A method for extracting and separating aromatic hydrocarbons from naphtha

Abstract

The application provides a method for extracting and separating aromatic hydrocarbons from naphtha. The method comprises: using an extractant to extract and treat the naphtha to obtain an extract phase and a raffinate phase; separating the extract phase to obtain aromatic hydrocarbons; the extractant comprises an ionic liquid shown in formula 1: aRX-bAlX3-cMX y Formula 1; in formula 1, R is selected from one of imidazole type cation, pyridine type cation and quaternary ammonium salt type cation; M is selected from one of copper ion, silver ion and zirconium ion; X is halogen ion; wherein a:b is 1:(1-2), a:c is 1:(0.01-1); y is selected from 1-4 and y is an integer. The extraction and separation method has excellent aromatic hydrocarbon distribution coefficient and extraction selectivity, and can realize efficient separation of aromatic hydrocarbons in naphtha.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of petrochemical industry, and relates to a method for extracting and separating aromatic hydrocarbons from naphtha. BACKGROUND

[0002] The separation of aromatic hydrocarbons and aliphatic hydrocarbons in naphtha and then application can help to realize the optimized utilization of naphtha resources, and is in good agreement with the concept of "molecular refining" of "oil if suitable, aromatic if suitable, and olefin if suitable". The separation of aromatic hydrocarbons in naphtha can significantly improve the utilization efficiency of naphtha. For example, in the process of producing olefins by steam cracking of naphtha, the aromatic hydrocarbons in naphtha are not easy to crack, which can cause coking of the cracking furnace, increase the operation cost and shorten the operation cycle. The separation of aromatic hydrocarbons in naphtha in advance before steam cracking can effectively avoid the above problems. In addition, benzene, toluene, xylene and the like in aromatic hydrocarbons are important basic organic chemical raw materials, and further processing of the raw materials can obtain aromatic hydrocarbon products with high added value.

[0003] Aromatic hydrocarbon extraction, also known as aromatic hydrocarbon extraction, is a liquid-liquid extraction or extractive distillation process for separating aromatic hydrocarbons from a hydrocarbon mixture using an extractant. The liquid-liquid extraction has lower energy consumption and is a commonly used technical means for separating aromatic hydrocarbons from straight-run naphtha. It is crucial to select a suitable extractant in the process of aromatic hydrocarbon extraction. The commonly used extractants in traditional industries include sulfolane, N-formyl morpholine and the like. However, such extractants are volatile, deteriorate easily, have high toxicity and cannot simultaneously have the problems of aromatic hydrocarbon distribution coefficient and extraction selectivity.

[0004] As a new type of green extraction solvent, ionic liquid has the advantages of not easy to volatilize, not easy to burn, small toxicity and designability, and has been widely used in the separation of aromatic hydrocarbons in naphtha. However, the existing ionic liquid still has unsatisfactory effect in the extraction and separation of aromatic hydrocarbons from naphtha, and it is still difficult to simultaneously have good aromatic hydrocarbon distribution coefficient and excellent extraction selectivity. Therefore, how to efficiently separate aromatic hydrocarbons from naphtha is a technical problem to be solved in the field. SUMMARY

[0005] The present application provides a method for extracting and separating aromatic hydrocarbons from naphtha, which uses an extractant with excellent extraction distribution coefficient and extraction selectivity, and can realize the efficient separation of aromatic hydrocarbons in naphtha. In addition, the method also has the advantages of simple process flow and low energy consumption.

[0006] The present application provides a method for extracting and separating aromatic hydrocarbons from naphtha, comprising: using an extractant to extract and treat naphtha to obtain an extract phase and a raffinate phase; and separating the extract phase to obtain aromatic hydrocarbons.

[0007] The extractant comprises an ionic liquid represented by formula 1:

[0008] aRX-bAlX3-cMX y Formula 1

[0009] In Formula 1, R is selected from one of imidazole cations, pyridine cations, and quaternary ammonium salt cations; M is selected from one of copper ions, silver ions, and zirconium ions; X is a halide ion.

