JP4424905B2 - Anatase type titania-silica composite, production method thereof and photocatalytic material - Google Patents
Anatase type titania-silica composite, production method thereof and photocatalytic material Download PDFInfo
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- JP4424905B2 JP4424905B2 JP2002367377A JP2002367377A JP4424905B2 JP 4424905 B2 JP4424905 B2 JP 4424905B2 JP 2002367377 A JP2002367377 A JP 2002367377A JP 2002367377 A JP2002367377 A JP 2002367377A JP 4424905 B2 JP4424905 B2 JP 4424905B2
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- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 title claims description 255
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 title claims description 187
- 239000000377 silicon dioxide Substances 0.000 title claims description 95
- 239000002131 composite material Substances 0.000 title claims description 44
- 230000001699 photocatalysis Effects 0.000 title claims description 40
- 238000004519 manufacturing process Methods 0.000 title claims description 21
- 239000000463 material Substances 0.000 title claims description 17
- 239000000843 powder Substances 0.000 claims description 39
- 229960000907 methylthioninium chloride Drugs 0.000 claims description 30
- 238000010438 heat treatment Methods 0.000 claims description 23
- 239000011941 photocatalyst Substances 0.000 claims description 20
- 238000002835 absorbance Methods 0.000 claims description 17
- 239000011259 mixed solution Substances 0.000 claims description 15
- 239000003795 chemical substances by application Substances 0.000 claims description 14
- 238000001027 hydrothermal synthesis Methods 0.000 claims description 14
- 239000000243 solution Substances 0.000 claims description 13
- 230000007423 decrease Effects 0.000 claims description 12
- 150000003609 titanium compounds Chemical class 0.000 claims description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 12
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 11
- 238000000354 decomposition reaction Methods 0.000 claims description 11
- 239000007864 aqueous solution Substances 0.000 claims description 10
- 150000003377 silicon compounds Chemical class 0.000 claims description 9
- 229910010413 TiO 2 Inorganic materials 0.000 claims description 8
- 239000002244 precipitate Substances 0.000 claims description 7
- 230000008859 change Effects 0.000 claims description 5
- 239000012153 distilled water Substances 0.000 claims description 5
- 239000002609 medium Substances 0.000 claims description 5
- -1 Komozai Substances 0.000 claims description 4
- 239000012736 aqueous medium Substances 0.000 claims description 4
- 239000003242 anti bacterial 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
- 230000001678 irradiating effect Effects 0.000 claims description 3
- 230000015556 catabolic process Effects 0.000 claims description 2
- 238000006731 degradation reaction Methods 0.000 claims description 2
- 238000001556 precipitation Methods 0.000 claims description 2
- RBTBFTRPCNLSDE-UHFFFAOYSA-N 3,7-bis(dimethylamino)phenothiazin-5-ium Chemical compound C1=CC(N(C)C)=CC2=[S+]C3=CC(N(C)C)=CC=C3N=C21 RBTBFTRPCNLSDE-UHFFFAOYSA-N 0.000 claims 4
- 241000255925 Diptera Species 0.000 claims 1
- 230000001476 alcoholic effect Effects 0.000 claims 1
- 239000012459 cleaning agent Substances 0.000 claims 1
- 230000001877 deodorizing effect Effects 0.000 claims 1
- 239000012629 purifying agent Substances 0.000 claims 1
- 239000002689 soil Substances 0.000 claims 1
- 239000013078 crystal Substances 0.000 description 41
- 239000000203 mixture Substances 0.000 description 40
- 239000000047 product Substances 0.000 description 39
- 239000010936 titanium Substances 0.000 description 30
- 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 description 26
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 16
- 230000007704 transition Effects 0.000 description 16
- 238000002441 X-ray diffraction Methods 0.000 description 13
- 230000000052 comparative effect Effects 0.000 description 12
- 238000005259 measurement Methods 0.000 description 12
- 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
- 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
- 239000000126 substance Substances 0.000 description 8
- 239000010419 fine particle Substances 0.000 description 7
- 238000000034 method Methods 0.000 description 7
- 238000001069 Raman spectroscopy Methods 0.000 description 6
- 238000000862 absorption spectrum Methods 0.000 description 6
- 229910000349 titanium oxysulfate Inorganic materials 0.000 description 6
- 238000005169 Debye-Scherrer Methods 0.000 description 5
- 230000005540 biological transmission Effects 0.000 description 5
- 239000002245 particle Substances 0.000 description 5
- 229910000348 titanium sulfate Inorganic materials 0.000 description 5
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 4
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 230000031700 light absorption Effects 0.000 description 4
- 229910021645 metal ion Inorganic materials 0.000 description 4
- 239000010703 silicon Substances 0.000 description 4
- 229910052710 silicon Inorganic materials 0.000 description 4
- 230000002195 synergetic effect Effects 0.000 description 4
- 229910052719 titanium Inorganic materials 0.000 description 4
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 3
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- 239000004115 Sodium Silicate Substances 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 3
- 230000003247 decreasing effect Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 239000011148 porous material Substances 0.000 description 3
- 238000000746 purification Methods 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 239000004065 semiconductor 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
- 238000001179 sorption measurement Methods 0.000 description 3
- 238000004611 spectroscopical analysis Methods 0.000 description 3
- XJDNKRIXUMDJCW-UHFFFAOYSA-J titanium tetrachloride Chemical compound Cl[Ti](Cl)(Cl)Cl XJDNKRIXUMDJCW-UHFFFAOYSA-J 0.000 description 3
- 238000000870 ultraviolet spectroscopy Methods 0.000 description 3
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 2
- 238000004438 BET method Methods 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 230000002378 acidificating effect Effects 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 238000004887 air purification Methods 0.000 description 2
