A method for complexation and separation of n-alkanes in direct coal liquefaction oil

Abstract

This invention discloses a method for complexing and separating n-alkanes in direct coal liquefaction oil, comprising the following steps: 1) reacting direct coal liquefaction oil with a complexing solution at 40-80°C to obtain a complex suspension; 2) separating the complex suspension to obtain a complex and a filtrate; 3) demulsifying the filtrate at 20-60°C to separate the oil phase and obtain a de-n-alkane oil product; wherein the complexing solution contains a complexing agent, an activator, and a solvent, the complexing agent being one or more of urea and thiourea, and the activator being a low-carbon alcohol. This invention effectively solves the problem of separating n-alkanes and isoalkanes in direct coal liquefaction oil.

Description

Technical Field

[0001] This invention relates to the field of n-alkane separation, and more specifically to a method for complexing and separating n-alkanes from direct coal liquefaction oil. Background Technology

[0002] Solvent oil is one of the main separation products of petroleum. It is an important basic oil used in organic chemical raw materials and industrial production, with wide applications and close ties to daily life, involving national economic sectors such as chemicals, electronics, pharmaceuticals, textiles, and machinery. The naphtha fraction in coal direct liquefaction oil is relatively low, generally between 15-30%, with extremely low sulfur content (below 0.25 mg / kg). The total fraction of cycloalkanes and aromatics can reach over 70%, and it contains no olefins. The presence of n-alkanes increases the pour point of coal direct liquefaction oil, reduces its low-temperature performance, and results in a low octane number (RON around 70). Therefore, effectively separating n-alkanes from coal direct liquefaction oil, lowering the pour point of the de-n-alkane oil, and improving the low-temperature performance of the oil meet the requirements for refining and upgrading coal direct liquefaction oil. Separating n-alkanes from coal direct liquefaction oil yields de-n-alkane oil. Compared to untreated direct coal liquefaction oil, de-n-alkane oil is safer and more environmentally friendly, with lower surface tension, stronger cohesion, easier recovery, higher reusability, better ductility, and lower cloud point, melting point, boiling point, and pour point, making it suitable as a lubricant for various instruments in low-temperature environments. Furthermore, because n-alkanes have poor thermal oxidation stability and are prone to producing peroxides at high temperatures, de-n-alkane oil exhibits superior stability and solubility compared to untreated direct coal liquefaction oil. In addition, de-n-alkane oil also has the advantage of low toxicity. Taking No. 6 solvent oil as an example, its main component is C6 alkanes, with approximately 25% n-hexane content. It is commonly used as a cleaning agent in printing, hardware, electronics, adhesives, rubber, defense industries, paints, chemicals, and greases.

[0003] Direct coal liquefaction oil suffers from drawbacks such as high pour point, low octane number, and low oil quality, which can be improved through n-alkane separation. Currently, the main methods for separating n-alkanes from oil products are molecular sieve methods and urea complexation methods. Molecular sieve adsorption separation of n-alkanes mainly utilizes their adsorption properties to effectively separate n-alkanes from oil products. While domestic molecular sieve dewaxing technology features simple equipment, it suffers from short molecular sieve lifespan, frequent regeneration, inability to operate year-round, high energy consumption, and low liquid wax recovery rates. In contrast, while foreign molecular sieve dewaxing technology offers lower energy consumption and higher purity separated n-alkanes, it involves cumbersome processes, complex equipment, and higher investment. More importantly, compared to urea dewaxing, it cannot produce heavy liquid wax, primarily because long-chain n-alkanes severely restrict their diffusion and adsorption / desorption rates on molecular sieves.

[0004] The urea complexation method relies on the complexation reaction between urea and n-alkanes to separate n-alkanes from oil products. In principle, the urea complexation method is superior to the molecular sieve adsorption method. The urea complexation method is commonly used to separate high-carbon-number n-alkanes from isoalkanes and cycloalkanes with similar carbon numbers. The components involved are relatively simple in molecular type and have large differences in molecular structure. However, the composition of direct coal liquefaction oil is more complex, with some compounds having small differences in molecular structure and similar complexation effects with urea molecules, making separation more difficult. Therefore, current technologies have not effectively separated n-alkanes from direct coal liquefaction oil. Summary of the Invention

[0005] In view of this, the main objective of the present invention is to provide a method for complexation and separation of n-alkanes in direct coal liquefaction oil, which effectively solves the problem of the difficulty in separating n-alkanes and isoalkanes in direct coal liquefaction oil.

