Chemistry of inorganic compounds – Carbon or compound thereof – Elemental carbon
Reexamination Certificate
1996-11-27
2002-11-05
Hendrickson, Stuart L. (Department: 1754)
Chemistry of inorganic compounds
Carbon or compound thereof
Elemental carbon
C423S460000, C502S432000
Reexamination Certificate
active
06475461
ABSTRACT:
This is a National stage application of PCT/JP96/00834, filed Mar. 29, 1996.
TECHNICAL FIELD
The present invention relates to a porous carbonaceous material which has micropore and/or sub-micropore structures which are suitable for the adsorption of small molecules such as nitrogen and oxygen, and to a manufacturing method therefor. In addition, the present invention provides a porous carbonaceous material which can be used in applications such as an adsorbing agent for use in separating and refining industrially used gases, and as a material for electrodes of a secondary battery.
BACKGROUND ART
Starting Material for Carbonaceous Materials
As starting materials for carbonaceous materials, carbonized plant and animal material such as lignite, brown coal, anthracite coal, coke, wood charcoal, coconut shell char; any kind of resin such as phenol resin, furan resin, vinylidene chloride copolymer, etc. which have been heat-treated (carbonized) in an atmosphere of inert gas; and the like can be used. In the present invention, these starting materials are called generic carbon compounds, and materials obtained by carbonization of carbon compounds are called carbonized charcoal.
Uses of Carbonaceous Materials
Because carbonaceous materials are chemically inactive, they are used in a wide range of applications such as adsorption agents, catalysts, electrode materials, structural materials for use in machines, etc.; however, these applications are closely related to the structure of the carbon.
That carbon which is referred to as porous carbon has special effects due to the development of pores. For example, using the adsorption phenomena, there are mixture separation and refining actions. In addition, the carbon used in electrical double layer capacitors, the carbon used in lithium secondary batteries, and the like display electrochemical storage effects.
The Structure of Carbonaceous Materials
The structure of the carbonaceous material can take various forms depending on the starting material, and the manufacturing method.
Char and activated carbon obtained by activating char comprise microcrystalline carbon (crystallite), and carbon which takes on a chain structure. When the carbonaceous material is a nongraphitizing carbon, the crystallites take on a structure which is layered in a disorderly manner, and a wide range of pores, from micropores to macropores, are formed in the gaps between these crystallites.
The crystallites are layers of net planes of six membered carbon rings of several parallel layers, and graphite carbon which has a six membered carbon ring structure bonds using hybridized orbitals SP
2
. A net plane comprising six membered ring carbon is called a basic plane.
A graphitizing carbon grows/develops crystallites by means of heating at a high temperature, and finally becomes graphite.
A nongraphitizing carbon and a graphitizing carbon which has not been completely graphitized usually contain unorganized carbon. Unorganized carbon is carbon other than graphite carbon which is chemically bonded to graphite carbon only; carbon which has a chain structure; carbon which is stuck around six membered ring carbon; carbon which is in the periphery (the prism plane) of six membered ring carbon; carbon which is held in cross-linked structures with other six membered carbon rings (crystallites), and the like. Unorganized carbon is bonded with oxygen atoms, hydrogen atoms, and the like in forms such as C—H, C—OH, C—OOH, and C═O; or is in the form of double bonded carbon (—C═C—).
Adsorption Action of Carbon
When pores have a diameter of 0.8 nm or less, they are called sub-micropores, when they have a diameter in the range of 0.8~2 nm, they are called micropores. Pore diameters within these spheres are approximately of the same order as the diameter of adsorbed molecules, and therefore these pores are believed to take part in the adsorption phenomena.
Because present measuring techniques are unable to directly observe the pore structure of pores in the sub-micropore range, the situation at present is such that it is not possible to establish this as a general theory.
It is believed that the quantity of small molecules, such as nitrogen and oxygen, adsorbed is correlated with the degree of development of micropores and/or sub-micropores, and that the extent of the quantity of small molecules, such as nitrogen and oxygen, adsorbed indicates the degree of development of micropores and/or sub-micropores.
Manufacturing Methods for Porous Carbonaceous Material; Activation Treatments
Methods for manufacturing porous carbonaceous material have variously been offered. In the following, representative manufacturing methods will be explained.
As commonly used methods for obtaining porous carbonaceous material, methods are known in which activation treatments are given in oxidizing gases such as steam, carbon dioxide, and air.
In activation treatments, the oxidation/corrosion (the carbon is gasified) of carbon occurs by means of an activating agent. In other words, new pores are formed in the surface of the carbonaceous material, and, in addition, open pores are made even larger. As a result, it is believed that the specific surface area and the pore volume are increased. However, in normal activation treatments, the activation yield (the carbon yield in other treatments) is of the level of 40~80%, and the carbon loss reaches 20~60%. In addition, it is not possible to form pores of a uniform pore diameter.
Here, the activation yield and the carbon yield take the weight of carbon compounds before treatment as 100, and express the weight after treatment.
As an example of steam activation, there is Japanese Patent Application, First Publication, No. Hei 1-242409; as an example of carbon dioxide activation, there is Japanese Patent Application, First Publication, No. Hei 5-132377; as a combination method of air (oxygen) activation with steam and/or carbon dioxide activation, there is Japanese Patent Application, Second Publication, No. Hei 5-49606; and in addition, as an example of activation by means of hydroxides of sodium, potassium, and the like, there is Japanese Patent Application, First Publication, No. Hei 2-97414 (Japanese Patent Application, Second Publication, No. Hei 5-82324).
Manufacturing Methods for Porous Carbonaceous Material; Carbonization of Resin
Methods of manufacturing porous carbonaceous material by means of carbonization of polymeric resins which have specific molecular structures are also known. When decomposing organic substances by carbonization, the carbon re-bonds in such a way as to form an aromatic structure of a six membered ring which is thermally stable. The proportion of components other than carbon contained within the resin starting material is still not clear.
As examples of the carbonization of polymeric resins, there are Japanese Patent Application, Second Publication, No. Sho 60-20322, Japanese Patent Application, First Publication, No. Hei 6-187972, U.S. Pat. No. 4,839,331, U.S. Pat. No. 3,960,768, and the like.
The above-mentioned U.S. Pat. No. 4,839,331 and U.S. Pat. No. 3,960,768 aim to reform the carbonaceous material by reacting sulfur compounds and halogens with polymeric resins beforehand. The present invention aims to reform the carbonaceous material by means of reacting a post-carbonization material (carbonized charcoal) with chlorine.
Manufacturing Methods for Porous Carbonaceous Materials; Others
As a manufacturing method which obtains porous carbonaceous material without making use of an activation treatment, there is Japanese Patent Application, First Publication, No. Hei
4-310209
. This application discloses a way of obtaining an adsorption agent with oxygen selectivity by means of heating coconut shell char, which has been crushed into granules, in an inert gas at 775 up to 900° C. while controlling the heating speed, and maintaining this for 8 hours.
Japanese Patent Application, First Publication, No. Sho 62-108722 discloses a method of forming pores in carbonaceous material by mixing organic metal compounds into a heated polyme
Hayashida Masayoshi
Inui Takashi
Nakamura Akihiro
Ohsaki Takushi
Wakaizumi Akira
Hendrickson Stuart L.
Nippon Sanso Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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