Mesophase pitch and preparation method thereof

Abstract

The preparation method comprises the following steps: S1, heating coal pitch powder with the softening point of 50-120 DEG C, introducing gas into the coal pitch after the coal pitch powder is softened, stirring at the same time, and keeping for 4-24 hours to obtain a pitch intermediate product; and S2, putting the asphalt intermediate product into a reaction kettle, carrying out high-temperature polymerization reaction at normal pressure, and stirring in the reaction process to obtain the mesophase asphalt with the softening point of 150-280 DEG C after the reaction is finished. According to the method, light components in the coal pitch are taken away from a reaction system by utilizing gas, so that the group components of the pitch are effectively adjusted, the distribution of the group components is more uniform, the reaction activity of a coal pitch intermediate product is improved, and the softening point-adjustable mesophase pitch is obtained through subsequent high-temperature polymerization reaction.

Description

Technical Field

[0001] The invention belongs to the technical field of mesophase asphalt and relates to a mesophase asphalt and a preparation method thereof. Background Art

[0002] Mesophase pitch is a liquid crystal flat macromolecular substance with an anisotropic structure, which is polymerized from petroleum-based asphalt, coal tar, heavy aromatics, etc. Its molecular weight is 400-4000, and its softening point is usually above 160°C. It is an excellent precursor for the preparation of high-performance carbon materials such as carbon fiber, foam carbon, C / C composite materials, high thermal conductivity carbon, and carbon electrodes.

[0003] Currently, the main methods for preparing mesophase pitch include thermal polycondensation, component optimization, hydrogenation modification, co-carbonization, catalytic polycondensation, pressure polymerization, toluene-insoluble polymerization, and combinations of these methods. For example, Chinese Patent Publication No. CN115851300A discloses a method for preparing mesophase pitch by adding lignin to FCC oil via co-carbonization. This method uses a fraction of FCC oil with a boiling point below 530°C as raw material, adds lignin, and undergoes a two-stage carbonization process. The first stage of the carbonization process is heat-treated at a temperature below 380°C, ultimately yielding a spinnable mesophase pitch. However, incomplete decomposition of the lignin may affect product quality, and the high reaction pressure during the second stage of heat treatment places high demands on the equipment's pressure resistance. Chinese patent application number CN202211556198.2 discloses a method for preparing intermediate phase asphalt using graphene-modified asphalt, wherein a dispersant with a molecular structure similar to that of matrix asphalt and graphene are mixed to obtain modified graphene with dispersant molecules adsorbed on the surface; the modified graphene and matrix asphalt are placed in a vacuum mixer, and the temperature is raised to the mixture until the mixture is in a semi-solid state and then stirred and mixed. The modified graphene is evenly dispersed in the liquid matrix asphalt through the dispersant molecules adsorbed on its surface, thereby obtaining matrix asphalt mixed with modified graphene; the matrix asphalt mixed with modified graphene is transferred to a reactor, the temperature and pressure are raised to preset values ​​and kept at this temperature and pressure for a predetermined time, thereby obtaining graphene-modified intermediate phase asphalt; however, in this technology, the addition of graphene will increase the manufacturing cost of the intermediate phase asphalt. Chinese patent application number CN202211133075.8 discloses a method for preparing mesophase asphalt by catalytic polycondensation by adding Lewis acid to medium-temperature coal tar pitch. The method comprises the following steps: first, drying the raw asphalt and Lewis acid to achieve an anhydrous state; weighing the Lewis acid and the raw asphalt in a certain mass ratio, mixing them uniformly, and loading them into a reactor. The entire operation is carried out under a dry inert atmosphere; adding a certain amount of a co-catalyst to the reactor under an inert environment; sealing the reactor, heating it, and conducting a thermal polycondensation reaction; after the reaction is completed, allowing it to stand to room temperature, taking out the product, grinding it into powder, and washing it with hydrochloric acid and sodium hydroxide to obtain the mesophase asphalt; however, the yield of the mesophase asphalt of this technology is low, less than 30%, and the softening point is difficult to control.

