Control of mesophase softening point and production yield by changing the solvent SBN via solvent desying.

Abstract

1. A process for producing a mesophase pitch, the process comprising contacting an isotropic pitch with a solvent under conditions sufficient to produce a solvent fraction containing the solvent and an insoluble fraction containing the mesophase pitch, and recovering the mesophase pitch, the contacting providing a solubility blend number (S BN ), which provides the mesophase pitch with a softening point ranging from 270° C. to 350° C. as measured according to ASTM D3104-14.

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims the benefit and priority of U.S. Provisional Application No. 63 / 180,845, filed on 28 April 2021, the disclosure of which is incorporated herein by reference. This disclosure relates to the technology of U.S. Provisional Patent Application No. 63 / 138,051, filed on 15 January 2021, which is incorporated herein by reference in its entirety. This disclosure relates to the technology of U.S. Provisional Patent Application No. 63 / 172,340, filed on April 8, 2021, which is incorporated herein by reference in its entirety.

[0002] field This disclosure relates to the production of mesophase pitch, typically for use in the manufacture of carbon fibers. [Background technology]

[0003] Isotropic pitch and mesophase pitch are carbon-containing raw materials that can be formed from residues generated during the processing of coal or petroleum raw materials, or by other methods such as acid-catalyzed condensation of low molecular weight aromatic species. For a given grade of carbon fiber, isotropic pitch can be used as the initial raw material. However, carbon fibers produced from isotropic pitch generally exhibit little molecular orientation and relatively poor mechanical properties. In contrast to carbon fibers formed from isotropic pitch, carbon fibers produced from mesophase pitch exhibit very favorable molecular orientation and relatively excellent mechanical properties. Therefore, it is desirable to identify systems and / or methods that can improve the ability to produce mesophase pitch suitable for carbon fiber production. U.S. Patent No. 4,208,267 describes a method for forming mesophase pitch. An isotropic pitch sample is solvent-extracted. The extract is then exposed to high temperatures ranging from 230°C to about 400°C to form mesophase pitch. U.S. Patent No. 5,032,250 describes a process for isolating mesophase pitch. An isotropic pitch containing a mesogen is combined with a solvent and subjected to dense phase or supercritical conditions, and the mesogen is phase-separated. U.S. Patent No. 5,259,947 describes a method for forming a solvated mesophase, which comprises (1) combining a carbonaceous aromatic isotropic pitch with a solvent, (2) applying sufficient stirring and sufficient heat to generate an insoluble material in the combination to form suspended liquid solvated mesophase droplets, and (3) recovering the insoluble material or liquid solvated mesophase as a solid. Other potentially relevant references include U.S. Patent No. 9,222,027, U.S. Patent Application Publication No. 2019 / 0382665, and U.S. Patent Application Publication No. 2020 / 0181497. [Brief explanation of the drawing]

[0004] [Figure 1] Figure 1 is a schematic diagram of a non-limiting example of the process described herein. [Figure 2] Figure 2 is an optically polarized microscope image of mesophase pitch with a softening point of 400°C+. [Figure 3] Figure 3 is an optically polarized microscope image of mesophase pitch with a softening point of 332°C. [Figure 4A] Figure 4A is an optical polarized light microscope image of insoluble substances separated from toluene. [Figure 4B] Figure 4B is an optical polarized light microscope image of insoluble substances separated from heptane:toluene (70:30). [Overview of the project]

[0005] summary A process for producing mesophase pitch, the process comprising contacting an isotropic pitch with a solvent under conditions sufficient to produce a solvent fraction containing the solvent and an insoluble fraction containing the mesophase pitch, and recovering the mesophase pitch, wherein the contacting is such that the mesophase pitch has a softening point ranging from 270°C to 350°C measured in accordance with ASTM D3104-14, and the solvent has a Solubility Blending Number (S BN ).

[0006] During the process, the solvent may have a Solubility Blending Number (S BN ) ranging from 30 to 90 SU. During the process, the contacting may include introducing the solvent at a rate of 3 to 8 ml per gram of the isotropic pitch. During the process, the solvent may include an aromatic solvent. During the process, the solvent may include heptane and toluene. The process may further include adjusting the ratio of heptane to toluene. During the process, the softening point may range from 270°C to 320°C. The process may include reducing the SBN of the solvent to increase the recovery rate of the mesophase precursor and to lower the softening point. During the process, the isotropic pitch can be produced by a process including providing a raw material having T5≧400°F (204°C) and T95≦1,400°F (760°C), and heating the raw material at a temperature ranging from about 420°C to about 520°C to produce a heat-treated product containing the isotropic pitch, wherein the heating is carried out under conditions sufficient to satisfy the relationship [X * Y]≧20,000 seconds, where X is the equivalent reaction time (ERT) in the heating and Y is the bromine number in the raw material measured in accordance with ASTM D1159. During the process, the isotropic pitch has at least one of the following physical properties: (a) a microresidual carbon content (MCR) measured in accordance with ASTM D4530-15 and ranging from about 30% to about 90%; (b) a softening point measured in accordance with ASTM D3104-14 and ranging from about 80°C to about 250°C; (c) a mesophase pitch content exceeding about 0.5 volume % measured in accordance with ASTM D4616-95(2018); and (d) a quinoline insoluble content exceeding about 1 mass % measured in accordance with ASTM D2318-15. During the process, the method may include adjusting the SBN to maintain the softening point of the mesophase precursor below 350°C.

