Composition, deep eutectic solvent, preparation method and application of deep eutectic solvent, and method for extracting and separating aromatic hydrocarbon in petroleum fraction

Abstract

The invention relates to the field of petroleum fraction separation, and discloses a composition, a deep eutectic solvent, a preparation method and application of the deep eutectic solvent, and a method for extracting and separating aromatic hydrocarbons in petroleum fractions. The invention relates to a composition. The composition is prepared from 1-ethyl-3-methylimidazole halide salt and 1-vinyl imidazole, wherein the molar ratio of the 1-ethyl-3-methylimidazole halide salt to the 1-vinyl imidazole is (0.2 to 5): 1. The eutecticevaporate solvent prepared from the composition is used for extracting and separating aromatic hydrocarbons in petroleum fractions, the obtained raffinate oil basically has no solvent residue, the subsequent aromatic hydrocarbon separation method is simple, and the extraction effect is obviously improved; and compared with the existing common extraction solvent, the aromatic hydrocarbon selectivity is higher.

Description

Technical Field

[0001] The invention relates to the field of petroleum fraction separation, and in particular to a composition, a low eutectic solvent, a preparation method and application thereof, and a method for extracting and separating aromatic hydrocarbons in petroleum fractions. Background Art

[0002] At present, the demand for high-quality fuels and chemical raw materials in my country's petrochemical industry has increased dramatically. The separation of aromatic / alkane mixed systems is one of the most important and difficult processes in the petrochemical industry. This is because many aromatics and alkanes have similar physical and chemical properties, especially when aromatics and alkanes with similar carbon numbers have very close boiling points, and the mixture of aromatics and alkanes easily forms azeotropes, which cannot be effectively separated by conventional distillation.

[0003] Solvent extraction is the most commonly used process in the separation of aromatic and alkane systems. It is a process that mainly uses the different solubility of each component in the aromatic extraction raw material in the organic solvent to achieve the separation of aromatics and alkanes. The solvent extraction method is very efficient in separating aromatics, and there are different process routes depending on the extraction solvent used. Among them, new solvents such as ionic liquids and low eutectic solvents with structural design characteristics are considered to be one of the most promising directions in the field of extraction and separation due to their excellent physical and chemical properties. The earliest person to conduct research on ionic liquid extraction was Rogers (Rogers RD, Seddon K R. Ionic liquids—Solvents of the future? [J]. Science, 2003, 302 (5646): 792-793.) at the University of Alabama in the United States. He used [BMIM] PF6 to extract aromatic compounds such as toluene, aniline, benzoic acid, chlorobenzene, etc. from water, and studied the distribution coefficients of various extracts in ionic liquids. Subsequently, many universities and research institutions at home and abroad began to explore the effects of new solvents such as ionic liquids and low eutectic solvents in the separation of aromatics and alkanes.

[0004] Deep eutectic solvents (DESs) are usually eutectic mixtures formed by hydrogen bonding of hydrogen bond donors (HBD) and hydrogen bond acceptors (HBA) in a certain stoichiometric ratio. They are known as new ionic liquids because of their simple preparation, low vapor pressure, good solubility, environmental friendliness, reusability, and strong design. Since they were first reported in 2003, they have been widely used in electrochemistry, energy, extraction solvents, and other fields.

[0005] In 2012, Kareem et al. (Kareem MA, Mjalli FS, Hashim MA, et al. Liquid-liquid equilibria for the ternary system (phosphonium based deep eutectic solvent-benzene-hexane) at different temperatures: A new solvent introduced [J]. Fluid Phase Equilibria, 2012, 314 (none): 52-59.) first used DES (TBPB + EG) to extract and separate aromatic hydrocarbons from aromatic-aliphatic mixtures. The results showed that DES can effectively separate benzene and hexane mixtures. It was also found that DES as an extractant plays a major role as a hydrogen bond donor (EG) in the extraction and separation process, while the hydrogen bond acceptor (TBPB) plays a secondary role. DES has achieved a separation effect similar to that of organic solvents, but it is difficult to achieve high extraction effect and high selectivity at the same time.

