Control of mesophase softening point and production yield by various solvents SBN through solvent deasphalting

Abstract

The present invention provides a method for producing mesophase pitch, comprising the steps of: 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 contact step comprises a solvent having a solubility blend number (SBN) such that the mesophase pitch has a softening point in the range of 270°C to 350°C as measured according to ASTM D3104-14.

Description

Technology Field

[0001] Cross-reference regarding related applications

[0002] This application claims the benefit and priority of U.S. Provisional Application No. 63 / 180,845 filed on April 28, 2021, the disclosure of which is incorporated herein by reference.

[0003] The present disclosure is technically related to U.S. provisional patent application No. 63 / 138,051 filed January 15, 2021, the full text of which is incorporated herein by reference.

[0004] The present disclosure is technically related to U.S. provisional patent application No. 63 / 172,340 filed on April 8, 2021, the full text of which is incorporated herein by reference.

[0005] Technology field

[0006] The present disclosure relates to the preparation of mesophase pitch for use in the manufacture of carbon fibers. Background Technology

[0007] Isotropic pitch and meso-phase pitch are carbon-containing feedstocks that can be formed from residues generated during the processing of coal or petroleum feedstocks or by other methods, such as the acid-catalyzed condensation of less aromatic species. For some grades of carbon fibers, isotropic pitch can be used as an initial feedstock. However, carbon fibers produced from isotropic pitch generally exhibit poor molecular orientation and relatively poor mechanical properties. In contrast to carbon fibers formed from isotropic pitch, carbon fibers produced from meso-phase pitch exhibit very desirable molecular orientation and relatively good mechanical properties. Therefore, it would be desirable to find a system and / or method that can improve the ability to produce meso-phase pitch suitable for manufacturing carbon fibers.

[0008] U.S. Patent No. 4,208,267 describes a method for forming a mesophase pitch. An isotropic pitch sample is solvent-extracted. The extract is then exposed to an elevated temperature in the range of 230°C to about 400°C to form a mesophase pitch.

[0009] U.S. Patent No. 5,032,250 describes a process for isolating mesophase pitch. Isotropic pitch containing mesogens is combined with a solvent, subjected to a dense phase or supercritical condition, and the mesogens are phase-separated.

[0010] U.S. Patent No. 5,259,947 describes a method for forming a solvated mesophase, comprising: (1) combining a carbonaceous aromatic isotropic pitch with a solvent; (2) stirring and applying sufficient heat to form a liquid solvated mesophase droplet in which an insoluble substance in the combination is suspended; and (3) recovering the insoluble substance as a solid or fluid solvated mesophase.

[0011] Other references of potential interest include U.S. Patent No. 9,222,027, U.S. Patent Publication No. 2019 / 0382665, and U.S. Patent Publication No. 2020 / 0181497.

[0012] Brief explanation of the drawing

[0013] FIG. 1 is a diagram of a non-limiting example of the method of the present disclosure.

[0014] Figure 2 is an optically polarized microscope image of meso-phase pitch having a softening point of 400°C+.

[0015] Figure 3 is an optical polarization microscope image of meso-phase pitch having a softening point of 332°C.

[0016] Figure 4a is an optical polarization microscope image of the solvent-separated insoluble material from toluene.

[0017] Figure 4b is an optically polarized microscope image of the solvent-separated insoluble material from heptane:toluene (70:30).

[0018] Summary of the Invention

[0019] The present invention provides a method for preparing mesophase pitch, comprising the steps of: 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 contact is a solubility blending number (S) such that the mesophase pitch has a softening point in the range of 270°C to 350°C as measured according to ASTM D3104-14. BN A method is provided that includes a solvent having ).

[0020] In the above method, the solvent has a solubility blend value (S) in the range of 30 to 90 SU. BN Can have ).

[0021] In the above method, the contact step may include the step of introducing a solvent at a rate of 3 to 8 ml per gram of isotropic pitch.

[0022] In the above method, the solvent may include an aromatic solvent.

[0023] In the above method, the solvent may include heptane and toluene.

[0024] The above method may additionally include a step of adjusting the ratio of heptane to toluene.

[0025] In the above method, the softening point may be in the range of 270°C to 320°C.

[0026] The above method is to increase the recovery yield of the mesophase precursor and lower the softening point of the solvent S BN It may include steps to lower it.

[0027] In the above method, the isotropic pitch can be produced by steps including providing a feedstock having T5 ≥ 400℉ (204℃) and T95 ≤ 1,400℉ (760℃), and heating the feedstock at a temperature in the range of about 420℃ to about 520℃ to produce a heat-treated product containing the isotropic pitch, wherein the heating is performed under conditions sufficient to satisfy the relationship [X*Y] ≥ 20,000 seconds, where X is the equivalent reaction time (ERT) of the heating and Y is the bromide value of the feedstock as measured according to ASTM D1159.

[0028] In the above method, the isotropic pitch has at least one of the following characteristics: (a) a micro carbon residue (MCR) in the range of about 30% to about 90% as measured according to ASTM D4530-15; (b) a softening point in the range of about 80°C to about 250°C as measured according to ASTM D3104-14; (c) a mesophase pitch content greater than about 0.5 volume% as measured according to ASTM D4616-95(2018); and (d) a quinoline insoluble content greater than about 1 weight% as measured according to ASTM D2318-15.

[0029] In the above method, the method maintains the softening point of the mesophase precursor at less than 350°C S BN It may include a step of adjusting. Specific details for implementing the invention

[0030] Detailed description of preferred embodiments

[0031] Various embodiments described herein provide a method for producing mesophase pitch. A significant amount of mesophase molecules (also known as mesophase precursors) exist as isotropic pitch. However, since they are not liquid crystals with a short range of order, they are not mesophase pitch due to their inability to align. It has been discovered that a high mesophase content can be achieved by concentrating the mesophase precursor through solvent deasphalting using a solvent having a high solubility number (e.g., greater than 70, preferably greater than 80, preferably greater than 90, preferably greater than 100) and by rearranging the mesophase precursor at an elevated temperature.

