Mesophase pitch and production method and production system therefor

Abstract

The present invention relates to the technical field of carbon materials. Disclosed are a mesophase pitch, and a production method and production system therefor. The method comprises: (1) performing a first thermal reaction on a hydrocarbon-containing raw material to obtain a first gas-phase stream and a first liquid-phase stream; and (2) carrying out a second thermal reaction on the first liquid-phase stream to obtain a second gas-phase stream and a second liquid-phase stream, wherein the content of anisotropic components in the first liquid-phase stream is not greater than 10%, and the average particle size of mesophase spheres in the anisotropic components is not greater than 20 μm. The method is simple to operate, and the obtained mesophase pitch has the characteristics of a moderate softening point, good spinnability, etc.

Description

Mesophase pitch and production method and production system thereof

[0001] Cross-reference to Related Applications

[0002] This application claims the benefit of Chinese Patent Application Nos. 202410823816.8 and 202410823930.0, filed on June 25, 2024, the contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present application relates to the technical field of carbon materials, in particular to a mesophase pitch and a production method and production system thereof. BACKGROUND

[0004] Mesophase pitch is a high-end carbon material precursor with developed anisotropic structure and is widely used in the fields of preparing high-performance carbon fibers, foam carbon, etc. Mesophase pitch is usually obtained by liquid-phase carbonization of a raw material rich in aromatic hydrocarbon components.

[0005] At present, the preparation methods of mesophase pitch mainly include the following: direct thermal polycondensation, hydrogenation treatment, catalytic modification, and co-carbonization, etc.

[0006] The direct thermal polycondensation method is the simplest process, but it has strict requirements on raw materials. Current research shows that mesophase pitch prepared by one-step thermal polycondensation has a high softening point and poor spinnability.

[0007] Hydrogenation treatment usually involves adding a hydrogen donor to pitch to add hydrogen, and then heat-treating the hydrogenated pitch to obtain mesophase pitch. CN114717018A discloses a process for continuously producing soluble mesophase spinning pitch. The process includes the following steps: preparing refined raw materials by modulating and pretreating raw materials, hydrogenating the refined raw materials to obtain refined products, performing hydrogenation / thermal polycondensation reaction on the refined products, distilling the products to obtain hydrogenated pitch, and then performing a moderate thermal polymerization process on the hydrogenated pitch to obtain mesophase pitch. CN111826187A and CN110041952A also belong to the category of hydrogenation treatment, and both of them obtain pitch with a high mesophase content. However, the hydrogenation treatment process is relatively complex and requires high equipment.

[0008] Catalytic upgrading method is to prepare mesophase pitch with controllable molecular structure by adding a certain proportion of catalyst / additive in the system and controlling the degree of reaction direction. CN113528178A discloses a method for preparing mesophase pitch using catalytic oil slurry, taking catalytic oil slurry as raw material and graphene as additive, and preparing high-performance mesophase pitch through two-step thermal polycondensation. CN106497591A discloses a preparation method of catalytic synthesis of mesophase pitch, which adopts purified pitch, pure aromatic hydrocarbon compound, boron trifluoride or boron trifluoride ether complex as catalytic polymerization, then adds pyridine in the cooled solid phase component, removes boron trifluoride through hot filtration to obtain high-purity polymerized pitch, and further removes small molecules to obtain mesophase pitch. The biggest problem of catalytic upgrading method is that the catalyst is difficult to be completely removed from the system, which will lead to too high ash content of mesophase pitch product and affect its spinning performance.

[0009] Co-carbonization method is to realize complementary advantages and improve the performance of carbon materials by matching two different raw materials. CN114381295A discloses a method for preparing high-quality carbon materials from tar, which mixes refined tar obtained by refining the tar with catalytic oil slurry in a certain proportion, and co-carbonizes to obtain high-quality mesophase pitch and needle coke. The mesophase pitch obtained by this method has a higher softening point.

[0010] Some researchers try to prepare mesophase pitch by combining the above methods, but the combination mode and effect are not as expected, and it is difficult to realize the industrial production of high-quality mesophase pitch. SUMMARY

[0011] In view of the problems and deficiencies in the existing mesophase pitch production process, the present application provides a mesophase pitch, a production method and a production system thereof. The production method is simple to operate and the obtained mesophase pitch has moderate softening point and good spinnability.

[0012] The applicant found in the research process that the direct thermal polycondensation method has high requirements for raw materials. Rich aromatic oil is a high-quality production raw material of mesophase pitch recognized in the field, but it also has problems such as wide molecular weight distribution and large difference in reaction activity of different fractions, which easily leads to large difference in reaction progress of different reaction activities in the raw material, especially the reaction of substances with high reaction activity is fast, and the reaction of substances with low reaction activity is slow, which further causes the properties of the whole reaction product system to be uneven and the spinnability to be poor. In the secondary polymerization method, the primary polymerization unit is usually operated at normal pressure or low pressure, and light components escape, and the viscosity of the system increases. The raw material, the primary polymerization unit and the secondary polymerization unit are not effectively associated, and are easy to over-polymerize. The applicant further found that by controlling the properties of the liquid phase stream in the first thermal reaction, the development process of mesophase pitch can be adjusted and the product quality can be improved.

[0013] The first aspect of the present application provides a method for producing mesophase pitch, comprising the following steps:

[0014] (1) subjecting a hydrocarbon-containing raw material to a first thermal reaction to obtain a first gas phase stream and a first liquid phase stream;

[0015] (2) subjecting the first liquid phase stream to a second thermal reaction to obtain a second gas phase stream and a second liquid phase stream;

[0016] wherein the content of anisotropic components in the first liquid phase stream is not more than 10%, and the average particle size of mesophase spherules in the anisotropic components is not more than 20 μm.

[0017] Preferably, the coefficient of variation of the diameter of the mesophase spherules is not more than 15%, preferably not more than 10%; wherein the coefficient of variation of the diameter of the mesophase spherules is calculated by the following formula:

[0018] wherein, N represents the number of all mesophase spherules in the field of view of the polarizing microscope analysis, x i represents the diameter of the i-th mesophase spherule in the field of view of the polarizing microscope analysis, in units of μm; represents the average value of the diameter of all mesophase spherules in the field of view of the polarizing microscope analysis, in units of μm.

[0019] Preferably, the reaction temperature of the first thermal reaction is 10-60°C higher than the reaction temperature of the second thermal reaction, preferably 20-50°C higher.

[0020] Preferably, the method further comprises separating the first gas phase stream and the second gas phase stream to obtain gas, light oil, middle distillate oil and heavy oil; and the method further comprises recycling at least part of the middle distillate oil to step (2) for the second thermal reaction.

[0021] The second aspect of the present application provides the mesophase pitch prepared by the method of the first aspect.

[0022] The third aspect of the present application provides a production system for mesophase pitch, comprising a first reaction unit, a second reaction unit and a settling unit connected in series; the liquid phase stream outlet of the first reaction unit is in communication with the inlet of the second reaction unit, and the liquid phase stream outlet of the second reaction unit is in communication with the inlet of the settling unit.

[0023] The second reaction unit is provided with at least two reactors in parallel, so as to configure the reaction in the second reaction unit as a continuous operation.

[0024] Preferably, the upper stream outlet of the settling unit is in communication with the inlet of the first reaction unit and / or with the inlet of the second reaction unit, preferably with the inlet of the second reaction unit.

[0025] The mesophase pitch production method and production system of the present application have one or more of the following effects compared with the prior art:

[0026] (1) The mesophase pitch production method provided by the present application can effectively control the reaction process by controlling the properties of the first liquid phase stream product, thereby realizing the dynamic balance between the hydrogen supply-thermal polymerization reaction of the reaction system, improving the problem of uneven product properties caused by too high reaction activity of part of the substances, and the production method is simple and the obtained mesophase pitch product has high quality.

[0027] (2) In a preferred embodiment, the mesophase pitch production method provided by the present application includes high-pressure one-step thermal reaction-low-pressure two-step thermal reaction. In the first-stage thermal reaction process, the system can be in a low-viscosity state under high-pressure conditions, and the side chains on the aromatic ring are broken to form free radicals. Under the synergistic action of the self-provided hydrogen-donating groups (the hydrogen-donating index represents the hydrogen-donating ability), excessive polycondensation is avoided, and the molecular weight of the system material tends to be uniform. In the low-pressure two-step thermal reaction process, the system continues to carry out dehydrogenation, cyclization, polycondensation and other reactions. The low-pressure condition is beneficial to the escape of light components between mesophases from the system, promotes the fusion of mesophases, and is more conducive to obtaining high-quality mesophase pitch.

