Removal of mercury from liquid hydrocarbons

Abstract: Impregnated carbon adsorbents for the removal of mercury from liquid hydrocarbons are used in a variety of applications. The activated carbon impregnated adsorbents in the present invention remain effective in removing mercury. Generally, these activated carbons are comprised of an activated carbon adsorbent impregnated with a composition containing metal halide or other reducing halide, supplemented according to the desired characteristics with other elements. The formulation of the impregnants in the present invention can be varied to adjust the performance characteristics so as to meet the desired mercury removal performance criteria, to achieve enhanced removal of organic bound mercury from liquid hydrocarbon, and to have other advantages useful in a variety of applications. These impregnated carbon adsorbents possess desirable qualities regarding their ability to remove even trace levels of mercury from liquid hydrocarbon without a leaching effect of the impregnants used. APPENDIX I. MERCURY REMOVAL FROM LIQUID NATURAL GAS/HYDROCARBONS 1. Yan, T. Y. Removal of mercury from natural gas and liquid hydrocarbons utilizing downstream guard chamber. U.S. Patent No. 4709118, Nov. 24, 1987. 2. Chao, C. C. Adsorbent compositions. U.S. Patent No. 4474896, Oct. 2, 1984. 3. Rollman, L. D. Sorption of metals from fluids using manganese nodule particles containing occluded sulphur. U.S. Patent No. 4338288, July 6, 1982. 4. Pelosi, J., Sugier, A. Absorption composition for removing mercury from gas or liquid contains sulphur and alumina, silica, silica-alumina, cement, silicate or calcium sulfate binder. DE Patent No. 3324091, Jan. 12, 1984. FR Patent No. 2529802, Jan. 13, 1984. 5. La Villa, F., Sugier, A. Process for removing mercury from a gas or a liquid by absorption on a copper sulfide containing solid mass. U.S. Patent No. 4094777, June 13, 1978. 6. Tokuyama Soda KK (TOKU). Heavy metal absorption agent - comprising hydrohalogenic acid salt or amino deriv. activated carbon. JP Patent No. 51003386, Jan. 12, 1976. 7. Holbein, B. E., Brener, D., Greer, C. W., Browne, E. N. Insoluble compositions for removing mercury from a liquid medium. U.S. Patent No. 4654322, Mar. 31, 1987. II. MERCURY REMOVAL BY AMALGAMATION REACTION 8. Manes, M. Silver Impregnated Carbon. U.S. Patent No. 3374608, Mar. 26, 1968. 9. Miyoshi Yushi KK. Mercury Removal from gases - by contacting with metal-plated plastic. JP Patent No. 62155926, July 10, 1987. 10. Capuano, I. A., Carr., L. P., Turley, P.A. Silver coated particles and a process for preparing them; reducing silver compound with hydrazine. U.S. Patent No. 4353741, Oct. 12, 1980. 11. Inst. Francais Du Petrole. Removal of mercury from gases or liqs. - using absorbent mass of metal on a ceramic support. FR Patent No. 2310795, Jan. 14, 1977. III. REMOVAL OF MERCURY VAPOR FROM GAS STREAMS 12. Sumitomo Chemical Co. Carbon absorbent for removing mercury vapor from air - carrying at least one chloride of alkali or transition metal. JP Patent No. 49066592, June 27, 1974. 13. Belozerov, I. M., Kurakin, V. I., Kalkorin, B. N. Mercury sepn. from air contg. dust and aerosols by passage through activated carbon then carbon impregnated with monochloroiodide. SU Patent No. 1163892, June 30, 1985. 14. Nippon Soda Co. LTD. Activated carbon contg. halides for mercury extn. - from air or gases, with excellent adsorptivity. JP Patent No. 49053590, May 24, 1974. 15. Nippon Soda Co. LTD. Activated carbon contg. chlorides for mercury extn. - from air or gases, with excellent adsorptivity. JP Patent No. 49053593, May 24, 1974. 16. Nippon Soda Co. LTD. Activated carbon contg. iodides for mercury extn. - from air or gases, with excellent adsorptivity. JP Patent No. 49053592, May 24, 1974. 17. Nippon Soda co. LTD. Removal of mercury from air or gases - using bromide-contg. activated carbon. JP Patent No. 49053591, May 24, 1974. 18. Tokuyama Soda KK. Mercury adsorber - comprising hydrogen halide and activated carbon. JP Patent No. 50158592, Dec. 22, 1975. 19. Belozovski, A. B., Balandinal E. A. Removing mercury from industrial gases - by sorption on activated carbon impregnated with ferric chloride for high capacity and safety. SU Patent No. 625752, Aug. 24, 1978. 20. Kokai, Tokkyo Koho. Absorbent for removal of mercury. JP Patent No. 6094138, May 27, 1985. 21. Osaka Soda KK. Mercury adsorbent for waste gases comprises active carbon loaded with metal halides and sulphur contg. organic cpd. JP Patent No. 62114632, May 26, 1987. 22. Knoblauch, K., Wybrands, K., Henning, K. D., Degel, J., Ruppert, H. Active carbon prodn. for removing mercury from gases - by impregnating with sulphur and iodine (CPD); SULPHUR IODINE COMPOUND. DE Patent No. 3715526, Nov. 17, 1988. 