A method for obtaining purified asphaltene sub-fractions from crude oil

Abstract

The present application belongs to the technical field of petroleum separation, and discloses a method for obtaining purified asphaltene sub-components from crude oil. The method of the present application first fully dissolves the crude oil sample and subsequent precipitates in a solvent, then adds a precipitant to the solution to obtain a precipitation system. After obtaining the precipitation system, the present application performs oscillation treatment on the precipitation system to obtain an oscillation liquid. The oscillation liquid is then subjected to solid-liquid separation, preferably centrifugal separation or filtration. After solid-liquid separation, the present application removes the liquid in the liquid phase to obtain a soluble component, which is a sub-component. Then, different volume ratios of solvent and precipitant are repeatedly added to separate multiple asphaltene sub-components. Compared with the gradual precipitation method for separating asphaltene sub-components, the method of the present application repeatedly fully dissolves the precipitates in the solvent, maximally releases non-asphaltene components, and makes the separated asphaltene sub-components purer.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of petroleum separation, and particularly relates to a method for obtaining and purifying asphaltene sub-components from crude oil. BACKGROUND

[0002] In the field of petroleum chemical technology, it is necessary to separate multiple pure asphaltene sub-components from crude oil for various purposes, such as establishing Re-Os isochron (isotope model age and isochron) using multiple sub-components of a single crude oil for radioisotope dating research.

[0003] In traditional organic geochemistry research, crude oil can be separated into four group components of saturated hydrocarbons, aromatic hydrocarbons, non-hydrocarbons and asphaltene. Asphaltene is not a group component with uniform internal properties, and can be further separated into multiple sub-components according to different solubility properties. Asphaltene molecules have the property of spontaneous aggregation, and multiple asphaltene molecules can form aggregates, flocculation and other structures, and stably exist in crude oil. In the process of gas invasion and other geological processes or artificial separation of asphaltene from crude oil, asphaltene molecules can further form new and more aggregates, flocculation and other structures. Saturated hydrocarbons, aromatic hydrocarbons, non-hydrocarbons and other non-asphaltene components mainly exist in the form of free-moving molecules in crude oil, part of which is adsorbed on the surface of asphaltene aggregates and flocculation structures, and part of which is wrapped inside the asphaltene structure. In the process of natural or artificial precipitation of asphaltene, the main component of the precipitate is asphaltene, which also includes the asphaltene structure originally possessed, the non-asphaltene components wrapped and adsorbed in the newly formed asphaltene structure, and the non-asphaltene components precipitated together under the interaction.

[0004] At present, the method of separating asphaltene from crude oil first and then separating asphaltene sub-fractions from the asphaltene is generally used to obtain asphaltene sub-fractions. Excessive precipitant, such as 40 times volume of n-heptane, is added to the crude oil, and asphaltene can be obtained after oscillation and solid-liquid separation. Such a method can effectively manage workload and meet the needs of some research. However, in this process, new and more asphaltene aggregates and flocculation structures can be further formed on the basis of the original, and at the same time, non-asphaltene components can be wrapped and adsorbed, and other non-asphaltene components can be co-precipitated. Such non-asphaltene components can be difficult to effectively remove in the later purification process of asphaltene. Similarly, the separation of asphaltene sub-fractions mainly relies on the binary solution of precipitant and solvent of asphaltene, and the gradual precipitation of asphaltene is achieved by gradually providing the proportion of precipitant. Non-asphaltene components are also inevitably present in the sub-fractions separated in the form of precipitation. In the process of separating asphaltene sub-fractions by using the gradual precipitation method, the proportion of precipitant in the binary solution of precipitant and solvent gradually increases, and in each step, non-asphaltene components are wrapped and adsorbed into the aggregates and flocculation structures of asphaltene, and participate in the precipitation of asphaltene, so that non-asphaltene components are distributed in each asphaltene sub-fraction.

