Method for separating aromatics and naphthenes from diesel and its application

Abstract

This invention provides a method for separating aromatics and cycloalkanes from diesel fuel and its application. The method first uses a primary extraction solvent to perform a primary extraction on the diesel fuel, obtaining alkane-rich and aromatic-rich components; then, a secondary extraction solvent is used to perform a secondary extraction on the alkane-rich components, obtaining alkanes-rich and cycloalkanes-rich components. This method can effectively remove aromatics and cycloalkanes from diesel fuel, thereby improving the cracking performance of the alkanes-rich components.

Description

Technical Field

[0001] This invention belongs to the field of petrochemicals, specifically relating to a method for separating aromatics and cycloalkanes from diesel fuel and its application. Background Technology

[0002] Steam cracking is a major technology for producing ethylene and propylene. Steam cracking feedstocks mainly include light hydrocarbons (such as ethane, propane, and butane), naphtha, diesel oil, condensate, and hydrotreated tail oil. Using straight-run diesel oil as a steam cracking feedstock to produce ethylene and other chemical products is one of the important methods to increase ethylene production and improve efficiency. However, the aromatic components in straight-run diesel oil, especially polycyclic aromatic hydrocarbons (PAHs), are undesirable components for steam cracking feedstocks. During cracking, they easily reduce ethylene yield, increase coking in furnace tubes, and shorten the operating cycle. Therefore, it is essential to treat straight-run diesel oil to improve the efficiency of steam cracking.

[0003] Currently, patents have been published on solvent extraction of straight-run diesel fuel to produce ethylene cracking feedstock and to improve the cetane number of the product.

[0004] CN201811508969.4 discloses a method for processing straight-run diesel. The goal of this method is to extract low-aromatic raffinate from the straight-run diesel as feedstock for ethylene cracking, thereby increasing the yield of trienes from steam cracking. In the example, the aromatic content of the feedstock decreased from 11% to 1.5%, effectively improving the yield of trienes in the cracking products. However, at the same time, the cycloalkanes increased from 38% to 41%, making it difficult to convert them into the target olefin products.

[0005] CN201410116185.2 discloses a composite solvent and its application method for extracting and separating aromatics and alkanes from diesel fractions. This composite extraction solvent has good selective solubility for aromatics, which can effectively separate aromatics from diesel fractions and improve the cetane number of diesel fractions. The composite solvent includes ionic liquids and organic solvents. The goal of this technology is to produce diesel fractions with high cetane numbers. In the optimal example 3, after solvent extraction, the alkanes in the raffinate fraction increased from <20% to 60% compared to the feedstock, while the aromatics decreased from 65% to <8%, and the cetane number was significantly improved. However, the cycloalkanes increased from 12% to 32%, and the large amount of cycloalkanes enrichment is not conducive to improving the yield of ethylene cracking trienes.

[0006] Patent 202110631930.7 discloses a method for producing aviation kerosene from coal tar rich in cyclic hydrocarbons. This method involves primary extraction of the feedstock using C6-C10 n-alkanes to separate a saturated hydrocarbon-rich fraction and a cyclic hydrocarbon-rich secondary fraction. The cyclic hydrocarbon-rich secondary fraction is then further extracted with a polar solvent to obtain an aromatic hydrocarbon-rich fraction and a cycloalkane-rich fraction. However, the use of a polar solvent to separate aromatics and cycloalkanes in this process requires further improvement in selectivity.

[0007] The aforementioned patents have limitations in removing cycloalkanes, and even exhibit cycloalkane enrichment, which restricts further improvement in the yield of trienes in the cracking unit. Therefore, further development of cycloalkane removal technology is needed. Summary of the Invention

[0008] To address the aforementioned problems, the present invention aims to provide a method for separating aromatics and cycloalkanes from diesel fuel and its application. This method can effectively remove aromatics and cycloalkanes from diesel fuel, thereby improving the cracking performance of alkane-rich components.

[0009] To achieve the above objectives, the present invention provides a method for separating aromatics and cycloalkanes from diesel fuel, comprising the following steps:

[0010] (1) Diesel was subjected to primary extraction using a primary extraction solvent to obtain alkane-rich and aromatic-rich components.