- 235000011114 ammonium hydroxide Nutrition 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 239000002519 antifouling agent Substances 0.000 description 2
- 230000015572 biosynthetic process 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
- 238000006243 chemical reaction Methods 0.000 description 2
- 229910052906 cristobalite Inorganic materials 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 239000000499 gel Substances 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- VKYKSIONXSXAKP-UHFFFAOYSA-N hexamethylenetetramine Chemical compound C1N(C2)CN3CN1CN2C3 VKYKSIONXSXAKP-UHFFFAOYSA-N 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000005416 organic matter Substances 0.000 description 2
- 235000012239 silicon dioxide Nutrition 0.000 description 2
- 238000003980 solgel method Methods 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
- 229910052905 tridymite Inorganic materials 0.000 description 2
- 238000000108 ultra-filtration Methods 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- ATRRKUHOCOJYRX-UHFFFAOYSA-N Ammonium bicarbonate Chemical compound [NH4+].OC([O-])=O ATRRKUHOCOJYRX-UHFFFAOYSA-N 0.000 description 1
- 229910003902 SiCl 4 Inorganic materials 0.000 description 1
- 239000004965 Silica aerogel Substances 0.000 description 1
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000003463 adsorbent Substances 0.000 description 1
- 239000000443 aerosol Substances 0.000 description 1
- 150000004703 alkoxides Chemical class 0.000 description 1
- 239000001099 ammonium carbonate Substances 0.000 description 1
- 235000012501 ammonium carbonate Nutrition 0.000 description 1
- 230000000844 anti-bacterial effect Effects 0.000 description 1
- 230000003373 anti-fouling effect Effects 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 239000004202 carbamide Substances 0.000 description 1
- 235000013877 carbamide Nutrition 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 239000008199 coating composition Substances 0.000 description 1
- 229910052681 coesite Inorganic materials 0.000 description 1
- 230000000536 complexating effect Effects 0.000 description 1
- 239000002781 deodorant agent Substances 0.000 description 1
- 238000004332 deodorization Methods 0.000 description 1
- 239000010881 fly ash Substances 0.000 description 1
- 238000010574 gas phase reaction Methods 0.000 description 1
- 239000004312 hexamethylene tetramine Substances 0.000 description 1
- 235000010299 hexamethylene tetramine Nutrition 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 235000011118 potassium hydroxide Nutrition 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 239000010453 quartz Substances 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
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Chemical compound [Si-]#[O+] LIVNPJMFVYWSIS-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
- 235000011121 sodium hydroxide Nutrition 0.000 description 1
- 235000019795 sodium metasilicate Nutrition 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 229910052682 stishovite Inorganic materials 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
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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するアナターゼ型チタニア−シリカ複合体、その製造法及び光触媒材料に関する。
【０００２】
【従来の技術】
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、製造法等に大きく依存し、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】
チタニアの製造法には、チタンのアルコキシドを原料に使用したゾル−ゲル法、四塩化チタン、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。またシリカは、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、触媒坦体等に応用されている。
【０００４】
更にシリカを含有するチタニアについては、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、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おり（９８０℃までアナターゼ相で存在、非特許文献１参照）、またアナターゼ型チタニア粒子にシリカを添加して、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て（特許文献１参照）、更に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、アナターゼ型からルチル型への相転移温度を約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、非特許文献２参照）。
【０００５】
そしてシリカゲル等とチタニア光触媒の複合化については、多孔性ゲル光触媒が知られており（特許文献２参照）、また半導体光触媒含有球状シリカゲル体及び製造方法並びに塗料組成物が知られている（特許文献３参照）。これらの特許文献の出願以前にも、すでにシリカゲル等へのチタニア光触媒の複合化についての報告があり（チタニア光触媒とシリカのゾル−ゲル混合物についての開示、非特許文献３参照）、またシリカゲル−チタニア触媒についての報告もある（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、非特許文献４参照）。
【０００６】
しかし、これら従来公知の製造法によるチタニア−シリカ複合体は、チタニアのアナターゼ相の安定性が高くなく、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機能の向上効果について具体的に且つ客観的な実験データが示されていない。
【特許文献１】
特開平１１−１５７９６６号公報
【特許文献２】
特開平１０−３２３５６８号公報
【特許文献３】
特開２００１−１０４７９９号公報
【非特許文献１】
窯業協会誌８６［３］１１９（１９７８）
【非特許文献２】
Ｊ．Ａｍ．Ｃｅｒａｍ．Ｓｏｃ．，８４［７］１５９１（２００１）
【非特許文献３】
Ｅｎｖｉｒｏｎ．Ｓｃｉ．Ｔｅｃｈｎｏｌ．，３０［２］６４７〜６５３（１９９６）
【非特許文献４】
Ｊ．Ｃａｔａｌ．，１５０［２］３１１〜３２０（１９９４）
【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。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、前記した従来技術のアナターゼ型の酸化チタンの相安定性は低く、１１００℃で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いる。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が求められているところ、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、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チタニアの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を相乗的に図ることができる新規のアナターゼ型チタニア−シリカ複合体その製造方法及び光触媒材料を提供するものである。
【０００８】
【課題を解決するための手段】
かくの如き課題を解決するための請求項１に記載の本発明に係るアナターゼ型チタニア−シリカ複合体は、チタン化合物とケイ素化合物とを水熱反応させることにより得られるアナターゼ型チタニア−シリカ複合体であって、チタニア（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１１００℃で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として存在すると共に該アナターゼ型チタニアの結晶子径が７０ｎｍ以下であり、下記の光触媒作用がシリカを含有しないアナターゼ型チタニアの２倍以上であることを特徴とする。
光触媒作用：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に加えた後、２０ｐｐｍ濃度のメチレンブルー水溶液２０mlを加え、全体の溶液のメチレンブルー濃度を１０ｐｐｍにした溶液に対し、ブラックライトによる紫外線を１時間照射し、該アナターゼ型チタニア−シリカ複合体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のメチレンブルーによる吸光度の変化（減少）により測定される光触媒作用。
【０００９】
前記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】
本発明に係るアナターゼ型チタニア−シリカ複合体としては、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、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、シリカ（ＳｉＯ２）が非晶質のシリカゲルであって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チタニア−シリカ複合体が好ましい。吸着物質の分解作用と光触媒作用との好ましい相乗効果が得られるからである。
【００１１】
本発明に係るアナターゼ型チタニア−シリカ複合体は、詳しくは後述するように、チタン化合物とケイ素化合物とを水熱反応させることにより得られるもので、チタニア（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１１００℃で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として存在すると共に該アナターゼ型チタニアの結晶子径が７０ｎｍ以下であり、その光触媒作用がシリカを含有しないアナターゼ型チタニアの２倍以上であるものである。
【００１２】
ここで、シリカ（ＳｉＯ２）の含有量はチタニア（ＴｉＯ２）に対して内部ｍｏｌ％で３０ｍｏｌ％以上、したがって３０〜９５ｍｏｌ％であり、アナターゼ型結晶相の安定性として、１２００℃で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すると共に該アナターゼ型チタニアの結晶子径が５０ｎｍ以下であるものが好ましい。
【００１３】
