A method for separating monocyclic aromatic hydrocarbons from petroleum

Abstract

This invention provides a method for separating monocyclic aromatic hydrocarbons from petroleum. The method includes the following steps: (1) petroleum is dissolved, subjected to solid-phase extraction, washed, and concentrated to obtain a crude petroleum hydrocarbon mixture; (2) the crude petroleum hydrocarbon mixture obtained in step (1) is subjected to chromatographic separation and elution to obtain monocyclic aromatic hydrocarbons; the stationary phase for solid-phase extraction in step (1) is neutral alumina; the stationary phase for chromatographic separation in step (2) is silica gel; the elution in step (2) includes a first elution and a second elution performed sequentially. The method provided by this invention can quickly separate monocyclic aromatic hydrocarbons from polycyclic aromatic hydrocarbons and saturated hydrocarbons from complex petroleum components. It is suitable for the separation and enrichment of alkylbenzene compounds in middle distillates, gas oil distillates, and crude oil. Further analysis of monocyclic aromatic hydrocarbons can provide a deeper understanding of their chemical composition and biomarker information, which is of certain significance for petroleum exploration.

Description

Technical Field

[0001] This invention belongs to the field of petroleum exploration and analysis technology, and relates to a method for separating monocyclic aromatic hydrocarbons, specifically a method for separating monocyclic aromatic hydrocarbons from petroleum. Background Technology

[0002] Hydrocarbons, as important components of petroleum, contain rich biomarker information, mainly including saturated hydrocarbons and aromatic hydrocarbons. Pre-separation of hydrocarbon components is often performed when analyzing hydrocarbon biomarker information. Monocyclic aromatic hydrocarbons (PAHs) are an important class of hydrocarbons in petroleum. They belong to the aromatic hydrocarbon class and possess chemical properties very similar to saturated hydrocarbons, but differ significantly from polycyclic aromatic hydrocarbons (PAHs). Therefore, during pre-separation of hydrocarbon components, PAHs are often mixed with saturated hydrocarbon components, making it difficult to obtain PAH components and conduct in-depth analysis. Column chromatography using silica gel or alumina as packing material is a commonly used technique for separating petroleum hydrocarbon components and has the potential to separate PAHs from petroleum.

[0003] CN1690704A discloses a method for determining the hydrocarbon composition of vacuum gas oil using solid-phase extraction and mass spectrometry (SPE). The method includes separating the vacuum gas oil into three components—saturated hydrocarbons, aromatic hydrocarbons, and gums—through solid-phase extraction; determining the relative content of the three components by weighing or gas chromatography; determining the hydrocarbon composition of the saturated and aromatic hydrocarbon components using mass spectrometry; and calculating the hydrocarbon composition of the vacuum gas oil using a normalization method based on the relative content of the saturated and aromatic hydrocarbons. The stationary phase used in the solid-phase extraction is silica with a specific surface area of ​​450-750 m². 2 The pore volume is 0.35-0.55 mL / g, and pores with a diameter of 290-350 nm account for 50-70% of the total pore volume. This method is rapid and accurate in determining vacuum gas oil with a small sample volume. Compared with ASTM D2549, this method has higher separation accuracy and significantly shorter separation and analysis time, but the sample throughput is greatly reduced.

[0004] CN106947515B discloses a method for solid-phase extraction to separate different types of compounds in crude oil or heavy oil. The method includes adding a crude oil or heavy oil sample to a stationary phase, washing the stationary phase with C5-C7 saturated hydrocarbons to extract the saturated hydrocarbon components, washing the stationary phase with chloroalkanes to extract the aromatic components, and then washing the stationary phase with a dichloromethane-ethanol mixture or ethanol to obtain a colloid. The stationary phase includes water-soluble salts of Group IB elements or Group Iron elements supported on alumina, wherein the content of the water-soluble salts of Group IB elements or Group Iron elements is 2.0-10.0 wt% based on alumina. This method can effectively separate saturated hydrocarbons and aromatics in crude oil or heavy oil samples, has a large sample throughput, and the separated components can be directly used for instrumental analysis to obtain the composition of the analytical sample.