[0032] In order to draw mesophase pitch into pitch-based carbon fibers, the physical properties of the mesophase must meet specific criteria to be processable at the spinning stage. One specific aspect is that the softening point of the mesophase is ideally less than 350°C while preserving a high mesophase content. The technical advancement of the present invention can solve the problem of maintaining a medium to high yield of mesophase while satisfying these spinning criteria defined by the softening point.

[0033] The softening point of the mesophase is the solvent solubility for aromatics as well as mesophase molecular precursors within the isotropic pitch (also S BN It has been found that it is determined by (also known as ). Specifically, mesophase molecules with a broad molecular weight distribution are produced through thermal dealkylation and thermal dehydrogenation from heavy hydrocarbons such as MCB and steam-cracking tar. The molecular composition of the mesophase precursor is related to the severity conditions of thermal dealkylation and thermal dehydrogenation. Different S during deasphalting BN By applying a solvent having, the feed can be fractionated largely into mesophase precursors and largely isopitch. Effectively, solvent S BNAdjusting it is like a knob for adjusting the softening point. The mesophase precursor undergoes realignment to form a mesophase crystal. The average molecular weight of the fractionated and realigned mesophase precursor affects the softening point of the corresponding mesophase.

[0034] All figures within the detailed description and claims of this application are formulated with values ​​indicated as “approximately” or “roughly,” taking into account experimental error and variation expected by those skilled in the art. Unless otherwise indicated, room temperature is approximately 23°C.

[0035] As used herein, “weight%” means weight percentage, “volume%” means volume percentage, “molar%” means mole percentage, “ppm” means parts per million, and “ppm wt” and “wppm” are used interchangeably to mean parts per million by weight. As used herein, all “ppm” are weight ppm unless otherwise specified. All concentrations of the present invention are expressed based on the total amount of the corresponding composition. All ranges expressed herein must include both endpoints as two specific embodiments, unless otherwise specified or indicated.

[0036] definition

[0037] For the purposes of this specification and the appended claims, the following terms are defined.

[0038] As used herein, the term “asphalten” refers to a substance that can be obtained from crude oil and has an initial boiling point of over 1,200°F (650°C), and is insoluble in zero-chain alkanes, such as hexane and heptane, i.e., paraffinic solvents.

[0039] As used herein, the term “Equivalent reaction or residence time (ERT)” refers to the severity of operation expressed as the residence time in seconds for a reaction having an activation energy of 54 kcal / mol in a reactor operating at 468°C. The ERT of operation is calculated as follows:

[0040]

[0041] Here, W is the dwell time of the operation (seconds); e is 2.71828; and E a is 225,936 J / mol; and R is 8.3145 J·mol -1 ·K -1 Igo; T rxn ≠ 10000 is the operating temperature expressed in Kelvin. In very general terms, the reaction rate doubles for every 12 to 13°C increase in temperature. Thus, a residence time of 60 seconds at 468°C is equivalent to 60 ERT, and increasing the temperature to 501°C will make the operation five times harsher, i.e., 300 ERT. Expressed in another way, 300 seconds at 468°C is equivalent to 60 seconds at 501°C, and the same product mixture and distribution must be obtained under any set of conditions.

[0042] As used herein, the term “pitch” refers to a viscoelastic carbonaceous residue obtained from the distillation of petroleum, coal tar, or an organic substrate. Unless otherwise specified herein, the term “pitch” refers to petroleum pitch (i.e., pitch obtained from the distillation of petroleum).

[0043] As used herein, the term "isotropic pitch" refers to a pitch containing unaligned molecules in an optically regular liquid crystal.

[0044] As used herein, the term "main column bottom (MCB)" refers to the bottom fraction from the fluid catalytic cracking process.

[0045] As used herein, the term "mesogen" refers to a mesophase pitch-forming material or a mesophase pitch precursor.

[0046] As used herein, the term "mesophase pitch" refers to a pitch that is a structurally regular optically anisotropic liquid crystal. Mesophase structures can be described and characterized by various techniques such as optical birefringence, light scattering, or other scattering mechanisms.

[0047] As used herein, the term “midcut solvent” refers to a recycled portion of the product generated during the upgrading of the steam cracker tar, wherein this recycled portion has an atmospheric boiling range of about 350°F (177°C) to about 850°F (454°C).

[0048] Solubility blending value (S BN ) and insoluble value (I N )

[0049] Solubility Blending Number (S BN ) and Insolubility Number (I N The SU value corresponding to ) is a value that can be used to characterize the solubility characteristics of the deasphalting solvent described herein.

[0050] When determining the insolubility and solubility values ​​for the deasphalting solvents described herein, the first step is to establish whether the deasphalting solvent contains n-heptane-insoluble asphaltenes. This is achieved by mixing 1 volume of the deasphalting solvent with 5 volumes of n-heptane and determining whether the asphaltenes are insoluble. Any convenient method may be used. One possibility is to observe a droplet of the mixture of the test liquid and the deasphalting solvent between a glass slide and a glass coverslip using transmitted light under an optical microscope at a magnification of 50 to 600×. If the asphaltenes are soluble, a few dark particles will be observed where present. If the asphaltenes are insoluble, a number of dark, usually brownish particles, typically 0.5 to 10 microns in size, will be observed. Another possible method is to place a droplet of the mixture of the test liquid and the deasphalting solvent onto a sheet of filter paper and dry it. If the asphaltene is insoluble, a dark ring or circle will be visible around the center of the yellowish-brown spot formed by the solvent. If the asphaltene is soluble, the color of the spot formed by the solvent will be relatively uniform. If the deasphalting solvent is found to contain n-heptane-insoluble asphaltene, the procedure described in the following three paragraphs is performed to determine the insolubility value and the solubility value. If the deasphalting solvent is found not to contain n-heptane-insoluble asphaltene, the insolubility value is assigned a value of 0, and the solubility value is determined by the procedure described in the section labeled "Deasphalting solvent without asphaltene".

