Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G15/00—Cracking of hydrocarbon oils by electric means, electromagnetic or mechanical vibrations, by particle radiation or with gases superheated in electric arcs
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G27/00—Refining of hydrocarbon oils in the absence of hydrogen, by oxidation
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G32/00—Refining of hydrocarbon oils by electric or magnetic means, by irradiation, or by using microorganisms
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G32/00—Refining of hydrocarbon oils by electric or magnetic means, by irradiation, or by using microorganisms
  • C10G32/02—Refining of hydrocarbon oils by electric or magnetic means, by irradiation, or by using microorganisms by electric or magnetic means
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B1/00—Electrolytic production of inorganic compounds or non-metals
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C1/00—Electrolytic production, recovery or refining of metals by electrolysis of solutions
  • C25C1/02—Electrolytic production, recovery or refining of metals by electrolysis of solutions of light metals
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C7/00—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells

Definitions

• the present invention relates to a process for removing nitrogen, sulfur, and heavy metals from sulfur-, nitrogen-, and metal-bearing shale oil, bitumen, heavy oil, or refinery streams. More particularly, the invention relates to a method of regenerating alkali metals from sulfides (mono- and polysulfides) of those metals. The invention further relates to the removal and recovery of sulfur from alkali metal sulfides and polysulfides.
• alkali metal such as sodium or lithium is reacted with the oil at about 350°C and 300-2000 psi.
• 1-2 moles sodium and 1-1.5 moles hydrogen may be needed per mole sulfur according to the following initial reaction with the alkali metal:
• R, R', R" represent portions of organic molecules or organic rings.
• the nitrogen is removed in the form of ammonia which may be vented and recovered.
• the sulfur is removed in the form of an alkali hydrosulfide, NaHS, which is separated for further processing.
• the heavy metals and organic phase may be separated by gravimetric separation techniques. The above reactions are expressed using sodium but may be substituted with lithium.
• Heavy metals contained in organometallic molecules such as complex porphyrins are reduced to the metallic state by the alkali metal. Once the heavy metals have been reduced, they can be separated from the oil because they no longer are chemically bonded to the organic structure. In addition, once the metals are removed from the porphyrin structure, the nitrogen heteroatoms in the structure are exposed for further denitrogenation.
• a washing step either with steam or with hydrogen sulfide to form a hydroxide phase if steam is utilized or a hydrosulfide phase if hydrogen sulfide is used.
• alkali nitride is presumed to react to form ammonia and more alkali hydroxide or hydrosulfide.
• a gravimetric separation such as centrifugation or filtering can separate the organic, upgraded oil, from the salt phase.
• H 2 S and NH 3 are formed respectively.
• the reaction to form hydrogen sulfide and ammonia is much less favorable thermodynamically than the formation of the sodium or lithium compounds so the parent molecules must be destabilized to a greater degree for the desulfurization of denitrogenation reaction to proceed.
• T. Kabe, A Ishihara, W. Qian, in Hydrodesulfurization and Hydrodenitrogenation, pp. 37, 110-112, Wiley- VCH, 1999 this destabilization occurs after the benzo rings are mostly saturated.
• Metallic sodium is commercially produced almost exclusively in a Downs-cell such as the cell described in U.S. Pat. No. 1,501,756.
• Such cells electrolyze sodium chloride that is dissolved in a molten salt electrolyte to form molten sodium at the cathode and chlorine gas at the anode.
• the cells operate at a temperature near 600 °C, a temperature compatible with the electrolyte used.
• the chlorine anode is utilized commercially both with molten salts as in the co-production of sodium and with saline solution as in the co-production of sodium hydroxide.
• Another objective of the present invention is to teach improvements in the process and device for recovering alkali metal from alkali metal sulfide generated by the sulfur removal and upgrading process.
• the present invention provides a process for removing nitrogen, sulfur, and heavy metals from sulfur-, nitrogen-, and metal-bearing shale oil, bitumen, heavy oil, or refinery streams.
