Electrochemical reduction of sulfur from sulfur-containing solid carbon-based materials

Abstract

A process for removing sulfur from a sulfur-containing solid carbon-based material includes adding a sulfur-containing solid carbon-based material to an aqueous electrolyte solution comprising an effective amount of an electrolyte in an electrochemical cell, and subjecting the aqueous electrolyte solution to an effective voltage and current to at least partially oxidize at least a portion of sulfur in the sulfur-containing solid carbon-based material, thereby generating oxidized sulfur and a reduced sulfur-containing solid carbon-based material. The reduced sulfur-containing solid carbon-based material has a lower sulfur content by wt. % than the sulfur-containing solid carbon-based material.

Description

PRIORITY CLAIM

[0001] The present application claims priority to U.S. Provisional Patent Application Ser. No. 63 / 724,986, entitled “Electrochemical Reduction of Sulfur from Sulfur-Containing Solid Carbon-Based Materials,” filed Nov. 26, 2024, the content of which is incorporated by reference herein in its entirety.BACKGROUND

[0002] Crude oil must typically be refined and processed to yield valuable products. Refining and processing involve subjecting the crude oil to various separations and chemical reactions that ultimately yield a spectrum of useful products such as transportation fuels (aviation gasoline, automobile gasoline, and diesel fuel), heating oil, and kerosene, asphalt and petroleum coke.

[0003] Petroleum coke (also referred to as petcoke and referred to herein simply as coke) is a high carbon product of petroleum refining. Coke is obtained by heating the heavy residue left over from distillation processes (also referred to as resid) in the presence of steam to produce a solid, carbonaceous material. The marketability of coke may depend on the amount of sulfur it contains. For example, coke with a relatively high sulfur content is referred to as fuel grade coke and is sold as fuel for coal-burning boilers, typically for power generation. Coke with a relatively low sulfur content is more desirable and can be used to make, for example, electrodes that are valuable for use in dry cells and in industrial electrical processes, such as the production of aluminum.SUMMARY

[0004] In accordance with an illustrative embodiment, a process for removing sulfur from a sulfur-containing solid carbon-based material comprises:

[0005] adding a sulfur-containing solid carbon-based material to an aqueous electrolyte solution comprising an effective amount of an electrolyte in an electrochemical cell, and

[0006] subjecting the aqueous electrolyte solution to an effective voltage and current to at least partially oxidize at least a portion of sulfur in the sulfur-containing solid carbon-based material, thereby generating oxidized sulfur and a reduced sulfur-containing solid carbon-based material,

[0007] wherein the reduced sulfur-containing solid carbon-based material has a lower sulfur content by wt. % than the sulfur-containing solid carbon-based material.

[0008] In accordance with another illustrative embodiment, a process for removing sulfur from a sulfur-containing solid carbon-based material comprises:

[0009] introducing an aqueous electrolyte solution comprising an effective amount of an electrolyte to an electrochemical cell comprising a cathode side comprising a cathode, an anode side comprising an anode and a membrane disposed between the cathode and the anode.

[0010] introducing a sulfur-containing solid carbon-based material to the anode side of the electrochemical cell, and

[0011] subjecting the aqueous electrolyte solution to an effective voltage and current, thereby generating electrolyte ions and hydrogen,

[0012] wherein the electrolyte ions pass through the membrane to at least partially oxidize at least a portion of sulfur in the sulfur-containing solid carbon-based material, thereby generating oxidized sulfur and a reduced sulfur-containing solid carbon-based material, and

[0013] wherein the reduced sulfur-containing solid carbon-based material has a lower sulfur content by wt. % than the sulfur-containing solid carbon-based material.

[0014] In accordance with yet another illustrative embodiment, a process for removing sulfur from a sulfur-containing solid carbon-based material comprises:

[0015] introducing an aqueous electrolyte solution comprising an effective amount of an electrolyte to an electrochemical cell comprising a cathode side comprising a cathode, an anode side comprising an anode and a membrane disposed between the cathode and the anode,

[0016] introducing a sulfur-containing solid carbon-based material and a first regenerated redox mediator received from the electrochemical cell to a vessel external to the electrochemical cell wherein the first regenerated redox mediator at least partially oxidizes at least a portion of sulfur in the sulfur-containing solid carbon-based material, thereby generating oxidized sulfur, a reduced sulfur-containing solid carbon-based material, and spent redox mediator, passing the spent redox mediator to the electrochemical cell, and

[0017] subjecting the spent redox mediator to an effective voltage and current to regenerate the spent redox mediator, thereby providing a second regenerated redox mediator,

[0018] wherein the reduced sulfur-containing solid carbon-based material has a lower sulfur content by wt. % than the sulfur-containing solid carbon-based material.BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In combination with the accompanying drawing and with reference to the following detailed description, the features, advantages, and other aspects of the implementations of the present disclosure will become more apparent, and several implementations of the present disclosure are illustrated herein by way of example but not limitation. In the accompanying drawings:

[0020] FIG. 1 illustrates a schematic diagram of a process and system for the electrochemical reduction of sulfur from a sulfur-containing solid carbon-based material in an electrolyte solution, according to an illustrative embodiment.

[0021] FIG. 2 illustrates a schematic diagram of a process and system with an ion permeable membrane for use in the electrochemical reduction of sulfur from a sulfur-containing solid carbon-based material in an electrolyte solution, according to another illustrative embodiment.

[0022] FIG. 3 illustrates a schematic diagram of a process and system with an ion permeable membrane and a redox mediator for use in the electrochemical reduction of sulfur from a sulfur-containing solid carbon-based material in an electrolyte solution, according to yet another illustrative embodiment.

[0023] FIG. 4 illustrates a schematic diagram of a process and system with an ion permeable membrane and a redox mediator utilizing a carbon container for use in the electrochemical reduction of sulfur from a sulfur-containing solid carbon-based material in an electrolyte solution, according to yet another illustrative embodiment.DETAILED DESCRIPTION

[0024] Various illustrative embodiments described herein are directed to processes and systems for the electrochemical reduction of sulfur from a sulfur-containing solid carbon-based material.Definitions

[0025] As used in this disclosure the word “comprises” or “comprising” is intended as an open-ended transition meaning the inclusion of the named elements, but not necessarily excluding other unnamed elements. The phrase “consists essentially of” or “consisting essentially of” is intended to mean the exclusion of other elements of any essential significance to the composition. The phrase “consisting of” or “consists of” is intended as a transition meaning the exclusion of all but the recited elements with the exception of only minor traces of impurities.

[0026] The terms “a,”“an,” and “the” are intended to include plural alternatives, e.g., at least one. The terms “including,”“with,” and “having,” as used herein, are defined as comprising (i.e., open language), unless specified otherwise.

