CN110857392B

CN110857392B - Method for separating alkaline nitride from heavy oil

Info

Publication number: CN110857392B
Application number: CN201810966413.3A
Authority: CN
Inventors: 赖婷婷; 王威; 刘泽龙; 汪燮卿
Original assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Current assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Priority date: 2018-08-23
Filing date: 2018-08-23
Publication date: 2022-01-04
Anticipated expiration: 2038-08-23
Also published as: CN110857392A

Abstract

The invention discloses a method for separating alkaline nitrides from heavy oil, which comprises the following steps: (1) in an alkane solvent, heavy oil containing alkaline nitride and transition metal salt are subjected to complex reaction, a complex reaction product is subjected to solid-liquid separation, and a precipitate obtained by separation is washed by the alkane solvent; (2) and (2) mixing the precipitate obtained in the step (1) with an organic solvent to obtain a mixed solution, carrying out alkali washing on the mixed solution, separating to obtain an organic phase, and washing the organic phase with water. The separation method of the invention has good selectivity to the alkaline nitride, the yield of the alkaline nitride is high, and the obtained alkaline nitride contains less impurities such as hydrocarbon, sulfide and the like.

Description

Method for separating alkaline nitride from heavy oil

Technical Field

The invention relates to a method for separating alkaline nitride from heavy oil.

Background

The mass fraction of nitrogen element in petroleum is approximately in the range of 0.05-0.6%, and the content of nitrogen element increases with the boiling point of the fraction, so that the nitride in petroleum is mainly distributed in heavy oil. The different forms of nitrides in petroleum can be classified into basic nitrides and non-basic nitrides, wherein basic nitrides refer to nitrides that can be titrated by perchloric acid. Alkaline nitrides tend to adsorb onto the catalyst acid center during heavy oil processing, poisoning the catalyst. The alkaline nitride in the heavy oil is unstable, and is easy to condense to generate coke to inactivate the catalyst, so that the product distribution is poor, and the conversion rate is reduced. Therefore, the composition distribution of the basic nitride in the heavy oil is very important to the heavy oil processing. However, the mass fraction of basic nitrogen compounds in heavy oil is low, and the structural and compositional characteristics of the basic nitrogen compounds in heavy oil can be fully understood after efficient separation.

At present, the separation of the basic nitride mainly comprises an acid extraction method, an acid modified silica gel column chromatography, a coordination column chromatography and a cation exchange chromatography. However, most of these methods are suitable for light distillate oil, and the separation efficiency is not high, such as acid extraction can only separate some alkaline nitrides with smaller molecular weight, the nitrides separated by coordination column chromatography have overlapping phenomenon with other components, and the adsorption loss of nitrides on the stationary phase is large. In addition, such methods have many steps, take a long time, and have a small sample throughput. Heavy oil has a high boiling point and many heteroatom compounds, and the method cannot effectively separate the basic nitride from the heavy oil.

Disclosure of Invention

The invention aims to overcome the problems in the prior art and provide a method for separating alkaline nitrides in heavy oil, which can be used for separating alkaline nitrides in heavy oil from different sources and has the advantages of large sample handling capacity, high separation efficiency, less impurities such as hydrocarbons, sulfides and the like in the obtained alkaline nitrides, good repeatability and the like.

In order to achieve the above object, the present invention provides a method for separating basic nitrogen compounds from heavy oil, wherein the method comprises the steps of:

(1) in an alkane solvent, heavy oil containing alkaline nitride and transition metal salt are subjected to complex reaction, a complex reaction product is subjected to solid-liquid separation, and a precipitate obtained by separation is washed by the alkane solvent;

(2) and (2) mixing the precipitate obtained in the step (1) with an organic solvent to obtain a mixed solution, carrying out alkali washing on the mixed solution, separating to obtain an organic phase, and washing the organic phase with water.

