Method for manufacturing mesophase pitch

Abstract

To provide a method for manufacturing mesophase pitch that can efficiently produce mesophase pitch with a full-flow structure. [Solution] A method for producing mesophase pitch, comprising: a solvent treatment step of removing solvent-insoluble components from petroleum-based residue using a solvent; a first heat treatment step of obtaining a reaction product by heating the solvent-treated petroleum-based residue under pressure at a temperature of 400°C or higher and 420°C or lower; a distillation step of removing light components from the reaction product and distilling the reaction product to obtain pitch; and a second heat treatment step of obtaining mesophase pitch by heating the pitch at a pressure of atmospheric pressure or higher and a temperature of 453°C or higher.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing mesophase pitch.

Background Art

[0002] Various carbon materials are essential and important members in promoting the electrification and electrification of society. Among them, needle coke is expected to have a large increase in demand in the future as a member of electric furnace electrodes and LIB anodes. The raw materials for needle coke are coal tar pitch, petroleum-based cracked residue oil, etc. However, as an intermediate in the manufacturing process, by passing through mesophase pitch with a full-flow structure, it is known that needle coke with excellent physical properties such as electric conductivity, strength, and elastic modulus can be manufactured. Passing through mesophase pitch with a flow structure is important not only in the manufacturing process of needle coke but also in the manufacturing process of high-performance carbon fibers.

[0003] Various studies have been made on the method for manufacturing mesophase pitch for obtaining various carbon materials. For example, Patent Document 1 discloses a method for manufacturing mesophase pitch by hydrogenating a pitch raw material. In this method, while hydrogenating the pitch raw material by heating a mixture of the pitch raw material and a hydrogen-donating reagent in a reaction vessel, the reagent vaporized by heating is led out of the reaction vessel and cooled to be liquefied, and the liquefied reagent is returned to the reaction vessel. Patent Document 2 discloses a stabilized mesophase pitch modified body characterized in that the elemental composition ratio (O / C) of oxygen O and carbon C measured by elemental analysis is 0.1 or more, the elemental composition ratio (N / C) of nitrogen N and carbon C is 0.02 or more, and the peak derived from the N1s orbital measured by X-ray photoelectron spectroscopy includes pyridine-type aromatic N (398 eV) and pyrrole-type aromatic NH (400 eV). Patent Document 3 discloses a process for producing mesophase pitch from an aromatic liquid feed material. The process includes a) introducing the aromatic liquid feed material and a steam feed source into a reactor operating under thermal polymerization conditions; b) maintaining thermal polymerization conditions in the reactor, including turbulence and a temperature high enough to induce thermal polymerization that converts the feed material into mesophase pitch and to produce coke; and c) discharging the mesophase pitch-containing product stream from the reactor after a residence time of less than one minute and long enough to convert at least one-third (by weight) of the feed material into mesophase pitch, thereby producing at least an order of magnitude more mesophase pitch than coke. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-31538 [Patent Document 2] Japanese Patent Publication No. 2018-141069 [Patent Document 3] Special Publication No. 2019-523791 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] To obtain high-performance carbon materials, it is desirable to use a mesophase pitch with a full-surface flow structure, but Patent Documents 1 to 3 do not describe a method for developing a mesophase pitch flow structure. To produce mesophase pitch with a full-flow structure, it is crucial to control the composition and structure of the raw materials. However, the crude raw materials, coal tar pitch and petroleum decomposition residues, are complex mixtures of heavy hydrocarbon compounds, and methods for identifying these components, as well as the mechanisms by which the flow structure is formed, are not fully understood. With the expected increase in demand for needle coke and high-performance carbon fibers, the ability to efficiently produce mesophase pitch with a full-flow structure would be useful, and the development of such manufacturing methods is needed.

