METHOD FOR STEPWISE EXTRACTION OF PHENOL AND PYRIDINE COMPOUNDS IN NAPHTHALENE OIL BY DEEP EUTECTIC SOLVENTS

Abstract

A method for stepwise extraction of phenol and pyridine compounds in naphthalene oil by deep eutectic solvents includes: mixing the naphthalene oil with alkane and the deep eutectic solvents, and performing phase separation to obtain a eutectic extracting phase and a raffinate phase; mixing the extracting phase with a first stripping agent, and performing phase separation to obtain a first stripping phase and recyclable deep eutectic solvents; distilling the first stripping phase to obtain a heteroatom mixture; and mixing the heteroatom mixture with a hydrogen bond acceptor extractant and alkane, and performing phase separation to obtain a phenol-containing extracting phase and a pyridine-containing raffinate phase; and mixing the phenol-containing extracting phase with a second stripping agent, performing phase separation to obtain a phenol-dissolved stripping solution and the hydrogen bond acceptor, and distilling the second stripping solution or the pyridine-containing raffinate phase to obtain a phenol or a pyridine product.

Claims

1. A method for stepwise extraction of phenol and pyridine compounds in naphthalene oil by deep eutectic solvents, comprising the following steps: step 1, mixing the naphthalene oil, alkane and the deep eutectic solvents, and performing phase separation to obtain a heteroatom eutectic phase and a hydrocarbon raffinate phase; step 2, mixing the heteroatom eutectic phase with a first stripping agent, and performing phase separation to obtain a first stripping organic phase and a first stripping raffinate phase; step 3, separating a heteroatom mixture in the first stripping organic phase from the first stripping agent by distillation, mixing the heteroatom mixture, alkane and a hydrogen bond acceptor extractant, and performing phase separation to obtain a phenol eutectic extracting phase and a pyridine raffinate phase; and step 4, mixing the phenol eutectic extracting phase with a second stripping agent, and performing phase separation to obtain a phenol compound; wherein, the deep eutectic solvents are a mixture of at least one of tetraethylammonium chloride, tetrabutylammonium chloride, tetrabutylammonium bromide and tetrabutylphosphonium bromide, and at least one of a glycolic acid, an oxalic acid, a citric acid and a p-toluenesulfonic acid; and the hydrogen bond acceptor extractant is at least one of tetraethylammonium chloride, tetrabutylammonium chloride, tetrabutylammonium bromide and tetrabutylphosphonium bromide.

2. The method for stepwise extraction of the phenol and pyridine compounds in the naphthalene oil by deep eutectic solvents according to claim 1, further comprising: distilling the hydrocarbon raffinate phase in the step 1 to obtain alkane and a naphthalene mixture, respectively; and circulating the alkane to the step 1 for reuse.

3. The method for stepwise extraction of the phenol and pyridine compounds in the naphthalene oil by deep eutectic solvents according to claim 1, wherein the first stripping agent is selected from at least one of acetone, ethyl acetate, carbon disulfide and tetrachloromethane; and the first stripping raffinate phase is the deep eutectic solvents, which is circulated to the step 1 for reuse.

4. The method for stepwise extraction of the phenol and pyridine compounds in the naphthalene oil by deep eutectic solvents according to claim 1, wherein the heteroatom mixture in the first stripping organic phase is separated from the first stripping agent by distillation, and the separated first stripping agent is circulated to the step 2 for reuse.

5. The method for stepwise extraction of the phenol and pyridine compounds in the naphthalene oil by deep eutectic solvents according to claim 1, wherein the second stripping agent is selected from at least one of acetone, ethyl acetate, carbon disulfide and tetrachloromethane; the mixture of the phenol eutectic phase and the second stripping agent is subjected to phase separation to obtain the phenol compound and the hydrogen bond acceptor extractant, and the hydrogen bond acceptor extractant obtained by phase separation is circulated to the step 3 for reuse.

6. The method for stepwise extraction of the phenol and pyridine compounds in the naphthalene oil by deep eutectic solvents according to claim 1, wherein the pyridine raffinate phase is separated by distillation to obtain the pyridine compound and the alkane, and the alkane is circulated to the step 3 for reuse.