[0028] (3) In a preferred embodiment, the first liquid phase stream and / or heavy oil obtained by separation generated in the mesophase pitch production process can be used for self-purification of the second reaction unit. On the one hand, the first liquid phase stream and heavy oil have good compatibility with the entire reaction system, which can ensure good purification effect. On the other hand, it is not necessary to wait for the second reaction unit to cool down before mechanical polishing. After the mesophase pitch product is discharged, the second reaction unit can be immediately purified to improve the efficiency. Most importantly, the use of the first liquid phase stream and heavy oil for purifying the second reaction unit can avoid excessive polymerization of the residual mesophase pitch product on the inner wall of the reaction unit into semi-coke or coke in the next preparation process, which seriously affects the properties of mesophase pitch. Moreover, the stream can be continuously used for the preparation of mesophase pitch after separation, and the method can be continuously performed, and the product has high quality. BRIEF DESCRIPTION OF DRAWINGS

[0029] FIG. 1 is a flowchart of a mesophase pitch production method according to one embodiment of the present application;

[0030] FIG. 2 is a flowchart of a mesophase pitch production method according to another embodiment of the present application;

[0031] Figure 3 is a polarized light photomicrograph (x 100) of the mesophase pitch product from Example 1 of the application;

[0032] Figure 4 is a polarized light photomicrograph (x 100) of the first liquid phase stream in Example 7 of the application;

[0033] Figure 5 is a polarized light photomicrograph (x 100) of the second liquid phase stream in Example 7 of the application;

[0034] Figure 6 is a polarized light photomicrograph (x 100) of the mesophase pitch product in Example 7 of the application.

[0035] BRIEF DESCRIPTION OF DRAWINGS

[0036] In Figure 1 : 1 is a hydrocarbon-containing feedstock, 2 is a first reaction unit, 3 is a first gas phase stream, 4 is a first liquid phase stream, 5 is a second reaction unit, 6 is a second gas phase stream, 7 is a carrier gas, 8 is mesophase pitch, 9 is a separation unit, 10 is a gas, 11 is a light oil, 12 is a middle distillate oil, 13 is a heavy oil.

[0037] In Figure 2: 1 is a hydrocarbon-containing feedstock, 2 is a first reaction unit, 3 is a first gas phase stream, 4 is a first liquid phase stream, 5 is a second reaction unit, 6 is a second gas phase stream, 7 is a carrier gas, 8 is mesophase pitch, 9 is a separation unit, 10 is a gas, 11 is a light oil, 12 is a middle distillate oil, 13 is a heavy oil, 14 is a stream after purification, 15 is a settling unit, 16 is an upper stream, 17 is a lower stream. DETAILED DESCRIPTION

[0038] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not critical to the properties. The endpoints of the ranges and any values are provided as approximations only and are understood to include values near the recited endpoints. The endpoints of the ranges and any values are provided as approximations only and are understood to include values near the recited endpoints. The endpoints of the ranges and any values are provided as approximations only and are understood to include values near the recited endpoints.

[0039] The description of the example embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. In the description, relative terms such as "lower," "upper," "horizontal," "vertical," "above," "below," "up," "down," "top," and "bottom" as well as derivative thereof (e.g., "horizontally," "downwardly," "upwardly," etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description only and do not require that the apparatus be constructed or operated in a particular orientation unless explicitly indicated otherwise. Terms concerning attachments, coupling and the like, such as "connected," "attached," "supported," and the like, are to be construed in an operational sense, that is, a connection between entities that allows interconnection with other entities, but does not necessarily mean directly connected to or in supporting

[0040] The first aspect of the present application provides a method for producing mesophase pitch, comprising the following steps:

[0041] (1) subjecting a hydrocarbon-containing raw material to a first thermal reaction to obtain a first gas phase stream and a first liquid phase stream;

[0042] (2) subjecting the first liquid phase stream to a second thermal reaction to obtain a second gas phase stream and a second liquid phase stream;

[0043] wherein the anisotropic component content in the first liquid phase stream is not more than 10%, and the average particle size of mesophase spherules in the anisotropic component is not more than 20 μm.

[0044] The present application improves the problem of product property non-uniformity and instability caused by too large difference in reaction activity of different substances in the reaction system by optimizing the property of the first liquid phase stream, and the obtained mesophase pitch product has better spinnability.

[0045] According to the present application, preferably, the anisotropic component content in the first liquid phase stream is not more than 5%, more preferably not more than 3%.

[0046] According to the present application, preferably, the average particle size of mesophase spherules in the anisotropic component in the first liquid phase stream is not more than 10 μm, more preferably not more than 6 μm, and most preferably not more than 5 μm.

[0047] The preferred embodiment is more conducive to controlling the development process of mesophase pitch and further improving the spinnability of the prepared mesophase pitch.

[0048] In the present application, the average particle size of mesophase spherules in the anisotropic component is obtained by polarizing microscope analysis software, extraction and analysis of mesophase spherules.

[0049] In the present application, the anisotropic component content in each stream is obtained by polarizing microscope test, and specifically, the union of the polarized light area in the field of view of the polarizing microscope at the initial state and the 90° rotation state and the total area ratio are determined.

[0050] According to a preferred embodiment of the present application, the coefficient of variation of the mesophase spherule diameter is not more than 15%, preferably not more than 10%, for example, it can be 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1% or 0, and more preferably not more than 7%; wherein the coefficient of variation of the mesophase spherule diameter is calculated by the following formula:

[0051] wherein, N represents the number of all mesophase spherules in the field of view of the polarizing microscope, x iThis represents the diameter of the i-th mesophase sphere within the field of view analyzed by polarizing microscope, in μm. This represents the average diameter of all mesophase microspheres within the field of view analyzed by polarizing microscope, expressed in μm.

[0052] In this invention, the coefficient of variation (CV) is the ratio of the standard deviation to the mean of the diameter of the mesophase microspheres. It represents the relative dispersion of the diameter of the mesophase microspheres and is used to measure the size uniformity of the mesophase microspheres. Adopting the above-mentioned preferred scheme is more conducive to further controlling the chemical reaction and physical change process in step (1), and more conducive to improving the performance of the product.

[0053] According to the present invention, preferably, the softening point of the first liquid phase stream is 110-160°C, more preferably 120-150°C, for example 120°C, 130°C, 140°C, or 150°C.

[0054] In this invention, the softening point is determined using the Mettler method. Specifically, a temperature 20°C lower than the expected softening point is selected as the starting temperature, and then the temperature is increased at a rate of 2°C / min. When the steel ball wrapped in the sample touches the detector during its descent, the temperatures of the two parallel samples are automatically recorded, and the average value of the test is taken as the softening point. If the temperature difference between the softening point test results of the two parallel samples exceeds 2°C, the test is repeated.

[0055] The present invention does not have any particular limitation on the means of controlling the product properties of the first liquid phase material flow; as long as the above requirements are met, the purpose of the present invention can be achieved.

[0056] According to the present invention, preferably, the hydrogen supply index of the hydrocarbon-containing feedstock is not less than 7 mg / g, preferably 7 to 20 mg / g, for example, 7 mg / g, 8 mg / g, 9 mg / g, 10 mg / g, 12 mg / g, 14 mg / g, 16 mg / g, 18 mg / g, 20 mg / g and any value between any two groups, preferably 7 to 15 mg / g.

[0057] The hydrogen supply index (PDQI) of the hydrocarbon feedstock is an indicator characterizing its hydrogen supply performance, representing the number of milligrams of β-position hydrogen atoms in aromatic cycloalkyl groups per gram of hydrocarbon feedstock. The PDQI is determined as follows: Hydrogen nuclear magnetic resonance (NMR) is performed using a superconducting nuclear magnetic resonance spectrometer. 1 ¹H-NMR analysis was performed using deuterated chloroform as solvent and tetramethylsilane as internal standard. The working frequency was 80 MHz and the scan width was 2 kHz. The scan yielded... 1 H-spectrum. Integrating the peaks at different shifts in the spectrum yields the cumulative intensity of different types of hydrogen content. PDQI=(H nβ / H t )×w(H)×10, where Hnβ for 1 Peak areas with shifts between 1.5 and 2.0 ppm in the H spectrum; H t for 1 The sum of the peak areas in the H spectrum; w(H) is the weight percentage of hydrogen obtained from elemental analysis test results according to standard SH / T 0656.

