Composite solvent for aromatic hydrocarbon extraction and method for extracting aromatic hydrocarbons

Abstract

The present invention provides a composite solvent for extracting aromatic hydrocarbons, comprising 20-80% by mass of alkyl sulfolane, 10-60% by mass of sulfolane, 5-15% by mass of chain sulfone, and 0.1-3% by mass of glycol ether. The present invention also provides a method for extracting aromatic hydrocarbons, comprising: subjecting an aromatic hydrocarbon-containing distillate oil to countercurrent contact with the composite solvent described above in an extractive distillation tower for extractive distillation to obtain an extract material and a raffinate material; and distilling the extract material in a solvent recovery tower to obtain an aromatic hydrocarbon product and a crude circulating solvent. Through the above-mentioned technical solution, the present invention can maintain high selectivity and solubility of the composite solvent for raw materials with large fluctuations in aromatic hydrocarbon content during the long-term operation of aromatic hydrocarbon extraction, thereby enabling the aromatic hydrocarbon extraction device to operate stably and efficiently for a long period of time.

Description

Technical Field

[0001] The present invention relates to the field of petrochemical industry, in particular to a composite solvent for extracting aromatic hydrocarbons and a method for extracting aromatic hydrocarbons. Background Art

[0002] There are two main processes for separating aromatics from gasoline fractions. One is liquid-liquid extraction, suitable for separating aromatics from broad-fraction feedstocks; the other is extractive distillation (ED). Liquid-liquid extraction requires large amounts of water to recover the solvent from the extraction tower overhead, resulting in high energy consumption. EDD also suffers from unstable operation within the EDD tower and low separation efficiency.

[0003] In the extraction and distillation separation of aromatic hydrocarbons, the use of composite solvents can achieve higher aromatic hydrocarbon separation effects. For example, CN111978143A discloses a solvent comprising 65-91% by mass of a main solvent and 9-35% by mass of a cosolvent, wherein the main solvent is selected from a sulfone compound or tetraethylene glycol, the sulfone compound is selected from sulfolane, 3-methylsulfolane, dimethyl sulfone or di-n-propyl sulfone, and the cosolvent is selected from diethylene glycol ether or glycol ether. For another example, CN108997077B discloses a composite solvent containing 50% by mass of methyl ethyl sulfone and 50% by mass of sulfolane for separating a C6-C8 fraction of cracked and hydrogenated gasoline with a high aromatic content. The separated mixed aromatics have a purity of 99.9% by mass and a yield of 99.9% by mass.

[0004] However, after longer-term experimental research, it was found that the existing composite solvents have insufficient solubility for wide-fraction gasoline feedstocks with low aromatic content, resulting in a significant decrease in aromatic yield, and the heavy components in the feedstock will accumulate in the solvent, affecting the long-term operation of the device. Summary of the Invention

[0005] The purpose of the present invention is to maintain the composite solvent's stable and high selectivity and solubility for raw materials with large fluctuations in aromatic content (especially low aromatic content raw materials) during the long-term operation of aromatic extraction.

[0006] To achieve the above-mentioned object, the present invention provides a composite solvent for aromatic hydrocarbon extraction, wherein the composite solvent comprises 20 to 80% by mass of alkyl sulfolane, 10 to 60% by mass of sulfolane, 5 to 15% by mass of chain sulfone, and 0.1 to 3% by mass of glycol ether; wherein the alkyl sulfolane, the chain sulfone, and the glycol ether are represented by Formula 1, Formula 2, and Formula 3, respectively;

[0007]

[0008] In Formula 1, R1, R2, R3 and R4 are each independently hydrogen, methyl or ethyl, and at least one of R1, R2, R3 and R4 is not hydrogen; in Formula 2, R5 and R6 are different from each other and are each independently phenyl or a C1 to C6 alkyl group; in Formula 3, n is an integer of 2-5, R7 and R8 are each independently hydrogen or a C1 to C6 alkyl group, and at least one of R7 and R8 is not hydrogen.

[0009] The present invention also provides a method for extracting aromatic hydrocarbons, which comprises: contacting the distillate oil containing aromatic hydrocarbons with the composite solvent as described above in countercurrent in an extractive distillation tower to perform extractive distillation to obtain an extract material and a raffinate material; and distilling the extract material in a solvent recovery tower to obtain an aromatic hydrocarbon product and a crude circulating solvent.

[0010] Through the above technical solution, the present invention can stably maintain the high selectivity and solubility of the composite solvent for raw materials with large fluctuations in aromatic content during the long-term operation of aromatic extraction, and avoid the accumulation of heavy components in the solvent, thereby enabling the aromatic extraction device to operate stably and efficiently for a long time.

[0011] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following detailed description, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

[0013] Figure 1 Schematic diagram of the structure of a reaction device in a preferred embodiment of the present invention.

