Thermal conversion of heavy hydrocarbons to mesophase pitch

Abstract

A method for producing mesophase bitumen, the method comprising: providing a raw material having a T5 ≥ 400°F (204°C) and a T95 ≤ 1,400°F (760°C); heating the raw material at a temperature of at least 450°C to produce a heat-treated product comprising mesophase bitumen, wherein the heating is carried out under reaction conditions sufficient to have an equivalent reaction time of greater than or equal to 1,000 seconds; and recovering the mesophase bitumen.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit and priority of U.S. Provisional Application No. 63 / 172340, filed April 8, 2021, the disclosure of which is incorporated herein by reference.

[0003] Related applications

[0004] This disclosure is technically related to U.S. Provisional Patent Application 63 / 138,051, filed January 15, 2021, the entire contents of which are incorporated herein by reference. Technical Field

[0005] This disclosure relates to the production of mesophase pitch, which is commonly used in the production of carbon fibers. Background Technology

[0006] 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 certain grades of carbon fibers. However, carbon fibers produced from isotropic pitch typically exhibit poor molecular orientation and inferior mechanical properties. In contrast, carbon fibers produced from mesophase pitch exhibit highly preferred molecular orientation and superior mechanical properties.

[0007] Conventionally, mesophase pitch can be prepared by thermally converting heavy aromatic hydrocarbons into isotropic pitch in a viscosity-reducing cracker at medium to high pressures (>400°C and >300 psi), followed by continuous isotropic pitch separation using a wiped film evaporator. The isotropic pitch is converted to the mesophase in a batch mode, typically under vacuum, at >420°C with long residence times (e.g., >6 hours). Batch methods are difficult to scale up due to temperature inhomogeneities and the high tendency for coke formation in large autoclaves. Existing techniques are typically limited to approximately 100-gallon sizes. The inefficient batch methods result in high production costs for mesophase.

[0008] The purpose of forming isotropic pitch in mesophase preparation methods is to generate and concentrate carbonaceous material, namely micro carbon residue (MCR), which may be a mesophase precursor. Autoclave methods for mesophase production typically operate at temperatures above 425°C with long residence times, low hydrocarbon partial pressures, and often in a vacuum. Therefore, the cost of mesophase preparation is very high, inevitably leading to expensive pitch-based carbon fibers.

[0009] Despite the exceptionally high performance of pitch-based carbon fibers compared to steel, pitch-based carbon fibers are limited to small-scale applications, such as satellites, sporting goods, and rocket engine nozzles, mainly due to the high cost of producing mesophase.

[0010] U.S. Patent 4,208,267 describes a method for forming mesophase bitumen. An isotropic bitumen sample is subjected to solvent extraction. The extract is then exposed to an elevated temperature in the range of 230°C to approximately 400°C to form mesophase bitumen.

[0011] 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 phase-separated.

[0012] U.S. Patent 5,259,947 describes a method for forming a solvated mesophase, 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.

[0013] US Patent Publication 2019 / 0078023 describes an integrated method for upgrading crude oil and oil residues to produce mesophase bitumen and other petrochemicals.

[0014] Other potential references of interest include U.S. Patent 4,518,483, U.S. Patent 9,222,027, U.S. Patent Publication 2019 / 0382665, and U.S. Patent Publication 2020 / 0181497. Brief description of the attached diagram

[0016] Figure 1 An exemplary method and system for the production of mesophases are shown.

[0017] Figure 2 This is an image of a solid product produced through an implementation scheme of this technological advancement.

[0018] Figure 3 This is an image of a solid product produced through an implementation scheme of this technological advancement. Summary of the Invention Invention Overview

[0020] A method for producing mesophase bitumen, the method comprising: providing a raw material having a T5 ≥ 400°F (204°C) and a T95 ≤ 1,400°F (760°C); heating the raw material at a temperature of at least 450°C to produce a heat-treated product comprising mesophase bitumen, wherein the heating is carried out under reaction conditions sufficient to have an equivalent reaction time of greater than or equal to 1,000 seconds; and recovering the mesophase bitumen.

[0021] In the method described, the temperature can be below 600°C.

[0022] In the method, the raw material may have a hydrogen content of 5.5 to 10% by weight.

[0023] In the method, the heating is the only heating step applied to the raw materials to produce mesophase pitch.

[0024] The method may also include injecting steam into a reactor in which heating occurs.