[0005] CN112229926B discloses a method for determining the composition and content of aromatics in high-temperature Fischer-Tropsch synthetic oil. First, the high-temperature Fischer-Tropsch synthetic oil to be tested is divided into two portions. The first portion is reacted with a bromine solution, resulting in separation of the layers. The upper organic phase is concentrated and loaded onto a solid-phase extraction column A. The sample is eluted with eluent I, and the eluent is collected, concentrated, and analyzed by gas chromatography-mass spectrometry (GC-MS) to determine the monocyclic aromatic hydrocarbons (PAHs) and their content. Then, the second portion of the high-temperature Fischer-Tropsch synthetic oil is directly loaded onto a solid-phase extraction column B, eluted with eluents I and II, and the eluent is collected, concentrated, and analyzed by GC-MS to determine the polycyclic aromatic hydrocarbons (PAHs) and their content. This technical solution achieves rapid separation of monocyclic and polycyclic aromatic hydrocarbons in high-temperature Fischer-Tropsch synthetic oil, effectively solving the problem of difficult qualitative and quantitative detection of aromatics in high-temperature Fischer-Tropsch synthetic oil.

[0006] The above-mentioned technical solutions have achieved the separation of saturated hydrocarbons and aromatic compounds in petroleum, but they do not address the monocyclic aromatics mixed in with saturated hydrocarbons. This does not meet the technical requirements for understanding the composition of monocyclic aromatic compounds in petroleum and mining biomarker information therein. Therefore, this invention proposes a method for separating monocyclic aromatics from petroleum to achieve the separation of monocyclic aromatics from saturated hydrocarbons. Summary of the Invention

[0007] The purpose of this invention is to provide a method for separating monocyclic aromatic hydrocarbons from petroleum, which can quickly separate monocyclic aromatic hydrocarbons from saturated hydrocarbons and polycyclic aromatic hydrocarbons, thereby meeting the technical needs for in-depth understanding of the composition of monocyclic aromatic hydrocarbon compounds in petroleum and mining biomarker information therein.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] This invention provides a method for separating monocyclic aromatic hydrocarbons from petroleum, the method comprising the following steps:

[0010] (1) After dissolving, solid-phase extraction, washing and concentration, crude petroleum hydrocarbon mixture is obtained;

[0011] (2) After chromatography separation and elution, the crude petroleum hydrocarbon mixture obtained in step (1) yields monocyclic aromatic hydrocarbons;

[0012] The stationary phase for solid-phase extraction in step (1) is neutral alumina;

[0013] The stationary phase for chromatography separation in step (2) is silica gel;

[0014] The elution in step (2) includes a first elution and a second elution performed sequentially.

[0015] This invention utilizes neutral alumina to adsorb polycyclic aromatic hydrocarbons (PAHs) and heteroatom-containing aromatic hydrocarbons with high electron cloud density in petroleum during solid-phase extraction. During rinsing, monocyclic aromatic hydrocarbons mix with saturated hydrocarbons, forming a crude petroleum hydrocarbon mixture. When the resulting crude petroleum hydrocarbon mixture is separated by chromatography, the silica gel exhibits different adsorption strengths for monocyclic aromatic hydrocarbons and saturated hydrocarbons. Nonpolar saturated hydrocarbons are eluted first, while highly polar monocyclic aromatic hydrocarbons are better retained on the silica gel surface. The method provided by this invention can rapidly separate monocyclic aromatic hydrocarbons from PAHs and saturated hydrocarbons from complex petroleum components. It is applicable to the separation and enrichment of alkylbenzene compounds in middle distillates, gas oil distillates, and crude oil. Further analysis of monocyclic aromatic hydrocarbons can provide a deeper understanding of their chemical composition and biomarker information, which is of certain significance for petroleum exploration.

[0016] Preferably, in the solid-phase extraction described in step (1), the filling height of neutral alumina in the solid-phase extraction column is 2-3 cm, for example, it can be 2 cm, 2.2 cm, 2.4 cm, 2.6 cm, 2.8 cm or 3 cm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0017] Preferably, the packing amount of neutral alumina in the solid phase extraction column is 0.8-1.2 g / cm, for example, it can be 0.8 g / cm, 0.9 g / cm, 1.0 g / cm, 1.1 g / cm or 1.2 g / cm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] In this invention, the packing amount of neutral alumina in the solid-phase extraction column is controlled within the range of 0.8-1.2 g / cm, which is beneficial for the adsorption of polycyclic aromatic hydrocarbons and heteroatom aromatic hydrocarbons in petroleum. When the packing amount is higher than 1.2 g / cm, monocyclic aromatic hydrocarbons containing long alkyl chains cannot be fully eluted. When the packing amount is lower than 0.8 g / cm, polycyclic aromatic hydrocarbons and heteroatom aromatic hydrocarbons will be mixed into the crude petroleum hydrocarbon components and mixed with monocyclic aromatic hydrocarbons in the subsequent separation.