23. DeJong, G. J., Vos Hendrik, J. Process for removing mercury from a gas; active carbon, adsorption of chlorine. U.S. Patent No. 4196173, April 1, 1980. 24. Belozovski, A. B., Skripnik, V. A., Farberova, B. A. Waste gas mercury vapor sorbent contg. activated carbon impregnated with chlorine deriv. of organic heterocyclic cpd. SU Patent No. 793615, Jan. 7, 1981. 25. Borzesti Comb Petro. Purifying residual gases contg. organic mercury cpds. - by passing over chlorine - impregnated active carbon adsorbent. RO Patent No. 58566, May 30, 1975. 26. Wiklund, J. E. method for separating gaseous, elementary mercury from a gas; mercury halides, washing, saturation, condensation, oxidation, complexing, absorption. U.S. Patent No. 4443417, April 17, 1984. 27. Audeh, C. A. Process for adsorbing mercury from natural gas; porous aluminum activated with mercuric salt. U.S. Patent No. 4717399, Jan. 5, 1988. 28. Ajinomoto KK. Extraction of mercury from gas contg. mercury vapor - using reaction prod. of gold ions with cuprous, stannous, or ferrous cpds. JP Patent No. 51001315, Jan. 8, 1976. 29. Aibe, T., Nishino, H., Noguchi, K. Process for removal of mercury vapor and adsorbent therefor; active carbon support with sulfur, and/or sulfate or nitrate of aluminum, vanadium, iron, cobalt, nickel, copper, zinc, or ammonium, and/or halogen compound. U.S. Patent No. 4500327, Feb. 19, 1985. 30. Puppe, L., Reiss, G. Mercury removal from gas, esp. hydrogen for catalytic hydrogenation - by contact with zeolite modified with transition metal and silver. DE Patent No. 2841565, April 3, 1980. 31. Takeda Chemical Ind. KK. Mercury vapor adsorbing agent comprises active carbon supporting sulfuric acid and/or nitric acid, and sulfate and nitrate cpds. of e.g. aluminum and copper. JP Patent No. 58156345, Sept. 17, 1982. 32. Institut Francais Petrol. A material to remove mercury that occurs in natural gas has been developed. Chemical Engineering, April 16, 1984, p. 10. 33. C Asia Ferr Metallurg. Mercury removal from gases - by contacting with liquid sorbent such as masout or solar oil. SU Patent No. 431895, Nov. 5, 1974. 34. Tarakad, R. R., Crawford, D. B. Removal of mercury from natural gas - by contact with hydrocarbon lig. U.S. Patent No. 4693731, Sept. 15, 1987. 35. Gebhard, R. S., Greenbank, M., Matviya, T. M. Mercury adsorbent carbon molecular sieves and process for removing mercury vapor from gas streams; oxidation, amalgamation. U.S. Patent No. 4708853, Nov. 24, 1987. 36. Henning, Keldenick, Knoblauch and Degel, Impregnated Activated Carbon for Mercury Removal. Gas Sep. Purif., Vol. 2, No. 1., 1988, Pages 20-2. 37. Miller, A. J., Tuckett, W. F., Removal of mercury from gas streams using hydrogen sulfide and amines. U.S. Patent No. 4044098, Aug. 23, 1977. IV. MERCURY REMOVAL FROM AQUEOUS SYSTEMS 38. Okahara, M., Ikeda, I., Selective mercury adsorbing agent comprises olefin polymer and porous solid, for gaseous and liquid media. U.S. Patent No. 4604321, Aug. 5, 1986. 39. Marchant, W. N. Removal of mercury from solutions; hydrocarbon dithiol-cellulose adsorbent. U.S. Patent No. 3864327, Feb. 4, 1975. 40. Asahi Chemical Ind. KK. Organic mercury compounds removal from sludge - using a powdered porous material impregnated with colloidal sulphur or sulphur compounds. JP Patent No. 51044588, Apr. 16, 1976. 41. Hayashi, M., Kaku, K., Nakamura, T., Ohishi, S., Tarao, R., Yamano, H. Agent for removing heavy metals; Dithiocarbamate sulfide compound, amorphous silica, and active carbon. U.S. Patent No. 4133755, Jan. 9, 1979. 42. Seitetsu Kagaku KK. Heavy metal esp. mercury collecting agent - comprising condensate of thio­ phenols with formaldehyde optionally supported on a substrate e.g. activated carbon. JP Patent No. 51101797, Sept. 8, 1976. 43. Sasaki, A. Heavy metal adsorbents of high selectivity, process for production of same, and adsorption process. U.S. Patent No. 4305827, Dec. 15, 1981. 44. Roper, W. Removal of mercury from solutions by upflow filtration. DE Patent No. 3438098, Apr. 30, 1986. 45. Bituminous coal surface modification to enhance mercury(II) removal from water. Asian Environ. Vol. 7, Nov. 3, 1985. Pages 22-9. 46. Conti, V., Piccinini, C. Method for the removal of metallic mercury; from industrial sewage waters, activated carbon having a large surface area. U.S. Patent No. 4093541, June 6, 1978. 47. Botwick, E. J., Smith, D. B. Mercury Recovery. U.S. Patent No. 3600285, Aug. 17, 1971. 48. Japanese Geon Co LTD. Treating waste liquor - containing organic mercury compounds. JP Patent No. 72027391, (No Date). 49. Nippon Kokan KK. Removing harmful impurities, e.g. mercury from waste liquor by passing downwards through column having acid-resistant resin filters packed with activated charcoal and coal. JP Patent No. 58128182, July 30, 1983. 50. Mitsubishi Chemical Ind. KK. Purification of waste water containing organo-mercury compounds by electrolysis and adsorption with activated carbon and/or chelate resin. JP Patent No. 56121682, Sept. 24, 1981. 