• the present invention further provides an electrolytic process of regenerating alkali metals from sulfides, polysulfides, nitrides, and polynitrides of those metals.
• the present invention further provides an electrolytic process of removing sulfur from a polysulfide solution.
• One non-limiting embodiment within the scope of the invention includes a process for oxidizing alkali metal sulfides and polysulfides electrochemically.
• the process utilizes an electrolytic cell having an alkali ion conductive membrane configured to selectively transport alkali ions, the membrane separating an anolyte compartment configured with an anode and a catholyte compartment configured with a cathode.
• An anolyte solution is introduced into the anolyte compartment.
• the anolyte solution includes an alkali metal sulfide and/or polysulfide and an anolyte solvent that partially dissolves elemental sulfur and alkali metal sulfide and polysulfide.
• a catholyte solution is introduced into the catholyte compartment.
• the catholyte solution includes alkali metal ions and a catholyte solvent.
• the catholyte solvent may include one of many non-aqueous solvents such as tetraethylene glycol dimethyl ether (tetraglyme), diglyme, dimethyl carbonate, dimethoxy ether, propylene carbonate, ethylene carbonate, diethyl carbonate.
• the catholyte may also include an alkali metal salt such as an iodide or chloride of the alkali metal.
• Applying an electric current to the electrolytic cell oxidizes sulfide and/or polysulfide in the anolyte compartment to form higher level polysulfide and causes high level polysulfide to oxidize to elemental sulfur.
• the electric current further causes alkali metal ions to pass through the alkali ion conductive membrane from the anolyte compartment to the catholyte compartment, and reduces the alkali metal ions in the catholyte compartment to form elemental alkali metal.
• Sulfur may be recovered in the liquid form when the temperature exceeds the melting point of sulfur and the sulfur content of the anolyte exceeds the solubility of the solvent.
• anolyte solvents have lower specific gravity compared to sulfur so the liquid sulfur settles to the bottom. This settling may occur within a settling zone in the cell where the sulfur may be drained through an outlet. Alternatively a portion of the anolyte solution may be transferred to a settling zone out of the cell where settling of sulfur may occur more effectively than in a cell.
• the melting temperature of sulfur is near 115 °C so the cell is best operated above that temperature, above 120 °C. At that temperature or above, the alkali metal is also molten if the alkali metal is sodium. Operation near a higher temperature, such as in the 125-150 °C range, allows the sulfur to fully remain in solution as it is formed from the polysulfide at the anode, then when the anolyte flows to a settling zone, within or external to the cell where the temperature may be 5-20 °C cooler, the declining solubility of the sulfur in the solvent results in a sulfur liquid phase forming which is has higher specific gravity and settles from the anolyte.
• the anolyte flows back toward the anodes where sulfur is forming through electrochemical oxidation of polysulfide, the anolyte has solubility has the capacity to dissolve the sulfur as it is formed, preventing fouling and polarization at the anodes or at membrane surfaces.
• a cell for electrolyzing an alkali metal sulfide or polysulfide where the cell operates at a temperature above the melting temperature of the alkali metal and where the cathode is wholly or partially immersed in a bath of the molten alkali metal with a divider between an anolyte compartment and a catholyte compartment.
• the catholyte essentially comprises molten alkali metal but may also include solvent and alkali metal salt.
• the divider may be permeable to alkali metal cations and substantially impermeable to anions, solvent and dissolved sulfur.
• the divider comprises in part an alkali metal conductive ceramic or glass ceramic.
• the divider may be conductive to alkali ions which include lithium and sodium.
• a cell for electrolyzing an alkali metal polysulfide is provided with an anolyte compartment and a catholyte compartment where the anolyte solution comprises a polar solvent and dissolved alkali metal polysulfide.
• the anolyte solution comprises a solvent that dissolves to some extent elemental sulfur.
