Manufacturing of oxidized fibers from hydrocarbons with high asphaltene content

Abstract

A method for manufacturing oxidized fibers is disclosed, comprising the steps of: chemically and / or thermally treating a hydrocarbon feedstock to increase the softening point of asphaltene contained in said feedstock to produce a liquid intermediate product; removing solid impurities from said liquid intermediate product; manufacturing a precursor fiber; and stabilizing and oxidizing said precursor fiber.

Description

Technology Field

[0001] The present disclosure relates to the production of oxidized fibers from a hydrocarbon feedstock with a high asphaltene content. Background Technology

[0002] PCT / CA2024 / 051360.

[0003] Compared to conventional textile fibers, oxide fibers have excellent mechanical properties including flame retardancy, high tensile strength, high tensile modulus, and fiber elongation, and can be used for applications such as vehicle / aircraft brake preforms, heat and flame barrier layers for transportation, heat, acoustic and vibration insulation liners, flame-retardant clothing, and intumescent meshes.

[0004] Oxidized fibers comprise traditionally oxidized and stabilized polyacrylonitrile (PAN) fibers, which provide inherent flame retardancy and thermal stability. Oxidized fibers can be carbonized to form carbon fibers. The production of high-quality carbon fibers from asphaltene is described in the co-pending PCT international application PCT / CA2024 / 051360, the entire contents of which are incorporated herein by reference where permitted.

[0005] In the field of this technology, there is still a need for alternative methods to manufacture oxidized fibers from hydrocarbon feedstocks, particularly oxidized fibers having mechanical properties suitable for weaving the oxidized fibers into fabrics and / or for resisting mechanical damage to products containing such oxidized fibers.

[0006] The present disclosure relates to a method for producing oxide fibers having excellent mechanical properties and a high limiting oxygen index (LOI) from an asphaltene-based precursor material produced from a hydrocarbon feedstock with a high asphaltene content.

[0007] In some embodiments, the method comprises the removal of non-asphalten molecular components, such as saturated components, aromatic components, and resin components. In some embodiments, the removed components are separated by condensation, for example, as distillates, and can be used for further processing as asphaltene-free hydrocarbons.

[0008] In one embodiment, a method for manufacturing oxidized fibers is disclosed, said method:

[0009] (a) a step of chemically and / or thermally treating a hydrocarbon feedstock to increase the softening point of the asphaltene contained in the feedstock to produce a liquid intermediate product;

[0010] (b) a step of removing solid impurities from the liquid intermediate product by, for example, filtration;

[0011] (c) a step of preparing a precursor fiber by, for example, melt-spinning; and

[0012] (d) preferably includes a step of stabilizing and oxidizing the fiber by treating the fiber in nitric acid and then heating it in a gas containing oxygen.

[0013] In some embodiments, the processing of step (a) is:

[0014] (a.1) A step of mixing a hydrocarbon feedstock containing asphaltene with an ammonium-, sulfur- and / or oxygen-containing compound;

[0015] (a.2) heating the mixture to a temperature (T1) of up to about 450°C in a gas flow environment of air, nitrogen, steam, oxygen-containing gas, or a combination thereof, stirring the mixture during heating, and maintaining the mixture at about T1 for a first period;

[0016] (a.3) heating the mixture to a second temperature (T2) and maintaining the mixture at approximately T2 for a second period;

[0017] (a.4) Optionally, the mixture is heated to a third temperature (T3) and the mixture is maintained at approximately T3 for a third period.

[0018] Optionally, the liquid phase recovered from step (e) may be further processed, for example by solvent recovery, to recover asphaltene, and said asphaltene may be used to manufacture precursor fibers. Thus, in some embodiments, said liquid phase may be dissolved in a solvent such as an n-alkane such as pentane or heptane to precipitate the asphaltene as a solid. Then, said asphaltene may be spun into precursor fibers, or optionally, spun into precursor fibers after heat treatment.

[0019] The above precursor fibers may be further chemically treated prior to oxidation to manufacture oxidized fibers. The temperature required for melt spinning the precursor material, the time and temperature required to stabilize the precursor fibers, and the yield of the oxidized fibers can be controlled by adjusting the amount of chemical additives, controlling the resin / asphalten content in the precursor, and controlling the processing temperature, time, and type of gas environment applied during processing.

[0020] In some embodiments, the method for manufacturing oxide fibers described herein does not include a carbonization step for manufacturing carbon fibers subsequently included in a product containing such oxide fibers.

[0021] In a preferred embodiment, the oxide fiber has a limiting oxygen index in the range of about 45% to about 55%. Brief explanation of the drawing

[0022] In the drawings, identical elements are given the same reference numerals. The drawings are not necessarily scaled, but instead focus on the principles of the invention. Furthermore, each illustrated embodiment is merely one of many possible arrangements utilizing the basic concept of the invention. FIG. 1 is a schematic diagram of one embodiment of a process for manufacturing oxidized fibers from a hydrocarbon feedstock. Specific details for implementing the invention

[0023] The present invention relates to a process for manufacturing oxidized fibers by first manufacturing precursor fibers from asphaltene-based precursor materials.

[0024] As used herein, "asphaltenes" refer to non-polar and non-volatile hydrocarbon compounds present in crude oils such as heavy oil and bitumen, which are insoluble in n-alkane solvents such as pentane or hexane and soluble in aromatic solvents such as benzene or toluene. The molecular structure of asphaltenes is difficult to determine because the molecules tend to aggregate in solution. These substances are highly complex mixtures containing numerous individual chemical species. Asphaltenes do not possess a specific chemical formula, individual molecules may differ in the number of atoms included in their structure, the average chemical formula may vary depending on the source, and the precise molecular structure is difficult to determine. Given these limitations, asphaltenes are composed primarily of polycyclic aromatic carbon ring units bonded to oxygen, nitrogen, and sulfur heteroatoms and aliphatic side chains of varying lengths, particularly chelated with trace amounts of heavy metals such as vanadium and nickel.

