Method for separating vinyltoluene and saturated c9 aromatic hydrocarbon, and extractant mixture

Abstract

The present invention relates to a method for separating vinyltoluene and a saturated C9 aromatic hydrocarbon represented by C9H12, and an extractant mixture. The method of the present invention comprises the steps of: (1) providing a stream containing vinyltoluene and a saturated C9 aromatic hydrocarbon; and (2) introducing the stream and an extractant mixture into an extractive distillation tower for extractive distillation, so as to obtain an overhead fraction and a bottom fraction, wherein the extractant mixture comprises N,N-dimethylformamide and glycerol, the overhead fraction contains the saturated C9 aromatic hydrocarbon and N,N-dimethylformamide, and the bottom fraction contains vinyltoluene and glycerol. The method of the present invention can be used for separating vinyltoluene and a saturated C9 aromatic hydrocarbon from lightweight cracked C9 aromatic hydrocarbons, thereby realizing a high yield and a high purity.

Description

Method for separating vinyltoluene and C9 saturated aromatic hydrocarbons and extractant mixture Technical Field

[0001] The present invention relates to aromatic hydrocarbon separation, in particular to a method for separating vinyl toluene and C9 saturated aromatic hydrocarbons from light cracked C9 aromatic hydrocarbons and an extractant mixture. Background Art

[0002] Cracked C9 is a byproduct of petroleum cracking, containing a large amount of C9 aromatics (also known as cracked C9 aromatics), such as indene, vinyltoluene, propylbenzene, methylethylbenzene, and trimethylbenzene. Currently, in most cases, C9 aromatics are used directly without treatment, for example as a gasoline blending component. They are also used to produce petroleum resins with very low added value, but most of the components contained in them are not fully utilized. Direct use of C9 aromatics results in low resource utilization and low economic added value.

[0003] A variety of methods have been proposed in the art to separate one or more components from cracked C9 or cracked C9 aromatics. For example, CN 107502386 A introduces a method for obtaining mixed aromatics by hydrogenation separation of cracked C9 fractions. The method includes: removing heavy components such as colloids from the cracked C9 fraction; low-temperature liquid-phase hydrogenation to remove easily polymerizable components such as diolefins; high-temperature gas-phase hydrogenation to remove monoolefins, sulfur and nitrogen; and distillation separation to obtain mixed aromatics with low non-aromatic content. The hydrogenation reaction of this process also removes active monomers such as styrene from the cracked C9 fraction, which results in low resource utilization, high cost and low economic added value.

[0004] Vinyltoluene, like 2-methylstyrene, is an important monomer in organic synthesis, particularly for pharmaceutical research and development. Traditionally, vinyltoluene has been synthesized by reacting ethanol with toluene. This method has numerous drawbacks, including expensive raw materials, low reaction efficiency, high energy consumption, and high equipment investment. Pyrolysis of C9 aromatics contains vinyltoluene. Therefore, efficient separation of vinyltoluene from pyrolysis of C9 aromatics would be a promising alternative to this synthesis.

[0005] The boiling points of the various components in the cracked C9 aromatics are similar. Among them, the boiling point of 2-methylstyrene is about 169°C, the boiling point of 3-methylstyrene is about 170°C, and the boiling point of 4-methylstyrene is about 171°C. Among the alkyl-substituted benzenes with nine carbon atoms (C9 saturated aromatic hydrocarbons), the boiling point of 2-ethyltoluene is about 165°C, the boiling point of 4-ethyltoluene is about 162°C, the boiling point of mesitylene is about 167°C, and the boiling point of para-trimethylbenzene is about 168°C. Because vinyltoluene and C9 saturated aromatic hydrocarbons have similar boiling points and similar structures, it is difficult to separate them from each other using ordinary distillation methods.

[0006] Extractive distillation has been proposed in the art for separation of substances. However, there is no report on the use of extractive distillation to separate vinyltoluene and C9 saturated aromatic hydrocarbons with a boiling point close to that of vinyltoluene.

[0007] Summary of the Invention

[0008] The present invention aims to overcome the difficulty in separating vinyltoluene and C9 saturated aromatic hydrocarbons in existing technologies. The present invention provides a method for separating vinyltoluene and C9 saturated aromatic hydrocarbons from a stream containing these hydrocarbons. The separation is performed by extractive distillation using an extractant mixture comprising N,N-dimethylformamide and glycerol. The method can be used to separate vinyltoluene and C9 saturated aromatic hydrocarbons from (light) cracked C9 aromatic hydrocarbons, achieving high yield and high purity.

[0009] In one aspect, the present invention provides a method for separating vinyltoluene and C9H 12 A method for producing C9 saturated aromatic hydrocarbons, comprising the steps of:

[0010] (1) providing a logistics containing vinyltoluene and C9 saturated aromatic hydrocarbons;

[0011] (2) passing the logistics and the extractant mixture into an extractive distillation tower for extractive distillation to obtain a tower top fraction and a tower bottom fraction, wherein the extractant mixture comprises a mixed solution of N,N-dimethylformamide and glycerol, the tower top fraction contains C9 saturated aromatic hydrocarbons and N,N-dimethylformamide, and the tower bottom fraction contains vinyltoluene and glycerol.

[0012] In another aspect, the present invention provides a method for separating vinyltoluene and C9H from light cracked carbon nine aromatics. 12 A method for producing C9 saturated aromatic hydrocarbons, comprising the steps of:

[0013] (1) A mixture of light cracked C9 aromatic hydrocarbons and an extractant is introduced into an extractive distillation tower for extractive distillation to obtain a tower top fraction and a tower bottom fraction, wherein the extractant mixture comprises N,N-dimethylformamide and glycerol, the tower top fraction contains C9 saturated aromatic hydrocarbon N,N-dimethylformamide, and the tower bottom fraction contains vinyltoluene and glycerol.

[0014] In another aspect, the present invention provides a method for separating vinyltoluene and C9H 12 The extractant mixture of C9 saturated aromatic hydrocarbons represented by the present invention comprises N,N-dimethylformamide and glycerol.

[0015] The inventors of the present invention unexpectedly discovered that vinyltoluene and C9 saturated aromatic hydrocarbons can be effectively separated by extractive distillation using an extractant mixture comprising N,N-dimethylformamide (DMF) and glycerol (GLY). The present invention was completed based on this discovery. The method of the present invention can continuously separate vinyltoluene and C9 saturated aromatic hydrocarbons from light cracked C9 aromatic hydrocarbons, achieving high yield and purity. For example, the purity of vinyltoluene can reach greater than or equal to 90%, and the yield can reach greater than or equal to 85%; the purity of C9 saturated aromatic hydrocarbons can reach greater than or equal to 65%. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG1 is a process flow diagram of one embodiment of the method of the present invention.

