JP6623364B2 - Titanium oxide aggregate for photocatalyst and method for producing the same - Google Patents
Titanium oxide aggregate for photocatalyst and method for producing the same Download PDFInfo
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- JP6623364B2 JP6623364B2 JP2015197494A JP2015197494A JP6623364B2 JP 6623364 B2 JP6623364 B2 JP 6623364B2 JP 2015197494 A JP2015197494 A JP 2015197494A JP 2015197494 A JP2015197494 A JP 2015197494A JP 6623364 B2 JP6623364 B2 JP 6623364B2
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- anatase
- calcium phosphate
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- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 title claims description 187
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 title claims description 115
- 239000011941 photocatalyst Substances 0.000 title claims description 21
- 238000004519 manufacturing process Methods 0.000 title description 16
- 239000002245 particle Substances 0.000 claims description 47
- -1 calcium phosphate compound Chemical class 0.000 claims description 40
- 239000001506 calcium phosphate Substances 0.000 claims description 30
- 229910000389 calcium phosphate Inorganic materials 0.000 claims description 28
- 235000011010 calcium phosphates Nutrition 0.000 claims description 28
- 239000013078 crystal Substances 0.000 claims description 27
- 239000010936 titanium Substances 0.000 claims description 25
- 238000010304 firing Methods 0.000 claims description 22
- 239000002243 precursor Substances 0.000 claims description 15
- 229910052719 titanium Inorganic materials 0.000 claims description 15
- 229910052698 phosphorus Inorganic materials 0.000 claims description 12
- 239000011574 phosphorus Substances 0.000 claims description 12
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 11
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 11
- 238000002441 X-ray diffraction Methods 0.000 claims description 11
- 238000000151 deposition Methods 0.000 claims description 4
- 239000002131 composite material Substances 0.000 claims description 3
- 238000004438 BET method Methods 0.000 claims 1
- 230000001699 photocatalysis Effects 0.000 description 49
- 239000002105 nanoparticle Substances 0.000 description 32
- 238000000034 method Methods 0.000 description 24
- 239000000463 material Substances 0.000 description 18
- 229910052586 apatite Inorganic materials 0.000 description 17
- VSIIXMUUUJUKCM-UHFFFAOYSA-D pentacalcium;fluoride;triphosphate Chemical compound [F-].[Ca+2].[Ca+2].[Ca+2].[Ca+2].[Ca+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O VSIIXMUUUJUKCM-UHFFFAOYSA-D 0.000 description 16
- 238000006243 chemical reaction Methods 0.000 description 12
- 239000000126 substance Substances 0.000 description 12
- XQAXGZLFSSPBMK-UHFFFAOYSA-M [7-(dimethylamino)phenothiazin-3-ylidene]-dimethylazanium;chloride;trihydrate Chemical compound O.O.O.[Cl-].C1=CC(=[N+](C)C)C=C2SC3=CC(N(C)C)=CC=C3N=C21 XQAXGZLFSSPBMK-UHFFFAOYSA-M 0.000 description 9
- 230000007547 defect Effects 0.000 description 9
- 229960000907 methylthioninium chloride Drugs 0.000 description 9
- 239000011163 secondary particle Substances 0.000 description 9
- 230000000052 comparative effect Effects 0.000 description 8
- 230000000149 penetrating effect Effects 0.000 description 8
- 239000002253 acid Substances 0.000 description 7
- 238000010306 acid treatment Methods 0.000 description 7
- 238000012360 testing method Methods 0.000 description 7
- 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 7
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 6
- 238000004458 analytical method Methods 0.000 description 6
- 230000007423 decrease Effects 0.000 description 6
- 238000009792 diffusion process Methods 0.000 description 6
- 238000002845 discoloration Methods 0.000 description 6
- 239000000843 powder Substances 0.000 description 6
- 150000003254 radicals Chemical class 0.000 description 6
- 230000007704 transition Effects 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 238000004876 x-ray fluorescence Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- 230000006872 improvement Effects 0.000 description 5
- 230000005855 radiation Effects 0.000 description 5
- 239000007788 liquid Substances 0.000 description 4
- 239000003973 paint Substances 0.000 description 4
- 125000002467 phosphate group Chemical group [H]OP(=O)(O[H])O[*] 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 230000005284 excitation Effects 0.000 description 3
- 238000006460 hydrolysis reaction Methods 0.000 description 3
- 229910052588 hydroxylapatite Inorganic materials 0.000 description 3
- 239000010954 inorganic particle Substances 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- XYJRXVWERLGGKC-UHFFFAOYSA-D pentacalcium;hydroxide;triphosphate Chemical compound [OH-].[Ca+2].[Ca+2].[Ca+2].[Ca+2].[Ca+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O XYJRXVWERLGGKC-UHFFFAOYSA-D 0.000 description 3
- 238000000746 purification Methods 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 239000002904 solvent Substances 0.000 description 3
- 241000282412 Homo Species 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 230000002776 aggregation Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000001354 calcination Methods 0.000 description 2
- XAAHAAMILDNBPS-UHFFFAOYSA-L calcium hydrogenphosphate dihydrate Chemical compound O.O.[Ca+2].OP([O-])([O-])=O XAAHAAMILDNBPS-UHFFFAOYSA-L 0.000 description 2
- 239000003054 catalyst Substances 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 235000019700 dicalcium phosphate Nutrition 0.000 description 2
- 239000012153 distilled water Substances 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 125000000524 functional group Chemical group 0.000 description 2
- 239000008187 granular material Substances 0.000 description 2
- 238000005469 granulation Methods 0.000 description 2
- 230000003179 granulation Effects 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 238000003837 high-temperature calcination Methods 0.000 description 2
- 230000007062 hydrolysis Effects 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 239000003960 organic solvent Substances 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 230000006798 recombination Effects 0.000 description 2
- 238000001694 spray drying Methods 0.000 description 2
- QDZRBIRIPNZRSG-UHFFFAOYSA-N titanium nitrate Chemical compound [O-][N+](=O)O[Ti](O[N+]([O-])=O)(O[N+]([O-])=O)O[N+]([O-])=O QDZRBIRIPNZRSG-UHFFFAOYSA-N 0.000 description 2
- QORWJWZARLRLPR-UHFFFAOYSA-H tricalcium bis(phosphate) Chemical compound [Ca+2].[Ca+2].[Ca+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O QORWJWZARLRLPR-UHFFFAOYSA-H 0.000 description 2
- SNOJPWLNAMAYSX-UHFFFAOYSA-N 2-methylpropan-1-ol;titanium Chemical compound [Ti].CC(C)CO.CC(C)CO.CC(C)CO.CC(C)CO SNOJPWLNAMAYSX-UHFFFAOYSA-N 0.000 description 1
- GRWPYGBKJYICOO-UHFFFAOYSA-N 2-methylpropan-2-olate;titanium(4+) Chemical compound [Ti+4].CC(C)(C)[O-].CC(C)(C)[O-].CC(C)(C)[O-].CC(C)(C)[O-] GRWPYGBKJYICOO-UHFFFAOYSA-N 0.000 description 1
- ZHJGWYRLJUCMRT-UHFFFAOYSA-N 5-[6-[(4-methylpiperazin-1-yl)methyl]benzimidazol-1-yl]-3-[1-[2-(trifluoromethyl)phenyl]ethoxy]thiophene-2-carboxamide Chemical compound C=1C=CC=C(C(F)(F)F)C=1C(C)OC(=C(S1)C(N)=O)C=C1N(C1=C2)C=NC1=CC=C2CN1CCN(C)CC1 ZHJGWYRLJUCMRT-UHFFFAOYSA-N 0.000 description 1
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical group OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 1
- 238000002835 absorbance Methods 0.000 description 1
- 239000003463 adsorbent Substances 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 238000004887 air purification Methods 0.000 description 1
- 230000001476 alcoholic effect Effects 0.000 description 1
- LFVGISIMTYGQHF-UHFFFAOYSA-N ammonium dihydrogen phosphate Chemical compound [NH4+].OP(O)([O-])=O LFVGISIMTYGQHF-UHFFFAOYSA-N 0.000 description 1
- 229910000387 ammonium dihydrogen phosphate Inorganic materials 0.000 description 1
- 235000011114 ammonium hydroxide Nutrition 0.000 description 1
- 150000008064 anhydrides Chemical class 0.000 description 1
- 230000000844 anti-bacterial effect Effects 0.000 description 1
- 230000003373 anti-fouling effect Effects 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 239000012298 atmosphere Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 239000001045 blue dye Substances 0.000 description 1
- 239000004566 building material Substances 0.000 description 1
- YHWCPXVTRSHPNY-UHFFFAOYSA-N butan-1-olate;titanium(4+) Chemical compound [Ti+4].CCCC[O-].CCCC[O-].CCCC[O-].CCCC[O-] YHWCPXVTRSHPNY-UHFFFAOYSA-N 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- YYRMJZQKEFZXMX-UHFFFAOYSA-L calcium bis(dihydrogenphosphate) Chemical compound [Ca+2].OP(O)([O-])=O.OP(O)([O-])=O YYRMJZQKEFZXMX-UHFFFAOYSA-L 0.000 description 1
