JP4145674B2 - Oxygen radical-containing calcium aluminate powder and method for producing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to PM (Particulate Matter) combustion catalyst, incineration ash removal catalyst, flue gas denitration catalyst, dioxin decomposition catalyst, oxidation coupling reaction catalyst, other various oxidation catalysts, or exhaust gas purification catalyst in diesel engine exhaust gas, environmental catalysis, air purification, antibacterial, antifungal, insecticide, deodorant, Jomozai, application development, such as moss inhibitors are expected, O ₂ is active oxygen species ^- and O ^- the The present invention relates to a calcium aluminate powder containing oxygen radicals at a high concentration and a method for producing the same.
[0002]
[Prior art]
O ₂ ^- or O ^- oxygen radicals is one of the active oxygen has been known to play an important role in the oxidation process of organic substances and inorganic substances. Extensive research has been conducted on O ₂ ⁻ adsorbed on the solid surface of oxide compounds (see Non-Patent Documents 1 and 2).
[0003]
[Non-Patent Document 1]
J. et al. H. Lunsford, “Catal. Rev.” 8, 135, 1973.
[0004]
[Non-Patent Document 2]
M.M. Che and A.A. J. et al. Tench, “Adv. Catal”, 32, 1, 1983.
[0005]
In these studies, O ₂ by irradiating high-energy radiation such as γ rays oxide compound surface ^- are creating.
[0006]
RO ₂ (R = alkali metal) is known as a crystal having O ₂ ⁻ as a constituent anion. However, since these compounds are easily decomposed at a low temperature of 300 ° C. or lower, they are used as an oxidation catalyst. Can not be used.
[0007]
In 1970, H.C. B. Bartl et al., In 12CaO · 7Al ₂ O ₃ (hereinafter referred to as C ₁₂ A ₇ ) crystal, 2 out of 66 oxygen atoms in a unit cell containing 2 molecules are not included in the network, It claims to exist as “free oxygen” in the existing space in the cage (see Non-Patent Document 3).
[0008]
[Non-Patent Document 3]
H. B. Bartl and T.W. Scheller, “Neuses Jarhrb. Mineral., Monatsh.” 1970, 547.
[0009]
Moreover, Hosono et al. 1 × 10 ¹⁹ / cm ³ in a C ₁₂ A ₇ crystal synthesized by a solid phase reaction in air at a temperature of 1200 ° C. using CaCO ₃ and Al ₂ O ₃ or Al (OH) ₃ as raw materials. the degree of O ₂ ^- that is inclusion found from the measurement of electron spin resonance, part of the free oxygen O ₂ ^- form (non-patent literature have proposed a model that exists in the gauge of 4).
[0010]
[Non-Patent Document 4]
H. Hosono and Y. Abe, “Inorg. Chem.” 26, 1193, 1997.
[0011]
C ₁₂ A ₇ is a stable oxide having a melting point of 1415 ° C. If the amount of O ₂ ^{— included} is increased and reversible uptake and release are possible, it can be used as an oxidation catalyst, antibacterial agent, and the like. It can be expected that the application will be opened.
[0012]
Further, Hosono et al. Examined C ₁₂ A ₇ which includes the O ₂ ⁻ , and used CaCO ₃ , Ca (OH) ₂ or CaO and Al ₂ O ₃ or Al (OH) ₃ as raw materials, and oxygen. In a dry oxidation atmosphere with a partial pressure of 10 ⁴ Pa or more and a water vapor partial pressure of 10 ² Pa or less, firing is performed at 1200 ° C. or more and less than 1415 ° C., and a solid-phase reaction is performed, thereby reducing O ₂ ⁻ and O ⁻ which are active oxygen species to 10 C ₁₂ A ₇ is obtained that is included at a high concentration of ²⁰ / cm ³ or more (see Patent Document 1).
[0013]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-3218.
[0014]
[Problems to be solved by the invention]
However, when C ₁₂ A ₇ containing active oxygen species at a high concentration found by Hosono et al. Is used industrially, there is a problem to be further solved.
