Method for separating alkanes, phenols and aromatic hydrocarbons from low-temperature coal tar

Abstract

The invention discloses a method for separating alkanes, phenols and aromatic hydrocarbons from low-temperature coal tar, which combines different non-polar solvents and polar solvents into two double-solvent systems A and B. The method comprises the following steps: extracting organic compounds with different polarities in the low-temperature coal tar by using the double-solvent system A; an upper layer extraction solution containing alkanes and a lower layer extraction solution containing phenols and aromatic hydrocarbons are obtained; recovering the solvent through distillation, and obtaining an alkane organic compound; and adding the lower-layer extract into a double-solvent system B, and carrying out cross-flow extraction and distillation to respectively obtain phenolic and aromatic hydrocarbon organic compounds. According to the technical scheme, alkanes, phenols and aromatic hydrocarbons in the low-temperature coal tar are effectively separated based on a double-solvent system. The method is simple in process, easy to operate and mild in condition, and the method for selectively separating various organic compounds in the low-temperature coal tar is provided.

Description

Technical Field

[0001] The present invention relates to a method for separating various organic compounds from low-temperature coal tar, specifically to a method for separating alkanes, phenols and aromatic hydrocarbons. Background Art

[0002] Low-temperature coal tar (LTCT) is a liquid product generated during the pyrolysis of coal. Organic compounds such as alkanes, alkenes, hydroxy-substituted aromatic hydrocarbons (phenols and alcohols), and aromatic hydrocarbons contained therein are raw materials for the production of fibers, pharmaceuticals, dyes, pesticides, etc. Since 2016, the production of medium and low-temperature coal tar in China has reached approximately 10 million t / a, and it is urgent to carry out deep processing on it to realize its value-added utilization.

[0003] At present, the efficient utilization of low-temperature coal tar mainly focuses on the fields of producing high-grade liquid fuels and value-added chemicals. Due to the presence of hydroxy compounds, in the process of directly catalytic hydrogenation of low-temperature coal tar to prepare high-grade liquid fuels, it will not only cause equipment corrosion and catalyst deactivation, block pipelines, but also affect the stability of refined oil products.

[0004] In recent years, separation methods such as distillation, solvent extraction, ionic liquid extraction, deep eutectic solvent extraction, supercritical fluid extraction, membrane separation, acid-base extraction, precipitation separation, and complex extraction-adsorption have been widely studied for separating organic compounds in low-temperature coal tar.

[0005] At present, the existing invention patents include: CN104147808A discloses an extractant for removing phenols in sewage. The volume ratio of methyl tert-butyl ketone and methyl isobutyl ketone or isoamyl alcohol in the phenol-removing extractant is 1:0 - 4:1, and the volume ratio of the phenol-containing wastewater to the phenol-removing extractant is 1 - 10:1, preferably (3 - 10):1. The extraction temperature is 40 - 85°C. The contents of unit phenols and polyhydric phenols are 1000 - 9000 and 1000 - 16000 mg / L respectively.

[0006] CN110016361B discloses a method for extracting coal tar by first adding a methanol solution of sodium methoxide to coal tar, stirring for 30 - 40 min, and then adding solvent oil and continuing to stir for 30 - 50 min, which overcomes the defects of large volume of the emulsion layer and poor acid reduction effect in the coal tar extraction method.

[0007] CN102585870A discloses a method for separating chain hydrocarbons and phenolic compounds in medium and low-temperature coal tar using a biphasic organic solvent.

[0008] CN112979426A discloses that all products are taken out by measuring lines, and the mixed components at each tower top are gradually returned to the feed of the previous tower for further refining to separate products such as high-purity phenol, o-cresol, 2,6-xylenol, and m,p-cresol, realizing the separation of mixed 2,5-xylenol and mixed 3,5-xylenol.

