Method for rapidly separating phenol and carbazole compounds by using silica gel

Abstract

The invention provides a method for rapidly separating phenol and carbazole compounds by using silica gel, which comprises the following steps: fully mixing n-pentane with crude oil or rock extract added with a proper amount of internal standard, dissolving, and precipitating to obtain asphaltene; transferring asphaltene into the upper end of a silica gel column, and leaching and separating by using a mixed solution of n-pentane and dichloromethane to obtain saturated hydrocarbon and aromatic hydrocarbon; and eluting the saturated hydrocarbon and aromatic hydrocarbon fractions in the silica gel column by using a mixed solution of n-pentane and diethyl ether to obtain phenol and carbazole fractions. The method is easy to operate, efficient, rapid, safe, environmentally friendly, wide in material source, suitable for batch sample analysis in oil reservoir geochemical research and capable of being used and popularized as a conventional crude oil family component separation method.

Description

Technical Field

[0001] The invention relates to the field of petroleum exploration and development, in particular to the field of reservoir geochemistry research and application, and specifically to a method for quickly separating phenols and carbazole compounds by using silica gel. Background Art

[0002] Non-hydrocarbon compounds, i.e. compounds containing N, S, and O heteroatoms, limit geochemical research and applications, which is largely related to the difficulty in separating and characterizing such compounds. Phenols and carbazole compounds are non-hydrocarbon compounds (NSO compounds). Due to their polarity, they often interact with oil, water, and rock, thus affecting oil viscosity, PVT properties, and reservoir wettability (affecting secondary oil recovery). Petroleum nitrogen compounds can be strongly and selectively adsorbed on mineral surfaces or solid organic matter, thus effectively indicating the direction and distance of oil and gas migration. Therefore, accurate and rapid separation of phenols and carbazole compounds is of great significance in oil exploration and development, and is an effective auxiliary tool for studying reservoir geochemistry and a new research direction for this discipline. Phenols and carbazole compounds have become potential tracers for oil-water distribution.

[0003] Alkylphenols and neutral nitrogen-containing compounds in non-hydrocarbon compounds are a class of polar micro-(trace) components in crude oil. The conventional separation and analysis process is complicated and difficult, and the requirements for experimental conditions and processes are very strict. Therefore, the separation and analysis methods of pyrrole compounds have become the key to their research. Many scholars have done a lot of work on the separation and analysis of such compounds, such as using anion exchange chromatography, ion exchange chromatography and alkaline extraction to separate trace alkylphenol compounds in crude oil; using acid-modified silica gel selective extraction, benzene dissolution in hydrochloric acid extraction and double column chromatography to separate alkaline and neutral nitrogen-containing compounds in crude oil. These methods are unique in separating such compounds, but the analysis process is long, labor-intensive, time-consuming and reagent-intensive, and it is difficult to adapt to the needs of large-scale sample analysis in reservoir geochemical research. Bowler et al. used C 18The column was used to separate alkylphenols and neutral nitrogen-containing compounds in crude oil, and then the alkylphenols and neutral nitrogen-containing compounds were analyzed by gas chromatography-mass spectrometry (GC-MS) respectively, achieving good results. After the 1960s, people first used the two-step method to detect compounds such as carbazole, and then gradually developed the SPE (solid phase extraction) method to separate non-hydrocarbon compounds. In recent decades, scholars at home and abroad have proposed various separation and analysis processes, which can be summarized as follows: (1) liquid chromatography; (2) high performance liquid chromatography; (3) separation-packed column rapid separation method; (4) alkaline-acid separation method. The classic effective separation method for pyrrole nitrogen-containing compounds - two-step liquid chromatography was first established by Later et al. Later, Li et al. made appropriate improvements and proposed that asphaltene must be precipitated before washing the column in order to effectively separate and characterize "free" nitrogen-containing compounds, and that the co-distillation of non-nitrogen heteroatoms can be reduced by repeating the alumina chromatography column steps. Bennett et al. established a rapid separation method using a packed column, i.e., a one-step method, which greatly simplified the separation procedure of pyrrole compounds. In the mid-1990s, China began to introduce a two-step method and used imported reagents to conduct research on pyrrole compounds. Bao Jianping et al. were the first to use a one-step method to separate nitrogen-containing compounds in China and achieved good results. Li Sumei et al. compared and evaluated the two separation methods of pyrrole nitrogen-containing compounds and the experimental results of using domestic and imported reagents in the two-step separation method. However, because the two-step separation method is time-consuming and requires a large amount of reagents, a one-step method was developed. The two-step separation process is long, and information on saturated hydrocarbons and aromatic hydrocarbons can be obtained at the same time, but information on phenols cannot be obtained; the one-step method is faster, but its recovery rate is low. In order to solve the problems of insufficient timeliness and economy in the separation of phenols and carbazole compounds and reduce pollution to the environment, it is urgent to establish a more convenient, efficient, economical and environmentally friendly separation method. Summary of the invention

