Method for preparing mesophase pitch from ethylene tar

Abstract

The invention belongs to the technical field of carbon material preparation, and discloses a method for preparing mesophase pitch from ethylene tar, and the preparation method comprises the following steps: (1) blending ethylene tar with a hydrogen donor solvent, and carrying out pre-pyrolysis to induce condensation polymerization of thermally unstable components; (2) extracting and separating the unstable components by using a solvent to obtain refined asphalt; (3) mixing the refined asphalt and a hydrogen donor solvent in a reaction kettle for thermal reaction to obtain thermal polycondensation asphalt; and (4) extracting the thermal polycondensation asphalt by using a solvent to obtain xylene or toluene insoluble substances. And (5) quickly reacting the insoluble substances in a reaction kettle to obtain the mesophase pitch. The mesophase pitch prepared by the invention has an optical texture with a low softening point, good spinnability and a streamline structure.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon material preparation, and relates to a method for preparing mesophase pitch by a dual process of hydrogen supply-preheating pyrolysis. Background Art

[0002] With the rapid development of the ethylene industry in China, the annual output of ethylene tar in China has been increasing year by year. By 2020, the output of Chinese ethylene tar reached 2.0514 million tons. The traditional use of ethylene tar is mainly as fuel for combustion, which not only causes a great waste of resources but also causes environmental pollution problems. In the current process of continuous development of energy and materials, high-performance carbon materials play an important role in many fields such as aerospace, chemical engineering, and new energy by virtue of their unique mechanical, electrical, and thermal properties. Mesophase pitch, as a precursor of high-performance carbon materials, has the advantages of high strength, high modulus, and good electrical and thermal conductivity. Therefore, it is possible to select ethylene tar to prepare high-quality spinnable mesophase pitch, because ethylene tar has the characteristics of moderate aromaticity, extremely low ash content, and low price. Therefore, using ethylene tar to prepare mesophase pitch precursors has great potential prospects, which not only improves the economic benefits of the ethylene industry, realizes the efficient utilization of resources, but also buffers the dependence on traditional petrochemical energy.

[0003] Although ethylene tar has many advantages in the preparation of mesophase pitch, it also faces many challenges. Due to the presence of aromatic olefin components, ethylene tar has a problem of high reactivity. How to reduce its high reactivity and increase its naphthene structure and methyl side chains is one of the bottlenecks in the preparation of high-quality spinnable mesophase, and it is also the key issue of this research. In terms of the preparation process, it is necessary to improve the efficiency of the reaction, further optimize the process, and improve the spinning potential of the prepared mesophase pitch. Therefore, it is of great theoretical and practical application value to carry out the preparation of mesophase pitch from ethylene tar. This article will deeply study the carbonization behavior and formation mechanism of mesophase pitch prepared from ethylene tar to add feasibility to realizing industrial development and improving its high added value.

[0004] The Chinese invention patent with the publication number CN118725891A discloses "a method for preparing a high thermal conductivity mesophase pitch-based carbon fiber and its precursor". This method directly adds a hydrogenation modifier to a highly aromatic raw pitch, conducts hydrogenation modification to obtain a modified pitch, and then conducts heat treatment on it to obtain mesophase pitch. This process is simple and has low requirements for operators. However, the properties of the prepared mesophase pitch are poor and it is not suitable for the preparation of high-performance pitch-based carbon fibers.

[0005] The Chinese invention patent with the publication number CN107163969A discloses "a method for preparing mesophase pitch from medium-temperature coal tar". This method obtains refined pitch with a low quinoline-insoluble content by preheating and cracking to cut the heavy components, and then conducts heat treatment under pressurized conditions to obtain mesophase pitch. This process is complex and requires reaction under high pressure, with high requirements for equipment and great difficulty in industrialization.

[0006] The Chinese invention patent with the publication number CN105238431B discloses "a method for preparing mesophase pitch by catalytic cracking slurry hydrogenation reduction - co-carbonization". This preparation method is complex, has high requirements for raw materials and production processes, and has the problem of difficult catalyst removal. Summary of the Invention

[0007] In order to solve the problem that ethylene tar has high reactivity in the preparation of mesophase pitch due to the presence of aromatic olefin components, the present invention proposes a dual process of hydrogen supply - preheating and cracking for preparing mesophase pitch. The present invention preheats and cracks ethylene tar in advance, fully reacts the components with high reactivity, removes the bad components in advance, and adds a hydrogen supply solvent in the subsequent reaction. The two means work together to solve the problem of high reactivity of ethylene tar. The method has a significant solution effect and is suitable for preparing high-quality mesophase pitch.

