Mesophase pitch production from blend of synthetic isotropic pitch and aromatic solvent

Abstract

Systems and methods are provided for producing mesophase pitch, including, forming isotropic pitch by reacting a feed and acid at an elevated temperature, wherein the feed comprises a single-ring aromatic compound or a multi-ring aromatic compound, or both, mixing the isotropic pitch with a first solvent comprising an aromatic solvent to give a mixture, heating the mixture to a temperature to give mesophase pitch; and washing the mesophase pitch with a second solvent, wherein the mesophase pitch comprises a softening point less than 400 °C.

Description

MESOPHASE PITCH PRODUCTION FROM BLEND OF SYNTHETIC ISOTROPIC PITCH AND AROMATIC SOLVENTFIELD

[0001] This disclosure relates to the production of pitch for manufacturing carbon products, such as fibers.BACKGROUND

[0002] The carbon fibers market has grown significantly. The growth can be can be attributed to increasing demand from a wide range of industries such as automotive (e.g., body parts such as deck lids, hoods, front end, bumpers, doors, chassis, suspension systems such as leaf springs, drive shafts), aerospace (such as aircraft and space systems), high performance aquatic vessels (such as yachts and rowing shells), airplanes, sports equipment (e.g., golf club, tennis racket, ski boards, snowboards, helmets, rowing or water skiing equipment), construction (non-structural and structural systems), military (e.g., flying drones, armor, armored vehicles, military aircraft), wind energy industries, energy storage applications, fireproof materials, carbon-carbon composites, carbon fibers, and in many insulating and sealing materials used in construction and road building (e.g., concrete), turbine blades, light weight cylinders and pressure vessels, off-shore tethers and drilling risers, medical, etc. Non-limiting properties of carbon fibers beneficial for high- performance applications include, for example, high bulk modulus and tensile modulus (depending on the morphology of the carbon fiber), high electrical and thermal conductivities, high specific density, etc.

[0003] Highly oriented carbon fibers with excellent mechanical properties from pitch precursors have been produced. For pitch-based carbon fibers or other pitch-based carbon composite materials, the properties (e.g., mechanical, electrical or thermal) are determined by the mesophase content (e.g., ordered morphology) in the precursor material, orientation and the crystallite size of the graphitic domains and their geometrical configurations within the resultant carbon fiber (texture of the fiber). Therefore, the subsequent graphitic structure and morphology are strongly correlated to the molecular orientation obtained in the green carbon materials prior to high temperature treatments. Petroleum byproducts with abundant aromatic fractions have been commonly used to produce mesophase pitch.SUMMARY

[0004] Disclosed herein is an example method of producing mesophase pitch, comprising: forming isotropic pitch by reacting a feed, paraformaldehyde, acetic acid, and sulfuric acid at a temperature in a range of 40 °C to 350 °C, wherein the feed comprises a single-ring aromaticcompound or a multi-ring aromatic compound, or both; mixing the isotropic pitch with a first solvent comprising an aromatic solvent to give a mixture; heating the mixture to a temperature of at least 350 °C to give mesophase pitch; and washing the mesophase pitch with a second solvent, wherein the mesophase pitch comprises a softening point less than 400 °C.

[0005] Further disclosed herein is an example method of producing mesophase pitch, comprising: preparing isotropic pitch by reacting a feed comprising an aromatic compound with paraformaldehyde, acetic acid, and sulfuric acid, wherein the aromatic compound comprises a single-ring aromatic compound or a multi-ring aromatic compound, or both; combining the isotropic pitch with a first solvent comprising an aromatic solvent; heating the isotropic pitch and the first solvent as combined to a temperature in a range of 350 °C to 500 °C to give mesophase pitch; and washing the mesophase pitch with a second solvent, wherein the mesophase pitch comprises a softening point less than 400 °C after the washing.

[0006] These and other features and attributes of the disclosed methods and systems of the present disclosure and their advantageous applications and / or uses will be apparent from the detailed description which follows.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] To assist those of ordinary skill in the relevant art in making and using the subj ect matter hereof, reference is made to the appended drawings, wherein:

[0008] FIG. 1 is a flow diagram of a method of producing mesophase pitch from a feed.

[0009] FIG. 2 is a diagram of a general scheme of reaction generally consistent with the Examples.

[0010] FIG. 3 is a diagram of synthetic pitches derived from mixed xylenes, and a representative depiction of a fiber pulled from mesophase pitch.

[0011] FIG. 4 is a plot of x-ray scattering data comparing xylene-derived isotropic and mesophase pitches.

[0012] FIG. 5A and FIG. 5B are Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) data of certain pitch from the Examples.

[0013] FIG. 6 is a plot of thermal gravimetric analysis (TGA) curves of certain pitches (in the Examples), depicting mass loss profiles.

[0014] FIG. 7 shows two optical micrographs acquired via reflected cross-polarized light microscopy via a waveplate, featuring birefringent droplets of mesophase pitch.

[0015] FIG. 8 is four images of pitch that compare mesophase content.

[0016] FIG. 9 is a plot of the x-ray scattering data of pitch.

[0017] FIG. 10A and FIG. 10B are plots of mass spectra of isotropic pitch and corresponding mesophase pitch.

[0018] Like reference numbers and designations in the various drawings indicate like elements.DETAILED DESCRIPTION

[0019] In various embodiments, systems and methods are provided for production of mesophase synthetic pitch, such as for forming carbon fibers from the mesophase pitch. Some aspects of the present disclosure are directed to a technique in which the mesophase pitch is formed from isotropic synthetic pitch. The mesophase pitch may be formed by thermal conversion of the synthetic pitch in an open system or a closed system. The synthetic pitch as feed for this thermal treatment (conversion) may be formed upstream from hydrocarbon by chemical synthesis (e.g., acid chemistry, acid catalysis), such as detailed in US Patent Application Publication No. US2024 / 0209208A1 (incorporated by reference herein in its entirety) based on International Publication No. WO2022 / 211869A1 having priority to US Application No. 63 / 167,354. Thus, overall, in this two-step production (hydrocarbons to isotropic pitch to mesophase pitch), the mesophase pitch may be formed from hydrocarbons. See also US Patent Application Publication No. 2024 / 0182788A1 (incorporated by reference herein in its entirety) based on International Publication No. WO2022 / 211986A1 having priority to US Application No. 63 / 167,319,

[0020] The first step may form isotropic pitch from hydrocarbon via acid catalysis. The hydrocarbons may include aromatic compounds, such as single-ring aromatic compounds and / or multi-ring aromatic compounds. The second step may form mesophase pitch by heating the isotropic pitch at higher temperatures (e.g., above the softening point). The heating of the isotropic pitch may be in the presence of an aromatic solvent, such as a single-ring aromatic compound and / or multi-ring aromatic compound (e.g., naphthalene), etc. The aromatic solvent can be the same as the aromatic compound of the original feed used to make the isotropic pitch). The heating of the isotropic pitch with the aromatic solvent may be in a vessel under a gas blanket. The vessel may be a sealed vessel (closed system) or an unsealed vessel (open system) under inert conditions. The formed mesophase pitch may be washed with solvent, such as toluene or pentane, or both, to remove smaller molecular weight components thereby concentrating the mesogenic molecules.

[0021] Embodiments herein can be associated with conversion of hydrocarbons (e.g., heavy hydrocarbons) to structured carbon matenals (e.g., carbon fibers) for composites, battery applications, aerospace, automotive and other applications where higher stiffness, thermal conductivity or light weight components are needed or beneficial.

[0022] Advantageously, mesophase pitch can be produced from certain petroleum byproducts. Production of high-quality mesophase pitches from petroleum byproducts (e.g., having abundantaromatic fractions) can be beneficial potentially due to lower cost of the feed and due to melt processability options for the produced mesophase pitches in comparison to the carbon fiber production from polyacrylonitrile (PAN) precursors.

[0023] Thus, a focus can be to synthesize mesophase pitch precursors beneficially from aromatic petroleum feedstocks utilizing economically viable scalable routes. In implementations of such a production route, the softening point (Ts) and rheological properties (e.g., viscosity and spinnability) of the generated mesophase pitch can correlate to the pitch chemistry, mesophase content, homogeneity in processing, and precursor material purity of the mesophase pitch. Yet, controlling these parameters utilizing conventional synthetic techniques that are economically feasible for various feedstocks is challenging.

[0024] Previously, synthetic pitches prepared by oligomerization of naphthalene using hydrogen fluoride / boron trifluoride (HF / BF3) catalyst addressed some issues (e.g., spinnability, purity, homogeneity in processing, etc.). Yet, use of this super acid catalyst in this chemistry raised concerns about the process and operational efficacy. In response, some implementations of the chemistry of conversion of single-nng aromatics (and / or multi-ring aromatics) to heavy hydrocarbon isotropic pitches utilized acid catalyst [e.g., sulfuric acid (H2SO4)] and paraformaldehyde.

[0025] Some techniques of thermal conversion of isotropic pitch to mesophase pitches with high mesophase conversion (up to 100%) from various feeds are discussed in International Publication No. WO2022 / 211986A1.

[0026] In contrast, embodiments herein give a scalable technique for synthesizing mesophase pitches from single-ring aromatic feedstocks (e.g., xylene isomers, etc.) giving the produced mesophase pitch generally being processable. The feedstock can include multi-ring aromatics. The mesophase pitches produced herein generally feature lower softening points (e.g., less than 400 °C, less than 350 °C, less than 325 °C, or less than 300 °C). A lower softening point with high mesophase content (e.g., >70%) is generally beneficial. A lower softening point with low mesophase content (e.g., <40%) is generally less beneficial. In general, the produced mesophase pitch can have a mesophase content ranging from 1 wt% to 100 wt% and a softening point in the range of 200 °C to 450 °C. In implementations, the produced mesophase pitch can have a substantial absence of solids that have high Ts(e.g., greater than 350 °C, greater than 325 °C, or greater than 300 °C), therefore giving the mesophase pitch general viscosity characteristics that are beneficial for melt spinning into fibers. In implementations to generate this mesophase pitch, a blend including at least a synthetic isotropic pitch and an aromatic solvent is subjected to thermal soaking [e.g., thermal annealing (isothermally)] at elevated temperatures for the thermalconversion to generate mesophase pitches of various compositions either in an open system or closed system. The operating temperature of the thermal conversion may be, for example, at least 350 °C (e.g., in the range of 350 °C to 500 °C), or at least 375 °C (e.g., in the ranges of 375 °C to 500 °C, or 375 °C to 475 °C). Both the open system and closed system can each be under a gas (e.g., as a gas blanket). The gas may be, for example, nitrogen (N2) or other gases (e.g., inert gases), and with a relatively small amount of air in the gas being generally acceptable if present. In the open system, the volatiles and / or low molecular weight reaction (low boiling point) components including products are stripped off. The low molecular weight reaction (low boiling point) products have a lower molecular weight than the average molecular of the products generated in the thermal conversion and a lower boiling point than the average boiling point of the products generated in the thermal conversion. The reaction can be conducted under an inert atmosphere (e.g., the gas being N2) in the open system. In a closed system, the reaction mixture is contained in a closed vessel sealed under the gas (e.g., N2, etc.), which can be inert. In a closed system, the reaction may generally be running under pressure for at least the reason that small molecules boil off inside the sealed reactor. The reaction being under pressure can lead to a different morphology of the produced mesophase pitch compared to the morphology of the mesophase pitch produced in a reaction under little or no pressure (e.g., in an open system).

