Production of hard carbons from asphaltene-rich hydrocarbons

Abstract

Non-amorphous hard carbons are produced by treating a hydrocarbon feedstock comprising asphaltenes to increase its softening point and producing an asphaltenes-based precursor material, purifying asphaltenes from the precursor material, treating the asphaltenes to increase its softening point, and oxidizing and pyrolyzing the asphaltenes. The asphaltenes can be powdered or spun into fibers prior to oxidation and pyrolysis. The non-amorphous hard carbons can have an d002-spacing larger than 0.35 nm and a ratio of ID / IG in their Raman spectra greater than 1.0.

Description

PRODUCTION OF HARD CARBONS FROM ASPHALTENE-RICH HYDROCARBONSField of the Invention

[0001] This disclosure relates to a process to produce hard carbons (HCs) from a hydrocarbon feedstock comprising asphaltenes. The resulting HCs are suitable for use as a negative electrode material, for example in a sodium-ion or lithium-ion battery.Background

[0002] The goal of reduction of carbon emissions has inspired research into a wide range of energy storage systems. Lithium-ion batteries (LIBs) are by far the most mature technology in current use, however, the scale of utilization of LIBs in the future may be hampered by the scarcity of lithium-containing minerals. Alternative battery systems based on sodium, potassium, and multivalent cations are in development, of which sodium-ion batteries (SIBs) have emerged as a promising system due to the abundance and widespread distribution of sodium-bearing minerals. One bottleneck in the commercial development of SIBs is the lack of negative electrode materials that can deliver stable performance in full-cell batteries with extended lifetime. Unlike its successful use in LIBs, graphite does not form thermodynamically stable intercalation compounds with sodium due to the weak sodium-carbon interactions, leading to unfavorable energetics.

[0003] Non-graphitizable carbon materials, variously known as hard carbons (HCs), are structurally suited for storing more sodium ions than graphite and thus may be promising for use in SIBs. Hard carbons are characterized by atomic structures consisting of stacks of graphene layers with interlayer spacings ranging from 0.34 to 0.40 nm, which are large enough to accommodate sodium ions.

[0004] Electrochemical performance of HCs is further influenced by particle morphology, surface area, pore microstructures, degree of graphitization, and heteroatom defects. These characteristics affect the capacity and mechanism of Na+ storage in HCs and are at least in part dependent on the materials used as carbon precursors.

[0005] There is a need in the art for methods for producing hard carbons from alternative carbon sources, such as a hydrocarbon material comprising asphaltenes.Summary

[0006] The present disclosure relates to non-amorphous hard carbons (HCs) which are produced by treating a hydrocarbon feedstock comprising asphaltenes to increase its softening point and producing an asphaltenes-based precursor material, purifying asphaltenes from the precursor material, treating the asphaltenes to increase its softening point, and oxidizing and pyrolyzing the asphaltenes. The asphaltenes can be powdered or spun into fibers prior to oxidation and pyrolysis. The non-amorphous hard carbons can have a carbon lattice (doo2) spacing larger than 0.35 nm and a ratio of ID / IG in their Raman spectra greater than 1.0. The non-amorphous HCs may be suitable for use as anode materials for sodium-ion and lithium-ion batteries.

[0007] In preferred embodiments, the asphaltene-based precursor material possess softening points greater than 150° C and are cross-linked through oxidation before being pyrolyzed into non-amorphous hard carbons. The obtained HCs can have a doo2 spacing larger than 0.35 nm and a prominent D-band peak in their Raman spectra.

[0008] In one aspect, disclosed is a process of producing non-amorphous hard carbon, comprising the steps of:(a) treating a hydrocarbon material comprising asphaltenes to produce an asphaltenes- based precursor material with an increased softening point;(b) dissolving the asphaltene-based precursor material in an n-alkane solvent to separate insoluble asphaltenes from soluble material;(c) recovering the asphaltenes, and treating the recovered asphaltenes with at least one stage of heat treatment in a nitrogen and / or steam atmosphere;(d) oxidizing the treated asphaltenes at an elevated temperature; and(e) pyrolyzing the oxidized asphaltenes to produce non-amorphous hard carbon.

[0009] In some embodiments, the treatment step (a) comprises the steps of:(a.1) mixing the hydrocarbon feedstock with a chemical additive comprising an ammonium-, sulfur- and / or oxygen-containing compound;(a.2) heating the mixture to a first temperature (Tl) up to about 480° C in a gas flowing environment of air, nitrogen, steam, an oxygen containing gas, or acombination thereof, stirring the mixture during heating, and holding the mixture at about Tl for a first period of time;(a.3) heating the mixture to a second temperature (T2) in a gas flowing environment of air, nitrogen, steam, an oxygen containing gas, or a combination thereof and holding the mixture at about T2 for a second period of time; and(a.4) optionally, heating the mixture to a third temperature (T3) in a gas flowing environment of air, nitrogen, steam, an oxygen containing gas, or a combination thereof and holding the mixture at about T3 for a third period of time.The mixing step can occur before, after or simultaneously with a heating step.

[0010] In preferred embodiments, Tl, T2 and T3 may be between about 300° to about 480° C, and the first, second and third periods of time may be between about 30 minutes to about 3 hours. Preferably, T1<T2<T3, where T3 is about 350° to about 450° C.

[0011] In preferred embodiments, the asphaltenes-based precursor material is a liquid and solid impurities are removed, such as by filtering the treated mixture.

[0012] Optionally, the heat treated asphaltenes may be ground into a powder prior to oxidation.

[0013] The temperature and the time required in the oxidation step and / or the pyrolysis step are sensitive to the softening point of the asphaltenes or asphaltenes- based precursor material. The softening points can be adjusted through a control of the relative amount of chemical additive in step (a), the treatment temperature and time and the type of gas environments in Tl, T2 and T3, and the resin / asphaltene content in the precipitated asphaltenes.

