Aromatic hydrocarbon oil for mesophase pitch and preparation method and application thereof

Abstract

The application provides an aromatic hydrocarbon oil for mesophase pitch and a preparation method and application thereof. The preparation method comprises the steps of purification, refining, reforming, conversion and purification. The method can convert and purify heavy residual oil into aromatic hydrocarbon oil with high aromatic hydrocarbon content, and the obtained aromatic hydrocarbon oil has narrow molecular weight distribution interval, low ash content and low sulfur content. The mesophase pitch prepared by using the aromatic hydrocarbon oil through different processes has high mesophase content, uniform molecular weight distribution, good large streamline body configuration of mesophase morphology, low ash content and sulfur content, suitable softening point and good spinnability, and is applied to the preparation of carbon fiber or graphite carbon foam and other carbon materials, and has excellent performance. Moreover, the equipment used in the method is all conventional industrial production equipment, so that the equipment investment and production difficulty of related enterprises for converting production of the aromatic hydrocarbon oil can be greatly reduced.

Description

Technical Field

[0001] This invention relates to an aromatic oil for mesophase asphalt, its preparation method and application, belonging to the field of petroleum deep processing technology. Background Technology

[0002] Mesophase pitch is a pitchy substance mainly composed of aromatic compounds. It is a mixture of flattened disc-shaped polycyclic aromatic hydrocarbons with a relative molecular mass of 370–2000, exhibiting a large C / H ratio (e.g., 1.72). Its softening point is mostly between 205 and 285°C, sometimes exceeding 300°C. Above its softening point, it generally has a low melt viscosity and remains stable for a relatively long time, facilitating subsequent processing of the liquid crystal melt. Furthermore, the density, heat capacity, and especially the viscosity of mesophase pitch show significant temperature dependence. After melting, mesophase pitch exhibits a distinct layered structure and is easily graphitized through high-temperature treatment, making it a typical easily graphitized carbon. By controlling the synthesis process to orient the carbon network plane along the fiber axis, high-performance pitch-based carbon fibers can be obtained. In addition, carbon materials prepared using mesophase pitch, such as foamed carbon materials, porous carbon materials, refractory materials, ultra-high power electrode materials, mesophase carbon microspheres, and fluorinated pitch, all possess higher performance than ordinary pitch products and have immeasurable application prospects.

[0003] Mesophase pitch is prepared from oil with high aromatic content (i.e., aromatic oil). Due to limitations in raw materials and process technology, the preparation of mesophase pitch is often carried out by simply treating the heavy residue oil by filtration or distillation or a combination of both. The resulting mesophase pitch generally suffers from defects such as insufficient mesophase content, large molecular weight distribution range, and undesirable mesophase morphology (low proportion of large streamline configuration). In addition, it also has disadvantages such as high ash and sulfur content, which limits the improvement of the performance of the carbon materials prepared subsequently.

[0004] Existing technologies also report methods for pretreatment of feedstock oils. For example, Chinese patent document CN112852464A discloses a pretreatment method for feedstock oils used in the preparation of spinnable mesophase pitch and high-performance pitch-based carbon fibers. This method uses one or more heavy distillation fractions above 300℃ from aromatic heavy oil, catalytic cracking slurry, coal tar, or ethylene tar as raw materials, and employs an ultrasonic-assisted filtration-deashing coupled enhanced extraction process. Furthermore, gel permeation chromatography is used to flexibly adjust the structure and composition of the refined feedstock, resulting in high-quality aromatic feedstock oil. However, this invention suffers from drawbacks such as complex equipment and processes, and low production efficiency. For instance, the ultrasonic thermal filtration coupled extraction system requires both stirring and ultrasonic treatment. As is well known, the limitations of ultrasonic equipment prevent large-scale production. If a factory were to switch to producing this refined aromatic feedstock oil, significant modifications to its existing equipment would be necessary. Furthermore, this invention only physically processes the raw material oil to obtain refined raw material oil, but does not effectively treat the heteroatoms in the raw material oil during the refining process. For example, the nitrogen-containing, sulfur-containing, and other heteroatom carbon compounds commonly found in petroleum are not effectively removed. As a result, when the refined raw material oil obtained by this invention is used to prepare mesophase pitch, the mesophase pitch produced also has a high heteroatom content due to the presence of a large number of heteroatoms in the refined raw material oil. Ultimately, the mechanical properties of the carbon fiber remain at a low level. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an aromatic oil for mesophase pitch, its preparation method, and its applications. The method of this invention can convert and purify heavy residue oil into an aromatic oil with a high aromatic content. The resulting aromatic oil has a narrow molecular weight distribution range and low ash and sulfur content. Mesophase pitch prepared from this aromatic oil through different processes exhibits high mesophase content, uniform molecular weight distribution, a well-defined streamlined mesophase morphology, low ash and sulfur content, a suitable softening point, and good spinnability. It demonstrates excellent performance when applied to the preparation of carbon materials such as carbon fibers or graphite carbon foams. Furthermore, the equipment used in this invention is conventional industrial production equipment, which can significantly reduce the equipment investment and production difficulty for relevant enterprises switching to the production of this aromatic oil.