[0008] The technical solution of the present invention:

[0009] A method for preparing mesophase pitch from ethylene tar, comprising the following steps:

[0010] Step 1: Mix ethylene tar with a hydrogen supply solvent and react in an N2 gas atmosphere for 120 - 240 min, with the reaction pressure being atmospheric pressure and the reaction temperature being 380 - 400 °C. After the reaction ends, preheated and cracked pitch is obtained;

[0011] Step 2: Extract the preheated and cracked pitch obtained in Step 1. The extraction temperature is from room temperature to 100 °C, the mass ratio of the preheated and cracked pitch to the extractant is 1:1 - 10, the extraction time is 180 min. The soluble components obtained after extraction are distilled at 80 - 150 °C to remove the solvent and obtain refined pitch;

[0012] Step 3: Vacuum-dry the refined pitch obtained in Step 2 for 12 h, add 10 - 30 wt.% of the hydrogen supply solvent to the refined pitch, and react at a temperature of 410 - 440 °C for 180 - 420 min to obtain heat-shrinkable polycondensation pitch;

[0013] Step 4: Grind the heat-shrinkable polycondensation pitch obtained in Step 3 through a 60-mesh sieve, mix it with an aromatic solvent at a mass ratio of 1:1 - 10, and conduct hot dissolution extraction at 30 - 110 °C for 120 min. After the extraction ends, insoluble components are obtained, and the insoluble components are vacuum-dried to remove the aromatic solvent;

[0014] Step 5: Heat the insoluble matter obtained in Step 4 to 360 - 390°C under the protection of N2 atmosphere for 20 - 60 min to obtain mesophase pitch.

[0015] In Step 1, the reaction temperature is 385 - 395°C and the reaction time is 120 - 190 min.

[0016] In Step 1, the hydrogen - donating solvent is tetralin or hydrogenated anthracene oil.

[0017] In Step 2, the mass ratio of pyrolytic pitch to the extractant is 1:5 - 10.

[0018] In Step 2, the extractant is toluene or xylene.

[0019] In Step 3, the hydrogen - donating solvent is hydrogenated anthracene oil or anthracene oil.

[0020] In Step 4, the aromatic solvent is benzene, xylene or toluene.

[0021] Through the synergistic effect of the hydrogen - donating and pre - pyrolysis dual processes, the present invention realizes the efficient regulation of ethylene tar components and the optimization of the mesophase structure. The specific beneficial effects include:

[0022] (1) Precise regulation of reaction activity: First, in the pre - pyrolysis process, a hydrogen - donating solvent is added to optimize the raw material components. After the combined action of pre - pyrolysis and the hydrogen - donating solvent in advance, the hydrogen - donating solvent provides hydrogen radicals during pre - pyrolysis to combine with the olefin components in ethylene tar, opening the double bonds and reducing their reaction activity. Then, the easily coking components are separated by extraction. The problem of high reaction activity of ethylene tar is solved more efficiently. Compared with the untreated raw material, the aromatic hydrogen in the refined pitch increases from 50% to 64%, and the naphthenic hydrogen increases from 50% to 64%. It shows that the pretreatment process can significantly optimize the reaction raw materials. Under the same conditions, the quinoline insoluble matter of the mesophase pitch directly obtained by thermal polycondensation of the refined pitch is reduced from 87.93% to 66.84% compared with the mesophase pitch obtained after adding 20 wt% of the hydrogen - donating solvent, further indicating that the addition of the hydrogen - donating solvent can reduce the reaction activity, improve the rheological properties of the system, and contribute to the formation of mesophase pitch molecules.

[0023] (2) Significantly improved product performance: The dual process increases the mesophase content to 82 - 97% (compared with 65% of the single process), and the optical texture shows a more excellent streamline orientation, which is particularly suitable for the preparation of high - performance carbon fiber precursors. Description of the Drawings

[0024] Figure 1 It is the nuclear magnetic resonance hydrogen spectrum analysis of the refined pitch obtained by pre - pyrolysis in Example 1 of the present invention.

[0025] Figure 2It is the infrared spectrogram of the mesophase pitch prepared in Example 1 of the present invention and Comparative Example 2.

[0026] Figure 3 It is the H / C ratio of the mesophase pitch prepared in Example 1 of the present invention and Comparative Example 2.

