A method for catalytically hydrogenating coal tar pitch and preparing mesophase pitch at low temperature and low pressure

Abstract

The present invention provides a method for catalytically hydrogenating coal tar and preparing mesophase asphalt at low temperature and low pressure. The method utilizes a catalyst and a co-catalyst that do not contain metal elements to achieve catalytic hydrogenation of coal tar under mild conditions of low temperature and low pressure. The method has low cost, and after the hydrogenation reaction is completed, the catalyst is converted into a gaseous state and can be blown away. The co-catalyst is an organic substance and participates in the subsequent polymerization of asphalt molecules, thus avoiding the problem of ash caused by residual traditional metal-containing catalysts and not introducing additional ash impurities. Ultimately, low-ash, high-performance mesophase asphalt is prepared. The prepared mesophase asphalt has a high mesophase content and a low softening point, and its polarized texture is a wide-area streamlined type. This indicates that the method provided by the present invention, after the hydrogenation reaction, the asphalt molecules obtained have stronger mobility and reaction activity, and the hydrogenation effect is excellent.

Description

Technical Field

[0001] The present invention relates to the technical field of asphalt materials, and in particular to a method for catalytically hydrogenating coal pitch and preparing mesophase asphalt at low temperature and low pressure. Background Art

[0002] Mesophase pitch is a polymer composed of various disc-shaped condensed-ring aromatic hydrocarbons with relative molecular masses ranging from 370 to 2000. Due to its abundant availability, low cost, excellent performance, and high carbon yield, mesophase pitch is widely used in the manufacture of a variety of important advanced carbon materials, such as ultra-high modulus carbon fibers, needle coke for ultra-high power electrodes, advanced fluorocarbon materials, and ultra-high surface area activated carbon. These advanced carbon materials have played a significant role in numerous fields, including defense, industry, and daily life. However, coal tar pitch is a mixture of various planar condensed-ring aromatic hydrocarbons with high aromaticity and few side chain groups. This results in high viscosity and difficult-to-control reactions when preparing mesophase pitch from it. Coal tar pitch is typically hydrogenated to increase its side chain or cycloalkane structure, thereby increasing the mobility of the asphalt molecules. This reduces the viscosity of the reaction system during the preparation of mesophase pitch, thereby controlling the smooth progress of the reaction. Therefore, in the prior art, coal tar pitch is typically hydrogenated when preparing mesophase pitch from coal tar pitch. In addition, the ash in asphalt mainly refers to the metal elements or oxides contained in the asphalt. When preparing mesophase asphalt-based carbon materials, they cannot be removed in the form of small molecules at high temperature like non-metallic elements such as nitrogen and sulfur. Instead, they will accompany the entire process of carbon material preparation. The molecular structure or size of the ash is completely different from the carbon layer structure, which is the main reason for the performance defects of the mesophase asphalt and its carbon materials.

[0003] In the prior art, the common methods for asphalt hydrogenation are: 1) hydrogenating the mesophase asphalt by Li-ethylenediamine, but Li-ethylenediamine is expensive, the operation is complicated and strict, and the Li + It is difficult to remove, and ash is formed after high-temperature treatment, which subsequently affects (reduces) the mechanical properties of the mesophase pitch-based carbon material; 2) The hydrogen supply solvent and coal tar co-carbonization hydrogenation method, this method involves the simultaneous hydrogenation and thermal polycondensation to form the mesophase pitch, the reaction temperature is high (greater than 420 ° C), the reaction process is complex, and the reaction degree is difficult to control; 3) Pure hydrogen hydrogenation method, this method needs to be carried out at high temperature and high pressure, usually the pressure must be above 10 MPa, the equipment requirements are strict, and the hydrogenation process is dangerous. 4) Catalytic hydrogenation method, the existing catalytic hydrogenation methods mainly use solid catalysts containing metal elements (Co-Mo-Al2O3; Ni-Mo-Al2O3) and organic metal catalysts (Fe3(CO) 12 、Mo(CO)6、RuS3(CO) 12While these catalysts can hydrogenate asphalt under relatively mild conditions, they are difficult to remove. The remaining metal elements become ash during high-temperature treatment, forming defects in the carbon material, significantly affecting the mechanical properties of the carbon material prepared from mesophase pitch. Therefore, providing a low-cost, mild reaction method for hydrogenating coal tar pitch to produce low-ash mesophase pitch is an urgent need in the prior art. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for catalytically hydrogenating coal tar pitch and preparing mesophase pitch at low temperature and low pressure. The method provided by the present invention can carry out coal tar pitch hydrogenation under mild reaction conditions of low temperature and low pressure, at low cost, and use a catalyst and co-catalyst that do not contain metal elements to catalyze the hydrogenation of coal tar pitch to prepare a low-ash, excellent-performance mesophase pitch.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for catalytically hydrogenating coal tar pitch and preparing mesophase pitch at low temperature and low pressure, comprising the following steps:

[0007] (1) mixing coal tar pitch, a hydrogen-donating agent, a catalyst, and a co-catalyst to obtain a mixture;

[0008] The catalyst is at least one of boron trifluoride, an organic solution of boron trifluoride, and a boron trifluoride tetrahydrofuran complex; the co-catalyst is an organic acid;

[0009] (2) hydrogenating the mixture obtained in step (1) under an inert atmosphere and sealed conditions to obtain hydrogenated coal pitch;

[0010] 8 to 65 minutes before the end of the hydrogenation reaction, the reaction system of the hydrogenation reaction is depressurized and purged with inert gas;

[0011] (3) subjecting the hydrogenated coal pitch obtained in step (2) to a thermal polycondensation reaction to obtain mesophase pitch.

[0012] Preferably, the ash content of the coal tar pitch in step (1) is less than 200 ppm.

[0013] Preferably, the hydrogen supply reagent in step (1) accounts for 1 wt% to 30 wt% of the coal tar pitch.

[0014] Preferably, the catalyst in step (1) accounts for 2 wt% to 30 wt% of the coal tar pitch.

[0015] Preferably, the mass ratio of the catalyst to the co-catalyst in step (1) is (0-5):(0-5).

[0016] Preferably, the heating rate of the hydrogenation reaction in step (2) is 1 to 10°C / min, the temperature of the hydrogenation reaction is 100 to 350°C, and the time of the hydrogenation reaction is 0.5 to 20h.

[0017] Preferably, the hydrogenation reaction in step (2) is carried out under stirring conditions; the stirring rate is 20 to 600 rpm.

[0018] Preferably, in step (2), the reaction system of the hydrogenation reaction is depressurized and purged with inert gas within 10 to 60 minutes before the end of the hydrogenation reaction.

[0019] Preferably, the flow rate of the inert gas in the inert gas purging treatment in step (2) is 30 to 500 mL / min.

[0020] Preferably, the temperature of the thermal polycondensation reaction in step (3) is 360-450° C.; and the time of the thermal polycondensation reaction is 2-17 hours.

[0021] The present invention provides a method for catalytically hydrogenating coal tar pitch and preparing mesophase asphalt at low temperature and low pressure. The method utilizes a catalyst and a co-catalyst that do not contain metal elements to achieve catalytic coal tar pitch hydrogenation under mild conditions of low temperature and low pressure, which is low-cost. After the hydrogenation reaction is completed, the catalyst is converted into a gaseous state and can be purged and removed. The co-catalyst is an organic substance and can partially participate in the subsequent polymerization of asphalt molecules, avoiding the problem of ash caused by residual traditional metal-containing catalysts and not introducing additional ash impurities. Ultimately, a low-ash, high-performance mesophase asphalt is prepared. The mesophase asphalt prepared by the method provided by the present invention has excellent performance, low ash content, high mesophase content, and a low softening point, which is completely lower than the softening point of coal-based mesophase asphalt prepared by traditional methods. In addition, the polarized texture of the mesophase asphalt obtained by the method provided by the present invention is wide-area streamlined, compared with the mosaic-type or fine streamlined optical texture of the mesophase asphalt prepared without hydrogenation. This indicates that the mobility and reaction activity of the asphalt molecules obtained by the method provided by the present invention after hydrogenation are stronger, and also indicates that the method provided by the present invention can achieve an excellent hydrogenation effect. The results of the embodiments show that the mesophase content of the mesophase asphalt prepared in the embodiments of the present invention is 100%, its polarized texture is wide-area streamlined, and the softening point is as low as 263°C; the method provided in the embodiments of the present invention utilizes a catalyst and a co-catalyst that do not contain metal elements to achieve catalytic coal tar hydrogenation under mild conditions of low temperature and low pressure, with low cost. The prepared mesophase asphalt has excellent performance, low ash content, high mesophase content, and a low softening point, a wide-area streamlined polarized texture, and an excellent hydrogenation effect. DETAILED DESCRIPTION

