Method for separating phenolic substances from phenol-containing coal tar

Abstract

Provided is a method for separating phenolic substances from phenol-containing coal tar. By subjecting phenol-containing coal tar to a distillation process, various phenol oil mixtures having different phenol distributions are obtained. Subsequently, by using a suitable separation means, various phenolic products are separated from various dephenolized phenol oils of different distillation ranges, obtaining different high-purity phenolic fine products.

Description

A method for separating phenolic substances from phenolic coal tar

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese Patent Application No. 2024115160685, filed in China on October 28, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure belongs to the field of coal coking product separation and organic synthesis technology, specifically relating to a method for separating phenolic substances from phenol-containing coal tar. Background Technology

[0004] Crude phenol is a mixture of phenolic substances and a major component of coal tar, a byproduct of coal-to-coke, semi-coke, and syngas production. The presence of hydroxyl groups in phenolic substances increases the oxygen content in coal tar, leading to additional hydrogen consumption during hydrogenation and adversely affecting the catalyst due to the generated water. In addition, high-purity phenolic substances have wide applications in pesticides, pharmaceuticals, and dyes. Currently, the development of coal chemical industry in China generates large quantities of coal tar, rich in phenolic oils and compounds. Separating these phenolic substances would save resources, generate high added value, and produce significant economic benefits. At present, the main industrial phenol removal technology is the alkaline washing method. While simple and efficient, this process consumes large amounts of strong acids and alkalis, resulting in high production costs, severe equipment corrosion, and the generation of large amounts of difficult-to-treat phenol-containing wastewater. These drawbacks severely limit the industrial application of the alkaline washing method.

[0005] Besides alkaline washing for phenol removal, other methods for removing phenol from industrial phenolic oil include extractive distillation and dual-solvent extraction. Extractive distillation involves continuously adding high-boiling-point solvents, such as triacetin, sulfolane, and diethylene glycol, to the top of a distillation column. Phenolic compounds are extracted into the solvent and exit the column bottom along with the solvent, while neutral oils and pyridines, being insoluble in the solvent, are distilled off from the top. For example, Chinese patent application CN201410162519.X discloses a method for extracting phenolic compounds from direct coal liquefaction oil using extractive distillation. However, practice has shown that simple extractive distillation is not ideal, especially for removing some high-boiling-point neutral oils and pyridines, making it difficult to obtain crude phenol products that meet national standards. Solvent extraction involves adding solvents with high solubility for phenols but low solubility for neutral oils to the phenolic oil system, thereby separating the phenolic substances from the phenolic oil. Common solvents include superheated water, aqueous salt solutions, and aqueous alcohol solutions. This method is effective for removing and extracting neutral oils. However, because phenols are weakly acidic and pyridines are weakly basic, pyridines are sometimes entrained during solvent extraction of phenols, posing a challenge for further separation of pyridines. Furthermore, dual-solvent extraction requires two solvents, making the process complex and lengthy. Summary of the Invention

[0006] This disclosure aims to at least partially address one of the technical problems in the related art. To this end, embodiments of this disclosure propose a method for separating phenolic substances from phenol-containing coal tar.

[0007] This disclosure provides a method for separating phenolic substances from phenol-containing coal tar, comprising the following steps:

[0008] S1: The phenol-containing coal tar is first distilled under atmospheric pressure to remove water, and then distilled under reduced pressure to obtain light oil fraction with a distillation range of <170℃, phenol oil fraction with a distillation range of 170-230℃, tricresol phenol oil fraction with a distillation range of 231-240℃, catechol phenol oil fraction with a distillation range of 241-260℃, and resorcinol / hydroquinone phenol oil fraction with a distillation range of 261-300℃; wherein, the water and the light oil fraction with a distillation range of <170℃ are mixed, heated and stirred, and allowed to stand to separate into layers to obtain phenol-removed wastewater and phenol-containing light oil fraction with a distillation range of <170℃;

[0009] S2: The phenolic oil fraction with a distillation range of 170–230°C mentioned in step S1 is purified and separated; wherein the phenolic oil fraction with a distillation range of 170–230°C includes a phenol / o-cresol phenolic oil fraction with a distillation range of 170–195°C, a mixed cresol phenolic oil fraction with a distillation range of 196–208°C, a mixed xylenol phenolic oil fraction with a distillation range of 209–222°C, and a 3,4-xylenol / m-p-isopropylphenol phenolic oil fraction with a distillation range of 223–230°C.

[0010] S3: Alkylation separation of the 231-240℃ tricresyl phenol oil fraction mentioned in step S1;

[0011] S4: Etherify the catechol phenolic oil fraction with a distillation range of 241-260℃ mentioned in step S1.

[0012] S5: Etherify the resorcinol / hydroquinone phenolic oil fraction with a distillation range of 261-300℃ mentioned in step S1.

[0013] In some embodiments, in step S1, the heating and stirring temperature is 50–80°C, and the stirring time is 0.5–1 h.

[0014] In some embodiments, step S2 specifically includes: refining and separating the phenol / o-cresol oil fraction with a distillation range of 170–195°C, the mixed cresol oil fraction with a distillation range of 196–208°C, the mixed xylenol oil fraction with a distillation range of 209–222°C, and the 3,4-xylenol / m-isopropylphenol oil fraction with a distillation range of 223–230°C.

[0015] In some embodiments, the specific steps of step S3 include:

[0016] S31: The tricrete oil fraction with a distillation range of 231-240℃ described in step S1 is subjected to an alkylation reaction with olefins under acid catalysis. Then, liquid alkali is added to the reaction product, and the product is then subjected to vacuum distillation to obtain phenol oil containing 6-tert-butyl-3,4-dicresol, 6-tert-butyl-3-methyl-4-ethylphenol, and 2,6-di-tert-butyl-p-isopropylphenol.

[0017] S32: Add liquid alkali to the phenol-containing oil obtained in step S31, heat to 60-80℃ and stir for 0.5-1h, keep warm and let stand for 1h, separate the layers, remove the water layer, then add water to the phenol oil layer to wash, and obtain dephenolized phenol oil; add sulfuric acid to the water layer to neutralize to neutral, and add a non-water-soluble solvent for extraction, separate the layers, and recycle the wastewater obtained. The obtained solvent layer is distilled to obtain crude 3-methyl-5-ethylphenol and crude 2,3,5-trimethylphenol; then purify the crude 3-methyl-5-ethylphenol and crude 2,3,5-trimethylphenol respectively to obtain refined 3-methyl-5-ethylphenol and refined 2,3,5-trimethylphenol.

[0018] In some embodiments, in step S31, the acid includes at least one of sulfuric acid, phosphoric acid, benzenesulfonic acid, p-toluenesulfonic acid, aminosulfonic acid, strong acid resin, and solid acid, preferably sulfuric acid, p-toluenesulfonic acid, or a strong acid resin; the olefin is an olefin with 3 to 12 carbon atoms.

[0019] And / or, the non-water-soluble solvent includes at least one of benzene solvents, ester solvents, ether solvents, haloalkane solvents, haloaromatic solvents, and ketone solvents.

[0020] In some embodiments, step S4, the etherification separation includes any of the following methods:

[0021] 1) Direct etherification separation: A catalyst and alkylating agent are added to the catechol phenolic oil fraction with a distillation range of 241-260℃ in step S1 to carry out an etherification reaction. The alkylating agent in the reaction product is recovered, and the remaining reaction product is subjected to vacuum distillation to obtain high-purity catechol dimethyl ether and crude 5-methoxyindene. Subsequently, the crude 5-methoxyindene is heated and mixed with mixed tricresylene, and then hydrobromic acid is added dropwise to carry out the reaction. Bromomethane is collected. The remaining reaction solution is then cooled and the hydrobromic acid aqueous solution is separated. The obtained solvent layer is washed with water and separated into layers. The aqueous layer is a hydrobromic acid solution. The feed layer is distilled to recover tricresylene and obtain high-purity 5-indene alcohol.

[0022] 2) Extraction with alkaline solution followed by etherification separation: An alkaline solution is added to the catechol phenolic oil fraction with a distillation range of 241-260℃ in step S1 for reaction. The reaction product is washed with water and separated into layers to obtain an aqueous layer and a dephenolized phenolic oil. Then, an alkylating agent is added to the aqueous layer for reaction. After the reaction product is cooled, it is allowed to stand and separate into layers to obtain an aqueous layer and a material layer. The aqueous layer is extracted with toluene and separated into layers. The wastewater layer is recycled and treated. The toluene layer and the material layer are mixed and first distilled under normal pressure to recover toluene, and then distilled under reduced pressure to collect catechol dimethyl ether and 5-methoxyindene in sequence.

[0023] In some embodiments, in step S4 (method 1), the alkylating agent includes at least one of iodoalkane, chloroalkane, disulfide, and dicarbonate; the catalyst includes at least one of sodium methoxide, sodium ethoxide, sodium hydroxide, potassium hydroxide, pyridine, methylaminopyridine, and 1,8-diazabicyclo(5,4,0)-7-undecene.

[0024] And / or, in step S4 (method 2), the alkaline solution includes at least one of a carbonate solution, a bicarbonate solution, and a hydroxide solution.

[0025] In some embodiments, step S5, the etherification separation includes any of the following methods:

[0026] 1) Direct etherification separation: Add a catalyst and alkylating agent to the resorcinol / hydroquinone phenolic oil fraction with a distillation range of 261-300℃ in step S1 to carry out the etherification reaction, recover the alkylating agent in the reaction product, and perform vacuum distillation on the remaining reaction product to obtain dimethyl terephthalate and dimethyl terephthalate.

