A method for separating an oil phenol mixture by ion liquid extraction combined with rectification

Abstract

This invention relates to the field of separating oil-phenol mixtures, specifically to a method for separating oil-phenol mixtures using ionic liquid extraction and distillation. The invention uses an ionic liquid as the extractant to extract and separate phenolic compounds from oil; then, flash evaporation is performed to remove neutral oil, and a mixture of phenol and a small amount of neutral oil is separated to obtain a regenerated ionic liquid extractant; finally, distillation is performed to remove the neutral oil, yielding a high-purity product of phenol, i.e., the phenol content in the product is 99.0%–99.4%. This invention does not use organic solvents, making it environmentally friendly; and it has the advantages of a simple separation process, low cost, high separation efficiency, regenerable separating agent, and low neutral oil content in the product.

Description

Technical Field

[0001] This invention relates to the field of separating oleophenol mixtures, and more specifically to a method for separating oleophenol mixtures by extraction and distillation using ionic liquids. Background Technology

[0002] Phenolic compounds are important chemical raw materials, widely used in the synthesis of fibers and plastics, the preparation of pesticides and pharmaceuticals, and other production fields such as fragrances and dyes. Currently, phenolic compounds mainly come from coal pyrolysis oil and coal liquefaction oil. In the future, the pyrolysis products of renewable carbon-containing resources, biomass, will become the main source of phenolic compounds. Research on the utilization of carbon sources from biomass resources is the foundation for achieving dual-carbon goals. The effective separation of phenolic compounds from oil-phenol mixtures such as coal tar, coal liquefaction oil, and biomass pyrolysis oil has significant economic benefits.

[0003] Currently, the most mature industrial method for separating oil-phenol mixtures is the alkaline washing method. This method first uses sodium hydroxide solution to react with phenolic compounds in the oil-phenol mixture (such as coal tar or coal liquefaction oil) to produce sodium phenolate, which dissolves in the aqueous phase and is thus separated from the oil phase. Next, the neutral oil entrained in the sodium phenolate aqueous solution is removed by steam stripping. Finally, sulfuric acid is added to the sodium phenolate solution to generate phenolic compounds.

[0004] Alkaline washing exhibits excellent selectivity for phenolic compounds in oil, yielding high-purity phenolic compounds. However, this process consumes large quantities of acid and alkali solutions, leading to high costs; furthermore, sulfuric acid acidification is highly corrosive to equipment, further increasing costs. Simultaneously, this method generates substantial amounts of phenol-containing wastewater, requiring hazardous waste treatment. To address these issues, there is an urgent need to develop novel methods for separating oil-phenol mixtures.

[0005] It has been reported that organic salts can extract phenolic compounds from coal tar. Studies have found that the organic salt choline chloride can extract phenolic compounds from oil; some researchers have proposed using dicationic liquids to extract phenolic compounds from simulated oil. These methods can efficiently separate phenolic compounds from oil, but the regeneration of the extractant involves back-extraction with organic solvents, which can cause some environmental pollution.

[0006] Furthermore, after extracting phenolic compounds from oil, the resulting phenolic product often contains a significant amount of neutral oil. Some researchers have found that back-extraction with low-carbon aliphatic hydrocarbons can remove neutral oil, reducing its content to as low as 1.9%. However, this method requires more solvent, wasting raw materials, and the product still contains a relatively high amount of neutral oil.

[0007] Therefore, it is of great significance to develop a method that does not use acids or bases, nor does it require organic solvents for back-extraction and regeneration of the extractant, and can reduce the neutral oil content in the product, improve the purity of phenols, and achieve green separation of phenolic compounds. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention provides a method for separating phenolic compounds from oil using ionic liquids as extractants, combined with distillation and extraction. This invention is environmentally friendly as it does not use organic solvents; it also offers advantages such as high separation efficiency, reusable separating agents, and low neutral oil content in the product phenolic compounds.

[0009] To achieve the above objectives, the technical solution of the present invention is as follows: A method for separating an oil-phenol mixture using ionic liquid extraction and distillation is a method that uses ionic liquid as an extractant, combined with flash evaporation and distillation, to finally obtain high-purity phenolic compounds. Among them, high-purity phenolic compounds refer to products with a phenol content of 99.0% to 99.4%.

