A preparation method and application of spinnable mesophase pitch

Abstract

The present invention belongs to the technical field of intermediate asphalt, and discloses a method for preparing a spinnable mesophase asphalt and its application. A fraction with a boiling point lower than 530°C in FCC oil slurry is used as a raw material, lignin is added, and a two-stage carbonization process is performed. The heat treatment temperature of the first stage of the carbonization process is lower than 380°C, and finally a spinnable mesophase asphalt is obtained. The present invention adds lignin in the carbonization process, so that the preparation process of the mesophase asphalt is simplified, and the raw materials used are cheap and easy to obtain, and the production cost is low. Finally, the yield and residual carbon value of the mesophase asphalt can be effectively improved, and the microcrystalline structure and spinning performance of the mesophase asphalt can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of intermediate asphalt, and specifically, mainly relates to a preparation method of spinnable intermediate phase asphalt and application thereof. Background Art

[0002] Mesophase asphalt is a nematic liquid crystal material with an anisotropic structure formed by the thermal polycondensation of coal tar, heavy oil, naphthalene or other aromatic compounds. It is recognized as an excellent matrix for high-performance asphalt-based carbon fibers. The structural composition, anisotropic structure content and spinning performance of mesophase asphalt are key factors that determine the performance of carbon fibers. In recent years, based on the research on the preparation of mesophase by traditional direct thermal polycondensation, preparation processes such as catalytic modification, hydrogenation modification, alkylation modification, co-carbonization and cross-linking modification have been developed, all of which have improved the quality of mesophase asphalt to a certain extent.

[0003] The raw materials and preparation process of mesophase asphalt are the key factors affecting the molecular structure and spinning performance of mesophase asphalt. In the preparation method of petroleum-based mesophase asphalt, adding different modifiers to the raw materials is an effective method to make up for the defects of the raw materials and optimize the preparation process. Song Huaihe et al. co-carbonized the catalytic cracking aromatic-rich fraction oil with coal tar, so that part of the alkyl side chains in the aromatic-rich oil were transferred to the coal tar asphalt molecules, realizing the hydrogenation and alkylation modification of coal tar asphalt, and improving the optical structure and microcrystalline structure of the final product mesophase asphalt; Cha Qingfang et al. co-carbonized catalytic cracking clarified oil and residual oil, and Cheng Xianglin et al. co-carbonized ethylene tar and waste polystyrene, all of which improved the quality of mesophase asphalt to a certain extent; in addition, for raw materials with a high degree of condensation, adding a hydrogen donor for carbonization can also optimize the structural properties of the mesophase product. Many studies have shown that for raw materials with different structural compositions, adding appropriate additives can play a role in adjusting the structural properties of the carbonized product.

[0004] For vacuum distillate, during the heat treatment process, the system will undergo free radical reaction. Since the heat treatment temperature reaches above 380°C, the vacuum distillate oil will crack, and a polycondensation reaction will occur after cracking. At such a high temperature, the free radical reaction is more intense, causing the system to quickly condense to form macromolecular compounds, and finally form a mesophase microcrystalline structure with poor molecular orientation. Therefore, the above-mentioned existing process methods will have the above-mentioned technical problems, and the petroleum-based mesophase asphalt finally prepared has problems such as low yield, many microcrystalline structure defects, and poor spinning performance, which seriously hinders the research and development of high-performance asphalt-based carbon fibers. Summary of the invention

[0005] In order to solve the technical problems in the prior art such as low yield of petroleum-based mesophase pitch, many microcrystalline structure defects, poor spinning performance, etc., the present invention provides a method for preparing spinnable mesophase pitch.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] Through the vacuum distillation process, the fraction with a boiling point below 530°C in the FCC oil slurry is cut as raw material, lignin is added, and a two-stage carbonization process is carried out. Among them, the heat treatment temperature of the first stage of the carbonization process is lower than 380°C, and finally a spinnable mesophase pitch is obtained.

[0008] Furthermore, the fraction with a boiling point below 530°C in the FCC oil slurry is used as a raw material, lignin is added, and the reaction is carried out at a temperature of 340-380°C and normal pressure for 1-6 hours; then the temperature is raised to 400-450°C, the autogenerated pressure is increased to 1-10 MPa, and carbonization is carried out at constant temperature and pressure for 1-14 hours to obtain a spinnable mesophase asphalt.

[0009] Preferably, the mass ratio of the lignin to the fraction with a boiling point below 530° C. in the FCC slurry oil is 0.01 to 0.3:1.

[0010] Specifically, the lignin is derived from coniferous trees or broadleaved trees, and the FCC slurry oil is derived from naphthenic crude oil or intermediate base crude oil.