[0027] Figure 4 It is the polarized light microscope photograph of the mesophase pitch prepared in Example 1 of the present invention and Comparative Example 3, where (a) is Comparative Example 3 and (b) is Example 1.

[0028] Figure 5 It is the infrared spectrogram of the mesophase pitch prepared in Example 1 of the present invention and Comparative Example 3.

[0029] Figure 6 It is the polarized light microscope photograph of the mesophase pitch prepared in Example 1 of the present invention and Comparative Example 4, where (a) is Example 1 and (b) is Comparative Example 4.

[0030] Figure 7 It is the polarized light microscope photograph of the mesophase pitch prepared in Example 4 of the present invention and Comparative Example 1.

[0031] Figure 8 It is the XRD pattern of the mesophase pitch prepared in Example 1 of the present invention and Comparative Example 5, where (a) is Example 1 and (b) is Comparative Example 5.

[0032] Figure 9 It is the polarized light microscope photograph of the mesophase pitch prepared in Example 1 of the present invention and Comparative Example 5, where (a) is Example 1 and (b) is Comparative Example 6. Detailed implementation manners

[0033] The present invention will be further described below in conjunction with embodiments.

[0034] Example 1

[0035] Step 1: Take ethylene tar and mix it with 10 wt.% hydrogenated anthracene oil, put it into a reaction kettle, and first purge the air in the kettle with N2 for 10 min to prevent asphalt oxidation. Heat up to 390 °C, and the reaction time is 180 min to obtain a pre-pyrolysis product.

[0036] Step 2: Put the pre-pyrolysis product into a vacuum drying oven and dry it for 12 h. Grind the dried pre-pyrolysis product and pass it through a 300-mesh sieve. Mix it with xylene solvent at a mass ratio of 1:10. The extraction temperature is 50 °C, and the extraction time is 180 min. Filter it to obtain the soluble matter, and distill the soluble matter to remove the solvent to obtain refined asphalt.

[0037] Step 3: Put the refined asphalt into a vacuum drying oven and dry it for 12 h to remove moisture. Mix the dried refined asphalt with 20 wt% of hydrogenated anthracene oil, put them together into a reaction kettle, first introduce N2 to purge for 10 min, and then heat up to 420 °C. Control the reaction time at 300 min, maintain the pressure in the kettle at 0.1 Mpa, turn on the stirrer with a rate of 30 rpm to obtain heat - polycondensed asphalt.

[0038] Step 4: Mix the heat - polycondensed asphalt obtained in Step 3 with xylene solvent at a mass ratio of 1:10, stir at 50 °C for 180 min, then filter to obtain the insoluble matter, and put it into a vacuum drying oven to dry at 150 °C for 120 min.

[0039] Step 5: Put the insoluble matter obtained in Step 4 into a high - pressure reaction kettle, first purge with N2 for 10 min, heat up to 380 °C, and the reaction time is 30 min to obtain mesophase pitch.

[0040] Example 2

[0041] Step 1: Take ethylene tar and mix it with 20 wt.% of tetralin, put them into a reaction kettle, first purge with N2 for 10 min to remove the air in the kettle to prevent asphalt oxidation. Heat up to 400 °C, and the reaction time is 240 min to obtain a pre - pyrolysis product.

[0042] Step 2: Put the pre - pyrolysis product into a vacuum drying oven and dry it for 12 h. Grind the dried pre - pyrolysis product through a 300 - mesh sieve, mix it with xylene solvent at a mass ratio of 1:10, the extraction temperature is 50 °C, the extraction time is 180 min, filter to obtain the soluble matter, and remove the solvent from the soluble matter by distillation to obtain refined asphalt.

[0043] Step 3: Put the refined asphalt into a vacuum drying oven and dry it for 12 h to remove moisture. Mix the dried refined asphalt with 20 wt% of hydrogenated anthracene oil, put them together into a reaction kettle, first introduce N2 to purge for 10 min, and then heat up to 420 °C. Control the reaction time at 300 min, maintain the pressure in the kettle at 0.1 Mpa, turn on the stirrer with a rate of 30 rpm to obtain heat - polycondensed asphalt.

[0044] Step 4: Mix the heat - polycondensed asphalt obtained in Step 3 with xylene solvent at a ratio of 1:10, stir at 50 °C for 180 min, then filter to obtain the insoluble matter, and put it into a vacuum drying oven to dry at 150 °C for 120 min.

[0045] Step 5: Put the insoluble matter obtained in Step 4 into a high - pressure reaction kettle, first purge with N2 for 10 min, heat up to 380 °C, and the reaction time is 30 min to obtain mesophase pitch.

