A method and system for liquid-liquid separation of aromatics from fuel oil products

Abstract

The method provided by the application uses one of N, N-dialkyl pyrrolidone and N, N-dialkoxy pyrrolidone as an extraction solvent, the boiling point of the extraction solvent is much higher than that of fuel oil products, the extraction solvent is easy to be directly separated by rectification, and the extraction solvent has great polarity and strong solubility to aromatic hydrocarbons, can be applied to various fuel oil products, and can extract almost all aromatic hydrocarbon components from the fuel oil products to extract oil; then, the extract oil is subjected to back extraction with a back extraction agent (a mixed solvent of water and a polyhydroxy solvent) to separate aromatic hydrocarbon phases and the extraction solvent, the aromatic hydrocarbon recovery rate is improved, the emulsification phenomenon of water and oil is reduced, and the back extraction efficiency is improved. Further, compared with the existing rectification recovery solvent technology, the method provided by the application can effectively reduce energy consumption and realize reuse of the extraction solvent.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fuel product separation, and particularly relates to a method and system for separating aromatic hydrocarbons from fuel products by liquid-liquid separation. BACKGROUND

[0002] Aromatic hydrocarbons are basic raw materials for chemical industry, and are widely used in the fields of synthetic resins, synthetic fibers, synthetic rubber, etc. Separating aromatic hydrocarbon components from diesel oil has great significance for improving the cetane number of diesel oil and providing raw materials for synthetic resins.

[0003] As an important means for separating aromatic hydrocarbons in industry, aromatic hydrocarbon solvent extraction process is a process in which different solubilities and relative volatilities of different hydrocarbon components in an extraction solvent are used to separate relatively pure aromatic hydrocarbons from a hydrocarbon mixture, and is also called liquid-liquid extraction or solvent extraction. Liquid-liquid extraction technology has the advantages of simple operation conditions and large processing capacity, and has been widely used in industry. For example, CN1408689A discloses a method for recovering aromatic hydrocarbon components from a hydrocarbon mixture by extraction and extractive distillation. The method mainly pre-fractionates diesel oil, sends a toluene fraction obtained by fractionation into a liquid-liquid extraction tower, and separates the solvent from the aromatic hydrocarbons by using a series of extractive distillation and vacuum distillation. This technology is mainly used for raw material mixtures with 60% to 99% aromatic hydrocarbons, and is not suitable for all types of diesel oil.

[0004] The most important thing for diesel extraction technology is the selection of extraction solvent. Commonly used solvents include glycols, sulfolane, N-formyl morpholine, N-methyl pyrrolidone, ionic liquids, etc. However, the above-mentioned commonly used extraction solvents each have certain problems. For example, sulfolane and N-formyl morpholine have low boiling points, and it is difficult to separate the solvent from heavy aromatic components and to recover the solvent. In order to improve the solubility and selectivity of aromatic hydrocarbons, a composite solvent is often used as an extraction solvent in the prior art. For example, CN103160310A discloses a composite solvent for extracting and separating aromatic hydrocarbons from a hydrocarbon mixture in the oil refining and chemical industries, and an extraction method thereof. The composite solvent is prepared by uniformly mixing a main solvent, a cosolvent and a modifier, can significantly increase the solubility and selectivity of the solvent for aromatic hydrocarbons, and improve the recovery rate of aromatic hydrocarbons. CN1660970A discloses a composite solvent for extractive distillation separation of aromatic hydrocarbons, which comprises a main solvent, a cosolvent and water. The composite solvent can be used for extractive distillation separation of aromatic hydrocarbons, can effectively reduce the solvent ratio, and can improve the yield of aromatic hydrocarbon products. However, the presence of water and aromatic components causes azeotropy, and also causes hydrolysis to occur. The use of a composite solvent can complicate the extraction process and is not conducive to industrial production. SUMMARY

[0005] Therefore, the application provides a method for separating aromatic hydrocarbons in fuel oil products by liquid-liquid separation, without adding cosolvents and / or modifiers, so as to realize efficient separation of aromatic hydrocarbons in fuel oil products and improve the recovery rate of aromatic hydrocarbons.

[0006] The application provides a method for separating aromatic hydrocarbons in fuel oil products by liquid-liquid separation, which comprises the following steps:

[0007] The fuel oil product is extracted by using an extraction solvent to obtain extracted oil and raffinate oil, wherein the main component of the extracted oil is aromatic hydrocarbons, and the main component of the raffinate oil is non-aromatic hydrocarbons; the extraction solvent is one of N,N-dialkyl (oxy) pyrrolidones, the boiling point of the extraction solvent is higher than the boiling point of the fuel oil product, and the boiling point is greater than 380 DEG C;

[0008] The extracted oil is back-extracted by using a back-extraction agent to obtain a back-extraction phase and a back-extraction raffinate phase, wherein the back-extraction raffinate phase is an aromatic hydrocarbon phase, and the back-extraction phase is an extraction solvent phase; the back-extraction agent comprises water and a polyhydroxy solvent, and the volume ratio of water to the polyhydroxy solvent in the back-extraction agent is greater than 1:1 and less than 10:1;

[0009] The back-extraction phase is subjected to vacuum rectification to obtain recovered extraction solvent;

[0010] The structure of the N,N-dialkyl (oxy) pyrrolidone is shown in formula I:

[0011]

[0012] R is an alkylene group, and n is greater than or equal to 0.

