Electrochemical treatment of heavy oil streams followed by caustic extraction or thermal treatment

Abstract

This invention relates to the electrochemical conversion of dibenzothiophene type molecules of petroleum feedstreams to mercaptans that can then be removed, in one embodiment, by caustic extraction. In another embodiment, the mercaptans can be thermally decomposed, removing sulfur as hydrogen sulfide. The conversion of dibenzothiophenes to mercaptans is performed by electrochemical means without the required addition of hydrogen and in the substantial absence of water.

1 . A process for removing sulfur from a sulfur-containing petroleum feedstream having at least a portion of its sulfur in the form of hindered dibenzothiophene compounds, comprising:
 a) passing a sulfur-containing petroleum feedstream to an electrochemical cell;   b) subjecting said feedstream to an effective voltage and current that will result in the conversion of at least a portion of said hindered dibenzothiophene compounds to mercaptan compounds;   c) passing the electrochemically treated petroleum feedstream containing said mercaptans compounds to a caustic treatment zone wherein it is contacted with an aqueous caustic solution wherein mercaptan-containing compounds are extracted by the aqueous caustic solution; and   d) collecting a reduced-sulfur petroleum product stream from the caustic treatment zone;   wherein the reduced-sulfur petroleum product stream has a lower sulfur content by wt % than the sulfur-containing petroleum feedstream.   
   
   
       2 . The process of  claim 1 , wherein the sulfur-containing petroleum feedstream is comprised of a bitumen. 
   
   
       3 . The process of  claim 2 , wherein the electrochemical cell is run at about 4 volts to about 500 volts and a current density of about 10 to about 1000 mA/cm 2 . 
   
   
       4 . The process of  claim 3 , wherein the aqueous caustic solution is a sodium hydroxide solution. 
   
   
       5 . The process of  claim 4 , wherein the sulfur-containing petroleum feedstream is comprised of a bitumen. 
   
   
       6 . The process of  claim 1 , wherein the sulfur-containing petroleum feedstream is a distillate boiling range hydrocarbon stream and an effective amount of an electrolyte is mixed with the mixture of water and distillate boiling range hydrocarbon stream. 
   
   
       7 . The process of  claim 6 , wherein the distillate boiling range hydrocarbon stream is a low sulfur automotive diesel oil. 
   
   
       8 . The process of  claim 6 , wherein the electrolyte is an organic electrolyte. 
   
   
       9 . The process of  claim 8 , wherein the organic electrolyte is selected from quaternary carbyl- and hydrocarbyl-onium salts. 
   
   
       10 . The process of  claim 8 , wherein the organic electrolyte is comprised of an organic soluble salt selected from the group consisting of 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluoro phosphate, 1-butyl-1-methyl pyrrolidinium trifluoro-methyl sulfonated, trihexyltetradecylphosphonium tris(pentafluoroethyl)trifluorophosphate and ethyl-dimethylpropyl-ammonium bis(trifluoro-methylsulfonyl)imide. 
   
   
       11 . The process of  claim 8 , wherein the electrolyte is an inorganic electrolyte selected from the group consisting of sodium hydroxide, potassium hydroxide and sodium phosphates. 
   
   
       12 . The process of  claim 6 , wherein the electrochemical cell is run at about 4 volts to about 500 volts and a current density of about 10 to about 1000 mA/cm 2 . 
   
   
       13 . The process of  claim 12 , wherein the aqueous caustic solution is a sodium hydroxide solution. 
   
   
       14 . The process of  claim 12 , at least a portion of the mercaptan compounds are alkylated biphenyl mercaptan compounds. 
   
   
       15 . A process for removing sulfur from a sulfur-containing petroleum feedstream having at least a portion of its sulfur in the form of hindered dibenzothiophene compounds, which method comprising:
 a) passing a sulfur-containing petroleum feedstream to an electrochemical cell;   b) subjecting said feedstream to an effective voltage and current that will result in the conversion of at least a portion of said hindered dibenzothiophene compounds to mercaptan compounds;   c) passing the electrochemically treated petroleum feedstream containing mercaptan compounds to a thermal decomposition zone wherein at least a portion of the mercaptans are decomposed to hydrogen sulfide at temperatures from about 302° F. to about 932° F. (150° C. to 500° C.); and   d) collecting a reduced-sulfur petroleum product stream from the thermal decomposition zone;   wherein the reduced-sulfur petroleum product stream has a lower sulfur content by wt % than the sulfur-containing petroleum feedstream.   
   
   
       16 . The process of  claim 15 , wherein the sulfur-containing petroleum feedstream is comprised of a bitumen. 
   
   
       17 . The process of  claim 16 , wherein the electrochemical cell is run at about 4 volts to about 500 volts and a current density of about 10 to about 1000 mA/cm 2 . 
   
   
       18 . The process of  claim 17 , wherein the thermal decomposition temperature is from about 482° F. to about 932° F. (250° C. to 500° C.). 
   
   
       19 . The process of  claim 18 , wherein the sulfur-containing petroleum feedstream is comprised of a bitumen. 
   
   
       20 . The process of  claim 15 , wherein the sulfur-containing petroleum feedstream is a distillate boiling range hydrocarbon stream and an effective amount of an electrolyte is mixed with the mixture of water and distillate boiling range hydrocarbon stream. 
   
   
       21 . The process of  claim 20 , wherein the distillate boiling range hydrocarbon stream is a low sulfur automotive diesel oil. 
   
   
       22 . The process of  claim 20 , wherein the electrolyte is an organic electrolyte. 
   
   
       23 . The process of  claim 22 , wherein the organic electrolyte is selected from quaternary carbyl- and hydrocarbyl-onium salts. 
   
   
       24 . The process of  claim 22 , wherein the organic electrolyte is selected from the organic soluble salt is selected from the group consisting of 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluoro phosphate, 1-butyl-1-methyl pyrrolidinium trifluoro-methyl sulfonated, trihexyltetradecylphosphonium tris(pentafluoroethyl)trifluorophosphate and ethyl-dimethylpropyl-ammonium bis(trifluoro-methylsulfonyl)imide. 
   
   
       25 . The process of  claim 20 , wherein the electrolyte is an inorganic electrolyte selected from the group consisting of sodium hydroxide, potassium hydroxide and sodium phosphates. 
   
   
       26 . The process of  claim 20 , wherein the electrolyte is an organic electrolyte selected from quaternary carbyl- and hydrocarbyl-onium salts. 
   
   
       27 . The process of  claim 20 , wherein the electrochemical cell is run at about 4 volts to about 500 volts and a current density of about 10 to about 1000 mA/cm 2 . 
   
   
       28 . The process of  claim 27 , at least a portion of the mercaptan compounds are alkylated biphenyl mercaptan compounds. 
   
   
       29 . The process of  claim 27 , wherein the thermal decomposition temperature is from about 482° F. to about 932° F. (250° C. to 500° C.).