- JUNWLZAGQLJVLR-UHFFFAOYSA-J calcium diphosphate Chemical compound [Ca+2].[Ca+2].[O-]P([O-])(=O)OP([O-])([O-])=O JUNWLZAGQLJVLR-UHFFFAOYSA-J 0.000 description 1
- FUFJGUQYACFECW-UHFFFAOYSA-L calcium hydrogenphosphate Chemical compound [Ca+2].OP([O-])([O-])=O FUFJGUQYACFECW-UHFFFAOYSA-L 0.000 description 1
- 229940043256 calcium pyrophosphate Drugs 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 239000013522 chelant Substances 0.000 description 1
- 239000007806 chemical reaction intermediate Substances 0.000 description 1
- 239000013065 commercial product Substances 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 235000019821 dicalcium diphosphate Nutrition 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 238000005562 fading Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 229910052587 fluorapatite Inorganic materials 0.000 description 1
- 150000004677 hydrates Chemical class 0.000 description 1
- BHEPBYXIRTUNPN-UHFFFAOYSA-N hydridophosphorus(.) (triplet) Chemical compound [PH] BHEPBYXIRTUNPN-UHFFFAOYSA-N 0.000 description 1
- 238000010335 hydrothermal treatment Methods 0.000 description 1
- 239000004816 latex Substances 0.000 description 1
- 229920000126 latex Polymers 0.000 description 1
- 210000004072 lung Anatomy 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 235000019837 monoammonium phosphate Nutrition 0.000 description 1
- 229910000150 monocalcium phosphate Inorganic materials 0.000 description 1
- 235000019691 monocalcium phosphate Nutrition 0.000 description 1
- 239000002086 nanomaterial Substances 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 229910000392 octacalcium phosphate Inorganic materials 0.000 description 1
- 239000011368 organic material Substances 0.000 description 1
- 239000005416 organic matter Substances 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 150000003017 phosphorus Chemical class 0.000 description 1
- 231100000572 poisoning Toxicity 0.000 description 1
- 230000000607 poisoning effect Effects 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000011164 primary particle Substances 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- IKNCGYCHMGNBCP-UHFFFAOYSA-N propan-1-olate Chemical compound CCC[O-] IKNCGYCHMGNBCP-UHFFFAOYSA-N 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000006479 redox reaction Methods 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- YIGWVOWKHUSYER-UHFFFAOYSA-F tetracalcium;hydrogen phosphate;diphosphate Chemical compound [Ca+2].[Ca+2].[Ca+2].[Ca+2].OP([O-])([O-])=O.[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O YIGWVOWKHUSYER-UHFFFAOYSA-F 0.000 description 1
- GBNXLQPMFAUCOI-UHFFFAOYSA-H tetracalcium;oxygen(2-);diphosphate Chemical compound [O-2].[Ca+2].[Ca+2].[Ca+2].[Ca+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O GBNXLQPMFAUCOI-UHFFFAOYSA-H 0.000 description 1
- JMXKSZRRTHPKDL-UHFFFAOYSA-N titanium ethoxide Chemical compound [Ti+4].CC[O-].CC[O-].CC[O-].CC[O-] JMXKSZRRTHPKDL-UHFFFAOYSA-N 0.000 description 1
- 229910000349 titanium oxysulfate Inorganic materials 0.000 description 1
- XJDNKRIXUMDJCW-UHFFFAOYSA-J titanium tetrachloride Chemical compound Cl[Ti](Cl)(Cl)Cl XJDNKRIXUMDJCW-UHFFFAOYSA-J 0.000 description 1
- 229910000391 tricalcium phosphate Inorganic materials 0.000 description 1
- 235000019731 tricalcium phosphate Nutrition 0.000 description 1
- 229940078499 tricalcium phosphate Drugs 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
Landscapes
- Inorganic Compounds Of Heavy Metals (AREA)
- Catalysts (AREA)
Description
本発明は、酸化チタン光触媒に関する。より詳しくは、マクロ孔を有し、アナターゼ含有率と結晶性とのバランスに優れ、高い光触媒活性を示す酸化チタン凝集体及びその製造方法に関する。 The present invention relates to a titanium oxide photocatalyst. More specifically, the present invention relates to a titanium oxide aggregate having macropores, having an excellent balance between anatase content and crystallinity, and exhibiting high photocatalytic activity, and a method for producing the same.
光触媒は、光照射下において有機物分解や表面超親水化の作用を示すことから、環境浄化、防汚、抗菌、防曇等の用途に利用されている。中でも酸化チタン光触媒は、光触媒活性が高く、価格が安く、化学的安定性が高いなどの理由から、光触媒市場において最も広く利用されており、その大部分を占めている。 BACKGROUND ART Photocatalysts are used for applications such as environmental purification, antifouling, antibacterial, and antifogging because they exhibit an action of decomposing organic substances and making surfaces superhydrophilic under light irradiation. Among them, the titanium oxide photocatalyst is most widely used in the photocatalyst market because of its high photocatalytic activity, low price and high chemical stability, and occupies most of it.
酸化チタンに紫外光が照射されると、電子励起で生じた電子とホールが、それぞれ酸素や表面吸着水と酸化還元反応してラジカル種を生成する。これらのラジカル種は高いエネルギーを持つため、原理上はほとんどの有機物を分解できると考えられている。 When the titanium oxide is irradiated with ultraviolet light, electrons and holes generated by the electron excitation undergo a redox reaction with oxygen and surface-adsorbed water, respectively, to generate radical species. Since these radical species have high energy, it is thought that most organic substances can be decomposed in principle.
酸化チタンの結晶相としては、常圧下では、アナターゼ、ブルッカイト、ルチルの３種が知られているが、ブルッカイトの結晶構造は一般的な製造方法では形成されにくいため、現在製造されている酸化チタンのほとんどはアナターゼとルチルである。アナターゼは準安定相であり、焼成等によってエネルギーを与えると高温安定相であるルチルに相転移する。 As the crystal phase of titanium oxide, three types of anatase, brookite, and rutile are known under normal pressure. However, since the crystal structure of brookite is difficult to be formed by a general production method, titanium oxide currently produced Most are anatase and rutile. Anatase is a metastable phase, and undergoes a phase transition to rutile, a high-temperature stable phase, when energy is applied by baking or the like.
経験的にアナターゼの方がルチルと比較して高い光触媒活性を有することが多いため、光触媒用途ではアナターゼを用いることが多い。アナターゼが高い光触媒活性を示す理由について、統一された学説は未だ無いが、準安定相であるアナターゼはマイルドな合成条件下で得られやすいために、ルチルと比較して比表面積値が高いことが多く、これが高い光触媒活性につながっていると説明されることが多い。 Empirically, anatase often has higher photocatalytic activity than rutile, and thus anatase is often used in photocatalytic applications. Although there is no unified theory as to why anatase exhibits high photocatalytic activity, anatase, which is a metastable phase, is easily obtained under mild synthesis conditions, and therefore, has a high specific surface area value compared to rutile. It is often described that this leads to high photocatalytic activity.
実際、市場に流通している光触媒用酸化チタン粉末の多くは、１次粒子径が１００ｎｍ以下、あるいは比表面積値が１０ｍ２／ｇ以上のアナターゼ含有率の高いナノ粒子が用いられている。
ナノ粒子はある程度凝集しているが、それでも微細であるために肺に吸入されやすい。近年、人体に対する有害性が益々懸念されており、例えば欧米を中心にナノマテリアルに対する規制強化の動きが見受けられる。そのため、実用上はナノ粒子を基材に固定した使用法に限定されている。
In fact, many of the titanium oxide powders for photocatalyst on the market use nanoparticles having a primary particle size of 100 nm or less or a specific surface area of 10 m 2 / g or more and having a high anatase content.
Although the nanoparticles are somewhat aggregated, they are still fine enough to be easily inhaled by the lungs. In recent years, there has been an increasing concern about harm to the human body. For example, there has been a movement to tighten regulations on nanomaterials mainly in Europe and the United States. For this reason, the method is practically limited to a method in which nanoparticles are fixed to a substrate.
酸化チタン光触媒を基材や塗料に固定する場合、光触媒市場において最も市場規模の大きい建築材料への利用では、基材や塗料に有機物が使用されることがほとんどであり、一方で酸化チタン光触媒は有機物を分解する作用を有するため、基材や塗料が酸化チタンと接触しないようにして保護する必要がある。また、ナノ粒子はハンドリング性が悪いだけでなく、嵩密度が低いために、運搬コストが高くなりやすい。さらに、液中で利用する場合には、ナノ粒子の回収は容易ではない。 When fixing titanium oxide photocatalysts to base materials and paints, most of the photocatalyst market uses organic materials in the base materials and paints for use in the largest building materials in the photocatalyst market, while titanium oxide photocatalysts use Since it has an action of decomposing organic substances, it is necessary to protect the base material and the paint so that they do not come into contact with titanium oxide. In addition, nanoparticles are not only poor in handling properties but also have low bulk density, so that transportation costs are likely to be high. Further, when used in a liquid, recovery of nanoparticles is not easy.
このような背景から、酸化チタンナノ粒子をスプレードライ（噴霧乾燥）等によって顆粒状に造粒する技術が用いられることがある。顆粒状に造粒することによって２次粒子径が増大し、ナノ粒子固有の低ハンドリング性、人体有害性が改善されるだけではなく、嵩密度や回収性についても改善を図ることが可能となる。 From such a background, a technique of granulating titanium oxide nanoparticles into granules by spray drying (spray drying) or the like is sometimes used. By granulating into granules, the secondary particle diameter is increased, and not only the low handling properties inherent to nanoparticles and the harmfulness to the human body are improved, but also the bulk density and recoverability can be improved. .
