System and method for preparing mesophase asphalt

Abstract

A system and method for preparing mesophase asphalt. The system for preparing mesophase asphalt comprises a prepolymerization reactor (2) and a continuous condensation separation reactor (3); the middle-upper part of the continuous condensation separation reactor (3) is provided with a feed inlet, a suction port, and an overflow port, and the overflow port is located above the feed inlet; the lower part and the bottom part of the continuous condensation separation reactor (3) are respectively provided with an introduction port and a discharge port; a discharge port of the prepolymerization reactor (2) is communicated with the feed inlet of the continuous condensation separation reactor (3) by means of a pipe; the overflow port is communicated with a feed port of the prepolymerization reactor (2) by means of a pipe; and the suction port is communicated with the introduction port by means of a pipe.

Description

A system and method for preparing mesophase pitch

[0001] This application claims priority to Chinese Patent Application No. 202411533991.X, filed on October 30, 2024, entitled "A System and Method for Preparing Mesophase Pitch", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to a system and method for preparing mesophase pitch, belonging to the field of materials technology, particularly the field of novel carbon materials technology. Background Technology

[0003] Existing technologies for the separation of mesophase asphalt mainly use settling tanks for intermittent operation, resulting in low production efficiency.

[0004] The applicant will briefly introduce some prior art that is closely related to this invention, so that those skilled in the art can better understand the situation of the prior art and the drawbacks of the prior art.

[0005] CN113680301A discloses a method and apparatus for preparing spinnable mesophase pitch. The core method for improving the composition of mesophase pitch is to achieve dynamic separation of components during the polymerization process. That is, the heavy components enter the low temperature zone and polymerize under relatively mild conditions, while the light components enter the high temperature zone to accelerate polymerization. This can both accelerate the reaction of the light components and inhibit the excessive polymerization of the heavy components. By employing a gradient non-isothermal thermal field corresponding to the molecular weight gradient, dynamic separation of components and gradient non-isothermal polymerization are achieved. Heavy components polymerize under milder conditions in the lower low-temperature zone, while lighter components polymerize more rapidly in the upper high-temperature zone. This accelerates the reaction of lighter components while suppressing excessive polymerization of heavy components, resulting in a narrower relative molecular weight distribution. The lower asphalt components with similar and moderate molecular weights can form an intermediate phase under mild conditions, reducing QI and BS, increasing BI-QS, and improving spinnability. By separately controlling the heating temperature of each section of the heating resistance wire, gradient heating at equal heights can be achieved to meet the temperature requirements of different locations. This eliminates the need for back-mixing, reducing energy consumption and allowing for continuous feeding at suitable locations and continuous discharge from the bottom, achieving a plug-flow continuous polymerization reaction. This system can operate continuously for at least 3000 hours, enabling continuous production of spinnable mesophase asphalt, and has significant potential for industrial applications.

[0006] However, in this prior art, because the light components move upward and the heavy components move downward, the heptane solubles (HS) with a relatively low density and higher hydrogen content cannot enter the heavy components and be discharged as mesophase asphalt products. This results in the mesophase asphalt having too small a HS ratio, too high a C / H ratio, and a softening point that is prone to exceed the standard. Furthermore, it is impossible to directly adjust the softening point of the product.

[0007] CN114405433A discloses a multi-stage reaction apparatus and preparation method for pure mesophase pitch used in spinning. The multi-stage reaction apparatus for high-purity mesophase pitch includes a primary reactor, a primary separator, a secondary reactor, a secondary separator, a tertiary reactor, and multiple feed pumps, all connected in series via pipelines. The primary separator has a by-product outlet at the bottom and a refined pitch outlet on the side, which is connected to the secondary reactor via a pipeline. The secondary separator has a mesophase pitch outlet at the bottom and a circulating pitch outlet on the side, which is connected to the tertiary reactor via a pipeline, and the circulating pitch outlet is connected to the secondary reactor via a pipeline. Furthermore, heat exchangers are installed between the primary reactor and the primary separator, and between the secondary reactor and the secondary separator, to cool the pitch. The preparation method of high-purity spinning mesophase pitch using a multi-stage reaction device includes the following steps: S1, the melted raw material pitch is pumped to the primary reactor, then cooled to 250-350℃, and then placed in a 200-360℃ separator for settling. The upper layer is first pumped into the secondary reactor through the refined pitch outlet, and then the lower layer is pumped out through the by-product outlet; S2, after the reaction in the secondary reactor, it is sent to a 300-360℃ secondary separator for settling. The upper layer is first pumped into the secondary reactor through the circulating pitch outlet, and then the lower layer is pumped into the tertiary reactor through the mesophase pitch outlet; S3, degassing is carried out in the tertiary reactor, and the light components are removed under negative pressure. The resulting product is the spinning mesophase pitch.

[0008] Although the multi-stage reaction device and preparation method are highly efficient and stable, and can be used for industrial production of mesophase asphalt, producing high-quality mesophase asphalt, the existing technology requires intermittent operation because both the primary and secondary separators use sedimentation separation, which prevents continuous production and significantly limits production efficiency.

