Method for simultaneously extracting phenolic compounds and nitrogen-containing compounds from naphthalene oil

Abstract

The invention discloses a method for simultaneously extracting phenolic compounds and nitrogen-containing compounds from naphthalene oil, belongs to the technical field of coal chemical industry, and can solve the problems of high process cost, cross contamination, poor recyclability, complex operation and the like in the existing extraction of phenolic compounds and nitrogen-containing compounds. The method comprises the following steps: heating and mixing a hydrogen bond acceptor and a hydrogen bond donor to prepare a eutectic solvent; mixing typical components in the naphthalene oil according to a certain proportion to obtain model naphthalene oil; mixing the eutectic solvent with model naphthalene oil according to a certain molar ratio, and performing extraction operation; adding a back-extractant into the extract phase to carry out back-extraction recovery on the phenolic compound and the nitrogen-containing compound; and carrying out rotary evaporation on the deep eutectic solvent, and recovering to obtain the regenerated deep eutectic solvent. According to the invention, when the hydrogen bond acceptor is choline chloride, the extraction efficiency of phenolic compounds (m-cresol) and nitrogen-containing compounds (quinoline) is not very high. When the hydrogen bond acceptor is tetrabutylammonium bromide or tetraethylammonium chloride, the extraction efficiency of the phenolic compound and the extraction efficiency of the nitrogen-containing compound are both 92% or above. The eutecticevaporate solvent used in the method is a novel green solvent, is green, environment-friendly, low in toxicity, low in preparation cost, low in raw material cost, stable in property and easy to recover, can realize efficient extraction of phenolic compounds and nitrogen-containing compounds, and has good economic benefits.

Description

Technical Field

[0001] The invention belongs to the separation field of coal chemical industry and petrochemical industry, and specifically relates to a method for simultaneously extracting phenolic compounds and nitrogen-containing compounds from naphthalene oil, which can obtain valuable phenolic compound and nitrogen-containing compound resources, is beneficial to the deep processing and utilization of coal tar, and is green and environmentally friendly. Background Art

[0002] Coal tar is a viscous liquid byproduct with a pungent odor produced during the dry distillation and pyrolysis of coal. Coal tar contains a large number of monomer compounds with a high melting point, but after dissolving in each other to form a low eutectic mixture, coal tar can remain liquid even at room temperature. Naphthalene oil is a 210-230°C fraction cut from coal tar by distillation, and its yield accounts for about 10% to 13% of the total amount of coal tar. Its components mainly contain 70% to 80% naphthalene, 4% to 6% phenolic substances, 3% to 5% heavy pyridine base, and the rest is naphthalene oil. On the one hand, phenolic compounds (such as metacresol) and nitrogen-containing compounds (such as quinoline) in naphthalene oil are important chemical raw materials and intermediates, and are widely used in chemical fields such as medicine, pesticides, printing and dyeing, and rubber; on the other hand, nitrogen oxides produced by nitrogen-containing compounds in oil products during processing will cause environmental pollution. In the hydrogenation process, nitrogen atoms will cause catalyst poisoning, reduce hydrogenation efficiency, and affect product stability. Phenolic compounds in oil products will increase hydrogen consumption and production costs during hydrogenation, and affect catalyst activity and oil stability, which is not conducive to the storage and transportation of oil products. Therefore, separating phenols and nitrogen-containing substances from naphthalene oil has extremely high economic benefits, and creates good reaction conditions for the subsequent deep processing of naphthalene oil, thereby improving the quality of the oil.

[0003] For the separation of phenolic compounds and nitrogen-containing compounds in naphthalene oil, alkali washing and acid washing are currently commonly used methods in industry, and there are problems such as large solvent consumption, high cost, wastewater discharge, and equipment corrosion. Hydrofining, traditional organic solvent extraction, supercritical extraction, ionic liquid extraction, etc. have also been used for the separation of phenolic compounds and nitrogen-containing compounds in oil. While achieving certain effects, there are also problems such as high process cost, cross contamination, poor recyclability, and complex operation. CN103937522A patent adds a complexing separation agent to coal tar for complexing reaction, and then achieves the purpose of separating phenolic compounds and nitrogen-containing compounds by distillation and back extraction. The method is simple in process, environmentally friendly, and does not produce phenolic wastewater, but the cost of using reagents is high. The dephenolization solvent used in CN112811500A is composed of an extractant, a co-extractant, and an antioxidant, but the use of a large amount of organic solvents makes the dephenolization efficiency low, and fails to effectively solve the problem of neutral oil entrainment. CN102746221A uses ethanol as a supercritical solvent to extract quinoline from washing oil. The present invention uses an acidic salt solution instead of sulfuric acid to enrich quinoline, which greatly reduces the production cost and makes the entire process simple and controllable, but the energy consumption is large and the impurity content of the produced quinoline is large.