[0006] Inspired by Kareem's research, more and more researchers have begun to study the extraction and separation capabilities of different DESs for aromatics. Although reports on the separation of aromatic-alkane systems by DESs show that DESs have a high selectivity for aromatics, DESs also have the problem of weak solubility for aromatic compounds, resulting in a generally low distribution coefficient for aromatics. This is also in line with the principle that selectivity and distribution coefficient cannot be increased at the same time. When one of the values ​​is too large, the other is relatively small, which also limits the application of DESs. The current focus of DESs research and development is to maximize its solubility for aromatics while maintaining its high selectivity.

[0007] The development of new solvent systems such as ionic liquids and low eutectic solvents suitable for the separation of aromatics in petroleum products of different fractions has certain economic value and social significance for improving the quality and efficiency of aromatic extraction technology and expanding the production of aromatic raw materials and products. Summary of the invention

[0008] The purpose of the present invention is to overcome the problem that the low eutectic solvent in the prior art is difficult to achieve high extraction effect and high selectivity at the same time, and to provide a composition, a low eutectic solvent and its preparation method and application, and a method for extracting and separating aromatic hydrocarbons from petroleum fractions. The low eutectic solvent prepared by the composition of the present invention is used to extract and separate aromatic hydrocarbons from petroleum fractions, and there is basically no solvent residue in the obtained raffinate oil, the subsequent aromatic hydrocarbon separation method is simple, and the extraction effect is significantly improved; and compared with the existing commonly used extraction solvents, it has higher aromatic hydrocarbon selectivity.

[0009] In order to achieve the above object, the present invention provides a composition on one hand, which comprises 1-ethyl-3-methylimidazole halide and 1-vinylimidazole; wherein the molar ratio of 1-ethyl-3-methylimidazole halide to 1-vinylimidazole is 0.2-5:1.

[0010] The second aspect of the present invention provides a low eutectic solvent, the solvent includes 1-ethyl-3-methylimidazole halide and 1-vinyl imidazole connected by hydrogen bonds. In the prior art, sulfolane is usually used as an extraction solvent, but because the boiling point of sulfolane is within the boiling range of kerosene and diesel fractions, it is difficult to recover the solvent through the distillation process, resulting in high separation energy consumption; at the same time, sulfolane will be partially decomposed to produce sulfur-containing corrosive substances, which has a certain impact on the long-term use of the device. The low eutectic solvent of the structure of the present invention obviously overcomes the defects of sulfolane, has a wide liquid temperature range (-55 to 250 ° C), a large density difference with petroleum fractions, extremely low saturated vapor pressure, and does not contain sulfur elements. It is applied to extract and separate aromatics from petroleum fractions, can extract petroleum fractions in a wide temperature range, and is easy to separate phases with petroleum fractions, and there is basically no solvent residue in the raffinate obtained, and the subsequent aromatic separation method is simple, which significantly improves the extraction effect and greatly saves processing costs.

[0011] A third aspect of the present invention provides a method for preparing a low eutectic solvent, the method comprising: the low eutectic solvent is obtained by subjecting the composition described in the first aspect to a melt reaction.

[0012] A fourth aspect of the present invention provides a use of the low eutectic solvent described in the second aspect or the low eutectic solvent prepared by the method described in the third aspect in the extraction and separation of aromatic hydrocarbons.

[0013] A fifth aspect of the present invention provides a method for extracting and separating aromatic hydrocarbons in petroleum fractions, the method comprising:

[0014] (1) contacting the petroleum fraction with the deep eutectic solvent in reverse order to obtain a raffinate oil and an extracted oil containing the deep eutectic solvent and aromatic hydrocarbons;

[0015] (2) separating the extracted oil containing the deep eutectic solvent and aromatic hydrocarbons in step (1) to obtain aromatic hydrocarbons and the deep eutectic solvent;

[0016] Wherein, the low eutectic solvent in step (1) is the low eutectic solvent described in the second aspect or the low eutectic solvent prepared by the method described in the third aspect.

[0017] Through the above technical solution, the beneficial effects of the present invention include:

[0018] The low eutectic solvent prepared from the specific composition of the present invention is used for extracting and separating aromatic hydrocarbons in petroleum fractions. There is basically no solvent residue in the obtained raffinate oil, the subsequent aromatic hydrocarbon separation method is simple, the extraction effect is significantly improved, the processing cost is greatly saved, and compared with the existing commonly used extraction solvents, it has higher aromatic hydrocarbon selectivity and has good application prospects in the field of aromatic hydrocarbon separation in petroleum fractions.

