Method for separating monoaromatic sterane compounds in crude oil and rock extract

Abstract

The invention provides a method for separating monoaromatic sterane compounds in crude oil and rock extracts, which is characterized by comprising the following steps: (1) carrying out first adsorption on the crude oil and / or rock extracts by using a chromatographic column filled with silica gel, and eluting by using a first solvent to obtain an eluent; and (2) carrying out second adsorption on the eluent by using a chromatographic column filled with heavy metal modified silica gel, eluting by using a second solvent, and eluting by using a third solvent to obtain the monoaromatic sterane component. According to the method, through two-step chromatographic separation, the mono-aromatic sterane compound can be efficiently extracted from a complex organic matter system, the technical means such as gas chromatography-mass spectrometry can be further used for analyzing the mono-aromatic sterane compound, and geochemical information of the mono-aromatic sterane compound is effectively utilized.

Description

Technical Field

[0001] The invention belongs to the technical field of petroleum exploration and analysis, and relates to a method for separating monoaromatic sterane compounds in crude oil and rock extracts. Background Art

[0002] Monoaromatic sterane compounds are an important class of biomarker compounds in crude oil and rock extracts. They are of great significance for evaluating maturity, especially the maturity of the high-maturity evolution stage. They can effectively supplement the lack of indication ability of biomarkers such as steranes commonly used in the high-maturity stage. Since the 1980s, petroleum geochemical scientists have paid attention to the ability of monoaromatic sterane compounds to indicate maturity. However, the content of monoaromatic sterane compounds in petroleum and rock extracts is generally very low, and the mass spectrum fragments are similar to other hydrocarbons. Its analysis is often interfered by alkane compounds, especially steranes and aromatic sterane compounds. Therefore, separating monoaromatic sterane compounds from complex organic mixtures and further characterizing and analyzing them is a reasonable way to effectively utilize the geochemical information contained in monoaromatic steranes. However, it is very difficult to separate monoaromatic sterane compounds because although they have aromatic ring structures, their aromaticity is extremely weak, and it is difficult to use conventional adsorbents to separate them from alkane compounds. With the existing separation methods, the monoaromatic sterane components obtained are still often mixed with alkanes or aromatic compounds. It is worth noting that due to the unique chemical properties of monoaromatic steranes, it is relatively easy to separate them from alkanes into the same component as other aromatic compounds. Further considering that heavy metals can form strong complexes with aromatic rings, it is hoped that the use of heavy metal-modified adsorbents can further separate monoaromatic steranes from alkanes.

[0003] In order to effectively utilize the geochemical information contained in monoaromatic sterane compounds, it is necessary to develop a convenient separation method for separating these compounds from crude oil and rock extracts. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a method for separating monoaromatic sterane compounds in crude oil and rock extracts. The method can efficiently extract monoaromatic sterane compounds from a complex organic system through two-step chromatographic separation, and can further use technical means such as gas chromatography-mass spectrometry to analyze the monoaromatic sterane compounds and effectively utilize their geochemical information.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention provides a method for separating monoaromatic sterane compounds in crude oil and rock extracts, the method comprising the following steps:

[0007] (1) using a chromatography column filled with silica gel to perform a first adsorption on the crude oil and / or rock extract, and eluting with a first solvent to obtain an eluate;

[0008] (2) using a chromatography column filled with heavy metal-modified silica gel to perform a second adsorption on the eluate, eluting with a second solvent, and then eluting with a third solvent to obtain a monoaromatic sterane component.

[0009] As a preferred technical solution of the present invention, the first solvent is a C5-C10 alkane solvent, for example, it can be C5 alkane, C6 alkane, C7 alkane, C8 alkane, C9 alkane or C10 alkane.

[0010] As a preferred technical solution of the present invention, the C5-C10 alkane solvent includes any one of n-pentane, n-hexane or n-heptane, or a combination of at least two of them. Typical but non-limiting examples of the combination include: a combination of n-pentane and n-hexane, a combination of n-hexane and n-heptane, a combination of n-heptane and n-pentane, or a combination of n-pentane, n-hexane and n-heptane, etc.