[0005] However, in some research, such as Re-Os radioisotope systemal dating with multiple asphaltene sub-fractions, it is necessary to separate asphaltene into multiple sub-fractions and remove as much co-precipitated and adsorbed non-asphaltene molecules as possible to exclude their interference. Non-hydrocarbons in non-asphaltene components also contain heteroatoms, polar functional groups and metal elements, including Re and Os. At the same time, non-asphaltene components mainly exist in the form of free molecules in crude oil, and free molecules can also exchange with adsorbed molecules. Therefore, the properties of the free and adsorbed parts of non-asphaltene components can be uniform, including Re-Os element content and isotope composition. Further, the properties of asphaltene sub-fractions separated by the traditional gradual precipitation method can tend to be uniform under the influence of non-asphaltene components. For example, the Re-Os element content and isotope composition of asphaltene sub-fractions of a certain crude oil can be different, which can be used to establish Re-Os isochron to date; however, the asphaltene sub-fractions separated by the traditional method can contain a large amount of non-hydrocarbons, and the Re-Os element content and isotope composition of non-hydrocarbons are consistent, which can make the Re-Os element content and isotope composition of asphaltene sub-fractions tend to be uniform, and thus lose the ability to accurately and precisely date.

[0006] Therefore, it is necessary to develop a new method to obtain a series of relatively pure asphaltene sub-fractions from crude oil, so as to obtain accurate and precise dating ability. SUMMARY

[0007] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a method for obtaining purified asphaltenes from crude oil.

[0008] The method provided by this invention skips the step of separating asphaltenes from crude oil and uses a gradual dissolution method, contrary to traditional gradual precipitation, to directly separate multiple asphaltenes sub-components from crude oil. The method of this invention can obtain a series of pure asphaltenes sub-components from crude oil.

[0009] This invention provides a method for obtaining purified asphaltenes sub-components from crude oil. The method involves fully dissolving the crude oil in a solvent, adding a precipitant, and then separating the majority of free non-asphaltene components and some non-asphaltene components adsorbed in the asphaltenes flocculent and aggregate structures through shaking and solid-liquid separation. The precipitate after solid-liquid separation is then fully dissolved in a solvent to release the adsorbed non-asphaltene components from the asphaltenes structure. Another precipitant is added, and the non-asphaltene components are removed through shaking and solid-liquid separation. Subsequently, the solvent ratio is gradually increased, and the process of dissolving, precipitating, shaking, and solid-liquid separation is repeated to obtain multiple asphaltenes sub-components. Furthermore, during this process, non-asphaltene components are more concentrated in the sub-components that were dissolved earlier; the sub-components separated later contain fewer non-hydrocarbon and other non-asphaltene components, resulting in purer asphaltenes.

[0010] Specifically, a method for obtaining purified asphaltenes from crude oil includes the following steps:

[0011] (1) Dissolve the crude oil sample in a solvent, then add a precipitant to obtain the first precipitation system, and then shake it to obtain the first shaking liquid;

[0012] (2) The first oscillating liquid is subjected to solid-liquid separation, and the obtained first precipitate is dissolved in a solvent to obtain a first mixture;

[0013] (3) Then, a precipitant is added to the first mixture to obtain a second precipitation system;

[0014] (4) The second precipitation system is shaken to obtain a second shaking liquid;

[0015] (5) The second oscillating liquid is subjected to solid-liquid separation to obtain a second precipitate and a liquid phase. The liquid in the obtained liquid phase is removed to obtain a soluble component, which is an asphaltene sub-component.

[0016] (6) The second precipitate is dissolved in a solvent, and the volume of the solvent in the second mixture is further increased compared with the solvent ratio in the first mixture in step (3);

[0017] (7) Add a precipitant to the second mixture to obtain a third precipitation system. Repeat steps (4) to (5) to separate an asphalt sub-component.

[0018] (8) Repeat steps (6) to (7) to separate multiple asphalt sub-components.

[0019] Preferably, in step (1), the solvent includes any one of dichloromethane, chloroform, tetrachloromethane, toluene, and benzene; more preferably, it is dichloromethane.

[0020] Preferably, in step (1), the precipitant includes any one of n-pentane, n-hexane, n-heptane, n-octane, petroleum ether, and acetone; more preferably, n-heptane.

[0021] Preferably, in step (1), the oscillation process takes longer than 0 hours, for example, from 1 minute to 16 hours.

[0022] Preferably, the temperature of the oscillation treatment can be selected from room temperature or additional heating or cooling, depending on the experimental purpose; the room temperature is 20-25°C.

[0023] In step (1), the ratio of crude oil to solvent can be flexibly set according to the experimental purpose and sample properties, preferably 1g:0.1-100mL, more preferably 1g:1-10mL, for example 1g:1mL.

[0024] In step (1), the ratio of crude oil to precipitant can be flexibly set according to the experimental purpose and sample properties, preferably 1g:0.1-100mL, more preferably 1g:40-60mL, for example 1g:40mL.

