Method for purifying asphaltene

Abstract

The invention belongs to the technical field of petrochemical engineering, and discloses a method for purifying asphaltene. The method comprises the following steps: fully dissolving asphaltene in a solvent, adding excessive precipitant, and separating to form precipitated asphaltene and non-asphaltene components such as non-hydrocarbon, aromatic hydrocarbon and saturated hydrocarbon which are kept dissolved in a manner of oscillation and solid-liquid separation. Compared with traditional Soxhlet extraction and other methods, the method provided by the invention has stronger desorption and dissolving capacities on adsorbed and co-precipitated non-asphaltene components such as non-hydrocarbon and the like by virtue of the solvent, and is more thorough in asphaltene purification. According to the method provided by the invention, purified asphaltene can be obtained, and help is provided for organic geochemical research of molecular structures and behaviors of asphaltene, molecular markers and the like and research of elements, isotopes and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of petrochemical engineering, and particularly relates to a method for purifying asphaltene. Background Art

[0002] In the field of petrochemical technology, for various purposes, it is necessary to purify asphaltene. Crude oil can be separated into four group components: saturated hydrocarbons, aromatic hydrocarbons, non-hydrocarbons, and asphaltene. To obtain purified asphaltene, it is necessary to remove non-asphaltene components such as saturated hydrocarbons, aromatic hydrocarbons, and non-hydrocarbons.

[0003] In crude oil, non-asphaltene components mainly exist in the form of freely movable molecules, and can also be adsorbed and encapsulated into asphaltene components. Asphaltene molecules have the property of spontaneous aggregation. During the formation of crude oil and the precipitation of asphaltene, multiple asphaltene molecules can form aggregates, flocculations and other structures through intermolecular forces, etc. Such structures can adsorb and encapsulate many non-asphaltene components. In addition, during the precipitation of asphaltene, non-asphaltenes can also be affected and co-precipitate with asphaltene.

[0004] In many scenarios, purified asphaltene is required. First, the study of the molecular structure and corresponding behavior characteristics of asphaltene is of great significance for solving the problems encountered in current petroleum exploration, development, storage and transportation, and petroleum processing fields. The study of the molecular structure of asphaltene requires purified asphaltene.

[0005] Secondly, the non-asphaltene components encapsulated in the asphaltene structure also play an important role. However, before their utilization, it is necessary to purify the asphaltene to remove the non-asphaltene components adsorbed on the surface of the asphaltene structure and co-precipitated with asphaltene. Non-asphaltene components themselves can carry rich geological information. For example, the molecular marker compounds in them can be used to invert the characteristics of the crude oil source rock and the history of oil and gas evolution, etc. However, the freely movable non-asphaltene components in crude oil are easily modified by geological processes, thus losing their original functions. The molecules adsorbed in the asphaltene structure can exchange with the same kind of molecules in the environment and are also easily modified by geological processes; while the encapsulated non-asphaltene components can be protected by the asphaltene structure from geological processes and thus retain their geological information. Therefore, non-asphaltene components such as molecular marker compounds encapsulated in the asphaltene structure can be released by oxidation, pyrolysis, etc., for inversion research on the characteristics of crude oil source rock and the history of oil and gas evolution, etc.

[0006] In addition, asphaltene and non-asphaltene may have different Re-Os isotope compositions. When using the asphaltene Re-Os radioactive isotope system for dating, it is also necessary to purify the asphaltene to remove the non-asphaltene components therein.

[0007] At present, asphaltene is generally purified by methods such as Soxhlet extraction, but the actual effect is limited and cannot fully meet the above research needs.

[0008] Therefore, there is an urgent need to provide a new method for purifying asphaltene. Summary of the Invention

[0009] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. For this purpose, the present invention provides a method for purifying asphaltene. The method provided by the present invention uses a binary solution of an asphaltene precipitant and a solvent, and by repeatedly dissolving and precipitating the asphaltene precipitate, non-asphaltene components such as adsorbed and co-precipitated non-hydrocarbons, aromatic hydrocarbons, and saturated hydrocarbons are desorbed and dissolved, separated from the asphaltene, so as to obtain purified asphaltene.