[0004] The raw materials used to prepare mesophase pitch include petroleum-based pitch, coal-based pitch, or aromatic hydrocarbons (pure aromatic hydrocarbons and their mixtures). Aromatic hydrocarbons have a narrow molecular weight distribution and low impurity content, making them extremely high-quality mesophase pitches. However, these materials are expensive, have low reactivity, and are therefore sold at a very high price. Petroleum-based pitch molecules contain a high number of alkanes, making them highly reactive but less likely to undergo aromatization, leading to their conversion to mesophase pitch. Compared to the aforementioned two, coal-based pitch has a higher degree of polymerization and is more easily converted into mesophase pitch with a planar aromatic macromolecular structure. However, its group composition significantly influences the reactivity of the pitch. In industrial production, the group composition of coal-based pitch is generally classified into toluene-soluble components (molecular weight 210-1000), quinoline-soluble components (molecular weight 1000-1800), and quinoline-insoluble components (molecular weight 1800-2600). The lower molecular weight components primarily impart good fluidity to the pitch, but exhibit lower reactivity; the higher molecular weight components exhibit poorer fluidity but higher reactivity.

[0005] In order to improve the reactivity of coal tar pitch, relevant researchers often use catalytic thermal polymerization, pressure polymerization, and co-carbonization to prepare mesophase pitch. However, the catalytic thermal polymerization method requires the addition of catalysts such as aluminum chloride and hydrofluoric acid to the pitch. These catalysts are difficult to separate from the product, increasing production costs and seriously reducing the performance of the prepared carbon material. The pressure polymerization method requires the reaction equipment to have extremely strong pressure resistance, which results in high equipment costs. The co-carbonization method requires the addition of additives such as graphene and carbon black to the pitch. These additives can reduce the activation energy required for the reaction, but they also face the problems of high production costs and difficulty in separating impurities.

[0006] In view of the above situation, it is urgent to study a method for preparing mesophase asphalt using coal tar pitch, which can adjust the group composition ratio of the asphalt, improve the activity of the coal tar pitch, make the group composition distribution of the asphalt more uniform, and obtain an mesophase asphalt with an adjustable softening point. Summary of the Invention

[0007] In view of the above-mentioned defects in the prior art, the purpose of the present invention is to provide an intermediate phase asphalt and a preparation method thereof, which utilizes gas to remove the light components in coal tar pitch from the reaction system, thereby effectively adjusting the group components of the asphalt, making its distribution more uniform, improving the reaction activity of the coal tar pitch intermediate, and obtaining an intermediate phase asphalt with an adjustable softening point through a subsequent high-temperature polymerization reaction.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] The first aspect of the present invention provides a mesophase pitch and a preparation method thereof, comprising the following steps:

[0010] S1, heating coal tar pitch powder with a softening point of 50-120°C, and introducing gas into the coal tar pitch after softening while stirring for 4-24 hours to obtain an intermediate asphalt product;

[0011] S2, placing the asphalt intermediate in a reactor under normal pressure for high-temperature polymerization reaction, stirring during the reaction process, and obtaining a mesophase asphalt with a softening point of 150-280°C after the reaction is completed.

[0012] Preferably, in step S1, the content of quinoline insoluble matter in the coal tar pitch is 1-6%.

[0013] Preferably, in step S1, the heating temperature is 200-300°C.

[0014] Preferably, in step S1, the gas is selected from one of air, nitrogen or rare gas, and the gas flow rate is 0.03-3 Nm 3 / h.

[0015] Preferably, in step S1, the rotation speed of the stirring paddle used during the stirring is 140-300 RPM.

[0016] Preferably, in step S1, the softening point of the asphalt intermediate is 2 to 40° C. higher than that of the coal tar pitch, and the quinoline insoluble matter content of the asphalt intermediate is consistent with that of the coal tar pitch.

