Method for separating phenolic substances in coal tar by constructing eutectic solvent based on betaine and organic acid

Abstract

The invention discloses a method for separating phenolic substances in coal tar by constructing a deep eutectic solvent based on betaine and organic acid, and belongs to the technical field of deep processing of coal tar. The halogen-free eutectic solvent is synthesized by taking betaine as a hydrogen bond acceptor and organic acid as a hydrogen bond donor. Mixing the eutectic solvent with phenol-containing oil, heating, stirring, cooling and standing to divide a system into a dephenolized oil phase (upper phase) and a phenol-containing eutectic solvent phase (lower phase); and then, a proper back-extraction agent is adopted to perform back extraction on the phenol-containing eutectic solvent phase, after back extraction, rotary evaporation is performed to respectively obtain a phenol product, a regenerated back-extraction agent and a regenerated eutectic solvent, and the regenerated back-extraction agent and the regenerated eutectic solvent can be recycled. According to the method, efficient separation is achieved through hydrogen-bond interaction between the eutectic solvent and the phenolic substances, use of strong acid and strong alkali and generation of phenolic wastewater in a traditional chemical extraction method are avoided, equipment corrosion is prevented through the halogen-free characteristic, the phenol resource recycling rate is increased, and the coal tar quality is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of deep processing of coal tar, and focuses on the separation and purification of phenolic substances in coal tar. Specifically, it is a method for efficiently extracting phenolic substances from phenol-containing oil using a deep eutectic solvent composed of betaine and organic acid as the extraction medium. Background Art

[0002] Coal tar, as a complex mixture generated by coal carbonization, contains a rich variety of organic compounds with high added value and occupies a very crucial position as a raw material resource in the chemical industry. In particular, phenolic substances in coal tar have unique chemical structures and properties, endowing them with extensive application values in many industries such as chemical engineering, medicine, and materials. With the continuous advancement of the modern industrial process, the demand for phenolic substances in various industries has been showing a continuous upward trend. Therefore, efficiently separating and purifying phenolic substances from coal tar is of core significance that cannot be ignored for improving the comprehensive utilization efficiency of coal resources and ensuring the stable supply of raw materials for related industries.

[0003] In the technology of separating phenolic substances from coal tar, although the traditional alkali washing - acid precipitation method and solvent extraction method have been applied for a long time and the alkali washing - acid precipitation process is mature, both of them have significant drawbacks. The alkali washing - acid precipitation operation is cumbersome, with large consumption of acids and alkalis, a large amount of phenol-containing wastewater, resulting in great environmental pressure and low separation efficiency, making it difficult to obtain high-purity phenol; although the solvent extraction method can separate phenolic substances, common organic solvents are highly toxic, volatile, have high recovery costs, and poor selectivity. These have restricted the application and popularization of traditional methods in large-scale industrial production. In recent years, deep eutectic solvents have emerged and received attention. They are formed by hydrogen bond association between hydrogen bond acceptors (such as quaternary ammonium salts) and hydrogen bond donors (such as amides, carboxylic acids), and have the advantages of simple synthesis, low cost, non-toxic or low toxicity, biodegradability, low volatility, etc., and have application potential in separation processes, promising to solve the problems of traditional solvents. However, some traditional deep eutectic solvents contain halogens, posing environmental and safety hazards, such as generating harmful halogenated substances. Therefore, developing halogen-free deep eutectic solvents for separating phenolic substances from coal tar is of great significance. It can not only retain the advantages of deep eutectic solvents but also avoid the negative problems of halogens, conforming to the concepts of green chemistry and sustainable development, providing a new way for the clean and efficient separation of phenolic substances from coal tar, and facilitating the environmentally friendly and efficient development of the coal tar deep processing industry.