7. The method for stepwise extraction of the phenol and pyridine compounds in the naphthalene oil by deep eutectic solvents according to claim 1, wherein the alkane in the step 1 is the same as or different from the alkane in the step 3, and is independently selected from n-hexane and cyclohexane.

8. The method for stepwise extraction of the phenol and pyridine compounds in the naphthalene oil by deep eutectic solvents according to claim 1, wherein, in the step 1, a mass ratio of the deep eutectic solvents to the naphthalene oil is 0.2-2, a mixing temperature is 30 C.-50 C., and the mixing lasts for 60 minutes-120 minutes.

9. The method for stepwise extraction of the phenol and pyridine compounds in the naphthalene oil by deep eutectic solvents according to claim 1, wherein, in the step 3, a mixing temperature is 30 C.-50 C.; in the step 2, a mass ratio of the first stripping agent to the heteroatom eutectic phase is 0.5-1, and the mixing lasts for 10 minutes-30 minutes; and in the step 4, a mass ratio of the second stripping agent to the phenol eutectic phase is 0.5-1, and the mixing lasts for 10 minutes-30 minutes.

10. The method for stepwise extraction of the phenol and pyridine compounds in the naphthalene oil by deep eutectic solvents according to claim 1, wherein, in the deep eutectic solvents, a molar ratio of the tetraethylammonium chloride, the tetrabutylammonium chloride, the tetrabutylammonium bromide or the tetrabutylphosphonium bromide to the glycolic acid, the oxalic acid, the citric acid or the p-toluenesulfonic acid is 2:1-1:2.

Description

DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 is a schematic diagram of a system for separating phenol and pyridine compounds in naphthalene oil according to one embodiment of the present application.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0026] The technical solutions of the present application are described in detail. Hereinafter, the following embodiments are implemented on the premise of the technical solutions of the present application, and the detailed implementation processes are given. However, the scope of protection of the present application is not limited to the following embodiments. The structures or experimental methods without specific conditions in the following embodiments are usually implemented according to conventional conditions.

[0027] The present application provides a method for stepwise extraction of phenol and pyridine compounds in naphthalene oil by deep eutectic solvents, which includes the following steps: [0028] step 1, mixing the naphthalene oil, alkane and the deep eutectic solvents, and performing phase separation to obtain a heteroatom eutectic phase and a hydrocarbon raffinate phase; [0029] step 2, mixing the heteroatom eutectic phase with a first stripping agent, and performing phase separation to obtain a first stripping organic phase and a first stripping raffinate phase; [0030] step 3, separating a heteroatom mixture in the first stripping organic phase from the first stripping agent, mixing the heteroatom mixture, alkane and a hydrogen bond acceptor extractant, and performing phase separation to obtain a phenol eutectic phase and a pyridine raffinate phase; and [0031] step 4, mixing the phenol eutectic phase with a second stripping agent, and performing phase separation to obtain a phenol compound; [0032] wherein, the deep eutectic solvents are a mixture of at least one of tetraethylammonium chloride, tetrabutylammonium chloride, tetrabutylammonium bromide and tetrabutylphosphonium bromide, and at least one of a glycolic acid, an oxalic acid, a citric acid and a p-toluenesulfonic acid; and the hydrogen bond acceptor extractant is at least one of tetraethylammonium chloride, tetrabutylammonium chloride, tetrabutylammonium bromide and tetrabutylphosphonium bromide.

[0033] In the present application, the deep eutectic solvents and the hydrogen bond acceptor are used as the extractants, combined with stripping, distillation and other modes, the phenol and pyridine compounds in the naphthalene oil can be highly selectively separated, the operation is simple and efficient, the extraction conditions are mild, the extractants can be recycled after drying, the stripping agent and the alkane solvent can be recycled through atmospheric distillation, and the involved reagents are not corrosive to equipment.

[0034] In the present application, the naphthalene oil refers to a naphthalene oil fraction of coal tar at 210-230 C. under an atmospheric pressure, and the naphthalene oil is rich in phenol and pyridine compounds and naphthalene derivatives. General composition ratios are as follows: a mass ratio of phenol to pyridine is greater than 2, and a mass of the naphthalene derivative exceeds 50%. In one embodiment, model oil is prepared according to a mass ratio of phenol:pyridine:aromatic hydrocarbon=2:1:3. Real naphthalene oil is quite different in composition, thus, the content of phenolic compounds is quantified by gas chromatography with area normalization prior to extraction and separation. The extraction and separation are finished according to the ratios in the present application. In the present application, the pyridine compound refers to pyridine, quinoline, and the like, and the phenol compound refers to phenol, ethylphenol, and the like.