[0010] In order to achieve the above-mentioned invention object, the present invention provides the following technical solutions:

[0011] A method for purifying asphaltene, characterized by comprising the following steps:

[0012] (1) Dissolve asphaltene in a solvent to obtain a mixed solution;

[0013] (2) Add a precipitant to the mixed solution obtained in step (1) to obtain a precipitation system;

[0014] (3) Oscillate the precipitation system obtained in step (2) to obtain an oscillated liquid;

[0015] (4) Separate the solid phase and the liquid phase of the oscillated liquid obtained in step (3) to obtain a precipitate and a liquid phase, that is, complete the primary purification of asphaltene;

[0016] (5) Dissolve the precipitate obtained in step (4) in a solvent to obtain a mixed solution;

[0017] (6) Add a precipitant to the mixed solution obtained in step (5), and repeat the operations of steps (3) to (4) to complete the secondary purification of asphaltene;

[0018] (7) Repeat steps (5) to (6) to purify asphaltene multiple times until there are no soluble components in the liquid phase obtained after the separation of the solid phase and the liquid phase, or the purity of asphaltene reaches the required level;

[0019] (8) Re-add a precipitant to the precipitate obtained after the last separation of the solid phase and the liquid phase in step (7) to obtain a precipitation system;

[0020] (9) Oscillate the precipitation system obtained in step (8) to obtain an oscillated liquid;

[0021] (10) Separate the solid phase and the liquid phase of the oscillated liquid obtained in step (9), and collect the precipitate, which is the purified asphaltene.

[0022] Preferably, in step (1), the solvent includes any one of dichloromethane, chloroform, toluene, and benzene; more preferably dichloromethane.

[0023] Preferably, in step (2), the precipitant includes any one of n-pentane, n-hexane, n-heptane, n-octane, petroleum ether, and acetone; more preferably n-heptane.

[0024] In step (1), the asphaltene is first fully dissolved in the solvent, and in step (2), an excessive amount of precipitant is used to promote the precipitation of the asphaltene, while the non-asphaltene components adsorbed or co-precipitated can still remain in the dissolved state, so as to achieve the purpose of separating and purifying the asphaltene.

[0025] Preferably, in step (1), the dosage of the asphaltene is greater than 20 g, for example, 21 - 100 g.

[0026] Preferably, in steps (1) and (2), the ratio of the asphaltene to the precipitant can be flexibly set according to the experimental purpose and the nature of the sample, preferably 1 g: 1 - 50 mL, more preferably 1 g: 15 - 50 mL, for example, 1 g: 20 mL.

[0027] Preferably, in steps (1) and (2), the volume ratio of the precipitant to the solvent is 90 - 99: 1 - 10, but does not include 95: 5, for example, 90: 10, 95: 5, 99: 1. Preferably 95: 5.

[0028] Preferably, in step (1), the dosage ratio of the asphaltene to the solvent can be flexibly set according to the experimental purpose and the nature of the sample, preferably 1 g: 0.5 - 90 mL, more preferably 1 g: 1 - 20 mL, for example, 1 g: 1 mL.

[0029] Preferably, in step (3), the time of the oscillation treatment is greater than 0 h. For example, it is 1 min to 16 h or 30 min to 12 h.

[0030] Preferably, the temperature of the oscillation treatment can be selected as room temperature or additional heating or cooling according to the experimental purpose; the room temperature is 20 - 25 °C.

[0031] Preferably, in step (4), the method of solid-liquid separation includes centrifugal separation or filtration.

[0032] Preferably, the rotation speed of the centrifugal separation > 0 revolutions per minute, and the centrifugal force ≥ 1 g.

[0033] Preferably, the rotation speed of the centrifugal separation ≥ 1 revolution per minute, and more preferably 2500 - 4500 revolutions per minute.

[0034] Preferably, the centrifugal force of the centrifugal separation ≥ 1 g, and more preferably 1000 - 2500 g.

[0035] Preferably, the time of centrifugal separation is 0 min or more, for example, 20 min - 60 min.

[0036] Preferably, the pore size of the filter membrane used for filtration is 0.1 μm or more, for example, 0.1 - 0.4 μm.

[0037] Preferably, in step (7), the method for judging that the liquid phase no longer contains soluble components includes any one of color observation, fluorescence observation, density measurement, viscosity measurement, distillation, freezing point test, sulfur content detection, organic chlorine content determination, gas chromatography (GC), gas chromatography - mass spectrometry (GC - MS), infrared spectroscopy, and atomic absorption spectroscopy.