[0017] Description of Reference Numerals

[0018] 1 Extraction distillation tower; 2 C9 saturated aromatic hydrocarbon refining tower; 3 Vinyl toluene refining tower;

[0019] a Light cracked C9 aromatics; b Extractant mixture; c Stream rich in C9 saturated aromatics; d Stream rich in vinyltoluene. DETAILED DESCRIPTION

[0020] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0021] Any specific numerical value disclosed herein (including the endpoints of a numerical range) is not limited to the exact value of the numerical value, but should be understood to also include values ​​close to the exact value, such as all possible values ​​within ±5% of the exact value. Moreover, for a disclosed numerical range, any combination of the endpoints of the range, between the endpoints and the specific points in the range, and between the specific points can be used to generate one or more new numerical ranges, and these new numerical ranges should also be considered to be specifically disclosed herein.

[0022] Except in the examples, all numerical values ​​of parameters herein are to be understood as being modified in all instances by the term "about", whether or not "about" actually precedes the numerical value.

[0023] Unless otherwise expressly indicated, throughout the specification and claims, the term "comprise" or variations thereof such as "include" or "comprising" will be understood to include the stated elements or components without excluding other elements or components. In addition, the term "comprise" or variations thereof such as "include" or "comprising" may also exclude other elements or components, that is, the term "consists of" or "consists essentially of."

[0024] In one aspect, the present invention provides a method for separating vinyltoluene and C9H 12 A method for producing C9 saturated aromatic hydrocarbons, comprising the steps of:

[0025] (1) providing a logistics containing vinyltoluene and C9 saturated aromatic hydrocarbons;

[0026] (2) passing the logistics and the extractant mixture into an extractive distillation tower for extractive distillation to obtain a tower top fraction and a tower bottom fraction, wherein the extractant mixture comprises N,N-dimethylformamide and glycerol, the tower top fraction contains C9 saturated aromatic hydrocarbons and N,N-dimethylformamide, and the tower bottom fraction contains vinyltoluene and glycerol.

[0027] In this context, "vinyltoluene" is selected from 1-methylstyrene, 2-methylstyrene, 3-methylstyrene and mixtures thereof. The boiling point of vinyltoluene depends on the amount of each of 1-methylstyrene, 2-methylstyrene and 3-methylstyrene, and is generally 169-171° C. In one embodiment, the vinyltoluene is 2-methylstyrene.

[0028] In this article, "C9H 12 The "C9 saturated aromatic hydrocarbons" referred to herein refer to a benzene ring having nine carbon atoms and all substituents being alkyl groups, and may include one or more of propylbenzene, ethylmethylbenzene, and trimethylbenzene. Some components of the C9 saturated aromatic hydrocarbons have a boiling point that is the same as or similar to that of the vinyltoluene, such as 2-ethyltoluene (boiling point of about 165°C), 4-ethyltoluene (boiling point of about 162°C), mesitylene (boiling point of about 167°C), paratrimethylbenzene (boiling point of about 168°C), and the like.

[0029] In one embodiment, the stream containing vinyltoluene and C9 saturated aromatic hydrocarbons consists of vinyltoluene and C9 saturated aromatic hydrocarbons, or consists essentially of vinyltoluene and C9 saturated aromatic hydrocarbons. In the latter case, vinyltoluene and C9 saturated aromatic hydrocarbons represent 85% or more by weight of the stream, preferably 90% or more by weight, more preferably 95% or more by weight, and most preferably 98% or more by weight.

[0030] The extractant mixture used in the present invention comprises N,N-dimethylformamide and glycerol. In one embodiment, the extractant mixture used in the present invention consists of N,N-dimethylformamide and glycerol. In another embodiment, the extractant mixture comprises N,N-dimethylformamide, glycerol, and an auxiliary extractant, wherein the auxiliary extractant is selected from sulfolane, dimethyl sulfoxide, and phenol. The amount of the auxiliary extractant is selected so as not to interfere with the extractive distillation process. In a preferred embodiment, the extractant mixture comprises 0-50% by weight, preferably 0-20% by weight, and more preferably 0-10% by weight of the auxiliary extractant. The total amount of N,N-dimethylformamide and glycerol accounts for 50-100% by weight of the extractant mixture, preferably 80-100% by weight, and more preferably 90-100% by weight. Preferably, in both embodiments, the mass ratio of N,N-dimethylformamide to glycerol is 0.05-0.5:1, preferably 0.06-0.12:1. The inventors of the present invention unexpectedly discovered that controlling the mass ratio of N,N-dimethylformamide to glycerol within the above range is helpful to obtain a better separation effect.

[0031] According to a preferred embodiment of the present invention, the overhead fraction and the bottom fraction can be refined separately to obtain vinyltoluene and C9 saturated aromatic hydrocarbons. For example, the overhead fraction containing C9 saturated aromatic hydrocarbons and N,N-dimethylformamide can be refined in a C9 saturated aromatic hydrocarbon refining tower, obtaining N,N-dimethylformamide at the top of the tower and a stream rich in C9 saturated aromatic hydrocarbons at the bottom of the tower. The bottom fraction containing vinyltoluene and glycerol can be refined in a vinyltoluene refining tower, obtaining a stream rich in vinyltoluene at the top of the tower and glycerol at the bottom of the tower. In the case where the extractant mixture contains an auxiliary extractant, the bottom fraction contains vinyltoluene, glycerol and an auxiliary extractant. Accordingly, the bottom fraction can be refined in a vinyltoluene refining tower, obtaining a stream rich in vinyltoluene at the top of the tower and a stream containing glycerol and an auxiliary extractant at the bottom of the tower.

[0032] The method of the present invention can effectively separate vinyltoluene and C9H 12 The C9 saturated aromatic hydrocarbons are particularly suitable for separating vinyl toluene and C9H from light cracked C9 aromatic hydrocarbons. 12 The present invention provides a method for separating vinyl toluene and C9H from light cracked C9 aromatic hydrocarbons. 12 A method for producing C9 saturated aromatic hydrocarbons, comprising the steps of:

[0033] (1) Light cracked C9 aromatic hydrocarbons and an extractant mixture are introduced into an extractive distillation tower for extractive distillation to obtain a tower top fraction and a tower bottom fraction, wherein the extractant mixture comprises N,N-dimethylformamide and glycerol, the tower top fraction contains C9 saturated aromatic hydrocarbons and N,N-dimethylformamide, and the tower bottom fraction contains vinyltoluene and glycerol.

[0034] In a preferred embodiment, the method of the present invention further comprises the following steps:

[0035] (2) passing the overhead fraction of step (1) into a C9 saturated aromatic hydrocarbon refining tower for refining, obtaining N,N-dimethylformamide at the top of the tower and a stream rich in C9 saturated aromatic hydrocarbons at the bottom of the tower;

[0036] (3) The bottom fraction of step (1) is passed into a vinyltoluene refining tower for refining, thereby obtaining a vinyltoluene-rich stream at the top of the tower and glycerol at the bottom of the tower.

