Siloxane Removal from Gases Using Lignite-Enhanced Activated Carbons and Adsorbent Media Used Therefor

Abstract

A method of removing siloxanes from a gas stream includes flowing the gas stream that carries siloxanes through an adsorbent media to remove at least part of the siloxanes from the gas stream, wherein the adsorbent media comprises lignite-based activated carbon. A spent adsorbent media is provided that contains the lignite-based activated carbon through which a gas stream containing siloxanes has been at least partially purified, and which may be regenerated.

1 . A method of removing siloxanes from a contaminated gas stream, comprising flowing the gas stream comprising siloxanes through an adsorbent media to remove at least part of the siloxanes from the gas stream, wherein said adsorbent media comprises lignite-based activated carbon. 
     
     
         2 . The method of  claim 1 , wherein the lignite-based activated carbon has pore sizes and a total pore volume, wherein at least about 25% of the total pore volume is from pore sizes of from 20 Å to 500 Å. 
     
     
         3 - 4 . (canceled) 
     
     
         5 . The method of  claim 1 , wherein the lignite-based activated carbon has a molasses decolorizing efficiency of at least 50. 
     
     
         6 - 7 . (canceled) 
     
     
         8 . The method of  claim 1 , wherein the lignite-based activated carbon has a BET surface area of from about 500 to about 650 m 2 /g. 
     
     
         9 . The method of  claim 1 , wherein the lignite-based activated carbon has a pH greater than 7. 
     
     
         10 . The method of  claim 1 , wherein the lignite-based activated carbon is in powder form or bound form. 
     
     
         11 . The method of  claim 1 , wherein the lignite-based activated carbon is in the form of granular particles, briquettes, or extruded pellets. 
     
     
         12 . (canceled) 
     
     
         13 . The method of  claim 1  wherein the lignite-based activated carbon is steam-activated unwashed lignite. 
     
     
         14 . The method of  claim 1 , wherein the adsorbent media comprises at least about 50 wt. % lignite-based activated carbon. 
     
     
         15 . (canceled) 
     
     
         16 . The method of  claim 1 , wherein the adsorbent media is present as a homogenous bed of the lignite-based activated carbon. 
     
     
         17 . The method of  claim 1 , wherein the adsorbent media comprises a blend of the lignite-based activated carbon and at least one different kind of adsorbent media. 
     
     
         18 - 20 . (canceled) 
     
     
         21 . The method of  claim 17 , wherein the adsorbent media comprises a blend of the lignite-based activated carbon and at least one different kind of activated carbon, and wherein at least one of the lignite-based activated carbon and the at least one different kind of activated carbon are impregnated with at least one impregnant that is a salt, an acid, or base. 
     
     
         22 - 23 . (canceled) 
     
     
         24 . The method of  claim 1 , wherein the flowing of the gas stream through the adsorbent media removes at least about 95 wt. % of the volatile siloxanes from the gas stream. 
     
     
         25 . The method of  claim 1 , wherein the flowing of the gas through the adsorbent media removes at least about 95 wt. % of the volatile siloxanes for a time period that is at least about 2× longer than for adsorbent media containing an equal volume and same bed geometry of bituminous coal-based activated carbon instead of the lignite-based activated carbon. 
     
     
         26 . (canceled) 
     
     
         27 . The method of  claim 1 , wherein the gas stream at the inlet side of the adsorbent media contains from about 1 ppm to about 25 ppm siloxanes, 
     
     
         28 - 38 . (canceled) 
     
     
         39 . The method of  claim 1 , wherein the gas stream comprises landfill gas emissions. 
     
     
         40 . The method of  claim 1 , wherein the gas stream comprises gas emissions from anaerobic digestion. 
     
     
         41 - 48 . (canceled)