Preparation method of high-purity spinnable mesophase pitch

Abstract

The invention provides a preparation method of high-purity spinnable mesophase pitch, which can provide a high-quality precursor for preparation of high-modulus pitch-based carbon fibers. The method comprises the following steps: putting fraction with a boiling point lower than 520 DEG C in catalytic cracking slurry oil into a special high-pressure reaction kettle with a plurality of auxiliary rods on the inner side of a kettle cover, reacting for 1-25 hours under the conditions that the temperature is 390-460 DEG C, the constant pressure is 0.01-10 Mpa and the stirring rotating speed is 1-600 r / min, cooling to room temperature after the reaction is finished, and obtaining high-purity mesophase pitch on a stirring shaft, a thermowell and the auxiliary rods in the kettle. The method has the advantages that the preparation process is simple, and the prepared mesophase pitch is high in anisotropic structure content (greater than 99%) and excellent in spinning performance.

Description

Technical Field

[0001] The invention relates to a method for preparing high-purity spinnable mesophase pitch, and relates to the fields of high-performance carbon fiber preparation and high-value utilization of petroleum processing by-products. Background Art

[0002] Mesophase pitch is a liquid crystal substance composed of a variety of flat disc-shaped polycyclic aromatic hydrocarbons with a relative molecular mass of 370 to 2000. It has both liquid form and crystal optical anisotropy. In recent years, based on the research on the preparation of mesophase by traditional direct thermal polycondensation, catalytic modification, hydrogenation modification, alkylation modification, co-carbonization, cross-linking modification, as well as thermal precipitation and thermal filtration processes have been developed, all of which have improved the quality of mesophase pitch to a certain extent. However, the mesophase pitch prepared by the existing process still has problems such as low purity and poor spinning performance, which seriously hinders the research and development of high-performance pitch-based carbon fibers.

[0003] From a mechanical point of view, as a liquid crystal, the mesophase pitch belongs to a non-Newtonian fluid, which is composed of isotropic pitch and anisotropic pitch. The climbing rod effect is a typical characteristic of non-Newtonian fluids. The climbing rod phenomenon was first demonstrated by Weissenberg in an interesting experiment at the Imperial College London in 1944. In the experiment, when the experimental rod was rotated in a beaker filled with viscoelastic fluid, the fluid showed the phenomenon of climbing upward along the stirring axis. This characteristic of non-Newtonian fluids is due to the non-linear relationship between its shear stress and shear strain rate, which enables the fluid to be stretched and oriented along the stirring axis and wrapped around the axis when stirred, thus producing a climbing rod effect. Non-Newtonian fluid mesophase asphalt also has a climbing rod effect in the liquid state. Utilizing this characteristic, the present invention designs a high-pressure reactor with multiple auxiliary rods on the inner side of the reactor cover for preparing high-purity mesophase asphalt, that is, during the reaction stirring process, the anisotropic asphalt in the generated mesophase asphalt climbs upward along the stirring shaft, thermocouple sleeve and auxiliary rods to separate the anisotropic asphalt from the isotropic asphalt, thereby obtaining an mesophase asphalt product with a high anisotropic structure content. Summary of the invention

[0004] In order to solve the problems of low purity, poor spinning performance, and complex process of petroleum-based mesophase asphalt in the prior art, the present invention provides a method for preparing high-purity spinnable mesophase asphalt. The raw material of the present invention is selected from the fraction with a boiling point lower than 520°C in the catalytic cracking oil slurry, and the reactor is a special high-pressure reactor with multiple auxiliary rods on the inner side of the reactor cover. The climbing rod effect of non-Newtonian fluid is used to prepare high-purity spinnable mesophase asphalt under certain process conditions. This method has a simple production process, and the prepared mesophase asphalt has a high anisotropic structure content and excellent spinning performance. It is a high-quality precursor for producing high-modulus asphalt-based carbon fibers.