[0009] CN113773871A discloses a continuous cyclic polymerization distillation reaction system for preparing mesophase asphalt, comprising: a counter-rotating twin-screw extruder, a magnetically driven constant-pressure stirrer, a static mixer, a static density separator, a first-stage counter-rotating twin-screw devouring extruder, a second-stage counter-rotating twin-screw devouring extruder, and a vacuum filter buffer tank; the main structure of the static density separator is arranged on a loss-in-weight weighing scale, the top of the main structure of the static density separator is the separator feed pipe, and the bottom outlet of the main structure of the static density separator is connected to the inlet of a volumetric metering pump; the outlet of the volumetric metering pump is connected to a third three-way solenoid valve; the third three-way solenoid valve has two passages, and by controlling the third three-way solenoid valve, the outlet of the volumetric metering pump can be connected to a heavy component conveying pipe and a light component conveying pipe separately; the heavy component conveying pipe is connected to the first-stage counter-rotating twin-screw devouring extruder; the light component conveying pipe is connected to the counter-rotating twin-screw extruder through a first three-way solenoid valve and the feed pipe of the conveying extruder.

[0010] Although this system can solve the problems of low production efficiency, impurity of mesophase asphalt composition, and low quality in the preparation of mesophase asphalt in the prior art, the system disclosed in the prior art uses a static density separator to separate and purify asphalt, which also requires intermittent operation and cannot achieve continuous production, thus greatly limiting the production efficiency.

[0011] Therefore, providing a novel system and method for preparing mesophase pitch has become a pressing technical problem to be solved in this field. Summary of the Invention

[0012] To address the aforementioned shortcomings and deficiencies, the present invention aims to provide a system and method for preparing mesophase asphalt. The system and method provided by the present invention can solve the problem of continuous refining during the preparation of mesophase asphalt and ensure the uniformity of the quality of the obtained mesophase asphalt product.

[0013] To achieve the above objectives, on the one hand, the present invention provides a system for preparing mesophase asphalt, wherein the system for preparing mesophase asphalt includes a prepolymerization reactor and a continuous condensation separation reactor, wherein the upper middle part of the continuous condensation separation reactor is provided with a feed inlet, a discharge outlet and an overflow outlet, and the overflow outlet is located above the feed inlet, and the lower part and bottom are respectively provided with an inlet and a outlet.

[0014] The outlet of the prepolymerization reactor is connected to the inlet of the continuous condensation separation reactor via a pipeline, the overflow outlet is connected to the inlet of the prepolymerization reactor via a pipeline, and the extraction outlet is connected to the inlet via a pipeline.

[0015] In one specific embodiment of the system described above in this invention, when the number of prepolymerization reactors is two or more, the two or more prepolymerization reactors are connected in series or in parallel.

[0016] In one specific embodiment of the system described above, an online viscosity meter is installed at the outlet of the continuous condensation separation reactor. This invention allows for the measurement of product viscosity using this online viscosity meter and the control of the discharge based on the measured viscosity data, ensuring product uniformity.

[0017] In one specific embodiment of the system described above in this invention, the system further includes a separator. The oil and gas outlet at the top of the continuous condensation separation reactor is connected to the inlet of the separator via a pipeline, and the recombinant component outlet of the separator is connected to the inlet of the prepolymerization reactor via a pipeline.

[0018] In one specific embodiment of the system described above in this invention, the separator is a condenser separator.

[0019] In one specific embodiment of the system described above in this invention, the distance between the extraction port and the top of the continuous condensation separation reactor is 25-50% of the total height of the continuous condensation separation reactor, and the distance between the inlet and the bottom of the continuous condensation separation reactor is 5-30% of the total height of the continuous condensation separation reactor.

[0020] In one specific embodiment of the system described above, the distance between the overflow port and the top of the continuous condensation separation reactor is 15-25% of the total height of the continuous condensation separation reactor.

[0021] In one specific embodiment of the system described above in this invention, the distance between the feed inlet of the continuous condensation separation reactor and the top of the continuous condensation separation reactor is 20-30% of the total height of the continuous condensation separation reactor.

[0022] On the other hand, the present invention also provides a method for preparing mesophase asphalt, wherein the method for preparing mesophase asphalt is implemented using the system for preparing mesophase asphalt described above, and includes the following steps:

[0023] Step (1): The precursor asphalt is sent to a prepolymerization reactor for thermal polycondensation to obtain the prepolymerization product (prepolymerized asphalt);

[0024] Step (2): The prepolymerization product is fed from the feed port to the continuous condensation separation reactor for further thermal condensation and separation, and the mesophase asphalt product is continuously discharged from the discharge port of the continuous condensation separation reactor; when the liquid level of the material in the continuous condensation separation reactor is not lower than the height of the overflow port, the liquid material is returned to the prepolymerization reactor through the overflow port for thermal condensation; after the mesophase asphalt product is obtained from the discharge port of the continuous condensation separation reactor, the liquid material is extracted from the extraction port and introduced into the lower part of the continuous condensation separation reactor through the inlet to react with the heavy material, so as to adjust the softening point of the mesophase asphalt product.