[0051] Asphaltene-containing deasphalting solvent

[0052] I for deasphalting solvents containing asphaltenes, such as heavy oils containing residues N and S BNThe determination requires testing the solubility of the deasphalting solvent in the test liquid mixture at a minimum volume ratio of two volumes of the deasphalting solvent to the test liquid mixture. The test liquid mixture is prepared by mixing two liquids in various ratios. One liquid is nonpolar (Test Solvent A) and is a solvent for asphaltenes in the deasphalting solvent. The other liquid is nonpolar (Test Solvent B) and is a non-solvent for asphaltenes in the deasphalting solvent. Test Solvent A is typically toluene, and Test Solvent B is typically n-heptane.

[0053] A convenient volume ratio of oil to the test liquid mixture, for example, 1 ml of oil to 5 ml of the test liquid mixture, is selected for the first test. Subsequently, various mixtures of the test liquid mixture are prepared by combining n-heptane and toluene in various known ratios. Each of these is mixed with a deasphalting solvent in a selected volume ratio of the deasphalting solvent to the test liquid mixture. Afterward, whether the asphaltene is soluble or insoluble is determined for each of these. Any convenient method may be used. For example, a droplet of the mixture of the test liquid mixture and the deasphalting solvent can be observed between a glass slide and a glass coverslip using transmitted light with an optical microscope at a magnification of 50 to 600×. If the asphaltene is soluble, a few dark particles will be observed where present. If the asphaltene is insoluble, a number of dark, usually brownish particles, generally 0.5 to 10 microns in size, will be observed. The results of combining all test liquid mixtures with deasphalting solvents are aligned as the percentage of toluene in the test liquid mixture increases. The desired value will be between the minimum percentage of toluene that dissolves the asphaltene and the maximum percentage of toluene that precipitates the asphaltene. More test liquid mixtures are prepared with percentages of toluene between these boundaries, combined with oil at a selected oil-to-test liquid mixture volume ratio, and it is determined whether the asphaltene is soluble or insoluble. The desired value will be between the minimum percentage of toluene that dissolves the asphaltene and the maximum percentage of toluene that precipitates the asphaltene. This process continues until the desired value is determined within the desired accuracy. Finally, the desired value is considered to be the average of the minimum percentage of toluene that dissolves the asphaltene and the maximum percentage of toluene that precipitates the asphaltene. This is the first reference point (T1) at the volume ratio (R1) of the selected oil to the test liquid mixture. This test is called the toluene equivalence test.

[0054] The second reference point can be determined by the same process as the first reference point, solely by selecting a different volume ratio of the deasphalting solvent to the test liquid mixture. Alternatively, a lower percentage of toluene than that determined for the first reference point may be selected, and such a test liquid mixture may be added to a known volume of oil until the asphaltene begins to precipitate. At that point, the volume ratio of oil (R2) to the test liquid mixture at the selected percentage of toluene (T2) in the test liquid mixture becomes the second reference point. Since the accuracy of the final value increases as the second reference point moves further away from the first reference point, the preferred test liquid mixture for determining the second reference point is 0% toluene or 100% n-heptane. This test is called the heptane dilution test.

[0055] Insoluble value (I N ) is defined as follows:

[0056]

[0057] Solubility blending value (S BN ) is defined as follows:

[0058]

[0059] Asphaltene-free deasphalting solvent

[0060] If the deasphalting solvent does not contain asphaltene, the insolubility value is 0 (zero). However, determining the solubility value for a deasphalting solvent that does not contain asphaltene requires the use of a test oil containing asphaltene, the insolubility value and solubility value of which have been determined in advance using the procedure described above. First, 1 volume of the test oil is mixed with 5 volumes of the deasphalting solvent. Insoluble asphaltene can be detected by the microscope or spot technique described above. If the oil is very viscous (greater than 100 centipoise), the oil may be heated to 100°C during mixing and then cooled to room temperature before the insoluble asphaltene is detected. Additionally, the spot test may be performed on the mixture of viscous oil in an oven at 50°C to 70°C. If insoluble asphaltene is detected, the deasphalting solvent is a non-solvent for the test oil, and the procedure of the following paragraph is performed. However, if insoluble asphaltene is not detected, the deasphalting solvent is a solvent for the test oil, and the procedure of the following paragraph is performed.

[0061] If insoluble asphaltenes are detected when 1 volume of test oil is mixed with 5 volumes of deasphalting solvent, small volume increments of deasphalting solvent are added to 5 ml of test oil until insoluble asphaltenes are detected. Volume of non-solvent oil (V NSO ) is equal to the average of the total volume of deasphalting solvent added for volume increment immediately before insoluble asphaltene is detected and the total volume added when insoluble asphaltene is first detected. The magnitude of the volume increment can be reduced to what is necessary for the desired accuracy. This is called the non-solvent oil dilution test. S BNTO A is the solubility blending value of the test oil and I NTO If 'a' is the insolubility value of the test oil, then the solubility value of the non-solvent oil (S BN ) is provided by the following formula:

[0062]

[0063] If no insoluble asphaltenes are detected when 1 volume of test oil is blended with 5 volumes of deasphalting solvent, the deasphalting solvent is the solvent oil for the test oil. The volume ratio of oil to the same test liquid mixture (R) as used to measure the insolubility value and solubility blending value for the test oil TO ) is selected. However, various mixtures of the test liquid are now prepared by blending petroleum oil and n-heptane in different known ratios instead of toluene and n-heptane. Each of these is R TO It is mixed with the test oil at the same volume ratio of oil to the test liquid mixture. Subsequently, whether the asphaltene is soluble or insoluble is determined for each, for example, by the microscopic or spot test methods discussed above. The results of blending all test liquid mixtures and oils are arranged as the percentage of deasphalting solvent in the test liquid mixture increases. The desired value will be between the minimum percentage of petroleum oil that dissolves the asphaltene and the maximum percentage of deasphalting solvent that precipitates the asphaltene. More test liquid mixtures are prepared with a percentage of deasphalting solvent between these boundaries, and the volume ratio of the selected test oil to the test liquid mixture (R TO It is blended with the test oil, and it is determined whether the asphaltene is soluble or insoluble. The desired value will be between the minimum percentage deasphalting solvent that dissolves the asphaltene and the maximum percentage deasphalting solvent that precipitates the asphaltene. This process continues until the desired value is determined within the desired accuracy. Finally, the desired value is considered to be the average of the minimum percentage deasphalting solvent that dissolves the asphaltene and the maximum percentage deasphalting solvent that precipitates the asphaltene. This is the volume ratio of the selected test oil to the test liquid mixture (R TO Reference point (T) at ) SO) is. This test is called the solvent-oil equivalence test. T TO For test liquids and test oils composed of different ratios of toluene and n-heptane, the volume ratio of the test oil to the test liquid mixture (R TO In the case where it is a reference point measured in advance at ), the solubility blend value of the deasphalting solvent (S BN ) is provided by the following formula:

[0064]

[0065] Mesophase pitch content by optical microscope

[0066] Unless otherwise specified herein, the mesophase pitch content of a sample is determined by an optical microscope according to the following procedure. A digital image of the sample is generated using an optical microscope. Then, a histogram of the total number of pixels of the digital image is generated by color intensity, where brighter intensity regions correspond to the mesophase pitch due to high refractive index. The image is divided into a mesophase pitch area and a non-mesophase pitch area through a threshold, and the area has an intensity below a specific threshold corresponding to the mesophase pitch. Subsequently, an estimate of the mesophase pitch content (% area) of the sample is obtained by subtracting the non-mesophase pitch area of ​​the image and dividing the total amount of the mesophase pitch area of ​​the image by the total area of ​​the image (this result can subsequently be extrapolated to correspond to an estimate of % volume).

[0067] Specific embodiments of the present invention will now be described in greater detail. While the following description relates to specific embodiments, those skilled in the art will understand that this is merely illustrative and that the present invention may be practiced in other ways. References to "the present invention" may refer to one or more, if not all, of the inventions defined by the claims. The use of headings is for convenience only and should not be construed as limiting the scope of the present invention to specific embodiments.

[0068] heavy feedstock

[0069] In the method of the present disclosure, heavy feedstocks may be characterized by a boiling range. One option for defining the boiling range is to use the initial boiling point and / or the final boiling point for the feedstock. Another option, which may provide a more representative description of the feedstock in some cases, is to characterize the feedstock based on the amount of feedstock boiling at one or more temperatures. For example, the “T5” boiling point for the feedstock is defined as the temperature at which 5% by weight of the feedstock boils. Similarly, the “T95” boiling point is the temperature at which 95% by weight of the feedstock boils. The percentage of feedstock boiling at a given temperature may be determined, for example, by the method specified in ASTM D2887 (or by the method of ASTM D7169 if ASTM D2887 is not suitable for the particular fraction). Generally, heavy feedstocks may have T5 ≥ 400℉ (204℃) and T95 ≤ 1,400℉ (760℃). Examples of such heavy feedstocks include those having a 1,050°F+ (566°C+) fraction. In some embodiments, the 566°C+ fraction may correspond to 1 weight% or more of the heavy feedstock (i.e., T99 above 566°C), or 2 weight% or more (T98 above 566°C), or 10 weight% or more (T90 above 566°C), or 15 weight% or more (T85 above 566°C), or 30 weight% or more (T70 above 566°C), or 40 weight% or more (T60 above 566°C), for example, about 1 weight% to about 40 weight% or about 2 weight% to about 30 weight%.

[0070] The heavy feedstock of the present disclosure may be characterized by reactivity as measured by its bromine number. The heavy feedstock of the present disclosure may have a bromine number of ≥3, or ≥5, or ≥10, or ≥30, or ≥40, e.g., about 3 to about 50, or about 5 to about 40, or about 10 to about 30, as measured according to ASTM D1159.

[0071] The heavy feedstock of the present disclosure may be characterized by its aromatic content. The heavy feedstock of the present disclosure may contain aromatic carbon of about 40 mol% or more, or about 50 mol% or more, or about 60 mol% or more, e.g., up to about 75 mol% or possibly much higher. The aromatic carbon content of the heavy feedstock may be determined according to ASTM D5186.

[0072] The heavy feedstock of the present disclosure may be characterized by an average number of carbon atoms. The heavy feedstock of the present disclosure may consist of hydrocarbons having an average number of carbon atoms of about 33 to about 45 (e.g., about 35 to about 40, or about 37 to about 42, or about 40 to about 45).

[0073] The heavy feedstock of the present disclosure may be characterized by micro carbon residue (MCR) as determined by ASTM D4530-15. The heavy feedstock of the present disclosure may have an MCR of about 5 wt% or more (e.g., about 5 wt% to about 45 wt%, or about 10 wt% to about 45 wt%).

[0074] The heavy feedstock of the present disclosure may be characterized by its hydrogen content. The heavy feedstock of the present disclosure generally has a hydrogen content of about 6 weight% to about 11 weight%, e.g., about 6 weight% to about 10 weight%.

[0075] The heavy feedstock of the present disclosure may be characterized by the cumulative concentration of polycyclic aromatic hydrocarbons (PNA) and polycyclic aromatic hydrocarbons (PAH). The feedstock of the present disclosure may have a cumulative concentration of partially hydrogenated PNA and partially hydrogenated PAH of about 20 wt% or more (e.g., about 50 wt% to about 90 wt%).

[0076] In some embodiments, a suitable heavy feedstock may contain elemental nitrogen of about 50 wppm to about 10,000 wppm or more (i.e., the weight of nitrogen in various nitrogen-containing compounds in the feedstock). Additionally or alternatively, the heavy feedstock may contain elemental sulfur of about 100 wppm to about 20,000 wppm, preferably about 100 wppm to about 5,000 wppm. Sulfur will generally exist as organically bonded sulfur. Examples of such sulfur compounds include a class of heterocyclic sulfur compounds such as thiophene, tetrahydrothiophene, benzothiophene, and their higher homologues and analogs. Other organically bonded sulfur compounds include aliphatic, naphthenic, and aromatic mercaptans, sulfides, and di- and polysulfides.

[0077] Examples of suitable heavy feedstocks include, but are not limited to, main column bottom (MCB), steam cracker tar, vacuum residue, deasphalted residue or rock, any of the foregoing in a hydrogenated or hydrogenated form, and any combination of the foregoing. A preferred heavy feedstock may be hydrogenated MCB. Another preferred example of a heavy feedstock is hydrogenated steam cracker tar. Steam cracker tar and subsequent hydrogenation may be produced / performed by any suitable method, including, for example, as disclosed in U.S. Patent No. 8,105,479, the entirety of which is incorporated herein by reference.