[0006] The technical solution of the present invention is as follows:

[0007] An aromatic oil for mesophase asphalt, wherein the aromatic oil has a weight-average molecular weight range of 800-1600, a 3- to 5-ring aromatic content ≥84wt%, an ash content ≤25ppm, and a sulfur content ≤0.01wt%.

[0008] According to a preferred embodiment of the present invention, the aromatic oil has a weight-average molecular weight range of 840-1510, a 3- to 5-cyclic aromatic hydrocarbon content of 84-92 wt%, an ash content of 20-25 ppm, and a sulfur content ≤0.01 wt%.

[0009] The above-mentioned method for preparing aromatic oils for mesophase asphalt includes the following steps:

[0010] (1) Purification: The heavy residue oil is washed in sequence with detergents sulfuric acid-phosphoric acid aqueous solution, hydrochloric acid aqueous solution, nitric acid aqueous solution and sodium hydroxide aqueous solution, and then dried to obtain purified residue oil;

[0011] (2) Refining: Distill the purified residue oil and take the fraction at 200-400℃ to obtain refined residue oil;

[0012] (3) Reforming: The refined residue oil is thoroughly mixed with decahydronaphthalene, and after the reaction, it is distilled at 200°C to obtain the reformed residue oil.

[0013] (4) Conversion: The reformate residue is thoroughly mixed with n-hexadecene and reacted to obtain the converted residue.

[0014] (5) Purification: The converted residue oil is heated and distilled under reduced pressure, and the resulting distillate is aromatic oil.

[0015] According to a preferred embodiment of the present invention, in step (1) the sulfuric acid-phosphoric acid aqueous solution, the mass ratio of sulfuric acid:phosphoric acid:water is (1-5):(1-5):(5-50).

[0016] According to a preferred embodiment of the present invention, in step (1), the mass concentration of the hydrochloric acid aqueous solution is 5-30%.

[0017] According to a preferred embodiment of the present invention, in step (1), the mass concentration of the nitric acid aqueous solution is 5-50%.

[0018] According to a preferred embodiment of the present invention, in step (1), the mass concentration of the sodium hydroxide aqueous solution is 5-40%.

[0019] According to a preferred embodiment of the present invention, in step (1), the washing steps for each detergent are as follows: the heavy residue oil and detergent are mixed and stirred thoroughly at 40-60°C, allowed to stand at room temperature to separate into layers, and the oil phase is taken; the oil phase is centrifuged to remove solids, and then washed with water 2-4 times to complete the washing steps.

[0020] According to a preferred embodiment of the present invention, in step (1), the drying temperature is 105°C. This drying temperature can effectively remove moisture while ensuring that the dried product does not deteriorate.

[0021] According to a preferred embodiment of the present invention, in step (2), the distillation pressure is 1000 Pa; and the fraction taken is at 250–400 °C.