Mode for Carrying Out the Invention

[0007] Detailed description of preferred embodiments The various embodiments described herein provide a process for the production of mesophase pitch. A significant amount of mesophase molecules (also known as mesophase precursors) are present in the isotropic pitch. However, they do not have liquid crystalline short-range order and thus cannot be aligned, so they are not mesophase pitch. It has been discovered that the mesophase precursors can be concentrated via solvent deresiduation using a solvent with a high dissolution degree (e.g., greater than 70, preferably greater than 80, preferably greater than 90, and preferably greater than 100) to achieve a high mesophase content by re-aligning the mesophase precursors at a high temperature. In order to stretch the mesophase pitch into pitch-based carbon fibers and be processable in the spinning stage, the physical properties of the mesophase need to meet certain criteria. One particular aspect is that the softening point of the mesophase is ideally below 350°C while maintaining a high mesophase content. The technical advancement of the present invention can address the problem of maintaining a medium to high yield of mesophase while meeting this spinning criterion defined by the softening point. It has been discovered that the softening point of a mesophase is controlled by the mesophase molecular precursor within an isotropic pitch, as well as by the solvent's solubility for aromatics (also known as SBN). Specifically, mesophase molecules with a broad molecular weight distribution are produced from heavy hydrocarbons such as MCB and steam crack tar through thermal dealkylation and thermal dehydrogenation. The molecular composition of the mesophase precursor is related to the harsh conditions of thermal dealkylation and thermal dehydrogenation. By applying solvents with different SBNs during desying, the feed can be divided into fractions mainly of the mesophase precursor and mainly of the isotropic pitch. In effect, adjusting the SBN of the solvent is like a handle for adjusting the softening point. The mesophase precursor is rearranged to form a mesophase crystal. The average molecular weight of the fractionated and rearranged mesophase precursor affects the softening point of the corresponding mesophase.

[0008] All numerical values ​​in the detailed description of the invention and the claims herein are modified with respect to the indicated values ​​by "about" or "approximately" to account for experimental errors and variations that can be expected by those skilled in the art. Unless otherwise specified, room temperature is approximately 23°C. As used herein, “mass%” means mass percentage, “volume%” means volume percentage, “mol%” means mole percentage, “ppm” means parts per million, and “ppm wt” and “wppm” are used interchangeably and mean parts per million on a weight basis. All “ppm” used herein refers to ppm by mass unless otherwise specified. All concentrations herein are expressed based on the total amount of the composition in question. All ranges herein shall include both endpoints as two specific embodiments unless otherwise described or indicated.

[0009] definition For the purposes of this specification and the appended claims, the following terms are defined: As used herein, the term "asphaltene" means a material obtained from crude oil, having an initial boiling point above 1,200°F (650°C), and being insoluble in straight-chain alkanes such as hexane and heptane, i.e., paraffinic solvents. As used herein, the term “Equivalent reaction or residence time (ERT)” means the strictness of the operation and is expressed as the residence time in seconds for a reaction with an activation energy of 54 kcal / mol in a reactor operating at 468°C. The ERT in operation is calculated as follows:

number

[0010] Solubility Blend Number (S BN ) and Insolubility Number (I N ) Solubility Blend Number (S BN ) and Insolubility Number (I N ) corresponding SU values are values that can be used to characterize the solubility of the dewaxing solvent described herein. The first step in determining the number of insoluble particles and soluble blends for the desying solvents described herein is to determine whether the desying solvent contains asphaltenes insoluble in n-heptane. This can be achieved by mixing one volume of the desying solvent with five volumes of n-heptane and determining whether the asphaltenes are insoluble. Any conventional method may be used. One possibility is to observe droplets of the test liquid mixture and the desying solvent between a glass slide and a glass coverslip using transmitted light with an optical microscope at a magnification of 50 to 600 times. If the asphaltenes are soluble, little or no dark particles will be observed, if any. If the asphaltenes are insoluble, many dark, usually brown particles, typically 0.5 to 10 microns in size, will be observed. Another possible method is to place droplets of the test liquid mixture and the desying solvent on a sheet of filter paper and allow them to dry. If the asphaltene is insoluble, a dark ring or circle is observed approximately in the center of the yellow to brown spot formed by the solvent. If the asphaltene is soluble, the color of the spot formed by the solvent is relatively uniform. If it is confirmed that the desymentation solvent contains asphaltene insoluble in n-heptane, the procedure described in the following three paragraphs is followed to determine the insoluble number and the number of dissolved blends. If it is not confirmed that the desymentation solvent contains asphaltene insoluble in n-heptane, the insoluble number is given as a value of 0, and the number of dissolved blends is determined by the procedure described in the section titled "Desymentation Solvents Without Asphaltene".

[0011] Asphaltene-containing dehiscence solvent For example, regarding desying solvents containing asphaltenes, such as heavy oil containing residual oil, N and S BNThe determination requires testing the solubility of the desylated solvent in the test liquid mixture with at least two volumes of the desylated solvent in a given ratio. The test liquid mixture is prepared by mixing two liquids in various ratios. One liquid is nonpolar (test solvent A) and is the solvent for the asphaltene in the desylated solvent. The other liquid is nonpolar (test solvent B) and is the non-solvent for the asphaltene in the desylated solvent. Test solvent A is typically toluene, and test solvent B is typically n-heptane. For the first test, a suitable volume ratio of oil to the test liquid mixture is selected, for example, 1 ml of oil to 5 ml of the test liquid mixture. Then, various mixtures of the test liquid mixture are prepared by mixing n-heptane and toluene in various known ratios. Each of these is mixed with the desying solvent in a selected volume ratio to the test liquid mixture. Then, for each of these, it is determined whether the asphaltene is soluble or insoluble. Any conventional method may be used. For example, droplets of the test liquid mixture and desying solvent can be observed between a glass slide and a glass coverslip using transmitted light with an optical microscope at a magnification of 50-600x. If the asphaltene is soluble, few, if any, dark particles are observed. If the asphaltene is insoluble, many dark, usually brown, particles are observed, usually 0.5-10 microns in size. The results of mixing the dehiscence solvent with all of the aforementioned test liquid mixtures are ordered by increasing the proportion of toluene in the test liquid mixture. The desired value is between the minimum proportion of toluene in which asphaltenes dissolve and the maximum proportion of toluene in which asphaltenes precipitate. More test liquid mixtures are prepared using toluene in proportions between these limits and mixed with the selected oil at a volume ratio to the test liquid mixture to determine whether the asphaltenes are soluble or insoluble. The desired value is between the minimum proportion of toluene in which asphaltenes dissolve and the maximum proportion of toluene in which asphaltenes precipitate. This process is continued until the desired value is determined within the desired range of accuracy. Finally, the desired value is considered to represent the minimum proportion of toluene in which asphaltenes dissolve and the maximum proportion of toluene in which asphaltenes precipitate. This is the first data point T1 at the volume ratio R1 of the selected oil to the test liquid mixture. This test is called the toluene equivalence test. The second data point can be determined by a process similar to that for the first data point, simply by selecting different volume ratios of the desyring solvent to the test liquid mixture. Alternatively, a lower percentage of toluene than that determined for the first data point can be selected, and the test liquid mixture can be added to a known volume of oil until asphaltenes begin to precipitate. The second data point is at point T2 of the volume ratio R2 of oil to the test liquid mixture, with the selected percentage of toluene in the test liquid mixture. The accuracy of the final number increases as the second data point moves further away from the first data point; therefore, preferred test liquid mixtures for determining the second data point are 0% toluene or 100% n-heptane. This test is called the heptane dilution test. Insoluble number (I N ) is defined as follows:

number

number

[0012] Asphaltene-free dehiscence solvent If the de-history solvent does not contain asphaltene, the insoluble number is zero. However, determining the number of dissolved blends for a de-history solvent that does not contain asphaltene requires using a test oil containing asphaltene whose insoluble number and number of dissolved blends have been determined in advance using the procedure described above. First, 1 volume of the test oil is mixed with 5 volumes of the de-history solvent. Insoluble asphaltene can be detected by the microscope or spot technique described above. If the viscosity of the oil is very high (greater than 100 centipoise), it may be heated to 100°C while mixing them and then cooled to room temperature before examining for insoluble asphaltene. Similarly, a spot test may be performed on a mixture of viscous oils in an oven at 50°C to 70°C. If insoluble asphaltene is detected, the de-history solvent is a non-solvent for the test oil, and the procedure described in the next paragraph should be continued. However, if insoluble asphaltene is not detected, the de-history solvent is a solvent for the test oil, and the procedure described in the paragraph following the next paragraph should be continued. If insoluble asphaltene is detected when 1 volume of the test oil and 5 volumes of the dehiscent solvent are mixed, small volumes of the dehiscent solvent are added to 5 ml of the test oil until insoluble asphaltene is detected. Volume of non-solvent oil (V NSO ) is equal to the average of the total volume of the desylated solvent added for the volume increment immediately before the detection of insoluble asphaltene and the total volume added when the insoluble asphaltene was first detected. The size of the volume increment may be reduced to the point required for the desired accuracy. This is called the dilution test of the non-solvent oil. BNTO This is the number of dissolved blends of the test oil, NTO If the number of insoluble components in the test oil is such that the number of soluble blends of non-solvent oils is (S BN ) is given by the following:

number

number

[0013] Mesophase pitch content measured by optical microscopy Unless otherwise specified herein, the mesophase pitch content in a sample is determined by optical microscopy according to the following procedure. A digital image of the sample is created using an optical microscope. Next, a histogram of the total number of pixels in the digital image is created, and areas with brighter intensity correspond to mesophase pitch due to a high refractive index. The image is divided into mesophase pitch and non-mesophase pitch regions by thresholding, and areas with intensity below a predetermined threshold correspond to mesophase pitch. An estimate of the mesophase pitch content of the sample in the % region (the result of which can be extrapolated as corresponding to an estimate of volume %) can be obtained by subtracting the non-mesophase pitch region of the image, and then dividing the total amount of the mesophase pitch region of the image by the total area of ​​the image. Next, certain aspects of the present invention will be described in more detail. While the following description relates to specific aspects, these are merely illustrative, and it will be understood by those skilled in the art that the invention can be carried out in other ways. References to “invention” mean one or more, but not necessarily all, of the inventions defined by the claims. The use of titles is for convenience only and should not be construed as limiting the scope of the invention to any particular aspect.

[0014] heavy quality raw material In the processes of this disclosure, the heavy feedstock may be characterized by a boiling point range. One option for defining the boiling point range is to use the initial boiling point and / or the final boiling point of the feedstock. Another option provides a more representative description of the feedstock in some cases and characterizes the feedstock based on the amount of the feedstock that boils at one or more temperatures. For example, the “T5” boiling point of a feedstock is defined as the temperature at which 5 mass% of the feedstock boils completely. Similarly, the “T95” boiling point is the temperature at which 95 mass% of the feedstock boils completely. The percentage of feedstock that boils at a given temperature can be determined, for example, by the method of ASTM D2887 (or, if ASTM D2887 is not suitable for a particular fraction, by the method of ASTM D7169). Generally, the heavy feedstock may have T5 ≥ 400°F (204°C) and T95 ≤ 1,400°F (760°C). Examples of such heavy raw materials include raw materials having a 1,050°F+ (566°C+) fraction. In one embodiment, the 566°C+ fraction can correspond to 1% by mass or more of the heavy raw material (i.e., T99 is 566°C or higher), or 2% by mass or more (T98 is 566°C or higher), or 10% by mass or more (T90 is 566°C or higher), or 15% by mass or more (T85 is 566°C or higher), or 30% by mass or more (T70 is 566°C or higher), or 40% by mass or more (T60 is 566°C or higher), for example, about 1% by mass to about 40% by mass, or about 2% by mass to about 30% by mass. The heavy raw materials of this disclosure may be characterized by reactivity as measured by bromine value. The heavy raw materials of this disclosure may have a bromine value measured in accordance with ASTM D1159, such as ≥3, or ≥5, or ≥10, or ≥30, or ≥40, for example, about 3 to about 50, or about 5 to about 40, or about 10 to about 30. The heavy raw materials of this disclosure may be characterized by their aromatic content. The heavy raw materials of this disclosure may contain about 40 moles or more aromatic carbon, or about 50 moles or more, or about 60 moles or more, for example, up to about 75 moles or more, or even higher aromatic carbon if possible. The aromatic carbon content of the heavy raw materials may be determined in accordance with ASTM D5186. The heavy raw materials of this disclosure may be characterized by their average carbon number. The heavy raw materials of this disclosure may consist of hydrocarbons having an average carbon number of about 33 to about 45 (for example, about 35 to about 40, or about 37 to about 42, or about 40 to about 45).

