでに公知とされている。
【０００７】
【発明が解決しようとする課題】
純粋なアナターゼ型の酸化チタンは，大気中における熱処理により容易にアナターゼ型からルチル型への相転移を生じ，光触媒活性の低下をもたらすと共に，相安定性が低いという本質的な課題がある。また，シリカ添加によるチタニアのアナターゼ型からルチル型への相転移に及ぼす抑制効果は知られているが，前記した開示技術のアナターゼ型の酸化チタンの相安定性は低く，１１００℃，１時間以上（さらには，１２００℃，１時間）の高温大気中における熱処理後においては，一般に，すでにアナターゼ型からルチル型への相転移が完全に終了しており，１１００℃，１時間以上（さらには，１２００℃，１時間）の大気中における高温熱処理後において，アナターゼ型チタニアとして存在しうる高い相安定性を有する報告例はほとんど無い。また，アナターゼ型の酸化チタンは，半導性物質中では優れた光触媒を示すが，光触媒活性をさらに一段と高めることもまた重要な課題とされている。一方，シリカは吸着能に優れるものの光触媒活性はほとんど無い。非晶質シリカは光透過性があるので，高い比表面積とその無数に発達した細孔を有し，かつ吸着能に優れるシリカとアナターゼ型チタニアを組み合わせることにより，吸着能と光触媒能の相乗効果が期待され，酸化チタンの光触媒用途を，をさらに多方面へ応用拡大することが求められている。本発明は，複合化方法・製造法の検討により，シリカとの複合化によるアナターゼ相の相安定性の際だった向上とアナターゼ型チタニアの光触媒性能の格段の向上およびその相乗効果を見出し，詳細な実験を基に完成したものである。
【０００８】
【課題を解決するための第１の手段】
かくの如き課題の解決のため，第一発明のアナターゼ型チタニア−シリカ複合体の要旨とするところは，チタニア（酸化チタン，ＴｉＯ２）に対して，内部ｍｏｌ％で１５〜９５ｍｏｌ％のシリカ（ＳｉＯ２）を含有し，該チタニアは，アナターゼ型結晶相からなり，実質的にルチル相を含有せず，１１００℃，１時間以上の大気中における熱処理後において，実質的にルチル相を含有せずアナターゼ型チタニアとして存在しうる相安定性を有し，１１００℃，１時間の大気中における熱処理後のアナターゼ型チタニアの結晶子径が７０ｎｍ以下であって，シリカ（ＳｉＯ２）を含有しないアナターゼ型チタニアの２倍以上の光触媒作用を有することを特徴とするアナターゼ型チタニア−シリカ複合体である。
【０００９】
このような組成のアナターゼ型チタニア−シリカ複合体は，半導性物質として様々な用途に好適であり，例えば光触媒としては，有機物分解性に優れ，水質浄化，脱臭，抗菌，防汚，大気浄化用として好適であり，応答性の高い光触媒作用を有し，非晶質シリカは光透過性があるので，高い比表面積とその無数に発達した細孔を有する非晶質シリカとの複合により，高い物質吸着性を付与することが可能で，吸着物質の分解作用と光触媒作用との相乗効果が得られる。
【００１０】
ここで，好適には，シリカ（ＳｉＯ２）が主として非晶質シリカとしてチタニア結晶微粒子表面に存在するチタニア−シリカ複合体及び／または該シリカ（ＳｉＯ２）が非晶質シリカマトリックスとして存在する非晶質シリカマトリックス中にチタニアが結晶微粒子として存在するチタニア−シリカ複合体及び／または該シリカ（ＳｉＯ２）が非晶質のシリカゲルであり，主として該非晶質シリカゲル表面にチタニアがアナターゼ型結晶微粒子として存在することが好ましい。これにより，吸着物質の分解作用と光触媒作用との相乗効果が得られるからである。
【００１１】
ここで，好適には，チタンの硫酸塩を使用するか，あるいは硫酸または硫酸イオン存在下において，チタンの酸性塩またはチタンの水酸化物を使用し，（１）水熱条件下における加水分解・結晶化工程あるいは（２）常圧下における加水分解・結晶化工程あるいは（３）沈殿形成剤の添加により溶液中より生成した沈殿析出物の水熱処理あるいは（４）沈殿形成剤の添加により溶液中より生成した沈殿析出物の加熱処理工程のいずれかを含む製造法により調製されたアナターゼ型チタニア−シリカ複合体が好ましい。チタンの硫酸塩から調製されたアナターゼ型チタニア−シリカ複合体は，後述する実施例にあるように極めて高いアナターゼ相の安定性を有するからである。また，好適には，このようにして調製されたアナターゼ型チタニア−シリカ複合体は，４００〜１２００℃，好ましくは，６００〜１０００℃の範囲で大気中における熱処理を行うことにより，光触媒性能を処理しない場合の２倍以上に，一段と高めることができる。
【００１２】
また，好適には，シリカ（ＳｉＯ２）の含有量が３０ｍｏｌ％以上であり，アナターゼ型結晶相の安定性として，１２００℃，１時間の大気中における熱処理後において，質量％でルチル相が１０％未満であって９０％以上がアナターゼ型チタニアとして存在しうる相安定性を有し，１２００℃，１時間の大気中における熱処理後のアナターゼ型チタニア結晶の結晶子径が５０ｎｍ以下であるアナターゼ型チタニア−シリカ複合体であることが好ましい。
【００１３】
また，光触媒作用として，アナターゼ型チタニア−シリカ複合体の試料粉末０．０１ｇを蒸留水２０ｍｌに加えたのち，２０ｐｐｍ濃度のメチレンブルー２０ｍｌを加え，全体の溶液（４０ｍｌ）のメチレンブルー濃度を１０ｐｐｍにした溶液にたいし，ブラックライトによる紫外線を１時間照射し，光触媒によるメチレンブルーの分解の程度を，分光光度計を用いた６６０ｎｍ付近のメチレンブルーによる吸光度の変化（減少）により測定する光触媒作用の評価試験において，紫外線照射後のメチレンブルーの吸光度（濃度）がシリカを複合しないアナターゼ型チタニアの場合の吸光度（濃度）の１／２以下であって，アナターゼ型チタニアの２倍以上のメチレンブルー分解能（光触媒能）を有し，光触媒能に優れることが好ましい。
【００１４】
【課題を解決するための第２の手段】
また，前記発明を達成するための第二発明のアナターゼ型チタニア−シリカ複合体の製造法の要旨とするところは，チタン化合物とケイ素化合物とを水性媒体中及び／またはアルコール媒体中に分散あるいは溶解することにより混合溶液を作製する混合液作製工程と，（１）該混合溶液を密閉容器中で所定の温度で水熱反応させる水熱反応工程あるいは（２）該混合溶液を常圧下反応容器中で所定の温度で加熱反応させる加熱反応工程あるいは（３）該混合溶液に沈殿形成剤の添加により溶液中より生成した沈殿析出物の水熱処理工程あるいは（４）該混合溶液に沈殿形成剤を加えて沈殿析出物を析出させ，該沈殿析出物を１０００℃以下の温度で加熱処理を行う沈殿形成・熱処理工程の（１）〜（４）の工程のうちいずれかを，含むことを特徴とするアナターゼ型チタニア−シリカ複合体の製造法である。
【００１５】
このようにすれば，チタン化合物とケイ素化合物を水性媒体中及び／またはアルコール媒体中に分散あるいは溶解することにより混合溶液が作製され，水熱反応工程において，その混合液が密閉容器中で所定の温度で水熱反応させられる。そのため，チタン化合物に由来するＴｉ成分（あるいは酸化チタン）とケイ素化合物に由来するＳｉ成分（あるいは酸化ケイ素）とが混合溶液中で分散あるいは溶解させられて，反応し易くなり，水熱反応（すなわち高温高圧水の存在かでの反応＝水熱合成）により分子単位で反応させられ，アナターゼ結晶として析出させられ，シリカ（ＳｉＯ２）が主として非品質シリカとしてチタニア結晶微粒子表面に存在するチタニア−シリカ複合体及び／または該シリカ（ＳｉＯ２）が非晶質シリカマトリックスとして存在する非晶質シリカマトリックス中にチタニアが結晶微粒子として存在するチタニア−シリカ複合体及び／または該シリカ（ＳｉＯ２）が非晶質のシリカゲルであり，主として該非晶質シリカゲル表面にチタニアがアナターゼ型結晶微粒子として存在する微構造が達成される。または，これらの混合溶液に沈殿形成剤（例えばアンモニア水や炭酸アンモニウム，水酸化ナトリウム，水酸化カリウム，あるいは尿素あるいはヘキサメチレンテトラミン等のアルカリ成分）を加えて場合により加熱し（尿素あるいはヘキサメチレンテトラミンの８０〜９５℃における加熱加水分解により），各成分の酸化物あるいは水酸化物あるいは炭酸塩などからなる沈殿析出物を析出させた後，該沈殿析出物を１０００℃以下の温度で加熱処理を行うことにより反応させられ，アナターゼ結晶として結晶析出させられ，上述のチタニア−シリカ複合体の微構造が達成される。または，これら混合溶液に沈殿形成剤を加えるかまたは加水分解によりゾルを形成させたのちゲルを得，該ゲルを１０００℃以下の温度で加熱処理あるいは温水処理あるいは水熱処理を行うことによりアナターゼ結晶として結晶析出させられ，上述のチタニア−シリカ複合体の微構造が達成される。なお。水熱反応工程における溶媒は，各成分の塩化合物とりわけチタン源として硫酸チタン，オキシ硫酸チタン，四塩化チタンなどを使用した場合に，加水分解により自発的に生成する酸性溶液中あるいは，例えばアンモニア水や炭酸アンモニウム，水酸化ナトリウム，水酸化カリウム，あるいは尿素あるいはヘキサメチレンテトラミン等のアルカリ成分の共存下や，中性溶媒中あるいは塩基性溶媒中のいずれの場合も適用できる。
