Process for the extraction of phenolic substances from coal tar

Abstract

The present application provides a method for extracting phenolic substances from coal tar, which comprises: primary extraction: extracting poor phenol oil by using a composite organic amine aqueous solution to obtain a dephenolized oil A and a rich phenol extraction phase A; secondary extraction: extracting a rich phenol fraction oil by using the rich phenol extraction phase A to obtain a dephenolized oil B and a rich phenol extraction phase B, wherein the poor phenol oil is obtained by mixing coal tar and the dephenolized oil B, and the rich phenol fraction oil is a fraction oil of the coal tar; acidification: acidifying the rich phenol extraction phase B by using an acidifying agent to obtain a crude phenol oil C and a composite organic amine aqueous solution rich in the acidifying agent through separation; and extractant regeneration: removing the acidifying agent from the composite organic amine aqueous solution rich in the acidifying agent to obtain the composite organic amine aqueous solution for recycling in the primary extraction step. The method of the present application is resource-saving, green and pollution-free, has low process energy consumption, and the crude phenol oil product has high purity.

Description

Technical Field

[0001] This invention relates to the field of coal chemical industry, and in particular to a method for extracting phenolic substances from coal tar. Background Technology

[0002] Coal tar is a major chemical product of coal chemical industry, a complex organic mixture formed by cooling coal after dry distillation and gasification. Based on different dry distillation temperatures, coal tar is classified into low-temperature coal tar, medium-temperature coal tar, and high-temperature coal tar. Prioritizing the extraction of phenolic compounds from coal tar can, on the one hand, reduce hydrogen consumption during coal tar hydrogenation and extend catalyst life; on the other hand, it can increase the economic added value of coal tar products.

[0003] Therefore, extracting phenolic compounds from coal tar is of great significance. Currently, the following two methods are used to extract phenolic compounds from coal tar:

[0004] 1) The alkaline washing method requires the use of a large amount of mineral acids and alkalis and fresh water during the production process, which will cause resource waste and environmental pollution.

[0005] 2) The dual-solvent extraction technology provided by patent CN110003939A uses a small molecule alcohol-water solution as the extractant to extract phenolic compounds from coal tar. The raffinate is stripped in a stripping tower to recover the small molecule alcohol extractant. The extracted phase is then heat-exchanged and passed through a dealcoholization tower to separate the small molecule alcohol, water, and phenolic compounds. The phenolic compounds are cooled by heat exchange with circulating cooling water to separate crude phenol and phenol-containing wastewater. The phenol-containing wastewater then enters a back-extraction tower, where methyl isobutyl ketone and diisopropyl ether are used as back-extraction agents to recover phenolic compounds from the phenolic water. Finally, crude phenol and back-extraction agents are separated by distillation. This process involves multiple distillations and stripping, resulting in high energy consumption and the introduction of multiple solvents, leading to low purity of the crude phenol oil product.

[0006] 3) Patent CN106986750A describes a method for extracting phenolic substances from coal liquefaction oil or coal tar. In this method, the coal tar is pre-distilled, and then the distillate oil is extracted and back-extracted in multiple stages. Then, the impurity oil in the extract phase is removed by stripping. The reaction process is complicated, and the multi-stage back-extraction is generally more than 3 stages. The amount of back-extraction agent is large and the reaction temperature is high. The reaction requires additional heating and has high energy consumption. Summary of the Invention

[0007] Existing technologies such as alkaline washing have problems of wasting resources and polluting the environment, dual solvent extraction methods have problems of high energy consumption and low purity of crude phenolic oil products, and stripping methods have problems of high energy consumption. In order to solve the above technical problems, the present invention provides a method for extracting phenolic substances from coal tar.