• the anolyte may comprise a solvent where one or more of the solvents includes: N,N- dimethylaniline, quinoline, tetrahydrofuran, 2-methyl tetrahydrofuran, benzene, cyclohexane, fluorobenzene, thrifluorobenzene, toluene, xylene, tetraethylene glycol dimethyl ether (tetraglyme), diglyme, isopropanol, ethyl propional, dimethyl carbonate, dimethoxy ether, dimethylpropyleneurea , formamide, methyl formamide, dimethyl formamide, acetamide, methyl acetamide, dimethyl acetamide, triethylamine, diethyl acetamide, ethanol and ethyl acetate, propylene carbonate, ethylene carbonate, and diethyl carbonate.
• the solvents includes: N,N- dimethylaniline, quinoline,
• a method for oxidizing sulfides and polysulfides electrochemically from an anolyte solution at an anode where the anolyte solution comprises in part an anolyte solvent that dissolves to some extent elemental sulfur.
• the anolyte solvent that dissolves to some extent elemental sulfur is one or more of the following: 7V,7V-dimethylaniline, quinoline, tetrahydrofuran, 2-methyl tetrahydrofuran, benzene, cyclohexane, fluorobenzene, thrifluorobenzene, toluene, xylene, tetraethylene glycol dimethyl ether (tetraglyme), diglyme, isopropanol, ethyl propional, dimethyl carbonate, dimethoxy ether, dimethylpropyleneurea , formamide, methyl formamide, dimethyl formamide, acetamide, methyl acetamide, dimethyl acetamide, triethylamine, diethyl acetamide, ethanol and ethyl acetate, propylene carbonate, ethylene carbonate, and diethyl carbonate.
• a cell for electrolyzing an alkali metal monosulfide or a polysulfide is provided with an anolyte compartment and a catholyte compartment where the anolyte solution comprises a polar solvent and dissolved alkali metal monosulfide or a polysulfide.
• the anolyte solution comprises a solvent that dissolves to some extent elemental sulfur.
• the anolyte may comprise a solvent where one or more of the solvents includes: ⁇ , ⁇ -dimethylaniline, quinoline, tetrahydrofuran, 2-methyl tetrahydrofuran, benzene, cyclohexane, fluorobenzene, thrifluorobenzene, toluene, xylene, tetraethylene glycol dimethyl ether (tetraglyme), diglyme, isopropanol, ethyl propional, dimethyl carbonate, dimethoxy ether, dimethylpropyleneurea, formamide, methyl formamide, dimethyl formamide, acetamide, methyl acetamide, dimethyl acetamide, triethylamine, diethyl acetamide, ethanol and ethyl acetate, propylene carbonate, ethylene carbonate, and diethyl carbonate.
• the solvents includes: ⁇ , ⁇ -dimethylaniline, quino
• a method for oxidizing monosulfide or polysulfides electrochemically from an anolyte solution at an anode where the anolyte solution comprises in part an anolyte solvent that dissolves to some extent elemental sulfur.
• the anolyte solvent that dissolves to some extent elemental sulfur is one or more of the following: ⁇ , ⁇ -dimethylaniline, quinoline, tetrahydrofuran, 2-methyl tetrahydrofuran, benzene, cyclohexane, fluorobenzene, thrifluorobenzene, toluene, xylene, tetraethylene glycol dimethyl ether (tetraglyme), diglyme, isopropanol, ethyl propional, dimethyl carbonate, dimethoxy ether, dimethylpropyleneurea, formamide, methyl formamide, dimethyl formamide, acetamide, methyl acetamide, dimethyl acetamide, triethylamine, diethyl acetamide, ethanol and ethyl acetate, propylene carbonate, ethylene carbonate, and diethyl carbonate.
• the anolyte solvent comprises from about 60-100 vol. % polar solvent and 0-40 vol. % apolar solvent.
• a blend of different anolyte solvents may help optimize the solubility of elemental sulfur and the solubility of sulfide and polysulfide.
• the separation of liquid phase sulfur from liquid phase anolyte includes one or more of the following: gravimetric, centrifugation.