しかし、造粒によって凝集体を形成すると、造粒前と比較して光触媒活性は低下してしまう。その理由として、有機物分解能力を持つと考えられるヒドロキシラジカル等のラジカル種や、分解される有機物の拡散経路が、複雑となり長くなるために、ラジカル種と有機物の接触頻度が減少するためと考えられている。特にナノ粒子が凝集することによって形成される孔は、ミクロ孔（２ｎｍ以下）やメソ孔（２〜５０ｎｍ）と微細であるため、拡散速度の低減が顕著である。 However, when an aggregate is formed by granulation, the photocatalytic activity decreases as compared to before the granulation. The reason is considered to be that radical species such as hydroxyl radicals, which are considered to have organic substance decomposing ability, and diffusion paths of decomposed organic substances are complicated and long, so that the frequency of contact between radical species and organic substances is reduced. ing. In particular, the pores formed by agglomeration of the nanoparticles are as fine as micropores (2 nm or less) and mesopores (2 to 50 nm), so that the diffusion rate is remarkably reduced.
このような凝集体内部における拡散速度低減の問題を解決するため、体積流量に優れるマクロ孔（５０ｎｍ以上）を凝集体内部に形成する技術が知られている。例えば特許文献１には、マクロ孔が略一軸方向に配向して形成されている多孔質酸化チタン粉末が、マクロ孔を有さない酸化チタン粉末と比較して高い光触媒活性を有することが報告されている。 In order to solve the problem of the reduction of the diffusion rate inside the aggregate, a technique of forming macropores (50 nm or more) having an excellent volume flow rate inside the aggregate is known. For example, Patent Document 1 reports that a porous titanium oxide powder having macropores oriented substantially uniaxially has a higher photocatalytic activity than a titanium oxide powder having no macropores. ing.
次に、凝集体を構成する酸化チタン粒子が高い光触媒活性を有するために材料として満たすべき要件について、背景技術を説明する。その要件としては、前述した結晶相がアナターゼであること及び比表面積値が高いことの他に、酸化チタンに含まれる欠陥量が少ないこと、すなわち結晶性が高いことが挙げられる。欠陥量を低減して高結晶性とすることの重要性は、アモルファス酸化チタンが光触媒作用をほとんど示さない実験事実によって裏付けられている。 Next, the background art will be described with respect to the requirements that must be satisfied as a material in order for the titanium oxide particles constituting the aggregate to have high photocatalytic activity. The requirements include that the crystal phase is anatase and that the specific surface area is high, and that the amount of defects contained in titanium oxide is small, that is, the crystallinity is high. The importance of reducing the amount of defects to have high crystallinity is supported by the experimental fact that amorphous titanium oxide shows almost no photocatalytic action.
欠陥が電子励起で生じた電子とホールの再結合中心として働き、これらを消費することが、光触媒活性を低下させる要因と考えられている。このような光触媒活性の低下につながる欠陥量を低減して結晶性を高めるためには、外部からエネルギーを与えて結晶を構成する原子を再配列する必要があり、通常は熱エネルギーの付与、すなわち焼成処理が行われている。 It is considered that the defect acts as a recombination center between an electron and a hole generated by the electronic excitation, and that the consumption thereof causes a reduction in the photocatalytic activity. In order to increase the crystallinity by reducing the amount of defects leading to such a decrease in photocatalytic activity, it is necessary to rearrange the atoms constituting the crystal by applying energy from the outside. A firing process has been performed.
しかし、エネルギーを付与することは、同時に、酸化チタン粒子の粒成長、すなわち比表面積値低下や、アナターゼからルチルへの相転移を助長する。すなわち、「アナターゼ含有率及び比表面積値が高いこと」と「結晶性が高いこと」はトレードオフの関係にあり、両者をバランスさせた高い光触媒活性を有する酸化チタンを製造することは容易ではない。 However, applying energy simultaneously promotes the grain growth of the titanium oxide particles, that is, the reduction of the specific surface area value and the phase transition from anatase to rutile. That is, "the high anatase content and the specific surface area value" and "the high crystallinity" are in a trade-off relationship, and it is not easy to produce titanium oxide having a high photocatalytic activity that balances both. .
このトレードオフ関係を解消する手段の一つとして、本発明者らはこれまでに酸化チタン粒子をアパタイトなどの無機粒子と複合化して焼成し、焼成後に無機粒子を除去する技術を報告している（非特許文献１〜５）。これらの技術を用いることにより、通常の焼成処理と比較して、高アナターゼ含有率及び高比表面積と、高結晶性とのバランスを改善することができる。 As one of the means for eliminating this trade-off relationship, the present inventors have reported a technique in which titanium oxide particles are combined with inorganic particles such as apatite and fired, and the inorganic particles are removed after firing. (Non-Patent Documents 1 to 5). By using these techniques, it is possible to improve the balance between the high anatase content and the high specific surface area and the high crystallinity, as compared with a normal baking treatment.
しかしながら、特許文献１の技術で得られる酸化チタン粉末については、マクロ孔の導入による光触媒活性の向上が図られているものの、それを構成する酸化チタン粒子自体の光触媒活性の向上は通常の焼成処理以外に図られていない。具体的には、６００℃以上の温度で焼成した場合に比表面積が低下し十分な光触媒活性が得られないと記述され、２００〜６００℃での焼成がなされているが、水熱処理後にこのような比較的低温域の焼成をする場合には、酸化チタン粒子に含まれる欠陥を十分に低減すること、すなわち結晶性を十分に高めることはできず、高い光触媒活性を有する酸化チタンは得られないと考えられる。 However, with respect to the titanium oxide powder obtained by the technique of Patent Document 1, although the improvement of the photocatalytic activity by introduction of macropores is attempted, the improvement of the photocatalytic activity of the titanium oxide particles constituting the powder is not achieved by a normal firing treatment. It is not planned other than. Specifically, it is described that when fired at a temperature of 600 ° C. or higher, the specific surface area decreases and sufficient photocatalytic activity cannot be obtained, and firing at 200 to 600 ° C. is performed. When firing in a relatively low temperature range, it is not possible to sufficiently reduce defects contained in the titanium oxide particles, that is, it is not possible to sufficiently increase the crystallinity, and titanium oxide having high photocatalytic activity cannot be obtained. it is conceivable that.
また、多孔質構造を形成した後に、比表面積が低下するほどの高い温度で焼成すると、マクロ孔が収縮や変形をして光触媒活性に影響すると考えられる。光触媒活性が低い酸化チタンは、きれいな状態を維持する用途に利用することは可能でも、高濃度の汚染物を浄化する用途に利用することは難しい。
さらに、水熱処理という高圧条件下で行われる合成法が必要であり、製造の再現性、安全性、コスト等の点で量産化が容易ではない。
In addition, when the porous structure is fired at a temperature high enough to reduce the specific surface area after forming the porous structure, the macropores are considered to shrink or deform to affect the photocatalytic activity. Titanium oxide having low photocatalytic activity can be used for applications that maintain a clean state, but is difficult to use for applications that purify high-concentration contaminants.
Furthermore, a synthesis method called hydrothermal treatment performed under high-pressure conditions is necessary, and mass production is not easy in terms of reproducibility of production, safety, cost, and the like.
また、非特許文献１〜５の技術で得られる酸化チタン粒子は、高アナターゼ含有率及び高比表面積と高結晶性（すなわち低欠陥濃度）とのバランスに優れ、高い光触媒活性を有している。これは、アパタイトなどの無機粒子が酸化チタン粒子間に介在することにより、焼成中の酸化チタン粒子同士の接触を妨げ、酸化チタンの相転移や粒成長を抑制するためと考えられる。しかし、得られる酸化チタン粒子は一般的な市販品と同様にナノ粒子であるため、ナノ粒子固有の低ハンドリング性、高人体有害性、低嵩密度及び低回収性については改善されていない。 In addition, the titanium oxide particles obtained by the techniques of Non-Patent Documents 1 to 5 have an excellent balance between a high anatase content, a high specific surface area, and high crystallinity (that is, low defect concentration), and have high photocatalytic activity. . This is presumably because inorganic particles such as apatite intervene between the titanium oxide particles, thereby hindering the contact between the titanium oxide particles during firing and suppressing the phase transition and grain growth of the titanium oxide. However, since the obtained titanium oxide particles are nanoparticles like general commercial products, the low handling properties, high harmfulness to humans, low bulk density and low recoverability inherent to nanoparticles have not been improved.
以上のように、従来の酸化チタンナノ粒子については、ナノ粒子固有の低ハンドリング性、高人体有害性、低嵩密度及び低回収性に課題がある。また、従来の酸化チタン凝集体については、低光触媒活性及び量産化に課題がある。したがって、ナノ粒子の課題を解決した凝集体でありながら、広い用途に利用できる高い光触媒活性を有する酸化チタン光触媒は、いまだ存在しないのが現状である。 As described above, conventional titanium oxide nanoparticles have problems in low handling properties, high harmfulness to humans, low bulk density, and low recoverability inherent to the nanoparticles. In addition, conventional titanium oxide aggregates have problems in low photocatalytic activity and mass production. Therefore, at present, there is no titanium oxide photocatalyst having high photocatalytic activity that can be used for a wide range of uses, even though it is an aggregate that has solved the problem of nanoparticles.
本発明は上記課題に鑑みてなされたものであり、粒子凝集に伴う光触媒活性低下を抑制し、同時に酸化チタン粒子自体の光触媒活性の向上を図ることにより、凝集体でありながら高い光触媒活性を有する酸化チタン光触媒及びその製造方法を提供することを目的とする。 The present invention has been made in view of the above problems, and suppresses a decrease in photocatalytic activity due to particle aggregation, and at the same time, aims to improve the photocatalytic activity of titanium oxide particles themselves, thereby having high photocatalytic activity while being an aggregate. An object of the present invention is to provide a titanium oxide photocatalyst and a method for producing the same.
