A method and system for preparing mesophase pitch

Abstract

The application discloses a mesophase pitch preparation method and a preparation system. The preparation method comprises the following steps: (1) separating liquid-phase materials obtained after ethylene tar treatment to obtain first light oil and first heavy oil; (2) the first light oil enters a first reaction unit to react in the presence of a first additive to obtain a reaction stream; and (3) the obtained reaction stream enters a second reaction unit to react with a carrier gas, and mesophase pitch and an oil-phase stream are obtained after treatment. The preparation system comprises a pretreatment unit, a first separation unit, a first reaction unit, a second reaction unit and a second separation unit. The method provides a high-value conversion process for ethylene tar, and the obtained mesophase pitch product has excellent spinnability, and the value of the ethylene tar is greatly improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of carbon-based materials, and particularly relates to a preparation method of mesophase pitch. BACKGROUND

[0002] The mesophase pitch is a high-quality carbon material precursor prepared from coal-based, petroleum-based, high-molecular polymer, and other aromatic compounds, and has been widely used in the preparation of needle coke, foamed carbon, high-performance pitch-based carbon fiber and other carbon materials. The high-performance pitch-based carbon fiber has high strength, high modulus, electrical conductivity and thermal conductivity, and is widely used in the field of aerospace.

[0003] CN1112852464A discloses a pretreatment method of raw material oil for preparing spinnable mesophase pitch and high-performance pitch-based carbon fiber. The >300 DEG C fraction in aromatic-rich oil is used as raw material, and after the filtration and extraction process under the assistance of ultrasonic coupling and strengthening, refined raw material oil is obtained by gel permeation chromatography separation. The high-performance pitch-based carbon fiber precursor with good spinnability is prepared by using the refined raw material oil as raw material.

[0004] CN106544758A discloses a preparation method of high-modulus pitch-based carbon fiber. The catalytic oil slurry is used as raw material for high-pressure hydrogenation pretreatment. The >400 DEG C heavy fraction obtained by distillation of the hydrogenation product is subjected to one-time thermal polycondensation, and then high-quality mesophase pitch is obtained by gas blowing under normal pressure for a certain period of time. The high-modulus carbon fiber is obtained by spinning, pre-oxidation, carbonization and graphitization.

[0005] CN113088327A discloses a method for producing mesophase pitch. The raw oil is separated into light and heavy fraction oils after fractionation. The light fraction oil is mixed with the heavy fraction oil after thermal polymerization to obtain mesophase pitch which can be used as raw material for high-performance pitch-based carbon fiber.

[0006] CN113862017A discloses a preparation method of solvated mesophase pitch and high-performance pitch-based carbon fiber. The de-asphalted oil, refined coal tar and anthracene oil are used as raw material oil. After hydrogen-donating thermal polycondensation, multi-stage, countercurrent and continuous extraction fractionation are carried out in a subcritical / supercritical solvent to obtain high-spinnable mesophase pitch containing 5-20% solvent. The high-performance pitch-based carbon fiber is obtained after melt spinning, pre-oxidation, carbonization and graphitization.

[0007] CN109929592A discloses a processing process and system of ethylene tar, the preheated ethylene tar is contacted with the coking reaction effluent from the delayed coking reaction system in the pretreatment reactor, the light component and the heavy component are obtained after separation, the heavy component enters the delayed coking system, after hydrogenation, the product is separated to obtain gas, gasoline, diesel and heavy oil fraction, the heavy oil fraction enters the catalytic cracking reaction system, and the catalytic diesel obtained after separation enters the pretreatment reactor.

[0008] CN114106863B discloses a mesophase pitch for spinning and a preparation method thereof, a wax oil fraction produced by liquid-phase hydrogenation of ethylene cracking tar in a suspension bed is used as a raw material, the raw material is subjected to vacuum distillation to obtain an aromatic-rich oil, and then subjected to two thermal polymerization reactions to obtain the mesophase pitch for spinning.

[0009] Ethylene tar is mainly composed of condensed ring aromatic hydrocarbons and aromatic alkenes, and has a low content of heteroatoms such as sulfur and nitrogen, but has a low initial coking temperature. When ethylene tar is used to prepare mesophase pitch, coke and other substances that seriously affect the quality of the product are easily generated. Therefore, how to ensure the quality of the mesophase pitch product is a technical problem to be solved in the field. SUMMARY

[0010] In view of the deficiencies in the prior art, the main purpose of the present application is to provide a method and system for preparing mesophase pitch from ethylene tar, which not only provides a high-value conversion process for ethylene tar, but also greatly improves the additional value of ethylene tar.