[0014] In preferred embodiments, the hard carbon product has an doo2-spacing of at least about 0.35 nm, and a ID / IG ratio of at least about 1.0, preferably in the range of about 1.5 to about 3.0.Brief Description of The Drawings

[0015] In the drawings, like elements are assigned like reference numerals. The drawings are not necessarily to scale, with the emphasis instead placed upon the principles of thepresent invention. Additionally, each of the embodiments depicted is but one of a number of possible arrangements utilizing the fundamental concepts of the present invention.

[0016] Figure 1 is a schematic overview of one embodiment of a process to produce precursor fibers from a hydrocarbon feedstock.

[0017] Figure 2 is a schematic overview of an alternative embodiment.Detailed Description of Preferred Embodiments

[0018] The present invention relates to a process to produce hard carbons (HCs) from a hydrocarbon feedstock, processed to extract asphaltenes, and treated to increase their softening point.

[0019] Embodiments disclosed herein are not limited by the source or nature of the hydrocarbon feedstock. The hydrocarbon feedstock can be any material of a thermoplastic nature that is liquid or becomes liquid upon heating, and comprises asphaltenes, preferably from about 5 % up to about 90 % by weight. While this disclosure demonstrates processes with petroleum-derived hydrocarbon materials, embodiments described herein can be used for processing other types of hydrocarbons such as those derived from coal, or other processing activities due to their similar thermoplastic nature.

[0020] Hydrocarbon feedstock that can be treated in accordance with the present disclosure includes hydrocarbon material derived from coal, heavy oil or bitumen, such as, for example, coal tar, coal-tar pitch, fluid catalytic cracker (FCC) or residual catalytic cracker (RCC) slurry oil, vacuum distillation residues (VDR) or vacuum refinery residue (VRR), asphalt, petroleum pitch and the like. Preferably, the hydrocarbon feedstock has a high content of asphaltenes, greater than about 5 wt%.

[0021] Asphaltenes are defined operationally as the n-heptane-insoluble, toluene-soluble component of a carbonaceous material. Asphaltenes do not have a specific chemical formula: individual molecules can vary in the number of atoms contained in the structure, and the average chemical formula can depend on the source - the exact molecular structures are difficult to determine. Given this limitation, asphaltenes are composed mainly of poly aromatic carbon ring units with oxygen, nitrogen, and sulfur heteroatoms, combined with trace amounts of heavy metals, particularly chelated vanadium and nickel, and aliphatic side chains of various lengths. Asphaltenes have a distribution of molecularmasses in the range of 400 u to 1500 u, but the average and maximum values are difficult to determine due to aggregation of the molecules in solution (Podgorski, D.C. (2013), Energy & Fuels, 27(3): 1268-1276).

[0022] Crude oils are customarily divided into saturate, aromatic, resin and asphaltenes (SARA) fractions according to their polarizability and polarity. The saturate fraction consists of nonpolar material including linear, branched, and cyclic saturated hydrocarbons (paraffins). Aromatics, which contain one or more aromatic rings, are slightly more polarized. Both resins and asphaltenes have polar substituents but resins are miscible with heptane or pentane, whereas asphaltenes are not.

[0023] Many naturally formed hydrocarbon materials are rich in asphaltenes. The content of asphaltenes in light crude oils is low, usually less than 2%, but can be as high as 20% in heavy oil or bitumen, such as Alberta oilsands bitumen. When bitumen is refined to remove light molecular weight hydrocarbons, the content of asphaltenes can increase to about 30%, for example, in residues such as vacuum distillation residues (VDR), also referred to as the bottom-of-the-barrel. Residues are conventionally used to produce asphalt, tar, paraffin wax, lubricating oil, heavy oils, pitch, and cokes. Coal tar is produced as a byproduct when coal is carbonized to make coke or gas. When distilled, coal tar produces creosotes as a product and coal-tar pitch as a residue that can be rich of asphaltenes.

[0024] Asphaltenes are a thermoplastic polymer, where single molecules are linked together by thermosensitive intermolecular attractive forces such as Van der Waals, dipole-dipole, and hydrogen bonding. The softening points and melting points of polymeric materials are generally related to their molecular mass, as well as the intra- and intermolecular forces within the polymer. Melting points of polymers with a molecular weight of 100 mol / g are well below -50° C, while those with a molecular weight larger than 400 mol / g are higher than 50° C. At very low temperatures, thermoplastic polymers are very brittle and exhibit high Young’s modulus, owing to the rigidity of crystalline and amorphous molecules. With temperature rise, there is usually a sudden drop of their rigidity and Young’s modulus, because of activation of molecular movement of the amorphous chain segments. The temperature point at which Young’s modulus drops quickly is termed as the glass point, Tg. This drop of Young’s modulus depends on theamorphous / crystalline ratio. Between Tg and Tm (melting temperature) is the rubber-fluid state, where the polymers are softened and can be pulled into filaments such as fibers.

[0025] The softening points of asphaltenes produced by solvent de-asphalting (SDA) of Alberta oilsands bitumen is known to be in the range of 160° to 170° C, while those from metallurgic pitch, are well below 150° C. The softening points of these materials are higher than their glass point and usually about 30-40° C lower than their melting points. Softening points can be measured by the Ring and Ball method (R&B) — ASTM D 3461- 76, DIN ISO 4625.

[0026] The softening points of petroleum materials are commonly increased by removing lighter fractions during thermal condensation, at temperatures in excess of 350° C. When temperature is increased, dehydrogenation, cross-linking, and condensation reactions occur, which releases gases comprising hydrogen, steam, hydrogen sulphide and low molecular weight hydrocarbons. As a result, the remaining materials will possess a higher average molecular weight with a lower H / C ratio and a higher softening point.