[0035] In one embodiment of the present application, the naphthalene oil is mixed with the alkane first to prepare a solution, and then, the solution is mixed with the deep eutectic solvents for extraction. In the present application, the alkane is not particularly limited, and may be any low-boiling-point alkane, such as n-hexane and cyclohexane. In another embodiment, a mass fraction of the naphthalene oil in the solution formed by the naphthalene oil and the alkane is 180 g/kg-360 g/kg. In yet another embodiment, a mass ratio of the deep eutectic solvents to the naphthalene oil is 0.2-2. A stirring operation should be carried out in the extraction process, a mixing and extraction temperature of the above solution and the deep eutectic solvents may be 30 C.-50 C., and the mixing and extraction may last for 60-120 minutes. After the extraction, the product is allowed to stand and wait for phase separation, a phase separation mode is not particularly limited in the present application, and the phase separation may be carried out by decantation or dropper suction, so as to obtain the heteroatom eutectic phase and the hydrocarbon raffinate phase. The heteroatom eutectic phase mainly includes the deep eutectic solvents and a heteroatom compound, and the hydrocarbon raffinate phase mainly includes naphthalene compounds and an alkane solvent.

[0036] A hydrocarbon extract phase may be distilled to recycle the alkane solvent, so as to obtain a naphthalene mixture. The distillation refers to, for example, atmospheric distillation, which is not particularly limited in the present application. The gathered alkane solvent can be recycled, and the naphthalene mixture may be output as a product and used as a raw material for other technologies.

[0037] The heteroatom eutectic phase is mixed with the first stripping agent, and the phase separation is carried out to obtain the first stripping organic phase and the first stripping raffinate phase.

[0038] In one embodiment, the first stripping agent is selected from acetone, ethyl acetate, carbon disulfide, tetrachloromethane, and the like. In another embodiment, a mass ratio of the first stripping agent to the heteroatom eutectic phase is 0.5-1. The heteroatom eutectic phase is mixed with the first stripping agent for heteroatom separation, a stirring operation may be carried out in the mixing process, a mixing temperature may be room temperature, which is 20 C.-30 C., and the mixing may last for 10 minutes-30 minutes; and then, phase separation is carried out to obtain the first stripping organic phase and the first stripping raffinate phase.

[0039] The first stripping raffinate phase mainly includes the deep eutectic solvents, which can be recycled after drying. The first stripping organic phase mainly includes the first stripping agent and the heteroatom compound. The first stripping organic phase may be distilled by atmospheric distillation, to separate the heteroatom mixture from the first stripping agent in the first stripping organic phase, so as to obtain the heteroatom compound with a yield of more than 98% and the first stripping agent respectively, wherein the first stripping agent obtained by distillation can be recycled.

[0040] The heteroatom mixture, the alkane and the hydrogen bond acceptor extractant are mixed, and the phase separation is carried out to obtain the phenol eutectic phase and the pyridine raffinate phase.

[0041] In one embodiment, the heteroatom mixture is mixed with the alkane solvent to prepare a solution, and then, the solution is mixed with the hydrogen bond acceptor extractant for extraction. In the present application, the alkane solvent is not particularly limited, and may be low-boiling-point alkane, such as n-hexane and cyclohexane. In another embodiment, a mass ratio of the alkane solvent to the heteroatom mixture is 1-5. In yet another embodiment, a molar ratio of the hydrogen bond acceptor extractant to the phenol in the naphthalene oil is 0.5-1. A stirring operation may be carried out in the mixing and extraction process, and a mixing and extraction temperature may be 30-50 C. After the extraction, phase separation may be carried out by decantation or dropper suction, so as to obtain the phenol eutectic phase and the pyridine raffinate phase. The phenol eutectic phase mainly includes the hydrogen bond acceptor extractant and target phenol, and the pyridine raffinate phase mainly includes the pyridine compound and the alkane solvent.

[0042] The pyridine compound with a purity of more than 99% may be obtained by distillation, such as atmospheric distillation, from the pyridine raffinate phase. The alkane solvent obtained by distillation can be recycled to the step 3 for reuse.