[0025] As a specific embodiment of the method described above in this invention, the precursor pitch includes one or a combination of several of the following: catalytic slurry, ethylene tar, vacuum residue, coal tar, and coal pitch.

[0026] As a specific embodiment of the method described above in this invention, in step (1), the temperature of the thermal polycondensation is 400-500℃, the pressure is 0.1-8MPa, and the time is 1-10h.

[0027] In one specific embodiment of the method described above, in step (2), the continuous condensation separation reactor is subjected to segmented temperature control. This segmented temperature control involves forming 5-10 temperature distribution segments from the top to the bottom of the reactor cavity, with each segment decreasing in temperature. The temperature difference between adjacent temperature segments is 1-4°C. The temperature of the segment closest to the top of the cavity is 370-450°C, and the temperature of the segment closest to the bottom of the cavity is 350-430°C. The pressure inside the continuous condensation separation reactor is 0.001-2 MPa, and the residence time of the material inside the reactor is 1-12 hours. The cavity of the continuous condensation separation reactor refers to the internal cavity used for the reaction. In some embodiments of the present invention, the continuous condensation separation reactor is cylindrical, and the cavity is a hollow cylinder.

[0028] In this invention, "pressure" refers to absolute pressure. Therefore, when the pressure value is <0.1MPa, the operation carried out in the reactor is a negative pressure operation.

[0029] As a specific embodiment of the method described above in this invention, in step (2), the liquid material extracted from the extraction outlet accounts for 1-15 wt% of the total feed amount of the continuous condensation separation reactor.

[0030] As a specific embodiment of the method described above in this invention, the method further includes: sending the oil and gas (cracking products) generated in step (2) to a separator through the oil and gas outlet at the top of the continuous condensation separation reactor, separating light components with a boiling point less than 350°C and heavy components with a boiling point greater than 350°C in the separator, and returning the heavy components to the prepolymerization reactor for thermal condensation, while directly discharging or collecting the light components with a boiling point less than 350°C.

[0031] As a specific embodiment of the method described above in this invention, when the separator is a condenser separator, the oil and gas generated in step (2) are sent to the separator through the oil and gas outlet at the top of the continuous condensation separation reactor. In the separator, light components with boiling points less than 350°C and heavy components with boiling points greater than 350°C are obtained by condensation separation. The heavy components are returned to the prepolymerization reactor for thermal condensation, while the light components with boiling points less than 350°C are directly discharged or collected.

[0032] In the method described above in this invention, in step (1), the heavy aromatic raw material undergoes thermal polycondensation in a prepolymerization reactor to increase its molecular weight and form prepolymerized asphalt. The prepolymerized asphalt enters the continuous condensation separation reactor through the feed inlet located in the upper middle part of the reactor. Utilizing the density difference between the heavy and light components, they are distributed within the reactor. The light components are located in the upper part, where the reactor temperature is higher, resulting in thermal polycondensation. The heavy components are located in the lower part, where the reactor temperature is lower, resulting in a slower thermal polycondensation reaction. This mainly achieves the fusion of the mesophase asphalt and the mesophase asphalt product is continuously discharged from the discharge outlet located at the bottom of the continuous condensation separation reactor.

[0033] Compared with the prior art, the beneficial technical effects achieved by the present invention include:

[0034] 1) This invention connects a prepolymerization reactor and a continuous condensation separation reactor in series, wherein the continuous condensation separation reactor can be operated continuously, thereby realizing the continuous preparation of mesophase asphalt products.

[0035] 2) In this invention, the mesophase asphalt produced by thermal polycondensation during the polymerization process in the continuous condensation separation reactor has a higher density, gradually moves downwards, and is continuously discharged from the bottom outlet of the continuous condensation separation reactor. Meanwhile, the lighter liquid component produced by pyrolysis has a lower density and moves upwards. When the liquid level of the material in the continuous condensation separation reactor is not lower than the overflow outlet height, this portion of the material overflows from the overflow outlet and returns to the prepolymerization reactor as raw material to continue thermal polycondensation. This ensures a constant residence time for the material during continuous operation. This invention, through the control of the overflow and bottom outlet of the continuous condensation separation reactor, enables the continuous production of homogenized mesophase asphalt products.

[0036] 3) In this invention, after obtaining mesophase asphalt product from the outlet of the continuous condensation separation reactor, liquid material (with a hydrogen content of 0.7-0.8 H / C and a molar ratio of 0.7-0.8) is extracted from the extraction outlet and introduced into the lower part of the continuous condensation separation reactor through the inlet to react with heavy material (with an H / C of 0.5-0.6 and a molar ratio of 0.5-0.6) to adjust the softening point of the asphalt product, thereby obtaining a mesophase asphalt product with excellent performance. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 is a schematic diagram of the system for preparing mesophase pitch provided in Embodiment 1-1 of the present invention.

[0039] Figure 2 is a schematic diagram of the system for preparing mesophase pitch provided in Embodiments 1-2 of the present invention.

[0040] Figure 3 is a schematic diagram of the system for preparing mesophase pitch provided in Embodiments 1-3 of the present invention.