[0010] A method for separating an oil-phenol mixture using ionic liquid extraction and distillation as described above comprises the following steps: (1) The ionic liquid extractant is added to the extraction tower from the top of the tower and the oil-phenol mixture is added to the bottom of the tower for extraction and separation. The dephenolized oil is obtained from the top of the tower and the ionic liquid extract is obtained from the bottom of the tower. (2) Flash evaporate the ionic liquid extract to remove some of the neutral oil; (3) The ionic liquid extract obtained in step (2) is flash-distilled a second time to remove phenol and a small amount of neutral oil, and the ionic liquid extractant is regenerated. (4) Add the phenol and a small amount of neutral oil obtained in step (3) to the distillation column. The distillate from the top of the column is returned to the raw material for further separation, and the high-purity phenolic compound is distilled from the bottom of the column.

[0011] Further, the ionic liquid extractant mentioned in step (1) is any one of tetraethylammonium bromide, 1-butyl-3-methylimidazolium bromide, and 1-ethyl-3-methylimidazolium bromide; the mass ratio of phenol in the ionic liquid extractant and oleophenol mixture is 0.8~1.2.

[0012] Further, the concentration of phenolic compounds in the oleophenol mixture in step (1) is 50 g / L to 200 g / L.

[0013] Furthermore, the extraction and separation temperature in step (1) is 20℃~50℃.

[0014] Furthermore, the flash evaporation conditions in step (2) are a temperature of 110~140℃ and a pressure of 0.02~0.05MPa.

[0015] Furthermore, the flash evaporation conditions in step (3) are a temperature of 160~180℃ and a pressure of 0.003~0.006MPa.

[0016] Furthermore, the distillation pressure in step (4) is 0.04~0.06 MPa.

[0017] The principle of this invention is as follows: the extraction and separation of phenolic compounds using ionic liquids relies on hydrogen bonding. Specifically, the ionic liquid can form hydrogen bonds with the phenolic hydroxyl groups in the phenolic compounds, extracting the phenolic compounds from the oil-phenol mixture into the ionic liquid phase and separating them from the oil phase. However, because the ionic liquid contains organic groups, the interaction between these organic groups and the aromatic structure of the extracted phenols with the neutral oil results in the entrainment of neutral oil in the ionic liquid phase during the extraction process.

[0018] Increasing temperature enhances the volatility of neutral oils; therefore, by controlling the conditions, a portion of the neutral oil in the ionic liquid phase is removed through a single flash evaporation. Simultaneously, increasing temperature reduces hydrogen bonding forces, decreasing the interaction between the ionic liquid and phenols. Under controlled conditions, a second flash evaporation is used to distill off both the neutral oil and phenolic compounds, regenerating the ionic liquid. The mixture of neutral oil and phenols obtained from the second flash evaporation is then separated by distillation. Since the neutral oil and phenols form a minimum azeotrope, the azeotrope is distilled off from the top of the column and returned to the feed mixture for the next separation cycle. High-purity phenolic compounds are obtained at the bottom of the column.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Compared with the alkaline washing method, the method of the present invention does not use acid or alkali and does not generate phenol-containing wastewater; the separation process is simple; and the extractant can be reused.

[0020] (2) Compared with the traditional organic salt extraction method, the method of the present invention does not use organic solvents, the extraction and separation process is environmentally friendly, the separation process is simple, the neutral oil content in the product is low, accounting for only 0.6%~1.0%, while the phenolic content in the product can reach 99.0%~99.4%. Attached Figure Description

[0021] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0022] To facilitate understanding of the present invention, a more comprehensive description will be given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0023] Except for Example 7, which uses phenolic oil fraction from coal pyrolysis oil in northern Shaanxi as a real oil-phenol mixture, in other embodiments of the present invention, phenol and butylbenzene are used as the phenolic compounds and neutral oil components in the simulated oil-phenol mixture, respectively. Example 1