[0022] The present invention provides a method for catalytically hydrogenating coal tar pitch and preparing mesophase pitch at low temperature and low pressure, comprising the following steps:

[0023] (1) mixing coal tar pitch, a hydrogen-donating agent, a catalyst, and a co-catalyst to obtain a mixture;

[0024] The catalyst is at least one of boron trifluoride, an organic solution of boron trifluoride, and a boron trifluoride tetrahydrofuran complex; the co-catalyst is an organic acid;

[0025] (2) hydrogenating the mixture obtained in step (1) under an inert atmosphere and sealed conditions to obtain hydrogenated coal pitch;

[0026] 8 to 65 minutes before the end of the hydrogenation reaction, the reaction system of the hydrogenation reaction is depressurized and purged with inert gas;

[0027] (3) subjecting the hydrogenated coal pitch obtained in step (2) to a thermal polycondensation reaction to obtain mesophase pitch.

[0028] The invention mixes coal tar pitch, hydrogen supply reagent, catalyst and co-catalyst to obtain a mixture.

[0029] In the present invention, the ash content of the coal tar pitch is preferably less than 200 ppm.

[0030] In the present invention, the hydrogen-donating agent is preferably at least one of tetralin, decalin, hydrogenated mixed aromatics, 1-tetradecene, α-methylstyrene, and hydrogenated anthracene oil. The hydrogen-donating agent preferably accounts for 1 to 30 weight percent of the coal tar pitch. The amount of the hydrogen-donating agent is controlled within the above range to appropriately increase the side chains of the coal tar pitch molecules while maintaining the planar structure of the condensed-ring aromatic molecules as much as possible, thereby producing a readily graphitizable mesophase pitch.

[0031] In the present invention, the catalyst is at least one of boron trifluoride, an organic solution of boron trifluoride, and a boron trifluoride tetrahydrofuran complex. In the present invention, the organic solution of boron trifluoride is preferably at least one of a boron trifluoride solution in diethyl ether and a boron trifluoride solution in acetic acid. In the present invention, the catalyst preferably accounts for 2 to 30 weight percent of the coal tar pitch. The amount of the catalyst is controlled within the above range to achieve optimal catalytic effect and efficiency, shortening the time required for gentle hydrogenation of the coal tar pitch.

[0032] In the present invention, the co-catalyst is an organic acid, preferably at least one of p-toluenesulfonic acid, benzenesulfonic acid, mellitic acid, trichloroacetic acid, and trinitrobenzenesulfonic acid. In the present invention, the mass ratio of the catalyst to the co-catalyst is preferably (0-5):(0-5). The present invention controls the mass ratio of the catalyst to the co-catalyst within the above range to obtain a better catalytic effect, reduce the reaction activation energy through the synergistic effect of the co-catalyst and the catalyst, and thus reduce the temperature conditions required for hydrogenation.

[0033] The present invention has no particular limitation on the mixing method of the coal tar pitch, hydrogen-donating agent, catalyst and co-catalyst. The components can be evenly mixed using a mixing method well known in the art.

[0034] After obtaining the mixture, the present invention performs a hydrogenation reaction on the mixture under an inert atmosphere and sealed conditions to obtain hydrogenated coal tar pitch.

