A method for in-situ extraction of oil-phenol mixture by coupling ion liquid extraction with back extraction and flash separation

Abstract

This invention provides a method for separating an oil-phenol mixture by in-situ extraction coupled with back-extraction and flash evaporation using ionic liquid. First, the oil-phenol mixture is countercurrently extracted in an extraction tower with a 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid to obtain a dephenolized oil and a phenol-containing extract. The extract then enters a back-extraction tower, where it is countercurrently contacted with low-carbon alkanes to remove most of the neutral oil, yielding a back-extraction extract and a back-extraction raffinate. The back-extraction raffinate is flashed in tank F1 to remove residual neutral oil, yielding a phenol-rich material; it is then flashed in tank F2 to obtain the phenol product and regenerate the ionic liquid extractant. The back-extraction extract is flashed in tank F3 to obtain a neutral oil-rich fraction and regenerate the back-extraction agent. The neutral oil-rich fraction is combined with the top product from tower F1 and returned to the extraction tower for phenol recovery. This invention features a simple and stable process with high separation efficiency, high phenol product purity, and a neutral oil content of less than 1%. The extractant and back-extraction agent used are reusable.

Description

Technical Field

[0001] This invention relates to a method for separating an oil-phenol mixture by coupling in-situ extraction with back-extraction and flash evaporation using ionic liquids. Background Technology

[0002] Phenolic compounds are important oxygen-containing components in low-temperature coal pyrolysis oil, coal tar, and petroleum processing by-products, and are widely used in the production of phenolic resins, pharmaceutical intermediates, pesticides, and fine chemicals. With the continuous advancement of coal grading and the development of unconventional oil resources, the efficient separation of phenolic compounds from complex oil-phenol mixtures has become a key technology in the process of high-value resource utilization. Oil-phenol mixtures typically consist of phenolic compounds and various neutral oil components, including aromatics, alkanes, and nitrogen-containing compounds, exhibiting complex compositions, significant polarity differences, and a wide boiling point distribution range. Furthermore, the boiling points of phenolic compounds and some neutral oils are close, sometimes even forming azeotropic systems, posing significant technical challenges to traditional separation methods.

[0003] Currently, industrial phenol separation commonly employs alkaline washing, distillation, and organic solvent extraction. Alkaline washing achieves phenol conversion and separation through acid-base reactions, but this method consumes large amounts of acid and base reagents, is complex, and generates significant amounts of high-salt wastewater, resulting in a heavy environmental impact. Distillation separation relies on differences in volatility to separate components, but for oleophenol systems with similar boiling points or azeotropic behavior, high reflux ratios and multi-stage tower equipment are often required, leading to high energy consumption and operating costs, limiting industrial applications. Organic solvent extraction technology has been widely studied due to its mild operating conditions, but traditional organic extractants typically suffer from limited selectivity, high volatility, and insufficient safety. Furthermore, neutral oil components are easily entrained during extraction, requiring additional subsequent separation steps, further increasing process complexity and energy consumption.

[0004] In recent years, ionic liquids have been considered a promising new type of green extraction medium due to their low vapor pressure, good thermal stability, high designability, and strong solubility for polar compounds. Existing research has shown that ionic liquids can selectively enrich phenolic substances through hydrogen bonding or intermolecular interactions. However, current ionic liquid extraction technologies generally suffer from problems such as difficulty in extractant regeneration, ineffective removal of neutral oil entrained in the system, and dispersed unit operations in the separation process, making it difficult to balance separation efficiency, energy consumption, and the requirements of continuous industrial operation. Therefore, there is an urgent need to develop a novel method for separating oil-phenol mixtures that can achieve highly selective separation of phenolic compounds, reduce separation energy consumption, and enable efficient recycling of extractants and auxiliary solvents.

[0005] This invention introduces an ionic liquid in situ to form a eutectic solvent with phenols in an oil-phenol mixture to enrich phenols, and couples back-extraction and flash evaporation separation processes to achieve efficient separation of phenolic compounds and regeneration of the extractant in the oil-phenol mixture, thereby improving the purity of phenolic products and reducing the overall energy consumption of the separation process. Summary of the Invention

[0006] The purpose of this invention is to address the problems existing in the separation of phenolic compounds from oil-phenol mixtures by proposing a highly efficient method for separating phenolic compounds. The method uses 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid as the extractant and low-carbon alkanes as the back-extraction agent. Phenolic compounds are extracted by forming a eutectic solvent with the extractant, and the back-extraction and flash evaporation processes are coupled to achieve phenolic purification and separation, as shown in the accompanying drawings. Figure 1 As shown, the extractant used in the method of the present invention has good thermal stability, the stripping agent is inexpensive and miscible with the extractant, and both the extractant and the stripping agent can be regenerated by flash evaporation.

[0007] The objective of this invention is achieved through the following technical solution.

[0008] A method for separating an oil-phenol mixture by coupling in-situ extraction with back-extraction and flash evaporation using ionic liquids, the method comprising the following steps: (1) Add 1-butyl-3-methylimidazolium tetrafluoroborate extractant M1 to the top of extraction tower T1, so that it comes into countercurrent contact with the oil-phenol mixture S1 entering from the bottom of the tower, and extract at a given temperature to obtain extract B1 and raffinate D1, where D1 is dephenolized oil; (2) Add low-carbon alkane back-extraction agent to the bottom of back-extraction tower T2, so that it comes into countercurrent contact with the extract B1 obtained in step (1) entering from the top of the tower, and back-extract at a given temperature to obtain back-extraction extract D2 and back-extraction raffinate B2; (3) Enter the back-extraction raffinate B2 obtained in step (2) into flash evaporator F1 for flash evaporation to obtain neutral oil-rich distillate. (3) Separate D3 and extract B3 from neutral oil; (4) Enter the extract B3 from step (3) into flash tank F2 for flash evaporation to obtain crude phenol product D5 and regenerated extractant B5. The regenerated extractant is cooled and returned to extraction tower T1 for reuse; (5) Enter the back-extraction liquid D2 obtained in step (2) into flash tank F3 for flash evaporation to obtain neutral oil-rich fraction B4 and regenerated back-extraction agent D4. The regenerated back-extraction agent is cooled and returned to back-extraction tower T2 for reuse. The neutral oil-rich fraction B4 is mixed with the neutral oil-rich fraction D3 in step (3) and cooled and returned to the raw material oil-phenol mixture for further extraction; The low-carbon alkane back-extractant mentioned in step (2) is selected from one of n-hexane, cyclohexane and n-heptane.

[0009] The method described above is characterized in that the molar ratio of the extractant to the phenol in the raw material in the extraction tower in step (1) is 0.5 to 1.0.

[0010] The method described above is characterized in that the temperature for in-situ extraction of phenolic compounds by ionic liquid in step (1) is 25°C to 45°C.

[0011] The method described above is characterized in that the mass ratio of the back-extraction agent to the extractant B1 in the back-extraction tower in step (2) is 1.38 to 2.49.

[0012] The method described above is characterized in that the temperature for back-extraction to remove neutral oil in step (2) is 25°C to 45°C.

[0013] The method described above is characterized in that the pressure in the flash tank F1 in step (3) is 0.05 atm to 0.1 atm and the temperature is 180°C to 200°C.

[0014] In the above method, the pressure in the flash tank F2 in step (4) is 0.01 atm to 0.05 atm, and the temperature is 210°C to 230°C.

