阅读说明：本技术 一种精准预测中间相沥青热分解进程的方法 (Method for accurately predicting mesophase pitch thermal decomposition process ) 是由 叶崇 吴晃 黄东 刘金水 叶高明 付灿龙 何佳 于 2021-09-30 设计创作，主要内容包括：本发明属于高性能炭材料制备技术领域,本发明公开了一种精准预测中间相沥青热分解进程的方法,首先将中间相沥青粉末样装入热分析仪通过改变恒温时间进行三组不同温度下的测试,得中间相沥青热分解失重量Δw与恒温时长t的数据,将其拟合得到幂函数Δw＝Ct～(b),对其求导,得到反应速率常数k＝bC；再根据阿伦尼乌斯方程k＝Aexp(-Ea/(RT)),求得中间相沥青的热分解反应活化能Ea和指前因子A,最后得到中间相沥青的分解反应动力学方程Δw＝exp(ln(A/b)-8.314Ea/T+blnt)。本发明可以精准预测相应中间相沥青的热分解进程,为中间相沥青基泡沫炭、中间相沥青基炭纤维及针状焦等的制备提供理论指导。(The invention belongs to the technical field of high-performance carbon material preparation, and discloses a method for accurately predicting a thermal decomposition process of mesophase pitch b The derivation is carried out to obtain a reaction rate constant k which is bC; and then, obtaining the thermal decomposition reaction activation energy Ea and the pre-pointing factor A of the mesophase pitch according to an Arrhenius equation k which is Aexp (-Ea/(RT), and finally obtaining a decomposition reaction kinetic equation delta w which is exp (ln (A/b) -8.314Ea/T + blnt) of the mesophase pitch. The invention can accurately predict the thermal decomposition process of corresponding mesophase pitch, namely mesophase pitch-based foam carbon and mesophase pitch-based carbonThe preparation of fiber, needle coke and the like provides theoretical guidance.)

1. A method for accurately predicting the thermal decomposition process of mesophase pitch is characterized by comprising the following steps:

(1) crushing the mesophase pitch to obtain a mesophase pitch powder sample;

(2) opening protective gas of a thermal analyzer, setting the flow rate to be 100 +/-1 mL/min, and carrying out peeling operation;

(3) filling the mesophase pitch powder sample obtained in the step (1) into a thermal analyzer, heating, and then carrying out constant temperature treatment for a period of time when the temperature is raised to a certain temperature;

(4) selecting three temperature points for testing, adjusting different constant temperature durations to obtain three groups of comparison data of mesophase pitch thermal decomposition weight loss delta w and constant temperature duration t at different temperatures, and fitting the three groups of data to obtain a power function delta w ═ Ct^bB is an index factor of constant temperature duration, C is three groups of data delta w corresponding to t^bThe slope of (a);

(5) converting the power function Δ w to Ct^bSimultaneously carrying out derivation on the constant temperature duration t on two sides to obtain a reaction rate constant k which is bC; according to an Arrhenius equation k, Aexp (-Ea/(RT)), logarithms are taken at two sides simultaneously to obtain lnk, lnA-Ea/(RT), lnk values of mesophase pitch thermal decomposition at three groups of different temperatures are taken as vertical coordinates, 1/T values are taken as horizontal coordinates for plotting, the slope is the value of-Ea/R, the intercept is the value of lnA, and R is a molar gas constant, so that the thermal decomposition reaction activation energy Ea and the pre-exponential factor A of the mesophase pitch can be obtained;

(6) finally, the kinetic equation Δ w of the mesophase pitch is exp (ln (a/b) -8.314Ea/T + blnt).

2. The method for accurately predicting the thermal decomposition process of mesophase pitch according to claim 1, wherein the mesophase pitch in the step (1) is one of naphthalene mesophase pitch, oil mesophase pitch and coal mesophase pitch.

3. The method for accurately predicting the thermal decomposition process of mesophase pitch according to claim 2, wherein the mesophase pitch has a mesophase content of > 95% and a softening point of > 200 ℃.

4. The method for accurately predicting the thermal decomposition process of mesophase pitch according to claim 1, wherein the particle size of the mesophase pitch powder sample in step (1) is more than 180 meshes.

5. The method for accurately predicting the thermal decomposition process of mesophase pitch according to claim 1, wherein the addition amount of the mesophase pitch powder sample in the step (3) is 25-30 mg.