[0004] The present invention proposes an innovative method, which uses a halogen-free low eutectic solvent to extract phenolic substances in phenol-containing oil, wherein betaine is a hydrogen bond acceptor, and formic acid, glycolic acid, and lactic acid are hydrogen bond donors. The method first selects a phenol-containing simulated oil with a specific mass ratio or directly uses an actual phenol-containing oil product, and adds a synthesized halogen-free low eutectic solvent to the simulated oil. Due to the effect of hydrogen bonds, the extractant and the phenolic substances in the oil form a stable two-phase system, the upper phase is the dephenolized oil phase, and the lower phase is the low eutectic solvent phase. In the regeneration link of the low eutectic solvent, the stripping technology is used. This technology can effectively recover the stripping agent and realize the recycling of the low eutectic solvent, which greatly improves the economy and environmental protection of the extraction process. This innovative method has opened up a new path for the environmentally friendly treatment of phenol-containing oil and the efficient recovery of phenols, has significant industrial application prospects and environmentally friendly value, and is expected to promote the coal tar deep processing industry to move towards a more environmentally friendly and efficient direction. Summary of the invention

[0005] Current research shows that the traditional method of separating phenolic substances from phenolic oil faces many difficulties such as severe environmental pollution, high cost, and poor degradability. Its complex process and expensive reagents lead to a significant increase in costs. The large amount of difficult-to-treat waste liquid and waste residue and difficult-to-degrade substances generated by separation bring tremendous pressure to the ecological environment and cause long-term negative impacts. Therefore, it is urgent to develop a new type of green, environmentally friendly and sustainable extractant. In response to this demand, the present invention innovatively adopts a halogen-free low eutectic solvent as an extractant, and relies on its hydrogen bonding with phenolic substances to achieve efficient extraction of phenolic substances, opening up a new path for phenolic oil treatment and phenol separation, which is expected to break through the limitations of traditional methods and help related industries to develop environmentally friendly and efficient development.

[0006] The method for separating phenolic substances from phenolic oil of the present invention comprises the following steps:

[0007] (1) Preparation of deep eutectic solvent

[0008] The hydrogen bond donor and the hydrogen bond acceptor are heated and mixed in a specific molar ratio, and the process is continued until a uniform transparent liquid is obtained. The hydrogen bond acceptor is preferably betaine, and the hydrogen bond donor includes formic acid, glycolic acid, lactic acid, etc.

[0009] (2) Extraction process

[0010] According to the set mass ratio, the low eutectic solvent prepared in step (1) is accurately weighed and added to the phenolic oil to be separated. Subsequently, it is heated and stirred to ensure that the two can fully react. After the reaction is completed, it is cooled and allowed to stand at room temperature until the upper and lower layers of liquid can be clearly observed to be stratified. At this time, the upper liquid phase is the oil phase from which the phenolic substances have been removed, and the lower liquid phase is the low eutectic solvent phase rich in phenolic substances.

[0011] (3) Back-extraction process:

[0012] Take an appropriate amount of back-extraction agent and add it to the eutectic solvent phase obtained in step (2). Then place it in a water bath and perform sufficient heating and stirring operations. After the back-extraction process is completed, take out the mixed system and let it stand and cool at room temperature until a clear and complete separation interface is formed between the eutectic solvent and the back-extraction agent. The upper layer is the back-extraction phase containing phenolic substances, and the lower layer is the eutectic solvent phase containing a small amount of back-extraction agent.

[0013] (4) Rotary evaporation regeneration process:

[0014] Perform rotary evaporation on the two phases obtained in step (3) respectively. Through evaporation, phenolic products and reusable back-extraction agent can be obtained from the upper phase, while the lower phase can obtain recyclable eutectic solvent. The regenerated back-extraction agent and eutectic solvent can be reused in step (3) and step (2) respectively.

[0015] In the above method, the concentration of phenol in the phenol-containing oil is 50 g / L to 200 g / L, such as 50 g / L, 100 g / L, 200 g / L.

[0016] In the above method, in step (1), the hydrogen bond acceptor is preferably one or more of formic acid, glycolic acid, and lactic acid.

[0017] In the above method, in step (1), the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is between 1:2 and 1:6.

[0018] In the above method, in step (1), the solution stirring temperature is 60 °C to 80 °C, and the stirring time is 30 min to 80 min.