[0058] According to a preferred embodiment of the present invention, the aromatic carbon content of the hydrocarbon-containing raw material is 45% to 90%, preferably 60% to 90%, for example, 60%, 65%, 70%, 75%, 80%, 85%, 90%, and any value between any two groups, more preferably 60% to 85%.

[0059] The aromatic carbon content (f) of the hydrocarbon-containing feedstock described in this invention A The aromatic carbon percentage (f) refers to the percentage of aromatic carbon atoms in a hydrocarbon-containing feedstock relative to the total number of carbon atoms. A )pass 13 C NMR, obtained with reference to SH / T 0793-2007.

[0060] According to the present invention, preferably, the total content of tricyclic aromatic hydrocarbons and tetracyclic aromatic hydrocarbons in the hydrocarbon-containing raw material is not less than 35 wt%, more preferably not less than 38 wt%, and more preferably 38 wt% to 60 wt%. The inventors of the present invention further discovered during their research that tricyclic and tetracyclic aromatic hydrocarbons, due to their strong molecular planarity, easily form larger planar molecules during thermal reactions through condensation and polymerization, affecting the liquid crystal structure of the system. Therefore, the preferred content of tricyclic and tetracyclic aromatic hydrocarbons in the hydrocarbon-containing raw material is more conducive to optimizing the liquid crystal order and optical texture content of the final product.

[0061] The total content of tricyclic and tetracyclic aromatic compounds in the hydrocarbon-containing raw material was determined by separating saturated hydrocarbon fractions, aromatic fractions, and colloidal fractions, along with the percentage content of each fraction, according to ASTM D2549-23. The separated saturated hydrocarbon and aromatic fractions were then subjected to mass spectrometry analysis according to ASTM D2786-91 and ASTM D3239-91. The relative abundance of alkanes, cycloalkanes of different ring numbers, and aromatic hydrocarbons of different ring numbers in the saturated hydrocarbon fraction was determined by summing the fragment peaks with the largest characteristic mass for each molecular type. This method yields the content of tricyclic and tetracyclic aromatic compounds, which, when summed, constitute the total content of the tricyclic and tetracyclic aromatic compounds.

[0062] According to the present application, preferably, the average carbon number of the hydrocarbon-containing raw material is 15-30, further preferably 18-25. The adoption of the preferred embodiment is advantageous for controlling the molecular size of the raw material, and is further advantageous for controlling the reaction progress of the system during the formation of the mesophase pitch, and is advantageous for obtaining a product with good system uniformity.

[0063] The average carbon number of the hydrocarbon-containing raw material refers to the average value of the number of carbon atoms in the hydrocarbon-containing raw material, and is used to characterize the molecular size of the oil product, and is calculated by the average molecular weight, the carbon content according to the formula: C=(MnxC%) / 12, wherein C refers to the number of carbon atoms, Mn refers to the average molecular weight of the hydrocarbon-containing raw material, and C% refers to the mass fraction of carbon in the hydrocarbon-containing raw material.

[0064] The average molecular weight is measured according to SH / T 0583-1994.

[0065] The carbon content is measured according to NB / SH / T 0656, and the organic matter in the sample is converted into gas by high-temperature combustion. The carbon dioxide and water vapor contents are measured by using infrared detectors, respectively, and the carbon content in the sample can be obtained according to the carbon dioxide content in the generated gas. The formula is as follows: A: the carbon content in the sample, mass fraction, %; B: the response value of the detector to the carbon in the sample after deducting the blank; C: the response value of the detector to the carbon in the standard sample after deducting the blank; D: the mass of the sample, mg; E: the mass of the standard sample, mg; and F: the carbon content in the standard sample, mass fraction, %.

[0066] The present application does not have special limitations on the source of the hydrocarbon-containing raw material, and includes but is not limited to coal-based raw materials and / or petroleum-based raw materials, and is preferably at least one selected from coal tar, coal tar pitch, petroleum heavy oil, ethylene tar, catalytic cracking slurry oil and thermal cracking residue oil. The coal tar, coal tar pitch, petroleum heavy oil, ethylene tar, catalytic cracking slurry oil and thermal cracking residue oil in the present application have the conventional definitions in the art, and the present application does not have special limitations thereon.

[0067] According to the present application, preferably, the hydrocarbon-containing raw material satisfies at least one of the following conditions, preferably at least two of the following conditions, and more preferably all of the following conditions:

[0068] a) the sulfur content is not higher than 0.5 wt%;

[0069] b) the solid content is not higher than 500 μg / g, preferably not higher than 100 μg / g;

[0070] c) the 5% distillation point temperature of the hydrocarbon-containing raw material is 350-420°C, preferably 360-400°C, and the 95% distillation point temperature of the hydrocarbon-containing raw material is 450-550°C, preferably 480-530°C.

[0071] According to the present application, preferably, the sulfur content of the hydrocarbon-containing raw material is not higher than 0.5wt%, preferably not higher than 0.3wt%. The hydrocarbon-containing raw material can be at least one of high-sulfur petroleum heavy oil, high-sulfur coking wax oil, high-sulfur catalytic cracking slurry oil, and high-sulfur thermal cracking residual oil after hydroprocessing, wherein high-sulfur generally refers to a sulfur content of 0.3wt% to 5wt%, preferably 1wt% to 4wt%, and further preferably 1.5wt% to 3wt%.

[0072] According to the present application, preferably, the solid content of the hydrocarbon-containing raw material is not higher than 500μg / g, preferably not higher than 100μg / g, and more preferably not higher than 50μg / g. The solid content of the hydrocarbon-containing raw material is tested by the carbonization ignition method according to Q / SH 0741-2018.

[0073] According to the present application, preferably, the 5% distillation point temperature of the hydrocarbon-containing raw material is 350℃ to 420℃, and more preferably 360℃ to 400℃, for example, 360℃, 370℃, 380℃, 390℃, or 400℃. The 95% distillation point temperature of the hydrocarbon-containing raw material is 450℃ to 550℃, and more preferably 480℃ to 530℃, for example, 480℃, 490℃, 500℃, 510℃, 520℃, or 530℃.

[0074] According to a preferred mode of the present application, the softening point of the second liquid phase stream obtained in step (2) is 220℃ to 260℃, for example, 220℃, 230℃, 240℃, 250℃, or 260℃, and more preferably 220℃ to 245℃.

[0075] According to a preferred mode of the present application, the anisotropic component content in the second liquid phase stream obtained in step (2) is not less than 80%, and more preferably 80% to 90%.

[0076] According to a preferred mode of the present application, the reaction temperature of the first thermal reaction is 10℃ to 60℃ higher than the reaction temperature of the second thermal reaction, and more preferably 20℃ to 50℃ higher.

[0077] According to a preferred mode of the present application, the reaction pressure of the first thermal reaction is 0.1MPa to 3MPa higher than the reaction pressure of the second thermal reaction, and more preferably 0.1MPa to 1.5MPa higher.

[0078] The production method of the mesophase pitch in the application preferably comprises high-pressure one-step thermal reaction-low-pressure two-step thermal reaction. In the first thermal reaction process, the system can be in a low viscosity state under high pressure, and the side chains on the aromatic ring are broken to form free radicals. Under the synergistic action of the hydrogen-donating groups (the hydrogen-donating index represents the hydrogen-donating ability) of the system, excessive polycondensation is avoided, the molecular weight of the system tends to be uniform, the system reaction is orderly, and the orientation of the planar aromatic hydrocarbon macromolecule is facilitated. In the low-pressure two-step thermal reaction process, the system continues to perform reactions such as dehydrogenation, cyclization, and polycondensation. The low pressure is conducive to the escape of light components between the mesophases from the system, and promotes the fusion of the mesophases. This preferred embodiment is more conducive to improving the properties of the product.

[0079] The conditions of the first thermal reaction and the second thermal reaction are not particularly limited in the application, and a person skilled in the art can appropriately match the conditions according to the property requirements of the first liquid phase stream and the properties of the raw materials.