[0022] According to a preferred embodiment of the present invention, in step (3), the mass of decahydronaphthalene is 5-35% of the mass of the refined residue oil.

[0023] According to a preferred embodiment of the present invention, in step (3), the reaction is carried out under the protection of an inert gas; the reaction temperature is 300–400°C, the reaction time is 0.5–5 hours, and the reaction pressure is 1.0–3.0 MPa. Preferably, the inert gas is nitrogen or argon.

[0024] According to a preferred embodiment of the present invention, in step (3), the distillation pressure is 1000 Pa and the distillation time is 60 min.

[0025] According to a preferred embodiment of the present invention, in step (4), the mass ratio of reformate residue oil to n-hexadecene is 1:(1-10).

[0026] According to a preferred embodiment of the present invention, in step (4), the reaction is carried out under the protection of an inert gas; the reaction temperature is 300–350°C, the reaction time is 2–5 hours, and the reaction pressure is 1.0–3.0 MPa. Preferably, the inert gas is nitrogen or argon.

[0027] According to a preferred embodiment of the present invention, in step (5), the reduced pressure heating distillation temperature is 200°C and the pressure is 1000Pa.

[0028] The above-mentioned application of aromatic oils for mesophase pitch is used in the preparation of mesophase pitch or carbon materials.

[0029] The technological principle of this invention:

[0030] This invention mainly consists of five parts: purification, refining, reforming, conversion, and purification. First, the ash and catalyst particles in the heavy residue oil are washed with acids (sulfuric acid-phosphoric acid aqueous solution, hydrochloric acid aqueous solution, nitric acid aqueous solution) to remove water-soluble inorganic salts and filter out water-insoluble ones. Then, sodium hydroxide is used to convert the organic acids in the residue oil into sodium organic acids, which are then dissolved in water and removed. Finally, the residue oil is washed with pure water and dried to obtain purified residue oil composed of pure hydrocarbons. The purified residue oil is then distilled to separate the useful components, yielding refined residue oil. Decahydronaphthalene is used to break down sulfur-containing organic molecules in the refined residue oil to separate sulfur, and some molecules are hydrogenated to obtain reformed residue oil. Then, the reformed residue oil is polymerized in n-hexadecene to average the molecular weight of the residue oil molecules. The small molecules produced in the reaction and the excess n-hexadecene are distilled off to obtain aromatic oil suitable for preparing high-quality mesophase asphalt.

[0031] The technical features and beneficial effects of this invention are as follows:

[0032] 1. The method of this invention uses various acid solutions to wash the heavy residual oil, so that the ash and metal oxides are fully dissolved in water and removed. In the reforming step of this invention, decahydronaphthalene reacts with the residual oil, on the one hand adding hydrogen to the residual oil molecules, lowering the softening point of the residual oil; on the other hand, it can break down the molecules of sulfur-containing compounds, causing them to break into elemental sulfur or hydrogen sulfide and escape. The reforming step of this invention avoids the use of catalysts, thus ensuring a low ash content in the residual oil, and the absence of hydrogen gas also improves the safety of the equipment. In the conversion step of this invention, the role of n-hexadecene is twofold: on the one hand, to average the molecular weight of the residual oil molecules; on the other hand, by adding this alkane to the residual oil molecules, the residual oil molecules have more side chains, forming a morphology similar to a multi-armed Guanyin, and the interlocking multi-arm morphology can enhance the mechanical properties of the product. The conversion steps and conditions of this invention work together as a whole to achieve their effect.

[0033] 2. This invention discloses for the first time a method for preparing aromatic oils with high aromatic content, narrow molecular weight distribution, and low ash and sulfur content from heavy residue oils with a wide molecular weight distribution through multiple processes such as purification, refining, reforming, conversion, and purification. The aromatic oils prepared using the process of this invention can produce mesophase pitch with a mesophase content of 98-100%, uniform molecular weight distribution, good streamlined morphology, low ash and sulfur content, suitable softening point, and good spinnability. Various carbon materials prepared from the obtained mesophase pitch exhibit good performance. For example, the strength of the prepared mesophase pitch carbon fibers (ungraphitized) can reach over 2500 MPa; the prepared graphite carbon foam has uniform pores and low density (≤0.5 g / cm³). 3 It has advantages such as high thermal conductivity (≥80W / m·K). Furthermore, the equipment used in this invention is conventional industrial production equipment, which can greatly reduce the equipment investment and production difficulty for relevant enterprises switching to the production of this aromatic oil. Attached Figure Description

