A solvent oil, its preparation method and uses

Abstract

The present application provides a solvent oil, a preparation method and use thereof. The solvent oil is used for refining treatment of coal liquefied pitch, has good solid-liquid separation effect, is easy to recycle and reuse, can obtain refined pitch with high yield, low ash content and low quinoline insoluble content under the condition of low solvent oil consumption, and can meet the application requirements of high-end carbon materials. The solvent oil contains C 10 ~C 16 paraffins, cycloparaffins with ring number of 1-3, monocyclic aromatic hydrocarbons, bicyclic aromatic hydrocarbons and tricyclic aromatic hydrocarbons; the content of the C 10 ~C 16 paraffins is 5.0-10.5 wt%, the content of the cycloparaffins is 10.0-25.3 wt%, the content of the monocyclic aromatic hydrocarbons is 30.0-44.0 wt%, the content of the bicyclic aromatic hydrocarbons is 20.0-50.0 wt%, and the content of the tricyclic aromatic hydrocarbons is 0.5-5.0 wt%; the nitrogen content of the solvent oil is 200-2500 ppm, the sulfur content is 5-500 ppm, and the distillation range of the solvent oil is 170-350 DEG C.

Description

TECHNICAL FIELD

[0001] The present application relates to the extraction refining treatment technology of coal liquefaction pitch, and particularly relates to a solvent oil and a preparation method and use thereof. BACKGROUND

[0002] Coal liquefaction pitch is a by-product in the process of coal direct liquefaction, accounting for about 20-30% of the coal amount, and mainly composed of asphaltene, liquefied heavy oil, unreacted coal, minerals and catalyst, with the characteristics of high ash, high sulfur and high calorific value. The 1080000 tons / year coal direct liquefaction demonstration device produces about 700000 tons of coal liquefaction pitch per year, which is mainly used for coal gasification or combustion, and the utilization is extensive, which affects the technical and economic benefits and the green development of the industry. Due to high-temperature hydrogenation, coal liquefaction pitch has the characteristics of high hydrogen-carbon ratio and high coking value, and is an excellent raw material for high-end carbon materials such as mesophase pitch carbon fiber and high-quality needle coke, but the components of coal liquefaction pitch are complex, and the ash content and solid content are high, so the refined pitch with ash content and quinoline insoluble content less than 1000 ppm, even 50 ppm, must be obtained through refining and separation to meet the requirements of high-end carbon materials.

[0003] Solvent extraction is an effective method for refining and separating coal liquefaction pitch, and the selection of solvent is the first key. There are four types of conventional extraction solvents: the first type is a chemical reagent, such as methanol, n-heptane, n-hexane, cyclohexane, carbon disulfide, acetone, benzene, toluene, tetrahydrofuran, furfural, N-methyl pyrrolidone, pyridine, N,N-dimethylacetamide and quinoline, or a mixture of one or more thereof; the second type is one or a mixture of more than one of aliphatic solvent oils such as petroleum ether, gasoline, kerosene and diesel; the third type is a mixture of one or more of coal tar distillate oils such as light oil, phenol oil, naphthalene oil, wash oil and anthracene oil; and the fourth type is a mixture of one or more of distillate oils in the process of coal direct liquefaction, such as coal liquefaction crude oil distillate and hydrogenated stable distillate oil.

[0004] Patent CN202311729937.8 discloses an extraction method of coal liquid residue, comprising the following steps: S1, grinding, primary drying, deashing treatment and secondary drying of the coal liquid residue; S2, adding an extractant to the coal liquid residue treated in step S1, and obtaining a filter cake and an extraction liquid after ultrasonic treatment and filtration; S3, repeating step S2 for the filter cake obtained in step S2 to obtain an extraction liquid and a raffinate residue; and collecting all the extraction liquids by rotary evaporation to obtain an extract. In step S2, the extractant is selected from any one of petroleum ether, methanol, cyclohexane, CS2, benzene, acetone and a mixture of CS2.

[0005] Patent CN202110614074.4 discloses a method for extracting coal direct liquefaction oil residue with coking crude benzene, which comprises: mixing coking crude benzene with coal direct liquefaction oil residue, then extracting, and then performing solid-liquid separation on the obtained mixture to obtain asphalt-like substances and mixed benzene. The invention mixes coal direct liquefaction oil residue with coking crude benzene, then extracts, and in the extraction process, the olefins and sulfur compounds in the coking crude benzene can further destroy the associated structure in the coal direct liquefaction oil residue, and at the same time, the purification of the coking crude benzene can be realized in the solvent recovery process, and the coking crude benzene is refined; the efficient extraction of the coal direct liquefaction oil residue is realized, and the asphalt-like substances with excellent quality are obtained, and the cost is low.

[0006] Patent CN201810812618.6 discloses a separation system and method for coal direct liquefaction oil residue. The separation system comprises an extraction device, a horizontal screw centrifuge, a disc centrifuge and a distillation device. The extraction agent is a tar-based solvent with a distillation range of 200-320°C, preferably wash oil and / or anthracene oil.

[0007] Patent CN201811649445.7 discloses a high-efficiency deashing method for coal liquefaction residue. The method uses two-stage static settling separation technology to remove the ash content of coal liquefaction residue to below 100 ppm, so that it can meet the conditions for preparing high-value-added carbon materials, thereby improving enterprise production efficiency and saving resources. The reagent used in the invention is economical and reasonable, the solvent required is easy to recycle, and the treatment process has the advantages of simple operation, good deashing effect, high efficiency, low energy consumption, and environmental protection. It solves the problems of long settling time, high energy consumption, and low deashing rate in current processes. The composite solvent is a mixture of aliphatic hydrocarbon solvent and aromatic hydrocarbon solvent in a mass ratio of 1:0.10-1, wherein the aliphatic hydrocarbon solvent is any one or more of n-heptane, 120# solvent oil, gasoline, kerosene, and diesel, and the aromatic hydrocarbon solvent is any one or more of light oil, phenol oil, naphthalene oil, wash oil, and anthracene oil.

[0008] Patent CN201510317246.6 provides a method for treating coal direct liquefaction residue. The method comprises: using an extraction solvent to extract coal direct liquefaction residue to obtain an extraction mixture; performing primary solid-liquid separation on the extraction mixture to obtain primary clear liquid and primary concentrated phase; performing secondary solid-liquid separation on part or all of the primary clear liquid to obtain secondary clear liquid and secondary concentrated phase; performing tertiary solid-liquid separation on part or all of the secondary clear liquid to obtain tertiary clear liquid and tertiary concentrated phase; performing secondary solid-liquid separation on part of the primary clear liquid, and performing clear liquid solvent recovery treatment on the remaining primary clear liquid to obtain primary pitch; performing tertiary solid-liquid separation on part of the secondary clear liquid, and performing clear liquid solvent recovery treatment on the remaining secondary clear liquid to obtain secondary pitch; and performing clear liquid solvent recovery treatment on all of the tertiary clear liquid to obtain tertiary pitch. The method can obtain three pitch products, which is beneficial to improve the additional income value of pitch in coal liquefaction residue. The extraction solvent includes but is not limited to one or more of the group consisting of tetrahydrofuran, furfural, N-methyl pyrrolidone, quinoline, toluene, coal direct liquefaction distillate oil or coal tar distillate oil.

[0009] Patent CN201310211245.4 provides a method for separating pitch-like substances from coal direct liquefaction residue and application. The method comprises the following steps: S1, mixing coal direct liquefaction residue with an extraction solvent, hot-solvent extraction, to obtain a hot-solvent extraction mixture; S2, performing solid-liquid separation on the hot-solvent extraction mixture to obtain an extraction liquid; and S3, performing solvent recovery on the extraction liquid to obtain pitch-like substances; wherein the extraction solvent is coal tar or coal tar distillate oil. Using coal tar or coal tar distillate oil as an extraction solvent to separate coal direct liquefaction residue to prepare pitch-like substances improves the extraction rate, reduces the cost, and obtains a pitch-like substance mixture with moderate volatile matter and high softening point. The pitch-like substances in the mixture can be used as raw materials for different grades of carbon materials according to their different properties.