[0041] Key reference numerals: 1. Raw material tank; 11. First raw material tank; 12. Second raw material tank; 2. Prepolymerization reactor; 21. First prepolymerization reactor; 22. Second prepolymerization reactor; 23. Third prepolymerization reactor; 24. Fourth prepolymerization reactor; 3. Continuous condensation separation reactor; 4. Condensation separator. Detailed Implementation

[0042] It should be noted that the term "comprising" and any variations thereof in the specification, claims, and accompanying drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices.

[0043] The "range" disclosed in this invention is given in the form of a lower limit and an upper limit. It can be one or more lower limits and one or more upper limits, respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower and upper limits define the boundaries of the particular range. All ranges defined in this way are composable, meaning that any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for specific parameters, it is also expected that ranges of 60-110 and 80-120 are also expected. Furthermore, if the listed minimum range values ​​are 1 and 2, and the listed maximum range values ​​are 3, 4, and 5, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5.

[0044] In this invention, unless otherwise specified, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this invention, and "0-5" is simply a shortened representation of these numerical combinations.

[0045] In this invention, unless otherwise specified, all embodiments and preferred embodiments mentioned in this invention can be combined with each other to form new technical solutions.

[0046] In this invention, unless otherwise specified, all technical features and preferred features mentioned in this invention can be combined with each other to form new technical solutions.

[0047] In this invention, unless otherwise specified, all steps mentioned herein may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying tables, drawings, and embodiments. The embodiments described below are some, but not all, embodiments of this invention, and are only used to illustrate the invention, and should not be considered as limiting the scope of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0049] Example 1-1

[0050] This embodiment provides a system for preparing mesophase asphalt, the structural diagram of which is shown in Figure 1. As can be seen from Figure 1, the system includes a raw material tank 1, a prepolymerization reactor 2, a continuous condensation separation reactor 3, and a condensation separator 4. The prepolymerization reactor 2 is provided with a first inlet, a second inlet, and a prepolymerized asphalt outlet at its upper, top, and bottom, respectively. The continuous condensation separation reactor 3 is cylindrical, with an inlet, an outlet, and an overflow outlet at its upper part, with the overflow outlet located above the inlet. The lower and bottom parts are provided with an inlet and a mesophase asphalt outlet, respectively. An online viscosity meter (not shown in Figure 1) is provided at the mesophase asphalt outlet, and an oil and gas outlet is provided at its top.

[0051] The outlet of the raw material tank 1 is connected to the first inlet of the prepolymerization reactor 2 via a pipeline, the prepolymerized asphalt outlet of the prepolymerization reactor 2 is connected to the inlet of the continuous condensation separation reactor 3 via a pipeline, the overflow outlet is connected to the second inlet of the prepolymerization reactor 2 via a pipeline, and the extraction outlet is connected to the inlet via a pipeline.

[0052] The oil and gas outlet at the top of the continuous condensation separation reactor 3 is connected to the inlet of the condensation separator 4 via a pipeline, and the heavy component outlet of the condensation separator 4 is connected to the second inlet of the prepolymerization reactor 2 via a pipeline.

[0053] Examples 1-2

[0054] This embodiment provides a system for preparing mesophase asphalt, the structural schematic of which is shown in Figure 2. As can be seen from Figure 2, the difference between this system and the system provided in Embodiment 1-1 is that it includes two prepolymerization reactors arranged in series, namely a first prepolymerization reactor 21 and a second prepolymerization reactor 22. The first prepolymerization reactor 21 is provided with a first feed inlet, a second feed inlet and a first prepolymerized asphalt outlet at its upper part, top and bottom, respectively. The second prepolymerization reactor 22 is provided with a third feed inlet and a second prepolymerized asphalt outlet at its upper part and bottom, respectively.

[0055] The outlet of the raw material tank 1 is connected to the first inlet of the first prepolymerization reactor 21 via a pipeline. The first prepolymerized asphalt outlet of the first prepolymerization reactor 21 is connected to the third inlet of the second prepolymerization reactor 22 via a pipeline. The second prepolymerized asphalt outlet of the second prepolymerization reactor 22 is connected to the inlet of the continuous condensation separation reactor 3 via a pipeline. The overflow port and the heavy component outlet of the condensation separator 4 are connected to the second inlet of the first prepolymerization reactor 21 via a pipeline.

[0056] Examples 1-3

[0057] This embodiment provides a system for preparing mesophase asphalt, the structural schematic of which is shown in Figure 3. As can be seen from Figure 3, the difference between this system and the system provided in Embodiment 1-1 is that it includes two prepolymerization reactors arranged in parallel, namely a third prepolymerization reactor 23 and a fourth prepolymerization reactor 24. The upper part, top and bottom of the third prepolymerization reactor 23 are respectively provided with a first inlet, a second inlet and a first prepolymerized asphalt outlet. The upper part, top and bottom of the fourth prepolymerization reactor 24 are respectively provided with a third inlet, a fourth inlet and a second prepolymerized asphalt outlet.

