A method for separating sulfur compounds from petroleum products

Abstract

This invention provides a method for separating sulfur-containing compounds from petroleum products. The method includes: dissolving the petroleum product to be treated in a first solvent to obtain an oil sample; sequentially wetting and activating a solid-phase extraction column using a first solvent and a second solvent; then adding the oil sample dropwise into the solid-phase extraction column, wherein the packing material in the solid-phase extraction column includes a strong cation exchange material modified with silver ions; after the added oil sample has completely entered the packing material of the solid-phase extraction column, eluting the solid-phase extraction column sequentially using a first solvent, a second solvent, and a third solvent to collect a first eluent, a second eluent, and a third eluent; wherein the first solvent is selected as a volatile non-polar or polar organic solvent; the second solvent includes acetone with a volume content of not less than 50%; and the third solvent is a mixture of a strongly polar solvent and diethylamine.

Description

Technical Field

[0001] This invention relates to a method for separating sulfur-containing compounds from petroleum products, belonging to the field of petrochemical analysis technology. Background Technology

[0002] Sulfur-containing compounds are among the major heteroatom compounds in petroleum, primarily including sulfide and thiophene sulfur-containing compounds. They are undesirable components in petroleum refining and combustion processes, leading to corrosion of petroleum refining units and catalyst poisoning and deactivation. During combustion, they produce environmentally toxic SO₂. x The sulfur content in gases and petroleum products is strictly limited. Therefore, desulfurization processes such as adsorption desulfurization and hydrodesulfurization are used during petroleum refining. Studies have found that the form of sulfur-containing compounds is closely related to their processing performance. Sulfide-containing compounds are easily desulfurized through hydrotreating, but aromatic thiophene compounds are difficult to desulfurize by hydrotreating, especially shielded sulfur-containing compounds such as 4,6-dimethyldibenzothiophene. Therefore, a deeper understanding of the content and molecular composition of different forms of sulfur-containing compounds is of great significance for the processing and utilization of petroleum resources.

[0003] Methods for separating thioethers and thiophenes have been extensively studied, mainly falling into two categories: coordination chromatography and chemical derivatization. The former utilizes the lone pair electrons of sulfur atoms in sulfur-containing compounds to form coordination interactions with transition metal ions, thus separating sulfur-containing compounds from hydrocarbon matrices or different forms of sulfur-containing compounds. The latter primarily utilizes the chemical properties of different forms of sulfur-containing compounds, such as oxidizing properties, to achieve the separation and enrichment of sulfur-containing compounds through chemical derivatization. Although the latter method can achieve selective separation of thioethers and thiophenes, it often requires an experimental cycle of about one week and demands highly skilled operators. While the former method has been widely reported, the separation materials often need to be self-made or modified from commercially available materials. Self-made or modified packing columns often have a shelf life of only one month, and the storage conditions are stringent, which undoubtedly increases the complexity and difficulty of the experiment, and also increases the difficulty of popularizing and standardizing the method.

[0004] Therefore, there is still a need to develop methods that are easy to obtain and implement to separate different forms of sulfur compounds from petroleum. Summary of the Invention

[0005] The purpose of this invention is to provide a method for separating different forms of sulfur-containing compounds from petroleum that is easy to obtain and implement.

[0006] To achieve the above objectives, the present invention provides a method for separating sulfur-containing compounds from petroleum products, comprising:

[0007] Step 1: Dissolve the petroleum product to be processed in the first solvent to obtain an oil sample;

[0008] Step 2: The solid-phase extraction column is wetted and activated sequentially with the first solvent and the second solvent, and then the oil sample is dropped into the solid-phase extraction column; wherein, the packing material in the solid-phase extraction column includes a strong cation exchange material modified with silver ions;

[0009] Step 3: After the added oil sample has completely entered the packing material of the solid-phase extraction column, the solid-phase extraction column is eluted with the first solvent to obtain the first eluent. Then, the solid-phase extraction column is eluted with the second solvent to obtain the second eluent. Finally, the solid-phase extraction column is eluted with the third solvent to obtain the third eluent. Among them, hydrocarbon compounds and a small amount of thiophene compounds are eluted into the first eluent, the remaining thiophene compounds are eluted into the second eluent, and sulfide compounds are eluted into the third eluent.