[0046] Example 3

[0047] Step 1: Without adding hydrogenated anthracene oil, directly put ethylene tar into the reaction kettle. First, purge with N2 for 10 min to remove the air in the kettle to prevent asphalt oxidation. Heat up to 390 °C and keep the reaction time for 180 min to obtain the pre-pyrolysis product.

[0048] Step 2: Put the pre-pyrolysis product into a vacuum drying oven and dry for 12 h. Grind the dried pre-pyrolysis product through a 300-mesh sieve, mix it with xylene solvent at a mass ratio of 1:10, keep the extraction temperature at 50 °C, and the extraction time for 180 min. Filter by suction to obtain the soluble matter, and distill the soluble matter to remove the solvent to obtain refined asphalt.

[0049] Step 3: Put the refined asphalt into a vacuum drying oven and dry for 12 h to remove moisture. Mix the dried refined asphalt with 20 wt% hydrogenated anthracene oil, put them together into the reaction kettle, first purge with N2 for 10 min, and heat up to 430 °C. Control the reaction time at 420 min, keep the pressure in the kettle at 0.1 Mpa, start stirring at a rate of 30 rpm to obtain the heat-shrinkage polycondensation asphalt.

[0050] Step 4: Mix the heat-shrinkage polycondensation asphalt obtained in Step 3 with xylene at a mass ratio of 1:5, stir at 50 °C for 180 min, then filter by suction to obtain the insoluble matter, and put it into a vacuum drying oven at 150 °C and dry for 120 min.

[0051] Step 5: Put the insoluble matter obtained in Step 4 into a high-pressure reaction kettle, first purge with N2 for 10 min, heat up to 390 °C, and keep the reaction time for 30 min to obtain mesophase asphalt.

[0052] Example 4

[0053] Step 1: Take ethylene tar and mix it with 5 wt.% hydrogenated anthracene oil, put it into the reaction kettle. First, purge with N2 for 10 min to remove the air in the kettle to prevent asphalt oxidation. Heat up to 380 °C and keep the reaction time for 180 min to obtain the pre-pyrolysis product.

[0054] Step 2: Put the pre-pyrolysis product into a vacuum drying oven and dry for 12 h. Grind the dried pre-pyrolysis product through a 300-mesh sieve, mix it with xylene solvent at a mass ratio of 1:10, keep the extraction temperature at 50 °C, and the extraction time for 180 min. Filter by suction to obtain the soluble matter, and distill the soluble matter to remove the solvent to obtain refined asphalt.

[0055] Step 3: Put the refined asphalt into a vacuum drying oven and dry for 12 h to remove moisture. Mix the dried refined asphalt with 20 wt% hydrogenated anthracene oil, put them together into the reaction kettle, first purge with N2 for 10 minutes, and heat up to 410 °C. Control the reaction time at 300 min, keep the pressure in the kettle at 0.1 Mpa, start stirring at a rate of 30 rpm to obtain the heat-shrinkage polycondensation asphalt.

[0056] Step 4: Mix the heat - polycondensed pitch obtained in Step 3 with xylene at a mass ratio of 1:1, stir at 50 °C for 180 min, then perform suction filtration to obtain the insoluble matter, and place it in a vacuum drying oven to dry at 150 °C for 120 min.

[0057] Step 5: Place the insoluble matter obtained in Step 4 into a high - pressure reactor, first purge with N2 for 10 min, heat up to 390 °C, and the reaction time is 30 min to obtain mesophase pitch.

[0058] Example 5

[0059] Step 1: Take ethylene tar and mix it with 15 wt.% hydrogenated anthracene oil, put it into a reaction kettle, first purge with N2 for 10 min to remove the air in the kettle to prevent asphalt oxidation. Heat up to 410 °C, and the reaction time is 180 min to obtain a pre - pyrolysis product.

[0060] Step 2: Place the pre - pyrolysis product into a vacuum drying oven to dry for 12 h, grind the dried pre - pyrolysis product through a 300 - mesh sieve, mix it with xylene solvent at a mass ratio of 1:10, the extraction temperature is room temperature, the extraction time is 180 min, perform suction filtration to obtain the soluble matter, and remove the solvent from the soluble matter by distillation to obtain refined pitch.

[0061] Step 3: Place the refined pitch into a vacuum drying oven to dry for 12 h to remove moisture, mix the dried refined pitch with 30 wt% anthracene oil, put them together into a reaction kettle, first introduce N2 to purge for 10 minutes, heat up to 410 °C. Control the reaction time at 300 min, maintain the pressure in the kettle at 0.1 Mpa, turn on the stirrer, and the rate is 30 rpm to obtain heat - polycondensed pitch.