[0019] This invention does not impose excessive limitations on the volume of the solid phase extraction column used; the specific selection can be made according to the actual application and requirements.

[0020] Preferably, the specific surface area of ​​the neutral alumina is 200-300 m² / g. 2 / g, for example, could be 200m 2 / g、220m 2 / g、260m 2 / g、280m 2 / g or 300m 2 / g, but not limited to the listed values, other unlisted values ​​within the range also apply.

[0021] Preferably, the average particle size of the neutral alumina is 70-150 μm, for example, it can be 70 μm, 90 μm, 110 μm, 130 μm or 150 μm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0022] Preferably, the neutral alumina is calcined neutral alumina.

[0023] Preferably, the roasting temperature is 400-500℃, for example, 400℃, 420℃, 440℃, 460℃, 480℃ or 500℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] Preferably, the roasting time is 4-6 hours, for example, 4 hours, 4.5 hours, 5 hours, 5.5 hours or 6 hours, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] Preferably, in the chromatography separation described in step (2), the filling height of silica gel in the chromatography separation column is 5-7 cm, for example, it can be 5 cm, 5.5 cm, 6 cm, 6.5 cm or 7 cm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] Preferably, the amount of silica gel packed in the chromatography column is 0.4-0.6 g / cm, for example, 0.4 g / cm, 0.45 g / cm, 0.5 g / cm, 0.55 g / cm or 0.6 g / cm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] In this invention, the amount of silica gel packed in the chromatography column is controlled within the range of 0.4-0.6 g / cm, which is beneficial for separating monocyclic aromatic hydrocarbons from saturated hydrocarbons. When the amount of silica gel packed is higher than 0.6 g / cm, high-carbon alkanes, especially n-alkanes, cannot be fully eluted and are mixed into the monocyclic aromatic hydrocarbon component. When the amount of silica gel packed is lower than 0.4 g / cm, monocyclic aromatic hydrocarbons are eluted into the saturated hydrocarbon component, resulting in a decrease in the yield of monocyclic aromatic hydrocarbons.

[0028] This invention does not impose excessive limitations on the size and volume of the chromatography column used, allowing for selection based on actual application and requirements.

[0029] Preferably, the specific surface area of ​​the silicone is 300-450 m². 2 / g, for example, could be 300m 2 / g、330m 2 / g, 350m 2 / g、380m 2 / g、400m2 / g、430m 2 / g or 450m 2 / g, but not limited to the listed values, other unlisted values ​​within the range also apply.

[0030] Preferably, the average particle size of the silica gel is 70-150 μm, for example, it can be 70 μm, 90 μm, 110 μm, 130 μm or 150 μm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0031] Preferably, the silica gel is dried silica gel.

[0032] Preferably, the drying temperature is 110-150℃, for example, it can be 110℃, 120℃, 130℃, 140℃ or 150℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0033] Preferably, the drying time is 4-6 hours, for example, 4 hours, 4.5 hours, 5 hours, 5.5 hours or 6 hours, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0034] Preferably, the content of monocyclic aromatic hydrocarbons in the petroleum is 0.1-20 wt%, for example, it can be 0.1 wt%, 0.5 wt%, 1 wt%, 5 wt%, 10 wt% or 20 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] The source of the petroleum mentioned in this invention includes Bohai crude oil.

[0036] Preferably, the solvent used for dissolving in step (1) is a first solvent.

[0037] Preferably, the first solvent comprises a nonpolar alkane solvent.

[0038] Preferably, the first solvent comprises any one or a combination of at least two of n-heptane, n-hexane, isooctane, n-pentane, or cyclohexane. Typical but non-limiting combinations include the combination of n-heptane and n-hexane, the combination of n-hexane and isooctane, the combination of isooctane and n-pentane, or the combination of n-pentane and cyclohexane, preferably n-hexane.

[0039] Preferably, the dissolution temperature in step (1) is 15-40°C, for example, it can be 15°C, 20°C, 25°C, 30°C, 35°C or 40°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] Preferably, the dissolution in step (1) is accompanied by ultrasound.

[0041] Preferably, the concentration of the dissolved petroleum in step (1) is 0.05-0.1 g / mL, for example, it can be 0.05 g / mL, 0.06 g / mL, 0.07 g / mL, 0.08 g / mL, 0.09 g / mL, or 0.1 g / mL, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0042] Preferably, before the solid phase extraction in step (1), the solid phase extraction column is wetted with a first solvent.

