JP3047011B2 - Carbon-metal composite and method for producing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an active composite material obtained from rice husk, and more particularly, to heating a mixture of rice husk and a specific metal salt under a reducing atmosphere. And a method for producing the same.

(Conventional technology and its problems) Charcoal has been used for a long time to remove unpleasant odors, to filter through ventilation for masks for controlling pathogens, and to filter for sewage disinfection.
It has been used as an adsorbent for gas and liquid purification, and has now become activated carbon. However, due to depletion of timber resources,
The raw material of activated carbon is changing from wood to coconut husks, coal, petroleum, etc., and it is currently dependent on overseas raw materials.

On the other hand, rice husks, which are a by-product of rice husk production, are produced in large quantities in Asia, including Japan, where rice is a staple food, but only a small part of it is used as charcoal. Most are left unused.

Rice husk consists of 71-87% cellulose-based organic matter and 13-29% inorganic matter, and 87-97% by weight of inorganic matter
Is silica. When this is heated in a reducing atmosphere, organic substances such as cellulose are carbonized, and are expected to exhibit a gas and liquid purifying action and the like, similarly to activated carbon.

By the way, when heat-treating a metal salt, it becomes particles of metal oxides and metals according to the processing atmosphere, and these particles show a catalytic action to activate various reactions, adsorb gases, and emit odorous substances and toxic substances. It is well known that it exhibits various useful effects such as detoxification, antibacterial and antifungal effects. In this case, an important issue is how to increase the specific surface area of the particles. Therefore, composites have been prepared by impregnating silica or activated carbon with a large specific surface area with a metal salt solution and heat-treating or performing vacuum deposition, but the preparation operation is complicated, It is difficult for the particles to be uniformly and finely dispersed to a high degree, or even to a high degree, it is easy to cause aggregation or to deteriorate,
To make matters worse, composites in which metal oxides and metal fine particles are highly dispersed as described above have disadvantages such as being extremely expensive with the current technology.

(Means for Solving the Problems) In view of the above situation, the present inventors have focused on the use of very inexpensive rice husks which are produced in large quantities and most of them are left unused.

Rice husks contain a large amount of cellulose with a large number of hydroxyl groups, and the hydroxyl groups firmly capture metal ions in the metal salt solution at the atomic level, and heat-process the resulting dried product. In this case, the trapped metal particles are in a highly dispersed state, are hardly aggregated, and furthermore, it is thought that cellulose can be used as a template to control the structure of a supported metal or the like. As a result of diligent studies on the composite of polished rice and metal, the impregnated porcelain with a metal salt solution, and the dried porcelain are heated under a reducing atmosphere, whereby the surface of the carbonized polished polished metal or metal compound ( It has been found that a composite in which particles of (oxide) are uniformly and finely dispersed can be obtained economically and inexpensively by a simple operation, and based on this finding, the present invention has been completed.

That is, the present invention relates to (1) Fe, Cu, Ag, Ti, Zn and
A carbon-metal composite comprising at least one metal and / or metal oxide selected from the group consisting of Mg and a reduced product of rice flakes supporting the same; , Ag, Ti, Zn and Mg impregnated with at least one solution of a salt of a metal selected from the group, and heated to 300 to 900 ° C. in a reducing atmosphere, thereby producing a carbon-metal composite. Is provided.

 Hereinafter, the present invention will be described in detail.

The metal of the metal salt used in the method for producing a carbon-metal composite of the present invention includes Fe (II) Fe (III), Ag (I
I), Cu (I), Cu (II), Ti (III), Ti (IV), Zn
(II) and Mg (II) (the value in parentheses indicates the valence). There are no particular restrictions on the type of salt, but hydrochloride,
Examples include inorganic salts such as nitrates and sulfates, and monobasic or polybasic organic salts such as acetates, oxalates, and citrates.

These metal salts are brought into contact with the rice husks as a solution dissolved in a solvent, and are absorbed or adsorbed. Any solvent can be used as long as it can dissolve metal salts such as water, alcohols, ketones, and amines. These can be used alone or in combination.

The rice husk containing the metal salt solution is dried by removing the solvent by heating or the like. The dried product is then heated at a relatively low temperature under a reducing atmosphere. The heating temperature is
300-900 ° C. Preferably it is 400-600 degreeC. The heating may be performed while increasing the temperature stepwise.

The heating under the reducing atmosphere may be performed under the condition that the air is shut off as in the case of performing the coal dry distillation, but is preferably performed under a nitrogen atmosphere industrially. In addition, a hydrogen atmosphere is preferable for reducing a metal salt to a metal.

The amount of the metal salt to be mixed is adjusted so that the weight ratio of the residual metal oxide or metal to the carbide after the heat treatment is in the range of 0.01 to 20%, preferably 0.1 to 10%.

