Methods for preparing mesophase pitch

Abstract

A method for preparing mesophase bitumen is described. The method typically includes providing feedstocks of T5 having a temperature ≥400°F (204°C) and T95 having a temperature ≤1,400°F (760°C), and heating the feedstocks at a temperature ranging from about 420°C to about 520°C to prepare a heat-treated product comprising isotropic bitumen. Typically, the heating is carried out under conditions sufficient to satisfy the relationship [X*Y] ≥ 20,000 seconds, where X is the equivalent reaction time of the heating, and Y is the bromine value of the feedstock as measured according to ASTM D1159. The method typically further includes mixing the isotropic bitumen with a mixture solubility value (S... BN The solvent of at least about 10 SU is contacted under conditions sufficient to prepare a solvent fraction containing the solvent and an insoluble fraction containing the mesophase pitch; and the mesophase pitch is recovered.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit and priority of U.S. Provisional Application 63 / 138,051, filed January 15, 2021, the disclosure of which is incorporated herein by reference. Technical Field

[0003] This disclosure relates to the preparation of mesophase pitch, which is commonly used in the preparation of carbon fibers. Background Technology

[0004] Isotropic pitch and mesophase pitch are carbonaceous raw materials that can be formed from residues generated during the processing of coal or petroleum feedstocks or through other methods (e.g., acid-catalyzed condensation of small aromatic compounds). Isotropic pitch can be used as a starting material for some grades of carbon fibers. However, carbon fibers prepared from isotropic pitch typically exhibit little molecular orientation and relatively poor mechanical properties. In contrast, carbon fibers prepared from mesophase pitch exhibit highly preferred molecular orientation and relatively superior mechanical properties. Therefore, it is desirable to find systems and / or methods that can improve the ability to prepare mesophase pitch suitable for carbon fiber production.

[0005] U.S. Patent 4,208,267 describes a method for forming mesophase bitumen. An isotropic bitumen sample is solvent extracted. The extract is then exposed to an elevated temperature in the range of 230°C to approximately 400°C to form mesophase bitumen.

[0006] U.S. Patent 5,032,250 describes a method for separating mesophase pitch. An isotropic pitch containing mesogens is combined with a solvent and subjected to dense phase or supercritical conditions, and the mesogens are then separated.

[0007] U.S. Patent 5,259,947 describes a method for forming a solvated mesophase, the method comprising: (1) combining a carbonaceous aromatic isotropic pitch with a solvent; (2) applying sufficient stirring and sufficient heat to cause the insoluble material in the combination to form suspended liquid solvated mesophase droplets; and (3) recovering the insoluble material as a solid or fluid solvated mesophase.

[0008] Other potentially interesting references include U.S. Patent 9,222,027, U.S. Patent Publication 2019 / 0382665, and U.S. Patent Publication 2020 / 0181497. Attached Figure Description

[0009] Figure 1This is a simplified diagram of a non-limiting embodiment of the method disclosed herein.

[0010] Figure 2 This is an optically polarized light micrograph of the isotropic bitumen (bitumen A) used to implement Example 2.

[0011] Figure 3 This is an optically polarized light micrograph of the isotropic bitumen (bitumen B) used in implementing Example 3.

[0012] Figure 4 This is an optically polarized light micrograph of the solid product recovered in Example 2.

[0013] Figure 5 This is an optically polarized light micrograph of the solid product recovered in Example 3. Summary of the Invention Invention Overview

[0015] According to this disclosure, it has now been found that heat-treating the feedstock under conditions with sufficiently harsh bromine values ​​relative to the heavy feedstock advantageously increases the formation of mesophase pitch precursor molecules, which can then develop into mesophase aggregates by solvent extraction.

[0016] Therefore, in one aspect, this disclosure relates to a method for preparing mesophase bitumen, the method comprising: providing a raw material having a T5 of ≥400°F (204°C) and a T95 of ≤1,400°F (760°C); heating the raw material at a temperature ranging from about 420°C to about 520°C to produce a heat-treated product comprising isotropic bitumen, 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 of the heating, and where Y is the bromine value of the raw material as measured according to ASTM D1159; and mixing the isotropic bitumen with a solubility blending number (S)... BN The solvent of at least about 10 SU is contacted under conditions sufficient to produce a solvent fraction containing the solvent and an insoluble fraction containing the mesophase pitch; and the mesophase pitch is recovered.

[0017] In another aspect, this disclosure relates to mesophase pitch prepared by the aforementioned method.

[0018] In another aspect, this disclosure relates to carbon fibers prepared from the aforementioned mesophase pitch.

[0019] In another aspect, this disclosure relates to a method for preparing mesophase pitch, the method comprising: providing a feedstock comprising at least one member selected from the group consisting of: major bottom product (MCB), hydrotreated MCB, steam cracker tar, hydrotreated steam cracker tar, vacuum residue, deasphalted residue, or rock, and mixtures or combinations thereof; heating the feedstock at a temperature ranging from about 420°C to about 520°C to produce a heat-treated product comprising 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 of the heating, and where Y is the bromine value of the feedstock as measured according to ASTM D1159; contacting the isotropic pitch with a solvent selected from monocyclic aromatic compounds, bicyclic aromatic compounds, alkanes, middle distillate solvents, and mixtures or combinations thereof, under conditions sufficient to produce a solvent fraction comprising the solvent and an insoluble fraction comprising the mesophase pitch; and recovering the mesophase pitch.

[0020] Detailed description of the preferred implementation scheme

[0021] The various embodiments described herein provide methods for preparing mesophase pitch via solvent extraction of isotropic pitch, which is formed by heat treatment under sufficiently harsh conditions of T5 with ≥400°F (204°C) and T95 with ≤1,400°F (760°C). Not wishing to be bound by theory, it is believed that mixed solubility values ​​(S... BN A deasphalting solvent with a solvency unit (SU) of at least 10 advantageously allows for the dissolution of low-hydrogen-content, large aromatic molecules in isotropic bitumen without disrupting the development of mesophase aggregates. Typically, the heat treatment of the heavy feedstock is carried out at a temperature ranging from about 420°C to about 520°C and a residence time of 5 minutes to 8 hours, more preferably from about 5 minutes to about 1 hour, and most preferably from 5 minutes to 30 minutes, for example, from about 10 minutes to about 30 minutes. It is not desirable to be bound by theory, but it is believed that heat treatment of the heavy feedstock at a sufficiently harsh degree relative to its reactivity, as measured by the bromine number of the heavy feedstock, advantageously leads to an increase in the formation of mesophase bitumen precursor molecules, which can then develop into mesophase aggregates by solvent extraction, thereby increasing the yield of mesophase bitumen in the solid product recovered from the insoluble fraction.