[0025] The method may also include injecting steam into the feedstock while it is being supplied to the reactor.

[0026] The method may further include injecting steam into a heat-treated product, the heat-treated product comprising mesophase pitch output from a reactor from which heating occurs.

[0027] In the method described, the yield of mesophase pitch can be greater than 1% by weight.

[0028] In the method, the yield of mesophase pitch can be from 10% to 50% by weight.

[0029] In the method, the yield of mesophase pitch can be from 10% to 60% by weight.

[0030] In the method, the reaction conditions may include an inert atmosphere, a temperature of 450°C to 520°C, and a pressure of 500 to 1,500 psig.

[0031] In the method, X is the equivalent reaction time (ERT) of heating, Y is the bromine value of the raw material as measured according to ASTM D1159, and the heating is carried out under reaction conditions sufficient to satisfy the relationship [X*Y]≥31,000 seconds.

[0032] The method may further include controlling the temperature of the heating step to make the equivalent reaction time greater than 1,000 seconds.

[0033] The method may include a raw material comprising about 1% to about 40% by weight of a fraction with a boiling point ≥1,050°F (566°C), based on the weight of the raw material.

[0034] In the method, the feedstock may include at least one member selected from the following: main column bottoms (MCB), hydrotreated MCB, steam cracker tar, hydrotreated steam cracker tar, heavy coker gas oil, steam cracker gas oil, vacuum residue, deasphalted residue or rock, and mixtures or combinations thereof.

[0035] In the method, the recovery of mesophase bitumen may include separating the mesophase bitumen from light hydrocarbons.

[0036] In the method, the heating can be carried out in a reactor, and the method also includes controlling the liquid linear velocity in the reactor, which causes the mesophase precursor to be in slurry form.

[0037] In the method, the control may include injecting steam.

[0038] The system includes: a reactor configured to receive a feedstock having a T5 ≥ 400°F (204°C) and a T95 ≤ 1,400°F (760°C) and heat the feedstock at a temperature of at least 450°C to produce a heat-treated product comprising mesophase pitch, wherein the reactor is configured to heat the feedstock under reaction conditions sufficient to have an equivalent reaction time of greater than or equal to 1,000 seconds; and a separation device in fluid communication with the reactor, wherein the separator is configured to separate the mesophase pitch from the effluent received from the reactor.

[0039] The system may further include a steam injector configured to inject steam into the reactor, the effluent, and / or the feedstock.

[0040] In the system, the separator can be a cyclone separator.

[0041] In the system, the separator can be a deasphalting device. Invention Details

[0043] Surprisingly, it has been discovered that mesophase pitch can be produced from slurry oil in a single thermal step. This unexpected result opens up new avenues for... Figure 1This illustrates the possibility of continuous, one-step thermal processing of mesophase bitumen. One embodiment of this technological advancement utilizes a single thermal step in a continuous flow tubular reactor at an operating pressure greater than 400 psig (measured at the reactor inlet). While operating at higher temperatures, the tubular reactor offers shorter residence times to mitigate coking compared to conventional methods, while also matching the run severity. For example, a continuous tubular reactor operating at 500°C with a 15-minute residence time corresponds to an equivalent secseverity of 4,000 secseverity. Steam can be co-fed into the tubular reactor before the reactor input or after the reactor output. Separation equipment, such as a cyclone separator via gravity separation or via a dissolving DAU (deasphalting unit), can separate the mesophase from the light hydrocarbons and steam.

[0044] The mesophase can be prepared via a one-step thermal processing, which differs from the two-step processing mentioned in the background section. Feedstocks with a relatively higher H content (i.e., 5.5% to 10% by weight, preferably 7% to 8% by weight) than isotropic pitch (i.e., 5-6% by weight), such as main column bottom product (MCB), can be directly converted into the mesophase at elevated temperatures. Exemplary embodiments of this technological advancement may include: (1) thermally treating the feedstock under harsh conditions above typical viscous cracking conditions; (2) setting the pressure to a constant (or substantially constant, varying by no more than + / - 10% during residence time) during the reaction, which causes the light distillate to be stripped from the reactor vessel; (3) the long residence time allows sufficient aromatic polymerization to form an ordered mesophase, which is anisotropic and can be measured by polarized light microscopy due to its inherent birefringence; and (4) recovering the mesophase by separating it from the light hydrocarbons, for example, in the case of a batch process, by a cyclone separator or simply by decanting the liquid product.