[0019] In the above method, in step (2), when treating the phenol-containing oil to be separated, the amount of the eutectic solvent used has a specific range, that is, for every 5 mL of the phenol-containing oil to be separated, 1 g to 6 g of the eutectic solvent is required.

[0020] In the above method, in step (2), the solution stirring temperature is 25 °C to 65 °C, and the stirring time is 2 min to 30 min.

[0021] In the above method, in step (3), the back-extraction solvent is selected from one or more of methanol, acetone, chloroform, and ethyl acetate.

[0022] In the above method, in step (3), when the volume of the back-extraction agent used is 5 mL, the mass range of the corresponding eutectic solvent should be controlled within 5 g.

[0023] In the above method, in step (3), the solution stirring temperature is room temperature such as 25 °C, and the stirring time is 15 min.

[0024] In the above method, in step (4), the rotary evaporation temperature of the upper and lower phases is 45 °C and the time is 15 min.

[0025] Beneficial effects

[0026] Compared with the prior art, the present invention mainly has the following beneficial effects:

[0027] (1) The extraction system of the present invention has excellent performance. When applied in extraction, the extraction rate of the target substance exceeds 94%. The high-efficiency extraction greatly improves the extraction amount. More high-purity products can be obtained with the same raw material input, reducing raw material waste and cost, and strongly supporting large-scale industrial production.

[0028] (2) Betaine, formic acid, glycolic acid, and lactic acid cooperate to construct a unique chemical environment. Their synergistic effect strengthens the selective recognition and binding of the target substance, accurately separating the target components in the complex mixture, improving the product purity and quality; at the same time, ensuring the stability of the extraction process, reducing the fluctuation of the extraction effect caused by external interference, and enhancing the process controllability and repeatability.

[0029] (3) The extraction agent selected in the present invention has good biocompatibility and environmental friendliness. There are no harmful waste and pollution emissions during extraction, which conforms to the concept of green environmental protection, helps the relevant industries to upgrade environmental protection, enables enterprises to gain a competitive advantage in the strict regulatory market, reduces the impact on the ecological environment, and achieves a win-win situation of economic and environmental benefits. Description of the drawings

[0030] Figure 1 Performance graph of the extraction efficiency of the extractant prepared in Example 1 for phenol in 5 mL of simulated oil at different dosages. Experimental conditions: molar ratio of hydrogen bond acceptor to hydrogen bond donor: 1:2, temperature: 25 °C, time: 30 min, initial phenol concentration: 200 g / L.

[0031] Figure 2 Performance graph of the extraction efficiency of the extractants prepared with different molar ratios of hydrogen bond acceptor / donor in Example 1 for phenol in 5 mL of simulated oil. Experimental conditions: extractant dosage: 4 g, temperature: 25 °C, time: 30 min, initial phenol concentration: 200 g / L.

[0032] Figure 3 Performance graph of the extraction efficiency of the extractant prepared in the present invention in Example 1 for phenol in 5 mL of simulated oil at different extraction times. Experimental conditions: extractant dosage: 4 g, molar ratio of hydrogen bond acceptor to hydrogen bond donor: 1:2, temperature: 25 °C, initial phenol concentration: 200 g / L.

[0033] Figure 4Performance graph of the extractant prepared in the present invention for the extraction efficiency of phenol in 5 mL of simulated oil at different extraction temperatures in Example 1. Experimental conditions: extractant dosage: 4 g; molar ratio of hydrogen bond acceptor to hydrogen bond donor: 1:2; time: 20 min; initial phenol concentration: 200 g / L.