[0080] Preferably, the conditions of the first thermal reaction comprise: the reaction pressure is 0.2-4 MPa, preferably the reaction pressure is 0.5-2 MPa, the reaction temperature is 420-480 ℃, preferably the reaction temperature is 430-470 ℃, and the residence time of the material in the reactor is 1-12 h, preferably the residence time of the material in the reactor is 2-8 h.

[0081] Preferably, the conditions of the second thermal reaction comprise: the reaction pressure is 233 pa (absolute pressure)-1 MPa, preferably the reaction pressure is normal pressure-0.5 MPa, the reaction temperature is 400-440 ℃, preferably the reaction temperature is 410-430 ℃, and the residence time of the material in the reactor is 2-24 h, preferably the residence time of the material in the reactor is 6-18 h.

[0082] In the application, the pressure refers to the gauge pressure unless otherwise specified.

[0083] According to a preferred embodiment of the application, the method further comprises:

[0084] The second liquid phase stream obtained in step (2) is contacted with a carrier gas for treatment (which can also be referred to as purging) to obtain the mesophase pitch.

[0085] And / or, the second liquid phase stream obtained in step (2) is subjected to vacuum treatment to obtain the mesophase pitch.

[0086] The use of the above preferred scheme is more conducive to further bringing out the light components that hinder the mesophases, so that the system forms polynuclear aromatic compounds, further increases the content of the mesophases, and high-quality mesophase pitch is obtained.

[0087] Preferably, the conditions for treating the second liquid phase stream obtained in step (2) with the carrier gas include a temperature of 350-450°C, preferably 400-420°C, and a time of 4-30h, preferably 6-20h. The contacting of the second liquid phase stream with the carrier gas can be carried out at normal pressure.

[0088] Preferably, the carrier gas is selected from at least one of water vapor, nitrogen, helium, neon, argon, more preferably water vapor and / or nitrogen.

[0089] Further, in the above method for producing mesophase pitch, the flow rate of the carrier gas is 0.01-0.2m 3 / (kg·h), preferably 0.03-0.1m 3 / (kg·h).

[0090] Preferably, the conditions for treating the second liquid phase stream obtained in step (2) with the carrier gas include a temperature of 350-450°C, preferably 400-420°C, and a time of 4-30h, preferably 6-20h. The contacting of the second liquid phase stream with the carrier gas can be carried out at normal pressure.

[0091] According to the present application, the first gas phase stream and the second gas phase stream can be treated according to the needs of the product to be produced. According to the present application, preferably, the method further comprises separating the first gas phase stream and the second gas phase stream to obtain gas, light oil, middle distillate oil and heavy oil. The present application does not particularly limit the specific operation of the separation.

[0092] According to the present application, preferably, the 95% distillation point temperature of the light oil is 230-270°C, preferably 240-260°C; the 5% distillation point temperature of the middle distillate oil is 210-250°C, preferably 230-250°C, and the 95% distillation point temperature of the middle distillate oil is 400-440°C, preferably 410-430°C.

[0093] According to the present application, preferably, the method further comprises recycling at least part of the middle distillate oil to step (2) for the second thermal reaction. Further preferably, the mass ratio of the middle distillate oil recycled to step (2) for the second thermal reaction to the first liquid phase stream is 0.05-0.3, for example 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, preferably 0.1-0.2. With this preferred embodiment, the viscosity of the reaction stream in the second reaction unit can be adjusted, thereby more favorably controlling the mesophase development process and favorably obtaining a product with moderate softening point, high mesophase pitch content and good spinnability.

[0094] According to a preferred embodiment of the present application, the method further comprises purifying the second reaction unit in which the second thermal reaction is performed. In the production process of the existing mesophase pitch, a high-pressure autoclave is usually used for intermittent operation. After the mesophase pitch is discharged from the autoclave, a large amount of mesophase pitch remains on the inner wall of the autoclave. If the cleaning is not performed, the residues on the inner wall will excessively polymerize into semi-coke and coke in the subsequent preparation process, which seriously affects the quality of the mesophase pitch. Therefore, the autoclave or reactor needs to be thoroughly purified after each production of mesophase pitch. CN113731978A discloses a cleaning method for cleaning the mesophase pitch reaction autoclave. The purification liquid (catalytic oil slurry 450-500°C fraction cutting oil) is injected into the reaction autoclave to be cleaned, the temperature and pressure in the autoclave are maintained at a certain level, and the stirring is started. After a period of time, the pressure is released, the cleaning liquid is discharged, and the process is repeated 3-5 times to complete the cleaning of the reaction autoclave. Although this method can quickly complete the cleaning process, the oil slurry fraction cutting oil is used to clean the autoclave, which greatly reduces its value. The most commonly used method is to polish the autoclave with a mechanical method after the autoclave is cooled to room temperature. This method is low in efficiency, has dead angles in the cleaning process, and causes scratches on the inner wall of the autoclave or reactor, which affects the service life of the device.

[0095] In the present application, the purification can also be referred to as cleaning.

[0096] In order to overcome the above-mentioned defects of the prior art, preferably, the purifying agent used in the purification of the present application comprises the first liquid phase stream and / or the heavy oil obtained by separating the first gas phase stream from the second gas phase stream, and further preferably, the purifying agent used in the purification is the first liquid phase stream.

[0097] By using this preferred embodiment, the first liquid phase stream and / or the heavy oil obtained by separation are used for self-purification of the second reaction unit in the production process of mesophase pitch. On the one hand, the first liquid phase stream and / or the heavy oil have good compatibility with the entire reaction system, which can ensure good purification effect. On the other hand, it is not necessary to wait for the second reaction unit to cool down before mechanical polishing. After the mesophase pitch product is discharged, the second reaction unit can be immediately purified to improve the efficiency. Most importantly, the first liquid phase stream and the heavy oil are used for purifying the second reaction unit, which avoids excessive polymerization of the residual mesophase pitch product on the inner wall of the reaction unit into semi-coke and coke in the subsequent preparation process, which seriously affects the properties of the mesophase pitch. Moreover, the stream can continue to be used for the preparation of mesophase pitch after separation, which can realize the continuous production process and high product quality.

[0098] The purification method of the present application is not particularly limited. Preferably, the purification comprises: after the second thermal reaction, introducing the purifying agent into the second reaction unit in which the second thermal reaction is carried out, and carrying out the purification treatment; more preferably, introducing the purifying agent into the second reaction unit in which the second thermal reaction is carried out, and carrying out the purification treatment when the amount of the purifying agent reaches 60% or more, preferably 60% to 70%, of the volume of the second reaction unit. The preferred embodiment can provide more thorough purification and improve the quality of the product.

[0099] According to a preferred embodiment of the present application, the purifying agent can be introduced in the form of spray from the top of the second reaction unit, and the spray can wash the side wall of the second reaction unit and move downward under the action of gravity.

[0100] Preferably, the purification is carried out under the conditions of a temperature of 300 to 400°C, preferably 300 to 350°C, and a pressure of normal pressure to 0.5 MPa, preferably normal pressure to 0.2 MPa.

[0101] The purification can be carried out once, twice or more, preferably 2 to 4 times.

[0102] The time for each purification is not particularly limited. Preferably, the time for each purification is 1 to 5 hours, more preferably 1 to 3 hours.

[0103] According to a preferred embodiment of the present application, an auxiliary gas can be optionally introduced during the purification. The auxiliary gas can be used as a gas flow disturbance to promote the contact between the purifying agent and the intermediate phase pitch product residue on the side wall. The auxiliary gas can be any gas that does not participate in the reaction, and is preferably nitrogen and / or an inert gas.

[0104] In the method of the present application, the temperature does not need to be lowered before the purification, and the purification can be directly carried out using the stream in the system, thereby improving the production efficiency and the quality of the product.

[0105] Preferably, the method comprises: after the purification, switching the second reaction unit to carry out the second thermal reaction.

[0106] Preferably, the second reaction unit is provided with at least two reactors. The at least two reactors can configure the method to be continuously operated. The present application does not particularly limit the method for arranging the at least two reactors. Preferably, at least one reactor carries out the second thermal reaction, and at least one reactor carries out the purification, so as to configure the method to be continuously operated. Specifically, when at least one reactor carries out the second thermal reaction, at least one reactor carries out the purification, when the reactor carrying out the second thermal reaction needs to be purified, the feed of the reactor is switched to the purifying agent, and when the reactor carrying out the purification is purified, the feed of the reactor is switched to the raw material for carrying out the second thermal reaction.

