Method for selectively extracting phenolic compounds in direct conversion liquid product of coal based on amino acid

Abstract

The invention relates to a method for selectively extracting phenolic compounds in a direct coal conversion liquid product based on amino acid, and belongs to the technical field of fine chemical separation in the coal chemical industry. The method comprises the following steps: by taking a coal direct conversion liquefaction product at a fraction section of 230-300 DEG C as a treatment object, dissolving an alkaline amino acid association extraction agent in an alkane solvent to construct an association extraction system, and extracting and separating an extraction phase formed by associating a phenolic compound and alkaline amino acid from the coal direct conversion liquefaction product, and extracting with a back-extractant and separating out alkaline amino acid, and distilling and recovering the back-extractant to obtain the high-purity phenolic compound with the purity of more than 90%. The separation method is simple and efficient, conditions are mild, the extraction agent is green, nontoxic and high in selectivity, and high-selectivity separation of the phenolic compounds in a complex system for directly converting the coal into the liquid product is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of separation of fine chemicals in coal chemical industry, and relates to a method for extracting and separating phenolic compounds from coal direct conversion liquefaction products, in particular to a method for selectively extracting phenolic compounds using bio-friendly amino acids. Background Art

[0002] Coal tar, coal direct liquefaction oil, coal mild cracking product oil and other coal direct conversion liquefaction products are important coal chemical products. Among them, high condensation and high boiling point phenolic compounds are potential chemical products and are widely used in the synthesis of pesticides, dyes, medicines, etc.

[0003] Due to the weak acidity of phenolic hydroxyl groups, there are B acid-L base interactions with alkaline nitrogen-containing compounds and widespread π-π interactions between aromatic rings, which makes the 230-300℃ fraction of coal direct conversion liquid products enriched with high condensation and high boiling point phenolic compounds, alkaline nitrogen-containing compounds and naphthalene derivatives. The development of a simple, efficient and green separation method for selectively extracting phenolic compounds from the 230-300℃ fraction of coal direct conversion liquid products where O and N heteroatom compounds coexist is of great significance in the value-added utilization process of fine chemicals of coal direct conversion liquid products.

[0004] The traditional industrial method for separating phenolic compounds is the alkaline washing method, which uses a strong alkaline solution to react with the acidic phenolic compounds, so that the phenol generates salts that dissolve in water, and then is reduced to obtain phenol, thereby achieving the separation result. Although the alkaline washing method can have a high extraction efficiency, it will produce a large amount of phenol-containing wastewater, and the strong alkaline solution is also prone to cause equipment corrosion.

[0005] Liquid-liquid extraction has the advantage of mild operating conditions and is widely used in the separation process. CN108395367A utilizes the property that phenolic compounds can form a low eutectic solvent with a hydrogen bond acceptor, uses a hydrogen bond acceptor piperazine compound as an associative extractant, and forms a low eutectic solvent insoluble in the oil phase with the phenolic compound, thereby achieving effective separation of phenolic compounds from oil products. Similarly, CN 112675574A utilizes imidazole and morpholine hydroxyl functionalized ionic liquids with double hydrogen bond acceptor sites as extractants, thereby achieving separation of phenolic compounds from oil products. CN 118480370A utilizes the polarity and hydrogen bond acceptor properties of phenolic substances, and uses a halogen-containing low eutectic solvent with a low boiling point alkane solvent to separate phenolic compounds from phenol oil by dual solvent extraction.

[0006] However, when these extractants are used to extract phenolic compounds from complex coal direct conversion liquid products mixed with alkaline nitrogen-containing compounds, alkaline nitrogen-containing compounds will be entrained, and only a mixture containing phenolic compounds can be obtained, and the purity of the phenolic compounds is low. Summary of the invention

[0007] The purpose of the present invention is to address the common problems in the selective separation of phenolic compounds in complex coal direct conversion liquid product systems, and to provide a method for selectively extracting phenolic compounds in coal direct conversion liquid products based on amino acids, so as to achieve highly selective separation of phenolic compounds with little entrainment of alkaline nitrogen-containing compounds under mild conditions.