[0006] To achieve the above-mentioned objective, this invention provides a method for the complexation and separation of n-alkanes in direct coal liquefaction oil, comprising the following steps:

[0007] 1) Coal direct liquefaction oil and complexing solution are subjected to complexation reaction at 40-80℃ to obtain complex suspension;

[0008] 2) Separate the complex suspension to obtain the complex and filtrate;

[0009] 3) The filtrate is placed at 20-60℃ to demulsify and separate the oil phase to obtain the de-n-alkane oil product;

[0010] The complexing solution comprises a complexing agent, an activator, and a solvent. The complexing agent is one or more of urea and thiourea, and the activator is a low-carbon alcohol.

[0011] Further, the activator is selected from any one of methanol, ethanol, ethylene glycol, isopropanol, glycerol, or a mixture thereof; preferably, it is selected from any one of methanol, ethanol, isopropanol, or a mixture thereof.

[0012] Furthermore, the solvent is water, preferably deionized water.

[0013] Further, the mass ratio of the complexing agent, activator, and solvent is (1-8):(1-8):1, preferably (1-5):(1-5):1, and more preferably (1-3):(1-3):1, for example 1:1:1, 1:1.5:1, 1:2:1, 1:2.5:1, 1:3:1, 3:1:1, 2.5:1:1, 2:1:1, 1.5:1:1, etc. Better complexation and separation effects can be achieved within the above mass ratio range.

[0014] Furthermore, the mass ratio of the complexing solution to coal direct liquefaction oil is (2-10):1, preferably (2-8):1, and more preferably (3-6):1, for example 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, etc. Better complexing and separation effects can be achieved within the above mass ratio range.

[0015] Furthermore, the temperature of the complexation reaction is preferably 40-60°C, such as 40°C, 45°C, 50°C, 55°C, 60°C, etc.; the complexation reaction time is 10-300 min, more preferably 30-300 min, and even more preferably 30-150 min.

[0016] Furthermore, the method further includes: after the complexation reaction is completed, cooling the reactants to 25-50°C, more preferably 25-35°C, such as 26°C, 28°C, 30°C, 32°C, etc., within the above temperature range so that the non-n-alkane components that have not undergone complexation reaction can be effectively separated from the complexed phase.

[0017] Furthermore, the demulsification temperature is preferably 30-60°C, such as 35°C, 40°C, 45°C, 50°C, 55°C, etc., to achieve better separation of n-alkanes and complexing agents; the demulsification time is 1-24h, preferably 3-24h, and more preferably 6-12h.

[0018] Furthermore, the temperature during the separation of the oil phase is 10–50°C to achieve efficient separation of the complexing agent from the oil phase; preferably, it is 20–50°C, more preferably, it is 20–40°C, such as 25°C, 30°C, 35°C, etc.

[0019] Furthermore, the n-alkane content in the coal direct liquefaction oil is 10–30 wt.%.

[0020] Furthermore, the n-alkane content in the de-n-alkane oil product is 5-20 wt.%, preferably 5-10 wt.%.

[0021] Furthermore, the method also includes step 4): hot water hydrolysis of the complex obtained in step 2) to separate the oil phase and obtain a n-alkane-rich oil product, thereby further realizing the efficient utilization of resources.

[0022] Furthermore, in steps 3) and 4), the aqueous phase is separated to obtain a solution containing a complexing agent. The aqueous phase mainly consists of an aqueous urea solution and also contains an alcohol activator. Preferably, the complexing agent solution obtained above can be reused as a complexing solution by adding appropriate components, thus realizing the recycling of complexing agents such as urea.

[0023] Furthermore, the hot water decomposition temperature is 40–100°C to achieve effective decomposition of the complex and improve the decomposition rate and efficiency; preferably, it is 50–90°C, more preferably, it is 60–80°C, such as 65°C, 70°C, 75°C, etc.