[0027] Various numerical ranges are disclosed herein. When Applicant discloses or claims a range of any type, Applicant's intent is to disclose or claim individually each possible number that such a range could reasonably encompass, including end points of the range as well as any sub-ranges and combinations of sub-ranges encompassed therein, unless otherwise specified. For example, all numerical end points of ranges disclosed herein are approximate, unless excluded by proviso.

[0028] Values or ranges may be expressed herein as “about,” from “about” one particular value, and / or to “about” another particular value. When such values or ranges are expressed, other embodiments disclosed include the specific value recited, from the one particular value, and / or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. It will be further understood that there are a number of values disclosed therein, and that each value is also herein disclosed as “about” that particular value in addition to the value itself. In another aspect, use of the term “about” means ±20% of the stated value, ±15% of the stated value, ±10% of the stated value, ±5% of the stated value, ±3% of the stated value, or ±1% of the stated value.

[0029] The terms “wt. %,”“vol. %” or “mol. %” refers to a weight, volume, or molar percentage of a component, respectively, based on the total weight, the total volume, or the total moles of material that includes the component. In a non-limiting example, 10 moles of component in 100 moles of the material are 10 mol. % of component.

[0030] The term “electrode” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an electrical conductor through which a current may flow. An electrode in an electrochemical cell is referred to as either an anode or a cathode. The anode is defined as the electrode at which electrons leave the cell and oxidation occurs (indicated by a plus symbol, “+”), and the cathode as the electrode at which electrons enter the cell and reduction occurs (indicated by a minus symbol, “−”). Each electrode may become either the anode or the cathode depending on the direction of current through the cell.

[0031] The term “electrolysis” is a technique that uses direct electric current to drive an otherwise non-spontaneous chemical reaction. For example, the electrolysis of water is the process of using electricity to electrochemically decompose water into oxygen and hydrogen.

[0032] The term “electrochemical cell” refers to a device that produces electrical energy through chemical reactions or uses electrical energy supplied to it to facilitate chemical reactions in it. An electrochemical cell for use herein can include an anode, a cathode, a separator between the anode and the cathode, and an electrolyte. An electrochemical cell for use herein may further include a current collector in electrical contact with an electrode and / or an electrolyte and may be used, in part, to provide a conductive path between the electrode and a load.

[0033] The term “anode” refers to an electrode in an electrochemical cell where oxidation occurs during discharge of the electrochemical cell. In some embodiments, an anode oxidizes material and releases positive ions to an electrolyte during discharge.

[0034] The term “cathode” refers to an electrode in an electrochemical cell where reduction occurs during discharge of the electrochemical cell. In some embodiments, a cathode is identified in an electrochemical cell as the negative electrode, where electrons are emitted during discharge after use by a load. In some embodiments, a cathode reduces positive ions received from an electrolyte during discharge.

[0035] The term “separator” refers to an ion conductive barrier used to separate anode and cathode compartments in an electrochemical cell. In some embodiments, a separator is a porous or semi-permeable membrane that restricts the passage of certain materials across the membrane. In some embodiments, a separator provides a physical spacing between the anode and the cathode in an electrochemical cell.

[0036] The term “membrane” refers to a web of material that extends in lateral dimensions, which may be orthogonal to a thickness dimension of the membrane. “Membrane” refers to a layer that is permeable to a first species of the electrolyte while substantially impermeable to a second species of the electrolyte. The membrane can be of any suitable material that can provide the selective permeability. “Substantially impermeable” refers to less than 10% of the second species passing through the membrane, or less than 1%, or less than 0.1%, or less than 0.01%, or less than 0.001% of the second species passing through the membrane.

[0037] The term “electrolyte” refers to an ionically conductive substance or composition and may include water, aqueous solutions, organic solvents, ionic liquids, metal salts, ions such as metal ions or inorganic ions, polymers, ceramics, and other components. An electrolyte may be a solid, in some embodiments. An electrolyte may be a liquid, such as a solvent containing dissolved ionic species. An electrolyte may be used, in some embodiments, for transporting ions between an anode and a cathode or from a cathode to an anode in an electrochemical cell.

[0038] The term “ionic solution” refers to a solvent including dissolved ionic species. An electrolyte is an example of an ionic solution. Useful solvents for ionic solutions include aqueous solvents containing water. Useful solvents for ionic solutions include non-aqueous solvents, such as organic solvents.

[0039] The term “selective ion transport” refers to a process where ions of different chemical species exhibit different transport rates. For example, selective ion transport may refer to a process where ions of a particular species are restricted from moving, while ions of another species may be permitted to move. In some embodiments, selective ion transport may be achieved through use of a semi-permeable membrane, such as a separator.

[0040] Applicant reserves the right to proviso out or exclude any individual members of any such group of values or ranges, including any sub-ranges or combinations of sub-ranges within the group, that can be claimed according to a range or in any similar manner, if for any reason Applicant chooses to claim less than the full measure of the disclosure, for example, to account for a reference that Applicant may be unaware of at the time of the filing of the application. Further, Applicant reserves the right to proviso out or exclude any members of a claimed group.

[0041] Although any processes and materials similar or equivalent to those described herein can be used in the practice or testing of the illustrative embodiments described herein, the typical processes and materials are herein described.

[0042] As mentioned above, petroleum coke (also referred to as petcoke and referred to herein simply as coke) is a high carbon content, solid product of petroleum refining. Coke is obtained by heating the heavy residue left over from distillation processes (also referred to as resid) in the presence of steam to produce a solid, carbonaceous material. The marketability of coke may depend, in certain instances, on the amount of sulfur it contains as the quality and extent of removal significantly impacts value creation of the coke and the health and safety of the final product.

[0043] The removal of sulfur and other major contaminants such as nitrogen and metals are important in industries such as the chemical and pharmaceutical industries. The quality and extent of removal significantly impacts the value creation and the health and safety of the final product. Present methods to remove sulfur and other contaminants include, for example, hydrotreating and use of metal sorbents. However, these methods are often complex, require significant investment, occur under harsh reaction conditions or require high temperature and pressure and their efficiency depends on the technology catalyst activity and particular feedstock used. In addition, many metal sorbents are either a single-use sorbent or require regeneration, which demands significant energy, treatment and cost.

[0044] The illustrative embodiments described herein overcome these and other drawbacks by providing processes and systems for the electrochemical reduction of sulfur from a sulfur-containing solid carbon-based material. Among other factors, it has been found that electrochemical operations occur at much milder conditions, does not require hydrogen, and has a lower carbon intensity (e.g., when powered by a renewable source).