6. The method for accurately predicting the thermal decomposition process of the mesophase pitch according to claim 5, wherein the temperature rise rate of the temperature rise treatment is 1-3 ℃/min, and the temperature is 300-500 ℃.

7. The method for accurately predicting the thermal decomposition process of the mesophase pitch according to claim 5, wherein the constant temperature time is 4-900 min.

8. The method for accurately predicting the thermal decomposition process of mesophase pitch according to claim 1, wherein the three temperature points selected in the step (4) are 320 ℃, 330 ℃, 340 ℃.

9. The method for accurately predicting the thermal decomposition process of mesophase pitch according to claim 1, wherein the molar gas constant R in the step (5) is 8.314J/(mol K).

Technical Field

The invention relates to the technical field of high-performance carbon material preparation, in particular to a method for accurately predicting a mesophase pitch thermal decomposition process.

Background

Mesophase pitch is an excellent precursor for manufacturing high-performance carbon materials (such as mesophase pitch-based foam carbon, mesophase pitch-based carbon fibers, needle coke, mesophase carbon microspheres, ultrahigh specific surface area activated carbon and the like), and is widely applied to the aspects of aerospace, national defense industry, advanced science and technology, daily life and the like.

The mesophase pitch is a macromolecular fused ring compound prepared from coal pitch, petroleum pitch, aromatic hydrocarbon compounds and the like through thermal polycondensation or catalytic polymerization, and the relative molecular mass is generally distributed between 370 and 2000. In the preparation process of the mesophase pitch-based foam carbon, the mesophase pitch-based carbon fiber, the needle coke and the like, the mesophase pitch is usually required to be subjected to high-temperature long-time heat treatment at the temperature of more than 300 ℃ under the protection of inert gas, and volatile matters generated by pyrolysis of small molecules or large molecules in a mesophase pitch system continuously escape. For example, the chinese patent for invention (CN105197912A) obtains a raw material of carbon nanotube/carbon foam composite material by spontaneous foaming of volatile components generated by thermal decomposition of mesophase pitch; the Chinese invention patent (CN100374367C) takes petroleum-based mesophase pitch as a raw material to prepare the foam carbon material through self-reaction foaming.

However, in the existing method for synthesizing other substances such as a foam carbon material, a composite material and the like by using the mesophase pitch, the thermal decomposition process of the mesophase pitch is not monitored, the constant temperature time of the heat treatment is too long, the production cost is high, the constant temperature time of the heat treatment is too short, and the foam formed by light components and pyrolysis components volatilized from the mesophase pitch in the heat treatment process is less, so that the preparation of the mesophase pitch-based foam carbon is not facilitated; and the heat treatment constant temperature time is too short, and light components are not completely removed, so that the melt spinning of the mesophase pitch fiber and the preparation of needle coke are not facilitated. Therefore, it is necessary to develop a method for accurately predicting the thermal decomposition process of mesophase pitch and accurately predict the duration of the constant temperature of the heat treatment.

Disclosure of Invention

In view of the above, the invention provides a method for accurately predicting a thermal decomposition process of mesophase pitch, which adopts a thermal analyzer to monitor the thermal decomposition process of mesophase pitch, and combines an arrhenius equation to obtain a thermal decomposition kinetic equation of mesophase pitch, so as to accurately predict the thermal decomposition process of mesophase pitch.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides a method for accurately predicting a mesophase pitch thermal decomposition process, which comprises the following steps:

(1) crushing the mesophase pitch to obtain a mesophase pitch powder sample;

(2) opening protective gas of a thermal analyzer, setting the flow rate to be 100 +/-1 mL/min, and carrying out peeling operation;

(3) filling the mesophase pitch powder sample obtained in the step (1) into a thermal analyzer, heating, and then carrying out constant temperature treatment for a period of time when the temperature is raised to a certain temperature;

(4) selecting three temperature points for testing, adjusting different constant temperature durations to obtain three groups of comparison data of mesophase pitch thermal decomposition weight loss delta w and constant temperature duration t at different temperatures, and fitting the three groups of data to obtain a power function delta w ═ Ct^bB is an index factor of constant temperature duration, C is three groups of data delta w corresponding to t^bThe slope of (a);