[0010] Where a:b is 1:(1~2), and a:c is 1:(0.01~1);

[0011] y is selected from 1 to 4 and y is an integer.

[0012] The method described above, wherein M is selected from at least one of copper ions and silver ions; and / or,

[0013] X is selected from either chloride ion or bromide ion.

[0014] In the method described above, R is selected from one of the cations shown in Formula 2, Formula 3, and Formula 4:

[0015]

[0016] In Formulas 2, 3, and 4, R1, R2, R3, and R4 are each independently selected from H or C1 to C8 alkyl groups.

[0017] The method described above, wherein R is selected from the cations represented by Formula 2 or Formula 3;

[0018] In Formula 2, R1 and R3 are each independently selected from C2 to C4 alkyl groups, and R2 is selected from H or methyl groups; in Formula 3, R1 is selected from C2 to C4 alkyl groups, and R2 is selected from H or methyl groups.

[0019] The method described above, wherein a:b is 1:(1.4 to 2); and / or a:c is 1:(0.2 to 0.7).

[0020] In the method described above, the mass ratio of the extractant to the naphtha is (0.5–7):1.

[0021] In the method described above, the mass ratio of the extractant to the naphtha is (1-4):1.

[0022] In the method described above, the extraction process is carried out at a temperature of 10–80°C for a time of 1–60 min.

[0023] In the method described above, the extraction process is carried out at a temperature of 10–40°C for a time of 1–20 min.

[0024] The method as described above, wherein the separation treatment comprises subjecting the extraction phase to a distillation treatment or a vacuum distillation treatment to remove the extractant from the extraction phase.

[0025] The implementation of the present application has at least the following advantages:

[0026] 1) The extractant used in the extraction separation method of the present application has obvious solubility difference for aliphatic hydrocarbons and aromatic hydrocarbons in naphtha, specifically, aromatic hydrocarbons are easily soluble in the extractant, so that the extractant has excellent aromatic hydrocarbon distribution coefficient, and at the same time that aromatic hydrocarbons are easily soluble in the extractant, aliphatic hydrocarbons are also difficult to dissolve in the extractant, so that the extractant also has excellent extraction selectivity, and can realize efficient separation of aromatic hydrocarbons in naphtha.

[0027] 2) The extraction separation of the present application has the advantages of simple process flow and low energy consumption. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 It is a process flow diagram for extracting and separating aromatic hydrocarbons from naphtha according to an embodiment of the present application;

[0029] Figure 2 It is a process flow diagram for extracting and separating aromatic hydrocarbons from naphtha according to another embodiment of the present application.

[0030] BRIEF DESCRIPTION OF DRAWINGS:

[0031] 1: extraction unit; 2: separation unit; 3: analysis unit;

[0032] a: naphtha; b: extractant; c: extraction system; d: extraction phase; e: raffinate phase; f: aromatic hydrocarbon; g: regenerated extractant. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0034] The present application provides a method for extracting and separating aromatic hydrocarbons from naphtha, comprising the following steps:

[0035] The naphtha is subjected to extraction treatment using an extractant to obtain an extraction phase and a raffinate phase; the extraction phase is subjected to separation treatment to obtain aromatic hydrocarbons;

[0036] The extractant comprises an ionic liquid represented by formula 1: aRX-bAlX3-cMXy Formula 1

[0037] In formula 1, R is selected from one of imidazole type cation, pyridine type cation, quaternary ammonium salt type cation; M is selected from one of copper ion, silver ion, zirconium ion; X is halogen;

[0038] Wherein, a:b is 1:(1-2); a:c is 1:(0.01-1); y is selected from 1-4 and y is an integer.

[0039] The extraction phase of the present application refers to a phase rich in aromatic hydrocarbons, and the raffinate phase refers to a phase rich in aliphatic hydrocarbons.