[0014] Description of Reference Numerals

[0015] Figure 1 In the figure, 101 is the first distillation tower, 102 is the second distillation tower, 103 is the extractive distillation tower, 104 is the solvent recovery tower, 105 is the stripping tower, 106 is the stripping agent distillation tower, 107 is the flash tank, 108 to 111 represent reflux tanks respectively; 1 to 29 represent pipelines respectively. DETAILED DESCRIPTION

[0016] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0017] The present invention provides a composite solvent for extracting aromatic hydrocarbons, the composite solvent comprising 20-80% by mass of alkyl sulfolane, 10-60% by mass of sulfolane, 5-15% by mass of chain sulfone, and 0.1-3% by mass of glycol ether; wherein the alkyl sulfolane, the chain sulfone, and the glycol ether are represented by Formula 1, Formula 2, and Formula 3, respectively;

[0018]

[0019] In Formula 1, R1, R2, R3 and R4 are each independently hydrogen, methyl or ethyl, and at least one of R1, R2, R3 and R4 is not hydrogen; in Formula 2, R5 and R6 are different from each other and are each independently phenyl or a C1 to C6 alkyl group; in Formula 3, n is an integer of 2-5, R7 and R8 are each independently hydrogen or a C1 to C6 alkyl group, and at least one of R7 and R8 is not hydrogen.

[0020] In the present invention, adding alkyl sulfolane to sulfolane is conducive to improving the solubility of the composite solvent to non-aromatic hydrocarbons, and then adding a small amount of chain sulfone derivatives with asymmetric structure can significantly improve the selectivity of the composite solvent under the premise of basically not changing the solubility. By adjusting the ratio of sulfolane and alkyl sulfolane, the composite solvent can be applied to raw materials with different aromatic hydrocarbon contents (especially low aromatic hydrocarbon content), and the addition of the chain sulfone derivatives with asymmetric structure can keep the composite solvent with high selectivity within the scope of the full extractive distillation tower. Adding a small amount of glycol ether to the composite solvent is conducive to reducing the surface tension between the gas and liquid phases during the extractive distillation process, which plays a role in reducing foaming. Since the reason for the decline in solubility and selectivity of the composite solvent during long-term recycling may be the accumulation of some hydrocarbon substances with higher boiling points, which are difficult to be removed by conventional solvent recovery and regeneration, if the C5- fraction obtained by pre-fractionation is used as a stripping agent to remove heavy components in the circulating solvent, the circulating solvent can be kept solubility and selectivity to aromatic hydrocarbons over a long period of time.

[0021] Among them, preferably, the alkyl sulfolane is at least one of 3-methylsulfolane, 2,4-dimethylsulfolane and 1,2,3,4-tetramethylsulfolane; the chain sulfone is at least one of ethyl methyl sulfone, methyl isopropyl sulfone and methyl phenyl sulfone; the glycol ether is tetraethylene glycol monomethyl ether and / or tetraethylene glycol dimethyl ether.

[0022] Among them, as a preferred embodiment, in the composite solvent, the content of the alkyl sulfolane is 60-80% by mass, the content of sulfolane is 10-34.9% by mass, the content of the chain sulfone is 5-10% by mass, and the content of the glycol ether is 0.1-3% by mass; preferably, the content of the alkyl sulfolane is 65-75% by mass, the content of sulfolane is 15-29.9% by mass, the content of the chain sulfone is 5-8% by mass, and the content of the glycol ether is 0.1-3% by mass.

[0023] Among them, as a preferred embodiment, in the composite solvent, the content of the alkyl sulfolane is 40-60% by mass, the content of sulfolane is 30-50% by mass, the content of the chain sulfone is 7-12% by mass, and the content of the glycol ether is 0.1-3% by mass; preferably, the content of the alkyl sulfolane is 45-55% by mass, the content of sulfolane is 35-45% by mass, the content of the chain sulfone is 9-12% by mass, and the content of the glycol ether is 0.1-3% by mass.

[0024] Among them, as a preferred embodiment, in the composite solvent, the content of the alkyl sulfolane is 20-49.9% by mass, the content of sulfolane is preferably 40-65% by mass, the content of the chain sulfone is 10-15% by mass, and the content of the glycol ether is 0.1-3% by mass; preferably, the content of the alkyl sulfolane is 25-40% by mass, the content of sulfolane is preferably 46-60% by mass, the content of the chain sulfone is 13-15% by mass, and the content of the glycol ether is 0.1-3% by mass.

[0025] The present invention also provides a method for extracting aromatic hydrocarbons, which comprises: contacting the distillate oil containing aromatic hydrocarbons with the composite solvent as described above in countercurrent in an extractive distillation tower to perform extractive distillation to obtain an extract material and a raffinate material; and distilling the extract material in a solvent recovery tower to obtain an aromatic hydrocarbon product and a crude circulating solvent.