[0010] Patent CN201310209911.0 discloses a method for separating liquefied heavy oil and asphalt-like substances from coal direct liquefaction residue. The method includes the following steps: S1, mixing the coal direct liquefaction residue with an extraction solvent, stirring, and performing thermal extraction to obtain a thermally extracted mixture; S2, performing a primary solid-liquid separation on the thermally extracted mixture to obtain a primary extract and a primary raffinate; S3, performing a secondary solid-liquid separation on the primary extract to obtain a secondary extract and a secondary raffinate; S4, recovering the solvent from the secondary extract to obtain an extract; and S5, mixing the extract with a subcritical reverse precipitation solvent, performing subcritical reverse solvent precipitation, and separating to obtain liquefied heavy oil and asphalt-like substances. This invention utilizes the difference in the solubility of the subcritical reverse precipitation solvent for organic matter in coal direct liquefaction residue under subcritical conditions, combined with a solid-liquid separation process, to effectively separate liquefied heavy oil and asphalt-like substances. The extraction solvent is one or more of the following: normal side-stream oil, reduced-volume side-stream oil, and hydrostabilized side-stream oil produced during the direct coal liquefaction process; the distillation range of the extraction solvent is 120–280°C; the subcritical reverse precipitation solvent is one or more of the following: normal top-volume oil, reduced-volume top-volume oil, and hydrostabilized top-volume oil produced during the direct coal liquefaction process; the distillation range of the subcritical reverse precipitation solvent is 40–160°C.

[0011] Developing high-efficiency, low-cost, easily recyclable, and industrially viable extraction solvent oils suitable for large-scale production is of great significance, considering the composition and physical properties of coal liquefaction pitch. Summary of the Invention

[0012] This invention provides a solvent oil, its preparation method, and its uses. Using the solvent oil provided by this invention for the refining of coal liquefaction pitch results in good solid-liquid separation, easy recycling and reuse of the solvent oil, and the ability to obtain refined pitch with high yield, low ash content, and low quinoline insoluble content with a low solvent oil consumption rate, thus meeting the application requirements of high-end carbon materials.

[0013] To achieve its objective, the present invention provides the following technical solution:

[0014] This invention provides a solvent oil containing C 10 ~C 16 Alkanes, cycloalkanes with 1 to 3 rings, monocyclic aromatics, dicyclic aromatics, and tricyclic aromatics;

[0015] Based on the total mass of the solvent oil, the C 10 ~C 16 The content of alkanes is 5.0–10.5 wt%, the content of cycloalkanes is 10.0–25.3 wt%, the content of monocyclic aromatics is 30.0–44.0 wt%, the content of dicyclic aromatics is 20.0–50.0 wt%, and the content of tricyclic aromatics is 0.5–5.0 wt%.

[0016] The solvent oil has a nitrogen content of 200–2500 ppm and a sulfur content of 5–500 ppm, and its distillation range is between 170 and 350°C.

[0017] Furthermore, the density of the solvent oil is 0.93–1.02 g / cm³. 3 .

[0018] The present invention also provides a method for preparing the solvent oil described above, comprising the following steps:

[0019] Coal tar distillate and crude coal direct liquefaction oil are mixed in a mass ratio of 10:90 to 90:10 and then subjected to hydrogenation. The mixture is then distilled to obtain a fraction with a distillation range of 170 to 350°C, thus obtaining the solvent oil.

[0020] In some embodiments, the coal tar distillate is a coal tar fraction with a distillation range of 170–400°C;

[0021] The crude oil from direct coal liquefaction is a crude oil fraction from direct coal liquefaction with a distillation range of 200–450°C.

[0022] In a preferred embodiment, the hydrogenation reaction is carried out in the presence of a hydrogenation catalyst, which includes a support and an active component; the active component includes Ni, Mo and P, and the mass contents of Ni, Mo and P in the hydrogenation catalyst are 4.71-5.89%, 8.87-10.93% and 0.74-0.87%, respectively.

[0023] In some embodiments, the support is an Al2O3-SiO2 support, for example, wherein the Al2O3 content is 45-72 wt% and the SiO2 content is 28-55 wt%.

[0024] In some embodiments, the conditions for the hydrogenation reaction include: a temperature of 350–380°C, a pressure of 8–15 MPa, a hydrogen-to-oil ratio (v / v) of 500–1000, and a volume hourly space velocity (VHSV) of 0.6–1.5 h⁻¹. -1 ;

[0025] Preferably, the hydrogenation reaction is carried out in a fixed-bed reactor, a suspended-bed reactor, or a fluidized-bed reactor.

[0026] The present invention also provides the application of the solvent oil described above or the solvent oil prepared by the preparation method described above in the refining treatment of coal liquefaction pitch.

[0027] The present invention also provides a method for refining coal liquefaction pitch, comprising the following steps:

[0028] (1) Coal liquefaction pitch and solvent oil are mixed evenly at a mass ratio of 1:2 to 4, heated to 80 to 130°C, and stirred at a constant temperature for 0.5 to 2 hours to obtain a mixed slurry; the solvent oil is the solvent oil described above or the solvent oil prepared by the preparation method described above.

[0029] (2) The mixed slurry is centrifuged to obtain a light phase and a heavy phase;

[0030] (3) Separate the solvent oil from the light phase to obtain refined coal liquefaction pitch;

[0031] Preferably, in step (2), the centrifugation is carried out in a horizontal screw centrifuge. Preferably, the centrifugation factor of the horizontal screw centrifuge is 600-1800g.

[0032] Preferably, the heavy phase is heated to 200-250°C to soften it into a fluid, and then the solvent oil therein is recovered.

[0033] Preferably, the solvent oil separated from the light phase and the solvent oil recovered from the heavy phase are mixed and recycled for use in step (1).

[0034] The technical solution provided by this invention has the following beneficial effects:

[0035] (1) Compared with the prior art, the solvent oil provided by the present invention can realize the low-cost and high-efficiency industrial production of coal liquefaction pitch refining. It can prepare refined pitch with high yield, low ash content and low quinoline insoluble content under the premise of low solvent oil consumption. For example, it can obtain refined pitch with ash content of less than 1000 ppm or even less than 100 ppm and quinoline insoluble content of less than 2000 ppm, while the yield reaches 48-58%, which can meet the application requirements of high-end carbon materials.

[0036] (2) The solvent oil provided by the present invention has a low preparation cost, a wide range of raw material sources, high extraction efficiency for coal liquefaction pitch, good solid-liquid separation effect, and easy recycling and reuse, making it suitable for large-scale industrial applications. Detailed Implementation

[0037] To facilitate understanding of the present invention, the following description, in conjunction with embodiments, will further illustrate the invention. It should be understood that the following embodiments are merely for a better understanding of the invention and do not imply that the invention is limited to these embodiments.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The term "and / or" may be used herein to include any and all combinations of one or more of the associated listed items.

[0039] This invention provides a solvent oil containing C 10 ~C 16 Alkanes, cycloalkanes with 1 to 3 rings, monocyclic aromatics, dicyclic aromatics, and tricyclic aromatics;

[0040] Based on the total mass of the solvent oil, the C 10 ~C 16 The content of alkanes is 5.0–10.5 wt%, the content of cycloalkanes is 10.0–25.3 wt%, the content of monocyclic aromatics is 30.0–44.0 wt%, the content of dicyclic aromatics is 20.0–50.0 wt%, and the content of tricyclic aromatics is 0.5–5.0 wt%.

[0041] The solvent oil has a nitrogen content of 200–2500 ppm and a sulfur content of 5–500 ppm, and the distillation range of the solvent oil is between 170 and 350°C.

[0042] Furthermore, the density of the solvent oil is 0.93–1.02 g / cm³. 3 .

[0043] The term "cycloalkanes with 1 to 3 rings" specifically refers to monocyclic alkanes, dicyclic alkanes, and tricyclic alkanes.