[0004] As a new type of green solvent, deep eutectic solvent (DES) has the characteristics of designability, good thermal stability, low green environmental toxicity, simple preparation process, and low raw material price, and has attracted extensive attention from researchers. CN109593540B provides a method for separating phenolic compounds based on deep eutectic solvent, but it is lacking in terms of solvent selectivity, stability, operating conditions, and economy. CN109181747B proposes a deep eutectic solvent prepared by using polyethylene glycol dicarboxylic acid and quaternary ammonium salt, which can effectively remove indole and quinoline from simulated coal tar at the same time, but the high cost of raw materials limits its application in large-scale production.

[0005] Compared with other methods, the deep eutectic solvent used in this scheme can form hydrogen bonds with hydrogen on the hydroxyl group of the phenolic compound (meta-cresol), and the H atoms in the deep eutectic solvent combine with the N atoms on the nitrogen-containing compound (quinoline) to form an acid-base reaction, which can extract the phenolic compound and the nitrogen-containing compound at the same time. Based on this, the method used in the present invention is simple to operate, mild in conditions, cheap, and environmentally friendly, laying a foundation for achieving efficient and clean separation of phenolic compounds and nitrogen-containing compounds. Summary of the invention

[0006] In order to overcome the complex problems of large solvent usage, high cost, wastewater discharge, equipment corrosion, etc. in the existing coal tar extraction and separation of phenolic compounds and nitrogen-containing compounds, in view of this, the present invention provides a deep eutectic solvent for simultaneously extracting phenolic compounds and nitrogen-containing compounds from naphthalene oil. The deep eutectic solvent used is non-toxic, biodegradable, simple to synthesize, low in energy consumption, low in cost, green and environmentally friendly, and can be recycled and reused, and has good economic benefits.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A method for simultaneously extracting phenolic compounds and nitrogen-containing compounds from naphthalene oil comprises the following steps:

[0009] (1) mixing a hydrogen bond acceptor and a hydrogen bond donor in a molar ratio of 1:1-1:5, stirring at 70-80° C. for 30-60 min until a uniform transparent liquid is formed, thereby preparing a deep eutectic solvent;

[0010] (2) mixing typical components in naphthalene oil in a certain proportion in a container, stirring at 20-30° C. for 30-40 min to obtain a model naphthalene oil;

[0011] (3) mixing the model naphthalene oil and the deep eutectic solvent in a molar ratio of 1:2-1:4, stirring at a temperature of 30-45° C. for 60 min, and performing an extraction operation;

[0012] (4) After the extraction is completed, the mixture is allowed to stand for 1 hour to separate the layers, and the upper and lower phases are separated to obtain a phenol / nitrogen compound-depleted naphthalene oil phase and a phenol / nitrogen compound-rich deep eutectic solvent phase;

[0013] (5) After the extraction process is completed, the lower DES phase is taken out as much as possible, a certain amount of deionized water is added to dilute the DES phase, and the mass ratio of the phenolic compounds and nitrogen-containing compounds in the stripping agent and the extraction phase is 10:1, and then the stripping agent is added and stirred at 30° C. for 30 minutes, and then allowed to stand for 1 hour to separate the layers, thereby obtaining a low eutectic solvent phase depleted of phenol / nitrogen compounds and a stripping phase rich in phenol / nitrogen compounds;

[0014] (6) Rotary evaporation of the low eutectic solvent to recover the regenerated low eutectic solvent, and repeating the extraction operation.

[0015] Preferably, in step (1), the hydrogen bond acceptor is choline chloride, tetrabutylammonium bromide, tetraethylammonium chloride, and the hydrogen bond donor is ethylenediamine, oxalic acid (dihydrate), malonic acid, methanesulfonic acid, p-toluenesulfonic acid (monohydrate), and oxalic acid (anhydrous).

[0016] Preferably, the model naphthalene oil in step (2) is aromatic hydrocarbons (methylnaphthalene, xylene), phenolic compounds (meta-cresol), and nitrogen-containing compounds (quinoline), and the main components of the model naphthalene oil are xylene (20%), methylnaphthalene (66% to 70%), meta-cresol (3% to 7%), and quinoline (3% to 7%).

