A method for obtaining indole and quinoline from coal tar foots oil

Abstract

The present application provides a method for obtaining indole and quinoline from coal tar wash oil, comprising the following steps: 1) using a first extractant to perform first extraction treatment on the coal tar wash oil to obtain a first extract liquid rich in nitrogen heterocyclic compounds and a first raffinate phase; 2) using a second extractant to perform second extraction treatment on the first extract liquid to obtain a second extract phase rich in nitrogen heterocyclic compounds and a second raffinate phase; 3) performing solvent separation treatment on the second extract phase to obtain nitrogen heterocyclic compounds; 4) after performing third extraction treatment on a system comprising the nitrogen heterocyclic compounds and an ammonium bisulfate solution, mixing the water phase with an alkali solution to perform neutralization reaction to obtain quinoline, and performing indole treatment on the organic phase to obtain indole; the method not only does not require harsh conditions, but also greatly improves the yield of indole and quinoline extracted from coal tar wash oil.

Description

Technical Field

[0001] This invention relates to a method for obtaining indole and quinoline from coal tar wash oil, belonging to the separation field of the coal chemical industry. Background Technology

[0002] Indoles and quinolines are important heterocyclic fine chemical intermediates, widely used in pharmaceuticals, pesticides, printing and dyeing, rubber, and other fine chemical industries. Coal tar, after distillation, yields different fractions, with the wash oil fraction being the main enriched portion of indoles and quinolines. Therefore, extracting indoles and quinolines from coal tar wash oil is an effective way to utilize coal tar resources.

[0003] Patent document CN103146415B discloses a method for extracting indole from medium-quality wash oil. After distilling the medium-quality wash oil to remove methylnaphthalene, an azeotropic agent is added and azeotropically distilled to obtain the indole main fraction. The azeotropic agent is separated from the indole by adding ethanol, ether, or water to the indole main fraction. The crude indole is then purified by recrystallization. The document "A New Method for Separating Quinoline from Wash Oil" discloses a quinoline refining method. First, the wash oil is distilled to obtain a quinoline-rich methylnaphthalene fraction (i.e., the quinoline fraction). Quinoline is then obtained by azeotropic distillation of the methylnaphthalene fraction with ethylene glycol, and finally, ethylene glycol is recovered.

[0004] However, although the two methods mentioned above can achieve the recovery of indole and quinoline respectively, how to use coal tar wash oil as raw material and simultaneously achieve efficient recovery of indole and quinoline is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] This invention provides a method for obtaining indole and quinoline from coal tar wash oil. This method achieves efficient recovery of indole and quinoline from coal tar wash oil while ensuring the purity of indole and quinoline.

[0006] This invention provides a method for obtaining indole and quinoline from coal tar wash oil, comprising the following steps:

[0007] 1) The coal tar wash oil is subjected to a first extraction treatment using a first extractant to obtain a first extract enriched with nitrogen heterocyclic compounds and a first raffinate phase;

[0008] 2) The first extract is subjected to a second extraction treatment using a second extractant to obtain a second extract phase and a second raffinate phase enriched with nitrogen heterocyclic compounds;

[0009] 3) The second extract phase is subjected to solvent separation to obtain nitrogen heterocyclic compounds;

[0010] 4) After a third extraction treatment of the system including the nitrogen heterocyclic compound and an aqueous solution of ammonium bisulfate, the aqueous phase is mixed with an alkaline solution for a neutralization reaction to obtain quinoline, and the organic phase is subjected to indole treatment to obtain indole;

[0011] Wherein, the first extractant is at least one of supercritical fluid, cyclodextrin, eutectic solvent, starch and its derivative solution; the second extractant is at least one of water, acidic aqueous solution, alkaline aqueous solution, neutral metal salt solution, ionic liquid, solid-liquid extraction resin.

[0012] According to one embodiment of the present invention, the first extractant is a supercritical fluid, the flow ratio of the supercritical fluid to the coal tar wash oil is 1:4-8, and the extraction temperature is 41-50℃;

[0013] The first extractant is the cyclodextrin, the mass ratio of the cyclodextrin to the coal tar wash oil is 1:4-10, the extraction temperature is 50-59℃, and the extraction time is 2-4h.

[0014] The first extractant is the deep eutectic solvent, the mass ratio of the deep eutectic solvent to the coal tar wash oil is 1:5-6, the extraction temperature is 61-80℃, and the extraction time is 1.5-3h;

[0015] The first extractant is the starch and its derivative solution, the mass ratio of the starch and its derivative solution to the coal tar wash oil is 1:3-5, the extraction temperature is 50-70℃, and the extraction time is 2-3h.

[0016] According to one embodiment of the present invention, the second extractant is at least one of the following: water, acidic aqueous solution, alkaline aqueous solution, neutral metal salt solution, and ionic liquid; the volume ratio of the second extractant to the first extract is 1-3:1; the extraction temperature is 60-100°C; and the extraction time is 30-120 min.

[0017] The second extractant is the solid-liquid extraction resin, the solid-liquid extraction resin loading is 5-15%, the extraction temperature is 60-80℃, and the extraction time is 120-360min.

[0018] According to one embodiment of the present invention, the solvent containing starch or starch derivative includes at least one of starch-water-organic solvent complex solution, carboxymethyl starch aqueous solution, sulfonated starch aqueous solution, phosphate starch aqueous solution, starch acetate aqueous solution, hydroxypropyl starch aqueous solution, and ethylenediamine modified starch aqueous solution;

[0019] The organic solvent mentioned herein includes at least one of ethanol, glycerol, dimethyl sulfoxide, and acetone.

[0020] According to one embodiment of the present invention, the acidic aqueous solution includes at least one of hydrochloric acid and sulfuric acid solution;

[0021] The alkaline aqueous solution includes at least one of sodium hydroxide solution, potassium hydroxide solution, and triethylamine aqueous solution;

[0022] The neutral metal salt solution includes at least one of sodium chloride solution, potassium chloride solution, and calcium chloride solution;

[0023] The ionic liquid includes at least one of the following: ionic liquid containing tetrafluoroborate ions and ionic liquid containing hexafluorophosphate ions.

[0024] The solid-liquid extraction resin includes at least one of the following: urethane resin, polyamide resin, polyether resin, styrene-difenylstyrene copolymer resin, copper- or molybdenum-loaded chelating resin, resin containing quaternary ammonium salt groups, and resin containing sulfonic acid groups.

[0025] According to one embodiment of the present invention, the mass ratio of starch, water and organic solvent in the starch-water-organic solvent compound is 1-30:49-89:10-50.

[0026] According to one embodiment of the present invention, the solid-liquid extraction resin has a porosity of 0.5 to 0.7 and a pore size of 4 to 5 nm.

[0027] According to one embodiment of the present invention, the volume ratio of the nitrogen heterocyclic compound to the ammonium bisulfate is 1:2-4.

