A column chromatography method for rapidly separating steranes from crude oil

Abstract

The present invention provides a method for quickly separating steranes from crude oil, comprising: removing asphaltenes from crude oil by using a centrifuge; eluting the sterane-rich fraction in crude oil with a mixed solvent of 1.5 ml of 90% n-hexane and 10% petroleum ether; mixing urea and absolute ethanol with the sterane-rich fraction, then adding n-hexane, and removing n-alkanes therein by filtration; using 13X molecular sieve as the solid-phase adsorbent of the chromatographic column and using isooctane as the eluent to purify sterane compounds. The beneficial effects of the present invention are as follows: The present invention can quickly separate asphaltenes from crude oil by using a centrifuge, reduce the content of n-alkanes in the sterane-rich fraction through the complexation reaction of n-alkanes with urea, and further purify the sterane-rich fraction by using a 13X molecular sieve chromatographic column. Compared with the existing separation methods, this method is simple and fast, and the separated steranes have higher purity, having strong popularization and practical value.

Description

Technical Field

[0001] The present invention belongs to the field of separation and purification of crude oil sterane compounds, and particularly relates to a column chromatography method for rapidly separating steranes in crude oil. Background Art

[0002] Sterane compounds are an important component of saturated hydrocarbons. By studying the content and ratio characteristics of sterane compounds, there are significant advantages in exploring the source of crude oil parent material and characterizing the maturity of crude oil. At the same time, in terms of the carbon isotope of its monomer hydrocarbon, it has important geological and geochemical significance. There are mainly two separation methods for sterane compounds. It is reported in the literature that the urea complexation method can achieve the purification of sterane compounds, but it also points out that the content of the separated sterane compounds is relatively low. Except for some samples with extremely high sterane content that can identify their peak patterns, it is difficult to effectively separate steranes by the above method for most samples. In addition, the combination of various molecular sieves with different pore sizes can also achieve the separation of hopane compounds. However, due to the cumbersome experimental steps and complex experimental procedures, the loss of sterane compounds is serious, and the content of the enriched steranes often fails to meet the requirements of the mass spectrometry detection threshold. Obviously, a more rapid and efficient separation method for sterane compounds in crude oil is needed. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, the present invention provides a method for rapidly separating steranes in crude oil. This method uses a neutral alumina chromatographic column and urea complexation to greatly remove n-alkanes, residual hopanes, and other heterocyclic compounds in the sterane-rich fraction. Using 13X molecular sieve as a solid-phase adsorbent can further purify sterane compounds. The method includes the following steps:

[0004] S1: Measure a predetermined amount of crude oil sample with a centrifuge tube, add petroleum ether to the centrifuge tube, perform centrifugation on the centrifuge tube with a centrifuge, and measure the filtrate on the top layer of the centrifuge tube to remove asphaltenes in the crude oil sample;

[0005] S2: Activate neutral alumina and 13X molecular sieve and fill them into different supporting chromatography devices respectively;

[0006] S3: Add the filtrate measured in step S1 into the supporting chromatography device filled with neutral alumina in step S2; elute the filtrate in this supporting chromatography device with an elution reagent to obtain an elution fraction; wherein the elution reagent is a mixed solution of n-hexane and petroleum ether, and this elution fraction is a fraction rich in steranes;

[0007] S4: Add urea and absolute ethanol to the elution fraction obtained in step S3, mix well, then add n-hexane liquid and filter to obtain a filtered filtrate, and this filtered filtrate is the filtrate after removing n-alkanes;

[0008] S5. Add the filtered filtrate obtained in step S4 to the supporting chromatography device filled with 13X molecular sieve in step S2, and elute the filtered filtrate in the supporting chromatography device with isooctane to obtain high-purity sterane.

[0009] Further, in step S1, the working parameters of the centrifuge are as follows: the rotation speed is 4000 r / min, and the centrifuge rotates for 5 min.

[0010] Further, in step S2, the supporting chromatography device includes a Pasteur pipette, a polytetrafluoroethylene tube, and a small funnel.

[0011] Further, the supporting chromatography device filled with neutral alumina is the first supporting chromatography device. The length of the Pasteur pipette of the first supporting chromatography device is 230 mm, the aperture is 7 mm, and 3 g of neutral alumina is filled in the Pasteur pipette.

[0012] The length of the polytetrafluoroethylene tube of the first supporting chromatography device is 10 mm, and the aperture of the polytetrafluoroethylene tube is 8 mm.

