Compositions and methods for producing carbon fibers from asphaltenes

Abstract

Starting from a high asphaltene feed with significant levels of sulfur and total metals, the present technology provides fibers containing high levels of asphaltenes but low levels of sulfur and total metals. Thus, the present technology provides fibers containing at least 30 wt.% asphaltenes, less than 1 wt.% sulfur, and less than 0.1 wt.% total metals based on the weight of the fiber. Additionally, methods for producing such asphaltene fibers, as well as methods for preparing carbon fibers from the asphaltene fibers, are provided.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Application No. 63 / 245,513, filed September 17, 2021, which is incorporated by reference in its entirety.

[0002] Technology Areas The present technology relates to compositions and methods for producing carbon fibers from asphaltenes. In particular, the present technology relates to fiber intermediates that contain high amounts of asphaltenes but low amounts of sulfur and metal impurities. The present technology further relates to methods for producing such fiber intermediates from high asphaltene feedstocks that have significant sulfur and metal impurities, as well as methods for producing carbon fibers from the fiber intermediates. Summary of the Invention

[0003] A brief overview of the technology The present technology provides fibers that contain high levels of asphaltenes but low levels of sulfur and total metals. Thus, the present technology provides fibers that contain at least 30 wt. % (as used herein, "wt. %" means "weight percent") asphaltenes, less than 1 wt. % sulfur, and less than 0.1 wt. % or less than 0.05 wt. % total metals, based on the weight of the fiber. These asphaltenic fibers can be used to produce high quality carbon fibers that are comparable to carbon fibers made from expensive polyacrylonitrile, but with fewer defects often found in pitch-based fibers.

[0004] The present technology also provided a method for producing such asphaltene fibers, as well as a method for preparing carbon fibers from the asphaltene fibers. These methods include melt spinning a fiber feedstock into fibers, as disclosed in any embodiment herein, the fiber feedstock comprising at least 30 wt% asphaltenes, less than 1 wt% sulfur content, and less than 0.1 wt% or less than 0.05 wt% total metals content. These methods may further comprise contacting a hydrocarbon feedstock with an effective amount of metallic sodium and an effective amount of an extrinsic capping agent at a temperature of 250-500°C to produce a mixture of sodium salt and a converted feedstock, the hydrocarbon feedstock comprising at least 1 wt% asphaltenes, at least 1 wt% sulfur content, and at least 0.1 wt% or at least 0.05 wt% total metals content, the converted feedstock comprising at least 30 wt% asphaltenes, light hydrocarbons, less than 1 wt% sulfur content, and less than 0.1 wt% or less than 0.05 wt% total metals content. These methods may further include stabilization by oxidizing the fibers to produce oxidized fibers, which can then be carbonized, for example, by heating the oxidized fibers to 1000° C. to 2000° C. in an inert, oxygen-free atmosphere.

[0005] The above is a summary of the disclosure and thus includes, where necessary, simplifications, generalizations, and omissions of details. Accordingly, those skilled in the art will appreciate that the summary is merely illustrative and is not intended to be limiting in any way. Other aspects, features, and advantages of the processes described herein, as defined by the claims, will become apparent from the detailed description set forth herein and taken in conjunction with the accompanying drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] Detailed description of the technology The following terms are used throughout, as defined below.

[0007] As used herein, singular articles such as "a" and "an" and "the" and similar referents, in the context of describing an element (particularly in the context of the claims below), should be construed to include both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Recitation of ranges of values ​​herein is merely intended to serve as a shorthand method of individually referring to each individual value falling within the range, unless otherwise indicated herein, and each individual value is incorporated herein as if it were individually recited herein. All methods described herein can be performed in any suitable order, unless otherwise indicated herein or clearly contradicted by context. The use of any and all examples or exemplary language (e.g., "etc.") provided herein is intended merely to better illustrate the embodiments and does not limit the scope of the claims, unless otherwise expressly stated. No language in the specification should be construed as indicating any non-claimed element as essential.

[0008] As used herein, "about" will be understood by one of ordinary skill in the art and will vary to some extent depending on the context in which it is used. If there are uses of the term that are not clear to a person of ordinary skill in the art, given the context in which the term is used, "about" will mean up to ±10% of the particular value.

[0009] As used herein, "asphaltene" refers to an oil component that is insoluble in n-pentane or another hydrocarbon as indicated. Asphaltenes may include polyaromatic molecules containing one or more heteroatoms selected from S, N, and O. Asphaltenes may also include other sulfur species, such as thiols, sulfates, thiophenes such as benzothiophene, hydrogen sulfide, and other sulfides.

[0010] In the fibers and methods of the present technology, "asphaltene content" refers to the total amount of asphaltene in the feedstock, as measured as the n-pentane insoluble fraction of the feedstock. However, in some aspects and embodiments of the present process, the asphaltene content is determined by the presence of a sufficient amount of one or more C 3-8 It can be measured as the insoluble fraction of a hydrocarbon feedstock that has been mixed with an alkane and then allowed to settle or otherwise be separated from the feedstock. 3-8 The alkane may be propane, butane, pentane, hexane, heptane, octane, isomers thereof, or a mixture of any two or more thereof. Thus, in some embodiments, the asphaltene content of the fiber or feed may be defined as the components insoluble in heptane. By "sufficient amount" is meant an amount greater than the amount at which no further precipitation / separation of the insoluble fraction is observed from the hydrocarbon feedstock. A detailed discussion of the physical properties and structure of asphaltenes and the process conditions (temperature, pressure, solvent / oil ratio) required to produce a particular asphaltenes is described in JG Spight, "Petroleum Asphaltenes Part 1: Asphaltenes, Resins and the Structure of Petroleum", Oil & Gas Science and Technology-Rev IFP, Vol 59 (2004) pp. 467-477, the entirety of which is incorporated herein by reference and for all purposes. The standard test method for determining heptane (C7) insoluble asphaltene content is described by ASTM standard D6560-17 and can be extended to any alkane, such as pentane.

[0011] As used herein, "hydrocarbon feedstock" refers to any material in which hydrocarbons are the predominant component that can be an input for refining, conversion, or other industrial processes. Hydrocarbon feedstocks may be solid or liquid at room temperature and may contain non-hydrocarbon components such as organic and inorganic materials containing heteroatoms (e.g., S, N, O, P, metals). Crude oil, refinery streams, chemical plant streams (e.g., steam cracked tar), and recycling plant streams (e.g., lubricating oil and pyrolysis oil from tires or municipal solid waste) are non-limiting examples of hydrocarbon feedstocks.