[0025] "Asphaltene-based precursor material" or "precursor material" is a material produced by implementing the embodiments disclosed herein, which is a high asphaltene content material that is treated to raise the softening point and modified to be suitable for fiber manufacturing.

[0026] "Limiting Oxygen Intake" or LOI is a measure of the flammability of polymeric materials. LOI is expressed as a percentage of the minimum concentration of oxygen required to sustain the combustion of a polymer. This can be measured by standardized tests such as ISO 4589 and ASTM D2863. LOI values ​​can be used to evaluate the relative flammability of different polymeric materials.

[0027] Methods for producing carbon fibers from a hydrocarbon feedstock, comprising chemical and heat treatment steps to increase the softening point of asphaltene in the hydrocarbon feedstock, are described in the co-pending PCT international application PCT / CA2024 / 051360, the entire contents of which are incorporated herein by reference where permitted.

[0028] Feedstock and Pretreatment

[0029] The embodiments disclosed herein are not limited by the source of the hydrocarbon feedstock. The hydrocarbon feedstock may be any material of thermoplastic properties that is liquid or becomes liquid upon heating, and preferably comprises about 5% by weight to about 90% by weight of asphaltene.

[0030] Hydrocarbon feedstocks that can be processed according to the present disclosure include, for example, hydrocarbon materials derived from coal, heavy oil or bitumen, such as coal tar, coal tar pitch, fluid catalytic cracker (FCC) or residue catalytic cracker (RCC) slurry oil, vacuum distillation residue (VDR) or vacuum residue oil (VRR), asphalt, petroleum pitch, etc. Preferably, the hydrocarbon feedstock has a high asphaltene content of more than about 5 weight percent. Since asphaltene is a thermoplastic polymer, it can be used to manufacture oxidized fibers.

[0031] Although the present disclosure illustrates a process using petroleum-derived hydrocarbon materials, the embodiments described herein may also be used for the treatment of other types of hydrocarbons, such as those derived from coal, or for other processing activities due to similar thermoplastic properties.

[0032] In a preferred embodiment, the hydrocarbon feedstock is treated to increase its softening point. Methods for increasing the softening point of a hydrocarbon material are known and are described in PCT patent application number PCT / CA2021 / 000092 filed October 15, 2021, the entire contents of which, where permitted, are incorporated herein by reference.

[0033] In some embodiments, for example, in the case of a feedstock with a high asphaltene content, the hydrocarbon feedstock may be pretreated to remove impurities that may have a negative effect on 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 the non-thermoplastic carbonaceous coke or inorganic material. The solvent should also have a boiling point of less than 300°C, preferably less than 200°C, so that it can be removed more easily. In a preferred embodiment, the solvent may include toluene, chloroform, tetrahydrofuran, and quinoline. Since toluene promotes the aggregation of impurities, it facilitates the impurity separation process compared to other solvents.

[0034] The above solvent may be added in an amount sufficient to dissolve substantially all thermoplastic components. For example, the solvent may be added at a ratio of 3 L to about 30 L per 1 kg of feedstock, and preferably at a ratio of 10 L to about 15 L per 1 kg of feedstock, while stirring.

[0035] Insoluble impurities will precipitate as a solid formed within the thermoplastic solvent mixture and can be removed by conventional solid removal methods.

[0036] Additionally, or alternatively, the hydrocarbon feedstock may be heated to liquefy the thermoplastic parts. Depending on the use of the feedstock and solvent, the selected temperature may be 100 °C to 400 °C. Preferably, the thermoplastic feedstock or a mixture of the feedstock and solvent is treated for about 1 hour to about 4 hours at a temperature of about 200 °C to 420 °C while stirring in an inert atmosphere or a steam environment, or a combination of both.

[0037] Heat treatment must be optimized to sufficiently remove any previously used solvent, promote cross-linking reactions, and remove volatile matter from the bulk material without generating additional carbonaceous coke particles. At the same heat treatment temperature, using an inert atmosphere is more likely to produce more coke particles than using steam. While higher heat treatment temperatures are more likely to produce more coke particles, they can increase the softening point by removing more volatile matter and solvent more rapidly.

[0038] Softening point control

[0039] Stepwise heat treatment with chemical additives described herein produces asphaltene-based precursor materials having different amounts of materials, with a content of materials insoluble in n-alkanes such as n-pentane or heptane being up to 95 weight percent. The softening point of these n-pentane or heptane-insoluble materials can be adjusted for the purpose of improving fiber extrusion ability, treating the precursor fibers more effectively in terms of reducing energy and greenhouse gas (GHG) emissions, and achieving higher mechanical properties.

[0040] Accordingly, chemical activation and heat treatment of the feedstock will increase the softening point of the asphaltene-based precursor material produced in at least one heating step to about 350 °C. The softening point is defined as the temperature at which the polymer flows under a given load during heating. The method used to determine the softening point described in this disclosure is the Ring and Ball method (R&B) - ASTM D 3461-76, DIN ISO 4625.

[0041] It is desirable to increase the softening point before the fiber manufacturing steps (i.e., melt spinning) because the feedstock is not yet in fiber form, so the effect of treatment on the fiber structure is not a concern.

[0042] Heat treatment involving chemical activation

[0043] Accordingly, the process disclosed in one embodiment comprises the step of treating a hydrocarbon feedstock with a chemical additive and the step of heating in at least one heating step, which will increase the softening point or melting point of an asphaltene-based precursor material produced through one or a combination of the following process steps to about 400 °C. The embodiments disclosed herein include any combination of the steps described herein, or include a process that omits any optional or preferred step.