[0038] Application of the above method for purifying asphaltene in the petroleum field.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] The present invention provides a method for purifying asphaltene, which fully dissolves asphaltene in a solvent, then adds an excessive precipitant, and separates the precipitated asphaltene and non - asphaltene components such as non - hydrocarbons, aromatic hydrocarbons, and saturated hydrocarbons that remain dissolved through oscillation and solid - liquid separation. Compared with traditional methods such as Soxhlet extraction, the method of the present invention has stronger desorption and dissolution capabilities for non - asphaltene components such as non - hydrocarbons adsorbed and co - precipitated by means of the solvent, and purifies asphaltene more thoroughly. The method provided by the present invention can obtain purified asphaltene, which helps in the research of organic geochemistry such as the molecular structure and behavior of asphaltene, molecular markers, as well as the research of elements and isotopes. Detailed implementation manners

[0041] In order to make those skilled in the art more clearly understand the technical solutions of the present invention, the following examples are listed for illustration. It should be noted that the following examples do not limit the scope of protection required by the present invention.

[0042] Unless otherwise specified, the raw materials, reagents, or devices used in the following examples can be obtained from conventional commercial channels or can be obtained by known existing methods.

[0043] A method for purifying asphaltene, comprising the following steps:

[0044] (1) Dissolve asphaltene in a solvent to obtain a mixed solution;

[0045] (2) Add a precipitant to the mixed solution obtained in step (1) to obtain a precipitation system;

[0046] (3) Oscillate the precipitation system obtained in step (2) to obtain an oscillated liquid;

[0047] (4) Separate the solid phase and the liquid phase from the oscillating liquid obtained in step (3) to obtain a precipitate and a liquid phase, thus completing the primary purification of asphaltene.

[0048] (5) Dissolve the precipitate obtained in step (4) in a solvent to obtain a mixed solution.

[0049] (6) Add a precipitant to the mixed solution obtained in step (5), and repeat the operations of steps (3) to (4) to complete the secondary purification of asphaltene.

[0050] (7) Repeat steps (5) to (6) to purify asphaltene multiple times until no soluble components remain in the liquid phase after the separation of the solid phase and the liquid phase, or the purity of asphaltene reaches the required level.

[0051] (8) Re-add a precipitant to the precipitate obtained after the last separation of the solid phase and the liquid phase in step (7) to obtain a precipitate system.

[0052] (9) Subject the precipitate system obtained in step (8) to oscillating treatment to obtain an oscillating liquid.

[0053] (10) Separate the solid phase and the liquid phase from the oscillating liquid obtained in step (9), and collect the precipitate, which is the purified asphaltene.

[0054] In the present invention, asphaltene is first fully dissolved in a solvent, and then a precipitant is added to the solution according to a volume ratio of the precipitant to the solvent of 90:10, 95:5, 99:1, etc., or other ratios more suitable for the working purpose to obtain a precipitate system. In the present invention, the solvent preferably includes any one of dichloromethane, toluene, benzene, and chloroform, and more preferably dichloromethane; the precipitant preferably includes any one of n-pentane, n-hexane, n-heptane, n-octane, petroleum ether, and acetone, and more preferably n-heptane; the dosage ratio of asphaltene to the solvent can be flexibly set according to the properties of asphaltene and the experimental purpose.

[0055] After obtaining the precipitate system, the present invention first subjects the precipitate system to oscillating treatment and then performs solid-liquid separation. In the present invention, the time of oscillating treatment is preferably 0 h or more, and more preferably 16 h; the temperature of oscillating treatment can be selected as room temperature or additional heating or cooling according to the experimental purpose; room temperature is 20 - 25 °C; the method of solid-liquid separation is preferably centrifugal separation or filtration; the rotation speed of centrifugal separation is preferably ≥1 revolution per minute, and more preferably 2500 - 4500 revolutions per minute; the centrifugal force of centrifugal separation is preferably ≥1 g, and more preferably 1000 - 2500 g; the time of centrifugal separation is preferably 0 min and above, and more preferably 10 - 15 min; the pore size of the filter membrane for filtration is 0.1 μm and above.

[0056] In a specific embodiment of the present invention, the dosage of the asphaltene sample is preferably ≥20 g to avoid too little eluted non-asphaltene components, which is not convenient for observation; the dosage ratio of asphaltene to solvent is preferably 1 g:1 mL; the volume ratio of the precipitant to the solvent is preferably 95:5 for the experiment.

[0057] After obtaining the precipitation system, the present invention performs an oscillation treatment on the precipitation system to obtain an oscillated liquid; the conditions of the oscillation treatment are the same as those of the above solution and will not be elaborated here.

[0058] After obtaining the oscillated liquid, the present invention separates the solid and liquid of the oscillated liquid and collects the precipitate. In the present invention, the conditions of the solid-liquid separation are the same as those of the above solution and will not be elaborated here; the present invention uses dichloromethane to collect the precipitate, that is, uses dichloromethane to completely dissolve the precipitate and transfer it to a container, and then evaporates the dichloromethane. The temperature for evaporating the dichloromethane is preferably 35 °C; the precipitate separated at each step is the asphaltene in the purification process.