[0011] The present application provides a method for preparing mesophase pitch, which comprises the following steps:

[0012] (1) ethylene tar enters a pretreatment unit for pretreatment, and the liquid phase material obtained after treatment is separated to obtain first light oil and first heavy oil;

[0013] (2) the first light oil obtained in step (1) enters a first reaction unit and reacts in the presence of a first additive to obtain a reaction stream;

[0014] (3) the reaction stream obtained in step (2) enters a second reaction unit and reacts with a carrier gas to obtain mesophase pitch and an oil phase stream after treatment.

[0015] In the above method for preparing mesophase pitch, as a preferred embodiment, the pretreatment unit in step (1) can optionally use a catalyst, preferably a catalyst. Further, the catalyst can be anhydrous aluminum chloride, and the addition amount of the catalyst is 1wt%~10wt%, preferably 2wt%~5wt%, based on the weight of ethylene tar.

[0016] In the preparation method of the mesophase pitch, as a preferred embodiment, the pretreatment in step (1) is carried out under the protection of an inert atmosphere, which is nitrogen and / or an inert gas, and the inert gas can be at least one of helium, neon, argon, krypton and xenon; preferably, the inert gas is nitrogen.

[0017] In the preparation method of the mesophase pitch, as a preferred embodiment, the pretreatment in step (1) is carried out under the protection of an inert atmosphere, which is nitrogen and / or an inert gas, and the inert gas can be at least one of helium, neon, argon, krypton and xenon; preferably, the inert gas is nitrogen.

[0018] In the preparation method of the mesophase pitch, as a preferred embodiment, the 95% distillation temperature of the first light oil in step (1) is 460-540°C, preferably 460-500°C.

[0019] In the preparation method of the mesophase pitch, as a preferred embodiment, the method for separating the liquid phase material obtained after the pretreatment unit in step (1) can use one or more of flash evaporation, steam stripping, atmospheric distillation, vacuum distillation, etc., and preferably, vacuum distillation is used.

[0020] In the preparation method of the mesophase pitch, as a preferred embodiment, the first heavy oil after the purification treatment can be used to produce mesocarbon microbeads.

[0021] In the preparation method of the mesophase pitch, as a preferred embodiment, the first additive in step (2) is one or more of methyl naphthalene, xylene, tetramethylbenzene, tetrahydronaphthalene, decahydronaphthalene, anthracene, dihydroanthracene, etc., and preferably, tetrahydronaphthalene is used.

[0022] In the preparation method of the mesophase pitch, as a preferred embodiment, the mass ratio of the first additive to the first light oil in step (2) is 1-50:100, preferably 10-30:100.

[0023] In the preparation method of the mesophase pitch, as a preferred embodiment, the operating conditions of the first reaction unit in step (2) are as follows: the reaction pressure is 0.1-3 MPa, preferably 0.1-3 MPa; the reaction temperature is 360-500°C, preferably 360-460°C; and the residence time of the material in the reactor is 1-20 h, preferably 2-10 h.

[0024] As a preferred embodiment of the preparation method of the mesophase pitch, the operating conditions of the second reaction unit in step (3) are as follows: the pressure at the top of the reactor is 20 Pa to 1000 kPa (absolute pressure), preferably 20 Pa to 500 kPa (absolute pressure); the reaction temperature is 350 to 500 DEG C, preferably 360 to 460 DEG C; and the residence time is 6 to 15 h, preferably 6 to 12 h.

[0025] As a preferred embodiment of the preparation method of the mesophase pitch, the carrier gas in step (3) can be one or more of water vapor, nitrogen, hydrogen, and inert gas, preferably water vapor or nitrogen; wherein the inert gas is one or more of helium, neon, argon, krypton, and xenon.

[0026] As a preferred embodiment of the preparation method of the mesophase pitch, the preparation method further comprises step (4), and the specific process of step (4) is as follows: the oil phase stream obtained in step (3) is separated to obtain gas, second light oil, and second heavy oil; wherein the 5% distillation temperature of the second heavy oil is 300 to 320 DEG C. Further, the second light oil can be returned to the pretreatment unit; and the second heavy oil can be returned to the first reaction unit and / or the second reaction unit for treatment, preferably returned to the second reaction unit for treatment.