[0043] Preferably, the solid-liquid ratio of the neutral alumina to the first solvent during wetting is 1:(1-3), for example, it can be 1:1, 1:1.5, 1:2, 1:2.5 or 1:3, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable. The unit of the solid-liquid ratio is g / mL.

[0044] Preferably, during the rinsing in step (1), the volume ratio of the first solvent to the dissolved petroleum is (12-30):1, for example, it can be 12:1, 15:1, 18:1, 21:1, 24:1, 17:1 or 30:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0045] During the rinsing process described in this invention, the volume ratio of the first solvent to the dissolved petroleum is controlled within the range of (12-30):1. This facilitates the entry of monocyclic aromatic hydrocarbons into saturated hydrocarbons, thereby improving the yield and purity of the separated monocyclic aromatic hydrocarbons. When the volume ratio is lower than 12:1, alkanes, especially high-carbon n-alkanes, cannot be fully eluted and instead mix into the monocyclic aromatic hydrocarbons. When the volume ratio is higher than 30:1, the monocyclic aromatic hydrocarbons are eluted into the saturated hydrocarbons, resulting in a decrease in the yield of monocyclic aromatic hydrocarbons.

[0046] Preferably, the concentration method in step (1) includes purging with a protective gas.

[0047] Preferably, the protective gas includes nitrogen and / or helium.

[0048] Preferably, the purging temperature is 15-40°C, for example, it can be 15°C, 20°C, 25°C, 30°C, 35°C or 40°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0049] Preferably, after concentration in step (1), the concentration of the crude petroleum hydrocarbon mixture is 0.05-0.1 g / mL, for example, it can be 0.05 g / mL, 0.06 g / mL, 0.07 g / mL, 0.08 g / mL, 0.09 g / mL or 0.1 g / mL, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0050] Preferably, before the chromatography separation in step (2), the chromatography column is wetted with a first solvent.

[0051] Preferably, the solid-liquid ratio of the silica gel to the first solvent during wetting is 1:(1-3), for example, it can be 1:1, 1:1.5, 1:2, 1:2.5 or 1:3, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable. The unit of the solid-liquid ratio is g / mL.

[0052] Preferably, the solvent used in the first elution in step (2) is the first solvent.

[0053] Preferably, during the first elution, the volume ratio of the first solvent to the crude petroleum hydrocarbon mixture obtained in step (1) is (7-10):1, for example, it can be 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1 or 10:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0054] Preferably, the solvent used in the second elution in step (2) is a second solvent.

[0055] Preferably, the second solvent is a mixture of the first solvent and a polar solvent.

[0056] Preferably, the polar solvent includes any one or a combination of at least two of dichloromethane, trichloromethane, or toluene. Typical but non-limiting combinations include a combination of dichloromethane and trichloromethane, a combination of trichloromethane and toluene, a combination of toluene and dichloromethane, or a combination of dichloromethane, trichloromethane, and toluene, preferably dichloromethane.

[0057] The polar solvent component in the second solvent of this invention is preferably dichloromethane, which has a low boiling point and a molecular weight that differs significantly from that of monocyclic aromatic hydrocarbons, thus avoiding the entrainment loss of monocyclic aromatic hydrocarbons due to solvent evaporation.

[0058] Preferably, in the second solvent, the volume ratio of the first solvent to the polar solvent is (5-10):1, for example, it can be 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0059] Preferably, during the secondary elution, the volume ratio of the second solvent to the crude petroleum hydrocarbon mixture obtained in step (1) is (5-8):1, for example, it can be 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1 or 8:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0060] As a preferred embodiment of the method described in this invention, the method includes the following steps:

[0061] (1) After petroleum is dissolved in the first solvent at 15-40℃, the concentration is 0.05-0.1g / mL. Solid phase extraction is carried out in a solid phase extraction column filled with 0.8-1.2g / cm neutral alumina. The solid phase extraction column is rinsed with the first solvent and concentrated by purging with protective gas to obtain crude petroleum hydrocarbon mixture.

[0062] The first solvent includes any one or a combination of at least two of n-heptane, n-hexane, isooctane, n-pentane, or cyclohexane, preferably n-hexane;

[0063] (2) After the crude petroleum hydrocarbon mixture obtained in step (1) is separated by chromatography on a column filled with 0.4-0.6 g / cm silica gel, monocyclic aromatic hydrocarbons are obtained after one elution and two elutions.