[0027] In implementations for the open system and / or closed system, the reaction mixture may include an aromatic solvent, such as at a weight percent (wt%) of the reaction mixture of less than 50 wt% (e.g., in the ranges of 1 wt% to 50 wt%, or 5 wt% to 50 wt%), less than 40 wt% (e.g., in the ranges of 1 wt% to 40 wt%, or 5 wt% to 40 wt%), or less than 30 wt% (e.g., in the ranges of 1 wt% to 30 wt%, or 5 wt% to 30 wt%). The aromatic solvent may be, for example, naphthalene, methyl naphthalene, xylene, toluene, tetralin, etc. to tune the produced mesophase pitch composition. In implementations, the same or similar compounds as the aromatics in the upstream feed to form (via chemical reaction) the isotropic pitch may be utilized as the aromatic solvent in this following formation of the mesophase pitch from the isotropic pitch (via thermal reaction). In implementations, aromatic solvents may reduce viscosity of the pitch and may slow the thermal reactions by diluting the isotropic pitch. Aromatic solvents may reduce the viscosity of the pitch in the closed system when the pitch is subjected to thermal reaction (pyrolysis). In implementations, this may reduce the tendency of higher molecular weight (more aromatic) species to associate to form coke in the pyrolysis. In an open system, the aromatic solvent will generally evaporate as the thermal reaction mixture is heated to the reaction temperature. The evaporated aromatic solvent may be carried off from the thermal reaction vessel by the gas (gas blanket) (e.g., inert gas such as N2), a carrier, or steam, etc.

[0028] For embodiments of the open system, a majority (greater than 50% by weight) of the aromatic solvent molecules are typically removed by evaporation pnor to pyrolysis. In implementations, the aromatic solvent molecules that remain (e.g., less than 5 wt% of the initial solvent) in the open system may participate in chemical reactions with feed material (isotropic pitch) at elevated temperatures. Subsequently (post-pyrolysis), unreacted aromatic solvent molecules (e.g., naphthalene, etc.) can be washed away from the mesophase pitch utilizing solvent (e.g., solvent mixture of toluene and pentane) as a wash agent. The thermal reaction and the wash can give low softening point mesophase products. The softening point may depend on the extent of thermal reaction at higher temperatures [e g., pyrolysis (heat treatment) temperature and time] and the subsequent wash. In one embodiment, the mesophase pitch produced within the closed system from a blend of synthetic pitch and naphthalene as feed when sealed under air, and then after a washing step, displayed smooth extensional flow behavior that can be one of the prerequisites for spinning the produced mesophase pitch.

[0029] In implementations, the materials with various mesophase contents obtained herein have high MCRT (e.g., at least 70%) and a softening point (Ts), for example, in the ranges of 290 °C to 320 °C, 280 °C to 325 °C, 270 °C to 330 °C, or 250 °C to 330 °C. Further, in embodiments, little or no puffing is observed in the spinnable temperature range. The mesophase pitch synthesized typically possesses relatively high product purity. These features of the synthesized mesophase pitch are generally appropriate for production of high-performance carbon fibers. The techniques are not limited to a single composition of mesophase pitch. Various single-ring aromatics (and mixtures thereof) can be precursor feedstocks in the initial synthesizing of the isotropic pitch utilized to subsequently form the mesophase pitch.

[0030] The MCRT is the micro carbon residue test (MCRT) per American Society for Testing and Materials (ASTM) standard D4530-15 (2020) “Standard Test Method for Determination of Carbon Residue (Micro Method)” (last updated June 9, 2020) of ASTM International. Here, for mesophase pitch and similar materials, the softening point (Ts) is per ASTM standard D3104-14a (2018) “Standard Test Method for Softening Point of Pitches (Mettler Softening Point Method)” (last updated December 12, 2018) of ASTM International. Here, the softening point (Ts) is the temperature at which a given material softens adequately such that the material falls through a distance of 1.9 millimeter (mm) under gravity.

[0031] The production of carbon fiber from pitch may include, for example, melt spinning, oxidization, carbonization, and graphitization. As known in the relevant art, pitch-based carbon fibers produced from mesophase pitch may be of such a structure that graphite crystals developed to some degree are extremely highly oriented in the direction of the fiber axis. For mesophasepitches generally, spinning orients mesophase material due to shear field and extensional field, and that the orientation of this mesophase translates to the orientation of the final graphitic crystals formed or the microstructure formed after graphitization.

[0032] The carbon fibers market has grown due to increasing demand for various applications. Carbon fiber can generally be considered a technologically relevant product from hydrocarbon that features high tensile modulus, tensile strength, electrical and thermal properties, and low specific density. Carbon fibers can be a beneficial component to form composite materials for higher performance applications and which has gained considerable attention in industry due to the aforementioned exceptional properties. Further, carbon fibers produced from mesophase pitch precursors show higher carbon yield, graphitization and orientation of crystalline domains leading to improvement in thermo-mechanical properties in comparison to PAN based counterparts (however, tensile strength is higher for PAN fibers). Mesophase pitches contain discotic nematic liquid crystalline phase formed by polynuclear planar aromatic hydrocarbons that allows for (facilitates) the melt-spinning operation to produce high performance carbon fibers thereof. The high degree of orientation offered by the discotic nematic mesophase during spinning is related to the superior mechanical, thermal, and electrical properties obtained in the final carbon fibers.

[0033] While dominant processes to produce mesophase pitches from isotropic pitches include thermal conversion (pyrolysis), catalytic routes have also been exercised to make pitches (e.g., synthetic naphthalene or pyrene pitches). The final graphitic structure and morphology obtained by high-temperature treatments can be correlated to the composition of the pitch precursors and molecular orientation obtained in the as-spun green carbon fibers. The composition (e.g., mesophase content), volatile evolution, solid content, sulfur content, extensional flow behavior, and softening point of the mesophase pitch can all play roles in the processes from initially spinning a green mesophase fiber to finally forming the carbon fiber product, and all these properties are inter-related. The forming of the carbon fiber product can include post processing steps such as stabilization, carbonization, and graphitization of the as spun-green pitch fiber.

[0034] At higher temperatures in the thermal treatment (pyrolysis) to give (produce) the pitch, a variety of complex reaction sequences can take place, which can lead to the formation of large planar anisotropic molecules. However, it can be difficult to control molecular composition during the pyrolysis because of the broad molecular weight distribution found in petroleum or coal-tar based aromatic feedstocks and the complexity of chemical reactions, as well as the subsequent processing steps that impact or govern the final composition of the isotropic and mesophase pitches formed thereof. To this end, synthetic pitches made from single-ring aromatics (and / orfeeds with known chemical structures) with acid chemistry' can provide a better handle to control composition and purity via tunable reaction conditions in implementations.

[0035] However, mesophase pitches derived from synthetic isotropic pitches via an acid chemistry route (e.g., as discussed in the aforementioned WO2022 / 211986A1) can have inaccessible softening points and are heterogenous and therefore are difficult to be spun into fibers. In the present disclosure, at least two distinct routes are presented that address or overcome this issue by adding aromatic solvents to the isotropic pitch. The addition of the aromatic solvents may plasticize the material during the synthesis and reduce coke formation (or material heterogeneity) in implementations. In the one approach (route), thermal chemistry is performed in a closed system in which solvent molecules may participate in chemical reactions while diluting the system. For the other route, the system is open (so that volatiles, solvent, and small molecules can escape) while performing thermal chemistry, in which the uniformly distributed solvent molecules (typically small amount) retained in the material at higher temperature may also participate in chemical reactions.

[0036] A characteristic in embodiments is the chosen solvent for the mesophase pitch synthesis can be the original precursor single-ring aromatic material (feed) used for the isotropic pitch synthesis, and thus simplifying the process. Such may depend on the cost and availability of the feedstock. Moreover, as noted, embodiments generally utilize acid chemistry (e.g., acid catalysis) to make the isotropic pitch composition, e.g., in which aromatic molecules grow in size to form polynuclear aromatics. While strong acids, such as sulfuric acid (H2SO4), may be employed, the acid chemistry can be considered mild acid chemistry in a relative sense in comparison to the harsh chemistry of HF / BF3 previously employed. The produced isotropic material is mixed with the same (or different) aromatic feed or a solvent as in the isotropic pitch production and subjected to thermal chemistry at higher temperature to further increase aromaticity to induce the formation of discotic mesogens to form mesophase pitch.

[0037] For this route, two distinct approaches (closed or open) may be implemented, as indicated in FIG. 1. Single-ring aromatic compounds (e.g., xylene, etc.) and multi-ring aromatic compounds can be feed. The feed composition specified can be an additional knob to adjust or optimize the composition of the intermediate isotropic pitch and the mesophase pitch via the thermal chemistry. In implementations of this treatment, contribution to the overall composition from higher molecular weight species increases, and subsequent washing generally removes unreacted solvent (if present) retained in the material either in the crystalline form [e.g., naphthalene (NP) crystallizes at lower temperatures with respect to the pyrolysis temperatures] or solvent form (low boiling point components). The washing step (e.g., 118 in FIG. 1) may be effective in removingsmaller molecular weight components that constitute primarily isotropic fraction, enhancing more anisotropic composition in the material. In addition to (or in lieu of) the washing to remove smaller molecular weight components, the material can be optionally heated (e.g., to 400 °C or to 450 °C) under inert and / or vacuum conditions to vaporize (boil off) smaller molecular weight components.