According to the method for separating the basic nitride from the heavy oil, the complex is formed by the transition metal salt and the basic nitride, so that the basic nitride is separated from the complex matrix, and then the basic nitride in the complex is dissociated by combining with subsequent alkali washing, so that the basic nitride is effectively separated from the heavy oil. Compared with the prior art, the separation method has the advantages of higher separation efficiency, larger sample treatment amount, less cross among components and the like, and the method has better selectivity on the alkaline nitride, high yield of the alkaline nitride and less impurities such as hydrocarbon, sulfide and the like in the obtained alkaline nitride. The method can be used as a method for removing the alkaline nitride in the heavy oil and a method for separating the alkaline nitride, and meets the requirement of a subsequent analysis technology on the purity of the alkaline nitride. In addition, the separation method provided by the invention is economic and efficient, simple in equipment, easy to implement, less in time consumption and suitable for various heavy oil samples.

Drawings

FIG. 1 is a flow diagram illustrating the separation of basic nitrogen compounds from heavy oil according to one embodiment of the present invention;

FIG. 2 is a substance type distribution diagram of an oil sample before separation and basic nitride obtained after separation in example 1 of the present invention.

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

The inventor of the invention develops a method for effectively separating alkaline nitride in heavy oil by adopting a chemical reaction method through research, the method has high separation efficiency, good selectivity to the alkaline nitride, high yield of the alkaline nitride, and less impurities such as hydrocarbon, sulfide and the like in the obtained alkaline nitride. The inventors of the present invention first form a complex of heavy oil containing basic nitride with a transition metal salt in an alkane solvent so that the basic nitride can be sufficiently complexed out to obtain a complex precipitate. And then dissolving and dispersing the complex precipitate into an organic solvent, and fully washing with an alkaline solution to destroy coordinate bonds of nitrogen in the complex, so that the alkaline nitride is dissociated out, and the separation and purification of the alkaline nitride and the separation of the alkaline nitride in the heavy oil are realized.

According to the invention, the method for separating the alkaline nitride from the heavy oil comprises the following steps:

In the present invention, the heavy oil containing basic nitrogen compounds may be various heavy oils known in the art, and for example, may be one or more selected from the group consisting of heavy crude oil, straight run vacuum wax oil, hydrogenated wax oil, coker wax oil, deasphalted oil, atmospheric residue and vacuum residue. The nitrides in different forms in the heavy oil can be divided into basic nitrides and non-basic nitrides, and the total nitrogen (including the basic nitrides and the non-basic nitrides) element content in the heavy oil is generally 10-10000 mug/g.

According to the present invention, in the step (1), the complexing reaction of the heavy oil containing basic nitride and the transition metal salt is performed in the alkane solvent, and preferably, in order to make the complexing reaction more sufficient, that is, to make the basic nitride and the transition metal salt in the heavy oil sufficiently complex to form a complex precipitate, the heavy oil containing basic nitride is mixed with the alkane solvent to sufficiently dissolve the heavy oil, and then the transition metal salt is added to the mixture of the heavy oil containing basic nitride and the alkane solvent to make the heavy oil and the transition metal salt perform the complexing reaction with the basic nitride. The alkane solvent is selected and used in the amount sufficient to dissolve heavy oil and facilitate the complexing of the basic nitride and the transition metal salt. Preferably, the alkane solvent is selected from one or more of saturated alkanes of C5-C8 and petroleum ether, wherein specific examples of the saturated alkanes of C5-C8 can be, for example: n-pentane, n-hexane, n-heptane, n-octane. Preferably, the alkane solvent used in the complexation reaction is used in an amount (volume) of 1 to 10 times the volume of the heavy oil.