[0027] The prior art discloses several methods developed for increasing softening points of isotropic pitch (Carbon Fibers, Technology & Engineering, 3rd Edition, J-B Donnet, R. C. Bansal, 1998, page 45). These include reducing pressure thermal condensation, wiped film evaporator, oxygen containing gas blow oxidation, sulphidation, additive method and PVC method. Mesophase pitch is made by polymerizing isotropic pitch to a higher molecular weight with its melting point preferably controlled within 230° C to 280° C. Mesophase pitch forms a thermotropic crystal, which allows the pitch to become organized and form linear chains without the use of tension. Many methods are known for either increasing or reducing the softening point and viscosity of mesophase pitch, depending on the type of raw pitch materials, including thermal modification, solvent modification, hydrogenation methods, and catalyst modifications using Lewis acids (e.g., A1C13, HF / BF3). These methods may be adapted to modulate the softening point of asphaltenes.

[0028] In one aspect, the softening point of the hydrocarbon feedstock is increased in the process to produce an asphaltene-based precursor material. Methods to increase the softening point of a hydrocarbon material are known, and examples are described in PCT Patent Application No. PCT / CA2021 / 000092 filed on 15 October 2021, the entire contents of which are incorporated herein by reference, where permitted.

[0029] In preferred embodiments, the hydrocarbon feedstock can be treated with a chemical additive and heating, in at least one heating stage, up to about 480° C, through one or a combination of the process steps described below. The treatment temperature must be higher than the thermal decomposition temperature of the chemical additive. However, all heat treatments are preferably performed at a temperature below 480° C in order to avoid carbonization or coke formation. This treatment increases the softening point and / or melting point of the resulting asphaltene-based precursor material.

[0030] An exemplary process is depicted in Figure 1, where a hydrocarbon feedstock is mixed with a chemical additive and heated to a first temperature (Tl) and held and stirred for a suitable period of time, with a flowing gas environment. The temperature of the hydrocarbon feedstock mixture is then adjusted to a second temperature (T2) which may lower or higher than Tl, and held for a second suitable period of time, again with stirring under a flowing gas environment. Optionally, the temperature of the mixture may then be adjusted to a third temperature (T3) which may be lower or higher than T2, and held for a third suitable period of time, again with stirring under a flowing gas environment. It is preferred that all stirring is done continuously.

[0031] In some embodiments, a suitable holding time for Tl is between about 1 hour to about 4 hours, the holding time at T2 is between about 0 minutes to about 3 hours, and the holding time at T3 is between about 0 minutes to about 3 hours.

[0032] Tl, T2 and optional T3 heat treatments are at temperatures at which decomposition of the chemical additive takes place, cross-linking or vulcanization reactions of hydrocarbon materials occur, and / or reactions between the flowing gases and the hydrocarbon materials take place. It is possible for all of these events to take place simultaneously, during any of the heat treatment stages.

[0033] In preferred embodiments, processing temperature and time are controlled to control the desired rate of reaction.

[0034] The chemical mixing step can occur at an ambient temperature before heating, or can occur after or during heating of the hydrocarbon feedstock in a first heating step. Stirring can occur after mixing and heating, or stirring can occur during any one or both of mixing and heating. As such, the method can be carried out as separately timed steps, orin different combinations of mixing, heating and stirring. Continuous stirring in a flowing gas environment is preferred.

[0035] The chemical additive serves to increase the softening point through cross-linking reactions in the precursor material, preferably without significantly altering the chemistry of the original hydrocarbon material. It is preferred to control dosage of chemical additives to avoid converting the material to a thermosetting plastic or coke by excessive crosslinking. In some embodiments, these chemical additives decompose into intermediate products that catalyze the process of cross-linking. The intermediate products from the decomposition of additives can be further decomposed into gaseous phases that can be easily removed from the reaction system. As a result, the chemistry of hydrocarbon materials is not altered through chemical bonding with elements of the additives.

[0036] In some embodiments, the chemical additive comprises a compound comprising an ammonium group, a sulfur atom and / or an oxygen atom, and preferably all three. In some embodiments, the ammonium-, sulfur- and / or oxygen-containing-compound may comprise (NH4)2SO4 (ammonium sulphate) (NH4)2S20s (ammonium persulfate), (NH4)2S20S (ammonium thiosulfate), (NH4)2SO3 (ammonium sulfite), NH4HSO4 (ammonium hydrogen sulfate), NH4HSO3 (ammonium hydrogen sulfite), and (NT S (ammonium sulfide), or combinations thereof. At elevated temperatures, these ammonium-, sulfur- and oxygen-containing-compounds decompose into a HSO42', HSO3', S2O?2', S20s2', S2O32", SO32’ containing compounds, SO2, or S, or combinations of such compounds. These decomposition products serve as catalysts, which can cause crosslinking and / or vulcanization of hydrocarbon feedstock material to alter the hydrocarbon feedstock material to have thermoplastic properties and an increased softening and / or melting point. The vulcanization or cross-linking can also lead to the hydrocarbon feedstock being converted into elastic (rubber), or thermosetting compounds.

[0037] In preferred embodiments, the chemical additive comprises ammonium sulphate, which thermally decomposes according to reactions (l)-(3):(NH4)2SO4 = NH4HSO4 +NH3 (1)2 NH4HSO4 = (NH4)2S2O7 + H2O (2)3(NH4)2S2O7= 2NH3+ 2N2 + 6SO2 + 9H2O (3)The overall reaction is 3(NH4)2SO4 = 4NHs + N2 +3SO2 + 6H2O (4)

[0038] The intermediate reaction products include pyrosulfate (S2O7)2‘ and SO2. These compounds are known to cause vulcanization of a polymer compound (rubber) to an elastic and final end-use product. The above-described reactions occur within a range of temperature from about 250° C to 500° C, which coincides with the temperature range in which depolymerization, cross-linking, chain cleavage, and cracking of hydrocarbon materials can occur. The adding of (NH4)2SO4 or other ammonium-, sulfur- and / or oxygen-containing-compounds can occur at a temperature above room temperature, for example, when the hydrocarbon materials are at a temperature above room temperature from a previous processing stage.

