Method for desulfurizing gasoline or diesel fuel for use in a fuel cell power plant

Abstract

A fuel processing method is operable to remove substantially all of the sulfur present in an undiluted oxygenated hydrocarbon fuel stock supply which contains an oxygenate and which is used to power a fuel cell power plant in a mobile environment, such as an automobile, bus, truck, boat, or the like, or in a stationary environment. The power plant hydrogen fuel source can be gasoline, diesel fuel, or other like fuels which contain relatively high levels of organic sulfur compounds such as mercaptans, sulfides, disulfides, and the like. The undiluted hydrocarbon fuel supply is passed through a desulfurizer bed wherein essentially all of the sulfur in the organic sulfur compounds reacts with the nickel reactant, and is converted to nickel sulfide, while the now desulfurized hydrocarbon fuel supply continues through the remainder of the fuel processing system. The method does not require the addition of steam or a hydrogen source to the fuel stream prior to the desulfurizing step. The method can be used to desulfurize either a liquid or a gaseous fuel stream, which contains an oxygenate such as MTBE, ethanol, methanol, or the like. The inclusion of the oxygenate serves to extend the useful life of the desulfurization method.

What is claimed is:  
     
         1 . A method for desulfurizing a hydrocarbon fuel stream so as to convert the hydrocarbon fuel stream into a low sulfur content fuel, which low sulfur content fuel is suitable for use in a fuel processing section in a fuel cell power plant, said method comprising the steps of: 
 a) providing a nickel reactant desulfurization station which is operative to convert sulfur contained in organic sulfur compounds contained in the fuel stream to nickel sulfide;    b) introducing a hydrocarbon fuel stream which contains an oxygenate into said nickel reactant desulfurization station; and    c) said oxygenate being present in said fuel stream in an amount which is effective to provide an effluent fuel stream at an exit end of said nickel reactant station which effluent fuel stream contains no more than about 0.05 ppm sulfur.    
     
     
         2 . The method of  claim 1  wherein the oxygenate is selected from the group consisting of water, alcohol, ether, and mixtures thereof.  
     
     
         3 . The method of  claim 2  wherein said oxygenate is present in amounts operable to provide an operating life for the method which is at least about three times the operating life of a desulfurinzing method which does not include an oxygenate in the fuel stream.  
     
     
         4 . The method of  claim 2  wherein the oxygenate is selected from the group consisting of water, MTBE, ethanol, methanol, and mixtures thereof.  
     
     
         5 . A method for desulfurizing a gasoline fuel stream so as to convert the gasoline fuel stream into a low sulfur content fuel, which low sulfur content fuel is suitable for use in a fuel processing section in a fuel cell power plant, said method comprising the steps of: 
 a) providing a nickel reactant desulfurization station which is operative to convert sulfur contained in organic sulfur compounds contained in the fuel stream to nickel sulfide;    b) introducing a gasoline fuel stream which contains an oxygenate into said nickel reactant desuffurization station; and    c) said oxygenate being present in said gasoline fuel stream in an amount which is effective to provide an effluent gasoline fuel stream at an exit end of said nickel reactant station which effluent gasoline fuel stream contains no more than about 0.05 ppm sulfur.    
     
     
         6 . The method of  claim 5  wherein the oxygenate is selected from the group consisting or water, alcohol, ether, and mixtures thereof.  
     
     
         7 . The method of  claim 6  wherein the oxygenate is selected from the group consisting of water, MTBE, ethanol, methanol, and mixtures thereof.  
     
     
         8 . A method for desulfurizing a gasoline fuel stream so as to convert the gasoline fuel stream into a low sulfur content fuel, which low sulfur content fuel is suitable for use in a fuel processing section of a fuel cell power plant, said method comprising the steps of: 
 a) providing a nickel reactant desulfurization station which is operative to convert sulfur contained in organic sulfur compounds contained in the fuel stream to nickel sulfide;    b) introducing a gasoline fuel stream which contains an oxygenate into said nickel reactant desulfurization station; and    c) said oxygenate being present in said gasoline fuel stream in an amount which is effective to provide a continuous gasoline fuel stream at an exit end of said nickel reactant station which continuous gasoline fuel stream contains on average no more than about 0.05 ppm sulfur.    
     
     
         9 . A method for desulfurizing a gasoline fuel stream so as to convert the gasoline fuel stream into a low sulfur content fuel, which low sulfur content fuel is suitable for use in a fuel processing section in a fuel cell power plant, said method comprising the steps of: 
 a) providing a nickel reactant desulfurization station which is operative to convert sulfur contained in organic sulfur compounds contained in the fuel stream to nickel sulfide;    b) introducing a gasoline fuel stream which contains an oxygenate into said nickel reactant desulfurization station; and    c) said oxygenate being converted to isobutylene and methanol by said nickel catalyst in amounts which are effective to inhibit carbon deposition in said nickel catalyst station and provide a continuous gasoline fuel stream at an exit end of said nickel reactant station which continuous gasoline fuel stream contains no more than about 0.05 ppm sulfur.    
     
     
         10 . A method for desulfurizing a gasoline fuel stream so as to convert the gasoline fuel stream into a low sulfur content fuel, which low sulfur content fuel is suitable for use in a fuel processing section in a fuel cell power plant, said method comprising the steps of: 
 a) providing a nickel reactant desulfurization station which is operative to convert sulfur contained in organic sulfur compounds contained in the fuel stream to nickel sulfide;    b) introducing a gasoline fuel stream which contains an oxygenate into said nickel reactant desulfurization station, said oxygenate being present in said gasoline fuel stream in an amount which is effective to provide a low sulfur content gasoline fuel stream at an exit end of said nickel catalyst station which low sulfur content gasoline fuel stream contains no more than about 0.05 ppm sulfur; and    c) said oxygenate being converted to isobutylene and methanol by said nickel reactant during said desulfurizing step, said low sulfur content gasoline fuel stream being formed so long as said nickel reactant continues to convert the oxygenate.    
     
