Method for separating n-alkanes from petroleum geological sample

Abstract

The invention discloses a method for separating n-alkanes from a petroleum geological sample. The method comprises the following steps: separating a saturated hydrocarbon component in a petroleum geological sample by adopting isohexane, adsorbing n-alkanes in the saturated hydrocarbon component through a molecular sieve, and desorbing the n-alkanes adsorbed by the molecular sieve by utilizing dichloromethane. By adopting the method for separating the n-alkanes, the loss of low-carbon-number and low-boiling-point compounds caused in the concentration process of the sample can be effectively avoided, and the n-alkanes, isoalkanes and cycloalkanes in the sample can be obtained more safely, efficiently and completely; meanwhile, additional organic solvent extraction operation and accompanying sample loss after the molecular sieve is dissolved by hydrofluoric acid are avoided.

Description

Technical Field

[0001] The present invention relates to a method for separating normal alkanes from petroleum geological samples. Background Art

[0002] The series of biomarker compounds (such as steranes, hopanes and acyclic isoprenoids) and non-biomarker compounds (such as n-alkanes and monomethyl isoalkanes) in the saturated hydrocarbon components of petroleum geological samples have important phase-indicating significance, especially playing an important role in the study of paleo-sedimentary environment, paleoclimate, paleobiological community, thermal evolution of organic matter, and oil and gas migration and accumulation.

[0003] Due to the limitations of current equipment, compound co-emission is common, hindering the application of molecular geochemical methods in paleoecological, paleoenvironmental, and oil-source correlation studies. First, due to the limited separation of chromatographic (GC) instruments, n-alkanes co-emit with other alkanes in some chromatographic and GC-MS analyses. This not only affects compound identification but also severely distorts quantitative and semi-quantitative organic geochemical indices, leading to misjudgments. Furthermore, when analyzing the carbon isotopes of individual hydrocarbons in saturated hydrocarbon components of petroleum geological samples using GC-irMS, the separation of different compounds is extremely poor. The isotopic values ​​of a single peak often represent a composite response of n-alkanes, isoalkanes, and even cycloalkanes (Ellis and Fincannon, 1998; Grice et al., 2008), resulting in significant isotopic distortion. Furthermore, when detecting certain low-concentration compounds, such as samples containing extremely low levels of specific biomarker compounds, even with selected ion scanning (SIM) the instrument detection limit (LOD) is still higher than the concentration of the substance, limiting analysis. Furthermore, in full scan mode, the large concentration differences between compounds (such as between normal-alkanes and biomarker compounds) can severely distort the detection of low-concentration compounds. Given this situation, it is necessary to separate the normal alkanes from other compounds (i-alkanes and cycloalkanes) within the saturated hydrocarbon fraction of petroleum geological samples to meet testing and analytical requirements.

[0004] At present, the methods for separating normal alkanes from saturated hydrocarbon components in petroleum geological samples can be generally divided into two types: molecular sieve method and urea complex method. Molecular sieve and SAPO-11 molecular sieve have low carbon number normal alkanes ( <C 14) has a low recovery rate (or complete absence) and a serious loss of isoalkanes (such as pristane and phytane), and cannot fully take into account the recovery rate of normal alkanes and other alkanes (isoalkanes and cycloalkanes). The ZSM-5 molecular sieve method has high pressure resistance requirements for pressurized equipment and experimental equipment, and cannot perform batch sample separation operations. More importantly, after various types of molecular sieves complex normal alkanes, hydrofluoric acid is needed to dissolve and crush the molecular sieves, and then use organic solvents to extract the normal alkanes. The existing operation method for desorbing normal alkanes from molecular sieves is complicated and time-consuming, and has high requirements for the experimental environment, and there are safety hazards. In the urea technology sequence, the recovery rate of alkanes in different carbon number ranges by urea complexation varies greatly, which is controlled by complex factors such as complexation temperature, time, solvent type, and urea dosage. Additional water removal and multiple concentration operations make this method complicated.