[0107] According to the present application, preferably, the method further comprises recovering the purified stream, and subjecting the recovered liquid phase stream to a settling treatment to obtain an upper stream and a lower stream. The upper stream is a mixture of isotropic components and anisotropic components, and the lower stream is mainly mesophase pitch (anisotropic components).

[0108] Preferably, the upper stream contains anisotropic components, preferably in an amount of 1% to 10%.

[0109] According to the present application, preferably, the method further comprises recycling the upper stream to step (1) for the first thermal reaction and / or to step (2) for the second thermal reaction, preferably to step (2) for the second thermal reaction. With this preferred embodiment, the small amount of mesophase pitch (anisotropic components) product contained in the upper stream can be returned to step (1) for the first thermal reaction and / or the second thermal reaction to serve as a nucleating agent for the system, promoting the formation of mesophase spheres and the development of mesophase. Further, returning to the second thermal reaction is more conducive to improving the consistency of the reaction process of the system because the upper stream is more similar in material properties to the system.

[0110] Preferably, as a specific embodiment, the upper stream can be introduced into the second reaction unit as feed for the second thermal reaction in the second reaction unit. Specifically, the upper stream can be introduced into the second reaction unit together with the first liquid phase stream from step (1) for thermal reaction, or the upper stream can be introduced after the first liquid phase stream from step (1) has been reacted in the second reaction unit for a period of time.

[0111] According to the present application, the settling treatment can be various settling treatments in the art, for example, it can be a thermal settling treatment.

[0112] According to the present application, preferably, as a specific embodiment, the settling treatment is carried out in the presence of an inert atmosphere, which is nitrogen and / or an inert gas, preferably nitrogen.

[0113] According to the present application, preferably, the conditions of the settling treatment include a temperature of 300 to 350℃, a pressure of normal pressure to 1MPa, and a time of 3 to 6h.

[0114] The present application provides a mesophase pitch prepared by the method of the first aspect.

[0115] The mesophase pitch prepared by the method of the present application has moderate softening point and good spinnability.

[0116] According to the present application, preferably, the softening point of the mesophase pitch is 275 to 292℃, and further preferably 280 to 290℃.

[0117] According to the present application, preferably, the anisotropic component content in the mesophase pitch is 95% to 100%.

[0118] The third aspect of the present application provides a production system of mesophase pitch, as shown in Fig. 2, which comprises a first reaction unit 2, a second reaction unit 5 and a settling unit 15 connected in series; the liquid phase stream outlet of the first reaction unit 2 is in communication with the inlet of the second reaction unit 5, and the outlet of the second reaction unit 5 is in communication with the inlet of the settling unit 15.

[0119] The second reaction unit is provided with at least two reactors in parallel, so as to configure the reaction in the second reaction unit as a continuous operation.

[0120] The present application does not particularly limit the specific arrangement of the at least two reactors of the second reaction unit, and preferably, at least one reactor is in communication with the outlet of the first reaction unit for performing a second thermal reaction; and at least one reactor is in communication with the outlet of the first reaction unit for purifying the liquid phase stream of the first reaction unit.

[0121] In the present application, the settling unit 15 can be various devices commonly used in the art. Preferably, the settling unit 15 is used for settling separation of the recovered second reaction unit purified stream.

[0122] The device provided by the present application can realize continuous reaction.

[0123] According to a preferred embodiment of the present application, the upper stream outlet of the settling unit is in communication with the inlet of the first reaction unit and / or the inlet of the second reaction unit, preferably the inlet of the second reaction unit. This preferred embodiment can recycle the upper stream to the first reaction unit and / or the second reaction unit, which can act as a nucleating agent to promote the generation of mesophase small balls and promote the development process of mesophase.

[0124] According to the present application, preferably, the system further comprises a separation unit, the inlet of which is in communication with the gas phase stream outlet of the first reaction unit and / or the gas phase stream outlet of the second reaction unit.

[0125] Preferably, the separation unit is used for separating the gas phase stream of the first reaction unit and / or the gas phase stream of the second reaction unit to obtain gas, light oil, middle distillate oil and heavy oil. Further preferably, the heavy oil outlet of the separation unit is in communication with the inlet of the second reaction unit for purifying the second reaction unit.

[0126] According to the present application, preferably, the middle distillate outlet of the separation unit is in communication with the inlet of the first reaction unit and / or the second reaction unit. This preferred embodiment allows the middle distillate to be recycled to the first reaction unit and / or the second reaction unit, which is more conducive to controlling the mesophase development process and obtaining a product with moderate softening point, high mesophase pitch content and good spinnability.

[0127] The system provided by the present application allows the second reaction unit to be purified using the materials within the system (the liquid phase stream obtained from the first reaction unit and / or the heavy oil obtained from the separation unit).

[0128] According to a preferred embodiment of the present application, the system further comprises a purging unit for purging the liquid phase stream obtained from the second reaction unit.

[0129] According to another preferred embodiment of the present application, the system further comprises a vacuum treatment unit for vacuum treatment of the liquid phase stream obtained from the second reaction unit.

[0130] The present application does not have specific limitations on the specific devices of the purging unit and the vacuum treatment unit, which can be any device capable of purging and vacuum treatment commonly used in the art.

[0131] The above preferred scheme is more conducive to further removing the light components that hinder the formation of polynuclear aromatic compounds in the mesophase, allowing the system to form polynuclear aromatic compounds, further increasing the mesophase content, and obtaining high-quality mesophase pitch.

[0132] The method and system of the present application are described in detail below with reference to FIGS. 1 and 2, respectively.

[0133] As shown in FIG. 1, the hydrocarbon-containing raw material 1 enters the first reaction unit 2, and after reaction, the first gas phase stream 3 and the first liquid phase stream 4 are obtained; wherein the first gas phase stream 3 flows out from the upper part of the first reaction unit, and the first liquid phase stream 4 enters the second reaction unit 5 for further reaction, generating the second gas phase stream 6 and the second liquid phase stream; wherein the second gas phase stream 6 enters the separation unit 9 together with the first gas phase stream 3, and after separation, the gas 10, the light oil 11, the middle distillate 12 and the heavy oil 13 are obtained; wherein the middle distillate 12 can be recycled to the second reaction unit 5 for treatment; after a period of reaction in the second reaction unit 5, the heated carrier gas 7 is introduced to purge the second liquid phase stream in the second reaction unit, and the mesophase pitch 8 obtained after the purging is taken out of the device as the product.

[0134] As shown in Figure 2: the hydrocarbon-containing raw material 1 enters the first reaction unit 2, and after reaction, a first gas phase stream 3 and a first liquid phase stream 4 are obtained; wherein the first gas phase stream 3 flows out from the upper part of the first reaction unit 2, and the first liquid phase stream 4 enters the second reaction unit 5 for further reaction, and a second gas phase stream 6 and a second liquid phase stream are generated by reaction; wherein the second gas phase stream 6 enters the separation unit 9 together with the first gas phase stream 3, and after separation, gas 10, light oil 11, middle distillate oil 12 and heavy oil 13 are obtained; wherein the middle distillate oil 12 can be recycled back to the second reaction unit 5 for treatment; after a period of time of reaction in the second reaction unit 5, the second liquid phase stream in the second reaction unit 5 is purged by the heated carrier gas 7, and the oil and gas stream generated during the purging process also enters the separation unit 9 for separation, and the intermediate phase pitch 8 obtained after the purging is taken out of the device as a product. After the purging is completed, the other reactor in the second reaction unit 5 is switched to continue the reaction, and in this period, part of the first liquid phase stream 4 and / or the heavy oil 13 is used to perform a rinsing and purifying operation on the first reactor in the second reaction unit 5, and during the purifying process, an auxiliary gas can also be optionally introduced, the above-mentioned operation is repeated for 3 times, and the purified stream 14 collected during the purifying process enters the sedimentation unit 15 for separation operation, and the upper stream 16 obtained by separation is a mixture of isotropic components and anisotropic components, and the lower stream 17 is an intermediate phase pitch which can be taken out of the device as a product. The upper stream 16 enters the second reaction unit 5 for further reaction.