[0019] The low eutectic solvent of the present invention has the characteristics of simple preparation process, low corrosion to equipment, easy recovery, green and environmental protection, etc., and can provide a separation solution for the separation and utilization of petroleum fraction components. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the nuclear magnetic resonance image of the deep eutectic solvent described in Example 1;

[0021] Figure 2 is the DSC graph of the deep eutectic solvent described in Example 1;

[0022] Figure 3 The present invention is a process flow chart for extracting and separating aromatic hydrocarbons from petroleum fractions.

[0023] Description of Reference Numerals

[0024] exist Figure 3 middle,

[0025] 1. Extraction tower; 2. Solvent recovery tower; 3. Low eutectic solvent;

[0026] 4. Petroleum fractions; 5. Raffinate oil; 6. Extracted oil containing low eutectic solvents and aromatics;

[0027] 7. Heat exchanger; 8. Aromatic components; 9. Reboiler. DETAILED DESCRIPTION

[0028] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0029] In the description of the present invention, it is necessary to understand that the terms "top", "bottom" and the like indicate orientations or positional relationships only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0030] In the present invention, unless otherwise specified, the "tower top pressure" refers to absolute pressure.

[0031] One aspect of the present invention provides a composition, which comprises 1-ethyl-3-methylimidazole halide and 1-vinylimidazole; wherein the molar ratio of 1-ethyl-3-methylimidazole halide to 1-vinylimidazole is 0.2-5:1.

[0032] The inventors found in the research process that the composition uses 1-ethyl-3-methylimidazolium halide and 1-vinylimidazole, and controls the molar ratio of 1-ethyl-3-methylimidazolium halide to 1-vinylimidazole to be within the range of 0.2-5:1, which is conducive to preparing the low eutectic solvent described in the second aspect of the present invention. When the molar ratio of 1-ethyl-3-methylimidazolium halide to 1-vinylimidazole is lower or higher than the range described in the present invention, since a stable and uniform hydrogen bond network cannot be formed between molecules, it does not reach the low eutectic solvent described in the present invention, and is only equivalent to a mixture of two solid salts.

[0033] In the present invention, the molar ratio of 1-ethyl-3-methylimidazole halide to 1-vinylimidazole is 0.2-5:1, such as 0.2:1, 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1 and any value in the range formed by any two of these values, preferably 1-3:1. This preferred embodiment is more conducive to obtaining the deep eutectic solvent described in the second aspect of the present invention.

[0034] According to the present invention, preferably, the 1-ethyl-3-methylimidazolium halide is 1-ethyl-3-methylimidazolium chloride or 1-ethyl-3-methylimidazolium bromide.

[0035] A second aspect of the present invention provides a low eutectic solvent, which comprises a hydrogen-bonded 1-ethyl-3-methylimidazole halide and 1-vinylimidazole.

[0036] According to the characterization of the nuclear magnetic resonance spectrum, it can be seen that the chemical shift of H on the hydrogen bond donor and the hydrogen bond acceptor is shifted, indicating that a hydrogen bond interaction occurs between the hydrogen bond acceptor 1-ethyl-3-methylimidazolium halide and the hydrogen bond donor 1-vinylimidazole (1-Vim). The solvent of the structure described in the present invention has been obtained, which can be referred to Figure 1 .

[0037] The schematic structural diagram of the solvent of the present invention can refer to formula (1). Formula (1) is a schematic structural diagram of Example 1 of the present invention (in this case, the molar ratio of 1-ethyl-3-methylimidazole halide to 1-vinylimidazole is 2:1).

[0038]

[0039] Preferably, the 1-ethyl-3-methylimidazolium halide salt is 1-ethyl-3-methylimidazolium chloride or 1-ethyl-3-methylimidazolium bromide.

[0040] In order to further improve the extraction and separation effect, more preferably, the 1-ethyl-3-methylimidazolium halide is 1-ethyl-3-methylimidazolium chloride.

[0041] The low eutectic solvent provided by the present invention has the characteristic of a wide liquid temperature range, which is beneficial to improving the extraction effect. Preferably, the solvent is liquid in the range of -55 to 250°C.

[0042] The liquid temperature range of the solvent of the present invention is measured by DSC method. Figure 2 It can be seen that the freezing point of this DES is lower than -55°C.