51. Dynamic mercury(II) adsorption characterization of iron oxide-dispersed activated carbon fibers. Carbon, Vol. 26, No. 6, 1988. pp. 903-5. 52. Removal of mercury(II) ion by activated carbon. Suishitsu Odaku Kenkyu, Vol. 10, Nov. 5, 1987. pp. 303-9. V. MERCURY REMOVAL BY CHEMICAL ADDITION 53. Goffman, M., Kudryk, V. Removal of mercury from sulfuric acid; Halogen or halide complexing. U.S. Patent No. 4336237, June 22, 1982. 54. Sumitomo Metal Mini KK (SUMM). Mercury removal from sulfuric acid - by complexing the metal with halogen and organic solvent. JP Patent No. 51124695, Oct. 30, 1976. 55. Sumitomo Metal Mini KK (SUMM). Mercury removal from sulfuric acid - by addition of organic solvent and adsorbing on activated carbon. JP Patent No. 51124696, Oct. 10, 1976. 56. Sumitomo Metal Mini HK (SUMM). Trace mercury removal from industrially produced sulfuric acid - by using activated carbon to adsorb mercurous halide obtained by adding halogen compounds and reducing agent to the sulfuric acid. JP Patent No. 51128693, Nov. 9, 1978. 57. Unitika KK. (NIRA). Treating mercury containing effluent by contact with activated charcoal after addition of reducing agent to effluent. JP Patent No. 59166288, Sept. 19, 1984. 58. Plessen, H., Gradl, R., Schimmel, G. Heavy metals removal from Odda process phosphoric acid by adjusting to pH 0.5-1.5 with ammonia and treating with diorganic dithiophosphorus compound and adsorbent; Cadmium, Mercury, Lead compounds. US Patent No. 4479924, Oct. 30, 1984. 59. Bikkulova, A. T., Bikbaeva, G. G., Lutfullina, M. G. Mercury removal from solutions containing chloride ion by complexing with dithio-pyryl-­ methyl-methane in chloroform. SU Patent No. 1204566, Jan. 15, 1986. 60. Berninger, C. J., Fitzpatrick, J. w., Lewis, DD Process for reducing the level of contaminating mercury in aqueous solutions; of anthraquinone sulfonic acids. US. Patent No. 3873581, Mar. 25, 1975. 61. Herold, R., Knoche, D. Mercury extraction from sludge by stirring with acetic acid solution; Mercury@. D. O. Patent No. 207993, Mar. 21, 1984. 62. Chisso Corp. (CHCC). Treating acidic waste water containing a mercury compound - using an acid e.g. sulfuric acid and metallic aluminum powder. JP Patent No. 74011809, Mar. 19, 1974. 63. Hanni, H., Righett, B., Wicki, G., Salami, E. Removing mercury from waste water by reducing ionic mercury to metallic state, separating mercury, and removing any ionic mercury with ion exchanger. BR Patent No. 8201651, Feb. 16, 1983. VI. PHYSICAL SEPARATION OF MERCURY FROM GAS STREAMS. 64. Specht, K., Durschmied, G. Separating mercury droplets from flowing carrier medium - by charging into spiral flow path to impinge on deflectors on outer wall before discharge via base holes. DD Patent No. 257593, June 22, 1988. 65. Eisenhut, H., Siegmann, W. D., Radler, J., Baz, V. I., Schpak, V. N., Musjalik, V. S. Extraction of mercury from low temperature natural gas with condenser at turbine outlet. DD Patent No. 218164, Jan. 30, 1985. VII. RELATED TECHNOLOGY. 66. Hilton, C. B. Efficient removal of iodide compounds from non-aqueous organic media using macro-­ reticulated strong-acid cation exchange resin with active sites in silver form; Sulphonated polystyrene di polyvinyl benzene copolymer. US Patent No. 4615806, Oct. 7, 1986. 67. Ottrok, L. Method for recovering gold, platinum or silver from an ore containing gold dust, platinum dust or silver dust; coating a silver coated surface with mercury, washing with ore mixed with water to form amalgam. US Patent No. 4671868, June 9, 1987. 68. Yan, T. Y. Mercury contaminated carbon sorbent treatment - for safe disposal and recovery of mercury. US Patent No. 4701212, Oct. 20, 1987. 69. Onuma, T. Mercury recovery from inorganic material - to oxidizing to convert to inorganic mercury and converting to metallic mercury in presence of tin compound. JP Patent No. 62284026, Dec. 9, 1987. 70. Yan, T. Y. Clean up and passivation of mercury in gas liquefaction plants. US Patent No. 4764219, Aug. 16, 1988. 71. Audeh, C. A. Process for preparing particulate aluminum metal for adsorbing mercury from natural gas. US Patent No. 4771030, Sept. 13, 1988. 72. Japan Gas-Chemical Co. (MITN). Vinyl chloride from kerosene-treated acetylene containing. JP Patent No. 71017765, (No Date). 73. Blumenthal, J. H. Hydrohalogenation of myrcene. US Patent No. 3413364, Nov. 26, 1968 74. Loo Wing, M. Recovery of mercury and caustic values from caustic sludges; slurrying, retorting. US Patent No. 4149879, Apr. 17, 1979. 75. Stauffer Chemical Co. Hydrometallurgical recovery of mercury. CA 875476, (No Date). 76. Sulfide treatment to inhibit ercury adsorption on activated carbon in the carbon-in-pulp gold recovery circuits. US Patent No. 4734270, Mar. 29, 1988. 77. Nazarenko, I. I., Kashina, L. I., Bakhareva, T. V. Removal of mercury compounds from contaminated water by pptn. with para-dimethyl-amino­ benzylidene-rhodanine in nitric acid solution. SU Patent NO. 945721, July 23, 1982. 78. Nitzsche, S., Wick, M. Method of reducing organo-metallic compounds. US Patent No. 3061424, Oct. 30, 1962.

