Membrane desulfurization of liquid hydrocarbon feedstreams

Abstract

The process of the present invention is directed to the desulfurization of a sulfur-containing unrefined hydrocarbon stream with a membrane separation apparatus, where sulfur compounds are concentrated in a sulfur-rich stream on a permeate side of the membrane, and a sulfur-lean stream is recovered as a retentate. The sulfur-rich stream, which has a small volume relative to the original unrefined hydrocarbon stream, is conveyed to a subsequent desulfurization apparatus or system, such as a hydrotreating system, to recover the hydrocarbons associated with the organosulfur compounds. The stream desulfurized by conventional processes, such as hydrotreating, and the hydrocarbons desulfurized by the membrane separation apparatus may be combined to provide a low sulfur hydrocarbon effluent with minimal or no loss of the original volume.

1 . A process for reducing the sulfur content of an unrefined liquid hydrocarbon feedstream containing sulfur compounds, the process comprising:
 providing a membrane separation unit containing a membrane having a porous substrate with a sulfur-selective material retained upon the surface of the substrate and/or within the pores of the substrate;   introducing the unrefined liquid hydrocarbon feedstream into the membrane separation unit;   concentrating the sulfur compounds in a first unrefined hydrocarbon stream as a liquid permeate of the membrane unit;   recovering as a liquid retentate of the membrane separation unit a second unrefined hydrocarbon separation product stream of reduced sulfur content;   recovering and subjecting the first unrefined hydrocarbon stream to a hydrodesulfurization process step and recovering a third stream that is substantially free of sulfur compounds; and   mixing the second unrefined hydrocarbon stream and the third product stream to provide a final product stream of low sulfur content.   
     
     
         2 . The process of  claim 1  in which the membrane separation unit is operated with a sweep stream on the permeate side of the membrane at a temperature between about 15° C. and about 60° C. 
     
     
         3 . The process of  claim 1  in which the membrane separation unit is operated with an imposed pressure differential across the membrane of between about 1 psi and about 15 psi. 
     
     
         4 . A process for reducing the sulfur content of a hydrocarbon feed stream comprising:
 a. providing a membrane separation unit containing a membrane having a porous substrate with a sulfur-selective material upon the surface of the substrate and/or within the pores of the substrate, the membrane having a first side and a second side;   b. conveying an unrefined liquid hydrocarbon feedstream past the first side of the membrane;   c. recovering a liquid permeate unrefined hydrocarbon stream from the second side of the membrane, the permeate unrefined hydrocarbon stream having a higher sulfur concentration than the unrefined hydrocarbon stream; and   d. recovering a liquid retentate unrefined hydrocarbon stream from the first side of the membrane, the retentate unrefined hydrocarbon stream having a lower sulfur concentration than the unrefined hydrocarbon stream.   
     
     
         5 . A process for reducing the sulfur content of a hydrocarbon feed that includes a first desulfurization stage and a second desulfurization stage, the process comprising:
 a. providing a membrane separation unit containing a membrane having a porous substrate with a sulfur-selective material upon the surface of the substrate and/or within the pores of the substrate, the membrane having a first side and a second side;   b. conveying an unrefined liquid hydrocarbon stream past the first side of the membrane;   c. recovering a liquid retentate unrefined hydrocarbon stream from the first side of the membrane, the retentate unrefined hydrocarbon stream having a lower sulfur content than the unrefined hydrocarbon stream; and   d. recovering a liquid permeate unrefined hydrocarbon stream having a higher sulfur content than the unrefined hydrocarbon stream from the second side of the membrane and treating it the second desulfurization stage.   
     
     
         6 . The process of  claim 5 , wherein the second desulfurization stage includes a hydrodesulfurization step. 
     
     
         7 . The process of  claim 5 , wherein the second desulfurization stage includes an oxidative desulfurization step. 
     
     
         8 . The process of  claim 1 , wherein the unrefined liquid hydrocarbon feedstream is crude oil. 
     
     
         9 . The process of  claim 1 , wherein the sulfur-selective material is selective to thiophenes. 
     
     
         10 . The process of  claim 5 , wherein the sulfur-selective material is selective to dibenzothiophenes. 
     
     
         11 . The process of  claim 1 , wherein the sulfur selective material comprises an ionic liquid. 
     
     
         12 . The process of  claim 11 , wherein the ionic liquid comprises a methyl-pyridinium based ionic liquid. 
     
     
         13 . The process of  claim 12 , wherein the methyl-pyridinium based ionic liquid comprises N-butyl-3-methyl-pyridinium methyl sulfate. 
     
     
         14 . The process of  claim 11 , wherein the ionic liquid comprises an imidazolium-based ionic liquid. 
     
     
         15 . The process of  claim 4 , wherein the unrefined liquid hydrocarbon feedstream is crude oil. 
     
     
         16 . The process of  claim 4 , wherein the sulfur-selective material is selective to thiophenes. 
     
     
         17 . The process of  claim 5 , wherein the unrefined liquid hydrocarbon feedstream is crude oil. 
     
     
         18 . The process of  claim 5 , wherein the sulfur-selective material is selective to thiophenes. 
     
     
         19 . The process of  claim 4 , wherein the sulfur selective material comprises an ionic liquid. 
     
     
         20 . The process of  claim 19 , wherein the ionic liquid comprises a methyl-pyridinium based ionic liquid. 
     
     
         21 . The process of  claim 20 , wherein the methyl-pyridinium based ionic liquid comprises N-butyl-3-methyl-pyridinium methyl sulfate. 
     
     
         22 . The process of  claim 19 , wherein the ionic liquid comprises an imidazolium-based ionic liquid. 
     
     
         23 . The process of  claim 5 , wherein the sulfur selective material comprises an ionic liquid. 
     
     
         24 . The process of  claim 23 , wherein the ionic liquid comprises a methyl-pyridinium based ionic liquid. 
     
     
         25 . The process of  claim 24 , wherein the methyl-pyridinium based ionic liquid comprises N-butyl-3-methyl-pyridinium methyl sulfate. 
     
     
         26 . The process of  claim 23 , wherein the ionic liquid comprises an imidazolium-based ionic liquid.