[0062] Step 4: Mix the heat - polycondensed pitch obtained in Step 3 with xylene at a mass ratio of 1:10, stir at 50 °C for 180 min, then perform suction filtration to obtain the insoluble matter, and place it in a vacuum drying oven to dry at 150 °C for 120 min.

[0063] Step 5: Place the insoluble matter obtained in Step 4 into a high - pressure reactor, first purge with N2 for 10 min, heat up to 390 °C, and the reaction time is 30 min to obtain mesophase pitch.

[0064] Example 6

[0065] Step 1: Take ethylene tar and mix it with 10 wt.% hydrogenated anthracene oil, put it into a reaction kettle, first purge with N2 for 10 min to remove the air in the kettle to prevent asphalt oxidation. Heat up to 390 °C, and the reaction time is 180 min to obtain a pre - pyrolysis product.

[0066] Step 2: Put the pre-pyrolysis product into a vacuum drying oven and dry it for 12 h. Grind the dried pre-pyrolysis product through a 300-mesh sieve, mix it with xylene solvent at a mass ratio of 1:10, keep the extraction temperature at 50 °C, and the extraction time at 180 min. Filter by suction to obtain the soluble matter, and distill the soluble matter to remove the solvent to obtain refined pitch.

[0067] Step 3: Put the refined pitch into a vacuum drying oven and dry it for 12 h to remove moisture. Mix the dried refined pitch with 20 wt% hydrogenated anthracene oil, put them together into a reaction kettle, first introduce N2 to purge for 10 minutes, and then heat up to 420 °C. Control the reaction time at 360 min, maintain the pressure in the kettle at 0.1 Mpa, start stirring at a rate of 30 rpm to obtain thermally condensed pitch.

[0068] Step 4: Mix the thermally condensed pitch obtained in Step 3 with xylene at a mass ratio of 1:10, stir at 50 °C for 180 min, then filter by suction to obtain the insoluble matter, and put it into a vacuum drying oven to dry at 150 °C for 120 min.

[0069] Step 5: Put the insoluble matter obtained in Step 4 into a high-pressure reaction kettle, first purge with N2 for 10 min, heat up to 380 °C, and the reaction time is 30 min to obtain mesophase pitch.

[0070] Comparative Example 1

[0071] Do not pre-pyrolyze the ethylene tar in advance, and directly let the ethylene tar participate in the reaction.

[0072] Step 1: Put the ethylene tar into a vacuum drying oven and dry it for 12 h to remove moisture. Mix the dried ethylene with 20 wt% hydrogenated anthracene oil, put them together into a reaction kettle, first introduce N2 to purge for 10 minutes, and then heat up to 420 °C. Control the reaction time at 300 min, maintain the pressure in the kettle at 0.1 Mpa, start stirring at a rate of 30 rpm to obtain thermally condensed pitch.

[0073] Step 2: Mix the thermally condensed pitch obtained in Step 1 with xylene at a mass ratio of 1:10, stir at 50 °C for 180 min, then filter by suction to obtain the insoluble matter, and put it into a vacuum drying oven to dry at 150 °C for 120 min.

[0074] Step 3: Put the insoluble matter obtained in Step 2 into a high-pressure reaction kettle, first purge with N2 for 10 min, heat up to 380 °C, and the reaction time is 30 min to obtain mesophase pitch.

[0075] Compared with Example 1, this comparative example does not add the pre-pyrolysis process. Compared with Example 1, it is only treated by the solvent hydrogenation process. As Figure 1As shown, compared with the raw material, the refined pitch obtained through pretreatment has an increase in naphthenic hydrogen from 11% to 18% and an increase in aromatic hydrogen from 50% to 64%. Naphthenes can be dehydrogenated and transformed into aromatic structures, increasing the aromaticity and providing a basis for the polycyclic aromatic hydrocarbon structure required for the formation of mesophase pitch. Aromatic hydrogen can directly participate in the polycondensation reaction, enabling molecules to form larger aromatic molecules through condensation reactions. At the same time, more naphthenic hydrogen and aromatic hydrogen maintain good fluidity during the reaction, contributing to the formation of mesophase pitch with a uniform structure.