[0015]
That is, C ₁₂ A ₇ containing a high concentration of oxygen radicals is converted into PM (Particulate Matter) combustion catalyst, incineration ash removal catalyst, flue gas denitration catalyst, dioxin decomposition catalyst, oxidative coupling reaction catalyst in diesel engine exhaust gas. When applied to various other oxidation catalysts, exhaust gas purification catalysts, environmental purification catalysts, air cleaners, antibacterial agents, antifungal agents, insect repellents, deodorants, algaecides, moss inhibitors, etc. In order to fully exhibit the functions, it is necessary to adopt various forms suitable for each application.
[0016]
When C ₁₂ A ₇ is used in powder form, it is desirable to efficiently reversibly take up and release oxygen radicals. Since reversible uptake and release of oxygen radicals are carried out through the surface of the particles constituting the powder, the surface area of the particles must be as large as possible in order to improve efficiency. For this reason, it is necessary to improve the specific surface area of the C ₁₂ A ₇ powder.
[0017]
As a method for improving the specific surface area of the powder, a method is generally used in which a lump or coarse powder that is the basis of the powder is wet-ground using water as a medium. However, C ₁₂ A ₇ not only reacts with water and releases oxygen radicals, but once reacted with water, it becomes impossible to take in oxygen radicals by any method thereafter.
[0018]
Thus C ₁₂ A ₇ is not forced to ground by a low dry grinding of grinding efficiency, since the stopping less than 10 m 2 / ^g at the maximum specific surface area, to exert the function as such an oxidation catalyst, an antibacterial agent not It was enough.
[0019]
[Means for Solving the Problems]
The present inventors have found that the above-mentioned problems of the C ₁₂ A ₇ powder can be solved only when acetone is used as a medium in the wet pulverization, unlike water as a medium, and the present invention has been achieved.
[0020]
That is, the present invention is a calcium aluminate powder comprising C ₁₂ A ₇ as a main component, containing oxygen radicals of 10 ²⁰ cm ⁻³ or more, and having a specific surface area of 10 m ² / g or more.
[0021]
The present invention also provides a calcium aluminate powder or lump containing C ₁₂ A ₇ as a main component, oxygen radicals of 10 ²⁰ cm ⁻³ or more, and a specific surface area of less than 10 m ² / g in the presence of acetone. An aluminate powder characterized by forming a calcium aluminate powder containing C ₁₂ A ₇ as a main component, containing 10 ²⁰ cm ⁻³ or more of oxygen radicals, and having a specific surface area of 10 m ² / g or more. It is a manufacturing method. Hereinafter, the present invention will be described in more detail.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, as a result of experimentally examining various methods for improving the specific surface area of the oxygen radical-containing calcium aluminate powder by the present inventor, almost no oxygen radicals are released only when wet grinding is performed using acetone as a medium. Moreover, it is based on the discovery that the oxygen radical-containing calcium aluminate can be pulverized to a high specific surface area without impairing the property of taking in oxygen radicals, and the above-mentioned problems of the prior art can be solved at once.
[0023]
The calcium aluminate in the present invention is composed of Ca, Al, and oxygen (O) as main elements, and crystalline 12CaO.7Al ₂ O ₃ (C ₁₂ A ₇ ) whose main mineral phase is crystalline. Other calcium aluminates include 3CaO · Al ₂ O ₃ (C ₃ A), CaO · Al ₂ O ₃ (CA), CaO · 2Al ₂ O ₃ (CA ₂ ), CaO · 6Al ₂ O ₃ (CA ₆ )), but only crystalline C ₁₂ A ₇ has the property of including oxygen radicals at a high concentration of 10 ²⁰ / cm ³ or more.
[0025]
The calcium aluminate used in the present invention can be obtained from various raw materials so as to have the aforementioned composition. Examples of the Ca source material used as the raw material include limestone (CaCO ₃ ), slaked lime (Ca (OH) ₂ ), and quick lime (CaO). Examples of the Al source material include alumina (Al ₂ O ₃ ), aluminum hydroxide (Al (OH) ₃ ), bauxite, and aluminum residual ash. Of these, CaCO ₃ and Al ₂ O ₃ can be particularly preferably used because they are easily available and highly safe.
[0026]
After mixing the raw materials, the oxygen radicals can be 10 ²⁰ / cm ³ by directly causing a solid phase reaction under controlled conditions of atmosphere and temperature, or by maintaining the conditions of controlled atmosphere and temperature after the solid phase reaction. Calcium aluminate can be obtained which can be included at the above high concentration. A specific example of the conditions for controlling the atmosphere and temperature is, for example, a dry oxidation atmosphere having an oxygen partial pressure of 10 ⁴ Pa or more and a water vapor partial pressure of 10 ² Pa or less, and a temperature of 1200 ° C. or more and less than 1415 ° C.