According to the present invention, in the step (1), the transition metal salt may be selected from various metal salts capable of forming a coordinate bond with nitrogen of the basic nitride, so that the basic nitride in the heavy oil can be sufficiently complexed out to form a complex precipitate. Preferably, the transition metal salt is a halide salt of at least one transition metal of groups IB, IIB, IVB and VIII of the periodic Table of the elements. More preferably, specific examples of the transition metal salt may be selected from, for example: one or more of copper chloride, zinc chloride, iron chloride, titanium tetrachloride, mercury chloride, cadmium chloride, cobalt chloride, nickel chloride, copper bromide, zinc bromide, iron bromide, titanium tetrabromide, mercury bromide, cadmium bromide, cobalt bromide, nickel bromide, copper iodide, zinc iodide, titanium tetraiodide, mercury iodide, cadmium iodide, cobalt iodide, and nickel iodide, and most preferably, the transition metal salt is selected from one or more of iron chloride, zinc chloride, and titanium tetrachloride. Although the basic nitride can be complex-precipitated as long as the transition metal salt is added, in order to allow the basic nitride in the heavy oil to be sufficiently complexed out to form a complex precipitate for better achieving the object of separating the basic nitride of the present invention, it is preferable that the transition metal salt is used in an amount (by mass) of 0.01 to 5%, preferably 1 to 3%, based on the mass of the heavy oil in step (1).

According to the present invention, in the step (1), the conditions of the complexation reaction generally include a reaction temperature and a reaction time, wherein the reaction temperature may be from room temperature to 150 ℃, preferably from 60 ℃ to 120 ℃, and the reaction time may be appropriately adjusted according to the reaction temperature, and for example, the reaction time may be from 0.5 to 24 hours, preferably from 1 to 10 hours. In order to make the complexation reaction more sufficient, the complexation reaction is preferably performed under stirring. More preferably, the method of the complexation reaction comprises: the alkane solvent is heated under reflux with a mixture of heavy oil containing basic nitride and a transition metal salt.

According to the present invention, in the step (1), the solid-liquid separation of the complex reaction product may be carried out by a conventional method such as filtration, centrifugation and the like.

According to the present invention, in the step (1), the separated precipitate is washed with an alkane solvent to further remove the heavy oil attached to the complex precipitate, and the washing method and conditions may be performed by a method conventional in the art, preferably, by washing until the complex precipitate is nearly colorless in the filtrate. Wherein, the alkane solvent can be the same as the alkane solvent used in the complex reaction, namely, each alkane solvent is independently selected from one or more of saturated alkane of C5-C8 and petroleum ether, wherein, the specific examples of the saturated alkane of C5-C8 can be as follows: n-pentane, n-hexane, n-heptane, n-octane. Preferably, the kind of the alkane solvent used for washing is the same as that used for the complexation reaction from the viewpoint of ease of operation and reagent saving.

According to the present invention, preferably, the method further comprises drying the precipitate obtained in step (1) before mixing the precipitate with the organic solvent to remove the alkane solvent, so that the complex precipitate obtained in step (1) can be more sufficiently dissolved and dispersed in the organic solvent, thereby better dissociating the basic nitride. The conditions and method of drying are not particularly limited, and in one embodiment of the present invention, the drying conditions include: the temperature is 60-120 ℃ and the time is 1-5 h.

According to the present invention, in the step (2), the organic solvent may be selected from various solvents capable of dissolving and dispersing the precipitate of the complex obtained in the step (1), and preferably, the organic solvent is selected from one or more of dichloromethane, chloroform, benzene, toluene, xylene and carbon disulfide. The amount of the organic solvent used in the present invention is not particularly limited, and is preferably 1 to 5 times the volume of the heavy oil from the viewpoint of enabling the organic solvent to be sufficiently mixed, dissolved and dispersed with the precipitate of the complex obtained in step (1).

According to the invention, in the step (2), alkali liquor is adopted to wash the complex precipitate so as to destroy the coordinate bond of nitrogen in the complex, thereby dissociating the basic nitride from the ligand into a free state, and realizing the separation and purification of the basic nitride and the separation of the basic nitride in the heavy oil. Therefore, the alkali used for alkali washing may be a strong alkali, preferably sodium hydroxide and/or potassium hydroxide, or a weak alkali, preferably ammonia water. The alkali is usually used in the form of an alkali solution, preferably an aqueous alkali solution, the concentration of the alkali solution is not particularly limited, and the concentration of the alkali solution is generally 1 to 30% by mass at normal temperature.