[0028] According to one embodiment of the present invention, the indoleation treatment includes the following steps:

[0029] The organic phase is mixed with a directional reaction reagent and a catalyst to carry out a directional synthesis reaction to obtain the indole;

[0030] The directional reaction reagents include at least one of ethylene glycol, aldehydes, and ketones.

[0031] According to one embodiment of the present invention, the second extraction phase further includes a reducing agent;

[0032] Wherein, when the second extractant is the acidic aqueous solution, the reducing agent is an alkaline solution;

[0033] When the second extractant is the alkaline aqueous solution, the reducing agent is an inorganic acid solution;

[0034] When the second extractant is the neutral metal salt solution, the reducing agent is a ferrous sulfate solution;

[0035] When the second extractant is a resin containing quaternary ammonium salt groups, the reducing agent is the inorganic acid solution;

[0036] When the second extractant is a copper-molybdenum chelating resin, the reducing agent is the ferrous sulfate solution;

[0037] When the second extractant is a resin containing sulfonic acid groups, the reducing agent is the alkaline solution.

[0038] The method for obtaining indole and quinoline from coal tar wash oil provided by this invention utilizes multi-stage extraction to purify and prepare quinoline and indole. By creatively selecting suitable first and second extractants and a directional reaction pathway, the preparation and purification of indole and quinoline are achieved. This provides a new research approach for obtaining indole and quinoline from coal tar wash oil and contributes to providing high-purity indole and quinoline products. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the process for obtaining indole and quinoline from coal tar washing oil in one embodiment of the present invention. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0041] Figure 1 This invention provides a method for obtaining indole and quinoline from coal tar wash oil, as described in one embodiment. Figure 1 As shown, the present invention provides a method for obtaining indole and quinoline from coal tar wash oil, comprising the following steps:

[0042] 1) The coal tar wash oil is subjected to a first extraction treatment using a first extractant to obtain a first extract enriched with nitrogen heterocyclic compounds and a first raffinate phase;

[0043] 2) The first extract is subjected to a second extraction treatment using a second extractant to obtain a second extract phase and a second raffinate phase enriched with nitrogen heterocyclic compounds;

[0044] 3) The second extract phase is subjected to solvent separation to obtain nitrogen heterocyclic compounds;

[0045] 4) After a third extraction treatment of the system including the nitrogen heterocyclic compound and an aqueous solution of ammonium bisulfate, the aqueous phase is mixed with an alkaline solution for a neutralization reaction to obtain quinoline, and the organic phase is subjected to indole treatment to obtain indole;

[0046] Wherein, the first extractant is at least one of supercritical fluid, cyclodextrin, eutectic solvent, starch and its derivative solution; the second extractant is at least one of water, acidic aqueous solution, alkaline aqueous solution, neutral metal salt solution, ionic liquid, solid-liquid extraction resin.

[0047] The method of the present invention is used to obtain indole and quinoline from coal tar wash oil, which is a fraction of coal tar at 230-300℃. Coal tar wash oil contains a certain amount of nitrogen heterocyclic compounds such as indole, quinoline, pyrazole, phenylhydrazine, and aniline. The method of the present invention can efficiently obtain indole and quinoline from coal tar wash oil.

[0048] In step 1), the first extractant can be at least one of supercritical fluid, cyclodextrin, eutectic solvent, starch and its derivative solution.

[0049] The first extraction process mainly utilizes the difference in solubility or partition coefficient of various components in coal tar wash oil in two immiscible (or slightly soluble) solvents to transfer nitrogen heterocyclic compounds in coal tar wash oil from the coal tar wash oil to the first extractant, resulting in a first extract containing nitrogen heterocyclic compounds and a first raffinate phase.

[0050] Specifically, the first extractant is mixed with coal tar wash oil, stirred at a certain temperature for a certain time, and then allowed to stand. After obvious two-phase separation occurs, the two phases are separated to obtain a first extract containing nitrogen heterocyclic compounds and a first raffinate phase. The first extract enters the subsequent second extraction process, and the first raffinate phase is a denitrified wash oil product that can be used as a clean wash oil product.

[0051] This invention does not limit the specific order of adding the first extractant and coal tar wash oil, the stirring and settling time, or the extraction temperature in the first extraction process. It also does not limit the instruments and equipment or specific operations for separating the first extract and the first raffinate after they have separated into layers, as long as the separation of the first extract and the first raffinate can be achieved.

[0052] In step 2), the second extractant can be at least one of water, acidic aqueous solution, alkaline aqueous solution, neutral metal salt solution, ionic liquid, or solid-liquid extraction resin.

[0053] When water or an ionic liquid is selected as the second extractant, the second extraction process utilizes the difference in solubility or partition coefficient between the nitrogen heterocyclic compound and the first extractant in two immiscible (or slightly soluble) solvents to transfer the nitrogen heterocyclic compound in the first extract to the second extractant, resulting in a second extract phase enriched with nitrogen heterocyclic compounds and a second raffinate phase. The second extract phase undergoes subsequent solvent separation treatment, and the second raffinate phase can be purified and refined to be used as the first extractant for the first extraction process.

[0054] When the second extractant is an acidic aqueous solution, an alkaline aqueous solution, or a neutral metal salt solution, the second extraction process utilizes the acidic aqueous solution, alkaline aqueous solution, or neutral metal salt solution to form a soluble salt with the nitrogen heterocyclic compound in the first extract, thereby increasing the water solubility of the nitrogen heterocyclic compound and transferring it to the aqueous phase. This achieves phase separation between the nitrogen heterocyclic compound and the first extractant, resulting in a second extract phase and a second raffinate phase containing the soluble salt of the nitrogen heterocyclic compound. The second extract phase undergoes subsequent solvent separation treatment, and the second raffinate phase can be purified and processed to be used as the first extractant in the first extraction process.

[0055] Specifically, the second extractant is mixed with the first extractant, stirred at a certain temperature for a certain time, and then allowed to stand. After obvious two-phase separation occurs, the two phases are separated to obtain a second extractant phase enriched with nitrogen heterocyclic compounds and a second raffinate phase. The second extractant phase is subjected to subsequent solvent separation treatment, and the second raffinate phase can be purified and refined into the first extractant for use in the first extraction treatment.

[0056] When a solid-liquid extraction resin is selected as the second extractant, during the second extraction process, the solid-liquid extraction resin forms hydrogen bonds, ion interactions, or ligand compounds with the nitrogen heterocyclic compounds in the first extractant. This causes the nitrogen heterocyclic compounds in the first extractant to transfer from the first extractant to the surface of the solid-liquid extraction resin in the form of a liquid or solid phase. The solid-liquid extraction resin containing nitrogen heterocyclic compounds constitutes the second extraction phase, while the first extractant is retained in the form of a liquid phase.