[0008] The method for selectively extracting phenolic compounds from coal direct conversion liquid products based on amino acids provided by the present invention is to use coal direct conversion liquefaction products in the 230-300° C. fraction as the processing object, construct an associative extraction system, and highly selectively separate phenolic compounds from the coal direct conversion liquefaction products, specifically comprising:

[0009] Basic amino acid is used as an associative extraction agent and dissolved in an alkane solvent to construct an associative extraction system;

[0010] The coal direct conversion liquefaction product is added to the association extraction system, after sufficient extraction, the basic amino acid and the phenolic compound are associated to form an extraction phase insoluble in the alkane solvent, and the phases are separated by standing to separate the extraction phase;

[0011] Adding a stripping agent to the extraction phase, fully extracting again, standing for phase separation, separating the basic amino acid insoluble in the stripping agent, and obtaining a stripping phase containing phenolic compounds;

[0012] The stripping agent in the stripping phase is distilled off to obtain high-purity phenolic compounds with a purity greater than 90%.

[0013] In the above method of the present invention, the raffinate phase after separating the extraction phase includes the remaining portion of the coal direct conversion liquid product from which the phenolic compounds are extracted and the alkane solvent in the associative extraction system. This portion of the raffinate phase can be further processed by conventional methods to extract and separate the basic nitrogen-containing compounds, and the alkane solvent can be separated by distillation and recycled for use in the associative extraction system to achieve the refining of aromatic hydrocarbons.

[0014] Furthermore, in the above method of the present invention, the separated basic amino acid can be continuously recycled as an associative extraction agent to construct an associative extraction system, and the stripping agent recovered by distillation can also be recycled.

[0015] By adopting the above method of the present invention, high-purity phenolic compounds with a purity greater than 90% can be separated, and the absolute entrainment rate of alkaline nitrogen-containing compounds in the phenolic compounds is less than 15%, which provides a new path for the selective separation of phenolic compounds in liquid products of direct coal conversion.

[0016] Specifically, the method of the present invention is suitable for treating the 230-300° C. fraction of coal direct conversion liquid products in which O and N heteroatom compounds coexist.

[0017] More specifically, the coal direct conversion liquid product may be any one of coal tar, coal direct liquefaction oil, coal mild cracking product oil, and the like.

[0018] In the present invention, the basic amino acid includes but is not limited to any one of lysine, arginine, histidine, citrulline or ornithine.

[0019] In the present invention, the alkane solvent is preferably a low-boiling alkane with a carbon chain length of C6 to C8, including but not limited to any one of n-hexane, cyclohexane, n-octane, n-heptane and the like.

[0020] Furthermore, the molar ratio of the basic amino acid to the phenolic compound in the treatment object in the present invention is preferably 0.5 to 4:1, so as to ensure that a better extraction effect is achieved by using less associated extractant.

[0021] Furthermore, the amount of the alkane solvent used in the present invention is preferably 1 to 5 times the mass of the treatment object.

[0022] Furthermore, the extraction process is preferably carried out at a temperature of 20-50°C, and a more preferred extraction temperature is 25°C.

[0023] Furthermore, the extraction time is preferably 30 to 180 minutes.

[0024] In the present invention, the stripping agent is selected from a medium polar solvent having a dielectric constant greater than that of the alkane solvent, preferably ether, ethyl acetate or carbon disulfide.

[0025] More specifically, the amount of the stripping agent used is preferably 1 to 3 times the mass of the extraction phase.

[0026] Furthermore, the re-extraction process of the stripping agent is preferably carried out at a temperature of 20-50°C, and a more preferred extraction temperature is 25°C.

[0027] Furthermore, the re-extraction time of the stripping agent is preferably 10 to 30 minutes.

[0028] Furthermore, the present invention specifically distills out the stripping agent in the stripping phase for recycling under the conditions of distillation temperature of 90-100° C. and pressure of 100-500 mbar.

[0029] Furthermore, in the present invention, the phenolic compound after distilling out the stripping agent is dried at 100°C.

[0030] The present invention uses basic amino acids as associative extractants, constructs an associative extraction system with an alkane solvent, and adds the system to a complex coal direct conversion liquid product system. Combined with the charge shielding surface density model analysis of COSMO-RS software, it is proved that the hydrogen bond and B acid-L base synergistic energy between the basic amino acids and the phenolic compounds in the system are greater than the interaction energy between the phenolic compounds and aromatic hydrocarbons and basic nitrogen-containing compounds in the alkane solvent, thereby breaking the original associative structure of the associative extractant and realizing the separation of phenolic compounds from the complex coal direct conversion liquid product system.