[0044] To address the problems of complex coal liquefaction pitch components, difficulty in extracting asphalt, difficulty in separating nano-sized particles, and difficulty in recovering and reusing extraction solvents, the present invention provides the above-mentioned solution mainly composed of C 10 ~C 16 Composed of alkanes, cycloalkanes with 1 to 3 rings, monocyclic aromatics, dicyclic aromatics, and tricyclic aromatics, with a distillation range between 170 and 350°C, and a preferred density of 0.93 to 1.02 g / cm³. 3 The inventors have discovered that using this solvent oil in the extraction and refining of coal liquefaction pitch can achieve efficient extraction, refining and separation of coal liquefaction pitch. Furthermore, this solvent oil is easy to recover and reuse, has good solid-liquid separation effect, high extraction rate, low solvent oil consumption, and can obtain refined pitch with characteristics such as high yield, low ash content and low quinoline insoluble content.

[0045] The present invention also provides a method for preparing the solvent oil described above, comprising the following steps:

[0046] Coal tar distillate and crude coal direct liquefaction oil are mixed in a mass ratio of 10:90 to 90:10 and then subjected to hydrogenation. The mixture is then distilled to obtain a fraction with a distillation range of 170 to 350°C, thus obtaining the solvent oil.

[0047] Preferably, the coal tar distillate is a coal tar fraction with a distillation range of 170–400°C. The specific preparation process of the coal tar fraction is well known in the art and can be obtained using conventional processes familiar to the art. For example, coal tar is obtained through coal dry distillation, and after pretreatment such as dehydration, desalination, and desolidification, it is then obtained through atmospheric distillation, vacuum distillation, or a combination of both to obtain a coal tar distillate with a distillation range of 170–400°C.

[0048] Preferably, the crude oil from direct coal liquefaction is a crude oil fraction with a distillation range of 200–450°C. The specific preparation process of the crude oil is well known in the art and can be obtained using conventional processes familiar to the art. For example, coal is washed, dried, ground, and sieved to below 100 micrometers, then mixed with a catalyst (e.g., a nano-sized iron-based catalyst) and a coal direct liquefaction circulating solvent to prepare a coal-oil slurry of a certain concentration, such as a 45 wt% coal-oil slurry. This slurry is then hydrogenated and liquefied at 450–460°C and 19 MPa. The liquefaction product is then passed through high- and medium-pressure separators and atmospheric and vacuum distillation to obtain crude oil with a distillation range of 200–450°C.

[0049] Further, the hydrogenation reaction is carried out in the presence of a hydrogenation catalyst. In a preferred embodiment, the hydrogenation catalyst comprises a support and an active component; the active component comprises Ni, Mo, and P, wherein the mass contents of Ni, Mo, and P in the hydrogenation catalyst are 4.71–5.89%, 8.87–10.93%, and 0.74–0.87%, respectively; preferably, the support is an Al2O3-SiO2 support, for example, wherein the Al2O3 content is 45–72 wt% and the SiO2 content is 28–55 wt%.

[0050] In a preferred embodiment, the conditions for the hydrogenation reaction include: a temperature of 350–380°C, a pressure of 8–15 MPa, a hydrogen-to-oil ratio (v / v) of 500–1000, and a volume hourly space velocity (VHSV) of 0.6–1.5 h⁻¹. -1 ;

[0051] Preferably, the hydrogenation reaction is carried out in a fixed-bed reactor, a suspended-bed reactor, or a fluidized-bed reactor.

[0052] The solvent oil provided in this invention is obtained by blending crude coal liquefaction oil fraction and coal tar fraction oil in a mass ratio of 10:90 to 90:10, and by hydrogenation and distillation. Compared with pure chemical reagents, it has the advantages of low cost and easy operation; compared with crude coal liquefaction oil alone, it has the advantages of stable properties, high extraction rate, and good swelling properties; compared with coal tar fraction oil alone, it has the advantages of low sulfur and nitrogen content, good solid-liquid separation effect, and easy recovery and reuse.

[0053] The solvent oil prepared by the method of this invention is particularly suitable for the efficient extraction of asphalt-soluble substances and the rapid removal of nanoscale solid particles from coal liquefaction pitch. The monocyclic, bicyclic, and tricyclic aromatic hydrocarbons contained in the solvent oil are beneficial for ensuring the efficient extraction of asphaltene, pre-asphaltene, and other asphaltene-like substances from coal liquefaction pitch. The alkanes and cycloalkanes contained in the solvent oil, on the one hand, help reduce the viscosity of the coal liquefaction pitch extraction system, and on the other hand, play a role in flocculating and recombining asphalt components, carrying nanoscale particles, enhancing solid-liquid separation, and increasing the solid particle removal rate. The main component of the provided solvent oil is C 10 ~C 16 The solvent oil, containing alkanes, monocyclic alkanes, dicyclic alkanes, tricyclic alkanes, monocyclic aromatics, dicyclic aromatics, and tricyclic aromatics, has a distillation range of 170–350°C and a density of 0.93–1.02 g / cm³. 3 While achieving efficient extraction, refining, and separation of coal liquefaction pitch, it also exhibits good swelling properties for raffinate solids and insolubles, ensuring the flowability and transportability of the material. Furthermore, the solvent oil is not easily lost through volatilization, is easy to operate, and is easy to distill, recover, and reuse, thus providing a guarantee for the industrial and large-scale application of coal liquefaction pitch extraction and refining technology.

[0054] In another aspect, the present invention also provides the application of the solvent oil described above or the solvent oil prepared by the preparation method described above in the refining treatment of coal liquefaction pitch.

[0055] In another aspect, the present invention provides a method for refining coal liquefaction pitch, comprising the following steps:

[0056] (1) Coal liquefaction pitch and solvent oil are mixed evenly at a mass ratio of 1:2 to 4, and stirred at a constant temperature of 80 to 130°C for 0.5 to 2 hours to obtain a mixed slurry; the solvent oil is the solvent oil described above or the solvent oil prepared by the preparation method described above.

[0057] (2) The mixed slurry is centrifuged to obtain a light phase and a heavy phase; the solvent oil of the present invention is used to extract coal liquefaction pitch through step (1), and then solid-liquid separation is achieved by continuous horizontal screw centrifugation to remove unreacted coal, minerals and catalysts and other solid insolubles, to obtain a centrifuged light phase and a centrifuged heavy phase, wherein the solid insolubles are enriched in the heavy phase.

[0058] (3) The solvent oil in the light phase is separated to obtain refined coal liquefaction pitch. Specifically, for example, the solvent oil is separated and recovered from the light phase by distillation to obtain refined coal liquefaction pitch.

[0059] The solvent oil provided by this invention is particularly suitable as a highly efficient refining and separation solvent for coal liquefaction pitch, enabling efficient extraction of soluble substances such as asphalt and rapid removal of nanoscale solid particles. The monocyclic, bicyclic, and tricyclic aromatic hydrocarbons contained in the solvent oil facilitate the efficient extraction of asphaltene, pre-asphaltene, and other asphaltene-like substances from coal liquefaction pitch. The alkanes and cycloalkanes contained in the solvent oil help reduce the viscosity of the coal liquefaction pitch extraction system, while also flocculating and recombining asphalt components, carrying nanoscale particles, enhancing solid-liquid separation, and increasing the solid particle removal rate. The solvent has a distillation range of 170–350℃ and a density of 0.93–1.02 g / cm³. 3 While achieving efficient extraction, refining and separation of coal liquefaction pitch, it also has good swelling properties for raffinate solid insoluble matter, ensuring the flowability and transportability of materials. At the same time, the solvent is not easily lost due to volatilization and is easy to recover and reuse by distillation. It is highly operable and can realize the industrial and large-scale application of coal liquefaction pitch extraction and refining technology.