[0008] A method for extracting phenolic substances from coal tar includes the following steps:

[0009] One-step extraction: The phenol-poor oil was extracted using a complex organic amine aqueous solution to obtain dephenolized oil A and phenol-rich extract phase A;

[0010] Secondary extraction: The phenol-rich extract phase A is used to extract the phenol-rich distillate oil to obtain dephenolized oil B and phenol-rich extract phase B. The phenol-poor oil is obtained by mixing water-oil and dephenolized oil B, and the phenol-rich distillate oil is the distillate oil of the raw material coal tar.

[0011] Acidification: The phenol-rich extract phase B is acidified with an acidifying agent, and crude phenol oil C and a complex organic amine aqueous solution rich in the acidifying agent are obtained by separation.

[0012] Extractant regeneration: The acidifier is removed from the aqueous solution of the complex organic amine rich in acidifier to obtain the aqueous solution of the complex organic amine, which is then recycled in the first extraction step.

[0013] Compared with related technologies, the method for extracting phenolic substances from coal tar provided by the present invention has the following beneficial effects:

[0014] 1. Using a composite organic amine aqueous solution as an extractant for recycling saves resources and is green and pollution-free;

[0015] 2. No multiple solvents are required; a two-stage extraction process is used, resulting in high purity crude phenolic oil products.

[0016] 3. Using the water-based oil and the raw coal tar as raw materials, coal tar raw materials with different phenol contents can be processed simultaneously. At the same time, the water-based oil has few impurities. Using the water-based oil as raw material, the method of extracting phenolic substances from coal tar in this invention can be carried out without steam stripping and distillation, and the process has low energy consumption.

[0017] 4. By mixing the water-oil with the dephenolized oil B to obtain the lean phenolic oil, the phenolic substances that were not extracted in the secondary extraction step can be recovered. At the same time, because the water-oil has few impurities, the total extraction yield of phenolic substances is ultimately improved.

[0018] 5. The phenol-rich extract phase A is obtained by extracting the phenol-poor oil, and its phenol content is still lower than that of the phenol-rich distillate oil. In the secondary extraction step, the lower phenols in the phenol-rich distillate oil exchange with the higher phenols in the phenol-rich extract phase A, which can improve the extraction rate of lower phenols. At the same time, because the content of higher phenols is reduced, the increase in neutral oil caused by higher phenols is reduced. Thus, by utilizing the difference in properties between phenol-rich oil and phenol-poor oil, the extraction yield of lower phenols is improved, and the content of neutral oil in the phenol-rich extract phase B is reduced. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein:

[0020] Figure 1 This is a schematic flowchart of the method for extracting phenolic substances from coal tar provided by the present invention.

[0021] Figure 2 This is a process flow diagram of the method for extracting phenolic substances from coal tar provided by the present invention. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Please refer to the following: Figure 1 and Figure 2 ,in, Figure 1 This is a schematic flowchart of the method for extracting phenolic substances from coal tar provided by the present invention. Figure 2 This is a process flow diagram of the method for extracting phenolic substances from coal tar provided by the present invention. The method includes the following steps:

[0024] 101. Single extraction: Extraction of phenol-poor oil with a composite organic amine aqueous solution to obtain dephenolized oil A and phenol-rich extract phase A;

[0025] In this embodiment, the composite organic amine aqueous solution is used as the extractant to extract the phenol-poor oil. The resulting extract phase is the phenol-rich extract phase A, and the phenol content of the phenol-rich extract phase A is greater than 40%. The raffinate phase is the dephenolized oil A.

[0026] In the aforementioned aqueous solution of complex organic amines, the total mass fraction of organic amine compounds is 20%-70%, and the mass fraction of water is 30%-80%.

[0027] The composite organic amine aqueous solution is a mixture of one or more organic amine compounds selected from monoethanolamine (MEA), diethanolamine (DEA), and triethanolamine (TEA) with water.

[0028] In one embodiment, the composite organic amine aqueous solution is a mixed aqueous solution of monoethanolamine and triethanolamine, wherein the mass fraction of monoethanolamine is 20%-25% and the mass fraction of triethanolamine is 5%-10%.