[0017] Preferably, in step S1, the softening point of the asphalt intermediate is 90-120° C., and the content of quinoline insoluble matter is 1-6%.

[0018] Preferably, in step S2:

[0019] The high temperature polymerization reaction temperature is 380-410° C., and the reaction time is 4-24 hours; and / or

[0020] The stirring blade used during the stirring is rotated at a speed of 140 to 300 RPM; and / or

[0021] During the high-temperature polymerization reaction, the rate of increase of the softening point is 3 to 15° C. / h.

[0022] Preferably, in step S2, the mesophase content of the mesophase asphalt is 45-90%.

[0023] The second aspect of the present invention provides a mesophase pitch prepared according to the method for preparing mesophase pitch according to the first aspect of the present invention.

[0024] The mesophase pitch and its preparation method provided by the present invention have the following beneficial effects:

[0025] 1. The present invention uses coal tar pitch as raw material and adjusts its group composition to obtain a pitch intermediate with moderate reactivity and more uniform group composition distribution. After high-temperature polymerization, this pitch intermediate can obtain high-quality mesophase pitch with different softening points and different anisotropic component contents.

[0026] 2. The present invention introduces gas into the coal tar pitch with low viscosity at a relatively low temperature. Small gas bubbles can remove light components in the coal tar pitch from the reaction system. This not only effectively removes components with low reactivity in the coal tar pitch and increases the softening point, but also makes the components of the entire system uniform and stable, and the reactivity of the asphalt intermediate is moderate. By controlling the reactivity of the asphalt intermediate, the softening point increase rate and final softening point of the asphalt in the subsequent high-temperature polymerization reaction can be controlled, thereby facilitating the preparation of an intermediate phase asphalt with a controllable softening point.

[0027] 3. The present invention adopts a purely physical method to effectively adjust the group components of coal tar pitch, making its distribution more uniform. The reaction activity can be controlled under normal pressure, that is, the rate of increase of the asphalt softening point in the high-temperature polymerization reaction is controllable, which is suitable for large-scale industrial production and low cost. DETAILED DESCRIPTION

[0028] In order to better understand the above technical solution of the present invention, the technical solution of the present invention is further described below with reference to embodiments.

[0029] Asphalt contains a variety of molecules with varying molecular weights. These molecules can generally be divided into toluene-soluble, quinoline-soluble, and quinoline-insoluble components, depending on their molecular weight range. Components with smaller molecular weights have lower reactivity, and some even do not participate in thermal polycondensation and decomposition reactions, escaping the reaction system as gases at high temperatures, which reduces the thermal reactivity of the asphalt to a certain extent. These smaller molecular weight components primarily enhance the fluidity of the liquid asphalt and separate more reactive molecules. Components with larger molecular weights, on the other hand, are relatively more reactive. During high-temperature polymerization reactions, they can further aggregate to form larger molecules, ultimately forming an intermediate phase. The present invention introduces gas into liquid coal tar with low viscosity at a relatively low temperature. During the process of gas entering and exiting the coal tar, small gas bubbles can bring some small molecular components out of the asphalt reaction system. This not only effectively removes components with low reactivity in the coal tar, but also increases the proportion of components with larger molecular weight in the asphalt to a certain extent, thereby increasing the probability of these large molecules colliding with each other and reacting. The specific realization phenomenon is that the reactivity of the asphalt intermediate (i.e., the rate of increase of the softening point) is effectively improved; based on this, the present invention controls the increase in the proportion of large molecular components in the asphalt by changing the gas flow rate, blowing time, blowing temperature, etc., thereby realizing the control of the reactivity of the asphalt intermediate, which is conducive to the preparation of an intermediate phase asphalt with a controllable softening point.