[0060] Using the solvent oil provided by this invention for the extraction and refining of coal liquefaction pitch according to the above-described refining method can achieve efficient solid-liquid separation, recover most of the solvent oil, reduce solvent consumption, and obtain refined pitch with characteristics such as high yield, low ash content, and low quinoline insoluble content, which can meet the application requirements of high-end carbon materials. For example, the refining method of this invention can obtain refined coal liquefaction pitch with an ash content of 50-1000 ppm, a quinoline insoluble content of 80-2000 ppm, a softening point of 150-190℃, and a yield of 48-58%.

[0061] Preferably, in step (2), the centrifugation is carried out in a horizontal screw centrifuge. Preferably, the centrifugation factor of the horizontal screw centrifuge is 600-1800g.

[0062] Preferably, the heavy phase obtained in step (2) is heated to 200-250°C to soften it into a fluid, and then the solvent oil therein is recovered. The solvent oil of the present invention is used for the refining of coal liquefaction pitch to separate a heavy phase with a high content of solid insoluble matter, which can be softened into a fluid with a viscosity of 200-2000 cp (measured by a rotational viscometer at 200-250°C). The solvent is easy to transport and recover. For example, the solvent can be recovered by continuously transporting the fluid to a vacuum spray dryer or a belt dryer. After recovering the solvent, a raffinate solid residue with a solvent residue of <2.5% and a yield of about 42.0-52.5% can be obtained.

[0063] Preferably, the solvent oil separated from the light phase and the solvent oil recovered from the heavy phase are mixed and recycled for use in step (1). Using the solvent oil of this invention for the refining of coal liquefaction pitch results in low solvent oil consumption, stable solvent oil properties, and easy recycling of the solvent oil. The solvent oil consumption rate is 0.2–1.0 wt% of the coal liquefaction pitch processing volume.

[0064] The formation process of coal liquefaction pitch is well known in the art. Specifically, after coal is washed, dried, ground, and sieved (e.g., sieved to below 100 micrometers), it is prepared into an oil-coal slurry. This slurry is then mixed with a catalyst (e.g., a nano-sized iron-based catalyst) and a coal direct liquefaction circulating solvent to prepare an oil-coal slurry of the desired concentration (e.g., 45 wt%). After hydrogenation liquefaction and separation, the resulting heavy product is obtained, for example, by hydrogenation liquefaction at 450–460°C and 19 MPa. The product is then separated into gaseous and liquid phases by high- and medium-pressure separators and atmospheric and vacuum distillation. The resulting heavy product is coal liquefaction pitch. Coal liquefaction pitch mainly consists of pitch-like substances, heavy liquefied oil, unconverted coal, minerals, and a catalyst. Unrefined coal liquefaction pitch has an ash content of, for example, 15.0–20.0 wt%, a quinoline-insoluble content of, for example, 40.0–50.0 wt%, and a softening point of, for example, 165–195°C.

[0065] Where specific experimental steps or conditions are not specified in the examples, the corresponding conventional experimental steps or conditions in this technical field can be followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0066] In the following examples and comparative examples:

[0067] Yield of refined coal liquefaction pitch: Where m R To improve the quality of refined coal liquefaction pitch, m o For the quality of coal liquefaction pitch raw materials;

[0068] Yield of solid residue from extraction: Where m s For the quality of the solid residue from extraction, m o For the quality of coal liquefaction pitch raw materials;

[0069] Solvent oil consumption rate: Among them G o For the quality of solvent oil feed, G R For the quality of solvent oil recovery, m o The quality of coal liquefaction pitch raw materials.

[0070] The preparation steps of the catalyst NiMoP / Al2O3-SiO2 used in the following examples are as follows:

[0071] Boehmite powder, SiO2 sol, dilute nitric acid (31.68 wt%), guar gum powder, and water were mixed in a mass ratio of 2:1:0.5:0.5:1, kneaded in a kneader, and extruded into cylinders with a diameter of 1.5–2.5 mm and a length of 5–10 mm. These cylinders were dried in an oven at 120 °C for 6 hours and then calcined in a muffle furnace at 550 °C for 6 hours to obtain an Al2O3-SiO2 support (Al2O3 to SiO2 mass ratio 60:40). A mixture containing nickel nitrate and (NH4)6Mo7O was prepared. 24 An aqueous solution of 4H2O and phosphoric acid was used to impregnate the previously obtained Al2O3-SiO2 support in the solution for 16 h in equal volume. The support was then dried at room temperature, dried in an oven at 120 °C for 6 h, and calcined at 550 °C for 4 h to obtain the NiMoP / Al2O3-SiO2 hydrogenation catalyst, wherein the mass contents of Ni, Mo and P were 5.3%, 9.8% and 0.8%, respectively.

[0072] Example 1

[0073] Preparation of solvent oil:

[0074] Coal tar distillate (boiling range 171–400℃) and crude coal direct liquefaction oil (boiling range 253–450℃) were mixed at a mass ratio of 10:90 and then passed through a fixed-bed reactor in the presence of the catalyst NiMoP / Al2O3-SiO2 at a temperature of 380℃, a pressure of 15 MPa, a hydrogen-to-oil ratio of 1000 (v / v), and a volumetric hourly space velocity of 0.6 h⁻¹. -1 Hydrogenation was completed under specific conditions, and then a fraction with a distillation range of 171–278℃ was obtained by distillation, yielding a fraction with a density of 0.9305 g / cm³. 3 The solvent oil contains 201 ppm nitrogen and 5 ppm sulfur. The solvent oil contains C... 10 ~C 16 The content of alkanes is 10.2 wt%, the total amount of cycloalkanes with 1 to 3 rings is 25.3 wt%, the content of monocyclic aromatics is 44.0 wt%, the content of dicyclic aromatics is 20.0 wt%, and the content of tricyclic aromatics is 0.5 wt%.

[0075] Refining of coal liquefaction pitch:

[0076] Coal liquefaction pitch with an ash content of 19.9 wt%, a quinoline insoluble content of 49.5 wt%, and a softening point of 194℃ was mixed with solvent oil at a mass ratio of 1:4. The mixture was then stirred at 80℃ for 2 hours to complete the extraction. The resulting slurry was continuously fed at a rate of 6.12 t / h into a horizontal screw centrifuge with a drum inner diameter of 760 mm and a centrifugal separation factor of 600 g. This process allowed soluble pitch and heavy liquefied oil to separate from unreacted coal, minerals, catalysts, and other solid insoluble substances. The separation yielded a centrifuged light liquid and a centrifuged heavy phase. After distilling to recover the solvent oil, the centrifuged light liquid yielded refined coal liquefaction pitch with an ash content of 201 ppm, a quinoline insoluble content of 385 ppm, a softening point of 150.1℃, and a yield of 48.2%. The centrifuged heavy phase was heated to 200℃ and softened into a fluid with a viscosity of 1998 cp. This fluid was continuously fed into a vacuum spray dryer, and after recovering the solvent oil, a raffinate solid residue with a solvent oil residue of 0.51 wt% and a yield of 52.07% was obtained.

[0077] The solvent oil consumption rate is 0.27 wt% of the coal liquefaction pitch treatment capacity. The recovered solvent has a distillation range of 175–275℃ and a density of 0.9304 g / cm³. 3 It is relatively stable and can be recycled and reused.

[0078] Example 2:

[0079] Preparation of solvent oil:

[0080] Coal tar distillate (boiling range 205–396℃) and crude coal direct liquefaction oil (boiling range 247–443℃) were mixed at a mass ratio of 11.4:88.6 and then passed through a fixed-bed reactor in the presence of the catalyst NiMoP / Al2O3-SiO2 at a temperature of 375℃, a pressure of 14 MPa, a hydrogen-to-oil ratio of 1000 (v / v), and a volume hourly space velocity of 0.6 h⁻¹. -1 Hydrogenation was completed under specific conditions, and then a fraction with a distillation range of 179–285°C was obtained by distillation, yielding a fraction with a density of 0.9482 g / cm³. 3 The solvent oil contains 501 ppm nitrogen and 33 ppm sulfur. The solvent oil contains C... 10 ~C 16 The content of alkanes is 10.5 wt%, the total amount of cycloalkanes with 1 to 3 rings is 22.8 wt%, the content of monocyclic aromatics is 44.0 wt%, the content of dicyclic aromatics is 21.4 wt%, and the content of tricyclic aromatics is 1.3 wt%.