[0025] In step (1), the initial ratio of precipitate to solvent can be flexibly set according to the experimental purpose and sample properties, preferably 1g:0.1-100mL, more preferably 1g:10-20mL; the initial volume ratio of solvent to precipitant is 10:90, 5:95, 1:99, or other ratios more suitable for the purpose, preferably 10:90; in subsequent steps, the total volume of solvent and precipitant remains unchanged, or is adjusted to a variable total volume according to the experimental purpose; the proportion of solvent is increased by 10%, 5%, 1%, or other ratios more suitable for the purpose or variable ratios in each step, preferably by 10% in each step.

[0026] Preferably, in step (2), the solid-liquid separation method includes centrifugal separation or filtration.

[0027] Preferably, the centrifugal separation speed is >0 rpm and the centrifugal force is ≥1g.

[0028] Preferably, the centrifugal separation speed is ≥1 rpm, and more preferably 3500-4500 rpm.

[0029] Preferably, the centrifugal force of the centrifugal separation is ≥1g, and more preferably 1000-2000g.

[0030] Preferably, the centrifugation time is 0 min or more, for example, 10 min to 60 min.

[0031] Preferably, the filter membrane used for filtration has a pore size of 0.1 μm or larger, for example, 0.1-0.5 μm.

[0032] Preferably, in step (5), the method of removing liquid from the obtained liquid phase includes at least one of natural evaporation, heating evaporation, reduced pressure evaporation, pressurized evaporation, and rotary evaporator evaporation.

[0033] This invention utilizes a combination of solvents and precipitants for asphaltene to achieve multi-stage separation of asphaltene in crude oil by gradually increasing the volume ratio of the solvent and promoting progressive dissolution.

[0034] Before adding the precipitant, the sample is fully dissolved in the solvent; this can effectively release non-asphaltite components from the asphaltenite structure into the liquid phase and preferentially enrich them in the early separated sub-components, while the asphaltenite purity of the later sub-components is significantly improved.

[0035] By skipping the traditional steps of separating asphaltenes from crude oil, and starting the secondary component separation directly from the crude oil sample, the introduction of new non-asphaltene components is avoided, which is beneficial for the purification of asphaltenes and the protection of original geological information.

[0036] Preferably, the present invention provides a method for obtaining purified asphaltenes from crude oil, comprising the following steps:

[0037] (1) Dissolve the crude oil sample thoroughly in the solvent;

[0038] (2) Add a precipitating agent to the above solution to obtain a precipitation system;

[0039] (3) The above precipitation system was shaken to obtain a shaking liquid;

[0040] (4) Separate the solid and liquid phases of the above-mentioned oscillating liquid;

[0041] (5) Dissolve the precipitate obtained in the solid-liquid separation in step (4) completely in the solvent;

[0042] (6) Add a precipitating agent to the above solution to obtain a precipitation system;

[0043] (7) The above precipitation system is shaken to obtain a shaking liquid;

[0044] (8) Separate the solid and liquid phases of the above-mentioned oscillating liquid;

[0045] (9) Remove the liquid from the liquid phase to obtain the soluble component, which is an asphaltene sub-component;

[0046] (10) Dissolve the precipitate obtained in the solid-liquid separation in step (8) fully in the solvent, with the solvent ratio being higher than that in the previous step;

[0047] (11) Repeat steps (6) to (9) to separate another asphalt sub-component;

[0048] (12) Repeat steps (10) to (11) to separate multiple asphalt sub-components.

[0049] This invention first fully dissolves the crude oil sample and subsequent precipitates in a solvent, then adds a precipitating agent to the solution to obtain a precipitation system. After obtaining the precipitation system, this invention shakes the precipitation system. After obtaining the shaking liquid, this invention performs solid-liquid separation on the shaking liquid. The preferred method for solid-liquid separation is centrifugation or filtration; after solid-liquid separation, this invention removes the liquid from the liquid phase to obtain a soluble component, i.e., a sub-component.

[0050] The method provided by this invention skips the step of separating asphaltenes from crude oil, avoiding the introduction of non-asphaltene components through encapsulation, adsorption, and co-precipitation caused by the formation of new asphaltenes aggregates and flocculation structures during this process. This is especially true for components existing in the form of encapsulation that are difficult to remove during subsequent purification. The method provided by this invention, by dissolving the sample in a solvent before adding the precipitant, can fully deconstruct the flocculated structure of asphaltenes, releasing more non-hydrocarbon and other non-asphaltene components existing in the form of adsorption, promoting the preferential dissolution of non-asphaltene components and even easily soluble asphaltenes, thus resulting in a purer asphaltenes in the solid phase. By gradually increasing the proportion of solvent, progressive dissolution is promoted, separating more secondary components.