Description: The present invention relates to impregnated carbon adsorbents for removal of mercury from liquid hydrocarbon, to processes for removing mercury from liquid hydrocarbon using impregnated carbon adsorbents and to the use of impregnated carbon adsorbents. 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. US-A-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. US-A-4474896 to C. C. Chao relates to polysulfide containing adsorbent compositions for removal of elemental mercury from gas or liquid streams. US-A-4338288 to Rollman, FR-B-2529802 to Pelosi, et al. and US-A-4094777 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 Patent No. 51003386 describes the use of activated carbon containing a hydrogen halide salt of a compound having one or more functional groups, while US-A-4654322 involves the use of a cysteine residue fixed to any insoluble carrier. Other references disclose removal of mercury by amalgamation, including US-A-3374608 to Manes, US-A-4353741 to Capuano, et al., Japanese Patent No. 62155926 to Miyoshi and FR-B-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 4 ⊕ . Similarly, SU-A-1163892 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 Patent 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. US-A-4708853 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. US-A-4094098 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. GB-B-2,187,725 discloses activated charcoal impregnated with transition metal salts preferably consisting of cobalt, nickel or zinc acetate. US-A-3,355,317 to Keith et al. discloses the use of the oxides of cobalt, copper, zinc, iron and molybdenum on activated carbon to remove hydrogen cyanide from tobacco smoke. US-A-2,920,050 and 2,920,051 both to Blacet et al. describe the preparation of whetlerite type filters which include copper. chromium, silver and molybdenum impregnants. US-A-4,801,311 to Tolles discloses a whetlerite type activated carbon filter material impregnated with and molybdenum and/or vanadium salts together with triethylenediamine. US-A-4,802,898 to Tolles discloses a whetlerite type activated carbon filter material impregnated with triethylenediamine, and optionally with copper and silver. US-A-4,531,953 to Groose discloses an activated carbon impregnated with copper. silver and/or chromium mixtures and triethylenediamine. [EP-A2-0 325 486 describes a method for removing mercury from a liquid hydrocarbon oil wherein a cupric compound and/or stannous compound supported on activated carbon can be used. AU-34853/89 describes a method for removing mercury from hydrocarbon oil wherein the hydrocarbon oil is contacted with a treating agent comprising activated carbon upon whose surface layer is supported at least one kind of metal selected from among iron, nickel, copper, zinc, aluminium and cadmium, its alloy and/or oxide, chloride, sulfide or their mixture. This method requires a heating step of the hydrocarbon oil before the same is contacted with the treating agent. EP-A1-0 385 742 which has been filed before the priority date of the present application but which has been published after said priority date and, therefore, establishes prior art according art. 54 (3) and (4) EPC, describes a method for removing mercury from a liquid hydrocarbon compound comprising contacting an adsorbent having an active component selected from the group consisting of copper compounds, tin compounds and mixtures thereof supported inter alia on active carbon.] 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 and a process which are 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. The present invention embodies an impregnated carbon adsorbent that removes mercury from liquid hydrocarbons by the reduction of non-elemental mercury compounds to elemental mercury. Once converted to a more adsorbable form, physical adsorption and/or chemisorption, to include further reaction with amalgamating impregnants occurs. The activated carbon adsorbent of the present invention is impregnated with a reducing agent selected from Sn⁺² and Ti⁺², each of which will act to efficiently convert organic mercury and organic mercury salts to elemental mercury for physical adsorption, in that each of these cations have sufficient reduction capability so as to facilitate this conversion. Chemisorption of the mercury with amalgamating impregnants such as Ag, Zn, Al, Au and alkali elements from the periodic table of elements is carried out in that these known amalgamating