[0006] The objective of the present invention is to provide a method for manufacturing mesophase pitch that can efficiently produce mesophase pitch with a full-flow structure. [Means for solving the problem]

[0007] [1] A method for producing mesophase pitch, comprising: a solvent treatment step of removing solvent-insoluble components from petroleum-based residue using a solvent; a first heat treatment step of obtaining a reaction product by heating the solvent-treated petroleum-based residue under pressure at a temperature of 400°C or higher and 420°C or lower; a distillation step of removing light components from the reaction product and distilling the reaction product to obtain pitch; and a second heat treatment step of obtaining mesophase pitch by heating the pitch at a pressure of atmospheric pressure or higher and a temperature of 453°C or higher. [2] The first heat treatment step is a step of heating the solvent-treated petroleum-based residue under a pressure of 4 MPa or more. The method for producing mesophase pitch as described in [1] above. [3] The first heat treatment step is a step of heating the solvent-treated petroleum-based residue for 0.5 hours or more and 1.5 hours or less. The method for producing mesophase pitch according to [1] or [2] above. [4] The second heat treatment step is a step of heating the pitch to a temperature of 453°C or higher and 470°C or lower. A method for manufacturing mesophase pitch according to any one of the above [1] to [3]. [5] The second heat treatment step is a step of heating the pitch for 1.0 hour or more and 5.0 hours or less. A method for manufacturing mesophase pitch according to any one of the above [1] to [4]. [6] The petroleum residue is at least one selected from the group consisting of cracked residue generated when heavy crude oil is cracked using a fluid catalytic cracking unit, vacuum distillation residue obtained by further reducing the pressure of the atmospheric distillation residue of crude oil and distilling it, residue after extracting heavy fractions from the vacuum distillation residue with propane, and ethylene bottom oil. A method for producing mesophase pitch according to any one of the above [1] to [5]. [7] The method further comprises a carbonization step of carbonizing the mesophase pitch, A method for producing mesophase pitch according to any one of the above [1] to [6]. [8] The carbonization process is carried out at a temperature of 450°C or higher and 650°C or lower, and the duration of holding the carbonization temperature is 0.5 hours or higher and 4 hours or lower. The method for producing mesophase pitch as described in [7] above. [9] When a polarized microscope image of the mesophase pitch is obtained and the mesophase pitch is determined according to the size of the optical tissue observed in the image and the area occupied by the optical tissue, the optical tissue score is 5.0 or higher. The method for producing mesophase pitch according to [7] or [8] above.

[10] When a polarized microscope image of the mesophase pitch is obtained and the mesophase pitch is determined according to the size of the optical tissue observed in the image and the area occupied by the optical tissue, the optical tissue score is 5.5 or higher. A method for producing mesophase pitch according to any one of the above [7] to [9]. [Effects of the Invention]

[0008] According to one aspect of the present invention, a method for manufacturing mesophase pitch that can efficiently produce mesophase pitch with a full-surface flow structure can be provided. [Brief explanation of the drawing]

[0009] [Figure 1] This is a polarized light microscope image of the mesophase pitch in Example 1. [Figure 2]It is a polarized light micrograph of the mesophase pitch of Example 2. [Figure 3] It is a polarized light micrograph of the mesophase pitch of Example 3. [Figure 4] It is a polarized light micrograph of the mesophase pitch of Example 4. [Figure 5] It is a polarized light micrograph of the mesophase pitch of Example 5. [Figure 6] It is a polarized light micrograph of the mesophase pitch of Comparative Example 1. [Figure 7] It is a polarized light micrograph of the mesophase pitch of Comparative Example 2. [Figure 8] It is a polarized light micrograph of the mesophase pitch of Comparative Example 3. [Figure 9] It is a polarized light micrograph of the mesophase pitch of Comparative Example 4. [Figure 10] It is a polarized light micrograph of the mesophase pitch of Comparative Example 5.

Mode for Carrying Out the Invention

[0010] In this specification, a numerical range represented by "~" means a range including the numerical value described before "~" as the lower limit value and the numerical value described after "~" as the upper limit value.

[0011] 〔First Embodiment〕 The method for producing a mesophase pitch according to this embodiment (hereinafter, also referred to as the production method according to this embodiment) includes a solvent treatment step of removing solvent-insoluble components from petroleum residues using a solvent, and a first heat treatment step of heating the solvent-treated petroleum residues under pressure at a condition of 400 °C or higher and 420 °C or lower to obtain a reaction product, a distillation step of removing light components from the reaction product and distilling the reaction product to obtain a pitch, and a second heat treatment step of heating the pitch at a condition of normal pressure or higher and 453 °C or higher to obtain a mesophase pitch. According to the manufacturing method of this embodiment, by having a solvent treatment step, a first heat treatment step, a distillation step, and a second heat treatment step in this order, a mesophase pitch with a full-flow structure can be efficiently manufactured.

