Electrolytic generation and purification of carbon

Abstract

The embodiments herein relate to methods, apparatus, and systems for forming and purifying solid carbon material from a molten carbonate salt electrolyte. Various embodiments also provide methods, apparatus, and systems for recycling certain materials including the carbonate salt electrolyte, carbon dioxide, water, etc. Advantageously, the system utilizes carbon dioxide in one or more processes, for example to purify the solid carbon and regenerate the carbonate salt electrolyte. These methods, apparatus, and systems provide an efficient technique to consume carbon dioxide in the production of solid carbon, with substantial advantages over systems that attempt to form solid carbon from a stream of carbon dioxide provided directly to an electrolysis reactor.

1 - 9 . (canceled) 
     
     
         10 . A method of producing and purifying carbon and recovering lithium carbonate, the method comprising:
 reducing carbonate ions at a cathode in a molten carbonate salt electrolyte in an electrolysis reactor to form at least carbon, wherein the molten carbonate salt electrolyte comprises an alkali metal carbonate;   producing a solid reaction product comprising the carbon, lithium oxide, and the alkali metal carbonate from the molten carbonate salt electrolyte;   transferring the solid reaction product to an extraction vessel;   providing carbon dioxide and a hydrogen-donor solvent to the extraction vessel at a target pressure to (i) produce alkali metal bicarbonate from the alkali metal carbonate, and (ii) form a mixture comprising purified solid carbon and a solution of (a) the alkali metal bicarbonate, (b) the carbon dioxide, and (c) the hydrogen-donor solvent;   separating the purified solid carbon from the mixture; and   removing the carbon dioxide and the hydrogen-donor solvent from the solution to provide recovered alkali metal carbonate.   
     
     
         11 . The method of  claim 10 , further comprising supplying the recovered lithium carbonate to the electrolysis reactor. 
     
     
         12 . The method of  claim 10 , wherein removing the carbon dioxide from the solution precipitates the recovered alkali metal carbonate in the hydrogen-donor solvent. 
     
     
         13 . The method of  claim 12 , further comprising after removing the hydrogen-donor solvent from the solution, supplying the hydrogen-donor solvent removed from the solution into the extraction vessel. 
     
     
         14 . The method of  claim 10 , further comprising after removing the carbon dioxide from the solution, supplying the carbon dioxide removed from the solution to the extraction vessel. 
     
     
         15 . The method of  claim 10 , wherein removing the carbon dioxide from the solution converts the alkali metal bicarbonate to the recovered alkali metal carbonate. 
     
     
         16 . The method of  claim 10 , wherein the target pressure is at least about 1 atmosphere, but is sufficiently low such that the carbon dioxide is not supercritical in the extraction vessel. 
     
     
         17 . The method of  claim 10 , further comprising drying the purified solid carbon and using the purified solid carbon to fabricate one or more device or material selected from the group consisting of: a battery, a capacitor, a polymer composite, a metal matrix composite, a carbon-carbon composite, a ceramic composite, and combinations thereof. 
     
     
         18 . The method of  claim 10 , wherein the purified solid carbon comprises one or more material selected from the group consisting of: activated carbon, amorphous carbon, carbon nanotubes, graphite, graphene, and fullerenes. 
     
     
         19 . A system for producing and purifying carbon and recovering lithium carbonate, the system comprising:
 an electrolysis reactor configured to produce a reaction product by reducing carbonate ions at a cathode in a molten carbonate salt electrolyte,
 wherein the electrolysis reactor comprises an anode comprising a transition metal, 
 wherein the molten carbonate salt electrolyte comprises lithium carbonate, and 
 wherein the reaction product comprises carbon, lithium oxide, and the lithium carbonate from the molten carbonate salt electrolyte; 
   an extraction vessel configured to hold carbon dioxide, a hydrogen-donor solvent, and a solid form of the reaction product therein,
 wherein the extraction vessel is configured to reach a target pressure of at least about 1 atmosphere while the reaction product, carbon dioxide, and hydrogen-donor solvent are held therein, thereby (i) producing lithium bicarbonate from the lithium carbonate, and (ii) forming a mixture comprising purified solid carbon and a solution of (a) the lithium bicarbonate, (b) the carbon dioxide, and (c) the hydrogen-donor solvent; 
   a separator for separating the purified solid carbon from the mixture; and   an evaporation reactor configured to receive the solution after the purified solid carbon is removed from the mixture,
 wherein the evaporation reactor is configured to evaporate the carbon dioxide and the hydrogen-donor solvent from the solution to provide recovered lithium carbonate. 
   
     
     
         20 . The system of  claim 19 , wherein the extraction vessel is configured to receive the carbon dioxide removed from the solution from the evaporation reactor. 
     
     
         21 . The system of  claim 20 , wherein the extraction vessel is configured to receive the hydrogen-donor solvent removed from the solution from the evaporation reactor. 
     
     
         22 . The system of  claim 20 , wherein the cathode comprises a transition metal. 
     
     
         23 . The system of  claim 22 , wherein the cathode comprises iron. 
     
     
         24 . The system of  claim 19 , wherein an anode in the electrolysis reactor comprises stainless steel. 
     
     
         25 . A method of producing carbon in an electrolytic reactor, the method comprising:
 outside the electrolytic reactor, reacting carbon dioxide with a lithium-containing precursor and producing lithium carbonate;   transferring the lithium carbonate to the electrolytic reactor;   in the electrolytic reactor cathodically reducing carbonate ions formed from the lithium carbonate to thereby form elemental carbon at a cathode of the electrolytic reactor, wherein reducing the carbonate ions is performed without introducing carbon dioxide to electrolytic reactor; and   purifying the elemental carbon.   
     
     
         26 . The method of  claim 25 , wherein the carbon dioxide and the lithium-containing precursor react with a hydrogen-donor solvent to form a solution comprising lithium bicarbonate, the carbon dioxide, and the hydrogen-donor solvent. 
     
     
         27 . The method of  claim 26 , further comprising removing the carbon dioxide from the solution to thereby precipitate the lithium carbonate in the hydrogen-donor solvent. 
     
     
         28 . The method of  claim 26 , further comprising separating the lithium carbonate from the hydrogen-donor solvent before transferring the lithium carbonate to the electrolytic reactor. 
     
     
         29 . The method of  claim 26 , wherein the hydrogen-donor solvent comprises water.