[0024] In a specific implementation, the hot water decomposition method is as follows: the complex obtained in step 2) is added to a container with water and placed in a constant temperature water bath for hot water decomposition.

[0025] Furthermore, the hot water desiccation time is 5-60 minutes, preferably 10-60 minutes, and even more preferably 10-30 minutes.

[0026] Furthermore, the n-alkane content in the n-alkane-rich oil is 5–40 wt.%, preferably 25–30 wt.%.

[0027] Further, in step 3), a demulsifier is added to the filtrate to demulsify; the demulsifier is one or a mixture of aqueous demulsifier and oil-based demulsifier, preferably an aqueous demulsifier.

[0028] Furthermore, the amount of the demulsifier added is 100-2000 ppm, which can achieve efficient demulsification and obtain the best oil-water separation effect under the above minimum dosage; preferably, it is 100-1000 ppm, and more preferably, it is 100-500 ppm.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] This invention involves a complexation reaction between direct coal liquefaction oil and a complexing solution. The complexing solution comprises a complexing agent, an activator, and a solvent. The complexing agent is one or more of urea and thiourea, and the activator is a low-carbon alcohol. During the complexation reaction at 40-80°C, the complexing agent can complex with n-alkanes in the direct coal liquefaction oil to form complex crystals, while isoalkanes cannot complex with the complexing agent, thereby separating the n-alkanes from the direct coal liquefaction oil. To increase the reaction rate and shorten the time to reach equilibrium, a low-carbon alcohol solution is added to the reaction system as an activator. The low-carbon alcohol solution has high polarity and low viscosity, which can promote the dissolution of complexing agents such as urea. Furthermore, the low-carbon alcohol solution can also promote the contact between the complexing agents such as urea and the n-alkanes in the oil phase, accelerating the reaction rate. Meanwhile, the low-carbon alcohol solution can dilute the liquid phase, allowing the generated complex to float freely in the liquid phase and aggregate into spheres, thus obtaining a complex suspension. The complex suspension is then separated to obtain the complex and the filtrate. The filtrate is demulsified at 20-60℃ to separate the oil phase, thus obtaining the de-n-alkane oil product.

[0031] Therefore, this invention effectively solves the problem of separating n-alkanes and isoalkanes in oil products, and can be widely applied to the removal or purification of n-alkanes for other purposes, such as lowering the pour point of oil products and refining paraffin wax. This invention efficiently separates n-alkanes from direct coal liquefaction oil, overcoming the defects of high pour point, low octane number, and low oil quality in raw direct coal liquefaction oil.

[0032] In addition, the present invention provides a method for recovering and recycling n-alkane-rich oil and urea solution. By decomposing the complex, the n-alkane-rich oil and urea solution are recovered, thereby further achieving the goal of efficient resource utilization and green chemical industry.

[0033] Other features and advantages of the present invention will be described in detail through the following specific embodiments. Detailed Implementation

[0034] The present application will be further described below with reference to the embodiments. However, the present application is not limited to the listed embodiments, but should also include equivalent improvements and modifications of the technical solutions defined in the appended claims.

[0035] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0036] Unless otherwise specified, experimental methods in the following examples are generally performed under standard conditions or as recommended by the manufacturer. Percentages and parts are weight percentages and parts by weight.

[0037] Unless otherwise specified, all experimental materials and reagents used in the following examples are available from commercially available sources.

[0038] The coal direct liquefaction oil originates from the Ordos branch of China Shenhua Coal-to-Oil Chemical Co., Ltd. The n-alkane content is approximately 10-20 wt.%.

[0039] The gas chromatograph-mass spectrometer is an Agilent 5975.