[0045] The various embodiments described herein provide methods for producing mesophase bitumen from heavy feedstocks having a T5 ≥ 400°F (204°C) and a T95 ≤ 1,400°F (760°C). However, other feedstocks from MCBs can be used in conjunction with this technological advancement.

[0046] Typically, the individual heat treatment of heavy raw materials is carried out at a temperature of about 450°C to about 520°C for 5 minutes to 8 hours, more preferably about 3 minutes to about 6 hours, even more preferably 5 minutes to 1 hour, for example about 10 minutes to about 60 minutes (or 1 hour), and most preferably a residence time of 5 minutes to 30 minutes.

[0047] All numerical values ​​described herein and within the claims are modified by the terms "approximately" or "roughly" and take into account experimental errors and biases that would be expected by one of ordinary skill in the art. Unless otherwise stated, room temperature is approximately 23°C.

[0048] As used herein, “wt%” means weight percentage, “volume%” means volume percentage, “molar%” means molar percentage, “ppm” means parts per million, and “ppm wt” and “wppm” are used interchangeably to mean by weight. All “ppm” used herein are wt ppm unless otherwise specified. All concentrations herein are based on total amounts of the compositions under discussion. All ranges expressed herein should include both endpoints as two specific embodiments unless otherwise specified or indicated.

[0049] definition

[0050] For the purposes of this specification and the appended claims, the following terms are defined.

[0051] As used herein, the term "equivalent reaction time" or "equivalent residence time" (ERT) refers to the severity of the operation, expressed in seconds as the residence time in a reactor operating at 468°C with an activation energy of 54 kcal / mol. The ERT for the operation is calculated as follows:

[0052]

[0053] Where W is the dwell time in seconds; e is 2.71828; Ea is 225,936 J / mol; and R is 8.3145 J·mol. -1 ·K -1 Trxn is the operating temperature expressed in Kelvin. In very common terminology, 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, and increasing the temperature to 501 °C will make the operation five times more demanding, or 300 ERTs. Alternatively, 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.

[0054] As used herein, the term "bitumen" refers to a viscoelastic carbonaceous residue obtained by distillation of petroleum, coal tar, or an organic matrix. Unless otherwise stated herein, the term "bitumen" refers to petroleum bitumen (i.e., bitumen obtained from petroleum distillation).

[0055] As used in this article, "isotropic pitch" refers to pitch containing molecules that are not optically ordered liquid crystal oriented.

[0056] As used herein, the term "main column bottom product (MCB)" refers to the bottom fraction from a fluidized catalytic cracking process. More specifically, MCB refers to the product fraction of the catalytic cracking process that boils within the boiling range of approximately 200°C to 650°C. However, the boiling range may vary depending on operating conditions.

[0057] As used in this paper, the term "mesophase pitch" or "mesophase" refers to pitch that is a structurally ordered, optically anisotropic liquid crystal. Mesophase structures can be described and characterized using various techniques, such as optical birefringence, light scattering, or other scattering techniques.

[0058] Test methods

[0059] Mesophase bitumen content as determined by optical microscopy

[0060] 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 an optical microscope. A histogram of the total pixel count of the digital image was then constructed using color intensity, where areas of lower intensity correspond to mesophase pitch, attributed to its high refractive index. The image was divided into mesophase pitch and non-mesophase pitch regions via thresholding, where areas with intensity below a certain threshold correspond to mesophase pitch. An estimate of the mesophase pitch content of the sample, expressed as a percentage of area, was obtained by subtracting the non-mesophase pitch area from the image and then dividing the total mesophase pitch area by the total area of ​​the image (this result can then be extrapolated to an estimate corresponding to a percentage of volume).

[0061] Certain 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. Any reference to this “invention” may refer to one or more, but not necessarily 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.