[0015] The method described above is characterized in that the pressure in the flash tank F3 in step (5) is 0.5 atm to 1 atm and the temperature is 70°C to 100°C.

[0016] The principle of this method is as follows: First, phenolic compounds (hydrogen bond donors) and 1-butyl-3-methylimidazolium tetrafluoroborate extractant (hydrogen bond acceptors) form a eutectic solvent through hydrogen bonds. The resulting eutectic solvent is insoluble in the oil phase after phenol removal, while other components in the oil-phenol mixture cannot form a eutectic solvent with the extractant. Simultaneously, the 1-butyl-3-methylimidazolium tetrafluoroborate used in this patent is an extractant screened from a large number of ionic liquids using the COSMO-SAC model. It exhibits the best overall performance in terms of phenolic solubility, selectivity, and thermal stability. Therefore, phenolic compounds in the oil-phenol mixture can be selectively separated using the 1-butyl-3-methylimidazolium tetrafluoroborate extractant, and the extractant can be regenerated by flash evaporation without decomposition at the regeneration temperature. Secondly, low-carbon alkanes are weakly polar substances and have good miscibility with oils, while the eutectic solvent formed by phenols and extractants is a strongly polar substance and is insoluble in low-carbon alkanes. Therefore, neutral oil entrained during the extraction process can be removed by back-extraction of low-carbon alkanes. At the same time, since the boiling point of low-carbon alkanes is significantly lower than that of neutral oils, high-purity low-carbon alkanes back-extraction agents can be regenerated by flash evaporation.

[0017] Compared with traditional methods, the advantages of this method are: (1) The extractant used is environmentally friendly, stable in properties and has high thermal stability, and will not undergo thermal decomposition; (2) The method of removing neutral oil from low-carbon alkanes is not limited by the boiling point of neutral oil and has good applicability to neutral oil or azeotropic systems with different temperature distributions; (3) This method uses an in-situ eutectic solvent extraction method to extract phenols, and the extractant can be regenerated at the same time as obtaining phenol products by flash evaporation, without the need for additional distillation or other units to regenerate the extractant; (4) This method does not use acid and alkali solvents, saves resources, generates no wastewater, has low cost and is environmentally friendly; (5) The extraction coupled flash evaporation process has lower energy consumption than the direct extraction distillation process; (6) The phenol mixture obtained by this method has high purity and low neutral oil content. Attached Figure Description

[0018] To more clearly illustrate the background technology and the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Figure 1 This is a process flow diagram for the in-situ extraction of ionic liquid coupled with back-extraction and flash evaporation to separate the oil-phenol mixture according to the present invention. The flow diagram mainly includes: The flow chart includes an extraction tower (T1), a back-extraction tower (T2), flash tanks (F1, F2, F3), a condenser, and a mixer. The main material flow is as follows: oil-phenol mixture feed (S1), fresh extractant feed (M1), dephenolized oil (D1), extract (B1), fresh back-extraction agent (M2), back-extraction extract (D2), back-extraction residue (B2), neutral oil-rich fraction (D3), phenol-rich fraction (B3), neutral oil-rich fraction (B4), regenerated back-extraction agent (D4), phenol product (D5), and regenerated extractant (B5).

[0019] Example 1 In this embodiment, a phenol-oil mixture was prepared to simulate oil based on the composition of actual low-temperature coal pyrolysis oil for separation experiments. The phenol-oil mixture used consisted of 30% m-cresol, 32.5% 1-methylnaphthalene, 32.5% tridecane, and 5% 3-methylpyridine, where 1-methylnaphthalene, tridecane, and 3-methylpyridine were neutral oil components. 1-Butyl-3-methylimidazolium tetrafluoroborate extractant at a flow rate of 314 kg / h was introduced from the top of extraction tower T1, while the phenol-oil mixture feedstock at a flow rate of 1000 kg / h was introduced from the bottom of the extraction tower (the molar ratio of extractant to intermediate cresol in the feedstock was 0.5:1). Countercurrent contact extraction was carried out in extraction tower T1 at a temperature of 25°C and a pressure of 1 atm. Raffinate D1 (dephenolized oil) was obtained at the top of the tower with a flow rate of 590.69 kg / h and a neutral oil content of 98.32%; extract B1 was obtained at the bottom of the tower with a flow rate of 723.32 kg / h and a phenol extraction rate of 97.91%. Extract B1 enters from the top of back-extraction column T2, while n-hexane back-extraction agent at a flow rate of 1800 kg / h enters from the bottom of the column. Countercurrent contact extraction is carried out in back-extraction column T2 at a temperature of 25°C and a pressure of 1 atm. The top of the column yields back-extraction extract D2 at a flow rate of 1915.0 kg / h, with a neutral oil removal rate of 97.72%. The bottom of the column yields back-extraction residue B2 at a flow rate of 608.33 kg / h, with a phenol content of 98.60% after removing the extractant. B2 enters flash evaporator F1 and is flashed at 0.1 atm and 180°C. The top of the flash evaporator yields a neutral oil-rich fraction D3 at a flow rate of 65.63 kg / h, with a neutral oil removal rate of 85.37%. The bottom of the flash evaporator yields a neutral oil-removed fraction B3 at a flow rate of 542.68 kg / h, with a phenol content of 99.52% after removing the extractant. B3 enters flash tank F2 and undergoes flash evaporation at 0.01 atm and 230°C. The top of the flash tank yields a phenol product with a flow rate of 232.92 kg / h and a purity of 99.51%; the bottom yields a regenerated extractant with a flow rate of 309.76 kg / h and a purity of 98.57%. The back-extraction extract D2 obtained from the top of back-extraction column T2 enters flash tank F3 and undergoes flash evaporation at 1 atm and 70°C. The top of the flash tank yields a regenerated back-extraction agent with a flow rate of 1788.79 kg / h and a purity of 99.19%; the bottom yields a neutral oil-rich fraction B4 with a flow rate of 126.21 kg / h, containing 96.58% neutral oil. B4 is mixed with D3, cooled, and returned to the extraction column for further extraction. The regenerated extractant is returned to the extraction column for reuse, and the regenerated back-extraction agent is returned to the back-extraction column for reuse.