[0059] When the liquid phase no longer contains soluble components or meets the requirements for the purity of asphaltene, a precipitant is added again to the precipitate obtained by solid-liquid separation to obtain a precipitation system; the precipitation system is subjected to an oscillation treatment to obtain an oscillated liquid; the oscillated liquid is separated into a solid phase and a liquid phase; the precipitate obtained by solid-liquid separation is collected. The precipitate collected this time is the purified asphaltene.

[0060] The method provided by the present invention gradually elutes the non-asphaltene components in the asphaltene by repeatedly dissolving and precipitating the asphaltene. The purified asphaltene components can be subjected to subsequent experiments as needed, and the present invention does not make specific limitations.

[0061] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention.

[0062] Example 1

[0063] Taking the asphaltene of the crude oil in the Pennsylvanian Tensleep Formation, Wind River Basin, Wyoming, USA as the research object, the asphaltene is purified by the method of the present invention. In this example, n-heptane is used as the precipitant and dichloromethane is used as the solvent. The specific process is as follows:

[0064] Weigh 25.3345 g of asphaltene, put it in a 1L glass bottle, and fully dissolve it in 25 mL of dichloromethane, then add 475 mL of n-heptane. At this time, the volume ratio of n-heptane to dichloromethane in the mixed solution is 90:10. Put the glass bottle into a shaker and shake it at room temperature (about 20°C) for 16 hours. Pour the mixed solution into a centrifuge tube and centrifuge it at 4500 rpm (about 1800g) for 15 minutes to separate the solid phase (precipitate) and the liquid phase. This is the first purification of asphaltene.

[0065] The solid phase (precipitate) was washed into the original glass bottle with 25 mL of dichloromethane, and 475 mL of n-heptane was added to the dichloromethane solution of asphaltene in the glass bottle, and the shaking and centrifugation were repeated to separate the solid phase (precipitate) and the liquid phase, thereby performing the second purification of the asphaltene;

[0066] This process is repeated until the asphaltene purity reaches the required level after the 10th purification, and the purification is stopped;

[0067] At this time, the mass of the precipitate is about 20g; 800mL of n-heptane is added to the precipitate to form a precipitation system; the precipitate system is placed in a shaker and shaken at room temperature (about 20°C) for 16 hours, the precipitate system is poured into a centrifuge tube, and centrifuged at 4500 rpm (about 1800g) for 15 minutes to separate the solid phase (precipitate) and the liquid phase; the precipitate is collected in a 22mL glass bottle with dichloromethane, and then the dichloromethane is evaporated at 35°C. The precipitate obtained this time is the purified asphaltene, and its mass is 19.9731g.

[0068] In this Example 1, the asphaltene of Wyoming crude oil is repeatedly dissolved and precipitated to induce the desorption and dissolution of non-asphaltene components such as adsorbed or co-precipitated non-hydrocarbons, aromatic hydrocarbons and saturated hydrocarbons, and separate from the asphaltene to obtain purified asphaltene to meet the needs of purified asphaltene in isotope research.

[0069] The initial asphaltene dosage was 25.3345 g, and the mass of the purified asphaltene was 19.0649 g, accounting for 75.3% of the total weight of the original sample; the adsorbed or co-precipitated non-asphaltene and some soluble asphaltene components removed by purification were 6.2696 g, accounting for 24.7%.

[0070] Comparative Example 1

[0071] The asphaltene of crude oil from the Pennsylvanian Tensleep Formation (Wind River Basin) in the Wind River Basin of Wyoming, USA was also studied, and the asphaltene was purified by Soxhlet extraction. The specific process is as follows:

[0072] Weigh 24.9061 g of 80-mesh asphaltene, wrap it in a degreased filter paper bag, put it into a filter paper cylinder, and load 150 mL of n-heptane into a 250-mL flat-bottom flask; place the filter paper cylinder containing the sample into the extraction tube, and connect the extraction tube to the flat-bottom flask; in the fume hood, place the flat-bottom flask part of the connected device into a water bath, and connect the extraction tube to a condenser reflux tube; set the water bath temperature to 99 °C, turn on the condenser reflux device, and start extraction; during this period, appropriately supplement the water bath and n-heptane; after one week, the n-heptane in the extraction tube is colorless; take a few drops of the n-heptane and drop them on the filter paper, and there is no residue after evaporation, stop Soxhlet extraction, disassemble the device, take out the degreased filter paper bag, put it into an oven, and dry it at 80 °C. The mass of the extracted asphaltene is 24.4817 g, accounting for 98.3% of the total weight of the original sample. The adsorbed or co-precipitated non-asphaltene and some easily soluble asphaltene components removed by extraction and purification are 0.4244 g, accounting for 1.7%, which is much less than the corresponding index of Example 1 of the present invention. As a comparison, the proportion of the adsorbed or co-precipitated non-asphaltene and some easily soluble asphaltene removed by purification in Example 1 of the present invention reaches 24.7%, which is 23.0% higher than that of Comparative Example 1 and 14.5 times that of Comparative Example 1. The corresponding components of the asphaltene obtained in Example 1 of the present invention are less and the purity is higher.

