Multi-stage supercritical water upgrading of asphaltenes for the production of high-quality mesophase pitch

Abstract

A system for upgrading asphaltenes includes an asphaltene treatment line, a series of asphaltene upgrade units, a series of carbon fiber production units, an aqueous collection unit, and a gaseous collection unit. The series of carbon fiber production unit includes a demetallizing unit that includes a first supercritical water (SCW) treatment unit and a first centrifugation unit, a desulfurizing unit that includes a second SCW treatment unit and a second centrifugation unit, and a polycondensation unit that includes a third SCW treatment unit and a third centrifugation unit. A method for mesophase pitch production from an asphaltene feedstock and a method for manufacturing carbon fibers from asphaltene feedstock are also described.

What is claimed: 
     
         1 . A system for upgrading asphaltenes, the system comprising:
 an asphaltene treatment line;   a series of asphaltene upgrade units, the series comprising:
 a demetallizing unit, wherein the demetallizing unit comprises a first supercritical water (SCW) treatment unit and a first centrifugation unit; 
 a desulfurizing unit, wherein the desulfurizing unit comprises a second SCW treatment unit and a second centrifugation unit; and 
 a polycondensation unit, wherein the polycondensation unit comprises a third SCW treatment unit and a third centrifugation unit; 
   a series of carbon fiber production units;   an aqueous collection unit; and   a gaseous collection unit.   
     
     
         2 . The system of  claim 1 , wherein the demetallizing unit comprises a demetallizing agent injection port. 
     
     
         3 . The system of  claim 1 , wherein the series of asphaltene upgrade units further comprises a mesophase pitch enrichment unit downstream of the polycondensation unit and upstream of the series of carbon fiber production units. 
     
     
         4 . The system of  claim 3 , wherein the mesophase pitch enrichment unit comprises a supercritical carbon dioxide treatment unit, an inert gas bubbling chamber, and a fourth centrifugation unit. 
     
     
         5 . The system of  claim 2 , wherein the demetallizing agent is selected from the group consisting of mineral acids, fatty acids, boron trifluoride ether, sodium hypochlorite, peroxyacetic acid, phosphorous compounds, and combinations thereof. 
     
     
         6 . The system of  claim 1 , wherein the series of carbon fiber production units comprises:
 a mesophase pitch inlet line in fluid communication with the series of asphaltene upgrade units;   a melt-spinning unit;   an oxidative stabilization unit;   a carbonization unit;   a surface treatment unit;   a sizing chamber; and   a winding unit.   
     
     
         7 . A method for mesophase pitch production from an asphaltene feedstock, the method comprising:
 introducing the asphaltene feedstock to an asphaltene treatment line;   introducing the asphaltene feedstock to a first SCW treatment unit of a demetallizing unit;   demetallizing the asphaltene feedstock, thereby producing a first mixture and a first reaction gas stream, wherein the first mixture comprises a first aqueous fraction and a first pitch;   separating the first aqueous fraction from the first pitch;   introducing the first pitch to a second SCW treatment unit of a desulfurizing unit;   desulfurizing the first pitch, thereby forming a second mixture and a second reaction gas stream, wherein the second mixture comprises a second aqueous fraction and a second pitch;   separating the second aqueous fraction from the second pitch;   introducing the second pitch to a third SCW treatment unit of a polycondensation stage;   performing a polycondensation reaction in the third SCW treatment unit, thereby forming a third reaction gas stream and a third mixture, wherein the third mixture comprises a third aqueous fraction and the mesophase pitch; and   separating the third aqueous fraction from the mesophase pitch, thereby producing the mesophase pitch.   
     
     
         8 . The method of  claim 7 , wherein the asphaltene feedstock, the first pitch, and the second pitch independently comprises an anisotropic ratio in a range from about 0:1 to about 1:0. 
     
     
         9 . The method of  claim 7 , wherein the mesophase pitch comprises an anisotropic ratio from about 0.75:0.25 to about 1:0. 
     
     
         10 . The method of  claim 7 , further comprising introducing a decomplexing agent into the first SCW treatment unit prior to demetallizing the asphaltene feedstock. 
     
     
         11 . The method according to  claim 10 , wherein the decomplexing agent is selected from the group consisting of mineral acids, fatty acids, boron trifluoride ether, sodium hypochlorite, peroxyacetic acid, phosphorous compounds, and combinations thereof. 
     