[0029] In one embodiment, the composite organic amine aqueous solution is a mixed aqueous solution of monoethanolamine, diethanolamine and triethanolamine, wherein the mass fraction of monoethanolamine is 15%-25%, the mass fraction of diethanolamine is 2%-10%, and the mass fraction of triethanolamine is 2%-10%.

[0030] The mass ratio of the composite organic amine aqueous solution to the lean phenolic oil is 1:5-5:1. The primary extraction step uses a tower-type, single-stage, or multi-stage extraction device. The feed temperature of the composite organic amine aqueous solution and the lean phenolic oil is 10℃-70℃. The composite organic amine aqueous solution and the lean phenolic oil are extracted by countercurrent or cocurrent contact extraction at an extraction temperature of 10℃-70℃ and an extraction pressure of atmospheric pressure.

[0031] It should be noted that the dephenolized oil A obtained in the first extraction step is directly fed into the coal tar post-processing process for water washing, tar hydrogenation, etc., which can reduce the hydrogen consumption during the coal tar hydrogenation process and extend the catalyst life.

[0032] 102. Secondary extraction: The phenol-rich extract phase A is used to extract the phenol-rich distillate oil to obtain dephenolized oil B and phenol-rich extract phase B. The phenol-poor oil is obtained by mixing water-oil with the dephenolized oil B, and the phenol-rich distillate oil is a fraction of the raw material coal tar.

[0033] In this embodiment, the phenol-rich extract phase A is used as the extractant to extract the phenol-rich distillate oil, and the resulting extract phase is the phenol-rich extract phase B. The raffinate phase is the dephenolized oil B, which is formed by removing some lower phenols from the phenol-rich distillate oil. The phenol-rich extract phase B has a higher total phenol concentration and a higher concentration of lower phenolic compounds than the phenol-rich extract phase A. The water-float oil is coal tar with a density of less than 1 obtained through coking and a phenol content of less than 30%. The water-float oil is the coal tar that floats on water obtained by directly cooling coal gas.

[0034] The mass ratio of the phenol-rich extract phase A to the phenol-rich distillate oil is 1:10-10:1. The secondary extraction step can be carried out in a tower, single-stage, or multi-stage extraction device. The feed temperature of the phenol-rich extract phase A and the phenol-rich distillate oil is 10℃-70℃. The phenol-rich extract phase A and the phenol-rich distillate oil are extracted by countercurrent or cocurrent contact extraction at an extraction temperature of 10℃-70℃ and an extraction pressure of atmospheric pressure.

[0035] The raw material coal tar can be one or more of the following: medium-low temperature coal tar, distillate oil of medium-low temperature coal tar, high temperature coal tar, distillate oil of high temperature coal tar, and light coal tar.

[0036] Preferably, the method for extracting phenolic substances from coal tar further includes the following steps:

[0037] Mixing: The water-based oil is mixed with the dephenolized oil B to obtain the phenol-poor oil.

[0038] By mixing the dephenolized oil B with the water-oil mixture evenly and performing the first extraction step, the extraction rate of the dephenolized oil B can be further improved.

[0039] Preferably, the method for extracting phenolic substances from coal tar further includes the following steps:

[0040] Distillation: The raw coal tar is distilled to obtain the phenol-rich distillate oil of the raw coal tar with a distillation temperature range of 100℃-240℃.

[0041] According to the determination, when the raw coal tar is distilled in stages at a pressure not higher than atmospheric pressure, the phenol content of the distillate oil obtained in the temperature range of room temperature to 240°C is 36.95%, and the phenol content of the distillate oil obtained in the temperature range of 100°C to 240°C is 37.55%. In this embodiment, the phenol-rich distillate oil is the distillate oil of the raw coal tar with a distillation temperature range of 100°C to 240°C.

[0042] 103. Acidification: The phenol-rich extract phase B is acidified with an acidifying agent, and crude phenol oil C and a composite organic amine aqueous solution rich in the acidifying agent are obtained by separation.