[0034] Figure 1 This is a hot-stage microscope image of the mesophase pitch prepared from the aromatic oil obtained in Example 5;

[0035] Figure 2 This is a hot-stage microscope image of mesophase pitch prepared from the aromatic oil obtained in Comparative Example 6.

[0036] Figure 3 This is a scanning electron microscope (SEM) image of carbon fiber prepared from the aromatic oil obtained in Comparative Example 5;

[0037] Figure 4 This is a scanning electron microscope (SEM) image of graphite carbon foam prepared from the aromatic oil obtained in Example 1;

[0038] Figure 5 This is a scanning electron microscope (SEM) image of graphite foam carbon prepared from the aromatic oil obtained in Comparative Example 2. Detailed Implementation

[0039] The technical solution of the present invention will be further described below with reference to the embodiments and accompanying drawings, but the scope of protection of the present invention is not limited thereto.

[0040] In the embodiments, the raw materials and reagents used are commercially available unless otherwise specified; the methods described are existing methods unless otherwise specified.

[0041] Source of raw materials

[0042] The heavy residue oil was purchased from Yanshan Petrochemical Refinery, and its technical specifications are: density: 1.08 g / cm³. 3 Viscosity: 21 Pa·S, Moisture: None, Pour Point: 22℃, Flash Point: 218℃.

[0043] Example 1

[0044] A method for preparing mesophase asphalt aromatic oil includes the following steps:

[0045] (1) Purification: Place the heavy residue oil in a stirred tank, add the detergent sulfuric acid-phosphoric acid aqueous solution, the mass ratio of sulfuric acid, phosphoric acid and water is 1:1:5, heat to 50℃ and stir thoroughly, then let stand at room temperature. After separation, take the oil phase and put it into a centrifuge to separate the solids. Return the upper clear liquid residue oil to the stirred tank and wash the residue oil 3 times with pure water.

[0046] The above steps were repeated using hydrochloric acid aqueous solution (5% by mass), nitric acid aqueous solution (5% by mass), and sodium hydroxide aqueous solution (5% by mass) as washing agents, respectively. Finally, the residue oil was heated to 105℃ and the moisture was dried to obtain purified residue oil.

[0047] (2) Refining: Place the purified residue oil obtained in step (1) into a distillation kettle, then turn on the vacuum pump to adjust the vacuum to 1000Pa, and heat it to 250-400℃ to obtain the refined residue oil.

[0048] (3) Reforming: The refined residue oil obtained in step (2) is thoroughly mixed with decahydronaphthalene (the mass of decahydronaphthalene is 5% of the mass of refined residue oil) and placed in a reactor. Under nitrogen protection, the pressure is increased to 1.0 MPa, the temperature is raised to 300℃ and kept constant for 5 hours. Then the temperature is reduced to 200℃, and the vacuum pump is turned on to 1000 Pa. This state is maintained for 60 minutes, and the distillate residue is collected to obtain reformed residue oil.

[0049] (4) Conversion: The reformate obtained in step (3) is mixed with n-hexadecene in a mass ratio of 1:1, pressurized to 1.0 MPa under nitrogen protection, heated to 300℃ and kept at the temperature for 5 hours to obtain the reformate.

[0050] (5) Purification: The converted residue oil obtained in step (4) is distilled at a pressure of 1000 Pa and a temperature of 200 °C. The distillate obtained is aromatic oil.