[0012] The present technology provides cost-effective fiber compositions that act as intermediates (e.g., prior to stabilization and / or carbonization) in carbon fiber production and processes for preparing carbon fibers from asphaltenes via such intermediates. Although these fiber compositions are rich in asphaltenes, these fiber compositions contain lower concentrations of deleterious impurities, such as sulfur and metals, than current asphaltene-containing fibers. Thus, in a first aspect, the present technology provides fibers that contain at least 30 wt.% asphaltenes, less than 1 wt.% sulfur, and less than 0.1 wt.% or less than 0.05% total metals, based on the weight of the fiber. For example, the fibers may comprise 30% to 100% asphaltenes by weight, e.g., 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 97%, 99%, or 100% asphaltenes by weight, or amounts between and including any two of the foregoing values. In any embodiment, the fibers may comprise at least 60% asphaltenes by weight, e.g., 60% to 100%, or 60% to 95% by weight.

[0013] The fibers of the present technology may have essentially any length and may have a diameter between 1 μm and 20 μm. Thus, the fibers may have a diameter of, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 μm, or a range between and including any two of the foregoing values, for example, 2 μm to 16 μm, or 5 μm to 15 μm, or 10 μm to 20 μm.

[0014] The fibers of the present technology have lower concentrations of key impurities than fibers typically produced from heavily contaminated asphaltenes. Thus, even when the asphaltenes have concentrations of sulfur greater than 1 wt%, greater than 2 wt%, or more, the present fibers have less than 1 wt% sulfur, such as less than 0.75 wt% sulfur, or less than 0.5 wt% sulfur, based on the weight of the fiber. (The amount of sulfur in the fiber is calculated as the weight percent of elemental sulfur present.) In any embodiment, the fiber may have between 0.01 wt% sulfur and less than 1 wt% sulfur, between 0.01 wt% sulfur and less than 0.75 wt% sulfur, between 0.01 wt% sulfur and less than 0.5 wt% sulfur, or even between 0.01 wt% sulfur and less than 0.3 wt% sulfur. For example, the fibers may have less than 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.075%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.75%, 0.8%, 0.9%, or 1% sulfur by weight, or a range between and including any two of the foregoing values, such as from 0.05% to less than 1% sulfur, or from 0.1% to less than 1%, or from 0.2% to 0.8%.

[0015] Similarly, the fibers have low concentrations of total metals. Even if the asphaltenes used to make the fibers have more than 0.05 wt.% total metals, more than 0.055 wt.% total metals, or more than 0.1 wt.% total metals, the fibers may have less than 0.1 wt.%, less than 0.09 wt.%, less than 0.08 wt.%, less than 0.07 wt.%, less than 0.6 wt.%, less than 0.05 wt.%, or even less than 0.04 wt.%, less than 0.03 wt.%, less than 0.02 wt.%, or less than 0.01 wt.% total metals. In any embodiment, the fibers may have between 0.00001% and less than 0.1% by weight total metals, or between 0.00001% and less than 0.05% by weight total metals, such as 0.00001%, 0.0001%, 0.001%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or less than 0.1% by weight total metals, or ranges between and including any two of the foregoing values. For example, the fibers may include between 0.001% and less than 0.09% by weight total metals, or between 0.001% and 0.025% by weight, or between 0.01% and 0.05% by weight total metals.

[0016] The total metals in the fiber may include at least one metal selected from the group consisting of alkali metals, alkaline earth metals, transition metals, post-transition metals, and metalloids. The metalloids may have an atomic weight of 82 or less. For example, the total metals may include at least one of vanadium, nickel, iron, arsenic, lead, cadmium, copper, zinc, chromium, molybdenum, silicon, calcium, sodium, potassium, aluminum, magnesium, manganese, titanium, or mercury. In any embodiment, the total metals in the fiber include at least vanadium and / or at least nickel.

[0017] In another aspect, the present technology provides a method of making the present fibers. The method includes melt spinning a fiber feedstock into any of the fibers described herein, the fiber feedstock comprising at least 30 wt% asphaltenes, a sulfur content of less than 1 wt%, and a total metals content of less than 0.1 wt% or less than 0.05 wt%. The fiber feedstock may comprise 30 wt% to 100 wt% asphaltenes, for example, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, 95 wt%, 97 wt%, 99 wt%, or 100 wt% asphaltenes, or amounts between and including any two of the foregoing values. In any embodiment, the fiber feedstock may comprise at least 60 wt.% asphaltenes, for example, between 60 wt.% and 100 wt.%, or between 60 wt.% and 95 wt.% asphaltenes.

[0018] The fiber feedstock is passed through a spinneret to undergo melt spinning in molten or liquid form. The present invention contemplates the use of any type of spinneret commonly known and used in the art to form carbon filaments and / or carbon fibers. Generally, the spinneret includes a nozzle head that receives the liquid-phase fiber feedstock and an extrusion plate. The nozzle head may include a reservoir, cavity, multiple holes, or similar holding area(s) for receiving the liquid-phase asphaltene stream from a pump and / or extruder. The extrusion plate is typically located at the end of the spinneret opposite where the fiber feedstock stream is received. The extrusion plate typically includes multiple openings of various sizes and shapes corresponding to the intended size and shape of the carbon-based filaments to be produced. Alternatively, the extrusion plate may have a single opening. From the nozzle head of the spinneret, the fiber feedstock stream passes through multiple openings in the extrusion plate to form the carbon-based filaments. In certain embodiments, the extrusion plate rotates relative to the nozzle head such that the carbon-based filaments protruding from the multiple openings wrap around themselves to create a wrapped carbon-based filament comprising multiple individual carbon-based filaments. In further embodiments of the present technology, the liquid-phase fiber feedstock stream may not be spun, but simply extruded through one or more openings in the nozzle head and extrusion plate. Thus, a non-rotating extrusion plate can produce a carbon-based filament comprising one or more individual filaments.

[0019] Melt spinning can be carried out at elevated temperatures. In any embodiment, the fiber raw material may be spun at a temperature not exceeding 40°C above the softening point of the fiber raw material as determined by the Mettler method (e.g., ISO5409-2:2007). Alternatively, the fiber raw material may be spun at a temperature in the range of at least 40°C, at least 45°C, at least 50°C, or at least 55°C above the Mettler softening point of the fiber raw material so that the degree of orientation of the mesophase region in the resulting carbon fiber is high. The degree of orientation of the mesophase region can further be increased by increasing the fiber diameter of the carbon fiber. The fiber diameter of the carbon fiber is usually 10 to 20 μm or less, but 13 to 18 μm may be preferred when an increased degree of orientation of the mesophase region is desired. Once the temperature for spinning is reached, the carbon is extruded through a nozzle having an opening diameter of, for example, 0.1 mm, and stretched to form carbon fibers. The mesophase is oriented in the direction of the fiber axis by stretching and tends to remain oriented in the direction of the fiber axis until the carbon solidifies. Thus, if the spinning temperature is low or if the fiber diameter is small, the carbon extruded through the nozzle opening will solidify immediately and the time for fiber axial orientation will be short. That is, the spun carbon fibers will have a low degree of orientation in the fiber axis direction. Furthermore, if the fiber diameter is too large, insufficiently drawn carbon fibers will be formed, which will result in a low degree of orientation in the fiber axis direction. In either embodiment, the fiber raw material may be spun at a temperature at least 40°C higher than the Mettler softening point and with a carbon fiber diameter up to 20% larger than normal. Thus, carbon fibers with a high degree of orientation in the fiber axis direction can be obtained.