[0009] CN105802651A discloses a method for separating phenolic compounds from medium and low temperature coal tar using ionic liquids. Using monoethanol formic acid as an extractant, reacting with medium and low temperature coal tar to obtain a mixed solution, adding diethyl ether to the lower phase of the stratified mixed solution to obtain a diethyl ether extract, and distilling the extract to obtain phenolic compounds, with an extraction rate as high as 98%.

[0010] The distillation processes involved in the above-mentioned inventions are characterized by high pollution, high energy consumption, and high carbon emissions. The relatively mature distillation processes still need to be further upgraded and improved. The acid-base extraction method involves acids and bases, and is prone to generating wastewater, waste acid, and waste alkali during the operation process, and has gradually been phased out, and is mostly used for analyzing the composition and content distribution of compounds. In addition, with the in-depth research on ionic liquids and deep eutectic solvents, these two types of solvents regarded as green solvents also have a series of disadvantages, including high price, high viscosity, and easy water absorption, which limit their use in future industrialization. Summary of the Invention

[0011] In view of the above problems, the present invention provides a method for separating alkanes, phenols, and aromatics from low-temperature coal tar by using a multi-component dual-solvent extraction system A and B and adopting a cross-flow extraction method. This method can better separate alkanes, phenols, and aromatic organic compounds in low-temperature coal tar, avoiding problems such as catalyst deactivation and equipment blockage caused by the presence of oxygen-containing compounds during the catalytic hydrogenation conversion process, and realizing the selective enrichment of organic compounds in low-temperature coal tar.

[0012] To achieve the above object, the present invention adopts the following technical solutions: successively put low-temperature coal tar into two dual-solvent systems A and B, and realize the selective separation of alkanes, phenols, and aromatics in low-temperature coal tar through multi-stage cross-flow extraction.

[0013] The method is as follows: (1) Configure the dual-solvent system A, take non-polar solvent 1① and polar solvent 1②, and prepare according to a certain ratio to obtain a stratified dual-solvent system A.

[0014] (2) Configure the dual-solvent system B, take non-polar solvent 2⑦ and polar solvent 2⑥, and prepare according to a certain ratio to obtain a stratified dual-solvent system B. The non-polar solvents used are organic solvents such as petroleum ether, n-hexane, cyclohexane, and carbon disulfide. The polar solvents are polar solvents such as alcohols, nitriles, and water.

[0015] (3) Add low-temperature coal tar to the dual-solvent system A. The volume ratio of the dual-solvent system A to the low-temperature coal tar is (10 - 15):1. Stir mechanically at 600 rpm / h at room temperature for 1 h. After standing and separating, transfer it to a separatory funnel for separation to obtain the upper extraction solution 1-1③ and the lower extraction solution 1-1④.

[0016] (4) The upper extraction solution 1-1③ enriches the alkane organic compounds in the low-temperature coal tar. Distill the upper extraction solution 1-1③ to obtain the alkane extract 1-1 and the non-polar solvent 1①, and the non-polar solvent ① is recycled; the lower extraction solution 1-1④ is rich in components such as phenols, aromatics, and asphaltenes. Distill the lower extraction solution 1-1④ to obtain the phenols, aromatics, and asphaltene extract 1-1 and the polar solvent 1②.

[0017] (5) Perform step (3) multiple times to obtain the upper extraction solution 1-n③. Perform step (4) multiple times. Distill the upper extraction solution 1-n③ to obtain the upper extract 1-n and the non-polar solvent 1②. Distill the lower extraction solution 1-n④ to obtain the lower extract 1-n⑤ and the polar solvent 1②, and the polar solvent 1② can be recycled.

[0018] (6) Add the lower extract 1-n⑤ to the dual-solvent system B. Stir mechanically at 600 rpm / h at room temperature for 1 h. After standing and separating, obtain the upper extraction solution 2-1⑧ and the lower extraction solution 2-1⑨. Distill the upper extraction solution 2-1⑧ to obtain the phenol extract 2-1 and the polar solvent 2⑥, and the polar solvent 2⑥ is recycled. The lower extraction solution 2-1⑨ contains components such as aromatics and asphaltenes.

