JP4570637B2 - Visible light responsive photocatalyst, method for producing the same, and photocatalyst using the same - Google Patents
Visible light responsive photocatalyst, method for producing the same, and photocatalyst using the same Download PDFInfo
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- JP4570637B2 JP4570637B2 JP2007100334A JP2007100334A JP4570637B2 JP 4570637 B2 JP4570637 B2 JP 4570637B2 JP 2007100334 A JP2007100334 A JP 2007100334A JP 2007100334 A JP2007100334 A JP 2007100334A JP 4570637 B2 JP4570637 B2 JP 4570637B2
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- -1 halogen platinum compound Chemical class 0.000 claims description 49
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- QGLKJKCYBOYXKC-UHFFFAOYSA-N nonaoxidotritungsten Chemical compound O=[W]1(=O)O[W](=O)(=O)O[W](=O)(=O)O1 QGLKJKCYBOYXKC-UHFFFAOYSA-N 0.000 description 1
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Description
本発明は可視光の照射下で励起可能な所謂可視光応答型光触媒及びその製造方法に関する。さらには、この可視光応答型光触媒を基材に固定したり、あるいは成形したりした光触媒体に関する。 The present invention relates to a so-called visible light responsive photocatalyst that can be excited under irradiation of visible light and a method for producing the same. Furthermore, the present invention relates to a photocatalyst body in which the visible light responsive photocatalyst is fixed to a base material or molded.
光触媒はそのバンドギャップ以上のエネルギーを持つ波長の光を照射すると励起し、強い触媒活性が発現するものである。特に有機物やＮＯｘなどの一部無機物の酸化・分解力が大きく、エネルギー源として低コストで、環境負荷の非常に小さい光を利用できることから、近年環境浄化や脱臭、防汚、殺菌などへの応用が進められている。また、光触媒が励起するとその表面が親水性になり水との接触角が低下することが見出され、この作用を利用して防曇、防汚などへの応用も進められている。 A photocatalyst is excited when irradiated with light having a wavelength equal to or greater than its band gap, and exhibits strong catalytic activity. In particular, some inorganic substances such as organic substances and NOx have large oxidizing and decomposing power, low cost as an energy source, and light with very little environmental impact can be used. In recent years, it has been applied to environmental purification, deodorization, antifouling, sterilization, etc. Is underway. Further, it has been found that when the photocatalyst is excited, its surface becomes hydrophilic and the contact angle with water decreases, and application to antifogging, antifouling and the like is being promoted utilizing this action.
光触媒としては、酸化物や硫化物などの金属化合物が一般的に用いられているが、高い光触媒活性を有する酸化チタンや酸化亜鉛などは、励起光の波長が４００ｎｍ以下の紫外線領域にあるため、紫外線ランプなど特別な光源が必要であり、利用分野が制限されている。一方、酸化鉄など励起光の波長を可視光部に有するものは光触媒活性が小さく、利用分野が大きく制限されている。 As the photocatalyst, metal compounds such as oxides and sulfides are generally used, but titanium oxide and zinc oxide having high photocatalytic activity are in the ultraviolet region where the wavelength of excitation light is 400 nm or less. Special light sources such as ultraviolet lamps are required, and the field of use is limited. On the other hand, those having a wavelength of excitation light such as iron oxide in the visible light portion have a small photocatalytic activity, and the application field is greatly limited.
そこで、可視光の照射下で充分高い光触媒活性を有する光触媒があれば、紫外線ランプなどの特別な光源が必要なくなり、可視光を多く含む通常の蛍光灯や太陽光などを利用でき、応用分野が拡大するものと考えられる。さらに、紫外線領域の波長で励起可能な光触媒を可視光の照射下でも励起するように処理すれば、紫外線領域のほか、可視光領域の光も有効に使うことができ、光触媒活性をより高めることができると期待されている。このため、可視光の照射下で励起可能な可視光応答型光触媒についての研究が行われている。例えば、酸化チタンなど紫外光領域で光触媒活性が発現する金属酸化物に異種の金属イオンを固溶させたり、前記の金属酸化物の構成成分である金属と酸素との組成比を変えたり、あるいは前記の金属酸化物と酸化鉄など可視光領域で光触媒活性が発現する化合物とを複合させる方法が提案されている。特開2000-262906公報には、平均粒径２ｎｍ以下の白金などの金属微粒子をルチル型二酸化チタン微粒子表面に担持したものを開示している。 Therefore, if there is a photocatalyst having a sufficiently high photocatalytic activity under irradiation of visible light, a special light source such as an ultraviolet lamp is not necessary, and ordinary fluorescent lamps and sunlight that contain a lot of visible light can be used. It is expected to expand. Furthermore, if a photocatalyst that can be excited at a wavelength in the ultraviolet region is treated so that it can be excited even under irradiation with visible light, light in the visible region as well as the ultraviolet region can be used effectively, further enhancing the photocatalytic activity. It is expected to be possible. For this reason, research has been conducted on visible light responsive photocatalysts that can be excited under irradiation of visible light. For example, different metal ions are dissolved in a metal oxide that exhibits photocatalytic activity in the ultraviolet region, such as titanium oxide, the composition ratio of the metal and oxygen that are constituents of the metal oxide is changed, or There has been proposed a method in which the metal oxide is combined with a compound that exhibits photocatalytic activity in the visible light region, such as iron oxide. Japanese Patent Application Laid-Open No. 2000-262906 discloses one in which metal fine particles such as platinum having an average particle diameter of 2 nm or less are supported on the surface of rutile titanium dioxide fine particles.