[0037] In this article, the term "light cracked C9 aromatics" is a stream obtained after removing heavy components from cracked C9 aromatics. The term "cracked C9 aromatics" refers to one of the by-products of petroleum cracking, which contains an aromatic fraction with nine carbon atoms. The aromatic fraction includes indene, vinyl toluene, propylbenzene, methylethylbenzene and trimethylbenzene, etc., which have different boiling points. There may also be fractions with more than nine carbon atoms in the cracked C9 aromatics, such as dicyclopentadiene. Generally, components with a boiling point greater than or equal to the boiling point of indene (about 182°C) are called heavy components of cracked C9 aromatics. The light cracked C9 aromatics are obtained after removing heavy components from cracked C9 aromatics, which may include vinyl toluene, propylbenzene, methylethylbenzene and trimethylbenzene. The light cracked C9 aromatics may contain some impurities, such as residual heavy components. Obviously, the light cracked C9 aromatics is also a stream containing vinyl toluene and C9 saturated aromatics.

[0038] Removal of heavy components from cracked C9 aromatics can be performed using various methods known in the art. For example, two towers can be used to process the cracked C9 aromatics, wherein the dicyclopentadiene contained in the cracked C9 aromatics is depolymerized to cyclopentadiene in the first tower, and the cyclopentadiene is removed. The stream after the dicyclopentadiene removal is then passed to a second tower to remove other heavy components, thereby obtaining the light cracked C9 aromatics.

[0039] The extractant mixture used in the present invention comprises N,N-dimethylformamide and glycerol. In one embodiment, the extractant mixture used in the present invention consists of N,N-dimethylformamide and glycerol. In another embodiment, the extractant mixture comprises N,N-dimethylformamide, glycerol, and an auxiliary extractant, wherein the auxiliary extractant is selected from sulfolane, dimethyl sulfoxide, and phenol. The amount of the auxiliary extractant is selected so as not to interfere with the extractive distillation process. In a preferred embodiment, the extractant mixture comprises 0-50% by weight, preferably 0-20% by weight, and more preferably 0-10% by weight of the auxiliary extractant. The total amount of N,N-dimethylformamide and glycerol accounts for 50-100% by weight of the extractant mixture, preferably 80-100% by weight, and more preferably 90-100% by weight. Preferably, in both embodiments, the mass ratio of N,N-dimethylformamide to glycerol is 0.05-0.5:1, preferably 0.06-0.12:1. The inventors of the present invention unexpectedly discovered that controlling the mass ratio of N,N-dimethylformamide to glycerol within the above range is helpful to obtain a better separation effect.

[0040] In the case where the extractant mixture contains an auxiliary extractant, the bottom fraction contains vinyltoluene, glycerol, and the auxiliary extractant. Accordingly, in step (3), the bottom fraction can be refined in a vinyltoluene refining tower to obtain a stream rich in vinyltoluene at the top of the tower and a stream containing glycerol and the auxiliary extractant at the bottom of the tower.

[0041] According to a preferred embodiment of the present invention, the extractant mixture enters the extractive distillation column from the top, and the light cracked C9 aromatics enter from the middle of the extractive distillation column. This arrangement allows for better countercurrent contact between the extractant mixture and the distillate in the extractive distillation column.

[0042] According to a preferred embodiment of the present invention, the feed temperature of the extractant mixture is 10-30°C, and can be fed at room temperature (25°C).

[0043] According to a preferred embodiment of the present invention, the extractant mixture and the light cracked C9 aromatics are introduced into the extractive distillation tower at a mass flow ratio of 0.1-1.5, preferably 0.1-0.6, more preferably 0.2-0.4.

[0044] According to a preferred embodiment of the present invention, the extractive distillation tower is provided with a light cracking C9 aromatic hydrocarbon feed pipeline, an extractant mixture feed pipeline, an extractive distillation tower overhead fraction discharge pipeline, and an extractive distillation tower bottom fraction discharge pipeline; wherein the extractive distillation tower is connected to the C9 saturated aromatic hydrocarbon refining tower through the extractive distillation tower overhead fraction discharge pipeline, and is connected to the vinyltoluene refining tower through the extractive distillation tower bottom fraction discharge pipeline.

[0045] In step (2), the N,N-dimethylformamide obtained at the top of the tower can be returned to the extractive distillation tower for recycling. In step (3), the glycerol and optional auxiliary extractant obtained at the bottom of the tower can be returned to the extractive distillation tower for recycling.

[0046] The C9 saturated aromatic hydrocarbon refining tower is provided with an overhead fraction discharge pipeline at the top and a bottom fraction discharge pipeline at the bottom; wherein the overhead fraction discharge pipeline is connected to the extractant mixture feed pipeline.

[0047] The top of the vinyltoluene refining tower is provided with a tower top fraction discharge pipeline, and the bottom of the tower is provided with a tower bottom fraction discharge pipeline; wherein the tower bottom fraction discharge pipeline of the vinyltoluene refining tower is connected to the extractant mixture feed pipeline.

[0048] Preferably, the operating conditions of the extractive distillation tower include: the number of theoretical plates is 50-90, the operating pressure is 5-20 kPa, the bottom temperature is 250-330° C., and the reflux ratio is 15-25.

[0049] Preferably, the operating conditions of the C9 saturated aromatic hydrocarbon refining tower include: the number of theoretical plates is 40-80, the operating pressure is normal pressure, the reflux ratio is 10-25, and the bottom temperature is 250-265°C.

[0050] Preferably, the operating conditions of the vinyltoluene refining tower include: the number of theoretical plates is 50-90, the operating pressure is normal pressure, the reflux ratio is 5-20, and the bottom temperature is 280-380°C.

[0051] In another aspect, the present invention provides a method for separating vinyltoluene and C9H 12 An extractant mixture of C9 saturated aromatic hydrocarbons is described, wherein the extractant mixture comprises N,N-dimethylformamide and glycerol, and the mass ratio of N,N-dimethylformamide to glycerol is 0.05-0.5:1, preferably 0.06-0.12:1. In one embodiment, the extractant mixture used in the present invention consists of N,N-dimethylformamide and glycerol. In another embodiment, the extractant mixture comprises N,N-dimethylformamide, glycerol, and an auxiliary extractant, wherein the auxiliary extractant is selected from sulfolane, dimethyl sulfoxide, and phenol. The amount of the auxiliary extractant is selected so as not to interfere with the extractive distillation. In a preferred embodiment, the extractant mixture comprises 0-50% by weight, preferably 0-20% by weight, and more preferably 0-10% by weight of the auxiliary extractant. The total amount of N,N-dimethylformamide and glycerol accounts for 50-100% by weight, preferably 80-100% by weight, and more preferably 90-100% by weight of the extractant mixture.

[0052] For example, the present invention may be embodied in the following embodiments:

[0053] 1. A method for separating 2-methylstyrene and mixed aromatics from light cracked C9 aromatics by extractive distillation, comprising the following steps:

[0054] (1) introducing raw material light cracked C9 aromatics and an extractant into an extractive distillation tower for extractive distillation, obtaining a fraction rich in mixed aromatics at the top of the tower and a fraction rich in 2-methylstyrene at the bottom of the tower; the extractant is a composite solution of N,N-dimethylformamide and glycerol;

[0055] (2) the mixed aromatic hydrocarbon-rich fraction obtained at the top of the tower in step (1) is passed into a mixed aromatic hydrocarbon refining tower for refining, the extractant obtained at the top of the tower is returned to the extractive distillation tower for recycling, and high-quality mixed aromatic hydrocarbons are obtained at the bottom of the tower;

[0056] (3) The 2-methylstyrene-rich fraction obtained at the bottom of the tower in step (1) is passed into a 2-methylstyrene refining tower for refining, and high-purity 2-methylstyrene is obtained at the top of the tower. The extractant obtained at the bottom of the tower is returned to the extractive distillation tower for recycling.