[0015] The heavy raw materials of this disclosure may be characterized by a microresidual carbon content (MCR) as determined by ASTM D4530-15. The heavy raw materials of this disclosure may have an MCR of about 5% by mass or more (for example, about 5% by mass to about 45% by mass, or about 10% by mass to about 45% by mass). The heavy raw materials of this disclosure may be characterized by their hydrogen content. The heavy raw materials of this disclosure generally have a hydrogen content of about 6% to about 11% by mass, for example, about 6% to about 10% by mass. The heavy raw materials of this disclosure may be characterized by the cumulative concentration of polynuclear aromatic hydrocarbons (PNAs) and polycyclic aromatic hydrocarbons (PAHs). The raw materials of this disclosure may have a cumulative concentration of partially hydrogenated PNAs and partially hydrogenated PAHs of about 20% by mass or more (e.g., about 50% to about 90% by mass). In one embodiment, a suitable heavy raw material may contain about 50 wppm to about 10,000 wppm of elemental nitrogen or more (i.e., the mass of nitrogen in various nitrogen-containing compounds in the raw material). Furthermore, or alternatively, the heavy raw material may contain about 100 wppm to about 20,000 wppm of elemental sulfur, preferably about 100 wppm to about 5,000 wppm of elemental sulfur. Sulfur usually exists as organically linked sulfur. Examples of such sulfur compounds include, for example, thiophenes, tetrahydrothiophenes, benzothiophenes, and a class of heterocyclic sulfur compounds such as their higher congeners and analogs. Other organically linked sulfur compounds include aliphatic, naphthenic, and aromatic mercaptans, sulfides, and di- and polysulfides. Examples of suitable heavy raw materials include, but are not limited to, main column bottoms (MCBs), steam cracker tar, vacuum residue, dehiscence residue or rock, any of the aforementioned hydroprocessed or hydrotreated forms, and any combination thereof. A preferred heavy raw material may be hydrogenated MCB. Another example of a preferred heavy raw material is hydrotreated steam cracker tar. Steam cracker tar and subsequent hydrotreatment can be produced / carried out by any suitable method, including, for example, the one disclosed in U.S. Patent No. 8,105,479 (which is incorporated herein by reference in its entirety).

[0016] heat treatment In the process of this disclosure, the heavy raw material is generally subjected to a heat treatment step to dealkylate and / or dehydrogenate the heavy raw material and produce isotropic pitch. As stated above, without wishing to be bound by any theory, it is believed that by carrying out the heat treatment step under sufficiently harsh conditions in relation to the reactivity of the raw material, mesogens are favorably formed in the resulting isotropic pitch, which can then be de-chronished to form aggregates of mesophase. Often, such conditions are harsher than those employed in visbreaking. More specifically, the heat treatment may generally be carried out at a temperature ranging from about 420°C to about 520°C, preferably about 480°C to about 510°C, for a residence time of about 5 minutes to 8 hours, more preferably about 5 minutes to about 1 hour, and most preferably about 5 minutes to about 30 minutes, for example, about 10 minutes to about 30 minutes. Generally, the harshness required for the heat treatment step depends on the bromine value of the heavy raw material. Typically, the severity required for the heat treatment conditions increases as the bromine value of the heavy raw material decreases. Generally, the heat treatment is [X * The process is carried out under conditions sufficient to satisfy the relationship Y]≧20,000 seconds (for example, ≧30,000 seconds, or ≧50,000 seconds, or ≧70,000 seconds, or ≧200,000 seconds, or ≧500,000 seconds, or ≧700,000 seconds) (wherein X is the equivalent reaction time in the heating and Y is the bromine value of the raw materials). For example, [X* Y] may range from approximately 20,000 to approximately 1,000,000 seconds, for example, approximately 30,000 to approximately 700,000 seconds, or approximately 50,000 to approximately 500,000 seconds, or approximately 50,000 to approximately 100,000 seconds. For example, in an embodiment in which the heavy raw material has a bromine value of 10 or more, the minimum ERT of the heat treatment step may be approximately 2,000 seconds or less, for example, a minimum ERT of 500 seconds. In an embodiment in which the heavy raw material has a bromine value of less than 10, the minimum ERT of the heat treatment step may be greater than approximately 2,000 seconds, for example, a minimum ERT of 10,000 seconds, or a minimum ERT of 8,000 seconds. The preferred pressure in the heat treatment step may range from about 200 psig (1,380 kPa-g) to about 2,000 psig (13,800 kPa-g), for example, from about 400 psig (2,760 kPa-g) to about 1,800 psig (12,400 kPa-g). The heat treatment may be carried out in any suitable vessel, such as a tank, pipe, tubular reaction vessel, or distillation column. An example of a suitable reactor structure that may be employed to carry out the heat treatment is described in U.S. Patent No. 9,222,027, which is incorporated herein by reference in its entirety. Generally, the heat treatment product is liquid. In some embodiments, the heat treatment product may be further processed, preferably by vacuum distillation, such as flushing, distillation, fractionation, or other types of separation methods based on boiling point range, to produce the isotropic pitch described herein. For example, the heat treatment product often comprises a light fraction containing one or more diesel and / or gasoline and a heavy fraction containing the isotropic pitch described herein. In such embodiments, the yield of the heavy fraction containing the isotropic pitch is typically more than about 50% by mass of the heat treatment product, for example more than about 60% by mass, preferably more than about 80% by mass.