[0044] Initially, the hydrocarbon feedstock is preferably mixed with a chemical additive that acts to increase the softening point through a crosslinking reaction in the precursor material without substantially altering the chemical properties of the original hydrocarbon material. It is desirable to control the amount of the chemical additive to avoid excessive crosslinking that could convert the material into a thermosetting plastic or coke. In some embodiments, these chemical additives will decompose into intermediate products that promote the crosslinking process. The intermediate products from the decomposition of the additives can be further decomposed into a gaseous phase and can be easily removed from the reaction system. As a result, the chemical properties of the hydrocarbon material are not altered through chemical bonding with the elements of the additive.

[0045] 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 a combination thereof. At an elevated temperature, these ammonium-, sulfur-, and oxygen-containing compounds are HSO4 2- , HSO 3- , S2O7 2- , S2O8 2- , S2O3 2- , SO3 2- It is decomposed into compounds such as containing compounds, SO2 or S, or combinations of these compounds. These decomposition products act as catalysts and induce crosslinking and / or vulcanization of the hydrocarbon feedstock, thereby modifying the hydrocarbon feedstock to have thermoplastic properties and an increased softening point or melting point. The vulcanization or crosslinking may also cause the hydrocarbon feedstock to be converted into an elastic (rubber) or thermosetting compound.

[0046] Ammonium sulfate is a preferred chemical additive, which is thermally decomposed according to reaction schemes (1) to (3):

[0047] (NH4)2SO4 = NH4HSO4 + NH3 (1)

[0048] 2NH4HSO4= (NH4)2S2O7+ H2O (2)

[0049] 3(NH4)2S2O7= 2NH3+ 2N2+ 6SO2+ 9H2O (3)

[0050] The overall reaction is as follows: 3(NH4)2SO4 = 4NH3 + N2 + 3SO2 + 6H2O (4)

[0051] The intermediate products of the above reaction are pyrosulfate (S2O7) 2- and SO2 are included. These compounds are known to induce vulcanization of polymer compounds (rubber) to produce an elastic final end-use product. The reactions described above occur within a temperature range of about 250 °C to 500 °C, which corresponds to the temperature range in which depolymerization, crosslinking, chain breaking, and decomposition of hydrocarbon materials may occur. The addition of (NH4)2SO4 or other ammonium-, sulfur-, and / or oxygen-containing compounds may occur at room temperature or above room temperature, for example, when the hydrocarbon feedstock is at a temperature higher than room temperature from a previous processing step.

[0052] The amount of the chemical additive added may be in the range of 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 environment, the desired increase in softening point, and the desired final rheological properties of the treated material.

[0053] In addition to those listed above, additional products generated from the decomposition of (NH4)2SO4 or other ammonium-, sulfur-, and oxygen-containing compounds are gaseous substances that are desirable not to chemically react with the hydrocarbon material being heat-treated.

[0054] heat treatment

[0055] After, before, or during mixing with chemical additives, the feedstock is heated to a first temperature (T1) and maintained and stirred for an appropriate period in a gas flow environment. Subsequently, the temperature of the hydrocarbon feedstock mixture is adjusted to a second temperature (T2), which may be lower or higher than T1, and is maintained for a second appropriate period while being stirred again in a gas flow 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 is maintained for a third appropriate period with continuous stirring again in a gas flow environment.

[0056] The above treatment temperatures T1, T2, and T3 must be higher than the thermal decomposition temperatures of the added chemical additives. However, it is preferable that the treatment be performed at a temperature that minimizes or avoids carbonization or coke formation, for example, below 480°C, preferably below 450°C.

[0057] In some embodiments, the retention time of T1 is about 1 hour to about 4 hours, the retention time of T2 is about 0 minutes to about 3 hours, and the retention time of T3 is about 0 minutes to about 3 hours.

[0058] T1, T2, and optional T3 of the process may be temperatures at which the decomposition of chemical additives occurs, and / or temperatures at which the crosslinking or vulcanization reaction of hydrocarbon materials occurs, and / or temperatures at which the reaction between the flowing gas and the hydrocarbon material occurs. Additionally, it is possible for all of these events to occur at the same temperature, which may be the second or third temperature of the process.

[0059] The mixing step may occur at ambient temperature prior to the heating step, or the mixing step may occur after the hydrocarbon feedstocks have been heated in the heating step. Stirring may occur after mixing and heating, or stirring may occur during either mixing or heating, or both. Accordingly, the method may be performed in time-separated steps, or in different combinations of mixing, heating, and stirring.

[0060] In a preferred embodiment, the processing temperature and time are controlled to control the reaction rate, which affects the processability of the precursor material for melt spinning and other activated carbon treatments.

[0061] The gas flow environment within the reactor may include air, pure nitrogen, pure steam, oxygen-containing gas, or a combination thereof. This gas environment serves to modify the initial hydrocarbon feedstock by attaching to hydrocarbon chains to lengthen them, cleaving side chains, or, if necessary, breaking down heavier molecules. The flowing gas also reduces the frequency of material deposition or adhesion to the inner surfaces of the processing equipment. Depending on the desired characteristics of the hydrocarbon material after processing, the selection of the type of gas flow, temperature, and residence time during processing may be modified. The selection of the gas environment can alter the effectiveness of chemical additives in achieving crosslinking. This can also affect changes in the chemical composition of the hydrocarbon feedstock being processed. For example, the gas can promote chain cleavage to remove specific side chains or molecular groups, and can promote dehydrogenation to induce a reduction in the H / C ratio, which may be desirable or necessary for specific applications of the processed hydrocarbon feedstock. The effectiveness of the change in the chemical composition of the initial hydrocarbon material described above depends on the type of treatment gas.