[0024] (1) Weigh 100.0 g of phenol, place it in a 100 ml beaker, add a small amount of butylbenzene to dissolve it, and then make up to 1000 mL in a volumetric flask to obtain a simulated oleophenol mixture with a phenol concentration of 100 g / L. (2) Measure 200 mL of the above oil-phenol mixture into a 500 mL flask, add 20 g of tetraethylammonium bromide ionic liquid (the mass ratio of ionic liquid to phenol is 1:1), place it in a 25℃ water bath and stir magnetically for 30 min, let it stand for 20 min, and separate the phases to obtain dephenolized oil and phenol-containing ionic liquid extract. (3) The composition of phenol and butylbenzene in the dephenolized oil and ionic liquid extract was analyzed by gas chromatography. The gas chromatograph used was a Shimadzu GC-2014 gas chromatograph with a polar RTX-5 column and an FID detector. The determination method was the internal standard method, with dichloromethane as the solvent and o-nitrotoluene as the internal standard. The chromatographic conditions were: injection port temperature 250℃, detector temperature 260℃, and nitrogen as the carrier gas. The dephenolized oil was directly injected into the gas chromatograph for analysis. The analysis results showed that the content of phenol in the dephenolized oil was 0.28% and the content of neutral oil was 99.72%. (4) Because the extractant ionic liquid is not volatile, it cannot be directly analyzed by gas chromatography. It is necessary to separate the ionic liquid. The specific method is as follows: Take a certain amount of ionic liquid extract and back-extract the extract with three times the volume of diethyl ether four times. Collect all the diethyl ether extract phase mixture and remove the diethyl ether by rotary evaporation in an oil bath at 110°C. The rotation speed is 50 r / min and the rotary distillation time is 2 h to obtain the oil-phenol mixture after the extractant ionic liquid has been removed. Then, analyze it by gas chromatography. The analysis results show that the content of phenol in the extract is 78.1% and the content of neutral oil is 21.9%. The phenol removal rate is calculated to be 97.9%. (5) The ionic liquid extract was added to flash evaporator 1, and a portion of the neutral oil was removed under the conditions of 110℃ and 0.02MPa. The composition of oleic acid in the neutral oil removed by flash evaporation and the ionic liquid extract after flash evaporation was analyzed by the above method. The results showed that the phenol content in the neutral oil removed by flash evaporation was 2.5%, and the neutral oil content was 97.5%. This part was returned to be mixed with the raw material and entered the next separation cycle. The neutral oil content in the ionic liquid extract was 3.1%, and the phenol content was 96.9%. (6) Add the extract from step (5) with some neutral oil removed to flash evaporator 2, change the conditions for a second flash evaporation, and distill off the phenol and a small amount of neutral oil at a temperature of 180℃ and a pressure of 0.006MPa, thereby regenerating the ionic liquid; collect the distillate and analyze its composition using the above gas chromatography analysis method. The content of neutral oil is 3.6% and the content of phenol is 96.4%; (7) The liquid distilled in step (6) is added to a distillation column and separated under a pressure of 0.05 MPa and a reflux ratio of 1.50 to obtain the overhead distillate and the bottom distillate. The composition is analyzed by the above gas chromatography method. The overhead distillate contains 39.8% neutral oil and 60.2% phenol. The overhead distillate is returned to be mixed with the raw material and enters the next separation cycle. The bottom distillate contains 0.8% neutral oil and 99.2% phenol, which meets the purity requirements for phenolic substances. Example 2