[0011] (2) The alkane-rich component is subjected to secondary extraction using a secondary extraction solvent to obtain a chain alkane-rich component and a cycloalkane-rich component;

[0012] The primary extraction solvent includes a primary main solvent and a primary secondary solvent, wherein the primary main solvent and the primary secondary solvent are each independently selected from one or more of furfural, N,N-dimethylformamide, morpholino, methylpyrrolidone, ethylene glycol methyl ether, and sulfolane.

[0013] The secondary extraction solvent includes a secondary primary solvent and a secondary secondary solvent. The secondary primary solvent is sulfolane and / or dimethyl sulfoxide, and the secondary secondary solvent is a C6-C10 alkanes and / or a C6-C10 cycloalkanes.

[0014] According to a specific embodiment of the present invention, preferably, the primary solvent and the primary secondary solvent are different.

[0015] According to a specific embodiment of the present invention, preferably, the diesel fuel comprises 25-60% alkanes, 30-35% cycloalkanes, and 10-41% aromatics by mass percentage.

[0016] According to a specific embodiment of the present invention, preferably, the diesel fuel is one or a combination of two or more of straight-run diesel fuel, catalytic diesel fuel, and coking diesel fuel.

[0017] According to a specific embodiment of the present invention, preferably, the amount of the primary auxiliary solvent added in the primary extraction solvent accounts for 5-40 wt% of the primary extraction solvent.

[0018] According to a specific embodiment of the present invention, preferably, the amount of the primary auxiliary solvent added in the primary extraction solvent accounts for 10-30 wt% of the primary extraction solvent.

[0019] According to a specific embodiment of the present invention, preferably, the amount of the secondary auxiliary solvent added in the secondary extraction solvent accounts for 5-40 wt% of the secondary extraction solvent.

[0020] According to a specific embodiment of the present invention, preferably, the amount of the secondary auxiliary solvent added in the secondary extraction solvent accounts for 10-30 wt% of the secondary extraction solvent.

[0021] According to a specific embodiment of the present invention, preferably, the temperature of the first-stage extraction is 70-130°C, more preferably 110-130°C.

[0022] According to a specific embodiment of the present invention, preferably, the temperature of the secondary extraction is 70-130°C, more preferably 110-130°C.

[0023] According to a specific embodiment of the present invention, preferably, in step (1), the agent-to-oil ratio is 0.5:1-5:1, more preferably 1:1-3:1.

[0024] According to a specific embodiment of the present invention, preferably, in step (2), the agent-to-oil ratio is 0.5:1-5:1, more preferably 1:1-3:1.

[0025] According to a specific embodiment of the present invention, preferably, the primary solvent is furfural, and the primary secondary solvent is N,N-dimethylformamide and / or methylpyrrolidone.

[0026] According to a specific embodiment of the present invention, preferably, the secondary primary solvent is sulfolane, and the secondary secondary solvent is one or a combination of two or more of n-hexane, n-heptane, n-octane, cyclohexane and their derivatives.

[0027] The present invention also provides the application of the above-described method for separating aromatics and cycloalkanes from diesel fuel in the preparation of ethylene cracking feedstock from diesel fuel.

[0028] According to a specific embodiment of the present invention, preferably, the alkane-rich component is used as a feedstock for ethylene cracking.

[0029] The present invention has the following beneficial effects:

[0030] The secondary extraction of this invention significantly improves the selectivity and solubility of the secondary extraction solvent for components such as cycloalkanes by adding cycloalkanes and / or alkanes as secondary auxiliary solvents to the secondary extraction solvent. The cycloalkanes in the resulting alkanes have a lower cycloalkane content, and their aromatic hydrocarbon content also decreases. The addition of these secondary auxiliary solvents not only creates a synergistic effect between the primary and secondary solvents, but also achieves further removal of cycloalkanes and aromatic hydrocarbons, which can effectively improve the cracking performance of the product. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the process for separating aromatics and cycloalkanes from diesel fuel. Detailed Implementation

[0032] 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.

[0033] The raw materials used in the following examples and comparative examples were straight-run diesel, coking diesel, and catalytic diesel, the specific compositions of which are shown in Table 1; the evaluation and analysis method was GC-MS analysis. A schematic diagram of the process for separating aromatics and cycloalkanes from diesel in this invention is shown below. Figure 1 As shown; unless otherwise specified, all "%" values ​​below refer to mass fractions.