According to the present invention, the conditions of the alkaline washing generally include: temperature and pressure. The temperature of the alkali washing is 30 to 50 ℃ from the viewpoint of sufficiently breaking the coordinate bond of nitrogen in the complex precipitate to dissociate the basic nitride, and the pressure of the alkali washing may be appropriately adjusted depending on the temperature of the alkali washing, and preferably, the pressure of the alkali washing is 0 to 1 MPa.

According to the present invention, the amount of alkali used, the number of times of alkali washing and the time of each alkali washing are not particularly limited, and it is preferable that the amount (volume) of alkali used for alkali washing is 1 to 5 times the volume of the heavy oil from the viewpoint of sufficiently breaking the coordinate bond of nitrogen in the complex precipitate to dissociate the basic nitride. The number of alkaline washing is 1-5, preferably 2-4, and the time of each alkaline washing is generally 1-10h, preferably 3-8 h.

According to the invention, the alkaline washing process can be carried out in a conventional manner, for example, by thoroughly mixing the mixture of the precipitate obtained in step (1) and the organic solvent with the alkaline solution, preferably, in order to more thoroughly wash the alkaline solution and to better achieve the object of the invention, the alkaline washing is also carried out under stirring. The rotation speed of the stirring can be 500-2000 rpm, and preferably 800-1200 rpm.

According to the invention, in the step (2), the method of mixing the precipitate obtained in the step (1) with the organic solvent to obtain a mixed solution, performing alkali washing, and then separating the organic phase can be performed in a conventional manner, for example, standing and layering, that is, after fully mixing the mixed solution of the precipitate obtained in the step (1) and the organic solvent with the alkali solution, performing standing and layering, allowing the alkaline nitride to enter the upper organic phase, allowing the transition metal salt to enter the lower aqueous phase, and then separating the upper organic phase.

According to the invention, the conditions for subjecting the organic phase to water washing in step (2) generally comprise: temperature and pressure. The temperature of the water washing is 30 to 50 ℃ from the viewpoint of sufficiently washing the impurities in the organic phase, and the pressure of the water washing may be appropriately adjusted depending on the temperature of the water washing, and preferably, the pressure of the water washing is 0 to 1 MPa. More preferably, the temperature and pressure of the water washing are the same as those of the alkali washing for the convenience of operation.

According to the present invention, the amount of washing water used, the number of times of washing and the time for each washing are not particularly limited, and it is preferable that the amount (volume) of washing water used is 1 to 5 times the volume of the heavy oil from the viewpoint of sufficiently washing the impurities in the organic phase. The number of washing times is 1-5, preferably 2-4, and the time for each washing time is generally 1-10h, preferably 3-8 h. Among them, the water washing water is preferably deionized water.

According to the invention, the washing can be carried out in a conventional manner, for example by thoroughly mixing the organic phase with water, then allowing the mixture to stand for demixing, and then separating the upper organic phase. Preferably, the water washing is also carried out under stirring for the purpose of more fully carrying out the object of the invention. The rotation speed of the stirring can be 500-2000 rpm, and preferably 800-1200 rpm.

According to the invention, the method also comprises drying the organic phase washed with water in the step (2), wherein the drying conditions and method can be carried out by adopting the conventional technology, and for the convenience of operation, the drying method is preferably nitrogen blow drying.