[0043] The phenol eutectic phase is mixed with the second stripping agent, and the phase separation is carried out to obtain the phenol compound.

[0044] In one embodiment, the second stripping agent is the same as or different from the first stripping agent, and may be selected from acetone, ethyl acetate, carbon disulfide, tetrachloromethane, and the like. In another embodiment, a mass ratio of the second stripping agent to the phenol eutectic phase is 0.5-1. The phenol eutectic phase is mixed with the second stripping agent for phenol separation, a stirring operation may be carried out in the mixing process, a mixing temperature may be room temperature, which is 20 C.-30 C., and the mixing may last for 10-30 minutes; and then, phase separation is carried out to obtain the second stripping organic phase containing the phenol compound and the second stripping raffinate phase. The second stripping organic phase mainly includes the phenol compound and the second stripping agent, and the second stripping raffinate phase mainly includes the hydrogen bond acceptor extractant.

[0045] The hydrogen bond acceptor extractant is obtained after drying the second stripping raffinate phase. The phenol compound with a purity of more than 90% may be obtained after distillation, such as atmospheric distillation, from the second stripping organic phase, and the second stripping agent obtained by distillation can be recycled to the step 4.

[0046] Therefore, the present application provides the method for extracting and separating the phenol and pyridine compounds in the naphthalene oil which is a typical mixture of a coal-based liquid. In this method, the naphthalene oil fraction of coal tar is rich in phenol, pyridine and naphthalene derivatives (210-230 C.) is used as a separation object, and the extraction and separation process includes: dissolving the naphthalene oil in the alkane solvent, using the acidic eutectic solvent as the extractant, completing liquid-liquid extraction by forming two phases with the alkane solvent, and capturing the heteroatom compound in the naphthalene oil fraction with the acidic eutectic solvent; then, obtaining the heteroatom compound (including acidic phenol and basic pyridine compounds) by stripping; then, highly selectively separating the phenol form pyridine compounds by using the characteristic that the hydrogen bond acceptor extractant is easy to be associated with the phenol to form the eutectic phase; and finally, the phenol and pyridine compounds are obtained by stripping and distillation respectively. According to the method in the present application, the operation is simple and efficient, the extraction conditions are mild, the extractants can be recycled after drying, and the stripping agent and the alkane solvent can be recycled through atmospheric distillation.

[0047] In the present application, the acidic deep eutectic solvent extractants separate the heteroatom compound through a hydrogen bond and acid-base synergy effect, and the phenol compounds are selectively separated from pyridine compounds by a structural difference that a pyridine group does not have a hydrogen bond donor site. An extraction principle is analyzed by combining with a charge screening surface density model of COSMO-RS software: (1) interaction energy between the extractant and the heteroatom compound is greater than that between the heteroatom compound and aromatic hydrocarbon in the alkane solvent, so that the extractant breaks an original association structure; and (2) a hydrogen bond interaction between the hydrogen bond acceptor extractant and the phenol is remarkable, and the phenol is highly selectively extracted by using the structural difference of the pyridine group lacks the hydrogen bond donor site. Preliminary screening is completed according to the calculation of the interaction energy, the preferred acidic deep eutectic solvent in the present application is selected from a binary composition of at least one of tetraethylammonium chloride, tetrabutylammonium chloride, tetrabutylammonium bromide and tetrabutylphosphonium bromide, and at least one of a glycolic acid, an oxalic acid, a citric acid and a p-toluenesulfonic acid; and the preferred hydrogen bond acceptor extractant is selected from at least one of tetraethylammonium chloride, tetrabutylammonium chloride, tetrabutylammonium bromide and tetrabutylphosphonium bromide.

[0048] Compared with a traditional acid-base extraction and separation method, the method for extracting and separating the phenol and pyridine compounds provided by the present application has the following advantages: (1) the technology is simple to operate, the extractant and the solvent are added for extraction at one time, and liquid-liquid extraction can be completed through a simple phase separation; (2) the separation conditions are mild, the temperature in the separation process ranges from 30 C. to 50 C., thus the technological energy consumption is low; (3) during separation, the organic solvent is used for stripping and the DES is used for extraction, both of which can be reused without water pollution; and (4) the overall technological operation has a high degree of continuity and has a very strong industrial scale-up potential.

