Sorbent comprising carbon and nitrogen and methods of using the same

Abstract

The present invention relates to sorbents including carbon and nitrogen. In various embodiments, the sorbent can remove mercury from a mercury-containing gas that includes sulfur(VI) such as SO 3 more efficiently than other sorbents. The sorbent can include a graphene edge comprising an active site for mercury oxidation and a nitrogen layer structure including cationic nitrogen atoms, neutral nitrogen atoms, or a combination thereof proximate the active site.

What is claimed is: 
     
         1 . A nitrogen-containing activated carbon sorbent, comprising:
 an activated carbon comprising nitrogen in a surface layer thereof, the activated carbon comprising a core comprising nitrogen, wherein the surface layer has a higher concentration of nitrogen than the core.   
     
     
         2 . The sorbent of  claim 1 , wherein the surface layer of the sorbent comprises a layer at the surface of the sorbent having a thickness of about 0.001% to about 49% of the largest dimension of the sorbent. 
     
     
         3 . The sorbent of claim I, wherein the core of the sorbent comprises about 0.001 wt % to about 6 wt % nitrogen. 
     
     
         4 . The sorbent of  claim 1 , wherein the surface layer of the sorbent comprises about 0.001 wt % to about 80 wt % nitrogen. 
     
     
         5 . The sorbent of  claim 1 , wherein the surface layer comprises cationic nitrogen atoms, neutral nitrogen atoms, or a combination thereof. 
     
     
         6 . The sorbent of claim I, wherein the sorbent is a halogen- or halide-promoted activated carbon. 
     
     
         7 . The sorbent of  claim 6 , wherein the halogen- or halide-promotion comprises promotion with HCl, HBr, HI, Br 2 , Cl 2 , I 2 , BrCl, IBr, ICl, ClF, PBr 3 , PCl 5 , SCl 2 , CuCl 2 , CuBr 2 , Al 2 Br 6 , FeI x  (x=1, 2, 3, or 4), FeBr y  (y=1, 2, 3, or 4), FeCl z  (z=1, 2, 3, or 4), MnBr 2 , MnCl 2 , NiBr 2 , NiCl 2 , NiI 2 , ZnBr 2 , ZnCl 2 , ZnI 2 , NH 4 Br, NH 4 Cl, NH 4 I, NH 4 F, (NH 4 ) 2 SO 4 , H 2 SO 4 , NH 4 SO 4 H, (NH 4 ) 2 S 2 O 3 , FeNH 4 (SO 4 ) 2 , Fe(NH 4 ) 2 (SO 4 ) 2 , FeNH 4 Br 4 , FeNH 4 Cl 4 , AlNH 4 (SO 4 ) 2 , NaBr, NaCl, NaI, Br − , Cl − , I − , KI, KCl, LiCl, LiBr, AgCl, AgBr, CHI 3 , CH 3 Br, AuBr, MgBr 2 , MgCl 2 , CaI 2 , CaBr 2 , CaCl 2 , hydrates thereof, or a combination thereof. 
     
     
         8 . A method of making the sorbent of  claim 1 , the method comprising:
 contacting activated carbon with a nitrogen-containing compound to form the surface layer, to form the nitrogen-containing activated carbon sorbent of  claim 1 .   
     
     
         9 . The method of  claim 8 , wherein forming the surface layer comprises contacting the activated carbon with an ammonium salt, ammonium precursor, ammonium compound, an ammonium halide, a methylammonium halide, an ammonium salt of an oxyacid of a Group VI element, an ammonium salt of an oxyacid of a Group V element, or a combination thereof. 
     