[0031] On the one hand, the extraction phase formed by the association of phenolic compounds and basic amino acids is insoluble in alkane solvents and can be separated from the alkane solvent after extraction equilibrium; on the other hand, there is no interaction between the basic amino acid associated extractant and the basic nitrogen-containing compounds represented by quinoline, and the alkaline properties of the basic amino acids will also induce a certain L-base-L-base mutual repulsion, thereby achieving the high selectivity of the basic amino acid associated extractant of the present invention for the extraction of phenolic compounds in a complex coal direct conversion liquid product system.

[0032] The present invention realizes highly selective extraction of phenolic compounds with less nitrogen-containing compounds in the presence of O and N heteroatom compounds, and obtains phenolic compounds with a purity of more than 90%. The process operation is simple, the separation conditions are mild, the used extractants and stripping agents can be recycled and reused, and the production cost is low.

[0033] Different from the conventional use of organic amine solvents, ionic liquids, and halogen-containing low-melting solvents as extractants for separating phenolic compounds, the present invention experimentally screened out highly selective, green and efficient alkaline amino acid associative extractants for use in the complex system of direct coal conversion to liquid products, achieving highly selective separation of phenolic compounds, and having great application potential for developing green separation methods for phenolic substances. Implementation

[0034] The specific implementation of the present invention is further described in detail below in conjunction with the examples. The following examples are only used to more clearly illustrate the technical solution of the present invention so that those skilled in the art can well understand and utilize the present invention, but not to limit the protection scope of the present invention.

[0035] The production processes, experimental methods or detection methods involved in the embodiments of the present invention, unless otherwise specified, are all conventional methods in the prior art, and their names and / or abbreviations are all conventional names in the field, and are very clear and unambiguous in the relevant application fields. Technical personnel in the field can understand the conventional process steps based on the names and apply the corresponding equipment, and implement them according to conventional conditions or the conditions recommended by the manufacturer.

[0036] The various instruments, equipment, raw materials or reagents used in the embodiments of the present invention are not particularly limited in terms of their sources, and are all conventional products that can be purchased through regular commercial channels, or can be prepared according to conventional methods well known to those skilled in the art.

[0037] The present invention utilizes bio-friendly amino acids to selectively extract phenolic compounds in coal direct conversion liquid products. The specific separation object is a real oil product or model oil in the 230-300°C fraction of coal direct conversion liquid products containing both O and N heteroatom compounds. The model oil is prepared with naphthol, quinoline and methylnaphthalene as raw materials in a molar ratio of 2:1:4.

[0038] S1: Add an alkane solvent to a real oil product or model oil according to the mass ratio, add a basic amino acid as an associative extractant according to the molar amount of the phenolic compound, place in a stirrable container, stir at room temperature, and after a period of time to reach extraction equilibrium, let stand for phase separation, and separate the phases by pouring or sucking to obtain an extraction phase and a raffinate phase.

[0039] S2: Take the above extraction phase, add the stripping agent, stir at room temperature, and after reaching the stripping equilibrium, centrifuge, separate the phases by pouring or pipetting to obtain the alkaline amino acid associated extractant and the stripping phase containing phenolic compounds.

[0040] S3: After drying the alkaline amino acid complex extractant, continue to recycle it.

[0041] S4: The stripping phase is subjected to atmospheric distillation to obtain phenolic compounds with a purity greater than 90%. The stripping agent regenerated by distillation can be recycled.

[0042] Among them, the basic amino acid used as the associated extractant is preferably selected from common basic basic amino acids such as lysine, arginine, histidine, citrulline or ornithine, and the extraction effects of the neutral amino acid proline and the acidic amino acid glutamic acid are compared.

[0043] The alkane solvent is preferably a low-boiling alkane with a carbon chain length of C6 to C8, such as n-hexane, cyclohexane, n-octane, and n-heptane.

[0044] Wherein, the stripping agent is preferably selected from ether, ethyl acetate or carbon disulfide.