[0051] The above-mentioned method for obtaining purified asphaltenes from crude oil has applications in the petroleum industry.

[0052] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0053] Compared to other existing methods, the method of this invention skips the step of separating asphaltenes from crude oil, avoiding the introduction of non-asphaltene components through encapsulation, adsorption, and co-precipitation caused by the formation of new asphaltenes aggregates and flocculation structures during this process. Compared to gradual precipitation methods for separating asphaltenes subcomponents, the method of this invention repeatedly and thoroughly dissolves the precipitate in a solvent, maximizing the release of non-asphaltene components. This results in purer separated asphaltenes subcomponents (especially those separated later), providing assistance for oil and gas geochemical research and organic geochemical studies of asphaltenes molecular structure, behavior, characteristic compounds, and elemental and isotopic studies in petroleum production.

[0054] The method of this invention achieves controllability of the separation process through solvent ratio gradient control, and has the advantages of simple operation and high separation efficiency. Detailed Implementation

[0055] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0056] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0057] The method provided by this invention skips the step of separating asphaltenes from crude oil, avoiding the introduction of non-asphaltene components through encapsulation, adsorption, and co-precipitation caused by the formation of new asphaltenes aggregates and flocculation structures during this process. This is especially true for components existing in the form of encapsulation that are difficult to remove in later purification processes. The method provided by this invention, by dissolving the crude oil sample in a solvent before adding the precipitant, can fully deconstruct the flocculated structure of asphaltenes, releasing more non-hydrocarbon and other non-asphaltene components existing in the form of adsorption, promoting the preferential dissolution of non-asphaltene components and even easily soluble asphaltenes, thus resulting in a purer asphaltenes in the solid phase. By gradually increasing the proportion of solvent, progressive dissolution is promoted, separating more asphaltenes secondary components.

[0058] The asphalt sub-components separated by the method provided by the present invention can be used for subsequent experiments as needed, and the present invention does not impose specific limitations.

[0059] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments thereof.

[0060] In a specific embodiment of the present invention, the amount of crude oil sample used is preferably ≥20g; the solvent is preferably dichloromethane, and the precipitant is preferably n-heptane; the ratio of crude oil to solvent is preferably 1g:1mL; the ratio of crude oil to precipitant is 1g:40mL; the initial ratio of precipitant to solvent is 1g:10mL; the initial volume ratio of solvent to precipitant is 10:90; in subsequent steps, the total volume of solvent and precipitant remains constant, and the proportion of solvent increases by 10% in each step. The separation steps are repeated until the proportion of precipitant in the binary solution drops to 0.

[0061] The oscillation treatment of the precipitation system was carried out at room temperature for 16 hours; the solid-liquid separation method was centrifugation at 4500 rpm (approximately 1800 g) for 15 minutes; the liquid removal method in the liquid phase was rotary evaporation. The soluble component in the liquid phase collected in each step is a sub-component.

[0062] Example 1

[0063] Using crude oil samples from Upper Cretaceous Cenomanian carbonate reservoirs in the Persian Gulf as the research object, the method of this invention was used to obtain purified asphaltene secondary components from the crude oil samples. The specific process is as follows:

[0064] Weigh 41.0167g of crude oil and place it in a 2L glass bottle. Dissolve it completely in 40mL of dichloromethane, then add 1600mL of n-heptane and mix thoroughly to obtain a precipitation system (Table 1). Place the glass bottle in a shaker and shake at room temperature (about 20℃) for 16 hours. Pour the shaken liquid into a centrifuge tube and centrifuge at 4500 rpm (>1000g) for 15 minutes to separate the solid phase (precipitate) and liquid phase. Use a rotary evaporator to remove the liquid (solvent and precipitant) from the liquid phase to obtain the soluble components. Collect the precipitate and soluble components separately in 22mL glass bottles with dichloromethane, then evaporate the dichloromethane to dryness at 35℃ and weigh. This step yields 2.1352g of precipitate and 39.2241g of soluble components, accounting for 5.2% and 95.6% of the crude oil mass, respectively. The total recovery rate is 100.8%, although some solvent may not have evaporated completely.