[0017] Isotropic pitch The isotropic pitch resulting from the heat treatment (and optionally subsequent separation steps) may be characterized by a microresidual carbon content (MCR) measured in accordance with ASTM D4530-15. Generally, the isotropic pitch of this disclosure may have an MCR of 30% by mass or more (e.g., preferably about 50% by mass or more, and more preferably about 60% by mass or more). For example, a suitable isotropic pitch may have an MCR ranging from about 30% by mass to about 90% by mass, preferably about 50% by mass to about 90% by mass, and more preferably about 60% by mass to about 90% by mass. Typically, the isotropic pitch has an MCR that is at least 5% higher, for example at least 10% higher, and more preferably at least 20% higher than the MCR of the heavy raw material. The isotropic pitches of this disclosure may be characterized by a softening point measured in accordance with ASTM D3104-14. Generally, the isotropic pitches of this disclosure may have a softening point of about 80°C or higher, preferably about 100°C or higher, more preferably about 120°C or higher, and even more preferably about 200°C (for example, preferably from about 80°C to about 250°C, more preferably from about 100°C to about 250°C, and even more preferably from about 150°C to about 250°C). The isotropic pitch of this disclosure may be characterized by a quinoline-insoluble substance content measured in accordance with ASTM D2318-15. Generally, the isotropic pitch of this disclosure may have a quinoline-insoluble substance content of about 1% by mass or more (for example, preferably about 2% by mass or more, more preferably about 5% by mass or more, for example, about 1% to about 10% by mass). The isotropic pitch of this disclosure may be characterized by its mesophase pitch content. Often, the isotropic pitch of this disclosure may have a mesophase pitch content greater than about 0.5 mass% and / or greater than about 0.5 volume%, for example, about 0.5 mass% to about 1 mass%, as measured in accordance with ASTM D4616-95 (2018). Alternatively, the isotropic pitch of this disclosure may have a mesophase pitch content less than 0.5 mass%, for example, about 0 mass% or about 0 volume%, as measured in accordance with ASTM D4616-95 (2018). The isotropic pitch of this disclosure may be characterized by its hydrogen content. Generally, the isotropic pitch of this disclosure may have a hydrogen content of less than about 8% by mass (for example, preferably about 6% by mass or less, e.g., about 4% to about 6% by mass). The isotropic pitch of this disclosure may be characterized by its sulfur content. Generally, the isotropic pitch of this disclosure may have a sulfur content of less than about 2% by mass (for example, preferably about 1% by mass or less, more preferably about 0.5% by mass or less), for example, about 0% by mass to about 2% by mass.

[0018] Dehybrid solvent In the process of this disclosure, the number of dissolved blends (S BN A suitable desying solvent can be selected based on the following. Typically, the desying solvent has at least about 10 solubility units ("SU") of S BN For example, suitable desying solvents for the technical advances of the present invention are about 70 to about 150 SU, for example, about 80 to about 130 SU, or about 90 to about 130 SU, or about 90 to about 150 SU, or about 50 to 60 SU, or about 70 to about 130 SU of S. BN It may have a moderate to high mesophase content. Preferably, to obtain the desired softening point for carbon fiber spinning while maintaining a moderate to high mesophase content, the SBN may be at a more appropriate level, 30 to 90 SU, and more preferably 50 to 90 SU. At SU levels above 100, the softening point rises to above 350°C. The desyring solvents of this disclosure may be characterized by their boiling point. In some embodiments, the desyring solvent may have an atmospheric boiling point range of approximately 65°C to 200°C, for example, about 100°C to about 175°C. Advantageously, the atmospheric boiling point range of the desyring solvent may be less than about 200°C to facilitate the recovery of the solvent from the extraction process described herein, for example, by distillation. As an example of a suitable dehiscence solvent, C2-C 10Paraffins, e.g., pentane, heptane, and butane; monocyclic aromatics such as toluene, xylene, ethylbenzene, and trimethylbenzene; polycyclic aromatics, e.g., naphthalene, methylnaphthalene, indan, tetralin, and anthracene; heteroatom-containing aromatics such as pyridine; other heteroatom compounds such as tetrahydrofuran; heavy naphtha, kerosene, and / or light diesel fractions; reuse portions of products generated during the improvement of heavy oil feedstocks, e.g., steam cracker tar; and other hydrocarbons or hydrocarbon-like fractions having a suitable melting point range. When reuse portions of products generated during the improvement of steam cracker tar are included in the desyring solvent, the distillation cut point for the reuse portion is a suitable boiling point range and / or suitable S BN It can be adjusted to provide the following. Typically, a suitable atmospheric boiling point range for the reuse portion is about 350°F (177°C) to about 850°F (454°C), i.e., a midcut solvent. A preferred heavy fuel oil feedstock improvement process for obtaining a midcut solvent is further described in U.S. Patent Application No. 2020 / 0071627, which is incorporated herein by reference in whole. In some embodiments, paraffin such as hexane or heptane may be included as a cosolvent to adjust the solubility parameters of the solvent mixture, preferably in an amount up to about 90% by volume, for example, about 10% by volume, based on the total volume of the solvent. For example, a preferred desying solvent may include about 0 to about 90 volume% paraffin, e.g., n-heptane, and about 10 to about 100 volume% toluene, e.g., 90 volume% toluene and 10 volume% n-heptane or or 80 volume% toluene and 20 volume% n-heptane or or 70 volume% toluene and 30 volume% n-heptane, or further or 10 volume% toluene and 90 volume% n-heptane. An example of a preferred desying solvent is shown in S BN The values ​​are shown in Table 1. [Table 1]

[0019] Solvent extraction In the process of this disclosure, typical solvent extraction conditions include mixing the isotropic pitch with the desylated solvent at a volume ratio of about 10:1 to about 1:1, for example, about 8:1 or less (desylated solvent: isotropic pitch). Typically, the extraction is carried out under conditions suitable for retaining the solvent in the solution phase. For example, the extraction may be carried out under extraction conditions including a temperature preferably in the range of about 90°C to about 350°C, preferably about 150°C to about 350°C, more preferably about 200°C to about 350°C, a total pressure in the range of about 15 psig (about 105 kPa-g) to about 800 psig (about 5,600 kPa-g), and a residence time of about 5 minutes to about 5 hours. Typically, the extraction may be carried out by stirring, for example, mechanical stirring using a rotary stirrer. A suitable stirring rate may range from approximately 10 RPM to approximately 8,500 RPM, for example, from approximately 50 RPM to approximately 5,000 RPM.