[0027] The second aspect of the present application provides a mesophase pitch obtained by the above preparation method.

[0028] Further, as a preferred embodiment of the mesophase pitch, the softening point of the mesophase pitch is 270 to 330 DEG C, and the mesophase form presents a broad-area type optical structure.

[0029] The third aspect of the present application provides a preparation method of carbon fiber, wherein the mesophase pitch obtained by the above preparation method is used as raw material to enter a spinning machine for spinning, and the carbon fiber obtained by spinning is subjected to pre-oxidation, carbonization, and graphitization treatment to obtain a carbon fiber product.

[0030] Further, in the preparation method of the carbon fiber, the spinning, pre-oxidation, carbonization, and graphitization treatment can all use any one of the existing mature processes in the field, and the specific operating conditions can be freely selected and adjusted as needed.

[0031] The fourth aspect of the present application provides a preparation system of mesophase pitch, and the preparation system comprises a pretreatment unit, a first separation unit, a first reaction unit, a second reaction unit, and a second separation unit; wherein:

[0032] The pretreatment unit is used to receive ethylene tar and perform pretreatment in the presence of an optional catalyst to obtain a gas phase stream and a liquid phase material after treatment;

[0033] a first separation unit for receiving and separating liquid phase materials from the processing unit, and obtaining a first light oil and a first heavy oil after separation;

[0034] a first reaction unit for receiving the first light oil from the first separation unit, and reacting in the presence of a first auxiliary agent to obtain a reaction stream;

[0035] a second reaction unit for receiving the reaction stream from the first reaction unit, and reacting with a carrier gas to obtain an intermediate pitch and an oil phase stream after processing.

[0036] In the preparation system of the intermediate pitch, as a preferred embodiment, the preparation system further comprises a second separation unit for receiving the oil phase stream from the second reaction unit, and obtaining a gas, a second light oil and a second heavy oil after separation.

[0037] In the preparation system of the intermediate pitch, as a preferred embodiment, the second light oil is communicated with the pretreatment unit through a pipeline and enters the pretreatment unit for processing.

[0038] In the preparation system of the intermediate pitch, as a preferred embodiment, the second heavy oil is communicated with the first reaction unit and / or the second reaction unit through a pipeline.

[0039] In the preparation system of the intermediate pitch, as a preferred embodiment, the first separation unit and the second separation unit adopt a device having a function of separating liquid phase materials, which can be at least one of a flash tank, a fractionating column and the like, and preferably adopts a fractionating column. The specific type of the fractionating column can be selected as required.

[0040] Compared with the prior art, the preparation method of the intermediate pitch has the following beneficial effects:

[0041] 1. In the preparation method and the preparation system of the intermediate pitch, the ethylene tar first enters the pretreatment unit, and the easy coking components in the ethylene tar are promoted to undergo condensation reaction under the action of a catalyst to remove the coking precursors, and the obtained pretreatment product is divided into a first light oil and a first heavy oil according to the distillation range. The content of carbon-carbon double bonds in the first light oil is greatly reduced compared with the untreated ethylene tar, and the thermal stability is obviously improved, thereby avoiding the problems of poor product uniformity and poor spinnability caused by directly using the ethylene tar as the raw material to prepare the intermediate pitch.

[0042] 2. In the preparation method of the intermediate pitch, the low-temperature catalytic condensation and separation operations are used to improve the thermal stability of the ethylene tar while retaining the aromatic-rich components. Through the synergistic effect of the catalysis, separation, hydrogen supply and heat treatment operations, the high-quality intermediate pitch is prepared from the ethylene tar.

[0043] 3、The preparation method and preparation system of mesophase pitch provided by the application, the second light oil obtained by the second separation unit is returned to the pretreatment unit for continuous reaction, so that the yield of the first light oil can be improved; the second heavy oil obtained by the second separation unit is returned to the second reaction unit, so that the second heavy oil can be used as a viscosity regulator to reduce the viscosity of the system, which is beneficial to the formation and development of the wide-range mesophase.

[0044] 4、The mesophase pitch obtained by the preparation method has a softening point of 270-330 DEG C and a mesophase content of greater than 95%, and the raw material used in the method is easy to obtain, the high-quality mesophase pitch product produced by the method has low cost, the method is beneficial to the realization of large-scale production and sustainable development of the high-quality mesophase pitch, and provides a high-value utilization method for the ethylene tar which is difficult to process.