[0027] 2) Alkaline extraction followed by etherification separation: An alkaline solution is added to the resorcinol / hydroquinone phenolic oil fraction with a distillation range of 261–300°C in step S1 for reaction. The reaction product is washed with water and separated into layers to obtain an aqueous layer and a dephenolized phenolic oil. Then, an alkylating agent is added to the aqueous layer for reaction. After cooling, the reaction product is allowed to stand and separate into layers to obtain an aqueous layer and a material layer. The aqueous layer is extracted with toluene and separated into layers. The wastewater layer is recycled and treated. The toluene layer and the material layer are mixed and first distilled at atmospheric pressure to recover toluene, and then distilled under reduced pressure to collect the dimethyl ether product and crude dimethyl ether. Subsequently, the crude dimethyl ether is heated and mixed with mixed trimethylbenzene, and then hydrobromic acid is added dropwise for reaction to collect bromoalkanes. The remaining reaction liquid is then cooled and the hydrobromic acid aqueous solution is separated. The solvent layer is washed with water and separated into layers. The aqueous layer is a hydrobromic acid solution. The material layer is distilled to recover trimethylbenzene and obtain 3-methoxyphenol and resorcinol.

[0028] In some embodiments, in step S5 (method 1), the alkylating agent includes at least one of iodoalkane, chloroalkane, disulfide, and dicarbonate; the catalyst includes at least one of sodium methoxide, sodium ethoxide, sodium hydroxide, potassium hydroxide, pyridine, methylaminopyridine, and 1,8-diazabicyclo(5,4,0)-7-undecene.

[0029] And / or, in step S5, method 2), the alkaline solution includes at least one of a carbonate solution, a bicarbonate solution, and a hydroxide solution.

[0030] The advantages and beneficial effects of this disclosure are as follows:

[0031] (1) According to the distribution of different phenolic substances in phenolic coal tar, the present invention adopts a more refined narrow-range distillation or fractionation method to obtain a mixture of various phenolic oils with different phenolic distributions. This facilitates the separation of various phenolic products from various dephenolized phenolic oils with different distillation ranges by appropriate separation methods. Furthermore, it can maximize the separation and utilization of phenolic products and oil products, and has good industrial application value and economic value.

[0032] (2) This embodiment utilizes the characteristic that the boiling point of methyl ethers of phenolic substances is significantly lower than that of the corresponding phenols, and also significantly lower than that of the oils in the same distillation segment. Simultaneously, it utilizes the characteristic that the boiling point and melting point of hydroquinone methyl ethers are significantly lower than those of the corresponding hydroquinones. This embodiment uses a methyl etherification reaction to separate phenol, o-cresol, 2,6-xylenol, and a small amount of m-p-cresol from the phenolic oil in the mixed phenol fraction. Utilizing the significantly lower boiling and melting points of hydroquinone methyl ethers, hydroquinone is separated from the phenolic oil through a methyl etherification reaction. The methyl etherification reaction employs a traditional alkaline catalytic method, and the process does not introduce new safety or environmental problems. It utilizes a large amount of phenolic resources, reducing the need for chemical synthesis of phenol, o-cresol, 2,6-xylenol, m-p-cresol, catechol, hydroquinone, resorcinol, 5-indanol, and methylhydroquinone, thus reducing carbon emissions and providing significant social benefits.

[0033] (3) In this embodiment, the phenols in the raw materials cresol oil, xylenol oil, and tricresol oil react with olefins to generate various tert-butylated phenols, increasing the boiling point difference between the tert-butylated phenol products and the phenol oil. Then, through distillation, phenol oil, tert-butylated phenol products, or intermediates that have undergone dephenolization or partial dephenolization can be obtained. The intermediates can then be further decomposed by acid catalysis and distilled to obtain various pure phenol products and their tert-butylated derivatives. This method yields a wide variety of products, allows for adjustments in the types of products produced, and features a flexible, stable, and safe production process. The raw materials are widely available and inexpensive, resulting in excellent economic benefits.

[0034] (4) The embodiments of this disclosure are particularly effective for separating cresol or m-p-cresol oil with high 2,6-xylenol and high o-ethylphenol content, and have high economic benefits. Therefore, the embodiments of this disclosure are most effective for separating cresol mixtures obtained by refining crude phenol from pyrolysis and gasification tar with high 2,6-xylenol and o-ethylphenol content. Detailed Implementation

[0035] The embodiments of this disclosure are described in detail below. These embodiments are exemplary and intended to explain this disclosure, and should not be construed as limiting this disclosure.

[0036] In this document, when values ​​are described as ranges, it should be understood that such disclosure includes disclosure of all possible subranges within that range, as well as the specific numerical values ​​falling within that range, regardless of whether the specific numerical value or specific subrange is explicitly specified.

[0037] In this article, the words “contain” and “include” and their various variations mean that other elements or wholes may be included but not specifically described.

[0038] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that there can be three kinds of relationships. For example, A and / or B can represent three cases: A exists alone, A and B exist simultaneously, and B exists alone.

[0039] This disclosure provides a method for separating phenolic substances from phenolic coal tar, comprising steps S1 to S5.

[0040] S1, the phenol-containing coal tar is first distilled at atmospheric pressure to remove water, and then distilled under reduced pressure to obtain light oil fraction with a distillation range of <170℃, phenol oil fraction with a distillation range of 170-230℃, tricresol phenol oil fraction with a distillation range of 231-240℃, catechol phenol oil fraction with a distillation range of 241-260℃, and resorcinol / hydroquinone phenol oil fraction with a distillation range of 261-300℃; wherein, the water and the light oil fraction with a distillation range of <170℃ are mixed, heated and stirred, and allowed to stand for separation to obtain phenol removal wastewater and phenol-containing light oil fraction with a distillation range of <170℃.

[0041] S2, the phenolic oil fraction with a distillation range of 170-230℃ mentioned in step S1 is purified and separated; wherein, the phenolic oil fraction with a distillation range of 170-230℃ includes a phenol / o-cresol phenolic oil fraction with a distillation range of 170-195℃, a mixed cresol phenolic oil fraction with a distillation range of 196-208℃, a mixed xylenol phenolic oil fraction with a distillation range of 209-222℃, and a 3,4-xylenol / m-p-isopropylphenol phenolic oil fraction with a distillation range of 223-230℃.

[0042] S3, alkylation separation of the tricresyl phenol oil fraction with a distillation range of 231-240℃ mentioned in step S1.

[0043] S4, the catechol phenol oil fraction with a distillation range of 241-260℃ mentioned in step S1 is subjected to etherification separation.

[0044] S5, the resorcinol / hydroquinone phenolic oil fraction with a distillation range of 261-300℃ described in step S1 is subjected to etherification separation.

[0045] In some embodiments, in step S1, the heating and stirring temperature is 50–80°C, and the stirring time is 0.5–1 h.

[0046] In some embodiments, step S2 specifically includes: refining and separating the phenol / o-cresol oil fraction with a distillation range of 170–195°C, the mixed cresol oil fraction with a distillation range of 196–208°C, the mixed xylenol oil fraction with a distillation range of 209–222°C, and the 3,4-xylenol / m-isopropylphenol oil fraction with a distillation range of 223–230°C.

[0047] In some embodiments, step S3 includes steps S31 to S32.

[0048] S31, the tricrete oil fraction with a distillation range of 231-240℃ mentioned in step S1 is subjected to an alkylation reaction with olefins under acid catalysis, and then liquid alkali is added to the reaction product, followed by vacuum distillation to obtain phenol oil containing 6-tert-butyl-3,4-dicresol, 6-tert-butyl-3-methyl-4-ethylphenol, and 2,6-di-tert-butyl-p-isopropylphenol.

[0049] S32: Add liquid alkali to the phenol-containing oil obtained in step S31, heat to 60-80℃ and stir for 0.5-1h, keep warm and let stand for 1h, separate the layers, remove the water layer, then add water to the phenol oil layer to wash, and obtain dephenolized phenol oil; add sulfuric acid to the water layer to neutralize to neutral, and add a non-water-soluble solvent for extraction, separate the layers, and recycle the wastewater obtained. The obtained solvent layer is distilled to obtain crude 3-methyl-5-ethylphenol and crude 2,3,5-trimethylphenol; then purify the crude 3-methyl-5-ethylphenol and crude 2,3,5-trimethylphenol respectively to obtain refined 3-methyl-5-ethylphenol and refined 2,3,5-trimethylphenol.

[0050] In some embodiments, in step S31, the acid includes at least one selected from sulfuric acid, phosphoric acid, benzenesulfonic acid, p-toluenesulfonic acid, aminosulfonic acid, strong acid resin, and solid acid, preferably sulfuric acid, p-toluenesulfonic acid, or a strong acid resin; the olefin is an olefin with C3 to C12 carbon atoms (e.g., propylene, butene, pentene, hexene, heptenene, octene, nonene, decene, undecene, dodecene, etc., preferably isobutylene);

[0051] And / or, the non-water-soluble solvent includes at least one of benzene solvents, ester solvents, ether solvents, haloalkane solvents, haloaromatic solvents, and ketone solvents.

[0052] In some embodiments, step S4, the etherification separation includes any of the following methods:

[0053] 1) Direct etherification separation: A catalyst and alkylating agent are added to the catechol phenolic oil fraction with a distillation range of 241-260℃ in step S1 to carry out an etherification reaction. The alkylating agent in the reaction product is recovered, and the remaining reaction product is subjected to vacuum distillation to obtain high-purity catechol dimethyl ether and crude 5-methoxyindene. Subsequently, the crude 5-methoxyindene is heated and mixed with mixed tricresylene, and then hydrobromic acid is added dropwise to carry out the reaction. Bromomethane is collected. The remaining reaction solution is then cooled and the hydrobromic acid aqueous solution is separated. The obtained solvent layer is washed with water and separated into layers. The aqueous layer is a hydrobromic acid solution. The feed layer is distilled to recover tricresylene and obtain high-purity 5-indene alcohol.