[0020] Contacting the isotropic pitch with the desyring solvent generates at least two types of product streams. One type of product stream may be a solvent phase fraction containing most of the desyring solvent and most of the heat treatment product, or a resulting separated heavy fraction that dissolves in the desyring solvent. At least a portion of the desyring solvent is typically recovered from the solvent phase fraction, for example by distillation, for reuse, and the recovered desyring solvent is reused for solvent extraction. A portion of the solvent phase obtained after the recovery of the desyring solvent generally contains supplemental pitch products, also known as desyring oil (DAO), which may optionally be reused in the heat treatment step. An insoluble fraction (the second type of product stream), also known as a lock, contains the remaining portion of the isotropic pitch, i.e., the portion that does not dissolve in the desyring solvent. Generally, the insoluble fraction contains the mesophase pitch as well as the accompanying residual solvent and mesophase pitch precursor. Furthermore, the insoluble fraction may be subjected to a heat treatment step, in which the remaining mesophase precursor is converted into mesophase pitch. Any heat treatment step may be carried out at a temperature ranging from about 300°C to about 350°C and in the presence of a solvent, preferably a low-boiling point solvent (e.g., having an atmospheric boiling point range of about 200°F (93.3°C) to about 650°F (343°C)). Any conventional separation method (e.g., one or more of drying, distillation, fractionation, other types of separation based on boiling point range, etc.) may be used to remove the residual solvent from the insoluble fraction. Optionally, the recovered residual solvent may be reused for solvent extraction. Generally, the yield of the remaining solid product recovered from the insoluble fraction after the removal of the residual solvent is at least about 10% by mass, preferably at least about 15% by mass, for example, about 10% by mass to about 50% by mass, or about 20% by mass to about 40% by mass. The recovered solid product typically contains about 30% by volume or more of an optically active fraction, for example, about 30% to about 95% by volume or about 50% to about 85% by volume. In one embodiment, the quinoline-insoluble substance content in the recovered solid product may be about 75% by mass or less, or about 50% by mass or less, or about 30% by mass or less, for example, about 0% to about 30% by mass.Furthermore, or alternatively, the content of toluene-insoluble substances in the recovered solid product. teeth It may be approximately 80% by mass or less, or approximately 60% by mass or less, or approximately 40% by mass or less, or approximately 30% by mass or less, for example, approximately 0% to approximately 30% by mass.

[0021] carbon fiber The mesophase pitch obtained from the solvent extraction process described herein may be used, for example, to form carbon fibers using a conventional melt spinning process. Melt spinning for carbon fiber formation is a known technique. For example, the book "Carbon-Carbon Materials and Composites" includes a chapter titled "Carbon Fiber Manufacturing" by DD Edie and RJ Diefendorf. Another example is the paper "Melt Spinning Pitch-Based Carbon Fibers," Carbon, v.27(5), p647, (1989).

[0022] Process Overview The processes disclosed herein may be batch, semi-batch, continuous, semi-continuous, or any combination thereof, preferably continuous. Figure 1 shows a schematic of a non-limiting exemplary process 100 of this disclosure. Heavy raw material 102 is in a container 104 [X *Under conditions sufficient to satisfy the relationship Y]≧20,000 seconds, the material is subjected to a heat treatment process (wherein X is the equivalent reaction time in the heating and Y is the bromine value of the raw material 102). The heat treatment process is carried out in a container 104 to form a heat treatment product 106 containing isotropic pitch. Often (but not required), the heat treatment product 106 may be subjected to a separation process to form a heavy fraction 108 and a light fraction 110 containing isotropic pitch. Optionally, the light fraction 110 may be mixed with fuel oil. The resulting heat treatment product 106 or heavy fraction 108 is passed through a solvent extractor 112 with a dehiscing solvent 114. The SBN of the dehiscent solvent 114 can be selected such that the mesophase pitch has a softening point ranging from 270°C to 350°C (or 270 to 340°C, or 280 to 320°C, or 270 to 310°C) as measured in accordance with ASTM D3104-14. Furthermore, when the solvent 114 is a combination of two or more solvents, the ratio of the two solvents can be dynamically controlled by changing the ratio based on feedback regarding the softening point of the mesophase pitch. The solvent can be introduced at a ratio of 3 to 8 ml per gram of isotropic pitch. Lowering the SBN of the solvent can lower the softening point while increasing the recovery rate of the mesophase precursor. The intention of using a low SBN solvent is to lower the softening point. Under similar conditions (as shown in the examples), those with a low SBN tend to have a lower mesophase content, but the intention is not to lower the mesophase content. However, for fiber spinning, the goal is to find a combination of a desired softening point and high mesophase content with a medium to high yield. The technological advances of the present invention can provide a handle for adjusting the softening point with yield. One side effect is that the mesophase content is reduced under the same conditions. The dehiscence conditions can be optimized so that the mesophase content is not compromised. Thus, although it may be counterintuitive, the reduction in the yield of the mesophase content is an improvement by producing a mesophase precursor with a more desirable softening point suitable for carbon fiber spinning. By adding the solvent 114, a solvent phase fraction 116 is formed, which contains most of the desying solvent 114 and a portion of most of the heat treatment product 106, or a heavy fraction 108 that dissolves in the desying solvent 114. An insoluble fraction 118, i.e., a lock, is also formed, which contains most of the insoluble portion of the heat treatment product 106 or the heavy fraction 108. Generally, the insoluble fraction 118 contains mesophase pitch and associated residual solvent and mesophase pitch precursor. Often (but not essential), as described herein, the insoluble fraction 118 may be subjected to a heat treatment step (omitted) to convert the remaining mesophase precursor into mesophase pitch. Often (but not essential), a portion of the solvent phase fraction 116 may be subjected to a separation step to form a recovered solvent stream 122 and desying oil (DAO) 120. Optionally, at least a portion of the recovered desying solvent stream 122 may be recycled to the solvent extractor 112 in combination with the desying solvent stream 122 or by an isolated stream. Additionally, optionally, at least a portion of the DAO 120 and / or at least a portion of the insoluble material 118 may be recycled to the container 104 in combination with the heavy raw material 102 or by an isolated stream.