前記の可視光応答型光触媒では、可視光の照射下での励起が充分に起こり得ず、可視光での光触媒活性が低かったり、光触媒活性が不安定であったりするため、さらなる改良が求められている。しかも、前記の可視光応答型光触媒では、種々の処理により光触媒粒子本来の励起がかえって阻害されてしまい、光触媒粒子に励起光を照射しても、元来の光触媒活性が得られなくなって、処理によってかえって光触媒活性が低下してしまうなどの問題が生じている。このため、本発明は、可視光下で高い光触媒活性を安定して発現する光触媒を提供しようとするものである。また、本発明は、この光触媒を工業的、経済的に有利に製造する方法、並びにこの光触媒を活用しやすくするために、本発明の光触媒を基材に固定したり、成形したりした光触媒体を提供しようとするものである。 In the above visible light responsive photocatalyst, excitation under visible light irradiation cannot occur sufficiently, and the photocatalytic activity under visible light is low or the photocatalytic activity is unstable, so further improvement is required. ing. Moreover, in the visible light responsive photocatalyst, the original excitation of the photocatalyst particles is inhibited by various treatments, and even if the photocatalyst particles are irradiated with excitation light, the original photocatalytic activity cannot be obtained, and the treatment In some cases, the photocatalytic activity is lowered. Therefore, the present invention is intended to provide a photocatalyst that stably exhibits high photocatalytic activity under visible light. The present invention also provides a method for producing the photocatalyst in an industrially and economically advantageous manner, and a photocatalyst obtained by fixing or molding the photocatalyst of the present invention on a substrate in order to facilitate the use of the photocatalyst. Is to provide.
本発明者らは鋭意研究を重ねた結果、ハロゲン化白金化合物を、異方性形状を有する光触媒粒子の表面に担持させれば、可視光の照射下で励起が可能であり、ハロゲン化白金化合物を担持した球状粒子のものと比べても、安定して高い光触媒活性が得られることを見出し、本発明を完成した。 As a result of intensive studies, the present inventors have found that platinum halide compounds can be excited under irradiation of visible light if supported on the surface of photocatalytic particles having an anisotropic shape. The present inventors have found that high photocatalytic activity can be stably obtained even when compared with the spherical particles carrying γ.
本発明は可視光応答型光触媒であって、４００〜８００ｎｍの波長を有する可視光の照射下で優れた光触媒活性を有しており、紫外線ランプなどの特殊な光源を必要としないため、一般家庭用途を中心に幅広い分野で光触媒作用を活用することができる。また、蛍光灯などの室内照明や太陽光でも、ＮＯｘや有機の環境汚染物質などを効果的に分解できるので、本発明の光触媒及びそれを用いた光触媒体は浄化材、脱臭材、防汚材、殺菌材、防曇材として好適なものである。 The present invention is a visible light responsive photocatalyst, has an excellent photocatalytic activity under irradiation of visible light having a wavelength of 400 to 800 nm, and does not require a special light source such as an ultraviolet lamp. Photocatalytic action can be utilized in a wide range of fields, mainly for applications. In addition, NOx and organic environmental pollutants can be effectively decomposed by indoor lighting such as fluorescent lamps and sunlight, so the photocatalyst of the present invention and the photocatalyst using the same are a purifying material, a deodorizing material, and an antifouling material It is suitable as a sterilizing material and anti-fogging material.
本発明は、光触媒粒子が異方性形状を有し、その粒子表面にハロゲン化白金化合物を担持した可視光応答型光触媒である。本発明における可視光応答型光触媒とは、可視光、即ち４００〜８００ｎｍの範囲の波長を有する光の照射により励起が可能であり、光触媒活性を発現する光触媒のことを言う。励起光の波長は、用いる光触媒粒子の種類によって異なり、４５０ｎｍ以下で励起するものもあれば、６００ｎｍ以下、あるいは、８００ｎｍ以下で励起する場合もある。励起の確認については、４００〜８００ｎｍの波長の可視光を光触媒に照射した際の光触媒活性を測定して、少しでも光触媒活性があることを確認できた場合、励起したものとみなしている。光触媒活性の測定方法としては、有機物の分解活性や後述するＮＯｘガスの除去活性、あるいは、水との接触角を測定しても良い。 The present invention is a visible light responsive photocatalyst in which photocatalyst particles have an anisotropic shape and a platinum halide compound is supported on the particle surface. The visible light responsive photocatalyst in the present invention refers to a photocatalyst that can be excited by irradiation with visible light, that is, light having a wavelength in the range of 400 to 800 nm, and exhibits photocatalytic activity. The wavelength of the excitation light varies depending on the type of photocatalyst particles used, and there are some that excite at 450 nm or less, and some that excite at 600 nm or less or 800 nm or less. Regarding confirmation of excitation, when the photocatalytic activity when the photocatalyst is irradiated with visible light having a wavelength of 400 to 800 nm is measured and it can be confirmed that there is even a small amount of photocatalytic activity, it is regarded as excited. As a method for measuring the photocatalytic activity, the decomposition activity of organic matter, the NOx gas removal activity described later, or the contact angle with water may be measured.