[0057] Specifically, a solid-liquid extraction resin is added to the first extraction solution, stirred and allowed to stand for a certain time at a certain temperature, and then the solid-liquid extraction resin is taken out to obtain a second extraction phase and a second raffinate phase enriched with nitrogen heterocyclic compounds on the surface. The second extraction phase is subjected to subsequent solvent separation treatment, and the second raffinate phase can be purified and refined into a first extractant for the first extraction treatment.

[0058] This invention does not limit the order of addition of the second extractant and the first extractant, the stirring and settling time, or the extraction temperature during the second extraction process, nor does it limit the instruments and equipment or specific operations for separating the second extractant from the first extractant.

[0059] The solvent separation process in step 3) specifically refers to using certain physical or chemical means to separate the nitrogen heterocyclic compound solution containing other substances (other substances are non-nitrogen heterocyclic compounds) to obtain an organic phase mixture containing only nitrogen heterocyclic compounds, wherein the composition of the nitrogen heterocyclic compounds is the same as that of the nitrogen heterocyclic compounds in the initial coal tar wash oil.

[0060] Specifically, common methods such as membrane separation, distillation, and rotary evaporation can be used to separate the nitrogen heterocyclic compound solution containing other substances into an organic phase mixture containing only nitrogen heterocyclic compounds. For example, a nitrogen heterocyclic compound solution containing other substances can be added to a rotary evaporation crude extraction device using rotary evaporation technology. Under reduced pressure and heating conditions, the organic phase mixture containing only nitrogen heterocyclic compounds can be enriched to obtain nitrogen heterocyclic compounds.

[0061] It should be noted that when a solid-liquid extraction resin is used as the second extractant, the second extract phase can be eluted with an eluent to obtain a solution containing nitrogen-containing heterocyclic compounds or soluble salts of nitrogen-containing heterocyclic compounds. Subsequently, the solution is subjected to solvent separation to obtain an organic phase mixture containing only nitrogen-containing heterocyclic compounds. This invention does not limit the specific type of eluent; common eluents such as ethanol, ethyl acetate, ethylene glycol, and triethylamine can be used as needed.

[0062] When the second extractant is an acidic aqueous solution, an alkaline aqueous solution, a neutral metal salt solution, or a solid-liquid extraction resin (which yields a solid-liquid extraction resin containing soluble salts of nitrogen heterocyclic compounds after elution), it is necessary to convert the soluble salts of nitrogen heterocyclic compounds in the solution into nitrogen heterocyclic compounds during solvent separation.

[0063] This invention does not limit the specific steps and methods for converting soluble salts of nitrogen heterocyclic compounds into nitrogen heterocyclic compounds.

[0064] Step 4) The third extraction process utilizes the difference in reaction between the quinoline component of the nitrogen heterocyclic compounds and the aqueous solution of ammonium bisulfate: the quinoline component reacts with ammonium bisulfate to form quinoline ammonium bisulfate salt, while other nitrogen heterocyclic compounds do not react with ammonium bisulfate. Quinoline ammonium bisulfate salt has high solubility in water and will be transferred to the aqueous phase, while other nitrogen heterocyclic compounds will remain in the organic phase, thus separating the aqueous phase rich in quinoline ammonium bisulfate salt and the organic phase containing other nitrogen heterocyclic compounds.

[0065] Specifically, a nitrogen heterocyclic compound is mixed with ammonium bisulfate and stirred for a certain period of time. The liquid after phase separation is then separated to obtain an aqueous phase rich in quinoline ammonium bisulfate salt and an organic phase containing other nitrogen heterocyclic compounds.

[0066] A neutralization reaction is carried out by mixing an aqueous phase rich in quinoline with an alkaline solution. The alkaline solution reduces quinoline ammonium bisulfate to quinoline. Quinoline, as an organic phase, is then clearly separated from the aqueous phase, and quinoline can be obtained by separation.

[0067] This invention does not limit the specific type of alkaline solution, and the type of alkaline solution can be selected according to the actual situation, such as sodium hydroxide solution. Similarly, this invention does not limit the separation method of quinoline as an organic phase and aqueous phase.

[0068] Indoleation of an organic phase refers to the preparation, separation, and purification of indole. On one hand, indole can be prepared using components in the organic phase, catalysts, and directional reaction reagents through a specific reaction pathway. On the other hand, purification methods can be used to separate indole from other nitrogen heterocyclic compounds in the organic phase to obtain indole.

[0069] Specifically, the organic phase is mixed with a directional reaction reagent, and a directional conversion reaction is carried out under heating and stirring, followed by separation and purification of indole.

[0070] This invention does not limit the type of directional reaction reagent or the directional conversion reaction pathway, nor does it limit the purification method. As long as it can fully purify indole and make full use of other nitrogen heterocyclic compounds in the organic phase, it is acceptable. For example, indole can be purified by distillation, crystallization, or other methods.

[0071] This invention effectively separates non-nitrogen heterocyclic compound impurities from wash oil through first and second extraction processes, achieving a high enrichment of nitrogen heterocyclic compounds. This lays the foundation for subsequent quinoline purification and indole reaction to prepare high-purity quinoline and indole products. The third extraction and indole processes are simple to operate and the reaction conditions are easy to control. This method simplifies the process of obtaining indole and quinoline from coal tar wash oil and improves the purity and yield of indole and quinoline.

[0072] Furthermore, in a specific embodiment of the present invention, the first extractant is a supercritical fluid, the flow ratio of the supercritical fluid to the coal tar wash oil is 1:4-8, and the extraction temperature is 41-50℃.

[0073] For example, the flow ratio of supercritical fluid to coal tar wash oil includes, but is not limited to, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, or any combination thereof; the extraction temperature includes, but is not limited to, 41℃, 42℃, 43℃, 44℃, 45℃, 46℃, 47℃, 48℃, 49℃, 50℃, or any combination thereof.

[0074] The first extractant is cyclodextrin, the mass ratio of cyclodextrin to coal tar wash oil is 1:4-10, the extraction temperature is 50-59℃, and the extraction time is 2-4h.

[0075] For example, the mass ratio of cyclodextrin to coal tar wash oil includes, but is not limited to, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9, 1:9.5, 1:10, or any two of these ranges; the extraction temperature includes, but is not limited to, 50℃, 51℃, 52℃, 53℃, 54℃, 55℃, 56℃, 57℃, 58℃, 59℃, or any two of these ranges; and the extraction time includes, but is not limited to, 2h, 2.2h, 2.4h, 2.6h, 2.8h, 3h, or any two of these ranges.

[0076] The first extractant is a deep eutectic solvent, with a mass ratio of deep eutectic solvent to coal tar wash oil of 1:5-6, an extraction temperature of 61-80℃, and an extraction time of 1.5-3h.