[0062] While heating and maintaining the above mixture, it is desirable to continuously stir the mixture of the hydrocarbon feedstock and the chemical additive. Stirring promotes heat transfer between the externally heated reactor wall and the feedstock, mixing of the feedstock and the additive, increased evaporation of volatile components, and mixing of the gaseous medium and the hydrocarbon feedstock.

[0063] Heating a mixture of hydrocarbon feedstocks and chemical additives with a flowing gas stream combines various molecular modification processes (depolymerization, crosslinking, cleavage, and decomposition) into a series of single-process conditions within a single treatment that can be adjusted to meet the requirements of various end products.

[0064] Since the above chemical additives are thermally decomposed into gaseous products, they induce only minimal changes to the chemical properties of the original hydrocarbon feedstock and facilitate removal from the hydrocarbon feedstock.

[0065] After a heat treatment step using at least one type of chemical additive, the hydrocarbon feedstock will have less aliphatic hydrogen. The resulting higher aromaticity is desirable when using the treated feedstock as a precursor material for manufacturing oxidized fibers.

[0066] In alternative embodiments, other chemical agents may be added before and / or during each stepwise heat treatment step for purposes other than controlling the softening point and asphaltene content. For example, chemical agents may be added to produce active fibers, and solids of any physical form may be added to alter the chemical, mechanical, electrical, thermal, and biological properties of the hydrocarbon feedstock. In some embodiments, the chemical agents may include 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.

[0067] In some embodiments, precursor materials recovered from different heat treatment steps may be combined and mixed to produce a mixed precursor material for the manufacture of precursor fibers. For example, spinnability and / or processability may be improved. In some embodiments, the precursor material may require less time and lower temperatures for oxidation and carbonization. In some embodiments, mechanical properties may be improved, such as achieving higher tensile strength, higher modulus of elasticity, and / or higher elongation before fracture.

[0068] Removal of solid impurities

[0069] Thermoplastic asphaltene-based precursor materials produced from chemical treatment at elevated temperatures may contain impurities that are liquid at elevated temperatures but are insoluble or otherwise solid. The impurities include non-thermoplastic portions within the bulk thermoplastic hydrocarbon feedstock. The impurities may also include inorganic materials, such as minerals derived from oil sands, and carbonaceous coke that may be generated from or during previous processing steps of upgrading or refining facilities.

[0070] It is desirable that the above-mentioned solid impurities be removed to produce precursor fibers of a fine diameter and oxide fibers having good consistency of mechanical properties.

[0071] When precursor fibers are extruded by melt spinning, the size of the solid particles remaining in the precursor prior to extrusion must be smaller than the diameter of the precursor fiber to be manufactured. Consequently, assuming the bulk precursor can be thinned, the size of any remaining solid particles will typically limit the diameter of the precursor fiber. If the maximum size of the solid particles is similar to the diameter of the precursor fiber to be manufactured, frequent fracture of the precursor fiber will occur. When a tensile load is applied to the fiber, fracture tends to occur preferentially at the fiber location containing the largest solid particles. As a result, if the fiber contains solid particles of large size and fraction, a wide range of fiber strength and a low average fiber strength will be measured.

[0072] It is preferable that the above-mentioned solid impurities be removed by using conventional liquid-solid separation techniques, such as physical, mechanical, chemical, magnetic, or electromagnetic methods, or combinations thereof. The above-mentioned precursor material may be dissolved in a solvent or mixed with a solvent to liquefy the thermoplastic precursor material or reduce its viscosity, which can facilitate liquid / solid separation.

[0073] Physical methods typically involve the sedimentation, centrifugation, or decanting of solid particles having a higher density, thereby moving the solid particles to the bottom of the product and removing the upper portion of the product for further separation.

[0074] Mechanical methods include filtration, which preferably forces a liquid to pass through a filter membrane with a pressure difference, so that the solid remains on the filter and the liquid is extracted. The pressure difference can be formed by pressurizing the feedstock above the filter or depressurizing the chamber below the filter (vacuum separation).

[0075] In some embodiments, the precursor material is filtered through a porous membrane having a pore size of 0.1 μm to 500 μm under a pressure of up to 100 psi.

[0076] Chemical methods involve adding chemicals to react with solid particles to form new compounds that can be easily separated by other methods. Other chemical methods involve using a solvent to dissolve the thermoplastic portion of a solid feedstock containing asphaltene, so that insoluble particles, such as fine mineral particles and coke particles, remain to be removed from the bulk material by other methods. The precursor material can be recovered by removing the solvent through evaporation. Additionally, or alternatively, a solvent may also be added to precipitate the asphaltene as insoluble in the solvents and to remove soluble components, thereby increasing the asphaltene concentration in the product.

[0077] Magnetic and / or electromagnetic methods can be used to remove magnetic chemical species, typically metal-containing compounds, that are magnetic or can be magnetized by an electric current.

[0078] The above asphaltene-based precursor material may be cooled during or after filtration or solid removal. The final cooling temperature may be room temperature or an intermediate temperature between room temperature and the temperature of the final heating step.

[0079] Solvent recovery of asphaltene

[0080] In some embodiments, the asphaltene-based precursor material may be treated to recover the asphaltene by a method such as solvent precipitation using n-pentane, hexane, or heptane after solid removal. The solvent then dissolves the n-alkane soluble components and can be discarded or recovered for other purposes. The solvent treatment involves dissolving the bulk material in a selected solvent and then recovering the precipitated insoluble material. This solvent recovery step can extract higher molecular weight materials having a higher softening point. Any alkane solvent may be used for this purpose. The solvent-to-feed ratio should be carefully selected to sufficiently remove low molecular weight materials that lower the softening point of the bulk material while maximizing the yield of the precipitate. A typical solvent-to-feed ratio that may be used is 5 L of solvent per 1 kg of feed: 30 L of solvent per 1 kg of feed. The precipitated portion may be recovered by using the liquid-solid separation methods mentioned above.