[0030] A method for preparing mesophase pitch of the present invention comprises the following steps:

[0031] S1, heating coal tar pitch powder with a softening point of 50-120°C, and introducing gas into the coal tar pitch after softening while stirring for 4-24 hours to obtain an intermediate asphalt product;

[0032] Specifically, coal tar powder with a softening point of 50-120°C is heated to 200-300°C, and after it is fully softened, a gas is introduced into it, wherein the gas is selected from one of air, nitrogen or rare gas, and the gas flow rate is 0.03-3Nm 3 / h, while stirring to ensure that the asphalt is kept in a stirred state when the gas is introduced. The stirring speed of the stirring paddle is 140-300 RPM, and the stirring is maintained for 4-24 hours to finally obtain the asphalt intermediate. The quinoline-insoluble content of the coal tar pitch powder is 1-6%.

[0033] The properties of the asphalt intermediate are measured to ensure that the softening point of the intermediate is 2-40°C higher than that of coal tar pitch, and that the quinoline-insoluble content of the intermediate is not significantly different from that of the coal tar pitch. Preferably, the quinoline-insoluble content of the intermediate is consistent with that of the coal tar pitch. In a specific embodiment, the intermediate has a softening point of 90-150°C and a quinoline-insoluble content of 1-6%.

[0034] In step S1, the present invention adopts a purely physical method to change the gas flow rate (0.03~3Nm 3 / h), blowing time (4 to 24h), blowing temperature (200 to 300℃), stirring speed (140 to 300RPM), etc. are used to control the increase in the proportion of large molecular components in the asphalt, thereby effectively adjusting the group components of the asphalt to make its distribution more uniform, realizing the control of the reaction activity of the asphalt intermediate, and facilitating the subsequent high-temperature polymerization reaction under normal pressure.

[0035] S2, placing the asphalt intermediate in a reactor under normal pressure for high-temperature polymerization reaction, stirring during the reaction process, and obtaining a mesophase asphalt with a softening point of 150-280°C after the reaction is completed.

[0036] Specifically, an asphalt intermediate product meeting the performance requirements of step S1 is placed in a reactor and subjected to a high-temperature polymerization reaction at normal pressure. The temperature of the high-temperature polymerization reaction is 380-410°C, the reaction time is 4-24 hours, stirring is performed during the reaction, and the rotation speed of the stirring paddle used for stirring is 140-300RPM. After the reaction, an intermediate phase asphalt with a softening point of 150-280°C and an intermediate phase content of 45-90% is obtained. During the above-mentioned high-temperature polymerization reaction, the rate of increase of the softening point is 3-15°C / h. The rate of increase of the softening point can be adjusted by controlling the reaction temperature and the rotation speed during stirring.

[0037] The mesophase asphalt and its preparation method of the present invention are further introduced below with reference to specific examples.

[0038] Example 1

[0039] The present embodiment provides a mesophase pitch and a preparation method thereof, and the specific process is as follows:

[0040] (1) A medium-temperature coal tar pitch with a softening point of 76.5°C and a quinoline insoluble content of 1.2% was heated to 260°C and nitrogen was continuously introduced for 10 hours at a gas flow rate of 0.2 Nm 3 / h, stirring was carried out while introducing gas, and the stirring blade speed used for stirring was 200RPM, to obtain an asphalt intermediate with a softening point of 103.2°C and a quinoline insoluble matter content of 1.2%.

[0041] (2) The asphalt intermediate prepared above was subjected to a high-temperature polymerization reaction at 400°C under normal pressure for 10 hours with stirring at a paddle speed of 200 RPM to obtain a mesophase asphalt. The properties of the mesophase asphalt were as follows: a softening point of 210°C, a mesophase content of 75%, and a softening point increase rate of 10.68°C / h during the reaction.

[0042] Example 2

[0043] The present embodiment provides a mesophase pitch and a preparation method thereof, and the specific process is as follows:

[0044] (1) A medium-temperature coal tar pitch with a softening point of 85°C and a quinoline insoluble content of 1.6% was heated to 260°C and nitrogen was continuously introduced for 8 hours at a gas flow rate of 0.2 Nm 3 / h, stirring was carried out while introducing gas, and the stirring blade speed used for stirring was 200RPM, to obtain an asphalt intermediate with a softening point of 91.1°C and a quinoline insoluble matter content of 1.6%.