[0017] Preferably, the composition ratio of the simulated naphthalene oil in step (2) is 3% meta-cresol + 3% quinoline + 74% methylnaphthalene + 20% xylene, 5% meta-cresol + 5% quinoline + 70% methylnaphthalene + 20% xylene, 7% meta-cresol + 7% quinoline + 66% methylnaphthalene + 20% xylene.

[0018] Preferably, the stripping agent in step (5) is petroleum ether.

[0019] Preferably, the rotary evaporation temperature in step (6) is 60° C. and the rotary evaporation time is 45 min.

[0020] Through the above technical scheme, compared with the existing technology, the technical scheme of the present invention uses hydrogen bond acceptors and hydrogen bond donors to prepare a low eutectic solvent, and through extraction, back extraction, rotary evaporation and other processes, a green process is provided for extracting phenolic compounds and nitrogen-containing compounds from naphthalene oil at the same time, which is simple to operate and environmentally friendly. Avoid using a large amount of acid and alkali to prevent corrosion to the equipment. The low eutectic solvent used in the present invention has good thermal stability and is biodegradable; the preparation process is simple and easy to regenerate and reuse. Specific implementation plan

[0021] The following will be combined with examples to further describe in detail the simultaneous extraction of phenolic compounds and nitrogen-containing compounds in naphthalene oil by the deep eutectic solvent provided by the present invention. The described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention. All other embodiments made by other personnel without making creative development premise belong to the scope of protection of the present invention.

[0022] Example 1

[0023] The present invention provides a method for simultaneously extracting phenolic compounds and nitrogen-containing compounds from naphthalene oil, comprising the following steps:

[0024] (1) Choline chloride and ethylenediamine were mixed in a molar ratio of 1:5, placed in an oil bath, and vigorously stirred at 80° C. for 50 min until a uniform transparent liquid was formed, thereby preparing a deep eutectic solvent;

[0025] (2) Weigh 7 g of methylnaphthalene, 0.5 g of m-cresol, 0.5 g of quinoline, and 2 g of xylene into a conical flask with a lid, stir for 30 min at 25° C., and prepare a model naphthalene oil with an initial concentration of 5% (5% m-cresol + 5% quinoline + 70% methylnaphthalene + 20% xylene);

[0026] (3) The total molar amount of quinoline and meta-cresol in the oil phase was mixed with the molar amount of DES in a ratio of 1:2, and placed in a 30°C water bath with magnetic stirring for 60 minutes. After the extraction was completed, the mixture was allowed to stand for 1 hour. The upper and lower phases were separated to obtain a naphthalene oil phase dephenolized and quinolined and a low eutectic solvent phase rich in phenol and quinoline. The upper oil phase was then taken and tested by gas chromatography. The extraction efficiency of meta-cresol was calculated to be 58.46%, and the extraction efficiency of quinoline was 6.66%.

[0027] Example 2

[0028] The present invention provides a method for simultaneously extracting phenolic compounds and nitrogen-containing compounds from naphthalene oil, comprising the following steps:

[0029] (1) Choline chloride and oxalic acid (dihydrate) were mixed in a molar ratio of 1:1, placed in an oil bath, and vigorously stirred at 70° C. for 30 min until a uniform transparent liquid was formed, thereby preparing a deep eutectic solvent;

[0030] (2) Weigh 7 g of methylnaphthalene, 0.5 g of m-cresol, 0.5 g of quinoline, and 2 g of xylene into a conical flask with a lid, stir for 30 min at 25° C., and prepare a model naphthalene oil with an initial concentration of 5% (5% m-cresol + 5% quinoline + 70% methylnaphthalene + 20% xylene);

[0031] (3) The total molar amount of quinoline and meta-cresol in the oil phase was mixed with the molar amount of DES in a ratio of 1:2, and placed in a 30°C water bath with magnetic stirring for 60 minutes. After the extraction was completed, the mixture was allowed to stand for 1 hour. The upper and lower phases were separated to obtain a naphthalene oil phase dephenolized and quinolined and a low eutectic solvent phase rich in phenol and quinoline. The upper oil phase was then taken and tested by gas chromatography. The extraction efficiency of meta-cresol was calculated to be 48.96%, and the extraction efficiency of quinoline was 85.92%.

