Oxidized fiber production from asphaltene-rich hydrocarbons

Abstract

A process of producing oxidized fibers, includes the steps of treating a hydrocarbon feedstock chemically and / or thermally to increase the softening point of asphaltenes contained in the feedstock, to produce a liquid intermediate product; removing solid impurities from the liquid intermediate product; producing precursor fibers; and stabilizing and oxidizing the precursor fibers.

Description

OXIDIZED FIBER PRODUCTION FROM ASPHALTENE-RICH HYDROCARBONS Field of the Invention

[0001] This disclosure relates to the production of oxidized fibers from asphaltene-rich hydrocarbon feedstock. Background

[0002] PCT / CA2024 / 051360.

[0003] Oxidized fiber having superior mechanical properties compared to ordinary textile fibers, including flame resistance, high tensile strength, high tensile modulus and elongation of fibers, and may be used in such applications as vehicle / aircraft brake preforms, transportation heat and flame blocking layers, thermal, acoustic and vibration insulation liners, flame-resistant apparel and intumescent meshes.

[0004] .

[0005] Oxidized fibers conventionally comprise oxidized and stabilized polyacrylonitrile (PAN) fibers, which provide inherent fire resistance and thermal stability. Oxidized fibers can be carbonized to form carbon fiber. The production of high-quality carbon fiber from asphaltenes is described in co-pending PCT International Application PCT / CA2024 / 051360, the entire contents of which are incorporated herein by reference, where permitted.

[0006] There remains a need in the art for alternative methods of preparing oxidized fibers from a hydrocarbon feedstock, and in particular, oxidized fibers mechanical properties suitable for weaving oxidized fibers into a fabric and / or to resist mechanical damage of products comprising such oxidized fibers.WSLEGAL\093616\00063\39680618v2Summary of the Invention

[0007] The present disclosure relates to methods to produce oxidized fibers with superior mechanical properties and high limiting oxygen index (LOI), from asphaltene-based precursor material produced from asphaltene-rich hydrocarbon feedstocks.

[0008] In some embodiments, the process comprises the removal of non-asphaltene molecular constituents such as saturate, aromatic, and resin components. In some embodiments, the removed components may be separated, for example by condensation as distillates, for further processing as hydrocarbons free of asphaltenes.

[0009] In one aspect, disclosed is a process of producing oxidized fibers, comprising the steps of: (a) treating a hydrocarbon feedstock chemically and / or thermally to increase the softening point of asphaltenes contained in the feedstock, to produce a liquid intermediate product; (b) removing solid impurities from the liquid intermediate product, such as by filtration; (c) producing precursor fibers such as by melt-spinning; and (d) stabilizing and oxidizing the fibers, preferably in nitric acid followed by heating in a gas comprising oxygen.

[0010] In some embodiments, the treatment of step (a) comprises the steps of: (a.1) mixing a hydrocarbon feedstock containing asphaltenes with an ammonium-, sulfur- and / or oxygen-containing-compound; 2WSLEGAL\093616\00063\39680618v2(a.2) heating the mixture to a temperature (T1) up to about 450° C in a gas flowing environment of air, nitrogen, steam, an oxygen containing gas, or a combination thereof, and stirring the mixture during heating, and holding the mixture at about T1 for a first period of time; (a.3) heating the mixture to a second temperature (T2) and holding the mixture at about T2 for a second period of time; (a.4) optionally, heating the mixture to a third temperature (T3) and holding the mixture at about T3 for a third period of time;

[0011] Optionally, a liquid phase recovered from step (e) may be further treated to recover asphaltenes, such as by solvent recovery, and the asphaltenes may be used to fabricate precursor fibers. Therefore, in some embodiments, the liquid phase may be dissolved in a solvent, such as an n-alkane such as pentane or heptane, to precipitate asphaltenes as solids. These asphaltenes may then be spun into precursor fibers, or optionally may be heat treated and then spun into precursor fibers.

[0012] The precursor fibers may be further treated chemically prior to oxidation to produce oxidized fibers. The temperature required to melt spin the precursor material, the time and temperature required to stabilize the precursor fibers, and the yield of oxidized fibers can be controlled through an adjustment of the amounts of chemical additives, the control of resin / asphaltene content in the precursors, and the treatment temperature and time and the type of gas environments being used during the treatment. 3WSLEGAL\093616\00063\39680618v2

[0013] In some embodiments, a method of producing oxidized fibers described herein does not include a carbonization step to produce carbon fibers, and are subsequently incorporated into a product comprising such oxidized fibers.

[0014] In preferred embodiments, the oxidized fibers have a limiting oxygen index in the range of about 45% to about 55%. 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 the present 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 oxidized fibers from a hydrocarbon feedstock. Detailed Description of Embodiments

[0017] The present invention relates to a process to produce oxidized fibers by first producing precursor fibers from an asphaltene-based precursor material.

[0018] As used herein, "asphaltenes" are non-polar and non-volatile hydrocarbon compounds present in crude oil such as heavy oil and bitumen, which are insoluble in an n-alkane solvent such as pentane or hexane and are soluble in aromatic solvents such as benzene or toluene. The molecular structure of asphaltenes is difficult to determine because the molecules tend to stick together in solution. These materials are extremely complex mixtures containing a large number of individual chemical species. Asphaltenes do not have a specific chemical formula: individual molecules can vary in the number of 4WSLEGAL\093616\00063\39680618v2atoms 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 polyaromatic 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.