[0045] (2) The asphalt intermediate prepared above was subjected to a high-temperature polymerization reaction at 390°C under normal pressure for 10 hours, with stirring at a paddle speed of 200 RPM, to obtain a mesophase asphalt. The properties of the mesophase asphalt were as follows: a softening point of 144.3°C, a mesophase content of 50%, and a softening point increase rate of 5.32°C / h during the reaction.

[0046] Example 3

[0047] The present embodiment provides a mesophase pitch and a preparation method thereof, and the specific process is as follows:

[0048] (1) A medium-temperature coal tar pitch with a softening point of 101.6°C and a quinoline insoluble content of 2.0% was heated to 280°C and nitrogen was continuously introduced for 4 h at a gas flow rate of 1 Nm 3 / h, stirring was carried out while introducing gas, and the stirring blade speed used for stirring was 200RPM, to obtain an asphalt intermediate with a softening point of 116.8°C and a quinoline insoluble matter content of 2.0%.

[0049] (2) The asphalt intermediate prepared above was subjected to a high-temperature polymerization reaction at 385°C under normal pressure for 10 hours with stirring at a paddle speed of 200 RPM to obtain a mesophase asphalt. The properties of the mesophase asphalt were as follows: a softening point of 154.6°C, a mesophase content of 61.5%, and a softening point increase rate of 3.78°C / h during the reaction.

[0050] Example 4

[0051] The present embodiment provides a mesophase pitch and a preparation method thereof, and the specific process is as follows:

[0052] (1) A medium-temperature coal tar pitch with a softening point of 76.5°C and a quinoline insoluble content of 1.2% was heated to 260°C and nitrogen was continuously introduced for 10 hours at a gas flow rate of 0.2 Nm 3 / h, stirring was carried out while introducing gas, and the stirring blade speed used for stirring was 150RPM, to obtain an asphalt intermediate with a softening point of 98.8°C and a quinoline insoluble matter content of 1.2%.

[0053] (2) The asphalt intermediate prepared above was subjected to a high-temperature polymerization reaction at 400°C under normal pressure for 10 hours with stirring at a paddle speed of 150 RPM to obtain a mesophase asphalt. The properties of the mesophase asphalt were as follows: a softening point of 198.3°C, a mesophase content of 72.3%, and a softening point increase rate of 9.95°C / h during the reaction.

[0054] Example 5

[0055] The present embodiment provides a mesophase pitch and a preparation method thereof, and the specific process is as follows:

[0056] (1) A medium-temperature coal tar pitch with a softening point of 76.5°C and a quinoline insoluble content of 1.2% was heated to 260°C and air was continuously introduced for 10 h at a gas flow rate of 0.2 Nm 3 / h, stirring was carried out while introducing gas, and the stirring blade speed used for stirring was 200RPM, to obtain an asphalt intermediate with a softening point of 112.6°C and a quinoline insoluble matter content of 1.2%.

[0057] (2) The asphalt intermediate prepared above was subjected to a high-temperature polymerization reaction at 400°C under normal pressure for 10 hours with stirring at a paddle speed of 200 RPM to obtain a mesophase asphalt. The properties of the mesophase asphalt were as follows: a softening point of 247.1°C, a mesophase content of 88.2%, and a softening point increase rate of 13.45°C / h during the reaction.

[0058] Example 6

[0059] The present embodiment provides a mesophase pitch and a preparation method thereof, and the specific process is as follows:

[0060] (1) A medium-temperature coal tar pitch with a softening point of 50°C and a quinoline insoluble content of 1% was heated to 200°C and argon was continuously introduced for 24 hours at a gas flow rate of 0.03 Nm 3 / h, stirring was carried out while introducing gas, and the stirring blade speed used for stirring was 300RPM, to obtain an asphalt intermediate with a softening point of 75.2°C and a quinoline insoluble matter content of 1%.