[0013] Preferably, the method further comprises: washing the raffinate oil to obtain a non-aromatic hydrocarbon component.

[0014] Preferably, the alkyl group in the N,N-dialkyl pyrrolidone is a C5-C10 alkyl group, and the number of carbon atoms in the alkoxy group in the N,N-dialkyl (oxy) pyrrolidone is 1-10.

[0015] Preferably, the extraction solvent is N,N-dialkyl hexyl pyrrolidone or N,N-dialkyl-3,6-dioxaoctyl pyrrolidone.

[0016] Preferably, the volume ratio of the extraction solvent to the fuel oil product is 0.5-10:1; the extraction temperature is 30-70 DEG C; and the extraction stage is 1-3 stages.

[0017] Preferably, the volume ratio of water to the polyhydroxy solvent in the back-extraction agent is 4-9:1; the agent-oil ratio in the back-extraction stage is 0.5-5:1; the back-extraction temperature is 35-100 DEG C; and the back-extraction stage is 1-3 stages.

[0018] Preferably, the operating temperature of the reduced pressure rectification is 45-200℃; and the pressure of the reduced pressure rectification is 5-20kP.

[0019] Preferably, the volume ratio of water to raffinate oil during the water washing is 0.5-1.5:1; and the temperature of the water washing is 30-70℃.

[0020] Preferably, the fuel oil product includes diesel fraction, reforming gasoline or cracking gasoline, and the volume content of aromatic hydrocarbon in the fuel oil product is 10-90%.

[0021] The present application also provides a system for liquid-liquid separation of aromatic hydrocarbon in fuel oil product, which comprises a solvent extraction column 1 provided with an extraction solvent inlet, a fuel oil product inlet, and a raffinate oil outlet and a raffinate oil outlet.

[0022] A stripping column 2 connected to the raffinate oil outlet of the solvent extraction column 1, the stripping column 2 is provided with a stripping agent inlet, a stripping phase outlet and a stripping raffinate phase outlet.

[0023] A reduced pressure rectification column 4 connected to the stripping raffinate phase outlet of the stripping column 2, the reduced pressure rectification column 4 is provided with a water outlet.

[0024] The method provided by the present application uses one of N,N-dialkyl pyrrolidone and N,N-dialkoxy pyrrolidone as the extraction solvent, the boiling point of the extraction solvent is much higher than that of the fuel oil product, which is easy to be directly rectified and separated, and has strong polarity and strong solubility to aromatic hydrocarbon, and can be applied to various fuel oil products, and can extract almost all aromatic hydrocarbon components from the fuel oil product to the raffinate oil; then the raffinate oil is separated from the aromatic hydrocarbon phase and the extraction solvent by using a stripping agent (a mixed solvent of water and a polyhydroxy solvent), which improves the recovery rate of aromatic hydrocarbon, and the polarity of the stripping agent is greater than that of the extraction solvent, which is greater than that of the aromatic hydrocarbon, so that the emulsification of water and oil can be relatively reduced, and the stripping efficiency is improved.

[0025] Further, the method provided by the present application can effectively reduce energy consumption and realize reuse of the extraction solvent.

[0026] Moreover, the raffinate oil obtained by extraction is washed with water to separate non-aromatic hydrocarbon components. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0028] Figure 1A system structure schematic diagram of liquid-liquid separation fuel oil product of the embodiment of the present application;

[0029] Figure 1 In the figure, 1 is a solvent extraction column, 2 is a back extraction column, 3 is a water washing column, 4 is a vacuum rectification column, 5 is an extraction solvent, 6 is a fuel oil product, 7 is a back extraction agent, 8 is an extracted oil, 9 is a raffinate oil, 10 is a non-aromatic oil, 11 is a water washing extraction phase, 12 is a back extraction residual phase, 13 is a back extraction phase, 14 is water (containing part of a polyhydroxy solvent), and 15 is a recycled extraction solvent;

[0030] Figure 2 A structure compound shown in formula III prepared by the embodiment of the present application 1 H NMR spectrum.

[0031] Figure 3 A structure compound shown in formula II prepared by the embodiment of the present application 1 H NMR spectrum. DETAILED DESCRIPTION

[0032] The present application provides a method for liquid-liquid separation of aromatic hydrocarbons in a fuel oil product, comprising the following steps:

[0033] An extraction solvent is used to extract the fuel oil product to obtain an extracted oil and a raffinate oil, wherein the main component of the extracted oil is aromatic hydrocarbons, and the main component of the raffinate oil is non-aromatic hydrocarbons; the extraction solvent is one of N,N-dialkyl (oxy) pyrrolidone, the boiling point of the extraction solvent is higher than the boiling point of the fuel oil product, and the boiling point is greater than 380℃;

[0034] A back extraction agent is used to back extract the extracted oil to obtain a back extraction phase and a back extraction residual phase, wherein the back extraction residual phase is an aromatic hydrocarbon phase, and the back extraction phase is an extraction solvent phase; the back extraction agent comprises water and a polyhydroxy solvent, and the volume ratio of water to the polyhydroxy solvent in the back extraction agent is greater than 1:1 and less than 10:1;

[0035] The back extraction phase is subjected to vacuum rectification to obtain a recycled extraction solvent;

[0036] The structure of the N,N-dialkyl (oxy) pyrrolidone is shown in formula I:

[0037]

[0038] R is an alkylene group, and n≥0.