[0049] The present application further provides a schematic diagram of a system for separating the phenol and pyridine compounds in the naphthalene oil. The naphthalene oil mixture F1, the alkane solvent Sol and the deep eutectic solvents E1 are mixed for extraction in a heteroatom extraction kettle DH to obtain the heteroatom eutectic phase (DES extracting phase) and the hydrocarbon raffinate phase, the hydrocarbon raffinate phase enters a solvent tower ST, the solvent obtained by distillation is recycled, and the naphthalene mixture enters a P3 storage tank. The DES extracting phase and the stripping agent are mixed in a stripping tower BE to obtain the heteroatom mixture F2, and the stripping agent is recycled. The heteroatom mixture F2, the hydrogen bond acceptor extractant E2 and the alkane solvent Sol are mixed in a phenol extraction kettle PH to obtain the phenol eutectic phase (DES extracting phase) and the pyridine raffinate phase. The phenol eutectic phase (DES extracting phase) and the stripping agent are mixed for stripping in the stripping tower BE to obtain a mixed phenol product P1, while the stripping agent is recycled. The pyridine raffinate phase enters the solvent tower ST, the solvent obtained by distillation is recycled, and the pyridine compound enters a P2 storage tank.

[0050] The technical solutions of the present application are further described below with reference to specific embodiments, but the scope of protection of the present application is not limited to the following embodiments. Unless otherwise specified, the raw materials, reagents and methods used in the embodiments are all conventional raw materials, reagents and methods in the art. In some of the following embodiments, model naphthalene oil prepared by ethylphenol, quinoline and methyl naphthalene according to a mass ratio of 2:1:3 is used as a raw material for determination.

Embodiment 1

[0051] Model naphthalene oil was used as a raw material and dissolved in cyclohexane to prepare a 180 g/kg solution. 100 g of the solution was added into a triangular flask with magnetic stirring, a DES extractant of tetraethylammonium chloride and an oxalic acid was prepared according to a molar ratio of 1:2, 18 g of the DES extractant (a mass ratio of the DES extractant to the naphthalene oil was 1) was added and stirred at 30 C. for 60 minutes, and then, phase separation was carried out to obtain a DES phase. 9 g of ethyl acetate was added as a stripping agent, an ethylphenol- and quinoline-dissolved strip solution was obtained after stripping for 30 minutes, and 8.82 g of ethylphenol and quinoline mixture was obtained after distillation, with a yield of 98.1%. Subsequently, 4.06 g of tetraethylammonium chloride (a molar ratio of the tetraethylammonium chloride to the phenol was 0.5) and 45 g of cyclohexane were added and stirred at 50 C. for 60 minutes, and then, phase separation was carried out to obtain a DES phase. The DES phase was added with 9 g of ethyl acetate and stirred at room temperature for 10 minutes. 6.19 g of ethylphenol was obtained by distilling a stripping organic phase, with a purity of 95%, and 2.63 g of quinoline was obtained by distilling an alkane solvent phase, with a purity of 99%.

Embodiment 2

[0052] Model naphthalene oil was used as a raw material and dissolved in cyclohexane to prepare a 180 g/kg solution. 100 g of the solution was added into a triangular flask with magnetic stirring, a DES extractant of tetraethylammonium chloride and a glycolic acid was prepared according to a molar ratio of 1:2, 36 g of the DES extractant (a mass ratio of the DES extractant to the naphthalene oil was 2) was added and stirred at 50 C. for 120 minutes, and then, phase separation was carried out to obtain a DES phase. 18 g of acetone was added as a stripping agent, an ethylphenol- and quinoline-dissolved strip solution was obtained after stripping for 30 minutes, and 8.28 g of ethylphenol and quinoline mixture was obtained after distillation, with a yield of 92%. Subsequently, 4.06 g of tetraethylammonium chloride (a molar ratio of the tetraethylammonium chloride to the phenol was 0.5) and 45 g of cyclohexane were added and stirred at 50 C. for 60 minutes, and then, phase separation was carried out to obtain a DES phase. The DES phase was added with 9 g of ethyl acetate and stirred at room temperature for 10 minutes. 5.75 g of ethylphenol was obtained by distilling a stripping organic phase, with a purity of 96%, and 2.53 g of quinoline was obtained by distilling an alkane solvent phase, with a purity of 99%.