[0058] The outlets of the first raw material tank 11 and the second raw material tank 12 are respectively connected to the first inlet of the third prepolymerization reactor 23 and the third inlet of the fourth prepolymerization reactor 24 through pipelines. The first prepolymerized asphalt outlet of the third prepolymerization reactor 23 and the second prepolymerized asphalt outlet of the fourth prepolymerization reactor 24 are connected to the inlet of the continuous condensation separation reactor 3 through pipelines. The overflow port and the heavy component outlet of the condensation separator 4 are connected to the second inlet of the third prepolymerization reactor 23 and the fourth inlet of the fourth prepolymerization reactor 24 through pipelines.

[0059] Example 2-Example 21

[0060] This series of embodiments provides a method for preparing mesophase pitch, which is implemented using the system for preparing mesophase pitch provided in Embodiments 1-1. The method includes the following steps:

[0061] Step (1): The heavy aromatic raw material is sent to the prepolymerization reactor for thermal polycondensation to obtain the prepolymerization product;

[0062] Step (2): The continuous condensation separation reactor is subjected to segmented temperature control. The pre-condensation product is fed from the feed port to the continuous condensation separation reactor for further thermal condensation and separation. The mesophase asphalt product is continuously discharged from the mesophase asphalt outlet of the continuous condensation separation reactor. When the liquid level of the material in the continuous condensation separation reactor is not lower than the overflow port, the liquid material is returned to the pre-polymerization reactor through the overflow port for thermal condensation. After obtaining the mesophase asphalt product from the outlet of the continuous condensation separation reactor, the liquid material is extracted from the extraction port and introduced into the lower part of the continuous condensation separation reactor through the inlet to react with the heavy material to adjust the softening point of the asphalt product.

[0063] When the viscosity of the mesophase asphalt product continuously discharged from the mesophase asphalt outlet of the continuous condensation separation reactor is lower than the target (kinematic viscosity of 50 Pa·s at 290℃), the mesophase asphalt outlet is closed, allowing the material to remain in the continuous condensation separation reactor for thermal condensation until the viscosity reaches the target. When the mesophase asphalt outlet is closed, the continuous condensation separation reactor continues to feed continuously. During this process, when the material liquid level exceeds the overflow port, the overflowing liquid material is returned to the prepolymerization reactor through the overflow port to continue thermal condensation, thereby achieving continuous operation of the device.

[0064] Step (3): The oil and gas generated in step (2) are sent to the condenser separator through the oil and gas outlet at the top of the continuous condensation separation reactor. The light component with a boiling point of less than 350°C and the heavy component with a boiling point of greater than 350°C are separated in the condenser separator. The heavy component with a boiling point of greater than 350°C is returned to the prepolymerization reactor for thermal condensation, while the light component with a boiling point of less than 350°C is directly discharged or collected.

[0065] Example 22

[0066] This embodiment provides a method for preparing mesophase pitch, which is implemented using the system for preparing mesophase pitch provided in Examples 1-2. The method includes the following steps:

[0067] Step (1): The catalytic slurry is sent to the first prepolymerization reactor for thermal polycondensation to obtain the first prepolymerization product; the first prepolymerization product is then sent to the second prepolymerization reactor for further thermal polycondensation to obtain the second prepolymerization product.

[0068] The pressure in the first prepolymerization reactor is 3 MPa, the temperature is 450℃, and the residence time of the material in the first prepolymerization reactor is 2 hours. The pressure in the second prepolymerization reactor is 1 MPa, the temperature is 420℃, and the residence time of the material in the second prepolymerization reactor is 3 hours.

[0069] Step (2): The operation steps and process parameters are the same as in Example 6, except that the second pre-condensation product is sent from the feed inlet to the continuous condensation separation reactor to continue thermal condensation and separation;

[0070] Step (3): The operation steps and process parameters are the same as in Example 6, except that the heavy components with a boiling point greater than 350°C obtained by separation are returned to the first prepolymerization reactor to continue thermal polycondensation.

[0071] The mesophase pitch product obtained in this embodiment has an optical anisotropy content of 97% and a softening point of 284°C. The yield of the mesophase pitch product is 27%.

[0072] Example 23

[0073] This embodiment provides a method for preparing mesophase asphalt, which is implemented using the system for preparing mesophase asphalt provided in Examples 1-3. The method includes the following steps:

[0074] Step (1): The catalytic slurry is sent to the third prepolymerization reactor and the fourth prepolymerization reactor respectively, so that the raw materials are thermally polycondensed in the third prepolymerization reactor and the fourth prepolymerization reactor in turn to obtain the third prepolymerization product and the fourth prepolymerization product; wherein, the reaction conditions in the third prepolymerization reactor and the fourth prepolymerization reactor are the same as the reaction conditions of the prepolymerization reactor in step (1) of Example 6.

[0075] Step (2): The operation steps and process parameters are the same as in Example 6, except that the third prepolymerization product and the fourth prepolymerization product are fed alternately from the feed inlet to the continuous condensation separation reactor to continue thermal condensation and separation;

[0076] Step (3): The operation steps and process parameters are the same as in Example 6, except that the heavy components with boiling points greater than 350°C obtained by separation are returned to the third and fourth prepolymerization reactors to continue thermal polycondensation.

[0077] The mesophase pitch product obtained in this embodiment has an optical anisotropy content of 97.1% and a softening point of 281°C. The yield of the mesophase pitch product is 26%.