本発明に係るアナターゼ型チタニア−シリカ複合体において、光触媒作用は、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に加えた後、２０ｐｐｍ濃度のメチレンブルー水溶液２０mlを加え、全体の溶液（４０ml）のメチレンブルー濃度を１０ｐｐｍにした溶液に対し、ブラックライトによる紫外線を１時間照射し、該アナターゼ型チタニア−シリカ複合体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のメチレンブルーによる吸光度の変化（減少）により測定される光触媒作用である。
【００１４】
また請求項３に記載の本発明に係るアナターゼ型チタニア−シリカ複合体の製造法は、前記した本発明に係るアナターゼ型チタニア−シリカ複合体の製造法であって、チタン化合物とケイ素化合物とを水性媒体中及び／又はアルコール媒体中に分散あるいは溶解して混合溶液を作製し、次に該混合溶液を密閉容器中で水熱反応させるか又は該混合溶液に沈殿形成剤を添加することにより生成した沈殿析出物を水熱反応させることを特徴とする。
【００１５】
本発明に係るアナターゼ型チタニア−シリカ複合体の製造法では、チタン化合物とケイ素化合物を水性媒体中及び／又はアルコール媒体中に分散あるいは溶解して混合溶液を作製し、あるいは更に該混合溶液から沈殿析出物を生成させ、これらを水熱反応工程において、密閉容器中で所定の温度で水熱反応させる。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）とが反応し易くなって、水熱反応（すなわち高温高圧水の存在下での反応＝水熱合成）により分子単位で反応し、アナターゼ結晶として析出する。結果として、前記したように、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、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、シリカ（ＳｉＯ２）が非晶質のシリカゲルであって、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チタニア−シリカ複合体が得られる。尚、沈殿形成剤としては、アンモニア水、炭酸アンモニウム、水酸化ナトリウム、水酸化カリウム、尿素、ヘキサメチレンテトラミン等のアルカリ成分を使用できる。
【００１６】
本発明に係るアナターゼ型チタニア−シリカ複合体の製造法において、チタン化合物としては、チタンの硫酸塩を用いるのが好ましい。チタンの硫酸塩としては、オキシ硫酸チタン、硫酸チタン等が挙げられるが、硫酸あるいは硫酸イオン存在下の四塩化チタン水溶液やペルオキソチタン酸水溶液等でもよい。オキシ硫酸チタンや硫酸チタン等を用いるか、又は硫酸あるいは硫酸イオン存在下で四塩化チタン水溶液、ペルオキソチタン酸水溶液、水酸化チタン等を用いて、２５０℃以下の水熱反応工程を組み合わせると、得られるアナターゼ型チタニア−シリカ複合体は、極めて高い光触媒能と相安定性を併せ持つものとなる。
【００１７】
またケイ素化合物としては、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シリカ原料を用いることができる。これらの人工シリカ原料は、純度等の特性を制御できる。
【００１８】
本発明に係るアナターゼ型チタニア−シリカ複合体の製造法において、前記した水熱反応工程の温度は３００℃以下とするが、２５０℃以下とするのが好ましい。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できる。
【００１９】
更に請求項５に記載の本発明に係る光触媒材料は、前記した本発明に係るアナターゼ型チタニア−シリカ複合体から成ることを特徴とする。本発明に係る光触媒材料は、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、水分解光触媒材料等として、様々な用途に用いることができる。
【００２０】
【発明の実施の形態】
本発明においては、チタン化合物とケイ素化合物とを水性媒体中及び／又はアルコール媒体中に分散あるいは溶解して混合溶液とするか、又は更に該混合溶液から沈殿析出物を生成させるが、かかる混合溶液中における合計の金属イオン濃度は通常０．００１ｍｏｌ／Ｌ〜５．０ｍｏｌ／Ｌとし、好ましくは０．１ｍｏｌ／Ｌ〜１．０ｍｏｌ／Ｌとする。
【００２１】
そして、前記のような混合溶液や沈殿析出物は、公知の適当な反応容器、一般的には圧力容器に収納し、所望の温度に加熱して、水熱反応させる。本発明においては、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】
【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に制約を受けるというものではない。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。
【００２３】
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時間保持して、水熱反応させた。その後、得られた生成物を、何れも限外濾過及び／又は遠心分離操作により固液分離した後、更に蒸留水を加えて再度撹拌してから限外濾過及び／又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し、６５℃で乾燥した。
【００２４】
次いで、得られた生成物の乾燥粉体の結晶相について、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、得られた生成物の乾燥粉体組成（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。得られた生成物の乾燥粉体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、生成物の乾燥粉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を加えてメチレンブルー濃度を１０ｐｐｍにて、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、生成物の乾燥粉体の光触媒性能を、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、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、生成物の乾燥粉体の光触媒性能を評価した。
【００２５】
かくして得られた生成物の乾燥粉体のＸ線回折図形を図１に示す。図１中、ＴｉＯ２は、本発明に係るアナターゼ型チタニア−シリカ複合体の製造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物の乾燥粉体の結晶子径も１４〜１５ｎｍの範囲にあった。また、生成物の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、得られた生成物の乾燥粉体の分析組成（Ｔｉ：Ｓｉ）を調べた結果、得られた生成物の乾燥粉体の組成は、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、チタニアの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チタニアの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の乾燥粉体（Ｔｉ：Ｓｉ＝１００：０及び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であるが、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、得られた生成物の乾燥粉体を大気中にて８００℃で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、チタニアの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℃で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℃で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。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℃で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℃で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に生成物の乾燥粉体の紫外可視光吸収スペクトルの測定結果を示す。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。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の乾燥粉体のバンドギャップを計算した結果を表１に示す。
【００２６】
【表１】
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１時間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社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、（ブラックライト）を１時間照射後において、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、１時間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。
【００２８】
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℃で乾燥し、実施例１と同様な測定を行った。
【００２９】
かくして得られた生成物の乾燥粉体の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、得られた生成物の乾燥粉体の組成は、出発組成に対応しほぼ同じであることが確認された。得られた生成物の乾燥粉体のラマン分光による測定結果及び透過型電子顕微鏡観察より、チタニアの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。シリカ含有量を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社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１時間照射後において、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、１時間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。
【００３０】
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。
【００３１】
かくして得られた生成物の乾燥粉体のＸ線回折図形より、いずれの出発組成の生成物も、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℃で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）。
【００３２】
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、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。
【００３３】
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、得られた生成物の乾燥粉体の分析組成（Ｔｉ：Ｓｉ）を調べた結果、得られた生成物の乾燥粉体の組成は、出発組成に対応しほぼ同じであることが確認された。得られた生成物の乾燥粉体のラマン分光による測定結果及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社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１時間照射後において、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。
【００３４】
【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、例えば光触媒材料としては、有機物分解性に優れるため、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ることができる。また、１１００℃で１時間の大気中における高温熱処理後においても、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℃で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）。更にシリカ成分（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】 本発明に係るアナターゼ型チタニア−シリカ複合体等について、Ｘ線回析図を示す図。
【図２】 本発明に係るアナターゼ型チタニア−シリカ複合体等（ＳｉＯ２＝５０ｍｏｌ％）について、各温度における熱処理物のＸ線回折図を示す図。
【図３】 本発明に係るアナターゼ型チタニア−シリカ複合体等について、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％）を示す図。
【図４】 本発明に係るアナターゼ型チタニア−シリカ複合体等について、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示す図。
【図５】 本発明に係るアナターゼ型チタニア−シリカ複合体等について、紫外可視光吸収スペクトルの測定結果を示す図。
【図６】 本発明に係るアナターゼ型チタニア−シリカ複合体等について、その光触媒性能を、１時間の紫外線照射後のメチレンブルーの吸光度として示す図。
【図７】 本発明に係るアナターゼ型チタニア−シリカ複合体（Ｔｉ：Ｓｉ＝５０：５０［ｍｏｌ％］試料）について、その光触媒性能を、５分間の紫外線照射後のメチレンブルーの吸光度として示す図。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an anatase-type titania-silica composite having a high photocatalytic action, a method for producing the same, and a photocatalytic material.