[0043] In this embodiment, the acidifying agent is industrial-grade carbon dioxide gas. Of course, it can also be other acidic gases, such as industrial-grade sulfur dioxide gas, gases containing carbon dioxide, etc., which are not specifically limited here.

[0044] The acidification step can be carried out in an acidification device, which can be a single-stage or multi-stage gas-liquid reaction device. The industrial-grade carbon dioxide gas reacts countercurrently or in parallel with the phenol-rich extract phase B, and the resulting reaction liquid enters the bottom of the acidification device. The acidification temperature is 10℃-70℃, and the acidification pressure (absolute pressure) is 0.1atm-20atm. After the reaction liquid is allowed to stand and separate, an aqueous phase of carbon dioxide-rich composite organic amine aqueous solution and an oil phase of crude phenol oil C can be obtained.

[0045] 104. Extractant regeneration: The acidifying agent is removed from the aqueous solution of the complex organic amine rich in acidifying agent to obtain the aqueous solution of the complex organic amine, which is then recycled in the first extraction step.

[0046] In this embodiment, the acidifying agent is industrial-grade carbon dioxide gas. The extractant regeneration step can be carried out in a regeneration device, which can be a single-stage or multi-stage gas-liquid reaction device, such as a desorption tower. After the acidifying agent-rich composite organic amine aqueous solution is heated to desorb carbon dioxide, the carbon dioxide is discharged from the top of the regeneration device tower. The regenerated composite organic amine aqueous solution enters the bottom of the regeneration device and is recycled back into the primary extraction step. The regeneration reaction temperature is 30℃-200℃, and the regeneration pressure (absolute pressure) is 0.1 atm-20 atm.

[0047] To enable those skilled in the art to clearly understand the details and operations of the above embodiments of the present invention, and to demonstrate the significant improvement in the performance of the method for extracting phenolic substances from coal tar in the embodiments of the present invention, the above technical solutions are illustrated through the following embodiments.

[0048] Examples A1-A6 and Comparative Examples a1-A3

[0049] Example A1 uses a mixed aqueous solution of 25% MEA and 5% DEA as the extractant; Example A2 uses a mixed aqueous solution of 25% MEA and 5% TEA as the extractant; Example A3 uses a mixed aqueous solution of 10% MEA, 10% DEA and 10% TEA as the extractant; Example A4 uses a mixed aqueous solution of 18.3% MEA, 9.3% DEA and 2.4% TEA as the extractant; Example A5 uses a mixed aqueous solution of 20% MEA, 8% DEA and 2% TEA as the extractant; Example A6 uses a mixed aqueous solution of 20% MEA, 2% DEA and 8% TEA as the extractant; Comparative Example a1 uses a 30% MEA aqueous solution as the extractant; Comparative Example a2 uses a 30% DEA aqueous solution as the extractant; and Comparative Example a3 uses a 30% TEA aqueous solution as the extractant.

[0050] Light coal tar was used as the extraction liquid. The extractant and light coal tar were subjected to a single extraction at a mass flow ratio of 3:1. The extraction temperature was 25℃, the pressure was atmospheric pressure, and the reaction time was 1.5 h. After the reaction reached equilibrium, the mixture was transferred to a separatory funnel and allowed to stand for 0.5 h, yielding an upper raffinate phase (dephenolized oil) and a lower phenol-rich extract phase (phenolamine solution). The phenolamine solution from the first extraction was directly acidified in a reaction flask by introducing industrial-grade carbon dioxide gas. The acidification temperature was 30℃, the acidification pressure was atmospheric pressure, and the reaction was stopped when the pH value of the solution no longer changed within 10 minutes. The water content, amine content, and total phenol content in the dephenolized oil and crude phenol products were determined by azeotropic distillation, acid-base titration, and double-ball metering tube method, respectively. The content of lower phenolic compounds (C6-C9) in the oil phase was quantitatively analyzed by gas chromatography. The results are shown in Table 1.