The method for separating basic nitrogen compounds from heavy oil according to the present invention will be described in detail with reference to fig. 1. Diluting and dissolving straight-run vacuum wax oil (VGO) with n-hexane, adding transition metal salt ferric chloride into the mixed solution, heating and refluxing at 80 ℃, carrying out a complex reaction, filtering the mixture after the complex reaction to obtain a precipitate, and continuously washing the precipitate with n-hexane until the filtrate is nearly colorless. And drying the filtered precipitate, dissolving and dispersing the dried precipitate in toluene, fully mixing the dried precipitate with a sodium hydroxide solution with the mass percentage concentration of 10%, standing and layering the mixed solution, separating out an upper organic phase after liquid separation, repeating the alkali washing process for 2 times, washing the organic phase for 3 times by using deionized water, and drying the organic phase obtained after water washing by using a nitrogen blow-drying instrument to obtain the alkaline nitride.

The separation method of the invention has good selectivity to the alkaline nitride, the yield of the alkaline nitride is high, and the obtained alkaline nitride contains less impurities such as hydrocarbon, sulfide and the like. The method can be used as a method for removing the alkaline nitride in the heavy oil and a method for separating the alkaline nitride, and meets the requirement of a subsequent analysis technology on the purity of the alkaline nitride.

The present invention will be described in detail below by way of examples.

In the following examples, basic nitrogen content of heavy oil as it is and basic nitrogen content of separated basic nitride were measured by SH0162 petroleum product basic nitrogen measurement method (potentiometric titration method).

The total nitrogen content of the heavy oil as it is was determined in the following examples by SH0704 petroleum and petroleum products nitrogen content determination.

The yield of basic nitride in the following examples is calculated as:

the content of the basic nitrogen element in the separated basic nitride is multiplied by the mass fraction of the basic nitride in the heavy oil/the content of the basic nitrogen element in the heavy oil is multiplied by 100%.

Example 1

This example illustrates the method of separating basic nitrogen compounds from heavy oil according to the present invention.

(1) Weighing 10g of a straight-run vacuum wax oil (VGO) raw sample (12mL) with the total nitrogen element content of 2400 mu g/g, diluting and dissolving the raw sample with 50mL of n-hexane, placing the diluted sample into a 250mL three-hole round-bottom flask, adding 0.2g of ferric chloride, refluxing for 3 hours at 80 ℃, carrying out a complex reaction, filtering the reacted mixture to obtain a precipitate, and continuously washing the precipitate with n-hexane until the filtrate is nearly colorless.

(2) Drying the filtered precipitate at 80 ℃ for 1h, dissolving and dispersing the precipitate in 40mL of toluene, transferring the dried precipitate to a 250mL separating funnel, adding 40mL of a 10% sodium hydroxide solution, fully and uniformly mixing (mixing at a stirring speed of 800 r/min), standing the mixed solution for layering, separating to obtain an organic phase, carrying out alkaline washing on the organic phase for 2 times at normal temperature and normal pressure by using 40mL of a 10% sodium hydroxide solution, carrying out alkaline washing on the organic phase to obtain an organic phase, washing the organic phase for 3 times at normal temperature and normal pressure by using 40mL of deionized water (mixing at a stirring speed of 800 r/min), and drying the organic phase obtained after washing by using a nitrogen blow-drying instrument to obtain the alkaline nitride. The alkaline nitride recovery is shown in table 1. The mass type distribution of the oil sample before separation and the basic nitride obtained after separation is shown in FIG. 2.

Example 2

Basic nitride was isolated by following the procedure of example 1 except that in step (1), 0.2g of zinc chloride was used as the transition metal salt. The alkaline nitride recovery is shown in table 1.

Example 3

Basic nitride was isolated by following the procedure of example 1 except that in step (1), 0.2g of titanium tetrachloride was used as the transition metal salt. The alkaline nitride recovery is shown in table 1.

Example 4

The basic nitride was isolated by the method of example 1, except that 50mL of n-hexane was replaced with 50mL of petroleum ether in the step (1). The alkaline nitride recovery is shown in table 1.