[0039] The present application does not have special limitations on the type and source of the fuel oil product, and is suitable for various fuel oil products, such as diesel oil fraction, reforming gasoline or cracking gasoline; the diesel oil fraction can be straight-run diesel oil, catalytic diesel oil or hydrogenated diesel oil.

[0040] In the embodiments of the present application, the types of the aromatic hydrocarbons in the fuel product can include monocyclic aromatic hydrocarbons, bicyclic aromatic hydrocarbons, and tricyclic aromatic hydrocarbons; and the volume content of the aromatic hydrocarbons in the fuel product is preferably 10-90%. The fuel product has a boiling point of 180-380℃.

[0041] In the present application, the fuel product is extracted (i.e. liquid-liquid extraction) by using an extraction solvent to obtain extracted oil and raffinate oil, wherein the main component of the extracted oil is aromatic hydrocarbons, and the main component of the raffinate oil is non-aromatic hydrocarbons. In the present application, the volume percentage content of the aromatic hydrocarbons in the extracted oil is preferably greater than or equal to 85%, more preferably 90-95%; the volume percentage content of the non-aromatic hydrocarbons in the extracted oil is preferably less than 15%, more preferably greater than 1% and less than 15%; the volume percentage content of the non-aromatic hydrocarbons in the raffinate oil is preferably greater than 73%, more preferably greater than 73% and less than or equal to 85%; and the volume percentage content of the aromatic hydrocarbons in the raffinate oil is preferably less than or equal to 27%, more preferably greater than 15% and less than or equal to 27%.

[0042] In the present application, the extraction solvent is one of N,N-dialkyl pyrrolidone and N,N-dialkoxy pyrrolidone. In the present application, the alkyl group in the N,N-dialkyl pyrrolidone is preferably C5-C10 alkyl group, more preferably C6-C8 alkyl group, which can be specifically n-pentyl, n-hexyl, n-heptyl or n-octyl. In the embodiments of the present application, the extraction solvent can be N,N-dinormal-hexyl pyrrolidone, the structure of which is shown in formula II:

[0043]

[0044] The boiling point of the N,N-dinormal-hexyl pyrrolidone is 430℃.

[0045] In the present application, the number of carbon atoms in the alkoxy group in the N,N-dialkoxy pyrrolidone is preferably 2-10, more preferably N,N-dialkyl-dioxyethyl pyrrolidone, N,N-dialkyl-dioxylbutyl pyrrolidone, N,N-dialkyl-dioxylhexyl pyrrolidone or N,N-dialkyl-3,6-dioxyl-octyl pyrrolidone (the structure of which is shown in formula III);

[0046]

[0047] In the present application, the boiling point of the N,N-dialkyl-3,6-dioxyl-octyl pyrrolidone is 450℃.

[0048] In the present application, the preparation method of the N,N-dialkyl (alkoxy) pyrrolidone is carried out at normal pressure and includes the following steps:

[0049] The intermediate product is obtained by preheating gamma-butyrolactone and mixing with alkoxy diamine, the alkoxy diamine is NH2-(RO) n -R-NH2.

[0050] The N,N-di-alkyl (alkoxy) pyrrolidone is obtained by heating the intermediate product, and water is discharged as by-product during the second reaction.

[0051] The structure of the N,N-di-alkyl (alkoxy) pyrrolidone is shown in formula I:

[0052]

[0053] R is alkylene, n≥0.

[0054] The preparation method provided by the application is carried out under normal pressure, and does not need to use a high-pressure reaction kettle, so that the requirement for equipment is not high, and the production energy consumption and cost are reduced.

[0055] The intermediate product is obtained by preheating gamma-butyrolactone and mixing with alkoxy diamine, the alkoxy diamine is NH2-(RO) n -R-NH2. In the application, the first reaction of the gamma-butyrolactone and the alkoxy diamine is aminolysis ring-opening to obtain the intermediate product; the gamma-butyrolactone is preheated to a set temperature, and the alkoxy diamine is added into the gamma-butyrolactone which has reached the reaction temperature, so that the raw materials rapidly react to generate the intermediate product. In the application, the structure of the intermediate product is shown in formula IV:

[0056]

[0057] The route of the aminolysis ring-opening reaction is as follows:

[0058]

[0059] The gamma-butyrolactone is preheated to the reaction temperature of the first reaction, and the temperature of the first reaction is preferably 50-180℃, more preferably 80-180℃, and in the embodiment of the application, the temperature can be specifically 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170 or 180℃.

[0060] After the gamma-butyrolactone is preheated to the reaction temperature of the first reaction, the alkoxy diamine is added into the gamma-butyrolactone which has been preheated to the set temperature, and the adding mode is preferably dropwise adding, and in the application, the dropwise adding rate is preferably 120 drops / min.

[0061] In the present application, the structure of the alkoxy diamine is NH2-(RO) n -R-NH2, wherein R is an alkylene group, preferably a C1-C10 alkylene group, which in the embodiments of the present application can be specifically a methylene group, an ethylene group, a propylene group or a butylene group. In the present application, n≥0, preferably 0, 1, 2, 3 or 4.