[0045] The non-limiting illustrative embodiments of the present disclosure are directed to systems and processes for removing sulfur from a sulfur-containing solid carbon-based material. In some embodiments, the process includes at least adding a sulfur-containing solid carbon-based material to an aqueous electrolyte solution comprising an effective amount of an electrolyte in an electrochemical cell, subjecting the aqueous electrolyte solution to an effective voltage and current to at least partially oxidize at least a portion of sulfur in the sulfur-containing solid carbon-based material, thereby generating oxidized sulfur and a reduced-sulfur solid carbon-based material, and separating the oxidized sulfur from the reduced-sulfur petroleum product stream. The reduced-sulfur solid carbon-based material has a lower sulfur content by wt. % than the sulfur-containing solid carbon-based material.

[0046] The foregoing non-limiting illustrative embodiments of the present disclosure will be specifically described below with reference to the accompanying drawings. For the purpose of clarity, some steps leading up to the electrochemical removal of sulfur from a sulfur-containing solid carbon-based material as illustrated in FIGS. 1-4 are omitted. In other words, one or more well-known processing steps which are not illustrated but are well-known to those of ordinary skill in the art have not been included in the figures. This is not intended to be interpreted as a limitation of any particular embodiment, or illustration, or scope of the claims.

[0047] Referring now to the drawings in more detail, FIGS. 1-4 illustrate a system including an electrochemical cell comprising a cathode, an anode and a membrane disposed between the cathode and the anode. It is to be understood that the system including the electrochemical cell and the anode and the cathode is not limited to the configuration of the embodiments shown in FIGS. 1-4, and other configurations are contemplated herein. For ease of understanding, specific examples mentioned in the following description are all illustrative and are not used to limit the protection scope of the present disclosure.

[0048] FIGS. 1-4 show a system 100 including an electrochemical cell 102 for containing an electrolyte solution 104 having a sulfur-containing solid carbon-based material 106 dispersed therein. Electrochemical cell 102 can be any conventional electrochemical cell known in the art. For example, electrochemical cell 102 may be divided or undivided. In some embodiments, electrochemical cell 102 can be composed of glass. Such systems can include, for example, stirred batch or flow through reactors. The foregoing may be purchased commercially or made using technology known in the art.

[0049] In some embodiments, the cell size of electrochemical cell 102 can range from about 0.5 meters to about 1.5 meters tall and from about 0.4 meters to about 3 meters wide. In some embodiments, the individual chamber thicknesses can range from about 0.5 millimeters (mm) to about 50 mm. It is to be understood that these dimensions are merely illustrative and any suitable dimension of electrochemical cell 102 is contemplated herein.

[0050] In some embodiments, electrochemical cell 102 can be made from corrosion resistant materials. Such corrosion resistant materials can include, for example, polyvinylidene fluoride, fluoroelastomers (e.g., Viton™), polyether ether ketone, fluorinated ethylene propylene, fiber-reinforced plastic, ethylene chlorotrifluoroethylene fluoropolymers (e.g., HALAR®), polyetherimides (e.g., Ultem®), perfluoroalkoxy, ethylene-tetrafluoroethylene resins (e.g., Tefzel™), ultra-high molecular weight polyethylene (e.g., TYVAR®), fiber-reinforced plastic-coated with Derakane 441-400 resin, graphite, titanium alloys (e.g., AKOT), tantalum, nickel-chromium-molybdenum materials (e.g., HASTELLOY®C-2000®), titanium, or combinations thereof.

[0051] In some embodiments, electrolyte solution 104 comprises one or more of water, one or more alcohols (a C1 to C6 alcohol such as methanol and ethanol), or both water and one or more alcohols as a polar solvent. In some embodiments, electrolyte solution 104 is composed only of water. In some embodiments, salts such as those described below can be added to improve conductivity.

[0052] Electrolyte solution 104 can also include an electrolyte to be reduced in electrochemical cell 102 as the sulfur of sulfur-containing solid carbon-based material 106 is oxidized. As used herein, the term “electrolyte” refers to a compound added to perform oxidation as well as the resulting anion that results from dissociation of that compound.

[0053] Suitable electrolytes include, for example, metal salts, acids and bases. All references to particular salts, bases and acids herein, by name or formula, as components of electrolyte solution 104 include the dissociated forms of those components. In some embodiments, suitable metal salts include alkali metal salts of nitrate, borate, halides, phosphate, phosphonates, carbonates, sulfates, and perchlorates. In some embodiments, metal salts can include halogen salts. Representative examples of metal salts for use as an electrolyte in electrolyte solution 104 include, but are not limited to, KI, NaI, LiI, BaI2, CaI2, MgI2, ZnI2, AlI3, KBr, NaBr, LiBr, BaBr2, CaBr2, MgBr2, ZnBr2, AlBr3, KCl, NaCl, LiCl, BaCl2, CaCl2, MgCl2, ZnCl2, AlCl3, K2SO4, Na2SO4, Li2SO4, BaSO4, CaSO4, MgSO4, ZnSO4, Al2(SO4)3, KNO3 NaNO3, LiNO3, Ba(NO3)2, Ca(NO3)2, Mg(NO3)2, Zn(NO3)2, Al(NO3)3, KF, NaF, LiF, BaF2, CaF2, MgF2, ZnF2, AlF3, K3PO4, Na3PO4, Li3PO4, Ba3(PO4)2, Ca3(PO4)2, Mg3(PO4)2, Zn3(PO4)2, AlPO4, K2SO3, Na2SO3, Li2SO3, BaSO3, CaSO3, MgSO3, ZnSO3, Al2(SO3)3, K2CO3, Na2CO3 Li2CO3, BaCO3, CaCO3, MgCO3, ZnCO3, Al2(CO3)3, K2S, Na2S, Li2S, BaS, CaS, MgS, ZnS, Al2S3, K2SiO3, Na2SiO3, Li2SiO3, BaSiO3, CaSiO3, MgSiO3, ZnSiO3, Al2(SiO3)3, KOH, NaOH, LiOH, Ba(OH)2, Ca(OH)2, Mg(OH)2, Zn(OH)2, Al(OH)3 and combinations thereof.

[0054] In some embodiments, electrolyte solution 104 can include an acid such as a strong Brønsted-Lowry acids in liquid or aqueous form. Suitable Brønsted-Lowry acids include, for example, sulfuric acid (H2SO4), phosphoric acid (H3PO4), perchloric acid (HClO4) and combinations thereof.

[0055] In some embodiments, electrolyte solution 104 can include a base such as a strong base. Suitable strong bases include, for example, potassium hydroxide (KOH), sodium hydroxide (NaOH), lithium hydroxide (LiOH) and combinations thereof.