[0004] The purpose of the present invention is to solve at least one of the above-mentioned deficiencies in the prior art. For example, one of the purposes of the present invention is to achieve rapid separation of phenol and carbazole compounds in crude oil or rock extracts, a second purpose of the present invention is to solve the problem of insufficient timeliness and economy in separating phenol and carbazole compounds, and a third purpose of the present invention is to reduce the pollution to the environment caused by the process of separating phenol and carbazole compounds.

[0005] In order to achieve the above object, the present invention provides a method for quickly separating phenol and carbazole compounds using silica gel, which may include the following steps:

[0006] The n-pentane is fully mixed and dissolved with crude oil or rock extract with an appropriate amount of internal standard, and asphaltene is obtained after precipitation; the asphaltene is transferred to the upper end of the silica gel column, and is eluted and separated with a mixture of n-pentane and dichloromethane to obtain saturated hydrocarbons and aromatic hydrocarbons; the silica gel column is eluted with a mixture of n-pentane and ether to obtain phenol and carbazole fractions; the phenolic compounds need to be derivatized.

[0007] Alternatively, the internal standard may be: 2-naphthol as the quantitative internal standard for phenolic compounds, and N-phenylcarbazole as the quantitative internal standard for carbazole compounds.

[0008] Optionally, the silica gel in the silica gel column may have a particle size of 70 to 230 meshes and be activated at 150 to 180° C. for at least 8 hours before use.

[0009] Alternatively, the preparation process of the silica gel column may include: adding a small amount of absorbent cotton to the bottom of a glass Pasteur pipette, and then filling the column with active silica gel.

[0010] Alternatively, the n-pentane may be of premium grade purity, and the dichloromethane may be redistilled analytical grade dichloromethane.

[0011] Optionally, the volume ratio of n-pentane to dichloromethane in the mixed solution 1 may be 8-9:1-2, for example, 9:1, 8:2, etc.

[0012] Optionally, the volume ratio of n-pentane to diethyl ether in the mixed solution 2 may be 6-7:3-4, such as 7:3, 6:4, etc.

[0013] Optionally, the step of using a mixture of n-pentane and dichloromethane for elution separation can be performed under the action of gravity.

[0014] Alternatively, the step of eluting the silica gel column with n-pentane and diethyl ether may be performed under the action of gravity.

[0015] Compared with the prior art, the beneficial effects of the present invention may include at least one of the following:

[0016] (1) The method of the present invention is applicable to the separation of crude oil and alkylphenol series, alkylcarbazole series, and benzocarbazole series.

[0017] (2) The silica gel column used in the present invention is filled with silica gel and a small amount of absorbent cotton, which solves the problems of large dosage, low recovery rate, long processing time and the like in the existing separation method, and can effectively ensure the separation effect of phenol and carbazole compounds.

[0018] (3) The separation components of the present invention can meet the quality requirements of subsequent chromatography, color quality, isotope and other analyses of phenol and carbazole compounds, and are simple to operate, efficient, fast, safe and environmentally friendly.

[0019] (4) Compared with the traditional SPE separation method, the recovery rate of the method of the present invention is significantly improved, which is suitable for batch sample analysis in reservoir geochemical research and can be promoted and used as a conventional separation method for crude oil group components. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings constituting a part of this application are used to provide a further understanding of the present invention. The above and other objects and / or features of the present invention will become more apparent through the following description in conjunction with the accompanying drawings, wherein:

[0021] Figure 1 The total ion current diagram of GC-MS of the alkylphenol (silylated derivative) and neutral nitrogen-containing compound fractions in Example 1 is shown;

[0022] Figure 2A shows the mass chromatogram of alkyl carbazole separated using silica gel in Example 1;

[0023] Figure 2B The mass chromatogram of benzocarbazole separated using silica gel in Example 1 is shown. DETAILED DESCRIPTION

[0024] Hereinafter, the present invention will be described in detail in conjunction with exemplary embodiments and drawings, but the following embodiments are only used to help understand the technology of the present invention and shall not be used as a further limitation on the protection scope of the present invention.