[0078] heat treatment

[0079] In the method of the present disclosure, the heavy feedstock generally undergoes a heat treatment step to dealkylate and / or dehydrogenate the heavy feedstock and produce isotropic pitch. As described above, although not intended to be theoretical, performing the heat treatment step under conditions of sufficiently high severity with respect to the reactivity of the feedstock is advantageously considered to induce the formation of mesogens in the resulting isotropic pitch, and this isotropic pitch is considered to be capable of growing into meso-phase aggregates through subsequent deasphalting. Often, these conditions are of a higher severity than that used for bis-breaking. More specifically, the heat treatment can generally be performed at a temperature in the range of about 420°C to about 520°C, preferably about 480°C to about 510°C, and at a residence time in the range of about 5 minutes to 8 hours, more preferably about 5 minutes to about 1 hour, most preferably about 5 minutes to about 30 minutes, e.g., about 10 minutes to about 30 minutes. Generally, the required severity of the heat treatment step depends on the bromine number of the heavy feedstock. Typically, as the bromine number of the heavy feedstock decreases, the required severity of the heat treatment conditions increases. Generally, the heat treatment is performed under conditions sufficient to satisfy the relationship [X*Y] ≥ 20,000 seconds (e.g., ≥ 30,000 seconds, or ≥ 50,000 seconds, or ≥ 70,000 seconds, or ≥ 200,000 seconds, or ≥ 500,000 seconds, or ≥ 500,000 seconds, or ≥ 700,000 seconds), where X is the equivalent reaction time of heating and Y is the bromine number of the feedstock. For example, [X*Y] may be in the range of about 20,000 seconds to about 1,000,000 seconds, e.g., about 30,000 seconds to about 700,000 seconds, or about 50,000 seconds to about 500,000 seconds, or about 50,000 seconds to about 100,000 seconds.For example, in an embodiment where the heavy feedstock has a bromine value of ≥10, the minimum ERT of the heat treatment step may be about 2,000 seconds or less, e.g., a minimum ERT of 500 seconds. In an embodiment where the heavy feedstock has a bromine value of <10, the minimum ERT of the heat treatment step may be greater than about 2,000 seconds, e.g., a minimum ERT of 10,000 seconds, or alternatively, a minimum ERT of 8,000 seconds.

[0080] Suitable pressures for the heat treatment step may be in the range of about 200 psig (1,380 kPa-g) to about 2,000 psig (13,800 kPa-g), e.g., about 400 psig (2,760 kPa-g) to about 1,800 psig (12,400 kPa-g). The heat treatment may be performed in any suitable vessel, such as a tank, piping, tubular reactor, or distillation column. Examples of suitable reactor configurations that may be used to perform the heat treatment are described in U.S. Patent No. 9,222,027, the full text of which is incorporated herein by reference.

[0081] Generally, the heat-treated product is a liquid. In certain embodiments, the heat-treated product may be further processed to produce the isotropic pitch described herein, preferably through vacuum distillation, such as flashing, distillation, fractionation, or another type of separation based on boiling range. For example, the heat-treated product will often contain one or more light fractions containing diesel and / or gasoline components 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 greater than about 50 weight percent of the heat-treated product, e.g., greater than about 60 weight percent, preferably greater than about 80 weight percent.

[0082] isotropic pitch

[0083] The isotropic pitch obtained as a result of heat treatment (and optional subsequent separation step(s)) can be characterized by micro carbon residue (MCR) as measured according to ASTM D4530-15. Generally, the isotropic pitch of the present disclosure may have an MCR of 30 wt% or more (e.g., preferably about 50 wt% or more, more preferably about 60 wt% or more). For example, a suitable isotropic pitch may have an MCR in the range of about 30 wt% to about 90 wt%, preferably about 50 wt% to about 90 wt%, more preferably about 60 wt% to about 90 wt%. Typically, the isotropic pitch has an MCR that is at least 5% greater than the MCR of the heavy feedstock, e.g., at least 10% greater, more preferably at least 20% greater.

[0084] The isotropic pitch of the present disclosure may be characterized by a softening point as measured according to ASTM D3104-14. In general, the isotropic pitch of the present 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 (e.g., preferably in the range of about 80°C to about 250°C, more preferably in the range of about 100°C to about 250°C, and even more preferably in the range of about 150°C to about 250°C).

[0085] The isotropic pitch of the present disclosure may be characterized by its quinoline insoluble content as measured according to ASTM D2318-15. Generally, the isotropic pitch of the present disclosure may have a quinoline insoluble content of about 1 wt% or more (e.g., preferably about 2 wt% or more, more preferably about 5 wt% or more, e.g., about 1 wt% to about 10 wt%).

[0086] The isotropic pitch of the present disclosure may be characterized by a mesophase pitch content. Often, the isotropic pitch of the present disclosure may have a mesophase pitch content greater than about 0.5 wt% and / or greater than about 0.5 volume% as measured according to ASTM D4616-95 (2018), e.g., about 0.5 wt% to about 1 wt%. Alternatively, the isotropic pitch of the present disclosure may have a mesophase pitch content less than 0.5 wt% as measured according to ASTM D4616-95 (2018), e.g., about 0 wt% to about 0 volume%.

[0087] The isotropic pitch of the present disclosure may be characterized by its hydrogen content. Generally, the isotropic pitch of the present disclosure may have a hydrogen content of less than about 8 weight% (e.g., preferably about 6 weight% or less, e.g., about 4 weight% to about 6 weight%).

[0088] The isotropic pitch of the present disclosure may be characterized by its sulfur content. Generally, the isotropic pitch of the present disclosure may have a sulfur content of less than about 2 weight% (e.g., preferably about 1 weight% or less, more preferably about 0.5 weight% or less), e.g., about 0 weight% to about 2 weight%.