[0002]
[Prior art]
Titania (TiO 2 ) Belongs to an n-type semiconductor, and among the three types of crystal phases (anatase, rutile, brookite), anatase titania exhibits an excellent photocatalytic action. Since the thermodynamic stable phase of titania is rutile and anatase is a metastable phase, in general, a phase transition from the anatase type to the rutile type is easily caused by heat treatment in the atmosphere. At high temperatures, anatase-type titania is extremely unstable. The phase transition from the anatase type to the rutile type is considered to occur at around 635 ° C. from the kinetic study, but the stability of the anatase phase largely depends on the particle size, impurities, composition, production method, etc. Depending on the precursor used, a phase transition from anatase type to rutile type starts to occur from around 500 ° C.
[0003]
Known methods for producing titania include sol-gel methods using titanium alkoxides as raw materials, and methods involving thermal decomposition and hydrolysis of titanium salt aqueous solutions such as titanium tetrachloride, titanium sulfate, and titanium oxysulfate. It has been. Silica has three types of polymorphs, quartz, tridymite, and cristobalite, and is used industrially in many fields. However, it is the main component of glass and is relatively easily converted into a glass state (amorphous). Can exist. Many amorphous silica materials are also used as industrial silica raw materials. As amorphous silica, for example, silica gel is applied to adsorbents, deodorizers, catalyst carriers, and the like by utilizing a high specific surface area and countlessly developed pores.
[0004]
Furthermore, for titania containing silica, the effect of silica addition on the phase transition from anatase type to rutile type is 4 -SiCl 4 -O 2 CVD-TiO2 synthesized by a gas phase reaction 2 ・ SiO 2 It was investigated in powder and it was found that the phase transition from anatase type to rutile type was suppressed (present in anatase phase up to 980 ° C., see Non-Patent Document 1), and silica was added to anatase type titania particles In addition, a ceramic having a photocatalytic function having a high photocatalytic activity with a low ratio of phase transition to a rutile type even after calcination at 1000 ° C. and a method for producing the same have been disclosed (see Patent Document 1), and further, titanium tetraisopropoxide and There has been a report on a powder synthesized by sol-gel method using tetraethyl orthosilicate, and the solid solution of silica in titania has been discussed, and the effect of increasing the phase transition temperature from anatase type to rutile type by about 300 ° C has been shown. (100% exists in anatase phase up to about 825 ° C., see Non-Patent Document 2).
[0005]
As for the composite of silica gel or the like and a titania photocatalyst, a porous gel photocatalyst is known (see Patent Document 2), and a semiconductor photocatalyst-containing spherical silica gel body, a production method, and a coating composition are known (Patent Document). 3). Prior to the filing of these patent documents, there has already been a report on the combination of titania photocatalysts with silica gel or the like (disclosure of a sol-gel mixture of titania photocatalyst and silica, see Non-Patent Document 3), and silica gel-titania. There are also reports on catalysts (influence of prehydrolysis on the structure and catalytic properties of titania-silica aerogels, see Non-Patent Document 4).
[0006]
However, the titania-silica composites produced by these conventionally known production methods do not have high stability of the anatase phase of titania, and more specifically and objectively improve the photocatalytic function by combining the titania photocatalyst with the silica component. Experimental data is not shown.
[Patent Document 1]
Japanese Patent Laid-Open No. 11-157966
[Patent Document 2]
Japanese Patent Laid-Open No. 10-323568
[Patent Document 3]
JP 2001-104799 A
[Non-Patent Document 1]
Journal of Ceramic Industry Association 86 [3] 119 (1978)
[Non-Patent Document 2]
J. et al. Am. Ceram. Soc. , 84 [7] 1591 (2001)
[Non-Patent Document 3]
Environ. Sci. Technol. , 30 [2] 647-653 (1996)
[Non-Patent Document 4]
J. et al. Catal. 150 [2] 311-320 (1994)
[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 atmosphere, resulting in a decrease in photocatalytic activity and low phase stability. Although the inhibitory effect of titania on the phase transition from anatase type to rutile type by addition of silica is known, the phase stability of the prior art anatase type titanium oxide is low, and the atmospheric temperature is high at 1100 ° C. for 1 hour. In general, after the heat treatment in the medium, the phase transition from the anatase type to the rutile type has already been completed. Anatase-type titanium oxide shows an excellent photocatalyst in a semiconducting material, but when it is required to further increase the photocatalytic activity, silica has an excellent adsorbing ability but has almost no photocatalytic activity. Amorphous silica is light transmissive, so it has a high specific surface area, infinitely developed pores, and a combination of silica and anatase-type titania, which have excellent adsorption ability, synergistic effect of adsorption ability and photocatalytic ability. Therefore, the application of titanium oxide as a photocatalyst is expected to be expanded to various fields. The present invention synergistically improves the phase stability of the anatase phase of titania and the photocatalytic performance of anatase-type titania by combining with silica by studying the composite method and production method. The present invention provides a novel anatase-type titania-silica composite, its production method, and a photocatalytic material.
[0008]
[Means for Solving the Problems]
The anatase-type titania-silica composite according to the present invention according to claim 1 for solving the problems as described above is obtained by hydrothermal reaction of a titanium compound and a silicon compound. And titania (TiO 2 ) To 15-95 mol% silica (SiO 2) 2 The titania exists as anatase titania after heat treatment in the atmosphere at 1100 ° C. for 1 hour, and the crystallite size of the anatase titania is 70 nm or less, and the following photocatalytic action does not contain silica. It is characterized by being at least twice as much as anatase titania.