[0019] "Asphaltene-based precursor material" or "precursor material" is a material produced by implementing embodiments disclosed herein, which is enriched in asphaltenes which have been treated to raise their softening point and be modified to be suitable for fiber production.

[0020] "Limiting oxygen intake" or LOI is a measure of flammability of a polymer material. LOI is the minimum concentration of oxygen, expressed as a percentage, that will support combustion of a polymer. It can be measured by standardized tests, such as the ISO 4589 and ASTM D2863. LOI values can be used to rank the relative flammability of different polymer materials.

[0021] Methods of producing carbon fibers from a hydrocarbon feedstock which include a chemical and heat treatment step to increase the softening point of asphaltenes in the feedstock are described in co-pending PCT International Application PCT / CA2024 / 051360, the entire contents of which are incorporated herein by reference, where permitted. Feedstock and Pre-Treatment

[0022] Embodiments disclosed herein are not limited by the source of the hydrocarbon feedstock. The hydrocarbon feedstock can be any material of a thermoplastic nature that 5WSLEGAL\093616\00063\39680618v2is liquid or becomes liquid upon heating, and comprise asphaltenes, preferably from about 5 % up to about 90 % by weight.

[0023] 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%. Asphaltenes are a thermoplastic polymer and as such can be used to produce oxidized fibers.

[0024] 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.

[0025] In preferred embodiments, the hydrocarbon feedstock is treated to increase its softening point. Methods to increase the softening point of a hydrocarbon material are known, and 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.

[0026] In some embodiments, for example with feedstock with high asphaltene content, the hydrocarbon feedstock may be pre-treated to remove impurities that may negatively affect the formation of precursor fibers. For example, the heavy hydrocarbon feedstock may be dissolved in a solvent to dissolve the thermoplastic portion of the hydrocarbon feedstock but not non-thermoplastic carbonaceous coke or inorganic materials. The 6WSLEGAL\093616\00063\39680618v2solvent must also have a boiling point below 300°C, and preferably below 200°C so it is more easily removed. In preferred embodiments, the solvent may comprise toluene, chloroform, tetrahydrofuran, and quinoline. Toluene is a preferred solvent as it promotes aggregation of impurities and hence, make the impurities separation process easier compared to other solvents.

[0027] The solvent may be added in a quantity sufficient to dissolve substantially all the thermoplastic components. For example, solvent may be added in a ratio of 3L to about 30 L per 1 kg of feedstock, and preferably 10 L to about 15 L per 1 kg of feedstock with mixing in place.

[0028] The insoluble impurities will be precipitated into solids formed within the thermoplastic solvent mixture and may be removed with conventional solid removal methods.

[0029] In addition, or alternatively, the hydrocarbon feedstock may be heated to liquify the thermoplastic portions. Depending on the feedstock and whether or not a solvent is used, the chosen temperature can be between 100° - 400°C. Preferably, the thermoplastic feedstock, or the feedstock and solvent mixture, is treated at temperatures between about 200° - 420°C under inert atmosphere or under steam environment, or a combination of the two, for between about 1 hour to about 4 hours with stirring in place.

[0030] Thermal treatment should be optimized to remove sufficient solvent if it was used previously, facilitate cross-linking reactions, and to remove volatiles from the bulk material while not producing further carbonaceous coke particles. At the same thermal treatment temperature, using an inert atmosphere is more likely to produce more coke particles than when using steam. The higher the thermal treatment temperature, it is more 7WSLEGAL\093616\00063\39680618v2likely to produce more coke particles, but it can remove more volatiles and solvents faster to increase the softening point. Softening Point Modification

[0031] A staged heat treatment with a chemical additive described within produces asphaltene-based precursor material, with different amount of material which is insoluble in an n-alkane-, such as n-pentane- or heptane-, up to 95% weight content. The softening points of these n-pentane or heptane-insoluble materials can be adjusted for the purpose of enhancing their ability to extrude fibers, processing the precursor fibers more effectively in terms of reducing energy, GHG emissions, and achieving higher mechanical properties.

[0032] Therefore, the chemical activation and heat treatment of the feedstock, in at least one heating stage, which will increase the softening point of the resulting asphaltene-based precursor material, up to about 350° C. The softening point is defined as the temperature at which a polymer flows under a given load upon heating. The method used to determine softening points described in this disclosure is the Ring and Ball method (R&B) — ASTM D 3461-76, DIN ISO 4625.

[0033] It is preferred to increase the softening point prior to fiber production steps (ie. melt spinning) because the feedstock is not in a fibrous form yet and the effect of treatment on the fiber structure is not a concern. Heat Treatment with Chemical Activation

[0034] Therefore, in one aspect, disclosed is a process comprises treating the hydrocarbon feedstock with a chemical additive and heating in at least one heating stage, which will increase the softening point or melting point of the resulting asphaltene-based precursor 8WSLEGAL\093616\00063\39680618v2material, up to about 400° C, through one or a combination of the following process steps. Embodiments disclosed herein include a process which comprises any combination of steps described herein, or omits any optional or preferred step.