[0062] In the present application, the molar ratio of the γ-butyrolactone and the alkoxy diamine is preferably (1-4):1, more preferably (2-3):1; in the embodiments of the present application, it can be specifically 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1 or 4:1.

[0063] In the present application, the time of the first-stage reaction is counted from the time when the alkoxy diamine is added, and the time of the first-stage reaction is preferably 2-30 min, more preferably 2-20 min; in the embodiments of the present application, it can be specifically 2, 5, 6, 10, 14, 15, 16, 20, 25 or 30 min.

[0064] After the first-stage reaction is completed to obtain the intermediate product, the present application warms the intermediate product for a second-stage reaction to obtain N,N-dialkoxy pyrrolidone. In the present application, the intermediate product is condensed and ring-closed in the process of the second-stage reaction to generate by-product water, and the by-product water is separated from the reaction system to promote the progress of the forward reaction and improve the yield of the target product. In the present application, the route of the second-stage reaction is:

[0065]

[0066] The warming temperature (i.e. the reaction temperature of the second-stage reaction) of the present application is preferably 200-300℃, more preferably 220-280℃; in the embodiments of the present application, it can be specifically 200, 210, 220, 230, 240, 250, 260, 270 or 280℃. The reaction time of the second-stage reaction is preferably 1-8h, more preferably 1-3h; in the embodiments of the present application, it can be specifically 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5 or 8h.

[0067] After the second stage reaction, the reaction liquid obtained in the present application is subjected to vacuum rectification, and the pure N,N-dialkyl (oxy) pyrrolidone is collected at the bottom of the column, and the γ-butyrolactone is collected at the top of the column for recycling. The mixture after the reaction is completely subjected to vacuum rectification to achieve high-purity collection of the target product, and the γ-butyrolactone is separated at the top of the column and can be recycled. In the present application, the temperature of the vacuum rectification is preferably 110-290°C, more preferably 120-250°C, and can also be 150-200°C; the pressure of the vacuum rectification is preferably 2-15 kP, and preferably 6-10 kP. In the present application, the vacuum rectification is carried out in a rectification column, and the number of plates of the rectification column is preferably 15-30, and more preferably 20; the vacuum rectification is carried out in a rectification column, and the reflux ratio of the rectification column is 1:5-1:20, and more preferably 1:15.

[0068] In the present application, the volume ratio of the extraction solvent to the fuel product is preferably 0.5-10:1, and in the examples it can be specifically 0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1 or 8:1; the extraction temperature is preferably 30-70°C, and in the examples it can be specifically 30, 35, 40, 45, 50, 55, 60, 65 or 70°C; the number of extraction stages is preferably 1-3, and in the examples it can be specifically 1, 2 or 3.

[0069] After obtaining the extracted oil, the present application uses a stripping agent to strip the extracted oil to obtain a stripping phase and a stripping residue phase, the stripping residue phase is an aromatic hydrocarbon phase, and the stripping phase is an extraction solvent phase. In the present application, the aromatic hydrocarbon phase is a phase with an aromatic hydrocarbon content of more than 98%; the extraction solvent phase is a mixed phase of the stripping agent and the extraction solvent. In the present application, the stripping agent includes water and a polyhydroxy solvent, and the polyhydroxy solvent preferably includes a polyol, and more preferably includes 1,3-propanediol, butanediol, pentanediol, hexanediol, heptanediol, triethylene glycol or tetraethylene glycol. In the present application, the volume ratio of water to polyhydroxy solvent is greater than 1:1 and less than 10:1, and is preferably 4-9:1, and in the examples it can be specifically 4:1, 5:1, 6:1, 7:1, 8:1 or 9:1. In the present application, the volume ratio of the extracted oil to the stripping agent in the extracted oil stripping stage is preferably 0.5-5:1, and in the examples it can be specifically 0.5:1, 0.8:1, 1:1, 1.3:1 or 1.5:1. In the present application, the mixed solvent obtained by the above-mentioned volume ratio of water and polyhydroxy solvent has a polarity greater than that of the extraction solvent described in the above technical solution, and the polarity of the extraction solvent is greater than that of the aromatic hydrocarbons in the fuel product, so that the degree of emulsification of water and oil can be reduced in the stripping process, thereby providing the stripping efficiency.

[0070] In the present application, the temperature of the back extraction is preferably 35-100℃, and in an embodiment can be specifically 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 or 100℃; the number of stages of the back extraction is preferably 1-3 stages, and in an embodiment can be specifically 1, 2 or 3 stages.

[0071] After obtaining the back extraction phase, the present application performs vacuum rectification on the back extraction phase to recover the extraction solvent. In the present application, the operating temperature of the vacuum rectification is preferably 45-200℃, more preferably 60-170℃, and in an embodiment can be specifically 45, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190 or 200℃; the pressure of the vacuum rectification is preferably 5-20kP, more preferably 15-20kP, and in an embodiment can be specifically 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20kP.