[0039] Further products that result from the decomposition of (NF kSCh or other ammonium-, sulfur- and oxygen-containing-compounds, outside of those listed above are gaseous substances that will not react with hydrocarbon materials being treated.

[0040] The dosage of (NFkkSCh or other ammonium-, sulfur- and oxygen-containing- compounds can be any value from about 0% to about 20% (by weight) of hydrocarbon feedstock, depending on the initial softening, or melting points of the hydrocarbon materials to be treated, the treatment temperature, the gaseous environment, the desired increase in softening point and the desired final rheological properties of the treated materials.

[0041] The flowing gas environment in the reactor for any heat treatment step may comprise pure nitrogen, pure steam, an oxygen-containing gas such as air, or combinations thereof. The gas environment serves to modify the hydrocarbon feedstock by chain elongation and / or cross-linking of the hydrocarbon materials, by cleaving side chains, or cracking heavier molecules when needed. Flowing gas also reduces the incidence of material getting deposited or stuck onto the inner sides of the treatment equipment. Depending on the properties of hydrocarbon materials required after treatment, the selection of the type of gas streams, and the temperature and residence time can be varied during treatment. The selection of gas environments may change the effectiveness of chemical additives in achieving cross-linking. It may also affect the alteration of chemical composition of the hydrocarbon feedstock being treated. For example, the gas may facilitate chain cleavage to remove certain side chains or molecular groups, and may facilitate dehydrogenation, leading to a decrease of the H / C ratio, which may be desired or necessary for certain applications of the treated hydrocarbon feedstock. The effectivenessof the above described alteration of chemical composition of the initial hydrocarbon materials is dependent of the type of processing gases.

[0042] It is preferred to continuously stir the mixture of hydrocarbon feedstock and chemical additives while heating and holding the mixture. Stirring improves heat transfer between the feedstock and the reactor wall being externally heated, mixing of additives with the feedstock, increases evaporation of volatile components, and encourages mixing of the gaseous medium with the hydrocarbon feedstock.

[0043] The heating of a mixture of the hydrocarbon feedstock with a chemical additive and with a flowing gas stream combines various processes of molecular modification (depolymerization, cross-linking, cleavage and cracking) into a set of single process conditions in a single treatment, which conditions which can be tailored to meet various requirements of the final products.

[0044] The additives, after treatment, convert to gaseous phases, thus making minimum changes to the chemistry of original hydrocarbon feedstock and which facilitates its removal from the hydrocarbon feedstock.

[0045] After treatment, the hydrocarbon feedstock will have less aliphatic hydrogen present. The resulting higher aromaticity is desirable when using the treated feedstock as a precursor material for making hard carbon.

[0046] In alternative embodiments, additional chemical agents could be added before and / or during at least one of the stepwise heat treatments for purposes other than the control of softening points and asphaltene content. For example, chemical agents could be added to produce activated carbon, adding solids of any physical forms to change chemical, mechanical, electrical, thermal, and biological properties of the hydrocarbon feedstock. In some embodiments, the chemical agents may comprise salts selected from the group consisting of potassium carbonate, potassium bicarbonate and potassium chloride, or from the group consisting of lithium acetate, lithium citrate, lithium carbonate, lithium bicarbonate, lithium hydrogen citrate, lithium chloride, sodium oxalate, sodium hydrogen phthalate, sodium hydrogen phthalate, sodium acetate, sodium citrate, sodium carbonate, sodium bicarbonate, sodium hydrogen citrate, sodium chloride, potassium oxalate, potassium hydrogen phthalate, potassium hydrogen phthalate, potassium acetate,potassium citrate, potassium carbonate, potassium bicarbonate, potassium hydrogen citrate, potassium chloride, and derivatives thereof.

[0047] The asphaltene-based precursor material resulting from the chemical treatment at an elevated temperature is thermoplastic, and in liquid form at an elevated temperature but may contain various solid impurities. The solid impurities are preferably removed through using conventional liquid-solid separation techniques such as physical, mechanical, chemical, magnetic or electro-magnetic methods, or combinations thereof. The precursor material can be dissolved in or mixed with a solvent to liquefy or reduce the viscosity of the thermoplastic precursor material, which can facilitate liquid / solid separation.

[0048] Physical methods of solids removal include sedimentation, centrifugation or decanting methods which take advantage of the higher density of solid particles than the thermoplastic liquid.

[0049] Mechanical methods include filtration, which preferably involves a pressure differential to force the liquid to pass through a filter membrane. The pressure differential may be created by pressurizing the feedstock above the filter or depressurizing the chamber below the filter (vacuum separation). In some embodiments, the material is filtered through a porous membrane with a pore sizes ranging from 0.1 pm to 500 pm, under pressure up to 100 psi.

[0050] Magnetic and / or electromagnetic methods can be used to remove magnetic species, usually metal-containing compounds, that are magnetic or can be magnetized by electric current.

[0051] Chemical methods include the addition of chemicals to react with the solid particles to form new compounds that can be easily separated by other methods. Another chemical method involves the use of a solvent to dissolve the thermoplastic portion of the solid feedstock, including asphaltenes, leaving the insoluble particles to be removed by other methods from the bulk material. The precursor material may be recovered by removing solvent through evaporation. Additionally, or alternatively, a solvent could also be added to precipitate asphaltenes as insoluble to the solvents and to remove soluble components to increase the asphaltene concentrations in the resulting products.