本発明者は上記課題を解決すべく鋭意研究した結果、アパタイトなどのリン酸カルシウム化合物粒子が内在する酸化チタンとの複合体を高温焼成して酸処理することにより、内部を貫通するマクロ孔を有し、高アナターゼ含有率及び高結晶性の２つの材料因子のバランスに優れた酸化チタン凝集体を得ることができ、凝集体でありながら高い光触媒活性を有する酸化チタン光触媒を実現できることを究明した。
特に、凝集体の結晶相、結晶性、比表面積、化学組成を制御することにより、従来の酸化チタンナノ粒子と比較して数倍以上の２次粒子径でありながら、ナノ粒子を上回る高い光触媒活性を有する酸化チタン光触媒が得られることを究明し、本発明を完成するに至った。
The present inventor has conducted intensive studies to solve the above-described problems, and has obtained a macropore that penetrates the inside by performing a high-temperature calcination of a complex with titanium oxide in which calcium phosphate compound particles such as apatite are present and performing an acid treatment. It has been found that a titanium oxide aggregate having an excellent balance between the two material factors of high anatase content and high crystallinity can be obtained, and a titanium oxide photocatalyst having high photocatalytic activity can be realized while being an aggregate.
In particular, by controlling the crystal phase, crystallinity, specific surface area, and chemical composition of the aggregates, it has a secondary particle diameter several times higher than conventional titanium oxide nanoparticles, but has a higher photocatalytic activity than nanoparticles It was clarified that a titanium oxide photocatalyst having the following formula was obtained, and the present invention was completed.
すなわち、本発明は、結晶質酸化チタン粒子の凝集体であって、該凝集体内部を貫通するマクロ孔を有し、ＣｕＫα線を用いて得られるＸ線回折パターンにおいて、ルチルとアナターゼに帰属されるピークの最強線の強度比（ルチル／アナターゼ）が０．５以下、且つ、アナターゼの結晶面（１０１）に帰属されるピークの半値幅２θが１．０°以下である、前記酸化チタン凝集体である。 That is, the present invention relates to an aggregate of crystalline titanium oxide particles, having macropores penetrating the inside of the aggregate, and belonging to rutile and anatase in an X-ray diffraction pattern obtained using CuKα radiation. Wherein the intensity ratio (rutile / anatase) of the strongest line of the peak is 0.5 or less, and the half width 2θ of the peak attributed to the anatase crystal plane (101) is 1.0 ° or less. It is a collective.
また、本発明は、リン酸カルシウム化合物粒子を酸化チタン前駆体中に分散させながら酸化チタンを析出する工程と、得られた酸化チタン−リン酸カルシウム化合物複合体を６００℃以上の温度で焼成する工程と、得られた焼成体を酸で処理してリン酸カルシウム化合物を溶解する工程と、を含む上記酸化チタン凝集体の製造方法である。 Further, the present invention provides a step of depositing titanium oxide while dispersing calcium phosphate compound particles in a titanium oxide precursor, and a step of firing the obtained titanium oxide-calcium phosphate compound complex at a temperature of 600 ° C. or higher. Treating the obtained fired body with an acid to dissolve the calcium phosphate compound.
本発明の酸化チタン凝集体は、２次粒子径が大きい凝集体でありながら、従来の酸化チタンナノ粒子を上回る高い光触媒活性を有している。
また、本発明の酸化チタン凝集体の製造方法は、マクロ孔を有し、高アナターゼ含有率及び高結晶性の２つの材料因子のバランスに優れ、高い光触媒活性を有する酸化チタン凝集体を製造することができる。
The titanium oxide aggregate of the present invention has higher photocatalytic activity than conventional titanium oxide nanoparticles, while being an aggregate having a large secondary particle diameter.
In addition, the method for producing a titanium oxide aggregate of the present invention produces a titanium oxide aggregate having macropores, a high anatase content and an excellent balance between two material factors of high crystallinity and high photocatalytic activity. be able to.
以下、本発明の酸化チタン凝集体及びその製造方法について、詳細に説明する。なお、説明が省略されている構造、特性、組成、製法等については、当該技術分野の当業者に知られているものと同一又は実質的に同一のものとすることができる。 Hereinafter, the titanium oxide aggregate of the present invention and the method for producing the same will be described in detail. Structures, characteristics, compositions, manufacturing methods, and the like, whose description is omitted, can be the same or substantially the same as those known to those skilled in the art.
本発明の酸化チタン凝集体は、凝集体内部を貫通するマクロ孔を有している。マクロ孔を有していないと、凝集体内部におけるラジカル種や有機物の拡散速度が低減して、十分な光触媒活性を得ることができない。マクロ孔の形状は特に限定されず、長さ方向の形状が略円柱状である貫通孔だけではなく、屈曲部分やテーパー状部分を含む貫通孔でもよい。体積流量等の観点から長さ方向の形状が略円柱状である貫通孔が好ましい。 The titanium oxide aggregate of the present invention has macropores penetrating the inside of the aggregate. If it does not have macropores, the diffusion rate of radical species and organic substances inside the aggregate is reduced, and sufficient photocatalytic activity cannot be obtained. The shape of the macro hole is not particularly limited, and may be a through hole including a bent portion or a tapered portion as well as a through hole having a substantially cylindrical shape in the length direction. From the viewpoint of the volume flow rate or the like, a through hole having a substantially cylindrical shape in the length direction is preferable.
上記マクロ孔とは、ＩＵＰＡＣの定義と同じく、直径０．０５０μｍ以上の孔を意味する。マクロ孔の直径が大きいと体積流量に優れ、小さいと凝集体の凝集力が増大し解砕され難くなるため、直径１〜１０μｍの範囲が好ましい。 The macro hole means a hole having a diameter of 0.050 μm or more as defined in IUPAC. When the diameter of the macropores is large, the volume flow rate is excellent, and when the diameter is small, the cohesive force of the aggregates is increased and it is difficult to disintegrate the aggregates.
本発明の酸化チタン凝集体を構成する酸化チタン粒子の結晶構造は、Ｃｕ管球を線源にＣｕＫα線を用いて連続スキャンしたＸ線回折パターンにおいて、ピーク帰属によって含有されていると判断される結晶相のうち、ルチルとアナターゼに帰属されるピークの最強線の強度比（ルチル／アナターゼ）が０．５以下であり、好ましくは０．３以下である。アナターゼの方がルチルと比較して経験的に高い光触媒活性を有することが多いため、ルチルの含有率が高くなると十分な光触媒活性を得ることができない。 The crystal structure of the titanium oxide particles constituting the titanium oxide aggregate of the present invention is determined to be contained by the peak assignment in an X-ray diffraction pattern obtained by continuously scanning Cu Cu radiation using a Cu bulb as a radiation source. In the crystal phase, the intensity ratio (rutile / anatase) of the strongest line of the peak attributed to rutile and anatase is 0.5 or less, preferably 0.3 or less. Anatase often has a higher photocatalytic activity empirically than rutile, so that when the content of rutile is high, sufficient photocatalytic activity cannot be obtained.
また、上記Ｘ線回折パターンにおいてアナターゼの結晶面（１０１）に帰属されるピークの半値幅２θが１．０°以下であり、好ましくは０．９°以下である。ピークの半値幅２θが大きいと結晶性が低く、欠陥を多く含むためこれが電子とホールの再結合中心として働き、十分な光触媒活性を得ることができない。 Further, in the X-ray diffraction pattern, the half width 2θ of the peak attributed to the crystal plane (101) of anatase is 1.0 ° or less, preferably 0.9 ° or less. If the half width 2θ of the peak is large, the crystallinity is low and the crystal contains many defects, so that it acts as a recombination center between electrons and holes, and it is not possible to obtain sufficient photocatalytic activity.
本発明の酸化チタン凝集体の比表面積は、好ましくは５ｍ２／ｇ以上、より好ましくは７ｍ２／ｇ以上である。比表面積が大きいと電子励起により生じた電子とホールの酸化チタン表面への拡散距離が短くなり、またラジカル種生成反応と有機物分解反応の反応面積が増加して光触媒活性が向上する。 The specific surface area of the titanium oxide aggregate of the present invention is preferably 5 m 2 / g or more, more preferably 7 m 2 / g or more. When the specific surface area is large, the diffusion distance of electrons and holes generated by the electronic excitation to the titanium oxide surface is shortened, and the reaction area of the radical species generation reaction and the organic matter decomposition reaction is increased, thereby improving the photocatalytic activity.
また、本発明の酸化チタン凝集体は、リン酸カルシウム化合物由来のリンを含んでもよい。このリン成分は、後述する製造方法で使用するリン酸カルシウム化合物粒子に由来するものであり、リン酸カルシウム化合物粒子を溶解除去する酸処理工程の条件を調整することにより、凝集体内部にリン酸カルシウム化合物粒子の一部やリン酸基を残すことができる。これにより、光触媒活性の向上効果が期待できる。 Moreover, the titanium oxide aggregate of the present invention may contain phosphorus derived from a calcium phosphate compound. This phosphorus component is derived from the calcium phosphate compound particles used in the production method described below, and by adjusting the conditions of the acid treatment step of dissolving and removing the calcium phosphate compound particles, a part of the calcium phosphate compound particles is contained inside the aggregate. And phosphate groups can be left. Thereby, the effect of improving the photocatalytic activity can be expected.