[0005] The method for preparing a high-purity spinnable mesophase pitch of the present invention comprises the following steps: (1) placing a fraction with a boiling point lower than 520°C in a catalytic cracking oil slurry in a special high-pressure reactor with a plurality of auxiliary rods on the inner side of the reactor cover for thermal polycondensation reaction; (2) reacting the raw materials for 1 to 25 hours at a temperature of 390 to 460°C, a constant pressure of 0.01 to 10 MPa, and a stirring speed of 1 to 600 r / min; (3) cooling to room temperature after the thermal polycondensation reaction is completed, and obtaining a high-purity mesophase pitch on the stirring shaft, thermocouple sleeve and auxiliary rods in the reactor.

[0006] In the step (1), the inner side of the lid of the specially made high-pressure reactor is provided with 1 to 200 auxiliary rods.

[0007] In the step (3), the cooling process includes slow cooling, natural cooling and rapid cooling.

[0008] The present invention also provides a spinnable mesophase pitch, which is prepared by the above method. The anisotropic structure content of the prepared spinnable mesophase pitch is greater than 99%.

[0009] Catalytic cracking oil slurry and its fractions with a boiling point below 520°C are mixtures of complex aromatic structures. Existing methods such as direct thermal polycondensation, catalytic modification, hydrogenation modification, thermal sedimentation, and hot filtration cannot achieve high purity (anisotropic structure content > 99). Some process routes are complex and have high requirements on equipment performance, resulting in high production costs.

[0010] In view of the above technical problems, the preparation method provided by the present invention uses the fraction with a boiling point lower than 520°C in the catalytic cracking oil slurry as a raw material, places it in a special high-pressure reactor with a plurality of auxiliary rods on the inner side of the reactor cover, and performs a thermal polycondensation reaction at a certain temperature, pressure, and stirring speed. As the reaction degree deepens, anisotropic structures are formed and gradually increase in the system, and a mixture of isotropic asphalt and anisotropic asphalt is formed in the reactor. This mixed fluid is a non-Newtonian fluid and has the characteristic of non-Newtonian fluid - climbing rod phenomenon. As the stirring shaft is stirred, the anisotropic asphalt formed in the system will climb upward along the stirring shaft, thermocouple sleeve and auxiliary rod, and finally the anisotropic asphalt is enriched on the stirring shaft, thermocouple sleeve and auxiliary rod. When the reaction stops and the reaction temperature drops to room temperature, the product in the system solidifies, and the isotropic asphalt solidifies and adheres to the stirring shaft, thermocouple sleeve and auxiliary rod, thereby obtaining a high-purity intermediate phase asphalt with an anisotropic structure content exceeding 99%.

[0011] Compared with the prior art, the method of the present invention has the following advantages:

[0012] 1. The petroleum-based mesophase asphalt prepared by the present invention has an anisotropic structure content of >99% and excellent spinning performance.

[0013] 2. The process flow of the present invention is simple, the requirements on equipment performance are low, and the cost is saved. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 for Figure 2 AA section view, Figure 2 This is a longitudinal cross-sectional view of the key structure of the special reactor.

[0015] Figure 1 and 2 Middle: 1-stirring blade, 2-stirring shaft, 3-thermocouple sleeve, 4-auxiliary rod (6 pieces), 5-kettle body, 6-kettle cover, 7-fixing nut (6 pieces), 8-bolt hole (6 pieces), 9-magnetic coupling stirring head, 10-pipeline inlet and outlet.

[0016] There are 6 auxiliary rods in this figure, which are included in the scope of claim 2. DETAILED DESCRIPTION

[0017] The following is a further description of the method provided by the present invention for preparing mesophase pitch in a special high-pressure reactor using the fraction with a boiling point below 520° C. in catalytic cracking slurry as raw material in conjunction with the examples.