[0020] The liquid-phase fiber feed stream may be heated to a temperature of about 200° C. to about 550° C., although of course the fiber feed stream may undergo some cooling as it travels through pumps, filters, and spinnerets. Depending on process requirements, if the viscosity of the liquid-phase fiber feed stream is too high to pass through the spinneret, it may be necessary to apply heat to the pumps, filters, and spinnerets to maintain the fiber feed stream in liquid phase for proper processing by the spinneret.

[0021] An embodiment of the method may include exposing the fiber filaments to a cross-flow of an inert gas once the fiber filaments are formed from the spinneret. The inert gas used in the cross-flow may include nitrogen, argon, etc., and is applied to the carbon-based filaments at a temperature of about 200° C. to about 400° C. The cross-flow of the inert gas assists in evaporating and cooling the carbon-based filaments as they exit the spinneret, thereby solidifying the filaments to obtain asphaltene-containing fibers. The carbon-based fibers are then collected and / or wound in a drawdown device. The drawdown device may include any type of filament and / or fiber collection equipment commonly known in the art, but in certain embodiments, the drawdown device may be a winding spool, which is generally a cylindrically shaped body that rotates to collect and wind up the carbon-based fibers. In addition to collecting the carbon-based fibers, the drawdown device may apply tension to the carbon-based fibers as they are collected and wound. The tension can be varied by changing the speed at which the drawdown device collects or winds the carbon-based filament. The tension can promote alignment of the carbon atoms in the fiber, resulting in increased tensile strength of the carbon fiber.

[0022] An embodiment of the invention includes stabilizing the carbon-based fibers in an air atmosphere at about 200°C to about 400°C for several hours once the carbon-based fibers are wound. The stabilization process oxidizes compounds within the carbon-based fibers to prevent relaxation and chain scission within the single fibers during carbonization. An embodiment of the invention includes carbonizing the stabilized asphaltene-based fibers by heating the stabilized carbon-based fibers to a temperature of about 1000°C to about 1500°C in an inert atmosphere such as nitrogen, argon, etc. Alternatively, the carbonization step may include heating the oxidized fibers to about 1000°C to about 2000°C in an inert, oxygen-free atmosphere. In any embodiment, the method may further include graphitizing the carbon fibers by heating the carbon fibers to above 2000°C up to about 3000°C in an oxygen-free atmosphere. Carbonization includes gradually heating (typically in a furnace) the asphaltene-based fibers to about the desired temperature. In one or more embodiments, the carbonization can be completed in less than about 24 hours. However, because the liquid-phase fiber feed stream used in the present process embodiment has a high carbon content, carbonization can be completed in less than about 12 hours, more preferably less than 3 hours. Although carbonization is typically the most time-consuming and rate-limiting step in traditional carbon fiber production, the present process of the present invention can be performed much more quickly due to the shorter carbonization residence time. During carbonization, non-carbon elements such as hydrogen, oxygen, nitrogen, and sulfur ("impurities") are released from the fiber feedstock in the form of H2, O2, N2, gaseous HCN, HN, HS compounds, etc., to produce essentially carbon fibers. However, the fiber feedstock of the present technology contains much lower concentrations of these impurities, especially sulfur and metals, resulting in higher quality carbon fibers than carbon fibers from previous asphaltene feedstocks. Carbon-carbon bonds form between the fiber feedstock structure and the carbon fibers to form a homogeneous, high-strength monolithic structure. Additionally, the fiber feed stream preferably has a low H / C ratio, thereby reducing exhaust emissions and increasing the yield (by weight) of carbon fibers from the liquid phase fiber feed stream.

[0023] These methods may further include preparing a fiber feedstock from a hydrocarbon having a high asphaltene content and a high concentration of sulfur and / or total metals. Thus, the methods may further include contacting the hydrocarbon feedstock with an effective amount of metallic sodium and an effective amount of an extrinsic capping agent at a temperature of 250-500° C. to produce a mixture of sodium salt and a converted feedstock (which may be used as a fiber feedstock in preferred cases), the hydrocarbon feedstock comprising at least 10 wt.% asphaltenes (or at least 20 wt.% asphaltenes or at least 30 wt.% asphaltenes), a sulfur content of at least 1 wt.%, and a total metal content of at least 0.1 wt.% or at least 0.05 wt.%, and the converted feedstock comprising at least 30 wt.% asphaltenes, a sulfur content of less than 1 wt.%, and a total metal content of less than 0.1 wt.% or less than 0.05 wt.%.

[0024] The hydrocarbon feedstock used in the present process contains asphaltenes (e.g., 1-100 wt%), and is typically high in asphaltenes and high in sulfur content and total metals. For example, the hydrocarbon feedstock may contain 10-100 wt% asphaltenes, e.g., 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, 95 wt%, 97 wt%, 99 wt%, or 100 wt% asphaltenes, or amounts between and including any two of the foregoing values. Thus, in any embodiment, the hydrocarbon feedstock may contain at least 30 wt% asphaltenes, e.g., 30 wt% to 99 wt%, or 100 wt% asphaltenes. In any embodiment, the hydrocarbon feed may comprise at least 60 wt% asphaltenes, e.g., 60 wt% to 100 wt%, or 60 wt% to 95 wt%, or 99 wt% asphaltenes. The sulfur content of the hydrocarbon feed may range from 0.5 wt% to 10 wt%, or 0.75 wt% to 10 wt%, or 1 wt% to 10 wt%, e.g., 0.5 wt%, 0.75 wt%, 1 wt%, 1.5 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, or ranges between and including any two of the foregoing values. For example, the sulfur content of the hydrocarbon feed may be from 1 wt% to 10 wt%, or 4 wt% to 9 wt%. In any of these process embodiments, the total metals content of the hydrocarbon feedstock may be between 0.015% and 1% by weight, or between 0.02% and 1% by weight, or between 0.05% and 1% by weight. For example, the total metals may be 0.015%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or ranges between and including any two of the foregoing values.In any embodiment, the total metals content of the hydrocarbon feed may be between 0.015% and 0.5% by weight, or between 0.02% and 0.5% by weight, or between 0.02% and 0.6% by weight, or between 0.05% and 0.4% by weight, or between 0.04% and 0.3% by weight.