[0035] Initially, the hydrocarbon feedstock is mixed with a chemical additive which 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 excessive cross-linking which can convert the material to a thermosetting plastic or coke. In some embodiments, these chemical additives will 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 out of 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 an ammonium-, sulfur- and / or oxygen-containing-compound. The chemical additive may comprise (NH4)2SO4(ammonium sulfate), (NH4)2S2O8 (ammonium persulfate), (NH4)2S2O3 (ammonium thiosulfate), (NH4)2SO3 (ammonium sulfite), NH4HSO4 (ammonium hydrogen sulfate), NH4HSO3 (ammonium hydrogen sulfite), and (NH4)2S (ammonium sulfide), or combinations thereof. At elevated temperatures, these ammonium-, sulfur- and oxygen- containing-compounds decompose into such compounds as HSO42-, HSO3-, S2O72-, S2O82-, S2O32-, SO32-containing compounds, SO2, or S, or combinations of such compounds. These decomposition products serve as catalysts, which can cause cross-linking and / or vulcanization of hydrocarbon feedstock material to alter the hydrocarbon feedstock 9WSLEGAL\093616\00063\39680618v2material to have thermoplastic properties and an increased softening or melting point. The vulcanization or cross-linking can also lead to the hydrocarbon feedstock being converted into elastic (rubber), or thermosetting compounds.

[0037] Ammonium sulphate is one preferred chemical additive, which thermally decomposes according to reactions (1) to (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 = 4NH3 + N2 +3SO2 + 6H2O (4)

[0038] The intermediate products of the reaction 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 addition of (NH4)2SO4or other ammonium-, sulfur- and / or oxygen-containing-compounds can occur at room temperature or above room temperature, for example, when the hydrocarbon feedstock is at a temperature above room temperature from a previous processing stage.

[0039] The dosage of the chemical additive can range from 0% to 20% (by weight) of the hydrocarbon feedstock to be treated, depending on the initial softening point or melting point of the hydrocarbon feedstock to be treated, the treatment temperature, the gaseous 10WSLEGAL\093616\00063\39680618v2environment, the desired increase in softening point and the desired final rheological properties of the treated materials.

[0040] Further products that result from the decomposition of (NH4)2SO4 or other ammonium-, sulfur- and oxygen-containing-compounds, outside of those listed above are gaseous substances that preferably do not chemically react with hydrocarbon materials being treated. Heat Treatment

[0041] After, before or during mixing with the chemical additive, the feedstock is heated to a first temperature (T1) 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 T1, and held for a second suitable period of time, again with stirring under a flowing gas environment. Preferably, the stirring is continuous. 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 continuous stirring under a flowing gas environment.

[0042] The treatment temperatures T1, T2 and T3 must be higher than the thermal decomposition temperature of the chemical additives being added. However, treatment is preferably performed at a temperature which minimizes or avoids carbonization or coke formation, such as a temperature below 480° C, preferably below 450° C.

[0043] In some embodiments, the holding time for T1 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. 11WSLEGAL\093616\00063\39680618v2

[0044] T1, T2 and optional T3 of treatment are temperatures at which decomposition of the chemical additive takes place, and / or they can be the temperatures at which cross- linking or vulcanization reactions of hydrocarbon materials occur, and / or they can be the temperatures at which reactions between the flowing gases and the hydrocarbon materials take place. It is also possible for all of these events to take place at the same temperature, which can be second or third temperature of the treatment.

[0045] The mixing step can occur at an ambient temperature before the step of heating, or the mixing step can occur after the hydrocarbon feedstocks are heated in the 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, or in different combinations of mixing, heating and stirring.

[0046] In preferred embodiments, processing temperature and time are controlled to control the rate of reaction, which affects the processability of the precursor material for melt-spinning and other activated carbon processing.

[0047] The flowing gas environment in the reactor may comprise air, pure nitrogen, pure steam, an oxygen-containing gas, or combinations thereof. The gas environment serves to modify the initial hydrocarbon feedstock by attaching to chains of the hydrocarbons and making the chains longer, 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 desired properties of hydrocarbon materials after treatment, the selection of the type of gas streams, the temperature and the residence time can be varied during treatment. The selection of gas environments may change the effectiveness of the chemical additive in achieving cross- 12WSLEGAL\093616\00063\39680618v2linking. 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 effectiveness of the above described alteration of chemical composition of the initial hydrocarbon materials is dependent of the type of processing gases.

[0048] It is preferred to continuously stir the mixture of hydrocarbon feedstock and chemical additive while heating and holding the mixture. Stirring improves heat transfer between the feedstock and the reactor wall which is 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.

[0049] The heating of a mixture of the hydrocarbon feedstock with a chemical additive with a flowing gas stream combines various processes of molecular modification (de- polymerization, 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.

[0050] The chemical additives thermally decompose to gaseous products, thus making minimum changes to the chemistry of original hydrocarbon feedstock and which facilitates its removal from the hydrocarbon feedstock.

[0051] After at least one heat treatment step with a chemical additive, the hydrocarbon feedstock will have less aliphatic hydrogen present. The resulting higher aromaticity is 13WSLEGAL\093616\00063\39680618v2desirable when using the treated feedstock as a precursor material for making oxidized fibers.