[0052] The asphaltene-based precursor material may be cooled during or after fdtration or solids rejection. The end temperature of cooling can be room temperature or anintermediate temperature between the room temperature and the last stage of heating temperature.

[0053] In some embodiments, the asphaltene-based precursor material, after optional solids removal, includes amounts of n-alkane-insoluble material, up to about 95%, and is then further processed to obtain purified asphaltenes by solvent purification with, for example, n-pentane, hexane or heptane. The solute comprises unwanted n-alkane soluble components and can be discarded or recovered for another purpose. Asphaltenes are not soluble and are thus purified.

[0054] The ratio of solvent to asphaltene-based material may be varied however, generally, the greater the amount of solvent, the higher the softening point of the recovered asphaltenes. In some embodiments, the solvent may be used in a ratio between about 4: 1 to about 25: 1, by weight. However, increasing the solvent ratio beyond about 10: 1 may not appreciably increase the softening point and thus may not be preferred.

[0055] The asphaltenes recovered by solvent purification may then be used to produce HCs, or in preferred embodiments, the asphaltenes may be treated to further increase its softening point, by one or more stages of heat treatment equivalent to those described above, with or without further chemical treatment. For example, the asphaltenes may be heat treated at about 280° to about 380° C, such as 300°, 310, 325°, or 350° C under a flowing gas, such as pure nitrogen and / or steam, for between about 1 hour to 3 hours. In preferred embodiments, the heating stage is repeated one or two times. In preferred embodiments, an additional amount of (NH4)2SO4 is added and mixed with the asphaltenes in a first heat treatment, followed by at least a second and preferably a third stage of heat treatment, in steam and / or nitrogen.

[0056] The purified and / or heat-treated asphaltenes are preferably milled or ground to produce a fine powder, prior to oxidation. For example, the asphaltenes may be ball milled for different time periods to produce precursor powders. The grinding conditions may be varied to produce powders of different sizes, for example between about 5 pm to about 100 pm. In ball milling, particle size is largely a function of grinding time. While smaller particles generally produce HCs with larger d-spacing, little benefit may be seen with particle sizes below about 20-30 pm.

[0057] The powdered asphaltene may then be oxidized at an elevated temperature with a flow of an oxy gen-containing gas. For example, oxidation treatment may be carried out by heating the asphaltenes at rates between 0.5 to 5° C / min to a temperature between 250°C and 350°C and holding at the temperature for a time from 10 to 180 minutes.

[0058] The oxidized powder may then be pyrolyzed to produce the desired HC material. For example, pyrolysis treatment may be carried out by heating the materials at a rate of 0.5 to 10° C / min to a temperature between 800°C and 1500°C and holding at the temperature for a time from 30 minutes to 180 minutes.

[0059] Oxidation and / or pyrolysis may be performed in any suitable oven, rotary furnace, belt furnace, or a stationary set of heating devices with controlled environments.

[0060] In some alternative embodiments, hard carbon fibers may be produced by first producing precursor fibers from either the asphaltene-based material produced by the at least one chemical activation and heat treatment stages described above, or from the purified asphaltene material produced by solvent rejection of n-alkane soluble material. As shown in Figure 2, the precursor fibers may be produced by as melt-spinning, wetspinning, or blowing spinning, electrostatic spinning. The precursor fibers may then be oxidized and pyrolyzed in like manner as the powder material described above.Examples

[0061] By way of further description, reference may be made to the following examples, which are intended to exemplify certain elements of the claimed invention, not limit them. Unless otherwise indicated, all parts and percentages are by weight.Example 1

[0062] A vacuum refinery residue was used as the feedstock hydrocarbon material. 20 kg of vacuum refinery residues was added with different amount of (NFfyfiSCfi solid powder, ranging from 3 to 8 wt. % of vacuum refinery residues, as listed in Table 1. The mixture was placed in a sealed cylindrical reactor and stirred at a rate of 30 RPM (revolutions per minute) as the mixture was treated with the following sequential steps:• 1ststep of heating to 350°C and held at 350°C for 120 minutes with a flow of N2 gas,• 2ndstep of heating to 420°C and held at 420°C for 60 minutes with a flow of N2gas,• 3rdstep of heating to 435°C and held at 435°C for 75 minutes with a flow of steam, and• 4thstep of filtering of the resulting hydrocarbons to remove any potential solid either formed during the processing or inherited from the feedstock before cooling to room temperature with a flow of N2 gas.

[0063] Each heating step was performed with continuous stirring.

[0064] The treated material after cooling was a solid, although the feedstock hydrocarbon material before treatment was a viscous liquid at room temperature and its softening point was below room temperature, but not measured. The treated materials have softening points that are substantially higher than the starting feedstock. The precursor yields and the softening points as affected by different dosages of (NELfkSCh are listed in Table 1.Table 1 Effect of chemical dosage on the softening points of vacuum refinery residue after the four steps of treatment in Example 1.Example 2

[0065] Sample C in Table 1, which was produced following the steps in Example 1, was dissolved in pentane with a ratio of 20: 1 of pentane over Sample C to produce pentane- insoluble asphaltenes solids. The obtained asphaltenes solids were placed in a sealed cylindrical reactor and were then heated to different temperatures as listed in Table 2 for 2 hours. Stirring at a speed of 30 RPM and a flow of N2 gas were maintained during the treatment. The softening points of the resulting material were measured and are seen to be substantially increased depending on the temperature of treatment, as compared to that of Sample C in Table 1 of Example 1.Table 2 The softening points of resulting samples after further treatments as described in Example 2Example 3