[0032] Example 3

[0033] The present invention provides a method for simultaneously extracting phenolic compounds and nitrogen-containing compounds from naphthalene oil, comprising the following steps:

[0034] (1) Choline chloride and malonic acid were mixed in a molar ratio of 1:2, placed in an oil bath, and vigorously stirred at 80° C. for 40 min until a uniform transparent liquid was formed, thereby preparing a deep eutectic solvent;

[0035] (2) Weigh 7 g of methylnaphthalene, 0.5 g of m-cresol, 0.5 g of quinoline, and 2 g of xylene into a conical flask with a lid, stir for 30 min at 25° C., and prepare a model naphthalene oil with an initial concentration of 5% (5% m-cresol + 5% quinoline + 70% methylnaphthalene + 20% xylene);

[0036] (3) The total molar amount of quinoline and meta-cresol in the oil phase was mixed with the molar amount of DES in a ratio of 1:2, and placed in a 30°C water bath with magnetic stirring for 60 minutes. After the extraction was completed, the mixture was allowed to stand for 1 hour. The upper and lower phases were separated to obtain a naphthalene oil phase dephenolized and quinolined and a low eutectic solvent phase rich in phenol and quinoline. The upper oil phase was then taken and tested by gas chromatography. The extraction efficiency of meta-cresol was calculated to be 68.60%, and the extraction efficiency of quinoline was 80.89%.

[0037] Example 4

[0038] The present invention provides a method for simultaneously extracting phenolic compounds and nitrogen-containing compounds from naphthalene oil, comprising the following steps:

[0039] (1) Choline chloride and methanesulfonic acid are mixed in a molar ratio of 1:2, placed in an oil bath, and vigorously stirred at 80° C. for 45 minutes until a uniform transparent liquid is formed, thereby preparing a deep eutectic solvent;

[0040] (2) Weigh 7 g of methylnaphthalene, 0.5 g of m-cresol, 0.5 g of quinoline, and 2 g of xylene into a conical flask with a lid, stir for 30 min at 25° C., and prepare a model naphthalene oil with an initial concentration of 5% (5% m-cresol + 5% quinoline + 70% methylnaphthalene + 20% xylene);

[0041] (3) The total molar amount of quinoline and meta-cresol in the oil phase was mixed with the molar amount of DES in a ratio of 1:2, and placed in a 30°C water bath with magnetic stirring for 60 minutes. After the extraction was completed, the mixture was allowed to stand for 1 hour. The upper and lower phases were separated to obtain a naphthalene oil phase dephenolized and quinolined and a low eutectic solvent phase rich in phenol and quinoline. The upper oil phase was then taken and tested by gas chromatography. The extraction efficiency of meta-cresol was calculated to be 72.39%, and the extraction efficiency of quinoline was 87.49%.

[0042] Example 5

[0043] The present invention provides a method for simultaneously extracting phenolic compounds and nitrogen-containing compounds from naphthalene oil, comprising the following steps:

[0044] (1) Choline chloride and p-toluenesulfonic acid (monohydrate) are mixed in a molar ratio of 1:1, placed in an oil bath, and vigorously stirred at 80° C. for 40 min until a uniform transparent liquid is formed, thereby preparing a deep eutectic solvent;

[0045] (2) Weigh 7 g of methylnaphthalene, 0.5 g of m-cresol, 0.5 g of quinoline, and 2 g of xylene into a conical flask with a lid, stir for 30 min at 25° C., and prepare a model naphthalene oil with an initial concentration of 5% (5% m-cresol + 5% quinoline + 70% methylnaphthalene + 20% xylene);

[0046] (3) The total molar amount of quinoline and meta-cresol in the oil phase was mixed with the molar amount of DES in a ratio of 1:2, and placed in a 30°C water bath with magnetic stirring for 60 minutes. After the extraction was completed, the mixture was allowed to stand for 1 hour. The upper and lower phases were separated to obtain a naphthalene oil phase dephenolized and quinolined and a low eutectic solvent phase rich in phenol and quinoline. The upper oil phase was then taken and tested by gas chromatography. The extraction efficiency of meta-cresol was calculated to be 88.36%, and the extraction efficiency of quinoline was calculated to be 93.20%.