[0054] 2) Extraction with alkaline solution followed by etherification separation: An alkaline solution is added to the catechol phenolic oil fraction with a distillation range of 241-260℃ in step S1 for reaction. The reaction product is washed with water and separated into layers to obtain an aqueous layer and a dephenolized phenolic oil. Then, an alkylating agent is added to the aqueous layer for reaction. After the reaction product is cooled, it is allowed to stand and separate into layers to obtain an aqueous layer and a material layer. The aqueous layer is extracted with toluene and separated into layers. The wastewater layer is recycled and treated. The toluene layer and the material layer are mixed and first distilled under normal pressure to recover toluene, and then distilled under reduced pressure to collect catechol dimethyl ether and 5-methoxyindene in sequence.

[0055] In some embodiments, in step S4 (method 1), the alkylating agent includes at least one of iodoalkane, chloroalkane, disulfide (e.g., dimethyl sulfate), and dicarbonate (e.g., dimethyl carbonate); the catalyst includes at least one of sodium methoxide, sodium ethoxide, sodium hydroxide, potassium hydroxide, pyridines, methylaminopyridines, and 1,8-diazabicyclo(5,4,0)-7-undecene.

[0056] And / or, in step S4 (method 2), the alkaline solution includes at least one of a carbonate solution, a bicarbonate solution, and a hydroxide solution.

[0057] In some embodiments, step S5, the etherification separation includes any of the following methods:

[0058] 1) Direct etherification separation: Add a catalyst and alkylating agent to the resorcinol / hydroquinone phenolic oil fraction with a distillation range of 261-300℃ in step S1 to carry out the etherification reaction, recover the alkylating agent in the reaction product, and perform vacuum distillation on the remaining reaction product to obtain dimethyl terephthalate and dimethyl terephthalate.

[0059] 2) Alkaline extraction followed by etherification separation: An alkaline solution is added to the resorcinol / hydroquinone phenolic oil fraction with a distillation range of 261–300°C in step S1 for reaction. The reaction product is washed with water and separated into layers to obtain an aqueous layer and a dephenolized phenolic oil. Then, an alkylating agent is added to the aqueous layer for reaction. After cooling, the reaction product is allowed to stand and separate into layers to obtain an aqueous layer and a material layer. The aqueous layer is extracted with toluene and separated into layers. The wastewater layer is recycled and treated. The toluene layer and the material layer are mixed and first distilled at atmospheric pressure to recover toluene, and then distilled under reduced pressure to collect the dimethyl ether product and crude dimethyl ether. Subsequently, the crude dimethyl ether is heated and mixed with mixed trimethylbenzene, and then hydrobromic acid is added dropwise for reaction to collect bromoalkanes. The remaining reaction liquid is then cooled and the hydrobromic acid aqueous solution is separated. The solvent layer is washed with water and separated into layers. The aqueous layer is a hydrobromic acid solution. The material layer is distilled to recover trimethylbenzene and obtain 3-methoxyphenol and resorcinol.

[0060] In some embodiments, in step S5 (method 1), the alkylating agent includes at least one of iodoalkane, chloroalkane, disulfide (e.g., dimethyl sulfate), and dicarbonate (e.g., dimethyl carbonate); the catalyst includes at least one of sodium methoxide, sodium ethoxide, sodium hydroxide, potassium hydroxide, pyridines, methylaminopyridines, and 1,8-diazabicyclo(5,4,0)-7-undecene.

[0061] And / or, in step S5, method 2), the alkaline solution includes at least one of a carbonate solution, a bicarbonate solution, and a hydroxide solution.

[0062] This embodiment of the invention obtains various pure hydroquinones, hydroquinone monoalkyl ethers, etc., by removing the alkyl group from the phenylalkyl ether in a trimethylbenzene solution with an aqueous hydrobromic acid solution; and produces bromoalkanes as byproducts, which can be reused as etherification reagents for various hydroquinones.

[0063] It should be noted that the phenol-free oil obtained in the above steps can be further separated and recovered into high-value materials based on composition analysis, and can also be hydrogenated to produce gasoline, diesel, etc.

[0064] It should also be noted that the various high-quality products obtained in the embodiments of this disclosure refer to products with a purity of 99% or higher.

[0065] The technical solution of this disclosure will be further described in detail below with reference to specific embodiments. Unless otherwise stated, all raw materials used in the embodiments are conventional commercially available products, or can be prepared by known methods; and the experimental methods in the embodiments that do not specify specific conditions are conventional methods and conditions well known in the art.

[0066] Example 1

[0067] A method for separating phenolic substances from phenolic coal tar includes the following steps:

[0068] S1. 800,000 parts of phenol-containing coal tar from coal pyrolysis of an energy company in Xinjiang were added to the bottom of a distillation column. First, 1,381 parts of water were removed by atmospheric distillation (200 mmHg), and then 10,805 parts of light oil with a distillation range of <170℃, 110,301 parts of phenol oil with a distillation range of 170–230℃, 16,445 parts of tricresol phenol oil with a distillation range of 231–240℃, 37,724 parts of catechol phenol oil with a distillation range of 241–260℃, and 97,486 parts of resorcinol / hydroquinone phenol oil with a distillation range of 261–300℃.

[0069] Then, the above 1381 parts of water and 10805 parts of light oil fraction with a distillation range of <170℃ were added to the reactor, heated to 60℃ and stirred for 1 hour. The phenol in the water dissolved in the light oil. After standing and separating, 1299 parts of wastewater with preliminary phenol removal and 10884 parts of light oil fraction with a distillation range of <170℃ containing phenol were obtained. The wastewater was sent to the wastewater treatment section.

[0070] S2, separation of phenolic oil fraction with a distillation range of 170–230℃:

[0071] The phenol oil fraction with a distillation range of 170–230℃ includes a phenol / o-cresol phenol oil fraction with a distillation range of 170–195℃, a mixed cresol phenol oil fraction with a distillation range of 196–208℃, a mixed xylenol phenol oil fraction with a distillation range of 209–222℃, and a 3,4-xylenol / m-p-isopropylphenol phenol oil fraction with a distillation range of 223–230℃.

[0072] 1) Separation of phenol / o-cresin oil fractions with a distillation range of 170–195℃:

[0073] Of the 110,301 phenol oil fractions with a distillation range of 170–230℃, 26,964.4 fractions were phenol / o-cresol phenol oil fractions with a distillation range of 170–195℃. Sampling analysis showed that the phenol content was 50.8%, with phenol comprising 41.75%, o-cresol 45.61%, 2,6-xylenol 8.53%, m- and p-cresol 3.86% (m-cresol 2.12%, p-cresol 1.74%), and other components 0.25%.

[0074] Take 13482 portions of the phenol / o-cresol oil fraction with a distillation range of 170–195℃ from step S1 (containing 2859.4 portions of phenol, 3123.8 portions of o-cresol, 584.2 portions of 2,6-xylenol, 264.4 portions of m- and p-cresol <145.2 portions of m-cresol and 119.2 portions of p-cresol>, 17.1 portions of other phenols, and 31 portions of aniline) and add it to the reaction vessel. Start stirring, add 98 portions of 50% sulfuric acid dropwise over 10 minutes, stir for 30 minutes, let stand for 30 minutes, and separate the layers. The resulting 150.8 portions of acidic aqueous layer (containing aniline hydrogen sulfate, pyridine, and its homologues sulfate) are collected in multiple batches and used for the recovery of aniline and pyridine and their homologues. The resulting oil layer is washed with 50 portions of water for 30 minutes, let stand for 1 hour, and the aqueous layer of 50.1 portions is separated. A portion (used to prepare the next batch of 50% sulfuric acid) was used to obtain a phenolic oil layer after the removal of alkaline substances. Then, 12,000 parts of a 30% sodium hydroxide aqueous solution were added dropwise to the phenolic oil layer after the removal of alkaline substances. Stirring was started, and the temperature was raised to 60°C and stirred for 1 hour. After standing for 1 hour, the layers separated, yielding 18,845.9 parts of aqueous solution and separating out 6,578.4 parts of dephenolized phenolic oil. Then, 5,600 parts of dimethyl sulfate were added dropwise to the separated aqueous solution, controlling the adding temperature to not exceed 60°C and the adding time to approximately 3 hours. After the addition was complete, the reaction was maintained at a gentle boiling temperature for 8 hours. Sampling and analysis showed that the reaction product contained 0.09% o-cresol. The reaction product was then cooled to 80°C and allowed to stand for separation. The lower water layer was removed, and the water layer was sent to a wastewater treatment plant. 100 parts of water were added to the material layer, and... Add 15 parts of sulfuric acid dropwise under stirring, wash for 1 hour to remove impurities, separate the layers, wash the layer with 100 parts of water once, separate the water completely, add the obtained layer to a distillation vessel (theoretical plate 250, add 100 parts of high-boiling-point solvent to the reboiler) for vacuum distillation (pressure -0.085MPa, reflux ratio 20-25:1), reflux for 2 hours every 6 hours of distillation, collect the following fractions: 42.6 parts of the fore fraction (containing 18.7 parts of anisole), 3221.8 parts of 99.85% anisole (containing 3217.0 parts of anisole, 4.5 parts of o-methyl anisole, and 0.3 parts of other fractions), 36.5 parts of the first middle fraction (containing 12.3 parts of anisole, 24.1 parts of o-methyl anisole, and 0.4 parts of other fractions), and 3409 parts of 99.83% o-methyl anisole. 1 part (containing 2.5 parts of anisole, 3403.2 parts of o-methyl anisole, 2.2 parts of m-p-methyl anisole, and 1.2 parts of other components), 91.7 parts of the second intermediate fraction (containing 58.3 parts of o-methyl anisole, 33.2 parts of m-p-methyl anisole, and 0.2 parts of other components), 321.9 parts of 80.8% m-p-methyl anisole (containing 0.1 parts of o-methyl anisole, 260.1 parts of m-p-methyl anisole, 61.5 parts of 2,6-dimethyl anisole, and 0.2 parts of other components), 562 parts of 99.68% 2,6-dimethyl anisole (containing 0.7 parts of m-p-methyl anisole, 560.2 parts of 2,6-dimethyl anisole, and 1.1 parts of other components), and 34.9 parts of the fraction after rectification (containing 22 parts of 2,6-dimethyl anisole).(3 parts, 4.3 parts unreacted phenol, 8.3 parts other components);

[0075] The first and second intermediate fractions are incorporated into the distillation product of the next batch of ethers; 99.85% anisole, 99.83% o-methyl anisole, and 99.68% 2,6-dimethyl anisole are sold directly as products; 80.8% m- and p-methyl anisole are used as raw materials to separate and obtain 99% m-methyl anisole, 99% p-methyl anisole, and 99% 2,6-dimethyl anisole. m- and p-methyl anisole are very important chemical raw materials, widely used in pharmaceuticals, fragrances, and organic synthesis intermediates.