[0089] Deasphalting solvent

[0090] In the method of the present disclosure, a suitable deasphalting solvent has a solubility combination value (S BN It can be selected based on ). Typically, the deasphalting solvent is S of at least about 10 units of solubility ("SU"). BN A deasphalting solvent suitable for the technical advancement of the present invention has an S of about 70 to about 150 SU, e.g., 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.BN It may have. Preferably, to obtain a desirable softening point for carbon fiber spinning, while maintaining a medium to high mesophase content, S BN The amount may be at a more suitable level of 30 to 90 SU, more preferably 50 to 90 SU. An amount of SU greater than 100 will raise the softening point to 350°C or higher.

[0091] The deasphalting solvent of the present disclosure may be characterized by a boiling range. In some embodiments, the deasphalting solvent may have an atmospheric boiling range of approximately 65°C to 200°C, e.g., about 100°C to about 175°C. Advantageously, the atmospheric boiling range of the deasphalting solvent may be less than about 200°C to facilitate the recovery of the solvent from the extraction process described herein, e.g., distillation.

[0092] Examples of suitable deasphalting solvents are C2-C such as pentane, heptane, and butane. 10 Paraffins; monocyclic aromatics such as toluene, xylene, ethylbenzene, and trimethylbenzene; polycyclic aromatics such as naphthalene, methylnaphthalene, indane, tetraline, and anthracene; aromatics containing heteroatoms such as pyridine; other heteroatom compounds such as tetrahydrofuran; heavy naphtha, kerosene, and / or light diesel fractions; recycled portions of products generated during the upgrading of heavy oil feedstocks such as steam cracker tar; and other hydrocarbons or hydrocarbon-like fractions having a suitable boiling range, but are not limited thereto. When the recycled portion of products generated during the upgrading of steam cracker tar is included in the deasphalting solvent, the distillation cut point for the recycled portion is a suitable boiling range and / or suitable S BNIt can be adjusted to provide. Typically, a suitable atmospheric boiling range for the recirculated portion is from about 350°F (177°C) to about 850°F (454°C), i.e., a mid-cut solvent. A preferred heavy oil feedstock upgrade process for obtaining a mid-cut solvent is further described in U.S. Patent Publication No. 2020 / 0071627, the full text of which is incorporated herein by reference. In some embodiments, a paraffin such as hexane or heptane may be included as a co-solvent to modify the solubility parameters of the solvent mixture, preferably in an amount of up to about 90 volume%, e.g., about 10 volume%, based on the total volume of the solvent. For example, a preferred deasphalting solvent may comprise about 0 to about 90 volume% of paraffin, e.g., n-heptane, and about 10 to about 100 volume% of toluene, e.g., 90 volume% toluene and 10 volume% n-heptane, or alternatively 80 volume% toluene and 20 volume% n-heptane, or alternatively 70 volume% toluene and 30 volume% n-heptane, or alternatively 10 volume% toluene and 90 volume% n-heptane. Examples of preferred deasphalting solvents include their related S BN It is shown in Table 1 along with the values.

[0093] Table 1

[0094]

[0095] Solvent extraction

[0096] In the method of the present disclosure, typical solvent extraction conditions include mixing isotropic pitch with a deasphalting solvent in a volume ratio of about 10:1 to about 1:1, e.g., about 8:1 or less (deasphalting solvent:isotropic pitch). Typically, extraction is performed under conditions suitable for maintaining the solvent in a liquid phase. For example, extraction may preferably be performed under extraction conditions comprising: a temperature 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, extraction may be performed under stirring, such as mechanical stirring using a rotary stirrer. Suitable stirring speeds may be in the range of about 10 RPM to about 8,500 RPM, for example, about 50 RPM to about 5,000 RPM.

[0097] Contacting isotropic pitch with a deasphalting solvent produces at least two types of product streams. One type of product stream may be a solvent fraction comprising most of the deasphalting solvent and most of the heat-treated product or the resulting separated heavy fraction portion that is soluble in the deasphalting solvent. At least a portion of the deasphalting solvent is typically recovered from the solvent fraction, for example by distillation, for the recycling and reuse of the deasphalting solvent recovered for solvent extraction. The portion of the solvent generated after the recovery of the deasphalting solvent generally comprises a supplementary pitch product, otherwise known as deasphalting oil (DAO), which can be optionally recycled to a heat treatment step. The insoluble fraction (the second type of product stream), otherwise known as rock, comprises the remainder of the isotropic pitch, i.e., the portion that is not soluble in the deasphalting solvent. Generally, the insoluble fraction comprises mesophase pitch as well as the incorporated residual solvent and mesophase pitch precursor. Additionally or alternatively, the insoluble fraction may undergo a subsequent heat treatment step to convert the remaining mesophase precursor into mesophase pitch. The optional heat treatment step may be performed at a temperature in the range of 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 in the range of about 200°F (93.3°C) to about 650°F (343°C)). One or more of any convenient form of separation, e.g., drying, distillation, fractionation, or another type of separation based on boiling range, may be used to remove residual solvent from the insoluble fraction. Optionally, the resulting recovered residual solvent may be recycled and reused for solvent extraction.Generally, the yield of the remaining solid product recovered from the insoluble fraction obtained after the removal of residual solvent is at least about 10 wt%, preferably at least about 15 wt%, e.g., about 10 wt% to about 50 wt%, or about 20 wt% to about 40 wt%. The recovered solid product typically comprises at least about 30 volume%, e.g., about 30 volume% to about 95 volume%, or about 50 volume% to about 85 volume% of an optically active fraction. In some embodiments, the amount of quinoline-insoluble content in the recovered solid product may be about 75 wt% or less, or about 50 wt% or less, or about 30 wt% or less, e.g., about 0 wt% to about 30 wt%. Additionally or alternatively, the amount of toluene-insoluble content in the recovered solid product may be about 80 weight% or less, or about 60 weight% or less, or about 40 weight% or less, or about 30 weight% or less, e.g., about 0 weight% to about 30 weight%.

[0098] carbon fiber

[0099] The mesophase pitch obtained from the solvent extraction process described herein can be used to form carbon fibers, for example, using a conventional melt spinning process. Melt spinning for the formation of carbon fibers is a known technique. For example, the literature ["Carbon-Carbon Materials and Composites"] includes a chapter by DD Edie and RJ Diefendorf titled "Carbon Fiber Manufacturing." Another example is the paper ["Melt Spinning Pitch-Based Carbon Fibers", Carbon , v.27(5), p 647, (1989)] is available.