[0051] Table 1. Measurement results of Examples A1-A6 and Comparative Examples a1-a3

[0052]

[0053]

[0054] In the table, "-" indicates that the product quantity is too small to be analyzed and tested.

[0055] To facilitate understanding and reading by those skilled in the art, the following sections first introduce the formulas for calculating extraction yield, acidification yield, total yield, and crude phenol oil residue.

[0056] 1. The formula for calculating the extraction yield is as follows:

[0057]

[0058] In the formula:

[0059] E 酚 Extraction rate of phenols, %.

[0060] ω1: Total phenol content in coal tar, %

[0061] m1: Mass of coal tar, in grams.

[0062] ω2: Total phenol content in dephenolized oil, %.

[0063] m2: Mass of the dephenolized oil, in grams.

[0064] 2. The formula for calculating the acidification yield is as follows:

[0065]

[0066] In the formula:

[0067] E 酸化 : Acidification rate of crude phenol precipitation, %.

[0068] x1: Phenol content in the phenolamine solution, %.

[0069] m 酚胺液 Mass of phenolamine solution, in grams.

[0070] m 粗酚 Mass of crude phenolic oil obtained from acidification, in g.

[0071] x2: Total phenol content in crude phenolic oil, %.

[0072] m2: Mass of the dephenolized oil, in grams.

[0073] 3. The formula for calculating the overall yield is as follows:

[0074] X 总 =E 酚 *E 酸化

[0075] In the formula:

[0076] X 总 Overall yield of the entire process, %.

[0077] E 酚 Extraction rate of phenolic compounds, %.

[0078] E 酸化 : Acidification rate of crude phenol precipitation, %.

[0079] 4. Formula for calculating crude phenolic oil residue rate:

[0080] σ=1-ω 酚 -ω 胺 -X 水

[0081] In the formula:

[0082] σ: Neutral oil content in the oil product, %.

[0083] ω 酚 Total phenol content in oil products, %.

[0084] ω 胺 : Amine content in oil products, %.

[0085] X 水 Water content in oil products, %.

[0086] As can be seen from Table 1, the amount of residual impurities in crude phenolic oil is related to the extraction yield, acidification yield, and composition of the extractant. The total yield of the composite extractant is higher, and the impurity content in the crude phenolic oil is lower. The composite organic amine aqueous solution has a better effect than the single extractant.

[0087] Examples B1-B2 and Comparative Examples B1-B2

[0088] A mixed aqueous solution of 20% MEA, 5% DEA, and 5% TEA by mass fraction was prepared as the extractant. Light coal tar was used as the phenol-poor oil. The extractant and light coal tar were extracted once at a mass flow ratio of 3:1. The extraction temperature was 25℃, the pressure was atmospheric pressure, and the reaction time was 1.5h. After the reaction reached equilibrium, the mixture was transferred to a separatory funnel and allowed to stand for 0.5h to obtain the upper raffinate phase, i.e., dephenolized oil (dephenolized oil A), and the lower phenol-rich extract phase, i.e., phenolamine solution (phenol-rich extract phase A).

[0089] In Comparative Example b1, the phenolamine solution extracted once was directly purged with industrial-grade carbon dioxide gas in a reaction flask for acidification. The acidification temperature was 30°C, and the acidification pressure was atmospheric pressure. The reaction was terminated when the pH value of the solution no longer changed within 10 minutes. The water content, amine content, and total phenol content in the dephenolized oil and crude phenol products were determined by azeotropic distillation, acid-base titration, and double-ball metering tube method, respectively. The content of lower phenolic compounds (C6-C9) in the oil phase was quantitatively analyzed by gas chromatography. The results are shown in Table 2.