[0062] Heavy raw materials

[0063] In the methods of this disclosure, heavy feedstocks may be characterized by their boiling range. One approach to defining the boiling range is to use the initial boiling point and / or final boiling point of the feed. Another approach, 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 a feed is defined as the temperature at which 5% by weight of the feed will boil. Similarly, the "T95" boiling point is the temperature at which 95% by weight of the feed will boil. The percentage of feed that boils at a given temperature can be determined, for example, by the method specified in ASTM D2887 (or, if ASTM D2887 is not suitable for a particular fraction, by the method in ASTM D7169). Typically, heavy feedstocks may have a T5 ≥ 400°F (204°C) and a T95 ≤ 1,400°F (760°C). Examples of such heavy feedstocks include those with a fraction of 1,050°F+ (566°C+). In some respects, the 566°C+ fraction may correspond to 1% or more by weight of heavy feedstock (i.e., T99 at 566°C or higher), or 2% or more by weight (T98 at 566°C or higher), or 10% or more by weight (T90 at 566°C or higher), or 15% or more by weight (T85 at 566°C or higher), or 30% or more by weight (T70 at 566°C or higher), or 40% or more by weight (T60 at 566°C or higher), for example, about 1% to about 40% by weight or about 2% to about 30% by weight.

[0064] The heavy feedstock of this disclosure can be characterized by its 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, for example, about 3 to about 50, or about 5 to about 40, or about 10 to about 30, as measured according to ASTM D1159.

[0065] The heavy feedstock of this disclosure may be characterized by its aromatic content. The heavy feedstock of this disclosure may contain 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 higher of aromatic carbon. The aromatic carbon content of the heavy feedstock can be determined according to ASTM D5186.

[0066] The heavy feedstock of this disclosure may be characterized by its average carbon number. The heavy feedstock of this disclosure may consist of hydrocarbons with 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).

[0067] The heavy feedstock of this disclosure is characterized by a microcarbon slag ratio (MCR) as determined by ASTM D4530-15. The heavy feedstock of this disclosure may have an MCR of about 5% by weight or higher (e.g., about 5% by weight to about 45% by weight, or about 10% by weight to about 45% by weight).

[0068] The heavy feedstock of this disclosure may be characterized by its hydrogen content. The heavy feedstock of this disclosure generally has a hydrogen content of about 6% to about 11% by weight, for example, about 6% to about 10% by weight, or about 7% to about 8% by weight.

[0069] The heavy feedstock of this disclosure is characterized by the cumulative concentration of polynuclear aromatic hydrocarbons (PNAs) and polycyclic aromatic hydrocarbons (PAHs). The feedstock of this disclosure may have a cumulative concentration of about 20% by weight or higher (e.g., about 50% by weight to about 90% by weight) of partially hydrogenated PNAs and partially hydrogenated PAHs.

[0070] In some respects, suitable heavy feedstocks may contain about 50 wppm to about 10,000 wppm of elemental nitrogen or more (i.e., the nitrogen weight of the various nitrogen-containing compounds in the feedstock). Alternatively or additionally, heavy feedstocks may contain about 100 wppm to about 20,000 wppm of elemental sulfur, preferably about 100 wppm to about 5,000 wppm of elemental sulfur. Sulfur will generally be present as organically bound sulfur. Examples of such sulfur compounds include heterocyclic sulfur compounds, such as thiophene, tetrahydrothiophene, benzothiophene, and their higher homologues and analogues. Other organically bound sulfur compounds include aliphatic, cycloalkanes, and aromatic thiols, sulfides, as well as disulfides and polysulfides.

[0071] Examples of suitable heavy feedstocks include, but are not limited to, main column bottom product (MCB), steam cracker tar, heavy coking gas oil, steam cracker gas oil, vacuum residue, deasphalted residue or residual oil, any of the foregoing hydroprocessing or hydrotreating forms, and any combination of the foregoing substances. 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 hydrotreating can be produced / carried out by any suitable method, including, for example, the method disclosed in U.S. Patent No. 8,105,479, the entire contents of which are incorporated herein by reference.