[0038] The amount of mesophase in the final material (mesophase pitch composition) can be adjusted by thermal severity (e.g., temperature and time of the thermal reaction). In implementations, the resulting heterogenous mesophase materials can be homogenous in a processing sense (little or no solid like objects found), with softening points in the ranges of less than 400 °C, less than 325 °C, or less than 300 °C. In implementations, the mesophase material may display a smooth extensional flow behavior. Therefore, this approach produces mesophase pitches with desired physical and flow (viscosity) properties to melt spin into carbon fibers or to make other carbon products by thermoplastic molding. FIG. 1 is depicted as a block (process) flow diagram. In some implementations of FIG. 1, processable mesophase pitches are made from single-ring aromatic feedstocks (e.g., xylene).

[0039] In the open system in implementations, the reaction mixture to give the mesophase pitch is pyrolyzed under inert conditions. Volatiles (e.g., low boiling point components or solvent molecules) and small molecular products produced by the thermal reaction are allowed to be carried away by a carrier gas (e.g., N2). In the closed system in implementations, the reaction mixture may be sealed under N2.

[0040] FIG. 1 is a method 100 of producing mesophase pitch from feed 102. The feed 102 includes a hydrocarbon (aromatic) compound(s). The method 100 forms or synthesizes isotropic pitch 104 (as an intermediate) from the feed 102. The method 100 forms the mesophase pitch 106 from the isotropic pitch 104 by thermal (heat) treatment of the isotropic pitch 104 resulting in thermal conversion to the mesophase pitch 106. The mesophase content of the mesophase pitch 106 (and the washed mesophase pitch 116) can be, for example, in the ranges of 1 wt% to 100 wt%, 10 wt% to 100%, 10 wt% to 90%, 40 wt% to 90 wt%, 40 wt% to 100 wt%, 50 wt% to 90 wt%, 50 wt% to 100 wt%, 60 wt% to 90 wt%, or 60 wt% to 100 wt%. As indicated, the synthesis of the mesophase pitch 106 from the isotropic pitch 104 can be in an open system or a closed system.

[0041] The feed 102 can include one or more single-ring aromatic compounds (single-ring aromatics), which are compounds having one aromatic ring. Single-ring aromatics include, for example, benzene, toluene, xylene, tetralin, etc. Xylene as feed can be a mixture of xylene isomers including o-xylene, m-xylene, and / or p-xylene. Tetralin is 1,2,3,4-tetrahydronaphthalene having has the chemical formula C10H12 and is a partially hydrogenated derivative of naphthalene. Thefeed 102 can include one or more multi-ring aromatic compounds (multi -ring aromatics), which are compounds having multiple aromatic rings (more than one aromatic ring). For instance, a two- ring aromatic compound (e.g., naphthalene, etc.) has two aromatic rings. A three-ring aromatic compound has three aromatic rings.

[0042] The reaction 108 of the feed 102 into the isotropic pitch 104 can be via an acid catalyst (e.g., acetic acid, H2SO4, etc.), such as in a vessel. The reaction 108 [chemical reach on(s)] may be a chemical reaction (chemical synthesis) in which heat may be applied. The reaction 108 may give the production of the isotropic pitch 104. The yield of the isotropic pitch 104 from the feed 102 via the reaction 108 may be, for example, in the range of 90% to 99%. The reaction 108 may form water as a byproduct so the final isotropic pitch product may be washed with water to remove acids and the trace amounts of uncreated compounds such as xylene and paraformaldehyde. The reaction 108 can be characterized as acid chemistry. For the reaction 108 of the feed 102 into the isotropic pitch 104, the feed 102 can be combined (e.g., in a vessel) with acid (e.g., acetic acid, or acetic acid and H2SO4, etc.) and paraformaldehyde to make a reaction mixture. The mixture can then be heated to produce the isotropic pitch 104. The mixture can be heated (e.g., in the vessel) to a temperature, for example, in the ranges of 40 °C to 300 °C, 40 °C to 350 °C, or 25 °C to 350 °C.

[0043] In implementations, the reaction 108 of the feed 102 into the isotropic pitch 104 may include (1) combining the feed 102 with acetic acid and paraformaldehyde, for example, at ambient temperature (e.g., in the range of 20 °C to 30 °C) to give a first mixture; (2) heating the first mixture to a temperature in the range of 40 °C to 300 °C (or 40 °C to 350 °C); and (3) mixing a second mixture including sulfuric acid and acetic acid with the first mixture at a temperature in the range of 40 °C to 300 °C (or 40 °C to 350 °C) to form a mix including the isotropic pitch 104 composition. Thus, again, the first mixture is heated to in the range of 40 °C to 300 °C (or 40 °C to 350 °C), and the reaction takes place to form the isotropic pitch including with the addition of the second mixture. Typically, a temperature is set, and the reaction is performed for a given amount of time.

[0044] The reaction conditions of this reaction 108 may be adjusted for the molecular weight distribution and the softening point of the isotropic pitch 104 compositions. Advantageously, the reaction 108 facilitates controlling the molecular weight distribution and the softening point by adjusting the molar ratio of sulfuric acid and paraformaldehyde. The softening point of the isotropic pitch 104 can increase with reaction time, the amount of sulfuric acid, and the amount of paraformaldehyde. This may be related to the increase in the molecular weight / distribution. Further, in implementations, little or no water is generally present in the reaction mixture of thereaction 108, and any residual acids can be removed by filtration after washing the residue comprising the isotropic pitch 104 composition with basic solution, thus facilitating the isolation of the isotropic pitch 104 as a highly pure material (e.g., starting materials quantitatively consumed, and isotropic pitch 104 purity is confirmed by mass spectrometry, 'H NMR, and13C NMR spectroscopy measurements).

[0045] Thus, techniques are provided that can produce high-quality synthetic isotropic pitch compositions, particularly with the ability to tune structural and other physical properties for addressing downstream application-specific needs. The isotropic pitch compositions may be used as precursors of production of mesophase pitches for carbon fiber manufacture to improve the production of highly oriented carbon fibers with desirable mechanical properties.

[0046] The method 100 includes mixing (block 110) a solvent (e.g., aromatic solvent) with the isotropic pitch 104, such as in a vessel or via in-line mixing. This mixture of the solvent and the isotropic pitch 104 has, for example, less than 23 wt% of the solvent (e.g., in the range of 2 wt% to 23 wt%), less than 25 wt% of the solvent (e.g., in the range of 3 wt% to 25 wt%), less than 30 wt% of the solvent (e.g., in the range of 5 wt% to 30 wt%), less than 40 wt% of the solvent (e.g., in the range of 3 wt% to 40 wt%), or less than 50 wt% of the solvent (e.g., in the range of 1 wt% to 50 wt%). The weight ratio of the solvent to the isotropic pitch 104 may be, for example, in the range of 0.1 to 0.5. In one example, the weight ratio is 0.3. This mixture (reaction mixture) of the solvent and the isotropic pitch 104 is for pyrolysis 112, 114 (thermal treatment, heat treatment, thermal conversion) of the mixture into the mesophase pitch 106. The solvent can be, for example, naphthalene, methyl naphthalene, xylene, toluene, tetralin, etc. The solvent(s) combined with the isotropic pitch 104 for the pyrolysis 112, 114 can be selected to adjust the composition of the mesophase pitch 106 (and thus of the washed mesophase pitch 116). In implementations, the solvent can be the same or similar as the feed 102. For instance, if the feed 102 is xylene (e.g., a mix of xylene isomers), the solvent added to (combined with) the generated isotropic pitch 104 product can be xylene. Employment of the feed 102 (or component(s) of the feed 102) as the solvent for the subsequent thermal conversion may facilitate ease of operation with the provision of the solvent. Moreover, for the pyrolysis 114 in the closed system, the reaction may be performed under pressure, for example, at least 1 pound per square inch gauge (psig), at least 5 psig, at least 20 psig, or in the ranges of 1 psig to 100 psig, or 20 psig to 100 psig. The pressure can be at least in part due to the solvent or low boiling point solvents boiling creating pressure. Thus, the reaction is under pressure for the closed system. This pressure in the pyrolysis 114 in the closed system also depends on the boiling point distribution of the entire reaction mixture including the amount of solvent added.

[0047] The mixture (from block 110) of the isotropic pitch 104 and the aromatic solvent is heated (e.g., in the pyrolysis 112 or 114) to a temperature to react to produce the mesophase pitch 106. The temperature (reaction temperature) may be, for example, at least 200°C (e.g., in the range of 200 °C to 500 °C), at least 300 °C (e.g., in the range of 300 °C to 500 °C), at least 350 °C (e.g., in the ranges of 350 °C to 475 °C, or 350 °C to 500 °C), at least 375 °C (e.g., in the ranges of 375 °C to 475 °C, or 375 °C to 500 °C), or at least 400 °C (e.g., in the range of 400 °C to 500 °C). In implementations, the reaction time may be shorter (e.g., seconds) at higher end portions of these temperature ranges and longer (e.g., hours) at lower end portions of these temperature ranges. The reaction time may be hours (e.g., 1 hour to 24 hours), minutes (e.g., 1 minute to 60 minutes), or seconds (e.g., 1 second to 60 seconds). In implementations, the reaction can be characterized as pyrolysis. As used herein, the term pyrolysis may generally be thermal conversion, thermal treatment, or heat treatment, and includes (in addition to any break down of molecules) dehydrogenation, condensation, aromatization, cyclization reactions to form larger aromatic planar molecule to increase molecular weight to form higher aromatic discotic mesophase.

[0048] In the pyrolysis 112, 114 the isotropic pitch 104 reacts (is thermally converted) at the reaction temperature to the mesophase pitch 106. In implementations, the aromatic solvent participates in the reaction to give the mesophase pitch 106. The resulting mesophase pitch 106 can have a softening point of less than 400 °C, less than 350 °C, less than 325 °C, or less than 300 °C. The reaction temperature and time can be specified to adjust or set the composition and molecular structures and thus physical properties (e.g., softening point, mesophase content) of the generated mesophase pitch 106, 116.

[0049] The reaction (e.g., pyrolysis) via the thermal treatment can be implemented in an open system (pyrolysis 112, e.g., in an unsealed vessel) or in a closed system (pyrolysis 114, e.g., in a sealed vessel, operating under pressure). The pyrolysis 112 (open system) and the pyrolysis 114 (closed system) may be in the alternative with respect to each other. The open system provides for a reaction mode in which volatiles or the smaller boiling point reaction products are carried away by a gas (e.g., inert gas or N2 gas in particular) - so the reaction vessel is not sealed (or under pressure). The thermal conversion (whether closed or open) should generally be performed under inert conditions.