[0005] There are many types of molecular sieves, such as type, type, type, ASM-5 type, SAPO type and Mordenite type (Ellis and Fincannon, 1998; Grice et al., 2008; invention patent CN 103869027B). Molecular sieves are the most common, have been produced industrially for many years, and are easily available. The separation effect of the normal alkane separation method using molecular sieves is still unsatisfactory. Summary of the Invention

[0006] In order to at least partially solve the above technical problems existing in the prior art, the embodiment of the present invention provides a method for separating normal alkanes from petroleum geological samples efficiently and conveniently, by isohexane, The use of molecular sieves and dichloromethane achieves a safer, more stable, higher recovery, more convenient and faster separation operation, making the acquisition of normal alkanes, isoalkanes and cycloalkanes more efficient and complete.

[0007] As one aspect of the present invention, a method for separating normal alkanes from a petroleum geological sample is provided, the method comprising: S1. wetting a chromatography column using chromatographic silica gel as a stationary phase with isohexane, and performing column chromatography separation on the petroleum geological sample using isohexane as an eluent to obtain an eluent solution containing saturated hydrocarbon components.

[0008] By adopting the above technical solution, the saturated hydrocarbon components in petroleum geological samples can be effectively separated, thereby avoiding the phenomenon of solvent conversion caused by using normal alkanes (such as n-hexane and n-pentane) as eluents when separating normal alkanes in petroleum geological samples using conventional methods, thereby causing the loss of low-carbon number and low-boiling point compounds.

[0009] In one or some possible embodiments, the method further includes: S2. The molecular sieve is placed in the elution solution containing saturated hydrocarbon components obtained in S1, and the normal alkanes in the elution solution containing saturated hydrocarbon components obtained in S1 are pre-adsorbed to obtain a sieve having normal alkanes adsorbed thereon. Molecular sieve and elution solution containing saturated hydrocarbon components after pre-adsorption.

[0010] In one or some possible embodiments, the method further includes: S3. The molecular sieve and the elution solution containing saturated hydrocarbon components after pre-adsorption are transferred to In the chromatographic column with molecular sieve as the stationary phase, isohexane is used as the eluent to obtain the adsorbed normal alkanes. Molecular sieve and elution product, wherein the elution product is a mixed solution of isoparaffins and cycloparaffins.

[0011] In one or some possible embodiments, the method further comprises: S4. treating the adsorbed normal alkane obtained in S3 with dichloromethane; Molecular sieve ultrasonic extraction was used to obtain normal alkane solution.

[0012] In one or some possible embodiments, the chromatography column is a quartz glass column with an inner diameter of 13 mm and a length greater than 60 mm.

[0013] It should be noted that the chromatography column of the present invention can be of any specification. When different chromatography columns are selected, the amounts of the corresponding reagents in S1 to S4 can be adjusted accordingly. In any embodiment of the present invention, the chromatography column is preferably a quartz glass column with an inner diameter of 13 mm and a length greater than 60 mm, and the amounts of the corresponding reagents in S1 to S4 are also adjusted accordingly.

[0014] In one or some possible embodiments, the chromatography silica gel is activated chromatography silica gel, and the activation of the chromatography silica gel comprises:

[0015] The chromatography silica gel was dried at 150° C. under vacuum for 12 h and then cooled to room temperature for use.

[0016] By adopting the above technical solution, the moisture adsorbed in the silica gel can be effectively removed, and the fixing ability of the silica gel in the chemical separation process can be improved.

[0017] In one or some possible embodiments, the ratio of the chromatographic silica gel, the petroleum geological sample and the eluent is: 2 g: 10 mg: 5 ml.

[0018] It should be noted that, in the present invention, according to the selection of the specifications of the chromatography column and the usage ratio of the above materials, the best effect of separating the saturated hydrocarbon components from the petroleum geological sample can be achieved.

[0019] In one or some possible embodiments, the petroleum geological sample is selected from one of black crude oil, rock extract, condensate oil or light oil.