そのメカニズムは必ずしも明らかではないが、例えば、凝集体内部に部分的に含まれるアパタイトなどのリン酸カルシウム化合物が反応中間生成物を吸着して酸化チタンの被毒を抑制することなどが考えられる。また、酸化チタン粒子の表面がリン酸基により修飾され、リンの電気陰性度により酸化チタンの表面電荷及び固体酸性が触媒反応に好適になることなどが考えられる。 Although the mechanism is not always clear, for example, it is conceivable that a calcium phosphate compound such as apatite partially contained in the aggregate adsorbs the reaction intermediate product and suppresses the poisoning of titanium oxide. It is also conceivable that the surface of the titanium oxide particles is modified with a phosphoric acid group, and the surface charge and solid acidity of the titanium oxide are suitable for a catalytic reaction due to the electronegativity of phosphorus.
凝集体に含まれるリンとチタンの重量比（Ｐ／Ｔｉ）は、大きいとリン酸カルシウム化合物やリン酸基による光触媒活性の向上効果が高くなり、小さいと酸化チタンの割合が増えて露出表面積が大きくなり高い光触媒活性が得られるため、０．００１〜０．１００の範囲が好ましく、０．００５〜０．０３０の範囲がより好ましい。 When the weight ratio (P / Ti) of phosphorus and titanium contained in the aggregate is large, the effect of improving the photocatalytic activity by the calcium phosphate compound or the phosphate group becomes high, and when the weight ratio is small, the proportion of titanium oxide increases and the exposed surface area increases. In order to obtain high photocatalytic activity, a range of 0.001 to 0.100 is preferable, and a range of 0.005 to 0.030 is more preferable.
酸化チタン凝集体の２次粒子としての球相当径の体積平均値は、大きいと通常のナノ粒子凝集体と比較して、ハンドリング性、人体有害性、回収性、嵩密度等の点で大きな改善につながる。一方、小さいと拡散経路が短くなり光触媒活性の向上につながる。１０〜２００μｍの範囲が好ましく、３０〜１００μｍの範囲がより好ましい。なお、球相当径の体積平均値とは、凝集体粒子を同一体積の球体と仮定してその球体の径に換算し、その体積分布データから求めた平均径を意味する。 If the volume average of the equivalent spherical diameter of the secondary particles of the titanium oxide aggregate is large, it is significantly improved in handling properties, harmfulness to the human body, recoverability, bulk density, etc., as compared with ordinary nanoparticle aggregates. Leads to. On the other hand, if it is small, the diffusion path becomes short, leading to improvement in photocatalytic activity. The range is preferably from 10 to 200 μm, more preferably from 30 to 100 μm. In addition, the volume average value of the equivalent sphere diameter means the average diameter obtained by assuming that the aggregated particles are spheres of the same volume, converting them into the diameter of the sphere, and obtaining the volume distribution data.
次に、本発明の酸化チタン凝集体の製造方法は、リン酸カルシウム化合物粒子を酸化チタン前駆体中に分散させながら酸化チタンを析出する工程と、得られた酸化チタン−リン酸カルシウム化合物複合体を６００℃以上の温度で焼成する工程と、得られた焼成体を酸で処理してリン酸カルシウム化合物を溶解する工程と、を含んでいる。 Next, the method for producing a titanium oxide aggregate of the present invention comprises the steps of: depositing titanium oxide while dispersing calcium phosphate compound particles in a titanium oxide precursor; and heating the obtained titanium oxide-calcium phosphate compound complex at 600 ° C. or higher. And a step of treating the obtained fired body with an acid to dissolve the calcium phosphate compound.
リン酸カルシウム化合物を用いることによって、従来法においてテンプレート材（焼成や溶解により除去して細孔を形成するために用いられる材料）として多く用いられてきた界面活性剤やラテックス粒子等の有機物では不可能であった、６００℃以上での高温焼成が可能となる。 By using a calcium phosphate compound, organic substances such as surfactants and latex particles, which have been widely used as a template material (a material used for forming pores by removing by baking or dissolving) in the conventional method, are impossible. High temperature firing at 600 ° C. or higher is possible.
使用するリン酸カルシウム化合物としては、リン酸一カルシウム、リン酸三カルシウム、リン酸四カルシウム、リン酸八カルシウム、ピロリン酸カルシウム、リン酸水素カルシウム（モネタイト）、リン酸水素カルシウム二水和物（ブルッシャイト）、アパタイト類、アモルファスリン酸カルシウムなどが挙げられる。中でも、粒子径と粒子形態の制御性の観点から、モネタイト、ブルッシャイト及びアパタイト類が好ましい。なお、これらの化合物は無水物又は水和物のいずれでもよい。 As the calcium phosphate compound to be used, monocalcium phosphate, tricalcium phosphate, tetracalcium phosphate, octacalcium phosphate, calcium pyrophosphate, calcium hydrogenphosphate (monetite), calcium hydrogenphosphate dihydrate (bruschite) , Apatites, amorphous calcium phosphate and the like. Above all, monetite, brushite and apatite are preferable from the viewpoint of controllability of particle diameter and particle morphology. These compounds may be either anhydrides or hydrates.
アパタイト類としては、ハイドロキシアパタイト、フルオロアパタイト、クロロアパタイト、炭酸アパタイトなどが挙げられ、酸化チタンとの親和性の観点から、ハイドロキシアパタイトが好ましい。なお、これらのアパタイトはその構成元素や官能基の一部が、他の元素や官能基で置換又は欠損していてもよい。 Examples of apatites include hydroxyapatite, fluoroapatite, chloroapatite, and carbonate apatite, and hydroxyapatite is preferred from the viewpoint of affinity with titanium oxide. In these apatites, some of the constituent elements and functional groups may be substituted or lacked by other elements or functional groups.
リン酸カルシウム化合物粒子の形状は、貫通孔を形成しやすいため、柱状、繊維状、針状等が好ましい。また、リン酸カルシウム化合物粒子の粒径は、貫通孔を形成しやすくするため、長径が１００ｎｍ以上であることが好ましい。 The shape of the calcium phosphate compound particles is preferably columnar, fibrous, acicular, or the like, since through-holes are easily formed. The calcium phosphate compound particles preferably have a long diameter of 100 nm or more in order to facilitate the formation of through holes.
使用する酸化チタン前駆体としては、チタンアルコキシド、チタンのキレート化合物、硫酸チタニル、四塩化チタン、過酸化チタン、硝酸チタンなどが挙げられる。中でもチタンアルコキシドは、安価であり微細な高比表面積の酸化チタン粒子が得られやすいため好ましい。 Examples of the titanium oxide precursor to be used include titanium alkoxide, a chelate compound of titanium, titanyl sulfate, titanium tetrachloride, titanium peroxide, and titanium nitrate. Among them, titanium alkoxide is preferable because it is inexpensive and easily obtains fine titanium oxide particles having a high specific surface area.
チタンアルコキシドとして、チタンテトラエトキシド、チタンテトラノルマルプロポキシド、チタンテトライソプロポキシド、チタンテトラノルマルブトキシド、チタンテトライソブトキシド、チタンテトラターシャルブトキシドなどが挙げられる。効率的な反応速度と反応制御の容易性の観点から、チタンテトラノルマルプロポキシド及びチタンテトライソプロポキシドが好ましい。 Examples of the titanium alkoxide include titanium tetraethoxide, titanium tetra-n-propoxide, titanium tetra-isopropoxide, titanium tetra-n-butoxide, titanium tetra-isobutoxide, and titanium tetra-tert-butoxide. From the viewpoints of an efficient reaction rate and ease of reaction control, titanium tetranormal propoxide and titanium tetraisopropoxide are preferred.
リン酸カルシウム化合物粒子を酸化チタン前駆体中に分散させながら酸化チタンを析出する工程では、酸化チタン前駆体が液体の場合には、その液中に直接分散させてもよく、また分散性の向上や反応速度の調整のために酸化チタン前駆体に溶媒を加えた混合溶液中に分散させてもよい。酸化チタン前駆体が固体の場合には、溶媒を加えて溶解した溶液中に分散させる。
使用する溶媒としては、酸化チタン前駆体を十分に混和又は溶解する無水の有機溶媒であれば特に限定されない。使用する酸化チタン前駆体がチタンアルコキシドの場合には、無水のアルコール系有機溶媒が好ましく、中でも無水エタノールが好ましい。
In the step of depositing the titanium oxide while dispersing the calcium phosphate compound particles in the titanium oxide precursor, when the titanium oxide precursor is a liquid, the titanium oxide precursor may be directly dispersed in the liquid. To adjust the speed, the titanium oxide precursor may be dispersed in a mixed solution obtained by adding a solvent. When the titanium oxide precursor is solid, it is dispersed in a solution in which a solvent is added and dissolved.
The solvent to be used is not particularly limited as long as it is an anhydrous organic solvent that sufficiently mixes or dissolves the titanium oxide precursor. When the titanium oxide precursor to be used is a titanium alkoxide, an anhydrous alcoholic organic solvent is preferable, and absolute ethanol is particularly preferable.