[0034] Table 1. Composition of diesel fuel:

[0035]

[0036] Example 1

[0037] This embodiment provides a method for separating aromatics and cycloalkanes in diesel fuel, which includes the following steps:

[0038] (1) Using straight-run diesel as raw material, primary extraction was carried out: using furfural as the primary solvent, primary extraction was carried out at a solvent-to-oil ratio of 0.5 and a temperature of 130℃ to separate aromatic component F-1 and alkane component G-1.

[0039] (2) Secondary extraction using G-1 as raw material: using sulfolane as the secondary main solvent and n-hexane as the secondary auxiliary solvent (addition ratio of 5%), secondary extraction was carried out at a solvent-to-oil ratio of 5 and a temperature of 70°C to separate the cycloalkane-rich component H-1 and the aliphatic component I-1. The aliphatic content of component I-1 was 75.1%, the cycloalkane content was 20.6%, and the aromatic content was 4.3%.

[0040] Example 2

[0041] This embodiment provides a method for separating aromatics and cycloalkanes in diesel fuel, which includes the following steps:

[0042] (1) Using catalytic diesel as raw material, primary extraction was carried out: furfural was used as the primary main solvent and N,N-dimethylformamide was used as the primary auxiliary solvent (addition ratio of 10%). Primary extraction was carried out at a solvent-to-oil ratio of 1 and a temperature of 130℃ to separate aromatic component F-2 and alkane component G-2.

[0043] (2) Secondary extraction using G-2 as raw material: Dimethyl sulfoxide was used as the secondary main solvent, and n-octane + cyclohexane (mass ratio 1:1) was used as the secondary auxiliary solvent (addition ratio of 10%). Secondary extraction was carried out at a solvent-to-oil ratio of 4 and a temperature of 80°C to separate the cycloalkane-rich component H-2 and the aliphatic component I-2. The aliphatic content of component I-2 was 60.1%, the cycloalkane content was 25.7%, and the aromatic content was 14.2%.

[0044] Example 3

[0045] This embodiment provides a method for separating aromatics and cycloalkanes in diesel fuel, which includes the following steps:

[0046] (1) Using coking diesel as raw material, primary extraction was carried out: furfural was used as the primary main solvent and methylpyrrolidone was used as the primary secondary solvent (addition ratio of 20%). Primary extraction was carried out at a solvent-to-oil ratio of 2 and a temperature of 120℃ to separate aromatic component F-3 and alkane component G-3.

[0047] (2) Secondary extraction using G-3 as raw material: using sulfolane as the secondary main solvent and n-decane as the secondary auxiliary solvent (addition ratio of 20%), secondary extraction was carried out at a solvent-to-oil ratio of 3 and a temperature of 90℃ to separate the cycloalkane-rich component H-3 and the aliphatic component I-3. The aliphatic content of component I-3 was 62.8%, the cycloalkane content was 26.3%, and the aromatic content was 10.9%.

[0048] Example 4

[0049] This embodiment provides a method for separating aromatics and cycloalkanes in diesel fuel, which includes the following steps:

[0050] (1) Using straight-run diesel as raw material, primary extraction was carried out: furfural was used as the primary solvent and methylpyrrolidone was used as the primary auxiliary solvent (addition ratio of 30%). Primary extraction was carried out at a solvent-to-oil ratio of 3 and a temperature of 110℃ to separate aromatic component F-4 and alkane component G-4.

[0051] (2) Secondary extraction using G-4 as raw material: Dimethyl sulfoxide was used as the secondary main solvent and cyclohexane was used as the secondary auxiliary solvent (addition ratio of 30%). Secondary extraction was carried out at a solvent-to-oil ratio of 2 and a temperature of 100°C to separate the cycloalkane-rich component H-4 and the aliphatic component I-4. The aliphatic content of component I-4 was 74%, the cycloalkane content was 21.3%, and the aromatic content was 4.7%.

[0052] Example 5

[0053] This embodiment provides a method for separating aromatics and cycloalkanes in diesel fuel, which includes the following steps:

[0054] (1) Using catalytic diesel as raw material, primary extraction was carried out: N,N-dimethylformamide was used as the primary main solvent and methylpyrrolidone was used as the primary auxiliary solvent (addition ratio of 40%). Primary extraction was carried out at a solvent-to-oil ratio of 2 and a temperature of 100℃ to separate aromatic component F-5 and alkane component G-5.