[0020] In one or some possible embodiments, in S2, the The molecular sieve is placed in the elution solution containing saturated hydrocarbon components obtained in S1, and the normal alkanes in the elution solution containing saturated hydrocarbon components obtained in S1 are pre-adsorbed to obtain a sieve having normal alkanes adsorbed thereon. The molecular sieve and the elution solution containing the saturated hydrocarbon components after pre-adsorption, comprising:

[0021] Under vacuum, the The molecular sieve was dried at 150 ° C for 12 hours and then cooled to room temperature to obtain the activated Molecular sieves;

[0022] will be activated The molecular sieve was placed in the elution solution containing saturated hydrocarbon components obtained in S1, ultrasonically shaken for 20 minutes, and refrigerated for 12 hours to pre-absorb the normal alkanes in the elution solution containing saturated hydrocarbon components obtained in S1, and the adsorbed normal alkanes were obtained. Molecular sieve and elution solution containing saturated hydrocarbon components after pre-adsorption.

[0023] By adopting the above technical solution, on the one hand, Molecular sieve activation can fully remove the water adsorbed in the molecular sieve, thereby improving the fixation capacity of the molecular sieve during the adsorption process; on the other hand, under refrigeration conditions, it can Molecular sieves can maximize the stable adsorption of normal alkanes in saturated hydrocarbon components.

[0024] In one or some possible embodiments, in said S2:

[0025] When the petroleum geological sample is black crude oil or rock extract, the The amount of molecular sieve used was 4 mg;

[0026] When the petroleum geological sample is condensate oil or light oil, the The amount of molecular sieve used was 6 mg.

[0027] In order to further adapt to the specifications of the chromatography column selected in the present invention, the usage of some materials is further optimized, such as:

[0028] In one or some possible embodiments, S3, in the chromatography column, the activated The amount of molecular sieve used is 2 g.

[0029] By adopting the above technical solution, the activated The amount of molecular sieve used is 2 g, which can completely adsorb normal alkanes in the saturated hydrocarbon components.

[0030] In one or some possible embodiments, in S4, the amount of dichloromethane used is 20 ml.

[0031] By adopting the above technical solution, in S4, dichloromethane is selected to extract the molecular sieve adsorbed with normal alkanes. The strong polarity of dichloromethane can be utilized to completely desorb the normal alkanes adsorbed on the molecular sieve. At the same time, the reagent (i.e., dichloromethane) has a low boiling point and a subsequent volatilization and concentration speed is fast. Compared with the use of hydrofluoric acid in the prior art, it is safe and easy to obtain.

[0032] In one or some possible embodiments, the adsorption of normal alkanes on S3 is carried out by using dichloromethane. When ultrasonic extraction of molecular sieves is performed, the single extraction time is controlled to be 30 minutes at room temperature, and this step needs to be repeated three times.

[0033] By adopting the above technical solution, on the one hand, by controlling the single extraction time, the pressure increase in the sample bottle caused by the excessive temperature of the ultrasonic pool can be effectively prevented; on the other hand, multiple extractions can completely desorb and adsorb normal alkanes.

[0034] The beneficial effects of the above technical solutions provided by the embodiments of the present application include at least:

[0035] The present invention is based on This type of molecular sieve uses reagents that are completely different from previous methods, from group component separation to normal alkane desorption, which reduces the experimental process, makes the operation simpler, safer and more convenient, and has higher recovery rate and stronger repeatability.

[0036] The present invention uses isohexane to separate saturated hydrocarbon components in petroleum geological samples, which can effectively avoid the loss of low carbon number and low boiling point compounds caused by the concentration process of the sample. After the molecular sieve adsorbs the normal alkanes in the saturated hydrocarbon components, the normal alkanes adsorbed by the molecular sieve are desorbed using dichloromethane, which can obtain the normal alkanes in the sample more safely, efficiently and completely. At the same time, it also avoids the additional organic solvent extraction operation after using hydrofluoric acid to dissolve the molecular sieve, as well as the accompanying sample loss.

[0037] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or understood by practicing the present invention. The purposes and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0039] Figure 1 is a gas chromatogram of the saturated hydrocarbon components in Example 1 of the present invention;

[0040] Figure 2 1 is a gas chromatogram of the mixed components of isoparaffins and cycloparaffins in Example 1 of the present invention;

[0041] Figure 3 is a gas chromatogram of normal alkanes in Example 1 of the present invention;

[0042] In the figure, the ordinate is relative abundance (%), and the abscissa is time (min). DETAILED DESCRIPTION

[0043] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0044] In the description of the present invention, it should be noted that the terms “include”, “including”, “have”, “contain”, etc. are all open terms, which mean including but not limited to.