[0061] (2) The asphalt intermediate prepared above was subjected to a high-temperature polymerization reaction at 380°C under normal pressure for 24 hours with stirring at a paddle speed of 300 RPM to obtain a mesophase asphalt. The properties of the mesophase asphalt were as follows: a softening point of 149.6°C, a mesophase content of 51.7%, and a softening point increase rate of 3.10°C / h during the reaction.

[0062] Example 7

[0063] The present embodiment provides a mesophase pitch and a preparation method thereof, and the specific process is as follows:

[0064] (1) A medium-temperature coal tar pitch with a softening point of 120°C and a quinoline insoluble content of 6% was heated to 300°C and argon was continuously introduced for 4 hours at a gas flow rate of 3 Nm 3 / h, stirring was carried out while introducing gas, and the stirring blade speed used for stirring was 140RPM, to obtain an asphalt intermediate with a softening point of 138.2°C and a quinoline insoluble matter content of 6%.

[0065] (2) The asphalt intermediate prepared above was subjected to a high-temperature polymerization reaction at 410°C under normal pressure for 4 hours with stirring at a paddle speed of 140 RPM to obtain a mesophase asphalt. The properties of the mesophase asphalt were as follows: a softening point of 197.1°C, a mesophase content of 65.8%, and a softening point increase rate of 14.73°C / h during the reaction.

[0066] Those skilled in the art should recognize that the above embodiments are merely intended to illustrate the present invention and are not intended to limit the present invention. As long as they are within the spirit of the present invention, any changes or modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A method for preparing mesophase asphalt, characterized in that: The following steps are involved: S1, heating coal tar pitch powder with a softening point of 50 to 120°C, introducing gas into the coal tar pitch after it softens, stirring it at the same time, and maintaining the temperature for 4 to 24 hours to obtain an asphalt intermediate; S2, placing the asphalt intermediate in a reactor under normal pressure for high temperature polymerization reaction, stirring during the reaction, and obtaining an intermediate phase asphalt with a softening point of 150 to 280° C. after the reaction.

2. The method for preparing mesophase pitch according to claim 1, characterized in that: In the step S1, the content of quinoline insoluble matter in the coal tar pitch is 1-6%.

3. The method for preparing mesophase pitch according to claim 1, characterized in that: In the step S1, the heating temperature is 200-300°C.

4. The method for preparing mesophase pitch according to claim 1, characterized in that: In step S1, the gas is selected from one of air, nitrogen or rare gas, and the gas flow rate is 0.03-3Nm 3 / h.

5. The method for preparing mesophase pitch according to claim 1, characterized in that: In the step S1, the rotation speed of the stirring paddle used during the stirring is 140-300 RPM.

6. The method for preparing mesophase pitch according to claim 1, characterized in that: In the step S1, the softening point of the asphalt intermediate is 2-40°C higher than that of the coal tar pitch, and the quinoline insoluble matter content of the asphalt intermediate is consistent with that of the coal tar pitch.

7. The method for preparing mesophase pitch according to claim 6, characterized in that: In the step S1, the softening point of the asphalt intermediate is 90-150°C, and the content of quinoline insoluble matter is 1-6%.

8. The method for preparing mesophase pitch according to claim 1, characterized in that: In step S2: The temperature of the high temperature polymerization reaction is 380-410° C., and the reaction time is 4-24 hours; and / or The stirring blade used during the stirring has a rotation speed of 140 to 300 RPM; and / or During the high temperature polymerization reaction, the rate of increase of the softening point is 3 to 15° C. / h.

9. The method for preparing mesophase pitch according to claim 1, characterized in that: In the step S2, the mesophase content of the mesophase asphalt is 45-90%.

10. A mesophase pitch prepared according to the method for preparing mesophase pitch according to any one of claims 1 to 9.