[0072] After obtaining the raffinate oil, the present application preferably performs water washing on the raffinate oil to separate the non-aromatic hydrocarbon component. In the present application, the volume ratio of the water used for the water washing to the raffinate oil is preferably 0.5-1.5:1, and in an embodiment can be specifically 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1 or 1.5:1. The temperature of the water washing is preferably 30-70℃, and in an embodiment can be specifically 30, 35, 40, 45, 50, 55, 60, 65 or 70℃.

[0073] In the present application, the water washing also obtains a water washing raffinate phase, and the non-aromatic hydrocarbon content of the water washing raffinate phase is greater than 98%.

[0074] The present application also provides a system for liquid-liquid separation of aromatic hydrocarbons in fuel oil products, which comprises a solvent extraction tower 1 provided with an extraction solvent inlet, a fuel oil product inlet, and a raffinate oil outlet and a raffinate oil outlet;

[0075] A back extraction tower 2 connected to the raffinate oil outlet of the solvent extraction tower 1, the back extraction tower 2 being provided with a back extraction agent inlet, a back extraction phase outlet and a back extraction raffinate phase outlet;

[0076] A vacuum rectification tower 4 connected to the back extraction raffinate phase outlet of the back extraction tower 2, the vacuum rectification tower 4 being provided with a water outlet;

[0077] In an embodiment of the present application, the system further comprises a water washing tower 3 connected to the raffinate oil outlet of the solvent extraction tower 1, the water washing tower 3 being provided with a non-aromatic hydrocarbon oil outlet and a water washing extraction phase outlet.

[0078] In one embodiment of the present application, the inlet of the extraction solvent 5 is arranged at the upper end of the solvent extraction column 1, the inlet of the fuel oil product 6 is arranged at the bottom end of the side wall of the solvent extraction column, the outlet of the extracted oil 8 is located at the bottom of the solvent extraction column 1, and the outlet of the raffinate oil 9 is located at the top of the solvent extraction column;

[0079] In one embodiment of the present application, the inlet of the stripping agent 7 is arranged at the upper end of the stripping column 2, the inlet of the extracted oil 8 is arranged at the bottom end of the side wall of the stripping column 2, the outlet of the stripped phase 13 is located at the bottom of the stripping column, and the outlet of the raffinate phase 12 is located at the top of the stripping column;

[0080] In one embodiment of the present application, the inlet of the stripped phase 13 is arranged at the bottom end of the side wall of the vacuum rectification column 4, the top of the vacuum rectification column 4 is provided with a solvent outlet, and the bottom is provided with an outlet of the recovered extraction solvent 15, which is communicated with the inlet of the extraction solvent 5 through a reflux pipeline.

[0081] The outlet of the raffinate oil 9 is communicated with the raffinate oil inlet at the bottom end of the side wall of the water washing column 3, the top of the water washing column 3 is provided with an outlet of the non-aromatic oil 10, and the bottom is provided with an outlet of the water washing extraction phase 11.

[0082] In one embodiment of the present application, the fuel oil product and the extraction solvent are respectively introduced into the solvent extraction column 1 for solvent extraction, the raffinate oil 9 is obtained at the top of the column, and the extracted oil 8 is obtained at the bottom of the column;

[0083] The extracted oil 8 enters the stripping column 2, the stripping agent 7 is introduced into the stripping column 2 to strip the extracted oil 8, the raffinate phase (aromatic phase) is collected at the top of the stripping column 2, and the stripped phase 13 is obtained at the bottom of the stripping column 2;

[0084] The stripped phase 13 enters the vacuum rectification column 4 for vacuum rectification, water or water containing part of the polyhydroxy solvent is collected at the top of the column, and the recovered extraction solvent 15 is obtained at the bottom of the column, which is refluxed to the extraction solvent inlet of the solvent extraction column 1;

[0085] The raffinate oil 9 obtained at the top of the solvent extraction column 1 enters the water washing column 3 for water washing, the non-aromatic oil 10 is collected at the top of the column, and the water washing extraction phase 11 is collected at the bottom of the column.

[0086] The embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0087] It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict; and all other embodiments obtained by those skilled in the art based on the embodiments in the present disclosure without creative labor are within the scope of protection of the present disclosure.

[0088] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this disclosure, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0089] Example 1

[0090] 1,8-Diamino-3,6-dioxaoctane was added dropwise to γ-butyrolactone preheated to a first temperature, and the first stage reaction was carried out at the first temperature. The molar ratio of γ-butyrolactone to 1,8-diamino-3,6-dioxaoctane was 2.5:1, the first temperature was 180℃, and the first stage reaction time was 15 min, to obtain the intermediate product.

[0091] The intermediate product was heated to 280℃ and reacted for 6 hours to obtain the product liquid. During the reaction, the by-product water was cooled and discharged.

[0092] The product was subjected to vacuum distillation at a temperature of 150℃ and a pressure of 6kPa to obtain the target product.

[0093] The present invention performs structural identification on the obtained target product, and the results are as follows: Figure 2 As shown, by Figure 2 It can be seen that the target product has the structure shown in Formula III:

[0094]

[0095] In this embodiment, the yield of the target product is 86%, the purity is 99%, and the boiling point is 450°C.

[0096] Example 2

[0097] 1,6-hexanediamine was added dropwise to preheated γ-butyrolactone, and the first stage reaction was carried out at the first temperature. The molar ratio of γ-butyrolactone to 1,6-hexanediamine was 3:1, the first temperature was 180℃, and the first stage reaction time was 20 min, to obtain the intermediate product.