     
         10 . The method of  claim 9 , wherein the ammonium salt, ammonium precursor, or ammonium compound is ammonium bromide, ammonium iodide, ammonium chloride, an organic halide with a formula of CH 3 NH 3 X (wherein X is Cl, Br or I), ammonium sulfate, ammonium hydrogen sulfate, ammonium sulfite, ammonium hydrogen sulfite, ammonium persulfate, ammonium pyrosulfate, ammonium thiosulphate, ammonium dithionite, ammonium aluminium sulfate, ammonium iron sulfate, ammonium sulfamate, ammonium phosphate, diammonium phosphate, ammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium thiophosate, ammonium nitrate, ammonium nitrite, ammonium carbonate, ammonium thiocyanate, ammonium sulfide, ammonium hydrogen sulfide, ammonium acetate, ammonium carbamate, ammonium carbonate, ammonium chlorate, ammonium chromate, ammonium fluoride, ammonium formate, ammonium hydroxide, ammonium perchlorate, sodium nitrite, sodium nitrate, lithium nitrite, lithium nitrate, barium nitrite, barium nitrate, cerium nitrite, cerium nitrate, FeNH 4 (SO 4 ) 2 , Fe(NH 4 ) 2 (SO 4 ) 2 , FeNH 4 Br 4 , FeNH 4 Cl 4 , AlNH 4 (SO 4 ) 2 , hydrates thereof, or a combination thereof. 
     
     
         11 . The method of  claim 8 , comprising forming the surface layer in the mercury-containing gas. 
     
     
         12 . The method of  claim 8 , comprising forming the surface layer comprises injecting the nitrogen-containing compound and the activated carbon in a flue gas in the same location or at different locations wherein:
 the nitrogen-containing compound is deposited on the activated carbon to form the sorbent within the flue gas,   the nitrogen-containing compound decomposes or vaporizes and then deposits on the activated carbon to form the sorbent,   the nitrogen-containing compound deposits on the carbon to form the sorbent, or   a combination thereof.   
     
     
         13 . The method of  claim 8 , wherein the surface layer is formed on the sorbent prior to injecting the sorbent into a mercury-containing gas. 
     
     
         14 . The method of  claim 8 , further comprising promoting the activated carbon comprising nitrogen in a surface layer thereof with a halogen- or halide-promoter. 
     
     
         15 . A method of making the sorbent of  claim 1 , the method comprising promoting the activated carbon comprising nitrogen in a surface layer thereof with a halogen- or halide-promoter. 
     
     
         16 . The method of  claim 15 , comprising performing the halogen- or halide-promotion in a mercury-containing gas 
     
     
         17 . The method of  claim 16 , further comprising combusting coal comprising a halogen- or halide-containing material to form the mercury-containing gas. 
     
     
         18 . The method of  claim 16 , further comprising adding the halogen- or halide-containing material to the coal. 
     
     
         19 . The method of  claim 18 , wherein the halogen- or halide-containing material comprises HCl, HBr, HI, Br 2 , Cl 2 , I 2 , BrCl, IBr, ICl, ClF, PBr 3 , PCl 5 , SCl 2 , CuCl 2 , CuBr 2 , Al 2 Br 6 , FeI x  (x=1, 2, 3, or 4), FeBr y  (y=1, 2, 3, or 4), FeCl z  (z=1, 2, 3, or 4), MnBr 2 , MnCl 2 , NiBr 2 , NiCl 2 , NiI 2 , ZnBr 2 , ZnCl 2 , ZnI 2 , NH 4 Br, NH 4 Cl, NH 4 I, NH 4 F, (NH 4 ) 2 SO 4 , H 2 SO 4 , NH 4 SO 4 H, (NH 4 ) 2 S 2 O 3 , FeNH 4 (SO 4 ) 2 , Fe(NH 4 ) 2 (SO 4 ) 2 , FeNH 4 Br 4 , FeNH 4 Cl 4 , AlNH 4 (SO 4 ) 2 , NaBr, NaCl, NaI, Br − , Cl − , I − , KI, KCl, LiCl, LiBr, AgCl, AgBr, CHI 3 , CH 3 Br, AuBr, MgBr 2 , MgCl 2 , CaI 2 , CaBr 2 , CaCl 2 , hydrates thereof, or a combination thereof. 
     
     
         20 . A method of using the sorbent of  claim 1  to reduce the mercury content in a mercury-containing gas, the method comprising:
 contacting the sorbent with the mercury-containing gas, to form a mercury-sorbent composition; and 
 separating at least some of the mercury-sorbent composition from the mercury-containing gas, to give a separated gas.