一個の一次粒子を最も安定な状態で平面上に静止させ、平面上への投影像を二つの平行線で挟み、その平行線の間隔が最小となるときの距離を粒子の幅または短軸径ｗといい、この２平行線に直角な方向の二つの平行線で粒子を挟むときの距離を粒子の長さまたは長軸径ｌといい、最大安定面に平行な面で挟むときの距離を粒子の高さｈという（ｌ＞ｗ＞ｈ）。立方体や球状の場合はｌ＝ｗ＝ｈであり等方性形状というが、本発明で用いる光触媒粒子は等方性形状ではなく、長軸径ｌが短軸径ｗあるいは高さｈよりも長いものであり、異方性形状を有しているものである。具体的には、一次粒子を電子顕微鏡で観察し、約１０００個の粒子の長軸径の算術平均値、短軸径の算術平均値、必要に応じて高さの算術平均値を求め、その長軸径の算術平均値が短軸径の算術平均値あるいは高さの算術平均値より大きい粒子を異方性形状を有するものとする。一般的に紡錘状粒子、棒状粒子、針状粒子、板状粒子等と呼ばれるものであり、本発明では異方性形状の光触媒粒子を用いることで、その長軸径と同じ従来の球状粒子を光触媒粒子として用いたものより、比表面積が増えるため、ハロゲン化白金化合物を分散させて担持することができ、それによって、光触媒粒子とハロゲン化白金化合物との相互作用が強くなるため、可視光の照射下で強く励起すると推測される。光触媒粒子としては、比表面積が５０〜５００ｍ２／ｇの範囲にある、所謂超微粒子のものが好ましく、５０〜３００ｍ２／ｇの範囲がより好ましい。このような針状の超微粒子は、０．０１〜０．５μｍの範囲の平均長軸径と、０．００１〜０．０５μｍの範囲の平均短軸径とを有しており、中でも軸比（平均長軸径／平均短軸径）が１．５以上の異方性形状の粒子（紡錘状粒子、棒状粒子、針状粒子と呼ばれるもの）が好ましく、１．５〜１０の範囲がより好ましく、２〜７の範囲がさらに好ましい。軸比が１．５以上であれば、可視光下で所望の励起が生じ易く、１．５〜１０の範囲であれば少なくとも所望の光触媒活性が得られ易い。尚、比表面積はＢＥＴ法により測定したものである。 One primary particle is placed on the plane in the most stable state, and the projected image on the plane is sandwiched between two parallel lines.The distance when the distance between the parallel lines is the minimum is the width or minor axis diameter of the particle. The distance when the particle is sandwiched between two parallel lines perpendicular to the two parallel lines is called the particle length or major axis diameter l, and the distance when the particle is sandwiched between the planes parallel to the maximum stable surface. The height of the particle is called h (l>w> h). In the case of a cube or a sphere, l = w = h, which is an isotropic shape, but the photocatalyst particles used in the present invention are not isotropic, and the major axis diameter l is longer than the minor axis diameter w or the height h. It has an anisotropic shape. Specifically, the primary particles are observed with an electron microscope, and the arithmetic average value of the major axis diameter, the arithmetic average value of the minor axis diameter of about 1000 particles, and the arithmetic average value of the height as required are obtained. Particles having an arithmetic average value of the major axis diameter larger than the arithmetic average value of the minor axis diameter or the arithmetic average value of the height have an anisotropic shape. Generally called spindle-shaped particles, rod-shaped particles, needle-shaped particles, plate-shaped particles, etc. In the present invention, by using anisotropic photocatalyst particles, conventional spherical particles having the same major axis diameter can be obtained. Since the specific surface area is larger than that used as the photocatalyst particles, it is possible to disperse and carry the platinum halide compound, thereby strengthening the interaction between the photocatalyst particles and the platinum halide compound. Presumed to be strongly excited under irradiation. The photocatalyst particles, the specific surface area is in the range of 50 to 500 m 2 / g, preferably those of so-called ultra-fine particles, and more preferably in the range of 50 to 300 m 2 / g. Such acicular ultrafine particles have an average major axis diameter in the range of 0.01 to 0.5 μm and an average minor axis diameter in the range of 0.001 to 0.05 μm. Particles having an anisotropic shape (average major axis diameter / average minor axis diameter) of 1.5 or more are preferred (what are called spindle-shaped particles, rod-shaped particles, and needle-shaped particles), and a range of 1.5 to 10 is more preferable. The range of 2-7 is more preferable. If the axial ratio is 1.5 or more, desired excitation is likely to occur under visible light, and if it is in the range of 1.5 to 10, at least desired photocatalytic activity is likely to be obtained. The specific surface area is measured by the BET method.
光触媒粒子には公知の物質を用いることができ、特に励起光の波長が４００ｎｍ以下の紫外線領域にあるものが好ましく、例えば、酸化チタン、酸化亜鉛、酸化タングステンなどの酸化物や、硫化亜鉛などの硫化物を用いることができる。その中でも、酸化チタンは光触媒活性が高いので好ましい。酸化チタンとしては、無水酸化チタン、含水酸化チタン、水和酸化チタン、水酸化チタン、チタン酸などと呼ばれるものを含み、アナターゼ型やルチル型など結晶形には特に制限は無く、不定形であっても良く、それらが混合したものであっても良い。また、光触媒粒子には、その励起に悪影響を与えない程度であれば、Ｖ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｚｎ、Ｒｕ、Ｒｈ、Ｐｄ、Ａｇ、Ａｕから選ばれる１種以上の異種元素または酸化物等の異種元素の化合物が、含まれていても良い。 A known substance can be used for the photocatalyst particles, and those having an excitation light wavelength in the ultraviolet region of 400 nm or less are preferable. For example, oxides such as titanium oxide, zinc oxide, and tungsten oxide, and zinc sulfide are preferable. Sulfides can be used. Among these, titanium oxide is preferable because of its high photocatalytic activity. Titanium oxide includes those called anhydrous titanium oxide, hydrous titanium oxide, hydrated titanium oxide, titanium hydroxide, titanic acid, etc. There are no particular restrictions on crystal forms such as anatase type and rutile type, and they are indefinite. Or they may be mixed. In addition, the photocatalyst particles may be one or more different elements selected from V, Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Ag, and Au, as long as they do not adversely affect the excitation. A compound of a different element such as an oxide may be contained.