Embodiment 3

[0053] Model naphthalene oil was used as a raw material and dissolved in hexane to prepare a 360 g/kg solution. 100 g of the solution was added into a triangular flask with magnetic stirring, DES extractant of tetrabutylammonium chloride and a citric acid was prepared according to a molar ratio of 1:2, 36 g of the DES extractant (a mass ratio of the eutectic extractant to the naphthalene oil was 1) was added and stirred at 40 C. for 60 minutes, and then, phase separation was carried out to obtain a DES phase. 36 g of ethyl acetate was added as a stripping agent, an ethylphenol- and quinoline-dissolved strip solution was obtained after stripping for 30 minutes, and 17.4 g of ethylphenol and quinoline mixture was obtained after distillation, with a yield of 96.66%. Subsequently, 8.12 g of tetraethylammonium chloride (a molar ratio of the tetraethylammonium chloride to the phenol was 0.5) and 36 g of hexane were added and stirred at 50 C. for 60 minutes, and then, phase separation was carried out to obtain a DES phase. The DES phase was added with 18 g of carbon disulfide and stirred at room temperature for 10 minutes. 12.61 g of ethylphenol was obtained by distilling a stripping organic phase, with a purity of 92%, and 4.79 g of quinoline was obtained by distilling an alkane solvent phase, with a purity of 99%.

Embodiment 4

[0054] Model naphthalene oil was used as a raw material and dissolved in cyclohexane to prepare a 360 g/kg solution. 100 g of the solution was added into a triangular flask with magnetic stirring, a DES extractant of tetrabutylammonium bromide and a p-toluenesulfonic acid was prepared according to a molar ratio of 1:2, 7.2 g of the DES extractant (a mass ratio of the DES extractant to the naphthalene oil was 0.2) was added and stirred at 50 C. for 60 minutes, and then, phase separation was carried out to obtain a DES phase. 36 g of acetone was added as a stripping agent, an ethylphenol- and quinoline-dissolved strip solution was obtained after stripping for 30 minutes, and 17.71 g of ethylphenol and quinoline mixture was obtained after distillation, with a yield of 98.41%. Subsequently, 16.24 g of tetraethylammonium chloride (a molar ratio of the tetraethylammonium chloride to the phenol was 1) and 18 g of cyclohexane were added and stirred at 50 C. for 60 minutes, and then, phase separation was carried out to obtain a DES phase. The DES phase was added with 18 g of carbon disulfide and stirred at room temperature for 10 minutes. 13.12 g of ethylphenol was obtained by distilling a stripping organic phase, with a purity of 90%, and 4.59 g of quinoline was obtained by distilling an alkane solvent phase, with a purity of 99%.

Embodiment 5

[0055] Model naphthalene oil was used as a raw material and dissolved in cyclohexane to prepare a 360 g/kg solution. 100 g of the solution was added into a triangular flask with magnetic stirring, a DES extractant of tetraethylammonium chloride and an oxalic acid was prepared according to a molar ratio of 1:2, 36 g of the DES extractant (a mass ratio of the DES extractant to the naphthalene oil was 1) was added and stirred at 50 C. for 60 minutes, and then, phase separation was carried out to obtain a DES phase. 18 g of ethyl acetate was added as a stripping agent, an ethylphenol- and quinoline-dissolved strip solution was obtained after stripping for 30 minutes, and 17.69 g of ethylphenol and quinoline mixture was obtained after distillation, with a yield of 98.29%. Subsequently, 16.24 g of tetraethylammonium chloride (a molar ratio of the tetraethylammonium chloride to the ethylphenol was 1) and 90 g of cyclohexane were added and stirred at 50 C. for 60 minutes, and then, phase separation was carried out to obtain a DES phase. The DES phase was added with 18 g of ethyl acetate and stirred at room temperature for 10 minutes. 12.29 g of ethylphenol was obtained by distilling a stripping organic phase, with a purity of 96%, and 5.41 g of quinoline was obtained by distilling an alkane solvent phase, with a purity of 99%.