[0052] In alternative embodiments, other chemical agents could be added before and / or during each 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 fibers, adding solids of any physical form to change the chemical, mechanical, electrical, thermal, and biological properties of the hydrocarbon feedstock. In some embodiments, the chemical agents may comprise a salt such as potassium carbonate, potassium bicarbonate and potassium chloride, 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 hydrogen citrate, and derivatives thereof, and combinations thereof.

[0053] In some embodiments, precursor material recovered from different stages of heat treatment may be combined and mixed to produce a mixed precursor material for precursor fiber production. For example, improving spinnability and / or processability may be improved. In some embodiments, the precursor material may require less time and lower temperature for oxidation and carbonization. In some embodiments, mechanical properties may be improved, for example, higher tensile strength, higher modulus and / or higher elongation before fracture may be achieved. Removal of Solid Impurities 14WSLEGAL\093616\00063\39680618v2

[0054] The thermoplastic asphaltene-based precursor material resulting from the chemical treatment at an elevated temperature is a liquid at an elevated temperature, but may contain non-meltable or otherwise solid impurities. Impurities include non-thermoplastic portions within the bulk thermoplastic hydrocarbon feedstock. The impurities may also comprise inorganic materials such as oilsands-derived minerals, and carbonaceous coke that can be produced from previous processing steps from the upgrading or refining facility or during pre-treatment steps.

[0055] The solid impurities are preferably removed to produce precursor fibers with fine diameters and to produce oxidized fibers with a good consistency in mechanical properties.

[0056] When precursor fibers are extruded by melt-spinning, the size of solid particles remaining in the precursor before extruding must be smaller than the diameter of precursor fibers to be fabricated. As a result, the size of any remaining solid particles will usually limit the diameter of precursor fibers, provided that bulk precursors can be thinned. Frequent breaking of precursor fibers will occur if maximum size of solid particles is comparable to the diameter of precursor fibers to be fabricated. Upon loading a fiber with tensile load, breaking of the fiber prefers to occur at the fiber location having the largest solid particles. As a result, a wide range of fiber strength and low average fiber strength will be measured if fibers have large size and fractions of solid particles.

[0057] 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 15WSLEGAL\093616\00063\39680618v2mixed with a solvent to liquefy or reduce the viscosity of the thermoplastic precursor material, which can facilitate liquid / solid separation.

[0058] Physical methods include sedimentation, centrifugation or decanting of solid particles that usually have higher density to the bottom of the resulting product and the top portion of the product is removed for further separation.

[0059] Mechanical methods include filtration, which preferably involves a pressure differential to force the liquid to pass through a filter membrane, leaving the solids on the filter and the liquid is extracted. The pressure differential may be created by pressurizing the feedstock above the filter or depressurizing the chamber below the filter (vacuum separation).

[0060] In some embodiments, the precursor material is filtered through a porous membrane with a pore sizes ranging from 0.1 µm to 500 µm, under pressure up to 100 psi.

[0061] 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 such as fine mineral and coke 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. 16WSLEGAL\093616\00063\39680618v2

[0062] Magnetic and / or electromagnetic methods may be used to remove magnetic species, usually metal-containing compounds, that are magnetic or can be magnetized by electric current.

[0063] The asphaltene-based precursor material may be cooled during or after filtration or solids rejection. The end temperature of cooling can be room temperature or an intermediate temperature between the room temperature and the last stage of heating temperature. Solvent Recovery of Asphaltenes

[0064] In some embodiments, the asphaltene-based precursor material, after solids removal, may be processed to recover asphaltenes, such as by solvent precipitation with n- pentane, hexane or heptane. The solvent will then dissolve n-alkane soluble components and can be discarded or recovered for another purpose. Solvent treatment includes dissolving the bulk material into a chosen solvent, then recovering the precipitated insoluble. This solvent recovery step can extract higher molecular weight materials with higher softening point. Any alkane solvents can be utilized for this purpose. Solvent to feedstock ratio must be carefully selected to maximize yield of the precipitates but also sufficiently remove the low molecular weight materials that lowers the softening point of the bulk material. Typical solvent to feedstock ratio that can be used is 5L solvent: 1kg feedstock to 30L solvent: 1 kg feedstock. The precipitated portion can be recovered by using liquid-solid separation methods as addressed above.

[0065] Optionally, the precipitated asphaltenes may be subjected to one or more stages of heat treatment as described above, with or without any chemical additives. Chemical 17WSLEGAL\093616\00063\39680618v2additives may be used to further increase the softening point. These steps may also result in the removal of heteroatoms in the material.

[0066] Optionally, the asphaltenes may be further treated to remove impurities by dissolving the asphaltenes in a suitable solvent, such as toluene, and removing solvent- insoluble material such as residual mineral solids and coke. Production of Precursor Fibers

[0067] The precursor material remaining after solids rejection or the precipitated or purified asphaltenes may then be used to produce precursor fibers, such as by melt- spinning, wet spinning, air-blowing, electrostatic spinning, or a similar method known to those skilled in the art.

[0068] In preferred embodiments, the resulting thermoplastic precursor material is processed by melt spinning, preferably at a temperature between about 250°C to about 350°C, and more preferably between 275°C to 325°C. Feedstocks with melt spinning temperature beyond 325°C may form carbonaceous coke particles during the melt spinning process and is thus not preferred. However, a higher melt spinning temperature allows less rigorous stabilization conditions.