[0056] In some embodiments, electrolyte solution 104 can include an effective amount of the electrolyte. The amount of the electrolyte in electrolyte solution 104 can vary widely depending on the particular electrolyte. In general, the amount of the electrolyte in electrolyte solution 104 should be any amount below the saturation of the electrolyte in electrolyte solution 104, i.e., an amount of the electrolyte that can be added to electrolyte solution 104 and still be dissolved.

[0057] In some embodiments, sulfur-containing solid carbon-based material 106 includes, for example, a sulfur-containing solid carbon-based material having a sulfur content of at least about 10 parts per million (ppm). In some embodiments, sulfur-containing solid carbon-based material 106 can have a sulfur content of about 0.001 wt. % to about 10 wt. %. In some embodiments, sulfur-containing solid carbon-based material 106 can have a sulfur content of about 3 wt. % to about 5 wt. %.

[0058] In an illustrative embodiment, the form of sulfur-containing solid carbon-based material 106 can include any of the forms capable of being adapted to feed to electrochemical cell 102 such as, for example, articles, products, materials, or portions thereof. For example, a portion of an article can take the form of chips, flakes, particles, powder, shredded pieces, or any other form other than the original form of the article and adapted to feed to electrochemical cell 102.

[0059] In an illustrative embodiment, as may be combined with one or more of the preceding paragraphs, sulfur-containing solid carbon-based material 106 can be in the form of solid particles, such as chips, flakes, or a powder. In another embodiment, sulfur-containing solid carbon-based material 106 may comprise particulates such as, for example, shredded plastic particles, chopped plastic particles, or plastic pellets.

[0060] In some embodiments, sulfur-containing solid carbon-based material 106 can be in particle form. In some embodiments, sulfur-containing solid carbon-based material 106 in particle form can have a particle size ranging from about 100 micrometers to about 10 millimeters. In some embodiments, the foregoing particle size of sulfur-containing solid carbon-based material 106 can be reduced by about 20% to about 80% to increase its contact surface area.

[0061] In some embodiments, suitable sulfur-containing solid carbon-based material 106 includes, for example, petroleum coke.

[0062] In some embodiments, suitable sulfur-containing solid carbon-based material 106 includes, for example, waste plastic, polymers, biomass and the like.

[0063] As used herein, a “waste plastic” refers to any post-industrial (or pre-consumer) and post-consumer plastics, such as, for example, one or more polyesters, one or more polyolefins (PO), and / or polyvinylchloride (PVC) that contain sulfur. As used herein, a “post-consumer plastic” is one that has been used at least once for its intended application for any duration of time regardless of wear, has been sold to an end use customer, or has been discarded into a recycle bin by any person or entity other than a manufacturer or business engaged in the manufacture or sale of the material. A “post-industrial plastic” (or “pre-consumer” plastic) includes all manufactured recyclable organic plastics that are not post-consumer plastics, such as a material that has been created or processed by a manufacturer and has not been used for its intended application, has not been sold to the end use customer, or has been discarded or transferred by a manufacturer or any other entity engaged in the sale or disposal of the material. Examples of post-industrial or pre-consumer plastics include rework, regrind, scrap, trim, out of specification materials, and finished materials transferred from a manufacturer to any downstream customer (e.g., manufacturer to wholesaler to distributor) but not yet used or sold to the end use customer.

[0064] In an illustrative embodiment, as may be combined with one or more of the preceding paragraphs, a waste plastic can be any organic synthetic polymer that is solid at 25° C. at 1 atm and contain sulfur. For example, in an illustrative embodiment, the organic synthetic polymers that are solid at 25° C. and 1 atmosphere of pressure may have a number average molecular weight (Mn) of at least about 300, or at least about 500, or at least about 1000, or at least about 5,000, or at least about 10,000, or at least about 20,000, or at least about 30,000, or at least about 50,000 or at least about 70,000 or at least about 90,000 or at least about 100,000 or at least about 130,000, or at least about 150,000 Daltons. The weight average molecular weight (Mw) of the polymers can be at least about 300, or at least about 500, or at least about 1000, or at least about 5,000, or at least about 10,000, or at least about 20,000, or at least about 30,000 or at least about 50,000, or at least about 70,000, or at least about 90,000, or at least about 100,000, or at least about 130,000, or at least about 150,000, or at least about 300,000 or at least about 400,000 Daltons. In an embodiment or in combination with any embodiment mentioned herein, the polymers have an average molecular weight, Mw, in the range of about 5,000 to about 150,000 Daltons. In an embodiment or in combination with any embodiment mentioned herein, the polymers have an average molecular weight, Mw, in the range of greater than about 150,000 to about 400,000 Daltons.

[0065] In some embodiments, sulfur-containing solid carbon-based material 106 can be functionalized in a pretreatment step to improve its contact surface area or wettability by, for example, chemical oxidation, heat treatment or other similar methods.

[0066] Turning back to FIGS. 1-4, system 100 further includes electrochemical cell 102 including a cathode 108, an anode 110 and a circuit 112. Cathode 108 and anode 110 can be any suitable corrosion stable, electrically conductive carbon or metal substrate. For example, in some embodiments, suitable conductive metal substrates include, for example, graphite (and other forms of carbon), gold, titanium, and platinum-group metal-based substrates such as platinum, palladium, and rhodium. In some embodiments, suitable conductive metal substrates include, for example, metals that remain relatively stable under neutral or alkaline conditions such as nickel, copper, silver, tin, steel, lead, iron, cobalt, molybdenum, and tungsten-based substrates. In some embodiments, suitable nickel-based substrates include, for example, nickel substrates, nickel alloy substrates (such as NiFe alloys and NiCo alloys and combinations thereof) and nickel oxide substrates. In some embodiments, one or both of cathode 108 and anode 110 is made primarily or entirely from nickel.

[0067] Cathode 108 and anode 110 may have any appropriate form. For example, cathode 108 and anode 110 may be in the form of a sheet, rod, bar, block or foil. A sheet is typically flat with opposing top and bottom sides. A sheet could also include a portion that is not flat, such as a portion that is bent to secure or otherwise accommodate positioning the sheet within electrochemical cell 102.

[0068] In operation, the electrochemistry, i.e. electrochemical reduction, in accordance with the non-limiting illustrative embodiments of the present disclosure can be performed on sulfur-containing solid carbon-based material 106 in electrolyte solution 104 utilizing any suitable temperature and pressure ranges in which the electrolyte in electrolyte solution 104 remains in liquid phase and stable and the integrity of electrochemical cell 102 is not compromised. In some embodiments, the electrochemistry in accordance with the non-limiting illustrative embodiments of the present disclosure can be performed on sulfur-containing solid carbon-based material 106 in electrolyte solution 104 at about a temperature of about 25° C. to about 90° C. and at a pressure of about atmospheric 1 bar.