[0040] The present invention will be described in detail below through embodiments:

[0041] Example 1

[0042] Weigh 82 parts urea, 90 parts isopropanol, 45 parts water, and 54 parts coal direct liquefaction oil into a flask, insert a stirrer, and place the flask in a 50°C constant temperature water bath for complexation reaction under stirring. After 60 min of reaction, set the temperature of the constant temperature water bath to 28°C to cool the complex suspension. While stirring, allow the temperature to cool naturally (at room temperature of 26°C) to 28°C, then remove the flask. Filter using a heated Buchner funnel and suction flask. After filtration, collect the filter cake and continue processing the filtrate. Place the filtrate in a 50°C constant temperature water bath for demulsification for 10 h. After demulsification, an oil-water two-phase mixture is obtained. Separate the mixture using a separatory funnel at room temperature of 26°C to obtain the de-n-alkane oil product (oil phase). The product was weighed, and the yield was calculated to be 70%. The product was then analyzed by gas chromatography-mass spectrometry to obtain its composition, and the content of n-alkane in the treated n-alkane-free oil was found to be 6.0%.

[0043] Example 2

[0044] Weigh 70 parts urea, 90 parts isopropanol, 45 parts water, and 60 parts coal direct liquefaction oil into a flask, insert a stirrer, and place the flask in a 50°C constant temperature water bath for complexation reaction under stirring. After 60 min of reaction, set the temperature of the constant temperature water bath to 28°C to cool the complex suspension. While stirring, allow the temperature to cool naturally (at room temperature of 26°C) to 28°C, then remove the flask. Filter using a heated Buchner funnel and suction flask. After filtration, collect the filter cake and continue processing the filtrate. Place the filtrate in a 50°C constant temperature water bath for demulsification for 10 h. After demulsification, an oil-water two-phase mixture is obtained. Separate the mixture using a separatory funnel at room temperature of 26°C to obtain the processed de-n-alkane oil product. The product was weighed, and the yield was calculated to be 62%. The product was then analyzed by gas chromatography-mass spectrometry to obtain its composition, and the content of n-alkane in the treated n-alkane-free oil was found to be 6.0%.

[0045] Example 3

[0046] 82 parts urea, 90 parts isopropanol, 33 parts water, and 54 parts coal direct liquefaction oil were weighed and placed in a flask. A stirrer was inserted, and the flask was placed in a 50°C constant-temperature water bath for complexation reaction under stirring. After 60 minutes of reaction, the temperature of the constant-temperature water bath was set to 28°C to cool the complexation suspension. The flask was removed after the temperature naturally cooled to 28°C (at room temperature of 26°C) under stirring. The mixture was then filtered using a heated Buchner funnel and a suction flask. After filtration, the filter cake was collected, and the filtrate was further processed. The filtrate was placed in a 50°C constant-temperature water bath for demulsification for 10 hours. After demulsification, an oil-water two-phase mixture was obtained. The mixture was separated using a separatory funnel at room temperature of 26°C to obtain the processed de-n-alkane oil product. The product was weighed, and the yield was calculated to be 58%. The product was then analyzed by gas chromatography-mass spectrometry to obtain its composition, and the content of n-alkane in the treated n-alkane-free oil was found to be 6.9%.

[0047] Example 4

[0048] 82 parts urea, 102 parts isopropanol, 45 parts water, and 54 parts coal direct liquefaction oil were weighed and placed in a flask. A stirrer was inserted, and the flask was placed in a 50°C constant temperature water bath for complexation reaction under stirring. After 60 minutes of reaction, the temperature of the constant temperature water bath was set to 28°C to cool the complexation suspension. While stirring, the temperature was allowed to cool naturally (at room temperature of 26°C) to 28°C, and then the flask was removed. The mixture was filtered using a heated Buchner funnel and a suction flask. After filtration, the filter cake was collected, and the filtrate was further processed. The filtrate was placed in a 50°C constant temperature water bath for demulsification for 10 hours. After demulsification, an oil-water two-phase mixture was obtained. The mixture was separated using a separatory funnel at room temperature of 26°C to obtain the processed de-n-alkane oil product. The product was weighed, and the yield was calculated to be 72%. The product was then analyzed by gas chromatography-mass spectrometry to obtain its composition, and the content of n-alkane in the treated n-alkane-free oil was found to be 6.3%.