[0045] 5、The preparation method and preparation system of mesophase pitch provided by the application, the content of S, N and other heteroatoms in the selected raw material is low, and the carbon fiber obtained after the mesophase pitch obtained by the preparation method is subjected to spinning, pre-oxidation, carbonization and graphitization treatment has few defects and high tensile strength. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 The figure is a schematic diagram of the preparation system of mesophase pitch. DETAILED DESCRIPTION

[0047] The method of the application will be described in further detail below in conjunction with the accompanying drawings and examples, but the following examples do not constitute a limitation on the method of the application.

[0048] The endpoints of the ranges and any values in the ranges disclosed herein are not limited to the precise values recited as implicitly split into the same smaller units as specifically delineated. For values which are expressed as ranges, any intervening value, and any other specified ranges between the stated ranges, are expressly included. For values which are expressed as points or discrete values, it is intended that any such intervening value is also explicitly contemplated. Any combination of ranges, any intervening value in those ranges, and any combination of ranges with intervening values in those ranges are expressly included.

[0049] 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, such as "connected," "attached," "supported," and the like, refer to structural relationships in which at least one structure is either directly on or indirectly on or supports at least one other structure or is fixed with respect to at least one other structure, as the terms are used in the present patent document, unless otherwise specified.

[0050] As Figure 1As shown, the present application provides a mesophase pitch preparation method, ethylene tar 1 enters the pretreatment unit 2, and is pretreated in the presence of optional catalyst, and the pretreated gas phase stream 3 and liquid phase material 4 are obtained, wherein the liquid phase material 4 enters the first separation unit 5, and after separation, the first light oil 6 and the first heavy oil 7 are obtained, wherein the first light oil 6 enters the first reaction unit 8, and is reacted with the first auxiliary agent to obtain the reaction stream 9, which enters the second reaction unit 10 for further reaction in the presence of carrier gas 12, and the mesophase pitch 13 and oil phase stream 11 are obtained after treatment; wherein the generated mesophase pitch 13 is discharged from the bottom of the second reaction unit, and can enter the subsequent spinning unit. The generated oil phase stream 11 enters the second separation unit 4 for separation to obtain gas 15, second light oil 16 and second heavy oil 17, and the second light oil 16 can be returned to the pretreatment unit 2 for reaction, and the second heavy oil 17 enters the second reaction unit 10 for further reaction.

[0051] In this paper, the carbon fiber strength is determined by GB / T 31290-2014 standard method.

[0052] In this paper, the process conditions for producing carbon fibers from mesophase pitch are that the spinning temperature is 30-50℃ higher than the softening point; the pre-oxidation medium is air, the pre-oxidation temperature is 250℃, and the pre-oxidation time is 2h; the carbonization and graphitization treatment are carried out in an inert atmosphere, the carbonization temperature is 1100℃, and the carbonization time is 1h; the graphitization temperature is 2500℃, and the graphitization time is 15min.

[0053] Example 1

[0054] Example 1 uses Figure 1The preparation method shown, ethylene tar (properties are shown in Table 1) into the pretreatment unit, the catalyst is anhydrous aluminum chloride, the catalyst dosage is 5wt% of the raw material, protected in nitrogen, the pretreatment unit reaction conditions are: the reaction temperature is 130℃, the reaction pressure is 5.0MPa, the residence time is 6h, the liquid phase material is obtained. The liquid phase material enters the first separation unit after separation to obtain the first light oil and the first heavy oil, wherein the 95% distillation temperature of the first light oil is 500℃. The first light oil enters the first reaction unit and is contacted with the first auxiliary agent, the first auxiliary agent is tetrahydro naphthalene, the first auxiliary agent dosage is 30wt% of the first light oil, the first reaction unit conditions are: the reaction temperature is 450℃, the reaction pressure is 3MPa, the residence time is 6h, the reaction oil obtained enters the second reaction unit, and continues to react under nitrogen blowing, the second reaction unit conditions are: the reaction temperature is 460℃, the reaction pressure is 0.5MPa, the residence time is 12h, the generated intermediate phase pitch enters the subsequent spinning unit, and carbon fiber can be obtained after spinning, pre-oxidation, carbonization and graphitization treatment, the oil phase stream generated in the second reaction unit enters the second separation unit, and after separation, gas, the second light oil and the second heavy oil are obtained, wherein the 5% distillation temperature of the second heavy oil is 320℃, the second light oil returns to the pretreatment unit for reaction, and the second heavy oil returns to the second reaction unit for continuous reaction, and the reaction results are shown in Table 2.