[0081] Refining of coal liquefaction pitch:

[0082] Coal liquefaction pitch with an ash content of 18.5 wt%, a quinoline insoluble content of 47.8 wt%, and a softening point of 189℃ was mixed with solvent oil at a mass ratio of 1:3.5. The mixture was then stirred at 85℃ for 1.5 hours to complete the extraction. The resulting slurry was continuously fed at a rate of 6.12 t / h into a horizontal screw centrifuge with a drum inner diameter of 760 mm and a centrifugal separation factor of 1300 g. This process facilitated the separation of soluble pitch substances, heavy liquefied oil, and unreacted coal, minerals, and catalysts. The insoluble matter was separated to obtain a centrifuged light liquid and a centrifuged heavy phase. After distilling to recover the solvent oil, the centrifuged light liquid yielded refined coal liquefaction pitch with an ash content of 83 ppm, a quinoline insoluble content of 132 ppm, a softening point of 152.3℃, and a yield of 49.1%. The centrifuged heavy phase was heated to 212℃ and softened into a fluid with a viscosity of 1875 cp. It was continuously fed into a vacuum belt dryer, and after recovering the solvent oil, a raffinate solid residue with a solvent oil residue of 0.65 wt% and a yield of 51.23% was obtained.

[0083] The solvent oil consumption rate was 0.33 wt% of the coal liquefaction pitch treatment capacity. The recovered solvent had a distillation range of 177–283℃ and a density of 0.9480 g / cm³. 3 It is relatively stable and can be recycled and reused.

[0084] Example 3:

[0085] Preparation of solvent oil:

[0086] Coal tar distillate (boiling range 198–388℃) and crude coal direct liquefaction oil (boiling range 215–412℃) were mixed at a mass ratio of 23.7:76.3 and then passed through a fixed-bed reactor in the presence of the catalyst NiMoP / Al2O3-SiO2 at a temperature of 375℃, a pressure of 13 MPa, a hydrogen-to-oil ratio of 900 (v / v), and a volume hourly space velocity of 0.7 h⁻¹. -1 Hydrogenation was completed under specific conditions, and then a fraction with a distillation range of 192–305℃ was obtained by distillation, yielding a fraction with a density of 0.9647 g / cm³. 3 The solvent oil contains 832 ppm nitrogen and 59 ppm sulfur. The solvent oil contains C... 10 ~C 16 The content of alkanes is 9.0 wt%, the total amount of cycloalkanes with 1 to 3 rings is 22.1 wt%, the content of monocyclic aromatics is 41.2 wt%, the content of dicyclic aromatics is 25.4 wt%, and the content of tricyclic aromatics is 2.3 wt%.

[0087] Refining of coal liquefaction pitch:

[0088] Coal liquefaction pitch with an ash content of 17.1 wt%, a quinoline-insoluble content of 46.1 wt%, and a softening point of 182℃ was mixed with solvent oil at a mass ratio of 1:3.2. The mixture was then stirred at 91℃ for 1.3 hours to complete the extraction. The resulting slurry was continuously fed at a rate of 12.38 t / h into a horizontal screw centrifuge with a drum inner diameter of 760 mm and a centrifugal separation factor of 665 g. This process facilitated the separation of soluble pitch substances and heavy liquefied oil from unreacted coal, minerals, and catalysts. The solvent was separated to obtain a centrifuged light liquid and a centrifuged heavy phase. After distilling to recover the solvent oil, the centrifuged light liquid yielded refined coal liquefaction pitch with an ash content of 734 ppm, a quinoline insoluble content of 1369 ppm, a softening point of 157.4℃, and a yield of 51.3%. The centrifuged heavy phase was heated to 219℃ and softened into a fluid with a viscosity of 1734 cp. It was continuously fed into a vacuum spray dryer, and after recovering the solvent oil, a raffinate solid residue with a solvent oil residue of 0.89 wt% and a yield of 49.14% was obtained.

[0089] The solvent oil consumption rate was 0.44 wt% of the coal liquefaction pitch treatment capacity. The recovered solvent had a distillation range of 197–303 °C and a density of 0.9640 g / cm³. 3 It is relatively stable and can be recycled and reused.

[0090] Example 4:

[0091] Preparation of solvent oil:

[0092] Coal tar distillate (boiling range 212–350℃) and crude coal direct liquefaction oil (boiling range 230–398℃) were mixed at a mass ratio of 37.5:62.5 and then passed through a fixed-bed reactor in the presence of the catalyst NiMoP / Al2O3-SiO2 at a temperature of 370℃, a pressure of 12 MPa, a hydrogen-to-oil ratio of 800 (v / v), and a volume hourly space velocity of 0.8 h⁻¹. -1 Hydrogenation was completed under specific conditions, and then a fraction with a distillation range of 204–317°C was obtained by distillation, yielding a fraction with a density of 0.9751 g / cm³. 3 The solvent oil contains 1160 ppm nitrogen and 87 ppm sulfur. The solvent oil contains C... 10 ~C 16 The content of alkanes is 8.4 wt%, the total amount of cycloalkanes with 1 to 3 rings is 18.5 wt%, the content of monocyclic aromatics is 38.4 wt%, the content of dicyclic aromatics is 31.1 wt%, and the content of tricyclic aromatics is 3.6 wt%.

[0093] Refining of coal liquefaction pitch:

[0094] Coal liquefaction pitch with an ash content of 16.3 wt%, a quinoline-insoluble content of 47.1 wt%, and a softening point of 188℃ was mixed with solvent oil at a mass ratio of 1:3.0. The mixture was then stirred at 95℃ for 1 hour to complete the extraction. The resulting slurry was continuously fed at a rate of 18.72 t / h into a horizontal screw centrifuge with a drum inner diameter of 760 mm and a centrifugal separation factor of 915 g. This process separates soluble pitch substances and heavy liquefied oil from unreacted coal, minerals, and catalysts. The material was separated to obtain a centrifuged light liquid and a centrifuged heavy phase. After distilling to recover the solvent oil, the centrifuged light liquid yielded refined coal liquefaction pitch with an ash content of 864 ppm, a quinoline insoluble content of 1796 ppm, a softening point of 162.8℃, and a yield of 52.5%. The centrifuged heavy phase was heated to 225℃ and softened into a fluid with a viscosity of 1598 cp. It was continuously fed into a vacuum spray dryer, and after recovering the solvent oil, a raffinate solid residue with a solvent oil residue of 1.34 wt% and a yield of 48.15% was obtained.

[0095] The solvent oil consumption rate is 0.65 wt% of the coal liquefaction pitch treatment capacity. The recovered solvent has a distillation range of 210–312℃ and a density of 0.9746 g / cm³. 3 It is relatively stable and can be recycled and reused.

[0096] Example 5:

[0097] Preparation of solvent oil:

[0098] Coal tar distillate (boiling range 245–360℃) and crude coal direct liquefaction oil (boiling range 217–378℃) were mixed at a mass ratio of 67.8:32.2 and then passed through a fixed-bed reactor in the presence of the catalyst NiMoP / Al2O3-SiO2 at a temperature of 365℃, a pressure of 11 MPa, a hydrogen-to-oil ratio of 700 (v / v), and a volumetric hourly space velocity of 1.0 h⁻¹. -1 Hydrogenation was completed under specific conditions, followed by distillation to separate a fraction with a distillation range of 209–324°C, yielding a density of 0.9804 g / cm³. 3 The solvent oil contains 1504 ppm nitrogen and 174 ppm sulfur. The solvent oil contains C... 10 ~C 16 The content of alkanes is 7.2 wt%, the total amount of cycloalkanes with 1 to 3 rings is 14.6 wt%, the content of monocyclic aromatics is 35.6 wt%, the content of dicyclic aromatics is 38.3 wt%, and the content of tricyclic aromatics is 4.3 wt%.