[0025] (1) Weigh 100.0 g of phenol, place it in a 100 ml beaker, add a small amount of butylbenzene to dissolve it, and finally make up to 1000 mL in a volumetric flask to obtain a simulated oleophenol mixture with a phenol concentration of 100 g / L. (2) Measure 200 mL of the above oil-phenol mixture into a 500 mL flask, add 24 g of 1-butyl-3-methylimidazolium bromide ionic liquid (the mass ratio of ionic liquid to phenol is 1.2:1), place it in a 25℃ water bath and stir magnetically for 30 min, let it stand for 20 min, and separate the phases to obtain dephenolized oil and phenol-containing ionic liquid extract; (3) The composition of phenol and butylbenzene in the dephenolized oil and ionic liquid extract was analyzed by gas chromatography, and the gas chromatography analysis method was the same as in Example 1; the analysis results showed that the content of phenol in the dephenolized oil was 0.28% and the content of neutral oil was 99.72%; the content of phenol in the extract was 73.4% and the content of neutral oil was 26.6%; the phenol removal rate was calculated to be 95.1%; (4) The ionic liquid extract was added to flash evaporator 1, and part of the neutral oil was removed under the conditions of 140°C and 0.05 MPa. The composition of oleic acid in the neutral oil removed by flash evaporation and the ionic liquid extract after flash evaporation was analyzed by the method described in Example 1. The results showed that the phenol content in the flash-evaporated oil was 2.0% and the neutral oil content was 98.0%. This part was returned to be mixed with the raw material and entered the next separation cycle. The neutral oil content in the ionic liquid extract was 3.0% and the phenol content was 97.0%. (5) The ionic liquid extract obtained in step (4) is added to flash evaporator 2. Phenol and a small amount of neutral oil are distilled off at a temperature of 160℃ and a pressure of 0.003MPa, and the ionic liquid is recovered. The distillate is collected and its composition is analyzed by the above gas chromatography method. The content of neutral oil is 3.1% and the content of phenol is 96.9%. (6) The liquid distilled in step (5) is added to a distillation column and separated under a pressure of 0.04 MPa and a reflux ratio of 1.45 to obtain the overhead distillate and the bottom distillate. The composition is analyzed by the above gas chromatography method. The overhead distillate contains 40.7% neutral oil and 59.3% phenol. The overhead distillate is returned to be mixed with the raw material and enters the next extraction cycle. The bottom distillate contains 0.6% neutral oil and 99.4% phenol, which meets the purity requirements for phenolic substances. Example 3

[0026] (1) Weigh 100.0 g of phenol, place it in a 100 ml beaker, add a small amount of butylbenzene to dissolve it, and then make up to 1000 mL in a volumetric flask to obtain a simulated oleophenol mixture with a phenol concentration of 100 g / L. (2) Measure 200 mL of the above oil-phenol mixture into a 500 mL flask, add 16 g of 1-ethyl-3-methylimidazolium bromide ionic liquid (the mass ratio of ionic liquid to phenol is 0.8:1), then place it in a 25℃ water bath and stir magnetically for 30 min, let it stand for 20 min, and separate the phases to obtain the dephenolized oil and the phenol-containing ionic liquid extract; (3) The composition of phenol and butylbenzene in the dephenolized oil and ionic liquid extract was analyzed by gas chromatography, and the gas chromatography analysis method was the same as in Example 1; the analysis results showed that the content of phenol in the dephenolized oil was 0.43% and the content of neutral oil was 99.57%; the content of phenol in the ionic liquid extract was 75.1% and the content of neutral oil was 24.9%; the phenol removal rate was calculated to be 96.7%; (4) The ionic liquid extract was added to flash evaporator 1, and a portion of the neutral oil was removed under the conditions of 140°C and 0.05 MPa. The composition of oleic acid in the neutral oil removed by flash evaporation and the ionic liquid extract after flash evaporation was analyzed by the method described in Example 1. The results showed that the phenol content in the flash-evaporated oil was 2.1%, and the neutral oil content was 97.9%. This portion was returned to be mixed with the raw material and entered the next separation cycle. The neutral oil content in the ionic liquid extract was 2.9%, and the phenol content was 97.1%. (5) The ionic liquid extract obtained in step (4) is added to flash evaporator 2. Phenol and a small amount of neutral oil are distilled off at a temperature of 160℃ and a pressure of 0.003MPa, and the ionic liquid is regenerated. The distillate is collected and its composition is analyzed by the gas chromatography method described above. The content of neutral oil is 3.0% and the content of phenol is 97.0%. (6) The liquid distilled in step (5) is added to a distillation column and separated under a pressure of 0.06 MPa and a reflux ratio of 1.55 to obtain the overhead distillate and the bottom distillate. The composition is analyzed by the above gas chromatography method. The overhead distillate contains 35.9% neutral oil and 64.1% phenol. The overhead distillate is returned to be mixed with the raw material and enters the next extraction cycle. The bottom distillate contains 1.0% neutral oil and 99.0% phenol, which meets the purity requirements for phenolic substances. Example 4