[0034] Figure 5 Performance graph of the extractant prepared in the present invention for the remaining amount of phenol in 5 mL of simulated oil at different initial phenol concentrations in Example 1. Experimental conditions: extractant dosage: 1 g - 6 g; molar ratio of hydrogen bond acceptor to hydrogen bond donor: 1:2; time: 20 min; temperature: 25°C. Detailed implementation manners

[0035] In order to fully highlight the core purpose, distinct features and outstanding advantages of the present invention, we will conduct an in-depth and comprehensive analysis and interpretation of the technical solutions in the embodiments. The raw materials used in the embodiments of the present invention can be obtained through regular commercial channels. The following will elaborate on the present invention in combination with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0036] (1) Preparation of the simulated oil required for the experiment

[0037] Considering the complex component composition of coal tar, phenol and toluene are specifically selected as raw materials in this experiment to prepare simulated oils with different concentration gradients. The preparation steps of the 200 g / L simulated oil are as follows: First, accurately weigh 200 g of phenol and place it in a 500 mL beaker. Subsequently, slowly pour an appropriate amount of toluene into the beaker and continuously stir it evenly with a glass rod until the phenol is completely dissolved to form a uniform mixed solution. Then, transfer the mixed solution in the beaker to a 1000 mL volumetric flask. Finally, use toluene as the solvent and slowly add it to the scale line of the volumetric flask. During the whole operation process, it should be ensured that the experimental environment is well ventilated and the operator wears protective equipment to avoid the harm caused by the volatilization of phenol and toluene to the human body.

[0038] (2) Preparation of the extractant

[0039] The extractant is generated through the reaction between a hydrogen bond acceptor and a hydrogen bond donor. In this experiment, betaine is specifically selected as the hydrogen bond acceptor, and one or a combination of formic acid, glycolic acid, and lactic acid is chosen as the hydrogen bond donor, and they are mixed according to a preset molar ratio. The preparation steps are as follows: First, accurately weigh the required raw material components, and then place all of them into a reaction flask equipped with a magnetic stirrer. Next, place the reaction flask in a magnetic stirring water bath with a temperature controlled in the range of 60 °C to 80 °C, turn on the stirring function to ensure that the mixture can fully react at a high temperature. When the mixture gradually turns into a transparent and homogeneous liquid form, it indicates that the deep eutectic solvent is successfully prepared. Finally, cool it at room temperature for subsequent experiments.

[0040] (3) Extraction process

[0041] Weigh the deep eutectic solvent and the simulated oil respectively according to a specific mass ratio, and place them into a reaction flask equipped with a magnetic stirrer. Then place the reaction flask in a water bath with a preset specific temperature, and stir for a certain period of time with a magnetic stirring device to ensure that the reaction can proceed fully. After the extraction process is completed, take out the reaction flask, let it cool naturally and stand at room temperature until the upper and lower two-phase liquids in the reaction flask are completely separated. The upper phase is the dephenolized oil phase, and the lower phase is the deep eutectic solvent phase. Use a graduated cylinder to accurately measure the volumes of the upper and lower layer liquids and record the relevant data truthfully. Use a pipette to respectively transfer a specific number of microliters of the upper phase liquid, and after dilution, perform gas chromatography analysis using the internal standard method.

[0042] (4) Investigate the optimal extraction conditions

[0043] During the extraction experiment process, the single-factor experiment method is used to conduct in-depth exploration, focusing on exploring the influence of the following factors on the separation efficiency of phenolic substances, and then accurately determining the optimal extraction conditions: the dosage relationship between the deep eutectic solvent (1 g to 6 g) and the simulated oil (5

[0044] ml). The molar ratio of the hydrogen bond acceptor to the hydrogen bond donor (1:2 to 1:6). The extraction time (2 min to 30 min).

[0045] The extraction temperature (25 °C to 65 °C). The initial phenol concentration (50 g / L, 100 g / L, 200 g / L).

[0046] (5) Investigate the recycling and regeneration ability

[0047] After the optimal extraction conditions were successfully screened and determined, ethyl acetate was used as the back-extraction agent to carry out the back-extraction experiment. During the back-extraction process, a significant layering phenomenon could be clearly observed. Among them, the upper layer was the back-extraction phase dissolved with phenolic substances, and the lower layer was the eutectic solvent phase containing the back-extraction solution. With the help of the rotary evaporation technique, phenolic products, regenerated back-extraction agent, and eutectic solvent could be effectively obtained. The core purpose of this step was to accurately evaluate the recycling performance of the extractant, and then provide key decision-making support and judgment basis for screening the most ideal extractant, strongly promoting the comprehensive optimization process of the entire extraction process in terms of efficiency, cost, and sustainability.