[0043] The present invention has no particular limitation on the preparation method of the above-mentioned low eutectic solvent, as long as the low eutectic solvent of the above-mentioned structure can be prepared. In order to further improve the extraction performance of the low eutectic solvent, the present invention also provides a preparation method of the above-mentioned low eutectic solvent. The preparation method provided by the present invention has a simple process and can be widely used.

[0044] A third aspect of the present invention provides a method for preparing a low eutectic solvent, the method comprising: the low eutectic solvent is obtained by subjecting the composition described in the first aspect to a melt reaction.

[0045] According to the present invention, preferably, the temperature of the melt reaction is 80-150°C, preferably 100-150°C, such as 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C and any value in the range formed by any two of these values. The use of this preferred embodiment is further conducive to obtaining the low eutectic solvent having the structure of the present invention. When the temperature of the melt reaction is higher than the range described in the present invention, many side reactions occur and impurities increase.

[0046] The present invention has a wide range of time selection for the melting reaction, which is based on obtaining the low eutectic solvent having the structure of the present invention. Preferably, the melting reaction time is 1-10 hours, preferably 3-5 hours.

[0047] According to the present invention, preferably, the melt reaction is carried out under stirring conditions.

[0048] The present invention has no particular limitation on the stirring time and speed, which can be appropriately selected according to specific circumstances.

[0049] According to a specific embodiment of the present invention, the composition of the first aspect is placed in an oil bath, condensed, refluxed and stirred to obtain a low eutectic solvent.

[0050] The fourth aspect of the present invention provides an application of the low eutectic solvent described in the second aspect or the low eutectic solvent obtained by the method described in the third aspect in extracting and separating aromatic hydrocarbons, preferably in extracting and separating aromatic hydrocarbons in petroleum fractions.

[0051] The deep eutectic solvent provided by the present invention can be used to process different raw materials or products in petroleum fractions. Preferably, the petroleum fractions are selected from at least one of gasoline, diesel and kerosene.

[0052] The gasoline, kerosene and diesel provided by the present invention have the conventional definitions in the art and are not particularly limited in the present invention.

[0053] Preferably, the diesel is light diesel.

[0054] The light diesel oil of the present invention refers to diesel oil with a distillation range of 180-380°C.

[0055] A fifth aspect of the present invention provides a method for extracting and separating aromatic hydrocarbons in petroleum fractions, the method comprising:

[0056] (1) contacting the petroleum fraction with the deep eutectic solvent in reverse order to obtain a raffinate oil and an extracted oil containing the deep eutectic solvent and aromatic hydrocarbons;

[0057] (2) separating the extracted oil containing the deep eutectic solvent and aromatic hydrocarbons in step (1) to obtain aromatic hydrocarbons and the deep eutectic solvent;

[0058] Wherein, the low eutectic solvent in step (1) is the low eutectic solvent described in the second aspect or the low eutectic solvent prepared by the method described in the third aspect.

[0059] In the method provided by the present invention, the reverse contact means that the low eutectic solvent contacts from top to bottom with gravity, and the petroleum fraction contacts from bottom to top.

[0060] Preferably, the reverse contact in step (1) is carried out in an extraction tower, and raffinate oil is obtained at the top of the tower, and extracted oil containing a low eutectic solvent and aromatics is obtained at the bottom of the tower.

[0061] The low eutectic solvent provided by the present invention can extract petroleum fractions in a wide temperature range. Preferably, the conditions for the reverse contact in step (1) include: a temperature of 30-100°C.

[0062] According to the present invention, preferably, the mass ratio of the deep eutectic solvent to the petroleum fraction is 1-10:1.

[0063] According to the present invention, preferably, the separation in step (2) is carried out in a solvent recovery tower, aromatics are obtained at the top of the tower, and a low eutectic solvent is obtained at the bottom of the tower.

[0064] According to the present invention, preferably, the separation conditions in step (2) include: the tower bottom temperature is 80-200° C.; and the tower top pressure is 1-10 kPa.

[0065] In the present invention, the extraction tower and solvent recovery tower are devices for extracting and separating aromatic hydrocarbons in petroleum fractions, and are not particularly limited and can be conventionally selected in the art.

[0066] The present invention has no particular limitation on the separation, and the separation can be performed by conventional technical means in the art. Preferably, the separation is vacuum distillation. With this preferred embodiment, the aromatic hydrocarbons and the deep eutectic solvent can be separated in a simple manner.

