Membrane desulfurization of liquid hydrocarbons using an extractive liquid membrane contactor system and method

Abstract

The process of the present invention is directed to the desulfurization of a sulfur-containing hydrocarbon stream with a membrane contactor, where sulfur compounds are concentrated in a sulfur-rich stream on a permeate side of the membrane using an extractive liquid, and a sulfur-lean stream is recovered as a retentate. The sulfur-rich stream, which has a small volume relative to the original hydrocarbon stream, is conveyed to a recovery zone to recover extractive liquid, and the remaining hydrocarbon stream having an increased concentration of sulfur compounds is passed to a downstream desulfurization apparatus or system, such as a hydrotreating system, to recover the hydrocarbons associated with the organosulfur compounds.

1 . A method of reducing the sulfur content of a sulfur-containing hydrocarbon feedstream comprising:
 passing the feedstream in contact with a membrane on a retentate side of a membrane separation unit;   passing an extractive liquid in contact with the membrane on a permeate side of the membrane separation unit under conditions in which the extractive liquid contacts the feedstream;   concentrating sulfur compounds in the extractive liquid in a permeate stream of the membrane separation unit;   recovering as a retentate stream a first hydrocarbon product stream of reduced sulfur content;   recovering and subjecting the permeate stream to a fractionation process step for recovery of at least a portion of the extractive liquid; and   recovering a resulting sulfur-rich hydrocarbon stream from the fractionation process step.   
     
     
         2 . The method of  claim 1 , wherein the sulfur-rich hydrocarbon stream is subjected to a hydrodesulfurization process step, and recovering a second hydrocarbon product stream of reduced sulfur content. 
     
     
         3 . The method of  claim 1 , further comprising mixing the first and second hydrocarbon product streams to provide a final product stream of reduced sulfur content. 
     
     
         4 . The method of  claim 1 , wherein the feedstream contains a plurality of different sulfur-containing compounds and at least certain of the sulfur-containing compounds are soluble in the extractive liquid. 
     
     
         5 . The method of  claim 4 , wherein the extractive liquid is selected from the group consisting of fumaronitrile; maleonitrile; glyoxal; 2-nitrofuran; acetonitrile; acrylonitrile; nitramine; isoxazole; furfural; 5-methylfurfural; benzoylacetonitrile; vinyl formate; methyl formate; oxazole; sulfuric acid; diketene; benzonitrile; acrolein; dimethyl-oxalate; furan; benzaldehyde; acetic anhydride; methacrylonitrile; dimethyl sulfide; lactic acid; acetic acid; dimethyl formamide; dimethyl sulfoxide; aqueous potassium hydroxide; furfuryl alcohol; vinylacetylene; nicotinonitrile; pyridazine; methylmaleic anhydride; acetaldehyde; cis-crotonitrie; 3-nitrobenzotrifluoride; methyl phenyl ketone; vinyl acetate; p-tolualdehyde; m-tolualdehyde; o-tolualdehyde; propylene-carbonate; methanol; methanol and aqueous sodium hydroxide; dimethylsulfoxide and methanol; 1-ethyl, 3-methylimidazolium ethyl sulfate; 1-ethyl, 3-methylimidazolium methyl sulfate; 1-ethyl, 3-methylimidazolium hexafluorophosphate; 1-butyl, 3-methylimidazolium tetrafluoroborate; 1-ethyl, 3-methylimidazolium bis(trifluoromethanesulfonyl)imidate; 1-n-propyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imidate; 1-n-butyl-3-methylimidazolium; 1-n-butyl-3-methylimidazolium trifluorotris(pentafluoroethyl)phosphate; 1-n-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imidate; and 1-n-decyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imidate. 
     
     
         6 . The method of  claim 1 , wherein target sulfur compounds comprise aliphatic sulfur molecules, and the extractive liquid is selected from the group consisting of acetonitrile; dimethyl sulfoxide; acrylonitrile; benzonitrile; dimethyl formamide; aqueous sodium hydroxide; aqueous potassium hydroxide; furfuryl alcohol; vinylacetylene; sulfuric acid; dimethylsulfoxide and methanol; furfural; and 5-methylfurfural. 
     
     
         7 . The method of  claim 1 , wherein target sulfur compounds comprise aromatic sulfur compounds including thiophenes, benzothiophenes and dibenzothiophenes, and the extractive liquid is selected from the group consisting of acetonitrile; furfural; benzonitrile; dimethyl sulfide; dimethyl formamide; methanol; lactic acid; propylene-carbonate; 5-methylfurfural; methyl formate; 1-ethyl, 3-methylimidazolium ethyl sulfate; 1-ethyl, 3-methylimidazolium methyl sulfate; 1-ethyl, 3-methylimidazolium hexafluorophosphate; 1-butyl, 3-methylimidazolium tetrafluoroborate; 1-ethyl, 3-methylimidazolium bis(trifluoromethanesulfonyl)imidate; 1-n-propyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imidate; 1-n-butyl-3-methylimidazolium trifluorotris(pentafluoroethyl)phosphate; and 1-n-butyl-3-methylimidazolium. 
     
     
         8 . The method of  claim 1 , wherein target sulfur compounds comprise alkyl derivatives of aromatic sulfur molecules including 4,6-dimethyl-dibenzothiophenes, and the extractive liquid is selected from the group consisting of acetonitrile; acrylonitrile; furfural; 5-methylfurfural; benzoylacetonitrile; vinyl formate; diketene; benzonitrile; acrolein; dimethyl-oxalate; benzaldehyde; acetic anhydride; methacrylonitrile; acetic acid; dimethyl formamide; dimethyl sulfoxide; aqueous potassium hydroxide; furfuryl alcohol; 1-ethyl, 3-methylimidazolium ethyl sulfate; 1-ethyl, 3-methylimidazolium methyl sulfate; 1-ethyl, 3-methylimidazolium hexafluorophosphate; 1-butyl, 3-methylimidazolium tetrafluoroborate; and 1-ethyl, 3-methylimidazolium bis(trifluoromethanesulfonyl)imidate. 
     
     
         9 . The method of  claim 1 , wherein the membrane is a porous membrane. 
     
     
         10 . The method of  claim 9 , wherein the porous membrane constitutes a controlled interface for contact between the hydrocarbon feedstream and the extractive liquid. 
     
     
         11 . The method of  claim 9 , wherein the porous membrane constitutes a non-dispersive contact interface between the extractive liquid and the hydrocarbon feedstream. 
     
     
         12 . The method of  claim 9 , wherein the porous membrane comprises a material which is insoluble in the hydrocarbon and the extractive liquid. 
     
     
         13 . The method of  claim 9 , wherein the porous membrane comprises a material which undergoes minimal swelling in the hydrocarbon and the extractive liquid. 
     
     
         14 . A liquid hydrocarbon desulfurization system comprising:
 a source of extractive liquid;   a membrane housing including
 a porous membrane having a retentate side and a permeate side, 
 a retentate portion configured and dimensioned for maximizing contact between a liquid hydrocarbon feedstream and the retentate side of the membrane, and 
 a permeate portion configured and dimensioned for maximizing contact between the extractive liquid and the retentate side of the membrane.