[0135] The present application and its effects are further illustrated by the following examples.

[0136] In the following examples and comparative examples, the test methods of the hydrogen supply index (PDQI), the aromatic carbon ratio, the contents of tricyclic aromatic hydrocarbon compounds and tetracyclic aromatic hydrocarbon compounds, and the average carbon number of the hydrocarbon-containing raw material are as described above in the detailed description.

[0137] The softening point of the intermediate phase pitch is determined by the Mettler method; the content of the anisotropic component is obtained by statistical analysis of the microstructure by a polarizing microscope; the microstructure (mosaic, fibrous, lamellar) is divided according to YB / T 077-2017, and the content of different microstructures is obtained by statistical analysis by a polarizing microscope; the surface roughness Ra of the carbon fiber is obtained by a non-contact measurement method by means of a μscan laser confocal microscope, and is analyzed by a chromatic aberration sensor and independent computer software. The spinning performance of the product is tested by a single-hole melt spinning machine, specifically, the spinning temperature is the softening point + 30℃, the spinning pressure is 1 MPa, and the winding speed is 300 m / min. If the yarn breaks, the continuous time stops counting.

[0138] Example 1

[0139] Example 1 uses the process flow shown in Figure 2. The properties of hydrocarbon-containing feedstock 1 (feedstock A) are analyzed in Table 1. Hydrocarbon-containing feedstock 1 enters the first reaction unit 2. The operating conditions of the first reaction unit 2 include: a reaction temperature of 430℃, a reaction pressure of 2MPa, and a residence time of 10h. The resulting first liquid phase stream 4 enters a reactor in the second reaction unit 5 for further reaction. The operating conditions of the second reaction unit 5 include: a reaction temperature of 410℃, a reaction pressure of atmospheric pressure, and a residence time of 20h. The second liquid phase stream obtained from the second reaction unit 5 continues to react under nitrogen purging: a purging temperature of 410℃, a purging time of 8h, and a nitrogen purging flow rate of 0.1m. 3 / (kg·h). The first gaseous stream 3 from the first reaction unit, the second gaseous stream 6 from the second reaction unit, and the oil and gas stream generated during the purging process enter the separation unit, where gas, light oil, middle distillate oil, and heavy oil are separated. The 95% distillation point of the light oil is 241℃, the 5% distillation point of the middle distillate oil is 250℃, and the 95% distillation point is 420℃. The middle distillate oil and the first liquid stream generated in the first reaction unit enter the second reaction unit together for further reaction, with a mass ratio of 0.1. The resulting intermediate phase pitch exits the device. After purging, the reaction is switched to another reactor in the second reaction unit. During this period, a portion of the first liquid stream is introduced and sprayed from the top of the first reactor in the second reaction unit for purification. When the amount of the first liquid stream reaches 60% of the height of the first reactor in the second reaction unit, the feeding is stopped, and the purification operation begins. The purification conditions are: temperature 350℃, pressure at atmospheric pressure, time 1 hour, repeated 3 times. The purified streams collected during the three purification processes all entered settling unit 15 for separation. The thermal settling conditions were: nitrogen atmosphere, temperature 350℃, atmospheric pressure, and time 3 hours. The upper stream obtained after separation (a mixture of isotropic and anisotropic components, with an anisotropic component content of 3%) and the first liquid phase stream entered the second reaction unit for further reaction, while the lower stream (mesophase pitch) exited the device. The properties of the obtained intermediate products are shown in Table 2, and the properties of the mesophase pitch product are shown in Table 3. The final polarized light micrograph of the mesophase pitch product is shown in Figure 3.

[0140] Example 2

[0141] Example 2 The process flow shown in Figure 2 was used. The properties of the hydrocarbon-containing feedstock 1 (Feedstock B) are shown in Table 1. The hydrocarbon-containing feedstock 1 was introduced into the first reaction unit 2, which was operated at a temperature of 440°C, a pressure of 2 MPa, and a residence time of 6 h. The first liquid phase stream 4 was introduced into one of the reactors of the second reaction unit 5, which was operated at a temperature of 420°C, a pressure of atmospheric pressure, and a residence time of 10 h. The second liquid phase stream from the second reaction unit 5 was reacted under nitrogen purge at a temperature of 410°C for 6 h at a nitrogen purge rate of 0.1 m3(kg-h). The first gaseous stream 3 from the first reaction unit, the second gaseous stream 6 from the second reaction unit, and the oil gas stream from the purge were introduced into a separation unit, which produced a gas, a light oil, a middle distillate, and a heavy oil. The light oil had a 95% distillation point of 220°C, and the middle distillate had a 5% distillation point of 230°C and a 95% distillation point of 420°C. The middle distillate was introduced into the second reaction unit along with the first liquid phase stream from the first reaction unit at a mass ratio of 0.15, and a mesophase pitch was produced. After the purge, the reaction was switched to the other reactor of the second reaction unit. During this time, a portion of the first liquid phase stream was introduced and sprayed from the top of the first reactor of the second reaction unit. The amount of the first liquid phase stream was 70% of the height of the first reactor of the second reaction unit, and the introduction of the first liquid phase stream was stopped and the purge was started. The purge was performed at a temperature of 300°C, a pressure of atmospheric pressure, and a time of 3 h for two cycles. The purged streams from the two cycles were introduced into a settling unit 15, which was operated at a temperature of 350°C, a pressure of atmospheric pressure, and a time of 2 h. The upper stream (a mixture of isotropic and anisotropic components, with an anisotropic component content of 2%) was introduced into the second reaction unit along with the first liquid phase stream, and the lower stream (mesophase pitch) was removed from the unit. The properties of the intermediate products are shown in Table 2, and the properties of the mesophase pitch product are shown in Table 3. 3

[0142] Example 3

[0143] ​Example 3 The process flow shown in Figure 2 was used. The properties of the hydrocarbon-containing feedstock 1 (Feedstock C) are shown in Table 1. The hydrocarbon-containing feedstock 1 was fed to the first reaction unit 2, which was operated at a temperature of 430°C, a pressure of 1.5 MPa, and a residence time of 8 h. The first liquid phase stream 4 obtained from the first reaction unit 2 was fed to one of the reactors of the second reaction unit 5, which was operated at a temperature of 410°C, a pressure of atmospheric pressure, and a residence time of 13 h. The second liquid phase stream obtained from the second reaction unit 5 was further reacted under nitrogen purging at a temperature of 400°C for 10 h at a nitrogen purging flow rate of 0.05 m3(kg-h). The first gaseous stream 3 obtained from the first reaction unit, the second gaseous stream 6 obtained from the second reaction unit, and the oil gas stream obtained from the purging process were fed to a separation unit, which produced gas, light oil, middle distillate, and heavy oil. The light oil had a 95% distillation point of 220°C, and the middle distillate had a 5% distillation point of 240°C and a 95% distillation point of 430°C. The middle distillate was fed to the second reaction unit together with the first liquid phase stream obtained from the first reaction unit at a mass ratio of 0.05, and the intermediate phase pitch produced was removed from the unit. After the purging was completed, the reaction was continued in the other reactor of the second reaction unit, during which part of the first liquid phase stream was introduced and sprayed from the top of the first reactor of the second reaction unit for purging. When the amount of the first liquid phase stream reached 70% of the height of the first reactor of the second reaction unit, the introduction of the first liquid phase stream was stopped, and the purging was started. The purging was carried out at a temperature of 330°C, a pressure of atmospheric pressure, and a time of 2 h, and the process was repeated three times. The purged streams collected during the three purging processes were fed to a settling unit 15 for separation under hot settling conditions at a temperature of 350°C, a pressure of atmospheric pressure, and a time of 6 h. The upper stream (a mixture of isotropic components and anisotropic components, with the content of the anisotropic components being 1.5%) obtained from the separation was fed to the second reaction unit together with the first liquid phase stream, and the lower stream (intermediate phase pitch) was removed from the unit. The properties of the intermediate product and the intermediate phase pitch product are shown in Tables 2 and 3, respectively. 3 3 3 Table 1 Properties of the hydrocarbon-containing feedstock

[0145] Example 4

[0146] In comparison with Example 1, the middle distillate in the feed to the second reaction unit was removed, i.e., the feed to the second reaction unit was only the first liquid phase stream, and the other conditions were the same as in Example 1. The properties of the intermediate product and the intermediate phase pitch product are shown in Tables 2 and 3, respectively.