[0081] Optionally, the precipitated asphaltene may be applied to one or more heat treatment steps with or without any chemical additives, as described above. Chemical additives may be used to further increase the softening point. These steps may also induce the removal of heteroatoms within the material.

[0082] Optionally, the asphaltene may be further treated to remove impurities by dissolving the asphaltene in a suitable solvent such as toluene and removing solvent-insoluble substances such as residual mineral solids and coke.

[0083] Manufacturing of precursor fibers

[0084] The precursor material remaining after solid removal or the precipitated or purified asphaltene can then be used to produce precursor fibers by, for example, melt spinning, wet spinning, air-blowing, electrostatic spinning, or similar methods known to those skilled in the art.

[0085] In a preferred embodiment, the resulting thermoplastic precursor material is preferably processed by melt spinning at a temperature of about 250 °C to about 350 °C, more preferably at 275 °C to 325 °C. Feedstocks having a melt spinning temperature exceeding 325 °C are undesirable because they may form carbonaceous coke particles during the melt spinning process. However, higher melt spinning temperatures allow for less stringent stabilization conditions.

[0086] The melt spinning device described above comprises a heating chamber, a device for uniformly distributing mass flow to all nozzles, a filter plate, and finally, a single-hole or multi-hole nozzle with a hole diameter of 0.3 mm or less. The heat-treated feedstock is extruded into a fiber shape at a heated temperature, and the extruded material is wound onto a winding drum to be thinned to a desired diameter at different winding speeds.

[0087] If the impurity removal steps are effectively completed, continuous melt spinning with high manufacturability can be achieved at winding speeds exceeding 500 m / min, or even exceeding 1000 m / min. The efficiency of impurity removal can be verified by using a scanning electron microscope (SEM) to observe melt-spun fibers with a diameter of less than 10 µm. When impurities are sufficiently removed by the various methods described above, there should be no particles protruding from the precursor fibers, and the fiber diameter distribution should be consistent with a standard deviation of less than 1 µm.

[0088] Stabilization and oxidation of precursor fibers

[0089] The melt-spun precursor fibers may subsequently be stabilized and oxidized. In some embodiments, the precursor fibers are stabilized by immersion in an aqueous solution, which coats the green precursor fibers and prevents aggregation between adjacent green fibers. The aqueous solution may comprise hydrochloric acid, nitric acid, sulfuric acid, phytic acid, potassium nitrate, potassium chloride, derivatives thereof, and / or mixtures thereof. The aqueous solution may be concentrated or diluted, and the dilution may be in the range of 1% to 100% by weight of the concentrated solution. The immersion time is 1 second to 100 minutes, preferably 5 seconds to 10 minutes.

[0090] The above aqueous solution preferably contains an oxidizing agent such as nitric acid. Nitric acid at a concentration of 40 volume% or less can be used for stabilization for a relatively short time, for example, from about 1 second to about 20 minutes. To improve the wettability of the fiber, a small amount of alcohol may be added, but care must be taken not to add excessive alcohol, as adding alcohol to nitric acid can induce rapid and dangerous gas generation.

[0091] Optionally, the stabilized precursor fiber may be applied for a short heating period of about 1 minute to about 1 hour, for example, at about 200°C to about 300°C.

[0092] The stabilized fiber can then be oxidized by heating to a temperature of about 150°C to about 350°C in the presence of oxygen (e.g., in air).

[0093] The above stabilization / oxidation process is preferably optimized to introduce sufficient oxygen and promote cross-linking reactions while minimizing mass loss during oxidation as much as possible. Increasing the oxidation temperature too rapidly may induce fiber fusion, while increasing it too slowly will unnecessarily increase operating costs. The mass change due to oxidation resulting from the optimized program will be within ±10 weight% of the initial weight of the fiber before acid treatment.

[0094] In some embodiments, the degree of oxidation can be determined by measuring the oxygen content using an elemental analyzer. Preferably, the oxidized fiber will have a mass-based oxygen content of 10% to 30% by weight.

[0095] If the fiber precursor material has a lower softening point, stricter oxidation is required, which is achieved by increasing the acid concentration, or the oxidation temperature, or the oxidation time, or a combination of all three of these conditions.

[0096] The oxide fiber produced from the implementation of the embodiments described in this specification will be heat-resistant and have flame retardancy with a limiting oxygen index of 30% to 55%.

[0097] Examples

[0098] For further explanation of the processes of the present disclosure, reference may be made to the following examples, which are intended to illustrate specific elements of the claimed invention, not to limit them. Unless otherwise specified, all parts and percentages are by weight.

[0099] Example 1

[0100] As a hydrocarbon feedstock, 20 kg of vacuum refinery residue was mixed with varying amounts of (NH4)2SO4 solid powder ranging from 3 to 8 weight percent relative to the vacuum refinery residue, as described in Table 1. The residue feedstock was a viscous liquid at room temperature, and its softening point was lower than room temperature but was not measured. The mixture was placed in a closed cylindrical reactor and stirred at a speed of 30 revolutions per minute (RPM) while the mixture was processed through the following sequential steps:

[0101] First heating step: heating to 350 ℃ and maintaining at 350 ℃ for 120 minutes under a flow of N2 gas;

[0102] Second heating step: heating to 420 ℃ and maintaining at 420 ℃ for 60 minutes under a flow of N2 gas; and

[0103] Third heating step: heating to 435 ℃ and maintaining at 435 ℃ for 75 minutes under steam flow.

[0104] The resulting hydrocarbons were subsequently filtered and then cooled to room temperature under a flow of N2 gas.

[0105] The resulting material is an asphaltene-based precursor material and is in solid form after cooling. The resulting materials have a substantially higher softening point than the starting feedstock and were used as precursors for producing precursor fibers through melt spinning. The precursor yield and softening point, which are affected by different (NH4)2SO4 input amounts, are listed in Table 1.