[0020] Example 2 In this embodiment, a phenol-oil mixture was prepared to simulate oil based on the composition of actual low-temperature coal pyrolysis oil for separation experiments. The phenol-oil mixture used consisted of 30% m-cresol, 32.5% 1-methylnaphthalene, 32.5% tridecane, and 5% 3-methylpyridine, where 1-methylnaphthalene, tridecane, and 3-methylpyridine were neutral oil components. A 1-butyl-3-methylimidazolium tetrafluoroborate extractant at a flow rate of 628 kg / h was introduced from the top of extraction tower T1, while the phenol-oil mixture feedstock at a flow rate of 1000 kg / h was introduced from the bottom of the extraction tower (the molar ratio of extractant to intermediate cresol in the feedstock was 1:1). Countercurrent contact extraction was carried out in extraction tower T1 at a temperature of 25°C and a pressure of 1 atm. Raffinate D1 (dephenolized oil) was obtained at the top of the tower with a flow rate of 558.98 kg / h and a neutral oil content of 98.20%; extract B1 was obtained at the bottom of the tower with a flow rate of 1069.02 kg / h and a phenol extraction rate of 97.98%. Extract B1 enters from the top of back-extraction column T2, while n-hexane back-extraction agent at a flow rate of 2662 kg / h enters from the bottom of the column. Countercurrent contact extraction is carried out in back-extraction column T2 at 25°C and 1 atm. The top of the column yields back-extraction extract D2 at a flow rate of 2775.26 kg / h, with a neutral oil removal rate of 94.15%. The bottom of the column yields back-extraction residue B2 at a flow rate of 955.76 kg / h, with a phenol content of 96.59% after removing the extractant. B2 enters flash evaporator F1 and is flashed at 0.1 atm and 180°C. The top of the flash evaporator yields a neutral oil-rich fraction D3 at a flow rate of 69.09 kg / h, with a neutral oil removal rate of 85.58%. The bottom of the flash evaporator yields a neutral oil-removed fraction B3 at a flow rate of 886.67 kg / h, with a phenol content of 99.35% after removing the extractant. B3 enters flash tank F2 and undergoes flash evaporation at 0.01 atm and 230°C. The top of the flash tank yields a phenol product with a flow rate of 263.33 kg / h and a purity of 99.34%; the bottom yields a regenerated extractant with a flow rate of 623.34 kg / h and a purity of 98.57%. The back-extraction extract D2 obtained from the top of back-extraction column T2 enters flash tank F3 and undergoes flash evaporation at 1 atm and 70°C. The top of the flash tank yields a regenerated back-extraction agent with a flow rate of 2638.78 kg / h and a purity of 99.18%; the bottom yields a neutral oil-rich fraction B4 with a flow rate of 136.48 kg / h, containing 90.60% neutral oil. B4 is mixed with D3, cooled, and returned to the extraction column for further extraction. The regenerated extractant is returned to the extraction column for reuse, and the regenerated back-extraction agent is returned to the back-extraction column for reuse.

[0021] Example 3 In this embodiment, a phenol-oil mixture was prepared to simulate oil based on the composition of actual low-temperature coal pyrolysis oil for separation experiments. The phenol-oil mixture used consisted of 30% m-cresol, 32.5% 1-methylnaphthalene, 32.5% tridecane, and 5% 3-methylpyridine, where 1-methylnaphthalene, tridecane, and 3-methylpyridine were neutral oil components. 1-Butyl-3-methylimidazolium tetrafluoroborate extractant at a flow rate of 314 kg / h was introduced from the top of extraction tower T1, while the phenol-oil mixture feedstock at a flow rate of 1000 kg / h was introduced from the bottom of the extraction tower (the molar ratio of extractant to intermediate cresol in the feedstock was 0.5:1). Countercurrent contact extraction was carried out in extraction tower T1 at a temperature of 45°C and a pressure of 1 atm. Raffinate D1 (dephenolized oil) was obtained at the top of the tower with a flow rate of 561.85 kg / h and a neutral oil content of 98.16%; extract B1 was obtained at the bottom of the tower with a flow rate of 752.16 kg / h and a phenol extraction rate of 97.77%. Extract B1 enters from the top of back-extraction column T2, while n-hexane back-extraction agent at a flow rate of 1800 kg / h enters from the bottom. Countercurrent contact extraction is carried out in back-extraction column T2 at a temperature of 25°C and a pressure of 1 atm. The top of the column yields back-extraction extract D2 at a flow rate of 1923.3 kg / h, with a neutral oil removal rate of 95.18%. The bottom of the column yields back-extraction residue B2 at a flow rate of 628.85 kg / h, with a phenol content of 96.31% after removing the extractant. B2 enters flash evaporator F1 and is flashed at 0.1 atm and 180°C. The top of the flash evaporator yields a neutral oil-rich fraction D3 at a flow rate of 66.12 kg / h, with a neutral oil removal rate of 86.01%. The bottom of the flash evaporator yields a neutral oil-removed fraction B3 at a flow rate of 562.72 kg / h, with a phenol content of 99.45% after removing the extractant. B3 enters flash tank F2 and undergoes flash evaporation at 0.01 atm and 230°C. The top of the flash tank yields a phenol product with a flow rate of 232.16 kg / h and a purity of 99.44%; the bottom yields a regenerated extractant with a flow rate of 309.52 kg / h and a purity of 98.61%. The back-extraction extract D2 obtained from the top of back-extraction column T2 enters flash tank F3 and undergoes flash evaporation at 1 atm and 70°C. The top of the flash tank yields a regenerated back-extraction agent with a flow rate of 1781.32 kg / h and a purity of 99.19%; the bottom yields a neutral oil-rich fraction B4 with a flow rate of 141.99 kg / h, containing 95.41% neutral oil. B4 is mixed with D3, cooled, and returned to the extraction column for further extraction. The regenerated extractant is returned to the extraction column for reuse, and the regenerated back-extraction agent is returned to the back-extraction column for reuse.

[0022] Example 4 In this embodiment, a phenol-oil mixture was prepared to simulate oil based on the composition of actual low-temperature coal pyrolysis oil for separation experiments. The phenol-oil mixture used consisted of 30% m-cresol, 32.5% 1-methylnaphthalene, 32.5% tridecane, and 5% 3-methylpyridine, where 1-methylnaphthalene, tridecane, and 3-methylpyridine were neutral oil components. 1-Butyl-3-methylimidazolium tetrafluoroborate extractant at a flow rate of 314 kg / h was introduced from the top of extraction tower T1, while the phenol-oil mixture feedstock at a flow rate of 1000 kg / h was introduced from the bottom of the extraction tower (the molar ratio of extractant to intermediate cresol in the feedstock was 0.5:1). Countercurrent contact extraction was carried out in extraction tower T1 at a temperature of 25°C and a pressure of 1 atm. Raffinate D1 (dephenolized oil) was obtained at the top of the tower with a flow rate of 590.69 kg / h and a neutral oil content of 98.32%; extract B1 was obtained at the bottom of the tower with a flow rate of 723.32 kg / h and a phenol extraction rate of 97.91%. Extract B1 enters from the top of back-extraction column T2, while cyclohexane back-extraction agent at a flow rate of 1800 kg / h enters from the bottom. Countercurrent contact extraction is carried out in back-extraction column T2 at a temperature of 25°C and a pressure of 1 atm. The top of the column yields back-extraction extract D2 at a flow rate of 1900.4 kg / h, with a neutral oil removal rate of 93.91%. The bottom of the column yields back-extraction residue B2 at a flow rate of 622.97 kg / h, with a phenol content of 97.55% after removing the extractant. B2 enters flash evaporator F1 and is flashed at 0.1 atm and 180°C. The top of the flash evaporator yields a neutral oil-rich fraction D3 at a flow rate of 67.24 kg / h, with a neutral oil removal rate of 89.44%. The bottom of the flash evaporator yields a neutral oil-removed fraction B3 at a flow rate of 555.73 kg / h, with a phenol content of 99.31% after removing the extractant. B3 enters flash tank F2 and undergoes flash evaporation at 0.01 atm and 230°C. The top of the flash tank yields a phenol product with a flow rate of 245.99 kg / h and a purity of 99.13%; the bottom yields a regenerated extractant with a flow rate of 309.74 kg / h and a purity of 98.43%. The back-extraction extract D2 obtained from the top of back-extraction column T2 enters flash tank F3 and undergoes flash evaporation at 1 atm and 81°C. The top of the flash tank yields a regenerated back-extraction agent with a flow rate of 1785.14 kg / h and a purity of 99.23%; the bottom yields a neutral oil-rich fraction B4 with a flow rate of 115.11 kg / h, containing 97.14% neutral oil. B4 is mixed with D3, cooled, and returned to the extraction column for further extraction. The regenerated extractant is returned to the extraction column for reuse, and the regenerated back-extraction agent is returned to the back-extraction column for reuse.