[0019] (7) Perform step (6) multiple times to obtain the upper extraction solution 2-n⑧.

[0020] (8) Distill the upper extraction solution 2-n⑧ to obtain the upper extract 2-n, the main component of which is phenolic organic compounds.

[0021] (9) Filter the lower extraction solution 2-n⑨ to obtain the lower extraction solution 2- (n+1) ⑨ (filtrate) and the lower residue 2- (n+1) .

[0022] (10) Distill the lower extraction solution 2- (n+1) ⑨ (filtrate) to obtain the lower extract 2- (n+1) (aromatics) and the recyclable non-polar solvent 2⑦.

[0023] The present invention has conducted in-depth research on the problems existing in the background technology and has made the following creative improvements to the existing methods: (1) Extract low-temperature coal tar by means of a double-solvent system based on the extraction principle, aiming to separate alkanes, phenols, and aromatic organic compounds in low-temperature coal tar. The solvents used are low-boiling polar solvents and non-polar solvents, which are a double-solvent system prepared by mixing different polar solvents in a certain proportion. The non-polar solvents used are organic solvents such as petroleum ether, n-hexane, n-heptane, and cyclohexane. The polar solvents are polar solvents such as alcohols, nitriles, and water.

[0024] (2) Recycling of solvents. Due to the boiling point difference between the extractant and the extraction solvent, through repeated extractions and atmospheric distillation, solvents and extracts are obtained, and the extractant can be reused.

[0025] (3) The separation process flow is simple, easy to operate, the equipment is simple and the cost is low, and there is no need for a high-temperature and high-pressure environment. The separation process has low energy consumption, no pollution, and no carbon dioxide emissions, and can achieve low-carbon environmental protection. Description of the Drawings

[0026] Figure 1 It is a process flow chart of a method for separating alkanes, phenols, and aromatics from low-temperature coal tar in this application.

[0027] Reference Numerals: In the process flow chart of this application, it includes 1 - non-polar solvent storage tank 1; 2 - polar solvent storage tank 1; 3 - stirring kettle 1; 4 - separator 1; 5 - distillation kettle 1; 6 - distillation kettle 2; 7 - stirring kettle 2; 8 - polar solvent storage tank 2; 9 - non-polar solvent storage tank 2; 10 - separator 2; 11 - distillation kettle 3; 12 - separator 3; 13 - distillation kettle 4; ① non-polar solvent 1; ② polar solvent 1; ③ upper extraction solution 1; ④ lower extraction solution 1; ⑤ lower extract 1; ⑥ polar solvent 2; ⑦ non-polar solvent 2; ⑧ upper extraction solution 2; ⑨ lower extraction solution 2.

[0028] As shown in the figure, there are a total of four solvent storage tanks, namely 1 - non-polar solvent storage tank 1, 2 - polar solvent storage tank 1, 8 - polar solvent storage tank 2, and 9 - non-polar solvent storage tank 2, which are used to store and recycle four different solvents required in the separation process.

[0029] As shown in the figure, non-polar solvent 1 ① and polar solvent 1 ② enter stirring kettle 3, and are prepared into a double-solvent system A in a certain proportion. Non-polar solvent 2 ⑦ and polar solvent 2 ⑥ enter stirring kettle 7, and are prepared into a double-solvent system B in a certain proportion.

[0030] Due to the different densities of the non-polar solvent and the polar solvent, both the double-solvent system A and the double-solvent system B are divided into upper and lower layers.

[0031] As shown in the figure, the dual-solvent system A and low-temperature coal tar enter a 3-stirring kettle at a volume ratio of (10 - 15):1, and are mechanically stirred at 600 rpm / h for 1 h at room temperature to achieve the primary extraction of low-temperature coal tar, obtaining a stratified extraction liquid 1. Repeating this step yields extraction liquids 1 - n.