[0027]
The calcium aluminate containing the high-concentration oxygen radicals obtained by the above operation is usually in the form of a lump, but is pulverized as necessary to prepare a powder. At this time, as a pulverizer, a coarse pulverizer such as a stamp mill, a top grinder, a jaw crusher, a roll crusher, a fine pulverizer such as a ball mill, a vibration mill, an attrition mill, etc., pulverized using a pulverizing medium such as a pulverized ball Can be used. However, in order to prevent calcium aluminate from reacting with moisture, pulverization is usually performed in a dry manner.
[0028]
As long as pulverization is carried out dry, oxygen radicals are not released from calcium aluminate, and the property of taking in oxygen radicals is not impaired. However, in dry pulverization, it is impossible to pulverize to a high specific surface area of 10 m ² / g or more. Therefore, the wet pulverization of the present invention is performed. At this time, the wet pulverizer may be any fine pulverizer such as a ball mill, a vibration mill, or an attrition mill. After the pulverization, further filtration, drying and pulverization are performed to prepare the oxygen radical-containing calcium aluminate powder of the present invention.
[0029]
The present inventor considers the reason why acetone is selected as a wet grinding medium in the present invention as follows. Since acetone does not react with calcium aluminate, oxygen radicals are hardly released during pulverization, and the property of taking in oxygen radicals is not impaired. Further acetone low viscosity, it is possible to transmit the momentum of grinding media such as grinding balls without loss efficiently calcium aluminate, is estimated to be possible to ground to high specific surface area of more than 10 m 2 / ^g. The above estimation is supported by the fact that the specific surface area is less than 10 m ² / g when wet pulverization is actually performed using methanol or ethanol having a viscosity higher than that of acetone.
[0030]
As described above, according to the present invention, a powder having a high specific surface area of 10 m ² / g or more can be obtained without impairing the excellent properties of calcium aluminate that includes high concentration oxygen radicals. PM (Particulate Matter) combustion catalyst in gas, incineration ash removal catalyst, flue gas denitration catalyst, dioxin decomposition catalyst, oxidation coupling reaction catalyst, other various oxidation catalysts, exhaust gas purification catalyst, environmental purification catalyst, air cleaner It is preferably used as an antibacterial agent, antifungal agent, insect repellent agent, deodorant agent, algaecide agent, moss inhibitor and the like.
[0031]
【Example】
Hereinafter, the present invention will be further described with reference to Examples and Comparative Examples.
[0032]
(Example 1) After mixing calcium carbonate (CaCO ₃ ) powder and alumina (γ-Al ₂ O ₃ ) powder, it was fired at 1300 ° C for 3 hours in the air to obtain a white powder. After cooling, X-ray diffraction measurement was performed to confirm that the powder was C ₁₂ A ₇ .
[0033]
Further, the powder was molded into a block shape with a mold and fired at 1250 ° C. for 2 hours in a dry oxidizing atmosphere having an oxygen partial pressure of 4 × 10 ⁴ Pa and a water vapor partial pressure of 10 ² Pa. The cooled block was pulverized with a stamp mill for 1 hour and then sieved off using a sieve having an opening of 1 mm. It was 0.9 m < ² > / g when the specific surface area of the obtained powder was measured by the BET 1 point method.
[0034]
This powder was measured ESR spectrum at room temperature and 77K, _{O 2} from the intensity of the respective absorption band ^- ion radicals and O ^- was determined the concentration of ions radicals were respectively 5 × ¹⁰ 20 ^{cm -3} .
[0035]
500 g of this powder, 1500 g of φ10 mm zirconia (ZrO ₂ ) grinding balls and 1 liter of acetone (about 790 g) are filled in a 2 liter polyethylene container, and continuously crushed for 192 hours at 72 revolutions per minute in a ball mill. did. The obtained powder was filtered, dried, and crushed, and then X-ray diffraction measurement was performed to confirm that it was C ₁₂ A ₇ . The _{O 2} to obtain the ESR spectrum from the measured ^- ion radicals and O ^- concentration of ions radicals were each 2 × ¹⁰ 20 ^{cm -3.} Furthermore, it was 15.6 m < ² > / g when the specific surface area was measured by the BET 1 point method.