[0023] The following examples illustrate the present invention. Numerous modifications and variations are possible, and it is understood that the present invention may be implemented in ways different from those specifically described herein, within the scope of the appended claims. Further details regarding the manufacture of isotropic pitch are provided in U.S. Provisional Patent Application No. 63 / 138,051 and will not be repeated here. [Examples]

[0024] Example 1. The severity of the isotropic pitch preparation affects the softening point of the corresponding mesophase. The isotropic pitch selected as the starting material is a product derived from steam cracker tar via thermal dealkylation and thermal dehydrogenation. Table 2 shows the harsh conditions for two isotropic pitch preparation processes and the physical properties of these isotropic pitches. To quantify the degree of harshness, the equivalent reaction time (ERT) is used, with higher numbers indicating harsher conditions. ERT represents the relative residence time under the specified process conditions with respect to typical bisbreaking conditions at 468°C with an activation energy of 54 kcal / mol. Isotropic pitch 1 was prepared under higher harshness (i.e., 1390 ERT) and de-calculated in heptane (SBN=0) at 230°C for 1 hour with a solvent / starting material ratio of 8 ml / 1 gram. The resulting mesophase has a softening point of 400°C+, a mesophase content of approximately 50%, and a recovery rate of 25%. The microscopic features of this mesophase are shown in Figure 2. On the other hand, isotropic pitch 2 was prepared under lower severity (i.e., 845ERT), and subjected to the de-syring process with a solvent ratio of 8 ml per gram of pitch. Unlike the 230°C, 1 hour used for isotropic pitch 1, the de-syring process was carried out at 280°C for 1.5 hours, yielding a mesophase pitch with approximately 60% mesophase content, 35% recovery, and a softening point of approximately 300°C. Since a higher de-syring temperature results in a higher mesophase softening point, the observation that the mesophase produced from isotropic pitch 2, which exhibits a softening point of 300°C, suggests that isotropic pitches prepared under lower severity conditions are more likely to produce mesophases with lower softening points compared to isotropic pitches prepared under higher severity conditions under similar de-syring conditions. This is probably because relatively light mesophase molecules were generated in the isotropic pitch under mild conditions, opposite to the severe conditions. The microscopic characteristics of the mesophase generated from isotropic pitch 2 are shown in Figure 3. [Table 2]

[0025] Example 2 (Comparison of mesophase precursor concentrations derived from isotropic pitch in high and low SBN solvents via solvent dehiscence). The isotropic pitch used in this example is the same as isotropic pitch 1 in Example 1. To concentrate the mesophase precursor, the solvent de-syringe process was carried out at room temperature instead of high temperature. Specifically, the de-syringe process was carried out under auto-regeneration pressure for 1 hour using 8 ml of solvent per gram, with a solvent / raw material ratio of 8 ml / gram. Table 3 summarizes the physical properties and yield of the precursor with respect to the change in SBN. Table 3 shows that solvent de-syringe at lower SBNs results in the additional capture of lighter, insoluble molecules that would have been dissolved in the high-SBN solvent. The additional concentration of lighter molecules contributes to a higher recovery rate and a lower softening point of the mesophase precursor. [Table 3]

[0026] Example 3 (Comparison of mesophase generation from isotropic pitch in high and low SBN solvents via solvent dehiscence) The isotropic pitch selected as the raw material is a product derived from Baytown MCB via thermal dealkylation and thermal dehydrogenation. The physical properties of the isotropic pitch are shown in Table 4. Solvents with different SBNs were introduced into the raw material at a ratio of 3 ml per gram of pitch. The mixture was sealed in an autoclave under inert conditions. To maintain the solvent in the liquid phase, the solvent extraction process was carried out at 280°C for 1 hour at 700 psi. After decane of the dissolved product, the insoluble substance (also known as mesophase) was recovered, and then washed and dried at 120°C for 1 hour to remove solvent residue. The yield and mesophase properties of this comparative study are summarized in Table 5, and the microscopic characteristics of the mesophase are summarized in Figures 4A and 4B. [Table 4] [Table 5] The comparative studies described above demonstrate that using a low-SBN solvent during desying improves the recovery rate from 26% to 48% and contributes to the recovery of lighter molecules, lowering the softening point from 400°C+ to 270°C. In contrast, lighter molecules may negatively impact mesophase formation under current conditions, which is reflected in a decrease in mesophase content.

[0027] All documents described herein, including priority documents and / or test procedures, are incorporated herein by reference to the extent that they are not inconsistent with this context. The forms of this disclosure are illustrated by the above general description and specific embodiments, description On the other hand, Book Various modifications can be made without deviating from the intent and scope of the disclosure. Therefore, this disclosure is not intended to be limited thereto. Similarly, the term “comprising” is considered to be synonymous with the term “including” for the purposes of U.S. law. Similarly, whenever the provisional expression “comprising” precedes a composition, component, or group of components, it is understood that the same composition or group of components is expected to be accompanied by the provisional expressions “consisting essentially of,” “consisting of,” “selected from the group of consisting of,” or “is,” prior to the enumeration of such composition, component, or group of components, and vice versa.