[0022] All numerical values ​​in the detailed description and claims herein are indicated by “about” or “approximately” and take into account experimental errors and variations that would be expected by one of ordinary skill in the art. Unless otherwise stated, room temperature is approximately 23°C.

[0023] As used herein, “wt%” means weight percentage, “volume%” means volume percentage, “molar%” means molar percentage, and “ppm” means parts per million. “wt ppm” and “wppm” are used interchangeably, meaning parts per million based on weight. Unless otherwise stated, all “ppm” as used herein means weight ppm. All concentrations herein are expressed based on the total amount of the compositions discussed. All ranges expressed herein should be included as both ends of the two specific embodiments, unless otherwise stated or indicated.

[0024] definition

[0025] For the purposes of this specification and the appended claims, the following terms are defined.

[0026] As used herein, the term "asphaltite" refers to a material that is available from crude oil and has an initial boiling point above 1,200°F (650°C), and that is insoluble in straight-chain alkanes, such as hexane and heptane, i.e., alkane solvents.

[0027] As used herein, the term "equivalent reaction time (ERT)" refers to the severity of the operation, expressed as the residence time in seconds in a reactor operating at 468 °C for a reaction with an activation energy of 54 kcal / mol. The ERT for the operation is calculated as follows:

[0028]

[0029] Where W is the dwell time of the operation, in seconds; e is 2.71828; E a It is 225,936 J / mol; R is 8.3145 J·mol. -1 ·K -1 ; and T rxn The temperature of the operation is expressed in Kelvin. Generally, the reaction rate doubles for every 12 to 13°C increase in temperature. Therefore, a residence time of 60 seconds at 468°C is equivalent to 60 ERTs, while raising the temperature to 501°C will make the operation five times more demanding, or 300 ERTs. In other words, 300 seconds at 468°C is equivalent to 60 seconds at 501°C, and the same product mixing and distribution should be obtained under either set of conditions.

[0030] As used herein, the term "bitumen" refers to a viscoelastic carbonaceous residue obtained by distillation of petroleum, coal tar, or an organic substrate. Unless otherwise stated herein, the term "bitumen" refers to petroleum bitumen (i.e., bitumen obtained by distillation of petroleum).

[0031] As used herein, the term "isotropic bitumen" refers to bitumen in which the molecules are not arranged in an optically ordered liquid crystal manner.

[0032] As used herein, the term "major bottom product (MCB)" refers to the bottom fraction obtained from a fluidized bed catalytic cracking process.

[0033] As used herein, the term "mesocrystalline unit" refers to mesophase pitch-forming material or mesophase pitch precursor.

[0034] As used herein, the term "mesophase pitch" refers to pitch that is a structurally ordered, optically anisotropic liquid crystal. Mesophase structures can be described and characterized by various techniques, such as optical birefringence, light scattering, or other scattering techniques.

[0035] As used herein, the term "middle fraction solvent" refers to the recycled portion of the product generated during the upgrading of tar in a steam cracker, wherein such recycled portion has an atmospheric boiling range of about 350°F (177°C) to about 850°F (454°C).

[0036] Test methods

[0037] Mixed solubility value (S) BN ) and Insolubility Number (I N )

[0038] Corresponding to the mixed solubility value (S) BN ) and the insoluble value (I N The SU value is a value that can be used to characterize the solubility performance of the deasphalting solvent described in this paper.

[0039] The first step in determining the insoluble and mixed solubility values ​​of the deasphalting solvent described herein is to determine 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 can be used. One possibility is to observe a drop of the mixture formed by the test liquid mixture and the deasphalting solvent between a slide and a coverslip using transmitted light at a magnification of 50 to 600x using an optical microscope. If the asphaltenes are dissolved, very few dark particles (if any) will be observed. If the asphaltenes are insoluble, many dark (usually brown) particles, typically 0.5 to 10 micrometers in size, will be observed. Another possible method is to place a drop of the mixture formed by the test liquid mixture and the deasphalting solvent on a piece of filter paper and allow it to dry. If the asphaltenes are insoluble, a dark ring or circle will be seen around the center of the yellowish-brown spot produced by the solvent. If the asphaltene is soluble, the spots produced by the solvent will be relatively uniform in color. If the deasphalting solvent is found to contain n-heptane-insoluble asphaltene, the insoluble value and the mixed solubility value are determined according to the procedures described in the following three paragraphs. If the deasphalting solvent is found to be free of n-heptane-insoluble asphaltene, the insoluble value is assigned to zero, and the mixed solubility value is determined by the procedures described in the section labeled "Deasphalting Solvents Free of Asphaltene".

[0040] Asphalt-containing deasphalting solvents

[0041] I of asphaltene-containing deasphalting solvents (e.g., heavy oil containing residual oil) N and S BN The determination requires testing the solubility of the deasphalting solvent in the test liquid mixture at the minimum of two volume ratios of the deasphalting solvent to the test liquid mixture. The test liquid mixture is prepared by mixing two liquids in different proportions. One liquid is nonpolar (test solvent A) and is the solvent for the asphaltenes in the deasphalting solvent. The other liquid is nonpolar (test solvent B) and is the non-solvent for the asphaltenes in the deasphalting solvent. Test solvent A is typically toluene, and test solvent B is typically n-heptane.