[0055] (2) Secondary extraction using G-5 as raw material: using sulfolane as the secondary main solvent and methylcyclohexane as the secondary auxiliary solvent (addition ratio of 40%), secondary extraction was carried out at a solvent-to-oil ratio of 1 and a temperature of 110℃ to separate the cycloalkane-rich component H-5 and the aliphatic component I-5. The aliphatic content of component I-5 was 60.6%, the cycloalkane content was 24.3%, and the aromatic content was 15.1%.

[0056] Example 6

[0057] This embodiment provides a method for separating aromatics and cycloalkanes in diesel fuel, which includes the following steps:

[0058] (1) Using coking diesel as raw material, primary extraction was carried out: methylpyrrolidone was used as the primary solvent and ethylene glycol methyl ether was used as the primary auxiliary solvent (addition ratio of 5%). Primary extraction was carried out at a solvent-to-oil ratio of 3 and a temperature of 90°C to separate the aromatic component F-6 and the alkane component G-6.

[0059] (2) Secondary extraction using G-6 as raw material: Dimethyl sulfoxide was used as the secondary main solvent and p-dimethylcyclohexane was used as the secondary auxiliary solvent (addition ratio of 5%). Secondary extraction was carried out at a solvent-to-oil ratio of 0.5 and a temperature of 120°C to separate the cycloalkane-rich component H-6 and the aliphatic component I-6. The aliphatic content of component I-6 was 72.9%, the cycloalkane content was 15.9%, and the aromatic content was 11.2%.

[0060] Example 7

[0061] This embodiment provides a method for separating aromatics and cycloalkanes in diesel fuel, which includes the following steps:

[0062] (1) Using straight-run diesel as raw material, primary extraction was carried out: ethylene glycol methyl ether was used as the primary solvent and sulfolane was used as the primary auxiliary solvent (addition ratio of 20%). Primary extraction was carried out at a solvent-to-oil ratio of 4 and a temperature of 80°C to separate aromatic component F-7 and alkane component G-7.

[0063] (2) Secondary extraction using G-7 as raw material: using sulfolane as the secondary main solvent and 1,3,5-trimethylcyclohexane as the secondary auxiliary solvent (addition ratio of 10%), secondary extraction was carried out at a solvent-to-oil ratio of 5 and a temperature of 130℃ to separate the cycloalkane-rich component H-7 and the aliphatic component I-7. The aliphatic content of component I-7 was 75.5%, the cycloalkane content was 19.9%, and the aromatic content was 4.6%.

[0064] Example 8

[0065] This embodiment provides a method for separating aromatics and cycloalkanes in diesel fuel, which includes the following steps:

[0066] (1) Using catalytic diesel as raw material, primary extraction was carried out: using sulfolane as primary solvent and furfural as primary auxiliary solvent (addition ratio of 30%), primary extraction was carried out at a solvent-to-oil ratio of 5 and a temperature of 70°C to separate aromatic component F-8 and alkane component G-8.

[0067] (2) Secondary extraction using G-8 as raw material: Dimethyl sulfoxide was used as the secondary main solvent and 1,2,4,5-tetramethylcyclohexane was used as the secondary auxiliary solvent (addition ratio of 20%). Secondary extraction was carried out at a solvent-to-oil ratio of 4 and a temperature of 70°C to separate the cycloalkane-rich component H-8 and the aliphatic component I-8. The aliphatic content of component I-8 was 59.4%, the cycloalkane content was 26%, and the aromatic content was 14.6%.

[0068] Example 9

[0069] This embodiment provides a method for separating aromatics and cycloalkanes in diesel fuel, which includes the following steps:

[0070] (1) Using coking diesel as raw material, primary extraction was carried out: ethylene glycol methyl ether was used as the primary solvent and sulfolane was used as the primary auxiliary solvent (addition ratio of 10%). Primary extraction was carried out at a solvent-to-oil ratio of 0.5 and a temperature of 130℃ to separate aromatic component F-9 and alkane component G-9.