[0026] Among them, optionally, the mass ratio of the composite solvent to the aromatic hydrocarbon-containing distillate oil entering the extractive distillation tower is 1 to 20, the theoretical plate number of the extractive distillation tower is 10 to 40, the reflux ratio is 0.2 to 2, the bottom temperature is 120°C to 185°C, and the top pressure is 0.1MPa to 0.3MPa; the theoretical plate number of the solvent recovery tower is 20 to 50, the reflux ratio is 0.5 to 2.0, the top pressure is 0.01MPa to 0.07MPa, and the bottom temperature is 150°C to 190°C.

[0027] Among them, optionally, when the aromatic content in the aromatic-containing distillate oil is less than 20% by mass, in the composite solvent, the content of the alkyl sulfolane is 60-80% by mass, the content of sulfolane is 10-34.9% by mass, the content of the chain sulfone is 5-10% by mass, and the content of the glycol ether is 0.1-3% by mass; preferably, the content of the alkyl sulfolane is 65-75% by mass, the content of sulfolane is 15-29.9% by mass, the content of the chain sulfone is 5-8% by mass, and the content of the glycol ether is 0.1-3% by mass.

[0028] Among them, optionally, when the aromatic hydrocarbon content in the aromatic hydrocarbon-containing distillate oil is 20-40% by mass, in the composite solvent, the content of the alkyl sulfolane is 40-60% by mass, the content of sulfolane is 30-50% by mass, the content of the chain sulfone is 7-12% by mass, and the content of the glycol ether is 0.1-3% by mass; preferably, the content of the alkyl sulfolane is 45-55% by mass, the content of sulfolane is 35-45% by mass, the content of the chain sulfone is 9-12% by mass, and the content of the glycol ether is 0.1-3% by mass.

[0029] Among them, optionally, when the aromatic content in the aromatic-containing distillate oil is greater than 40% by mass and not more than 60% by mass, in the composite solvent, the content of the alkyl sulfolane is 20-49.9% by mass, the sulfolane content is preferably 40-65% by mass, the content of the chain sulfone is 10-15% by mass, and the content of the glycol ether is 0.1-3% by mass; preferably, the content of the alkyl sulfolane is 25-40% by mass, the sulfolane content is preferably 45-60% by mass, the content of the chain sulfone is 13-15% by mass, and the content of the glycol ether is 0.1-3% by mass.

[0030] Among them, optionally, the method also includes: countercurrently contacting part or all of the crude circulating solvent with a stripping agent and circulating water in a stripping tower to perform stripping, to obtain a stripping material and a stripping residue material; the stripping agent contains hydrocarbons below C5; the stripping material is distilled in a stripping agent distillation tower to obtain a first heavy fraction and a first circulating stripping agent; the stripping residue material is flashed in a flash tank to obtain a refined circulating solvent and a second circulating stripping agent; the refined circulating solvent is introduced into the solvent recovery tower to separate the water in the refined circulating solvent as the circulating water.

[0031] Wherein, optionally, 0.1 to 20 mass% of the crude circulating solvent is subjected to the stripping; the stripping conditions in the stripping tower include: the theoretical plate number is 5 to 10, the tower top pressure is 0.2 MPa to 0.8 MPa, the stripping agent inlet temperature is 20°C to 50°C, the mass ratio of the stripping agent to the crude circulating solvent entering the stripping tower is 0.2 to 3:1, the tower inlet temperature of the circulating water is 30°C to 60°C, and the mass ratio of the circulating water to the crude circulating solvent entering the stripping tower is 0.2 to 0.6:1.

[0032] Among them, optionally, the distillation conditions in the stripping agent distillation tower include: the theoretical plate number is 10 to 30, the top pressure is 0.1 MPa to 0.4 MPa, the bottom temperature is 150° C. to 210° C., and the reflux ratio is 0.1 to 1.

[0033] Wherein, optionally, the flash evaporation conditions in the flash tank include: pressure of 0.1MPa to 0.7MPa and temperature of 50°C to 100°C.

[0034] Optionally, the method further comprises fractionating the gasoline fraction raw material to obtain the aromatic-containing distillate oil, a light distillate oil lighter than the aromatic-containing distillate oil, and a heavy distillate oil heavier than the aromatic-containing distillate oil, wherein the initial distillation point of the aromatic-containing distillate oil is any temperature between 40°C and 70°C, and the final distillation point of the aromatic-containing distillate oil is any temperature between 85°C and 180°C.

[0035] Optionally, the gasoline fraction raw material is selected from one or more of FCC gasoline, DCC gasoline, LTA gasoline, reformed gasoline, cracking hydrogenated gasoline and coal tar gasoline fractions; and the aromatic content in the aromatic fraction oil is 5 to 60% by mass.