【００１６】
ここで，好適には，チタン化合物がチタンの硫酸塩であることを特徴とする。このようにすれば，相安定性に優れるアナターゼ型チタニア−シリカ複合体が得られる。チタンの硫酸塩としては，オキシ硫酸チタン，硫酸チタンなどが好ましいものとしてあげられ，硫酸あるいは硫酸イオン存在下の四塩化チタン水溶液，ペルオキソチタン酸水溶液なども好ましい。特に，オキシ硫酸チタン，硫酸チタンなどが好ましいものとしてあげられ，硫酸あるいは硫酸イオン存在下の四塩化チタン水溶液，ペルオキソチタン酸水溶液，水酸化チタンなどを使用し，水熱反応工程を組み合わせることにより２５０℃以下で直接的に合成されたアナターゼ型チタニア−シリカ複合体及びその大気中における熱処理物は，極めて高い光触媒能と相安定性を併せ持つ。テトラ−ｉ−プロポキシチタンや，テトラ−ｎ−プロポキシチタンチタンやテトラ−ｎ−ブトキシチタンなどに代表されるチタンのアルコキシドはもちろん，チタンＩＩＩ価塩にはペルオキソ二硫酸アンモニウム，過酸化水素などの酸化剤を共存させると好適である。
【００１７】
ここで，好適には，ケイ素化合物がシリカゾル，シリカゲル，ケイ酸ナトリウム，Ｓｉのアルコレート（アルコキシド），シリカヒューム，シリカエアロゾル，フライアシュ等の人工原料から選ばれた一つないし二つ以上であることが好ましい。これら人工シリカ原料は，純度など特性を制御できるからである。
【００１８】
また，好適には，前記水熱反応工程の前記所定の温度が３００℃以下である。このましくは２５０℃以下が良い。このようにすれば，比較的低い温度で水熱反応が行われるため，フッ素樹脂等の樹脂製の容器を圧力容器内に利用することが可能となる。
【００１９】
本発明にしたがうところのアナターゼ型チタニア−シリカ複合体は，様々な用途，例えば光触媒としては，有機物分解性に優れるため，水質浄化，脱臭，抗菌，防汚，大気浄化用として好適に用いられる。具体的には，水質浄化剤，脱臭剤，悪臭・有機ガス分解剤，抗菌剤，抗カビ剤，抗藻剤，防汚剤，親水材料，大気浄化剤，水分解光触媒材料である。以下の実施例において，光触媒性能の評価は，その評価法として一般的なメチレンブルーを用いたが，例えば，アセトアルデヒド，フェノール，ＮＯｘ，トリメチルアミン，トリハロメタンや，イプコナゾールなどの農薬の分解等，現在アナターゼ型のチタニアが応用されているすべての用途に有利に用いられ得る。
【００２０】
【発明の実施の形態】
本発明においては，それぞれの目的とする固溶体組成を与える比率において，チタン化合物とケイ素化合物を水性媒体中及び／またはアルコール媒体中に溶解せしめられて，混合溶液とされるのであるが，そのような混合溶液中における合計の金属イオン濃度は，０．００１ｍｏｌ／Ｌ〜５．０ｍｏｌ／Ｌの範囲において，決定され，０．１ｍｏｌ／Ｌ〜１．０ｍｏｌ／Ｌの範囲が生産性を考慮し，好ましいものである。
【００２１】
そして，そのような混合溶液は，公知の適当な反応容器，一般的には圧力容器に収納されて，所望の温度に加熱せしめられ，以て水熱反応が進行せしめられる。該混合溶液には何も加えないかまたは，塩酸，硝酸，硫酸等の酸や，アンモニア水，水酸化ナトリウム水溶液，尿素，ヘキサメチレンテトラミン等の塩基あるいは塩基性物質を発生する物質が共存しうる。本発明にあっては，製造装置の観点からして，より低温における水熱反応工程が好ましく，３００℃以下において水熱反応が進行せしめられ，特に２５０℃以下の温度が有利に採用される一方，その下限は概略９０℃程度とされる。低温の場合は長時間の保持が必要となる。
【００２２】
あるいは，該混合溶液にアンモニア水，水酸化ナトリウム水溶液などの沈殿形成剤を加えるか，あるいは尿素，ヘキサメチレンテトラミン等を加えた後に７０〜１００℃の範囲で加熱して沈殿析出物を析出させるか，加水分解により沈殿析出物，ゲルを析出させる。該混合溶液が混合アルコキシド溶液であるときは，直接乾燥させ，ゲルを得るか，空気中の水分あるいは，蒸留水や，アンモニア水などにより，加水分解せしめ，沈殿析出物，ゲルを形成させた後，沈殿析出物を場合により水洗浄した後乾燥させ，該沈殿析出物，ゲルの乾燥物を１０００℃以下の温度で加熱処理を行うことによりアナターゼ型チタニア−シリカ複合体を得る。
【００２３】
【実施例】
以下に，本発明の実施例を示し，本発明を更に具体的に明らかにするが，本発明が，そのような実施例の記載によって，何等の制約を受けるものでないことは言うまでもないところである。また，本発明には，以下の実施例の他にも，更には上記した具体的記述以外にも，本発明の趣旨を逸脱しない限りにおいて，当業者の知識に基づいて，種々なる変更，修正，改良等を加え得るものであることが理解されるべきである。
【００２４】
実施例 １
チタン化合物としてオキシ硫酸チタン（ＴｉＯＳＯ４）を用い，これを溶解した水溶液と，ケイ素化合物としてオルトケイ酸テトラエチル（Ｓｉ（ＯＣ２Ｈ５）４）を，チタンとケイ素の合計の金属イオンの濃度が０．２ｍｏｌ／Ｌとなり，かつＴｉ：Ｓｉ＝１００：０，９０：１０，８５：１５，８０：２０，７０：３０，５０：５０，３０：７０，１０：９０，０：１００［ｍｏｌ％］の組成比になるように混合した以外，何も加えず，混合溶液（溶液は酸性の状態）を調製した。次いで，この得られた混合溶液をステンレス製圧力容器に納めたフッ素樹脂製容器中に収容し，それを回転させることにより内容物を撹拌しながら加熱し，２００℃の温度で２４時間保持し，水熱反応させた。その後，その得られた生成物を，何れも限外濾過及び／または遠心分離操作により固液分離し，分離後さらに蒸留水を加えて再度撹拌した後，限外濾過及び／または遠心分離操作する工程を繰り返して得られた生成物を洗浄後，６５℃で乾燥させた。
【００２５】
次いで，この得られた乾燥物の結晶相について，Ｘ線回折により同定する一方，Ｘ線回折図形より，デバイ・シェラーの式を用いて，結晶子径の測定を行い，更に標準試料にシリコンを用いて，格子定数の測定を行った。また，大気中の熱処理により生じたアナターゼ型からルチル型への相転移の割合（ルチルの割合（質量％）：ＦＲ）をＸ線回折ピークの積分強度（アナターゼ１０１の積分強度：ＩＡ（１０１），ルチル１１０の積分強度：ＩＲ（１１０））よりＳｐｕｒｒらの式：
ＦＲ＝１／｛１＋０．７９［ＩＡ（１０１）／ＩＲ（１１０）］｝
（Ｒ．Ａ．Ｓｐｕｒｒら，Ａｎａｌ．Ｃｈｅｍ．，２９，７６０−７６２（１９５７））により計算した。また，ＩＣＰ（誘導結合高周波プラズマ）発光分光分析により，得られた生成物の組成（Ｔｉ：Ｓｉ）を定量分析した。生成物の粒子径，形態は透過型電子顕微鏡により観察した。得られた生成物はラマン分光による測定を行った。また，ＢＥＴ法による比表面積測定を行った。さらに紫外可視吸光光度計を使用し，拡散反射光を積分球検出器により測定し，得られた生成物の乾燥粉体の紫外可視光吸収スペクトルを測定した。この紫外可視光吸収スペクトルから生成物（半導体）のバンドギャップを計算した。さらに，得られた生成物の乾燥粉体０．０１ｇを秤量して蒸留水２０ｍＬ中に入れ，５分間超音波分散後，２０ｐｐｍ濃度のメチレンブルー水溶液２０ｍＬを加えメチレンブルー濃度を１０ｐｐｍに，撹拌しながら紫外線（ブラックライト）を６０分間照射したのち，メチレンブルー水溶液と粉体を分離し，溶液中のメチレンブルー濃度を紫外可視吸光光度計により測定し，合成粉体（半導体）の光触媒性能を，メチレンブルーの紫外線（ブラックライト）照射下における分解の程度を調べることにより評価した。また，光触媒性能の高い試料は，別にして，紫外線（ブラックライト）の照射を５分間とした以外は同様にして，溶液中のメチレンブルー濃度を紫外可視吸光光度計により測定し，合成粉体の光触媒性能を評価した。
【００２６】