[0035] In the present invention, the heating rate of the hydrogenation reaction is preferably 1 to 10°C / min, more preferably 3 to 6°C / min. The present invention controls the heating rate of the hydrogenation reaction within the above range to allow the hydrogenation process to proceed more smoothly. In the present invention, the temperature of the hydrogenation reaction is preferably 100 to 350°C, more preferably 120 to 330°C. In the present invention, the time of the hydrogenation reaction is 0.5 to 20h, more preferably 2 to 18h. The present invention controls the temperature and time of the hydrogenation reaction within the above range to avoid overreaction, so that the reaction system only stays in the coal tar molecule hydrogenation stage, and reduces the generation of thermal polycondensation reaction. In the present invention, the pressure of the hydrogenation reaction is preferably autogenous pressure (usually <4MPa).

[0036] In the present invention, the hydrogenation reaction is preferably carried out under stirring conditions; the stirring rate is preferably 20 to 600 rpm.

[0037] The present invention depressurizes the reaction system of the hydrogenation reaction and purges it with an inert gas within 8 to 65 minutes before the end of the hydrogenation reaction, preferably depressurizes the reaction system of the hydrogenation reaction and purges it with an inert gas within 10 to 60 minutes before the end of the hydrogenation reaction. The present invention removes the catalyst, part of the co-catalyst, and small molecule gases that have been converted into gas from the reaction system by depressurizing the reaction system of the hydrogenation reaction and purging it with an inert gas.

[0038] In the present invention, the flow rate of the inert gas in the inert gas purging treatment is preferably 30 to 500 mL / min.

[0039] After obtaining the hydrogenated coal pitch, the present invention performs a thermal polycondensation reaction on the hydrogenated coal pitch to obtain the mesophase pitch.

[0040] In the present invention, the equipment for the thermal polycondensation reaction is preferably a high-temperature, high-pressure reactor. In the present invention, the temperature of the thermal polycondensation reaction is preferably 360-450°C, more preferably 370-440°C. In the present invention, the duration of the thermal polycondensation reaction is preferably 2-17 hours, more preferably 5-16 hours. Controlling the temperature and duration of the thermal polycondensation reaction within the above ranges facilitates the preparation of a mesophase pitch with a 100% mesophase content and a low softening point.

[0041] The method provided by the present invention for catalytically hydrogenating coal tar pitch and preparing mesophase pitch at low temperature and low pressure is simple and controllable to operate, low in cost, and suitable for large-scale production. The obtained mesophase pitch can be used to prepare carbon fiber, foamed carbon, electrode materials, impregnating agents, artificial graphite and other materials.

[0042] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0043] Example 1

[0044] The method for catalytically hydrogenating coal pitch at low temperature and low pressure to prepare mesophase pitch comprises the following steps:

[0045] (1) In a reactor, 500 g of coal tar pitch with an ash content of 50 ppm, 25 g of decahydronaphthalene hydrogen donor, 35 g of boron trifluoride-acetic acid solution catalyst, and 17.5 g of p-toluenesulfonic acid co-catalyst were mixed to obtain a mixture;

[0046] The decahydronaphthalene hydrogen donor accounts for 5 wt% of the coal tar pitch; the boron trifluoride-acetic acid solution catalyst accounts for 7 wt% of the coal tar pitch; the mass ratio of the catalyst to the co-catalyst is 2:1;

[0047] (2) In an inert atmosphere and sealed conditions, the mixture obtained in step (1) was heated to 260° C. at a heating rate of 3° C. / min, and hydrogenated at 260° C. for 8 h to obtain hydrogenated coal pitch with an ash content of 45 ppm;

[0048] The reaction system of the hydrogenation reaction is depressurized and purged with inert gas within 40 minutes before the end of the hydrogenation reaction;

[0049] (3) The hydrogenated coal pitch obtained in step (2) was subjected to a thermal polycondensation reaction at 405° C. for 10 hours to obtain a mesophase pitch with an ash content of 63 ppm.