[0147] Example 5

[0148] ​Example 5 used the process flow shown in Figure 2. Compared with Example 1, the operating conditions of the first reaction unit and the second reaction unit were slightly adjusted. The operating conditions of the first reaction unit were: reaction temperature 470°C, reaction pressure 2 MPa, residence time 2 h; the operating conditions of the second reaction unit were: reaction temperature 430°C, reaction pressure 0.5 MPa, residence time 10 h. After purging, the purified liquid introduced into the second reaction unit was heavy oil obtained from the separation unit. The properties of the obtained intermediate product and mesophase pitch product were shown in Table 2 and Table 3, respectively.

[0149] Table 2 Properties of the obtained intermediate product in Example

[0150] Note: " / " in the table means that there is no anisotropic component in the first liquid phase stream, i.e. no mesophase spheres are generated.

[0151] Table 3 Properties of the obtained mesophase pitch in Example

[0152] Table 4 Spinning performance of the obtained mesophase pitch in Example and the surface roughness of the carbon fiber

[0153] Note: "0" represents continuous spinning for more than 30 min; "A" represents continuous spinning for 3-30 min; "X" represents continuous spinning for less than 3 min

[0154] Example 6

[0155] Example 6 used the process flow shown in Figure 2. Compared with Example 1, the only difference was that the hydrocarbon-containing raw material was raw material D, the properties of which were shown in Table 5, and the operating conditions were shown in Table 6. The properties of the obtained intermediate product and mesophase pitch product were shown in Table 7 and Table 8, respectively.

[0156] Comparative Example 1

[0157] According to the method of Example 6, except that the operating conditions were adjusted, as shown in Table 6. The properties of the obtained intermediate product and mesophase pitch product were shown in Table 7 and Table 8, respectively.

[0158] Comparative Example 2

[0159] According to the method of Example 6, except that the hydrocarbon-containing raw material was raw material E, the properties of which were shown in Table 5, and other conditions were unchanged. The properties of the obtained intermediate product and mesophase pitch product were shown in Table 7 and Table 8, respectively.

[0160] Comparative Example 3

[0161] According to the method of Example 6, except that the hydrocarbon-containing raw material was raw material F, the properties of which were shown in Table 5, and other conditions were unchanged. The properties of the obtained intermediate product and mesophase pitch product were shown in Table 7 and Table 8, respectively.

[0162] Table 5 Properties of hydrocarbon-containing feedstock

[0163] Table 6 Operating conditions

[0164] Table 7 Properties of intermediate product

[0165] Table 8 Properties of mesophase pitch

[0166] Note: o: continuous spinning for more than 30 min; Δ: continuous spinning for 3-30 min; x: continuous spinning for less than 3 min

[0167] Example 7 uses the production process flow shown in Figure 1. The properties of the hydrocarbon-containing feedstock 1 (feedstock G) are shown in Table 9. The hydrocarbon-containing feedstock A enters the first reaction unit, and the conditions of the first reaction unit are: the reaction temperature is 460°C, the reaction pressure is 2 MPa, and the residence time is 6 h. The liquid phase stream obtained from the first reaction unit enters the second reaction unit for further reaction, and the conditions of the second reaction unit are: the reaction temperature is 430°C, the reaction pressure is 0.5 MPa, and the residence time is 12 h. The liquid phase stream obtained from the second reaction unit continues to react under nitrogen blowing, and the reaction temperature is 420°C, the blowing time is 6 h, the nitrogen blowing flow rate is 0.1 m 3 / (kg·h). The oil and gas products produced in the first reaction unit, the second reaction unit and the blowing process enter the fractionation unit, and gas, light oil, middle distillate oil and heavy oil are separated. The 95% distillation point temperature of the light oil is 230°C, the 5% distillation temperature of the middle distillate oil is 235°C, and the 95% distillation temperature is 410°C. The middle distillate oil enters the second reaction unit for further reaction together with the first liquid phase stream generated in the first reaction unit, and the mass ratio of the two is 0.1. The properties of the intermediate stream obtained are shown in Table 10, and the properties of the mesophase pitch product are shown in Table 11. The polarized light micrographs of the first liquid phase stream, the second liquid phase stream and the final mesophase pitch product are shown in Figures 4, 5 and 6 respectively. As shown in Figure 4, the first liquid phase stream is 100% isotropic structure, and the polarized light micrograph is dark overall. As shown in Figure 5, both isotropic components and anisotropic components exist in the second liquid phase stream, and the anisotropic components account for a larger proportion. Figure 6 is the mesophase pitch product, and the anisotropic content is 100%.

[0168] Example 8

[0169] Compared with Example 7, the middle distillate oil in the feed of the second reaction unit is cancelled, i.e. the feed of the second reaction unit only has the first liquid phase stream, and the other conditions are the same as those in Example 7. The properties of the obtained intermediate stream and mesophase pitch product are shown in Tables 10 and 11 respectively.

[0170] Table 9 Properties of hydrocarbon-containing feedstock

[0171] Example 9

[0172] Compared with Example 7, the operating conditions of the first reaction unit and the second reaction unit were slightly adjusted, the reaction temperature of the first reaction unit was 450°C, the reaction pressure was 1.5 MPa, the residence time was 8 h, the reaction temperature of the second reaction unit was 400°C, the reaction pressure was 1 MPa, the residence time was 18 h, the liquid phase stream obtained from the second reaction unit was continuously reacted under nitrogen purge, the nitrogen purge flow rate was 0.2 m 3 / (kg-h). Other conditions were exactly the same as in Example 7. The properties of the obtained intermediate stream and the mesophase pitch product were shown in Table 10 and Table 11, respectively.

[0173] Example 10

[0174] Compared with Example 7, the second reaction unit had no purging stage, vacuum treatment was used, the pressure was -0.1 MPa, the temperature was 300°C, the time was 4 h, the residence time of the second reaction unit was 16 h, other conditions were exactly the same as in Example 7. The properties of the obtained intermediate stream and the mesophase pitch product were shown in Table 10 and Table 11, respectively.

[0175] Table 10 Properties of the intermediate stream obtained in Examples 7-10

[0176] Table 11 Properties of the mesophase pitch obtained in Examples 7-10

[0177] Note: o: continuous spinning is achieved for more than 30 min; Δ: continuous spinning is achieved for 3-30 min; x: continuous spinning is less than 3 min

[0178] Examples 11 and 12

[0179] Examples 11 and 12 used the process flow shown in Figure 1. The feedstock used was a hydrocarbon-containing feedstock (Feedstock H), the properties of which were shown in Table 12, the operating conditions of the first reaction unit and the second reaction unit were shown in Table 13. The properties of the obtained intermediate stream and the mesophase pitch product were shown in Table 14 and Table 15, respectively.

[0180] Comparative Example 4

[0181] The same as example 11 except that the feedstock was adjusted to be Feedstock I, and the properties were shown in Table 12, and the operating conditions were the same as example 11. The properties of the obtained intermediate product and mesophase pitch product were shown in Table 14 and Table 15, respectively. Due to the low hydrogen donor index value of Feedstock I, the product softening point was too high.

[0182] Table 12 Properties of hydrocarbon-containing feedstock

[0183] Table 13 Operating conditions

[0184] Table 14 Properties of intermediate product

[0185] Table 15 Properties of mesophase pitch

[0186] Note: o: continuous spinning for more than 30 min; Δ: continuous spinning for 3-30 min; x: continuous spinning for less than 3 min

[0187] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application, and all fall within the protection scope of the present application.

Claims

1. A method for producing mesophase pitch, characterized by, The method comprises the following steps: (1) subjecting a hydrocarbon-containing raw material to a first thermal reaction to obtain a first gas phase stream and a first liquid phase stream; (2) subjecting the first liquid phase stream to a second thermal reaction to obtain a second gas phase stream and a second liquid phase stream; In the first liquid phase stream, the content of anisotropic components is not more than 10%, and the average particle size of mesophase spherules in the anisotropic components is not more than 20 μm.