• the alkali metal polysulfide is of the class including sodium polysulfide and lithium polysulfide.
• the present invention may provide certain advantages, including but not limited to the following:
• Figure 1 shows an overall process for removing nitrogen, sulfur, and heavy metals from sulfur-, nitrogen-, and metal-bearing oil sources using an alkali metal and for regenerating the alkali metal.
• Figures 2A and 2B show schematic processes for converting alkali metal hydrosulfide to alkali metal polysulfide and recovering hydrogen sulfide.
• Figure 3 shows a schematic cross-section of an electrolytic cell which utilizes many of the features within the scope of the invention.
• Figure 4 shows a schematic of several electrolytic cells operated in series to extract alkali metal and oxidize alkali metal sulfide to polysulfide and low polysulfide to high polysulfide and high polysulfide to sulfur.
• FIG. 1 The overall process is shown schematically in Figure 1 of one non-limiting embodiment for removing nitrogen, sulfur, and heavy metals from sulfur-, nitrogen-, and metal-bearing oil sources using an alkali metal and for regenerating the alkali metal.
• an oil source 102 such as high-sulfur petroleum oil distillate, crude, heavy oil, bitumen, or shale oil
• An alkali metal (M) 106 such as sodium or lithium, is also introduced into the reaction vessel, together with a quantity of hydrogen 108.
• the alkali metal and hydrogen react with the oil and its contaminants to dramatically reduce the sulfur, nitrogen, and metal content through the formation of sodium sulfide compounds (sulfide, polysulfide and hydrosulfide) and sodium nitride compounds.
• sodium sulfide compounds sulfide, polysulfide and hydrosulfide
• sodium nitride compounds sodium nitride compounds.
• Examples of the processes are known in the art, including but not limited to, U.S. Patent Nos. 3,785,965; 3,787,315; 3,788,978; 4,076,613; 5,695,632; 5,935,421; and 6,210,564.
• R, R', R" represent portions of organic molecules or organic rings.
• the nitrogen is removed in the form of ammonia 112, which may be vented and recovered.
• the sulfur is removed from the oil source in the form of an alkali hydrosulfide (MHS), such as sodium hydrosulfide (NaHS) or lithium hydrosulfide (LiHS).
• MHS alkali hydrosulfide
• NaHS sodium hydrosulfide
• LiHS lithium hydrosulfide
• the reaction products 113 are transferred to a separation vessel 114. Within the separation vessel 114, the heavy metals 116 and upgraded oil organic phase 118 may be separated by gravimetric separation techniques.
• the alkali hydrosulfide (MHS) is separated for further processing.
• the alkali hydrosulfide stream may be the primary source of alkali metal and sulfur from the process of the present invention.
• a medium to high polysulfide i.e. M 2 S X ; 4 ⁇ x ⁇ 6
• hydrogen sulfide will be released and the resulting mixture will have additional alkali metal and sulfide content where the sulfur to alkali metal ratio is lower.
• the hydrogen sulfide 110 can be used in the washing step upstream where alkali sulfide and alkali nitride and metals need to be removed from the initially treated oil.
• FIG. 2A A schematic representation of this process is shown in Fig. 2A.
• the following reaction may occur:
• x:y represent the average ratio of sodium to sulfur atoms in the solution.
• the alkali metal hydrosulfide can be reacted with sulfur.
• a schematic representation of this process is shown in Fig. 2B.
• the following reaction may occur:
• the alkali metal polysulfide may be further processed in an electrolytic cell to remove and recover sulfur and to remove and recover the alkali metal.
• One electrolytic cell 120 is shown in Fig. 1.
• the electrolytic cell 120 receives alkali polysulfide 122. Under the influence of a source electric power 124, alkali metal ions are reduced to form the alkali metal (M) 126, which may be recovered and used as a source of alkali metal 106.
• Sulfur 128 is also recovered from the process of the electrolytic cell 120.
• a detailed discussion of one possible electrolytic cell that may be used in the process within the scope of the present invention is given with respect to Fig. 3.