[0069] The melt spinning apparatus includes heating chamber, a device to evenly distribute mass flow for all nozzles, filtering plates and finally, single- or multiple-hole nozzle with hole diameter smaller than or equal to 0.3 mm. The heat-treated feedstock is extruded into fibrous shape at elevated temperatures and the extruded material is wound on a winding drum to be thinned to a desired diameter at different winding speeds. 18WSLEGAL\093616\00063\39680618v2

[0070] If the impurities removal steps are completed effectively, continuous melt spinning with high productivity can be reached, with winding speed above 500 m / min, and even above 1000 m / min. Efficiency of impurities removal can be verified by using scanning electron microscope (SEM) to observe the melt spun fibers with diameter below 10 µm. If the impurities are sufficiently removed from various methods indicated previously, there should not be any particles protruding out of the precursor fibers and diameter distribution of the fibers should be consistent, with a standard deviation less than 1 µm. Stabilization and Oxidation of Precursor Fibers

[0071] The melt spun precursor fibers can then be stabilized and oxidized. In some embodiments, the precursor fibers are stabilized by soaking in an aqueous solution which coats the green precursor fibers and prevents cohesion between adjacent green fibers. The aqueous solution may comprise hydrochloric acid, nitric acid, sulfuric acid, phytic acid, potassium nitrate, potassium chloride, their derivatives, and / or mixtures thereof. The aqueous solution can be concentrated or dilute, a dilution can be in the range of 1 wt.% to 100 wt.% of concentrated solution. The soaking time is from 1 second to 100 minutes, preferentially from 5 seconds to 10 minutes.

[0072] The aqueous solution preferably comprises an oxidizing agent, such as nitric acid. Nitric acid with concentrations no more than 40 vol.% can be used for stabilization, for a relatively short period of time such as between about 1 second to about 20 minutes. To improve wetting of the fibers, alcohol in a small amount can be added, with care taken not to add too much alcohol as adding an alcohol to nitric acid can lead to abrupt and hazardous gas formation. 19WSLEGAL\093616\00063\39680618v2

[0073] Optionally, the stabilized precursor fibers may be subjected to a short heating period, for example up to about 200° to about 300° C, for about 1 minute to about 1 hour.

[0074] The stabilized fibers may then be oxidized through heating in the presence of oxygen (such as under air) to temperatures between about 150°C to about 350°C.

[0075] The stabilization / oxidation process is preferably optimized to reduce mass loss during oxidation as much as possible while incorporating enough oxygen and facilitating cross-linking reactions. Increasing oxidation temperature too fast can result in fusing of fibers and too slow will unnecessarily increase operation cost. The mass change from oxidation with optimized program will be within ± 10 wt.% relative to the initial weight of the fibers before acid treatment.

[0076] In some embodiments, the degree of oxidation may be checked by measuring the oxygen content through using an elemental analyzer. Preferably, oxidized fibers will have an oxygen content by mass between 10 wt.% and 30 wt.%.

[0077] If the fiber precursor material has a lower softening point, more rigorous oxidation is required and it is attained by increasing the acid concentration, or oxidation temperature, or oxidation time, or a combination of all three thereof.

[0078] The oxidized fibers resulting from implementation of embodiments described herein will be heat-resistant, and flame-resistant with limited oxygen index between 30% and 55%. Examples

[0079] By way of further description of the process of the present disclosure, reference may be made to the following examples, which are intended to exemplify certain elements 20WSLEGAL\093616\00063\39680618v2of the claimed invention, not limit them. Unless otherwise indicated, all parts and percentages are by weight. Example 1

[0080] 20 kg of vacuum refinery residues as hydrocarbon feedstock was added with different amount of (NH4)2SO4solid powder, ranging from 3 to 8 wt. % of vacuum refinery residues, as listed in Table 1. The residue feedstock was a viscous liquid at room temperature and its softening point was below room temperature, but not measured. 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: • 1st step of heating to 350°C and held at 350° C for 120 minutes with a flow of N2 gas; • 2nd step of heating to 420°C and held at 420°C for 60 minutes with a flow of N2gas; and • 3rd step of heating to 435°C and held at 435°C for 75 minutes with a flow of steam.

[0081] The treated resulting hydrocarbons were then filtered before cooling to room temperature with a flow of N2 gas.

[0082] The resulted material is asphaltene-based precursor material, and after cooling is in solid form. The resulted materials have softening points substantially higher than the starting feedstock were used as precursors to produce precursor fibers through melt- spinning. The precursor yields and softening points as affected by different dosage of (NH4)2SO4 are listed in Table 1. 21WSLEGAL\093616\00063\39680618v2Table 1 Effect of chemical dosage on the melt-spinning temperature of vacuum refinery residue after the four steps of treatment in Example 1. Items Sample A Sample B Sample C Sample D Sample E (NH ) SO ( t %) 3 5 6 7 8Example 2

[0083] 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 asphaltenes solids, which are pentane-insoluble. The obtained asphaltenes solids were placed in a sealed cylindrical reactor and were then heated to different temperatures as listed in Table 2 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 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 2 Items Sample C-1 Sample C-2 Sample C-3 Sample C-4Sample C-5Example 3 22 WSLEGAL\093616\00063\39680618v2