[0076] Comparative Example 2

[0077] Step 1: Mix ethylene tar with 10 wt.% hydrogenated anthracene oil, put it into a reaction kettle, and first purge the air in the kettle with N2 for 10 min to prevent asphalt oxidation. Heat up to 390 °C, and the reaction time is 180 min to obtain a pre-pyrolysis product.

[0078] Step 2: Put the pre-pyrolysis product into a vacuum drying oven and dry it for 12 h. Grind the dried pre-pyrolysis product through a 300-mesh sieve, mix it with xylene solvent at a mass ratio of 1:10, the extraction temperature is 50 °C, the extraction time is 180 min, filter to obtain the soluble matter, and distill the soluble matter to remove the solvent to obtain refined pitch.

[0079] Step 3: Compared with Example 1, no hydrogen-donating solvent was added in this Step 3, and other experimental steps were the same as those in Example 1.

[0080] In this comparative example, only in Step 3 was no hydrogen-donating solvent added, and the raw material was only treated by the cooperation of pre-pyrolysis and hydrogen-donating processes in Step 1. As Figure 2 shown, the peak ratio of the C-H stretching vibration peak on the aromatic ring to the aliphatic C-H stretching vibration absorption peak at 2920 cm -1 -1 of the mesophase obtained in Comparative Example 2 is higher than that in Example 1. It shows that the addition of a hydrogen-donating solvent can significantly reduce the reaction activity. By providing hydrogen radicals, it provides more naphthenic structures and alkyl branches, promotes the high-frequency progress of hydrogen transfer reactions during thermal polycondensation, weakens the intermolecular forces between polycyclic aromatic hydrocarbons, thereby improving the aromaticity in the system and reducing the system viscosity. As -1 shown, at the same time, the H / C ratio of the mesophase pitch obtained in Example 1 is higher than that in Comparative Example 2. Figure 3 shown, at the same time, the H / C ratio of the mesophase pitch obtained in Example 1 is higher than that in Comparative Example 2.

[0081] Comparative Example 3

[0082] Step 1: Mix ethylene tar with 10 wt.% hydrogenated anthracene oil, put it into a reaction kettle, and first purge the air in the kettle with N2 for 10 min to prevent asphalt oxidation. Heat up to 390 °C, and the reaction time is 180 min to obtain a pre-pyrolysis product.

[0083] Step 2: Place the pre-pyrolysis product in a vacuum drying oven and dry it for 12 h. Grind the dried pre-pyrolysis product through a 300-mesh sieve, mix it with xylene solvent at a mass ratio of 1:10, with an extraction temperature of 50 °C and an extraction time of 180 min. Filter by suction to obtain the soluble matter, and distill the soluble matter to remove the solvent to obtain refined pitch.

[0084] Step 3: Place the refined pitch in a vacuum drying oven and dry it for 12 h to remove moisture. Mix the dried refined pitch with 10 wt% hydrogenated anthracene oil, put them together into a reaction kettle, first purge with N2 for 10 min, and then heat up to 420 °C. Control the reaction time at 300 min, maintain the pressure in the kettle at 0.1 Mpa, turn on the stirrer with a rate of 30 rpm to obtain the pitch after thermal polycondensation.

[0085] Step 4: Mix the pitch obtained by thermal polycondensation in Step 3 with xylene or toluene at a mass ratio of 1:10, stir at 50 °C for 180 min, then filter by suction to obtain the insoluble matter, and place it in a vacuum drying oven at 150 °C for 120 min.

[0086] Step 5: Place the insoluble matter obtained in Step 4 into a high-pressure reaction kettle, first purge with N2 for 10 min, heat up to 380 °C, and the reaction time is 30 min to obtain mesophase pitch.

[0087] In this comparative example compared with Example 1, the addition amount of the hydrogen-donating solvent in Step 3 is less. As Figure 4 shown, the mesophase obtained in Comparative Example 3 has a higher proportion of 64% mosaic-type optical texture. At the same time, as Figure 5 shown, the peak ratio of the C-H stretching vibration peak on the aromatic ring to the aliphatic C-H stretching vibration absorption peak at 2920 cm -1 at 3050 cm -1 of the mesophase obtained in Comparative Example 3 is higher than that in Example 1. It shows that the proportion of the hydrogen-donating solvent added in Comparative Example 3 is not enough to inhibit the excessive thermal polycondensation of the raw materials, and cannot effectively improve the aromaticity of the system and reduce the viscosity of the system. Adding an appropriate proportion of the hydrogen-donating solvent is beneficial to the dehydrogenation aromatization reaction.