Photocatalytic action: 0.01 g of anatase-type titania-silica composite sample powder was added to 20 ml of distilled water, and then 20 ml of a 20 ppm methylene blue aqueous solution was added to make the total solution methylene
[0009]
The anatase-type titania-silica composite having the above composition is suitable for various applications as a semiconducting substance. For example, as a photocatalyst, it is excellent in organic matter decomposability, water purification, deodorization, antibacterial, antifouling, air It is suitable for purification, has a highly responsive photocatalytic action, and amorphous silica is light transmissive. Therefore, it can be combined with amorphous silica having a high specific surface area and countlessly developed pores. Therefore, it is possible to impart a high substance adsorbing property, and a synergistic effect between the decomposition action of the adsorbing substance and the photocatalytic action is obtained.
[0010]
The anatase titania-silica composite according to the present invention includes silica (SiO 2 Titania-silica composite, which is mainly present as amorphous silica on the surface of titania crystal fine particles, silica (SiO 2 Titania-silica composite in which titania is present as crystalline fine particles in an amorphous silica matrix in which amorphous silica is present as an amorphous silica matrix, silica (SiO 2 ) Is an amorphous silica gel, and a titania-silica composite in which titania is present mainly as anatase crystal fine particles on the surface of the amorphous silica gel is preferable. This is because a preferable synergistic effect between the decomposition action of the adsorbed substance and the photocatalytic action can be obtained.
[0011]
The anatase type titania-silica composite according to the present invention is obtained by hydrothermal reaction of a titanium compound and a silicon compound, as will be described in detail later. 2 ) To 15-95 mol% silica (SiO 2) 2 And the titania exists as anatase titania after heat treatment in the atmosphere at 1100 ° C. for 1 hour, and the crystallite size of the anatase titania is 70 nm or less, and its photocatalytic action is anatase containing no silica. It is more than twice the type titania.
[0012]
Here, silica (SiO 2 ) Content of titania (TiO 2 ) With respect to the internal mol% of 30 mol% or more, and therefore 30 to 95 mol%, and the stability of the anatase type crystal phase is 10% by mass% of the rutile phase after heat treatment in the atmosphere at 1200 ° C. for 1 hour. It is preferable that 90% or more exist as anatase titania and the crystallite diameter of the anatase titania is 50 nm or less.
[0013]
In the anatase-type titania-silica composite according to the present invention, the photocatalytic action is carried out by adding 0.01 g of anatase-type titania-silica composite sample powder to 20 ml of distilled water, and then adding 20 ml of 20 ppm aqueous methylene blue solution. The solution (40 ml) having a methylene blue concentration of 10 ppm was irradiated with ultraviolet light from black light for 1 hour, and the degree of decomposition of methylene blue by the anatase titania-silica complex was determined at 660 nm using a spectrophotometer. It is a photocatalytic action measured by a change (decrease) in absorbance due to.
[0014]
The method for producing an anatase-type titania-silica composite according to the present invention according to claim 3 is a method for producing the anatase-type titania-silica composite according to the present invention, wherein a titanium compound and a silicon compound are used. Produced by dispersing or dissolving in an aqueous medium and / or alcohol medium to produce a mixed solution, and then hydrothermally reacting the mixed solution in a sealed container or adding a precipitation-forming agent to the mixed solution The precipitated precipitate is hydrothermally reacted.
[0015]
In the method for producing an anatase-type titania-silica composite according to the present invention, a titanium compound and a silicon compound are dispersed or dissolved in an aqueous medium and / or an alcohol medium to prepare a mixed solution, or further precipitated from the mixed solution. Precipitates are generated, and these are hydrothermally reacted at a predetermined temperature in a sealed container in a hydrothermal reaction step. 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 likely to react with each other, resulting in a hydrothermal reaction (that is, a reaction in the presence of high-temperature high-pressure water = It reacts in molecular units by hydrothermal synthesis) and precipitates as anatase crystals. As a result, as described above, silica (SiO 2 Titania-silica composite, which is mainly present as amorphous silica on the surface of titania crystal fine particles, silica (SiO 2 Titania-silica composite in which titania is present as crystalline fine particles in an amorphous silica matrix in which amorphous silica is present as an amorphous silica matrix, silica (SiO 2 ) Is an amorphous silica gel, and a titania-silica composite in which titania exists mainly as anatase type crystal fine particles on the surface of the amorphous silica gel is obtained. In addition, as a precipitation formation agent, alkaline components, such as ammonia water, ammonium carbonate, sodium hydroxide, potassium hydroxide, urea, hexamethylenetetramine, can be used.
[0016]
In the method for producing an anatase-type titania-silica composite according to the present invention, it is preferable to use titanium sulfate as the titanium compound. Examples of the titanium sulfate include titanium oxysulfate and titanium sulfate, but a titanium tetrachloride aqueous solution or a peroxotitanic acid aqueous solution in the presence of sulfuric acid or sulfate ions may also be used. When titanium oxysulfate, titanium sulfate, or the like is used, or a hydrothermal reaction step of 250 ° C. or lower is combined with an aqueous solution of titanium tetrachloride, aqueous peroxotitanic acid, titanium hydroxide in the presence of sulfuric acid or sulfate ions, The anatase-type titania-silica composite thus obtained has both extremely high photocatalytic ability and phase stability.
[0017]
As the silicon compound, artificial silica materials such as silica gel, sodium silicate, Si alcoholate (alkoxide), silica fume, silica aerosol, fly ash and the like can be used. These artificial silica raw materials can control properties such as purity.
[0018]
In the method for producing an anatase-type titania-silica composite according to the present invention, the temperature of the hydrothermal reaction step is 300 ° C. or less, preferably 250 ° C. or less. In this way, 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]
Furthermore, the photocatalyst material according to the present invention described in claim 5 is characterized by comprising the anatase-type titania-silica composite according to the present invention. The photocatalyst material according to the present invention is a water purification agent, deodorant, malodor / organic gas decomposition agent, antibacterial agent, antifungal agent, antialgae agent, antifouling agent, hydrophilic material, air purification agent, water decomposition photocatalyst material, etc. Can be used for various purposes.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, a titanium compound and a silicon compound are dispersed or dissolved in an aqueous medium and / or an alcohol medium to form a mixed solution, or a precipitate is further generated from the mixed solution. The total metal ion concentration in the inside is usually 0.001 mol / L to 5.0 mol / L, preferably 0.1 mol / L to 1.0 mol / L.
[0021]
The mixed solution and precipitates as described above are accommodated in a known appropriate reaction vessel, generally a pressure vessel, and heated to a desired temperature to cause a hydrothermal reaction. In the present invention, from the viewpoint of the production apparatus, a hydrothermal reaction step at a lower temperature is preferred, and the hydrothermal reaction is allowed to proceed at 300 ° C. or lower, and particularly, a temperature of 250 ° C. or lower is advantageously employed. The lower limit is about 90 ° C. When the temperature is low, it is necessary to hold for a long time.