• a more detailed discussion relating to the recovery of sulfur 128 is given with respect to Fig. 4, below.
• the vessel where the reaction depicted in Figures 2A and 2B occurs could be the anolyte compartment of the electrolytic cell 120 depicted in Figure 1, the thickener 312 depicted in Figure 4, or in a separate vessel conducive to capturing and recovering the hydrogen sulfide gas 110 generated.
• sulfur generated in the process depicted in Figure 1 could be used as an input as depicted in Figure 2B.
• FIG. 3 shows a schematic sectional view of an electrolytic cell 300 which utilizes many of the features within the scope of the invention.
• the cell is comprised of a housing 310, which typically is an electrical insulator and which is chemically resistant to solvents and sodium sulfide.
• a cation conductive membrane 312, in this case in the form of a tube, divides the catholyte compartment 314 from the anolyte compartment 316.
• a cathode 324 Within the catholyte compartment is a cathode 324.
• the cathode 324 may be configured to penetrate the housing 310 or have a lead 326 that penetrates the housing 310 so that a connection may be made to negative pole of a DC electrical power supply (not shown).
• anode 326 which in this case is shown as a porous mesh type electrode in a cylindrical form which encircles the membrane tube 312.
• a lead 328 penetrates the housing so that a connection may be made with a positive pole of the DC power supply.
• An anolyte solution flows through an anolyte inlet 330.
• the anolyte is comprised of a mixture of solvents and alkali metal sulfides. As anolyte flows in through the inlet 330 anolyte also flows out of the outlet 332. In some cases a second liquid phase of molten sulfur may also exit with the anolyte.
• a second outlet may be provided from the anolyte compartment at a location lower than the anolyte outlet 332.
• the second, lower outlet may be used more for removal of molten sulfur that has settled and accumulated at the cell bottom.
• the space between the cathode 324 and the membrane 312 is generally filled with molten alkali metal. As the cell operates, alkali metal ions pass through the membrane 312 and reduce at the cathode 324 to form alkali metal in the catholyte compartment 314 resulting in a flow of alkali metal through the catholyte outlet 334.
• a cell may have multiple anodes, cathodes, and membranes. Within a cell the anodes all would be in parallel and the cathodes all in parallel.
• electrolytic cell housing 310 is preferably an electrically insulative material such as most polymers.
• the material also is preferably chemically resistant to solvents.
• Polytetrafluoroethylene (PTFE) is particularly suitable, as well as Kynar® polyvinylidene fluoride, or high density polyethylene (HDPE).
• the cell housing 310 may also be fabricated from a non insulative material and non-chemically resistant materials, provided the interior of the housing 310 is lined with such an insulative and chemically resistant material.
• Other suitable materials would be inorganic materials such as alumina, silica, alumino-silicate and other insulative refractory or ceramic materials.
• the cation conductive membrane 312 preferably is substantially permeable only to cations and substantially impermeable to anions, polyanions, and dissolved sulfur.
• the membrane 312 may be fabricated in part from an alkali metal ion conductive material. If the metal to be recovered by the cell is sodium, a particularly well suited material for the divider is known as NaSICON which has relatively high ionic conductivity at room temperature.
• a typical NaSICON composition substantially would be Na 1+x Zr 2 Si x P 3 _ x 0 12 where 0 ⁇ x ⁇ 3.
• Other NaSICON compositions are known in the art.
• a particularly well suited material for the divider would be lithium titanium phosphate (LTP) with a composition that is substantially, Li (1+x+ y) Al x Ti (1 _ x _y ) (P0 4 ) 3 where 0 ⁇ x ⁇ 0.4, 0 ⁇ y ⁇ 0.2.
• LTP lithium titanium phosphate
• Other suitable materials may be from the ionically conductive glass and glass ceramic families such as the general composition Li 1+x Al x Ge 2 _ X P0 4 .
• Other lithium conductive materials are known in the art.