[0077] For example, the mass ratio of the deep eutectic solvent to the coal tar wash oil includes, but is not limited to, 1:5, 1:5.2, 1:5.4, 1:5.6, 1:5.8, 1:6, or any two of these ratios; the extraction temperature includes, but is not limited to, 61℃, 62℃, 64℃, 66℃, 68℃, 70℃, 72℃, 74℃, 76℃, 78℃, 80℃, or any two of these ratios; and the extraction time includes, but is not limited to, 1.5h, 1.6h, 1.8h, 2.0h, 2.2h, 2.4h, 2.6h, 2.8h, 3h, or any two of these ratios.

[0078] The first extractant is a starch and its derivative solution, with a mass ratio of starch and its derivative solution to coal tar wash oil of 1:3-5. The extraction temperature is 50-70℃, and the extraction time is 2-3 hours.

[0079] For example, the mass ratio of starch and its derivative solutions to coal tar wash oil includes, but is not limited to, 1:3, 1:3.2, 1:3.4, 1:3.6, 1:3.8, 1:4, 1:4.2, 1:4.4, 1:4.6, 1:4.8, 1:5, or any combination thereof; the extraction temperature includes, but is not limited to, 50℃, 52℃, 54℃, 56℃, 58℃, 60℃, 62℃, 64℃, 66℃, 68℃, 70℃, or any combination thereof; the extraction time includes, but is not limited to, 2h, 2.2h, 2.4h, 2.6h, 2.8h, 3h, or any combination thereof.

[0080] When the first extractant is selected according to the above type and corresponding mass ratio, extraction temperature and extraction time, the extraction efficiency can be greatly improved and time costs can be saved while ensuring the final extraction effect.

[0081] Furthermore, in a specific embodiment of the present invention, the second extractant is at least one of water, acidic aqueous solution, alkaline aqueous solution, neutral metal salt solution, and ionic liquid, the volume ratio of the second extractant to the first extract is 1-3:1, the extraction temperature is 60-100℃, and the extraction time is 30-120min.

[0082] Specifically, for example, when the second extractant is selected from the above types, the volume ratio of the second extractant to the first extract is including but not limited to 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1, 3:1, or any two of these ranges; the extraction temperature is including but not limited to 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, or any two of these ranges; the extraction time is including but not limited to 30min, 40min, 50min, 60min, 70min, 80min, 90min, 100min, 110min, 120min, or any two of these ranges.

[0083] It is understandable that when the second extractant is selected from the above-mentioned water, acidic aqueous solution, alkaline aqueous solution, neutral metal salt solution, or ionic liquid, a reasonable selection can be made within the above-mentioned volume ratio, extraction temperature, and extraction time range according to the specific type.

[0084] The second extractant is a solid-liquid extraction resin with a resin loading of 5-15%, an extraction temperature of 60-80℃, and an extraction time of 120-360 min.

[0085] For example, the solid-liquid extraction resin loading includes, but is not limited to, a range of 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or any two of these; the extraction temperature includes, but is not limited to, a range of 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C, 78°C, 80°C, or any two of these; and the extraction time includes, but is not limited to, a range of 120 min, 140 min, 160 min, 180 min, 200 min, 220 min, 240 min, 260 min, 280 min, 300 min, 320 min, 340 min, 360 min, or any two of these.

[0086] When the second extractant is selected according to the above type and corresponding extraction conditions, not only can the efficient separation of nitrogen heterocyclic compounds from the first extractant be achieved and costs be saved, but also the side reactions in the extraction process can be effectively controlled, and the excessive amount of the second extractant can be avoided from affecting the stability of indole and quinoline in the nitrogen heterocyclic compounds.

[0087] Furthermore, in a specific embodiment of the present invention, the starch and its derivative solution includes at least one of the following: starch-water-organic solvent complex solution, carboxymethyl starch aqueous solution, sulfonated starch aqueous solution, phosphate starch aqueous solution, starch acetate aqueous solution, hydroxypropyl starch aqueous solution, and ethylenediamine modified starch aqueous solution;

[0088] The organic solvent includes at least one of ethanol, glycerol, dimethyl sulfoxide, and acetone.

[0089] The aforementioned starch and its derivative solutions exhibit excellent extraction performance due to their high solubility and stability, and their ability to form hydrogen bonds or van der Waals forces with nitrogen heterocyclic compounds. Furthermore, these starch and its derivative solutions demonstrate high recyclability, facilitating reuse, and possess low toxicity and biodegradability, making them environmentally friendly.

[0090] Furthermore, in a specific embodiment of the present invention, the acidic aqueous solution includes at least one of hydrochloric acid and sulfuric acid solution; the alkaline aqueous solution includes at least one of sodium hydroxide solution, potassium hydroxide solution, and triethylamine aqueous solution; the neutral metal salt solution includes at least one of sodium chloride solution, potassium chloride solution, and calcium chloride solution; the ionic liquid includes at least one of ionic liquid containing tetrafluoroborate ions and ionic liquid containing hexafluorophosphate ions; the solid-liquid extraction resin includes at least one of urethane resin, polyamide resin, polyether resin, styrene-difenylstyrene copolymer resin, copper- or molybdenum-loaded chelating resin, resin containing quaternary ammonium salt groups, and resin containing sulfonic acid groups.

[0091] The aforementioned second extractant not only has excellent extraction capabilities, ensuring extraction results, but is also simple and readily available, effectively controlling the cost of obtaining indole and quinoline from coal tar wash oil.

[0092] Furthermore, in a specific embodiment of the present invention, the mass ratio of starch, water and organic solvent in the starch-water-organic solvent compound is 1-30:49-89:10-50.

[0093] For example, the mass ratio of starch, water, and organic solvent includes, but is not limited to, 1:50:49, 1:89:10, 1:49:50, 1:60:39, 5:49:46, 5:88:7, 10:50:40, 10:60:30, 10:70:20, 10:80:10, 20:50:30, 20:60:20, 20:70:10, 30:50:20, 30:60:10, or any combination thereof.

[0094] When starch, water, and organic solvent are combined in the above-mentioned mass ratio to form a compound solution, the extraction effect can be guaranteed while avoiding waste of raw materials.

[0095] Furthermore, in one embodiment of the present invention, the solid-liquid extraction resin has a porosity of 0.5-0.7 and a pore size of 4-6 nm.

[0096] For example, the porosity of the solid-liquid extraction resin includes, but is not limited to, a range of 0.5, 0.55, 0.6, 0.65, 0.7 or any two of these; and the pore size includes, but is not limited to, a range of 4.2 nm, 4.4 nm, 4.6 nm, 4.8 nm, 5.0 nm, 5.2 nm, 5.4 nm, 5.6 nm, 5.8 nm, 6.0 nm or any two of these.

[0097] When the porosity and pore size of the solid-liquid extraction resin are within the above range, it not only has a superior extraction effect, but also has stable physicochemical properties, good selectivity, strong adsorption capacity and easy elution, which can effectively reduce the loss of nitrogen heterocyclic compounds in the second extraction process.