[0051] Example 2

[0052] A method for preparing mesophase asphalt aromatic oil includes the following steps:

[0053] (1) The preparation of purified residual oil is the same as in Example 1;

[0054] (2) The preparation of refined residue oil is the same as in Example 1;

[0055] (3) Reforming: The refined residue oil obtained in step (2) is thoroughly mixed with decahydronaphthalene (the mass of decahydronaphthalene is 15% of the mass of refined residue oil) and placed in a reactor. Under nitrogen protection, the pressure is increased to 2.0 MPa, the temperature is raised to 400℃ and kept constant for 2 hours. Then the temperature is reduced to 200℃, and the vacuum pump is turned on to 1000 Pa. This state is maintained for 60 minutes, and the distillate residue is collected to obtain reformed residue oil.

[0056] (4) Conversion: The reformate obtained in step (3) is mixed with n-hexadecene at a mass ratio of 1:10, pressurized to 1.0 MPa under nitrogen protection, heated to 350°C and kept at that temperature for 3 hours to obtain the reformate.

[0057] (5) Purification: The converted residue oil obtained in step (4) is distilled at a pressure of 1000 Pa and a temperature of 200 °C. The distillate obtained is aromatic oil.

[0058] Example 3

[0059] A method for preparing mesophase asphalt aromatic oil includes the following steps:

[0060] (1) Purification: Place the heavy residue oil in a stirred tank, add the detergent sulfuric acid-phosphoric acid aqueous solution, the mass ratio of sulfuric acid, phosphoric acid and water is 5:1:50, heat to 50℃ and stir thoroughly, then let stand at room temperature. After separation, take the oil phase and put it into a centrifuge to separate the solids. Return the upper clear liquid residue oil to the stirred tank and wash the residue oil 3 times with pure water.

[0061] The above steps were repeated using hydrochloric acid aqueous solution (30% by mass), nitric acid aqueous solution (50% by mass), and sodium hydroxide aqueous solution (40% by mass) as washing agents, respectively. Finally, the residue oil was heated to 105℃ and the moisture was dried to obtain purified residue oil.

[0062] (2) Refining: Place the purified residue oil obtained in step (1) into a distillation kettle, then turn on the vacuum pump to adjust the vacuum to 1000Pa, and heat it to 250-400℃ to obtain the refined residue oil.

[0063] (3) The preparation of reformate residue oil is the same as in Example 1.

[0064] (4) The preparation of the converted residue oil is the same as in Example 1.

[0065] (5) The purification steps are the same as in Example 1 to obtain aromatic oil.

[0066] Example 4

[0067] A method for preparing mesophase asphalt aromatic oil includes the following steps:

[0068] (1) The preparation of purified residue oil is the same as in Example 3.

[0069] (2) The preparation of refined residue oil is the same as in Example 3.

[0070] (3) Reforming: The refined residue oil obtained in step (2) is thoroughly mixed with decahydronaphthalene (the mass of decahydronaphthalene is 15% of the mass of refined residue oil) and placed in a reactor. Under nitrogen protection, the pressure is increased to 2.0 MPa, the temperature is raised to 400℃ and kept constant for 2 hours. Then the temperature is reduced to 200℃, and the vacuum pump is turned on to 1000 Pa. This state is maintained for 60 minutes, and the distillate residue is collected to obtain reformed residue oil.

[0071] (4) Conversion: The reformate obtained in step (3) is mixed with n-hexadecene at a mass ratio of 1:10, pressurized to 1.0 MPa under nitrogen protection, heated to 350°C and kept at that temperature for 3 hours to obtain the reformate.

[0072] (5) Purification: The converted residue oil obtained in step (4) is distilled at a pressure of 1000 Pa and a temperature of 200 °C. The distillate obtained is aromatic oil.

[0073] Example 5

[0074] A method for preparing mesophase asphalt aromatic oil includes the following steps:

[0075] (1) Purification: Place the heavy residue oil in a stirred tank, add the detergent sulfuric acid-phosphoric acid aqueous solution, the mass ratio of sulfuric acid, phosphoric acid and water is 5:1:20, heat to 50℃ and stir thoroughly, then let stand at room temperature. After separation, take the oil phase and put it into a centrifuge to separate the solids. Return the upper clear liquid residue oil to the stirred tank and wash the residue oil 3 times with pure water.