[0040] R in the ionic liquid shown in formula 1 can be selected from imidazole type cation, pyridine type cation, quaternary ammonium salt type cation commonly used in the art; halogen refers to four elements of fluorine, chlorine, bromine and iodine.

[0041] a:b refers to the molar ratio of cation R to metal Al; a:c refers to the molar ratio of cation R to metal M.

[0042] It should be noted that the value of y needs to make MX y Satisfy the positive and negative valence is 0.

[0043] R belongs to the cationic part in the ionic liquid, AlX3, MX y And RX X halide reacts to form a double metal complex anion, which belongs to the anionic part in the ionic liquid, the cationic part and the anionic part are connected by ionic bond, and the M metal and the halide connected to the metal Al are connected by covalent bond.

[0044] The method for extracting and separating aromatic hydrocarbons from naphtha of the present application has obvious solubility difference of the extractant used in aliphatic hydrocarbons and aromatic hydrocarbons in naphtha, specifically, aromatic hydrocarbons are easily dissolved in the extractant, therefore the extractant has excellent aromatic hydrocarbon distribution coefficient, while aromatic hydrocarbons are easily dissolved in the extractant, aliphatic hydrocarbons are also difficult to dissolve in the extractant, therefore the extractant also has excellent extraction selectivity, which can realize efficient separation of aromatic hydrocarbons in naphtha. In addition, the method also has the advantages of simple process flow and low energy consumption.

[0045] Especially for naphtha raw materials with low aromatic hydrocarbon content (the content of aromatic hydrocarbons in naphtha ≤50wt%), compared with traditional sulfolane, N-formyl morpholine and existing ionic liquid extractant, the extraction separation effect of the extractant of the present application is more obvious.

[0046] The extractant of the present application can be prepared by a conventional preparation method in the art. For example, the preparation method of [Emim]Cl-2.0AlCl3-0.65AgCl includes: first, synthesizing a basic ionic liquid by stirring [Emim]Cl and AlCl3 at a molar ratio of 1:2 at 120°C for 2 hours under N2 protection, then adding 0.65 molar ratio of AgCl and stirring at 150°C for 4 hours, and no solid is precipitated after standing at room temperature for 48 hours, thus synthesizing the ionic liquid extractant of [Emim]Cl-2.0AlCl3-0.65AgCl. The remaining extractants can be prepared by the preparation method, and will not be described here.

[0047] Further, M is selected from at least one of copper ions, silver ions, and zirconium ions; and / or, X is selected from one of chloride ions and bromide ions. The copper ions include monovalent copper ions and divalent copper ions, and preferably monovalent copper ions; the zirconium ions include divalent zirconium ions, trivalent zirconium ions, and tetravalent zirconium ions, and preferably tetravalent zirconium ions.

[0048] In a preferred embodiment, when R is selected from one of the cations of formula 2, formula 3, and formula 4, the extractant has a better extraction separation effect on aromatic hydrocarbons in naphtha.

[0049]

[0050] In formula 2, formula 3, and formula 4, R1, R2, R3, and R4 are each independently selected from H or C1-C8 alkyl.

[0051] The C1-C8 alkyl includes C1-C8 straight-chain alkyl and branched-chain alkyl, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, etc.

[0052] Further, R is selected from the cation of formula 2 or formula 3, and in formula 2, R1 and R3 are each independently selected from C2-C4 alkyl, and R2 is selected from H or methyl; in formula 3, R1 is selected from C2-C4 alkyl, and R2 is selected from H or methyl.

[0053] Further, a:b is 1:(1.4-2); and / or, a:c is 1:(0.2-0.7).

[0054] The present inventors have found that when the mass ratio of the extractant to naphtha is (0.5-7):1, and further preferably (1-4):1, excellent extraction separation effect can be achieved without excessive extractant, and lower separation cost can be considered.

[0055] In the present application, the mass ratio of the extractant to naphtha can be referred to as the agent-to-oil ratio.