かくして得られた生成物の６５℃乾燥粉体のＸ線回折図形を，図１に示す。図中，ＴｉＯ２は，本発明のアナターゼ型チタニア−シリカ複合体の製法と同じ方法で合成した本発明組成以外の純粋なアナターゼ型ＴｉＯ２の比較例である。このＸ線回折図より，Ｔｉ：Ｓｉ＝１００：０，９０：１０，８５：１５，８０：２０，７０：３０，５０：５０［ｍｏｌ％］のいずれの出発組成の生成物も，アナターゼ型結晶構造のみが結晶相として同定されることから，アナターゼ型結晶構造を有し，実質的にルチル相を含有しないことが，確認された。アナターゼ型結晶の２００のミラー指数の回折線からデバイ・シェラーの式を用いて，結晶子径の測定を行った結果，いずれの組成の生成粉体の結晶子径も１４〜１５ｎｍの範囲にあった。また，生成物の６５℃乾燥粉体に標準物質としてＳｉを加えた試料のＸ線回折図形より，Ｔｉ：Ｓｉの組成の変化に対し，回折ピーク位置のシフトはほとんど観察されず，組成に対する格子定数（ａ軸，ｃ軸）の微妙な変化を除いて，顕著な変化は観察されなかった。なおＴｉ：Ｓｉ＝３０：７０，１０：９０と，ＳｉＯ２量が多い試料ではアナターゼの回折ピークが小さくなり，比較例であるＴｉ：Ｓｉ＝０：１００では完全な非晶質として同定された。ＩＣＰ（誘導結合高周波プラズマ）発光分光分析により，得られた生成物の分析組成（Ｔｉ：Ｓｉ）を調べた結果，得られた生成物の組成は，出発組成に対応しほぼ同じであることが確認された。得られた生成物の６５℃乾燥粉体のラマン分光による測定結果より，いずれの試料もアナターゼ型結晶に由来するピークのみが観察されたが，生成物中のＳｉ含有量が増えるにしたがい，ピーク強度の減少がはっきり観察され，Ｔｉ：Ｓｉ＝５０：５０［ｍｏｌ％］試料では，アナターゼ型結晶に由来するピークは同定されるものの，極めて弱いことが解った。これより，アナターゼ型結晶表面に，シリカ成分が非晶質として存在しているか，Ｓｉ含有量の多い組成物の場合は，非晶質シリカマトリックス中にアナターゼ型結晶が存在する微構造であることが理解された。透過型電子顕微鏡により生成物（Ｔｉ：Ｓｉ＝１００：０および５０：５０［ｍｏｌ％］試料）を比較観察した結果，比較試料の純粋なアナターゼ型チタニアと比較し，Ｔｉ：Ｓｉ＝５０：５０試料は粒子の輪郭がはっきりせず，ぼけているように観察され，高倍率の格子像の観察される写真からも，非晶質シリカの存在が，ラマン分光測定の結果と兼ねあわせ理解された。ＢＥＴ法による比表面積測定の結果から，比表面積は １００〜４５０ｍ２／ｇの範囲にあり，ＳｉＯ２＝３０ｍｏｌ％までは１００〜１３０ｍ２／ｇであり，ＳｉＯ２＝３０〜９０ｍｏｌ％とＳｉＯ２量が増大するにつれ比表面積は増加し，１５０〜４５０ｍ２／ｇとなった。比較例であるＳｉＯ２＝１００ｍｏｌ％では２００ｍ２／ｇと比表面積は急に低下した。次に，得られた生成物の６５℃乾燥粉体を大気中８００℃，１時間加熱処理した粉体のラマン分光測定の結果より，乾燥粉体と同様に，８００℃熱処理粉体はいずれの試料もアナターゼ型結晶に由来するピークのみが観察されたが，生成物中のＳｉ含有量が増えるにしたがい，ピーク強度の減少がはっきり観察され，Ｔｉ：Ｓｉ＝５０：５０［ｍｏｌ％］試料では，アナターゼ型結晶に由来するピークは同定されるものの，極めて弱いことが解り，アナターゼ型結晶表面に，シリカ成分が非晶質として存在しているか，Ｓｉ含有量の多い組成物の場合は，非晶質シリカマトリックス中にアナターゼ型結晶が存在する微構造であることが理解された。得られた生成物（Ｔｉ：Ｓｉ＝５０：５０）を大気中，種々の温度で１時間加熱処理した粉体のＸ線回折図形を，図２に示す。また，大気中の熱処理により生じたアナターゼ型からルチル型への相転移の割合をＸ線回折ピーク（アナターゼ１０１ルチル１１０）の積分強度よりＳｐｕｒｒらの式により計算した結果を図３に示す。大気中の熱処理により生じたアナターゼ型からルチル型への相転移は，シリカ含有量の増大にともない抑制され，高温側へシフトし，シリカ含有量１５ｍｏｌ％では１１００℃処理後も１００％アナターゼ型であり，シリカ含有量３０ｍｏｌ％では１２００℃処理後９５％以上がアナターゼ型であった。シリカ含有量５０ｍｏｌ％では１３００℃，１時間処理後も１００％アナターゼ型であって，極めて高い相安定性を示すことが確認された。透過型電子顕微鏡観察結果より，比較例である純粋なアナターゼ型チタニアと比較し，本発明のアナターゼ型チタニア−シリカ複合体は，大気中８００℃，１時間の処理後もほとんど粒子成長（結晶子成長）せず，熱処理前と同様な微細な粒子径を保っていることが解った。アナターゼ型結晶の２００のミラー指数の回折線からデバイ・シェラーの式を用いて，結晶子径の測定を行った結果を大気中における熱処理温度に対して図４に図示する。図中，ＴｉＯ２は，本発明のアナターゼ型チタニア−シリカ複合体の製法と同じ方法で合成した本発明組成以外の純粋なアナターゼ型ＴｉＯ２の比較例である。シリカをアナターゼ型結晶と複合化することにより，結晶子の成長が大幅に抑制されることが解る。シリカ（ＳｉＯ２）の含有量が３０ｍｏｌ％以上であり，１２００℃，１時間の大気中における熱処理後において，アナターゼ型チタニア結晶の結晶子径が５０ｎｍ以下であることが確認され，シリカ（ＳｉＯ２）の含有量が５０ｍｏｌ％試料は，１２００℃，１時間の大気中における熱処理後のアナターゼ型チタニア結晶の結晶子径は４０ｎｍであった。図５に，生成物の紫外可視光吸収スペクトルの測定結果を図示する。図中，ＴｉＯ２は，本発明のアナターゼ型チタニア−シリカ複合体の製法と同じ方法で合成した本発明組成以外の純粋なアナターゼ型ＴｉＯ２の比較例である。Ｔｉ：Ｓｉの組成の変化にともない，吸収スペクトルの吸収端が短波長側に微妙にシフトしていくことが観察される。この吸収スペクトルから生成物（半導体）のバンドギャップを計算した結果を表１に示す。
【００２７】
Ｓｉ含有量の増大にしたがい，バンドギャップは若干ずつ増大し，組成制御により，若干ではあるがバンドギャップを変化させうることが解る。メチレンブルーの分解を用いて紫外線（ブラックライト）照射下における合成粉体の光触媒性能を評価した結果を，紫外線（ブラックライト）を６０分照射後のメチレンブルーの吸光度（濃度）の変化で図６に示す。図中，ＴｉＯ２は図に示した本発明のアナターゼ型チタニア−シリカ複合体の製法と同じ方法で合成した本発明組成以外の水熱合成された純粋なアナターゼ型ＴｉＯ２の比較例である。また，ＳＴ−０１は，市販されている石原産業製の純粋なアナターゼ型ＴｉＯ２光触媒で比較例である。比較例である水熱合成された純粋なアナターゼ型ＴｉＯ２及び市販されている石原産業製の純粋なアナターゼ型ＴｉＯ２光触媒ＳＴ−０１が，紫外線（ブラックライト）を６０分照射後において，メチレンブルーの吸光度（濃度）が光触媒無添加の場合（ＭＢ試料）の約２／３から１／２まで低下している程度であるのに対し，Ｓｉ成分を含有する本発明のアナターゼ型チタニア−シリカ複合体はいずれも，６０分照射の間にメチレンブルーの吸光度（濃度）が急激に減少し，約１／３以下であって，Ｔｉ：Ｓｉ＝７０：３０，５０：５０［ｍｏｌ％］組成では，ほぼ吸光度（濃度）がゼロであって，極めて高速かつ著しい低下を示すことが解る。さらに，図６において最も優れる性能を示したＴｉ：Ｓｉ＝５０：５０［ｍｏｌ％］組成物について，大気中における熱処理効果について，６００〜１０００℃で１時間熱処理した試料について，紫外線（ブラックライト）の照射時間を５分間と１／１２に短縮した以外は同様にして，溶液中のメチレンブルー濃度を紫外可視吸光光度計により測定し，大気中における熱処理後の合成粉体の光触媒性能を評価した結果を図７に示す。これより，６００〜１０００℃と熱処理温度が高くなるにつれてメチレンブルーの吸光度（濃度）が減少し，１０００℃処理試料では，ほぼ吸光度（濃度）がゼロ付近であって，５分間という短時間の照射であっても，極めて高速かつ著しい低下（高い優れた光触媒能）を示すことが解る。
【００２９】
実施例 ２
チタン化合物としてオキシ硫酸チタン（ＴｉＯＳＯ４）を用い，これを溶解した水溶液と，ケイ素化合物としてオルトケイ酸テトラエチル（Ｓｉ（ＯＣ２Ｈ５）４）を，チタンとケイ素の合計の金属イオンの濃度が０．２ｍｏｌ／Ｌとなり，かつＴｉ：Ｓｉ＝１００：０，９０：１０，８５：１５，７０：３０，５０：５０［ｍｏｌ％］の組成比になるように混合した溶液に，溶液を中和するのに必要な量の２倍量のアンモニア水を加え，沈殿物スラリーを含む混合溶液を用いた以外は実施例 １と全く同様な合成操作を行い，生成物を得，洗浄後，６５℃で乾燥させ，実施例 １と同様な測定を行った。
【００３０】