[0022]
【Example】
Examples of the present invention will be shown below to clarify the present invention more specifically, but the present invention is not limited to such examples. In addition to the following examples, in addition to the specific description described above, the present invention includes various changes, modifications, and modifications 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 and the like can be added.
[0023]
Example 1
Titanium oxysulfate (TiOSO) as a titanium compound 4 ) And an aqueous solution in which this is dissolved, and tetraethyl orthosilicate (Si (OC 2 H 5 ) 4 ) With a total metal ion concentration of titanium and silicon of 0.2 mol / L, and Ti: Si = 100: 0, 90:10, 85:15, 80:20, 70:30, 50:50, A mixed solution (solution is in an acidic state) was prepared by adding nothing except mixing at a composition ratio of 30:70, 10:90, and 0: 100 [mol%]. Next, this mixed solution is accommodated in a fluororesin container contained in a stainless steel pressure vessel, and the contents are heated while stirring by rotating it, and kept at a temperature of 200 ° C. for 24 hours. Reacted. Thereafter, after the obtained product is solid-liquid separated by ultrafiltration and / or centrifugation, distilled water is further added and stirred again, followed by ultrafiltration and / or centrifugation. Repeatedly, the resulting product was washed and dried at 65 ° C.
[0024]
Next, the crystal phase of the obtained dry powder of the product is identified by X-ray diffraction, while the crystallite diameter is measured from the X-ray diffraction pattern using the Debye-Scherrer equation, and further the standard sample The lattice constant was measured using silicon. Further, the ratio of the phase transition from the anatase type to the rutile type caused by the heat treatment in the atmosphere (rutyl ratio (mass%): F R ) Is the integrated intensity of the X-ray diffraction peak (integrated intensity of anatase 101: I A (101), integrated intensity of rutile 110: I R (110)), the equation of Spurr et al .: F R = 1 / {1 + 0.79 [I A (101) / I R (110)]} (RA Spur et al., Anal. Chem., 29, 760-762 (1957)). Further, the dry powder composition (Ti: Si) of the obtained product was quantitatively analyzed by ICP (inductively coupled radio frequency plasma) emission spectroscopic analysis. The particle diameter and form of the product were observed with a transmission electron microscope. The obtained dry powder of the product was measured by Raman spectroscopy. Moreover, the specific surface area measurement by BET method was performed. Furthermore, using an ultraviolet-visible absorptiometer, diffuse reflected light was measured with an integrating sphere detector, and an ultraviolet-visible light absorption spectrum of the obtained dry powder of the product was measured. From this ultraviolet-visible light absorption spectrum, the band gap of the product dry powder was calculated. Furthermore, 0.01 g of the obtained dry powder of the product was weighed and placed in 20 ml of distilled water, ultrasonically dispersed for 5 minutes, 20 ml of 20 ppm aqueous methylene blue solution was added, and the methylene blue concentration was stirred at 10 ppm. After irradiating with ultraviolet light (black light) for 60 minutes, the methylene blue aqueous solution and the powder were separated, and the concentration of methylene blue in the solution was measured with an ultraviolet-visible spectrophotometer. Evaluation was made by examining the degree of decomposition under ultraviolet (black light) irradiation. For samples with high photocatalytic performance, the concentration of methylene blue in the solution was measured with an ultraviolet-visible spectrophotometer in the same manner except that the irradiation with ultraviolet light (black light) was performed for 5 minutes. Performance was evaluated.
[0025]
The X-ray diffraction pattern of the dry powder of the product thus obtained is shown in FIG. In FIG. 1, TiO 2 Is pure anatase TiO other than the composition of the present invention synthesized by the same method as the method for producing the anatase titania-silica composite according to the present invention. 2 It is a comparative example. From this X-ray diffraction pattern, the product of any starting composition of Ti: Si = 100: 0, 90:10, 85:15, 80:20, 70:30, 50:50 [mol%] is anatase type. Since only the crystal structure is identified as the crystal phase, it was confirmed that it has an anatase type crystal structure and substantially does not contain a rutile phase. As a result of measuring the crystallite size from the diffraction line of the Miller index of 200 of the anatase type crystal using the Debye-Scherrer equation, the crystallite size of the dry powder of the product of any composition is 14 to 15 nm. Was in range. Further, from the X-ray diffraction pattern of the sample obtained by adding Si as a standard substance to the dry powder of the product, the shift of the diffraction peak position is hardly observed with respect to the change in the composition of Ti: Si, and the lattice constant ( Except for subtle changes in the a-axis and c-axis), no significant changes were observed. Ti: Si = 30: 70, 10:90 and SiO 2 In the sample with a large amount, the diffraction peak of anatase became small, and it was identified as completely amorphous in the comparative example Ti: Si = 0: 100. As a result of examining the analysis composition (Ti: Si) of the dry powder of the obtained product by ICP (inductively coupled radio frequency plasma) emission spectroscopic analysis, the composition of the dry powder of the obtained product is the starting composition. Corresponding and confirmed to be almost the same. From the measurement results by Raman spectroscopy of the dry powder of the obtained product, only the peak derived from the anatase type crystal was observed in any sample, but as the Si content in the product increased, the peak intensity The decrease was clearly observed, and it was found that in the Ti: Si = 50: 50 [mol%] sample, although the peak derived from the anatase crystal was identified, it was very weak. From this, the silica component is present as amorphous on the surface of titania anatase type crystal, or in the case of a composition having a high Si content, the microstructure in which the anatase type crystal of titania exists in the amorphous silica matrix It was understood that. As a result of comparative observation of the dry powder of the product (Ti: Si = 100: 0 and 50:50 [mol%] samples) with a transmission electron microscope, it was compared with pure anatase titania as a comparative sample, and Ti: Si = 50: 50 Samples were observed as blurry with no clear outline of the particles. From the photograph of the high-magnification lattice image, the presence of amorphous silica was also combined with the results of Raman spectroscopic measurement. It was also understood. From the results of specific surface area measurement by the BET method, the specific surface area is 100 to 450 m. 2 / G, SiO 2 = 100-130m up to 30mol% 2 / G, but SiO 2 = 30-90 mol% and SiO 2 As the amount increases, the specific surface area increases, 150-450m 2 / G. Comparative example SiO 2 = 200m at 100mol% 2 / G and specific surface area suddenly decreased. Next, from the result of Raman spectroscopic measurement of the powder obtained by heat-treating the obtained dry powder at 800 ° C. for 1 hour in the air, as with the dry powder, In the sample, only a peak derived from the anatase type crystal was observed, but as the Si content in the product increased, a decrease in peak intensity was clearly observed, and in the Ti: Si = 50: 50 [mol%] sample, Although the peak derived from the anatase type crystal is identified, it is understood that the peak is extremely weak, and the silica component is present as an amorphous state on the surface of the titania anatase type crystal, or in the case of a composition having a high Si content, It was understood that this is a microstructure in which anatase-type crystals exist in an amorphous silica matrix. FIG. 2 shows X-ray diffraction patterns of powders obtained by heat-treating the obtained product (Ti: Si = 50: 50) in the atmosphere at various temperatures for 1 hour. Further, FIG. 3 shows the result 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 integral intensity of the X-ray diffraction peak (