[0072] Heat treatment

[0073] In the methods disclosed herein, heavy feedstocks typically undergo a heat treatment step to dealkylate and / or dehydrogenate the heavy feedstock and produce isotropic pitch and mesophase pitch. Advantageously and unexpectedly, it has been found that the yield of mesophase pitch can be increased by using higher temperatures in a single heating step. More specifically, the heat treatment can typically be carried out at a temperature of about 450°C to about 550°C, preferably about 480°C to about 510°C, for about 5 minutes to 8 hours, more preferably about 5 minutes to about 1 hour, and most preferably about 5 minutes to about 30 minutes, for example, a residence time of about 10 minutes to about 30 minutes. Generally, the necessary severity of the heat treatment conditions increases as the bromine value of the heavy feedstock decreases. Typically, heat treatment is carried out under conditions sufficient to satisfy the relationship [X*Y] ≥ 31,000 seconds (e.g., ≥ 40,000 seconds, or ≥ 50,000 seconds, or ≥ 60,000 seconds, or ≥ 100,000 seconds, or ≥ 200,000 seconds, or ≥ 500,000 seconds), where X is the equivalent reaction time of heating, and Y is the bromine value of the feedstock. For example, [X*Y] can range from about 31,000 to about 1,000,000 seconds, for example, from about 40,000 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 embodiments where the bromine value of the heavy feedstock is ≥ 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 embodiments where the bromine value of the heavy feedstock is <10, the minimum ERT of the heat treatment step can be greater than about 2,000 seconds, for example, a minimum ERT of 10,000 seconds or a minimum ERT of 8,000 seconds.

[0074] Suitable pressures for the heat treatment step can be 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), and most preferably about 1,000 psig (6,894 kPa-g), measured at the reactor inlet. 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 for heat treatment are described in U.S. Patent 9,222,027, the entire contents of which are incorporated herein by reference.

[0075] Mesophase asphalt

[0076] The resulting mesophase pitch obtained by heat treatment (and optional subsequent separation steps (one or more)) is characterized by a microcarbon slag (MCR) measured according to ASTM D4530-15. Typically, the mesophase pitch of this disclosure may have an MCR of 30% by weight or more (e.g., preferably about 50% by weight or more, even more preferably about 60% by weight or more).

[0077] Any characterization of the softening point is measured according to ASTM D3104-14.

[0078] The mesophase pitch content was measured according to ASTM D4616-95 (2018).

[0079] carbon fiber

[0080] The mesophase pitch obtained by the methods 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 titled "Carbon Fiber Manufacturing" by D.D ...

[0081] Process Overview

[0082] The method disclosed in this paper can be a continuous or semi-continuous method, but a continuous method is preferred. Figure 1 A summary of a non-limiting example process 100 of this disclosure is shown. A heavy feedstock 102 undergoes a heat treatment step in a vessel (preferably a tubular reactor) 104 under conditions sufficient to satisfy the relationship [X*Y] ≥ 31,000 seconds, where X is the equivalent reaction time of heating, and Y is the bromine value of the feedstock 102 (or, the severity such that heating produces an ordered liquid crystal mesophase). The heat treatment step in vessel 104 results in the formation of a heat-treated product or effluent 106 comprising mesophase pitch. Optionally, the heat-treated product 106 may undergo a separation step in a separator 108 to form light hydrocarbons and a vapor fraction 110 and mesophase pitch 112. An optional steam injector 114 may inject steam 116 into the feedstock 102 before vessel 104, into vessel 104, or into the effluent 106 after vessel 104.

[0083] The following provides exemplary details on how to perform the method of Figure 4. A heavy hydrocarbon feed (e.g., MCB) can be fed into a tubular reactor operated at pressures of 500 to 1,500 psig and sufficiently harsh conditions (e.g., >1,000 equivalent seconds, preferably >2,000 equivalent seconds) to prepare a mesophase precursor. The temperature in the tubular reactor can be from 450°C to 600°C, or more preferably from 450°C to 520°C. The formed mesophase precursor can be maintained in slurry form in the tubular reactor to prevent reactor blockage. This can be accomplished by increasing the liquid linear velocity in the tubular reactor to, for example, >1 ft / s, or preferably >4 ft / s. Optionally, steam can be injected around the reactor tubes or at the outlet of the reactor tubes to increase the linear velocity. The effluent can be fed into a separator, such as a cyclone separator, operating at ambient pressures up to 50 psig, to separate the light hydrocarbons (and steam) from the mesophase. The mesophase yield can be 10 to 60%, preferably 13 to 50%, depending on the severity (the higher the severity, the higher the mesophase yield). Light hydrocarbons and steam can be further separated by conventional distillation to recover light hydrocarbons. Optionally, the light hydrocarbons can be recycled to the inlet of the tubular reactor.