[0100] Process Overview

[0101] The process disclosed herein may be a batch, semi-batch, continuous, semi-continuous process, or any combination thereof, preferably a continuous process. FIG. 1 illustrates an overview of an exemplary process (100) of the present disclosure that is not limiting. A heavy feedstock (102) undergoes a heat treatment step in a vessel (104) under conditions sufficient to satisfy the relationship [X*Y] ≥ 20,000 seconds, where X is the equivalent reaction time of heating and Y is the bromine value of the feedstock (102). The heat treatment step performed in the vessel (104) results in the formation of a heat-treated product (106) containing isotropic pitch. Often (though not necessarily), the heat-treated product (106) may undergo a separation step to form a heavy fraction (108) and a light fraction (110) containing isotropic pitch. Optionally, the light fraction (110) may be blended with fuel oil. The resulting heat-treated product (106) or heavy fraction (108) is passed through a solvent extractor (112) together with a deasphalting solvent (114). S of the deasphalting solvent (114) BN The mesophase pitch may be selected to have a softening point in the range of 270°C to 350°C (or 270 to 340°C, or 280 to 320°C, or 270 to 310°C) as measured according to ASTM D3104-14. Additionally, when the solvent (114) is a combination of two or more solvents, the ratio of the two solvents may be dynamically controlled by changing the ratio based on feedback regarding the softening point of the mesophase pitch. The solvent may be introduced at a ratio of 3 to 8 ml per gram of isotropic pitch. S of the solvent BN Lowering can increase the recovery yield of mesophase precursors while lowering the softening point. Low S BN The use of a solvent is intended to lower the softening point. Under the same conditions (as shown in the examples), low S BNAlthough having it tends to have a low mesophase content, it is not intended to set a lower mesophase content. However, for fiber spinning, the goal is to find a combination of high mesophase content, medium to high yield, and a desirable softening point. Current technological advancements can provide a knob for adjusting the softening point along with the yield. One side effect is that the mesophase content decreases under the same conditions. Deasphalting conditions can be optimized so that the mesophase content does not decrease. Thus, although it may be counterintuitive, the reduction in mesophase content at the time of acquisition is mitigated by the resulting mesophase precursor producing a mesophase pitch having a more desirable softening point suitable for carbon fiber spinning.

[0102] The addition of the solvent (114) results in the formation of a solvent fraction (116) comprising most of the deasphalting solvent (114) and most of the portion of the heat-treated product (106) or heavy fraction (108) that is soluble in the deasphalting solvent (114). An insoluble fraction (118), i.e., rock, is also formed comprising most of the portion of the heat-treated product (106) or heavy fraction (108) that is insoluble. Generally, the insoluble fraction (118) comprises mesophase pitch as well as the incorporated residual solvent and mesophase pitch precursor. Often (though not necessarily), as described herein, the insoluble fraction (118) may undergo a subsequent heat treatment step (not shown) to convert the remaining mesophase precursor into mesophase pitch. Often (though not necessarily), a portion of the solvent fraction (116) may undergo a separation step to form a recovered solvent stream (122) and deasphalted oil (DAO) (120). Optionally, at least a portion of the recovered deasphalted solvent stream (122) may be recirculated to the solvent extractor (112) in combination with the deasphalted solvent stream (122) or via a separate stream. Additionally, optionally, at least a portion of the DAO (120) and / or at least a portion of the insoluble material (118) may be recirculated to the vessel (104) in combination with the heavy feedstock (102) or via a separate stream.

[0103] The following examples are illustrative of the invention. Many modifications and variations are possible, and it should be understood that, within the scope of the appended claims, the invention may be practiced differently from as specifically described herein.

[0104] Further description of the preparation of isotropic pitch is provided in U.S. Provisional Patent Application No. 63 / 138,051 and is not repeated herein.

[0105] Examples

[0106] Example 1(The manufacturing severity of isotropic pitch affects the corresponding mesophase softening point.)

[0107] The isotropic pitch selected as the feedstock is a product from vapor-cracking tar via thermal dealkylation and thermal dehydrogenation. Table 2 shows the severity conditions of the two isotropic pitch manufacturing processes and the characteristics of these isotropic pitches. Equivalent reaction time (ERT) is used to quantify the degree of severity, with higher values ​​indicating greater severity. ERT refers to the relative residence time under specified process conditions in relation to typical non-breaking conditions at 468°C with an activation energy of 54 kcal / mol. Isotropic pitch 1, prepared at higher severity (i.e., 1390 ERT), was prepared at 230°C for 1 hour with a solvent-to-feed ratio of 8 ml to 1 gram, using heptane (S BNDeasphalting is performed at = 0). The resulting mesophase has a softening point of 400°C+ with a mesophase content of nearly 50% and a recovery yield of 25%. The microscopic characteristics of this mesophase are shown in Fig. 2. In contrast, isotropic 2, prepared with a lower severity (i.e., 845 ERT) by performing the deasphalting process at a ratio of 8 ml of solvent per 1 g of pitch, has a softening point of nearly 300°C with a mesophase content of nearly 60% and a recovery yield of 35% even when the deasphalting process is performed at 280°C for 1.5 hours, in contrast to when isotropic pitch 1 is performed at 230°C for 1 hour. Since higher deasphalting temperatures increase the softening point of the mesophase, observations suggest that the mesophase produced from isotropic pitch 2, which exhibits a softening point of 300°C, is more likely to produce a mesophase with a lower softening point under similar deasphalting conditions compared to isotropic pitch produced under higher harshness. This is likely due to the generation of relatively harder mesophase molecules of isotropic pitch under mild conditions, in contrast to harsh conditions. The microscopic features of the mesophase produced from isotropic pitch 2 are shown in Fig. 3.

[0108] Table 2 (ERT and bulk characteristics of selected isotropic pitch feedstock)

[0109]

[0110] Example 2 (High and low S through solvent deasphalting) BN Comparison of mesophase precursor concentrations from isotropic pitch in a solvent).