[0036]
(Example 2) powder 250g of a specific surface area of 0.9 m ² / g in Example 1, alumina .phi.10 mm _(Al 2 O ₃₎ made by grinding balls 700g and acetone 0.5 l (about 390 g), 1-liter alumina The container was filled and pulverized continuously for 96 hours with a vibration mill. The obtained powder was filtered, dried, and crushed, and then X-ray diffraction measurement was performed to confirm that it was C ₁₂ A ₇ . The _{O 2} obtained from ESR spectroscopy ^- ion radicals and O ^- concentration of ions radicals were respectively 3 × ¹⁰ 20 ^{cm -3.} Furthermore, it was 11.8 m < ² > / g when the specific surface area was measured by the BET 1 point method.
[0037]
(Comparative Example 1) A powder obtained by continuous grinding, filtration, drying and crushing with a ball mill in the same manner as in Example 1 except that 1 liter of ethanol (about 795 g) was used instead of acetone. By diffraction measurement, it was confirmed to be C ₁₂ A ₇ . The _{O 2} obtained from ESR spectroscopy ^- ion radicals and O ^- concentration of ions radicals were respectively 3 × ¹⁰ 20 ^{cm -3.} Furthermore, it was 6.7 m < ² > / g when the specific surface area was measured by the BET 1 point method.
[0038]
(Comparative Example 2) Powder obtained by continuous pulverization, filtration, drying and pulverization with a vibration mill in exactly the same manner as in Example 2 except that 0.5 liters of methanol (about 390 g) was used instead of acetone. By X-ray diffraction measurement, it was confirmed to be C ₁₂ A ₇ . The _{O 2} obtained from ESR spectroscopy ^- ion radicals and O ^- concentration of ions radicals were each 2 × ¹⁰ 20 ^{cm -3.} Furthermore, it was 5.2 m < ² > / g when the specific surface area was measured by the BET 1 point method.
[0039]
(Example 3) Thermogravimetric analysis / differential thermal analysis (TG / DTA) measurement was performed on carbon fine powder (manufactured by Denki Kagaku Kogyo Co., Ltd., powdered acetylene black) in the atmosphere, and an exothermic peak appeared at 610 ° C. Since a significant weight reduction was observed at 610 ° C., the combustion temperature of carbon fine powder was set at 610 ° C. After mixing 10 parts by weight of the oxygen radical-containing calcium aluminate powder of Example 1 with 1 part by weight of this carbon fine powder, TG / DTA measurement was performed in the atmosphere. The combustion temperature was 430 ° C.
[0040]
(Comparative Example 3) After mixing 10 parts by weight of the oxygen radical-containing calcium aluminate powder of Comparative Example 1 with 1 part by weight of the carbon fine powder used in Example 3, TG / DTA measurement was performed in the atmosphere. The temperature was 520 ° C.
[0041]
【The invention's effect】
According to the present invention, calcium aluminate containing oxygen radicals at a high concentration can be made into a powder having a high specific surface area without impairing the characteristics. Therefore, PM (Particulate Matter) combustion catalyst in diesel engine exhaust gas, incineration ash Detoxification catalyst, flue gas denitration catalyst, dioxin decomposition catalyst, oxidation coupling reaction catalyst, other various oxidation catalysts, exhaust gas purification catalyst, environmental purification catalyst, air cleaner, antibacterial agent, insecticide, insecticide, deodorant The oxygen radical-containing calcium aluminate powder that is suitably used as an algaecide, moss inhibitor, etc. can be easily provided with high reproducibility, and is very useful industrially.

Claims (2)

A calcium aluminate powder comprising C ₁₂ A ₇ as a main component, containing oxygen radicals of 10 ²⁰ cm ⁻³ or more, and having a specific surface area of 10 m ² / g or more. A powder or lump of calcium aluminate containing C ₁₂ A ₇ as a main component, containing oxygen radicals of 10 ²⁰ cm ⁻³ or more and having a specific surface area of less than 10 m ² / g is pulverized in the presence of acetone to give C ₁₂ A method for producing a calcium aluminate powder, comprising a calcium aluminate powder containing A ₇ as a main component, containing oxygen radicals of 10 ²⁰ cm ^-3 or more and having a specific surface area of 10 m ² / g or more.