[0013] The diameter of the small funnel of the first supporting chromatography device is 100 mm, and the aperture at the bottom of the funnel is 7 mm.

[0014] Further, in step S5, the supporting chromatography device filled with 13X molecular sieve is the second supporting chromatography device;

[0015] The length of the Pasteur pipette of the second supporting chromatography device is 300 mm, the aperture is 7 mm, and 2 g of 13X molecular sieve is filled in the Pasteur pipette.

[0016] Further, in step S2, the particle size of the neutral alumina filled in the supporting chromatography device is 100 - 200 μm. In step S3, 1.5 mL of elution reagent is used to elute the filtrate in the supporting chromatography device. The elution reagent contains 90% by mass of n-hexane and 10% by mass of petroleum ether; the outflow rate of the elution reagent is 1 mL / min.

[0017] Further, in step S4, the mass of urea is 5 g, the absolute ethanol is 15 ml, and the n-hexane is 10 ml.

[0018] Further, in step S2, the particle size of the 13X molecular sieve filled in the supporting chromatography device is 60 μm. In step S5, 5 mL of isooctane is used to elute the supporting chromatography device.

[0019] Further, in step S2, the activation process of the neutral alumina and 13X molecular sieve is as follows: Place the neutral alumina and 13X molecular sieve activation sieves in a muffle furnace at 450 °C for 4 h.

[0020] Further, in step S1, the capacity of the centrifuge tube is 10 mL, the weight of the crude oil sample measured by the centrifuge tube is 100 mg, and the volume of petroleum ether added is 5 mL.

[0021] The beneficial effect of a method for rapidly separating steranes from crude oil according to the present invention is as follows: The method includes the following steps: adding petroleum ether to a crude oil sample and centrifuging to obtain a filtrate; filling different matching chromatography devices with neutral alumina and 13X molecular sieve; eluting the filtrate with an elution reagent, adding urea, absolute ethanol, and n-hexane liquids to the elution fraction and then filtering to obtain a filtered filtrate, and finally adding the filtered filtrate to a matching chromatography device filled with 13X molecular sieve and eluting with isooctane to obtain high-purity steranes. In this method, by adding petroleum ether to the crude oil sample and centrifuging, asphaltenes in the crude oil can be rapidly removed; the matching chromatography device filled with neutral alumina can remove most of the hopanes, as well as aromatic and non-hydrocarbon components in the crude oil. Urea complexation can remove n-alkanes in the sterane-rich fraction; the matching chromatography device filled with 13X molecular sieve as a stationary phase can adsorb hopane compounds, playing a role in purification. Compared with the original method, this method has a better separation effect on sterane compounds, higher experimental efficiency, and strong popularization and practical value. Description of the Drawings

[0022] Figure 1 TIC diagram (total ion current diagram) of the crude oil sample;

[0023] Figure 2 Partially enlarged TIC diagram (m / z217 mass spectrometry diagram) of the crude oil sample;

[0024] Figure 3 TIC diagram of the sterane-rich fraction from which n-alkanes have been removed;

[0025] Figure 4 Partially enlarged TIC diagram of steranes in the sterane-rich fraction from which n-alkanes have been removed;

[0026] Figure 5 TIC diagram of the separated sterane compounds;

[0027] Figure 6 Partially enlarged TIC diagram of the separated sterane compounds. Detailed Embodiments

[0028] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described below in conjunction with the accompanying drawings.

[0029] Please refer to Figures 1 to 6 , this embodiment provides a column chromatography method for rapidly separating sterane compounds from crude oil, including the following steps:

[0030] S1. Take an appropriate amount of crude oil sample in a centrifuge tube, add petroleum ether, place it in a centrifuge and rotate. After taking out the top filtrate of the centrifuge tube, reserve it. Among them, the capacity of the centrifuge tube is 10 mL, the weight of the crude oil sample is 100 mg, and the volume of petroleum ether added is 5 mL.

[0031] Specifically, the method to fully precipitate asphaltene is to put the centrifuge tube into a centrifuge at 4000 r / min for 5 min.