[0012] In this specification, "mesophase pitch" means pitch (solid at room temperature) obtained by the second heat treatment step, or pitch that forms an optically anisotropic structure when the carbide of said pitch is observed with a polarizing microscope. Furthermore, in this specification, when a polarized microscope image of the mesophase pitch is obtained and the mesophase pitch is determined according to the size of the optical structure observed in the image and the area occupied by the optical structure, a mesophase pitch with an optical structure score of 5.0 or higher (preferably 5.5 or higher) is defined as a "mesophase pitch with a full-surface flow structure". The method for determining the optical tissue score will be described later.

[0013] The inventors of the present invention have hypothesized a molecular-level mechanism in which a fully flowable mesophase pitch (FDMC) mainly consists of a mesogenic component that exhibits anisotropy through molecular stacking and a matrix component that promotes molecular stacking of the mesogenic component, and have completed the present invention. A mesogenic component is a polycyclic aromatic compound (for example, a polycyclic aromatic compound with 8 or more rings). Mesogenic molecules have a sheet-like condensed six-membered ring structure and can be stacked by so-called π-π stacking. However, in the raw material residue oil, only a few molecules of aromatic molecules with a low degree of condensation are stacked to form molecular aggregates, and these aggregates are randomly dispersed without orientation toward each other, so they do not exhibit macroscopic optical anisotropy. In addition, amorphous solid carbon contained in trace amounts in the raw material residue oil maintains its amorphous solid state even after heat treatment and does not contribute to optical anisotropy. Therefore, in order to exhibit optical anisotropy in a full-flow structure, it is necessary to remove amorphous solids (corresponding to the solvent treatment step in this embodiment), increase the degree of condensation of aromatic molecules to form mesogen precursors and promote molecular stacking (corresponding to the first heat treatment step in this embodiment), and further, allow the stacked domains of the mesogen precursors to be oriented and immobilized. Orientation and immobilization of domains are achieved by polymerization of mesogen precursors or by increasing the degree of 6-membered ring condensation of mesogen precursors and converting them into mesogen molecules, thereby crosslinking and stacking of domains (corresponding to the second heat treatment step in this embodiment). However, since mesogen precursors are not originally stacked but exist in a random state, a certain degree of fluidity is necessary for the mesogen precursors to stack and for the stacked domains of the mesogen precursors to orient themselves. Mesogen precursors and mesogen molecules themselves do not possess fluidity even when heated, so the matrix molecules play this role. Therefore, the matrix molecules must have a high affinity for mesogen precursors and mesogens and must become fluid when heated. At the same time, the concentration of mesogen precursors must be high enough to allow the mesogen precursors to interact with each other and stack, and for the domains to interact with each other and orient themselves. Therefore, molecules that are neither matrix, mesogen precursor, nor mesogen are removed by distillation (corresponding to the distillation step in this embodiment).

[0014] Therefore, in the manufacturing method according to this embodiment, first, solvent-insoluble components are removed from the petroleum-based residue (solvent treatment step). This is because solvent-insoluble components (solids) are amorphous and do not contribute to the overall flow structure. In the subsequent first heat treatment step, the solvent-treated petroleum-based residue is heated under pressure at a temperature between 400°C and 420°C. By heating petroleum-based residues under pressure, the decomposition of petroleum-based residues is suppressed. Furthermore, heating petroleum-based residues to over 400°C promotes dehydrogenation and cyclization of the petroleum-based residues. On the other hand, heating petroleum-based residues above 420°C increases the likelihood of carbonization, so the upper limit must be set to 420°C or lower. Therefore, in the first heat treatment step, by heating the petroleum-based residue under pressure at a temperature between 400°C and 420°C, dehydrogenation and cyclization of the petroleum-based residue can be promoted while avoiding decomposition and carbonization of the petroleum-based residue. As a result, it is thought that the maximum amount of mesogen precursors is generated, and molecular stacking of the mesogen precursors is further promoted. In the subsequent distillation process, light components are removed from the reaction product to obtain pitch. These light components have a boiling point below 300°C and do not contribute to the full-flow structure. Furthermore, in the second heat treatment step that follows, the light components have a small molecular weight and do not undergo polycondensation, so they do not become mesogens or matrix. In the subsequent second heat treatment step, the pitch is heated at atmospheric pressure or above and at a temperature of 453°C or above to obtain mesophase pitch. If the pitch is heated below 453°C, a flow structure cannot be obtained, and therefore, conversion to mesogen is considered to be insufficient. For this reason, the lower limit of the heating temperature in the second heat treatment step must be set to 453°C or higher. Heating at 453°C or higher makes it easier for the domains of the mesogen precursor generated in the first heat treatment step to crosslink and stack, and as a result, the mesogen precursor is easily converted to mesogen.