Embodiment 6

[0056] Model naphthalene oil was used as a raw material and dissolved in cyclohexane to prepare a 360 g/kg solution. 100 g of the solution was added into a triangular flask with magnetic stirring, a DES extractant of tetraethylammonium chloride and an oxalic acid was prepared according to a molar ratio of 1:2, 36 g of the DES extractant (a mass ratio of the DES extractant to the naphthalene oil was 1) was added and stirred at 50 C. for 60 minutes, and then, phase separation was carried out to obtain a DES phase. 18 g of ethyl acetate was added as a stripping agent, an ethylphenol- and quinoline-dissolved strip solution was obtained after stripping for 30 minutes, and 17.48 g of ethylphenol and quinoline mixture was obtained after distillation, with a yield of 97.11%. Subsequently, 27.36 g of tetrabutylammonium chloride (a molar ratio of the tetrabutylammonium chloride to the ethylphenol was 1) and 90 g of cyclohexane were added and stirred at 50 C. for 60 minutes, and then, phase separation was carried out to obtain a DES phase. The DES phase was added with 18 g of ethyl acetate and stirred at room temperature for 10 minutes. 12.40 g of ethylphenol was obtained by distilling a stripping organic phase, with a purity of 94%, and 5.08 g of quinoline was obtained by distilling an alkane solvent phase, with a purity of 99%.

Embodiment 7

[0057] Model naphthalene oil was used as a raw material and dissolved in hexane to prepare a 360 g/kg solution. 100 g of the solution was added into a triangular flask with magnetic stirring, a DES extractant of tetraethylammonium chloride and an oxalic acid was prepared according to a molar ratio of 2:1, 36 g of the DES extractant (a mass ratio of the DES extractant to the naphthalene oil was 1) was added and stirred at 50 C. for 60 minutes, and then, phase separation was carried out to obtain a DES phase. 18 g of carbon tetrachloride was added as a stripping agent, an ethylphenol- and quinoline-dissolved strip solution was obtained after stripping for 30 minutes, and 17.66 g of ethylphenol and quinoline mixture was obtained after distillation, with a yield of 98.11%. Subsequently, 31.68 g of tetrabutylammonium bromide (a molar ratio of the tetrabutylammonium bromide to the ethylphenol was 1) and 90 g of cyclohexane were added and stirred at 50 C. for 60 minutes, and then, phase separation was carried out to obtain a DES phase. The DES phase was added with 36 g of carbon tetrachloride and stirred at room temperature for 10 minutes. 13.08 g of ethylphenol was obtained by distilling a stripping organic phase, with a purity of 90%, and 4.58 g of quinoline was obtained by distilling an alkane solvent phase, with a purity of 99%.

Embodiment 8

[0058] Model naphthalene oil was used as a raw material and dissolved in hexane to prepare a 360 g/kg solution. 100 g of the solution was added into a triangular flask with magnetic stirring, a DES extractant of tetraethylammonium chloride and an oxalic acid was prepared according to a molar ratio of 2:1, 36 g of the DES extractant (a mass ratio of the DES extractant to the naphthalene oil was 1) was added and stirred at 50 C. for 60 minutes, and then, phase separation was carried out to obtain a DES phase. 18 g of carbon tetrachloride was added as a stripping agent, an ethylphenol- and quinoline-dissolved strip solution was obtained after stripping for 30 minutes, and 17.72 g of ethylphenol and quinoline mixture was obtained after distillation, with a yield of 98.45%. Subsequently, 31.68 g of tetrabutylphosphonium bromide (a molar ratio of the tetrabutylphosphonium bromide to the ethylphenol was 1) and 90 g of cyclohexane were added and stirred at 50 C. for 60 minutes, and then, phase separation was carried out to obtain a DES phase. The DES phase was added with 36 g of carbon tetrachloride and stirred at room temperature for 10 minutes. 13.27 g of ethylphenol was obtained by distilling a stripping organic phase, with a purity of 89%, and 4.45 g of quinoline was obtained by distilling an alkane solvent phase, with a purity of 99%.