[0076] 2) Alkylation separation of mixed cresol and phenolic oil fractions with a distillation range of 196–208℃:

[0077] 20,000 portions of phenolic oil fraction with a distillation range of 170–230°C obtained from step S1 distillation were added to a distillation vessel, and 5,230 portions of mixed cresol phenolic oil with a distillation range of 196–208°C were obtained by distillation. The phenolic product content in the phenolic oil was 48.7%, and the phenolic composition was as follows: o-cresol 22.91%, 2,6-xylenol 15.67%, m-cresol 23%, p-cresol 15.33%, o-ethylphenol 6.08%, 2,4-xylenol 9.75%, and 2,5-xylenol 6.92%.

[0078] Add 5230 parts of the above-mentioned mixed cresol oil (containing 583.5 parts of o-cresol, 399.1 parts of 2,6-xylenol, 585.8 parts of m-cresol, 390.4 parts of p-cresol, 154.8 parts of o-ethylphenol, 248.3 parts of 2,4-xylenol, and 176.2 parts of 2,5-xylenol) with a distillation range of 196-208℃ to the reactor, along with 75 parts of sulfuric acid. Heat to 90℃ with stirring, then introduce 2080 parts of isobutylene for 6 hours. After the isobutylene is introduced, maintain the reaction temperature for 2 hours. Then add 202 parts of 31% liquid alkali to neutralize to pH=8. Separate the aqueous layer and add the remaining layer to a high-efficiency distillation column (reflux ratio of 18-23:1). Distillation yields 109.5 parts of diisobutylene and 705 parts of sulfuric acid. Two parts of 99.3% 6-tert-butyl-2-cresol, 472.5 parts of 99.1% 2-tert-butyl-4-cresol, and 1854.2 parts of mixed tert-butylphenol (containing 754.2 parts of 6-tert-butyl-3-cresol, 582.2 parts of 4-tert-butyl-2,6-dimethylphenol, 360.6 parts of 6-tert-butyl-2,4-dimethylphenol, and 154.8 parts of 6-tert-butyl-2-ethylphenol), and 895.3 parts of residue in the autoclave (containing 256 parts of 4-tert-butyl-2,5-dimethylphenol, 237.6 parts of 4,6-di-tert-butyl-2-cresol, 160 parts of 2,6-di-tert-butyl-4-cresol, 181.3 parts of 4,6-di-tert-butyl-3-cresol, and 52.7 parts of 4,6-di-tert-butyl-2-ethylphenol).

[0079] Add 148 parts of strong acid resin to the above 1854.2 parts of mixed tert-butylphenol (containing 754.2 parts of 6-tert-butyl-3-cresol, 582.2 parts of 4-tert-butyl-2,6-dimethylphenol, 360.6 parts of 6-tert-butyl-2,4-dimethylphenol, and 154.8 parts of 6-tert-butyl-2-ethylphenol), start stirring, heat to 110°C, and then introduce 471 parts of isobutylene for 4 hours. Maintain the reaction at 110°C for another hour, and then take samples. Analysis showed that the product was qualified when the 6-tert-butyl-3-cresol content was 0.13%. After filtration, the filter cake was reused, and the filtrate was subjected to vacuum distillation to obtain 54 parts of the first fraction, 918.7 parts of other fractions (containing 568.2 parts of 4-tert-butyl-2,6-dimethylphenol and 350.5 parts of 4-tert-butyl-2,4-dimethylphenol), and 1219 parts of residue (containing 203.5 parts of 4,6-di-tert-butyl-2-ethylphenol and 1011.7 parts of 4,6-di-tert-butyl-3-cresol).

[0080] The 1219 parts of the reactor residue, along with the aforementioned 895.3 parts of reactor residue (containing 256 parts of 4-tert-butyl-2,5-dimethylphenol, 237.6 parts of 4,6-di-tert-butyl-2-cresol, 160 parts of 2,6-di-tert-butyl-4-cresol, 181.3 parts of 4,6-di-tert-butyl-3-cresol, and 52.7 parts of 4,6-di-tert-butyl-2-ethylphenol), were added to a high-efficiency distillation column and distilled at -0.095 MPa to obtain 624 parts of a mixture of 2,6-di-tert-butyl-4-cresol, 4-tert-butyl-2,5-dimethylphenol, and 4,6-di-tert-butyl-2-cresol (containing 227.2 parts of 4,6-di-tert-butyl-2-cresol, 245.8 parts of 4-tert-butyl-2,5-dimethylphenol, and 2... The distillate consisted of 151 parts of 4,6-di-tert-butyl-4-cresol, 41.5 parts of the first intermediate fraction (containing 10.7 parts of 4,6-di-tert-butyl-2-cresol, 8.9 parts of 2,6-di-tert-butyl-4-cresol, 8.9 parts of 4-tert-butyl-2,5-dicresol, and 12.9 parts of 4,6-di-tert-butyl-2-ethylphenol), 225.9 parts of 99.2% 4,6-di-tert-butyl-2-ethylphenol, and 103.4 parts of the second intermediate fraction (containing 86.1 parts of 4,6-di-tert-butyl-3-cresol and 17.3 parts of 4,6-di-tert-butyl-2-ethylphenol), and 1096.2 parts of residue (4,6-di-tert-butyl-3-cresol). The first and second intermediate fractions were reused in the rectification of the next batch of residue.

[0081] 12.7 parts of concentrated sulfuric acid were added to the above 624 parts of a mixture of 2,6-di-tert-butyl-4-cresol, 4-tert-butyl-2,5-dicresol, and 4,6-di-tert-butyl-2-cresol. The mixture was stirred and heated to 200°C for 3 hours. The gas phase analysis showed that 4-tert-butyl-2,5-dicresol was 0.08%. After cooling the reaction product, 9.1 parts of 31% liquid alkali were added to neutralize it to pH=7.5. The aqueous layer was separated, and the resulting material layer was added to a distillation column for distillation to obtain 109.5 parts of 99.7% o-cresol, 70.3 parts of 99.8% p-cresol, and 165.8 parts of 99.5% 2,5-dicresol. The recovered 259.8 parts of isobutylene were reused.

[0082] The above-mentioned 225.9 parts of 99.2% 4,6-di-tert-butyl-2-ethylphenol were added to the reactor, along with 5 parts of concentrated sulfuric acid. The mixture was stirred and heated to 195°C for 3 hours. Gas phase analysis showed the 6-tert-butyl-2-ethylphenol content to be 0.22%. The reaction product was cooled, and 13.6 parts of 31% liquid alkali were added to neutralize to pH 7.5. The aqueous layer was separated, and the remaining material layer was added to a distillation column for distillation to obtain 116.6 parts of 99.5% o-ethylphenol. The recovered 104.9 parts of isobutylene were reused, leaving a residue of 10... 96.2 parts; 1096.2 parts of residue from the reactor and 18 parts of concentrated sulfuric acid were added to the reactor, and the temperature was raised to 150℃ and maintained for 2 hours. When the gas chromatography-mass spectrometry showed that the content of 6-tert-butyl-m-cresol was 40.3%, the reaction was stopped. After the reaction product was cooled slightly, it was neutralized to neutral pH with 46.5 parts of 31% liquid alkali. After standing, the water layer was separated, and the obtained material layer was distilled under reduced pressure to obtain 317.6 parts of 99.7% high-purity m-cresol and 312.3 parts of 99.3% 6-tert-butyl-3-cresol. The recovered 445.7 parts of isobutylene were reused.

[0083] The aforementioned 918.7 parts of other fractions (including 568.2 parts of 4-tert-butyl-2,6-xylenol and 350.5 parts of 4-tert-butyl-2,4-xylenol) were added to the reactor, along with 12.7 parts of concentrated sulfuric acid. The mixture was stirred and heated to 200°C for 3 hours. The gas phase analysis showed that the content of 4-tert-butyl-2,6-xylenol was 0.10%. After cooling the reaction product, 34.5 parts of 31% liquid alkali were added to neutralize it to pH=8.0. The aqueous layer was separated, and the resulting material layer was added to a 2,6-xylenol distillation column for distillation to obtain 389.9 parts of 99.8% 2,6-xylenol and 237.1 parts of 99.3% 2,4-xylenol. The recovered 243.2 parts of isobutylene were reused.

[0084] 3) Alkylation separation of mixed xylenol phenolic oil fraction with a distillation range of 209–222℃:

[0085] 20,000 portions of phenolic oil fraction with a distillation range of 170–230°C obtained from step S1 distillation were added to a distillation vessel, and 5,042 portions of mixed xylenol phenolic oil fraction with a distillation range of 209–222°C were obtained by distillation. The phenolic product content in the phenolic oil was 47.6%, and the phenolic composition was: 2,4 / 2,5-xylenol 25%, 3,5-xylenol 23%, m-p-ethylphenol 32%, 2,3-xylenol 8.1%, and 3,4-xylenol 8%.