[0069] In some embodiments, a process of the present disclosure can be conducted by mixing an effective amount of a solvent (aqueous or organic) such as water and the electrolyte with sulfur-containing solid carbon-based material 106 to be treated. By “effective amount of solvent” is meant the minimum amount of solvent needed to maintain the solid wet and ensure electric conductivity with the electrodes, i.e., the minimum amount of solvent needed to create ions to oxidize the sulfur in sulfur-containing solid carbon-based material 106 resulting in a reduction of sulfur in sulfur-containing solid carbon-based material 106 by at least about 10%, or about 90%, or at least about 95%, e.g. from about 10% to about 95%, when subjected to an effective electrical voltage and current through circuit 112 as discussed below. The oxidized sulfur, i.e., sulfur oxide, can either stay in electrolyte solution 104 or be removed as a gas.

[0070] In some embodiments, electrolyte solution 104 and sulfur-containing solid carbon-based material 106 to be treated are introduced into electrochemical cell 102 and subjected to an effective electrical voltage and current through circuit 112. The applied cell voltage, that is, the total voltage difference between the cathode and anode will vary depending upon the cell design and electrolytes used. Electrochemical cell 102 may receive input energy (i.e., electricity) from an intermittent source such as solar power (including photovoltaic and reflective), wind power, tidal power, wave power, batteries, and other intermittent energy sources known in the art and combinations thereof. Alternatively, or in addition, electrochemical cell 102 may receive input energy from a non-intermittent source, such as an electricity grid (e.g., a regional electricity grid, a municipal electricity grid, or a microgrid), natural gas, coal, nuclear, and other non-intermittent sources known in the art and combinations thereof. Electrochemical cell 102 may therefore be electrically connectable to an intermittent energy input, a non-intermittent source, or a combination thereof. In particular embodiments, electrochemical cell 102 may receive input energy from the photovoltaic panel.

[0071] In some embodiments, the amount of voltage can be about 3 volts to about 10 volts, resulting in a current density of about 50 mA to about 500 mA.

[0072] With regard to FIGS. 2-4, system 100 can further include a membrane 114 for electrochemical cell 102. In some embodiments, membrane 114 is an ion-permeable membrane. For example, in some embodiments, membrane 114 may be a porous material that can filter any suitable electrolyte in electrolyte solution 104 in the electrochemical applications described herein and are permeable to cations (i.e., positive ions), such as H+, Li+, K+, Na+, Cs+, and / or NH4+ ions, or anions (i.e., negative ions), such as hydroxide ions. The term “effectively impermeable” refers to a membrane that prevents crossover of at least about 90%, such as at least about 95%, at least about 97%, at least about 98%, or at least about 99% of active materials for a time period ranging from about 1 month to about 1 year. In some embodiments, membrane 114 may be permeable to anions such as hydroxyl (OH−) ions and impermeable to hydrogen. In some embodiments, membrane 114 is stable in the temperature range of from about 0° C. to about 150° C.

[0073] Suitable membranes for membrane 114 include those that are commercially available from such sources as Gore, Chemours, Asahi Kasei, AGC, Dongyue, Solvay, Ballard, Fumatech BWT GmbH (BWT Group) and Evonik, or can be made by methods known in the art. In some embodiments, the type of material the membranes (for proton and anion exchange membranes) can be formed of includes, for example, perfluorosulfonic acid polymers (PFSA) or polyarylethers with, e.g., quaternary ammonium or phosphonium salts.

[0074] In operation, the electrochemistry in accordance with the non-limiting illustrative embodiments of the present disclosure will be carried out as discussed above by subjecting electrochemical cell 102 to an effective electrical voltage and current through circuit 112 to create anions such as hydroxyl (OH−) ions and cations such as such as H+, Li+, K+, Na+, Cs+, and / or NH4+ ions from the solvent (e.g., water) in electrolyte solution 104. The ions can react with the carbon material to oxidize the sulfur in sulfur-containing solid carbon-based material 106 resulting in a decreased concentration of sulfur in sulfur-containing solid carbon-based material 106.

[0075] System 100 can further include a redox mediator 116. In some embodiments, redox mediator 116 is present in electrolyte solution 104. The use of redox mediator 116 can lead to lower energy consumption, higher reaction selectivity, and the ability to carry out reactions under milder conditions.

[0076] In some embodiments, redox mediator 116 can be any heteropolyacid compound and related polyoxometalates, which have acid properties as well as efficient oxidizing properties. In one embodiment, the heteropolyacid compound and related polyoxometalate comprise at least 12, 18, 24, 30 or up to 132 metal atoms. The number of oxygen atoms is determined by the number of metal atoms present in the heteropolyacid compound and related polyoxometalate, and the particular structure adopted by the cluster.

[0077] In some embodiments, the heteropolyacid compound and related polyoxometalate may have a major metal atom component and an oxygen component, and optionally one or more further heteroatom components selected from P, Si, S, Ge, Fe, W, V, Mo, Mn, Se, Te, As, Sb, Sn, and Ti. In some embodiments, the heteropolyacid compound and related polyoxometalate can contain one or more, such as two, P or S heteroatom components. In some embodiments, the metal atoms in the heteropolyacid compound and related polyoxometalate are selected from the group consisting of Mo, W and V, and combinations thereof. In addition to any of the W, Mo, and / or V atoms present, the heteropolyacid compound and related polyoxometalate may further comprise Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and / or Zn. In addition to any of the W, Mo, V and / or Nb atoms present, the heteropolyacid compound and related polyoxometalate may further comprise Sn, Pb, Al, and / or Hg.

[0078] In some embodiments, the heteropolyacid compound and related polyoxometalate comprise a Dawson-type structure.

[0079] In some embodiments, the heteropolyacid compound and related polyoxometalate comprise a Keggin-type structure, such as a mixed metal Keggin-type structure.

[0080] For example, the heteropolyacid compound and related polyoxometalate may have the general formula [W12−xMoxXO40]n or Dawson [W18−xMoxXO62]y−, where X may be selected from P, S and Si. The value of x may be varied, and may be 1 or 2. One or more, such as two, metal atoms may be replaced with, for example, Fe or Mn.

[0081] In some embodiments, the heteropolyacid compound and related polyoxometalate may be of formula [X2M18O62]n−, where M is a metal selected from Mo, W and V, and mixtures thereof, X is selected from P and S and mixtures thereof, and n is 3, 4, 5 or 6, where the polyoxometalate is provided with one or more balancing counter cations.

[0082] In some embodiments, the heteropolyacid compounds include Keggin heteropolyanions (represented by the formula XM12O40x−8), Dawson structures (X2M18O622x−16); Keggin and Dawson lacunary anions, XM11O39x−12 and X2M17O612x−20; Anderson type ([Xn+M6O24](12−n)−, [Xn+(OH)6M6O18](6−n)−); and transition metal complexes thereof.