[0049] Example 5

[0050] 82 parts urea, 90 parts isopropanol, 45 parts water, and 54 parts coal direct liquefaction oil were weighed and placed in a flask. A stirrer was inserted, and the flask was placed in a 40°C constant-temperature water bath for complexation reaction under stirring. After 60 minutes of reaction, the temperature of the constant-temperature water bath was set to 28°C to cool the complexation suspension. The flask was removed after the temperature naturally cooled to 28°C (at room temperature of 26°C) under stirring. The mixture was then filtered using a heated Buchner funnel and a suction flask. After filtration, the filter cake was collected, and the filtrate was further processed. The filtrate was placed in a 50°C constant-temperature water bath for demulsification for 10 hours. After demulsification, an oil-water two-phase mixture was obtained. The mixture was separated using a separatory funnel at room temperature of 26°C to obtain the processed de-n-alkane oil product. The product was weighed, and the yield was calculated to be 61%. The product was then analyzed by gas chromatography-mass spectrometry to obtain its composition, and the content of n-alkane in the treated n-alkane-free oil was found to be 6.1%.

[0051] Example 6

[0052] 82 parts urea, 90 parts isopropanol, 45 parts water, and 54 parts coal direct liquefaction oil were weighed and placed in a flask. A stirrer was inserted, and the flask was placed in a 60°C constant temperature water bath for complexation reaction under stirring. After 60 minutes of reaction, the temperature of the constant temperature water bath was set to 28°C to cool the complexation suspension. While stirring, the temperature was allowed to cool naturally (at room temperature of 26°C) to 28°C, and then the flask was removed. The mixture was filtered using a heated Buchner funnel and a suction flask. After filtration, the filter cake was collected, and the filtrate was further processed. The filtrate was placed in a 50°C constant temperature water bath for demulsification for 10 hours. After demulsification, an oil-water two-phase mixture was obtained. The mixture was separated using a separatory funnel at room temperature of 26°C to obtain the processed de-n-alkane oil product. The product was weighed, and the yield was calculated to be 62%. The product was then analyzed by gas chromatography-mass spectrometry to obtain its composition, and the content of n-alkane in the treated n-alkane-free oil was found to be 5.7%.

[0053] Example 7

[0054] 82 parts urea, 90 parts isopropanol, 45 parts water, and 54 parts coal direct liquefaction oil were weighed and placed in a flask. A stirrer was inserted, and the flask was placed in a 50°C constant temperature water bath for complexation reaction under stirring. After 30 minutes of reaction, the temperature of the constant temperature water bath was set to 28°C to cool the complexation suspension. While stirring, the temperature was allowed to cool naturally (at room temperature of 26°C) to 28°C, and then the flask was removed. The mixture was filtered using a heated Buchner funnel and a suction flask. After filtration, the filter cake was collected, and the filtrate was further processed. The filtrate was placed in a 50°C constant temperature water bath for demulsification for 10 hours. After demulsification, an oil-water two-phase mixture was obtained. The mixture was separated using a separatory funnel at room temperature of 26°C to obtain the processed de-n-alkane oil product. The product was weighed, and the yield was calculated to be 63%. The product was then analyzed by gas chromatography-mass spectrometry to obtain its composition, and the content of n-alkane in the treated n-alkane-free oil was found to be 5.9%.

[0055] Example 8

[0056] 82 parts urea, 90 parts isopropanol, 45 parts water, and 54 parts coal direct liquefaction oil were weighed and placed in a flask. A stirrer was inserted, and the flask was placed in a 50°C constant temperature water bath for complexation reaction under stirring. After reacting for 150 min, the temperature of the constant temperature water bath was set to 28°C to cool the complexation suspension. While stirring, the temperature was allowed to cool naturally (at room temperature of 26°C) to 28°C, and then the flask was removed. The mixture was filtered using a heated Buchner funnel and a suction flask. After filtration, the filter cake was collected, and the filtrate was further processed. The filtrate was placed in a 50°C constant temperature water bath for demulsification for 10 h. After demulsification, an oil-water two-phase mixture was obtained. The mixture was separated using a separatory funnel at room temperature of 26°C to obtain the processed de-n-alkane oil product. The product was weighed, and the yield was calculated to be 54%. The product was then analyzed by gas chromatography-mass spectrometry to obtain its composition, and the content of n-alkane in the treated n-alkane-free oil was found to be 6.1%.