[0084] U.S. Patent 4,518,483 claims to first extract the asphaltenes (heptane-insoluble matter) from a heavy hydrocarbon feedstock (MCB, etc.), followed by conversion of the asphaltenes into an intermediate phase in a batch-mode hot soaking unit. Vacuum distillation or steam stripping is then performed to concentrate the intermediate phase by removing lighter substances. Given that asphaltenes have a relatively high softening point compared to MCB, asphaltenes would be very difficult to feed and process. In contrast, the continuous method of this technological advancement is designed to convert heavy feedstocks as a whole. Furthermore, the intermediate phase is produced without the aid of stripping to concentrate the intermediate phase. The harshness conditions differ from those of U.S. Patent 4,518,483; instead, the intermediate phase can be separated by gravity using a cyclone separator.

[0085] The following embodiments illustrate the present invention. Many improvements and modifications are possible, and it should be understood that, within the scope of the appended claims, the invention can be practiced in ways other than those specifically described herein. Example

[0086] Example 1: High-Severity Thermal Conversion of Heavy Hydrocarbon Feedstock

[0087] Main column bottom product (MCB) from the refinery site is used to produce the mesophase via a single thermal reaction (i.e., only one heating step is applied to the MCB feedstock to produce the mesophase). The MCB feedstock used in the examples has approximately 6% of the 566°C+ fraction (567°C for T94.5). Table 1 shows the severity conditions and corresponding equivalent reaction times (ERTs) for three mesophase bitumen preparation methods. ERT is used to quantify the severity level, with higher numbers indicating greater severity. ERT refers to the relative residence time under specified process conditions relative to typical viscous cracking conditions with an activation energy of 54 kcal / mol at 468°C. Viscosity crackers typically operate at 300 to 1,000 ERTs. The mesophase production process is carried out in an autoclave, where the feedstock is heat-treated under high pressure in an inert environment. The MCB undergoes thermal dealkylation and dehydrogenation to remove light substances, while polymerization is performed to prepare a condensed aromatic ring structure. The products can separate into two phases at elevated temperatures, with one phase being the total liquid product (TLP) and the other remaining as a solid. TLP typically has a softening point below 100°C, while the solid has a softening point above 250°C. As the severity of the MCB conversion increases, the yield of the solid increases, while the yield of TLP decreases, as shown in Table 1. At 460°C, the solid product exhibits the following characteristics: Figure 2 The mesophase characteristics shown indicate a mesophase content greater than 80%. The H content is 4.81 wt%, falling within the typical H range of 4.5 wt% to 5 wt% for mesophase. Similarly, the solids recovered at 470 °C and 480 °C also exhibit mesophase optical characteristics under a microscope, and the solid yield can reach 46% at 480 °C, with a mesophase content of 75-85%.

[0088] The data in Table 1 show that the mesophase yield can be 10 to 50 wt%, or preferably 13 to 46 wt%, greater than 1 wt%, greater than 13 wt%, or greater than 22 wt%. Although the data in Table 1 were generated by a high-pressure autoclave in batch mode, kinetics demonstrate that this technological advancement will produce similar amounts of mesophase in a continuous process with the same residence time.

[0089] Table 1. Process conditions and ERT for the production of selected isotropic bitumen

[0090] Batch number 1 2 3 4 ERT 2378 3907 6334 850 Temperature (°C) 460 470 480 440 Pressure (psi) 1000 1000 1000 1000 Duration of stay (h) 1 1 1 1 TLP Yield (wt%) 64.4 46.8 22.8 80 TLP MCR (%) 40.2 44.8 58.2 24.1 Mesophase yield (wt%) 13.2 22.4 46 Negligible Mesophase MCR (%) 60 72.1 74.5 0 Material balance excluding gases (%) 78.0 69.6 69.2 81.5

[0091] Example 2: Low-Cruelty Thermal Conversion of Heavy Hydrocarbon Feedstock

[0092] The feedstock used in this embodiment was the same as that in Example 1. MCB was heat-treated at 440°C under 1,000 psi of N2 for 1 hour. The corresponding ERT was approximately 850, representing typical viscous cracking conditions. Due to the low severity and lack of recovery of mesophase materials, the TLP yield reached 81.5%, with the remainder being gases and light distillates, as shown in Table 1, lot number 4. The comparison between Examples 1 and 2 demonstrates that temperature is a crucial variable in the effectiveness of increasing mesophase yields via a one-step thermal conversion that embodies the advancements of this technology.