[0050] The pyrolysis 112, 114 may be performed under a gas (e.g., gas blanket). The pyrolysis 112, 114 may be performed under an inert atmosphere, such as under an inert gas (e.g., N2). Again, in the pyrolysis 112 in the open system, volatiles and / or smaller molecular- weight reaction products may be stripped off from the reaction mixture (and carried away, for example, with the gas blanket or steam). The volatiles have a lower boiling point or greater volatility lower than theaverage boiling point or average volatility of the reaction mixture. The smaller molecular-weight reaction products have a molecular weight less than the average molecular weight of the products of the pyrolysis.

[0051] The mesophase pitch 106 may be washed 118 to give the mesophase pitch 116 (e.g., washed mesophase pitch). The washing may remove unreacted solvent (e.g., NP, xylene, etc.) (if present) in the mesophase pitch 106. The washing agent may be solvent. The mesophase pitch 106 can be washed, for example, with solvent such as toluene, pentane, a mixture of toluene and pentane, and the like. In implementations, this washing 118 (washing step) may remove smaller molecular weight components (e.g., including those of an isotropic fraction) from the mesophase pitch 106 enhancing more anisotropic composition to give the washed mesophase pitch 116. The washed mesophase pitch may be labeled as the final mesophase pitch in implementations. The washed mesophase pitch 116 can be more homogenous than the mesophase pitch 106 upstream of the washing. The washing 118 may improve the material by concentrating higher molecular weight components in the mesophase pitch 116. Moreover, as noted, the amount of mesophase in the washed mesophase pitch 116 can be adjusted by thermal severity (temperature and time of reactions) of the upstream pyrolysis 112 or 114 in implementations. Washing can also be used to remove (e.g., via a filter) solids formed during the thermal reaction. The solvent washing 118 of the mesophase pitch 106 may facilitate control of the softening point of the washed mesophase pitch 116, with more uniform (narrow temperature window) softening point, in the absence of high softening point solids (e.g., coke) or lower boiling point components. In embodiments, the washed mesophase pitch 116 has a softening point, for example, less than 400 °C (e.g., in the range of 200 °C to 400 °C), less than 350 °C (e.g., in the range of 200 °C to 350 °C), less than 325 °C (e.g., in the range of 200 °C to 325 °C), or less than 300 °C (e.g., in the range of 200 °C to 300 °C). The washed mesophase pitch 116 may be generally homogenous in terms of softening point and flow. The mesophase pitch 106 may be heterogenous due to the presence of small molecules, solvent, and crystallized solvent (IP) utilized for mixing (prior to pyrolysis).

[0052] The washing 118 of the mesophase pitch 106 can provide for more homogeneity in the washed mesophase pitch 116 among the liquid crystalline phases or even among the coke formation. In implementations, a mesophase system can have some fraction of coke, which in some instances can be problematic with spinning the mesophase pitch composition into carbon fiber. The term homogenous here for the washed mesophase pitch 116 may be in the sense that the flow properties are beneficially homogenous due to a narrow distribution of softening point of different phases in the materials (coke does not soften), e.g., the material flow properties are consistent with the expected rheological / flow characteristics of the pitch as a result. What can bebeneficial is a mesophase pitch without additional solids (coke) and thus to avoid a material heterogenous in a sense of different portions of the material softening at different temperature ranges.

[0053] The resulting mesophase materials (mesophase pitch 116) can be significantly homogenous when heated above softening points in having few or no solid-like objects with relatively low softening points (e.g., less than 400 °C, less than 350 °C, less than 325 °C, or less than 300 °C), and in some embodiments, the mesophase pitch 116 exhibits smooth extensional flow behavior. Therefore, the method 100 may produce mesophase pitches with desired physical and flow properties to melt spin into carbon fibers or to make other carbon products. The isotropic pitch 104 and the mesophase pitch 106, 116 are generally solid below a softening point. However, solids (e.g., coke) therein can have higher or inaccessible softening points. Therefore, when the mesophase pitch 116 is heated such that the majority of the mesophase pitch 116 becomes softened, those materials with higher softening points may generally remain solid until adequate heat is applied to raise temperature to their softening temperature. This is an issue to process (e.g., melt spinning) to make fibers, since the solids with high softening points can lead to instabilities while spinning, breaking off the fiber. Or if the high softening-point solid content is significantly present (e.g., 10 wt% to 50 wt % or more), the mesophase pitch 116 materials may causes instabilities during the extensional flow. Again, the washing 118 away (e.g., via a toluene / pentane mixture) of unreacted solvent (e.g., naphthalene) and smaller molecular weight components from the mesophase pitch 106 may result in the mesophase pitch 116 being more homogenous and promote (advance) the pitch 116 as low-softening point (e.g., less than 325 °C) mesophase product. As mentioned, an aspect is the washing 118 removes smaller molecular weight components together with solids (if any), so thus the washing 118 can be characterized as concentrating the mesophase pitch.

[0054] In implementations, the presence of the aromatic solvent with the isotropic pitch 106 in the pyrolysis 112, 114 reduces coking (formation of coke) in the pyrolysis (e.g., in the heating of the mixture of the aromatic solvent and the isotropic pitch 104) compared to if the aromatic solvent were not present in the pyrolysis. In implementations, the presence of the aromatic solvent with the isotropic pitch 104 in the pyrolysis 112, 114 or the washing 118 of the mesophase pitch 106 with solvent (e.g., toluene or pentane, or both), or a combination thereof, reduces a distribution of different softening points of material in the mesophase pitch or reduces amount of solids that soften at different temperature ranges in the mesophase pitch, or a combination thereof.

[0055] In the pyrolysis 112, 114, the presence of air (especially excessive air or large amounts of air) can be problematic for the process, such as causing crosslinking of the pitch material.Therefore, as indicated, the pyrolysis 112, 114 reactions may be performed under inert conditions (under an inert gas). However, for neomesophase production after the washing 118 is performed, air (e.g., a relatively small amount of air) may be introduced (added) to the reaction vessel (or wash vessel if different). The air may be added, for example, to the head space of the vessel. The pitch material may be heated (reheated) in the vessel under pressure in presence of the air to produce (generate) neomesophase pitch from isotropic pitch remaining in the mesophase material. The presence of the air may facilitate or promote formation of the neomesophase content. The amount of air in the vessel (e.g., in the head space) may be a relatively small amount, e.g., in the range of 0.1 wt% to 10 wt% (or greater) of the gas and / or vapor in the vessel (e.g., in the head space of the vessel). As mentioned, this production of neomesophase may be performed under pressure, such as in the ranges of 5 psig to 100 psig, or 5 psig to 50 psig. As the vessel contents are heated, solvent in the vessel vaporizes increasing pressure in the vessel.

[0056] In conclusion, embodiments provide for forming mesophase pitch in synthetic isotropic pitch compositions derived from hydrocarbon (e.g., single-ring and / or multi-ring aromatic feedstocks). The forming of the mesophase pitch includes co-feeding single-ring aromatic solvents and / or multi-ring aromatic solvents (e.g., naphthalene) with the derived isotropic pitch. In a first general step, the synthetic isotropic pitch is produced by acid catalytic reaction of aromatic feedstock. Subsequently, in a second general step, thermal treatment of the isotropic pitch in the presence of solvent (e.g., identical aromatic feedstock as for producing the isotropic pitch, or other aromatic solvents, or mixtures thereof) to further increase the molecular weight of the isotropic pitch to form more anisotropic mesogenic molecules to form the mesophase pitch.

[0057] In embodiments, the processes may include heat treating a blend of an isotropic pitch and a single-ring aromatic material, to produce a pitch by heat treatment at higher temperature (e.g. greater than 350 °C) within an enclosed vessel under inert conditions, to produce mesophase content of about 5 vol% to 100 vol%, based on the total volume of the reacted pitch, and softening point (Ts) in the range of 200 °C to 400 °C. In implementations, NP is utilized as a solvent at less than 23% by mass of the mixture, or less than 30% by mass of the mixture. The weight fraction of the solvent can vary, for example, from 0.1% to 50% relative to the isotropic pitch by weight. The solvent can be selected from multiple solvents including the aromatic feed used to make the isotropic pitch or other aromatic solvents (e.g., xylene, tetralin, etc.) to tune the pitch composition. The aromatic solvent may include naphthalene, methyl naphthalene, toluene, xylene, or tetralin, or any combinations thereof. In implementations with the reaction chamber (vessel) closed, the solvent molecules may condense back, while higher temperature may induce additional chemical reactions under pressure in comparison to the reaction in the absence of solvent. Aromatic solventsmay reduce the viscosity and may participate in chemical reactions with original feed material. After the thermal conversion, a majority of the unreacted or retaining solvent molecules including the lower molecular weight components from the pitch could be removed, for example, by solvent deasphalting. Additionally, temperature and time can be used as a handle to produce mesophase pitch with different composition molecular structures, and thus physical properties (e.g., softening point, mesophase content, etc.). Moreover, as indicated, the material in an open chamber or reactor (under inert atmosphere) after subjecting to heating in the closed chamber or reactor, can be reheated to remove the lower boiling point components, thereby concentrating the mesogenic molecules.

[0058] In embodiments, the reaction mixture (isotropic pitch and feed aromatics) for the mesophase pitch can be heat treated to provide a more uniform reaction temperature for mesophase formation in a reaction chamber. In an open system, the low boiling point components are allowed to be stripped away by the carrier gas (e.g., N2), further concentrating the aromatics during chemical reactions. In this case of the open system, the temperature gradients might be larger. For the open system, the majority of the aromatic solvent (along with the low molecular components present in the pitch and in byproducts of reaction) may leave the heating chamber (vessel). In implementations, the remnant solvent feed present in the vessel at higher temperature takes part in additional chemical reactions leading to a new composition of matter (different mesophase molecular structures depending on the added solvent and reaction conditions). Thus, additionally having the aromatic solvent advantageously may give a different mesophase composition than in the absence of solvent. This technique may involve subsequent washing of the resulting mesophase material in solvent (e.g., pentane) and in which solvent selection and amounts (and washing time) may give control of softening point of the pitch material. Washing may remove most or all of the remaining unreacted solvent molecules (e.g., naphthalene) and / or small molecular weight components. The washing step may improve the property' of the pitch material by concentrating the higher molecular weight components, resulting in a system that exhibits homogeneity in processing (e.g., spinning) in the liquid crystalline state. In several embodiments, after the washing, the mesophase materials have softening points less than 300°C.