[0047] Example 6

[0048] The present invention provides a method for simultaneously extracting phenolic compounds and nitrogen-containing compounds from naphthalene oil, comprising the following steps:

[0049] (1) Tetrabutylammonium bromide and methanesulfonic acid are mixed in a molar ratio of 1:3, placed in an oil bath, and vigorously stirred at 80° C. for 60 min until a uniform transparent liquid is formed, thereby preparing a deep eutectic solvent;

[0050] (2) Weigh 7 g of methylnaphthalene, 0.5 g of m-cresol, 0.5 g of quinoline, and 2 g of xylene into a conical flask with a lid, stir for 30 min at 25° C., and prepare a model naphthalene oil with an initial concentration of 5% (5% m-cresol + 5% quinoline + 70% methylnaphthalene + 20% xylene);

[0051] (3) The total molar amount of quinoline and meta-cresol in the oil phase was mixed with the molar amount of DES in a ratio of 1:2, and placed in a 30°C water bath with magnetic stirring for 60 minutes. After the extraction was completed, the mixture was allowed to stand for 1 hour. The upper and lower phases were separated to obtain a naphthalene oil phase dephenolized and quinolined and a low eutectic solvent phase rich in phenol and quinoline. The upper oil phase was then taken and tested by gas chromatography. The extraction efficiency of meta-cresol was calculated to be 92.73%, and the extraction efficiency of quinoline was calculated to be 97.77%.

[0052] Example 7

[0053] The present invention provides a method for simultaneously extracting phenolic compounds and nitrogen-containing compounds from naphthalene oil, comprising the following steps:

[0054] (1) Tetraethylammonium chloride and methanesulfonic acid are mixed in a molar ratio of 1:1, placed in an oil bath, and vigorously stirred at 80° C. for 40 min until a uniform transparent liquid is formed, thereby preparing a deep eutectic solvent;

[0055] (2) Weigh 7 g of methylnaphthalene, 0.5 g of m-cresol, 0.5 g of quinoline, and 2 g of xylene into a conical flask with a lid, stir for 30 min at 25° C., and prepare a model naphthalene oil with an initial concentration of 5% (5% m-cresol + 5% quinoline + 70% methylnaphthalene + 20% xylene);

[0056] (3) The total molar amount of quinoline and meta-cresol in the oil phase was mixed with the molar amount of DES in a ratio of 1:2, and placed in a 30°C water bath with magnetic stirring for 60 minutes. After the extraction was completed, the mixture was allowed to stand for 1 hour. The upper and lower phases were separated to obtain a naphthalene oil phase dephenolized and quinolined and a low eutectic solvent phase rich in phenol and quinoline. The upper oil phase was then taken and tested by gas chromatography. The extraction efficiency of meta-cresol was calculated to be 98.18%, and the extraction efficiency of quinoline was 98.37%.

[0057] Example 8

[0058] The present invention provides a method for simultaneously extracting phenolic compounds and nitrogen-containing compounds from naphthalene oil, comprising the following steps:

[0059] (1) Tetraethylammonium chloride and p-toluenesulfonic acid (monohydrate) are mixed in a molar ratio of 1:1, placed in an oil bath, and vigorously stirred at 80° C. for 40 min until a uniform transparent liquid is formed, thereby preparing a deep eutectic solvent;

[0060] (2) Weigh 7 g of methylnaphthalene, 0.5 g of m-cresol, 0.5 g of quinoline, and 2 g of xylene into a conical flask with a lid, stir for 30 min at 25° C., and prepare a model naphthalene oil with an initial concentration of 5% (5% m-cresol + 5% quinoline + 70% methylnaphthalene + 20% xylene);

[0061] (3) The total molar amount of quinoline and meta-cresol in the oil phase was mixed with the molar amount of DES in a ratio of 1:2, and placed in a 30°C water bath with magnetic stirring for 60 minutes. After the extraction was completed, the mixture was allowed to stand for 1 hour. The upper and lower phases were separated to obtain a naphthalene oil phase dephenolized and quinolined and a low eutectic solvent phase rich in phenol and quinoline. The upper oil phase was then taken and tested by gas chromatography. The extraction efficiency of meta-cresol was calculated to be 96.99%, and the extraction efficiency of quinoline was calculated to be 97.30%.