[0045] Existing methods for separating normal alkanes from petroleum geological samples typically use n-hexane and / or n-pentane to dissolve the saturated hydrocarbon components separated from the petroleum geological samples. However, after using these two organic solvents to dissolve the saturated hydrocarbon components, the subsequent extraction of normal alkanes involves a solvent conversion, that is, switching from n-hexane and / or n-pentane to isooctane, which complicates the separation operation. Furthermore, isooctane has a high boiling point and evaporates slowly at room temperature and normal pressure. Even under negative pressure, its addition can result in a significant loss of low-boiling-point, low-carbon-number normal alkanes and isoalkanes (such as pristane and phytane). After the solvent conversion, molecular sieves need to be added to the saturated hydrocarbon components dissolved in isooctane for adsorption. After the adsorption is completed, the remaining liquid phase is a mixed solution of isoalkanes and cycloalkanes. This mixed solution needs to be evaporated and concentrated before testing on the machine. In practice, it was found that low-boiling-point compounds in the sample (pristane, phytane, and isoalkanes with a carbon number less than 18) were significantly lost during the volatilization process, interfering with the subsequent quantitative, semi-quantitative, and isotopic analysis of isoalkanes and cycloalkanes.

[0046] In the prior art, when obtaining normal alkanes, highly corrosive acids (such as hydrofluoric acid and hydrochloric acid) are usually used to dissolve the stationary phase (molecular sieve) and organic solvents are used to perform multiple extraction and separation steps on the acid solution. The involvement of highly corrosive substances increases the risk factor of the separation operation, and the hydrofluoric acid reagent is not easy to store and obtain in the laboratory, making the separation operation difficult to implement.

[0047] As the existing technology was not as good as the inventors' expectations, the inventors made the present invention after further research and development.

[0048] The embodiment of the present invention uses isohexane to separate saturated hydrocarbon components in petroleum geological samples, which can effectively avoid the loss of low carbon number and low boiling point compounds caused by the sample during solvent conversion and concentration; Molecular sieves adsorb normal alkanes in saturated hydrocarbon components, and then dichloromethane is used to desorb the normal alkanes adsorbed by the molecular sieves, avoiding the use of highly corrosive acids. At the same time, this method can obtain normal alkanes in the sample more safely, efficiently and completely, avoiding the loss of isoalkanes and cycloalkanes.

[0049] The present invention will be further described below with reference to specific examples, but the scope of protection of the present invention is not limited by the following examples. Unless otherwise specified, the sources of materials involved in the examples are all conventional commercial products.

[0050] Example 1

[0051] This example separates normal alkanes from rock extracts using the following steps:

[0052] S1. Activate 35-70 mesh chromatography silica gel at 150°C for 12 hours and cool to room temperature. Fill quartz glass chromatography column I (chromatography column I has an inner diameter of 13 mm and a length greater than 60 mm) with 2 g of the activated chromatography silica gel and moisten the chromatography silica gel (i.e., the stationary phase) with isohexane.

[0053] S2. Transfer 10 mg of the rock extract sample to chromatography column I and add 5 mL of isohexane for elution to obtain an eluate solution containing saturated hydrocarbon components;

[0054] S3, 60 ~ 80 mesh The molecular sieve was activated at 150 °C for 12 h, cooled to room temperature and set aside;

[0055] S4, take the activated 4 mg of molecular sieve was placed in the elution solution containing saturated hydrocarbon components obtained from S2, ultrasonically shaken for 20 minutes, and refrigerated (5°C) for 12 hours to pre-adsorb normal alkanes in the elution solution containing saturated hydrocarbon components obtained from S2 to obtain a sieve adsorbed with normal alkanes. Molecular sieve and elution solution containing saturated hydrocarbon components after pre-adsorption;

[0056] S5, take the activated 2g molecular sieves were filled into quartz glass chromatography column II;

[0057] S6, the adsorption of normal alkanes obtained in S4 The molecular sieve and the elution solution containing the saturated hydrocarbon component after pre-adsorption were transferred to the chromatography column II prepared by S5, and 5 mL of isohexane was added for elution to obtain the column adsorbed with normal alkanes. Molecular sieve and elution product (wherein, the elution product is a mixed solution of isoparaffins and cycloparaffins);

[0058] S7, use 20mL of dichloromethane to remove the normal alkanes adsorbed in S6. The molecular sieve ultrasonic extraction was repeated for 20 min three times, and the three solutions were mixed to obtain a normal alkane solution.