[0071] (2) Secondary extraction using G-9 as raw material: using sulfolane as the secondary main solvent and methylcyclohexane as the secondary auxiliary solvent (addition ratio of 30%), secondary extraction was carried out at a solvent-to-oil ratio of 3 and a temperature of 80℃ to separate the cycloalkane-rich component H-9 and the aliphatic component I-9. The aliphatic content of component I-9 was 64.2%, the cycloalkane content was 24.9%, and the aromatic content was 10.9%.

[0072] Example 10

[0073] This embodiment provides a method for separating aromatics and cycloalkanes in diesel fuel, which includes the following steps:

[0074] (1) Using straight-run diesel as raw material, primary extraction was carried out: using sulfolane as primary solvent and N,N-dimethylformamide as primary auxiliary solvent (addition ratio of 10%), primary extraction was carried out at a solvent-to-oil ratio of 1 and a temperature of 130℃ to separate aromatic component F-10 and alkane component G-10.

[0075] (2) Secondary extraction using G-10 as raw material: Dimethyl sulfoxide was used as the secondary main solvent and p-dimethylcyclohexane was used as the secondary auxiliary solvent (addition ratio of 40%). Secondary extraction was carried out at a solvent-to-oil ratio of 2 and a temperature of 90°C to separate the cycloalkane-rich component H-10 and the aliphatic component I-10. The aliphatic component I-10 had a 75% aliphatic content, a 20.5% cycloalkane content, and a 4.5% aromatic content.

[0076] Example 11

[0077] This embodiment provides a method for separating aromatics and cycloalkanes in diesel fuel, which includes the following steps:

[0078] (1) Using straight-run diesel as raw material, primary extraction was carried out: furfural was used as the primary solvent and methylpyrrolidone was used as the primary auxiliary solvent (addition ratio of 10%). Primary extraction was carried out at a solvent-to-oil ratio of 2 and a temperature of 120℃ to separate aromatic component F-11 and alkane component G-11.

[0079] (2) Secondary extraction using G-11 as raw material: using sulfolane as the secondary main solvent and 1,3,5-trimethylcyclohexane + methylcyclohexane (mass ratio 1:1) as the secondary auxiliary solvent (addition ratio of 20%), secondary extraction was carried out at a solvent-to-oil ratio of 1 and a temperature of 100℃ to separate the cycloalkane-rich component H-11 and the aliphatic-rich component I-11. The aliphatic content of component I-11 was 75.7%, the cycloalkane content was 19.9%, and the aromatic content was 4.4%.

[0080] Example 12

[0081] This embodiment provides a method for separating aromatics and cycloalkanes in diesel fuel, which includes the following steps:

[0082] (1) Using coking diesel as raw material, primary extraction was carried out: furfural was used as the primary main solvent and methylpyrrolidone was used as the primary secondary solvent (addition ratio of 30%). Primary extraction was carried out at a solvent-to-oil ratio of 3 and a temperature of 110℃ to separate the aromatic component F-12 and the alkane component G-12.

[0083] (2) Secondary extraction using G-12 as raw material: using sulfolane as the secondary main solvent and 1,2,4,5-tetramethylcyclohexane as the secondary auxiliary solvent (addition ratio of 10%), secondary extraction was carried out at a solvent-to-oil ratio of 0.5 and a temperature of 110℃ to separate the cycloalkane-rich component H-12 and the aliphatic component I-12. The aliphatic content of component I-12 was 62.2%, the cycloalkane content was 25.8%, and the aromatic content was 12%.

[0084] Example 13

[0085] This embodiment provides a method for separating aromatics and cycloalkanes in diesel fuel, which includes the following steps:

[0086] (1) Using straight-run diesel as raw material, primary extraction was carried out: N,N-dimethylformamide was used as the primary main solvent and methylpyrrolidone was used as the primary auxiliary solvent (addition ratio of 40%). Primary extraction was carried out at a solvent-to-oil ratio of 2 and a temperature of 100℃ to separate the aromatic component F-13 and the alkane component G-13.

[0087] (2) Secondary extraction using G-13 as raw material: using sulfolane as the secondary main solvent and n-hexane as the secondary auxiliary solvent (addition ratio of 30%), secondary extraction was carried out at a solvent-to-oil ratio of 5 and a temperature of 120℃ to separate the cycloalkane-rich component H-13 and the aliphatic component I-13. The aliphatic content of component I-13 was 73.4%, the cycloalkane content was 22%, and the aromatic content was 4.6%.