[0025] The hydrocarbon feedstocks for the process have the asphaltenes and impurities characteristics described herein. These feedstocks are or may be derived from raw crude oils (e.g., petroleum, heavy oil, bitumen, shale oil, and oil shale). The hydrocarbon feedstock may also be the non-distillation residue remaining after distillation of raw crude oils (also known as "vacuum residue" or "vac.resid."), or asphaltene-containing fractions obtained from solvent-deasphalting processes.

[0026] The hydrocarbon feedstock is 800-1200 kg / m at 15.6°C or 60°F. 3 For example, the density may be 800, 825, 850, 875, 900, 925, 975, 1000, 1050, 1100, 1150, or 1200 kg / m 3 , or a range between and including any two of the preceding values. Thus, in any embodiment, the density may be, for example, 850 to 1200 kg / m 3 , 900~1200kg / m 3 , 950~1200kg / m 3 , or 925~1100kg / m 3 may be also possible.

[0027] In the method of the present technology, the hydrocarbon feedstock is contacted with an effective amount of metallic sodium and an effective amount of an exogenous capping agent. Any suitable source of metallic sodium may be used, including, for example, but not limited to, electrochemically produced metallic sodium as described in US8,088,270, the entirety of which is incorporated herein by reference. The effective amount of sodium in the metallic state and used in the contacting step varies depending on the heteroatom, metal, and asphaltenes concentrations, impurities in the hydrocarbon feedstock and residual feedstock, the degree of impurity conversion or removal desired, the temperature used, and other conditions. In any embodiment, a stoichiometric or superstoichiometric amount of metallic sodium, for example, 1 to 3 molar equivalents of metallic sodium relative to the sulfur content, may be used to remove all or nearly all of the sulfur content. In either embodiment, the hydrocarbon or residual feed is contacted with greater than 1 molar equivalent of metallic sodium relative to the sulfur content in the feed, for example, 1.1, 1.15, 1.2, 1.25, 1.3, 1.4, 1.5, 2, 2.5, or 3 molar equivalents of metallic sodium.

[0028] The exogenous capping agent used in the present process is typically used to cap radicals formed when sulfur and other heteroatoms are stripped by metallic sodium during the contacting step. Some feedstocks may inherently contain small amounts of naturally occurring capping agents ("endogenous capping agents"), but such amounts are insufficient to substantially cap all free radicals generated by the present process. An effective amount of exogenous (i.e., added) capping agent is used in the present process, for example, 1 to 1.5 moles of capping agent (e.g., hydrogen) per mole of sulfur, nitrogen, or oxygen present may be used. It is within the skill of the art to determine the effective amount of exogenous capping agent required to carry out the present process for a particular hydrocarbon feedstock used in accordance with the disclosure herein. Exogenous capping agents may include hydrogen, hydrogen sulfide, natural gas, methane, ethane, propane, butane, pentane, ethene, propene, butene, pentene, dienes, isomers of the foregoing, or mixtures of any two or more thereof. In any embodiment, the exogenous capping agent is hydrogen and / or C 1-6 Acyclic alkanes and / or C 2-6 It may also be an acyclic alkene or a mixture of any two or more thereof.

[0029] The contacting step is carried out at a temperature of about 250° C. to about 500° C., so that the metallic sodium is in a molten (i.e., liquid) state. For example, the contacting step may be carried out at about 250° C., about 275° C., about 300° C., about 325° C., about 350° C., about 375° C., about 400° C., about 425° C., about 450° C., about 500° C., or a range between and including any two of the aforementioned temperatures. Thus, in any embodiment, the contacting may be carried out at about 275° C. to about 425° C., or about 300° C. to about 400° C. (e.g., about 350° C.).

[0030] In any embodiment, the contacting step may be performed at a pressure of about 400 to about 3000 psi, e.g., about 400 psi, about 500 psi, about 600 psi, about 750 psi, about 1000 psi, about 1250 psi, about 1500 psi, about 2000 psi, about 2500 psi, about 3000 psi, or a range between and including any two of the foregoing values, e.g., about 500 psi to about 3000 psi.

[0031] The reaction of sodium metal with heteroatom contaminants in the hydrocarbon / resid feedstock is relatively fast and complete within minutes. Combination mixing of the feedstock with sodium metal further accelerates the reaction and is commonly used in industrial scale for this reaction. However, in certain embodiments, longer residence times may be required to improve the degree of conversion or operating conditions may be adjusted to target the removal of certain heteroatom impurities. Thus, in any embodiment, the contacting step is carried out for about 1 minute to about 120 minutes, e.g., about 1 minute, about 5 minutes, about 7 minutes, about 9 minutes, about 10 minutes, about 15 minutes, about 30 minutes, about 45 minutes, about 60 minutes, about 75 minutes, about 90 minutes, about 105 minutes, or about 120 minutes, or any range between and including any two of the foregoing values. Thus, in any embodiment, the time may be in the range of about 1 minute to about 60 minutes, about 5 minutes to about 60 minutes, about 1 minute to about 15 minutes, about 60 minutes to 120 minutes, etc.

[0032] In any embodiment of the process, it may be necessary to dilute the hydrocarbon feed with a diluent if the increased asphaltene content in the hydrocarbon feed results in a viscosity that is too high for the sodium treatment process. Since asphaltenes are aromatic, the diluent typically contains an aromatic. The diluent may be a single compound, such as benzene, toluene, xylene, trimethylbenzene (e.g., 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, etc.), ethylbenzene, cumene, naphthalene, methylnaphthalene (e.g., 1-methylnaphthalene, or other isomers thereof), a mixture of any two or more thereof, or a refinery intermediate that is aromatic (e.g., light cycle oil, heavy cycle oil, reformate). The amount of diluent required will vary depending on the asphaltene content of the feed and the viscosity required for processing. A higher asphaltene content in the feed may require more diluent than a feed with a lower asphaltene content. It is within the skill of the art to select the appropriate amount of diluent to allow processing of the asphaltene in the process.

[0033] The efficiency of removal of sulfur content from the hydrocarbon feed relative to the conversion feed (also known as conversion efficiency) may be at least 40% by weight, at least 50% by weight, at least 60% by weight, at least 70% by weight, at least 80% by weight, at least 90% by weight, at least 95% by weight, at least 96% by weight, at least 97% by weight, at least 98% by weight, at least 99% by weight, or 100% by weight, or a range between and including any two of the foregoing values, such as 40% to 99%, or 40% to 95%. When the effective amount of sodium metal is greater than the stoichiometric amount, the efficiency of conversion of the sulfur content can be very high, such as at least 90%.