[0032] Based on the extraction principle of "like dissolves like", alkane compounds in low-temperature coal tar have a relatively high solubility in non-polar solvent 1①. Phenolic compounds are polar compounds and have a relatively high solubility in polar solvent 2⑥. Compared with non-polar solvent 1①, condensed aromatic hydrocarbons have a greater solubility in non-polar solvent 2⑦.

[0033] As shown in the figure, the extraction liquid 1 obtained in the 3-stirring kettle 1 enters a 4-separator 1 and is allowed to stand for stratification, obtaining an upper-layer extraction liquid 1 - 1③ and a lower-layer extraction liquid 1 - 1④. Repeating this step yields an upper-layer extraction liquid 1 - n③ and a lower-layer extraction liquid 1 - n④.

[0034] The upper-layer extraction liquid 1 - 1③ is enriched with alkanes in low-temperature coal tar; the lower-layer extraction liquid 1 - 1④ is enriched with components such as phenols, aromatic hydrocarbons, and asphaltenes.

[0035] As shown in the figure, the upper-layer extraction liquid 1③ enters a 5-distillation kettle 1, and the lower-layer extraction liquid 1④ enters a 6-distillation kettle 2. Utilizing the difference in boiling points between the solvent and the extract, the boiling point of the solvent is lower than that of the extract.

[0036] When distilling the upper-layer extraction liquid 1③ and the lower-layer extraction liquid 1④, when the temperature reaches the boiling point of the solvent, the solvent is separated.

[0037] As shown in the figure, after the upper-layer extraction liquid 1 - n③ is distilled in the 5-distillation kettle 1, the separation of non-polar solvent 1① and alkanes is achieved, and finally, an alkane extract 1 - n and non-polar solvent 1① are obtained.

[0038] As shown in the figure, after the lower-layer extraction liquid 1④ is distilled in the 6-distillation kettle 2, the separation of polar solvent 1② and the lower-layer extract 1 - n⑤ is achieved. Finally, the lower-layer extract 1 - n⑤ and polar solvent 1② are obtained.

[0039] As shown in the figure, the obtained non-polar solvent 1① and polar solvent 1② enter a 1-non-polar solvent storage tank 1 and a 2-polar solvent storage tank 1 respectively, realizing the recycling of the solvent.

[0040] As shown in the figure, the lower-layer extract 1 - n⑤ enters a 7-stirring kettle 2 and is mixed with the dual-solvent system B, and is mechanically stirred at 600 rpm / h for 1 h at room temperature. The lower-layer extract 1 - n⑤ is extracted with the dual-solvent system B to obtain a stratified extraction liquid 2. Repeating this step yields extraction liquids 1 - n.

[0041] As shown in the figure, the extract 2 obtained from the 7-stirred tank 2 enters the 10-separator 2 for static settling and stratification, obtaining the upper-layer extract 2-1⑧ and the lower-layer extract 2-1⑨. Repeating this step yields the upper-layer extract 2-n⑧ and the lower-layer extract 2-n⑨.

[0042] The upper-layer extract 2-1⑧ contains phenolic extractives 2-1 and polar solvent 2, while the lower-layer extract 2-1⑨ contains components such as non-polar solvents, aromatic hydrocarbons, and asphaltenes.

[0043] As shown in the figure, after the upper-layer extract 2-n⑧ is distilled in the 11-distillation kettle 3, the separation of the polar solvent 2⑥ from the phenolic extractives is achieved, finally obtaining the upper-layer extract 2-n and the polar solvent 2⑥. The polar solvent 2⑥ can enter the 8-polar solvent storage tank 2 for recycling.

[0044] The main component of the upper-layer extract 2-n is phenolic organic compounds.

[0045] As shown in the figure, the lower-layer extract 2-n⑨ is filtered through the 12-separator 3 to obtain the lower-layer extraction solution 2- (n+1) ⑨ (filtrate) and the lower-layer raffinate 2- containing heavy asphalt (n+1) , and after the filtrate is distilled multiple times in the 13-distillation kettle 4, the separation of the non-polar solvent 2⑦ from the lower-layer extract 2- (n+1) is achieved.