リン酸カルシウム化合物粒子を酸化チタン前駆体中に分散させながら、酸化チタン前駆体の加水分解を進めることにより、リン酸カルシウム化合物粒子の周囲に酸化チタン微粒子が析出する。大気中の水分によっても加水分解は進行するが、必要に応じて水を適量添加してもよい。加水分解の反応条件は、酸化チタン前駆体を十分に加水分解できる効率的な条件であれば特に限定されない。例えば、大気中にて２５〜３０℃の温度で１〜５時間、加水分解する。
上記工程で得られた酸化チタン−リン酸カルシウム化合物複合体は、リン酸カルシウム化合物粒子が凝集した凝集体の周囲に微細な酸化チタンナノ粒子が多数析出し、さらにそれが複数連結した構造をなしている。
By promoting hydrolysis of the titanium oxide precursor while dispersing the calcium phosphate compound particles in the titanium oxide precursor, titanium oxide fine particles precipitate around the calcium phosphate compound particles. Although hydrolysis proceeds by atmospheric moisture, an appropriate amount of water may be added as necessary. The hydrolysis reaction conditions are not particularly limited as long as they are efficient conditions that can sufficiently hydrolyze the titanium oxide precursor. For example, it hydrolyzes at 25-30 degreeC in air | atmosphere for 1-5 hours.
The titanium oxide-calcium phosphate compound complex obtained in the above step has a structure in which a large number of fine titanium oxide nanoparticles are precipitated around an aggregate in which the calcium phosphate compound particles are aggregated, and a plurality of fine titanium oxide nanoparticles are connected.
得られた酸化チタン−リン酸カルシウム化合物複合体は、酸化チタン粒子の結晶性を高めるため、焼成する必要がある。本発明の製造方法では、酸化チタン−リン酸カルシウム化合物複合体の状態で焼成することにより、酸化チタンの相転移や粒成長を抑制しながら高温焼成が可能となり、高アナターゼ含有率及び高結晶性の２つの材料因子のバランスに優れた酸化チタン粒子を得ることができる。 The obtained titanium oxide-calcium phosphate compound complex needs to be fired in order to increase the crystallinity of the titanium oxide particles. In the production method of the present invention, by calcination in the state of the titanium oxide-calcium phosphate compound complex, high-temperature calcination can be performed while suppressing the phase transition and grain growth of titanium oxide. Titanium oxide particles having an excellent balance between the two material factors can be obtained.
そのメカニズムは必ずしも明らかではないが、アパタイトなどのリン酸カルシウム化合物粒子あるいはそれから溶出した成分が酸化チタンナノ粒子間に適度に介在することによって、焼成中の酸化チタンナノ粒子同士の過度の接触を妨げ、相転移や粒成長を抑制する効果につながると考えられる。 Although the mechanism is not always clear, calcium phosphate compound particles such as apatite or components eluted therefrom moderately intervene between the titanium oxide nanoparticles, thereby preventing excessive contact between the titanium oxide nanoparticles during firing and causing phase transition and the like. It is considered that this leads to an effect of suppressing grain growth.
焼成温度は、６００℃以上である。焼成温度が低いと酸化チタンナノ粒子の欠陥を十分に除去することができず、高い光触媒活性を得ることができない。
一方、焼成温度が高すぎると、アナターゼ含有率及び比表面積の低下による影響が結晶性の向上による効果を上回り、光触媒活性が低下する可能性がある。また、工程の経済性も低下する。焼成温度は好ましく１０００℃以下、より好ましくは９００℃以下である。
焼成時間は、欠陥を十分に除去できれば特に限定されず、焼成温度と工程の経済性との兼ね合いで適宜設定される。
The firing temperature is 600 ° C. or higher. If the firing temperature is low, defects of the titanium oxide nanoparticles cannot be sufficiently removed, and high photocatalytic activity cannot be obtained.
On the other hand, if the calcination temperature is too high, the effect due to the decrease in the anatase content and the specific surface area exceeds the effect due to the improvement in crystallinity, and the photocatalytic activity may be reduced. Also, the economics of the process are reduced. The firing temperature is preferably at most 1000 ° C, more preferably at most 900 ° C.
The firing time is not particularly limited as long as the defect can be sufficiently removed, and is appropriately set in consideration of the firing temperature and the economics of the process.
得られた焼成体は、マクロ孔を形成し酸化チタンの露出表面積を高めるため、酸で処理してリン酸カルシウム化合物を溶解除去する必要がある。酸化チタン−リン酸カルシウム化合物複合体からリン酸カルシウム化合物粒子の凝集体が溶解除去されることにより、酸化チタン凝集体を貫通するマクロ孔が形成されると考えられる。 In order to form macropores and increase the exposed surface area of titanium oxide, the obtained fired body needs to be treated with an acid to dissolve and remove the calcium phosphate compound. It is considered that macropores penetrating the titanium oxide aggregate are formed by dissolving and removing the aggregate of calcium phosphate compound particles from the titanium oxide-calcium phosphate compound complex.
なお、酸処理によりリン酸カルシウム化合物を構成するカルシウムは比較的容易に除去されるが、リン酸基は完全に除去されずに凝集体内部に残存しやすい。残存したリン酸基は凝集体を構成する酸化チタン粒子の表面を修飾し、前述の通り、光触媒活性の向上に寄与すると考えられる。 The calcium constituting the calcium phosphate compound is relatively easily removed by the acid treatment, but the phosphate group is not completely removed and tends to remain in the aggregate. It is considered that the remaining phosphate groups modify the surface of the titanium oxide particles constituting the aggregate and contribute to the improvement of the photocatalytic activity as described above.
使用する酸の種類は、塩酸、硫酸及び硝酸等が挙げられる。揮発性が高く酸処理後に酸化チタン表面に残留しにくいため、塩酸が好ましい。
酸の濃度や処理時間は、リン酸カルシウム化合物粒子を所定量（一部又は全部）溶解除去できれば特に限定されず、使用する酸の種類と工程の経済性との兼ね合いで適宜設定される。
なお、酸処理後は得られた凝集体を水洗して酸を除去し乾燥するため、水洗工程及び乾燥工程が必要に応じて追加される。
Examples of the type of acid used include hydrochloric acid, sulfuric acid, and nitric acid. Hydrochloric acid is preferred because it has high volatility and hardly remains on the titanium oxide surface after acid treatment.
The concentration of the acid and the treatment time are not particularly limited as long as the calcium phosphate compound particles can be dissolved and removed in a predetermined amount (part or all), and are appropriately set depending on the type of the acid used and the economics of the process.
After the acid treatment, the obtained aggregate is washed with water to remove the acid and dried, so that a washing step and a drying step are added as necessary.
以下、本発明の酸化チタン凝集体及びその製造方法について、実施例及び比較例を参照して具体的に説明する。なお、本発明はこれらの実施例によって限定されるものではなく、本発明の技術的思想を逸脱しない範囲で種々の変更が可能である。 Hereinafter, the titanium oxide aggregate of the present invention and the method for producing the same will be specifically described with reference to Examples and Comparative Examples. It should be noted that the present invention is not limited by these embodiments, and various changes can be made without departing from the technical idea of the present invention.
［実施例１］
リン酸二水素アンモニウム１．２ｇと硝酸カルシウム四水和物４．１ｇを蒸留水１６０ｍｌに溶解し、水溶液のｐＨが１０になるように２９ｍａｓｓ％のアンモニア水を添加した。大気中室温で３時間撹拌してハイドロキシアパタイト粒子を析出させた後、濾過により固液分離して１１０℃で乾燥した。
[Example 1]
1.2 g of ammonium dihydrogen phosphate and 4.1 g of calcium nitrate tetrahydrate were dissolved in 160 ml of distilled water, and 29 mass% ammonia water was added so that the pH of the aqueous solution became 10. After stirring at room temperature for 3 hours in the air to precipitate hydroxyapatite particles, the mixture was separated into solid and liquid by filtration and dried at 110 ° C.
得られたアパタイト粒子２５０ｍｇをチタンテトライソプロポキシド（和光純薬工業(株)製）５ｇ中に分散させながら、大気中室温で２時間加水分解して酸化チタンを析出させ、前駆体となる酸化チタン−アパタイト複合体を得た。
次いで、得られた複合体を大気中６００℃で焼成した。昇温速度は１０℃／ｍｉｎ、最高温度での保持時間は１時間とした。
その後、得られた焼成体を１ｍｏｌ／ｌの塩酸を用いて室温で５分間、酸処理をしてアパタイトを溶解除去し、遠心分離器を用いて蒸留水で５回水洗して試料を得た。
While dispersing 250 mg of the obtained apatite particles in 5 g of titanium tetraisopropoxide (manufactured by Wako Pure Chemical Industries, Ltd.), the dispersion is hydrolyzed at room temperature in the air for 2 hours to precipitate titanium oxide, thereby oxidizing the precursor. A titanium-apatite composite was obtained.
Next, the obtained composite was fired at 600 ° C. in the air. The heating rate was 10 ° C./min, and the holding time at the highest temperature was 1 hour.
Thereafter, the obtained fired body was subjected to an acid treatment with 1 mol / l hydrochloric acid at room temperature for 5 minutes to dissolve and remove apatite, and washed with distilled water five times using a centrifuge to obtain a sample. .
試料のマクロ孔の形状及びマクロ孔の直径は、走査型電子顕微鏡で観察した画像により確認した。凝集体断面の観察像を図１に示す。試料はナノ粒子から構成される凝集体であり、その内部を略直線的に貫通するマクロ孔や、やや屈曲して貫通するマクロ孔が形成されていた。マクロ孔の直径は１〜５μｍの範囲であった。 The shape of the macropore and the diameter of the macropore of the sample were confirmed by an image observed with a scanning electron microscope. An observation image of the cross section of the aggregate is shown in FIG. The sample was an aggregate composed of nanoparticles, in which macropores penetrating substantially linearly and macropores penetrating slightly bent were formed. The diameter of the macropores was in the range of 1-5 μm.