本発明の可視光応答型光触媒は、前記の光触媒粒子の表面に、ハロゲン化白金化合物を担持させたものである。担持させるハロゲン化白金化合物は微量であるため、その組成を特定することは難しいが、蛍光Ｘ線分析によってハロゲン元素と白金とが検出されるような化合物であり、本発明ではハロゲン化白金化合物と呼んでいる。このようなハロゲン化白金化合物としては、本出願人の特願2001-39177号に記載しているものを用いることができ、無機系ハロゲン化白金化合物が好ましく、具体的には、ＰｔＣｌ2、ＰｔＣｌ4、ＰｔＣｌ4・2Ｈ2Ｏ、Ｈ2 [Ｐｔ（ＯＨ）2Ｃｌ4]・ｎＨ2Ｏ等の白金塩化物や、ＰｔＢｒ2、ＰｔＢｒ4等の白金臭化物、ＰｔＩ2、ＰｔＩ4等の白金ヨウ化物、ＰｔＦ4等の白金フッ化物などの白金ハロゲン化物またはその水和物、塩化白金酸、塩化白金酸塩、ブロモ白金錯塩、ヨウ化白金酸塩等のハロゲン化白金酸、ハロゲン化白金酸塩またはハロゲン化白金錯塩、それらの水和物が挙げられる。あるいは、ハロゲン化白金化合物と光触媒粒子とが反応し、Ｍ［ＰｔＸｎ］（Ｍ：光触媒粒子、Ｘ：ハロゲン、ｎ＝４または６）で表されるようなハロゲン化白金錯体を形成して、ハロゲン化白金化合物が光触媒粒子表面と強固に結合しているとも考えられる。ハロゲン化白金化合物の中でも塩素元素と白金の化合物である塩化白金化合物は効果が高く好ましい。 The visible light responsive photocatalyst of the present invention is obtained by supporting a platinum halide compound on the surface of the photocatalyst particles. Since the amount of the platinum halide compound to be supported is very small, it is difficult to specify its composition, but it is a compound in which a halogen element and platinum are detected by fluorescent X-ray analysis. In the present invention, I'm calling. As such a platinum halide compound, those described in Japanese Patent Application No. 2001-39177 of the present applicant can be used, and an inorganic platinum halide compound is preferable. Specifically, PtCl 2 , PtCl 4, PtCl 4 · 2H 2 O , H 2 [Pt (OH) 2 Cl 4] · nH 2 O , etc. platinum chlorides and, PtBr 2, PtBr 4 like platinum bromide, PtI 2, PtI 4 like platinum iodide , Platinum halides such as platinum fluoride such as PtF 4 or hydrates thereof, chloroplatinic acid, chloroplatinate, bromoplatinum complex, haloplatinate, etc. Or platinum halide complex salt and those hydrates are mentioned. Alternatively, the platinum halide compound and the photocatalyst particles react to form a halogenated platinum complex represented by M [PtXn] (M: photocatalyst particles, X: halogen, n = 4 or 6). It is also considered that the platinum compound is firmly bonded to the surface of the photocatalyst particles. Among the halogenated platinum compounds, a platinum chloride compound which is a compound of chlorine element and platinum is preferable because of its high effect.
ハロゲン化白金化合物の含有量は、光触媒粒子に対しＰｔ換算で０．０１〜５重量％の範囲が好ましく、０．０１〜１重量％の範囲がより好ましく、０．０１〜０．７重量％の範囲がさらに好ましい。ハロゲン化白金化合物の含有量が０．０１〜５重量％の範囲であれば少なくとも可視光下での高い光触媒活性が得られ易くなるため好ましい。 The content of the platinum halide compound is preferably in the range of 0.01 to 5% by weight, more preferably in the range of 0.01 to 1% by weight, and 0.01 to 0.7% by weight with respect to the photocatalyst particles. The range of is more preferable. If the content of the platinum halide compound is in the range of 0.01 to 5% by weight, at least high photocatalytic activity under visible light is easily obtained, which is preferable.
本発明の可視光応答型光触媒は、前記の光触媒粒子を、媒液中に懸濁させてからハロゲン化白金化合物の水溶液を添加するか、またはハロゲン化白金化合物の水溶液中に光触媒粒子を添加して撹拌すると、吸着作用により、光触媒粒子の表面にハロゲン化白金化合物を含有させることができる。しかし、光触媒粒子とハロゲン化白金化合物とを媒液中で撹拌下、加熱すれば、ハロゲン化白金化合物の歩留まりを高めることができるので好ましい。すなわち、本発明は、光触媒粒子とハロゲン化白金化合物とを媒液中で加熱して、光触媒粒子の表面にハロゲン化白金化合物を担持させる可視光応答型光触媒の製造方法である。光触媒粒子とハロゲン化白金化合物とを媒液中で加熱する温度は、５０〜２５０℃の範囲が好ましく、５０〜１００℃の範囲がより好ましく、７０〜１００℃の範囲が最も好ましい。加熱温度が５０〜２５０℃の範囲であれば少なくともハロゲン化白金化合物の歩留まりが高くなり易いため好ましい。１００℃以上の温度では本発明を適用するには、オートクレーブなどの高温高圧装置を用いて行うことができる。 The visible light responsive photocatalyst of the present invention is obtained by suspending the photocatalyst particles in a medium and then adding an aqueous solution of a platinum halide compound, or adding photocatalyst particles in an aqueous solution of a platinum halide compound. When stirred, a platinum halide compound can be contained on the surface of the photocatalyst particles by an adsorption action. However, it is preferable to heat the photocatalyst particles and the platinum halide compound in a liquid medium while stirring, because the yield of the platinum halide compound can be increased. That is, the present invention is a method for producing a visible light responsive photocatalyst in which a photocatalyst particle and a platinum halide compound are heated in a medium to carry the platinum halide compound on the surface of the photocatalyst particle. The temperature at which the photocatalyst particles and the platinum halide compound are heated in the medium is preferably in the range of 50 to 250 ° C, more preferably in the range of 50 to 100 ° C, and most preferably in the range of 70 to 100 ° C. A heating temperature in the range of 50 to 250 ° C. is preferred because at least the yield of the platinum halide compound tends to be high. In order to apply the present invention at a temperature of 100 ° C. or higher, a high temperature and high pressure apparatus such as an autoclave can be used.