[0064] Compared with the prior art, the present invention has the following beneficial effects:

[0065] This invention utilizes neutral alumina to adsorb polycyclic aromatic hydrocarbons (PAHs) and heteroatom-containing aromatic hydrocarbons with high electron cloud density in petroleum during solid-phase extraction. During rinsing, monocyclic aromatic hydrocarbons mix with saturated hydrocarbons, forming a crude petroleum hydrocarbon mixture. When the resulting crude petroleum hydrocarbon mixture is separated by chromatography, the silica gel exhibits different adsorption strengths for monocyclic aromatic hydrocarbons and saturated hydrocarbons. Nonpolar saturated hydrocarbons are eluted first, while highly polar monocyclic aromatic hydrocarbons are better retained on the silica gel surface. The method provided by this invention can rapidly separate monocyclic aromatic hydrocarbons from PAHs and saturated hydrocarbons from complex petroleum components. It is applicable to the separation and enrichment of alkylbenzene compounds in middle distillates, gas oil distillates, and crude oil. Further analysis of monocyclic aromatic hydrocarbons can provide a deeper understanding of their chemical composition and biomarker information, which is of certain significance for petroleum exploration. Attached Figure Description

[0066] Figure 1 This is a flowchart of Example 1, showing the separation of monocyclic aromatic hydrocarbons from petroleum;

[0067] Figure 2 The images show the full scan chromatogram and mass chromatogram of the monocyclic aromatic hydrocarbons isolated in Example 1, obtained by gas chromatography-mass spectrometry analysis. Detailed Implementation

[0068] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the invention and should not be considered as specific limitations thereof. To illustrate the technical solution of the present invention, the oil source in the following embodiments is Bohai crude oil.

[0069] Example 1

[0070] This embodiment provides a method for separating monocyclic aromatic hydrocarbons from petroleum, the flowchart of which is shown below. Figure 1 As shown, the method includes the following steps:

[0071] (1) Petroleum was dissolved in n-hexane at 30°C to a concentration of 0.08 g / mL. Solid phase extraction was performed in a solid phase extraction column filled with neutral alumina with a height of 2.5 cm and a filling amount of 1 g / cm. The solid phase extraction column was rinsed with n-hexane. The volume ratio of n-hexane to dissolved petroleum used during rinsing was 18:1. After concentration by nitrogen purging, a crude petroleum hydrocarbon mixture with a concentration of 0.7 g / mL was obtained. The neutral alumina was calcined at 450°C for 5 h and cooled in a vacuum dryer before filling. The solid phase extraction column was wetted with n-hexane before solid phase extraction. The solid-liquid ratio of neutral alumina to n-hexane during wetting was 1:2 g / mL.

[0072] (2) The crude petroleum hydrocarbon mixture obtained in step (1) was separated by chromatography on a silica gel stationary phase with a packing height of 6 cm and a packing amount of 0.5 g / cm. After one elution with n-hexane, it was then eluted a second time with a mixture of n-hexane and dichloromethane at a volume ratio of 10:1 to obtain monocyclic aromatic hydrocarbons. The volume ratio of n-hexane to crude petroleum hydrocarbon mixture used in the first elution was 9:1, and the volume ratio of the mixture of n-hexane and dichloromethane to crude petroleum hydrocarbon mixture in the second elution was 6:1. The silica gel was dried at 150 °C for 6 h before packing. Before chromatography, the chromatography column was wetted with n-hexane. The solid-liquid ratio of silica gel to n-hexane during wetting was 1:1.6 g / mL.

[0073] Example 2

[0074] This embodiment provides a method for separating monocyclic aromatic hydrocarbons from petroleum, the method comprising the following steps:

[0075] (1) Petroleum was dissolved in n-heptane at 40°C to a concentration of 0.1 g / mL. Solid phase extraction was carried out in a solid phase extraction column with a packing height of 2 cm and a packing amount of 1.2 g / cm of neutral alumina stationary phase. The solid phase extraction column was rinsed with n-heptane and concentrated by nitrogen purging to obtain a crude petroleum hydrocarbon mixture with a concentration of 0.1 g / mL. The neutral alumina was calcined at 500°C for 4 h and cooled in a vacuum dryer before packing. The solid phase extraction column was wetted with n-heptane before solid phase extraction. The solid-liquid ratio of neutral alumina to n-heptane during wetting was 1:1 g / mL.