Example 5

Basic nitride was isolated according to the method of example 1, except that, in the step (1), 10g of a straight-run vacuum wax oil (VGO) as it is (12mL) was diluted with 50mL of n-hexane and dissolved, and then placed in a 250mL three-hole round-bottom flask, and 0.2g of ferric chloride was added thereto with stirring at room temperature, mixed with stirring, and subjected to a complexation reaction. The alkaline nitride recovery is shown in table 1.

Example 6

The basic nitride was isolated by the same procedure as in example 1, except that, in the step (1), the temperature of the reflux reaction was 120 ℃ and the reflux time was 1 hour. The alkaline nitride recovery is shown in table 1.

Example 7

The basic nitride was isolated by following the procedure of example 1 except that, in the step (2), the organic solvent used for dissolving and dispersing the precipitate was 40mL of dichloromethane. The alkaline nitride recovery is shown in table 1.

Example 8

The basic nitride was separated by the same method as in example 1 except that, in the step (2), the alkali solution used for the alkali washing was 40mL of 20% by mass aqueous ammonia. The alkaline nitride recovery is shown in table 1.

Example 9

Basic nitride was isolated by following the procedure of example 1 except that in step (1), 0.1g of ferric chloride was used as the transition metal salt. The alkaline nitride recovery is shown in table 1.

Example 10

Basic nitride was isolated by following the procedure of example 1 except that in step (1), 0.3g of ferric chloride was used as the transition metal salt. The alkaline nitride recovery is shown in table 1.

Comparative example 1

This comparative example serves as a reference method for illustrating the separation of basic nitrogen compounds from heavy oil.

10g of straight-run vacuum wax oil (VGO) with the total nitrogen content of 2400 mu g/g is taken, 12mL is directly taken, diluted and dissolved by 30mL of dichloromethane, transferred to a separating funnel, added with 30mL of hydrochloric acid solution with the concentration of 3mol/L to extract alkaline nitride therein, stood for layering, taken out of a water phase, and extracted repeatedly for 2 times. Neutralizing the collected water phase with a sodium hydroxide solution with the mass percentage concentration of 40% until the solution is strongly alkaline (pH is 12), re-extracting the organic matters in the water phase with 50mL of dichloromethane, washing the obtained organic phase with deionized water for 2 times, and blow-drying the solvent with a nitrogen blow-dryer to obtain the alkaline nitride.

The alkaline nitride recovery is shown in table 1.

TABLE 1

As can be seen from the results of table 1, the method for separating basic nitrogen compounds from heavy oil according to the present invention can effectively separate and recover basic nitrogen compounds from heavy oil, and the recovery rate of basic nitrogen compounds is more than 70%, and is significantly improved as compared to the comparative example. As can be seen from fig. 2, the basic nitrides obtained by the method for separating basic nitrides from heavy oil of the present invention contain fewer impurities such as hydrocarbons and sulfides.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims

1. A method for separating alkaline nitride from heavy oil is characterized by comprising the following steps:

(2) mixing the precipitate obtained in the step (1) with an organic solvent to obtain a mixed solution, carrying out alkali washing on the mixed solution, separating to obtain an organic phase, and washing the organic phase with water;

wherein, in the step (1), the alkane solvent is selected from one or more of saturated alkanes of C5-C8 and petroleum ether, wherein, the saturated alkanes of C5-C8 are selected from at least one of n-pentane, n-hexane, n-heptane and n-octane; the transition metal salt is a halogen salt of at least one transition metal in groups IB, IIB, IVB and VIII of the periodic table of elements;

in the step (2), the organic solvent is one or more selected from dichloromethane, chloroform, benzene, toluene, xylene and carbon disulfide.

2. The separation method according to claim 1, wherein the heavy oil is selected from one or more of heavy crude oil, straight run vacuum wax oil, hydrogenated wax oil, coker wax oil, deasphalted oil, atmospheric residue, and vacuum residue; the total nitrogen content of the heavy oil is 10-10000 mug/g.