[0055] Example 2

[0056] Example 2 uses Figure 1 The preparation method shown is basically the same as that of Example 1. The difference lies in that the catalyst dosage is 2wt% of the raw material, protected in nitrogen, the pretreatment unit reaction conditions are: the reaction temperature is 170℃, the reaction pressure is 3.0MPa, and the residence time is 3h; the first light oil enters the first reaction unit, the first reaction unit conditions are: the first auxiliary agent is decahydro naphthalene, the first auxiliary agent dosage is 10wt% of the first light oil, the first reaction unit conditions are: the reaction temperature is 420℃, the reaction pressure is 3MPa, and the residence time is 15h, and the reaction results are shown in Table 2.

[0057] Example 3

[0058] Example 3 uses Figure 1 The preparation method shown is basically the same as that of Example 1. The difference lies in that the first reaction unit conditions are: the first auxiliary agent dosage is 20wt% of the first light oil, the first reaction unit conditions are: the reaction temperature is 380℃, the reaction pressure is 2MPa, and the residence time is 12h; the second reaction unit conditions are: the reaction temperature is 420℃, the reaction pressure is 1000Pa (absolute pressure), and the residence time is 6h, and the reaction results are shown in Table 2.

[0059] Comparative Example 1

[0060] Comparative Example 1 differs from Example 1 in that Comparative Example 1 does not have a pre-treatment unit and a first separation unit, and is otherwise substantially the same as Example 1.

[0061] Comparative Example 2

[0062] Comparative Example 2 differs from Example 2 in that Comparative Example 2 does not have a first reaction unit, and does not have a first auxiliary agent present, and is otherwise substantially the same as Example 2.

[0063] The mesophase pitch obtained in the above examples and comparative examples was tested for softening point, mesophase pitch content, and spinnability, and the carbon fiber obtained by spinning, pre-oxidizing, carbonizing, and graphitizing the mesophase pitch was tested for tensile strength, and the results are shown in Table 2.

[0064] Table 1 Raw Material Properties

[0065]

[0066]

[0067] Table 2 Mesophase Pitch and Carbon Fiber Properties

[0068]

Claims

1. A method for preparing mesophase pitch, the method comprising the following steps: (1) ethylene tar is introduced into a pretreatment unit for pretreatment, and a liquid phase material obtained after the pretreatment is separated to obtain a first light oil and a first heavy oil; the pretreatment is carried out under the protection of an inert atmosphere, and the pretreatment conditions are as follows: the reaction temperature is 120-240℃, the reaction pressure is 0.01-10 MPa, and the residence time is 0.1-12 h; the 95% distillation temperature of the first light oil is 460-540℃; (2) the first light oil obtained in step (1) is introduced into a first reaction unit to react in the presence of a first additive, and a reaction stream is obtained; the first additive is one or more of methyl naphthalene, dimethylbenzene, mesitylene, tetralin, decalin, anthracene and dihydroanthracene; the operation conditions of the first reaction unit are as follows: the reaction pressure is normal pressure-5 MPa, and the reaction temperature is 360-500℃; (3) the reaction stream obtained in step (2) is introduced into a second reaction unit to react with a carrier gas, and mesophase pitch and an oil phase stream are obtained after the treatment; the operation conditions of the second reaction unit are as follows: the absolute pressure at the top of the reactor is 20 pa-1000 kpa, and the reaction temperature is 350-500℃; the carrier gas is one or more of water vapor, nitrogen, hydrogen and inert gas, wherein the inert gas is one or more of helium, neon, argon, krypton and xenon.

2. The process for preparing mesophase pitch according to claim 1, characterized in that: The pretreatment unit in step (1) uses a catalyst, and the catalyst is anhydrous aluminum chloride; the addition amount of the catalyst is 1 wt%-10 wt% of the weight of the ethylene tar.

3. The process for preparing mesophase pitch according to claim 1, characterized by: The pretreatment unit in step (1) uses a catalyst, and the catalyst is anhydrous aluminum chloride; the addition amount of the catalyst is 2 wt%-5 wt% of the weight of the ethylene tar.

4. The process for preparing mesophase pitch according to claim 1, characterized by: The inert atmosphere in step (1) is nitrogen and / or inert gas, and the inert gas is at least one of helium, neon, argon, krypton and xenon.