[0023] Example 5 In this embodiment, a phenol-oil mixture was prepared to simulate oil based on the composition of actual low-temperature coal pyrolysis oil for separation experiments. The phenol-oil mixture used consisted of 30% m-cresol, 32.5% 1-methylnaphthalene, 32.5% tridecane, and 5% 3-methylpyridine, where 1-methylnaphthalene, tridecane, and 3-methylpyridine were neutral oil components. 1-Butyl-3-methylimidazolium tetrafluoroborate extractant at a flow rate of 314 kg / h was introduced from the top of extraction tower T1, while the phenol-oil mixture feedstock at a flow rate of 1000 kg / h was introduced from the bottom of the extraction tower (the molar ratio of extractant to intermediate cresol in the feedstock was 0.5:1). Countercurrent contact extraction was carried out in extraction tower T1 at a temperature of 25°C and a pressure of 1 atm. Raffinate D1 (dephenolized oil) was obtained at the top of the tower with a flow rate of 590.69 kg / h and a neutral oil content of 98.32%; extract B1 was obtained at the bottom of the tower with a flow rate of 723.32 kg / h and a phenol extraction rate of 97.91%. Extract B1 enters from the top of back-extraction column T2, while n-heptane back-extraction agent at a flow rate of 1800 kg / h enters from the bottom of the column. Countercurrent contact extraction is carried out in back-extraction column T2 at 25°C and 1 atm. The top of the column yields back-extraction extract D2 at a flow rate of 1901.4 kg / h, with a neutral oil removal rate of 94.14%. The bottom of the column yields back-extraction residue B2 at a flow rate of 621.89 kg / h, with a phenol content of 97.57% after removing the extractant. B2 enters flash evaporator F1 and is flashed at 0.1 atm and 180°C. The top of the flash evaporator yields a neutral oil-rich fraction D3 at a flow rate of 67.03 kg / h, with a neutral oil removal rate of 89.37%. The bottom of the flash evaporator yields a neutral oil-removed fraction B3 at a flow rate of 554.85 kg / h, with a phenol content of 99.32% after removing the extractant. B3 enters flash tank F2 and undergoes flash evaporation at 0.01 atm and 230°C. The top of the flash tank yields a phenol product with a flow rate of 245.11 kg / h and a purity of 99.15%; the bottom yields a regenerated extractant with a flow rate of 309.74 kg / h and a purity of 98.47%. The back-extraction extract D2 obtained from the top of back-extraction column T2 enters flash tank F3 and undergoes flash evaporation at 1 atm and 100°C. The top of the flash tank yields a regenerated back-extraction agent with a flow rate of 1786.66 kg / h and a purity of 99.15%; the bottom yields a neutral oil-rich fraction B4 with a flow rate of 114.77 kg / h, containing 95.65% neutral oil. B4 is mixed with D3, cooled, and returned to the extraction column for further extraction. The regenerated extractant is returned to the extraction column for reuse, and the regenerated back-extraction agent is returned to the back-extraction column for reuse.

[0024] Example 6 In this embodiment, a phenol-oil mixture was prepared to simulate oil based on the composition of actual low-temperature coal pyrolysis oil for separation experiments. The phenol-oil mixture used consisted of 30% m-cresol, 32.5% 1-methylnaphthalene, 32.5% tridecane, and 5% 3-methylpyridine, where 1-methylnaphthalene, tridecane, and 3-methylpyridine were neutral oil components. 1-Butyl-3-methylimidazolium tetrafluoroborate extractant at a flow rate of 314 kg / h was introduced from the top of extraction tower T1, while the phenol-oil mixture feedstock at a flow rate of 1000 kg / h was introduced from the bottom of the extraction tower (the molar ratio of extractant to intermediate cresol in the feedstock was 0.5:1). Countercurrent contact extraction was carried out in extraction tower T1 at a temperature of 25°C and a pressure of 1 atm. Raffinate D1 (dephenolized oil) was obtained at the top of the tower with a flow rate of 590.69 kg / h and a neutral oil content of 98.32%; extract B1 was obtained at the bottom of the tower with a flow rate of 723.32 kg / h and a phenol extraction rate of 97.91%. Extract B1 enters from the top of back-extraction column T2, while n-hexane back-extraction agent at a flow rate of 1000 kg / h enters from the bottom. Countercurrent contact extraction is carried out in back-extraction column T2 at a temperature of 25°C and a pressure of 1 atm. The top of the column yields back-extraction extract D2 at a flow rate of 1098.7 kg / h, with a neutral oil removal rate of 84.99%. The bottom of the column yields back-extraction residue B2 at a flow rate of 624.59 kg / h, with a phenol content of 94.04% after removing the extractant. B2 enters flash evaporator F1 and is flashed at 0.1 atm and 180°C. The top of the flash evaporator yields a neutral oil-rich fraction D3 at a flow rate of 67.32 kg / h, with a neutral oil removal rate of 89.45%. The bottom of the flash evaporator yields a neutral oil-removed fraction B3 at a flow rate of 557.26 kg / h, with a phenol content of 99.07% after removing the extractant. B3 enters flash tank F2 and undergoes flash evaporation at 0.01 atm and 230°C. The top of the flash tank yields a phenol product with a flow rate of 247.52 kg / h and a purity of 99.07%; the bottom yields a regenerated extractant with a flow rate of 309.74 kg / h and a purity of 98.43%. The back-extraction extract D2 obtained from the top of back-extraction column T2 enters flash tank F3 and undergoes flash evaporation at 1 atm and 70°C. The top of the flash tank yields a regenerated back-extraction agent with a flow rate of 974.91 kg / h and a purity of 99.22%; the bottom yields a neutral oil-rich fraction B4 with a flow rate of 123.82 kg / h, containing 96.78% neutral oil. B4 is mixed with D3, cooled, and returned to the extraction column for further extraction. The regenerated extractant is returned to the extraction column for reuse, and the regenerated back-extraction agent is returned to the back-extraction column for reuse.