[0093] Example 3: Cost-effective continuous one-step thermal method for mesophase production

[0094] Current commercial practice produces mesophase from isotropic bitumen in a batch mode with long residence times, medium to high temperatures, and possibly under vacuum. Batch methods can lead to significant fouling problems due to over-coking. Mesophase handling in this method is labor-intensive because the mesophase needs to be sampled at elevated temperatures before it solidifies in the reactor vessel. Overall, commercial batch methods result in high production costs for the mesophase. In contrast, this technologically advanced one-step thermal method, using a continuous flow tubular reactor and separator, can produce the mesophase directly from the isotropic bitumen, rather than from isotropic bitumen as an intermediate product of the MCB. The tubular reactor can be operated at >400 psig, higher temperatures, but shorter residence times to mitigate coking, while matching the batch severity shown in Table 1. For example, a continuous tubular reactor operating at 500°C with a 15-minute residence time corresponds to a severity of 4,000 equivalent seconds, similar to batch 2 in Table 1. Co-feeding steam to the tubular reactor can further mitigate coke formation. A cyclone separator can separate the mesophase from light hydrocarbons and steam via gravity separation. This continuous configuration enables cost-effective solutions for producing mesophases and significantly reduces costs.

[0095] All documents described herein, including any priority documents and / or experimental procedures, are incorporated herein by reference to all rights, without prejudice to the invention. It will be apparent from the foregoing overview 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 that this disclosure be limited thereto. Similarly, 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 term “comprising,” it should be understood that the same composition or group of elements preceding the listed composition, element, or elements, and vice versa, is also considered to have the transitional terms “substantially composed of,” “composed of,” “selected from,” or “is” preceding the listed composition, element, or elements.

Claims

1. A method for producing mesophase bitumen, the method comprising: a feedstock having T5 > 400 o F (204°C) and T95 < 1,400 o F (760°C), wherein the feedstock comprises 1 wt% or more of a fraction boiling > 566°C (1,050 o F) based on the weight of the feedstock; The raw material is heated to a temperature of at least 450°C to produce a heat-treated product comprising mesophase pitch, wherein the heating is carried out under reaction conditions sufficient to have an equivalent reaction time (ERT) greater than or equal to 1,000 seconds, wherein the ERT is calculated as follows: where W is the heating residence time in seconds; e is 2.71828; Ea is 225,936 J / mol; R is 8.3145 J-mol -1 · K -1 ; and Trxn is the heating temperature in Kelvin; and The mesophase pitch is recovered.

2. The method of claim 1, wherein the temperature is below 600°C.

3. The method of claim 1, wherein the raw material has a hydrogen content of 5.5 to 10% by weight.

4. The method of claim 1, wherein the heating is the only heating step applied to the raw material to produce the mesophase pitch.

5. The method of claim 1, further comprising injecting steam, wherein the steam is injected into a reactor, into the feedstock when the feedstock is supplied to the reactor, or into a heat-treated product comprising mesophase pitch output from a reactor from which heating occurs.

6. The method of claim 1, wherein the yield of the mesophase pitch is greater than 1 wt%.

7. The method of claim 1, wherein the reaction conditions include an inert atmosphere, a temperature of 450°C to 520°C, and a pressure of 500 to 1,500 psig.

8. The method of claim 1 wherein X is the equivalent reaction time (ERT) of said heating, and wherein Y is the bromine value of said feedstock as measured according to ASTM D 1159, and said heating is conducted under reaction conditions sufficient to satisfy the relationship [X Y] > 31,000 seconds.

9. The method of claim 1, further comprising controlling the temperature of the heating step such that the equivalent reaction time is greater than 1,000 seconds.

10. The process of claim 1, wherein the feedstock comprises from 1 wt% to 40 wt% of a fraction having a boiling point > 1,050 o F(566°C) based on the weight of the feedstock.

11. The method of claim 1, wherein the feedstock comprises at least one member selected from: main tower bottom product (MCB), hydrotreated MCB, steam cracker tar, hydrotreated steam cracker tar, heavy coking gas oil, steam cracker gas oil, vacuum residue, deasphalted residue or residual oil, and mixtures or combinations thereof.

12. The method of claim 1, wherein recovering the mesophase bitumen comprises separating the mesophase bitumen from light hydrocarbons.

13. The method of claim 1, wherein the heating is carried out in a reactor, and the method further comprises controlling the liquid linear velocity in the reactor, such that the mesophase precursor is in slurry form.

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