[0042] For the first test, choose a convenient volume ratio of oil to test liquid mixture, such as 1 ml oil to 5 ml test liquid mixture. Various mixtures of the test liquid mixture are then prepared by blending n-heptane and toluene in various known proportions. Each of these is mixed with the deasphalting solvent at a selected volume ratio of deasphalting solvent to test liquid mixture. For each of these, it is then determined whether the asphaltenes are soluble or insoluble. Any convenient method can be used. For example, a drop of the mixture formed by the test liquid mixture and deasphalting solvent between a slide and a coverslip can be observed using transmitted light at magnification of 50 to 600x under an optical microscope. If the asphaltenes are dissolved, very few dark particles (if any) will be observed. If the asphaltenes are insoluble, many dark (usually brown) particles, typically 0.5 to 10 micrometers in size, will be observed. The results of blending the deasphalting solvent with all of the test liquid mixtures are sorted according to the percentage of toluene added to the test liquid mixture. The desired value will be between the minimum percentage of toluene that dissolves the asphaltenes and the maximum percentage of toluene that precipitates the asphaltenes. Prepare more test liquid mixtures with toluene percentages within these limits, blend them with oil at a selected oil-to-liquid mixture volume ratio, and determine whether the asphaltenes are soluble or insoluble. The desired value will be between the minimum toluene percentage of dissolved asphaltenes and the maximum toluene percentage of precipitated asphaltenes. Continue this process until the desired value is determined within the desired precision. Finally, take the desired value as the average of the minimum toluene percentage of dissolved asphaltenes and the maximum toluene percentage of precipitated asphaltenes. This is the first baseline point T1 at the selected oil-to-liquid mixture volume ratio R1. This test is called the toluene equivalent test.

[0043] The second benchmark can be determined using the same process as the first benchmark, except by selecting a different volume ratio of the deasphalting solvent to the test liquid mixture. Alternatively, a lower percentage of toluene can be selected than the percentage determined for the first benchmark, and the test liquid mixture can be added to a known volume of oil until the asphaltenes just begin to settle. At this point, the volume ratio R2 of the oil to the test liquid mixture, at the selected toluene percentage T2, becomes the second benchmark. Since the precision of the final figure increases as the second benchmark moves further away from the first benchmark, the preferred test liquid mixture for determining the second benchmark is 0% toluene or 100% n-heptane. This test is called the heptane dilution test.

[0044] Insoluble value I N Defined as:

[0045]

[0046] Mixed solubility value S BN Defined as:

[0047]

[0048] Deasphalting solvent without asphalt

[0049] If the deasphalting solvent does not contain asphaltenes, the insoluble value is zero. However, the determination of the mixed solubility value of a deasphalting solvent without asphaltenes requires the use of a test oil containing asphaltenes, for which the insoluble value and the mixed solubility value have been pre-determined using the procedure just described. First, 1 volume of the test oil is blended with 5 volumes of the deasphalting solvent. Insoluble asphaltenes can be detected by microscopy or spot technique as described above. If the oil is very viscous (greater than 100 centipoise), it can be heated to 100°C during blending and then cooled to room temperature before searching for insoluble asphaltenes. Alternatively, the spot test can be performed on blends of viscous oils in an oven at 50°–70°C. If insoluble asphaltenes are detected, the deasphalting solvent is a non-solvent for the test oil, and the procedure in the next paragraph should be followed. However, if no insoluble asphaltenes are detected, the deasphalting solvent is a solvent for the test oil, and the procedure in the next paragraph should be followed.

[0050] If insoluble asphaltene is detected when 1 volume of the test oil is blended with 5 volumes of the deasphalting solvent, a small volume increment of the deasphalting solvent is added to 5 ml of the test oil until insoluble asphaltene is detected. The volume V of the non-solvent oil... NSO This is equal to the average of the total volume of deasphalting solvent added before the detection of insoluble asphaltene and the total volume added when insoluble asphaltene is first detected. The size of the volume increment can be reduced to the size required for desired accuracy. This is called a non-solvent oil dilution test. If S BNTO It is the mixed solubility value of the test oil, and I NTO If the insolubility value of the test oil is S, then the mixed solubility value S of the non-solvent oil is S. BN It is given by the following formula:

[0051]

[0052] If no insoluble asphaltene is detected when 1 volume of the test oil is blended with 5 volumes of the deasphalting solvent, then the deasphalting solvent is the solvent oil of the test oil. Select the same oil-to-test liquid mixture volume ratio R used to measure the insoluble value and the mixed solubility value of the test oil. TOHowever, various mixtures of the test liquid are now prepared by blending different known proportions of petroleum and n-heptane instead of toluene and n-heptane. Each of these is mixed with the test oil, the volume ratio of oil to test liquid mixture being equal to R. TO Then, determine whether the asphaltene in each of them is soluble or insoluble, for example, by the microscopic or spot test methods discussed above. The results of blending the oil with all of the aforementioned test liquid mixtures are sorted according to the percentage increase in deasphalting solvent in the test liquid mixture. The desired value will be between the minimum percentage of oil dissolving asphaltene and the maximum percentage of deasphalting solvent precipitating asphaltene. Prepare more test liquid mixtures with deasphalting solvent percentages between these limits, and place them at the selected test oil to test liquid mixture volume ratio (R... TO The asphaltene is blended with the test oil to determine whether it is soluble or insoluble. The desired value will be between the minimum deasphalting solvent percentage for dissolving the asphaltene and the maximum deasphalting solvent percentage for precipitating the asphaltene. This process is continued until the desired value is determined within the desired precision. Finally, the desired value is taken as the average of the minimum deasphalting solvent percentage for dissolving the asphaltene and the maximum deasphalting solvent percentage for precipitating the asphaltene. This is based on the volume ratio R of the selected test oil to test liquid mixture. TO The reference point T below SO The test is called the solvent oil equivalent test. If T TO For test oils containing test liquids composed of different proportions of toluene and n-heptane, the volume ratio R of the test oil to test liquid mixture is... TO The mixed solubility value S of the deasphalting solvent is then determined based on a pre-measured reference point. BN It is given by the following formula:

[0053]

[0054] Mesophase pitch content determined by optical microscopy

[0055] Unless otherwise stated herein, the mesophase pitch content of the samples was determined by optical microscopy according to the following procedure. A digital image of the sample was generated using optical microscopy. A histogram of the total number of pixels in the digital image was then prepared by color intensity, where brighter areas correspond to mesophase pitch due to its high refractive index. The image was divided into mesophase pitch and non-mesophase pitch regions by thresholding, where areas with intensity less than a specific threshold correspond to mesophase pitch. An estimate of the mesophase pitch content of the sample, expressed as an area percentage (%), was then obtained by subtracting the area of ​​the non-mesophase pitch from the image and subsequently dividing the total area of ​​the mesophase pitch in the image by the total area of ​​the image (this result can then be extrapolated to an estimate corresponding to a volume percentage).

[0056] Specific aspects of the invention will now be described in more detail. Although the following description refers to specific aspects, those skilled in the art will understand that these are merely exemplary and that the invention can be practiced in other ways. References to this “invention” may refer to one or more, but not all, of the invention as defined by the claims. The use of headings is merely for convenience and should not be construed as limiting the scope of the invention to the specific aspects.