[0034] The fiber raw material of the present technology typically contains less than 1 wt% sulfur, such as less than 0.75 wt% sulfur, or even less than 0.5 wt% sulfur. In any embodiment, the fiber raw material may have between 0.01 wt% sulfur and less than 1 wt% sulfur, or less than 0.75 wt% sulfur, less than 0.5 wt% sulfur, or even less than 0.3 wt% sulfur. For example, the fiber may have 0.01 wt%, 0.02 wt%, 0.03 wt%, 0.04 wt%, 0.05 wt%, 0.075 wt%, 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.75 wt%, or less than 1 wt% sulfur, or ranges between and including any two of the foregoing values.

[0035] The fiber feedstock of the present technology has a low metal concentration compared to the hydrocarbon feedstock. The metal content of the fiber feedstock may be at least 20% lower, for example 20% to 100% lower, compared to the hydrocarbon feedstock. Examples of the percentage reduction (total or individual) of metals in the converted feedstock compared to the hydrocarbon feedstock include 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 97%, 98%, 99%, 100%, or ranges between and including any two or more of the foregoing values. Thus, in any embodiment, the percentage reduction may be 20% to 99%, 20% to 95%, 70% to 99%, or 70% to 100%. The metal may be any of the metals disclosed herein. In some embodiments, the metal is selected from iron, vanadium, nickel, or a combination of any two or more thereof. For example, the vanadium content of the converted feedstock is reduced by at least 20% compared to the hydrocarbon feedstock or the residual feedstock. Similarly, in either embodiment, the nickel content of the converted feed is reduced by at least 20% compared to the hydrocarbon feed or the residual feed.

[0036] The method may also include pretreating the impurity-containing hydrocarbon feedstock before contacting with metallic sodium. In some cases, the hydrocarbon feedstock may be pretreated to concentrate impurities in the residual feedstock, which is then used to prepare the fiber of the present technology. For example, raw crude oil may be distilled to produce one or more light distillate fractions (e.g., refined feedstocks that may be used for other purposes) and atmospheric residual fractions (residual feedstocks) that have a higher sulfur content and a higher asphaltene content than both the refined feedstock and the raw crude (i.e., the hydrocarbon feedstock). Alternatively, the hydrocarbon feedstock may be pretreated to remove a portion of the undesirable impurities to provide a refined hydrocarbon feedstock with a lower concentration of impurities, but which meets at least one of the asphaltene specifications and sulfur and metal specifications for the hydrocarbon feedstock herein that will be treated with sodium or a sodium alloy according to the present process. The pretreatment process may include a separation process, or a treatment process, or a combination of any two or more thereof.

[0037] In any embodiment, the pretreatment process may include a separation process that includes one or more of physical separations using energy (heat), phase addition (solvent or absorbent), pressure change, or application of an external field or gradient to concentrate impurities in the residual feed. The separation process may include gravity separation, flash vaporization, distillation, condensation, drying, liquid-liquid extraction, back extraction, absorption, centrifugation, electrostatic separation, and variations thereof. The separation process may further include a solvent extraction process, including a solvent deasphalting process such as Residual Oil Supercritical Extraction (ROSE®). For example, the hydrocarbon feed may be desalted to remove salts and water, an API separator may be used to separate water and solids from the oil, or a distillation column may be used to separate high sulfur high boiling products from low sulfur low boiling products in the crude oil. Separation processes such as adsorption, filtration, permeation, or variations thereof may also require solid agents or partitions. Each of the disclosed separation processes results in a refined feed having a lower concentration of impurities than the hydrocarbon feed, and a residual feed having a higher concentration of impurities than the refined feed. In either embodiment, the residual feed contains a higher concentration of impurities than the hydrocarbon feed. In either embodiment, the pretreatment process further provides a gas phase impurity stream (e.g., H2S, water, NH3, and light hydrocarbon gases such as methane, ethane, and propane). Such gas phase impurities can be removed using absorption processes, sulfur recovery processes, or other processes known in the art.

[0038] The process of the present technology produces a mixture comprising a conversion feedstock (or fiber feedstock) and sodium salts. The process may further comprise separating the sodium salts from the conversion / fiber feedstock. The sodium salts are composed of particles that are very fine (e.g., <10 μm) and cannot be completely removed by standard separation techniques (such as filtration or centrifugation). In either embodiment, the separation may comprise heating a mixture of sodium salts and the conversion / fiber feedstock having elemental sulfur to a temperature of about 150° C. to 500° C. to provide a sulfur-treated mixture comprising agglomerated sodium salts, and separating the agglomerated sodium salts from the sulfur-treated mixture to provide a desulfurized conversion / fiber feedstock and separated sodium salts. The separation may be performed by any suitable method (e.g., centrifugation, filtration) as described in U.S. Pat. No. 10,435,631, the entire contents of which are incorporated herein by reference for all purposes.

[0039] Depending on the nature of the desulfurized conversion / fiber feedstock, a significant amount of alkali metal content may remain, e.g., up to more than 1% by weight in some cases. In some embodiments, such residual alkali metals are present at concentrations of about 400 ppm to about 10,000 ppm, e.g., about 400, about 600, about 800, about 1,000, about 1,200, about 1,400, about 1,600, about 2,000, about 2,500, about 3,000, about 4,000, about 5,000, about 7,500, or even about 10,000 ppm, or ranges between and including any two of the foregoing values. Some of the alkali metal content may be ionically associated with naphthenate salts, or may be finely dispersed in the metallic state, or may be ionically associated with sulfur, oxygen, or nitrogen that remain bound to the organic molecules of the oil.

[0040] Since the alkali metal content needs to be low to ultimately provide high quality carbon fiber, removal of the residual alkali metal from the conversion / fiber feedstock is necessary. Also, if a significant amount of the alkali metal is desorbed from the system, a large amount of make-up feedstock is required to maintain the process. Thus, if the conversion feedstock contains unreacted metallic sodium, the method may further include substantially removing the unreacted metallic sodium from the conversion feedstock. By "substantially remove" it is meant that a majority of the sodium is removed, e.g., at least 90%, at least 95%, at least 98%, or at least 99% by weight of the sodium.

[0041] Thus, in another aspect, the present technology provides a demetallization process that includes adding a salt former to the desulfurized conversion / fiber feedstock to form a second mixture, the salt former converting the residual alkali metal to an alkali metal salt. Any suitable salt former may be used as long as the resulting salt is easily removed from the conversion / fiber feedstock. In some embodiments, the salt former may be selected from the group consisting of elemental sulfur, hydrogen sulfide, formic acid, acetic acid, propanoic acid, and water. In some embodiments, acetic acid is used to form a sodium acetate salt that is relatively easily removed in solid form. Typically, the amount of salt former added is equal to about 1 to about 4 times the molar amount of the residual alkali metal, for example, 1, 1.25, 1.5, 2, 2.5, 3, 3.5 molar equivalents, or a range between and including any two of the foregoing values. For example, in some embodiments, the amount is equal to about 1 to about 2 molar equivalents.

