Methods and Compositions for the Removal of Mercury From Gases

Abstract

This invention relates to methods and compositions for removing contaminants from fluids, for example, the removal of mercury contaminants by oxidation. The compositions and methods provided herein are robust and accomplish efficient removal of contaminants from fluid streams without the need for relatively expensive activated carbon. In addition, the methods and compositions of the present invention do not pose risks to the safety of workers through the injection of highly toxic, highly corrosive elemental bromine to directly oxidize the mercury. The compositions and methods of the present invention are versatile and apply to a wide range of contaminants including, but not limited to, mercury, lead, cadmium, thallium, and hydrogen sulfides. Further, the compositions and methods contained herein are capable of efficient contaminant removal over a wide range of temperatures and pressures.

1 . A process for removal of contaminants in a fluid, said process comprising the steps of:
 contacting said contaminants in said fluid with a trihalide salt provided on a substrate; wherein said trihalide salt comprises a trihalide anion and cationic nitrogen counter ion, thereby generating one or more reaction products resulting in removal of said contaminants in said fluid.   
     
     
         2 . The process of  claim 1 , wherein said trihalide salt is an oxidation agent and said one or more reaction products are oxidation products. 
     
     
         3 . The process of  claim 1 , wherein said one or more reaction products are deposited on said substrate. 
     
     
         4 . The process of  claim 2 , wherein said oxidation products are formed in the gas phase. 
     
     
         5 . The process of  claim 2 , wherein said oxidation products are formed in the condensed phase. 
     
     
         6 . The process of  claim 1 , wherein said fluid comprises an exhaust gas, source gas or process gas. 
     
     
         7 . The process of  claim 1 , wherein said contaminants comprise elemental mercury (Hg 0 ). 
     
     
         8 . The process of  claim 2 , wherein said one or more oxidation products comprise Hg 2+  and/or Hg 1+ . 
     
     
         9 . (canceled) 
     
     
         10 . The process of  claim 8 , further comprising a step of removing said Hg 2+  and/or Hg 1+  oxidation products and contaminants from said substrate by treatment of said substrate with an organic solvent or halogenated hydrocarbon solvent. 
     
     
         11 . The process of  claim 10 , further comprising a step of removing said Hg 2+  and Hg 1+  from said substrate by collecting said substrate, passing said organic solvent or halogenated hydrocarbon solvent through it, and evaporating said organic solvent or halogenated hydrocarbon solvent to collect the Hg 2+  and Hg 1+  salts. 
     
     
         12 . The process of  claim 1 , wherein said trihalide anion has the formula (FX1):
   [X 1 —X 2 —X 3 ]—  (FX1);
   wherein each of X 1 , X 2 , and X 3  is independently Br, Cl, F or I.   
     
     
         13 . The process of  claim 12 , wherein each of X 1 , X 2 , and X 3  is Br or Cl. 
     
     
         14 . The process of  claim 12 , wherein said trihalide anion has the formula: [Br—Br—Br] − , [Br—Br—Cl] −  or [Br—Br—I] − . 
     
     
         15 . The process of  claim 1 , wherein said cationic nitrogen counter ion is an ammonium cation. 
     
     
         16 . The process of  claim 15 , wherein said ammonium cation is characterized by one or more N—H bonds. 
     
     
         17 . The process of  claim 15 , wherein said ammonium cation is a quaternary ammonium cation. 
     
     
         18 . The process of  claim 15 , wherein said ammonium cation is a quarternary alkylammonium cation. 
     
     
         19 . The process of  claim 1 , wherein said cationic nitrogen counter ion comprises a heterocyclic nitrogen containing group. 
     
     
         20 . (canceled) 
     
     
         21 . The process of  claim 19 , wherein said heterocyclic nitrogen containing group is a pyridinium, quinolinium, isoquinolinium or imidazolium group. 
     
     
         22 . The process of  claim 1 , wherein said cationic nitrogen counter ion has the formula (FX2) or (FX3): 
       
         
           
           
               
               
           
         
         wherein each of R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7  and R 8  is independently hydrogen, C 1 -C 20  alkyl, C 3 -C 20  cycloalkyl, C 5 -C 30  aryl, C 5 -C 30  heteroaryl, C 5 -C 20  alkylaryl or C 5 -C 20  arylalkyl, or wherein any of R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , or R 8  together with the atoms to which they are attached combine to form one or more carbocyclic or heterocyclic 4, 5, 6, 7, 8 or 9 membered rings. 
       
     
     
         23 . The process of  claim 22 , wherein said trihalide salt is an ammonium trihalide salt comprising at least one of: a tetramethylammonium tribromide, tetraethylammonium tribromide, tetrapropylammonium tribromide, tetrabutylammonium tribromide, tetrapentylammonium tribromide, tetrahexylammonium tribromide, tetraheptylammonium tribromide, pyridinium tribromide, n-butylpyridinium tribromide, quinolinium tribromide, isoquinolinium tribromide or an imidazolium tribromide. 
     