[0086] Add 5042 parts of the above-mentioned xylenol phenolic oil fraction with a distillation range of 209-222℃ and 150 parts of concentrated sulfuric acid to the reactor. Start stirring, heat the oil bath to 80℃, and introduce 1300 parts of isobutylene for 8 hours. After the introduction is complete, maintain the reaction temperature for 2 hours. Take samples for analysis. The results show that the content of 6-tert-butyl-2,3-xylenol is 0.26%, which is qualified. Then add 400 parts of liquid alkali and 200 parts of water to the reaction product to neutralize to pH=7-8. Separate the layers. Wash the material layer once with 200 parts of water to separate the water. The material layer is first subjected to atmospheric distillation to recover 73.2 parts of diisobutylene, and then subjected to vacuum distillation to obtain 3212.5 parts of phenolic oil (containing 3, 5-Dimethylphenol, etc.), further distillation yielded 492.3 parts of 99.3% antioxidant 6-tert-butyl-2,4-dimethylphenol, 556.5 parts of a mixture of 4-tert-butyl-2,5-dimethylphenol and 6-tert-butyl-3,4-dimethylphenol, 505.7 parts of 98.3% 2,6-di-tert-butyl-p-ethylphenol, and 356.5 parts of a mixture of 4,6-di-tert-butyl-2,3-dimethylphenol and 4,6-di-tert-butyl-m-ethylphenol (of which the former accounted for 82.03%). The residue in the reactor was a total of 923 parts of a mixture of 4,6-di-tert-butyl-2,3-dimethylphenol and 4,6-di-tert-butyl-m-ethylphenol (the latter accounted for 92.40%).

[0087] Add 8.3 parts of concentrated sulfuric acid to the above 556.5 parts of the mixture of 4-tert-butyl-2,5-dimethylphenol and 6-tert-butyl-3,4-dimethylphenol, heat to 200°C and maintain for 2 hours, then cool to below 100°C, neutralize with liquid alkali to neutral pH, and then distill under reduced pressure to obtain 205.9 parts of 99.5% 2,5-dimethylphenol and 169.1 parts of 99.3% 3,4-dimethylphenol;

[0088] Add 5.3 parts of concentrated sulfuric acid to the above mixture of 356.5 parts of 4,6-di-tert-butyl-2,3-dimethylphenol and 4,6-di-tert-butyl-m-ethylphenol, heat to 200°C and maintain for 2 hours, then cool to below 100°C, neutralize with liquid alkali to neutral pH, and then distill under reduced pressure to obtain 165.8 parts of 85.3% 2,3-dimethylphenol and 415.9 parts of 93.2% m-ethylphenol;

[0089] Add 200 parts of methanol to 165.8 parts of 85.3% 2,3-xylenol and heat to dissolve. Then add 2 parts of activated carbon for decolorization. After filtration, concentrate the filtrate to recover 101 parts of methanol. Cool the remaining material to 5°C to crystallize. Filter to obtain 121.6 parts of 95.8% 2,3-xylenol. Add 70 parts of methanol to 121.6 parts of 95.8% 2,3-xylenol and heat to dissolve. Then cool to 0°C to crystallize. Filter to obtain 104.1 parts of 99.1% 2,3-xylenol.

[0090] 415.9 parts of 93.2% m-ethylphenol were dissolved by adding 200 parts of methanol and heating. The solution was then slowly cooled to -10°C and kept warm for 1 hour. After filtration, the solution was rinsed with 20 parts of cold methanol and dried to obtain 339.8 parts of 99.2% m-ethylphenol.

[0091] 3212.5 parts of phenolic oil (containing 3,5-xylenol, etc.) were stirred and 591 parts of 31% liquid alkali and 325 parts of water were added to extract 3,5-xylenol. The extraction temperature was 80℃, and the mixture was stirred for 1 hour and allowed to stand for 1 hour. The layers separated, with the lower layer being an aqueous layer (containing 3,5-xylenol, etc.). The upper layer of phenolic oil was washed once with 100 parts of water and allowed to stand to separate, yielding 2639 parts of dephenolized phenolic oil. The mother liquor and washing liquid were combined, and 229.5 parts of 98% sulfuric acid were added dropwise under stirring to neutralize to pH 6-7. Then, 1000 parts and 300 parts of methyl isobutyl ketone were added sequentially for extraction twice. The separated aqueous layer was used for wastewater treatment, and the resulting material layer was added to a distillation vessel for distillation. 1292 parts of methyl isobutyl ketone were recovered for reuse, and 534.2 parts of 99.3% 3,5-xylenol were obtained. The total extraction rate of 3,5-xylenol was 96.1%.

[0092] 4) Alkylation separation of 3,4-xylenol / m-p-isopropylphenol phenol oil distillate with a distillation range of 223–230℃:

[0093] 20,000 parts of the phenolic oil fraction with a distillation range of 170–230℃ obtained from step S1 distillation were added to a distillation vessel. Distillation yielded 5,365 parts of 3,4-xylenol / m-p-isopropylphenol phenolic oil fraction with a distillation range of 223–230℃. The phenolic product content in the phenolic oil was 44.8%, and the phenolic composition was: m-p-ethylphenol 0.6%, 3,5-xylenol 3.2%, 3,4-xylenol 41.5%, m-isopropylphenol 23.6%, p-isopropylphenol 19.3%, 2-ethyl-3-cresol 5.6%, 3-ethyl-5-cresol 3.5%, and others 2.7%.

[0094] Add 5365 parts of the above-mentioned 3,4-xylenol / m-p-isopropylphenol phenol oil fraction and 150 parts of concentrated sulfuric acid to the reactor. Start stirring, heat the oil bath to 75°C, and introduce 1500 parts of isobutylene for 10 hours. After the introduction is complete, maintain the reaction temperature for 2 hours. Take a sample for analysis. The content of 2-tert-butyl-p-isopropylphenol is 0.09%, which is qualified. Then add 400 parts of liquid alkali and 200 parts of water to the reaction product to neutralize to pH=7-8. Separate the layers. Wash the layer with 200 parts of water to remove all water. The resulting layer is first recovered under normal pressure to obtain 83.2 parts of diisobutylene, and then distilled under reduced pressure to obtain 3126.3 parts of phenol oil (containing 76.5 parts of 3,5-xylenol, 83.6 parts of 3-ethyl-5-cresol, and 19.3 parts of other phenols, etc.). Further distillation yielded 1341.9 parts of 99.64% 6-tert-butyl-3,4-dimethylphenol (containing 1337.1 parts of 6-tert-butyl-3,4-dimethylphenol and 4.8 parts of 6-tert-butyl-m-isopropylphenol), 168.5 parts of a mixture of 6-tert-butyl-3,4-dimethylphenol and 6-tert-butyl-m-isopropylphenol (containing 101.2 parts of 6-tert-butyl-3,4-dimethylphenol and 67.3 parts of 6-tert-butyl-m-isopropylphenol), 716.1 parts of 99.68% 6-tert-butyl-m-isopropylphenol (containing 713.8 parts of 6-tert-butyl-m-isopropylphenol and 2.3 parts of 6-tert-butyl-3,4-dimethylphenol), and 66.9 parts of the first transition fraction (containing 6.8 parts of 6-tert-butyl-m-isopropylphenol). 2,6-Di-tert-butyl-p-ethylphenol / 4,6-di-tert-butyl-m-ethylphenol 27.3 parts, 2,6-di-tert-butyl-p-isopropylphenol 32.8 parts), 99.66% 2,6-di-tert-butyl-p-isopropylphenol 758.7 parts (containing 756.1 parts of 2,6-di-tert-butyl-p-isopropylphenol and 2.6 parts of 4,6-di-tert-butyl-2-ethyl-3-cresol), 74.3 parts of the second transition fraction (containing 48.5 parts of 2,6-di-tert-butyl-p-isopropylphenol and 25.8 parts of 4,6-di-tert-butyl-2-ethyl-3-cresol), 99.71% 4,6-di-tert-butyl-2-ethyl-3-cresol 102.7 parts (containing 102.4 parts of 4,6-di-tert-butyl-2-ethyl-3-cresol, other 0 parts). 0.3 parts), 83.7 parts of residue (including 20.9 parts of 4,6-di-tert-butyl-2-ethyl-3-cresol and 62.8 parts of other components); of which 99.66% 2,6-di-tert-butyl-p-isopropylphenol was sold directly as an antioxidant; a mixture of 6-tert-butyl-3,4-dimethylphenol and 6-tert-butyl-m-isopropylphenol was used for re-distillation to prepare 99% 6-tert-butyl-3,4-dimethylphenol and 6-tert-butyl-m-isopropylphenol; after the first transition fraction was concentrated to a certain amount, it was used to separate m-isopropylphenol, m-ethylphenol, p-ethylphenol and antioxidant 2,6-di-tert-butyl-p-ethylphenol; after the second transition fraction was concentrated to a certain amount, it was used to separate antioxidant 2,6-di-tert-butyl-p-ethylphenol and 2-ethyl-3-cresol;

[0095] Concentrated sulfuric acid (1.5% of the weight of each phenolic substance) was added to 1341.9 parts of 99.64% 6-tert-butyl-3,4-dimethylphenol, 716.1 parts of 99.68% 6-tert-butyl-m-isopropylphenol, and 102.7 parts of 99.71% 4,6-di-tert-butyl-2-ethyl-3-methylphenol. The mixture was heated to 200°C and maintained for 2 hours, then cooled to below 100°C and neutralized with liquid alkali to neutral pH. The mixture was then subjected to vacuum distillation to obtain 862.6 parts of 99.8% 3,4-dimethylphenol, 480.4 parts of 99.78% m-isopropylphenol, and 50.9 parts of 99.81% 2-ethyl-3-methylphenol, respectively.