[0025] Example 7 In this embodiment, a phenol-oil mixture was prepared to simulate oil based on the composition of actual low-temperature coal pyrolysis oil for separation experiments. The phenol-oil mixture used consisted of 30% m-cresol, 32.5% 1-methylnaphthalene, 32.5% tridecane, and 5% 3-methylpyridine, where 1-methylnaphthalene, tridecane, and 3-methylpyridine were neutral oil components. 1-Butyl-3-methylimidazolium tetrafluoroborate extractant at a flow rate of 314 kg / h was introduced from the top of extraction tower T1, while the phenol-oil mixture feedstock at a flow rate of 1000 kg / h was introduced from the bottom of the extraction tower (the molar ratio of extractant to intermediate cresol in the feedstock was 0.5:1). Countercurrent contact extraction was carried out in extraction tower T1 at a temperature of 25°C and a pressure of 1 atm. Raffinate D1 (dephenolized oil) was obtained at the top of the tower with a flow rate of 590.69 kg / h and a neutral oil content of 98.32%; extract B1 was obtained at the bottom of the tower with a flow rate of 723.32 kg / h and a phenol extraction rate of 97.91%. Extract B1 enters from the top of back-extraction column T2, while n-hexane back-extraction agent at a flow rate of 1800 kg / h enters from the bottom of the column. Countercurrent contact extraction is carried out in back-extraction column T2 at a temperature of 45°C and a pressure of 1 atm. The top of the column yields back-extraction extract D2 at a flow rate of 1905.2 kg / h, with a neutral oil removal rate of 89.42%. The bottom of the column yields back-extraction residue B2 at a flow rate of 618.14 kg / h, with a phenol content of 95.63% after removing the extractant. B2 enters flash evaporator F1 and is flashed at 0.1 atm and 180°C. The top of the flash evaporator yields a neutral oil-rich fraction D3 at a flow rate of 67.11 kg / h, with a neutral oil removal rate of 89.34%. The bottom of the flash evaporator yields a neutral oil-removed fraction B3 at a flow rate of 551.03 kg / h, with a phenol content of 99.12% after removing the extractant. B3 enters flash tank F2 and undergoes flash evaporation at 0.01 atm and 230°C. The top of the flash tank yields a phenol product with a flow rate of 241.31 kg / h and a purity of 99.11%; the bottom yields a regenerated extractant with a flow rate of 309.72 kg / h and a purity of 98.43%. The back-extraction extract D2 obtained from the top of back-extraction column T2 enters flash tank F3 and undergoes flash evaporation at 1 atm and 70°C. The top of the flash tank yields a regenerated back-extraction agent with a flow rate of 1786.01 kg / h and a purity of 99.18%; the bottom yields a neutral oil-rich fraction B4 with a flow rate of 119.16 kg / h, containing 95.76% neutral oil. B4 is mixed with D3, cooled, and returned to the extraction column for further extraction. The regenerated extractant is returned to the extraction column for reuse, and the regenerated back-extraction agent is returned to the back-extraction column for reuse.

[0026] Example 8 In this embodiment, a phenol-oil mixture was prepared to simulate oil based on the composition of actual low-temperature coal pyrolysis oil for separation experiments. The phenol-oil mixture used consisted of 30% m-cresol, 32.5% 1-methylnaphthalene, 32.5% tridecane, and 5% 3-methylpyridine, where 1-methylnaphthalene, tridecane, and 3-methylpyridine were neutral oil components. 1-Butyl-3-methylimidazolium tetrafluoroborate extractant at a flow rate of 314 kg / h was introduced from the top of extraction tower T1, while the phenol-oil mixture feedstock at a flow rate of 1000 kg / h was introduced from the bottom of the extraction tower (the molar ratio of extractant to intermediate cresol in the feedstock was 0.5:1). Countercurrent contact extraction was carried out in extraction tower T1 at a temperature of 25°C and a pressure of 1 atm. Raffinate D1 (dephenolized oil) was obtained at the top of the tower with a flow rate of 590.69 kg / h and a neutral oil content of 98.32%; extract B1 was obtained at the bottom of the tower with a flow rate of 723.32 kg / h and a phenol extraction rate of 97.91%. Extract B1 enters from the top of back-extraction column T2, while n-hexane back-extraction agent at a flow rate of 1800 kg / h enters from the bottom of the column. Countercurrent contact extraction is carried out in back-extraction column T2 at a temperature of 25°C and a pressure of 1 atm. The top of the column yields back-extraction extract D2 at a flow rate of 1915.0 kg / h, with a neutral oil removal rate of 97.72%. The bottom of the column yields back-extraction residue B2 at a flow rate of 608.33 kg / h, with a phenol content of 98.60% after removing the extractant. B2 enters flash evaporator F1 and is flashed at 0.1 atm and 180°C. The top of the flash evaporator yields a neutral oil-rich fraction D3 at a flow rate of 65.63 kg / h, with a neutral oil removal rate of 85.37%. The bottom of the flash evaporator yields a neutral oil-removed fraction B3 at a flow rate of 542.68 kg / h, with a phenol content of 99.52% after removing the extractant. B3 enters flash tank F2 and undergoes flash evaporation at 0.01 atm and 230°C. The top of the flash tank yields a phenol product with a flow rate of 232.92 kg / h and a purity of 99.51%; the bottom yields a regenerated extractant with a flow rate of 309.76 kg / h and a purity of 98.57%. The back-extraction extract D2 obtained from the top of back-extraction column T2 enters flash tank F3 and undergoes flash evaporation at 1 atm and 100°C. The top of the flash tank yields a regenerated back-extraction agent with a flow rate of 1790.31 kg / h and a purity of 99.05%; the bottom yields a neutral oil-rich fraction B4 with a flow rate of 124.68 kg / h, containing 96.74% neutral oil. B4 is mixed with D3, cooled, and returned to the extraction column for further extraction. The regenerated extractant is returned to the extraction column for reuse, and the regenerated back-extraction agent is returned to the back-extraction column for reuse.

[0027] Example 9 In this embodiment, a phenol-oil mixture was prepared to simulate oil based on the composition of actual low-temperature coal pyrolysis oil for separation experiments. The phenol-oil mixture used consisted of 30% m-cresol, 32.5% 1-methylnaphthalene, 32.5% tridecane, and 5% 3-methylpyridine, where 1-methylnaphthalene, tridecane, and 3-methylpyridine were neutral oil components. 1-Butyl-3-methylimidazolium tetrafluoroborate extractant at a flow rate of 314 kg / h was introduced from the top of extraction tower T1, while the phenol-oil mixture feedstock at a flow rate of 1000 kg / h was introduced from the bottom of the extraction tower (the molar ratio of extractant to intermediate cresol in the feedstock was 0.5:1). Countercurrent contact extraction was carried out in extraction tower T1 at a temperature of 25°C and a pressure of 1 atm. Raffinate D1 (dephenolized oil) was obtained at the top of the tower with a flow rate of 590.69 kg / h and a neutral oil content of 98.32%; extract B1 was obtained at the bottom of the tower with a flow rate of 723.32 kg / h and a phenol extraction rate of 97.91%. Extract B1 enters from the top of back-extraction column T2, while n-hexane back-extraction agent at a flow rate of 1800 kg / h enters from the bottom of the column. Countercurrent contact extraction is carried out in back-extraction column T2 at a temperature of 25°C and a pressure of 1 atm. The top of the column yields back-extraction extract D2 at a flow rate of 1915.0 kg / h, with a neutral oil removal rate of 97.72%. The bottom of the column yields back-extraction residue B2 at a flow rate of 608.33 kg / h, with a phenol content of 98.60% after removing the extractant. B2 enters flash evaporator F1 and is flashed at 0.1 atm and 180°C. The top of the flash evaporator yields a neutral oil-rich fraction D3 at a flow rate of 65.63 kg / h, with a neutral oil removal rate of 85.37%. The bottom of the flash evaporator yields a neutral oil-removed fraction B3 at a flow rate of 542.68 kg / h, with a phenol content of 99.52% after removing the extractant. B3 enters flash tank F2 and undergoes flash evaporation at 0.01 atm and 230°C. The top of the flash tank yields a phenol product with a flow rate of 232.92 kg / h and a purity of 99.51%; the bottom yields a regenerated extractant with a flow rate of 309.76 kg / h and a purity of 98.57%. The back-extraction extract D2 obtained from the top of back-extraction column T2 enters flash tank F3 and undergoes flash evaporation at 0.5 atm and 70°C. The top of the flash tank yields a regenerated back-extraction agent with a flow rate of 1791.27 kg / h and a purity of 99.05%; the bottom yields a neutral oil-rich fraction B4 with a flow rate of 123.73 kg / h, containing 96.77% neutral oil. B4 is mixed with D3, cooled, and returned to the extraction column for further extraction. The regenerated extractant is returned to the extraction column for reuse, and the regenerated back-extraction agent is returned to the back-extraction column for reuse.