[0045] For the raffinate phase after the extraction phase is separated, the basic nitrogen-containing compounds therein can be separated by conventional separation methods, and then the light phase of the alkane solvent can be separated by distillation and recycled to finally obtain neutral condensed aromatics. The focus of the present invention is to extract phenolic compounds from the extraction phase with high selectivity, and the subsequent separation process of the raffinate phase will not be described in detail. Example

[0046] Example 1

[0047] Weigh 25 g of model oil and place it in a conical flask with magnetic stirring. Add 75 g of n-hexane and 7.1 g of lysine to form an associative extraction system. Stir at 25 °C for 60 min and let stand for phase separation. The lower layer is the extraction phase formed by the association of naphthol and lysine, and the upper layer is the raffinate phase containing quinoline, methylnaphthalene and n-hexane.

[0048] The upper raffinate phase was taken out and weighed, and the mass concentrations of naphthol and quinoline therein were detected by gas chromatography. The concentrations were calculated by subtraction method, and the naphthol extraction rate of the extraction phase was 96.1%, and the quinoline entrainment rate was 14.5%.

[0049] Add 30 g of stripping agent ether to the remaining extraction phase, stir at 25° C. for 20 min, and centrifuge to obtain a stripping phase containing naphthol and solid lysine.

[0050] The solid lysine was dried at 50°C for 30 min to remove a small amount of entrained organic matter, and 6.8 g of lysine was obtained, which was further recycled as an extractant.

[0051] The stripping phase was evaporated under reduced pressure, and the ether was recovered and recycled as a stripping agent. The residue was dried to obtain 7.22 g of naphthol solid with a purity of 93.5%.

[0052] Example 2

[0053] Weigh 25 g of model oil and place it in a conical flask with magnetic stirring. Add 50 g of n-heptane and 5.2 g of arginine to form an associative extraction system. Stir at 35 °C for 60 min and let stand for phase separation. The lower layer is the extraction phase formed by the association of naphthol and arginine, and the upper layer is the raffinate phase containing quinoline, methylnaphthalene and n-heptane.

[0054] The upper raffinate phase was taken out and weighed, and the mass concentrations of naphthol and quinoline therein were detected by gas chromatography. The concentrations were calculated by subtraction method, and the naphthol extraction rate of the extraction phase was 91.5%, and the quinoline entrainment rate was 12.7%.

[0055] Add 15 g of stripping agent ether to the remaining extraction phase, stir at 25° C. for 20 min, and centrifuge to obtain a stripping phase containing naphthol and solid arginine.

[0056] The solid arginine was dried at 50°C for 30 minutes to remove a small amount of entrained organic matter, and 5.9 g of arginine was obtained, which was further recycled as an extractant.

[0057] The stripping phase was evaporated under reduced pressure, and the ether was recovered and recycled as a stripping agent. The residue was dried to obtain 6.84 g of naphthol solid with a purity of 94.0%.

[0058] Example 3

[0059] Weigh 25 g of model oil and place it in a conical flask with magnetic stirring. Add 100 g of n-octane and 3.9 g of histidine to form an associative extraction system. Stir at 45 °C for 90 min and let stand for phase separation. The lower layer is the extraction phase formed by the association of naphthol and histidine, and the upper layer is the raffinate phase containing quinoline, methylnaphthalene and n-octane.

[0060] The upper raffinate phase was taken out and weighed, and the mass concentrations of naphthol and quinoline therein were detected by gas chromatography. The naphthol extraction rate of the extraction phase was 86.5%, and the quinoline entrainment rate was 10.4% by difference subtraction method.

[0061] 45 g of ethyl acetate as a stripping agent was added to the remaining extraction phase, stirred at 25° C. for 20 min, and centrifuged to obtain a stripping phase containing naphthol and solid histidine.

[0062] The solid histidine was dried at 50°C for 30 min to remove a small amount of entrained organic matter, and 3.5 g of histidine was obtained, which was further recycled as an extractant.

[0063] The stripping phase was evaporated under reduced pressure, and ethyl acetate was recovered and recycled as a stripping agent. The residue was dried to obtain 6.42 g of naphthol solid with a purity of 94.8%.

[0064] Example 4

[0065] Weigh 25 g of model oil and place it in a conical flask with magnetic stirring. Add 125 g of cyclohexane and 9.6 g of ornithine to form an associative extraction system. Stir at 45 °C for 90 min and let stand for phase separation. The lower layer is the extraction phase formed by the association of naphthol and ornithine, and the upper layer is the raffinate phase containing quinoline, methylnaphthalene and cyclohexane.