[0076] (2) The crude petroleum hydrocarbon mixture obtained in step (1) was separated by chromatography on a silica gel stationary phase with a packing height of 7 cm and a packing amount of 0.4 g / cm. After elution with n-heptane once, it was eluted a second time with a mixture of n-heptane and dichloromethane at a volume ratio of 10:1 to obtain monocyclic aromatic hydrocarbons. The volume ratio of n-heptane to crude petroleum hydrocarbon mixture used in the first elution was 10:1, and the volume ratio of n-heptane and dichloromethane mixture to crude petroleum hydrocarbon mixture in the second elution was 5:1. The silica gel was dried at 150 °C for 6 h before packing. Before chromatography, the chromatography column was wetted with n-heptane. The solid-liquid ratio of silica gel to n-heptane during wetting was 1:3 g / mL.

[0077] Example 3

[0078] This embodiment provides a method for separating monocyclic aromatic hydrocarbons from petroleum, the method comprising the following steps:

[0079] (1) Petroleum was dissolved in isooctane at 15°C to a concentration of 0.05 g / mL. Solid phase extraction was carried out in a solid phase extraction column with a packing height of 3 cm and a packing amount of 0.8 g / cm of neutral alumina stationary phase. The solid phase extraction column was rinsed with isooctane and concentrated by nitrogen purging to obtain a crude petroleum hydrocarbon mixture with a concentration of 0.1 g / mL. The neutral alumina was calcined at 400°C for 6 h and cooled in a vacuum dryer before packing. The solid phase extraction column was wetted with isooctane before solid phase extraction. The solid-liquid ratio of neutral alumina to isooctane during wetting was 1:3 g / mL.

[0080] (2) The crude petroleum hydrocarbon mixture obtained in step (1) was separated by chromatography on a silica gel stationary phase with a packing height of 5 cm and a packing amount of 0.4 g / cm. After elution with isooctane once, it was eluted a second time with a mixture of isooctane and dichloromethane at a volume ratio of 10:1 to obtain monocyclic aromatic hydrocarbons. The volume ratio of isooctane to crude petroleum hydrocarbon mixture used in the first elution was 7:1, and the volume ratio of isooctane to trichloromethane mixture to crude petroleum hydrocarbon mixture in the second elution was 8:1. The silica gel was dried at 150°C for 6 h before packing. The chromatography column was wetted with isooctane before chromatography. The solid-liquid ratio of silica gel to isooctane during wetting was 1:1 g / mL.

[0081] Example 4

[0082] This embodiment provides a method for separating monocyclic aromatic hydrocarbons from petroleum. Except for replacing all n-hexane with n-pentane in steps (1) and (2), the method is the same as in Example 1.

[0083] Example 5

[0084] This embodiment provides a method for separating monocyclic aromatic hydrocarbons from petroleum. Except for replacing all n-hexane with cyclohexane in steps (1) and (2) by the same volume, the method is the same as in Example 1.

[0085] Example 6

[0086] This embodiment provides a method for separating monocyclic aromatic hydrocarbons from petroleum. Except for the amount of neutral alumina filled in step (1) being 0.2 g / cm, the method is the same as in Example 1.

[0087] Example 7

[0088] This embodiment provides a method for separating monocyclic aromatic hydrocarbons from petroleum. Except for the amount of neutral alumina filled in step (1) being 2 g / cm, the method is the same as in Example 1.

[0089] Example 8

[0090] This embodiment provides a method for separating monocyclic aromatic hydrocarbons from petroleum. Except for the silica gel filling amount in step (2), which is 0.1 g / cm, the method is the same as in Example 1.

[0091] Example 9

[0092] This embodiment provides a method for separating monocyclic aromatic hydrocarbons from petroleum. Except for the silica gel filling amount of step (2) being 1.2 g / cm, the method is the same as in Example 1.

[0093] Example 10

[0094] This embodiment provides a method for separating monocyclic aromatic hydrocarbons from petroleum. Except for the volume ratio of n-hexane to dissolved petroleum used in step (1) during rinsing, which is 8:1, the rest of the method is the same as in Example 1.

[0095] Example 11

[0096] This embodiment provides a method for separating monocyclic aromatic hydrocarbons from petroleum. Except for the washing step (1), in which the volume ratio of n-hexane to dissolved petroleum is 35:1, the method is the same as in Example 1.

[0097] Performance testing

[0098] The yields of the obtained monocyclic aromatic hydrocarbons were tested using the methods provided in Examples 1-11, and the results are shown in Table 1.

[0099] Table 1

[0100]

[0101]

[0102] As can be seen from Examples 1-5, the method provided by the present invention can achieve a 100% yield of monocyclic aromatic hydrocarbons separated from petroleum. Figure 2 The images show the full scan and mass chromatograms of the monocyclic aromatic hydrocarbons separated in Example 1. In the mass chromatogram, m / z represents the ratio of protons to charge (mass-to-charge ratio), and the corresponding image represents the chromatogram of the sample at that mass-to-charge ratio. It can be clearly seen that the main chromatographic peaks in the full scan chromatogram are all monocyclic aromatic hydrocarbons, proving that the method has a good separation effect.