かくして得られた生成物の６５℃乾燥粉体のＸ線回折図形より，Ｔｉ：Ｓｉ＝１００：０，９０：１０，８５：１５，７０：３０，５０：５０［ｍｏｌ％］のいずれの出発組成の生成物も，アナターゼ型結晶構造のみが結晶相として同定され，アナターゼ型結晶構造を有し，実質的にルチル相を含有しないことが，理解された。アナターゼ型結晶の２００のミラー指数の回折線からデバイ・シェラーの式を用いて，結晶子径の測定を行った結果，いずれの組成の生成粉体の結晶子径も１０〜２０ｎｍの範囲にあった。得られた生成物の分析組成（Ｔｉ：Ｓｉ）を調べた結果，得られた生成物の組成は，出発組成に対応しほぼ同じであることが確認された。得られた生成物の６５℃乾燥粉体のラマン分光による測定結果および透過型電子顕微鏡観察より，アナターゼ型結晶表面に，シリカ成分が非晶質として存在しているか，Ｓｉ含有量の多い組成物の場合は，非晶質シリカマトリックス中にアナターゼ型結晶が存在する微構造であることが理解された。大気中の熱処理により生じたアナターゼ型からルチル型への相転移は，シリカ含有量の増大にともない抑制され，高温側へシフトし，シリカ含有量１５ｍｏｌ％では１１００℃処理後も１００％アナターゼ型であることが確認され，シリカ含有量３０ｍｏｌ％以上では１２００℃処理後も９０％以上がアナターゼ型であることが確認された。５０ｍｏｌ％では１３００℃処理後も１００％アナターゼ型であることが確認された。メチレンブルーの分解を用いて紫外線（ブラックライト）照射下における合成粉体の光触媒性能を評価した結果，比較例である水熱合成された純粋なアナターゼ型ＴｉＯ２及び市販されている石原産業製の純粋なアナターゼ型ＴｉＯ２光触媒ＳＴ−０１が，紫外線（ブラックライト）を６０分照射後において，メチレンブルーの吸光度（濃度）が光触媒無添加の場合（ＭＢ試料）の約２／３から１／２まで低下している程度であるのに対し，シリカ成分を含有する本発明のアナターゼ型チタニア−シリカ複合体はいずれも，６０分照射の間にメチレンブルーの吸光度（濃度）が急激に減少し，約１／３以下であって，Ｔｉ：Ｓｉ＝７０：３０，５０：５０［ｍｏｌ％］組成では，ほぼ吸光度（濃度）がゼロであって，極めて高速かつ著しい低下を示すことが解った。さらに，大気中で熱処理６００〜１０００℃で１時間熱処理することで性能が向上し，高い優れた光触媒能を示した。
【００３１】
実施例 ３
実施例 １において，オルトケイ酸テトラエチルの代わりにシリカゲルを使用し，かつＴｉ：Ｓｉ＝４０：６０，２０：８０，５：９５［ｍｏｌ％］の組成比になるように混合した以外は実施例 １と同様に試料を調製した。評価も乾燥物を走査型電子顕微鏡（ＳＥＭ）観察した以外実施例 １と類似の測定を行った。
【００３２】
かくして得られた生成物の６０℃乾燥粉体のＸ線回折図形より，いずれの出発組成の生成物は，結晶相としては，アナターゼ型結晶構造のみが同定され，アナターゼ型結晶構造を有し，実質的にルチル相を含有しないことが理解された。また，非晶質シリカゲル表面にアナターゼ型結晶の析出粒子の存在がＳＥＭにより確認された。シリカ成分（シリカゲル）との複合化により，吸着能と同時に光触媒性能が向上し，アナターゼ型の安定性も向上した（１２００℃，１時間処理後も１００％アナターゼ型であることが確認された）。
【００３３】
実施例 ４
チタン化合物としてオキシ硫酸チタン（ＴｉＯＳＯ４）を用い，これを溶解した水溶液と，ケイ素化合物としてケイ酸ナトリウム（メタケイ酸ナトリウムＮａ２ＳｉＯ３・９Ｈ２Ｏ）を，チタンとケイ素の合計の金属イオンの濃度が０．２ｍｏｌ／Ｌとなり，かつＴｉ：Ｓｉ＝１００：０，９０：１０，８５：１５，７０：３０，５０：５０，３０：７０［ｍｏｌ％］の組成比になるように混合した以外，何も加えず，調製した混合溶液（溶液は酸性の状態）を用いた以外は実施例 １と全く同様な合成操作を行い，生成物を得，洗浄後，６５℃で乾燥させた。 次いで，この得られた乾燥物の結晶相について，実施例 １と同様な測定を行った。
【００３４】
かくして得られた生成物の６５℃乾燥粉体のＸ線回折図形より，Ｔｉ：Ｓｉ＝１００：０，９０：１０，８５：１５，７０：３０，５０：５０，３０：７０［ｍｏｌ％］のいずれの出発組成の生成物も，アナターゼ型結晶構造のみが結晶相として同定され，アナターゼ型結晶構造を有し，実質的にルチル相を含有しないことが，理解された。アナターゼ型結晶の２００のミラー指数の回折線からデバイ・シェラーの式を用いて，結晶子径の測定を行った結果，いずれの組成の生成粉体の結晶子径も１０〜２０ｎｍの範囲にあった。ＩＣＰ（誘導結合高周波プラズマ）発光分光分析により，得られた生成物の分析組成（Ｔｉ：Ｓｉ）を調べた結果，得られた生成物の組成は，出発組成に対応しほぼ同じであることが確認された。得られた生成物の６５℃乾燥粉体のラマン分光による測定結果および透過型電子顕微鏡観察より，アナターゼ型結晶表面に，シリカ成分が非晶質として存在しているか，Ｓｉ含有量の多い組成物の場合は，非晶質シリカマトリックス中にアナターゼ型結晶が存在する微構造であることが理解された。大気中の熱処理により生じたアナターゼ型からルチル型への相転移は，シリカ含有量の増大にともない抑制され，高温側へシフトし，シリカ含有量１５ｍｏｌ％では１１００℃処理後も１００％アナターゼ型であることが確認され，シリカ含有量３０ｍｏｌ％以上では１２００℃処理後も１００％アナターゼ型であることが確認された。メチレンブルーの分解を用いて紫外線（ブラックライト）照射下における合成粉体の光触媒性能を評価した結果，比較例である水熱合成された純粋なアナターゼ型ＴｉＯ２及び市販されている石原産業製の純粋なアナターゼ型ＴｉＯ２光触媒ＳＴ−０１が，紫外線（ブラックライト）を６０分照射後において，メチレンブルーの吸光度（濃度）が光触媒無添加の場合（ＭＢ試料）の約２／３から１／２まで低下している程度であるのに対し，シリカ成分を含有する本発明のアナターゼ型チタニア−シリカ複合体はいずれも，６０分照射の間にメチレンブルーの吸光度（濃度）が急激に減少し，約１／３以下であって，Ｔｉ：Ｓｉ＝７０：３０，５０：５０［ｍｏｌ％］組成では，ほぼ吸光度（濃度）がゼロであって，極めて高速かつ著しい低下を示すことが解った。さらに，大気中で熱処理６００〜１０００℃で１時間熱処理することで性能が向上し，高い優れた光触媒能を示した。
【００３５】
【発明の効果】
以上の説明から明らかなように，本発明にしたがうところのアナターゼ型チタニア−シリカ複合体は，様々な用途に好適であり，例えば光触媒としては，有機物分解性に優れ，水質浄化，脱臭，抗菌，防汚，大気浄化用として好適に用いられ，応答性の高い光触媒作用を有する。とくに，水質浄化剤，脱臭剤，悪臭・有機ガス分解剤，抗菌剤，抗カビ剤，抗藻剤，防汚剤，親水材料，大気浄化剤，水分解光触媒材料に用いられる。また，１１００℃，１時間以上（好適には，１２００℃，１時間）の大気中における高温熱処理後において，実質的にルチル相を含有せずアナターゼ型チタニアとして存在しうる高い相安定性を持つ。（本発明では，シリカ含有量５０ｍｏｌ％を含む組成のアナターゼ型チタニア−シリカ複合体では，１３００℃，１時間の大気中熱処理後も１００％アナターゼ型を保つことができることを実証した。）さらにはシリカ成分（シリカゲル）との複合化により，物質吸着性をも同時に有することが可能であり，物質吸着能と光触媒作用の相乗作用により，一段と性能に優れるため，現在アナターゼ型のチタニアあるいはシリカが応用されている多くの用途に有利に用いられ得るとともに，新しい用途が拡大する可能性がある。
【図面の簡単な説明】
【図１】実施例１において得られた各種の６５℃乾燥物についてのＸ線回折図を示す図である。
【図２】実施例１において得られた生成物（ＳｉＯ２＝５０ｍｏｌ％）の各温度における熱処理物のＸ線回折図を示す図である。
【図３】実施例１において得られた生成物の大気中における熱処理により生じたアナターゼ型からルチル型への相転移量（質量％）について，Ｘ線回折ピーク（アナターゼ１０１ルチル１１０）の積分強度より計算した結果を示す図である。
【図４】実施例１において得られた生成物の大気中における熱処理物のアナターゼ型結晶の結晶子径を大気中における熱処理温度に対しプロットした図である。
【図５】実施例１において得られた生成物の紫外可視光吸収スペクトルの測定結果を示す図である。
【図６】実施例１において得られた生成物の光触媒性能を，メチレンブルーの分解を用いて紫外線（ブラックライト）照射下において評価した結果を，６０分間の紫外線照射後のメチレンブルーの吸光度（相対的な濃度）として示す図である。
【図７】実施例１において得られた熱処理（仮焼）温度の異なる試料（Ｔｉ：Ｓｉ＝５０：５０［ｍｏｌ％］試料）の光触媒性能を，メチレンブルーの分解を用いて紫外線（ブラックライト）照射下において評価した結果を，５分間の紫外線照射後のメチレンブルーの吸光度（相対的な濃度）として示す図である。[0001]
TECHNICAL FIELD OF THE INVENTION
INDUSTRIAL APPLICABILITY The present invention has a high photocatalytic action, has excellent phase stability of anatase phase, has excellent organic matter decomposability, is suitably used for water purification, deodorization, antibacterial, antifouling, air purification, and also has a substance adsorption property. The present invention relates to an excellent anatase-type titania-silica composite and a method for producing the same.