試料の結晶構造と結晶性は、粉末Ｘ線回析装置（Ｐｈｉｌｉｐｓ社製、Ｘ‘ｐｅｒｔ Ｐｒｏ ＭＰＤ）を用いて分析した。Ｃｕ管球を線源にＣｕＫα線を用いて連続スキャンしたＸ線回折パターンにおいて、帰属された結晶相はアナターゼのみであり、結晶面（１０１）に帰属されるピークの半値幅２θは０．８３°であった。
試料の比表面積は、比表面積測定装置（ユアサアイオニクス(株)製、ＣＨＥＭＢＥＴ−３０００）を用いて測定した。Ｎ２−ＢＥＴ１点法により測定した比表面積は、３３ｍ２／ｇであった。
The crystal structure and crystallinity of the sample were analyzed using a powder X-ray diffractometer (manufactured by Philips, X'pert Pro MPD). In an X-ray diffraction pattern obtained by continuously scanning Cu Cu radiation using a Cu bulb as a radiation source, the assigned crystal phase is only anatase, and the half width 2θ of the peak assigned to the crystal plane (101) is 0.83. °.
The specific surface area of the sample was measured using a specific surface area measurement device (CHEMBET-3000, manufactured by Yuasa Ionics Inc.). The specific surface area measured by the N 2 -BET one-point method was 33 m 2 / g.
試料に含まれるリンとチタンの重量比（Ｐ／Ｔｉ）は、蛍光Ｘ線分析装置（(株)堀場製作所製、ＸＧＴ−５０００）を用いて測定した。重量比（Ｐ／Ｔｉ）は０．０２１であった。
試料の球相当径は、走査型電子顕微鏡の観察像を用いて測定した。２次粒子の球相当径の体積平均値は４０μｍであった。
The weight ratio of phosphorous to titanium (P / Ti) contained in the sample was measured using a fluorescent X-ray analyzer (XGT-5000, manufactured by Horiba, Ltd.). The weight ratio (P / Ti) was 0.021.
The sphere equivalent diameter of the sample was measured using an observation image of a scanning electron microscope. The volume average value of the equivalent spherical diameter of the secondary particles was 40 μm.
試料の光触媒活性は、メチレンブルー色素を分解対象物とした退色試験によって評価した。まず、０．０２ｍＭのメチレンブルー溶液５０ｍｌに得られた試料１０ｍｇを加えた。この溶液を暗所で２４時間撹拌した後、３６５ｎｍのＵＶを０．５ｍＷ／ｃｍ２の強度で照射した。各照射時間でのメチレンブルー濃度を、分光光度計の６６４ｎｍの吸光度から測定した。１次反応と仮定して算出された反応速度定数は０．０１１３ｍｉｎ−１であった。 The photocatalytic activity of the sample was evaluated by a fading test using a methylene blue dye as a decomposition target. First, 10 mg of the obtained sample was added to 50 ml of a 0.02 mM methylene blue solution. After the solution was stirred in the dark for 24 hours, UV of 365 nm was irradiated at an intensity of 0.5 mW / cm 2 . The methylene blue concentration at each irradiation time was measured from the absorbance at 664 nm of the spectrophotometer. The reaction rate constant calculated assuming the first-order reaction was 0.0113 min -1 .
［実施例２］
焼成温度を７００℃とした以外は実施例１と同様の手順で試料を得た。また、実施例１と同様の方法で試料を評価した。走査型電子顕微鏡の観察像によると、試料はナノ粒子から構成される凝集体であり、その内部を貫通するマクロ孔が形成されていた。マクロ孔の直径は１〜５μｍの範囲であった。
[Example 2]
A sample was obtained in the same procedure as in Example 1 except that the firing temperature was 700 ° C. The sample was evaluated in the same manner as in Example 1. According to the observation image of the scanning electron microscope, the sample was an aggregate composed of nanoparticles, and macropores penetrating the inside thereof were formed. The diameter of the macropores was in the range of 1-5 μm.
Ｘ線回折パターンにおいて帰属された結晶相はアナターゼのみであり、結晶面（１０１）に帰属されるピークの半値幅２θは０．４８°であった。Ｎ２−ＢＥＴ１点法により測定した比表面積は１８ｍ２／ｇであった。蛍光Ｘ線分析で測定されたリンとチタンの重量比（Ｐ／Ｔｉ）は０．０１４であり、走査型電子顕微鏡の観察像から測定した２次粒子の球相当径の体積平均値は８２μｍであった。メチレンブルー退色試験において算出された反応速度定数は０．０１２１ｍｉｎ−１であった。 The crystal phase assigned in the X-ray diffraction pattern was only anatase, and the half-width 2θ of the peak assigned to the crystal plane (101) was 0.48 °. The specific surface area measured by the N 2 -BET one-point method was 18 m 2 / g. The weight ratio of phosphorus to titanium (P / Ti) measured by X-ray fluorescence analysis was 0.014, and the volume average value of the equivalent spherical diameter of the secondary particles measured from an image observed with a scanning electron microscope was 82 μm. there were. The reaction rate constant calculated in the methylene blue discoloration test was 0.0121 min -1 .
［実施例３］
焼成温度を８００℃とした以外は実施例１と同様の手順で試料を得た。また、実施例１と同様の方法で試料を評価した。走査型電子顕微鏡の観察像によると、試料はナノ粒子から構成される凝集体であり、その内部を貫通するマクロ孔が形成されていた。マクロ孔の直径は１〜５μｍの範囲であった。
[Example 3]
A sample was obtained in the same procedure as in Example 1 except that the firing temperature was set to 800 ° C. The sample was evaluated in the same manner as in Example 1. According to the observation image of the scanning electron microscope, the sample was an aggregate composed of nanoparticles, and macropores penetrating the inside thereof were formed. The diameter of the macropores was in the range of 1-5 μm.
Ｘ線回折パターンにおいて帰属された結晶相はルチルとアナターゼであり、その最強線の強度比（ルチル／アナターゼ）は０．１であった。結晶面（１０１）に帰属されるピークの半値幅２θは０．３３°であり、Ｎ２−ＢＥＴ１点法により測定した比表面積は９ｍ２／ｇであった。蛍光Ｘ線分析で測定されたリンとチタンの重量比（Ｐ／Ｔｉ）は０．００７であり、走査電子顕微鏡の観察像から測定した２次粒子の球相当径の体積平均値は７６μｍであった。メチレンブルー退色試験において算出された反応速度定数は０．０１３８ｍｉｎ−１であった。 The crystal phases assigned in the X-ray diffraction pattern were rutile and anatase, and the intensity ratio of the strongest line (rutile / anatase) was 0.1. The half value width 2θ of the peak attributed to the crystal plane (101) was 0.33 °, and the specific surface area measured by the N 2 -BET one-point method was 9 m 2 / g. The weight ratio of phosphorus to titanium (P / Ti) measured by X-ray fluorescence analysis was 0.007, and the volume average value of the equivalent spherical diameter of the secondary particles measured from an image observed by a scanning electron microscope was 76 μm. Was. The reaction rate constant calculated in the methylene blue discoloration test was 0.0138 min -1 .
［比較例１］
アパタイト粒子を添加しないこと、および焼成温度を５００℃としたこと以外は実施例１と同様の手順で試料を得た。また、実施例１と同様の方法で試料を評価した。走査型電子顕微鏡の観察像によると、試料はナノ粒子から構成される凝集体でありマクロ孔は認められなかった。
[Comparative Example 1]
A sample was obtained in the same procedure as in Example 1, except that no apatite particles were added and the firing temperature was set at 500 ° C. The sample was evaluated in the same manner as in Example 1. According to the observation image of the scanning electron microscope, the sample was an aggregate composed of nanoparticles and no macropores were observed.
Ｘ線回折パターンにおいて帰属された結晶相はアナターゼのみであり、結晶面（１０１）に帰属されるピークの半値幅２θは０．６６°であった。Ｎ２−ＢＥＴ１点法により測定した比表面積は２８ｍ２／ｇであり、蛍光Ｘ線分析で測定されたリンとチタンの重量比（Ｐ／Ｔｉ）は０．０００であった。メチレンブルー退色試験において算出された反応速度定数は０．００２４ｍｉｎ−１であり、実施例１〜３と比較して低い値であった。 The crystal phase assigned in the X-ray diffraction pattern was only anatase, and the half-width 2θ of the peak assigned to the crystal plane (101) was 0.66 °. The specific surface area measured by the N 2 -BET one-point method was 28 m 2 / g, and the weight ratio of phosphorus to titanium (P / Ti) measured by X-ray fluorescence analysis was 0.000. The reaction rate constant calculated in the methylene blue discoloration test was 0.0024 min −1 , which was lower than those in Examples 1 to 3.
［比較例２］
アパタイト粒子を添加しないこと以外は実施例１と同様の手順で試料を得た。また、実施例１と同様の方法で試料を評価した。走査型電子顕微鏡の観察像によると、試料はナノ粒子から構成される凝集体でありマクロ孔は認められなかった。
[Comparative Example 2]
A sample was obtained in the same procedure as in Example 1 except that no apatite particles were added. The sample was evaluated in the same manner as in Example 1. According to the observation image of the scanning electron microscope, the sample was an aggregate composed of nanoparticles and no macropores were observed.