[0084] 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, to produce asphaltenes solids, which are pentane-insoluble. The obtained asphaltenes solids were placed in a sealed cylindrical reactor and were then heated to 325oC and held at the temperature for 120 minutes. Stirring at a speed of 30 RPM and a flow of N2gas 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 3 Items Sample C-6 Sample C-7 Sample C-8 Sample C-4 Ratio of pentane overExample 4

[0085] Samples A to E in Table 1, which were produced following the steps in Example 1, were 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 1. Table 4 The softening points of the resulted new samples produced following the steps described in Example 4 Items Sample A-1SampleSample Sample Sample B-1C-4 D-1 E-1Example 5

[0086] 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 R and S in Table 5) were measured and are seen to be increased as compared with that of Sample C-6. 23 WSLEGAL\093616\00063\39680618v2Table 5 The softening points of the resulted new samples produced following the steps described in Example 5 Additional treatments applied to Sample C-6 in Table 3 Conditions S l C 6 S l C 61 S l C 62Example 6

[0087] An asphaltene-rich hydrocarbon materials with an asphaltene content of 76 wt. % was treated with conditions listed in Table 6. 2 kg of feedstock (Sample W in Table 6) was mixed with 3.5 wt.% (NH4)2SO4powder. 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 6. 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). Table 6 Effect of treating conditions on the spinning temperature and winding speed of the feedstock following the steps described in Example 6. Sample ID Sample W(feedstock)Sample X Sample YExample 7 24 WSLEGAL\093616\00063\39680618v2

[0088] A vacuum refinery residue feedstock different from that in Example 1 was used as the feedstock hydrocarbon material. The current vacuum refinery has lower softening point than that used in Example 1.20 kg of the current vacuum refinery residues was added with different amount of (NH4)2SO4 solid powder, ranging from 0 to 6 wt. % of vacuum refinery residues, as listed in Table 7. 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 (NH4)2SO4are listed in Table 7. Lower yields but higher melt-spinning temperatures were measured for the current vacuum refinery residues than the vacuum refinery resides tested in Example 1. Because lower softening points of the current vacuum refinery residues, more components with smaller molecules were evaporated, leading to lower product yield but higher softening points or melt spinning temperature. Table 7 Effect of chemical dosage on yield, spinning temperature and winding speed Items Sample Z-0 Sample Z-1 Sample Z-2 Sample Z-3 (NH ) SO ( t %) 0 4 5 6Example 8

[0089] An asphaltene-rich hydrocarbon material with an asphaltene content of 76 wt. % was treated with the same conditions as Sample X listed in Table 6. The obtained Sample X was further processed to produce Sample X-1 and Sample X-2 following the conditions listed in Table 8. Sample X-1 was heated to 280oC to remove solid impurities using a filter with a pore size of 5 µm. Sample X-2 was obtained by dissolving Sample X in toluene with 15 liters of toluene per 1 kg of Sample X. All the samples in Table 8 were melt spun into precursor fibers. Sample X, which did not have an impurities-removal step, had high melt spin productivity but non-consistent fibers, as the fibers had an average diameter of 14.5 µm with a large standard deviation of 2.8 µm. Sample X-1 was produced by heating Precursor Sample X to liquid and filtering the liquid with a filter with 5 µm pore size. The 25 WSLEGAL\093616\00063\39680618v2precursor fibers produced had more consistent fibers. Both Sample X and Sample X-1 had the same melt spin temperature. Sample X-2 has a much-reduced spin temperature (from 260oC to 152oC), even after a thermal treatment at 250oC for 4 hours with stirring in flowing N2 gas to remove the solvent. Because of the removal of impurity solids, the precursor fibers had an average diameter of 8.6 µm with a standard deviation of 0.7 µm. However, as the treatment step was not fully effective in removing the residual solvents, melt spin temperature had a decrease from 255°C to 152°C. Fiber diameters were measured from SEM images. More than 20 measurements obtained for each sample to calculate the average and standard deviation. Table 8 Effect of Impurities removal Treatment Wind IDImpuritiesT(°C) / Time Melt Spin T ing Average Dia. ° speedExample 9

[0090] An asphaltene-rich hydrocarbon material with an asphaltene content of 76 wt. % was treated with the same conditions as Sample X listed in Table 6. The obtained Sample X was first dissolved in toluene with a toluene / Sample X-ratio of 15:1 and filtered to remove solid impurities using a 1.0 µm filter. The liquid obtained after filtration was further 26 WSLEGAL\093616\00063\39680618v2processed to produce Sample X-2 following the conditions listed in Table 8, and Samples X-3, X-4 and X-5 following the conditions listed in Table 9. All the samples after treatments were spun into precursor fibers. The treatments have increased the spin temperatures without reducing their spinnability in terms of fiber diameter consistency and winding speed. Table 9 Effect of Thermal treatment Sample Sample X-2 Sample X-3 Sample X-4 Sample X-5Example 10