[0028] Example 10 In this embodiment, a phenol-oil mixture was prepared to simulate oil based on the composition of actual low-temperature coal pyrolysis oil for separation experiments. The phenol-oil mixture used consisted of 30% m-cresol, 32.5% 1-methylnaphthalene, 32.5% tridecane, and 5% 3-methylpyridine, where 1-methylnaphthalene, tridecane, and 3-methylpyridine were neutral oil components. 1-Butyl-3-methylimidazolium tetrafluoroborate extractant at a flow rate of 314 kg / h was introduced from the top of extraction tower T1, while the phenol-oil mixture feedstock at a flow rate of 1000 kg / h was introduced from the bottom of the extraction tower (the molar ratio of extractant to intermediate cresol in the feedstock was 0.5:1). Countercurrent contact extraction was carried out in extraction tower T1 at a temperature of 25°C and a pressure of 1 atm. Raffinate D1 (dephenolized oil) was obtained at the top of the tower with a flow rate of 590.69 kg / h and a neutral oil content of 98.32%; extract B1 was obtained at the bottom of the tower with a flow rate of 723.32 kg / h and a phenol extraction rate of 97.91%. Extract B1 enters from the top of back-extraction column T2, while n-hexane back-extraction agent at a flow rate of 1800 kg / h enters from the bottom of the column. Countercurrent contact extraction is carried out in back-extraction column T2 at a temperature of 25°C and a pressure of 1 atm. The top of the column yields back-extraction extract D2 at a flow rate of 1915.0 kg / h, with a neutral oil removal rate of 97.72%. The bottom of the column yields back-extraction residue B2 at a flow rate of 608.33 kg / h, with a phenol content of 98.60% after removing the extractant. B2 enters flash evaporator F1 and is flashed at 0.1 atm and 200°C. The top of the flash evaporator yields a neutral oil-rich fraction D3 at a flow rate of 70.35 kg / h, with a neutral oil removal rate of 90.21%. The bottom of the flash evaporator yields a neutral oil-removed fraction B3 at a flow rate of 537.98 kg / h, with a phenol content of 99.64% after removing the extractant. B3 enters flash tank F2 and undergoes flash evaporation at 0.01 atm and 230°C. The top of the flash tank yields a phenol product with a flow rate of 228.22 kg / h and a purity of 99.63%; the bottom yields a regenerated extractant with a flow rate of 309.76 kg / h and a purity of 98.57%. The back-extraction extract D2 obtained from the top of back-extraction column T2 enters flash tank F3 and undergoes flash evaporation at 1 atm and 70°C. The top of the flash tank yields a regenerated back-extraction agent with a flow rate of 1788.79 kg / h and a purity of 99.19%; the bottom yields a neutral oil-rich fraction B4 with a flow rate of 126.21 kg / h, containing 96.58% neutral oil. B4 is mixed with D3, cooled, and returned to the extraction column for further extraction. The regenerated extractant is returned to the extraction column for reuse, and the regenerated back-extraction agent is returned to the back-extraction column for reuse.

[0029] Example 11 In this embodiment, a phenol-oil mixture was prepared to simulate oil based on the composition of actual low-temperature coal pyrolysis oil for separation experiments. The phenol-oil mixture used consisted of 30% m-cresol, 32.5% 1-methylnaphthalene, 32.5% tridecane, and 5% 3-methylpyridine, where 1-methylnaphthalene, tridecane, and 3-methylpyridine were neutral oil components. 1-Butyl-3-methylimidazolium tetrafluoroborate extractant at a flow rate of 314 kg / h was introduced from the top of extraction tower T1, while the phenol-oil mixture feedstock at a flow rate of 1000 kg / h was introduced from the bottom of the extraction tower (the molar ratio of extractant to intermediate cresol in the feedstock was 0.5:1). Countercurrent contact extraction was carried out in extraction tower T1 at a temperature of 25°C and a pressure of 1 atm. Raffinate D1 (dephenolized oil) was obtained at the top of the tower with a flow rate of 590.69 kg / h and a neutral oil content of 98.32%; extract B1 was obtained at the bottom of the tower with a flow rate of 723.32 kg / h and a phenol extraction rate of 97.91%. Extract B1 enters from the top of back-extraction column T2, while n-hexane back-extraction agent at a flow rate of 1800 kg / h enters from the bottom of the column. Countercurrent contact extraction is carried out in back-extraction column T2 at a temperature of 25°C and a pressure of 1 atm. The top of the column yields back-extraction extract D2 at a flow rate of 1915.0 kg / h, with a neutral oil removal rate of 97.72%. The bottom of the column yields back-extraction residue B2 at a flow rate of 608.33 kg / h, with a phenol content of 98.60% after removing the extractant. B2 enters flash evaporator F1 and is flashed at 0.05 atm and 180°C. The top of the flash evaporator yields a neutral oil-rich fraction D3 at a flow rate of 70.41 kg / h, with a neutral oil removal rate of 90.23%. The bottom of the flash evaporator yields a neutral oil-removed fraction B3 at a flow rate of 537.91 kg / h, with a phenol content of 99.65% after removing the extractant. B3 enters flash tank F2 and undergoes flash evaporation at 0.01 atm and 230°C. The top of the flash tank yields a phenol product with a flow rate of 228.15 kg / h and a purity of 99.64%; the bottom yields a regenerated extractant with a flow rate of 309.76 kg / h and a purity of 98.57%. The back-extraction extract D2 obtained from the top of back-extraction column T2 enters flash tank F3 and undergoes flash evaporation at 1 atm and 70°C. The top of the flash tank yields a regenerated back-extraction agent with a flow rate of 1788.79 kg / h and a purity of 99.19%; the bottom yields a neutral oil-rich fraction B4 with a flow rate of 126.21 kg / h, containing 96.58% neutral oil. B4 is mixed with D3, cooled, and returned to the extraction column for further extraction. The regenerated extractant is returned to the extraction column for reuse, and the regenerated back-extraction agent is returned to the back-extraction column for reuse.