5. The process for preparing mesophase pitch according to claim 1, characterized by: The pretreatment conditions in step (1) are as follows: the reaction temperature is 130-220℃, the reaction pressure is 0.5-5 MPa, and the residence time is 0.5-6 h.

6. The process for preparing mesophase pitch according to claim 1, characterized by: The 95% distillation temperature of the first light oil in step (1) is 460-500℃.

7. The process for preparing mesophase pitch according to claim 1, characterized by: The first additive in step (2) is tetralin.

8. The process for preparing mesophase pitch according to claim 1, characterized by: The mass ratio of the first additive to the first light oil in step (2) is 1-50:

100.

9. The process for preparing mesophase pitch according to claim 1, characterized by: The mass ratio of the first additive to the first light oil in step (2) is 10-30:

100.

10. The process for preparing mesophase pitch according to claim 1, characterized by: The operation conditions of the first reaction unit in step (2) are as follows: the reaction pressure is 0.1-3 MPa; the reaction temperature is 360-460℃; and the residence time of the material in the reactor is 1-20 h.

11. The process for preparing mesophase pitch according to claim 10, characterized by: The operation conditions of the first reaction unit in step (2) are as follows: the residence time of the material in the reactor is 2-10 h.

12. The process for preparing mesophase pitch according to claim 1, characterized by: The operation conditions of the second reaction unit in step (3) are as follows: the absolute pressure at the top of the reactor is 20 pa-500 kpa; the reaction temperature is 360-460℃; and the residence time is 6-15 h.

13. The process for preparing mesophase pitch according to claim 12, characterized by: The residence time of the material in the reactor is 6-12 h.

14. The process for preparing mesophase pitch according to claim 1, characterized by: The carrier gas in step (3) is water vapor or nitrogen.

15. The process for preparing mesophase pitch according to claim 1, characterized by: The preparation method further comprises a step (4), and a process of the step (4) is as follows: after the oil phase stream obtained in the step (3) is separated, gas, second light oil and second heavy oil are obtained; wherein the 5% distillation temperature of the second heavy oil is 300-320 ℃.

16. The process for preparing mesophase pitch according to claim 15, characterized by: The second light oil is returned to the pretreatment unit; and the second heavy oil is returned to the first reaction unit and / or the second reaction unit for treatment.

17. The process for preparing mesophase pitch according to claim 16, characterized by: The second heavy oil is returned to the second reaction unit for treatment.

18. An intermediate phase pitch obtained by the preparation method in any one of claims 1-17.

19. The mesophase pitch according to claim 18, characterized by: The intermediate phase pitch has a softening point of 270-330 ℃ and a mesophase form of a broad-range optical structure.

20. A carbon fiber preparation method, in which the intermediate phase pitch in any one of claims 18-19 or the intermediate phase pitch obtained by the preparation method in any one of claims 1-17 is used as a raw material to enter a spinning machine for spinning, and the spun carbon fiber is subjected to pre-oxidation, carbonization and graphitization treatment to obtain a carbon fiber product.

21. A preparation system of an intermediate phase pitch for implementing the method in any one of claims 1-17, the preparation system comprising a pretreatment unit, a first separation unit, a first reaction unit, a second reaction unit and a second separation unit; wherein: the pretreatment unit is used to receive ethylene tar and perform pretreatment in the presence of an optional catalyst, and after the treatment, a gas phase stream and a liquid phase material are obtained; the first separation unit is used to receive and separate the liquid phase material from the pretreatment unit, and after the separation, a first light oil and a first heavy oil are obtained; the first reaction unit is used to receive the first light oil from the first separation unit, and perform reaction in the presence of a first additive, and a reaction stream is obtained; the second reaction unit is used to receive the reaction stream from the first reaction unit, and perform reaction by contacting with a carrier gas, and after the treatment, an intermediate phase pitch and an oil phase stream are obtained.

22. A system for producing mesophase pitch according to claim 21, characterized in that: The preparation system further comprises the second separation unit, which is used to receive the oil phase stream from the second reaction unit, and after the separation, gas, second light oil and second heavy oil are obtained.

23. A system for producing mesophase pitch according to claim 22, characterised in that: The second light oil is communicated with the pretreatment unit through a pipeline and enters the pretreatment unit for treatment.

24. A system for producing mesophase pitch according to claim 22, characterized in that: The second heavy oil is communicated with the first reaction unit and / or the second reaction unit through a pipeline.

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