[0059] In the embodiments of the present invention, it is necessary to explain that:

[0060] In S1, the amount of chromatographic silica gel used here is the optimal amount for achieving the subsequent separation of saturated hydrocarbon components after multiple experiments; when the mesh size of the silica gel and / or the specifications of the chromatography column are changed, the amount of silica gel used is also changed accordingly to achieve the effect of separating the saturated hydrocarbon components from the geological sample;

[0061] In S2, an eluent containing saturated hydrocarbon components is obtained. This is because: this embodiment is carried out under the illumination of a fluorescent lamp, and the inventors have observed that the fluorescent components (i.e., aromatic hydrocarbon components) remain at the bottom of the chromatography column and have not yet flowed into the eluent. Therefore, it is believed that the eluent obtained ultimately contains saturated hydrocarbon components.

[0062] In S4, here The dosage of molecular sieve is determined after many experiments. Molecular sieves can maximize the stable adsorption of normal alkanes in saturated hydrocarbon components; when When the mesh number of the molecular sieve changes, The amount of molecular sieve used also changes accordingly to achieve the optimal effect of adsorbing normal alkanes from the saturated hydrocarbon components;

[0063] In S5, here The dosage of molecular sieve is determined after many experiments. The molecular sieve can further completely adsorb the remaining normal alkanes in the elution solution containing saturated hydrocarbon components after pre-adsorption; when When the mesh size of the molecular sieve and / or the specifications of the chromatography column are changed, The dosage of molecular sieve also changes accordingly to achieve efficient and complete adsorption of normal alkanes from saturated hydrocarbon components.

[0064] The inventors concentrated the mixed solution of isoparaffins and cycloparaffins obtained in S6 and the normal alkane solution obtained in S7 to 0.5 mL, and then injected them into a gas chromatograph for component analysis three times. The test equipment and test conditions are as follows: Agilent 7890A gas chromatograph, the detector is a hydrogen ion flame detector (FID, the detector temperature is 310°C), the chromatographic column type is an HP-5 column (specifications 60m×0.25mm, thickness 0.25μm), the temperature program starts at 50°C and is maintained for 10 minutes, then increases to 70°C at a rate of 4°C / min, and then increases to 310°C at a rate of 8°C / min (maintained for 40 minutes). The carrier gas is 99.999% nitrogen at a flow rate of 1 mL / min, the injection mode is a splitless injection of 1 μL, and the injection port temperature is 310°C.

[0065] The analysis results are as follows Figures 1 to 3 and as shown in Table 1 below.

[0066] Table 1: Comparison of repeated results of the experiment of separating normal alkanes in Example 1

[0067]

[0068] From the above results, we can see that:

[0069] Before the separation of normal alkanes, the gas chromatogram of saturated hydrocarbon components Figure 1 Let’s look at the carbon number range of normal alkanes in the sample: 12 –C 33 The most significant isoalkanes are pristane and phytane, and the content of monomethyl isoalkanes is extremely low. 27 –C 29 Mainly regular steranes, among which C 27 The content of sterane is extremely high, and no other types of cycloalkanes are found. Among them, pristane / phytane=0.02, C 27 - / C 29 -sterane = 14.42. The identification of the above compounds can be confirmed by co-injection of standard samples and gas chromatography-mass spectrometry analysis.

[0070] After separation, gas chromatograms of isoparaffin and cycloparaffin components are combined Figure 2 The types and distribution of the compounds are basically consistent with the distribution of isoalkanes and cycloalkanes before the separation operation, mainly acyclic isoprenoids and regular sterane series. Acyclic isoprenoids are mainly pristane and phytane, and the carbon number range of regular sterane is C 27 –C 29 The content of hopane compounds was extremely low. In the three repeated experiments, the standard deviation of the relative content of each compound was mostly less than 2%, and the results were stable.