[0025] Exemplary Embodiment 1

[0026] This exemplary embodiment provides a method for quickly separating phenol and carbazole compounds using silica gel, comprising the following steps:

[0027] S01: Add n-pentane to an appropriate amount of internal standard crude oil or rock extract, mix and dissolve them thoroughly, and obtain asphaltene after precipitation.

[0028] In this embodiment, a proper amount of crude oil or rock extract is first weighed, and then a proper amount of internal standard is added, the internal standard can be: 2-naphthol for the quantitative internal standard of phenolic compounds, N-phenylcarbazole for the quantitative internal standard of carbazole compounds, and then a proper amount of n-pentane is added for mixed dissolution. Preferably, the amount of internal standard added is 60-120% of the compound with the highest content in the series of compounds, which can make the quantitative error of the internal standard and the calibrated compound smaller in the same content range.

[0029] S02: The asphaltene is transferred to the upper end of the silica gel column and eluted and separated using a mixture of n-pentane and dichloromethane to obtain saturated hydrocarbons and aromatic hydrocarbons.

[0030] In this embodiment, the silica gel column can be a glass Pasteur pipette with a small amount of absorbent cotton added to the bottom to prevent leakage of silica gel, and the column is filled with active silica gel; the silica gel particle size can be 70-230 mesh, such as 80 mesh, 110 mesh, 150 mesh, 200 mesh, 210 mesh, etc., and the above-mentioned silica gel can be kept in a muffle furnace or oven at 150-180°C (such as 151°C, 166°C, 170°C, 179°C, etc.) for at least 8 hours before use to change the activity of the silica gel so that it can fully adsorb phenols and carbazole compounds.

[0031] The dichloromethane is redistilled analytical pure dichloromethane, and the volume ratio of the mixed solution of n-pentane and dichloromethane can be 8-9:1-2, such as 9:1, 8:2, etc. The polarity of the mixed solution with this volume ratio can completely wash the saturated hydrocarbons and aromatic hydrocarbon compounds from the silica gel column.

[0032] In this embodiment, based on 100 mg to 500 mg of crude oil or rock extract, the amount of n-pentane and dichloromethane mixed solution used can be 5 to 6 ml to flush the chromatographic column to obtain saturated hydrocarbons and aromatic hydrocarbons. For example, the amount of the mixed solution used can be 5 ml, 5.6 ml, 6 ml, etc.

[0033] S03: Use a mixture of n-pentane and ether to elute the silica gel column to obtain phenol and carbazole fractions. Phenolic compounds need to be derivatized. The main purpose is to use BSTFA + 1% TMCS to silylate the hydroxyl groups in the phenolic compounds to reduce their polarity and increase the volatility of such compounds in gas chromatography column analysis. In addition, it also enables the derivatized compounds and nitrogen-containing compounds to meet the conditions for separation and analysis on the same type of chromatographic column.

[0034] In this embodiment, the mixed liquid can be a solvent in which the volume ratio of n-pentane and ether can be 6-7:3-4 (for example, 7:3, 6:4, etc.). The polarity of the solvent in this volume ratio can completely wash phenols and carbazole compounds from the silica gel column, and phenol and carbazole distillates are obtained after elution and concentration; based on 100mg-500mg of crude oil or rock extract, the elution amount can be 5-6ml, for example, 5ml, 5.8ml, 6ml, etc.

[0035] The n-pentane is high-grade pure n-pentane.

[0036] In order to better understand the above exemplary embodiments, they are further described below in conjunction with specific embodiments.

[0037] Example 1

[0038] This example provides a method for separating phenol and carbazole compounds using silica gel, which specifically includes the following steps:

[0039] Step 1: Weigh a certain amount of crude oil sample (100 mg) and add an appropriate amount of internal standard. Then add high-grade pure n-pentane to the crude oil sample and let it stand overnight to precipitate asphaltene.

[0040] Step 2: Prepare a silica gel column by inserting a small amount of cotton wool into the bottom of a glass Pasteur pipette (0.57 cm inner diameter, 23 cm total length). Fill the column with active silica gel (approximately 2 g). Transfer the precipitated asphaltene to the upper end of the silica gel column.

[0041] Step 3: Mix 5 ml of n-pentane and dichloromethane in a volume ratio of 9:1 and use it to wash the silica gel column to elute and separate the saturated hydrocarbons and aromatic hydrocarbons from the silica gel column.

[0042] Step 4: 5 ml of a mixture of n-pentane and ether in a volume ratio of 7:3 was used to elute the silica gel column to obtain phenol and carbazole fractions. Among them, the phenolic compounds were derivatized to obtain silylated derivatives of alkylphenols.