[0057] Example 9

[0058] 82 parts urea, 90 parts isopropanol, 45 parts water, and 54 parts coal direct liquefaction oil were weighed and placed in a flask. A stirrer was inserted, and the flask was placed in a 50°C constant temperature water bath for complexation reaction under stirring. After 60 minutes of reaction, the temperature of the constant temperature water bath was set to 28°C to cool the complexation suspension. While stirring, the temperature was allowed to cool naturally (at room temperature of 26°C) to 28°C, and then the flask was removed. The mixture was filtered using a heated Buchner funnel and a suction flask. After filtration, the filter cake was collected, and the filtrate was further processed. 300 ppm of the aqueous demulsifier polyoxyethylene propylene glycol ether was added to the filtrate, and the mixture was placed in a 50°C constant temperature water bath for demulsification for 10 hours. After demulsification, an oil-water two-phase mixture was obtained. The mixture was separated using a separatory funnel at room temperature of 26°C to obtain the processed de-n-alkane oil. The product was weighed, and the yield was calculated to be 74%. The product was then analyzed by gas chromatography-mass spectrometry to obtain its composition, and the content of n-alkane in the treated n-alkane-free oil was found to be approximately 5.5%.

[0059] Example 10

[0060] Following the method of Example 9, the filter cake collected after filtration was washed with petroleum ether with a boiling range of 60-90°C. The amount of petroleum ether used was 3 ml / g of coal direct liquefaction oil feedstock. The yield of the de-n-alkane oil product was significantly increased to 96.82%. At the same time, the n-alkane content in the paraffin by-product after decomposition was increased from 28.91% before washing to 63.33%.

[0061] Comparative Example 1

[0062] 10 parts urea, 10 parts isopropanol, 50 parts water, and 50 parts coal direct liquefaction oil were weighed and placed in a flask. A stirrer was inserted, and a complexation reaction was carried out under stirring at room temperature (25℃). After reacting for 20 minutes, the flask was removed. The mixture was filtered using a heated Buchner funnel and a suction flask. After filtration, the filter cake was collected, and the filtrate was further processed. The filtrate was placed in a 35℃ constant temperature water bath for demulsification for 10 hours. After demulsification, an oil-water two-phase mixture was obtained. The mixture was separated at room temperature (25℃) using a separatory funnel to obtain the processed oil phase product. The product was weighed, and the yield of the oil phase product was calculated to be 65%. The product was then analyzed using gas chromatography-mass spectrometry to obtain its composition, revealing that the content of n-alkanes in the processed de-n-alkane oil was 16.7%.

[0063] In Comparative Example 1 above, the separation effect of n-alkane was poor due to the unsuitable ratio of complexing agent, activator and solvent.

[0064] In summary, this invention solves the problem of effectively separating long-chain n-alkanes from isoalkanes through urea complexation of n-alkanes, thereby efficiently separating n-alkanes from coal direct liquefaction oil and improving the defects of high pour point, low octane number, and low oil quality in raw coal direct liquefaction oil. Furthermore, this invention provides a method for recovering n-alkane-rich oil and recycling urea solution, further achieving the goals of efficient resource utilization and green chemical engineering. Based on the typical n-alkane composition of feedstock oils, it is easy to design urea complexation separation processes for other purposes by changing the reaction conditions, such as lowering the oil pour point or refining paraffin wax. This invention greatly expands the application of urea complexation separation of n-alkanes in oil refining.

[0065] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is impossible to exhaustively list all embodiments here. All obvious variations or modifications derived from the technical solutions of the present invention are within the spirit and scope of the present invention.

Claims

1. A method for complexation and separation of n-alkane in direct coal liquefaction oil, characterized in that: Includes the following steps: 1) Coal direct liquefaction oil and complexing solution are subjected to complexation reaction at 40-80℃ to obtain complex suspension; after the complexation reaction is completed, the reactants are cooled to 25-50℃; 2) Separate the complex suspension to obtain the complex and filtrate; 3) The filtrate is placed at 20-60℃ to demulsify and separate the oil phase to obtain the de-n-alkane oil product; The complexing solution comprises a complexing agent, an activator, and a solvent. The complexing agent is one or more of urea and thiourea, and the activator is a low-carbon alcohol. The mass ratio of the complexing agent, activator, and solvent is (1~8):(1~8):

1.