[0046] In summary, the attached drawings clearly show the high-efficiency, energy-saving, green, and low-carbon production process of the present invention.

[0047] Beneficial Effects The separation of alkanes, phenols, and aromatic hydrocarbons in low-temperature coal tar can be achieved at room temperature.

[0048] The reagents used in the separation process are cheap and easily available.

[0049] The extraction agent has a low boiling point and can be recycled.

[0050] The extraction agent has good selectivity for alkanes, phenols, and aromatic hydrocarbons.

[0051] The designed separation process flow is simple, easy to operate, and has low equipment costs.

[0052] The equipment is simple and does not require a high-temperature and high-pressure environment.

[0053] The separation process has low energy consumption, no pollution, no carbon dioxide emissions, and can achieve low-carbon environmental protection.

[0054] This technical solution has the characteristics of low-carbon, clean, and high-value utilization of coal tar. Specific Embodiments Examples

[0055] Two dual solvent systems A and B are prepared respectively, wherein the dual solvent system A is prepared from polar solvent 1 and non-polar solvent 1 in a certain proportion, and the dual solvent system B is prepared from polar solvent 2 and non-polar solvent 2 in a certain proportion. The selective separation of alkanes, phenols and aromatic organic compounds in low-temperature coal tar is achieved. The method is as follows: firstly, two dual solvent systems are prepared, and then the separation of alkanes, phenols and aromatic organic compounds in low-temperature coal tar is carried out in sequence. The specific process is as follows: (1) Preparation of the dual solvent system. Preparation of dual solvent system A: Take petroleum ether (30-60°C) and methanol in a volume ratio of 2:1, mix them thoroughly, and let them stand to separate into layers to obtain dual solvent system A; Preparation of dual solvent system B: Take methanol and carbon disulfide in a volume ratio of 1:1, mix them thoroughly, and let them stand to separate into layers to obtain dual solvent system B; (2) Enrichment methods and processes for alkanes, phenols and aromatics in low-temperature coal tar: Low-temperature coal tar is added to the dual solvent system A, and the volume ratio of low-temperature coal tar to dual solvent system A is 1:4. Under room temperature conditions, the mixture is stirred at a speed of 600 rpm for 1 h, allowed to stand for 30 min, and separated by a separatory funnel to obtain an upper layer extraction solution 1-1 and a lower layer extraction solution 1-1, wherein the upper layer extraction solution 1-1 is enriched with alkanes in the low-temperature coal tar. The upper layer extraction solution 1-1 is distilled to obtain petroleum ether and an upper layer extract 1-1, and the petroleum ether is recycled, and the upper layer extract 1-1 is enriched with alkanes. The lower layer extraction solution 1-1 contains components such as phenols, aromatics, and heavy asphalt. Repeat the above steps to separate the lower layer extraction solution 1-n and the upper layer extraction solution 1-n from the lower layer extraction solution 1-1, distill the upper layer extraction solution 1-n to obtain the upper layer extraction solution 1-n and petroleum ether, and recycle the petroleum ether; add the lower layer extraction solution 1-n to the dual solvent system B, stir at 600 rpm for 1 h under room temperature, stand for 30 min to separate the layers, and separate with a separatory funnel to obtain the upper layer extraction solution 2-1 and the lower layer extraction solution 2-1, wherein the upper layer extraction solution 2-1 is enriched with phenolic organic compounds. Distill the upper layer extraction solution 2-1 to obtain methanol and the upper layer extraction solution 2-1, and recycle the methanol. The lower layer extraction solution 2-1 contains components such as aromatic hydrocarbons and heavy asphalt. Repeat the above steps to separate the upper layer extraction solution 2-n and the lower layer extraction solution 2-n from the lower layer extraction solution 2-1, distill the upper layer extraction solution 2-n to obtain the upper layer extraction solution 2-n and methanol, and recycle the methanol. Filter the lower layer of the extract solution 2-n to obtain the residue 2- (n+1) and the lower extraction solution 2- (n+1) , extract 2- (n+1) It is heavy asphalt. Distill the lower layer extraction solution 2- (n+1) , and obtain the lower layer extract 2- (n+1)and carbon disulfide, with carbon disulfide recycled, and the lower-layer extract 2- (n+1) contains aromatic organic compounds.