[0067] The low eutectic solvent of the present invention can be recycled and reused. According to the present invention, preferably, the low eutectic solvent obtained at the bottom of the solvent recovery tower is returned to step (1) for recycling.

[0068] According to a preferred embodiment of the present invention, the low eutectic solvent 3 enters the extraction tower 1 from the middle and upper part, the petroleum fraction 4 enters the extraction tower 1 from the middle and lower part, and the raffinate 5 (raffinate oil rich in saturated hydrocarbons) after countercurrent extraction flows out from the top of the extraction tower, and the extracted oil 6 containing the low eutectic solvent and aromatics is sent to the solvent recovery tower 2 from the bottom of the extraction tower through the heat exchanger 7, and the aromatic component 8 is obtained at the top of the solvent recovery tower 2. Part of the low eutectic solvent 3 obtained at the bottom of the tower is returned to the extraction tower 1 for recycling through the heat exchanger 7, and part of it is returned to the solvent recovery tower 2 after passing through the reboiler 9 to provide heat for the solvent recovery tower 2.

[0069] The present invention will be described in detail below through examples.

[0070] In the following examples, the extraction effect of the solvent is expressed in terms of distribution coefficient (D) and selectivity (S).

[0071] The distribution coefficient (D) is the ratio of the actual molar fractions of the extracted substance in the two phases (the extracted phase and the raffinate phase) after the extraction system reaches equilibrium.

[0072] Selectivity (S) is the ratio of the distribution coefficients of the components to be separated, which quantitatively indicates the difficulty of the extractant in separating the system to be separated. The larger the S value, the better the separation effect.

[0073] The distribution coefficient (D) and selectivity (S) are calculated as follows:

[0074]

[0075]

[0076]

[0077] where x i is the mole fraction of aromatics, x j is the mole fraction of alkane, and D arom is the partition coefficient of aromatics, D alkane is the distribution coefficient of alkanes, I and II are the raffinate phase and the extracted phase respectively, and S represents the selectivity of the extractant to aromatics.

[0078] In the following examples, the mass ratio of the deep eutectic solvent to the petroleum fraction is referred to as the agent-oil ratio.

[0079] Example 1

[0080] Weigh hydrogen bond acceptor 1-ethyl-3-methylimidazolium chloride (EmimCl) and hydrogen bond donor 1-vinylimidazole (1-Vim), the molar ratio of EmimCl to 1-Vim is 2:1, and condense and reflux and stir for 3 hours in an oil bath at 100°C and 300 rpm to obtain DES. The synthesized DES is well sealed and stored in a desiccator for use in extraction experiments.

[0081] The nuclear magnetic resonance spectrum of DES prepared in Example 1 is given as an example. Figure 1 As shown. It can be seen that the chemical shift of H on the hydrogen bond donor and the hydrogen bond acceptor shifts, indicating that a hydrogen bond occurs between EmimCl and Vim, proving the formation of a low eutectic solvent with the structure described in the present application.

[0082] The DSC diagram of DES prepared in Example 1 is given as an example. Figure 2 It can be seen that the freezing point of the DES is lower than -55°C, and the solvent is liquid in the range of -55 to 250°C.

[0083] At a dosage-oil ratio of 2:1, the synthesized DES was used to extract the 10 model oils in Table 1 for 30 min at 40°C, and the distribution coefficients and aromatic selectivity were calculated. The compositions of the 10 simulated oils are shown in Table 1, and the extraction results are shown in Table 2.

[0084] Table 1

[0085] Hydrocarbon mole fraction / % Model oil 1 Model oil 2 Model oil 3 Model oil 4 Model Oil 5 Dodecane 51 61 72 81 91 Tetralin 49 39 28 19 9 Hydrocarbon mole fraction / % Model oil 6 Model Oil 7 Model oil 8 Model oil 9 Model oil 10 n-Heptane 50 60 71 80 90 Toluene 50 40 29 20 10

[0086] Example 2

[0087] The DES synthesized in Example 1 was used as the extraction solvent, at a solvent-oil ratio of 4:1, and at 60° C., the model oil 4 in Table 1 was extracted once with the synthesized DES for 30 min, and the distribution coefficient and aromatic selectivity were calculated. The results are shown in Table 2.

[0088] Example 3

[0089] The DES synthesized in Example 1 was used as the extraction solvent, at a solvent-oil ratio of 6:1, and at 50° C., the model oil 4 in Table 1 was extracted once with the synthesized DES for 30 minutes, and the distribution coefficient and aromatic selectivity were calculated. The results are shown in Table 2.