[0002]
[Prior art]
Titanium oxide (titania, TiO 2 ) Belongs to the n-type semiconductor, and among the three crystal phases (anatase, rutile, and brookite), anatase-type titania exhibits excellent photocatalytic action. Since the thermodynamically stable phase of titania is rutile and anatase is a metastable phase, generally, heat treatment in the atmosphere easily causes a phase transition from the anatase type to the rutile type. At high temperatures, anatase-type titania is extremely unstable. The phase transition from the anatase type to the rutile type is said to occur around 635 ° C from kinetic studies. However, the stability of the anatase phase greatly depends on the particle size, impurities, composition, manufacturing method, etc. Depending on the precursor used, a phase transition from an anatase type to a rutile type starts at around 500 ° C.
[0003]
Known methods for producing titanium oxide include a sol-gel method using an alkoxide of titanium as a raw material, and a method of thermal decomposition or hydrolysis of an aqueous solution of titanium salt such as titanium tetrachloride or titanium sulfate or titanium oxysulfate. ing.
[0004]
Silica has three polymorphs, quartz, tridymite, and cristobalite, and is used industrially in many fields. However, it is the main component of glass and exists in the glass state (amorphous) relatively easily. Can. Many amorphous silica materials are also used as industrial silica raw materials. As an amorphous silica, for example, silica gel has been applied to an adsorbent, a deodorant, a catalyst carrier and the like by utilizing a high specific surface area and an innumerably developed pore.
[0005]
For titania containing silica, pure anatase TiO 2 The effect of silica addition on the phase transition from anatase type to rutile type, (1) TiCl 4 -SiCl 4 -O 2 CVD-TiO synthesized by gas phase reaction 2 ・ SiO 2 It has been investigated in powders and found to suppress the phase transition from anatase to rutile (present in anatase phase up to 980 ° C.). (Yoko Suyama, Akio Kato, Journal of the Ceramic Society of Japan 86 [3] 119 (1978)) Also, (2) silica is added to anatase type titania particles, and the ratio of phase transition to rutile type even at 1000 ° C. firing is small, and photocatalyst A ceramic having a high activity and a photocatalytic function and a method for producing the same are disclosed. (JP-A-11-157966) Furthermore, (3) there is a report on a powder synthesized by a sol-gel method using titanium tetraisopropoxide and tetraethyl orthosilicate, and the solid solution of silica in titania is discussed. The effect of increasing the phase transition temperature from the anatase type to the rutile type by about 300 ° C. is shown (100% exists up to about 825 ° C. in the anatase phase). (K. Okada et al., J. Am. Ceram. Soc., 84 [7] 1591 (2001).)
[0006]
Regarding the combination of silica gel and the like with a titania photocatalyst, there are a porous gel photocatalyst (JP-A-10-323568), a spherical silica gel body containing a semiconductor photocatalyst, a production method, and a coating composition (JP-A-2001-104799). The phase stability of titania by the production method is not high, and no concrete and objective evidence based on experimental data on the effect of improving the photocatalytic ability by combining a titania photocatalyst with a silica component has been shown. In addition, prior to these applications, complexation of a titania photocatalyst with silica gel or the like (disclosure of a sol-gel mixture of a titania photocatalyst and silica, X. Fu et al., Environ. Sci. Technology, 30 [2] 647-653 ( 1996))) or a silica gel-titania catalyst (the effect of pre-hydrolysis on the structure and catalytic properties of titania-silica airgel, JB Miller et al., J. Catal, 150 [2] 311-320 (1994)). ) Etc. are disclosed in the literature, and similar techniques are already known.
[0007]
[Problems to be solved by the invention]
Pure anatase-type titanium oxide easily undergoes a phase transition from anatase-type to rutile-type by heat treatment in the air, causing a reduction in photocatalytic activity and an inherent problem of low phase stability. Further, although the effect of suppressing the phase transition of titania from anatase type to rutile type by adding silica is known, the phase stability of the anatase type titanium oxide disclosed in the above-mentioned disclosed technology is low, and it is 1100 ° C. for 1 hour or more. After the heat treatment in a high-temperature atmosphere at 1200 ° C. for 1 hour, the phase transition from anatase type to rutile type has already been completely completed, and the temperature has generally been completed at 1100 ° C. for 1 hour or more. After high-temperature heat treatment in the air (1200 ° C., 1 hour), there are almost no reports showing high phase stability that may exist as anatase titania. In addition, anatase-type titanium oxide shows an excellent photocatalyst in a semiconductive material, but it is also important to further enhance the photocatalytic activity. On the other hand, silica has excellent adsorption ability, but has almost no photocatalytic activity. Amorphous silica has optical transparency, so it has a high specific surface area and countless developed pores. By combining silica and anatase-type titania with excellent adsorption capacity, the synergistic effect of adsorption capacity and photocatalytic capacity Therefore, it is required to expand the application of titanium oxide to photocatalysts in various fields. The present invention, by examining the complexing method and manufacturing method, has found a remarkable improvement in the phase stability of the anatase phase due to complexing with silica, a marked improvement in the photocatalytic performance of anatase-type titania, and a synergistic effect thereof. It was completed based on a simple experiment.
[0008]
[First means for solving the problem]
In order to solve such problems, the gist of the anatase-type titania-silica composite of the first invention is that titania (titanium oxide, TiO2) is used. 2 ), 15 to 95 mol% of silica (SiO 2 The titania is composed of an anatase-type crystal phase, does not substantially contain a rutile phase, and after heat treatment in the atmosphere at 1100 ° C. for 1 hour or more, contains substantially no rutile phase and contains anatase Phase anatase titania after heat treatment in air at 1100 ° C. for 1 hour has a crystallite size of 70 nm or less, and silica (SiO 2) 2 ), Which has a photocatalytic action twice or more that of anatase-type titania containing no anatase-type titania.
[0009]
The anatase-type titania-silica composite having such a composition is suitable for various uses as a semiconductive substance. For example, as a photocatalyst, it is excellent in decomposing organic substances, and purifies water, deodorizes, antibacterial, antifouling, and air purifies. It is suitable for use, has a highly responsive photocatalytic action, and since amorphous silica has optical transparency, it combines with a high specific surface area and its combination with amorphous silica having innumerably developed pores. It is possible to impart high substance adsorbing property, and a synergistic effect between the decomposition action of the adsorbed substance and the photocatalytic action is obtained.
[0010]
Here, preferably, silica (SiO 2 ) Is mainly present as amorphous silica on the surface of the titania crystal fine particles, and / or the silica (SiO 2) 2 ) Is present as an amorphous silica matrix, and a titania-silica composite in which titania is present as fine crystal particles in the amorphous silica matrix and / or the silica (SiO 2) 2 ) Is amorphous silica gel, and titania is preferably present as fine anatase crystal particles mainly on the surface of the amorphous silica gel. Thereby, a synergistic effect between the decomposition action of the adsorbed substance and the photocatalysis action can be obtained.
[0011]
Here, preferably, a sulfate of titanium is used, or an acidic salt of titanium or a hydroxide of titanium is used in the presence of sulfuric acid or sulfate ions. The crystallization step or (2) the hydrolysis / crystallization step under normal pressure or (3) the hydrothermal treatment of the precipitate formed from the solution by the addition of the precipitate-forming agent or (4) the solution from the solution by the addition of the precipitate-forming agent The anatase-type titania-silica complex prepared by a production method including any one of the heat treatment steps of the generated precipitate is preferable. This is because the anatase-type titania-silica complex prepared from the sulfate of titanium has extremely high anatase phase stability, as described in Examples described later. Preferably, the anatase-type titania-silica composite thus prepared is subjected to a heat treatment in the air at a temperature in the range of 400 to 1200 ° C., preferably 600 to 1000 ° C., to thereby improve the photocatalytic performance. It can be further increased to twice or more of the case where it is not performed.