[0057] 2. The method for separating 2-methylstyrene and mixed aromatics from light cracked C9 aromatics by extractive distillation as described in Scheme 1, wherein the light cracked C9 aromatics are light cracked C9 aromatics obtained by removing dicyclopentadiene and heavy components from cracked C9 aromatics.

[0058] 3. The method for separating 2-methylstyrene and mixed aromatics from light cracked C9 aromatics by extractive distillation as described in Scheme 2, wherein the heavy fraction is a component having more than 10 carbon atoms.

[0059] 4. The method for separating 2-methylstyrene and mixed aromatics from light cracked C9 aromatics by extractive distillation as described in Scheme 2, wherein the light cracked C9 aromatics are C6 to C9 aromatics.

[0060] 5. The method for separating 2-methylstyrene and mixed aromatics from light cracked carbon nine aromatics by extractive distillation as described in Scheme 1, wherein the mass ratio of the N,N-dimethylformamide to the glycerol is 0.05-0.5:1, preferably 0.06-0.12:1.

[0061] 6. The method for separating 2-methylstyrene and mixed aromatics from light cracked carbon nine aromatics by extractive distillation as described in Scheme 1, wherein the extractant enters from the distillation section of the extractive distillation tower and the feed temperature of the extractant is 10-30°C.

[0062] 7. The method for separating 2-methylstyrene and mixed aromatics from light cracked C9 aromatics by extractive distillation as described in Scheme 1, wherein the mass flow rate ratio of the extractant to the raw material is 0.1-1.5, preferably 0.1-0.6, and more preferably 0.2-0.4.

[0063] 8. The method for separating 2-methylstyrene and mixed aromatics from light cracked carbon nine aromatics by extractive distillation as described in Scheme 1, wherein the operating conditions of the extractive distillation tower include: a theoretical plate number of 50-90, an operating pressure of 5-20 kPa, a bottom temperature of 300-330°C, and a reflux ratio of 15-25.

[0064] 9. The method for separating 2-methylstyrene and mixed aromatics from light cracked C9 aromatics by extractive distillation as described in Scheme 1, wherein the operating conditions of the mixed aromatics refining tower include: a theoretical plate number of 40-80, an operating pressure of atmospheric pressure, a reflux ratio of 10-25, and a bottom temperature of 250-265°C.

[0065] 10. The method for separating 2-methylstyrene and mixed aromatics from light cracked C9 aromatics by extractive distillation as described in Scheme 1, wherein the operating conditions of the 2-methylstyrene refining tower include: a theoretical plate number of 50-90, an operating pressure of atmospheric pressure, a reflux ratio of 5-20, and a bottom temperature of 360-380°C.

[0066] Example

[0067] The present invention will be further described below with reference to the examples, but the scope of the present invention is not limited to these examples.

[0068] The light cracked C9 aromatics used in the following examples are composed of the following components (by weight): 5.6% allylbenzene, 3.7% n-propylbenzene, 10.6% 2-ethyltoluene, 2.3% 3-ethyltoluene, 3.7% 4-ethyltoluene, 7.2% 1,3,5-trimethylbenzene, 2.8% 1,2,4-trimethylbenzene, 1.8% 1,2,3-trimethylbenzene, 6.6% isopropylbenzene, 55.1% 2-methylstyrene, and 0.6% dicyclopentadiene.

[0069] The following examples all adopt the process flow shown in Figure 1. Specifically, light cracked C9 aromatics a are fed from the middle of the extractive distillation tower 1, and the extractant mixture b is fed from the upper part of the extractive distillation tower 1 at room temperature to perform extractive distillation to obtain a top fraction and a bottom fraction. The top fraction of the extractive distillation tower 1 is passed to the C9 saturated aromatic hydrocarbon refining tower 2 for refining, DMF is obtained at the top of the tower, and a stream c rich in C9 saturated aromatic hydrocarbons is obtained at the bottom of the tower, wherein the DMF obtained at the top of the tower is returned to the extractive distillation tower 1 for recycling. The bottom fraction of the extractive distillation tower 1 is passed to the vinyltoluene refining tower 3 for refining, a stream d rich in vinyltoluene is obtained at the top of the tower, and GLY and an optional auxiliary extractant are obtained at the bottom of the tower, wherein the GLY and the optional auxiliary extractant obtained at the bottom of the tower are returned to the extractive distillation tower 1 for recycling.

[0070] Test Method

[0071] The quality of the vinyltoluene-rich stream d and the vinyltoluene therein, and the C9 saturated aromatic hydrocarbon-rich stream c and the C9 saturated aromatic hydrocarbons therein obtained in the examples and comparative examples were tested, and the corresponding purities and yields were calculated. For the light cracked C9 aromatic hydrocarbons used, the C9 saturated aromatic hydrocarbons were n-propylbenzene, 2-ethyltoluene, 3-ethyltoluene, 4-ethyltoluene, 1,3,5-trimethylbenzene, 1,2,4-trimethylbenzene, 1,2,3-trimethylbenzene and isopropylbenzene, and the vinyltoluene was 2-methylstyrene.

[0072] Purity and yield were calculated using the following formulas:

[0073] Purity of vinyltoluene = mass of vinyltoluene / mass of stream d enriched in vinyltoluene × 100%;

[0074] Purity of C9 saturated aromatic hydrocarbons = mass of C9 saturated aromatic hydrocarbons / mass of stream c rich in C9 saturated aromatic hydrocarbons × 100%;

[0075] Yield of vinyl toluene = mass of vinyl toluene / mass of vinyl toluene in light cracked C9 aromatics × 100%;

[0076] Yield of C9 saturated aromatic hydrocarbons = mass of C9 saturated aromatic hydrocarbons / mass of C9 saturated aromatic hydrocarbons in light cracked C9 aromatic hydrocarbons × 100%,

[0077] The mass of vinyltoluene in the light cracked C9 aromatics is the product of the content of vinyltoluene (55.1%) and the input amount of light cracked C9 aromatics;

[0078] The mass of mixed aromatics in light cracked C9 aromatics is the product of the content of C9 saturated aromatics (3.7% + 10.6% + 2.3% + 3.7% + 7.2% + 2.8% + 1.8% + 6.6%) and the input amount of light cracked C9 aromatics.