elements in the context of the present invention "fix" the mercury to the surface of the carbon enhancing the strength of adsorption and is not dependent on equilibrium forces. The activated carbon adsorbent is impregnated so as to result in a composition comprising by weight from 0,5 to 25%, preferably from 1% to 25% of Sn²⁺ and Ti²⁺. These activated carbons are also impregnated with by weight from 0,5 to 15%, preferably from 1% to 15% Ag, Zn, Al, Au and/or alkali elements, which function as amalgamating or reactive agents. In one process of the present invention enhanced mercury removal capability is achieved by using an activated carbon impregnated whith a metal halide wherein said halide being selected from I, Br and Cl and said metal being selected from K and Ca. The metal halides used in the process of the present invention facilitate the mercury conversion and removal process. The metal K or Ca serves as the "vehicle" for the depositing and/or maintaining the I, Br and Cl halides on the carbon surface. The use of one or more of these impregnants on activated carbon efficiently converts organo-mercury and weakly adsorbable compounds present in liquid hydrocarbon to the desired inorganic mercury halides, after which adsorption of that mercury can efficiently occur. The activated carbon adsorbent used in one process of the present invention is impregnated to contain, depending on the particular characteristics desired, a final composition by weight of containing a mixture from 0.5% to 25% metal halide. Poor mercury removal efficiency (shown in Table 1) is most likely due to the nature of the mercury species present in the liquid hydrocarbon. (Mercury in an organic form is difficult to adsorb.) Uses for the present invention include the treatment of liquid hydrocarbon prior to olefin production, liquid propane gas and liquid natural gas processing, or similar operations. Other applications include the prevention of mercury poisoning of precious metal catalysts and the prevention of metal embrittlement damage to piping and equipment, as well as any other situation in which high and in particular, low-level concentrations of mercury are to be removed from liquid hydrocarbon. The advantages of the present invention over other ways of removing mercury include that it permits mercury removal from hydrocarbon via the novel concept of the impregnating compounds in activated carbon so that the impregnants perform as reactant or reducing agents. In this sense the activated carbon may selectively adsorb efficient levels of mercury that would otherwise escape less effective mercury removal systems. As a result of the reactant-impregnated carbon's ability in the present invention to convert mercury to more readily adsorbable forms, these carbons perform their mercury removal function in a manner not previously contemplated, and in a manner that significantly increases the capacity of filters using these carbons in removing trace levels of mercury that is not possible through the use of other activated carbons. The following examples further illustrate the present invention Initial Carbon Screening Tests (Comparison Examples) : A variety of impregnated and non-impregnated carbons have been tested to determine their effectiveness for removing mercury from liquid hydrocarbon. The carbons differed in types of impregnants, pore structure and activity as well as source of raw material. The carbons tested included coconut based carbon (PCB), high activity coal-based carbon (BPL and Filtrasorb 400), medium activity coal-based carbon (CWS), BPL carbon impregnated with (by weight) 1% Ag, CWS carbon impregnated with 4% Ag, as well as a coal based surface modified carbon having a highly reactive surface (CAT). Additional impregnated carbons currently used in a variety of applications included other impregnated coal-based carbon formulations. The results of the initial tests presented in Table I reveal the poor mercury adsorptive capacity of these carbons in comparison to the impregnated carbons tested in the Tables that follow. All carbon materials enumerated in the examples are produced and assigned by CALGON CARBON Corporation and their denominations are as indicated. CB = Coal based activated carbon CNB = Coconut based activated carbon NI = Non-impregnated Impregnated Carbon Test Preparations and Procedures: In the preparation process, the activated carbons tested were first pulverized and oven dried. Carbon dosages in the procedure ranged from .0003 to 5 grams per 100 grams of C5-C7 industrial grade natural gas condensate. The carbon/hydrocarbon mixture was placed in an air tight vessel with no head space and allowed to equilibrate with stirring for 24 hours. The carbon was removed from the samples by filtration prior to analysis for residual mercury concentration. The test samples were