[0048] Example 1

[0049] (1) Preparation of phenol-containing simulated oil: Weigh 200 g of phenol and place it in a 500 mL beaker. Add an appropriate amount of toluene solution to the beaker and stir continuously until the two are completely miscible. Pour the solution in the beaker into a 1000 ml volumetric flask and make up to the mark with toluene to prepare a phenol-containing simulated oil with a concentration of 200 g / L.

[0050] (2) Weigh 1 g to 6 g of betaine-formic acid eutectic solvent respectively, and the molar ratio of betaine to formic acid in this solvent is set to 1:2, 1:3, 1:4, 1:5, 1:6 respectively. At the same time, measure 5 mL of simulated oil and add them together into a reaction flask equipped with a magnetic stirrer. Then, place the reaction flask in a water bath at a temperature in the range of 25°C to 65°C and stir for different lengths of time from 2 min to 30 min with the help of the magnetic stirrer at a constant temperature. After the extraction process is completed, transfer the mixture in the reaction flask to a separating funnel and let it stand and cool at room temperature until the upper and lower layers of liquid are clearly and completely separated. Among them, the upper layer is the de-phenolized oil phase, and the lower layer is the eutectic solvent phase. Use a measuring cylinder to accurately measure the volumes of the upper and lower phases, use a pipette to accurately transfer a specific amount of the upper-phase liquid, and after appropriate dilution, carry out gas chromatography analysis by the internal standard method.

[0051] (3) Back-extraction process: After the extraction process is completed, specific treatment is carried out on the deep eutectic solvent phase. Precisely measure 5 mL of ethyl acetate and add it thereto. Then, place the mixed system in a water bath pot with the temperature precisely controlled at 25 °C and continuously stir for 20 min under constant temperature conditions to ensure that the reaction can proceed fully. After the reaction is completed, let it stand at room temperature to ensure that the two phases can be completely and clearly separated. At this time, the upper layer is the back-extraction phase dissolved with phenolic compounds, and the lower layer is the deep eutectic solvent phase containing the back-extraction solution. Pour the upper and lower phases into a rotary evaporation flask respectively, and use label paper to clearly mark each component and the corresponding mass information. Place the rotary evaporation flask in an environment at 45 °C for rotary evaporation for 15 min, and then successfully obtain phenolic substances, regenerated back-extraction agent, and deep eutectic solvent respectively.

[0052] It is calculated that under the optimal extraction conditions of betaine-formic acid deep eutectic solvent (extraction agent dosage: 4 g; betaine-formic acid molar ratio: 1:2; extraction time: 15 min; extraction temperature: 25 °C; initial phenol concentration: 200 g / L), the phenol extraction rate is 98.5%, and the final phenol concentration in the oil is 5.68 g / L. The extraction agent can be recycled more than 5 times, and the extraction rate after 5 cycles can reach more than 92%. The 5-cycle efficiencies are 98%, 97.3%, 96.1%, 95.5%, and 92.4% respectively.

[0053] Example 2

[0054] (1) Preparation of phenol-containing simulated oil: Weigh 200 g of phenol and place it in a 500 mL beaker. Add an appropriate amount of toluene solution to the beaker and continuously stir until the two are completely miscible. Pour the solution in the beaker into a 1000 ml volumetric flask and make up to the scale with toluene to prepare a phenol-containing simulated oil with a concentration of 200 g / L.

[0055] (2) Weigh 1 g to 6 g of betaine-glycolic acid deep eutectic solvent respectively, and the molar ratio of betaine to glycolic acid in this solvent is set as 1:2, 1:3, 1:4, 1:5, 1:6 respectively. At the same time, measure 5 mL of simulated oil and add them together into a reaction flask equipped with a magnetic stirrer. Then, place the reaction flask in a water bath pot with the temperature in the range of 25 °C to 65 °C and stir for different lengths of time from 2 min to 30 min with the help of the magnetic stirrer at a constant temperature. After the extraction process is completed, transfer the mixed liquid in the reaction flask to a separating funnel and let it stand and cool at room temperature until the upper and lower layers of liquid are completely and clearly separated. Among them, the upper layer is the de-phenol oil phase, and the lower layer is the deep eutectic solvent phase. Use a graduated cylinder to precisely measure the volumes of the upper and lower phases, use a pipette to accurately transfer a specific amount of the upper-phase liquid, and carry out gas chromatography analysis by the internal standard method after appropriate dilution.