[0066] The upper raffinate phase was taken out and weighed, and the mass concentrations of naphthol and quinoline therein were detected by gas chromatography. The concentrations were calculated by subtraction method, and the naphthol extraction rate of the extraction phase was 88.1%, and the quinoline entrainment rate was 14.8%.

[0067] Add 50 g of carbon disulfide, a stripping agent, to the remaining extraction phase, stir at 25° C. for 20 min, and centrifuge to obtain a stripping phase containing naphthol and solid ornithine.

[0068] The solid ornithine was dried at 50°C for 30 minutes to remove a small amount of entrained organic matter, and 9.2 g of ornithine was obtained, which was further recycled as an extractant.

[0069] The stripping phase was evaporated under reduced pressure, and carbon disulfide was recovered and recycled as a stripping agent. The residue was dried to obtain 6.67 g of naphthol solid with a purity of 92.8%.

[0070] Example 5

[0071] Weigh 25 g of model oil and place it in a conical flask with magnetic stirring. Add 75 g of n-heptane and 14.2 g of lysine to form an associative extraction system. Stir at 25 °C for 60 min and let stand for phase separation. The lower layer is the extraction phase formed by the association of naphthol and lysine, and the upper layer is the raffinate phase containing quinoline, methylnaphthalene and n-heptane.

[0072] The upper raffinate phase was taken out and weighed, and the mass concentrations of naphthol and quinoline therein were detected by gas chromatography. The concentrations were calculated by subtraction method, and the naphthol extraction rate of the extraction phase was 99.4%, and the quinoline entrainment rate was 10.6%.

[0073] 42 g of ethyl acetate as a stripping agent was added to the remaining extraction phase, and the mixture was stirred at 25° C. for 20 min and centrifuged to obtain a stripping phase containing naphthol and solid lysine.

[0074] The solid lysine was dried at 50°C for 30 min to remove a small amount of entrained organic matter, and 13.9 g of lysine was obtained, which was further recycled as an extractant.

[0075] The stripping phase was evaporated under reduced pressure, and ethyl acetate was recovered and recycled as a stripping agent. The residue was dried to obtain 7.33 g of naphthol solid with a purity of 95.3%.

[0076] Example 6

[0077] Weigh 25 g of model oil and place it in a conical flask with magnetic stirring. Add 75 g of n-octane and 15.6 g of arginine to form an associative extraction system. Stir at 25°C for 60 min and let stand for phase separation. The lower layer is the extraction phase formed by the association of naphthol and arginine, and the upper layer is the raffinate phase containing quinoline, methylnaphthalene and n-octane.

[0078] The upper raffinate phase was taken out and weighed, and the mass concentrations of naphthol and quinoline therein were detected by gas chromatography. The concentrations were calculated by subtraction method, and the naphthol extraction rate of the extraction phase was 97.2%, and the quinoline entrainment rate was 14.7%.

[0079] 42 g of ether as a stripping agent was added to the remaining extraction phase, and the mixture was stirred at 25° C. for 20 min and centrifuged to obtain a stripping phase containing naphthol and solid arginine.

[0080] The solid arginine was dried at 50°C for 30 minutes to remove a small amount of entrained organic matter, and 15.2 g of arginine was obtained, which was further recycled as an extractant.

[0081] The stripping phase was evaporated under reduced pressure, and the ether was recovered and recycled as a stripping agent. The residue was dried to obtain 7.31 g of naphthol solid with a purity of 93.5%.

[0082] Example 7

[0083] Weigh 25 g of model oil and place it in a conical flask with magnetic stirring. Add 75 g of cyclohexane and 15.6 g of histidine to form an associative extraction system. Stir at 25 °C for 60 min and let stand for phase separation. The lower layer is the extraction phase formed by the association of naphthol and histidine, and the upper layer is the raffinate phase containing quinoline, methylnaphthalene and cyclohexane.

[0084] The upper raffinate phase was taken out and weighed, and the mass concentrations of naphthol and quinoline therein were detected by gas chromatography. The naphthol extraction rate of the extraction phase was 98.3% and the quinoline entrainment rate was 14.9% by difference subtraction method.