[0015] Therefore, according to the manufacturing method of this embodiment, a mesophase pitch with a full-surface flow structure can be efficiently manufactured by performing the first and second heat treatment steps under strictly controlled conditions. In this specification, "efficiently" means that the yield of mesophase pitch in the full-flow structure is high (e.g., 35% or more).

[0016] <Petroleum-based residues> First, let me explain the petroleum-based residues that are used as raw materials. In this specification, petroleum residue means residues generated in either the petroleum refining process or the petrochemical process. In the manufacturing method according to this embodiment, the petroleum residue is preferably at least one selected from the group consisting of cracked residue (e.g., CLO) generated when heavy crude oil is cracked using a fluid catalytic cracking (FCC), vacuum-heated residue (e.g., VR) obtained by further reducing the pressure and distilling the atmospheric distillation residue of crude oil, residue after extracting heavy fractions (preferably heavy fractions suitable for lubricating oil) from the vacuum-heated residue with propane (e.g., PDAS), and ethylene bottom oil. FCC is an abbreviation for Fluid Catalytic Cracking. CLO is an abbreviation for Clarified Oil, also known as decomposed oil. CLO is also commonly referred to as decanted oil and is frequently used in research on binder pitch for steel. VR is an abbreviation for Vacuum Residue, also known as vacuum residue. PDAS is an abbreviation for Propane Deasphalted Asphalt, also known as propane-deasphalted asphalt. Ethylene bottom oil is a liquid produced along with ethylene during naphtha cracking, and it refers to the heavy fraction with the highest boiling point among the naphtha cracking fractions.

[0017] Each step of the manufacturing method according to this embodiment will be described.

[0018] <Solvent treatment process> The solvent treatment process is a process that uses a solvent to remove solvent-insoluble components from petroleum-based residues. Solvent-insoluble matter refers to the insoluble portion of petroleum-based residue when it is dissolved in a solvent. Methods for removing solvent-insoluble components include known solvent treatment methods (e.g., solvent extraction, reduced-pressure heating, reduced-pressure distillation, reduced-pressure concentration, and filtration). Suitable solvents include, for example, pyridine, quinoline, tetrahydrofuran (THF), aliphatic hydrocarbons (e.g., pentane and hexane), and aromatic hydrocarbons (e.g., benzene, toluene, and xylene). These solvents may be used individually or in combination.

[0019] <First heat treatment step> The first heat treatment step is a step in which the solvent-treated petroleum-based residue is heated under pressure at a temperature of 400°C to 420°C to obtain a reaction product. The first heat treatment step can be carried out using a known heating device (e.g., an autoclave). From the viewpoint of generating a larger amount of mesogen precursor, the pressure, temperature, heating rate, and time in the first heat treatment step are preferably within the following ranges.

[0020] ·pressure The pressure in the first heat treatment step is preferably 4 MPa or higher, more preferably 4.5 MPa or higher, and even more preferably 4.8 MPa or higher. The pressure in the first heat treatment step is, for example, 20 MPa or less.

[0021] ·temperature The temperature in the first heat treatment step is preferably 350°C to 470°C, more preferably 380°C to 440°C, and even more preferably 400°C to 420°C.

[0022] • Heating rate The heating rate is preferably 5°C / min to 20°C / min, and more preferably 5°C / min to 15°C / min.

[0023] ·time The heating time in the first heat treatment step is preferably 0.5 hours or more and 1.5 hours or less, more preferably 0.8 hours or more and 1.2 hours or less.

[0024] The first heat treatment step is preferably carried out under conditions of 4.0 MPa or higher, 400°C to 420°C, and 0.5 hours to 1.5 hours.

[0025] • Stirring speed The first heat treatment step is preferably carried out while stirring the solvent-treated petroleum-based residue. The stirring means is not particularly limited. The stirring speed is, for example, between 150 rpm and 1200 rpm.

[0026] The first heat treatment step is preferably carried out under an inert gas atmosphere. Examples of inert gases include nitrogen, helium, and argon. The inert gas may be a single gas or a mixture of two or more gases. Nitrogen is preferred as the inert gas.