     
         12 . The method according to  claim 7 , further comprising, prior to producing the mesophase pitch:
 introducing the mesophase pitch to a mesophase enrichment unit downstream of the polycondensation stage, wherein the mesophase enrichment unit comprises a supercritical carbon dioxide treatment unit, an inert gas bubbling unit, and a fourth centrifugation unit;   introducing the mesophase pitch to the supercritical carbon dioxide treatment unit of the mesophase enrichment unit;   operating the fourth treatment unit, thereby forming a fourth mixture and a fourth reaction gas stream, wherein the fourth mixture comprises an enriched mesophase pitch and a fourth aqueous fraction;   introducing the fourth mixture to the inert gas bubbling unit of the mesophase enrichment unit;   introducing an inert gas to the fourth treatment mixture;   removing the fourth gas stream from the enriched mesophase pitch and the fourth aqueous fraction;   introducing the enriched mesophase pitch and the fourth aqueous fraction to the fourth centrifugation unit; and   separating the fourth aqueous fraction from the enriched mesophase pitch, thereby producing the enriched mesophase pitch.   
     
     
         13 . The method of  claim 12 , wherein the inert gas is nitrogen gas. 
     
     
         14 . A method for manufacturing carbon fibers from asphaltene feedstock, the method comprising:
 introducing the asphaltene feedstock to an asphaltene treatment line;   introducing the asphaltene feedstock to a first SCW treatment unit of a demetallizing unit;   demetallizing the asphaltene feedstock, thereby producing a first mixture and a first reaction gas stream, wherein the first mixture comprises a first aqueous fraction and a first pitch;   separating the first aqueous fraction from the first pitch;   introducing the first pitch to a second SCW treatment unit of a desulfurizing unit;   desulfurizing the first pitch, thereby forming a second mixture and a second reaction gas stream, wherein the second treatment mixture comprises a second aqueous fraction and a second pitch;   separating the second aqueous fraction from the second pitch;   introducing the second pitch to a third SCW treatment unit of a polycondensation stage;   performing a polycondensation reaction in the third SCW treatment unit, thereby forming a third reaction gas stream and a third mixture, wherein the third mixture comprises a third aqueous fraction and a mesophase pitch;   separating the third aqueous fraction from the mesophase pitch;   producing the mesophase pitch; and   introducing the mesophase pitch fraction to a series of carbon fiber production units, thereby producing carbon fibers.   
     
     
         15 . The method according to  claim 14 , further comprising:
 introducing the mesophase pitch to a mesophase enrichment unit downstream of the polycondensation stage, wherein the mesophase enrichment unit comprises a supercritical carbon dioxide treatment unit, an inert gas bubbling unit, and a fourth centrifugation unit;   introducing the mesophase pitch to the fourth treatment unit of the mesophase enrichment unit;   operating the fourth treatment unit, thereby forming a fourth mixture and a fourth reaction gas stream, wherein the fourth mixture comprises an enriched mesophase pitch and a fourth aqueous fraction;   introducing the fourth treatment mixture to the inert gas bubbling unit of the mesophase enrichment unit;   introducing an inert gas to the fourth treatment mixture;   removing the fourth gas stream from the enriched mesophase pitch and the fourth aqueous fraction;   introducing the enriched mesophase pitch and the fourth aqueous fraction to the fourth centrifugation unit;   separating the fourth aqueous fraction from the enriched mesophase pitch; and   producing the enriched mesophase pitch.   
     
     
         16 . The method according to  claim 15 , further comprising introducing a decomplexing agent into the first SCW treatment unit prior to demetallizing the asphaltene feedstock. 
     
     
         17 . The method according to  claim 16 , wherein the decomplexing agent is compound selected from the group consisting of mineral acids, fatty acids, boron trifluoride ether, sodium hypochlorite, peroxyacetic acid, phosphorous compounds, and combinations thereof. 
     
     
         18 . The method according to  claim 15 , wherein the series of carbon fiber production units comprises:
 a screw-extruder comprising a gear pump, a multi-filament spinneret, and a wind-up device;   an oxidative stabilization unit;   a carbonization unit;   a sizing unit; and   a winding unit.   
     
     
         19 . The method according to  claim 15 , wherein the enriched mesophase pitch has an anisotropic ratio from about 0.85:0.15 to about 1:0.