[0036] Optionally, part or all of the light fraction oil is used as the stripping agent to participate in the stripping.

[0037] Particularly preferably, referring to Figure 1The gasoline fraction feedstock enters the first fractionating tower 101 via pipeline 1. The overhead vapor is condensed and enters the reflux tank 108 via pipeline 2. A portion of the light fraction (C5- fraction) returns to the top of the first fractionating tower 101 via pipeline 3, another portion of the light fraction enters the lower part of the stripping tower 105 via pipeline 4, and the remaining light fraction enters the gasoline pool as a product. The C6+ fraction obtained in the bottom of the first fractionating tower 101 enters the second fractionating tower 102 via pipeline 5. The overhead vapor of the second fractionating tower 102 is condensed and enters the reflux tank 109 via pipeline 6. Part of the condensate is returned to the top of the second fractionating tower 102 via pipeline 7, and the remaining condensate enters the middle part of the extractive distillation tower 103 as a distillate oil containing aromatics via pipeline 8. The heavy fraction obtained in the bottom of the second fractionating tower 102 enters the gasoline pool via pipeline 9. The crude circulating solvent enters the upper portion of the extractive distillation tower 103 via pipeline 10, where it is countercurrently contacted with the aromatics-containing distillate oil for extractive distillation. The overhead vapor from the extractive distillation tower 103 is condensed and enters a reflux drum 110 via pipeline 11. A portion of the condensate is returned to the top of the extractive distillation tower 103 via pipeline 12, and the remaining condensate is withdrawn via pipeline 13 as a raffinate containing non-aromatic products. The extract obtained in the bottom of the extractive distillation tower 103 enters the solvent recovery tower 104 via pipeline 14. The extract is subjected to vacuum distillation in the solvent recovery tower 104. The overhead vapor from the solvent recovery tower 104 is condensed and enters a reflux drum 111 via pipeline 15. A portion of the condensate is returned to the top of the tower 104 via pipeline 16, and the remaining condensate is withdrawn via pipeline 17 as an aromatic product. The crude circulating solvent obtained in the bottom of the tower 104 is discharged via pipeline 18. A portion of the crude circulating solvent enters the upper portion of stripping tower 105 via line 19, while the remainder returns to extractive distillation tower 103 via line 10. Circulating water enters the upper portion of stripping tower 105 via line 20. The overhead stream from stripping tower 105 enters stripping agent distillation tower 106 via line 21, and the bottom stream from stripping tower 105 enters flash tank 107 via line 26. The vapor from the overhead of stripping agent distillation tower 106 condenses via line 22 and enters reflux tank 112. Part of the condensate returns to the top of 106 via line 23, while another portion returns to stripping tower 105 via line 24 as the first circulating stripping agent. The remainder is discharged into the gasoline pool. The heavy component obtained from the bottom of stripping agent distillation tower 106 enters the gasoline pool via line 25. The steam obtained from the top of the flash tank 107 is used as the second circulating stripping agent and enters the top condenser of the stripping agent distillation tower 106 through pipeline 27. After merging with the stream from pipeline 22, it enters the reflux tank 112. The stream obtained from the bottom of the flash tank 107 is used as the refined circulating solvent and enters the bottom of the solvent recovery tower 104 through pipeline 28. The water in the refined circulating solvent is separated in the solvent recovery tower 104 and enters the water bag of the reflux tank 111 at the top of the solvent recovery tower 104. It is then recycled as circulating water to the stripping tower 105 ( Figure 1 not shown).

[0038] The present invention is further described in detail below by way of examples. Unless otherwise specified, the raw materials used in the examples can be obtained from commercial sources. The raw materials for Examples 1-12 and Comparative Examples 1-6 are shown in Table 1.

[0039] Table 1

[0040] composition Raw material 1 Raw material 2 Raw material 3 The raw material entering the first fractionation tower 101 from pipeline 1 Alkanes, mass% C5- 8.50 11.12 14.58 C6 11.06 8.52 4.6 C7 5.02 4.05 4.92 C8 8.55 2.78 2.46 C9+ 4.99 7.44 7.19 Olefins and cycloalkanes, mass % C5- 7.55 10.48 6.15 C6 11.48 7.57 3.13 C7 6.27 5.67 2.77 C8 5.89 4.81 1.66 C9+ 3.87 3.93 1.13 Aromatics, mass% C6 0.88 1.45 3.99 C7 3.91 7.80 9.38 C8 5.95 9.04 15.74 C9+ 16.08 15.34 22.3 26.82 33.63 52.51 The aromatics-containing distillate oil enters the extractive distillation tower 103 via pipeline 8 Aromatic content 18.20％ 35.38％ 59.83％ Distillation range, ℃ 55-155 53-165 48-158 The light fraction (C5- fraction) enters the stripping tower 105 via pipeline 4 Distillation range, ℃ 25-54 28-52 20-47

[0041] Example 1

[0042] according to Figure 1 The process is as follows: a catalytic cracking gasoline fraction (raw material 1) is used as raw material (composition is shown in Table 1) and enters a first distillation tower 101 through pipeline 1; the extractant is composed of 1,2,3,4-tetramethyl sulfolane, sulfolane, methyl phenyl sulfone, and tetraethylene glycol monomethyl ether, with mass percentages of 70%, 20%, 8%, and 2%, respectively; the composition of the aromatics-containing distillate oil entering the extractive distillation tower 103 through pipeline 8 is shown in Table 1; the main operating conditions are shown in Table 2; the aromatics purity and yield of the aromatics product produced through pipeline 17 are shown in Table 3.