[0011] As a preferred technical solution of the present invention, the heavy metal includes any one of gold, silver, copper, iron, mercury, lead or cadmium, or a combination of at least two of them. Typical but non-limiting examples of the combination include: a combination of gold and silver, a combination of silver and copper, a combination of copper and iron, a combination of iron and mercury, a combination of mercury and lead, a combination of lead and cadmium, a combination of cadmium and lead, or a combination of gold, copper and lead, etc.

[0012] As a preferred technical solution of the present invention, the second solvent is a C5-C10 alkane solvent, for example, it can be C5 alkane, C6 alkane, C7 alkane, C8 alkane, C9 alkane or C10 alkane.

[0013] As a preferred technical solution of the present invention, the C5-C10 alkane solvent includes any one of n-pentane, n-hexane or n-heptane, or a combination of at least two of them. Typical but non-limiting examples of the combination include: a combination of n-pentane and n-hexane, a combination of n-hexane and n-heptane, a combination of n-heptane and n-pentane, or a combination of n-pentane, n-hexane and n-heptane, etc.

[0014] As a preferred technical solution of the present invention, the third solvent is a volatile polar solvent.

[0015] As a preferred technical solution of the present invention, the volatile polar solvent includes any one of dichloromethane, chloroform or ethanol, or a combination of at least two of them. Typical but non-limiting examples of the combination include: a combination of dichloromethane and chloroform, a combination of chloroform and ethanol, a combination of ethanol and dichloromethane, or a combination of dichloromethane, chloroform and ethanol, etc.

[0016] As a preferred technical solution of the present invention, the silica gel is dried before being filled into the chromatography column.

[0017] As a preferred technical solution of the present invention, the method for separating monoaromatic sterane compounds in crude oil and rock extracts comprises the following steps:

[0018] (1) using a chromatography column filled with silica gel to perform a first adsorption on the crude oil and / or rock extract, and eluting with a C5-C10 alkane solvent to obtain an eluate;

[0019] The C5-C10 alkane solvent includes any one of n-pentane, n-hexane or n-heptane, or a combination of at least two thereof;

[0020] (2) using a chromatography column filled with silica gel modified with heavy metals to perform a second adsorption on the eluate, wherein the heavy metals include any one or a combination of at least two of gold, silver, copper, iron, mercury, lead or cadmium; after eluting with a C5-C10 alkane solvent, eluting with a volatile polar solvent to obtain a monoaromatic sterane component;

[0021] The C5-C10 alkane solvent includes any one of n-pentane, n-hexane or n-heptane, or a combination of at least two thereof;

[0022] The volatile polar solvent includes any one of dichloromethane, chloroform or ethanol, or a combination of at least two thereof.

[0023] Compared with the prior art solutions, the present invention has at least the following beneficial effects:

[0024] The present invention provides a method for separating monoaromatic sterane compounds in crude oil and rock extracts. The method can efficiently extract monoaromatic sterane compounds from a complex organic system through two-step chromatographic separation, and can further use technical means such as gas chromatography-mass spectrometry to analyze the monoaromatic sterane compounds and effectively utilize their geochemical information. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic flow chart of a method for separating monoaromatic sterane compounds from crude oil and rock extracts provided in Example 1 of the present invention;

[0026] Figure 2 The total ion chromatogram of the crude oil saturated fraction, saturated hydrocarbon component and monoaromatic sterane component separated in Example 1 of the present invention is shown in the gas chromatography-mass spectrometry (GC-MS);

[0027] Figure 3 The GC-MS extraction mass chromatogram of a series of monoaromatic sterane compounds in the monoaromatic sterane component of crude oil separated in Example 1 of the present invention;

[0028] Figure 4 This is a GC-MS extraction mass chromatogram of a series of monoaromatic sterane compounds corresponding to the crude oil saturated hydrocarbon component separated in Example 1 of the present invention.

[0029] The present invention is further described in detail below. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0031] The specific embodiment of the present invention provides a method for separating monoaromatic sterane compounds in crude oil and rock extracts, the method comprising the following steps:

[0032] (1) using a chromatography column filled with silica gel to perform a first adsorption on the crude oil and / or rock extract, and eluting with a first solvent to obtain an eluate;

[0033] (2) using a chromatography column filled with heavy metal-modified silica gel to perform a second adsorption on the eluate, eluting with a second solvent, and then eluting with a third solvent to obtain a monoaromatic sterane component.