[0011] The present invention also provides a spinnable mesophase pitch obtained by the above preparation method. The prepared spinnable mesophase pitch has an anisotropic structure content of 98-99%, a softening point of 228-253°C, a residual carbon value of 85-93wt.%, and an orientation degree of mesophase microcrystalline molecules of 0.94-0.98.

[0012] Furthermore, the spinnable mesophase asphalt prepared by the preparation method provided by the present invention can be used to prepare asphalt-based carbon fibers.

[0013] The fraction with a boiling point below 530°C cut from FCC oil slurry by vacuum distillation is rich in polycyclic aromatic hydrocarbons and contains a small amount of alkyl side chains. Generally, cracking and condensation reactions can occur above 380°C to prepare mesophase asphalt. Since the heat treatment temperature reaches above 380°C, the vacuum distillate oil will crack, and condensation reactions will occur simultaneously after cracking. At such a high temperature, the free radical reaction is more intense, causing the system to quickly condense to form macromolecular compounds, and finally forming a mesophase microcrystalline structure with poor molecular orientation.

[0014] In view of the above technical problems, the preparation method provided by the present invention uses lignin as an additive and finally prepares high-quality mesophase asphalt through a two-stage carbonization process. Specifically:

[0015] Lignin is an aromatic polymer compound with a spatial network structure, and the structural units are connected by ether bonds and CC bonds, wherein the alkyl ether bonds can be broken at 220°C, and the ether bond breaking is accompanied by the dehydration of the alkyl chain. When the temperature reaches above 335°C, the methoxy groups in the lignin begin to fall off, and the aromatic rings begin to undergo condensation reactions, and a mesophase structure can be formed under certain conditions. After lignin is added to the entire reaction system of the present invention, when the heat treatment temperature reaches above 335°C, the lignin begins to undergo cracking and condensation reactions, and as the condensation reaction deepens, a mesophase structure will gradually be formed. The mesophase structure formed by the condensation of lignin can be used as an initial core to induce the isotropic structure in the system to be converted into an anisotropic structure, and to a certain extent reduce the activation energy of the pyrolysis reaction of the vacuum distillate oil, so that the vacuum distillate oil undergoes a thermal polycondensation reaction at a relatively low temperature. When the system temperature is low, the thermal polycondensation reaction of the vacuum distillate oil is relatively mild, the active free radicals in the system are fully combined, the volatilization of light components is reduced, and the yield of the carbonization product is increased; in addition, the lower reaction temperature is conducive to the full arrangement and combination of the molecular aromatic sheets formed by condensation in the system, thereby forming an intermediate phase structure with larger crystal characteristic size, fewer lattice defects and higher molecular orientation, which is manifested macroscopically as high anisotropic structure content and large flow domain structure size under polarized light.

[0016] Although the temperature of the second stage carbonization exceeds 400°C, the core structure molecules formed by the lignin in the first stage carbonization can induce the cracking of the distillate oil, which greatly alleviates the free radical reaction in the carbonization process of this stage, making the actual reaction temperature relatively low, which is conducive to the arrangement and combination of molecular aromatic sheets formed by the condensation of the system, further reducing lattice defects, and obtaining a mesophase structure with a high molecular orientation. Therefore, the present invention can obtain an interphase asphalt product with high anisotropic structure content, high yield, high residual carbon value, orderly microcrystalline structure, and good spinning performance by adding lignin to the FCC oil slurry vacuum distillate and then undergoing two-stage low-temperature thermal polycondensation processes.

[0017] The present invention adds lignin in the carbonization process, simplifies the preparation process of mesophase asphalt, and the raw materials used are cheap and easily available, and the production cost is low. Ultimately, the yield and residual carbon value of the mesophase asphalt can be effectively improved, and the microcrystalline structure and spinning performance of the mesophase asphalt can be improved. DETAILED DESCRIPTION

[0018] The present invention discloses a method for preparing a spinnable mesophase pitch and its application. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve the same. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art, and they are all considered to be included in the present invention. The method and application of the present invention have been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the method and application described herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0019] In order to enable those skilled in the art to better understand the present invention, the present invention is further described in detail below in conjunction with specific implementation methods.