[0043] Example 2

[0044] Using the raw materials and extractant of Example 1, Figure 1 Aromatic products were extracted using the same process as in Example 1, except that the equipment did not include a stripping tower or stripping agent distillation tower. Stream 19 was fed directly to flash tank 107, and streams 27 and 28 were returned to the bottom of solvent recovery tower 104. The purity and yield of the aromatic products are shown in Table 3. As can be seen, due to the incomplete separation of a small amount of heavy components in the solvent, the selectivity of the composite solvent decreased, resulting in lower purity and yield of the aromatic products than in Example 1.

[0045] Example 3

[0046] Aromatic hydrocarbon extraction was performed according to the method of Example 1. The extractant consisted of 2,4-dimethylsulfolane, sulfolane, methyl isopropyl sulfone, and tetraglyme, with mass percentages of 50%, 39%, 10%, and 1%, respectively. The main operating conditions are shown in Table 2, and the purity and yield of the aromatic hydrocarbon product are shown in Table 3. Compared with Example 1, it can be seen that the yield of the aromatic hydrocarbon product is still significantly reduced.

[0047] Example 4

[0048] Aromatic hydrocarbon extraction was performed according to the method of Example 1. The extractant consisted of 3-methylsulfolane, sulfolane, ethyl methyl sulfone, and tetraethylene glycol monomethyl ether, with weight percentages of 25%, 60%, 14%, and 1%, respectively. The main operating conditions are shown in Table 2, and the purity and yield of the aromatic hydrocarbon product are shown in Table 3. Compared with Example 1, it can be seen that the yield of the aromatic hydrocarbon product is still significantly reduced.

[0049] Comparative Example 1

[0050] Aromatic hydrocarbon extraction was performed according to the method of Example 1. A sulfolane-methyl ethyl sulfone composite solvent was used as the extractant, with a mass ratio of 1:1. The main operating conditions are shown in Table 2, and the purity and yield of the aromatic hydrocarbon product are shown in Table 3. Compared with Example 1, it can be seen that the yield of the aromatic hydrocarbon product is still significantly reduced.

[0051] Comparative Example 2

[0052] Aromatic hydrocarbon extraction was performed according to the method of Example 1. A sulfolane / 3-methylsulfolane composite solvent was used as the extractant, with a mass ratio of 3:1. The main operating conditions are shown in Table 2, and the purity and yield of the aromatic hydrocarbon product are shown in Table 3. Compared with Example 1, it can be seen that the purity and yield of the aromatic hydrocarbon product are reduced.

[0053] Table 2

[0054]

[0055] Table 3

[0056] composition Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Purity of aromatic products, mass% 99.92 97.75 99.90 99.91 99.29 98.47 Aromatic product yield, mass % 99.9 98.3 97.2 96.3 93.6 95.6

[0057] Example 5

[0058] according to Figure 1 The process is as follows: the catalytic cracking gasoline fraction (raw material 2) is used as the raw material (the composition is shown in Table 1) and enters the first distillation tower 101 through pipeline 1. The extractant is composed of 2,4-dimethyl sulfolane, sulfolane, methyl isopropyl sulfone, and tetraglyme, with the mass percentages of 50%, 39%, 10%, and 1%, respectively. The composition of the aromatics-containing distillate oil entering the extractive distillation tower 103 through pipeline 8 is shown in Table 1. The main operating conditions are shown in Table 4. The aromatic purity and yield of the aromatics product produced through pipeline 17 are shown in Table 5.

[0059] Example 6

[0060] Using the raw materials and extractant of Example 5, Figure 1 Aromatic products were extracted using the same process as in Example 5, except that the equipment did not include a stripping tower or stripping agent distillation tower. Stream 19 was fed directly to flash tank 107, and streams 27 and 28 were returned to the bottom of solvent recovery tower 104. The purity and yield of the aromatic products are shown in Table 5. It can be seen that due to the incomplete separation of a small amount of heavy components in the solvent, the selectivity of the composite solvent decreased, resulting in lower purity and yield of the aromatic products than in Example 5.