[0088] Comparative Example 4

[0089] Step 1: Take ethylene tar and mix it with 10 wt.% hydrogenated anthracene oil, put them into a reaction kettle, first purge with N2 for 10 min to remove the air in the kettle to prevent asphalt oxidation. Heat up to 390 °C, and the reaction time is 180 min to obtain the pre-pyrolysis product.

[0090] Step 2: Put the pre-pyrolysis product into a vacuum drying oven and dry it for 12 h. Grind the dried pre-pyrolysis product through a 300-mesh sieve, mix it with xylene at a mass ratio of 1:10, with an extraction temperature of 50 °C and an extraction time of 180 min. Filter by suction to obtain the soluble matter, and distill the soluble matter to remove the solvent to obtain refined pitch.

[0091] Step 3: Put the refined pitch into a vacuum drying oven and dry it for 12 h to remove moisture. Mix the dried refined pitch with 30 wt% hydrogenated anthracene oil, put them together into a reaction kettle, first purge with N2 for 10 min, and then heat up to 420 °C. Control the reaction time at 300 min, maintain the pressure in the kettle at 0.1 Mpa, turn on the stirrer at a rate of 30 rpm to obtain thermally condensed pitch.

[0092] Step 4: Mix the thermally condensed pitch obtained in Step 3 with xylene at a mass ratio of 1:10, stir at 50 °C for 180 min, then filter by suction to obtain the insoluble matter, and put it into a vacuum drying oven at 150 °C for 120 min.

[0093] Step 5: Put the insoluble matter obtained in Step 4 into a high-pressure reaction kettle, first purge with N2 for 10 min, heat up to 380 °C, and the reaction time is 30 min to obtain mesophase pitch.

[0094] In this comparative example compared with Example 1, the addition amount of the hydrogen-donating solvent in Step 3 is relatively high. As Figure 6 shown, compared with the mesophase obtained in Example 1, the mesophase content in Comparative Example 4 decreased from 86% to 57%. At the same time, as Figure 7 shown, compared with Example 1, the carbon layer spacing d002 in Comparative Example 4 increased from 0.3470 to 0.3493. It shows that the excessive hydrogen-donating solvent provides a large amount of hydrogen free radicals, which affects the formation of polycyclic aromatic hydrocarbon macromolecules and thus cannot be arranged orderly.

[0095] Comparative Example 5

[0096] Step 1: Take vinyl tar and mix it with 20 wt.% hydrogenated anthracene oil, put it into a reaction kettle, first purge with N2 for 10 min to remove the air in the kettle to prevent asphalt oxidation. Heat up to 390 °C, and the reaction time is 180 min to obtain the pre-pyrolysis product.

[0097] Step 2: Put the pre-pyrolysis product into a vacuum drying oven and dry it for 12 h. Grind the dried pre-pyrolysis product through a 300-mesh sieve, mix it with xylene solvent at a mass ratio of 1:10, with an extraction temperature of 50 °C and an extraction time of 180 min. Filter by suction to obtain the soluble matter, and distill the soluble matter to remove the solvent to obtain refined pitch.

[0098] Step 3: Put the refined asphalt into a vacuum drying oven and dry it for 12 h to remove moisture. Mix the dried refined asphalt with 20 wt% of hydrogenated anthracene oil, put them together into a reaction kettle, first purge with N2 for 10 min, and then heat up to 420 °C. Control the reaction time at 300 min, maintain the pressure in the kettle at 0.1 Mpa, turn on the stirrer at a rate of 30 rpm to obtain thermally condensed asphalt.

[0099] Step 4: Mix the thermally condensed asphalt obtained in Step 3 with xylene at a mass ratio of 1:10, stir at 50 °C for 180 min, then filter to obtain the insoluble matter, and put it into a vacuum drying oven to dry at 150 °C for 120 min.

[0100] Step 5: Put the insoluble matter obtained in Step 4 into a high-pressure reaction kettle, first purge with N2 for 10 min, heat up to 380 °C, and the reaction time is 30 min to obtain mesophase pitch.

[0101] In this comparative example, too much hydrogenated anthracene oil was added in Step 1. As Figure 8 shown, it led to a decrease in the mesophase content from 86% to 40%, indicating that adding hydrogenated anthracene oil in the pre-pyrolysis stage provided a large number of hydrogen free radicals, which combined with the aromatic olefin components in the ethylene tar, reduced its reaction activity, generated a large number of small components, and affected the formation of mesophase.