本発明で用いる異方性形状を有する光触媒粒子としては公知の方法で製造されたものを用いることができる。例えば、酸化チタンは、含水酸化チタンを水酸化ナトリウム、炭酸ナトリウム、シュウ酸ナトリウム等の塩基性ナトリウム化合物で処理した後、塩酸で処理する方法が知られている。このような方法で得られた酸化チタンは微粒子であり、所謂紡錘状のものであるため、好ましく用いられる。得られた紡錘状酸化チタン微粒子は、通常行われる手法で濾別、洗浄を行い、光触媒粒子として、ハロゲン化白金化合物を担持する工程に用いることができる。また、得られた紡錘状酸化チタン微粒子を洗浄後、乾燥あるいは焼成して、光触媒粒子として用いることもできる。 As the photocatalyst particles having an anisotropic shape used in the present invention, those produced by a known method can be used. For example, a method is known in which titanium oxide is treated with hydrochloric acid after treating hydrous titanium oxide with a basic sodium compound such as sodium hydroxide, sodium carbonate, or sodium oxalate. Titanium oxide obtained by such a method is a fine particle and is preferably used because it has a so-called spindle shape. The obtained spindle-shaped titanium oxide fine particles can be filtered and washed by a conventional method, and used in a step of supporting a platinum halide compound as photocatalyst particles. The obtained spindle-shaped titanium oxide fine particles can be used as photocatalyst particles after washing or drying or firing.
ハロゲン化白金化合物としては、無機系ハロゲン化白金化合物が好ましく、具体的には、ＰｔＣｌ2、ＰｔＣｌ4、ＰｔＣｌ4・2Ｈ2Ｏ、Ｈ2 [Ｐｔ（ＯＨ）2Ｃｌ4]・ｎＨ2Ｏ等の白金塩化物やＰｔＢｒ2、ＰｔＢｒ4等の白金臭化物、ＰｔＩ2、ＰｔＩ4等の白金ヨウ化物、ＰｔＦ4等の白金フッ化物などの白金ハロゲン化物またはその水和物、塩化白金酸、塩化白金酸塩、ブロモ白金錯塩、ヨウ化白金酸塩等のハロゲン化白金酸、ハロゲン化白金酸塩またはハロゲン化白金錯塩、それらの水和物などを用いることができ、特にハロゲン化白金酸、ハロゲン化白金酸塩またはハロゲン化白金錯塩、それらの水和物などのハロゲン化白金酸化合物が好ましく用いられる。ハロゲン化白金酸化合物として具体的には、塩化白金酸、塩化白金酸塩、ブロモ白金錯塩、ヨウ化白金酸塩などを用いることができ、特に塩化白金酸化合物を用いるのが好ましい。 As the platinum halide compound, an inorganic platinum halide compound is preferable. Specifically, PtCl 2 , PtCl 4 , PtCl 4 .2H 2 O, H 2 [Pt (OH) 2 Cl 4 ] .nH 2 O, etc. platinum chlorides or PtBr 2, PtBr 4 like platinum bromide, platinum iodide, such PtI 2, PtI 4, platinum halide or a hydrate thereof, such as platinum fluoride such as PtF 4, chloroplatinic acid, platinum chloride Halogenated platinic acid such as acid salts, bromoplatinum complex salts, iodinated platinates, halogenated platinates or halogenated platinum complex salts, hydrates thereof, etc. can be used. Halogenated platinic acid compounds such as platinum salts, platinum halide complexes, and hydrates thereof are preferably used. Specific examples of the halogenated platinic acid compound include chloroplatinic acid, chloroplatinate, bromoplatinum complex, and iodoplatinate, and it is particularly preferable to use a chloroplatinate compound.
媒液としては、水、アルコール、トルエンなどの無機系、有機系の液を用いることもできるが、工業的には水が取り扱い易く好ましい。また、媒液に用いる水には加熱前、加熱途中、加熱後に、塩酸、硫酸、硝酸、フッ酸などの酸、あるいはアンモニア、アミン類、水酸化ナトリウムなどのアルカリを添加しても良い。得られた光触媒は粉末とする場合、公知の方法によって洗浄後、濾別、乾燥を行っても良く、必要に応じて粉砕を行っても良い。 As the medium, inorganic or organic liquids such as water, alcohol, and toluene can be used. However, industrially, water is preferable because it is easy to handle. In addition, before, during or after heating, an acid such as hydrochloric acid, sulfuric acid, nitric acid, or hydrofluoric acid, or an alkali such as ammonia, amines, or sodium hydroxide may be added to the water used for the medium. When the obtained photocatalyst is powdered, it may be filtered and dried by a known method, and may be pulverized if necessary.
また、前記の光触媒粒子とハロゲン化白金化合物と担持促進剤とを水などの媒液中で混合するか、または、前記の光触媒粒子とハロゲン化白金化合物とを水などの媒液中で混合し、次いで、担持促進剤を添加するなどして、光触媒粒子とハロゲン化白金化合物と担持促進剤とを媒液中で反応させることでも、本発明の可視光応答型光触媒を製造できる。この方法も、白金化合物の歩留まりを高くできるので、好ましい製造方法の一つである。特に、反応を前記の方法のように、加熱下で行うと、ハロゲン化白金化合物の歩留まりがさらに向上するので、最も好ましい方法である。この方法に用いる光触媒粒子、ハロゲン化白金化合物、媒液については前記のものを用いることができ、加熱条件も前記の条件で行うことができる。 Further, the photocatalyst particles, the platinum halide compound and the loading accelerator are mixed in a medium such as water, or the photocatalyst particles and the platinum halide compound are mixed in a medium such as water. Then, the visible light responsive photocatalyst of the present invention can also be produced by reacting the photocatalyst particles, the halogenated platinum compound and the support accelerator in a liquid medium by adding a support accelerator. This method is also a preferable production method because the yield of the platinum compound can be increased. In particular, when the reaction is carried out under heating as in the above-described method, the yield of the platinum halide compound is further improved, which is the most preferable method. The photocatalyst particles, the halogenated platinum compound, and the liquid medium used in this method can be those described above, and the heating conditions can also be performed under the above conditions.