[0057] Heavy raw materials

[0058] In the methods of this disclosure, the heavy feedstock can be characterized by its boiling range. One option for defining the boiling range is to use the initial boiling point and / or the final boiling point of the feed. Another option, which may provide a more representative description of the feed in some cases, is to characterize the feed based on the amount of feed that boils at one or more temperatures. For example, the “T5” boiling point of the feed is defined as the temperature at which 5% by weight of the feed will evaporate. Similarly, the “T95” boiling point is the temperature at which 95% by weight of the feed will boil. The percentage of feed that will boil at a given temperature can be determined, for example, by the method specified in ASTM D2887 (or by the method in ASTM D7169 if ASTM D2887 is not applicable to a particular fraction). Typically, the heavy feedstock may have a T5 of ≥400°F (204°C) and a T95 of ≤1,400°F (760°C). Examples of such heavy feedstocks include those having a fraction of 1,050°F+ (566°C+). In some aspects, the 566°C+ fraction may correspond to 1 wt% or more (i.e., T99 at 566°C or higher), or 2 wt% or more (T98 at 566°C or higher), or 10 wt% or more (T90 at 566°C or higher), or 15 wt% or more (T85 at 566°C or higher), or 30 wt% or more (T70 at 566°C or higher), or 40 wt% or more (T60 at 566°C or higher), for example, from about 1 wt% to about 40 wt% or from about 2 wt% to about 30 wt% of the heavy feedstock.

[0059] The heavy feedstock of this disclosure can be characterized by reactivity, as measured by its bromine value. The heavy feedstock of this disclosure may have a bromine value of ≥3, or ≥5, or ≥10, or ≥30, or ≥40, as measured according to ASTM D1159, for example, from about 3 to about 50, or from about 5 to about 40, or from about 10 to about 30.

[0060] The heavy feedstock of this disclosure can be characterized by its aromatic content. The heavy feedstock of this disclosure may include about 40 mol% or more, or about 50 mol% or more, or about 60 mol% or more, for example up to about 75 mol% or possibly even higher of aromatic carbon. The aromatic carbon content of the heavy feedstock can be determined according to ASTM D5186.

[0061] The heavy feedstock of this disclosure can be characterized by an average carbon number. The heavy feedstock of this disclosure may consist of hydrocarbons having an average carbon number 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).

[0062] The heavy feedstock of this disclosure can be characterized by a microcarbon residue (MCR) as determined by ASTM D4530-15. The heavy feedstock of this disclosure may have an MCR of about 5% by weight or more (e.g., about 5% by weight to about 45% by weight, or about 10% by weight to about 45% by weight).

[0063] The heavy feedstock of this disclosure can be characterized by its hydrogen content. The heavy feedstock of this disclosure typically has a hydrogen content of about 6% to about 11% by weight, for example, from about 6% to about 10% by weight.

[0064] The heavy feedstock disclosed herein can be characterized by the cumulative concentration of polynuclear aromatic hydrocarbons (PNAs) and polycyclic aromatic hydrocarbons (PAHs). The feedstock disclosed herein may have a cumulative concentration of about 20% by weight or more (e.g., about 50% by weight to about 90% by weight) of partially hydrogenated PNAs and partially hydrogenated PAHs.

[0065] In some aspects, suitable heavy feedstocks may include about 50 wppm to about 10,000 wppm or more of elemental nitrogen (i.e., the weight of nitrogen in the various nitrogen-containing compounds within the feedstock). Additionally or alternatively, the heavy feedstock may include about 100 wppm to about 20,000 wppm of elemental sulfur, preferably about 100 wppm to about 5,000 wppm of elemental sulfur. Sulfur will generally be present as organically bonded sulfur. Examples of such sulfur compounds include heterocyclic sulfur compounds, such as thiophene, tetrahydrothiophene, benzothiophene, and their higher homologues and analogues. Other organically bonded sulfur compounds include aliphatic thiols, cycloalkane thiols and aromatic thiols, sulfides, as well as disulfides and polysulfides.

[0066] Examples of suitable heavy feedstocks include, but are not limited to, major bottoms product (MCB), steam cracker tar, vacuum residue, deasphalted residue or rock, any of the foregoing in hydrotreated or hydro-processed form, and any combination of the foregoing. A preferred heavy feedstock may be hydrotreated MCB. Another preferred example of a heavy feedstock is hydrotreated steam cracker tar. Steam cracker tar and subsequent hydrotreatment can be prepared / performed by any suitable method, including, for example, the method disclosed in U.S. Patent 8,105,479, which is incorporated herein by reference in its entirety.

[0067] Heat treatment

[0068] In the methods of this disclosure, the heavy feedstock typically undergoes a heat treatment step to dealkylate and / or dehydrogenate the heavy feedstock and prepare isotropic pitch. As mentioned above, it is not desirable to be bound by theory, but it is believed that carrying out the heat treatment step under sufficiently harsh conditions with respect to the reactivity of the feedstock advantageously results in the formation of mesocrystalline units in the resulting isotropic pitch, which can then develop into mesophase aggregates by solvent extraction. Typically, such conditions are more harsh than those used in viscosity-reducing cracking. More specifically, the heat treatment is typically carried out at temperatures ranging from about 420°C to about 520°C, preferably from about 480°C to about 510°C, and at residence times ranging from about 5 minutes to 8 hours, more preferably from about 5 minutes to about 1 hour, and most preferably from about 5 minutes to about 30 minutes, for example, from about 10 minutes to about 30 minutes. Typically, the harshness required for the heat treatment step depends on the bromine value of the heavy feedstock. Typically, the harshness required for the heat treatment conditions increases as the bromine value of the heavy feedstock decreases. Typically, the heat treatment is carried out 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 ≥ 700,000 seconds), where X is the equivalent reaction time of the heating, and Y is the bromine value of the feedstock. For example, the range of [X*Y] can be from about 20,000 to about 1,000,000 seconds, for example from about 30,000 seconds to about 700,000 seconds, or from about 50,000 seconds to about 500,000 seconds, or from about 50,000 seconds to about 100,000 seconds. For example, in the embodiment where the heavy feedstock has a bromine value of ≥ 10, the minimum ERT of the heat treatment step can be about 2,000 seconds or less, for example, a minimum ERT of 500 seconds. In the 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, for example, a minimum ERT of 10,000 seconds, or a minimum ERT of 8,000 seconds.