[0042] In some embodiments, the addition of the salt former may be carried out at a temperature of at least 150° C., e.g., about 150° C., about 200° C., about 250° C., about 300° C., about 350° C., about 400° C., about 450° C., or within a range between and including any two of the foregoing values. In some embodiments, the addition of the salt former may be carried out at a temperature of about 150° C. to about 450° C.

[0043] In certain embodiments, the addition of the salt former is carried out at a pressure of at least about 15 psi. In some embodiments, the addition of the salt former is carried out at a pressure of about 15 psi, about 25 psi, about 50 psi, about 100 psi, about 150 psi, about 200 psi, about 250 psi, about 300 psi, about 400 psi, about 500 psi, about 1,000 psi, about 1,500 psi, about 2,000 psi, about 2,500 psi, or within a range between and including any two of the foregoing values. For example, in some embodiments, the addition is carried out at about 50 psi to about 2,500 psi.

[0044] The demetallization process may include separating the alkali metal salts from the second mixture to provide a desulfurized and demetallized conversion / fiber feedstock. For example, separating the alkali metal salts from the second mixture may include filtering, settling, or centrifuging the second mixture to remove the alkali metal salts and provide a desulfurized conversion / fiber feedstock.

[0045] The conversion feedstock may also include light hydrocarbons, i.e., any low molecular weight hydrocarbons that cause the softening point of the conversion feedstock to be less than 200° C. For example, the light hydrocarbons may include light gas oils and light hydrocarbons. In some embodiments, the light hydrocarbons may further include some heavy gas oils, as well as light gas oils and lighter hydrocarbons. When the conversion feedstock includes light hydrocarbons, the method may further include isolating a fiber feedstock from the conversion feedstock. In some embodiments, the method includes removing at least a portion of the light hydrocarbons to increase the softening point of the conversion feedstock to at least 200° C., at least 225° C., at least 250° C., or at least 275° C. to provide the fiber feedstock. In any embodiment of the method, removing the light hydrocarbons to provide the fiber feedstock may include distilling a light fraction from the conversion feedstock. The distillation of the light hydrocarbons may be performed, for example, by atmospheric distillation, vacuum distillation, or a combination thereof. In either embodiment, light hydrocarbons corresponding to and including light gas oils are removed, for example hydrocarbons having a boiling point of up to 343°C.

[0046] Similarly, when the converted feedstock includes an aromatic solvent used to dilute the asphaltenes described herein, the fiber feedstock may be isolated by distilling the aromatic solvent from the converted feedstock to provide the fiber feedstock. Alternatively, at least a portion of the aromatic solvent and light hydrocarbons may be distilled from the converted feedstock to provide the fiber feedstock.

[0047] Fiber raw materials are also converted into C 3-8 The asphaltenes may be isolated from the converted feed by diluting with a hydrocarbon or a mixture of any two or more of said hydrocarbons to cause the asphaltenes to precipitate, and recovering the precipitated asphaltenes to provide a fiber feed.

[0048] The process may further include recovering metallic sodium from the separated sodium salt. In any embodiment, the process may further include electrolyzing the separated sodium salt to provide metallic sodium. The separated sodium salt may include one or more of sodium sulfide, sodium hydrogen sulfide, or sodium polysulfide. The electrolysis may be carried out in an electrochemical cell, for example, according to U.S. Pat. No. 8,088,270 or U.S. Provisional Patent Application No. 62 / 985,287, the entire contents of each of which are incorporated herein by reference for all purposes. The electrochemical cell may include an anolyte compartment, a catholyte compartment, and a NaSICON membrane separating the anolyte compartment from the catholyte compartment. A cathode containing metallic sodium is disposed in the catholyte in the catholyte compartment. An anode containing sodium salt is disposed in the anolyte in the anolyte compartment. A power source is electrically connected to the anode and the cathode. In any embodiment, the separated sodium salt is dissolved in an organic solvent prior to electrolyzing the salt to provide metallic sodium.

[0049] An exemplary embodiment of the process of the present technology will now be described. In one exemplary embodiment of the present technology, a hydrocarbon feedstock, typically having an asphaltene content of at least 30 wt%, and containing sulfur and total metal impurities as described herein (e.g., a sulfur content of at least 1 or at least 0.75 wt%, and total metals of at least 0.02 wt%, at least 0.05 wt%), is charged into a reactor (continuous or batch) with an effective amount of metallic sodium and an exogenous capping agent as described herein. Optionally, a solvent, such as an aromatic solvent, may be mixed with the hydrocarbon feedstock if it is too viscous to flow conveniently at the temperature at which it is used. In some embodiments of the present process, the hydrocarbon feedstock is a residual feedstock. That is, the first hydrocarbon feedstock is processed to remove lighter hydrocarbons, resulting in a residual feedstock enriched in asphaltene content to at least 30 wt%. The lighter hydrocarbons refined against the first hydrocarbon feedstock may be processed into other products, such as fuels.

[0050] The reaction of sodium may be carried out at high temperatures and pressures as described herein and is typically completed within minutes to obtain a mixture of sodium salt and converted feedstock ("first mixture"). The converted feedstock comprises a hydrocarbon oil having a sulfur content less than the sulfur content in the hydrocarbon feedstock. To the extent that the converted feedstock has an asphaltene content of less than 30 wt%, for example because the feedstock started out as such or was mixed with a solvent, the converted feedstock requires further processing to ensure that the fiber feedstock contains a minimum amount of at least 30% asphaltenes.

[0051] Optionally, the first mixture (of sodium salts and the converted feedstock) is transported from the reactor to a second vessel where the sodium salts are agglomerated into particles large enough to be easily separated from the converted feedstock. Any suitable agglomeration method may be used, but agglomeration with elemental sulfur at high temperatures as described herein may be used. The resulting mixture of agglomerated sodium salts, metals, and the converted feedstock ("second mixture") may then be separated by any suitable process and device, such as a centrifuge, to obtain a converted feedstock free of precipitated metals and sodium salts. If the converted feedstock contains less than 30 wt.% asphaltenes or has a softening point below 200°C, the process includes separating light hydrocarbons from the converted feedstock to raise the softening point above 200°C (or even higher) to provide a fiber feedstock. Optionally, the sodium salts may be electrolyzed in an electrolytic cell using a sodium ion selective ceramic membrane, such as a NaSiCON membrane, to provide metallic sodium and elemental sulfur, as described herein. The sodium metal and elemental sulfur may be recycled in the process. EXAMPLES

[0052] Example 1 - Preparation of fibers from high asphaltene feedstock (vacuum residue) A series of six desulfurization runs were carried out, each of which involved reacting 500 g of vacuum residue with 52.7 g of elemental sodium under hydrogen at 370° C. and 750 psig for 60 minutes. To remove excess sodium, 8.4 g of sulfur was added and the mixture was held with stirring at 350° C. and 300 psig for 120 minutes. The reactor contents were centrifuged to recover the supernatant layer. Pairs of these layers were collected and analyzed for residual sodium content, which were 3640 ppm, 4267 ppm, and 4000 ppm, respectively. The samples were then reacted with 15% excess acetic acid at 300° C. and 300 psig to remove sodium. The samples were centrifuged to remove sodium acetate formed during the reaction.