[0050] Polarizing microscope and Image J software were used to detect that the mesophase content of the mesophase pitch prepared in Example 1 was 100%, the polarizing texture thereof was wide-area streamlined, and the softening point thereof was 265° C. as determined by the ring and ball method.

[0051] Example 2

[0052] The method for catalytically hydrogenating coal pitch at low temperature and low pressure to prepare mesophase pitch comprises the following steps:

[0053] (1) In a reactor, 500 g of coal tar pitch with an ash content of 50 ppm, 25 g of decalin hydrogen donor, 35 g of boron trifluoride-acetic acid solution catalyst and 35 g of p-toluenesulfonic acid co-catalyst were mixed to obtain a mixture;

[0054] The decahydronaphthalene hydrogen donor accounts for 5 wt% of the coal tar pitch; the boron trifluoride-acetic acid solution catalyst accounts for 7 wt% of the coal tar pitch; the mass ratio of the catalyst to the co-catalyst is 1:1;

[0055] (2) In an inert atmosphere and sealed conditions, the mixture obtained in step (1) was heated to 240° C. at a heating rate of 3° C. / min, and hydrogenated at 240° C. for 8 h to obtain hydrogenated coal pitch with an ash content of 43 ppm;

[0056] The reaction system of the hydrogenation reaction is depressurized and purged with inert gas within 40 minutes before the end of the hydrogenation reaction;

[0057] (3) The hydrogenated coal pitch obtained in step (2) was subjected to a thermal polycondensation reaction at 405° C. for 10 hours to obtain a mesophase pitch with an ash content of 60 ppm.

[0058] Polarizing microscope and Image J software were used to detect that the mesophase content of the mesophase pitch prepared in Example 2 was 100%, the polarizing texture thereof was wide-area streamlined, and the softening point thereof was 263° C. detected by the ring and ball method.

[0059] Example 3

[0060] The method for catalytically hydrogenating coal pitch at low temperature and low pressure to prepare mesophase pitch comprises the following steps:

[0061] (1) In a reactor, 500 g of coal tar pitch with an ash content of 50 ppm, 25 g of tetralin hydrogen donor, 35 g of boron trifluoride-tetrahydrofuran complex catalyst, and 35 g of benzenesulfonic acid co-catalyst were mixed to obtain a mixture;

[0062] The tetralin hydrogen donor accounts for 5 wt% of the coal tar pitch; the boron trifluoride-tetrahydrofuran complex catalyst accounts for 7 wt% of the coal tar pitch; the mass ratio of the catalyst to the co-catalyst is 1:1;

[0063] (2) In an inert atmosphere and sealed conditions, the mixture obtained in step (1) was heated to 240° C. at a heating rate of 5° C. / min, and hydrogenated at 240° C. for 8 h to obtain hydrogenated coal pitch with an ash content of 48 ppm;

[0064] The reaction system of the hydrogenation reaction is depressurized and purged with inert gas within 40 minutes before the end of the hydrogenation reaction;

[0065] (3) The hydrogenated coal pitch obtained in step (2) was subjected to a thermal polycondensation reaction at 405° C. for 10 hours to obtain a mesophase pitch with an ash content of 62 ppm.

[0066] Polarizing microscope and Image J software were used to detect that the mesophase content of the mesophase pitch prepared in Example 3 was 100%, the polarizing texture thereof was wide-area streamlined, and the softening point thereof was 270° C. as determined by the ring and ball method.