[0106]

[0107] Example 2

[0108] Sample C of Table 1, prepared according to the steps of Example 1, was dissolved in pentane such that the ratio of pentane to Sample C was 20:1 to produce a pentane-insoluble asphaltene solid. The obtained asphaltene solid was placed in a closed cylindrical reactor and subsequently heated to different temperatures listed in Table 2 and maintained for 120 minutes. During the process, stirring at a speed of 30 revolutions per minute and the flow of N2 gas were maintained. The softening point of the resulting material was measured and found to increase substantially with the treatment temperature compared to the softening point of Sample C of Table 1 of Example 1.

[0109]

[0110] Example 3

[0111] Sample C of Table 1, prepared according to the steps of Example 1, was dissolved in different ratios of pentane relative to Sample C as described in Table 3 to produce a pentane-insoluble asphaltene solid. The obtained asphaltene solid was placed in a closed cylindrical reactor, heated to 325°C, and maintained at that temperature for 120 minutes. During the process, stirring at a speed of 30 revolutions per minute and the flow of N2 gas were maintained. The softening point of the resulting material was measured and found to increase with the ratio of solvent relative to Sample C, as described in Table 3.

[0112]

[0113] Example 4

[0114] Samples A to E of Table 1, prepared according to the steps of Example 1, were further processed according to the steps for Sample C-4 of Table 2 of Example 2. The softening points of the resulting samples were measured and were found to have increased compared to the softening points of Samples A to E of Table 1 of Example 1.

[0115]

[0116] Example 5

[0117] Sample C-6 of Table 3 in Example 3 was further treated under the conditions listed in Table 5. The softening points of the newly generated samples (Samples R and S in Table 5) were measured and were found to have increased compared to the softening point of Sample C-6.

[0118]

[0119] Example 6

[0120] A hydrocarbon material with a high asphaltene content of 76 wt% was treated under the conditions listed in Table 6. 2 kg of feedstock (Sample W in Table 6) was mixed with 3.5 wt% (NH4)2SO4 powder. Sample X was prepared by treating the mixture with two stages of heating, and Sample Y was treated with three stages of heating as described in Table 6. These treatments resulted in an increase in the spinning temperature of the precursor fiber and an improvement in the winding speed compared to the feedstock (Sample W).

[0121]

[0122] Example 7

[0123] A vacuum residue oil feedstock different from that of Example 1 was used as the feedstock hydrocarbon material. This vacuum residue oil has a lower softening point than that used in Example 1. To 20 kg of this vacuum residue oil, different amounts of (NH4)2SO4 solid powder ranging from 0 to 6 weight percent relative to the vacuum residue oil were added, as described in Table 7. The same processing steps and procedures as those of Example 1 were used to process this mixture. The precursor yield and melt spinning temperature affected by different (NH4)2SO4 input amounts are listed in Table 7. For this vacuum residue oil, a lower yield but a higher melt spinning temperature were measured compared to the vacuum residue oil tested in Example 1. Due to the lower softening point of this vacuum residue oil, more components with smaller molecules evaporated, resulting in a lower product yield but a higher softening point or melt spinning temperature.

[0124]

[0125] Example 8

[0126] A hydrocarbon material with a high asphaltene content of 76 wt% was processed under 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 according to the conditions listed in Table 8. Sample X-1 was heated to 280°C 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 at a rate of 15 liters of toluene per 1 kg of Sample X. All samples in Table 8 were melt-spun into precursor fibers. Sample X, which did not undergo an impurity removal step, exhibited high melt-spun manufacturability but showed inconsistent fibers with an average diameter of 14.5 µm and a large standard deviation of 2.8 µm. Sample X-1 was prepared by heating the precursor Sample X into a liquid and filtering the liquid through a filter with a pore size of 5 µm. The produced precursor fibers had more consistent fibers. Samples X and X-1 had the same melt spinning temperature. Sample X-2 had a significantly reduced spinning temperature (from 260°C to 152°C) even after heat treatment at 250°C for 4 hours while stirring in flowing N2 gas to remove the solvent. Due to 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, because the treatment step was not completely effective in removing residual solvent, the melt spinning temperature was reduced from 255°C to 152°C. Fiber diameters were measured from SEM images. More than 20 measurements were obtained to calculate the mean and standard deviation for each sample.

[0127]

[0128] Example 9

[0129] A hydrocarbon material with a high asphaltene content of 76 wt% was treated under the same conditions as Sample X listed in Table 6. The obtained Sample X was first dissolved in toluene such that the toluene / Sample X ratio was 15:1, and then filtered using a 1.0 µm filter to remove solid impurities. The liquid obtained after filtration was further processed to prepare Sample X-2 according to the conditions listed in Table 8, and to prepare Samples X-3, X-4, and X-5 according to the conditions listed in Table 9. All samples after processing were spun into precursor fibers. These treatments increased the spinning temperatures without reducing the consistency of fiber diameter and spinnability in terms of winding speed.

[0130]

[0131] Example 10

[0132] The precursor prepared according to the conditions of Sample C-4 in Table 3 of Example 3 was used to determine the stabilization conditions of the precursor fiber. Stabilization is achieved by heating the precursor fiber in a heat treatment furnace equipped with flowing hot air. Approximately 10 g of precursor fiber obtained by melt-spinning the precursor sample C-4 of Table 3 was immersed for 1 minute in various diluted HNO3 solutions (vol%) having the concentrations listed in Table 10 prior to stabilization treatment. The acid-immersed precursor fiber was then directly introduced into a stabilization heat treatment furnace preheated to 200°C, further heated to 280°C at a heating rate of 3.0°C / min, and maintained at 280°C for 50 minutes. The samples were removed from the heat treatment furnace at the end of the holding period for weight measurement. The weight change after stabilization was recorded and listed in Table 10. The highest weight increase was obtained when the concentration of the HNO3 solution was 15%.