[0012]
Preferably, silica (SiO 2) is used. 2 ) Is 30 mol% or more, and as a stability of the anatase type crystal phase, after heat treatment in the air at 1200 ° C. for 1 hour, the rutile phase is less than 10% by mass and 90% or more is anatase. Is preferably an anatase-type titania-silica composite having a phase stability that can exist as type-titania, and having a crystallite size of anatase-type titania crystal of 50 nm or less after heat treatment in air at 1200 ° C. for 1 hour. .
[0013]
As a photocatalytic action, 0.01 g of anatase-type titania-silica composite powder was added to 20 ml of distilled water, 20 ml of 20 ppm methylene blue was added, and the methylene blue concentration of the whole solution (40 ml) was adjusted to 10 ppm. In contrast, in a photocatalytic evaluation test in which the degree of methylene blue decomposition by a photocatalyst is measured by the change (decrease) in the absorbance of methylene blue near 660 nm using a spectrophotometer, The absorbance (concentration) of methylene blue after ultraviolet irradiation is less than half the absorbance (concentration) of anatase-type titania without silica and has a methylene blue resolution (photocatalytic ability) more than twice that of anatase-type titania. However, the photocatalytic ability is preferably excellent.
[0014]
[Second means for solving the problem]
The gist of the method for producing the anatase-type titania-silica composite of the second invention for achieving the above-mentioned invention is that a titanium compound and a silicon compound are dispersed or dissolved in an aqueous medium and / or an alcohol medium. And (1) a hydrothermal reaction step in which the mixed solution is hydrothermally reacted at a predetermined temperature in a closed vessel, or (2) a mixed solution in a reaction vessel under normal pressure. Or (3) a hydrothermal treatment step of a precipitate formed from the solution by adding a precipitate-forming agent to the mixed solution, or (4) a precipitation-forming agent to the mixed solution. And depositing a precipitate, and subjecting the precipitate to a heat treatment at a temperature of 1000 ° C. or lower, which includes any one of the steps (1) to (4) of the precipitate formation / heat treatment step. Anatase titania and symptoms - a process for producing silica complex.
[0015]
In this way, a mixed solution is prepared by dispersing or dissolving the titanium compound and the silicon compound in an aqueous medium and / or an alcohol medium, and in a hydrothermal reaction step, the mixed solution is subjected to a predetermined method in a closed container. Hydrothermal reaction at temperature. Therefore, the Ti component (or titanium oxide) derived from the titanium compound and the Si component (or silicon oxide) derived from the silicon compound are dispersed or dissolved in the mixed solution, so that they easily react, and the hydrothermal reaction (ie, The reaction in the presence of high-temperature and high-pressure water = hydrothermal synthesis) causes a reaction in molecular units, precipitates as anatase crystals, and forms silica (SiO 2 ) Is mainly present on the surface of the titania crystal fine particles as non-quality silica and / or the silica (SiO 2) 2 ) Is present as an amorphous silica matrix, and a titania-silica composite in which titania is present as fine crystal particles in the amorphous silica matrix and / or the silica (SiO 2) 2 ) Is amorphous silica gel, and a microstructure in which titania is present as fine anatase-type crystal fine particles mainly on the surface of the amorphous silica gel is achieved. Alternatively, a precipitate-forming agent (for example, aqueous ammonia, ammonium carbonate, sodium hydroxide, potassium hydroxide, or an alkaline component such as urea or hexamethylenetetramine) is added to these mixed solutions, and the mixture is heated as necessary (urea or hexamethylenetetramine). , By heating at 80 to 95 ° C.) to precipitate precipitates composed of oxides, hydroxides, carbonates, etc. of the respective components, and heat-treat the precipitates at a temperature of 1000 ° C. or lower. By carrying out the reaction, the crystals are precipitated as anatase crystals, and the above-described microstructure of the titania-silica complex is achieved. Alternatively, a gel is obtained by adding a precipitation-forming agent to these mixed solutions or forming a sol by hydrolysis, and the gel is subjected to heat treatment, hot water treatment or hydrothermal treatment at a temperature of 1000 ° C. or less to form anatase crystals. The crystals are precipitated, and the above-described microstructure of the titania-silica composite is achieved. In addition. The solvent in the hydrothermal reaction step may be an acidic solution spontaneously generated by hydrolysis when using a salt compound of each component, particularly titanium sulfate, titanium oxysulfate, titanium tetrachloride, or the like as a titanium source. It can be applied in the coexistence of alkali components such as ammonium carbonate, sodium hydroxide, potassium hydroxide, or urea or hexamethylenetetramine, or in a neutral solvent or a basic solvent.
[0016]
Here, preferably, the titanium compound is a sulfate of titanium. In this way, an anatase-type titania-silica composite having excellent phase stability can be obtained. Preferred examples of the sulfate of titanium include titanium oxysulfate and titanium sulfate, and an aqueous solution of titanium tetrachloride and an aqueous solution of peroxotitanic acid in the presence of sulfuric acid or sulfate ions are also preferable. In particular, titanium oxysulfate, titanium sulfate, and the like are preferable. An aqueous solution of titanium tetrachloride, an aqueous solution of peroxotitanic acid, titanium hydroxide, or the like in the presence of sulfuric acid or sulfate ions is used, and a hydrothermal reaction step is used to combine the two. The anatase-type titania-silica composite directly synthesized at a temperature of less than ℃ and its heat-treated product in the atmosphere have extremely high photocatalytic activity and phase stability. Oxidizing agents such as ammonium peroxodisulfate, hydrogen peroxide and the like are not limited to titanium alkoxides represented by tetra-i-propoxytitanium, tetra-n-propoxytitanium titanium, tetra-n-butoxytitanium and the like, as well as titanium trivalent salts. It is preferable to coexist.
[0017]
Here, preferably, the silicon compound is one or more selected from artificial raw materials such as silica sol, silica gel, sodium silicate, alcoholate (alkoxide) of Si, silica fume, silica aerosol, and fly ash. Is preferred. This is because these artificial silica raw materials can control characteristics such as purity.
[0018]
Preferably, the predetermined temperature in the hydrothermal reaction step is 300 ° C. or less. Preferably, the temperature is 250 ° C. or less. In this case, since the hydrothermal reaction is performed at a relatively low temperature, a resin container such as a fluororesin can be used in the pressure container.
[0019]
The anatase-type titania-silica composite according to the present invention is suitably used for water purification, deodorization, antibacterial, antifouling, and air purification because of its various uses, for example, as a photocatalyst, because of its excellent decomposability of organic substances. Specifically, they are a water purification agent, a deodorant, an odor / organic gas decomposition agent, an antibacterial agent, an antifungal agent, an antialgal agent, an antifouling agent, a hydrophilic material, an air purification agent, and a water decomposition photocatalytic material. In the following examples, photocatalytic performance was evaluated using a general method of methylene blue, such as acetaldehyde, phenol and NO. x It can be advantageously used in all applications where anatase-type titania is currently used, such as decomposition of pesticides such as trimethylamine, trimethylamine, trihalomethane and ipconazole.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
In the present invention, a titanium compound and a silicon compound are dissolved in an aqueous medium and / or an alcohol medium to obtain a mixed solution in such a ratio as to give a desired solid solution composition. The total metal ion concentration in the mixed solution is determined in the range of 0.001 mol / L to 5.0 mol / L, and the range of 0.1 mol / L to 1.0 mol / L is preferable in consideration of productivity. Things.
[0021]
Such a mixed solution is housed in a known suitable reaction vessel, generally a pressure vessel, and heated to a desired temperature, whereby the hydrothermal reaction proceeds. Nothing may be added to the mixed solution, or an acid such as hydrochloric acid, nitric acid, sulfuric acid or the like, or a substance generating a base or a basic substance such as aqueous ammonia, aqueous sodium hydroxide, urea, hexamethylenetetramine may coexist. . In the present invention, from the viewpoint of the production apparatus, a hydrothermal reaction step at a lower temperature is preferable, and the hydrothermal reaction proceeds at 300 ° C. or less, and particularly, a temperature of 250 ° C. or less is advantageously employed. , The lower limit of which is about 90 ° C. When the temperature is low, long-term holding is required.
[0022]
Alternatively, a precipitate-forming agent such as aqueous ammonia or an aqueous sodium hydroxide solution may be added to the mixed solution, or urea, hexamethylenetetramine or the like may be added and then heated at 70 to 100 ° C. to precipitate a precipitate. , A precipitate and a gel are precipitated by hydrolysis. When the mixed solution is a mixed alkoxide solution, it is directly dried to obtain a gel, or is hydrolyzed with water in the air, distilled water, ammonia water, etc. to form a precipitate and a gel. The precipitate is optionally washed with water and then dried, and the precipitate and the dried gel are subjected to a heat treatment at a temperature of 1000 ° C. or less to obtain an anatase-type titania-silica complex.
[0023]
【Example】
Hereinafter, examples of the present invention will be shown to clarify the present invention more specifically. Needless to say, the present invention is not limited by the description of such examples. In addition, in addition to the following embodiments, and in addition to the above-described specific description, various changes and modifications may be made to the present invention based on the knowledge of those skilled in the art without departing from the spirit of the present invention. It should be understood that improvements can be made.
