Activated carbon has long been used to remove mercury from a stream of liquid and/or gas hydrocarbon. These carbons are useful in a variety of industrial applications and often involve the use of special impregnants to remove mercury that would not otherwise be removed through the use of base carbons. Impregnated activated carbons, as well as formulations of silica, aluminumna and other materials, have been known and used for many years largely for removal of elemental mercury in gas phase and aqueous applications. However, due to the chemical state of the mercury present in liquid hydrocarbons, these formulations have limited effectiveness in removing mercury in non-aqueous liquid applications.
U.S. Pat. No. 4,709,118 (Mobil Oil Corp.) teaches mercury removal from liquid hydrocarbon by incorporating elemental Bismuth or Tin or a mixture of these into a Silica, Alumina, or other non-reactive substrate including activated carbon. U.S. Pat. No. 4,474,896 to C. C. Chao relates to polysulfide containing adsorbent compositions for removal of elemental mercury from gas or liquid streams.
U.S. Pat. Nos. 4,338,288 to Rollman, French Pat. No. 2529802 to Pelosi, et al. and U.S. Pat. No. 4,094,777 to La Villa et al. involve the removal of mercury and/or heavy metals from gas and liquid medium using a variety of sulfur containing sorbents to include manganese nodule particles containing occluded sulfur, alumina and silicate type support media containing elemental sulfur or copper sulfide.
Japanese Pat. No. 51003386 describes the use of activated carbon containing a hydrogen halide salt of a compound having one or more functional groups, while U.S. Pat. No. 4,654,322 involves the use of a cysteine residue fixed to any insoluble carrier. Other references disclose removal of mercury by amalgamation, including U.S. Pat. No. 3,374,608 to Manes, U.S. Pat. No. 4,353,741 to Capuano, et al., Japanese Pat. No. 62155926 to Miyoshi and French Pat. No. 2310795 to Inst. Francais du Petrole.
The greatest number of references relating to the removal of mercury vapor specifically from gas streams involved the use of halogens. Japanese Patents No. 49066592 to Sumitomo Chemical Co. discloses an activated carbon carrying one or more chlorides of Li, Na, K, Mg, Ba, Zn, Al, Sn, Mn, Fe, Co, Ni, and NH.sup.4. Similarly, Swiss Pat. No. 1163982 to Belozerov, et al. describes a process for removal of mercury vapor from air containing dusts and aerosols by passage through activated carbon followed by treatment with activated carbon impregnated with monochloroiodide.
Japanese Patent Nos. 49053590, 49053593, 49053592 and 49053591 to Nippon Soda Co. LTD. claim the use of activated carbons containing halides for removal of mercury from gases. In Pat. No. 49053590, the use of activated carbons containing halides of Group III-VIII metals provides excellent adsorptive capacity for Hg. Patent No. 49053593 specifies the use of chlorides of Group I metals impregnated on activated carbons and Patent Nos. 49053592 and 49053591 specify similar iodide and bromide compounds, respectively. Other patents describe the use of hydrogen halide and ferric chloride, respectively, impregnated on activated carbon for removal of mercury vapor from gas streams, while references describe the use of metal salts, metals in combination with sulfur or silver and mineral acids.
U.S. Pat. No. 4,708,853 to Calgon Carbon describes the use of sulfur impregnated molecular sieve activated carbon for removal of mercury from natural gas An independent study on gas separation purification (Henning et al.) evaluated the mercury removal performance of impregnated activated carbons. The carbons studied include the following impregnates: Potassium Iodide, Sulfuric Acid, Sulfuric acid/Potassium Iodide, Sulphur, and Sulphur/Potassium Iodide. The sulphur impregnations were found to be most effective for mercury removal from gas streams.
U.S. Pat. No. 4,094,098 relates to the removal of mercury vapor via a process which involves the addition of hydrogen sulfide gas and amines into the natural gas stream effecting precipitation of mercury as the sulfide while the amines absorb the excess hydrogen sulfide.
Other references disclose mercury removal from aqueous systems, by chemical addition and by physical separation. Other references involving technology not related to mercury removal applications include the use of mercury or mercury compounds in manufacturing processes, safe handling and disposal of mercury removal adsorbent materials and decontamination of equipment, elimination of interferences due to mercury or mercury compounds present in industrial processes and analytical techniques utilizing and evaluating mercury containing compounds.
It is an objective of the present invention to provide an adsorbent which is effective in removing mercury from liquid hydrocarbons, and, in particular, effective in removing even trace levels of mercury through the impregnation of the activated carbon adsorbent with reactant/reducing agents. It is a further objective of the invention to provide a carbon adsorbent for use in a variety of non-aqueous industrial and other mercury removal applications.