(Action) When the rice husk is heated to 300-900 ° C in a reducing atmosphere, the organic substances such as cellulose are carbonized and converted into activated carbon-like substances. At the same time, silica, which is the majority of the inorganic substances contained, is heated during heating. And remains as silica without change. These activated carbon substances and silica have a large specific surface area. The metal salt that has been previously mixed with rice hulls changes to metal oxides or metal particles depending on the type and characteristics of the metal salt upon heating, but it is reduced to the hydroxyl level of cellulose at the atomic level. Because they are trapped, they do not become large particles but are uniformly, finely and highly dispersed on the surface of activated carbon-like substance or silica. In other words, when producing a metal or metal oxide support, only a single heating operation under a reducing atmosphere, the metal or metal oxide is supported on an activated carbon-silica composite having a high specific surface area and a multifunctionality,
As a result, a metal-activated carbon-silica composite exhibiting more multidimensional functions and superior functions can be obtained. Further, in the composite obtained in this way, it is possible to control the size of particles generated from the metal salt. This can be performed more precisely by changing the type and content of the metal salt used, and can be adjusted to any desired size. Further, by controlling the heating conditions, the specific surface area of the composite finally obtained can be changed and adjusted.

(Effect of the Invention) The carbon-metal composite of the present invention in which fine particles of a metal or a metal oxide formed from a metal salt are highly dispersed on the surface of carbonized rice husk has a large surface activity, and can be used as various catalysts or It is a useful active substance for adsorbing and removing odors and harmful substances and for detoxification.

The complex of the present invention is one in which activated carbon-like substances derived from rice husks and particles derived from metals are effective in purifying gases and liquids, but are more specific in addition to the action of absorbing malodorous substances. It is conceivable that it also has properties. For example,
When an iron salt is used, even when heated in a reducing atmosphere, γ-Fe ₂ O
₃ and Fe ₃ O ₄ particles are generated, the magnetic susceptibility is increased, and a material that can be applied to fields in which magnets are applied, such as controlling plant growth (see, for example, Nikkei Sangyo Shimbun March 9, 1989), is obtained.

(Examples) Next, the present invention will be described in more detail based on examples.

EXAMPLE _{1 Fe (NO 3) 3 ·} 9H 2 O 11.2g was dissolved in ethanol 640Cc, added 50g from chaff dried thereto and stirred at room temperature. Ethanol was evaporated while heating, and the reddish brown rice cake was heated at 300 ° C. for 30 minutes and further at 400 ° C. for 1 hour while flowing nitrogen to obtain a black complex.

The specific surface area was 111 m ² / g, and although a small peak of Fe ₂ O ₃ was observed in X-ray diffraction, it was almost amorphous. The measured susceptibility was 7.0 emu / g.

Example 2 A black composite was obtained in the same manner as in Example 1, except that the heating condition was changed to a stepwise heating method of 300 ° C. for 30 minutes, 400 ° C. for 2 hours, and 500 ° C. for 1 hour. The specific surface area of this product is 13
It was 4 m ² / g, and although the peak of Fe ₂ O ₃ was observed in the X-ray diffraction, it was almost amorphous. Measurement of magnetic susceptibility 9.
It was 1 emu / g.

Example 3 In Example 2, water was used instead of ethanol used.
Using 500 cc and the other method was the same to obtain a complex.
The specific surface area of this product was 144 m ² / g, and although a small peak of Fe ₂ O ₃ was observed in X-ray diffraction, it was substantially amorphous. The measured susceptibility was 9.1 emu / g.

Examples 4 to 8 Carbon composites corresponding to each metal were produced in the same manner as in Example 1 except that water was used as a solvent, using the metal salts shown in Table 1.

The obtained products were all confirmed to be amorphous by X-ray diffraction.

Example _{9 Fe (NO 3) 3 ·} 9H 2 O 0.88g, Cu (NO 3) 2 · 6H 2 O 0.5
4 g was dissolved in 500 cc of water, and the same procedure as in Example 1 was carried out, except that 30 g of rice cake was added thereto. The specific surface area of the obtained product was 335 m ² / g, and it was amorphous by X-ray diffraction.

REFERENCE EXAMPLE As a comparative example, a mixture obtained by heating rice husks without mixing a metal salt was used as a comparative example, and together with the product of the present invention obtained in the examples, the ability to adsorb odorous substances was measured. Dimethyl sulfide (750pp
m) and dimethylamine (1150 ppm) were placed in a 1000 cc glass container containing 0.1 g each, and contacted for 5 hours. The quantification was performed by gas chromatography.

 The results are shown in Table 2.

As compared with the comparative example, the examples of the present invention adsorb more malodorous substances, indicating that the adsorption effect is excellent.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Makoto Toba 1-1-1 Higashi, Tsukuba City, Ibaraki Pref., Institute of Chemical Technology, Industrial Technology Institute (72) Inventor Tatsuo Murakami 55 Yokohoonji, Kamiichi-cho, Nakashinagawa-Gun, Toyama Prefecture Fuji Chemical (56) References JP-A-48-93591 (JP, A) JP-A-49 / 53593 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B01J 20/20

Claims (2)

(57) [Claims] The present invention is characterized by comprising at least one kind of metal and / or metal oxide selected from the group consisting of Fe, Cu, Ag, Ti, Zn and Mg, and a reduced form of rice flakes supporting the metal and / or metal oxide. A carbon-metal composite. 2. A method of impregnating moromi with at least one solution of a salt of a metal selected from the group consisting of Fe, Cu, Ag, Ti, Zn and Mg, and heating the solution to 300 to 900 ° C. in a reducing atmosphere. A method for producing a carbon-metal composite.