[0061] Example 7

[0062] Aromatic hydrocarbon extraction was performed according to the method of Example 5. The extractant consisted of 1,2,3,4-tetramethylsulfolane, sulfolane, methyl phenyl sulfone, and tetraethylene glycol monomethyl ether, with mass percentages of 70%, 20%, 8%, and 2%, respectively. The main operating conditions are shown in Table 4, and the purity and yield of the aromatic hydrocarbon product are shown in Table 5. Compared with Example 5, it can be seen that the purity of the aromatic hydrocarbon product was significantly reduced due to the poor selectivity of the solvent for this raw material.

[0063] Example 8

[0064] Aromatic hydrocarbon extraction was performed according to the method of Example 5. The extractant consisted of 3-methylsulfolane, sulfolane, ethyl methyl sulfone, and tetraethylene glycol monomethyl ether, with mass percentages of 25%, 60%, 14%, and 1%, respectively. The main operating conditions are shown in Table 4, and the purity and yield of the aromatic hydrocarbon product are shown in Table 5. Compared with Example 5, it can be seen that the yield of the aromatic hydrocarbon product was significantly reduced due to the insufficient solubility of the solvent for the raw materials.

[0065] Comparative Example 3

[0066] Aromatic hydrocarbon extraction was performed according to the method of Example 5. A sulfolane-methyl ethyl sulfone composite solvent was used as the extractant, with a mass ratio of 1:1. The main operating conditions are shown in Table 4, and the purity and yield of the aromatic hydrocarbon product are shown in Table 5. Compared with Example 5, it can be seen that the yield of the aromatic hydrocarbon product is significantly reduced.

[0067] Comparative Example 4

[0068] Aromatic hydrocarbon extraction was performed according to the method of Example 5. A sulfolane / 3-methylsulfolane composite solvent was used as the extractant, with a mass ratio of 3:1. The main operating conditions are shown in Table 4, and the purity and yield of the aromatic hydrocarbon product are shown in Table 5. Compared with Example 5, it can be seen that the purity and yield of the aromatic hydrocarbon product are reduced.

[0069] Table 4

[0070]

[0071] Table 5

[0072] composition Example 5 Example 6 Example 7 Example 8 Comparative Example 3 Comparative Example 4 Purity of aromatic products, mass% 99.93 97.62 99.67 99.91 99.50 98.02 Aromatic product yield, mass % 99.9 98.5 99.0 97.1 95.3 96.5

[0073] Example 9

[0074] according to Figure 1 The process is as follows: a catalytic cracking gasoline fraction (raw material 3) is used as raw material (composition is shown in Table 1) and enters a first distillation tower 101 via pipeline 1; the extractant is composed of 3-methyl sulfolane, sulfolane, ethyl methyl sulfone, and tetraethylene glycol monomethyl ether, with mass percentages of 25%, 60%, 14%, and 1%, respectively; the composition of the aromatics-containing distillate oil entering the extractive distillation tower 103 via pipeline 8 is shown in Table 1; the main operating conditions are shown in Table 6; the aromatics purity and yield of the aromatics product extracted via pipeline 17 are shown in Table 7.

[0075] Example 10

[0076] Using the raw materials and extractant of Example 9, Figure 1 Aromatic products were extracted using the same process as in Example 9, except that the equipment did not include a stripping tower or stripping agent distillation tower. Stream 19 was fed directly to flash tank 107, and streams 27 and 28 were returned to the bottom of solvent recovery tower 104. The purity and yield of the aromatic products are shown in Table 7. It can be seen that due to the incomplete separation of a small amount of heavy components in the solvent, the selectivity of the composite solvent decreased, resulting in lower purity and yield of the aromatic products than in Example 9.

[0077] Example 11

[0078] Aromatic hydrocarbon extraction was performed according to the method of Example 9. The extractant consisted of 1,2,3,4-tetramethylsulfolane, sulfolane, methyl phenyl sulfone, and tetraethylene glycol monomethyl ether, with mass percentages of 70%, 20%, 8%, and 2%, respectively. The main operating conditions are shown in Table 6, and the purity and yield of the aromatic hydrocarbon product are shown in Table 7. Compared with Example 9, the purity of the aromatic hydrocarbon product was significantly reduced.

[0079] Example 12

[0080] Aromatic hydrocarbon extraction was performed according to the method of Example 9. The extractant consisted of 2,4-dimethylsulfolane, sulfolane, methyl isopropyl sulfone, and tetraglyme, with mass percentages of 50%, 39%, 10%, and 1%, respectively. The main operating conditions are shown in Table 6, and the purity and yield of the aromatic hydrocarbon product are shown in Table 7. Compared with Example 9, the purity of the aromatic hydrocarbon product was significantly reduced.