[0098] Furthermore, in one specific embodiment of the present invention, the volume ratio of the nitrogen heterocyclic compound to the ammonium bisulfate is 1:2-4.

[0099] For example, the volume ratio of nitrogen heterocyclic compound to ammonium bisulfate includes, but is not limited to, 1:2, 1:2.2, 1:2.4, 1:2.6, 1:2.8, 1:3, 1:3.2, 1:3.4, 1:3.6, 1:3.8, 1:4, or any combination thereof.

[0100] The above volume ratio not only ensures the full reaction between quinoline and ammonium bisulfate in nitrogen heterocyclic compounds, but also avoids the situation where excessive ammonium bisulfate affects the subsequent reduction of quinoline, thus greatly saving costs.

[0101] Furthermore, in a specific embodiment of the present invention, the indoleation treatment includes the following steps:

[0102] An organic phase is mixed with a directional reaction reagent and a catalyst to carry out a directional synthesis reaction to obtain indole; wherein the directional reaction reagent includes at least one of ethylene glycol, aldehyde compounds, and ketone compounds.

[0103] When the directional reaction reagent is ethylene glycol, the directional synthesis reaction adopts the alkanolamine method to prepare indole. During the reaction, ethylene glycol provides hydroxyl and methylene bridges, and under the action of a catalyst, it undergoes a condensation reaction with aniline in the nitrogen heterocyclic compound to generate indole.

[0104] Specifically, ethylene glycol is mixed with an organic phase and a catalyst, and indole is prepared under certain temperature and pressure. The indole is then separated to obtain the final indole product.

[0105] The present invention does not limit the volume ratio of the organic phase to ethylene glycol, for example 10:1, 10.2:1, 10.4:1, 10.6:1, 10.8:1, 11:1, 11.2:1, 11.4:1, 11.6:1, 11.8:1, 12:1.

[0106] This invention does not limit the type of catalyst; any common catalyst used in the preparation of indole by the alcoholamine method can be selected, such as at least one of complex metal catalysts, supported metal catalysts, and silver-based catalysts.

[0107] This invention does not limit the reaction conditions; any common reaction conditions used in the preparation of indole by the alcohol amine method are acceptable, such as a reaction temperature of 180-350℃ and a reaction pressure of 0.5MPa.

[0108] When the directional reaction reagent is an aldehyde or ketone compound, the directional synthesis reaction adopts the Fisher indole synthesis method. During the reaction, the aldehyde or ketone compound provides a carboxyl group, which condenses with phenylhydrazine in the nitrogen heterocyclic compound under the action of a catalyst to form a phenylhydrazone. The phenylhydrazone does not need to be separated and is immediately isomerized to an enamine under acid catalysis, and then undergoes a [3,3]σ migration reaction to form a diimine. After aromatization, the imine forms a ring to give an acetal amine. Subsequently, the amino group is protonated, releasing ammonia and losing a proton to form an aromatic indole ring.

[0109] Specifically, an organic phase, an aldehyde or ketone compound, and a catalyst are mixed and prepared under specific temperature and pressure conditions to obtain indole. The indole is then separated to obtain the final indole product.

[0110] The present invention does not limit the volume ratio of the organic phase to the aldehyde or ketone compound, for example it can be 10:1, 10.2:1, 10.4:1, 10.6:1, 10.8:1, 11:1, 11.2:1, 11.4:1, 11.6:1, 11.8:1, or 12:1.

[0111] This invention does not limit the type of catalyst; any common catalyst used in Fisher's indole synthesis method can be selected, such as sulfuric acid, hydrochloric acid, phosphoric acid, formic acid, p-toluenesulfonic acid, zinc chloride, titanium chloride, etc.

[0112] This invention does not limit the specific type of aldehyde compound; common aldehyde compounds such as formaldehyde and acetaldehyde can be selected. Similarly, this invention does not limit the specific type of ketone compound, such as acetone, cyclopentanone, and cyclohexanone.

[0113] This invention does not limit the reaction conditions; any common reaction conditions used for the synthesis of Fisher indole are acceptable, such as a reaction temperature of 20-100℃.

[0114] When the directional reaction reagents include ethylene glycol, aldehydes, or ketones, the stepwise synthesis of indole via the alcoholamine method and the Fisher synthesis of indole can be achieved by adjusting the catalyst type and reaction conditions.

[0115] For example, an organic phase, ethylene glycol, aldehydes or ketones, and a catalyst are mixed. The reaction temperature is first controlled at 20-100℃. After a certain reaction time, the reaction system is heated to 180-350℃ and the pressure is adjusted to 0.5MPa. After another certain reaction time, indole is obtained by separation and purification.

[0116] It should be noted that if an acidic solution is used as the catalyst in the directed synthesis reaction, the indole originally present in the organic phase may be converted into indole proton salt. In order to ensure the final indole yield, a certain amount of alkaline solution needs to be added after the reaction to reduce the indole proton salt. After obtaining indole, it can be separated and purified. The specific amount of alkaline solution corresponds to the amount of acidic solution added.

[0117] This invention does not limit the specific type of alkaline solution, such as common sodium hydroxide solution or potassium hydroxide solution.

[0118] The above-mentioned indole treatment process can not only improve the yield of indole by preparing and purifying indole, but also the raw materials required for the above-mentioned indole treatment come from nitrogen heterocyclic compounds, making full use of the effective components in nitrogen heterocyclic compounds and avoiding the introduction of too many external impurities.

[0119] In one specific embodiment of the present invention, the second extraction phase further includes a reducing agent;

[0120] Wherein, when the second extractant is an acidic aqueous solution, the reducing agent is an alkaline solution; when the second extractant is an alkaline aqueous solution, the reducing agent is an inorganic acid solution; when the second extractant is a neutral metal salt solution, the reducing agent is ferrous sulfate; when the second extractant is a resin containing quaternary ammonium salt groups, the reducing agent is the aforementioned inorganic acid solution; when the second extractant is a copper-molybdenum chelating resin, the reducing agent is ferrous sulfate; when the second extractant is a resin containing sulfonic acid groups, the reducing agent is an alkaline solution.

[0121] When the second extractant is of the type described above, the nitrogen heterocyclic compounds in the second extract phase exist in the form of soluble salts. During the solvent separation process, a corresponding reducing agent can be added to reduce the soluble salts of nitrogen heterocyclic compounds in the second extract phase to nitrogen heterocyclic compounds.

[0122] Specifically, in step 3), the second extract phase is mixed with the corresponding reducing agent mentioned above, and after reacting for a certain period of time, solvent separation is performed.

[0123] Using the aforementioned reducing agents not only enables effective reduction, but these reducing agents are also simple and readily available, effectively controlling extraction costs.