[0088] Example 14

[0089] This embodiment provides a method for separating aromatics and cycloalkanes in diesel fuel, which includes the following steps:

[0090] (1) Using catalytic diesel as raw material, a primary extraction was carried out: methylpyrrolidone was used as the primary solvent and ethylene glycol methyl ether was used as the primary auxiliary solvent (the addition ratio was 5%, the solvent-to-oil ratio was 3, and the temperature was 90℃, and the primary extraction was carried out to separate the aromatic component F-14 and the alkane component G-14.

[0091] (2) Secondary extraction using G-14 as raw material: Dimethyl sulfoxide was used as the secondary main solvent and n-octane was used as the secondary auxiliary solvent (addition ratio of 30%). Secondary extraction was carried out at a solvent-to-oil ratio of 4 and a temperature of 130°C to separate the cycloalkane-rich component H-14 and the aliphatic component I-14. The aliphatic content of component I-14 was 58.5%, the cycloalkane content was 25.4%, and the aromatic content was 16.1%.

[0092] Example 15

[0093] This embodiment provides a method for separating aromatics and cycloalkanes in diesel fuel, which includes the following steps:

[0094] (1) Using coking diesel as raw material, primary extraction was carried out: ethylene glycol methyl ether was used as the primary solvent and sulfolane was used as the primary auxiliary solvent (addition ratio of 20%). Primary extraction was carried out at a solvent-to-oil ratio of 4 and a temperature of 80°C to separate the aromatic component F-15 and the alkane component G-15.

[0095] (2) Secondary extraction using G-15 as raw material: using sulfolane as the secondary main solvent and n-decane + n-octane (mass ratio 1:1) as the secondary auxiliary solvent (addition ratio of 40%), secondary extraction was carried out at a solvent-to-oil ratio of 3 and a temperature of 110℃ to separate the cycloalkane-rich component H-15 and the aliphatic component I-15. The aliphatic content of component I-15 was 62.4%, the cycloalkane content was 26.1%, and the aromatic content was 11.5%.

[0096] Example 16

[0097] This embodiment provides a method for separating aromatics and cycloalkanes in diesel fuel, which includes the following steps:

[0098] (1) Using straight-run diesel as raw material, primary extraction was carried out: using sulfolane as primary solvent and furfural as primary auxiliary solvent (addition ratio of 30%), primary extraction was carried out at a solvent-to-oil ratio of 5 and a temperature of 70°C to separate aromatic component F-16 and alkane component G-16.

[0099] (2) Secondary extraction using G-16 as raw material: Dimethyl sulfoxide was used as the secondary main solvent and cyclohexane was used as the secondary auxiliary solvent (addition ratio of 10%). Secondary extraction was carried out at a solvent-to-oil ratio of 2 and a temperature of 120°C to separate the cycloalkane-rich component H-16 and the aliphatic component I-16. The aliphatic content of component I-16 was 75.4%, the cycloalkane content was 20%, and the aromatic content was 4.6%.

[0100] Example 17

[0101] This embodiment provides a method for separating aromatics and cycloalkanes in diesel fuel, which includes the following steps:

[0102] (1) Using straight-run diesel as raw material, primary extraction was carried out: furfural was used as the primary solvent and methylpyrrolidone was used as the primary auxiliary solvent (addition ratio of 30%). Primary extraction was carried out at a solvent-to-oil ratio of 2 and a temperature of 120℃ to separate aromatic component F-17 and alkane component G-17.

[0103] (2) Secondary extraction using G-17 as raw material: using sulfolane as the secondary main solvent and n-octane as the secondary auxiliary solvent (addition ratio of 20%), secondary extraction was carried out at a solvent-to-oil ratio of 1 and a temperature of 100℃ to separate the cycloalkane-rich component H-17 and the aliphatic component I-17. The aliphatic content of component I-17 was 74.1%, the cycloalkane content was 20.9%, and the aromatic content was 5.0%.