[0103] A comparison of Examples 6 and 7 with Example 1 shows that the neutral alumina packing amount in the solid-phase extraction column of the present invention is controlled within the range of 0.8-1.2 g / cm, which is beneficial for adsorbing polycyclic aromatic hydrocarbons and heteroatom aromatic hydrocarbons in petroleum. When the packing amount is higher than 1.2 g / cm, monocyclic aromatic hydrocarbons containing long alkyl chains cannot be fully eluted. When the packing amount is lower than 0.8 g / cm, polycyclic aromatic hydrocarbons and heteroatom aromatic hydrocarbons will be mixed with crude petroleum hydrocarbon components and mixed with monocyclic aromatic hydrocarbons in subsequent separation, resulting in a yield of monocyclic aromatic hydrocarbons exceeding 100% and a decrease in the purity of the obtained monocyclic aromatic hydrocarbons.

[0104] A comparison of Examples 8 and 9 with Example 1 shows that, in this invention, the amount of silica gel packed in the chromatography column is controlled within the range of 0.4-0.6 g / cm, which is beneficial for separating monocyclic aromatic hydrocarbons from saturated hydrocarbons. When the amount of silica gel packed is less than 0.4 g / cm, monocyclic aromatic hydrocarbons are eluted into the saturated hydrocarbon component, resulting in a decrease in the yield of monocyclic aromatic hydrocarbons. When the amount of silica gel packed is greater than 0.6 g / cm, high-carbon alkanes, especially n-alkanes, cannot be fully eluted and are mixed into the monocyclic aromatic hydrocarbon component, resulting in a monocyclic aromatic hydrocarbon yield exceeding 100% and a decrease in the purity of the obtained monocyclic aromatic hydrocarbons.

[0105] A comparison of Examples 10, 11, and Example 1 shows that during the rinsing process described in this invention, the volume ratio of the first solvent to the dissolved petroleum is controlled within the range of (12-30):1. This facilitates the entry of monocyclic aromatic hydrocarbons into saturated hydrocarbons, thereby improving the yield and purity of the separated monocyclic aromatic hydrocarbons. When the volume ratio is lower than 12:1, alkanes, especially high-carbon n-alkanes, cannot be fully eluted and are mixed into the monocyclic aromatic hydrocarbons. Therefore, the yield of monocyclic aromatic hydrocarbons exceeds 100%, and the purity of the obtained monocyclic aromatic hydrocarbons decreases. When the volume ratio is higher than 30:1, monocyclic aromatic hydrocarbons are eluted into saturated hydrocarbons, resulting in a decrease in the yield of monocyclic aromatic hydrocarbons.

[0106] In summary, this invention provides a method for separating monocyclic aromatic hydrocarbons (PAHs) from petroleum. During solid-phase extraction, neutral alumina adsorbs PAHs and heteroatom-containing PAHs with high electron cloud density from petroleum. During rinsing, PAHs mix with saturated hydrocarbons, forming a crude petroleum hydrocarbon mixture. When the resulting crude petroleum hydrocarbon mixture is subjected to chromatographic separation, silica gel exhibits different adsorption strengths for PAHs and saturated hydrocarbons; nonpolar saturated hydrocarbons are eluted first, while highly polar PAHs are better retained on the silica gel surface. The method provided by this invention can rapidly separate PAHs from PAHs and saturated hydrocarbons from complex petroleum components, and is suitable for the separation and enrichment of alkylbenzene compounds in middle distillates, gas oil fractions, and crude oil. Further analysis of PAHs can provide a deeper understanding of their chemical composition and biomarker information, which is significant for petroleum exploration.

[0107] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A process for separating monocyclic aromatic hydrocarbons from petroleum, characterized by, The method comprises the following steps: (1) dissolving, solid phase extraction, washing and concentrating the petroleum to obtain a crude petroleum hydrocarbon mixture; (2) chromatographically separating and eluting the crude petroleum hydrocarbon mixture obtained in step (1) to obtain monocyclic aromatic hydrocarbons; In step (1), the stationary phase for the solid phase extraction is neutral alumina; In step (1), the solvent for the dissolving is a first solvent; The first solvent comprises a non-polar alkane solvent; In step (1), before the solid phase extraction, the solid phase extraction column is wetted with the first solvent; In step (1), the method for the concentrating comprises purging with a protective gas; In step (2), the stationary phase for the chromatographic separation is silica gel; In step (2), the eluting comprises sequentially performing a first elution and a second elution; In step (2), before the chromatographic separation, the chromatographic separation column is wetted with the first solvent; In step (2), the solvent used for the first elution in the eluting is the first solvent; In step (2), the solvent used for the second elution in the eluting is a second solvent; The second solvent is a mixture of the first solvent and a polar solvent; The polar solvent comprises any one or a combination of at least two of dichloromethane, trichloromethane or toluene.