担持促進剤としては、例えば、水素化ホウ素ナトリウム、硫化水素等の水素化合物、ホルムアルデヒド、アセトアルデヒド等のアルデヒド類、クエン酸、ギ酸等の有機酸、硫化ナトリウム、硫化アンモニウム等の硫黄化合物、亜リン酸、次亜リン酸及びそれらの塩、ヒドラジンなどの還元作用を有する化合物が挙げられ、これらから選ばれる１種を用いるか、または２種以上を組み合わせて用いても良い。担持促進剤の含有量は、適宜設定することができるが、添加するハロゲン化白金化合物中のＰｔ１重量部に対して、０．５〜１０００重量部の範囲が好ましく、１〜５００重量部の範囲がより好ましく、５〜１００重量部の範囲がさらに好ましい。担持促進剤の含有量が、０．５〜１０００重量部の範囲であれば少なくとも充分な効果が得られ易いため好ましい。 Examples of the loading promoter include hydrogen compounds such as sodium borohydride and hydrogen sulfide, aldehydes such as formaldehyde and acetaldehyde, organic acids such as citric acid and formic acid, sulfur compounds such as sodium sulfide and ammonium sulfide, and phosphorous acid. And compounds having a reducing action such as hypophosphorous acid and salts thereof, hydrazine and the like, and one kind selected from these may be used, or two or more kinds may be used in combination. The content of the loading accelerator can be set as appropriate, but is preferably in the range of 0.5 to 1000 parts by weight, preferably in the range of 1 to 500 parts by weight with respect to 1 part by weight of Pt in the added platinum halide compound. Is more preferable, and the range of 5 to 100 parts by weight is more preferable. If the content of the loading accelerator is in the range of 0.5 to 1000 parts by weight, it is preferable because at least a sufficient effect can be easily obtained.
担持促進剤は、光触媒粒子とハロゲン化白金化合物のいずれもが含まれない媒液中、あるいは、光触媒粒子、ハロゲン化白金化合物のどちらか一方が含まれる媒液中、さらには、光触媒粒子、ハロゲン化白金化合物のいずれもが含まれる媒液中のいずれかに添加し、担持促進剤の存在下で、光触媒粒子、ハロゲン化白金化合物を撹拌などの手段で混合することができる。あるいは、担持促進剤は、媒液中で光触媒粒子、ハロゲン化白金化合物を撹拌などの手段で混合した後に添加することもできる。さらには、担持促進剤は、加熱処理を行なう場合、加熱前、加熱途中、加熱終了直後に、光触媒粒子、ハロゲン化白金化合物を含む媒液中に添加したり、加熱前においては光触媒粒子、ハロゲン化白金化合物のいずれもが含まれない媒液中あるいは光触媒粒子、ハロゲン化白金化合物のどちらか一方が含まれる媒液中に添加することができる。 The loading accelerator is contained in a liquid medium containing neither the photocatalyst particles nor the platinum halide compound, or in a liquid medium containing either the photocatalyst particles or the platinum halide compound. Any of the platinum halide compounds can be added to any medium containing the platinum halide compound, and the photocatalyst particles and the platinum halide compound can be mixed by means such as stirring in the presence of the loading accelerator. Alternatively, the loading accelerator can be added after mixing the photocatalyst particles and the platinum halide compound by a means such as stirring in a liquid medium. Furthermore, when the heat treatment is performed, the loading accelerator is added to the liquid catalyst containing the photocatalyst particles and the platinum halide compound before heating, in the middle of heating, or immediately after the heating, or before the heating, It can be added in a liquid medium not containing any of the platinum halide compounds or in a liquid medium containing either the photocatalyst particles or the platinum halide compounds.
担持促進剤を使用すると、担持促進剤とハロゲン化白金化合物とが錯体のような化合物を形成して、光触媒粒子の表面に析出する場合があり、例えば、次亜リン酸を用いた場合、リン元素、ハロゲン元素、白金元素を含有した組成となると考えられ、このような化合物を含めて本発明ではハロゲン化白金化合物と呼ぶ。 When a loading accelerator is used, the loading accelerator and a platinum halide compound may form a complex-like compound and precipitate on the surface of the photocatalyst particles. For example, when hypophosphorous acid is used, It is considered that the composition contains an element, a halogen element, and a platinum element, and such a compound is referred to as a halogenated platinum compound in the present invention.
本発明の可視光応答型光触媒を、光触媒反応に実際に用いる場合、必要に応じて、基材に固定させたり、光触媒を成形・造粒して成形体として用いるのが便利である。基材としては例えば、金属、タイル、ホーロー、セメント、コンクリート、ガラス、プラスチック、繊維、木材、紙などの種々の材質で形成されたものであり、その形状としては板状、波板状、ハニカム状、球状、曲面状など種々の形状のものを用いることができる。このような基材に光触媒を固定するには公知の方法、例えば、光触媒を基材表面に塗布あるいは吹きつけた後、乾燥、焼成する方法、光触媒とバインダとを含む塗液を基材表面に塗布あるいは吹きつけた後、乾燥、必要に応じて加熱する方法などで行うことができる。バインダとしては無機系樹脂、有機系樹脂を用いることができ、光触媒反応により分解され難いバインダ、例えばセメント、コンクリート、石膏、珪酸化合物、シリカ、ケイ素化合物、シリコーン樹脂、フッ素樹脂などのバインダが好ましい。また、光触媒を成形して用いる場合には、必要に応じて粘土、珪藻土、有機系樹脂、無機系樹脂などのバインダと混合した後、任意の形状に成形することができる。 When the visible light responsive photocatalyst of the present invention is actually used for a photocatalytic reaction, it is convenient to fix it to a base material or to form and granulate the photocatalyst to be used as a molded body, if necessary. The base material is formed of various materials such as metal, tile, enamel, cement, concrete, glass, plastic, fiber, wood, paper, etc., and the shape is plate, corrugated, honeycomb Various shapes such as a shape, a spherical shape, and a curved shape can be used. In order to fix the photocatalyst to such a base material, for example, a method of applying or spraying the photocatalyst to the surface of the base material, followed by drying and baking, a coating liquid containing the photocatalyst and a binder is applied to the base material surface. After applying or spraying, it can be performed by drying, heating as necessary. As the binder, an inorganic resin or an organic resin can be used, and a binder that is difficult to be decomposed by a photocatalytic reaction, for example, a binder such as cement, concrete, gypsum, silicic acid compound, silica, silicon compound, silicone resin, and fluorine resin is preferable. Moreover, when shape | molding and using a photocatalyst, after mixing with binders, such as clay, diatomaceous earth, organic resin, and inorganic resin, it can shape | mold into arbitrary shapes.