[0069] Suitable pressures for the heat treatment step can 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 can be carried out in any suitable vessel, such as a tank, pipe, tubular reactor, or distillation column. Examples of suitable reactor configurations that can be used to perform the heat treatment are described in U.S. Patent 9,222,027, the entire contents of which are incorporated herein by reference.

[0070] Typically, the heat-treated product is a liquid. In some respects, the heat-treated product may be further processed to prepare the isotropic bitumen described herein, for example via flash distillation, distillation, fractionation, another type of separation based on boiling range, preferably vacuum distillation. For example, the heat-treated product often contains one or more light fractions containing diesel and / or gasoline components and heavy fractions containing the isotropic bitumen described herein. In these respects, the yield of the heavy, isotropic bitumen-containing fraction is typically greater than about 50% by weight of the heat-treated product, for example greater than about 60% by weight, preferably greater than about 80% by weight.

[0071] Isotropic asphalt

[0072] The isotropic bitumen produced from the heat treatment (and optionally one or more subsequent separation steps) can be characterized by a trace carbon residue (MCR) measured according to ASTM D4530-15. Typically, the isotropic bitumen of this disclosure may have an MCR of 30 wt% or greater (e.g., preferably about 50 wt% or greater, even more preferably about 60 wt% or greater). For example, suitable isotropic bitumen may have an MCR ranging from about 30 wt% to about 90 wt%, preferably from about 50 wt% to about 90 wt%, even more preferably from about 60 wt% to about 90 wt%. Typically, the isotropic bitumen has an MCR at least 5% greater than that of the heavy feedstock, for example at least 10% greater, more preferably at least 20% greater.

[0073] The isotropic bitumen of this disclosure can be characterized by its softening point as measured according to ASTM D3104-14. Typically, the isotropic bitumen 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 (e.g., 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).

[0074] The isotropic bitumen of this disclosure can be characterized by the quinoline insoluble content measured according to ASTM D2318-15. Typically, the isotropic bitumen of this disclosure may have a quinoline insoluble content of about 1% by weight or more (e.g., preferably about 2% by weight or more, even more preferably about 5% by weight or more, e.g., from about 1% by weight to about 10% by weight).

[0075] The isotropic bitumen of this disclosure can be characterized by its mesophase bitumen content. Typically, the isotropic bitumen of this disclosure may have a mesophase bitumen content greater than about 0.5 wt% and / or greater than about 0.5 vol%, for example, from about 0.5 wt% to about 1 wt%, as measured according to ASTM D4616-95 (2018). Alternatively, the isotropic bitumen of this disclosure may have a mesophase bitumen content less than 0.5 wt%, for example, about 0 wt% or about 0 vol%, as measured according to ASTM D4616-95 (2018).

[0076] The isotropic bitumen of this disclosure can be characterized by its hydrogen content. Typically, the isotropic bitumen of this disclosure may have a hydrogen content of less than about 8% by weight (e.g., preferably about 6% by weight or less, such as from about 4% to about 6% by weight).

[0077] The isotropic bitumen of this disclosure can be characterized by its sulfur content. Typically, the isotropic bitumen of this disclosure may have a sulfur content of less than about 2% by weight (e.g., preferably about 1% by weight or less, even more preferably about 0.5% by weight or less), for example, from about 0% by weight to about 2% by weight.

[0078] Deasphalting solvent

[0079] In the method disclosed herein, the mixture solubility value (S) can be used as a basis. BN To select a suitable deasphalting solvent, the following steps are taken: (The deasphalting solvent typically has an S content of at least about 10 solubility units (“SU”). BN For example, a suitable deasphalting solvent may have an S content of from about 10 to about 150 SU, such as from about 10 to about 130 SU, or from about 10 to about 70 SU, or from about 10 to about 50 SU, or from about 70 to about 130 SU. BN .

[0080] The deasphalting solvent disclosed herein can be characterized by its boiling range. In some aspects, the deasphalting solvent may have an atmospheric boiling range of about 65°C to 200°C, for example, from 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 solvent recovery from the extraction processes described herein, for example, via distillation.

[0081] Examples of suitable deasphalting solvents include, but are not limited to, C2-C. 10Alkanes, such as pentane, heptane, and butane; monocyclic aromatic compounds, such as toluene, xylene, ethylbenzene, and trimethylbenzene; polycyclic aromatic compounds, such as naphthalene, methylnaphthalene, indane, tetrahydronaphthalene, and anthracene; aromatic compounds including heteroatoms, such as pyridine; other heteroatom compounds, such as tetrahydrofuran; heavy naphtha, kerosene, and / or light diesel oil fractions; recycled portions of products generated during the upgrading of heavy oil feedstocks, such as steam cracker tar; and other hydrocarbon or hydrocarbon-like fractions with suitable boiling ranges. When the recycled portion of products generated during the upgrading of steam cracker tar is included in the deasphalting solvent, the distillation cutoff point of the recycled portion can be adjusted to provide a suitable boiling range and / or suitable S BN Typically, the suitable atmospheric boiling range of the recycle portion is from about 350°F (177°C) to about 850°F (454°C), i.e., the middle distillate solvent. Preferred methods for upgrading heavy oil feedstocks to obtain the middle distillate solvent are further described in U.S. Patent Publication 2020 / 0071627, which is incorporated herein by reference in its entirety. In some aspects, alkanes such as hexane or heptane may be included as co-solvents to alter the solubility parameters of the solvent mixture, preferably in an amount of up to about 90% by volume, for example, about 10% by volume, based on the total volume of the solvents. For example, preferred deasphalting solvents may include from about 0 to about 90 vol% alkanes, such as n-heptane, and from about 10 to about 100 vol% toluene, such as 90 vol% toluene and 10 vol% n-heptane, or 80 vol% toluene and 20 vol% n-heptane, or 70 vol% toluene and 30 vol% n-heptane, or 10 vol% toluene and 90 vol% n-heptane. Examples of preferred deasphalting solvents and their associated S BN The values ​​are depicted in Table 1.

