Stock material or miscellaneous articles – Structurally defined web or sheet – Honeycomb-like
Reexamination Certificate
2002-01-31
2004-03-02
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Structurally defined web or sheet
Honeycomb-like
C428S408000, C428S036900, C428S188000, C428S454000, C428S474400, C428S484100, C428S364000, C428S532000, C428S702000, C428S703000, C428S439000, C428S440000, C423S414000, C423S449100, C423S44500R, C502S413000, C502S416000, C106S660000, C106S661000, C106S662000, C106S665000, C106S672000, C106S677000, C106S681000, C106S802000, C106S803000, C106S122000, C106S148100, C106S243000, C106S270000, C106S271000, C422S177000, C422S180000, C422S211000, C422S222000
Reexamination Certificate
active
06699561
ABSTRACT:
This application asserts the priority date of German Patent application No. 10104882.3, which was filed on Feb. 1, 2001.
FIELD OF THE INVENTION
The present invention concerns an activated carbon molded or shaped body, referred to hereinafter as a molded body.
The activated carbon molded body may be more particularly for example in honeycomb form and may be used as an adsorption filter.
The invention also concerns uses of the activated carbon molded body.
BACKGROUND OF THE INVENTION
In the area relating to passenger compartment air filtration in motor vehicles, the requirements being made on odor filter systems are becoming increasingly demanding. The available structural space is becoming smaller and smaller and the filtration properties are to be better and better, with as far as possible a further reduction in the air resistance of the filter. A further problem is that the passive systems which are used nowadays can only be viewed as pure odor filter systems. Pollutants such as benzene and toluene, over the service life of the filter, become increasingly concentrated therein and are discharged again as from a certain level of loading in the filter. It is possible to avoid that undesirable side effect within the period of use of such a filter by increasing the amount of sorbents used. That inevitable results in an increase in the amount of structural space required or an increase in air resistance. Both of those are absolutely undesirable for new developments for motor vehicles and for the major part also cannot be implemented from a technical point of view in the present day air conditioning systems. Another alternative would be the premature replacement of a filter of that kind, which however is highly cost-intensive and in addition particularly time-intensive, as the replacement of such a filter generally has to be carried out in a specialist workshop.
A similar problem arises in the area of the tank venting systems for motor vehicles. The available structural space is becoming smaller and smaller but the demands on the filter systems are ever increasing for ecological reasons. Hitherto a reduction in the vapor fuels emitted from a tank has been achieved by the use of additional activated carbon. As there is only a limited structural space available it is not possible to travel too far along that path. That applies in particular if the admissible amount of fuel which passes into the environment within 24 hours has to be reduced to about 20% of the previously involved value, as is required for example in California as from the year 2001.
Many different endeavours have already been undertaken to satisfy the above-indicated requirements. In that respect, the men skilled in the art agree that these technical problems can only be satisfactorily resolved with adsorption filters of honeycomb form, as the honeycomb geometry affords the advantage of a large surface area for contact with a fluid flowing therethrough and only a low pressure drop at the filter.
Therefore, various operating procedures have been set forth, for producing activated carbon molded bodies of that kind involving a honeycomb structure. U.S. Pat. Nos. 4,399,052 and 5,820,967 each disclose honeycomb structures in which a starting material is extruded and then pyrolised. In that case the starting material is a mixture of various constituents, but activated carbon is not contained in the starting material. The honeycombs disclosed admittedly enjoy good abrasion resistance and hardness as well as suitable electrical conductivity for appropriate regeneration, but the mesoporous adsorber structure which is to be endeavoured to provide for tank ventilation cannot be produced with the resins disclosed for production purposes.
U.S. Pat. No. 5,515,063 proposes the production of an activated carbon molded body, without making use of an extrusion process. In this case, the passages in the activated carbon molded body are formed by a passage-forming material. Under pyrolysis conditions, the passage-forming material at least partially evaporates and leaves the passages behind in the honeycomb structure.
U.S. Pat. Nos. 6,097,011 and 4,518,704 disclose activated carbon molded bodies in which activated carbon is applied to a ceramic structure or matrix. In other words, the stability aspect is ensured by the ceramic main body, but the adsorption capability is limited because the total proportion of activated carbon in such activated carbon molded bodies is relatively low.
EP 0 492 081 discloses a honeycomb structure which is produced with the avoidance of a sintering operation at elevated temperatures. Therefore, production of the proposed honeycomb structure involves avoiding the use of clay or similar materials as the starting material, as relatively high temperatures would be required to produce a ceramic support structure. On the other hand, the use of relatively high temperatures for processing the main body of that structure is not possible as that results in cracks and fissures in the honeycomb structure.
Finally, U.S. Pat. No. 5,914,294 discloses a monolithic activated carbon molded body which, besides methyl cellulose, basically does not contain any organic constituents in the initial mixture employed. This has the disadvantage however or requiring relatively high combustion temperatures for producing the honeycomb structure.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an activated carbon shaped or molded body which can be produced more particularly in honeycomb form and can be used as an adsorption filter.
Another object of the present invention is to provide an activated carbon body which is such that it can be produced by a relatively simple operating procedure.
Still another object of the present invention is to provide a use of an activated carbon molded body.
Yet another object of the present invention is to provide a process for the regeneration of an activated carbon molded body, which involves simple implementation with enhanced operational results.
In accordance with the present invention the foregoing and other objects are attained by an activated carbon molded body, more particularly for example in honeycomb form and for example for use as an adsorption filter, which can be obtained from a mixture containing activated carbon, water, novolak powder, clay, cellulose ether, liquid starch, wax, polyacrylamide and soap, by thoroughly mixing the constituents, extruding the mixture to form a monolithic shaped or molded body and cutting same to size, drying the molded body produced and pyrolysis thereof.
In the use aspect the foregoing and other objects are achieved by use of an activated carbon molded body as an adsorption filter.
Furthermore in the regeneration process the foregoing and other objects are attained by a process for the regeneration of an adsorption filter wherein the adsorption filter is subjected to the action of a heating power of between 10 and 35 W and more particularly between 10 and 23 W and a desorption air flow is set to between 0.1 and ≧0.65 m/sec.
The activated carbon molded body in accordance with the invention, after the pyrolysis operation, has an advantageously high activated carbon component of more than 70% by weight, which can afford persuasive efficiency data. Another particularly surprising consideration is the especially good electrical conductivity of the activated carbon body according to the invention, which makes it possible to implement regeneration of an activated carbon molded body which is used as an adsorption filter, by applying an electrical voltage thereto. The specific insulation resistance of the activated carbon molded body according to the invention, in relation to a cube with an edge length of 1 cm and measured between two mutually opposite side faces thereof, is between 0.1 and 5 &OHgr; at a temperature of 23° C.
The mixture of the starting materials from which the item referred to as the green body is produced contains between 30 and 40% by weight of activated carbon, preferably between 32 and 38% by weight and particularly pre
Boss Wendy
Helsa-Werke Helmut Sandler GmbH & Co. KG
Hoffmann & Baron , LLP
Jones Deborah
LandOfFree
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