[0056] Table 1 Distribution of Main Compounds at Each Stage of Extracting Low-Temperature Coal Tar with a Dual-Solvent System

[0057] The dual-solvent extraction and separation method used in the present invention has the advantages of high selectivity, simple operation, and being green and low-carbon. The alkanes, phenols, and aromatic organic compounds separated from low-temperature coal tar can be applied in various fields such as chemical engineering, materials, medicine, and aerospace. For example, long-chain alkanes can be used as automotive fuels and solvents; phenolic compounds have certain antibacterial properties, can damage bacterial cell membranes or interfere with their metabolic functions, and can also be used as disinfectants and preservatives; while aromatic organic compounds can not only be used as fuel additives to improve the combustion performance by increasing the fuel octane number, but can also be catalytically hydrogenated to cycloalkanes with high density and high thermal stability for use as aviation fuels, rocket propellants, and sealing coatings.

[0058] Therefore, the present invention can achieve high-value utilization of low-temperature coal tar. The specific embodiments described herein are only illustrative of the concept of the present invention. Those skilled in the technical field to which the present invention pertains can make various modifications or supplements to the described specific examples or use similar methods for substitution, but will not deviate from the spirit of the present invention or exceed the scope defined by the claims.

Claims

1. A method for separating alkanes, phenols and aromatic hydrocarbons from low-temperature coal tar, characterized in that, The method comprises the following steps: (1) Configure a dual-solvent system A. Take non-polar solvent 1① and polar solvent 1② and prepare them in a certain proportion to obtain a layered dual-solvent system A; (2) Configure a dual-solvent system B. Take non-polar solvent 2⑦ and polar solvent 2⑥ and prepare them in a certain proportion to obtain a layered dual-solvent system B. The non-polar solvents used are organic solvents such as carbon disulfide, petroleum ether, n-hexane, and cyclohexane. The polar solvents are polar solvents such as alcohols, nitriles, and water; (3) Add low-temperature coal tar to the dual-solvent system A. The volume ratio of the dual-solvent system A to the low-temperature coal tar is 15:1 to 10:

1. Magnetically stir at 600 rpm / h at room temperature for 1 h. After mixing and standing for stratification, place it in a separating funnel for separation to obtain the upper extraction solution 1-1③ and the lower extraction solution 1-1④; (4) The upper extraction solution 1-1③ is enriched with alkane organic compounds in low-temperature coal tar. Distill the upper extraction solution 1-1③ to obtain an alkane extract 1-1 and non-polar solvent 1①, and non-polar solvent 1① is recycled; the lower extraction solution 1-1④ contains components such as phenols, aromatics, and asphaltenes; (5) Repeat step (3) to obtain extract 1-n, non-polar solvent 1①, and upper extraction solution 1-n③. Distill the lower extraction solution 1-n④ to obtain lower extract 1-n⑤ and polar solvent 1②, and polar solvent 1② is recycled; (6) Add the lower extract 1-n⑤ to the dual-solvent system B. At room temperature, magnetically stir at 600 rpm / h for 1 h and then let it stand. After standing and stratifying, obtain the upper extraction solution 2-1⑧ and the lower extraction solution 2-1⑨. Distill the upper extraction solution 2-1⑧ to obtain a phenol extract 2-1 and polar solvent 2⑥, and polar solvent 2⑥ is recycled. The lower extraction solution 2-1⑨ contains components such as aromatics and asphaltenes; (7) Repeat step (6) to obtain extract 2-n, polar solvent 2⑥, and upper extraction solution 2-n⑧; (8) Distill the upper extraction solution 2-n⑧ to obtain the upper extract 2-n, the main component of which is phenolic organic compounds; (9) Filter the lower extraction solution 2-n⑨ to obtain the lower extraction solution 2- (n+1) ⑨ and the lower raffinate 2- containing heavy asphalt (n+1) ; (10) Distill the lower extraction A method for separating alkanes, phenols, and aromatics from low-temperature coal tar, characterized in that the method comprises the following steps: (1) Configure a dual-solvent system A. Take non-polar solvent 1① and polar solvent 1② and prepare them in a certain proportion to obtain a layered dual-solvent system A; (2) Configure a dual-solvent system B. Take non-polar solvent 2⑦ and polar solvent 2⑥ and prepare them in a certain proportion to obtain a layered dual-solvent system B. The non-polar solvents used are organic solvents such as carbon disulfide, petroleum ether, n-hexane, and cyclohexane. The polar solvents are polar solvents such as alcohols, nitriles, and water; (3) Add low-temperature coal tar to the dual-solvent system A. The volume ratio of the dual-solvent system A to the low-temperature coal tar is 15:1 to 10:

1. Magnetically stir at 600 rpm / h at room temperature for 1 h. After mixing and standing for stratification, place it in a separating funnel for separation to obtain the upper extraction solution 1-1③ and the lower extraction solution 1-1④; (4) The upper extraction solution 1-1③ is enriched with alkane organic compounds in low-temperature coal tar. The upper extraction solution 1-1③ is distilled to obtain an alkane extract 1-1 and a non-polar solvent 1①, and the non-polar solvent 1① is recycled; the lower extraction solution 1-1④ contains components such as phenols, aromatics, and asphaltenes; (5) Repeat step (3) to obtain an extract 1-n, a non-polar solvent 1①, and an upper extraction solution 1-n③. The lower extraction solution 1-n④ is distilled to obtain a lower extract 1-n⑤ and a polar solvent 1②, and the polar solvent 1② is recycled; (6) Add the lower extract 1-n⑤ to the double-solvent system B, and magnetically stir at 600 rpm / h for 1 h at room temperature and then let it stand. After standing and separating, an upper extraction solution 2-1⑧ and a lower extraction solution 2-1⑨ are obtained. The upper extraction solution 2-1⑧ is distilled to obtain a phenol extract 2-1 and a polar solvent 2⑥, and the polar solvent 2⑥ is recycled. The lower extraction solution 2-1⑨ contains components such as aromatics and asphaltenes; (7) Repeat step (6) to obtain an extract 2-n, a polar solvent 2⑥, and an upper extraction solution 2-n⑧; (8) Distill the upper extraction solution 2-n⑧ to obtain an upper extract 2-n, the main component of which is phenolic organic compounds; (9) Filter the lower extraction solution 2-n⑨ to obtain the lower extraction solution 2- (n+1) ⑨ and the lower raffinate 2- containing heavy asphalt (n+1) ; (10) Distill the lower extraction solution 2- (n+1) ⑨ to obtain the lower extract 2- containing aromatic organic compounds (n+1) and a non-polar solvent, and the non-polar solvent is recycled.

2. The method for separating alkanes, phenols and aromatic hydrocarbons from low-temperature coal tar according to claim 1, characterized in that, The non-polar solvent 1① in the double-solvent system A is an alkane solvent, including organic solvents such as gasoline, kerosene, petroleum ether, n-hexane, and n-heptane. The polar solvent 1② is alcohols, nitriles, amines, and sulfones. The volume ratio of the non-polar solvent 1 to the polar solvent 1 is 2:1 to 10:1, and after mixing, it separates into two phases.

3. The method for separating alkanes, phenols and aromatic hydrocarbons from low-temperature coal tar according to claim 1, characterized in that, The non-polar solvent 2⑦ in the double-solvent system B is an organic solvent such as light oil, wash oil, and carbon disulfide, and the polar solvent 2⑥ is alcohols, nitriles, amines, and sulfones. The volume ratio of the polar solvent 2⑥ to the non-polar solvent 2⑦ is 1:1 to 10:1, and after mixing, it separates into two phases.

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