• the membrane 312 may have a portion of its thickness which has negligible through porosity such that liquids in the anolyte compartment 316 and catholyte compartment 314 cannot pass from one compartment to the other but substantially only alkali ions (M + ), such as sodium ions or lithium ions, can pass from the anolyte compartment 316 to the catholyte compartment 314.
• M + alkali ions
• the membrane may also be comprised in part by an alkali metal conductive glass-ceramic such as the materials produced by Ohara Glass of Japan.
• the anode 326 is located within the anolyte compartment 316. It may be fabricated from an electrically conductive material such as stainless steel, nickel, iron, iron alloys, nickel alloys, and other anode materials known in the art. The anode 326 is connected to the positive terminal of a direct current power supply. The anode 326 may be a mesh, monolithic structure or may be a monolith with features to allow passage of anolyte through the anode structure. Anolyte solution is fed into the anolyte compartment through an inlet 330 and passes out of the compartment through and outlet 332. The electrolytic cell 300 can also be operated in a semi-continuous fashion where the anolyte compartment is fed and partially drained through the same passage.
• the electronically conductive cathode 324 is in the form of a strip, band, rod, or mesh.
• the cathode 324 may be comprised of most electronic conductors such as steel, iron, copper, or graphite.
• a portion of the cathode may be disposed within the catholyte compartment 314 and a portion outside the catholyte compartment 314 and cell housing 310 for electrical contact.
• a lead 325 may extend from the cathode outside the cell housing 310 for electrical contact.
• an alkali ion conductive liquid which may include a polar solvent.
• Non-limiting examples of suitable polar solvents are as tetraethylene glycol dimethyl ether (tetraglyme), diglyme, dimethyl carbonate, dimethoxy ether, propylene carbonate, ethylene carbonate, diethyl carbonate and such.
• An appropriate alkali metal salt such as a chloride, bromide, iodide, perchlorate, hexafluorophosphate or such, is dissolved in the polar solvent to form that catholyte solution. Most often the catholyte is a bath of molten alkali metal.
• Anolyte solution is fed into the anolyte compartment 316.
• the electrodes 324, 326 are energized such that there is an electrical potential between the anode 326 and the cathode 324 that is greater than the decomposition voltage which ranges between about 1.8V and about 2.5V depending on the composition.
• alkali metal ions such as sodium ions
• sodium ions pass through the membrane 312 into the catholyte compartment 314, sodium ions are reduced to the metallic state within the catholyte compartment 314 with electrons supplied through the cathode 324, and sulfide and polysulfide is oxidized at the anode 326 such that low polysulfide anions become high polysulfide anions and/or elemental sulfur forms at the anode.
• sulfur is formed it is dissolved into the anolyte solvent in entirety or in part. On sulfur saturation or upon cooling, sulfur may form a second liquid phase of that settles to the bottom of the anolyte compartment 316 of the electrolytic cell.
• the sulfur may be removed with the anolyte solution to settle in a vessel outside of the cell or it may be directly removed from a settling zone 336 via an optional sulfur outlet 338, as shown in Fig. 3.
• a mode of operation may be to have the anolyte of one electrolytic cell flow into a second cell and from a second cell into a third cell, and so forth where in each successive cell the ratio of sodium to sulfide decreases as the polysulfide forms become of higher order.
• Figure 4 is non-limiting schematic of four electrolytic cells, 402, 404, 406, 408 operated in series to extract alkali metal and oxidize alkali metal sulfide to low alkali metal polysulfide, to oxide low alkali metal polysulfide to higher alkali metal polysulfide, and to oxide higher alkali metal polysulfide to high alkali metal polysulfide, and to oxide high alkali metal polysulfide to sulfur.
• the electrolytic cells 402, 404, 406, and 408 may be operated such that only in the final cell is sulfur produced but where alkali metal is produced at the cathode of all of them.
• an alkali metal monosulfide such as sodium sulfide (Na 2 S) may be introduced into the first electrolytic cell 402.