[0083] In some embodiments, redox mediator 116 can include a metal oxyanion or a non-metal oxyanion. Suitable metal oxyanions include, for example, manganese, chromium, copper, iron, tin, selenium, tantalum, or a combination thereof. Suitable non-metal oxyanions include, for example, chloro, fluoro, bromo, iodo, carbon, sulfur, nitrogen, phosphorus, or a combination thereof. In some embodiments, redox mediator 116 can have the form of an oxidized redox mediator. For example, as one skilled in the art will readily appreciate, an oxidized redox mediator can be derived from the initial redox mediator 116 added to electrochemical cell 102.

[0084] In some embodiments, redox mediator 116 can have any suitable concentration in electrolyte solution 104, such as a concentration of about 0.1 M to about 10 M.

[0085] In operation, the electrochemistry in accordance with the non-limiting illustrative embodiments of the present disclosure will be carried out as discussed above where redox mediator 116 can facilitate charge transfer from the electrode to sulfur-containing solid carbon-based material 106 through the electrolyte by becoming reduced or oxidized. Redox mediator 116 can then flow outside electrochemical cell 102 and be treated to reverse the reduction or oxidation that occurred in electrochemical cell 102.

[0086] As shown in FIG. 4, system 100 can further include a vessel 124 for receiving sulfur-containing solid carbon-based material 106 via a line 122. In some embodiments, system 100 includes electrochemical cell 102 containing electrolyte solution 104, together with cathode 108, anode 110 and circuit 112 for electrochemical cell 102. Electrochemical cell 102 receives a spent redox mediator 116-2 from vessel 124 via a line 126. In operation, the electrochemistry in accordance with the non-limiting illustrative embodiments of the present disclosure will be carried out by subjecting electrochemical cell 102 to an effective electrical voltage and current through circuit 112 as discussed above to regenerate spent redox mediator 116-2 to provide a regenerated redox mediator 116-1. The redox mediator is routed externally in either continuous or batch mode. During this process, spent redox mediator 116-2 undergoes electrochemical reactions within electrochemical cell 102. By applying an effective electrical voltage and current through circuit 112, spent redox mediator 116-2 is regenerated, restoring to its original oxidative state. Regenerated redox mediator 116-1 can then be reused in system 100.

[0087] Regenerated redox mediator 116-1 and electrolyte solution 104 can then exit electrochemical cell 102 through a line 118 to a pump 120. Pump 120 can be any suitable pump for increasing the pressure of regenerated redox mediator 116-1 and electrolyte solution 104 for sending a pressurized regenerated redox mediator to vessel 124 through line 121. For example, pump 120 may be a centrifugal pump, a rotary pump including an impeller, or alternatively may be any other suitable fluid pump.

[0088] The pressurized regenerated redox mediator then enters vessel 124 where it reacts with sulfur-containing solid carbon-based material 106 to oxidize the sulfur resulting in a decreased concentration of sulfur in sulfur-containing solid carbon-based material 106. The sulfur-depleted solid carbon-based material can be removed from vessel 124 along with the oxidized sulfur product through line 128.

[0089] In some embodiments, one or more surfactants can be included in system 100. The one or more surfactants serve to lower the surface tension and contact surface area of sulfur-containing solid carbon-based material 106. The one or more surfactants can be an anionic, a cationic, a zwitterionic, and / or a non-ionic surfactant. In some embodiments, an anionic surfactant includes a surfactant with functional groups such as sulfate, sulfonate, phosphate, and / or carboxylates. Suitable anionic surfactants include, for example, dioctyl sodium sulfosuccinate, perfluorooctanesulfonate (PFOS), perfluorobutanesulfonate, alkyl-aryl ether phosphates, and alkyl ether phosphates. In some embodiments, a cationic surfactant is a primary, secondary, or tertiary amine that can become positively charged at a pH<10. Suitable cationic surfactants include, for example, cetrimonium bromide (CTAB), cetylpyridinium chloride (CPC), benzalkonium chloride (BAC), benzethonium chloride (BZT), dimethyldioctadecylammonium chloride, and dioctadecyldimethylammonium bromide (DODAB). In some embodiments, a zwitterionic surfactant has both cationic and anionic centers. Suitable zwitterionic surfactants include, for example, phospholipids phosphatidylserine, phosphatidylethanolamine, phosphatidylcholine, sphingomyelins, and betaines. In some embodiments, a surfactant is a non-ionic surfactant with covalently bonded oxygen-containing hydrophilic groups, which are bonded to hydrophobic parent structures. Suitable non-ionic surfactants include, for example, ethoxylates, fatty alcohol ethoxylates, alkylphenol ethoxylates (e.g., nonoxynols and Triton X-100), fatty acid ethoxylates, ethoxylated amines and / or fatty acid amides, fatty acid esters of polyhydroxy compounds, fatty acid esters of glycerol (e.g., glycerol monostearate and glycerol monolaurate), fatty acid esters of sorbitol (e.g., sorbitan monolaurate, sorbitan monostearate, sorbitan tristearate, Tweens: TWEEN® 20, TWEEN® 40, TWEEN® 60, and TWEEN® 80) terminally blocked ethoxylates (e.g., poloxamers), fatty acid esters of sucrose, and alkyl polyglucosides (e.g., decyl glucoside, lauryl glucoside, and octyl glucoside).

[0090] In some embodiments, the mass ratio of the one or more surfactants include, for example, in electrolyte solution 104 to the total mass of electrolyte solution 104 can be about 0% to about 60%.

[0091] According to an aspect of the present disclosure, a process for removing sulfur from a sulfur-containing solid carbon-based material comprises:

[0092] adding a sulfur-containing solid carbon-based material to an aqueous electrolyte solution comprising an effective amount of an electrolyte in an electrochemical cell, and

[0093] subjecting the aqueous electrolyte solution to an effective voltage and current to at least partially oxidize at least a portion of sulfur in the sulfur-containing solid carbon-based material, thereby generating oxidized sulfur and a reduced sulfur-containing solid carbon-based material,

[0094] wherein the reduced sulfur-containing solid carbon-based material has a lower sulfur content by wt. % than the sulfur-containing solid carbon-based material.

[0095] In non-limiting illustrative embodiments, as may be combined with one or more of the preceding paragraphs, the sulfur-containing solid carbon-based material comprises petroleum coke.

[0096] In non-limiting illustrative embodiments, as may be combined with one or more of the preceding paragraphs, the sulfur-containing solid carbon-based material has a sulfur content of from about 0.001 wt. % to about 10 wt. %.