[0027] (1) Weigh 200.0 g of phenol, place it in a 100 ml beaker, add a small amount of butylbenzene to dissolve it, and then make up to 1000 mL in a volumetric flask to obtain a simulated oleophenol mixture with a phenol concentration of 200 g / L. (2) Measure 200 mL of the above oil-phenol mixture into a 500 mL flask, add 40 g of tetraethylammonium bromide ionic liquid (the mass ratio of ionic liquid to phenol is 1:1), then place it in a 25℃ water bath and stir magnetically for 30 min, let it stand for 20 min, and separate the phases to obtain dephenolized oil and phenol-containing ionic liquid extract. (3) The composition of phenol and butylbenzene in the dephenolized oil and ionic liquid extract was analyzed by gas chromatography, and the gas chromatography analysis method was the same as in Example 1. The analysis results showed that the content of phenol in the dephenolized oil was 0.48% and the content of neutral oil was 99.52%; the content of phenol in the extract was 77.6% and the content of neutral oil was 22.4%, and the phenol removal rate was calculated to be 98.4%. (4) The extract was added to flash evaporator 1 for flash evaporation. The flash evaporation conditions were 110°C and 0.02 MPa to remove some of the neutral oil. The composition of oleic acid in the neutral oil removed by flash evaporation and the ionic liquid extract after flash evaporation was analyzed by the method described in Example 1. The results showed that the phenol content in the flash evaporated oil was 2.7% and the neutral oil content was 97.3%. This part was returned to be mixed with the raw material and entered the next separation cycle. The neutral oil content in the ionic liquid extract was 3.4% and the phenol content was 96.6%. (5) The extract from which the neutral oil was removed in step (4) was added to flash evaporator 2. Phenol and a small amount of neutral oil were distilled off at a temperature of 180°C and a pressure of 0.006 MPa, and the ionic liquid was recovered. The distillate was collected and its composition was analyzed by the gas chromatography method described above. The content of neutral oil was 3.8% and the content of phenol was 96.2%. (6) The liquid distilled in step (5) is added to a distillation column and separated under a pressure of 0.05 MPa and a reflux ratio of 1.50 to obtain the overhead distillate and the bottom distillate. The composition is analyzed by the above gas chromatography method. The overhead distillate contains 40.9% neutral oil and 59.1% phenol. The overhead distillate is returned to be mixed with the raw material and enters the next extraction cycle. The bottom distillate contains 0.9% neutral oil and 99.1% phenol, which meets the purity requirements for phenolic substances. Example 5

[0028] (1) Weigh 50.0 g of phenol, place it in a 100 ml beaker, add a small amount of butylbenzene to dissolve it, and finally dilute it to a 1000 mL volumetric flask to obtain a simulated oleophenol mixture with a phenol concentration of 50 g / L. (2) Measure 200 mL of the above oil-phenol mixture into a 500 mL flask, add 10 g of tetraethylammonium bromide ionic liquid (the mass ratio of ionic liquid to phenol is 1:1), then place it in a 25℃ water bath and stir magnetically for 30 min, let it stand for 20 min, and separate the phases to obtain dephenolized oil and phenol-containing ionic liquid extract. (3) The composition of phenol and butylbenzene in the dephenolized oil and ionic liquid extract was analyzed by gas chromatography, and the gas chromatography analysis method was the same as in Example 1. The analysis results showed that the composition of the dephenolized oil was 0.26% phenol and 99.74% neutral oil; the content of phenol in the extract was 78.0% and the content of neutral oil was 22.0%, and the phenol removal rate was calculated to be 96.0%. (4) The extract was added to flash evaporator 1 for flash evaporation at a temperature of 110°C and a pressure of 0.02 MPa to remove part of the neutral oil. The composition of oleic acid in the neutral oil removed by flash evaporation and the ionic liquid extract after flash evaporation was analyzed by the method in Example 1. The results showed that the phenol content in the flash-evaporated oil was 2.8% and the neutral oil content was 97.2%. This part was returned to be mixed with the raw material and entered the next separation cycle. The neutral oil content in the ionic liquid extract was 3.1% and the phenol content was 96.9%. (5) The extract from which the neutral oil was removed in step (4) was added to flash evaporator 2. Under the conditions of temperature 180℃ and pressure 0.006MPa, a small amount of neutral oil and phenol were distilled off, and the ionic liquid was recovered. The distillate was collected and its composition was analyzed by the above gas chromatography method. The content of neutral oil was 3.4% and the content of phenol was 96.6%. (6) The liquid distilled in step (5) is added to a distillation column and separated under a pressure of 0.05 MPa and a reflux ratio of 1.50 to obtain the overhead distillate and the bottom effluent. The composition is analyzed by the above gas chromatography method. The overhead distillate contains 41.0% neutral oil and 59.0% phenol. The overhead distillate is returned to be mixed with the raw material and enters the next extraction cycle. The bottom distillate contains 0.8% neutral oil and 99.2% phenol, which meets the purity requirements for phenolic substances. Example 6