[0027] <Distillation Process> The distillation process involves removing light components from the reaction product and distilling the reaction product to obtain pitch. The distillation process can be carried out using known distillation equipment. The distillation process may be carried out under atmospheric pressure or under reduced pressure. The temperature during the distillation process is preferably between 310°C and 330°C. The time in the distillation process is preferably 0.5 hours or more and 3.0 hours or less, more preferably 0.8 hours or more and 2.0 hours or less, and even more preferably 1.0 hour or more and 1.5 hours or less.

[0028] The distillation process is preferably carried out at atmospheric pressure (0.1 MPa), at a temperature of 310°C to 330°C, and for a period of 0.5 hours to 3.0 hours.

[0029] <Second heat treatment step> The second heat treatment step is to obtain mesophase pitch by heating the pitch under conditions of atmospheric pressure or above and a temperature of 453°C or above. The second heat treatment step can be carried out using a known heating device (e.g., an autoclave). In the second heat treatment step, the pressure, temperature, heating rate, and time are preferably within the following ranges from the viewpoint of converting a larger amount of the mesogen precursor into mesogen.

[0030] ·pressure The pressure in the second heat treatment step may be at atmospheric pressure (0.1 MPa) or under pressurized pressure. When the second heat treatment step is carried out under pressure, the pressure is, for example, 3.5 MPa or higher, more preferably 5.0 MPa or higher. The pressure in the first heat treatment step is, for example, 20 MPa or less.

[0031] ·temperature The temperature in the second heat treatment step is preferably 453°C to 490°C, more preferably 453°C to 480°C, even more preferably 453°C to 470°C, and even more preferably 460°C to 470°C.

[0032] • Heating rate The heating rate is preferably 5°C / min to 50°C / min, more preferably 10°C / min to 40°C / min.

[0033] ·time The heating time in the second heat treatment step is preferably 1.0 hour or more and 6.0 hours or less, more preferably 1.0 hour or more and 5.0 hours or less.

[0034] The second heat treatment step may be carried out under the conditions of atmospheric pressure, a temperature of 453°C to 470°C, and a duration of 1.0 hour to 5.0 hours. The second heat treatment step may be carried out under conditions of 3.5 MPa or higher, 453°C to 470°C, and 1.0 hour to 5.0 hours.

[0035] • Stirring speed The second heat treatment step is preferably carried out while stirring the pitch. The stirring means is not particularly limited. The stirring speed is, for example, 150 rpm to 1200 rpm.

[0036] The second heat treatment step is preferably carried out under an inert gas atmosphere. As the inert gas, the inert gas described in the first heat treatment step can be used.

[0037] (Optical structure of mesophase pitch) In the manufacturing method according to the first embodiment, when a polarized microscope image of the mesophase pitch is acquired and the mesophase pitch is determined according to the size of the optical structure observed in the image and the area occupied by the optical structure, it is preferable that the optical structure score is 5.0 or higher, and more preferably 5.5 or higher. If the optical tissue score is 5.0 or higher, the optical tissue in the entire or nearly entire field of view (e.g., 90% or more) of the observation area consists of "Flow domains" and "Flow types". If the optical tissue score is 5.5 or higher, the optical tissue in the entire or nearly entire field of view (e.g., 90% or more) of the observation area consists of "Flow domains" and "Flow types", or consists only of "Flow types". The higher the optical tissue score, the closer the proportion of "Flow types" approaches 100%.

[0038] (Method for determining optical tissue score) The method for determining the optical structure score is described below. Specific determination methods are explained in the Examples section. (i) Isao Mochida, Shuichi Matsuoka, Keiko Maeda, et al. Proceedings of the 16th Coal Science Conference and the 46th Joint Conference of the Fuels Association (1979), pp. 200-206. (ii) Isao Mochida, Yozo Korai, Journal of the Fuel Association, Vol. 64, No. 10 (1985), pp. 796-808

[0039] [Applications of Mesophase Pitch] The mesophase pitch produced by the manufacturing method according to the first embodiment, and the carbide (pitch carbide) obtained by the manufacturing method according to the second embodiment described later, can be applied, for example, to general-purpose carbon materials and high-performance carbon materials. Examples of general-purpose carbon materials include binders for electrodes (e.g., steel binders), high-density isotropic carbon, isotropic carbon materials, graphite, and heat-resistant materials. Mesophase pitch can be suitably used in high-performance carbon materials by taking advantage of its properties such as high elasticity and high conductivity of carbides. Examples of high-performance carbon materials include carbon electrodes (e.g., needle coke, etc.) and carbon fiber raw materials (e.g., impregnation materials for electrodes, etc.).