次に実施例によって本発明をさらに説明するが、これらは本発明を限定するものではない。 The following examples further illustrate the present invention but are not intended to limit the invention.
実施例１
純水０．５リットルに、ヘキサクロロ塩化白金酸６水和物０．６７５ｇ（ＴｉＯ２に対しＰｔとして０．５重量％相当）を添加、撹拌し、平均長軸径６４ｎｍ、平均短軸径１３ｎｍ（軸比４．９）、比表面積１６０ｍ２／ｇの異方性形状を有する紡錘状酸化チタン微粒子５０ｇを添加した後、次いで、次亜リン酸水溶液（５０％水溶液）を１．４４ミリリットル添加し、９０℃で１時間加熱処理を行った。加熱処理後、冷却してから濾過、洗浄し、１１０℃で１昼夜乾燥した後、ライカイ機にて粉砕し、淡黄色を呈した本発明の可視光応答型光触媒粒子（試料Ａ）を得た。
Example 1
To 0.5 liter of pure water, 0.675 g of hexachlorochloroplatinic acid hexahydrate (corresponding to 0.5% by weight as Pt with respect to TiO 2 ) is added and stirred, and the average major axis diameter is 64 nm and the average minor axis diameter is 13 nm. After adding 50 g of spindle-shaped titanium oxide fine particles having an anisotropic shape (axial ratio of 4.9) and specific surface area of 160 m 2 / g, 1.44 ml of hypophosphorous acid aqueous solution (50% aqueous solution) was then added. Then, heat treatment was performed at 90 ° C. for 1 hour. After the heat treatment, it was cooled, filtered, washed, dried at 110 ° C. for one day and night, and then pulverized with a lycaly machine to obtain the visible light responsive photocatalyst particles (sample A) of the present invention having a pale yellow color. .
実施例２
平均長軸径３６ｎｍ、平均短軸径９．５ｎｍ（軸比３．８）、比表面積１９０ｍ２／ｇの異方性形状を有する紡錘状酸化チタン微粒子を用いた以外は、実施例１と同様にして淡黄色を呈した本発明の可視光応答型光触媒粒子（試料Ｂ）を得た。
Example 2
The same as in Example 1 except that spindle-shaped titanium oxide fine particles having an anisotropic shape with an average major axis diameter of 36 nm, an average minor axis diameter of 9.5 nm (axial ratio of 3.8), and a specific surface area of 190 m 2 / g were used. Thus, a visible light responsive photocatalyst particle (sample B) of the present invention having a pale yellow color was obtained.
実施例３
平均長軸径６４ｎｍ、平均短軸径１３ｎｍ（軸比４．９）、比表面積１２０ｍ２／ｇの異方性形状を有する紡錘状酸化チタン微粒子を用いた以外は、実施例１と同様にして淡黄色を呈した本発明の可視光応答型光触媒粒子（試料Ｃ）を得た。
Example 3
Except for using spindle-shaped titanium oxide fine particles having an anisotropic shape with an average major axis diameter of 64 nm, an average minor axis diameter of 13 nm (axial ratio of 4.9), and a specific surface area of 120 m 2 / g, the same as in Example 1 was used. Visible light responsive photocatalyst particles (sample C) of the present invention having a pale yellow color were obtained.
比較例１〜３
実施例１〜３で用いた異方性形状を有する紡錘状酸化チタン微粒子を、それぞれ比較例１〜３（試料Ｄ〜Ｆ）とする。
Comparative Examples 1-3
The spindle-shaped titanium oxide fine particles having an anisotropic shape used in Examples 1 to 3 are referred to as Comparative Examples 1 to 3 (Samples D to F), respectively.
比較例４
異方性形状を有する酸化チタン微粒子に替えて、球状の光触媒酸化チタン粒子（ＳＴ−０１：石原産業製（平均粒子径４．５ｎｍ、比表面積３２０ｍ２／ｇ））を用いた以外は実施例１と同様にして、淡黄色を呈した可視光応答型光触媒粒子（試料Ｇ）を得た。
Comparative Example 4
Example in which spherical photocatalytic titanium oxide particles (ST-01: manufactured by Ishihara Sangyo Co., Ltd. (average particle diameter 4.5 nm, specific surface area 320 m 2 / g)) were used instead of the titanium oxide fine particles having an anisotropic shape. In the same manner as in Example 1, visible light responsive photocatalyst particles (sample G) having a pale yellow color were obtained.