[0124] Example 1

[0125] 1) A solvent prepared by cyclodextrin / methylimidazolium salt ionic liquid at a ratio of 1:3 was used as the first extractant and subjected to first extraction treatment with coal tar wash oil at a ratio of 1:8. The temperature was controlled at 60℃, the stirring rate was 350r / min, the stirring time was 3h, and the mixture was allowed to stand for 30min. The solutions after separation were separated by liquid-liquid separation to obtain the first extract and the first raffinate phase.

[0126] 2) The first extract and H2SO4 solution were mixed at a volume ratio of 1:1 for the second extraction treatment. The temperature was controlled at 80℃, stirred for 20 min, and allowed to stand for 30 min. The second extract phase and the second raffinate phase were separated by liquid-liquid separation. The second raffinate phase was filtered and recycled.

[0127] 3) Take the second extract phase and add ferrous sulfate solution as a reducing agent at a volume ratio of 1:2. Then, use a rotary evaporator with the rotation speed controlled at 120 RPM, temperature at 80℃, evaporation time at 30 min, evaporation vacuum at 0.1 MPa, and evaporation condensate temperature at 10℃ to carry out rotary evaporation enrichment to obtain nitrogen heterocyclic compounds.

[0128] 4) Mix the nitrogen heterocyclic compound with ammonium bisulfate solution at a volume ratio of 6:1 and perform a third extraction under stirring to transfer quinoline to the aqueous phase in the form of ammonium bisulfate salt, while other nitrogen heterocyclic compounds remain in the organic phase. After phase separation, an aqueous phase rich in quinoline and an organic phase rich in indole are obtained.

[0129] An indole-rich organic phase was mixed with an ethylene glycol solution at a molar ratio of 1:2.5, and a zinc chloride catalyst was added. The mixture was heated to 90°C and stirred for 1 hour to generate indole and other byproducts. Indole was then separated by fractional distillation and other methods.

[0130] The content of components in coal tar was determined by gas chromatography-mass spectrometry and thermogravimetric analysis according to GB / T 38397-2019. Coal tar wash oil samples were analyzed according to GB / T 38397-2019 to obtain the indole / quinoline content (W1). The final indole / quinoline content (W2) was measured according to GB / T 38397-2019, representing the purity. The mass of indole / quinoline in the wash oil sample (M1) was obtained by multiplying W1 by the mass of W1. The extracted indole / quinoline mass (M2) was obtained by multiplying W2 by the mass of the final product. The yield was calculated by dividing M2 by M1. The purity of indole was 93.1%, with a yield of 97.8%; the purity of quinoline was 95%, with a yield of 92.5%.

[0131] Example 2

[0132] 1) Hydroxypropyl starch aqueous solution was used as the first extractant and was used to perform the first extraction treatment with coal tar wash oil at a mass ratio of 1:4. The temperature was controlled at 55℃, the stirring rate was 250r / min, the stirring was carried out for 2h, and the mixture was allowed to stand for 30min. The solutions after separation were separated by liquid-liquid separation to obtain the first extract and the first raffinate phase.

[0133] 2) The first extract was mixed with triethylamine solution (w = 10%) at a volume ratio of 1.6:1 for a second extraction. The temperature was controlled at 80℃, and the mixture was stirred for 25 min, allowed to stand for 10 min, and then separated using a separatory funnel to obtain the second extract phase and the second raffinate phase. The second raffinate phase was filtered and recycled.

[0134] 3) Add ferrous sulfate solution as a reducing agent to the second extract phase at a volume ratio of 1:2, and then use a rotary evaporator with the rotation speed controlled at 120 RPM, temperature at 80℃, evaporation time at 30 min, evaporation vacuum at 0.1 MPa, and evaporation condensate temperature at 10℃ to enrich the nitrogen heterocyclic compound.

[0135] 4) Mix the nitrogen heterocyclic compound with ammonium bisulfate solution at a volume ratio of 5:1 and perform a third extraction under stirring to transfer quinoline to the aqueous phase in the form of ammonium bisulfate salt, while indole and other nitrogen heterocyclic compounds remain in the organic phase.

[0136] Phase separation yielded an aqueous phase rich in quinoline and an organic phase rich in indole. The organic phase rich in indole was mixed with HCl at a molar ratio of 1:1.2, and copper powder catalyst was added. The mixture was heated to 75°C and stirred for 4 hours to generate an indole and byproduct solution.

[0137] Indole and byproduct solution were separated by distillation. Sodium hydroxide was added to the byproduct solution at a volume ratio of 1:1 and reacted for 30 min. The second indole was obtained by distillation and purified. The second indole and the first indole constitute indole.

[0138] Following the method in Example 1, the purity of indole was found to be 98.9%, with a yield of 98.5%; the purity of quinoline was found to be 98.7%, with a yield of 97.2%.

[0139] Example 3

[0140] 1) Supercritical CO2 was used as the first extractant and was used to perform the first extraction treatment with coal tar wash oil at a flow ratio of 1:6. The temperature was controlled at 35℃ and the pressure at 20MPa. The solutions after separation were separated by liquid-liquid separation to obtain the first extract and the first raffinate.

[0141] 2) Mix the first extract with water at a volume ratio of 1:2 for a second extraction process. Control the temperature at 80℃, stir for 30 min, let stand for 10 min, and then separate the second extract phase and the second raffinate phase by gravity sedimentation.

[0142] 3) The second extract phase was enriched by rotary evaporation using a rotary evaporator with a rotation speed of 120 RPM, a temperature of 80℃, a evaporation time of 30 min, a evaporation vacuum of 0.1 MPa, and a evaporation condensate temperature of 10℃ to obtain nitrogen heterocyclic compounds.

[0143] 4) Mix the nitrogen heterocyclic compound with ammonium bisulfate solution at a volume ratio of 4:1 and perform a third extraction under stirring to transfer quinoline to the aqueous phase in the form of ammonium bisulfate salt, while indole and other nitrogen heterocyclic compounds remain in the organic phase. After phase separation, an aqueous phase rich in quinoline and an organic phase rich in indole are obtained.

[0144] An organic phase rich in indole is mixed with an ethylene glycol solution at a volume ratio of 1:3, heated to 85°C, and reacted for 3.5 h to generate indole and other byproducts. The crude indole is obtained by separation through fractionation or crystallization.

[0145] Following the method in Example 1, the purity of indole was found to be 95.0%, with a yield of 96.2%; the purity of quinoline was found to be 95.1%, with a yield of 90.5%.

[0146] Example 4

[0147] 1) A deep eutectic solvent composed of 1-ethyl-3-methylimidazolium acetate and 1-ethyl-3-methylimidazolium sulfate was used as the first extractant and was used with coal tar wash oil at a volume ratio of 1:5 for the first extraction treatment. The system temperature was controlled at 80℃, stirred for 40 min, and allowed to stand for 15 min. The solutions after separation were separated by liquid-liquid separation to obtain the first extract and the first raffinate phase.