[0029] (1) Weigh 100.0 g of phenol and place it in a 100 ml beaker. Add a small amount of butylphenol and then dilute to a 1000 mL volumetric flask to obtain a simulated oleophenol mixture with a phenol concentration of 100 g / L. (2) Measure 200 mL of the above oil-phenol mixture into a 500 mL flask, add 20 g of tetraethylammonium bromide ionic liquid (the mass ratio of ionic liquid to phenol is 1:1), then place it in a 25℃ water bath and stir magnetically for 30 min, let it stand for 20 min, and separate the phases to obtain dephenolized oil and phenol-containing ionic liquid extract. (3) The composition of phenol and butylbenzene in the dephenolized oil and ionic liquid extract was analyzed by gas chromatography, and the gas chromatography analysis method was the same as in Example 1. The analysis results showed that the composition of the dephenolized oil was 0.28% phenol and 99.72% neutral oil; the content of phenol in the extract was 77.3% and the content of neutral oil was 22.7%, and the phenol removal rate was calculated to be 98.0%. (4) The extract was added to flash evaporator 1 and a portion of the neutral oil was removed at a temperature of 120°C and a pressure of 0.03 MPa. The composition of oleic acid in the neutral oil removed by flash evaporation and the ionic liquid extract after flash evaporation was analyzed by the method described in Example 1. The results showed that the phenol content in the flash-evaporated oil was 2.2% and the neutral oil content was 97.8%. This portion was returned to be mixed with the raw material and entered the next separation cycle. The neutral oil content in the ionic liquid extract was 3.0% and the phenol content was 97.0%. (5) The ionic liquid extract from which some neutral oil was removed in step (4) was added to flash evaporator 2. Phenol and a small amount of neutral oil were distilled off at a temperature of 170°C and a pressure of 0.005 MPa, and the ionic liquid was recovered. The distillate was collected and its composition was analyzed by the gas chromatography method described above. The content of neutral oil was 3.5% and the content of phenol was 96.5%. (6) The oil-phenol mixture distilled in step (5) is added to a distillation column and separated by distillation at a pressure of 0.05 MPa and a reflux ratio of 1.50 to obtain the overhead distillate and the bottom distillate. The composition is analyzed by the above gas chromatography method. The overhead distillate contains 38.8% neutral oil and 61.2% phenol. The overhead distillate is returned to be mixed with the raw material and enters the next extraction cycle. The bottom distillate contains 0.8% neutral oil and 99.2% phenol, which meets the purity requirements of phenolic substances. Example 7

[0030] (1) Using the phenolic oil fraction of coal pyrolysis oil from northern Shaanxi as raw material, the concentration of phenolic compounds was found to be 194 g / L by the national standard method (GB / T 24200-2009); (2) Measure 200 mL of the above pyrolysis oil into a 500 mL flask, add 38.8 g of tetraethylammonium bromide ionic liquid (the mass ratio of ionic liquid to phenol is 1:1), then place it in a 20℃ water bath and stir magnetically for 30 min, let it stand for 20 min, and separate the phases to obtain dephenolized oil and phenol-containing ionic liquid extract. (3) The content of phenolic compounds in the dephenolized oil was analyzed by the national standard method (GB / T 24200-2009). The analysis results showed that the composition of the dephenolized oil in the extract was 0.49% phenolic compounds and 99.51% neutral oil. (4) The extract was back-extracted, and the back-extraction steps were the same as in Example 1. Then, the content of phenolic compounds was analyzed by the national standard method (GB / T24200-2009). The analysis results showed that the content of phenolic compounds in the extract was 76.0%, the content of neutral oil was 24.0%, and the removal rate of phenolic compounds was calculated to be 98.1%. (5) The phenol-containing ionic liquid extract obtained in step 2 was added to flash tank 1 and a portion of the neutral oil was removed under the conditions of temperature 110℃ and pressure 0.02MPa. The composition of the flash-evaporated ionic liquid extract was analyzed by the above-mentioned ether back-extraction and the national standard method (GB / T 24200-2009). The results showed that the neutral oil content was 3.3% and the phenolic compound content was 96.7%. The neutral oil obtained by flash evaporation was analyzed by the method of Example 1. Its composition was: neutral oil content 97.4% and phenolic compound content 2.6%. This part was returned to be mixed with the raw material and entered the next separation cycle.