[0079] Example 1

[0080] (1) Light cracked C9 aromatic hydrocarbons a are fed from the middle of an extractive distillation tower 1, and an extractant mixture b (a mixed solution of N,N-dimethylformamide (DMF) and glycerol (GLY), with a mass ratio of 0.1:1) is fed from the upper part of the extractive distillation tower 1 at room temperature, and extractive distillation is performed to obtain a top fraction and a bottom fraction, wherein the mass flow ratio of the extractant mixture b to the light cracked C9 aromatic hydrocarbons a is 0.5. The operating conditions of the extractive distillation tower 1 include: a theoretical plate number of 60, an operating pressure of 15 kPa, a bottom temperature of 320°C, and a reflux ratio of 20.

[0081] (2) The overhead fraction from step (1) is passed to a C9 saturated aromatic hydrocarbon refining tower 2 for refining, wherein the operating conditions of the C9 saturated aromatic hydrocarbon refining tower 2 include: operation at atmospheric pressure, a theoretical plate number of 60, a reflux ratio of 15, and a bottom temperature of 258° C. DMF is obtained at the top of the tower, and a stream c rich in C9 saturated aromatic hydrocarbons is obtained at the bottom of the tower.

[0082] (3) The bottom fraction from step (1) is passed to a vinyltoluene refining tower 3 for refining. The operating conditions of the vinyltoluene refining tower 3 include: operation at atmospheric pressure, a theoretical plate number of 60, a reflux ratio of 15, and a bottom temperature of 377°C. A vinyltoluene-rich stream d is obtained at the top of the tower, and GLY is obtained at the bottom of the tower.

[0083] The purity and yield of vinyltoluene and C9 saturated aromatic hydrocarbons were calculated as described above and the results are listed in Table 1.

[0084] Example 2

[0085] (1) Light cracked C9 aromatic hydrocarbons a are fed from the middle of an extractive distillation tower 1, and an extractant mixture b (a mixed solution of N,N-dimethylformamide (DMF) and glycerol (GLY), with a mass ratio of 0.15:1) is fed from the upper part of the extractive distillation tower 1 at room temperature to perform extractive distillation to obtain a top fraction and a bottom fraction, wherein the mass flow ratio of the extractant mixture b to the light cracked C9 aromatic hydrocarbons a is 0.5. The operating conditions of the extractive distillation tower 1 include: a theoretical plate number of 60, an operating pressure of 10 kPa, a bottom temperature of 310°C, and a reflux ratio of 15.

[0086] (2) The overhead fraction from step (1) is passed to a C9 saturated aromatic hydrocarbon refining tower 2 for refining, wherein the operating conditions of the C9 saturated aromatic hydrocarbon refining tower 2 include: operation at normal pressure, a theoretical plate number of 70, a reflux ratio of 15, and a bottom temperature of 258° C. DMF is obtained at the top of the tower, and a stream c rich in C9 saturated aromatic hydrocarbons is obtained at the bottom of the tower.

[0087] (3) The bottom fraction from step (1) is passed to a vinyltoluene refining tower 3 for refining. The operating conditions of the vinyltoluene refining tower 3 include: operation at atmospheric pressure, a theoretical plate number of 70, a reflux ratio of 10, and a bottom temperature of 377°C. A vinyltoluene-rich stream d is obtained at the top of the tower, and GLY is obtained at the bottom of the tower.

[0088] The purity and yield of vinyltoluene and C9 saturated aromatic hydrocarbons were calculated as described above and the results are listed in Table 1.

[0089] Example 3

[0090] (1) Light cracked C9 aromatic hydrocarbons a are fed from the middle of an extractive distillation tower 1, and an extractant mixture b (a mixed solution of N,N-dimethylformamide (DMF) and glycerol (GLY), with a mass ratio of 0.12:1) is fed from the upper part of the extractive distillation tower 1 at room temperature, and extractive distillation is performed to obtain a top fraction and a bottom fraction, wherein the mass flow ratio of the extractant mixture b to the light cracked C9 aromatic hydrocarbons a is 0.5. The operating conditions of the extractive distillation tower 1 include: a theoretical plate number of 70, an operating pressure of 10 kPa, a bottom temperature of 330°C, and a reflux ratio of 20.

[0091] (2) The overhead fraction from step (1) is passed to a C9 saturated aromatic hydrocarbon refining tower 2 for refining, wherein the operating conditions of the C9 saturated aromatic hydrocarbon refining tower 2 include: operation at normal pressure, a theoretical plate number of 60, a reflux ratio of 15, and a bottom temperature of 259° C. DMF is obtained at the top of the tower, and a stream c rich in C9 saturated aromatic hydrocarbons is obtained at the bottom of the tower.

[0092] (3) The bottom fraction from step (1) is passed to a vinyltoluene refining tower 3 for refining. The operating conditions of the vinyltoluene refining tower 3 include: operation at atmospheric pressure, a theoretical plate number of 60, a reflux ratio of 20, and a bottom temperature of 377°C. A vinyltoluene-rich stream d is obtained at the top of the tower, and GLY is obtained at the bottom of the tower.

[0093] The purity and yield of vinyltoluene and C9 saturated aromatic hydrocarbons were calculated as described above and the results are listed in Table 1.

[0094] Example 4

[0095] (1) Light cracked C9 aromatic hydrocarbons a are fed from the middle of an extractive distillation tower 1, and an extractant mixture b (a mixed solution of N,N-dimethylformamide (DMF) and glycerol (GLY), with a mass ratio of 0.35:1) is fed from the upper part of the extractive distillation tower 1 at room temperature, and extractive distillation is performed to obtain a top fraction and a bottom fraction, wherein the mass flow ratio of the extractant mixture b to the light cracked C9 aromatic hydrocarbons a is 0.3. The operating conditions of the extractive distillation tower 1 include: a theoretical plate number of 80, an operating pressure of 10 kPa, a bottom temperature of 300°C, and a reflux ratio of 15.

[0096] (2) The top fraction of step (1) is passed into a C9 saturated aromatic hydrocarbon refining tower 2 for refining, wherein the operating conditions of the C9 saturated aromatic hydrocarbon refining tower 2 include: operation at normal pressure, a theoretical plate number of 60, a reflux ratio of 20, a bottom temperature of 258° C., DMF is obtained at the top of the tower, and a stream c rich in C9 saturated aromatic hydrocarbons is obtained at the bottom of the tower.

[0097] (3) The bottom fraction from step (1) is passed to a vinyltoluene refining tower 3 for refining. The operating conditions of the vinyltoluene refining tower 3 include: operation at atmospheric pressure, a theoretical plate number of 60, a reflux ratio of 15, and a bottom temperature of 377°C. A vinyltoluene-rich stream d is obtained at the top of the tower, and GLY is obtained at the bottom of the tower.

[0098] The purity and yield of vinyltoluene and C9 saturated aromatic hydrocarbons were calculated as described above and the results are listed in Table 1.

[0099] Example 5

[0100] (1) Light cracked C9 aromatic hydrocarbons a are fed from the middle of an extractive distillation tower 1, and an extractant mixture b (a mixed solution of N,N-dimethylformamide (DMF) and glycerol (GLY), with a mass ratio of 0.08:1) is fed from the upper part of the extractive distillation tower 1 at room temperature, and extractive distillation is performed to obtain a top fraction and a bottom fraction, wherein the mass flow ratio of the extractant mixture b to the light cracked C9 aromatic hydrocarbons a is 0.3. The operating conditions of the extractive distillation tower 1 include: a theoretical plate number of 60, an operating pressure of 10 kPa, a bottom temperature of 320°C, and a reflux ratio of 20.