[0148] 2) Mix the first extract with 30% sodium sulfate solution at a volume ratio of 3:1, stir for 15 min, let stand for 5 min, and separate by gravity sedimentation to obtain the second extract phase and the second raffinate phase;

[0149] 3) The second extract phase was added to the reducing agent ferrous sulfate solution at a volume ratio of 1:2. Then, rotary evaporation was carried out using a rotary evaporator with the rotation speed controlled at 120 RPM, temperature at 80℃, evaporation time at 30 min, evaporation vacuum at 0.1 MPa, and evaporation condensate temperature at 10℃ to obtain nitrogen heterocyclic compounds.

[0150] 4) Mix the nitrogen heterocyclic compound with ammonium bisulfate solution at a volume ratio of 1:2 and perform a third extraction under stirring to transfer quinoline to the aqueous phase in the form of ammonium bisulfate salt, while indole and other nitrogen heterocyclic compounds remain in the organic phase. After phase separation, an aqueous phase rich in quinoline and an organic phase rich in indole are obtained.

[0151] An organic phase rich in indole was mixed with an acetone solution at a volume ratio of 1:1 and a copper powder catalyst was added. The mixture was heated to 120°C and reacted for 4 hours to generate indole and other byproducts. The crude indole was obtained by separation by distillation.

[0152] Following the method in Example 1, the purity of indole was 95.1%, with a yield of 86.1%; the purity of quinoline was 90.3%, with a yield of 87.7%.

[0153] Example 5

[0154] 1) The ethylenediamine-modified starch aqueous solution and coal tar wash oil were subjected to a first extraction treatment at a mass ratio of 1:5. The temperature was controlled at 65℃, the stirring rate was 100r / min, the stirring time was 2.5h, and the mixture was allowed to stand for 20min. The solutions after separation were separated by liquid-liquid separation to obtain the first extract and the first raffinate phase.

[0155] 2) The first extract was mixed with an ionic liquid containing tetrafluoroborate ions at a volume ratio of 1:2 for a second extraction treatment. The temperature was controlled at 85℃, stirred for 15 min, and allowed to stand for 25 min. The second extract phase and the second raffinate phase were separated by liquid-liquid separation. The second raffinate phase was filtered and recycled.

[0156] 3) Take the second extract phase and use a rotary evaporator with the rotation speed controlled at 120 RPM, temperature at 80℃, evaporation time at 30 min, evaporation vacuum at 0.1 MPa, and evaporation condensate temperature at 10℃ to enrich the nitrogen heterocyclic compound.

[0157] 4) Mix the nitrogen heterocyclic compound with ammonium bisulfate solution at a volume ratio of 5:1 and perform a third extraction under stirring to transfer quinoline to the aqueous phase in the form of ammonium bisulfate salt, while other nitrogen heterocyclic compounds remain in the organic phase. After phase separation, an aqueous phase rich in quinoline and an organic phase rich in indole are obtained.

[0158] An indole-rich organic phase was mixed with an ethylene glycol solution at a molar ratio of 1:3, and a zinc chloride catalyst was added. The mixture was heated to 95°C and stirred for 1.5 h to generate indole and other byproducts. Indole was then separated by fractional distillation and other methods.

[0159] Following the method in Example 1, the purity of indole was found to be 96.6%, with a yield of 98.5%; the purity of quinoline was found to be 96.0%, with a yield of 93.8%.

[0160] Example 6

[0161] 1) A starch-water-acetone compound solution was used as the first extractant, wherein the mass ratio of starch, water and acetone was 10:60:30. The first extraction was carried out with coal tar wash oil at a mass ratio of 1:5. The temperature was controlled at 65℃, the stirring rate was 300r / min, the stirring time was 2.5h, and the mixture was allowed to stand for 40min. The solutions after separation were separated by liquid-liquid separation to obtain the first extract and the first raffinate phase.

[0162] 2) The first extract was mixed with 10% of a sulfonic acid group-containing resin at a mass ratio of 1:0.1 for a second extraction treatment. The resin used had a porosity of 0.6 and a pore size of 4.5 nm. The temperature was controlled at 70℃. The mixture was stirred for 180 min and allowed to stand for 20 min. The second extract phase and the second raffinate phase were separated by a filtration device. The second raffinate phase was recovered by distillation and recycled.

[0163] 3) Ethanol was added to the second extract phase at a mass ratio of 1:2, and ferrous sulfate solution was added to the reducing agent at a mass ratio of 1:1. Then, rotary evaporation was carried out using a rotary evaporator with the rotation speed controlled at 120 RPM, temperature at 80℃, evaporation time at 30 min, evaporation vacuum at 0.1 MPa, and evaporation condensate temperature at 10℃ to enrich the nitrogen heterocyclic compound.

[0164] 4) Mix the nitrogen heterocyclic compound with ammonium bisulfate solution at a volume ratio of 1:3 and perform a third extraction process under stirring, so that quinoline is transferred to the aqueous phase in the form of ammonium bisulfate salt, while indole and other nitrogen heterocyclic compounds are retained in the organic phase;

[0165] Phase separation yielded an aqueous phase rich in quinoline and an organic phase rich in indole. The organic phase rich in indole was mixed with HCl solution at a molar ratio of 1:1.5, and copper powder catalyst was added. The mixture was heated to 80°C and stirred for 5 hours to generate indole and a solution of byproducts.

[0166] Indole and by-product solution were separated by distillation. Sodium hydroxide was added to the by-product solution at a volume ratio of 1:1 and reacted for 40 min. The second indole was obtained by distillation and purified. The second indole and the first indole constitute indole.

[0167] Following the method in Example 1, the purity of indole was found to be 99.2%, with a yield of 99.1%; the purity of quinoline was found to be 99.0%, with a yield of 98.5%.

[0168] Example 7

[0169] The operation steps in this embodiment are basically the same as those in embodiment 1, except that:

[0170] 1) The first extractant used is an aqueous solution of sulfonated starch.

[0171] Following the method in Example 1, the purity of indole was 97.9%, with a yield of 98.1%; the purity of quinoline was 98.1%, with a yield of 95.1%.

[0172] Example 8

[0173] The operation steps in this embodiment are basically the same as those in embodiment 2, except that:

[0174] 1) The first extractant used is an aqueous solution of carboxymethyl starch.

[0175] Following the method in Example 1, the purity of indole was found to be 98.4%, with a yield of 97.9%; the purity of quinoline was found to be 99.1%, with a yield of 97.9%.

[0176] Example 9

[0177] The operation steps in this embodiment are basically the same as those in embodiment 4, except that:

[0178] 1) The first extractant used is an aqueous solution of phosphate starch.

[0179] Following the method in Example 1, the purity of indole was found to be 96.4%, with a yield of 98.1%; the purity of quinoline was found to be 95.1%, with a yield of 93.0%.