[0032] Reference Figure 1 、 Figure 2 , Figure 1 、 Figure 2 are the total ion chromatogram and mass spectrum of the crude oil sample respectively;

[0033] S2. Place neutral alumina and 13X molecular sieve in an incubator at 450 °C for 4 h of activation and then fill them into the supporting chromatography column device. There are differences in the adsorption of n-alkanes, steranes and hopanes in saturated hydrocarbons by 100 - 200 um neutral alumina. During the process of eluting the crude oil with a mixed reagent, the first 0.5 ml of the eluate mainly contains n-alkanes, the 0.5 - 1.5 ml of the eluate has high abundance of steranes, and the 1.5 - 3 ml of the eluate contains high abundance of hopane compounds. By collecting the first 1.5 ml of the eluate, most of the hopane compounds, aromatics and non-hydrocarbon compounds in the crude oil can be removed. Urea complexation can completely remove the n-alkanes in the sterane-rich fraction. 13X molecular sieve has a strong adsorption effect on hopanes. Using 13X molecular sieve as the solid phase filler, the hopane compounds in the sterane-rich fraction from which n-alkanes have been removed can be further removed, further improving the purity of steranes. In the conventional operation, after neutral alumina and 13X molecular sieve are activated at 450 °C in a muffle furnace for 4 h, they need to be placed in an incubator at 120 °C for 12 h of constant temperature before being filled into the supporting chromatography device. In this embodiment, the activated neutral alumina and 13X molecular sieve are directly filled into the supporting chromatography device, which can improve the separation effect of sterane compounds.

[0034] Specifically, the supporting neutral alumina chromatography device is composed of a Pasteur pipette, a polytetrafluoroethylene tube and a small funnel. Among them, the length of the Pasteur pipette is 230 mm, the aperture of the Pasteur pipette is 7 mm, and 3 g of neutral alumina is filled in the Pasteur pipette. The length of the polytetrafluoroethylene tube is 10 mm, and the aperture of the polytetrafluoroethylene tube is 8 mm. The diameter of the small funnel is 100 mm, and the aperture at the bottom of the funnel is 7 mm.

[0035] The length of the Pasteur pipette of the supporting 13X molecular sieve chromatography device is 300 mm, and the aperture of the Pasteur pipette is 7 mm.

[0036] S3. Transfer the filtrate in the centrifuge tube to the upper end of a supporting chromatography device filled with neutral alumina, and elute the sterane-rich fraction in the crude oil with a mixed reagent.

[0037] Specifically, the volume of the elution for the crude oil sample in the supporting chromatography device is 1.4 times the amount of the packing material.

[0038] The neutral alumina filled in the supporting chromatography device has a particle size of 100 - 200 μm, and 1.5 mL of the mixed reagent is used to elute the sterane-rich fraction.

[0039] Preferably, the sterane-rich fraction is separated with the mixed reagent, and the outflow rate of the mixed reagent is 1 mL / min.

[0040] S4. Add urea and absolute ethanol to the elution fraction obtained in step S3, mix well, then filter after adding n-hexane liquid to obtain a filtered filtrate, which is the filtrate after removing n-alkanes; the mass of urea used in this process is 5 g, the absolute ethanol is 15 ml, and the n-hexane is 10 ml.

[0041] Specifically, the volume of the absolute ethanol mixed with the sterane-rich fraction is 1.5 times that of the n-hexane used.

[0042] Reference Figure 3 、 Figure 4 , Figure 4 、 Figure 5 are respectively the TIC diagram and the partially enlarged TIC diagram of the sterane-rich fraction excluding n-alkanes;

[0043] S5. Elute with 5 mL of isooctane to obtain a high-purity sterane (compound) fraction.

[0044] Specifically, a Pasteur pipette is filled with 2 g of 13X molecular sieve; the particle size of the filled 13X molecular sieve is 60 μm. Before using the mixed reagent to elute the sterane compound, the 13X molecular sieve is dried for 10 min.

[0045] Reference Figure 5 、 Figure 6 To verify the experimental effect of a method for quickly separating steranes in crude oil provided by the present invention, gas chromatography-mass spectrometry detection is performed on the separated high-purity sterane fraction. After step S5, the total ion current diagram (TIC) of the separated high-purity sterane is measured. It can be seen from the chromatogram that the peak shape distribution of the sterane compound is clear and comparable to the mass spectrum of m / z 217.

[0046] In summary, the present invention uses a centrifuge to remove asphaltenes from crude oil, elutes the sterane-rich fraction with a mixed solvent of 90% n-hexane and 10% petroleum ether, mixes anhydrous ethanol, urea with the sterane-rich fraction, adds n-hexane and then filters to remove n-alkanes therein; purifies the sterane compound with 13X molecular sieve, and the separation effect of the sterane compound is good, having strong promotion value.

