Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Inorganic carbon containing
Reexamination Certificate
2002-04-03
2004-01-06
Bell, Mark L. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Inorganic carbon containing
C502S182000, C502S183000, C502S416000, C502S417000, C106S472000, C106S474000, C106S400000, C106S492000
Reexamination Certificate
active
06673738
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photocatalytic active carbon capable of demonstrating a stable deodorizing and adsorbing ability for a prolonged period of time by combining the adsorbing action of active carbon with the decomposing and sterilizing action of a photocatalyst, and in particular to colored photocatalytic active carbon and coloring active carbon including the photocatalytic active carbon, which while maintaining the adsorbing action and the decomposing and sterilizing action, comes to be rich in color variations and capable of improving visual design and handling by subjecting the surface of the active carbon to coloring treatment and/or treatment with a compound having coloring or discoloring properties upon hydration, and to a deodorant and adsorption product using them.
2. Description of the Related Art
Active carbon is carbon whose ability to adsorb gas, pigments etc. has been improved by subjecting a starting material (material of active carbon) such as wood, sawdust, dry-distillated wood, charcoal, coconut shell or lignin to special treatment (activating treatment), and active carbon is the most widely used adsorbent at present in the field of deodorants and adsorption products, such as water purification, deodorants in refrigerators or shoe cupboards, filters in an air cleaners, etc. because of its low price and its high ability to adsorb odor components such as household odors, VOC gas causing sick house, such as formalin, ethyl benzene or xylene, and adsorbed components such as water.
However, the adsorption of such active carbon is non-stationary and governed by adsorption equilibrium, so that once a predetermined amount of adsorbed components and water are adsorbed, the active carbon looses its adsorption ability and comes to be in an inactivated state.
To regenerate the adsorption ability of active carbon in this inactivated state, the active carbon is subjected to heat treatment or treatment with inert gas at high temperatures in order to remove the adsorbed components and water from micropores on the surface of the active carbon.
When adsorbed components are adsorbed strongly into the micropores on the surface of the active carbon, the active carbon is heated at a high temperature of about 500 to 800° C. for several hours thereby carbonizing the adsorbed components, and in the presence of water vapor, these carbonized materials on the surface are gasified by heating at 900 to 1200° C. for several hours, whereby the active carbon is activated for regeneration.
However, these methods of regenerating active carbon are problematic because the regeneration cost is increased due to the necessity for a special regeneration furnace, and the concentration of water vapor, the activating temperature, the activating time etc. in the regeneration furnace are hardly regulated; thus causing a loss in several to several tens % of the adsorption ability every time active carbon is regenerated
Accordingly, these regeneration treatment methods are not used for a deodorant or adsorption product using conventional active carbon, and in almost all cases, the whole of the deodorant or adsorption product, or the active carbon therein, is exchanged with a new one.
However, the active carbon has a relatively high adsorption ability as described above, to reach a saturated state in a short time, and therefore, the active carbon should be exchanged frequently, but this exchange is very troublesome in circumstances where it is actually used.
Further, there is the problem that the active carbon just after activating treatment cannot be visually distinguishable from the one in a saturated state, and thus the time for exchange cannot be judged with the naked eyes, and for this reason and owing to the troublesome operation of exchange, the active carbon is often left even after the time for exchange.
Further, the active carbon is black and thus inferior in design, and thus almost all deodorants or adsorption products using active carbon commercially available at present are devised such that their active carbon cannot be seen from the outside by encapsulating the active carbon in a package or box. Thus this not only makes it further difficult to judge the time of exchange with the naked eyes, but also deprives the active carbon of the opportunity thereof to contact with the air so that the good adsorption ability of the active carbon cannot be sufficiently demonstrated.
These problems seem to be solved by simply coloring the active carbon, but the surface of the active carbon is a mass of carbon onto which a hydrophilic coating is hardly applied, and even if coated with the coating, the active carbon is very poor in coloring because of its original black color, thus making achievement of various color variations is difficult.
The means of decomposing adsorbed components captured in micropores on the surface of active carbon is studied and developed very recently by mixing active carbon with a photocatalyst such as titanium dioxide or by permitting a photocatalyst to be carried via a binder such as an adhesive on the surface of active carbon.
That is, the active carbon mixed with the photocatalyst or having the photocatalyst carried thereon is studied extensively at preset because even if such active carbon reaches saturated with adsorbed components captured in the micropores on the surface of the active carbon, the active carbon can decompose the adsorbed components by the photocatalyst upon irradiation of the active carbon with sunrays or lights containing UV rays from an incandescent lamp, thus regenerating the adsorption ability of the active carbon in order to maintain and secure the adsorption action thereof for a prolonged period of time.
However, when the active carbon and photocatalyst are mixed, the photocatalyst is apart from adsorbed components on the surface of active carbon, thus lowering the action of decomposing the adsorbed components, and the photocatalyst is a powder easily scattered and inferior in handling and recovery, and the scattered photocatalyst scatters UV rays to further lower the decomposition action.
Further, the active carbon and the photocatalyst are hardly mixed because of a difference in specific gravity and particle diameter, and as a result there is the problem that qualities are varied and the desired adsorption and photocatalytic action cannot be achieved.
On the other hand, when the photocatalyst is carried via a binder such as an adhesive on the surface of active carbon, the photocatalyst is embedded in the binder, or the micropores on the surface of active carbon are covered with the binder, and as a result there is the problem that the action of the photocatalyst to decompose the adsorbed components is weakened, and the adsorbing ability of active carbon is reduced, and further there is the problem that the binder itself is subjected to the decomposition action of the photocatalyst and thus exfoliated and released from the surface of the active carbon.
Further, there is the problem that the decomposition action of the photocatalyst is directed to only the adsorbed components based on organic materials so that when water is adsorbed, there is no or less effect.
This adsorbed water can be removed by the simple treatment such as slightly heating active carbon or drying it under sunrays, but as described above, the active carbon even just after activation cannot be distinguished with the naked eyes from the one in a saturated state (i.e. the one having lost the adsorption ability), and therefore, the active carbon after saturated with water is often still left in a refrigerator.
As a result of extensive study for solving the problems described above, the present inventors found that a coating of a photocatalyst is formed and carried by means of vapor deposition on the surface of active carbon, whereby the photocatalyst can be made close to micropores on the surface of active carbon, and by means of vapor deposition without using a binder or the like, a reduction caused by imbedding, in the
Nishimura Motoyoshi
Ueda Toshiya
Bell Mark L.
Hailey Patricia L.
Jordan and Hamburg LLP
K.K. Ueda Shikimono Kojyo
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