[0076] The above steps were repeated using hydrochloric acid aqueous solution (15% by mass), nitric acid aqueous solution (25% by mass), and sodium hydroxide aqueous solution (20% by mass) as washing agents, respectively. Finally, the residue oil was heated to 105℃ and the moisture was dried to obtain purified residue oil.

[0077] (2) Refining: Place the purified residue oil obtained in step (1) into a distillation kettle, and then turn on the vacuum pump to adjust the vacuum to

[0078] At 1000 Pa, the temperature was increased to 250–400 °C to obtain refined residue oil.

[0079] (3) Reforming: The refined residue oil obtained in step (2) is thoroughly mixed with decahydronaphthalene (the mass of decahydronaphthalene is 15% of the mass of refined residue oil) and placed in a reactor. Under nitrogen protection, the pressure is increased to 3.0 MPa, the temperature is raised to 400℃ and kept constant for 2 hours. Then the temperature is reduced to 200℃, and the vacuum pump is turned on to 1000 Pa. This state is maintained for 60 minutes, and the distillate residue is collected to obtain reformed residue oil.

[0080] (4) Conversion: The reformate obtained in step (3) is mixed with n-hexadecene at a mass ratio of 1:5, pressurized to 3.0 MPa under nitrogen protection, heated to 350°C and kept at that temperature for 5 hours to obtain the reformate.

[0081] (5) Purification: The converted residue oil obtained in step (4) is distilled at a pressure of 1000 Pa and a temperature of 200 °C. The distillate obtained is aromatic oil.

[0082] Comparative Example 1

[0083] A method for preparing aromatic oil, as described in Example 1, except that in step (3), the mass of decahydronaphthalene is 2% of the mass of the refined residue oil, and the other steps are the same as in Example 1.

[0084] Comparative Example 2

[0085] A method for preparing aromatic oil, as described in Example 1, except that in step (3), the mass of decahydronaphthalene is 40% of the mass of refined residue oil, and the other steps are the same as in Example 1.

[0086] Comparative Example 3

[0087] A method for preparing aromatic oil, as described in Example 5, except that the mass ratio of reformate residue oil to n-hexadecene in step (4) is adjusted to 1:0.5, and the other steps are the same as in Example 5.

[0088] Comparative Example 4

[0089] A method for preparing aromatic oil, as described in Example 5, except that the mass ratio of reformate residue oil to n-hexadecene in step (4) is adjusted to 1:11, and the other steps are the same as in Example 5.

[0090] Comparative Example 5

[0091] A method for preparing aromatic oil includes the following steps: distilling heavy residue oil under reduced pressure at 1000 Pa, taking the fraction at 300-350℃, and filtering the distillate through a 0.5 μm filter screen to obtain aromatic oil.

[0092] Comparative Example 6

[0093] A method for preparing aromatic oil includes the following steps: distilling heavy residue oil under reduced pressure at 1000 Pa, taking the fraction at 250-350℃, and filtering the distillate through a 0.5 μm filter screen to obtain aromatic oil.

[0094] Test case

[0095] The aromatic oils prepared in the above examples and comparative examples were used to prepare mesophase pitch using conventional methods, and carbon fibers and graphite carbon foams were prepared using this mesophase pitch for performance comparison.

[0096] The conventional method for preparing mesophase asphalt is a two-stage process, which involves: a pressurization stage at 420℃ and 2.0MPa for 5 hours, and a depressurization stage at 400℃ and 5000Pa for 4 hours.

[0097] Spinability test: The same mass of asphalt sample to be tested is spun at a drawing rate of 400 m / min. The longest continuous spinning time is the spinnability test.

[0098] The carbon fiber preparation method is as follows: mesophase pitch is spun into precursor fiber under a pressure of 0.05 MPa and a drawing rate of 400 m / min. The precursor fiber is oxidized at a constant temperature of 300℃ for 10 min. The oxidized fiber is heated to 1000℃ and held at a constant temperature for 10 min under nitrogen protection.