[0091] The precursor prepared according to the conditions for Sample C-4 in Table 3 of Example 3 was used to determine the condition of stabilization of precursor fiber. The stabilization is achieved by heating precursor fibers in a furnace with flowing hot air. About 10 grams of precursor fibers obtained by melt-spinning Precursor Sample C-4 in Table 3 was soaked in various diluted HNO3 solutions (vol%) with concentrations listed in Table 10 for one minute prior to stabilization treatment. The acid-soaked precursor fibers were then dropped directly in the stabilization furnace pre-heated to 200oC, and further heated to 280oC at a heating rate of 3.0oC / min and held at 280oC for 50 minutes. The samples were taken out of the furnace at the end of the hold period for weight measurements. The weight changes after stabilization are recorded and listed in Table 10. The highest weight gain is obtained when the concentration of HNO3 solution is at 15%. 27 WSLEGAL\093616\00063\39680618v2Table 10 Weight changes after stabilization of the precursor fibers with and without acid soaking. SampleSample Sample Sample Sample Sample C-4-1C-4-2 C-4-3 C-4-4 C-4-5 C-4-6Example 11

[0092] The precursor prepared according to the conditions for Sample C-4 in Table 3 of Example 3 was used to determine the effect of soaking time on the stabilization of precursor fiber. The stabilization is achieved by heating precursor fibers in a furnace with hot air. About 10 grams of precursor fibers obtained by melt-spinning Precursor Sample I was soaked in 15% (vol) HNO3 solution (vol%) for different periods of time as listed in Table 11. The acid-soaked precursor fibers were then dropped directly in the stabilization furnace pre-heated to 200oC, and further heated to 280oC at a heating rate of 3.0oC / min and held at 280oC for 50 minutes. The samples were taken out of the furnace at the end of the hold period for weight measurements. The weight changes after stabilization are recorded and listed in Table 8. The highest weight gain is obtained when the soaking time is at 1 minute. Table 11 Effect of acid soaking time on weight changes after stabilization of the precursor fibers Soaking time (minute) 1 10 15 20 W i ht l i ( t%) 87 36 52 48Example 12

[0093] The precursor prepared according to the conditions for Sample C-4 in Table 3 of Example 3 was used to determine the effect of stabilization hold temperature and time on the stabilization of precursor fibers. The stabilization is achieved by heating precursor fibers in a furnace with hot air. About 10 grams of precursor fibers obtained by melt-spinning Precursor Sample C-4 was soaked in 15% (vol) HNO3solution (vol%) for 1 minute. The 28 WSLEGAL\093616\00063\39680618v2acid-soaked precursor fibers were then dropped directly in the stabilization furnace pre- heated to 200oC, and further heated to different temperatures at a heating rate of 3.0oC / min and held at the temperature for different length of time, as detailed in Table 12. The samples were taken out of the furnace at the end of the hold period for weight measurements. The weight changes after stabilization are recorded and listed in Table 12. The weight gain after stabilization was peaked at a longer time when the hold temperature is lower. Table 12 Effect of stabilization temperature and time on weight changes after stabilization of the precursor fibers. Sample Hold temperature Hold time Weight gain Oxygen ID (oC) (minute) (wt%) limitingExample 13

[0094] The precursor fiber prepared according to the conditions for Sample X-1 in Table 8 of Example 8 was used to determine the effect of stabilization hold temperature and time on the stabilization of precursor fibers. The stabilization is achieved by heating precursor fibers in a furnace with hot air. About 10 grams of precursor fibers of Sample X-1 in Table 8 were soaked in 15% (vol) HNO3 solution (vol%) for 1 minute. The acid-soaked precursor fibers were then dropped directly in the stabilization furnace pre-heated to 200oC, and further heated to 300oC at a heating rate of 3.0oC / min and held at the temperature for 29 WSLEGAL\093616\00063\39680618v2different length of time, as detailed in Table 13. The samples were taken out of the furnace at the end of the hold period to determine the weight changes, oxygen content and limiting oxygen index. As listed in Table 13, oxidized fibers have weight gain from stabilization and oxygen content measured by elemental analyzer of 20 – 22 wt.%. All three samples exhibited flame resistance, with their measured limited oxygen index (%) values of 45 and 50%. Table 13 Effect of stabilization time on weight changes, oxygen content and limiting oxygen index after stabilization of the precursor fibers. Sample ID Hold T (oC)Hold timeWeight gain Oxygen Content LOI (minute)(wt.%) (wt.%) (%)Example 14

[0095] The precursor fibers were prepared according to the conditions for Sample C-4, Sample X-3 and Sample X-4, as detailed in Example 2 and Example 9, respectively. These precursor samples were oxidized using conditions listed in Table 14. All the samples were placed in the oxidation furnace pre-heated to 150oC and taken out of the furnace at the end of the hold period of oxidation. The oxidized fibers were tested to determine their mechanical properties including tensile strength, tensile modulus, and elongation before fracture, as tabulated in Table 14. 30 WSLEGAL\093616\00063\39680618v2Table 14 Mechanical properties of selected oxidized fibers. Hold Hold Heating Weight Tensile Tensile El n ti nInterpretation.

[0096] 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.

[0097] 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 or feature may be combined with any other element or feature in different embodiments, unless there is an obvious or inherent incompatibility, or it is specifically excluded. 31 WSLEGAL\093616\00063\39680618v2

[0098] 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.

[0099] 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.

[0100] The term "about" or "~" can refer to a variation of ± 5%, ± 10%, ± 20%, or ± 25% of the value specified. For"about 50" percent can in some embodiments carry a variation from 45 to 55 percent. For integer ranges, the term "about" or "~" can include one or two integers greater than and / or less than a recited integer atend of the range. Unless indicated otherwise herein, the term "about" or "~" is intended to include values and ranges proximate to the recited range that arein terms of the functionality of the composition, or the embodiment.