[0098] The intermediate product was heated to 260℃ and reacted for 8 hours to obtain the product liquid. During the reaction, the by-product water was cooled and discharged.

[0099] The product was subjected to vacuum distillation at a temperature of 140℃ and a pressure of 6kPa to obtain the target product.

[0100] The present invention performs structural identification on the obtained target product, and the results are as follows: Figure 3 As shown, by Figure 3 It can be seen that the target product has the structure shown in Formula II:

[0101]

[0102] Example 3

[0103] Using diesel fraction A (composition shown in Table 1) as feedstock, diesel fraction A was first fed into an extraction tower to obtain hexylene (-C6H) from Example 2. 12 Using N,N-di-n-hexylpyrrolidone (Formula II) as the central compound and N,N-di-n-hexylpyrrolidone (Formula II) as the extraction solvent, diesel fraction A is extracted in an extraction tower to obtain extractable oil (containing most of the aromatics and a small amount of extraction solvent) and raffinate oil (mainly non-aromatics, with a small amount of aromatics). The extractable oil is then fed into a back-extraction tower, where a mixed solvent of 1,3-propanediol and water at a volume ratio of 1:9 is used as the back-extraction agent for a single extraction to obtain a back-extracted phase (extraction solvent) and a back-extraction residue phase (aromatics). The raffinate oil is then fed into a water washing tower for washing at a water-oil volume ratio of 1:1 to separate the non-aromatic components. The back-extracted phase is then fed into a vacuum distillation tower for vacuum distillation to obtain the extraction solvent.

[0104] The main operating conditions of the scheme in this embodiment are shown in Table 2, and the separation results of each stage are shown in Table 3.

[0105] Example 4

[0106] Using diesel fraction A (composition shown in Table 1) as feedstock, diesel fraction A first enters an extraction tower. Using N,N-di-3,6-dioxooctylpyrrolidone (Formula III) with 3,6-dioxooctyl (-C2H4-O-C2H4-O-C2H4-) as the central component obtained in Example 1 as the extraction solvent, diesel fraction A is extracted in the extraction tower to obtain extract oil (containing most aromatics and a small amount of extraction solvent) and raffinate oil (mainly non-aromatics, with a small amount of aromatics). The extract oil continues to enter a back-extraction tower, where a mixed solvent of 1,3-propanediol and water at a volume ratio of 1:9 is used as the back-extraction agent for a single extraction, yielding a back-extracted phase (extraction solvent) and a back-extracted residual phase (aromatics). The raffinate oil continues to enter a water washing tower for washing, with a water-oil volume ratio of 1:1, separating the non-aromatic components. The back-extracted phase continues to enter a vacuum distillation tower for vacuum distillation to obtain the extraction solvent.

[0107] The main operating conditions of this embodiment are shown in Table 2, and the separation results of each stage are shown in Table 3.

[0108] Example 5

[0109] The diesel fraction A (composition see Table 1) was used as the raw oil, and the N,N-dimer-3,6-dioxaoctylpyrrolidone (Formula III) with 3,6-dioxaoctyl (-C2H4-O-C2H4-O-C2H4-) as the center body obtained in Example 1 was used as the extraction solvent. The diesel fraction A was extracted in the extraction tower to obtain the extracted oil (containing most of the aromatic hydrocarbons and a small amount of the extraction solvent) and the raffinate oil (mainly composed of non-aromatic hydrocarbons and a small amount of aromatic hydrocarbons). The extracted oil was continuously introduced into the back-extraction tower, and the mixed solvent of 1,3-propanediol and water with a volume ratio of 1:7 was used as the back-extraction agent for secondary extraction to obtain the back-extraction phase (extraction solvent) and the back-extraction raffinate phase (aromatic hydrocarbons). The raffinate oil was continuously introduced into the water washing tower for water washing, and the non-aromatic hydrocarbon component was separated at a water to oil volume ratio of 1:1. The back-extraction phase was continuously introduced into the vacuum rectification tower for vacuum rectification to obtain the extraction solvent.

[0110] The main operating conditions of the example scheme are shown in Table 2, and the separation results of each stage are shown in Table 3.

[0111] Example 6

[0112] The diesel fraction B (composition see Table 1) was used as the raw oil, and the N,N-dimer-n-hexylpyrrolidone (Formula II) with n-hexyl (-C6H 12 -) as the center body obtained in Example 2 was used as the extraction solvent. The diesel fraction B was extracted in the extraction tower to obtain the extracted oil (containing most of the aromatic hydrocarbons and a small amount of the extraction solvent) and the raffinate oil (mainly composed of non-aromatic hydrocarbons and a small amount of aromatic hydrocarbons). The extracted oil was continuously introduced into the back-extraction tower, and the mixed solvent of 1,3-propanediol and water with a volume ratio of 1:9 was used as the back-extraction agent for secondary extraction to obtain the back-extraction phase (extraction solvent) and the back-extraction raffinate phase (aromatic hydrocarbons). The raffinate oil was continuously introduced into the water washing tower for water washing, and the non-aromatic hydrocarbon component was separated at a water to oil volume ratio of 1:1. The back-extraction phase was continuously introduced into the vacuum rectification tower for vacuum rectification to obtain the extraction solvent.