     
         24 . The process of  claim 23 , wherein said ammonium trihalide salt is sorbed on a surface of said substrate. 
     
     
         25 . The process of  claim 1 , wherein said substrate exhibits a surface area per unit volume selected over the range of 0.1 m 2 /g to 8000 m 2 /g. 
     
     
         26 . The process of  claim 1 , wherein said substrate is substantially unreactive with respect to said trihalide salt. 
     
     
         27 . (canceled) 
     
     
         28 . The process of  claim 1 , wherein said substrate comprises particles and/or fibers. 
     
     
         29 . (canceled) 
     
     
         30 . The process of  claim 28 , wherein said particles have a cross sectional dimension selected over the range of 0.1 μm to 500 mm. 
     
     
         31 . (canceled) 
     
     
         32 . (canceled) 
     
     
         33 . The process of  claim 28 , wherein said fibers have a cross sectional dimension selected over the range of 0.1 μm to 100 μm. 
     
     
         34 . The process of  claim 28 , wherein said fibers have a length in the range of 0.9 μm to 50 cm. 
     
     
         35 . (canceled) 
     
     
         36 . The process of  claim 1 , wherein said substrate is selected from the group consisting of: fly ash, particle ash, Portland cement, pozzolan, volcanic ash, energetically modified cement, silica fume, clay, talc, talcum powder, gypsum, gypsum powder, montmorillonite, bentonite, sand, rock wool, mineral wool, glass wool, ceramic wool, fiberglass and any combination of these. 
     
     
         37 . The process of  claim 1 , wherein said substrate is fly ash. 
     
     
         38 . (canceled) 
     
     
         39 . The process of  claim 1 , wherein said substrate contains less than 69% carbon by mass. 
     
     
         40 . The process of  claim 1 , wherein said trihalide salt is provided at a concentration selected from the range of 0.1% to 30%. 
     
     
         41 . (canceled) 
     
     
         42 . The process of  claim 1 , wherein said process is carried out at a temperature selected from the range of 273 K to 800 K. 
     
     
         43 . The process of  claim 1 , wherein said contacting step comprises injecting or blowing said trihalide salt provided on said substrate into said fluid or blowing said trihalide salt provided on said substrate into said fluid. 
     
     
         44 . The process of  claim 1 , wherein said contaminant is elemental mercury (Hg 0 ), lead, thallium, cadmium, uranium, hafnium, beryllium, hydrogen sulfide, mercaptan, a nitrogen oxide compound or any combination of these. 
     
     
         45 . (canceled) 
     
     
         46 . (canceled) 
     
     
         47 . The process of  claim 1 , wherein said fluid is a flue gas from a power plant and said contaminant is elemental mercury (Hg 0 ). 
     
     
         48 . The process of  claim 1 , wherein said fluid is natural gas and said contaminant is elemental mercury (Hg 0 ), hydrogen sulfide, one or more mercaptans, or any combination of these. 
     
     
         49 . The process of  claim 1 , wherein said substrate comprises a substrate that has additionally been modified by deposition of a halide salt, said halide salt being chosen from fluoride, chloride, bromide or iodide combined with a counterion chosen from lithium, sodium, potassium, calcium, or ammonium or quaternary ammonium. 
     
     
         50 . A process for producing a material for the removal of mercury from a gas, said process comprising the steps of:
 providing a substrate; and   contacting said substrate with a trihalide salt comprising a trihalide anion and cationic nitrogen counter ion;   wherein said substrate is selected from the group comprising: fly ash, particle ash, Portland cement, pozzolan, volcanic ash, energetically modified cement, silica fume, clay, talc, talcum powder, gypsum, gypsum powder, montmorillonite, bentonite, sand, rock wool, mineral wool, glass wool, ceramic wool, fiberglass and any combination of these.   
     
     
         51 . (canceled) 
     
     
         52 . (canceled) 
     
     
         53 . (canceled) 
     
     
         54 . (canceled) 
     
     
         55 . (canceled) 
     
     
         56 . (canceled) 
     
     
         57 . (canceled) 
     
     
         58 . (canceled) 
     
     
         59 . (canceled) 
     
     
         60 . (canceled) 
     
     
         61 . (canceled) 
     
     
         62 . A process for removal of contaminants in a fluid, said process comprising the steps of:
 contacting said contaminants in said fluid with a trihalide salt provided on a substrate;   wherein said trihalide salt comprises a trihalide anion and cationic nitrogen counter ion, thereby resulting in removal of said contaminants in said fluid.   
     
     
         63 . (canceled) 
     
     
         64 . (canceled) 
     
     
         65 . (canceled) 
     
     
         66 . The process of  claim 62 , wherein said contaminants comprise oxidized mercury in the +1 oxidation state, and/or oxidized mercury in the +2 oxidation state. 
     
     
         67 . The process of  claim 62 , wherein said contaminants comprise elemental mercury (Hg 0 ).