[0067] Example 4

[0068] The method for catalytically hydrogenating coal pitch at low temperature and low pressure to prepare mesophase pitch comprises the following steps:

[0069] (1) In a reactor, 500 g of coal tar pitch with an ash content of 50 ppm, 25 g of 1-tetradecene hydrogen donor, 25 g of boron trifluoride-tetrahydrofuran complex catalyst, and 25 g of benzenesulfonic acid co-catalyst were mixed to obtain a mixture;

[0070] The 1-tetradecene hydrogen donor accounts for 5 wt% of the coal tar pitch; the boron trifluoride-tetrahydrofuran complex catalyst accounts for 5 wt% of the coal tar pitch; the mass ratio of the catalyst to the co-catalyst is 1:1;

[0071] (2) In an inert atmosphere and sealed conditions, the mixture obtained in step (1) was heated to 280° C. at a heating rate of 5° C. / min, and hydrogenated at 280° C. for 8 h to obtain hydrogenated coal pitch with an ash content of 47 ppm;

[0072] The reaction system of the hydrogenation reaction is depressurized and purged with inert gas within 30 minutes before the end of the hydrogenation reaction;

[0073] (3) The hydrogenated coal pitch obtained in step (2) was subjected to a thermal polycondensation reaction at 410° C. for 8 h to obtain a mesophase pitch with an ash content of 60 ppm.

[0074] Polarizing microscope and Image J software were used to detect that the mesophase content of the mesophase pitch prepared in Example 4 was 100%, the polarizing texture thereof was wide-area streamlined, and the softening point thereof was 263° C. as determined by the ring and ball method.

[0075] In summary, the mesophase pitch prepared in the embodiments of the present invention all had a mesophase content of 100%, a wide-area streamlined polarization texture, and a softening point as low as 263°C. The methods provided in the embodiments of the present invention utilize a catalyst and co-catalyst that do not contain metal elements to achieve catalytic coal tar pitch hydrogenation under mild conditions of low temperature and low pressure. This is low-cost, and the prepared mesophase pitch exhibits excellent performance, including low ash content, high mesophase content, and a low softening point. The polarization texture exhibits a wide-area streamlined polarization texture, resulting in excellent hydrogenation results.

[0076] 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 principles 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 mesophase pitch by catalytic hydrogenation of coal pitch at low temperature and low pressure, comprising the following steps: (1) mixing coal tar pitch, a hydrogen-donating agent, a catalyst, and a co-catalyst to obtain a mixture; The catalyst is at least one of boron trifluoride, an organic solution of boron trifluoride, and a boron trifluoride tetrahydrofuran complex; the co-catalyst is an organic acid; (2) hydrogenating the mixture obtained in step (1) under an inert atmosphere and sealed conditions to obtain hydrogenated coal pitch; 8 to 65 minutes before the end of the hydrogenation reaction, the reaction system of the hydrogenation reaction is depressurized and purged with inert gas; (3) subjecting the hydrogenated coal pitch obtained in step (2) to a thermal polycondensation reaction to obtain mesophase pitch.

2. The preparation method according to claim 1, characterized in that The ash content of the coal tar pitch in the step (1) is less than 200 ppm.

3. The preparation method according to claim 1, characterized in that The hydrogen supply reagent in step (1) accounts for 1 wt% to 30 wt% of the coal tar pitch.

4. The preparation method according to claim 1, characterized in that The catalyst in step (1) accounts for 2 wt% to 30 wt% of the coal tar pitch.

5. The preparation method according to claim 1, characterized in that The mass ratio of the catalyst to the co-catalyst in step (1) is (0-5):(0-5).

6. The preparation method according to claim 1, characterized in that The heating rate of the hydrogenation reaction in step (2) is 1 to 10° C. / min, the temperature of the hydrogenation reaction is 100 to 350° C., and the time of the hydrogenation reaction is 0.5 to 20 h.

7. The preparation method according to claim 1, characterized in that The hydrogenation reaction in step (2) is carried out under stirring conditions; the stirring rate is 20 to 600 rpm.

8. The preparation method according to claim 1, characterized in that In the step (2), the reaction system of the hydrogenation reaction is depressurized and purged with inert gas within 10 to 60 minutes before the end of the hydrogenation reaction.

9. The preparation method according to claim 1 or 8, characterized in that The flow rate of the inert gas in the inert gas purging treatment in step (2) is 30 to 500 mL / min.

10. The preparation method according to claim 1, characterized in that The temperature of the thermal polycondensation reaction in step (3) is 360-450° C.; and the time of the thermal polycondensation reaction is 2-17 hours.