[0059] Embodiments may be based on a blend of synthetic pitch and aromatic feed offers a beneficial route to control the composition and flow properties of the anisotropic pitch material formed. In one embodiment, a neomesophase material results, which can be further heat treated to produce high mesophase materials at a faster rate. The route can produce high mesophase materials obtained herein having high MCRT (e.g., greater than 75%) and lower softening points, appropriate for production of high-performance carbon fibers. It is apparent that mesophasepitches with higher mesophase contents (e.g., greater than 60%) prepared with this approach can be spun into fiber form, and can be subsequently stabilized, carbonized and graphitized to form high-modulus, high-strength carbon fibers. This approach is not limited to one composition; mesophase materials from various single aromatics (e.g., toluene, naphthalene, tetralin, mixed aromatics, etc.) can be produced in a scalable manner.

[0060] An embodiment is a method of producing mesophase pitch, including forming isotropic pitch by reacting a feed, paraformaldehyde, acetic acid, and sulfuric acid at a temperature in a range of 40 °C to 350 °C, wherein the feed includes a single-ring aromatic compound or a multiring aromatic compound, or both. In implementations, the feed can be or include the single-ring aromatic compound, wherein the single-ring aromatic compound is, for example, toluene, xylene, or tetralin, or any combinations thereof. In implementations, the feed can be the single-ring aromatic compound that is, for example, xylene isomers. The method includes mixing the formed isotropic pitch with a first solvent (e.g., an aromatic solvent) to give a mixture. In implementations, the first solvent as an aromatic solvent can include, for example, naphthalene, methyl naphthalene, toluene, xylene, or tetralin, or any combinations thereof. In implementations, the aromatic solvent comprises naphthalene. In implementations, the aromatic solvent is the same as the feed. In implementations, the mixture can include the first solvent (e.g., aromatic solvent), for instance, in a range of 1% to 50% by weight. The method includes heating the mixture to a temperature of at least 350 °C to give mesophase pitch, and washing the mesophase pitch with a second solvent (e.g., toluene or pentane, or both), wherein the mesophase pitch comprises a softening point less than 400 °C. In implementations, the presence of the first solvent in the mixture reduces coking (formation of coke) in the heating of the mixture compared to if the first solvent were not present in the heating of the mixture (e.g., if the mixture was simply the isotropic pitch without the first solvent). In implementations, the presence of the first solvent in mixture or the washing of the mesophase pitch with the second solvent, or a combination thereof, reduces a distribution of different softening points of material in the mesophase pitch or reduces amount of solids that soften at different temperature ranges in the mesophase pitch, or a combination thereof. In implementations, the heating of the mixture involves heating the mixture in a vessel under a gas in the vessel, wherein the gas comprises an inert gas (e.g., N2). heating the mixture comprises heating the mixture in a sealed vessel as a closed system, and wherein heating the mixture gives a reaction under pressure in the sealed vessel, heating the mixture comprises heating the mixture in an unsealed vessel as an open system, and wherein the method comprises removing volatiles and low boiling point reaction components and at least some of the first solvent from the unsealed vessel during the heating. The mesophase content of the formed mesophase pitch before and / orafter washing can be, for example, in the ranges of 1 v % to 100 wt%, 10 wt% to 100%, 10 wt% to 90%, 40 wt% to 90 wt%, 40 wt% to 100 wt%, 50 wt% to 90 wt%, 50 wt% to 100 wt%, 60 wt% to 90 wt%, or 60 wt% to 100 wt%. In implementations, the mesophase pitch after the washing comprises the softening point in a range of 200 °C to 400 °C.

[0061] Another embodiment is a method of producing mesophase pitch, including preparing isotropic pitch by reacting a feed including an aromatic compound with paraformaldehyde, acetic acid, and sulfuric acid, wherein the aromatic compound(s) can include a single-ring aromatic compound or a multi-ring aromatic compound, or both. In implementations, the aromatic compound includes the single-ring aromatic compound(s) comprising toluene, xylene, or tetralin, or any combinations thereof. In implementations, the aromatic compound includes the single-ring aromatic compound comprising xylene. The method includes combining the isotropic pitch with a first solvent comprising an aromatic solvent (e.g., the aromatic compound). In implementations, the isotropic pitch and the first solvent as combined comprise the first solvent at less than 50 wt%. The method includes heating the isotropic pitch and the first solvent as combined to a temperature in a range of 350 °C to 500 °C to give mesophase pitch. In implementations, the heating can involve, for example, heating the isotropic pitch and the first solvent as combined in a vessel under an inert atmosphere in the vessel. In implementations, the presence of the first solvent with the isotropic pitch reduces formation of coke in the heating of the isotropic pitch. The method includes washing the mesophase pitch with a second solvent (e.g., toluene or pentane, or both), wherein the mesophase pitch comprises a softening point less than 400 °C after the washing. In implementations, the method includes after washing the mesophase pitch, reheating the mesophase pitch in the presence of air under pressure (e.g., in the ranges of 5 psig to 100 psig, or 5 psig to 50 psig), thereby converting residual isotropic pitch (of the mesophase pitch) into neomesophase pitch. The amount of air may be a relatively small amount, such as in the range of 0. 1 wt% to 10 wt% of the gas and / or vapor in the vessel (e.g., in the head space of the vessel) in which the reheating is performed. As the vessel contents are heated, solvent in the vessel vaponzes increasing pressure in the vessel. The method may include forming carbon fibers from the mesophase pitch. The method may include forming a graphite product for a battery from the mesophase pitch.Additional Embodiments

[0062] Accordingly, the present disclosure may provide for forming mesophase pitch in synthetic isotropic pitch compositions derived from hydrocarbon single-ring or multi-ring aromatic feedstocks by co-feeding single-ring and / or multi-ring aromatic solvents and heattreating the mixture. The methods and systems may include any of the various features disclosed herein, including one or more of the following statements.

[0063] Embodiment 1. A method of producing mesophase pitch, comprising: forming isotropic pitch by reacting a feed, paraformaldehyde, acetic acid, and sulfuric acid at a temperature in a range of 40 °C to 350 °C, wherein the feed comprises a single-ring aromatic compound or a multiring aromatic compound, or both; mixing the isotropic pitch with a first solvent comprising an aromatic solvent to give a mixture; heating the mixture to a temperature of at least 350 °C to give mesophase pitch; and washing the mesophase pitch with a second solvent, wherein the mesophase pitch comprises a softening point less than 400 °C.

[0064] Embodiment 2. The method of Embodiment 1, wherein the feed comprises the singlering aromatic compound comprising toluene, xylene, or tetralin, or any combinations thereof.

[0065] Embodiment 3. The method of Embodiment 1, wherein the feed comprises the singlering aromatic compound comprising xylene isomers.

[0066] Embodiment 4. The method of any preceding Embodiment, wherein the mixture comprises the first solvent in a range of 1% to 50% by weight.

[0067] Embodiment 5. The method of any preceding Embodiment, wherein the aromatic solvent comprises naphthalene, methyl naphthalene, toluene, xylene, or tetralin, or any combinations thereof.

[0068] Embodiment 6. The method of any one of Embodiments 1 to 4, wherein the aromatic solvent comprises naphthalene.

[0069] Embodiment 7. The method of any one of Embodiments 1 to 4, wherein the aromatic solvent is same as the feed.

[0070] Embodiment 8. The method of any preceding Embodiment, wherein heating the mixture comprises heating the mixture in a vessel under a gas in the vessel, and wherein the gas comprises an inert gas.

[0071] Embodiment 9. The method of any preceding Embodiment, wherein presence of the first solvent in the mixture reduces coking in the heating of the mixture.

[0072] Embodiment 10. The method of any preceding Embodiment, wherein presence of the first solvent in mixture or the washing of the mesophase pitch with the second solvent, or a combination thereof, reduces a distribution of different softening points of material in the mesophase pitch or reduces an amount of solids that soften at different temperature ranges in the mesophase pitch, or a combination thereof.

[0073] Embodiment 11. The method of any preceding Embodiment, wherein heating the mixture comprises heating the mixture in a sealed vessel as a closed system, and wherein heating the mixture gives a reaction under pressure in the sealed vessel.

[0074] Embodiment 12. The method of any one of Embodiments 1 to 10, wherein heating the mixture comprises heating the mixture in an unsealed vessel as an open system, and wherein the method comprises removing volatiles and low boiling point reaction components and at least some of the first solvent from the unsealed vessel during the heating.

[0075] Embodiment 13. The method of any preceding Embodiment, wherein the second solvent comprises toluene or pentane, or both, and wherein the mesophase pitch after the washing comprises the softening point in a range of 200 °C to 400 °C.

[0076] Embodiment 14. A method of producing mesophase pitch, comprising: preparing isotropic pitch by reacting a feed comprising an aromatic compound with paraformaldehyde, acetic acid, and sulfuric acid, wherein the aromatic compound comprises a single-ring aromatic compound or a multi-ring aromatic compound, or both; combining the isotropic pitch with a first solvent comprising an aromatic solvent; heating the isotropic pitch and the first solvent as combined to a temperature in a range of 350 °C to 500 °C to give mesophase pitch; and washing the mesophase pitch with a second solvent, wherein the mesophase pitch comprises a softening point less than 400 °C after the washing.

[0077] Embodiment 15. The method of Embodiment 14, wherein the aromatic compound comprises the single-ring aromatic compound comprising toluene, xylene, or tetralin, or any combinations thereof, and wherein the isotropic pitch and the first solvent as combined comprise the first solvent at less than 50 weight percent.

[0078] Embodiment 16. The method of Embodiment 14 or Embodiment 15, wherein presence of the first solvent with the isotropic pitch reduces formation of coke in the heating of the isotropic pitch.

[0079] Embodiment 17. The method of Embodiments 14 to 16, wherein the aromatic compound comprises the single-ring aromatic compound comprising xylene.

[0080]

[0081] Embodiment 18. The method of Embodiments 14 to 17, wherein the aromatic solvent comprises the aromatic compound.

[0082] Embodiment 19. The method of Embodiments 14 to 18, wherein heating comprises heating the isotropic pitch and the first solvent as combined in a vessel under an inert atmosphere in the vessel.

[0083] Embodiment 20. The method of Embodiments 14 to 19, wherein the second solvent comprises toluene or pentane, or both.

[0084] Embodiment 21. The method of Embodiments 14 to 20, comprising after washing the mesophase pitch, reheating the mesophase pitch in presence of air under pressure, thereby converting residual isotropic pitch into neomesophase pitch.