[0020] Example 1

[0021] 160 g of vacuum distillate oil with a boiling point of less than 530° C. of cycloalkyl FCC oil slurry and 1.6 g of broad-leaved wood lignin are mixed evenly and placed in a stainless steel high-pressure reactor; nitrogen is introduced to evacuate the air in the reactor, the temperature in the reactor is raised to 80° C., stirring is started, the reaction temperature reaches 360° C., and the reaction is carried out at constant temperature and pressure for 2 hours. The temperature is then raised to 450° C., the pressure in the reactor is autogenously compressed to 4 MPa, and carbonization is carried out at constant temperature and pressure for 4 hours to obtain an intermediate phase pitch with an anisotropic structure content of 99%, a softening point of 253° C., and a residual carbon value of 90 wt.%. The yield is 67%, the orientation degree of the intermediate phase microcrystalline molecular arrangement is 0.94, and the spinnability is good.

[0022] Example 2

[0023] 160g of vacuum distillate oil with a boiling point below 530°C of intermediate base FCC oil slurry and 3.2g of broad-leaved wood lignin are mixed evenly and placed in a stainless steel high-pressure reactor; nitrogen is introduced to evacuate the air in the reactor, the temperature in the reactor is raised to 80°C and stirring is started, the reaction temperature reaches 345°C, and the reaction is carried out at constant temperature and normal pressure for 6 hours, then the temperature is raised to 400°C, the pressure in the reactor is autogenously compressed to 1MPa, and carbonization is carried out at constant temperature and pressure for 14 hours to obtain an intermediate phase pitch with an anisotropic structure content of 98%, a softening point of 228°C, and a residual carbon value of 85wt.%, with a yield of 75%, an orientation degree of intermediate phase microcrystalline molecular arrangement of 0.95, and good spinnability.

[0024] Example 3

[0025] 160 g of vacuum distillate oil with a boiling point of less than 530° C. of cycloalkyl FCC oil slurry and 1.6 g of coniferous wood are mixed evenly and placed in a stainless steel high-pressure reactor; nitrogen is introduced to evacuate the air in the reactor, the temperature in the reactor is raised to 80° C., stirring is started, the reaction temperature reaches 355° C., and the reaction is carried out at a constant temperature and pressure for 1 hour. The temperature is then raised to 438° C., the pressure in the reactor is autogenously compressed to 5 MPa, and carbonization is carried out at a constant temperature and pressure for 8 hours to obtain an intermediate phase pitch with an anisotropic structure content of 99%, a softening point of 231° C., and a residual carbon value of 93wt.%. The yield is 72%, the orientation degree of the intermediate phase microcrystalline molecular arrangement is 0.98, and the spinnability is good.

[0026] Example 4

[0027] 160 g of vacuum distillate oil with a boiling point of less than 530° C. of cycloalkyl FCC oil slurry and 48 g of coniferous wood are mixed evenly and placed in a stainless steel high-pressure reactor; nitrogen is introduced to evacuate the air in the reactor, the temperature in the reactor is raised to 80° C., stirring is started, the reaction temperature reaches 365° C., and the reaction is carried out at constant temperature and pressure for 2 hours. The temperature is then raised to 430° C., the pressure in the reactor is autogenously compressed to 10 MPa, and carbonization is carried out at constant temperature and pressure for 9 hours to obtain an intermediate phase pitch with an anisotropic structure content of 98%, a softening point of 236° C., and a residual carbon value of 92 wt.%. The yield is 69%, the orientation degree of the intermediate phase microcrystalline molecular arrangement is 0.96, and the spinnability is good.

[0028] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a spinnable mesophase pitch, characterized in that: The fraction with a boiling point below 530°C in FCC oil slurry is used as raw material, lignin is added, and a two-stage carbonization process is carried out; the reaction is carried out at a temperature of 340-380°C and normal pressure for 1-6 hours; then the temperature is raised to 400-450°C, the autogenerated pressure is increased to 1-10MPa, and carbonization is carried out at constant temperature and pressure for 1-14 hours to obtain a spinnable mesophase pitch.

2. The preparation method according to claim 1, characterized in that: The mass ratio of the lignin to the fraction with a boiling point below 530° C. in the FCC oil slurry is 0.01 to 0.3:

1.

3. The preparation method according to claim 1, characterized in that: The lignin is derived from coniferous trees or broadleaved trees, and the FCC slurry oil is derived from naphthenic crude oil or intermediate base crude oil.

4. A spinnable mesophase pitch, characterized in that: The method is as described in any one of claims 1 to 3.

5. The spinnable mesophase pitch according to claim 4, characterized in that: The mesophase asphalt has an anisotropic structure content of 98-99%, a softening point of 228-253° C., a residual carbon value of 85-93wt.%, and an orientation degree of mesophase microcrystalline molecules of 0.94-0.

98.

6. Use of the spinnable mesophase pitch according to any one of claims 4 to 5 in the preparation of pitch-based carbon fibers.