[0024]
Example 1
Titanium oxysulfate (TiOSO) 4 ), And an aqueous solution in which this is dissolved, and tetraethyl orthosilicate (Si (OC 2 H 5 ) 4 ), The concentration of the total metal ion of titanium and silicon is 0.2 mol / L, and Ti: Si = 100: 0, 90:10, 85:15, 80:20, 70:30, 50:50, A mixed solution (solution was in an acidic state) was prepared without adding anything except that the composition ratios were 30:70, 10:90, 0: 100 [mol%]. Next, the obtained mixed solution was accommodated in a fluororesin container housed in a stainless steel pressure vessel, and the contents were heated by rotating the container while stirring, and held at a temperature of 200 ° C. for 24 hours. The hydrothermal reaction was performed. Thereafter, all the obtained products are subjected to solid-liquid separation by ultrafiltration and / or centrifugation. After separation, distilled water is further added and the mixture is stirred again, followed by ultrafiltration and / or centrifugation. The product obtained by repeating the steps was washed and dried at 65 ° C.
[0025]
Next, while the crystal phase of the obtained dried product is identified by X-ray diffraction, the crystallite diameter is measured from the X-ray diffraction pattern using the Debye-Scherrer equation, and silicon is added to the standard sample. The lattice constant was measured using this method. Further, the ratio of the phase transition from the anatase type to the rutile type caused by the heat treatment in the atmosphere (the ratio of rutile (% by mass): F R ) To the integrated intensity of the X-ray diffraction peak (the integrated intensity of anatase 101: I A (101), integrated intensity of rutile 110: I R (110)) From Spurr et al .:
F R = 1 / ｛1 + 0.79 [IA (101) / I R (110)]｝
(RA Spurr et al., Anal. Chem., 29, 760-762 (1957)). The composition (Ti: Si) of the obtained product was quantitatively analyzed by ICP (inductively coupled high frequency plasma) emission spectroscopy. The particle size and morphology of the product were observed with a transmission electron microscope. The obtained product was measured by Raman spectroscopy. The specific surface area was measured by the BET method. Further, the diffuse reflection light was measured with an integrating sphere detector using an ultraviolet-visible absorption spectrophotometer, and the ultraviolet-visible light absorption spectrum of the obtained dried powder of the product was measured. The band gap of the product (semiconductor) was calculated from the ultraviolet-visible absorption spectrum. Further, 0.01 g of the dry powder of the obtained product was weighed and placed in 20 mL of distilled water, and after ultrasonic dispersion for 5 minutes, 20 mL of an aqueous solution of methylene blue having a concentration of 20 ppm was added thereto to adjust the methylene blue concentration to 10 ppm. (Black light) for 60 minutes, the methylene blue aqueous solution and the powder were separated, and the methylene blue concentration in the solution was measured with an ultraviolet-visible absorptiometer, and the photocatalytic performance of the synthetic powder (semiconductor) was measured using the methylene blue ultraviolet light ( (Black light) was evaluated by examining the degree of decomposition under irradiation. For samples with high photocatalytic performance, the methylene blue concentration in the solution was measured using an ultraviolet-visible absorption spectrophotometer in the same manner except that irradiation of ultraviolet light (black light) was performed for 5 minutes. The photocatalytic performance was evaluated.
[0026]
The X-ray diffraction pattern of the product at 65 ° C. dried powder is shown in FIG. In the figure, TiO 2 Is pure anatase TiO other than the composition of the present invention, which is synthesized by the same method as the method for producing the anatase titania-silica composite of the present invention. 2 This is a comparative example. From this X-ray diffraction diagram, it can be seen that the products of any starting composition of Ti: Si = 100: 0, 90:10, 85:15, 80:20, 70:30, 50:50 [mol%] are anatase type Since only the crystal structure was identified as the crystal phase, it was confirmed that the crystal structure had an anatase-type crystal structure and contained substantially no rutile phase. The crystallite diameter was measured from the diffraction line of the Miller index of 200 of the anatase crystal using the Debye-Scherrer equation. As a result, the crystallite diameter of the resulting powder of any composition was in the range of 14 to 15 nm. Was. Also, from the X-ray diffraction pattern of a sample obtained by adding Si as a standard substance to the dried powder at 65 ° C., almost no shift in the diffraction peak position was observed with respect to the change in the composition of Ti: Si, and the lattice relative to the composition No significant change was observed except for subtle changes in the constants (a-axis and c-axis). Note that Ti: Si = 30: 70, 10:90 and SiO: 2 In the sample having a large amount, the diffraction peak of anatase was small, and the sample was identified as completely amorphous in Ti: Si = 0: 100 as the comparative example. As a result of examining the analytical composition (Ti: Si) of the obtained product by ICP (inductively coupled high frequency plasma) emission spectroscopy, it was found that the composition of the obtained product was almost the same, corresponding to the starting composition. confirmed. From the results of Raman spectroscopy of the powder obtained at 65 ° C., only peaks derived from anatase-type crystals were observed in all samples. However, as the Si content in the product increased, the peaks increased. A decrease in the intensity was clearly observed, and it was found that in the sample of Ti: Si = 50: 50 [mol%], the peak derived from the anatase crystal was identified but extremely weak. From this, the silica component is present as amorphous on the surface of the anatase crystal, or in the case of a composition having a high Si content, the microstructure is such that the anatase crystal exists in the amorphous silica matrix. Was understood. As a result of comparative observation of the products (Ti: Si = 100: 0 and 50:50 [mol%] samples) by a transmission electron microscope, as compared with pure anatase titania of a comparative sample, Ti: Si = 50: 50 The sample was observed with blurred particles without sharp outlines, and the high-magnification lattice image showed that the presence of amorphous silica was combined with the results of Raman spectroscopy. . From the results of the specific surface area measurement by the BET method, the specific surface area is 100 to 450 m. 2 / G in the range of 2 = 100-130m up to 30mol% 2 / G and SiO 2 = 30-90 mol% and SiO 2 The specific surface area increases as the volume increases, and 2 / G. Comparative example of SiO 2 = 200m at 100mol% 2 / G and the specific surface area dropped sharply. Next, from the results of Raman spectroscopy of the powder obtained by heating the obtained product at 65 ° C. in air at 800 ° C. for 1 hour, the 800 ° C. heat-treated powder was found to be in the same manner as the dry powder. In the sample, only the peak derived from the anatase type crystal was observed, but as the Si content in the product increased, the peak intensity was clearly reduced, and the Ti: Si = 50:50 [mol%] sample was used. Although the peak derived from the anatase crystal was identified, it was found to be extremely weak. In the case where the silica component was present as amorphous on the surface of the anatase crystal or the composition had a high Si content, the peak was non- It was understood that the microstructure was such that anatase-type crystals were present in the crystalline silica matrix. FIG. 2 shows an X-ray diffraction pattern of a powder obtained by subjecting the obtained product (Ti: Si = 50: 50) to heat treatment in the air at various temperatures for one hour. FIG. 3 shows the results of calculating the ratio of the phase transition from the anatase type to the rutile type caused by the heat treatment in the atmosphere from the integrated intensity of the X-ray diffraction peak (
[0027]
It can be seen that the band gap gradually increases with an increase in the Si content, and the band gap can be slightly changed by controlling the composition. FIG. 6 shows the results of evaluating the photocatalytic performance of the synthetic powder under ultraviolet (black light) irradiation using the decomposition of methylene blue, in terms of changes in the absorbance (concentration) of methylene blue after irradiation with ultraviolet (black light) for 60 minutes. . In the figure, TiO 2 Is a pure hydrothermally synthesized anatase-type TiO2 other than the composition of the present invention, which is synthesized by the same method as the method for producing the anatase-type titania-silica composite of the present invention shown in the figure. 2 This is a comparative example. ST-01 is a commercially available pure anatase TiO manufactured by Ishihara Sangyo. 2 Photocatalyst is a comparative example. Comparative Example of Pure Hydrothermally Synthesized Pure Anatase TiO 2 And commercially available pure anatase TiO manufactured by Ishihara Sangyo 2 After the photocatalyst ST-01 was irradiated with ultraviolet light (black light) for 60 minutes, the absorbance (concentration) of methylene blue was reduced from about 2/3 to 1/2 of the case without the photocatalyst (MB sample). In contrast, in all of the anatase-type titania-silica composites of the present invention containing a Si component, the absorbance (concentration) of methylene blue rapidly decreased during irradiation for 60 minutes, and was about 1/3 or less. , Ti: Si = 70: 30, 50:50 [mol%], the absorbance (concentration) is almost zero, indicating that the composition exhibits a very high speed and a remarkable decrease. Further, regarding the composition of Ti: Si = 50: 50 [mol%] showing the best performance in FIG. 6, the effect of the heat treatment in the air was examined for the sample heat-treated at 600 to 1000 ° C. for 1 hour. The methylene blue concentration in the solution was measured using an ultraviolet-visible absorptiometer in the same manner except that the irradiation time was reduced to 1/12 of 5 minutes, and the photocatalytic performance of the heat-treated synthetic powder in air was evaluated. Is shown in FIG. Thus, the absorbance (concentration) of methylene blue decreases as the heat treatment temperature increases to 600 to 1000 ° C., and the absorbance (concentration) of the sample treated at 1000 ° C. is almost zero, and the irradiation is performed for a short time of 5 minutes. It can be seen that even at this point, it shows an extremely high speed and a significant decrease (high excellent photocatalytic ability).