[0040] [Second Embodiment] The manufacturing method of the second embodiment differs from that of the first embodiment in that it further includes a carbonization step. In other respects, it is the same as the first embodiment. In the description of the second embodiment, components identical to those of the first embodiment will be omitted or simplified.

[0041] <Carbonization process> The carbonization step is a step of carbonizing the mesophase pitch obtained in the second heat treatment step. The carbonization method is not particularly limited, but one example is heating the mesophase pitch under an inert gas atmosphere. As the inert gas, the inert gas described in the first heat treatment step can be used.

[0042] From the viewpoint of ensuring proper carbonization, the carbonization temperature, the time the carbonization temperature is maintained, and the heating rate in the carbonization process are preferably within the following ranges.

[0043] ·Carbonization temperature The carbonization temperature is preferably 450°C to 650°C, more preferably 470°C to 650°C, and even more preferably 500°C to 650°C.

[0044] • Holding time at carbonization temperature The holding time for carbonization temperature refers to the time spent holding the material after reaching the desired carbonization temperature. The holding time at the carbonization temperature is preferably 0.5 hours or more and 4 hours or less, more preferably 0.5 hours or more and 3 hours or less, and even more preferably 0.5 hours or more and 2 hours or less.

[0045] • Heating rate The heating rate in the carbonization process is preferably 1°C / min to 5°C / min, more preferably 1°C / min to 4°C / min, and even more preferably 1°C / min to 3°C / min.

[0046] The carbonization process is preferably carried out under conditions where the carbonization temperature is between 450°C and 650°C, and the duration of holding this carbonization temperature is between 0.5 hours and 4 hours. The carbonization apparatus is not particularly limited as long as it is capable of carbonizing mesophase pitch in a low-oxygen atmosphere (preferably in an inert gas atmosphere), and known carbonization apparatuses can be used.

[0047] The present invention is not limited to the embodiments described above, and any modifications, improvements, etc., that can achieve the objectives of the present invention are included in the present invention. [Examples]

[0048] The following describes examples of the present invention. The present invention is not limited in any way by these examples.

[0049] [Methophase pitch manufacturing method] [Example 1] (Solvent treatment process) Ethylene bottom oil (CBO) was used as the raw material. This CBO is a decomposition residue produced along with ethylene when naphtha is decomposed using a steam cracker (SC). A CBO solution was prepared consisting of CBO (50% by mass) and tetrahydrofuran (THF) (50% by mass). The CBO solution was stirred at 300 rpm for 30 minutes using a hot plate stirrer (Heidolph, part number: MR Hei-TeC), and then filtered under reduced pressure using quantitative filter paper. Insoluble THF remained on the quantitative filter paper. THF was removed from the filtrate by concentrating it under reduced pressure at 60°C and 0.008 MPa. In this manner, THF-insoluble components were removed from CBO, and solvent-treated CBO was obtained. The THF-insoluble portion of CBO was less than 0.5% by mass relative to the total volume of the CBO solution. 150 g was weighed from the solvent-treated CBO. This was used as the sample, and the first heat treatment step was performed.

[0050] (First heat treatment step) The sample (solvent-treated CBO (150g)) was placed in an autoclave equipped with a stirring blade. After replacing the inside of the autoclave with nitrogen gas, the initial pressure was set to 0.5 MPa. Next, the sample was heated to 410°C at a rate of 10°C / min while being stirred at 200 rpm using a band heater, and then heated at 410°C for 1 hour to convert the sample into a heavy oil. The pressure during the reaction was controlled at 5 MPa. Next, the band heater was removed, and the heavy oil, which was the reaction product, was air-cooled to below 30°C to vent the gas from the system. The heavy oil was recovered directly from the autoclave and quantified, and the yield from the previous process (solvent-treated CBO) was calculated.

[0051] (Distillation process) Next, the heavy oil was distilled at atmospheric pressure and 320°C (heating rate 10°C / min) for 1 hour to remove the light components and convert it into pitch. The pitch was quantified, and the yield from the previous process (CBO after the first heat treatment) was calculated.