[0065] The precipitate was transferred to a 250 mL round-bottom flask and completely dissolved in 20 mL of dichloromethane. Heptane was added to the solution at a solvent-to-precipitant ratio of 10:90, i.e., 180 mL of heptane, to obtain the precipitate system (Table 1). The total volume of solvent and precipitant was 200 mL. The glass bottle was placed in a shaker and shaken at room temperature (approximately 20 °C) for 16 hours. The shaken liquid was poured into centrifuge tubes and centrifuged at 4500 rpm (>1000 g) for 15 minutes to separate the solid phase (precipitate) and liquid phase. The liquid phase (solvent and precipitant) was removed using a rotary evaporator to obtain the soluble components. The precipitate and soluble components were collected in a 250 mL round-bottom flask and a 22 mL glass bottle, respectively, using dichloromethane. The dichloromethane was then evaporated to dryness at 35 °C, and the mass of the soluble components was measured.

[0066] Repeat the steps described above, including transferring the precipitate to a round-bottom flask, dissolving it in solvent, adding the precipitant, shaking, solid-liquid separation, sample collection, and weighing, until the solvent ratio reaches 100% (Table 1). In each repeated procedure, the total volume of solvent (dichloromethane) and precipitant (n-heptane) was set at 200 mL, and the solvent was gradually increased and the precipitant decreased by 10% at a time.

[0067] This process was repeated to obtain a total of 11 components, including 10 soluble components and 1 precipitated component from the final step. The latter 10 components are mainly asphaltenes and can be referred to as asphaltenes sub-components (Table 1).

[0068] The initial sample amount was 41.0167 g, and a total of 41.3549 g was recovered, basically achieving mass balance (100.8%; some reagents in the first soluble component may not have been evaporated to dryness).

[0069] Table 1: Separation of secondary components in crude oil asphalt in Example 1

[0070]

[0071]

[0072] Comparative Example 1

[0073] Similarly, taking crude oil samples from the Cretaceous Cenomanian carbonate reservoir in the Persian Gulf as the research object, a different approach was adopted than the method of this invention. First, the asphaltene of the crude oil was separated, and then the asphaltene sub-components were separated by a gradual precipitation method.

[0074] The specific content of Comparative Example 1 is as follows:

[0075] First, the asphaltene in crude oil was separated using n-heptane: 41.8526 g of crude oil was weighed and placed in a 2 L glass bottle. 1600 mL of n-heptane was added and mixed thoroughly to obtain a precipitation system. The glass bottle was placed in a shaker and shaken at room temperature (approximately 20 °C) for 16 hours. The shaken liquid was poured into a centrifuge tube and centrifuged at 4500 rpm (>1000 g) for 15 minutes to separate the solid phase (precipitate) and liquid phase. The reagents (solvent and precipitant) in the liquid phase were removed using a rotary evaporator to obtain the soluble components. The precipitate and soluble components were collected separately with dichloromethane, and the dichloromethane was evaporated to dryness at 35 °C and weighed.

[0076] This step yielded 2.3856 g of precipitate and 40.1366 g of soluble components, accounting for 5.7% and 95.9% of the crude oil, respectively, with a total recovery rate of 101.6%. It is possible that some solvent in the soluble components did not evaporate completely. Therefore, the precipitate percentage in the first step of Example 1 of the method of this invention (5.2%) is significantly lower than the asphaltene obtained by the traditional method (5.7%), indicating that the solvent has a significant effect on removing non-asphaltene components.

[0077] Subsequently, the asphaltene was separated into multiple sub-components using a progressive precipitation method: the same combination of precipitant and solvent, n-heptane and dichloromethane, was used, with the total volume maintained at 200 mL; unlike Example 1, the proportion of precipitant was increased by 10% in each step, starting from a solvent to precipitant volume ratio of 90:10.

[0078] In the specific operation, the asphaltene was first transferred to a 250mL round-bottom flask and fully dissolved in 180mL of dichloromethane. Then, 20mL of n-heptane was added according to the predetermined ratio to obtain a precipitation system (Table 2). The glass bottle was placed in a shaker and shaken at room temperature (about 20℃) for 16 hours. The shaken liquid was poured into a centrifuge tube and centrifuged at 4500 rpm (>1000g) for 15 minutes to separate the solid phase (precipitate) and liquid phase. However, no precipitation was formed under this solvent and precipitant ratio. The solution was poured back into the round-bottom flask, and the reagent was removed using a rotary evaporator. The steps of dissolving the sample in the round-bottom flask in solvent, adding precipitant, shaking, solid-liquid separation, sample collection and weighing were repeated, with the proportion of precipitant increased by 10%. This process was repeated until the precipitant accounted for 70%, at which point precipitation first appeared. The precipitate is one asphaltene sub-component.