[0090] Example 4

[0091] Weigh EmimCl and 1-Vim, and stir under condensation reflux in an oil bath at 120°C and 300 rpm for 4 h to obtain DES according to the molar ratio of EmimCl to 1-Vim of 1.5:1. Seal the synthesized DES well and store it in a desiccator for use in extraction experiments.

[0092] The model oil 4 in Table 1 was extracted once with the synthesized DES at a ratio of 2:1 at 40°C for 30 min, and the distribution coefficient and aromatic selectivity were calculated. The results are shown in Table 2.

[0093] Example 5

[0094] Weigh EmimCl and 1-Vim, and stir under condensation reflux in an oil bath at 130°C and 300 rpm for 4 h to obtain DES according to the molar ratio of EmimCl to 1-Vim of 2.5:1. Seal the synthesized DES well and store it in a desiccator for use in extraction experiments.

[0095] The model oil 4 in Table 1 was extracted once with the synthesized DES at a ratio of 2:1 at 40°C for 30 min, and the distribution coefficient and aromatic selectivity were calculated. The results are shown in Table 2.

[0096] Example 6

[0097] The method of Example 1 was followed, except that the molar ratio of 1-ethyl-3-methylimidazole halide to 1-vinylimidazole was 4.5:1, to obtain DES. The synthesized DES was well sealed and stored in a desiccator for use in extraction experiments.

[0098] The model oil 4 in Table 1 was extracted once with the synthesized DES at a ratio of 2:1 at 40°C for 30 min, and the distribution coefficient and aromatic selectivity were calculated. The results are shown in Table 2.

[0099] Comparative Example 1

[0100] Using sulfolane as solvent, at a solvent-oil ratio of 2:1, at 40°C, the model oil 4 in Table 1 was extracted once for 30 min, and the distribution coefficient and aromatic selectivity were calculated. The results are shown in Table 2.

[0101] Comparative Example 2

[0102] Using dimethyl sulfoxide as solvent, at a solvent-oil ratio of 2:1, at 40°C, the model oil 4 in Table 1 was extracted once for 30 min, and the distribution coefficient and aromatic selectivity were calculated. The results are shown in Table 2.

[0103] Comparative Example 3

[0104] Using N,N-dimethylformamide (DMF) as solvent, at a solvent-oil ratio of 2:1, at 40°C, the model oil 4 in Table 1 was extracted once for 30 min, and the distribution coefficient and aromatic selectivity were calculated. The results are shown in Table 2.

[0105] Comparative Example 4

[0106] Using N-methylpyrrolidone (NMP) as solvent, at a solvent-oil ratio of 2:1, at 40°C, the model oil 4 in Table 1 was extracted once for 30 min, and the distribution coefficient and aromatic selectivity were calculated. The results are shown in Table 2.

[0107] Comparative Example 5

[0108] The method of Example 1 was followed, except that 1-methylimidazole (1-Mim) was used as a hydrogen bond donor to obtain DES. The synthesized DES was well sealed and stored in a desiccator for use in extraction experiments.

[0109] The model oil 4 in Table 1 was extracted once with the synthesized DES at a ratio of 2:1 at 40°C for 30 min, and the distribution coefficient and aromatic selectivity were calculated. The results are shown in Table 2.

[0110] Table 2

[0111]

[0112]

[0113] It can be seen from the results in Table 2 that, compared with conventional organic solvents, the extraction solvent provided by the present invention has better extraction selectivity and is suitable for use as an aromatic hydrocarbon extraction solvent.

[0114] Example 7

[0115] Process flow such as Figure 3 shown.

[0116] The DES synthesized in Example 1 was used as the extraction solvent, at a solvent-oil ratio of 4:1, at an extraction tower temperature of 50°C, a solvent recovery tower kettle temperature of 120°C, and a solvent recovery tower top pressure of 3kPa, the gasoline fraction was subjected to countercurrent extraction, and the solvent was recovered by vacuum distillation to obtain raffinate oil and extracted oil. The composition results of the gasoline raw material, raffinate oil and extracted oil are shown in Table 3.

[0117] It can be seen from Table 3 that the N content in the raffinate oil did not increase relative to the gasoline feedstock, indicating that there was essentially no DES residue in the raffinate oil.