[0052] (Second heat treatment step) The pitch after the distillation process was placed in an autoclave. After purging the autoclave with nitrogen gas, the temperature was raised to 460°C at a rate of 40°C / min using a band heater, and the pitch was heated at 5 MPa and 460°C for 3 hours to obtain mesophase pitch. Next, the band heater was removed, and the mesophase pitch was air-cooled to below 30°C to vent the gas from the system. The mesophase pitch was recovered directly from the autoclave and quantified, and the yield from the previous process (distillation process) was calculated.

[0053] [Example 2] The mesophase pitch of Example 2 was obtained in the same manner as in Example 1, except that the pressure in the second heat treatment step was changed from 5 MPa to atmospheric pressure (0.1 MPa).

[0054] [Example 3] The mesophase pitch of Example 3 was obtained in the same manner as in Example 1, except that the pressure in the second heat treatment step was changed from 5 MPa to 10 MPa.

[0055] [Example 4] In the second heat treatment step, the pitch was heated at atmospheric pressure (0.1 MPa) and 470°C for 1 hour, except that the mesophase pitch of Example 4 was obtained in the same manner as in Example 1.

[0056] [Example 5] The mesophase pitch of Example 5 was obtained in the same manner as in Example 1, except that the temperature in the second heat treatment step was changed from 460°C to 470°C.

[0057] [Comparative Example 1] The mesophase pitch of Comparative Example 1 was obtained in the same manner as in Example 1, except that the first heat treatment step and distillation step were not performed.

[0058] [Comparative Example 2] The mesophase pitch of Comparative Example 2 was obtained in the same manner as in Example 2, except that the first heat treatment step was not performed.

[0059] [Comparative Example 3] The mesophase pitch of Comparative Example 3 was obtained in the same manner as in Example 1, except that the first heat treatment step was not performed.

[0060] [Comparative Example 4] The mesophase pitch of Comparative Example 4 was obtained in the same manner as in Example 1, except that the first heat treatment step was omitted and the pressure in the second heat treatment step was changed from 5 MPa to 10 MPa.

[0061] [Comparative Example 5] The mesophase pitch of Comparative Example 5 was obtained in the same manner as in Example 4, except that the temperature in the second heat treatment step was changed from 470°C to 450°C.

[0062] 〔evaluation〕 <Optical structure of mesophase pitch> The mesophase pitch was observed using a polarizing microscope (Leica Microsystems, DM2700P) in the following manner. A sample (solid, 0.5 g) was taken from the mesophase pitch obtained in each example. This sample was encapsulated in resin, and the resin was polished to prepare a sample for microscopic observation. The polarizing microscope was set to crossed nicols, and a quartz plate was placed inside to observe the sample for microscopic observation. Figures 1-10 are polarizing microscope images of the optical structure of mesophase pitch in Examples 1-5 and Comparative Examples 1-5. Note that the polarizing microscope images of Examples 1-2 show the "flow domain" when observed in a different field of view.

[0063] <Optical structure score of mesophase pitch> For determining the optical structure score, mesophase pitch (solid, 2g) obtained in the second heat treatment step was used as the sample. The optical structure score was determined according to the method described in (i) above in the proceedings of the 16th Coal Science Conference and the 46th Joint Conference of the Fuels Association, and (ii) in the Fuels Association Journal, following the steps (1) to (3) below. The results are shown in Table 2.

[0064] (Judgment method) (1) Two polarized light microscope images were obtained for each sample, with different fields of view. The observation area per image was 1.2 mm × 1.8 mm. (2) After visually confirming the size of the optical tissue, it was measured on the image. (3) In accordance with the criteria shown in Table 1, the optical tissue was scored according to the size of the optical tissue observed in the image and the area occupied by the optical tissue, and the average score for each sample was calculated.

[0065] [Table 1]

[0066] Furthermore, the mesophase pitch obtained in each example was evaluated according to the following evaluation criteria. Examples 1-5 and Comparative Example 3 yielded a mesophase pitch with a full-surface flow structure (see Figures 1-5 and 8). Specifically, in Examples 1 and 2, only the optical structure of the "Flow domain" was observed. In Examples 3 to 5 and Comparative Example 3, both the optical structure of the "Flow domain" and the "Flow type" were observed. Comparative Examples 1-2 and 4-5 had low optical tissue scores because tissues other than the "Flow domain" were observed (see Figures 6-7 and 9-10).