[0079] Use a rotary evaporator to remove the liquid (solvent and precipitant) from the liquid phase to obtain the soluble components; use dichloromethane to collect the precipitate and soluble components into a 22mL glass bottle and a 250mL round-bottom flask, respectively, and then evaporate the dichloromethane to dryness at 35℃ and weigh the precipitate.

[0080] Following the established steps and proportions, solvent and precipitant were added to the soluble portion in the round-bottom flask, followed by shaking, solid-liquid separation, collection of the precipitate, and rotary evaporation of the reagent in the liquid phase. This process was repeated until the proportion of precipitant reached 100% (Table 2), which is the final step. By the end of the experiment, a total of five sub-components of asphaltene were obtained, including four precipitates and one soluble component from the final step (Table 2).

[0081] The initial sample usage was 41.8526 g, and a total of 42.5242 g was recovered, basically achieving mass balance (101.6%). However, some reagents may not have been evaporated completely during the separation of asphaltene and the soluble components in the final step, and some sample may have been lost during the operation.

[0082] Compared to Example 1, the method used in Comparative Example 1 separated significantly fewer sub-components, and the mass of each sub-component or its proportion in the crude oil was also higher. The higher percentage of sub-components in Comparative Example 1 is due to both the smaller number of sub-components and the greater amount of non-asphaltene components adsorbed, encapsulated, and co-precipitated during the sub-component separation process compared to Example 1. Specifically, the sum of the four precipitated sub-components in Comparative Example 1 (5.3%) was higher than the percentage of precipitate separated from the crude oil in Example 1 (5.2%). Furthermore, in Comparative Example 1, 0.1639 g of sub-components remained dissolved in 100% pure precipitant, representing 0.4% of the total, a significant portion of which consisted of non-hydrocarbon and other non-asphaltene components.

[0083] Table 2: Separation of secondary components of crude oil asphaltene in Comparative Example 1

[0084]

[0085] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for obtaining a purified asphaltene sub-fraction from crude oil, characterized in that, The method comprises the following steps: 41.0167 g of crude oil is weighed into a 2 L glass bottle and completely dissolved in 40 mL of solvent, then 1600 mL of precipitant is added, mixed thoroughly, and a precipitation system is obtained, wherein the solvent is dichloromethane and the precipitant is n-heptane; the glass bottle is placed in a shaker and shaken at room temperature for 16 hours; the shaking liquid is poured into a centrifuge tube and centrifuged at 4500 rpm for 15 minutes to separate the solid phase and the liquid phase; the solvent and the precipitant in the liquid phase are removed using a rotary evaporator to obtain the soluble component therein; the solid phase and the soluble component are collected in a 22 mL glass bottle using dichloromethane, and then the dichloromethane is evaporated at 35 DEG C; the precipitate is 2.1352 g and the soluble component is 39.2241 g; The precipitate is transferred to a 250 mL round-bottom flask and dissolved in 20 mL of dichloromethane, n-heptane is added to the solution according to a solvent to precipitant ratio of 10:90 to obtain a precipitation system, the round-bottom flask is placed in a shaker and shaken at room temperature for 16 hours, the shaking liquid is poured into a centrifuge tube and centrifuged at 4500 rpm for 15 minutes to separate the solid phase and the liquid phase, the solvent and the precipitant in the liquid phase are removed using a rotary evaporator to obtain the soluble component therein; the solid phase and the soluble component are collected in a 250 mL round-bottom flask and a 22 mL glass bottle using dichloromethane, and then the dichloromethane is evaporated at 35 DEG C; the mass of the soluble component is weighed; The steps of transferring the precipitate to a round-bottom flask, dissolving in a solvent, adding a precipitant, shaking, separating the solid and liquid phases, and collecting and weighing the sample are repeated, and in each repeated process, the total volume of the solvent dichloromethane and the precipitant n-heptane is determined to be 200 mL, and the solvent is gradually increased and the precipitant is gradually reduced by 10% each time; In this way, a total of 10 soluble components and 1 precipitate in the last step are obtained, and the last 10 are mainly asphaltene and are referred to as asphaltene sub-components.

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