[0029]
Example 2
Titanium oxysulfate (TiOSO) 4 ), And an aqueous solution in which this is dissolved, and tetraethyl orthosilicate (Si (OC 2 H 5 ) 4 ) Is determined when the total metal ion concentration of titanium and silicon is 0.2 mol / L and Ti: Si = 100: 0, 90:10, 85:15, 70:30, 50:50 [mol%]. Exactly the same as in Example 1 except that twice the amount of ammonia water required to neutralize the solution was added to the solution mixed to obtain the composition ratio, and a mixed solution containing a precipitate slurry was used. A synthesis operation was performed to obtain a product, which was washed, dried at 65 ° C., and subjected to the same measurement as in Example 1.
[0030]
From the X-ray diffraction pattern of the thus obtained product dried at 65 ° C., any of the starting materials of Ti: Si = 100: 0, 90:10, 85:15, 70:30, and 50:50 [mol%] was obtained. It was also understood that the product of the composition also had only the anatase crystal structure identified as a crystal phase, had an anatase crystal structure, and contained substantially no rutile phase. The crystallite diameter was measured using the Debye-Scherrer equation from the diffraction line of the Miller index of 200 of the anatase crystal, and as a result, the crystallite diameter of the resulting powder of any composition was in the range of 10 to 20 nm. Was. As a result of examining the analytical composition (Ti: Si) of the obtained product, it was confirmed that the composition of the obtained product was almost the same, corresponding to the starting composition. From the results of Raman spectroscopy of the obtained product at 65 ° C. dried powder and observation by transmission electron microscopy, it was found that the silica component was present as an amorphous component on the surface of the anatase type crystal or that the Si content was high. It was understood that the case (1) had a microstructure in which an anatase type crystal was present in an amorphous silica matrix. The phase transition from anatase type to rutile type caused by heat treatment in the atmosphere is suppressed with an increase in silica content, and shifts to a higher temperature side. At a silica content of 15 mol%, 100% anatase type remains after 1100 ° C treatment. It was confirmed that at a silica content of 30 mol% or more, 90% or more was anatase even after treatment at 1200 ° C. At 50 mol%, it was confirmed that the composition was 100% anatase even after treatment at 1300 ° C. As a result of evaluating the photocatalytic performance of the synthetic powder under ultraviolet (black light) irradiation using the decomposition of methylene blue, a hydrothermally synthesized pure anatase TiO was obtained as a comparative example. 2 And commercially available pure anatase TiO manufactured by Ishihara Sangyo 2 After the photocatalyst ST-01 was irradiated with ultraviolet light (black light) for 60 minutes, the absorbance (concentration) of methylene blue was reduced from about 2/3 to 1/2 of the case without the photocatalyst (MB sample). In contrast, in all of the anatase-type titania-silica complexes of the present invention containing a silica component, the absorbance (concentration) of methylene blue rapidly decreased during irradiation for 60 minutes, and was about 1/3 or less. , Ti: Si = 70: 30, 50:50 [mol%], the absorbance (concentration) was almost zero, indicating a very high speed and a significant decrease. Furthermore, the performance was improved by performing heat treatment at 600 to 1000 ° C. for 1 hour in the air, and a high and excellent photocatalytic activity was exhibited.
[0031]
Example 3
Example 1 Example 1 was repeated except that silica gel was used instead of tetraethyl orthosilicate, and mixing was performed so that the composition ratios were Ti: Si = 40: 60, 20:80, and 5:95 [mol%]. A sample was prepared in the same manner as described above. Evaluation was performed in the same manner as in Example 1 except that the dried product was observed with a scanning electron microscope (SEM).
[0032]
From the X-ray diffraction pattern of the thus-obtained product dried at 60 ° C., only the anatase type crystal structure was identified as the crystal phase of the product of any starting composition, and the product had the anatase type crystal structure. It was understood that it contained substantially no rutile phase. Also, the presence of anatase-type crystal precipitated particles on the surface of the amorphous silica gel was confirmed by SEM. By combining with the silica component (silica gel), the photocatalytic performance was improved simultaneously with the adsorption ability, and the stability of the anatase type was also improved (it was confirmed that the composition was 100% anatase type even after treatment at 1200 ° C for 1 hour). .
[0033]
Example 4
Titanium oxysulfate (TiOSO) 4 ) And sodium silicate (sodium metasilicate Na) as a silicon compound. 2 SiO 3 ・ 9H 2 O), the concentration of the total metal ion of titanium and silicon was 0.2 mol / L, and Ti: Si = 100: 0, 90:10, 85:15, 70:30, 50:50, 30:70 Except for mixing so as to have a composition ratio of [mol%], nothing was added, and the same synthetic operation as in Example 1 was performed except that the prepared mixed solution (solution was in an acidic state) was used. After washing, it was dried at 65 ° C. Next, the same measurement as in Example 1 was performed on the crystal phase of the obtained dried product.
[0034]
From the X-ray diffraction pattern of the thus obtained product dried at 65 ° C., Ti: Si = 100: 0, 90:10, 85:15, 70:30, 50:50, 30:70 [mol%] It was understood that only the anatase-type crystal structure was identified as the crystal phase, and that the product having any of the starting compositions had the anatase-type crystal structure and contained substantially no rutile phase. The crystallite diameter was measured using the Debye-Scherrer equation from the diffraction line of the Miller index of 200 of the anatase crystal, and as a result, the crystallite diameter of the resulting powder of any composition was in the range of 10 to 20 nm. Was. As a result of examining the analytical composition (Ti: Si) of the obtained product by ICP (inductively coupled high frequency plasma) emission spectroscopy, it was found that the composition of the obtained product was almost the same, corresponding to the starting composition. confirmed. From the results of Raman spectroscopy of the obtained product at 65 ° C. dried powder and observation by transmission electron microscopy, it was found that the silica component was present as an amorphous component on the surface of the anatase type crystal or that the Si content was high. It was understood that the case (1) had a microstructure in which an anatase type crystal was present in an amorphous silica matrix. The phase transition from anatase type to rutile type caused by heat treatment in the atmosphere is suppressed with an increase in silica content, and shifts to a higher temperature side. At a silica content of 15 mol%, 100% anatase type remains after 1100 ° C treatment. When the silica content was 30 mol% or more, it was confirmed that the silica was 100% anatase even after the treatment at 1200 ° C. As a result of evaluating the photocatalytic performance of the synthetic powder under ultraviolet (black light) irradiation using the decomposition of methylene blue, a hydrothermally synthesized pure anatase TiO was obtained as a comparative example. 2 And commercially available pure anatase TiO manufactured by Ishihara Sangyo 2 After the photocatalyst ST-01 was irradiated with ultraviolet light (black light) for 60 minutes, the absorbance (concentration) of methylene blue was reduced from about 2/3 to 1/2 of the case without the photocatalyst (MB sample). In contrast, in all of the anatase-type titania-silica complexes of the present invention containing a silica component, the absorbance (concentration) of methylene blue rapidly decreased during irradiation for 60 minutes, and was about 1/3 or less. , Ti: Si = 70: 30, 50:50 [mol%], the absorbance (concentration) was almost zero, indicating a very high speed and a significant decrease. Furthermore, the performance was improved by performing heat treatment at 600 to 1000 ° C. for 1 hour in the air, and a high and excellent photocatalytic activity was exhibited.
[0035]
【The invention's effect】
As is clear from the above description, the anatase-type titania-silica composite according to the present invention is suitable for various uses. For example, as a photocatalyst, it is excellent in organic matter decomposability, water purification, deodorization, antibacterial, It is suitably used for antifouling and air purification, and has a highly responsive photocatalytic action. In particular, it is used for water purification agents, deodorants, odor / organic gas decomposers, antibacterial agents, antifungal agents, antialgal agents, antifouling agents, hydrophilic materials, air purifiers, and water decomposition photocatalytic materials. Further, after high-temperature heat treatment in the air at 1100 ° C. for 1 hour or more (preferably 1200 ° C. for 1 hour), it has a high phase stability that does not substantially contain a rutile phase and can exist as anatase-type titania. . (In the present invention, it was demonstrated that an anatase-type titania-silica composite having a silica content of 50 mol% can maintain 100% anatase type even after heat treatment in the air at 1300 ° C. for 1 hour.) By combining with a silica component (silica gel), it is possible to have a substance-adsorbing property at the same time, and the synergistic effect of the substance-adsorbing ability and photocatalysis further enhances the performance. It can be used to advantage in many applications where it is being used, and new applications may be expanded.
[Brief description of the drawings]
FIG. 1 is a diagram showing X-ray diffraction diagrams of various dried products at 65 ° C. obtained in Example 1.
FIG. 2 shows the product (SiO 2) obtained in Example 1. 2 = 50 mol%) at different temperatures.
FIG. 3 is an integrated intensity of an X-ray diffraction peak (
FIG. 4 is a diagram in which the crystallite diameter of an anatase crystal of a heat-treated product of the product obtained in Example 1 in the air is plotted against the heat treatment temperature in the air.
FIG. 5 is a view showing a measurement result of an ultraviolet-visible light absorption spectrum of a product obtained in Example 1.
FIG. 6 shows the results of evaluating the photocatalytic performance of the product obtained in Example 1 under irradiation of ultraviolet light (black light) using decomposition of methylene blue. FIG.
FIG. 7 shows the photocatalytic performance of samples (Ti: Si = 50: 50 [mol%]) obtained at different heat treatment (calcination) temperatures obtained in Example 1 using ultraviolet light (black light) using decomposition of methylene blue. It is a figure which shows the result of evaluation under irradiation as a light absorbency (relative density | concentration) of methylene blue after ultraviolet irradiation for 5 minutes.
Claims (6)
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