[0030] Example 12 In this embodiment, a phenol-oil mixture was prepared to simulate oil based on the composition of actual low-temperature coal pyrolysis oil for separation experiments. The phenol-oil mixture used consisted of 30% m-cresol, 32.5% 1-methylnaphthalene, 32.5% tridecane, and 5% 3-methylpyridine, where 1-methylnaphthalene, tridecane, and 3-methylpyridine were neutral oil components. 1-Butyl-3-methylimidazolium tetrafluoroborate extractant at a flow rate of 314 kg / h was introduced from the top of extraction tower T1, while the phenol-oil mixture feedstock at a flow rate of 1000 kg / h was introduced from the bottom of the extraction tower (the molar ratio of extractant to intermediate cresol in the feedstock was 0.5:1). Countercurrent contact extraction was carried out in extraction tower T1 at a temperature of 25°C and a pressure of 1 atm. Raffinate D1 (dephenolized oil) was obtained at the top of the tower with a flow rate of 590.69 kg / h and a neutral oil content of 98.32%; extract B1 was obtained at the bottom of the tower with a flow rate of 723.32 kg / h and a phenol extraction rate of 97.91%. Extract B1 enters from the top of back-extraction column T2, while n-hexane back-extraction agent at a flow rate of 1800 kg / h enters from the bottom of the column. Countercurrent contact extraction is carried out in back-extraction column T2 at a temperature of 25°C and a pressure of 1 atm. The top of the column yields back-extraction extract D2 at a flow rate of 1915.0 kg / h, with a neutral oil removal rate of 97.72%. The bottom of the column yields back-extraction residue B2 at a flow rate of 608.33 kg / h, with a phenol content of 98.60% after removing the extractant. B2 enters flash evaporator F1 and is flashed at 0.1 atm and 180°C. The top of the flash evaporator yields a neutral oil-rich fraction D3 at a flow rate of 65.63 kg / h, with a neutral oil removal rate of 85.37%. The bottom of the flash evaporator yields a neutral oil-removed fraction B3 at a flow rate of 542.68 kg / h, with a phenol content of 99.52% after removing the extractant. B3 enters flash tank F2 and undergoes flash evaporation at 0.01 atm and 210°C. The top of the flash tank yields a phenol product with a flow rate of 231.41 kg / h and a purity of 99.50%; the bottom yields a regenerated extractant with a flow rate of 311.26 kg / h and a purity of 97.33%. The back-extraction extract D2 obtained from the top of back-extraction column T2 enters flash tank F3 and undergoes flash evaporation at 1 atm and 70°C. The top of the flash tank yields a regenerated back-extraction agent with a flow rate of 1788.79 kg / h and a purity of 99.19%; the bottom yields a neutral oil-rich fraction B4 with a flow rate of 126.21 kg / h, containing 96.58% neutral oil. B4 is mixed with D3, cooled, and returned to the extraction column for further extraction. The regenerated extractant is returned to the extraction column for reuse, and the regenerated back-extraction agent is returned to the back-extraction column for reuse.

[0031] Example 13 In this embodiment, a phenol-oil mixture was prepared to simulate oil based on the composition of actual low-temperature coal pyrolysis oil for separation experiments. The phenol-oil mixture used consisted of 30% m-cresol, 32.5% 1-methylnaphthalene, 32.5% tridecane, and 5% 3-methylpyridine, where 1-methylnaphthalene, tridecane, and 3-methylpyridine were neutral oil components. 1-Butyl-3-methylimidazolium tetrafluoroborate extractant at a flow rate of 314 kg / h was introduced from the top of extraction tower T1, while the phenol-oil mixture feedstock at a flow rate of 1000 kg / h was introduced from the bottom of the extraction tower (the molar ratio of extractant to intermediate cresol in the feedstock was 0.5:1). Countercurrent contact extraction was carried out in extraction tower T1 at a temperature of 25°C and a pressure of 1 atm. Raffinate D1 (dephenolized oil) was obtained at the top of the tower with a flow rate of 590.69 kg / h and a neutral oil content of 98.32%; extract B1 was obtained at the bottom of the tower with a flow rate of 723.32 kg / h and a phenol extraction rate of 97.91%. Extract B1 enters from the top of back-extraction column T2, while n-hexane back-extraction agent at a flow rate of 1800 kg / h enters from the bottom of the column. Countercurrent contact extraction is carried out in back-extraction column T2 at a temperature of 25°C and a pressure of 1 atm. The top of the column yields back-extraction extract D2 at a flow rate of 1915.0 kg / h, with a neutral oil removal rate of 97.72%. The bottom of the column yields back-extraction residue B2 at a flow rate of 608.33 kg / h, with a phenol content of 98.60% after removing the extractant. B2 enters flash evaporator F1 and is flashed at 0.1 atm and 180°C. The top of the flash evaporator yields a neutral oil-rich fraction D3 at a flow rate of 65.63 kg / h, with a neutral oil removal rate of 85.37%. The bottom of the flash evaporator yields a neutral oil-removed fraction B3 at a flow rate of 542.68 kg / h, with a phenol content of 99.52% after removing the extractant. B3 enters flash tank F2 and undergoes flash evaporation at 0.05 atm and 230°C. The top of the flash tank yields a phenol product with a flow rate of 232.13 kg / h and a purity of 99.50%; the bottom yields a regenerated extractant with a flow rate of 310.54 kg / h and a purity of 90.54%. The back-extraction extract D2 obtained from the top of back-extraction column T2 enters flash tank F3 and undergoes flash evaporation at 1 atm and 70°C. The top of the flash tank yields a regenerated back-extraction agent with a flow rate of 1788.79 kg / h and a purity of 99.19%; the bottom yields a neutral oil-rich fraction B4 with a flow rate of 126.21 kg / h, containing 96.58% neutral oil. B4 is mixed with D3, cooled, and returned to the extraction column for further extraction. The regenerated extractant is returned to the extraction column for reuse, and the regenerated back-extraction agent is returned to the back-extraction column for reuse.

[0032] Example 14 In this embodiment, a phenol-oil mixture was prepared to simulate oil based on the composition of actual low-temperature coal pyrolysis oil for separation experiments. The phenol-oil mixture used consisted of 30% m-cresol, 32.5% 1-methylnaphthalene, 32.5% tridecane, and 5% 3-methylpyridine, where 1-methylnaphthalene, tridecane, and 3-methylpyridine were neutral oil components. A 1-butyl-3-methylimidazolium tetrafluoroborate extractant with a purity of 98.57% and a flow rate of 305.76 kg / h was mixed with a pure 1-butyl-3-methylimidazolium tetrafluoroborate extractant with a flow rate of 12.61 kg / h and introduced from the top of extraction tower T1. The phenol-oil mixture feedstock with a flow rate of 1000 kg / h entered from the bottom of the extraction tower (the molar ratio of extractant to intermediate cresol in the feedstock was 0.5:1). Countercurrent contact extraction was carried out in extraction tower T1 at a temperature of 25°C and a pressure of 1 atm. The top of the column yielded raffinate D1 (phenol-free oil) with a flow rate of 591.16 kg / h and a neutral oil content of 98.25%. The bottom of the column yielded extract B1 with a flow rate of 722.84 kg / h and a phenol extraction rate of 97.87%. Extract B1 entered from the top of the back-extraction column T2. ​​Hexane (99.19% purity, flow rate 1788.79 kg / h) and hexane back-extraction agent (flow rate 25.70 kg / h) were mixed and then entered from the bottom of the back-extraction column. Countercurrent contact extraction was carried out in back-extraction column T2 at 25°C and 1 atm. The top of the column yielded back-extraction extract D2 with a flow rate of 1915.0 kg / h and a neutral oil removal rate of 97.25%. The bottom of the column yielded raffinate B2 with a flow rate of 608.33 kg / h and a phenol content of 98.52% after removing the extractant. B2 enters flash tank F1 and is flashed at 0.1 atm and 180°C. The top of the flash tank yields a neutral oil-rich fraction D3 with a flow rate of 65.22 kg / h, where the neutral oil removal rate is 86.12%. The bottom of the flash tank yields a neutral oil-removed fraction B3 with a flow rate of 543.04 kg / h and a phenol content of 99.36% after extractant removal. B3 enters flash tank F2 and is flashed at 0.01 atm and 230°C. The top of the flash tank yields a phenol product with a flow rate of 233.48 kg / h and a purity of 99.36%. The bottom of the flash tank yields a regenerated extractant with a flow rate of 309.56 kg / h and a purity of 98.48%. The back-extraction extract D2 obtained from the top of the back-extraction tower T2 enters flash tank F3 and is flashed at 1 atm and 70°C. The top of the flash tank yields a regenerated stripping agent with a flow rate of 1787.83 kg / h and a purity of 99.18%; the bottom of the flash tank yields a neutral oil-rich fraction B4 with a flow rate of 126.76 kg / h, containing 96.56% neutral oil. B4 is mixed with D3 and cooled before being returned to the extraction tower for further extraction. The regenerated extractant is returned to the extraction tower for reuse, and the regenerated stripping agent is returned to the back-extraction tower for reuse.At the start of the cycle, the regenerated extractant was mixed with the fresh extractant, and the regenerated back-extractant was mixed with the fresh back-extractant. After three cycles, the top of flash tank F2 yielded a phenol product with a flow rate of 235.14 kg / h and a purity of 99.31%; the bottom of flash tank yielded a regenerated extractant with a flow rate of 309.49 kg / h and a purity of 99.47%. The top of flash tank F3 yielded a regenerated back-extractant with a flow rate of 1786.90 kg / h and a purity of 99.18%; the bottom of flash tank yielded a neutral oil-rich fraction with a flow rate of 128.12 kg / h, of which the neutral oil content was 96.58%.