[0101] (2) The top fraction of step (1) is passed into a C9 saturated aromatic hydrocarbon refining tower 2 for refining, wherein the operating conditions of the C9 saturated aromatic hydrocarbon refining tower 2 include: operation at normal pressure, a theoretical plate number of 60, a reflux ratio of 20, a bottom temperature of 258° C., DMF is obtained at the top of the tower, and a stream c rich in C9 saturated aromatic hydrocarbons is obtained at the bottom of the tower.

[0102] (3) The bottom fraction from step (1) is passed to a vinyltoluene refining tower 3 for refining. The operating conditions of the vinyltoluene refining tower 3 include: operation at atmospheric pressure, a theoretical plate number of 60, a reflux ratio of 10, and a bottom temperature of 377°C. A vinyltoluene-rich stream d is obtained at the top of the tower, and GLY is obtained at the bottom of the tower.

[0103] The purity and yield of vinyltoluene and C9 saturated aromatic hydrocarbons were calculated as described above and the results are listed in Table 1.

[0104] Example 6

[0105] (1) Light cracked C9 aromatic hydrocarbons a are fed from the middle of an extractive distillation tower 1, and an extractant mixture b (a mixed solution of N,N-dimethylformamide (DMF) and glycerol (GLY), with a mass ratio of 0.24:1) is fed from the upper part of the extractive distillation tower 1 at room temperature, and extractive distillation is performed to obtain a top fraction and a bottom fraction, wherein the mass flow ratio of the extractant mixture b to the light cracked C9 aromatic hydrocarbons a is 0.3. The operating conditions of the extractive distillation tower 1 include: a theoretical plate number of 60, an operating pressure of 20 kPa, a bottom temperature of 310°C, and a reflux ratio of 15.

[0106] (2) The overhead fraction from step (1) is passed to a C9 saturated aromatic hydrocarbon refining tower 2 for refining, wherein the operating conditions of the C9 saturated aromatic hydrocarbon refining tower 2 include: operation at normal pressure, a theoretical plate number of 70, a reflux ratio of 15, and a bottom temperature of 258° C. DMF is obtained at the top of the tower, and a stream c rich in C9 saturated aromatic hydrocarbons is obtained at the bottom of the tower.

[0107] (3) The bottom fraction from step (1) is passed to a vinyltoluene refining tower 3 for refining. The operating conditions of the vinyltoluene refining tower 3 include: operation at atmospheric pressure, a theoretical plate number of 60, a reflux ratio of 15, and a bottom temperature of 377°C. A vinyltoluene-rich stream d is obtained at the top of the tower, and GLY is obtained at the bottom of the tower.

[0108] The purity and yield of vinyltoluene and C9 saturated aromatic hydrocarbons were calculated as described above and the results are listed in Table 1.

[0109] Example 7

[0110] (1) Light cracked C9 aromatic hydrocarbons a are fed from the middle of an extractive distillation tower 1, and an extractant mixture b (a mixed solution of N,N-dimethylformamide (DMF) and glycerol (GLY), with a mass ratio of 0.43:1) is fed from the upper part of the extractive distillation tower 1 at room temperature, and extractive distillation is performed to obtain a top fraction and a bottom fraction, wherein the mass flow ratio of the extractant mixture b to the light cracked C9 aromatic hydrocarbons a is 0.3. The operating conditions of the extractive distillation tower 1 include: a theoretical plate number of 60, an operating pressure of 10 kPa, a bottom temperature of 295°C, and a reflux ratio of 20.

[0111] (2) The top fraction of step (1) is passed into a C9 saturated aromatic hydrocarbon refining tower 2 for refining, wherein the operating conditions of the C9 saturated aromatic hydrocarbon refining tower 2 include: operation at normal pressure, a theoretical plate number of 60, a reflux ratio of 20, a bottom temperature of 258° C., DMF is obtained at the top of the tower, and a stream c rich in C9 saturated aromatic hydrocarbons is obtained at the bottom of the tower.

[0112] (3) The bottom fraction from step (1) is passed to a vinyltoluene refining tower 3 for refining. The operating conditions of the vinyltoluene refining tower 3 include: operation at atmospheric pressure, a theoretical plate number of 60, a reflux ratio of 10, and a bottom temperature of 372° C. A vinyltoluene-rich stream d is obtained at the top of the tower, and GLY is obtained at the bottom of the tower.

[0113] The purity and yield of vinyltoluene and C9 saturated aromatic hydrocarbons were calculated as described above and the results are listed in Table 1.

[0114] Example 8

[0115] (1) Light cracked C9 aromatic hydrocarbons a are fed from the middle of an extractive distillation tower 1, and an extractant mixture b (a mixed solution of N,N-dimethylformamide (DMF) and glycerol (GLY), with a mass ratio of 0.06:1) is fed from the upper part of the extractive distillation tower 1 at room temperature, and extractive distillation is performed to obtain a top fraction and a bottom fraction, wherein the mass flow ratio of the extractant mixture b to the light cracked C9 aromatic hydrocarbons a is 0.3. The operating conditions of the extractive distillation tower 1 include: a theoretical plate number of 60, an operating pressure of 10 kPa, a bottom temperature of 301°C, and a reflux ratio of 20.

[0116] (2) The overhead fraction of step (1) is passed into a C9 saturated aromatic hydrocarbon refining tower 2 for refining, wherein the operating conditions of the C9 saturated aromatic hydrocarbon refining tower 2 include: operation at normal pressure, a theoretical plate number of 60, a reflux ratio of 20, and a bottom temperature of 258° C. DMF is obtained at the top of the tower, which is optionally returned to the extractive distillation tower 1 for recycling, and a stream c rich in C9 saturated aromatic hydrocarbons is obtained at the bottom of the tower.

[0117] (3) The bottom fraction from step (1) is passed to a vinyltoluene refining tower 3 for refining. The operating conditions of the vinyltoluene refining tower 3 include: operation at atmospheric pressure, a theoretical plate number of 60, a reflux ratio of 10, and a bottom temperature of 374°C. A vinyltoluene-rich stream d is obtained at the top of the tower, and GLY is obtained at the bottom of the tower, which can optionally be returned to the extractive distillation tower for recycling.

[0118] The purity and yield of vinyltoluene and C9 saturated aromatic hydrocarbons were calculated as described above and the results are listed in Table 1.