     
         11 . A method for desulfurizing a liquid gasoline fuel stream so as to convert the gasoline fuel stream into a low sulfur content fuel, which low sulfur content fuel is suitable for use in a fuel processing section in a fuel cell power plant, said method comprising the steps of: 
 a) providing a nickel reactant desulfurization station which is operative to convert sulfur contained in organic sulfur compounds contained in the fuel stream to nickel sulfide;    b) maintaining said nickel reactant desulfurization station at a temperature in the range of about 300° F. to about 450° F.;    c) introducing a liquid gasoline fuel stream which contains an oxygenate into said nickel reactant desulfurization station, said oxygenate being present in said gasoline fuel stream in an amount which is effective to provide a low sulfur content gasoline fuel stream at an exit end of said nickel reactant station which low sulfur content gasoline fuel stream contains no more than about 0.05 ppm sulfur; and    d) said oxygenate being converted to isobutylene and methanol by said nickel reactant during said desulfurizing step, said low sulfur content gasoline fuel stream being formed so long as said nickel reactant continues to convert the oxygenate.    
     
     
         12 . A method for desulfurizing a liquid gasoline fuel stream so as to convert the gasoline fuel stream into a low sulfur content fuel, which low sulfur content fuel is suitable for use in a fuel processing section in a fuel cell power plant, said method comprising the steps of: 
 a) providing a nickel reactant desulfurization station which is operative to convert sulfur contained in organic sulfur compounds contained in the fuel stream to nickel sulfide;    b) maintaining said nickel reactant desulfurization station at a temperature in the range of about 300° F. to about 450° F.;    c) introducing a mixture of about 2% to about 5% water and a liquid gasoline fuel stream, which mixture contains an oxygenate, into said nickel reactant desulfurization station, said oxygenate being present in said mixture in an amount which is effective to provide a low sulfur content gasoline fuel stream at an exit end of said nickel reactant station, which low sulfur content gasoline fuel stream contains no more than about 0.05 ppm sulfur; and    d) said oxygenate being consumed by said nickel reactant during said desulfurizing step, said low sulfur content gasoline fuel stream being formed so long as said nickel reactant continues to consume the oxygenate.    
     
     
         13 . The method of  claim 12  wherein the water in said mixture is derived by recirculating a portion of a selective oxidizer output back to an inlet to said nickel reactant station.  
     
     
         14 . The method of  claim 12  wherein the water in said mixture is the sole oxygenate in said mixture.  
     
     
         15 . The method of  claim 12  wherein the oxygenate includes an alcohol present in said gasoline fuel stream.  
     
     
         16 . The method of  claim 14  wherein the alcohol is selected from the group consisting of methanol, ethanol, propanol, and mixtures thereof.  
     
     
         17 . The method of  claim 12  wherein said oxygenate is an ether.  
     
     
         18 . The method of  claim 16  wherein said oxygenate is MTBE.  
     
     
         19 . The method of  claim 12  wherein said recirculated portion of the selective oxidizer output is between 1% and 10% of the total selective oxidizer output.  
     
     
         20 . A method for desulfurizing a liquid gasoline fuel stream so as to convert the gasoline fuel stream into a low sulfur content fuel, which low sulfur content fuel is suitable for use in a fuel processing section in a fuel cell power plant, said method comprising the steps of: 
 a) providing a nickel reactant desulfurization station which is operative to convert sulfur contained in organic sulfur compounds contained in the fuel stream to nickel sulfide;    b) maintaining said nickel reactant desulfurization station at a temperature in the range of about 300° F. to about 450° F.; and    c) introducing a mixture of a fuel cell selective oxidizer output recycle, which recycle contains hydrogen and water; and a liquid gasoline fuel, into said nickel reactant desulfurization station, said selective oxidizer output recycle being present in an amount which is effective to provide a low sulfur content gasoline fuel stream at an exit end of said nickel reactant station, which low sulfur content gasoline fuel stream contains no more than about 0.05 ppm sulfur.    
     
     
         21 . The method of  claim 20  wherein said selective oxidizer recycle comprises about 1% to about 10% of total selective oxidizer output.  
     
     
         22 . A method for desulfurizing a gaseous fuel stream so as to convert the gaseous fuel stream into a low sulfur content fuel, which low sulfur content fuel is suitable for use in a fuel processing section in a fuel cell power plant, said method comprising the steps of: 
 a) providing a nickel reactant desulfurization station which is operative to convert sulfur contained in organic sulfur compounds contained in the fuel stream to nickel sulfide;    b) introducing a gaseous fuel stream which contains a fuel cell selective oxidizer recycle mixture of hydrogen and water into said nickel reactant desulfurization station; and    c) said selective oxidizer recycle mixture being present in said gaseous fuel stream in an amount which is effective to provide an effluent gaseous fuel stream at an exit end of said nickel reactant station which effluent gaseous fuel stream contains no more than about 0.05 ppm sulfur.    
     
     
         23 . The method of  claim 21  wherein the gaseous fuel is selected from the group consisting of methane, ethane, propane and butane.  
     
     
         24 . The method of  claim 21  wherein the desulfurization station operates in a temperature range of about 250° F. to about 450° F.  
     
     
         25 . The method of  claim 21  wherein said recirculated portion of the selective oxidizer output is between 1% and 10% of the total selective oxidizer output.