Method of making modified activated carbon

Abstract

An activated carbon substrate which is pre-treated to make an exposed surface of the activated carbon substrate substantially hydrophilic, coated with a carbon precursor to form a coated activated carbon, and then the coated activated carbon substrate is heated to carbonize the carbon precursor to from the modified activated carbon. The modified activated carbon comprises a uniform porous carbon membrane formed on an exposed surface of the activated carbon substrate. The carbon membrane can mediate the absorption and/or adsorption kinetics of the activated carbon substrate. The modified activated carbon, which can be incorporated into one or more components of a cigarette, can selectively remove gaseous constituents from mainstream smoke during smoking.

What is claimed is: 
     
         1 . A modified activated carbon comprising an activated carbon substrate and a uniform porous carbon membrane formed on an exposed surface of the activated carbon substrate. 
     
     
         2 . The modified activated carbon of  claim 1 , wherein the modified activated carbon is in the form of beads, granules or fibers. 
     
     
         3 . The modified activated carbon of  claim 1 , wherein the carbon membrane comprises from about 1 to 150% by weight of the activated carbon substrate. 
     
     
         4 . The modified activated carbon of  claim 1 , wherein the carbon membrane comprises from about 20 to 80% by weight of the activated carbon substrate. 
     
     
         5 . The modified activated carbon of  claim 1 , wherein the carbon membrane has a surface porosity at least 10% different than the surface porosity of the activated carbon substrate. 
     
     
         6 . The modified activated carbon of  claim 1 , wherein the carbon membrane has a mean surface porosity at least 25% less than the mean surface porosity of the activated carbon substrate and/or the modified activated carbon has an average surface area of at least 50 m 2 /g or at least 200 m 2 /g. 
     
     
         7 . The modified activated carbon of  claim 1 , wherein the carbon membrane covers at least 80% of the exposed surface of the activated carbon substrate and/or the carbon membrane has an average thickness having a standard deviation that is less than about 25% of the average thickness. 
     
     
         8 . The modified activated carbon of  claim 1 , wherein the carbon membrane has an average thickness of from about 1 micron to 0.1 mm. 
     
     
         9 . A cigarette comprising activated carbon particles wherein the modified activated carbon particles are dispersed in tobacco cut filler and/or located in a filter element of the cigarette, the activated carbon particles comprising an activated carbon substrate and a uniform porous carbon membrane formed on an exposed surface of the activated carbon substrate. 
     
     
         10 . The cigarette of  claim 9 , wherein the carbon membrane comprises from about 1 to 150% by weight of the activated carbon substrate. 
     
     
         11 . The cigarette of  claim 9 , wherein the carbon membrane comprises from about 20 to 80% by weight of the activated carbon substrate. 
     
     
         12 . The cigarette of  claim 9 , wherein the carbon membrane has a surface porosity at least 10% different than the surface porosity of the activated carbon substrate. 
     
     
         13 . The cigarette of  claim 9 , wherein the carbon membrane has a mean surface porosity at least 25% less than the mean surface porosity of the activated carbon substrate and/or the modified activated carbon has an average surface area of at least 50 m 2 /g or at least 200 m 2 /g. 
     
     
         14 . The cigarette of  claim 9 , wherein the carbon membrane covers at least 80% of the exposed surface of the activated carbon substrate and/or the carbon membrane has an average thickness having a standard deviation that is less than about 25% of the average thickness. 
     
     
         15 . The cigarette of  claim 9 , wherein the carbon membrane has an average thickness of from about 1 micron to 0.1 mm. 
     
     
         16 . The cigarette of  claim 9 , wherein the activated carbon particles are incorporated in filler paper and have an average particle size of 10 to 100 microns. 
     
     
         17 . The cigarette of  claim 9 , wherein the cigarette includes about 10 to about 200 mg of the activated carbon particles. 
     
     
         18 . The cigarette of  claim 9 , wherein the activated carbon substrate is a substrate selected from the group consisting of beads, granules and fibers and/or the activated carbon substrate has an average particle size of from about 100 microns to 5 mm or from about 200 microns to 2 mm. 
     
     
         19 . The cigarette of  claim 9 , wherein the activated carbon substrate has an average pore size of less than about 500 Angstroms, the activated carbon substrate has a pore size distribution comprising greater than about 20% micropores and fewer than about 80% mesopores and/or the activated carbon substrate has an average surface area of greater than 50 m 2 /g or greater than 200 m 2 /g.