[0090] Comparative Example B2 involved a secondary extraction of the phenolamine solution obtained from the first extraction with light coal tar at a mass flow ratio of 3:1. Example B1 involved a secondary extraction of the phenolamine solution obtained from the first extraction with light coal tar distillate at a mass flow ratio of 3:1, with the distillation temperature range being room temperature to 240°C. Example B2 involved a secondary extraction of the phenolamine solution obtained from the first extraction with light coal tar distillate at a mass flow ratio of 3:1, with the distillation temperature range being 100°C to 240°C, the extraction temperature being 25°C, the pressure being atmospheric pressure, and the reaction time being 1.5 h. After the reaction reached equilibrium, the mixture was transferred to a separatory funnel and allowed to stand for 0.5 h, yielding an upper raffinate phase, i.e., dephenolized oil (dephenolized oil B), and a lower phenol-rich extract phase, i.e., phenolamine solution (phenol-rich extract phase B). The phenolamine solution obtained from the second extraction was then directly purged with industrial-grade carbon dioxide gas in a reaction flask for acidification. The acidification temperature was 30°C, the acidification pressure was atmospheric pressure, and the reaction was stopped when the pH value in the solution no longer changed within 10 minutes. The water content, amine content, and total phenol content in the dephenolized oil and crude phenol products were determined by azeotropic distillation, acid-base titration, and double-ball metering tube method, respectively. The content of lower phenolic compounds (C6-C9) in the oil phase was quantitatively analyzed by gas chromatography. The results are shown in Table 2.

[0091] Table 2. Results of phenolic compound determination by two-stage cross-flow extraction with 20% MEA + 5% DEA + 5% TEA.

[0092]

[0093] As can be seen from Table 2, the crude phenolic oil obtained by secondary extraction using coal tar from the 100℃-240℃ distillation range has a lower residue rate. Secondary extraction using coal tar from the 100℃-240℃ distillation range can not only increase the content of low-grade phenolic compounds in the crude phenolic oil, but also reduce the concentration of impurities in the crude phenolic oil, which is beneficial to reducing the investment in subsequent refining equipment and production costs.

[0094] Example C1 and Comparative Examples C1-C2

[0095] Prepare an aqueous solution containing 20% ​​MEA, 5% DEA, and 5% TEA by mass as the extractant.

[0096] In Example C1, coal tar with a phenol content of 23.42% was used as a lean phenol oil. The extractant and coal tar with a phenol content of 23.42% were extracted once at a mass flow ratio of 3:1. The extraction temperature was 25°C, the pressure was atmospheric pressure, and the reaction time was 1.5 h. After the reaction reached equilibrium, the mixture was transferred to a separatory funnel and allowed to stand for 0.5 h to obtain the upper raffinate phase, i.e., dephenolized oil (dephenolized oil A), and the lower phenol-rich extract phase, i.e., phenolamine solution (phenol-rich extract phase A). Using a distillate oil with a phenol content of 33.65% as the phenol-rich distillate oil, the phenolamine solution from the first extraction was subjected to a second extraction with coal tar containing 23.42% phenol at a mass flow ratio of 3:1. The extraction temperature was 25℃, the pressure was atmospheric pressure, and the reaction time was 1.5 h. After the reaction reached equilibrium, the mixture was transferred to a separatory funnel and allowed to stand for 0.5 h to obtain the upper raffinate phase, i.e., the dephenolized oil (dephenolized oil B), and the lower phenol-rich extract phase, i.e., the phenolamine solution (phenol-rich extract phase B). The phenolamine solution from the second extraction was directly purged with industrial-grade carbon dioxide gas in a reaction flask for acidification. The acidification temperature was 30℃, the acidification pressure was atmospheric pressure, and the reaction was stopped when the pH value in the solution no longer changed within 10 minutes. The water content, amine content, and total phenol content in the dephenolized oil and crude phenol products were determined by azeotropic distillation, acid-base titration, and double-ball metering tube method, respectively. The content of lower phenolic compounds (C6-C9) in the oil phase was quantitatively analyzed by gas chromatography. The results are shown in Table 3.