[0119] Example 9

[0120] (1) Light cracked C9 aromatic hydrocarbons a are fed from the middle of an extractive distillation tower 1, and an extractant mixture b (a mixed solution of N,N-dimethylformamide (DMF), glycerol (GLY) and dimethyl sulfoxide as an auxiliary extractant, with a mass ratio of 1:9:90) is fed from the upper part of the extractive distillation tower 1 at room temperature to perform extractive distillation to obtain a top fraction and a bottom fraction, wherein the mass flow ratio of the extractant mixture b to the light cracked C9 aromatic hydrocarbons a is 0.3. The operating conditions of the extractive distillation tower 1 include: a theoretical plate number of 60, an operating pressure of 10 kPa, a bottom temperature of 277°C, and a reflux ratio of 20.

[0121] (2) The overhead fraction from step (1) is passed to a C9 saturated aromatic hydrocarbon refining tower 2 for refining, wherein the operating conditions of the C9 saturated aromatic hydrocarbon refining tower 2 include: operation at atmospheric pressure, a theoretical plate number of 60, a reflux ratio of 20, and a bottom temperature of 258° C. DMF is obtained at the top of the tower, and a stream c rich in C9 saturated aromatic hydrocarbons is obtained at the bottom of the tower.

[0122] (3) The bottom fraction from step (1) is passed to a vinyltoluene refining tower 3 for refining. The operating conditions of the vinyltoluene refining tower 3 include: operation at atmospheric pressure, a theoretical plate number of 60, a reflux ratio of 10, and a bottom temperature of 290° C. A stream d rich in vinyltoluene is obtained at the top of the tower, and a mixed liquid of GLY and dimethyl sulfoxide is obtained at the bottom of the tower.

[0123] The purity and yield of vinyltoluene and C9 saturated aromatic hydrocarbons were calculated as described above and the results are listed in Table 1.

[0124] Example 10

[0125] (1) Light cracked carbon nine aromatic hydrocarbons a are fed from the middle of an extractive distillation tower 1, and a mixed solution of an extractant mixture b (a mixture of N,N-dimethylformamide (DMF), glycerol (GLY) and cyclopentane) in a mass ratio of 1:9:10) is fed from the upper part of the extractive distillation tower 1 at room temperature to perform extractive distillation to obtain a top fraction and a bottom fraction, wherein the mass flow ratio of the extractant mixture b to the light cracked carbon nine aromatic hydrocarbons a is 0.3. The operating conditions of the extractive distillation tower 1 include: a theoretical plate number of 60, an operating pressure of 10 kPa, a bottom temperature of 280°C, and a reflux ratio of 20.

[0126] (2) The overhead fraction from step (1) is passed to a C9 saturated aromatic hydrocarbon refining tower 2 for refining, wherein the operating conditions of the C9 saturated aromatic hydrocarbon refining tower 2 include: operation at atmospheric pressure, a theoretical plate number of 60, a reflux ratio of 20, and a bottom temperature of 258° C. DMF is obtained at the top of the tower, and a stream c rich in C9 saturated aromatic hydrocarbons is obtained at the bottom of the tower.

[0127] (3) The bottom fraction of step (1) is passed to a vinyltoluene refining tower 3 for refining, wherein the operating conditions of the vinyltoluene refining tower 3 include: operation at atmospheric pressure, a theoretical plate number of 60, a reflux ratio of 10, and a bottom temperature of 377° C. A stream d rich in vinyltoluene is obtained at the top of the tower, and a mixed liquid of GLY and sulfolane is obtained at the bottom of the tower.

[0128] The purity and yield of vinyltoluene and C9 saturated aromatic hydrocarbons were calculated as described above and the results are listed in Table 1.

[0129] Example 11

[0130] (1) Light cracked C9 aromatic hydrocarbons a are fed from the middle of an extractive distillation tower 1, and an extractant mixture b (a mixed solution of N,N-dimethylformamide (DMF), glycerol (GLY) and phenol, with a mass ratio of 1:9:10) is fed from the upper part of the extractive distillation tower 1 at room temperature to perform extractive distillation to obtain a top fraction and a bottom fraction, wherein the mass flow ratio of the extractant mixture b to the light cracked C9 aromatic hydrocarbons a is 0.3. The operating conditions of the extractive distillation tower 1 include: a theoretical plate number of 60, an operating pressure of 10 kPa, a bottom temperature of 276°C, and a reflux ratio of 20.

[0131] (2) The overhead fraction from step (1) is passed to a C9 saturated aromatic hydrocarbon refining tower 2 for refining, wherein the operating conditions of the C9 saturated aromatic hydrocarbon refining tower 2 include: operation at atmospheric pressure, a theoretical plate number of 60, a reflux ratio of 20, and a bottom temperature of 258° C. DMF is obtained at the top of the tower, and a stream c rich in C9 saturated aromatic hydrocarbons is obtained at the bottom of the tower.

[0132] (3) The bottom fraction from step (1) is passed to a vinyltoluene refining tower 3 for refining. The operating conditions of the vinyltoluene refining tower 3 include: operation at atmospheric pressure, a theoretical plate number of 60, a reflux ratio of 10, and a bottom temperature of 300° C. A stream d rich in vinyltoluene is obtained at the top of the tower, and a mixed liquid of GLY and phenol is obtained at the bottom of the tower.

[0133] The purity and yield of vinyltoluene and C9 saturated aromatic hydrocarbons were calculated as described above and the results are listed in Table 1.

[0134] Example 12

[0135] (1) Light cracked C9 aromatic hydrocarbons a are fed from the middle of an extractive distillation tower 1, and a mixed solution of an extractant mixture b (a mixture of N,N-dimethylformamide (DMF), glycerol (GLY) and dimethyl sulfoxide, with a mass ratio of 1:9:10) is fed from the upper part of the extractive distillation tower 1 at room temperature, and extractive distillation is performed to obtain a top fraction and a bottom fraction, wherein the mass flow ratio of the extractant mixture b to the light cracked C9 aromatic hydrocarbons a is 0.3. The operating conditions of the extractive distillation tower 1 include: a theoretical plate number of 60, an operating pressure of 10 kPa, a bottom temperature of 276°C, and a reflux ratio of 20.

[0136] (2) The overhead fraction from step (1) is passed to a C9 saturated aromatic hydrocarbon refining tower 2 for refining, wherein the operating conditions of the C9 saturated aromatic hydrocarbon refining tower 2 include: operation at atmospheric pressure, a theoretical plate number of 60, a reflux ratio of 20, and a bottom temperature of 258° C. DMF is obtained at the top of the tower, and a stream c rich in C9 saturated aromatic hydrocarbons is obtained at the bottom of the tower.

[0137] (3) The bottom fraction from step (1) is passed to a vinyltoluene refining tower 3 for refining. The operating conditions of the vinyltoluene refining tower 3 include: operation at atmospheric pressure, a theoretical plate number of 60, a reflux ratio of 10, and a bottom temperature of 310°C. A stream d rich in vinyltoluene is obtained at the top of the tower, and a mixed liquid of GLY and dimethyl sulfoxide is obtained at the bottom of the tower.

[0138] The purity and yield of vinyltoluene and C9 saturated aromatic hydrocarbons were calculated as described above and the results are listed in Table 1.

[0139] Comparative Example 1

[0140] Example 6 was repeated, except that only DMF was used as the extractant.