[0099] Refining of coal liquefaction pitch:

[0100] Coal liquefaction pitch with an ash content of 15.5 wt%, a quinoline insoluble content of 43.6 wt%, and a softening point of 177℃ was mixed with solvent oil at a mass ratio of 1:3.0. The mixture was then stirred at 104℃ for 1 hour to complete the extraction. The resulting slurry was continuously fed at a rate of 6.01 t / h into a horizontal screw centrifuge with a drum inner diameter of 760 mm and a centrifugal separation factor of 1783 g. This process facilitated the separation of soluble pitch substances, heavy liquefied oil, and unreacted coal, minerals, and catalysts. The insoluble matter was separated to obtain a centrifuged light liquid and a centrifuged heavy phase. After distilling to recover the solvent oil, the centrifuged light liquid yielded refined coal liquefaction pitch with an ash content of 51 ppm, a quinoline insoluble content of 94 ppm, a softening point of 169.5℃, and a yield of 54.4%. The centrifuged heavy phase was heated to 234℃ and softened into a fluid with a viscosity of 1321 cp. It was continuously fed into a vacuum belt dryer, and after recovering the solvent oil, a raffinate solid residue with a solvent oil residue of 1.87 wt% and a yield of 46.47% was obtained.

[0101] The solvent oil consumption rate was 0.87 wt% of the coal liquefaction pitch treatment capacity. The recovered solvent had a distillation range of 215–325℃ and a density of 0.9798 g / cm³. 3 It is relatively stable and can be recycled and reused.

[0102] Example 6:

[0103] Preparation of solvent oil:

[0104] Coal tar distillate (boiling range 172–350℃) and crude coal direct liquefaction oil (boiling range 205–380℃) were mixed at a mass ratio of 79.3:20.7 and then passed through a fixed-bed reactor in the presence of the catalyst NiMoP / Al2O3-SiO2 at a temperature of 360℃, a pressure of 10 MPa, a hydrogen-to-oil ratio of 600 (v / v), and a volumetric hourly space velocity of 1.2 h⁻¹. -1 Hydrogenation was completed under specific conditions, followed by distillation to separate a fraction with a distillation range of 217–332°C, yielding a product with a density of 0.9933 g / cm³. 3 The solvent oil contains 1848 ppm nitrogen and 297 ppm sulfur. The solvent oil contains C... 10 ~C 16 The content of alkanes is 6.5 wt%, the total amount of cycloalkanes with 1 to 3 rings is 11.8 wt%, the content of monocyclic aromatics is 32.8 wt%, the content of dicyclic aromatics is 44.1 wt%, and the content of tricyclic aromatics is 4.8 wt%.

[0105] Refining of coal liquefaction pitch:

[0106] Coal liquefaction pitch with an ash content of 15.0 wt%, a quinoline insoluble content of 42.4 wt%, and a softening point of 171℃ was mixed with solvent oil at a mass ratio of 1:2.8. The mixture was then stirred at 117℃ for 0.8 h to complete the extraction. The resulting slurry was continuously fed at a rate of 19.97 t / h into a horizontal screw centrifuge with a drum inner diameter of 760 mm and a centrifugal separation factor of 1530 g. This process facilitated the separation of soluble pitch substances, heavy liquefied oil, and unreacted coal, minerals, and catalysts. The separation of insoluble matter yields a centrifuged light liquid and a centrifuged heavy phase. The centrifuged light liquid is distilled to recover the solvent oil, yielding refined coal liquefaction pitch with an ash content of 552 ppm, a quinoline insoluble content of 1074 ppm, a softening point of 174.7℃, and a yield of 55.5%. The centrifuged heavy phase is heated to 238℃ to soften it into a fluid with a viscosity of 689 cp, and continuously fed into a vacuum spray dryer. After recovering the solvent oil, a raffinate solid residue with a solvent oil residue of 2.06 wt% and a yield of 45.44% is obtained.

[0107] The solvent oil consumption rate was 0.94 wt% of the coal liquefaction pitch treatment capacity. The recovered solvent had a distillation range of 215–330℃ and a density of 0.9926 g / cm³. 3 It is relatively stable and can be recycled and reused.

[0108] Example 7:

[0109] Preparation of solvent oil:

[0110] Coal tar distillate (boiling range 171–300℃) and crude coal direct liquefaction oil (boiling range 203–448℃) were mixed at a mass ratio of 86.2:13.8 and then passed through a fixed-bed reactor in the presence of the catalyst NiMoP / Al2O3-SiO2 at a temperature of 355℃, a pressure of 9 MPa, a hydrogen-to-oil ratio of 600 (v / v), and a volume hourly space velocity of 1.3 h⁻¹. -1 Hydrogenation was completed under specific conditions, followed by distillation to separate a fraction with a distillation range of 228–336 °C, yielding a product with a density of 1.0101 g / cm³. 3 The solvent oil contains 2165 ppm nitrogen and 426 ppm sulfur. The solvent oil contains C... 10 ~C 16 The content of alkanes is 5.8 wt%, the total amount of cycloalkanes with 1 to 3 rings is 11.2 wt%, the content of monocyclic aromatics is 31.8 wt%, the content of dicyclic aromatics is 46.5 wt%, and the content of tricyclic aromatics is 4.7 wt%.

[0111] Refining of coal liquefaction pitch:

[0112] Coal liquefaction pitch with an ash content of 15.3 wt%, a quinoline-insoluble content of 40.4 wt%, and a softening point of 166℃ was mixed with solvent oil at a mass ratio of 1:2.7 and stirred at a constant temperature of 128℃ for 0.5 h to complete the extraction. The resulting slurry was continuously fed into a horizontal screw centrifuge with a drum inner diameter of 760 mm and a centrifugal separation factor of 1200 g at a rate of 9.09 t / h. This process facilitated the separation of soluble pitch substances, heavy liquefied oil, and unreacted coal, minerals, and catalysts. The insoluble matter was separated to obtain a centrifuged light liquid and a centrifuged heavy phase. After distilling to recover the solvent oil, the centrifuged light liquid yielded refined coal liquefaction pitch with an ash content of 667 ppm, a quinoline insoluble content of 1245 ppm, a softening point of 186.2℃, and a yield of 57.8%. The centrifuged heavy phase was heated to 246℃ and softened into a fluid with a viscosity of 387 cp. It was continuously fed into a vacuum spray dryer. After recovering the solvent oil, a raffinate solid residue with a solvent oil residue of 2.23 wt% and a yield of 43.16% was obtained.

[0113] The solvent oil consumption rate was 0.96 wt% of the coal liquefaction pitch treatment capacity. The recovered solvent had a distillation range of 225–333℃ and a density of 1.005 g / cm³. 3 It is relatively stable and can be recycled and reused.

[0114] Example 8:

[0115] Preparation of solvent oil:

[0116] Coal tar distillate (boiling range 300–396℃) and crude coal direct liquefaction oil (boiling range 204–350℃) were mixed at a mass ratio of 90:10 and then passed through a fixed-bed reactor in the presence of the catalyst NiMoP / Al2O3-SiO2 at a temperature of 350℃, a pressure of 8 MPa, a hydrogen-to-oil ratio of 500 (v / v), and a volumetric hourly space velocity of 1.5 h⁻¹. -1 Hydrogenation was completed under specific conditions, followed by distillation to separate a fraction with a distillation range of 247–349 °C, yielding a product with a density of 1.0196 g / cm³. 3 The solvent oil contains 2490 ppm nitrogen and 500 ppm sulfur. The C content in this solvent oil is... 10 ~C 16 The content of alkanes is 5.0 wt%, the total amount of cycloalkanes with 1 to 3 rings is 10.5 wt%, the content of monocyclic aromatics is 30.0 wt%, the content of dicyclic aromatics is 49.5 wt%, and the content of tricyclic aromatics is 5.0 wt%.