[0078] Compared to Example 6, Examples 22 and 23 of the present invention, under the premise of obtaining mesophase asphalt products with basically similar properties, wherein in Example 22, the first prepolymerization reactor and the second prepolymerization reactor are connected in series, and the first prepolymerization reactor and the second prepolymerization reactor are continuously fed and discharged, so as to realize continuous production, while in Example 23, the third prepolymerization reactor and the fourth prepolymerization reactor are connected in parallel, and the prepolymerization can be carried out alternately in the third prepolymerization reactor and the fourth prepolymerization reactor by switching the valve, so as to ensure that the prepolymerization is continuous and uninterrupted.

[0079] Comparative Example 1

[0080] This comparative example provides a method for preparing mesophase pitch, which differs from Example 6 in that:

[0081] This comparative example only performed step (1), but not steps (2) and (3), and the heavy aromatic raw materials and parameters used in step (1) were the same as those in Example 6.

[0082] Comparative Example 2

[0083] This comparative example provides a method for preparing mesophase pitch, which differs from Example 6 in that: although the method in this comparative example involves two-stage reactions, step (2) uses a conventional batch reactor or tubular reactor, and the method includes the following steps:

[0084] Step (1): The precursor asphalt is sent to a prepolymerization reactor for thermal polycondensation to obtain the prepolymerization product;

[0085] Step (2): The prepolymerization product is fed from the feed port to a conventional batch reactor or tubular reactor. After the prepolymerization product enters, the reactor is closed. Then the reactor is heated to 390°C and the pressure is 0.2MPa. After holding at the temperature for 5 hours, the reaction is completed. The bottom or top of the reactor is opened to discharge the product.

[0086] Comparative Example 3

[0087] This comparative example provides a method for preparing mesophase bitumen, which differs from Example 6 only in that the continuous condensation separation reactor is not subjected to segmented temperature control, i.e., the continuous condensation separation reactor has no temperature gradient.

[0088] Comparative Example 4

[0089] This comparative example provides a method for preparing mesophase bitumen, which differs from Example 6 only in that the continuous condensation separation reactor is not equipped with an overflow port, an extraction port, and an inlet port.

[0090] Comparative Example 5

[0091] This comparative example provides a method for preparing mesophase bitumen, which differs from Example 6 only in that the continuous condensation separation reactor is not equipped with an extraction port and an inlet port.

[0092] The specific substances and composition information of the heavy aromatic feedstocks used in this series of embodiments and Comparative Examples 1-5 are shown in Table 1. The various process parameters involved in the prepolymerization reactor in step (1) are shown in Table 2. The various process parameters involved in the continuous condensation separation reactor or conventional batch reactor or tubular reactor in step (2) include, for example, the number of temperature segments or temperature ranges formed from the top to the bottom of the cavity of the continuous condensation separation reactor (denoted as N), the temperature difference between adjacent temperature segments (denoted as ΔT), and the temperature of the segment closest to the top of the cavity (denoted as T). 顶 The temperature of the section closest to the bottom of the cavity (denoted as T) 底 The following parameters are provided in Table 3: pressure (denoted as P) within the continuous condensation separation reactor, residence time of the material within the reactor (denoted as t), the ratio of the distance between the outlet and the top of the reactor to the total height of the reactor (denoted as l1), the ratio of the distance between the inlet and the bottom of the reactor to the total height of the reactor (denoted as l2), the ratio of the distance between the overflow outlet and the top of the reactor to the total height of the reactor (denoted as l3), the ratio of the distance between the feed inlet and the top of the reactor to the total height of the reactor (denoted as l4), and the percentage of liquid material extracted from the outlet relative to the total feed amount of the reactor (denoted as w). The properties and yield data of the obtained mesophase asphalt product are shown in Table 4.

[0093] Table 1

[0094] Table 2

[0095] Table 3 Note: t is calculated as the ratio of the volume of the cavity between the feed inlet and the outlet of the mesophase asphalt in the continuous condensation separation reactor to the material outflow rate from the outlet of the mesophase asphalt.

[0096] Table 4 Note: The softening points in Table 4 were measured using the Mettler cup method, and the optical structures were measured using a polarizing microscope.

[0097] As can be seen from the experimental data in Tables 1-4 above, Examples 2-19 of the present invention can obtain mesophase pitch products with both high optical anisotropy content and low softening point, and the yield is high.

[0098] Compared with Example 6 of the present invention, in Example 20 of the present invention, the distance between the outlet and the inlet of the continuous condensation separation reactor is too close. The optical anisotropy content and yield of the mesophase asphalt product obtained are slightly lower than those of Example 6, and the softening point of the mesophase asphalt product is higher. This is because the distance between the outlet and the inlet of the continuous condensation separation reactor is too close, so the H / C ratio of the liquid material (used as a co-carbonizing agent) extracted from the outlet is similar to the H / C ratio of the heavy material at the inlet, which cannot achieve the effect of introducing light components for co-carbonization to improve the softening point of the mesophase asphalt product.