[0053] A sample of the desulfurized vacuum bottom was then treated with 10:1 w / w ratio of n-pentane, resulting in a significant proportion of asphaltenes in the mixture that precipitated from solution. The mixture was centrifuged and the recovered asphaltenes were washed with approximately 1:1 w / w ratio of n-pentane and recentrifuged to recover the asphaltenes. A total of 133 g of asphaltenes were recovered. The amounts of sulfur and metals in the asphaltenes compared to the vacuum residue feed are shown in Table 1.

[0054] (Table 1) TIFF2024533579000001.tif26128

[0055] These asphaltenes were then successfully melt spun to form fibers with diameters of 10 microns. The fibers were stabilized (in the presence of oxygen) and carbonized (in the absence of oxygen) at temperatures up to 1000°C. The tensile strength of the fibers was measured to be 0.8 GPa, and the elastic modulus was measured to be 33 GPa.

[0056] Example 2A - Preparation of Fibers from High Asphaltene Feed A series of six desulfurization runs was carried out, each consisting of a 300 g sample with 89.7% asphaltene mixed with 200 g of 1-methylnaphthalene to dissolve the asphaltene. 35.5 g of sodium was added to the mixture and heated to 350° C. under hydrogen at 750 psig pressure with stirring. The mixture was allowed to react for 60 minutes. To remove excess sodium, 8.9 g of sulfur was added and the mixture was held at 350° C. and 300 psig with stirring for 120 minutes. The main results of the product after centrifugation to remove sodium sulfide crystals are shown in Table 1.

[0057] (Table 2) TIFF2024533579000002.tif21128

[0058] The resulting converted feedstock was vacuum distilled to an atmospheric equivalent temperature of 250° C. to remove the 1-methylnaphthalene fraction.

[0059] The distilled converted feedstock was then melt spun successfully to form 12 micron diameter fibers with 78.6% asphaltene. Stabilization and carbonization (i.e. graphitization) of the fibers was performed up to 1000°C. The tensile strength of the fibers was measured to be 1.0 GPa and the elastic modulus was measured to be 32 GPa.

[0060] Example 2B - Preparation of Fibers from High Asphaltene Feed A 375 g sample of asphaltene (66.42% C7A, 82.66% C5A) was mixed with 125 g of 1,2,4-trimethylbenzene to dissolve the asphaltene. Sodium (51.1 g) was added to the mixture and heated to 370° C. under 750 psig hydrogen pressure with stirring. The mixture was allowed to react for 30 minutes. To remove excess sodium, 8.5 g of sulfur was added and the mixture was held at 350° C. and 300 psig with stirring for 120 minutes. The key results of the converted feed product after centrifugation to remove sodium sulfide crystals are shown in Table 1.

[0061] (Table 2) TIFF2024533579000003.tif21128

[0062] The resulting converted feedstock is distilled to remove the 524° C.- fraction. The remaining 524° C.+ fraction (fiber feedstock) has a softening point above 200° C. Melt spinning (to provide asphaltene-containing fiber), stabilization, and graphitization are carried out as in Example 1 to provide carbon fiber.

[0063] Example 3 - Preparation of fibers from high asphaltene feedstock (derived from bitumen) Solid asphaltene feedstock was produced by treating bitumen with sufficient amount of n-pentane. 350g of asphaltene was then mixed with 350g of mineral oil and treated with sodium at 350°C and 1500 psig. The main results are summarized in Table 3. The results in Table 4 clearly show that molten metallic sodium efficiently removes impurities and improves the physical properties of asphaltene. The sulfur content was reduced by 97.4%, the 524°C bottoms content was reduced by more than 48%, and metals were reduced by >97%.

[0064] Table 3. Main results of desulfurization of asphaltene with sodium TIFF2024533579000004.tif95128

[0065] The resulting converted feedstock is distilled to remove the 524° C.− fraction. The remaining 524° C.+ fraction (fiber feedstock) has a softening point above 200° C. Melt spinning (to provide asphaltene-containing fiber), stabilization, and graphitization are carried out as in Example 1 to provide carbon fiber.

[0066] Equivalent Although specific embodiments have been illustrated and described, those skilled in the art, after reading the foregoing specification, may preferentially employ modifications, equivalent substitutions, and other types of alterations to the processes and products of the technology described herein. Each aspect and embodiment described above may also include or incorporate variations or features as disclosed for any or all of the other aspects and embodiments.

[0067] The technology is also not limited to specific embodiments that are intended as single illustrations of individual aspects of the technology described herein. As will be apparent to those skilled in the art, many modifications and variations of the technology can be made without departing from its spirit and scope. In addition to the methods listed herein, functionally equivalent methods within the scope of the technology will be apparent to those skilled in the art from the foregoing description. Such modifications and variations are intended to fall within the scope of the appended claims. It is to be understood that the technology of the present invention is not limited to specific methods, materials, compositions, or conditions, which of course can vary. It is further to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting. Thus, it is intended that the specification be considered as exemplary only with respect to the breadth, scope, and spirit of the technology, as indicated solely by the appended claims, the definitions therein, and any equivalents thereof.

[0068] The embodiments illustratively described herein may suitably be practiced in the absence of any element or elements, or any limitation or limitations not expressly disclosed herein. Thus, for example, the terms "comprising," "including," "containing," and the like, should be interpreted expansively and without limitation. Furthermore, the terms and expressions used herein are used as terms of description and not of limitation, and the use of such terms and expressions is not intended to exclude any equivalents of the features or portions thereof shown and described, although it is understood that various modifications are possible within the scope of the claimed technology. Similarly, the use of terms such as "comprising," "including," "containing," and the like, should be understood to disclose embodiments using the terms "consisting essentially of" and "consisting of." The phrase "consisting essentially of" is understood to include the elements expressly described and those additional elements that do not materially affect the basic and novel characteristics of the claimed technology. The phrase "consisting of" excludes any elements not specified.