[0104] Example 18

[0105] This embodiment provides a method for separating aromatics and cycloalkanes in diesel fuel, which includes the following steps:

[0106] (1) Using straight-run diesel and coking diesel mixed at a mass ratio of 1:1 as raw materials, primary extraction was carried out: furfural was used as the primary main solvent and methylpyrrolidone was used as the primary secondary solvent (addition ratio of 30%). Primary extraction was carried out at a solvent-to-oil ratio of 2 and a temperature of 120℃ to separate aromatic component F-18 and alkane component G-18.

[0107] (2) Secondary extraction using G-18 as raw material: using sulfolane as the secondary main solvent and n-octane as the secondary auxiliary solvent (addition ratio of 20%), secondary extraction was carried out at a solvent-to-oil ratio of 1 and a temperature of 100℃ to separate the cycloalkane-rich component H-18 and the aliphatic component I-18. The aliphatic content of component I-18 was 67.9%, the cycloalkane content was 23.0%, and the aromatic content was 9.1%.

[0108] Example 19

[0109] This embodiment provides a method for separating aromatics and cycloalkanes in diesel fuel, which includes the following steps:

[0110] (1) Using straight-run diesel and catalytic diesel mixed at a mass ratio of 1:1 as raw materials, primary extraction was carried out: furfural was used as the primary main solvent and methylpyrrolidone was used as the primary secondary solvent (addition ratio of 30%). Primary extraction was carried out at a solvent-to-oil ratio of 2 and a temperature of 120℃ to separate aromatic component F-19 and alkane component G-19.

[0111] (2) Secondary extraction using G-19 as raw material: using sulfolane as the secondary main solvent and n-octane as the secondary auxiliary solvent (addition ratio of 20%), secondary extraction was carried out at a solvent-to-oil ratio of 1 and a temperature of 100℃ to separate the cycloalkane-rich component H-19 and the aliphatic component I-19. The aliphatic content of component I-19 was 65.1%, the cycloalkane content was 22.9%, and the aromatic content was 12.0%.

[0112] Comparative Example 1

[0113] This comparative example provides a method for separating aromatics and cycloalkanes in diesel fuel, which includes the following steps:

[0114] Using straight-run diesel as feedstock, a primary extraction was performed: furfural was used as the primary solvent and methylpyrrolidone was used as the primary auxiliary solvent (added at a ratio of 10%). The primary extraction was carried out at a solvent-to-oil ratio of 2 and a temperature of 120°C, separating an aromatic-rich component F1 and an alkane-rich component G1. Component G1 contained 63.3% alkanes, 31.2% cycloalkanes, and 5.5% aromatics.

[0115] Comparative Example 2

[0116] This comparative example provides a method for separating aromatics and cycloalkanes in diesel fuel, which includes the following steps:

[0117] Using straight-run diesel as feedstock, sulfolane as the main solvent, and 1,3,5-trimethylcyclohexane + methylcyclohexane (mass ratio 1:1) as the additive solvent (addition ratio of 20%), extraction was carried out at a solvent-to-oil ratio of 1 and a temperature of 100℃ to separate the cycloalkane-rich component H2 and the aliphatic-rich component I2. Component I2 had an aliphatic content of 67%, a cycloalkane content of 24.4%, and an aromatic content of 8.6%.

[0118] Comparative Example 3

[0119] This comparative example provides a method for separating aromatics and cycloalkanes in diesel fuel, which includes the following steps:

[0120] (1) Using straight-run diesel as raw material, primary extraction was carried out: furfural was used as the primary solvent and methylpyrrolidone was used as the primary auxiliary solvent (addition ratio of 10%). Primary extraction was carried out at a solvent-to-oil ratio of 2 and a temperature of 120°C to separate aromatic component F3 and alkane component G3.

[0121] (2) Secondary extraction using G3 as raw material: Using sulfolane as the secondary main solvent, secondary extraction was carried out at a solvent-to-oil ratio of 1 and a temperature of 100°C to separate cycloalkane-rich component H3 and alkane-rich component I3. Component I3 had an alkane content of 70.9%, a cycloalkane content of 22.2%, and an aromatic content of 6.9%. The specific schemes of the examples and comparative examples are shown in Tables 2 and 3.