[0085] Embodiment 22. The method of Embodiments 14 to 21, comprising forming carbon fibers from the mesophase pitch.

[0086] Embodiment 23. The method of Embodiments 14 to 22, comprising forming a graphite product for a battery from the mesophase pitch.

[0087] To facilitate a better understanding of the present invention, the following examples of certain aspects of some embodiments are given. In no way should the following examples be read to limit, or define, the entire scope of the disclosure.

[0088] While the disclosure has been described with respect to a number of embodiments and examples, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope and spirit of the disclosure as disclosed herein. Although individual embodiments are discussed, the present disclosure covers all combinations of all those embodiments.

[0089] Many alterations, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description without departing from the spirit or scope of the present disclosure and that when numerical lower limits and numerical upper limits are listed herein, ranges from any lower limit to any upper limit are contemplated.

[0090] EXAMPLES

[0091] These Examples are given only as examples and not meant to limit the present techniques. In the Examples, synthetic isotropic pitches were synthesized from mixed xylenes (as single-ring aromatics) using an acid catalyst (H2SO4) in the presence of paraformaldehyde. The synthetic procedure was in accordance with the disclosure in the aforementioned US patent application based on WO2022 / 211869A9, and as generally discussed above. In some of the Examples, naphthalene (NP) solvent was added to the isotropic pitches at room temperature so that in the resulting mixture has 23 wt% of NP relative to pitch. This is 23 wt% NP and 77 wt% isotropic pitch. Alternatively, higher solvent content may be chosen with the precursor isotropic pitch. Alternatively, a lower NP concentration (e.g., 1-22 wt%) or higher NP concentration (e.g., 24-40 wt%) can be considered.

[0092] In this example, thermal treatment of the isotropic pitch with the naphthalene was performed utilizing a high temperature oven above 390 °C for different times to convert isotropicpitches into mesophase pitches. To run pyrolysis under a closed system (e.g., vessel), a metallic crucible was used, and the samples were loaded in a glove box to give an inert atmosphere during reactions. Additionally, N2 was purged inside the chamber holding the reaction mixture in the glove box. For open system pyrolysis, a thermal gravimetric analysis (TGA) oven and hot-stage microscope were utilized, both were purged with N2 gas. Presence of mesophase was visualized by polarized light microscopy and confirmed by x-ray scattering. Thermal characterization was performed with TGA. Molecular composition of the produced mesophase pitch was evaluated using Fourier-transform ion cyclotron resonance (FTICR) mass spectrometry. Green mesophase pitch fibers were pulled under inert atmosphere (e.g., glove box) above the softening temperature of the produced mesophase pitch materials.

[0093] Production of mesophase pitch from isotropic synthetic pitch:

[0094] To produce mesophase pitch from isotropic pitch, 20 grams of the synthetic isotropic pitch was added to a vessel which was subsequently sealed under inert conditions inside a glove box. The material was then heated via a high temperature oven to 400 °C or 425 °C with a heating rate of 25 °C / min and then maintained at the temperature for 2-24 hours (matenal was contained within the vessel). After isothermal heat treatment, the chamber was cooled to room temperature over time period of 2h and then, the vessel was opened and degassed inside a fume hood. The heat treatment was followed by a deasphalting step to remove the lighter products from the material and this permitted to form a more homogenous system. For this washing step (deasphalting), approximately 10 grams of pitch material was added to a beaker and dissolved in 10 milliliters (ml) of toluene (at about 1 : 1 wt% mixture) and stirred at 70 °C for 10 minutes. Subsequently, 100 ml of pentane was added, and the mixture stirred at room temperature for 10 minutes before placing the beaker to dry ice. The material was cooled by the dry ice for 1 hour and then filtered. The filter cake was subsequently washed with excess pentane and dried in a vacuum oven at 50 °C overnight to remove the remaining light products. Open system measurements were performed in a TGA at 425 °C under N2 atmosphere. In this case, the volatiles or lighter / low boiling point reaction products were stripped off from the pitch sample via carrier gas (N2). Even though, washing is utilized to remove lighter molecules (e.g., in the closed heating), the sample could be taken after heating, open the vessel and reheat to higher temperatures (e.g., 425 °C), maintain there (e.g., for 10 minutes) to remove the lighter molecules (low boiling point); thus, a washing step can be avoided. This may be implemented in an industrial setting and thus reducing cost by avoiding washing steps.

[0095] Production of mesophase pitch from isotropic synthetic pitch in the presence of naphthalene solvent:

[0096] For a closed system, 20 grams of synthetic isotropic pitch and 6 grams of naphthalene were added to a vessel and was sealed under inert conditions. This is considered 23 wt% naphthalene solvent in the mixture. The weight ratio of naphthalene to isotropic pitch is 0.3. The material (isotropic pitch and naphthalene) was then heated via a high temperature oven to 400 °C or 425 °C with a heating rate of 25 °C / min and kept isothermal for 2-24 hours. When the heat treatment was completed, the reaction vessel was cooled to room temperature, opened, and subsequently degassed inside a fume hood. A control experiment was performed in which the pitch and the naphthalene solvent were enclosed within the crucible (reaction vessel) at ambient conditions. Even in this case, the sample amount was such that it filled the crucible with less (or minimum) air gap (head space within the crucible) when subjected to pyrolysis. This was done to reduce or minimize the oxidation at higher temperatures. The terms crucible and reaction chamber are used interchangeably.

[0097] The heat treatment was followed by a deasphalting step of the material (product of the heat treatment) to remove the lighter products from the material. Approximately 10 ml of the material was added to a beaker and dissolved in 10 ml of toluene (about 1: 1 wt% mixture) and stirred at 70 °C for 10 minutes. Subsequently, 100 g of pentane was added and stirred at room temperature for 10 minutes before placing the beaker to dry ice. The material was cooled by the dry ice for 1 hour and then the material was filtered. The filter cake was washed with excess pentane and dried in a vacuum oven at 50 °C overnight to remove the remaining light products.

[0098] For an open system, mesophase pitches with and without solvent were also heat treated under inert conditions as stated above. However, with an open system, the volatiles and majority of solvent molecules escaped from the heating chamber via carrier N2 gas during the heat treatment.

[0099] FIG. 2 is a general scheme 200 of reaction generally consistent with the Examples. The depicted general scheme 200 gives two steps 202, 204 to produce synthetic mesophase pitches 206 from mixed xylenes 208 (different isomers). Step 202 (synthesis) may have a reaction time of seconds (e.g., 5-60 seconds) to several hours (e.g., 2-24 hours) and the temperature may be, for example, 25-350 °C. Step 204 (reaction that can be a thermal conversion) may have a reaction time of seconds (e.g., 5-60 seconds) to several hours (e.g., 2-24 hours) and the temperature may be, for example, 350-500 °C, 350-500 °C, or 400-450 °C. Indicated is the hypothesized molecular weight growth at each of the two steps 202, 204.

[0100] The mixed xylenes 208 can be analogous to the feed 102 of FIG. 1. The produced mesophase pitch 206 can be analogous to the mesophase pitch 106, 116 of FIG. 1.

[0101] The first step 202 may be analogous to the reaction 108 of FIG. 1. The isotropic pitch 210 formed as a precursor or intermediate may be analogous to the isotropic pitch 104 of FIG. 1. The second step 204 may be analogous to the pyrolysis 112, 114 of FIG. 1.

[0102] The reaction temperature of the second step 204 reaction may be, for example, at least 200°C (e.g., in the range of 200 °C to 500 °C), at least 300 °C (e.g., in the range of 300 °C to 500 °C), at least 350 °C (e.g., in the ranges of 350 °C to 475 °C, or 350 °C to 500 °C), at least 375 °C (e.g., in the ranges of 375 °C to 475 °C, or 375 °C to 500 °C), or at least 400 °C (e.g., in the range of 400 °C to 500 °C). As discussed, the second step 204 reaction time may be hours (e.g., 1 hour to 24 hours), minutes (e.g., 1 minute to 60 minutes), or seconds (e g., 1 second to 60 seconds). The second step 204 reaction time may be, for example, in the range of 3 seconds to 24 hours. In implementations, the reaction can be characterized as pyrolysis. As used herein, the term pyrolysis may generally be thermal conversion, thermal treatment, or heat treatment, and includes (in addition to any break down of molecules) condensation, aromatization, cyclization reactions to form larger aromatic planar molecule to increase molecular weight to form discotic nematic phase.

[0103] Results and Discussion

[0104] FIG. 3 notes the synthetic pitches 210, 206 derived from mixed xylenes (e.g., 208 of FIG. 2) and shows a representative depiction of a fiber 304 pulled 302 from the mesophase pitch 206 at 310 °C under inert conditions. The isotropic pitch 210 (e.g., prepared or formed as in the synthesis 202 of FIG. 2) was a yellowish powder. The mesophase pitch 206 prepared as depicted (e.g., formed as in the heat treatment 204 of FIG. 2) was a dark or blackish material. In the thermal conversion 204 (heat treatment), the isotropic pitches 210 were heat treated at 400 °C, 425 °C for different times. Thus, FIG. 3 is a scheme 300 consistent with the Examples and depicts forming mesophase pitch 206 by thermal conversion 204 (via heat treatment) from isotropic pitch 210 and hand pulling 302 carbon fibers from the mesophase pitch 206 by heating above the softening point. Again, a pulled carbon fiber 304 is shown.

[0105] The molecular weight distribution can be tuned (adjusted, set, specified) by utilizing (specifying) different reaction conditions (e.g., stoichiometry, concentration of H2SO4 in the reaction mixture, time and temperature of reaction, etc ). The molecular weight may grow primarily by bridging the aromatic groups to form longer chain-like molecules [e.g., see FIG. 2 (scheme 200)]. This is consistent with the FTICR-MS spectrum as shown in FIG. 5 A, where a population of trimer and higher orders in the molecular weight distribution are observed, which agrees with the nuclear magnetic resonance (NMR) measurements.

[0106] Morphology and molecular order of the pitch materials were investigated using x-ray scattering and polarized light microscopy measurements. Isotropic pitches displayed amorphousnature (a broad high angle peak maximum located at about 4.8 A). The physical properties of the xylene-derived pitch materials are listed in the Table 1. The isotropic material based on mixed xylene precursor had a softening point of 181 °C. When subjected to pyrolysis in the presence of solvent (e.g., naphthalene), the resulting materials after toluene / pentane washing showed homogenous birefringence with a dense grainy texture.