2. The method of claim 1, wherein, In step (1), in the solid phase extraction, the filling height of the neutral alumina in the solid phase extraction column is 2-3 cm; The filling amount of the neutral alumina in the solid phase extraction column is 0.8-1.2 g / cm; The specific surface area of the neutral alumina is 200-300 m 2 / g; The average particle size of the neutral alumina is 70-150 μm; The neutral alumina is calcined neutral alumina; The calcination temperature is 400-500 ℃; The calcination time is 4-6 h.

3. The method of claim 1, wherein, In step (2), in the chromatographic separation, the filling height of the silica gel in the chromatographic separation column is 5-7 cm; The filling amount of the silica gel in the chromatographic separation column is 0.4-0.6 g / cm; The specific surface area of the silica gel is 300-450 m 2 / g; The average particle size of the silica gel is 70-150 μm; The silica gel is dried silica gel; The drying temperature is 110-150 ℃; The drying time is 4-6 h.

4. The method of claim 1, wherein, The content of the monocyclic aromatic hydrocarbons in the petroleum is 0.1-20 wt%.

5. The method of claim 1, wherein, The first solvent comprises any one or a combination of at least two of n-heptane, n-hexane, isooctane, n-pentane or cyclohexane.

6. The method of claim 5, wherein, The first solvent is n-hexane.

7. The method of claim 1, wherein, In step (1), the dissolving temperature is 15-40 ℃.

8. The method of claim 1, wherein, In step (1), the dissolving is accompanied by ultrasonic.

9. The method of claim 1, wherein, After the dissolving in step (1), the concentration of the petroleum is 0.05-0.1 g / mL.

10. The method of claim 1, wherein, In the wetting, the solid-liquid ratio of the neutral alumina to the first solvent is 1:(1-3), and the unit of the solid-liquid ratio is g / mL.

11. The method of claim 1, wherein, In step (1), the solvent used for the washing is the first solvent.

12. The method of claim 1, wherein, In step (1), the volume ratio of the first solvent to the petroleum after the dissolving is (12-30):

1.

13. The method of claim 1, wherein, The protective gas comprises nitrogen and / or helium.

14. The method of claim 1, wherein, The purging temperature is 15-40 ℃.

15. The method of claim 1, wherein, After the concentrating in step (1), the concentration of the crude petroleum hydrocarbon mixture obtained is 0.05-0.1 g / mL.

16. The method of claim 1, wherein, In the wetting, the solid-liquid ratio of the silica gel to the first solvent is 1:(1-3), and the unit of the solid-liquid ratio is g / mL.

17. The method of claim 1, wherein, The volume ratio of the first solvent to the crude petroleum hydrocarbon mixture obtained in step (1) is (7-10):

1.

18. The method of claim 1, wherein, The polar solvent is dichloromethane.

19. The method of claim 1, wherein, The volume ratio of the first solvent to the polar solvent in the second solvent is (5-10):

1.

20. The method of claim 1, wherein, The volume ratio of the second solvent to the crude petroleum hydrocarbon mixture obtained in step (1) is (5-8):

1.

21. The method of claim 1, wherein, The method comprises the following steps: (1) Petroleum is dissolved in the first solvent at 15-40℃ to a concentration of 0.05-0.1 g / mL, and then solid-phase extraction is performed in a solid-phase extraction column filled with 0.8-1.2 g / cm of neutral alumina. The solid-phase extraction column is washed with the first solvent, concentrated by blowing with a protective gas, and then a crude petroleum hydrocarbon mixture is obtained; The first solvent comprises any one or a combination of at least two of n-heptane, n-hexane, isooctane, n-pentane or cyclohexane; (2) The crude petroleum hydrocarbon mixture obtained in step (1) is subjected to chromatographic separation in a chromatographic separation column filled with 0.4-0.6 g / cm of silica gel, and then single-ring aromatic hydrocarbons are obtained after one-time elution and two-time elution.

Images