[0047] The above is the preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes and substitutions, which should be covered by the protection scope of the present invention.

[0048] In this article, the front, back, up, down and other orientation words are defined based on the positions of the components in the drawings and the positions of the components relative to each other, only for the clarity and convenience of expressing the technical solution. It should be understood that the use of the orientation words should not limit the scope of protection requested by the present application.

[0049] Without conflict, the above embodiments and the features in the embodiments in this article can be combined with each other.

[0050] The above is only the preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for rapidly separating steranes from crude oil, characterized in that: It includes the following steps: S1: Measure a predetermined amount of crude oil sample with a centrifuge tube, add petroleum ether to the centrifuge tube, perform centrifugation on the centrifuge tube with a centrifuge, and measure the filtrate on the top layer of the centrifuge tube to remove asphaltenes in the crude oil sample; S2: Activate neutral alumina and 13X molecular sieve and then fill them into different supporting chromatography devices respectively; the supporting chromatography device filled with neutral alumina is the first supporting chromatography device, and the supporting chromatography device filled with 13X molecular sieve is the second supporting chromatography device. The particle size of the neutral alumina filled in the first supporting chromatography device is 100 - 200 μm; S3: Add the filtrate measured in step S1 into the first supporting chromatography device in step S2; elute the filtrate in this supporting chromatography device with an elution reagent to obtain an elution fraction; where the elution reagent is a mixed solution of n - hexane and petroleum ether, and this elution fraction is a fraction rich in steranes; use 1.5 mL of elution reagent to elute the filtrate in the first supporting chromatography device. The elution reagent contains 90% by mass of n - hexane and 10% by mass of petroleum ether; the flow rate of the elution reagent is 1 mL / min; S4: Add urea and absolute ethanol to the elution fraction obtained in step S3, mix well, then add n - hexane liquid and filter to obtain a filtered filtrate, and this filtered filtrate is the filtrate after removing n - paraffins; S5: Add the filtered filtrate obtained in step S4 into the second supporting chromatography device in step S2, and elute the filtered filtrate in this supporting chromatography device with isooctane to obtain high - purity steranes.

2. The method for rapidly separating steranes from crude oil according to claim 1, wherein In step S1, the working parameters of the centrifuge are as follows: the rotation speed is 4000 r / min, and the centrifuge rotates for 5 min.

3. A method for rapidly separating steranes from crude oil according to claim 1, characterized in that, In step S2, the first supporting chromatography device includes a Pasteur pipette, a polytetrafluoroethylene tube, and a small funnel.

4. A method for rapidly separating steranes from crude oil according to claim 3, characterized in that, The length of the Pasteur pipette of the first supporting chromatography device is 230 mm, the aperture is 7 mm, and 3 g of neutral alumina is filled in the Pasteur pipette; The length of the polytetrafluoroethylene tube of the first supporting chromatography device is 10 mm, and the aperture of the polytetrafluoroethylene tube is 8 mm; The diameter of the small funnel of the first supporting chromatography device is 100 mm, and the aperture at the bottom of the funnel is 7 mm.

5. A method for rapidly separating steranes from crude oil according to claim 3, characterized in that, In step S5, the Pasteur pipette included in the second supporting chromatography device has a length of 300 mm and an aperture of 7 mm, and 2 g of 13X molecular sieve is filled in the Pasteur pipette of the second supporting chromatography device.

6. A method for rapidly separating steranes from crude oil according to claim 1, wherein In step S4, the mass of urea is 5 g, the absolute ethanol is 15 ml, and the n - hexane is 10 ml.

7. A method for rapidly separating steranes from crude oil according to claim 1, characterized in that, In step S2, the particle size of the 13X molecular sieve filled in the second supporting chromatography device is 60 μm. In step S5, 5 mL of isooctane is used to elute the supporting chromatography device.

8. A method for rapidly separating steranes from crude oil according to claim 1, characterized in that, In step S2, the activation process of neutral alumina and 13X molecular sieve is as follows: Place neutral alumina and 13X molecular sieve in a muffle furnace at 450 °C and activate for 4 h.

9. A method for rapidly separating steranes from crude oil according to claim 1, characterized in that, In step S1, the capacity of the centrifuge tube is 10 mL, the weight of the crude oil sample measured by the centrifuge tube is 100 mg, and the volume of petroleum ether added is 5 mL.

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