[0062] Example 9

[0063] The present invention provides a method for simultaneously extracting phenolic compounds and nitrogen-containing compounds from naphthalene oil, comprising the following steps:

[0064] (1) Tetraethylammonium chloride and malonic acid are mixed in a molar ratio of 1:2, placed in an oil bath, and vigorously stirred at 80° C. for 40 min until a uniform transparent liquid is formed, thereby preparing a deep eutectic solvent;

[0065] (2) Weigh 7 g of methylnaphthalene, 0.5 g of m-cresol, 0.5 g of quinoline, and 2 g of xylene into a conical flask with a lid, stir for 30 min at 25° C., and prepare a model naphthalene oil with an initial concentration of 5% (5% m-cresol + 5% quinoline + 70% methylnaphthalene + 20% xylene);

[0066] (3) The total molar amount of quinoline and meta-cresol in the oil phase was mixed with the molar amount of DES in a ratio of 1:2, and placed in a 30°C water bath with magnetic stirring for 60 minutes. After the extraction was completed, the mixture was allowed to stand for 1 hour. The upper and lower phases were separated to obtain a naphthalene oil phase dephenolized and quinolined and a low eutectic solvent phase rich in phenol and quinoline. The upper oil phase was then taken and tested by gas chromatography. The extraction efficiency of meta-cresol was calculated to be 95.60%, and the extraction efficiency of quinoline was calculated to be 96.40%.

[0067] Example 10

[0068] The present invention provides a method for simultaneously extracting phenolic compounds and nitrogen-containing compounds from naphthalene oil, comprising the following steps:

[0069] (1) Tetrabutylammonium bromide and oxalic acid (anhydrous) were mixed in a molar ratio of 1:2, placed in an oil bath, and vigorously stirred at 80° C. for 35 minutes until a uniform transparent liquid was formed, thereby preparing a deep eutectic solvent;

[0070] (2) Weigh 7.4 g of methylnaphthalene, 0.3 g of m-cresol, 0.3 g of quinoline, and 2 g of xylene into a conical flask with a lid, stir for 30 min at 25° C., and prepare a model naphthalene oil with an initial concentration of 3% (3% m-cresol + 3% quinoline + 74% methylnaphthalene + 20% xylene);

[0071] (3) The total molar amount of quinoline and meta-cresol in the oil phase was mixed with the molar amount of DES in a ratio of 1:3, and placed in a 45°C water bath with magnetic stirring for 60 minutes. After the extraction was completed, the mixture was allowed to stand for 1 hour. The upper and lower phases were separated to obtain a naphthalene oil phase dephenolized and quinolined and a low eutectic solvent phase rich in phenol and quinoline. The upper oil phase was then taken and tested by gas chromatography. The extraction efficiency of meta-cresol was calculated to be 92.02%, and the extraction efficiency of quinoline was 99.90%.

[0072] Embodiment 11

[0073] The present invention provides a method for simultaneously extracting phenolic compounds and nitrogen-containing compounds from naphthalene oil, comprising the following steps:

[0074] (1) Tetrabutylammonium bromide and oxalic acid (anhydrous) were mixed in a molar ratio of 1:2, placed in an oil bath, and vigorously stirred at 80° C. for 35 minutes until a uniform transparent liquid was formed, thereby preparing a deep eutectic solvent;

[0075] (2) Weigh 7 g of methylnaphthalene, 0.5 g of m-cresol, 0.5 g of quinoline, and 2 g of xylene into a conical flask with a lid, stir for 30 min at 25° C., and prepare a model naphthalene oil with an initial concentration of 5% (5% m-cresol + 5% quinoline + 70% methylnaphthalene + 20% xylene);

[0076] (3) The total molar amount of quinoline and meta-cresol in the oil phase was mixed with the molar amount of DES in a ratio of 1:4, and placed in a 45°C water bath with magnetic stirring for 60 minutes. After the extraction was completed, the mixture was allowed to stand for 1 hour. The upper and lower phases were separated to obtain a naphthalene oil phase dephenolized and quinolined and a low eutectic solvent phase rich in phenol and quinoline. The upper oil phase was then taken and tested by gas chromatography. The extraction efficiency of meta-cresol was calculated to be 96.86%, and the extraction efficiency of quinoline was calculated to be 99.92%.