[0099] The preparation method of graphite carbon foam is as follows: put mesophase pitch into a high temperature and high pressure autoclave, heat it to 500℃ at 1000Pa, keep it at a constant temperature for 10 minutes, pressurize it to 20MPa and keep it at a constant temperature for 5 hours, cool it and take it out, and keep it at 2800℃ for 15 minutes to obtain graphite carbon foam.

[0100] The performance test data are shown in Table 1-2 below.

[0101] Table 1 Comparison of parameters of aromatic oils and mesophase pitch prepared in the examples and comparative examples

[0102]

[0103] As can be seen from Table 1, the difference between Comparative Example 4 and Example 5 is that the mass ratio of reformate residue oil to n-hexadecene in step (4) is adjusted to 1:11. Therefore, its data are similar to those of Example 5, indicating that using too high a proportion of n-hexadecene in the system will not affect the performance of aromatic oil, but will affect the economy due to the addition of too much n-hexadecene (therefore, Comparative Example 4 will not be discussed further).

[0104] The molecular weight distribution ranges of Examples 1-5 are all relatively small and similar. However, in Comparative Example 1, the proportion of decahydronaphthalene added was too low, resulting in insufficient hydrogen atoms for the residue oil, thus leading to a wider molecular weight distribution range. In Comparative Example 2, the proportion of decahydronaphthalene added was too high, resulting in an excessively high number of hydrogen atoms for the residue oil molecules. This resulted in a lower molecular weight distribution range, but the softening point of the subsequently prepared mesophase pitch was too low. Comparative Examples 5-6 used different distillation temperature ranges, and the resulting products did not exhibit well control over their molecular weight distribution range. Furthermore, the softening point of the prepared mesophase pitch was also relatively high, affecting spinning performance.

[0105] The aromatic oils prepared in Examples 1-5 had relatively low ash and sulfur contents, while the ash and sulfur contents of Comparative Examples 1-3 were similar to those in the examples, indicating that acid and alkali treatment of the residue oil can effectively reduce the ash and sulfur contents. In Comparative Examples 5-6, the method of producing refined residue oil through filtration and direct distillation could not effectively remove ash and sulfur.

[0106] Table 2. Performance comparison of mesophase pitch products prepared in the examples and comparative examples.

[0107]

[0108] As can be seen from Table 2, the mesophase pitch carbon fibers prepared in the examples all have high tensile strength and modulus, while the relevant data of Comparative Examples 1 to 6 (except for Comparative Example 4) are all low, especially Comparative Examples 5 to 6 which have the lowest values.

[0109] In addition, the graphite carbon foams prepared in the examples also have low density, good thermal conductivity, good compressive strength and modulus, which cannot be achieved by the comparative examples (except for Comparative Example 4).

[0110] It is evident that the method for preparing aromatic oils using the present invention has better performance compared to conventional methods.

[0111] Figure 1-5 This further demonstrates that the aromatic oil preparation method of the present invention has better effects than traditional methods.

[0112] Figure 1 The mesophase pitch with a large streamline shape is prepared from the aromatic oil obtained in Example 5. Figure 2 It is a finely fragmented, mosaic-structured mesophase pitch prepared from the aromatic oil obtained in Comparative Example 6.

[0113] Figure 3 This is a SEM cross-sectional image of carbon fibers prepared from the aromatic oil obtained in Comparative Example 5. The mesophase pitch carbon fibers prepared from the aromatic oil obtained by acid and alkali treatment of residue oil have virtually no pore defects, while the mesophase pitch carbon fibers prepared by conventional methods have more or less large pore defects, and some carbon fibers also have cracks.

[0114] Figure 4 and Figure 5 The images show cross-sectional views of graphite carbon foams prepared from the aromatic oils obtained in Example 1 and Comparative Example 2, respectively. It can be seen that the graphite carbon foam prepared in the examples has a more uniform pore structure with smaller size variations; while the graphite carbon foam prepared in the comparative example has uneven pore sizes.