[0056] (3) Back-extraction process: After the extraction process is completed, specific treatment is carried out on the eutectic solvent phase. Precisely measure 5 mL of ethyl acetate and add it thereto. Then, place the mixed system in a water bath pot with the temperature precisely controlled at 25 °C and continuously stir for 20 min under constant temperature conditions to ensure that the reaction can proceed fully. After the reaction is completed, let it stand at room temperature to ensure that the two phases can be completely and clearly separated. At this time, the upper layer is the back-extraction phase dissolved with phenolic compounds, and the lower layer is the eutectic solvent phase containing the back-extraction solution. Pour the upper and lower phases into a rotary evaporation flask respectively, and use label paper to mark the components and the corresponding mass information in detail. Place the rotary evaporation flask in an environment at 45 °C for rotary evaporation for 15 min, and then successfully obtain phenolic substances, regenerated back-extraction agent, and eutectic solvent respectively.

[0057] It is calculated that under the optimal extraction conditions of betaine-glycolic acid eutectic solvent (extraction agent dosage: 5 g; betaine-glycolic acid molar ratio: 1:2; extraction time: 15 min; extraction temperature: 25 °C; initial phenol concentration: 200 g / L), the phenol extraction rate is 94.3%, and the final phenol concentration in the oil is 14.8 g / L. The extraction agent can be recycled more than 5 times, and the extraction rate after 5 cycles can reach more than 89%. The 5-cycle efficiencies are 93.1%, 92.5%, 91.3%, 90.5%, and 89.4% respectively.

[0058] Example 3

[0059] (1) Preparation of phenol-containing simulated oil: Weigh 200 g of phenol and place it in a 500 mL beaker. Add an appropriate amount of toluene solution to the beaker and continuously stir until the two are completely miscible. Pour the solution in the beaker into a 1000 ml volumetric flask and make up to the scale with toluene to prepare a phenol-containing simulated oil with a concentration of 200 g / L.

[0060] (2) Weigh 1 g to 6 g of betaine-lactic acid eutectic solvent respectively, and the molar ratio of betaine to lactic acid in the solvent is set to 1:2, 1:3, 1:4, 1:5, 1:6 respectively. At the same time, measure 5 mL of simulated oil and add them together into a reaction flask equipped with a magnetic stirrer. Then, place the reaction flask in a water bath pot with the temperature in the range of 25 °C to 65 °C and stir for different lengths of time from 2 min to 30 min with the help of the magnetic stirrer at a constant temperature. After the extraction process is completed, transfer the mixed solution in the reaction flask to a separatory funnel and let it stand and cool at room temperature until the upper and lower layers of liquid are completely and clearly separated. Among them, the upper layer is the de-phenol oil phase, and the lower layer is the eutectic solvent phase. Precisely measure the volumes of the upper and lower phases with a graduated cylinder, accurately pipette a specific amount of the upper-phase liquid with a pipette gun, and carry out gas chromatography analysis by the internal standard method after appropriate dilution.

[0061] (3) Back-extraction process: After the extraction process is completed, specific treatment is carried out on the deep eutectic solvent phase. Precisely measure 5 mL of ethyl acetate and add it thereto. Then, place the mixed system in a water bath pot with the temperature precisely controlled at 25 °C and continuously stir for 20 min under constant temperature conditions to ensure that the reaction can proceed fully. After the reaction is completed, let it stand at room temperature to ensure that the two phases can be completely and clearly separated. At this time, the upper layer is the back-extraction phase dissolved with phenolic compounds, and the lower layer is the deep eutectic solvent phase containing the back-extraction solution. Pour the upper phase and the lower phase into a rotary evaporation flask respectively, and at the same time, use label paper to clearly mark each component and the corresponding mass information. Place the rotary evaporation flask in an environment at 45 °C for rotary evaporation for 15 min, and then successfully obtain phenolic substances and regenerated deep eutectic solvent respectively.