[0071] After separation, the gas chromatogram of the separated normal alkanes Figure 3 Let’s look at the carbon number distribution of normal alkanes: 12 –C 33 The relative abundance and distribution characteristics of each normal alkane are basically consistent with those of the normal alkane in the saturated hydrocarbon component before separation. In the three repeated experiments, the standard deviation of the relative content of each compound is mostly less than 3%, and the results are stable.

[0072] As a comparative example of the present invention, "isooctane is used to dissolve isoparaffin and cycloparaffin components, The method of "absorb n-alkanes by molecular sieve and desorb n-alkanes by hydrofluoric acid" is used to separate n-alkanes from the sample. The specific operation is as follows:

[0073] In the first step, 35-70 mesh chromatography silica gel was activated at 150°C for 12 hours, cooled to room temperature, 2 g of the activated chromatography silica gel was filled into a quartz chromatography column, and the chromatography silica gel was wetted with n-hexane (i.e., the stationary phase was wetted);

[0074] In the second step, 10 mg of the rock extract of sample No. 698 was transferred to the chromatography column prepared in the first step and eluted with 5 mL of n-hexane to obtain an eluate containing saturated hydrocarbon components;

[0075] In the third step, at 70° C., the n-hexane reagent in the elution solution containing the saturated hydrocarbon component in the second step is evaporated, the saturated hydrocarbon component is dissolved in isooctane as a solvent, and the solution is concentrated to <0.5 mL to obtain an isooctane solution containing the saturated hydrocarbon component;

[0076] The fourth step is to use 60-80 mesh The molecular sieve was activated at 150°C for 12 h, cooled to room temperature and then used;

[0077] Step 5: Take 2g of the activated Molecular sieves are packed into the chromatography column;

[0078] Step 6: Transfer the isooctane solution containing saturated hydrocarbon components obtained in step 3 to the molecular sieve chromatography column prepared in step 5, and elute the chromatography column with 20 mL of isooctane three times to obtain a mixed solution of isoparaffins and cycloparaffins;

[0079] Step 7: Transfer the molecular sieve eluted in step 6, blow dry with nitrogen, add 45 mL of acid solution (36%–38% HCl: 40% HF = 2:1, volume ratio), shake well, and acid-hydrolyze the molecular sieve to obtain an acid solution.

[0080] Step 8: Add 15 mL of n-hexane to the acid solution obtained in step 7 three times to extract the n-alkanes therein;

[0081] The solutions obtained in the second step, the sixth step, and the eighth step were concentrated respectively, and then analyzed using equipment consistent with the embodiment of the present invention. The statistical results are shown in Table 2.

[0082] Table 2: Comparison of repeated results of the comparative example separation method of normal alkanes

[0083]

[0084]

[0085] The test results in Table 2 show that compared with the present invention:

[0086] From the perspective of separation operations, the comparative operation involves steps such as organic solvent conversion (iso-octane), strong acid (hydrofluoric acid, hydrochloric acid) dissolution, multiple organic solvent extractions and liquid separation. This separation method is more complicated, more dangerous, and has higher requirements on experimental equipment and experimental personnel's operating skills. At the same time, hydrofluoric acid reagent is difficult to obtain, so most laboratories cannot complete the experiment.

[0087] From the separation effect, the distribution range of normal alkanes in the sample of unseparated saturated hydrocarbons is nC 14 –nC 33The original pristane / phytane ratio was 0.07, C 27 - / C 29 The sterane ratio was 9.65. The addition of isooctane in the comparative example, due to its high boiling point, resulted in a significant loss of low-carbon n-alkanes, pristane, and phytane. The percentages of alkanes with varying carbon numbers varied widely, with relative standard deviations of over 20% across three replicates. This presents significant drawbacks when used for semi-quantitative analysis.

[0088] In summary, the present invention is based on The method uses molecular sieves, isohexane and dichloromethane, and reagents completely different from previous methods are used from the separation of group components to the desorption of normal alkanes. This not only reduces the experimental process and simplifies the operation, making the method safer and more convenient, with higher recovery rate and strong reproducibility; it also makes the acquisition of normal alkanes, isoalkanes and cycloalkanes more efficient and complete.