2. The method of claim 1, wherein, In the first liquid phase stream, the content of anisotropic components is not more than 5%, preferably not more than 3%; and / or, in the first liquid phase stream, the average particle size of mesophase spherules in the anisotropic components is not more than 10 μm, more preferably not more than 5 μm; Preferably, the coefficient of variation of the diameter of the mesophase spheres is not greater than 15%, preferably not greater than 10%; wherein the coefficient of variation of the diameter of the mesophase spheres is calculated by the following formula: wherein N denotes the number of all the mesophase spherules within the field of view of the polarizing microscope analysis, x i D, denotes the diameter of the i-th mesophase spherule within the field of view of the polarizing microscope analysis, in μm; represents the average value of the diameters of all mesophase spherules in the field of view of a polarizing microscope, in units of μm.

3. The method of claim 1 or 2, wherein, The softening point of the first liquid phase stream is 110-160°C, preferably 120-150°C.

4. The method according to any one of claims 1-3, wherein, the hydrogen-donating index of the hydrocarbon-containing raw material is not less than 7 mg / g, preferably 7-20 mg / g, more preferably 7-15 mg / g; and / or, the aromatic carbon ratio of the hydrocarbon-containing raw material is 45%-90%, preferably 60%-90%; and / or, in the hydrocarbon-containing raw material, the total content of tricyclic aromatic hydrocarbon compounds and tetracyclic aromatic hydrocarbon compounds is not less than 35 wt%, preferably not less than 38 wt%, more preferably 38 wt%-60 wt%; and / or, the average carbon number of the hydrocarbon-containing raw material is 15-30, further preferably 18-25; Preferably, the hydrocarbon-containing raw material satisfies at least one of the following conditions: a) the sulfur content is not higher than 0.5 wt%; b) the solid content is not higher than 500 μg / g, preferably not higher than 100 μg / g; c) the 5% distillation point temperature of the hydrocarbon-containing raw material is 350°C-450°C, preferably 400°C-450°C, and the 95% distillation point temperature of the hydrocarbon-containing raw material is 450°C-550°C, preferably 480°C-530°C.

5. The method of any of claims 1-4, wherein, The softening point of the second liquid phase stream obtained in step (2) is 220-260°C, and the content of anisotropic components is not less than 80%; Preferably, the softening point of the second liquid phase stream obtained in step (2) is 220-245°C, and the content of anisotropic components is 80%-90%.

6. The method of any of claims 1-5, wherein, The reaction temperature of the first thermal reaction is 10-60°C higher than the reaction temperature of the second thermal reaction, preferably 20-50°C higher; and / or, the reaction pressure of the first thermal reaction is 0.1-3 MPa higher than the reaction pressure of the second thermal reaction, preferably 0.1-1.5 MPa higher; and / or, the conditions of the first thermal reaction include: the reaction pressure is 0.2-4 MPa, preferably the reaction pressure is 0.5-2 MPa, the reaction temperature is 420-480°C, preferably the reaction temperature is 430-470°C, and the residence time of the material in the reactor is 1-12 h, preferably the residence time of the material in the reactor is 2-8 h; And / or, the second thermal reaction is carried out under the conditions of a reaction pressure of 233 Pa (absolute pressure) to 1 MPa, preferably a reaction pressure of normal pressure to 0.5 MPa, a reaction temperature of 400 to 440 ℃, preferably a reaction temperature of 410 to 430 ℃, and a residence time of the material in the reactor of 2 to 24 h, preferably a residence time of the material in the reactor of 6 to 18 h.

7. The method of any of claims 1-6, wherein, The method further comprises: processing the second liquid phase stream obtained in step (2) by contacting with a carrier gas to obtain mesophase pitch; and / or, vacuum processing the second liquid phase stream obtained in step (2) to obtain mesophase pitch; Preferably, the processing of the second liquid phase stream obtained in step (2) by contacting with a carrier gas is carried out under the conditions of a temperature of 350 to 450 ℃, preferably 400 to 420 ℃, and a time of 4 to 30 h, preferably 6 to 20 h; Preferably, the carrier gas is at least one selected from the group consisting of water vapor, nitrogen, helium, neon, and argon, more preferably water vapor and / or nitrogen; Preferably, the vacuum processing of the second liquid phase stream obtained in step (2) is carried out under the conditions of a pressure of -0.1 MPa to 0 MPa, preferably -0.1 MPa to -0.05 MPa, and a temperature of 300 to 400 ℃, preferably 300 to 350 ℃.

8. The method of any of claims 1-7, wherein, The method further comprises separating the first gas phase stream and the second gas phase stream to obtain gas, light oil, middle distillate oil, and heavy oil; Preferably, the method further comprises recycling at least part of the middle distillate oil to step (2) for the second thermal reaction; Preferably, the mass ratio of the middle distillate oil recycled to step (2) for the second thermal reaction to the first liquid phase stream is 0.05 to 0.3, preferably 0.1 to 0.2; Preferably, the 5% distillation point temperature of the middle distillate oil is 210 to 250 ℃, preferably 230 to 250 ℃, and the 95% distillation point temperature of the middle distillate oil is 400 to 440 ℃, preferably 410 to 430 ℃.

9. The method of any of claims 1-8, wherein, The method further comprises purifying the second reaction unit for the second thermal reaction; The purifying agent used in the purifying comprises the first liquid phase stream and / or the heavy oil obtained by separating the first gas phase stream and the second gas phase stream, preferably the purifying agent used in the purifying is the first liquid phase stream; Preferably, the purifying comprises: after the end of the second thermal reaction, introducing the purifying agent into the second reaction unit for the second thermal reaction to carry out purifying treatment; further preferably, the purifying agent is introduced into the second reaction unit for the second thermal reaction, and when the amount of the purifying agent reaches more than 60% of the volume of the second reaction unit, purifying treatment is carried out; Preferably, the purifying is carried out under the conditions of a temperature of 300 to 400 ℃, preferably 300 to 350 ℃, and a pressure of normal pressure to 0.5 MPa, preferably normal pressure to 0.2 MPa; Preferably, the method comprises switching to carry out the second thermal reaction after the end of the purifying. Preferably, the second reaction unit is provided with at least two reactors, at least one reactor performing the second thermal reaction, and at least one reactor performing purification, so as to configure the method to be operated continuously.

10. The method of claim 9, wherein, The method further comprises recovering the purified stream, and subjecting the recovered liquid phase stream to a settling treatment to obtain an upper stream and a lower stream. Preferably, the content of the anisotropic component in the upper stream is 1% to 10%. Preferably, the method further comprises recycling the upper stream to step (1) to perform the first thermal reaction and / or to step (2) to perform the second thermal reaction, preferably to step (2) to perform the second thermal reaction. Preferably, the conditions of the settling treatment comprise: being performed in an inert atmosphere, at a temperature of 300 to 350°C, and for a time of 3 to 6h.

11. The mesophase pitch prepared by the method of any one of claims 1 to 10. Preferably, the softening point of the mesophase pitch is 275 to 292°C, further preferably 280 to 290°C. Preferably, the content of the anisotropic component in the mesophase pitch is 95% to 100%.

12. A system for producing mesophase pitch, characterized by, The system comprises a first reaction unit, a second reaction unit, and a settling unit connected in series; the liquid phase stream outlet of the first reaction unit is in communication with the inlet of the second reaction unit, and the outlet of the second reaction unit is in communication with the inlet of the settling unit. The second reaction unit is provided with at least two reactors connected in parallel, so as to configure the reaction performed in the second reaction unit to be operated continuously.

13. The system of claim 12, wherein, The settling unit is used to subject the recovered second reaction unit purified stream to a settling separation; Preferably, the upper stream outlet of the settling unit is in communication with the inlet of the first reaction unit and / or the inlet of the second reaction unit, preferably the inlet of the second reaction unit.

14. The system of claim 12 or 13, wherein, The system further comprises a separation unit, the inlet of the separation unit being in communication with the gas phase stream outlet of the first reaction unit and / or the gas phase stream outlet of the second reaction unit; Preferably, the heavy oil outlet of the separation unit is in communication with the inlet of the second reaction unit, for purifying the second reaction unit; Preferably, the middle distillate oil outlet of the separation unit is in communication with the inlet of the first reaction unit and / or the second reaction unit.

15. The system of any of claims 12-14, wherein, The system further comprises a purging unit, which is used to purge the liquid phase stream obtained from the second reaction unit; And / or, the system further comprises a vacuum treatment unit, which is used to subject the liquid phase stream obtained from the second reaction unit to a vacuum treatment.

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