[0099] Compared with Embodiment 6 of the present invention, in Embodiment 21 of the present invention, the distance between the inlet of the continuous condensation separation reactor and the bottom of the reactor is too close, causing the co-carbonized material that has not formed a mesophase to be discharged before it can be converted into mesophase pitch. Although this can reduce the softening point of the mesophase pitch product, it results in the optical structure content of the mesophase pitch product being too low.

[0100] Compared to Example 6 of the present invention, Comparative Example 1 only underwent a single thermal polycondensation reaction. In order to obtain a product with a higher mesophase content, the reaction time needs to be increased. Although the overall yield of the product in Comparative Example 1 was slightly improved, due to the wide molecular weight distribution inside the prepolymerization reactor, when the light components were finally converted into mesophase asphalt at the same temperature, the heavy components underwent excessive thermal polycondensation, and some unconvertible components could not be removed. Therefore, the resulting mesophase asphalt product had a poor optical structure and a significantly excessive softening point.

[0101] Compared to Example 6 of the present invention, although Comparative Example 2 involved a two-stage reaction, the second stage reaction was carried out in a conventional batch reactor or tubular reactor, and sedimentation occurred simultaneously with thermal polycondensation. Because it was difficult to determine the boundary between the mesophase and homogeneous bitumen, a large amount of mesophase product was discarded as homogeneous bitumen, and the discharge of mesophase bitumen could not be controlled. Some mesophase bitumen had to be sacrificed to ensure the quality of the product at the bottom of the reactor, resulting in an overall low yield. Furthermore, because the reaction temperature of the entire second stage reaction was constant, it was impossible to achieve thermal polycondensation of light and heavy components at different temperatures, leading to over-polymerization of the heavy components. Although the resulting mesophase bitumen product had a good optical structure, its softening point was high. In addition, Comparative Example 2 could not achieve continuous production and could only be operated intermittently, resulting in low production efficiency.

[0102] Compared to Example 6 of the present invention, Comparative Example 3 did not perform segmented temperature control on the continuous condensation separation reactor, i.e., the continuous condensation separation reactor had no temperature gradient. Since Comparative Example 3 could also achieve continuous refining and preparation of mesophase pitch, the yield of its mesophase pitch product was higher than that of Comparative Example 2, but still lower than that of Example 6. Furthermore, because the reaction temperature of the entire second stage reaction was constant, it was impossible to achieve thermal condensation of light and heavy components at different temperatures, leading to excessive condensation of the heavy components. Although the resulting mesophase pitch product had a better optical structure, its softening point was relatively high.

[0103] Compared to Example 6 of the present invention, the continuous condensation separation reactor in Comparative Example 4 was not equipped with an overflow port, an exhaust port, or an inlet port. Since Comparative Example 4 can also achieve continuous refining and preparation of mesophase asphalt, the overall yield is higher than that of Comparative Example 2, but still lower than that of Example 6. Furthermore, Comparative Example 4 can adjust the thermal condensation temperature according to the distribution of light and heavy components in the continuous condensation separation reactor, allowing the light components to react at a higher temperature and the heavy components at a lower temperature, preventing excessive thermal reaction. Compared to Comparative Example 3, the softening point and optical structure of the mesophase asphalt product obtained in Comparative Example 4 are improved. However, since the continuous condensation separation reactor in Comparative Example 4 is not equipped with an exhaust port or an inlet port, it is impossible to improve the softening point of the mesophase asphalt product by introducing materials with a high H / C ratio at the bottom. Therefore, the softening point of the mesophase asphalt product obtained in Comparative Example 4 is still significantly worse than that of Example 6. In addition, because the continuous condensation separation reactor used in Comparative Example 4 was not equipped with an overflow port, the light components floated on the top of the continuous condensation separation reactor and underwent high-temperature thermal reaction at low pressure, causing a large number of cracking reactions to occur, which ultimately resulted in a low yield of mesophase asphalt.

[0104] Compared to Example 6 of the present invention, the continuous condensation separation reactor in Comparative Example 5 was not equipped with an extraction port and an inlet port. This resulted in the lower part of the continuous condensation separation reactor producing entirely macromolecules with excessively low HS content, leading to a higher softening point for the mesophase asphalt product. However, compared to Comparative Example 4, the continuous condensation separation reactor in Comparative Example 5 was equipped with an overflow port, allowing the lighter components to return as raw materials to the prepolymerization reactor for thermal condensation under pressure. This prevented excessive cracking and converted them into prepolymerized asphalt, which then re-entered the continuous condensation separation reactor for further reaction. Consequently, the yield of the mesophase asphalt product obtained in Comparative Example 5 was higher than that in Comparative Example 4.

[0105] The above description is merely a specific embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any substitution of equivalent components or equivalent changes and modifications made within the scope of protection of this patent should still fall within the scope of this patent. Furthermore, the technical features, technical features and technical inventions, and technical inventions in this invention can be freely combined and used.