[0026]
[Table 1]
It can be seen that the band gap gradually increases as the Si content increases, and that the band gap can be slightly changed by composition control. The results of evaluating the photocatalytic performance of the synthetic powder under ultraviolet (black light) irradiation using decomposition of methylene blue are shown in FIG. 6 as the change in absorbance (concentration) of methylene blue after 1 hour of ultraviolet light (black light) irradiation. . In the figure, TiO 2 The hydrothermally synthesized pure anatase TiO other than the composition of the present invention synthesized by the same method as the production method of the anatase titania-silica composite of the present invention shown in the figure 2 It is a comparative example. ST-01 is a commercially available pure anatase TiO manufactured by Ishihara Sangyo Co., Ltd. 2 It is a comparative example with a photocatalyst. Hydrothermally synthesized pure anatase TiO as a comparative example 2 And commercially available pure anatase TiO manufactured by Ishihara Sangyo 2 In Photocatalyst ST-01, the absorbance (concentration) of methylene blue was lowered from about 2/3 to ½ of the case where no photocatalyst was added (MB sample) after (black light) was irradiated for 1 hour. On the other hand, all of the anatase titania-silica composites of the present invention containing the Si component rapidly decreased in methylene blue absorbance (concentration) during 1 hour irradiation, being about 1/3 or less, It can be seen that in the Ti: Si = 70: 30, 50:50 [mol%] composition, the absorbance (concentration) is almost zero, showing a very high speed and a significant decrease. Further, with respect to the Ti: Si = 50: 50 [mol%] composition that showed the most excellent performance in FIG. 6, the heat treatment effect in the atmosphere was tested for ultraviolet light (black light) for a sample heat-treated at 600 to 1000 ° C. for 1 hour. As a result of measuring the concentration of methylene blue in the solution with an ultraviolet-visible spectrophotometer and evaluating the photocatalytic performance of the synthetic powder after heat treatment in the atmosphere in the same manner except that the irradiation time of was reduced to 1/12 for 5 minutes. Is shown in FIG. From this, the absorbance (concentration) of methylene blue decreases as the heat treatment temperature increases to 600 to 1000 ° C., and in the 1000 ° C. treated sample, the absorbance (concentration) is almost zero, and irradiation with a short time of 5 minutes Even in such a case, it can be seen that extremely high speed and remarkable decrease (high excellent photocatalytic ability) are exhibited.
[0028]
Example 2
Titanium oxysulfate (TiOSO) as a titanium compound 4 ) And an aqueous solution in which this is dissolved, and tetraethyl orthosilicate (Si (OC 2 H 5 ) 4 ), 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 Example 1 except that twice the amount of ammonia water necessary to neutralize the solution was added to the solution mixed so as to have a composition ratio, and a mixed solution containing a precipitate slurry was used. A synthesis operation was performed to obtain a product. After washing, the product was dried at 65 ° C., and the same measurement as in Example 1 was performed.
[0029]
From the X-ray diffraction pattern of the dry powder of the product thus obtained, any starting composition of Ti: Si = 100: 0, 90:10, 85:15, 70:30, 50:50 [mol%] was obtained. It was also understood that the product was only identified as an anatase type crystal structure as a crystal phase, had an anatase type crystal structure and contained substantially no rutile phase. As a result of measuring the crystallite diameter from the diffraction line of the Miller index of 200 of the anatase type crystal using the Debye-Scherrer equation, the crystallite diameter of the product powder of any composition was in the range of 10 to 20 nm. It was. As a result of examining the analytical composition (Ti: Si) of the obtained product, it was confirmed that the composition of the dry powder of the obtained product was almost the same corresponding to the starting composition. From the measurement result of the dried powder of the obtained product by Raman spectroscopy and observation with a transmission electron microscope, the silica component is present as amorphous on the surface of the titania anatase crystal, or the composition of the Si content is high. In some cases, it was understood that the microstructure has anatase-type crystals in an amorphous silica matrix. The phase transition from the anatase type to the rutile type caused by heat treatment in the atmosphere is suppressed as the silica content increases and shifts to the high temperature side, and at a silica content of 15 mol%, it remains 100% anatase after treatment at 1100 ° C. It was confirmed that when the silica content was 30 mol% or more, 90% or more after the treatment at 1200 ° C. was anatase type. When the silica content was 50 mol%, it was confirmed that the silica content was 100% anatase after treatment at 1300 ° C. As a result of evaluating the photocatalytic performance of the synthetic powder under ultraviolet (black light) irradiation using decomposition of methylene blue, hydrothermally synthesized pure anatase TiO as a comparative example 2 And commercially available pure anatase TiO manufactured by Ishihara Sangyo Co., Ltd. 2 In the photocatalyst ST-01, after the ultraviolet ray (black light) was irradiated for 1 hour, the absorbance (concentration) of methylene blue was lowered from about 2/3 to 1/2 of the case where no photocatalyst was added (MB sample). On the other hand, in any of the anatase-type titania-silica composites of the present invention containing a silica component, the absorbance (concentration) of methylene blue rapidly decreases during 1 hour irradiation, and is about 1/3 or less. In the composition of Ti: Si = 70: 30, 50:50 [mol%], it was found that the absorbance (concentration) was almost zero, indicating a very high speed and a significant decrease.
[0030]
Example 3
Example 1 except that silica gel was used in place of tetraethyl orthosilicate and mixing was performed so that the composition ratios were Ti: Si = 40: 60, 20:80, 5:95 [mol%]. Samples were prepared in the same manner as above. Evaluation was also performed in the same manner as in Example 1 except that the dried product was observed with a scanning electron microscope (SEM).
[0031]
From the X-ray diffraction pattern of the dry powder of the product thus obtained, the product of any starting composition was identified only as an anatase type crystal structure as a crystal phase, having an anatase type crystal structure, It was understood that it did not contain a rutile phase. The presence of precipitated particles of anatase type crystals on the amorphous silica gel surface was confirmed by SEM. Compositing with silica component (silica gel) improved the photocatalytic performance as well as the adsorption ability, and also improved the stability of the anatase type (confirmed to be 100% anatase type after treatment at 1200 ° C. for 1 hour) .