Claims

1. A method for preparing mesophase asphalt aromatic oil, characterized in that, The aromatic oil has a weight-average molecular weight range of 800-1600, a 3- to 5-cyclic aromatic hydrocarbon content ≥84wt%, an ash content ≤25ppm, and a sulfur content ≤0.01wt%. The method for preparing the aromatic oil for mesophase asphalt includes the following steps: (1) Purification: The heavy residue oil is washed in sequence with detergents sulfuric acid-phosphoric acid aqueous solution, hydrochloric acid aqueous solution, nitric acid aqueous solution and sodium hydroxide aqueous solution, and then dried to obtain purified residue oil; (2) Refining: Distill the purified residue oil and take the fraction at 200-400℃ to obtain refined residue oil; (3) Reforming: The refined residue oil is thoroughly mixed with decahydronaphthalene, and after the reaction, it is distilled at 200°C. The distillate residue is collected to obtain reformed residue oil. (4) Conversion: The reformate residue is thoroughly mixed with n-hexadecene and reacted to obtain the converted residue. (5) Purification: The converted residue oil is heated and distilled under reduced pressure, and the resulting distillate is aromatic oil.

2. The method for preparing mesophase pitch aromatic oil according to claim 1, characterized in that, The aromatic oil has a weight-average molecular weight range of 840-1510, a 3-5 ring aromatic hydrocarbon content of 84-92 wt%, an ash content of 20-25 ppm, and a sulfur content ≤0.01 wt%.

3. The method for preparing mesophase pitch aromatic oil according to claim 1, characterized in that, Step (1) includes one or more of the following conditions: i. In a sulfuric acid-phosphoric acid aqueous solution, the mass ratio of sulfuric acid:phosphoric acid:water is (1-5):(1-5):(5-50); ii. The mass concentration of the hydrochloric acid aqueous solution is 5-30%; iii. The mass concentration of the nitric acid aqueous solution is 5-50%; iv. The mass concentration of the sodium hydroxide aqueous solution is 5-40%; v. The washing steps for each detergent are as follows: Mix the heavy residue oil and detergent, stir thoroughly at 40-60℃, let stand at room temperature to separate the layers, and take the oil phase; remove the solids from the oil phase by centrifugation, and then wash with water 2-4 times to complete the washing steps; vi. The drying temperature is 105℃.

4. The method for preparing mesophase pitch aromatic oil according to claim 1, characterized in that, In step (2), the distillation pressure is 1000 Pa; the fraction taken at 250-400℃ is used.

5. The method for preparing mesophase pitch aromatic oil according to claim 1, characterized in that, Step (3) includes one or more of the following conditions: i. The mass of decahydronaphthalene is 5-35% of the mass of refined residue oil; ii. The reaction is carried out under inert gas protection; the reaction temperature is 300-400℃, the reaction time is 0.5-5 hours, and the reaction pressure is 1.0-3.0 MPa; iii. The distillation pressure is 1000 Pa and the distillation time is 60 min.

6. The method for preparing mesophase pitch aromatic oil according to claim 5, characterized in that, The inert gas mentioned in condition ii is nitrogen or argon.

7. The method for preparing mesophase pitch aromatic oil according to claim 1, characterized in that, In step (4), the mass ratio of reformate residue to n-hexadecene is 1:(1-10).

8. The method for preparing mesophase pitch aromatic oil according to claim 1, characterized in that, In step (4), the reaction is carried out under the protection of an inert gas; the reaction temperature is 300-350℃, the reaction time is 2-5 hours, and the reaction pressure is 1.0-3.0MPa.

9. The method for preparing mesophase pitch aromatic oil according to claim 8, characterized in that, In step (4), the inert gas is nitrogen or argon.

10. The method for preparing mesophase pitch aromatic oil according to claim 1, characterized in that, In step (5), the reduced pressure heating distillation temperature is 200℃ and the pressure is 1000Pa.

11. The application of the mesophase pitch aromatic oil prepared by the method for preparing mesophase pitch aromatic oil according to any one of claims 1 or 2, characterized in that, It is used in the preparation of mesophase pitch or carbon materials.

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