• sodium ions are transported from the anolyte compartment to the catholyte compartment where the alkali ions are reduced to form alkali metal.
• Sulfide is oxidized in the anolyte compartment to form a low polysulfide, such as Na 2 S 4 .
• the low alkali metal polysulfide is transported to the anolyte compartment of a second electrolytic cell 404.
• sodium ions are transported from the anolyte compartment to the catholyte compartment where the alkali ions are reduced to form alkali metal.
• the low polysulfide is oxidized in the anolyte compartment to form a higher polysulfide, such as Na 2 S 6 .
• the higher alkali metal polysulfide is transported to the anolyte compartment of a third electrolytic cell 406.
• sodium ions are transported from the anolyte compartment to the catholyte compartment where the alkali ions are reduced to form alkali metal.
• the higher polysulfide is oxidized in the anolyte compartment to form a high polysulfide, such as Na 2 S 8 .
• the high alkali metal polysulfide is transported to the anolyte compartment of a fourth electrolytic cell 408. Under the influence of a DC power supply, sodium ions are transported from the anolyte compartment to the catholyte compartment where the alkali ions are reduced to form alkali metal.
• High polysulfide is oxidized in the anolyte compartment to form sulfur, which is subsequently removed from the anolyte compartment and recovered.
• the multi-cell embodiment described in relation to Figure 4 enables alkali metal and sulfur to be formed more energy efficiently compared to a single cell embodiment.
• the reason for the energy efficiency is because it requires less energy to oxidize lower polysulfides compared to higher polysulfides.
• the voltage required to oxidize polysulfides to sulfur is about 2.2 volts, whereas monosulfide and low polysulfide may be oxidized at a lower voltage, such as 1.7 volts.
• Table 1 Decomposition voltage and energy (watt-hour/mole) of sodium and lithium chlorides and sulfides
• the open circuit potential of a sodium/polysulfide cell is as low as 1.8V when a lower polysulfide, Na 2 S 3 is decomposed, while the voltage rises with rising sulfur content.
• a planar NaSICON or Lithium Titanium Phosphate (LTP) membrane is used to regenerate sodium or lithium, respectively.
• NaSICON and LTP have good low temperature conductivity as shown in Table 2.
• the conductivity values for beta alumina were estimated from the 300°C conductivity and activation energy reported by May. G. May, J. Power Sources ⁇ , 1 (1978).
• An electrolytic flow cell utilizes a 1" diameter NaSICON membrane with approximately 3.2 cm active area.
• the NaSICON is sealed to a scaffold comprised of a non- conductive material that is also tolerant of the environment.
• a scaffold material is alumina. Glass may be used as the seal material.
• the flow path of electrolytes will be through a gap between electrodes and the membrane.
• the anode (sulfur electrode) may be comprised of aluminum.
• the cathode may be either aluminum or stainless steel. It is within the scope of the invention to configure the flow cell with a bipolar electrodes design.
• Anolyte and catholyte solutions will each have a reservoir and pump.
• the anolyte reservoir will have an agitator.
• the entire system will preferably have temperature control with a maximum temperature of 150°C and also be configured to be bathed in a dry cover gas.
• the system preferably will also have a power supply capable of delivering to 5 VDC and up to 100 mA/ cm 2 .

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  • 2014-03-14 KR KR1020157027244A patent/KR102258315B1/ko active IP Right Grant
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  • 2014-03-14 EP EP14770492.8A patent/EP2970780B1/de active Active
  • 2014-03-14 CA CA2906000A patent/CA2906000C/en active Active
  • 2014-03-14 CN CN201480018989.7A patent/CN105189706A/zh active Pending
  • 2014-03-14 CN CN201710099325.3A patent/CN106757146B/zh active Active
  • 2014-03-14 WO PCT/US2014/027292 patent/WO2014152393A1/en active Application Filing
• 2016
  • 2016-07-18 HK HK16108477.7A patent/HK1220476A1/zh unknown

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