[0117] Refining of coal liquefaction pitch:

[0118] Coal liquefaction pitch with an ash content of 17.9 wt%, a quinoline insoluble content of 40.1 wt%, and a softening point of 165℃ was mixed with solvent oil at a mass ratio of 1:2.5. The mixture was then stirred at 130℃ for 0.5 hours to complete the extraction. The resulting slurry was continuously fed at a rate of 19.85 t / h into a horizontal screw centrifuge with a drum inner diameter of 760 mm and a centrifugal separation factor of 1800 g. This process facilitated the separation of soluble pitch substances, heavy liquefied oil, and unreacted coal, minerals, and catalysts. The separation of insoluble matter yields a centrifuged light liquid and a centrifuged heavy phase. The centrifuged light liquid is distilled to recover the solvent oil, yielding refined coal liquefaction pitch with an ash content of 998 ppm, a quinoline insoluble content of 1992 ppm, a softening point of 190.0℃, and a yield of 58.0%. The centrifuged heavy phase is heated to 250℃ to soften it into a fluid with a viscosity of 201 cp, and continuously fed into a vacuum spray dryer. After recovering the solvent oil, a raffinate solid residue with a solvent oil residue of 2.28 wt% and a yield of 42.98% is obtained.

[0119] The solvent oil consumption rate was 0.98 wt% of the coal liquefaction pitch treatment capacity. The recovered solvent had a distillation range of 245–353℃ and a density of 1.0196 g / cm³. 3 It is relatively stable and can be recycled and reused.

[0120] Comparative Example 1: (Compared to Example 1, a separate low-range coal direct liquefaction crude oil fraction was used)

[0121] The crude oil from direct coal liquefaction is distilled to extract a fraction with a distillation range of 70–171℃, yielding a density of 0.7678 g / cm³. 3 The solvent oil contained 77 ppm nitrogen and 5 ppm sulfur. The resulting solvent oil contained C6–C6... 16 The content of alkanes is 36.1 wt%, the total amount of cycloalkanes with 1 to 3 rings is 38.9 wt%, the content of monocyclic aromatics is 24.7 wt%, and the content of dicyclic aromatics is 0.3 wt%.

[0122] Coal liquefaction pitch with an ash content of 19.9 wt%, a quinoline-insoluble content of 49.5 wt%, and a softening point of 194℃ was mixed with solvent oil at a mass ratio of 1:4 and stirred at a constant temperature of 80℃ for 2 hours to complete the extraction. The resulting slurry was continuously fed at a rate of 6.12 t / h into a horizontal screw centrifuge with a drum inner diameter of 760 mm and a centrifugal separation factor of 600 g, thereby separating soluble pitch substances and heavy liquefied oil from unreacted coal, minerals, and catalysts. Separation of materials; after centrifuging the light liquid and recovering the solvent oil by distillation, refined coal liquefaction pitch with ash content of 190 ppm, quinoline insoluble content of 367 ppm, softening point of 110.1℃, and yield of 13.1% was obtained; the solvent content of the centrifuged heavy phase was 19.3%, which was difficult to soften into a fluid for solvent recovery, resulting in a solvent consumption rate as high as 16.81 wt% (based on the amount of coal liquefaction pitch processed); it also resulted in a distillation range of 70-150℃ and a density of 0.7432 g / cm³ for the recovered solvent. 3 Its properties have changed significantly and it cannot be reused.

[0123] The solvent oil in this comparative example has low content of monocyclic and bicyclic aromatic hydrocarbons and high content of alkanes and cycloalkanes, resulting in low extraction yield of coal liquefaction pitch and poor swelling properties of the raffinate. It also cannot be continuously transported by centrifugation, making it difficult to apply on an industrial scale.

[0124] Comparative Example 2: (The mass ratio of coal tar distillate oil to crude coal direct liquefaction oil is different compared to Example 1)

[0125] Coal tar distillate (boiling range 171–400℃) and crude coal direct liquefaction oil (boiling range 253–450℃) were mixed at a mass ratio of 3:97 and then passed through a fixed-bed reactor in the presence of the catalyst NiMoP / Al2O3-SiO2 at a temperature of 380℃, a pressure of 15 MPa, a hydrogen-to-oil ratio of 1000 (v / v), and a volume hourly space velocity of 0.6 h⁻¹. -1 Hydrogenation was completed under specific conditions, followed by distillation to separate a fraction with a distillation range of 170–280°C, yielding a product with a density of 0.8347 g / cm³. 3 The solvent oil contains 101 ppm nitrogen and 15 ppm sulfur. The carbon content in this solvent oil is... 10 ~C 16 The content of alkanes is 26.5 wt%, the total amount of cycloalkanes with 1 to 3 rings is 49.3 wt%, the content of monocyclic aromatics is 20.3 wt%, and the content of dicyclic aromatics is 3.9 wt%.

[0126] Coal liquefaction pitch with an ash content of 19.9 wt%, a quinoline insoluble content of 49.5 wt%, and a softening point of 194℃ was mixed with solvent oil at a mass ratio of 1:4 and stirred at 80℃ for 2 hours to complete the extraction. The resulting slurry was continuously fed at a rate of 6.12 t / h into a horizontal screw centrifuge with a drum inner diameter of 760 mm and a centrifugal separation factor of 600 g to separate soluble pitch substances and heavy liquefied oil from unreacted coal, minerals, catalysts, and other solid insoluble substances. The process involved centrifuging the light liquid and the heavy phase. After distilling to recover the solvent oil from the light liquid, refined coal liquefaction pitch with an ash content of 198 ppm, a quinoline-insoluble content of 380 ppm, a softening point of 135.3℃, and a yield of 30.1% was obtained. The heavy phase contained 25.7% solvent, making it difficult to soften into a fluid for solvent recovery, resulting in a solvent consumption rate as high as 18.03 wt% (based on the amount of coal liquefaction pitch processed). This also resulted in a distillation range of 175–260℃ and a density of 0.8128 g / cm³ for the recovered solvent. 3 Its properties have changed significantly and it cannot be reused.

[0127] This solvent has low content of monocyclic and bicyclic aromatic hydrocarbons and high content of alkanes and cycloalkanes, resulting in low extraction yield of coal liquefaction pitch and poor swelling properties of the raffinate. It also cannot continuously transport the centrifuged heavy phase, making it difficult to apply on an industrial scale.

[0128] Comparative Example 3: (Compared to Example 8, a separate coal tar distillate was used)

[0129] Coal tar distillate (distillation range 300–396℃) was processed in a fixed-bed reactor in the presence of NiMoP / Al2O3-SiO2 catalyst at a temperature of 350℃, a pressure of 8 MPa, a hydrogen-to-oil ratio of 500 (v / v), and a volumetric hourly space velocity of 1.5 h⁻¹. -1 Hydrogenation was completed under specific conditions, and then a fraction with a distillation range of 240–330℃ was obtained by distillation, yielding a fraction with a density of 1.0467 g / cm³. 3 The solvent oil contains 5210 ppm nitrogen and 2167 ppm sulfur. The solvent oil contains C... 10 ~C 16 The content of alkanes is 2.4 wt%, the total amount of cycloalkanes with 1 to 3 rings is 4.2 wt%, the content of monocyclic aromatics is 18.8 wt%, the content of dicyclic aromatics is 72.1 wt%, and the content of tricyclic aromatics is 2.5 wt%.

[0130] Coal liquefaction pitch with an ash content of 17.9 wt%, a quinoline-insoluble content of 40.1 wt%, and a softening point of 165℃ was mixed with solvent oil at a mass ratio of 1:2.5 and stirred at a constant temperature of 130℃ for 0.5 h to complete the extraction. The resulting slurry was continuously fed at a rate of 19.85 t / h into a horizontal screw centrifuge with a drum inner diameter of 760 mm and a centrifugal separation factor of 1800 g, thereby separating soluble pitch substances and heavy liquefied oil from unreacted coal, minerals, and catalysts. The material was separated to obtain a centrifuged light liquid and a centrifuged heavy phase. After distilling to recover the solvent oil, the centrifuged light liquid yielded refined coal liquefaction pitch with an ash content of 10,150 ppm, a quinoline insoluble content of 22,480 ppm, a softening point of 187.4℃, and a yield of 59.7%. The centrifuged heavy phase was heated to 250℃ and softened into a fluid with a viscosity of 187 cp. It was then continuously fed into a vacuum spray dryer. After recovering the solvent oil, a raffinate solid residue with a solvent oil residue of 4.56 wt% and a yield of 42.23% was obtained.