[0107] The polarized light micrograph (taken via quarter wave plate) of the xylene-derived mesophase pitch material displayed more uniform grainy birefringent texture throughout the sample. The xylene-derived mesophase pitch material was prepared by co-pyrolyzing xylenederived isotropic pitch material with naphthalene in a sealed vessel (sealed under ambient conditions) at 400 °C for 4 hours. With the reaction performed under pressure, a completely different morphology (unique) is generated.

[0108] FIG. 4 is a plot 400 of the x-ray scattering data of the xylene-derived mesophase pitch. The x-ray scattering data indicates a weak mesophase reflection corresponding to a scattering vector, q, of about 1.79 reciprocal angstroms (A-1) (curve 402, shifted vertically for clarity). The isotropic sample (curve 404) shows a broad reflection.

[0109] The data indicates a clear high angle reflection at a spacing of about 3.5 A (corresponding scattering vector q~l .79 A'1), due to nematic order, but lower in intensity than the pitch prepared in the absence of solvent. In addition, a second contribution to the intensity profile is also evident at a spacing of about 3.76 A (corresponding scattering vector q~l .67 A'1), which is presumably due to the presence of material that is not well ordered (lower order parameter in comparison to the reflection corresponding to the nematic material at the scattering vector q~l .79 A'1). It can be reasonably hypothesized that the material underwent condensation chemistry, thereby increasing the molecular size and aromaticity, subsequently increasing the strength of intermolecular interactions (evidently smaller molecular spacing in comparison to isotropic pitch). The x-ray observation is corroborated by the optical data, which showed fine grainy texture indicating relatively short-range nematic order (e.g., few microns) than seen in mesophase pitches studied previously. This mesophase material is mesophase material co-existing with a neomesophase material, where the neomesophase material can be readily transformed into a mesophase at higher temperatures. A longer residence time during thermal conversion at higher temperature in the presence of solvent may yield higher mesophase content in the final material as well. Strikingly, these samples had smooth extensional flow behavior above the softening point, and as a result fiber formation was found feasible (e.g., as indicated with pulling fibers noted with respect to FIG. 3).

[0110] FIG. 5A and FIG. 5B are mass spectra (FTICR-mass spectra) of certain pitch from the Examples. Molecular weight (MW) is given along the base axis. The mass spectra (i) is of synthetic isotropic pitch made from xylene isomers, as discussed. The mass spectra (ii) is of the corresponding mesophase pitch made from the isotropic pitch with naphthalene within a sealed vessel (sealed under air) as a closed pyrolysis system. The mass spectra (iii) is of the corresponding mesophase pitch after being washed with a toluene / pentane mixture. The curve 502 is the molecular weight (mw) distribution. The curve 504 is the Z Class or hydrogen deficiency, and is a measure of aromaticity, with lower negative numbers meaning higher aromaticity (higher C / H ratio). The width of each peak in curve 504 represents the average number of isomers for each molecular weight distribution peak value of 502. To be specific, the curves 502, 504 are distributions made via projections of the data along their respective axes.[OHl] The mass spectra (i) of the isotropic pitch indicated a broad distribution of molecular weights with modulations of intensities approximately at every multiple of monomer masses, starting from trimers. The comparison spectra (ii) of different mesophase pitch samples prepared in the closed environment (sealed under air) indicated that the sample pyrolyzed with naphthalene solvent has an increased aromaticity (Z-class, which is a measure of aromaticity). After washing the mesophase pitch with toluene / pentane mixture, the spectra (iii) indicated that the lower molecular weight tail end was reduced in its contribution as expected. The Tsof the washed mesophase pitch was measured to be 297.6 °C. The Tsmeasurement is generally a continuous heating measurement.

[0112] Further, the mesophase pitch samples as prepared in the presence of naphthalene solvent indicate much broader Z-class for different bands. The bands that are attributed to the molecular components associated with trimer, tetramer or higher fractions etc., show an increase in the z- class intensity distribution suggesting a substantial increase in aromaticity or mesogenic nature of the material. The bands associated with multi-monomer components in the mesophase materials prepared by co-pyrolyzing with the solvent system show a generally continuous distribution in comparison to the isotropic feed material.

[0113] FIG. 6 is a plot of TGA curves of certain pitches (in the Examples), depicting mass loss profiles. The thermal stability of the isotropic and mesophase synthetic pitches was determined by TGA performed at a heating rate of 10°C min'1from room temperature to 700 °C under N2 atmosphere. The curve 600 is for the synthetic isotropic pitch. The curve 602 is for a blend of the isotropic pitch (77 wt% of the blend) and naphthalene (23 wt% of the blend) before being subjected to heating. The curve 604 is for the mesophase pitch derived from isotropic pitch alone by heating at 400 °C for 4 hours and sealed under N2 during the heating (pyrolysis). The curve606 is for the mesophase pitch derived from isotropic pitch (with naphthalene) by heating at 400 °C for 4 hours and sealed under air (head space in the reactor vessel) during the heating (pyrolysis). The curve 608 is for the mesophase pitch derived from isotropic pitch / naphthalene blend by heating at 425 °C for 4 hours and sealed under N2 during the heating (pyrolysis).

[0114] Again, the mass loss profiles for the pitches are depicted in FIG. 6. The isotropic synthetic pitch showed less than 2% weight loss up to 240 °C, then a loss of 5% weight at 340 °C, and subsequent loss of -60% at 540 °C; and finally, a char yield of -31% at 700 °C is obtained. A blend (before pyrolysis) of the isotropic synthetic pitch (77 wt%) and naphthalene (23 wt%) showed 29% weight loss at 340 °C that includes evaporation of naphthalene and volatiles or low boiling point reaction products from the pristine isotropic synthetic pitch. After taking the 5% reduction of mass of the pristine isotropic material at this temperature into consideration, it is estimated that approximately 5-6% of the naphthalene solvent retained in the material. The final remaining weight of the blend at 700 °C is about 24%, which is higher than the expected value considering the total mass fraction of the isotropic material in the blend (70%), in comparison to the mass loss of the pure material at that temperature (about 31%). This also clearly suggests that the remnant naphthalene solvent molecules also take part in chemical reaction at higher temperatures for the blend material subjected to pyrolysis, but in an open system where the volatiles or the reaction products are permitted to be stripped away. The mesophase pitch prepared with 23 wt% naphthalene within the closed crucibles (sealed in air) displays a one-step decomposition with an onset at approximately 280 °C and the mass-loss saturating at approximately 550 °C; subsequently yielding 55 % char at 700 °C. All these analytical results indicate that heat treatment in the presence of naphthalene and subsequent processing steps (e.g., washing) generates a different anisotropic material.

[0115] Inspired from the TGA results, a second method to prepare mesophase pitches in an open system (under N2) in which the volatiles or the reaction products were allowed to be carried away by the flowing N2 gas. To demonstrate the efficacy of this approach, a TGA system was utilized to conduct isothermal pyrolysis and in situ microscopy experiments using a hot stage. The main rationale for these experiments was founded on the TGA observation that approximately 5-6% of the naphthalene solvent was retained at higher temperatures (e.g., 350 °C) when blended with isotropic pitch. It is likely that remnant naphthalene could participate in chemical reactions, which could lead to an alternate path for making mesophase pitches of different composition.

[0116] To illustrate such, two isotropic pitch samples were prepared. The first was isotropic pitch with no NP. The second was isotropic pitch in a blend in which the isotopic pitch was 77wt% of the blend and naphthalene (NP) was 23 wt% of the blend. The mesophase pitches generated from these two samples were analyzed via optical microscopy.

[0117] FIG. 7 shows cross-polarized light micrographs acquired via a waveplate (a and b). Cross-polarized light micrographs were acquired via a quarter-wave plate. FIG. 7 (a) is from a mesophase pitch derived by 1 hour of pyrolysis at 425 °C of the first sample [isotropic pitch (without NP)]. FIG. 7 (b) is from a mesophase pitch derived by 1 hour of pyrolysis at 425 °C of the second sample [isotropic pitch (with NP)]. To form the mesophase pitch, these two samples of isotropic pitch (one without NP and one with NP) were heated to 425 °C and held isothermal inside the TGA instrument (equipped with continuous purging with N2 gas). After heating for 1 hour, the sample without NP showed mesophase droplets (see FIG. 7 (a)), with an area coverage of about 36%, while the sample with NP (see FIG. 7 (b)) showed much larger droplets with a mesophase content of about 63% (approximately 75% greater than the sample without NP). Thus, the presence of NP solvent assisted with the rate of thermal conversion, though the mechanism is not clear at this point. It is noted that the volatiles and reaction products were allowed to escape from the reaction chamber and were carried away by the N2 gas flow. The presence of small crystalline particles of NP were evident in the optical micrographs of the sample prepared with NP, which can be washed away with toluene / pentane solvent or by pulling vacuum above the melting point of NP (approximately 78 °C). The scalability of this approach by performing pyrolysis inside a carbonation oven (or other ovens such as MCR unit or larger reactors) under inert atmosphere is assumed feasible.

[0118] In a second approach, isotropic pitch was placed in a vessel sealed under N2 atmosphere, and a blend of isotropic pitch (77 vrt% of the blend) and NP (23 wt% of the blend) was placed in a vessel sealed under N2 atmosphere. For both, the thermal reaction was conducted under the inert atmosphere (N2) at 425 °C for 4 hours. After the reaction, both mesophase pitch products were washed with a toluene / pentane mixture. The mesophase pitch prepared without NP solvent showed a softening point of about 318.1 °C, while the mesophase pitch prepared with NP for the same duration showed a softening point of about 263.5 °C. Strikingly, the mass spectra shown in FIGS. 10A and 10B indicate that the mesophase pitch products prepared with and without NP, respectively, have nearly identical peak positions for the populations of molecular components (trimer and higher orders), while the average peak position shifts to lower molar mass in comparison to the pristine isotropic pitch. However, Z-class versus carbon number plots clearly indicate that aromaticity shows higher values after pyrolysis, indicating the formation of more condensed mesogenic discotic species. In addition, it is clearly discernible that the mesophase pitches have a narrower and continuous population of molar masses at each bands that correspondto multiples of monomer masses in comparison to the isotropic pitch. The low molecular weight [e.g., below 400 Daltons (Da)] contributions were also significantly lower in the mesophase products due to deasphalting step performed after the thermal conversion. These differences in molecular mass distribution may lead to changes in the material physical properties including the flow behavior (e.g., viscosity, softening point). Table 1 summarizes the properties of the pitch.