(5) converting the power function Δ w to Ct^bSimultaneously carrying out derivation on the constant temperature duration t on two sides to obtain a reaction rate constant k which is bC; according to an Arrhenius equation k, Aexp (-Ea/(RT)), logarithms are taken at two sides simultaneously to obtain lnk, lnA-Ea/(RT), lnk values of mesophase pitch thermal decomposition at three groups of different temperatures are taken as vertical coordinates, 1/T values are taken as horizontal coordinates for plotting, the slope is the value of-Ea/R, the intercept is the value of lnA, and R is a molar gas constant, so that the thermal decomposition reaction activation energy Ea and the pre-exponential factor A of the mesophase pitch can be obtained;

(6) finally, the kinetic equation Δ w of the mesophase pitch is exp (ln (a/b) -8.314Ea/T + blnt).

Preferably, the mesophase pitch in the step (1) is one of naphthalene mesophase pitch, oil mesophase pitch and coal mesophase pitch; the mesophase pitch has a mesophase content of > 95% and a softening point of > 200 ℃.

Preferably, the particle size of the mesophase pitch powder sample in step (1) is > 180 mesh.

Preferably, the addition amount of the mesophase pitch powder sample in the step (3) is 25-30 mg; the heating rate of the heating treatment is 1-3 ℃/min, and the temperature is 300-500 ℃; the constant temperature duration is 4-900 min.

Preferably, the three temperature points selected in step (4) are 320 ℃, 330 ℃ and 340 ℃.

Preferably, the molar gas constant R in step (5) is 8.314J/(mol. K).

According to the technical scheme, compared with the prior art, the invention has the following beneficial effects:

the method for accurately predicting the thermal decomposition process of the mesophase pitch can accurately predict the thermal decomposition process of the mesophase pitch, better optimize the preparation processes of the mesophase pitch-based foam carbon, the mesophase pitch-based carbon fiber, the needle coke and the like, accurately determine the constant temperature duration of heat treatment, has simple prediction steps and is suitable for popularization and application.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

FIG. 1 shows the power function Δ w ═ Ct obtained by the thermal decomposition of mesophase pitch at 320 ℃, 330 ℃ and 340 ℃ in step (4) of example 1 of the present invention^bIs shown inLike, wherein C at 320 deg.C, 330 deg.C, 340 deg.C are 0.2435, 0.3253, 0.4147, respectively;

FIG. 2 is a graph showing lnk lnA-Ea/(RT) as a function of the mesophase pitch thermally decomposed at 320 ℃ and 330 ℃ and 340 ℃ in step (5) of example 1 of the present invention.

Detailed Description

The invention provides a method for accurately predicting a mesophase pitch thermal decomposition process, which comprises the following steps:

(1) crushing the mesophase pitch to obtain a mesophase pitch powder sample;

(2) opening protective gas of a thermal analyzer, setting the flow rate to be 100 +/-1 mL/min, and carrying out peeling operation;

(3) filling the mesophase pitch powder sample obtained in the step (1) into a thermal analyzer, heating, and then carrying out constant temperature treatment for a period of time when the temperature is raised to a certain temperature;

(4) selecting three temperature points for testing, adjusting different constant temperature durations to obtain three groups of comparison data of mesophase pitch thermal decomposition weight loss delta w and constant temperature duration t at different temperatures, and fitting the three groups of data to obtain a power function delta w ═ Ct^bB is an index factor of constant temperature duration, C is three groups of data delta w corresponding to t^bThe slope of (a);

(5) converting the power function Δ w to Ct^bSimultaneously carrying out derivation on the constant temperature duration t on two sides to obtain a reaction rate constant k which is bC; according to an Arrhenius equation k, Aexp (-Ea/(RT)), logarithms are taken at two sides simultaneously to obtain lnk, lnA-Ea/(RT), lnk values of mesophase pitch thermal decomposition at three groups of different temperatures are taken as vertical coordinates, 1/T values are taken as horizontal coordinates for plotting, the slope is the value of-Ea/R, the intercept is the value of lnA, and R is a molar gas constant, so that the thermal decomposition reaction activation energy Ea and the pre-exponential factor A of the mesophase pitch can be obtained;

(6) finally, the kinetic equation Δ w of the mesophase pitch is exp (ln (a/b) -8.314Ea/T + blnt).