[0056] When the naphtha is treated by extraction with the extractant, most of the aromatic hydrocarbons in the naphtha can be enriched in the extractant at an extraction temperature of 10-80℃ and an extraction time of 1-60 min. Further, the extraction temperature is preferably 10-40℃ and the extraction time is preferably 1-20 min.

[0057] Further, the extractant in the extract phase can be separated and removed by taking advantage of the difference in boiling point between the extractant and the aromatic hydrocarbons, thereby obtaining the aromatic hydrocarbons.

[0058] In a specific embodiment, the separation of the extractant from the aromatic hydrocarbons in the extract phase can be achieved by distillation at 110℃ under reduced pressure for 30 min.

[0059] The extraction and separation method of the present application can be used to separate the aromatic hydrocarbons in the naphtha by batch operation or by continuous operation.

[0060] For example, a magnetic stirrer and a separatory funnel commonly used in small-scale research can be used to mix the naphtha and the extractant and to separate them by standing, and then the extractant in the extract phase can be removed by distillation or distillation under reduced pressure, thereby obtaining the aromatic hydrocarbons.

[0061] A device commonly used in the chemical industry for extraction and separation can also be used to achieve continuous operation to separate the aromatic hydrocarbons in the naphtha.

[0062] Figure 1 The process flow for extracting and separating the aromatic hydrocarbons from the naphtha according to an embodiment of the present application is shown in FIG. 1. Figure 1 As shown in FIG. 1, the extraction and separation device used in the process includes an extraction unit 1, a separation unit 2, and an elution unit 3 connected in sequence.

[0063] The extraction unit 1 is used to mix the naphtha and the extractant, and includes two inlets and one outlet. The two inlets can be used to feed the naphtha a and the extractant b, respectively. After mixing, the obtained extraction system c is discharged from the outlet of the extraction unit 1.

[0064] The separation unit 2 is used to separate the extraction system c by standing, and includes one inlet and two outlets. The inlet receives the extraction system c discharged from the outlet of the extraction unit 1. After standing separation in the separation unit 2, the obtained extract phase d is discharged from the bottom outlet, and the raffinate phase e is discharged from the top outlet.

[0065] The resolving unit 3 is used to realize the process of separating the aromatic hydrocarbon f and the extractant in the extraction phase d, and the resolving unit 3 comprises one inlet and two outlets, the inlet receives the extraction phase d discharged from the separating unit 2, after the extraction phase d is treated by distillation or vacuum distillation or the like in the resolving unit 3, the separated aromatic hydrocarbon f is discharged from the top outlet and collected, and the separated extractant is the regenerated extractant g which can be collected alone or returned to the extraction unit 1 to participate in the next extraction and separation process.

[0066] Figure 2 The process flow diagram for extracting and separating aromatic hydrocarbons from naphtha according to another embodiment of the present application is shown in FIG. 3. Figure 2 As shown in FIG. 3, the extraction and separation device used in the process is connected between the outlet of the regenerated extractant g at the bottom of the resolving unit 3 and the inlet of the extraction unit 1, so as to realize the recycling of the regenerated extractant g.

[0067] Hereinafter, the ionic liquid extractant, the preparation method and the application thereof provided by the present application will be further described in detail through specific examples.

[0068] It should be noted that, in the following examples, unless otherwise specified, the raw materials used can be obtained by commercial purchase or prepared by conventional methods, and the experimental methods without specific conditions are conventional methods and conventional conditions known in the art.

[0069] Examples 1-25 and Comparative Examples 1-7

[0070] The device shown in FIG. 1 is used to implement the operation of extracting and separating aromatic hydrocarbons from naphtha, and the device comprises an extraction unit 1, a separating unit 2 and a resolving unit 3 which are sequentially connected. Figure 1 As shown in FIG. 1, the device comprises an extraction unit 1, a separating unit 2 and a resolving unit 3 which are sequentially connected. Figure 1

[0071] The extraction unit 1 is provided with a naphtha inlet, an extractant inlet and an extraction system outlet.