[0089] Although the present invention has been described in considerable detail and with particularity with respect to several embodiments, it is not intended to limit the present invention to any of these details or embodiments or any particular embodiment, so as to effectively encompass the intended scope of the present invention. In addition, the present invention has been described above with respect to embodiments foreseen by the inventors for the purpose of providing a useful description, and those insubstantial modifications of the present invention that are not currently foreseen may still represent equivalent modifications of the present invention.

[0090] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, illustrative uses of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0091] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. A method for separating normal alkanes from petroleum geological samples, characterized in that: include: S1. Wetting a chromatography column with chromatographic silica gel as the stationary phase with isohexane and using isohexane as the eluent, performing column chromatography separation on a petroleum geological sample to obtain an eluent solution containing saturated hydrocarbon components.

2. The method for separating normal alkanes from petroleum geological samples according to claim 1, wherein: Also includes: S2. The molecular sieve is placed in the elution solution containing saturated hydrocarbon components obtained in S1, and the normal alkanes in the elution solution containing saturated hydrocarbon components obtained in S1 are pre-adsorbed to obtain a sieve having normal alkanes adsorbed thereon. Molecular sieve and elution solution containing saturated hydrocarbon components after pre-adsorption.

3. The method for separating normal alkanes from petroleum geological samples according to claim 2, wherein: Also includes: S3. The S2 obtained adsorbed with normal alkanes The molecular sieve and the elution solution containing saturated hydrocarbon components after pre-adsorption are transferred to In the chromatographic column with molecular sieve as the stationary phase, isohexane is used as the eluent to obtain the adsorbed normal alkanes. Molecular sieve and elution product, wherein the elution product is a mixed solution of isoparaffins and cycloparaffins.

4. The method for separating normal alkanes from petroleum geological samples according to claim 3, wherein: Also includes: S4. using dichloromethane to obtain the adsorption of normal alkanes in S3. Molecular sieve ultrasonic extraction was used to obtain normal alkane solution.

5. The method for separating normal alkanes from petroleum geological samples according to claim 1 or 3, characterized in that: The chromatography column is a quartz glass column with an inner diameter of 13 mm and a length greater than 60 mm.

6. The method for separating normal alkanes from petroleum geological samples according to claim 1, wherein: The chromatography silica gel is activated chromatography silica gel, and the activation of the chromatography silica gel comprises: The chromatography silica gel was dried at 150° C. under vacuum for 12 h and then cooled to room temperature for use.

7. The method for separating normal alkanes from petroleum geological samples according to claim 1, wherein: The usage ratio of the chromatography silica gel, the petroleum geological sample and the eluent is: 2g:10mg:5ml.

8. The method for separating normal alkanes from petroleum geological samples according to claim 1, wherein: The petroleum geological sample is selected from one of black crude oil, rock extract, condensate oil or light oil.

9. The method for separating normal alkanes from petroleum geological samples according to claim 2, wherein: In S2, the The molecular sieve is placed in the elution solution containing saturated hydrocarbon components obtained in S1, and the normal alkanes in the elution solution containing saturated hydrocarbon components obtained in S1 are pre-adsorbed to obtain a sieve having normal alkanes adsorbed thereon. The molecular sieve and the elution solution containing the saturated hydrocarbon components after pre-adsorption, comprising: Under vacuum, the The molecular sieve was dried at 150 ° C for 12 hours and then cooled to room temperature to obtain the activated Molecular sieves; will be activated The molecular sieve was placed in the elution solution containing saturated hydrocarbon components obtained in S1, ultrasonically shaken for 20 minutes, and refrigerated for 12 hours to pre-absorb the normal alkanes in the elution solution containing saturated hydrocarbon components obtained in S1, and the adsorbed normal alkanes were obtained. Molecular sieve and elution solution containing saturated hydrocarbon components after pre-adsorption.

10. The method for separating normal alkanes from petroleum geological samples according to claim 2, characterized in that: In said S2: When the petroleum geological sample is black crude oil or rock extract, the The amount of molecular sieve used was 4 mg; When the petroleum geological sample is condensate oil or light oil, the The amount of molecular sieve used was 6 mg.

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