[0077] Example 12

[0078] The present invention provides a method for simultaneously extracting phenolic compounds and nitrogen-containing compounds from naphthalene oil, comprising the following steps:

[0079] (1) Tetrabutylammonium bromide and oxalic acid (anhydrous) were mixed in a molar ratio of 1:2, placed in an oil bath, and vigorously stirred at 80° C. for 35 minutes until a uniform transparent liquid was formed, thereby preparing a deep eutectic solvent;

[0080] (2) Weigh 6.6 g of methylnaphthalene, 0.7 g of m-cresol, 0.7 g of quinoline, and 2 g of xylene into a conical flask with a lid, stir for 30 min at 25° C., and prepare a model naphthalene oil with an initial concentration of 7% (7% m-cresol + 7% quinoline + 66% methylnaphthalene + 20% xylene);

[0081] (3) The total molar amount of quinoline and meta-cresol in the oil phase was mixed with the molar amount of DES in a ratio of 1:2, and placed in a 45°C water bath with magnetic stirring for 60 minutes. After the extraction was completed, the mixture was allowed to stand for 1 hour. The upper and lower phases were separated to obtain a naphthalene oil phase dephenolized and quinolined and a low eutectic solvent phase rich in phenol and quinoline. The upper oil phase was then taken and tested by gas chromatography. The extraction efficiency of meta-cresol was calculated to be 97.84%, and the extraction efficiency of quinoline was calculated to be 99.94%.

[0082] Example 13

[0083] The present invention provides a method for simultaneously extracting phenolic compounds and nitrogen-containing compounds from naphthalene oil, comprising the following steps:

[0084] (1) Tetraethylammonium chloride and oxalic acid (dihydrate) were mixed in a molar ratio of 1:1, placed in an oil bath, and vigorously stirred at 80° C. for 30 min until a uniform transparent liquid was formed, thereby preparing a deep eutectic solvent;

[0085] (2) Weigh 7 g of methylnaphthalene, 0.5 g of m-cresol, 0.5 g of quinoline, and 2 g of xylene into a conical flask with a lid, stir for 30 min at 25° C., and prepare a model naphthalene oil with an initial concentration of 5% (5% m-cresol + 5% quinoline + 70% methylnaphthalene + 20% xylene);

[0086] (3) The total molar amount of quinoline and meta-cresol in the oil phase was mixed with the molar amount of DES in a ratio of 1:2, and the mixture was placed in a 30°C water bath with magnetic stirring for 60 min. After the extraction was completed, the mixture was allowed to stand for 1 h. The upper and lower phases were separated to obtain a naphthalene oil phase dephenolized and quinolined and a low eutectic solvent phase rich in phenol and quinoline. The upper oil phase was then taken and tested by gas chromatography. The extraction efficiency of meta-cresol was calculated to be 94.40%, and the extraction efficiency of quinoline was calculated to be 98.37%;

[0087] (4) adding petroleum ether as a stripping agent to the extraction phase in a ratio of 10:1 between the stripping agent and the phenolic compounds and the nitrogen-containing compounds in the extraction phase, stirring for 30 min at 30° C., standing for 1 h to separate the layers, and repeating the operation 3 times to obtain a low eutectic solvent phase depleted of phenol and quinoline and a stripping phase rich in phenol and quinoline;

[0088] (5) The low eutectic solvent is rotary evaporated to recover the regenerated low eutectic solvent, and the above extraction process is repeated three times to obtain the extraction rates of m-cresol of 88.76%, 78.39% and 64.25% respectively; the extraction rates of quinoline of 97.05%, 90.20% and 67.47% respectively.

[0089] The different conditions and related data of Examples 1-13 refer to Table 1

[0090] Table 1. Relevant conditions and data of Examples 1-13

[0091]

[0092] Note: The extraction time in Examples 1-13 is 60 min.

[0093] According to the data in Table 1, according to the comparison of the data of Examples 1-5 and 6-13, when the hydrogen bond acceptor is choline chloride, the extraction efficiency of phenolic compounds and nitrogen-containing compounds is not very high. When the hydrogen bond acceptor is tetrabutylammonium bromide, although the extraction efficiency of phenolic compounds and nitrogen-containing compounds is high, the bromide ion will greatly increase the viscosity of DES, and the longer chain length will cause DES to dissolve more neutral oil components. When the hydrogen bond acceptor is tetraethylammonium chloride, the extraction efficiency of phenolic compounds and nitrogen-containing compounds is above 92%. Compared with choline chloride, tetraethylammonium chloride is surrounded by four ethyl groups, and tetraethyl sodium chloride can form a stronger interaction force, and the steric hindrance is small, and it can form a more stable hydrogen bond with the hydrogen bond donor, strengthen the acidity of the organic acid, and thus achieve efficient extraction of phenolic compounds and nitrogen-containing compounds.