[0097] In non-limiting illustrative embodiments, as may be combined with one or more of the preceding paragraphs, the electrochemical cell is run at about 3 volts to about 10 volts and a current density of about 50 mA to about 500 mA.

[0098] In non-limiting illustrative embodiments, as may be combined with one or more of the preceding paragraphs, the electrolyte comprises a solution comprising an alkali metal salt of one or more of a nitrate, a borate, a halide, a phosphate, a phosphonate, a carbonate, a sulfate, and a perchlorate.

[0099] In non-limiting illustrative embodiments, as may be combined with one or more of the preceding paragraphs, the electrolyte comprises a strong Brønsted-Lowry acid.

[0100] In non-limiting illustrative embodiments, as may be combined with one or more of the preceding paragraphs, the electrolyte comprises a base.

[0101] In non-limiting illustrative embodiments, as may be combined with one or more of the preceding paragraphs, subjecting the aqueous electrolyte solution to the effective voltage and current to at least partially oxidize at least a portion of the sulfur in the sulfur-containing solid carbon-based material to generate the oxidized sulfur and the reduced sulfur-containing solid carbon-based material comprises generating electrolyte ions in the aqueous electrolyte solution to at least partially oxidize at least a portion of the sulfur.

[0102] In non-limiting illustrative embodiments, as may be combined with one or more of the preceding paragraphs, the process further comprises adding a surfactant to the aqueous electrolyte solution.

[0103] In non-limiting illustrative embodiments, as may be combined with one or more of the preceding paragraphs, the sulfur-containing solid carbon-based material is in particle form and the process further comprises reducing a particle size of the sulfur-containing solid carbon-based material in particle form prior to adding the sulfur-containing solid carbon-based material to the aqueous electrolyte solution.

[0104] In non-limiting illustrative embodiments, as may be combined with one or more of the preceding paragraphs, the process further comprises functionalizing the sulfur-containing solid carbon-based material.

[0105] According to another aspect of the present disclosure, a process for removing sulfur from a sulfur-containing solid carbon-based material comprises:

[0106] introducing an aqueous electrolyte solution comprising an effective amount of an electrolyte to an electrochemical cell comprising a cathode side comprising a cathode, an anode side comprising an anode and a membrane disposed between the cathode and the anode,

[0107] introducing a sulfur-containing solid carbon-based material to the anode side of the electrochemical cell,

[0108] subjecting the aqueous electrolyte solution to an effective voltage and current, thereby generating electrolyte ions and hydrogen,

[0109] wherein the electrolyte ions pass through the membrane from one side to the other side of the electrochemical cell to at least partially oxidize at least a portion of sulfur in the sulfur-containing solid carbon-based material, thereby generating oxidized sulfur and a reduced sulfur-containing solid carbon-based material,

[0110] wherein the reduced sulfur-containing solid carbon-based material has a lower sulfur content by wt. % than the sulfur-containing solid carbon-based material.

[0111] In non-limiting illustrative embodiments, as may be combined with one or more of the preceding paragraphs, the sulfur-containing solid carbon-based material comprises petroleum coke.

[0112] In non-limiting illustrative embodiments, as may be combined with one or more of the preceding paragraphs, the sulfur-containing solid carbon-based material has a sulfur content of from about 0.001 wt. % to about 10 wt. %.

[0113] In non-limiting illustrative embodiments, as may be combined with one or more of the preceding paragraphs, the electrochemical cell is run at about 3 volts to about 10 volts and a current density of about 50 mA to about 500 mA.

[0114] In non-limiting illustrative embodiments, as may be combined with one or more of the preceding paragraphs, the electrolyte comprises one of an alkali metal salt of one or more of a nitrate, a borate, a halide, a phosphate, a phosphonate, a carbonate, a sulfate, and a perchlorate, a strong Brønsted-Lowry acid or a base.

[0115] In non-limiting illustrative embodiments, as may be combined with one or more of the preceding paragraphs, one of the aqueous electrolyte solution or the anode further comprises a redox mediator.

[0116] In non-limiting illustrative embodiments, as may be combined with one or more of the preceding paragraphs, the sulfur in the sulfur-containing solid carbon-based material is reduced by at least about 10%.

[0117] In non-limiting illustrative embodiments, as may be combined with one or more of the preceding paragraphs, the process further comprises adding a surfactant to the aqueous electrolyte solution.

[0118] In non-limiting illustrative embodiments, as may be combined with one or more of the preceding paragraphs, the sulfur-containing solid carbon-based material is in particle form and the process further comprises reducing a particle size of the sulfur-containing solid carbon-based material in particle form prior to introducing the sulfur-containing solid carbon-based material to the anode side of the electrochemical cell.

[0119] In non-limiting illustrative embodiments, as may be combined with one or more of the preceding paragraphs, the process further comprises functionalizing the sulfur-containing solid carbon-based material.

[0120] According to yet another aspect of the present disclosure, a process for removing sulfur from a sulfur-containing solid carbon-based material comprises:

[0121] introducing an aqueous electrolyte solution comprising an effective amount of an electrolyte to an electrochemical cell comprising a cathode side comprising a cathode, an anode side comprising an anode and a membrane disposed between the cathode and the anode,

[0122] introducing a sulfur-containing solid carbon-based material and a first regenerated redox mediator received from the electrochemical cell to a vessel external to the electrochemical cell wherein the first regenerated redox mediator at least partially oxidizes at least a portion of sulfur in the sulfur-containing solid carbon-based material, thereby generating oxidized sulfur, a reduced sulfur-containing solid carbon-based material, and spent redox mediator,

[0123] passing the spent redox mediator to the electrochemical cell, and

[0124] subjecting the spent redox mediator to an effective voltage and current to regenerate the spent redox mediator, thereby providing a second regenerated redox mediator,

[0125] wherein the reduced sulfur-containing solid carbon-based material has a lower sulfur content by wt. % than the sulfur-containing solid carbon-based material.

[0126] In non-limiting illustrative embodiments, as may be combined with one or more of the preceding paragraphs, the sulfur-containing solid carbon-based material comprises petroleum coke.

[0127] In non-limiting illustrative embodiments, as may be combined with one or more of the preceding paragraphs, the sulfur-containing solid carbon-based material has a sulfur content of from about 0.001 wt. % to about 10 wt. %.

[0128] In non-limiting illustrative embodiments, as may be combined with one or more of the preceding paragraphs, the electrochemical cell is run at about 3 volts to about 10 volts and a current density of about 50 mA to about 500 mA.

[0129] In non-limiting illustrative embodiments, as may be combined with one or more of the preceding paragraphs, the sulfur in the sulfur-containing solid carbon-based material is reduced by at least about 10%.