[0085] 63 g of carbon disulfide as a stripping agent was added to the remaining extraction phase, stirred at 25° C. for 20 min, and centrifuged to obtain a stripping phase containing naphthol and solid histidine.

[0086] The solid histidine was dried at 50°C for 30 min to remove a small amount of entrained organic matter, and 14.9 g of histidine was obtained, which was further recycled as an extractant.

[0087] The stripping phase was evaporated under reduced pressure, and carbon disulfide was recovered and recycled as a stripping agent. The residue was dried to obtain 7.39 g of naphthol solid with a purity of 93.6%.

[0088] Comparative Example 1

[0089] Except that the associative extractant lysine in Example 1 was replaced by the neutral amino acid proline of the same mass, the other conditions were the same as those in Example 1.

[0090] Under this associative extraction system, the extraction rate of naphthol was 75.2% and the entrainment rate of quinoline was 67.6%.

[0091] Since the entrainment rate of quinoline in the extraction phase was too high and the selectivity of the associative extractant could not be demonstrated, the subsequent back-extraction operation was not performed.

[0092] Comparative Example 2

[0093] Except that the associated extractant lysine in Example 1 was replaced by the acidic amino acid glutamic acid of the same mass, the other conditions were the same as those in Example 1.

[0094] Under this associative extraction system, the extraction rate of naphthol was 78.6% and the entrainment rate of quinoline was 83.4%.

[0095] Since the entrainment rate of quinoline in the extraction phase was too high and the selectivity of the associative extractant could not be demonstrated, the subsequent back-extraction operation was not performed.

[0096] Comparative Example 3

[0097] The method of Example 1 in CN 108395367A was adopted to extract naphthol from the model oil using piperazine as an extractant.

[0098] Weigh 25 g of model oil and place it in a conical flask with magnetic stirring. Add 75 g of n-hexane and 2.1 g of piperazine (the molar ratio to naphthol is 0.5:1) to form an association extraction system. Stir in a 30°C water bath for 30 min and then let stand for 15 min. The lower layer is the extraction phase formed by the association of naphthol and piperazine, and the upper layer is the raffinate phase containing quinoline, methylnaphthalene and n-hexane.

[0099] The upper raffinate phase and the lower extraction phase were separated by vacuum filtration, and the volume of the upper raffinate phase and the concentrations of naphthol and quinoline therein were determined by GC. The results showed that the naphthol extraction rate of the extraction phase was 95.2%, and the quinoline entrainment rate was 90.6%.

[0100] Since the entrainment rate of quinoline in the extraction phase was too high and the selectivity of the extractant could not be demonstrated, the subsequent back-extraction operation was not performed.

[0101] Comparative Example 4

[0102] The method of Example 3 in CN 112675574A was adopted to extract naphthol from the model oil using 1-hydroxyethyl-3-methylimidazole nitrate ionic liquid as an extractant.

[0103] Weigh 25 g of model oil and place it in a conical flask with magnetic stirring, add 75 g of n-hexane and 5 g of 1-hydroxyethyl-3-methylimidazolium nitrate ionic liquid (mass ratio to model oil is 1:5) to form an associative extraction system, stir at room temperature for 10 to 60 min, and let stand for 30 min. The lower layer is the extraction phase formed by the ionic liquid and naphthol, and the upper layer is the raffinate phase containing quinoline, methylnaphthalene and n-hexane.

[0104] The upper raffinate phase was separated and its naphthol and quinoline concentrations were determined by GC. The extraction rate of naphthol by the ionic liquid was calculated to be 95.2%, and the entrainment rate of quinoline was 90.6%.

[0105] Since the entrainment rate of quinoline in the extraction phase was too high and the extraction selectivity of the ionic liquid could not be demonstrated, the subsequent stripping operation was not performed.

[0106] Comparative Example 5

[0107] The method of Example 1 in CN 118480370A was adopted to extract naphthol from the model oil using a polar deep eutectic solvent as an extractant.

[0108] Weigh 25 g of model oil and place it in a conical flask with magnetic stirring, add 75 g of n-hexane and 12.5 g of a polar low eutectic solvent prepared with a molar ratio of choline chloride and formamide of 1:1 (mass ratio to the model oil is 0.5:1) to form an associative extraction system, stir at 25 °C for 60 min, and let stand to separate layers, wherein the lower layer is the extraction phase of naphthol and the polar low eutectic solvent, and the upper layer is the raffinate phase containing quinoline, methylnaphthalene and n-hexane.