[0096] To the aforementioned 3126.3 parts of phenolic oil (containing 76.5 parts of 3,5-xylenol, 83.6 parts of 3-ethyl-5-cresol, and 19.3 parts of other phenols, etc.), 179 parts of 31% liquid alkali and 350 parts of water were added and stirred to extract the 3,5-xylenol, etc. The extraction temperature was 80℃, and the mixture was stirred for 1 hour, allowed to stand for 1 hour, and allowed to separate into layers. The lower layer was an aqueous layer (containing 3,5-xylenol, etc.). The upper layer of phenolic oil was washed once with 100 parts of water, allowed to stand, and allowed to separate into layers to obtain 2938.5 parts of dephenolized phenolic oil. The mother liquor and washing liquid were combined, and 70 parts of 98% sulfuric acid were added dropwise under stirring to neutralize to pH 6-7. Then, methyl isobutyl ketone was added for extraction twice (200 parts of methyl isobutyl ketone were added each time). The aqueous layer was used for wastewater treatment, and the resulting material layer was added to a distillation vessel for distillation. 395.2 parts of methyl isobutyl ketone were recovered for reuse, and 67.8 parts of 99.5% 3,5-xylenol and 68 parts of 95.2% 3-ethyl-5-cresol were also obtained.

[0097] Subsequently, 68 parts of 95.2% 3-ethyl-5-cresol and 140 parts of 95% ethanol were added to a stainless steel crystallizing vessel. The mixture was stirred and heated to 60°C to completely dissolve the material. Then, it was cooled to 25°C with circulating water for 2 hours, and then cooled to 0°C with chilled brine for 2 hours. The mixture was then held at this temperature for 2 hours, centrifuged, and dried under reduced pressure hot water at 30°C to obtain 57.5 parts of 99.6% 3-ethyl-5-cresol with a crystallization yield of 88.5%.

[0098] S3, Alkylation separation of tricresyl phenol oil fraction with a distillation range of 231–240°C:

[0099] Analysis of the tricresol phenolic oil fraction with a distillation range of 231–240℃ obtained from the distillation in step S1 showed that its phenol content was 45.58%, and the composition of phenolic substances (excluding non-phenolic substances) was as follows: 3,4-xylenol 0.87%, p-isopropylphenol 5.67%, m-isopropylphenol 6.89%, 2,3,5-tricresol 28.01%, 3-ethyl-2-cresol 0.21%, 3-methyl-5-ethylphenol 38.21%, 4-ethyl-3-cresol 15.79%, butylphenol 4.01%, and others 0.24%.

[0100] 14,000 parts of the above-mentioned tricresol phenolic oil fraction (containing 6,381.2 parts of phenolic substances) were added to the reactor, along with 150 parts of p-toluenesulfonic acid. Stirring was started, and the temperature was raised to 90°C. Isobutylene was introduced for 6 hours, followed by a 2-hour incubation period. Sampling and analysis showed that 2-tert-butylisopropylphenol content was 0.26%, which was acceptable. Then, a mixture of 142.5 parts of liquid alkali and 375 parts of water was added for neutralization. Subsequent vacuum distillation yielded a product containing 2,3-tert-butylisopropylphenol. 11892.2 parts of phenolic oil containing 5-trimethylphenol, 3-methyl-5-ethylphenol, etc.; 72.5 parts of 96.6% 6-tert-butyl-3,4-dimethylphenol; 1286 parts of 97.5% 6-tert-butyl-3-methyl-4-ethylphenol; 511.5 parts of 99.1% 2,6-di-tert-butyl-p-isopropylphenol (antioxidant); 1049 parts of residue (including 626.5 parts of 4,6-di-tert-butyl-m-isopropylphenol and 219.3 parts of tri-tert-butylphenol);

[0101] The 11892.2 parts of phenol-containing oil were added to the reactor, and 4092 parts of 31% liquid alkali were added while stirring. The temperature was raised to 60-80℃, and after adding the liquid alkali, the mixture was stirred for 1 hour, allowed to stand for 1 hour, and separated into layers. The aqueous layer was separated, and then 200 parts of water were added to the phenol oil layer for washing once, yielding 7646.5 parts of dephenolized phenol oil. Then, the aqueous layer (including wash water) was added to the reactor, stirred, and 98% sulfuric acid was added dropwise at around 40℃ to neutralize to around pH 7. While adding sulfuric acid, 4000 parts of methyl isobutyl ketone were added for extraction. After adding the material, the mixture was stirred for 1 hour, allowed to stand for 1 hour, and separated into layers. The aqueous layer was then extracted once more with 1000 parts of methyl isobutyl ketone, and separated into layers. The aqueous layer was sent to the wastewater recovery system. The solvent layers were combined and the water was separated. The solvent layer was washed once with 200 parts of water, and the separated water was reused in the next batch (washed and dephenolized phenolic oil). The solvent layer was added to a high-efficiency distillation column for atmospheric distillation to obtain 4962 parts of methyl isobutyl ketone for recycling. Then, it was subjected to vacuum distillation (reflux ratio of 20:1) to obtain 2446.0 parts of crude 3-methyl-5-ethylphenol with a content of 87.1% (including 291.1 parts of 2,3,5-trimethylphenol and 2130.5 parts of 3-methyl-5-ethylphenol) and 1670.5 parts of crude 2,3,5-trimethylphenol with a content of 85.5% (including 1428.3 parts of 2,3,5-trimethylphenol and 225.8 parts of 3-methyl-5-ethylphenol).

[0102] 2446.0 parts of crude 87.1% 3-methyl-5-ethylphenol and 6000 parts of ethanol were added to a reactor for crystallization. Stirring was started, and the mixture was heated in a water bath to 60°C to completely dissolve the material. Then, the mixture was cooled to 25°C in a cold water bath, followed by a cooling to 0°C in a brine bath for 2 hours, and held at that temperature for 1 hour. The mixture was then filtered, dried under vacuum, and air-dried to obtain 1743.3 parts of 98.1% 3-methyl-5-ethylphenol and 6662.4 parts of filtrate. Subsequently, 1743.3 parts of 98.1% 3-methyl-5-ethylphenol and 2000 parts of ethanol were added to the reactor for recrystallization. Stirring was started, and the mixture was heated in a water bath to 70°C to completely dissolve the material. Then, the mixture was cooled to 25°C in a cold water bath, followed by a cooling to 0°C in a brine bath. The sample was cooled to -10℃ for 3 hours, held at that temperature for 1 hour, filtered, dried by vacuum, and air-dried to obtain 1531.6 parts of 99.6% 3-methyl-5-ethylphenol and 2187.1 parts of filtrate (the secondary mother liquor can be used for the purification of crude 3-methyl-5-ethylphenol); of which 6662.4 parts of the primary crystallization filtrate were added to a distillation apparatus equipped with a condenser to recover 5899.6 parts of solvent for reuse, and after evaporation, 698.7 parts of material (containing 59.54% 3-methyl-5-ethylphenol and 40.03% 2,3,5-trimethylphenol) were obtained. This part of the material was added to the aforementioned alkali-washed phenolic material methyl isobutyl ketone solution for the joint distillation of crude 3-methyl-5-ethylphenol and 2,3,5-trimethylphenol.

[0103] Add 1670.5 parts of 85.5% crude 2,3,5-trimethylphenol and 3500 parts of petroleum ether at 90-120℃ to a reactor. Start stirring and heat in a water bath to 90℃ to completely dissolve the materials. Then, cool in a cold water bath to 50℃, then cool naturally to room temperature, and finally cool in an ice-water bath to 10℃. Hold at this temperature for 2 hours, filter, dry under vacuum, and air dry to obtain 1169.9 parts of 96.2% 2,3,5-trimethylphenol and 3930.2 parts of filtrate. Then, add 90.1 parts of 96.2% 2,3,5-trimethylphenol to a melt crystallizer, heat in an oil bath to 97℃ to dissolve it, then slowly cool at 0.5℃ / hr to 53℃ and hold at this temperature for 5 hours to allow the 2,3,5-trimethylphenol to fully crystallize. Then, release the uncrystallized product. The first 8.4 parts of the crystal (containing 28.6% 3-methyl-5-ethylphenol and 70.9% 2,3,5-trimethylphenol) were added to the aforementioned alkali-washed phenolic material methyl isobutyl ketone solution for distillation of crude 3-methyl-5-ethylphenol and crude 2,3,5-trimethylphenol. Then, the temperature was increased to 94°C at 0.2°C / hr and held for 2 hours to melt some of the material, collecting 78.5 parts of 2,3,5-trimethylphenol with a content of 99.1%. After cooling, it was a white solid with a single melt crystallization yield of 89.75%. The remaining material was rapidly heated and melted, yielding 3.1 parts of 2,3,5-trimethylphenol with a content of 91.29%, which was added to the next batch of crude 2,3,5-trimethylphenol for solvent crystallization.

[0104] 3930.2 parts of filtrate were added to a distillation apparatus equipped with a condenser and heated to recover 3368.3 parts of solvent for reuse. After evaporation to dryness, 498.6 parts of material were obtained (including 39.5% 3-methyl-5-ethylphenol and 60.4% 2,3,5-trimethylphenol). This part of material was added to the aforementioned alkali-washed phenolic material methyl isobutyl ketone solution and the crude products of 3-methyl-5-ethylphenol and 2,3,5-trimethylphenol were distilled together.

[0105] Two parts of concentrated sulfuric acid were added to the 72.5 parts of 96.6% 6-tert-butyl-3,4-dimethylphenol obtained above, and the temperature was raised to 185°C and maintained for 2 hours. When the content of 6-tert-butyl-3,4-dimethylphenol was detected by gas chromatography, the reaction was stopped. Then the reaction solution was cooled to less than 100°C and neutralized to neutral pH with 2.8 parts of 30% liquid alkali. After that, 45.4 parts of 99.3% 3,4-dimethylphenol were obtained by vacuum distillation, and 21 parts of isobutylene were recovered and reused.