[0069] Moreover, when features or aspects of the disclosure are described in terms of a Markush group, one of ordinary skill in the art will recognize that the disclosure is also described with respect to any individual member or subgroup of members of the Markush group. Each of the narrower genera and subgeneric groupings falling within the generic disclosure also form part of the invention. This includes the generic description of the invention with a proviso or negative limitation that removes any subject matter from the genus, regardless of whether the cut material is expressly described herein.

[0070] As will be understood by those skilled in the art, for any and all purposes, particularly in terms of providing a written description, all ranges disclosed herein also include any and all possible subranges and combinations of those subranges. For any recited range, it is easily recognized that the range is fully described and can be broken down into at least equal halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, each range discussed herein can be easily broken down into a lower third, a middle third, an upper third, etc. As will also be understood by those skilled in the art, all terms such as "up to," "at least," "greater than," "less than," etc., refer to ranges that are inclusive of the recited numbers and can be subsequently broken down into subranges as discussed above. Finally, as will be understood by those skilled in the art, a range includes each individual component.

[0071] All publications, patent applications, issued patents, and other documents (e.g., journals, articles, and / or textbooks) referenced herein are incorporated by reference herein as if each individual publication, patent application, issued patent, or other document was specifically and individually indicated to be incorporated by reference in its entirety. Definitions contained in the documents incorporated by reference are excluded if they conflict with definitions in this disclosure.

[0072] Other embodiments, along with the full scope of equivalents to which the claims are entitled, are defined as being within the scope of the following claims.

Claims

1. A fiber comprising, based on the weight of said fiber, at least 30 wt. % asphaltenes, less than 1 wt. % sulfur, and less than 0.1 wt. % total metals.

2. The fiber of claim 1, comprising (i) 30 to 100 wt. % asphaltenes, or (ii) at least 60% asphaltenes.

3. The fiber of claim 1, comprising (i) from 0.01% by weight sulfur to less than 1% by weight sulfur, or (ii) less than 0.75% by weight sulfur.

4. The fiber of claim 1, comprising (i) from 0.00001% to less than 0.1% by weight of total metals, or (ii) from 0.001% to less than 0.05% by weight of total metals.

5. 10. The fiber of claim 1, wherein the total metals comprise at least one metal selected from the group consisting of alkali metals, alkaline earth metals, transition metals, post-transition metals, and metalloids having an atomic weight of 82 or less; and optionally, the total metals comprise at least one of vanadium, nickel, iron, arsenic, lead, cadmium, copper, zinc, chromium, molybdenum, silicon, calcium, sodium, potassium, aluminum, magnesium, manganese, titanium, or mercury.

6. The fiber of claim 1, having a diameter of (i) 1 um to 20 um, or (ii) 2 um to 16 um, or (iii) 5 um to 15 um.

7. 10. A method for producing a fiber, comprising melt spinning a fiber feedstock into the fiber of any one of claims 1 to 6, wherein the fiber feedstock comprises at least 30 wt% asphaltenes, a sulfur content of less than 1 wt%, and a total metals content of less than 0.1 wt%.

8. contacting the hydrocarbon feedstock with an effective amount of metallic sodium and an effective amount of an extrinsic capping agent at a temperature of 250-500°C to produce a mixture of sodium salts and the converted feedstock; Further comprising: the hydrocarbon feedstock comprises at least 1 wt. % asphaltenes, a sulfur content of at least 1 wt. %, and a total metals content of at least 0.1 wt. %; The conversion feedstock comprises at least 30 wt.% asphaltenes, optionally light hydrocarbons, a sulfur content of less than 1 wt.%, and a total metals content of less than 0.1 wt.%. The method of claim 7.

9. 9. The method of claim 8 further comprising separating the sodium salt from the conversion feed.

10. 10. The method of claim 9, wherein the conversion feed comprises unreacted sodium metal, the method further comprising substantially removing the unreacted sodium metal from the conversion feed.

11. 10. The method of claim 8, further comprising isolating said fiber feedstock from said converted feedstock.

12. The method of any one of claims 9, further comprising: (i) removing at least a portion of the light hydrocarbons to increase the softening point of the converted feedstock to at least 200°C to provide the fiber feedstock; or (ii) removing at least a portion of the light hydrocarbons to increase the softening point of the converted feedstock to at least 250°C to provide the fiber feedstock.

13. 9. The method of claim 8, wherein the hydrocarbon feedstock is diluted with an aromatic solvent; and optionally, the aromatic solvent is selected from the group consisting of 1-methylnaphthalene, trimethylbenzene, benzene, toluene, xylene, ethylbenzene, cumene, naphthalene, aromatic refinery intermediates, and mixtures of any two or more thereof. The method according to claim 8 .

14. 14. The method of claim 13, wherein isolating the fiber feedstock comprises distilling the aromatic solvent from the converted feedstock to provide the fiber feedstock.

15. The isolating step comprises isolating the converted raw material to C ３－８ 12. The method of claim 11, comprising diluting with a hydrocarbon or a mixture of any two or more thereof to precipitate asphaltenes, and recovering the precipitated asphaltenes to provide the fiber feedstock.

16. (i) the sulfur content of the hydrocarbon feedstock is in the range of 1 wt. % to 15 wt. %; and / or (ii) the hydrocarbon feedstock comprises 30 to 100 wt. % asphaltenes; and / or (iii) the total metals content of the hydrocarbon feed is from 0.05 wt.% to 1 wt.%; The method of claim 7.

17. 9. The method of claim 8, wherein the extrinsic capping agent is hydrogen, hydrogen sulfide, natural gas, methane, ethane, propane, butane, pentane, ethene, propene, butene, pentene, diene, an isomer of the foregoing, or a mixture of any two or more thereof.

18. 9. The method of claim 8, wherein the hydrocarbon feedstock is combined with metallic sodium at a pressure of from about 500 psig to about 3000 psig; and optionally, the reaction of the hydrocarbon feedstock with metallic sodium occurs for a time period of from 1 minute to 120 minutes.

19. 10. The method of claim 9, wherein removing the light hydrocarbons comprises distilling a light fraction from the converted feedstock; optionally, distilling the light hydrocarbons is performed by atmospheric distillation, vacuum distillation, or a combination thereof.

20. The method of claim 7 , wherein the melt spinning is single-hole melt spinning.

21. 8. The method of claim 7, further comprising oxidizing the fibers to produce oxidized fibers; optionally, the fibers are oxidized by heating the fibers to 200-400°C in air.

22. 22. The method of claim 21, further comprising carbonizing the oxidized fibers to produce carbon fibers.

23. 23. The method of claim 22, wherein the carbonizing comprises heating the oxidized fibers to 1000°-2000° C. in an inert, oxygen-free atmosphere.

24. 23. The method of claim 22, further comprising graphitizing the carbon fibers by heating the carbon fibers in an oxygen-free atmosphere above 2000°C up to 3000°C.