[0130] In non-limiting illustrative embodiments, as may be combined with one or more of the preceding paragraphs, the process further comprises adding a surfactant to the aqueous electrolyte solution.

[0131] In non-limiting illustrative embodiments, as may be combined with one or more of the preceding paragraphs, the sulfur-containing solid carbon-based material is in particle form and the process further comprises reducing a particle size of the sulfur-containing solid carbon-based material in particle form prior to introducing the sulfur-containing solid carbon-based material to the vessel.

[0132] In non-limiting illustrative embodiments, as may be combined with one or more of the preceding paragraphs, the process further comprises functionalizing the sulfur-containing solid carbon-based material.

[0133] Various features disclosed herein are, for brevity, described in the context of a single embodiment, but may also be provided separately or in any suitable sub-combination. All combinations of the embodiments are specifically embraced by the illustrative embodiments disclosed herein just as if each and every combination was individually and explicitly disclosed. In addition, all sub-combinations listed in the embodiments describing such variables are also specifically embraced by the present compositions and are disclosed herein just as if each and every such sub-combination was individually and explicitly disclosed herein.

[0134] It will be understood that various modifications may be made to the embodiments disclosed herein. Therefore, the above description should not be construed as limiting, but merely as exemplifications of preferred embodiments. For example, the functions described above and implemented as the best mode for operating the present invention are for illustration purposes only. Other arrangements and methods may be implemented by those skilled in the art without departing from the scope and spirit of this invention. Moreover, those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.

Claims

1. A process for removing sulfur from a sulfur-containing solid carbon-based material, comprising:adding a sulfur-containing solid carbon-based material to an aqueous electrolyte solution comprising an effective amount of an electrolyte in an electrochemical cell; andsubjecting the aqueous electrolyte solution to an effective voltage and current to at least partially oxidize at least a portion of sulfur in the sulfur-containing solid carbon-based material, thereby generating oxidized sulfur and a reduced sulfur-containing solid carbon-based material;wherein the reduced sulfur-containing solid carbon-based material has a lower sulfur content by wt. % than the sulfur-containing solid carbon-based material.

2. The process according to claim 1, wherein the sulfur-containing solid carbon-based material comprises petroleum coke.

3. The process according to claim 1, wherein the sulfur-containing solid carbon-based material has a sulfur content of from about 0.001 wt. % to about 10 wt. %.

4. The process according to claim 1, wherein the electrochemical cell is run at about 3 volts to about 10 volts and a current density of about 50 mA to about 500 mA.

5. The process according to claim 1, wherein the electrolyte comprises a solution comprising an alkali metal salt of one or more of a nitrate, a borate, a halide, a phosphate, a phosphonate, a carbonate, a sulfate, and a perchlorate.

6. The process according to claim 1, wherein the electrolyte comprises one of a strong Brønsted-Lowry acid or a base.

7. The process according to claim 1, wherein subjecting the aqueous electrolyte solution to the effective voltage and current to at least partially oxidize at least a portion of the sulfur in the sulfur-containing solid carbon-based material to generate the oxidized sulfur and the reduced sulfur-containing solid carbon-based material comprises generating electrolyte ions in the aqueous electrolyte solution to at least partially oxidize at least a portion of the sulfur.

8. The process according to claim 1, wherein the sulfur in the sulfur-containing solid carbon-based material is reduced by at least about 10%.

9. The process according to claim 1, wherein the sulfur-containing solid carbon-based material is in particle form and the process further comprises reducing a particle size of the sulfur-containing solid carbon-based material in particle form prior to adding the sulfur-containing solid carbon-based material to the aqueous electrolyte solution.

10. A process for removing sulfur from a sulfur-containing solid carbon-based material, comprising:introducing an aqueous electrolyte solution comprising an effective amount of an electrolyte to an electrochemical cell comprising a cathode side comprising a cathode, an anode side comprising an anode and a membrane disposed between the cathode and the anode;introducing a sulfur-containing solid carbon-based material to the anode side of the electrochemical cell;subjecting the aqueous electrolyte solution to an effective voltage and current, thereby generating electrolyte ions and hydrogen;wherein the electrolyte ions pass through the membrane from one side to the other side of the electrochemical cell to at least partially oxidize at least a portion of sulfur in the sulfur-containing solid carbon-based material, thereby generating oxidized sulfur and a reduced sulfur-containing solid carbon-based material;wherein the reduced sulfur-containing solid carbon-based material has a lower sulfur content by wt. % than the sulfur-containing solid carbon-based material.

11. The process according to claim 10, wherein the sulfur-containing solid carbon-based material comprises petroleum coke.

12. The process according to claim 10, wherein the sulfur-containing solid carbon-based material has a sulfur content of from about 0.001 wt. % to about 10 wt. %.

13. The process according to claim 10, wherein the electrochemical cell is run at about 3 volts to about 10 volts and a current density of about 50 mA to about 500 mA.

14. The process according to claim 10, wherein one of the aqueous electrolyte solution or the anode further comprises a redox mediator.

15. The process according to claim 10, wherein the sulfur in the sulfur-containing solid carbon-based material is reduced by at least about 10%.

16. The process according to claim 10, wherein the sulfur-containing solid carbon-based material is in particle form and the process further comprises reducing a particle size of the sulfur-containing solid carbon-based material in particle form prior to introducing the sulfur-containing solid carbon-based material to the anode side of the electrochemical cell.

17. A process for removing sulfur from a sulfur-containing solid carbon-based material, comprising:introducing an aqueous electrolyte solution comprising an effective amount of an electrolyte to an electrochemical cell comprising a cathode side comprising a cathode, an anode side comprising an anode and a membrane disposed between the cathode and the anode;introducing a sulfur-containing solid carbon-based material and a first regenerated redox mediator received from the electrochemical cell to a vessel external to the electrochemical cell wherein the first regenerated redox mediator at least partially oxidizes at least a portion of sulfur in the sulfur-containing solid carbon-based material, thereby generating oxidized sulfur, a reduced sulfur-containing solid carbon-based material, and spent redox mediator;passing the spent redox mediator to the electrochemical cell; andsubjecting the spent redox mediator to an effective voltage and current to regenerate the spent redox mediator, thereby providing a second regenerated redox mediator;wherein the reduced sulfur-containing solid carbon-based material has a lower sulfur content by wt. % than the sulfur-containing solid carbon-based material.

18. The process according to claim 17, wherein the sulfur-containing solid carbon-based material comprises petroleum coke.

19. The process according to claim 17, wherein the sulfur-containing solid carbon-based material has a sulfur content of from about 0.001 wt. % to about 10 wt. %.

20. The process according to claim 17, wherein the electrochemical cell is run at about 3 volts to about 10 volts and a current density of about 50 mA to about 500 mA.

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