[0010] The first solvent is a volatile nonpolar or polar organic solvent; the second solvent includes acetone with a volume content of not less than 50%; and the third solvent is a mixture of a strongly polar solvent and diethylamine.

[0011] According to a specific embodiment of the present invention, the petroleum products include one or more of vacuum distillate oil, coking wax oil and crude oil.

[0012] According to a specific embodiment of the present invention, the first solvent includes one or a combination of two or more solvents such as n-hexane, n-pentane, and dichloromethane.

[0013] According to a specific embodiment of the present invention, the second solvent comprises acetone with a volume content of not less than 50% and the remaining content of an organic solvent with a polarity weaker than acetone; more preferably, the organic solvent with a polarity weaker than acetone comprises at least one of dichloromethane and trichloromethane.

[0014] According to a specific embodiment of the present invention, the strongly polar solvent in the third solvent includes at least one of methanol and acetonitrile.

[0015] According to a specific embodiment of the present invention, the volume content of diethylamine is 5-20% based on the total volume of the third solvent being 100%; more preferably, the volume content of diethylamine is 10%.

[0016] According to a specific embodiment of the present invention, the silver ion-modified strong cation exchange material is selected from Ag. + -SCX (i.e., SCX modified with silver ions). Ag + -SCX is a commercially available material and is easily obtained.

[0017] According to a specific embodiment of the present invention, in step one, the ratio of the amount of petroleum product to be treated to the amount of the first solvent is 10-100 mg: 1 mL; more preferably, the ratio of the amount of petroleum product to be treated to the amount of the first solvent is 60 mg: 1 mL.

[0018] According to a specific embodiment of the present invention, the mass ratio of the packing material in the solid phase extraction column to the weight of the petroleum oil in step one is 0.5-1.5g:10-100mg.

[0019] According to a specific embodiment of the present invention, in step two, the ratio of the volume of the first solvent to the mass of the packing material in the solid-phase extraction column is 4-10 mL: 1 g.

[0020] According to a specific embodiment of the present invention, in step two, the volume ratio of the second solvent to the mass of the packing material in the solid-phase extraction column is 4-10 mL: 1 g.

[0021] According to a specific embodiment of the present invention, in step three, the mass ratio of the first solvent to the packing material in the solid-phase extraction column is 10-30 mL: 0.5-1.5 g; more preferably, in step three, the mass ratio of the first solvent to the packing material in the solid-phase extraction column is 20 mL: 0.5-1.5 g.

[0022] According to a specific embodiment of the present invention, in step three, the mass ratio of the second solvent to the packing material in the solid-phase extraction column is 10-30 mL: 0.5-1.5 g; more preferably, in step three, the mass ratio of the second solvent to the packing material in the solid-phase extraction column is 20 mL: 0.5-1.5 g.

[0023] According to a specific embodiment of the present invention, in step three, the mass ratio of the third solvent to the packing material in the solid-phase extraction column is 11-33 mL: 0.5-1.5 g.

[0024] The technical solution provided by this invention can achieve rapid separation of different forms of sulfur-containing compounds in petroleum. The method uses commercially available materials without additional modification treatment, and can directly separate and enrich thiophene and thioether compounds in petroleum. The separated components can be further subjected to elemental analysis to determine the content of different forms of sulfur-containing compounds. Alternatively, after conversion by methylation reaction, the detailed molecular composition of different forms of sulfur-containing compounds can be analyzed by electrospray ionization high-resolution mass spectrometry. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the process for separating different forms of sulfur-containing compounds (thiophene-type sulfur-containing compounds and thioether-type sulfur-containing compounds) from petroleum products in Example 2.

[0026] Figure 2 The above are gas chromatograms of each eluent in Example 1.

[0027] Figure 3 For Examples 2, 3, and 4, the eluent was methylated and then analyzed by positive ion electrospray ionization (+ESI) high-resolution mass spectrometry (HRMS) to obtain the relative abundance diagrams of various types of compounds in the methylated products of thioether and thiophene components.