[0097] Comparative Example C1 involved a single extraction of coal tar with a phenol content of 23.41% using the same extraction conditions as Example C1, yielding a single-extraction phenolamine solution. This solution was then subjected to a second extraction of coal tar with a phenol content of 23.41% using the same extraction conditions as Example C1, yielding a second-extraction phenolamine solution. This second-extraction phenolamine solution was then acidified under the same conditions as Example C1. The water content, amine content, and total phenol content in the dephenolized oil and crude phenol products were determined using azeotropic distillation, acid-base titration, and double-ball metering tube methods, respectively. The content of lower phenolic compounds (C6-C9) in the oil phase was quantitatively analyzed using gas chromatography. The results are shown in Table 3.

[0098] Comparative Example C2 involved a single extraction of a distillate oil with a phenol content of 33.65% using the same extraction conditions as in Example C1, yielding a single-extraction phenolamine solution. This solution was then subjected to a second extraction of the same phenolamine solution using the same extraction conditions as in Example C1, yielding a second-extraction phenolamine solution. The second-extraction phenolamine solution was then acidified under the same conditions as in Example C1. The water content, amine content, and total phenol content in the dephenolized oil and crude phenol product were determined using azeotropic distillation, acid-base titration, and double-ball metering tube methods, respectively. The content of lower phenolic compounds (C6-C9) in the oil phase was quantitatively analyzed using gas chromatography. The results are shown in Table 3.

[0099] Table 3. Results of phenolic compound determination obtained from coal tar extraction at different concentrations.

[0100] Comparative Example C1 Comparative Example C2 Example C1 Primary extraction yield 65.13％ 56.32％ 64.54％ Secondary extraction yield 29.00％ 15.24％ 56.05％ Crude phenolic oil phenol content 68.05％ 70.83％ 77.76％ Neutral oil content 10.80％ 4.86％ 4.78％ Acidification yield 63.50％ 70.39％ 70.26％

[0101] As can be seen from Table 3, Example C1 uses a two-stage extraction process involving lean phenolic oil and rich phenolic distillate oil to increase the content of phenolic compounds in crude phenolic oil and reduce the content of neutral oil, which is beneficial for the subsequent refining and processing of crude phenolic oil.

[0102] Compared with existing technologies, the method for extracting phenolic substances from coal tar provided by this invention uses a composite organic amine aqueous solution as an extractant for recycling, which saves resources, is green and pollution-free, does not require multiple solvents, and produces crude phenolic oil products with high purity.

[0103] Using a composite organic amine aqueous solution, the overall yield is high and the impurity content in the crude phenol oil is low.

[0104] Secondary extraction using the 100℃-240℃ distillate fraction not only increases the content of low-grade phenolic compounds in crude phenolic oil, but also reduces the concentration of impurities in crude phenolic oil, and helps to reduce investment in subsequent refining equipment and production costs.

[0105] Using the water-based oil and the raw coal tar as raw materials, coal tar raw materials with different phenol contents can be processed simultaneously. At the same time, the water-based oil has fewer impurities. Using the water-based oil as raw material, the method of extracting phenolic substances from coal tar in this invention can be performed without steam stripping and distillation, resulting in low energy consumption.

[0106] The lean phenol oil is obtained by mixing the water-based oil with the dephenolized oil B, which can recover the phenolic substances that were not extracted in the secondary extraction step. At the same time, the water-based oil has fewer impurities, ultimately improving the total extraction yield of phenolic substances.

[0107] The phenol-rich extract phase A is obtained by extracting the phenol-poor oil, and its phenol content is still lower than that of the phenol-rich distillate oil. In the secondary extraction step, the lower phenols in the phenol-rich distillate oil exchange with the higher phenols in the phenol-rich extract phase A, which can improve the extraction rate of lower phenols. At the same time, because the content of higher phenols is reduced, the increase in neutral oil caused by higher phenols is reduced. Thus, by utilizing the difference in properties between phenol-rich oil and phenol-poor oil, the extraction yield of lower phenols is improved, and the content of neutral oil in the phenol-rich extract phase B is reduced.