[0073] Comparative Example 2

[0074] Similarly, taking the asphaltene of the crude oil from the Pennsylvanian Tensleep Formation, Wind River Basin, Wyoming, USA as the research object, compared with Example 1, in Comparative Example 2, except that the volume ratio of n-heptane to dichloromethane in the solution is changed to 95:5, other conditions are the same as those in Example 1.

[0075] In this Comparative Example 2, weigh 25.0127 g of asphaltene. After purification, the mass of the asphaltene is 21.9713 g, accounting for 87.8% of the total weight of the original sample; the mass of the adsorbed or co-precipitated non-asphaltene and some easily soluble asphaltene components removed by purification is 3.0414 g, accounting for 12.2%, which is less than the corresponding index of Example 1 of the present invention. As a comparison, the proportion of the adsorbed or co-precipitated non-asphaltene and some easily soluble asphaltene removed by purification in Example 1 of the present invention reaches 24.7%, which is 12.6% higher than that of Comparative Example 2 and 2.0 times that of Comparative Example 2. The corresponding components of the asphaltene obtained in Example 1 of the present invention are less and the purity is higher.

[0076] The above embodiments are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for purifying asphaltene, characterized in that: The following steps are involved: (1) dissolving asphaltene in a solvent to obtain a mixed solution; (2) adding a precipitant to the mixed solution obtained in step (1) to obtain a precipitation system; (3) shaking the precipitation system obtained in step (2) to obtain a shaking liquid; (4) separating the solid phase and the liquid phase of the oscillated liquid obtained in step (3) to obtain a precipitate and a liquid phase; (5) dissolving the precipitate obtained in step (4) in a solvent to obtain a mixed solution; (6) adding a precipitant to the mixed solution obtained in step (5), and repeating the operations from step (3) to step (4) to complete the re-purification of the asphaltene; (7) Repeating steps (5) to (6) to purify the asphaltene multiple times until the solid phase and the liquid phase are separated and the obtained liquid phase no longer contains soluble components or the purity of the asphaltene reaches a required level; (8) adding a precipitant to the precipitate obtained after the last separation of the solid phase and the liquid phase in step (7) to obtain a precipitation system; (9) shaking the precipitation system obtained in step (8) to obtain a shaking liquid; (10) The oscillated liquid obtained in step (9) is separated into a solid phase and a liquid phase, and the precipitate is collected to obtain the purified asphaltene.

2. The method according to claim 1, characterized in that In step (1), the solvent includes any one of dichloromethane, chloroform, toluene and benzene.

3. The method according to claim 1, characterized in that In step (2), the precipitant includes any one of n-pentane, n-hexane, n-heptane, n-octane, petroleum ether and acetone.

4. The method according to claim 1, characterized in that: In step (1), the amount of asphaltene used is greater than 20 g; and / or, in step (1) and step (2), the ratio of asphaltene to precipitant is 1 g: 1 to 50 mL.

5. The method according to claim 1, characterized in that In step (1) and step (2), the volume ratio of the precipitant to the solvent is 90-99:1-10, but does not include 95:

5.

6. The method according to claim 1, characterized in that In step (1), the ratio of asphaltene to solvent is 1 g: 0.5-90 mL.

7. The method according to claim 1, characterized in that In step (4), the solid-liquid separation method includes centrifugal separation or filtration.

8. The method according to claim 7, characterized in that The pore size of the filter membrane used for the filtration is 0.1 μm or above.

9. The method according to any one of claims 1 to 7, characterized in that: In step (7), the method for determining whether the liquid phase no longer contains soluble components includes any one of color observation, fluorescence observation, density measurement, viscosity measurement, distillation, freezing point test, sulfur content detection, organic chlorine content determination, gas chromatography, gas chromatography-mass spectrometry, infrared spectroscopy, and atomic absorption spectroscopy.

10. Application of the method according to any one of claims 1 to 9 in the petroleum field.