[0028] Figure 4 The diagram shows the distribution of equivalent double bond number (DBE) and carbon number of the S1 class compounds of sulfide and thiophene components in Examples 2, 3, and 4. Detailed Implementation

[0029] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0030] Example 1

[0031] This embodiment provides a method for separating sulfur-containing compounds from petroleum products, including:

[0032] Step 1: Dissolve 20 mg of the petroleum product to be treated (a simulated petroleum product obtained by mixing 5 mg of n-hexadecane, 5 mg of n-dodecylcyclohexane, 5 mg of 4,6-dimethyldibenzothiophene and 5 mg of n-dodecyl sulfide) in 1 mL of n-hexane to obtain an oil sample;

[0033] Step 2: The solid-phase extraction column is sequentially wetted and activated with 4 mL of n-hexane and 4 mL of acetone, and then the oil sample is added dropwise into the solid-phase extraction column; wherein the solid-phase extraction column is packed with 750 mg of Ag packing material. + -SCX;

[0034] Step 3: After the added oil sample has completely entered the packing material of the solid phase extraction column, use 20 mL of n-hexane to elute the solid phase extraction column and collect the first eluent. Then use 20 mL of acetone to elute the solid phase extraction column and collect the second eluent. Finally, use 22 mL of a mixture of acetonitrile and diethylamine (10% diethylamine by volume) to elute the solid phase extraction column and collect the third eluent.

[0035] The first, second, and third eluents were analyzed by gas chromatography, and the results are as follows: Figure 2 As shown, hydrocarbon compounds are eluted into the first eluent, a small amount of thiophene compounds are eluted into the first eluent, and mainly into the second eluent as an adjuvant. Thioether compounds are eluted into the third eluent, thus effectively separating the thiophene and thioether compounds.

[0036] Example 2

[0037] This embodiment provides a method for separating sulfur-containing compounds from petroleum products, including:

[0038] Step 1: Dissolve 60 mg of the petroleum product to be treated (vacuum distillate) in 1 mL of n-hexane to obtain an oil sample;

[0039] Step 2: The solid-phase extraction column is sequentially wetted and activated with 4 mL of n-hexane and 4 mL of acetone, and then the oil sample is added dropwise into the solid-phase extraction column; wherein the solid-phase extraction column is packed with 750 mg of Ag packing material. + -SCX;

[0040] Step 3: After the added oil sample has completely entered the packing material of the solid phase extraction column, use 20 mL of n-hexane to elute the solid phase extraction column and collect the first eluent. Then use 20 mL of acetone to elute the solid phase extraction column and collect the second eluent. Finally, use 22 mL of a mixture of acetonitrile and diethylamine (10% diethylamine by volume) to elute the solid phase extraction column and collect the third eluent.

[0041] The first and second eluents were mixed to obtain the thiophene eluent, and the third eluent was the thioether eluent. The thiophene and thioether eluents were then subjected to methylation reactions and analyzed using positive ion electrospray ionization high-resolution mass spectrometry. The procedure is as follows: Figure 1 As shown, the results are as follows Figure 3 , Figure 4 As shown.

[0042] The methylation reaction of the thiophene eluent and the thioether eluent separately includes: purging the thiophene eluent and the thioether eluent separately under slight nitrogen to remove the original eluent; then adding 5 mL of dichloromethane solvent to redissolve them in a 20 mL reaction flask; adding 50 mg of silver tetrafluoroborate and 0.2 mL of iodomethane; placing a clean magnetic ball with an outer layer of Teflon material inside the reaction flask; and wrapping the reaction flask with aluminum foil to isolate it from light. The reaction is stirred at room temperature for 48 hours to complete the methylation reaction.

[0043] Example 3

[0044] This embodiment provides a method for separating sulfur-containing compounds from petroleum products.

[0045] The difference between this embodiment and Embodiment 2 is that the petroleum product to be processed is coking wax oil instead of vacuum distillate oil.

[0046] The results are as follows Figure 3 , Figure 4 As shown.

[0047] Example 4

[0048] This embodiment provides a method for separating sulfur-containing compounds from petroleum products.