[0066] Sample C in Table 1, which produced following the steps in Example 1, was dissolved in pentane with different ratios of pentane over Sample C, as listed in Table 3. The insoluble asphaltenes solids were placed in a sealed cylindrical reactor and were then heated to and held at 325°C for 120 minutes. Stirring at a speed of 30 RPM and a flow of N2 gas were maintained during the treatment. The softening points of the resulting material were measured and are seen to increase with the ratio of solvents over Sample C, as listed in Table 3.Table 3 The softening points of Sample C after further treatments as described in Example 3Example 4

[0067] Samples A to E in Table 1, which were produced following the steps in Example 1, were each further treated following steps for Sample C-4 of Table 2 in Example 2. The softening points of the resulting samples were measured and are seen to be increased as compared with those of Samples A to E in Table 1 of Example 1Table 4 The softening points of the resulted new samples produced following the steps described in Example 4Example 5

[0068] Sample C-6 in Table 3 of Example 3 was further treated with the conditions listed in Table 5. The softening points of the resulting new samples (Samples C-6-1 and C-6-2 inTable 5) were measured and are seen to be increased as compared with that of Sample C- 6.Table 5 The softening points of the resulted new samples produced following the steps described in Example 5Example 6

[0069] The precursor prepared according to the conditions for Sample C-4 in Table 2 of Example 2 was processed following the steps below to produce non-amorphous hard carbons: i. Grinding Sample C-4 into powders through ball milling for different time periods as listed in Table 6 to produce precursor powders. ii. Heating the powders to 300°C at a rate of 1.5 °C / min and holding at 300°C for 60 minutes in a furnace with a flow of air. iii. Pyrolysis of the oxidized powders obtained from Step ii by heating them to 1200°C at a rate of 3 °C / min and holding at 1200°C for 120 minutes in a furnace with a flow of nitrogen gas.

[0070] The powders obtained following the above indicated treatment were ground into fine powders for X-ray diffraction testing to determine the distance between adjacent graphene layers, termed as d-spacing, which is half of the hexagonal graphite crystallographic spacing (0.673 nm), or the calculated (002) peak d-spacing, identified as doo2-spacing. The value of doo2-spacing of the powders is listed in Table 6, together with the doo2-spacing of crystalline graphite.Table 6 Effect of grinding time on the doo2-spacing of the materials obtained following the treatment steps in described in Example 6.Example 7

[0071] The precursor produced according to the conditions for Sample C-4 in Table 2 of Example 2 was processed following the steps below to produce hard carbons: i. Grinding precursor Sample C-4 into powders through ball milling for 5 minutes to produce precursor powders with an average particle size of 53.7 pm. ii. Heating the precursor powders to different temperatures as listed in Table 7 at a rate of 1.5 °C / min and holding the materials at the temperature for 60 minutes in a furnace with a flow of air. iii. Pyrolysis of the oxidized powders obtained from Step ii by heating them to 1200°C at a rate of 3 °C / min and holding at 1200°C for 120 minutes in a furnace with a flow of nitrogen gas.

[0072] The resulting materials were used to determine doo2-spacing. The results obtained are listed in Table 7.Table 7 Effect of oxidation temperature on the doo2-spacing of the materials obtained following the treatment steps in Example 7.Example 8

[0073] The precursor produced according to the conditions for Sample C-4 in Table 2 of Example 2 was processed following the steps below to produce hard carbons: i. Grinding precursor Sample C into powders through ball milling for 10 minutes to produce precursor powders. ii. Heating the precursor powders to 275°C at a rate of 1.5 °C / min and holding at 275°C for 60 minutes in a furnace with a flow of air. iii. Heating the oxidized powders obtained from Step ii to 1200°C and holding at 1200°C for different time periods as listed in Table 8 in a furnace with a flow of nitrogen gas.

[0074] The resulting materials were used to determine doo2-spacing. The results obtained are listed in Table 8.Table 8 Effect of heating rate and hold temperatures on the doo2-spacing of the materials obtained following the treatment steps in Example 8.Example 9

[0075] The precursor produced according to the conditions for Sample C-4 in Table 2 of Example 2 was processed following the steps below to produce hard carbons: i. Grinding Precursor Sample C4 into powders through ball milling for 5 minutes to produce precursor powders with an average particle size of 53.7 pm. ii. Heating the precursor powders to 300°C at a rate of 1.5 °C / min and holding the materials at the temperature for different time periods as listed in Table 9 in a furnace with a flow of air. iii. Pyrolysis of the oxidized powders obtained from Step ii by heating them to 800°C at a rate of 3 °C / min and holding at 800°C for 120 minutes in a furnace with a flow of nitrogen gas.

[0076] Raman spectroscopy of the powders obtained from Step iii was also conducted to measure the scattering of monochromatic light with molecular vibrations and phonons of the carbon solid. The Raman spectrum usually exhibits two main peaks, one peak at 1355 cm1is termed as D-band, the other at 1579 cm1is called G-band. The G-band is a graphitic band corresponding to in-plane C-C vibrations, while the D-band is a disordered band that reflects the existence of disorder and lattice defects in the structure, like in the case of hard carbons. The intensities of D and G peaks, ID and IG, were measured and their ID / IG ratios are determined and listed in Table 9, together with the results of doo2-spacing.Table 9 Effect of oxidation temperature on the doo2-spacing and ID / IG ratio of the materials obtained following the treatment steps in Example 9.Example 10

[0077] The precursor produced according to the conditions for Sample C-4 in Table 2 of Example 2 was processed following the steps below to produce hard carbons: i. Grinding Precursor Sample C4 into powders through ball milling for 5 minutes to produce precursor powders with an average particle size of 53.7 pm. ii. Heating the precursor powders to 300°C at different rates as listed in Table 10 and holding the materials at the temperature for 60 minutes in a furnace with a flow of air. iii. Pyrolysis of the oxidized powders obtained from Step ii by heating them to 800°C at a rate of 3 °C / min and holding at 800°C for 120 minutes in a furnace with a flow of nitrogen gas.