[0082] Table 1

[0083] solvent <![CDATA[S BN (SU)]]> Toluene 100 Monocyclic aromatic compounds 90-100 Bicyclic aromatic compounds ～120 10 vol%: 90 vol% n-Heptane: Toluene 90 20 vol%: 80 vol% n-Heptane: Toluene 80 70 vol%: 30 vol% n-Heptane: Toluene 30 90 vol% : 10 vol% n-Heptane : Toluene 10 Middle distillate solvents 100-120 30 vol%: 70 vol% n-Heptane: Middle Distillate Solvent 70-84

[0084] Solvent extraction

[0085] In the methods of this disclosure, typical solvent extraction conditions include mixing the isotropic bitumen with the deasphalting solvent at a volume ratio (deasphalting solvent: isotropic bitumen) from about 10:1 to about 1:1, for example, about 8:1 or less. Typically, the extraction is carried out under conditions suitable for maintaining the solvent in a liquid phase. For example, the extraction may preferably be carried out under extraction conditions including a temperature ranging from about 90°C to about 350°C, preferably from about 150°C to about 350°C, even more preferably from about 200°C to about 350°C; a total pressure ranging from about 15 psig (~105 kPa-g) to about 800 psig (~5,600 kPa-g); and a residence time ranging from about 5 minutes to about 5 hours. Typically, the extraction can be carried out under agitation, for example, mechanical agitation using a rotary stirrer. Suitable agitation rates can range from about 10 RPM to about 8,500 RPM, for example, from about 50 RPM to about 5,000 RPM.

[0086] Contacting the isotropic bitumen with the deasphalting solvent produces at least two types of product streams. One type of product stream may be a solvent phase fraction, which comprises a large portion of the deasphalting solvent and a large portion of the heat-treated product or the resulting separated heavy fraction soluble in the deasphalting solvent. Typically, at least a portion of the deasphalting solvent is recovered from the solvent phase fraction, for example by distillation, to recycle and reuse the recovered deasphalting solvent in the solvent extraction. The solvent phase fraction resulting after the recovery of the deasphalting solvent typically contains supplemental bitumen product, also known as deasphalted oil (DAO), which may optionally be recycled to the heat treatment step. The insoluble fraction, also known as rock (the second type of product stream), comprises the remaining portion of the isotropic bitumen, i.e., the portion insoluble in the deasphalting solvent. Typically, the insoluble fraction comprises mesophase bitumen as well as entrained residual solvent and mesophase bitumen precursors. Optionally, the softening point of the insoluble fraction can be reduced by mixing it with a low-softening-point isotropic bitumen (e.g., <200°C) or a low-boiling-point solvent (e.g., having a normal-pressure boiling point ranging from about 200°F (93.3°C) to about 650°F (343°C)). In this regard, the low-softening-point isotropic bitumen or low-boiling-point solvent can be mixed with the insoluble fraction in an amount ranging from about 10 vol% to about 60 vol%, more preferably from about 10 vol% to about 40 vol%, and even more preferably from about 10 vol% to about 20 vol%. Additionally or alternatively, the insoluble fraction can undergo a subsequent heat treatment step to convert the remaining mesophase precursor into mesophase bitumen. Optional heat treatment steps can be carried out at temperatures ranging from about 300°C to about 350°C and can be performed in the presence of a solvent, preferably a low-boiling-point solvent (e.g., having a normal-pressure boiling point ranging from about 200°F (93.3°C) to about 650°F (343°C)). Any convenient form of separation can be used to remove residual solvent from the insoluble fraction, such as one or more drying, distillation, fractionation, another type of separation based on boiling range, etc. Optionally, the recovered residual solvent can be recycled and reused for solvent extraction. Typically, the yield of the residual solid product recovered from the insoluble fraction after removal of residual solvent is at least about 10% by weight, preferably at least about 15% by weight, for example from about 10% by weight to about 50% by weight, or from about 20% by weight to about 40% by weight. The recovered solid product typically contains about 30% by volume or more of the optically active fraction, for example from about 30% by volume to about 95% by volume or from about 50% by volume to about 85% by volume. In some respects, the amount of quinoline-insoluble matter in the recovered solid product may be about 75% by weight or less, or about 50% by weight or less, or about 30% by weight or less, for example from about 0% by weight to about 30% by weight.Alternatively or additionally, the amount of toluene-insoluble matter in the recovered solid product may be about 80% by weight or less, or about 60% by weight or less, or about 40% by weight or less, or about 30% by weight or less, for example from about 0% by weight to about 30% by weight.

[0087] carbon fiber

[0088] The mesophase pitch obtained by the solvent extraction method described herein can be used to form carbon fibers, for example, by using conventional melt spinning methods. Melt spinning for forming carbon fibers is a known technique. For example, the book “Carbon-Carbon Materials and Composites” includes a chapter entitled “Carbon Fiber Manufacturing” written by D.D ...

[0089] Methodology Overview

[0090] The methods disclosed herein may be intermittent, semi-intermittent, continuous, semi-continuous, or any combination thereof, with a preference for continuous methods. Figure 1A summary of a non-limiting embodiment of the method 100 of this disclosure is shown. Heavy feedstock 102 undergoes a heat treatment step in container 104 under conditions sufficient to satisfy the relationship [X*Y] ≥ 20,000 seconds, where X is the equivalent reaction time of the heating, and Y is the bromine number of feedstock 102. The heat treatment step performed in container 104 results in the formation of a heat-treated product 106 comprising isotropic bitumen. Typically (though not required), the heat-treated product 106 may undergo a separation step to form a heavy fraction 108 and a light fraction 110 comprising isotropic bitumen. Optionally, the light fraction 110 may be blended with fuel oil. The resulting heat-treated product 106 or heavy fraction 108 is passed together with a deasphalting solvent 114 into a solvent extractor 112. This results in the formation of solvent phase fraction 116, which comprises a large portion of the deasphalting solvent 114 and a large portion of the heat-treated product 106 or heavy fraction 108 soluble in the deasphalting solvent 114. An insoluble fraction 118, i.e., rock, is also formed, comprising a large portion of the insoluble portion of the heat-treated product 106 or heavy fraction 108. Typically, insoluble fraction 118 contains mesophase bitumen as well as entrained residual solvent and mesophase bitumen precursor. Typically (though not desired), as described herein, insoluble fraction 118 may undergo subsequent heat treatment steps (not shown) to convert the remaining mesophase precursor into mesophase bitumen and / or mixing steps (not shown) to lower the softening point of insoluble fraction 118. Typically (though not desired), a portion of solvent phase fraction 116 may undergo separation steps to form a recovered solvent stream 122 and deasphalted oil (DAO) 120. Optionally, at least a portion of the recovered deasphalting solvent stream 122 may be recycled to the solvent extractor 112 in combination with or via a separate stream from the deasphalting solvent stream 112. Additionally, at least a portion of the DAO 120 and / or at least a portion of the insoluble matter 118 may optionally be recycled to the container 104 in combination with or via a separate stream from the heavy feedstock 102. Detailed Implementation

[0091] The following examples illustrate the invention. Many modifications and variations are possible, and it is to be understood that, within the scope of the appended claims, the invention may be practiced in ways not specifically described herein.