[0072] The separating unit 2 is provided with an extraction system inlet, an extraction phase outlet and a raffinate phase outlet, and the extraction system inlet is communicated with the extraction system outlet of the extraction unit 1.

[0073] The resolving unit 3 is provided with an extraction phase inlet, an aromatic hydrocarbon outlet and a regenerated extractant outlet, and the extraction phase inlet is communicated with the extraction phase outlet of the separating unit 2.

[0074] The method for extracting and separating aromatic hydrocarbons from naphtha by using the above device comprises the following steps:

[0075] 1) The naphtha a enters the extraction unit 1 from the naphtha inlet, the extractant b enters the extraction unit 1 from the extractant inlet, and the naphtha a and the extractant b are fully mixed in the extraction unit 1 to obtain the extraction system c. ​

[0076] 2) The extraction system c is output from the extraction system outlet and input into the separation unit 2 from the extraction system inlet for separation, to obtain the extraction phase d and the raffinate phase e respectively; the raffinate phase e is discharged from the raffinate phase outlet and collected;

[0077] 3) The extraction phase d is output from the extraction phase outlet and input into the stripping unit 3 from the extraction phase inlet, and is distilled under reduced pressure at 110°C for 30 min, to obtain the aromatic hydrocarbon f and the regenerated extraction agent g;

[0078] 4) The aromatic hydrocarbon f is discharged from the aromatic hydrocarbon outlet and collected; the regenerated extraction agent g is discharged from the regenerated extraction agent outlet and collected.

[0079] In the above examples and comparative examples, the composition (simulated composition) of the naphtha and the extraction conditions are shown in Table 1.

[0080] Table 1

[0081]

[0082]

[0083] In Table 1, 1) [Emim] + refers to 1-ethyl-3-methylimidazolium cation, [Bmim] + refers to 1-butyl-3-methylimidazolium cation, [Empy] + refers to 1-ethyl-3-methylpyridinium cation, [Et3NH] + refers to triethylamine cation, [SCN] － refers to thiocyanate; 2) the agent / oil ratio refers to the mass ratio of the extraction agent to the naphtha.

[0084] It should be particularly pointed out that the purity of the regenerated extraction agent separated in Example 9 is 99.88%. The extraction agent used in Example 10 is the regenerated extraction agent obtained in Example 9, and the purity of the regenerated extraction agent separated in Example 10 is 99.71%.

[0085] As can be seen from Example 9 and Example 10, the extraction agent recovered by the present application still has a very high purity and can be recycled multiple times.

[0086] In the above examples and comparative examples, the aromatic hydrocarbon distribution coefficient, the extraction selectivity, the extraction performance index and the single extraction de-aromatization rate and other parameters are used to characterize the effect of extracting and separating the aromatic hydrocarbon from the naphtha. The calculation formula of the above parameters is as follows:

[0087] 1. Aromatic hydrocarbon distribution coefficient

[0088]

[0089] In formula 1, D2 represents the distribution coefficient of aromatic hydrocarbon, i.e. the equilibrium distribution relationship of aromatic hydrocarbon in two phases, represents the mass fraction of aromatic hydrocarbon in the extraction phase, represents the mass fraction of aromatic hydrocarbon in the raffinate phase.

[0090] 2. Extraction selectivity

[0091]

[0092] In formula 2, S represents the extraction selectivity, D2 represents the distribution coefficient of aromatic hydrocarbon, and D1 represents the distribution coefficient of aliphatic hydrocarbon. D1 is calculated in the same way as D2.

[0093] 3. Extraction performance index

[0094] PI = S x D2 Formula 3

[0095] In formula 3, PI represents the extraction performance index, S represents the extraction selectivity, and D2 represents the distribution coefficient of aromatic hydrocarbon.