[0032]
Example 4
Titanium oxysulfate (TiOSO) as a titanium compound 4 ) And an aqueous solution in which this is dissolved, and sodium silicate (sodium metasilicate Na) as a silicon compound 2 SiO 3 ・ 9H 2 O), 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, 30:70 Except that they were mixed so that the composition ratio was [mol%], nothing was added, and the synthesized solution was exactly the same as in Example 1 except that the prepared mixed solution (the solution was in an acidic state) was used. After washing, it was dried at 65 ° C. Subsequently, the measurement similar to Example 1 was performed about the crystal phase of the obtained dried material.
[0033]
From the X-ray diffraction pattern of the 65 ° C. dry powder of the product thus obtained, Ti: Si = 100: 0, 90:10, 85:15, 70:30, 50:50, 30:70 [mol%] In any of the starting compositions, it was understood that only the anatase type crystal structure was identified as the crystalline phase, had the anatase type crystal structure and contained substantially no rutile phase. As a result of measuring the crystallite diameter from the diffraction line of the Miller index of 200 of the anatase type crystal using the Debye-Scherrer equation, the crystallite diameter of the product powder of any composition was in the range of 10 to 20 nm. It was. As a result of examining the analysis composition (Ti: Si) of the dry powder of the obtained product by ICP (inductively coupled radio frequency plasma) emission spectroscopic analysis, the composition of the dry powder of the obtained product is the starting composition. Correspondingly, it was confirmed that they were almost the same. From the measurement result of the dried powder obtained by Raman spectroscopy and observation with a transmission electron microscope, the silica component is present as an amorphous substance on the anatase crystal surface or the composition has a high Si content. It was understood that this is a microstructure in which anatase-type crystals exist in an amorphous silica matrix. The phase transition from the anatase type to the rutile type caused by heat treatment in the atmosphere is suppressed as the silica content increases and shifts to the high temperature side, and at a silica content of 15 mol%, it remains 100% anatase after treatment at 1100 ° C. It was confirmed that it was 100% anatase type even after treatment at 1200 ° C. when the silica content was 30 mol% or more. As a result of evaluating the photocatalytic performance of the synthetic powder under ultraviolet (black light) irradiation using decomposition of methylene blue, hydrothermally synthesized pure anatase TiO as a comparative example 2 And commercially available pure anatase TiO manufactured by Ishihara Sangyo Co., Ltd. 2 In the photocatalyst ST-01, after the ultraviolet ray (black light) was irradiated for 1 hour, the absorbance (concentration) of methylene blue was lowered from about 2/3 to 1/2 of the case where no photocatalyst was added (MB sample). In contrast, in any of the anatase-type titania-silica composites of the present invention containing a silica component, the absorbance (concentration) of methylene blue rapidly decreased during irradiation for 60 minutes, being about 1/3 or less. In the composition of Ti: Si = 70: 30, 50:50 [mol%], it was found that the absorbance (concentration) was almost zero, indicating a very high speed and a significant decrease.
[0034]
【The invention's effect】
As is apparent from the above description, the anatase-type titania-silica composite according to the present invention is suitable for various uses. For example, as a photocatalytic material, it is excellent in organic matter decomposability. It can be used as an agent, malodorous / organic gas decomposing agent, antibacterial agent, antifungal agent, antialgae agent, antifouling agent, hydrophilic material, air purification agent, and water decomposition photocatalytic material. Further, even after high-temperature heat treatment in the atmosphere at 1100 ° C. for 1 hour, it has a high phase stability that does not substantially contain a rutile phase and can exist as anatase titania (in the present invention, a silica content of 50 mol% is reduced). In the anatase-type titania-silica composite having the composition, the 100% anatase type can be maintained even after heat treatment in air at 1300 ° C. for 1 hour). Furthermore, by combining with silica component (silica gel), it is possible to have substance adsorbability at the same time, and because of the synergistic action of substance adsorbing ability and photocatalytic action, it is superior in performance. It can be used advantageously for many applications that are being applied, and new applications may be expanded.
[Brief description of the drawings]
FIG. 1 is an X-ray diffraction pattern of an anatase titania-silica composite according to the present invention.
[Fig. 2] Anatase-type titania-silica composite according to the present invention (SiO2) 2 = 50 mol%) is a diagram showing an X-ray diffraction pattern of the heat-treated product at each temperature.
FIG. 3 is a diagram showing the amount of anatase-type to rutile-type phase transition (mass%) generated by heat treatment in air for the anatase-type titania-silica composite according to the present invention.
FIG. 4 is a graph showing the crystallite size of an anatase-type crystal of a heat-treated product in the atmosphere for the anatase-type titania-silica composite according to the present invention.
FIG. 5 is a diagram showing the measurement results of the ultraviolet-visible light absorption spectrum of the anatase-type titania-silica composite according to the present invention.
FIG. 6 is a graph showing the photocatalytic performance of the anatase-type titania-silica composite according to the present invention as the absorbance of methylene blue after 1 hour of ultraviolet irradiation.
FIG. 7 is a graph showing the photocatalytic performance of the anatase titania-silica composite (Ti: Si = 50: 50 [mol%] sample) according to the present invention as the absorbance of methylene blue after 5 minutes of ultraviolet irradiation.
Claims (6)
光触媒作用：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に加えた後、２０ｐｐｍ濃度のメチレンブルー水溶液２０mlを加え、全体の溶液のメチレンブルー濃度を１０ｐｐｍにした溶液に対し、ブラックライトによる紫外線を１時間照射し、該アナターゼ型チタニア−シリカ複合体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のメチレンブルーによる吸光度の変化（減少）により測定される光触媒作用。 A titanium compound and a silicon compound anatase form of titania is obtainable by hydrothermal reaction - a silica complex, titania (T iO 2) to manually Internal mol% 15 ~ 95mol% of silica (SiO 2) containing, the titania Ri der crystallite diameter 70nm or less of the anatase form of titania as well as present as anatase type titania Te after heat treatment odor in the atmosphere of one hour at 1 100 ° C., the photocatalytic action of the following anatase titania is characterized in that at least twice the anatase form of titania containing no silica mosquitoes - silica composite.
Photocatalytic action: 0.01 g of anatase-type titania-silica composite sample powder was added to 20 ml of distilled water, and then 20 ml of a 20 ppm methylene blue aqueous solution was added to make the total solution methylene blue concentration 10 ppm. The photocatalytic action is measured by irradiating UV light for 1 hour and measuring the degree of degradation of methylene blue by the anatase-type titania-silica complex by the change (decrease) in absorbance by 660 nm of methylene blue using a spectrophotometer.
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