[0031] (6) The extract from which the neutral oil was removed in step (5) was added to flash evaporator 2. The neutral oil and phenolic compounds were distilled off at a temperature of 180℃ and a pressure of 0.006MPa, and the ionic liquid was recovered. The distilled liquid was collected and its composition was analyzed by the national standard method (GB / T 24200-2009). The results showed that the content of neutral oil was 3.9% and the content of phenolic compounds was 96.1%. (7) The liquid distilled in step (6) is added to a distillation column and distilled at a pressure of 0.05 MPa and a reflux ratio of 1.50 to obtain the top distillate and the bottom distillate.

[0032] The composition of the overhead and bottom effluents of the column was analyzed using the national standard method (GB / T 24200-2009). The results showed that the overhead distillate contained 38.9% neutral oil and 61.1% phenolic compounds, and the overhead distillate could be returned to the feed for further separation. The bottom distillate contained 0.8% neutral oil, which is less than 1%, and 99.2% phenolic compounds, meeting the purity requirements for phenolic substances.

[0033] The embodiments described above are merely specific examples of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for separating an oil-phenol mixture using ionic liquid extraction and distillation, characterized in that, It is a method that uses ionic liquid as an extractant, combined with flash evaporation and distillation, to finally obtain high-purity phenolic compounds, wherein the oil-phenol mixture is a mixture of phenol and butylbenzene or a phenolic oil fraction of coal pyrolysis oil. Among them, high-purity phenolic compounds refer to products with a phenol content of 99.0% to 99.4%; The specific steps of the method are as follows: (1) The ionic liquid extractant is added to the extraction tower from the top of the tower and the oil-phenol mixture is added to the bottom of the tower for extraction and separation. The phenol-free oil is obtained from the top of the tower and the ionic liquid extract is obtained from the bottom of the tower. The ionic liquid extractant is any one of tetraethylammonium bromide, 1-butyl-3-methylimidazolium bromide and 1-ethyl-3-methylimidazolium bromide. (2) The extract is flash-evaporated to remove some of the neutral oil; the flash-evaporation conditions are a temperature of 110~140℃ and a pressure of 0.02~0.05MPa; (3) The ionic liquid extract obtained in step (2) is flash-evaporated a second time to remove phenol and a small amount of neutral oil, and the ionic liquid extractant is regenerated; the conditions for the second flash evaporation are a temperature of 160~180℃ and a pressure of 0.003~0.006MPa. (4) Add the phenol and a small amount of neutral oil obtained in step (3) to the distillation column. The distillate from the top of the column is returned to the raw material for further separation, and the high-purity phenolic compound is distilled from the bottom of the column.

2. The method for separating an oil-phenol mixture by extraction and distillation using an ionic liquid according to claim 1, characterized in that, The mass ratio of phenol in the ionic liquid extractant and oleophenol mixture is 0.8~1.

2.

3. The method for separating an oil-phenol mixture by extraction and distillation using an ionic liquid according to claim 1, characterized in that, The concentration of phenolic compounds in the oleophenol mixture in step (1) is 50 g / L to 200 g / L.

4. The method for separating an oil-phenol mixture by extraction and distillation using an ionic liquid according to claim 1, characterized in that, The extraction and separation temperature in step (1) is 20℃~50℃.

5. The method for separating an oil-phenol mixture by extraction and distillation using an ionic liquid according to claim 1, characterized in that, The distillation pressure in step (4) is 0.04~0.06MPa.

Images