[0111] The isotropic pitch used in this example is the same as isotropic pitch 1 of Example 1. To concentrate the mesophase precursor, the solvent deasphalting process is performed at room temperature instead of an elevated temperature. Specifically, the deasphalting process is performed under self-pressure for 1 hour at a solvent ratio of 8 ml to 1 gram of feed. Table 3 shows S BN This summarizes the precursor characteristics and yield according to changes in. This is due to lower S BN S with high solvent deasphalting BN It shows that it induces the additional capture of harder molecules among insoluble substances that are otherwise soluble in the solvent. Additional concentrations of harder molecules contribute to a higher recovery yield and a lower softening point of the mesophase precursor.

[0112] Table 3 (I S BN and high S BN Comparison of Yield and Mesophase Precursor Characteristics in Solvent Deasphalting

[0113]

[0114] Example 3 (High and low S through solvent deasphalting) BN Comparison of mesophase formation from isotropic pitch in a solvent).

[0115] The isotropic pitch selected as the feedstock is a product from Baytown MCB obtained through thermal dealkylation and thermal dehydrogenation. The characteristics of the isotropic pitch are presented in Table 4. Different S BNA solvent containing [the solvent] is introduced into the feedstock at a rate of 3 ml per gram of pitch. This mixture is sealed in an autoclave under an inert environment. The solvent extraction process is operated at 700 psi for 1 hour at 280°C to maintain the solvent in a liquid phase. The insoluble material (also known as the mesophase) is collected after the soluble material is separated by a gradient, subsequently washed, and dried at 120°C for 1 hour to remove residual solvent. The yields and mesophase characteristics of this comparative study are summarized in Table 5, and the microscopic characteristics of the mesophase are illustrated in Figures 4a and 4b.

[0116] Table 4 (Bulk characteristics of selected isotropic pitch feedstock)

[0117]

[0118] Table 5 (I S BN and high S BN Yield in solvent deasphalting and

[0119] Comparison of mesophase characteristics)

[0120]

[0121] Comparative studies on low S during deasphalting BN It is shown that the use of a solvent contributes to the recovery of harder molecules, resulting in an improvement in recovery yield from 26% to 48% and a reduction in the softening point from 400°C+ to 270°C. In contrast, harder molecules are likely to have an adverse effect on mesophase formation under current conditions, which is reflected in the reduction of mesophase content.

[0122] All literature described herein, including any prior art and / or test procedures, is incorporated herein by reference to the extent that it is not inconsistent with the specification. As is evident from the general description and specific embodiments foregoing, the forms of the present disclosure are illustrated and described, but various modifications may be made without departing from the technical spirit and scope of the present disclosure. Accordingly, the present disclosure is not intended to be limited thereto. Likewise, the term “comprising” is considered synonymous with the term “including” for the purposes of U.S. law. Likewise, whenever a composition, element, or group of elements precedes the transitional phrase “comprising,” as is understood, the same group of compositions or elements having the transitional phrases “essentially consisting of,” “consisting of,” “selected from a group consisting of,” or “is” precedes the reference to such composition, element, or elements, and vice versa.

[0123] When numerical lower and upper limits are listed herein, any range of lower to any upper limits is considered. The present disclosure is described in relation to, but is not limited to, specific embodiments. Modifications or variations suitable for operation under specific conditions will be apparent to those skilled in the art. Accordingly, the following claims are intended to be interpreted as encompassing all such modifications or variations that fall within the true technical spirit or scope of the present disclosure.

Claims

Claim 1 A method for preparing mesophase pitch comprises the steps of: 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; recovering the mesophase pitch; and adjusting the ratio of a first solvent to a second solvent based on the softening point of the mesophase pitch, wherein the contact step results in a Solubility Blending Number (S) that causes the mesophase pitch to have a softening point in the range of 270°C to 350°C as measured according to ASTM D3104-14. BN A manufacturing method comprising a solvent having ), wherein the solvent comprises a first solvent which is a nonpolar solvent of asphaltene and a second solvent which is a nonpolar nonsolvent of asphaltene. Claim 2 In claim 1, the solvent has a solubility blend value in the range of 30 to 90 SU (S BN A manufacturing method having ). Claim 3 A manufacturing method according to claim 1, wherein the contact step comprises the step of introducing a solvent at a rate of 3 to 8 ml per gram of isotropic pitch. Claim 4 A manufacturing method according to claim 1, wherein the second solvent comprises an aromatic solvent. Claim 5 A manufacturing method according to claim 1, wherein the first solvent comprises heptane and the second solvent comprises toluene. Claim 6 A manufacturing method according to claim 5, further comprising the step of adjusting the ratio of a first solvent containing heptane to a second solvent containing toluene to 50 volume% or more. Claim 7 A manufacturing method according to claim 1, wherein the softening point is in the range of 270℃ to 320℃. Claim 8 In claim 1, in order to increase the recovery yield of the mesophase precursor and lower the softening point, the solvent S BN A manufacturing method that additionally includes a step of lowering. Claim 9 A method of manufacturing according to claim 1, wherein the isotropic pitch is produced by steps comprising: providing a feedstock having T5 ≥ 400℉ (204℃) and T95 ≤ 1,400℉ (760℃); and heating the feedstock at a temperature in the range of 420℃ to 520℃ to produce a heat-treated product comprising the isotropic pitch, wherein the heating is performed under conditions sufficient to satisfy the relationship [X*Y] ≥ 20,000 seconds, where X is the equivalent reaction time (ERT) of the heating and Y is the bromine value of the feedstock as measured according to ASTM D1159. Claim 10 A method of preparation according to claim 1, wherein the isotropic pitch has at least one of the following characteristics: (a) a micro carbon residue (MCR) in the range of 30% to 90% as measured according to ASTM D4530-15; (b) a softening point in the range of 80°C to 250°C as measured according to ASTM D3104-14; (c) a mesophase pitch content greater than 0.5 volume% as measured according to ASTM D4616-95(2018); and (d) a quinoline insoluble content greater than 1 weight% as measured according to ASTM D2318-15. Claim 11 In paragraph 8, S maintains the softening point of the mesophase precursor below 350℃. BN A manufacturing method comprising a step of adjusting.

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