[0081] Comparative Example 5

[0082] Aromatic hydrocarbon extraction was performed according to the method of Example 9. A sulfolane-methyl ethyl sulfone composite solvent was used as the extractant, with a mass ratio of 1:1. The main operating conditions are shown in Table 6, and the purity and yield of the aromatic hydrocarbon product are shown in Table 7. Compared with Example 9, it can be seen that the yield of the aromatic hydrocarbon product is still significantly reduced.

[0083] Table 6

[0084]

[0085] Comparative Example 6

[0086] Aromatic hydrocarbon extraction was performed according to the method of Example 9. A sulfolane / 3-methylsulfolane composite solvent was used as the extractant, with a mass ratio of 3:1. The main operating conditions are shown in Table 6, and the purity and yield of the aromatic hydrocarbon product are shown in Table 7. Compared with Example 9, it can be seen that the purity and yield of the aromatic hydrocarbon product are reduced.

[0087] Table 7

[0088] composition Example 9 Example 10 Example 11 Example 12 Comparative Example 5 Comparative Example 6 Purity of aromatic products, mass% 99.95 98.10 99.62 99.71 99.37 97.89 Aromatic product yield, mass % 99.9 98.7 99.7 99.6 97.4 98.2

[0089] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0090] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. To avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0091] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A composite solvent for aromatic hydrocarbon extraction, characterized in that: The composite solvent contains 20-80% by mass of alkyl sulfolane, 10-60% by mass of sulfolane, 5-15% by mass of chain sulfone and 0.1-3% by mass of glycol ether; Wherein, the alkyl sulfolane, the chain sulfone and the glycol ether are represented by Formula 1, Formula 2 and Formula 3 respectively; Formula 1: ; Formula 2: ; Formula 3: ; In Formula 1, R1, R2, R3 and R4 are each independently hydrogen, methyl or ethyl, and at least one of R1, R2, R3 and R4 is not hydrogen; In Formula 2, R5 and R6 are different from each other and are each independently a phenyl group or a C1 to C6 alkyl group; In Formula 3, n is an integer of 2-5, R7 and R8 are each independently hydrogen or a C1 to C6 alkyl group, and at least one of R7 and R8 is not hydrogen.

2. The composite solvent according to claim 1, wherein The alkyl sulfolane is at least one of 3-methylsulfolane, 2,4-dimethylsulfolane and 1,2,3,4-tetramethylsulfolane; the chain sulfone is at least one of ethyl methyl sulfone, methyl isopropyl sulfone and methyl phenyl sulfone; and the glycol ether is tetraethylene glycol monomethyl ether and / or tetraethylene glycol dimethyl ether.

3. The composite solvent according to claim 1 or 2, wherein In the composite solvent, the content of the alkyl sulfolane is 60-80% by mass, the content of sulfolane is 10-34.9% by mass, the content of the chain sulfone is 5-10% by mass, and the content of the glycol ether is 0.1-3% by mass.

4. The composite solvent according to claim 3, wherein The content of the alkyl sulfolane is 65-75% by mass, the content of sulfolane is 15-29.9% by mass, the content of the chain sulfone is 5-8% by mass, and the content of the glycol ether is 0.1-3% by mass.

5. The composite solvent according to claim 1 or 2, wherein In the composite solvent, the content of the alkyl sulfolane is 40-60% by mass, the content of sulfolane is 30-50% by mass, the content of the chain sulfone is 7-12% by mass, and the content of the glycol ether is 0.1-3% by mass.

6. The composite solvent according to claim 5, wherein The content of the alkyl sulfolane is 45-55% by mass, the content of sulfolane is 35-45% by mass, the content of the chain sulfone is 9-12% by mass, and the content of the glycol ether is 0.1-3% by mass.

7. The composite solvent according to claim 1 or 2, wherein In the composite solvent, the content of the alkyl sulfolane is 20-49.9% by mass, the content of the sulfolane is 40-60% by mass, the content of the chain sulfone is 10-15% by mass, and the content of the glycol ether is 0.1-3% by mass.

8. The composite solvent according to claim 7, wherein The content of the alkyl sulfolane is 25-40% by mass, the content of the sulfolane is 46-60% by mass, the content of the chain sulfone is 13-15% by mass, and the content of the glycol ether is 0.1-3% by mass.

9. A method for extracting aromatic hydrocarbons, characterized in that: The method includes: The aromatic hydrocarbon-containing distillate oil is countercurrently contacted with the composite solvent according to any one of claims 1 to 8 in an extractive distillation tower for extractive distillation to obtain an extract material and a raffinate material; The extracted material is distilled in a solvent recovery tower to obtain aromatic hydrocarbon products and crude circulating solvent.