Ｘ線回折パターンにおいて帰属された結晶相はアナターゼとルチルであり、アナターゼに帰属されるピークの強度は弱く、最強線の強度比はルチル／アナターゼが０．６であった。結晶面（１０１）に帰属されるピークの半値幅２θは０．２８°であった。Ｎ２−ＢＥＴ１点法により測定した比表面積は４ｍ２／ｇであり、蛍光Ｘ線分析で測定されたリンとチタンの重量比（Ｐ／Ｔｉ）は０．０００であった。メチレンブルー退色試験において算出された反応速度定数は０．００５２ｍｉｎ−１であり、実施例１〜３と比較して低い値であった。 The crystal phases assigned in the X-ray diffraction pattern were anatase and rutile, the peak attributed to anatase was weak, and the intensity ratio of the strongest line was 0.6 for rutile / anatase. The half value width 2θ of the peak attributed to the crystal plane (101) was 0.28 °. The specific surface area measured by the N 2 -BET one-point method was 4 m 2 / g, and the weight ratio of phosphorus to titanium (P / Ti) measured by X-ray fluorescence analysis was 0.000. The reaction rate constant calculated in the methylene blue discoloration test was 0.0052 min −1 , which was lower than those in Examples 1 to 3.
［比較例３］
アパタイト粒子を添加しないこと以外は実施例２と同様の手順で試料を得た。また、実施例１と同様の方法で試料を評価した。走査型電子顕微鏡の観察像によると、試料はナノ粒子から構成される凝集体でありマクロ孔は認められなかった。
[Comparative Example 3]
A sample was obtained in the same procedure as in Example 2 except that no apatite particles were added. The sample was evaluated in the same manner as in Example 1. According to the observation image of the scanning electron microscope, the sample was an aggregate composed of nanoparticles and no macropores were observed.
Ｘ線回折パターンにおいて帰属された結晶相はアナターゼとルチルであり、アナターゼに帰属されるピークの強度は弱く、最強線の強度比はルチル／アナターゼが５．３であった。結晶面（１０１）に帰属されるピークの半値幅２θは、アナターゼに帰属されるピークの強度が弱く、算出が不可能であった。Ｎ２−ＢＥＴ１点法により測定した比表面積は３ｍ２／ｇであり、蛍光Ｘ線分析で測定されたリンとチタンの重量比（Ｐ／Ｔｉ）は０．０００であった。メチレンブルー退色試験において算出された反応速度定数は０．００４８ｍｉｎ−１であり、実施例１〜３と比較して低い値であった。 The crystal phases assigned in the X-ray diffraction pattern were anatase and rutile, the intensity of the peak attributed to anatase was weak, and the intensity ratio of the strongest line was 5.3 for rutile / anatase. The half-value width 2θ of the peak attributed to the crystal plane (101) could not be calculated because the intensity of the peak attributed to anatase was weak. The specific surface area measured by the N 2 -BET one-point method was 3 m 2 / g, and the weight ratio of phosphorus to titanium (P / Ti) measured by X-ray fluorescence analysis was 0.000. The reaction rate constant calculated in the methylene blue discoloration test was 0.0048 min −1 , which was lower than those in Examples 1 to 3.
［比較例４］
市販の酸化チタンナノ粒子（石原産業(株)製、ＳＴ−０１）を、いずれの処理もすることなくそのまま用いた。また、実施例１と同様の方法で試料を評価した。走査型電子顕微鏡の観察像によると、試料はナノ粒子から構成される凝集体でありマクロ孔は認められなかった。
[Comparative Example 4]
Commercially available titanium oxide nanoparticles (ST-01, manufactured by Ishihara Sangyo Co., Ltd.) were used without any treatment. The sample was evaluated in the same manner as in Example 1. According to the observation image of the scanning electron microscope, the sample was an aggregate composed of nanoparticles and no macropores were observed.
Ｘ線回折パターンにおいて帰属された結晶相はアナターゼのみであり、結晶面（１０１）に帰属されるピークの半値幅２θは１．７５°であった。Ｎ２−ＢＥＴ１点法により測定した比表面積は３２１ｍ２／ｇであった。蛍光Ｘ線分析で測定されたリンとチタンの重量比（Ｐ／Ｔｉ）は、０．０００であり、走査型電子顕微鏡の観察像から測定した２次粒子の球相当径の体積平均値は４μｍであった。メチレンブルー退色試験において算出された反応速度定数は０．００４８ｍｉｎ−１であり、実施例１〜３と比較して低い値であった。
上記実施例及び比較例の調製条件及び評価結果の概要を、下記表１及び２にまとめて示す。
The crystal phase assigned in the X-ray diffraction pattern was only anatase, and the half value width 2θ of the peak assigned to the crystal plane (101) was 1.75 °. The specific surface area measured by the N 2 -BET one-point method was 321 m 2 / g. The weight ratio of phosphorus to titanium (P / Ti) measured by X-ray fluorescence analysis was 0.000, and the volume average value of the equivalent spherical diameter of the secondary particles measured from the observation image of the scanning electron microscope was 4 μm. Met. The reaction rate constant calculated in the methylene blue discoloration test was 0.0048 min −1 , which was lower than those in Examples 1 to 3.
Tables 1 and 2 below summarize the preparation conditions and evaluation results of the above Examples and Comparative Examples.
上記の結果より、アパタイト粒子を添加した実施例１及び２と、アパタイト粒子を添加しなかった比較例２及び３の比較から、酸化チタンをアパタイトと複合化することにより、焼成に伴うアナターゼからルチルへの相転移と比表面積低下を抑制できることが分かる。また、酸処理でアパタイトを溶解除去することにより、凝集体内部を貫通するマクロ孔が形成されることが分かる。これらの特性や構造が、本発明の高い光触媒活性につながったものと考えられる。 From the above results, a comparison between Examples 1 and 2 in which apatite particles were added and Comparative Examples 2 and 3 in which no apatite particles were added shows that titanium oxide was combined with apatite to convert anatase to rutile during firing. It can be seen that the phase transition to and the decrease in specific surface area can be suppressed. In addition, it can be seen that by dissolving and removing apatite by acid treatment, macropores penetrating the inside of the aggregate are formed. These properties and structures are considered to have led to the high photocatalytic activity of the present invention.
また、実施例１〜３の比較から、焼成温度が高いほどピーク半値幅２θが小さくなり酸化チタン粒子の結晶性が高くなるが、一方で比表面積は低下し８００℃ではルチルが生成することが分かる。８００℃の焼成温度であれば比表面積が低下しルチルが若干生成していても、高温焼成に伴う高結晶性化の寄与が高く、光触媒活性は高いことが分かる。 From the comparison of Examples 1 to 3, the higher the firing temperature, the smaller the peak half-width 2θ and the higher the crystallinity of the titanium oxide particles. I understand. At a firing temperature of 800 ° C., even if the specific surface area is reduced and rutile is slightly generated, the contribution of high crystallinity associated with the high-temperature firing is high and the photocatalytic activity is high.
さらに、実施例１〜３と比較例４の比較から、実施例１〜３の光触媒活性は、市販の酸化チタンナノ粒子（ＳＴ−０１）と比較して２．４〜２．９倍高いことが分かる。さらにその２次粒子径は、同市販品と比較して１０〜２０倍であることが分かる。すなわち本発明により、高ハンドリング性、低人体有害性、高回収性及び高嵩密度と、高光触媒活性とを同時に満たす光触媒材料を提供できることが分かる。 Furthermore, from the comparison between Examples 1 to 3 and Comparative Example 4, the photocatalytic activity of Examples 1 to 3 is 2.4 to 2.9 times higher than that of commercially available titanium oxide nanoparticles (ST-01). I understand. Further, it can be seen that the secondary particle diameter is 10 to 20 times that of the commercial product. That is, it can be seen that the present invention can provide a photocatalytic material that simultaneously satisfies high handling properties, low harmfulness to the human body, high recoverability, high bulk density, and high photocatalytic activity.
本発明の酸化チタン凝集体は、従来の酸化チタンナノ粒子に比べて、ハンドリング性、人体有害性、回収性及び嵩密度が改善され、さらに光触媒活性が向上している。
また、本発明の酸化チタン凝集体の製造方法は、マクロ孔を有し、高アナターゼ含有率及び高結晶性の２つの材料因子のバランスに優れた、高い光触媒活性を有する酸化チタン凝集体を製造することができる。
The titanium oxide aggregate of the present invention has improved handling properties, harmfulness to the human body, recoverability, and bulk density, as well as improved photocatalytic activity, as compared with conventional titanium oxide nanoparticles.
Further, the method for producing a titanium oxide aggregate of the present invention produces a titanium oxide aggregate having macropores, a high anatase content, and a high balance of two material factors of high crystallinity and high photocatalytic activity. can do.
したがって、本発明の酸化チタン凝集体及びその製造方法は、空気浄化材、水浄化材、吸着材、濾材等に関わる環境浄化分野と窯業分野、外装材、内装材、防曇材、塗料材等に関わる建設分野、及び触媒、触媒担体等に関わる化学工業分野において利用され、産業の発展に寄与することが期待される。
Accordingly, the titanium oxide aggregate of the present invention and the method for producing the same can be used in the fields of environmental purification and ceramics related to air purification materials, water purification materials, adsorbents, filter materials, etc., exterior materials, interior materials, anti-fog materials, paint materials, etc. It is expected to contribute to the development of industry by being used in the field of construction related to, and in the field of chemical industry related to catalysts and catalyst carriers.
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