[0118] Table 3

[0119]

[0120]

[0121] Note: Yield = Raffinate oil mass (extracted oil mass) / raw oil mass × 100%

[0122] Example 8

[0123] Process flow such as Figure 3 shown.

[0124] The DES synthesized in Example 1 was used as the extraction solvent, and the solvent-oil ratio was 4:1. Under the conditions of an extraction tower temperature of 50°C, a solvent recovery tower kettle temperature of 160°C, and a solvent recovery tower top pressure of 1.5 kPa, the light diesel oil fraction was subjected to countercurrent extraction, and the solvent was recovered by vacuum distillation to obtain raffinate oil and extracted oil. The composition results of the light diesel oil raw material, raffinate oil and extracted oil are shown in Table 4.

[0125] It can be seen from Table 4 that the N content in the raffinate oil did not increase relative to the light diesel feedstock, indicating that there was basically no DES residue in the raffinate oil.

[0126] Table 4

[0127] Light diesel raw materials Extraction of residual oil Extraction of oil Yield, wt% / 16.6 83.4 N content, μg / g 22 17 / Hydrocarbon composition, wt% Alkanes 13.4 50.9 2.4 Cycloalkanes 4.3 15.5 1.2 Monocyclic aromatic hydrocarbons 38.8 27.4 36.8 PAHs 43.5 6.2 59.6 Total aromatics 82.3 33.6 96.4 total 100 100 100

[0128] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A composition, characterized in that The composition comprises 1-ethyl-3-methylimidazole halide and 1-vinyl imidazole, wherein the molar ratio of the 1-ethyl-3-methylimidazole halide to the 1-vinyl imidazole is 0.2-5:

1.

2. The composition according to claim 1, wherein The molar ratio of 1-ethyl-3-methylimidazole halide to 1-vinylimidazole is 1-3:1; Preferably, the 1-ethyl-3-methylimidazolium halide salt is 1-ethyl-3-methylimidazolium chloride or 1-ethyl-3-methylimidazolium bromide.

3. A deep eutectic solvent comprising a hydrogen-bonded 1-ethyl-3-methylimidazolium halide and 1-vinylimidazole.

4. The solvent according to claim 3, wherein 1-ethyl-3-methylimidazolium halide is 1-ethyl-3-methylimidazolium chloride or 1-ethyl-3-methylimidazolium bromide; Preferably, the solvent is liquid in the range of -55 to 250°C.

5. A method for preparing a deep eutectic solvent, the method comprising: The deep eutectic solvent is obtained by subjecting the composition according to claim 1 or 2 to a melt reaction.

6. The method according to claim 5, wherein: The temperature of the melt reaction is 80-150°C, preferably 100-150°C; Preferably, the melting reaction time is 1-5 h, preferably 3-5 h.

7. Use of the deep eutectic solvent according to claim 3 or 4 or the deep eutectic solvent obtained by the method according to claim 5 or 6 in extracting and separating aromatic hydrocarbons, preferably in extracting and separating aromatic hydrocarbons in petroleum fractions.

8. A method for extracting and separating aromatic hydrocarbons from petroleum fractions, the method comprising: (1) contacting the petroleum fraction with the deep eutectic solvent in reverse order to obtain a raffinate oil and an extracted oil containing the deep eutectic solvent and aromatic hydrocarbons; (2) separating the extracted oil containing the deep eutectic solvent and aromatic hydrocarbons in step (1) to obtain aromatic hydrocarbons and the deep eutectic solvent; Wherein, the low eutectic solvent in step (1) is the low eutectic solvent according to claim 3 or 4 or the low eutectic solvent prepared by the method according to claim 5 or 6.

9. The method according to claim 8, wherein: The conditions for the reverse contact in step (1) include: a temperature of 30-100° C.; Preferably, the mass ratio of the deep eutectic solvent to the petroleum fraction is 1-10:

1.

10. The method according to claim 8, wherein: The separation in step (2) is carried out in a solvent recovery tower; Preferably, the separation conditions in step (2) include: the tower bottom temperature is 80-200° C.; the tower top pressure is 1-10 kPa; Preferably, the separation is vacuum distillation; Preferably, the low eutectic solvent obtained at the bottom of the solvent recovery tower is returned to step (1) for recycling; Preferably, the petroleum fraction is selected from at least one of gasoline, diesel and kerosene.

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