[0078] The resulting materials were used to determine doo2-spacing and Raman and ID / IG ratios. The results obtained are listed in Table 10.Table 10 Effect of heating rate during oxidation treatment on the doo2-spacing and ID / IG ratio of the materials obtained following the treatment steps in Example 10.Example 11

[0079] The precursor produced according to the conditions for Sample C4 in Table 2 of Example 2 was processed following the steps below to produce hard carbons: i. Grinding Precursor Sample C4 into powders through ball milling for 5 minutes to produce precursor powders with an average particle size of 53.7 pm. ii. Heating the precursor powders to 300°C at a rate of 1.5 °C / min and holding the materials at the temperature for 60 minutes in a furnace with a flow of air. iii. Pyrolysis of the oxidized powders obtained from Step ii by heating them to 800°C at different rates as listed in Table 11 and holding at 800°C for 120 minutes in a furnace with a flow of nitrogen gas.

[0080] The resulting materials were used to determine doo2-spacing and ID / IG ratios. The results obtained are listed in Table 11.Table 11 Effect of heating rate and hold temperatures on the doo2-spacing and ID / IG ratio of the materials obtained following the treatment steps in Example 11.Example 12

[0081] The precursor prepared according to the conditions for Sample C4 in Table 2 from Example 2 was used to fabricate precursor fibers through melt-spinning under the conditions listed in Table 12. The precursor was wound into precursor fibers with diameters listed in Table 12. The precursor fibers were treated following the same steps as described in Example 6 to produce hard carbon fibers. The doo2-spacing and ID / IG ratio of the resulting fiber material are listed in Table 12.Table 12 The measured doo2-spacing and ID / IG ratio of the hard carbon fibers obtained following the processes describe in Example 12.Example 13

[0082] An asphaltene-rich hydrocarbon material with an asphaltene content of 76 wt. % was treated with conditions listed in Table 13. 2 kg of feedstock (Sample W in Table 13) was mixed with 3.5 wt.% (N kkSCh powder. Sample X was produced by treating the mixture following two steps of heating, while Sample Y was treated following three steps of heating as listed in Table 13. The treatments led to an increase of spinning temperature and an improvement in winding speed of the precursor fibers, as compared to the feedstock (Sample W). The resulting precursor fibers were treated following the samesteps as described in Example 6 to produce hard carbon fibers. The doo2-spacing of the resulting fiber material are listed in Table 13.Table 13 Effect of treating conditions on the doo2-spacing of the hard carbon obtained following the steps described in Example 13.Example 14

[0083] A vacuum refinery residue feedstock different from that in Example 1 was used as the feedstock hydrocarbon material. These vacuum refinery residues have a lower softening point than that used in Example 1. 20 kg of the current vacuum refinery residues was added with different amount of (NEU SCfi solid powder, ranging from 0 to 6 wt. % of vacuum refinery residues, as listed in Table 14. The same processing steps and procedures as those in Example 1 were used to process the current mixture. The precursor yields and the temperature of melt-spinning as affected by different dosage of (NEU^SCfi are listed in Table 14. Lower yields but high melt-spinning temperatures were measured for these vacuum refinery residues than the vacuum refinery resides tested in Example 1. Because lower softening points of these vacuum refinery residues, more components with smaller molecules were evaporated, leading to lower product yield but higher spinning temperature. The resulting precursor fibers were treated following the same steps as described in Example 6 to produce hard carbon fibers. The d-spacing of the resulting fiber material are listed in Table 14.Table 14 Effect of chemical dosage on the doo2-spacing of the hard carbon fibers obtained following the steps described in Example 14.Interpretation and Scope

[0084] In different aspects and embodiments, the disclosed invention may comprise any combination of elements, steps, substeps, or conditions described herein.

[0085] The corresponding structures, materials, acts, and equivalents of all means or steps plus function elements in the claims appended to this specification are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed.

[0086] References in the specification to "one embodiment", "an embodiment", etc., indicate that the embodiment described may include a particular aspect, feature, structure, or characteristic, but not every embodiment necessarily includes that aspect, feature, structure, or characteristic. Moreover, such phrases may, but do not necessarily, refer to the same embodiment referred to in other portions of the specification. Further, when a particular aspect, feature, structure, or characteristic is described in connection with an embodiment, it is within the knowledge of one skilled in the art to affect or connect such module, aspect, feature, structure, or characteristic with other embodiments, whether or not explicitly described. In other words, any module, element, step or feature may be combined with any other module, element, step or feature in different embodiments, unless there is an obvious or inherent incompatibility, or it is specifically excluded.

[0087] It is further noted that the claims may be drafted to exclude any optional element. As such, this statement is intended to serve as antecedent basis for the use of exclusive terminology, such as "solely," "only," and the like, in connection with the recitation of claim elements or use of a "negative" limitation. The terms "preferably," "preferred,""prefer," "optionally," "may," and similar terms are used to indicate that an item, condition or step being referred to is an optional (not required) feature of the invention.

[0088] The singular forms "a," "an," and "the" include the plural reference unless the context clearly dictates otherwise. The term "and / or" means any one of the items, any combination of the items, or all of the items with which this term is associated. The phrase "one or more" is readily understood by one of skill in the art, particularly when read in context of its usage.

[0089] The term "about" orcan refer to a variation of ± 5%, ± 10%, ± 20%, or ± 25% of the value specified. For example, "about 50" percent can in some embodiments carry a variation from 45 to 55 percent. For integer ranges, the term "about"can include one or two integers greater than and / or less than a recited integer at each end of the range. Unless indicated otherwise herein, the term "about" oris intended to include values and ranges proximate to the recited range that are equivalent in terms of the functionality of the composition, or the embodiment.