[0043] like Figure 1 The total ion current diagram of the GC-MS of the above-mentioned alkylphenol (silylated derivative) and neutral nitrogen-containing compound fraction is shown, wherein IS1 is internal standard 1, which is 2-naphthol; IS2 is internal standard 2, which is N-phenylcarbazole.

[0044] from Figure 1 The retention time of various compounds was analyzed. The silylated alkylphenol series (C0-C3) elutes between 22-48 min, the C0-C4 substituted alkylcarbazole and C0-C4 substituted alkylbenzocarbazole series elute between 60-75 min and 76-88 min, respectively, showing good separation and detection effects.

[0045] Figure 2A is the mass chromatogram of alkyl carbazole separated by silica gel. Figure 2B The mass chromatogram of benzocarbazole separated by silica gel.

[0046] As can be seen from Figures 2A and 2B, alkylphenols and neutral nitrogen-containing compounds can be separated from crude oil using a silica gel chromatography column; by using appropriate chromatography-mass spectrometry conditions, alkylphenols and neutral nitrogen-containing compounds can be detected simultaneously with a single injection.

[0047] Example 2

[0048] In this example, the phenols and carbazole compounds separated in Example 1 were subjected to GCMS analysis, and the results of the GCMS analysis are shown in Table 1. Table 1 shows the GCMS identification results of a mixed standard sample consisting of 20 monomeric alkylphenol compounds. The 20 monomeric alkylphenol compounds identified include C0-substituted phenol, 3 methylphenol isomers, 8 C2-substituted alkylphenol isomers, and 8 C3-substituted alkylphenol isomers. In the mass spectrum of the silylated alkylphenol compound, its M + The abundance of fragments of -15 is relatively high and is often its base peak, so the mass-to-charge ratios of 151, 165, 179 and 193 can be used to detect C0-C3 substituted silylated phenol derivatives.

[0049] Table 1 Phenol and carbazole compound components separated and obtained in Example 1

[0050]

[0051]

[0052] Although the present invention has been described above by combining with exemplary embodiments, it will be apparent to those skilled in the art that various modifications and changes may be made to the exemplary embodiments of the present invention without departing from the spirit and scope defined in the claims.

Claims

1. A method for rapidly separating phenol and carbazole compounds using silica gel, characterized in that: The method comprises the following steps: The n-pentane is fully mixed and dissolved with crude oil or rock extract with an appropriate amount of internal standard, and asphaltene is obtained after precipitation; The asphaltenes are transferred to the upper end of the silica gel column and eluted and separated using a mixture of n-pentane and dichloromethane to obtain saturated hydrocarbons and aromatic hydrocarbons; The silica gel column was eluted with a mixture of n-pentane and ether to obtain phenol and carbazole fractions; the phenolic compounds needed to be derivatized.

2. The method for rapid separation of phenol and carbazole compounds using silica gel according to claim 1, characterized in that: The internal standards are: 2-naphthol as the quantitative internal standard for phenolic compounds, and N-phenylcarbazole as the quantitative internal standard for carbazole compounds.

3. The method for rapid separation of phenol and carbazole compounds using silica gel according to claim 1, characterized in that: The particle size of the silica gel in the silica gel column is 70-230 meshes, and the silica gel is activated at 150-180° C. for at least 8 hours before use.

4. The method for rapid separation of phenol and carbazole compounds using silica gel according to claim 1, characterized in that: The preparation process of the silica gel column comprises: adding a small amount of absorbent cotton at the bottom of a glass Pasteur pipette, and then filling the column with active silica gel.

5. The method for rapid separation of phenol and carbazole compounds using silica gel according to claim 1, characterized in that: The n-pentane is of premium grade purity, and the dichloromethane is redistilled analytical grade dichloromethane.

6. The method for rapid separation of phenol and carbazole compounds using silica gel according to claim 1, characterized in that: The volume ratio of n-pentane to dichloromethane in the first mixed solution is 8-9:1-2.

7. The method for rapid separation of phenols and carbazole compounds using silica gel according to claim 1, characterized in that: The volume ratio of n-pentane to ether in the mixed solution 2 is 6-7:3-4.

8. The method for rapid separation of phenol and carbazole compounds using silica gel according to claim 1, characterized in that: The step of using a mixed solution of n-pentane and dichloromethane for elution separation is carried out under the action of gravity.

9. The method for rapid separation of phenol and carbazole compounds using silica gel according to claim 1, characterized in that: The step of eluting the silica gel column with n-pentane and ether is performed under the action of gravity.

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