[0113] The main operating conditions of the example scheme are shown in Table 2, and the separation results of each stage are shown in Table 3.

[0114] Example 7

[0115] The diesel fraction B (composition shown in Table 1) was used as the raw oil, and the diesel fraction B was first introduced into an extraction tower, and N,N-dicyclo-3,6-dioxaoctyl pyrrolidone (formula III) with 3,6-dioxaoctyl (-C2H4-O-C2H4-O-C2H4-) as the center was used as the extraction solvent to extract the diesel fraction B in the extraction tower, and an extracted oil (containing most of the aromatic hydrocarbons and a small amount of the extraction solvent) and a raffinate oil (mainly composed of non-aromatic hydrocarbons and a small amount of aromatic hydrocarbons) were obtained; the extracted oil was continuously introduced into a back-extraction tower, and a mixed solvent of tetraethylene glycol and water with a volume ratio of 1:9 was used as the back-extraction agent for secondary extraction, and a separation extraction phase (extraction solvent) and a back-extraction residue phase (aromatic hydrocarbons) were obtained; the raffinate oil was continuously introduced into a water washing tower for water washing, and a non-aromatic hydrocarbon component was separated at a water to oil volume ratio of 1:1; and the back-extraction phase was continuously introduced into a vacuum rectification tower for vacuum rectification to obtain the extraction solvent.

[0116] The main operating conditions of the embodiment scheme are shown in Table 2, and the separation results of each stage are shown in Table 3.

[0117] Example 8

[0118] The diesel fraction C (composition shown in Table 1) was used as the raw oil, and the diesel fraction C was first introduced into an extraction tower, and N,N-dicyclo-3,6-dioxaoctyl pyrrolidone (formula III) with 3,6-dioxaoctyl (-C2H4-O-C2H4-O-C2H4-) as the center was used as the extraction solvent to extract the diesel fraction C in the extraction tower, and an extracted oil (containing most of the aromatic hydrocarbons and a small amount of the extraction solvent) and a raffinate oil (mainly composed of non-aromatic hydrocarbons and a small amount of aromatic hydrocarbons) were obtained; the extracted oil was continuously introduced into a back-extraction tower, and a mixed solvent of 1,3-propanediol and water with a volume ratio of 1:7 was used as the back-extraction agent for secondary extraction, and a separation extraction phase (extraction solvent) and a back-extraction residue phase (aromatic hydrocarbons) were obtained; the raffinate oil was continuously introduced into a water washing tower for water washing, and a non-aromatic hydrocarbon component was separated at a water to oil volume ratio of 1:1; and the back-extraction phase was continuously introduced into a vacuum rectification tower for vacuum rectification to obtain the extraction solvent.

[0119] The main operating conditions of the embodiment scheme are shown in Table 2, and the separation results of each stage are shown in Table 3.

[0120] Example 9

[0121] The diesel fraction C (composition shown in Table 1) was used as the raw oil, and the diesel fraction C was first introduced into an extraction tower, and N,N-dicyclo-3,6-dioxaoctyl pyrrolidone (formula III) with 3,6-dioxaoctyl (-C2H4-O-C2H4-O-C2H4-) as the center was used as the extraction solvent to extract the diesel fraction C in the extraction tower, and an extracted oil (containing most of the aromatic hydrocarbons and a small amount of the extraction solvent) and a raffinate oil (mainly composed of non-aromatic hydrocarbons and a small amount of aromatic hydrocarbons) were obtained; the extracted oil was continuously introduced into a back-extraction tower, and a mixed solvent of 1,3-propanediol and water with a volume ratio of 1:7 was used as the back-extraction agent for secondary extraction, and a separation extraction phase (extraction solvent) and a back-extraction residue phase (aromatic hydrocarbons) were obtained; the raffinate oil was continuously introduced into a water washing tower for water washing, and a non-aromatic hydrocarbon component was separated at a water to oil volume ratio of 1:1; and the back-extraction phase was continuously introduced into a vacuum rectification tower for vacuum rectification to obtain the extraction solvent. 12-)N,N-dicyclohexylpyrrolidone (Formula II) as the extraction solvent, diesel fraction C is extracted in the extraction column to obtain extracted oil (containing most of the aromatic hydrocarbons and a small amount of extraction solvent) and raffinate oil (mainly non-aromatic hydrocarbons, a small amount of aromatic hydrocarbons); the extracted oil continues to enter the back-extraction column, and a mixed solvent of 1,3-propanediol and water in a volume ratio of 1:7 is used as the back-extraction agent for secondary extraction to obtain a back-extraction phase (extraction solvent) and a back-extraction raffinate phase (aromatic hydrocarbons); the raffinate oil continues to enter the water washing column for water washing, with a water / oil volume ratio of 1:1, to separate the non-aromatic hydrocarbon component; and the back-extraction phase continues to enter the vacuum rectification column for vacuum rectification to obtain the extraction solvent.

[0122] The main operating conditions of the embodiment scheme are shown in Table 2, and the separation results of each stage are shown in Table 3.