[0122]

[0123]

[0124] As shown in Tables 2 and 3, based on the results of Example 11 and Comparative Example 3, the addition of a cycloalkane auxiliary solvent to the secondary extraction solvent significantly increased the selectivity and solubility of the mixed solvent for components such as cycloalkane. Compared with secondary extraction using only a single solvent, the cycloalkane content in the alkane component decreased by 2.3 percentage points, and the aromatic content in the alkane component also decreased by 2.5 percentage points. The addition of this secondary auxiliary solvent not only created a synergistic effect between the primary and secondary solvents, but also achieved further removal of cycloalkane and aromatic hydrocarbons, effectively improving the cracking performance of the product.

Claims

1. A method for separating aromatics and cycloalkanes from diesel fuel, comprising the following steps: (1) Diesel fuel was subjected to primary extraction using a primary extraction solvent to obtain alkane-rich and aromatic-rich components; (2) The alkane-rich component is subjected to secondary extraction using a secondary extraction solvent to obtain a chain alkane-rich component and a cycloalkane-rich component; The primary extraction solvent includes a primary main solvent and a primary secondary solvent, wherein the primary main solvent and the primary secondary solvent are each independently selected from one or more of furfural, N,N-dimethylformamide, morpholino, methylpyrrolidone, ethylene glycol methyl ether, and sulfolane. The secondary extraction solvent comprises a primary secondary solvent and a secondary secondary solvent. The primary secondary solvent is sulfolane and / or dimethyl sulfoxide, and the secondary secondary solvent is a C6-C10 alkanes and / or C6-C10 cycloalkanes. In the secondary extraction solvent, the amount of the secondary auxiliary solvent added accounts for 5-40 wt% of the total amount of the secondary extraction solvent. The temperature for the secondary extraction is 70-130℃; The diesel fuel, by weight percentage, comprises 25-60% alkanes, 30-35% cycloalkanes, and 10-41% aromatics. The temperature for the first-stage extraction is 70-130℃.

2. The method for separating aromatics and cycloalkanes from diesel fuel according to claim 1, wherein, The primary solvent is different from the primary secondary solvent.

3. The method for separating aromatics and cycloalkanes in diesel fuel according to claim 1, wherein, The diesel fuel is one or a combination of two or more of the following: straight-run diesel fuel, catalytic diesel fuel, and coking diesel fuel.

4. The method for separating aromatics and cycloalkanes in diesel fuel according to claim 1, wherein, In the primary extraction solvent, the amount of the primary auxiliary solvent added accounts for 5-40 wt% of the primary extraction solvent.

5. The method for separating aromatics and cycloalkanes from diesel fuel according to claim 1 or 4, wherein, In the primary extraction solvent, the amount of the primary auxiliary solvent added accounts for 10-30 wt% of the primary extraction solvent.

6. The method for separating aromatics and cycloalkanes in diesel fuel according to claim 1, wherein, In the secondary extraction solvent, the amount of the secondary auxiliary solvent added accounts for 10-30 wt% of the secondary extraction solvent.

7. The method for separating aromatics and cycloalkanes in diesel fuel according to claim 1, wherein, The temperature of the first-stage extraction is 110-130℃.

8. The method for separating aromatics and cycloalkanes in diesel fuel according to claim 1, wherein, The temperature for the secondary extraction is 110-130℃.

9. The method for separating aromatics and cycloalkanes from diesel fuel according to claim 1, wherein, In step (1), the agent-to-oil ratio is 0.5:1-5:

1.

10. The method for separating aromatics and cycloalkanes from diesel fuel according to claim 1 or 9, wherein, In step (1), the agent-to-oil ratio is 1:1-3:

1.

11. The method for separating aromatics and cycloalkanes from diesel fuel according to claim 1, wherein, In step (2), the agent-to-oil ratio is 0.5:1-5:

1.

12. The method for separating aromatics and cycloalkanes from diesel fuel according to claim 1 or 11, wherein, In step (2), the agent-to-oil ratio is 1:1-3:

1.

13. The method for separating aromatics and cycloalkanes from diesel fuel according to claim 1, wherein, The primary solvent is furfural, and the primary secondary solvent is N,N-dimethylformamide and / or methylpyrrolidone.

14. The application of the method for separating aromatics and cycloalkanes from diesel fuel according to any one of claims 1-13 in the preparation of ethylene cracking feedstock from diesel fuel; The alkane-rich component is used as a feedstock for ethylene cracking.

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