In the present invention, the mesophase pitch in the step (1) is preferably one of a naphthalene mesophase pitch, an oil mesophase pitch, and a coal mesophase pitch, and is more preferably an oil mesophase pitch; the mesophase pitch preferably has a mesophase content of > 95%, more preferably > 97%, a softening point of > 200 ℃ and more preferably > 250 ℃.

In the present invention, the particle size of the mesophase pitch powder-like of the step (1) is preferably > 180 mesh, and more preferably > 200 mesh;

specifically, the mesophase pitch powder sample is preferably obtained by grinding into powder by using a mortar and then sieving with a 180-mesh sieve; it is further preferably obtained by grinding into powder with a mortar and then sieving with a 200-mesh sieve.

Further, the specific process of the peeling operation in the step (2) is as follows: two clean 90 μ L alumina crucibles were loaded into the reference and sample ends of the thermal analyzer, respectively, for peeling.

In the present invention, the amount of the mesophase pitch powder sample added in the step (3) is preferably 25 to 30mg, and more preferably 28 mg.

Specifically, the mesophase pitch powder sample is added to the sample end of the thermal analyzer.

In the present invention, the temperature increase rate of the temperature increase treatment in the step (3) is preferably 1 to 3 ℃/min, more preferably 2 ℃/min, and the temperature is preferably 300 to 500 ℃, more preferably 320 to 340 ℃. The constant temperature duration is preferably 4-900 min, and further preferably 5-850 min.

In the present invention, the three temperature points selected in the step (4) are preferably 320 ℃, 330 ℃, 340 ℃.

Further, the arrhenius equation K is Aexp (-Ea/(RT)) with a molar gas constant R of 8.314J/(mol · K) and a thermodynamic temperature scale T (thermal decomposition temperature-273 ℃) K of mesophase pitch.

The technical solutions provided by the present invention are described in detail below with reference to examples, but they should not be construed as limiting the scope of the present invention.

Example 1

This embodiment is a specific implementation manner of the present invention, and specifically includes the following steps:

(1) grinding the oil system mesophase pitch into powder, and sieving the powder by a 200-mesh sieve to obtain a mesophase pitch powder sample;

(2) opening protective gas of a thermal analyzer, setting nitrogen flow to be 100mL/min, respectively loading two clean 90-microliter alumina crucibles into a reference end and a sample end of the synchronous thermal analyzer, and carrying out peeling operation;

(3) filling 28mg of screened mesophase pitch powder sample into a crucible at the sample end, raising the temperature to 320 ℃ at the heating rate of 2 ℃/min, and then carrying out testing at constant temperature for different times;

(4) selecting two temperature points of 330 ℃ and 340 ℃, testing at constant temperature for different time to obtain three groups of comparison data of mesophase pitch thermal decomposition weight loss delta w and constant temperature time t at different temperatures, and fitting the three groups of data to obtain a power function delta w ═ Ct^0.42C at 320 ℃, 330 ℃ and 340 ℃ is 0.2435, 0.3253 and 0.4147 respectively;

(5) converting the power function Δ w to Ct^0.42Simultaneously carrying out derivation on the constant temperature duration t on the two sides to obtain a reaction rate constant k which is 0.42C; according to an Arrhenius equation k, Aexp (-Ea/(RT)), logarithms are taken at two sides simultaneously to obtain lnk, lnA-Ea/(RT), the lnk values of mesophase pitch thermal decomposition at three groups of different temperatures are taken as ordinate, the 1/T value is taken as abscissa for plotting, the slope is the value of-Ea/R, the intercept is the value of lnA, so that the thermal decomposition reaction activation energy Ea of the mesophase pitch is 80.49kJ/mol, and the index factor A is 1266794;

(6) substituting k equal to Aexp (-Ea/(RT)) into the power function Δ w equal to Ct by k equal to 0.42C^0.42After a series of reduction, known parameters are substituted into the equation Δ w ═ exp (14.92-9681/T +0.42lnt) of the kinetics of the decomposition reaction of the mesophase pitch.

From example 1, the invention provides a method for accurately predicting the thermal decomposition process of mesophase pitch, the thermal decomposition process of mesophase pitch can be accurately predicted by using the technology, the preparation processes of mesophase pitch-based foam carbon, mesophase pitch-based carbon fiber, needle coke and the like are better optimized, the duration of constant temperature of heat treatment is accurately determined, and the technical test method has simple process flow and is easy to realize large-scale production.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.