3. The separation method according to claim 1, wherein in the step (1), the alkane solvent used in the complexation reaction is used in an amount of 1 to 10 times the volume of the heavy oil.

4. The separation method according to claim 1, wherein in the step (1), the transition metal salt is selected from one or more of copper chloride, zinc chloride, iron chloride, titanium tetrachloride, mercuric chloride, cadmium chloride, cobalt chloride, nickel chloride, copper bromide, zinc bromide, iron bromide, titanium tetrabromide, mercuric bromide, cadmium bromide, cobalt bromide, nickel bromide, copper iodide, zinc iodide, titanium tetraiodide, mercuric iodide, cadmium iodide, cobalt iodide and nickel iodide.

5. The separation method according to claim 4, wherein in the step (1), the transition metal salt is one or more selected from the group consisting of ferric chloride, zinc chloride and titanium tetrachloride.

6. The separation method according to any one of claims 1 to 5, wherein the transition metal salt is used in an amount of 0.01 to 5 wt% based on the mass of the heavy oil in step (1).

7. The separation method according to claim 6, wherein in the step (1), the transition metal salt is used in an amount of 1 to 3 wt% based on the mass of the heavy oil.

8. The separation method according to any one of claims 1 to 5, wherein in the step (1), the conditions of the complexation reaction include: the reaction temperature is between room temperature and 150 ℃, the reaction time is between 0.5 and 24 hours, and the complex reaction is carried out under stirring.

9. The separation method according to claim 8, wherein in the step (1), the conditions of the complexation reaction include: the reaction temperature is 60-120 ℃, the reaction time is 1-10h, and the complex reaction is carried out under stirring.

10. The separation method according to any one of claims 1 to 5, wherein in the step (1), the complexing reaction comprises: the alkane solvent is heated under reflux with a mixture of heavy oil containing basic nitride and a transition metal salt.

11. The separation method according to any one of claims 1 to 5, further comprising drying the precipitate obtained in step (1) to remove the alkane solvent therefrom before mixing the precipitate with the organic solvent.

12. The separation method of claim 11, wherein the drying conditions comprise: the temperature is 60-120 ℃ and the time is 1-5 h.

13. The separation method according to claim 1, wherein the organic solvent is used in an amount of 1 to 5 times by volume of the heavy oil.

14. The separation method according to claim 1, wherein in the step (2), the alkali used for alkali washing is selected from one or more of sodium hydroxide, potassium hydroxide and ammonia water, the alkali is used in the form of alkali liquor, and the mass percent concentration of the alkali liquor is 1-30%;

the alkaline washing conditions include: the temperature is 30-50 ℃, and the pressure is 0-1 MPa;

the dosage of alkali liquor used for alkali washing is 1-5 times of the volume of the heavy oil;

the number of times of alkaline washing is 1-5, and the time of each alkaline washing is 1-10 h.

15. The separation method according to claim 14, wherein in the step (2), the base is an aqueous solution of a base.

16. The separation method as claimed in claim 1, wherein the alkali washing is performed under stirring in step (2) at a rotation speed of 500-.

17. The separation method as claimed in claim 16, wherein the alkali washing is performed under stirring in step (2) at a rotation speed of 800-.

18. The separation method according to claim 1, wherein in the step (2), the conditions for washing the organic phase with water comprise:

the temperature is 30-50 ℃, and the pressure is 0-1 MPa;

the dosage of the water washing water is 1 to 5 times of the volume of the heavy oil;

the washing times are 1-5 times, and the washing time is 1-10 h.

19. The separation method as claimed in claim 1, wherein the water washing is performed under stirring in step (2) at a rotation speed of 500-.

20. The separation method as claimed in claim 19, wherein the water washing is performed under stirring in step (2) at a rotation speed of 800-.

21. The separation method according to any one of claims 1 and 13 to 20, further comprising drying the organic phase washed with water in step (2).

22. The separation method of claim 21, wherein the drying method is nitrogen blow drying.