[0096] 4. Single extraction dearomatization rate

[0097]

[0098] In formula 4, P represents the single extraction dearomatization rate, represents the mass fraction of aromatic hydrocarbon in the extraction phase, represents the mass fraction of aromatic hydrocarbon in naphtha, m E represents the mass of the extraction phase, m F represents the mass of naphtha.

[0099] In the above examples and comparative examples, the composition of the extraction phase and the raffinate phase, the mass of the extraction phase, the distribution coefficient of aromatic hydrocarbon D2, the extraction selectivity S, the extraction performance index PI, and the single extraction dearomatization rate P are shown in Table 2. The higher the extraction performance index PI, the more excellent the aromatic hydrocarbon distribution coefficient and the extraction selectivity can be considered, and the better the extraction separation effect is indicated.

[0100] Table 2

[0101]

[0102]

[0103] In Table 2, 1) the composition of the raffinate phase and the extraction phase is obtained after correction according to the correction factor of each substance after chromatographic analysis detection; 2) D2, S, PI and P are obtained by retaining two decimal places after calculation according to the composition of the raffinate phase and the extraction phase in Table 1 and Table 2.

[0104] As can be seen from the data in Table 2, compared with traditional sulfoxide, N-formyl morpholine and [Bmim]Cl-1.0CuCl, [Bmim]Cl-1.0AlCl3, [Bmim][SCN] and other extractants, the ionic liquid extractant containing bimetallic complex anion used in the application has good aromatic hydrocarbon distribution coefficient and extraction selectivity, and has excellent extraction separation effect on aromatic hydrocarbons in naphtha.

[0105] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for extracting and separating aromatic hydrocarbons from naphtha, characterized in that, include: Naphtha is extracted using an extractant to obtain an extract phase and a raffinate phase; the extract phase is then separated to obtain aromatic hydrocarbons. The extractant includes the ionic liquid shown in Formula 1: aRX-bAlX3-cMX y Formula 1 In Formula 1, R is selected from one of imidazole cations, pyridine cations, and quaternary ammonium salt cations; M is selected from one of copper ions, silver ions, and zirconium ions; X is a halide ion. Where a:b is 1:(1~2), a:c is 1:(0.1~0.7); y is selected from 1 to 4 and y is an integer.

2. The method according to claim 1, characterized in that, M is selected from at least one of copper ions and silver ions; and / or, X is selected from either chloride ion or bromide ion.

3. The method according to claim 1 or 2, characterized in that, R is selected from one of the cations shown in Formula 2, Formula 3, and Formula 4: Formula 2 Formula 3 Formula 4 In Formulas 2, 3, and 4, R1, R2, R3, and R4 are each independently selected from H or C1-C8 alkyl groups.

4. The method according to claim 3, characterized in that, R is selected from the cations shown in Formula 2 or Formula 3; In Formula 2, R1 and R3 are each independently selected from C2 to C4 alkyl groups, and R2 is selected from H or methyl groups; in Formula 3, R1 is selected from C2 to C4 alkyl groups, and R2 is selected from H or methyl groups.

5. The method according to any one of claims 1, 2, and 4, characterized in that, The mass ratio of the extractant to the naphtha is (0.5~7):

1.

6. The method according to claim 3, characterized in that, The mass ratio of the extractant to the naphtha is (0.5~7):

1.

7. The method according to claim 5, characterized in that, The mass ratio of the extractant to the naphtha is (1~4):

1.

8. The method according to claim 6, characterized in that, The mass ratio of the extractant to the naphtha is (1~4):

1.

9. The method according to claim 1, characterized in that, The extraction process is carried out at a temperature of 10~80℃ for a time of 1~60 min.

10. The method according to claim 9, characterized in that, The extraction process is carried out at a temperature of 10~40℃ for 1~20 min.

11. The method according to claim 1, characterized in that, The separation process includes: distilling the extract phase to remove the extractant from the extract phase.

12. The method according to claim 11, characterized in that, The distillation process includes vacuum distillation.

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