[0141] The purity and yield of vinyltoluene and C9 saturated aromatic hydrocarbons were calculated as described above and the results are listed in Table 1.

[0142] Comparative Example 2

[0143] Example 6 was repeated, except that only GLY was used as the extractant.

[0144] The purity and yield of vinyltoluene and C9 saturated aromatic hydrocarbons were calculated as described above and the results are listed in Table 1.

[0145] Comparative Example 3

[0146] Example 6 was repeated, except that the extractant mixture was a mixed solution of N,N-dimethylformamide (DMF) and glycerol (GLY), wherein the mass ratio of the two was 0.67:1.

[0147] The purity and yield of vinyltoluene and C9 saturated aromatic hydrocarbons were calculated as described above and the results are listed in Table 1.

[0148] Table 1

[0149] As can be seen from Table 1, the method of the present invention effectively separates vinyltoluene and C9 saturated aromatic hydrocarbons, achieving improved purity and yield.

[0150] The present application is not limited to the specific details of the above-mentioned embodiments. Within the technical concept of the present application, a variety of simple modifications can be made to the technical solution of the present application, and these simple modifications all fall within the protection scope of the present application.

[0151] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner unless there is any contradiction. In order to avoid unnecessary repetition, this application will not further describe various possible combinations.

[0152] In addition, the various implementation methods of the present application can be arbitrarily combined, as long as they do not violate the concept of the present application, they should also be regarded as the content of the invention of the present application.

Claims

1. A method for separating vinyltoluene and C9 saturated aromatic hydrocarbons represented by C9H 12 comprising the following steps: (1) Provide a stream containing vinyltoluene and C9 saturated aromatic hydrocarbons; (2) Feed the said stream and the extractant mixture into an extractive distillation column for extractive distillation to obtain a top fraction and a bottom fraction, wherein the extractant mixture comprises N,N-dimethylformamide and glycerol, the top fraction contains C9 saturated aromatic hydrocarbons and N,N-dimethylformamide, and the bottom fraction contains vinyltoluene and glycerol.

2. The method according to claim 1, wherein, The stream containing vinyltoluene and C9 saturated aromatic hydrocarbons consists essentially of or consists of vinyltoluene and C9 saturated aromatic hydrocarbons; and / or The extractant mixture comprises N,N-dimethylformamide, glycerol and an auxiliary extractant, wherein the auxiliary extractant is selected from sulfolane, dimethyl sulfoxide, phenol; and / or The mass ratio of the N,N-dimethylformamide to the glycerol is 0.05 - 0.5:1, preferably 0.06 - 0.12:

1.

3. The method according to claim 2, wherein The extractant mixture contains 0 - 50 wt%, preferably 0 - 20 wt%, more preferably 0 - 10 wt% of the auxiliary extractant, and the total amount of N,N-dimethylformamide and glycerol accounts for 50 - 100 wt%, preferably 80 - 100 wt%, more preferably 90 - 100 wt% of the extractant mixture.

4. A method for separating vinyltoluene and C9 saturated aromatic hydrocarbons represented by C9H 12 from light cracked C9 aromatic hydrocarbons, comprising the following steps: (1) Feed light cracked C9 aromatic hydrocarbons and an extractant mixture into an extractive distillation column for extractive distillation to obtain a top fraction and a bottom fraction, wherein the extractant mixture comprises N,N-dimethylformamide and glycerol, the top fraction contains C9 saturated aromatic hydrocarbons and N,N-dimethylformamide, and the bottom fraction contains vinyltoluene and glycerol.

5. The method according to claim 4, further comprising the following steps: (2) Feed the top fraction of step (1) into a C9 saturated aromatic hydrocarbon refining column for refining, to obtain N,N-dimethylformamide at the top and a stream rich in C9 saturated aromatic hydrocarbons at the bottom; (3) Feed the bottom fraction of step (1) into a vinyltoluene refining column for refining, to obtain a stream rich in vinyltoluene at the top and glycerol at the bottom.

6. The method according to claim 4, wherein, The mass ratio of the N,N-dimethylformamide to the glycerol is 0.05 - 0.5:1, preferably 0.06 - 0.12:1; and / or The extractant mixture comprises N,N-dimethylformamide, glycerol and an auxiliary extractant, wherein the auxiliary extractant is selected from sulfolane, dimethyl sulfoxide, phenol.

7. The method according to claim 6, wherein, The extractant mixture contains 0 - 50 wt%, preferably 0 - 20 wt%, more preferably 0 - 10 wt% of the auxiliary extractant, and the total amount of N,N-dimethylformamide and glycerol accounts for 50 - 100 wt%, preferably 80 - 100 wt%, more preferably 90 - 100 wt% of the extractant mixture.

8. The method according to claim 4, wherein The extractant mixture is fed into the upper part of the extractive distillation column, and the feed temperature is 10 - 30 °C; and / or The mass flow ratio of the extractant mixture to the light cracked C9 aromatic hydrocarbons is 0.1 - 1.5, preferably 0.1 - 0.6, more preferably 0.2 - 0.4; and / or The operating conditions of the extractive distillation column include: the number of theoretical plates is 50 - 90, the operating pressure is 5 - 20 kPa, the bottom temperature of the column is 250 - 330 °C, and the reflux ratio is 15 - 25.

9. The method according to claim 5, wherein The operating conditions of the C9 saturated aromatic hydrocarbon refining column include: the number of theoretical plates is 40 - 80, the operating pressure is atmospheric pressure, the reflux ratio is 10 - 25, and the bottom temperature of the column is 250 - 265 °C; and / or The operating conditions of the vinyltoluene refining column include: the number of theoretical plates is 50 - 90, the operating pressure is atmospheric pressure, the reflux ratio is 5 - 20, and the bottom temperature of the column is 280 - 380 °C.

10. The method according to claim 5, wherein, In step (2), the N,N-dimethylformamide obtained at the top of the column is returned to the extractive distillation column for recycling, and In step (3), the glycerol obtained at the bottom of the column is returned to the extractive distillation column for recycling.

11. An extractant mixture for separating vinyltoluene and the C9 saturated aromatic hydrocarbon represented by C9H by extractive distillation, wherein the extractant mixture comprises N,N-dimethylformamide and glycerol, and the mass ratio of the N,N-dimethylformamide to the glycerol is 0.05-0.5:1, preferably 0.06-0.12:

1. 12 The C9 saturated aromatic hydrocarbon represented by C9H is separated from vinyltoluene by extractive distillation using the extractant mixture.

12. The extractant mixture according to claim 11, wherein, The extractant mixture contains N,N-dimethylformamide, glycerol and an auxiliary extractant, wherein the auxiliary extractant is selected from sulfolane, dimethyl sulfoxide, phenol.

13. The extractant mixture according to claim 12, wherein, The extractant mixture contains 0 - 50%, preferably 0 - 20%, more preferably 0 - 10% of the auxiliary extractant, and the total amount of N,N-dimethylformamide and glycerol accounts for 50 - 100% by weight, preferably 80 - 100% by weight, more preferably 90 - 100% by weight of the extractant mixture.

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