2. The method for complexation and separation of n-alkane according to claim 1, characterized in that: The activator is selected from any one of methanol, ethanol, ethylene glycol, isopropanol, glycerol, or a mixture thereof; and / or, the solvent is water.

3. The method for complexation and separation of n-alkane according to claim 2, characterized in that: The activator is selected from any one of methanol, ethanol, isopropanol, or a mixture thereof.

4. The method for complexation and separation of n-alkane according to claim 1, characterized in that: The mass ratio of the complexing agent, activator, and solvent is (1~5):(1~5):1; and / or, The mass ratio of the complexed solution to direct coal liquefaction oil is (2~10):

1.

5. The method for complexation and separation of n-alkane according to claim 4, characterized in that: The mass ratio of the complexing agent, activator, and solvent is (1~3):(1~3):1; and / or, The mass ratio of the complexed solution to direct coal liquefaction oil is (2~8):

1.

6. The method for complexation and separation of n-alkane according to claim 5, characterized in that: The mass ratio of the complexed solution to direct coal liquefaction oil is (3~6):

1.

7. The method for complexation and separation of n-alkane according to any one of claims 1-6, characterized in that: Step 1) The temperature of the complexation reaction is 40~60℃; the time of the complexation reaction is 10~300 min.

8. The method for complexation and separation of n-alkane according to claim 7, characterized in that: The complexation reaction time in step 1) is 30~300 min.

9. The method for complexation and separation of n-alkane according to claim 8, characterized in that: The complexation reaction time in step 1) is 30~150 min.

10. The method for complexation and separation of n-alkane according to any one of claims 1-6, characterized in that: After the complexation reaction is complete, the reactants are cooled to 25-35°C.

11. The method for complexation and separation of n-alkane according to any one of claims 1-6, characterized in that: Step 3) The demulsification temperature is 30~60℃; the demulsification time is 1~24 h; and / or, The temperature during the separation of the oil phase is 10~50℃.

12. The method for complexation and separation of n-alkane according to claim 11, characterized in that: Step 3) The demulsification time is 3~24 h; and / or, The temperature during the separation of the oil phase is 20~50℃.

13. The method for complexation and separation of n-alkane according to claim 12, characterized in that: Step 3) The demulsification time is 6-12 hours; and / or, The temperature during the separation of the oil phase is 20~40℃.

14. The method for complexation and separation of n-alkane according to claim 1, characterized in that: The method further includes step 4): hot water hydrolysis of the complex obtained in step 2) to separate the oil phase and obtain a n-alkane-rich oil product.

15. The method for complexation and separation of n-alkane according to claim 14, characterized in that: In steps 3) and 4), the aqueous phase is separated to obtain a solution containing a complexing agent.

16. The method for complexation and separation of n-alkane according to claim 14, characterized in that: The hot water decomposition temperature is 40~100℃; and / or, The hot water desiccation time is 5-60 minutes.

17. The method for complexation and separation of n-alkane according to claim 16, characterized in that: The hot water decomposition temperature is 50~90℃; and / or, The hot water desiccation time is 10~60 min.

18. The method for complexation and separation of n-alkane according to claim 17, characterized in that: The hot water decomposition temperature is 60~80℃; and / or, The hot water desiccation time is 10~30 min.

19. The method for complexation and separation of n-alkane according to claim 1, characterized in that: In step 3), a demulsifier is added to the filtrate to demulsify; the demulsifier is one or a mixture of aqueous and oil-based demulsifiers; and / or, The amount of demulsifier added is 100~2000 ppm.

20. The method for complexation and separation of n-alkane according to claim 19, characterized in that: The demulsifier is an aqueous demulsifier; and / or, The amount of demulsifier added is 100~1000 ppm.

21. The method for complexation and separation of n-alkane according to claim 20, characterized in that: The amount of the demulsifier added is 100~500 ppm.