10. The method according to claim 9, wherein: The mass ratio of the composite solvent to the aromatic hydrocarbon-containing distillate entering the extractive distillation tower is 1-20, the number of theoretical plates of the extractive distillation tower is 10-40, the reflux ratio is 0.2-2, the tower bottom temperature is 120° C.-185° C., and the tower top pressure is 0.1 MPa-0.3 MPa; The solvent recovery tower has a theoretical plate number of 20 to 50, a reflux ratio of 0.5 to 2.0, a tower top pressure of 0.01 MPa to 0.07 MPa, and a tower bottom temperature of 150° C. to 190° C.

11. The method according to claim 9, wherein When the aromatic content of the aromatic hydrocarbon-containing distillate is less than 20% by mass, the composite solvent comprises 60-80% by mass of alkyl sulfolane, 10-34.9% by mass of sulfolane, 5-10% by mass of chain sulfone, and 0.1-3% by mass of glycol ether; When the aromatic content of the aromatic hydrocarbon-containing distillate is 20-40% by mass, the composite solvent comprises 40-60% by mass of alkyl sulfolane, 30-50% by mass of sulfolane, 7-12% by mass of chain sulfone, and 0.1-3% by mass of glycol ether; When the aromatic content in the aromatic-containing distillate oil is greater than 40% by mass and not greater than 60% by mass, in the composite solvent, the content of the alkyl sulfolane is 20-49.9% by mass, the content of the sulfolane is 40-60% by mass, the content of the chain sulfone is 10-15% by mass, and the content of the glycol ether is 0.1-3% by mass.

12. The method according to claim 11, wherein When the aromatic content of the aromatic hydrocarbon-containing distillate is less than 20% by mass, the composite solvent comprises 65-75% by mass of alkyl sulfolane, 15-29.9% by mass of sulfolane, 5-8% by mass of chain sulfone, and 0.1-3% by mass of glycol ether; When the aromatic content of the aromatic hydrocarbon-containing distillate is 20-40% by mass, in the composite solvent, the content of the alkyl sulfolane is 45-55% by mass, the content of sulfolane is 35-45% by mass, the content of the chain sulfone is 9-12% by mass, and the content of the glycol ether is 0.1-3% by mass; When the aromatic content in the aromatic-containing distillate oil is greater than 40% by mass and not greater than 60% by mass, in the composite solvent, the content of the alkyl sulfolane is 25-40% by mass, the content of the sulfolane is 46-60% by mass, the content of the chain sulfone is 13-15% by mass, and the content of the glycol ether is 0.1-3% by mass.

13. The method according to any one of claims 9 to 12, wherein: The method further includes: Part or all of the crude circulating solvent is countercurrently contacted with a stripping agent and circulating water in a stripping tower to perform stripping to obtain a stripping material and a stripping residue; the stripping agent contains hydrocarbons below C5; The stripping material is distilled in a stripping agent distillation tower to obtain a first heavy fraction and a first circulating stripping agent; Flashing the stripping residue in a flash tank to obtain a fine circulating solvent and a second circulating stripping agent; The refined circulating solvent is introduced into the solvent recovery tower to separate water from the refined circulating solvent as the circulating water.

14. The method according to claim 13, wherein: 0.1-20 mass% of the crude circulating solvent is subjected to the stripping; the stripping conditions in the stripping tower include: the number of theoretical plates is 5-10, the tower top pressure is 0.2 MPa-0.8 MPa, the stripping agent inlet temperature is 20°C-50°C, the mass ratio of the stripping agent to the crude circulating solvent entering the stripping tower is 0.2-3:1, the tower inlet temperature of the circulating water is 30°C-60°C, and the mass ratio of the circulating water to the crude circulating solvent entering the stripping tower is 0.2-0.6:1; The distillation conditions in the stripping agent distillation tower include: theoretical plate number of 10-30, tower top pressure of 0.1 MPa-0.4 MPa, tower bottom temperature of 150° C.-210° C., and reflux ratio of 0.1-1; The flash evaporation conditions in the flash tank include: a pressure of 0.1 MPa to 0.7 MPa and a temperature of 50° C. to 100° C.

15. The method according to any one of claims 9 to 14, wherein: The method further comprises fractionating the gasoline fraction raw material to obtain the aromatic hydrocarbon-containing distillate oil, a light distillate oil lighter than the aromatic hydrocarbon-containing distillate oil, and a heavy distillate oil heavier than the aromatic hydrocarbon-containing distillate oil, wherein the initial boiling point of the aromatic hydrocarbon-containing distillate oil is any temperature between 40° C. and 70° C., and the final boiling point of the aromatic hydrocarbon-containing distillate oil is any temperature between 85° C. and 180° C.; The gasoline fraction raw material is selected from one or more of FCC gasoline, DCC gasoline, reformed gasoline, cracking hydrogenated gasoline and coal tar gasoline fractions; the aromatic content in the aromatic fraction oil is 5-60% by mass.

16. The method according to claim 15, wherein Part or all of the light fraction oil is used as the stripping agent in claim 13 or 14 to participate in the stripping in claim 13 or 14.

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