Abstract:
A smoking article includes a tobacco rod in axial alignment with a filter section with a catalyst bed disposed between the tobacco rod and the filter section. The catalyst bed may be heated from an external portable heating source or may be heated by the internal evolving gases of combustion of the tobacco.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a smoking article which includes a catalyst bed therein and more particularly to a smoking article which reforms the mainstream smoke of a smoking article by heating a selected catalyst disposed within the smoking article. 
     In the combustion of tobacco in a smoking article, many difference gaseous constituents are released during the combustion. Some of these gaseous components are toxic, others are not. Most cigarette products include a cellulose acetate filter on the mouth end of the cigarettes to remove a substantial percentage of the solid particulates as well as the removal of a large quantity of condensing gases evolved from the combustion of the tobacco. It is also become common place to use activated charcoal in combination with a cellulose acetate filter for the removal of noxious gases and particulate materials in the smoke stream. 
     In U.S. Pat. No. 5,657,772 to Duke et al, Duke et al teaches a filter for a smoking article which incorporates particles coated with platinum for reducing selective volatiles which are present in the mainstream smoke in a smoking article. Moreover, in U.S. Pat. No. 5,211,684 to Shannon et al, a smoking article is taught which contains a catalytic composition as part of the fuel element for reducing carbon monoxide in mainstream smoke from combustion of tobacco in a smoking article. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a smoking article which includes a catalytic smoke reformer therein. 
     It is another object of the present invention to provide a smoking article which uses a catalyst as a distinct component of the smoking article which is heated slightly above ambient temperature in order to enhance smoke reformer activity. 
     It is even a further object to use catalytic combustion of whole smoke as the heat source for aerosol formation and thereby generate a chemically simple smoke for a consumer. 
     It is also an object to use a catalyst in a cigarette to combust carbon monoxide. 
     More particularly, the present invention provides a smoking article which includes a tobacco rod in axial alignment with a filter section with a catalyst bed disposed between the tobacco rod and the filter section, the catalyst bed being maintained at a preselected temperature above 100° C. 
     In the present invention, a cooling chamber may be disposed between the catalyst bed and the filter and the catalyst bed may be in heat communication with a heating source, such as a heating pad which circumscribes the catalyst, or the tobacco rod may be provided with a centrally disposed channel therein which extends the longitudinal length of the tobacco rod for providing heating smoke or smoke at an elevated temperature of at least 100° C. as the means for providing heat to the catalyst bed. The portable heating pad usually consists of a self-sustaining solid-solid or a solid-liquid exothermic reactor which is packed in a disposable wrapper that envelopes a catalyst bed. Even further, flavorings may be added to the smoking article and in one particular embodiment may be disposed between the catalyst bed and the filter section. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A better understanding of the invention will be had upon reference to the following description in conjunction with the accompanying drawings in which like numerals refer to like parts throughout the several views and wherein: 
         FIG. 1  is a perspective view of one preferred embodiment of the smoking article of the present invention; 
         FIG. 2  is a cross-sectional side elevation of the smoking article of  FIG. 1 ; 
         FIG. 3  is a cross-sectional view of a second embodiment of the present invention; 
         FIG. 4  is a cross-sectional view of a third embodiment of the present invention; and, 
         FIG. 5  is a cross-sectional view of a fourth embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in  FIGS. 1 and 2 , a smoking article  10  is comprised of a tobacco section  12 , a heated catalysis section  14 , a cooling section  16 , and a filter section  18 . A cigarette wrapper  22  encases tobacco  32  and extends towards the mouth end of the cigarette. Cigarette wrapper  22  also encases a cooling chamber  36  adjacent to the filter section  18 . An external heat source, such as a heating pad  24 , circumscribes the catalyst bed  34 . The portable heating pad  24  generally includes a self-sustaining solid-solid or solid-liquid exothermic reactor packed in a disposable wrapper. The catalyst bed  34  is generally in the form of meshes, honeycombed structures, granules, and the like. The particular catalyst for making up the meshes or honeycombed structures is determined by the specific smoke components which are to be reformed. The ability to alter specific smoke components depends on the nature of the catalyst, the effective surface area of the catalyst, and its surface temperature. For example, oxidation/reduction catalyst reduce NOx and oxide CO. Low temperature CO oxidation catalyst include base and noble metal oxides. Platinum and/or palladium metals and metal alloys coated on metal substrates are usable for oxidation-reduction catalyst. The degree of conversion of the smoke components depends on the specific type catalyst and reaction temperature employed. Depending upon the desired extent of smoke chemistry modification, the catalyst bed may include a plurality of different types of catalysts. 
     In the smoking of a smoking article, as set forth in  FIGS. 1 and 2 , the lighting end or tobacco end of the smoking article  10  is lit and the smoke passes from the tobacco section  12  into the catalyst section  14  which is heated by a heating pad  24  to at least 100° C. and controlled in a desired temperature range wherein selected smoke components reform as they pass through the catalyst bed  34 . The mainstream smoke, including the reformed smoke components, is then cooled in the cooling section  16  prior to entering the filter section  18 . In the filter section  18 , the particulates and condensible materials are removed from the smoke stream prior to entering the mouth of the smoker. 
     In  FIG. 3  is shown a second embodiment of the present invention wherein a smoking article  110  differs from the smoking article  10  in that a flavor section  116  is disposed between the heated catalyst section  14  and the filter section  18 . The flavor section  116  includes a flavor source  136  which may be tobacco or any other flavor source which will be vaporized upon contact with the mainstream smoke which is the by-product of combustion of the tobacco  32  in the tobacco section  12 . 
     In  FIG. 4  is shown a smoking article  210  which differs from the smoking article  10  and  110  of  FIGS. 2 and 3 , respectively, in that the tobacco section  212  is provided with tobacco  232  and a central hollow section  242  which extends from the terminating or lighting end of tobacco section  212  to the catalyst bed  234 . The mainstream smoke from the tobacco section  212  flows through the channel  242  and upon contacting the catalyst bed  234 , catalytic after-burning takes place resulting in the oxidation of CO and reduction of NOx. The quality of the reform smoke depends, however, on the specific catalyst and its temperature. 
     In  FIG. 5  is another embodiment of the present invention. The smoking article  310  is a modification of the smoking article  210  of  FIG. 4  wherein a flavor section  116 , including a flavor source, such as tobacco  136 , is disposed between the catalyst  234  and the filter section  18 . 
     The foregoing detailed description is given primarily for clearness of understanding and no unnecessary limitations are to be understood therefrom for modifications will become obvious to those skilled in the art upon reading this disclosure and may be made without departing from the spirit of the invention and scope of the appended claims.