[0090] As will be understood by one skilled in the art, for any and all purposes, particularly in terms of providing a written description, all ranges recited herein also encompass any and all possible sub-ranges and combinations of sub-ranges thereof, as well as the individual values making up the range, particularly integer values. A recited range includes each specific value, integer, decimal, or identity within the range. Any listed range can be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, or tenths. As a non-limiting example, each range discussed herein can be readily broken down into a lower third, middle third and upper third, etc.

[0091] As will also be understood by one skilled in the art, all language such as "up to", "at least", "greater than", "less than", "more than", "or more", and the like, include the number recited and such terms refer to ranges that can be subsequently broken down into sub-ranges as discussed above. In the same manner, all ratios recited herein also include all sub-ratios falling within the broader ratio.

Claims

CLAIMS1. A process of producing non-amorphous hard carbon, comprising the steps of:(a) treating a hydrocarbon material comprising asphaltenes to produce an asphaltenes- based precursor material with an increased softening point;(b) dissolving the asphaltene-based precursor material in an n-alkane solvent to separate insoluble asphaltenes from soluble material;(c) recovering the precipitated asphaltenes, and treating the recovered asphaltenes with at least one stage of heat treatment in a nitrogen and / or steam atmosphere;(d) oxidizing the treated asphaltenes at an elevated temperature; and(e) pyrolyzing the oxidized asphaltenes to produce non-amorphous hard carbon.

2. The process of claim 1, wherein the treatment step (a) comprises:(a.1) mixing the hydrocarbon feedstock with a chemical additive comprising an ammonium-, sulfur- and / or oxygen-containing compound;(a.2) heating the mixture to a first temperature (Tl) up to about 480° C in a gas flowing environment of air, nitrogen, steam, an oxygen containing gas, or a combination thereof, stirring the mixture during heating, and holding the mixture at about Tl for a first period of time;(a.3) heating the mixture to a second temperature (T2) in a gas flowing environment of air, nitrogen, steam, an oxygen containing gas, or a combination thereof and holding the mixture at about T2 for a second period of time; and(a.4) optionally, heating the mixture to a third temperature (T3) in a gas flowing environment of air, nitrogen, steam, an oxygen containing gas, or a combination thereof and holding the mixture at about T3 for a third period of time.

3. The process of claim 2, wherein each of Tl, T2 or T3 is between about 300° to about 480° C, and the first, second or third period of time is each between about 30 minutes to about 3 hours.

4. The process of claim 3, wherein T1<T2<T3, and T3 is between about 350° to about 480° C.

5. The process of any one of claims 1 to 4, wherein the asphaltenes-based precursor material is a liquid, and solid impurities in the precursor material are removed prior to solidifying the precursor material.

6. The process of claim 5 wherein solid impurities are removed by filtration.

7. The process of any one of claim 1 to 6, wherein the precipitated asphaltenes are treated in step (d) with at least one step equivalent to a step described in at least one of claim 2 (a.l) to (a.4).

8. The process of any one of claims 1 to 7, wherein the chemical additive comprises an ammonium-, sulfur- and / or oxygen-containing-compound, such as ammonium sulfate, (NH4)2S20S (Ammonium persulfate), (NH4)2S2O3 (Ammonium thiosulfate), (NT SOs (Ammonium Sulfite), NH4HSO4 (Ammonium hydrogen sulfate), NH4HSO3 (Ammonium hydrogen sulfite), (NH4)2S (Ammonium sulfide).

9. The process of any one of claims 2 to 8, wherein each of Tl, T2 and T3 may be between about 300° to about 480° C, and the first, second and third periods of time may be between about 30 minutes to about 3 hours.

10. The process of any one of claims 2 to 9, wherein Tl is about 300° to 350°C, held for 120 minutes with a flow of N2 gas, T2 is up to about 420° C, held for about 60 minutes with a flow of N2 gas; and T3 is up to about 435°C, held for about 75 minutes with a flow of steam.

11. The process of any one of claims 1 to 10 wherein the dosage of the chemical additive is between about 1% to 20% of the hydrocarbon feedstock, preferably between about 3% to about 8%.

12. The process of any one of claim 1 to 11 wherein the hydrocarbon feedstock comprises any hydrocarbon with a thermoplastic nature that is liquid or becomes liquid upon heating and having an asphaltene content between about 5 % to about 95 %, such as a residue material.

13. The process of any one of claims 1 to 12, wherein the asphaltenes treated in step (c) are ground into a powder or spun into a precursor fiber prior to oxidation.

14. The process of claim 13 wherein the treated asphaltenes are ground into a powder having a particle size between about 5 pm to about 100 pm, preferably between about 10 pm to about 60 pm.

15. The process of claim 13 wherein the treated asphaltenes are spun into precursor fibers having a diameter between about 5 pm to about 10 pm.

16. The process of any one of claims 1 to 15 wherein the treated asphaltenes are oxidized at a temperature between about 200° C to about 350° C in air.

17. The process of claim 16 wherein the treated asphaltenes are oxidized by heating at a rate of between about 0.5 to about 4.0° C per minute.

18. The process of any one of claims 1 to 16 wherein the oxidized asphaltenes are pyrolyzed at a temperature between about 750° to about 1500° C, preferably between about 800° to about 1200° C., preferably wherein the heating rate is between about 0.5° to about 15° C per minute.

19. Non-amorphous hard carbon produced in accordance with any method claimed or described herein, with doo2-spacing larger than 0.35 nm, preferably greater than 0.37, 0.38 nm or 0.39 nm, and a ratio of ID / IG in their Raman spectra greater than 1.0, preferably greater than 1.5.

20. The hard carbon of claim 19 which is a powder or a fiber.

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