Claims

1. A system for preparing mesophase pitch, characterized in that, The system for preparing mesophase asphalt includes a prepolymerization reactor and a continuous condensation separation reactor. The continuous condensation separation reactor is provided with an inlet, an outlet, and an overflow in the upper middle part, with the overflow located above the inlet. The lower part and bottom are respectively provided with an inlet and an outlet. The outlet of the prepolymerization reactor is connected to the inlet of the continuous condensation separation reactor via a pipeline, the overflow outlet is connected to the inlet of the prepolymerization reactor via a pipeline, and the extraction outlet is connected to the inlet via a pipeline.

2. The system according to claim 1, characterized in that, When there are two or more prepolymerization reactors, the two or more prepolymerization reactors are connected in series or in parallel.

3. The system according to claim 1 or 2, characterized in that, The discharge port of the continuous condensation separation reactor is equipped with an online viscosity meter.

4. The system according to claim 1 or 2, characterized in that, The system also includes a separator. The oil and gas outlet at the top of the continuous condensation separation reactor is connected to the inlet of the separator via a pipeline, and the heavy component outlet of the separator is connected to the inlet of the prepolymerization reactor via a pipeline.

5. The system according to claim 1 or 2, characterized in that, The distance between the extraction port and the top of the continuous condensation separation reactor is 25-50% of the total height of the continuous condensation separation reactor, and the distance between the inlet and the bottom of the continuous condensation separation reactor is 5-30% of the total height of the continuous condensation separation reactor.

6. The system according to claim 1 or 2, characterized in that, The distance between the overflow outlet and the top of the continuous condensation separation reactor is 15-25% of the total height of the continuous condensation separation reactor.

7. The system according to claim 1 or 2, characterized in that, The distance between the feed inlet and the top of the continuous condensation separation reactor is 20-30% of the total height of the reactor.

8. A method for preparing mesophase pitch, characterized in that, The method for preparing mesophase pitch is implemented using the system for preparing mesophase pitch according to any one of claims 1-7, and includes the following steps: Step (1): The heavy aromatic raw material is sent to the prepolymerization reactor for thermal polycondensation to obtain the prepolymerization product; Step (2): The prepolymerization product is fed from the feed port to the continuous condensation separation reactor for further thermal condensation and separation, and the mesophase asphalt product is continuously discharged from the discharge port of the continuous condensation separation reactor; when the liquid level of the material in the continuous condensation separation reactor is not lower than the height of the overflow port, the liquid material is returned to the prepolymerization reactor through the overflow port for thermal condensation; after the mesophase asphalt product is obtained from the discharge port of the continuous condensation separation reactor, the liquid material is extracted from the extraction port and introduced into the lower part of the continuous condensation separation reactor through the inlet to react with the heavy material, so as to adjust the softening point of the mesophase asphalt product.

9. The method according to claim 8, characterized in that, When there are two or more prepolymerization reactors, and the two or more prepolymerization reactors are connected in series, step (1) includes: first, sending the heavy aromatic raw material to the first prepolymerization reactor for thermal polycondensation, then sending the prepolymerization product obtained from the first prepolymerization reactor to the second prepolymerization reactor for thermal polycondensation, until the thermal polycondensation is completed in the last prepolymerization reactor, and sending the prepolymerization product obtained from the last prepolymerization reactor from the feed port to the continuous condensation separation reactor to continue thermal polycondensation and separation; When there are two or more prepolymerization reactors and the two or more prepolymerization reactors are connected in parallel, step (1) includes: feeding heavy aromatic raw materials into each of the parallel prepolymerization reactors, so that the heavy aromatic raw materials take turns to undergo thermal polycondensation in each of the parallel prepolymerization reactors, and then feeding the prepolymerization products obtained from each of the parallel prepolymerization reactors from the feed inlet to the continuous condensation separation reactor to continue thermal polycondensation and separation.

10. The method according to claim 8 or 9, characterized in that, The heavy aromatic feedstock includes one or a combination of several of the following: catalytic slurry, ethylene tar, vacuum residue, coal tar, and coal pitch.

11. The method according to claim 8 or 9, characterized in that, In step (1), the temperature of the thermal polycondensation is 400-500℃, the pressure is 0.1-8MPa, and the time is 1-10h.

12. The method according to claim 8 or 9, characterized in that, In step (2), the continuous condensation separation reactor is subjected to segmented temperature control. The segmented temperature control is to form 5-10 segments of temperature distribution from the top to the bottom of the cavity of the continuous condensation separation reactor, with the temperature difference between adjacent temperature segments being 1-4℃. The temperature of the segment closest to the top of the cavity is 370-450℃, and the temperature of the segment closest to the bottom of the cavity is 350-430℃. The pressure inside the continuous condensation separation reactor is 0.001-2MPa, and the residence time of the material in the continuous condensation separation reactor is 1-12h.

13. The method according to claim 8 or 9, characterized in that, In step (2), the liquid material extracted from the extraction outlet accounts for 1-15 wt% of the total feed of the continuous condensation separation reactor.

14. The method according to claim 8 or 9, characterized in that, The method further includes: sending the oil and gas generated in step (2) to the separator through the oil and gas outlet at the top of the continuous condensation separation reactor, separating light components with boiling points less than 350°C and heavy components with boiling points greater than 350°C in the separator, and returning the heavy components to the prepolymerization reactor for thermal condensation.

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