[0102] Comparative Example 6

[0103] Step 1: Only take ethylene tar and put it into a reaction kettle. First, purge with N2 for 10 min to remove the air in the kettle to prevent asphalt oxidation. Heat up to 390 °C, and the reaction time is 180 min to obtain a pre-pyrolysis product.

[0104] Step 2: Put the pre-pyrolysis product into a vacuum drying oven and dry it for 12 h. Grind the dried pre-pyrolysis product through a 300-mesh sieve, mix it with xylene solvent at a mass ratio of 1:10, the extraction temperature is 50 °C, the extraction time is 180 min, filter to obtain the soluble matter, and remove the solvent from the soluble matter by distillation to obtain refined asphalt.

[0105] Step 3: Put the refined asphalt into a vacuum drying oven and dry it for 12 h to remove moisture. Mix the dried refined asphalt with 20 wt% of hydrogenated anthracene oil, put them together into a reaction kettle, first purge with N2 for 10 min, and then heat up to 420 °C. Control the reaction time at 300 min, maintain the pressure in the kettle at 0.1 Mpa, turn on the stirrer at a rate of 30 rpm to obtain thermally condensed asphalt.

[0106] Step 4: Mix the thermally condensed asphalt obtained in Step 3 with xylene at a mass ratio of 1:10, stir at 50 °C for 180 min, then filter to obtain the insoluble matter, and put it into a vacuum drying oven to dry at 150 °C for 120 min.

[0107] Step 5: Put the insoluble matter obtained in Step 4 into a high-pressure reactor, first purge with N2 for 10 min, heat up to 380 °C, and the reaction time is 30 min to obtain mesophase pitch.

[0108] In this comparative example, compared with Example 1, hydrogenated anthracene oil was not added in Step 1. As Figure 9 shown, due to the absence of hydrogenated anthracene oil, in Step 1, only the high reactivity problem of ethylene tar was solved through pretreatment, and the high reactivity problem of ethylene tar could not be completely and efficiently solved. Therefore, the mesophase pitch obtained in this comparative example shows a mosaic type as the main optical texture and a porous structure appears.

Claims

1. A method for preparing mesophase pitch from ethylene tar, characterized in that: The following steps are involved: Step 1, mixing ethylene tar with a hydrogen supply solvent and reacting them in a N2 gas atmosphere for 120-240 minutes, the reaction pressure is normal pressure, the reaction temperature is 380-400°C, and after the reaction is completed, a pre-pyrolysis asphalt is obtained; Step 2: extracting the pyrolysis asphalt obtained in step 1, the extraction temperature is room temperature to 100°C, the mass ratio of pre-pyrolysis asphalt to extractant is 1:1 to 10, the extraction time is 180 minutes, and the soluble components obtained after extraction are distilled at 80 to 150°C, and the solvent is removed to obtain refined asphalt; Step 3, vacuum drying the refined asphalt obtained in step 2 for 12 hours, adding 10-30wt.% of a hydrogen-donating solvent to the refined asphalt, reacting at a temperature of 410-440° C. for 180-420 minutes to obtain a thermally polycondensed asphalt; Step 4, grinding the heat-condensed asphalt obtained in step 3 through a 60-mesh sieve, and mixing it with an aromatic solvent at a mass ratio of 1:1 to 10, the extraction temperature is 30 to 100° C., the extraction time is 120 min, and an insoluble component is obtained after the extraction is completed. The insoluble component is subjected to vacuum drying to remove the aromatic solvent; Step 5: Heat the insoluble matter obtained in step 4 to 360-390° C. under N 2 atmosphere protection for 20-60 min to obtain mesophase asphalt.

2. The method for preparing mesophase pitch from ethylene tar according to claim 1, characterized in that: In step 1, the hydrogen supply solvent is tetralin or hydrogenated anthracene oil, and the added amount thereof is not more than 30 wt.% of the ethylene tar.

3. The method for preparing mesophase pitch from ethylene tar according to claim 1, characterized in that: In step 1, the reaction temperature is 385-395° C. and the temperature is kept at 120-190 min.

4. The method for preparing mesophase pitch from ethylene tar according to claim 1, characterized in that: In step 2, the extractant is one or a mixture of two or more of benzene, toluene or xylene.

5. The method for preparing mesophase pitch from ethylene tar according to claim 1, characterized in that: In step 3, the hydrogen-donating solvent is hydrogenated anthracene oil.

6. The method for preparing mesophase pitch from ethylene tar according to claim 1, characterized in that: In step 4, the aromatic solvent is one or a mixture of two or more of benzene, xylene or toluene.

Images