[0180] Comparative Example 1

[0181] The operating steps of this comparative example are basically the same as those of Example 1, except that:

[0182] 1) The first extractant used is sodium hydroxide solution.

[0183] Following the method in Example 1, the purity of indole was found to be 85.6%, with a yield of 85.7%; the purity of quinoline was found to be 89.6%, with a yield of 84.1%.

[0184] Comparative Example 2

[0185] The operating steps of this comparative example are basically the same as those of Example 1, except that:

[0186] 2) The second extractant used is a dichloromethane solution.

[0187] Following the method in Example 1, the purity of indole was found to be 87.8%, with a yield of 84.4%; the purity of quinoline was found to be 89.7%, with a yield of 87.3%.

[0188] Comparative Example 3

[0189] The operating steps of this comparative example are basically the same as those of Example 3, except that:

[0190] 1) The first extractant used is BmimBF4.

[0191] Following the method in Example 1, the purity of indole was found to be 91.7%, with a yield of 81.5%; the purity of quinoline was found to be 89.7%, with a yield of 86.0%.

[0192] Comparative Example 4

[0193] The operating steps of this comparative example are basically the same as those of Example 3, except that:

[0194] 2) The second extractant used is n-butyl ether.

[0195] Following the method in Example 1, the purity of indole was found to be 87.4%, with a yield of 84.5%; the purity of quinoline was found to be 88.1%, with a yield of 86.0%.

[0196] Comparative Example 5

[0197] The operating steps for this comparative example are basically the same as those for comparative example 4, except that:

[0198] 1) The first extractant used was BmimPF6.

[0199] Following the method in Example 1, the purity of indole was found to be 90.7%, with a yield of 82.4%; the purity of quinoline was found to be 86.7%, with a yield of 83.5%.

[0200] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for obtaining indole and quinoline from coal tar wash oil, characterized in that, Includes the following steps: 1) The coal tar wash oil is subjected to a first extraction treatment using a first extractant to obtain a first extract enriched with nitrogen heterocyclic compounds and a first raffinate phase; the first extractant is at least one of supercritical CO2, starch and its derivative solution; 2) The first extract is subjected to a second extraction treatment using a second extractant to obtain a second extract phase and a second raffinate phase enriched with nitrogen heterocyclic compounds; the second extractant is at least one of acidic aqueous solution, alkaline aqueous solution, neutral metal salt solution, and ionic liquid, the volume ratio of the second extractant to the first extract is 1-3:1, the extraction temperature is 60-100℃, and the extraction time is 30-120 min; or, the second extractant is a solid-liquid extraction resin, the loading of the solid-liquid extraction resin is 5-15%, the extraction temperature is 60-80℃, and the extraction time is 120-360 min; The acidic aqueous solution includes at least one of hydrochloric acid and sulfuric acid solution; The alkaline aqueous solution includes at least one of sodium hydroxide solution, potassium hydroxide solution, and triethylamine aqueous solution; The neutral metal salt solution includes at least one of sodium chloride solution, potassium chloride solution, and calcium chloride solution; The ionic liquid includes at least one of the following: ionic liquid containing tetrafluoroborate ions and ionic liquid containing hexafluorophosphate ions. The solid-liquid extraction resin includes at least one of urethane resin, polyamide resin, polyether resin, copper or molybdenum-loaded chelating resin, resin containing quaternary ammonium salt groups, and resin containing sulfonic acid groups. 3) The second extract phase is separated to obtain a nitrogen heterocyclic compound; When the second extractant is a system as follows, a reducing agent is added before separation: When the second extractant is an acidic aqueous solution, the reducing agent is an alkaline solution; When the second extractant is an alkaline aqueous solution, the reducing agent is an inorganic acid solution; When the second extractant is a neutral metal salt solution, the reducing agent is a ferrous sulfate solution; When the second extractant is a resin containing quaternary ammonium salt groups, the reducing agent is an inorganic acid solution; When the second extractant is a copper- or molybdenum-loaded chelating resin, the reducing agent is a ferrous sulfate solution. When the second extractant is a resin containing sulfonic acid groups, the reducing agent is an alkaline solution; 4) The nitrogen heterocyclic compound and ammonium bisulfate are mixed and subjected to a third extraction treatment. The resulting aqueous phase is mixed with an alkaline solution and subjected to a neutralization reaction to obtain quinoline. The organic phase is then subjected to indole treatment to obtain indole.

2. The method according to claim 1, characterized in that, When an ionic liquid is selected as the second extractant, the second extraction process transfers the nitrogen heterocyclic compounds in the first extractant to the second extractant, resulting in a second extract phase enriched with nitrogen heterocyclic compounds and a second raffinate phase. When the second extractant is an acidic aqueous solution, an alkaline aqueous solution, or a neutral metal salt solution, the second extraction process transfers the nitrogen heterocyclic compound to the aqueous phase, achieving phase separation between the nitrogen heterocyclic compound and the first extractant, and obtaining a second extract phase and a second raffinate phase containing soluble salts of the nitrogen heterocyclic compound. When a solid-liquid extraction resin is selected as the second extractant, the second extraction process causes the nitrogen heterocyclic compounds in the first extract to transfer from the first extract to the surface of the solid-liquid extraction resin, and the solid-liquid extraction resin containing nitrogen heterocyclic compounds constitutes the second extraction phase.

3. The method according to claim 1, characterized in that, The first extractant is supercritical CO2, the flow ratio of supercritical CO2 to coal tar wash oil is 1:4-8, and the extraction temperature is 41-50℃. The first extractant is the starch and its derivative solution, the mass ratio of the starch and its derivative solution to the coal tar wash oil is 1:3-5, the extraction temperature is 50-70℃, and the extraction time is 2-3h.

4. The method according to claim 1, characterized in that, The starch and its derivative solutions include at least one of the following: starch-water-organic solvent complex solution, carboxymethyl starch aqueous solution, sulfonated starch aqueous solution, phosphate starch aqueous solution, starch acetate aqueous solution, hydroxypropyl starch aqueous solution, and ethylenediamine modified starch aqueous solution; The organic solvent mentioned herein includes at least one of ethanol, glycerol, dimethyl sulfoxide, and acetone.

5. The method according to claim 4, characterized in that, The mass ratio of starch, water, and organic solvent in the starch-water-organic solvent compound is 1-30:49-89:10-50.

6. The method according to claim 1, characterized in that, The solid-liquid extraction resin has a porosity of 0.5~0.7 and a pore size of 4~5 nm.

7. The method according to claim 1, characterized in that, The volume ratio of the nitrogen heterocyclic compound to the ammonium bisulfate is 1:2-4.

8. The method according to claim 7, characterized in that, The indole treatment includes the following steps: The organic phase was mixed with a directional reaction reagent and a catalyst to carry out a directional synthesis reaction to obtain indole; The directional reaction reagents include at least one of ethylene glycol, aldehydes, and ketones.

Images