[0028] Where numerical lower and upper limits are given herein, any range from any lower limit to any upper limit shall be considered. No such limitation shall be made even if this disclosure is described in terms of a particular aspect. Appropriate changes / modifications for operation under specific conditions should be obvious to those skilled in the art. Therefore, the following claims are intended to be construed to encompass all such changes / modifications so as to fall within the true spirit / scope of this disclosure. Another aspect of the present invention may be as follows: [1] A process for manufacturing mesophase pitch, The process involves contacting isotropic pitch with a solvent under conditions sufficient to produce a solvent fraction containing the solvent and an insoluble fraction containing mesophase pitch, and This includes recovering the mesophase pitch, The contact is performed by dissolving a number of blends (S) such that the mesophase pitch has a softening point ranging from 270°C to 350°C as measured in accordance with ASTM D3104-14. BN A process involving a solvent having ). [2] The number of dissolution blends (S) of the solvent ranging from 30 to 90 SU BN The process described in [1] above, wherein the process has the following characteristics: [3] The process according to [1] or [2], wherein the contact includes introducing the solvent at a rate of 3 to 8 ml per gram of isotropic pitch. [4] The process according to any one of [1] to [3], wherein the solvent includes an aromatic solvent. [5] The process according to any one of [1] to [4], wherein the solvent comprises heptane and toluene. [6] The process according to [5], further comprising adjusting the ratio of heptane to toluene. [7] The process described in any of [1] to [6] above, wherein the softening point ranges from 270°C to 320°C. [8] The process according to any one of [1] to [7], further comprising reducing the SBN of the solvent in order to increase the recovery rate of the mesophase precursor and to lower the softening point. [9] The isotropic pitch is To provide raw materials having T5 ≥ 400°F (204°C) and T95 ≤ 1,400°F (760°C), and The product is manufactured by a process that includes heating the raw material at a temperature ranging from approximately 420°C to approximately 520°C to produce a heat-treated product containing the isotropic pitch. The aforementioned heating is [X * The procedure was carried out under conditions sufficient to satisfy the relationship Y] ≥ 20,000 seconds. The process according to any one of [1] to [8] above, wherein X is the equivalent reaction time (ERT) in the heating, and Y is the bromine value of the raw material, measured in accordance with ASTM D1159.

[10] The process according to any one of [1] to [9] above, wherein the isotropic pitch has at least one of the following physical properties: (a) Microresidual carbon content (MCR) measured in accordance with ASTM D4530-15, ranging from approximately 30% to 90%; (b) Softening point measured in accordance with ASTM D3104-14, ranging from approximately 80°C to approximately 250°C; (c) Mesophase pitch content greater than approximately 0.5 volume%, measured in accordance with ASTM D4616-95 (2018); and (d) Quinoline-insoluble substance content greater than approximately 1% by mass, as measured in accordance with ASTM D2318-15.

[11] The process according to [8], wherein the method comprises adjusting the SBN to maintain the softening point of the mesophase precursor below 350°C.

Claims

1. A process for manufacturing mesophase pitch, The process involves contacting isotropic pitch with a solvent under conditions sufficient to produce a solvent fraction containing the solvent and an insoluble fraction containing mesophase pitch, and This includes recovering the mesophase pitch, The contact is configured such that the mesophase pitch has a softening point ranging from 270°C to 350°C, as measured in accordance with ASTM D3104-14, by a number of dissolution blends (S BN Includes a solvent having ) The solvent comprises a first solvent which is a nonpolar solvent for asphaltenes and a second solvent which is a nonpolar non-solvent for asphaltenes. Furthermore, the method includes adjusting the ratio of the first solvent to the second solvent based on the softening point of the mesophase pitch. The isotropic pitch is To provide raw materials having T5 ≥ 400°F (204°C) and T95 ≤ 1,400°F (760°C), and A process manufactured by a step comprising heating the raw material at a temperature ranging from 420°C to 520°C to produce a heat-treated product containing the isotropic pitch.

2. The solvent has a number of dissolution blends (S) ranging from 30 to 90 SU. BN The process according to claim 1, comprising:

3. The process according to claim 1, wherein the contact includes introducing the solvent at a rate of 3 to 8 ml per gram of isotropic pitch.

4. The process according to claim 1, wherein the solvent includes an aromatic solvent.

5. The process according to claim 1, wherein the first solvent comprises heptane and the second solvent comprises toluene.

6. The process according to claim 5, further comprising adjusting the ratio of the first solvent containing heptane to the second solvent containing toluene to 50% by volume or more.

7. The process according to claim 1, wherein the softening point ranges from 270°C to 320°C.

8. The process according to claim 1, further comprising reducing the SBN of the solvent in order to increase the recovery rate of the mesophase precursor and to lower the softening point.

9. The aforementioned heating is [X * The experiment was conducted under conditions sufficient to satisfy the relationship Y ≥ 20,000 seconds. The process according to claim 1, wherein X is the equivalent reaction time (ERT) in the heating, and Y is the bromine value of the raw material, measured in accordance with ASTM D1159.

10. The process according to claim 1, wherein the isotropic pitch has at least one of the following physical properties: (a) Microresidual carbon content (MCR) ranging from 30% to 90%, measured in accordance with ASTM D4530-15; (b) Softening point measured in accordance with ASTM D3104-14, ranging from 80°C to 250°C; (c) Mesophase pitch content greater than 0.5 volume percent as measured in accordance with ASTM D4616-95 (2018); and (d) Quinoline-insoluble substance content exceeding 1% by mass, as measured in accordance with ASTM D2318-15.

11. The process according to claim 8, wherein the method comprises adjusting the SBN to maintain the softening point of the mesophase precursor below 350°C.

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