[0092] Example

[0093] Example 1: Preparation of Isotropic Asphalt

[0094] Five isotropic bitumens (bitumen A, bitumen B, bitumen C, bitumen D, and bitumen E) and one comparative isotropic bitumen (bitumen F) were prepared by heat-treating heavy feedstocks with properties summarized in Table 2 under the conditions summarized in Table 3. For bitumen A and bitumen B (but not bitumen C, bitumen D, bitumen E, or bitumen F), the heavy fractions were separated by air distillation after the heat treatment. The heavy feedstocks used for bitumen A and B were products obtained by upgrading steam cracker tar according to the method described in U.S. Patent Publication 2020 / 0071627; the heavy feedstocks used for bitumen C, bitumen D, and bitumen F were hydrotreated MCB; and the heavy feedstock used for bitumen E was (non-hydrotreated) MCB.

[0095] Table 2: Properties of heavy feedstocks used to prepare asphalt AF

[0096] Asphalt A Asphalt B Asphalt C Asphalt D Asphalt E Asphalt F (Comparative Example) Boiling point at normal pressure (°F) >650 >650 -- -- -- -- bromine value <5 <5 10.1 10.1 31.7 10.1 Softening point (°C) <30 <30 <30 <30 <30 <30 Hydrogen content (wt%) 8 8 8.5 8.5 7.96 8.5 Sulfur content (wt%) 0.6 0.6 0.3 0.3 1.87 0.3 Trace carbon residue rate (%) 15.3 15.3 4 4 5.8 4

[0097] Table 3: Heat Treatment Conditions

[0098]

[0099] Figure 2 and Figure 3 Optical micrographs of asphalt A and asphalt B are depicted separately. As can be seen from these figures, little or no intermediate phase is observed. Table 4 describes the properties of the resulting isotropic asphalt (asphalt AE) and comparative asphalt (asphalt F).

[0100] Table 4: Properties of Isotropic Asphalt

[0101]

[0102] As can be seen from Table 4, asphalt A and asphalt C exhibit moderate MCR, while asphalt B and asphalt D exhibit high MCR. These results are expected because the heat treatment conditions used to form asphalt B and asphalt D are more demanding compared to asphalt A and asphalt C.

[0103] Examples 2-6 and Comparative Examples: Solvent Extraction of Isotropic Pitch

[0104] In each of Examples 2-6 and the Comparative Examples, the isotropic asphalt (asphalt A, asphalt B, asphalt C, asphalt D, asphalt E, or asphalt F, respectively) was introduced into 500 ml of Hastelloy. TM In a C276 high-pressure reactor, toluene was then introduced at a ratio of 8 ml toluene per gram of isotropic pitch, i.e., S BN The deasphalting solvent is 100 SU. The resulting mixture is sealed in the autoclave and placed under an inert nitrogen atmosphere.

[0105] For Examples 2, 3, and 6, solvent extraction was carried out in the autoclave at 230°C under autogenous pressure, and for Examples 4, 5, and the comparative example, solvent extraction was carried out at 280°C. For Examples 2, 3, 4, and 6, the solvent / isotropic bitumen mixture was stirred for 1 hour; for Example 5, stirring for 85 minutes; and for the comparative example, stirring for 3 hours. In each case, the mixture was then cooled to room temperature. During the extraction, pressures of 160 psig and 350 psig were generated for the runs carried out at 230°C and 280°C, respectively. After decantation of the solvent phase fraction, the insoluble phase fraction (if any) was collected and subsequently dried for 30 minutes to remove residual solvent and prepare the recovered solid product.

[0106] like Figure 1 and Figure 2 As described in the figure, almost no or no mesophase pitch was observed in the isotropic pitch, thus confirming the formation of mesophase pitch during solvent extraction.

[0107] Figure 4 and 5 Optical micrographs of the recovered solid products obtained from Examples 2 and 3 are depicted respectively. The results of the recovered solid products of Examples 2-6 and the Comparative Examples are summarized in Table 5.

[0108] Table 5: Recovered Solid Products

[0109] Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example Isotropic asphalt Asphalt A Asphalt B Asphalt C Asphalt D Asphalt E Asphalt F Yield (wt%) 30 44 23 30 26 0 Trace carbon residue rate (MCR) (%) 76 75 86.2 84.3 -- -- Photoactive fraction (area %) 75 30 >95 30-40 >75 --

[0110] As can be seen from Table 5, solid products were recovered in each of Examples 2-6, but not in the comparative examples. These results were expected because each of the bitumen AEs had a higher ERT×bromine value compared to bitumen F.

[0111] Example 7: Solvent extraction of isotropic bitumen using a deasphalting solvent with SU of 10.

[0112] In Example 7, isotropic bitumen was prepared by heat treatment of a molten tar heavy feedstock having the following properties: MCR of 24.2%, hydrogen content of 6.9% by weight, and bromine value of approximately 40. The heat treatment was carried out under the following conditions: temperature of 460°C; pressure of 1,000 psig; residence time of 35 minutes; and ERT of 1,387 seconds. The resulting isotropic bitumen exhibited the following properties: MCR of 35.1%; hydrogen content of 5.32% by weight; softening point of <30°C; and mesophase bitumen content of 0% by volume.

[0113] The obtained isotropic asphalt was introduced into 500 ml of Hastelloy. TMIn a C276 autoclave, a mixture of 90 vol%:10 vol% n-heptane:toluene was then introduced at a ratio of 8 ml solvent per gram of isotropic pitch, i.e., S BN The deasphalting solvent is 10 SU. The resulting mixture is sealed in the autoclave and placed under an inert nitrogen atmosphere.