評価１：ＮＯｘ除去率、ＮＯ転化率の評価
１１０℃×３０分間乾燥後、デシケータ中で放冷した試料４ｇを秤量し、４ｃｍ×２０ｃｍのパイレックス(登録商標)ガラス製皿に均一に広げた。次にこの皿を反応装置（図１）内のスペーサー上に、試料が上となるように設置し、試料の表面と石英窓との距離が５ｍｍとなるようにスペーサを調整して、空気が漏れないよう密閉した。次に、この反応装置を図２に示すように接続し、清浄空気で約３．０ｐｐｍに希釈されたＮＯガスを３リットル／分の流速で流入させた。このとき、ＮＯガスは温度が２５℃、標準湿度が５０％となるように予め調整した。
Evaluation 1: Evaluation of NOx removal rate and NO conversion rate After drying at 110 ° C. for 30 minutes, 4 g of the sample allowed to cool in a desiccator was weighed and spread uniformly on a 4 cm × 20 cm Pyrex (registered trademark) glass dish. Next, this dish is placed on the spacer in the reaction apparatus (FIG. 1) so that the sample is on top, the spacer is adjusted so that the distance between the surface of the sample and the quartz window is 5 mm, and the air is Sealed to prevent leakage. Next, this reactor was connected as shown in FIG. 2, and NO gas diluted to about 3.0 ppm with clean air was introduced at a flow rate of 3 liters / minute. At this time, the NO gas was adjusted in advance so that the temperature was 25 ° C. and the standard humidity was 50%.
次いで、反応装置上部より光を照射した。光源として通常の蛍光灯（２５００ルックス：照度計にて測定）と、この蛍光灯の波長が４００ｎｍ未満の微弱紫外線を、ガラスフィルター（Ｙ−４１：旭ガラス製）にてカットしたものを用いた。 Subsequently, light was irradiated from the upper part of the reaction apparatus. As a light source, a normal fluorescent lamp (2500 lux: measured with an illuminometer) and a weak ultraviolet ray having a wavelength of less than 400 nm were cut with a glass filter (Y-41: Asahi Glass). .
反応装置に流入したＮＯガスは、光触媒試料と接触し、反応してＮＯ２ガスとなり、ＮＯ3 −となって固定され除去される。未反応のＮＯガス、生成したＮＯ２ガスは、反応装置出口より外部へ流出する。この時、電磁弁を３分間隔で切り替えることで反応装置入口と出口部分から、ガスの一部を採取し、化学発光式ＮＯｘ分析計（ＭＬ９８４１Ａ：モニターラボ社製）にてＮＯガス濃度及びＮＯｘガス（ＮＯガス、ＮＯ２ガスの総量）濃度を測定した。得られた濃度値から、次式（１）に従ってＮＯｘ除去率を、また、次式（２）に従ってＮＯ転化率を算出した。
式（１）：ＮＯｘ除去率
＝（（ＮＯｘ入口―ＮＯｘ出口）／ＮＯｘ入口 ）× １００ （％）
式（２）：ＮＯ転化率
＝（（ＮＯ入口―ＮＯ出口）／ＮＯ入口 ）× １００ （％）
The NO gas flowing into the reaction apparatus comes into contact with the photocatalyst sample, reacts to become NO 2 gas, becomes NO 3 −, and is fixed and removed. Unreacted NO gas and generated NO 2 gas flow out from the reactor outlet. At this time, by switching the solenoid valve at intervals of 3 minutes, a part of the gas was sampled from the inlet and outlet of the reactor, and the NO gas concentration and NOx were measured with a chemiluminescent NOx analyzer (ML9841A, manufactured by Monitor Lab). The gas (total amount of NO gas and NO 2 gas) concentration was measured. From the obtained concentration value, the NOx removal rate was calculated according to the following equation (1), and the NO conversion rate was calculated according to the following equation (2).
Formula (1): NOx removal rate = ((NOx inlet−NOx outlet) / NOx inlet) × 100 (%)
Formula (2): NO conversion rate = ((NO inlet−NO outlet) / NO inlet) × 100 (%)
前記の方法にしたがって、実施例１〜３及び比較例１〜４の試料Ａ〜ＧのＮＯｘ除去率、ＮＯ転化率を測定した結果を表１に示す。本発明の可視光応答型光触媒は、波長が４００〜８００ｎｍの可視光の照射下での光触媒活性が、高いことがわかった。 Table 1 shows the results of measuring the NOx removal rate and NO conversion rate of Samples A to G of Examples 1 to 3 and Comparative Examples 1 to 4 in accordance with the above method. It was found that the visible light responsive photocatalyst of the present invention has high photocatalytic activity under irradiation with visible light having a wavelength of 400 to 800 nm.
本発明の光触媒を、バインダを用いて基材に固定させたり、粘土を用いて光触媒を成形・造粒して光触媒体としても、可視光の照射下での光触媒活性が高く、安定していることが確認され、しかも、紫外線照射下での光触媒活性も高く、照射する光が有効に使用でき、優れた光触媒活性を有していることを確認した。 The photocatalyst of the present invention is fixed to a base material using a binder, or the photocatalyst is molded and granulated using clay, so that the photocatalyst is high and stable under visible light irradiation. In addition, it was confirmed that the photocatalytic activity under ultraviolet irradiation was high, and the irradiated light could be used effectively and had excellent photocatalytic activity.
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| JPH1015392A (en) * | 1996-07-02 | 1998-01-20 | Natl Inst For Res In Inorg Mater | Photocatalyst for removing organohalogen compound contained in water and method for removing organohalogen compound contained in water |
| JPH1081517A (en) * | 1996-09-04 | 1998-03-31 | Ishihara Sangyo Kaisha Ltd | Superfine titanium oxide and its production |
| JP2000262906A (en) * | 1999-03-19 | 2000-09-26 | Akio Komatsu | Metal-carrying titanium dioxide photocatalyst and method for mass production of the same |
| JP2002239395A (en) * | 2001-02-15 | 2002-08-27 | Ishihara Sangyo Kaisha Ltd | Photocatalyst, method for manufacturing the same and photocatalyst body using the same |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US11452994B2 (en) | 2017-08-08 | 2022-09-27 | Samsung Electronics Co., Ltd. | Method for producing photocatalyst and photocatalyst filter for air cleaning |
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