[0119] Table 1 gives the physical properties of different pitch materials. The mesophase pitch was prepared within a high temperature oven. For the yield calculation in the blend, the blend was considered to have 23 wt% naphthalene solvent with the synthetic pitch composition in the starting material. The yield is the total mass of the final product divided by the mass of the starting material. Yield can change, for example, from 30% to 90%, depending for instance on isotropic composition as well as thermal treatment conditions. A few example numbers for yield are given in Table 1 below.Table 1. Physical Properties of Pitch

[0120] In order to examine the composition of the pyrolyzed samples sealed under N2, polarized optical microscopy experiments were performed. The samples were cooled down to room temperature after pyrolysis and embedded in epoxy subsequently mirror polished to get crosssections. The images as shown in FIG. 8 indicate liquid crystal ordering in mesophase materials prepared in the presence (FIG. 8 c, d) and absence (FIG. 8 a, b) of naphthalene solvent. The crosspolarized light images and the corresponding fluorescent light images of the synthetic pitch(without NP) sample pyrolyzed at 425 °C for 4 hours indicate about 35% of mesophase content. This sample shows a broader distribution of mesophase droplets and droplet aggregates in comparison to the sample prepared with naphthalene under identical pyrolysis conditions, where the sample prepared with naphthalene showed only 25% mesophase and more homogenous (similar size) droplets. Longer pyrolysis may increase the mesophase content while the softening point remains in a reasonably lower temperature range, suitable for fiber spinning. The mesophase content can be further increased either by increasing the reaction temperature or time, or both.

[0121] FIG. 8 shows four optical micrographs of pitch samples. Images (a) and (c) (large area) are cross-polarized light micrographs acquired via a full wave-plate. Images (b) and (d) are the corresponding fluorescent light micrographs (acquired with Xex= 450-490 nm). The images compare mesophase content after 4 hours of py rolysis of isotropic pitch (in the absence of NP) at 425 °C, 4h performed inside a closed vessel under inert conditions within a high temperature oven. The sample shown in images (a) and (b) was prepared by pyrolyzing pristine synthetic pitch material. The sample shown in images (c) and (d) was prepared by pyrolyzing at 425 °C, 4h, a blend of synthetic pitch with 23 wt% naphthalene in the blend (after washing). Both samples were sealed under inert conditions within the crucibles and N2 gas was purged during the thermal conversion to give the inert conditions. In the fluorescence images, darker regions represent the mesophase while lighter regions represent the isotropic phase. The fluorescent emissions of pitch aromatic molecules are quenched by aromatic association with adjacent molecules, e.g., pi-bonds, pi-pi stacking, and other electron transfer, resulting in images that depict the two distinct phases in high contrast. See, for example, U.S. Published Patent Application No. 2024 / 0035972A1, which is incorporated by reference herein in its entirety.

[0122] FIG. 9 is a plot of x-ray scattering data that are x-ray scattering results from the isotropic synthetic pitch and the mesophase pitch formed thereof (prepared at 425 °C, by heat treatment for 4 hours and deasphalted). The molecular order in these samples were examined by the x-ray scattering. The curve 900 is for the synthetic isotropic pitch. The isotropic pitch was prepared from xylene isomers. The curve 902 is for the mesophase pitch prepared from the isotropic pitch without the presence of NP. The curve 904 is for the mesophase pitch prepared from a blend of isotropic pitch and NP (23 wt%).

[0123] The isotropic pitch showed a broad reflection indicating amorphous nature. The mesophase samples prepared with NP solvent at 425 °C (4 hours) and solvent deasphalted, clearly showed a peak at 3.5 A indicative of mesophase order in both systems. See the representation noted by reference numeral 906. In addition, a low intensity reflection at 6.5 A is discernible in both mesophase samples. See the representation noted by reference numeral 908. This reflectionis originating from the electron density contrast between the aromatic core and side groups or flexible segments. These measurements confirm discotic nematic nature of the mesophase samples corroborating the optical microscopy measurements.

[0124] FIG. 10A and FIG. 10B are plots of mass spectra of the isotropic pitch and corresponding mesophase pitches prepared with and without naphthalene solvent using a closed system under inert conditions. The pyrolysis was performed within a vessel sealed under N2 at 425 °C for 4 hours and the chamber kept under inert conditions during the pyrolysis and solvent deasphalted). The mass spectra (i) is for the synthetic isotropic pitch prepared from xylene isomers. The mass spectra (ii) is for the mesophase pitch prepared from the synthetic pitch with 23 wt% NP in the blend (after washing). The mass spectra (iii) is for the mesophase pitch prepared from the synthetic pitch without NP. The data suggests that the degree of condensation (or aromaticity) increases with heat treatment. For both mesophase samples (with and without solvent), the Z-class for a given distribution is higher and the MW is extending to higher numbers in comparison to isotropic pitch material. This may mean that more planar aromatic molecules with mesogenic nature are being generated. The curve 1002 is the molecular weight (mw) distribution. The curve 1004 is the Z Class or hydrogen deficiency, and is a measure of aromaticity, with lower negative numbers meaning higher aromaticity (higher C / H ratio). The width of each peak in curve 1004 represents the average number of isomers for each molecular weight distribution peak value of 1002. To be specific, the curves 1002, 1004 are distributions made via projections of the data along their respective axes.

[0125] Revisiting the TGA runs (FIG. 6) on samples prepared under N2 sealed vessel, the pristine synthetic pitch pyrolyzed for 4 hours at 425 °C indicated a mass loss of about 71 % at 700 °C. Interestingly, the mesophase sample obtained with a blend of synthetic isotropic pitch and 23 wt% NP solvent in the blend under identical process conditions indicated a mass loss of about 66% at 700 °C. Both samples were sealed under N2 as discussed. It was also determined that the yield of the products (going from isotropic pitch to mesophase pitch) after the thermal reaction and washing steps was found to be very high, as listed in Table 1. Without NP, after heat treatment at 425 °C for 4 hours, a yield of about 81% was obtained, and after the washing step, a yield of about 58% was obtained relative to the original mass of the isotropic pitch. In the presence of NP, a yield of 88% was obtained after the pyrolysis and a final yield of 58% after the washing step. When the crucible was opened within a hood, low boiling point products escaped from the crucible. Thus, embodiments may provide a scalable pathway for improving pitch composition, thereby facilitating to make anisotropic pitches of different mesophase content and physical properties for different applications.

Claims

CLAIMS:

1. A method of producing mesophase pitch, comprising: forming isotropic pitch by reacting a feed, paraformaldehyde, acetic acid, and sulfuric acid at a temperature in a range of 40 °C to 350 °C, wherein the feed comprises a single-ring aromatic compound or a multi-ring aromatic compound, or both; mixing the isotropic pitch with a first solvent comprising an aromatic solvent to give a mixture; heating the mixture to a temperature of at least 350 °C to give mesophase pitch; and washing the mesophase pitch with a second solvent, wherein the mesophase pitch comprises a softening point less than 400 °C.

2. The method of claim 1, wherein the feed comprises the single-ring aromatic compound comprising toluene, xylene, or tetralin, or any combinations thereof.

3. The method of claim 1, wherein the feed comprises the single-ring aromatic compound comprising xylene isomers.

4. The method of any preceding claim, wherein the mixture comprises the first solvent in a range of 1% to 50% by weight.

5. The method of any preceding claim, wherein the aromatic solvent comprises naphthalene, methyl naphthalene, toluene, xylene, or tetralin, or any combinations thereof.

6. The method of any one of claims 1 to 4, wherein the aromatic solvent comprises naphthalene.

7. The method of any one of claims 1 to 4, wherein the aromatic solvent is same as the feed.

8. The method of any preceding claim, wherein heating the mixture comprises heating the mixture in a vessel under a gas in the vessel, and wherein the gas comprises an inert gas.

9. The method of any preceding claim, wherein presence of the first solvent in the mixture reduces coking in the heating of the mixture.

10. The method of any preceding claim, wherein presence of the first solvent in mixture or the washing of the mesophase pitch with the second solvent, or a combination thereof, reduces a distribution of different softening points of material in the mesophase pitch or reduces an amount of solids that soften at different temperature ranges in the mesophase pitch, or a combination thereof.

11. The method of any preceding claim, wherein heating the mixture comprises heating the mixture in a sealed vessel as a closed system, and wherein heating the mixture gives a reaction under pressure in the sealed vessel.

12. The method of any one of claims 1 to 10, wherein heating the mixture comprises heating the mixture in an unsealed vessel as an open system, and wherein the method comprises removing volatiles and low boiling point reaction components and at least some of the first solvent from the unsealed vessel during the heating.

13. The method of any preceding claim, wherein the second solvent comprises toluene or pentane, or both, and wherein the mesophase pitch after the washing comprises the softening point in a range of 200 °C to 400 °C.

14. A method of producing mesophase pitch, comprising: preparing isotropic pitch by reacting a feed comprising an aromatic compound with paraformaldehyde, acetic acid, and sulfuric acid, wherein the aromatic compound comprises a single-ring aromatic compound or a multi-ring aromatic compound, or both; combining the isotropic pitch with a first solvent comprising an aromatic solvent; heating the isotropic pitch and the first solvent as combined to a temperature in a range of 350 °C to 500 °C to give mesophase pitch; and washing the mesophase pitch with a second solvent, wherein the mesophase pitch comprises a softening point less than 400 °C after the washing.

15. The method of claim 14, wherein the aromatic compound comprises the single-ring aromatic compound comprising toluene, xylene, or tetralin, or any combinations thereof, and wherein the isotropic pitch and the first solvent as combined comprise the first solvent at less than 50 weight percent.

16. The method of claim 14 or claim 15, wherein presence of the first solvent with the isotropic pitch reduces formation of coke in the heating of the isotropic pitch.

17. The method of any of claims 14 to 16, wherein the aromatic compound comprises the single-ring aromatic compound comprising xylene.

18. The method of any of claims 14 to 17, wherein the aromatic solvent comprises the aromatic compound.

19. The method of any of claims 14 to 18, wherein heating comprises heating the isotropic pitch and the first solvent as combined in a vessel under an inert atmosphere in the vessel.

20. The method of any of claims 14 to 19, wherein the second solvent comprises toluene or pentane, or both.

21. The method of any of claims 14 to 20, comprising after washing the mesophase pitch, reheating the mesophase pitch in presence of air under pressure, thereby converting residual isotropic pitch into neomesophase pitch.

22. The method of any of claims 14 to 21, comprising forming carbon fibers from the mesophase pitch.

23. The method of any of claims 14 to 22, comprising forming a graphite product for a battery from the mesophase pitch.

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