[0101] 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 32WSLEGAL\093616\00063\39680618v2listed 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.

[0102] 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. 33WSLEGAL\093616\00063\39680618v2

Claims

CLAIMS 1. A process of producing oxidized fibers, comprising the steps of: (a) treating a hydrocarbon feedstock chemically and / or thermally to increase the softening point of asphaltenes contained in the feedstock, to produce a liquid intermediate product; (b) removing solid impurities from the liquid intermediate product; (c) producing precursor fibers; and (d) stabilizing and oxidizing the precursor fibers.

2. The process of claim 1, wherein the treatment of step (a) comprises the steps of: (a.1) mixing a hydrocarbon feedstock containing asphaltenes with chemical additive comprising an ammonium-, sulfur- and / or oxygen-containing-compound; (a.2) heating the mixture to a temperature (T1) up to about 450° C in a gas flowing environment of air, nitrogen, steam, an oxygen containing gas, or a combination thereof, and stirring the mixture during heating, and holding the mixture at about T1 for a first period of time; (a.3) heating the mixture to a second temperature (T2) 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) and holding the mixture at about T3 for a third period of time; 34WSLEGAL\093616\00063\39680618v23. The process of claim 1 or 2, wherein a liquid phase recovered from step (a) is dissolved in a solvent to produce insoluble asphaltenes, which are used to produce the precursor fibers.

4. The process of claim 3, wherein the solvent comprise an n-alkane solvent, such as pentane, in a ratio of about 5:1 to about 20:1 litres / kg.

5. The process of any one of claims 1 to 4, wherein the chemical additive comprises (NH4)2SO4(ammonium sulfate), (NH4)2S2O8(ammonium persulfate), (NH4)2S2O3(ammonium thiosulfate), (NH4)2SO3(ammonium sulfite), NH4HSO4(ammonium hydrogen sulfate), NH4HSO3(ammonium hydrogen sulfite), and (NH4)2S (ammonium sulfide), or combinations thereof 6. The method of claim 5 wherein the chemical additive comprises (NH4)2SO4.

7. The process of claim 5 or 6 wherein the chemical additive is added in an amount between about 1% and about 15% by weight of the hydrocarbon feedstock, preferably between about 3% and 8% by weight of the hydrocarbon feedstock.

8. The process of any one of claims 1 to 7 wherein the step of rejecting solids from the liquid phase in step (b) comprises filtering the liquid phase through a filter having a pore size between about 0.1 um to about 500 um.

9. The process of claim 3 or 4 wherein the insoluble asphaltenes are subjected to at least one stage of heat treatment between about 300° C to about 380° C, for between about 0 minutes to about 3 hours, with or without a chemical additive.

10. The process of any one of claims 1 to 9, wherein the hydrocarbon feedstock comprises a hydrocarbon material derived from coal, heavy oil or bitumen, such as, for example, coal 35WSLEGAL\093616\00063\39680618v2tar, coal-tar pitch, fluid catalytic cracker (FCC) or residual catalytic cracker (RCC) slurry oil, vacuum distillation residue, vacuum refinery residue, asphalt, petroleum pitch; or asphaltenes recovered from an intermediate product of claim 1.

11. The process of claim 10, wherein the hydrocarbon feedstock comprises asphaltenes recovered from an intermediate product of claim 1, and the asphaltenes are mixed with (NH4)2SO4 prior to heat treatment at T1, T2 and T3.

12. The process of any one of claims 1 to 11, wherein in step (d) the precursor fibers are soaked in a nitric acid solution, between about 0% to about 25% vol concentration, for between about 0 minutes and 30 minutes.

13. The process of claim 12 wherein the nitric acid solution has a concentration between about 5% and 25%.

14. The process of claim 13 wherein the soaked precursor fibers are heat treated at between about 200° C to about 350° C, preferably 240° C to about 320° C, for between about 1 minute to about 120 min.

15. The process of any one of claims 1 to 14, which does not include a carbonization step.

16. The process of any one of claims 1 to 15, wherein the resulting oxidized fibers have a limiting oxygen index in the range of about 45% to about 55%.

17. A process of producing oxidized fibers, consisting essentially of the steps of: (a) mixing a hydrocarbon feedstock containing asphaltenes with a chemical additive comprising an ammonium-, sulfur- and / or oxygen-containing-compound; 36WSLEGAL\093616\00063\39680618v2(b) heating the mixture to a temperature (T1) up to about 450° C in a gas flowing environment of air, nitrogen, steam, an oxygen containing gas, or a combination thereof, and stirring the mixture during heating, and holding the mixture at about T1 for a first period of time; (c) heating the mixture to a second temperature (T2) and holding the mixture at about T2 for a second period of time; (d) optionally, heating the mixture to a third temperature (T3) and holding the mixture at about T3 for a third period of time; (e) removing solid impurities, such as by filtration; (f) producing precursor fibers such as by melt-spinning; and (g) stabilizing and oxidizing the fibers.

18. The process of claim 17 wherein the precursor fibers are stabilized and oxidized by soaking in nitric acid followed by heating in a gas comprising oxygen. 37WSLEGAL\093616\00063\39680618v2

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