[0067] (Evaluation Criteria) A: Optical tissue score of 5.5 or higher B: Optical tissue score is 4.5 or higher, but less than 5.5. C: Optical tissue score is less than 4.5

[0068] <Manufacturing efficiency> The yield of mesophase pitch was used as an indicator of manufacturing efficiency. The results are shown in Table 2. The mesophase pitch yield is the yield from the CBO (raw material) before solvent treatment. Furthermore, the efficiency of the manufacturing process was evaluated according to the following criteria. (Evaluation Criteria) A: Yield of 35.0% or higher B: Yield is between 30.0% and less than 35.0% C: Yield is less than 30.0%

[0069] [Table 2]

[0070] As shown in Table 2, Examples 1 to 5, in which the solvent treatment step, the first heat treatment step, the distillation step, and the second heat treatment step were carried out in this order, showed higher optical structure scores and higher mesophase pitch yields compared to Comparative Examples 1 to 4, in which the first heat treatment step was not carried out, and Comparative Example 5, in which the second heat treatment step was carried out at a temperature of less than 453°C. Comparing Example 1 and Comparative Example 3, which differ only in whether or not the first heat treatment step was performed, the yield of Example 1 (36.4%) was 5.6% higher than the yield of Comparative Example 3 (30.8%). Comparing Example 4 and Comparative Example 5, which differed only in the temperature during the second heat treatment step, Example 4 showed a high optical structure score (5.60), while Comparative Example 5 showed a low optical structure score (3.00) because isotropic structures (iso) were observed in the optical structure. Based on the above, it was confirmed that, by strictly controlling the manufacturing conditions, mesophase pitch with a full-flow structure can be efficiently manufactured using the manufacturing methods of Examples 1 to 5.

Claims

1. A solvent treatment process that uses a solvent to remove solvent-insoluble components from petroleum-based residues, A first heat treatment step involves heating the solvent-treated petroleum-based residue under pressure at a temperature of 400°C to 420°C to obtain a reaction product. A distillation step to remove light components from the reaction product and distill the reaction product to obtain pitch, The process includes a second heat treatment step of obtaining a mesophase pitch by heating the aforementioned pitch under conditions of atmospheric pressure or above and a temperature of 453°C or above. A method for manufacturing mesophase pitch.

2. The first heat treatment step is a step of heating the solvent-treated petroleum-based residue under a pressure of 4 MPa or more. A method for producing mesophase pitch according to claim 1.

3. The first heat treatment step is a step of heating the solvent-treated petroleum-based residue for 0.5 hours or more and 1.5 hours or less. A method for producing mesophase pitch according to claim 1 or claim 2.

4. The second heat treatment step is a step of heating the pitch to a temperature of 453°C or higher and 470°C or lower. A method for manufacturing mesophase pitch according to any one of claims 1 to 3.

5. The second heat treatment step is a step of heating the pitch for 1.0 hour or more and 5.0 hours or less. A method for producing mesophase pitch according to any one of claims 1 to 4.

6. The aforementioned petroleum-based residue is at least one selected from the group consisting of cracking residue generated when heavy crude oil is cracked using a fluid catalytic cracking unit, vacuum distillation residue obtained by further reducing the pressure of the atmospheric distillation residue of crude oil, the residue after extracting the heavy fraction from the vacuum distillation residue with propane, and ethylene bottom oil. A method for manufacturing mesophase pitch according to any one of claims 1 to 5.

7. The invention further comprises a carbonization step for carbonizing the mesophase pitch, A method for producing mesophase pitch according to any one of claims 1 to 6.

8. The carbonization process is carried out under the conditions of a temperature of 450°C or higher and 650°C or lower, and a holding time of 0.5 hours or higher and 4 hours or lower. A method for producing mesophase pitch according to claim 7.

9. When a polarized microscope image of the mesophase pitch is acquired, and the mesophase pitch is determined according to the size of the optical tissue observed in the image and the area occupied by the optical tissue, the optical tissue score is 5.0 or higher. A method for producing mesophase pitch according to claim 7 or claim 8.

10. When a polarized microscope image of the mesophase pitch is acquired, and the mesophase pitch is determined according to the size of the optical tissue observed in the image and the area occupied by the optical tissue, the optical tissue score is 5.5 or higher. A method for manufacturing mesophase pitch according to any one of claims 7 to 9.

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