[0106] 25 parts of concentrated sulfuric acid were added to the 1286 parts of 97.5% 6-tert-butyl-3-methyl-4-ethylphenol obtained above, and the temperature was raised to 190°C and maintained for 1.5 hours. When the content of 6-tert-butyl-3-methyl-4-ethylphenol was detected by gas chromatography, the reaction was stopped. Then the reaction solution was cooled to less than 100°C and neutralized to neutral pH with 70 parts of 30% liquid alkali. After that, 839.5 parts of 99.1% 3-methyl-4-ethylphenol were obtained by vacuum distillation, and 284 parts of isobutylene were recovered and reused.

[0107] Ten parts of concentrated sulfuric acid were added to the 1049 parts of reactor residue obtained above, and the temperature was raised to 200°C and maintained for 2 hours. When the content of tert-butylphenol was detected by gas chromatography, the reaction was stopped. Then the reaction solution was cooled to less than 100°C and neutralized to neutral pH with 28 parts of 30% liquid alkali. After that, it was distilled under reduced pressure to obtain 113.8 parts of 99.6% phenol and 394.5 parts of 99.4% p-isopropylphenol, respectively. 428 parts of isobutylene were recovered and reused.

[0108] S4, direct etherification separation of catechol phenolic oil fraction with a distillation range of 241–260℃:

[0109] 7321 parts of catechol phenolic oil fraction (containing 37.8% phenol, 78.6% catechol, and 10.3% 5-indanol) with a distillation range of 241–260°C from step S1 were added to the reactor, along with 10660 parts dimethyl carbonate and 2110 parts DBU (1,8-diazabicyclo[5.4.0]undec-7-ene). The mixture was purged with nitrogen twice, heated to 180°C, stirred, and kept at this temperature for 10 hours. Sampling and analysis showed that the reaction product contained 0.38% o-methoxyphenol. The reaction product was then cooled to room temperature and added to a distillation vessel. 7631 parts of dimethyl carbonate were recovered by atmospheric distillation for reuse. The remaining material was added to… The mixture was fed into a reactor and subjected to an excess of carbon dioxide gas for reaction. The mixture separated into layers, and the separated DBU carbonate was heated to decompose and recover the DBU catalyst for reuse. The decomposed carbon dioxide was then recovered under pressure. The remaining material after catalyst recovery was fed into a distillation column for vacuum distillation (pressure -0.098 MPa, reflux ratio 25:1, temperature 128–132 °C). When the phthalic acid content was found to be 98.5% by chromatographic analysis, phthalic acid was collected, totaling 2324.4 parts of 99.6% phthalic acid, with a distillation yield of 85.69%. Further distillation yielded 620 parts of 99.2% 5-methoxyindene, with a distillation yield of 90.2%. The residue in the reactor was dephenolized phenolic oil.

[0110] Add 620 parts of 99.2% 5-methoxyindene and 650 parts of mixed trimethylbenzene to the reaction vessel, heat to 120°C, and then add 47% hydrobromic acid dropwise to carry out the reaction. The bromomethane gas generated by the reaction is cooled to -10°C through a condenser and a second cold trap and enters the bromoalkanes storage tank (-15°C). After the reaction is complete, stop collecting bromoalkanes. A total of 1300 parts of 47% hydrobromic acid was added dropwise, and 388.1 parts of bromomethane were collected, with a yield of 98.3%. Then, after slightly cooling the reaction solution, separate the hydrobromic acid aqueous solution. Wash the solvent layer once with 50 parts of water, separate the layers, and combine the aqueous layers to obtain 959.3 parts of 28.6% hydrobromic acid solution (which can be used to recover 47% hydrobromic acid by heating and reuse). 635.7 parts of trimethylbenzene are recovered and reused in the distillation vessel of the material layer. Then, the remaining material layer is distilled to obtain 521.6 parts of 99.6% 5-indene alcohol.

[0111] S5, direct etherification separation of resorcinol / hydroquinone phenol oil fraction with a distillation range of 261–300℃:

[0112] 14,000 parts of resorcinol / hydroquinone oil fraction (31.5% phenol content, of which resorcinol is 36.92% and hydroquinone is 49.66%) with a distillation range of 261–300℃ from step S1 were added to the reactor, along with 19,650 parts of dimethyl carbonate and 5,403 parts of DBU. The mixture was purged with nitrogen twice, heated to 180℃, stirred, and kept at this temperature for 12 hours. Sampling and analysis showed that the reaction product contained 0.42% p-methoxyphenol. The reaction product was then cooled to room temperature and added to a distillation vessel. 14,070 parts of dimethyl carbonate were recovered by atmospheric distillation for reuse. The remaining material was added to the reactor, and excess carbon dioxide gas was introduced for reaction. The mixture separated into layers, and the separated DBU was... BU carbonate is heated and decomposed to obtain catalyst DBU, which is then recovered and reused. The carbon dioxide produced during decomposition is recovered and reused under pressure. The remaining material after catalyst recovery is added to a distillation vessel for vacuum distillation (pressure -0.098 MPa, reflux ratio 25-30:1, temperature 135-145℃) to obtain 2282 parts of terephthalic acid dimethyl ether with a purity of 99.4% and a yield of 82.6%. 791.8 parts of intermediate fraction are collected (containing 439.4 parts of terephthalic acid dimethyl ether and 348.8 parts of m-phthalic acid dimethyl ether). 1697.1 parts of 99.2% m-phthalic acid dimethyl ether are collected with a yield of 82.4%, and further distillation yields 628.6 parts of intermediate product (which can be used for enrichment and recovery of naphthalene ether and other substances). The residue in the distillation vessel is phenolic oil.

[0113] Example 2

[0114] This embodiment is basically the same as Embodiment 1, except that: in step S4, the separation method for the catechol phenolic oil fraction with a distillation range of 241-260℃ is: extraction with alkaline solution followed by etherification separation. Specifically: 7321 parts of the catechol phenolic oil fraction with a distillation range of 241-260℃ from step S1 (of which, the phenol content is 37.8%, catechol accounts for 78.6% of the phenol, and 5-indanol accounts for 10.3%) are added to the reactor, along with 7020 parts of 31% sodium hydroxide aqueous solution. The mixture is stirred, heated to 60℃ and kept at that temperature for 2 hours, allowed to stand for 1 hour, and separated into layers. The aqueous layer is then separated. The mixture is then washed once with 400 parts of water, separated into layers, and the water is completely separated to obtain 10152 parts of aqueous layer (mixed disodium phenolate aqueous solution) and 4556 parts of dephenolized phenolic oil.

[0115] Then, the 10152 parts of the aqueous layer were added to the reactor, and stirring was started. 3430.3 parts of dimethyl sulfate were then added dropwise, controlling the dropping temperature to not exceed 80°C, with a dropping time of approximately 3 hours. After the addition was complete, the reaction was maintained at a gentle boil for 10 hours. Sampling and analysis showed that the reaction product contained 0.15% o-methoxyphenol. The reaction product was then cooled to 80°C and allowed to stand to separate into layers. The lower aqueous layer was removed, and the aqueous layer was extracted once with 1000 parts of toluene. The layers separated again; the aqueous layer was sent to the wastewater treatment plant, and the toluene layer was mixed with the material layer and sent to the treatment plant. In the distillation kettle, 986 parts of toluene were first recovered and reused by atmospheric distillation, followed by vacuum distillation (pressure -0.098 MPa, reflux ratio 25:1, temperature 128-132℃). When the phthalic acid content was 98.5% according to chromatographic analysis, phthalic acid was collected. A total of 2364 parts of 99.3% phthalic acid were collected, with a yield of 86.8%. Distillation was continued to collect 622.4 parts of 99.5% 5-methoxyindene, with a distillation yield of 91.2%. The residue in the kettle was recovered (containing a small amount of o-methoxyphenol, etc.).

[0116] Example 3

[0117] This embodiment is basically the same as Embodiment 1, except that: in step S5, the separation method of the resorcinol / hydroquinone phenol oil fraction with a distillation range of 261-300℃ is: extraction with alkaline solution followed by etherification separation. Specifically: 14,000 parts of the resorcinol / hydroquinone phenol oil fraction with a distillation range of 261-300℃ from step S1 (of which, the phenol content is 31.5%, and the phenols are: resorcinol 36.92% and hydroquinone 49.66%) are added to the reactor, and 12,803 parts of 31% sodium hydroxide aqueous solution are added. Stirring is started, the temperature is raised to 60℃ and kept at that temperature for 2 hours, and then allowed to stand for 1 hour. The layers are separated, the water layer is removed, and then washed once with 720 parts of water. The layers are separated again, and the water is completely removed to obtain 17,895.8 parts of water layer and 9,593 parts of dephenolized phenol oil.

[0118] Then, 17895.8 parts of the aqueous layer were added to the reactor, stirring was started, and 6000 parts of dimethyl sulfate were added dropwise, controlling the dropping temperature to not exceed 60℃, with a dropping time of approximately 6 hours. After the addition was complete, the reaction was maintained at a gentle boil for 12 hours. Samples were taken for analysis, and the results showed that the reaction product contained 0.13% p-methoxyphenol. The reaction product was then cooled to 80℃ and allowed to stand to separate into layers. The lower aqueous layer was removed, and the aqueous layer was extracted once with 1000 parts of toluene. The layers separated again, and the aqueous layer was sent to the wastewater treatment plant. The toluene layer was mixed with the material layer and sent to a distillation vessel. 986 parts of toluene were recovered by atmospheric distillation and reused. Further reduced pressure distillation (pressure -0.098 MPa, reflux ratio 20–30:1, temperature 135–145 °C) yielded 2328.8 parts of 99.2% diphenyl ether, with a yield of 84.1%. 688.7 parts of the middle fraction were collected (containing 391.6 parts of diphenyl ether and 297.1 parts of m-phenyl ether). 1745.5 parts of 99.3% m-phenyl ether were collected, with a yield of 84.7%. The distillation residue was collected and used to extract naphthalene ether and tetrahydronaphthalene ether.