[0033] Example 15 In this embodiment, low-temperature coal pyrolysis oil was used as the oil-phenol mixture for separation experiments. Its phenol content was 30.06%, and the substances in the oil other than phenols were neutral oil components. 1-Butyl-3-methylimidazolium tetrafluoroborate extractant at a flow rate of 314 kg / h was introduced from the top of extraction tower T1, while the oil-phenol mixture feedstock at a flow rate of 1000 kg / h was introduced from the bottom of the extraction tower (the molar ratio of extractant to intermediate cresol in the feedstock was 0.5:1). Countercurrent contact extraction was carried out in extraction tower T1 at a temperature of 25°C and a pressure of 1 atm. Raffinate D1 (phenol-free oil) was obtained at the top of the tower with a flow rate of 591.43 kg / h and a neutral oil content of 98.96%; extract B1 was obtained at the bottom of the tower with a flow rate of 723.10 kg / h and a phenol extraction rate of 97.95%. Extract B1 enters from the top of back-extraction column T2, while n-hexane back-extraction agent at a flow rate of 1800 kg / h enters from the bottom of the column. Countercurrent contact extraction is carried out in back-extraction column T2 at a temperature of 25°C and a pressure of 1 atm. The top of the column yields back-extraction extract D2 at a flow rate of 1878.43 kg / h, with a neutral oil removal rate of 90.97%. The bottom of the column yields back-extraction residue B2 at a flow rate of 644.67 kg / h, with a phenol content of 84.76% after removing the extractant. B2 enters flash evaporator F1 and is flashed at 0.1 atm and 180°C. The top of the flash evaporator yields a neutral oil-rich fraction D3 at a flow rate of 48.67 kg / h, with a neutral oil removal rate of 94.50%. The bottom of the flash evaporator yields a neutral oil-removed fraction B3 at a flow rate of 596.00 kg / h, with a phenol content of 99.02% after removing the extractant. B3 enters flash tank F2 and undergoes flash evaporation at 0.05 atm and 230°C. The top of the flash tank yields a phenol product with a flow rate of 284.50 kg / h and a purity of 99.02%; the bottom yields a regenerated extractant with a flow rate of 311.50 kg / h and a purity of 98.52%. The back-extraction extract D2 obtained from the top of back-extraction column T2 enters flash tank F3 and undergoes flash evaporation at 1 atm and 70°C. The top of the flash tank yields a regenerated back-extraction agent with a flow rate of 1721.17 kg / h and a purity of 99.32%; the bottom yields a neutral oil-rich fraction B4 with a flow rate of 157.26 kg / h, containing 90.12% neutral oil. B4 is mixed with D3, cooled, and returned to the extraction column for further extraction. The regenerated extractant is returned to the extraction column for reuse, and the regenerated back-extraction agent is returned to the back-extraction column for reuse. Detailed Implementation

[0034] The method for separating an oil-phenol mixture by coupling in-situ extraction with back-extraction and flash evaporation using ionic liquids, provided by the present invention, will be described in further detail below with reference to embodiments. However, this does not limit the present invention. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0035] In this embodiment of the invention, gas chromatography-mass spectrometry (GC-MS) was used to analyze the composition of the liquid products. The GC-MS system used was an Agilent 7890B / 5977A, the chromatographic column was a weakly polar capillary column (HP-5), and the detector was a single quadrupole mass spectrometer detector. The determination method was external standard normalization. The GC-MS conditions were as follows: injection port temperature 280°C, split injection, split ratio 30:1, injection volume 1µL, and carrier gas flow rate maintained at 20mL / min. The column temperature was started at 100°C and maintained for 1 min, then increased to 280°C at a rate of 10°C / min and maintained at that temperature for 10 min.

Claims

1. A method for separating an oil-phenol mixture by coupling in-situ extraction with back-extraction and flash evaporation using ionic liquids, the method comprising the following steps: (1) Add 1-butyl-3-methylimidazolium tetrafluoroborate extractant M1 to the top of the extraction tower T1, so that it comes into countercurrent contact with the oil-phenol mixture S1 entering from the bottom of the tower, and extract at a given temperature to obtain extract B1 and raffinate D1, where D1 is dephenolized oil. (2) Add low-carbon alkane back-extraction agent to the bottom of the back-extraction tower T2, so that it comes into countercurrent contact with the extract B1 obtained in step (1) entering from the top of the tower, and back-extract at a given temperature to obtain back-extraction extract D2 and back-extraction residue B2. (3) The back-extraction residue B2 obtained in step (2) is fed into flash tank F1 for flash evaporation to obtain neutral oil-rich fraction D3 and neutral oil-free extract B3. (4) The extract B3 obtained in step (3) after removing neutral oil is fed into flash tank F2 for flash evaporation to obtain crude phenol product D5 and regenerated extractant B5. The regenerated extractant is cooled and returned to extraction tower T1 for reuse. (5) The back-extraction liquid D2 obtained in step (2) is flashed into flash tank F3 to obtain neutral oil-rich fraction B4 and regenerated back-extraction agent D4. The regenerated back-extraction agent is cooled and returned to back-extraction tower T2 for reuse. Neutral oil-rich fraction B4 is mixed with neutral oil-rich fraction D3 in step (3) and cooled and returned to the raw material oil-phenol mixture for further extraction. in, The low-carbon alkane back-extractant mentioned in step (2) is selected from one of n-hexane, cyclohexane and n-heptane.

2. The process method according to claim 1, characterized in that, In step (1), the molar ratio of the extractant to the phenolic compounds in the oleophenol mixture in the extraction tower is 0.5 to 1.

0.

3. The process method according to claim 1, characterized in that, The temperature for in-situ extraction of phenolic compounds using ionic liquid in step (1) is 25°C to 45°C.

4. The process method according to claim 1, characterized in that, In step (2), the mass ratio of the stripping agent to the extractant B1 in the stripping tower is 1.38 to 2.

49.

5. The process method according to claim 1, characterized in that, The temperature for back-extraction to remove neutral oil in step (2) is 25°C to 45°C.

6. The process method according to claim 1, characterized in that, The pressure in the flash tank F1 described in step (3) is 0.05 atm ~ 0.1 atm, and the temperature is 180°C ~ 200°C.

7. The process method according to claim 1, characterized in that, The pressure in the flash tank F2 described in step (4) is 0.01 atm to 0.05 atm, and the temperature is 210°C to 230°C.

8. The process method according to claim 1, characterized in that, The pressure in the flash tank F3 described in step (5) is 0.5 atm to 1 atm, and the temperature is 70°C to 100°C.

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