[0034] In the present invention, a silica gel adsorbent is used to retain crude oil and / or rock extract samples, a small molecule alkane solvent of a first solvent is used to elute the saturated fraction, and the monoaromatic sterane compounds are weakly retained on the silica gel and are eluted together into the saturated fraction; a heavy metal-modified silica gel adsorbent is used to further separate the saturated hydrocarbons and the monoaromatic sterane compounds in the saturated fraction, a second solvent is used to elute the saturated hydrocarbon compounds to obtain a saturated hydrocarbon component, and a third solvent is further used to elute the monoaromatic sterane compounds to obtain a monoaromatic sterane component. Among them, the reason for selecting a heavy metal-modified silica gel adsorbent to separate saturated hydrocarbons and monoaromatic sterane compounds is that the monoaromatic sterane compounds are aromatic compounds, which have a large π bond of a benzene ring and can form a complex with heavy metal ions, and saturated hydrocarbons do not have any functional groups and electron-rich structures, while heavy metal ions and saturated hydrocarbon compounds do not produce an interaction force.

[0035] In a specific embodiment of the present invention, the dried silica gel is loaded into a glass chromatography column and fully tapped and compacted, and a non-polar small molecule alkane solvent is used to wet the filler.

[0036] In a specific embodiment of the present invention, the temperature for drying the silica gel can be 100-150° C., preferably 120° C.; and the time can be 2-6 hours, preferably 4 hours.

[0037] In a specific embodiment of the present invention, the amount of silica gel loaded in the chromatography column can be 3 to 6 g, preferably 4 g. However, this amount is not limited to the above amount, and can be adjusted according to the volume of the specific chromatography column, the mass of the crude oil and / or rock extract, and the content of the monoaromatic sterane compounds, and is not further limited here.

[0038] In a specific embodiment of the present invention, the non-polar small molecule alkane solvent that wets the silica gel can be any one of n-pentane, n-hexane or n-heptane.

[0039] In a specific embodiment of the present invention, the amount of the first solvent can be 10 to 30 mL, preferably 20 mL. Before the first adsorption, the first solvent is used to dissolve the crude oil and / or rock extract, and the amount used is 1 to 5 mL. The mass of the crude oil and / or rock extract dissolved by the first solvent can be 10 to 50 mg. However, it is not limited to the above amount, and can be adjusted according to the specific mass of the crude oil and / or rock extract and the content of its monoaromatic sterane compounds, and is not further limited here.

[0040] In one specific embodiment of the present invention, the heavy metal-modified silica gel is loaded into a glass chromatography column and fully tapped and compacted, and a non-polar small molecule alkane solvent is used to wet the filler.

[0041] In a specific embodiment of the present invention, the non-polar small molecule alkane solvent that wets the heavy metal-modified silica gel can be any one of n-pentane, n-hexane or n-heptane.

[0042] In a specific embodiment of the present invention, the amount of heavy metal-modified silica gel in the chromatography column is 1 to 3 g, preferably 2 g. However, this amount is not limited to the above amount and can be adjusted according to the content of the monoaromatic sterane compound in the eluent of step (1), and is not further limited here.

[0043] In a specific embodiment of the present invention, the amount of the second solvent can be 20-50 mL, preferably 30 mL, but is not limited to the above amount, and can be adjusted according to the content of saturated hydrocarbons in the eluent in step (1), and is not further limited here.

[0044] In a specific embodiment of the present invention, the amount of the third solvent may be 10-30 mL, preferably 20 mL, but is not limited to the above amount, and may be adjusted according to the content of the monoaromatic sterane compound in the eluent of step (1), and is not further limited here.