[0119] 1000 parts of the above-mentioned 99.3% m-phenylenediamine and 1000 parts of mixed trimethylbenzene were added to the reaction vessel, the temperature was raised to 120°C, and then 47% hydrobromic acid was added dropwise to carry out the reaction. The bromomethane gas generated by the reaction was cooled to -10°C through a condenser and a second cold trap and entered the bromoalkanes storage tank (-15°C). After the reaction was completed, the collection of bromoalkanes was stopped. A total of 3000 parts of 47% hydrobromic acid were added dropwise, and 1036.2 parts of bromomethane were collected, with a yield of 97.8%. Then, after slightly cooling the reaction solution, the hydrobromic acid aqueous solution was separated. The solvent layer was washed once with 50 parts of water, and the layers were separated. The aqueous layers were combined to obtain 2139.8 parts of a 23.0% hydrobromic acid solution (which can be used to recover 47% hydrobromic acid by heating and reuse). 986.1 parts of trimethylbenzene were recovered and reused in the distillation vessel of the material layer. Then, the remaining material layer was distilled to obtain 388.2 parts of 99.8% 3-methoxyphenol and 382.1 parts of 99.5% resorcinol.

[0120] In this disclosure, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0121] Although embodiments of the present disclosure have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present disclosure. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present disclosure.

[0122] All embodiments disclosed herein can be executed individually or in combination with other embodiments, and are all considered to be within the scope of protection claimed by this disclosure.

Claims

1. A method for separating phenolic substances from phenol-containing coal tar, characterized in that, Includes the following steps: S1: The phenol-containing coal tar is first distilled under atmospheric pressure to remove water, and then distilled under reduced pressure to obtain light oil fraction with a distillation range of <170℃, phenol oil fraction with a distillation range of 170-230℃, tricresol phenol oil fraction with a distillation range of 231-240℃, catechol phenol oil fraction with a distillation range of 241-260℃, and resorcinol / hydroquinone phenol oil fraction with a distillation range of 261-300℃; wherein, the water and the light oil fraction with a distillation range of <170℃ are mixed, heated and stirred, and allowed to stand to separate into layers to obtain phenol-removed wastewater and phenol-containing light oil fraction with a distillation range of <170℃; S2: The phenolic oil fraction with a distillation range of 170–230°C mentioned in step S1 is purified and separated; wherein the phenolic oil fraction with a distillation range of 170–230°C includes a phenol / o-cresol phenolic oil fraction with a distillation range of 170–195°C, a mixed cresol phenolic oil fraction with a distillation range of 196–208°C, a mixed xylenol phenolic oil fraction with a distillation range of 209–222°C, and a 3,4-xylenol / m-p-isopropylphenol phenolic oil fraction with a distillation range of 223–230°C. S3: Alkylation separation of the 231-240℃ tricresyl phenol oil fraction mentioned in step S1; S4: Etherify the catechol phenolic oil fraction with a distillation range of 241-260℃ mentioned in step S1. S5: Etherify the resorcinol / hydroquinone phenolic oil fraction with a distillation range of 261-300℃ mentioned in step S1.

2. The method for separating phenolic substances from phenol-containing coal tar according to claim 1, characterized in that, In step S1, the heating and stirring temperature is 50-80℃, and the stirring time is 0.5-1h.

3. The method for separating phenolic substances from phenol-containing coal tar according to claim 1 or 2, characterized in that, The specific steps of step S2 include: refining and separating the phenol / o-cresol oil fraction with a distillation range of 170-195℃, the mixed cresol oil fraction with a distillation range of 196-208℃, the mixed xylenol oil fraction with a distillation range of 209-222℃, and the 3,4-xylenol / m-isopropylphenol oil fraction with a distillation range of 223-230℃.

4. The method for separating phenolic substances from phenol-containing coal tar according to any one of claims 1 to 3, characterized in that, The specific steps of step S3 include: S31: The tricrete oil fraction with a distillation range of 231-240℃ described in step S1 is subjected to an alkylation reaction with olefins under acid catalysis. Then, liquid alkali is added to the reaction product, and the product is then subjected to vacuum distillation to obtain phenol oil containing 6-tert-butyl-3,4-dicresol, 6-tert-butyl-3-methyl-4-ethylphenol, and 2,6-di-tert-butyl-p-isopropylphenol. S32: Add liquid alkali to the phenol-containing oil obtained in step S31, heat to 60-80℃ and stir for 0.5-1h, keep warm and let stand for 1h, separate the layers, remove the water layer, then add water to the phenol oil layer to wash, and obtain dephenolized phenol oil; add sulfuric acid to the water layer to neutralize to neutral, and add a non-water-soluble solvent for extraction, separate the layers, and recycle the wastewater obtained. The obtained solvent layer is distilled to obtain crude 3-methyl-5-ethylphenol and crude 2,3,5-trimethylphenol; then purify the crude 3-methyl-5-ethylphenol and crude 2,3,5-trimethylphenol respectively to obtain refined 3-methyl-5-ethylphenol and refined 2,3,5-trimethylphenol.

5. The method for separating phenolic substances from phenolic coal tar according to claim 4, characterized in that, In step S31, the acid includes at least one of sulfuric acid, phosphoric acid, benzenesulfonic acid, p-toluenesulfonic acid, aminosulfonic acid, strong acid resin, and solid acid; the olefin is an olefin with 3 to 12 carbon atoms. And / or, the non-water-soluble solvent includes at least one of benzene solvents, ester solvents, ether solvents, haloalkane solvents, haloaromatic solvents, and ketone solvents.

6. The method for separating phenolic substances from phenol-containing coal tar according to any one of claims 1 to 5, characterized in that, In step S4, the etherification separation includes any of the following methods: 1) Direct etherification separation: A catalyst and alkylating agent are added to the catechol phenolic oil fraction with a distillation range of 241-260℃ in step S1 to carry out an etherification reaction. The alkylating agent in the reaction product is recovered, and the remaining reaction product is subjected to vacuum distillation to obtain high-purity catechol dimethyl ether and crude 5-methoxyindene. Subsequently, the crude 5-methoxyindene is heated and mixed with mixed tricresylene, and then hydrobromic acid is added dropwise to carry out the reaction. Bromomethane is collected. The remaining reaction solution is then cooled and the hydrobromic acid aqueous solution is separated. The obtained solvent layer is washed with water and separated into layers. The aqueous layer is a hydrobromic acid solution. The feed layer is distilled to recover tricresylene and obtain high-purity 5-indene alcohol. 2) Extraction with alkaline solution followed by etherification separation: An alkaline solution is added to the catechol phenolic oil fraction with a distillation range of 241-260℃ in step S1 for reaction. The reaction product is washed with water and separated into layers to obtain an aqueous layer and a dephenolized phenolic oil. Then, an alkylating agent is added to the aqueous layer for reaction. After the reaction product is cooled, it is allowed to stand and separate into layers to obtain an aqueous layer and a material layer. The aqueous layer is extracted with toluene and separated into layers. The wastewater layer is recycled and treated. The toluene layer and the material layer are mixed and first distilled under normal pressure to recover toluene, and then distilled under reduced pressure to collect catechol dimethyl ether and 5-methoxyindene in sequence.

7. The method for separating phenolic substances from phenolic coal tar according to claim 6, characterized in that, In method 1), the alkylating agent includes at least one of iodoalkane, chloroalkane, disulfide, and dicarbonate; the catalyst includes at least one of sodium methoxide, sodium ethoxide, sodium hydroxide, potassium hydroxide, pyridine, methylaminopyridine, and 1,8-diazabicyclo(5,4,0)-7-undecene. And / or, in method 2), the alkaline solution includes at least one of a carbonate solution, a bicarbonate solution, and a hydroxide solution.

8. The method for separating phenolic substances from phenolic coal tar according to any one of claims 1 to 7, characterized in that, In step S5, the etherification separation includes any of the following methods: 1) Direct etherification separation: Add a catalyst and alkylating agent to the resorcinol / hydroquinone phenolic oil fraction with a distillation range of 261-300℃ in step S1 to carry out the etherification reaction, recover the alkylating agent in the reaction product, and perform vacuum distillation on the remaining reaction product to obtain dimethyl terephthalate and dimethyl terephthalate. 2) Alkaline extraction followed by etherification separation: An alkaline solution is added to the resorcinol / hydroquinone phenolic oil fraction with a distillation range of 261–300°C in step S1 for reaction. The reaction product is washed with water and separated into layers to obtain an aqueous layer and a dephenolized phenolic oil. Then, an alkylating agent is added to the aqueous layer for reaction. After cooling, the reaction product is allowed to stand and separate into layers to obtain an aqueous layer and a material layer. The aqueous layer is extracted with toluene and separated into layers. The wastewater layer is recycled and treated. The toluene layer and the material layer are mixed and first distilled at atmospheric pressure to recover toluene, and then distilled under reduced pressure to collect the dimethyl ether product and crude dimethyl ether. Subsequently, the crude dimethyl ether is heated and mixed with mixed trimethylbenzene, and then hydrobromic acid is added dropwise for reaction to collect bromoalkanes. The remaining reaction liquid is then cooled and the hydrobromic acid aqueous solution is separated. The solvent layer is washed with water and separated into layers. The aqueous layer is a hydrobromic acid solution. The material layer is distilled to recover trimethylbenzene and obtain 3-methoxyphenol and resorcinol.

9. The method for separating phenolic substances from phenolic coal tar according to claim 8, characterized in that, In method 1), the alkylating agent includes at least one of iodoalkane, chloroalkane, disulfide, and dicarbonate; the catalyst includes at least one of sodium methoxide, sodium ethoxide, sodium hydroxide, potassium hydroxide, pyridine, methylaminopyridine, and 1,8-diazabicyclo(5,4,0)-7-undecene. And / or, in method 2), the alkaline solution includes at least one of a carbonate solution, a bicarbonate solution, and a hydroxide solution.