analyzed by hydrobromic acid extraction followed by ICP/Mass Spectrometry quantifying the two major mercury isotopes. Mercury liberation tests subsequently performed on liquid hydrocarbon indicated the liberation of elemental mercury vapor upon addition of aqueous stannous chloride. Mercury vapor was not liberated from the liquid hydrocarbon in the absence of reducing agent stannous chloride. As a result of these tests, it was determined that the mercury content of the liquid hydrocarbon was most likely not in an elemental state. It was discovered that the presence of stannous chloride acted as a reducing agent and potassium iodide acted as a reactant, thereby significantly enhancing adsorption of mercury on activated carbon by converting what appears to be organic-bound mercury into a more readily adsorbable form of mercury. The stannous cation reduces the mercury to its elemental state, whereas the potassium iodide reacts so as to form a mercury halide salt. The concept of converting organic mercury to a more adsorbable form was first tested with equilibrium isotherm studies using a 1% Ag impregnated coal based carbon (BPL) to which an aqueous SnCl₂ solution was added. A 2% KI impregnated pelleted wood based carbon was included to evaluate the halogen reaction concept. Table II sets forth the results of these studies and demonstrates the fundamental effectiveness of the impregnated carbons in reducing concentrations of mercury. These tests dramatically demonstrate the potential of certain carbon formulation concepts and the particularly remarkable results that these concepts (such as with the wood based pellet carbon impregnated with 2% KI) were capable of attaining. It is important to note that in all Tables describing all isotherm and column tests, the minimum reliable mercury detection limit was determined to be 3 µg/kg; as such, due to the analytical limitations of the method used to evaluate the amount of residual mercury present, the Tables use "<3 µg/kg" as the lowest residual mercury figure. In the case of the impregnated carbons of the present invention, readings well below the reliable detection limit of 3 µg/kg were often obtained, indicating that even more efficient mercury removal may actually be obtained by practicing the present invention that indicated in the Tables by the minimum reliable figure. Further, the base figure of <3µg/kg artificially holds the mercury removal percentages below the levels they would otherwise be if a more accurate residual mercury measurement were possible. CB = Coal based activated carbon WB = Wood based activated carbon NI = Non-impregnated Follow-up studies were conducted using impregnations of coal based activated carbons with 2% Sn⁺² as SnCl₂, and coal based activated carbon with 2% Ag + 2% Sn⁺² as SnCl₂. A wood based 2% KI impregnated activated carbon, a high activity coconut carbon impregnated with 2% KI (GRC-11); a control sample of the non-impregnated coal based carbon (CWS) was also included in the study. Due to the expected enhanced capability of these impregnated carbons for mercury removal, carbon dosages were lowered significantly to provide data distinguishing each carbon's level of performance. The results of these studies demonstrates the effectiveness of impregnated carbons in reducing high- as well as low-level concentrations of mercury. Table III sets forth the results of these selected carbon isotherm test. The impregnated carbons tested in this initial phase clearly demonstrate greatly enhanced mercury removal performance over the performance characteristics of the non-impregnated base carbons. CB = Coal based activated carbon CNB = Coconut based activated carbon WB = Wood based activated carbon NI = Non-impregnated Both the Table II and Table III preliminary tests both illustrate the superior performance of these impregnated carbons for mercury removal over the carbons as tested in Table I. The Table II and III tests results establish the effectiveness of reactant/reducing agent impregnated carbons in removing mercury from liquid hydrocarbon. The Table II and III studies also show that well-balanced performance in all critical areas is attained with the present invention composition containing either metal halides. Theoretically, Sn⁺², Sn⁺³, Ti⁺², Ti⁺³, and Cu have the requisite structure to act as reactant/reducing agents. The Table I and II compositions show that these impregnated carbons perform extremely well in removing even trace levels of mercury from a liquid hydrocarbon media. Good performance is also attained in all critical areas with the present invention using specialized compositions containing Ag, Zn, Al, Au and alkali elements. Other agents may also be added, depending on the desired performance characteristics; The compositions used can be tailored to meet specific desired performance