[0108] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for extracting phenolic substances from coal tar, characterized in that, The method includes the following steps: One-step extraction: The phenol-poor oil was extracted using a complex organic amine aqueous solution to obtain dephenolized oil A and phenol-rich extract phase A; Secondary extraction: The phenol-rich extract phase A is used to extract the phenol-rich distillate oil to obtain dephenolized oil B and phenol-rich extract phase B. The phenol-poor oil is obtained by mixing water-oil with the dephenolized oil B, and the phenol-rich distillate oil is a distillate oil of the raw material coal tar. Acidification: The phenol-rich extract phase B is acidified with an acidifying agent, and crude phenol oil C and a complex organic amine aqueous solution rich in the acidifying agent are obtained by separation. Extractant regeneration: The acidifier is removed from the aqueous solution of the complex organic amine rich in acidifier to obtain the aqueous solution of the complex organic amine, which is then recycled in the first extraction step.

2. The method for extracting phenolic substances from coal tar according to claim 1, characterized in that, It also includes the following steps: Mixing: The water-based oil is mixed with the dephenolized oil B to obtain the phenol-poor oil.

3. The method for extracting phenolic substances from coal tar according to claim 1, characterized in that, It also includes the following steps: Distillation: The raw material coal tar is distilled to obtain the phenol-rich distillate oil with a distillation temperature range of 100℃-240℃ and a pressure not exceeding atmospheric pressure.

4. The method for extracting phenolic substances from coal tar according to claim 1, wherein the water-oil is coal tar with a density of less than 1 obtained by coking and a phenol content of less than 30%.

5. The method for extracting phenolic substances from coal tar according to claim 1, characterized in that, The raw material coal tar is one or more of the following: medium-low temperature coal tar, distillate oil of medium-low temperature coal tar, high temperature coal tar, distillate oil of high temperature coal tar, and light coal tar.

6. The method for extracting phenolic substances from coal tar according to claim 1, characterized in that, The composite organic amine aqueous solution is a mixture of two or more organic amine compounds selected from monoethanolamine, diethanolamine, and triethanolamine with water.

7. The method for extracting phenolic substances from coal tar according to claim 1, characterized in that, The composite organic amine aqueous solution is a mixed aqueous solution of monoethanolamine and triethanolamine, with a mass fraction of 20%-25% for monoethanolamine and 5%-10% for triethanolamine; or, the composite organic amine aqueous solution is a mixed aqueous solution of monoethanolamine, diethanolamine and triethanolamine, with a mass fraction of 15%-25% for monoethanolamine, 2%-10% for diethanolamine and 2%-10% for triethanolamine.

8. The method for extracting phenolic substances from coal tar according to claim 1, characterized in that, The mass ratio of the composite organic amine aqueous solution to the phenol-poor oil is 1:5-5:1, and the mass ratio of the phenol-rich extract phase A to the phenol-rich distillate oil is 1:10-10:

1.

9. The method for extracting phenolic substances from coal tar according to claim 1, characterized in that, The primary extraction step and the secondary extraction step employ a tower-type, single-stage, or multi-stage extraction device. The feed temperature of the composite organic amine aqueous solution, the lean phenol oil, the phenol-rich extract phase A, and the phenol-rich distillate oil is 10℃-70℃, the extraction temperature is 10℃-70℃, and the extraction pressure is atmospheric pressure.

10. The method for extracting phenolic substances from coal tar according to claim 1, characterized in that, The acidification step uses a single-stage or multi-stage gas-liquid reaction device, with an acidification temperature of 10℃-70℃ and an acidification pressure of 0.1atm-20atm. The extractant regeneration step uses a single-stage or multi-stage gas-liquid reaction device, with a regeneration reaction temperature of 30℃-200℃ and a regeneration pressure of 0.1atm-20atm.

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