[0049] The difference between this embodiment and Embodiment 2 is that the petroleum product to be processed is crude oil instead of vacuum distillate.

[0050] The results are as follows Figure 3 , Figure 4 As shown.

[0051] Figure 3 The relative abundances of various compounds obtained by high-resolution mass spectrometry analysis of the thioether and thiophene components eluted in Examples 2, 3, and 4 after methylation. Figure 3 It can be seen that for the sulfide and thiophene components of the petroleum products to be processed, such as vacuum distillate oil, coking wax oil and crude oil, the relative abundance of S1 compounds is always the highest, and sulfur-containing compounds with multiple heteroatoms such as S2, O1S1, O2S1 and N1S1 are also detected.

[0052] Figure 4 This is a diagram showing the equivalent double bond and carbon number distribution of S1-type compounds after methylation of the thioether and thiophene components eluted in Examples 2, 3, and 4. Figure 4 It can be seen that thiophene compounds, including biomarker sulfur-containing compounds, are effectively separated from thioether compounds, and this method has good applicability to different types of samples such as vacuum distillate oil, crude oil, and secondary processed oil products.

Claims

1. A method for separating sulfur-containing compounds from petroleum products, wherein, include: Step 1: Dissolve the petroleum product to be processed in the first solvent to obtain an oil sample; Step 2: The solid-phase extraction column is wetted and activated sequentially with the first solvent and the second solvent, and then the oil sample is dropped into the solid-phase extraction column; wherein, the packing material in the solid-phase extraction column includes a strong cation exchange material modified with silver ions; Step 3: After the added oil sample has completely entered the packing material of the solid phase extraction column, the solid phase extraction column is eluted with the first solvent to obtain the first eluent. Then, the solid phase extraction column is eluted with the second solvent to obtain the second eluent. Finally, the solid phase extraction column is eluted with the third solvent to obtain the third eluent. The first solvent is a volatile nonpolar or polar organic solvent; the second solvent includes acetone with a volume content of not less than 50%; and the third solvent is a mixture of a strongly polar solvent and diethylamine.

2. The method according to claim 1, wherein, The petroleum products include one or more of vacuum distillate oil, coking wax oil, and crude oil.

3. The method according to claim 1, wherein, The first solvent includes one or a combination of two or more of the solvents selected from n-hexane, n-pentane, and dichloromethane.

4. The method according to claim 1, wherein, The second solvent comprises acetone comprising at least 50% by volume and the remaining portion comprising an organic solvent with a polarity weaker than that of acetone.

5. The method according to claim 4, wherein, The organic solvents with weaker polarity than acetone include at least one of dichloromethane and trichloromethane.

6. The method according to claim 1, wherein, The strongly polar solvent in the third solvent includes at least one of methanol and acetonitrile.

7. The method according to claim 1, wherein, Based on the total volume of the third solvent being 100%, the volume content of diethylamine is 5-20%.

8. The method according to claim 7, wherein, With the total volume of the third solvent being 100%, the volume content of diethylamine is 10%.

9. The method according to claim 1, wherein, Silver ion-modified strong cation exchange material uses Ag + -SCX.

10. The method according to claim 1, wherein, In step one, the ratio of the amount of petroleum product to be treated to the amount of the first solvent is 10-100 mg: 1 mL.

11. The method according to claim 1, wherein, The mass ratio of the packing material in the solid phase extraction column to the weight of the petroleum oil in step one is 0.5-1.5g:10-100mg; In step two, the volume ratio of the first solvent to the mass of the packing material in the solid-phase extraction column is 4-10 mL: 1 g. In step two, the ratio of the volume of the second solvent to the mass of the packing material in the solid-phase extraction column is 4-10 mL: 1 g.

12. The method according to claim 1, wherein, In step three, the mass ratio of the first solvent to the packing material in the solid-phase extraction column is 10-30 mL : 0.5-1.5 g; In step three, the mass ratio of the second solvent to the packing material in the solid-phase extraction column is 10-30 mL : 0.5-1.5 g; In step three, the mass ratio of the third solvent to the packing material in the solid-phase extraction column is 11-33 mL : 0.5-1.5 g.

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