Process for removing mercury from a coal tar product

Abstract

A process for removing mercury from a coal tar product is described. A coal tar stream is contacted with a solvent to remove a product, and the product stream is contacted with an adsorbent material to remove elemental mercury, organic mercury compounds, and/or inorganic mercury compounds. Alternatively, the coal tar stream can be treated in a catalytic distillation zone of a fractionation zone.

What is claimed is: 
     
         1 . A process for removing mercury from a coal tar product comprising:
 providing a coal tar stream;   contacting the coal tar stream with a solvent in a solvent extraction zone to remove at least one product from the coal tar stream forming at least one product stream and a remainder coal tar stream, the at least one product stream containing one or more of elemental mercury, organic mercury compounds, and inorganic mercury compounds;   contacting the at least one product stream with an adsorbent material in an mercury removal zone, the adsorbent material comprising one or more adsorbents, an ion exchange material, or mixtures thereof to remove the one or more of elemental mercury, organic mercury compounds, and inorganic mercury compounds; and   separating the remainder coal tar stream into at least two fractions.   
     
     
         2 . The process of  claim 1  further comprising separating the solvent from the at least one product stream before contacting the at least one product stream. 
     
     
         3 . The process of  claim 1  further comprising separating the solvent from the at least one product stream and recycling the separated solvent to the solvent extraction zone. 
     
     
         4 . The process of  claim 1  wherein the at least one product stream contains organic mercury compounds, and further comprising converting the organic mercury compounds to elemental mercury before contacting the at least one product stream. 
     
     
         5 . The process of claim I wherein the solvent comprises a supercritical fluid, an ionic liquid, a polar solvent, and combinations thereof. 
     
     
         6 . The process of  claim 5  wherein solvent comprises the supercritical fluid and wherein the supercritical fluid is selected from the group consisting of supercritical NH3, supercritical CO 2 , supercritical ethane, supercritical propane, supercritical butane, supercritical water, and combinations thereof. 
     
     
         7 . The process of  claim 5  wherein the solvent comprises the ionic liquid, and wherein the ionic liquid is selected from the group consisting of imidazolium-based ionic liquid, pyrrolidinium-based ionic liquid, pyridinium-based ionic liquid, sulphonium-based ionic liquids, phosphonium-based ionic liquids, ammonium-based ionic liquids, caprolactam-based ionic liquids, and combinations thereof. 
     
     
         8 . The process of  claim 5  wherein the solvent comprises the polar solvent, and wherein the polar solvent is selected from the group consisting of pyridine, N-methyl pyrrolidone, methylene chloride, benzyl alcohol, formamide, dimethylformamide, dimethylsulfoxide, dimethylsuccinate, dimethyladipate, dimethylglutarate, propylene carbonate, methyl soyate, ethyl lactate, tripropylene glycol (mono)methyl ether 1,3-dioxolane and combinations thereof. 
     
     
         9 . The process of  claim 1  wherein the adsorbent material is the one or more adsorbents and wherein the adsorbent is a noble metal deposited on a support selected from the group consisting of molecular sieves, alumina, activated carbons, and silica gel. 
     
     
         10 . The process of  claim 1  wherein the adsorbent material is the one or more adsorbents and wherein the adsorbent is a silver impregnated zeolite selected from the group consisting of faujasites (13X, CaX, NaY, CaY, and ZnX), chabazites, clinoptilolites and LTA (3A, 4A, 5A) zeolites. 
     
     
         11 . The process of  claim 1  wherein the adsorbent material is the one or more adsorbents and wherein the adsorbent is sulfur or a metal sulfide on an activated carbon support or an activated alumina support or other supports to bind the active reagents for mercury removal in the form of beads or pellets. 
     
     
         12 . The process of  claim 1  wherein the adsorbent material is the one or more adsorbents and wherein the adsorbent is a metal sulfide, metal oxide, or metal carbonate on a support, the metal is selected from the group consisting of copper, silver, gold, antimony, lead, and manganese, and the support selected from the group consisting of activated alumina, clay, or activated carbon. 
     
     
         13 . The process of  claim 1  wherein the adsorbent material is the one or more adsorbents and wherein the adsorbent is a metal, a metal oxide, or a metal carbonate on a support, the metal selected from the group consisting of copper, silver, gold, antimony, lead and manganese, and the support selected from the group consisting of activated alumina, clay, and activated carbon, wherein the adsorbent is sulfided by sulfur compounds in the mercury removal zone to produce a sulfided adsorbent and wherein the sulfided adsorbent removes mercury. 
     
     
         14 . The process of  claim 1  wherein the adsorbent material is the ion exchange material and wherein the ion exchange material contains chemically bound sulfide groups. 
     
     
         15 . The process of  claim 1  wherein the adsorbent material is the ion exchange material and wherein the ion exchange material comprises a cation exchange material. 
     
     
         16 . The process of  claim 1  further comprising processing at least one of the fractions to produce at least one additional product. 
     
     
         17 . A process for removing mercury from a coal tar product comprising:
 providing a coal tar stream, the coal tar stream containing one or more of elemental mercury, organic mercury compounds, and inorganic mercury compounds;   introducing the coal tar stream into a catalytic distillation zone of a fractionation zone to separate the coal tar stream into at least two fractions, the catalytic distillation zone positioned above a bottoms outlet and below a first product draw of the fractionation zone, the catalytic distillation zone containing a catalyst, the organic and ionic mercury compounds reacting in the presence of the catalyst to form elemental mercury in the catalytic distillation zone; and   treating at least one of the fractions to remove the elemental mercury.   
     
     
         18 . The process of  claim 17  further comprising introducing hydrogen into the catalytic distillation zone. 
     
     
         19 . The process of  claim 17  wherein the catalyst comprises at least one Group VIB, Group VIIB, or Group VIIIB metal, a noble metal catalyst, or a zeolitic catalyst. 
     
     
         20 . The process of  claim 17  wherein the catalytic distillation zone operates at a temperature in a range of about 35° C. to about 320° C.