[0123] Table 1 Composition of diesel fraction in the example

[0124]

[0125]

[0126] Table 2 Main operating conditions of the technical scheme of Examples 3-9

[0127]

[0128]

[0129] Table 3 Separation results of each stage in the scheme of Examples 3-9

[0130]

[0131]

[0132] As can be seen from the results in Table 3, in the solvent extraction stage, N,N-dicyclohexylpyrrolidone or N,N-dicyclohexyl-3,6-octylpyrrolidone is used as the diesel extraction solvent, and the aromatic hydrocarbon content of the extracted oil is about 90 m%, and the non-aromatic hydrocarbon content of the raffinate oil is about 80 m%, which can excellently separate the aromatic and non-aromatic components in diesel; in the extracted oil back-extraction stage, water and a polyhydroxy solvent are used as the back-extraction agent to increase the polarity and improve the separation effect of aromatic hydrocarbons and extraction solvent, as can be seen from Table 3, the extraction temperature has little effect on the back-extraction stage, and 35°C can be selected as the operating temperature, and the aromatic hydrocarbon content in the raffinate phase after back-extraction for two times can be as high as 99%; in the raffinate oil water washing stage, as can be seen from Table 3, the operating temperature has little effect on this stage.

[0133] Effect of the ratio of water and polyhydroxy solvent in the back-extraction agent of Comparative Example 1 on the results

[0134] According to the scheme of Example 3, the difference is that in the present comparative example, the stripping agent is water: 1,3-propanetriol with a volume ratio of 1:1, 1:2, 1:3, 1:4, 1:5, and the results are shown in Table 4.

[0135] Table 4 Influence of the ratio of water and polyhydroxy solvent in the stripping agent on the results

[0136]

[0137]

[0138] The results show that the greater the proportion of polyhydroxy solvent in the stripping agent, the more likely it is to reduce the extraction capacity of the stripping agent. Compared with Example 3, a moderate proportion should be selected in comprehensive consideration, so the best volume ratio of water to polyhydroxy solvent is 7:1.

[0139] Influence of the ratio of stripping agent to oil on the results in the oil extraction stripping stage of Comparative Example 2

[0140] According to the scheme of Example 4, the difference is that in the present comparative example, the ratio of stripping agent to oil is 1:3, 1:3.5, 1:4, 1:4.5, 1:5, and the results are shown in Table 5.

[0141] Table 5 Influence of the ratio of stripping agent to oil on the results in the oil extraction stripping stage

[0142]

[0143] The results show that as the amount of stripping agent decreases, the aromatic content in the raffinate phase decreases significantly. Compared with Example 4, the best ratio of stripping agent to oil in the oil extraction stripping stage is 1:1.

[0144] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any changes or substitutions within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for separating aromatic hydrocarbons from fuel oil products by liquid-liquid separation, comprising the following steps: extracting a fuel oil product with an extraction solvent to obtain an extract oil and a raffinate oil, wherein the main component of the extract oil is aromatic hydrocarbons and the main component of the raffinate oil is non-aromatic hydrocarbons; the extraction solvent is one of N, N-dialkyl pyrrolidone and N, N-dialkoxy pyrrolidone, the boiling point of the extraction solvent is higher than the boiling point of the fuel oil product, and the boiling point is greater than 380℃; back-extracting the extract oil with a back-extraction agent to obtain a back-extraction phase and a back-extraction residue phase, wherein the back-extraction residue phase is an aromatic hydrocarbon phase, and the back-extraction phase is an extraction solvent phase; the back-extraction agent comprises water and a polyhydroxy solvent, and the volume ratio of water to the polyhydroxy solvent in the back-extraction agent is greater than 1:1 and less than 10:1; subjecting the back-extraction phase to vacuum rectification to obtain recovered extraction solvent; the structure of the N, N-dialkyl pyrrolidone or the N, N-dialkoxy pyrrolidone is shown in formula I: ； R is an alkylene group, and n≥0.

2. The method of claim 1, wherein, The method further comprises washing the raffinate oil with water to obtain a non-aromatic hydrocarbon component.

3. The method according to claim 1 or 2, characterized in that, The number of carbon atoms of R in the N, N-dialkyl pyrrolidone is 5-10, and the number of carbon atoms of R in the N, N-dialkoxy pyrrolidone is 1-10.

4. The method of claim 3, wherein, The extraction solvent is N, N-dinormal hexyl pyrrolidone or N, N-dialkyl-3, 6-dioxaoctyl pyrrolidone.

5. The method according to claim 1 or 2, characterized in that, The volume ratio of the extraction solvent to the fuel oil product is 0.5-10:1; the extraction temperature is 30-70℃; and the extraction is carried out for 1-3 stages.

6. The method of claim 1 or 2, wherein, The volume ratio of water to the polyhydroxy solvent in the back-extraction agent is 4-9:1; the back-extraction temperature is 35-100℃; and the back-extraction is carried out for 1-3 stages.

7. The method of claim 1, wherein, The operation temperature of the vacuum rectification is 45-200℃; and the pressure of the vacuum rectification is 5-20 kPa.

8. The method of claim 2, wherein, When washing, the volume ratio of water to the raffinate oil is 0.5-1.5:1; and the washing temperature is 30-70℃.

9. The method of claim 1 or 2, wherein, The fuel oil product comprises diesel distillate, reforming gasoline or cracking gasoline, and the volume content of aromatic hydrocarbons in the fuel oil product is 10-90%.

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