[0131] The solvent oil consumption rate is 1.93 wt% of the coal liquefaction pitch processing volume, which is relatively large and costly. Moreover, the ash content of the extracted and refined pitch is as high as 10,000 ppm or more, which cannot meet the raw material requirements of high-end carbon materials.

[0132] Comparative Example 4 (compared to Example 3, no hydrogenation was performed during the preparation of the solvent oil)

[0133] Coal tar distillate (boiling range 198–388℃) and crude coal direct liquefaction oil (boiling range 215–412℃) were mixed at a mass ratio of 23.7:76.3. The mixture was then distilled to obtain a fraction with a boiling range of 200–305℃, yielding a density of 0.9947 g / cm³. 3 The solvent oil contains 2759 ppm nitrogen and 1341 ppm sulfur. The solvent oil contains C... 10 ~C 16 The content of alkanes is 5.0 wt%, the total amount of cycloalkanes with 1 to 3 rings is 17.1 wt%, the content of monocyclic aromatics is 28.8 wt%, the content of dicyclic aromatics is 44.0 wt%, and the content of tricyclic aromatics is 5.1 wt%.

[0134] Coal liquefaction pitch with an ash content of 15.3 wt%, a quinoline-insoluble content of 40.4 wt%, and a softening point of 166℃ was mixed with solvent oil at a mass ratio of 1:2.7 and stirred at a constant temperature of 128℃ for 0.5 h to complete the extraction. The resulting slurry was continuously fed into a horizontal screw centrifuge with a drum inner diameter of 760 mm and a centrifugal separation factor of 1200 g at a rate of 9.09 t / h. This process facilitated the separation of soluble pitch substances, heavy liquefied oil, and unreacted coal, minerals, and catalysts. The insoluble matter was separated to obtain a centrifuged light liquid and a centrifuged heavy phase. After distilling to recover the solvent oil, the centrifuged light liquid yielded refined coal liquefaction pitch with an ash content of 859 ppm, a quinoline insoluble content of 1731 ppm, a softening point of 175.2℃, and a yield of 57.9%. The centrifuged heavy phase was heated to 248℃ and softened into a fluid with a viscosity of 299 cp. It was continuously fed into a vacuum spray dryer. After recovering the solvent oil, a raffinate solid residue with a solvent oil residue of 4.05 wt% and a yield of 43.89% was obtained.

[0135] The solvent oil consumption rate was 1.78 wt% of the coal liquefaction pitch treatment capacity. The recovered solvent had a distillation range of 155–270℃ and a density of 0.9256 g / cm³. 3 Its properties have changed significantly, and it cannot be recycled.

[0136] This solvent has not undergone hydrogenation treatment. The crude coal liquefaction oil in it is prone to cracking and coking during the heating and cooling processes of extraction and distillation, resulting in high consumption rate and changes in properties, making it unusable.

[0137] Table 1 Summary of Experimental Results

[0138]

[0139] The experimental results above show that, compared with the comparative example, the solvent oil of this invention, used for the refining of coal liquefaction pitch, can achieve a relatively high refined pitch yield (above 48%) with a lower solvent oil consumption rate, while maintaining relatively low ash content (50-1000 ppm) and quinoline insoluble content (80-2000 ppm), and low solvent oil residue in the extraction residue. The solvent oil of this invention exhibits excellent solid-liquid separation when treating coal liquefaction pitch, is easy to recycle, and achieves a good balance between low solvent oil consumption, high yield, low ash content, and low quinoline insoluble content in the refined pitch; the softening point of the obtained refined coal liquefaction pitch is between 150 and 190°C.

[0140] It is readily understood that the above embodiments are merely illustrative examples for clear explanation and do not imply that the invention is limited thereto. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A solvent oil, characterized by, The solvent oil contains C 10 16 paraffins, cycloparaffins having a ring number of 1 to 3, monocyclic aromatic hydrocarbons, di- cyclic aromatic hydrocarbons, and tricyclic aromatic hydrocarbons;​ said C 10 ~C 16 the content of paraffins is 5.0-10.5 wt%, the content of cycloparaffins is 10.0-25.3 wt%, the content of monocyclic arenes is 30.0-44.0 wt%, the content of bicyclic arenes is 20.0-50.0 wt%, the content of tricyclic arenes is 0.5-5.0 wt%; The nitrogen content of the solvent oil is 200-2500 ppm, the sulfur content is 5-500 ppm, the distillation range of the solvent oil is between 170-350°C; the density of the solvent oil is 0.93-1.02 g / cm 3 ; The preparation method of the solvent oil comprises the following steps: The coal tar distillate oil and the direct coal liquefaction crude oil are mixed in a mass ratio of 10:90-90:10, and then subjected to a hydrogenation reaction, and then subjected to distillation cutting to obtain a fraction segment with a distillation range of 170-350 DEG C, thereby obtaining the solvent oil.

2. The solvent oil according to claim 1, characterized by, The coal tar distillate oil is a coal tar distillate with a distillation range of 170-400 DEG C. The direct coal liquefaction crude oil is a direct coal liquefaction crude oil distillate with a distillation range of 200-450 DEG C.

3. The solvent oil according to claim 1, characterized by, The hydrogenation reaction is carried out in the presence of a hydrogenation catalyst, and the hydrogenation catalyst comprises a carrier and an active component; the active component comprises Ni, Mo and P, and the mass content of the Ni, Mo and P in the hydrogenation catalyst is 4.71-5.89%, 8.87-10.93% and 0.74-0.87%, respectively.

4. The solvent oil according to claim 3, characterized in that, The carrier is an Al2O3-SiO2 carrier, wherein the content of Al2O3 is 45-72 wt%, and the content of SiO2 is 28-55 wt%.

5. The solvent oil according to any one of claims 1 to 4, characterized in that, The conditions of the hydrogenation reaction include: temperature 350-380℃, pressure 8-15 MPa, hydrogen / oil ratio v / v 500-1000, volume space velocity 0.6-1.5 h -1 .

6. The solvent oil according to claim 5, characterized in that, The hydrogenation reaction is carried out in a fixed bed reactor, a suspension bed reactor or a boiling bed reactor.

7. The solvent oil according to any one of claims 1-6 is used in the refining treatment of coal liquefaction pitch.

8. A method for refining coal liquefaction pitch, characterized by, The method comprises the following steps: (1) the coal liquefaction pitch and the solvent oil are mixed in a mass ratio of 1:2-4, and then uniformly heated to 80-130 DEG C, and then stirred at a constant temperature for 0.5-2 h to obtain a mixed slurry; the solvent oil is the solvent oil according to any one of claims 1-6; (2) the mixed slurry is subjected to centrifugal separation to obtain a light phase and a heavy phase; (3) the solvent oil in the light phase is separated to obtain refined coal liquefaction pitch.

9. The coal liquefaction pitch refining method according to claim 8, characterized by, In step (2), the centrifugal separation is carried out in a horizontal screw centrifuge.

10. The coal liquefaction pitch refining method according to claim 9, characterized by, The centrifugal separation factor of the horizontal screw centrifuge is 600-1800 g.

11. The coal liquefaction pitch refining process according to any one of claims 8 to 10, characterized by, The heavy phase is heated to 200-250 DEG C to soften the heavy phase into a fluid, and then the solvent oil is recovered therefrom.

12. The coal liquefaction pitch refining method according to claim 11, characterized by, The solvent oil separated from the light phase and the solvent oil recovered from the heavy phase are mixed and then recycled to step (1).

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