Embodiment 9

[0059] Model naphthalene oil was used as a raw material and dissolved in cyclohexane to prepare a 360 g/kg solution. 100 g of the solution was added into a triangular flask with magnetic stirring, a DES extractant of tetrabutylammonium chloride and a p-toluenesulfonic acid was prepared according to a molar ratio of 1:2, 36 g of the DES extractant (a mass ratio of the DES extractant to the naphthalene oil was 1) was added and stirred at 50 C. for 60 minutes, and then, phase separation was carried out to obtain a DES phase. 18 g of ethyl acetate was added as a stripping agent, an alkylphenol- and quinoline-dissolved strip solution was obtained after stripping for 10 minutes, and 18.96 g of ethylphenol and quinoline mixture was obtained after distillation, with a yield of 98.7%. Subsequently, 16.24 g of tetraethylammonium chloride (a molar ratio of the tetraethylammonium chloride to the ethylphenol was 1) and 90 g of cyclohexane were added and stirred at 50 C. for 60 minutes, and then, phase separation was carried out to obtain a DES phase. The DES phase was added with 36 g of ethyl acetate and stirred at room temperature for 30 minutes. 13.04 g of ethylphenol was obtained by distilling a stripping organic phase, with a purity of 89%, and 5.92 g of quinoline was obtained by distilling an alkane solvent phase, with a purity of 94%.

Embodiment 10

[0060] A DES of tetraethylammonium chloride and an oxalic acid circulated for five times was used as a DES extractant, the tetraethylammonium chloride was used as a hydrogen bond acceptor extractant, cyclohexane was used as a solvent and ethyl acetate was used as a stripping agent to carry out an experiment, and a model mixture was dissolved in the cyclohexane to prepare a 360 g/kg solution. 100 g of the solution was added into a triangular flask with magnetic stirring, 36 g of DES extractant (a mass ratio of the DES extractant to the naphthalene oil was 1) was added and stirred at 50 C. for 60 minutes, and then, phase separation was carried out to obtain a DES phase. 18 g of ethyl acetate was added as a stripping agent, an alkylphenol- and quinoline-dissolved strip solution was obtained after stripping for 30 minutes, and 18.7 g of ethylphenol and quinoline mixture was obtained after distillation, with a yield of 96.3%. Subsequently, 16.24 g of tetraethylammonium chloride (a molar ratio of the tetraethylammonium chloride to the phenol was 1) and 90 g of cyclohexane were added and stirred at 50 C. for 60 minutes, and then, phase separation was carried out to obtain a DES phase. The DES phase was added with 36 g of carbon disulfide and stirred at room temperature for 10 minutes. 12.77 g of ethylphenol was obtained by distilling a stripping organic phase, with a purity of 95%, and 5.93 g of quinoline was obtained by distilling an alkane solvent phase, with a purity of 97%.

Embodiment 11

[0061] An industrial naphthalene oil sample was used as a raw material and dissolved in cyclohexane to prepare a 180 g/kg solution. 100 g of the solution was added into a triangular flask with magnetic stirring, a DES extractant of tetraethylammonium chloride and an oxalic acid was prepared according to a molar ratio of 1:2, 18 g of the DES extractant (a mass ratio of the DES extractant to the naphthalene oil was 1) was added and stirred at 30 C. for 60 minutes, and then, phase separation was carried out to obtain a DES phase. 9 g of ethyl acetate was used as a stripping agent, a strip solution containing phenolic compounds and pyridine compounds was obtained after stripping for 30 minutes, and 8.21 g of heteroatom mixture was obtained after distillation, with a yield of 104% (it was determined through GC-MS quantification of the naphthalene oil by an area normalization method that a total content of the phenol and pyridine compounds in the naphthalene oil was 43.86 wt. %, and the slight excess might be due to trace impurities in the raw material). Subsequently, 4.06 g of tetraethylammonium chloride (a molar ratio of the tetraethylammonium chloride to the phenol was 0.5) and 45 g of cyclohexane were added and stirred at 50 C. for 60 minutes, and then, phase separation was carried out to obtain a DES phase. The DES phase was added with 9 g of ethyl acetate and stirred at room temperature for 10 minutes. 6.19 g of phenol mixture was obtained by distilling a stripping organic phase, with a purity of 90%, and 1.52 g of pyridine derivative was obtained by distilling an alkane solvent phase, with a purity of 99%.

[0062] Certainly, there are many other embodiments in the present application, and those skilled in the art may make various corresponding changes and transformations according to the present application without departing from the spirit and essence of the present application, but these corresponding changes and transformations should belong to the scope of protection of the claims in the present application.