[0018] Embodiment 1:

[0019] 160g of distillate oil with a boiling point below 520°C in catalytic cracking oil slurry is placed in a special high-pressure reactor body 5, covered with a reactor cover 6, and a nut 7 is tightened above the bolt hole 8 to seal the reactor well. High-purity nitrogen is introduced through the pipeline inlet and outlet 10 to evacuate the air in the reactor, and the initial nitrogen pressure is set to 0.01MPa; then, when the temperature in the reactor is raised to 80°C, stirring is started through the magnetic coupling stirring head 9, and the speed is adjusted to 300r / min. After reacting for 16 hours at a reaction temperature of 410°C and a pressure of 0.01MPa, the reaction is stopped and the temperature is naturally cooled to room temperature. On the stirring shaft 2, the thermocouple sleeve 3 and the auxiliary rod 4, a mesophase pitch with an anisotropic structure content of 99.5% and a softening point of 235°C is obtained, and the spinning performance is excellent.

[0020] Embodiment 2:

[0021] 160g of distillate oil with a boiling point below 520℃ in catalytic cracking oil slurry is placed in a special high-pressure reactor body 5, covered with a reactor cover 6, and nuts 7 are tightened above bolt holes 8 to seal the reactor well. High-purity nitrogen is introduced through the pipeline inlet and outlet 10 to evacuate the air in the reactor, and the initial nitrogen pressure is set to 3MPa; then, when the temperature in the reactor is raised to 80℃, stirring is started through the magnetic coupling stirring head 9, and the speed is adjusted to 300r / min. After reacting for 9 hours at a reaction temperature of 430℃ and a pressure of 3MPa, the reaction is stopped and the temperature is naturally cooled to room temperature. On the stirring shaft 2, the thermocouple sleeve 3 and the auxiliary rod 4, a mesophase pitch with an anisotropic structure content of 100% and a softening point of 252℃ is obtained, and the spinning performance is excellent.

[0022] Embodiment 3:

[0023] 160g of distillate oil with a boiling point below 520℃ in catalytic cracking oil slurry is placed in a special high-pressure reactor body 5, covered with a reactor cover 6, and nuts 7 are tightened above bolt holes 8 to seal the reactor well. High-purity nitrogen is introduced through the pipeline inlet and outlet 10 to evacuate the air in the reactor, and the initial nitrogen pressure is set to 4MPa; then, when the temperature in the reactor is raised to 80℃, stirring is started through the magnetic coupling stirring head 9, and the speed is adjusted to 500r / min. After reacting for 3.5h at a reaction temperature of 460℃ and a pressure of 4MPa, the reaction is stopped, and the temperature is rapidly cooled to room temperature with cold water. On the stirring shaft 2, the thermocouple sleeve 3 and the auxiliary rod 4, a mesophase pitch with an anisotropic structure content of 99.1% and a softening point of 287℃ is obtained, and the spinning performance is excellent.

Claims

1. A method for preparing high-purity spinnable mesophase pitch, characterized in that The following steps are involved: (1) The fraction with a boiling point below 520°C in the catalytic cracking oil slurry is placed in a special high-pressure reactor with multiple auxiliary rods on the inner side of the reactor cover for thermal polycondensation reaction; (2) The raw materials are reacted for 1 to 25 hours under the conditions of a temperature of 390 to 460°C, a constant pressure of 0.01 to 10 MPa, and a stirring speed of 1 to 600 r / min; (3) After the thermal polycondensation reaction is completed, it is cooled to room temperature, and a high-purity mesophase asphalt is obtained on the stirring shaft, thermocouple sleeve and auxiliary rods in the reactor.

2. The method for preparing mesophase asphalt according to claim 1, characterized in that: In the step (1), the inner side of the lid of the specially made high-pressure reactor is provided with 1 to 200 auxiliary rods.

3. The method for preparing mesophase asphalt according to claim 1, characterized in that: In the step (3), the cooling process includes slow cooling, natural cooling and rapid cooling.

4. The high-purity spinnable mesophase pitch according to claim 1, characterized in that: The anisotropic structure content is high (>99%) and the spinning performance is excellent, and it can be used to prepare high modulus asphalt-based carbon fibers.

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