[0109] The upper raffinate phase and the lower extraction phase were taken out respectively, weighed, and the composition was determined by GC-MS, wherein the extraction rate of naphthol was 98.9%, and the entrainment rate of quinoline was 86.5%.

[0110] Since the entrainment rate of quinoline in the extraction phase was too high and the extraction selectivity of the polar deep eutectic solvent could not be demonstrated, the subsequent back-extraction operation was not performed.

[0111] Application Example 1

[0112] Weigh 25 g of coal tar 230-300 ° C fraction (provided by Shaanxi Coal and Chemical Industry Group Shenmu Tianyuan Chemical Co., Ltd., the phenol content was 21.5%, and the nitrogen-containing compounds were 13.9% measured by GC-MS area normalization method), put it in a conical flask with magnetic stirring, add 100 g of n-heptane and 10.8 g of lysine to form an association extraction system, stir at 45 ° C for 60 min, and stand for phase separation, wherein the lower layer is the extraction phase formed by the association of phenol and lysine, and the upper layer is the raffinate phase formed by nitrogen-containing compounds, aromatic hydrocarbons and n-heptane.

[0113] The upper raffinate phase was taken out and weighed, and the mass concentrations of phenol and nitrogen-containing compounds therein were detected by gas chromatography. The concentrations were calculated by subtraction method, and the phenol extraction rate of the extraction phase was 93.2%, and the nitrogen-containing compound entrainment rate was 14.1%.

[0114] Add 45 g of stripping agent ether to the remaining extraction phase, stir at 25° C. for 20 min, and centrifuge to obtain a stripping phase containing phenol and solid lysine.

[0115] The solid lysine was dried at 50°C for 30 min to remove a small amount of entrained organic matter, and 10.2 g of lysine was obtained for recycling.

[0116] The stripping phase was evaporated under reduced pressure, and the ether was recovered and recycled as a stripping agent. The residue was dried to obtain 5.50 g of phenol product with a purity of 91.1%.

[0117] The above embodiments of the present invention do not describe all the details in detail, nor limit the present invention to the above embodiments. Various changes, modifications, substitutions and variations made by ordinary technicians in this field without departing from the principles and purpose of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for selectively extracting phenolic compounds from coal direct conversion liquid products based on amino acids, wherein the coal direct conversion liquefaction product in the 230-300°C fraction is used as the treatment object and the following treatment is performed: The basic amino acid associative extractant is dissolved in an alkane solvent to construct an associative extraction system, the coal direct conversion liquefaction product is added for full extraction, so that the basic amino acid and the phenolic compound are associated to form an extraction phase insoluble in the alkane solvent, and the extraction phase is separated by standing for phase separation; Adding a stripping agent to the extraction phase, fully extracting again, standing for phase separation, separating the basic amino acid insoluble in the stripping agent, and obtaining a stripping phase containing phenolic compounds; The stripping agent in the stripping phase is distilled off to obtain high-purity phenolic compounds with a purity greater than 90%.

2. The method according to claim 1, characterized in that The liquid product of direct coal conversion is coal tar, coal direct liquefaction oil or coal mild cracking product oil.

3. The method according to claim 1, characterized in that The basic amino acid is any one of lysine, arginine, histidine, citrulline or ornithine.

4. The method according to claim 1, characterized in that The alkane solvent is a low boiling point alkane with a carbon chain length of C6 to C8.

5. The method according to claim 1, characterized in that The molar ratio of the basic amino acid to the phenolic compound in the treatment object is 0.5-4:

1.

6. The method according to claim 1, characterized in that The amount of the alkane solvent used is 1 to 5 times the mass of the treatment object.

7. The method according to claim 1, characterized in that The stripping agent is a medium polar solvent having a dielectric constant greater than that of the alkane solvent.

8. The method according to claim 7, characterized in that The stripping agent is ether, ethyl acetate or carbon disulfide.

9. The method according to claim 1, characterized in that The amount of the stripping agent used is 1 to 3 times the mass of the extraction phase.

10. The method according to claim 1, characterized in that The separated basic amino acid is further recycled as an associative extraction agent to construct an associative extraction system, and the stripping agent recovered by distillation is also recycled.