characteristics for any number of industrial or other needs. The second phase of carbon isotherm testing included evaluation of alternative metal halide impregnants in facilitating mercury removal from liquid hydrocarbon. Metal halide impregnated carbons were prepared in the laboratory including KCl, KBr, CaCl₂, CuCl₂, FeCl₃, and ZnCl₂ on lmm wood based pellets. The data set forth in Table IV clearly indicates the chloride, iodide, and bromide halides in conjunction with a wide variety of metals also exhibit enhanced mercury removal capacity compared to the materials in Table I. WB = Wood based activated carbon A third phase of isotherm testing was performed on laboratory prepared impregnated carbons to evaluate the effects on mercury removal capacity versus impregnant loading. The 1mm pelleted wood based activated carbon was impregnated to contain levels ranging from 2 wt.% to 25 wt% KI. Similar impregnations were prepared using SnCl₂ and silver. The test results set forth in Table V indicate excellent mercury removal performance at all impregnant loadings tested. The combination of excellent carbon capacity and low mercury content of the hydrocarbons makes it extremely difficult to evaluate impregnant loading mercury capacity relationships. WB= Wood based activated carbon LP = Carbon prepared in laboratory Column Tests Column testing of impregnated carbons was also conducted so as to evaluate mercury removal performance in a column treatment system. Column beds containing non-impregnated and 2% KI impregnated activated carbon pellets were used to treat an industrial hydrocarbon containing 38 µg/kg mercury. The tests were conducted under identical operating conditions, allowing a 30 minute contact time. The test results set forth in Table VI clearly show the mercury removal advantage attained with the impregnated product over the non- impregnated base carbon. Column Conditions: 5 cm³/min (5cc/min) Flow Rate 30 minute EBCT 0,305m (1 Ft.) Bed Depth Ambient Temperature and Pressure An additional column study was conducted on a 1mm wood based pellet impregnated to contain 2% KI. The study was designed to define the bed depth required to achieve mercury removal to below detectable limits when treating liquid hydrocarbon at an arbitrarily selected 163l/min.m² (4 GPM/Sq.Ft.) loading rate. The segmented column design allowed the extraction of treated hydrocarbon at various bed depths during the treatment process. An industrial grade liquid hydrocarbon containing 18 µg/kg mercury was used in the laboratory study. The data set forth in Table VII indicates a 50% reduction in mercury concentration is achieved within the first 30.5cm (12 inches) of the carbon column. Complete removal of mercury to below the minimum mercury detection limit of 3 µg/kg is demonstrated within 2.06m (6.75 ft.) of the carbon bed. Isotherm and Column Test Conclusions : The precise reaction that occurs to create the observed effectiveness of the impregnated carbons as tested is not readily apparent. Determining the actual identification and concentrations of the various mercury compounds present would be extremely difficult due to the varying characteristics and very low concentrations of individual components that may or may not be present in a particular sample. Based on well known organo-mercury chemistry, the organo-mercury compounds may be present in a variety of forms to include mercaptides with or without halides, dialkylmercury compounds, and organo-mercury salt compounds. The reactions of each type of organic mercury compound is consistent with the probable removal mechanism whereby metal halides or reducing agents as impregnants convert mercury to an inorganic mercury halide salt or to elemental mercury during the removal process. The essential ingredient in the impregnant metal halides used in one process of the present invention for facilitating mercury conversion and removal are the I, Br and Cl halides. When Sn⁺² and Ti⁺² are used to reduce organic mercury to its elemental state, depending on the application to be made, from about 0.5% to 25% reducing agent by weight of carbon adsorbent is used. The amalgamating agent comprises from about 0.5% to 15%, preferably 1 to 15%, of amalgamating agent by weight of impregnated carbon adsorbent. In short, the isotherm and column tests conducted using the above indicated carbons yielded outstanding mercury adsorptive results that had previously been thought impossible to obtain. Carbon Impregnant Leach Testing : Leach tests were run to determine if any of the impregnants used resulted in undesirable leaching of the impregnants. The data set forth in Tables VIII and IX indicates that significant levels of the impregnants and ash constituents do not leach from the carbon during treatment in either a column or in equilibrium (batch) form. Batch