[0045] To better illustrate the present invention and facilitate understanding of the technical solution of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0046] Example 1

[0047] This embodiment provides a method for separating monoaromatic sterane compounds in crude oil and rock extracts. The flow chart is as follows: Figure 1 As shown, the method comprises the following steps:

[0048] (1) Weigh 30 mg of crude oil sample (the crude oil sample was taken from the heavy oil area of ​​Shengli Oilfield. Previous studies have shown that the crude oil in this area contains monoaromatic sterane compounds) and dissolve it in 1 mL of n-hexane solvent; fill 4 g of silica gel baked at 120°C for 4 h into a glass chromatography column and wet it with n-hexane solvent, then drop the dissolved sample into the chromatography column; elute with 25 mg of n-hexane to obtain the saturated fraction, and concentrate the sample to 1 mL under a gentle nitrogen purge;

[0049] (2) Then, 2 g of silver-modified silica gel adsorbent is filled into another glass chromatography column, which is moistened with n-hexane, and the sample concentrated to saturation is dripped into the chromatography column; 30 mL of n-hexane is used for elution to obtain the saturated hydrocarbon component, and then 20 mL of dichloromethane solvent is used for elution to obtain the monoaromatic sterane component.

[0050] The saturated fraction, saturated hydrocarbon fraction and monoaromatic sterane fraction separated were analyzed by gas chromatography-mass spectrometry. Figure 2 It can be seen that the total ion chromatograms of the saturated hydrocarbon component and the saturated fraction are almost the same, and the monoaromatic sterane composition is very different from the two, indicating that the saturated hydrocarbon compounds are well concentrated in the saturated fraction, and also indicating that the content of monoaromatic sterane compounds in the original oil sample is very low; Figure 3 It is a monoaromatic sterane component. Through the extraction mass chromatography of a series of monoaromatic sterane compounds, it can be confirmed that the compounds with different alkyl substitutions are effectively separated and enriched in the monoaromatic sterane component. Figure 4 This is the extraction mass chromatogram of a series of monoaromatic sterane compounds corresponding to the saturated hydrocarbon component. It can be seen from the chromatogram that no monoaromatic sterane compounds are detected in this component, indicating that the monoaromatic sterane compounds are effectively retained by the heavy metal-modified adsorbent and are not eluted in advance, but are completely enriched in the target component.

[0051] The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed structural features, that is, it does not mean that the present invention must rely on the above-mentioned detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0052] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0053] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0054] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for separating monoaromatic sterane compounds from crude oil and rock extracts, characterized in that: The method comprises the following steps: (1) using a chromatography column filled with silica gel to perform a first adsorption on the crude oil and / or rock extract, and eluting with a first solvent to obtain an eluate; (2) using a chromatography column filled with heavy metal-modified silica gel to perform a second adsorption on the eluate, eluting with a second solvent, and then eluting with a third solvent to obtain a monoaromatic sterane component.

2. The method according to claim 1, characterized in that The first solvent is a C5-C10 alkane solvent.

3. The method according to claim 2, characterized in that The C5-C10 alkane solvent includes any one of n-pentane, n-hexane or n-heptane, or a combination of at least two of them.

4. The method according to claim 1, characterized in that: The heavy metal includes any one of gold, silver, copper, iron, mercury, lead or cadmium, or a combination of at least two of them.

5. The method according to claim 1, characterized in that The second solvent is a C5-C10 alkane solvent.

6. The method according to claim 5, characterized in that The C5-C10 alkane solvent includes any one of n-pentane, n-hexane or n-heptane, or a combination of at least two of them.

7. The method according to claim 1, characterized in that The third solvent is a volatile polar solvent.

8. The method according to claim 7, characterized in that The volatile polar solvent includes any one of dichloromethane, chloroform or ethanol, or a combination of at least two thereof.

9. The method according to claim 1, characterized in that: The silica gel is dried before being filled into the chromatography column.

10. The method according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: (1) using a chromatography column filled with silica gel to perform a first adsorption on the crude oil and / or rock extract, and eluting with a C5-C10 alkane solvent to obtain an eluate; The C5-C10 alkane solvent includes any one of n-pentane, n-hexane or n-heptane, or a combination of at least two thereof; (2) using a chromatography column filled with silica gel modified with heavy metals to perform a second adsorption on the eluate, wherein the heavy metals include any one or a combination of at least two of gold, silver, copper, iron, mercury, lead or cadmium; after eluting with a C5-C10 alkane solvent, eluting with a volatile polar solvent to obtain a monoaromatic sterane component; The C5-C10 alkane solvent includes any one of n-pentane, n-hexane or n-heptane, or a combination of at least two thereof; The volatile polar solvent includes any one of dichloromethane, chloroform or ethanol, or a combination of at least two thereof.

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