[0062] It is calculated that under the optimal extraction conditions of betaine-lactic acid deep eutectic solvent (extraction agent dosage: 5 g; betaine-lactic acid molar ratio: 1:2; extraction time: 15 min; extraction temperature: 25 °C; initial phenol concentration: 200 g / L), the phenol extraction rate is 97.0%, and the final phenol concentration in the oil is 6.43 g / L. The extraction agent can be recycled more than 5 times, and the extraction rate after 5 cycles can reach more than 91%. The 5-cycle efficiencies are 96.2%, 95.3%, 93.1%, 92.5%, and 91.4% respectively.

Claims

1. A method for separating phenolic substances from coal tar by constructing a deep eutectic solvent based on betaine and organic acid, which is characterized in that, The following steps are involved: (1) Extraction agent preparation Preparation of a deep eutectic solvent: heating and mixing a hydrogen bond donor and a hydrogen bond acceptor according to a specific molar ratio until a uniform and transparent liquid is formed; the hydrogen bond acceptor is preferably selected from betaine, and the hydrogen bond donor is selected from an organic acid; (2) Extraction operation Accurately measure the low eutectic solvent prepared in step (1), add the low eutectic solvent to the phenol oil system to be separated according to a predetermined mass ratio, and then heat and stir to allow the two to react fully. After the reaction process is completed, stand and cool at room temperature until the upper and lower phases of liquid in the system form a clear and completely stratified interface, and then separate the upper and lower phases, wherein the upper liquid phase is the dephenolized oil phase, and the lower liquid phase is the low eutectic solvent phase enriched with phenolic substances. ; (3) Stripping step Add an appropriate amount of stripping agent to the deep eutectic solvent phase obtained in step (2), and heat and stir in a water bath to complete the stripping process. After completion, cool the mixture to room temperature and stand until the deep eutectic solvent and the stripping agent form a clear and completely separated interface, the upper layer is the stripping phase containing phenolic substances, and the lower layer is the deep eutectic solvent phase containing a trace amount of stripping agent; (4) Rotary evaporation regeneration process The two phases obtained in step (3) are subjected to rotary evaporation treatment respectively. Through evaporation, the upper phase can obtain a phenolic product and a reusable stripping agent, while the lower phase can obtain a reusable low eutectic solvent. The regenerated stripping agent and low eutectic solvent can be reused in step (3) and step (2), respectively.

2. The method according to claim 1, wherein The concentration of phenol in the phenol-containing oil is between 50 g / L and 200 g / L.

3. The method according to claim 1, characterized in that, In step (1), the organic acid is preferably one or more of formic acid, glycolic acid, and lactic acid; in step (1), the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is between 1:2 and 1:6; in step (1), the stirring time of the solution is maintained at 30 minutes to 80 minutes, and the stirring temperature is set at 60° C. to 80° C.

4. The method according to claim 1, wherein In step (2), when the phenol-containing oil to be separated is treated, the amount of the low eutectic solvent used has a specific range, that is, 1 g to 6 g of the low eutectic solvent is required for every 5 mL of the phenol-containing oil to be separated.

5. The method according to claim 1, characterized in that In step (2), the solution is stirred at a temperature of 25°C to 65°C, and the stirring time is 2 min to 30 min.

6. The method according to claim 1, characterized in that In step (3), the stripping solvent is selected from one or more of methanol, acetone, chloroform and ethyl acetate.

7. The method according to claim 1, characterized in that, In step (3), when the volume of the stripping agent used is 5 mL, the mass range of the corresponding low eutectic solvent should be controlled within 5 g.

8. The method according to claim 1, wherein In step (3), the solution is stirred at room temperature, such as 25° C., and the stirring time is 15 min.

9. The method according to claim 1, wherein In step (4), the rotary evaporation temperature of the upper and lower phases is 45° C., and the time is 15 min.

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