[0133]

[0134] Example 11

[0135] The precursor prepared according to the conditions of Sample C-4 in Table 3 of Example 3 was used to determine the effect of immersion time on the stabilization of the precursor fiber. Stabilization is achieved by heating the precursor fiber in a heat treatment furnace equipped with hot air. Approximately 10 g of precursor fiber obtained by melt spinning precursor sample I was immersed in a 15% (vol) HNO3 solution (vol%) for different times as listed in Table 11. The acid-immersed precursor fiber was then directly introduced into a stabilization heat treatment furnace preheated to 200°C, and subsequently heated further to 280°C at a heating rate of 3.0°C / min and maintained at 280°C for 50 minutes. The samples were removed from the heat treatment furnace at the end of the holding period for weight measurement. The weight change after stabilization was recorded and is listed in Table 8. The highest weight increase was obtained when the immersion time was 1 minute.

[0136]

[0137] Example 12

[0138] The precursor prepared according to the conditions of Sample C-4 in Table 3 of Example 3 was used to determine the effect of stabilization holding temperature and time on the stabilization of the precursor fiber. Stabilization was achieved by heating the precursor fiber in a heat treatment furnace equipped with hot air. Approximately 10 g of precursor fiber obtained by melt spinning precursor sample C-4 was immersed in a 15% (vol) HNO3 solution (vol%) for 1 minute. The acid-immersed precursor fiber was then directly introduced into a stabilization heat treatment furnace preheated to 200°C, and subsequently further heated to different temperatures at a heating rate of 3.0°C / min, and held at those temperatures for different times as detailed in Table 12. The samples were removed from the heat treatment furnace at the end of the holding period for weight measurement. The weight change after stabilization was recorded and listed in Table 12. The weight increase after stabilization reached its peak at a longer time when the holding temperature was lower.

[0139]

[0140] Example 13

[0141] Precursor fibers prepared according to the conditions of Sample X-1 in Table 8 of Example 8 were used to determine the effect of stabilization holding temperature and time on the stabilization of the precursor fibers. Stabilization was achieved by heating the precursor fibers in a heat treatment furnace equipped with hot air. Approximately 10 g of precursor fibers from Sample X-1 in Table 8 were immersed in a 15% (vol) HNO3 solution (vol%) for 1 minute. The acid-immersed precursor fibers were then directly introduced into a stabilization heat treatment furnace preheated to 200°C, and subsequently heated further to 300°C at a heating rate of 3.0°C / min, and held at that temperature for varying times as detailed in Table 13. The samples were removed from the heat treatment furnace at the end of the holding period to determine weight change, oxygen content, and limiting oxygen index. As described in Table 13, the oxidized fibers exhibited a weight increase due to stabilization and an oxygen content of 20 to 22 wt% as measured by an elemental analyzer. All three samples exhibited flame retardancy, and the measured limiting oxygen index (%) values ​​were 45 and 50%.

[0142]

[0143] Example 14

[0144] Precursor fibers were prepared according to the conditions of Sample C-4, Sample X-3, and Sample X-4 as described in detail in Examples 2 and 9, respectively. These precursor samples were oxidized using the conditions listed in Table 14. All samples were placed in an oxidation heat treatment furnace preheated to 150°C and removed from the heat treatment furnace at the end of the oxidation holding period. The oxidized fibers were tested to determine their mechanical properties, including tensile strength, tensile modulus, and elongation at break, as summarized in Table 14.

[0145]

[0146] analysis

[0147] In the claims added to this specification, corresponding structures, materials, actions, and equivalents for all means or steps having added functional elements are intended to include any structure, material, or action for performing said function in combination with other claimed elements as specifically claimed.

[0148] References in the specification such as "one embodiment," "some embodiment," etc., indicate that the described embodiment may include a specific aspect, feature, structure, or characteristic, but not all embodiments necessarily include such aspect, feature, structure, or characteristic. Furthermore, such phrases may refer to the same embodiment mentioned in other parts of the specification, but are not necessarily so. Moreover, where a specific aspect, feature, structure, or characteristic is described in relation to a given embodiment, relating or combining such module, aspect, feature, structure, or characteristic with other embodiments is within the knowledge of those skilled in the art, regardless of whether it is 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 obvious or inherent incompatibility or it is specifically excluded.

[0149] Additionally, it should be noted that the claims may be written to exclude any optional elements. Accordingly, this statement is intended to provide an antecedent basis for the use of exclusive terms such as "only," "only," etc., in connection with the description of claim elements or the use of "negative" limitations. Terms such as "preferably," "preferred," "preferred," "optional," "may," and similar terms are used to indicate that the mentioned item, condition, or step is an optional (non-essential) feature of the invention.

[0150] Unless the context clearly requires otherwise, singular expressions include plural references. The term "and / or" means any one of the items associated with this term, any combination of the items, or all of said items. The phrase "one or more" is readily understood by those skilled in the art, particularly when grasped from the context of its use.

[0151] The terms “about” or “~” may refer to a variation of ±5%, ±10%, ±20%, or ±25% of a specified value. For example, “about 50” percent may have a variation range of 45 to 55 percent in some embodiments. For integer ranges, the terms “about” or “~” may include one or two integers greater than and / or less than the integer mentioned at each end of the range. Unless otherwise specified in this specification, the terms “about” or “~” are intended to include values ​​and ranges close to the mentioned range that are equivalent to the mentioned range in terms of the functionality of the composition or embodiment.