equilibrium leach studies were conducted similar to the isotherm adsorption studies. Pulverized 10 g doses of non-impregnated base and the 2% KI impregnated pellet carbons were contacted with approximately 150 g of hydrocarbon and allowed to equilibrate with mixing for 36 hours. The liquor was then pressure filtered through 0.45 µm nylon pads for removal of carbon and submitted for analysis. A blank, untreated aliquot of the hydrocarbon was also filtered and submitted. The column leach studies were performed with the 4 mm nonimpregnateg and impregnated carbons loaded into 2.54 cm (1") diameter columns to 0.305m (1 foot) bed depths (approximately 67 g). Liquid hydrocarbon was introduced upflow into the dry carbon bed simulating the worst case scenario for impregnant leaching, that being the initial wet down/degassing process. The first bed volume of treated liquor was collected, filtered through 0.45 µm nylon pads for removal of fines, and submitted for analysis. A 5 cm³/min (5 cc/min) flow rate was used allowing for a 30 minute EBCT. A significant increase in temperature was observed during the initial wet down process, which quickly dissipated as the liquid level progressed up the bed. Approximately 10 bed volumes of hydrocarbons 1500cm³ (1500 cc) were treated with each carbon column prior to termination of the studies. Additional samples were collected after 1, 5 and 10 bed volumes for mercury analysis presented previously in Table VI. The data set forth in Table VIII indicates that significant levels of the impregnants and ash constituents do not leach from the carbon during treatment. The 43.6 µg/kg potassium concentration found in the impregnated carbon treated liquor represents 0.0015% of the total potassium available on the carbon surface and is only twice the concentration of potassium in the original untreated hydrocarbon. WB = Wood based activated carbon. NI = Nonimpregnated WI = Potassium Iodide The previously discussed mercury removal performance testing also provided valuable tools for the evaluation of impregnant leachability during normal treatment processes. The additional leach tests conducted also suggest that the impregnants do not leach from the activated carbon upon exposure to liquid hydrocarbon. The data set forth in Table IX indicates an actual reduction in potassium and iron upon treatment and the iodide level remained below the analytical detection limits. In short, the impregnated carbons used in the process of the present invention do not appear to result in undesired leeching of the impregnants.

Claims: An activated carbon adsorbent for the removal of mercury from liquid hydrocarbon, said carbon adsorbent being impregnated with a reducing agent, wherein said reducing agent is an ion selected from Sn²⁺ and Ti²⁺, said reducing agent comprising from 0.5 to 25% by weight of said impregnated carbon adsorbent, and wherein said carbon adsorbent is additionally impregnated with an amalgamating agent selected from Ag, Zn, Al, Au and alkali elements from the periodic table of elements, said amalgamating agent comprising from 0.5 to 15% by weight of said impregnated carbon adsorbent. A process for removing mercury from liquid hydrocarbon whereby organic bound mercury in said liquid hydrocarbon is adsorbed by an activated carbon, said carbon adsorbent being impregnated with a reactant metal halide wherein said metal is selected from K and Ca and said halide being selected from I, Br and Cl, said metal halide comprising from 0.5 to 25% by weight of said impregnated carbon adsorbent. A process for removing mercury from liquid hydrocarbon whereby organic bound mercury in the hydrocarbon is reduced to an elemental state by contact with a reducing agent impregnated on an activated carbon adsorbent, said reducing agent being an ion selected from Sn²⁺ and Ti²⁺ impregnated in said carbon adsorbent to convert said organic bound mercury to said elemental state, said reducing agent comprising from 0.5 to 25% by weight of said impregnated carbon adsorbent, and wherein said carbon adsorbent is additionally impregnated with an amalgamating agent selected from Ag, Zn, Al, Au and alkali elements from the periodic table of elements, said amalgamating agent comprising 0.5 to 15% by weight of said impregnated carbon adsorbent. Use of an activated carbon adsorbent, wherein said carbon adsorbent being impregnated with a reactant metal halide wherein said metal is selected from K and Ca and said halide is selected from, I, Br and Cl, said metal halide comprising from 0.5 to 25% by weight of said impregnated carbon adsorbent for the removal of mercury from liquid hydrocarbon.

Inventors: MCNAMARA JAMES D, MCNAMARA, JAMES D.
Applicants: CALGON CARBON CORP, CALGON CARBON CORPORATION
Application year: 1990
Main classification: C10G25
IPC codes: B01J20, B01D15, C10G25, C04B41