[0094] Through the test of the above specific implementation scheme, the present invention provides a natural and efficient low eutectic solvent for simultaneously extracting phenolic compounds and nitrogen-containing compounds from naphthalene oil, which has a short reaction equilibrium time, cheap raw material preparation, simple operation and separation process, and its constituent substances are all natural components, non-toxic and pollution-free, and has good dephenolization and denitrification effects.

[0095] The embodiments in this specification mainly focus on the selection and mixing ratio of hydrogen bond acceptors and hydrogen bond donors in the deep eutectic solvent. Due to the different structures and compositions of hydrogen bond donors and hydrogen bond acceptors, the deep eutectic solvents formed have great differences in the dephenolization and denitrification effects on the model naphthalene oil. Therefore, similar parts between the embodiments can be referenced to each other.

[0096] The above is only a specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make various modifications, equivalent replacements, improvements, etc. to the above embodiments within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the above embodiments will not constitute a limitation to the present invention, and its limitation scope should be the widest scope consistent with the principles and innovations disclosed in the present technical solution.

Claims

1. A method for simultaneously extracting phenolic compounds and nitrogen-containing compounds from naphthalene oil, characterized in that: The method comprises the following steps: (1) mixing a hydrogen bond acceptor and a hydrogen bond donor in a molar ratio of 1:1-1:5, stirring at 70-80° C. for 30-60 min until a uniform transparent liquid is formed, thereby preparing a deep eutectic solvent; (2) mixing typical components in naphthalene oil in a certain proportion in a container, stirring at 20-30° C. for 30-40 min to obtain a model naphthalene oil; (3) mixing the model naphthalene oil and the deep eutectic solvent in a molar ratio of 1:2-1:4, stirring at a temperature of 30-45° C. for 60 min, and performing an extraction operation; (4) After the extraction is completed, the mixture is allowed to stand for 1 hour to separate the layers, and the upper and lower phases are separated to obtain a phenol / nitrogen compound-depleted naphthalene oil phase and a phenol / nitrogen compound-rich deep eutectic solvent phase; (5) After the extraction process is completed, the lower DES phase is taken out as much as possible, a certain amount of deionized water is added to dilute the DES phase, and the mass ratio of the phenolic compounds and nitrogen-containing compounds in the stripping agent and the extraction phase is 10:1, and then the stripping agent is added and stirred at 30° C. for 30 minutes, and then allowed to stand for 1 hour to separate the layers, thereby obtaining a low eutectic solvent phase for removing phenol / nitrogen compounds and a stripping phase rich in phenol / nitrogen compounds; (6) Rotary evaporation of the low eutectic solvent to recover the regenerated low eutectic solvent, and repeating the extraction operation.

2. A method for extracting phenolic compounds and nitrogen-containing compounds from naphthalene oil simultaneously according to claim 1, wherein the hydrogen bond acceptor in the step (1) is choline chloride, tetrabutylammonium bromide, or tetraethylammonium chloride, and the hydrogen bond donor is ethylenediamine, oxalic acid (dihydrate), malonic acid, methylsulfonic acid, p-toluenesulfonic acid (monohydrate), or oxalic acid (anhydrous).

3. A method for extracting phenolic compounds and nitrogen-containing compounds from naphthalene oil simultaneously according to claim 1, wherein the model naphthalene oil in the step (2) is aromatic hydrocarbons (methylnaphthalene, xylene), phenolic compounds (meta-cresol), and nitrogen-containing compounds (quinoline), and the model naphthalene oil main components are xylene (20%), methylnaphthalene (66% to 70%), meta-cresol (3% to 7%), and quinoline (3% to 7%).

4. A method for extracting phenolic compounds and nitrogen-containing compounds from naphthalene oil simultaneously according to claim 1, wherein the simulated naphthalene oil in the step (2) consists of 3% meta-cresol + 3% quinoline + 74% methylnaphthalene + 20% xylene, 5% meta-cresol + 5% quinoline + 70% methylnaphthalene + 20% xylene, and 7% meta-cresol + 7% quinoline + 66% methylnaphthalene + 20% xylene.

5. A method for simultaneously extracting phenolic compounds and nitrogen-containing compounds from naphthalene oil according to claim 1, wherein the stripping agent in the step (5) is petroleum ether.

6. A method for simultaneously extracting phenolic compounds and nitrogen-containing compounds from naphthalene oil according to claim 1, wherein the rotary evaporation temperature in the step (6) is 60° C. and the rotary evaporation time is 45 min.

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