[0152] As understood by those skilled in the art, particularly in terms of providing description requirements, all ranges described herein also include all possible sub-ranges and combinations thereof, as well as individual values ​​constituting the ranges, particularly integer values. A mentioned range includes each specific value, integer, decimal, or identifier within that range. Any enumerated range can be readily recognized as sufficiently describing and enabling the same range to be divided into at least the same half, third, quarter, fifth, or tenth parts. As a non-limiting example, each range discussed herein can be readily divided into a lower third, a middle third, an upper third, and so on.

[0153] Furthermore, as understood by those skilled in the art, all expressions such as “up to,” “at least,” “exceeding,” “less than,” “greater than,” “greater than,” etc., include the stated number, and such terms also refer to ranges that can be subdivided into sub-ranges as discussed above. In the same way, all ratios described herein also include all sub-ratios that fall within the broader ratio.

Claims

Claim 1 A method for manufacturing oxidized fibers comprising: (a) chemically and / or thermally treating a hydrocarbon feedstock to increase the softening point of asphaltene contained in the feedstock to produce a liquid intermediate product; (b) removing solid impurities from the liquid intermediate product; (c) manufacturing a precursor fiber; and (d) stabilizing and oxidizing the precursor fiber. Claim 2 In paragraph 1, the processing of step (a) above is: (a.1) A step of mixing a hydrocarbon feedstock containing asphaltene with a chemical additive containing an ammonium-, sulfur- and / or oxygen-containing compound; (a.2) heating the mixture to a temperature (T1) of about 450°C or lower in a gas flow environment of air, nitrogen, steam, oxygen-containing gas, or a combination thereof, stirring the mixture while heating, and maintaining the mixture at about T1 for a first time; (a.3) heating the mixture to a second temperature (T2) and maintaining the mixture at approximately T2 for a second time; and (a.4) Optionally, a method for manufacturing oxidized fibers comprising the step of heating the mixture to a third temperature (T3) and maintaining the mixture at approximately T3 for a third time. Claim 3 A method for manufacturing oxidized fibers according to claim 1 or 2, wherein the liquid phase recovered from step (a) is dissolved in a solvent to produce insoluble asphaltene, and the insoluble asphaltene is used to produce the precursor fiber. Claim 4 A method for manufacturing oxidized fibers according to claim 3, wherein the solvent comprises an n-alkane solvent such as pentane in a ratio of about 5:1 to about 20:1 liter / kg. Claim 5 A method for manufacturing oxidized fibers according to 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 a combination thereof. Claim 6 A method for manufacturing oxide fibers according to claim 5, wherein the chemical additive comprises (NH4)2SO4. Claim 7 A method for manufacturing oxide fibers according to claim 5 or 6, wherein the chemical additive is added in an amount of about 1% to about 15% by weight of the hydrocarbon feedstock, preferably in an amount of about 3% to 8% by weight of the hydrocarbon feedstock. Claim 8 A method for manufacturing oxide fibers according to any one of claims 1 to 7, wherein the step of removing a solid from the liquid phase in step (b) comprises the step of filtering the liquid phase through a filter having a pore size of about 0.1 μm to about 500 μm. Claim 9 A method for manufacturing oxide fibers according to claim 3 or 4, wherein the insoluble asphaltene undergoes at least one heat treatment step at about 300°C to about 380°C for about 0 minutes to about 3 hours, with or without the use of chemical additives. Claim 10 A method for manufacturing oxidized fibers, wherein, in any one of claims 1 to 9, the hydrocarbon feedstock comprises, for example, a hydrocarbon material derived from coal, heavy oil, or bitumen such as coal tar, coal tar pitch, fluid catalytic cracker (FCC) or residue catalytic cracker (RCC) slurry oil, vacuum distillation residue, pneumatic refining residue, asphalt, or petroleum pitch; or asphaltene recovered from the intermediate product of claim 1. Claim 11 A method for manufacturing oxide fibers according to claim 10, wherein the hydrocarbon feedstock comprises asphaltene recovered from the intermediate product of claim 1, and the asphaltene is mixed with (NH4)2SO4 before heat treatment at T1, T2, and T3. Claim 12 A method for manufacturing oxidized fibers according to any one of claims 1 to 11, wherein in step (d), the precursor fiber is immersed in a nitric acid solution with a concentration of about 0 volume% to about 25 volume% for about 0 minutes to 30 minutes. Claim 13 A method for manufacturing oxidized fibers according to claim 12, wherein the nitric acid solution has a concentration of about 5% to 25%. Claim 14 A method for manufacturing oxidized fibers according to claim 13, wherein the immersed precursor fibers are heat-treated at about 200°C to about 350°C, preferably 240°C to about 320°C, for about 1 minute to about 120 minutes. Claim 15 A method for manufacturing oxidized fibers that does not include a carbonization step in any one of claims 1 to 14. Claim 16 A method for manufacturing oxide fibers according to any one of claims 1 to 15, wherein the oxide fiber produced has a limiting oxygen index in the range of about 45% to about 55%. Claim 17 A method for manufacturing oxidized fibers, wherein the method essentially comprises: (a) mixing a hydrocarbon feedstock containing asphaltene with a chemical additive containing an ammonium-, sulfur- and / or oxygen-containing compound; (b) heating the mixture to a temperature (T1) of about 450°C or lower in a gas flow environment of air, nitrogen, steam, oxygen-containing gas or a combination thereof, stirring the mixture during heating, and maintaining the mixture at about T1 for a first time; (c) heating the mixture to a second temperature (T2) and maintaining the mixture at about T2 for a second time; (d) optionally heating the mixture to a third temperature (T3) and maintaining the mixture at about T3 for a third time; (e) removing solid impurities, for example by filtration; (f) manufacturing a precursor fiber, for example by melt spinning; and (g) stabilizing and oxidizing the fiber. Claim 18 A method for manufacturing oxidized fibers according to claim 17, wherein the precursor fiber is stabilized and oxidized by immersing it in nitric acid and then heating it in a gas containing oxygen.

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