[0114] The solvent extraction process was carried out in an autoclave at 280°C and autogenous pressure. The solvent / isotropic bitumen mixture was stirred for 1 hour and then cooled to room temperature. During the extraction process, a pressure of 350 psig was generated. After decanting the solvent phase fraction, the insoluble phase fraction was collected and subsequently dried for 30 minutes to remove residual solvent and prepare the recovered solid product.

[0115] The recovered solid product exhibited the following properties: a yield of 21 wt%; a photoactivity fraction of 90 wt%; and a softening point of >400 °C. These results confirm that: S BN A deasphalting solvent of 10 SU can effectively produce solid products containing mesophase bitumen.

[0116] All documents described herein are incorporated herein by reference, including any priority documents and / or test procedures, to the extent that they are not inconsistent with this document. It will be apparent from the foregoing general description and specific embodiments that, while the form of this disclosure has been illustrated and described, various modifications may be made without departing from the spirit and scope of this disclosure. Therefore, it is not intended to limit this disclosure. Similarly, for purposes of U.S. law, the term “comprising” is considered synonymous with the term “including.” Likewise, whenever the transitional phrase “comprising” precedes a composition, element, or group of elements, it should be understood that the same group of compositions or elements is also contemplated, wherein the transitional phrase “substantially constitutes…,” “consisting of…,” “selected from…,” or “is” precedes the description of the said composition, one or more elements, and vice versa.

Claims

1. A method for preparing mesophase pitch, the method comprising: Provide raw materials having a T5 temperature of ≥204°C and a T95 temperature of ≤760°C; Define the satisfying relation [X] [Y] ≥ 20,000 seconds of heat treatment conditions for the raw material, where X is the equivalent reaction time ERT of the heat treatment, and where Y is the bromine value of the raw material as measured according to ASTM D1159; The raw material is heated under conditions including a temperature ranging from 420°C to 520°C to prepare a heat-treated product comprising isotropic pitch. contacting the isotropic pitch with a solvent having a mixed solubility value S BN a solvent of at least 10 SUs under conditions sufficient to produce a solvent fraction comprising the solvent and an insoluble fraction comprising mesophase pitch; and The mesophase pitch is recovered.

2. The method according to claim 1, wherein the raw material has a bromine value of ≥ 10, and wherein the heating is performed at an ERT of at least 2,000 seconds.

3. The method according to claim 1, wherein the raw material has a bromine value of < 10, and wherein the heating is performed at an ERT of at least 4,000 seconds.

4. The method of claim 1, wherein the heating is performed at a temperature ranging from 420°C to 510°C.

5. The method of claim 1, wherein the raw material comprises a fraction having a boiling point of ≥ 566°C, ranging from 1 wt% to 40 wt% based on the weight of the raw material.

6. The method of claim 1, wherein the feedstock comprises at least one member selected from the group consisting of: main bottom product MCB, hydrotreated MCB, steam cracker tar, hydrotreated steam cracker tar, vacuum residue, deasphalted residue or rock, and mixtures or combinations thereof.

7. The method according to claim 1, wherein the isotropic asphalt has at least one of the following properties: (a) The range of trace carbon residue rate (MCR) measured according to ASTM D4530-15 is from 30% to 90%; (b) The softening point is measured in accordance with ASTM D3104-14 and ranges from 80°C to 250°C. (c) The content of mesophase bitumen greater than 0.5% by volume, as measured according to ASTM D4616-95 (2018); and (d) The content of quinoline insolubles greater than 1% by weight, as measured according to ASTM D2318-15.

8. The method of claim 7, wherein the isotropic bitumen has a trace carbon residue rate (MCR) of at least 60% as measured according to ASTM D4530-15.

9. The method according to claim 1, the method further comprising separating the heat-treated product to prepare heavy fractions and light fractions comprising the isotropic asphalt.

10. The method of claim 1, wherein the insoluble fraction comprises a residual amount of the solvent, and wherein recovering the mesophase pitch comprises removing at least a portion of the residual solvent to form a recovered solid product, and wherein the yield of the recovered solid product is at least 10% by weight, and wherein the recovered solid product comprises at least 30% by volume of a photoactive fraction.

11. The method of claim 1, wherein during the contact process, the volume ratio of the isotropic bitumen to the solvent ranges from 10:1 to 1:

1.

12. The method of claim 1, wherein the solvent has an S content ranging from 10 SU to 130 SU. BN .

13. The method of claim 1, wherein the solvent has an S content ranging from 10 SU to 100 SU. BN .

14. The method of claim 1, wherein the solvent is selected from monocyclic aromatic compounds, bicyclic aromatic compounds, alkanes, middle distillate solvents and mixtures or combinations thereof, and wherein the solvent comprises from 10 to 100 vol% of a monocyclic aromatic compound and from 10 vol% to 90 vol% of n-heptane based on the volume of the solvent.

15. The method of claim 1, wherein the contact is performed at a temperature ranging from 90°C to 350°C.

16. The method of claim 1, wherein the contact is performed at a temperature ranging from 150°C to 350°C, a pressure ranging from 15 psig to 800 psig, and a residence time ranging from 5 minutes to 5 hours.

17. The method of claim 1, further comprising separating the solvent phase to form a recovered solvent stream and a deasphalted oil stream.

18. The method of claim 17, further comprising recycling at least a portion of the recovered solvent stream to the solvent extraction process, and the method further comprising recycling at least a portion of the deasphalted oil stream to the heat treatment process.

19. Carbon fibers prepared from mesophase pitch prepared by any one of claims 1-18.

20. A method for preparing mesophase pitch, the method comprising: Provide raw materials comprising at least one member selected from the group consisting of: main bottom product MCB, hydrotreated MCB, steam cracker tar, hydrotreated steam cracker tar, vacuum residue, deasphalted residue or rock, and mixtures or combinations thereof. Define the satisfying relation [X] [Y] ≥ 20,000 seconds of heat treatment conditions for the raw material, where X is the equivalent reaction time ERT of the heat treatment, and where Y is the bromine value of the raw material as measured according to ASTM D1159; The raw material is heated under conditions including a temperature ranging from 420°C to 520°C to prepare a heat-treated product comprising isotropic pitch. The isotropic pitch is contacted with a solvent selected from monocyclic aromatic compounds, bicyclic aromatic compounds, alkanes, middle distillate solvents, and mixtures or combinations thereof under conditions sufficient to prepare a solvent fraction containing the solvent and an insoluble fraction containing the mesophase pitch; and The mesophase pitch is recovered.

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